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teachme
11-24-2006, 01:41 AM
hi friends..
i have been trying to get a stepper motor working well for a few weeks
but i am not able to find a solution for my problems..
(stepper motor 12v, 400ma, unipolar)..
(uc at89c51, driver uln 2003)..
i am using a wall adapter to supply 12v, and 7805 regulator for the uc..
but the motor does not rotate, gives a humming noise..
when i check the supply it shows only 5v..
i also tried to use two seperate supplies.. it runs fur a while(one or two rotations)..
but i have ended up loosing 4 of my 89c51(i dont know why)..(the programmer does not detect them)..
could someone help me by pointing out my mistakes so that
i can rectify them and proceed with my project..
looking forward to some help :(
thanks in advance..

docel
11-24-2006, 02:01 AM
Use a 12v car/ Emergency light battery and see. Wall units DOnt give 400ma. unless they are meant for Printers and other high-end electronic equipment. The hum maybe due to insufficient Voltage/Regulation and may be 50 or 100H?z ripple on load. The measured 5V measured is proof enough.

Have you Bypassed the 89C51 power line and 'Zener diode' ed the Vcc pin of the ULN2003???

teachme
11-24-2006, 01:54 PM
thanks for the reply..
i thought that the uln 2003 had the diodes inbuilt for protection..
if i have to put a zener, could you enlighten me on that please..
where do i have to add the doide.. 1n4148 i suppose..
thanks a lot for your help..

docel
11-24-2006, 02:41 PM
No . 12V Zener diodefrom Battery to pin 9. The motor leads connect to the battery direct.

praghu_cool
11-25-2006, 01:58 AM
go for ULN2803 it can sink 500ma connect 9th pin to Gnd 10th to Vcc no need of any diodes ,,,,,
1)check the coil sequence U have connected ...

Connect the common lead to the positive of your battery or power supply.
Connect any one of the other four leads to ground. This will be Coil 4.
With Coil 4 still grounded, connect another lead to ground. If the shaft does not move, you have Coil 2. If the shaft jogs clockwise, you have Coil 3. If the shaft jobs counter-clockwise, you have Coil 1.
Repeat until you have identified all four coils.

2)first operete at lower frequency then gradually increase the frequency

praghu_cool
11-25-2006, 01:59 AM
go for ULN2803 it can sink 500ma connect 9th pin to Gnd 10th to Vcc no need of any diodes ,,,,,
1)check the coil sequence U have connected ...

Connect the common lead to the positive of your battery or power supply.
Connect any one of the other four leads to ground. This will be Coil 4.
With Coil 4 still grounded, connect another lead to ground. If the shaft does not move, you have Coil 2. If the shaft jogs clockwise, you have Coil 3. If the shaft jobs counter-clockwise, you have Coil 1.
Repeat until you have identified all four coils.

2)first operete at lower frequency then gradually increase the frequency

Pallav
11-26-2006, 12:41 AM
use at least 1.5 Amps power supply as stepper is inductive and takes high peak on start and use diodes for protection and also decoupling caps on ULN for protecting it from spikes...

praghu_cool
11-26-2006, 02:52 AM
hai pallav ,, can u please explain me about decoupling capacitors u mentioned ......

teachme
12-17-2006, 12:45 AM
thanks a lot all for your help..
i finally detected the problem..
my power source used to get loaded..
and did not give more than 150 ma for any application..
also i suppose i was treating the 89c51 very "harshly"..
(connecting led from 5v to the pin!!)..
now i have understood the internal pin diagram..
and am "behaving properly with the 8051..
i am building a micromouse(dont ask me how i was ignorant about the
internal pin connection of the 8051)..
now i have gone as much as
1.making the mouse acc ahead,attain a speed
2.detect a front obstacle
3.dec and then stop
4.take a 90 deg turn and continue
5.simulated my maze solving code in vb
6.now need to integrate both the parts..
THANKS A LOT FOR ALL YOUR HELP.. :D