Monday, August 01, 2005


Steppin' in, steppin' out...

I've made a few changes to the Meccano prototype, now known locally as "Da Witch" (due to the recycled front panel from a Da[ta S]witch) as you can see from this illustration:

This picture shows a sturdy steel brace laid across the rails. If you look carefully, you'll see a protrusion from the brace resting on a small white cylinder under the turntable - this is the cam.

Tests show that a more controlled approach is needed to rotating the turntable and controlling the feed, so I've had to learn about stepper motors.

On the front left corner, you can see a fitted breadboard area that comes wired in to the prototype's power supplies. Next to that is the stripped chassais of an old 5 1/4" floppy drive, with just the stepper motor left on it. The motor is a 6-lead centre-tapped motor with 2 tapped coils running at 12V. This is handy because it allows the motor to be stepped in both directions without having to reverse current flow.

The lowest component count I've managed for the driver is 2 chips - a PIC and an ULN2003 darlington driver. Both are very common and low cost parts, and no other bits are needed; the LEDs are just for my own personal confidence building exercises :)

Vik :v)

Very nice :)
...Just as a side note, how do you feel about dropping a component off of the "acceptable parts" list? I, for one, am trying to not include any prebuilt motors...... Still need magnet wire and neodymium magnets for my sanity, but....
For driving it, I'm actually looking at a three-component system, with a whole lot more wires going into it - shift register, 4-bit comparator, and darlington array. That way I don't need a programmer I don't have :)
But yeah... the possibilities of building a motor, possibly around the actual thing you want to turn, intrigue me.
I think it's a great idea for a future stage of the project. If you can design one, that would be fantastic. But right now I've no RepRap to make one on, so...

One thought: There could be a lot of similarity between some of the technology needed to wind an intricate motor assembly, and the device I was thinking of to wiire-wrap components instead of using exotic solders.

Want to compare notes?

Vik :v)
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