View Full Version : Stepper motor driver ckt. problem

05-19-2006, 02:10 PM
hello friends,

its very urgent as my B.tech final yr. PPT. is scheduled to be on 24th may and i have not been able to make my steper motor run by my driver chip UCN5804B through parallel port programming.

i have gone throgh the tutorial books on parallel port and robotics control by BOOKSBYBIBIN and accordingly designed my breadboard ckt. Before explaining my problem ,letme tell u how far have i tested my circuit.

i have got my breadboard ckt. tested by multimeter till the chip's input.Till now i have successfully connected my parallel port to the breadboard by DB25 connector and also tested the signals in the board by outporting and inporting signals through C program.

after this , i have connected the pins 2, 3,4,5,6 and ground and +5V from SMPS to the UCN5804B chip but i not getting any pulse in A,B,C,D terminals of the same.

Here, I have also connected +5V on the left side of the ckt. from SMPS and connected the ckt. Ground to pin7 of UCN. I have also identified the six wires of my stepper motor and shorted the ‘b’ and ‘e’ wires of the motor and connected the rest four wires to A,B,C,D pins of UCN.

Referring the stepper wire ckt. as given in :- ------

05-19-2006, 02:11 PM
The datasheet of steppre driver UCN5804B is:-


So, after telling u all the things I have done till now ,my problems and queries are :-
1. I am not getting any signal in the A,B,C,D pins of UCN
2. Do I have to short the ‘b’ and ‘e ‘ wires of stepper motor and connect them to the ckt. Gnd., and connect the rest four phase wires of the motor to A,B,C,D of the UCN Pins randomly??

Plz. Do reply

05-19-2006, 09:01 PM
I have worked on the UCN5804B chip, its a bit tricky to get her working.
Try the following procedure:

Connect LEDs at the output (1,3,6,8) of the driver. LEDs cathode goes to the chip while anode goes to the "+5V" supply through 470ohms resistor.

At the step input terminal (pin11), connect a 1k resistor(pull-up) to +5V.


Now, to test the circuit, pulse the pin11 with a wire connected to gnd. each time you touch this wire to pin11, you shall see a change in the pattern of the leds, depecting the various half step sequences.

If this works, then your chip is working properly. Now, follow the circuit given below but only after testing the above procedure.


Hope this helps.
Mohit Bhoite

05-21-2006, 01:00 AM
thanks a lot mohit for the help.

i had one thing to ask that after testing the chip as u have said, i should remove the resistors and connect as per the circuit or should the resistors be left in the pins(1,3,6,8 and 11) of the chip?

05-21-2006, 01:34 AM
after the testing, exactly follow the circuit that was posted earlier and u'll be fine.
Mohit Bhoite

05-21-2006, 02:33 AM
hi mohit,

i tested the circuit as u said but i think there happens some shortcircuit when i connect the pin 11 to ground in order to pulse it bcoz it is also connected to +5V thrugh 1K resistor.

I did just the same as u said but the wire of pin 11 is getting heated up and its insulation began to smell. so i disconnected the enitire ckt. from smps and found that the pins 4,5,13,12 (gnd. pins) have gone black and breadboardbelow them have melted, i think the chip has burnt. :cry:

05-21-2006, 12:06 PM
Hey if your motor is unipolar one and you are not adamant on using UCN5804B chip then I have one solution to get the things working as you dont have much time.

Use a 74HCT245 buffer to take the signal from the parallel port and then route the output of the buffer into a ULN2803.

I will tell you the connections here verbally without any circuit diagram, they are very simple.


Pin 1 - Vcc
Pin 2 to 9 - Input
Pin 10- Gnd
Pin 11 to 18 - Output
Pin 19 - Gnd
Pin 20 - Vcc

here the I/O map is



Pin 1 to 8 - Input
Pin 9 - GND
Pin 10 - 12V or 5V as per your motor ratings
Pin 11 to 18 - Output

here the I/O map is


Just connect the common terminal of your stepper motor to positive end of the supply.

Now sending a zero on any of the input pins energizes the corresponding coil connected to it.

Well for me this configuration works fine...........hope it works for you too.

If any problem persists then post it here, I will try to resolve it.

05-21-2006, 07:09 PM
Thats odd. simple calculations will reveal that current flowing through the resistor is mere 5mA (5Volts/1K). so shorting can be completely ruled out. Secondly, the chip has internal thermal shutdown, so that should save the chip. And even if shorting occurs, theres no way for extra current to flow into the chip.
There 'must' be something wrong in the connections. Double check the connections. Are you sure you are supplying 5v and not 12v ?

All the best.
Mohit Bhoite[/i]

05-22-2006, 09:26 PM
no mohit, i think u didnot get it what i meant.

u have earlier said to connect pin11 of chip to +5V thrugh 1k resistor and then u have said to pulse it by connecting it to a wire at ground. so, pin 11 is getting both +v and gnd, shorting might have occured.

plz reply soon.

05-23-2006, 12:48 AM
The purpose of that arrangement is to give smooth negative going pulse at pin 11(since transistion occurs at a negative edge in this IC). 1K resistor acts like a pull up resistor, keeping the pin11 at 5volts ideally. When you connect it to gnd, the voltage at pin11 is pulled to gnd.These are very basic fundamentals, plz dont get them wrong.
My suggestions come with my own testings, its unfortunate that they dont work in your case.
All the best.
Mohit Bhoite

05-26-2006, 04:57 AM
mohit, i thnk the pulse that u talked abt, should be given from parallel port program rather than connecting pin 11 to +5v first and then keep it grounding momentarily. i did it thru the program and fortunately i got the pulses and then everythng began to work nicely.

well friends, i think the problem was just loose connection, anyways but now everything is working fine and my motors are rotaing at desired speed(by controlling the delay in my program)

thanks a lot for ur all help. this is the most active community i have ever seen, thanks once again. u all were very supportive.

05-26-2006, 04:14 PM
Hello Gaurav,
I'm so glad that everything worked out for you. Congo!
Mohit Bhoite