DIYbanter - View Single Post

Terry Casey

In article ,
says...

Just that they could be being overdriven slightly so ('a little
brighter' ) so they may not last as long?

Because you are running AC there isn't much that you could do easily
to lower the output voltage to 4V (AC), especially if the load varies
a lot (no lights on, all lights on etc).

You could try a series resistor (as mentioned elsewhere) but that
would really only affect the 'lights all on' condition.

Don't forget that 4VAC is 5.66V peak. Assuming tha there is a
silicon diode in the lights themselves, the actual resulting
DC voltage might be as high as 5V if there is a fair sized
electrolytic smoothing the output and allowing for the typical
0.7V drop across the diode.

With 4.5VDC fed to the same diode, the same forward drop will
still be experienced, leaving only 3.8V on the output of the
diode.

Checking back, I note that the OP says that 'Polarity doesn't
appear to matter' which implies a bridge rectifier. This will
have twice the diode forward voltage drop so 4.25VDC maximum
from a 4VAC input or 3.1V on the bridge output from a 4.5VDC
input.

On that basis, I wouldn't bother to do anything further.

--

Terry

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