High Country Tek HAD Series - Manual (Page 4)

HAD Product Manual
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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 4/8
Do not adjust the unit to supply more current than is required to fully shift the valve; additional current may
exceed the coil's rating, will reduce the useful range of the control input and may damage the valves coil.
6. Adjust the control input to fully shift the B coil and check system response. If the coil has not fully shifted,
adjust the MAX pot as necessary.
7. The MIN, MAX, and CROSSOVER pots interact and the hydraulic system response may change as it warms
up. Warm up the system and repeat steps 1 through 6 until the system reacts as desired.
Ramp (Optional)
Depending on the model number, your unit may have one or more RAMP pots. Ramp time is the time it takes for an
output to reach its desired setting in relation to a given change in input. The following illustration explains the
adjustment procedure for a unit with RAMP adjustments in both directions for each coil. Only adjust what is supplied
on your specific model and needed for your own application. See the RAMP section in Figure, 4 for an explanation of
different ramp options.
1. Set the RAMP UP pot/s to the desired value by quickly switching the command for that coil from minimum to
maximum, while observing the speed of response. Note that the minimum control input is just above or below
the crossover point. Turning the ramp pot adjustment CW increases the ramp time.
2. Set the RAMP DOWN pot/s the same way, but going from maximum command to minimum command for
each coil.
Dither (Optional)
The DITHER AMP pot (if equipped) is set fully CCW (no dither) at the factory. Dither is used to keep the valve
moving back and forth a small amount at all times to avoid hysteresis and stiction. You can
visit our website for further
explanation of hysteresis and stiction.
If the valve shift is erratic or if the valve sticks, adjust the DITHER AMP pot for the desired amplitude.
Note that the dither may cause both coils to be energized at the midpoint of the control input. The higher the
dither amplitude, the larger the control input region is where both coils can be energized simultaneously.
Dither acts as if the control input were changing and it may crossover the point between the COIL A and B. If
necessary, the user may adjust the Min pots to add a larger Deadband to reduce any undesired system response.
System Wiring Best Practices
All sophisticated electronic systems require attention as to how various components are wired together to insure reliable
operation without interference to or from other components. What follows is a brief explanation of issues associated
with PWM Valve Drivers and some tips to help you avoid difficulties arising from noise generated by inductive
switching.
The industry technique most commonly used to control proportional hydraulic valves is called Pulse Width Modulation
(PWM). PWM varies the effective voltage across and inductor by applying the full supply voltage to the coil then
quickly switching it off. Regulating the ratio of on time verses off time of the pulse at a fast enough frequency, an
average voltage is seen across the coil and this can be controlled to position a hydraulic valve with a high degree of