Custom Electronic Load Makes Use Of Gaming PC Tech

At first glance, you might think the piece of hardware pictured here is a modern gaming computer. It’s got water cooling, RGB LED lighting, and an ATX power supply, all of which happen to be mounted inside a flashy computer case complete with a clear window. In truth, it’s hard to see it as anything but a gaming PC.

In actuality, it’s an incredible custom electronic load that [EE for Everyone] has been developing over the last four months that’s been specifically designed to take advantage of all the cheap hardware out there intended for high-performance computers. After all, why scratch build a water cooling system or enclosure when there’s such a wide array of ready-made ones available online?

The “motherboard” with single load module installed.

Inside that fancy case is a large PCB taking the place of the original motherboard, to which four electronic load modules slot into. Each of these loads is designed to accept a standard Intel CPU cooler, be it the traditional heatsink and fan, or a water block for liquid cooling. With the current system installed [EE for Everyone] can push the individual modules up to 275 watts before the temperatures rise to unacceptable levels, though he’s hoping to push that a little higher with some future tweaks.

So what’s the end game here? Are we all expected to have a massive RGB-lit electronic load hidden under the bench? Not exactly. All of this has been part of an effort to design a highly accurate electronic load for the hobbyist which [EE for Everyone] refers to as the “Community Edition” of the project. Those smaller loads will be derived from the individual modules being used in this larger testing rig.

We’ve actually seen DIY liquid cooled electronic loads in the past, though this one certainly sets the bar quite a bit higher. For those with more meager requirements, you might consider flashing a cheap imported electronic load with an open source firmware to wring out some extra functionality.

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A DIY Electronic Load With A Twist

If you’re testing a power supply or battery pack, an electronic load is a nice tool to have. By watching the voltage as you crank up the resistance, you can verify the unit’s real-world capabilities quickly and easily. But [Xavier Bourlot] wanted a bit more information than is generally afforded by these devices, so he came up with his own scratch built load that can measure the voltage at multiple points in the circuit.

Now at first glance, it might not be obvious why you’d want such a capability. But [Xavier] is looking to do something very specific with this device: analyze the efficiency of DC-DC converters. The idea is that if the electronic load can measure the voltage on both sides of the converter, it can calculate what kind of losses are being incurred.

Could you do this with a multimeter and a traditional electronic load? Sure. But if it’s the kind of thing you’ll be doing a lot of, it’s not hard to see why this method would be preferable.

But even if you ignore the converter analysis capabilities, this looks to be a very useful device to have around the lab. [Xavier] says it can sink more than 5 amps, and handle an input voltage as high as 100 volts. Powered by an ATmega328P, the load is also fully programmable and even features an I2C expansion port that you can use to hang additional hardware or sensors on. The stock firmware is already quite capable, and the list of future enhancements has some very interesting entries such as the ability to log data over serial or to a SD card.

We’ve seen a number of programmable electronic load projects over the years, ranging from Arduino shields to VFD equipped units that would be the pride of any hacker’s bench.

Liquid Cooling Keeps This Electronic Load’s MOSFETs From Burning

Problem: your electronic load works fine, except for the occasional MOSFET bursting into flames. Solution: do what [tbladykas] did, and build a water-cooled electronic load.

One can quibble that perhaps there are other ways to go about preventing your MOSFETs from burning, including changes to the electrical design. But he decided to take a page from [Kerry Wong]’s design book and go big. [Kerry]’s electronic load was air-cooled and capable of sinking 100 amps; [tbladykas] only needed 60 or 70 amps or so. Since he had an all-in-one liquid CPU cooler on hand, it was only natural to use that for cooling.

The IXYS linear MOSFET dangles off the end of the controller PCB, where the TO-247 device is soldered directly to the copper cold plate of the AiO cooler. This might seem sketchy as the solder could melt if things got out of hand, but then again drilling and tapping the cold plate could lead to leakage of the thermal coupling fluid. It hasn’t had any rigorous testing yet – his guesstimate is 300 Watts dissipation at this point – but as his primary endpoint was to stop the MOSFET fires, the exact details aren’t that important.

We’ve seen a fair number of liquid-cooled Raspberry Pis and Arduinos before, but we can’t find an example of a liquid-cooled electronic load. Perhaps [tbladykas] is onto something with this design.

Spot This DIY Electronic Load’s Gracefully Hidden Hacks

Sometimes it’s necessary to make do with whatever parts one has on hand, but the results of squashing a square peg into a round hole are not always as elegant as [Juan Gg]’s programmable DC load with rotary encoder. [Juan] took a design for a programmable DC load and made it his own in quite a few different ways, including a slick 3D-printed enclosure and color faceplate.

The first thing to catch one’s eye might be that leftmost seven-segment digit. There is a simple reason it doesn’t match its neighbors: [Juan] had to use what he had available, and that meant a mismatched digit. Fortunately, 3D printing one’s own enclosure meant it could be gracefully worked into the design, instead of getting a Dremel or utility knife involved. The next is a bit less obvious: the display lacked a decimal point in the second digit position, so an LED tucked in underneath does the job. Finally, the knob on the right could reasonably be thought to be a rotary encoder, but it’s actually connected to a small DC motor. By biasing the motor with a small DC voltage applied to one lead and reading the resulting voltage from the other, the knob’s speed and direction can be detected, doing a serviceable job as rotary encoder substitute.

The project’s GitHub repository contains the Arduino code for [Juan]’s project, which has its roots in a design EEVblog detailed for an electronic load. For those of you who prefer your DIY rotary encoders to send discrete clicks and pulses instead of an analog voltage, a 3D printed wheel and two microswitches will do the job.

ZPB30A1 Electronic Load Gets An Open Firmware

Importing cheap equipment and test gear is something of a mixed blessing. It allows you to outfit your lab without emptying your bank account, but on the other hand there’s usually a reason it’s cheap. Of course, the retail price of a piece of hardware shouldn’t be the metric by which we measure its quality, but there’s got to be a few corners cut someplace when they are selling this stuff for a fraction of what the name brands are charging.

A perfect example is the ZHIYU ZPB30A1 electronic load, available from various online importers for about $30 USD. While the price is right for an adjustable load that can handle up to 110 W, it’s got some pretty glaring shortcomings. In an effort to address at least some of those issues, [Luca Zimmermann] has been working on an open source replacement firmware for the load’s STM8S microcontroller.

[Luca] quickly discovered that the device’s STM8S005K6 chip is write protected, so unfortunately you can’t just flash a new firmware to it. If you want to unlock additional features, you need to perform a brain transplant. Luckily these chips are quite cheap, and you can probably add a couple of them to your cart when you order he ZPB30A1.

With the new GPLv3 licensed firmware installed, the device gains constant power and resistances modes (stock firmware can only do constant current), serial logging, and support for adjusting the value of the shunt resistor. There’s even a basic menu system to shuffle through the new modes. There’s still a couple features that haven’t been implemented, such as automatic shutdown, but it’s already a considerable upgrade from the stock software. Now we just need some details on the slick custom enclosure that [Luca] has put his upgraded ZPB30A1 into.

If this looks too easy, you can always go the DIY Arduino route for your load testing needs, or build a monster than can sink up to 1 kW.

[Thanks to Benik3 for the tip.]

Beefy 100 Amp Electronic Load Uses Two MOSFETs

[Kerry Wong] had some extreme MOSFETs (IXTK90N25L2) and decided to create a high current electronic load. The result was a two-channel beast that can handle 50 A per channel. Together, they can sink 400 W and can handle a peak of 1 kW for brief periods. You can see a demo in the video below.

An electronic load is essentially a load resistor you can connect to a source and the resistance is set by an input voltage. So if the load is set to 10 A and you connect it to a 12 V source, the MOSFET should look like a 1.2 ohm resistor. Keep in mind that’s 120 watts–more power than a common incandescent light bulb. So you are going to need to carry some heat away.

The circuit is pretty simple. The FETs accept a voltage on their gates that sets them to look effectively like a resistor that varies with the voltage. A very small source resistor develops a voltage based on current (only 75 mV for a 50 A draw). That voltage feeds a comparator which generates the gate voltage after looking at the input control voltage. Each millivolt into the comparator translates to an additional 1.33 A through the load.

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A Simple Programmable Electronic Load Using The Arduino

Some projects are both educational and useful. We believe that [Jasper’s] Arduino based electronic load is one of those project.

[Jasper’s] electronic load can not only act as a constant current load, but also as a constant power and constant resistive load as well. The versatile device has been designed for up to 30V, 5A, and 15W. It was based on a constant current source that is controlled by a DAC hooked up to the Arduino. By measuring both the resulting voltage and current of the load, the system can dynamically adapt to achieve constancy. While we have seen other Arduino based constant loads before, [Jasper’s] is very simple and straight forward compartively. [Jasper] also includes both the schematic and Arduino code, making it very easy to reproduce.

There are tons of uses for a voltage controlled current source, and this project is a great way to get started with building one. It is an especially great project for putting together your knowledge of MOSFET theory and opamp theory!