New Guy Help with ID chip creation

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vin7102
 
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New Guy Help with ID chip creation

Post by vin7102 »

Hello,

I'm brand new to this technology and never tried anything like this but it seems simple. I have some equipment that uses flow meters to send material usage to a 24v Allen Bradley PLC. Problem I'm having is the flow meters sometimes get switched around and each have different calibration settings. I was thinking of installing small chips into each meter and its only job is to output the calibration setting, Thats all I need it to do.

My meters have 24v source, ground, and I have an available output pin on the m12 cable for sending this info to the PLC. I would imagine it could be binary, string, hex, or whatever else my PLC can read but I'm not sure.

This is my first attempt at getting information about this entire project so any info or advice (hardware I need to buy, programmer, type of chip...) would be greatly appreciated.
I was looking at the Arduino products and they seem pretty simple and straight forward but not sure if its right for this type of application.

Thanks Guys and sorry for the ignorance,
Vince

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zener
 
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Re: New Guy Help with ID chip creation

Post by zener »

Well, since you have 1 wire available you might look at Dalles (Maxim) 1-wire devices. Of course your PLC would have to speak 1-wire, or maybe you could get an adapter to convert to RS-232 or something it can speak. You would want an EEProm device such as DS2430,31,32,33 depending on how much memory you need. Good luck!

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lyndon
 
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Re: New Guy Help with ID chip creation

Post by lyndon »

For something like this, I'd forget about the dallas etc. chips and just use the raw Arduino or Teensy or any board that has a programmable micro and serial output. By the time you're done messing with 1Wire chips you would have spent enough time to pay for many Arduinos!

I assume your PLC can take RS232 input? Basically, you'd just program each board with a different calibration setting and have it transmitted to the PLC at power up. Perhaps have the setting sent over each minute if the PLC doesn't have a way of requesting them.

I don't see the need to build any hardware other than perhaps some custom cables.

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zener
 
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Re: New Guy Help with ID chip creation

Post by zener »

I suppose it depends on how much hardware he wants at the sensor end. An Arduino might be a bit much, but maybe a teensy might fit. The advantage of the Dalles approach is it is a single TO-92 on that end.

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philba
 
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Re: New Guy Help with ID chip creation

Post by philba »

I agree with the 1-wire approach - it's really simple and the package can be encapsulated with epoxy or a couple layers of shrink wrap (i.e. completely sealed) and then most likely hidden away in the connector for the flow meters. Any board, even a teensy, will require more packaging and probably be external to the meter.

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lyndon
 
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Re: New Guy Help with ID chip creation

Post by lyndon »

You guys seem to be missing the most relevant part: it has to connect to a PLC. Unless his PLC that will read a 1Wire sensor or allow I/O programming down to the microsecond timing level, it's not likely to work.
Judging from the phrase "material flow" and that he's even considering an Arduino, I'm guessing that the flowmeters are physically large enough to accomodate something the size of a Teensy.

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philba
 
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Re: New Guy Help with ID chip creation

Post by philba »

Since he said he has a spare wire, I assume that he can use something on the PLC side (maybe your teensy idea there) to turn it into a serial connection. One teensy for all of the them seems like a more economical idea. But then again, maybe the PLC has a 1-wire plugin.

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adafruit_support_mike
 
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Re: New Guy Help with ID chip creation

Post by adafruit_support_mike »

In this specific case, I'd question whether you need a chip at all.

If I read your requirements correctly, you have two devices and want a way to tell them apart. You have one wire that the PLC can read.

I'd get a couple 10k resistors, wire the one in device A between ground and the input line, and wire the one in device B between VCC and the input line. The PLC will read device A's line as a low signal (which is a 1 in Allen-Bradley language IIRC), and device B's line as a high signal (Allen-Bradley 0).

It's dirt cheap, dead simple, durable, won't glitch, and requires nothing more than a simple read from the PLC.

If your PLC has a free ADC, you can expand the voltage-as-id idea to as many values as your ADC can reliably resolve.

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