Hi Mike, On Mon, 13 Nov 2000 12:46:20 +0000, "M. G. Devour" <mdev...@eskimo.com> wrote:
>> > The next question is: How can I build in a fuse or >> > breaker to prevent any possibility of my clients (or >> > myself) getting electrocuted in case of accident? >> >> I've never heard of a small AC-DC transformer shorting 120VAC to the >> output; they only die, to my knowledge... > >Would it be too disruptive just to put a resistor in series with the >output as a worst case current limit? Select the value such that it >limits current to a non-lethal value at 120 volts, while only dropping >a little voltage at the design output level. A 10,000 ohm resistor is good. It will limit the current to about 12 milliamps at 120 volts. It's noticeable (so you can disconnect), but not life threatening. >Another easy alternative is to put a zener diode "crowbar" circuit on >the output. This consists of a low current fuse in series with one or >both of the supply output leads, and a zener diode connected between >the + and - leads after the fuses. > >This setup causes the fuse(s) to blow if the output voltage exceeds the >zener's reverse bias breakdown voltage, or if the polarity of the >supply should reverse, either of which will cause the zener to conduct. Yup. That's about the best way to do it from a line-voltage supply without getting into double isolation (two transformers, with a regulated DC supply in between). -- Dean -- from (almost) Duh Moyn (CDP, KB0ZDF) -- The silver-list is a moderated forum for discussion of colloidal silver. To join or quit silver-list or silver-digest send an e-mail message to: silver-list-requ...@eskimo.com -or- silver-digest-requ...@eskimo.com with the word subscribe or unsubscribe in the SUBJECT line. To post, address your message to: silver-list@eskimo.com Silver-list archive: http://escribe.com/health/thesilverlist/index.html List maintainer: Mike Devour <mdev...@eskimo.com>
