Push and hold switch with delayed pulse

Thread Starter


Joined Mar 16, 2011
I have a small project and I am having trouble remembering how to do the simple stuff. It has been over 20 years since I have had to do any simple circuits. The downside of doing everything with microprocessors for 10 years and then moving into an IT position 15 years ago.

I have an existing third party module, that is a black box. It runs on 3-4 AAA batteries. Pressing a momentary switch causes the module to activate, playing sound and flashing a number of LEDs in sequence. This activity continues until you press the momentary switch again, which cause the activity to stop. To give more specifics it is a sound and light module for a 'toy' Star Wars light saber.

The problem is that the switch is way to sensitive. You just touch it and the circuit will activate/deactivate. So to prevent accidental activation/deactivation what I want to do is add a delay circuit in front of the module such that you need to press and hold a momentary button for a few seconds before passing along a pulse to activate the black box module. If the button is released before the push and hold time passes no pulse should be passed along. The push and hold time does not to be very accurate, but should be in the range of 2-4 seconds.

My thought was maybe an RC ramp up in front of a 555 timer. So when you press and hold the momentary switch the RC charges or drains. If you hold it long enough the 555 triggers a pulse that activates my black box module.

Limitations are that the circuit must run off of the same 3-4 AAA batteries and must be small enough to fit into the light saber hilt. So a 555, a transistor and a few resistors and caps will fit, but not a relay.

Does this sound like the right type of approach?