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  • Author Author: ntewinkel
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Thermistors for Hummingbird Feeder Heating and Monitoring - Intro (blog 1)

ntewinkel
Thermistors for Hummingbird Feeder Heating and Monitoring - Intro (blog 1)

Hi all!

I'm , and I've been a software engineer for my entire career. I'm also a hobbyist maker for fun. I love it when I'm able to use my software skills to make things happen "in real life".
I’ve been a member of element14 for over a decade, but I’ve never had much time to participate in challenges like this one. I’ve usually been able to build something fun a few times a year, but now, finally, I have a summer off to participate in a challenge like this one!

For the last several years I’ve been working on an easier way of keeping my hummingbird feeders warm during winter.
I live on Vancouver Island (in BC, Canada), where we have a lot of Anna’s hummingbirds that overwinter and depend on hummingbird feeders to get through the more difficult times of winter.

Hummingbird in the snow

Most of the winter is mild, and by that I mean “cold but not freezing”; however, we do get snow and freezing temperatures, so it can be a challenge to keep the nectar from freezing at those times. I’ve been using USB-powered hand-warmers, controlled with bi-metal temperature switches, to automatically keep them warm. This generally works well, but the temperature can swing a fair bit.

As I didn’t fully trust the system, I’ve been using WiFi connected temperature sensors to track the feeder temperatures. To my happy surprise, the heating setup actually worked quite well, not only to keep the nectar from freezing, but also to not overheat the nectar.

feeder temperature chart
The blue line in the chart above is the outdoor temperature, and the pink line shows the nectar temperature - the nectar temperature varies a lot, but the thermostat is doing its job for the most part.

During our extreme cold snap last winter it also alerted me that the heater wouldn’t be able to keep up - something I was able to easily rectify by adding extra layers of bubblewrap insulation.

hummingbird feeder in bubblewrap

I’ve been using ESP-based boards with digital sensors (including the DHT11, DS18B20, and BME280) for this purpose, but when I saw this challenge I wondered if maybe thermistors could provide me with the temperature tracking that I need, and hopefully also for the temperature control that I want for the USB powered heater. Thermistors are a fraction of the price of the other sensors, and they are also much smaller.

Here is a picture showing how my current temperature sensor probe was set up - the glass feeder bottle gets covered with insulation so that the temperature sensor gets an approximate reading of the nectar temperature.

nectar temperature probe placement

During the summer, I've kept the BME sensor running as an easy way to track the weather near my house.
temperature sensor near hummingbird feeder in summer

For this challenge, element14 and Molex provided me with a kit of thermistors of various values, so that I can do some testing and exploring... some might say experimenting! with them.
Molex thermistors experimenting kitMolex thermistors experimenting kit contents

My plan is to connect the thermistors provided in the kit for this challenge to my ESP8266 based Wemos D1 mini microcontrollers to track temperature data of a bottle of water that will be kept outside, tracking temperatures over the course of a few days or maybe weeks.

To be honest, I have a fair bit to learn about thermistors - before this challenge I had not really considered them, and I had no idea there were this many types! The kit contains 10 thermistors, so my first task will be to figure out why the world needs so many different types!

The first part of the experimenting will be to see what the difference is between the various different thermistors provided in the kit: will all of them work with my micro controller? Does accuracy vary across the range? Does the accuracy matter for my use cases? Will they work for my ideal temperature tracking range (-20C to +40C) ? Will they work in outdoor, potentially wet, environments? Will they work well for my specific purpose of tracking liquid temperature inside a glass bottle?

My goal for this challenge will be for me to learn more about thermistors, sharing what I learn along the way, and to determine if thermistors are a good option for my hummingbird feeder temperature control and monitoring project.

My ultimate Long-term goal is to create an easily-reproducible hummingbird feeder heater / monitoring system that is reliable yet inexpensive to build for anyone else wanting to do the same for their hummingbirds.

I also hope that I’m able to share with and learn from all of the other participants in this challenge.

I invite you to stay tuned, follow along, and hopefully we can all learn a few things along the way :)

  • Nice project Nico.

    I was surprised to see a Hummingbird on my first Alaskan cruise. We were off Columbia Glacier and at least a mile from land when this large Hummingbird appeared off the ship. I knew they migrated, but I was still surprised to see it.

  • in reply to robogary

    That makes sense, good idea. I only use the heater setup from about October to March, as that’s when the night time temperatures can dip close to freezing. The setup I have right now is just easy - set it and forget it, but the whole thing can definitely be refined a lot. Since I already have the microcontroller reporting the temperature, I should be able to also have it switch the heater on and off. And as it’s already Internet connected, it can probably ping some weather station to check when sunrise and sunset are.

  • in reply to ntewinkel

    "For phasing back the temperature, do you mean for after-dark when the birds are sleeping, as a way to reduce energy use and avoid spoilage?" yes, but only in the winter. Online sources say daylight is about 8 hours long in the winter on Vancouver Island. 

  • in reply to robogary

    Hi !

    >“is there a target nectar temperature the hummingbirds prefer ?”

    I don’t think they are fussy about the temperature, as long as it’s not frozen (or weirdly too warm, I suppose?), but I was aiming for about 10 C, based mostly on spring and fall temperatures in my area. My goal was to keep it reasonably warm to avoid them having to deal with ice water shock in the mornings, and cool enough to avoid spoilage. The reason for the temperature range I’m getting is because the only real thermostat switches I could find anywhere close to my target temperature were the KSD9700 that are rated for 15 degrees C.

    In summer the nectar gets much warmer, so I imagine the precise temperature doesn’t matter too much. Most people around here seem to switch the feeders with ones kept in the house to keep them liquid, so that would be closer to 21 degrees, with much wilder temperature variations.

    Interesting that the article talks about potential shock for them drinking near-frozen nectar, so my current temperature range, even though not quite what I had planned, seems like a good safe way to avoid it.

    I’ve recently checked out a few other temperature switch ICs too, including TI’s TMP709, but a lot of these things are designed for automotive and computer temperatures, or for fridges and freezers, and are not great for my circa-10 range. I noticed a few other options recently that I could try, and in the last few days of research for this project I’ve seen some references to using a thermistor-based switch, so that might be a stretch goal for this challenge Slight smile

    For phasing back the temperature, do you mean for after-dark when the birds are sleeping, as a way to reduce energy use and avoid spoilage?

  • Nice chart on the nectar temperature. For the most part the nectar stays in the 10C-15C range, is there a target nectar temperature the hummingbirds prefer ? I found this article on hummingbird nectar temperature https://birdgap.com/hummingbirds-drink-cold-nectar/   It might be helpful to keep the hummingbird nectar warm early in the morning and phase back the temperature setpoint a bit in the evening when they arent feeding.