Square Wave 745NC Non-Contact Dispense Valve
5
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Block Diagram of Circuit Operation
Input Signal
Hold Voltage 5 VDC
Spike Voltage 5 VDC
Spike and Hold
Driver Circuit
a
b
c
d
Operation of a Spike and Hold Driver Circuit
a. The input signal source controls the valve actuation timing. The on-time, duty cycle, and
operating frequency of the valve are determined from the input signal. When the input signal is
low (0 VDC) the circuit is not energized. When the input signal goes high (5–24 VDC) the circuit
will energize the spike and hold driver circuit.
b. The spike and hold driver circuit controls which voltage is supplied to the valve. When the spike
and hold driver circuit receives a high input signal, the spike and hold driver circuit will apply the
spike voltage to actuate the valve. The spike and hold driver circuit will apply the spike voltage
from 1 to 30 ms before transitioning to the hold voltage.
CAUTION
Not using a spike and hold driver circuit as recommended may cause permanent damage to the
actuation solenoid.
c. The hold voltage should be set to 5 VDC to provide a safe voltage profile to prevent permanent
damage to the actuation solenoid.
d. The spike voltage is set to 24 VDC for a minimum of 1 ms and no longer than 30 ms to actuate
the valve to its open state.
CAUTION
Failure to reduce the voltage will result in permanent damage to the actuation solenoid if the valve is left
on longer than 30 ms.
To avoid damaging the actuation solenoid, do not cycle the valve at continuous high frequencies for
periods greater than 30 minutes. The actuation solenoid requires periodic dwell time to protect coil
integrity and performance.
Important note: We recommend use of a Zener bi-directional diode to ensure 24 VDC spike
voltage dissipates quickly to maximize actuation solenoid performance.
(Step 5 starts on page 6)
