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Tank level monitoring
#11
I looked at ultrasonic measuring designs as well. What worried me was how those systems performed when they got wet, which is clearly what would happen in a boat tank. I couldn't see any way to waterproof them while retaining their functionality.

The immersed rod systems were most appealing to me for their simplicity. I saw a couple of commercial products that used a few stainless rods of varying lengths - I think I might be able to duplicate that using 1/8 inch brass brazing rods. Another way to do it would be to use some double sided copper board (long and thin) etched to create measurement points down either side.

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#12
water proof ultrasonic

https://www.newegg.com/Product/Product.a...lsrc=aw.ds

even cheaper on ebay.

an industrious lad could could adapt a Car Parking Backup Sensors Kit.
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#13
Cool! I'm going to give it a shot.

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#14
(07-26-2017, 11:16 AM)jim321 Wrote: water proof ultrasonic

https://www.newegg.com/Product/Product.a...lsrc=aw.ds

even cheaper on ebay.

an industrious lad could could adapt a Car Parking Backup Sensors Kit.

Ultrasound also work well with non-conduction fluids like fuel and other hydrocarbons. A sensor for this project should be easy to connect to the Raspberry interface, analog, I2C, On/off or other simple interface. It should also be cost effective. 

I found it from Aliexpress also : https://www.aliexpress.com/item/Ultrasonic-Module-Distance-Measuring-Transducer-Sensor-Waterproof-DC-5V/32330248071.html

Some programming and interfacing is needed to measure the distance, e.g. the liquid level.

I'll order one and check it out .


Ole
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#15
you may need two ,..one for send and one for receive to get better resolution .

there are kits on ebay for cars that contain 4 units
http://www.ebay.com/itm/4-Parking-Sensor...YT&vxp=mtr
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#16
(07-31-2017, 06:26 PM)jim321 Wrote: you may need two ,..one for send and one for receive  to get better resolution .

there are kits on ebay for cars that contain 4 units
http://www.ebay.com/itm/4-Parking-Sensor...YT&vxp=mtr

Hey, that made me think of parking sensors for boats... really useful for solo mooring. Does exist that on any commercial boat?
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#17
(08-06-2017, 01:55 PM)Sailoog Wrote:
(07-31-2017, 06:26 PM)jim321 Wrote: you may need two ,..one for send and one for receive  to get better resolution .

there are kits on ebay for cars that contain 4 units
http://www.ebay.com/itm/4-Parking-Sensor...YT&vxp=mtr

Hey, that made me think of parking sensors for boats... really useful for solo mooring. Does exist that on any commercial boat?

That would be really cool, specially for us from Scandinavia who go bow in, it's impossible to judge the distance from the bow to the pontoon at 40' distance.  

Ole
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#18
I have done some more work on the tank level monitoring using the inductive sensors. I now have a working demo on my project page,
Tank level monitoring.

So far the python script is stand alone as this is the first step to just make it work and send messages to SignalK. It need to integrated into Openplotter.  It uses an extension module to get more digital IO pins (rather limited in the RPi). As you can have up to 128 IO pins the config need to be quite versatile as the tank level monitoring is just one example.  One could extend the tab which already deal with IO pins to accomodate for the  PCF8572 and PCF8574A chips/modules.


However, as the video in my page show the prof of concept work and the prototype in my office works fine.  


There are several ways to integrate this tank level monitoring or a general IO pin interface into the Openplotter. 
- One is to extend the GPIO (add I2C IO boards) section to make it possible to call a python script with a range of pins as parameters and use the status of these pins as input to the script. 

- A second alternative is to make a tool in the "tools" menu and make a "tank level" entry or a more general entry to deal with digital IO pins. 

- Yet another alternative is to start from the I2C menu and include the digital IO pins boards as I2C devices and call functions that handle the different IO boards (they each have a unique address) one by one. One board might be level monitoring, while another might be different types of alarms.

The last alternative might offer the most flexibility as you can have a rather large number of boards, each with very different sensors.



Ole
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