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Automation: Need a point in the right direction

Re: Automation: Need a point in the right direction

Postby WalterMo » Tue Feb 22, 2011 8:20 pm

Your chosen stepping motor has a rather low impedance, that means the motor current must be higher and the voltage lower.
Therefore I would use a stronger motor driver board, e.g. the Pololu:
http://www.watterott.com/index.php?page ... &info=1418

One month ago I have posted an application of it to an Arduino:
viewtopic.php?f=6&t=2421&p=15691&hili

Additionally I would glue a heatsink onto the IC A4983.

Regarding the laser holder to the gear's shaft: Do you not know someone with a lathe in the basement? :wink:
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Re: Automation: Need a point in the right direction

Postby Zeppelin1007 » Wed Feb 23, 2011 2:38 am

Unfortunately, i do not know anyone with a lathe. Though, i am at an engineering college and my other guitarist whos about 100miles away is a mechanical engineer. So i wouldn't be surprised if i could get someone to turn me something here.

So i take it since using such a high current motor, and ending up having to use that board, i should just go with using 2 driver boards? one for laser motor one for turntable. Ill probably end up ordering everything tonight/tomorrow. Backing it down to around 2amps

Thanks again everyone! I get this up and running im sure i'll come up with something to give back to the david community
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Re: Automation: Need a point in the right direction

Postby Zeppelin1007 » Fri Mar 18, 2011 10:29 am

Alright guys well its been almost a month but i havent let this one die!

Most of my parts have arrived! Even better, my guitarist and friend, who's also a ME student, milled me out a block of aluminum to go right on my phidget motor. Dug out an unused 9V 16Amp PSU i got from a previous job as well as some LCDs.

I have one question before i start playing with everything. I have the Allegro A4983 board with current limiting. Thats fantastic, especially because my motor runs at 3V@2.5A..I've read the data sheet on current limiting, but i'm a bit confused on the process of safely setting it up.

It says attach a motor in Full Step mode, with no timing. Ok, so one, i assume, connect the motor, and don't tell it to turn?

It says the current will be 70% of what it should be, so ok, meter in series with motor and allegro. Take reading, multiply by 0.7, and i get my number of where its currently at. Be it that i have this beefy 9V supply, id prefer to run the motors at 9V. Am i correct so far on the process? The part im lost at, is, it says the limit is dependent on what Vdd equals. So do i have to do any math there? or is it simply the fact that if Vdd=5V, versus Vdd=3.5v, i'll simply get different current readings? I just wanna make sure i do this right and not blow it

and yes, i have a heatsink ready to go on this thing.

Thanks guys! Pics will be coming in a new thread soon.

Thanks guys!
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