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Post by ChrisV on Jan 14, 2016 1:16:49 GMT
I’ve got to get rid of the dew on my scope. I have a dew shield, but its not enough especially when my scope is pointing UP, and this happens a lot given the limited view from my backyard. So I’m going to go all out – build an arduino based automated dew heater controller.
The reason ? 1 = why not. 2 = there’s some really great low price arduino boards and sensors out now. I’ve seen a few versions on different websites, but want to design my own. 3 = I need something to do on cloudy nights. The controller:
- reads the ambient temperature/humidity and calculates the dew point.
- another sensor reads the temperature on each bit of glass on the scope. Have to figure out best placement of heater and sensor.
- The difference between these drives each heater element. Once a lens drop to within ~5oC of the dew point (this seems to be threshold most use; and it will be adjustable on my build) the heater turns on. The level of heating increases as the lens temperature approaches dew point.
I’m starting with a build to independently control up to 3 heaters.
What could go wrong ?
For the controller:
- 1x Arduino UNO R3
- 1x DHT22 Digital temperature/humidity sensor – to measure ambient
- 1x LCD display – to show stuff and set up temp thresholds etc.
- 3x (for each heater) DS18B20 temperature sensor to measure temperature of each bit of glass being heated.
- 3x (for each heater) MOSFET driver model – to drive each heater element.
I’ve ordered all of the above on ebay for ~ $35 incl delivery from Hong Kong !!! Each DS18B20/MOSFET pair is $7.50, so it would only be $20 to build a unit that controls only 1x heater.
For each heater element need:
- Nichrome wire. There’s a few different designs around – with nichrome and resistors – but I like the look of the nichrome. I’ll need to shield it – might start with heatshrink, Velcro and some sort of plastic/rubber base.
- Some wire – dual core marine grade for the heater, and thinner for the temperature sensors.
- Will also need a jiffy box, wires, plugs/sockets and crap.
Costed these bits at about $20-25. So all up ~ $50 to control 3x heaters.
For me the mucking around bit will be getting the layout of the heating element and sensor. If anyone has any ideas about their experience of the best arrangement for putting together the heating elements - let me know.
Chris
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Post by Dragon Man on Jan 14, 2016 4:29:38 GMT
Chris, I made my own heater system.
Because I don't know anything about electronics, or Watts, or all those technical words, I made mine the simple way I think it should work. And it does
Years later and I still use it. It has never failed me. I run it from a 12 volt power supply.
The control box is just a simple on/off affair with 3 sockets and 3 switches. No temperature controllers. The parts:
Assembled: For the straps I use Nichrome wire as the elements.
I measured my length of wire needed to get slightly warmish, twisted the ends so I could solder wire through the loops, and then laid down black gaffer tape, glue side up, and laid the wire onto the glue face. Then I laid a strip of felt on top of the wires to prevent some of the heat getting out one side, then placed another piece of Gaffer tape over all that with the edge overlapping by about 1/4" so I could fold both lengths of gaffer over each other to seal them.Here it is in use:I hope that makes sense
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Post by ChrisV on Jan 15, 2016 11:58:48 GMT
Thanks for the low down on how you put the heating elements together.
As for the rest. Unfortunately I'm an electronics geek from way back. So it's got be an over the top electronics project.
Chris
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Post by Rick in NWArk on Jan 15, 2016 19:00:21 GMT
LOL Chris! I can't add anything here, but I'm very interested to watch your progress... dew can be a big problem for me during certain times of the year.
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Post by ChrisV on Jan 30, 2016 0:06:00 GMT
The sensors arrived from HK. Written some of the code, so going to breadboard it this weekend while its cloudy and raining.
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Post by davy on Jan 30, 2016 22:06:32 GMT
hi chris ,,can a heater be added to a wind rain and snow shield,,id be very intrested in one of those,weve had three snow falls in last 24hrs and in between them we have had rain and wind wash away each previous snow fall. can we expect a tutorial on the build. always fancied trying out the Arduino..thing that puts me off is my shaky hands,you would think I was an alcoholic coming off the bevy the way they shake trying to solder..lol
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Post by ChrisV on Jan 31, 2016 4:09:56 GMT
What the hell is a wind/rain/snow shield ? And how/why do you stay outside in those conditions. As long as a dew heater can work in those conditions then a controller should be OK (humidity sensors might have a problem though - I'd have to check that). The main advantage of an automatic controller is that it will use less power (hopefully) than a manual controller - I run everything off a battery. If you run everything off mains power, like Ken, then this is completely unnecessary. Attached is a pic of it so far. I've breadboarded a prototype from the sensors I bought and the rest is old arduino stuff I already had. I made the heater strap last night while watching the football on telly (following Ken's advice above). The display shows then ambient temperature, humidity and dew point. The next line shows the temperature of the sensor which which be placed in the lens to be heated and the % level at which the heater is running. In the pic it is at 0% as the lens temp is more than 5C above dew point.. As you can see its mostly modular components so not much soldering will be needed - I'm a bit shaky too. It will be even more modular with less soldering when the arduino stuff I've ordered arrives. Virtually all of the soldering will be plugs and sockets when I eventually box it. I wanted to do this as most of the DIY controllers I've seen online have built stuff from scratch. This is unnecessary now with the really cheap modular stuff available - so anyone can do it.
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Post by Dragon Man on Jan 31, 2016 10:20:00 GMT
Nice looking heater strap
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Post by ChrisV on Jan 31, 2016 21:26:05 GMT
Thanks. But need some better felt or insulation as it gives off more (wasted) heat from the back of the strap. Or is that what they are like ? Think I'll go find some rubber or something
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Post by davy on Feb 1, 2016 1:33:09 GMT
Question on heating / cooling scopes. When we take a scope outdoors we leave it to get it to ambient temp,orion scopes have cooling fans on some newts to make it cooler faster to give us better seeing due to thermal currents in the scope,so heat travels to cold if I remember correctly ,so on a refractor outside and cooling to ambient temp on a cold night and dew forming due to the difference in temps along the body of a scope rather than wrap a dew heater round the lens,would it not be better with more a spiralling dew heater or an electric heated sleeping bag to control the heat over the full body of the scope...only a thought..davy
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Post by Dragon Man on Feb 1, 2016 5:02:13 GMT
Chris, they will lose a small amount of heat through the outer surface but it won't be much. The best bet might be to use a layer of felt, then a layer of Alfoil, then another layer of felt if you feel it may need it. It might not with the Alfoil there. I haven't tried this yet but any I make in the future will be done that way.
Just have to make sure that the Alfoil can't touch the Nichrome wire.
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Post by Rick in NWArk on Feb 1, 2016 16:49:39 GMT
Cool stuff guys... learning a lot!
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Post by ChrisV on Feb 11, 2016 4:30:35 GMT
Okay. Have boxed the prototype to see if it works. Here it is the other night: Connected to a heater strap which is just under the dew shield Ambient temp/humdity sensor on side of box Upper line of display has the ambient temp, humidity and dew point. It was very humid and there was dew on everything Even on the inside of the dew shield. But not the corrector lens ! Give it a few more nights, then I'm happy. Then I'll make a smaller modular version that anyone can make (when the parts come). Clear lens ...
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Post by Dragon Man on Feb 11, 2016 6:23:05 GMT
Well done Chris. Looks very . . errr . . technical That'll give AstroZap some competition
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Post by ChrisV on Feb 11, 2016 9:12:08 GMT
Might be a bit techo, but i have an engineering background and have been playing around with arduino for a few years. I might be crap at astrovideo (getting less so with the advice from you and others) but i can do this.
Having made it i find it a bit scary what they charge for the things. Might put it up as a diy kit here and iceinspace. It will be easy to make - much easier than the ones I've seen which build it all from scratch.
Basically just a bit of drilling, a few plugs, minimal soldering and uploading a program.
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Post by Dragon Man on Feb 11, 2016 13:04:18 GMT
Sounds like a good idea Chris.
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Post by Rick in NWArk on Feb 22, 2016 20:11:15 GMT
Very cool, Chris!
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Post by ChrisV on Apr 13, 2016 7:56:28 GMT
Distracted by other things. Finally got the new Arduino board and display. The circuit roughly Its all plug and play for the components. Stuck them together for testing before "jiffy boxing it up".
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Post by ChrisV on Apr 13, 2016 8:01:42 GMT
Then whack it in the jiffy box and off its goes ! The display swaps between showing ambient temp/humidity/dew point AND heated element temp/heater drive Seems to work - above pics from quite a dewy night - BUT NOT ON MY GLASS ! Ha - defeated the elements !! Its been going for a week now and hasn't blown up yet. I've put the build and code up on the DIY section in IceInSpace if interested. Now for my next project ... getting video astronomy to work without procrastinating and fiddling with bits and pieces.
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Post by Dragon Man on Apr 13, 2016 12:00:58 GMT
LOL! Makes mine look like it was made by the Flintstones Oh well, it still works
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