Panel to ADEM(r) Interfacing
Overview
On various Caterpillar engines, the ADEM(r) system is used to control the engine operation, and the EMIT Brain (Annunciator) is used to monitor and protect the compressor (which falls under the CAT category “Driven Equipment”). In some cases, the ADEM is generically called an ECU (Engine Control Unit). Similar to other ECUs (E.g. older CAT EIS, or Waukesha ESM) the ADEM features a number of connections that are used by the panel to control engine operation- primarily start/stop and speed control.
The interfacing and operation between older “ADEM 3” and newer “ADEM 4” ECUs are similar, but vary in some ways. This document describes how the Brain and/or panel is wired to the ADEM in different cases, and how the control operates.
Start / Stop / Fault Control
The ADEM has signals connected for controlling start/stop of the engine, and return signal(s) for signifying an engine shutdown. These signals vary on different engines, but the Brain is set up generically enough that the main variance between panels is not in functionality, but how it is wired. In general, CAT will publish a document describing customer interfacing to the ECU, and the wiring can be adapted to fit the engine requirements.
Brain -> CAT Interface
The Brain is configured to be in a general ADEM-interfacing mode by going to “Brain Setup” -> “Outputs Setup” -> “System Output Scheme”, and selecting “CAT ADEM”. This tells the system that the logic should be used to drive an ADEM.
In this mode, the following pins are used for driving the ADEM:
- DIG OUT 2 (Pin 69): This pin will be ON (at battery voltage) when the engine is intended to be running, and OFF (floating) when the engine is intended to be stopped. This should be wired to a relay coil. On ADEM 3 systems, this can close a NO contact from DIGITAL RETURN to RUN/START. On ADEM 4 systems, there is sometimes an additional STOP input that is wired to the NC side of this relay, and is grounded during stop.
- DIG OUT X / A4 Driven Equip Ready: One digital output can be configured as the A4 Driven Equipment Ready pin by going to “Settings” -> “Brain / Brain Setup” -> “Output Setup” -> “Output to Function Assignment” and then selecting an unused digital output and changing the function to “ADEM 4 DRIVEN EQUIP READY”. This pin will be on (at battery power) when D.E.R. should be in RUN and off (floating) when D.E.R. should be stopped/faulted. This is intended to drive a relay coil, and the output of the relay is used the same as the normal Driven Equipment Ready relay mentioned above. The A4 D.E.R. logic differs by having the relay on during STANDBY mode and through startup. This allows the CAT panel alarm to be cleared in standby. Normal startup procedure in this case is to hit RESET on the panel, clear the CAT alarm, then press START on the panel. Note: This also could easily be used with A3 systems, but is not as necessary.
Note: During a normal shutdown, the Brain removes DRIVEN EQUIPMENT READY, which causes the CAT panel to fault. At this point, the CAT panel will not allow the fault to be cleared while the DRIVEN EQUIPMENT READY is still out of RUN position. This is why this is wired differently as listed. For A3 systems, this problem was not relevant because the CAT panel could be cleared by rotating the switch to briefly remove power, which is not an option on the newest CAT panels.
On some older panels, driven equipment ready was driven from Pin 10 of the Brain. This pin goes to ground when the Brain reaches the full RUN state (and the fuel valve should come on).
From the CAT factory, the DIGITAL EQUIPMENT READY is wired to always run with a jumper, which should be removed during panel installation. Some older ADEM 3 systems also have a NORMAL STOP input which should be permanently wired to DIGITAL RETURN.
CAT->Brain interface
The CAT panel has one return signal to tell the Brain that the engine is running. On Panel schematics, this is called “ADEM RUN SIGNAL”, and closes a relay to ground. The contact of the relay is wired to digital input 27, which is automatically filled in as a normal digital input called “ADEM RUN STATUS”.
The coil side of the relay is wired to two terminal blocks. On old ADEM systems, the run signal is ground during run, so the other coil side of the relay is wired to keyswitch power. On some ADEM systems, the run signal is power during run, so the other side of the coil is wired to ground. Both cases result in a relay that is powered during run. The relay should go from off to on when the unit starts, and the input on the Brain (DI-27) will go from faulted to unfaulted when the relay comes on.
E-Stop
The E-Stop on the EMIT panel has two contacts, one of which is wired to a digital input on the Brain, and the other is wired to the ADEM. This way, when the E-Stop is pressed both systems should get the signal.
The panel schematic wiring table shows how the E-Stop ADEM contact is wired on different engines. In general, the connection to the E-Stop on the CAT panel is broken to additionally flow through the EMIT Panel E-Stop. Most ADEM panels have a jumper installed for this purpose that can be removed to add the EMIT E-Stop.
Note: Some ADEM systems have two separate E-Stop loops running through the emergency stop switches’ contacts. One is maintained to ground for a digital E-Stop signal, and the other is maintained to power to supply fuel valve power. In this scenario, it is only the digital ground loop that is broken and routed through the EMIT panel.
Note 2: CG-137 has two e-stop loops in parallel that both have to be broken at the same time. For this engine the E-stop needs three contact blocks to add our E-stop to the CAT loop- 2 for the CAT loop and 1 for the Brain shutdown.
Speed Control
There are two speed control signal types to the ADEM: “Idle” signal, and speed target. Each are discussed below.
Idle Signal
Typically, the ADEM has one input that is used to idle the engine when grounded. This is usually called “IDLE/RATED SPEED” on the CAT engine schematic, though for newer ADEMs an input has to be configured to have this function. When closed to DIGITAL RETURN, the ADEM will run normal speed. When open, the ADEM will make the engine hold idle speed, also called “Engine Lo Idle”.
From the Panel, the idle signal can be controlled by the IDLE speed selector switch, an Idle Permissive relay (controlled by a digital out that holds idle until the engine is warmed up), or both. The Brain will also output the minimum speed on the analog out used for speed control, but usually this is not the same as low idle speed. For example, the CAT system might be configured where the speed at lowest analog input value (Min Hi idle) is 1100 rpm, when the low idle speed is 900.
There is some variance between engines as to whether ground = IDLE or ground = RUN. For this reason, the idle relay has both the normally open and normally closed contacts wired to terminal blocks, and only one of those two connections actually go to the ADEM, depending on model. Which terminal block to use is shown on the wiring table on the last page of the schematic.
Speed Target Signal
The Brain can output a target speed signal on one of the analog outs. This can be wired to the ADEM in various ways to control the speed of the engine.
During the Brain “Speed Output” setup, the user selects an output, what type of analog output it is, and what speeds it corresponds to.
Newer ADEM systems have both 4-20 mA (current) inputs and voltage input(s) that can be configured as the speed target input. Older systems tend to have only a voltage input for speed.
- Current Input: When the Brain outputs 4mA, the engine runs at the configured “Min Hi Idle” speed. When the Brain outputs 20mA, the engine runs at the configured “Max Hi Idle” speed. In between, the input target is scaled linearly.
- Voltage input: Typically on older systems, the voltage input expects 0.5v – 4.5v for the min to max speed. From the factory this comes from a potentiometer.
Panel Switches
Except on a few very old panels, the panels will have an IDLE/MANUAL/AUTO selector switch and a manual +/- switch. When in IDLE, the Brain will output the minimum speed, and the IDLE relay will be on. When in MANUAL, the Brain will change the output speed as the SPEED+ or SPEED- switches are held. When in AUTO, the Brain will output the configured auto speed- either a fixed speed, or based off of a sensor condition (e.g. suction pressure). If another manual speed knob exists on the ADEM in this case, it should be unwired and removed to avoid confusion from having two manual speed knobs.
- DI-23 to DI-26 NOT used for speed control switches: In this case, the Brain will always output the AUTO condition- either a fixed speed, or based off of a sensor condition (e.g. suction pressure)- on the analog output. The MANUAL selector location can be used to toggle a relay that selects the signal from the potentiometer to send to the ADEM in place of the Brain target. The IDLE selector location can be used to toggle the idle relay.
EDT (Data) Connection
Optionally, the EDT module can be added to the panel to pull data from the ADEM and bring it into the ETS system. Currently, this is only for reading (not writing) data, and has two main benefits:
- The CAT data is available over Modbus from the EIM with the compressor data
- EIM datalogs will include the CAT data for both long-term logs and shutdown logs
New ADEM systems have one primarily data link- the CAN data link. This is wired to the EDT “ECU CAN” port. This can be wired by either directly connecting to terminal blocks in the CAT panel, or by connecting to the triangular CAN connector in the CAT panel with an EMIT-supplied harness. The CAT wire colors are as follows, and will always be grouped together:
- CAN L: Green
- CAN H: Yellow
- CAN Cmn: Dark Gray
Older ADEM 3 systems have both the CAN data link and the CDL (Cat Data Link), with a variety of data on each. The CAN data link can still be connected as described above, and an additional connection added for the CDL pins. These are connected as follows:
- CDL+ (Pink in the CAT panel): To EDT “CDL” “A”
- CDL- (Purple in the CAT panel): To EDT “CDL” “B”
