mjcumming
Posts: 7
Joined: Sun Oct 14, 2018 8:17 pm

Boat lift - inclinometer or IMU

Sun Oct 14, 2018 9:48 pm

Hi All,

Looking for some help with a project....

I have a boat lift that lifts the boat via 4 large tanks. A simple vacuum motor blows air into the tanks. I need to control the airflow into each tank to have the boat come up evenly and I do this with 4 manual valves to control how the tanks fill.

I would like to automate this using a PI. My plan is to use either an IMU or inclinometer (but these seem hard to find) and then 4 sprinkler valves controlled by the PI.

My question is which sensor type do I use... all I really need is the inclination of the lift on 2 axises. Accuracy of +/- 2-3 degrees is probably good enough. I have spent a fair bit of time researching various options. I am not sure an IMU will do the job? Do I need to find an inclinometer instead - but these seem hard to find an no one really talks about them WRT to PI's.

Any thoughts?

Mike

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OutoftheBOTS
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Re: Boat lift - inclinometer or IMU

Mon Oct 15, 2018 9:25 am

An IMU will do the job you need, my favorite is the MPu9250.

The Accelerometer part of the IMU will do what you want. Although it is called a accelerometer it reads linear force, unless rapidly accelerating to create high G-forces this linear force will be the direction of gravity pulling on the IMU or as u call it an inclinometer. :)

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bensimmo
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Location: East Yorkshire

Re: Boat lift - inclinometer or IMU

Mon Oct 15, 2018 12:54 pm

The IMU will be fine and probably more than you need.

Have a plane with your smart phone if you have one.
Find a bubble (spirit)level app (or in Google type in ' spirit level ' and it will give you one in the browser.
The IMU will give you that, the ability to get a bubble level.

The hard part will be working out the motor pump to tilt direction and pid settings (if used) to make it work really nicely.
But it sound like an interesting project.

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bensimmo
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Location: East Yorkshire

Re: Boat lift - inclinometer or IMU

Mon Oct 15, 2018 1:02 pm

Here is the SenseHAT (an all in one official HAT for the Pi) being used as a spirit level.
http://www.suppertime.co.uk/blogmywiki/ ... -sensehat/
There will be similar for other IMU setups.

Edit to add for info/
Inclinometer from an IMU http://ozzmaker.com/inclinometer-using- ... ry-pi-imu/
/Edit

The MPU-6050 another old but we'll used IMU will might get you a lot of examples too.


As for the best one, I don't know.
But the Gyroscope will probably help with rotations along with the accelerometers.

mjcumming
Posts: 7
Joined: Sun Oct 14, 2018 8:17 pm

Re: Boat lift - inclinometer or IMU

Mon Oct 15, 2018 10:59 pm

Thank you for the responses. I was worried that an IMU wouldn't work due to the slow nature of the lift. It typically takes about 4 minutes to raise the boat. I did review the video done by Oz showing the car rotating on the screen. Was worried that the movements were so quick that they wouldn't apply to my use case. The spirit level is cool - I didn't find that example before - thank you.

For controlling the sprinkler valves, I was thinking of something like http://www.keyestudio.com/keyestudio-rp ... hield.html

These valves are 24 volts and the above relay board should handle the current and voltage.

I have 3 other questions ....

1. I need to control the vacuum motor - 120v 10 amps. It seems there a quite a few different approaches to this - open to anything that is easy and reliable.
2. I need to know when the boat is out of the water. I was going to use a float switch but was wondering if I could use a different sensor and measure height. Would an US sensor be able to tolerate being in an outdoor environment (fresh water). It wouldn't be exposed directly to moisture but would be in a damp moist environment.
3. Push buttons - I need a way to tell the PI to lift and lower the boat. Also would add a stop button. I haven't been able to find any switches that I think would last in this setting.

Thank you for the help,

Mike

JumpZero
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Joined: Thu Mar 28, 2013 7:35 pm
Location: 127.0.0.1

Re: Boat lift - inclinometer or IMU

Tue Oct 16, 2018 8:11 am

mjcumming wrote:
Mon Oct 15, 2018 10:59 pm
1. I need to control the vacuum motor - 120v 10 amps. It seems there a quite a few different approaches to this - open to anything that is easy and reliable.
To do this you need a motor contactor rated 10A minimum
something like this https://www.schneider-electric.com/en/p ... contactors
But maybe you have already one in your motor starter panel (a motor protection thermal relay must be included as well)
From the Pi you can drive the contator ON or OFF position, diretcly or through a relay (better)
--
Jmp0

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