Rudder position pypilot

[IslandInfedel]

Would this be the correct way to hook this rudder position sensor to my pypilot (which is going to opencpn)?








“Rudder Feedback

3 wires are used for optional rudder feedback.

Black - GND

Yellow - voltage angle, from GND to Vcc

Red - +5v
A potentiometer with 3 wires can be connected to these 3 wires. The potentiomter should range from 1k ohms to 100k ohms. Recommend 10k.

A potentiometer with only 2 wires can connect to yellow and black pins. A resistor should be added from red to yellow of 1k ohms.

A hall effect sensor with analog output can be connected to these 3 wires.”

https://pypilot.org/schematics/hbridge_datasheet.htm





This is the sensor

VDO Single Station Rudder Angle Sensor - 12/24V - 10-180 OHM [A2C1102950001

https://www.amazon.com/VDO-Single-St.../dp/B07J2VMJ1S

[Bill O]

This looks similar to my 2 wire set up on the prototype hydraulic controller Sean made for us and we hooked it up straight to the controller (no resistor).
Phoenix's Flight: Pypilot Open-Source Marine Autopilot for Hydraulic Steering

Last time, we saw Sean he had a new hydraulic controller and told us most rudder indicators were running 3 wires. He did say to use a 1k resistor if we were going to stick w/the 2 wire set up with the new controller (spare).

Would contact Sean on the pypilot forum to make sure your drawing is correct.

[Schnapsy]

Some informations here... :

https://www.schnaps.fr/articles.php?...=881&tconfig=4

If this could help...

[Bill O]

Thanks for the info Schnapsy
Very rusty on my French these days and thanks to the internet came away w/this from Schnapsy's link.

The Raymarine 5V (red wire) connects to the + terminal of the sensor, just as the ground (black wire) connects to the - terminal.
Then insert a 180 ohm resistor on the third Raymarine wire (green wire) which is also connected to the positive terminal of the sensor and the 5V supply.
And There you go !

It is for a Raymarine, but should work similarly for the pypilot w/different color connector wires.

As Sean suggested, would go w/the 1k resistor on the red instead of the 180 ohm resistor on the green as explained above.

[tanngrisnir]

Hi, I'll have a crack at this one.
Short answer, probably OK, It may not be optimal but it should work if you accept two limitations.

• Firstly, because your potentiometer is quite low resistance it will draw more current and run hotter, OK as it is rated for 12/24v but your resistor needs to be of an appropriate power rating to dissipate heat safely.
• Secondly, if you reduce the current draw to an acceptable level then the voltage range for your rudder angle is reduced. This may be acceptable as calibration will allow you to setup the high and low voltage corresponding to hard over rudder angles, but it will be less precise. In practice the ADC will be at least 8 bits so the angle measuring software probably smooths the value anyway.

Recommended configuration ( 10 KOhm potentiometer & 1 KOhm resistor ) you will have:
current from 4.5 microA - 4.5mA and voltage from 0.05-4.55V. Your ADC range 4.5V


Using your vdo ( 10-180 Ohm potentiometer & 1 KOhm resistor ) you will have:
current from 4.24mA-4.29mA but a voltage of only 0.762-0.05V, a range of only 0.7ish V.
You loose precision as you are only using a small proportion of the available input voltage range.

Other extreme, 10-180 Ohm potentiometer and 180 Ohm resistor:
current from 13.9mA-26.3mA and a voltage range of 2.5-0.26V
Much higher current draw but a healthier voltage range of 2V

It all comes down to deciding the minimum voltage range you need to determine rudder angle at the precision you require and choosing a resistor to give you that range.



Really you want your potentiometer to be much higher resistance, and your current limiting resistor keeps everything cool. I think if you want to use the VDO 1 KOhm will not give you an acceptable input range, perhaps 500 Ohm will be good enough.

I would definitely use larger than 180 Ohm, as that pulls 5x the current of the recommended configuration.

[Bronno Mulder]

I installed like described here: 500ohm between Red and Yellow. When I connect the pypilot I get the message portpin/starboardpin fault. Do you have any idea what could be the reason? I use the potentiometer 2 pins, 10-190 ohm. Thanks.

[Tehani]

Originally Posted by IslandInfedel

Would this be the correct way to hook this rudder position sensor to my pypilot (which is going to opencpn)?




“Rudder Feedback

3 wires are used for optional rudder feedback.

Black - GND

Yellow - voltage angle, from GND to Vcc

Red - +5v
A potentiometer with 3 wires can be connected to these 3 wires. The potentiomter should range from 1k ohms to 100k ohms. Recommend 10k.

A potentiometer with only 2 wires can connect to yellow and black pins. A resistor should be added from red to yellow of 1k ohms.

A hall effect sensor with analog output can be connected to these 3 wires.”

https://pypilot.org/schematics/hbridge_datasheet.htm

This is the sensor

VDO Single Station Rudder Angle Sensor - 12/24V - 10-180 OHM [A2C1102950001

https://www.amazon.com/VDO-Single-St.../dp/B07J2VMJ1S

Using a 2-pin adjustable resistor (this is not a potentiometer) doesn't sound like a good idea to me.

A potentiometer is a voltage divider, in such a way that the output voltage of the central connection corresponds linearly with the movement of the cursor:
Vo = Vi * Rc / Rt
Vo is output voltage.
Vi is input voltage.
Rc is the resistance from the cursor terminal to the 0v terminal.
Rt is the total resistance of the potentiometer from end to end, and is constant.
Thus, the output voltage covers the entire range from 0v to Vi, proportional to the angle of rotation of the cursor.

Let's see the case of a 2-terminal variable resistor:
Vo = Vi * Rv / (Rv + Rs)
Rv is the value of the variable resistor.
Rs is the value of the current limiting resistor.
Here we see that Rv is multiplying and also in the denominator added to Rs.
The result is not linear at all. It would only be approximately so if Rs were much larger than Rv, constituting what we call a constant current source, but then the maximum value of Vo would be very low in all cases.

To try to achieve a linear effect, while also limiting the maximum current, a cheap voltage regulator (7805, better 7803) could be used configured as a current source. (Attached image).
You just have to be careful with the Rs and Rv values ​​so that the whole range of Rv is useful.

[AKA-None]

Also remember that pots come in linear and logarithmic

[Tehani]

Originally Posted by AKA-None

Also remember that pots come in linear and logarithmic

It is evident that we are not going to put an audio pot here...

[AKA-None]

Originally Posted by Tehani

It is evident that we are not going to put an audio pot here...

Not everyone who will read this in the future may be aware of the distinction