HAD Product Manual
________________________________________________________________________________
High Country Tek, Inc.
208 Gold Flat Court
Nevada City, CA, 95959.
Tel: (1) 530 265-3236
www.hctcontrols.com 021-00141 Rev B2.1
5/8
resolution. PWM control of inductive devices causes voltage spikes on the power supply or battery positive wires.
These voltage spikes are a product of Flyback Current which is result of the decaying magnetic field of an inductor
(valve coil) when voltage is removed during the PWM switching. These spikes of voltage can generate electromagnetic
noise that may affect the operation of other components or sensors within the system.
The best solution to avoid problems stemming from these current spikes is to first dedicate an isolated, regulated power
supply for powering sensitive sensors (Not all sensor manufacturers filter their inputs or outputs). Secondly, it is
recommended that all power, input and output cables used on the PWM module and its valve control wires be twisted
pair and/or shielded and grounded at one end. Routing of the cables to and from the valves should be in separate cable
bundles and routed separately from cables that go to delicate instruments. Greater physical separation between the
positive battery wires and the wires to and from sensitive sensors helps minimize the noise coupling. If it is necessary
to cross cables that connect to sensitive instruments, cross the cables at a 90° angle in order to reduce noise coupling.
Power cables for PWM modules should come directly from the battery or main system power supply and run separately
from those going to other equipment. Finally, if necessary we recommend installing a commonly available engine noise
filter on the battery line they are available at most auto parts stores.
Trouble shooting
If the set up procedure does not achieve the desired results, double check the wiring, perform the following tests and
record the test results.
Tools required:
A battery operated multi-meter and a small screwdriver are required.
Check the power input:
The card will not function correctly unless the +POWER to PWR COM voltage is at least 11 V. If this voltage is more
than 30 V the card may be damaged.
Check the control input you are using:
Pot input: Measure the wiper voltage between the VOLT and SIG COM terminals. With a 10 K ohm pot, the wiper
will go from 0 to 9 V. The difference in voltage should be more than 5 V from minimum to maximum. The voltage
must not be less than 0 V or more than 10 V.
Current loop input: Measure the current into the CUR terminal. The difference in current should be at least 10 mA
from minimum to maximum. The current must not be negative or more than 20 mA. If a current meter is not available,
measure the voltage from the CUR terminal to the SIG COM terminal and divide by 150 for an approximate reading.
Voltage input: The difference in voltage between the VOLT and SIG COM terminals should be greater than 5 V from
minimum to maximum. The voltage must not be less than -5 V or more than +10 V.
NOTE: Only one type control input at a time may be connected.
Verify the coil is not shorted:
If the +COIL to -COIL is shorted, the valve driver will shut down its output until the short is removed. Disconnect the
wires going to the +COIL and -COIL terminals and measure the resistance between the wires. Verify it is correct for
the coil being driven.
(4 pages)
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