KnowNothing & CapacitorX
KnowNothing KnowNothing
CapacitorX CapacitorX
KnowNothing KnowNothing
Hey CapacitorX, I’ve been tinkering with a little RC circuit that should keep a signal steady, but every time I hit the button the voltage does a weird jump. Do you think there’s a way to design it so it stays calm and doesn’t freak out? Maybe we can brainstorm a trick to tame the spikes together!
CapacitorX CapacitorX
Hey, that spike is probably the inrush current finding a path the first time the button closes. Put a small series resistor right at the input of the RC network—say 100 Ω to start. That will clamp the surge and give the capacitor a bit of breathing room. Make sure the capacitor’s ESR is low; a ceramic with a 10 µF value and a 100 kΩ resistor for the time constant is a solid baseline. Then measure the voltage at the node when the button opens and closes; if you still see a hiccup, add a small bleed resistor across the capacitor so it can discharge a little more gently. Keep the wiring short and shielded—tension in the wire can look like a spike. Once you’re done, log the values and the waveform so you can double‑check every tweak. If it still jumps, we’ll swap the capacitor for a low‑ESR type and re‑measure. Let me know the exact values you’re using.
KnowNothing KnowNothing
Sounds like a plan! I’ll grab a 100 Ω resistor, a 10 µF ceramic, and that 100 kΩ you mentioned. I’ll wire it up, watch the oscilloscope, and log the readings—maybe I’ll forget the values, but hey, that’s another learning moment! Let me know if I need to switch the capacitor or add that bleed resistor. Let’s keep it calm and steady!
CapacitorX CapacitorX
Good, put the 100 Ω right at the button contact, the 10 µF in series with the 100 kΩ to form the time constant, and the bleed resistor across the capacitor—start with 1 kΩ and see how the rise changes. If the spike still shows up, swap the ceramic for a low‑ESR type, maybe 10 µF X7R with 1 pF ESR or a 10 µF NP0. Keep the oscilloscope probe grounded close to the node; any floating ground will give you phantom spikes. Log the rise time and peak; if the peak is still above the expected 1.5× Vcc, add a small series diode to clamp the inrush. Once the waveform is flat, double‑check the values again—every tweak is a data point. Let me know the readings.
KnowNothing KnowNothing
Got it, I’ll start with the 100 Ω at the button, the 10 µF X7R, the 100 kΩ, and the 1 kΩ bleed. I’ll log the rise time and peak, but I might forget the exact numbers—oops! If the spike stays, I’ll try a different capacitor or add that diode. Let me know if I should double‑check anything else while I’m at it.
CapacitorX CapacitorX
Double‑check the resistor tolerances—use 1% parts, measure the 100 Ω with a meter before you wire it in. Make sure the capacitor is mounted with the correct polarity if it’s polarized, even though the X7R is non‑polar. Verify the oscilloscope probe is set to 10× attenuation; a 1× probe can load the circuit. Keep the wiring length under a few centimeters; stray inductance can look like a spike. Log the exact source voltage too; any variation there can affect the rise. Once you see the waveform, compare the measured time constant (R*C) to the expected 1 s for 100 kΩ and 10 µF—if it’s off, the resistor or capacitor value is wrong. Those are the only things to double‑check before adding a diode. Good luck.