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How to Make Thermal Sensors

Thermal sensors are used to measure the amount of heat in the environment or generated by devices and machines. Thermal sensors come in many forms, ranging from the thermometer to complex electronic sensors designed to give high-accuracy readouts of thermal information. Building your own simple thermal sensor is a bit difficult, as it requires moderate knowledge about electronic circuitry and aptitude for building electronics. For the seasoned electronics expert, this isn't a difficult task. A simple analogue thermal sensor can be made with inexpensive components and 10 minutes of assembly time.

Things You'll Need

Soldering iron
On/Off switch with leads
NTC-type 10K ohm thermistor
10K resistor
Short wire lead
1K resistor
Electronics kit light bulb with leads
AA Battery caddy with leads
Two AA batteries

Instructions

- 1
  Beginning with the positive lead of the battery caddy, solder the positive lead to a lead on the on/off switch.
- 2
  Solder the NTC-type 10K ohm resistor and the standard 10k ohm resistor in parallel. The NTC-type resistor will cause an increase in voltage via lowered resistance as temperature increases. The standard 10k ohm resistor regulates the thermal resistor and is optional, though recommended.
- 3
  Solder one end of the two parallel resistors to the other lead of the on/off switch.
- 4
  Solder a short wire lead ̵1; the voltage output lead ̵1; to the free (negative) end of the parallel resistors.
- 5
  Solder one 1K ohm resistor to the negative end of the parallel resistors.
- 6
  Solder the other (negative end) of the 1K resistor to the negative lead on the battery caddy.
- 7
  Solder one lead from the electronics kit lightbulb to the voltage output lead from Step 4.
- 8
  Solder the other lead from the electronics kit lightbulb to the negative lead on the battery caddy.
- 9
  Add two AA batteries to the battery caddy and turn on the switch. If everything is connected properly, the light bulb will turn on. As heat is applied to the thermal resistor (by your hands or otherwise), resistance will decrease and the light bulb intensity will increase. The light bulb serves as a very rudimentary, yet functional thermal sensor.

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