User manual

MCP355X SENSOR APPLICATION

DEVELOPER’S BOARD USER’S GUIDE

Chapter 2. Hardware Description

2.1 OVERVIEW

The MCP355X Sensor Application Developer’s Board’s purpose is to ease develop-

ment of small signal sensor MCP355X applications such as weigh scales. There are

two circuits, or channels, to allow for comparison of different approaches to signal

conditioning circuits. The first channel is a low-cost, low-power signal conditioning

circuit that uses Microchip’s MCP6XX amplifiers. This circuit is intended to be a

reference design for low power, low cost MCP355X applications requiring intermediate

ranges of signal gain.

The second channel uses a precision amplifier with high gain. It is intended to be a

reference design for MCP355X circuits that can require higher resolution.

The board has jumper connections and screw terminals to connect external sensors

such as load cells or RTD temperature sensors. The board easily accomodates both

4-wire and 6-wire load cells sensor connections.

The system includes two PICmicro MCUs for firmware development and data analysis

through either an LCD display or graphically on a PC using a USB connection. A

PIC16F877 communicates with the two MCP355X channels, push-buttons and LCD

display.

For data analysis on the PC the USB PIC18F4550 is used. This device collects the

post processed PIC16F877 data and passes it via USB to the PC for display on

DataView software.

FIGURE 2-1: MCP355X Sensor Application Developer’s Board Functional Block Diagram and

Results.

Push Button Control Switches

PIC18F4550

PIC16F877

SPI

LCD Display

GAIN

CHANNEL 1

USB to PC running DataView

MCP3551 ΔΣ

ADC

GAIN

CHANNEL 2

Sensor Input Connections

MCP3551 ΔΣ

ADC