Motor Stepper Example

[DougB]

I am using a microstepper from allmotion that microsteps at 1/256th step per step input

I plan to use a 16F676 to provide step & direction signals to the motor controller

I have a -5v to +5v input siggnal to the pic a/d

How do I configure the pic to apply the hightest resolution on the input
and calculate the steps & direction for the output.

I am stumped right now.

0v means the motor doesn't move.

the input signal is derived from an electrolytic tilt sensor condtioning board

[hansknec]

Well first of all you need to get that - 5V off the PIC before you burn it up. I'm surprised you haven't seen smoke yet. The voltage references need to stay between the range of 0 to Vcc. You are going to have to get yourself an op-amp and offset that -5V up to a zero volt potential and then divide your signal down. The resolution is what it is. You will get 10 bit resolution as the signal at the input pin varies between vref- and vref+ potential. If you want higher resolution or the ability to use your -5V to +5V signal directly then you will need a separate ADC. Funny... I don't see PIC16F676 as a device offered by Microchip.

[mslaney]

Thanks for the help.
I decided to get an L297 and L298 from ST. It'll drive a bipolar with a pulse from the PIC. However, there is WAY too much wiring to interface and use the L298. It works but it takes too much time.
Is there a single chip solution for a bi-polar motor?

I think DougB meant PIC16F876.

[mister_e]

Funny... I don't see PIC16F676 as a device offered by Microchip.

Funny...
http://www.microchip.com/stellent/id...cName=en010213
and worldwide available from Digikey and others

[Luciano]

Bipolar Stepper Motor Driver with Translator

* * *
L6228 (1.4 Arms)
http://www.st.com/stonline/books/pdf/docs/9454.pdf

* * *
L6208 (2.8 Arms)
http://www.st.com/stonline/books/pdf/docs/7514.pdf

* * *
APPLICATION NOTE AN1451
L6208 FULLY INTEGRATED TWO PHASE STEPPER MOTOR DRIVER
http://www.st.com/stonline/books/pdf/docs/8607.pdf

Modern motion control applications need more flexibility that can be addressed only with specialized IC products. The L6208 is a fully integrated stepper motor driver IC specifically developed to drive a wide range of two phase (bipolar) stepper motors. This IC is a one-chip cost effective solution that includes several unique circuit design features. These features, including a decoding logic that can generate three different stepping sequences, allow the device to be used in many applications including microstepping. The principal aim of this development project was to produce an easy to use, fully protected power IC. In addition several key functions such as protection circuit and PWM current control drastically reduce external components count to meet requirements for many different applications.

* * *
APPLICATION NOTE AN1495
MICROSTEPPING STEPPER MOTOR DRIVE USING PEAK DETECTING CURRENT CONTROL
http://www.st.com/stonline/books/pdf/docs/8700.pdf

* * *
One project with L6208
http://www.otocoup.com/CarteL6208_e.htm#Specif

* * *

Regards,

Luciano

[DougB]

Funny...
http://www.microchip.com/stellent/id...cName=en010213
and worldwide available from Digikey and others

There is a 16F676 PIC, I have one on my desk.
ww1.microchip.com/downloads/en/DeviceDoc/40039c.pdf

[mslaney]

Hey Mister E!!!
Thanks for the tips on the chips!

[mslaney]

And you too Luciano. The drivers look like the right thing. I may continue hacking printer motors for my project.

I truly hate the L297/298 arrangement!

[mslaney]

How do I cycle through an array in reverse order?

Ok, I ditched the bi-polar and I'm using a pic and mosfets to drive a uni motor. No translator.
I can spin the motor both ways with the following code but there has to be a more elegant way....I'm thinking I could cut the code in half.

Here's a clip of the program:

'Array vars
stepccw VAR BYTE(4) 'coils
stepcw var byte(4)
'Load Arrays
stepcw[0] = %10100000
stepcw[1] = %01100000
stepcw[2] = %01010000
stepcw[3] = %10010000

stepccw[0] = %10010000
stepccw[1] = %01010000
stepccw[2] = %01100000
stepccw[3] = %10100000

CW:
steps = 0
for delaytime = 1 to 27
steps = steps + 1
portb = stepccw[steps //4]
pause 10
next

pause 1000
steps = 0
CCW:
for delaytime = 27 to 1 step -1
steps = steps + 1
portb = stepcw[steps //4]
pause 10
next

pause 1000
goto cw