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How do I Boost Voltage on this simple circuit?

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richfan

New Member
Hi Everyone,

My dog keeps digging in my kitchen trash, so I decided to build a motion sensing alarm that I could place in the trash can! :D
So . . . I bought a "6 volt PIR sensor module" ( 276-033 ) from Radio Shack and a 6v Piezo buzzer and I hooked it all up with a six volt power supply. It worked but you can barely hear the buzzer. I'm guessing it's because the circuit board of the sensor module drops the voltage.

So then I bought a 4-5V reed relay and with that in there, it doesn't work at all because the module doesnt put out enough to trigger the relay. If I jumper the relay's signal terminal, the siren is plenty loud. So my question is, what the easiest way to increase the output voltage of the motion sensor? (I can't find a 1 volt relay! :mad:)

Any suggestions for a newbie?

By the way, in my frustration, hooked up a pressure sensitive switch to the buzzer and the dog no longer digs in the trash!!! :eek::D

Rich
 
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pcbheaven.com

New Member
First of all, you could place your trash in a bin that closes. :D

Just kidding. Well, what you lack of, is power. It would be better to have a 9V battery and use some 7806T to stabilise it to 6Volts @ 1A current. That would be enough. I hope you do not have some kind of buzzer that would require the whole power that NY demands to operate........
 

tcmtech

Banned
Most Helpful Member
One bullet cures all animal training problems!;)

If its still digging in the trash after getting shot.... :eek:

You have a whole new realm of problems to ponder on!:D
 

richfan

New Member
:D:D:D:D
That's too funny!!

OK, a voltage regulator (I had to Google 7806T). I'm not sure I understand how a regulated 6v into the module will increase the signal output from the module. Do you mean that the 9v to 6V regulated drop is different than the 6v I have coming straight from the old computer speaker power supply I'm robbed to do this project? :p

I'm sorry, I'm working off of my memory from high school electronics 30 years ago! :confused:

I would hook the regulated 6v up as power to the motion sensor module?

Thanks,

Rich
 

audioguru

Well-Known Member
Most Helpful Member
Add a transistor instead of a voltage regulator.
Use a properly calculated series resistor for its base. The PIR turns on the transistor and the transistor turns on the piezo buzzer. The piezo buzzer will be the same volume as when it has 6V.
 

pcbheaven.com

New Member
I see...

Well, this is an idea how to connect the 7806...


You said that the PIR and the buzzer are 6v rated. You need 6v stable. The 7806 will be powred with 9V and you will get an output of 6V for your things. This output shall remain stable at 6V as long as you do not draw a hell of a current. I hope it will be enough for your PIR and the buzzer or relay.

You could also use a transistor instead of the 7806, but the 7806 is dead easy to connect, just 3 wires and that's it, 6V out of 9 (or 12).

As you mentioned, the circuit brown outs when you draw a lot of current. I think that your speakers had a very small power supply. The 7806 can supply up to 1A.

What are the ratings for the buzzer the relay and the PIR?
 

audioguru

Well-Known Member
Most Helpful Member
The problem is with the PIR, not with the power supply. The power supply is already 6V and it is fine because the piezo beeper is loud when connected directly to the 6V.

A transistor is needed to amplify the feeble output of the PIR and drive the beeper with 6V.
 

richfan

New Member
Yes AudioGuru that's it!

Yes! I simply need a very low voltage/low current "relay" to switch a full six volts to the buzzer! That's what I was originally trying to do with the SPST Reed Relay. Can you make a suggestion on a suitable transistor, say from Radio Shack, and (I'm embarrassed to ask) how to make the connections? The only thing I can remember from 30 years ago high school electronics is that there are 3 pins, there are PNP or NPN types. Now I don't have the foggiest what that even means anymore!! :confused: (Google is my friend)

Thanks so much for everyone's help. I really appreciate it and my son is learning as well!!


Rich
 

mneary

New Member
Almost any NPN transistor (2N3904, 2N2222, BC537, etc) will do. Large ones are ok too. (TIP31, TIP121, etc.) 1k ohms from PIR output to base; Emitter to 0V; collector to buzzer (or relay if you prefer). You would like a small (1N914/1N4148) diode across the buzzer/relay; cathode on collector, anode to +V . Again, a big diode is OK (e.g. 1N4001 thru 1N4007 etc.)

[edit] The reason I chose 1k is that the app note for the PIR suggested 330 as a series resistor for a test LED. 1k should provide plenty of current (2-3 mA) for a typical transistor (gain 50 or better) to turn on. [/edit]
 
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Hero999

Banned
How much current does the buzzer require?

You need a transistor as already mentioned above.
 
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