Discussion in "PIC Microcontroller Discussion" started by    cestudent    Nov 10, 2008.
Mon Nov 17 2008, 01:28 am
#11
well there is a practical problem

lets say your stepper has 8 steps for 1 revolution, you running your program and at step 5 your program resets,
and you again start from step 1, where as the position of motor is not the same in this case and its aligned different way now. you will not be sure if on first run motor will stay, move backward one step or forward 1 step. so everytime this happens your program behaves in correctly.

I suggest you to give some dummny rotations somehow to setup motor and getting it ready for rotation. after that check it as experimenter said. 1 step means 1 step
Mon Nov 17 2008, 03:11 am
#12


thanx ExperimenterUK for ur help and advice
i have a question when I output .1 this means that the stepper has to move one step right ?

cestudent



To move one step you need to switch the coils on and off in a well
defined sequence of four stages.
" output .1" is just the first of four stages.

read http://www.8051projects.net/stepper-motor-interfacing/
This tutorial tells us that you need to have two coils on at any one time,
so I suspect your switching pattern is wrong.
Can you post a diagram ?

The excellent moving diagram in the tutorial could give the impression
that the four stages rotate the motor by a complete revolution.
In practice it will be just a single step.

Edited........
Actually I'm wrong there, each change of output *would* count as a single step
or half step.
The key thing is to make changes one at a time, and in the right sequence.






[ Edited Mon Dec 01 2008, 10:21 pm ]
Sun Nov 23 2008, 06:10 pm
#13
thank u ExperimenterUK & Ajay , i got it

i appreciate ur help to me


[ Edited Sun Nov 23 2008, 06:12 pm ]
Sun Nov 30 2008, 11:40 pm
#14
hello guys am coming with new problem and i need ur help

am using ULN2804 chip for motor it works well for just a short period then it become hot ant then it burn !!
there is a problem in the circuit , more infor: am using 9v - 6 wires stepper motor
and am connecting supply ground with ULN2804 ground

Am attaching my circuit that am used and uln datasheet
Attachment


[ Edited Sun Nov 30 2008, 11:46 pm ]
Sun Nov 30 2008, 11:56 pm
#15
sorry here the circuit
Attachment
Mon Dec 01 2008, 01:41 am
#16
The 2804 is intended to be driven at 6-15 volts.
It may not be getting enough drive current at 5 volts, use the 2803 instead.

You need to connect pin 10 to enable the 2803/4 internal protection diodes.
Connect it to +9 volts or through a 1 Watt Zener diode to ground.
The Zener voltage should be as high as possible up to about 45 volts.


The 2804 is rated at 500mA, which may not be enough.
You could try connecting the 8 drivers of the chip in parallel
to get 4 higher current drivers.
What is the resistance of a single stepper motor coil ?



[ Edited Mon Dec 01 2008, 02:16 am ]
Mon Dec 01 2008, 11:22 pm
#17
hello experimenter ,
I did what u said, I connect pin 10 to +9v and pin 9 to the ground when i did that the stepper doesn't move but it just Shaking from inside !

also i tried parallel connection it works only if i do the same connection as the previous circuit

the resistance of a single coil is 40 ohms


[ Edited Mon Dec 01 2008, 11:24 pm ]
Tue Dec 02 2008, 12:43 am
#18


hello experimenter ,
I did what u said, I connect pin 10 to +9v and pin 9 to the ground when i did that the stepper doesn't move but it just Shaking from inside !

cestudent


Better stop doing that then
The Zener idea should work.

Lack of drive current still looks like the most likely problem,
paralleling the outputs should have helped.

Which pins did you connect together ?

What switching sequence are you using ?


Tue Dec 02 2008, 12:53 am
#19




Which pins did you connect together ?
i connect pin18 to pin 17 , then pin 16 to 15 .... and last pin 12 to pin 11 in the output side
from the input side i used the same sequence pin 1 to pin 2 and like this....


What switching sequence are you using ?

full step , i am enabling each coil at a time

0001
0010
0100
1000



ExperimenterUK




[ Edited Tue Dec 02 2008, 12:54 am ]
Tue Dec 02 2008, 02:19 am
#20


i connect pin18 to pin 17 , then pin 16 to 15 .... and last pin 12 to pin 11 in the output side
from the input side i used the same sequence pin 1 to pin 2 and like this...

i am enabling each coil at a time
0001
0010
0100
1000

cestudent


Certainly looks OK.
Take a look at this page for a working layout and the example in "C" that goes with it.
Note the crossover on data 1 + data 2
http://www.doc.ic.ac.uk/~ih/doc/stepper/control2/

It may be best to start by changing to a 2803 or 2003.
How many steps per second are you expecting ?

When pin 1 is high what voltage is there on pin 18 ?
Are all gates the same when on ?





[ Edited Tue Dec 02 2008, 02:26 am ]

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