DC Dual Flasher Circuit

The DC Dual Flasher Circuit was primarily intended to operate as the flasher unit for the railroad crossing signal. Since its inception in the Basement, the flasher circuit has gone on to powering solenoids on pinball machines, strobe lights in model aircrafts and even flashing the lights on a school bus stop arm.

The DC Dual Flasher comes in two forms; A fixed flasher circuit set to a specific speed. The default speed is 45 flash cycles per minute, equivalent to the speed that a crossing signal flashes at. Of course you can customize it to cycle at any speed you like!

The Variable flasher circuit has a range of speeds, adjusted with a small trimmer resistor on the card. This is ideal for any project where a specific frequency is desired and cannot be achieved with fixed components alone.

Or perhaps the application calls for the ability to adjust the speed of the flash, such as a strobe flasher. The trimmer is then replaced with a panel-mounted potentiometer and you can adjust the speed within the designated range from a control knob.

The Dual Flasher circuit makes use of the 555 Timer IC which is a simple, yet versatile integrated circuit. The timer operates as an Astable Multivibrator and the timing for the cycles is controlled by the value of the two resistors and one capacitor preceding it. And then on the output, there are two driver transistors and one inverter transistor which give the flasher it’s left and right or top and bottom flasher channels. This flasher circuit is versatile itself in that it can be used in almost any DC application where the circuit has to be cycled on and off. Perhaps its only limitation is that the driver transistors are only capable of supporting 600mA per channel. But with more than half an Amp, that’s plenty to operate a dozen lights or more, or perhaps a pair of relay coils or even a medium power solenoid.

Connecting your DC Dual Flasher and Variable Flasher circuits is a snap! With compression terminals to fasten and secure your wires, simply strip your wire, slide it into the terminal and tighten it down with a small screwdriver.
Make certain when you connect power to your flasher circuit that you do not connect it to reverse polarity. Positive to Positive and Negative to Negative. And do not ever connect it to Alternating current! (AC)

Typical connection illustrated here.

Alternate connection illustrated here.

And this connection illustrated here is used when you must use two different power sources. (i.e. 1.5 volt lamps)