Dew Heater Service #830
Replies: 21 comments 44 replies
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Thanks for your post, I have dew heaters working but would like to explore your code . Currently the 12V - 33 ohm resistor array heater is controlled by a pulse width modulator set to 33% which keeps the plexi-dome clean but also adds a little heat to the ZWO ASI178 body. Heater position should be high and away from the camera body if possible. I look forward to your improvements. Bill in Southern California
…Sent from my iPad
On Dec 2, 2021, at 4:20 AM, Curtis ***@***.***> wrote:
As a companion service to allsky, I built a dew heater (yes, yet another dew heater!) system with the software implemented as a service. It is relatively simple: uses a DHT22 to sense temperature and humidity, calculates dew point using these parameters, closes or opens a relay based upon dew point and other parameters. It also has minimum and maximum temperature set points which will switch the relay on/off independent of dew point.
My physical dew heater is a hacked USB dew heater for camera lenses (because I had an extra), but this should also work with a high temp resistor circuit.
I have not yet extensively tested this code so if you want to pitch in and test here is the link:
https://github.com/Curtis2012/dewheater
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You're welcome! Its public on github so all yours to do what you want with it. Happy to incorporate changes too. At this point the temp control is pretty primitive, just on/off based on dew point and/or other parameters. My thought is that its just a dew heater so super accurate temp control is really not needed. There are configurable offsets for the cut-in/out points to allow for some rudimentary hysteresis compensation. I use this same style of dew heater on my astrophotography gear. It just wraps around the lens. I did the same for the initial version of this system. There is room under the dome, with a Raspberry Pi HQ Cam, to just wrap it around the lens body of the HQ cam. No reason that this same code could not be adapted to support a few different styles of heater hardware implementation. |
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Holy dome temps Batman!!! "Dec 03 15:24:02 allsky python3[406]: Safety temperature exceeded, shutting down" Until I installed the dew heater software I didn't know how hot it got under that acrylic dome here in the Tropics (duh!). It hit 52C today! I originally put the safety shut down logic in to handle the event of a malfunctioning dew heater, but now I see that I need to add some fans that help ventilate the dome too. The temp of the Pi itself was in normal ranges during this event, it just got really hot under the dome. Next up...fans/ventilation project! |
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Considering the air is not clean and eventually the inside of the dome will become dirty maybe a better idea would be to have a cover rotate above the dome to shield the hot sun. This could be accomplished with your present app plus a small routine to excite a model airplane servo to rotate a cover over the dome top. Model airplane servos are strong and cheap, around 10 bux USD, operate from 5 volts, rotate about 170 degrees, 5V pulse width modulated 5Volt logic input signal. Bill acj
…Sent from my iPad
On Dec 3, 2021, at 12:42 PM, Curtis ***@***.***> wrote:
Holy dome temps Batman!!!
"Dec 03 15:24:02 allsky python3[406]: Safety temperature exceeded, shutting down"
Until I installed the dew heater software I didn't know how hot it got under that acrylic dome here in the Tropics (duh!). It hit 52C today! I originally put the safety shut down logic in to handle the event of a malfunctioning dew heater, but now I see that I need to add some fans that help ventilate the dome too. The temp of the Pi itself was in normal ranges during this event, it just got really hot under the dome.
Next up...fans/ventilation project!
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I've thought about that solution too. I have a bunch of small servo motors on hand that would work. Having a self closing dome would be cool too! It doesn't really even need to be a full dome, any shape that shades most of the acrylic dome should work. Even just a wide diameter disk or arch rotated in/out of position by a servo would work. |
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An very simple solution, though not as cool, would be to simply paint most of the acrylic dome white except for a small view port for the lens. I think I will give that a try first. |
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AllSkayCam Tropical Edition... I painted the entire housing white, including most of the acrylic dome (my attempt at masking off a circle on top of the dome came out a bit ghetto, but it works). It helped, but temps still got over 45C under the dome today. Maybe a glycol cooler for under the dome... ; )
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thanks "curtis2012", will have a look. |
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Let me know how it works out for you. I've included "beta" in the title in the readme file because I have not yet tested this code extensively. A bit more field testing by others would be good. |
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OK, will do but at first i'm studying this interesting site about the Raspi services. So my answer will have time. |
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Looks like a good overview. Creating a basic user service is actually really simple. The code does not have to be any different for it to be a service (it can be, but it doesn't have to be). |
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Hello "Curtis2012" |
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Peter,
Thanks. I will take a look.
I am currently fixing some bugs and adding some features, I will make
sure to test for this problem. I should push the changes to the main
branch in a few days.
Curtis
Peter Altschul ***@***.***> escribió:
… Hello "Curtis2012"
I tested your "DewHeater"-Program now with manualy "implented"
humidity, temperature variables (see below) , but only the
"cycleRelay" is working fine and then:
`Temp = 0.0C Humidity 80.0% Dew Point = -3.0C`
`Dew heater min temp reached, turning dew heater on`
`Dew heater off`
no Relay-activity. So i think, a "dewHeater ON" command in module
**checkTemps(self)** is missing?
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I haven't forgotten about this, just got busy with other things. Will push new code soon. |
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New version committed to main today! Substantially refactored the code. I like this version much better. Added "fakeDewPoint" parameter to config file for testing purposes. If set then temp will be set to below dewpoint. |
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I will test it ASAP but now we are in preparation for X-mas and for the End of Year a trip to Finland for 2 weeks with seeing aurora borealis. |
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Peter, no rush, just discovered a bug and have fixed it. Also expanded the functionality of "fake dew point". Will push revised code by tomorrow. That should be the last change for a while. Have good trip, I've yet to see the aurora borealis...definitely on my todo list! I understand it is particularly active this year. |
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Changes merged to master. |
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Many thanks Curtis2012 for your effort. I think, all is working because my tests are ok. I had only to change the on-off state in case of inverse states in my circuit, but no problem. |
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Good, glad its working for you. I am also working on a sun cover. My plan is a half dome that rotates over the acrylic dome under stepper motor control. I've drawn up the half dome in Fusion 360, now just need to 3D print it. I have stepper motors on hand. Just need to write the code and figure out the mounting details. I will probably implement the sun awning control code as a separate service from dew heater. |
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Peter, I think that supporting inverted on/off logic is a good feature, so I created a branch and added it. Appears to work fine on my config, but I am running non-inverted logic. Would be good to test on an actual inverted logic config. It would be great if you could test that when you have the time. I added a Boolean field to the config file "invertOnOff" that controls this behavior. I've created this code in a new branch. Link below: https://github.com/Curtis2012/dewheater/tree/FEAT-invert_on_off |
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Peter, I revised the code and pushed it to github (to the FEAT-invert_on_off branch). Re line 144, 124 self.status. The original logic in that area of code would fall thru to an assignment of the self.status so that should have worked as intended. However, I moved the logic to handle invertOnOff into the ConfigClass. The value to use to set the relay on/off is now set during config processing. This cleans up the code in the dewheater.on/off methods as they no longer need to handle invertOnOff logic, they just use a pre-configured value to set on/off. I also updated the status display. InvertOnOff and status display appear to working correctly on my end. I have a high = on circuit for my relay and if invertOnOff is true it inverts its behavior, so should function correctly on a low = on circuit. Please confirm when you can. Thanks, Curtis |
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Yes, the signal for Relay is correct also in my case, but the Status-Display was wrong in case of "invertOnOff = true". |
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Thanks Peter, I will take a look at that. |
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All is fine now, nothing to view dear Curtis2012. |
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Good. I was just looking at the code and wondering how the "invertOnOff" display could possibly be wrong. I think I just misinterpreted your post. Thanks. |
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Steppers require extra circuitry and can be power hungry unless you put the step driver into sleep mode when the final position is reached. It seems pulsing a simple DC motor and using limit switches would draw minimum power at a super cheap cost to build. Another idea : An RC Servo ($10) does not require a driver, runs on low power 5V, includes a strong gear box . Just putting some ideas on the table.
…Sent from my iPad
On Dec 21, 2021, at 5:29 PM, Curtis ***@***.***> wrote:
Good, glad its working for you.
I am also working on sun cover. My plan is a half dome that rotates over the acrylic dome under stepper motor control. I've drawn up the half dome in Fusion 360, now just need to 3D print it. I have stepper motors on hand. Just need to write the code and figure out the mounting details.
I will probably implement the sun awning control code as a separate service from dew heater.
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Thanks for the input. I'm considering steppers because I have them already, but I will look at the power requirements. I think the power required to move the motor will be quite small and then I can depower the motor/controller completely after the move. In this case the installation is connected to power so the power consumption is not a big concern. |
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Note that "having them already" is a significant consideration in my case. I live in Panama so I have to import any parts that I need. |
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Ok, yes I understand about getting parts in some countries, a friend lives in Brazil and has to pay taxes on incoming parts. Old PC scanners and printers have a good collection of steppers and DC motors plus lots of nylon gears, maybe junk shops are your treasure source. I use the EZSTEPPER board from Sparkfun.com, this low cost step driver has start/stop/direction/fractional stepping and SLEEP mode pins and you will find it easy to implement in code, just use one port per pin, 5V or 3.3V logic levels. I built a 7 channel wireless remote controlled antenna tuner with NMEA17 gear head.stepper and DC motor control. One of my controller buttons put the stepper into sleep mode to save the little battery but the Arduino still draws power. Just an FYI regular everyday LEDs make decent photo sensors, I used them in a Solar Panel sun tracker circuit controlling large DC motors. I just remembered there is a IRIS type mechanism project on thingiverse.com to cover the Allsky. Good Luck, nice to know folks build from scratch. |
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Its not so bad here in Panama, I can ship small stuff in duty free, and pick it up near my home about 7 days after hits Miami. I used to live in Belize...very tedious and very expensive there. I just have the steppers & controllers on hand already and they should work for this. I like the iris idea, if nothing else for the cool factor. Will take a look. Thanks for the input. |
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Latest version of code merged to main. |
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Just found a minor bug and fixed it, relating to minTempOn. There was a typo in this variable name...one downside to interpreted languages: it just becomes a new variable! As a result once minTempOn was set to true it would never go false again (even though the relay would be turned off). Fixed and merged to main. |
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Post your progress when possible, I’m fine tuning my enclosure design because I was anxious to use the camera (3 years now) and never finished the electronics container. Good Luck ..
…Sent from my iPad
On Dec 24, 2021, at 4:44 AM, Curtis ***@***.***> wrote:
Its not so bad here in Panama, I can ship small stuff in duty free, and pick it up near my home about 7 days after hits Miami. I used to live in Belize...very tedious and very expensive there. I just have the steppers & controllers on hand already and they should work for this.
I like the iris idea, if nothing else for the cool factor. Will take a look.
Thanks for the input.
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Will do. I plan to print a prototype of the half dome on Monday. And also an external cowling for a fan. |
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Looks promising. How about documenting what the dependencies are? Such as which python version, pip requirements, etc? For someone who just tries to clone it and then run the python script they wont be able to out of the box. |
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Not a bad idea, but the dependencies are not extensive and there have been quite a few clones with no request for assistance. Are you interested in contributing to this effort? |
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Absolutely. I'm not programming though. For someone who is just following the Allsky install, they might not know how to get things setup so this works. I'll go through the steps again in a bit and post them. It was too difficult. The biggest issue is not knowing if this was done with python2 or python3 since 2 is no longer supported, I'll have to walk through it again today and post back. what would be cool would be to use 2 sensors. 1 for inside and 1 for outside, then do a difference between them and turn the relay on when the difference is "X" between them with X being a config setting. Seen this before with some other things to turn the relay on. Other thing to consider is to make the DHT sensor a config option. Some may want to use the DHT11 vs DHT22. Lukily I had some of the DHT22 laying around but normally use the DHT11. |
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All good ideas I think. I was already planning to add an external DHT. I have python3 installed on the Rpi where this runs so Im pretty sure its all python3 compliant, but I will confirm. |
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I was just helping someone troubleshoot an install, so I did an install from scratch on a RPi 3B+ running a fresh install of Raspian Buster. Below are my rough notes which I will refine and add to the repository. Dew Heater Service Install 1 The following instructions were created by installing dewheater on a fresh install of Raspian Buster. 2 Install source code 3 Install libraries 3.5 meteocalc 4 Configure Service ● dewheater.service - dewheater |
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Also include how to get this working with a Pi 4. https://forums.adafruit.com/viewtopic.php?f=19&t=165722 |
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Hi all,
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The first error is a common issue on Rpis and in most cases you can safely ignore it.
The second is not finding the GPIO library. This normally does not require explicitly importing, but maybe in your environment. Import that library explicitly and see if that helps.
Re displaying in the GUI, you will have to ask one of the GUI developers here.
En 29 de enero de 2022 10:05, en 10:05, ON2ON-HAM ***@***.***> escribió:
Hi all,
Strugling with 2 errors on my end, hopelully someone can give some
help.
Also i would like to read out the data of the sensor, and post it on
the GUI/Web page of Allsky.
Thanks in advance
73 ON2ON
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For importing the module look through the steps for setting up a DHT sensor
by Adafruit. Make sure when you do it you are doing it for python3 &
pip3. You may have to do it for python & pip depending on your
environment, but you should be running python3 as python2 is no longer
supported.
You can also use their sample scripts to query the sensor which you can
pipe to a text file. In the allsky settings you can specify this file as
the extra file. For example I have a python script that I run like this:
dht11.py > temp.txt
The other thing you can do it setup NodeRed and do things from there. I
use Home Assistant for many, many things and I have NodeRed running on the
Allsky Pi that will take the DHT sensor and push out MQTT to my HA server
which is then on my Dashboard. I have a sensor sitting up by the camera
and another sitting in the enclosure for the PI. I can turn the sensor on
through HA by running the dewheateron.py script through a remote exec
command. It also reports the status of the heater if it is on or off. All
this keeps my images clean with no text.
Here is what my HA looks like for Astro:
[image: image.png]
And NodeRed on the Allsky PI:
[image: image.png]
…On Sat, Jan 29, 2022 at 9:48 AM Curtis ***@***.***> wrote:
The first error is a common issue on Rpis and in most cases you can safely
ignore it.
The second is not finding the GPIO library. This normally does not require
explicitly importing, but maybe in your environment. Import that library
explicitly and see if that helps.
Re displaying in the GUI, you will have to ask one of the GUI developers
here.
En 29 de enero de 2022 10:05, en 10:05, ON2ON-HAM ***@***.***> escribió:
>Hi all,
>Strugling with 2 errors on my end, hopelully someone can give some
>help.
>Also i would like to read out the data of the sensor, and post it on
>the GUI/Web page of Allsky.
>Thanks in advance
>73 ON2ON
>
>
>
>
>
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Great ! thank you both for the help, i'll get to it. |
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Test is working now ! relay is switching ! thanks again,, now to get some DHT values into a text file ;)
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@ON2ON-HAM See the Wiki page "Overlays Explained". It will tell you exactly what to do from an Allsky point of view. |
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Thanks Eric !, but it is not yet implemented for my HQ Camera ... |
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So I have put all this in place and is working. |
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Making it a separate process, as I assume you intend above, should work. Alternatively, it could just be added to the DewHeaterService code which would make for a cleaner implemenation (no additional scripts/processes/config files, utilize existing exception handling code, etc...). |
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I think this is a worthwhile feature so I created an "add-logging" branch off DewHeater "main" branch. Im travelling now so not in a good position to make this change, but anyone who is interested is welcome to pull and take a shot at it. |
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Here is what I use for logging (from time to time), basically it's my script I use for putting data on the images (text file), but instead of writing one line to the text file, I append with a datastamp, each new data pull (crontab) to the same file over and over again., You can even edit the python script, to write it like a CSV file, and later use it in any way you like , I just use a Crontab to run the scripts over and over, each 5 minutes or so.
These python3 scripts are for my BME280 sensor, but easy modified for use with the DHT11/22 :
Or this result , as a Comma separated appended line, for a database use for example 👍 |
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Update,,/,, based on the sensor fom the Dewheater, i created this Dbase using RRD, makes a very nice graph, as a PNG that can be used in the /var/www/html/allsky folder. I tried it with outdoor and indoor sensors (DHT11 and DHT22) as you can see in the graph, hopping values during the sensor change (test only). |
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Thats funny I came up with the same code doing a Google |
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DewHeater Service now supports either DHT22 or BME280! I pushed the latest version of the DHT/BME code to the "merge_BME280_and_DHT_support" branch. It has been up and running on my allskycam for about a week now, but could use more testing (especially in a colder environment). Open tasks:
Volunteers welcome! |
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Well just in time I have been playing with a BME280. Brad |
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Good! The code currently supports one or the other, but Im planning to mod it to support 2 of either type concurrently. Which to use for dew heater control would be set in config file. |
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Recently promoted some changes to master. Including support for either BME280 or DHT22 sensor. Details here: |
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As a companion service to allsky, I built a dew heater system (yes, yet another dew heater!) with the software implemented as a service. It is relatively simple: uses a DHT22 to sense temperature and humidity, calculates dew point using these parameters, closes or opens a relay based upon dew point and other parameters. It also has minimum and maximum temperature set points which will switch the relay on/off independent of dew point.
My physical dew heater is a hacked USB dew heater for camera lenses (because I had an extra), but this should also work with a high temp resistor circuit.
I have not yet extensively tested this code so if you want to pitch in and test here is the link:
https://github.com/Curtis2012/dewheater
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