SCHEDULING REVISITED

THE MAGAZINE FOR COMPUTER APPLICATIONS Circuit Cellar Online offers articles illustrating creative solutions and unique applications through complete projects, practical tutorials, and useful design techniques.

	SCHEDULING REVISITED
by George Martin Start ı Experience Required? ı An Example ı Requirements ı Estimating ı User Interface ı Breaking it Down ı Sources and PDF REQUIREMENTS First, you have to put down some mechanical requirements to bind your project: ı the board mounting area has a straight edge for rotational orientation ı the board is held down with simple clamps ı the board has targets for registration ı calibration from week to week in the field is OK ı stepper motors meet the speed requirements. If this is not true, then you need servo motors, and thereıs a lot more expense involved ı you can purchase an XıY table suitable for this project. (This is probably not true, but for this article letıs pretend.) ı XıY motion is with steppers and Z motion is with an air solenoid. You need shop air for the glue dispenser, so a small air solenoid is not asking too much. Next, you have to list some electrical requirements: ı stepper motors have hardware drivers available ı limit switch and emergency stop switches are available on the XıY table ı the PCıs power supply can drive the motors ı one ISA card will fit all the interface electronics And finally, some software requirements: ı the user can program the unit by moving the dispenser (with a joystick or keyboard input) and record locations and dispensing amounts ı the user can also enter an ASCII text file with program commands ı the program will be written in C and run under DOS ı calibration is a requirement ı speed of operation is not a major requirement in this device This is a good first pass. I suggest you present this to management and make sure they understand what youıre about to do. You should say things like, "Now, you realize that this wonıt run under Windows." If you donıt point out these things, youıll be sorry. If marketing needs Windows, then you need to include that in your estimates. And really, if Windows takes more time and effort but is absolutely necessary, now is the time to have that discussion. PREVIOUS • NEXT Circuit Cellar provides up-to-date information for engineers. Visit www.circuitcellar.com for more information and additional articles. For subscription information, call (860) 875-2199, subscribe@circuitcellar.com or subscribe online. ıCircuit Cellar, the Magazine for Computer Applications. Posted with permission.