Pontentiometer question

Fordprefect42

Fordprefect42

Well-Known Member
Does anyone have a good explanation of a potentiometer? I’m setting up some qb96 boards on a meanwell xlg240-h-ab and want to add a dimmer switch. Saw a post on here suggesting connecting a 100k potentiometer for that driver.

So I get that a potentiometer will reduce current by adding resistance. I’m curious about what the 100k means? In picking a potentiometer do I need one rated for a certain amperage as I would for wiring? Any specific suggestions for this model driver?

I’m a noob on this and do not have an electrical background so want to understand what I am doing a bit better, and avoid blowing stuff up.

Don’t blow something up today is one of the top 79 rules I live by.
 
Fordprefect42

Fordprefect42

Well-Known Member
GBAUTO said:
A potentiometer is a voltage divider.
The 100k is the resistance value of the internal circuitry.

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Thanks. Got that much. I got that there were resistors that reduce the current. I guess what I am ultimately fishing for is how do I know if the specs on a potentiometer are compatible with the driver? For example I know that the qb96 boards are limited to something like 6000 mamps before they will blow. Is there anything similar I need to understand for a potentiometer?
 
GBAUTO

GBAUTO

Well-Known Member
Fordprefect42 said:
Thanks. Got that much. I got that there were resistors that reduce the current. I guess what I am ultimately fishing for is how do I know if the specs on a potentiometer are compatible with the driver? For example I know that the qb96 boards are limited to something like 6000 mamps before they will blow. Is there anything similar I need to understand for a potentiometer?
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The dimming leads on the driver only see a command signal, either a digital PWM, 0-10v, or a resistor circuit.
I think the driver supplies less than 100 micro-amps to the dimmer circuit, so the power through the dimming circuit is practically nothing.
Your driver is essentially a constant-voltage supply. That means the current supplied is divided between the boards.
I think your driver can supply approx. 4200mA @ 54V.
I use the rapid dimmers, they're pretty much plug-and-play.
 
Fordprefect42

Fordprefect42

Well-Known Member
GBAUTO said:
The dimming leads on the driver only see a command signal, either a digital PWM, 0-10v, or a resistor circuit.
I think the driver supplies less than 100 micro-amps to the dimmer circuit, so the power through the dimming circuit is practically nothing.
Your driver is essentially a constant-voltage supply. That means the current supplied is divided between the boards.
I think your driver can supply approx. 4200mA @ 54V.
I use the rapid dimmers, they're pretty much plug-and-play.
Click to expand...
Ok thanks that is really helpful. I’ll likely pick up a couple of the ones recd upthread, but good to know it doesn’t seem to be a safety hazard.
 
Rocket Soul

Rocket Soul

Well-Known Member
Fordprefect42 said:
Does anyone have a good explanation of a potentiometer? I’m setting up some qb96 boards on a meanwell xlg240-h-ab and want to add a dimmer switch. Saw a post on here suggesting connecting a 100k potentiometer for that driver.

So I get that a potentiometer will reduce current by adding resistance. I’m curious about what the 100k means? In picking a potentiometer do I need one rated for a certain amperage as I would for wiring? Any specific suggestions for this model driver?

I’m a noob on this and do not have an electrical background so want to understand what I am doing a bit better, and avoid blowing stuff up.

Don’t blow something up today is one of the top 79 rules I live by.
Click to expand...
That driver has an internal dimmer aswell which sorta works like a "master", remove the rubber knob to see the hole behind, and use a small screwdriver to adjust upwards, intensity will go up but at some point you will see flickering and then the light goes off. Just adjust down a bit from there until you have as intense as possible. This will be your highest possible intensity. These drivers are a bit weird, constant power. They will try to feed as much as they can until they cannot raise voltage enough, more amps and the lights out.
For day to day its easier with an external pot but you can manage with out a dimmer if you can measure output or power consumption. The internal dimmer gives you little idea of how much power your using.
 
Fordprefect42

Fordprefect42

Well-Known Member
Rocket Soul said:
That driver has an internal dimmer aswell which sorta works like a "master", remove the rubber knob to see the hole behind, and use a small screwdriver to adjust upwards, intensity will go up but at some point you will see flickering and then the light goes off. Just adjust down a bit from there until you have as intense as possible. This will be your highest possible intensity. These drivers are a bit weird, constant power. They will try to feed as much as they can until they cannot raise voltage enough, more amps and the lights out.
For day to day its easier with an external pot but you can manage with out a dimmer if you can measure output or power consumption. The internal dimmer gives you little idea of how much power your using.
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Yeah I knew that dimmer screw was there. I figured at this point it’s going to wind up running me close to 600 bucks anyway after all of the framing and miscellaneous so why not spend a few dollars more to make it more convenient. Was going to mount the driver somewhere on the frame, and don’t want to screw with removing it, turning it upside down and popping the rubber cover. I’m not sure about the 8020.net quick framing versus extruded aluminum yet, but drawing the line at decorations like the t-slot color strips.
 
raggyb

raggyb

Well-Known Member
I want to learn this too but dont even use leds! I guess like GBAUTO says

"Your driver is essentially a constant-voltage supply. That means the current supplied is divided between the boards.
I think your driver can supply approx. 4200mA @ 54V."

fair warning anything I say might make it blow up. I guess LED's are DC right? stupid Q but that probably matters for the dimmer choice, AC vs DC. Also is there a dimmer control connection and does it take digital signal or analog? Or are you just going inline to the light's power input? I think you intend in line basically. I'm gonna chat because I'm interested now.

What would potentiometer need not to fail? it prob needs to be rated to handle that current which in this case is no more than the same as without, or say at least double (8.4A dc). It needs to have excellent max power rating? 4.2A x 54V = 250W or triple that to be safe? I don't know what other specs they give. Does this need a capacitor somewhere for flutter. Do Q boards handle power flutter? Do they ever blow? even if they handle it might not hurt if you could properly add a cap? Maybe one's in the pot?

GB says rapid dimmers are plug and play so probably that but i'm just shootin the shit. have a good one
 
Rocket Soul

Rocket Soul

Well-Known Member
raggyb said:
I want to learn this too but dont even use leds! I guess like GBAUTO says

"Your driver is essentially a constant-voltage supply. That means the current supplied is divided between the boards.
I think your driver can supply approx. 4200mA @ 54V."

fair warning anything I say might make it blow up. I guess LED's are DC right? stupid Q but that probably matters for the dimmer choice, AC vs DC. Also is there a dimmer control connection and does it take digital signal or analog? Or are you just going inline to the light's power input? I think you intend in line basically. I'm gonna chat because I'm interested now.

What would potentiometer need not to fail? it prob needs to be rated to handle that current which in this case is no more than the same as without, or say at least double (8.4A dc). It needs to have excellent max power rating? 4.2A x 54V = 250W or triple that to be safe? I don't know what other specs they give. Does this need a capacitor somewhere for flutter. Do Q boards handle power flutter? Do they ever blow? even if they handle it might not hurt if you could properly add a cap? Maybe one's in the pot?

GB says rapid dimmers are plug and play so probably that but i'm just shootin the shit. have a good one
Click to expand...
The external dimmer controls the driver, it doesnt really handle any power like an ac dimmer. And yes, all leds are DC unless you have a builtin converter but this usually means theyre a bit crappy.

Theres a lot of info if you go to ledgardeners youtube, especially the quantum board torture video is fun too watch.

Dimmer is 3 in 1 dimming, resistive, pwm and something more, theres a thread on 3 in 1 dimming if you search the forum.
 
raggyb

raggyb

Well-Known Member
Rocket Soul said:
The external dimmer controls the driver, it doesnt really handle any power like an ac dimmer. And yes, all leds are DC unless you have a builtin converter but this usually means theyre a bit crappy.

Theres a lot of info if you go to ledgardeners youtube, especially the quantum board torture video is fun too watch.

Dimmer is 3 in 1 dimming, resistive, pwm and something more, theres a thread on 3 in 1 dimming if you search the forum.
Click to expand...
Mm, thanks. i thought pwm is different application from a potentiometer but need to do more review. I'm missing something though, if you say the dimmer controls the driver and no power really, then driver is just a dc to dc amp? so power into driver would have to be dc also for a potentiometer to work as a dimmer I think or is that wrong?
 
Rocket Soul

Rocket Soul

Well-Known Member
The driver is ac to dc but will also do dc to dc.
The external dimmer does not pass nor input nor output thru the dimmer, it just controls the driver amps. You do not need to be worried about getting shocked thru those dimmer leads. Power thru those wires is minimal afaik.
 
D

DukeFluke

Well-Known Member
Rocket Soul said:
The driver is ac to dc but will also do dc to dc.
The external dimmer does not pass nor input nor output thru the dimmer, it just controls the driver amps. You do not need to be worried about getting shocked thru those dimmer leads. Power thru those wires is minimal afaik.
Click to expand...
Good to know. I'm about to hook up my AB drivers and wanted to know if I could be shocked by touching the exposed metal of the potentiometer
 
raggyb

raggyb

Well-Known Member
Following up with my homework for today. Found out that very generally, pwm could be used to turn led's on and off rapidly, so fast that eye can't detect but that would lower the power output. Not the case with the Meanwell.

Looked up the meanwell driver spec and think just buy meanwell brand dimmer, but anyhow, as you mentioned '3 in 1 dimming via potentiometer'. so OP has a meanwell ab, so can use built in potentiometer & 3 in 1 dimming function. sounds like an either or.
then it get's confusing. 3 in 1 dimming is patented by Meanwell. A Mean Well LED driver with 3-in-1 dimming is compatible with dimming controllers that use the below signal types:
  • 1-10V*
  • PWM Signal
  • Resistance
(*some models accept a 0-10V input). The LED driver will automatically detect which type of dimming signal is being used and then adjust the output of the LED driver accordingly, causing the LED lights to dim.

so which one is better? this is nice info here, https://www.ledsupply.com/blog/top-3-solutions-for-dimming-leds/ . I summarize as potentiometers are ugly, 1-10v requires a current SINKING dimmer, and in this case pwm does not make the meanwell output pwm. Works best if driver is close to fully loaded. See link.

All 3 options reduce the voltage of the constant current so not much difference. I imagine this doesn't change the spectrum. Also ask Meanwell.

Note i never did any of this shit so go ahead and clarify, no problemo.
 
Attikus112

Attikus112

Well-Known Member
The driver functions exactly the same way for each of the dimming modes. The only reason i would use 0-10v or pwm over the potentiometer would be if you're trying to automate the dimming functionality or have it digitally controlled. See page 4 of the datasheet. Also as others have said, there's no significant current going though this potentiometer (100uA i think) so you don't need a heavy-duty potentiometer.
 
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