The data sheet on such switches tells nothing. What do they do, close a contact between the extra pin and the barrel? ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
While you're at it... pick a three-legged regulator, test it's output with input floating (but ground connected)... apply a current-limited voltage to the output, gradually up from zero to say 3.5V and see what current, if any, is drawn from your test supply. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
Hmmm.... I didn't realize they were so bad, I'll have to think about that.
To my original question, I've come up with this kind of configuration, I'm not sure if it would work.... basically when no 9V battery is plugged into the jack, it's switch is closed and I'm using a comparator to trigger some transistors to route my 3V, then when the
9V is plugged in, the switch opens and the 9V feeds the regulator.... this seem reasonable?
--
No, they open an internal fixed contact and connect the moving contact
to the barrel, just like in a switching phone jack.
Here's a typical case:
http://products.cui.com/CUI_PJ-030C-SMT_Datasheet.pdf?fileID=5957
What usually happens is that the internal battery + is connected to
pin 1, battery - is connected to pin 3, and circuit ground is
connected to pin 2.
Then, when the external supply is plugged in, its + is connected to
pin 1, the circuit between battery minus and circuit ground is broken,
and the external supply minus will be connected to pin 2.
What I don't understand is Panfilero's scheme.
If it's only 15 ma then you can use a small analog switch like shown below, it is a SPDT implemented in transmission gates from Fairchild, or anything similar. Depending on the load you may want some hold-up capacity on the output a schmitt intervening the regulator output and the S(elect) input to the switch.
Please view in a fixed-width font such as Courier.
Does the switch OPEN when barrel is plugged in? The only description I've found for a barrel connector with switch say switch is NORMALLY OPEN and closes when barrel is inserted...
formatting link
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
By your reference, is pin 2 connected to pin 3 until the plug is inserted? Or vice versa? ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
This link implies 2-3 is open until plug insertion, then 2-3 is closed...
formatting link
If I can get the switch polarity correct (as in my reference) I think I have a simple solution to panfilero's problem. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
This would be the usual battery backup type of circuit, you don't say where the 3V PIN comes from, but I assume it's from the line. So remove the line power and the 9V kicks in...
Please view in a fixed-width font such as Courier.
--
In the top circuit you've turned on the top FET and turned off the
bottom one, but you're back-feeding 3V into the regulator since you
haven't broken its return to ground.
Is that bad?
Probably, but it needs a little more study on your part.
In the bottom circuit you've turned off the top FET and turned on the
bottom one, but you've opened up the mechanical switch, so the
regulator is referenced to ground, but floating.
Careful. If the regulator backfeeds the 3V to the input, it's possible the relay won't drop out when the 9V is removed (typical guaranteed dropout is something like 5%-10% of nominal voltage (0.45~0.9V on a 9V relay)- less at low temperatures). A diode at the regulator input would isolate it (and protect against the common occurence of a momentarily reversed 9V battery)
One could replace the electromechanical relay with an appropriate form CMOS SSR, but it will have a bit of voltage drop.
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
Good point. The 3 volts from the battery can't get to the relay coil, but if there's a big cap on the input to the circuit, intended to keep the circuit powered for the brief time that the relay takes to drop out, it could possibly keep the relay energized if the reg backfeeds. The isolation diode is good cheap protection against that. Thanks!
I didn't have anything better than a BSS84 in my library, so it struggles at 3V gate drive.
Likewise I had no 3-legged regulator, so I used LM317. With a
3-legged regulator I doubt the need for the 2N7000, its gate resistor and the diode.
But it's something to start with.
Good exercise, I learned how to make a symbol act like a real jack ;-) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
At your current levels, replacing FET's with 2N3904 and 2N3906 works better. ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 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.
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