jase1973

On 23/08/2015 at 01:07, clertem said:

Hi  m000c400,

Great work !

I am working on a similar project as yours and would be interested to know what type of NEMA 17 ones you chose (these are sold in a variety of torque / steps) ?

I can see on your photo above that the RA stepper is directly connected to the mount shaft, and I am surprised that the idle torque of the motor is enough to immobilize the mount. Is it the same for the other axis (we can't see the other side). I have tried with a couple of CNC pulleys and belt for the DECL axis but unfortunately the weight of the scope+camera was too high and the belt was skipping on the pulleys all the time...

Another thing I am interested in is how you actually fixed the motors to the mount. I've been working a lot on possible design for this and came up with little successful results... The one I have for the moment is kind of supported by the counterweight shaft using a circular bracket. 

Originally the motors I got (from the bin of our engineering building at Uni) were too fast and I had to go with a worm/gear combo of about 40:1 ratio. Tests were OK on the RA axis, but the way I've got it mounted is not great and the motor vibrates, thus worm moving slowly out of its gear. I am surprised that you have achieved a working RA tracking simply on a direct connection like this !

I just have to solve that mechanical part, because for the rest, it's pretty allright. I'm driving them by an arduino (with dual stepper driver shield).

I've posted where I am so far here : 

I've also created a 3D model of the SkyWatcher EQ3 Mount piece 

http://www.123dapp.com/project/Skywatcher%20EQ3%20Mount/3366365

Thanks for helping,

Regards

Mathieu

There are 3D printables on thingiverse for NEMA 17 mounts for both the EQ5 and the EQ3-2

(If you know anyone with a 3d printer)

On 19/01/2019 at 06:25, kman42 said:

I got the scope and mount both secondhand. The mount is a Skywatcher EQ5.

I thought skywatchers were white, it it marked skywatcher in any way?

On 14/01/2019 at 12:19, kman42 said:

I just did some tests with the tracking mount.  After getting perfect polar alignment using the drift technique, I achieved a tracking accuracy ratio of 9000/FL (compared to the general rule of 500/FL for untracked astrophotography). In other words I was able to shoot 45 second exposures at 200mm and 30 second exposures at 300mm with no streaking. This was pointing at Sirius (almost at the zenith)  where tracking times will be the worst. 

question for you re your mount, did you get it new? who made it?

I assumed mine was Orion as it came with my 2nd hand scope. 

20 hours ago, kens said:

There's no known polarscope that can make sigma Oct bright enough to find easily ?

I thought most polarscopes were pretty standard. My three mounts (Vixen SP, EQ6 and Avalon) all take the same scope. So I have three unused bits of kit. 

If you want it for AP then there are better, sometimes simpler, methods for polar alignment using imaging and/or guide camera.

http://www.avalon-instruments.com/support/13-troubleshooting/104-polar-alignment-using-the-new-skywatcher-polar-scope

how about the 4 stars that are listed here for polar allignment?

11 hours ago, kman42 said:

I'm in Australia so a polar scope would be noe use to me unfortunately... I have to resort to other means!

they cater for the southern polar axis too...

On 04/11/2018 at 20:09, kman42 said:

I don't do astrophorography often, but when I do I still use it. If I can get the polar alignment right, it's very accurate and consistent. 

Question, do you have a polarscope. I'm looking for one but havn't found one to fit yet.

On 04/11/2018 at 20:09, kman42 said:

I don't do astrophorography often, but when I do I still use it. If I can get the polar alignment right, it's very accurate and consistent. 

just tested mine on the breadboard, inbetween the clouds and seems to be staying on track so far. need to solder it up and make a box.

I just found visual frustrating due to the speed things move and not always being able to reach the slowmo control to keep things centered.

Startests are suddenly easier

Thanks for the handy project.

10 minutes ago, Dr_Ju_ju said:

A very good controller is Tom Carpenters', AstroEq (https://www.astroeq.co.uk/tutorials.php) which is Arduino based, and can be controlled from a PC etc....

It's an interim solution while I am putting an rduinoscope together. http://rduinoscope.byethost24.com/rDUINO_step1.html

I've revised the code to suit my application and my irresistible urge to change things.

I've used an 8255 driver as I had them to hand and I've wired the microstepping up to the arduino so I can see what difference a change in stepsize makes and it's easy to reverse in code the motor direction after soldering everything.

this particular code is using 1/16th steps and a 16t and 40t pulleys, so needs to step 2.5x faster

#define STEP_PIN 2
#define DIR_PIN 3
#define Mzero 10
#define Mone  11
#define Mtwo  12
#define Denable 5

 
void setup() {
  digitalWrite(DIR_PIN, HIGH);
  digitalWrite(STEP_PIN, LOW);
  pinMode(DIR_PIN, OUTPUT);
  pinMode(STEP_PIN, OUTPUT);
  digitalWrite(Mzero, LOW);
  digitalWrite(Mone, LOW);
  digitalWrite(Mtwo, HIGH);
  digitalWrite(Denable, LOW);
 
}
void loop() {
    
      digitalWrite(STEP_PIN,HIGH); 
      delay(37);
        digitalWrite(STEP_PIN,LOW);
      delay (38);
     
}

On 03/11/2018 at 11:16, kman42 said:

I can't remember sorry. It was a long time ago. I think instructions on quarter stepping motors are pretty well documented though.

no problem. I've gotten past that now but I've killed 2 drivers by being silly.

Are you still using it or have you moved on. I'm just trying to get something going while I build an rduinoscope controller.

On 22/04/2017 at 04:42, kman42 said:

I recently completed a little project in which I built a low-cost motorised drive for my EQ5 mount. I thought I'd share my results for other people looking for a solution, as commercial drives tend to start at $200 in Australia.

My drive only turns the RA axis, as it is primarily for astrophotography. Because of this, I don't need any tracking systems - it is simply a motor that spins the RA axis at the correct rate of 1 revolution per 24 hours.

My drive system uses a 4 wire, bipolar stepper motor, driven by an A4988 stepper driver and an Arduino Nano, all powered using a 12V battery. The stepper motor runs in quarter-steps, and drives the pre-existing RA fine-turning gear via a V-belt. This way, I still have full manual control over the mount if I wish. Here is a parts list in Australian dollars inc. postage. Everything was purchased from either Ebay or the local Jaycar:

1. Nema 14 4 wire bipolar stepper motor : $22 

2. A4988 stepper driver: $7.55

3. Arduino Nano V3.0: $6.52

4. 2x T2.5 5mm bore timing pulleys: $20.80

5. T2.5 6mm wide, 145mm long timing belt: $6

6. 4-prong locking plug (male and female): $4

7. Jiffy box: $1.95

8. 2x DPDT switches: $4

9. Locking 2 way connector: $3

10. Alligator clips: $4

For a total cost of $79.80

 

The counter-weights for the EQ5 weigh 11.5kg in total. The maximum distance the weights can be placed on the counterweight rod is 0.33 metres, therefore the maximum torque that a motor would ever need to turn the mount is 11.5x2x0.33 = 7.59 Nm.

The RA fine adjustment knob on the EQ5 mount turns 144 rotations for every full rotation of the telescope's RA axis. Therefore, the maximum torque I would need to apply to the RA fina adjustment gear is 7.59/144 = 0.0527 Nm or 5.27 Ncm.

I chose a Nema 14 Stepper motor with 18 Ncm holding torque and a maximum current draw of 0.8A per phase. This motor takes 200 steps to complete a revolution; therefore, if I want to revolve the telescope every 24 hours, I'm looking at 1 rotation of the RA fine adjustment knob every 10 minutes, or 1 step of the motor every 3 seconds. Using quarter steps to smooth out the motion, thats 1 quarter step every 0.75 seconds.

The arduino is programmed with a ridiculously simple code:

const int stepPin = 3; 

 
void setup() {
  pinMode(stepPin,OUTPUT); 
 
}
void loop() {
    
      digitalWrite(stepPin,HIGH); 
      delay(375);
        digitalWrite(stepPin,LOW);
      delay (375);
}

This sends a pulse to the A4988 'step' input every 0.75 seconds. That's all the programming done.

 

The arduino is powered via 12V, which then outputs 5V to the stepper driver logic controls, while 12V also goes to the stepper driver motor voltage input. The unit is controlled with a power switch stop and start the motor, and a switch to reverse the motor's rotation by swapping the wires to one of the poles. 

 

The RA fine-adjustment shaft needed to be modified to fit the T2.5 pulley. First, I bored the pulley to 6mm to match the shaft. Then, the locking nut of the shaft was removed and the brass nut with the external thread was cut down to be flush with the housing. New notches were cut to faciulitate tightening of the brass nut, and a hole was drilled into the side of the housing to accept a locking screw to replace the locking nut, which no longer fit. The result of this was that the RA shaft now had enough room to fit the T2.5 pulley. After this, the motor was bolted in place using mechano peices, and a hole was drilled in the cover for the 3 prong locking connector. Once the cover was fitted to the mount, the 4-prong connector was the only visible sign of any modifications. 

 

 

Below are some pictures to illustrate the build:

 

The original mount with the RA drive case attached:

 

 

The original mount with the RA drive case removed to show where the motor will go:

 

 

The modified shaft with the T2.5 gear:

 

 

 

 

 

 

The stepper motor in place. The triangular plate ensures the motor can never move enough that the belt loses tension: 

 

 

 

The 4 prong locking connector - the motor's wires run through this:

 

 

The completed control unit - the circuit boards were held in place using RTV silicone. The entire circuit was soldered before dropping the whole thing into the box. Made things much easier:

 

 

The completed unit. I put a neo magnet on one of the tripod's leg bolts, and the control unit just clips on to the magnet when in use. The magnet is strong enough that it will never get bumped off.

 

 

All that is left is to test its accuracy with some photos!

Nice work, I can't tell from the pictures, but did you tie ms2 high to enable quarter stepping?

1 hour ago, jase1973 said:

many thanks,

I'm just waiting for them to process my login

1 hour ago, jase1973 said:

many thanks,

I'm just waiting for them to process my login

1 hour ago, John78 said:

Sign up then in, then copy the workspace using the button at the top, the right click on the part and say export...

Then choose these options and click export, STL file of the part will download.

thanks for that, what was the inside diameter of the assembled ring?

1 minute ago, John78 said:

Sign up then in, then copy the workspace using the button at the top, the right click on the part and say export...

Then choose these options and click export, STL file of the part will download.

many thanks,

I'm just waiting for them to process my login

On 05/07/2018 at 13:28, John78 said:

What size ID do you need?

 

edit : https://cad.onshape.com/documents/b3ca32c49f683181ced7b9c2/w/19a8c116ef8133bc74aad3f1/e/e6c74e997361be5499a91b39

The rings to that design are in part studio 2, Its probably not too robust to dimension changes - need to make a parametric model of it really.

Hi John, Ive taken a look as I'm intersted in some rings too. I can't see a way to download as stl.

any suggestions?