Dùng màn hình Nokia đo nhiệt độ sử dụng DS18B20

Nguồn: ivica.novakovic - [website]

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Sử dụng màn hình của điện thoại cũ cho nhiều ứng dụng

Nokia 3310 có LCD (84x84 pixels), that isn't that hard to get and can be very useful in DIY (do it yourself) electronics.

This page describes a device I designed to test such a display and turned out to be the circuit that I am proud to share with you. Since my motto is �simplicity in construction�, with a few parts you will be able to create a relatively accurate and visually appealing thermometer.

Đặc tính kỹ thuật : Điện áp....................... 3 - 3.3 V Giới hạn đo(1) ....................-55 do 125' C Bước nhảy tối thiểu ............ 0,1 ' C Sai số tối đa ................... +/- 0,5 ' C Max. resolution ............. 0,0625 ' C Temp. refreshed every.... 1,2 sec. Kích thước................... 40 * 38 mm 2 modes of display .........normal/inverse Llcd ............................. 84*48 pixels Dòng điện (2)................. 0,2 mA - 0,8 mA

Range of -55 to 125°C is possible if ONLY the sensor is in that area not the whole device! Amperage of the device varies because of the conversion of DS18B20 (measuring the temperature and reading the measured temperature), that lasts about 700ms and at that time the device uses 0.8mA, for the next 500ms the device is in �sleep� mode and uses 0.2mA.

The LCD supports two modes of operation (normal and inverse), the jumper placed on the back of the device is used for changing modes.	Negative temperatures are given a �minus�, the bar shows temperatures normally but with an added minus.	In this picture I charged the device with a 3.6V lithium battery. Do not use a greater voltage then this because the Nokia 3310 LCD works with 2.7 to 3.3V!!! Careful!

Tổng quan

	Lcd First we need to extract/salvage the LCD from the Nokia 3310 mobile phone. Be extremely careful and patient during this process, because as you know the display is just a thin piece of glass that is very sensitive. There is an 8 pin connector on the back of the display, in our case it's glued to the glass (Nokia 3210 has �rubber� connectors so this one is much easier to use). This is a Phillips PCD8544 display, it can be easily found on the net if you want more information about it.
	Mạch in The second step is making the board which is small and isn't that difficult to make. Pay close attention while gluing the plastic edges on the board because they will be holding your LCD. Double check connector positions before gluing. In the bottom corners I glued two plastic separators so the LCD leans on them and not the solder points.
	Bố trí linh kiện On the back side we can see the layout of elements, they aren't hard to find and there aren't that many of them. I placed the temperature sensor DS18B20 in a socket for testing purposes, it is also possible to connect the sensor at a distance by adding wire (I haven't tested 1 wire sensors at a distance yet).

Sơ đồ-Mạch in

Mạch in	Linh kiện

Điều chỉnh tương phản

If by any chance the contrast isn't to your liking, it can be changed during the programming of Pic12F629, in the program location D2h. the current value A9h is the one I use with my LCD and don't know it will be for other LCDs. The value can be set to anything between 80h and FFh, 80h being minimum contrast and FFh maximum.

Downloads

Tải chương trình:	Nokia LCD Thermometer � PIC12F629 - in hex
	Nokia Lcd Thrmometer - PIC12F675 - in hex
Tải mạch điện và mạch in:	Nokia Lcd Thermometer - made in Protel 99 SE
	Nokia Lcd Thermometer.pdf - PCB in pdf

Since I have noticed that there is a problem with programming these microcontrollers you should read the short how-to for programming PIC12F629/675 microcontrollers.

This device was just a test and I hope to have many more circuits that utilize this LCD soon because I'm very fond of its easy implementation.