An Inexpensive Cell Phone Trigger For Your Preheater.... That Gives You Piece Of Mind

I wanted to finally reveal an electronics project that some of you may want to build.

It is cold outside, the engines need to be warmed for long periods of time, and no one wants to go to the hangar and wait for hours while the engine slowly soaks in heat.

This solution is called the “Hangar Buddy”, and it is based on an incredible project by Maria DeGrazia. You may have seen it in the EAA Experimenter under the name “piWarmer”. This is my version that has been greatly expanded upon to do WAY more.

So what is this thing? It is a device that lets you start preheating your engine with a text message. It uses an inexpensive GSM cell phone provider and an inexpensive GSM cell modem to do this. This lets you start heating your plan without the use of WiFi or the need for an LTE signal.

In addition to starting your preheater of choice, it is also a device that is designed to give you some piece of mind about your hangar.

  • It can tell you if you have a dripping fuel sampler.
  • It can tell you if you left the lights on.
  • It can tell you how cold your hangar is.
  • It has a security model so only specific phone numbers can send a command.
  • It also has a small screen that lets you see the device’s status when setting it up.
  • It also has a high gain antenna that can be placed so you can find signal.

The code has been reengineered to be a “platform” and easy to add new abilities to the device.

Depending on the sensors and displays you want to add, you can build it for as little as $100, less if you have parts laying around. The typical phone bill should be around $9 a month.

You can find the source code, plans, and instructions at

Let me know if you build one.


The is an Open Source project, and the wiring diagram is included. 

Soldering is required to complete the project.

I am not selling anything, nor do I see a single dollar. This is being provided to help the community.

All software provided “as-is”. Instructions do not include an engine heater. The parts list includes a GFCI adapter.

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Comment by David J. Beaulieu on December 31, 2017 at 9:51pm

Thanks for posting ... pretty neat project to try once I get some time.

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