Microchip Technology Humidity Sensor PICtail User Manual page 10

Humidity Sensor PICtail™ Demo Board User's Guide
The +5V single supply voltage from the PICkit™ 1 Flash Starter Kit board is bypassed
with two bulk 1 μF capacitors near the header, and two local 0.1 μF capacitors (one for
each Integrated Circuit (IC)).
A 6-pin header for ICSP™ (In-Circuit Serial Programming™) is available as an alternate
interface for programming the on-board PIC16F690. This allows the user to modify the
program that comes with the Humidity Sensor PICtail™ Demo Board (with the MPLAB
ICD 2 or PICkit™ 2 microcontroller programmer).
FIGURE 1-1:
The test points make it easier to test key points in the circuit using common lab
equipment. The test points are:
• GND – Is connected to ground plane, and is for any lab equipment
• +5V – Positive supply voltage (at board edge); it provides a means to power this
board with a laboratory power supply (when not connected to the PICkit™ 1 Flash
Starter Kit)
• V
INT
• V
CM
• V
SEN
measurements)
More details on the circuit and on its design can be found in Appendix A. "Schematic
and Layouts" and AN1016, "Detecting Small Capacitive Sensors Using the MCP6291
and PIC16F690 Devices" (DS01016).
DS51594A-page 6
PICtail™ Demo Board
Ambient
Humidity
+5V
GND
Test Points Vsen
Vcm
Vint
Humidity Sensor PICtail™ Demo Board Block Diagram.
– Integrator's input (a square wave during measurements)
– Op amp's common mode voltage (at its inverting input)
– Integrator's output of the integrator (a triangle wave during
Humidity Sensor
Humidity
Sensor
+5V
Op Amp
GND
MCP6291
10
N.C.
2
Microcontroller
6
PIC16F690
to
PICkit™ 1 Flash
Starter Kit
ICSP™
© 2005 Microchip Technology Inc.
®