What is this electronic component?

[The Natural Philosopher]

The legend saying BUZ(zer) us a bit of a hint.;..

[Gordon Henderson]

Poor mans tap sensor. Done that before. The load cell on the main weighing platform could be used, but that would mean keeping the amplifier and ADCs going - which would quickly kill the batteries. A piezo disc thingy can generate a good enough spike to generate a wake-up interrupt to the microcontroller. I bet you have to 'tap' the scales, wait for them to zero then stand on them...

Gordon

[cd]

Nope, it's generating a voltage from the pressure applied to it same as a mic does. It's simply not being used as intended (so far as one can tell without seeing it).

[Dave Liquorice]

Legend comes from the PCB design software when you place a piezo transducer. B-)

I quite like the idea of it being a reference in a bridge measuring circuit. When you say the scales "didn't work" until it was back in circuit do you mean they didn't power up at all or powered up but wouldn't measure anything. If the scales didn't power up it could be the "tap" sensor.

[DerbyBorn]

"Dave Liquorice" wrote in news: [e-mail]:

The display was blank before I resoldered the component, It is not mechanically linked to anything - it hangs off the edge of the circuit board. To switch on the scales one does tap the platform. I had assumed the load cells were the key device here. I will try and check this out.

[DerbyBorn]

DerbyBorn wrote in news:XnsA4205C11296E5TrainJPlantntlworldc@81.171.92.222:

I think you have solved it. I picked up the scales so that the load cells would not sense anything. when I tapped the platform the scales switched on. Thanks

[Johny B Good]

That does seem the most likely explanation. However, our electronic bathroom scales make a beep once you've stood still for long enough for it to get a reliable average set of readings for it to hold the display at the measured weight reading (it might even beep to indicate completion of the zero calibrate phase but I can't recall whether this is the case without paying it another visit to test this hypothesis).

This too requires you to tap the front right hand corner to switch it on and allow it to calibrate the zero setting. I've simply assumed that it used that corner load cell to detect the wake up tap but strain guages, afaiaa, require current flow to produce their signal voltages so there might well be another piezo transducer simply to detect the wake up tap using a more economic circuit. Alternatively, the piezo transducer might be one and the same using some cunning circuitry to let it do double duty as both a microphone and a speaker.

BTW, I'd expect such a transducer, when used solely as a wake up tap detector, to have a small lead weight soldered/glued to the centre of its diaphragm to magnify its output when the vibrations are routed via its mounting to the circuit board. Since this doesn't seem to be the case here, that suggests the possibility that it's also meant to give acoustic feedback beeps to the user in regard of its readyness/captured reading states. Maybe the beep driver circuit has failed (or was faulty from new) in this case.

[The Natural Philosopher]

I' think you should let microphone manufacturers know this. They have been supplying microphones without lead weights for years.

There could be a Nobel Prize in it for you.

[Tim Watts]

No, his idea is valid. You are trying to detect subsonic, not audio, with a toe-tap.

[meow2222]

It works fine without a weight, so you think a business should spend time & money attaching weights? I dont.

NT

[The Natural Philosopher]

dont be silly.

[The Natural Philosopher]

Exactly.

[john james]

But we know that soldering the wire back on again saw it start working again, so it clearly doesn?t need any lead weight.

[The Natural Philosopher]

At best lead would act as an expensive mechanical semi-low pass filter. All of which is cheaper to do electronically.

even piezo gyros don't use lead weights. Piezos go down to DC as strain gauges ..

all that is necessary is that vibration gets to the unit.

which it will one way or another. Tapping is not subsonic anyway. Standing on it is.

[Tim Watts]

I didn't say it didn;t work. I said his idea made sense. What's wrong with that?

[Tim Watts]

I suppose you are the expert in scale design?

The thought process is not remotely silly. Heavier mass sensors work better at low frequencies.

[Tim Watts]

Clearly - but the suggestion is not daft - perhaps unnecessary.

[meow2222]

that's been explained

NT

[Tim Watts]

In that case, nothing.

[The Natural Philosopher]

i certainly am an expert in analogue circuit design, of which a scale is simply an example, and th characteristics of audio transducers, of which a piezo cell is an example.

No they dont.