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Author Topic: What to use  (Read 771 times)

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Offline dognapper0Topic starter

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What to use
« on: January 24, 2010, 10:24:49 AM »
I am planning to create a scoring machine for fencing. I need to time shorts between different lines. I am wondering if there is a way to time all of these things without needing an external oscillator. I have an AVR (Atmel Atmega 8 ) from the $50 Robot.

I will have a constant short between A and B lines on one side (and A'B' on the other side), but if that is broken for 14ms, I need to have a light go on (I can program that). If that is broken and it the A line shorts to C' (or A' to C), then a different light will go on. A hit from A to B' should not st off a light, even if A-B is broken. T

A           A'

B           B'
C           C'

Do I need a different chip or can I use oscillators and rig a system of timers. I also am not sure if I need to have a different timer for this.
One thing I am thinking may work is having the timer start and at 14ms, see if there is continuity between the two circuits. This could pose a problem because it is Possible to pop off and them back on, not really what should be a valid touch.

Any help or guidance would be greatly appreciated.
« Last Edit: January 24, 2010, 10:40:32 AM by dognapper0 »

Offline Soeren

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Re: What to use
« Reply #1 on: January 24, 2010, 11:11:58 AM »
Hi,

A -controller would be serious overkill.
I made such a system about 8..12 years ago, with a CMOS4017 as the active element - I'll see if I can find it, but I don't know if the files are on an older PC at home though.
Regards,
Sren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
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Offline dognapper0Topic starter

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Re: What to use
« Reply #2 on: January 24, 2010, 01:56:45 PM »
That's what I was thinking... I just wasn't sure about how to do this. I also have very little experience with the coding for this sort of thing. I understand that it is rather simple to figure out. I was under the impression there would be a better system. Are you using interrupts to code in your system. I also only have the AVR programmer. I am on a very limited budget (Why I'm building a scoring machine and not buying a $700 cheap one), so I don't think I can afford to get much more.

Offline Soeren

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Re: What to use
« Reply #3 on: January 27, 2010, 07:38:14 PM »
Hi,


A few questions before I can finish the circuit:
- I assume A is tip, B is the rest of the weapon and C the "vest"?

- Is it meant just for practise or do you plan on using it for tournaments?

- What voltage will you be using and battery or mains supply?
A battery keeps you from hooking the contestant up to the mains if something goes wrong and makes it more portable.

I seem to recall a short but nasty buzz marking a regular touch, but don't remember if that was on a ground hit as well:
- would you like a buzzer, for what length of time and on either kind of hit or...?

- Should the "lamps" be low voltage lamps (or LEDs)?

- Should they stay on until manually reset or should they stay on for a certain time and then go off?
I imagine they should stay on for some time, say a minute and then go off and be able to be reset manually sooner , but more than 30 years  have passed, since I was active in the sport myself and I'm sure lots of things may have changed since then.

- is this solely for the foil or would it need a double hit marking for the pe as well?

- How precise would the 14ms need to be?

Quote from: Wikipedia on foil
[...] In order to register, the button must be depressed with a force of at least 4.90 newtons (500 grams-force) for at least 15 milliseconds.

I assume it's what you have translated to 14ms?

I also have very little experience with the coding for this sort of thing.

You don't need any coding unless you use a microcontroller.


I understand that it is rather simple to figure out.

Hehe, If I had a buck for each time I've heard that, from someone asking other people to do something for them, I would be filthy rich by now ;D
Please don't ever use such a statement as it conveys a mixture of "why haven't you finished it allready", "I am not able to figure out simple" and/or "'though it's simple, I'd prefer to let others do it for me".


I was under the impression there would be a better system.

There's allways a better system (and a vast number of opinions to go with each), but in the end, what does the job correctly and with minimal parts/coding/assembly/whatever can be termed good enough - the average fencer couldn't care less what goes on inside the box I'm sure.


Are you using interrupts to code in your system. I also only have the AVR programmer.

CMOS4093 (not 4017, my mistake) is not a microcontroller but 4 Schmitt trigger NAND gates and the only "coding" that goes into that is "hardware coding", connecting the logic up the right way round.
I have made the decoding "matrix" for it and just needs your answers to decide what else to put into the circuit.


I am on a very limited budget (Why I'm building a scoring machine and not buying a $700 cheap one), so I don't think I can afford to get much more.

Oh, you can get a used one for $249 on eBay (perhaps even lower), Wireless for $349, USB to PC for $149 and regular boxes from slightly over $400.

What I have in mind would be less than $10 (for the circuit ex. box, lamps, buttons and power).

You could use your Arduino instead and it would be easier to modify should you decide to use it for another weapon, but you could probably use that board for better things.

The ideal would be to use a cheap microcontroller with 11+ I/O lines and a few "glue" parts, but then you'd have to make a programmer yourself and to learn how to code the program and burn it into the controller.
Regards,
Sren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

Offline Pratheek

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Re: What to use
« Reply #4 on: January 29, 2010, 05:39:31 AM »
I am wondering if there is a way to time all of these things without needing an external oscillator.

You can build it without an external oscillator(as long as you are not particular about the timing).

The Atmega8,which you already have, will be more than enough to handle the task.

I would suggest you to go ahead and use the microcontroller, it will be a lot more cheaper and simpler than other options.


 


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