Earth Listener power supply

I have built the Earth Listener. It works fine (haven’t tested the lighhtning sensor yet, though).
However, when I replaced the 5V USB power supply by a 6.5 V == power source, I found that the temperature was far too low, and seemingly not changing.
When I went back to USB, it was more or less OK again.
Is the reading of the sensors dependen on the power? 6.5V is within the specs of the Arduino!

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We have test the Earth Listener via an external power supply (6V DC / 1A )
and it works well. The temperature measurement are ok. No to far or low in comparison with USB power supply or USB from PC.

I think Your external power supply does not have enough power. The VM211 consumes 400mA.
What was the power of Your 6,5V power adaptor? If it less than 0,4A (400mA), then this can result in not correct working sensors.

All the sensors are powered with 3V3 via the power converter on sensor board. If voltage to low like 4,8V due (to little power => <400mA). The sensors does not have 3V3 anymore.

Best regards,
Velleman support

My power supply was 6 V 2.1 A, so that’s clearly not the problem.

I also have a few 12V power supplies. I guess the Arduino can handle that as well.

Hi @ jjge,

Have you tried with a 9V power supply or power bank @ 5V 1A?

The Arduino board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable, hence the wrong values from the sensor? If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts.

See info @ Specs and documentation (Power) Arduino Mega ,
under technical specs & documentation.

Velleman Support

May I use this past thread re vm211 power supply to ask if it is better to power it via the usb port with its suppkied usb cable (5.2v 2A) or if i can use the port below (5.5x2.1mm barrel connector) and feed it 9V 2A or 12V 2A?
I have chargers for all options just curious what the vm211 likes best.
So far i have used the usb only, (and indeed I had variable results) as i wasnt sure i could use the barrel port and at which voltages.
Currently i am using a 2A usb charger for huawei phones and working well.
It was previously on a usb hub which provided variable amperes (depending on load) and i have experienced sensors values fluctuations. The hub was delivering around 400 mah, which i believe was the amperes it detected the unit needed (the hub can go up to 2.4A but i have never seen more than 400 on its display when the Vm211 was connected, even using RGB led and RTC clock in it
Many thanks

Hi @Nicdip,

The VM211 accepts 5VDC (min 750mA) via USB cable and both 9V 2A or 12V 2A via the power plug.
However, we do recommend using a USB power supply. That way, you bring 5V directly to the Arduino Mega and you do not need to use the internal power convertor. Using the internal power convertor will dissipate heat to bring the supply voltage down to the necessary 5V.

For example, if you would use a 12V power supply and the VM211 uses 500mA, that’s a heat dissipation of (12V-5V)*0.5A = 3.5W. This will heat up the internal circuits of the Arduino Mega and might as a result give higher temperatures values on the sensor. Via the code, you can alter the fixed offset values to compensate this, see, topic “compensation” at the bottom of the page, but that’s a lot of work if you can just use a USB power supply ;-).


I will keep using the usb 5v then.
Thank you very much