Dimming an outdoor landscape lighting transformer

[Brian H]

The AC power between Line and Neutral. Swings from Positive to Negative with Neutral being the reference.
The solid state device {triac} used for dimming has a minimum voltage across it to turn On. So when the AC is just crossing across the zero potential. It will not turn on for a short time until the voltage is again above the minimum. That causes some distortion in the AC that maybe causing the slight hum.

[dave w]

FWIW the heavy duty transformer I was "dimming" without problems was a big monster made for a Motorola multi pocket battery charger. (For Brian who is also ex-Motorolan, is was the old MX radio, six or eight pocket, rapid charger) This was a high quality in construction and materials component. As Brian pointed out the small wall warts are made to be cheap, lower quality and did not like the triac turn delay very much. As Brian pointed out, if your landscape transformer is made for "dimming" then you should not have any problems. Once you get everything installed and all your landscape lights working, set the XPDI3 for the lighting level you desire, let it run for five or six hours and the check the transformer or the case for warmth. Unless you have bookoo lights it should be not much more than luke-warm. But since you are using LED lights I imagine it will be cool.

[CliffyJ]

Good tips Dave, will do!