PLC as timming device?

aikon · Mar 17, 2007

Hi,

Im totaly blank on PLC's, so I dont know if this is possible or not.

I want to bulid a device to give me "elapsed time" and "speed at finish" for some motorsport Im doing.

Is it possible to use a PLC as a timing device? It has to have better than .01 sec acuracy, preferably .001 sec if possible.

If so, do I need a secific type?

Thanks in advance.

Geir

dchartier · Mar 17, 2007

Hello aikon;

Is it possible to use a PLC as a timing device?

Basically, yes, most plcs will have some real-time clock function that you can access and use in math functions.

It has to have better than .01 sec acuracy, preferably .001 sec if possible.

This could be a little more problematic; it will depend on the accuracy of the RTC of the model you choose. And in most cases I would not count on more than 0.1 sec accuracy. For something more precice and accurate, I would use an independannt time signal.
Hope this helps,
Daniel Chartier

aikon · Mar 18, 2007

Thanks for the reply.

dchartier said:
For something more precice and accurate, I would use an independannt time signal.

What do you mean by "independant time signal"?

Geir

randylud · Mar 18, 2007

Check with the specs for a processor before you buy one and make sure it can do .001 sec timing with the timing instructions such as RTO or whatever it is called in the one you buy. Retentive timers will allow you to start and stop the timing and hold the accumulated value until you can do some calculations with it and then reset. Think of this as a stop watch function. Many AB and other manufacturers have processors with .001 second time bases available.

kamenges · Mar 18, 2007

I personally wouldn't use a plc for this. I don't think you could consistently get the response you need. Some models may come with built-in high speed inputs. But many won't let you freeze a realtime clock value based on a high speed input.

You may want to look into a dedicated device for this. I don't have the time to look around right now but you should be able to find something. If you do go with a plc look at the specs carefully and make sure you can do what you want. If you want to use a timer and you need <0.001 second response you will need a scan time that is that short also.

Keith

aikon · Mar 18, 2007

kamenges said:
... You may want to look into a dedicated device for this. ...

If anyone could help to find examples of dedicated device that I can use, I would be greatful.

Geir

MichaelG · Mar 18, 2007

Look at http://www.rabbitsemiconductor.com
for build you own

Or http://www.microgate.it for off the shelf

Depends on the budget

ymillinium · Mar 19, 2007

plc as a timer

aikon said:
Hi,

Im totaly blank on PLC's, so I dont know if this is possible or not.

I want to bulid a device to give me "elapsed time" and "speed at finish" for some motorsport Im doing.

Is it possible to use a PLC as a timing device? It has to have better than .01 sec acuracy, preferably .001 sec if possible.

If so, do I need a secific type?

Thanks in advance.

ofcourse you can .i think siemense is the best

jimbo3123 · Mar 19, 2007

aikon said:
If anyone could help to find examples of dedicated device that I can use, I would be greatful.

Geir

Sorry, I couldn't resist.

CaseyK · Mar 19, 2007

Do you need that much accuraccy?

Can you afford the extra cost?

Will other variables, such as timing light mounting vibration, wire lead inductances, precision sensor positioning, etc have an affect.

For drag racing, if it were all that serious, you'd have profeesional timing equipment anyway.

For county line road racing, 1/100's doesn't really mattaer.

Logic would be simple to through in who was the winner, if anyone redlined, etc.

Setting up staging wouldn't be difficult, and with a little work, a handicap could be added.

aikon · Mar 19, 2007

CaseyK said:
Do you need that much accuraccy?

Can you afford the extra cost?

Will other variables, such as timing light mounting vibration, wire lead inductances, precision sensor positioning, etc have an affect.

For drag racing, if it were all that serious, you'd have profeesional timing equipment anyway.

It's for Dragracing. But only for practice.

The pricetag for the pro equipment is arond 6,000.- USD.

So I thout it migt be possible to build my own kit, less expensive.

Geir

PLC as timming device?

aikon

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dchartier

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aikon

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randylud

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kamenges

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aikon

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MichaelG

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ymillinium

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jimbo3123

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CaseyK

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aikon

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