Astro Heater

Overview

This is a dew heater running open source firmware.

Personally, I'm sick of seeing companies charge $300+ (USD, yes really) for basic dew heaters and then have the audacity to lock the user into their proprietary software — so I made my own.

This dew heater takes user input from a dial and keeps the heater band at a contant temperature (typically withing +/-3 degrees f). There are future plans to expand this functionality, see Potential Features below.

Parts List

Component	Details
ESP32 WROOM	I used a 38-pin dev board from DORHEA
DS18B20 Temp Probe	or similar three-lead temp probe
IRF3708PBF MOSFET	-
128x64 I2C OLED Display (x2)	I used two SSD1306's Make sure one can be running on IIC Address 0x3C and the other is on 0x3D
Heater Band	Just find the cheapest 10W heater band available to you; no controller required
10kΩ Potentiometer	-
Momentary Button (x2)	-
10kΩ Resistor	-
220Ω Resistor	-
Male/Female USB plugs (optional)	If you don't want to use plugs, you can hardwire the heater and power USBs directly to the ESP32
SHT30	Ambient temp/humidity sensor

Assembly

Assemble the pieces on a breadboard or blank PCB using the below wiring:

Component	Wiring
OLED Display 0x3C	SDA -> GPIO 21, SCL -> GPIO 22
OLED Display 0c3D	SDA -> GPIO 21, SCL -> GPIO 22
DS18B20 Sensor	Data -> GPIO 4, VCC -> 3.3V, GND -> GND
Potentiometer	Output -> GPIO 34
Heater Power	MOSFET Drain -> Heater(-), Heater(+) to 5V Source
Button 1	GPIO 13
220Ω Resistor	MOSFET Gate -> Resistor -> GPIO26
10kΩ Resistor	MOSFET Source -> Resistor -> MOSFET Drain
ESP32	5V source -> 5V pin, GND source -> GND pin
Button 2	GPIO 12
SHT30	SDA -> GPIO 21, SCL -> GPIO 22

Note: All GPIO pins refer to the ESP32

Installation

1. Clone or Download:
   Clone this repository or download firmware.ino to your computer.
2. Open in Arduino IDE:
   • Open firmware.ino in the Arduino IDE.
   • Connect your ESP32 board.
   • Important: Use ESP32 Board Manager version 2.0.14. Later versions may contain I2C issues affecting the OLED displays.
3. Install Libraries:
   Ensure all libraries referenced at the top of firmware.ino are installed in your Arduino IDE.
4. Update WiFi Credentials:
   If connecting heater to WiFi network, update the credentials in the firmware before uploading to your ESP32. Set ssis and password at top of script to your SSID and Password.
5. Compile and Upload:
   Compile and upload the firmware to your ESP32.

Usage

Basic Operation

Wrap the heater band around your scope, placing the temperature probe inside the band touching the scope body.

Power on your dew heater by plugging it into a 5V 2A USB source — the screens should illuminate.

Enable/Disable WiFi using on screen prompts. If WiFi is enabled, wait for the ESP32 to connect and then note the displayed IP address.

After the splash screens, you may select a target temperature with the pot from 0-100°f.

The heater will being to warm until the temp probe reaches the target temperature. Once the temp falls back below the target, the heater will kick on again.

Screen 2 (0x3D) will output a graph to show temp probe readings and heater state for the last 30min.

Locking Target Temp

Depending on your specific setup, the potentiometer reading may fluctuate as the heater is drawing power and the temp probe is reading within 0-4° of the target. If this is the case, use the button to lockout the pot once you have selected your target temp.

To change the target temp, press the lockout button again to toggle the lock.

Automatic Mode

While the target temp is locked, you may press the secondary button to engage automatic mode. In auto mode, the ESP32 will read the ambient temperature and humidity to determin the dew point. The target temp will then be set to 3 degrees above the dew point.

Webpage

While powered on and connected to WiFi, the heater will output a webpage at the IP address displayed during startup. Navigate to this address using another device to view current/target temperature, set a new target temp (while the device is locked), toggle auto mode remotely, and view a 6hr temp graph.

Note: Don't forget to set your SSID and Password in the firmware before flashing to your ESP32.

FAQ

Really? $300 for a Proprietary Dew Heater??

Ok, maybe I fudged a bit there — but at the time of writing the Pegasus DewMaster 2 is $279 before VAT and Shipping costs, and that's also before buying the actual heating bands as well.

Now, this current setup doesn't do quite as much as the DewMaster, but it is a whole lot cheaper. I built my personal setup for ~$50, and you could do it cheaper if you got better deals or already had some of the parts.

See the Potential Features section below to see some things which might be added soon to truly make this a replacement for the Pegasus.

How much does this all cost?

About $50 if you have to buy everything, but you can save some money if you get better deals than I did or have some of these parts already laying around.

I tried to use common components so you might be able to find somebody willing to part with a resistor or two.

I'm having problems with my dew heater

Ok, that's not really a question, but check out the Troubleshooting section below!

This seems pretty basic, are you going to add more features?

Short Answer: Probably

Long Answer: I have a job and a life, but part of my life is Astronomy, so I'll add new features as I think of them and have the time to implement them. I won't be keeping any sort of update schedule, but you can follow this repo to be notified of the changes.

I have a great idea for this project which needs to be added!

That's great! That's the beauty of FOSS, feel free to make a fork of this project and get working on it! :)

If you just have a feature you'd like to request, make an issue report and tag it as feature request.

I found a bug

Ooh, not good. Create an issue report and I'll take a look.

Try to include as much info as you can to help me recreate the bug: ESP32 model#, part#'s, Serial Monitor outputs etc.

Make sure to tag your post with bug.

Why the GPLv3 License?

Pretty simply put, I don't want anyone to try and charge money for this code (that includes me). I'm putting this out into the world so anyone can put together their own dew heater that just works. I want to make sure you have the right to use this code, for free, in perpetuity — and GNU's GPL license allows me to do that.

Check out https://www.gnu.org/licenses/gpl-3.0.en.html to learn more.

Potential Features & Fixes

• Settings Menu:
  Include a settings menu to adjust defaults, view IP addresses, toggle automatic mode temp delta, etc.

• Error Handling:
  Current code returns an error when the temp probe is not connected or probe is misread. In an error state, heater is automatically on. Add toggle to adjust default heater state.

• Celsius/Fahrenheit Toggle

• WiFi Access Point:
  Add a mode for ESP32 to broadcast its own network when nearby WiFi is unavailable.

Troubleshooting

Troubleshooting steps will be added as issues are identified.