9V PS

A variation on this...

What you want to do is determine whether wall-wart is active or not, when active, disconnect battery, and vice versa.

Just need to put comparator in the right place.

Tomorrow... time for "The White Queen" ;-) ...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:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Can't use the switch in the barrel connector?

A changeover SSR + dual diode + resistor will work, and may be the simplest- 3 parts or 4 simple parts- but probably not the cheapest.

Eg.

The cheapest/simplest might be a prebiased transistor, a dual diode and depletion mode MOSFET and a resistor-- 4 parts, or 7 simple parts.

Maybe someone else has other ideas..

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward" 
speff@interlog.com             Info for manufacturers: http://www.trexon.com 
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

Those belly-to-belly body-to-body MOS devices solve the issue of a over/under conduction.

If you have a barrel connector that opens a switch to ground when the plug is inserted, it's a trivial exercise with 2 discrete PMOS devices and one resistor.

...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:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Focusing on just the minimum parts requirement, here are

2 possibilities: the first uses 3 parts and the second uses 2 parts 3 parts (with drawback of extra diode drop when powered from battery):

Battery - ------------------------+ | D1 D2 | Battery + --->|--->|---+---load---+ | | Supply + --->|--------+ | D3 | | Supply - ------------------------+

I know you didn't want relays, but here's one anyway, in case you change your mind:

+-----------------+ | | +------|

From a previous SED thread, where an unregulated wall-wart was involved...

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)...

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

--
| 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:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

Found the jack on the SparkFun site...

...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:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

On Sat, 21 Sep 2013 19:32:39 -0700, OldGuy wrote:

--- Version 4 SHEET 1 1172 680 WIRE 144 -32 -96 -32 WIRE 352 -32 240 -32 WIRE 608 -32 352 -32 WIRE 832 -32 704 -32 WIRE 656 64 656 32 WIRE 192 80 192 32 WIRE 352 80 352 -32 WIRE 192 192 192 160 WIRE 704 192 544 192 WIRE 832 192 832 -32 WIRE 832 192 784 192 WIRE -96 240 -96 -32 WIRE -16 240 -96 240 WIRE 128 240 64 240 WIRE 656 240 656 144 WIRE 544 288 544 192 WIRE 544 288 512 288 WIRE 592 288 544 288 WIRE -96 336 -96 240 WIRE -16 336 -96 336 WIRE 448 336 64 336 WIRE -96 384 -96 336 WIRE 832 384 832 192 WIRE -96 512 -96 464 WIRE 192 512 192 288 WIRE 192 512 -96 512 WIRE 352 512 352 160 WIRE 352 512 192 512 WIRE 512 512 512 384 WIRE 512 512 352 512 WIRE 656 512 656 336 WIRE 656 512 512 512 WIRE 832 512 832 464 WIRE 832 512 656 512 WIRE -96 592 -96 512 FLAG -96 592 0 SYMBOL res 80 224 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 10k SYMBOL pnp 240 32 M270 WINDOW 0 7 148 VLeft 2 WINDOW 3 31 174 VLeft 2 SYMATTR InstName Q1 SYMATTR Value 2N3906 SYMBOL npn 128 192 R0 SYMATTR InstName Q3 SYMATTR Value 2N3904 SYMBOL res 176 64 R0 SYMATTR InstName R3 SYMATTR Value 1k SYMBOL voltage -96 368 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR Value PULSE(0 9 1 1u 1u 1 2) SYMATTR InstName V1 SYMBOL res 336 64 R0 WINDOW 0 40 47 Left 2 SYMATTR InstName R4 SYMATTR Value 180 SYMBOL pnp 608 32 R270 WINDOW 0 7 148 VLeft 2 WINDOW 3 31 174 VLeft 2 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL npn 592 240 R0 SYMATTR InstName Q5 SYMATTR Value 2N3904 SYMBOL res 672 48 M0 SYMATTR InstName R5 SYMATTR Value 1k SYMBOL voltage 832 368 M0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR Value 9 SYMATTR InstName V2 SYMBOL npn 448 288 R0 SYMATTR InstName Q4 SYMATTR Value 2N3904 SYMBOL res 80 320 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R2 SYMATTR Value 100k SYMBOL res 800 176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R6 SYMATTR Value 10k TEXT -80 544 Left 2 !.tran 10 TEXT -56 424 Left 2 ;WALL-WART TEXT 696 424 Left 2 ;BATTERY TEXT 360 168 Left 2 ;LOAD TEXT 32 544 Left 2 ;John Fields TEXT 32 576 Left 2 ;22 September 2013

-- JF

Also on Digikey, with more technical detail...

Some may wonder how I made a symbol that can show as an open or closed switch AND functionally perform that way...

PSpice can do conditional netlisting templates.

When the (text) character "|" is present (switch shows closed because that "text" does the visual closing), the presence of that "text" satisfies a conditional and it netlists as a wire... otherwise an open ;-)

I also do fuses, snip-out trim, and laser cut simulations that way. ...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:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

BTW, having recently gone through the thinking of a similar situation (high-reliability and at maybe 100x or 1000x the current, but basically the same concept), you might want to give some thought to your actual requirements vis-a-vis various situations on either power port.

In particular, are glitches of any concern?

Consider the "simple" solution with a relay- and input coming from a big AC adapter. Unplug the barrel connector and you get a brief glitch (maybe a millisecond or two) as the contacts transfer. If the AC power fails or is switched off, you could get a 1-second glitch with voltage out dropping to maybe a volt before the battery takes over.

In a pathological situation, the AC adapter output could drop to about half a volt if it is very cold without the relay dropping out (the spec says "must drop out" is 5% of rated voltage, IIRC), which would likely be outside the operating range of whatever you've got this connected to.

Re-writing your design goal, might read as follows...

Battery backup is disabled when AC powered DC source is not avail. Battery power drain must be minimal and circuit as simple as possible for power fail backup. Either source may range from 9V by +/- 40%.

Discussion ===== A reed relay would switch in 1ms, slower than solid state but can be held with a cap and a 12V coil can turn on with 8V worst case to disable the battery.

The external DC source will have a diode bridge & cap suitable for direct connect to load with battery disable to load with only a few mA drive and contact rating with no significant voltage drop @ 400mA

--
I believe he wants the battery backup to be _enabled_ when the AC 
powered DC source is not available.

That's the way I read it too, after realizing, it's sort of like a clock radio with battery back-up... AC goes away, battery keeps clock on-time so you're not late for work ;-)

...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:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

on 9/22/2013, John Fields supposed :

Interesting. Thanks. But you must sell 2N390x's. lol

Could Q4 be eliminated? Q5 base to Q3 collector?

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@netfront.net ---

Jim Thompson wrote on 9/22/2013 :

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: snipped-for-privacy@netfront.net ---

Jim Thompson used his keyboard to write :

SparkFun is fun but a little pricey except when it is the only place to get what ya want.

--- news://freenews.netfront.net/ - complaints: snipped-for-privacy@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:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.

On Mon, 23 Sep 2013 16:08:40 -0700, OldGuy wrote:

--- Yup, good catch!

Plus, the price of parts for onesies from DigiKey goes down to USD

1.18.

Here's REV A:

Version 4 SHEET 1 1172 680 WIRE 144 -32 -96 -32 WIRE 352 -32 240 -32 WIRE 608 -32 352 -32 WIRE 832 -32 704 -32 WIRE 192 64 192 32 WIRE 352 64 352 -32 WIRE 656 64 656 32 WIRE 192 192 192 144 WIRE 544 192 192 192 WIRE 704 192 544 192 WIRE 832 192 832 -32 WIRE 832 192 784 192 WIRE 656 240 656 144 WIRE 192 256 192 192 WIRE 544 288 544 192 WIRE 592 288 544 288 WIRE -96 304 -96 -32 WIRE -16 304 -96 304 WIRE 128 304 64 304 WIRE 832 320 832 192 WIRE -96 352 -96 304 WIRE -96 480 -96 432 WIRE 192 480 192 352 WIRE 192 480 -96 480 WIRE 352 480 352 144 WIRE 352 480 192 480 WIRE 656 480 656 336 WIRE 656 480 352 480 WIRE 832 480 832 400 WIRE 832 480 656 480 WIRE -96 560 -96 480 FLAG -96 560 0 SYMBOL res 80 288 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R1 SYMATTR Value 100k SYMBOL pnp 240 32 M270 WINDOW 0 7 148 VLeft 2 WINDOW 3 31 174 VLeft 2 SYMATTR InstName Q2 SYMATTR Value 2N3906 SYMBOL npn 128 256 R0 SYMATTR InstName Q1 SYMATTR Value 2N3904 SYMBOL res 176 48 R0 SYMATTR InstName R2 SYMATTR Value 10k SYMBOL voltage -96 336 R0 WINDOW 3 24 96 Invisible 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR Value PULSE(0 9 1 1u 1u 1 2) SYMATTR InstName V1 SYMBOL res 336 48 R0 WINDOW 0 40 47 Left 2 SYMATTR InstName RL SYMATTR Value 180 SYMBOL pnp 608 32 R270 WINDOW 0 7 148 VLeft 2 WINDOW 3 31 174 VLeft 2 SYMATTR InstName Q4 SYMATTR Value 2N3906 SYMBOL npn 592 240 R0 SYMATTR InstName Q3 SYMATTR Value 2N3904 SYMBOL res 640 48 R0 SYMATTR InstName R3 SYMATTR Value 10k SYMBOL res 800 176 R90 WINDOW 0 0 56 VBottom 2 WINDOW 3 32 56 VTop 2 SYMATTR InstName R4 SYMATTR Value 100k SYMBOL Misc\\battery 832 304 R0 WINDOW 0 -58 13 Left 2 WINDOW 3 -47 99 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName V2 SYMATTR Value 9V TEXT -80 512 Left 2 !.tran 10 TEXT -56 424 Left 2 ;WALL-WART TEXT 672 424 Left 2 ;BATTERY TEXT 376 56 Left 2 ;LOAD TEXT 32 512 Left 2 ;John Fields TEXT 32 544 Left 2 ;24 September 2013 TEXT -64 544 Left 2 ;REV A,

-- JF