PIR sensor to activate a voice activated circuit

Thread Starter

2electrified

Joined Sep 5, 2011
30
@Scott, the schematic you modified with my circuit, are you saying this would replace the entire LM324N chip or just one of the quads its using? According to the specs on the LM324N this is a quad chip. Does that mean its using all 4 quads or just one and if its only just one part the chip how do I test to see which part of the quad its using?
 

ScottWang

Joined Aug 23, 2012
6,963
@Scott - I put a voltmeter across the red and black wires that run from the speaker to voice activated box and I am not getting any voltage reading. This is normal? Even when I talk into the speaker - the meter doesn't change. Thank for your schematic.
What you set for the voltmeter, is Vac or Vdc?
If you set it on the dc range then set it on the 20 Vac and 2Vac, and try it again, or if have the o'scope to measure it and can see the waveform more clearly.
 

ScottWang

Joined Aug 23, 2012
6,963
@Scott, the schematic you modified with my circuit, are you saying this would replace the entire LM324N chip or just one of the quads its using? According to the specs on the LM324N this is a quad chip. Does that mean its using all 4 quads or just one and if its only just one part the chip how do I test to see which part of the quad its using?
I' don't know the details of the device, and I'm just thinking if the device want to works then it should be have the circuits similar like that.

How is the LM324, does it put on the pcb of the voice system activated box?
If you want to know how the connections of LM324 then you should trace the connections of each pin.
 

ian field

Joined Oct 27, 2012
6,539
@Scott - I put a voltmeter across the red and black wires that run from the speaker to voice activated box and I am not getting any voltage reading. This is normal? Even when I talk into the speaker - the meter doesn't change. Thank for your schematic.
If you're using a speaker as a microphone, its a good plan to use a grounded base front end stage on the amplifier, it has a low input impedance that gives a better match to a speaker voice coil, it also does well on voltage gain.

There are some examples here:

http://ee.old.no/20/

The Philips kits generally used 150R speakers, which doubled as microphones in various projects.
 

Thread Starter

2electrified

Joined Sep 5, 2011
30
Thanks Scott and Ian for your input so far. I greatly appreciate it. I will let you know how things work out. I still may need to post a question or two in the future.
 
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