hughgilhespie

Hi Choo Choo, I am happy to help in any way I can so please feel free to contact me. Regards, Hugh

Hi Choo Choo, I have recently travelled the same route you are proposing. My observatory is a Pulsar 2.2 metre, the more modern design which has an exposed internal dome flange suitable for attaching a timing belt. I went with a 25 mm wide T10 timing belt glued in place with CT1 adhesive. You need to be a bit careful to make sure that the tooth pitch is close to 10 mm across the bit where the ends of the belt meet but this isn't too difficult. I didn't bother with measuring the torque needed as several others have used this system successfully using motors rated at 2 Newton Metres or better. I chose a geared stepper with a holding torque before the gearbox of 1.89 Nm and a 4.25:1gear reduction. This gave a theoretical maximum torque of around 10 Nm, more than enough. The other Pulsar domes that I know of that use the timing belt system only use one drive motor and that's what I did. The motor itself drives through an 18 tooth pinion. To keep the pinion in contact with the timing belt, there is a spring loaded pinch wheel running on the reverse side of the flange. The whole motor assembly is fitted on a pivot arm that is securely attached to the dome wall. These mechanical complications are required to cope with the distinct lack of circularity and the variations in thickness of the dome flange. If you are making your own they may not be necessary. My dome automation is a work in progress but I have got the basic motor rotation of the dome working so I can confirm that this design works well. For various reasons I chose to use a stepper motor rather than a basic DC motor. Obviously this adds some complexity but it offers a lot of benefits too in terms of more precise control and an easy way to detect potentially serious problems such as the dome jamming and the motor burning out - or worse! Hope this is helpful. Regards, Hugh

Hi, Re posts #751 and #752, I have implemented a rotary encoder for manual focus. My focuser is based on one of the excellent Robert Brown designs rather than the AAF2 one but the details are probably still relevant. My build is based on an Arduino Nano, the CH340G, Rev. 3 type and the DRV8825 driver board. The Quadrature.h library is used to support the rotary encoder. My manual focus uses a Bourns Optical Rotary Encoder (RE) to control manual focusing. Turning the encoder knob progressively increases (or decreases) the focus motor speed. Between forward (In) and reverse (Out) movements there is a 'Neutral' position. Travel limits are set up using the Windows app. If the focuser reaches the preset travel limits, the motor stops, a RED led lights and the buzzer sounds until the RE is moved back to 'Neutral'. When the RE is in it's 'Neutral' position, a GREEN led lights. The focuser position information is shown on the LED display after each movement. This method of using a RE for manual focus is somewhat different to Robert Brown's. His way is to move the focuser a set distance, the actual distance being varied according to the RE position. I haven't tried Robert's method so I can't comment on it but my varying speed method gives a very smooth and intuitive way to manually focus. The rest of the software and all the hardware is exactly as per RB's design. If anyone wants a copy of my code I am happy to provide it. Please PM me and I will send a copy. Usual warnings, I am definitely not any sort of expert so I can't be a lot of help if it doesn't work for you! Regards, Hugh

Hi Corpze, I would also like to hear about this. Ideally I would like an ASCOM driver that interfaces an Arduino Mega to the ASCOM Safety Monitor. I am happy to connect my cloud and rain sensors to the Arduino - as well as lots of other bits and pieces - but I have no idea how to get the safety status information shared with ASCOM. Regards, Hugh

Hi Robert, Brilliant - many thanks. I am looking forward to a very focused Christmas!! Regards, Hugh

Hi Robert, Thanks for posting this, it looks to be just what I want and I have ordered a suitable Nano and the 5:1 NEMA17 motor and DRV8825 board. I intend to make the full version with 16 x 2 LCD and push buttons. I have downloaded the files I think I need from Sourceforge but I am a bit confused about the details regarding the construction for the full version using the DRV8825 driver. Is there a schematic for this? I can't see one in the Sourceforge file lists? Also the PDF 'myFOCUSERDRV8825.pdf' refers to the Arduino code being for a mimimal system but the sketch 'Focuserv125_DRV8825_F.ino' seems to have the code for all the bells and whistles, so is this the code I need to use? Sorry if I'm being dim but I am relly keen to use your design, fits my requirements to a T. Regards, Hugh