E3B

E3B USER'S GUIDE
for use with the QT310 and QT320 family
The E3B eval board works with
Quantum’s QT31x and QT32x
QTouch ICs. Either type of device
can be inserted into the 8-pin DIP
socket.
QT31x - single-channel devices
use the QTouch-1 sense pad.
QT32x - two-channel devices use
both the QTouch-1 and QTouch-2
sense pads.
Both series of devices use the
header strip for feature cloning of
setups or uploading and download-
ing of information to and from a
host such as a PC. The board and these two series of devices are compatible with
QT3View windows software.
For detailed information about the ICs for this board please refer to the QT310
and QT320 datasheets (or datasheets for future devices in these series).
To begin using the board right away:
1. Insert 2 AAA alkaline batteries into the battery holders. Make sure the small
power switch is ‘off’.
2. Hold the board in one hand on the battery side of the board, keeping your fingers
away from the QTouch pad areas, and generally the entire lower right quadrant of
the board on either surface to prevent the IC from calibrating to your fingertips.
3. Turn on the power switch.
4. Touch either 'QTouch' pad area (QT320) or the QTouch-1 pad (QT310). The
corresponding LED will change state when touched, in a way that depends on
how the chip was setup using the cloning adaptor (see factory defaults).
If you are touching on or around the touch pads when you turn the switch on, it will
calibrate to ignore your fingers. If this happens, take your fingers away and cycle the
power switch again.
Because of Kirchoff's Current Law ("all currents must return to their origin", which also
applies to capacitive fields), the sensor is less sensitive if you are not holding it or if
the board's ground is not electrically coupled to something else. Thus, placing the
board on your desk will result in less sensitivity than if you hold it by the batteries or
connect the board's ground to something larger (or to earth ground).
Unstable operation will occur if you simply place the board on a desktop and try it,
unless rubber feet are used. The board will rock when touched leading to strong varia-
tions in background signals which will affect operation. Make sure the board is firm
and cannot rock, even by a slight amount.
An external piece of metal foil or a wire loop can be connected to the board and
attached to the rear of a surface of your choice (plastic, glass, wood, or stone will all
work fine) to create fully self-calibrating touch buttons (be sure to connect the board's
ground to something else for best results - or, power from an external power supply.
External power - please note! When using external power, limit the voltage to 5v
DC max, using the marked connection points. Be sure to remove the batteries first, or
you may cause an explosion or leakage hazard as the batteries will try to charge up
from the external supply!
Overview
Fast Start
Quantum Research Group Ltd. www.qprox.com techsupport@qprox.com
US: +1 (412) 391-7367 UK: +44 (0)23 8045 3934 QProx is a trademark of QRG Ltd. R1.0 03/02
LEDs
The LEDs are driven directly from the IC. Depending on whether the output(s) have
been configured as active-low or active high, the LEDs may be normally off or on
respectively.
R3 / R4 Series Resistors
These resistors are used to reduce the currents induced by ESD transients to safe
levels. They also roll off the edges of the QT pulses thus reducing RF harmonics to an
even lower level. The values are not critical but they should not be so large that they
interfere with sensing. Typical values range from 1K to 47K. When connecting the EXT
pins to a larger Cx load, it may be necessary to reduce one or both of these resistances.
If a lowering of the resistor increases sensitivity, the resistor value is too high.
C3 Balance Capacitor
The C3 balance capacitor exists to balance the sensitivity of the two sensing channels
to make them equal. Without this capacitor, Sensor 1 will appear more sensitive than
Sensor 2. The inequality can be used to advantage in some applications. The other
methods of making the channels appear equal include a) reducing C1 relative to C2,
and b) changing the trip-point threshold via the cloning process (or both in conjunction).
C3 is a 5pF capacitor which can also be implemented by intentionally adding some stray
Cx to channel 1.
C1 / C2 Capacitors
The C1 and C2 capacitors (referred to generically as Cs or ‘sample’ capacitors) are
socketed and can be replaced for experimentation. Generally, higher values of Cs will
increase sensitivity. This increase is proportional to Cs. Use decent grade capacitors
(avoid cheap ceramic capacitors in favor of plastic film types or at worst, X7R 5% types
for best results). A typical minimum total value of Cs is 2nF on this board.
'Ext' Sense Connector Pads
These pins (EXT1, EXT2) provide a way to connect the device to external sensing
electrodes. The load should have low capacitance (Cx) for best results. High Cx will
decrease apparent sensitivity. Shielded cable can be used over limited distances,
usually with an increase in C1 and/or C2 to compensate for the increased Cx loading.
'Out' Connections
The Out pins (Out1, Out2) are driven directly by the Out pins of the IC. Be careful not to
load these pins excessively, keeping source or sink current to under 2mA. The onboard
LED is also driven from this line (see schematic diagram). Depending on the cloned
Setups of IC, this output may be active high or active low.
It is not advised to connect an external pullup resistor to a voltage source other than
the same source powering the board. An external voltage source can back-feed the
board with current and attempt to charge the batteries via the internal clamp diodes in
the device, and in general is not good practice.
Power Connections
The provided connection points (+PWR, GND) can be used to power the board. The
voltage should be between +2.5 and +5 volts DC, regulated. Power should be free from
switching noise and short-term fluctuations for best performance. Almost any linear
regulator will work. Be sure not to share this power with other circuits that may inject
noise or supply fluctuations into the board, as erroneous operation will result (example:
relays, digital logic, etc). If external power is used, be sure to remove the batteries.
Batteries
Use 2x AAA alkaline batteries for best performance. External power may be used if the
batteries are removed. Power consumption depends on the operating mode chosen.
Board
Details
Page 2

E3B

Mfr. #:
Manufacturer:
Description:
BOARD EVAL FOR QT310 & QT320
Lifecycle:
New from this manufacturer.
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