"PCTherm" Project

This project actually consists of three projects. The first is the remote PICmicro® MCU with a DS1820 digital thermometer chip. This interfaces to a PC ISA card via an RS-485 interface. Last, the User interfaces to this application using a Visual Basic interface. When I built the prototype, I first worked on the PICmicro MCU USART interface to the remote temperature sensor and then developed the Visual Basic interface for the user.

Click Here to look at the PICmicro MCU code executing on the ISA card.

The ISA card circuit used for this application is in pdf format and can be seen Here.

The bill of materials for ISA card circuit is listed in the table below.

Part Description

U1 PIC16F877-04/P

U2 75176 RS-422/RS-485 Interface

U3 74LS138 3 to 8 Demultiplexor

U4 - U5 74LS85 Value Comparators

CR1 Red LED (Any Type)

Y1 4 MHz Ceramic Resonator with Internal Capacitors

R1 4.7K, 1/4 Watt Resistor

R2 220 Ohm, 1/4 Watt Resistor

C1, C3 - C5 0.1 uF, 16 Volt Tantalum Capacitor

J3 4x1 Screw Terminal

Miscellaneous ISA Prototyping Cards, Sockets, Wiring

Click Here to look at the PICmicro MCU code executing on the remote temperature sensor card.

The Remote card circuit that I created for this application is:

The bill of materials for ISA card circuit is listed in the table below.

Part Description

PIC16HV540 PIC16HV540-JW

7805 7805 +5 Volt Regulator

DS1820 DS1820 TO-92 Package

75176 75176 RS-422/RS-485 Interface

4 MHz 4 MHz Ceramic Resonator with Internal Capacitors

10K 2x 10K, 1/4 Watt Resistor

3x 0.1 uF 0.1 uF, Tantalum Capacitors

Connector 4x1 Screw Terminal

Miscellaneous Prototyping Cards, Sockets, Wiring

To Connect the remote card to the PC ISA card, I used standard, 4 Conductor telephone cable wired as:

Color Function

Red +12 Volts

Black Ground

Yellow "A" Pin (Positive RS-485 Voltage I/O) of 75176

Green "B" Pin (Positive RS-485 Voltage I/O) of 75176

Click Here to load the Visual Basic application that will display/monitor the temperature read by the remote card.