I thought I'd wait before proposing a solution. I'm glad I did.
The simplest thing to do would to use a couple of diodes in series with the
supply. Each diode will give about 0.6 volts of a drop. 5 in series would
give a 3 volt drop. 1N4007 diodes would be fine providing the current is less
The other solution would be to use s 7809 voltage regulator. I'm not sure how
well it would perform with only 12 volts input but it's worth a try. Again
this should work if the current is less than 1A.
On Fri 28 Apr 2006 00:32, Brendan Kehoe wrote:
> This is very OT, but I don't know of other lists that might be as useful
> for this sort of thing. :)
>> We're trying to find an easy way to convert a 12v DC current to 9V DC
> for a community wireless broadband scheme. We've got a tiny Ethernet
> switch that wants 9V, but a 230->13.6V transformer, who has two contacts
> (+13.6V, and a ground). A junction box feeds one device, a WRAP board,
> that wants 12V. But the switch wants 9V.
>> I found that a 3.1V zener diode would do the job, but a) I've found no
> one in Ireland who sells them, and b) it would require a bit of a
> hardware hack to put it together which doesn't feel like it'd be the
> safest approach.
>> Anyone know of a device already available that would take a 12V DC
> signal (like comes in a car's 12V adapter) and step it easily down to 9V
>> Feel free to reply off-list to reduce traffic, and I'll post a summary
>> Thanks for any tips,
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