ESP8266 Fuel Sender Help

[vijaysub]

Currently have a SignalK/OpenCPN setup that I would like to connect my fuel senders to. The gauge is a Faria fuel gauge (12v) and the sender is a KUS SSL style fuel gauge with two wire (signal and ground). The big issue is I would like to also keep my old analog gauges active. From what I can tell the 12V from the gauge gets sent to the sender at 125mW and the analog gauge reads the resistance back. I have a resistance circuit built for a ESP8266 but I was wondering how I should connect it up to the existing analog circuit. I take it I have to somehow bring the voltage down from 12V to 3.3 on the signal line? How does that effect the resistance that is going to go to the analog unit?
Link to Sender https://kus-usa.com/wp-content/uploa...US_SSS-SSL.pdf

Thanks
Vijay

[GordMay]

Greetings and welcome aboard the CF, Vijay.

Ask KUS?
1-(954) 463-1075
https://kus-usa.com/contact-us/

[conachair]

If the gauge works on voltage drop then measuring the voltage with an esp8266 isn't too hard, though the built in ADV isn't that great, better off with something like an ADS1115 voltage sensor. A tidy way to go would be design a board with header sockets for the esp and a surface mount ADS1115 , JLCPCB do this quite cheap then you could add the resister network surface mount as well and have channels free to measure battery voltage as well. I got some with 2 voltage sensors and various other bits - code is very much work in progress but voltage, current and barometer work - available here if it's any use, in micropython >
https://github.com/boatybits/boatymonpy
Came out at £40 for 5 boards.

[vijaysub]

Thanks for the info.I actually have some of those laying around from a reef-pi fishtanks project I did a couple of months ago. Will I be able to run this in parallel with the original gauge? Thanks for the GitHub link that is amazing!

[conachair]

Also, there was some code in openplotter to change the values into signalk in a previous version of openplotter, maybe a search on the openplotter forums might find something -
OpenMarine

[mrm]

If I remember correctly, ESP8266 ADC input range is 0-1V.
What you want to measure is voltage going to analog gauge. I would follow these steps:
- measure voltage with the multimeter when tank is full;
- to be on the safe side, measure the same voltage with analog gauge disconnected, see if it is higher and what the difference is;
- while doing that you might measure resistance of the disconnected gauge, to know what load is seen by the sender in original setup;
- now simply connect a voltage divider between sender signal and ground, and use the output voltage as input to ESP (possibly with some voltage clamping diodes thrown in).


I would use a precision, 10 kOhm multi turn variable resistor (potentiometer) as a voltage divider. They are sealed, so perfect for the expected usage environment. Simply adjust with full tank, to get around 0.9V output. If input impedance of ESP will alter the reading once connected, simply readjust slightly.

[vijaysub]

Thanks everyone for the information. I'll build the circuit based on recommendations and further review of the the data sheets and let you know how it goes.

Vijay

[conachair]

Originally Posted by mrm

If I remember correctly, ESP8266 ADC input range is 0-1V.
What you want to measure is voltage going to analog gauge. I would follow these steps:
- measure voltage with the multimeter when tank is full;
- to be on the safe side, measure the same voltage with analog gauge disconnected, see if it is higher and what the difference is;
- while doing that you might measure resistance of the disconnected gauge, to know what load is seen by the sender in original setup;
- now simply connect a voltage divider between sender signal and ground, and use the output voltage as input to ESP (possibly with some voltage clamping diodes thrown in).


I would use a precision, 10 kOhm multi turn variable resistor (potentiometer) as a voltage divider. They are sealed, so perfect for the expected usage environment. Simply adjust with full tank, to get around 0.9V output. If input impedance of ESP will alter the reading once connected, simply readjust slightly.

Though probably just as easy to fit an ADS1115 with a couple of resisters to drop the voltage, esp8266 ADC isn't great. The ADS can work in differential mode so no need to worry about any earth loop and have a couple of spare differential inputs to monitor battery voltage at the same time. Any calibration can be done in software in the ESP. Signalk/openplotter makes it easy to save to a database which is just great for monitoring.

[vijaysub]

Conachair,

Thanks for the link to your PCB and Micropython. I was able to write a quick sensor for the ADS1115 to get the resistance and voltages. I wasn't sure how to send it to signalK but I am using your example to learn how!

I am not a coder so muddling thru this at my own pace

Vijay

[Lake-Effect]

The A/D on an ESP8266 isn't terrible. I've been using it for battery voltage. It should be sufficient for fuel level, assuming enough swing between empty and full voltages. Especially if the OP's gauge is that KUS reed-switch type (limited number of steps!)

From datasheets, I believe that many A/D inputs want to be fed by a source of less than 10k resistance, so that has to be considered when designing the voltage divider. (mrm's divider circuit satisfies this requirement)

[conachair]

Originally Posted by vijaysub

Conachair,

Thanks for the link to your PCB and Micropython. I was able to write a quick sensor for the ADS1115 to get the resistance and voltages. I wasn't sure how to send it to signalK but I am using your example to learn how!

I am not a coder so muddling thru this at my own pace

Vijay

Ask away! I'm not a programmer either, use the CNP language a lot - cut and paste! Though python I'm getting much fonder of as a few days later you might actually understand what you wrote