Hello, everyone! I am trying to design a piezo buzzer for the payload section of a three-engine cluster rocket (the "Goliath" by Semroc).

The idea is to try to do a "poor man's" rocket locator beacon using sound rather than a radio transmitter and receiver. I find that when I am looking for a lost rocket it is usually hidden in tall grass or behind something where I can't see it but I could *hear* it if it were making a nice, loud noise.

I have tried out a couple of piezo buzzers and they seem good and loud *if* you feed them about 12 volts. That leads to my problem: What sort of battery should I use to power this thing? Is there a fairly small, light battery that would work? Has anybody tried this? So far I have just tested the buzzers with 8 AA alkaline batteries. That many AA's is far too heavy and bulky to be viable. Maybe AAA's? How about those 12V camera batteries - anyone have experience with them?

Another option: Does anyone know of a piezo buzzer that is good and loud when operating from less than 12 volts?

Any ideas, brainstorming, pointing in the right direction or other helpful advice is welcomed!

- Brock

__________________
Brock R. Wood, NAR 87453; Playing with model rockets since the purchase of an Estes "Launcher's Special" parts assortment in 1976.

Our recently updated Sport Launch system incorporates a 12V piezo-electric device in the system's Command Console to provide an audible indication of continuity, in addition to the LED indicator; sometimes, under certain lighting conditions, the LED's actual visible state can be misinterpreted, even though it's a high brightness LED.

The particular piezo used is a Radio Shack device, P/N 273-074, and generates a constant tone when energy is applied. In our application, we chose to create an oscillating tone, as this would be more noticeable (annoying?), and this was achieved by feeding a 6.6Hz square wave, generated by a 555 timer, into the transistor driving the piezo. The photo below shows the entire set of circuits used in our Command Console; the piezo is located in the upper right of the PCB, and only uses a few of the components seen in the photo. Most everything else on the board has to do with other functions of the system.

I've not had the occasion to actually measure the SPL of the device when activated in the enclosed console, but we typically locate our Sport Rack about 40'-50' away from the LCO desk, and the piezo is audible at that location when the LCO is checking continuity.

I'm not sure this answers many of your questions, but hope that it helps.

Attached Thumbnails

 

__________________
John
YORF #003
SAM #004

Unless you want the mental challenge of the design, it hard to go wrong using the Pratt Hobbies MicroBeacon @ $12

http://www.pratthobbies.com/proddetail.asp?prod=MB-12

Off the shelf solution! Thanks so much for the information!

- Brock

__________________
Brock R. Wood, NAR 87453; Playing with model rockets since the purchase of an Estes "Launcher's Special" parts assortment in 1976.

Or you could use a personal attack alarm like this. It has audio and visual. Set off by pulling on the keychain. Also known as a "corn finder" for when the rocket ends up in the cornfield. You may be able to find something similar at your local "dollar store":

http://www.protectmefirst.com/produ...7%7D-Light.html

__________________
Tim Barr
NAR 51403 SR

Coolness: 130 decibels! That should do it! "Corn finder." I like it!

So, you hook it up so it starts sounding when the ejection charge pops the nose off of the rocket? If so, how would that work? Hook the keychain to the main tube and the other part to the the nose cone? Vice versa?

Or do you just pull the chain and let the thing go off while the rocket is still on the launch pad? You would still need to attach it so that the sounder gets pulled out of the main tube at ejection, no?

Or I guess you could mount it in the "payload bay" with a small hole cut in the payload bay tube so you can hear it. You would then set it off before you launch the rocket?

What is your preferred method of using this nifty thing? Something different from the above?

Hmm. With all these good "no homemade circuit needed" ideas, I will never have to use the soldering iron again. Which is a bummer, actually! So nobody will actually want to see the nifty time-delay-before-on circuit I found in one of Forrest Mims' books last night. I even breadboarded it. The idea of the delay circuit was to silence the sounder beacon while on the launch pad. I *knew* there was a reason I kept those surplus N-channel MOSFET's in the parts bin! I may still post the circuit here, just in case anyone needs to make use of it.

- Brock

__________________
Brock R. Wood, NAR 87453; Playing with model rockets since the purchase of an Estes "Launcher's Special" parts assortment in 1976.

Here's a couple of designs to start from-

http://www.jbgizmo.com/page6.html

__________________
brianc -- NAR 83726 \ TRA 11640 \ L2

Here is what I came up with. The white alarm I got from my local dollar store. It's a door alarm, and when the magnet is moved away from the alarm, it goes off. My idea was to tape the magnet to the side of the alarm with a single piece of 1/2" masking tape. I was going to attach the alarm to the shock cord and the magnet to the parachute. The idea being that when the parachute deployed it would pull the magnet away from the alarm, setting it off. Haven't tried it, so don't know how well it would work.

The black alarms I got off Ebay. They were really cheap, $3 or $4 apiece. They're so-called personal alarms. They go off when you either press the button, or pull out the lanyard. These are a lot louder than the door alarm. I was going to attach the alarm to the shock cord, and the lanyard to the parachute. The little clips attached to the lanyards that get pulled out, were really stiff. Very hard to pull out. So I ground the "ears" off with my Dremel. They pull out much easier now. I plan on using one of these with my Level 1 cert rocket, to slightly increase my chances of a successful recovery.

Attached Thumbnails

     

By the way, the personal alarms are rated at something like 130db, almost twice as loud as the 70db piezo buzzer from Radio Shack, and I think louder than the Micro Beacon from Pratt Hobbies. But the personal alarms are larger and heavier, and have no flashing light.

How much current does that piezo buzzer need? You can get 12V in a tiny package if you gang up some of the 'button' (hearing aide type) batteries.