Help picking sensors

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Lost Bob
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Joined: Oct 7th, 2012, 9:50 pm

Help picking sensors

Post by Lost Bob »

I will have a Arduino mega on onboard my rov and I could use some help picking sensors. I have no arduino experience, coding or otherwise. My only electronic experience is with multi-rotors with no gps or other sensors ( KK2.1 board ).

I was looking at :

SparkFun 9 Degrees of Freedom Breakout - MPU-9150 https://www.sparkfun.com/products/11486. This should give my heading: will it also give my depth ? Can I combine this sensor with some code to show a horizon line across my screen, like fpv planes ?
AttoPilot Voltage and Current Sense Breakout - 180A https://www.sparkfun.com/products/10644. Measure my batteries amps and voltage.
SparkFun Digital Temperature Sensor Breakout - TMP102 https://www.sparkfun.com/products/11931. Measure the temp inside my hull.

I would like to be able to see my thruster output, like a bar graph on the bottom of the screen or similar. More coding ?

Please tell me what am I missing.
Thanks Bob
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Moki
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Location: The Netherlands

Re: Help picking sensors

Post by Moki »

For depth you will need something like a MS5803-14A, or buy the Openrov depth sensor.. Which combines a MPU-9150 with a MS5308-14A.

But lots of coding is needed.
Lost Bob
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Joined: Oct 7th, 2012, 9:50 pm

Re: Help picking sensors

Post by Lost Bob »

I like that openrov module. Is arduino compatible or just rasp ?
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Moki
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Location: The Netherlands

Re: Help picking sensors

Post by Moki »

Both, i think.

The Openrov depth sensor is I2C compatible. So it should work on both.
But i have little knowledge on Arduino, but i seem to have read somewere that the Openrov is Arduino based.
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Moki
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Re: Help picking sensors

Post by Moki »

Btw, the MS5308-14A only measures pressure. So it will tell you the depth below the watersurface.
Not the distance to the seafloor.
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KR2_Diving
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Joined: Aug 30th, 2012, 11:43 am
Location: Currently: NW Suburbs of Chicago. Originally: NE Wisconsin

Re: Help picking sensors

Post by KR2_Diving »

Hey Bob!
I have a few comments for you that hopefully will help point you in the right direction!

Lost Bob wrote:I will have a Arduino mega on onboard my rov and I could use some help picking sensors. I have no arduino experience, coding or otherwise. My only electronic experience is with multi-rotors with no gps or other sensors ( KK2.1 board ).
The Arduino Mega packs quite the punch for the price! I am using on in my ROV as well! There are more than enough I/O available to perform all the tasks you might want to!

It will take some programming, but there are enough resources out there that you should basically be able to Copy and Paste most of the code you need! Many of the sensors you have listed below have sample code right on the Adafruit or Sparkfun Site!
Lost Bob wrote: SparkFun 9 Degrees of Freedom Breakout - MPU-9150 https://www.sparkfun.com/products/11486. This should give my heading: will it also give my depth ? Can I combine this sensor with some code to show a horizon line across my screen, like fpv planes ?
Wow! That little beauty has quite a bit of functionality! I just had a quick glance through the sample code, and one thing that stood out at me is that there are a LOT of FLOAT data types defined! If you are planning on doing anything else with your MEGA (which you should, like drive thrusters, communicate with surface, etc...) it is likely that the you will not be able to use much of the functionality of this sensor, unless you rewrite a lot of the code. It will hog a lot of the limited processing power of the Arduino.
Don't get me wrong, it CAN be done, and the re-write is not to complicated... but it is not as "out of the box" as it could be...

Any as Moki mentioned, you will need a separate sensor to determine depth.

Lost Bob wrote: AttoPilot Voltage and Current Sense Breakout - 180A https://www.sparkfun.com/products/10644. Measure my batteries amps and voltage.
Bigger is NOT always better. IN this case, if you have a 180A sensor connected to the Arduino, you will only have an accuracy of 170mA (The Analog input will return a value from 0 to 1023. So 1024 / 180A = 5.68 units per AMP...

I would recommend a much smaller sensor, or even multiple sensors. For example if your thruster is only going to draw 15 to 20A, then a 30A sensor would be perfect! (1024 / 30A =34.13 units / Amp = accuracy of 29mA!

Another way to look at it... if you have a 180A sensor, but the max you will ever draw is 40A, you are only using 22% of the range of the sensor... Its like having a Ferrari, but never taking it out of 2nd gear!
Lost Bob wrote: SparkFun Digital Temperature Sensor Breakout - TMP102 https://www.sparkfun.com/products/11931. Measure the temp inside my hull.
I like this sensor and even considered getting a few for my ROV. I was thinking it was small enough to mount on / near each of my Batteries or ESC's to have a way to keep an eye on things and prevent overheating!
Lost Bob wrote: I would like to be able to see my thruster output, like a bar graph on the bottom of the screen or similar. More coding ?
The Arduino is not capable of processing video. It IS capable of generating the data necessary, and interfacing with an OSD (On Screen Display) to generate the display you want! (This also goes for your comment about a "horizon" line on your screen. This will require an OSD. I have done a bit of research on this and made some notes on THIS thread.

For a basic ROV, the biggest thing you are missing at the moment, is how are you planning on getting your control signals from the Surface to the MEGA inside the ROV? For Example, I am using Serial Coms (MAX488) via RS485 protocol. I have posted some of my notes and code HERE.

Hope this helps! Don't Let any of what i said above scare you away... I had almost NO experience with any of this stuff before I started... There are so many resouces out there... and chances are... someone else has already tried what you are trying... and they have posted about it! I have found that simply adding ARDUINO to my search points me to exactly what i need to know. For example: "MAX488 ARDUINO"

best of luck and happy diving!

Ryan
"KR2_Diving"
Lost Bob
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Joined: Oct 7th, 2012, 9:50 pm

Re: Help picking sensors

Post by Lost Bob »

Thanks for the help guys !

I just ordered this on e-bay for $10 : http://www.ebay.com/itm/9-Axis-10DOF-At ... OC:CA:1120

@ Ryan - I will send my signal thru cat5 ( if I can find some stranded stp somewhere, besides a 1000' box ). I was hoping to send it straight to my laptop and use Monterey for my OSD, with a gamepad. Here's the thread. viewtopic.php?f=15&t=1147&hilit=monterey.
If that doesn't work, I have an Uno for topside and I will probably be using your code.
Bigger is NOT always better
Ya, I hear you. The only reason I chose the 180A was because they are all the same price. They also come in 45 and 90 amp versions . I was planning on something like 4 - 3s 5000mah lipos for powering everything but the camera and 1 - 3s 1000mah for the camera. So really, I would need 2 of them. 45's should be big enough, eh ?
Lost Bob
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Joined: Oct 7th, 2012, 9:50 pm

Re: Help picking sensors

Post by Lost Bob »

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