Measuring current
From Open renewables
I've been looking for something that we can easily use on breadboards for prototyping and for the DIYer, which means surface mount is out of the picture. Unfortunately a lot of the pre packaged solutions are surface mount.
There are a few different ways of doing this, including:
measuring voltage drop over a "shunt" resistor
Use a very low resistance (5mOhm or so) in series with the incoming voltage. We measure the voltage drop over the small resistor.
There are custom amplifiers for this, but they seem to be mostly surface mount:
- Linear's 6100
- maxim 4173 as used by Tim Nolan's ppt solar charger
We can also do this with through hole devices, but we need more components. Here is a circuit using 3 opamps, with a pic. Thanks to DocJC!
pros:
- simple,
- easy to DIY,
- low cost: £1 per current sensor.
cons:
- lose a small amount of power due to the shunt resistor (at 15Amps, voltage drop on a 0.005Ohm resistor = 0.075V, so power loss is 1.125W. At 12V input this is a 0.6% loss in power).
using a Hall effect IC to measure the magnetic field caused by a current
Read more information about the Hall effect. They usually come with an onboard controller that gives a nice output that we can plug straight into a micro controller. For example:
pros:
- low power loss,
- easy to use
cons:
- expensive (at least £6 per current sensor)
