Looking to design a circuit to control 2 individual LED strips, Dimming and Mixing Colours.

Thread Starter

muffinman92

Joined Dec 2, 2018
4
Hi All,

First time posting here, I hope I found the right website for this.

I want to create some Bi-colour LED Tube lights 3200k-5600k (Similar to the Quasar Science Led Tubes.)

Please see my attachment drawing below to show you what I am trying to achieve.

Sorry, I am very new to electronics.

I am looking for recommended parts I should be purchasing to make something like this. Or do I need to design my own PCB?

Basically, the idea is to have a rotary switch and as you turn it clockwise one of the led strips (5600k) light up and the other (3200k) dimms down. And then as you turn anti-cockwise the reverse happens. The brighter LED strip starts to dim and the other Led strip starts to brighten up.

(usually on these things when the knob is at the half way mark both led strips would be on at 100%)
  • It would be great to include a secondary rotary switch to control the over-all power going to the Led Strips. So then this second rotary switch can be used to determine the peak brightness that the LEDs can reach. from 0-100% of brightness.

So then not only can I choose the colour temprature that I want but I also can choose the brightness.

Basically here at 00:30 is an example of what I want to achieve -
(Rotation of a rotary swtich to change colour temprature, while also having a second rotary switch to adjust overall brightness.)

This video shows a guy making a bi colour led panel using two PWM @ 10:17 -
(Ideally I want this but just with 1 Knob)

And then a second knob to controll brightness from 0-100%

What kind of electronics should I be researching to achieve this? Is it some kind of PWM board that I need?

I appriciate I might need something different to a 12v 5a power supply to make this work. I just know thats what it takes to run one of these strips.

DualPWM.jpg

I hope this all makes sense!

Thanks :)
 
Last edited:

Hymie

Joined Mar 30, 2018
720
Such a circuit that might work with two of the PWM units in the link (below) could be made simply using a pair of twin ganged pots wired as shown (rather than a single pot controlling the brightness of a single unit).

However with the overall brightness set at maximum, only one of the PWM could be set at maximum (with the other at minimum), or both at 50% if the overall brightness is set at maximum.

In the diagram the pots R1a and R1b are twin ganged controlling the overall brightness; pots R2a and R2b are also twin ganged pots (but wired in anti-phase) increasing/decreasing the brightness of one or other PWM unit.
You might need to experiment with the pot values (I would suggest you start with all at 200KΩ); use of logarithmic pots might be better, given the response of the human eye to differing light levels.

https://www.ebay.com/itm/New-12V-24V-20A-Max-PWM-DC-Motor-Stepless-Variable-Speed-Controller-25kHz-Switch/111930282177

2 PWM control.jpg
 

Thread Starter

muffinman92

Joined Dec 2, 2018
4
Thanks for the
Such a circuit that might work with two of the PWM units in the link (below) could be made simply using a pair of twin ganged pots wired as shown (rather than a single pot controlling the brightness of a single unit).

However with the overall brightness set at maximum, only one of the PWM could be set at maximum (with the other at minimum), or both at 50% if the overall brightness is set at maximum.

In the diagram the pots R1a and R1b are twin ganged controlling the overall brightness; pots R2a and R2b are also twin ganged pots (but wired in anti-phase) increasing/decreasing the brightness of one or other PWM unit.
You might need to experiment with the pot values (I would suggest you start with all at 200KΩ); use of logarithmic pots might be better, given the response of the human eye to differing light levels.

https://www.ebay.com/itm/New-12V-24V-20A-Max-PWM-DC-Motor-Stepless-Variable-Speed-Controller-25kHz-Switch/111930282177

View attachment 164895
Thanks for the useful knowledge, I will try my best to understand what you are telling me :) I Really appriciate the drawing.

I currently have 2 of these PWM units:

https://www.ebay.com/itm/Mini-DC-5A-Motor-PWM-Speed-Control-DC-3-35V-High-Speed-Control-Switch-LED-Dimmer/123064048023?ssPageName=STRK:MEBIDX:IT&_trksid=p2057872.m2749.l2649

Are they similar to the one you have suggested? Just smaller?

And Im guessing when you say Pots you mean (potentiometer) ?

Excuse my ignorence, but what components are the R1A, R1B, R2A,R2B? And what do the -//- Symbols represent?

Just so I can understand your diagram a little better. I have looked a a schmatic symbol cheat-sheet but can't seem to decode your diagram.

Thanks! :)
 

Thread Starter

muffinman92

Joined Dec 2, 2018
4

Hymie

Joined Mar 30, 2018
720
Before buying what might be (relatively) expensive twin ganged pots, you could test the proposed circuit using discrete pots of your chosen value – adjusted to various positions to observe the effect on the PWM output.
 

oz93666

Joined Sep 7, 2010
693
Just a few comments on the videos ...

Product in the first video is an outrageous price ,, hundreds of pounds for 10 pounds worth of components !!

In the second video the builder is using very low power strips , the leds are spaced far apart ,

You can find strips like these ....
they will give out 3 times more light than the ones in the video , so you can either make the panel smaller , or keep the same size but 3 times light output ...

the smaller the led the more efficient , 5050s are the worst , 15% less light for the same power input.
 

Thread Starter

muffinman92

Joined Dec 2, 2018
4
Just a few comments on the videos ...

Product in the first video is an outrageous price ,, hundreds of pounds for 10 pounds worth of components !!

In the second video the builder is using very low power strips , the leds are spaced far apart ,

You can find strips like these ....
they will give out 3 times more light than the ones in the video , so you can either make the panel smaller , or keep the same size but 3 times light output ...

the smaller the led the more efficient , 5050s are the worst , 15% less light for the same power input.

Thanks for the heads up on that. These are the stips I have purchased:

https://www.ebay.co.uk/itm/High-CRI95-SMD5630-LED-Strip-Light-Daylight-White-Neutral-White-EF120-140lm-W/173052714164?ssPageName=STRK:MEBIDX:IT&var=471985656994&_trksid=p2057872.m2749.l2649

As I need them to have a high CRI 95+ and Good color temp, (3200k-5600k)
 
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