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btec project - alert device

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danrogers

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Hi all, for my btec project I have to design (not make, but I want to make aswel) some kind of electronic solution to a problem.

My idea is to make something similar to a baby monitor, although instead of transmitting audio, it will pick up audio above an adjustable level, and wirelessly send a signal to the receiver that will sound a buzzer and flash a light.

This project is rather more advanced than some of the others that people are doing and I'm struggling to know where to start! I've just been looking at rf devices on the maplins website but im not sure what I would need or how to design the circuitry.

I have attached a simple block diagram hopefully to make this idea a bit clearer!

Any help/advice would be very greatly appreciated!


Any help/advice would be very greatly appriciated!

Regards,,

Dan
 

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  • Block Wiring Diagram Draft.doc
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My idea is to make something similar to a baby monitor, although instead of transmitting audio, it will pick up audio above an adjustable level,
OK, so the audio and "processing" stages of the transmitter need to amplify the input from the microphone, probably rectify it and add a bit of smoothing, then a comparator will compare the rectified audio with some adjustable voltage and set its output when the audio exceeds the limit.

and wirelessly send a signal to the receiver that will sound a buzzer and flash a light.
The output of the comparator can be used to enable the transmitter.
Probably the best thing to use would be a pair of the small licence free modules which operate around 433Mhz.
The output of the receiver can enable the buzzer and light.

OK, a few initial thoughts for you, the devil of course is in the detail.

JimB
 
Hi Jim! Sorry I've taken so long to reply. Thanks very much for your thoughts! Would **broken link removed** be suitable module's to use as they seem to be 433Mhz?

Do you have any idea on the type of amplifier I would need to process the microphone input? Also I've not used any comparators before so I'm not sure on that but I guess that would depend alot on the specs of the amplifier stages.

Any more advice?

Thanks :)
 
Hi Jim! Sorry I've taken so long to reply. Thanks very much for your thoughts! Would **broken link removed** be suitable module's to use as they seem to be 433Mhz?
Yes, that is the sort of thing I had in mind.

Do you have any idea on the type of amplifier I would need to process the microphone input?
Something based on an OP-AMP would be my first choice.
Something like a TL072 would be OK. You could use a 741, but there will be howls from the gallery here telling you that it is old/obsolete/poor performance!

Also I've not used any comparators before so I'm not sure on that but I guess that would depend alot on the specs of the amplifier stages.
Have a look here:
**broken link removed**
for information about comparators.

If you use a TL072, that is two OP-AMPs in one package, you could use one OP-AMP for the amplifier and the second OP-AMP for the comparator.

JimB
 
What will prevent false alarms from aircraft, police sirens and motorcycles?
 
Jim, thank you so much mate. I'm going to have a look through that link on comparators over lunch today.

TL072 sounds like a good choice if I can use the two stages correctly.

Do you have any thoughts on the recieving end of the system? I guess I could use the OP from the RF module to switch a latch of some sort on or possibly a timed latch?


Audio Guru, very good point that I havent put much thought into yet, but it will make a good subject to discuss on the project. I not sure but I guess I could put a sheild around the mic of some sort to try and make it directional?

Dan
 
Hi there,

No problem! A Btec is a qualification here in the UK, i think it stands for Business and Technology Education Council. Im retraining (at the age of 27) and doing an electronic engineering apprenticeship.
 
Any other thoughts guys? I'm waiting on some op amps and the RF modules, not sure what to do next for the best!
 
dan, I would suggest starting a new thread with ALL of the details of what you have and what you're trying to do, there have been no new posts here because we're still a bit confused about your intent, abilities and tools. Take a few minutes to collect your thoughts ideas and means on paper and then respond fully in a new thread with an appropriate title and links so that users can educate themselves about the specifics of what you're trying to do.
 
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