And now for something completely stupid. The Tweety Bird noise toy.

[nomadradio]

Now and again day-to-day life just drives me to do something stupid, if only for the sake of variety. This is a chore I have procrastinated for ten or fifteen years, maybe more. I'll guess that this wiring diagram for the traditional analog "Tweety Bird" noise toy has made the rounds over the last few decades. The CA3046 chip shown has been discontinued for a while. It's the most primitive integrated circuit you'll find. Only contains five NPN transistors. That's all. Two of them are connected together at the emitter, called a differential pair. I'm pretty sure this wiring diagram is correct. A guy who worked for me decades ago built a batch of them from this graphic and they worked. But it annoyed me that it isn't a proper schematic. Doesn't show me what's really going on.

That irresistible urge to do something stupid took over and I translated it into a proper schematic diagram.



Maybe. And that's my reason for posting it today. Free proofreaders. If you find an error, I'd be grateful to see what it is. My patience has been consumed, and I refuse to look at it any more for a while.

Yeah, I have a batch of this chip. Might just do something stupid like make some of these. But only if I think they'll sell.

73

 

[brandon7861]

I got bored and put it into CircuitLab. Everything to the left of the mouse cursor is the circuit posted above using discrete transistors (and a 100k output resistor to keep the simulation output clean).

Everything to the right of the cursor is an astable 555 with a low frequency and small duty cycle to produce a short pulse to the relay to simulate a button press. The bottom mosfet and associated RC keeps the relay off for a moment so the simulation can start before the button is pressed. The moment the switch (relay) is released, the capacitor across it begins to charge back up and that drops the voltage supplying the oscillator as it fizzles out.

Zooming in on the oscillation, it looks like


I have no idea if this is how the circuit actually behaves in real life, but I am tempted to put one together and find out. Just not tonight. If anyone wants a different point probed and the sim re-run, I can do that tomorrow at work.

 

[TM86]

Thanks for posting that, Nomad. Not sure I've ever actually heard that particular effect on the air but at least now if I do I'll know what's making it.

 

[AudioShockwav]

Apologies to Nomad
Thread cleaned
Back to the actual subject matter of the device.

73
Jeff

 

[midnight special]

Thanks for posting that, Nomad. Not sure I've ever actually heard that particular effect on the air but at least now if I do I'll know what's making it.

here is my tweety bird key up and noisemaker with echo turned on,,, i have had this closw to 30 years now,,, whoever made it did it dead bug style and shrink wrapped it,,

 

[TM86]

here is my tweety bird key up and noisemaker with echo turned on,,, i have had this closw to 30 years now,,, whoever made it did it dead bug style and shrink wrapped it,,

Thanks! Doesn't sound anything like I thought it would from the waveform posted up above.

 

[nomadradio]

That's definitely the right noises. A single pitch sweep up when you key the mike, and a repeating doo-doo-doo if you close the switch across the 10uf cap C1.

The circuit analysis made me scratch my head, but I never learned to simulate. My favorite simulator was always solder.

73

 

[brandon7861]

I could have done something wrong in the sim. Its not expensive software either, just an online sim with a cheap subscription. I should have just tossed one together to test it.

 

[nomadradio]

Finally got a wild hair to lay out this toy. Here's the first approximation. Green traces are on top, red on the bottom. I only use two-sided pc boards.

If someone finds an error here, please speak up. Probably won't try to order this one right away.

73

 

[brandon7861]

If someone finds an error here, please speak up.

I gave it a once over, looks good!