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Arduino dummy load packs great information how things work

Programmable dummy load is great device for testing power supplies, batteries. It is up to you how you want to set load behave – like constant resistance or constant current or constant power. Wigman27 wrote extensive instructable on how he built his own version of dummy load. He used sandard technique that is used in most cases – MOSFET act as variable resistor controlled through op amp. Microcontroller takes care of reading and setting voltages to sustain selected level. Current flow is controlled with BUK954R8 – 60E MOSFET. MOSFET gate is driven by LM324 Op-Amp which accepts DAC (MCP4922) control voltage. Microcontroller reads sense voltage from MCP3204 ADC. There is also a temperature sensor on heatsink which keeps an eye and turns fan if things get hot. Key parameters of load are: max Voltage input – 24V; max load current – 8A; max dissipated power – 50W; min load current – 15mA; load current error – 3mA. Project explanation is really great even for novice. If you are not going to built power load, then material may serve as refreshing… Continue reading

Arduino based programmable load

Programmable electronic loads can be handy in many testing applications. It can be used to test power supplies, batteries or tuning other equipment. Practically speaking building controller based load isn’t that hard. All you need to do is to drive MOSFET at some point. This point can be maintained by reading voltage and current on the load. Jasper have built an Arduino controlled electronic load that can withstand 30V and 5A but max 15W. Transistor Gate is with voltage that is set on MCP4725 I2C DAC. The opamp based circuit takes care of maintaining gate voltage at level so the current would stay at desired level. Current is measured with 0.1ohm current sense resistor. Resistor voltage level is amplified and then fed to microcontroller ADC. Arduino Nano is connected to computer through virtual serial port, so parameters can be read and set through terminal screen. Initial code is freely available, but there can be much more improvements made like pulsed load and different modes of operation. Continue reading

Programmable electronic load as Arduino shield

Digitally controlled electronic loads are great for many purposes. First of all you can test batteries by discharging them with known current or measure power supply capabilities at high loads and so on. Jakub has been testing batteries and power supplies for some time, but his setup was manual. Eventually he decided to build more automatic solution and so he came up with electronic load Arduino shield. The load is based on FET which gate is controlled by op-amp which allows to maintain constant voltage or constant current across load. The load can withstand 70W power dissipation with up to 10A current. Custom PC software allows reading voltage and current data also it accepts control commands like setting constant power and constant resistance modes. The FET on shield has to dissipate quite a lot heat so there is an active cooler installed which keeps temperature within safe margins. Continue reading