To test real capacity of a power supply, we need a load with variable current consumption. If we have high power variable resistor such as tapped wire-wound resistor, we can directly connect this resistor and make some measurement. Unfortunately, this kind of high power resistor is expensive and not so flexible getting wide adjustment range. You can test power supplies and related devices at maximum peak output current without resorting to arrays of power resistors, using this dummy load circuit, which is nothing but a simple transistor current sink circuit.
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3 I'm working on a power supply build and need a dummy load. I've found many mentions here that are good for a few amps, but I need one that's good for 30A or more. at 5V. I thought about just using some high wattage LEDs or something but they all require 30V or more. Being variable isn't a hard requirement but would be nice. Variable Dummy Load for Power Supply Testing It is easy to find on the Internet many designs of voltage sources, with which we can power our circuits designs. It would be very useful to know how to test a voltage source in order to determine if its characteristics are good or not. This variable dummy load is helpful in power supply testing by providing virtual load which can be adjusted to draw certain current. It act like a high power variable resistor but. You use an active-load test circuit to ensure that a power supply for a microprocessor or for other digital loads supplies 100A transient currents. This active load can provide a dc load for a power supply, and it can rapidly switch between dc levels. These transient loads simulate the fast logic switching in the microprocessor.
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I have used this to test the outputs of a few different power supplies now, up to 60V and about 8A using the 10 ohms emitter resistors and 18V 30A using the 0.75 ohms resistors. The heat sinks didn't get warm with their fans blowing, and the transistors didn't get very hot either. EEVblog #102 - DIY Constant Current Dummy Load for Power Supply and Battery Testing. EEVblog August 1, 2010 EEVblog, EEVblog - Podcast Comments Off 52,099 Views. Dave grabs a few junkbox parts and builds a useful constant current load for switch mode power supply, battery testing, and other applications. Podcast: Download. February 11, 2020 When it comes to testing power supplies, it's useful to have a dummy load to put the gear through its paces. While it's possible to just use some old heating elements or. What do you use for PSU testing and for power supply circuit testing? Electronic loads are nice, but you could buy 20 resistors for the price of one of these devices, and a resistor works for AC, too, which is even more expensive for electronic loads.
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The best way to test the correct operation of a circuit is to test it whilst it is under the expected load range. For purely resistive circuits with minimal voltage fluctuations, this can easily be done by placing a suitable valued resistor across the voltage potential. Variable Dummy Load for Power Supply Testing. How to test a voltage source to know if it is good or not?. What is the percentage regulation?.. 20 Amp Variable Power Supply with an output voltage from 1.5 to 15 volts using the LM317 regulator and 4 2N3055 power transistors to amplify the current capacity.
DescriptionIn this video, we cover building a simple resistive dummy load to test out the power supplies on our vintage computers. We cover using power resis. If they we're perfectly equal (they aren't) this means I made a 0.2ohm 2.5W resistor. sqrt (2.5/0.2) = 3.54A would be the limit current in theory but remember that one resistor might be more stressed than the others because it has more resistance (R*I^2 for constant current, so the bigger the R, the worse for the poor resistor). Note:
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I made my dummy load switchable. You can draw a big current and then by flipping the switch the current almost doubles. The lowest resistance I got from this circuit was 1.8 Ohms. That means with 12 volts connected you can draw a little under 7 Amps. and this transistor has no troubles with that (provided the heat-sink is up to it). 4 Answers Sorted by: 17 how can i test this power supply? Start by using the right load. The supply is rated for 10 A maximum at 12 V. By Ohm's law, that means the smallest valid load resistance is (12 V)/ (10 A) = 1.2 Ω. By connecting a 700 mΩ resistor to the supply, you violated it's current spec. Again by Ohm's law, (12 V)/ (700 mΩ) = 17 A.
