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NMEA-2000: Analog Convertor for Engine Data
|Author||Topic: NMEA-2000: Analog Convertor for Engine Data|
posted 08-08-2011 09:30 AM ET (US)
[Seeks] a system to convert analog engine signals to NMEA-2000. After a little searching, I found a company called Albatross Control Systems that looks pretty interesting. The interface module is called the Alba-Engine. I love the HDS-7 and would like to actually collect as much data as possible for my twin Johnson 70HP motors. Will be adding a Lowrance EP-60 Fuel Flow. I used them on a previous boat and are a great and CHEAP instrument. It would be great to have something that can basically splice into the wiring harness and display the engine temperature, water pressure, oil pressure, and RPM.
posted 08-08-2011 12:02 PM ET (US)
Try this. I am getting close to buying one myself.
posted 08-08-2011 01:51 PM ET (US)
Which product? The RS11 looks like it may be the ticket. I guess you have to program the thing for output. Sounds like it could be a challenge. But very cool non the less. Any one ever try it?
posted 08-08-2011 03:07 PM ET (US)
You should use SMALL BOAT ELECTRICAL for this topic. This thread will move there.
posted 08-08-2011 09:35 PM ET (US)
[Moved to SMALL BOAT ELECTRICAL.]
posted 08-08-2011 09:37 PM ET (US)
I think the device being suggested is the RS11:
The manufacturer's website says this device is in the preliminary stage of development.
posted 08-09-2011 11:35 AM ET (US)
Thanks for posting the link.
The RS11 is for sale and in stock (USD $230) on their website:
The device is fully developed. I think you are referring to an update to an older version of the RS11 that adds NMEA 2000 protocols like fuel tank level
Also cool for people like me that want engine monitoring capabilities.
posted 08-09-2011 12:28 PM ET (US)
The RS11 at a price of $230 is an excellent way to convey engine data to NMEA-2000 devices from older engines with analog sensors. I think you should buy one, configure it, and install it. Then give us a detailed report on how it works, complete with screen shots. You would be blazing a trail that many will follow.
posted 08-09-2011 11:21 PM ET (US)
Don't tempt me.I [will] give it a try and see what happens. Just ordered the RS11. I [am] spending more time in my Boston Whaler boat while it [is] on the trailer than in the water.
posted 08-10-2011 12:01 PM ET (US)
Good, I have been looking to get one for my bigger boat as I want to add few things, but not have to get new sensors on everything. However, it has been moved to a winter project, summer is quite short where I am. Do tell how it works.
posted 08-16-2011 04:19 PM ET (US)
Quick update: [The RS-11 analogue to NMEA-2000 convertor] came in the mail. [I] have not been able to set up the RS11 because it needs to be connected to the [NMES-2000 network] and my laptop at the same time. [I] will post when any progress is made.
posted 08-19-2011 10:32 AM ET (US)
I need some expertise. The RS11 uses an algorithm based on voltage. From what I understand, you record two sets of data points (voltage and value [water pressure, oil pressure, oil temp, etc]) which are then used to form a linear line using y=mx+b where (value)= m*voltage+b
From there, the RS11 will display any value based on the voltage (derived from linear equation)
What I am trying to do: Have my engines' temperature readings displayed WITHOUT having a temperature sending probe
Is it possible:
posted 08-19-2011 10:39 AM ET (US)
Also, which voltage reading is most beneficial to use:
At the battery
At the wiring harness
at the key switch (Accessory pole)
As of right now, the voltage is displayed on the HDS-7 but that is only for 1 of 2 motors/batteries. With the RS11, the voltage for port and starboard will be displayed on the HDS-7
posted 08-19-2011 11:12 AM ET (US)
To convert voltage to temperature reading on the gauge you will need a sensor that converts temperature to voltage.
posted 08-19-2011 11:52 AM ET (US)
So the circuit is open and there are 0 volts in the wire going from the wiring harness to buzzer?
posted 08-19-2011 11:54 AM ET (US)
Or is the overheat alarm wire hot but alarm is not activated until a certain voltage is reached?
posted 08-19-2011 12:38 PM ET (US)
I cannot make any reasonable inference about the circuit you have connected to because I don't have any knowledge of that circuit, and you have not provided me with any information about it, other than to say the circuit consists of "wires connecting to the engine overheat alarms."
Typically alarm circuits are just switches which either close or open depending upon the logic arrangement of the circuit. A switch that just closes or opens will not be able to create a voltage that varies in proportion to temperature.
A device which has a resistance that varies with temperature is called a thermistor. See
If a constant voltage is applied to a thermistor through a fixed resistance, the voltage across the thermistor will vary with the resistance of the thermistor. In this way you can create a voltage that varies with temperature.
posted 08-19-2011 03:02 PM ET (US)
Jim, sorry for not clarifying.
I am talking about the brown wire (based on OMC wire color code in Reference)that is in the wiring harness running from the motor to the console.
Maybe you are confused because I am not being clear.
1)If you want engine temperature displayed on an analog gauge, you need the sender that screws into the powerhead.
2)Voltage fluctuation moves the gauge up and down.
3)In order for the RS11 to send correct information, it must be programmed with NoLand's software. To do this, the RS11 must be plugged into a NMEA 2000 network, A display ( my HDS-7) AND connected to a Windows computer via a serial port
4) The Tachometer is easy to set up because the user enters the PPR (pulses per revolution) for their respective motor.
5) The other 4 inputs on the RS11 are called "Analog Inputs" labeled A1 A2 A3 and A4
6) These inputs need to:
7) The RS11 only needs 2 data points to be able to plot a linear line, for example water temperature:
a)Data point 1 (Stick a thermometer in the tell tale, record temperature say 80F, then go to the back of your water temp gauge and measure the volts from the S pole, say 2V
8) So, theoretically, it is possible to convert any analog signal to NMEA 2000 given the variables numerical voltage reading to any other system function.
9) I do not have the aftermarket temperature senders that screw into the back of the power head. My thinking is:
a) My OMC motors have over heat alarms that will buzz when the engine temperature reaches a certain level.
b) These alarms (in my console) are connected to the engine by a brown wire.
c) Is the brown wire "cold" until current is released by the over heat sensor OR is the brown wire "hot" at all times with fluctuating voltage that only closes the buzzer's circuitry at a certain voltage?
d)IF the wire is hot at all times (with fluctuating voltage), I can make the data points I need too have temperature displayed on the NMEA 2000 network WITHOUT having to purchase and install the wiring/aftermarket senders.
I hope this helps.
posted 08-19-2011 04:01 PM ET (US)
On an OMC engine that TAN wire could be the alarm common wire, or it could be a lead from an ENGINE TEMPERATURE SENSOR.
If the TAN wire is the alarm common, it is just a WIRED-OR arrangement so that any alarm sensor that closes that circuit to ground causes the alarm to sound. This cannot be used as a source of voltage [that is proportional to temperature].
If your engine has an ENGINE TEMPERATURE SENSOR you can use that circuit as an input to one of the analogue converters for your analog to digital convertor project, but you would have to supply current to the sensor. This is normally done by the TEMPERATURE GAUGE that wires to the sensor
If you don't have the engine TEMPERATURE SENSOR and a GAUGE, you could just install a sensor and connect it to the 12-volt distribution through a suitable resistance (to be determined). In this way you could get a voltage at the sensor that varies with engine temperature, and you could use this.
posted 08-20-2011 08:48 AM ET (US)
More on the alarm circuit TAN wire:
This conductor is typically wired to 12-Volts through the buzzer or alarm sounder. Any of the alarm circuit switches can pull this circuit to ground and sound the buzzer. If you were to measure the voltage on the TAN wire, you would probably find that it was around 12-Volts most of the time when an alarm was not sounding, and around 0-Volts when an alarm was sounding. There won't be any intermediate voltage, other than perhaps the 12-Volts drifting around a bit as the battery voltage changes due to battery charging or battery discharging.
I don't see any use for the alarm circuit as a means of deducing the engine temperature. Also, the alarm circuit is going to be actuated by other circuits not related to temperature, such as the NO OIL and LOW OIL warning circuits.
As I said before, if you want to convert an analog voltage into a digital reading of temperature, you will first have to employ a device to convert engine temperature into an analog voltage with some proportional relationship. This is done by a thermistor, or, as it is called in an outboard motor, a cylinder head temperature sensor.
posted 08-20-2011 09:44 AM ET (US)
Understood. I will purchase the senders soon and wire them.
Right now I am having issues regarding the engine PPR setting to display the correct tachometer. Will post with update soon
posted 08-20-2011 11:05 AM ET (US)
When you add the temperature sensor, you will also have to add a resistor in series with the 12-volts feeding it. In this way you will have two resistors in series, one fixed and one variable. We call the fixed resistor connector to the +12-Volts as R1, and the variable resistor (the temperature sensor) R2. The wiring will look like this
Voltage A = 12 x R2/R1+R2
You don't want too much current flowing in the circuit. R2 will have a pre-determined resistance. You can select R1 to adjust the current:
Current = 12/(R1+R2)
I happen to have a temperature sensor from my old OMC engine. At room temperature its resistance is 750-ohms. As its temperature rises, its resistance tends to drop. When immersed in some very warm water, the sensor resistance was down to 125-ohms.
If we used R1 = 100-ohms, then the voltage at A would have been
AT ROOM TEMPERATURE
AT VERY WARM WATER TEMPERTURE
posted 08-20-2011 02:38 PM ET (US)
Another option: use an LM35 integrated circuit to generate a voltage proportional to temperature. See
posted 08-22-2011 09:39 AM ET (US)
Thank you for the guidance.
This weekend I installed the RS11. As of right now, The Port and Starboard tachometer settings are getting a little annoying. I spoke with the lead tech at NoLand Engineering about the setting for PPR (pulses per revolution) which must be correct for the RS11 to output the correct tachometer numbers.
The installation manual says that it is normally half the total cylinders (for outboards) ie, if your motor is a V8, the value for PPR should be 004. My motors are 3cyl (making the PPR 1.5 per the manual) but the input can only be a whole number. The tech said to try a value of 1, 2, 3 or 4. Well none of these settings worked. A value of 001 gave me an idle RPM reading of 9999. I figured it would be a process of elimination and increased my value by one until the value of 015 gave me the correct number for port. but resulted in a high number for starboard. I figure something is wrong as both motors are identical and were purchased together. The value 18 ended up giving my the correct RPM at idle.
By this time, my twins had been running on the hose for about an hour and the sun had been down for 30 minutes. The sound is music (to me) but not to the neighbors and the HOA police came and yelled at me.
The next morning I tested the RPM settings while on the water and max RPM output was around 1400. After spending hours trying to get the right reading, I gave up. Last night I found a link to the Faria instruments install PDF which has all PPRs for most manufacturers and models. According to Faria, PPR is equal to half the poles connected to the alternator. My model happens to have 12 poles, making the correct PPR value as 006. I will try this setting later tonight.
Analog inputs 1-4 were next on the list. The Lowrance HDS-7 has one power cord and with this, the user can see overlay the source voltage for monitoring. With one (1) motor connected to one(1) RS11, you can connect four analog inputs. When two motors are connected to one (1) RS11, analog inputs A1 and A2 are dedicated to the Port side (instance 0) and A3-A4 are dedicated to the Starboard side (instance 1). Having dual batteries and zero analog volt gauges, I decided to use A1 for port battery voltage and A3 for Starboard battery voltage, using the Violet wire at the key switch as if it were connected to the "S" pole.
The setup was rather easy as voltage readings are constant so for data set 1 I used
Now I have "Port alternator voltage" and "Starboard alternator voltage."
My thinking is that A3 and A4 will be used for motor trim indication. I wanted to use it for engine temperature, but the motor trim indication is free. Since I have to purchase a sender for motor temperature, I want to hook it up to an analog gauge. In the even the Lowrance goes down, I want to atleast have engine temp on the dash.
posted 08-22-2011 10:29 AM ET (US)
Link to Faria Alternator pole information:
posted 08-22-2011 12:08 PM ET (US)
Most two-cycle outboard engines use permanent magnet alternators as I describe in my article on that topic:
There is no correlation whatsoever between the number of cylinders and the tachometer pulse frequency ratio to to engine speed. If someone told you there was, I would be suspicious of that advice.
It is very common for larger outboard engines to have a tachometer pulse setting of "6" which corresponds to 12-poles in the alternator.
posted 08-22-2011 12:37 PM ET (US)
That information is in their instructions:
Last sentence on page 4
The program software is very picky and sometimes updates have to be sent multiple times for the information to register.
Unfortunately, I did not realize the need for multiple updates until it was time to wire the Port/Starboard Volts. Initially, the proper information was entered and "sent" via the Serial Port but nothing happened. This is when I realized that if the value on the main display (HDS-7) did not change, the update was not successful (contrary to the message received on my laptop).
posted 08-22-2011 03:06 PM ET (US)
The instructions say regarding tachometer pulse calibration:
"The...simple case is with ignition-sensed [this is a very obscure phrase which has little meaning to me but perhaps means that the tachometer pulses are derived or "sensed" from the spark ignition signal--jimh] gasoline engines. The number of pulses per revolution (ppr) is usually one-half the number of cylinders."
Yes, like a four-cycle engine would have.
Two-cycle outboard engines have alternator-based tachometer pulse generation; the instructions say:
"[In] an alternator sensed [this is a bit clearer, the tachometer signal is "sensed" or derived from the alternator, not from the spark ignition--jimh] tach signal....the ppr depends on the number of poles in the alternator....The ppr value for this case is probably between '12' and '36', so pick a number, enter it into the RS11, and start testing...."
posted 08-23-2011 01:13 AM ET (US)
If you thought that part was confusing, try reading through the whole thing. They give conflicting pieces of information through the website manual, the physical manual, and the information given when the user clicks the "help" button in their software.
So my PPR value should be 006 (half the number of alternator poles) per the Faria instrument documentation?
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