# LED lighting setup

Alright, so I bought my son a battery operated Jeep for Christmas that we're trying to make look like his dad's. It came with a number of lighting components like his dad's, but hilariously the driving lights on the back bar are just plastic housing sans lights. I popped them open and there's space for 7 lights in each housing (so 14 total), but given some quick math I'm thinking of omitting the center light and just doing the 6 that are in ring (12 total). For simplicity sake I'd prefer to keep it to 12 volts so we can just use an 8 AA battery holder rather than two 9v (I have a perfect spot I can mount a flat 8 AA battery holder for easy access. I'm working with white 3v 20mA diodes. Have I totally miscalculated that I could do four parallel series of 3 each, needing 4 resistors (I think 150 ohm each??)? I should also mention I'm going to mount a switch on the dashboard so my son can flip them on and off as he wants, but it's illuminated. The switch supports 12 or 24v. So, if I'm adding an illuminated switch into the equation do I need to go all the way to 24v? If so should I just wire all 7 LEDs?

Usually math helps me make decisions but in this case it's twisting me around a bit. Any help would be much appreciated.

• 12v, 3 series and 4 parallel with 150 ohms is a reasonable solution. Nov 22, 2021 at 2:14
• Your calculations are perfect for a 12VDC solution. Your battery pack will last 2x longer if you go with a 330 ohm resistor. Slightly dimmer but your son will be just as happy. Nov 22, 2021 at 2:14
• Choosing narrow beam <30,000 mcd LEDs @ 20 mA in < = 20 deg are more important than the choice of R. But it means you can use less current. 30,000 mcd at 20 mA at arms length is hard to look at and possibly harmful closer so 5~10 mA is adequate for these types in 4500' to 5000'K Nov 22, 2021 at 3:39