Forrest

You're looking for some simple sort of constant current controller?

How about a small light bulb?  :-)

Otherwise you _might_  be able to find a PTC resistor that works as-is
or in combination with a standard resistor.

One problem is going to be heat. At 10mA & a 5V supply, you're going
to drop about 3.8V across the "controller" & dissipate 38mW (R=380ohm)
 . At 60V, the dissipation is ~0.6 watt. (R=5k8). Any active component
dissipating this much is probably going to want a heatsink of some
kind unless there is good airflow.

Another alternative would be to use a simple switcher (eg the "Black
regulator") But at increased cost & component count.

Richard P


2008/7/17 Forrest W Christian <forrestc@imach.com>:
> I seem to quite often need to run a "voltage present" LED on a very wide
> range of voltages...  For instance, in one case the input voltage can
> run from 5 to 60VDC, or more.
>
> I need to power this LED from the power source, but need to regulate the
> current so that the LED is pretty much constant output across the
> voltage range.
>
> I'm aware of the standard schematic using a PNP, a Zener, and a couple
> of resistors, but would prefer something with lower part count.
>
> I'm also aware of the LM317HV, but the cost there is prohibitive (I
> would need the HV becuase of the higher voltage range input).
>
> Of course there's always the option of putting a regular voltage
> regulator and resistor in, but again, that gets somewhat costly.
>
> I'm hoping I can find something just marginally more expensive than
> putting a current limiting resistor in place.   Is there some magic
> circuit I've missed...
>
> -forrest
> --
> http://www.piclist.com PIC/SX FAQ & list archive
> View/change your membership options at
> http://mailman.mit.edu/mailman/listinfo/piclist
>
-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist