Smallest keychain security alarm?

[billdz]

I've had success using cheap keychain security alarm beepers to find rockets in high grass. We can rig the beeper so that the cord is pulled and the alarm sounds at ejection. I'm using beepers similar to those at https://www.walmart.com/ip/TSV-3pcs...-Elderly-Security-Safe-Sound-Safety/294629456 .

At a recent launch, I saw a guy using a much smaller beeper. He left before I could speak with him, and I have not found anything similar with Google searches. His beeper was cylindrical in shape and looked similar to the device at https://www.amazon.com/Smallest-Keychain-Flashlight-flashlight-Emergency/dp/B08PNTYSGC?th=1, except it was a beeper, not a flashlight. A beeper like that would be useful for small rockets, although it is probably not as loud as my 140 dB beepers.

Anyone have any info about the smallest beepers, and where to buy?

Thanks,
Bill

 

[Egoldee]

Probably was a Pratt Hobbies Micro beacon.
Unfortunately I think they don't make them anymore.

 

[billdz]

Probably was a Pratt Hobbies Micro beacon.
Unfortunately I think they don't make them anymore.

Thanks for the reply. It looks similar to the Pratt beacon but I don't think the Pratt is the one I saw. The Pratt appears to be attached to a string. The one I saw was attached to a lanyard with a mini phono plug at the end. The plug goes into a jack on the beeper, and the beeper goes off when the plug is pulled.

 

[Alan R]

I've been thinking about one of these also. I see lots of these little things on Amazon. Every one I see though has a problem with the design if I want to use it in a rocket. For it to be functional, the alarm trigger needs to pull but there's no loop or connector opposite the trigger that would hold the main unit steady.
Hard to explain but I think you know what I mean. I see some small ones but they would need a case or a hole drilled in order to be functional.

 

[DigBaddy]

I've been thinking about one of these also. I see lots of these little things on Amazon. Every one I see though has a problem with the design if I want to use it in a rocket. For it to be functional, the alarm trigger needs to pull but there's no loop or connector opposite the trigger that would hold the main unit steady.
Hard to explain but I think you know what I mean. I see some small ones but they would need a case or a hole drilled in order to be functional.

I drilled a hole opposite the pin on the cheap ones...still too big for many rockets but there's a lot of plastic there to drill and make them work better in what you can use them in.

 

[billdz]

I drilled a hole opposite the pin on the cheap ones...still too big for many rockets but there's a lot of plastic there to drill and make them work better in what you can use them in.

I just attach the lanyard/pin to the nose cone, securely tape the beeper to the shock cord (no tape over the speaker) leaving some slack (but not too much) on the cord between the beeper and the nose cone, and thus the pin comes out when the shock cord straightens after ejection. The first time I used one of these beepers, instead of taping I attached the beeper's keychain to the shock cord with a quik link, but it broke off, the ring connecting the keychain to the beeper was quite flimsy and it broke off (see attached photo).

Such a trigger is only needed if you are at a large launch where the rocket may sit on the pad for a long length of time. If the rocket will launch shortly after it is on the pad and ready, you can just pull the pin before launch, it will not be too loud when sealed inside the rocket, and you won't have to worry whether it will trigger properly.

Has anyone seen a smaller beeper, other than the Pratt?

 

[allensmith]

I’ve used this one.

Personal Alarm Keychain for Women... https://www.amazon.com/dp/B091D3P2VY?ref=ppx_pop_mob_ap_share

The pin pulls from the top, not the side. I slightly pulled the pin ahead of launch, not enough to activate it, but enough to break its “grip” on the pin. At ejection, the pin came the rest of the way out and it began screaming. It also flashes.

 

[hobie1dog]

I'm still searching for suitable models

 

[RokitFlyr]

 

[RokitFlyr]

I use these. Not the smallest, but work well. I took the clips off and added a loop of Kevlar to attach to the shock cord. Just be sure to get ones with a metal pullpin. The plastic pins will break.

 

[billdz]

I use these. Not the smallest, but work well. I took the clips off and added a loop of Kevlar to attach to the shock cord. Just be sure to get ones with a metal pullpin. The plastic pins will break.

That does look nice. Do you have a link where to buy?

These things have always been pretty cheap, less than $10 on Amazon and eBay, but if you're really cheap you can get them for under $3 at Temu, AliExpress and other Chinese sites.

 

[tim cubbedge]

That does look nice. Do you have a link where to buy?

We sell them at our club.

 

[DigBaddy]

I've been thinking about one of these also. I see lots of these little things on Amazon. Every one I see though has a problem with the design if I want to use it in a rocket. For it to be functional, the alarm trigger needs to pull but there's no loop or connector opposite the trigger that would hold the main unit steady.
Hard to explain but I think you know what I mean. I see some small ones but they would need a case or a hole drilled in order to be functional.

I've been trying to safely disassemble one of these to design a different case that can be printed, but the beeper/speaker thing is glued in there securely and does not want to be easily removed....

 

[Alan R]

I've been trying to safely disassemble one of these to design a different case that can be printed, but the beeper/speaker thing is glued in there securely and does not want to be easily removed....

Just epoxy a kevlar string opposite the pull chain. Or if you've disassembled, post a pic that shows where you can drill a hole safely through the case.

 

[DigBaddy]

Just epoxy a kevlar string opposite the pull chain. Or if you've disassembled, post a pic that shows where you can drill a hole safely through the case.

I'll have to go find a modified one later. The goal I had with disassembly and printing a new carrier was to make it smaller and fit in smaller tubes; rearrange the components...

 

[Alan R]

The ones that @RokitFlyr posted above:
Keychain alarms at walmart

Looks like these and most other skinny types would work fine in 38mm and above.

 

[DigBaddy]

The ones that @RokitFlyr posted above:
Keychain alarms at walmart

Looks like these and most other skinny types would work fine in 38mm and above.

Yes, but I have a pile of the other ones I can use if I can make this work instead of buying a bunch more.

 

[RokitFlyr]

That does look nice. Do you have a link where to buy?

These things have always been pretty cheap, less than $10 on Amazon and eBay, but if you're really cheap you can get them for under $3 at Temu, AliExpress and other Chinese sites.

I got them on E-bay. They are about $5 ea. Cheap, considering the $ spent on the rockets! Just search "personal key chain alarm". When I get a chance, I'll post a pic of one installed on a shock cord later. They're out in the garage after unloading from last weekends launch. Used 2 of them, worked perfectly.

 

[hobie1dog]

I got them on E-bay. They are about $5 ea. Cheap, considering the $ spent on the rockets! Just search "personal key chain alarm". When I get a chance, I'll post a pic of one installed on a shock cord later. They're out in the garage after unloading from last weekends launch. Used 2 of them, worked perfectly.View attachment 579832

Thanks for the picture. Do you have a measurement on how wide it is to know what size rockets it will fit in?

 

[billdz]

Thanks for the picture. Do you have a measurement on how wide it is to know what size rockets it will fit in?

3.15" x 0.98" x 0.59", according to https://www.walmart.com/ip/iMESTOU-...Wolf-Alarm-Anti-lost-Keychain-I0X9/2281871121.

 

[hobie1dog]

3.15" x 0.98" x 0.59", according to https://www.walmart.com/ip/iMESTOU-...Wolf-Alarm-Anti-lost-Keychain-I0X9/2281871121.

thanks It says that the 120 db alarm is push button activated

 

[RokitFlyr]

3.15" x 0.98" x 0.59", according to https://www.walmart.com/ip/iMESTOU-...Wolf-Alarm-Anti-lost-Keychain-I0X9/2281871121.

Those are not the same thing. 2.9"x 1.3"x 0.5". Or, go to e-bay and look....

 

[billdz]

Those are not the same thing.

That's from the link posted by Alan R above in #16. What are the dimensions of yours?

 

[RokitFlyr]

Yes, but I have a pile of the other ones I can use if I can make this work instead of buying a bunch more.

I did not post the walmart alarms. Mine are from E-bay......

 

[JSW]

There was also a build thread for a simple piezo device called "the Screamer" in NAR Sport Rocketry magazine (March/April 2022). Picture below. I found several of the components on Amazon (85db Piezo, Battery Holder), although haven't tried to build.

 

[hobie1dog]

I'm still searching the web for a 140 db model that's small.

 

[DarthMuffin]

I'm still searching the web for a 140 db model that's small.

Anything small you see listed with that spec is lying. That is gunshot loud, but constantly. A full competition car stereo at full volume might be able to do that, but nothing you can fit in a rocket. 85db is fine, that level is already on the threshold of hearing damage for extended exposure.

 

[rharshberger]

Anything small you see listed with that spec is lying. That is gunshot loud, but constantly. A full competition car stereo at full volume might be able to do that, but nothing you can fit in a rocket. 85db is fine, that level is already on the threshold of hearing damage for extended exposure.

85db is the OSHA 8 hour TWA (time weighted average), and has no application to these type personal alarms, they are designed to be very loud to get peoples attention or scare someone away.

 

[DarthMuffin]

85db is the OSHA 8 hour TWA (time weighted average), and has no application to these type personal alarms, they are designed to be very loud to get peoples attention or scare someone away.

That's why I said it was "fine". Nobody is holding one of these up to their ear for 8 hours.

 

[hobie1dog]

When I end up getting one of these, I'll measure the decibel level with my meter.