| Author |
Message |
zbasicandy
Joined: 26 Jan 2006
|
|
| Back to top |
|
 |
GTBecker
Joined: 18 Jan 2006
Location: Cape Coral
|
|
Posted: 03 August 2006, 16:19 PM Post subject: Sound Sensor to ZX-XX |
|
|
| Quote: | Schematic of Sound Sensor R1
|
The LM741 does not operate well as a 5-volt single supply amplifier;
it's specification is 10v minimum. The 741 design (a god-send in it's
day) is 37 years old, I understand. A contemporary device will likely
work much better.
Tom
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
Posted: 03 August 2006, 16:54 PM Post subject: Sound Sensor |
|
|
For some unknown reason it works just fine in this application.
Total parts cost ~$2.00 plus Electret Mic.
|
|
| Back to top |
|
|
GTBecker
Joined: 18 Jan 2006
Location: Cape Coral
|
|
Posted: 03 August 2006, 19:23 PM Post subject: Re: Sound Sensor |
|
|
| zbasicandy wrote: | ... some unknown reason ...
|
Exactly. That is not good engineering. You've specified a part in an inappropriate - and probably inoperable - environment. If it works for you, that's not good enough.
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
Posted: 03 August 2006, 19:46 PM Post subject: Sound Sensor |
|
|
Again, we will stand on the merits of this design.
If you have a better low cost circuit please feel
free to post it on another link.
------------------------------------------
ZBasicAndy's neighbor
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
Posted: 03 August 2006, 20:05 PM Post subject: Sound Sensor |
|
|
| Quote: | | If it works for you, that's not good enough. |
To make Tom feel happy ... replace the LM741 with a CA3140E.
----------------------------------
ZBasicAndy
|
|
| Back to top |
|
|
GTBecker
Joined: 18 Jan 2006
Location: Cape Coral
|
|
Posted: 03 August 2006, 20:27 PM Post subject: Re: Sound Sensor |
|
|
If you want a challenge to your design, I invite you simply remove the amplifier, altogether. Connect the microphone directly to the rectifying/peak detecting diode. The opamp, even if powered properly, isn't configured for gain, anyway; it's just an inverting unity-gain stage, biased at 0.9v. Pull the IC and jumper pins 2 and 6, input to output. I'll bet that works just as poorly.
Assuming somehow the amplifier is working, still what you've done is biased the amplifier output to 0.9v above ground, then lost 0.7v of that to the series diode. Your smoothed peaks should be about 0.2v!
You built this circuit, you say, and it yielded peaks of a volt out? I doubt it. Am I wrong or just annoying?
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
Posted: 03 August 2006, 20:50 PM Post subject: Sound Sensor |
|
|
The LM741 with a CA3140E will both work.
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
| Back to top |
|
|
GTBecker
Joined: 18 Jan 2006
Location: Cape Coral
|
|
Posted: 03 August 2006, 22:14 PM Post subject: Sound Sensor to ZX-XX |
|
|
> ... please breadboard and test it thoroughly...
Wise.
Could you please describe how your circuit works? It appears to defy
rational design and requires some explanation, don't you agree?
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
Posted: 03 August 2006, 22:15 PM Post subject: Sound Sensor |
|
|
| Quote: | | Connect the microphone directly to the rectifying/peak detecting diode |
Tom's Design flaws
#1 The output of any Electret Mike is just a few millivolts! Good luck in trying to increase this signal to the ADC input without an opamp amplifier!!!! Elementary Electronics 101
#2. Impedance mismatch will occur if you don't interface the Electret mike properly. You will lose your signal. Elementary Electronics 101
|
|
| Back to top |
|
|
GTBecker
Joined: 18 Jan 2006
Location: Cape Coral
|
|
Posted: 03 August 2006, 22:40 PM Post subject: Re: Sound Sensor |
|
|
> ... GetADC(pinx,single) the value will range from 0.0 to 1.0 volts...
> ... The range varies between .35 to 1.0 using the GetADC(pinx,single)...
Which is correct? If the latter is correct, you've got a serious problem, Andy. It is not possible to produce a five-volt output from your circuit. I don't believe it will even yield a legitimate volt, so I doubt the former, too. Do you have a scope?
> ... without an opamp amplifier...
Your schematic shows R13 and R17 are both 1k. If that is correct your amplifier has no gain, Andy.
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
Posted: 03 August 2006, 22:59 PM Post subject: Sound Sensor |
|
|
From the original post.
| Quote: | | The operation of the sound sensor is very simple. The Electret Mic just outputs a few millivolts. The LM741 has a gain factor of ~1000 to feed into the ZX-xx analog input |
I did not review the schematic ... R17 should be 1 Meg.
I just fired my neighbor.
| Quote: | | Connect the microphone directly to the rectifying/peak detecting diode |
Tom's Design flaws
#1 The output of any Electret Mike is just a few millivolts! Good luck in trying to increase this signal to the ADC input without an opamp amplifier!!!! Elementary Electronics 101
#2. Impedance mismatch will occur if you don't interface the Electret mike properly. You will lose your signal. Elementary Electronics 101
Post your circuit when you ever get it to work.
|
|
| Back to top |
|
|
GTBecker
Joined: 18 Jan 2006
Location: Cape Coral
|
|
Posted: 03 August 2006, 23:03 PM Post subject: Re: Sound Sensor |
|
|
> ... R17 should be 1 Meg.
OK, that makes some sense (if the amplifier works at all). What about the output voltage? How do you get five volts - or even one volt - out of that circuit?
|
|
| Back to top |
|
|
zbasicandy
Joined: 26 Jan 2006
|
|
Posted: 03 August 2006, 23:38 PM Post subject: Sound Sensor |
|
|
The output is @ 3.06 VDC. When there is a loud noise the amplifer
amplifies the input signal 1000 times to several hundred millivolts RMS A.C.
Thats why we get a "signal range" from (single-float) .35 to ~1.0 on the
analog input. That's our circuit which works! If you don't believe us please
build this circuit yourself!
Now what about "your no gain" circuit that you designed that is
better with impedance mismatches, more expensive and works?
|
|
| Back to top |
|
|
|
