EEVblog #102 - DIY Constant Current Dummy Load for Power Supply and Battery Testing
Why Electrical Engineering Stack Exchange recommends it
Electronics Stack Exchange answerers and askers point to it as the standard simple op-amp and MOSFET constant current load design, both for explaining how such circuits work and as a base for their own modified builds.
Recommended by 3 people across 3 different months, 2011 to 2021.
What it is
EEVblog #102 is Dave Jones building a constant current dummy load from junkbox parts. It uses a dual op-amp and a power transistor, and is meant for testing switch mode power supplies and batteries. He explains the circuit and demonstrates it on the bench.
What people said
Recommends abdullah kahraman · 2011-12 · Electrical Engineering Stack Exchange · on “Beginner information related to constant current dummy loads”
Edited I got a great source for you, from Dave again! Here is [this video] the EEVblog #102 - DIY Constant Current Dummy Load for Power Supply and Battery Testing. And here is some info from that: The circuit uses two OP-AMPs to set the constant current. The first OP-AMP (IC1A), is configured as a voltage follower. What it does is; it takes the voltage at its non-inverting pin (pin 3) and shows it in its output (pin 1). This configuration is used because of its very high input impedance and very low output impedance. Second OP-AMP (IC1B), is configured as a voltage follower too, however in the negative feedback there is Q1. So in this case (as its general behavior), OP-AMP will try to equalize th
Recommends Andrés · 2017-06 · Electrical Engineering Stack Exchange · on “Constant current load”
Let's briefly analyze how this works: We are trying to put transistor Q2 into the linear region, effectively behaving as a variable resistor such that there's always a given current passing through it. To do this we need: 1. To measure the current. 2. To control the current, i.e. the transistor. To achieve (1) we use R15. Since it is 1 ohm, for every amp it will have 1V. R11/C4 provide lowpass filtering to smooth the signal. U2 amplifies the signal since it is a non-inverting op amp.The output gain will be (1+(R12+R13)/R14). This is a value between 100 and 150. This is quite ridiculous to be honest. Doesn't look good to be honest. But to answer your questions: (3). No. Don't use it on AC. As
Recommends YoussefAly97 · 2021-11 · Electrical Engineering Stack Exchange · on “Why was this MOSFET destroyed?”
Then I would suggest learning to walk before we can run. How about you build an adjustable constant current load like this link [this video] and see how your test devices react in a steady state at various load currents and output voltages, then we can move one to testing transients?
Cites user1022934 · 2016-11 · Electrical Engineering Stack Exchange · on “Noise in op amp design or EMI?”
Sorry for the long post, but I've been trying to work this out in my head. The circuit I’m working on is based on EEVBlog's dummy load [this video] . The circuit works by using an op amp to set the voltage at a current shunt resistor and burning rest of the voltage across a mosfet. [LINK] The voltage is set at the op amp by filtering a PWM signal from an Atmega328P. This is my first mixed analog-digital board, so it seemed like a useful design to start with; not too surprisingly I’m having issues with it. In short, I have a lot of noise in the lines connected/near the op amp. Screenshots of the relevant schematic and pcb layout areas are in this imgur link [LINK] . (I don't have enough reputation
Cites Jakub · 2018-07 · Electrical Engineering Stack Exchange · on “How to switch dummy load circuit on/off with pwm?”
I built pretty much the simplest dummy load for testing batteries I found on youtube ( EEVBlog #102 [this video] ) , but I modified it little bit. I used 0R1 resistor, because I needed bigger currents from battery (expecting little bit over 2A max). I also use rail-to-rail operational amplifier TS912. I use voltage on sense resistor for feedback to have more control over the current. Also, I use my ATMega32 to control this circuit. It works perfectly in these two "modes": Constant current: I set voltage on DAC and it sets the current Constant load: I check battery voltage to calculate DAC output, therefore current to maintain constant load I need to add PWM switching, switching on/off with ATMega
Cites MicroservicesOnDDD · 2019-01 · Electrical Engineering Stack Exchange · on “Why the actual charge current of a battery is not improving when I shifted to larger current capacity battery charger power supply?”
More Cells in Series Enables Full Current Charges If you need faster charging at the upper end of the voltage range, you may have to use a different configuration, such as 2S1P, 2S2P, ... The 2S part is 2 cells in series. The nominal voltage in that case would be 3.7 x 2 = 7.4 volts. So, to charge really fast, right up to 4.2 volts, which is the typical max, you actually have to be able to charge up to the 8.4 volts (4.2 x 2), or even 3S at 12.6 volts (4.2 x 3). Nearly-Charged Batteries Charge Slower in Constant Voltage Mode Most likely, you have a low charging current because the constant voltage part of the charging curve has already kicked in. This actually means that your cell or battery