Build Your 4017 Decade Counter – A Brilliant 9-Step Sequence

Description

This innovative circuit incorporates a pulsating LED as the timing signal for a 4017 decade counter. Common flashing LEDs, such as DSE category Z-4044, exhibit a typical flashing frequency of approximately 2Hz, resulting in the outputs Q0 through Q9 cycling through their states at this rate. Specifically, Q0 will illuminate for a duration of roughly half a second, followed by Q1, Q2, and so on, until Q8, after which the sequence restarts from Q0. A maximum of nine outputs are available for utilization. For a reduced number of outputs, connecting an earlier output to MR, pin 15, is possible. If MR is not implemented, it should be connected to ground (0V).

Circuit diagram:

Potential applications for this circuit include controlling distinct sets of holiday illumination, for instance, Christmas lights. The resistor between CP0 and ground can range from approximately 330Ohm to approximately 10kOhm. Lower resistance values will enhance the LED’s brightness if desired. With a 4.7kOhm resistor applied to CP0 (pin 14), the clock input will alternate between voltages of roughly 2V and 7V. For driving loads capable of delivering up to 40W at voltages up to 60V, each output can be connected to the gate of a 2N3055E or equivalent MOSFET (MTP3055E, for example), as depicted for Q0.

More about components

The 2N3055E MOSFET represents a crucial component within this design. This N-channel MOSFET is a three-terminal device frequently utilized for switching and amplifying current. Its source and drain terminals provide pathways for current flow, while the gate terminal is controlled by a small voltage signal, enabling the MOSFET to switch between conducting and non-conducting states. The MTP3055E MOSFET is a direct equivalent, performing the same function. The selection of the MOSFET depends on its voltage and current handling capabilities to ensure appropriate operation within the circuit's specifications. It is important to verify these parameters before use.