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Subject: Re: [AN1x-list] an1x construction. (Wall Warts of all sorts)

From: Bruce Wahler <bruce@...>
Date: 2001-10-01

Peter,

>Could it be an idea to use standard power supplies, that you just shove into
>your piece of equipment? All synths take the same voltages (12v, 5v,
>0v, -12v I'd imagine) anyway.

That approach is often used, and it helps with the time-to-market, but it
doesn't solve the main issue: power hazards inside the box. Regulatory
agencies say to the manufacturers, "Look you're responsible for any power
that goes INSIDE your devices; your not responsible for anything that goes
on OUTSIDE the devices." Then they define a fairly difficult set of
standards for voltages above 40-50V, and an easier set of rules for lower
voltages. Why? Because the safety of electrical products is based on two
things: the distance between parts at different voltages, which affects
the tendency to arc or short-circuit; and the amount of power that might be
dumped into a device in the case of a failure, causing fire. In both
cases, the higher the voltage, the more likely that the result is hazardous.

As a designer, if I allow 120/240V into a product, I have to demonstrate
that there is an extremely low chance of that voltage linking to a part
that would either a) shock the user or b) cause a fire. Because of the
nature of high voltages -- i.e., their increased ability to arc through the
air or break through insulating materials -- this can be difficult,
especially in small spaces. If I can lower the voltage, many of the
problem areas become safe. It also becomes easier to demonstrate their
safety, so I win twice.

Regards,

-BW

--
Bruce Wahler
Design Consultant
Ashby Solutions™
www.ashbysolutions.com
CloneWheel Support Group moderator
978.386.7389 voice
978.964.0547 fax
bruce@...