vault backup: 2025-11-06 17:21:38

lighting-controls.md

@@ -29,8 +29,35 @@ Southwire 64350501
 SIMpull® 16/2 Low Voltage Signal Cable, Blue
 ```
 
-This method is compliant with NEC 725.136(I)(1),
+This method is compliant with
+[[nfpa-70_725_control-circuits#725.136(I) Other Applications.|NEC 725.136(I)(1)]],
 which allows control circuits to share a raceway with power conductors
 if either all of the power conductors or all of the control conductors
 are themselves in a raceway,
 or in metal-sheathed, metal-clad, non–metallic-sheathed, or Type UF cable.
+
+### Triac Dimming
+
+Triac dimmers work by chopping the AC power waveform.
+This reduces the output power, so the lamp dims.
+
+> [!info]
+> "Triac" refers to the electronic component
+> that does the wave-chopping.
+
+There are two subtypes based on which side of the wave is chopped.
+
+* Magnetic Low Voltage (MLV)** -- AKA "Leading Edge" or "Forward Phase"
+* Electronic Low Voltage (ELV)** -- AKA "Trailing Edge" or "Reverse Phase"
+
+> [!important]
+> The "magnetic" and "electronic" of MLV and ELV
+> are holdovers from pre-LED days.
+> They have nothing to do with how they are used today.
+> They are, unfortunately, the most common terms.
+
+> [!important]
+> "Triac" is sometimes used in contrast to ELV erroneously to mean MLV
+
+There also exist "universal" dimmers,
+which can be switched between the two subtypes.