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Re: Need 5VDC 100mA to 12VDC 1A converter

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Sorry for the late response. I took a few days off of work for the Jewish
New Year. Happy New Year everyone. May everything you design, program and/or
build work the first time.

I've rec'd parts and have done some experimentation. The solenoid draws
800mA at 12V, 400mA at 6V, and doesn't work reliably at less than 6V. (That
seems like a hell of a lot of current for a small, weak solenoid. Whatever.)

No matter how you slice it, that solenoid requires 400mA to run, or damn
close to it. Within the constraints of this project, using a cap simply
won't work. Keeping the solenoid open long enough for somebody to open the
door requires too big of a capacitor, and the recharge time of the cap is
too long.

For various reasons, I do not want to put batteries in the product.

Hobby motors also draw a lot of current.

Therefore, I am stuck with a wall wart. I'm not very happy about that, but
there's no choice.

In one post, somebody asked whether, in power failure, doors were left
locked or unlocked. The answer is locked, but they can still be opened with
a key.

Thanks, everyone, for all your feedback.

Mike



Re: Need 5VDC 100mA to 12VDC 1A converter
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That should be configurable.  I worked in one building with such
specs, but the problem was the doors lead from the elevator banks
to the offices.  In case of fire the elevators homed to the
basement, the doors were locked, and the stairwells were only
accessible from inside the offices, thus cooking anyone waiting
for an elevator.

--
 "This is a wonderful answer. It's off-topic, it's incorrect,
  and it doesn't answer the question."  --  Richard Heathfield

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Re: Need 5VDC 100mA to 12VDC 1A converter

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That'd be a pretty complicated latch design!

Does anybody know of a good page on solenoid latch designs, such as for door
locks and cash drawers? Seeing a few examples would be nice :).

Thanks,

Mike



Re: Need 5VDC 100mA to 12VDC 1A converter
Hi Mike
 I think you are missing one thing. It only takes
the 12V to actuate the solenoid. The voltage and
current can be quit a bit less to actually hold
it open once it is actuated. Look at setting up,
for experimenting, a large cap with a series resistor
to something like 20VDC. Place a 1 amp diode in series with
a low voltage supply that you'll use to hold the coil.
 Experiment with different holding and charging voltages.
You may find that it is not all that impractical after
all.
Dwight


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Re: Need 5VDC 100mA to 12VDC 1A converter


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Hi Dwight,

The voltage isn't as much an issue as the current, however, I've noticed
that the actuation voltage is not that much higher than the hold voltage.

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I've done quite a bit of experimentation with this solenoid already. It will
not hold reliably without >350mA (or something like that).

The opening of the solenoid is so quick, I can't see the current on a
digital meter. It didn't make sense to bother with a big setup for measuring
that initial spike, once I saw that the hold current requirements were so
far out of line with my what I had hoped to see.

I'll play around with the solenoid some more. Really, I'd like to replace
the whole latching mechanism. I've gotten some interesting ideas from other
portions of this thread.

Mike



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