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Simple PIR circuit, need review Answered

Hi,
I'm working on a simple circuit. The idea is to have a portable device that lights up when I stand up at night.

I have a PIR sensor that triggers 3 LEDS.
I use a LM741 as an OpAmp
The leds are type 3528. Though these LEDs are supposed to be powered with 12v, I'll use a 9v battery.

My main concern is the battery life, tha'ts why I use 100k resistors in stand-by, to limit the current.
R3 is used to fine-tune the threshold on the inverting voltage.

PIR outputs:
   3.3v when it detects motion,
   ?v otherwise (but yet >0)

Could anyone give me some tips or advice on how to improve my circuit?

Thanks,
Antonio

Comments

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mpilchfamily
mpilchfamily

6 years ago

IF your concerned about battery life then don't use a 9V battery. They do not have a good amount of capacity to start with .

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stills
stills

Reply 6 years ago

Hi,
the fact is that using 6 1.5v batteries takes much fore space. and I'm concerned about battery life, because, 9v batteries have low capacity.

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mpilchfamily
mpilchfamily

Reply 5 years ago

Yes 6 AA batteries would be much better then a 9V battery. Sure it takes up a lot of space but if you want better capacity using standard batteries it will take up space and add weight. Now if you go with a lithium Ion battery you can get better capacity at smaller sizes and lower weights.

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stills
stills

Reply 5 years ago

And what about the circuit? No matter wich battery I use the question remains the same.

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mpilchfamily
mpilchfamily

Reply 5 years ago

The LEDs need 12V So you give then 12V. You also need a current limiting resistor in line with the LEDs. Otherwise they will pull as much current as they can till either they give out or the battery does.