Although we've been using dimmers for years, I still get questions about whether or not it's okay to put a pinspot on a dimmer. Some people say it's not a good idea and others say they've been doing it for years and they're not going to stop doing it. What's the truth about dimming pinspots? …I did some tests with a pinspot on a Lex Slimmer Dimmer, and in the process, I found an interesting phenomenon. When the dimming level dropped to around 10 percent, the voltage waveform went completely haywire, and the transformer in the pinspot started buzzing loudly. Whatever the cause of the malfunction, the DC current in the circuit shot up, and if I had let it continue, it would have burned up the transformer. I suspect that's why dimmers designed for fluorescent lamps can only dim to 10 percent or, in some cases, 1 percent. They are probably built to avoid this from happening and damaging the circuit. The magnetic ballast in a fluorescent lamp is an inductor, just like the primary side of a transformer, and they are susceptible to the same dimming pitfalls as a pinspot…Pinspots really inexpensive these days. I recently bought some for $10 apiece, and that was the retail price. If you're trying to design a lighting system on a budget, pinspots can really help you stretch the budget and fill out your design. But don't let a $10 pinspot throw a spanner in the works and ruin a $200 dimmer module. You can use a dry contact closure to turn pinspots on and off, and if you must dim them, do it at your own peril, because it can cause damage to your equipment.
-Richard Cadena, from "Focus on Fundamentals," PLSN, Feb. 2011
