Reddit reviews Install Essentials 513T Mini Piezo Siren

We found 4 Reddit comments about Install Essentials 513T Mini Piezo Siren. Here are the top ones, ranked by their Reddit score.

Mini Piezo SirenDesigned as a pain generator, keeps thieves from sitting inside the vehicle while siren is activeWorks great for motorcyclesCan be used as a "pain generator" inside the vehicleProduces a loud alarm - To deter would-be thievesWorks great for motorcyclesCan be used as a "pain generator" inside the vehicle

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4 Reddit comments about Install Essentials 513T Mini Piezo Siren:

u/sharpsliceofmango · 12 pointsr/Shoplifting

This is a piezo siren

https://www.amazon.com/Install-Essentials-513T-Piezo-Siren/dp/B0009SUEX6

Its probably connected to an alarm system with motion sensors that is armed when they close the store for the night.

u/Australiapithecus · 6 pointsr/AskElectronics

Firstly, as /u/PotatoPotato142 has pointed out, a little 9v battery hasn't got a hope of operating that horn. (I assumed you knew that and were using a suitable battery; my bad).

You'll need a car/bike battery or similar that can supply a few amps. More than the current rating of the horn itself, in practice - since a horn is basically switching on and off at its operating frequency, peak current will be higher than the average current. I guesstimate maybe 4x or more.

> From my understanding, once you apply at least 0.6V to the base, the collector-emitter basically become a straight wire, with a small resistance.

Nope. Transistors are linear (within reason/specs, and grossly oversimplified for explanatory purposes) devices, not switches.

Again, grossly oversimplifying for explanatory purposes (and stating that to avoid a repeat of the whole "are transistors voltage- or current-operated devices?" academic argument 😉):

Below ~0.6v or so (depends on transistor type/size/construction) base-emitter voltage, they're off / open circuit.
Between ~0.6v and some upper limit (again, depends on …) they act sort of like variable resistors - as the base-emitter voltage (which also means higher base-emitter current) increases, the collector-emitter 'resistance' decreases.
The ratio of that change (i.e. base voltage to 'resistance') is the Hfe, or 'gain', of the transistor.
At some point they 'saturate', reaching their minimum 'resistance'.

You can use them as switches - in fact it's pretty common, especially in digital/logic circuits - but you need to drive them into saturation.

Now, you said "with a small resistance". Define "small" 😉.

Because, for a MJE3055, that "small resistance" at saturation amounts to ~0.8Ω. Which does seem quite small - but Ohm's Law will tell you that, if your load is drawing 10A, that 0.8Ω will drop 8v across it.

And to drive it into saturation, you need to raise the base voltage high enough. "High enough" varies somewhat with collector-emitter current, but in the case of a MJE3055 passing 10A, it means "high enough that there's 3.3A flowing through the base-emitter junction". I'll leave you to figure out the datasheet & do the maths on that 😉

NOW … having been through everything and said all that: have you thought about using a piezo siren like this? (No affiliation; simply the first one that came up when I searched Amazon for "piezo siren'). Ear-piercingly loud little f'ers, and commonly used in portable movement/theft alarms like you seem to be making. They'll even usually operate off a 9v battery for a few minutes before draining it…

u/Tec_ · 2 pointsr/CarAV

Are you talking about this

Clifford is a Directed Electronics brand and that's a Directed part.

u/Foruncande · 1 pointr/homedefense

Get this little alarm that hooks up to your alarm system. It's incredibly loud and next to impossible to sit in the car with it going off. You'd wake up if it went off.

https://www.amazon.com/gp/aw/d/B0009SUEX6/ref=ox_sc_saved_image_13?ie=UTF8&amp;psc=1&amp;smid=ATVPDKIKX0DER