In continuation of my threads “LED: current, voltage questions” and “Solar Light Circuit Board”, let’s see if I learned something:
I have 10 solar lights and would like to supply extra power to supplement the charging from the solar panel so that the lights stay on longer.
1) My power supply (WallWart) : 120VAC, 19 watt, output:12VDC, 800ma, 16.5VDC no load
2) Each light is 7 feet apart for a total run of 70 feet.
3) I would like to supply maximum 50ma to each light at a max of 1.3v. Since the power supply may be running at night I want to ensure that the inductor doesn’t get too high a voltage and in turn blow the LED. 10 lights at 50ma= 500ma which a safe load for the power supply.
4) I want to run 18 or 20 gauge stranded wire from the power supply to the middle light (go 35feet each way) and hook up the lights in parallel. Any significant concern about voltage drop over 35 feet?
5) Since the batteries may be full at some time I will assume a voltage output of 16.5 v and battery voltage of 1.3 volts. 16.5 – 1.3= 15.2v, 15.2/50ma=304 ohms, 15.2 X .05= 0.76 watt. Use 300 ohm 1 watt resistor installed on the positive end of the battery of each light (easiest place to solder)?
6) Do I require a diode at the power supply to prevent ‘feedback/draining battery’ when the power supply is disconnected from the 120AC?
Any other suggestions/comments?
I have 10 solar lights and would like to supply extra power to supplement the charging from the solar panel so that the lights stay on longer.
1) My power supply (WallWart) : 120VAC, 19 watt, output:12VDC, 800ma, 16.5VDC no load
2) Each light is 7 feet apart for a total run of 70 feet.
3) I would like to supply maximum 50ma to each light at a max of 1.3v. Since the power supply may be running at night I want to ensure that the inductor doesn’t get too high a voltage and in turn blow the LED. 10 lights at 50ma= 500ma which a safe load for the power supply.
4) I want to run 18 or 20 gauge stranded wire from the power supply to the middle light (go 35feet each way) and hook up the lights in parallel. Any significant concern about voltage drop over 35 feet?
5) Since the batteries may be full at some time I will assume a voltage output of 16.5 v and battery voltage of 1.3 volts. 16.5 – 1.3= 15.2v, 15.2/50ma=304 ohms, 15.2 X .05= 0.76 watt. Use 300 ohm 1 watt resistor installed on the positive end of the battery of each light (easiest place to solder)?
6) Do I require a diode at the power supply to prevent ‘feedback/draining battery’ when the power supply is disconnected from the 120AC?
Any other suggestions/comments?