Both of the stepper drivers are use a 74194 - Bidirectional Universal Shift Register from the 74LS or 74HC - TTL families of logic devices to produce the stepping function. A diagram at the bottom of this page shows the difference between the 74194 - UNIPOLAR and BIPOLAR step pattern generators.
The UNIPOLAR driver uses a ULN2003 - eight segment, darlington IC as its output device.
The BIPOLAR driver uses a L293D - four segment, 1/2 H-Bridge IC as its output device.
These stepper drivers have only basic control functions: Forward, Reverse and Stop and Step rate adjustment. The calculated Step rate adjustment range of the drivers is 0.72 (1.39 sec) to 145 steps per second. (Lower and higher step rates are also possible.)
The only step angle for these drivers is the design step angle of the motor itself. 'Half-stepping' is not possible with either of the driver circuits.
Click Here For The UNIPOLAR Stepper Driver Page (2008)
Click Here For The BIPOLAR Stepper Driver Page (2008)
Comparison Of The UNIPOLAR and BIPOLAR Step Pattern Circuits
2007 - Stepper Motor Drivers (74194)
Click Here For The Original - Unipolar Stepper Driver Page (2007)
The 2007 Unipolar Driver circuitboard is no longer available. It has been replaced by the 2008 version shown above.
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Please Read Before Using These Circuit Ideas
The explanations for the circuits on these pages cannot hope to cover every situation on every layout. For this reason be prepared to do some experimenting to get the results you want. This is especially true of circuits such as the "Across Track Infrared Detection" circuits and any other circuit that relies on other than direct electronic inputs, such as switches.
If you use any of these circuit ideas, ask your parts supplier for a copy of the manufacturers data sheets for any components that you have not used before. These sheets contain a wealth of data and circuit design information that no electronic or print article could approach and will save time and perhaps damage to the components themselves. These data sheets can often be found on the web site of the device manufacturers.