KA08 - Relays not switching


Did anyone get the KA08 board working (this board is similar to the KA05 board, but designed for the Arduino Yun: velleman.eu/products/view/?id=420276 )?

The KA05 works great with an Arduino Uno, but I can’t get the KA08 version running with an Arduino Yun. I think the jumper is set correctly (using the middle pin and PWR pin), and 2 power supplies are used (5V for the Yun and 12V for the KA08 board itself).
The output indicator leds blink correctly when testing the example project for the KA08, but the relays are not switching. I can only hear a very silent ‘click’, much more silent compared to switching relays on the KA05 board. It looks like the relays try to switch, but don’t have enough power to do so.

When looking at the schematics provided in the KA08 manual, I don’t see how the relays could get their required 12 volts from the board: they are connected to the voltage regulator, which always outputs 5V to the relays? Or am I misreading the schematics?

Kind regards,

You are correct about the schematics, we will post an updated schematic soon.
However, the shield should work if it receives 12VDC.
Can you check the voltage across the relay coils?

The strange thing is that the pcb seems to be according to the schematics, as far as I can tell. If I measure the voltage across the relay coils, I get a voltage of around 4.95V (when activating the output and using a 12V power supply for the shield)

We’ll assemble a sample and check. Thanks for reporting this. Stay tuned.

Can you please check your PCB version, is it '1 or '2 ?


Thanks for looking into this!

It’s version PKA08’2 of the pcb


To our valued customers:

It looks like some KA08 kits have been shipped with 12V instead of 5V relays, most likely due to human error.
People that have received the wrong relays can send us a ticket and we’ll make sure you’ll receive the correct parts asap.

Please keep the 12V relays for future projects, no need to return them.
We do apologize for this inconvenience.

Okay, thanks! I’ve created a corresponding support ticket