How on earth do you one up 50 years of 555 timer projects? I have no clue. Regardless, it’s always fun and rewarding to put a little circuit together on a breadboard!
I can think of one application that is still potentially relevant today. I am going to experiment with using the 555 timer as a level translator.
Every maker, hobbyist and Tinkerbelle alike at some point attempts to interface a microcontroller with 3.3V outputs to a WS2812B (neopixel) which has a 5V referenced input. Perhaps the 555 timer can serve as the level translator in such a situation and save the day (assuming you keeps some in your parts kit).
As a first test I tied the both the trigger and threshold inputs low.
With no DC loads on the ‘CV‘ terminal, the threshold voltages internal to the 555 timer are 1/3VCC for the trigger input and 2/3VCC for the threshold input. When the active low reset input is input high, the 555 timer should output approximately VCC. The original 555 was designed with BJTs and consequentially has a TTL output that only rises to VCC minus 1 to 2 diode drops. When the reset input is driven low, the reset circuitry should override the trigger input and force the output of the 555 to be low.
I wired up one of my 555 timers of unknown provenance on a breadboard as shown in the schematic above
I have my doubts that is a genuine Texas Instruments IC (fingers crossed that some sweeet 555 swag might come my way :hearteyes)
I set my power supply to 16 V and input a narrow 3V reset pulse with my signal generator. The response of the 555 timer was captured with my oscilloscope:
Okay the 555 timer isn’t screaming fast. But, it is certainly fast enough for a WS2812’s 1 Mbit serial data protocol. However, the asymmetry in propagation delays is effectively stretching the input pulse width. This could be problematic for the WS2812’s pulse width signaling scheme. There is more to ponder on this topic.
TODO: I’ll mount a 555 to piece of copper clad and make some detailed timing measurements.
Of course, take this blog with a grain of salt. There are so, so many ICs available for logic level translation. But, if you have a stash of 555 timers in your parts bin, perhaps a 555 timer may be good enough. As a bonus, the 555 still comes in a breadboard/perfboard friendly 8-DIP package
Thanks for reading and take care!