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Topic: PWM RF dimmer as analog 5v input for dimming buckpuck (Read 1 time) previous topic - next topic


Nov 22, 2012, 12:37 pm Last Edit: Nov 22, 2012, 12:39 pm by Suaveman Reason: 1
I've been wanting to build an arduino led dimmer for a while now, and i finally got the parts i had been waiting for. I have a mega 2560.

I have a rough understanding of how to use an analog input (0-5v) to scale pwm outputs. I can't write scripts at all, but have seen enough examples to be able to figure out how to modify examples i have seen to fit my application.

Basically, i want to use one of those pwm led dimmers with the rf controls, the 12-24v 8a cheapo dealextreme/ebay black box ones, to act as an analog input, and use the scale adjustment, to use the dimmer remote to dim the buckpuck/led attached to the arduinos digital output.

A few questions-

Will this even work? Feeding a pwm output 5v signal into an analog input? Whats the current limit as far as how much dc can be put into the analog input?

I want to use the 5v out wire from the buckpuck for the input to the rf dimmer, or should i be using a 5v on the mega? if so which pin?

should i attach the ground for the dimmer ground input to the buckpuck input ground? I'm pretty sure so since the 5v ref is coming from the puck.

On the output side, i assume i need to attach the positive wire (from rf dimmer) to the analog input, and the ground i don't know where to put. Arduino board or the buckpuck? If the arduino which pin? PWM ground, or one of the grounds next to p-in?

Finally, i've read about this inverted pwm thing, and while i don't mind using the down for up and up for down on the remote, is there an easy jumper/solder or software solution to this issue?

Alternatively, is there a programmable rf remote kit for arduino's that would accomplish this? I don't want to get ahead of myself as far as scripting something like that, but in the future it would be nice to add a few more lights w/o more remotes/dimmers.

Any help/advice is much apprecciated.  :)


Please post links to all the hardware you mention (datasheets if possible), we can then find out what they are.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]


Well, i think its a generic 2650, but i don't think that matters much. I got it off ebay-


buckpuck 700ma drivers-


Generic square 10w smd led diodes, they work with the pucks, just haven't been able to dim yet. Also 2 5w smd's wired in parallel i already have running driverless off a wallwart and the same pwm dimmer as below.

12v 8a rf pwm dimmer-


The idea is to translate (if possible) a higher voltage pwm input from the dimmer (lets say 10v max, it just depends on my voltage source, which is flexible as i have a ton of sepics) to a digital pwm output to the buckpucks. The higher the input voltage from the dimmer the better, as it acts kind funny when i hooked it up to the 5v out on the buckpuck, prob too low of an input voltage.


Nov 25, 2012, 10:35 am Last Edit: Nov 25, 2012, 10:40 am by Suaveman Reason: 1
So after fiddling around with just the dimmer, and the buckpuck wired up to a wallwart and a sepic, i was able to get it to dim. The problem is that the dimmer doesnt like working at voltages below ~10-12v. I figured this out by hooking up a 5v dc source to the input and a multi to the out, and it did not change voltage or turn on/off, as well the hot side (+) of the dimmer shorts to each other, so when i hooked the reference pin to the control, it just shorted through and the light did not go on. Even while hooked up to a 5v dc wall wart.

Basically i had the 12v 1.25a input from the WW going into a sepic kicking out ~12.5v, then the output from the sepic to the dimmer, and then to the driver inputs. It dim's 0-100, but the arduino is not involved. This prob could have been accomplished with a cheap cc driver, but i was advised against doing so as it could stress the driver switching it on/off with pwm. It works for the buckpuck though.

Still, i want to learn how to dim it via the arduino, so i can have one remote, one dimmer connnected to an analog input that translates to a inverterted (since buckpucks are on 100% at 0, off when you short the 5v ref to the control wire.

The problem i see, is, is it dangerous to pump 1a 12v pwm signal into an analog input on an arduino? Whats the voltage range for those inputs, and/or current ratings?

So heres the idea i had, use a mosfet switched on/off via pwm of the 12v 1a (doesn't have to be that high of amperage, and being that its going to be used in a dc backup lighting system, and effeciency is a factor, i'd most likely use a very low current 12v source. For now it works. Anyway, switch the mosfet on/off using the dimmer using pwm, to switch the 5v reference on/off and thus dim.

Is there an easier way to do this? IE translate a 12v pwm signal into a 5v signal while not losing linearity as it dims?

I know putting a sepic between the output of the dimmer and the analog input would do this, as it would just smooth out the pwm and kick out a 5v signal regardless of the input voltage. I'm pretty sure just pwm switching a msofet with the 12v pwm dimmer output on/off for the control/ref would accomplish this.

So Then Connect the 5v ref to one side of the mosfet, the output of the msofet to the analog input on the arduino (5v), wire the ground output from the dimmer to led negative if i'm not mistaken, and take the control pin and attach it to a digital output on the arduino. Use the scaling script i ran across on the web in regards to dimming leds relative to an analog input range, and it should work. Then i can wire up as many buckpucks to each digital output to pwm as necessary, and an additional dimmer/remote if i wan't to have seperate on/off & dimming channels for each light. Or a multichannel one to simplify things.

Am i missing some kind of rf remote that can interface with an arduino and provide a linear (or pwm) 0-5v input to an analog pin? This workaround using a 12v dimmer seems kind of cumbersome, and i don't want a handful of remotes for each light if possible.

Any ideas or mistakes i made in understanding how to accomplish this?


EDIT- another idea i just had, was to wire the sepic after the pwm, to smooth out the frequency, while dimming still takes place as it's being pwm'd at the input (the sepic). Still no arduino involved, but could this work for "dumb" cc drivers that can get stressed/fail due to being switched off rapidly via pwm input? I know theses sepic units have low pass filters, and if they clean up the pwm noise, it sould dim without stressing dumb drivers.

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