Tech In Plain Sight: Tasers Shooting Confetti

October 16, 2024 by Al Williams 41 Comments

One of the standard tropes in science fiction is some kind of device that can render someone unconscious — you know, like a phaser set to stun. We can imagine times when being aggressively knocked out would lead to some grave consequences, but — we admit — it is probably better than getting shot. However, we don’t really have any reliable technology to do that today. However, if you’ve passed a modern-day policeman, you’ve probably noticed the Taser on their belt. While this sounds like a phaser, it really isn’t anything like it. It is essentially a stun gun with a long reach thanks to a wire with a dart on the end that shoots out of the gun-like device and shocks the target at a distance. Civilian Tasers have a 15-foot long wire, while law enforcement can get longer wires. But did you know that modern Tasers also fire confetti?

It sounds crazy, and it isn’t celebratory. The company that makes the Taser — formerly, the Taser company but now Axon — added the feature because of a common complaint law enforcement had with the device. Interestingly, many things that might be used in comitting a crime are well-understood. Ballistics can often identify that a bullet did or did not come from a particular weapon, for example. Blood and DNA on a scene can provide important clues. Even typewriters and computer printers can be identified by variations in their printing. But if you fire a taser, there’s generally little evidence left behind.

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A Phone? A Ham Radio? Relax! It’s Both!

October 15, 2024 by Al Williams 23 Comments

A lot of hams like to carry a VHF radio. Of course, nearly everyone wants to carry a phone. Now, thanks to the kv4p HT, you don’t have to carry both. The open-source device connects to your Android smartphone and turns it into a radio transceiver. You can build it yourself for about $35. Check out the video below.

The device uses an ESP32 and only transmits one watt, but it has lots of features like APRS and scanning.

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A VIC-20 With No VIC

October 13, 2024 by Al Williams 6 Comments

[DrMattRegan] has started a new video series to show his latest recreation of a Commodore VIC-20. The core of the machine is [Ben Eater’s] breadboard 6502 design. To make it a VIC-20, though, you need a “VIC chip” which, of course, is no longer readily available. Many people, of course, use FPGAs or other programmable logic to fake VIC chips. But [Matt] will build his with discrete TTL logic. You can see the first installment of the series below.

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Approximating An ADC With Successive Approximation

October 12, 2024 by Al Williams 17 Comments

[Igor] made a VU meter with LEDs using 8 LEDs and 8 comparators. This is a fast way to get one of 8 bits to indicate an input voltage, but that’s only the equivalent of a 3-bit analog to digital converter (ADC). To get more bits, you have to use a smarter technique, such as successive approximation. He shows a chip that uses that technique internally and then shows how you can make one without using the chip.

The idea is simple. You essentially build a specialized counter and use it to generate a voltage that will perform a binary search on an unknown input signal. For example, assuming a 5 V reference, you will guess 2.5 V first. If the voltage is lower, your next guess will be 1.25 V. If 2.5 was the low voltage, your next guess will be 3.75 V.

The process repeats until you get all the bits. You can do this with a microcontroller or, as [Igor] shows, with a shift register quite simply. Of course, you can also buy the whole function on a chip like the one he shows at the start of the video. The downside, of course, is the converter is relatively slow, requiring some amount of time for each bit. The input voltage also needs to stay stable over the conversion period. That’s not always a problem, of course.

If that explanation didn’t make sense, watch the video. An oscilloscope trace is often worth at least 1,000 words.

There are, of course, many ways to do such a conversion. Of course, when you start trying to really figure out how many bits of resolution you have or need, it gets tricky pretty fast.

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What’s Your SWR? Are You Sure?

October 12, 2024 by Al Williams 11 Comments

If you are involved in any sort of radio transmission, you probably have at least heard of SWR or standing wave ratio. Most transmitters can measure it these days and most ham radio operators have tuners that measure it, also. But what are you measuring? [KI8R] points out that if your coax has loss — and what coax doesn’t? — you are probably getting an artificially low reading by measuring at the transmitter.

The reason is that most common SWR-measuring instruments pick up voltage. If you measure, for example, 10V going out and 1V going back, you’d assume some SWR from that. But suppose your coax loses half the voltage (just to make an obvious example; if your coax loses half the voltage, you need new coax).

Now, you really have 5V getting to your antenna, and it returns 2V. The loss will affect the return voltage just like the forward voltage. Reflecting 2V from 5 is a very different proposition from reflecting 1V out of 10!

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Repairing A Component On A Flex Connector

October 11, 2024 by Al Williams 15 Comments

It used to be you could crack open a TV or radio and really work on the components inside. The smallest thing in there was maybe a disc capacitor a little smaller than your pinky’s nail. Nowadays, consumer electronic boards are full of tiny SMD components. Luckily [StezStix Fix?] has a microscope and the other tools you need. Someone sent him an Amazon Echo Show with a bad touchscreen. Can it be fixed?

The video below shows that it can, but there’s a twist. The bad capacitor was mounted on one of those flexible PCB cables that are so hard to work with. It is hard enough not to damage these when you aren’t trying to remove and replace a component from the surface of the cable.

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Wimbledon Goes Automated

October 10, 2024 by Al Williams 4 Comments

When you think of tennis, you probably think of Wimbledon, the All England Club’s famous competition that has run for 147 years. Part of that history has always been line judges who call the ball in or out, sometimes to the ire of players and fans alike. But line judges will be no more at Wimbledon. They are moving to ELC or electronic line calling on all courts in both the main draw and the qualifying tournaments, according to [Tumaini Carayol] writing in The Guardian.

Of course, in 2007, the competition started using “Hawk-Eye,” which allows for review and challenges of the calls. ELC has also been used in other venues, such as the US Open, which has also done away with all line judges.

In fact, the only grand slam tournament that isn’t using ELC now is the French Open. There is some concern, however. The increased availability of line judges will cut down on the demand for new line judges at lesser tournaments. However, these jobs are a common pathway for aspiring chair judges to gain experience and exposure.

According to the Bloomberg video below, the system uses cameras and microphones to keep track of the ball’s position. Other reports say there are 18 cameras and, apparently, the system uses a computer-generated voice to call “out,” “fault,” or “foot fault.”

Apparently, there are some downsides, however. Last month at the US Open, play was halted because the remote office of the technicians operating the ELC system had to evacuate due to a fire alarm.

[Lewin Day] thinks tech will ruin sports. He may be right. Of course, we are more likely to play sports on technology.

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