boost regulator led flashlight

Conceptcar3 · Mar 28, 2007

Hi guys, do any of you happen to know of an LED flashlight that boost regulates 1.5v from 1 aaa battery to ~5-6v with 40mA delivered? If someone could tell me where I could get a circuit that does this (white LED) that would be excellent! I have heard the elly upconverts 1.5v to 5v, so that is perfect, but I am unsure of the mA delivered. Any help is GREATLY appreciate!!

thanks in advance.

cage · Mar 28, 2007

This circuit is great for driving a led from a single cell. It works even with a button cell.
http://www.emanator.demon.co.uk/bigclive/joule.htm
Elly circuitry supplies about 300mA.

Conceptcar3 · Mar 28, 2007

i am looking to regulate it so it does NOT exceed 40mA. If I used a 15ohm resistor before the out put to the LED on the elly circuit would this accomplish the task? and do you know if the voltage output is 5v? Thanks for the help!

For my purposes, 50mA = dead diode!

cage · Mar 28, 2007

Conceptcar3 said:
i am looking to regulate it so it does NOT exceed 40mA. If I used a 15ohm resistor before the out put to the LED on the elly circuit would this accomplish the task? and do you know if the voltage output is 5v? Thanks for the help! For my purposes, 50mA = dead diode!

What forward voltage drop does the led have? I think in one thread someone said it elly circuit would regulate to 5V.

Conceptcar3 · Mar 28, 2007

haha its actually not an LED, its a... dare i say it on this forum... LASER diode; thus the need for amp regulation. I have determined now that the 15ohm resistor would regulate the 300mA down to 40mA, and if the driver is regulated to 5v, that is the perfect voltage for this diode. However, if it is substantially less, like 3.5-4.5v, this wont due for my purposes.

cage · Mar 28, 2007

Conceptcar3 said:
haha its actually not an LED, its a... dare i say it on this forum... LASER diode; thus the need for amp regulation. I have determined now that the 15ohm resistor would regulate the 300mA down to 40mA, and if the driver is regulated to 5v, that is the perfect voltage for this diode. However, if it is substantially less, like 3.5-4.5v, this wont due for my purposes.

You can measure output voltage after disconnecting ellys led.

2xTrinity · Mar 28, 2007

Conceptcar3 said:
haha its actually not an LED, its a... dare i say it on this forum... LASER diode; thus the need for amp regulation. I have determined now that the 15ohm resistor would regulate the 300mA down to 40mA, and if the driver is regulated to 5v, that is the perfect voltage for this diode. However, if it is substantially less, like 3.5-4.5v, this wont due for my purposes.

The Elly is voltage regulated, about 5V unloaded. It relies on voltage sag of the batteries and drive to keep the current within reasonable limitation. That's also the reason why substituting a Cree LED, which operates at lower voltage, causes it to be driven harder. Also, dropping in a battery with lower resistance, such as a Lithium primary, causes the light to become a lot brighter.

Conceptcar3 · Mar 28, 2007

so would using a simple 15ohm resistor not be sufficient to prevent current from exceeding 40mA b/c the current is constantly changing dependant upon battery power??? If it is voltage regulated to 5v, and operates at 300milliamps, ohms law says I need 16.66666 ohms of resistance lol, thus why I say 15ohm resistor... but would that suffice?

cage · Mar 28, 2007

Resistor value depends on the forward voltage drop. Resistors limit current by dropping voltage as load gets bigger.

Conceptcar3 · Mar 28, 2007

gotcha, so I read on another thread that the elly only boost converts to 3.2v? some say 5v, others say this- does anyone know the actual voltage boost produced by the elly?

cage · Mar 28, 2007

Load induced by the led pulls output voltage down. With a small load the driver would propably try to keep the voltage stable at 5V

sysadmn · Mar 28, 2007

Conceptcar3 said:
Hi guys, do any of you happen to know of an LED flashlight that boost regulates 1.5v from 1 aaa battery to ~5-6v with 40mA delivered? If someone could tell me where I could get a circuit that does this (white LED) that would be excellent! I have heard the elly upconverts 1.5v to 5v, so that is perfect, but I am unsure of the mA delivered. Any help is GREATLY appreciate!! thanks in advance.

I like this, but you'd have to jigger with values to get the voltage and current limit correct:

http://edusite10.tripod.com/led3/onetran/regulated.htm

You can do it with SMD components in very little space.

boost regulator led flashlight

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