Modify LED RGB Amplifier for more Amperage

[stuee]

Hi all.
I have a 12v led amplifier thats rated at 12A.
opening it up i see the transistors are small and not heatsinked. Is there a way to increase this to around 19A? I have taken photos and named some parts but the small dil have no markings on them, not sure how to work out what they are or if some smarty pants will know.

Thanks

 

[ronsimpson]

Is there a way to increase this to around 19A?

Yes. Get two amplifiers.

I want my car to go twice as fast. But:
The wheels will fall off. The engine will blow up. The wiper blades can not function with twice the wind. The steering will shake. Your insurance company will not talk to you. Your mother will yell.
But the radio will probably work just fine.

 

[Tony Stewart]

These MOSFET need at least 10V Vgs to be used as 24A switches with a heatsink to dump 2.5W
The unmarked chips are simply optoisolators that put in enough current to drive the gate input capacitance fast enough for slow switching rates of > 1kHz to prevent flicker at PWM dimming .

If I chose a 12V PC PSU with enough Amps and chose each RGB string to be greater than 10~11.5V for max. Efficiency

Should be easy to design an Aluminum clad PCB heatsink with 1.5" muffin fan 6mΩ * 19²A=2.2W each.

 

[stuee]

So keep the same mosfets and just make a heatsink for them? Or change them to???.

Thanks

 

[Tony Stewart]

what switching rate , LEDs and PSU are you using?

It all depends on these and your ability to make any necessary changes.

Also what dimming functions are you planning?

 

[stuee]

The Led strips are 4x 5m strips all joined daisy chained to eachother

Specifications:
LED Type: 5050 PLCC-2 SMT SMD LED
LED Quantity: 300 leds/5 Meter or 60 leds/Meter
Color:RGB
Working Input Voltage: DC12V
Working Current: ≤6A /5 Meter
Power Consumption: ≤72W /5 Meter
Protection Rank: IP65(Silicone Tube Enclosure)
Drive Mode:Constant Voltage

And the PSU is 230v -50hz- 4a >>>>> +12v1 22A / +12v2 20A (Computer PSU)

 

[ChrisP58]

My first thought was that it could be as simple as changing the mosfets, but to make sure I understood the parameters that they operated under, I tried reverse engineering the schematic.

But now I'm a bit confused. My best guess of the schematic shows that, if the resistor values are correct, it shouldn't work at all.

I see the three optocouplers.
I see three 2K resistors that I assume are the current limit resistors for the opto LEDs
I see three more 2K resistors that i would guess are in series from the opto outputs to the gates,
And then I see three more resistors of two different values. Two 75 ohm and one 200 ohm. For three identical circuits I would have expected those three parts to be the same.

But, if these last three parts are the gate-source pulldown resisors, I don't see how anything would work.

12 volts through 2K into a 200 ohm load would deliver only about one volt to the gate which is half what it would take to start to turn it on, let alone run it to saturation. For the two with 75 ohms, the gate-source voltage is only 0.43Volts.

Can you doublecheck the resistor values? Better yet, can you draw a schematic that matches the hardware?

 

[Tony Stewart]

The Led strips are 4x 5m strips all joined daisy chained to eachother

Specifications:
LED Type: 5050 PLCC-2 SMT SMD LED
LED Quantity: 300 leds/5 Meter or 60 leds/Meter
Color:RGB
Working Input Voltage: DC12V
Working Current: ≤6A /5 Meter
Power Consumption: ≤72W /5 Meter
Protection Rank: IP65(Silicone Tube Enclosure)
Drive Mode:Constant Voltage

And the PSU is 230v -50hz- 4a >>>>> +12v1 22A / +12v2 20A (Computer PSU)

Sorry Stuee but you can't string these in series. The first tracks will glow hotter than the LEDs and the last LED's will be dimmer than the first. . You'll have to feed power another way. (e.g. radial or with AWG 16 or loop.

How do you change colors? Just a switch? R or G or B?

( the board layout makes perfect sense to me but the name is fake.. It doesn't amplify anything. It is a 6 milliohm switch that when toggles fast in PWM can dim the LEDs 12A max with present layout, 24A max with a more expensive metal clad board. )

 

[discostuee]

Thanks again for all the input.
Ive taken into consideration you comments and decided im going to split it up (its basically going around my floor arer.

On stretch will be 18m and the other 9m.
the remote i was using was **broken link removed**
I was going to put the controller on on end and the apmlifier inline about halfway.
Can you tell me what the smaller 4dil chips are as i might redraw this and make a second one with a heatsink and smaller casing as this is pretty big and bulky. then i can use one on each run.

thanks

 

[discostuee]

Haha, i just realised, my account at work has a different to my home computer, not sure how that happened ??

 

[discostuee]

So?? any idea what the optoisolators are so i can make another one of these

 

[ChrisP58]

So?? any idea what the optoisolators are so i can make another one of these

What markings are there on the parts themselves?

There are many different opto's that could be used. The final choice will depend somewhat on the components around them. Draw up and post an accurate schematic of what you do know. From there it will be easier to match the opto to the needs of the circuit.

 

[discostuee]

their is only markings on the ones ive listed in the photos at the start.

 

[ChrisP58]

Your original unit was rated for 12 amps total, so each of the three channels would be good for 4 amps.

You said you wanted to increase the current to 19 amps.
Is that 19 amps total? (3 channels of 6.5 amps)
Or do you want 3 channels of 19 amps each? (57 amps total)

 

[stuee]

19A total so 6.5a per chan or higher.
thanks