A nice half an hour project ...

Just got inspired from the pak-lites. There are
using a 9V Batterie with two 5mm LEDs and two
brightness levels. The professional and original
ones can be found at 9voltlight.com.

I had an old 9V Battery lying around, as well as
some small switches and two kingbright 5mm white LEDs.
I figured out that there should be an ~30Ohm Resistor
for high, but had only an 47Ohm Resistor so its not
as bright on high as it could be. For the low mode
I took an 1kOhm resitor. The two leds are connected in
series with the switch, so that either the 47Ohm or the
1kOhm resistor are in series.

The low mode is a bit lower than the low mode of my
L1 and the high mode is a bit lower than the opalec
newbeam.

It was an really easy build, which is just waiting
to got epoxied. It took me about half an hour. Its
the ideal cheap night task light.



Maybe the next one I build should have an regulated
currentsource (simple FET currentsource). Just for fun. /ubbthreads/images/graemlins/blush.gif

Cheers
Ralf

Cool. I've made several versions myself, including some with constant current regulators.

FYI, the original uses 150 ohms for high, and adds an additional 3000 ohms for low.

Doug Owen

Thanks Doug for the Information.
Just thought yesterday night, the low is still
a bit high. But maybe there are using different
LEDs (maybe from nichia) for me the high with
47 Ohm could be still a bit more high. 150Ohms
seems to still underdrive them.

From the cpf EE University I picked up the formula
for the nichias and put that in my calculator.
that will give 3mA for a 1000Ohm and about 15mA for
150Ohm, 36mA for 47Ohm. /ubbthreads/images/graemlins/smile.gif

Cheers
Ralf

Doug are there some pictures of yours?

Cheers
Ralf

[ QUOTE ]
Ralf said:
Thanks Doug for the Information.
Just thought yesterday night, the low is still
a bit high. But maybe there are using different
LEDs (maybe from nichia) for me the high with
47 Ohm could be still a bit more high. 150Ohms
seems to still underdrive them.

From the cpf EE University I picked up the formula
for the nichias and put that in my calculator.
that will give 3mA for a 1000Ohm and about 15mA for
150Ohm, 36mA for 47Ohm. /ubbthreads/images/graemlins/smile.gif

Cheers
Ralf

[/ QUOTE ]

The actual currents (with 9.0 Volts in) for my PacLite are 1.0 mA on low (.280 and 2.87 Vf), 16 mA for high (3.16 and 3.32 Volts for Vf).

Sure, you can drive 'em harder, but the maker was looking for very long run times......

Doug Owen

[ QUOTE ]
Ralf said:
Doug are there some pictures of yours?

Cheers
Ralf

[/ QUOTE ]

Not really, although I suppose I could take a couple. If I emailed them to you, can you post them here (I can't)?

Doug Owen

Doug, PM sent ...

Cheers
Ralf

Don mind to share some pictures of mod?

Thanks.