mr-16 led lights

tconley

tconley

New member
Does anyone know if the mr-16 LED light like the ones sold by best hong kong will support dimming? I have seen reference to PWM in some of the transformer documentation but I just wanted to check. I was planning to use these to light up show elements and to simulate lightning effects.


Lights

Transformer
 
That documentation is not very useful. I could not tell if the LEDs needed some sort of current limiting (I suspect that they do), and the second document was just a marketing blurb about some sort of controller (not a transformer). I am pretty certain, though, that those LEDs should be dimmable through either PWM or current control. It is hard to talk about how to design for these parts, though, because of the poor documentation.

My initial impulse would be to drive those LEDs from the combination of a Ren-C controller and a Grinch board (after modifying the Grinch board so that its current-limiting feature works). In that circumstance I don't think that you need any SSR at all ,just the Grinch board and a 12V DC power supply. This is a fairly simple approach, although this approach doesn't allow you to drive the LEDs at their max (the parts on the Grinch board are only good for 90 mA or 120 mA per output).

A second approach would be to use the 595 board with a DC power supply in place of the Grinch (again, no SSR) and find some way to limit the current. A third approach would be modify an SSR board for use with a Renard (or Firegod) board to do the dimming (since the PICs cannot directly drive those LEDs).

BTW, how many of those things are you thinking of? Just a few (less than 10, say) or quite a few?

--

Phil
 
Since it uses 12VAC at 2.3 watts (200 ma), could you use the standard SSR and just feed the SSR with 12VAC instead of 120VAC? A transformer from an old trickle battery charger for your car would work and not use their transformer/power supply.

The SSR resitor would need to be resized (10 times lower?).

The FGdimmer is already PMW and I gather Renard has that capability also.
 
I would really look hard at LED lamp substitutes (sp). I know some one that spent $600.00 on the LED Par 38's and every one of them blew out withen 3 weeks. He was very disapointed. If you want to do color changing and dimming look at Chauvet LED lighting. It uses DMX512 as a controll so you can use it with Vixen. Here is a link of the units I use.

http://chauvetlighting.com/fixtures/colorsplashjr_fix.shtml

If anyone is intrested in any Chauvet products let me know, I am a dealer and will get you a great deal.
Brian
 
I've also read about similar "experiences" with the LED floods on PC - I am going to "try" making some of my own - and see what happens!
 
What is the proper way of driving those modules? In particular, how is the current through the LEDs determined? For some strange reason, I am skeptical that just hooking them up to a AC or DC power supply is the right thing to do.

--

Phil
 
P. Short said:
What is the proper way of driving those modules? In particular, how is the current through the LEDs determined? For some strange reason, I am skeptical that just hooking them up to a AC or DC power supply is the right thing to do.

--

Phil
Click to expand...

I am assuming they are setup to have a full wave rectifier built in and also have a limiting resistor built in, but that is just a guess. That would allow for AC and DC operation.
 
Not to revive a dead topic, but yesterday I received some MR16 LEDs in the mail from the group buy by WireKat over on PC. I ordered one red, one green and one blue light. They all seem to work fine on AC, nice and bright.

I also tried dimming them using PWM from a DC supply (a 9V transistor battery was all that I could find). The hardware that I used was a custom controller (similar to Renard, but using a smaller PIC) with a 2N3904 transistor to drive the LED. One oddity that I've noticed is that the intensities of the LEDs on the blue lamp seemed to vary quite a bit at lower intensity (although maybe this might just be aiming). The other oddity that I noticed is that when ramping, the lower intensities end up brighter than I would have expected, it doesn't fade to dark as quickly as I would have liked (at least, the blue one didn't).

Also, I took some scope pictures of the current waveforms when it was powered from 12VAC, I'll post them later.

Anyway, this makes it seem that it will be possible to dim the lights nicely using the PWM/DC version of Renard (give or take any bug fixes) using SSRs modified for DC use (as previously discussed).

--

Phil

P.S. this is all preliminary, there is a lot more work to be done.

Phil
 
FWIW, some current waveforms. They were measured using a 1 Ohm resistor in series with the light, powere from a 12.6VAC transformer.

The first one (bottom) is the red light, the second one is the green light, and the third one is the blue light. The last one (top) is the blue light with the 12VAC waveform superimposed.

--

Phil
 

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