1w LED strobe

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mtown52
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1w LED strobe

Post by mtown52 » Sat May 20, 2006 4:41 pm

I am building an RV9 aircraft and need wingtip strobes. I want to use leds and need a circuit that gives a double flash about every second or so. Hopefully someone has some ideas? [email protected]
Mike, in Tasmania

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Chris Smith
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Post by Chris Smith » Sat May 20, 2006 7:56 pm

A simple strobe. You charge a small cap up on the flop, of a flip flop circuit. Using a simple 555 your set your timing to one second on, one off, and while the flip flop discharges the cap, it then flops and charges the cap, and vice versa. If you chose your cap size just right, and your voltage value high enough to make the led very bright, the over all current flow over time will almost match the Leds maximum limits. You can use voltages much higher than the led is rated for, as the discharge rate of that cap will be less over all on time. However some Leds don’t like high voltages, standard ones can run as high as 100 volts easily, for very short durations. Also you need to snub any over shoot similar to a relay or coil when it relaxes, by attaching a reverse diode to ground to catch the ringing of the cap as it discharges. Reverse voltage is more detrimental to a LED than short high volt forward voltages. Also have the led driven directly from a FET to deliver a quick response, current handling capabilities, and a buffer between the 555 and the circuit. You can also use a second FET on the cap charge cycle that turns on during the negative cycle of the out put on the 555.

Also, if they still have any left over, All Electronics has a great road side flasher that uses a White Led, a solar recharger panel, and a 14 pin chip that strobes the led bright enough to give you a head ache, and all for 6 bucks US.

It even comes with batteries and it can be trimmed even smaller than its couple ounce size.

If you cant find them at All Electronics, [http://www.allelectronics.com/] I have a few spare boards minus the package and solar panel.

rshayes
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Post by rshayes » Sat May 20, 2006 9:21 pm

You are probably better off using the normal arc lamps for aircraft use. These typically draw about 25 to 50 watts of power from the aircraft power source. The efficiency of the arc lamps is about the same or possibly better than the LEDs and the power handling capacity of an arc lamp is substantially higher. The radiation pattern is also broader, which is desirable in an aircraft application.

Most LEDs have enough series resistance in the die to substantially reduce their efficiency when they are pulsed at currents very much above their rated current. Getting total light output equal to that of an arc lamp might require many LEDs, as well as an elaborate heatsink.

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dacflyer
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Post by dacflyer » Sat May 20, 2006 9:38 pm

i fly a ultralight , and i can tell you right now,, no one will see that 1 watt led good at all, especially in the day time..

if you need a strobe power supply for aircraft, i have a 4 channel one here
i'll sell ya,, cheap !..and you can get the heads that you want fairly cheap also.. as a matter of fact, i built my heads myself..and the power supply came from a dual head unit. from star headlight and lantern co.
guys at the airport say they can easily me 5 miles out..they said its the brightest they ever seen on a ultralight or expermental aircraft..
and i run it on a 7Ah hr 12 volt battery, and i get at least 4 hrs use before the battery gets low..
i am in process of utilizing the onboard power from my engine, as soon as i find me a good rectifier/regulator...

let me know if i can be of more help..

well tomorrow is last day of the lumberton airshow here,,,its been great here.. www.mafsac.com
:D

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