On Saturday, 24 September 2016 18:18:37 UTC+1, The Natural Philosopher wrote:
On 24/09/16 18:04, Andrew Gabriel wrote:
In article ,
Scott writes:

I've got 12 volt halogen spots run from a torriodal transformer - five
units from each transformer. Can I replace these with LCDs or would
this cause problems with under-loading the transformer? I have read
something about having to have one conventional lamp in the circuit
but I don't fancy this as I would rather have them all the same.

Electronic transformers have a minimum load, but a toroidal
transformer probably doesn't. The voltage will be higher, but
an LED probably has a switched-mode PSU inside which will
compensate for this (although there are some cheap ones which
just use a resistor).

Actually the cheap way to drop LED voltage for mains uses is a series
capacitor. Then FW bridge rect and if you want smoothing caps, and put
the LED chips in series.

for e.g a 7W LED you need 30mA or about 7.5k impedance at 50hz.

About 0.47uF.

need to add a resistor too

Frankly I'd lose the toroids and use mains lamps.

+1 for LEDs.


NT