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I have a data terminal project that will gather user info via a membrane keypad. I would like to include some form of feedback to the user.

I could do this with the LCD character display (I guess?), but I'm wondering if anyone has a good recommendation on a piezo-type PCB- mounted (through-hole for now) beeper that I can trigger after each user keypress.

The ones I tested in the shop are WAY TOO LOUD!, even the 5-volt variety. I've seen (heard) these used before. What do folks use?

Also, I could ditch the piezo and go with a tactile membrane keypad, but I'm sure that adds more cost, and I'd like to keep it inexpensive. (But that said, I would use a piezo if "cheap enough", which I understand is a relative proposition.) Any ideas?? Thanks!

-mpm

D from BC · Accepted Answer

Piezo too loud??Is that the type with the built in oscillator?Perhaps use a raw piezo driven by a gated oscillator and vary theamplitude to taste.Ex: Schmitt oscillator + attenuator + watch piezoChoice of frequency will also have an affect on loudness perception.D from BC

mpm · Answer

Maybe I should have said "Sonalert" instead of Piezo. Yes. WAY too loud!!

I'll have to dig up the part#, but the one I used was a little round blue thing, about 0.75" diameter, maybe 1/2" tall. A watch piezo might work. didn't think about that. Aren't they flimsy to solder, though??

-mpm

D from BC · Answer

k..got a better idea..(If soldering on a watch piezo is a pita..)I think most computers have a piezo..With wires attached already!If the computer doesn't need to beep.. Borrow the piezo for testing.These days, I think it's only there to alert users that the CPU isoverheating due to coolers clogged with dust.That or... mod the Sonalert or check Digikey for a raw piezo withwires attached*.*I don't know if Digikey stocks that.D from BC

Michael A. Terrell · Answer

How about a piece of packing tape over the opening in the Piezo?-- Service to my country? Been there, Done that, and I've got my DD214 toprove it.Member of DAV #85.Michael A. TerrellCentral Florida

Gordon S. Hlavenka · Answer

Pager motor. Almost silent, but unmistakable tactile feedback. Costs under a buck.

I set up a demo using both a pager motor and a small solenoid that "thumped" the back of the keypad. The combination felt almost exactly like getting a mild electric shock :-)

PopMed · Answer

Most Sonalerts that I've run into are loud =3D 85 to 95 db or extra loudThese are difficult to attenuate mechanically because of the multiplelargesound ports.  Radio Shack sells a much softer piezo buzzer which putsout 70 db.The sound is emitted through a single hole which can be furthermuffled withclosed-cell foam or tape (paper to plastic to metal depending ondesired levelof attenuation).  It's designed for thru-hole PCB mounting and israted at 12 voltsthough will likely run at 5 volts.  Cat no. is 273-074, stocked atmost RS storesand goes for $3.49 US.They also carry a piezo element without drive circuitry for $1.99 cat.no. 273-073.Leads are already connected and drive could be supplied by a pair of555 timers togenerate audio pulses.  Better would be a $1 PIC with ZERO externalcomponentsto drive it with software (adding 2 tone beeps and raspberries wouldbe trivial).  PICswork happily down to 3 volts or less.  You might also be able togenerate drive-pulses in your logic circuitry. ...

mpm · Answer

Actually, I found several piezo's there last night. For example:

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How do you drive these things with a uPC? Can I just bit bang it, or apply DC. (5 volt, 20mA or less max avail from port pin)?

As for mounting, can I just stick it to the case with a dab of silicone? tape? I do not want to tool an expensive cabinet with mounting tabs, etc...

-mpm

John Larkin · Answer

Snap domes are cheap.John

Brendan Gillatt · Answer

You could light up the edges of the keyboard with some SMD LEDs - makesit look all futuristic and swish too ;]- --Brendan Gillattbrendan {at} brendangillatt {dot} co {dot} uk Key:

Frithiof Andreas Jensen · Answer

"mpm"  skrev i en meddelelse news:If *I* am said user - or sharing the office with one - then glue will find it's way into that piezo b****! ;-)Tactile is the way, I.M.O.!!

John Fields · Answer

---You don't want just a bare piezo bender, you want one mounted in ahousing.--- ---The kind you're looking at don't have an internal oscillator soyou'll either have to bit-bang it at its resonant frequency or use agated hardware oscillator to drive it.  Both at about a 50% dutycycle.If you want to bit-bang it, it would probably be a good idea to doit like this: (View in Courier)                  +V                  |                [BUZZER]                  |                  CµCI/O>--[4K7]---B 2N3904                  E                  |                 GND---Get one with a flat rear surface or a flange mount housing and youcan RTV it or use double-sided sticky tape to secure it anywhere youwant.-- JF

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