@TedW posted:Tom, here are a few “dimmers”(actually voltage adjustment) that I and a large number of OGR members use. You may already have some laying around. I use either xfrmr ACV acc power or a dedicated 30 amp DC power supply for all my led lighting. The buck converters are readily available in a variety of configurations from the Bay, Amazon or distributor of your choice.
Proper LED dimmers do not adjust voltages. LEDs are current-driven devices, not voltage driven. Their brightness is determined by the amount of current going through them. Changing the voltage (e.g. using a buck-converter) will sorta kinda change the brightness, but this is because when you change the voltage, the current changes as well, but the relationship is non-linear and there is an absolute voltage below which the LED will not work.
There are several ways around this, but the most common one is to use pulse-width modulation (PWM) to turn the LEDs on and off at a rate too high to see. The voltage is always the same and the current is determined by the duty cycle of a square wave.
The first of the two pictures you show is in fact a PWM controller, not a voltage controller. Those little buck-converters in the second picture have many useful applications, but dimming LEDs isn't one of them. PWM controllers are cheap, readily available, and will support the linear control of brightness across a very wide range.
