Chapter 1. Product Overview; Introduction; Kit Contents; Humidity Sensor Pictail™ Demo Board - Microchip Technology Humidity Sensor PICtail User Manual

Humidity sensor pictail demo board

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Table Of Contents

Table of Contents

1.1

INTRODUCTION

The Printed Circuit Board (PCB) discussed in this user's guide is described as follows:

• Order Number:

• Assembly Number:

• Board Name:

This board supports the capacitive humidity sensor application note AN1016. It

measures the capacitance of a relative humidity sensor (or capacitor) plugged into the

board. The on-board microcontroller sends the measured and calculated data to a PC

(Personal Computer) for display.

Items discussed in this chapter include:

• Kit Contents

• Humidity Sensor PICtail™ Demo Board

• Associated Tools

• Initial Set-up

1.2

KIT CONTENTS

• Humidity Sensor PICtail™ Demo Board – This is an assembled and tested

Printed Circuit Board (PCB).

• CD-ROM – Provided separately in the shipping box; it contains the files and

literature mentioned in this user's guide.

• Humidity Sensor (HS1101LF) – Provided separately in the shipping box.

• Bag of Capacitors – Provided separately in the shipping box. These capacitors

are provided for the user's convenience; they make it easy to try out this board's

functionality, and to verify its accuracy.

1.3

HUMIDITY SENSOR PICTAIL™ DEMO BOARD

The circuit operation is detailed in AN1016, "Detecting Small Capacitive Sensors Using

the MCP6291 and PIC16F690 Devices" (DS01016)

The Humidity Sensor PICtail™ Demo Board contains the circuitry represented in

Figure 1-1. The ambient relative humidity changes the capacitance of the humidity

sensor (HS1101LF from Humirel). This sensor is connected to a MCP6291 op amp and

a resistor to form an inverting (Miller) integrator. The PIC16F690 microcontroller sends

a square wave to the input of the integrator, which the integrator converts to a triangle

wave at its output. The firmware controls the magnitude of the triangle wave and

measures the integration time. The microcontroller measures the time it takes for the

triangle wave to rise and fall. These times are converted to a capacitance value.

A 14-pin header is provided for connecting to the PICkit™ 1 Flash Starter Kit, which

acts like a docking station. It includes a two-wire serial bus that transfers the data, and

two more wires for board power (+5V and GND inputs). This interface also supports

programming of the on-board PIC16F690.

HUMIDITY SENSOR PICTAIL™

DEMO BOARD USER'S GUIDE