Twin T circuit wanted

Can someone supply a single transistor circuit that will give a damped sine wave when a pulse is applied? to emulate a bell sound

Reply to
default
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Damped? Do you mean compressed to a sequare wave?

You can do a 180 degree phase shift in a double T RC network how ever, that produces a sine wave. etc..

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ect.

Reply to
Jamie

Damped as in decaying, just like a bell.

Seems to me John Larkin or Jim Thompson posted something like this a long time ago. Searching didn't find exactly what I want. I'm building a set of mechanical chimes but wanted something to use until I work out the kinks - and test the pic timing.

Reply to
default

If you've got a PIC, why not use it?

Reply to
krw

The pic is just putting out de multiplexed pulses (only 4 outputs on the chip expanded to 12) to operate solenoids to strike chimes. Pics don't make sine waves very well without a lot of extra effort. The end goal is a mechanical chime system that can be programmed for different melodies.

I have a goal in mind, I'm not interested in changing the goal, and this is just a little side excursion to aid in testing.

Reply to
default

I did a bell simulator once, but I used several, three or four, damped-ringing LC resonators. A single one didn't sound very bell-like. Turns out that bells have a number of nearby resonant modes, each with not-quite harmonics. Complex.

The thing I did drove loudspeakers in the bow of a ship to go bong-bong-bong every 30 seconds in the fog, so a crew guy didn't have to stand there all night whacking a bell.

Why not use the PIC and a dac? The code would be interesting.

John

Reply to
John Larkin

A good bell sound takes the first, third, and fifth harmonics (three sine waves), with damping times of 1, 1/3, 1/5 respectively. It can be done with three LC sections and some buffer amplification, for the speaker drive.

Reply to
whit3rd

If all you're doing is debugging (getting the timing right), just PWM the chimes. Even a PIC oughta be able to handle that.

Right, so use the PIC, then throw away the code. It's often easier than building hardware, to be thrown away.

Reply to
krw

If you reduce the gain of the amplifier portion of the circuit you will get what you want

Reply to
David Eather

I once powered a CD4047 based oscilator driving a 50 ohm speaker from a 1000uF capacitor. it made a gong-like sound if you charged the capacitor and then used the capacitor to power the circuit.

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Reply to
Jasen Betts

It'll do pwm easily. A bell is a decaying sine wave (or two or three). frequency constant (although the harmonic mix may change as it rings) with the amplitude decreasing.

Sine wave is necessary for a good (clean) sound.

Yeah I guess. The project is intended for a specific purpose, but I figure I might just keep the test set and use it as a unique doorbell. Who wants to listen to boring Westminster chimes when you can have something like "Pictures at an Exhibition?" or something different each time it is used?

The ultimate goal is not to make noise - but to drive actual chime bars mechanically. I'm finding home-made strikers more of a challenge than I thought they would be.

Reply to
default

I want the finished product to have mechanical chimes, the electronic bells (twelve, with the ability to strike 2-4 at the same time, or strike one while another is still ringing down)

To get the timing for the music I thought a little excursion into electronic bells would be helpful, because the mechanical parts are unwieldy, and I haven't committed to a mechanical design I'm satisfied with - then I thought this might also make a killer doorbell . . . a bit of "mission creep" is setting in.

Reply to
default

Yeah. I tried that with a square wave and fet amplitude control, with a little L-C massaging on the output it doesn't sound bad, but it is too much hardware. Seems to me, back in the day, they used single twin T oscillators to get the sounds of drums, base drum and tom-tom, as well as bells from fairly simple one transistor circuits.

Reply to
default

A good bell sound is made with large heavy pieces of metal.

Reply to
default

Nonsense. You said you needed this for debug. It doesn't need to be perfect. If the PWM frequency is high enough... Store the waveform, if need be.

I'd rather hear nothing, but a simple "bong" beats them all.

Reply to
krw

,---------, | |5V .-. - | | --- | |4k7 | '-' === | GND ,-----------------------------o-----o | | | Damped Sine | .-.1M o-------o Out | | | | -> ~1Vpp | | | | | 10k 10k '-' | | ___ ___ || | |/ o---|___|---o--|___|--o--||---o---| BC547 | | | || |>

| --- | 10u | | ---100n | o------ | | | | | | === | | --- | || || | | --- 10u '----||-----o----||---' | | || | || .-. | 10n .-. 10n | | .-."Q"Pot | | | | | | | | | | PIC o------------' === === === Narrow Pulse GND GND GND to Ring

(created by AACircuit v1.28 beta 10/06/04

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Reply to
john jardine

To simulate the chimes, why not a PC with a sound card? There must be tons of suitable software around.

John

Reply to
John Larkin

MP3 player.

Reply to
krw

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Reply to
George Herold

I don't want to simulate, I want hardware making sound.

A PC for a door bell is overkill - and the real thing will be mechanical that is a design goal.

Reply to
default

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