[sdiy] Improving LED response when driven from half-wave rectifier

[Tom Wiltshire]

Like this one?

http://webphysics.davidson.edu/Course_Material/Py310/WK13_circuit3.jpg

(replace 'load' with 'LEDs')

It *is* beautifully simple.

T.

On 5 Sep 2012, at 20:51, Stewart Pye wrote:

> Hi Justin,
> 
> Yes. Use the non inverting VCCS. LED in feedback loop, current setting resistor from - input to GND, input to + input.  (Fig 4.2 in Op Amp Cookbook 3rd Ed).
> If you put the LED's back to back you can do away with the half wave rectifiers so all you need is one op amp. Just make sure the op amp you use can supply the required current. You could use a bicolour LED so It's red when +ve and green when -ve.
> 
> Regards,
> Stewart.
> 
> 
> 
> 
> On 9/5/2012 8:32 PM, Neil Johnson wrote:
>> Justin Owen <juzowen at gmail.com> wrote:
>>> Ah - putting it in the feedback loop? The same way you would with a Vactrol? Yes - I'll take a look at that.
>> Yep.  Bonus points if you do it so that the LED driver circuit does
>> not load the signal it is monitoring.
>> 
>> Neil
> 
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