How to Wire A Solar Panel to Use as a Photoswitch

	A Photoswitch For All Of Your Lights
Bebi	A Photoswitch For All Of Your Lights	Bebi

Inspired by LA7QZ on the SSCA Discussion Board, as diagramed below is a simple FET switch that will work to switch up to a 13 amp load (with a 100% safety factor). Of course, you wouldn't need quite as powerful of a switch if you were to switch to (pardon the pun) Bebi Electronics LED lighting!

A few cautions about the circuit. First, of course, this is all at your own risk!

Next, whether you wire the resistor between the panel and the blocking diode or between the controller and the solar panel, is based on if your controller has a steering diode in the input. Just to cut down on wire, I'd first try installing the switch between the panel and the controller and see if it works. If it doesn't, then you would have to run more wire out to the solar panels.

The value of the resistor isn't really all that critical. The 'optional capacitor' shown is to keep a 'flicker' from the circuit. As shown, using a 2.2 uF capacitor (watch the polarity that you hook it up correctly, if you connect an electrolytic backwards, they tend to pop!) and a 100k resistor will give a delay of ~0.7 seconds, going to a 680k resistor will delay 4.5 seconds.

The bypass switch is if you would like to have the lights to regardless of the sunlight condition.

I show an IRF540 FET just because it is relatively common. You should be aware that the tab (the metal thingy with the hole at the top) is connected internally to the #2 pin of the FET, and needs to be insulated from other conductors. If the load causes the tab to become warm, you may need to add a heat sink to it.

Lastly, the wire going from the IRF540 back to the negative bus must be of a sufficient gauge so as to be able to safely handle the current load from all of the lights.

If you would like more information, please contact us at sales@bebi-electronics.com.

A Photoswitch For All Of Your Lights