It also analyzes transistor’s characteristics such as voltage and gain. The maximum input voltage is 5 Volts. The main limitation is the ‘leakage’ current of electrolytic capacitors. If RT is set to 1 Megohm, the calculated step rate will be 0. 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. It is an irreplaceable tool for troubleshooting and repairing electronic equipment by determining performance and health of electrolytic capacitors.

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In a practical application the direction of the stepper load, a heating duct damper for example, would bring the temperature represented by the voltage at R IN back to the range between the HIGH and LOW voltage setpoints.

I wired everything steppee you suggested, e voila! The next circuit uses TIP Darlington type transistors to increase the current capacity of the driver circuit to 5 amps per winding.

Bipolar Stepper Motor Driver (2012)

Making the bases of both Q2 and Q3 LOW at the same time can be used to reset the SN to its starting position without having to remove the circuit power. The main limitation is the ‘leakage’ current of electrolytic capacitors. Given the tolerances of actual components and the leakage currents of electrolytic capacitors the actual CLOCK rates may be wtepper or higher. These may be helpful in understanding stepper motor operation and control.

Bipolar Stepper Motor Driver

The limit switches at the outputs of the comparators are used to prevent the damper from going beyond its minimum and maximum positions by to stopping the motor. To avoid duplication, the diagrams from the Unipolar driver web page have been reused on the Bipolar driver page. If you have any questions or comments please send them to the email address on the Circuit Index page.


The maximum RPM at which stepper motors will operate properly is low when compared to other motor types and the torque the motor produces drops rapidly as its speed increases. If the circuit board is to be placed in a plastic case, do the assembly work on a wood or metal surface that is connected to earth. This would cause the motor to move incorrectly or not at all during normal operation.

An external clock with a step rate greater than steps per second can be connected to the driver circuit by removing capacitor C1. Consult the particular device’s datasheet for their specifications. Potentiometer “R IN” could be a temperature or light sensing circuit.

To use the ‘disable’ inputs of the Lthe section of copper trace between pins 1 and 16 of IC 3 must be cut and a jumper connected between pins 1 and 9. There is a limit to this approach as control of the step rate becomes less accurate as the capacitance increases and at some point the timer will stop working due to the leakage currents of the capacitors.

The explanations for the circuits on these pages cannot hope to cover every situation on every layout. The next diagram shows the modifications that are required for the circuit board followed by the schemtice for the output disable circuit.

The circuit above replaces the direction control switch with a “window” type voltage comparator circuit. When the drivers are disabled, only the power to the motor is turned off, the rest of the circuit remains active.


Basic Stepper Motor Driver By – musicpenny

The connections in the following diagram will allow the motor to make single steps. The step and direction controls for the Bipolar motor driver are the same as those for the Unipolar motor driver.

A pad is provided for this connection as well. In the above items the “calculated” minimum and maximum CLOCK frequencies are valid for the nominal part values shown.

The photo of the circuitboard shows the tab of the regulator cut off, this is an option that is available on request. Additional capacitance can be added to the IC 1 circuit to provide slower motor step rates. The direction of the motor can be controlled by another circuit or the parallel output port of a PC. The SNNE’s drivers are enabled in pairs, the ‘Y’ coil’s drivers enabled via pin 1 and ‘X’ coil’s drivers enabled via pin 9.

A good practice is to touch the work surface before touching the circuitboard. The driver is designed for hobby and learning uses. The circuit above replaces the direction control switch with a “window” type voltage comparator circuit. These data sheets can often be found on the web site of the device manufacturers.

Users of this circuit will have to determine motor phasing and power requirements for themselves.