Wireless fencing scoring system - Page 1
Forum section: electronics / projects

author: yasinhamid
author_rank: Newbie
timestamp: March 04, 2016, 12:36:24 pm
content: Hi,I am looking for a simple system that I can use for fencing (sport) practice. First I would like to explain how the scoring in fencing/epee sport works. The epee (weapon) has a tip, which is just a simple switch. When you hit your opponent you basically close the switch. Your weapon is connected with wires to scoring equipment. Which records that the switch was closed and just lights a light. In epee a double or draw is allowed, when you and your opponent hit each other within 40ms.The problem is that the equipment is quite expensive and as fencing is not a showbiz sport, it doesn't attract sponsors, so small clubs lack proper funding. Starting wireless set is 170 euros, which is quite a lot for many clubs, schools or just for home practice, mostly here in Eastern Europe.So I was thinking that I could build very basic scoring recording system for just few euros. As the wired system si cumbersome I was thinking about wireless system. Each fencer would connect the transmitter to their weapon a the transmitter would just transmit a hit (switch closed) signal. The receiver would just react to the signal from weapon. First I was thinking about Bluetooth transmitters, as these days almost everyone owns a smartphone, which would listen to the weapon transmitters. Than I was thinking about very basic system connected to very simple receiver. These days one can buy fully functional computer like raspberry pi for something like 30 Euros.So I would like to ask if anyone have ever heard about such system, such hardware or if anyone could point where to look and what would be better approach.

author: Marco
author_rank: Super Contributor
timestamp: March 04, 2016, 02:10:02 pm
content: 170 Euros is quite a bit of money, but won't fencing equipment just be expensive period?Googling a bitit seems this project has been tackled many times, and it's not entirely trivial. The main problem being that the "connection" between the electronics and the mat has hard to predict impedance (it has to go through the fencer's body and his shoes). If you're an EE wizard you could have this up and running pretty quick, for us lesser gods it seems quite a bit of work.Bluetooth would be the go to protocol, has frequency hopping so is relatively immune to interference. Any old mobile or laptop could be used to count the score.PS. pi would be ridiculously overpowered and power hungry, this is microcontroller territory.

author: MK14
author_rank: Super Contributor
timestamp: March 04, 2016, 02:25:22 pm
content: Maybe you could replace the (end of tip) switch, with an extremely tiny battery + SOT23 MCU (6 pin) + Bluetooth (or similar) + switch. Not much bigger than a match head. Obviously surface mounted parts. Possibly potted to try to make it robust enough.The switch could power up the module. It then stays on, and repeatedly transmits (with a retry delay, to save the battery) until it is successfully reaches the phone/scoreboard/etc. Then switches itself off again, until the next player hit.

author: yasinhamid
author_rank: Newbie
timestamp: March 04, 2016, 02:33:15 pm
content: Thanks for info. Yeah I know the mat is a problem. But for practice/beginners the mat detection is not necessary. Some clubs practice without the mats. Its true that raspberry is too powerful, I was actually thinking about something like arduino. I am software guy, so I prefer do everything by software.

author: Marco
author_rank: Super Contributor
timestamp: March 04, 2016, 03:07:52 pm
content: Don't guard hits have to be ignored too in epee fencing?If it's just about sending the button press, yeah, find a cheap arduino clone and some tutorial for using HC-05 bluetooth modules and go to work.

author: ajb
author_rank: Super Contributor
timestamp: March 04, 2016, 05:33:39 pm
content: Does the epee typically have a mechanical switch? I thought hits were typically detect by making electrical contact between the tip and the opponent's clothing (which would make any sort of wireless system tricky).Quote from: yasinhamid on March 04, 2016, 12:36:24 pmThis part is going to make a lot of off-the-shelf wireless solutions tricky. You'll need to make sure that the end-to-end latency of any wireless system is controlled to far better than 40ms. How strict do you need that 40ms window to be? Absolute latency isn't necessarily a problem, but uncertainty in the latency is. Perhaps bluetooth has some way of dealing with this for the sake of audio links.

author: rfeecs
author_rank: Frequent Contributor
timestamp: March 04, 2016, 06:49:19 pm
content: I actually built a scoring machine some forty years ago. The wired machine is easy, just some simple logic and timers. If you can rig up some reels, like the overhead kind with bungee cords, that would be easiest.I also tried to do a wireless system back then, but for foil. As you know, each weapon (foil, epee, saber) is scored differently. For epee, the whole body is target. But for foil, you only score for touches on the vest target area (the lame). The blade, bell, and strip don't register and are grounded out in a wired system. For the wireless system, I put some sort of signal like a square wave on the vest and tried to detect it with the tip button, relying on capacitive coupling with ground. You would still pick up that signal if you touched off target, but it was at a slightly lower level, so there was some threshold that had to be set. Needless to say, it didn't work very well.For epee, you have to lock out the second touch unless they are almost simultaneous. But I think the biggest problem is rejecting touches to the bell (hand guard). Doesn't seem like an easy problem.