single lane race timer?

[stanfield]

is there a way to build a simple circuit that will start a timer for a single lane boat race. I am a tech teacher and want to add time trials for the design of boats. they will be tested in a 6" pvc. basically lift a gate, start switch starts timer (display time) and when it hit the end stop the timer, reset and run again.

Make sense? I can buy one from Kelvin or other sources but can not spend the $$$$ for what I think should be very simple.

any help would be GREATLY appreciated.


thanks :?

 

[ljcox]

What time scale do you want?

Examples:- 0 to 9.9 seconds?, 0 to 59 minutes? 0 to 9 hours?

Have you done a search in this forum for "timer" or "counter" there have been many posts on these.

Have you searched the internet? see for example www.discovercircuits.com

Post your results so we can assist if necessary. There is no point in us re-inventing the wheel for you.

Len

 

[stanfield]

I have researched both timer and counter and have only come up with count down timers or delay timers, counters I have not found really anything.

I just searched for "stopwatch" and found a doc it only goes to 99. I need something that will go to say 5 min, some boats are really slow.

I attached the file it is a digital stopwatch schematic.

where would i add the triggers both start and stop? can I build this on a breadboard?

I am not an electronic master by any means.

thanks

 

[ljcox]

I just searched for "stopwatch" and found a doc it only goes to 99. I need something that will go to say 5 min, some boats are really slow.

Do you want to count the seconds also?

Say 0 to 9min 59 sec.

Len

 

[stanfield]

yes that would be the best

 

[Misterbenn]

several ways of doing this really. as your not a master of electronics i would sugest this as the best:

this will only count in decimals so you might have to measure in 100s of seconds
ok you want a clock first, somthing to set the time base for your counter. if you know how to make one a 555 Astable would be perfect, if not use a RC circuit. I've used a 555 Astable in my circuit i would think you want a time base of about 1second
The 7segment counter/ decoder powers the 7 segment displays, with "10" pin acting as the clock for the next counter decoder. as i say this only counts up in 1, 10, 100, 1000. you can keep adding an extra digit onto it.


if you really need a time format number (9:59) i could make a few changes to the circuit if you want?
Also i assume you want it so it activates when the gate is opend and stoped when the boat reaches the end? if you design a sensor arangment for that as well??

but why not just use a stop watch??

 

[ljcox]

The circuit will need a 100 nF ceramic bypass capacitors across each 4026.

You could make a 4026 work as a modulo 6 counter by inserting a 7 input AND gate (one input inverted) to detect when the outputs = 6 and thus apply a reset.

It also needs start and stop logic, but that is easy. I suggest an RS flop Flop.

The 555 oscillator won't be very accurate, a crystal osc would be better.

Len

 

[ljcox]

Here is my suggestion Edit - it is based on the circuit posted by Misterbenn. Text below and circuit edited to correct errors and to affect a minor improvement.

Circuit description

When the power is turned on C1 is discharged so the output of IC6a goes high and applies a reset pulse to the counters & IC5b.

When the voltage across C1 reaches the upper threshold of IC6a, the reset pulse is terminated.

When the start button is pressed, Q2 goes high and the counter starts counting.

When the stop button is pressed, as J is low and K is high, Q2 will be set low and the counter stops counting.

When the reset button is pressed, counters and Flip Flops are restored to their initial states.

Counter IC3 counts in modulo 6 because when the count reaches 6, b is low and e is high. Thus the output of IC7a goes low and after a delay of about 10 microseconds IC3 is reset. The purpose of the delay is to filter out decoding spikes that may be present in either the b or e signals.

Len

 

[Misterbenn]

nd of course the 7 segment displays need current limiting resistors on the inputs.

 

[Jay.slovak]

I think, any PIC could do the job. Pretty cheap, simple and Precise...
But If you don't know MCU's then this solution is Fine.

 

[stanfield]

thanks for all the help I will try this and see what happens.

the reason I don't want to use a stopwatch is 1, not as exciting as a timer, 2, kids cheat to win if given a chance.

thanks again

 

[ljcox]

I modified the circuit and description posted above to correct minor errors and affect a minor improvement.

Len

 

[Tonytee]

Single Lane derby car timer

Hi, I am trying to build a derby car timer. I need a circuit diagram (Probably something like what that guy is using for his boats) The difference is that I need an optical clock starter at the top of the track, and an optical clock stopper at the bottom of the track. I also need the display to show 1 digit full second display, as well as 4 point second accuracy (Ex: 1.2635 seconds) I am going to use this as a development tool to build the fastest car I can, so that any small modifications would be noticed.

Any Ideas

Thanks,
TT

 

[InventionUnlimited]

When I was at school, we had simple input/output boxes connected to all the PCs in the technology classrooms. I cant remember the name of the software we used - but it was a really really basic language - even more basic than BASIC. Something like that would be really simple to do if your classes are equipped with such boxes. Or you could just connect your start/stop switches to the parallel port of a PC, and use the PC for timekeeping, very simple in both software and hardware terms. (and no circuit building)