Power on the controller only with the power supply (instead of USB)

Hi there Yaeltex!

I have a question regarding to my external power plug of my Yaeltex controller the ‘Holltesizer v2’.
It powers the LED inside the controller, and also the Yaeltex controller itself.

I noticed when I have everything connected to Ableton (Power Supply and USB), a little touch or wiggle on the external power it will disconnect from Ableton, the controller leds going off and everything will re-connect after a while.

When I unplug the USB and I do the same (wiggle power plug a bit) everything is working fine and the leds are staying on.

Is there some way to fix this? I do think that when the device sees a little drop in power it ask the usb to take over. It got my attention because in the last show I performed, the stage manager touched the power supply a little and then the above happened.

Perhaps the following is the solution, as one of the Yaeltex team members on Instagram message mentioned: ‘the USB is always looking at the power stability to know when to power the unit. Maybe there is a way to avoid that feature, and tell the controller that it can only be powered through the external power supply’.

I do have knowledge of the Arduino files and I already modified some colors, so please let me know if ‘telling the controller that it can only be powered through the external power supply’ would be an option and how to do this in the Arduino code:)

Once again, thank you for helping out!

All the best,

Hello @jeffrey.frugte!

Welcome to the forum!

I see the instagram conversation, and the pictures.

Could you please share with me a schematic or a diagram on how the power supply on the side of the controller is wired to power the LEDs and the controller?

Normally Yaeltex controllers take power from the USB supply.
When an external power supply is detected, there is a hardware circuit that switches to get the power from it.

If the power supply is unstable, it will switch this circuit on and off.

We suggest a 5 Volt / 3 Amp power supply for our controllers, and yours have quite a lot of LEDs (7 x 64 for encoder rings + 128 buttons = 576 LEDs)
So if you added a screen and more LEDs, then we’d suggest you use a bigger power supply, at least 4 amps.

With this draw of current, any instability will make the voltage drop very quickly if there is a disconnect of the power supply, even when the switch is quite fast. And obviously, the USB can’t supply this current while the controller detects the change and switches the brightness to lower the current needed, so the controller will restart.

This is how things are on the hardware side.

Software-wise, we can prevent the controller from starting or operating when the power supply is not connected.

On the file utils.ino there is a routine called ChangeBrigthnessISR() that is triggered whenever there is a change in the power supply (connection or disconnection) and a flag that indicates this change.
As soon as this happens all the LEDs are turned off (the ones that our controller operates) and the controller changes the brightness accordingly.

On the loop.ino then the feedback is shown again as it was before the switch if the flag that indicates the change is high.

This operation can be changed and the flag could indicate whether the power supply is connected, and then the loop cycle could stop operating if it ain’t the case, until it is reconnected.

We can’t be sure this will prevent the controller from restarting though, since like I mentioned earlier, the voltage changes are quite fast and we can’t be sure the software will detect this on time.

Now regarding the controller not starting until there is a power supply present, this can be done on the InitFb() method on feedback.ino. The execution can be held there until the power supply is detected, and when this happens, continue starting the controller.

These are first ideas, we can keep working on them.

Let me know if you need further help on how to implement them.


Hi Franco,

Thank you for your fast response, super helpful.

Please see attached the schematic overview of the Holltesizer with the power supply to the controller and to the leds etc.

I do use a power supply with 5V and 8A in order to get everything working properly. Yaeltex = 3A and the Ledstrip is 2.88A - so it must be enough.

As everything works fine without the usb connected (everything fully bright) I do think that we need to disable power over USB in order to get everything working correctly, so the controller will not rely on the USB power anymore.

So, no start up of the controller board (the Kilowatt), unless the power plug is plugged in.

As I do know how to search and change things in Arduino, I’m not a skilled programmer, so yes any help with the code to get the above workable would be really much appreciated!!

Looking forward, cheers!

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@jeffrey.frugte I see!

Thanks for sharing the diagram with us.

Another idea that came up here, maybe you can try this easily, is to split the power in two, and supply to the LEDs, arduino with screen as a whole, and the controller with a different supply.

As it is now wired, the LEDs consumption might be lowering the voltage of the power supply and making the controller reset.

The problem with the software solution is that if the USB will be connected anyway, the power circuit of the controller will still detect it and take it as a valid supply, then even if we tell the controller to halt or not to start, the switcher circuit will still switch to it when there is an external power drop and the restart will still be inevitable.

This is a guess obviously cause I still haven’t tried the software trick, but splitting the power supply seems like a much safer solution.

If you can try this let us know if it works, otherwise we can follow the software fix path and see where it leads.


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Hi @francoytx,

once again thank you for your reply:)

Yes we will have a look into splitting the power, as for now I lowered the brightness of the leds on power (which I had set on 90, back to 60), and set the maximum output of the leds from 255 to 200 which fixed the ‘problem’ for now.

Maybe I play with those (Yaeltex leds on 70 and LED strip on 170) but for now its working perfectly!

Perhaps in the future we can have a look into a software trick, but no rush at all.

Many thanks, speak soon!