please give advice on my project. I am trying to determine if this is feasible, (money and effort wise).

goal:
I want to make a little white noise (or imitation white noise) maker. It will run off a single AA or AAA battery (possibly 2 batteries). Initially i just need a basic one with speaker and on off switch, and maybe a switch for high low volume. It will be used to soothe a baby (white noise has that effect on babies). Small design is wanted.

comments - concerns:
I am concerned with power usage, and want a design that is extremely simple and low power, with as few components as possible.
I don't know the difference between white and pink noise, and don't really care, as this will only be heard by the human ear and not used for random value generation.
I have found many circuits online that require multiple ICs but if I can get away with it I would rather have no ICs (they usually require at least one 9v battery too - which is bad for me)
Since I don't mind if it is not true white noise I have thought to use a recording and loop it, but I am thinking that would cost more to make than a circuit that generates the noise - is this assumption accurate?
I am not an electronics guy, so I don't know diddly, but I did once get a radio signal by connecting headphones to a diode, I want something almost as simple.
If you come up with any suggestions and in total it would cost more than $2 in components could you let me know the approx price please?

 

Hello.

What should be the frequency range?
Is it for audio use or RF?

Greetings,
Bertus

 

I can create a wav file for you containing x seconds of pink noise. You can play it with a mp3 player in a continious loop.

 

Hello,

White noise and pink noise are different.
http://www.ptpart.co.uk/show.php?contentid=71

Greetings,
Bertus

 

Hello,
White noise and pink noise are different.
http://www.ptpart.co.uk/show.php?contentid=71

As I learned pink noise is equal to band limited white noise source. As long as the signal is sampled the correct thing will be to call it pink noise.

 

EDN published a design using a single PIC 12F508 uC (microcontroller) that generates random noise.
http://www.edn.com/article/CA200385.html

This could run on two or three AA, C, or D batteries. The uC's themselves are less than $1. However, you would need to build or buy a PIC programmer. PICkit 1 kits run around $35, and can be used for many future projects.

 

The reverse breakdown of diodes is often used in noise generation. Here is an app note from Maxim that may be an interesting read. They use a diode and some amplifiers to increase the power level.

It doesn't meet the single AA or AAA requirement but it may be a good place to start...

http://www.maxim-ic.com/appnotes.cfm/appnote_number/3469

 

Whatever circuit you use to make white or pink noise needs an amplifier and a speaker for the sound to be heard. An amplifier driving a speaker needs a lot more voltage than from one or two battery cells and the battery will last for a short amount of time anyway because the speaker making sound is work being done.

 

Audio white noise is simple, but you want a speaker, which means amplification. It is the amplifier, not the WN generator, that takes juice and adds to the complexity. As was mentioned, a simple diode (zener) conducting electricity will make WN.

The other thing is voltage. You want low voltage and low current, but while it doesn't seem very loud, WN is every frequency going simultaniously. I suspect your batteries if their small are bound to be sucked dry in hours. The amount of wattage in two AA's is only slightly larger than a 9V, and ultimately that's where it is at.

 

You can build your own (there's lots of information on the web), but the easiest solution is probably to pick up an old, cheap AM transistor radio. Tune it to an unused station and you'll have a decent noise source. The TV used to be a nice source of white noise also after the stations signed off the air, but, uh, that was a few years ago...

Pick up a used wall-wart at the local thrift store, wire it to the radio, and you can just plug it in and run the radio from wall power. Much easier than messing around with batteries.

 

I like that one. If you get any pesky stations you can wrap in aluminum foil.

 

bertus - yes it is for audio
Bill_Marsden - I did not know that a speaker playing white noise would drain more juice
someonesdad - thanks - that is actually a perfect answer for me, except I want to make it cheap (to manufacture in bulk) and it has to be small enough to be clipped to a baby's clothing.

Bill Marsden brings up a good point about the white noise. And it makes me want to ask another question relating to the speaker & battery.
I know that 2 AA batteries would be about 5 Amp hours. Bill mentioned that it may only go for an hour, does that mean the circuit/speaker would pull about 5 amps!?

by the way thanks for your replies, very thought provoking.

 

Two AA alkaline battery cells can power an audio amplifier for 20 hours at 100mA (their capacity is 2500mAh at only 10mA and 200mAh at 100mA). But you will never find an audio amplifier that works from a battery as low as 2V to 3V.

Six AA alkaline battery cells make a 6V to 9V battery that can power an LM386 amplifier for 50 hours and the volume will be good.

Maybe you are thinking of making a squeaking low volume electronic greeting card?

 

You can do it with a CMOS logic chip, like a hex inverter. Use one or more inverters as a noise generator, then finally into 2 inverters as a push-pull output pair to drive the speaker.

You will only need some mW (maybe 50mW ?) at 3v to make a soft audible white noise sound.

 

Audioguru - thanks for your guru advice. the volume i am thinking of is similar to that of an iphone speaker, or a small transistor radio with volume at about half, which is not loud.

The_RB - sounds like that could be a good way to go, thanks for the lead.

 

Why would you want to clip a white noise generator to a baby?

 

You can do it with a CMOS logic chip, like a hex inverter. Use one or more inverters as a noise generator, then finally into 2 inverters as a push-pull output pair to drive the speaker.

You will only need some mW (maybe 50mW ?) at 3v to make a soft audible white noise sound.

Two Cmos inverters form a square-wave generator, not a white-noise (random frequencies) generator.
One Cmos Schmitt-trigger inverter forms a square-wave generator. It also is not random.

A 3V battery quickly drops to 2V which is too low for an ordinary CD4xxx Cmos IC. Even a 74HCxxx Cmos IC will have an extremely low output current at 2V and 3V.

 

You don't clip it to the baby -- you just place it near to the darling infant to mask out noises and help lull them to sleep. Trust me, you'll understand better once you're a parent.

 

Pointless and demeaning commentary deleted

 

Pointless and demeaning commentary deleted

Thank you for your useful input...