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Delayed One-Shot Pulse Timer Module

by tomparsons2

Published on December 4, 2015

This circuit generates a single positive pulse after a prescribed delay.  The length of the delay and the pulse width are independently adjustable with the potentiometers.  This module is required in order to activate the i25 MP3 player bit and/or the i17 timeout bit just by powering up the circuit.  The MP3 player and timeout bits require a pulse going from zero to 5 volts in order to trigger them.  Simply turning power on to a littleBits circuit doesn’t provide this zero to 5 volt pulse, so I created this module.

I’m working on a different project where I need the MP3 player bit to start playing when the power is first turned on, rather than requiring a pulse from a pushbutton or other input sensor.  This module provides the necessary pulse upon power-up.

One example application might be where you plug your littleBits circuit into an outlet controlled by a light switch.  When the light switch is turned on, the littleBits i25 MP3 player will start playing track one.  Alternatively, turning on the light switch could trigger an i17 timeout bit set in either the on-off or off-on mode.  Or, you could use the pulse from this module to activate an output for a certain duration.  For example you could activate a pulsating littleBits horn for 20 seconds whenever the light switch is turned on.  This module makes this possible.

Duration: 2 hours

How To Make It


Assemble Circuit on the Board Assemble breadboard with electronic components, per schematic drawing.  I used one Megohm (max) potentiometers which allow the delay and/or pulse to vary from zero to approx 20 seconds.  If you want a longer delay, install a higher resistance potentiometer (or fixed resistor).
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Connect board to Proto Connect breadboard to Proto module (remove center jumper on Proto).
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