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Feb 21, 2019, 08:51 PM
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Build Log

DIY LED Afterburner(s) - very cheap to make

I have never really worried much about not having any 'Afterburners' on jets that the full scale version does have it, but I had bought a few of the various Afterburner 'kits' that have been around over the years. eg RC Lander, done as a ring of LEDs to go on the very exhaust of the jet.
These had numerous fitting issues and downsides so I never actually used any.....

When RCgeek started selling some, and with the 'new' idea of using LEDs on the actual EDF motor, it began to seem a more useful idea.
But the cost to get those to Australia is a LOT!! Too much for even one jet, let alone a bunch of them!
So I decided to make up my own version.

4stripes from RCG also 'reminded' me of the idea to make my own, based on that 'on the motor' idea, and it raised my enthusiasm to actually do something!

A single 10W LED makes it easier to do than using many smaller LED's.....

If you only switch the LED On... and Off.... then the driving circuit is extremely simple.
If you want it to Flicker at the On/Off transition region then that gets notably more complex compared to just On/Off, but is still not that hard to implement.

Then there is a third option/possibility, where you have 'unlimited' control of the colours and timings - though what variations and true needs of these possibilities are there? This would be done with the use of a microprocesser unit, such as an Aduino Nano etc. Very small and very cheap.

I decided that my criteria is to at least have 'Flickering'.
So HOW to achieve that?
There seems to be two main ways for the moment. A 'local' on board controller. Or via using another TX channel and doing it at the TX itself.

On the TX you could just form a process Mixed from the Throttle Channel, to vary the On/Off behaviour of the on board RC Switch you would have to control the LED in the aircraft. Thus any form of flickering etc you could want is easy enough to create.

For an on board controller, you need some circuitry designed to form this desired flickering pattern. One simple way is to use an Arduino, though seems like an overkill. But it is small and would do it all fine - with infinitely more capability than you would ever even need or use.
Another circuit would be to build some system that checks the throttle command value and then uses a timer, or more, to generate pulsing/flickering..... hmmm, the effort to design and build this is much more effort than using a SIMPLE and cheap, overkill, Arduino!!
An Arduino also has a 'standard' ability to read PWM signals too - so in all ways it is all ready set and tailored to do everything and anything this task could need!

Using an Arduino means it is all self contained - no need for TX setup/programming at all..... so really, this is the most universally workable idea!

Another Arduino benefit is that is could be used to do other tasks too... many other tasks! Like.... ummm... who knows....
It can also drive an RGB 10W LED version, which then means you can ue any colours you want... in any sequences, patterns, reasons, you want.

An Arduino cannot drive a 10W LED directly itself..... the LED needs too much Current. So a little bit of extra circuitry is needed to take the Arduino signals and switch a more powerful Transistor or FET to drive the LED. Just one channel to drive a plain 'yellow' LED, or three channels to drive and RGB LED version.

This whole assembly (of all required electronics) would be done as a 'control unit' and all that needs is the input lead (12v), and the output lead that runs to the LED. You would either heatshrink it all, otherwise put it into a small case/box.

An Arduino Nano costs approx AUD$3.80 from China. And the rest of the few components about 30c....
The 10W LED in Yellow or RGB, is approx AUD$4.00 (You can get 10W, 20W, 30W, 50W, 100W !!)
So in total all the parts are well under $10.

Hmmm, you also need a roll of Aluminium Tape... $10 approx. This is to line the exhaust ducting of the jet, so that lighting reflects all the way down to the rear end.
But that roll/amount would do a LOT of jets! So in total the cost is still sub $10.

I have pondered over the way I would want the Afterburner to work/look......

I wondered if I want... need.... any colors. Maybe at various AB stages. I sort of thought that maybe you see some 'blue', or orangey/blue, at some stages.
So I looked at a heap of jets with AB's in use, or coming into use..... overall it seems that really they most often are just 'nothing' there, and then a pretty well instant switch to yellow/WHITE. Not Orange... not Yellow... but more White than Yellow.....

So I did buy both the Yellow LED version and the RGB version in case. To get a more White biased Yellow (or any other shades/colors) you would need to use RGB.....

Plus if you are more towards 'White' then that uses more light to achieve that, so the output is even brighter - than say for just yellow.

Using the RGB version also means you can CHANGE it simply just via the Arduino programming to whatever you want in the future also.

Another thing I was pondering was CONTRAST.
White/Yellow is less of a contrast to the outside of the aircraft than, say, Orange would be... or even plain Yellow.....
So you have this trade-off issue of better contrast versus true colors of a full scale jet AB.

Then another pondering....
With the Arduino being massively more capable, you can even take another TX/RX Channel dedicated to real-time color changing. In various ways, but for eg you could use a Pot that runs the LED output across a colour range. eg from White, through yellow to orange, to red - and via all the shades between those.
Or use an OpenTX LUA script that gives you a complete colour control panel! To dial in ANY colour... RGB... set you want!
I guess this is something it should include in the Arduino coding done, as it is pretty easy and may as well be ready to utilise it... or just not use it if you don't want to.

So next is on to the prototyping.............
Last edited by PeterVRC; Sep 15, 2019 at 07:59 PM.
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Feb 21, 2019, 09:34 PM
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Full scale jets

So off I went to check more images and videos of various jet types, to see what AB colors they have....
Hmmm, mainly towards a darker orange.... and I could not find any of the ones I had seen in more of a white/yellow....

Interesting was the F-4 Phantoms having anything from orange, darker orange, to a BLUISH color!
This video below, of a group of F-4's taking off, has a number of variations across them.

So what this means is the best is to make it PROGRAMMABLE, with the RGB LED version, Then you can make any jet have its 'right' colors, or even alter them at times etc.

8 x F-4 AUP Phantom II taking off with full afterburner (3 min 58 sec)
Mar 18, 2019, 03:47 AM
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Design Choice

It took a while for some of the possible useful parts to come from China.....

The first useful item is a Constant Current LED Driver module, which you can set to feed the exact Current (MilliAmps) to optimise the LED output, but it also makes it a constant no matter what charge level the Voltage source, battery, is at.
It is actually a DC-DC Step Down device, but the IC used supports Constant Current output also. So this means it can take any Input Voltage from 5v to 35v, and output a Constant Current - which is done by varying the output VOLTAGE precisely to achieve that resultant.
It is just perfect for this use because it means you can use any Lipo source up to 8S, plus the unit also has a PWM Control Input which can alter the output level. This input is sort of an On/Off input that a PWM signal means it will turn on and off rapidly, at the PWM High/Low ratio. A LOW input turns it ON, and a High turns it Off. So if a PWM signal is 70% high, and 30% Low periods, the LED will be run at 30% brightness.

This unit is ALMOST all you need... but unfortunately not quite.....

It is not actually needed as a DIMMER at all..... but just as a Constant Current source, to assure constant full brightness for any input Voltage.... plus the ability to turn the LED On and Off,, under a Digital Signal Level control (The PWM input control).
For this use it will be OFF..... for Throttle levels under, say, 70%. Then ON.... for Throttle levels 80% or higher.
And for 70% to 80% Throttle range it will FLICKER On and Off erratically - plus the 'erratic flicker' will increase in ON time as it rises from 70% to 80%, where it then becomes that solid ON.

So this needs a way to form those control inputs to the unit.....
An RC "PWM signal" is NOT the same form of PWM !!! RC is more of a "PPM on PWM" sort of signal, and is not just a 'normal' PWM signal then.
But we want to... need to.. use the RC Throttle PWM signal to form the real PWM signal. To read the Throttle value to do the LED Driver module On/Off controls.

This could be done with circuitry made up, but the multiple parts and their costs - even though low - cannot beat an Arduino Nano, which is only $5
This LED Driver Module is $1.75
An Arduino can read RC PWM.... and coding, programming it, can form whatever 'normal' PWM output you need to control the LED Driver module..
An Arduino can also be reprogrammed to any changes you might ever think to want/need.... changes in anything.... On or Off points, Flicker manner etc. It is also very small, and about the same footprint as the LED Driver Module so it can sit back to back with that (I think).
So it is just the best choice/option to use!

I already have those, and other Arduinos, so I began the coding the other night - but found some simple things I didn't know how to achieve and need to read up a bit on those. But all things are simple and quick enough to find, read, learn anyway. I should get it working within a few days....
Plus I need to test if the Arduino Nano and LED Driver Module being NEAR each other will bother the Arduino (interference due to the Switching Circuit of the LED Driver). At worst they would need to be kept as separate items, which is no worse than if you have a unit that needs to run from an SBEC anyway.

Mar 18, 2019, 03:57 AM
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Hmmm, I just thought of a better idea....
In the Arduino programming, it could be made to have read TWO RC PWM inputs.
The Throttle, and also another dedicated Channel just for Afterburner Control.
The reason for this is that you could control it as per I laid out above..... but have multiple programmed sequences, and use the 'Control Channel' to choose alternate operations.
There are even a lot of other uses that reading another Channel, or even more, could have it do.

And if there is no Control Channel connected, it defaults to one of the sequences....

Which just made me think of the recent years of Freewing jets that include a Control Unit.... which is probably just an Atmega processor set up to do all the tasks that each plane has it do...? I have not checked if it is Atmega (as per Arduino use) or some other dedicated LSI chip. But that concept is the same thing as this Afterburner 'processor'. Create a unit that can be 'made' to control things you want/need....
Mar 19, 2019, 06:00 AM
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Version 1

I joined the Arduino Nano and 350mA Constant Current Driver back to back - the Nano is just a bit longer than the driver board, but also a bit narrower.
There is no interference affecting the Nano operation.
I have not decided how to Enclose it yet..... box? Acetate sheet box? 3D Printed light weight box? Thin wall heatshrink?

I did discover a 'problem'. The Nano needs 7v to 12v (technically up to 20v even) to run it, whilst the LED Driver can be 5v to 35v - thus the Nano sets the Voltage to choose.
That is a range of value in Lipo cells from 2S to 3S .
To make it 'universal' up to 8S you would need an SBEC or cheap regulator - but with that 7v to 12v range of output. You can modify any SBEC to do that... or notably cheaper is just to buy the common DC-DC convertors from eBay.
BUT this method means another small module = larger total volume/size.

OR...... you could just use 3S of the balance connector, to any battery type....
You can modify a 6S JST-XH connector to take 3,4,5,6S with still one KEY at one end, so that it clips on securely to any of those 3,4,5,6S balance leads still.
The Current used by the AB System is very low, so any cell imbalance from doing it that way will be insignificant.
I will most likely use this method.

For Version1 I just whipped up a system that a RISING Throttle signal passing through 2000uS will trigger a rapidly increasing frequency flickering sequence which then turns to solid LED ON. But coming down through that it just changes to LED OFF instantly.
There are various ways to make this real-time programmable - to change trigger points etc. Either via attached Trim Pot(s), or via RC command - or include both. eg a Trim Pot you can alter to set where the trigger/flash point begins.
For the moment the plain "Flicker-ON, instant-Off" seems fine enough.... though I guess I should just add the on board Trim Pot control mode also really. Just in case I want to 'tune' it.
Without either type, you can still plug in a PC (Notebook etc) and alter the programming that way.

My 3D Printer is 'sick' and awaiting some parts to fix/improve it, so I can't make the 3D Printed motor mount for the LED yet!!
Though even that needs to be made "EDF Specific" to suit the motor/EDF type it will be attached to.
I am not sure how Universal I can make that be.

It is also possible that making a LED mount to the Ducting WALL, right after the EDF, could still light it all up just as well anyway.... so I will try that idea too. The aluminium tape that the Ducting will be lined with could very well 'scatter' the light enough/plenty and thus still even it all out fine anyway.

AfterBurner LED unit (0 min 56 sec)
Sep 06, 2019, 09:49 AM
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August new ideas....

With too many projects underway I only got to dabble a bit here and there with the Afterburner project. But I did those bits more, and more, and it is actually all done now.....
Along that way I changed the design ideas a fair bit!

There are two systems - A "Simple" version one and a "More Detailed" versionone. You could always use the 'More Detailed' version to run the Simple Version system/code on anyway, but the Simple Version is smaller and fractionally cheaper.

The Simple Version runs just one LED system - though you could still add multiple LEDs to have more power and thus greater Brightness.

The More Detailed Version runs two separate LED 'channels' so they can be individually controlled, and set up to form a more complex interaction of lighting. eg A Yellow LED and a Red LED (or Blue), and mix those colors in varied Flickering Rates and.or Brightnesses. This version can also easily fit and run more features - such as include a Gear Door Sequencer, and/or Strobe LED - even with variable Strobe rate/pattern options etc.

All forms use a MUCH smaller DC-DC Convertor that I found - which is also much cheaper than the original chosen one!
The Simple Version can run from a Digispark USB, or USB Micro, type Microcontroller and they are very cheap! Thus it forms a very cheap, and very small Control Unit. This one could actually still have a Strobe light system included really - hmm, I better add that......

The More Detailed Version uses an Arduino Nano, or Ardunio Pro Mini, (use the much cheaper clone versions of those!) and they have a LOT more memory and capabilities. Thus why a lot more more Features can be included within those. But they are clearly LARGER microcontrollers and thus need more space to fit them somewhere. They are not THAT big..... so in most cases they would still easily fir anyway, but the Digistump version is very small !
Last edited by PeterVRC; Sep 06, 2019 at 09:56 AM.
Sep 06, 2019, 09:56 AM
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Afterburner DIY Kit

A zip file is attached with a document outlining how to make the DIY Afterburner. It lists parts, eBay sources, a programming guide etc.... all you will need to know to build it.

There is more to come..... the document is largely done/complete, but I do have some more bits to add to it - when they are done.

This first generation will still be a very good way to have Afterburners in any EDF jets you want to!!
The total cost is approx USD $5 for all the parts! And many are ordered as a 'bunch' of the parts so there are extras that can be used for the 'next' afterburner you need/want, make.....
Sep 07, 2019, 09:48 AM
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I completed the wiring etc for the first "real use" Afterburner unit. I got everything sorted out optimally.
Though I FORGOT to add an AfterBurner Trigger Point POT to it..... to allow real-time, on-site, adjustment of the Trigger point of the Afterburner LED activation. DOH.
Its default is 1900uS, but I should have made that 1800uS because that is a more common/typical useful trigger point really. I will edit that and reflash the AB unit.... rather than the effort to add a Pot now.

This one uses a "Y" for the Throttle Signal, so I used 22AWG servo lead to assure it passes the full SBEC Current capability to the RX.

There is fractional Light Leak in the Mig-17 I installed it into. I need to find that and block it fully.

It is VERY bright!!!
100% of the LED's emitted light heads STRAIGHT REARWARDS, thus it ALL gets out the rear of the exhaust!
But if need be a Twin 10W LED version can be put in.... 'fighting daylight' is always an issue with Afterburner LED systems! But at least this has a BIG head start with its huge brightness!

Next is to make up an Arduino ProMini (and/or Arduino Nano) version that will have the Trigger Point Pot.... and two Strobe/Flashing Light outputs.... and a HIGHLY programmable Gear Door Sequencer... included..

DIY RC Afterburner LED unit - Installed in the Avios Mig-17 (0 min 22 sec)
Sep 08, 2019, 09:16 AM
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Afterburner "Flicker version" updates

When I flight tested the AB unit I found that it had a random/sporadic flick of the LED when stationary on the ground. "Something" was injecting a trigger into the system.
The Digistump USB Micro version is very poorly suited to debugging so that was not going to be easy do at all.
I decided that it could be noise - either getting into the system via a wire, or maybe close proximity to something (RX RF?) in the aircraft... or otherwise a software bug, most likely to do with the PWM reading system.

I tried a large power supply Capacitor and it didn't help....
I was going to try with a very low value Capacitor, for noise, high frequency, removal - but I forgot to try that....

I ended up deciding to 'filter' the AB Trigger by averaging out the PWM value in the program code so that any spurious values would be 'absorbed' into insignificance.
That worked to get rid of it....
I do suspect it is something to do with the SoftRCPulseIin library - though it still could really be a noise issue.

Some new update files are below, plus the Libraries used int he code, and updates to the DIY document.
Last edited by PeterVRC; Sep 15, 2019 at 08:07 PM.
Sep 15, 2019, 08:06 PM
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V2.0 code

I changed a few code sections to improve various things, but the main change of V2.0 is the TWO Modes of operation.
The prior "Constant Flicker" when the AB is on, and now an added "Constant ON, after a Flicker sequence" mode.

Mode 1 is a more common Afterburner sequence you will see in jets, but Mode 0 is still an important format many jets have too. (eg the Mig-17)

Pin3 of the Digistump USB Micro, or A3 of any other Arduino (Nano, ProMini,ProMicro etc) is the Mode Pin to select the Mode of operation.
If that is Grounded then it is Mode 1. Open/Floating it is Mode0.
You could just add a pin header to allow fitting a jumper to that.
The Mode can also be changed in real-time.

Sep 16, 2019, 07:57 AM
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@PeterVRC - how about V2.1 and remote ON/OFF function if you have a spare channel ? If the PWM from the receiver is in the middle 1400-1600ms range it's AB is permanently OFF if you'd like to save as much juice from your battery as possible.
If PWM is low ~900-1100ms you've got:
Mode 1: Off, or Afterburner ON = Flicker constantly (for older era jets)
If PWM is high 1900-2100ms:
Mode 2: Off, or Afterburner ON via a short Flicker (for AB ignition) and the ON Solidly (for more modern jets)
Just an idea. Thank you for posting!
Sep 16, 2019, 08:36 AM
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That is a workable idea.... no real negatives to having that option.
Mind you it is very low power.... 10W uses about 700mA.... only when the Afterburner LED is ON of course.
And even less if it is flickering. eg Duty Cycle 60% region.

But I will alter/add that next time I load it up.....
Sep 16, 2019, 01:37 PM
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There is a small bug that took me an hour to figure out how to open those *.ino files. I was pulling my hair out until I figured out that the name of the file can not contain "(" or ")" character. You were using them to differentiate Nano and ATTiny versions - LED_AB_10wYellow_Flickering(ATT85)_V1.ino
Sep 16, 2019, 06:30 PM
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Good find... I guess. hehe.
I tried it.. they don't report the error very well, thus it would be hard to find!

I use another editor and cut/paste between them when required so it didn't reject that filename as it is Window compliant really.

But I will change the names now!

I didn't seem to read your prior post totally correctly(!), but I see better now what you meant in ALL the aspects.
eg Another channel to do Enable, Disable, plus the Mode too.
A good 'advancement' in the evolution, hehe.
Sep 17, 2019, 07:42 AM
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Check this other Blog for the 'Super DIY unit".... it has the AB modes, and PWM mode control stuff in it.
I will add it to this AB only unit once I verify the Digistump has the ports/pins that can also do it.

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