Memo & OhmGuru
OhmGuru
Hey Memo, I was tweaking a 555‑timer based LED blink circuit the other day and discovered a tweak that cuts the duty cycle by 25% without changing the period. Thought it might interest you because the math is pretty clean, but the practical impact on power consumption is huge. What do you think about the trade‑off between a shorter on‑time and the total energy saved?
Memo
That’s a neat trick. Shortening the duty cycle reduces average current, so power goes down roughly in proportion to the on‑time. The trade‑off is that you’re losing some visibility or brightness, but if the LED is only a small part of the total draw, the energy saved can be significant, especially in battery‑powered gear. Just make sure the 555 still sees the same discharge path and that the timing capacitor’s charge curve doesn’t introduce glitches. Overall, if the aesthetic impact is minimal, I’d lean toward the lower duty cycle.
OhmGuru
Good call, Memo. I’ll drop a quick schematic in my mind: 555 with a 10 µF cap, two 100 kΩ resistors, pull‑up 3.3 V. If you replace one 100 kΩ with a 75 kΩ, the on‑time drops from 75 % to 50 %. The LED stays on long enough to be seen, but the average current halves. I did the math: P_avg = V²/R * duty, so halving duty cuts P_avg by half, ignoring the tiny quiescent current of the 555. Just remember the 555’s internal discharge transistor can get a bit hot if you push the duty too low – it likes to stay in the linear region, not the cut‑off. And if you’re on a breadboard, keep the wire lengths short, otherwise the 1 kΩ path can pick up interference. Happy low‑power hacking!
Memo
Nice breakdown, just watch that discharge transistor, keep the wires short and the timing resistor values clean – that 75 kΩ tweak really cuts the on‑time without messing up the period, so the average current will drop by half. Good call on the 1 kΩ path; a tidy layout will keep the noise low and the LED bright enough. Happy low‑power hacking!
OhmGuru
Glad that hits the mark, Memo. Remember, the trick is that 75 kΩ sits right next to the discharge pin; keep it on the same side of the board as the 555 so the 1 kΩ return is a clean, short stub. And if you ever want a brighter LED for the same power budget, swap in a low‑current driver instead of just tightening the duty cycle. Happy tinkering!
Memo
Got it—keep that 75 kΩ right beside the discharge pin for a clean return, and swap in a low‑current driver if you need more brightness without upping the power. Happy tinkering!