[redbeard (Damien)]

I was keen to put an electric focuser onto my Meade ETX 125 and I had a spare Meade focuser that fitted the bill.

I wanted the electronics to be as simple as possible by using off the shelf modules. And also to share with others who may want to build one.

I used a 'L298N DC Stepper Motor Driver Module Dual H Bridge Control Board' from Ebay under $5 and a Nano Arduino micro $7. 6 buttons, 4 LED's and 3 connections.
4 buttons are for speed, 2 other buttons for focuser travel in and out, 4 LED's to indicate the speed setting and a power, USB and focuser connection. I've set this up to how I wan't to use it but any types of buttons and switches can used to suit users needs.

I also wanted PC control as I was already driving the ETX from the laptop.
It also works with Ascom, (Meade classic focuser).

By manipulating the I/O pins on the motor control module, you control how it works eg: dynamic braking, standby mode, speed (pwm), and motor direction.
It's quite easy. Simply make one pin a 0, and the other pin a 1 and the motor turns in one direction. Reverse the logic and the motor turns the other way. Speed is set by connecting another I/O pin in PWM mode and sending a value 0 - 255 to set the speed. Dynamic braking is set with two 1's and standby mode is set with two 0's.

So really just another home brew DC controller. Happy to share info if anyone is interested.

Cheers,
Damien