Finally had an attempt to get my focusser up and running.
In the end stuck with the Rev 4 board, with the bluetooth option and the 2 line lcd. Just got the circuits together and given it the first test run. After a few bits adjustments, I'm happy to say that I've got it running. This project is brilliant.
Just need to figure out why the temp probe isn't giving a readout - I suspect that I've got it connected wrong.
Connected via bluetooth with no problems what so ever. I can see this being a very useful part of my telescope once I have it fitted.
Wanted to say thank you for creating this project and for your very hard work on it. Pretty sure that you don't get enough thanks for all the hard work.
Regards
Colin Dawson.
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Hi Colin
In the firmware you have enabled the temperature probe?
Is the temperature reading always the same?
You can check using the Arduino IDE
Connect the controller with USB
Start the Arduino IDE and open the serial port monitor (CTRL+SHIFT+M) (make sure baud rate is 9600)
Wait a few seconds till the controller is running
Make sure that the serial does not send line endings (bottom right of window)
In the send box, type :83# and click SEND
The controller should reply with c1#, where 1 is a probe present, if its 0, then probe is not connected, not defined in firmware, or wired incorrectly
Regards
Robert
For the probe
Check you have a 4.7K resistor between signal and 5V
The probe should have 3 wires - yellow, red and black. Black is gnd, red is 5V and yellow is signal
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I got the temp probe sorted. Turns out that the cable run is too long. I think there might be a voltage drop issue. So, I've connected the probe cable directly to the board. This means that rather than mounting it on the scope with the motor, I'm going to have to have it remote. Shouldnt be a problem in the grand scheme, as I'll always have the focuser box not too far from the scope. Actually, I'm wondering if the 5 meter cable run that I made up for the motor is too long now.
Anyways, the main point is that it'sll 100% functional now.
Thanks again for producing this project. I'm looking forward to getting this working on my scope.
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Hi Colin
That is a very long way. The maximum recommended is around 2m for the probe and the stepper motor cable. Why do you need to mount the controller unit so far way? Are you not controlling it via the computer?
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The reason for the long cable is so that I can have a box for of controls for the telescope. The idea is that this will contain all the electrical stuff that I can get away with - AutoStar, Laptop, Dew controller, USB Hub, Focusser controller. 12V PSU and a connection for an external power tank. (so that I can switch between the PSU and off grid power.
I'm trying to keep the amount of kit that I have attached to the scope to a minimum as there I have to break it down everytime that it's not in use.
At the moment the box for the laptop ect doesn't exist - it's a project for later on, once I have all the parts working. The reason for the 5meter run, is that's the length of the cables that I'm running from the control box to the scope. Idea being that I can put the box into a small tent next to the scope to use as a control centre.
At the moment, I've got the temp sensor connected to the control circuit, and I'm aware that it'll need to detect ambient air temp - at least that's what I think the idea is, so I think I'll be able to put it somewhere convenient.
That said, there's still an option for me to make up a much shorter cable and figure out a way of mounting the focuser on the scope itself. I've not completely ruled that out... yet ;-)
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I think I would be more tempted to mount the focuser box on the tripod leg of the mount. The temp probe of the focuser needs to be mounted on the telescope tube - preferably mid point for a refractor - as it has to measure temperature of the tube as it contracts due to temperatures falling.
An ambient temp sensor is what the dew controller provides.
The long cable runs for a stepper cable could really have two significant effects on focuser performance - the fact that voltage drops occur hence less voltage at the stepper motor - lower torque, as well as a reshaping of the waveforms due to the cable impedance meaning missed steps and a higher back emf ifunplugged when power on, which would definately blow more than the drv8825 chip, most likely the entire controller itself. Twisted pair wire such as Ethernet cable would be a very bad choice due to its very small core diameter, its not designed to carry anything near the current required for a stepper motor.
Regards
Robert
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I've just made up a much shorter cable for my stepper and wired the temp probe back in as well. It's all working.
The new cable means that the focus controller will need to stay near the scope, but that's not a problem as the Bluetooth connection will be more or less line of sight over less than 5 meters.
The cable that I'm using is 7 core 20 AWG unshielded. Both ends are soldered to GX16-7 plugs. This provides a strong connection and both the temp probe and stepper can be mounted on the scope permentantly.
Now that you've explained where the temp probe should be located, I get it I'm going to tape that on to tube of my SCT, not sure where just yet, that's'a thing for later.
My focus is now shifted to how exactly I'm going to mount the motor, and GX16-7 socket to the scope. Not to mention try and tidy up the cables a bit.
So far, I haven't noticed any missed steps and the torque isn't really an issue as it's an SCT, so it's not like the motor is load bearing. Actually, I'm considering powering the coil down to save power - but that's something I'm going to leave for later when I've got everything mounted, so that I can do some tests to see if it's ok to power down the coils between moves.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
Finally had an attempt to get my focusser up and running.
In the end stuck with the Rev 4 board, with the bluetooth option and the 2 line lcd. Just got the circuits together and given it the first test run. After a few bits adjustments, I'm happy to say that I've got it running. This project is brilliant.
Just need to figure out why the temp probe isn't giving a readout - I suspect that I've got it connected wrong.
Connected via bluetooth with no problems what so ever. I can see this being a very useful part of my telescope once I have it fitted.
Wanted to say thank you for creating this project and for your very hard work on it. Pretty sure that you don't get enough thanks for all the hard work.
Regards
Colin Dawson.
Hi Colin
In the firmware you have enabled the temperature probe?
Is the temperature reading always the same?
You can check using the Arduino IDE
Connect the controller with USB
Start the Arduino IDE and open the serial port monitor (CTRL+SHIFT+M) (make sure baud rate is 9600)
Wait a few seconds till the controller is running
Make sure that the serial does not send line endings (bottom right of window)
In the send box, type :83# and click SEND
The controller should reply with c1#, where 1 is a probe present, if its 0, then probe is not connected, not defined in firmware, or wired incorrectly
Regards
Robert
For the probe
Check you have a 4.7K resistor between signal and 5V
The probe should have 3 wires - yellow, red and black. Black is gnd, red is 5V and yellow is signal
Hi Robert.
I got the temp probe sorted. Turns out that the cable run is too long. I think there might be a voltage drop issue. So, I've connected the probe cable directly to the board. This means that rather than mounting it on the scope with the motor, I'm going to have to have it remote. Shouldnt be a problem in the grand scheme, as I'll always have the focuser box not too far from the scope. Actually, I'm wondering if the 5 meter cable run that I made up for the motor is too long now.
Anyways, the main point is that it'sll 100% functional now.
Thanks again for producing this project. I'm looking forward to getting this working on my scope.
Hi Colin
That is a very long way. The maximum recommended is around 2m for the probe and the stepper motor cable. Why do you need to mount the controller unit so far way? Are you not controlling it via the computer?
The reason for the long cable is so that I can have a box for of controls for the telescope. The idea is that this will contain all the electrical stuff that I can get away with - AutoStar, Laptop, Dew controller, USB Hub, Focusser controller. 12V PSU and a connection for an external power tank. (so that I can switch between the PSU and off grid power.
I'm trying to keep the amount of kit that I have attached to the scope to a minimum as there I have to break it down everytime that it's not in use.
At the moment the box for the laptop ect doesn't exist - it's a project for later on, once I have all the parts working. The reason for the 5meter run, is that's the length of the cables that I'm running from the control box to the scope. Idea being that I can put the box into a small tent next to the scope to use as a control centre.
At the moment, I've got the temp sensor connected to the control circuit, and I'm aware that it'll need to detect ambient air temp - at least that's what I think the idea is, so I think I'll be able to put it somewhere convenient.
That said, there's still an option for me to make up a much shorter cable and figure out a way of mounting the focuser on the scope itself. I've not completely ruled that out... yet ;-)
I think I would be more tempted to mount the focuser box on the tripod leg of the mount. The temp probe of the focuser needs to be mounted on the telescope tube - preferably mid point for a refractor - as it has to measure temperature of the tube as it contracts due to temperatures falling.
An ambient temp sensor is what the dew controller provides.
The long cable runs for a stepper cable could really have two significant effects on focuser performance - the fact that voltage drops occur hence less voltage at the stepper motor - lower torque, as well as a reshaping of the waveforms due to the cable impedance meaning missed steps and a higher back emf ifunplugged when power on, which would definately blow more than the drv8825 chip, most likely the entire controller itself. Twisted pair wire such as Ethernet cable would be a very bad choice due to its very small core diameter, its not designed to carry anything near the current required for a stepper motor.
Regards
Robert
I've just made up a much shorter cable for my stepper and wired the temp probe back in as well. It's all working.
The new cable means that the focus controller will need to stay near the scope, but that's not a problem as the Bluetooth connection will be more or less line of sight over less than 5 meters.
The cable that I'm using is 7 core 20 AWG unshielded. Both ends are soldered to GX16-7 plugs. This provides a strong connection and both the temp probe and stepper can be mounted on the scope permentantly.
Now that you've explained where the temp probe should be located, I get it I'm going to tape that on to tube of my SCT, not sure where just yet, that's'a thing for later.
My focus is now shifted to how exactly I'm going to mount the motor, and GX16-7 socket to the scope. Not to mention try and tidy up the cables a bit.
So far, I haven't noticed any missed steps and the torque isn't really an issue as it's an SCT, so it's not like the motor is load bearing. Actually, I'm considering powering the coil down to save power - but that's something I'm going to leave for later when I've got everything mounted, so that I can do some tests to see if it's ok to power down the coils between moves.
Have a look in the firmware zip file for the folder User Builds and Bracket Examples
There is a sub-folder SCT which will give you some ideas