> Hi Aaron,
> I looked at the op-amp / FET circuit and considered it. The problem though
> is that it's a linear regulator. I'd be dissipating at least 25 watts
> through the fets. It's not hard to find fets that can handle this, but it's
> just so wasteful and basically the same result as using big power
> resistors.... I might just end up using power resistors to start with if I
> cannot find a better way.
> Sent from Samsung tablet
> Aaron Oliver-Taylor <aaron.oliver.tay...@gmail.com> wrote:
> How about a constant current source - use an op-amp and high current
> mosfet (or several in parallel) to obtain a precise current. This
> programmable constant current dummy load uses a constant current source
> like this, you could use this idea:
> This also might be of use:
> Aaron Oliver-Taylor
> *Email* aaron.oliver.tay...@gmail.com
> *Web* aayotee.wordpress.com
> On Thu, Oct 4, 2012 at 12:06 PM, IrradiatedHaggis <hs_t...@codemaven.me>wrote:
>> Hi all,
>> Hoping someone can help me... I'm working on a DLP resin based 3d
>> printer. I have a modified LED Pico projcetor which I have removed the LEDs
>> from and replaced them with a UV LED. Currently I have a 5W LED on it for a
>> proof-of-concept. It works, but I need to upgrade to a more powerful LED
>> for cure times to be at all reasonable.
>> I'm looking at using the CBT-120-UV-C11-G382-22 UV LED from Luminus
>> Devices, which is explicitly designed for this purpose. It is an insane
>> (and expensive) diode that is ideal for my purposes... With 11 Watts of
>> actual optical power output it is one of the brightest LEDs on the market.
>> The problem is, I need 18amps at 3.7 volts to drive it. So... My question
>> is, how can I get this?
>> Ideally, I'd like to run off of 5V. Using a regular resistor to power it
>> from 5V I need about 0.08 ohms capable of at least 25 watts (I think). That
>> is going to get _Very_ hot and is simply an insane waste of power. Thats
>> assuming my power calculation is correct.... Do I use the full 5V for power
>> dissipation in the resistor, or the 1.3 volt difference between the diode
>> voltage drop and the power supply? If it's the full 5V then I actually need
>> a 90 watt resistor....
>> So obviously I need a switchin constant current regulator. A linear
>> regulator just will not do here. But I cannot find an LED drivers that will
>> work at 18 amps.... And those that approach it (16 amps is the largest I
>> can find) will not work at output voltages below 15v since they're intended
>> to drive multiple LEDs in series. Does anyone know of any regulators that
>> would work?
>> I did find one buck regulator that is intended to drive a white LED at 9A
>> (on pcb-components.de). Hypothetically, could I use two of these in
>> parallel? I'm thinking that with switching constant current regulators
>> running two in parallel is probably not possible... I don't know how they
>> would behave. Any thoughts on this?
>> Anyway, just thought I'd drop a line here and ask if anyone has any
>> experience in this area or could provide some suggestions /advice for
>> lighting those LEDS up.
>> Sent from Samsung tablet