The idle hold and speed target output work independently, either or both can be used with an ECU.
For idle hold, a condition will be specified where the engine will not be allowed out of idle until the condition is met. For example, a lubricant temperature might be required to be above certain temperature before the engine can go to full speed. Setting up the idle hold condition is shown in the next section. When the idle hold is active, a chosen digital output will be ON. This output is typically wired to a relay and then the output of the relay to an ECU input that keeps the engine at idle. For an ADEM, this input is called "IDLE / RATED SPEED". This output can also be wired to an Idle Permissive lamp. The idle hold can also be used if an EMIT Governor is present, and an annunciator sensor is desired as the controlling sensor.
For speed control target, an analog output will be used to specify the target speed. The ECU will interpret this signal as some speed the engine should be operating and will run accordingly. This target can be based upon a sensor condition, or can be fixed to one speed. Optionally, IDLE/AUTO/MANUAL and SPEED+/- switches can be wired to the annunciator to function similarly to the EMIT governor. In other scenarios, an AUTO/MANUAL switch can be used to physically disconnect the speed signal and connect it to a potentiometer on the ECU panel.
Idle Hold Setup
The idle hold setup is shown on the following page. (Note: On some older versions, this was on the first page of speed control setup, but the options are the same).
Speed Control Setup 1
To specify an idle hold condition, select “Yes” for using idle hold. If desired, select an output pin that will be ON during idle hold. Select the second button to specify the sensor and condition which will define the idle hold.
During idle hold, the annunciator will perform the following three actions:
- If an EMIT speed controller is present, it will send a message to the governor to remain in idle
- If specified, the annunciator will turn ON the digital output configured
- If using speed control output (remaining part of this page), the annunciator will send the idle speed setpoint on the analog out used
Speed Control Setup 1
The first page of speed control output setup is shown below. This page sets up the electrical settings of the output.
If using an analog output for speed setpoint, select "Yes" on this page to begin setup.
If using DI-23 to DI-26 for speed control switches, select "Yes" on that line, and enter an idle rpm for when the switch is at "Idle". This idle RPM will also be used when the idle hold condition is active, if used. If not using DI-23 to DI-26 for speed control switches, the idle speed is not available, because it will be set on the external ECU.
The next button can be selected to choose an output for the speed setpoint. All available outputs are shown, including expansion modules. This output will be wired to the ECU or Governor at the speed control input.
The 'output type' selection is for the output type of the analog output. The options are 4-20mA, 1-5V, 0-5V, and 0.5-4.5V. The selection should match what the ECU or Governor speed input is expecting. CAT panels generally expect 0.5V to 4.5V.
The last two settings are the low and high speed values when the ECU or Governor speed input is at its limits. These values are based on what the ECU or Governor expects, and the RPM values don’t necessarily have to ever be reached. On some ECUs these values match idle speed and overspeed.
Speed Control Setup 2
The second page for speed control setup configures the actual control settings for the speed.
Speed Control Output Setup 2
The control type can be either “Fixed Speed”, “Control to Sensor Value”, or "Pass Through". If fixed speed is used, the only other setting needed is the speed setpoint. In this case, the annunciator will simply output a fixed analog value to keep the speed at this point. If "Pass Through" is used (which is not common), the annunciator will pass an analog input to the analog output.
If controlling to a sensor value, more settings are available, which are outlined below.
- Choose Sensor: Select this button to choose the sensor the speed is controlling around. If this sensor is too low or high the speed will be adjusted. Most commonly this will be suction or final discharge pressure.
- Setpoint: This is the target value for the sensor chosen. For some types of sensors, such as discharge or manifold, this setpoint should be held fairly close. For some, such as suction, the speed will spend a lot of time near the limits and the setpoint is more of a cross-over point when the sensor goes from high/low or low/high.
- Deadband: The deadband defines a region around the setpoint where the speed will not change.
- Change Rate: The change rate defines the percentage of the operating range that the rpm will swing in one second. For example, if set to 50% then it will take two seconds to ramp from the low to the high range if required. Setting to a lower value will slow down the control. Suction control will usually be in the 1-5% range to cause slow changes, and discharge control will be higher, generally 10-20%.
- Positive or Negative Control: This setting controls the direction the speed will change to meet the target setpoint. For positive control, increasing the RPM will increase the sensor, such as manifold or discharge pressure. For negative control, increasing the RPM will decrease the sensor, such as suction pressure.
- Auto Operating Range: This defines the operating RPM range for the speed output. If the output reaches one of these limits and the sensor is still out of setpoint range, the RPM will be clamped to this value. These limits keep the engine from going too fast or slow when trying to meet the setpoint.
After reviewing the entered settings, select “Submit” to save.