This page features a Unipolar Stepper Motor driver that uses an EDE1200 (Unipolar) Stepper Motor Controller IC produced by eLab Digital Engineering. to provide 5 control functions, including half-stepping.

  The circuit uses a ULN2008 darlington driver as its output device that can drive motors drawing up to 1.0 amperes per phase.

  NOTE: The circuitboard for this EDE1200 stepper driver contains an error, therefore resistors R6, R7 and R8 are mounted on the back of the board. Due to this error, the boards are being offered assembled and at cost.

  This EDE1200 Stepper Motor Controller circuit has the following control inputs and modes of operation:

1. STEP INPUT - Each time the STEP input (Pin 9) goes LOW, the motor will move one step, depending on how the other four inputs are set.

2. HALF STEP MODE - When the HALF STEP input (Pin 10) is LOW, the motor will move in Half Steps.

3. DIRECTION - The DIRECTION input (Pin 7) controls the motor's direction of rotation depending on the input level (HIGH or LOW). The motor's true direction of rotation depends on order that the motor's coils are connected to the driver.

4. RUN MODE - When the RUN input (Pin 10) is HIGH, the motor will run at the pulse rate at Pin 9 (STEP INPUT). When the RUN input (Pin 10) is LOW, the motor will run at 1 of 8 selectable speeds as set by 3 DIP switches (SA, SB and SC) mounted on the the circuitboard.

5. FREE SPIN MODE - When the FREE SPIN input (Pin 6) is LOW, the four outputs of the driver are switched OFF and the the motor turns freely, regardless of the other inputs. The FREE SPIN input does not have a terminal block position on the circuitboard.

  For more detailed explanations of controls for the EDE1200, refer to the devices datasheet which can be found on this eLab Digital Engineering page.

•   The circuit requires an external oscillator or other source to provide the STEP input signal. This input must be between '0' and +5 volts and be free of noise and bounce to prevent false stepping. A 555 timer circuit or logic device would be suitable as an input. Open collector devices will also work as each of the inputs has a 'pull-up' resistor. A 5uF capacitor and a push button switch connected to the STEP input will also work.

•   All other inputs can be switches or electronic inputs but should not be allowed to bounce while the motor is stepping.

•   The FREE SPIN input does not have a terminal block positon but is accessable via a pad on the circuitboard.

  NOTE: The speeds indicated in the FREE RUN mode tables are approximate and will vary with the resonator's (X-1) actual oscillating frequency.

  NOTE: The following table has been copied from the eLab Digital Engineering datasheet for the EDE1200 IC.

•   EDE1200 Unipolar Stepper Motor Controller IC. Provides all control inputs and generates the output's drive patterns.

•   ECS Inc. ZTT-4.00MG - 4.0MHz Ceramic Resonator ( Digikey Part X902-ND ) Generates the CLOCK frequecy used by the EDE1200 chip.

•   ULN2803 - 8 Segment, Darlington, High Current, High Voltage Peripheral Driver. In this circuit 2 output segments are connected in parallel allowing a maximum output current of 1 amp per phase.

•   LM7805 - Positive 5 Volt Regulator. Provides regulated power for the EDE1200 IC and can supply power to external control circuits.

    For a 12 volt supply, external circuits can draw up to 100 milliamps.

    For a 24 volt supply, external circuits can draw up to 25 milliamps.

  It is not the purpose of this page to provide full explanations of how these devices work. Detailed explanations can be found through datatsheets that are available from many source on the internet and from suppliers.

  The following circuit was used to test the operation and functions of the EDE1200 stepper driver circuit. In actual circuits, the inputs should be noise and bounce free although a toggle switch will work.

  Two sources for the EDE1200 Stepper Motor Controller IC are:

1. eLab Digital Engineering - The manufactures 'Product Overview' page - Part EDE1200

2. Jameco Electronics Part Number - 141532

  All other components or their equivalents are available from a number suppliers. (DigKey part numbers are shown.)

  Although the EDE1200 is sensitive to damage from static discharge, once it is installed in its socket the IC is very safe as all of its pins are connected to the 5 volt supply or to common through low impedance paths.

  When handling or assembleing the circuitboard, avoid nonconductive surfaces such as plastics or glass. 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. Also avoid carpeted areas during assembly.

  A good practice is to touch the work surface before touching the circuitboard.

Circuitboards And Parts

  The following picture is of an assembled circuitboard for the Unipolar Stepper Motor Driver. The board measures 1.9 inches by 2.9 inches and has been commercially made. The board has a protective coating on the copper side but has been not tinned or silkscreened.

  The photo shows a header pins at the upper left of the board. This will not be included with the circuitboard.

  The prototype circuitboard does not have a terminal block position for the DISABLE OUTPUTS input but a pad is provided on the PCB.

  The relative positions of the terminal blocks at the ends of the circuitboard correspond with those in the schematic diagram and the test circuit schematics.

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  NOTE: The circuitboard for this EDE1200 stepper driver contains an error, therefore resistors R6, R7 and R8 are mounted on the back of the board. Due to this error, the boards are being offered assembled at no extra cost.

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•  The price for 1 Assembled circuitboard including the EDE1200 IC is 31.50 dollars US plus postage.

•  The price for 1 Assembled circuitboard without the EDE1200 IC is 20.00 dollars US plus postage.

•  The price for 1 kit and all parts and a circuit board with the EDE1200 IC is 31.50 dollars US plus postage.

•  The price for 1 kit of parts and a circuit board but without the EDE1200 IC is 20.00 dollars US plus postage.

•  The price for 1 circuitboard is 8.50 dollars US plus postage.

 If you are interested in a circuitboard and parts for this circuit please send an email to the following address: rpaisley4@cogeco.ca

 NOTE: If a future version of this board is produced, the only significant change will be the addition of a terminal block position for the "DISABLE OUTPUTS" input.

•   There is no minimum step speed at which stepper motors cannot operate.

•   All functions of the motor driver can be controlled by another circuit or the parallel output port of a PC with suitable characteristics. Refer to the EDE1200's datasheet for some examples.

•   Each stepper motor will have its own power requirements and as there is a great variety of motors available. This page cannot give information in this area. Users of this circuit will have to determine motor phasing and power requirements for themselves.

•   As this circuit can HALF-STEP, the power supply should be rated at twice the rated phase current of the motor.

•   Power for the motors can be regulated or filtered and may range from 12 to 24 volts with currents up to 2,000 milliamps depending on the particular motor.

•   Motors that operate at voltages lower than 12 volts can also be used with this driver but a separate supply of of 9 to 12 volts will be needed for the control portion of the circuit in addition to the low voltage supply for the motor. The circuitboard would also have to be modified.

  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.

  Although the circuits are functional the pages are not meant to be full descriptions of each circuit but rather as guides for adapting them for use by others. If you have any questions or comments please send them to the email address on the Circuit Index page.

15 November, 2011