Here are 2 choices: PUT 2N6028 ckt. to drive an SCR; select R & C for desired time. Other " Solar Gleaner" normally used to start a motor with minimum sun. No extra charge for spares?? Last one, use a red LED for ZD1 or 3 V ZD. FDS 9435- SMT, LL, 30V, 5A, P CH FET.

 

Thanks Bernard, parts are on order for BOTH versions

 

In bright sun the open circuit solar cell voltage is 5.94V. The dc resistance of the solenoid is 3.4 ohms.

Good. So here is what I came up with:

We need a Voltage Sensitive Switch (which draws much less than 1mA) to monitor the capacitor voltage, and CutIn when the voltage is somewhat less than the open-circuit voltage of the panel, so I picked 5.25V. When the VSS turns on, it dumps the capacitor charge into the 3.9Ω solenoid, causing the capacitor voltage to drop rapidly. The VSS should CutOut when the capacitor voltage reaches a low value, turning everything off so that the solar panel can recharge the capacitor for a new cycle.

Here is a circuit that I have simulated (not built):



Current pulse detail:



I plot the capacitor voltage V(c) and the current in the solenoid I(L1). Note the CutIn voltage is defined by the voltage divider consisting of R1 and R2. When the voltage at the tap gets to ~0.6V, Q1 begins turning on, initiating the discharge cycle.

So that the owl moves every 60 sec, or so, the Solar Panel has to be generating a bit less than 1mA. Note that the circuit behaves as described by Picky. The first cycle is longer than the subsequent ones, and the cycles are on the order of 40s. That is a function of Q=i*t = C*ΔV, or t=C*ΔV/i = 0.01*(5.25-1)/1e-3 = 42s.

I initially tried to make the VSS switch the solenoid directly, but it became much easier to make the VSS first, and then add Q3 to drive the very low resistance of the solenoid.

I attach the .asc file if someone wants to play with it some more...

Hey, if it works, do I get a ride in the P51D? I'll trade for a ride in the PA20 (or '182)...

 

P.B. ckts. in # 21 were not quite ready for your project, but have modified them but not tested. With a small SP, V 4.2, 80 mA, 10000 cap. charged up in about 1 sec. so slowed it down by adding 4.7 k in series & added a shottky diode for discharge path. Might work in MikeML 's simpler ckt. to give 1 min. cycle time.

 

If you have really ordered some parts, then might as well throw this one in. PUT is 2N6028. D 1 might not be needed as C1 should discharge to about 1 V, but I would sleep better with it in, maybe 1N4002.

 

MikeML and Bernard I am going to build all of these and see which one works best.

THANK YOU!

 

MikeML and Bernard I am going to build all of these and see which one works best.

THANK YOU!

Can't find a source for the 2N6027

Is there a more readily available substitute?

 

I have some, 2N6028's in stock, you are welcome to one. Found a listing on " All Electronics", CAT # 2N6028, 3/$1.00, & other goodies like LM393, 555, 556, 1N4148,& a triac- no SCR's.

 

Thanks Bernard. I got them at All Electronics. Mouser didn't have them and Digikey had a minimum order qty of 2500. Don't know what I would do with that many owls!

 

Seen these at the neighborhood store, for $1: ----> http://www.dollartree.com/Plastic-Solar-Powered-Dancing-Owls-4-/p357310/index.pro

 

Cute Externet!