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555 counter curcuit

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ubuntupokemoninc

Sun Dec 12 2010, 04:17AM

Banned on 1/22/2011 for repeated rule violations after multiple warnings.
Registered Member #3299 Joined: Sat Oct 09 2010, 08:11PM
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I am in science Olympiad for school, one of my events is called battery buggy,
basicly i need to create a car that runs on 4.5volts, and the give me a distance, i set the car, and the person who gets the closest to the distance they gave us wins, as soon as i heard, 555 counter poped in my head,

found this, not sure if its what i need

basically if I put a pot on pin 5 to set the lenth and a push botton switch to trigger the curcuit, it will cycle threw the time, and then be off unless triggered again, is the curcuit i showed you what i described, if so will it stay on for say 20 seconds or more, what values should i use for this?

Adam Munich

Sun Dec 12 2010, 04:36AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Seach "monostable 555 timer"

Sulaiman

Sun Dec 12 2010, 07:51AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

A 555 timer is good and you should get close to your target.
like robot wars, the best machine doesn't mean the best result.
practice, practice, practice.

For better accuracy you would need some kind of 'dead-recconing'
- counting wheel rotations is fairly obvious
- if the rules allow it, ...
a piece of string/cotton of the target length attached to the start line could be used to stop the vehicle.
This is a better engineering approach
(guaranteed result, cheap, simple, reliable)

So, take a reel of cotton with you as if it is allowed you don't need anything else! tie one end of the line to the on/off switch and thread the line through to the rear of the vehicle. Attach the other end to the START line.
At the correct distance the thread will turn off the motor AND hold the length..... can't lose.

Thomas W

Sun Dec 12 2010, 10:52AM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
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Posts: 1276

id use a 4017B chip or 2 and use a switch attached to a wheel as a clock to count how many turns it goes around
on monday or tuesday when im back at school il make a mock up on circuit wizard if your interested :)

ubuntupokemoninc

Sun Dec 12 2010, 04:07PM

Banned on 1/22/2011 for repeated rule violations after multiple warnings.
Registered Member #3299 Joined: Sat Oct 09 2010, 08:11PM
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Posts: 220

I already drew up the circuit and ran a test on on circuit maker pro,

the thing is is the cap needs to be huge, and the pot needs to also have a huge value!

but it work on the scope on my program thanks everyone

Adam Munich

Sun Dec 12 2010, 04:24PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

How huge?

Steve Conner

Sun Dec 12 2010, 04:34PM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

For long time delays, it's often better to use a 4060

instead. That's what is hooked up to the browning control on a toaster.

Ash Small

Sun Dec 12 2010, 05:42PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

If you want to be able to program the distance exactly and you have access to a PC notebook, and you can get an old HP dot matrix printer, you could do what I plan to do for my current project.

Use one drivewheel (a three wheeler would make sense here) and write a simple DOS program to run one of the stepper motors using the existing HP circuitry.

All the software stuff is easy to get and you can program it to go any distance you like. (just work out how many 'line feed' commands or whatever you need to send to the circuitry to drive it an inch, or whatever.

Any programmable stepper motor design would work, I've just suggested the simplest and cheapest method I can think of, and one I'm planning to use myself.

EDIT: on second thoughts you might need a parallel port on the notebook (printer port). someone may be able to suggest a way round this, though.

Ruben

Fri Dec 17 2010, 03:44AM

Registered Member #3263 Joined: Sat Oct 02 2010, 04:43AM
Location: Sydney, Australia
Posts: 34

Any AVR, PIC etc can be rigged up quite simply to drive a stepper motor. (google < micro controller of your choice> stepper motor)

This should give you quite accurate results provided you're able to set the distance in software prior to your run, and you can ensure that the wheels dont slip.

Using the 555 or another delay based method will mean you get varying distances as your batteries drain. this will be a royal pita as you try to calibrate things

Does your competition have any other pertinent rules?

ubuntupokemoninc

Fri Dec 17 2010, 09:44PM

Banned on 1/22/2011 for repeated rule violations after multiple warnings.
Registered Member #3299 Joined: Sat Oct 09 2010, 08:11PM
Location: Bantown, USA
Posts: 220

All batteries are provided so we will just keep switching them out, because we don't have to pay for them

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