A drone is shown hovering in the sky, with two bright lights shining from its underside.

2025 Component Abuse Challenge: Overdriven LEDs Outshine The Sun

November 6, 2025 by Aaron Beckendorf 9 Comments

Tagging wildlife is never straightforward in the best of times, but it becomes a great deal more complicated when you’re trying to track flying insects. Instead of trying to use a sensor package, [DeepSOIC] attached tiny, light retroreflectors to bees and hornets, then used a pulsed infrared light mounted on a drone to illuminate them. Two infrared cameras on the drone track the bright dot that indicates the insect, letting the drone follow it. To get a spot bright enough to track in full sunlight, though, [DeepSOIC] had to drive some infrared LEDs well above their rated tolerances.

The LEDs manage to survive because they only fire in 15-µs pulses at 100 Hz, in synchrony with the frame rate of the cameras, rather like some welding cameras. The driver circuit is very simple, just a MOSFET switch driven by an external pulse source, a capacitor to steady the supply voltage, and a current-limiting resistor doing so little limiting that it could probably be removed. LEDs can indeed survive high-current pulses, so this might not really seem like component abuse, but the 5-6 amps used here are well beyond the rated pulse current of 3 amps for the original SFH4715AS LEDs. After proving the concept, [DeepSOIC] switched to 940 nm LEDs, which provide more contrast because the atmosphere absorbs more sunlight around this wavelength. These new LEDs were rated for 5A, so they weren’t being driven so far out of spec, but in tests they did survive current up to 10A.

We’ve seen a similar principle used to drive laser diodes in very high-power pulses a few times before. For an opposite approach to putting every last bit of current through an LED, check out this low-power safety light.

Continue reading “2025 Component Abuse Challenge: Overdriven LEDs Outshine The Sun” →

A frame from the two billion frames per second camera

Filming At The Speed Of Light, About One Foot Per Nanosecond

October 19, 2025 by John Elliot V 26 Comments

[Brian Haidet] published on his AlphaPhoenix channel a laser beam recorded at 2 billion frames per second. Well, sort of. The catch? It’s only a one pixel by one pixel video, but he repeats it over and over to build up the full rendering. It’s a fascinating experiment and a delightful result.

For this project [Brian] went back to the drawing board and rebuilt his entire apparatus from scratch. You see in December last year he had already made a video camera that ran at 1,000,000,000 fps. This time around, in order to hit 2,000,000,000 fps at significantly improved resolution, [Brian] updated the motors, the hardware, the oscilloscope, the signalling, the recording software, and the processing software. Basically, everything.

One of the coolest effects to come out of this new setup is how light appears to travel noticeably faster when coming towards the camera than when moving away from it. It’s an artifact of the setup: laser beams that reflect off of fog particles closer to the camera arrive sooner than ones that bounce back from further away. Or, put another way, it’s special relativity visualized in an experiment in [Brian]’s garage. Pretty cool.

If you found all this intriguing and would like to know more, there’s some bonus material that goes into much more depth.

An oscilloscope display is shown, showing two plots. A blue plot is shown at one level, and over multiple exposures at different places, it jumps to a higher level. Another yellow trace is shown which, at some point after the blue trace has jumped to a higher level, also jumps cleanly to a higher level. The yellow line is labeled "CFD output," while the blue line is labeled "leading edge discriminator."

A Constant-Fraction Discriminator For Sub-Nanosecond Timing

May 8, 2025 by Aaron Beckendorf 3 Comments

Detecting a signal pulse is usually basic electronics, but you start to find more complications when you need to time the signal’s arrival in the picoseconds domain. These include the time-walk effect: if your circuit compares the input with a set threshold, a stronger signal will cross the threshold faster than a weaker signal arriving at the same time, so stronger signals seem to arrive faster. A constant-fraction discriminator solves this by triggering at a constant fraction of the signal pulse, and [Michael Wiebusch] recently presented a hacker-friendly implementation of the design (open-access paper).

A constant-fraction discriminator splits the input signal into two components, inverts one component and attenuates it, and delays the other component by a predetermined amount. The sum of these components always crosses zero at a fixed fraction of the original pulse. Instead of checking for a voltage threshold, the processing circuitry detects this zero-crossing. Unfortunately, these circuits tend to require very fast (read “expensive”) operational amplifiers.

This is where [Michael]’s design shines: it uses only a few cheap integrated circuits and transistors, some resistors and capacitors, a length of coaxial line as a delay, and absolutely no op-amps. This circuit has remarkable precision, with a timing standard deviation of 60 picoseconds. The only downside is that the circuit has to be designed to work with a particular signal pulse length, but the basic design should be widely adaptable for different pulses.

[Michael] designed this circuit for a gamma-ray spectrometer, of which we’ve seen a few examples before. In a spectrometer, the discriminator would process signals from photomultiplier tubes or scintillators, such as we’ve covered before.

Taking “Movies” Of Light In Flight

December 25, 2024 by Elliot Williams 10 Comments

This one isn’t clickbait, but it is cheating. [Brian Haidet], the guy behind Alpha Phoenix, has managed to assemble movie footage of a laser beam crossing his garage, using a rig he put together for just a few hundred dollars. How, you ask? Well, for the long version, you’re going to want to watch the video, also embedded below. But we’ll give you the short version here.

Light travels about a foot in a nanosecond. What have you got that measures signals on a nanosecond scale pretty reliably? Of course, it’s your oscilloscope. The rest of [Brian]’s setup includes a laser that can pull off nanosecond pulses, a sensor with a nanosecond-ish rise time, and optics that collect the light over a very small field of view.

He then scans the effective “pinhole” across his garage, emitting a laser pulse and recording the brightness over time on the oscilloscope for each position. Repeating this many thousands of times and putting them all together relative to the beginning of each laser pulse results in a composite movie with the brightness at each location resolved accurately enough to watch the light beam fly. Or to watch different time-slices of thousands of beams fly, but as long as they’re all the same, there’s no real difference.

Of course, this isn’t simple. The laser driver needs to push many amps to get a fast enough rise time, and the only sensor that’s fast enough to not smear the signal is a photomultiplier tube. But persistence pays off, and the results are pretty incredible for something that you could actually do in your garage.

Photomultiplier tubes are pretty damn cool, and can not only detect very short light events, but also very weak ones, down to a single photon. Indeed, they’re cool enough that if you get yourself a few hundred thousand of them and put them in a dark place, you’re on your way to a neutrino detector. Continue reading “Taking “Movies” Of Light In Flight” →

Building An Automotive Load Dump Tester

October 13, 2024 by Dave Rowntree 11 Comments

For those who have not dealt with the automotive side of electronics before, it comes as somewhat of a shock when you find out just how much extra you have to think about and how tough the testing and acceptance standards are. One particular test requirement is known as the “load dump” test. [Tim Williams] needed to build a device (first article of three) to apply such test conditions and wanted to do it as an exercise using scrap and spares. Following is a proper demonstration of follow-through from an analytical look at the testing specs to some interesting hand construction.

The load dump test simulates the effect of a spinning automotive alternator in a sudden no-load scenario, such as a loose battery terminal. The sudden reduction in load (since the battery no longer takes charging current) coupled with the inductance of the alternator windings causes a sudden huge voltage spike. The automotive standard ISO 7637-2:2011 dictates how this pulse should be designed and what load the testing device must drive.

The first article covers the required pulse shape and two possible driving techniques. It then dives deep into a case study of the Linear Tech DC1950A load dump tester, which is a tricky circuit to understand, so [Tim] breaks it down into a spice model based around a virtual transistor driving an RC network to emulate the pulse shape and power characteristics and help pin down the specs of the parts needed. The second article deals with analysing and designing a hysteric controller based around a simple current regulator, which controls the current through a power inductor. Roughly speaking, this circuit operates a bit like a buck converter with a catch diode circulating current in a tank LC circuit. A sense resistor in the output path is used to feedback a voltage, which is then used to control the driving pulses to the power MOSFET stage. [Tim] does a good job modeling and explaining some of the details that need to be considered with such a circuit.

Continue reading “Building An Automotive Load Dump Tester” →

This Air Particulate Sensor Can Also Check Your Pulse Rate

March 26, 2024 by Lewin Day 7 Comments

The MAX30105 is an optical sensor capable of a great many things. It can sense particulate matter in the air, or pick up the blinking of an eye. Or, you can use it as a rudimentary way to measure your heart rate and blood oxygen levels. It’s by no means a medical grade tool, but this build from [Taste The Code] is still quite impressive.

The MAX30105 contains red, green, and infrared LEDs, and a very sensitive light detector. The way it works is by turning on its different LEDs, and then carefully measuring what gets reflected back. In this way it can measure particles in the air, such as smoke, which is actually what it was designed for originally. Or, if you press your finger up against it, it can measure the light coming back from your blood and determine its oxygenation level. By detecting the variation in the light over time, it’s possible to pick up your pulse, too.

Getting this data out of the sensor is remarkably easy. One need only hook it up to a suitable microcontroller like the ESP8266 and use the MAX3010X library to talk to it. [Taste The Code] did exactly that, and also hooked up a screen for displaying the captured data. Alternatively, if you want the raw data from the sensor, you can get that too.

It should be noted that this build was done for educational purposes only. You shouldn’t rely on a simple DIY device for gathering useful medical data; there are reasons the real gear is so expensive, after all. We’ve looked at this sensor before, too, not long after it first hit the market. Continue reading “This Air Particulate Sensor Can Also Check Your Pulse Rate” →

Tattoo-Removal Laser Brought Out Of Retirement For A Megawatt Of Fun

October 11, 2023 by Dan Maloney 13 Comments

We’ve got to say that [Les Wright] has the most fun on the internet, at least in terms of megawatts per dollar. Just look at his new video where he turns a $30 eBay tattoo-removal laser into a benchtop beast.

The junk laser in question is a neodymium:YAG pulse laser that clearly has seen better days, both externally and internally. The original pistol-grip enclosure was essentially falling apart, but was superfluous to [Les]’ plans for the laser. Things were better inside the business end of the gun, at least in terms of having all the pieces in place, but the teardown still revealed issues. Chief among these was the gunk and grunge that had accumulated on the laser rod and the flash tube — [Les] blamed this on the previous owner’s use of tap water for cooling rather than deionized water. It was nothing a little elbow grease couldn’t take care of, though. Especially since the rest of the laser bits seemed in good shape, including the chromium:YAG Q-switch, which allows the lasing medium to build up a huge pulse of photons before releasing them in one gigantic pulse.

Cleaned up and with a few special modifications of his own, including a custom high-voltage power supply, [Les]’ laser was ready for tests. The results are impressive; peak optical power is just over a megawatt, which is enough power to have some real fun. We’ll be keen to see what he does with this laser — maybe blasting apart a CCD camera?

Continue reading “Tattoo-Removal Laser Brought Out Of Retirement For A Megawatt Of Fun” →