Test Machine Control Box
Serial Control and Data Logging for a Test Machine
-Mini ITX format motherboard in a small case, with a 1U format ATX PSU and CF memory cards for the operating system and logged data.
More pictures:
The Front of the Control Box
The Back of the Control Box
Inside, Looking from the Front
Inside, Looking from the Back
Custom Boot Logo -nerdy but nice!
Comments on the Photos:
- Sorry about the quality of the photos; they are scans of photographs.
- The case is a better fit than the photos show -when the photos were taken, not all the case screws were in place.
- The IDE data cable was removed for clarity in the inside photos.
- The Boot Screen photo is not very clear but it shows a photo of the test machine.
What Does It Do Again?
Good question. At work, we have a machine to test materials in compression and tension, up to 2.5 tonnes load. We wrote our own software to control the machine and log the test data. We wanted a dedicated computer to use with this machine and chose a mini ITX motherboard as they are compact and cheap.
Spec:
- VIA Epia VE-5000 motherboard
- 128MB PC-133 RAM (Kingston)
- 64MB CF Card for the OS
- 64MB CF Card for the Logged Data
- 1U ATX mains PSU with fan
- Metal case (from RS Components Pt.222-042) Dimensions: 203x279x65mm (8" x 11" x 2 3/4")
Construction:
The first problem I came across was that the motherboard did not draw enough power to keep the PSU on so I had to add a high wattage resistor to draw some more power from the 12v output. If I remember right, I had to draw about 7 Watts of extra power using this resistor before the power supply was stable.
The next problem was the case, which I had ordered from RS Components -it was smaller inside than I had anticipated. If you look at the inside photos, you can see two rails that run the length of the case. These rails intrude into the case's internal space by 20mm each side. Everything fitted in, but only just.
I made an aluminium strip to mount the power resistor and CF card holders on and attached it to the case rails.
The mains socket was relocated from the powersupply the outside of the case. I had to extend the PSU Earth Wire (mains ground) to the metal case. The result was good, but in retrospect, I should have saved myself the trouble and used an external PSU and a DC to ATX converter board.
I cut a hole in the side of the case to allow access to the removable CF card which stores the test results.
The end panels of the case are made of aluminium so it was easy to make the rectangular cutout for the ATX connector panel. The rest of the case is steel. The case is quite strong once all the screws are tight and I finished it off by adding a power switch, LED and some feet for the case.
BIOS Hack:
I stripped out the BIOS code that tries to look for a network boot server to reduce the boot-up time. I also added a custom boot splash screen.
Operating system:
FreeDOS seemed a suitable choice for such a simple computer. All I needed was a simple and reliable OS to format the data card and run the text-based software.
Control Program:
The Test Machine is controlled using simple ASCII commands, sent over a serial RS-232 cable. The control program is written in Q-BASIC, which is easy to work with and fine for this simple application. Being an interpreted language, it can be easily modified in future if need be. From a cold start it takes 6 seconds to boot the computer, load the OS and start the control program!
Links:
www.freedos.org/ A Free, DOS-type Operating System.
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Last Updated : 30th November, 2003
