Hi Ling

You are correct about the heat, at 40A the
D1D40 will generate 90W no thats not a typo
thats 90W!

As this will be used for continuous periods
that may be a little to much, I suppose I
could include a heat feedback to switch
it off if it gets to hot.

Thanks for your assistance

Jon





--On Friday, August 15, 2003 12:16 PM +0800 SM Ling <ipal11@SINGNET.COM.SG>
wrote:

> If it is a frequent switching, try a DC solid-state relay, something like
> CRYDOM: D1D40.  It can be controlled from 3.5-32V directly.  Regardless of
> the type of load, remember to put in the flywheel diode at the output,
> there will have enough back-emf to kill the junction if not taken care
> of.  It is quieter than mechanical relay, but you will need to take care
> of the heat.
>
> Ling SM
>
>> > I am building a small system with PIC control which
>> > has to switch large currents +30A at 12/24V. The
>> > frequency is quite low i.e. once per hou. This
>> > is not really my area so I need some advice.
>
>> > Jon
>
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