Non-linear (DC voltage-dependent) resistance PUBLIC

A prototype non-linear resistance, with similar characteristics to an incandescent lamp/bulb.

A first step towards a more comprehensive simulation of an incandescent lamp or bulb.

The hot:cold resistance of an incandescent mains lamp, as might be used for domestic lighting, is about 5:1. I used this as the basis for modifying an existing model (see Acknowledgement).

This simulation shows a non-linear resistance curve between two fixed points: the "filament" resistances when cold (Rcold) and hot (Rhot). Cold and hot correspond to zero and rated voltage respectively. The shape of the non-linear curve agrees, very roughly, with some measurements I have made on a real bulb.

The calculation of Rhot is straightforward: use any two of rated voltage, rated wattage and Ihot (Ihot being the current at rated volts). The determining of Rcold is trickier because of the difficulty of measuring a resistance with zero volts! I extrapolated back to zero using the smallest reliable measurements from test meters.

There are some more calculation details on the schematic.

Limitations: positive DC only; no inrush current from cold.

Acknowledgement: https://www.circuitlab.com/circuit/gcv8pd/non-linear-resistors-and-capacitors-rc-simulation-example/