Jump to content

Stargazers Lounge Uses Cookies

Like most websites, SGL uses cookies in order to deliver a secure, personalised service, to provide social media functions and to analyse our traffic. Continued use of SGL indicates your acceptance of our cookie policy.

Gina

Arduino dew heater control

Recommended Posts

Another Arduino Application :D

I have two possible versions in mind. The simpler one uses a dew heater, power MOSFET and digital temperature sensor plus Arduino. Then probably a display of the temperature and a pot to set the temperature. Alternatively, this could be controlled from computer.

The second (deluxe) version adds a humidity+temperature sensor eg. DHT22 and permits setting the heater temperature to a degree or two above ambient.

One Arduino could control several dew heaters.

Diagrams to follow...

Share this post


Link to post
Share on other sites

Arrr...dew...eno by Arduino Annie aka Gina :angel8:

Edited by Gina
  • Like 1

Share this post


Link to post
Share on other sites

Were you thinking of the arduino to drive a local display of temperature?

Yes. That's one idea :)

Share this post


Link to post
Share on other sites

Strikes me the arduino is a powerful enough device to be self contained excepting the heater drivers and the display. Less wires tieing me to the computer is better.

Share this post


Link to post
Share on other sites

Strikes me the arduino is a powerful enough device to be self contained excepting the heater drivers and the display. Less wires tieing me to the computer is better.

Absolutely - I agree. My Arduino controlled camera cooling control runs entirely independently from the computer and TBH I find that better. Saves a USB connection.

Share this post


Link to post
Share on other sites

An LCD display as I'm using with my camera cooling can be used to display temperatures. It can also display the local humidity and dew point.

In the deluxe version, ambient temperature and humidity would be sensed with a DHT22 whilst the individual heaters could use 1-wire DS18B20 digital temperature sensors. The dew heaters could be commercial units, a string of resistors or nichrome wire. I shall use nichrome wire wrapped round the base of the dew shields. The DS18B20s could be placed inside the dew shield to sense the temperature where the dew would cause problems (eg. at the edge just outside the objective lens of a refractor).

As in commercial heater controls or LED strip controls, the power applied to the dew heater would be controlled with a power MOSFET, in turn driven from a PWM digital output on the Arduino. The sketch would measure the ambient temperature and humidity and calculate the dew point. Then control the PWM output to control power to the dew heater to maintain the temperature at a degree or two above the dew point. I already have this functionality built into my camera cooling control except that the camera requires cooling whereas the scope needs heating. Fail safe checking could be included in the setup to detect overheating and close down the system.

Share this post


Link to post
Share on other sites

Provisional parts list :-

  1. Arduino (Nano is sufficient)
  2. Dew heaters
  3. Power MOSFETs
  4. Ferrite rings to make interference suppressors
  5. DS18B20 digital temperature sensors
  6. DHT22 humidity and temperature sensor
  7. LCD display (2 lines of 16 chars)
  8. Push button switches to control functions.

Plus various resistors, capacitors, connectors and a box to put it in.

Edited by Gina

Share this post


Link to post
Share on other sites

Circuit diagram for controlling 3 dew heaters :-

post-13131-0-18505500-1348091264_thumb.p

Share this post


Link to post
Share on other sites

I've done a dew heater control using a 555 IC that is controlled by a potentiometer. The cycle time is about once a second, this should reduce the switching noise. There's no need to switch a dew heater many times a second.

Nowadays I would consider using a PicAXE instead of an Arduino, I had a quick look and it's possible to contol two dew heaters with separate pots. A display or temperature sensors would be slightly more complex but still achievable. A typical small PICAxe costs about £2 and needs almost no support components.

But if, for example, you already have an Arduino that's controlling a focuser or two and has a few spare pins it may be possible to add a dew heater for no cost other than a MOSFET to control the dew heater and some sensor components.

Chris

Share this post


Link to post
Share on other sites

Yes, I shall be using an Arduino for controling focus too. Haven't got round to designing that yet :D

I used a 555 plus pot to provide crude manual control for my camera cooling at first - before I developed the Arduino based control.

Share this post


Link to post
Share on other sites

Quite interested in this Gina, how far along are you with it :)

Which project are you referring to George?
  1. Arduino Dew Heater Control - abandoned in favour of the simple approach with LED light controllers.
  2. Wide-field camera lens focussing - I'm going to use the DC motor/gearboxes I already have and see how much and how fine I need to turn a pulley that drives the camera focus sleeve by a toothed belt. Then I can decide on stepper motors etc.
  3. Camera set-point cooling control - pretty much finished and working.

Items 2 and 3 are covered in other threads.

Share this post


Link to post
Share on other sites

Hi Guys,

I am about to build my Arduino Uno controller, have the parts but I'm confused about the libraries after following the thread started by mitaccio on Cloudynights.com. Can anyone throw any unambiguous light on this please?

Share this post


Link to post
Share on other sites

You only need libraries to access specific functions. I guess ypou will be using PWM output to control the heater strip. This is standard to the arduino and doesn't need any extra libraries,

Share this post


Link to post
Share on other sites

Thanks for replying. I'm using a DHT22 and 4 DS18B20's, plus 2x16 LCD display so will need the coding for those. What I have found is this from cloudynights.com:

http://michiana-astro.org/projects/dewctrl/libraries.zip

The code hasanumber of include lines:

#include <EEPROM.h>

#include <OneWire.h>

#include <DallasTemperature.h>

#include <LiquidCrystal.h>

#include <dht11.h>

#include <math.h>

I'm trying to find out if those libraries have to programmed to the Arduino too. I think they do!!

However, I am guessing and very much stand to be corrected.

Gina, I've trawled through the arduino.cc site but so far have found no specific reference to this project, but it does have code for the sensors and LCD, so I imagine I'll need to implement those .

I'm on a big learning curve here, so any pointers would be most welcome.

Tahnks

Phil

Share this post


Link to post
Share on other sites

Phil, I am curently having a go at the same thing.

You need to download the libraries and install them into your arduino files.

One wire and Dallas here: http://www.hacktronics.com/Tutorials/arduino-1-wire-tutorial.html

DHT here: http://learn.adafruit.com/dht

I think the liquid crystal is included anyway, a good tutorial for it here:

I am not sure about the others, I have just started this week so have a steep learning curve!

Good luck

Jason.

Share this post


Link to post
Share on other sites

Thanks Jason,

I had already found the adafruit one, the hacktronic one should be useful too.

Just waiting for the Uno anf the DHT22 to come, then I can get going with it.

I'm going for 4 outputs, one of which will be keeping a box of EPs up to temperature, so when swapping I won't have to wait for dew control to operative. The other outputs will be corrector plate on the SCT, EP in use and finder objective.

I think once I have mine working properly, I'll write it all up in an easily digestible form, to include all the coding. What I have seen on the forums so far is fragmented and sometimes not too easy to work out. In the meantime I'll put progress notes up here.

Are you using Darlingtons of MOSFETS for the power handling?

Phil

Share this post


Link to post
Share on other sites

I am also using a DH22, I have mosfets to handle the power to 4 heaters, OTA, guide scope, finder scope and telrad. I have working dew heaters that I made with 555 chips and mosfets, I just want to automate it, I can then move the existing controls to a portable power pack I will be making.

I havn't done any programing before so this is going take a while. I have also found bits of info here and there, I am curnently trying to put it all together.

I think I am going to make up a single heater first, so I can test it on a spare finder scope while I am out using the scope.

I look forward to seing how you get along with it.

Jason.

Share this post


Link to post
Share on other sites

This is very sililar to what I do for my camera cooling control and I have the code for that - in fact I think I put the bulk of it in my Peltier TEC camera cooling thread. But you would be better working from the bottom up and learning as you go. It's important that you understant what is happening rather than blindly following already written code. There are examples you can go by. But if you need any help just say :) Good luck :)

Share this post


Link to post
Share on other sites

That's my thoughts Gina, I want to understand how the program works thats why I an taking my time.

I have started with simple sketches for each sensor alone and the LCD, now I am trying to make them all work together.

Jason.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

By using this site, you agree to our Terms of Use.