Building your own box

[Triton]

A high school student of mine wishes to build an elecronic scoring box for our fencing club.
I know others have put together their own bungee system for reels and such, but I have not seen any plans or designs for anyone who wants to design the scoring box itself.
To me, this would be a difficult task, lacking the expertise in electronics, but some of my students feel that it would be an interesting challenge. I think it's an interesting challenge too, and if the club manages to get a working box out of the experiment, so much the better.

I'm hoping some of the armorers out there might be able to provide some guidance on this matter. For instance, if any of you have ever built anything like this yourselves, or at least can describe what needs to go into the design. Any advice you can provide would be most welcome.

Triton

[SJCFU#2]

I would suggest that your student start off by thoroughly reading Appendix B to the Material Rules for the performance requirements.

I also recommend letting your student pay for all the parts on their own. The cost of parts could end up exceeding that of some of the "club" machines currently available.

[DHCJr]

What SJCFU#2 states about Appendix B is quite true. 20 years ago the boxes were more complicated mechanically then they are now. If you were to go the route of mechancically building a box, it would be a lot more expensive than to buy a box.

First of all check to see how their programming skills as well as their electronic skills. A basic box is built with at most 4 external connectors, the 2 for the floor cords (if you wanted to be fancy you could have double stripping), one for the piste ground and possibly one for external lights. These along with some lights, are connected Programable Chip.

The key is translating what is into Appendix B into a program.

[klauver]

I would like to find out about the new "wireless" boxes that they are now testing.
Does anyone know anything about this?

[neevel]

In addition to the simple digital on/off states of the inputs, there are also some analog values to be considered (such as detecting whether or not the resistance between the A and C lines is less than 400 ohms for anti-blocking). This means that there will either need to be some analog circuitry outside of the PROM, or use of A/D convertors. Donald is correct that nowadays building a box is as much of a programming task as a hardware task. You still need to pay attention to the analog circuitry that is feeding the raw signals into the chip, though-- there have been microprocessor boxes that are prone to getting spoofed by things like static electricity or cross-line leakage currents and parasitic capacitances caused by sweat.

Unless your students already have access to a PROM burner and an electronics lab, it will be considerably more expensive to build your own one-off scoring box than to buy one (there are 3 decent 3-W boxes I can think of for under $400).

-Dave

[klauver]

While I was at dinner I realized that the answer to most of the problem would be to use the new RFID technology. Not only could it be used in a low power situation like ours, but would also have the benefit where the tournament host could assign a unique RFID ident to each participant. The recievers at each piste would be able to identify a specific fencer, monitor check in times, etc.
You could go so far as building in a vibrator that would alert a fencer when they are on deck.
As someone mentioned above, encryption technology is advanced enough that it would be near impossible to intercept. Also, bout committees would hand out the RFID's randomly at check-in for each event so that no one whould have enough time to break the signal.

[PeterGustafsson]

Hi!

Originally posted by neevel
Unless your students already have access to a PROM burner and an electronics lab, it will be considerably more expensive to build your own one-off scoring box than to buy one (there are 3 decent 3-W boxes I can think of for under $400).

-Dave

If one simplifies the task to building a epee-only box suitable for club use, but not necessarily competition use, would that money estimate still stand?

Have a nice time!

Peter Gustafsson

[neevel]

Originally posted by PeterGustafsson
Hi!



If one simplifies the task to building a epee-only box suitable for club use, but not necessarily competition use, would that money estimate still stand?

An epee-only box could probably be put together with components that would be available off the shelf at a Radio Shack, so it could be done much cheaper.

[Triton]

Thanks to all who responded for the advice so far...

The student in question, Jeff, does indeed have the programming ability required for the job. In fact, he thinks that will be the easy part. However, we have to work on getting the program to conform to the requirements of the rules. Cost is definitely something to watch as well. If this home-built box looks like it's going to cost too much to be worthwhile, then we'll rethink the idea.

At this point, the project has but two objectives: Jeff gets to have fun tinkering, and maybe the club can use the box for practicing.

We'll let you know how (or if) it turns out. And we still might need to pick your brains a bit more on some specifics.

Thanks again,
Triton

[EricS]

Building a FIE-compliant machine is the hardest part--when starting my scoring machine design, I had the first working prototype(foil only) in about two weeks. Making it comply with the FIE rules took over a year!

If he wants to design a scoring machine that doesn't take resistances into account, he should be able to build one with a microcontroller and a very simple circuit. Tell him to think 'keypad scanning matrix' which should get him started.

He could also build a relay box, which would be quite interesting. He'd have to locate a good source for multiple pole relays--Radio Shack just doesn't stock that kind of thing anymore.

In any case, it's quite an involved project. If your student has the motivation, time, and energy--go for it!

[telkanuru]

The real problem with the epee-only box is the cut-out time. PIC will solve that, tho. Oh, for cost, it should be noted that nice places like fairchild/national semiconductor will send you some free samples of most of their parts if you say you're in R&D. Not that I've tried, or anything...

Oh, and this reminds me of the time my friends and I programmed a little box attached to the floor cord to say "FINISH HIM" when one fencer was ahead 4-0.

[D+F+P=Hadouken!]

Thats funny, mine says "Fatality!" whenever a match ends.