[SOLVED] How to read battery current - help needed

[Alkeshwr]

Hello......how can I read battery current in ma using pic 16f877a?

 

[jayanth.devarayanadurga]

Amplify current using op-amp and then feed it to adc.

 

[Alkeshwr]

But adc just reads the voltage....

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is there any formula to convert voltage into current?

 

[tpetar]

Hello......how can I read battery current in ma using pic 16f877a?

You didnt specify which battery, what type, answer can be different.

For battery best is to use Hall sensor to eliminate power waste on current shunt (current shunt as secondoption).

 

[Alkeshwr]

li ion 18650 cell....

 

[tpetar]

But adc just reads the voltage....
is there any formula to convert voltage into current?

In both cases you measure voltage. If you use current shunt for measuring you should use OpAmp to amp voltage from mV range 50mV-100mV to 0V-4,5V (5V). In uC software you make calc that showing digit on display means amperage.

 

[Alkeshwr]

Ratings:4.2v, 2000mah

 

[tpetar]

Then you can use Hall sensor as ACS712-05 for up to 5A or I suggest ACS712-20 for up to 20A.

That Hall sensor request passing current through his body on dedicated pins.

See project example:

Part1
https://embedded-lab.com/blog/?p=4469

Part 2
https://embedded-lab.com/blog/?p=4529

 

[jayanth.devarayanadurga]

The load at the op amp output will give some proportional voltage for input current. That voltage should be in the range of 0v to 5v for adc input. So you are giving dc volt as adc input.

actual current is 2 mA. Op-amp o/p is 2V, say. adc vref+ is 5v. So, adc max value is 1023 for 5v but the voltage is 2v.
for 2v adc input adc reading is 409.2

409.2 represents 2v and also 2 mA

(409.2 * 5) / 1023 = 2. It can be either 2V or 2 mA.

You can use this also. http://www.nex-robotics.com/products/sensors/acs709-37-5amp-hall-effect-current-sensor-module.html

 

[Alkeshwr]

where should i connect the +ve input of op amp?

 

[jayanth.devarayanadurga]

See my last post. You can use that sensor.

 

[Alkeshwr]

I got it! Thanks...

 

[jayanth.devarayanadurga]

You can read these. http://electronics.stackexchange.c...sor-output-voltage-cannot-be-read-by-arduino
https://www.ti.com/lit/an/slyt173/slyt173.pdf
https://www.ti.com/lit/an/sloa098/sloa098.pdf

 

[Alkeshwr]

but guys for shaunt resistor and opamp methords, the amperage and voltage must be in proportion like.....4volts and 4 amperes.....what should i do if my batteries are of 4.2v and can pump out 3c current?

 

[tpetar]

Shunt resistor will waste battery power, I suggest usage of Hall sensor, but its your project. Why not to try, maybe you have "Die hard" mark of battery. ;-)

 

[Alkeshwr]

Can u guide me how to use hall sensors?

 

[tpetar]

Can u guide me how to use hall sensors?

Read post #8



Also you can see simple 3-digit LED current metter with cheap ACS712.

https://coolcircuit.com/project/digital_amp_meter/picmicro_digital_amp_meter.html
https://electro-hobby.ucoz.com/blog/3_digits_digital_ammeter/2012-01-05-130

;-)