Tone Decoder to Latch - Sensitivity

Thread Starter

PointyUK

Joined Sep 22, 2013
9
Hi All,

After a bit of googling I managed to cobble together the following circuit...
which works as required, I am however trying to make it as versatile as possible and allow plenty of adjustments/tuning.

I can adjust the mic gain with R5 and the tone required to activate the LM567 with R7. I know I can replace R9 with a pot to adjust the latch output time. What I don't know is how to change to number of pulses/length of pulse needed to activate the latch.

The tone the mic is picking up can be anything from a single beep which is about 200ms in length to a constant stream of beeps that sounds like a continuous tone. The circuit fires fine on a single beep, so what I would like to do is be able to adjust it so that it only fires on 5 beeps or a continuous tone of about 1 second.

Finally I had to put much larger values for the Power-on reset for the 555 than the suggested norm (10K/0.1uF) to stop it firing on power up. Any ideas why?

Thanks in advance for any help you can give a newbie.

Les
 

bertus

Joined Apr 5, 2008
22,270
Hello,

Did you use any decoupling capacitors at the chips?
Decoupling or Bypass Capacitors, Why?
For the NE555 I would use a 10 μF capacitor paralel to a 0.1 μF capacitor,
as the NE 555 is well known to have a harsh influence on the powerline.
Without them the circuit will act unpredictable.
Perhaps that is why you needed to "adjust" your reset circuit.

Bertus
 

Alec_t

Joined Sep 17, 2013
14,280
so what I would like to do is be able to adjust it so that it only fires on 5 beeps or a continuous tone of about 1 second.
You could perhaps have a pulse integrator between the 567 and the 555, so that each pulse from the 567 lowers the Trig input of the 555 step-wise.
Any ideas why?
Probably due to the charge time of C3,C4?
 

Thread Starter

PointyUK

Joined Sep 22, 2013
9
Hello,

Did you use any decoupling capacitors at the chips?
Decoupling or Bypass Capacitors, Why?
For the NE555 I would use a 10 μF capacitor paralel to a 0.1 μF capacitor,
as the NE 555 is well known to have a harsh influence on the powerline.
Without them the circuit will act unpredictable.
Perhaps that is why you needed to "adjust" your reset circuit.

Bertus
Thanks for the suggestion, I will add that to the design.

You could perhaps have a pulse integrator between the 567 and the 555, so that each pulse from the 567 lowers the Trig input of the 555 step-wise.
Not sure what you mean Alec, the 567 sends a low pulse, I just don't know how to make the 555 latch require a longer pulse to fire.

Regards,

Les
 

Alec_t

Joined Sep 17, 2013
14,280
Try this:-
Connect the 567 output to one end of a 33k resistor instead of to the 555 trig input.
Connect the other end of the 33k to V+ via the parallel combination of a 10uF cap and a 680k resistor.
Connect that 'other end' of the 33k to the 555 trig input.
 

Thread Starter

PointyUK

Joined Sep 22, 2013
9
Try this:-
Connect the 567 output to one end of a 33k resistor instead of to the 555 trig input.
Connect the other end of the 33k to V+ via the parallel combination of a 10uF cap and a 680k resistor.
Connect that 'other end' of the 33k to the 555 trig input.

Thanks for trying to help, and I am probably being stupid, but I don't understand. We seem to have 3 ends of the 33k resistor!

Maybe a drawing would help.

Regards,

Les
 
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