In message , ian field
writes

"Ian Jackson" wrote in message
...
In message , rf
writes
Roger Dewhurst wrote:
You can get simple to use regulator chips that drop the voltage
down, you only need a couple of components to make a working voltage
regulator. Ask on News:sci.electronics.basic - the folk on there are
usually very helpful and should explain all you need.


Why not just drop the voltage through a few diodes? Very simple. Very
cheap.

A *few* diodes at a couple of ten cents per each. A single 7809 for less
that a $.

More like "a *few* diodes at a couple of cents per each".

3V to drop = 5 diodes @ 0.6V per diode. No other circuitry required. More
than good enough for the job.
--
Ian

The forward conduction knee curve on diodes isn't *that* sharp, depending on
current draw and rating of the diode the drop can be as low as 0.55V and as
high as 1.1V.

For most 'normal' Si diodes, that isn't really the case. The actual
voltage drop does, of course, increase with current, but at 'sensible'
currents, you can reckon on around 0.65V per diode. How much current is
the Tardis toy going to take? 1A max? 4 or 5 1N4000-series diodes should
work fine in this application. I've used this non-elegant 'KISS'
technique on several occasions, and haven't found any problems.
--
Ian