by Anthony Smith @ edn.com:
The simple current-limiting load switch shown in Figure 1 will be familiar to most readers. In this circuit, a high level signal applied to the input switches on MOSFET Q2, which energizes the load. The load current is limited by negative feedback applied via Q1.
Load switch with self-resetting circuit breaker - [Link]
A DIY 60W adjustable electrical load project from Electro-Labs:
In this project, we are building a useful board which should take place on your bench. It is an adjustable electrical load which can sink up to 5A @ 60W continuously. This board will come to aid when you need to draw an exact amount of current from a supply. For instance to learn the current rating of a power supply, measure the heat dissipated on a circuit element, discharge a battery etc.
The electrical load lets you monitor the current by using the ampermeter on it. A multiturn variable resistor is used to set the current precisely. The circuit is powered by a 15V-18V power adapter. A large heatsink on the board helps dissipating the heat generated on the MOSFET which is the main component used for limiting the current.
DIY 60W adjustable electrical load - [Link]
Inspired from one of Dave Jones EEVBlog videos on dummy load, Lee has built his own programmable constant current resistive load that allows you to draw a set current from any power supply source. His design is based on Arduino Leonardo and uses the high-power BUK954R8-60E MOSFET to control the amount of current flowing through the load path.
Constant current resistive load controlled by Arduino – [Link]
by Ryan Roderick, Intersil @ edn.com:
The fundamentals to translating the analog world into the digital domain reduces to a handful of basic parameters. Voltage, current, and frequency are electrical parameters that describe most of the analog world. Current measurements are used to monitor many different parameters, with one of them being power to a load.
There are many choices of sensing elements to measure current to a load. The choices of current sensing elements can be sorted by applications as well as the magnitude of the current measured. This write up is part one of a three part series that discusses different types of current sensing elements. The focus of this paper is evaluating current measurements using a shunt (sense) resistor. The paper explains how to choose a sense resistor, discuss the inaccuracies associated with the sensing element and the paper discusses extraneous parameters that compromises the overall measurement.
Sensing Elements for Current Measurements - [Link]
by Deivaraja Ramasamy @ www.edn.com:
This Design Idea is able to turn off inductive loads at a very fast rate. When connected to a load (here 15mH + 10Ω), the modified freewheeling path in the clamping circuit based around M2 reduces the turn off time to 450µs. A simple freewheeling diode in place of the clamping circuit takes about 4ms to turn off the load.
Low-side switch with fast turn-off for inductive loads - [Link]
Juan Ignacio Cerrudo @ ssihla.wordpress.com writes:
The design is based on some of the various diy electronics loads out there (like the one from Dave Jones). The mosfet is a P45N03LT , most likely I took it from some of the PC power supply I’ve “recycled”. I’m using two 25k potentiometers, one for coarse adjustment and the other for fine adjustment (10 turn pots are kind of expensive…). The control voltage varies between 0 and 5 volts and is divided by two with a couple of 10k resistors. The op-amp is an OPA2336, It has rail to rail output so the load can sink roughly up to 2,5. The op amp is powered with a 7805.
Constant Current Electronic Load - [Link]
Dave grabs a few junkbox parts and builds a useful constant current load for switch mode power supply, battery testing, and other applications.
EEVblog #102 – DIY Constant Current Dummy Load for Power Supply and Battery Testing - [Link]
Jasper @ jasper.sikken.nl writes:
I designed an electric load. Using an Arduino Nano, the load can be programmed, and the voltage and current are measured. You can set a constant current (CC), a constant power (CP), or a constant resistance (CR) load by simply typing it in to the Arduino Serial Monitor. The circuit is designed for up to 30V, 5A, and 15W. An opamp, a mosfet, and a small sense resistor form the constant current circuit. The current is set using a DAC. Two other opamps measure the power supply voltage and the current. The circuit is powered from the Arduino USB voltage. I reflow soldered the board using the hacked toaster oven at the hackerdojo. Here are pictures of the reflow soldering process
Arduino based programmable load - [Link]
Here’s an interesting open source project on Kickstarter the Re:Load Pro by Nick Johnson of Arachnid Labs:
A constant current load for testing your projects. 6 amps, 60 volts and 25 watts in a workbench-friendly package with a USB interface.
The Re:Load Pro is an active load. It acts as a current sink, always drawing the same amount of current regardless of the voltage across it.
Active loads are incredibly useful for all sorts of electronics testing requirements. You can use one to see how a power supply performs under load, check if a battery lives up to its manufacturer’s specifications for capacity or current draw, test motor drivers, or a variety of common constant-current tasks, such as testing LEDs, or even doing electroplating. With computer control of the load, you can even do your own IV-curve tracing.
Re:Load Pro – A DC active load - [Link]