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FrSky – Magnetic (Hall) RPM sensor for the glow fuel engine?

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I would like to made a RPM sensor for the glow fuel engine that works with FrSky Tandem X20S transmitter and telemetry system of the FrSky. I don't know why Frsky doesn't make an RPM sensor for glow fuel engines. They have only GAS Suite but it work only with gas engine…

I can't find it ready-made anywhere, so I have to do it yourself. Finally I found a promising wiring diagram here!

But I don't fully understand it, plus I should figure out how to implement it with the FrSky Smart Port RPM and Temperature Sensor.

Could someone advise in more detail how to implement that wiring when using the Melexis US5881 Hall-effect switch and the FrSky Smart Port RPM and Temperature Sensor? 

I made the attached picture. Could someone explain to which pin do I connect which pin? This is my biggest problem with this.

Melexis US5881 Hall-effect switch have three pins:
1 = VDD (supply voltage)
2 = GND (ground pin)
3 = Out (output, open drain)

FrSky Smart Port RPM and Temperature Sensor have these pins:
Smart Port S + –  (three pins)
A and B  (two pins)

Take a look at the drawing I edited to here, where I have clarified things. See question marks. I would like to find out those pins…


RPM Wiring by ED
Posted : 11/04/2023 6:36 pm
Barry Cole
Posts: 74
Illustrious Member Admin
IMG 1306

I understand that this will work.

Posted : 12/04/2023 8:35 am