DIY manual motor focuser

[msacco]

Hello! I've seen those videos recently: https://www.youtube.com/watch?v=1zwboVgzugw and https://www.youtube.com/watch?v=2qVNxvnkGug which is a tutorial about it, and it looks really awesome I thought about doing it myself, but before I do I just want to make sure I actually understand it, is it just as simple as connecting 2 motors plus to minus and then when you move one manually the other should move as well?

Can someone explain about it maybe? Thanks!

 

[Stargazer33]

Basically, if you rotate a coil in a magnetic field (the motor acts as a dynamo) it generates a current. This current is then used to drive the other motor. Reversing the direction of rotation of the first motor reverses the current polarity and therefore the direction of rotation in the driven motor.

[msacco]

28 minutes ago, Stargazer33 said:

Basically, if you rotate a coil in a magnetic field (the motor acts as a dynamo) it generates a current. This current is then used to drive the other motor. Reversing the direction of rotation of the first motor reverses the current polarity and therefore the direction of rotation in the driven motor.

So what I thought is actually what happens right?

I also thought of going on a different approach maybe, I thought of something like this and then simply wire it to a motor and a battery, sounds pretty easy and nice to me, what do you think?

[Stargazer33]

I believe so. You would have to wire it up so that each contact on the motor had a positive and negative wire attached. This could be a single wire from the negative terminal of the battery that was soldered to one contact on the motor and then put a link wire from that contact to the other.

You would then need to take two wires from the positive terminal of the battery, one going to each switch. The other side of the 'up' switch would then be soldered to one of the motor contacts and the other side of the 'down' switch would be soldered to the other motor contact.

A couple of things to consider are that the battery is strong enough to drive the motor, that you have a motor that will rotate more than 360° and that you have gearing to reduce the rotation of the motor down to something useable.

[Dr_Ju_ju]

If you are going down the route of a powered solution, instead of the simple back to back servo motors, then I'd suggest looking up a simple Arduino controlled motors e.g. https://sourceforge.net/projects/arduinoascomfocuserpro2diy/ which doesn't need a computer to drive it, but can use simple switches that you linked to...

[msacco]

On 02/01/2019 at 23:11, Stargazer33 said:

I believe so. You would have to wire it up so that each contact on the motor had a positive and negative wire attached. This could be a single wire from the negative terminal of the battery that was soldered to one contact on the motor and then put a link wire from that contact to the other.

You would then need to take two wires from the positive terminal of the battery, one going to each switch. The other side of the 'up' switch would then be soldered to one of the motor contacts and the other side of the 'down' switch would be soldered to the other motor contact.

A couple of things to consider are that the battery is strong enough to drive the motor, that you have a motor that will rotate more than 360° and that you have gearing to reduce the rotation of the motor down to something useable.

I'll look into that, thanks.

On 03/01/2019 at 00:01, Dr_Ju_ju said:

If you are going down the route of a powered solution, instead of the simple back to back servo motors, then I'd suggest looking up a simple Arduino controlled motors e.g. https://sourceforge.net/projects/arduinoascomfocuserpro2diy/ which doesn't need a computer to drive it, but can use simple switches that you linked to...

Interesting!! I actually ended up getting something similar after watching the following video:

Towards the end of the video you can see the ending result I want, which seems fairly easy, and thats pretty much built in arduino. The only thing I'll need to figure is how I reduce the motor speed which I'll probably need, but I assume there are so many ways to achieve that so I assume I'll manage to get it working, what do you think?

[Dr_Ju_ju]

The one I linked to, can use different types of motors with different driver modules etc. It just depends on how much you want to spend... as it's designed for focusers, it is intrinsically slow, but can be set to do whatever speed want, It can even be built\configured for wifi operation, so totally hands free.

I've built a number of them & they all work as expected. 

[msacco]

55 minutes ago, Dr_Ju_ju said:

The one I linked to, can use different types of motors with different driver modules etc. It just depends on how much you want to spend... as it's designed for focusers, it is intrinsically slow, but can be set to do whatever speed want, It can even be built\configured for wifi operation, so totally hands free.

I've built a number of them & they all work as expected. 

That actually does look amazing, never got the chance to work with arduino tho.

Im looking for a very cheap solution, so I don't want to buy an arduino kit for 25$, generally is it possible to buy an arduino motherboard only? Something like that for example and just program it to whatever I need?

[Dr_Ju_ju]

These are the Arduino Nano's that I use, off of eBay (https://www.ebay.co.uk/itm/Mini-Device-for-Arduino-Nano-V3-0-with-PRO-ATMEGA328P-Module-Board-Hot-New-NN/263998923005?hash=item3d778fe0fd:g:xkgAAOSw4JZby1gn:rk:7:pf:0) the most expensive part is usually the motor, but you can get a combined motor & driver (https://www.ebay.co.uk/itm/28BYJ-48-Stepper-motor-and-ULN2003A-driver-module-Ideal-for-Ardunio/132377433188?hash=item1ed24f5464:g:sAAAAOSwZPZZ8xLg:rk:13:pf:0) so your 25$ starts to look more like 15$ with all the components\fittings etc...

[msacco]

17 hours ago, Dr_Ju_ju said:

These are the Arduino Nano's that I use, off of eBay (https://www.ebay.co.uk/itm/Mini-Device-for-Arduino-Nano-V3-0-with-PRO-ATMEGA328P-Module-Board-Hot-New-NN/263998923005?hash=item3d778fe0fd:g:xkgAAOSw4JZby1gn:rk:7:pf:0) the most expensive part is usually the motor, but you can get a combined motor & driver (https://www.ebay.co.uk/itm/28BYJ-48-Stepper-motor-and-ULN2003A-driver-module-Ideal-for-Ardunio/132377433188?hash=item1ed24f5464:g:sAAAAOSwZPZZ8xLg:rk:13:pf:0) so your 25$ starts to look more like 15$ with all the components\fittings etc...

Awesome! I haven't read too much from the pdf instructions(its freaking long ^^), but I've seen that the motor type you need depends on the focuser or something similar?

[Dr_Ju_ju]

It all depends on how much torque is required to rotate and hold the focuser, for visual only, i.e. just EP's, then the one I linked to should suffice.

At a pinch they may be ok for lightweight imaging cameras, but for me, with a focal reducer\OAG & camera\filter wheel\main camera, I'm using beefier nema 17 stepper motors with a planetary gearbox i.e. https://www.ebay.co.uk/itm/Nema-17-Stepper-Geared-Motor-27-1-Planetary-Gearbox-0-4A-CNC-Robot-3D-Printer/122598500009?epid=1044827377&hash=item1c8b70a6a9:g:WD8AAOSwf~9ZaIoa  yes, they are more expensive, but I don't have to worry about it losing focus by slippage...

[msacco]

3 hours ago, Dr_Ju_ju said:

It all depends on how much torque is required to rotate and hold the focuser, for visual only, i.e. just EP's, then the one I linked to should suffice.

At a pinch they may be ok for lightweight imaging cameras, but for me, with a focal reducer\OAG & camera\filter wheel\main camera, I'm using beefier nema 17 stepper motors with a planetary gearbox i.e. https://www.ebay.co.uk/itm/Nema-17-Stepper-Geared-Motor-27-1-Planetary-Gearbox-0-4A-CNC-Robot-3D-Printer/122598500009?epid=1044827377&hash=item1c8b70a6a9:g:WD8AAOSwf~9ZaIoa  yes, they are more expensive, but I don't have to worry about it losing focus by slippage...

Since Im not really planning on imaging atm, or at least not with a camera, long exposure images, or anything that at least from what I think requires such accuracy, hopefully the first motor will be enough

A few more questions, in case I do lose focus, how do I control it? And did I understood correctly, and the whole point is that the focus is 100% automatic? Or I do need to set targets etc somehow? And what is there sny bug difference between arduino nano and uno? As it seems to be pretty much the same price but uno having 12 dc port which might be useful.

Again, I did not go deeply into the pdf yet, so if I can find it there, feel free to not answer that.

Thanka for all the help! Appreciate it  I have skywatcher 200p btw.

[Dr_Ju_ju]

It can be auto-focusing, but only if you are using cameras and a computer with appropriate software, as all auto-focusers, uses multiple images taken through the scope, to reduce the diameter of stars to their minimum i.e. focussed.

You control it with a pair push button switches (e.g. https://www.ebay.co.uk/itm/12mm-Round-Metal-Push-Button-Momentary-Switch-Black-White-Red-Green-Blue-Yellow/122653316205?hash=item1c8eb5146d:m:mAkIWaxKl1Kd84H1oPFQZbg:rk:3:pf:1&frcectupt=true) mounted in a small enclosure with either a wired (cheapest\simplest) connection, or even WiFi control (but more expensive etc.)

FYI, the Uno is much bigger than the Nano, with more input\output ports, but as the Nano does all that's needed for a focuser, there's no point going for the Uno, unless you have one kicking around.

 

 

[msacco]

18 minutes ago, Dr_Ju_ju said:

It can be auto-focusing, but only if you are using cameras and a computer with appropriate software, as all auto-focusers, uses multiple images taken through the scope, to reduce the diameter of stars to their minimum i.e. focussed.

You control it with a pair push button switches (e.g. https://www.ebay.co.uk/itm/12mm-Round-Metal-Push-Button-Momentary-Switch-Black-White-Red-Green-Blue-Yellow/122653316205?hash=item1c8eb5146d:m:mAkIWaxKl1Kd84H1oPFQZbg:rk:3:pf:1&frcectupt=true) mounted in a small enclosure with either a wired (cheapest\simplest) connection, or even WiFi control (but more expensive etc.)

FYI, the Uno is much bigger than the Nano, with more input\output ports, but as the Nano does all that's needed for a focuser, there's no point going for the Uno, unless you have one kicking around.

 

 

So overall, until I'll get to imaging etc there's not much difference between this and what I wanted to do with the 2 ch relay and remote isn't it?

[Dr_Ju_ju]

correct, but you are future proofing yourself, when you want to move on to imaging....

[msacco]

14 minutes ago, Dr_Ju_ju said:

correct, but you are future proofing yourself, when you want to move on to imaging....

Possibly, tbh it just feels a bit complex to make and I really fear not buying something good or correct/not do it properly, even tho Im pretty familiar with making that kind of things.

[Dr_Ju_ju]

It was just a suggestion.....