Wesley BC-620-4CA - Manual (Page 20)

16 Curtis 1234/36/38 Manual,
OS
11
When a 3-wire potentiometer is used, the controller provides full fault
protection in accordance with EEC requirements. The pot is used in its voltage
divider mode, with the controller providing the voltage source and return. Pot
High provides a current limited 5V source to the pot, and Pot Low provides
the return path. This is the throttle shown in the basic wiring diagram (Figure 3)
for the drive throttle and for the brake throttle.
The ET-XXX electronic throttle is typically used only as a drive throttle.
The ET-XXX contains no built-in fault detection, and the controller will detect
only open wiper faults. It is the responsibility of the OEM to provide any ad-
ditional throttle fault detection necessary.
Throttle Type 3
For these 2-wire resistive potentiometers, shown in Figure 6, full throttle request
corresponds to 5 kΩ measured between the pot wiper pin and the Pot Low pin.
2 — INSTALLATION & WIRING: Throttle Wiring
Broken wire protection is provided by the controller sensing the current flow
from the wiper input (pin 16 or 17) through the potentiometer and into Pot
Low (pin 18). If the Pot Low input current falls below 0.65 mA, a throttle
fault is generated and the throttle request is zeroed. Note: Pot Low (pin 18)
must not be tied to ground (B-).
Throttle Type 4
Type 4 throttles operate in wigwag style. No signals to the controller’s forward
and reverse inputs are required; the direction is determined by the wiper input
value. Only 0–5V voltage sources and 3-wire potentiometers can be used as
Type 4 throttles. The controller interface for Type 4 throttles is the same as for
Type 2 throttles; see Figure 5. The neutral point will be with the wiper at 2.5
V, measured between pot wiper input (pin 16) and I/O ground return (pin 7).
The controller will provide increasing forward speed as the wiper input value is
increased, and increasing reverse speed as the wiper input value is decreased.
When a 3-wire pot is used, the controller provides full fault protection.
When a voltage throttle is used, the controller will detect open breaks in the
wiper input but cannot provide full throttle fault protection.
Fig. 6 Wiring for Type 3
throttles.