Measuring High Voltage in Millimeters (and Other HV Probe Tricks)

I work a lot with high voltages and others frequently replicate my projects, so I often get asked “What voltage is needed?”. That means I need to be able to measure high voltages. Here’s how I do it using a Fluke high voltage probe as well as my own homemade probe. And what if you don’t have a probe? I have a solution for that too.

How Long Is Your Spark?

The simplest way to measure high voltage is by spark length. If your circuit has a spark gap then when a spark occurs, that’s a short-circuit, dumping all your built up charge. When your spark gap is at the maximum distance at which you get a spark then just before the spark happens is when you have your maximum voltage. During the spark the voltage rapidly goes to zero and depending on your circuit it may start building up again. The voltage before the spark occurred is related to the spark length, which is also the spark gap width.

The oscilloscope photo below shows this changing voltage. This method is good for a rough estimate. I’ll talk about doing more precise measurements when I talk about high voltage probes further down.

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How To Hack A Spacecraft To Die Gracefully

Last week, the Rosetta spacecraft crashed into comet 67P/Churyumov-Gerasimenko after orbiting it since 2014. It was supposed to do that: the mission was at an end, and the mission designers wanted to end it by getting a close look at the surface of the comet. But this raises an interesting problem: how do you get a device that is designed to never stop to actually stop?
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Connecting Inexpensive pH Probes with Ease


We’ve mentioned that it’s hard to find someone not selling or crowd funding something at Maker Faire. Despite the fact that [Ryan Edwards] is selling his boards, we still got the feeling that he’s a hacker who is selling just to make sure the idea he had is available for other hackers to use. He showed us his interface boards for inexpensive pH probes.

Since we’re always looking for more chemistry hacks to run, it was nice to hear [Ryan’s] description on how these probes (which can be had for around $9 on eBay) actually work. It turns out it’s all about salt. When it comes to the electronics, the board provides a connector for the probe on one edge, and pins for voltage, ground, and I2C on another. Rig this up with your microcontroller of choice and you’ll be building your own automatic pool doser, fish tank minder, or one of a multitude of food-related hacks.

Head on over to Sparky’s Widgets to see a few other demo applications.

EMF oscilloscope probe

[Tuomas Nylund] wanted a way to visualize the electromagnetic fields (EMF) around him. He figured the oscilloscope was the tool best suited for the task, but he needed a way to pick up the fields and feed them into one of the scope’s probes. He ended up building this EFM probe dongle to accomplish the task.

He admits that this isn’t much more than just an inductor connected to the probe and should not be used for serious measurements. But we think he’s selling himself short. It may not be what he considers precision, but the amplification circuit and filtering components he rolled into the device appear to provide very reliable input signals. We also appreciate the use of a BNC connector for easy interface. Check out the demo video after the break to see the EMF coming off of a soldering station controller, from a scanning LCD screen, and that of a switch-mode power supply.

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Hacking the green goose for fun and profit

[Troy] recently got his hands on a greengoose starter kit and like any HAD reader would do, proceeded to probe it mercilessly.

The greengoose appears to be some sort of location-tracking device which reports back to a server on the position and location of radio transmitters relative to it. [Troy] managed to not only get the base-station’s firmware, but to also hack it and greengoose’s data to his own server. As if that wasn’t good enough he broke down the packet structure for us. Good job [Troy].

Looks like the greengoose could be a fun tool for anyone interested tweeting the whereabouts of their cat, or checking if the toilet seat lid is down. Let’s see what people come up with.

DIY signal generator probe

A signal generator is a handy bit of kit and with the right components, it’s pretty easy to build one. Fabricating a proper signal generator probe is another matter entirely. [Frank]’s DIY signal generator probe does exactly what it claims to, and is very cheap to boot.

After [Frank] made a simple signal generator with a few parts he had lying around, he needed a probe. Not wanting to deal with poking loose wires around his circuits, he decided to modify a scope probe. Six dollars and two weeks later, [Frank] had a suitable scope probe on his doorstop shipped from halfway around the world.

The strain relief on the probe was removed, and the resistors and trim cap on the PCB was desoldered. All that was left to do was solder a piece of wire from the BNC jack to the probe lead. The strain relief was put back on and clearly labeled for use as a signal generator probe. Not bad for 10 minutes of work.

Scanning tunneling microscope under GPL3

ChemHacker has posted schematics and code for a scanning tunneling microscope. [Sacha De’Angeli] finalized the proof-of-concept design for version 0.1 and released all of the information under the Gnu general public license version 3. You’ll need to build a sensor from a combination of a needle, a piezo, and a ring of magnets. There’s an analog circuit that gathers data from the probe, which is then formatted by and Arduino and sent to your computer.

We haven’t really dabbled in this type of equipment, though we did cover an STM earlier in the year. Take a look at the video after the break and then help jump-start are imagination by sharing your plans for this equipment in the comments.

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