Current budget calculator
Add every part you're powering. See steady and peak current per rail against what your board can safely supply.
How it works
Add up each rail's current twice: steady (what it draws most of the time) and peak (the short bursts). Regulators and USB ports care about both:
- Steady current heats a linear regulator: power = (Vin − Vout) × I. An AMS1117 dropping 5 V to 3.3 V at 500 mA turns 0.85 W into heat.
- Peak current causes brownouts. The ESP32's Wi-Fi bursts of about 240 mA, a servo starting or a SIM800L transmitting can pull the rail down and reset the board (“Brownout detector was triggered”).
Rules of thumb
- Stay under about 70 % of the safe limit on both rails.
- Servos, LED strips, relays and GSM modules get their own 5 V supply. Join the grounds, not the positive rails.
- Put a 470 µF–1000 µF capacitor near the ESP32's 3.3 V pin if it resets on Wi-Fi connect.
- The figures here are typical datasheet values. Measure your real board with a USB power meter.