# Strobing led for model aircraft

#### ltodd2

Joined Sep 9, 2017
13
Hi
I've been wanting to make a double flash strobe like you get on aircraft but for models. Was looking at the addressable led like the ws2812 but then found a site that sells this type of thing. I want to make my own and smaller but I'm not sure how its done. Thenone on this site uses a cree led, 90mah lipo and it does 2 flashes of 20ms each and he sends 1000mha to the led in that time. Attached is a screen shot of the device. I'm guessing the brains is tbe 6 pin ic but all we know from it is LJ4C. Anyone know what it is or who this works please.
Thanks

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#### Bernard

Joined Aug 7, 2008
5,352
Best bet might be a micro controller but if not in to coding like me, a surface mount 556, dual 555,
should work.
What is available V ?
What is time space between flashes ?
What is time between groups ?

#### AnalogKid

Joined Aug 1, 2013
8,251
As above, nothing will be smaller and cheaper than a microcontroller (uC) - IF IF IF you already have a software development platform and programming hardware. If not, then it will take one or two very low cost ICs and some misc parts. What is your skill set for assembling either through-hole or surface mount circuits by hand?

ak

#### ltodd2

Joined Sep 9, 2017
13
Best bet might be a micro controller but if not in to coding like me, a surface mount 556, dual 555,
should work.
What is available V ?
What is time space between flashes ?
What is time between groups ?
Hi Bernard
I'm looking at a 3.7 lipper for power. I'm looking for somthing like you get on aircraft so every 1 second you get 2 short but close together flashes then remaining time and repeat if that makes sense. I'm wanting to get as small as poss and light as poss. Prob have this as driver with external leds
Lee

#### ltodd2

Joined Sep 9, 2017
13
As above, nothing will be smaller and cheaper than a microcontroller (uC) - IF IF IF you already have a software development platform and programming hardware. If not, then it will take one or two very low cost ICs and some misc parts. What is your skill set for assembling either through-hole or surface mount circuits by hand?

ak
Hi
Arduino based I'm ok. My first attempt was with arduino and was looking at making small board based on attiny. Soldering is good but never tried smd but up for trying

Lee

#### bassbindevil

Joined Jan 23, 2014
52
Consider getting a flashlight driver board that has the Attiny and some 7135 constant current chips. NANJG is one brand to search for. There's lots of custom firmware for these, with source code, at forums like candlepower and budget light. Programming hardware is cheap.

#### Tonyr1084

Joined Sep 24, 2015
4,028
I must be out of touch, but my first thought was a decade counter. A brief output from output #2 then #4, leaving 0,1,3,5-9 out. If you sweep the 10 outputs once every second, you'll get 0.1 (100 mS) flashes from 2 & 4 separated by 100 mS of dark. If the flashes are too close together you can switch to 2 & 5 or 2 & 6. I've chosen those numbers for the sake of choosing something. You can go with output 0 and 2 if you want. using 0 & 5 would give you a flash every half second.

Parts count would require a timer (555) and a CD4017 decade counter. A couple resistors and a capacitor for the timer and a resistor for the two LED's. You don't need a resistor for each LED since neither is lit simultaneously. Both cathodes can be tied to the resistor and to ground (or negative in your circuit). However, I am dubious as to whether this will work with 3.7 V. I'd go with two 18650's. But the weight might be something you're trying to avoid. Are we talking about RC controlled aircraft? Or just a desk model?

Then again, I resist designing circuits the new-fangled way. I'm an old fashioned fart. I prefer logic versus code. But that's me.

#### AnalogKid

Joined Aug 1, 2013
8,251
My read is that all LEDs are on or off together, not in sequence.

TS:
How many LEDs?
Do they all flash together, or sequentially?

ak

#### Tonyr1084

Joined Sep 24, 2015
4,028
@AnalogKid My take is that there are, lets consider a single wing tip: Typically there is a red Navigation light on the left wingtip. Some aircraft are configured with as many as three xenon strobes, two forward and a single aft strobe. Other aircraft just have a single strobe on each wing tip. In the case of the DC-10, an aircraft I have considerable experience with exterior lighting, on the wingtip, both fore and aft strobes flash at the same time followed closely by a second strobe on the leading edge. Just multiply that by 2, one set for each wingtip.

The model builder wants to flash a couple (probably super-bright) LED's, one each wingtip. To simulate the double flash the TS is asking for, both left and right wing tips can be equipped with a single LED on each tip and flash in unison. Two flashes for the particular aircraft the model builder is building. A single CD4017 and an NE555 along with a few resistors, a capacitor and to drive both LED's simultaneously, a transistor; probably just a 2N2222 or a 2N3904 NPN type transistor to make each light flash when powered by the 4017. Probably a couple steering diodes too to prevent one output from feeding back into the other. But again, it's my approach to use logic versus code. I'm sure it can be done with code too. But beyond the microprocessor you'll also need some support electronics, passive and active. But I don't know that for sure. I don't do micro's. Not yet anyway. Probably will never give up being stubborn either.

#### Tonyr1084

Joined Sep 24, 2015
4,028
@ltodd2 If you want to go with a shorter flash time you can substitute the 555 for a double-D flipflop. You'll have to use the set and reset pins to generate the clock pulse, but you'll also need a few more components. I've made a DD flipflop do exactly that. Using just one of the two DD's you can generate the clock pulse, with the second you can cycle between high and low, creating a circumstance where you can get a shorter flash and a longer duration between flashes. I'll look through my doc's and see if I can find it. I'm sure I have it - the DD arrangement. I, too, like lower parts counts. This was an early approach to solving a particular problem with the 4017 in the configuration I was after. I'll post it when I find it.

#### Tonyr1084

Joined Sep 24, 2015
4,028
Didn't take long to find it at all.

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#### Tonyr1084

Joined Sep 24, 2015
4,028
Here's a closeup of the clock pulse generator.

#### Rich2

Joined Mar 3, 2014
134
I made something similar with just a 555 timer. It only does 1 brief flash every 3 seconds but looks very like a planes wing strobe. I used a high power wide angle LED on a heat sink all powered by 2 x 18650 batteries.

If you were happy with one flash the circuit is a lot smaller than a decade counter 2 flash circuit would be.

I made it to attract attention to my laser Level when it's been set up on the floor on CDM sites. So no one would kick it or trip over it.

#### Rich2

Joined Mar 3, 2014
134
Also 16340 batteries could be substituted for less weight.

#### ltodd2

Joined Sep 9, 2017
13
Thanks all for the replies. Just to clarify this is to go on drones. The main reason is to aid is seeing it as the flash would be better than solid light. I was going the microprocessor way using ws2812b LEDs which would allow for a solid red and green and using the white led for the flash but they are not the brightest but would allow you to know which way its facing.
Then i found the item in my first post. A pre made strobe but you would need a few for each side. they do make just the led and just add power but on drone its going to need its own power. So im thinking of making my own as just the driver and battery and connect separate LEDs. This way would not allow for a solid red/green but could use high power red/green for the flash in place of white. His also takes input from the rc to control them but i dont need that.
Im not sure how he has made it flash so bright and runs for 2-4 hours from a 90mha batt and putting 1000ma into the led for the flash.
Needs to be as small as i can possibly make it.

Thanks
Lee

#### jpanhalt

Joined Jan 18, 2008
8,459
Considering all of the problems "drone" regulations are causing the FAA and, since the FAA doesn't differentiate, modelers flying fixed wing, emulating a full-scale aircraft at night is not a good idea. If it were for daytime scale effect, I see much less of a problem.

Things to come:
Remote identification REQUIRED. Are you prepared? Is your FAA drone license up to date?

#### djsfantasi

Joined Apr 11, 2010
5,913
Do all the flashes need to be synchronized? An ATTiny85 is all you need to flash one led. It’s an 8 pin IC. You can duplicate the ATTiny85 for each led. Or, you can drive a BJT/ MOSFET to drive several LEDs in sync.

The code is simple. I’ve provided sample code below. This code works for one LED or several with a BJT or MOSFET (2N7000) driver.

Code:
#define lightPin 4
#define shortTime 3000
#define longTime 7000
#define onTime 1000
void setup() {
pinMode(lightPin,OUTPUT);
digitalWrite(lightPin,LOW);
}

void main() {
long endTime =0;
endTime=millis() + longTime;
while( millis()<endtime);
digitalWrite(lightPin, HIGH);
delay(onTime);
digitalWrite(lightPin,LOW);
endTime=millis() + shortTime;
While(millis()<endTime);
digitalWrite(lightPin,  HIGH);
delay(onTime);
digitalWrite(lightPin, LOW);
}
SparkFun makes a reasonable programmer for the ATTiny series of chips that lets you use the Arduino IDI to develop and upload your programs

#### Bernard

Joined Aug 7, 2008
5,352
Keeping @jpanhalt's comments in mind, consider flashing red & green LEDs at 20 to 30% duty cycle to lower power consumed. A unijunction or programmable unijunction , PUT, can flash LEDs.
Drop the double flash.

#### Tonyr1084

Joined Sep 24, 2015
4,028
Actually, when it comes to Aeronautical Rules, the number of flashes and the manor of the strobes CAN have a meaning that I don't know of. You COULD be simulating a distant aircraft and some approaching REAL aircraft could strike the drone, which could cause problems - even catastrophic failure of a manned aircraft. I wouldn't want to be THAT guy flying THAT drone when that happened.

#### MisterBill2

Joined Jan 23, 2018
4,846
An easy option is to contact the applications folks at CREE and explain what you want to put on your product. Using an arduino will drain more power than those 20 millisecond flashes of the LEDs. You can do it with a binary counter, not a 4017, because the need is for two 20 millisecond flashes with two seconds between the flash bursts. You can do it with two ICs and an oscillator module. The binary counts pulses and when it reaches 2mseconds it enables the 4017, which then triggers the flash sequence off of counts 1 and 4 and then resets both counters on count 6. The actual spacing may need some adjustment. The clock source for the 4017 will need to have 20 milliseconds between rising edges, that can come from some tap on the binary counter, You could use a CD4060 with a built in oscillator and avoid needing the separate clock oscillator module. So there is your whole circuit except for the two MPSA13 transistors that drive the power transistors for sending the power to the LEDS. NO PROGRAMMING and no micro-board with the big battery drain. Total IC cost about \$3 if you don't look for the best pricing.