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  #81  
Old 22-07-2018, 11:27 AM
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adavis (Andrew)
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Hi Chris, I am having a few issues with the dew heater, I was hoping that you might be able to help me out.

1. the DHT22 is reading WAY his, like 235 degrees high, and a corresponding 1000% humidity.

2. the temp sensor is not reading at all. When I run the test code it errors out citing pin 3,5,6 but the instructions say to use pin 12, though Ising 3,5,6 produce the same results.

I am wondering if you have a version of the code that works with a single sensor and heater, Im wanting to use it for camera use, so only need one.

cheers
Andrew
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  #82  
Old 22-07-2018, 05:50 PM
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Its been a while since I've looked at the build.

Are you using a nano?

To start, have you tried the v4a-test-DHT22, its on the github link from post #80. That will just test the DHT22 - on pin 2. Don't worry about connecting the DS18B20 sensors or the heater mosfets. This will print the data via the serial monitor on your computer (rather than the OLED display).

When you get that sorted I can help you out with a single channel version - its a minor change.
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  #83  
Old 23-07-2018, 08:55 AM
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adavis (Andrew)
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Hey, THANKS for picking up the response so fast.

Yes, Nano, and the latest test file from GitHub.
Heres the output.

Dew Heater Controller
DHT22 test - serial output to computer
Digital pin Status Temp (C) Humidity (%) Dew Point
2 OK 230.4 998.4 397.0
2 OK 230.4 1024.0 399.5
2 OK 230.4 998.4 397.0
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  #84  
Old 24-07-2018, 03:32 PM
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adavis (Andrew)
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To round out the solution in case anyone else has the same issue that I did......


It turns out that I have a DHT11 temp/humidity sensor, not the DHT22.
The fix was to simply replace every occurrence of DHT22 with DHT11 in the code and it works a treat now.


cheers
Andrew
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  #85  
Old 25-07-2018, 03:08 PM
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Glad to see you got it resolved. Be interesting to see how it goes.

Looks like the DHT11 has lower temperature accuracy than the DHT22, 2C versus 0.5C. Also it says its best for 20-80% humidity versus 0-100% humidity for the DHT22.

I'm sure it will all be fine as its all pretty gross control - fuzzy logic-like.
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  #86  
Old 10-03-2019, 10:33 PM
Paullus (Paul)
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Hi everyone,


My mate Josh and I built a couple of these dew controller over the past few weeks. Josh ordered the parts via ebay and Jaycar (whichever was cheapest/most convenient) and generally speaking it was fairly straight forward thanks to Chris' (and others) instructions and coding. The only major issue I had was getting the display to work, as the ones we ordered were SPI by default and needed slightly different pinning to get them to work as I2C. My particular display didn't need the SCL/SDA pins swapped, and also need an extra pin from the Digital 4 Signal pin to the RES(ET) on the display. I also had to do some minor soldering to on the display board to convert it to I2C, as per the instructions printed on the board.


I used the V4 program as I think the V5 shares the same D4S pin that my display used and I didn't have enough room to squeeze in the momentary switch. I was almost finished construction when I discovered the V5 and decided it wasn't worth the effort to fix those couple of issues. All 4 channels have been tested and are all working fine with the V4 program.


I did a very tight build in a smaller jiffy box where I spent more time measuring and piecing it together in my mind than I did actually constructing it. It'd be quicker and easier to use the next size up (which I had) but opted for the compactness of the smaller box.


Anyway here's some photos of the finished product. Now I just need some clear nights to put it to use.
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  #87  
Old 10-03-2019, 11:00 PM
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Someone is still making them, great! Thanks for reporting your build Paul and Josh. I've got mine in a larger box, but I also have another Arduino in there with a focus stepper controller and a usb3 hub.

I should go back and fix the instructions - scl and sda shouldn't be swapped.

I'm on about v7 now, just never uploaded. Gone back to a 16*2 lcd display - easier to see with my glasses etc. Also changed to a different ambient temperature/humidity sensor on I2C.

Also, there can be issues with long lines to heater if you have a close parallel line to a sensor - the heater signal can screw up sensor reading. I've now fixed that. I'll get my act together and upload it all.

Last edited by ChrisV; 11-03-2019 at 12:24 AM.
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  #88  
Old 28-04-2019, 10:10 AM
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Astroman (Andrew Wall)
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I'm starting to look into this again, combining this heater with a Stepper controlled Dustcap. Still deciding whether to add a Light to the Dust cover for flats, so I don't have to be out with the telescope.
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  #89  
Old 17-05-2019, 06:47 AM
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Quote:
Originally Posted by ChrisV View Post
Someone is still making them, great! Thanks for reporting your build Paul and Josh. I've got mine in a larger box, but I also have another Arduino in there with a focus stepper controller and a usb3 hub.

I should go back and fix the instructions - scl and sda shouldn't be swapped.

I'm on about v7 now, just never uploaded. Gone back to a 16*2 lcd display - easier to see with my glasses etc. Also changed to a different ambient temperature/humidity sensor on I2C.

Also, there can be issues with long lines to heater if you have a close parallel line to a sensor - the heater signal can screw up sensor reading. I've now fixed that. I'll get my act together and upload it all.

Hi, can you post the code for the LCD 2 lines?? Thanks. Also i sent you a pm i hope you can give me a hand here..

This is exactly what i need for my project.
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  #90  
Old 25-05-2019, 03:42 AM
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Hi, just found this thread and love the simple sulotion regarding components, i have also reviewed the code a bit and was thinking if there is possible to change channel 4 (both ds18b20 and the 12v output) to a fan controller loop to cool a primary mirror.
For me, two dew heater channels is enough but a fan output would be awesome.
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  #91  
Old 25-05-2019, 09:15 AM
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Hi Daniel. Should be simple enough. How is the fan cooler supposed to be controlled?
- does it just turn on for a certain amount of time or
- oes it sense the mirror temp and turn the fan on until the mirror drops to within a few degrees of ambient?
Let me know.

One other thing. Don't get the components for a week or two as I'm making some changes - different ambient temp/humidity sensor, and big changes to the code. I'll have it all up on GitHub soon.

Chris
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  #92  
Old 25-05-2019, 08:51 PM
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Sounds interesting Chris. Look forward to what you have in mind. This is one project I do plan on doing now, since my guide-scope developed dew the other night, cutting short my imaging session. Would have been nice to have it automatically take care of it for me. I just have to fit it in somewhere between setting up the automation of my roll off roof observatory and taking images.
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  #93  
Old 25-05-2019, 11:52 PM
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New update on github
http://github.com/ChrisV77/TelescopeDewHeaterController

It has a few more options
- ambient temperature/humidity - can use either DHT22 or AM2320 (change in wiring)
- display: 16x2 LCD or 128x64 OLED (no change to wiring)

Also
- improved some odd behaviour due to interference between DS18B20 sensor and heater output if wires run close to each other
- has a switch to change mode
- optional output to computer and simple control via arduino serial monitor (I'll be making a windows app for this soon)
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  #94  
Old 26-05-2019, 01:44 AM
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Quote:
Originally Posted by ChrisV View Post
Hi Daniel. Should be simple enough. How is the fan cooler supposed to be controlled?
- does it just turn on for a certain amount of time or
- oes it sense the mirror temp and turn the fan on until the mirror drops to within a few degrees of ambient?
Let me know.

One other thing. Don't get the components for a week or two as I'm making some changes - different ambient temp/humidity sensor, and big changes to the code. I'll have it all up on GitHub soon.

Chris
Actually, I have choosen a different kind of DHT sensor, the AM2301, mainly because the enclosure, and some tests show it is on pair with dht22 in accuracy.

Regarding the fan, it should be set probably something like this;

Temp diff > 3 degrees C - 100% fan (Both under or over primary mirror temp)

Temp diff between 2-3 degrees C - 75% fan
Temp diff between 1-2 degrees C - 50% fan
Temp diff between 0-1 degrees C - 0% fan

I am thinking taking the differential temperature measurements from the ambient DHT- sensor and the DS18B20 attached to the primary mirror.

It should be doable uding the 4th channel of the IR540 board i presume?

Regards, Daniel.
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  #95  
Old 26-05-2019, 12:31 PM
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Yes, but you might want to put a diode across the fan for back EMF protection.
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  #96  
Old 20-06-2019, 04:53 AM
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Yes, but you might want to put a diode across the fan for back EMF protection.
I will do that, thanks for the heads up!

I have now gotten all of my pieces and fired it up, the LCD works fine but i have problems with my ambient sensor, beeing the AM2301 (DHT21)

When i try with a stand alone "dhttype dht21" -code it works fine, but i get error (intermittent readings and at wrong values) when trying your code, do you know if the support for the DHT21 is not in the DHT.h you are using?

Both works on floats so i don't think it that kind of error.
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  #97  
Old 20-06-2019, 05:41 AM
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Ukastronomer (Jeremy)
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I think my definition of easy is paypal and an astro supplier, also I paid about the same for a new one rather than home made but good luck
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  #98  
Old 20-06-2019, 09:12 AM
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You need to read the advertising Jeremy. It doesn't just say 'easy', it says 'easy to make'

But that Ukrainian store pointed out by Matthew in another thread is excellent value. Certainly worth looking at if you don't want to spend loads and don't want to bother making one
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  #99  
Old 29-06-2019, 12:27 AM
Corpze (Daniel)
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Does anyone have a photograph or schematics of the connections of the mosfet 4ch board?

I just can't get my head around how to get mine working.
All four channels are set to 100%, even if i have all signal cables disconnected.

The connections I have made is GND and Signal between the Arduino and the input to the mosfet board.
On the 12v side of the mosfet board I have connected 12v and GND to the 12v input terminal, the ch1 - ch4 i have connected 12v and gnd to the phono terminals.

Some questions i have are;
Do you guys also connect the 5v+ to the input side of the mosfet board?

I have attached a photo but it isn't the best one.
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  #100  
Old 04-07-2019, 03:30 PM
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Like this Daniel. You can warm the DS18B20 to make it turn off the heater, or ditto for the DHT22 to turn heater on.

Check the wiring input to the mosfet from the arduino
S = signal from arudino pin 9 for CH1, etc
+/- = +5V, ground from arduino. If you have the Nano then its a simple connect for each channel
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