Pypilot working on my Nicholson 44

[Kris]

Sean and Kris, I've been reading this thread with great interest. I have a Nicholson 38 ketch with a 12v Neco installation and have a Tinypilot with Sean's Pypilot motor controller ready to connect up to the existing Neco relays once I manage to get down to the boat for a prolonged period. I'm very interested in not using relays and benefiting from motor current sensing, reduced power etc, but I'm not experienced enough with this stuff to fully understand. Are you using the IBT-2 motor controller or the Pololu one? How is it connected to the Pypilot and to the Neco motor unit? Do you have any diagrams? Thanks in advance for any tips and pointers.

Hey Phil, I can only encourage you to install the Tinypilot, as it is a far superior solution to the Neco control unit. Current sensing is great, but I think controlling motor PWM is waaaay cooler, as it lets you drive to motor much more smoothly and efficiently. I am not sure if Sean·s motor controller lets you drive the Neco to the max as I do not remember the max current. My Neco takes 24 volts and peaks around 200-300watts, so that should be around 20 amps on your 12 volt system. I use the IBT2 that handles up to 44 amps. My Neco on 24 volt only takes around 10 amps max, so the IBT2 is ample strong and probably long lived.

The Neco has a motor that is a bit more complex. There is a diagram and a description that was done by Daniele Fua, a really cool guy who was of much help to the community. You can find the documents posted earlier here in this thread. If your Neco control unit does not work anymore, you can just convert to the Tinypilot. I am a liveaboard cruiser and I opted for a switch box to be able to use both controls for redundancy. If you go for the full conversion, you can relatively easily reuse the end switches and the rudder angle sensor integrated into the Neco drive unit.

With the relays the motor is controlled at 100% juice and then forced to a halt, as the relays short the coil of the motor, thus magnetically braking the movement of the motor. This is a reliable but power hungry solution. The H-Bridge in Sean·s driver can nicely start and stop the motor and does not brake the motor like using the relays does. On the other hand there is a voltage drop on the H-Bridge but given how little the motor controller heats up during use, I do not think there is much energy lost there.

At the moment I am just trying to implement the last update of Sean, and drive the clutch with a PWM signal instead of an always-on signal when engaged. My clutch coil takes around 30-40 watts. It stays engaged with around 33% PWM so there is around 20 last watts to be saved with this last update.

Thanks for the update Kris. I've had long email exchanges with Daniele Fua, a really helpful guy. I went with Sean's motor controller planning to use the Neco relays, but the lower current consumption and better control of direct motor control seems like a good idea. The Neco drive unit is fused at 25 amps and probably peaks at around 20, so I don't think the motor controller will handle that. I'm looking at a Pololu unit to handle the current. Any info on the best way to control it would be really helpful.

Yes: Hello Daniele Fua if your read this! And thanks for everything!

I am using an IBT2 controller. It costs around 10 euros on Amazon, and available mostly everywhere. It is quite easy to set up. 
LPWM and RPWM on the IBT2 controller go to D9 and D10 on the Arduino
L_EN and R_EN go to 5V or you can wire that to the H-bridge lower pins.
R_IS and L_IS can be wired together and they can then go through a resistor (1K maybe?) to analog 1 pin on the Arduino, the current sense pin (my measurements are not accurate, but it still lets me limit the current for safety or end-switch function)

Then for the Shunt coil, you can drive that either from the clutch, so it is on when the pilot is engaged. Or it is better to wire 2 diodes to the lower H-Bridge pins and then drive the shunt coil through a MOSFET or NPN transistor. You can also use a little NPN transistor circuit board ready made, available on Amazon or Ebay. In this case the shunt coil is energized every time the pilot asks for movement, but when the pilot is engaged but idle, there is no extra consumption on this coil. The polarity of the shunt coil is always the same regardless the rotation direction. The shunt coil creates a basic magnetic field for the motor to be able to start. Like in a permanent magnet motor, this field always has the same polarity (or direction).

I drive the clutch just from the clutch pin though the same NPN transistor.

And then for the serial coil on the Neco drive, you have to wire that in serial with the IBT2 motor controller. So from your battery you go to serial coil positive, from serial coil negative, you go to IBT2 battery positive, then from IBT2 battery negative you go to your battery negative on the boat.

Use leds with little resistors to figure out how the arduino controls everything. Please double check this description of mine with Daniele Fua's wiring diagram to guess the positive and negative.

I had a bit of trouble setting up the motor.ino code. I think in the end I went with PWM style 2 and 2NV2HN (or similar thing) active.

Oh and then I also found out that the rudder feedback pin expects a voltage that is lower than 1.2V if I remember correctly. So you have to do a voltage divider there or add some resistors. I think Sean had low resistance potentiometers on hand and wanted to reduce current even more, so he stuck resistors before the potentiometer to even further lower the consumption. Maybe I will use an automotive style rotary encoder for this purpose later for better accuracy and longevity.

I have no experience with the Pololu, sorry. Let me know if you need more help with anything.