An easy Option for Building focuser for non electronics background
Arduino Focuser, fully ASCOM complaint
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brownrb
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hi
i would like to make arduino ascom focuser but i do not have any background in electronics, what is the easy Option for buiding arduion ascom focuser????
my Project will by on the Lunt 80 ed & GSO 200MM f/5,any idea start up ???
what do i need??/
The easiest build (without too much soldering etc is the Arduino Uno + L293D motor shield option.
This will give you full and half stepping without having to do any driver adjustments (unlike for the DRV8825 which requires the POT on the driver board to be adjusted first).
The Lunt ED80 with f/5 means a CFZ (critical focus zone) of around (5 * 5 * 2.2) = 55 microns. You really cannot determine step size until the folder is built and attached, because it will vary depending on how it is connected, if you used a belt drive, or gears, or direct connect.
Once it is all working, the pdf manual will explain how to calculate your step size (because it is best to have around 10 steps of the stepper in the critical focus zone).
Once you have calculated that then you will know what step mode (full or half) etc to use.
I would recommend the NEMA17-PG27 as the best option stepper motor. It has high torque and lots of steps. This is suitable for imaging trains that weights up to 3+kg. Thats a lot of weight! Direct drive onto the focuser shaft is best, but you must setup the focuser minimum 0 and maximum points correctly - failure to do so will have the stepper try to power your focuser below 0 or past the point of maximum travel and could cause damage - again the manual provides examples on how to do this. I think its best to buy a good motor first, else if you buy a cheaper one that does not do the trick you are forced into buying a better one anyway. The NEMA17-PG27 is very very good and highly recommended.
You might find that the cheaper 28BYJ-48 stepper motor does not have enough grunt when the scope is pointing to zenith and you will experience slippage, which over time could lead to focuser damage.
Slippage causes the 0 and Max points of the focuser to change over time. This means the focal point (lets say 14010 is the position of the stepper where you have best focus) changes. The next session you have to focus again and it might be 15000, then the next night 15670 etc, always moving, eventually the focuser will attempt to drive past the maximum point of the focuser and that can cause real damage to a rack and pinion focuser. This explains why some people like to use a belt drive so if this happens, the belt drive can slip and damage might be averted.
What I am describing here in terms of slippage is common to all focuser solutions you might purchase today (bar one or two professional versions which have built-in hard wired position switches which are used for 0 and max position). But they cost an arm and a leg. Maybe 2 arms and 2 legs!
If you do things right (good stepper + good setup as outlined in the manual) the chances of failure are very small.
Also you really need to operate with coil power ON (else you will get slippage) and the 28BYJ-48
does tend to run rather hot.
In summary, a NEMA17-PG27 + Arduino Uno + L293D Motor Shield will suit either of your scopes
Cheers
Robert
Last edit: brownrb 2015-12-14
Dear Robert
thank you for you info
i would like to clarify same points:
thank you
regards
sami
Sami
1. page 34 of the pdf says that
Cfz in microns = focal_ratio x focal_ratio x 2.2
so for f7 this is 7 x 7 x 2.2 or about 109 microns.
step size cannot be calculated until you have measured how far the focuser will travel in one revolution of the focuser knob. See page 59 Appendix E
Lets take an example. My stepper is direct connected to the focuser shaft. I am using full stepping. I have a pg5 stepper. my stepper thus has 200 x 5 steps per revolution (a standard stepper has 200 steps, the pg5 has a 1:5 gear ratio) which is 1000 steps per revolution.
I connect up the focuser software and using a digital caliper, measure where the focuser is now, move it 1000 steps out and measure where it is now. It comes back and says 3cm
So to work out the step size for this focuser divide 3cm by 1000 which is .003 or 3 microns
If each step takes 3 microns and the cfz is 109 microns, then there are 109/3 = 36 steps in the critical focus zone,
Focal points? Max points? see next point
Connect the stepper to the focuser. Start the software and connect. Set full steps. Set the position to 0 (type in 0 as the position and then click set position button). 0 position or minimum has now been set.
Click +100 button. If focuser does NOT move at all then check reverse direction as its trying to move the wrong way.
To set Maximum steps'position, start to move focuser out, click 1000. If focuser is not yet near the end of travel keep going till the focuser is about 1cm before full travel of focuser. Note the stepper position in steps. Enter the stepper position into maxsteps box and click set max steps button. Now min and max positions are set. Do NOT change. If you mess things up by changing step mode etc you will need to repeat. Once step mode is set do not change else you will have wrong values for min and max.
Where to set the position of focuser so image is in focus? It will be different for every telescope and also change depending on eyepiece, or focal reducer, or using a filter or ccd camera etc. You have to experiment to find place where it is in focus. Start with the moon or bright star, set the focuser position to mid way between 0 and maxsteps, eg, If maxsteps was 31000 then enter 15500 as the focuser position and click goto position button. Then look in eyepiece or take image. If out of focus, move -500/ Look again in eyepiece or take image. If focus worse, then u went the wrong way, so click +500 two times. Check again and repeat till you are near focus. Then reduce moves by using the 100 or 10 button. Soon focus looks best, so remember the setting. Now you have setting for this equipment or image train. If you change image train (filters/eyepiece/camera/focal reducer etc) then you will need to do this again.
Last edit: brownrb 2015-12-26
Dear Robert
can you pplease guide me how to hookup the arduion uno with easydriver and how to hookup arduion neno with easydriver on breadboard i am deadlock on hooking the jumper cable with breadboard and power
i a wish that you do a video Tutorial on youtube how step by step building the Arduino ASCOM Focuser Pro DIY for dummies like me
regards
sami
Last edit: sami aldoseri 2015-12-27
Dear Robert
thank you for the info and support
i waiting to receive same part Tomorrow and i will Begin building the Arduino foucser ,
and i would like get help from you if any issue with building it , and i will update you with post
thank you again
best regards
sami
https://www.dropbox.com/s/dc1ck5oyj4s97bf/myFocuser%20Breadboarding%20Nano%20and%20EasyDriver.mp4?dl=0
This is 300MB+ so might take a while to download
Dear Robert
thank you ,
i am downloading the video now, do you have more video to share with Different type of combination !!!! i would like to see
best regards
Hi Sami
There are no other videos. The principle is the same, one wire at a time as shown in the above video. The important thing with the easydriver is NOT to connect 5V from the arduino to the 5V of the easydriver. Only connect the grounds together. The 12V battery supply powers the stepper motor and the easydriver board.
Be sure NEVER to connect the 12v the wrong way around on the easydriver else there will be smoke and the easydriver will blow up.
The only other videos on youtube are about setup and operation
Last edit: brownrb 2015-12-28
thank you Robert
i will update on the hooking up , Wish me luck
Dear Robert
i finsh from building prototype of ( NEMA17-PG27 + Arduino Uno + L293D Motor Shield) that you recommend ,
and i test it and all thing was working perfect, but i note when i Touching the motor it was very hot ofter 10min!!!!!!!????????? i did connect with 12vDC power the Arduino Uno??
any Suggestions on why the NEMA17-PG27 very hot ??????
and i will finhing from Second prototype of ( NEMA17-PG5 stepper moter + easydiver v44 araduion nano) to day . do i need to setting the current on easydriver!!!????
regards
for the NEMA17-PG27 + Arduino Uno + L293D Motor, there is no way to adjust current. So I would set to full steps and coil power off. This should be good for your telescope.
For Nema17+PG5 and Nano and Easydriver - yes you will need to set the current. Once set it will be fine to operate with coil power on and half or 1/4 stepping. There should be some posts here (you will need to view them) on how to set the current if you if you not have a multimeter.
see
https://sourceforge.net/p/arduinofocuscontrollerpro/discussion/general/thread/4783012b/
Robert
Last edit: brownrb 2016-01-02
Dear Robert
i do not know if i doing The correct way by lowering the volt from 12v to 9v on the input with ( arduion uno + l293d ) but for more than 30 min i can not feel the stepper motor can hot !!!!( coil power on + half step) In the normal using situation What is the heat on motor???? is the motor came A little warm !!!! or ????
from you experience do you think i will any Issue on that??? and how do i speed up the Movement for the motor,it is vrey slow in moving ??
Hi Sami
If it works on 9V and is not hot then that is good. No problem.
As for the speed. Are you using the windows application? Have you tried the speed settings under the setting menu *slow medium fast" - do these make a difference? You must be connected to the controller before sending these commands. There should be a noticable difference in speed between slow, medium and fast
What is the name of the Arduino .ino file you are using to program the Arduino?
Are you using the PG27 stepper motor?
In the arduino .ino file, what does your line read
const int stepsPerRevolution = 1028; // NEMA17-PG5 motor
or does it read read
const int stepsPerRevolution = 5370; // NEMA17-PG27 motor
Dear robert
i am using the pg27 stepper and the arduion.ino is l293d_m i use Windows application? and tried the speed settings under thefast setting take more than one minute for doing 10000 step
how do i to find in the read line in the arrsdunduion.ino
Last edit: sami aldoseri 2016-01-03
Dear Robert
in shematic v102 for easydriver, the output connector showing it is for NEMA17 HYBRIS not for the nema17 pg27 can you please Tell me what is wire color for each from nema17 pg27 to eastdriver :
A1
A2
B1
B2
i was testing it and i haed very high noise from motor!!!!!!
regards
Hi Sami
You must have installed the Arduino program, otherwise how could you upload the firmware file to the Arduino Uno?
You double click on the arduino firmware file that you are using, you said "Focuserv152_L293D_M.ino" and it will load into the Arduino program.
Then scroll down and it is about line 80.
If you have no line numbers then click File, the click Preferences, and then check the box called "Display Line Numbers" then click OK. That turns on Line numbers.
For you, line 80 should read
// const int stepsPerRevolution = 1028; // NEMA17-PG5 motor
and line 85 should read
const int stepsPerRevolution = 5370; // NEMA17-PG27 motor
If your lines are different then change them to the above, as you need to tell the controller to use a value of 5370 if using a PG-27.
Once you have done that, then connect the Arduino UNO again and upload the file to the Arduino UNO.
To travel 10000 steps on a PG27 will take time. You should be using FULL steps with the PG27 stepper motor.
The thing to remember is this - when you are using the telescope, once you have the focus set, then there is no need to travel that many steps, typically maybe plus or minus 100.
For example, I have my PG27 set to position 5725 on one of my scopes. When I turn off the controller saves that position. Next night, I know I am close to focus, so maybe use a bahtinov mask (or auto focus software) and that night it might be 5714 is best focus. The next night best focus might be 5738. It does not vary much from night to night. There is no need to travel 10000 steps each night. You only need to do that during the "initial focuser setup"
You are lucky I am still up, just doing some imaging.
pg60 of the pdf has the connections, attched is the wiring you use for the pg27 to the rs232 connector
You wire the easydriver to the rs232 the same in the schematic.
If its a loud vibration type noise it is more likely to be the wires are to the wrong pins - which is probably what it is with yours, The diagram on page60 shows that
easydriver -> rs232 -> nema-pg27
B2 -> 1 -> blue
B1 -> 2 -> red
A2 -> 3 -> green
A1 -> 4 -> black
If you get some high pitched noise etc, REMEBER that you have to adjust the vref POT on the easydriver board. Once adjusted you should find the noise will be gone or much reduced.
Robert
Last edit: brownrb 2016-01-05
Dear Robert
i would like to thank you offerd and help with me in building the arduion foucser DIY
i finsh from it and fix to my Lunt 80mm ED, and i calculate my step size = 3.46 microns for the full step and for the half step = 1.73 microns, whatis the best step size to work with ?????? i will SGP software in ascom to control the foucser
i noted that when i connecting the power to easy driver the stepper motor start making sound is it normal ??????? or ?????
thank you
regards
sami
Last edit: sami aldoseri 2016-01-09
Hi Sami
Best to use full steps.
If the motor is making a sound when connected - that normally means the little pot on the Easydriver board needs to be adjusted. Can you tell me if you have this and how did you set it?
Cheers
Robert
Dear Robert
i have adjust the Current by using Multimeter the red, on the TP1, and black to GND next to the +5V , and the reading to 2.1 voltage ,i am using breadboard to hookup the easydriver & arduion nano !!!!!
how do you do the djust the Current on the easydriver ??? or the DRV 8825 ??/
Last edit: sami aldoseri 2016-01-10
See this thread
http://sourceforge.net/p/arduinofocuscontrollerpro/discussion/general/thread/4783012b/
It is also covered on the pdf on page 72. I prefer to use the current method as that is more accurate. Remember that you should have set the focuser to FULL steps with coil power ON
Dear robert
do the power voltage & current input will Affect on the easydiver current output to the stepper ( i am using 12v 3amp power the the motor driver)?????
Sami
yes. The 2.1v on Ref is still probably a bit too high, 1.75v measured on the ref pad is probably a better value to aim for.
with the stepper NOT connected to the telescope
Last edit: brownrb 2016-01-10
Dear robert
can i use moonlite ascom driver with you arduion pro diy :
the like: https://focuser.com/downloads.php
also i get Bipolar Stepper Motor Driver ST-6128 ,if you please can update the arduion code for st-6128 ,i would like to fit it on my other Newtonian telescope my next foucser
best regards
sami