Help making small squeaker

[JGUN]

Guys,

I need help with what I would need to make a small squeaker device that would emmit random squeeks, like a mouse. Doesnt have to break ear drums loud, but would like some options there as well.
Would prefer the components be able to take below zero temperatures.

The "body" or enclosure to hold the components would be whatever size PVC pipe with end caps.

Would also like to see what my options are for controlling the unit for nightime use only.

OK, thats kind of the idea of what I would like to do, any direction on parts needed etc would be greatly appreciated.

Very willing to give more details if I have missed something important.

Would run off of a small 9 volt battery, AA, or AAA batteries preffered.

 

[KrisBlueNZ]

Hello and welcome to Electronics Point

Well, this is a new one! A device that makes random squeaks, put inside a PVC pipe, that can operate below freezing!

I guess a good start would be an MP3 player, playing a single long track consisting of squeaks at random intervals. You could make a circuit that makes squeaking sounds, but it would probably work out bigger than a minimal MP3 player.

You would need an amplifier and a small speaker. Digikey have a good selection guide at http://www.digikey.com/product-sear...s-ics/linear-amplifiers-audio/2556583?stock=1 for amplifiers. Reduce your options by selecting output power range of, say, 100 mW to 5W, and mono output type. This device looks good: http://www.digikey.com/product-detail/en/IS31AP4991-GRLS2-TR/706-1164-1-ND

It's rated to produce 1.2W into an 8 ohm load, with a supply voltage of 5.0V. It draws a quiescent (idle) current of 4.8 mA typically, which will affect your battery life. There are probably other devices available with lower quiescent currents. Another possibility to save power is to shut down the amplifier except when a squeak is being generated; you could use the second channel of the MP3 file to supply a burst of audio that can be detected by a circuit that powers up the amplifier during the squeak.

With battery power, you don't really have the option of making it "break eardrums loud". A lot depends on the quality and efficiency of the speaker.

I'm not sure how you would fare with running components below freezing. Generally, consumer-grade devices are rated to operate from 0~70 degrees Celsius (although that ISSI amplifier I linked to is rated down to -40). I don't know if you'll be able to find an MP3 player that's rated for below zero. Ditto for a speaker!

You want the unit to run only when it's dark? This can be done pretty easily using a light-dependent resistor: http://www.digikey.com/product-detail/en/PDV-P8103/PDV-P8103-ND. Some circuitry is required but it's not complicated.

What do you think?

 

[BobK]

Another alternative would be to use a small microcontroller. It could wait a random amount of time, then output a squeek as a varying PWM signal to a push-pull output stage, which is nothing more than 2 transistors, making a class D amplifier. You would use a wave table to approximate a mouse squeek, which you would have to analyze from a recording. Or, if the mouse squeek does not have to be that accurate, a simple square wave might do.

Bob

 

[BobK]

Just out of curiosity, this is not an offer, how much would you be willing to pay for something custom built to do what you want?

Bob

 

[KrisBlueNZ]

Good idea Bob! That could be done with a fast PIC with plenty of ROM for the waveform(s). You would need a pretty high PWM cycle frequency to accurately reproduce a squeak, but it would be doable. The dark detection could be done by periodic wake-up, enabling the LDR with an output pin and using an internal comparator. Sleep mode could be used in between squeaks. Average current drain could be tiny - it could run for weeks or months on a charge. Class D using low-Vgs MOSFETs with a bridge-tied load would generate a watt or two into a low-impedance load. Good thinking there!

 

[BobK]

Thanks Kris. And yes, a full H-bridge would give you 4X the power if needed.

Bob