After loosing my hobby room in an old industrial building in the beginning of this year, I had to move to "smaller projects".
My appartment has no real hobby room and my neighbours are a little clairaudient to use my machines within the appartment. I can tell you, it really sucks to use a fret saw again, if you are used to a CNC mill
Now this issue and my spinal disc problems since summer last year led to something else. I learned to program AVR mikrocontrollers and design PCB´s.
One of my first own project´s I´m going to show you now, a really tiny radar drive.
In the past I always used a bigger geared motor and a small wire to drive my radars, but was never really happy with it, since you always see the wire. The reason for this was, that I always found the small geared motors (with 4-6mm diameter) too expensive and not steady enough. I used those once and changed the motor at least once a year since something broke him.
In addition to this, these motors with planetary gears are just 6mm in Diameter but at least 25mm long, so they would never fit within a 1/48 scale radar housing and pretty loud at running.
Motivated by a thread in a german forum where somebody used tiny stepper motors to drive a all-round light, I thought okay I´m building this, but much smaller.
I found some very small stepper motors (6mm diameter and 7mm length) on the net, bought them and started to test with an old ULN driver.
Unfortunately those small motors have a step size of 18°.
So in "full step mode" at the low rpm of a radar drive you see the single steps since it´s running just with 10 Hz.
So I had to find something else and remembered the "micro stepping" feature of my CNC mill.
So I again searched the net and found this
http://www.pololu.com/product/1182A tiny stepper driver which is capable of 1/16 microstepping and current limiting and is normally used for 3D printer stepper motors, so should be big enough to drive a 6mm stepper motor
1/16 means I could run the driver with > 100Hz so the single steps can´t be seen with bare eye (same effect your TV uses to make moving pictures).
After the delivery of the driver I built up the control on a breadboard, which you can see in the following pictures.
And it really worked
at 12V motor voltage and around 200mA current.
https://www.youtube.com/watch?v=NQnGqK-JMAM