Small soler cell question

[nyoo]

Colin55, if you are willing, please could you send the URL of your website?

I'm interested in the concept of a voltage mutiplier circuit. And I'm quite willing to use prefab circuits to achieve my goal. As it is, my RF transmiiter is cannabalised from a toy car.

(I regularly see garden lights for USD 3.00 in the shops near me.)

 

[colin55]

Here is the link to the 5 page article on Solar Garden Lights; How They Work and how to modify them:

Solar Light

 

[nyoo]

Thank you. Now I know how the professionals approach these small solar cells. That gives me enough scope to buy or build.

The RF transmitter probably doesn't want an oscillator, but I now see a way forward.

 

[nyoo]

If you all have time for one last question....

Here's what I came up with. "Transmit a signal when the sun is shining."
RF transmitter (indicated by Rload) runs at 3V, 22 mA, shuts off at 2.7V.

6V = two 3V solar cells in series.
1K chosen to shut off the RF transmitter load when it's cloudy.
The zener is 1/4-watt (not 25-watt).
Your examples showed a circuit like this could tolerate a transistor, so I used one.
I've quit worrying about extra current from the solar cells, it's a myth.

Will this work?

Thanks for your help.

 

[colin55]

The trouble with the circuit is this:
The device you are powering will gradually receive current and the voltage will gradually rise. If the device is a micro or oscillator, the oscillator will not start-up.
This is the funny thing about oscillators - that no-one or book will tell you.
They need a heavy current to reliably start-up.
That's why you need either a Schmitt Trigger in the voltage-delivering section and/or some form of capacitor across the load.

 

[nyoo]

Like this, using the supercap?

 

[colin55]

It needs a microcontroller to shut down when not needed and have a sense line to detect when the sun comes up



**broken link removed**

 

[nyoo]

Aha!

I can do that. Thank you.