Proton BASIC Community

HI everyone how to use shunt resistor in proton i am working on CT transformer but i don't know how to shunt CT volts is (+) and shunt volts is (-) ,

Have a look at this:

https://www.electronics-tutorials.ws/transformer/current-transformer.html

Charlie

Quote from: charliecoutas on Sep 07, 2025, 07:23 PMHave a look at this:

https://www.electronics-tutorials.ws/transformer/current-transformer.html

Charlie

Hi I'm measure DC Amps with using shunt resistor
Without using any IC
Using 16f684

OK, so you are not working on a C.T. that's for AC.

What is the value of your shunt resistor and the maximum current that you are measuring?

Commercial shunt resistors usually have an output of 60mV or 75mV at the rated current so you will need to amplify the output to bring it up to a level suitable for use with a PIC. 

The 16F684 does not have an internal reference voltage so you will need to amplify the input closer to 5 volts.  I would suggest using a different PIC that has an internal voltage reference for the AtoD converter which will allow you to use a lower input voltage. possibly 1.024 volts.

If you are using your own resistor you will need to calculate the resistor value to give the correct input voltage at the maximum expected current which ideally would be 5 volts for your 16F684.  Then calculate the resistor wattage

Quote from: See_Mos on Sep 08, 2025, 01:57 PMOK, so you are not working on a C.T. that's for AC.

What is the value of your shunt resistor and the maximum current that you are measuring?

Commercial shunt resistors usually have an output of 60mV or 75mV at the rated current so you will need to amplify the output to bring it up to a level suitable for use with a PIC. 

The 16F684 does not have an internal reference voltage so you will need to amplify the input closer to 5 volts.  I would suggest using a different PIC that has an internal voltage reference for the AtoD converter which will allow you to use a lower input voltage. possibly 1.024 volts.

If you are using your own resistor you will need to calculate the resistor value to give the correct input voltage at the maximum expected current which ideally would be 5 volts for your 16F684.  Then calculate the resistor wattage

Hello sir 0.05 ohm
12v 20amps maximum

Abdullah why don't you look at using a INA190 if possible as it will make your life a lot simpler.

So that is 1 volt and 1 watt at 20 amps.

 you could change to a different PIC that has internal voltage reference and set it to 1.024 volts.

Using an operational amplifier in differential mode would be a better way and you could use the 16F684

Quote from: Craig on Sep 09, 2025, 08:27 AMINA190

Sir this not available in Pakistan

Whenever I have needed to measure currents, small or large. I have used the old, and reliable, method of a tiny valued shunt resistor, and an op-amp to amplify the voltage on it. Then this gets transferred to an ADC input.

If a base 10 resistance and amplication is used, the calculation for converting the voltage to current is very simple. So I always use a 0.01 Ohm, or 0.1 Ohm, or 1 Ohm resistor (depending on how high a current is being measured), and a base 10 amplification. The smaller the resistor, the less wattage required to get through it, so it will not get too hot. But it also needs more amplification from the op-amp. However they are so simple to build and use and alter if required, they are almost perfect. Unless absolute accuracy is required, just use standard 1% to 5% resistors, because the dedicate current shunting resistors are absolutely crazy prices for what they actually are. i.e. A resistor!

There are several methods of wiring the resistor to the op-amp, depending on if the current is being measured high-side or low-side, but they are all straightforward. My favourite method is low-side and a non-inverting op-amp, amplifying the tiny voltage across the low resistance resistor. To keep the resistor a bit cooler, a small fan is very effective.

I have used some of the standard INxxx devices for measuring current, and they are very good, but their method is very much the same, with a shunt resistor, either internally junctioned or an external resistor, and what comes out the device is a value per-unit of current, via I2C.

I've also used MOSFETs as current loads, but I have found that they are not as reliable over time, and MOSFETS have a tendency to go crazy and destroy themselves for the slightest reason. i.e. Switch them on too fast with some current load on them, and they go pop, do not give the gate enough ooomphhh and they go pop, go slightly over current and they go pop! Just three of the things that always make me suspicious of MOSFETs. So unless you know MOSFETs inside out, I would stick with a resistor and an op-amp. Very reliable.