A bit of a one off question about accurate voltage readings.  Ultimately, the goal is to get proper voltage indications so I know when the battery is getting too low.

The setup is such that I have a 2S (7V) lipo connected to a 12V step-up regulator feeding to an OSD device that gives me telemetry as well as voltage readings.

My question is as the voltage drops on the lipo, would I expect to see a linear drop in the 12V reading in the OSD?  I know Pololu regs are known to keep their voltage true so my concern is if the reg will compensate for the voltage drop and try to keep 12V for as long as possible before slowing dropping.  In this case it is not linear.  Put another way, I would see a precipitous drop in voltage at the very tail end of the battery life.

Pololu makes a few different models. The one I just looked at has a minimum voltage of 2.5V which means it will output 12V until your lipo is down to under 2.5V ( not good ) I think you will need a way to monitor your lipo voltage too.

Scott

Thanks Scott this is what I suspected. Oh man this is gonna get tricky lol.

It is pretty easy. If you have lipo with balance port, you can just plug this into the port. It automatically goes off when the voltage is below 3.3V per cell.

https://www.amazon.com/Battery-Monitor-V...B013U1CP08

Thanks voodoo. For this particular application though I really want the voltage reading to go through to the OSD.

Yes, that it is one of the characteristics of a voltage regulator. It will give you either a constant voltage output of a preset value, or no voltage at all. Which means it's either on (at the preset voltage) or off (at zero voltage).

What is the reason that you cannot just connect a LiPo to the OSD device? Does it require a constant 12V supply?

(26-Sep-2019, 07:34 PM)SnowLeopardFPV Wrote: What is the reason that you cannot just connect a LiPo to the OSD device? Does it require a constant 12V supply?

Funny you ask.

You can connect the 2S to the Tarot OSD.

Lol thanks Voodoo. It was the vtx throwing me off with its 7-24V rating. To stay on the safe side, I figured I would send stepped up 12V to the Tarot which in turn feeds the GPS at its own regulated 5V but the camera and VTX at VCC. What I wanted to avoid was connecting the 2S to the OSD but having only the signal wires going from the OSD to both the camera and VTX while power for them was coming from a separate 12V step-up. Basically it's just an issue of cable management and my OCD is pretty strong lol.

For now, I think I will just keep it simple and 2S to everything. The camera can handle as low as 5V. So the only thing between the OSD system and the lipo will be a cap for noise mitigation. (Is there even noise in a RC car?? lol no idea.)

(26-Sep-2019, 10:01 PM)the.ronin Wrote: So the only thing between the OSD system and the lipo will be a cap for noise mitigation.  (Is there even noise in a RC car??  lol no idea.)

If it's got motors (which I guess it has ) then there will be some element of noise, yes. You may not need a cap though. Either fit one for peace of mind, or just suck it and see