Push button status logging

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Micksshed

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I have 5x pushbuttons and any one can be pushed at any time I want to capture "button pushed" with a cheap datalogger like OM-EL-USB-3 0-30vdc single channel. It will record only every minute so I need a circuit to capture the button push. I was thinking of 5 x 555 1.5 minute monostables with a differant voltage devider on each output and this connected to the logger via diodes. Any better ideas please?
 
Micksshed said:
No. It should be only one at a time. Two or more at a time is an error!
Click to expand...

If two or more could be pushed at the same time, would that error condition need to be logged?
Can you explain what you're trying to do?
Sometimes it is easier to help solve your problem...than help solve your solution.

Ken
 
Its a hand held device, and one of the buttons will be pressed if a particular event happens, and so on for five differant events. No need to record the error but it might be a good idea to do so.

Mike
 
It looks like your logger will resolve 600 levels at 30V. I might suggest an R-2R ladder digital-to-analog converter. Each switch represents a binary bit of a 5-bit word...32 levels. By pressing a switch it outputs a specific voltage. Only five specific voltages are valid...plus zero. If more than one switch is pressed a non-valid voltage is outputted. You would need to sort the valid from non-valid in a database after the download.

Ken
 

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Thanks Ken, but am i not still stuck with the logger recording every minute -- long after the button push?
Mike
 
How often will a button be pushed? What's the maximum and minimum time between button pushes that you expect?

Ken
 
Micksshed said:
Thanks Ken, but am i not still stuck with the logger recording every minute -- long after the button push?
Mike
Click to expand...

Maybe I am missing something here but those little data loggers and an entire family like them are programmed to start recording data when you tell them to:

Program the logger to begin recording immediately, or at a specific date and time.
Click to expand...

This is done using a software bundle included with the data logger. Using the software you tell the logger how long to record and how often to sample during that time frame. Initially you program in the DTG (Date Time Group).

This is an example of the unit you have or mentioned. and there is no easy way that I know of to use an external button to trigger a start record process. Unless I am missing something here? The link should be similar to what you have.

Ron
 
Hi Ron,
Yes, this is the logger I plan to use I will programme it to start @9am to 9pm with a sample reading every minute. The button press is to record an event not to start the logger.
Mike
 
Reloadron,

Yup, you missed the earlier posts. The logger is acquiring brief voltage readings at 1 minute intervals. A button push (voltage) would only be detected if it were held down for a minute or longer. The R-2R ladder would differentiate which button was pushed, but the voltage level would have to be held "accurately" for more than a minute, like a sample and hold. Any ideas?

Ken
 
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Micksshed said:
Hi Ron,
Yes, this is the logger I plan to use I will programme it to start @9am to 9pm with a sample reading every minute. The button press is to record an event not to start the logger.
Mike
Click to expand...

OK, so you start the logger @9 AM and run it till 9PM for a period of 12 hours. The logger will record whatever voltage is at its input terminals every min for 12 hours. During the 12 hours the logger will take 720 samples of whatever is out there.

The only input the logger has is two wires for single channel operation. This particular logger has a range of 0 to 30 VDC with I believe was 50 mV resolution.

So the buttons pressed are not connected to the logger then? These buttons will trigger an event elsewhere the logger is to record? What is the logger to be connected to?

Ron
 

OK, now I understand as I sat here confused and yes, I missed it. The woosh I heard was it going over my head.

Yeah, maybe some sort of sample and hold as you describe would work. These little loggers are not quite dead accurate at their timing so a min can be 59 or 61 seconds. The trick being to have the signal you want to record available when the logger looks for it.

Thanks Ken
Ron
 
Sorry I am not explaining myself very well.
The buttons "are" connected to the logger. The user presses button A if event A happens and B if event B happenr etc. etc.
Mike
 
OK, I am getting a handle on this. Let me ask you something. Does the logger have to be portable or can it be connected to a PC during the measurement process? Reason I ask is a simple logger having more than one channel could be used. The problem is it would need connected to a PC to use a reasonable one. One channel to measure whatever and one channel for event markers using Ken's suggestion. Additionally do you need 0 to 30 volts or would 0 to 10 volts work?

Ron
 
It has to be portable and small(ish) and not be connected to a pc. I know I could go for a five channel logger but now the price goes up!I am not tied to any voltage if 0-10volt works then thats good. The 30volt came from the max for the logger.
Mike
 
What I had in mind was a cheap starter kit data acquisition kit something like these. Unfortunately, they need to be tethered to a PC. So that precludes using them. I have used them and like the software and what they can do.

Would be nice if there was a stand alone unit out there with a few channels for the cheap. I'll try and think of other options.

Ron
 
I am surprised no one suggested using a PIC, all you need is 5 ports and internal flash memory and a simple program.

Mike
 
I thought about that, but PWM-out to create an analog voltage level might be a problem. I don't know how long it takes to establish a stable voltage level. And there is no spec on the logger as to its acquisition time. But that would be a very good solution.

Ken
 
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