LED Light Panel DIY

[Spencerleehorton]

Again let me be more specific, I will need this for video so pwm is out.
I have a Xbox 12.47v dc Psu which is 12.2A as power to power both lights and want to control and dim both lights.
Also I'm still really confused about what current it is pulling due to 21 leds connected by positive with every 3 leds there is a 150 ohm resistor across from positive to negative. The positive 12v is connected one side and the negative is connected the other side.

Regards

Spence

 

[Spencerleehorton]

This is a drawing of how I've connected it all.
So I think I have it all connected in parallel?

 

[Spencerleehorton]

Right,

trying to put some clarity back into this, each set of 3 leds pulls 0.020mA so each strip pulls 140mA x 33 strips on one panel = 4.62amps and on the other 38 strips = 5.32amps
so this Xbox psu rated at 12.2amps should easily be able to cope with both as only 9.94amps will be pulled in total.

Does anyone agree so far?

 

[Spencerleehorton]

ive put a 10k pot on the negative feed back to the psu negative and i can adjust voltage this way, goes from 7.96v to 8.68v
not so bright now so need another option to get back up to 12v, i think im dropping 3.5v as this is the led dissipation.

 

[PRR]

> a drawing of how I've connected it all.

Surely not. Or I am confused by diode-symbol versus module symbol.

The electrical situation has to be more like this:

 

[Spencerleehorton]

this is starting to drive me crazy!!, there must be a simple way of doing this!!!

i have a 19v laptop adapter which is 2.7A i plug this into the buck converter and i can get 12v, the buck converter has 2 trimmers.
one for voltage and one for current. when i attach a pot to the 200k trimmer i only get 5v out of it, this must be cause the trimmer is going from 200k and when i put a 10k or 20k pot in parallel it then going down to 10k or 20k.
right, yes that was the problem, too low pot in parallel with trimmer, now put on higher K pot 470k and can tweak trimmer to 12v top end then go between 1.31v to 12v.

 

[Spencerleehorton]

ah, i did wonder whether i had the resistors in the right place as its not exactly clear where they are on the strip, but i'm sure your right, im going to test AMPs again and see what i get now.

 

[Spencerleehorton]

ive now managed to set the output current using the other trimmer to 2.6A for this 2.7A laptop power supply, so all sorted!!!