Jump to content

sgl_imaging_challenge_2021_annual.thumb.jpg.3fc34f695a81b16210333189a3162ac7.jpg

Best motor for DIY DC motor focus unit


Astroboffin
 Share

Recommended Posts

Hi,

Am looking to build my own motor focus unit, and there are many different mini 12v DC motors available and some are already geared down with there own Mini gearbox fitted, so what RPM do I need, I have found one that is 5 RPM, but seems very slow.....

Does anybody know the actual specs of the Skywatcher DC motor, including RPM at 12v and power draw in amps..

Also I plan on fitting directly to my focus shaft with no extra gears or belts in between, so one turn of the motor will be one turn of the focus shaft, and the one I have seen at 5 RPM will mean one revolution every 12 seconds at 12v, does that seem either too slow or too fast.......I can't make my mind up, bearing in mind that the controller will be using a PWM to power it, so at say half speed of 6v that will be 24 seconds per revolution...and so on..

Any info much appreciated

Regards

AB

Link to comment
Share on other sites

Have you looked at servo drives, might be a good option, you can link 2 together, if you get the same potential Thelwall drive each other. Excuse the speeling as um ok n hols and a bit drunk. If you turn 1 out put the other will turn with no Ower needed. 1 will generate power from emf and power the other. If non of thjs makes sense, pm me and I will be happy to help

  • Like 1
Link to comment
Share on other sites

Have you looked at servo drives, might be a good option, you can link 2 together, if you get the same potential Thelwall drive each other. Excuse the speeling as um ok n hols and a bit drunk. If you turn 1 out put the other will turn with no Ower needed. 1 will generate power from emf and power the other. If non of thjs makes sense, pm me and I will be happy to help

Hi,

I have seen this option while surfing the net, maybe it was your website or blog I saw it on

Anyway enjoy your hols....

Regards

AB

Link to comment
Share on other sites

I used one of these when building a motorised focus unit for my Skymax180:  http://www.ebay.co.uk/itm/New-DC-6V-12V-8-16RPM-Long-Shaft-Turbine-Worm-Gear-Motor-Slow-Reduction-Gear-Box-/161634173562?pt=LH_DefaultDomain_3&hash=item25a225c27a - not sure if it will be suitable for directly driving your focus knob.

I used it together with a couple of pulleys and a belt and I reckon the focus knob turns at something like 2-3rpm.  I control it using a Shoestring FCUSB Controller though I'm sure there are cheaper ways of controlling it, especially if you're a dab hand with electronics (I'm not).

  • Like 1
Link to comment
Share on other sites

Im about to attempt the same thing - just waiting a couple pulleys and a belt. The motor i went for is 3.5rpm, but i got a speed controller as well for fine focusing.

This is the motor i got - http://pages.ebay.com/link/?nav=item.view&id=390993664036&alt=web

That motor looks practically identical as the one used in the Sywatcher auto focusers that are available, interesting thanks

Regards

AB

Link to comment
Share on other sites

Have read through this thread http://stargazerslounge.com/topic/218975-arduino-ascom-focuser-mark2/page-1?hl=+arduino +focuser in which TekyDave uses a simple Arduino Nano that drives an eBay cheepo driver\motor configuration (http://www.ebay.co.uk/itm/High-Quality-5V-Stepper-Step-Motor-Driver-Board-ULN2003-28BYJ-48-For-Arduino-/381292009597?pt=LH_DefaultDomain_3&hash=item58c6c6587d). 

If you plough through the thread, there are links to a second one by RBrown that also uses a Nano, but has different layouts\drivers for different types of motors e.g. bi-polar driven by different drive boards e.g. 8825 A4983 etc...

Edit:

Forgot to add that the motors I'm using for my focusers are these http://www.omc-stepperonline.com/nema-14-bipolar-stepper-54v-08a-18ncm255ozin-14hs130804s-p-93.html

with pulleys and belts from http://beltingonline.co.uk/

hope this helps

Edited by Dr_Ju_ju
  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.