need help with project

[NIGHTHAWK]

stepper 24v 12v

I am doing a project on the development of a microcontroller based solar panel tracker. This is a prototype and the solar panel is powered by a stepper motor (7.5 degrees unipolar PM35S-048 having 5 wires. Drive voltage is 24v and coil resistance is 50 ohm.)I am using the 8255 PPI along with the 8051 microcontroller. I connected a sensor ciruit to port A of 8255 which acts as input port and connected the stepper motor to the port B which acts as output port. I used a ULN2003 ic in between the stepper motor and the 8051 microcontroller to achieve the required power rating. I used a 12v adaptor for the purpose of stepper motor Vcc. I wrote the assembly level program and ran it on the 8051 assembly kit by connecting the pins accordingly however I was unable to get any rotation of the stepper motor. My project is due in 2 days and I am in a ditch. If any one is willing to help me out and if any one has any info on this please do reply so that I may send you detailed information. I would be grateful for the help. Please reply As soon as possible

Added after 6 minutes:

sorry but i forgot to tell my id it's sandeep_p_84@yahoo.co.in

 

[VVV]

12v uln ic

I am willing to give it a try.
But before we get into further details, can you check that the rest of the circuit is working?
Take out the micro and the 8255 and then drive the pins of the ULN2003 "by hand", in the right sequence to see if the stepper actually works. Otherwise you will waste a lot of time.

The 8255 needs some programming, so maybe that is the problem, but first let's make sure everything else is working, I mean the signals to and from the 8255 and then the signals between the 8051 and the 8255. These you can buzz out with your meter.

 

[sunish]

hai
here the problem is the stepper i am going to use is bipolar
with 1.8 degree step angle,6A
how can i interface the same with the 8051?

reg

ml[/i]

 

[NIGHTHAWK]

great to know that you guys are willing to help. i am 100% sure that the program is right. i simply replaced the ULN 2003 Ic and the stepper motor with 4 LED's connected to port B of the 8255 and it works perfectly. (both clockwise and anti clockwise directions ). as for VVV's idea of rotating the stepper motor by hand that's a cool idea. i wonder why i did not try it out.

the main problem definitely lies with the stepper motor interfacing. perhaps it is not getting the required power. i will check it out. i am using a 12 v adaptor for the Vcc of the stepper motor. hope it works. if any of you guys have any more suggestions please do give them

 

[IanP]

If you know that the circuit works correctly with LEDs and should, but doesn't want to, work with stepper motor then you may have problem with the 12V power adapter which you use as the motor's ..
Can you measure the voltage when you tried to run/test the stepper ..
Is it still 12V or less?

Regards,
IanP

 

[NIGHTHAWK]

yes, i am getting a voltage of 12v. the stepper motor is rated at 24v and 600mA. i was told that a voltage of 12v would be enough. i connected the common wire of the stepper motor to the 12v. i grounded the negative from the adaptor and then connected the remaining four wires to the ULN 2003. i am new to the use of stepper motors. do i need to apply a voltage of 12v to the remaing wires also. i am asking cause the microcontroller gives a volotage of 5v and a meagre current which i amplified with the help of the ULN IC. i don't know whether what i am doing is correct. please let me know
do you guys think i should try with a transformer and a rectifier of higher rating.
any help would be appreciated

 

[VVV]

Well, if the motor is rated at 24V, you should power it at about 24V.
However, I would expect it to rotate, at least at no load, even with 12V.
Try to simply power one coil at a time, by connecting it directly across the 12V adapter. If you do this in the right sequence, the motor should rotate. You only need to see one step or two.

Anyway, you should try to power it at about 24V. Actually, since the ULN2003 is rated at 0.5A, you should choose a voltage that does not cause a higher current than that.

As for the LED test, that is great. I hope you drove the LED's with the ULN2003 (basically, the LED's are in parallel with the motor windings). If this works, then clearly the motor is either defective or it cannot work at 12V.

I hope you are trying a low enough frequency, to allow the motor to develop enough torque. You probably are, since you were able to see the LEDs turn on in sequence.

 

[NIGHTHAWK]

hey guys thanks for all the help. instead of banging my head over the 24 v stepper motor. i simply replaced it witha 5 v 1.8 deg stepper motor and achieved what i started out to do
thanks for all the help everyone