20 Watt led control

Hi!

I'm using this schematic with 20 watt rgb led.(in picture there is 3 different leds.) Power is going from 2 x 12 V lit-ion battery packs. Led voltage and current is set up with DC-DC Step-down Adjustable. For red color it is set up to 14 V, 300 mA, for green and blue 20 V, 300 mA. 5 V is from DC-DC step down 5 V 3 А module. Mosfets is N channel IRF3205PBF. Gate and source resistor is 10k, gate to Arduino is 100 Om. Buttons is used in pull up mode. Potentiometer is 10 k.

So my question is why Arduino burns down after some time off work? Microcontroller is going hot and that's all.

Picture with connections is here: Schematic!!! Connections is as in to picture!

So my question is why Arduino burns down after some time off work

You need a constant current supply not a constant voltage supply. The forward voltage on an LED changes with temperature and the longer it is on the hotter it will get.


Not obvious here whey the Arduino itself would overheat if it is being supplied correctly with 5 V and all the grounds are common, but definitely unhealthy for the LEDs.

I'd increase gate resistors value to 220 Ohm. If that mosfets fed by PWM average current through control pins can be too high with 100 Ohm resistors.

Grumpy_Mike:
You need a constant current supply not a constant voltage supply. The forward voltage on an LED changes with temperature and the longer it is on the hotter it will get.

Blue ones is constant current supply! It is set up to 300 mA!

Paul__B:

Not obvious here whey the Arduino itself would overheat if it is being supplied correctly with 5 V and all the grounds are common, but definitely unhealthy for the LEDs.

Maybe better solution is use 6 V in to Vin pin? All grounds are common. What is unhealthy for LEDs?

alesam:
I'd increase gate resistors value to 220 Ohm. If that mosfets fed by PWM average current through control pins can be too high with 100 Ohm resistors.

Yes! I think this can be reason too!

heninsh:
Blue ones is constant current supply! It is set up to 300 mA!

So what exactly are the blue ones? Can you please supply a link.

For red color it is set up to 14 V, 300 mA

If it was constant current you would not set it up for 14V.

So my question is why Arduino burns down after some time off work?

Can you be a bit more specific about the wording please.
What burns up? Things do not burn down that is only something that applies to buildings.
Do you mean “after some time of working”?

Does anything get hot?

heninsh:
Blue ones is constant current supply! It is set up to 300 mA!

The description of the blue ones doesn’t exactly inspire you with confidence, it says

  1. The Fixed turn the lamp current to 0.1 times the value of the constant current (at the when 2 identify been the 'is full);

Have you configured it for constant current? The problem with then turning the load on and off is that the voltage shoots up when it is off, causing voltage spikes that have to die down when it turns on. I don’t think that board is designed to be switched like you are doing.

For red color it is set up to 14 V, 300 mA

If it was constant current you would not set it up for 14V.

So my question is why Arduino burns down after some time off work?

Can you be a bit more specific about the wording please.
What burns up? Things do not burn down that is only something that applies to buildings.
Do you mean “after some time of working”?

Does anything get hot?

Weird setup (wrong parts).

You should have used something like this.
This module can drive, and PWM, your 20watt 18watt COB LED directly.

Make sure you have a large enough heatsink on the LED.
Leo..

heninsh:
Maybe better solution is use 6 V in to Vin pin?

Very bad idea! The "Vin" pin should be completely avoided in all "real world" projects.

heninsh:
What is unhealthy for LEDs?

Being driven at a constant voltage instead of a constant current.

To be clearer on what Mike is saying, almost all "constant current" supplies actually have a capacitor across the output, necessary to maintain stability of the regulator circuit. This means that they cannot actually "track" rapid variations in the load; of course a set of LEDs does not vary as a load so this does not matter.

However, if you arrange - with your FET - to rapidly switch the load on and off, then each time the load is switched off, the constant current charges the capacitor to a progressively higher voltage, and when it is switched on again, the applied voltage is much higher resulting in a burst of a much higher current until the capacitor discharges sufficiently. This is clearly extremely unhealthy for the LEDs.

Grumpy_Mike:
Have you configured it for constant current?
The problem with then turning the load on and off is that the voltage shoots up when it is off, causing voltage spikes that have to die down when it turns on. I don’t think that board is designed to be switched like you are doing.
If it was constant current you would not set it up for 14V.
Can you be a bit more specific about the wording please.
What burns up? Things do not burn down that is only something that applies to buildings.
Do you mean “after some time of working”?

Does anything get hot?

There is option to set up current with potentiometer!
For red color voltage is 12-14 V!
After few minutes of work, arduino microcontroller gets hot and nothing work. Arduino is burn!

Wawa:
Weird setup (wrong parts).

You should have used something like this.
This module can drive, and PWM, your 20watt 18watt COB LED directly.

Make sure you have a large enough heatsink on the LED.
Leo..

Thank You for info! I have large enough heatsink for LED.

Disconnect D3, D5 and D6 from the Nano to see if it still has its overheating problem.
If so, suspect the potentiometer is wired incorrectly causing a high load across the power rails at an end of scale position and thus warming up its Schottky diode.

Thank You all! All works as expected! So ehat I did:

  1. Decrease voltage and current for red color from 14 V 330 mA to 12.5 V 300 mA. For green and blue from 20 V 330 mA to 18.5 V and 300 mA.

  2. Changed 100 Om resistors to 220 Om.

  3. Changed 24 V to 5 V DC-DC to new one.

  4. Changed heat sink to biggest!

Where was problem I don't know, but all work!

Well, it remains that you are using the wrong components to current control LEDs, so all we can say is - don't be terribly surprised if you encounter future problems. :roll_eyes: