Schlage PIB300 User Manual page 46

HandKey II Manual
An open collector transistor driver drives each one of these outputs. Open collector refers
to a transistor configuration capable of sinking current (by "pulling down" one side of a
load to ground) but not able to source current – e.g. the transistor output is incapable
of supplying current to drive up the output voltage and must rely on an external voltage
source to accomplish this.
HandReader outputs, when measured to ground, generally show around 4.5 volts when
they are inactive and no load is attached. This voltage is developed by a combination
diode and series resistor pull up to the internal +5 volt supply of the HandReader. These
outputs are pulled up internally to insure that they remain in a known condition if used to
output Wiegand or magnetic stripe data to some external device.
If one of the outputs is shorted to ground, there will be approximately 5 mA of current
flowing through the short, but no damage will occur. Because of the open collector
structure of the outputs, each output is free to float to whatever external voltage is applied
(when inactive). For example, if one side of a relay coil is connected to an external +12
volt power source and the other side of the relay coil is measured with respect to the
ground of the external power source, the measurement will be +12 volts.
If the ground of the external power source (+12 volt return) is tied to the ground of the
HandReader, and the free relay coil wire connected to the LOCK output, the LOCK
output pin will read +12 volts also (when inactive). This is because the LOCK output is not
active and free to "float" to whatever external voltage is applied. When a hand is verified,
the LOCK output becomes active and essentially looks like a short to the HandReader
ground. This "short" causes the full +12 volts of the external power source to be placed
across the relay coil, energizing the relay. The ground of the external +12 volt source must
be tied to the HandReader ground to make a complete circuit path.
All HandReader outputs are rated at +24 volts DC maximum with a maximum current
draw of 100 mA. This means that it is acceptable to use up to a +24 volt DC external
power supply to energize external devices. Whatever external relay is used should be
chosen to match the external power supply voltage. For example, if the external relay coil
is rated at 15 volts, a 15 volt external power supply should be used. In no case should the
external voltage be higher than +24 VDC.
Each HandReader has a protection mechanism built in to protect against voltage
transients (spikes) coming back into the HandReader from an external relay coil.
Transients from an "opening" or de-energizing relay coil can reach several hundred volts.
This protection is on all HandReader outputs and will limit reverse spikes to approximately
28 volts to protect the open collector transistor driver. HandReader outputs are NOT
designed to switch AC voltages. DC voltages MUST be used and the correct polarities
MUST be maintained.
!
NOTE
Relays or devices connected to the lock and auxiliary outputs must not exceed 0.1 A
current draw.
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