hiya,

i made a thread a few weeks ago and then forgot about it, thanks for the help people gave me even though i didn't respond!

i have decided to use a stepper motor in my project. it will be used to rotate a beam through 360 degrees very slowly (about 1.5 rpm) then when it reaches a full circle, reverse direction and rotate back to the start position. i found a stepper driver circuit which uses 5V inputs to control step and direction and so now i need a circuit which will control these inputs.

unfortunately i am still an absolute beginner and have no clue how to do anything as far as designing circuits goes, i can solder them and that's about it! could you give me some tips about what sorta thing i need to make? i'll keep my eye on this post a lot more as you guys seem to be super quick at replying!

thanks! Alex

 

Have you selected a stepper motor for your project? Can you provide a part number for the motor you have selected?

Also can you provide a sketch of the stepper motor driver circuit you mentioned?

hgmjr

 

yeah i already have the motor... it's an astrosyn bipolar 1.8dg per step. 9-12V 0.16A. it says Y129 on the back but i dont know about a proper part number.

this is the driver i was looking at getting;
http://www.quasarelectronics.com/3187.htm

so i'd like to build some sort of timing circuit which will provide inputs to this driver. there are step and direction inputs so i guess i need 2 timing circuits?

one which will provide a pulse every 0.12s to the step input so that the motor will half-step one position forwards. (i'll be using the half step mode on the driver)
The second will provide a pulse every 45 seconds to the direction input so that the motor changes stepping direction.

can i make some sort of monostable 555 timing circuit?

thanks again!

 

How precise are you needing the 360 degree rotation to be? In other words, are there any adverse consequences if the motor over rotates to 361.8 degrees or more?

hgmjr

 

no not particularly, there will be issues with cable entanglement if it continues for more than 2 complete turns but i hope the circuit is a little more accurate than that! basically, no, it doesn't need to be super precise.

 

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Astrosyn is in Kent, England.
Tel: +44(0)1634 815175
Request for information page is here:
http://www.astrosyn.com/home.html#quotation
You could ask them for a datasheet, giving the information you did above. You really need to know how much torque it has,

The driver kit you're looking at is rather expensive and maximum overkill for your particular stepper motor. Look up the datasheet for a MC3479 2-Phase Stepper Motor Driver IC on ONsemi.com - it is a single IC that will provide the same functionality as the kit, but at a lower current level (up to 350mA per coil at up to 16.3v) which is still more than your stepper can handle.

This beam that you are rotating - what is it's size (L, W, H), and approximate weight? Is the beam going to be carrying anything?

If the beam will be of an appreciable length or weight, you may need to consider a gear or belt reduction drive to multiply the torque of the stepper, as well as giving much more precise control over the angle of the beam.

 

i found the data for the motor i have - it has 1 kg - cm holding torque.

the motor is to rotate a microphone, this will be mounted on the end of a microphone stand style boom roughly 1m long. the microphone is very light, about 350g, and the boom will be pretty light too. in total i think the load will be less than 1.5kg...

i may consider a belt drive system, i guess that would help the beam rotate nice and smoothly so long as it doesnt slip when the motor is reversed.

i already order the overkill circuit coz my boss was paying and i don't have much time left to get a prototype up and running. there is a pot to reduce the current to the coils so i'll just turn that down low.

so will a 555 circuit produce a 5V square wave? i'm pretty sure that if i get that to happen at the right timing the thing will step as quickly as i want it to... then i need another one much slower to change the direction every 45ish seconds right?

 

Well, you could use a 555 timer for a clock.

However, trying to use another 555 to time when to reverse the direction won't work very well, I'm afraid. It would be impossible to get the timing correct, and keep it there.

However, you could use a snap-action single-pole double-throw (SPDT) toggle switch. One side hooked to +5v, the other side to ground, and the common to the direction control on the stepper driver board. When the beam strikes the switch, it toggles the direction of the step.

This is another reason to use a reduction drive; to give the stepper motor more torque to get sufficient mechanical advantage to toggle the switch.