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Parts explanation of Room temperature controller

PIC16F873

The output of a temperature sensor is analog voltage. Therefore, conversion to a digital signal is required using an A/D converter. With this equipment, PIC16F873 with a built-in A/D converter is used.

Temperature sensor ( LM35DZ )

LM35 series of National Semiconductor is used. It is D type which was used this time, and it can be measured from 0°C to +100°C. The output of a sensor is set to 0V at 2°C, and +10mV/°C is outputted.

Operational amplifier ( LM358 )


This operational amplifier can operate with a a single power supply.

PNP transistor ( 2SA1015 )

This transistor is used for the scan of LED and BCD-SW. Since LED is a common anode type, a PNP type is used.

NPN transistor ( 2SC1815 )

This transistor is used for the drive of the relay for external device control.

Positive Voltage Regulator ( 7805 )

This is a regulator for +5V output. Since LED is made to turn on by +5V, 1A type is used.

Sensor cover

The cover of a mini jack is used for the sensor cover. I did not use the portion of the pin of a jack but used only the case. LM35DZ is shown under the cover.
BCD-SW ( RDS610 )

This is a DIP Rotary Code Switch made by SAGAMI. The BCD code is outputted.

IC socket

Since PIC16F873 are removed when rewriting a program, its IC socket is indispensable. 873 is 28 pins slim type DIP, so it can use two IC sockets for 14 pins.
Switching diode ( 1S1588 )

This is a switching diode. These switching diodes are used for adverse current prevention of BCD-SW, and used for control of the back electromotive force generated in a relay.
Ceramic resonator

This is a ceramic resonator for 4MHz.

7 segment LED for a current temperature

The size is 12mm in width, 18.8mm in height and 8mm in depth.
7 segment LED for a preset temperature

The size is 7mm in width, 11mm in height and 5mm in depth.
Slide switch

This switch is used for the control mode change. Below preset temperature or above.
Control circuit drive display LED

This is LED which displays the drive state of a control circuit. Green is for circuit 1 and an orange is for circuit 2.
Relay ( G6C-2117P-US )

This is a relay which drive the external circuit. It is made by OMRON. Since there is polarity in this relay at a drive coil, it will not operate, if it connects conversely.The specification of a point of contact is shown below.
250VAC : 8A / 30VDC : 8A
Resistor

1/6W type is used altogether.
Potentiometer
This potentiometer is used for adjusting the gain of an OP amplifier. This is 25 rotation type.


15 rotation type
Rectification diode bridge

100V-1A diode bridge is used for rectification.
Electrolytic capacitor

This capacitor is used for the filter of a power supply.
Multilayer ceramic capacitor

This capacitor is used for oscillation prevention of a regulator.
Printed circuit board

This printed circuit board has 27 x 36 holes. However, part mounting cannot be performed near the corner.
Stud

This is the parts for attaching a printed circuit board in a case.
Transformer


This is the small transformer which secondary side output is 10V-300mA.
Output socket


This is a socket which connects an external circuit ( ventilation fan ).
Case


The size is 150mm in width, 54mm in height and 170mm in depth.
Fuse


This is the small fuse of 1A.
Sensor connection plug


This is the mini jack of the stereotype used with audiovisual apparatus.
Shielded cable


This is the cable which connects a temperature sensor and a control part.
AC cable / protector


This is the AC code of 700W type.
A protector is used in order to prevent the crack by the case.
Acrylics board ( purple )


This is the purple acrylics board used for the front of LED. The display of LED becomes clear with this acrylics board.
Character seal


This is the character seal used for the name display of a panel.
Terminal


This is a terminal for changing a display to test mode. Red part is the short pin for short-circuiting terminals.
Test pin

This is the test pin attached to the checkpoint of a circuit. Since the tip is a ring, connection of a hook chip etc. is easy.
Terminal


This is a terminal for connecting a power cable.
Heat sink

Many heat occurs in a regulator. Heat sink was not attached at the beginning. But, since it got as hot as it cannot touch, heat sink was attached.
Tantalum Capacitor


This capacitor is used in order to stabilize the output voltage of a temperature sensor.