# help with dog whistle using 555 timer

Discussion in 'General Electronics Chat' started by itel933, Sep 9, 2010.

1. ### itel933 Thread Starter Member

Aug 26, 2010
38
0
I buillt this dog whistle,I replaced the potentiometer with 4 momentary switches inline with a resistor. (each button has a different resistance on it, thereby creating a different tone) they are connected with a common to the trigger/threshold pins on the 555 timer

when I powered on the timer and pressed a button I am getting the same tone, regardless of the button pressed. is there a way to make it so that each button isolates the other resistors (i think that since they all share the common that I am getting all the resistors to working together)

Is this possible with the 555 timer or do I have to use another IC?

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2. ### hgmjr Moderator

Jan 28, 2005
9,030
214
So you have replaced the switch in your schematic with four switches each switch with its own series resistor. If I have interpreted your hookup correctly, all you have done with the different resistors is to change the voltage that powers the 555. That will not have much effect at all on the frequency.

hgmjr

3. ### itel933 Thread Starter Member

Aug 26, 2010
38
0
no I replaces the Potentiometer, not the on off switch

4. ### eblc1388 Senior Member

Nov 28, 2008
1,542
102
What is the four resistor values you have used that is each controlled by a momentary switch?

Go here: 555 Calculator and put in the resistor values and get back each of the output frequency.

Is it possible that the resistance values are so closed together that the frequency change is only slightly?

PackratKing likes this.

Mar 24, 2008
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6. ### Bernard AAC Fanatic!

Aug 7, 2008
4,172
396
Messey, but may be possible: bias neg. input of a comparator to about 3/4 of +V; on resistor side of SW, connect anode of 1N914, cathode to .01 μF, other side to ground. Bypass cap with 10M- 22MΩ. Connect cathode- cap junction to + comp. input. With SW open comp. should be low, SW closed + will go to almost +V, causing output to go high. Frequency will be slightly altered.

7. ### ale2121 Active Member

Mar 20, 2009
71
0
the switch in this schematic (between pin 4 and the +voltage), is simply turning the circuit on and off. I believe you should be putting your tone switches, along with resistors, in between pins 7 and 8.

8. ### Audioguru New Member

Dec 20, 2007
9,411
896
The 10uF capacitor feeding the piezo transducer is not needed because the piezo transducer is a capacitor.
The 10uF capacitor should bypass the 9V at pin 8 and pin 1 or between pin 4 and pin 1 of the 555.