LED Current problem
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Posts: 46,084
Hello,
I am using an LM3914 led bar graph driver connected to the BS2sx to drive a
custom LED array. Each segment of the LED consists of four resistors in series.
They require about 100 mA per segment. I am interested in using a pnp
transistor to drive 100mA into the LEDs (using the sinking output from the
LM3914 to drive the base of the pnp transisor) My available voltages are 5v, 8v
and ground... Any help will be greatly appreciated.. this is for a school
project!
Thanks,
J
Tim McDonough <tim@m...> wrote: From: "J. Clark Hughes"
> Tim:
>
> I didn't imply that you were counting cycles. You want to detect IF the
thing
> is open or closed, right? That's what the door sensors on cars do. Not
sure
> why there's confusion on this point... You can measure tilt if you want
to, or
> you can measure light. Heck, you can measure changes in volume if you
can
> correlate that to the thing being opened -- knock yourself out. I would
use a
> switch, but it's a free world (as is this advice).
I wasn't completely sure what you meant and was just trying to clarify my
application in case there was some confusion and for the benefit of others
who might be following this thread. My intent was not to trivialize any
suggestion or dismiss it out of hand.
The container has a hinged door through which material is added. The door
is a part of a larger lid that is completely removed to empty the
container. Sensing tilt or light is attractive because a single sensor,
possibly mounted on the PCB with the rest of the electronics, can detect
both the door open or the lid off. In either case we do not want the device
to measure while the container is "open". We do not need to know which
scenario caused it to open.
For a "one off" system switches would be the obvious choice. They are
simple to use and cheap as you point out. Our application ultimately
involves thousands of containers so the cost of two switches per container
(door+lid) plus the labor to install and wire them, etc. can add up
quickly.
Thanks to all for the suggestions received so far. Cyber brainstorming is a
great way to look at options we may not have otherwise considered.
Tim
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I am using an LM3914 led bar graph driver connected to the BS2sx to drive a
custom LED array. Each segment of the LED consists of four resistors in series.
They require about 100 mA per segment. I am interested in using a pnp
transistor to drive 100mA into the LEDs (using the sinking output from the
LM3914 to drive the base of the pnp transisor) My available voltages are 5v, 8v
and ground... Any help will be greatly appreciated.. this is for a school
project!
Thanks,
J
Tim McDonough <tim@m...> wrote: From: "J. Clark Hughes"
> Tim:
>
> I didn't imply that you were counting cycles. You want to detect IF the
thing
> is open or closed, right? That's what the door sensors on cars do. Not
sure
> why there's confusion on this point... You can measure tilt if you want
to, or
> you can measure light. Heck, you can measure changes in volume if you
can
> correlate that to the thing being opened -- knock yourself out. I would
use a
> switch, but it's a free world (as is this advice).
I wasn't completely sure what you meant and was just trying to clarify my
application in case there was some confusion and for the benefit of others
who might be following this thread. My intent was not to trivialize any
suggestion or dismiss it out of hand.
The container has a hinged door through which material is added. The door
is a part of a larger lid that is completely removed to empty the
container. Sensing tilt or light is attractive because a single sensor,
possibly mounted on the PCB with the rest of the electronics, can detect
both the door open or the lid off. In either case we do not want the device
to measure while the container is "open". We do not need to know which
scenario caused it to open.
For a "one off" system switches would be the obvious choice. They are
simple to use and cheap as you point out. Our application ultimately
involves thousands of containers so the cost of two switches per container
(door+lid) plus the labor to install and wire them, etc. can add up
quickly.
Thanks to all for the suggestions received so far. Cyber brainstorming is a
great way to look at options we may not have otherwise considered.
Tim
To UNSUBSCRIBE, just send mail to:
basicstamps-unsubscribe@yahoogroups.com
from the same email address that you subscribed. Text in the Subject and Body of
the message will be ignored.
Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Do You Yahoo!?
Yahoo! Tax Center - online filing with TurboTax
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