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| INTRODUCTION:
An accurate thermometer with 12 LEDs ranging from 8C to 30C
There are 12 LEDs on the display representing 2 degree Celsius steps. If 2 LEDs are on, then the temperature reading is in between the two. This circuit uses a micro-controller with a program running inside. It runs from 2 AA batteries which up to 5 months.
This circuit can be applied to a range of themes to create a variety of projects.
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This project is available in our shop now!.
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| CIRCUIT DESCRIPTION |
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| The circuit is based around a PIC micro-controller that has a program running in it.
The temperature sensor is a thermistor (TS1) which is connected into a potential divider by R7. The output voltage from the potential divider is sampled by the ADC (Analogue to Digital Converter) inside the PIC and is given a value from 0-255 which is proportional to the voltage.
The sampled value is turned into the final LED output with a little maths and displayed on one of 12 3mm LEDs. These are calibrated in 2 degree Celcius steps.
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Circuit Diagram
The PCB is in the shape of a traditional thermometer due to the line of 12 LEDs and overall measures 4.05" x 1.1" (103mm x 28mm)
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The PCB has markings on showing the temperature each LED represents in Celsius and Fahrenheit. |
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| CONSTRUCTION |
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The LEDs can be soldered directly to the PCB and use the scale on the PCB as part of the finished product.
Alternatively, a spacer can be used to set all the LEDs at the same height. This can be piece of 1mm thick material such as HIPS or acrylic cut to a height of 7mm.
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The holes 3mm in diameter and spaced 6mm apart from center to center.
An outline template of the PCB is available below - Resources |
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