Rudder Position Feedback

[cwford]

I have a question about rudder feedback and end stops for the pyPilot:

1. I am reading the voltage related to my rudder position with a separate Pi Zero and an analog-to-digital converter and using that voltage along with the related rudder position to create a software rudder angle indicator through a Python program. It works well.
2. The motor board on the pyPilot has three pins: one for +5VDC and two for the rudder position stops.
3. Normally, a Hall effect sensor and magnets connected to the rudder position sensor would close when the rudder is at the stop position port or starboard.
4. It occurs to me that I can also use my rudder angle indicator software to set my port and starboard rudder position stops, then drive the voltage at the two rudder position pins on the motor board through the Pi's GPIO.
5. It appears that the voltage at either pin is 5VDC when the Hall effect sensor and magnet meet at the desired end stop.
6. All the Hall effect sensor is doing is acting as a switch and closing a circuit.
7. My Question: Can someone tell me if all I need to do is drive one of the two rudder end stop pins on the pyPilot motor board to +5VDC in order to accomplish the same thing as having a Hall effect sensor and magnet meet, and thereby indicating an end stop?

Thank you,

Clyde Ford
"Mystic Voyager"
Willard 30 PH

[cwford]

Answered my own question:

1. RPi GPIO only goes hi to 3.3V not 5V
2. So simply going with a 3.3V relay to simulate a magnet next to Hall effect sensor
3. Driving the relay from 3.3V off a Pi GPIO pin

Thanks

[Hakan]

cwford..
Just be careful to find a relay small enough:

The operating voltage of the GPIO pins is 3.3v with a maximum current draw of 16mA (<50 mW for the coil).

[cwford]

Thanks so much, Hakan,


I'm actually thinking going to a transistor switch might be better. Here's the circuit I've designed:






Have I overlooked anything big?


If you celebrate the holidays, Happy Holidays!


Clyde
Aboard "Mystic Voyager"
30' Willard PH

[nohal]

What are you exactly trying to do? If pull the "Rudder endpoints" to ground than you would be probably creating a low-side switch (NPN transistor, no R2)

For example https://www.baldengineer.com/low-sid...or-switch.html has a nice explanation how to do this kind of stuff.

[cwford]

Thanks, Nohal,


That's exactly what I'm trying to do, pull the "Rudder endpoints" to ground. Very much appreciate the Bald Engineer reference. Everything I'd seen on the RPi used a PNP BJT but an NPN BJT seems much more like the way to go.




Clyde Ford
Aboard "Mystic Voyager"
30' Willard PH