Boeeerb/PiGlow

Hearing a strange noise

Opened this issue · 7 comments

mopby commented

Hello,
thanks for your PiGlow Python Script :) Works like a charm.

I noticed a beep sound (like a high frequency humming) which gets stronger and louder as the brightness increases. Is it normal? Or is my PiGlow broken?

I deattached it and the sound was gone. Also, when i don't run anything so the led are off theres no noise.

BTW: Its a Raspberry Pi 2

Thanks in advance,
Manu

electronicsguy commented

I also hear that HF noise, with piglow on my Raspberry Pi B+. I don't know what the source is but my guess is its from the PWM used to control the LED brightness. People report a similar effect running LEDs with the Arduino: http://forum.arduino.cc/index.php?topic=272158.0

mopby commented

interestingly the sound disappears when using "node-piglow" with node.js
even dimming and max. brightness doesn't cause that hf noise

electronicsguy commented

How did you use it with node.js? Can you point to any references? Thanks.

mopby commented

I used the node-piglow from manuel ernst (link is at the official pimoroni site of piglow)

i got my piglow changed from the company i bougt but the strange hf noise continues

electronicsguy commented

Thanks for the link. wrt. the noise, its not a defect in the board per se, but an artefact of PWM. so the fact that it continues means both boards are working well :)

electronicsguy commented

@mopby FYI: here's a link which explains in detail, the source of the PWM induced noise: allaboutcircuits. "Piezoelectric effects" and "Magnetostriction". Enjoy :)

This discussion has some info as well: SE

wisq commented

Came across this GH issue while discussing a similar noise with some colleagues. If it's of any use to illustrate this issue, here's a video I took of an "ISS Above" (http://www.issabove.com/) device lighting up its LEDs to indicate that the International Space Station is currently overhead: https://www.youtube.com/watch?v=mACahTYARTI

I have no idea if the ISS Above is using this particular Python script or not. While I've hacked mine for SSH access, I haven't looked deeply into its code; it's mainly sold as a complete hands-off product. So (for now) this is purely an informational addendum to this GH issue.