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Why is my 555 timer keyboard starting with noise? Answered

Hi!!! :/) I have made a 555 timer keyboard using a tactile button series with resistors, but rather than staying silent until I press a button, it makes noise as soon as I start it. All the buttons function properly, raising the note in intervals but it starts with sound. I have thoroughly searched my button/resistor series for accidental bridges between joints but have found none. This is my first "real" soldering/perfboard projects, so mistakes could have been made! Could there be any other reason for this noise? I cannot find somewhere else where the circuit may be completing. I have included the schematic I am using.

Any help would be appreciated ]:>) 
Thanks!!!!

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user
icengBest Answer (author)2017-06-02

To calm a 555 add a 0.01 to 0.1 uF capacitor to pin_5 and ground..

Another concern, is the wiring to the buttons which can capture radio waves and cause the sensitive flip-flops in the IC to trip if there is no calming cap...

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user
ToggleSwitch (author)iceng2017-06-03

I'll add that capacitor! Thanks!!!

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rickharris (author)2017-06-02

The output of the 555 is dependent on the charging and discharging of the capacitor C1. and resistor R5

When you turn on the capacitor has to go through a charge cycle to set the 555 times up ready for use. I expect this is where the noise comes from.

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ToggleSwitch (author)rickharris2017-06-02

I will try letting the capacitor completely charge/discharge.

Thanks so much!!!!

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