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Need some help with amplifying a sound

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large_ghostman

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I am still going to mess with a 741 at some point, i make make a tiny amp just to make any sounds the controller makes (like door left open alarm) a little bit louder (no need to be deafening! just a bit louder than the pic can do on its own)
 

audioguru

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In North America the sirens on ambulances, fire trucks and police cars sweep the frequencies, the sound does not just jump between two frequencies like in Europe. The sweeping sound can be heard well during background noises and echoes.

I know what. A big dog. Train the dog to bark when the light burns out.
There is a big dog living pretty far from me. It hears a siren long before we hear it and it "copies" the sweeping of the frequencies.
Do any European dogs go, "doo, dee, doo, dee" like your sirens?:D
 

large_ghostman

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In North America the sirens on ambulances, fire trucks and police cars sweep the frequencies, the sound does not just jump between two frequencies like in Europe. The sweeping sound can be heard well during background noises and echoes.

I know what. A big dog. Train the dog to bark when the light burns out.
There is a big dog living pretty far from me. It hears a siren long before we hear it and it "copies" the sweeping of the frequencies.
Do any European dogs go, "doo, dee, doo, dee" like your sirens?:D

Our dog doo dee doo dee all over the kitchen floor last week! i like sweeping frequency idea,this is now just to make a small increase in the sounds i already had planned. Also a while back i had one of those 8 Ohm speakers from a pc, hooked up and working on a pic, but when i think about it now, it seems like a bad idea. I mean 5V output from pic (ok its a frequency like pwm, not straight DC) but 8 Ohms, so that is
625 mA, I also think it has to be an inductive load? (not sure, but pretty sure it must be as its a coil, yes Inductive, magnet and a coil, so gotta be inductive). No idea why the pic didnt blow the pin's, unless the driver fets and diodes inside clamped it somehow????
Anyway my point is, even if i use that chip we dont talk about, and use one of the circuits above (or like it), then its going to be better than doing it straight from the pic. Power wise????? dose not matter, it is a signal for different things no need to be loud. Also i have never done any opamp amplifier stuff, so yet another little chance to learn something.Should be ready to try out new heaters tomorrow.

forgot to add i am off to bed now, but will try and get a chance to sim those circuits tomorrow, see if i can use the sim to spot which is better circuit! looking forward to trying that out, always good to see if you can put things you learn into practice.
 

audioguru

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The maximum allowed output from a PIC is only 25mA which is no good to drive an 8 ohm speaker.
You need a powerful amplifier and a penetrating sound to be heard in another room.
 

alec_t

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.... and you won't get much out of a 741, either.
 

audioguru

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A 741 opamp can drive a load as low as 2000 ohms. But nobody makes a 2000 ohm speaker (maybe the piezo transducer in a beeper?).
Most 741 opamps do not work from a supply as low as 5V. From a 10V supply its output will swing maybe 6V peak-to-peak which is 2.12V RMS.
2.12V RMS in a 2000 ohm speaker produces the "very loud" output power of 0.002W.
 

large_ghostman

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Sorry guy's i didnt explain very well. The loud alarm isnt now needed (it is, but short term i have sorted it), for a loud alarm i will use a smoke detector , the other sounds are just like a heart beat type bleep, and when the incubator door has been open too long (say while candling), and mostly general type stuff, those dont have to be loud, and is probally a better way to drive a small speaker, rather than directly from a pic. Then it also link's the datasheet to the real world, i can mess with the 741 and see what effect different low specs have, rather than just read that it does x or y because of z, i will get to see how it's limitation's relate to the real world. the i can alter stuff, and eventually use a different opamp and see why the specs make it better
 

cowboybob

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We had a old velleman thermostat kit, i took the thermistor out and added a LDR, so when light goes out, the relay on the board triggers, this is now wired to mums radio turned up full blast :D. It will do for a couple of days while i work on the whole thing, and get the new heaters in

Very elegant solution, LG.

I'm impressed...
 

large_ghostman

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thank you. took me a while tho to think of it:rolleyes:. Took ages to dawn on me that its just a comparator circuit, the chip dosnt care if it comparing voltage from a ldr or thermistor. the really hard bit was getting mum to give me the radio, i had to promise loads of time that i wasn't going to take the back off.
 

NorthGuy

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I have messages on all my hardware alarms sent to my cell phone. It is loud enough to wake me up at night and it follows me everywhere I go. Such alarm will let you know that something wenr haywire even if you're at school or anywhere else.
 

ronv

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Don't overlook the suggestion of the diode in post 10. The life goes way up as the voltage goes down.
 

large_ghostman

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I am in uk so I dont have the 120V option, I am now running a mixed system with a LSR to switch on a IR heat lamp if needed, It is taking a while to get the brooders built. The weather has been bad so dad has had, alot to do and i cant build the wooden frames on my own. But I will have it solved soon!
 

large_ghostman

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ok so after posting last I had a new heater blow!, we have had short (3-10 seconds) on and off all day.
There is another type of heater i mentioned before, these are elements designed for hair things, they run from 110V or 240V, so i might try those with a diode, or try to get a high wattage bulb (seems hard in uk) and run that with a diode.
The part about voltage down life up has got me thinking. Also i will look into how they make those suppression units you can get on the multi sockets. Anyone know whats actually in those?
 

4pyros

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If you use a AC heater with a diode you will get a quarter of the wattage.
 

large_ghostman

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ok i nearly said something stupid about resistor ladder! forget i mentioned it
 
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