Whistle responder circuit

Thread Starter

Motanache

Joined Mar 2, 2015
537
http://www.learningelectronics.net/circuits/whistle-responder-schematic-circuit.html



I want to build this circuit, but his output will go to a micro controller.

First step
When I whistle to flash an LED

a) I not understand, how a logic gate is a use as operational amplifier (IC1A)
b) How do I change the filter to change the crossover frequency (IC1B)
c) Know such a scheme with fewer components ?
d) Instead of 4049 (NOT) can use CD4093(NAND)?
 

AnalogKid

Joined Aug 1, 2013
9,249
Many logic gates are simply very high gain amplifiers. It is important that you do not substitute another hex inverter for the 4049. This is one of the original CMOS IC's, before the addition of input protection and output buffers. The 4093 is one of my favorite parts, but it is the worst choice for this circuit because it has a buffered output stage (that's why the part number always ends in B) and it has an internal Schmidt trigger stage. This is a very non-linear section that will not pass low level audio.

When biased correctly, the 4049 makes a decent microphone amplifier. Here is how this type of bandpass filter usually is drawn:
http://www.circuitdb.com/?p=305
It is about as low a parts count as you can have for a bandpass filter. The equations to change the two cutoff frequencies are not simple. You can find them on the web if you really want to change things.

ak
 

Thread Starter

Motanache

Joined Mar 2, 2015
537
<It is important that you do not substitute another hex inverter for the 4049.>
Thank you very much for your answer

Unfortunately, I have only one store of electronic component in town and they do not have this IC.
I have on the table 74LS06.

Have to find another solution to make the circuit .....

Other circuit from 40 series tha are finding the store:
CD4001
CD4011
CD4013
CD4017
CD4020BE
CD4026
CD4030
CD4040
CD4060
CD4066
CD4066BE
CD4069
CD4098BE
The place where I want to introduce thi circuit is verry small.
I want tooobtain very small size.

1. Trying with a microcontroller?
2. To get an initial microphone signal amplification with transistors ?
3 And the band pass filter to make it all with a single transistor ?
 
Last edited:

MikeML

Joined Oct 2, 2009
5,444
This circuit is crying out for opamps. Since you are going into a micro, you do not need the oscillator and buzzer driver IC1 e & f or the transistor, so it could nicely be done with a quad opamp IC.
 

Thread Starter

Motanache

Joined Mar 2, 2015
537
"so it could nicely be done with a quad opamp IC."
OK.
I have TL074.
But power is only 5V.

I do not know if it will work well at this voltage. GND will be at 2.5V
 

MikeML

Joined Oct 2, 2009
5,444
stage a is a mic preamp
stage b is a bridged-T narrow bandpass filter
stage c makes pulses only when the amplitude of the filtered output is > than a threshold.
stage d rectifies and filters the pulses to make a logic level when the signal is detected.


What is the center frequency of the filter?

The TL074 is not suitable for low-voltage, single supply operation.
 

Thread Starter

Motanache

Joined Mar 2, 2015
537
"What is the center frequency of the filter?"
2KHz
"stage c makes pulses only when the amplitude of the filtered output is > than a threshold"
The amplitude of what?
At the output of a digital circuit where we have just 0-logical and 1-logical ?:(
R7/R8=aprox. 1/2

He expects to charge C4 as a whistle to be sufficiently long in time.

I probably do not know:
'before the addition of input protection and output buffers"

The output of these gates can also take continuous values?:eek:
 

Thread Starter

Motanache

Joined Mar 2, 2015
537
R4/R5=100k/200R ???????????????
This only to be more efficient filter at low signal?

After amplify the signal 'we' decrease it?

I want to understand how it works so I can use another IC
 

Dodgydave

Joined Jun 22, 2012
9,951
Unfortunately, I have only one store of electronic component in town and they do not have this IC.
I have on the table 74LS06.

Have to find another solution to make the circuit .....

Other circuit from 40 series tha are finding the store:
CD4001
CD4011
CD4013
CD4017
CD4020BE
CD4026
CD4030
CD4040
CD4060
CD4066
CD4066BE
CD4069
CD4098BE
The place where I want to introduce thi circuit is verry small.
I want tooobtain very small size.

1. Trying with a microcontroller?
2. To get an initial microphone signal amplification with transistors ?
3 And the band pass filter to make it all with a single transistor ?
use a cd4069 hex inverter
 
Last edited:

Alec_t

Joined Sep 17, 2013
12,065
The output of these gates can also take continuous values?
For the special case of an unbuffered gate, i.e. the CD4049 or CD4069UB, yes. For the other gates in your list, no.
R3 tries to make the IC1a steady state input voltage the same as the output voltage. Because IC1a is merely an inverting amplifier, this results in both voltages being at the gate switching threshold, i.e. about half the supply voltage. A slight change at the input (due to the mic) results in a big change at the output.
 

Sensacell

Joined Jun 19, 2012
2,821
I built a whistle remote control around an LM567 tone decoder IC many years ago, worked well.
I don't think you will achieve enough reliability with a single stage band pass filter, loud noises will still wreak havoc.
 

Thread Starter

Motanache

Joined Mar 2, 2015
537
I built a whistle remote control around an LM567 tone decoder IC many years ago, worked well
Please give me details. I do not want to do unnecessary experiments, if you know how to do.


What I tried ...:
- I did a tone generator ~2KHz with a small speaker
- I did this preamplifier:
(instead a piezo I used a microphone, powered correctly)


- The result I saw with the soft Visual Analyser:


Only 5 cm away from the transmitter, the reception frequency can be distinguished from the noise !!!!
And that after using two transistors for amplification !!!!

An integrated solution would be super!
LM324 si 4069 remains to try them.
 

Thread Starter

Motanache

Joined Mar 2, 2015
537
I bought HEF4069UBP.
The first part, signal amplification, goes very well.
Instead of R3=4M7 I put 1M5, I had no other resistor.

However, the gain is good, may detect the signal at 2m from the sound source.

The second stage, the filter did not work. I had no signal output.
 

Thread Starter

Motanache

Joined Mar 2, 2015
537
HEF4069UBP has not been very helpful.
Voltage gain around 30dB -> approximate 30X

And LM324 have 30x gain at the frequency of 20KHz.

I have not to get a "5V" amplitude !
 
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