Author Options:

how to make a current meter with microcontrollel PIC 16f877? Answered

i want to make a current meter with microcontroller and LCD 16x2 as display.
what components do i need?
and what is CT?


The forums are retiring in 2021 and are now closed for new topics and comments.

9 years ago

Depending on if the current you are trying to measure is AC or DC, the approach will be somewhat different.

A very common and effective means of measuring current is by using what is called a shunt. A shunt is just a small resistor with a known value. When the current flows through the shunt, there is a voltage drop across it. The shunt needs to be a small resistance value, so that excessive voltage is not dropped across it.

Because the voltage drop is small, it then needs amplifiication to bring it up to a magnitude that will make better use of the input voltage range of the A/D converter in your microprocessor. The type of circuit is often called a differential amplifier, as it amplifies the voltage differnece between its two inputs.

There are resistors made specifically for current measurement, so keep an eye out for those as you search. I've purchased shunts in the 50 to 300 amp range from sources like www.allelectronics.com (surplus) and www.jameco.com.
Shunts and current sense resistors often have separate terminals for the load current and the amplifier connections, for higher accuracy, so use those properly.

There are some good app notes from electronic component manufactures our there on current sensing, so definitely google those during your research.

The processor will then take a reading, convert it from a bindary value into digits (ususally ASCII) that can be displayed on your LCD.

That is a bit of a high level description, hope it helps.