bigdaddylee82
bigdaddylee82 UltraDork
10/16/18 11:37 p.m.

I'm planning a little LED upgrade project, and need something dimmable.   Goal would be to use a switched potentiometer.  So I've been shopping LED drivers with remote On/Off Dimming.

I "think" I found what I want/need, but I'm cornfuzed about how it works, really about how to wire it.

Mean Well DC-DC LED Driver with PWM dimming with remote ON/OFF

So my confusion is pin/wire 23 and 21.  Do I still supply 12V+ to pin 23 if I'm using a Potentiometer?  I'm assuming the pot goes between 12V+ and pin 21, right?

After writing that, I read through the spec sheet again.

I guess if I'm going to use the the dimming and remote on off feature, I can't use a switched pot, I have to use something that gets me below 0.8V but not the open circuit the switched pot would provide?

Dr. Hess
Dr. Hess MegaDork
10/17/18 9:05 a.m.

I think that is saying that you have to supply the dimming signal with pulse width modulation for it to dim the LED, not just provide a low voltage.  Try to find a 555 or 556 timer circuit that does PWM.  Should be pretty easy to build.

APEowner
APEowner GRM+ Memberand Dork
10/17/18 2:28 p.m.

That's looking for a PWM input signal on pin 21 with a frequency of 100 to 1000 Hz. 

bigdaddylee82
bigdaddylee82 UltraDork
10/17/18 4:43 p.m.

I'm obviously over my head.

I assumed that I just varied the voltage to pin 21, i.e. potentiometer, and the driver handled the PWM frequency changes to the LED.

I just want to turn a knob that has a decent range, from off to small nuclear flash. 

Dr. Hess
Dr. Hess MegaDork
10/17/18 5:52 p.m.
bigdaddylee82
bigdaddylee82 UltraDork
10/17/18 7:35 p.m.

In reply to Dr. Hess :

There's a lot going on there, is Rpwadj is a variable resistor/pot? I've got a 20KΩ pot.

If I used the random online µs to Hz converter I found correctly, that circuit diagram only goes down to 1026 Hz.  As APEowner pointed out I need 100-1000 Hz.  I imagine that the frequency can be changed with different values for components, but at this point I know just enough to know what most of those symbols are, not what to change to get the frequency range.

 

bigdaddylee82
bigdaddylee82 UltraDork
10/17/18 7:41 p.m.
Dr. Hess
Dr. Hess MegaDork
10/17/18 8:08 p.m.

Yeah, that rpawadj is the adjustable resistor that sets the pulse width in that circuit. 555 timers are really versatile little chips.  I'm sure there's another schematic floating on teh Intr4w3bz, y0, that has more adjustments or suggestions. 

 

Anyway, yeah, if you can buy one for five bucks that someone else already did all the R&D on, go for it.

Dr. Hess
Dr. Hess MegaDork
10/17/18 8:09 p.m.

Also note that the ebay onr says '.8'  amps, or about 10 watts at 12V, but the listing says 8 amps.  Roll the dice.

bigdaddylee82
bigdaddylee82 UltraDork
10/17/18 8:20 p.m.

Talk about coincidence, look what a Google search for the pictures of the guts of that eBay dimmer turned up.

Some aquarium folks are using that eBay PWM and the very same LDD series Mean Well Drivers from my original post to have cheap dimmable LEDs for their little fishies. laugh

https://www.plantedtank.net/forums/20-diy/1008498-manual-pwm-dimmer-ldd-h.html

Driver, "drives" LEDs, eBay dimmer, provides adequate signal to driver for dimming.

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