AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Claxton, Dean J" 
<dean.j.claxton@t...> wrote:

> ... I placed a pair of 1N5404
> diodes in series for ... drop
> of around 1.4V (to be on the
> safe side ... the diodes get
> rather toasty ...

This seems to be a reasonable solution to me, assuming you can't find 
an obvious way to turn down the voltage.

The problem with putting diodes in parallel is that they may not 
share the current particularly equally. You can get around that by 
just using more than are strictly necessary, say five instead of 
three.

Another approach would be to use a resistor and a diode in series 
instead of two diodes. Suppose, for example, the current really is 
three amps and you decide to put one amp through each of three 
diodes. If you measure the voltage and it is still high by, say, 0.3 
volts, then just put a 0.3 ohm resistor in series with each diode. 
This will drop the additional voltage and ensure you get even sharing 
of the current.

One thing to remember, though, is that when you heatshrink the whole 
lot together, there's the same amount of heat coming out of your 
bumdle whether you have two or six diodes in there. Things may run 
cooler while you have the diodes separated, but when you mash them 
together they could be almost as hot once again.

Graham.