in headers for J2, J3 and J4 are facing
the outside edge of the board. If you look at the solder side of the
PC board, the square pad is pin1. Make sure you put the shunt on J5.
The finishing board should look similar to this picture.

The motors are connected
to J2 and J3. Incorrect motor winding connections may damage the driver
chip; see the picture below for proper motor connections.  

 

             
Figure 2 Stepper Motor connections

The
MD4 is a basic design of 8031 microcontroller; the design is very similar
to the MD-2 board except that this board has the on-board +5V regulator
so it does not require a dual voltage power supply to run. . It uses
two Allegro UDN2540B ICs as motor drivers. The U1 is 8031AH microcontroller
which can be replaced with any 80C32, 87C51, 87C52 or flash base microcontroller
89C51, 89C52 families.

The port P1.0~P1.7 generate the step sequences to
drive the stepper motors with U2 and U3 (UDN2540B). The port P3.4 and
P3.5 enable/disable the power supply to the motors. You may wonder why
does the design use Q2 & Q3 to turn on/off the power to the J2 motor
instead of the using the enable pin on U2? Well, in some applications,
which require the motor to lift a heavy load, if the simple belt drive
or gears drive system is used, then when the motor is stopped, the holding
torque of the motor alone may not able to hold the load in place. Of
course using the worm gear or lead screw can easy solve the problem
but they are not cost effective. If we apply some low voltage to the
motor after it stop, that enough to lock the motor in place without
overheat the motor, this way will increases the holding torque and serves
the same purpose without adding cost to the whole system.   

When Q2 is cut off, theres still some voltages apply to the motor winding
thru R9. You may need to change the R9 value depending on the motor
winding resistance. The R9 is omitted if there is no need to increase
the motor holding torque.

In our EPROM sample code, we configured
the J4 as input ports for controlling the two motors. Their functions
are as follows:  

                 J4-Pin1-------- Motor0 enable  

                 J4-Pin4-------- Motor0 direction  

                 J4-Pin6-------- Motor1 enable  

                 J4-Pin8-------- Motor1 direction  

Shorting the pin1 to ground (pin2) will turn on the Motor0 in one direction, with
the Pin4 shorts to ground first then Pin1, the Motor0 will rotate in
opposite direction. Same functions are on Pin6 and Pin8 for Motor1.
Jumper J6 and J7 are not used in our sample code, but you may change
the program so that with the different jumper setting on J6 & J7,
the motor will run at different speed.

You can download the Intel hex
code and the source
file here. We offer the MD4 as a kit so you can build it
yourself and customize it as needed.

These parts can be purchased from
us:

Parts List

High quality double sided MD4 bareboard          $6.00  

8031AH 12MHZ Microcontroller(removed from board)
$0.30  

27C64 Programmed EPROM                           $0.50  

Two UDN2540B                                     $2.00  

12MHZ or 11.0592MHZ Crystal                      $1.00  

74LS373                                          $0.10  

74LS04                                           $0.10  

TIP30                                            $0.30  

7805 linear voltage regulator                    $0.25  

Order the KIT which includes all the components for
just $9.50 plus shipping/handling.