ICON Pro Analogue Inputs and NMEA-2000 Network Data

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jimh
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ICON Pro Analogue Inputs and NMEA-2000 Network Data

Postby jimh » Fri May 15, 2020 9:16 am

In an article I wrote in the REFERENCE section regarding advanced rigging for the E-TEC engine, I mention that use of an analogue input on the ICON Pro Series RPM gauge for sensing the TRIM SENSOR will not result in that data being send to the NMEA-2000 network from the ICON Pro RPM gauge. This method is discussed in some further detail herein.

If the ICON Pro RPM gauge is configured to get TRIM position from its analogue input, the concern is then to know if the data developed from that input is going to be sent back onto the NMEA-2000 network as being the engine trim position, so that other NMEA-2000 display devices can then read the trim position and display the data. As best as I can recall, based on advice from informed sources, I do not believe the ICON Pro RPM gauge will do that. However, to verify this information, so I performed a bench test that would reveal the outcome. The test was as follows:

An ICON Pro RPM gauge had its analogue input at P1-7 (marked "Trim") wired to a variable resistance. The gauge was configured to read the trim data from the P1-7 input, the sender type was set to "EVINRUDE" and the sender calibration procedure was run.

The P1-7 lead was terminated to ground via an 82-Ohm resistor. This resistor was used in the calibration procedure as the "down" trim position (or "0% TRIM"). The 82-Ohn resistor was then shunted with a 47-Ohm resistor, creating an 29.8-Ohm resistor; this value was used for the "up" trim position (or "100% TRIM"). It was then possible to create intermediate readings of trim by shunting the 82-Ohm resistor with other values of resistance greater than 47-Ohms, producing intermediate readings of trim between 0 and 100%. For example, shunting with a 100-Ohm resistor created a 45-Ohm resistance, which produced a reading of TRIM = 74%.

(Of course, it would have been simpler to test with an actual trim sender, but I did not have one handy.)

Confident that I had properly set up the ICON Pro RPM gauge to read engine trim data via its analogue input, I then connected the ICON Pro RPM gauge to the bench's NMEA-2000 network. Also on the network was a Lowrance HDS-8 multifunction display.

On the HDS-8 multifunction display, a page was already available to show engine trim data, having been set up to read it from my E-TEC engine. As expected, the trim data from the ICON Pro RPM gauge did not appear. This was expected, for two reasons:

--the HDS was set up to get its engine data from the E-TEC engine on my boat, and that engine was not on the network;

--the HDS did find the ICON Pro RPM gauge on the network, but it saw NO DATA coming from the gauge.

In order for the trim data from the ICON Pro RPM gauge to be available to other devices on the NMEA-2000 network, the ICON Pro RPM gauge would have to send a PGN to the network normally sent by an engine, then include the trim data in that PGN. But the ICON Pro RPM gauge does not send any data at all to the network, or at least no data that the Lowrance MFD diagnostic utility can recognize.

On this basis, I conclude that when the ICON Pro RPM gauge analogue input is used to create engine trim position data, that data is only available on the ICON Pro RPM gauge itself, or on other downstream gauges.

To test if the trim data was available on other downstream gauges in the ICON Pro Series, I tried to configure the ICON Pro SPEEDOMETER gauge to shown the trim data. Unfortunately, the ICON Pro SPEEDOMETER gauge cannot display engine trim, no matter where the data comes from; it just does not have a setting for engine trim.

The ICON Pro SPEEDOMETER gauge does have a setting for FUEL TANK 1 LEVEL. As it happens, I have already configured the ICON Pro RPM gauge to measure fuel tank level via one of its analogue inputs (P1-6). It was then possible to test if the ICON Pro RPM gauge makes this data available to the ICON Pro SPEEDOMETER. The ICON Pro SPEEDOMETER was configured for one of its display pages to show FUEL TANK 1 LEVEL. And, indeed, the ICON Pro SPEEDOMETER was able to show the fuel tank level data, which was actually coming from the analogue input to the ICON Pro RPM gauge.

While this does not prove that in a similar manner the trim data will be available, it does suggest that. And, indeed, a report of success in seeing the trim data on a dedicated ICON Accessory TRIM gauge confirms that outcome.

There is a further consideration about using the ICON Pro RPM gauge analogue input to read trim sender resistance: assuming this configuration is used in an E-TEC engine with an EMM that supports reading the trim position from the sender, will the relatively low voltage (about 1.5-Volts) supplied by the ICON Pro RPM gauge analogue connection give enough electrical power to the circuit to permit the E-TEC EMM to also sense the voltage. This was tested on the bench as follows:

The voltage supplied to the trim sender from the ICON Pro RPM gauge was monitored using an accurate DVM, and the resistance of the trim sender was varied. The voltage at the trim sender--the portion of the circuit connected to the E-TEC EMM--was monitored to see if any change occurred. The results were as follows:

Voltage at the EMM-circuit end of trim sender resistor (i.e., not the ground side) varied as follows:

    TRIM VDC
    1% = 1.253
    56% = 0.904
    60% = 0.881
    74% = 0.782
    100% = 0.521
This suggests that a voltage variation of about 0.73-Volts is enough for the ICON Pro RPM gauge to sense the position. With the E-TEC EMM in normal trim sender electrical configuration, the voltage supplied would tend to be much higher. The source of voltage is the battery, or 12-Volts. The series resistance is nominally 47-Ohm. The sender resistance varies from about 10-Ohms to 88-Ohms. That suggests that the normal input voltage for the EMM trim circuit would vary between 2.1 to 7.8-Volts, a much wider range.

Since no E-TEC engine was available on the bench, this configuration could not be tested.