PS2 3V board, how many LEDs can the headlamp circuit handle?

Both the PS32 board and the PS/2 use the same FET to drive the lights, and they'll handle the same amount of current.  Eight LED's won't make them break a sweat.  I've put four 60ma bulbs on the PS/2 and PS32 board lighting output and had no problems.

@gunrunnerjohn posted:

Both the PS32 board and the PS/2 use the same FET to drive the lights, and they'll handle the same amount of current.  Eight LED's won't make them break a sweat.  I've put four 6ma bulbs on the PS/2 and PS32 board lighting output and had no problems.

Do you mean four 6V bulbs (incandescent)?

The point though is a PS2 3V board's 6V output should easily support 8 LEDs.  560 Ohms per LED would be a good starting point.  As with the PS3, you can mix/match resistor values for multiple LEDs to tune individual brightness.  The brightness will be different between PS2 3V and PS3 with the same resistor so some experimentation is in order.  A simple calculation (not technically correct but good enough for matter at hand) is to think of the PS2 3V lighting output as 6V DC.  Then, using say ~3V as the LED voltage, the resistor drops 3V.  So the LED current is 3V / Resistor or ~5 mA (i.e., 3V / 560 Ohms = 0.005 Amps).

Missed a zero Stan, it was 4 60ma bulbs.   Yes, I was talking incandescent bulbs, the stock PS/2 bulbs.

Those pesky missing zeroes.

OK.  So 4 x 60mA = 240 mA.  More than enough capability to drive dozens of LEDs with resistors chosen for typical LED currents as used in interior/cab lighting - say ~5 mA.

Yep, the actual FET is rated at 1.7A continuous, so the limitations are farther down the line.  Since these are PWM from the PV ~20VDC line, I suspect you could drive more, but that's all I'd feel comfortable doing.

This has been discussed in previous OGR threads but what can be confusing in an LED conversion is if you measure the DC output voltage (using a DC voltmeter) from a PS2 lighting circuit you'll only read maybe 2 or 3V DC.  How can that be?!

So as GRJ points out, the PS2 lighting circuit bulb outputs are really pulses of ~20V.  Then the techno-babble takes over with RMS voltage vs. average voltage and away we go down the rabbit-hole.

As mentioned previously, a good starting point is to just assume you're starting from a 6V DC output and calculate your LED resistor value(s) accordingly.  Yes, there may be an oddball application which pushes the boundaries and requires doing more math...but I can't recall such a situation here on OGR.

Got more involved than I thought it would but at least I know I can run the same amount of LEDs off a PS2 3V board headlamp circuit as I do a PS32 board. Converting the GS4 with the PS2 3V board to LEDs will be a nice project this winter.