Finn4d ago

Probably I have fixed an issue with my Heltec V4 Meshtastic node - sometimes it was rebooting randomly, often while sending a message or doing a traceroute.

I assumed it was because of a voltage drop while transmitting, maybe the BMS undervoltage protection board adds some current limitation or the cables to the battery are too long and thin. At least I have read somewhere something like that could be a reason.

Grabbed my box for electronic components, found a 470 µF capacitor and soldered it between the Heltec board and the power switch.

Until now: No sudden reboots anymore!

#Meshtastic

Show threadBruno PY2TOZ

@finn What a coincidence! I'm trying to tackle this very issue right now. My #heltecv4 reboots on TX if the battery is under 3.7V and power is set to 22 dBm+.

I tried to insert a 1000uF cap just like you did, but it didn't work. I measured the voltage sag and it takes way longer to recover to baseline, whereas the capacitor can handle it just for a fraction of a second.

I wonder what I'm doing wrong... My temp solution was reducing TX power, which negates the only advantage of having a V4 😮‍💨

Mar 18 at 12:43amWeb
Show threadFinn3d ago

@py2toz Oh, that sounds bad, I don't have any idea for this. I guess I was lucky, added the capacitor and it worked.

Also I didn't mease anything. A multimeter probably is too slow, right? How did you measure the voltage drop?

Show threadBruno PY2TOZ3d ago

@finn Yes, multimeters are usually slow. I'm using a bench power supply whose ampmeter is a bit faster. But maybe (certainly) an oscilloscope would be more appropriate.

I'll try another capacitor when I have the chance. Maybe I was just unlucky (or my Heltec unit has an entirely different issue 😅).

Show threadDaniel3d ago

@py2toz @finn Maybe interesting to you: the heltec v4 have a non linear relationship between power consumption and tx power:

https://chaos.social/@djh/116186281960690673

Daniel (@[email protected])

Interesting tx power measurements for #HeltecV4 on #MeshCore 🔋 Summary: Set tx to 10-17 dBm; bigger tx values increases power consumption by a lot for very little benefit: https://github.com/meshcore-dev/MeshCore/issues/1708 That plus powersaving changes in v1.13 and now v1.14 will make these devices viable solar powered repeaters 😍

chaos.social
Show threadBruno PY2TOZ3d ago
@djh @finn Oh, that changes everything. This is excellent info! I assume that MeshCore's TX settings mentioned in the thread are in dBm (and not an arbitrary unit), right?
Show threadDaniel3d ago

@py2toz @finn I'm not an expert on this, what I'm doing is

set tx 17

for my experimental heltec v4 repeater via the serial command line interface.

I believe I read that the heltec v4 has an amplifier that gets applied on top of what you set as tx. But again best to double check this, I'm pretty new to this 🙏