Re: LM3914 --help :/

On 02 Dec 2005 16:44:24 +0000, the renowned John Devereux
<jdREMOVE@xxxxxxxxxxxxxxxxxx> wrote:

>"John B" <spamj_baraclough@xxxxxxxxxxxxxxxxxxx> writes:
>
>> On 02/12/2005 the venerable blender@xxxxxxxxx etched in runes:
>>
>> > but exactly how does it modulate the chain inputof comarators, to
>> > disable all leds the + input of comparators should become higher than
>> > -... am I rigth ?
>>
>> You need to understand how an Eccles-Jordan Multivibrator works, then
>> all will become clear.
>
>
>But it seems to be going the wrong way! When the final led turns on,
>the voltage drops. This is coupled through the capacitor to Rhi. This
>*reduces* the voltage accross the resistor chain so the indication
>will go overrange. I would expect that to turn off all the lights the
>indication would need to go to zero instead.
>
>However, looking at the block diagram more closely, it appears that
>the "load" on the reference also determines the LED brightness. So
>presumably injecting a current into it switches the leds off!

Yes, there's a 10:1 current mirror thing going on with the comparator
outputs vis-a-vis the reference output current.

But why the 100 ohm resistor?


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

Relevant Pages

  • Re: LM3914 --help :/
    ... >> but exactly how does it modulate the chain inputof comarators, ... >> disable all leds the + input of comparators should become higher than ...
    (sci.electronics.design)
  • Re: LM3914 --help :/
    ... On 02/12/2005 the venerable blender@xxxxxxxxx etched in runes: ... > but exactly how does it modulate the chain inputof comarators, ... > disable all leds the + input of comparators should become higher than ...
    (sci.electronics.design)
  • Re: LM3914 --help :/
    ... > but exactly how does it modulate the chain inputof comarators, ... > disable all leds the + input of comparators should become higher than ...
    (sci.electronics.design)
  • Re: LM3914 --help :/
    ... >> but exactly how does it modulate the chain inputof comarators, ... >> disable all leds the + input of comparators should become higher than ... *reduces* the voltage accross the resistor chain so the indication ... indication would need to go to zero instead. ...
    (sci.electronics.design)