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How can i combine circuits?

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Member level 5
Sep 29, 2009
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How can i combine the two circuits in a way that when the microphone is off only the photo diode will lit the led an vice verse? Should i use a pnp and npn at the outputs of the op amps?

why you are using two op amp and two NPN transistor,use one op amp and at PIN 3 connect photo diode in series one variable resistor , output of this op amp will be connected to NPN transistor at collector side in series you connect LED.

I'm using two because i have the LMV722M op amp
but this is a good idea, I'll use the first half as a preamp and second half as trigger
i will try it
PS: I've got a sound sensor (upper half of the circuit) and a light/dark sensor
In this case i have to find a switch to commute between three modes

Ok...if i use the op amp as preamp and comparator i will need more switches in my case - limited space - Using the switches i already have i will use each op amp as comparator for the trigger, one switch to toggle between sound and light sensor and one for light/dark. I think this conclude my space usage in the box. The only thing i am concerned about is "Will the circuit do the job?"
I'm waiting yours opinions.

you want to toggle between..
1.sound and light sensor and
2. one more switch is for light/dark
if so by sensor you are detecting light
if not then is that only for sound and light?
if you want to detect light i will suggest small circuit just put NPN phototransistor at collector side 2N222 transistor variable resistor across it and at output side use one relay .. i think by this your circuit space will reduce half only for light/dark ckt i am telling ok

SW1 Modes:
1. Light mode;
2. Sound mode.

When SW1 is in Light mode (sound mode is disabled) then with SW2 i can choose:
1'. Light activated trigger;
1''. Dark activated trigger.
with BPW34 photodiode

I'm building the circuit as we speaking...unfortunately i can do it only half an hour a day so maybe at the end of this week will be finish. I will let you know the result
PS: Instead of the transistor at the output of the op amp i will use a optocoupler.
I used the LMV721 in the circuit because i did not find a spice model for LMV722M that i will use it in the reality.

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