0-10v PWM dimming problem


Ive got a problem that is driving me crazy and i need some help. I'm trying to finish the last part of my controller but i'm coming up with a problem.

I have the following LED drivers from Meanwell:

LPF 90D 48 Datasheet:

These drivers allow for dimming in the following forms:

0-100K resistance
0-10V PWM

I should of gotten the ELN series drivers but at the time i did'nt realise there were different types, so i'm stuck with the LPF series :frowning:

Here is the background to wait i have tried:

The kit came shipped with 2 pots which allow the dimming for the 2 drivers i have. Both worked fine and dimmed up and down. But i want to control it with my Mega.

I next tried the following circuit, but it would not dim at all:

Controlling + lead:

So next i tried this circuit using the 10v supply to control the - lead:

I then tried the following circuit as the 2 previous would not work. This i could get the drivers to dim but with the Arduino fading from 0-5v i could only get the circuit to output 3.5v-6.5v. If i could get this to do the full 0-10V then i would be set.

I must be missing something simple but i just cant figure it out!!

Your help would be greatly appreciated to finally finish the project!

Thanks in Advance,


You need to use a PNP transistor, not an NPN.

If its something that simple ill bang my head against the wall lol. Thankyou for the reply. Now would it be wired like the first picture ( Controlling the + lead ) or in the second picture ( Controlling the - lead )???

Don't throw away the NPN yet, you need to use two transistors like this:

(Those resistors look a little high to me, I'd use 1k for each of them)

You might also need a pulldown resistor between DIM+ and GND. There might already be one inside the driver but you never know. Measure the voltage at DIM+ when it's switched on, if it's high you need a pulldown.

Hi Fungus,

I measured the dimming terminals of the driver and it does have +10VDC across them. So im assuming the pull down resistor would parallel the driver in your diagram? Any idea what value for the pull down?

(Not my diagram, just one I found with google...)

No idea. Try 1K. If that works, go higher. If it doesn't, go lower.

Fungus you are a superstar!!! That circuit worked perfect with the 1K pulldown!! You have no idea what a relief this is!

If i was in Spain i would buy you a case of beer!!! Thankyou so much for your help!!!


You need to use a PNP transistor, not an NPN.

Can you explain why just the NPN alone wouldn't work?

And the data sheet states "Please DO NOT connect "DIM-" to "-Vin".

Where else does it get connected?

Hi Rick,

I tried using a NPN connected to DIM - but it just will not dim on the LPF series. I dont have the know how to figure out why but beleive me i tried!

The Dim- is purely for the dimming circuit and the -Vin is where you connect the LEDs to. If you connect them both to the same GND you will blow either the driver dimming circuit or your LEDs.
On the driver you have:

DIM- and DIM+ for the dimming circuit

V- and V+ for the LED circuit.

Hope this helps.

Can you explain why just the NPN alone wouldn't work?

because the top circuit you have aranged as a common collector amplifier, or a emitter follower, and as such it provides unity voltage gain, ie, the emitter follows the voltage of the base (- 0.6 v or so), which means the best you could hope to have on the dimmer if the v-out of the arduino was 0-5v was 0-4.4v.

And I would say in the second diagram, haven't you connected the transistor backwards, with the collector to the dimmer?

I am kinda in the same situation I want to control the 0-10V dimmable led driver with a arduino but I had a idea of a different way to go about it. If there is 10V when measured across the grey and purple that leads me to believe there is a pull up in the driver that is set to 10V what about just placing the transistor across the grey and purple and pulsing it that way. that way a separate 10V power source is not necessary.

I'm facing the same problem right now with the LCM-40. Could someone make a summary of the used schematic to solve this issue? It's not totaly clear for me how to wire all the needed stuff and which parts are necessary.