MeanWell LED Drivers: 3 in 1 Dimming Function.

PDX Joe

PDX Joe

Well-Known Member
To follow up on my last question about potentiometers and resistors... let me ask this question, which I think is more succinct. I think this was alluded to earlier, but wasn't explicitly answered.

Does the power rating of a potentiometer have to match the power rating of a resistor? For example: if you use a 100k Ohm pot with a 1 Watt power rating, then do you need to use a 10K resistor with a 1 Watt power rating? Or can you use the 100k Ohm/ 1 Watt pot with a 10k resistor rated for 1/4 Watt power?
 
PDX Joe

PDX Joe

Well-Known Member
guod said:
1/4 Watt for both is enough for the dimming port...
Click to expand...
Thanks for the response. But, do the power ratings have to match? It seems like there are more pot options with 1/2 watt and 1 watt power ratings. So, if I went with a 1/2 watt pot then would I have to go with a 1/2 watt resistor too? Or can I stick with the 1/4 watt resistor?
 
JavaCo

JavaCo

Well-Known Member
PDX Joe said:
Thanks for the response. But, do the power ratings have to match? It seems like there are more pot options with 1/2 watt and 1 watt power ratings. So, if I went with a 1/2 watt pot then would I have to go with a 1/2 watt resistor too? Or can I stick with the 1/4 watt resistor?
Click to expand...
Doesn't matter in this case since the internal workings of the driver do the dimming. The pot just gives you the control so there is no load to speak of on the pot. You could use lower or higher wattage resistors and it won't make a difference. IF you had a circuit where the pot itself was doing the actual dimming then it would matter. You would want to resistors and pot to match or to be higher than the load it is going to be under during operation.
 
PDX Joe

PDX Joe

Well-Known Member
JavaCo said:
Doesn't matter in this case since the internal workings of the driver do the dimming. The pot just gives you the control so there is no load to speak of on the pot. You could use lower or higher wattage resistors and it won't make a difference. IF you had a circuit where the pot itself was doing the actual dimming then it would matter. You would want to resistors and pot to match or to be higher than the load it is going to be under during operation.
Click to expand...
Ahhh, now I get it... so the power capacity doesn't even really matter in this case, only resistance matters, because it is essentially controlling a signal to the driver. Well, here is the pot I want to use... mainly because it looks good. And... here is the resistor I chose. Does this look kosher?

http://www.mouser.com/Search/ProductDetail.aspx?R=P16NP104KAB15virtualkey61330000virtualkey72-P16NP-100K

http://www.mouser.com/Search/ProductDetail.aspx?R=RC55LF-D-10K-B-Bvirtualkey66200000virtualkey66-RC55LF-D-10K

Thanks!!!
 
JavaCo

JavaCo

Well-Known Member
PDX Joe said:
Ahhh, now I get it... so the power capacity doesn't even really matter in this case, only resistance matters, because it is essentially controlling a signal to the driver. Well, here is the pot I want to use... mainly because it looks good. And... here is the resistor I chose. Does this look kosher?

http://www.mouser.com/Search/ProductDetail.aspx?R=P16NP104KAB15virtualkey61330000virtualkey72-P16NP-100K

http://www.mouser.com/Search/ProductDetail.aspx?R=RC55LF-D-10K-B-Bvirtualkey66200000virtualkey66-RC55LF-D-10K

Thanks!!!
Click to expand...
Well pretty sure those parts have not been blessed by a rabbi, but yeah, they will work. Just not kosher.
 
PDX Joe

PDX Joe

Well-Known Member
JavaCo said:
Well pretty sure those parts have not been blessed by a rabbi, but yeah, they will work. Just not kosher.
Click to expand...
Thanks again for the help. Apologies to any of our Jewish friends on here, didn't mean to offend... just a little bit of my native "northeastener" slipping out. Shalom!
 
PDX Joe

PDX Joe

Well-Known Member
So, if a potentiometer has a 20% tolerance, then does the resistor need to be 20k to make up the tolerance difference or should one stick with a 10k resistors?
 
V

VegasWinner

Well-Known Member
I decided to use an led controller for my leds and COB's. I am going to build the circuit energizer for the COB's and us a typhon controller, http://shop.stevesleds.com/Typhon-Typhoon-LED-Controller-8794102479.htm it controls 4 channels with start and stop times independent of each other. This controller can control lights in both bloom and veg spaces simultaneously removing light timers from the system and using a single controller. I was going to buy the built regulator,but the shipping costs were too much for me, and i have some electronics skills from my background. The Typhon controller is a arduino uno style unit already programmed. peace
 
V

VegasWinner

Well-Known Member
Kit arrived today and I assembled both units and tested them with my Storm Controller. I connected PWM and GND pins to the input and got the click and the red led turned on with a lights on, and got the click and led off with lights off. It works. I will now wire each to an outlet on a duplex receptacle,placed in an duplex box with cover, label them Veg & Bloom, plug the drivers into their respective outlet, and let the Storm Controller be the timer, dimmer, temperature sensor, and fan controls, all in one small package. No more timers for each light, just connect the dimmer circuit with a tap to the relay switch and On/Off, dimming control for both light fixtures and blue and red leds too. bonus. thanks for the idea, it works, with this unit to assemblyhttps://www.sparkfun.com/products/11042 or the pre-assembled unit. A storm X control has 16 pwm circuits the most on any arduino device so far. peace.
 
optzulu

optzulu

Well-Known Member
Hello guys I have a question I remember to read a post here on the forum but cant find it anymore.
It was about dimming leds and how it works, So what I remember is that dimming a cob is a bad idea to win effi% for example you have a hlg185-1750 and you are running it at 1.75a you change your mind and want to run them at 1400ma so you bring the amperes down. The driver will still suck up 1750ma but wil send a 1400ma signal to the chip you will win effi% and less heating in the chip itself. But the driver will still suck 1750ma is that right ore was I just to stoned and....
Cheers
 
B

brianakee

New Member
I am pretty sure I understand the math about how to calculate low limiter R and variable R, via potentiometer. Assuming one Meanwell HLG series, if we are want to dim one controller between 10% and 100%, the suggestion is to use a 10kohm limiting resistor and a 100kohm pot. The issue that I have is that putting resistors in series has an additive effect on resistance. Meaning that 100kohm + 10kohm is going to provide 110kohm of total resistance. Max R to reach 100% output should be 100kohm, which we would be exceeding with combination of 10kohm R and 100kohm pot.

Does this extra resistance hurt anything?

Wouldn't it be better to use a 10kohm resistor and on 90kohm pot?
I realize that 90kohm pots are probably difficult to acquire, but we could easily wire resistors in parrallel with the pot to achieve the appropriate min/max resistance ratings that we are looking for. Resistance calculations are not all that difficult, especially with the online calculators available.
 
Z

Zulunature

Well-Known Member
brianakee said:
I am pretty sure I understand the math about how to calculate low limiter R and variable R, via potentiometer. Assuming one Meanwell HLG series, if we are want to dim one controller between 10% and 100%, the suggestion is to use a 10kohm limiting resistor and a 100kohm pot. The issue that I have is that putting resistors in series has an additive effect on resistance. Meaning that 100kohm + 10kohm is going to provide 110kohm of total resistance. Max R to reach 100% output should be 100kohm, which we would be exceeding with combination of 10kohm R and 100kohm pot.

Does this extra resistance hurt anything?

Wouldn't it be better to use a 10kohm resistor and on 90kohm pot?
I realize that 90kohm pots are probably difficult to acquire, but we could easily wire resistors in parrallel with the pot to achieve the appropriate min/max resistance ratings that we are looking for. Resistance calculations are not all that difficult, especially with the online calculators available.
Click to expand...

Simple answer is no - it's very difficult to make potentiometers exacting, you can get them but the prices are frankly unbelievable, that's part of the reason for wanting the resistor to ensure that the driver gets the correct voltage for maximum output.

ie. I had 4 pots ... 2 of which had readings of 97Kohm and 1 @ 95kohm, the final one was only 91Kohm so that 10K resistor just took it up to the 100K required for full power.

One other that I ordered came in at only 85Kohm so if I'd used that I'd of needed a 15K+ resistor which would have resulted in only being able to dim to 15%.

Anyway hope that helps.
 
B

brianakee

New Member
Zulunature said:
ie. I had 4 pots ... 2 of which had readings of 97Kohm and 1 @ 95kohm, the final one was only 91Kohm so that 10K resistor just took it up to the 100K required for full power..
Click to expand...
Makes perfect sense.

Basically you are suggesting that the extra 10k is a buffer for crappy pots. :lol:
I have never actually measured resistance across any of my pots, so I just assumed they are pretty close.

Do you think that the extra resistance does anything negative or positive to the driver?
My initial though would be that the drivers are probably slightly underrated, or have tolerances that in some cases might allow extra output. If this is the case, then I would expect that an additional 10%(+/-) resistance would allow access to that extra output. That might be good if you want to get more output, but it might also decrease the life of the driver by running at Max+ output.


Thanks!
 
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