Over the past few years, I’ve built up a few battery packs for myself and for other people. Most of them worked fine – in fact, one of the first packs I built over five years ago is still in service, working fine in a torch in the bottom of my cupboard.
The big problem with soldering to batteries is that you tend to damage the plastic separator, and the cell seals. This – as you might guess – is not a Good Thing™. In some cases, solder can splatter over the cell’s pressure relief vent. There’s a reason the datasheets make a big fuss about the vent – in an overpressure situation, the vent is used to release the excess pressure in the cell. Needless to say, blocking the vent with solder is never a good plan, unless you’re trying to get a Darwin Award, or you happen to enjoy watching your battery pack undergoing rapid, uncontrolled self-disassembly.
In industry, resistance welding is used instead of soldering. Not only are the welded joints smaller than solder blobs, but they cause less damage to the cell. The only problem is the cost of resistance welding equipment. A low-end resistance welding machine can cost upwards of GB 2,000.
The Poor Man’s Battery Tab Welder - [Link]
Radu Motisan writes:
Here is an electric fence, perimeter protection circuit, designed to run on batteries, and provide configurable pulses of up to 20KV, to protect a tent perimeter against bears or other animals, out in the wild.
The high voltage generated is not dangerous because of the low current (and power), but it will produce intense pain.
Electric Fence – 20KV pulses for perimeter defense - [Link]
I found some old pictures of me playing around with a flyback, and I wanted to test out this awesome gallery thing I found, so I mushed them together, and well, here they are!
High-voltage arcs using a flyback transformer from a monitor - [Link]
Matt Renaud writes:
It’s time for a little confession: I don’t always spend as much time on my power supply designs as I should. Sometimes I get excited about my latest circuit and after looking for just the right tubes, output transformers, coupling caps, and low noise resistors, the power supply design becomes almost an after thought. Sometimes things turn out ok and there are no problems. Other times I end up with bad voltages, unacceptable power supply sag, channel crosstalk, or worst of all, a hum that I just can’t seem to eliminate. It’s at these times that I always wish I had taken a little more time to get it right.
The truth is, there is no reason to suffer power supply set backs like this. The design of basic tube power supplies is actually very straight forward. And, if we rely on the excellent work of those who’ve come before us (O. H. Schade, N. H. Roberts, D. L Waidelich, H. J. Reich), we don’t even need to tackle any advanced math or taxing mental gyrations to arrive at some truly excellent power supply designs.
Power Supply Design for Vacuum Tube Amplifiers - [Link]
Luca is building a Nixie clock, and in this post he covers the high voltage power supply section.
Nixie tubes are digit displays that use ~170V between the digit wire and a wire mash, to agitate the gas inside the tube. This surrounds the digit wire with a orange glow and it becomes visible through the tube.
Luca is using the MAX1771 based DC/DC boost converter to supply the high voltage required. This DC/DC steps up the 9-12V input to 180V output, as a bonus it has an additional 5V output for the rest of the circuit board.
Nixie clock HV power supply - [Link]
Powering the Imaging on IMAGE – [via]
The IMAGE spacecraft was launched from Vandenberg AFB in 2000 to study the aurora borealis or “Northern Lights”. IMAGE was the first satellite mission dedicated to imaging the Earth’s magnetosphere, the region of space controlled by the Earth’s magnetic field and containing extremely tenuous plasmas of both solar and terrestrial origin. IMAGE is an acronym for Imager for Magnetopause-to-Aurora Global Exploration.
This is the high voltage power converter module for the Far-Ultraviolet (FUV) imaging instrument in the IMAGE satellite. It converts 28V to 5000V DC for the Wideband Imaging Camera (WIC). The WIC images the whole Earth and the auroral oval from satellite distances greater than 4 Earth radii to the center of the Earth. It selects the spectral range between 140 nm and 160 nm in the ultraviolet part of the optical spectrum.
Here is a good intro video on the science, and subsequent satellite missions: “What triggers the sudden, magnificent movements of the aurorae that appear around the far poles of the earth? It’s been a nagging question of space science for decades.”
Thinking outside the planar - [Link]
Flyback transformers are found in monitors, TVs or anything with a CRT, and are sometimes known as Line OutPut Transformers, or just LOPT. They are used for generating high voltage for the CRT, which is needed to create an electric field, which in turn accelerates electrons towards the screen, which finally excite phosphors and create the image you see. Flybacks are designed to work best anywhere between 15 to 150 kHz, so some experimentation is required to find the intended operating frequency. TV flybacks are generally designed for upper audio frequencies, which is the cause of the high pitched noise heard from a muted TV.
Flyback Transformer Drivers - [Link]
Fun with a few 9V batteries. (244 of them) @ The Custom Geek… [via]
So I needed a break from working on a project again, and I remembered that I had a bunch of 9V batteries and thought, ‘I wonder if that would be enough voltage to hold an arc?‘. The answer is yes, it would. So I made a little video of melting some alligator clips and crispifying some LED’s, a CD, and a cap. Or at least trying to blow up the cap, that was one tough cookie..
I used 244 9V batteries, that were not new, but not dead. When you do the math, this should be 2,196 Volts, but that is when they are new. I measured (in blocks) 2,000 volts total. Lots of sparky..
Fun with a few 9V batteries. (244 of them) - [Link]
Teravolt.org – DIY High Voltage Capacitors… [via]
Sure making a cap out of paper is fun and all, but making a high voltage one is even more fun!
You don’t need lots of money to make high voltage capacitors, in fact some pretty decent ones can be made with some cheap and readily available materials. This is because capacitors are very simple devices; consisting only of a dielectric and two plates. Most often a capacitor’s plates are just aluminum foil, and reynold’s wrap is easy enough to obtain, but what about the dielectric?
Enter the overhead projector sheet. Transparencies as they are commonly known as are nothing but acetate film, and while this is not the ideal dielectric for a capacitor it still does quite a good job. Typically a four mil OHP sheet can withstand 14kV before breaking down. As for obtaining them, the cheapest I have found these sheets is $10 for a box of 100, enough for about 16 capacitors.
How you make the capacitors is a rather trivial task, all that needs to be done is some cutting, flattening and rolling. Below I have an image that explains the process. Multiple sheets of OHP sheet are used to increase the capacitor’s voltage rating, and two sets of sheets are used so the capacitor can be rolled up.
DIY High Voltage Capacitors – [Link]