Small Radio

Does anyone not reading my other thread have any ideas what the power drain would be for a very small radio?

I basically want an audible noise for as few milliwatts as possible, and run from a 12V lead acid battery.

TIA jack

Reply to
spamfree
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The 'few mW as possible' and 'noise' suggests to me - piezo. A lot of them are spec'd for 12V, too. I think 5mA (maybe a little more) would be typical. So 60mW, roughly speaking. I think a custom design would be able to do better on power consumption -- but those figures are for off-the-shelf and very cheap designs (about $1.)

Jon

Reply to
Jonathan Kirwan

Wow, thanks Jon. That's going to make things a lot less expensive and complicated. I could buy two, one for a spare :-) Any ideas what they would be called and what sort of outlets would sell these? I will try a google search for Australia. Thanks, jack

Reply to
spamfree

If you want to hear it I'd avoid piezo. Also, a bigger speaker will draw less power for a given sound output.

Reply to
Homer J Simpson

Thanks again Homer. All I can find so far are piezo earphones for crystal sets. Interesting about the big speakers. I've got plenty of them. Does the impedance affect the efficiency?

To be honest, all I want is a bit of noise audible at the front door, that gives the impression of someone being home. A crystal set that received several close stations would be fine, and whatever speaker I used I would tape to a panel of the front door to act as a sound board. Afterall, no-one will be listening to the information or music, and especially not inside the house :-)

I thought I read somewhere about piezo being augmented with a horn. Perhaps attached to my door panel? If I can get some 24/7 noise with

10 mA, I could run the thing for 4 weeks from a 12Ah battery with NO charging. So any charging would be cream on the jam, so to speak.

Thanks again, jack

Reply to
spamfree

Well, someone else thinks piezo are hard to hear. They use them in fire alarms a lot, so I have to disagree a bit on that point. However, they are higher freq (3kHz to 4kHz area) and if you have hearing troubles at high freqs, then they may be dampened a bit. Ambient environment can also make or break this.

They are called piezo alarms or buzzers. You need to be a bit careful, though. Some piezos are sold without the driver circuit, depending instead on you fabricating one. Those will be the really cheap ones. You want those that are ready to go, I guess. Go to

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and enter 'piezo' in the search. Then look down for 'buzzers' and click that. You can then select frequencies or current draw, etc. and do a further search. Or google these three words, piezo buzzer 12V. That will get you some web sites to examine, selling them.

Jon

Reply to
Jonathan Kirwan

Thanks Jon, I think I may have misled you with my term "noise". I really want the noise of habitation. Music, voices etc. An LED light will come on at dusk and go off at dawn, and 24/7 I want the sound of a muffled radio to be audible from inside the house.

At present, I'm leaning towards a simple crystal set tuner with a half watt amplifier kit driving a large speaker?

Any suggestions towards simplicity, cheapness, and above all, sound power to electrical power efficiency will be most helpful.

Thanks, jack

Reply to
spamfree

Genrally no.

A piezo type would be fine for that.

Reply to
Homer J Simpson

Won't fool the determined. Some alarm stickers on the doors and windows work better. A flickering blue light looks like a TV.

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Reply to
Homer J Simpson

Thanks Homer The determined will get in anywhere, but one must ask why they would be determined to break into a crappy old house amongst thousands of mansions.

That's a great idea about the stickers, although it might advertise that you have got something to protect.

The flickering blue light is pure genius. I wonder if there is a flickering LED array that could simulate a TV. That should be easy and cheap to incorporate. Thanks again, jack

Reply to
spamfree

Stickers are useless, unless the stickers are from a local alarm company. Lots of places with those cheap, generic flea market stickers get hit. In fact, its an advertisement that the owner has something worth stealing, but is too damn cheap to buy real protection.

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Service to my country? Been there, Done that, and I\'ve got my DD214 to
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Reply to
Michael A. Terrell

It eliminates the smash in idiots. They prefer to try elsewhere. Another tip is to find the biggest dog dish you can, bash it up so it looks well chewed, and write Tiny on the side with a marker.

Reply to
Homer J Simpson

Hi, Jack. The power requirement for your radio is going to be determined by the volume of the speaker. Your radio circuit current apart from that will be much less. An older 9V transistor radio I built many moons ago had a current draw with the sound turned all the way down of 30mA or so. That would be around 250mW, much less than the power required to drive the speaker loud enough to hear outside. Thatw ill probably take a few watts, at least. With the efficiency of audio outputs in general, you can depend on several watts consumed to get two or three watts at the speaker. Even with a DC-to-DC converter, that will mean around a 1/2A current draw from your battery.

Many small radios (particularly those that operate on 9VDC) have provision for an external car cigarette lighter adapter, allowing them to run directly off 12VDC. You also might want to look into this -- it would be less hassle than a DC-to-DC converter, and you won't have to worry about electrical noise from the converter causing problems.

I'd also recommend looking into a 12VDC marine battery, if you're buying one instead of scrounging it. They are made for deep discharge, and can put out the 1/4 to 1/2A you'll need (even with a DC- to-DC converter) for a longer time than an automotive battery.

Good luck Chris

Reply to
Chris

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