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PyPilot Cetec Benmar
#1
I have a vintage Cetec Benmar 21r Coursesetter with a direct drive motor on my Fast Passage 39. The control head appears to be coroded and not working. I am contemplating sending it back and having them go through it. The direct drive motor seems to be in good working shape.

Instead of sending back and getting wrapped around that axle, I am considering putting together a pypilot solution.

From what I am gathering, I will need:

1. Rpi4
2. TinyPilot Hat
3. Pypilot motor controller

The -> Plug hat into Rpi4, install tinypilot or pypilot?, plugin motor controller, configure, run wires to motor & calibrate.

What am I missing?

Has anyone married up pypilot motor controller with a Cetec Benmar direct drive motor? From my understanding, the direct drive motor is super simple (two wire) motor - but I need to verify.

I am looking for for any feedback or recommendations.

Thanks,
Lewis
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#2
I think you have the right idea for what hardware is required. tinypilot is a linux distribution as opposed to openplotter. It is targeting the pi zero w, but can run on pi 1-3 (not pi 4 yet) You can run pypilot on any distribution.

If powering the motor moves the rudder and flipping the wires moves the other way then it should work. See if you can measure how many amps it draws because the regular controller begins to heat up around 7 or 8 amps. It can supply more in bursts but for best efficiency to keep the controller cool the motor should draw less than this with the regular controller.
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#3
(2020-04-27, 06:35 PM)seandepagnier Wrote: I think you have the right idea for what hardware is required.   tinypilot is a linux distribution as opposed to openplotter.   It is targeting the pi zero w, but can run on pi 1-3 (not pi 4 yet)    You can run pypilot on any distribution.

If powering the motor moves the rudder and flipping the wires moves the other way then it should work.   See if you can measure how many amps it draws because the regular controller begins to heat up around 7 or 8 amps.   It can supply more in bursts but for best efficiency to keep the controller cool the motor should draw less than this with the regular controller.

Thanks for the response.

Are most people running the tinypilot distro on pi zero or installing pypilot on raspbian with a pi4?

What is the best method for for testing the draw of the motor? Is there an option to get a controller that can handle more amps? If so, what does that look like?
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#4
You can measure the current draw with an ammeter powering the motor,.

I have two options for controller right now. up to 7 amps and up to 20 amps. I am also working on new designs to lower price and improve the controller.
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#5
(2020-05-03, 04:42 AM)seandepagnier Wrote: You can measure the current draw with an ammeter powering the motor,.

I have two options for controller right now. up to 7 amps and up to 20 amps.  I am also working on new designs to lower price and improve the controller.

Did anybody ever get the Cetec Benmar drive to work with pypilot?

I also have a Autohelm wind vane and auxiliary rudder w/trim tab.  Ideally I would like to setup an old tiller-pilot with this rather than the Cetec/Benmar for downwind and it would use wayyyy less power.  I have an old authelm tillerpilot to work with.  Has this been done yet?
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#6
I'm in a similar situation to the OP. I have a Benmar Compu-Course 220 hooked up to a Benmar S-Power unit. The power unit seems to work but the boat will turn slowly to starboard when I engage the Compu-Course 220. I'm considering replacing it with a pypilot.

I'm not sure what kind of motor controller is required since the S Power unit seems to have a different input. Ships power is 12V, 20A and then the control is from the Compu-Course controller in a 0V to 8V range with a +4V reference; three wires: 0V (SIG GND), 4V REF, +8V. This appears to be fairly low current but I don't know how much.

Any idea if a controller for this exists? If not, I suppose I could build one from Pypilot motor controller plus voltage divider.
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#7
the pypilot motor controller uses digital communication between computer and controller. So you would have to modify the source code to make it read an analog signal, but not sure it's worthwhile compared to a complete pypilot setup.
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#8
Can the output voltage to the drive unit be adjusted? My drive unit expects between 0 and 8 volts with 4 volts being on course, 8 volts would be full helm to one direction, 0 volts full helm the other way. There is a dip switch in the drive unit to flip the port/starboard vs 0/8 volts input.
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#9
the pypilot motor controller outputs -12 to +12 volts (or whatever you supply it with) to reverse polarity to the motor to drive it in both directions.

the pypilot autopilot computer communicates with the controller with digital logic.

So it achieve 0-8 volts with 4 volts average you would need to make your own motor controller. This should be relatively easy if you have used arduino much, you can modify motor.ino. It already has a mode for rc motor controllers which outputs pwm pulses. You would want to extend this from 0-100% and then add an 8 volt regulator. The arduino would need to drive external transistors to modulate the 8 volts to emulate a DAC.

I recommend you simply replace all of the electronics instead. This way you need to attach the wires directly from the brushed dc motor to the pypilot motor controller and do not need to modify source code and add additional hardware, but it is up to you. Either way you will find support here.
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