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Using a Bistable (Pulse) Timer

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Basic Pulsing LED or Bulb
Lets start with a very basic flashing LED (or bulb – just wire the same but remove the 1K resistor). If connected as shown to the NO (normally open) contact the LED will switch on for the time set by the PULSE VR2 pre-set, and the OFF time will be set by the PAUSE VR1 pre-set. The timer will start pulsing as soon as you switch power ON, it does not need a trigger, and will continue until power is removed.

Alternating Flashing LED’s
In this circuit we have added a second LED or bulb, so now the Green and Red will alternate, so when one is OFF the other is ON. By adjusting VR1 and VR2 you can have them flashing at the same rate as each other, or one ON longer than the other.

Pulsing Buzzer.
In this circuit we have connected a miniature buzzer to the NO (Pulse) contact so you can have a short Beep. By adjusting VR1 you can vary the OFF time of the buzzer.

Simple Welding Light Simulator.
In this application we are simulating the bright lights of a welding machine. An Ultra bright white, and a Blue LED are wired as shown. By varying the Pulse and Pause times it can be very effective, for a low cost. There are commercially available welding simulators available which will give a more realistic effect.

Light House Beacon Light.
In this circuit we are using a ultrabright LED as a light house search light. Because the light revolves in real life, and when it is not facing you, you just see a glow, we have added a second resistor in the NO (Normally Closed) contact. This resistor is a higher value at 47K which reduces the voltage to the LED. When the timer is in Pulse the LED just glows.

Simple Pelican Crossing
In this first circuit the Lamps in A & B come on at the same time. You will notice there are no resistors as these Lamps normally use a 12v filament bulb rather than an LED.

Simple Alternating Pelican Crossing.
In this circuit we have wired each lamp to a separate contact on the relay so that the lamps A & B alternate ON and OFF. Note no dropping resisters are used as these are normally 12v filament Bulbs.

In all the above circuits we have a second set of contacts that are unused. This could be used to give a repeat
indication back at the control panel if required.