MK139 Operating delay and sensitivity

I have recently completed this circuit. I intend to use it in one-clap and pulse mode. I have two questions.

  1. The relay operates approximately one second after the clap - for my purposes (operating a stage effect) I need it instantaneous. Is the 1 second delay standard? Can it be adjusted by changing the value of a component? Or is a chip faulty or have I damaged a component in construction?

  2. The clap LED operates at low sound levels, the relay requires louder sounds. However, it seems that this sensitivity is variable and sometimes time-dependent. After a period of inactivity the relay operates at very low sound levels, which could cause difficulties.
    Is this behaviour normal? Is a chip faulty? Have I damaged a component (capacitor) in construction?

I’ve just built one and it behaves as you decribe. I will use the double clap mode to get around false triggers but this means a minimum cycle time of just over three seconds between pulses. To some extent I’ve got around this by adding a diode and condenser to the IC2 output in order to hold the relay closed for longer in pulse mode. So in effect I have an on time of 2 seconds and off time of 1 . I appreciate that this probably won’t help your application.

The circuit needs to detect a ‘silence’ after a clap, to avoid false triggering.
This explains why the relay only activates 1s after the clap.
The unit has ‘auto-sensitivity’. This means that it switches to a less sensitive mode in a noisy environment, again to avoid false triggering. It has been designed to work well in a living room without causing frustration due to false triggering. If you do not want this auto-adjust mode, remove transistor T1.
We can understand that this unit is less suited for stage. Did you try the ‘one clap’ mode ?

Hi Roadster (or anyone else).
I was interested by what you said about obtaining a longer pulse on the relay. I need the relay to operate for about two seconds when its triggered - any suggestions about what components need to be added or changed.

Many thanks in advance.