# Seg 4: Experimental principle of LM35

1. Experiment and code
1. Experimental principle

The principle of such experiment is very simple. The voltage data is sensed by the temperature sensor LM35, which would be sent to the analog port (A0 is used in this experiment) on the Arduino board. Then the Celsius (Centigrade) temperature can be output by the linear relationship between the voltage and temperature. For example, in this experiment, we know the linear relationship for the temperature LM35 by one Celsius temperature/10mV. Thus, we can get the voltage value n from the analog port A0 connected LM35 on the Arduino board. Not that, the data n is discrete and located on the range of 0~1024. So, we should change the discrete data n into a continuous voltage to get the Celsius temperature. In fact, the computation is simple. We know that, as for the analog ports A0~A5, the value range is 0~1024, and 1024 is corresponding to 5V. Therefore, if we know the value in A0 port, then we can obtain the discrete voltage value within 0~1024; i.e., the value is n. Then, we can compute the Celsius temperature. Assume that the continue voltage in port A0 on Arduino board is denoted by U. Then, we have the following compute formula by the principle A0 and the linear relationship between Celsius temperature and the continuous voltage. ,

where vol is the Celsius temperature we should compute, n can be achieved from analog port A0 on the Arduino. Therefore, we can compute the continuous voltage in A0 by equation (1). Then, we substitute the U into equation (2), the Celsius temperature can thus be obtained. In addition, the value of vol (i.e., Celsius temperature) could display on the serial monitor on the Arduino software platform.

# Seg 2: Features of temperature sensor LM35

1. Be familiar with temperature sensor

According to the output signal modes, it can be divided into 3 types: digital temperatures, logic output temperature, and analog temperature. In such experiment, the LM35 series sensors is a precise integrated circuit temperature sensor on the development of LM135. Its output voltage is proportional to the centigrade temperature linearly.

Thus the LM35 make interfacing to readout or control circuitry especially easy. The device is used with single power supplies, or with plus and minus supplies. As the LM35 draws only 60 μA from the supply, it has very low self-heating of less than 0.1°C in still air. The LM35 is rated to operate over a −55°C to +150°C temperature range, while the LM35C is rated for a −40°C to +110°C range (−10° with improved accuracy). The LM35 series is available packaged in hermetic TO transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic TO-92 transistor package. The LM35D is also available in an 8-lead surface-mount small outline package and a plastic TO-220 package.

Features

Calibrated Directly in Celsius (Centigrade) temperature sensors, with an output voltage linearly

Linear + 10 mV/°C Scale Factor proportional to the Centigrade temperature. Thus the

0.5°C Ensured Accuracy (at +25°C) LM35 has an advantage over linear temperature

Rated for Full −55°C to +150°C Range sensors calibrated in ° Kelvin, as the user is not

Suitable for Remote Applications required to subtract a large constant voltage from the output to obtain convenient Centigrade scaling. The

Low Cost Due to Wafer-Level Trimming LM35 does not require any external calibration or

Operates from 4 to 30 V trimming to provide typical accuracies of ±¼°C at

Less than 60-μA Current Drain room temperature and ±¾°C over a full −55°C to

+150°C temperature range. Low cost is assured by

Low Self-Heating, 0.08°C in Still Air trimming and calibration at the wafer level. The low

Nonlinearity Only ±¼°C Typical output impedance, linear output, and precise inherent

Low Impedance Output, 0.1 W for 1 mA Load calibration of the LM35 make interfacing to readout or control

# Seg 4: Order of the pins for the nixie tube and coding

1. Order of the pins of the nixie tube

Similarly, why do we know the order the pin? If we do not know the order of the pins, we do not know how to connect to the pins of nixietube. For example, if we want to display the digital number 5, how can we connect the dupon lines from the pins of nixie tube to the ports on the Arduino? To connect to the Arduino board rightly, we must know the connect rules.

1. re-know the nixie tube

We firstly know the pins of nixie tube from the followings in Figure 6-6. Figure 6-6 Pins connection of nixie tube

1. As shown on the left subfigure of Figure 6-6, the digital number is labeled from the lower left by the counterclockwise, and the number of point is 5. All of the number is 1~10.
2. The letter label is marked from up to down by the clockwise. It is a~h, respectively, where the number of point is “h” as the last location.
3. Digital number 3 and 8 is the common port, which is the common anode or cathode. Figure 6-6 is the common cathode nixie tube; that is, all of the negative pins are connected a common port 3 or 8.
1. Coding of nixie tube

What is coding? To make the nixie tube display the designed digital number, we should let the LED to be conduction. For example, we want to display number 5 in Figure 6-6, how? Firstly, the polarity is must be right. In such experiment, the nixie tube is the common cathode. Thus, the common cathode should be connected to the GND port on the Arduino. Other pins must be corresponding to the ports on the Arduino to display the right digital number. This is coding. For example, in the letter view, if let the pins of a,c,d,f,g set as a high voltage level (or 1), and other pins is set as low level, (or 0), then, the corresponding segments would be light and digital number 5 can be displayed on the nixie tube. Since the decimal point “h” would not affect the display of digital number, it can be conducted or not. In this experiment, the decimal point is conducted. From the digital view, pins 2,4,5,7,9,10 are conducted, and the other remaining ones are not. Therefore, if we use binary code to express this segment, it can be coded as {0,1,1,1,0,1,1,1}. That is, there are two segments dark among of the eight segments in the nixie tube. Then, digital number “5″ can be displayed correctly. By this coding method, we can get other digital number coding, as shown in Table 6-2.

Table 6-2 Digital number coding scheme for the common cathode nixie tube

 Arduino ports Nixietube pins 0 1 2 3 4 5 6 7 8 9 4 1(e) 1 0 1 0 0 0 1 0 1 0 5 2(d) 1 0 1 1 0 1 1 0 1 1 6 4(c) 1 1 0 1 1 1 1 1 1 1 7 5(Dp) 1 1 1 1 1 1 1 1 1 1 8 6(b) 1 1 1 1 1 0 0 1 1 1 9 7(a) 1 0 1 1 0 1 1 1 1 1 10 9(f) 1 0 0 0 1 1 1 0 1 1 11 10(g) 0 0 1 1 1 1 1 0 1 1

Note that, to avoid the error of connection to Arduino, or convenience, we had better encode the digital number by one-defined rule. For example, in this experiment, let the digital ports on Arduino board correspond to the pins of nixietube for small to big (1~10). Certainly, there are many encoding schemes by following different ones’ habits. But the effect of display and the code is the same.