Power and Data Hub Mk2, with automated Dew Control.

[JAS]

I have spent a fair amount of time making an Arduino controlled automatic dew heater.

I have never programmed anything before and my electronics knowledge is very limited, but I thought I would give it a go! I brought an Arduino Mega , a DHT22 temperature and humidity sensor , some Dallas one wire temperature sensors and an LCD display.

I started by looking around at various tutorials on the net. I then did a sketch for each component I would be using to understand how they work, and then put a sketch together for the heaters. This works by measuring the ambient temperature and humidity, the temperature that dew forms can be calculated from this. There is also a temperature sensor with each dew heater band to measure the local temperature. The heat output is set to keep the local temperature at each heater band a preset level above the calculated dew temperature to stop dew forming.

I later added control of the cooling fan for the primary mirror on my 200pds. This will automatically turn the fan on if the mirror is warmer than the ambient temperature and then turn off once the temperatures equalise. This only works for the first 3o minutes the system is on.

Here is the thread for the development of my controller, Phil’s and Gina’s.

http://stargazerslou...heater-control/

I put together a circuit diagram to fit onto a 94 x 71mm pad board from Bitsbox, I had to use this board to replace the old manually controlled heater circuit board that was in the hub.

The circuit has a single 12v input, this feeds the Arduino, 9v via a regulator and all of the heaters and the cooling fan.

I built the circuit but then added the fan control and buzzer later. I also used some ferrite rings for noise suppression, this is going into the hub alongside data cables, USB ect. They could be intergrated into the circuit as I did or added to the neutral lead from the circuit to the heater.

After testing it over several nights of imaging, I decided to go ahead and integrate it into my power and data hub that I built last year, here: http://stargazerslou...0625-mount-hub/

I also changed all of the power sockets for more secure locking sockets, although they are not waterproof, I think they will offer some extra protection. I got them from ebay

http://www.ebay.co.u...984.m1497.l2649

http://www.ebay.co.u...984.m1497.l2649

They do these in 2,3,5 and 8 pin and are a very good price.

I also added some extra buttons and an 8 pin outlet for a future project.

The symbols before the temperature readout of each heater indicate the amount of power currently going to that heater.

The temperature sensors on each heater band are very small and only need 2 wires to work, they also all work on the same 2 wires. So I made a small hub to sit on the side of the mount to save cabling.

My sketch is attached below, I am sure there are much neater/ better ways to program this but I am very happy with the way it works.

All of the hard work and head scratching has paid off.

And a big thanks to all who have contributed.

Jason.

DEW-HEATER-SKETCH.pdf

[Stargazer51N]

Wow Jason that's an amazing set up. It looks so professional. Talk about choosing a big project to learn Arduino! I've dabbled with a UNO a bit but this has spurred me on to try harder.

[Gina]

Brilliant Lovely neat job Well done

[Islander]

That's a very neat and clean setup. Nice job with the Arduino too

[simonmc]

Thats a really nice setup. Love the enclosure you made. I have seen alot worse commercial ones...

Simon

[yesyes]

That looks fantastic. How do you make these front panels so nice?

[JAS]

Thanks for the kind words everyone, I thought I would throw myself in the deep end with the Arduino so that I would have to learn it all properly. Still a way to go yet, but I am getting there

I am having problems with the Arduino being reset by the auto focuser board that I am using , so I am playing with the SGL automation group's auto focuser sketch at the moment. I have managed to combine the 2 sketches using millis to hold the dew heaters so they run every 10 secounds as in my original sketch while the focuser continues to run, and a software serial along with the normal serial to feed back from the heaters.

It works but the focuser is taking 6 to 10 secounds to respond to a comand , I might just add a nano to run the focuser.

Chris,

The front panels are cut out and engraved by a local company, I just draw it out in CAD and they can cut it from that. The plastic is black with a white coating, so they contrast when engraved, it is held in place by the sockets and double sided tape.

Jason.