Testing PWM Driver

thekameleon · Post by **thekameleon** » Fri Mar 08, 2013 10:20 pm

Anyone got a good way of testing a PWM driver without hooking everything up?

lnevo · Post by **lnevo** » Sat Mar 09, 2013 5:17 am

AA and 9V batteries work I believe.

DrewPalmer04 · Post by **DrewPalmer04** » Sat Mar 09, 2013 7:16 am

Yep. Hook up the LEDs. Then two AA batteries in series will give you 3v or 30%. One AA will give 1.5v or 15%

thekameleon · Post by **thekameleon** » Sun Mar 10, 2013 4:42 am

Will that work with n a PWM driver? I would think on only a 1 -10v dimmable driver... I'd love to find a PWM generator.

DrewPalmer04 · Post by **DrewPalmer04** » Sun Mar 10, 2013 5:03 am

It'll work

thekameleon · Post by **thekameleon** » Sun Mar 10, 2013 11:32 am

Ok... Does this mean the PWM LED drivers support both dimming and PWM?

DrewPalmer04 · Post by **DrewPalmer04** » Sun Mar 10, 2013 11:40 am

Well I think you mean:

PWM is driver specific. I.E. meanwell "P"

Analog is linear: I.E. meanwell "D" people report being able to use both PWM and analog on the D drivers with no issue.

PWM drivers should only use PWM in my opinion. But you wanted to "test" the PWM driver. So supplying voltage (constant) is ok for testing. But you'll want to use PWM signal if you want PWM drivers.

rimai · Post by **rimai** » Sun Mar 10, 2013 2:27 pm

Depends on the driver.
What driver are you referring to?
If meanwell, the D version uses analog signal. You can however use PWM, but the dimming curve won't be linear.
The P version uses PWM signal. You can also use analog signal, but the dimming will be linear, but with a slight offset.
For testing purposes, you can use 9V battery just fine.
Other drivers may not work with analog signals as the meanwell does.

thekameleon · Post by **thekameleon** » Mon Mar 11, 2013 7:52 am

It worked yet, if the 2 AA, I tested with is actually 30%... That is going to be one bright fixture.

thekameleon · Post by **thekameleon** » Tue Mar 12, 2013 4:14 am

After reading this article: http://pcbheaven.com/wikipages/PWM_Modulation/ I totally understand now. The PWM drivers are not interpreting the signal and determining the output based on the clock or duty cycle. Instead they are smoothing out the pulses into a voltage using capacitors and resistors to filter the signal. This could have a number of advantages, however it also means applying a 1 - 10v analog circuit will work just as well. And if I wanted to convert an analog circuit to handle a PWM all I need to do is create a proper filter in front of the signal. one cool thing with PWM is I could isolate it from my driver. So not that it is important or anything, but the Reef angel when I adjust the values from 0 - 255 am I changing the clock or duty cycle?

And he is a brainstorming thought... I could turn the Digital IO Expansion module into a serial transceiver, couldn't I?

rimai · Post by **rimai** » Tue Mar 12, 2013 7:51 am

I changes duty cycle.
The frequency is always the same.
Yes, you can do that with the I/O

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