M8021-2 IC

This is a simple chip that will generate a bell sound. I tried Google, it shows lot of circuits using this chip, but no vendors. Anyone know sources for this part?

I am also interested in other cheap circuits to generate a simple bell tone. I know sonalert has a series that does it, but I would rather not spend the $14 I saw quoted.

This chip is available from the website below. But it says M-8021 "Ding Dong Door Chime IC" and doesn't have the -2 after 8021.

http://www.escol.com.my/ICS.html

Not sure about availability and postage charges...

Allen

 

I'll try the capacitor across the piezo buzzer idea. It sounds interesting.
Might even work for a 555 circuit.

A 555 should make more than enough current to quick-charge the cap each cycle. Be sure to use a series diode. I used a 4093 oscillator driving a PNP 2N4403.

ak

 

During the boring age in 1980, I was used the ne555 and two 74ls90, added some resistors and a small amplifier, also plus some resistors and LEDs, this will be a music generator and LEDs flashing show, today you may using ne555, CD4518 x2, some resistors, LM380, the output of CD4511 add the resistors and make it as voltage adder, and send the results to the LM380.

 

I was thinking of the cap across a CMOS 555 circuit. Something really quick and dirty.

 

Bill,

A couple options I have used.

Ken

 

I'll try the capacitor across the piezo buzzer idea. It sounds interesting.

Might even work for a 555 circuit.

Might not be quite that simple.

I suggest taking an example from the textbook drum synth circuit.

Usually a damped twin-T oscillator so the ringing deca

OK, second try. Evidently the chip I named is pretty close to unobtanium. Rather than start a second thread I've renamed this one.

Does anyone have another idea, such a op amp circuit or other?

Just trying not to reinvent the wheel.

Do you want to imitate a continuous ringing electric bell, or one you chime that rings and decays?

The prime suspect for a ring/decay bell is similar to the drum sound circuit.

Usually a damped twin-T oscillator.

 

I can get these sound modules from China. In less than a month if need be but I also run boxes on the slow route.

The small speaker makes it sound cheap.

You could use a PIC16F1709 it has D/A. the modules cost less than $1 I think and not difficult to obtain.

One taiwanese seller has these doorbells but he isnt at the lower end of prices, with enclosure its $5 or so + shipping.

 

Thanks guys, I want to build a really simple circuit for someone, one that softly chimes occasionally and lights a light when power is applied. It needs to be unobtrusive yet noticeable. Money is tight right now, time even more so, which is why cheap comes into play. Thanks for the ideas.

I bought a bunch of USB power bricks for less than $3 ea yesterday to power the sucker. I plan to disassemble one to see if it it a switcher or transformerless, I'll post pics on another thread.

If anyone is interested I'll post pics of what I come up with.

 

OK, first draft.

 

OK, first draft.

I have done similar circuits in the past. They did not sound very bell-like. I think most of the problem is with the decay waveshape. Also, a bell usually has more than one frequency. The multiple frequencies beat against each giving some "character" to the sound.

A friend did a bell sound for a model train crossing gate. He used a PIC microcontroller and had the project published in the October 2011 issue of Nuts and Volts magazine. He used a recording of a real bell sound.

Here are the files related to the project which includes the digitized bell sound:
http://www.nutsvolts.com/uploads/magazine_downloads/Train_set.zip

You may be able to find the complete article on-line.

 

$12.99 on eBay:

Beat me to it.

 

Beat me to it.

And still funny.

ak

 

Beat me to it.

Last time I played with an electric bell; I wired it in series with the low impedance winding of a valve TV vertical output transformer.

A senior member of staff at the school I was at was dumb enough to hold the wires attached to the high impedance winding while I pressed the bell push.

 

I've been playing with LTspice and come up with the arrangement below for a bell-sound with a decay envelope and tremolo. Doesn't sound too bad, and needs only a CD4049, a CD4066 and a handful of passive components.

When the button is pressed and held, C1 applies an envelope-control voltage which decays over ~ 1sec. This is summed, via Trim1, with a 20kHz triangle wave. The result switches CD4066 transmission gate U1a, thus providing PWM gain-control to a ~500Hz triangle-wave tone signal. R3/C2 filter out much of the 20kHz from U1a output, leaving a decaying tone signal. This is further modulated by a ~5-15Hz tremolo triangle wave in a similar PWM arrangement comprising Trim2 and U1b, then low-pass filtered by R4/C3. The trimmers set the modulation depth.
Each triangle-wave generator can be made from a couple of CD4049 inverters, like this:

The proof is in the pudding, so I've attached the simulation result as a .wav file (just delete the .txt extension).

 

PWM gain control? I would like to explore this concept on another thread.. I'm always interested in alternate forms of AGC (which is also a amplitude modulation technique).

My latest working schematic...