A Simple Programmable Electronic Load Using the Arduino

Arduino Electronic Load

Some projects are both educational and useful. We believe that [Jasper's] Arduino based electronic load is one of those project.

[Jasper's] electronic load can not only act as a constant current load, but also as a constant power and constant resistive load as well. The versatile device has been designed for up to 30V, 5A, and 15W. It was based on a constant current source that is controlled by a DAC hooked up to the Arduino. By measuring both the resulting voltage and current of the load, the system can dynamically adapt to achieve constancy. While we have seen other Arduino based constant loads before, [Jasper's] is very simple and straight forward compartively. [Jasper] also includes both the schematic and Arduino code, making it very easy to reproduce.

There are tons of uses for a voltage controlled current source, and this project is a great way to get started with building one. It is an especially great project for putting together your knowledge of MOSFET theory and opamp theory!

An Arduino Programmable Load

load

Having a big block of hot to dump current into is a very useful thing to have if you’re testing batteries, power supplies, high power LEDs, electroplating, or any thing else that would normally require a huge resistor. [Jakub] found himself in need of an electronic load, and instead of a transistor and a pot, decided to make something more automatic: a programmable load built around an Arduino shield.

The idea behind this load is pretty simple: connect a device to a FET and shunt resistor to measure current. Drive the gate of the FET with an op-amp that maintains either constant current or constant voltage. Control everything with a DAC, and you have a programmable load controlled by an Arduino.

With such a small form factor, getting rid of all that heat was bound to be a problem. For this, [Jakub] is using a 50×50 mm BGA style heat sink with a 5V fan. If it’s good enough for a big CPU, it should be able to handle dumping 70 Watts into a FET. There’s also a conservative application of thermal paste and a very small thermistor underneath the FET that’s able to be read by the Arduino. It might slowly heat up your room, but it’s not going to catch fire.

With the Arduino sketches [Jakub] wrote for his load he was able to characterize a pair of Idea batteries and figure out how much charge a three-year-old recyclable battery had. It’s a great piece of work, and if [Jakub] is willing to go through the hassle of a Kickstarter, it would make a fine crowdfunded product.

Building a DC Constant Current/Power Electric Load

By just looking at the picture above, we’re pretty sure that most Hackaday readers will have guessed by now that much power can be dissipated by this electric load. For those who don’t know, an electric load (or dummy load) is a device used to simulate a load on a system for testing purposes. This is quite handy when measuring battery capacities or testing power supplies.

The heart of the device that [Kerry] designed is based on 6 power MOSFETs, a few operational amplifiers and an Arduino compatible ATmega328p microcontroller. Sense resistors are used to measure how much current is passing through the MOSFETs (and therefore the load), the MCP4921 Digital to Analog Converter (DAC) from microchip is used to set the current command, and the load’s voltage is measured by the ATmega ADC. Measuring the latter allows a constant power load mode (as power = current * voltage). In his article, [Kerry] shows that he can simulate a load of up to 200W.

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