Re: Current-driving a powerful IR-illuminator array

In article <122qe4949dsh4e4@xxxxxxxxxxxxxxxxxx>, "Meindert Sprang" <ms@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:
"BW" <bjorn@xxxxxxxxxxxx> wrote in message
news:1143810662.678320.268540@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Hi! I want to drive a fairly powerful IR-illuminator array using
high-efficiency IR-LED's (Agilent HSDL-4230 to be specific), which can
support continous currents of 100 mA and peak currents of up to 500 mA.
I want perhaps 40 of these.. and essentially I want to flash them all
in sync to an electronic camera shutter of around 1 ms width, with a
duty-cycle of perhaps 1-to-30. Now when googling around for suitable
circuits, most refer to relatively small power demands, with LEDs that
use a current of only a tenth of this.. both with resistors and with
MAX-circuits etc.

I once used the following approach to drive 25 IR leds in sync with a camera
frame sync: From a 12V power supply I drove 5 strings of leds, each string
having 5 leds in series. Each led string was connected anode to +12V,
cathode to the collector of an NPN transistor, the emitter was connected to
ground through a 10ohm resistor. By driving the base from 5V, the circuit
behaves like a current source of (5-0.7)/10 = 430mA. Need more current,
increase the drive voltage. All bases were connected together though a 10ohm
resistor.
The total current draw is 2.2 A while each led gets 430mA.

I still toying with a system to flash Led's in sync with a camera. Edmund Optics
makes a flasher, but its not heavy enough for my case.I don't see much of a problem
making my circuit, even though its going to peak at 65 watts. I probably will use Fet switching
to make the common connection at ground.

greg
.

Relevant Pages

  • Re: Running, Steaming and Anchor lites
    ... into existing bayonet or bipin lampholders. ... I'm not trying to dissuade you from getting new nav lights. ... On the other hand if the bad connection is ... Someone else thought I could replace just the bulbs with LEDs. ...
    (rec.boats.cruising)
  • Re: FPGA quiz3, or where Antti did give up and does not know answer or acceptable workaround
    ... LEDS <= do64s(63 downto 60); ... you'd obviously need a sync or reset pulse. ... frequency, 4Mhz, 500Khz exactly the same odd behaviour ...
    (comp.arch.fpga)
  • Re: Digital Current Control for LED array
    ... >>> voltage across them assuming they are of the same type. ... >>light output levels due to differences in phosphor coating (for white ... >>LEDs) thermal conductivity of the package and other physical ... A parallel connection sets the Voltage of each LED as fixed and NOT the current. ...
    (sci.electronics.design)
  • Troubleshooting connection loss (novice question)
    ... My DSL connection usually runs well, but about once every seven to ten days I lose my Internet connection. ... I've not been able to regain my Internet connection without a reboot. ... NIC LEDs: NIC is Intel Pro/100 M with two LEDs. ... When I have an Internet connection, the eth0 monitor shows continuous activity, even when I'm not accessing anything. ...
    (comp.os.linux.networking)
  • Re: Troubleshooting connection loss (novice question)
    ... My DSL connection usually runs well, ... I've not been able to regain my Internet ... NIC LEDs: NIC is Intel Pro/100 M with two LEDs. ... The eth0 monitor shows zero activity. ...
    (comp.os.linux.networking)