Thanks for the reply, Wilf.
Not having any FET's on hand, I went ahead and tried
substituting a plain old 3904 NPN (not PNP as suggested on the
BFTGU page) transistor for the FET in the SimD1 V3 - and it
seems to work! Now that the basic circuit is functioning, I am on
to subtler problems.
I am trying to create a "cricket" circuit using a piezo buzzer. I'm
using a FLED to "chirp" the buzzer on and off. The circuit works
successfully when I test it with a lamp. However, to make it work
with actual sunset will require some tweaking, as that is a much
more gradual fading of the light. The circuit basically comes on if
the solar cell voltage is less than the cap voltge, right? The
problem is that the decreasing voltage in the discharging cap
catches up with the not-so-quickly decreasing solar cell voltage,
as the sun slowly sets.
I had the idea this morning to put a small capacitor (100uF)
across my added 3904 which seems to help a lot with getting a
clean start to the chirping. Nonetheless, when the circuit stops
beeping, I can get it to beep some more by completely blocking
the solar cell with my hand. Maybe the answer is to use bigger
capacitors at a lower voltage (using a 2.7v solar cell instead of
Or perhaps there is a way to make the circuit use the first pulse
of energy that comes through as a trigger for a transistor(s) that
stays on until the capacitor discharges regardless of anything
else that happens with the light from that point on.
Or is it part of the problem the fact that I substituted a 3904 for
From its description, is seems that the SIMD1 Solar Regulator
may have somewhat of a "latch on and stay on" capability, but 2V
is too low for my FLED/piezo buzzer to run - is there a way to get
the "latching on" that the Solar Regulator has, without the voltage
Any thoughts would be appreciated.
--- In beam@y..., Wilf Rigter <wilf.rigter@p...> wrote:
> Hi Dave,
> The 2N7000 is commonly available and will work fine at 5V.
> applications that use a "D1" solar engine, you will want to use
> stored energy after the SE triggers. Normally these SEs charge
a battery or
> capacitor during the day and power a load as long as possible
> night. There is no merit in not using all stored energy as would
be the case
> in a "popper" circuit driving a solar powered photovore, where
> time is proportional to the depth of discharge and where more
> shallow discharges of energy might be more efficient than less
> deeper discharges. It comes down to your application: the
type of load you
> want to control with SIMD1 SE will determine the output device
> and may even require some minor circuit adaptation
> the circuit your application. As far as suitable FETs are
> was some discussion on this recently in :
> As noted, suitable TO92 style FETs are few and far between
but there are
> some excelent choices in the TO220 style power FET family.
> -----Original Message-----
> From: dgreen@s... [mailto:dgreen@s...]
> Sent: Sunday, June 03, 2001 3:03 AM
> To: beam@y...
> Subject: [beam] FET for SimD1 V3 SE
> I saw this message (copied below) posted a while ago and
> an additional question: What specific FET would work best for
> the SimD1 V3 solar engine? anyone got a specific part #?
> a 2N7000 work?
> --- In beam@y..., "Eric Seale" <Eric.Seale@p...> wrote:
> > --- In beam@y..., gord1812@n... wrote:
> > > now if there is a tutoral on the D1 SE ?
> > >
> > > I'm using Wilf Rigter's SIMD1 V2 diagram. Looking at the
> PNP or PNP
> > > version I see the load has 3 connections. I want to set up a
> FLED to
> > > flassh when the light goes down. ..Fled has two leads
> ...where/what is
> > > the
> > > 3rd connection???
> > Sounds like you're working from this page:
> > http://bftgu.botic.com/assy_se_noct_SIMD1V2.html
> > The FLED's two leads need to connect to Vcc and ground; in
> order to
> > hook this up to a SIMD1 V2, you really need to add a FET (the
> > to the load are Vcc, Ground, and an enable -- the load needs
> > draw power when the enable is "high").
> > Once you add a FET, you've really got a SIMD1 V3:
> > http://bftgu.botic.com/assy_se_noct_SIMD1V3.html
> > Then the FLED just goes where the "Pummer" block is
> > the proper polarity, natch').
> > > I'd also like to use this circuit to run a P-vore's SE after
> > > lights
> > > go down.
> > That'd work too, though you'll have to be careful. Most P-vore
> > circuits are built as dual-SEs; they pretty much rely on having
> > incoming solar power in order to work. You might be better
> to use
> > Bob Shannon's "Smart Cap" circuit (either Bob's original
> > version, or my trimmed down variant):
> > http://bftgu.botic.com/assy_se_noct_smartcap.html
> > Eric
> > -----------------------------------------------------------------
> > Eric Seale | BEAM from the Ground Up!
> > bftgu@m... | http://bftgu.botic.com
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