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Designing a Better Test Box for Fencing

The idea behind this was born of part necessity and part boredom. As primarily an epeeist, I’ve had my fair share of faulty weapons and would end up having to use the connection detector on my multimeter to debug any problems. This was not the most practical approach. However, instead of shelling out $15 for a box with LEDs I decided to go and make my own.

The first thing I wanted to avoid was using two batteries. A regularly used tester would see maybe an hour of on time in a couple years and I really wanted to make the case as light and slim as possible. However, that left me with a different problem. The reason most testers use two batteries (AA) is because the general forward voltage for LEDs between 1.8 and 2.2V, just over the 1.2 or 1.5V you’d find in an NiMH or alkaline AA. There are a few ways to go about boosting the voltage to the necessary levels, but the approach I took was to use a circuit called a joule thief.

I found an easy-to-follow instructable and made a quick trip down to the EE lab to see if there were and toroid magnets which I could use to make the inductor. Lucky, there were. I only managed to get 7ish complete turns around however, it seems to work just fine:

IMG_9708I wanted to see how low the voltage could drop before the LED would become unusable so I hooked up the circuit to my bench supply. I slowly dropped the voltage to the point where the LED was no longer emitting any detectable light which was around 0.3V

DS2000Above is a capture at 0.3V in. The top waveform is from the toroid output to the base of the 3904 and the bottom waveform was of the LED. This makes it much easier to see the LED being powered by higher voltage pulses from the joule thief circuit. The capture below was taken at around 1.5V in and shows the difference in frequency relative to voltage (excuse the different time bases):

Newfile1iHaving solved the issue of the voltage supply à la joule thief, the test circuit is then a simple matter of wiring up three pins to connect to a body cord and then foil or epee. IMG_9712Above is a photo of the body cord that will be connected to the pins in the test box (the test box whose housing needs to be made). The middle pin (B) is connected to the collector of the 3904. The left pin (A) is then connected to a green LED whose cathode is connected to the emitter or the 3904, such that when the circuit is closed the LED will turn on (the weapon is working). The same is done for the right pin (C) with a second LED. Thus completes the wiring component of the test box, I’ll cover the housing in another post when the fab shop reopens.

Caught in the Rain


Weather has never really been a concern of mine in the past. If I got caught out in the rain I usually just wait it out or run through until I could find shelter. However, when you’re commuting to work at an office building you really can’t show up late or soaking wet just because you didn’t know it was supposed to rain. This is where the motivation for this project comes from. Now those of you who are, perhaps, more collected might be wondering why I don’t just check my phone every morning like a normal person. Those of you, perhaps, do not realize the small miracles that must occur each morning for me to walk out the door, on time, with all the necessary belongings for the day.

I wanted something simple. I wanted to know weather (whether) or not the forecast called for rain during any of the hours of the day where I would most likely be walking outside (say 8-9 in the morning and 5:30-6:30 in the evening). I wanted to know as soon as I got up, in a very simple and intuitive way that even my morning grogginess couldn’t obscure.

This project gave me the perfect opportunity to use the Intel Galileo I’ve had sitting under my desk. While it definitely could have been done with an Arduino, the Galileo happens to have a built in ethernet jack and I didn’t have an ethernet shield lying around (or Arduino).

I started with the data. I needed easy access to some simple weather info which Yahoo happens to provide in xml. It’s pretty basic and doesn’t really offer the hourly data I wanted but, it’s a start. The Galileo is running a javascript environment called galileo-io which is based on the Johnny-Five Arduino framework (essentially javascript for the arduino). Getting the data I want is quite simple. In this case I’m only concerned with one value, the first instance of code in the yweather:forecase tag (the present forecast). Yahoo provides a simple guide which explains each code, making it easy to create a binary situation: rain/thunderstorms bad, everything else-whatever. I created a simple list of values that I could compare the given code to that, if matched, would indicate some sort of rain. Adding a simple delay() then allows me to have this GET request run every day, making sure that the Galileo will always have relevant data.

Pretty straight-forward so far, and the hardware side is no different. Having essentially narrowed this down to a two-case problem (rain or no rain) I could get away with having a single LED turning on or off. But that’s not really what I’m going for. My hope it to connect it to the audio controller that currently controls the LED strips in my room, in order create a much more immersive and dynamic visual (think flashing lights or gentle fades for thunderstorms and showers). I, unfortunately, don’t have access to my room right now but I’ll be sure to post an update once I have something more visually interesting to show.

Things to Come

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