Soldering Iron Selection Calculator

Total Stall Current assumes every servo is simultaneously fighting maximum resistance and drawing its full worst-case current, while Avg Operating Current takes roughly 40% of that per-servo stall figure and further scales it down by your entered Duty Cycle % — the fraction of time servos are actually moving rather than holding. In a typical robotic arm with a 30% duty cycle, this means Avg Operating Current can be a small fraction of Total Stall Current, but your power supply still needs to be rated for the stall figure to survive the worst case.

Min PSU Current is based on Total Stall Current plus a 20% safety margin, not the average operating draw, because a power supply that's only sized for average current will brown out the moment multiple servos stall at once — for example, if a robotic arm hits a mechanical limit or an obstruction on several joints simultaneously. Undersizing here is one of the most common causes of erratic or resetting servo behavior in hobby builds.

Duty Cycle % is the percentage of time your servos are actively moving under load rather than sitting still holding a position, and it only affects Avg Operating Current and the runtime estimate — it has no effect on Total Stall Current or Min PSU Current, which are always worst-case. A servo that sweeps back and forth constantly might have a duty cycle close to 100%, while one that moves briefly then holds a fixed pose (like most robotic arm joints) is typically much lower — the calculator defaults to 30% as a reasonable middle ground.

The Runtime output is calculated by dividing a fixed 2000 mAh battery capacity by Avg Operating Current, so it's meant purely as a reference point, not tailored to whatever pack you actually own. If your battery has a different capacity, scale the runtime proportionally — for example, double the result for a 4000 mAh pack — since the relationship between capacity and hours is linear given the same average current draw.