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RC Plane Piezo locator circuit request please.

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SKT

New Member
G'day all,

I have some very basic electronics experience and my soldering skills are acceptable. My main past time is rc aircraft and I am wanting to build a piezo sounding locating device for a downed rc aircraft.

There are available such units but rely on power to the main rc rc which is not always part of the scenario.

What I propose is the following and I would appreciate any assistance with this project.....

An extremely loud piezo alarm sounding on off on off etc, powered from a single 1.5v AAA battery or similar power source.
The trigger would be a relay of some sort that relies on an aprox 5v source being outputted from a channel off the rc rx. This could be triggered by turning the output of the rc rx off thus removing the 5v source or if power to the rc rx was lost then again the 5v source to the relay would be removed, thus triggering the piezo.

I'd like to keep the weight as low as possible as it's, as stated, going to be mounted into a rc model aircraft. Somewhere as close to or below 100g would be nice but I'd accept the battery would probably be the heaviest component..
The piezo needs to be really loud. I mean really loud. The aircraft could be in thick grass, up in a tree, even behind thick shrub foliage. I'd also like to see a dual output so a piezo could be mounted on the top and underneath of the craft. There's a good chance it could land upside down thus muffling the piezo if it crashes upside down, and vice versa.
I'd like to incorporate a simple switch so as to deactivate the alarm when the rc plane is not powered and sitting on the shed shelf.

I'm not sure how difficult this will be and I will add I'm in Australia so not sure what discreet components I will need are available to me but I am willing to do the work and get the results.

Again, any assistance is highly appreciated.

-Scott
 
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audioguru

Well-Known Member
Most Helpful Member
Would the loudness and high pitch from a smoke detector be good enough? With a 9V battery they are VERY loud and do not use much current. You could make a circuit that stepped up the 1.5V from an AAA cell to 9V, make a beeping circuit then make a bridged audio amplifier to drive the piezo that is already in a tuned housing.

A friend lost his RC electric ducted fan jet. Its internal motor and fan produced enough sound to be found.
I also lost a fairly new RC airplane but it flew too far away for any kind of sound device to be heard. The manufacturer sent me a replacement for half price.
 

SKT

New Member
I think a smoke alarm level sound would work pretty well, atleast a lot better than the current option.

How do you propose I implement the relay trigger based on a loss of aprox 5v?
 

cowboybob

Well-Known Member
Most Helpful Member
Welcome, SKT!

I am an RC fan also.

While it would be entertaining to design and build such a device,

this:
https://www.hobbyking.com/hobbyking/store/__13064__Signal_loss_Alarm_Lost_Plane_Finder.html

would be very much cheaper and easier, assuming you have a spare servo output on your recvr.

This one (identical) is even cheaper:
http://www.banggood.com/Wholesale-L...paign=all-us&gclid=CJLd8uf33bwCFXBk7Aod8isACA

Only 1ma draw (from existing onboard supply) so long as Tx signal (actually, one of the recvr's servo outputs) is present. 35ma when activated (by loss of Tx sig).
 

SKT

New Member
G'day gowboybob.
From personal experience those devices are fine if your craft goes down on a dead flat field with no traffic. And still you need to be within 5-15m to hear them.

Unfortunately my aircraft don't go down in that sort of terrain.

Not being much with electronics, thus my request here, I can't see the planned relay drawing much if any current and the goal is to have the extremely loud piezo power off the connected AAA or similar battery connected to the device.

Thx for the links but a more effective locating 'siren', for lack of a better name, is required.
 

alec_t

Well-Known Member
Most Helpful Member
Do you have a spare Rx channel you can devote to triggering the siren? If not, won't you have to wait for the Rx battery to go flat before the siren sounds?
 

SKT

New Member
Do you have a spare Rx channel you can devote to triggering the siren? If not, won't you have to wait for the Rx battery to go flat before the siren sounds?

I do and currently run a siren triggered by a switch much like the devices linked to by cowboybob, on my RC tx. The problem is loss of power to the RC rx means no siren.
 

audioguru

Well-Known Member
Most Helpful Member
I think the little Chinese Lost Airplane finder is too small to be loud enough. It is simply to prevent you from stepping on the airplane when you are very close and it is in tall grass.

These days we use a transistor or a Mosfet instead of a power-hungry relay to connect and disconnect things.
 
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