Simple Arduino based motorised focuser solution

[The Thing]

Hi All,
Here's a fun project for some of you.

I came across this on CloudyNights Forum a month or so ago while looking for a solution. Ready made one seem to average about £300, this cost £35. I blew up the temperature sensor but heyho. Thats the small circuit board. The instructions are fairly easy to follow, its a project started by anat on CloudyNights forum
This is his picture of the main components. Mine are a bit nicer looking.


I got everything from Keyestudio.com, there is a list at the bottom of this post. The three boards, Arduino Leonardo, Stepper Drivers and Screen/Buttons just slot together. The temperature sensor requires some wiring. The stepper motor has 5 wires. Ignore the centre red and connect the others to the motor driver board screw terminals in the order they come out of the motor, doesn't matter where you start. You now have a working motor focus controller - except you need to upload the software to the Leonardo. anat provides an upload.exe on his website that will do this via a USB cable. I used the Arduino programming environment (IDE) so I could fiddle with the code but I'm like that. It all worked first time.

My version


The next problem is that you need to be able to have the motor on the telescope not on the desk. I opted to use network cable for this as some manufacturers do these days. I used the LAN sockets off two old broadband routers for the motor end sockets (I made two motor ends for two scopes) and a bit of an old network wall socket for the controller end. You need 4 wires or 7 if your going to use the temperature sensor (LAN cable has 8 conductors). This requires soldering. It may suit better to find a push fit solution using ribbon cable and block connectors which is what my old Lakeside motor focus controller on my SCT uses.

The Stepper Motor


Then there is attaching the motor to drive the focuser. My solution after carefully examining the latest expensive solutions was to use a piece of 40mm aluminium tube I had lying around. This fits over the focuser onto a flange when the knobs have been removed. This was the same size on both focusers I put motors on so may be standard is. the motor is also 40mm, neat. I used a stainless steel jubilee clip to fasten the tube to the focuser.

I split the tube, actually cut a slot out of it so I could access the grub screws in the connecting collar. there are holes behind as well as the connecting collar has screws both sides. I bent the tabs on the motor so I could screw them to the tube. The LAN socket is attached with lots of hot glue which also helps stick on the motor.

The motor has to be mounted off center as you can see from the diagram, the drive shaft is not in the middle due to the built in 64:1 gear box. To do this I cut a circle of paper the size of the tube, made a hole in the middle for the motor shaft, placed this over the motor shaft  so it was offset from the motor body and held this up to the tube so the paper disc covered the end of the tube and then marked the screw holes for the tabs. Suprisingly it all went together first time.



I bought a box for it to go in but its a bit small, has no holes for the buttons and screen and I've used glue to attach sockets and a captive USB lead for connection. Also I found you need a separate power supply for the motor board (socket on the board) as the USB cable doesn't provide enough juice. I am using 7v, I burnt out a motor using 12v that the board is rated for, if there is not enough power the motor is very slow and may not turn your focuser. I should buy the same stepper motor in a 12v version which would make power supply easier and give it more grunt.

Have fun!

Duncan

Purchased Parts List

Code Select Expand

Keyestudio L298P Shield/2A High Current Dual Motor Drive Module for arduino
$7.22 USD 1 $7.22 USD

Keyestudio 1602LCD Keypad Shield For Arduino LCD Display ATMEGA2560 For Raspberry Pi UNO Blue Screen Blacklight Module $5.66 USD 1 $5.66 USD

Free shipping !Keyestudio DS18B20 Temperature Sensor Module for Arduino
$2.67 USD 1 $2.67 USD

Free shipping! keyestudio ATmega32U4 leonardo R3 development board +1M Micro USB Cable For For Arduino DIY Project
$6.47 USD 1 $6.47 USD

Free shipping!3 PCS (Keyestudio 5V Stepper Motor 28BYJ-48+ULN2003 Driver board
) for Arduino $10.94 USD 1 $10.94 USD

Shipping and handling $0.00 USD
Insurance $0.00 USD
Total $32.96 USD
Payment $32.96 USD
From amount £26.18 GBP
To amount $32.96 USD

[Roberto]

Well done Duncan!  Cool project and nicely explained 

Roberto