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

[KA4HJH]

On Sep 5, 2012, at 2:36 PM, Neil Johnson wrote:

> Hi,
> 
> Tim Ressel wrote:
>> I use a modified Howland Current Pump to drive LEDs, especially bi-color.
>> 
>> Here is the schematic:
>> https://dl.dropbox.com/u/5536133/led_driver1.pdf
> 
> Well, I guess if you like complexity...
> 
> You can do it with an op-amp and single resistor if you're ok with the
> LED fully floating.

The brightness of LEDs varies exponentially with the current so if you really want to get fancy you need an expo convertor. This is easily done with an MCU and a look-up table. It looks quite nice. 8D


Terry Bowman, KA4HJH
"The Mac Doctor"