Ada Audits the Classification Numbers
Ada re-derives this chapter’s own numbers step by step, at full precision
ADA · CALCULATION AUDIT
Ada Audits the Classification Numbers
A door controller can drive a relay strike, a solenoid bolt, or a motorized latch, and the same “open” command hides very different loads: the strike pulls 1.5 A at 12 V for 18 W, its 80 mA coil still needs a driver and flyback path, and a 0.5 A solenoid dissipates 6 W held but only about 1 W when pulsed 10 s every 60 s. A companion vent load of 1.2 N at a 35 mm arm sets a 0.105 N m target once a 2.5x margin is applied. This audit re-derives each figure and asks whether one software verb can quietly cross a torque, startup-current, switched-power, or thermal boundary, so the selection record must name the matching physical proof.
Companion to the chapter Choosing the Right Actuator — every number here comes from that chapter.
The mathematics checks whether the chapter's examples point to the same classification boundary. The physics reminder is that torque, startup current, contact power, and coil heat are different failure surfaces even when the software command looks identical.
The chapter's values
Use only the chapter values above: a 1.2 N vent load at a 35 mm arm, a 2.5x margin, a 12 V fan at 0.7 A running and 2.1 A startup, a 1.5 A door strike at 12 V, an 80 mA relay coil, and a 0.5 A solenoid pulsed for 10 s every 60 s.
The worked checks
| Check | Arithmetic | Classification Evidence |
|---|---|---|
| Vent torque | 1.2 N x 0.035 m = 0.042 N m |
The vent is a positioned-motion problem, so torque and final-state evidence matter. |
| Margin target | 0.042 N m x 2.5 = 0.105 N m |
The actuator family must clear the load with margin, not merely rotate in free air. |
| Fan running power | 12 V x 0.7 A = 8.4 W |
A continuous-flow actuator needs a real power driver and process evidence. |
| Fan startup ratio | 2.1 A / 0.7 A = 3.0 |
The startup case is three times the running current, so normal current alone is not a safe sizing record. |
| Door strike load | 12 V x 1.5 A = 18 W |
The relay or driver switches a DC load; command acknowledgement does not prove the door moved or secured. |
| Relay coil boundary | 12 V x 0.080 A = 0.96 W |
The coil is smaller than the strike load, but it still needs a transistor driver and flyback path. |
| Solenoid duty heat | 12 V x 0.5 A = 6 W; 10 / 60 = 0.1667; 6 W x 0.1667 = 1.0 W |
The pulsed heat case is about one watt before enclosure effects; continuous hold is six watts. |
Audit conclusion: actuator classification is quantitative evidence. The same software verb can cross a torque boundary, a startup-current boundary, a switched-power boundary, or a thermal boundary, so the selection record must name the physical proof that matches the family.
Every number above is taken from the chapter’s own examples and re-derived step by step.