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

[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.

[slapdash]

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.

I'm using vertical blind.

[aratti]

Good to know.

Did you try to pull your blind up with the stepper and with 500 mA max current you can supply to your stepper ?
(I suggest you to replace the ULN2003a with ULN2803a. This has 8 transitors, you can parallel them obtaining 4 couples and doubling the output current in this way)

Is it working ?

Does the stepper run smoothly ?

Can you install the two limit switches?

Al.