DC converter whistle

Hello, I’m trying out a mini battery module and what surprised me is a high-frequency shriek that’s louder than most my phone adapters. I was wondering if I could modify the device to increase the converter’s frequency into 100+ khz range. I’m a complete amateur in electronics, but I have a soldering iron and I would probably be able to change an SMD cap or two. Any thoughts?

Hello Jiří,
the switching chip is working near the MHz frequencies and this noise is some kind of sub-harmnonic frequency which is created by the inductor, or the the capacitor.
Which firmware on your module do you use? Is the module sleeping or is the MCU running all the time? Is the sound constant or it is audible only few seconds when for example you press the module button?

Do you use new or older batteries? Lower battery voltage means biggger current spikes which can lead also to this noise.

I try to take a look if the noise is created by inductor or capacitor.

I used bigclownlabs/bcf-generic-node-battery-mini:v1.7.1, there is also a lux meter tag connected, but nothing else.
Oddly enough, the noise is gone now. The led is blinking (it didn’t yesterday), and half hour ago it suddenly stopped sending data (it works again after manual reset). I used the batteries that came in the package with the battery module just few days ago (Varta industrial somethings), but I didn’t have the presence of mind to check their voltage when I got them. They are at 0.5V now (measured when powering the running module, out of circuit they are about 0.9V).

When I powered the module back on, it started blinking in a pattern (three short, one long), not sure if it was blinking like that before and I just didn’t notice. Also, while it’s not whistling constantly any more (as it did yesterday), it’s clicking in sync with the led flashes.

Ah, also stopped sending data altogether.

Hello Jiří,
after investigation we’ve discovered that we had a bug in latest battery-modules released binary which was not powering down the Core Module. Also when the module is not sleeping then the DC/DC chip was running constantly and you heard the continuous buzzing noise.

Please update Core Module to the lastest 1.7.2 firmware. If you use dongle, please update also this firmware to 1.7.2 and update the gateway bcg. We’ve fixed some issues with pairing.

Please try it and let us know if the noise issue went away. These high-frequency noises can be eliminated also by our enclosures. You can download and 3D print or buy them in our shop.

Here are some general tips that I’ve written just before I’ve heard about that bug in generic-firmware. I think it is still relevant so I keep that here:

Also the red LED turns on for a second when you first power-up the Core Module. The blinking is probably because the voltage is so low, that the Core Module is randomly reseting in the loop.

The generic-node firmware is created in a way, that the data are send periodically every few minutes, but if the value changes rapidly, then it is send immediately. This works fine for temperature, pressure and humidity, but you’ve mentioned that you also have the luxmeter. It is possible that the illuminance in the place where you put the Core Module was changing very often and has been send wirelessly every few seconds and drain the battery after a shorter time than usual.

If you really want to have running Core Module on batteries as long as possible - the best solution is to create your own firmware based on generic firmware source code and set the period of sending the data to the minimum and maybe disable the code which sends the values immediatelly when they change rapidly.

Thanks for the quick fix.
Just for the record, the light level is constant and changes just about twice a day. I actually had a problem that the messages were sent too far apart, which made the chart display in node red look weird. It’s just there to know whether light is on.

So far, no problem an no noise with the new firmware. Thanks. :slight_smile: