Circuit's Blog :
Return to BlogLED Glowies with Temperature Sensor
Posted Feb 06, 2012 at 2:31 pm
Figure 1
The Glowies were built around a PIC12F675 microcontroller which has built-in analog to digital converters while the core of the unit is a silicon diode used as a temperature sensor.
The ADCs are being used to measure the forward voltage of two identical diodes wherein one of the diodes is lightly insulated from the ambient temperature while the other diode sticks out a little from the Glowie and serves as the main temperature sensor. The light insulation makes it slower to catch up to temperature changes that are detected by comparing the main sensor to the insulated one. This will result for the Glowie not to know the actual temperature but will be quite good at detecting temperature changes.
The red LED will lit in an upwards temperature change while the blue LED will light up in downwards change. A flickering of the LEDs is a result of borderline changes in temperature where the Glowie measures and reacts many times per second. The LED will light solid in strong changes. If there are no changes in the temperature detected, the Glowie goes to sleep which signifies low power consumption unless LED is lit.
Comments on this post:
Featured Products
Sullins Connectors
Wire-to-board interconnection options from Sullins feature a wide range of sizes and applications
MCC Voltage Suppressors
MCC’s TVS series high-power suppressors protect sensitive components from voltage spikes and transients
Bourns RS-485 Eval Boards
Evaluation boards that streamline evaluating circuit protection on RS-485 serial device ports
2 years ago: Really good circuit.
The Glowies use a small microcontroller, but they are really quite simple in both parts and function. The core of the unit is a silicon diode used as a temperature sensor (actually, two of them). This is very simple, and is very well-understood application – and you can’t get much cheaper!
The electrical characteristics of a silicon diode changes depending on temperature. Specifically, the forward voltage will change depending on the temperature. It’s not much, but it’s enough to measure
gesunde ernahrung