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schmitt trigger for solar panel Answered


I'm building a solar panel project that may use the charge battery and so on. As solar output is not consistent, I have a capacitor array to store charge before deliver it to the end devices.

However if the solar output power is lower than the end devices(example charging phone) power load, it will probably on and off since the solar output is not enough. I would like to use by capacitor array to reduce the on and off rate by design a Schmitt trigger or perhaps it a flip flop circuit.

For example if my Solar panel max voltage is 12v and my  device using 5v thru a voltage regulator that need min of 6v. So I would like to design a circuit to do this

1) When capacitor array discharge to 6v, terminate the circuit to regulator.
2) Wait for the solar panel to charge the capacitor up to 12V
3) Upon reach 12 V, allow the current to pass thru regulator again. Repeat step 1

I tried so search Schmitt trigger circuit but I cannot find the suitable one as most Schmitt trigger  is with a Vref and signal input. Since my voltage input(capacitor charging and solar panel) is variable, I do not have Vref. I still believe it can be achieved, perhaps my mind stuck at one concept only



3 years ago

Why so complicated?
If you only need to charge a phone get a step down converter for 5V.
Use a diode to seperate the caps from the panels and they will not destroy the panels when the sun is blocked.
And yes, these step down converters shut off if the input voltage is too low.


Reply 3 years ago

Hey thanks for the help. Phone charging is only part of it, I just would like to collect charges when the solar panel yield lesser than load. I tested by step down converter. If the input voltage is not suffice, the output will become unregulated and low voltage and its still draining current but the load device can't function.

So that why I plan to stop the loading and allow for the capacitor to charge. At 100ma solar input it takes about 20 mins to charge the capacitor. Besides that, what is the impact of reverse voltage to a solar panel?


Reply 3 years ago

Try what happens if you feed a dark solar panel with 12V ;)
Ok, actually don't...
Most panels have a built in protection diode anyway unless salvaged from stuff like garden lights and so on.
If unprotected the solar cell will use electricity and can even heat up and burn out.
So if possible you should avoid that for charging, but as said most panels have the diodes build in anyway.