View Full Version : Can anyone help with BCD
April 27th, 2002, 01:15 PM
Iím beginning in the world of PLCís and our part time instructor has given us a problem that most students in the class cannot make sense out of it. We are using ďZelio-Soft ď software because itís free to use. I know I canít ask you to do my project for me, but all I need to know is how itís going to fit on a ladder diagram. The Zelio program only allow the user to put three inputs and one output on one rung.
He does not want us to use counters.
Can anyone explain to me, and how itís going to work with the program Iím using
Binary counter "truth table"
Input1 output4 output3 output2 output1
start off off off off
1st push off off off on
2nd push off off on off
3rd push off off on on
4th push off on off off
5th push off on off on
6th push off on on off
7th push off on on on
8th push on off off off
9th push on off off on
10th push on off on off
11th push on off on on
12th push on on off off
13th push on on off on
14th push on on on off
15th push on on on on
Any explaination in simple terms (English is my second language)would be greatly appreciated.
April 27th, 2002, 01:43 PM
I assume the program allows internal bits. If that is the case, the first hint is to use one of these bits as an indicator (flag bit) to show a specific stage is completed. I also assume it allows at least some branching and parallel contacts. If so, the second hint is to use holding contacts to "latch" on each stage completed bit.
If the software allows neither of these things, then it is worth less than you paid for it!
April 27th, 2002, 02:33 PM
You're thread title is for help with BCD. But the bit pattern you posted isn't BCD - it's straight binary.
Look at the pattern of each individual bit, and get some clues. Bit0 changes state whenever the button is pushed. Bit1 changes state whenever the button is pushed and Bit0 is ON. Etc.
I find it rather hard to beleive that any PLC package, even a free one, does not allow more than 3 contacts on a rung. (One output, I can beleive). How does it handle branching?
Even with this limitation, it can be done. But you're right, we're not going to tell you exactly how. Tom and I have given you enough hints (although two different methods) to do this. Post again with your logic and where your stuck, and we'l see what we can do.
April 28th, 2002, 03:28 AM
Just an FYI. Zelio Soft is a Sqaure D/Telemecanique programming language for there Zelio Logic Relay...ie a Smart relay. The software can be found at:
The Zelio Logic Relay can be found at:
This is a very simple device but it does allow branching (the ladder mode) is premade so you insert the inputs and connect the dots kind of thing. The outputs can be set, reset, activated on state change or pulse activated...ie pushbutton turns on and turns off. It has a limited number of Internal bits, timers and counters. It uses a drag and drop insertion method and the ability to right click the device to change its type...ie insert an XIO input and right click to change to XIC
Kind of a cheap way to train for plc, but guess it would allow you to get some of the basics.
April 28th, 2002, 04:07 AM
Now I see what the instructor wants. Using 1 pushbutton you turn on/off the 4 outputs in sequence until all 4 are on. That is why you called it BCD...it is using 4 places and depending on where you are in the sequence determines how many outputs are on.
For a beginner this is an aggressive project. I will give you this clue to get you started. The program has activation on level for the outputs, this means 1 N.O. pushbutton can turn it on then off. Create the first line using a N.O. contact and output (right click the output) then set to activate on level. Once you understand how this works and how to branch using conditions you should get the idea. Note this was to get you started, doesnt mean you have to use the level activation though. The neat thing about this Zelio Soft is the built in simulation, look at that closely too. Take the time to go thru Phil's tutorial on this site and read the MANUAL for that device..use the HELP files/examples. Buy Phil's book as a reference.
Its the middle of the night(cant sleep) and I am sitting here tinkering with your project myself, nice little exercise. I think I retract my statement about this being a cheap start for teaching ladder, it has some features (like the simulation) that makes it
a decent starter package...not too mention that its free. Hopefully though you get to advance to a real plc one day.
April 28th, 2002, 06:24 AM
Just realized the links dont work. Lets try that again.
April 28th, 2002, 06:35 AM
Zelio Logic Relay (http://www.squared.com/us/products/relays_timers.nsf/unid/9DD36F412920298185256A22004ED21A/$file/relays&timersFrameset.htm)
Zelio Soft Program (http://www.squared.com/us/internet/software.nsf/07a0210021262d45862564b5006e4f84/c3ec9c5a950a9b8385256a5e005eb808?OpenDocument)
I think I got it now
April 28th, 2002, 07:46 AM
Without seeing what the software can do then this is a bit of a guesss for me. Have a look at the on off bits and change off to 0 and on to 1. Then do the binary to decimal conversion and what do you get. If the software is smart enough then the is a quite elegant way to do it. Regards Alan Case
April 28th, 2002, 05:04 PM
Alan I didnt understand that post, what exactly were you saying?
The Zelio soft is a simple ladder program. The device has 4 outputs but they want to use 1 input to turn on/off the outputs in the sequence posted. The program is simple but does include timers/counters and I want to use those in the sequence but the project entails doing without therefore its has been a good little exercise. I played with it early this AM after getting back from one of those 1 AM call ins.
Was this a facetious post?
April 29th, 2002, 06:19 AM
Hi Ron. No, this was not a facetious post. What I was trying to say is I have never seen the zelio software so I don't know its capabilities. If you look at the bits in binary, then take the decimal equivalent of them, you can see that it is a progression of 1, 2, 3, 4 etc up to 15. ie every time the button is pressed 1 is added to the decimal total. If the program is smart enough to work in integers, then every on of the input increases the integer (one shot may be needed). Then decode the 4 least significant bits of the word to give the outputs. Regards Alan