How to convert AK-LED-DRIVER module to default to OFF?

Support
#1

Hi there!

I bought a couple of AK-LED-DRIVER modules. Their default behavior is ON when CTRL is left unconnected/floating. How would I go about converting these to default to OFF?

My first thought was to simply solder a 10K resistor as a pull-down between CTRL and GND. But then what about the internal pull-up that’s already present? Would they interfere somehow? My electronics knowledge is rather limited, unfortunately (software guy dabbling in hardware design from time to time). So, any help would be greatly appreciated!

Thanks!

#2

Hello @Gerald,

The CTRL pin is basically for controlling the LED dimming with a microcontroller (using PWM) or as an ON/OFF toggle. If you fix the pin to ground (directly or via pull-down) you won’t be able to turn the LED back on.

More info about the CTRL pin here.

#3

Thanks for getting back to me, Ivan.

So there seems to be no way to override the default behavior, then? My intention here was to provide a safety mechanism of sorts for my application. I use 12 36W LEDs, where only one of them will be powered at a time. Having all 12 powered at the same time would overload the power source. But this is exactly what would happen in case the MCU is disconnected (plugged connection) and all CTRL lines are left floating.

I had a look at the data sheet of the driver chip. It uses an internal pull-up on Vset/CTRL. Hence my suspicion that I can’t treat CTRL as I would a simple logic line and add a pull-down to define its default behavior.

Do you perhaps see another way? Any pointers would be appreciated.

#4

BTW, two of the 13 modules I bought seem to be broken. LED- and GND are directly connected. I only noticed after I had soldered all wires and checked for continuity with a multimeter. So technically I can’t be sure that I didn’t cause the damage myself somehow, although I never applied power to the modules.

I’m asking in hopes that this is a known issue and that the two modules can possibly be saved by checking/replacing components, before I go and order replacements.

#5

We don’t have cases of failed boards so far. We test them with a real HBLED before shipping. Did you tried to turn them on to see what happens?

Regarding the pull-down, you can try with a 10K resistor. In case it’s too much for your microcontroller (which it shouldn’t) another solution could be to use a MOSFET.

#6

Thanks for taking the time, Ivan.

I forgot to mention, CTRL is also shorted to ground on both modules. So, no. I haven’t tried to power them up in their current state. Especially not with one of the rather expensive LEDs connected.

I think I’ll better just order replacements and hope they’ll arrive in time…

#7

Dang, I just went to your shop and saw the modules are out of stock! Please tell me this is temporary and you’ll get new ones in soon.

I would appreciate a fast response, in case I have to look for an alternative. Thank you!

#8

Hello @Gerald,

Yes. It’s temporary as we already have a new batch. I’m told they will be available tomorrow or the next day.