Introduction: Heat Sensing Sprayer

The hot summer days bring two things. Obviously, one would be the heat and the other is a craving for something to cool yourself off with. Well, thankfully, your friend PranP1 has been at his lab cleverly crafting a concoction for your cool craving. Essentially a sprayer, but not just any sprayer, an automatic sprayer. And not just any automatic sprayer, a heat sensing automatic sprayer. Once it senses temperature above 30 degrees Celsius, the sprayer will receive a tug on its trigger. The hotter it is, the harder the tug. In case you need a spray, but the thermistor doesn't sense the heat, manual mode can be initiated. In which you simply use the body heat in your fingers to heat up the thermistor and spray. Using a thermistor, an Arduino, and some other components, this clever contraption will help you beat the heat in style.

Essentially this is a glorified fan, but you know... more fun.

Step 1: Materials

You will need:

1k resistor
1k thermistor
Jumper Wire
Rubber band
9 Volt battery and snap connector

Step 2: Construct the Circuit

All the connections above can be made on a breadboard. Some key connections include:

1) Thermistor and Resistor are connected to each other (on the same row)

2) Connect the resistor to GND and the thermistor to GND and Analog pin 0

3) Make a GND and a 5 V connection at the top where the power supply generally is

4) Connect the Negative and the positive servo wires to the + and - on the breadboard and the other one to Digital pin 11

This circuit didn't work for me that well, but it might work for you. So I decided to make a different circuit.

1) Essentially build the same circuit you would for the Sweep program in your arduino and upload that.

2) Now instead of just applying power regularly, put a 1k thermistor in between the V-in and the red wire of the 9 Volt snap connector. This will block the power from coming unless heat is applied.

Step 3: Upload the Code

Go to the link below to copy and paste the code you see in the above screenshot.

Also thanks to for the code and the circuit. I modified the circuit to work with a sprayer while they used it as an analog thermometer. Either way here is the link to the original:

Also, the other methods code is to just use the sweep code that is already in the Arduino example programs. Look for it under servos

Step 4: Sprayer

The sprayer will need some work but can be summed down to these steps:

1) First, just for safety wash the sprayer out and keep it completely empty

2) Now take the Servo and tape it on to the sprayer firmly as I did. Be sure to keep it aligned with the sprayers trigger

3) Now Tape the Sprayer to the ground to give it some weight. This will ensure it won't topple over and make sure that the servo pulls the trigger

Then for the rubber band

First, put the rubber band around one of the spokes of the Servo
Next tie the rubber band around the sprayer. Now test it out by attaching power (the 9 Volt battery) to the GND and V-in pins of the Arduino. The project is done. If it doesn't work try tinkering around with it. I eventually got the correct config.

Step 5: Done

After a couple tests and a couple different configurations in terms of rubber bands and placements of the sprayer and servo, I got the project working. A pretty nifty device that can be used at home when working as opposed to a fan. It can also be used outside when playing around in the sun. At the beach perhaps while lying down on your blanket. Maybe you want to encourage some marathon runners, simply put it on a nearby table and it will automatically start spraying them. The possibilities aren't endless, but when it comes to situations where you need to cool down, the heat sensing sprayer is an option unlike any other.


Maker Saga (author)2017-08-08

This is actually pretty cool. Nice work. Here's an interesting idea; You could make a 360 degree "aimbot" scanning version of this using an non-contact heat sensing module that triggers a relay which is connected to a spinning base motor on the normally ON pin, and a solenoid to pull the sprayer on the normally OFF pin. The whole unit would spin until it detects heat, then stops spinning and sprays until the heat source is cool again, then it would resume spinning. I made something similar for a flashlight tag robot turret using a light sensor instead of a heat sensor. You could also use a sound sensor as a "hunter hunter bot" which fires back at sources of paintball gunfire. Imagine a quiet study room turret bot which sprays loud people with water!

PranP1 (author)Maker Saga2017-08-08

That's actually a great idea, maybe something I could work on for Version 2 of the sprayer. Your hunter robot is pretty neat as well. Thanks for the kind words.

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