Bridging EMC and Router

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24 Dec 2010 05:20 #6235 by atmegaist
Will do!

At the moment the 74194 + L293D bridge seems to be the way to go (or at least that's what makes the most sense at the moment... Subject to change, lol). I know it's probably not the most efficient method but my first goal is going to just be to eliminate the Arduino. Hopefully some fine-tuning opportunities will present themselves along the way.

Thanks again for the help! B)

I'll be around.

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20 Feb 2011 04:29 #7322 by atmegaist
Greetings, all

I know it's been a while but I wanted to mention that I seem to have everything running (at least for the x-axis... Ran out of diodes.) and it's looking good to begin building the table!

I realize my approach isn't optimal but MUCH was learned about a few new kinds of ICs (binary counters and decoders) and 1" of axis travel was achieved in the "real world"! (I didn't have a lead screw, per se, so a bolt had to do...)

I loosely followed the design provided by Tom McGuire found here:

cratel.wichita.edu/blogs/tommcguire/the-stepper-motor-driver/

The main difference was that I didn't feel comfortable using the resistor/zener combo for the voltage regulator so I put the ICs on their own 5V circuit with the motor power on a separate circuit. I'm not at all suggesting that his approach to the voltage regulation was poor. I was simply limited by my knowledge of the analog side of electronics and didn't want to blow up my "took-a-week-to-arrive" parts.

Anyway, no microstepping or other bells and whistles yet but it's definitely enough to get a desktop "prototype" together.

Thanks again for the help/suggestions!

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20 Feb 2011 12:41 #7325 by BigJohnT
Replied by BigJohnT on topic Re:Bridging EMC and Router
Cool, post a photo if you have one.

John

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20 Feb 2011 18:41 - 20 Feb 2011 18:43 #7329 by atmegaist
The Arduino in the image is just being used as a 5V power supply for the counter/decoder. It doesn't handle any other part of the circuit. Also, the 9V supply is disconnected in this image but simply connects to the +/- rails of the smaller breadboard.

The next step (yes... pun most definitely intended) is to implement microstepping. I hope this can somehow be done logically with what I have but I guess we'll have to see.

Other than that this setup runs quite well at just under 1"/s. Quiet motor, no jitters, and I keep waiting for the transistors to heat up but they haven't yet. (Probably will once I get larger/higher voltage motors).

The only issue is, again, when operating at small increments I lose a good bit of resolution. This is also with a 33 pitch "lead screw" (bolt) and I doubt that any larger-scale screw will have so many threads/in so it looks like it's microstepping or nothing.
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Last edit: 20 Feb 2011 18:43 by atmegaist.

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20 Feb 2011 19:02 #7331 by BigJohnT
Replied by BigJohnT on topic Re:Bridging EMC and Router
Pretty Cool! I like messing with my Arduino Uno. I'm working on a multiplexed input to a MAX6675 thermocouple device.

Are you feeding it step and direction with EMC?

John

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20 Feb 2011 20:33 - 20 Feb 2011 20:42 #7333 by atmegaist

Pretty Cool! I like messing with my Arduino Uno. I'm working on a multiplexed input to a MAX6675 thermocouple device.

I'd be interested to hear how the 6675 project turns out. Always intrigued by I/O expansion.

Also - I checked out your plasma build... VERY impressive!

Are you feeding it step and direction with EMC?

I am, indeed. In fact, I marked a 1" length on the bolt attached to the stepper, made a simple file with a 1" cut along the x axis and sent it to the driver thinking, "Well, at least I'll be able to see how close this is to accurate" (thinking I would need to make some adjustments) and I just about fell out of the chair when the nut traveled right up to the 1" mark and stopped cold. +10 for EMC!!!

I used to operate a Gerber Sabre for a small shop and always thought, "Man, I'd really like one of these at the house but there's NO way I could afford one". Haha - total cost so far: $21.85.
Last edit: 20 Feb 2011 20:42 by atmegaist.

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20 Feb 2011 22:32 #7336 by atmegaist
Quick question: the motors I'm currently using are from an old typewriter and operate at 7.5 degrees/step which I'm coming to find out is WAY too high for a CNC application.

For this first build I think I'm going to stick to a 12"x12" setup much like LumenLab's micRo. Do you think a 60oz, 24V motor would handle carrying/pushing a small dremel or would I need a more powerful motor?

Thanks

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20 Feb 2011 22:58 #7337 by BigJohnT
Replied by BigJohnT on topic Re:Bridging EMC and Router
With proper gearing and acceleration and max speed set just about any stepper will move your gantry. Will it move as fast as you want and with enough power... that is the question only you can answer.

Look in the Configuring EMC section of the wiki for several good pages on steppers. I like the Automation Direct steppers they give you a torque/speed/voltage chart and they are cost effective.

John

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21 Feb 2011 04:48 #7343 by atmegaist
That makes sense. I attempted slowing things down and the motor's ability to resist opposing forces increased exponentially. Might try running the motor at full voltage, too.

Thanks again!

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