J
Jim Thompson
Guest
On Mon, 23 Sep 2013 16:10:44 -0700, OldGuy <OldGuy@nospam.com> wrote:
OK. I think John Fields design fills your bill. Just be sure to have
an adequate filter cap to hold up the supply if the wart-wart is slow
coming up.
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
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480)460-2350 Fax: Available upon request | Brass Rat |
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I love to cook with wine. Sometimes I even put it in the food.
Jim Thompson wrote on 9/22/2013 :
On Sat, 21 Sep 2013 19:32:39 -0700, OldGuy <OldGuy@spamfree.com
wrote:
Looking for the simplest way to this.
AC powered 9V wall-wart or 9V battery powering a circuit.
9V battery is alkaline so is not charged by 9V AC supply.
Load is < 50 ma.
When AC is on, power from the AC to 9v PS.
AC off, power from 9V battery.
9V battery only supplies power when 9V AC is off.
The catch: the 9V AC PS output may be lower than the 9V battery or
visa versa.
So a simple two diode scheme will not fly.
Minimum parts and no relays.
Suggestions please.
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From a previous SED thread, where an unregulated wall-wart was
involved...
http://www.analog-innovations.com/SED/PowerSwitching_Battery-Wallwart.pdf
If I understand your situation correctly, it might be as simple as
using a barrel connector with a built-in switch (from R/S, as I
remember buying them)...
http://www.analog-innovations.com/SED/PowerSwitching_OldGuy.pdf
If you have a more complex situation, like wall-wart hard-wired in
place, I have other solutions to detect that it's live and switch
accordingly.
...Jim Thompson
Wall-wart and battery hardwired in.
Wall-wart "off" when AC power fails.
No mechanical switches to control electronics state: on or off.
Always on.
--- news://freenews.netfront.net/ - complaints: news@netfront.net ---
OK. I think John Fields design fills your bill. Just be sure to have
an adequate filter cap to hold up the supply if the wart-wart is slow
coming up.
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: Contacts Only | |
| Voice
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.