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View Full Version here: : Focusser control with Raspberry PI


Trekrider
01-11-2017, 08:10 PM
I'm looking at trying to control a Feather Touch, HSM20, Handy Stepper Motor from a Raspberry PI 3+. Adafruit make a DC & Stepper Motor HAT that looks like it will do the job.

Does anyone have the pinout and/or specs on the HSM20 or better yet, has anyone done it?

fsr
10-11-2017, 01:10 AM
It seems like it uses it's own dedicated controller. On the site it says that "This "Handy" stepper motor unit works exclusively on the Focuser Boss II electronic focuser".
Do you know what's the pinout from the HSM20? Maybe the stepper is directly connected to the RJ connector, maybe not.

Garbz
11-01-2018, 01:05 AM
Do you have a multimeter? There are various guides on how to identify the pinout of a stepper motor using a multimeter by measuring the resistance.

Failing that if you use a few resistors in series to limit the current you can just play around with the wiring until you manage to get it to move.

Trekrider
11-01-2018, 09:03 AM
Thanks Chris, If I knew the HSM20 was just a stepper motor that would be fine but I don't want to spend $300 on one only to find out that some of the electronics are in the unit making it unusable with a standard driver.

Trekrider
03-07-2018, 10:44 AM
I thought I would do an update in case anyone else wanted to try and do this. My advice would be DON'T - there are much cheaper ways of doing it than using the HSM20.

I initially went down the non-DIY route first and got the HSM20 and a HitecAstro Mount Hub Pro V4 as the advertising states "Feather touch focusers can be used with a current limiting adaptor", I also confirmed by email with them that it would work. Long story short - it doesn't which left me with an expensive paperweight. Apparently it was my fault as the MHP V4 website also states "Compatible with any unipolar stepper motor" and the Feather touch HSM20 is a Bipolar stepper motor. Anyway, enough sour grapes and moving on.

I put together an Arduino based controller (MyFocuserPro 2 by Robert Brown) and it works a treat in testing. I just need to put together a box for it to go in and I'm done. With my 2" draw tube I had to set the max limit to 50,000 (default is 10,000) steps but this gives me a very smooth control over the full range. A 5 Volt supply seems to work best on it.

The pinout on the HSM20 RJ45 is as follows:

Pin 1
Pin 2 - Not Used
Pin 3 - Winding A-
Pin 4
Pin 5
Pin 6 - Winding A+
Pin 7 - Winding B+
Pin 8 - Winding B-

I'm still testing but I believe pins 1, 4 and 5 are the thermocouple - I will update when I work it out.