604-00038 Parallax Inc, 604-00038 Datasheet - Page 5

• Manufacturer Part Number: 604-00038
• Description: IC SENSOR TOUCH/PROXMTY 1CH 8DIP
• Manufacturer: Parallax Inc
• Series: QProx™r
• Type: Capacitiver

Specifications of 604-00038

• Touch Panel Interface: 1, 2-Wire
• Number Of Inputs/keys: 1 Key
• Resolution (bits): 14 b
• Data Interface: Serial
• Voltage Reference: Internal
• Voltage - Supply: 2.5 V ~ 5.5 V
• Current - Supply: 1.5mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Output Type: Logic
• Input Type: Logic
• Product: Microcontroller Accessories
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Interface: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant

operation. To prevent this, the sensor includes a timer which
monitors detections. If a detection exceeds the timer setting,
the timer causes the sensor to perform a full recalibration
(when not set to infinite). This is known as the Max
On-Duration feature.
After the Max On-Duration interval, the sensor will once again
function normally, even if partially or fully obstructed, to the
best of its ability given electrode conditions. There are two
finite timeout durations available via strap option: 10 and 60
seconds (Table 2-1).
2.1.4 D
It is desirable to suppress detections generated by electrical
noise or from quick brushes with an object. To accomplish
this, the QT113 incorporates a detect integration counter that
increments with each detection until a limit is reached, after
which the output is activated. If no detection is sensed prior
to the final count, the counter is reset immediately to zero. In
the QT113, the required count is 3.
The Detection Integrator can also be viewed as a 'consensus'
filter, that requires three detections in three successive bursts
to create an output.
2.1.5 F
The QT113 has no recalibration pin; a forced recalibration is
accomplished only when the device is powered up. However,
supply drain is low so it is a simple matter to treat the entire
IC as a controllable load; simply driving the QT113's Vdd pin
directly from another logic gate or a microcontroller port
(Figure 2-2) will serve as both power and 'forced recal'. The
source resistance of most CMOS gates and microcontrollers
are low enough to provide direct power without problem. Note
that most 8051-based micros have only a weak pullup drive
capability and will require CMOS buffering. 74HC or 74AC
series gates can directly power the QT113, as can most other
microcontrollers.
Option strap configurations are read by the QT113 only on
powerup. Configurations can only be changed by powering
the QT113 down and back up again; again, a microcontroller
can directly alter most of the configurations and cycle power
to put them in effect.
2.1.6 R
The QT113's response time is highly dependent on burst
length, which in turn is dependent on Cs and Cx (see Figures
4-1, 4-2). With increasing Cs, response time slows, while
m icro controller
Figure 2-2 Powering From a CMOS Port Pin
C MO S
ORCED
ETECTION
ESPONSE
S
ENSOR
T
I
NTEGRATOR
IME
P O RT X .m
P O RT X .n
R
ECALIBRATION
O U T
Q T11 0
V d d
V s s
0 . 0 1 µ F
- 5 -
increasing levels of Cs reduce response time. Figure 4-3
shows the typical effects of Cs and Cx on response time.
2.2 OUTPUT FEATURES
The QT113 is designed for maximum flexibility and can
accommodate most popular sensing requirements. These
are selectable using strap options on pins OPT1 and OPT2.
All options are shown in Table 2-1.
2.2.1 DC M
The output of the QT113 can respond in a DC mode, where
the output is active-low upon detection. The output will
remain active-low for the duration of the detection, or until the
Max On-Duration expires (if not infinite), whichever occurs
first. If a max on-duration timeout occurs first, the sensor
performs a full recalibration and the output becomes inactive
until the next detection.
In this mode, three Max On-Duration timeouts are available:
10 seconds, 60 seconds, and infinite.
Infinite timeout is useful in applications where a prolonged
detection can occur and where the output must reflect the
detection no matter how long. In infinite timeout mode, the
designer should take care to be sure that drift in Cs, Cx, and
Vdd do not cause the device to ‘stick on’ inadvertently even
when the target object is removed from the sense field.
2.2.2 T
This makes the sensor respond in an on/off mode like a flip
flop. It is most useful for controlling power loads, for example
in kitchen appliances, power tools, light switches, etc.
Max On-Duration in Toggle mode is fixed at 10 seconds.
When a timeout occurs, the sensor recalibrates but leaves
the output state unchanged.
2.2.3 H
The QT113 output has a full-time HeartBeat™ ‘health’
indicator superimposed on it. This operates by taking 'Out'
into a 3-state mode for 300µs once after every QT burst. This
output state can be used to determine that the sensor is
operating properly, or, it can be ignored using one of several
simple methods.
The HeartBeat indicator can be sampled by using a pulldown
resistor on Out, and feeding the resulting negative-going
pulse into a counter, flip flop, one-shot, or other circuit. Since
Out is normally high, a pulldown resistor will create negative
HeartBeat pulses (Figure 2-3) when the sensor is not
detecting an object; when detecting an object, the output will
remain low for the duration of the detection, and no
HeartBeat pulse will be evident.
If the sensor is wired to a microcontroller as shown in Figure
2-4, the microcontroller can reconfigure the load resistor to
either ground or Vcc depending on the output state of the
QT113, so that the pulses are evident in either state.
Table 2-1 Output Mode Strap Options
DC Out
DC Out
DC Out
Toggle
EART
OGGLE
ODE
B
EAT
M
O
ODE
™ O
Pin 3 to:
UTPUT
Gnd
Gnd
Vdd
Vdd
Tie
O
UTPUT
UTPUT
Pin 4 to:
Gnd
Gnd
Vdd
Vdd
Tie
Duration
Max On-
infinite
10s
60s
10s