Buzzer and TTGO

[tecnatron]

TTGO
Regardless of whether the active buzzer (buzzer) works or not or whether or not it blocks the operation of the firmware, insert a 47uF / 25 VL electrolytic capacitor on the audio-buzzer output of the TTGO.

The capacitor serves to separate the direct voltage, which is necessarily present since the driving signal is a square wave at about 1000 Hz, with a non-zero average value. DC voltage tends to short to ground if not separated by a capacitor. This explains why reception is "blocked". In some cases it "holds", in others the power supply tends to short. It can be seen by seeing how the power indicator light dims, for example. If so, take an oscilloscope measurement.
Once this is done, if the firmware lock problem persists, move the buzzer a little to another position, farther away from the microcontroller board.

[PE1PSI]

Hi. Does the capacitor need to be in series with the buzzer?

Since recently I found that MySondy Go is behaving off when the buzzer is on. It is pretty deaf. Ik does not seem to decode properly en does not send location updates to the app. As soon as I turn the buzzer off, the issue is gone. It seems your suggestion may solve this.

Thanks,
Dave

[IZ4PNN]

Hi Dave,
yes the capacitor need to be in series.
It also appears that higher impedance buzzers do not create this problem.

[tecnatron]

Good morning, Dave.

Communicate, here, the results of your tests, thanks.

[PE1PSI]

I had added a capacitor of 47nF (not 47uF) and the buzzer still made sound. It was a bit quiet though and therefore I went to 100nF. I was convinced the issue should have been solved and I tested it to find that I still had the same issue. Then I removed the buzzer and tested it on 5v. It only made a little tick/plop sound. So it means this is a passive type. I exchanged it for a different one that is also passive and I have the same issue.

When turning the buzzer off via the app, the device receives really good. When the buzzer is active, the device turns deaf. A strong signal is still decoded. And on weak signals it still shows a s-meter reading while not decoding.

I'm not sure what is causing the issue. Is it the power that it takes and therefore gives power issues for the rest of the board? Or may it be harmonics?

Any other idea's on what to try? Maybe a resistor instead of capacitor? Any suggestions on a value?

[IZ4PNN]

Hi, this depends on the brand of buzzer you use.
Many buzzers do not create any problems.
I use the buzzer without capacitor.
I can only advise you to do some tests.

[PE1PSI]

I tried a few different buzzers with capacitor and finally with a resistor. It now works like 95% perfect. I do find that when receiving the first frames it will often beep but not decode and not show a GPS location. I think when the buzzer is off it will decode just fine when the LED blinks.

For me this is fine. As soon as the signal gets just a little stronger it decodes perfectly. After tuning the antenna and tuning in the app I receive way over 100KM which is way more than needed.

Thanks for all the work done to make this possible for us all.

[Thierry50]

good evening, you used passive buzzer, for me no problem with this buzzer