Binari coder

Hi,

I am working on an alarm system, on PLC, I was^planning on making a keyboard, 16 inputs, and coding them to 4 outputs (binari) with external IC to spare the inputs on the plc,

I had some wrong information, and they told me I needed a multiplexer. Now that was WRONG, what I need is a coder.
But i don 't seem to find such a thing. I looked on Farnell but can 't find a coder, can anyone give a hand?

Info about coders is also welcome ...

If you have the right kind (DC) and number of I/O (4 in + 4 out), you can do the coding in the PLC. You'll have to construct an external diode matrix though.

I guess you could still use the (1-of-16 multiplexer) IC by driving its address lines with four outputs from the PLC to be able to sense which alarms are active. Here again you'll need DC outputs to do that.

it doesn 't sense the sensors, it is for the input of the keyboard

Flurk said:

it doesn 't sense the sensors, it is for the input of the keyboard

Click to expand...

Well then, if the keys are normally open, dry contact type you can go with what I described in the first paragraph.

Flurk,

some considerations which should help you do your homework:

1. Get your naming right. What you need is not a "coder". I don't know of such things as coders, I only know of encoders and decoders. And that's not because of my limited knowledge, believe me. Some examples of encoders are the famous 74147 and 74148. Logic schedules of these IC's are to be found on the net. Be very happy most of us do understand what you mean. For example: your sentence "it doesn 't sense the sensors, it is for the input of the keyboard" doesn't make sense at all. A keyboard doesn't need input, it gives output to the inputs of the PLC.
2. What if two switches are closed at the same time? You can't get two numbers - that's what your 4-bit code is giving: the hex number of the closed switch - to the PLC at the same time. With simply 16 inputs you can!
3. Did you consider on the other hand that it's possible to have not a single one of the switches closed at some time? How would you detect this situation?
4. What about the voltage levels? Most IC's work on slightly, but dangerously, different voltage levels (5V, 15V) than PLC's (24V or even more). You could circumvent thes eproblems by building the encoder in the form of a diode matrix, but the still the points 2 and 3 would have to be solved.
   [/list=1]
   Another approach would be to widen up the solution given to you in a previous post (thread started December 3rd, 2003 03:32 PM) from 10 to 16 switches.
   However, on December 23rd, 2003 10:36 AM you redefined your assignment in this thread .
   In this two threads (three including this one) started by you, I think you would have received enough information from different people, viewing the problem from different angles to start studying.
   
   As has been said earlier on different threads of this kind: don't expect us to do your homework. We are all here to help each other by giving hints, tips and information, not by doing someone elses work for them.
   
   Regards,

I don't know of such things as coders...

Click to expand...

Too bad for you. I used to date one. She worked as programmer for
insurance company...

Too bad for you. I used to date one. She worked as programmer for insurance company...

Click to expand...

Well, Panic Mode,

that kind of coder I know AND like. It seemed I forgot about people and only thought about electronics. Could it be I'm already transforming to a robot as has been suggested in another thread. I thought I was still far enough away from the 1000 post boundary stated there .

Kind regards,