November 2012
Intermediate to advanced
496 pages
12h 2m
English
Content preview from Using LEDs, LCDs and GLCDs in Microcontroller Projects
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11.7 PROJECT 11.7 – Temperature and Pressure Display
This project is about the design of a microcontroller based device to measure the ambient temperature and the pressure and to display them on a 2 × 16 LCD. The temperature will be displayed on the first row and the pressure on the second row. The display is in floating point format as follows:
There are many analogue and digital temperature sensors available. The one used in this project is the LM35DZ integrated circuit analogue temperature sensor. This is a small 3-pin sensor, where one of the pins is connected to +V, the other one to GND, and the third one is the output pin. The output voltage is proportional to temperature and is given by
(11.1) 
Thus, for example, at 10°C the output voltage is 100 mV, at 25°C the output voltage is 250 mV, and so on.
The ambient pressure sensor used in this project is the MPX4115A. This sensor generates an analogue voltage proportional to the ambient pressure. The device is available either in a 6-pin or an 8-pin package.
The pin configuration of a 6-pin sensor is:
| Pin | Description |
| 1 | Output voltage |
| 2 | Ground |
| 3 | +5 V supply |
| 4–6 | not used |
and for an 8-pin sensor:
| Pin | Description |
| 1 | not used |
| 2 | +5 V supply |
| 3 | Ground |
| 4 | Output voltage |
| 5–8 | not used |
Figure 11.25 shows pictures ...
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