DIY tracer for AK...

[Docv400]

I've been thinking about doing this for a while now and I finally found the time to start it.

The idea is to have an Ultra-Violet LED mounted in the hop unit, so it shines directly onto the BBs as they feed into the hop, just before they're fired, and to have it powered by 2 AA/AAA cells through a micro reed switch activated by a Neodymium magnet mounted in the top of the mag.

UV LEDs make tracer BBs glow brighter than an equivalent white LED (even though the LEDs are not very bright to look at), and they glow for longer too.

 

 

Parts required;

1. 3mm UV LED

2. Micro-miniature reed switch

3. AA/AAA cell holders

4. 2mm dia X 1mm thick Neodymium disc magnets (1 for each mag you want to use for tracers)

Tiny, but very strong for their size...

5. Light duty equipment wire and shrink-wrap to suit.

I got all the parts from Maplins, except the magnets, which are from E-Magnets...

 

First job is to drill a 3.5mm hole in the top of the hop, just behind the adjuster assembly.

Form the 'legs' of the LED so they sit to the left of the hop adjuster assembly, and trim them a little, then solder on a length of wire to each leg (+ve is the long leg...before you trimmed them )

Then, epoxy the LED into the hole so it's pointing down into the feed tube.

 

Next, you need to make a slot in the top of the magwell to house the reed switch. I made mine just behind the aperture for the hop feed tube.

Drill a line of 3mm holes as close as you can to each other, then file/Dremel them into a slot.

 

Put your chosen mag into the receiver and mark the top through the slot, then drill a 3mm hole in the top of the mag.

Stick a magnet onto a piece of clear tape and put a small blob of epoxy on the magnet (I use Araldite), then stick the tape onto the mag, with the magnet in the hole, and stand top-down somewhere to set.

I've epoxied the cell holders onto the top of the inner top cover/plate.

 

That's where I'm up to so far.

Next I'll be epoxying the reed switch into the slot and wiring it all together.

Then when the mag with the magnet is inserted into the gun the LED will light up and I'll have tracer fun

[Xaccers]

Nice one Doc.

 

An alternative to the reed switch would be a pressure switch, the advantage being, it'll work with any mag, and you can control when the tracer is active, so you can turn it on, spray a bit to see where your shots are going, turn it off and keep spraying.

[Catman]

Nice! great idea with the magnet

[Tommygunn]

Excellent little mod.

 

Would it be possible to mod this to an M4/M16 hop unit, maybe in the small gap between the feed tube and just in front of the gearbox?

 

Concerning the UV LED is it possible to file the dome flat, or even slightly concave, polish it back to clarity and maintain its functionality.

[England Wonder]

are you running the LED direct drive? I thought most LEDs needed 3.5v to run

Depending on what chargers you have access to you might be able to run it from a single lithium cell. You'd also get more power for the weight and bulk being added to the gun

[Docv400]

Nice one Doc.

 

An alternative to the reed switch would be a pressure switch, the advantage being, it'll work with any mag, and you can control when the tracer is active, so you can turn it on, spray a bit to see where your shots are going, turn it off and keep spraying.

I'll probably fit a manual switch in the circuit at some point, I just wanted to test the theory first. You could do away with the magnetic switch altogether of course, but I like doing stuff like this just for fun

 

 

Excellent little mod.

Would it be possible to mod this to an M4/M16 hop unit, maybe in the small gap between the feed tube and just in front of the gearbox?

Concerning the UV LED is it possible to file the dome flat, or even slightly concave, polish it back to clarity and maintain its functionality.

I think you could do it to just about any gun, even pistols , as the LED is so small and you can use really thin wires. I think you could put one in the feed tube itself.

I was going to do my MP7 or M4 first but I had the AK apart...

The LED doesn't interfere with the nozzle if that's what you're thinking, or are you thinking of putting it somewhere else? I don't think you'd lose much illumination 'strength' if you didn't polish it.

 

 

are you running the LED direct drive? I thought most LEDs needed 3.5v to run

Depending on what chargers you have access to you might be able to run it from a single lithium cell. You'd also get more power for the weight and bulk being added to the gun

the LED is rated at a 'max forward voltage' of 4.3V, it's fine on 3V.

I also toyed with the idea of running it from the gun's pack through an appropriate resistor but it's a pain arranging the wiring. I'll probably do it that way on my MP7 just because of the lack of space.

Bulk? two AAAs? I agree though, I'm just trying it out at the moment, I'll probably 'tweak' it a few times yet.

[Tommygunn]

The LED doesn't interfere with the nozzle if that's what you're thinking, or are you thinking of putting it somewhere else?

I was just thinking as to the smallest space you could squeeze an LED into if you shaved it down.

[Fanrish]

Nice alternative there! Tempted to fit it to one of my AEGs now...

 

The only concern I'd have is whether the BBs get enough illumination before being fired (especially on full auto). Have you given it a try yet? Would love to see some pics/videos of the result if so

[MooCow]

as above... my concern is also the same as fanrish...

would like to see how effective just one UV LED would do on the effects on full auto... and to those of you that are kind enough to test out for other people... a request for you guys

 

if you could tell us what your rate of fire is... that'd be great and if your UV LED is ultra bright ones or if you could specify it's output etc that'd be great too... i know it's alot to ask but it'd be an idea for the people that are interested in doing this as well incase the auto is no good over 10r/s or whatever the actual figure is...

 

and something's just crossed my mind... if you have the UV LED just behind the hop rubber itself... wouldnt that mean the round will only get a chance to have it's short moment from the back of the hop chamber to the inside of the hop? as the nozzle will be blocking any UV from going to the back of the round chambered or going to the top of the next one in the feed tube (unless you have a clear nozzle ) as i'm deciding to make myself a tracer mag for my AK but with a pressure switch on the top instead... just so that i'll know there's less chance of me from cocking it up. the wiring/circuit and the gun that is

[Docv400]

I've not finished it yet so I can't say how effective it is, but playing around with the LEDs and BBs beforehand suggests it will be OK.

I'm sure it will be much more effective than the LED-in-the-mag method, particularly in semi, with some time between shots.

The light from the LED 'fills' the feed tube quite nicely but I'm thinking another one may be needed in the feed tube itself.

You can get a 5mm UV LED instead which puts out a fair bit more light than the 3mm (400-500mcd against 90mcd) but with free space inside an AEG being at a premium it may not be practical.

I'll finish it as soon as I get another reed switch, I managed to crack the capsule in that one , which was the last one my local Maplins had in stock. I've ordered some more online.

I'll try and video it when it's done but I'm not sure how clear it'll be on camera.

[Catman]

Film the tracer going off at night The TM tracer unit at night makes you feel like your in Star Wars or something

 

A secondary LED in the feed tube would definately be a good idea

[Docv400]

I've decided to go for lighting 'overkill' rather than find out when it's all together that one's not enough.

I've drilled two more holes in the hop, this time front and back in the feed tube itself, there's plenty of room here on the AK for the thin wires.

That should do it.

I wrapped a 6mm drill shank in Mylar tape (non stick outer skin) until it was a snug fit in the feed tube, then epoxied the LEDs in place.

 

I'm trying to source some miniature 2-pin plugs to connect it all up (so each section is separate for easy gun stripping in future).

I really want some like the ones on PC cooling fan leads, the tiny white ones. Anyone know their proper 'type' name, if they have one?

[MooCow]

ahh stuff it! the UV led's arent that expensive... (compared to tracer mags/tracer units) im going to buy a load of them and stick it on a parallel circuit on a high capacity mini r/c battery like... a ladder of UV led's and just stick it down the side of the mag... might end up having space for 2 shots but it'll be brighter than tac lights at least... lol

[Xaccers]

JST?

 

[Docv400]

Excuse my ignorance but what coin is that? Nickel, Dime, Quarter?

They still look a little big for this application, I'd like something around 5mm W x 3mm D x 10mm L max for an assembled pair.

[Xaccers]

Excuse my ignorance but what coin is that? Nickel, Dime, Quarter?

They still look a little big for this application, I'd like something around 5mm W x 3mm D x 10mm L max for an assembled pair.

 

Their length connected is 15-20mm off the top of my head

[England Wonder]

the LED is rated at a 'max forward voltage' of 4.3V, it's fine on 3V.

I also toyed with the idea of running it from the gun's pack through an appropriate resistor but it's a pain arranging the wiring. I'll probably do it that way on my MP7 just because of the lack of space.

Bulk? two AAAs? I agree though, I'm just trying it out at the moment, I'll probably 'tweak' it a few times yet.

the LEDs I've played with in the past needed 3 NiMh cells from a direct drive. I'd run it on a 14250cell (same width as AA but have the length), 3.6v

[Docv400]

3 LEDs fitted and wired now, just waiting on the reed switch...

Had to Dremel out a tiny bit around the hop unit to accomodate the forward feed tube LED and it's wires.

Should be fully operational by Friday

[bjorn]

Thats pretty good.

 

Might try to build something myself with the 5mm UV leds into my upcoming airsoft platform - the A&K M249 Para.

 

I think there is a fairly good possibility to build something very easy into the box mag?

 

Somewhere in the feeding tube?

 

 

Bjorn

[Docv400]

The closer to the point of firing you gan place them the better, although in a 249 you don't really need to worry about the BBs sitting around losing their glow before being fired

[MattCFII]

I have a project going that has very similar threads running through it, it's almost creepy! Docv400, do you ever go to Airsoft Mechanics? I almost added a UV LED to act as a resistor (I have almost 100 of them laying around so if any body wants some cheap let me know) and eventually burn them out with the 8.4v of my battery but hey I have 100 of them. However, I have a TM tracer unit already and got a 12v relay instead of the planned 5v. I think you may have finally inspired me to put the LEDs in there. Do you think a single 5mm UV LED with a mcd of 2000-3000 (maybe even more with the over volts) be bright enough to light up BBs?

 

My project is a realism/safety mod using a Anti-braking MOSFET to make my AK bolt have to be pulled when a fresh magazine is inserted or not fire at all without a mag. I originally had a pressure switch in the mag well but found it was a little too easy too move the magazine just a bit and open back up the switch and another switch with a longer throw was too large to mount. Now I'm on to a reed switch myself and to the exact same tiny Neodymium magnets mounted in my magazines eventually. But I've found that they have to be all but touching my read switch so installing it could get interesting. How many ampere turns is your reed switch rated for Doc?

 

Link to my thread at Airsoft Mechanics on the project:

http://forums.airsoftmechanics.com/index.php?topic=807.0

[Docv400]

I've seen AM mentioned a few times on forums but never visited it. I might have to now though

 

If you put the LED(s) in a tracer unit then I doubt they'd 'charge' the BBs enough because of the speed they're going past the LED.

At 330fps, (that's nearly 4000"/sec) the BB's only going to be exposed to the glow of the LED for around 0.00025secs (I think that's right, but then I have been up since 1500 yesterday...nightshift )

That's why tracer units, as I understand, have a seriously bright flash unit to give the BBs as much exposure as possible.

 

If the magnet isn't triggering the switch until it's almost touching, try changing the orientation of it, e.g. so one of the the poles is next to the switch as opposed to having it side-on. You could also try altering the way the switch is aligned with regard to the contact strips themselves.

 

The reed switch I'm using is only rated to switch up to 0.5A, plenty for the task. The spec doesn't quote a figure for ampere turns.(whatever that means )

You can get Rhodium plated contact ones which are rated at 75-95 ampere turns, they are much larger though.

Reed switches

 

[fallingdown_]

i was putting 5 or 6 uv leds in a silencer attached to a momentary switch but judging from what you are saying above, maybe its too little light too late and for too short a time. i did see some huge mcd rating on leds now on ebay. not sure how realistic the figures are but maybe they would work. it would have the disadvantage of turning the silencer into a torch i suspect but might work for this idea. excellent idea on the switch by the way, very smart. maybe you could also modify a mag to do as per g&p. i seem to recall that if the bb was 'fired' it would only need a extra small light burst to reignite (if those are the correct words for luminous). cant remember where i read that. so the 2 working in concert might be extra bright.

 

amazing idea tho. congrats. really interested to hear how you get on and best of luck with it.

[MattCFII]

I've seen AM mentioned a few times on forums but never visited it. I might have to now though

 

If you put the LED(s) in a tracer unit then I doubt they'd 'charge' the BBs enough because of the speed they're going past the LED.

At 330fps, (that's nearly 4000"/sec) the BB's only going to be exposed to the glow of the LED for around 0.00025secs (I think that's right, but then I have been up since 1500 yesterday...nightshift )

That's why tracer units, as I understand, have a seriously bright flash unit to give the BBs as much exposure as possible.

Sorry I didn't make myself clear, since I have a TM Tracer unit I didn't pursue mounting the LED in the hopup chamber. I wasn't talking about making a suppressor mounted unit out of LEDs. I did the math like you did when I started my DIY tracer unit project awhile ago of a tracer mag and knew it was going to be very difficult to get them to work with LEDs in the few milliseconds you had with it in the suppressor body. The TM Tracer unit made the DIY mag tracer and the hopup mounted projects go by the wayside. I really though about the hopup chamber and had the UV LEDs but just didn't want to change things that much but now that I have other wires running around in there and seeing you do it makes me finally want to get it done.

 

Why did you add so many LEDs? was it to get enough power to illuminate then consistently? Or was it to be sure to charge them in the chamber instead of just the vertical chute so even if you hadn't shot in awhile you would get even the first BB charged? Does having the LED on the top of the hopup have any FPS drop? I could see if their was a leak in the install that you could have less FPS, which is why I never really though about mounting one there as well.

 

BTW, not sure if you've seen it but here's a thread on some one doing this to an M4 which gave me the idea in the first place:

<a href="http://airsoftrecon.forumup.org/viewtopic....irsoftrecon#996" target="_blank">http://airsoftrecon.forumup.org/viewtopic....irsoftrecon#996</a>

 

If the magnet isn't triggering the switch until it's almost touching, try changing the orientation of it, e.g. so one of the the poles is next to the switch as opposed to having it side-on. You could also try altering the way the switch is aligned with regard to the contact strips themselves.

 

The reed switch I'm using is only rated to switch up to 0.5A, plenty for the task. The spec doesn't quote a figure for ampere turns.(whatever that means )

You can get Rhodium plated contact ones which are rated at 75-95 ampere turns, they are much larger though.

Reed switches

My switch is a .5 amp mini epoxy bodied one that is more designed for mounting instead of this kind of use which maybe the problem. I wanted to go for the epoxy body just for more ruggedness. Ampere-turns is the rating of how sensitive the reed switch is to magnetic fields, the smaller the ampere-turns the more sensitive it is to magnetic fields. Unfortunately, the specific model switches I ordered don't have an ampere-turn rating on my spec sheet, so I can't really compare them exactly to yours. How far away from your reed switch can your tiny magnets be and still activate the the switch? Do you know the gauss rating of your magnets (there isn't a good way to convert gauss to ampere-turns but it does give me rough figure to work with). I'm hoping for maybe 5-10mm so I have some room for the magazine to shift and such. If you are getting that I'll change out my switch.

 

I've tried different orientations and the best way I can get the switch to close is by placing the magnet on the ends of the switch. If I use a larger magnet that's not Neodymium I can activate it by being close to the body but practically touching it. IF I could get this switch to work it looks like I'd have to mount it vertically and protrude through the hole in my mag well that I made for my pressure switch so it would be contacting the magnets in the top of my magazine. But even then I think that the same movement of the mag would open back up the reed switch momentarily, requiring me to retract the bolt. I moved to a reed switch because I thought I would end up with more closed "throw" distance to play with than my pressure switch but so far it would be even less distance with a reed...

 

Why the cut out in the body for the reed switch? To make the switch and magnet closer or to make mounting easier?

[Docv400]

...Why did you add so many LEDs? was it to get enough power to illuminate then consistently? Or was it to be sure to charge them in the chamber instead of just the vertical chute so even if you hadn't shot in awhile you would get even the first BB charged? Does having the LED on the top of the hopup have any FPS drop? I could see if their was a leak in the install that you could have less FPS, which is why I never really though about mounting one there as well.

I found that having just the one tended to light only half the BB, which might look good when it's spinning but I'd rather have the full brightness, so hence the other two. The 5mm UV LEDs light the BB right through but would be more difficult to mount in the space available.

There's no loss of air/fps because the LED is mounted outside of the sealed area formed where the nozzle meets the hop rubber.

 

How far away from your reed switch can your tiny magnets be and still activate the the switch? Do you know the gauss rating of your magnets (there isn't a good way to convert gauss to ampere-turns but it does give me rough figure to work with). I'm hoping for maybe 5-10mm so I have some room for the magazine to shift and such. If you are getting that I'll change out my switch.

I just tried it with just the one magnet and it's approx 1mm, so I tried it with various numbers and 7 stacked together gives approx 3mm trigger distance. As you discovered, they trigger sooner if the magnet is placed near the 'pivot' ends of the contact arms, i.e. at the ends of the capsules. I'm going to experiment a bit more with the number and placing of the magnets, maybe one at each end would be more effective, maybe a 'North' at one end and a 'South' at the other...we'll see.

E-Magnets don't quote a Gauss figure for the ones I got, just a 'pull' rating, in this case 0.1kg.

I'll maybe order some of the rectangular neodymium magnets as well, maybe one of the same length as the switch capsule mounted in-line with it will be the best solution, with the poles at each end of the capsule?

Why the cut out in the body for the reed switch? To make the switch and magnet closer or to make mounting easier?

Yes and yes!

it was the only way to do it really. you couldn't fit it on either surface of the receiver 'floor' because the mag virtually touches the underside and the thickness of the receiver would place it too far away from the magnet(s) if placed on top. If you had a plastic receiver and used a good sized magnet, then you could probably get away with it on the top surface.

 

Edit; Just ordered some Neodymium 'rod' magnets from E-Magnets. They are 3mm dia X 13mm L.