Fnirsi IPS3608: A Bench Power Supply With Serious Flaws

September 20, 2025 by Maya Posch 16 Comments

Fnirsi is one of those brands that seem to pop up more and more often, usually for portable oscilloscopes and kin. Their IPS3608 bench power supply is a bit of a departure from that, offering a mains-powered PSU that can deliver up to 36 VDC and 8 A in a fairly compact, metal enclosure. Recently [Joftec] purchased one of these units in order to review it and ended up finding a few worrying flaws in the process.

One of the claims made on the product page is that it is ‘much more intelligent than traditional power supplies’, which is quite something to start off with. The visual impression of this PSU is that it’s somewhat compromised already, with no earth point on the front next to the positive and negative banana plug points, along with a tilting screen that has trouble staying put. The USB-C and -A ports on the front support USB-PD 3.0 and a range of fast charge protocols

The ‘intelligence’ claim seems to come mostly from the rather extensive user interface, including a graphing function. Where things begin to fall apart is when the unit locks up during load testing presumably due to an overheating event. After hooking up an oscilloscope, the ripple at 1 VDC was determined to be about 200 mV peak-to-peak at 91 kHz. Ripple increased at higher voltages, belying the ’10 mV ultra-low ripple’ claim.

A quick teardown revealed the cause for the most egregious flaw of the unit struggling to maintain even 144 Watt output: a very undersized heatsink on the SMPS board. The retention issues with the tilting issue seemed to be due to a design choice that prevents the screen from rotating without breaking plastic. While this latter issue could be fixed, the buggy firmware and high ripple on the DC output make this €124 ‘285 Watt’ into a hard pass.

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The FNIRSI HRM-10 Internal Resistance Meter

October 17, 2024 by Dave Rowntree 16 Comments

Occasionally, we find fun new electronic instruments in the wild and can’t resist sharing them with our readers. The item in question is the FNIRSI HRM-10 Internal resistance meter, which we show here being reviewed by [JohnAudioTech].

So what does it do, and why would you want one? The device is designed to measure batteries so you can quickly determine their health. Its operating principle also allows it to do a decent job of measuring low-resistance parts, which is not necessarily as easy to achieve with the garden variety multimeter, especially the low-end ones. We reckon it would be useful in the field for checking the resistance of switches and relays, possibly in automotive or industrial applications. The four-pin connector is needed because there are two wires per probe, making a Kelvin (also known as four-wire) connection.

Likely, the operating principle is to apply a varying load to the battery under test and then measure the voltage drop. The slope of the voltage sag vs load is a reasonable estimate of the resistance of the source, at least for the applied voltage range. The Kelvin connection uses one pair of wires to apply the test current from a relatively low-impedance source and the second pair to measure the voltage with a high input impedance. That way, the resistance of the probe wires can be calibrated out, giving a much more accurate measurement. Many lab-grade measurement equipment works this way.

Circling back to the HRM-10, [John] notes that it also supports limit testing, making it a helpful gauging tool for the workbench when sorting through many batteries. Data logging and the ability to upload to a computer completes the feature set, which is quite typical for this level of product now. Gone are the days of keeping a manual logbook next to the instrument stack and writing everything down by hand!

We’ve touched on measuring battery internal resistance before, but it was a while ago. Regarding Kelvin connections, here’s a quick guide and a hack upgrading a cheap LCR to support 4-wire probes.

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PCB Design Review: HAB Tracker With ATMega328P

July 10, 2024 by Arya Voronova 15 Comments

Welcome to the Design Review Central! [VE3SVF] sends us their board, and it’s a HAB (High Altitude Balloon) tracker board. It’s got the venerable ATMega28P on it, a LoRa modem and a GPS module, and it can be powered from a LiIon battery. Stick this board with its battery onto a high-altitude balloon, have it wake up and transmit your coordinates every once in a while, and eventually you’ll find it in a field – if you’re lucky. Oherwise, it will get stuck hanging on a tree branch, and you will have to use a quadcopter to try and get it down, and then, in all likelihood, a second quadcopter so that you can free the first one. Or go get a long ladder.

The ATMega328P is tried and true, and while it’s been rising in price, it’s still available – with even an updated version that sports a few more peripherals; most importantly, you’re sure to find a 328P in your drawer, if not multiple. Apart from that, the board uses two modules from a Chinese manufacturer, G-Nice, for both GPS and Lora. Both of these modules are cheap, making this tracker all that more accessible; I could easily see this project being sold as a “build your own beacon” kit!

Let’s make it maybe a little nicer, maybe a little cheaper, and maybe decrease the power consumption a tad along the way. We’ll use some of the old tricks, a few new ones, and talk about project-specific aspects that might be easy to miss.

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PCB Design Review: Switching Regulator Edition

June 18, 2024 by Arya Voronova 18 Comments

This article was prompted by a friend of mine asking for help on a board with an ESP32 heart. The board outputs 2.1 V instead of 3.3 V, and it doesn’t seem like incorrectly calculated feedback resistors are to blame – let’s take a look at the layout. Then, let’s also take a look at a recently sent in design review entry, based on an IC that looks perfect for all your portable Raspberry Pi needs!

What Could Have Gone Wrong?

Here’s the board in all its two-layer glory. This is the kind of board you can use to drive 5 V or 12 V Neopixel strips with a firmware like WLED – exactly the kind of gadget you’ll want to use for LED strip experiments! 3.3 V power is provided by a Texas Instruments TPS54308 IC, and it’s the one misfiring, so let’s take a look.

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Cheap Musical Tesla Coil Put Through Its Paces

May 1, 2024 by Lewin Day 4 Comments

Once upon a time, musical Tesla coils were something you primarily saw at high-voltage hobby meets. They’ve become more popular in recent years, and now you can even buy cheap examples online. [mircemk] decided to buy one and gave it a whirl.

The device comes with a power supply capable of delivering 2 amps at 48 V. It’s a solid-state design, relying on SMD MOSFETs to generate high-voltage, high-frequency output that makes the sparks we all know and love. The pancake coil is key to the design, and is made using a trace on the PCB — a neat technique compared to making one with a laborious winding operation.

The coil can be used to simply generate sparks, or it can be modulated musically. In this mode of operation, it’s intended to be driven by square wave audio for simplicity’s sake. As seen in [mircemk]’s video, the sound quality is pretty decent for a cheap device, and the Super Mario theme is readily recognizable. As a guide, he also demonstrates how to drive the device using an Arduino set up for square wave audio output.

If you prefer to build your own singing Tesla coil, you can go that route instead. Or, you could buy one of these and hack it, and drop us a line with what you come up with! Similar devices are all over the ‘net. Continue reading “Cheap Musical Tesla Coil Put Through Its Paces” →

A graph from the article, showing dead zones and error bars for the ESP32 ADC

RP2040, ESP32, And An Atmega Have An ADC-Off

March 7, 2024 by Arya Voronova 31 Comments

[Simon Monk] got frustrated with bad ADC performance when tinkering with an ESP32 board, and decided to put three of the nowadays-iconic boards to the test – a classic ESP32 devboard, a Pi Pico with an RP2040, and an Arduino Uno R3 with an ATmega328P. To do that, he took a bench PSU, added a filter circuit to it, went through the entire ADC range for each board, took a large number of samples at different points and plotted the results. The plots show us both linearity and precision, as well as ADC dead zones, and the results are quite surprising.

The ESP32 doesn’t only have the most limited ADC with maximum 1V input, it also produces the worst results out of all three, with large error bars and sizeable dead zones at both ends. The Pi Pico, despite being colloquially known for its subpar ADC, produces better results than the ESP32. However, both of them are dwarfed by the ATMega328P’s performance. If you need a dedicated ADC, it might just be a good idea to put an ATMega328P on your board.

The example code is provided, and we are wondering whether there are methodology errors. For instance, the ATMega328P code is written in Arduino-supplied C++, but ESP32 and RP2040 in particular used MicroPython, which does more than just running the code, and MicroPython for ESP32 in particular creates a WiFi access point – something known to induce noise into ADC readings. Nevertheless, this is a fun comparison, and we like when hackers do microcontroller standoffs like that – for instance, check out this review from 2017 which pits a dozen microcontrollers of the time against each other!

What The Artisan 3-in-1 CNC Offers (If One Has The Table Space)

November 1, 2023 by Donald Papp 34 Comments

I never feel like I have enough space in my workshop. The promise of consolidating tools to make the most of limited space drew me to the Snapmaker Artisan, a plus-sized 3-in-1 tool combining 3D printer, laser engraver, and CNC machine.

Smaller than three separate tools, but still big.

Jacks of all trades may be masters of none, but it is also true that a tool does not need to be a master of its functions to be useful. For many jobs, it enough to simply be serviceable. Does a machine like the Artisan offer something useful to a workshop?

Snapmaker was kind enough to send me an Artisan that I have by now spent a fair bit of time with. While I have come to expect the occasional glitch, having access to multiple functions is great for prototyping and desktop manufacturing.

This is especially true when it allows doing a job in-house where one previously had to outsource, or simply go without. This combo machine does have something to offer, as long as one can give it generous table space in return.

What It Is

The Artisan is a large dual-extrusion 3D printer, CNC router, and diode-based laser engraver. To change functions, one physically swaps toolheads and beds. Very thankfully, there are quick-change fixtures for this.

Driving the Artisan is Snapmaker’s software Luban (GitHub respository). Named for the ancient Chinese master craftsman, it is responsible for job setup and control. For laser and CNC work, there are convenient built-in profiles for a variety of paper, plastic, leather, and wood products.

The unit is enclosed, nicely designed, and — while I have come to expect the occasional glitch — serviceable at all three of its functions. The size and stature of the machine warrants some special mention, however.

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