Hello,
I am looking for a sensor to find the current depth. It will be a device that sits in the bottom of the ocean and can get current depth and know when it is coming up in depth. I don't want to spend anymore than $20 on something like this. It only has to work for a max of 40m
Good luck on a $20 price point. I would have suggested a bubbler method another method would be to lower a delta pressure sensor to the bottom. Both methods rely on measuring pressure. Wither way you are looking at 40 meters plus of tubing like Tygon or Wires to the bottom.
Ron
Can’t you measure the surface from some data point and work out change in depth ?
It would be interesting to know why you want to do this anyway ? The bottom of the sea is a hostile environment , 40m is about 4 atmospheres of pressure and the salt corrosive . How will you get your output to the surface ?
The budget is unrealistic .
hammy:
Can’t you measure the surface from some data point and work out change in depth ?
It would be interesting to know why you want to do this anyway ? The bottom of the sea is a hostile environment , 40m is about 4 atmospheres of pressure and the salt corrosive . How will you get your output to the surface ?
The budget is unrealistic .
So this device is going to sit at the bottom of the ocean on a cray pot and when it is getting pulled up it will activate a GPS signal. I am trying to find something to know when it is getting pulled up, so i was thinking a pressure sensor.. thoughts on what else i should try?
For the $20 price point a rock tied to a length of marked string ought to work.
srnet:
For the $20 price point a rock tied to a length of marked string ought to work.
then what is a more reasonable price for something like this??
How much do you plan to spend for the GPS, cable, microcontroller, radio, power supply, salt water proof enclosure, etc. ?
A high quality waterproof pressure sensor and 40 m of cable will set you back $200-300.
wolfleader:
So this device is going to sit at the bottom of the ocean on a cray pot and when it is getting pulled up it will activate a GPS signal. I am trying to find something to know when it is getting pulled up, so i was thinking a pressure sensor.. thoughts on what else i should try?
The GPS will only work on the surface. So it will only send when the pot is on the surface. Pressure switch to turn it off below a preset depth. No matter how you slice and dice it I don't see it happening for under $20 USD.
Ron
there won't be anything connecting it to the surface the whole Arduino kit will be sitting underwater. I have a design in mind for how to water seal it.
I should clarify i was looking at a $20 price point for the sensor, however obviously if it costs more then I would be happy to pay for it.
Would anyone be able to link me one?
The Maximum depth is 50m however it will be used between 10-30m on average.
GPS does not work underwater. Your favorite search engine can find depth sensors.
wolfleader:
there won't be anything connecting it to the surface the whole Arduino kit will be sitting underwater. I have a design in mind for how to water seal it.
Can you tell us how ?
Per your post in another forum and as posted here. GPS will not work underwater. That said you can use a pressure sensor referenced to atmosphere to measure depth. Atmospheric pressure at sea level is about 101,325 Pa, which is equivalent to 760 mm Hg, 29.9212 inches Hg, or 14.696 psi. For every 33 feet (10.06 meters) you go down, the pressure increases by one atmosphere.
When pressure is atmospheric the pot should be on the surface and a GPS should work but that is as good as it gets.
Ron
Ron_Blain:
Per your post in another forum and as posted here. GPS will not work underwater. That said you can use a pressure sensor referenced to atmosphere to measure depth. Atmospheric pressure at sea level is about 101,325 Pa, which is equivalent to 760 mm Hg, 29.9212 inches Hg, or 14.696 psi. For every 33 feet (10.06 meters) you go down, the pressure increases by one atmosphere.When pressure is atmospheric the pot should be on the surface and a GPS should work but that is as good as it gets.
Ron
Hi Ron,
I haven't posted this in another forum only here 
Could you link me an appropriate sensor for this?
My plan was to have the GPS start once it was on the surface anyway.
My plan was to have the GPS start once it was on the surface anyway.
In that case, the problem is trivial.
Use a cheap pressure activated switch, for example, to cut off all power as soon as the box is submerged, and turn it back on when the box pops up on the surface. The box must handle at least 5 atmospheres without leaking water.
jremington:
In that case, the problem is trivial.Use a cheap pressure activated switch, for example, to cut off all power as soon as the box is submerged, and turn it back on when the box pops up on the surface. The box must handle at least 5 atmospheres without leaking water.
thanks,
however, I don't think that one will work underwater
it's hard trying to find one that will be able to go underwater even if it's only checking for surface pressure.
would something like this be fine?
The MS5803 reportedly does a good job; I have tested it's successor the MS5837 and it also did really well under water.
Note that both the link and my own test are fresh water environments; in marine environments the sensors may have a harder time. Cost of the MS5837 I remember is just under USD 20 in small quantities (the bare sensor, that is - on a breakout board they'll cost more). The MS5803 should be significantly cheaper.
however, I don't think that one will work underwater
Of course it will. The switch would be inside the box, with the threaded coupler connecting to the water outside.