BEAM 1381 solar engine problem

[circuitBurn]

Hi everyone,

I've built the following circuit on my breadboard:http://www.solarbotics.net/library/circuits/se_t1_1381.html

I can't get the solarengine to fire with a motor in circuit. I've used an LED and it works exactly as expected; at 2.1V the engine fires. With the motor (both a small pager motor and a larger DC motor from a Tamiya kit) and the voltage climbs to the maximum output of the solar cell, about 2.4V and stays put.

I'm assuming I'm not generating enough current to the motor to start it turning, but I've tried lowering the resistor value to 1K and down as low as 120ohm to no avail. Any input is appreciated!

Thanks,

cb

 

[kaczchris]

Try the miller engine:

http://www.solarbotics.net/library/circuits/se_t1_mse.html

I run pager motors with this simpler and more efficient setup without a resistor at all and it works great.

One question for you, are you using the 1381 or an alternative?
I am looking for a working alternative to the 1381 and have not found one...

 

[CDRIVE]

First off is a gripe. Schematics should include component ID's. This way responders can reference U1, M1, Q1, R3, C5, PV1, etc without explaining what component there referencing. Since you have only one resistor in that circuit I'll call it R1.

Try reducing R1 to 1K. If that doesn't help reduce it to 470R. Depending on the resistance of the motor (M1) it may have to go even lower. If you need an explanation as to why I'll provide one after you've assigned ID's to all components.

Note: The values of R1 and C1 are not carved in stone. As anticipated load current increases R1 and C1 have to be sized accordingly.

Chris

Edit: I'm also curious why your circuit doesn't employ a base current limiting resistor on (Q2) motor driver? I would add one.

Edit2: Oops, how did I miss that? You already lowered R1 to 120R to no avail. Try increasing C1. You're circuit may be switching on and off faster than your DMM can see. Or it may be sitting at some point in between on and off. Equilibrium, so to speak. I still think there should be an R2.

 

[CDRIVE]

Just another note here. I've been reading the 1381 data sheet. My copy from Panasonic does not specify any Max sink or source output current.

Chris

 

[CDRIVE]

You seem to have disappeared but while you've been absent the other solar engine thread has been active.
https://www.electronicspoint.com/miller-solar-engine-1381-replacement-t262497p3.html

The more I read the data sheets for these two chips the more I'm convinced that the 2N3904 isn't providing enough current gain to drive your motor. What's the current draw?

Chris