Pulse Count Problem

Hey...good question...

Sorry I've got no simple solution, I'd use a microcontroller, two inputs two counts, and then add 'em together.

One would think there'd be a simple cunning way of doing it .

Del

This seems profoundly straightforward and on the money. Alternatives such as sending the pulses through diodes would result in missed pulses, unless the pulses never overlap or have predictable regularities. Plenty simple and cunning enough. 10 points for good answer... 5 bonus points for the first good answer.

There are ready made microprocessors and the manufacturers call them counters. I wonder why?

There are some that will accept the stated signal switched voltage and there are that will accept 2 inputs which I am sure you could in some way ad together. They can be configured so they take all sorts of signal sorts and shapes and will have high def filters in them if you want them. You never need to loose a pulse ever as long as you know the spec you are working to.

I have worked with quite a few from the RS range and never had an application that could not be worked out. No programming needed as it is all already in the box ready to be configured. This can be a pain and is the only drawback, you need to speak funny languages to decypher some technicians translation of Bangladenglish!

What is it with these manuals?

While I agree that Del has the most elegant solution, if the chap doesn't have PIC experience or programming gear, and can afford in his app. to lose the odd count, then a couple of 1N4148's (and maybe a couple of R's & C's) is by far the quickest and most cost-effective solution.

We'd need to know the full story before finding the best answer.

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I would go to RS Components and look up their range of counters. They do lots of counters and most will give you a scaling function which you can use to re-calculate the total it should display from the counted amount of pulses.

I would look at RS number 500-6485 part number H7CX-A11SD1

This is a counter that supports your 24VDC signal and does give you pre set functions for batch output and scaling. (please check with them before going with my suggestions)

You can find them on http://rswww.com/cgi-bin/bv/rswww/home.do?returningUser=N&cacheID=ukie

or phone UK (United Kingdom) 01536 402888

Do the actual pulses fire with a time lapse? Could these pulses fire transistors, each feeding the counter?

James

It states the pulses are 24Vdc switching. I read that as the pulses are in fact 24Vdc on or off. That makes them readable by the counter on the input as they are. No need for further transistors.

If the square waves are not synchronized, each might trigger an input to a counter, Yes?

James

Yes that is correct. This is in my mind why I think he might want or need a scaling factor. That way you can determine the total count depending on a pre determined amount of pulses.

I had a VISION....... sorry, flashback. I jumped to the conclusion, two conveyors feeding products, merge. A dark sensor registers the passing can of dog food.

Yada yada yada. (Bla, bla bla in French)

James

Need to know more about the source signals and what is counting them.

If you have two pulse trains with short, fairly infrequent pulses on each, they could be OR'd with a couple of diodes, and you'd only miss the odd coincidental pulse pair.

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Two quick off topic questions. What time is it in U.K. now. What is your national electrical standard called? 6:38PM east coast, here.

James

Hi, James,

Local time 23:44 GMT.

"What is your national electrical standard called?" - not 100% sure what you mean here - wiring must conform to IEE Wiring Regulations (now 17th edition, I think!) which is a British Standard.

Rgds, John

5 hours difference.

Ours is National Electrical Code (NEC) Canada's is close to ours.

I will try and find IEE on Web.

James

If you want to do it cheap and dirty, you could shorten the pulse width with a CR network and 'OR' them with diodes as has been suggested..

But there is always the coincident pulses problem, whereby they will be counted a 1 not 2.... you could also add an AND gate etc to catch the coincident ones....but you will end up with a glitch prone mess... This is why I made the suggestions in my initial post.

Del

Del you want to get a spike out of eachTTL pulse coming in to be counted.Good idea!

And you are worried about 2 from 2 strings appearing at same Real time .

In that situation you foresee one pulse getting LOST.***

You (or some Circit tinkerer )can take care of this *** situation thus:

A Chip receives 2 pulses at 2 input gates at same(or within the resolution time of the Spike generator) Real time. This Chip has a simple Logic " When 2pulses arrive at very close intervals--it gives out 2 countable pulses with a short(but countable)gap in time".

If you want a simple and relatively cheap solution:

Use an Automation Direct DL-05 and use the first 2 inputs X0 & X1 (high speed counters)

and add the two counter values , you have a lot more that you can do with this unit , but the device is under $125.00 and software for it is cheep $99.00.

No problem the out put can be done several ways! but this is the most simple off the shelf method others I could recommend would more expensive but no software or programing ie. two counter modules and a summer module give AGM in Tucson AZ. a call

They can set you up there for a combined pulse train out put or a total count , even combine the units in one module or board w/ plug in modules if required.

Jon Russell

2 off 1N4148 = about £0.02 (don't know what that is in $).

No offence taken the dude ( and question ) just did not sound like a board level inquiry, more like a shop floor level ...help!!

Jon

I like automation direct.com I had the hardest time convincing a plant to change over from European electrical parts to those sold in America. But, does the individual want to sit down and build a small electronic circuit to solve his problem or buy something prepackaged? (The plant was foreign operated and really didn't understand all we need is a compatible product)

James

That sounds a lot of money in my book.

I know you can get of the shelf counters starting from £25 range going up to what you say in your web page but to start there is not the right approach.

Start at the bottom and go up until you get what does the job, most logical way of getting to choose the right product from a CUSTOMER'S point of view.

RS components does pre-configured counters that will do the job starting around £100 figure. You can then stack features if you like.

You won't make many friends with your sales technique

I merely offered another solution, fortunately we live in a world full of choice. If I have offended you or anyone else I appologise.

Rob

You might want to look at Koyo Counters.

I've used these and they're easy to configure and use. Some models have dual inputs which is what you're looking for, I believe.