## Re: Capacitor Charging Question

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• If you are using a 5V solar cell operating at 3.2V or less, the solar cell current will be nearly constant and the cap charging time equation becomes
Message 1 of 14 , Dec 31, 2006
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If you are using a 5V solar cell operating at 3.2V or less, the solar
cell current will be nearly constant and the cap charging time
equation becomes

dT=C*dV/Isc

According to your experiment, using a 1380L (3.2V) with the 4700uF
cap the time between pops is about 30 secs.

That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A (0.5mA)

The energy stored in the cap with 4700uF charged to 3.2V (which is
completely discharged into the load) is 0.5V*V*C =0.024J

Let's see how that works for the 1F cap with the 1381C trigger.

Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset voltage),
the initial charging time from 0V to the operating voltage (2.4V) is
1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's 2.88 J of stored
energy.

After reaching the 2.4V operating voltage and using approximantly the
same discharge energy per pop of 0.024J (10mA * 1sec) with the 1F
capacitor voltage dropping dV=10mV every pop, the charging time
between pops is 1F * 0.01V / 0.0005A = 20 seconds which is faster
that the 4700uF case because once initialized, the solar cell
operates constantly at 2.4V nearer to its maximum power point.

wilf

--- In beam@yahoogroups.com, Gary Tolley <grogyan@...> wrote:
>
> Tk,
> There is a formula to calculate the charge time of a cap.
> http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> or
> http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capchg.html
>
> ater a quick search on google.
>
> Gary T
>
>
> >OK, I have a working solarpopper based on Wilfs "Photopopper v8"
> >circuit posed back in September. Slick circuit...simple and
elegant.
> >
> >I have a Radio Shack 4700uF 35v capacitor...it is massive but I
> >figured it would be OK for testing purposes. With this capacitor
and
> >a 1381L as indicated in the plans, it works and charges very
quickly
> >and drives the 6mm motors just fine.
> >
> >As a test, I wanted to see what a 1381C (2.4v) and the 1.0F 2.5v
> >Aerogel Super Capacitor would do. I have a few of these so it is
> >worth checking out because they are tiny. This capacitor is MUCH
> >smaller and if I could drive the 6mm motors from the 2.4v, then it
> >might be something worth implementing.
> >
> >Here is the deal...the 1F capacitor takes FOREVER to charge. Maybe
I
> >am confused on my basic electronics but shouldn't a 1F capacitor
> >charge in a bit more than double the time as the 4700uF capacitor?
> >
> >Under an incandecent bulb I did the following...I tested both the
> >4700uF and 1F with the 1381C triggering at 2.4v. The 4700uF was
> >triggering rather rapidly (several times per minute)...I am not
sure
> >the 2.4v will be adequate to drive the motors but that is not the
> >point right now...the 1F took about 90 minutes to charge. It was
> >painfully long. Just how much more capacity does the 1F have?
> >
> >Can someone shed some light on why the 1F is taking so long to
charge?
> >
> >tk
> >
> >
>
• Wow...that is some good information. The math seems to bear out my observations which is good, but the cool thing is that once the 1F gets charged, it will
Message 2 of 14 , Jan 1, 2007
• 0 Attachment
Wow...that is some good information. The math seems to bear out my
observations which is good, but the cool thing is that once the 1F
gets charged, it will fire pretty quick afterwards. If there is a
design that can live on only 2.4 volts then this could be
interesting.

2.4 volts seems pretty weak...not enough to really drive the motors
well. Is it possible to put 2 1F 2.5 capacitors in series and use the
1381L (3.2 volts) or higher trigger? Dividing the charge between the
two, keeping both under the 2.5v rating but reaping the benefit of
the added discharge voltage? Yea, it would take quite awhile to
initially charge but might perform well afterwards.

Sorry if these are obvious questions...I am electronically
challenged. I took basic electronics in high school nearly 20 years
ago and that's it. One of these days I'm going to blow something up
but it will be fun getting there!

tk

--- In beam@yahoogroups.com, "wilf_nv" <wrigter@...> wrote:
>
> If you are using a 5V solar cell operating at 3.2V or less, the
solar
> cell current will be nearly constant and the cap charging time
> equation becomes
>
> dT=C*dV/Isc
>
> According to your experiment, using a 1380L (3.2V) with the 4700uF
> cap the time between pops is about 30 secs.
>
> That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A (0.5mA)
>
> The energy stored in the cap with 4700uF charged to 3.2V (which is
> completely discharged into the load) is 0.5V*V*C =0.024J
>
> Let's see how that works for the 1F cap with the 1381C trigger.
>
> Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset voltage),
> the initial charging time from 0V to the operating voltage (2.4V)
is
> 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's 2.88 J of
stored
> energy.
>
> After reaching the 2.4V operating voltage and using approximantly
the
> same discharge energy per pop of 0.024J (10mA * 1sec) with the 1F
> capacitor voltage dropping dV=10mV every pop, the charging time
> between pops is 1F * 0.01V / 0.0005A = 20 seconds which is faster
> that the 4700uF case because once initialized, the solar cell
> operates constantly at 2.4V nearer to its maximum power point.
>
> wilf
>
> --- In beam@yahoogroups.com, Gary Tolley <grogyan@> wrote:
> >
> > Tk,
> > There is a formula to calculate the charge time of a cap.
> > http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> > or
> > http://hyperphysics.phy-astr.gsu.edu/hbase/electric/capchg.html
> >
> > ater a quick search on google.
> >
> > Gary T
> >
> >
> > >OK, I have a working solarpopper based on Wilfs "Photopopper v8"
> > >circuit posed back in September. Slick circuit...simple and
> elegant.
> > >
> > >I have a Radio Shack 4700uF 35v capacitor...it is massive but I
> > >figured it would be OK for testing purposes. With this capacitor
> and
> > >a 1381L as indicated in the plans, it works and charges very
> quickly
> > >and drives the 6mm motors just fine.
> > >
> > >As a test, I wanted to see what a 1381C (2.4v) and the 1.0F 2.5v
> > >Aerogel Super Capacitor would do. I have a few of these so it is
> > >worth checking out because they are tiny. This capacitor is MUCH
> > >smaller and if I could drive the 6mm motors from the 2.4v, then
it
> > >might be something worth implementing.
> > >
> > >Here is the deal...the 1F capacitor takes FOREVER to charge.
Maybe
> I
> > >am confused on my basic electronics but shouldn't a 1F capacitor
> > >charge in a bit more than double the time as the 4700uF
capacitor?
> > >
> > >Under an incandecent bulb I did the following...I tested both the
> > >4700uF and 1F with the 1381C triggering at 2.4v. The 4700uF was
> > >triggering rather rapidly (several times per minute)...I am not
> sure
> > >the 2.4v will be adequate to drive the motors but that is not the
> > >point right now...the 1F took about 90 minutes to charge. It was
> > >painfully long. Just how much more capacity does the 1F have?
> > >
> > >Can someone shed some light on why the 1F is taking so long to
> charge?
> > >
> > >tk
> > >
> > >
> >
>
• Hi tk With two 1F caps in series, which gives you a combined cap of 0.5F @ 5V, and a 1381L (3.2V) trigger, the initial charging time with a solar cell
Message 3 of 14 , Jan 1, 2007
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Hi tk

With two 1F caps in series, which gives you a combined cap of 0.5F @ 5V,  and  a 1381L (3.2V) trigger, the initial charging time with a solar cell supplying 0.5mA constant current

dT (charging  time)=Capacitance*dV(voltage change) /Isc(solar cell current)

0.5F * 3.2V / 0.5ma  = 3200 seconds = 53 minutes

Note that, with a Ge diode in series with the solar cell and charged up to 3.2V, the cap should hold that voltage for quite a while in the dark (i.e. overnight) and won't take long to start popping when the light comes back on.

btw what solar cell are  you using?

Now consider the discharge cycle.  If each pop from the 0.5F sol;ar popper is assumed to be equivalent to a 4700uf cap discharging completely from 3.2V to 0V and depending on the timing cap and the load, such an equivalent  pop might be 15mA (average) * 3.2V * 0.5 sec during which the capacitor voltage drops 15mV.

The recharge time between pops would be:

0.5F * 0.015V / 0.5ma = 15 seconds and with I(sc)=30mA the popping time would be

wilf

----- Original Message -----
Sent: Monday, January 01, 2007 11:54 AM
Subject: [beam] Re: Capacitor Charging Question

Wow...that is some good information. The math seems to bear out my
observations which is good, but the cool thing is that once the 1F
gets charged, it will fire pretty quick afterwards. If there is a
design that can live on only 2.4 volts then this could be
interesting.

2.4 volts seems pretty weak...not enough to really drive the motors
well. Is it possible to put 2 1F 2.5 capacitors in series and use the
1381L (3.2 volts) or higher trigger? Dividing the charge between the
two, keeping both under the 2.5v rating but reaping the benefit of
the added discharge voltage? Yea, it would take quite awhile to
initially charge but might perform well afterwards.

Sorry if these are obvious questions... I am electronically
challenged. I took basic electronics in high school nearly 20 years
ago and that's it. One of these days I'm going to blow something up
but it will be fun getting there!

tk

--- In beam@yahoogroups. com, "wilf_nv" <wrigter@... > wrote:
>
> If you are using a 5V solar cell operating at 3.2V or less, the
solar
> cell current will be nearly constant and the cap charging time
> equation becomes
>
> dT=C*dV/Isc
>
> According to your experiment, using a 1380L (3.2V) with the 4700uF
> cap the time between pops is about 30 secs.
>
> That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A (0.5mA)
>
> The energy stored in the cap with 4700uF charged to 3.2V (which is
> completely discharged into the load) is 0.5V*V*C =0.024J
>
> Let's see how that works for the 1F cap with the 1381C trigger.
>
> Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset voltage),
> the initial charging time from 0V to the operating voltage (2.4V)
is
> 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's 2.88 J of
stored
> energy.
>
> After reaching the 2.4V operating voltage and using approximantly
the
> same discharge energy per pop of 0.024J (10mA * 1sec) with the 1F
> capacitor voltage dropping dV=10mV every pop, the charging time
> between pops is 1F * 0.01V / 0.0005A = 20 seconds which is faster
> that the 4700uF case because once initialized, the solar cell
> operates constantly at 2.4V nearer to its maximum power point.
>
> wilf
>
> --- In beam@yahoogroups. com, Gary Tolley <grogyan@> wrote:
> >
> > Tk,
> > There is a formula to calculate the charge time of a cap.
> > http://ourworld. compuserve. com/homepages/ Bill_Bowden/ rc.htm
> > or
> > http://hyperphysics .phy-astr. gsu.edu/hbase/ electric/ capchg.html
> >
> > ater a quick search on google.
> >
> > Gary T
> >
> >
> > >OK, I have a working solarpopper based on Wilfs "Photopopper v8"
> > >circuit posed back in September. Slick circuit...simple and
> elegant.
> > >
> > >I have a Radio Shack 4700uF 35v capacitor... it is massive but I
> > >figured it would be OK for testing purposes. With this capacitor
> and
> > >a 1381L as indicated in the plans, it works and charges very
> quickly
> > >and drives the 6mm motors just fine.
> > >
> > >As a test, I wanted to see what a 1381C (2.4v) and the 1.0F 2.5v
> > >Aerogel Super Capacitor would do. I have a few of these so it is
> > >worth checking out because they are tiny. This capacitor is MUCH
> > >smaller and if I could drive the 6mm motors from the 2.4v, then
it
> > >might be something worth implementing.
> > >
> > >Here is the deal...the 1F capacitor takes FOREVER to charge.
Maybe
> I
> > >am confused on my basic electronics but shouldn't a 1F capacitor
> > >charge in a bit more than double the time as the 4700uF
capacitor?
> > >
> > >Under an incandecent bulb I did the following... I tested both the
> > >4700uF and 1F with the 1381C triggering at 2.4v. The 4700uF was
> > >triggering rather rapidly (several times per minute)...I am not
> sure
> > >the 2.4v will be adequate to drive the motors but that is not the
> > >point right now...the 1F took about 90 minutes to charge. It was
> > >painfully long. Just how much more capacity does the 1F have?
> > >
> > >Can someone shed some light on why the 1F is taking so long to
> charge?
> > >
> > >tk
> > >
> > >
> >
>

• I m using the solar cell that comes with the old Solarbotics Solarpopper 4.2 kit but I do have other options. I have some of the new Russian-made cells
Message 4 of 14 , Jan 1, 2007
• 0 Attachment
I'm using the solar cell that comes with the old Solarbotics
Solarpopper 4.2 kit but I do have other options.

I have some of the new Russian-made cells Solarbotics has for sale.
For some odd reason they sent me one with the Miller circuit etched
on the back and one did not. It also seems odd that the non-etched
one says 6.7v @ 15mA on the back...they state that it is very
efficient but on their website they have one the same exact size
rated at 6.7v @ 31mA

I also have several 3v 22mA thin-film cells I could use. They are
lighter but have a larger footprint.

I'm going to try out the dual caps and diode and see how it runs.

thanx again...tk

--- In beam@yahoogroups.com, "wilf rigter" <wrigter@...> wrote:
>
>
> Hi tk
>
> With two 1F caps in series, which gives you a combined cap of 0.5F
@ 5V, and a 1381L (3.2V) trigger, the initial charging time with a
solar cell supplying 0.5mA constant current
>
> dT (charging time)=Capacitance*dV(voltage change) /Isc(solar cell
current)
>
> 0.5F * 3.2V / 0.5ma = 3200 seconds = 53 minutes
>
> Note that, with a Ge diode in series with the solar cell and
charged up to 3.2V, the cap should hold that voltage for quite a
while in the dark (i.e. overnight) and won't take long to start
popping when the light comes back on.
>
> btw what solar cell are you using?
>
> Now consider the discharge cycle. If each pop from the 0.5F sol;ar
popper is assumed to be equivalent to a 4700uf cap discharging
completely from 3.2V to 0V and depending on the timing cap and the
load, such an equivalent pop might be 15mA (average) * 3.2V * 0.5
sec during which the capacitor voltage drops 15mV.
>
> The recharge time between pops would be:
>
> 0.5F * 0.015V / 0.5ma = 15 seconds and with I(sc)=30mA the popping
time would be
>
> wilf
>
>
> ----- Original Message -----
> From: kinkyme360
> To: beam@yahoogroups.com
> Sent: Monday, January 01, 2007 11:54 AM
> Subject: [beam] Re: Capacitor Charging Question
>
>
> Wow...that is some good information. The math seems to bear out
my
> observations which is good, but the cool thing is that once the
1F
> gets charged, it will fire pretty quick afterwards. If there is a
> design that can live on only 2.4 volts then this could be
> interesting.
>
> 2.4 volts seems pretty weak...not enough to really drive the
motors
> well. Is it possible to put 2 1F 2.5 capacitors in series and use
the
> 1381L (3.2 volts) or higher trigger? Dividing the charge between
the
> two, keeping both under the 2.5v rating but reaping the benefit
of
> the added discharge voltage? Yea, it would take quite awhile to
> initially charge but might perform well afterwards.
>
> Sorry if these are obvious questions...I am electronically
> challenged. I took basic electronics in high school nearly 20
years
> ago and that's it. One of these days I'm going to blow something
up
> but it will be fun getting there!
>
> tk
>
> --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> >
> > If you are using a 5V solar cell operating at 3.2V or less, the
> solar
> > cell current will be nearly constant and the cap charging time
> > equation becomes
> >
> > dT=C*dV/Isc
> >
> > According to your experiment, using a 1380L (3.2V) with the
4700uF
> > cap the time between pops is about 30 secs.
> >
> > That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A (0.5mA)
> >
> > The energy stored in the cap with 4700uF charged to 3.2V (which
is
> > completely discharged into the load) is 0.5V*V*C =0.024J
> >
> > Let's see how that works for the 1F cap with the 1381C trigger.
> >
> > Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset
voltage),
> > the initial charging time from 0V to the operating voltage
(2.4V)
> is
> > 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's 2.88 J of
> stored
> > energy.
> >
> > After reaching the 2.4V operating voltage and using
approximantly
> the
> > same discharge energy per pop of 0.024J (10mA * 1sec) with the
1F
> > capacitor voltage dropping dV=10mV every pop, the charging time
> > between pops is 1F * 0.01V / 0.0005A = 20 seconds which is
faster
> > that the 4700uF case because once initialized, the solar cell
> > operates constantly at 2.4V nearer to its maximum power point.
> >
> > wilf
> >
> > --- In beam@yahoogroups.com, Gary Tolley <grogyan@> wrote:
> > >
> > > Tk,
> > > There is a formula to calculate the charge time of a cap.
> > > http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> > > or
> > > http://hyperphysics.phy-
astr.gsu.edu/hbase/electric/capchg.html
> > >
> > > ater a quick search on google.
> > >
> > > Gary T
> > >
> > >
> > > >OK, I have a working solarpopper based on Wilfs "Photopopper
v8"
> > > >circuit posed back in September. Slick circuit...simple and
> > elegant.
> > > >
> > > >I have a Radio Shack 4700uF 35v capacitor...it is massive
but I
> > > >figured it would be OK for testing purposes. With this
capacitor
> > and
> > > >a 1381L as indicated in the plans, it works and charges very
> > quickly
> > > >and drives the 6mm motors just fine.
> > > >
> > > >As a test, I wanted to see what a 1381C (2.4v) and the 1.0F
2.5v
> > > >Aerogel Super Capacitor would do. I have a few of these so
it is
> > > >worth checking out because they are tiny. This capacitor is
MUCH
> > > >smaller and if I could drive the 6mm motors from the 2.4v,
then
> it
> > > >might be something worth implementing.
> > > >
> > > >Here is the deal...the 1F capacitor takes FOREVER to charge.
> Maybe
> > I
> > > >am confused on my basic electronics but shouldn't a 1F
capacitor
> > > >charge in a bit more than double the time as the 4700uF
> capacitor?
> > > >
> > > >Under an incandecent bulb I did the following...I tested
both the
> > > >4700uF and 1F with the 1381C triggering at 2.4v. The 4700uF
was
> > > >triggering rather rapidly (several times per minute)...I am
not
> > sure
> > > >the 2.4v will be adequate to drive the motors but that is
not the
> > > >point right now...the 1F took about 90 minutes to charge. It
was
> > > >painfully long. Just how much more capacity does the 1F have?
> > > >
> > > >Can someone shed some light on why the 1F is taking so long
to
> > charge?
> > > >
> > > >tk
> > > >
> > > >
> > >
> >
>
• Hmmm... so the 0.5ma current I derived from your timing measurements is very low compared to the rated output current of the cell. Keep in mind that the rated
Message 5 of 14 , Jan 1, 2007
• 0 Attachment
Hmmm... so the 0.5ma current I derived from your timing measurements
is very low compared to the rated output current of the cell. Keep in
mind that the rated currrent is measured in very bright light. Can
you measure current during charging to confirm the value and that it
is not low because of some other problem?

--- In beam@yahoogroups.com, "kinkyme360" <tskunka@...> wrote:
>
> I'm using the solar cell that comes with the old Solarbotics
> Solarpopper 4.2 kit but I do have other options.
>
> I have some of the new Russian-made cells Solarbotics has for sale.
> For some odd reason they sent me one with the Miller circuit etched
> on the back and one did not. It also seems odd that the non-etched
> one says 6.7v @ 15mA on the back...they state that it is very
> efficient but on their website they have one the same exact size
> rated at 6.7v @ 31mA
>
> I also have several 3v 22mA thin-film cells I could use. They are
> lighter but have a larger footprint.
>
> I'm going to try out the dual caps and diode and see how it runs.
>
> thanx again...tk
>
>
>
> --- In beam@yahoogroups.com, "wilf rigter" <wrigter@> wrote:
> >
> >
> > Hi tk
> >
> > With two 1F caps in series, which gives you a combined cap of
0.5F
> @ 5V, and a 1381L (3.2V) trigger, the initial charging time with
a
> solar cell supplying 0.5mA constant current
> >
> > dT (charging time)=Capacitance*dV(voltage change) /Isc(solar
cell
> current)
> >
> > 0.5F * 3.2V / 0.5ma = 3200 seconds = 53 minutes
> >
> > Note that, with a Ge diode in series with the solar cell and
> charged up to 3.2V, the cap should hold that voltage for quite a
> while in the dark (i.e. overnight) and won't take long to start
> popping when the light comes back on.
> >
> > btw what solar cell are you using?
> >
> > Now consider the discharge cycle. If each pop from the 0.5F
sol;ar
> popper is assumed to be equivalent to a 4700uf cap discharging
> completely from 3.2V to 0V and depending on the timing cap and the
> load, such an equivalent pop might be 15mA (average) * 3.2V * 0.5
> sec during which the capacitor voltage drops 15mV.
> >
> > The recharge time between pops would be:
> >
> > 0.5F * 0.015V / 0.5ma = 15 seconds and with I(sc)=30mA the
popping
> time would be
> >
> > wilf
> >
> >
> > ----- Original Message -----
> > From: kinkyme360
> > To: beam@yahoogroups.com
> > Sent: Monday, January 01, 2007 11:54 AM
> > Subject: [beam] Re: Capacitor Charging Question
> >
> >
> > Wow...that is some good information. The math seems to bear out
> my
> > observations which is good, but the cool thing is that once the
> 1F
> > gets charged, it will fire pretty quick afterwards. If there is
a
> > design that can live on only 2.4 volts then this could be
> > interesting.
> >
> > 2.4 volts seems pretty weak...not enough to really drive the
> motors
> > well. Is it possible to put 2 1F 2.5 capacitors in series and
use
> the
> > 1381L (3.2 volts) or higher trigger? Dividing the charge
between
> the
> > two, keeping both under the 2.5v rating but reaping the benefit
> of
> > the added discharge voltage? Yea, it would take quite awhile to
> > initially charge but might perform well afterwards.
> >
> > Sorry if these are obvious questions...I am electronically
> > challenged. I took basic electronics in high school nearly 20
> years
> > ago and that's it. One of these days I'm going to blow
something
> up
> > but it will be fun getting there!
> >
> > tk
> >
> > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> > >
> > > If you are using a 5V solar cell operating at 3.2V or less,
the
> > solar
> > > cell current will be nearly constant and the cap charging
time
> > > equation becomes
> > >
> > > dT=C*dV/Isc
> > >
> > > According to your experiment, using a 1380L (3.2V) with the
> 4700uF
> > > cap the time between pops is about 30 secs.
> > >
> > > That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A (0.5mA)
> > >
> > > The energy stored in the cap with 4700uF charged to 3.2V
(which
> is
> > > completely discharged into the load) is 0.5V*V*C =0.024J
> > >
> > > Let's see how that works for the 1F cap with the 1381C
trigger.
> > >
> > > Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset
> voltage),
> > > the initial charging time from 0V to the operating voltage
> (2.4V)
> > is
> > > 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's 2.88 J of
> > stored
> > > energy.
> > >
> > > After reaching the 2.4V operating voltage and using
> approximantly
> > the
> > > same discharge energy per pop of 0.024J (10mA * 1sec) with
the
> 1F
> > > capacitor voltage dropping dV=10mV every pop, the charging
time
> > > between pops is 1F * 0.01V / 0.0005A = 20 seconds which is
> faster
> > > that the 4700uF case because once initialized, the solar cell
> > > operates constantly at 2.4V nearer to its maximum power point.
> > >
> > > wilf
> > >
> > > --- In beam@yahoogroups.com, Gary Tolley <grogyan@> wrote:
> > > >
> > > > Tk,
> > > > There is a formula to calculate the charge time of a cap.
> > > > http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> > > > or
> > > > http://hyperphysics.phy-
> astr.gsu.edu/hbase/electric/capchg.html
> > > >
> > > > ater a quick search on google.
> > > >
> > > > Gary T
> > > >
> > > >
> > > > >OK, I have a working solarpopper based on
Wilfs "Photopopper
> v8"
> > > > >circuit posed back in September. Slick circuit...simple
and
> > > elegant.
> > > > >
> > > > >I have a Radio Shack 4700uF 35v capacitor...it is massive
> but I
> > > > >figured it would be OK for testing purposes. With this
> capacitor
> > > and
> > > > >a 1381L as indicated in the plans, it works and charges
very
> > > quickly
> > > > >and drives the 6mm motors just fine.
> > > > >
> > > > >As a test, I wanted to see what a 1381C (2.4v) and the
1.0F
> 2.5v
> > > > >Aerogel Super Capacitor would do. I have a few of these so
> it is
> > > > >worth checking out because they are tiny. This capacitor
is
> MUCH
> > > > >smaller and if I could drive the 6mm motors from the 2.4v,
> then
> > it
> > > > >might be something worth implementing.
> > > > >
> > > > >Here is the deal...the 1F capacitor takes FOREVER to
charge.
> > Maybe
> > > I
> > > > >am confused on my basic electronics but shouldn't a 1F
> capacitor
> > > > >charge in a bit more than double the time as the 4700uF
> > capacitor?
> > > > >
> > > > >Under an incandecent bulb I did the following...I tested
> both the
> > > > >4700uF and 1F with the 1381C triggering at 2.4v. The
4700uF
> was
> > > > >triggering rather rapidly (several times per minute)...I
am
> not
> > > sure
> > > > >the 2.4v will be adequate to drive the motors but that is
> not the
> > > > >point right now...the 1F took about 90 minutes to charge.
It
> was
> > > > >painfully long. Just how much more capacity does the 1F
have?
> > > > >
> > > > >Can someone shed some light on why the 1F is taking so
long
> to
> > > charge?
> > > > >
> > > > >tk
> > > > >
> > > > >
> > > >
> > >
> >
>
• You ask a very good question...I might be able to measure the current if I knew how. ;-) I have a basic analog Radio Shack multimeter...I m not sure how to
Message 6 of 14 , Jan 2, 2007
• 0 Attachment
You ask a very good question...I might be able to measure the current
if I knew how. ;-) I have a basic analog Radio Shack multimeter...I'm
not sure how to measure current with it.

I tried out the dual 1F cap and sure enough, once the thing gets
charged, it triggers at a very regular interval. I seem to have some
loss of charge when idle...perhaps I need a bigger diode? I'm using a
1N914 right now.

tk

--- In beam@yahoogroups.com, "wilf_nv" <wrigter@...> wrote:
>
> Hmmm... so the 0.5ma current I derived from your timing
measurements
> is very low compared to the rated output current of the cell. Keep
in
> mind that the rated currrent is measured in very bright light. Can
> you measure current during charging to confirm the value and that
it
> is not low because of some other problem?
>
>
> --- In beam@yahoogroups.com, "kinkyme360" <tskunka@> wrote:
> >
> > I'm using the solar cell that comes with the old Solarbotics
> > Solarpopper 4.2 kit but I do have other options.
> >
> > I have some of the new Russian-made cells Solarbotics has for
sale.
> > For some odd reason they sent me one with the Miller circuit
etched
> > on the back and one did not. It also seems odd that the non-
etched
> > one says 6.7v @ 15mA on the back...they state that it is very
> > efficient but on their website they have one the same exact size
> > rated at 6.7v @ 31mA
> >
> > I also have several 3v 22mA thin-film cells I could use. They are
> > lighter but have a larger footprint.
> >
> > I'm going to try out the dual caps and diode and see how it runs.
> >
> > thanx again...tk
> >
> >
> >
> > --- In beam@yahoogroups.com, "wilf rigter" <wrigter@> wrote:
> > >
> > >
> > > Hi tk
> > >
> > > With two 1F caps in series, which gives you a combined cap of
> 0.5F
> > @ 5V, and a 1381L (3.2V) trigger, the initial charging time
with
> a
> > solar cell supplying 0.5mA constant current
> > >
> > > dT (charging time)=Capacitance*dV(voltage change) /Isc(solar
> cell
> > current)
> > >
> > > 0.5F * 3.2V / 0.5ma = 3200 seconds = 53 minutes
> > >
> > > Note that, with a Ge diode in series with the solar cell and
> > charged up to 3.2V, the cap should hold that voltage for quite a
> > while in the dark (i.e. overnight) and won't take long to start
> > popping when the light comes back on.
> > >
> > > btw what solar cell are you using?
> > >
> > > Now consider the discharge cycle. If each pop from the 0.5F
> sol;ar
> > popper is assumed to be equivalent to a 4700uf cap discharging
> > completely from 3.2V to 0V and depending on the timing cap and
the
> > load, such an equivalent pop might be 15mA (average) * 3.2V *
0.5
> > sec during which the capacitor voltage drops 15mV.
> > >
> > > The recharge time between pops would be:
> > >
> > > 0.5F * 0.015V / 0.5ma = 15 seconds and with I(sc)=30mA the
> popping
> > time would be
> > >
> > > wilf
> > >
> > >
> > > ----- Original Message -----
> > > From: kinkyme360
> > > To: beam@yahoogroups.com
> > > Sent: Monday, January 01, 2007 11:54 AM
> > > Subject: [beam] Re: Capacitor Charging Question
> > >
> > >
> > > Wow...that is some good information. The math seems to bear
out
> > my
> > > observations which is good, but the cool thing is that once
the
> > 1F
> > > gets charged, it will fire pretty quick afterwards. If there
is
> a
> > > design that can live on only 2.4 volts then this could be
> > > interesting.
> > >
> > > 2.4 volts seems pretty weak...not enough to really drive the
> > motors
> > > well. Is it possible to put 2 1F 2.5 capacitors in series and
> use
> > the
> > > 1381L (3.2 volts) or higher trigger? Dividing the charge
> between
> > the
> > > two, keeping both under the 2.5v rating but reaping the
benefit
> > of
> > > the added discharge voltage? Yea, it would take quite awhile
to
> > > initially charge but might perform well afterwards.
> > >
> > > Sorry if these are obvious questions...I am electronically
> > > challenged. I took basic electronics in high school nearly 20
> > years
> > > ago and that's it. One of these days I'm going to blow
> something
> > up
> > > but it will be fun getting there!
> > >
> > > tk
> > >
> > > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> > > >
> > > > If you are using a 5V solar cell operating at 3.2V or less,
> the
> > > solar
> > > > cell current will be nearly constant and the cap charging
> time
> > > > equation becomes
> > > >
> > > > dT=C*dV/Isc
> > > >
> > > > According to your experiment, using a 1380L (3.2V) with the
> > 4700uF
> > > > cap the time between pops is about 30 secs.
> > > >
> > > > That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A (0.5mA)
> > > >
> > > > The energy stored in the cap with 4700uF charged to 3.2V
> (which
> > is
> > > > completely discharged into the load) is 0.5V*V*C =0.024J
> > > >
> > > > Let's see how that works for the 1F cap with the 1381C
> trigger.
> > > >
> > > > Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset
> > voltage),
> > > > the initial charging time from 0V to the operating voltage
> > (2.4V)
> > > is
> > > > 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's 2.88 J
of
> > > stored
> > > > energy.
> > > >
> > > > After reaching the 2.4V operating voltage and using
> > approximantly
> > > the
> > > > same discharge energy per pop of 0.024J (10mA * 1sec) with
> the
> > 1F
> > > > capacitor voltage dropping dV=10mV every pop, the charging
> time
> > > > between pops is 1F * 0.01V / 0.0005A = 20 seconds which is
> > faster
> > > > that the 4700uF case because once initialized, the solar
cell
> > > > operates constantly at 2.4V nearer to its maximum power
point.
> > > >
> > > > wilf
> > > >
> > > > --- In beam@yahoogroups.com, Gary Tolley <grogyan@> wrote:
> > > > >
> > > > > Tk,
> > > > > There is a formula to calculate the charge time of a cap.
> > > > >
http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> > > > > or
> > > > > http://hyperphysics.phy-
> > astr.gsu.edu/hbase/electric/capchg.html
> > > > >
> > > > > ater a quick search on google.
> > > > >
> > > > > Gary T
> > > > >
> > > > >
> > > > > >OK, I have a working solarpopper based on
> Wilfs "Photopopper
> > v8"
> > > > > >circuit posed back in September. Slick circuit...simple
> and
> > > > elegant.
> > > > > >
> > > > > >I have a Radio Shack 4700uF 35v capacitor...it is
massive
> > but I
> > > > > >figured it would be OK for testing purposes. With this
> > capacitor
> > > > and
> > > > > >a 1381L as indicated in the plans, it works and charges
> very
> > > > quickly
> > > > > >and drives the 6mm motors just fine.
> > > > > >
> > > > > >As a test, I wanted to see what a 1381C (2.4v) and the
> 1.0F
> > 2.5v
> > > > > >Aerogel Super Capacitor would do. I have a few of these
so
> > it is
> > > > > >worth checking out because they are tiny. This capacitor
> is
> > MUCH
> > > > > >smaller and if I could drive the 6mm motors from the
2.4v,
> > then
> > > it
> > > > > >might be something worth implementing.
> > > > > >
> > > > > >Here is the deal...the 1F capacitor takes FOREVER to
> charge.
> > > Maybe
> > > > I
> > > > > >am confused on my basic electronics but shouldn't a 1F
> > capacitor
> > > > > >charge in a bit more than double the time as the 4700uF
> > > capacitor?
> > > > > >
> > > > > >Under an incandecent bulb I did the following...I tested
> > both the
> > > > > >4700uF and 1F with the 1381C triggering at 2.4v. The
> 4700uF
> > was
> > > > > >triggering rather rapidly (several times per minute)...I
> am
> > not
> > > > sure
> > > > > >the 2.4v will be adequate to drive the motors but that
is
> > not the
> > > > > >point right now...the 1F took about 90 minutes to
charge.
> It
> > was
> > > > > >painfully long. Just how much more capacity does the 1F
> have?
> > > > > >
> > > > > >Can someone shed some light on why the 1F is taking so
> long
> > to
> > > > charge?
> > > > > >
> > > > > >tk
> > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
• You should invest in a digital multimeter (
Message 7 of 14 , Jan 4, 2007
• 0 Attachment
You should invest in a digital multimeter (<\$20) which is far
more sensitive than a basic needle type meter and which will
avoid influencing the circuit you are measuring.

In general, the meter is set to the DC ma Current range and the
leads are connected to com and ma. The meter leads are then
inserted between the +V of the battery and the positive (Vcc)
bus of the circuit. Be sure to return the meter setting to
DC Volts after you finish the current measurements.

wilf

--- In beam@yahoogroups.com, "kinkyme360" <tskunka@...> wrote:
>
> You ask a very good question...I might be able to measure the
current
> if I knew how. ;-) I have a basic analog Radio Shack
multimeter...I'm
> not sure how to measure current with it.
>
> I tried out the dual 1F cap and sure enough, once the thing gets
> charged, it triggers at a very regular interval. I seem to have
some
> loss of charge when idle...perhaps I need a bigger diode? I'm using
a
> 1N914 right now.
>
> tk
>
>
> --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> >
> > Hmmm... so the 0.5ma current I derived from your timing
> measurements
> > is very low compared to the rated output current of the cell.
Keep
> in
> > mind that the rated currrent is measured in very bright light.
Can
> > you measure current during charging to confirm the value and that
> it
> > is not low because of some other problem?
> >
> >
> > --- In beam@yahoogroups.com, "kinkyme360" <tskunka@> wrote:
> > >
> > > I'm using the solar cell that comes with the old Solarbotics
> > > Solarpopper 4.2 kit but I do have other options.
> > >
> > > I have some of the new Russian-made cells Solarbotics has for
> sale.
> > > For some odd reason they sent me one with the Miller circuit
> etched
> > > on the back and one did not. It also seems odd that the non-
> etched
> > > one says 6.7v @ 15mA on the back...they state that it is very
> > > efficient but on their website they have one the same exact
size
> > > rated at 6.7v @ 31mA
> > >
> > > I also have several 3v 22mA thin-film cells I could use. They
are
> > > lighter but have a larger footprint.
> > >
> > > I'm going to try out the dual caps and diode and see how it
runs.
> > >
> > > thanx again...tk
> > >
> > >
> > >
> > > --- In beam@yahoogroups.com, "wilf rigter" <wrigter@> wrote:
> > > >
> > > >
> > > > Hi tk
> > > >
> > > > With two 1F caps in series, which gives you a combined cap of
> > 0.5F
> > > @ 5V, and a 1381L (3.2V) trigger, the initial charging time
> with
> > a
> > > solar cell supplying 0.5mA constant current
> > > >
> > > > dT (charging time)=Capacitance*dV(voltage change) /Isc(solar
> > cell
> > > current)
> > > >
> > > > 0.5F * 3.2V / 0.5ma = 3200 seconds = 53 minutes
> > > >
> > > > Note that, with a Ge diode in series with the solar cell and
> > > charged up to 3.2V, the cap should hold that voltage for quite
a
> > > while in the dark (i.e. overnight) and won't take long to start
> > > popping when the light comes back on.
> > > >
> > > > btw what solar cell are you using?
> > > >
> > > > Now consider the discharge cycle. If each pop from the 0.5F
> > sol;ar
> > > popper is assumed to be equivalent to a 4700uf cap discharging
> > > completely from 3.2V to 0V and depending on the timing cap and
> the
> > > load, such an equivalent pop might be 15mA (average) * 3.2V *
> 0.5
> > > sec during which the capacitor voltage drops 15mV.
> > > >
> > > > The recharge time between pops would be:
> > > >
> > > > 0.5F * 0.015V / 0.5ma = 15 seconds and with I(sc)=30mA the
> > popping
> > > time would be
> > > >
> > > > wilf
> > > >
> > > >
> > > > ----- Original Message -----
> > > > From: kinkyme360
> > > > To: beam@yahoogroups.com
> > > > Sent: Monday, January 01, 2007 11:54 AM
> > > > Subject: [beam] Re: Capacitor Charging Question
> > > >
> > > >
> > > > Wow...that is some good information. The math seems to bear
> out
> > > my
> > > > observations which is good, but the cool thing is that once
> the
> > > 1F
> > > > gets charged, it will fire pretty quick afterwards. If
there
> is
> > a
> > > > design that can live on only 2.4 volts then this could be
> > > > interesting.
> > > >
> > > > 2.4 volts seems pretty weak...not enough to really drive
the
> > > motors
> > > > well. Is it possible to put 2 1F 2.5 capacitors in series
and
> > use
> > > the
> > > > 1381L (3.2 volts) or higher trigger? Dividing the charge
> > between
> > > the
> > > > two, keeping both under the 2.5v rating but reaping the
> benefit
> > > of
> > > > the added discharge voltage? Yea, it would take quite
awhile
> to
> > > > initially charge but might perform well afterwards.
> > > >
> > > > Sorry if these are obvious questions...I am electronically
> > > > challenged. I took basic electronics in high school nearly
20
> > > years
> > > > ago and that's it. One of these days I'm going to blow
> > something
> > > up
> > > > but it will be fun getting there!
> > > >
> > > > tk
> > > >
> > > > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> > > > >
> > > > > If you are using a 5V solar cell operating at 3.2V or
less,
> > the
> > > > solar
> > > > > cell current will be nearly constant and the cap charging
> > time
> > > > > equation becomes
> > > > >
> > > > > dT=C*dV/Isc
> > > > >
> > > > > According to your experiment, using a 1380L (3.2V) with
the
> > > 4700uF
> > > > > cap the time between pops is about 30 secs.
> > > > >
> > > > > That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A
(0.5mA)
> > > > >
> > > > > The energy stored in the cap with 4700uF charged to 3.2V
> > (which
> > > is
> > > > > completely discharged into the load) is 0.5V*V*C =0.024J
> > > > >
> > > > > Let's see how that works for the 1F cap with the 1381C
> > trigger.
> > > > >
> > > > > Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset
> > > voltage),
> > > > > the initial charging time from 0V to the operating
voltage
> > > (2.4V)
> > > > is
> > > > > 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's 2.88
J
> of
> > > > stored
> > > > > energy.
> > > > >
> > > > > After reaching the 2.4V operating voltage and using
> > > approximantly
> > > > the
> > > > > same discharge energy per pop of 0.024J (10mA * 1sec)
with
> > the
> > > 1F
> > > > > capacitor voltage dropping dV=10mV every pop, the
charging
> > time
> > > > > between pops is 1F * 0.01V / 0.0005A = 20 seconds which
is
> > > faster
> > > > > that the 4700uF case because once initialized, the solar
> cell
> > > > > operates constantly at 2.4V nearer to its maximum power
> point.
> > > > >
> > > > > wilf
> > > > >
> > > > > --- In beam@yahoogroups.com, Gary Tolley <grogyan@> wrote:
> > > > > >
> > > > > > Tk,
> > > > > > There is a formula to calculate the charge time of a
cap.
> > > > > >
> http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> > > > > > or
> > > > > > http://hyperphysics.phy-
> > > astr.gsu.edu/hbase/electric/capchg.html
> > > > > >
> > > > > > ater a quick search on google.
> > > > > >
> > > > > > Gary T
> > > > > >
> > > > > >
> > > > > > >OK, I have a working solarpopper based on
> > Wilfs "Photopopper
> > > v8"
> > > > > > >circuit posed back in September. Slick
circuit...simple
> > and
> > > > > elegant.
> > > > > > >
> > > > > > >I have a Radio Shack 4700uF 35v capacitor...it is
> massive
> > > but I
> > > > > > >figured it would be OK for testing purposes. With this
> > > capacitor
> > > > > and
> > > > > > >a 1381L as indicated in the plans, it works and
charges
> > very
> > > > > quickly
> > > > > > >and drives the 6mm motors just fine.
> > > > > > >
> > > > > > >As a test, I wanted to see what a 1381C (2.4v) and the
> > 1.0F
> > > 2.5v
> > > > > > >Aerogel Super Capacitor would do. I have a few of
these
> so
> > > it is
> > > > > > >worth checking out because they are tiny. This
capacitor
> > is
> > > MUCH
> > > > > > >smaller and if I could drive the 6mm motors from the
> 2.4v,
> > > then
> > > > it
> > > > > > >might be something worth implementing.
> > > > > > >
> > > > > > >Here is the deal...the 1F capacitor takes FOREVER to
> > charge.
> > > > Maybe
> > > > > I
> > > > > > >am confused on my basic electronics but shouldn't a 1F
> > > capacitor
> > > > > > >charge in a bit more than double the time as the
4700uF
> > > > capacitor?
> > > > > > >
> > > > > > >Under an incandecent bulb I did the following...I
tested
> > > both the
> > > > > > >4700uF and 1F with the 1381C triggering at 2.4v. The
> > 4700uF
> > > was
> > > > > > >triggering rather rapidly (several times per
minute)...I
> > am
> > > not
> > > > > sure
> > > > > > >the 2.4v will be adequate to drive the motors but that
> is
> > > not the
> > > > > > >point right now...the 1F took about 90 minutes to
> charge.
> > It
> > > was
> > > > > > >painfully long. Just how much more capacity does the
1F
> > have?
> > > > > > >
> > > > > > >Can someone shed some light on why the 1F is taking so
> > long
> > > to
> > > > > charge?
> > > > > > >
> > > > > > >tk
> > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
• Cool...a coworker well versed in electronics and I went through this earlier today with his multimeter. We were getting 2.5 microamps under a bright halogen
Message 8 of 14 , Jan 4, 2007
• 0 Attachment
Cool...a coworker well versed in electronics and I went through this
earlier today with his multimeter. We were getting 2.5 microamps
under a bright halogen light. The cell is rated at 15 milliamps so
something is amiss either with the cell, the capacitors or my
understanding. I am betting on the latter! ;-)

His thought is that the process of charging the capacitor wasn't
drawing the current from the cell. Thus the low readings. I'm not
sold on that theory.

I was planning on connecting the cell directly to a load and
performing the same test. I will also try that Russian cell with
similar ratings to use as a comparison.

Overall, the thing works well under 50w desk lamp once charged so I
and it is VERY annoying. Buzzing every few seconds!

I'm planning out the circuit board so I can take the next step and go
from the breadboard to actual bot. If I feel ambitious I may try
adding a secondary circuit that is dark activated...so if things go
pitch black, it becomes a simple pummer. I'm using 2 1F capacitors so
I might as well take advantage.

I'm getting some good ideas...I've been spending alot of time
absorbing the on-line information and processing the great help from
the kind folks here in the group.

thanks!

tk

--- In beam@yahoogroups.com, "wilf_nv" <wrigter@...> wrote:
>
>
> You should invest in a digital multimeter (<\$20) which is far
> more sensitive than a basic needle type meter and which will
> avoid influencing the circuit you are measuring.
>
> In general, the meter is set to the DC ma Current range and the
> leads are connected to com and ma. The meter leads are then
> inserted between the +V of the battery and the positive (Vcc)
> bus of the circuit. Be sure to return the meter setting to
> DC Volts after you finish the current measurements.
>
> wilf
>
> --- In beam@yahoogroups.com, "kinkyme360" <tskunka@> wrote:
> >
> > You ask a very good question...I might be able to measure the
> current
> > if I knew how. ;-) I have a basic analog Radio Shack
> multimeter...I'm
> > not sure how to measure current with it.
> >
> > I tried out the dual 1F cap and sure enough, once the thing gets
> > charged, it triggers at a very regular interval. I seem to have
> some
> > loss of charge when idle...perhaps I need a bigger diode? I'm
using
> a
> > 1N914 right now.
> >
> > tk
> >
> >
> > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> > >
> > > Hmmm... so the 0.5ma current I derived from your timing
> > measurements
> > > is very low compared to the rated output current of the cell.
> Keep
> > in
> > > mind that the rated currrent is measured in very bright light.
> Can
> > > you measure current during charging to confirm the value and
that
> > it
> > > is not low because of some other problem?
> > >
> > >
> > > --- In beam@yahoogroups.com, "kinkyme360" <tskunka@> wrote:
> > > >
> > > > I'm using the solar cell that comes with the old Solarbotics
> > > > Solarpopper 4.2 kit but I do have other options.
> > > >
> > > > I have some of the new Russian-made cells Solarbotics has for
> > sale.
> > > > For some odd reason they sent me one with the Miller circuit
> > etched
> > > > on the back and one did not. It also seems odd that the non-
> > etched
> > > > one says 6.7v @ 15mA on the back...they state that it is very
> > > > efficient but on their website they have one the same exact
> size
> > > > rated at 6.7v @ 31mA
> > > >
> > > > I also have several 3v 22mA thin-film cells I could use. They
> are
> > > > lighter but have a larger footprint.
> > > >
> > > > I'm going to try out the dual caps and diode and see how it
> runs.
> > > >
> > > > thanx again...tk
> > > >
> > > >
> > > >
> > > > --- In beam@yahoogroups.com, "wilf rigter" <wrigter@> wrote:
> > > > >
> > > > >
> > > > > Hi tk
> > > > >
> > > > > With two 1F caps in series, which gives you a combined cap
of
> > > 0.5F
> > > > @ 5V, and a 1381L (3.2V) trigger, the initial charging time
> > with
> > > a
> > > > solar cell supplying 0.5mA constant current
> > > > >
> > > > > dT (charging time)=Capacitance*dV(voltage change) /Isc
(solar
> > > cell
> > > > current)
> > > > >
> > > > > 0.5F * 3.2V / 0.5ma = 3200 seconds = 53 minutes
> > > > >
> > > > > Note that, with a Ge diode in series with the solar cell
and
> > > > charged up to 3.2V, the cap should hold that voltage for
quite
> a
> > > > while in the dark (i.e. overnight) and won't take long to
start
> > > > popping when the light comes back on.
> > > > >
> > > > > btw what solar cell are you using?
> > > > >
> > > > > Now consider the discharge cycle. If each pop from the
0.5F
> > > sol;ar
> > > > popper is assumed to be equivalent to a 4700uf cap
discharging
> > > > completely from 3.2V to 0V and depending on the timing cap
and
> > the
> > > > load, such an equivalent pop might be 15mA (average) * 3.2V
*
> > 0.5
> > > > sec during which the capacitor voltage drops 15mV.
> > > > >
> > > > > The recharge time between pops would be:
> > > > >
> > > > > 0.5F * 0.015V / 0.5ma = 15 seconds and with I(sc)=30mA the
> > > popping
> > > > time would be
> > > > >
> > > > > wilf
> > > > >
> > > > >
> > > > > ----- Original Message -----
> > > > > From: kinkyme360
> > > > > To: beam@yahoogroups.com
> > > > > Sent: Monday, January 01, 2007 11:54 AM
> > > > > Subject: [beam] Re: Capacitor Charging Question
> > > > >
> > > > >
> > > > > Wow...that is some good information. The math seems to
bear
> > out
> > > > my
> > > > > observations which is good, but the cool thing is that
once
> > the
> > > > 1F
> > > > > gets charged, it will fire pretty quick afterwards. If
> there
> > is
> > > a
> > > > > design that can live on only 2.4 volts then this could be
> > > > > interesting.
> > > > >
> > > > > 2.4 volts seems pretty weak...not enough to really drive
> the
> > > > motors
> > > > > well. Is it possible to put 2 1F 2.5 capacitors in series
> and
> > > use
> > > > the
> > > > > 1381L (3.2 volts) or higher trigger? Dividing the charge
> > > between
> > > > the
> > > > > two, keeping both under the 2.5v rating but reaping the
> > benefit
> > > > of
> > > > > the added discharge voltage? Yea, it would take quite
> awhile
> > to
> > > > > initially charge but might perform well afterwards.
> > > > >
> > > > > Sorry if these are obvious questions...I am
electronically
> > > > > challenged. I took basic electronics in high school
nearly
> 20
> > > > years
> > > > > ago and that's it. One of these days I'm going to blow
> > > something
> > > > up
> > > > > but it will be fun getting there!
> > > > >
> > > > > tk
> > > > >
> > > > > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> > > > > >
> > > > > > If you are using a 5V solar cell operating at 3.2V or
> less,
> > > the
> > > > > solar
> > > > > > cell current will be nearly constant and the cap
charging
> > > time
> > > > > > equation becomes
> > > > > >
> > > > > > dT=C*dV/Isc
> > > > > >
> > > > > > According to your experiment, using a 1380L (3.2V) with
> the
> > > > 4700uF
> > > > > > cap the time between pops is about 30 secs.
> > > > > >
> > > > > > That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A
> (0.5mA)
> > > > > >
> > > > > > The energy stored in the cap with 4700uF charged to
3.2V
> > > (which
> > > > is
> > > > > > completely discharged into the load) is 0.5V*V*C
=0.024J
> > > > > >
> > > > > > Let's see how that works for the 1F cap with the 1381C
> > > trigger.
> > > > > >
> > > > > > Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C reset
> > > > voltage),
> > > > > > the initial charging time from 0V to the operating
> voltage
> > > > (2.4V)
> > > > > is
> > > > > > 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's
2.88
> J
> > of
> > > > > stored
> > > > > > energy.
> > > > > >
> > > > > > After reaching the 2.4V operating voltage and using
> > > > approximantly
> > > > > the
> > > > > > same discharge energy per pop of 0.024J (10mA * 1sec)
> with
> > > the
> > > > 1F
> > > > > > capacitor voltage dropping dV=10mV every pop, the
> charging
> > > time
> > > > > > between pops is 1F * 0.01V / 0.0005A = 20 seconds which
> is
> > > > faster
> > > > > > that the 4700uF case because once initialized, the
solar
> > cell
> > > > > > operates constantly at 2.4V nearer to its maximum power
> > point.
> > > > > >
> > > > > > wilf
> > > > > >
> > > > > > --- In beam@yahoogroups.com, Gary Tolley <grogyan@>
wrote:
> > > > > > >
> > > > > > > Tk,
> > > > > > > There is a formula to calculate the charge time of a
> cap.
> > > > > > >
> > http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> > > > > > > or
> > > > > > > http://hyperphysics.phy-
> > > > astr.gsu.edu/hbase/electric/capchg.html
> > > > > > >
> > > > > > > ater a quick search on google.
> > > > > > >
> > > > > > > Gary T
> > > > > > >
> > > > > > >
> > > > > > > >OK, I have a working solarpopper based on
> > > Wilfs "Photopopper
> > > > v8"
> > > > > > > >circuit posed back in September. Slick
> circuit...simple
> > > and
> > > > > > elegant.
> > > > > > > >
> > > > > > > >I have a Radio Shack 4700uF 35v capacitor...it is
> > massive
> > > > but I
> > > > > > > >figured it would be OK for testing purposes. With
this
> > > > capacitor
> > > > > > and
> > > > > > > >a 1381L as indicated in the plans, it works and
> charges
> > > very
> > > > > > quickly
> > > > > > > >and drives the 6mm motors just fine.
> > > > > > > >
> > > > > > > >As a test, I wanted to see what a 1381C (2.4v) and
the
> > > 1.0F
> > > > 2.5v
> > > > > > > >Aerogel Super Capacitor would do. I have a few of
> these
> > so
> > > > it is
> > > > > > > >worth checking out because they are tiny. This
> capacitor
> > > is
> > > > MUCH
> > > > > > > >smaller and if I could drive the 6mm motors from the
> > 2.4v,
> > > > then
> > > > > it
> > > > > > > >might be something worth implementing.
> > > > > > > >
> > > > > > > >Here is the deal...the 1F capacitor takes FOREVER to
> > > charge.
> > > > > Maybe
> > > > > > I
> > > > > > > >am confused on my basic electronics but shouldn't a
1F
> > > > capacitor
> > > > > > > >charge in a bit more than double the time as the
> 4700uF
> > > > > capacitor?
> > > > > > > >
> > > > > > > >Under an incandecent bulb I did the following...I
> tested
> > > > both the
> > > > > > > >4700uF and 1F with the 1381C triggering at 2.4v. The
> > > 4700uF
> > > > was
> > > > > > > >triggering rather rapidly (several times per
> minute)...I
> > > am
> > > > not
> > > > > > sure
> > > > > > > >the 2.4v will be adequate to drive the motors but
that
> > is
> > > > not the
> > > > > > > >point right now...the 1F took about 90 minutes to
> > charge.
> > > It
> > > > was
> > > > > > > >painfully long. Just how much more capacity does the
> 1F
> > > have?
> > > > > > > >
> > > > > > > >Can someone shed some light on why the 1F is taking
so
> > > long
> > > > to
> > > > > > charge?
> > > > > > > >
> > > > > > > >tk
> > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
• Go step by step. Measure the solar cell current by itself just across the cell terminals. Then add a discharged cap in series (observe cap polarity) and
Message 9 of 14 , Jan 4, 2007
• 0 Attachment
Go step by step. Measure the solar cell current by itself just across
the cell terminals. Then add a discharged cap in series (observe cap
polarity) and measure again. That should give the same reading,
observe the reading after the cap has charged to near the threshold.
Should be the same reading. Now add the solar engine. Any change?
Add the motor. Any change? Observe what you find at each step and
you can pinpoint where things go wrong. Mind you the popping every
few seconds sounds promising and there may not be any problem.

wwilf

--- In beam@yahoogroups.com, "kinkyme360" <tskunka@...> wrote:
>
> Cool...a coworker well versed in electronics and I went through
this
> earlier today with his multimeter. We were getting 2.5 microamps
> under a bright halogen light. The cell is rated at 15 milliamps so
> something is amiss either with the cell, the capacitors or my
> understanding. I am betting on the latter! ;-)
>
> His thought is that the process of charging the capacitor wasn't
> drawing the current from the cell. Thus the low readings. I'm not
> sold on that theory.
>
> I was planning on connecting the cell directly to a load and
> performing the same test. I will also try that Russian cell with
> similar ratings to use as a comparison.
>
> Overall, the thing works well under 50w desk lamp once charged so I
giggle
> and it is VERY annoying. Buzzing every few seconds!
>
> I'm planning out the circuit board so I can take the next step and
go
> from the breadboard to actual bot. If I feel ambitious I may try
> adding a secondary circuit that is dark activated...so if things go
> pitch black, it becomes a simple pummer. I'm using 2 1F capacitors
so
> I might as well take advantage.
>
> I'm getting some good ideas...I've been spending alot of time
> absorbing the on-line information and processing the great help
from
> the kind folks here in the group.
>
> thanks!
>
> tk
>
>
>
> --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> >
> >
> > You should invest in a digital multimeter (<\$20) which is far
> > more sensitive than a basic needle type meter and which will
> > avoid influencing the circuit you are measuring.
> >
> > In general, the meter is set to the DC ma Current range and the
> > leads are connected to com and ma. The meter leads are then
> > inserted between the +V of the battery and the positive (Vcc)
> > bus of the circuit. Be sure to return the meter setting to
> > DC Volts after you finish the current measurements.
> >
> > wilf
> >
> > --- In beam@yahoogroups.com, "kinkyme360" <tskunka@> wrote:
> > >
> > > You ask a very good question...I might be able to measure the
> > current
> > > if I knew how. ;-) I have a basic analog Radio Shack
> > multimeter...I'm
> > > not sure how to measure current with it.
> > >
> > > I tried out the dual 1F cap and sure enough, once the thing
gets
> > > charged, it triggers at a very regular interval. I seem to have
> > some
> > > loss of charge when idle...perhaps I need a bigger diode? I'm
> using
> > a
> > > 1N914 right now.
> > >
> > > tk
> > >
> > >
> > > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> > > >
> > > > Hmmm... so the 0.5ma current I derived from your timing
> > > measurements
> > > > is very low compared to the rated output current of the cell.
> > Keep
> > > in
> > > > mind that the rated currrent is measured in very bright
light.
> > Can
> > > > you measure current during charging to confirm the value and
> that
> > > it
> > > > is not low because of some other problem?
> > > >
> > > >
> > > > --- In beam@yahoogroups.com, "kinkyme360" <tskunka@> wrote:
> > > > >
> > > > > I'm using the solar cell that comes with the old
Solarbotics
> > > > > Solarpopper 4.2 kit but I do have other options.
> > > > >
> > > > > I have some of the new Russian-made cells Solarbotics has
for
> > > sale.
> > > > > For some odd reason they sent me one with the Miller
circuit
> > > etched
> > > > > on the back and one did not. It also seems odd that the non-
> > > etched
> > > > > one says 6.7v @ 15mA on the back...they state that it is
very
> > > > > efficient but on their website they have one the same exact
> > size
> > > > > rated at 6.7v @ 31mA
> > > > >
> > > > > I also have several 3v 22mA thin-film cells I could use.
They
> > are
> > > > > lighter but have a larger footprint.
> > > > >
> > > > > I'm going to try out the dual caps and diode and see how it
> > runs.
> > > > >
> > > > > thanx again...tk
> > > > >
> > > > >
> > > > >
> > > > > --- In beam@yahoogroups.com, "wilf rigter" <wrigter@> wrote:
> > > > > >
> > > > > >
> > > > > > Hi tk
> > > > > >
> > > > > > With two 1F caps in series, which gives you a combined
cap
> of
> > > > 0.5F
> > > > > @ 5V, and a 1381L (3.2V) trigger, the initial charging
time
> > > with
> > > > a
> > > > > solar cell supplying 0.5mA constant current
> > > > > >
> > > > > > dT (charging time)=Capacitance*dV(voltage change) /Isc
> (solar
> > > > cell
> > > > > current)
> > > > > >
> > > > > > 0.5F * 3.2V / 0.5ma = 3200 seconds = 53 minutes
> > > > > >
> > > > > > Note that, with a Ge diode in series with the solar cell
> and
> > > > > charged up to 3.2V, the cap should hold that voltage for
> quite
> > a
> > > > > while in the dark (i.e. overnight) and won't take long to
> start
> > > > > popping when the light comes back on.
> > > > > >
> > > > > > btw what solar cell are you using?
> > > > > >
> > > > > > Now consider the discharge cycle. If each pop from the
> 0.5F
> > > > sol;ar
> > > > > popper is assumed to be equivalent to a 4700uf cap
> discharging
> > > > > completely from 3.2V to 0V and depending on the timing cap
> and
> > > the
> > > > > load, such an equivalent pop might be 15mA (average) *
3.2V
> *
> > > 0.5
> > > > > sec during which the capacitor voltage drops 15mV.
> > > > > >
> > > > > > The recharge time between pops would be:
> > > > > >
> > > > > > 0.5F * 0.015V / 0.5ma = 15 seconds and with I(sc)=30mA
the
> > > > popping
> > > > > time would be
> > > > > >
> > > > > > wilf
> > > > > >
> > > > > >
> > > > > > ----- Original Message -----
> > > > > > From: kinkyme360
> > > > > > To: beam@yahoogroups.com
> > > > > > Sent: Monday, January 01, 2007 11:54 AM
> > > > > > Subject: [beam] Re: Capacitor Charging Question
> > > > > >
> > > > > >
> > > > > > Wow...that is some good information. The math seems to
> bear
> > > out
> > > > > my
> > > > > > observations which is good, but the cool thing is that
> once
> > > the
> > > > > 1F
> > > > > > gets charged, it will fire pretty quick afterwards. If
> > there
> > > is
> > > > a
> > > > > > design that can live on only 2.4 volts then this could
be
> > > > > > interesting.
> > > > > >
> > > > > > 2.4 volts seems pretty weak...not enough to really
drive
> > the
> > > > > motors
> > > > > > well. Is it possible to put 2 1F 2.5 capacitors in
series
> > and
> > > > use
> > > > > the
> > > > > > 1381L (3.2 volts) or higher trigger? Dividing the
charge
> > > > between
> > > > > the
> > > > > > two, keeping both under the 2.5v rating but reaping the
> > > benefit
> > > > > of
> > > > > > the added discharge voltage? Yea, it would take quite
> > awhile
> > > to
> > > > > > initially charge but might perform well afterwards.
> > > > > >
> > > > > > Sorry if these are obvious questions...I am
> electronically
> > > > > > challenged. I took basic electronics in high school
> nearly
> > 20
> > > > > years
> > > > > > ago and that's it. One of these days I'm going to blow
> > > > something
> > > > > up
> > > > > > but it will be fun getting there!
> > > > > >
> > > > > > tk
> > > > > >
> > > > > > --- In beam@yahoogroups.com, "wilf_nv" <wrigter@> wrote:
> > > > > > >
> > > > > > > If you are using a 5V solar cell operating at 3.2V or
> > less,
> > > > the
> > > > > > solar
> > > > > > > cell current will be nearly constant and the cap
> charging
> > > > time
> > > > > > > equation becomes
> > > > > > >
> > > > > > > dT=C*dV/Isc
> > > > > > >
> > > > > > > According to your experiment, using a 1380L (3.2V)
with
> > the
> > > > > 4700uF
> > > > > > > cap the time between pops is about 30 secs.
> > > > > > >
> > > > > > > That means Isc must be 0.0047F * 3.2V / 30 = 0.0005A
> > (0.5mA)
> > > > > > >
> > > > > > > The energy stored in the cap with 4700uF charged to
> 3.2V
> > > > (which
> > > > > is
> > > > > > > completely discharged into the load) is 0.5V*V*C
> =0.024J
> > > > > > >
> > > > > > > Let's see how that works for the 1F cap with the
1381C
> > > > trigger.
> > > > > > >
> > > > > > > Using C=1F and Isc = 0.5ma and dV=2.4V (the 1381C
reset
> > > > > voltage),
> > > > > > > the initial charging time from 0V to the operating
> > voltage
> > > > > (2.4V)
> > > > > > is
> > > > > > > 1F * 2.4V / 0.0005A = 4800 seconds = 80 min. That's
> 2.88
> > J
> > > of
> > > > > > stored
> > > > > > > energy.
> > > > > > >
> > > > > > > After reaching the 2.4V operating voltage and using
> > > > > approximantly
> > > > > > the
> > > > > > > same discharge energy per pop of 0.024J (10mA * 1sec)
> > with
> > > > the
> > > > > 1F
> > > > > > > capacitor voltage dropping dV=10mV every pop, the
> > charging
> > > > time
> > > > > > > between pops is 1F * 0.01V / 0.0005A = 20 seconds
which
> > is
> > > > > faster
> > > > > > > that the 4700uF case because once initialized, the
> solar
> > > cell
> > > > > > > operates constantly at 2.4V nearer to its maximum
power
> > > point.
> > > > > > >
> > > > > > > wilf
> > > > > > >
> > > > > > > --- In beam@yahoogroups.com, Gary Tolley <grogyan@>
> wrote:
> > > > > > > >
> > > > > > > > Tk,
> > > > > > > > There is a formula to calculate the charge time of
a
> > cap.
> > > > > > > >
> > > http://ourworld.compuserve.com/homepages/Bill_Bowden/rc.htm
> > > > > > > > or
> > > > > > > > http://hyperphysics.phy-
> > > > > astr.gsu.edu/hbase/electric/capchg.html
> > > > > > > >
> > > > > > > > ater a quick search on google.
> > > > > > > >
> > > > > > > > Gary T
> > > > > > > >
> > > > > > > >
> > > > > > > > >OK, I have a working solarpopper based on
> > > > Wilfs "Photopopper
> > > > > v8"
> > > > > > > > >circuit posed back in September. Slick
> > circuit...simple
> > > > and
> > > > > > > elegant.
> > > > > > > > >
> > > > > > > > >I have a Radio Shack 4700uF 35v capacitor...it is
> > > massive
> > > > > but I
> > > > > > > > >figured it would be OK for testing purposes. With
> this
> > > > > capacitor
> > > > > > > and
> > > > > > > > >a 1381L as indicated in the plans, it works and
> > charges
> > > > very
> > > > > > > quickly
> > > > > > > > >and drives the 6mm motors just fine.
> > > > > > > > >
> > > > > > > > >As a test, I wanted to see what a 1381C (2.4v) and
> the
> > > > 1.0F
> > > > > 2.5v
> > > > > > > > >Aerogel Super Capacitor would do. I have a few of
> > these
> > > so
> > > > > it is
> > > > > > > > >worth checking out because they are tiny. This
> > capacitor
> > > > is
> > > > > MUCH
> > > > > > > > >smaller and if I could drive the 6mm motors from
the
> > > 2.4v,
> > > > > then
> > > > > > it
> > > > > > > > >might be something worth implementing.
> > > > > > > > >
> > > > > > > > >Here is the deal...the 1F capacitor takes FOREVER
to
> > > > charge.
> > > > > > Maybe
> > > > > > > I
> > > > > > > > >am confused on my basic electronics but shouldn't
a
> 1F
> > > > > capacitor
> > > > > > > > >charge in a bit more than double the time as the
> > 4700uF
> > > > > > capacitor?
> > > > > > > > >
> > > > > > > > >Under an incandecent bulb I did the following...I
> > tested
> > > > > both the
> > > > > > > > >4700uF and 1F with the 1381C triggering at 2.4v.
The
> > > > 4700uF
> > > > > was
> > > > > > > > >triggering rather rapidly (several times per
> > minute)...I
> > > > am
> > > > > not
> > > > > > > sure
> > > > > > > > >the 2.4v will be adequate to drive the motors but
> that
> > > is
> > > > > not the
> > > > > > > > >point right now...the 1F took about 90 minutes to
> > > charge.
> > > > It
> > > > > was
> > > > > > > > >painfully long. Just how much more capacity does
the
> > 1F
> > > > have?
> > > > > > > > >
> > > > > > > > >Can someone shed some light on why the 1F is
taking
> so
> > > > long
> > > > > to
> > > > > > > charge?
> > > > > > > > >
> > > > > > > > >tk
> > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>
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