Autopilot from a wiper motor?

[Sir_Crabs_A_Lot]

Greetings all!

I'm running OCPN 5.0 under Win10 on a HP ProBook 6470b.

Boat is a 25' steamboat, cable steered from a wheel. I plan on using an automotive wiper motor and a toothed belt to the wheel as an autopilot, controlled from OCPN. I've seen this done on YouTube with tiller sailboats but they never say how to wire it up. Can someone here enlighten me as to:

1. How to connect the motor correctly (through relays or whatever) to the battery bank. There is no alternator and the steam engine doesn't use electricity.

2. How to control the motor correctly from the laptop, in terms of data lines. There is a plain USB 2.0 port that is currently used for my GPS Puck.

The ports I have available to me are two USB "SS" (3.0?) ports, an eSATA port (whatever that is!), what I think is a firewire port, an HDMI port, a telephone port, an ethernet port, and a 15 pin D connection that may be meant for a secondary display.

If given a wiring diagram to follow I can do an adequate job of soldering up a system. I've constructed the electrical system on the boat from scratch, after all.

Ryan

[Bill O]

Originally Posted by Sir_Crabs_A_Lot

Greetings all!

I'm running OCPN 5.0 under Win10 on a HP ProBook 6470b.

Boat is a 25' steamboat, cable steered from a wheel. I plan on using an automotive wiper motor and a toothed belt to the wheel as an autopilot, controlled from OCPN. I've seen this done on YouTube with tiller sailboats but they never say how to wire it up. Can someone here enlighten me as to:

1. How to connect the motor correctly (through relays or whatever) to the battery bank. There is no alternator and the steam engine doesn't use electricity.

2. How to control the motor correctly from the laptop, in terms of data lines. There is a plain USB 2.0 port that is currently used for my GPS Puck.

The ports I have available to me are two USB "SS" (3.0?) ports, an eSATA port (whatever that is!), what I think is a firewire port, an HDMI port, a telephone port, an ethernet port, and a 15 pin D connection that may be meant for a secondary display.

If given a wiring diagram to follow I can do an adequate job of soldering up a system. I've constructed the electrical system on the boat from scratch, after all.

Ryan

Ryan,
Look up Pypilot. Sean (the creator of pypilot) uses a wiper motor to drive is autopilot. I'm sure he has already done what you want to do. Also he has no engine in his sailboat and run everything off solar/batteries.


Bill O.

[Lake-Effect]

Cool idea. I might be tempted to use a vehicle power window motor.

[seandepagnier]

The power window motors seem to be a good size for dingy and kayak autopilots. Maybe with a light enough helm it can work on larger boats.

The biggest struggle for the autopilot is running in light wind, with unbalanced helm with current against the waves. A motor that can move the helm faster will work in more difficult conditions. A very weak motor is sufficient much of the time.

[rgleason]

Maybe a wiper motor from a big bus would be better? They must be stronger motors due to the size of the winshield blades. Perhaps there are some other good ideas?

[Bill O]

I believe Sean used a heavy duty truck or bus wiper motor. Something that could handle continuous duty and a decent amount of torque would be important features of any motor used.


Bill O.

[a64pilot]

Originally Posted by rgleason

Maybe a wiper motor from a big bus would be better? They must be stronger motors due to the size of the winshield blades. Perhaps there are some other good ideas?

I’m pretty sure that the CPT autopilot is or was an over the road truck windshield wiper motor, I was told it’s a 24V motor but running it at 12V somehow increases its torque?

[seandepagnier]

At 24 volts the motor has more speed and torque. The main advantage to running at only 12 volts is it would be more quiet.

[GILow]

Or try using the wiper motor to drive a threaded rod. MUCH more mechanical advantage.

[a64pilot]

Originally Posted by boat_alexandra

At 24 volts the motor has more speed and torque. The main advantage to running at only 12 volts is it would be more quiet.

I didn’t understand how lower voltage could result in more torque myself. That is why I put the question mark there, it didn’t make sense. Lower voltage may also slow it down some, maybe at 24V it was too fast and therefore jerky?

[a64pilot]

Originally Posted by GILow

Or try using the wiper motor to drive a threaded rod. MUCH more mechanical advantage.

Are you talking jack screw? You just reinvented the linear actuator

[model 10]

Originally Posted by a64pilot

I didn’t understand how lower voltage could result in more torque myself. That is why I put the question mark there, it didn’t make sense. Lower voltage may also slow it down some, maybe at 24V it was too fast and therefore jerky?

Here it goes; so a dumb dc motor on 24v might see 6a. With the same load, a 12 v motor would see 12a. 12a gives more torque than 6a would. The higher voltage would increase the speed of the motor. Think about how some turbine engines have a 48v start system. It's not to get the engine turning, it's get it going fast enough to start.

[seandepagnier]

Originally Posted by Ecos

Here it goes; so a dumb dc motor on 24v might see 6a. With the same load, a 12 v motor would see 12a.

yes

12a gives more torque than 6a would.

Not in this case. The 12v motor has less turns of larger gauge wire, so it produces the same torque at 12a that the 24v motor does at 6a.

The higher voltage would increase the speed of the motor. Think about how some turbine engines have a 48v start system. It's not to get the engine turning, it's get it going fast enough to start.

Yes, higher voltage increases speed which is much noisier especially if there is a gear reduction. If the controller cannot limit the acceleration of the motor, then yes, it would be more jerky at 24v compared to 12v.

pypilot allows limiting the acceleration and also maximum speed so you can even use a 12v motor on a 24v system with a 0.5 max speed setting. In this case it's important to limit the maximum current/speed. If you allowed a higher max speed of 0.6 or more (1.0 is 24 volts) it could exceed the normal continuous rating of the motor, but an autopilot does not move the motor all the time so you can maybe slightly get more speed/power this way with some motors without risk of damage. It is a good idea to use a sensor for the motor temperature to avoid damaging it.

[seandepagnier]

I have printed 10mm wide and 5mm pitch toothed sprockets for both the wiper motor and the steering wheel. These along with the wiper motor and toothed belt completes a basic drive system.

[KathyinCa]

Where is the new post button? I dont see how to introduce myself?