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1
AstroEQ Support / Re: Both motors not rotating
« on: May 03, 2015, 05:25:02 »
I used 7.5degree/step, 150 gear ratio and 360 worm ratio for both RA and DEC, no ustep.
I just opened the motor box and found it has 6 wires. I guess two center pins are used. I also looked at the motor wiring, probably it's different. The two wires which looks like center pins are not connected to 1 and 6 of RJ11.
I'll consider either make an adapter cable, or just go for custom NEMA23 motors. Thanks!
I just opened the motor box and found it has 6 wires. I guess two center pins are used. I also looked at the motor wiring, probably it's different. The two wires which looks like center pins are not connected to 1 and 6 of RJ11.
I'll consider either make an adapter cable, or just go for custom NEMA23 motors. Thanks!
I don't know if the RJ11 is a standard, all I know is skywatcher use if for there D-A kit, so I used it to for compatibility. You can check if you have a multimeter - measure the resistance between pins 2 and 5 (or 3 and 4) of the RJ11 connector of the motor, if it is low resistance, then the connections are the same.
What settings have you used in the config utility?
Do the motors move at any speed? (e.g. 1x, 2x) or is it not moving at all.
2
AstroEQ Support / Both motors not rotating
« on: May 03, 2015, 04:26:40 »
Hi Tom,
So I got the AstroEQ from you. I just configured and tested it with my Losmandy G11 S.
While I plan to install Nema23 motors in the future, currently I'm still playing with the original motors.
It has Hurst motors, 7.5degree/step, 150:1 gear box and 360:1 worm.
The problem I only hear hiss from the motor but it seems not rotating. But when I try the slewing buttons of EqMod, while it only gives a stronger hiss when the button is pressed down, I did hear it rotates when I release the button. I guess it's a backlash compensation operation.
So I think the problem is it does rotate without any load (when compensating backlash). But when there's a load it doesn't work.
I've set the current limit to maximum (clockwise to the end). The Hurst motor has a voltage rating of 12V and current rating of 300mA. I don't think current is the problem. But could voltage be? This motor has high voltage rating than most motors.
Or is it because the wiring of the motors is different? Is the RJ11 wiring a standard which most manufacturers will follow?
Regards,
Yao
So I got the AstroEQ from you. I just configured and tested it with my Losmandy G11 S.
While I plan to install Nema23 motors in the future, currently I'm still playing with the original motors.
It has Hurst motors, 7.5degree/step, 150:1 gear box and 360:1 worm.
The problem I only hear hiss from the motor but it seems not rotating. But when I try the slewing buttons of EqMod, while it only gives a stronger hiss when the button is pressed down, I did hear it rotates when I release the button. I guess it's a backlash compensation operation.
So I think the problem is it does rotate without any load (when compensating backlash). But when there's a load it doesn't work.
I've set the current limit to maximum (clockwise to the end). The Hurst motor has a voltage rating of 12V and current rating of 300mA. I don't think current is the problem. But could voltage be? This motor has high voltage rating than most motors.
Or is it because the wiring of the motors is different? Is the RJ11 wiring a standard which most manufacturers will follow?
Regards,
Yao
3
AstroEQ Support / Re: 0.5 arcsec/ustep limit
« on: April 19, 2015, 12:21:38 »
Hi Tom,
Thank you very much for the explanation. So the problem is that it needs high interruption frequency to give accurate timing. That makes sense.
About the hardware design, maybe we can use an external crystal/counter which triggers one interrupt pin when one ustep should happen. Then possibly we can get very high accuracy and resolution with high-frequency crystal and a large (e.g. 32-bit) counter? Since only one interruption is required for one ustep, we won't need high interruption frequency in this way.
I don't really know much about embedded device programming, maybe it's a stupid idea.
Regards,
Yao
Thank you very much for the explanation. So the problem is that it needs high interruption frequency to give accurate timing. That makes sense.
About the hardware design, maybe we can use an external crystal/counter which triggers one interrupt pin when one ustep should happen. Then possibly we can get very high accuracy and resolution with high-frequency crystal and a large (e.g. 32-bit) counter? Since only one interruption is required for one ustep, we won't need high interruption frequency in this way.
I don't really know much about embedded device programming, maybe it's a stupid idea.
Regards,
Yao
4
AstroEQ Support / Re: 0.5 arcsec/ustep limit
« on: April 18, 2015, 14:54:17 »
Hi Tom,
Thank you very much for the explanation. I see your point. But that's probably for very high gearbox reduction ratio and high speed, right?
I want to directly couple a 0.9degree/step (400steps/rev) NEMA23 motor to a 1/360 worm on Losmandy G11. I plan to use 1/32 microstep to get 0.28125 arcsec/ustep resolution.
For tracking, 1x sidereal is ~15arcsec/sec. Then sidereal tracking requires only 15/0.28125 = 53.33 usteps/sec. The 16MHz processor should be able to handle that easily, right?
I just checked your code in AstroEQ.cpp, I see you did disable microstep for GOTO. So I think 16MHz should be able to handle very high speed. In my case, 800x GOTO speed using full steps requires 53.33/32*800 = 1333.33 fullsteps/sec. With the 400circles/step processor cost you mentioned, that's only 400*1333.33 = 533.33 KHz, which is much lower than the 16MHz clock. Thus I think the processor should no be a limiting factor in my case, right?
Even if I add an 1/5.18 ratio gear box, the processor should still be OK I think. But if the gearbox ratio is sth like 1:120, I agree that's a big problem. But If we decrease the GOTO speed, it should still be possibly to make it work, right?
Regards,
Yao
Thank you very much for the explanation. I see your point. But that's probably for very high gearbox reduction ratio and high speed, right?
I want to directly couple a 0.9degree/step (400steps/rev) NEMA23 motor to a 1/360 worm on Losmandy G11. I plan to use 1/32 microstep to get 0.28125 arcsec/ustep resolution.
For tracking, 1x sidereal is ~15arcsec/sec. Then sidereal tracking requires only 15/0.28125 = 53.33 usteps/sec. The 16MHz processor should be able to handle that easily, right?
I just checked your code in AstroEQ.cpp, I see you did disable microstep for GOTO. So I think 16MHz should be able to handle very high speed. In my case, 800x GOTO speed using full steps requires 53.33/32*800 = 1333.33 fullsteps/sec. With the 400circles/step processor cost you mentioned, that's only 400*1333.33 = 533.33 KHz, which is much lower than the 16MHz clock. Thus I think the processor should no be a limiting factor in my case, right?
Even if I add an 1/5.18 ratio gear box, the processor should still be OK I think. But if the gearbox ratio is sth like 1:120, I agree that's a big problem. But If we decrease the GOTO speed, it should still be possibly to make it work, right?
Regards,
Yao
Its not really a hard set limit, you can in some gearing combinations go higher. The main issue is how fast the processor on AstroEQ is. It takes time to perform all of the commands in to motor routine (about 200 clock cycles, which was heavily optimised down from several thousand). There are two motors, which means that the repetition rate for the interrupt routines can't be any less than 400 clock cycles, otherwise it would never do anything but move the motors - commands from EQMOD would not be handled and the whole thing would crash.
IVal is what governs the repetition rate, which is why when you enter values into the configuration utility, if the resulting IVal is less than ~450, it will complain that it cannot support that configuration, specifically to avoid the situation where the repetition rate would be faster than the processor can handle.
In many cases it seems that if you go much beyond 0.5arcsec/ustep resolution, this limit is reached. However it is actually possible to get to resolutions of ~0.25arcsec/ustep for some combinations. It's hard to say which though as it is a minimisation problem with 4 independent variables.
5
AstroEQ Support / 0.5 arcsec/ustep limit
« on: April 17, 2015, 04:03:33 »
Hi guys,
Hopefully my AstroEQ is coming soon
I saw in the following post:
http://astroeq.co.uk/forum/index.php?topic=9.0
It's mentioned AstroEQ has a 0.5 arcsec/ustep limit. Why is there a limit?
The original motor/gear of my mount (Losmandy G11 S) gives 0.5 arcsec/fullstep resolution. I don't know whether it uses microsteps or not. Probably no I guess. With motors replaced I wanted to go beyond 0.5 arcsec/ustep because I heard that micro steps are not so accurate as full steps for most motors. For 15 arcsec/ustep sidereal rate, 0.5 arcsec/ustep doesn't require a very high control frequency. So probably it's not a hardware limit? Can I change it? I can accept it if that decreases the maximum achievable goto speed.
Many mounts today provides higher resolution than 0.5 arcsec/ustep, for example, iOptron CEM60 and SkyWatcher EQ8.
Regards,
Yao
Hopefully my AstroEQ is coming soon
I saw in the following post:
http://astroeq.co.uk/forum/index.php?topic=9.0
It's mentioned AstroEQ has a 0.5 arcsec/ustep limit. Why is there a limit?
The original motor/gear of my mount (Losmandy G11 S) gives 0.5 arcsec/fullstep resolution. I don't know whether it uses microsteps or not. Probably no I guess. With motors replaced I wanted to go beyond 0.5 arcsec/ustep because I heard that micro steps are not so accurate as full steps for most motors. For 15 arcsec/ustep sidereal rate, 0.5 arcsec/ustep doesn't require a very high control frequency. So probably it's not a hardware limit? Can I change it? I can accept it if that decreases the maximum achievable goto speed.
Many mounts today provides higher resolution than 0.5 arcsec/ustep, for example, iOptron CEM60 and SkyWatcher EQ8.
Regards,
Yao
6
AstroEQ Availability / Re: AstroEQ Availability [Currently Unavailable]
« on: March 10, 2015, 22:39:42 »
Hi,
Could you also add one more to your Easter batch? I plan to use it for my Losmandy G11 non-Goto.
I need it shipped to Sydney, Australia. When you are ready to accept orders, please do notify me and I'll make the payment. I don't want to miss this batch
Thank you very much!
Could you also add one more to your Easter batch?
I plan to use it for my Losmandy G11 non-Goto.I need it shipped to Sydney, Australia. When you are ready to accept orders, please do notify me and I'll make the payment. I don't want to miss this batch
Thank you very much!
Hi,
Currently AstroEQ is unavailable. I am hoping to make a small batch at Easter. If you want one sooner, there is always the option of building a controller around the Arduino Mega. There is a schematic at http://astroeq.co.uk/buildown .
In terms of protecting the board, when AstroEQ is connected to EQMOD the motors are always powered - essentially locked in place when not moving, so it isn't possible to turn them by hand. When unpowered, their probably won't be an issue turning the motors by hand - obviously it depends on the size of the motor how much voltage you can generate by spinning them.
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