Arduino dew heater control

[Gina]

This is my schematic for the 4 dew heater Arduino control. It currently shows a 16 x 2 LCD display but I haven't quite decided on this. I have a 20 x 4 LCD which would be better as it could show all the data at a time. OTOH I am putting the controller on the dovetail so the display will be at all sorts of angles when in use so (unlike my DSLR temperature control) will not be easily viewable. Also the 20 x 4 LCD is pretty large and that may be a problem. I may rely on computer display instead, though admittedly I do like a local readout and I like systems that will work without a computer connection. This will be determined by physical space in the end.

The switches control which dew heaters are on and the pot controls the LCD backlight brightness.

[drhemlock2]

thanks Philr for the code and gina for the diag i plan to build this next as my other aquarium controller has been going well. will post here what i find.

doc

[JAS]

Gina,

I used your schematic but addad a diode to each output, a reset switch, a piezo buzzer for overheat alarm and added a L7809CV 9v voltage regulator to the circuit. This allowed me to use one 12v feed for the Arduino and the heaters.

I now have it all integrated into my hub and have been using it for nerly 2 weeks now and all is working great. I was concerned about noise. Having it all in the same box with the data lines, but I have been imaging over this last week and no problems have shown themselves.

I will be puting the DHT22 on or near the scope as Phil has said also, the heat from the box is minimal but it held the temp up by about 4-6 degrees! I have been looking into a remote readout/ control, but I dont think the control part is required, I have used it from -6 to +10 and have not had to adjust anything. I am not a fan of the Arduino serial output, so I have downloaded a program called Putty, I have read that you can customize it to read serial like the LCD.

I would definitely recommended the 4 line LCD if you can fit it in, you can see all info at a glance, Phil has set his to scroll but he is having problems reading it, personally I would not want to be waiting for the info I want to scroll past!

Just need to sort the front panel for the hub now.

Jason.

Sent from my LT15i using Tapatalk 2

[Gina]

I have a couple of boxes I could put the dew controller in but neither are big enough for the 20 x 4 LCD display. That leaves these options :-

1. Buy a bigger box.
   
2. Use a 16 x 2 LCD display.
   
3. Don't use a display.
   
4. Put the 20 x 4 LCD in a separate box on the pier head and run a data cable from the control box.
   
5. Provide test points and plug the 20 x 4 display into the control box for testing.
   

Option 1 will take time particularly with Christmas in the offing and delayed postal services. At first thoughts I think I favour 3 or 4.

[JAS]

Option 4 sonds like a good idea to me , you could always unplug it if you change your mind.

I think I would rather settle with a 2 line dispay than no display at all, just in case there was any issue with the serial.

Jason.

[Gina]

Yes,

Option 4 sonds like a good idea to me , you could always unplug it if you change your mind.

I think I would rather settle with a 2 line dispay than no display at all, just in case there was any issue with the serial.

Jason.

Yes, I agree. I think Option 4 too. I have some multicore cable. There's room in my power distribution and DSLR cooling control box which is at the pier head.

[JAS]

That sounds like a plan Gina

[Gina]

Plan under way - have cut hole in power distribution box top for 20 x 4 LCD display.

[philr]

I have located a new red on black LCD that has a much faster response time. This one has been used by someone and is known to work, so just waiting for it to arrive.

Scrolling is not a problem, since the whole loop sequence time is 12 seconds, having a static display is nice but won't speed anything up. So, I recon I will stick with that. Not forgetting that once the whole system is calibrated and working, one will probably not need to worrying about what the LCD says. The 4 LED's I've fitted give an instant and clear indication that the heaters are on or off, and that the duty cycle is working correctly.

I can't get over how good this thing is!

Phil

[JAS]

I can't get over how good this thing is!

Phil

I know what you mean Phil, its great no to have to worry about keeping the heaters adjusted throughout the night.

Glad you have sorted the LCD out, there is allways somthing that doesnt quite go as planed!

I just realised where you are, I am just the other side of Frome from you!

Jason.

[JAS]

The 4 LED's I've fitted give an instant and clear indication that the heaters are on or off, and that the duty cycle is working correctly.

I am still undecided on this point, I had leds on the old setup and I have been using one to check the heaters are functioning when I setup, I will probebly add them and hook them up later if I go with them.

I was nearly caught out by the rain on Saterday night, and it got me thinking about somthing I read a while back about Arduino cloud and rain sensors. The thing is I dont recall where I saw it!

I am going to look into it, I could then mount a plate or box maybe on the wall inside the obsy with them both on and the DHT22, so they are exposed when the roof is open.

Jason.

[philr]

Hi Jason,

Right, if you are just the other side of Frome, you might be interested in Beckington Astronomers. I've just joined the group, a very friendly bunch who have monthly meetings and talks in the old village infants school. If you don't know of them they are on the web:

http://www.beckingtonas.org/

£10 a year. It would be good to see you there.

Re- rain and sensors; its the DHT22 that needs to be kept dry, apparently they don't even like dew on the sensing element. So I have mounted mine facing downwards in a protective surround, so far no problems.

I must say that your box looks a very technical a well made job.

Phil

[JAS]

I am 2 mins away from Beckington, I know of the group but have not joined yet, I will get on and join.

There is another group mendip and district viewers, I will PM you the link as it is run through a local astro shop,( Dont want to upset the mods ).

Jason.

[George]

I am still undecided on this point, I had leds on the old setup and I have been using one to check the heaters are functioning when I setup, I will probebly add them and hook them up later if I go with them.

I was nearly caught out by the rain on Saterday night, and it got me thinking about somthing I read a while back about Arduino cloud and rain sensors. The thing is I dont recall where I saw it!

I am going to look into it, I could then mount a plate or box maybe on the wall inside the obsy with them both on and the DHT22, so they are exposed when the roof is open.

Jason.

There's 2 sensors I know of:

http://www.ebay.co.uk/itm/280992276053?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649

http://www.hobby-boards.com/store/products/Leaf-Wetness-Sensor.html

[Gina]

I think by the time one of those responds everything will be drenched

[JAS]

Thanks George,

Do you have any experiance with eather sensor?

I was thinking a cloud detector as a first warning and then a rain sensor to back i up.

I think by the time one of those responds everything will be drenched

You are probably right Gina.

I have slept for a couple of hours in the workshop while imaging in the past, I had this in mind to wake me should it rain. I would prefer to be woken after 30 secounds of rain than 30 mins!

5am starts mean that if I didnt get a little sleep I wouldnt be able to get out much, and we all know how few chances there are so I make the most of whats avalible.

Jason.

[George]

I think by the time one of those responds everything will be drenched

They are supposedly quite good Gina, 1 raindrop is all that it takes to register a short and they can be rigged to park your scope and close the roof. They do need some mild heating to the rear as dew itself can cause a trigger

http://www.dppobservatory.net/ROR/ROR.php

[JAS]

.

Re- rain and sensors; its the DHT22 that needs to be kept dry, apparently they don't even like dew on the sensing element. So I have mounted mine facing downwards in a protective surround, so far no problems.

Phil

I woud interested to see what you have done here Phil, could you post a pic?

I must say that your box looks a very technical a well made job.

Phil

Thankyou

In a earlyer post you said about a temp diference between your DHT22 and a thermometer, how much difference have you settled with? I dont have anything decent to compare mine with, I tried my multi meter but it does not go below 0!

Jason.

[philr]

Jason,

Photo's as requested. Its just bodged at the moment, I'll be tidying it up tomorrow probably by mounting it on a balsa wood block strapped to the dovetail bar. However, it works as is.

I used a small plastic box and discarded the lid.

[Gina]

Just where have you mounted the DS18B20s? I was thinking of mounting them inside the dew shields on the ED80 and ST80 but I can't do that with my lenses in the widefield rig.

[JAS]

Thanks Phil, that gives me somthing to think about.

Gina, I have mounted my Dallas sensors inside the dew sheids along with the heaters on my OTA and Guid scope. On the finder scope I have put it under the heater strap.

I have not found any diference in performance from eather method

Jason.

[Gina]

Thanks Jason

[philr]

Re DS18B20's. On the SCT, I've fixed mine inside the rim of the corrector plate mount, so it senses the true temperature of the metal; that works. For the EP and ED80 straps, I've mounted them inside the straps where there isn't heater wire, so they contact the surface of each item; they work. I don't think positioning is too critical, since the temperature differential required can be set at will in the compiling.

Phil

[Gina]

Thanks Phil - I'll try to do the same

[philr]

Gina,

I have a new sketch with individually adjustable duty cycles for all 4 outputs. The libraries stay the same. I can post that if you like.

It may not be too long before we have BlueTooth control as well.

Phil