How to program PIC16F877A stepper motor revolution [Full circuit & 3/4 Code]

[slapdash]

I am most likely missing something, but what about this

ForwardM:
LCDOUT $FE,1
LCDOUT $FE,$80,"OPENING BLIND"
LCDOUT $FE,$C0,"DAYLIGHT"
FOR i = 1 TO 500 ' ?? will equal 10 revolutions ??
portb = %1100
pause speed
portb = %0110
pause speed
portb = %0011
pause speed
portb = %1001
pause speed
NEXT i
GOTO Main

I tried this code but the motor also seems to rotate without stop.

Unless you are counting steps (and have limits preset), I see no way of detecting end of travel of your blind, which means you can drive it beyond it's stop position in either open or close mode.

I thought it's possible to count the motor step (limit the step). Is there anyway to achieve this?

I've thinking again, how about use the inside sensor, double the sensor to set the stop position. When the blind is open and the 2nd sensor which is located in the room detect the light, it will stop the motor. This is meant the 1st sensor use to start the motor and 2nd sensor use to stop the motor.

Same thing goes to close operation. if the outside = 0 and the inside = 0 the blind will close.

to summary this,

open operation:

1st sensor = 1 (motor start) then 2nd sensor = 1 (motor stop)

close operation:

1st sensor = 0 (motor start) then 2nd sensor = 0 (motor stop)

My question is, how can i use any label that prevent the motor spinning like the stop/pause function?

[mackrackit]

I tried this code but the motor also seems to rotate without stop.

I forgot to say i needs to be a word size variable, as a byte it can never reach 500

I thought it's possible to count the motor step (limit the step). Is there anyway to achieve this?

If you do not have a preset limit like Melanie mentioned you can make the stepper stop, but it may not always stop in the exact same place. If there is some drag on the mechanism for example.

You could use a light sensor, but what if there is enough light to start but not stop. Or attach a couple of micro limit switched that a hit on full open or full close. There are many ways to make some sort of encoder. If the blind are only rotating 90 degrees a pot fixed to a blade may work.

[mister_e]

I forgot to say i needs to be a word size variable

Really ??? Everyone have it's own project

[mackrackit]

Really ??? Everyone have it's own project

Every one is a smart _ _ _

The variable "i" needs to be WORD sized.

[Archangel]

<b>Open Loop Solution</b>
How powerful is that stepper motor? You know what happens to a stepper motor when it stalls? At worst it demagnetizes, at best, nothing.
Stepper motors have no commutator, no brushes, no sparks, no increase in current (to speak of), very unlike a brushed motor which gets very Ticked Off when it stalls. So here is a thought, rig up a counter and count the steps between the ends of travel, and drive your motor that many steps + a few extra.

[Charles Linquis]

A common trick is to logically AND the limit switches with one of the phases.
That way the stepper will always stop in the same place, and the position sensitivity of the limit switch (or opto) is decreased by at least 4.

This is easy to do in software.

[aratti]

Slapdash, I don't know what kind of blind you are trying to move with a unipolar stepper motor. They should be very light!

Remember that to use an open loop system (relying only on the steps count) with a minimum of confidence, you should use at maximum half the torque the motor can produce.

Even so every open loop system has at least one switch for the zero position. This means that at power up the system search for the zero and set the internal counter offsetting possible drift.
You are using a unipolar stepper which I doubt has the necessary torque for your application, so very likely you will need a gearbox to increase the mechanical torque at the expense of the speed.
Naturally the number of steps per turn of the gearbox shaft should take into account the gearbox ratio.

Further more I suggest you to take into seriuos consideration the needs of two limit switches.

If you could let us know what kind of blind you are moving and the type of stepper you are using it will make life easier in helping you.

Al.