AB keypad

Thought I'd show off a fun little proof of concept I recently cooked up. The client wanted a simple numeric keypad entry device for an Allen Bradley PLC. They didn't want a PanelView due to cost, size, etc. There are several external USB/PS2 numeric keypads available for cheap, like this one for example:

http://digitpads.com/

I have one of these laying around:

http://www.advantech.com.tw/EPC/newsletter/v23-05-01_00/mbpc_23.htm

It's an embedded 486 with compact flash as a HDD, DC powered, no moving parts. Only connections required are a serial port, power and PS2. I loaded up a stripped down GNU/Linux system(a whole 2.7MB) and used my open source DF1/pccc software to cook up a simple program to read from the keyboard and write to whatever PLC register(eg N7:0). The quickie, see-if-it-works program is 76 lines.

The CF is mounted read-only, so it doesn't care if you don't shut it down properly. You can treat it pretty badly. You can't buy that exact embedded model any more, but models that are more than sufficient start at around $300.

Punch in numbers, hit enter and they magically show up in your data table, works great!!

Congratulations on your project. I am sure it was fun doing it.

PS: There are lots of HMI operator screens (not Allen-Bradley Panelviews) with various combinations of graphics, text lines, and keypads, all for less than $300.

I keep on trying to find a reason for the cmore micro... I want to try them and the price is right, but every time I use it as a 'fix' or project I never get the project


PS. Nice job on the project

Jason Valenzuela said:

Thought I'd show off a fun little proof of concept I recently cooked up. The client wanted a simple numeric keypad entry device for an Allen Bradley PLC. They didn't want a PanelView due to cost, size, etc. There are several external USB/PS2 numeric keypads available for cheap, like this one for example:

http://digitpads.com/

I have one of these laying around:

http://www.advantech.com.tw/EPC/newsletter/v23-05-01_00/mbpc_23.htm

It's an embedded 486 with compact flash as a HDD, DC powered, no moving parts. Only connections required are a serial port, power and PS2. I loaded up a stripped down GNU/Linux system(a whole 2.7MB) and used my open source DF1/pccc software to cook up a simple program to read from the keyboard and write to whatever PLC register(eg N7:0). The quickie, see-if-it-works program is 76 lines.

The CF is mounted read-only, so it doesn't care if you don't shut it down properly. You can treat it pretty badly. You can't buy that exact embedded model any more, but models that are more than sufficient start at around $300.

Punch in numbers, hit enter and they magically show up in your data table, works great!!

Click to expand...

No offense but this wouldn't be allowed in my plant. You are the only one in the world that knows how that system works. Your customer is now required to come to you for any support or upgrades and if you get hit by a bus they'll have to start over.

Again no offense.

Over on control.com you'd be greeted as a conquering hero !

Did you build your own Linux kernel, or use something packaged ? The smallest ones I've ever used are Damn Small Linux and Puppy Linux, and they weigh in around 50 MB. But then, they're made for light desktop work and not embedded.

What language is your PCCC/DF1 application written in ? Is it part of a Sourceforge project ?

In response to allscott:

No offense taken, and I understand your point. But as a counter argument consider that every bit of software I used is open source, and I mean EVERYTHING. From the lowest level boot loaders, kernel, serial port drivers, my PCCC/DF1 packages and the top level application itself is completely free and available in source code format. Try that with anything proprietary. Anyone with decent *nix and C background wouldn't have much trouble with it at all.

In response to Eddie:

I found a project called buildroot, found here:

http://buildroot.uclibc.org/

It worked great for building the complete file system, kernel and all. Although in the end I just downloaded a vanilla kernel from kernel.org and stripped it down even more. The buildroot system uses a scaled down C library(uclibc) and a program called busybox that replaces most of the shell utilities. Together they are much smaller than glibc and the multitude of GNU programs. Not that it matters much these days, I don't think you can even buy CF cards smaller than 512MB anymore.

My PCCC/DF1 software is written in C. It has a sourceforge project page.



Lancie1:

Any recommendations?

Lancie1: Any recommendations?

Click to expand...

Automation Direct

http://web2.automationdirect.com/adc/Shopping/Catalog/Operator_Interfaces

has the C-More as GIT mentioned, plus several other Allen-Bradley compatible HMI panels at low prices. Then there are Red Lion

http://www.redlion.net/Products/HumanMachineInterface.html

, Entertron, Omron, Moeller, and many others.

Thanks for the pointers, I'll take a sniff. Off the top of your head do you know of any that utilize the typical button types found on everyday keyboards. This is not for an environment that would require anything close to NEMA 4/4X(basically it's an office), in addition it will be used quite frequently by the operator. I was leaning towards the standard keyboard style because they are more comfortable and faster to use than the typical membrane buttons found on the heavy duty industrial stuff.

The HMI should be picked based on the functions it will need to perform. The Automation Direct Optimate 1500 and 1510 have 5 actual function keys, 15-key keypad, and 3 indicator lights, for less than $250.

http://web2.automationdirect.com/adc/Shopping/Catalog/Operator_Interfaces/Optimate_Text_Panels/Optimate_1000_Series/OP-1500

In an office environement and wanting a standard keyboard, I would probably just use a Personal Computer running a HMI program. There are several cheap HMI operator programs, but I have no experience to point at in this area. Others may chime in about that.

$139.

Thats nearly impossible to beat with a home grown solution. And it does something your home grown solution does not: it displays the number.

http://www.optimate.com/products/optimate/414.html

The optimate is a good product with a proven track record. You can get it directly from optimate, Automation Direct also sells them.

That Optimate thing is pretty cute, however I have to have a number pad. The application calls for the operator to enter a range of values, probably from 1 to 50. The little $139 guy isn't quite right for that. Like Lancie1 mentioned, given the environment and frequency of use I went with a standard keyboard type interface. Not to mention if they break the number pad, I can replace it for around $20 from any number of manufacturers.

The embedded platform provided me with something that I won't come back to find solitare running on, complaining about some Windows update, or Clippy popping up mentioning something to the tune of "It looks like you are developing an HMI, how can I help?". It also has no fans, no rotary HD, in fact no moving parts at all.

Jason,
What happens if the operator makes a mistake when entering a number?
How does he know if the numbers are correct?

The application is for an operator to choose a vehicle that he wishes to monitor on his screen. The PLC is tracking the vehicles around a track. The PLC is also controlling the video switchers that control what is being viewed. If he chooses an invalid or out of range value, that's easy to deal with. I may still use small display(Dataliner-like), to indicate which vehicle is currently being monitored.

Jason Valenzuela said:

The application is for an operator to choose a vehicle that he wishes to monitor on his screen. The PLC is tracking the vehicles around a track. The PLC is also controlling the video switchers that control what is being viewed. If he chooses an invalid or out of range value, that's easy to deal with. I may still use small display(Dataliner-like), to indicate which vehicle is currently being monitored.

Click to expand...

This last post is the most interesting of all. You must give us more information. What sort of vehicles are being monitored? Is this a Nascar race? How is the PLC tracking vehicles?

Heh, it's a theme park. To be more specific, ride vehicles carrying guests around a track. There is a separate system, provided by a different contractor that controls the vehicles, and therefore knows where they are. How it does it, interesting as it may be, I don't care. My PLC communicates with theirs in order to determine where the vehicles are. The operator wants to view vehicle X, tells my PLC to show him X by entering it on my keypad, and I make the required system switching so vehicle X is now displayed on his screen.