by Dan Meeks @ edn.com:
This Design Idea is a solid state relay (SSR) which uses a triac to switch AC loads at high current. There are plenty of simple SSR circuits available, but this may be the simplest circuit that achieves turn-on and turn-off only when the AC line voltage is near zero.
Simple SSR has zero-cross on/off switching – [Link]
by Francesc Casanellas @ edn.com:
Figure 1 illustrates a digitally programmable precision resistance that can serve as a microprocessor-driven power-supply load in custom-designed ATE (automatic-test equipment). An 8-bit current-output DAC, IC1, a DAC08, drives current-to-voltage converter IC2A, which in turn drives the gate of power MOSFET Q1. The device under test connects to J1 and J2. In operation, current from the device under test develops a voltage across sampling resistors R8A and R8B.
Digitally programmable resistor serves as test load – [Link]
by Vladimir Rentyuk @ edn.com
Suppose that you need to test a 1.5V, AA-size alkaline battery. You can apply a short circuit and measure current, or you can measure open-circuit voltage, but neither method properly tests the battery. A suitable test current of approximately 250 mA gives you a more reasonable test. You can use a 6Ω resistive load at 1.5V, which produces an output voltage of 1.46V at an ambient temperature of 25°C if the battery is in excellent condition. A poor battery might produce less than 1.2V. Given the load, the output current at 1.2V will be 200 mA instead of 250 mA. The battery will have just 80% of a full load current. Instead, you can use the circuit in Figure 1 to produce a constant-current load.
Circuit provides constant-current load for testing batteries – [Link]
With a package outline of just 1.2 x 2mm the Micrel MIC95410 is able to switch loads of 7A in the voltage range of 0.5 to 5.5 V. The switch provides high-side switching and the company anticipates it will find applications in the field of computing generally and in ultra-dense embedded computer boards where high-current, low-voltage rails from sub-1V to 5.5V are required to be sectioned. The integrated 6.6 mΩ RDS(ON) N-channel MOSFET ensures low voltage drop and low power dissipation while delivering up to 7A of load current.
A separate 2.7 to 9 V supply is necessary to power the chip’s logic. The chip also includes a TTL-logic level control input (CTL); a high level enables the switch and a logic low level disables the switch and discharges the output. The OFF-state current from the bias supply (VS) and the power switch OFF-state leakage current (IOFF) are both below 1μA. A capacitor can be connected at the GC input to provide switch slew-rate limiting to help reduce inrush current to the input supply voltage.
Tiny Power Switch good for 7Amps – [Link]
A DIY dynamic electronic load by Jay_Diddy_B over at EEVblog Forum:
The dynamic load steps the load current so that the transient response of the power supply being tested can be observed.
0-5A maximum continuous current
0-5A pulsed current at 330Hz
DIY dynamic electronic load – [Link]
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]