Instructables

Silence your digital watch for stealthy standardized exam taking

Picture of Silence your digital watch for stealthy standardized exam taking
Purpose: Silence your digital watch beeps and alarms. Following this modification, your digital watch will be permanently silent.

Method: Remove spring-diaphragm amplification

Target audience: This is especially useful for standardized test takers (MCAT, SAT, LSAT, GRE, etc.) and others who need the element of surprise in whatever they are timing.

Step 1: Get a cheap watch somehow

Picture of Get a cheap watch somehow
I paid the kind folks at the Walmart jewelery counter a visit. I traded my $9 for this fine Casio watch.

Perhaps you can find a digital watch around the house.

Step 2: Remove rear plate

Picture of Remove rear plate

You will likely need a phillips pattern electronic (watch size) screw driver for this. Flat head could also be improvised to work very easily. I highly recommend the Stanley 6-pack of screwdrivers with rotating top for convenience.

Step 3: Identify and remove small amplifier spring

Picture of Identify and remove small amplifier spring
In the image you will see a very, very small spring that connects to the piezo on the rear plate to give the watch an amplified beeping sound when you press any button. This mechanism should be conserved across most inexpensive digital watches.

Find and remove that spring and the beeping will stop. If you are lucky, the spring will simply fall out when you open the watch.

You could also remove the piezo that is glued to the inside of the cover but as you can see from my scratches, that is more difficult.

Step 4: Reassemble

Picture of Reassemble
Reassemble your watch by replacing the rear plate.

Test the buttons to ensure the beeping has stopped.

Step 5: Stealth mode

Picture of Stealth mode
You now own an experimental prototype Skunkworks F-117 watch. Best of luck to you
 
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Bongmaster1 year ago
actually the back plate is a piezo sounder, not a diaphragm. its is the thing making the sound, the spring is only the electrical contact. so all this does is disables the piezo by removing said contact.
so its not a "experimental prototype Skunkworks F-117 watch" its a watch with a disabled piezo ;)
ghwhitcher (author)  Bongmaster1 year ago
I wrote this all up as diabling the piezo but then I couldn't figure why it was a piezo if it had no electrical activity. I deduced that the spring just buzzed that piece and amplified it where a piezo should be turning it into a voltage. I didn't think there could be a speaker behind that plate.
its because that plate (the metal backplate and the ceramic disk together) are the speaker, the spring is the + and the connection where the backplate touches the metal on the watch workings (normally a bit bent up) is the - (or the other way round, probably doesn't matter X3 )..
also did u know a piezo speaker/sounder can act as a knock sensor? its what they use in electronic drum kits :)
ghwhitcher (author)  Bongmaster1 year ago
So piezo is grounded to the backplate and the spring drives it (or other way around like you say). I think the piezo still is a surface that acts like a diaphragm to amplify the sound though right? When I put my ear near the watch after removing the spring I can still hear an extremely quiet beep...

Like an automotive knock sensor? That's pretty cool about electronic drum sets
yea but the whole thing, as in the backplate, is the piezo, the spring is just the wire for it. its probably better to look up piezo's on wiki or something that wil give u a much better explanation than i can X3

in short a piezo is made up of ceramic disk on a metal plate normally a thin disk of brass or something,
there is no speaker behind the ceramic since the ceramic and the metal plate are the speaker itself. the metal is the negative side, and is wired thus, and the ceramic is the positive and is wired accordingly, connect it up to any sound source and u will hear it, wont be too good tho since its high range.

another use for piezo is in inkjet printers, the print head has tiny piezos in them that pulses to send the ink droplets onto the paper.. the pulse forces the ink out the nozzle.