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Topic: INA219 measuring same power supply. (Read 163 times) previous topic - next topic

MrBodger

Apr 14, 2019, 09:43 pm Last Edit: Apr 15, 2019, 08:20 am by MrBodger
Back to tinkering after a bit of a break.  :)


I wish to measure a vehicles 12v battery remotely, built the arduino uno and HC-05 06?
(oops changed the devices name, silly me)   :)

So i have it all working, swapped the uno for a pro mini and its now running at 26mA
whilst sending data from a 12v battery.  Does power change with distance from sender
to receiver?

Arduino powered through an LM2596. I could probably reduce this but maybe not needed?


I have noticed it reads approx 0.5v too low, but the amps reading is spot on. This maybe down
to the INA219 being a cheap one? First one i could get posted quickly to see if it will do what
I need.

Not yet tested as the voltage drops to see if it stays at 0.5v or varies, I can get a better
INA219 later or add some calibration to it.


My question.  What are the downsides to using the 12v supply to power the arduino and take readings
on the INA219 at the same time?


Thanks in advance   :)


MrBodger

Wrong section or answered too many times already?

Thanks  :)


MorganS

It is hard to find the actual question you are asking. The best way I can answer your final question is "If what you have works, don't change it."

Can you draw a schematic? A pencil sketch photographed with a phone is actually preferable to the popular online service starting with "F".

Can you post your code?
"The problem is in the code you didn't post."

MrBodger

#3
Apr 16, 2019, 11:31 pm Last Edit: Apr 16, 2019, 11:32 pm by MrBodger
Its just that most INA219 projects they seem to recommend using batteries to power the
Arduino and not use the actual power source they are monitoring.

Wondering if there is a reason for that, is it because most are measuring smaller power sources
where the load from the Arduino would drain it too much, but where sub 40mA is not an issue
for my 65Ah 12V battery.

Thanks


MorganS

Other way around: the INA219 need 3-5V but measures up to 26V.

You have no shunt in your schematic. You aren't measuring current?
"The problem is in the code you didn't post."

TomGeorge

Everything runs on smoke, let the smoke out, it stops running....

bluejets

You have no shunt in your schematic. You aren't measuring current?
Op is more than likely using an INA219 module of which Vin+ and Vin- are the onboard shunt.

MrBodger

Thanks, currently there is nothing connected to the VIN-. not checking current
just testing the BT distance and the voltage accuracy at present.

But yes as above VIN+ / - is the shunt on board the INA219.

It was 0.5v low using jumper wires for everything. But since soldering the LM2596 on
the 12v in and 5v out that has improved.


Getting some erratic programming issues though, dodgy jumper wires i presume, unless its
a dodgy Pro Mini?


Whilst testing previously I would just remove TX/RC from the BT board and connect that to
my Uno to program. But i was having to remove the Pro-Mini and connect only to the Uno.

Anything else connected caused issues.


No reason not to use the same 12v battery then? 

Thanks  :)


racpi

i'm using one in a pretty similar situation , it reads consistently 0.2v low over the intended input range  . i just add a calibration value to the reading.
i wonder if the cheap modules use out of spec devices and thats why they are so cheap.
richard

bluejets

#9
Apr 19, 2019, 01:35 am Last Edit: Apr 19, 2019, 01:36 am by bluejets
Rather confusing when you state it's an ina219 then something entirely different, then you have 26mA, then further you say nothing connected to the current sensor.
Along with other things one is left trying to decipher the lot but no luck.
A real headshaker and good contender for the "what the....??? " awards.

Best if you want specific help, be more specific.
One start point would be , where are you measuring the so called low voltage and how.

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