12vman
03-31-2007, 03:45 AM
I found a simple way to build a day/nite photo switch using my solar panels. If you have enough panel to create at least 200/300 mA. above what you are trying to charge, You're in luck.. *;)
I wanted to control some outdoor lighting but I didn't have a photocell circuit. I drank a few beers and pondered on the issue for a while and VALA!
In my junk drawer, I had a relay with a 12 v.d.c. coil that required 60 mA. to operate it. I also had a LM7812 voltage regulator. I scratched my head and went Hmmm... * 8)
http://www.radioshack.com/product/index.jsp?productId=2062600&cp=&sr=1&origkw=voltag e+regulators&kw=voltage+regulators&parentPage=sear ch
The LM7812 regulator will handle up to 35 v.d.c. on the input and produce a well regulated 12 v.d.c. output at 1 amp. Thermally protected and everything. My panels, While charging on a good day, Never exceed say.. 15-16 volts d.c. BEFORE the charge controller. Well within the input range of the LM7812..
I connected the input of the regulator to the lines coming from the panels before the charge controller. Now I have an unregulated source of d.c. to the device BUT it will never exceed the maximum input level but provide a regulated 12 v.d.c. to whatever I need to use it for just so the load doesn't exceed 1 amp. The output of the regulator will now produce when the panels start in the morning and shut down when the sun goes down. Even on a cloudy day the panels will produce enough current to operate a small relay. Works sweet!!
I did install a diode across the coil of the relay to shunt the kick back voltage that is produced when the coil opens up during set up or if you need to disconnect it during the day for some reason..
This set up is only going to steal milliamps from your charge. I don't see that hurting anything. The supply to the relay for what you are wanting to operate would come direct from the battery, Past your charge controller. There's 2 separate circuits going on here and there isn't any conflict with anything. The commons (negatives) of the input/output of "Most" charge controllers are bonded together so there isn't any ground loop issues to worry about..
The load side of this set up is only limited to the current limitations of the relay and the amount you feel comfortable of "Stealing" from your charge level from the panels to operate the coil of the relay..
If you use a S.P.D.T. relay, You can turn something on at night and then turn something on during the day! Pretty cool.. * ;D
I wanted to control some outdoor lighting but I didn't have a photocell circuit. I drank a few beers and pondered on the issue for a while and VALA!
In my junk drawer, I had a relay with a 12 v.d.c. coil that required 60 mA. to operate it. I also had a LM7812 voltage regulator. I scratched my head and went Hmmm... * 8)
http://www.radioshack.com/product/index.jsp?productId=2062600&cp=&sr=1&origkw=voltag e+regulators&kw=voltage+regulators&parentPage=sear ch
The LM7812 regulator will handle up to 35 v.d.c. on the input and produce a well regulated 12 v.d.c. output at 1 amp. Thermally protected and everything. My panels, While charging on a good day, Never exceed say.. 15-16 volts d.c. BEFORE the charge controller. Well within the input range of the LM7812..
I connected the input of the regulator to the lines coming from the panels before the charge controller. Now I have an unregulated source of d.c. to the device BUT it will never exceed the maximum input level but provide a regulated 12 v.d.c. to whatever I need to use it for just so the load doesn't exceed 1 amp. The output of the regulator will now produce when the panels start in the morning and shut down when the sun goes down. Even on a cloudy day the panels will produce enough current to operate a small relay. Works sweet!!
I did install a diode across the coil of the relay to shunt the kick back voltage that is produced when the coil opens up during set up or if you need to disconnect it during the day for some reason..
This set up is only going to steal milliamps from your charge. I don't see that hurting anything. The supply to the relay for what you are wanting to operate would come direct from the battery, Past your charge controller. There's 2 separate circuits going on here and there isn't any conflict with anything. The commons (negatives) of the input/output of "Most" charge controllers are bonded together so there isn't any ground loop issues to worry about..
The load side of this set up is only limited to the current limitations of the relay and the amount you feel comfortable of "Stealing" from your charge level from the panels to operate the coil of the relay..
If you use a S.P.D.T. relay, You can turn something on at night and then turn something on during the day! Pretty cool.. * ;D