This kit allows you to measure degrees  C.  It will display on a LCD display (3.5 Digits)  

 

 

Model A

 

Model B

 

 

Kit Model  A Includes:

  • 78L09                 Voltage Regulator   1pc.

  • 0.1MF                 Capacitor              1pc.

  • 10MF                  Capacitor              1pc.

  • 10K Ohms 1/%      Resistor                1pc.

  • 100K Ohms           Trimmer                1pc.

  • LM35                   IC                       1pc.

  • LCD35                  LCD                     1pc.

  • 1N4148                Diode                    4pc.

  • 2P Terminal Block  Connector             1pc. 

  • PCB                                               1pc.

Kit Model  B Includes:

  • LM317                 Voltage Regulator   1pc.

  • 0.1MF                 Capacitor              1pc.

  • 10MF                  Capacitor              1pc.

  • 240 Ohms            Trimmer                1pc.

  • 1.5K Ohms           Trimmer                1pc.

  • 10K Ohms 1/%      Resistor                1pc.

  • 100K Ohms           Trimmer                1pc.

  • LM35                   IC                       1pc.

  • LCD35                 LCD                     1pc.

  • 1N4148                Diode                   4pc.

  • 2P Terminal Block  Connector             1pc. 

  • PCB                                               1pc.

Schematic:  

 

Model A

 

Model B

 

This kit utilizing EID 3.5 digit voltmeter display to show very accurate temperature (degrees C) readings using only few external components. 

 

The temperature reading obtains from the LM35 (solid state temperature transducer) in a form of voltage, 1mV per degree Centigrade. The device (LM35) output is linearly proportional to their ambient temperature. For example at room temperature 25 degrees Centigrade the output voltage is 250mV DC. According to the specification (National Semiconductor TM)  the device provide typical accuracy of +/-0.25 degree C at room temperature, and +/-0.75 degree Centigrade at full  operating temperature rang of -55 to 150C.

 

Note, even thought the device is specified to operate below 0 degree Centigrade., this kit shows temperature range of 0-60 Degrees Centigrade. This due to the display operation temperature limitations. To obtain higher temperature readings 0-150C use extension wire between the device and the board. Be advise you should compensate the lost of wire voltage via P1.

 

The board is power of 11-16V DC or AC. The diodes bridge D1-D4 (model A only), together with the capacitor C1, will convert input AC voltage to DC Voltage (See above kit drawing model A). Additionally, the diode bridge ensures that the polarity of the bridge output remains the same regardless of the input voltage polarity. It's what we call "dummy-proof." Let's say, for example, the board is powered by a 12V car battery, the output polarity remains the same no matter how you connect the power to the board's diodes bridge.

 

The other side of the diodes bridge drives the voltage regulator U1 (regulator). Regulators usually having three legs, it converts varying input voltages and produces a constant regulated output voltage. They are available in a variety of outputs. The most common part numbers of the regulator starts with the numbers 78 or 79, and finish with two digits indicating the output voltage. The number 78 represents positive voltage, and 79 a negative one. The 78XX series of voltage regulators are designed for positive input. And the 79XX series is designed for negative input. The LM78XX series typically has the ability to drive currents up to 1A. Application such as this, required less then 150mA, 78LXX can be used. Therefore, we used the 78L09 as regulator to power this board. As mentioned above, the component has three legs: Input leg which can hold up to 36VDC (we recommend not to exceed 24V), Common leg (GND) and an output leg with the regulator's voltage. For maximum voltage regulation, adding capacitor C2 in parallel between the common leg and the output is usually recommended. C2 a 0.1MF capacitor is used. This eliminates any high frequency AC voltage that could otherwise combine with the output voltage. See above circuit diagram for the kit.  

 

In model B, we substitute the diode bridge and the 78L08 regulator with adjustable regulator Lm317. Together with two resistor R1 and R2 provide regulated output voltage of about 9VDC. 

 

Calculating the LM317 output voltage:

 

V_LM317 = 1.25V + (1.25V/R1) * 1.5K = 9.0625V

 

Finally, since the sensor output can generate voltage up to 1.5V at 150C, the sensor output voltage connected to the display via the voltage divider R3 and P1 combination. This will insure 10:1 voltage ratio needed to drive the displays input of 0-200mV.

 

 

Description and SKU#

Price

Picture

LCD Deg. C display Kit model A

EID-K-TEMP-LCD-35A-ASM Fully assembled

EID-K-TEMP-LCD-35A-KIT Kit

 

29.00

22.95

EID-K-TEMP-LCD-35A-PCB PCB Only

9.99

 

 

LCD Deg. C display Kit model B

EID-K-TEMP-LCD-35B-ASM Fully assembled

EID-K-TEMP-LCD-35B-KIT Kit

 

26.00

19.95

EID-K-TEMP-LCD-35B-PCB PCB Only

9.99

 

 

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