The stepper motor driver
You don’t need a high powered PC to run this. In fact you might want to find a machine that is old enough to have a printer port. A 25 pin D-Sub connector was the standard for many years but now they’ve all gone to USB ports. If your computor has no such thing you may be able to buy a printer card to plug into it or it may be possible to run with a USB to Printer adapter. Any way here is a chart that shows basicly how we will connect the stepper motor driver circuit to the printer port connector.
The Schematic has been revised to correct some errors in the connections to the IC’s (sorry).
         
So here is a new Schematic to get a basic idea of what to connect. You will see two ICs (intigrated circuits) used in the schematic they are the CD4516 a binary up/down counter and the CD4028 which is a BCD to decimal decoder. You can find more detailed specs on these parts here:
http://www.datasheetcatalog.com/datasheets_pdf/C/D/4/5/CD4516BE.shtml
http://www.datasheetcatalog.com/datasheets_pdf/C/D/4/0/CD4028BE.shtml
For those who want to make a PC board here is a board layout
 and here is a print file (StepCheapBottom)
This is designed to work with a varity of stepper motors, 5 or 6 wire unipolar types. Its also made to operate from about 9 volts to up to about 24 volts. Below is a bread board layout of the circuit but I can offer a PC board layout for those of you who want something a little more professional. You will need 3 of these for the X, Y, and Z motors.
One nice thing about this circuit is if you have a motor that is rated for 12 volts and has a resistance of 24 ohms then calculate the wattage of the motor like so: 12 * ( 12/24 ) = 6 Watts. Then put something close to a 6 watt bulb in the socket. Then use a 24 volt ( 12 * 2 ) power supply to run the circuit. It’s an easy way to get a more or less optimum preformance out of the motor.
As an examlpe of where to get motors here are some pictures of an old computor floppy drive.
 
 
And another good place to get motors is out of old printers. Here’s a really nice one from an old Panasonic KX-Pxxxx 24 pin printer
  
 Here is a parts list:
Ref. Qty Description
C1 Cap 1Â Capacitor 10 volt or more and about 200 uf
Part No. Mfg. Source Source Part No.
EEU-FC1J221 Panasonic Digi-Key P10346-ND
Ref. Qty Description
R1 Res 1Â Resistor 1000 ohms
[if your voltage is > 15 volts this should be 1/2 watt or more]
Part No. Mfg. Source Source Part No.
5073NW1K000J12AFX Phoenix Digi-Key PPC1.0KW-1CT-ND
Ref. Qty Description
R3 Res 1Â Resistor 100K ohm
Part No. Mfg. Source Source Part No.
ERO-S2PHF1003 Panasonic Digi-Key P100KCACT-ND
Ref. Qty Description
Zener 1 Zener Diode [ Voltage regulator for ICs]
Part No. Mfg. Source Source Part No.
1N4735A-T Diodes_Inc Digi-Key 1N4735ADICT-ND
Ref. Qty Description
D1-D4 4 Diodes [ to clamp voltage spikes]
Part No. Mfg. Source Source Part No.
1N4004-TP Diodes_Inc Digi-Key 1N4004-TPMSCT-ND
Ref. Qty Description
U1Â 1Â IC BCD Up/Down Counter 16-DIP
Part No. Mfg. Source Source Part No.
CD4516BE Texas_Instruments Digi-Key 296-2075-5-ND
Ref. Qty Description
U2Â 1Â IC Decoder CMOS BCD-DEC 16-DIP
Part No. Mfg. Source Source Part No.
CD4028BE Texas_Instruments Digi-Key 296-2045-5-ND
Ref. Qty Description
Q1-Q4 4Â MOSFET N-CH 100V 12A TO-220AB
Part No. Mfg Source Source Part No.
RFP12N10L Fairchild_Semiconductor Digi-Key RFP12N10L-ND
Ref. Qty Description
R2Â 1Â Socket Hldr Lamp Wedge 23 Series
Part No. Mfg.
23-35 (PC) Lighting_Components_and_DesignÂ
Source Source Part No.
ALLIED Electronics 931-2335
Ref. Qty Description
Conn. 1Â Connector 25 Pin D-Sub Male
[You need this to connect to the computer]
Part No. Mfg. Source Source Part No.
171-025-113R001 Norcomp_Inc. Digi-Key 4225ME-ND