60110Re: [beam] help with a type 1 solar engine pummer...
- Aug 2, 2010Hi Keith,
I don't remember this pummer design but it does not look all
This circuit actually uses a combination of type 1, type 3
and nocturnal SEs. The PNP transistor and SE circuit stays
off while the solar cell is charging the battery (type 3).
When the solar cell current drops at dusk, the PNP turns on
and charges the 47uf cap (nocturnal) . If the battery
voltage is higher than the trigger voltage of the 1381, the
NPN turns on and powers the LED (or other load)(type 1).
Positive feedback through the 100K resistor provides base
current to the PNP and loads the solar cell output to latch
the SE on. The load remains energized until the 1381 turns
off when the battery voltage falls below the 1381 reset
level. Alternatively the SE is also shut off, (ie at dawn)
when solar cell output rises above the battery and starts
recharging for another cycle and the PNP turns off.
Since your solar cell output voltage is only 2.25V this is
too low to properly charge two series nicad batteries (2.4V)
required to power a red or green LED.
Use two of these solar cells in series to raise the
available charging voltage to charge two nicads.
With one solar cell you can try a super cap instead of the
battries but the LED on time will be greatly reduced. In
addition the 1381 trigger level has to be chosen to be about
be "somewhat" lower than the fully charged super cap or
battery level (ie 2.3V for a 2.4V nicad and 2V for the super
cap). If the load is a LED, a 82 ohm series resistor should
be used to limit the LED current to about 10ma.
----- Original Message -----
From: "Keith Anderson" <supernurseman@...>
Subject: [beam] help with a type 1 solar engine pummer...
Date: Mon, 02 Aug 2010 21:42:26 -0000
>I want to make my first pummer, using a variant of type 1
>(1381 based) solar engine. (here's the link:
>I have pretty much everthing I need except the 1381. My
>solar cell is scavenged from an LED yard stake-light, and
>puts out about 2v (it starts at 2.25v, and gradually drops
>down to about 2.1v).
>What flavor of 1381 do I need to get? Solarbotics suggests
>a 1381g (2.4v) but another site suggests that a 1381j
>(2.7v) is the most common. Does it matter? Is it related to
>the output of the solar cell, or is it dependent on the
>batteries? I also understand I can substitute a supercap
>for the batteries (which I may do later...)
>Any help appreciated.
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