Equipment - Motorized Focuser

Below are descriptions of the motorization of my Newtonian Telescopes (JMI EV and RCF focusers w/DC motors) and my Meade 8" SCT (stepper motor driven focus knob.)
More information on the software/firmware used for this is here.

Recently (6/2015) I decided to motorize the focuser of my 8" Meade SCT. For this I bored out a 60 tooth MXL timing pulley to fit over the focuser knob. There is a factory bracket w/3-screws under the focusing knob and a 1/8" aluminum plate was made that fits over the focusing knob and screws down with the same 3-screws. This supports the focuser motor and it's 20 tooth pulley. I decided to use a 20:1 reduced tin-can stepper for this focuser. Total cost for everything would be around $50 (eBay.) The stepper motor for this is still around as of Jun '15. Another option that might be a bit more compact would be to flip the motor over and have the pulley higher up on the focuser knob, but it works well as-is. I also have a more powerful 50:1 reduced stepper motor that's a drop-in replacement should I decide that more torque is required.

The Arduino UNO compatible microcontroller communicates across it's USB interface. My plan is to run the motor off a 12V supply jumpered into the driver from the Arduino's power jack. For the control lines, I simply soldered a header on the Big Easy Driver (BED, SparkFun/eBay/etc.) and plugged it into the UNO. The only tricky part was the Enable pin on the BED, for which I used a longer pin angled to reach Pin 7 of the UNO... and the two jumpers soldered on (step and dir pins) and plugged into the UNO's pins 3 and 4.

Motorized 1-1/4" (RCF) and 2" Event Horizon (EV-2n) Focusers, Jims Mobile
The motors cost about $50 (for two) and are 1000:1 Pololu micro-gear motors. Gears to fit the shafts were bought from SDP/SI and cost about $50 also (for two sets). I went with a model# A-1B-2MYK05064 for the focuser shaft and a A-1B-2MYK05020H for the motor shaft. The gear for the focuser shaft is metric 3mm, but the shaft is 3/16" (4.76mm) so I drilled the gear to 0.187" ID to fit the shaft. Then, I used sheet metal (aluminum) to fabricate brackets to hold the motor in place. Two different brackets were made. On one focuser the bracket cups the motor and mounts flat against the back. On the other it cups the motor and screws down above & below the focuser's bearing block.

The focuser motor for the small telescope (JMI RCF-mini) is installed and working. I also completed and installed the controller/computer interface for it. Unfortunately, it's been cloudy and I haven't gotten to really try it out. The other focuser motor, for the JMI EV2n focuser is basically complete too. The 1000:1 gear motors make the movement a bit on the slow side. I don't even need the pwm control to slow the motors down, full speed is fine. In retrospect something 2x as fast might have been better. But, for imaging, they can move the focuser with a precision that would be impossible to do by hand and overkill is probably the way to go with the roughly 0.0006" depth of focus I'm working with (fast f/4 Newtonians.) Below is a picture of the motor drive on the JMI Event Horizon focuser.

The Arduino Pro microcontroller running at 5V has two aux. protoboards. One board has a SN754410NE Quad-H driver that runs the motor and allows it to change direction. The other has a MAX232 chip to translate the standard RS232 level signals to/from logic level for the Arduino. Also on that board is a 5V/1A 7805 voltage regulator to power all of this from 12VDC (Arduino/MAX232/Quad-H/Gear-motor). ...I wouldn't do it this way now. I'd get myself an Arduino "shield" protoboard and build the voltage regulator and H-bridge on that, then plug it in. I'd also skip the RS232 stuff and just use the Arduino UNO's USB.