Piezo Voltage Acticated Switch

Thank you.

Yep, which means properly engineering an electrical circuit is going to be just as difficult if not moreso than a mechanical one that's properly encapsulated.
Why you think it is impossible to do this mechanically I don't know, because if you can properly encapsulate an electric circuit then you can properly encapsulate a mechanical one, and the mechanical on will have fewer failure points and consume absolutely zero battery power.

Please elaborate on how designing an electronics cct could be more difficult. I've been asked to design an electronic alternative and that it what I will do. I will post my results when I am finished. The reason that I have been asked to do this is because the mechanical one is failing enough to have someone want something more reliable. If you had bought a $10,000 piece of eqpt and retrieved it after its first deployment to find that it is water logged and destroyed then you would want this too, especially if it was happening all the time. Sometimes this will come up under ice and if it cannot be located then upwards of $250,000 worth of eqpt is lost along with all of the data.

This will work and I will have this community to thank in the end.

All that says zotz is the mechanical one was designed improperly.

Simple logic. If you can protect an electrical circuit from the conditions you can protect a mechanical one. A mechanical pressure switch is several orders of magnitude more simple than an electrical circuit. The only problem is the design of the existing switch.

Don't forget, a piezo element is in FACT a mechanical swithc, you're just reading it via the electrical voltage that is induced during a pressure change. You are in fact trying to electrically read from a mechanical device.

None of this is going to help even the slightest bit if it comes up under ice.

At this time I am only considering responses that are in support of designing an electronic switch. You're input is welcomed but, unless it provides insight to an electronic switch, it will not be considered.

Mechanical pressure switches ARE electronic switches. So are Piezo based ones.. I'm sorry that you're so blind that you don't realize that you already have a more basic solution other than adding more complexity to a system that already obviously doesn't need it.

You have still not explain why the original switch fails, because the new one could just as easily fail the same way.

I think you need a better ideas guy on the project. Don't use pressure sensing! Design the beacon to be self contained and pressure proof as top priority. No o-rings or external interface needed.

When it gets to the surface it will rock and bob on the waves etc. Use an accelerometer to measure tilt, or even a couple of mercury switches etc. It should be very easy to tell the difference between captive on the ocean bottom and bobbing on the surface.

Who was the person who thought the best system was to use pressure sensing??

Yes, because an active accelerometer and associated circuitry is going to be so much less temperamental than a single switch.. with an inactive period of 2 years or better.....

Here is one proposal,,,

The accelerometer/mercury switch has already been done and works in some situations, but in the heavy current area that this will be in it will not work. I like that you have come up with this and I am impressed because it shows that you are keen to the situation.

The other proposal has also been done. This is good! All have been done before and I am really impressed with your solutions.

Cmon...there has to be a way to do this using at least the transistor. Maybe even a peizo with a darlington to amplify the small signal.

I am quite impressed with these ideas though.

Sorry I just re-read my post and it sounds arrogant or judgemental. I was just dumbfounded that you would use some mechanical device with moving parts and o-rings in a $10000 device that will be exposed to 12000 PSI for 2 years.

Actually I'm still dumbfounded. Motion sensing just seems the best way to me. And/or maybe a temperature sensor, the water will be MUCH warmer at the surface than at great depth.

Hi. Allow me to toss more methods to the table, as I believe it is not matter of making a switch work, it is matter of designing a fail-proof method.

That beacon apparatus will rise as a bullet towards the surface.
Flowing all around it, a lot of fast conductive seawater.

--- Magnets interact with moving conductive fluid, being capable of generating an electric signal (magnetohydrodynamics). That signal can trigger an electrical action so when such signal stops at surfacing, it can activate the beacon.

I do not see moving parts. I see no mechanical pressure sensors. I see no trickle battery consumption. I see no ports that can leak inside. But needs someone knowledgeable in this subject. Am not.

---Method two on the table: The device is anchored upside down at the sea floor.
(OR rises inverted)

Then the release happens, its buoyancy turns it 'upright' and an internal mercury switch starts some timing to activate in a few minutes, by then it has surfaced.

---Method three: The same triggering-to-release-anchor receiver can awaken it.

If the receiver/release mechanism stays with the anchor, it is lost equipment forever. Move the release receiver to the device and will also awaken it when released from the anchor.

---Method four: the device can have a reed switch internally, held open by a tethered magnet to the anchor. When shoots up, the magnet detaches and the device is awakened.

What I do not get at all is what the device does at the bottom for 2 years with no energy consumption. Well , that is not part of the question posted.


Miguel

Very nice ideas...so:

What I do not get at all is what the device does at the bottom for 2 years with no energy consumption. Well , that is not part of the question posted.

The device is gathering data about the ocean...one of the scientists that works in the same office as I was awarded the Nobel Prize in accompaniment with a number of other well known scientists and Al Gore for their work and contributions to research on global warming...An Inconvenient Truth is the name of the film that illustrated the use of the data gathered.

I really like these ideas but I will have to tell you that the peizo activated NPN Darlington voltage switch is what I have been told to use to make work, so I want to see some ccts on how this will work because I know it will work.

You know you want to make this work.

Hi.
You are forcing the method to use a piezoelectric trigger.

Well, to satisfy your obsession; You could make a wet 'cage' chamber within the device.
Inside that chamber, a sphere that can move floats, stuck to its 'ceiling'
When surfaces, will loose flotation and by its weight will drop hitting on top of a piezoelectric disc, generating a pulse to awaken the electronics.
This involves a moving part (sphere) to 'hammer' the piezo sensor.

There is dozens of methods, but only the design team with the knowledge of all the details can make the decision.

Or the moving sphere could rattle with the sea surface motion hitting the piezo element.
The electronic circuit is just a microphone amplifier with vox.

That sphere, if magnetic, could activate a reed switch at the bottom of the cage when surfaces... but again it is against your piezo forcing; which has been promoted against by several members in this thread.

What powers for 2 years the data collecting module ?

Miguel
-Scuba diver since '72-

What powers for 2 years the data collecting module ?

4 x 1.5V C cell batteries.