DIY Tracer unit
In this project I will show you step by step, how to make your own tracer unit. But before we start the steps I just want to explain the basics of how airsoft tracer units they work.
To get anything out of a tracer unit you must buy special tracer BB's. Normal bulits will NOT work. This is because airsoft tracers work by charging a special "glow in the dark" material that has been added to the special tracer BB's. Thease special BB's cost a bit more, so you must be prepared to pay for it.
To charge the glow in the dark tracer BB's all you need is light. So realy all you need is a light source. Sounds simple? Well acturaly that's because is is pretty simple ;-) so most people with a bit of skills and a soldering iron can make there own tracer unit.
But here at AirsoftTech.Dk we don't just show you how to make it we also want to tell you all the technical details about how it works.
How tracers work
Tracer BB's are as I mentioned made of a material that absorbs light and sends it back out over a period of time. See: "https://en.wikipedia.org/wiki/Fluorescence" if you want more details on the BB materials. So when you shine bright light on the BB's they start to glow. When the glowing BB's get's shot out of your guns with high velocity the glowing BB's will be precived as a line of light [or a trace of the BB's flight path].
In the real world Tracers are mostly used when you use machine guns, and they have a couple of effects. One beneficial effect of the tracers is that you can see where you are hitting, so you can ajust your "aim or lack there of". Another effect is that they can look verry scarry, and ofcause COOL. In airsoft tracers are used in / on all sorts of guns to help you ajust your aim in low light (or darkness) situations.
Note that I wrote "in / on" because there are 2 kind's of tracer units in the airsoft world. Internal (usualy build into the hop-up unit) units, and external (usualy build into what looks like a supressor) units. But in the real world it's acturaly the bullit's that has a layer of material that catch fire when you shoot the bullit's. So it make sence to put the tracer unit inside the gun. But the easy way is to pack it into a tube so that it looks like a supressor.
First step - Aquire the building materials.
1. The most important part is of cause the light source.
2. A Power regulator to supply power for the LED from a battery.
3. The housing for the tracer unit.
Let's go through the materials you need one by one so you get a sence of what you are looking fore.
The light source:
The important thing to know is that the BB's best absorbs ultraviolet light, so you som light source that transmit's ultraviolet light. Almost all white light's also transmit this form of light, so any white light could be used, but the most efficient thing to use is a pure UV light. You can get thease in many shapes, sizes and power ratings. But you realy need small high brightness ones. Because the BB's will only be in contact with the light verry short ammount of time. And you need to fit the light into the gun. When you need small high birghtness light sorces LED's are the way to go.
On E-Bay o found thease 2 candidates:
10 x 3mm Bright UV / Purple 5000 mcd LED Bulb Light
Price: US $0.99
Peak Wave Length (nm) : 395 ~ 405
Forward Voltage (V) : 3.2 ~ 3.8
Luminous Intensity Typ Iv (mcd) : 3000(Typical) ~ 5000(Max)
Max Peak Forward Current(IFP): 75mA
Max Continuous Forward Current(IFM): 20mA
Details about 100PCS LED Diode 3MM white COLOR BLUE LIGHT Super Bright
Price: US $1.24
Peak Wave Length (nm) : 460 ~ 470
Forward Voltage (V) : 3.0 ~ 3.4
Luminous Intensity Typ Iv (mcd) : 6000(Typical) ~ 8000(Max)
Max Peak Forward Current(IFP): 75mA
Max Continuous Forward Current(IFM): 20mA
The main difference between the 2 options is the price (around 1$ for 10 UV's or 100 BLUE). But wait one of them is BLUE ??? I just said we need UV ?? Well the thing is that tracer BB's reacts best to light comming from "Low" wave length light sources like UV (395 ~ 405 nm) but near UV (Blue is close to UV 460 ~ 470) will also work, just not as good. So I recomment getting UV but if you can't find UV bright blue should also work just fine.
10 pcs 1W High Power UV LED Bulb
Price: US $4.84
Wave Length UV (395-405nm)
DC Forward Voltage: 3.2V~3.6V
Forward Current: 350mA
Now this is a Relay high power LED that will realy light up the BB's. It can put out LOADS og UV light, so it should realy make the BB's glow allot. It's ALLOT more expensive, but still within most budget's. Just what you want is it not ??? Well read on a bit and you will see the catch!
The power regulator:
LED's need to be protected. If you attach a 7-12v battery directly to an LED like the one's I have just shown you will destory it. So the battery power needs to be limited. When you find your LED's you should note there "Forward Voltage" and also there "Max Continuous Forward Current" because we will need it to make the system. They will probably be around 3-4v and around 20mA. Thease values are what you need to step the battery power down to.
To drive the LED's theres multriple options, the most simple option is to use a linear regulator and a resistor. The LM7805 will step down voltage to 5 volts and then use a resistor to lower it the last way. [use a resistor calculator like: http://led.linear1.org/1led.wiz to find the resistor value] In most cases a 100 ohm resistor is good enough.
Another way to go is to use what's called a "Buck Converter" and on E-bay you should just find a small one that can be ajusted from your battery voltage (plus som extra for safety) down to 3v or less.
I personaly found thease:
DC-DC 4.75V-23V to 1V-17V Step Down Module Bock Converter
Conversion efficiency: 96% (maximum)
Output Current: 3A.
5 peaces for only 2$
The main advantage with this option is that they can be regulated to be directly within the "Forward Voltage" range of your LED's. So no other part's are neded. And it does not matter what the inpot voltage is as long at it's lower than the max input (23V for thease.). Be aware that you NEED a multi meter to set the buck converter's output correctly. Or you risk burning the LED's.
What LED's to go for?
Well I personaly don't need 100 blue LED's so I would select UV and accept I only get 10 for the same cost. (10 should give me plenty replacements if they burn out). The 1W high power LED's i would not reccomend using them unless you are building the tracer as an external device. If you are planing to put the tracer in a silencer at the end of the barrel the BB's will need alot more light because they will be exposed for longer, then you may want to considder the 1W power LED. (But you will not be able to use the LM7805 as the regulator)
What regulator to go for?
With reguards to the power stepdown, the linear regulators are quite in efficient, and at higher input voltages they can get to hot and burn out quite quickly. The Linear regulators like the 7805 works as a variable resistor, which varies its value to keep the output voltage constant (5V for the 7805). It means that the regulator dissipates alot of power. This is bad bacause it may get to hot and stop working.
The folowing formula can be used to calculate the power loss:
P = delta V * I = Eg. (11.1V - 5V) * 0.020A [20mA] = 0.122W
The LM7805 in the TO220 package can handle the folowing power:
C = 125C - ( W * 65 C/W ) = 125C - ( 0.122W * 65 C/W) = 125C - 7.92C = 117.08 C
Meaning that at an ambiant temperature of up to 117 deg. So this will be no problem.
A fully charged 3S lipo get's up to around MAX 4.2*3 = 12.6 and a LED with a power rating at let's say 60mA the calculation would be.
(12.6-5)*0.06=0.456W , (125 - 0.456*65) = 70.36 C
So for low power led's you should be safe with the LM7805 :-)
But what about high power led's at let's sat 300mA ?
12.6-5*0.3 = 2.2W , (125 - 2.2*65) = -23.2 C => Meaning it should be negative 23.2 deg for it to not break :-(
So for high power LED's you HAVE to go for option nr 2 !!!
The same current also goes through the resistor but only at the 5V output power:
5V*60mA = 0.3 W so in this case you would NOT be able to use a 0.25W resistor (Witch is the most common one).
5V*20mA = 0.1 W So with a led of 20 mA you could use a normal 1/4 Watt resistor.
5V*300mA = 1.5 W So you would need a HUGE resistor ....
So what about option nr 2?
A buck converter on the other hand is mutch more efficient, because it does not just work as a resistor. Instead it works by turning power on and off rapidly. So to calculate the power it dissipates this formula can be used instead:
Pin = Pout / Efficiency
Pout = V * I => E.g. 3.3V * 300mA = 0.99 W (Let's say 1W )
Efficiency can varry from device to device but must of them performs at 80% or better so let's use that (80% => 0.8)
Pin = 1W / 0.8 = 1.25 W
And the power disapated in the buck converter is:
Pout - Pin = 1.25W - 1W = 0.25W So it's ALOT lower compared to the 2.2W that the LM7805 would take.
So what does all this mean to the common man:
It means that the world is not that simple ;-) That's why I have made som simple guidelines:
Less than 40mA Continuous Forward Current => You can use LM7805 with a normal 1/4W resistor.
40-60mA Continuous Forward Current => You can use a LM7805 but you need to use a 1/2W resistor.
60-80mA Continuous Forward Current => You can use a LM7805 but you need to use a 1W resistor but you should realy be using a buck convertor to be sure.
Above 80mA => You should use a buck converter.
Can't i just use a buck converter always? -> Yes you can, but they cost alittle bit more (but not much).
Now to the step by step guide.
Connect the input ground to the ground of the battery.
(On almost all battery's it's the black wire)
Connect the input power to to positive side of the battery.
(On almost all battery's it's the red wire)
3. (If you use the linear regulator)
Solder the resistor to the output pin of the power regulator.
The other end of the resistor is now the output of the regulator.
3. (if you use the buck converter)
Turn the small knub to set the voltage som where within the LED's forward voltage rating.
soldered the output power of the regulator to the LED's input. (The leg that has the small metal plade inside the LED)
The other side of the LED goes to the ground of the regulator.
If you are giong to use the LM7805 this is the scematic that you can use as a refference.
If you are using a buck converter it's a bit more simple. You can folow this diagram.
It's also an option to purchage FIXED voltage Buck Converters. On these there are no screws, so make sure you get a 3.3v Version!
In this video I show how the priciples work.
Packing it together Now you have the tracer electronic's made. So now to packing it into a tracer unit.
As I mentioned before you have 2 options:
Hop Up unit instalation, internaly.
Or packing it into a silencer type tracer unit.
The fist thing I will show you is how to place the unit into a hop-up chaimber so that it can sit inside the gun it self. To acheave this you must ofcause first open you gun and extract the hop-up chaimber. You can find disassembly guides for almost all kind of guns here: Disassembly Guides
Acturaly the tracer LED don't go into the chaimber, it goes into the feeding tube. Drilling into the chaimber would be too risky, as you risk the BB's getting jammed or just nor feeding correctly. So I very much reccomend putting the LED in the feeding tube instead.
The first step is to drill a hole the same diameter of the LED, so if you purchaced a 3mm LED get a 3mm drill bit and drill a hole into the feeding tube. The LED from the tracer goes into this hole, but to make sure it don't block the BB's you can cut off the top of the LED. But be carefull not to cut to much because if you damage the mettal inserts inside the LED it will not work any longer. So cut first then test the LED with the trace before installing it. You can fix it in place with any kind of glue. Personaly I like working with fast drying superglue.
When it's in there you can run wires from the LED down to the battery compartment so that you can store the tracer unit together with the battery (If theres enough room). To wire it in you can connect it directly to the battery, or you can wire it into the motor wires so that it turns on at the same time as you pull the trigger.
This way is the easyest way to wire it up.
The disadvantage of wiring it up like shown above is that the unit will always be glowing, so a tiny ammount of light may shine out of the barrel, and while most people won't notice, night vision googles will pick this up quite easely. And another disadvantage is that because the light is always shining the battery will also be drained more quickly.
So another way is to wire it up in parallel with the motor. So only while the motor is onn the light will be shining. But be carefull !!! When the motor is turning and you release the trigger, the motor spinning will create a voltage, this voltage may be quite big and can damage the unit, so you have to add som protective components.
What you should doo is to add a Schottky diod (A big one !!!) Add this to any of the input wires to the tracer unit.
The protection diod should be big because it has to handle all the current the free spinnig motor creates.
The other way of dooing it is to make a Silencer looking device at the end of your barrel and adding the unit into here. The problem is now you have to eighther run wires down your barrel or add a battery to the tracer inside. You can get som pretty small lipo batteries that will last you quite some time and still fit inside.
When the here is a video that shows you how to make an external tracer.
So is that it then? Was that all I can possibly get to know?
NO theres lot's more, but i think the above info should be enough right :-)
One last thing: "Kind of a Teaser" -> How would you like to controll your tracer with a mosfet?? Getting only every second or third bullit to light up? Well go subscribe to my Youtube Channel, and later (ETA first quater 2017) I will show you how to doo just that.
GO HERE to find my Youtube Channel AirsoftTech.dk