I just received another Designing With LEDs post about Hollywood Lighting LED replacement lamp for fluorescent fixtures. This post reviews a 48 inch T8 replacement LED lamp.
Quoting from the post:
I used to think triacs were electrically noisy and a crude way to dim a light, but I now understand the advantage of not having to string a separate line for dimming control information.
The TRIAC operates by delaying turn on until part way through the cycle of AC current. When conduction begins it happens very quickly which gives a spike of current that creates electromagnetic interference or EMI. This is the buzzing noise you may hear when you listen to AM radio and turn on the dimmer.
The TRIAC does have this advantage. But I don’t see why not using it causes one to have to add wiring. The dimmer can be controlled remotely by using the existing wiring to carry the signal from the dimmer to the light. This may not be inexpensive, but it may be cheaper than having an electrician add wiring.
The dimmer can also send a signal by the same radio signal method as a garage door opener. IR or infrared could also be used. I just bought three remote shutter fobs for cell phone cameras. This uses Bluetooth to control the camera. Something similar could be used to ‘press’ the dimmer buttons.
Another way to send a signal is to run a fiber optic cable between dimmer and light. The reason to use fiber is the fiber is nonconductive, so fire and safety hazards are not an issue. I predict that someday the electric outlets will have a fiber optic connector for not only light and other controls, but also for data Comm at very high speeds. The fibers will be included with the electric wiring.
So the TRIAC and SCRs have been used for decades. But they are best for AC power. If low voltage DC power is used, then the MOSFET can be used. Either way, the EMI can be minimized by filter capacitors and inductors. Most dimmers skimp on these to save money. You can add them to an existing dimmer for a few dollars.
I noticed that the LED lamp requires that the original ballast be disconnected. This is a gotcha, since most people do not feel comfortable working with AC wiring. Rightly so, since it’s a shock and safety hazard. It’s better to have a professional do the work, but that can get expensive. So keep this in mind when researching your upgrade to new lighting.
