With LM35 with digital multimeter production electronic thermometer, LM35 THERMOMETER
Keywords: with LM35 with digital multimeter making electronic thermometer
Make an electronic thermometer with LM35 with digital multimeter
Author: Du Yong
There are now many fans with digital multimeters, but there is no measurement of temperature. Here, you will introduce a DIY temperature measuring instrument whose measurement accuracy is ± 0.1 ° C, and the measurement range is from 10 to 110 ° C. This thermometer is used. The measurement is accurate, the reading is intuitive, and the temperature time response is fast. It is a good helper for homes and monitoring temperatures. The specific method of making is described below.
First, the material 1. Old remote control housing is only three light-emitting diof holes, 1 power switch hole, 1 adjustment screw hole, and the diameter of the selected light emitting diode, according to the surface of Figure 2. The potentiometer and switch size are determined. The circuit boards in the remote control are all removed, only the battery box and button rubber plate are kept.
2. The cable uses the thin and soft mouse cord of the bad computer. There are 5 core wires in the mouse line. As long as three of them, you can use a multimeter. 3. Temperature detection 1) LM35 temperature sensor ("Electronic News" is also published, here is no longer described) 1; 2) 1 piece (length 15mm, width of 4mm) of the small circuit board. Welding 1M35 to the small circuit board; 3) Probe housing, find a automatic pencil outer cylinder or stainless steel outer cylinder (diameter 6mm), intercepted length 35mm; 4) 1 piece of white iron or stainless steel sheet of finger head cover size It is all plated with solder.
4. Instrument digital multimeter 1 piece (with 200mV gear).
Second, the production 1. Circuit board takes out the remote control protocol, press the copper plate according to its size, and then cut a piece of cardboard in the copper sizes. Draw a circuit diagram on a cardboard. The drawn circuit drawings are then fixed with transparent glue on the copper. Follow the cardboard (pattern), then tighten the paper, and take the line with a small knife. Wash the circuit board with a fine sandpaper, wash the circuit board, wash the dust, wipe off the water, check the circuit under the light, check there is a way to miss the moment, it is best to use alcohol pine fragrance to coil the circuit board. After drying, you can plug-ins, solder.
2. The probe housing taken after the probe is plated onto a solder, and the stainless steel sheet plated is plated on the table in the table, and then the top of the probe shell is plated on the stainless steel tin sheet. After heating the tin, take the soldering iron, wait for the soldier, use the scissors to cut the excess edge, preferably to repair the corner, and then put it into the probe bucket ~ therefrom. The three lines of the mouse line are welded to the three lines of the small line plate. At this time, it is necessary to record the color and wiring position of the three lines, preferably in the probe bucket containing 1m35, and then use 502 The gum fat sealing tub probe is made. The other end of the mouse line is welded to the respective position of the circuit board, and the end of the lead wire is fixed to the front end of the remote control housing, preventing the inner soldering wire in the front end of the remote control.
Third, circuit and debugging
The above circuit consists of three parts, and the first portion BG1, BG2, T1 components constitute a boost circuit, first disconnect the input of the LM7805, and the power supply measurement C2 should be measured between 10 to 11V, such as the circuit. The vibration is changed to 12 two wires.
BG1 was used with A1050 β ≥ 200, and Bg2 was c8050 β ≥ 150. The second part consists of a battery voltage test circuit such as IC2 LM358, and there is only a green light when normal voltage. Red light is on when the battery voltage is below 2V. IC23 foot voltages use low power consumption, high brightness to reduce power consumption in 2V. The third portion constitutes a temperature measurement circuit by IC3 CA3140, IC4 1M35 and other components, and this partial circuit is not debugged by the circuit parameter assembly. The display temperature of the header can be calibrated as long as W1 is adjusted. After all of the assembled, the number table hit the 200mV block, put the probe in the armpit, and immediately turn on the board and digital table switch, adjust W1 to adjust the display value of the digital table to 37 ° C. Can.
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