2. Wiring the LED

To set up head tracking, we will be using an LED-based model. This model uses a webcam to detect LEDs, and track their motion. We only need one LED for this. Many suggest using infrared LEDs. Webcams can detect IR very easily, so by removing the IR filter on a webcam and then installing a visual light filter, IR LEDs can give an excellent result. That said, you can make this work reliably using only a bright-white LED and no webcam modifications.

Parts:

  • 1x Bright white 5mm LED (or IR if you will be doing webcam modifications)
  • 1x Watch battery OR 2 AA batteries with the proper battery holder.
  • 1x Small toggle switch (not needed if you are willing to take batteries in and out

Tip: If you do not have soldering experience, use the LED and watch battery, it requires no experience or soldering equipment

First we will be filing down the LED tip. LEDs are designed with a focusing lens built in. By using a file (or even the concrete outside) flatten the tip, and then buff the sides so they are not glossy. This allows the LED to be seen easily from any angle.

The Easy Way:

If you have no experience in soldering, you can simply tape the LED to the watch battery. Make sure to have the proper orientation, LEDs only work in one direction. If you got a typical 5mm white LED, a single watch battery should power it with nothing else needed. When you want to turn it off, slide a piece of paper between the battery and the side of the LED that you did not tape. It should look like this.

SEE ALSO
Quest 3S Review – Value That Can't Be Beat, With the Same Rough Edges as Its Siblings

8

The ‘Right’ Way:

If you want a switch, long lasting batteries, and have soldering experience, this method is for you. Using a battery pack with 2 AA or 2 AAA batteries, solder one pole of the toggle switch to one of the battery terminals. Then use a length of wire approximately 6 inches long to connect the switch to the LED. Then use another 6 inch long length of wire to connect the LED back to the other battery terminal. Test the switch, it should turn the LED on and off.

Now that you have the LED wired in your chosen way, use hot glue to secure the LED to the front of the HMD. Make sure that the LED sticks out from the front of the unit for maximum turning radius.

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Ben Lang
Ben is the world's most senior professional analyst solely dedicated to the XR industry, having founded Road to VR in 2011—a year before the Oculus Kickstarter sparked a resurgence that led to the modern XR landscape. He has authored more than 3,000 articles chronicling the evolution of the XR industry over more than a decade. With that unique perspective, Ben has been consistently recognized as one of the most influential voices in XR, giving keynotes and joining panel and podcast discussions at key industry events. He is a self-described "journalist and analyst, not evangelist."
  • seanlumly

    This is a wonderful project, and it’s great that there is an exploration into wireless transmission video from a much stronger PC! If latencies can be reduced enough (encode/transmission/decode), or bandwidth increases enough, this may lead to very low cost headsets with great performance. What is most interesting is that cloud-rendering (eg. brigade3.com) suddenly seems much more realistic, and could blow the doors open for realism in VR at easy-to-explore prices.

    Soon VR headsets will be as interchangeable as monitors or TVs. The hardware won’t matter that much with some being better than others. What will matter is the system driving it and the eco-system of software.

    • Ohaple

      Thanks for the nice comment, I agree with much of what you said. I am working right now to reduce latencies, and will have an update on my channel very soon to showcase it!

    • KYOUDA

      please help me
      freetrack can detect my led but when i select mouse emulation and absolute then the mouse just stays in one position help me please

      • Heliosurge

        Has anyone considered using a Wii mote with 2 ir leds? Recall a project for head tracking used that

  • Chris W. Morris

    You could also start with a $50 “Poppy” stereoscopic viewer for smartphones, and just add tracking. B-)

    • Ohaple

      Yeah, that is the idea, in the article I suggest Durovis Dive. I plan to review the Dive in a few days when mine comes, but they are a great company overall. You can certainly modify other units to add tracking. Making your own only saves some cost

  • Alkapwn

    A suggestion for the LED for people who may not want or know how to solder. Get an LED reading light or keychain light from the dollar store. This way you can mount that to the top and still have an on/off switch.

    • Ohaple

      Good idea. I am working on a new design that doesn’t even require an LED, check my channel for more info on it coming soon. Thanks for the feedback

      • braxtron

        why not just use the phone camera’s flash

  • Hec Wilk

    free track doesn’t seem to have a mac version. anything out there like it that works on mac?

    • Ohaple

      Yes sir. The gyroscopic mouse. I have annotated the current video found in the writeup above to include a link to my newer video where I show how to incorporate a USB Gyroscopic mouse. This adds $10-20 to the project cost, but yields a much better result and is mac compatible.

  • Scruff_McGee

    What a cool project! I’m having some success right now with TriDef 3d launching Steam, and then using Android Limelight to use Nvidia’s Shield stream to my Galaxy Note 3. The parts are on the way for the headset, I can’t wait to try to build this, thanks for putting up the instructions man!

    • Ohaple

      Sounds like you have the hang of it! I will be interested to see how it turns out for you. Check my channel for more updates to the project.

  • Hec Wilk

    Just got all my parts in ( using the android gyro-mouse) and all seems to be working except tridef. Can’t figure out what I’m doing wrong. Halo doesn’t work, and team fortress 2 through steam isn’t working. And it only seems to be on games, everything else in tridef works fine. I’m running windows 7 bootcamp on a 2013 Mac mini.

    • Ohaple

      Some people have reported issues using splashtop with tridef 3d if you do not have a Geforce graphics card. Try using kainy in stead of splashtop if you are on android.

  • James Addison

    I am having trouble getting my mouse to move with the led. The program free track won’t let me enable my mouse. Also I am having trouble with the splash program also. I really need help. I’ve built the box and it is awesome with dive games, but that’s all I can play. I’ve made it this far. Help me make it all the way.

    • Ohaple

      Check my channel later today, I have a video that addresses both of your questions. A guide is also being made for roadtovr that updates and improves this project. :)

  • Anibal

    Great job! You are using aspheric lenses? what FOV do you get?

    • Ohaple

      For everyone in the comments, it is much better to contact me on youtube or twitter, as I do not check this as often.

      @Anibal I don’t know how to calculate the FOV, but it seems similar to sitting 12 inches from my 21 inch monitor. I do not know if they are aspheric, as they were taken from binoculars. They do not distort the shapes.

      • CannibalPig

        Im going to try building this project, but i cant seem to find any 5x 1-2″ Lenses anywhere online. Could i just the lenses already in 5x reading glasses, or must i use round magnifier lenses?

  • alberto

    Visit my blog: http://www.virtualystudio.blogspot.com , how make a hmd with a smartphone, i think that use freetrack is the past, 80% of smartphones have gyroscope. Using Freepie application you can move the cursor of windows with the movement of your smartphone.

  • handballnut

    Where do I get those lens things

  • KYOUDA

    please help me
    freetrack can detect my led but when i select mouse emulation and absolute then the mouse just stays in one position help me please

  • MartyMcC

    Hi,
    A few years ago there was a guy called Johnny Lee who got excellent head tracking using a wii remote (check out here: http://youtu.be/Jd3-eiid-Uw?list=UUTW58h2zg8r9O0bGmMt2L5Q ) is there any way this method could be used for head tracking here as i’d say the results would be better than current method?

  • NikeWaffles

    I built the headset, got splashtop and everything, but I have an AMD video card
    as you may know, TRIdef3D only works in full screen (with amd video cards) and Splashtop wont work with fullscreen . And If I use tight VNC Its much too lagy

    With Oculus rift games, I cant look up and down with the Freetrack mouse control.

  • braxtron

    you really want a current limiting resistor in your led circuit, adds minimal complexity and ensures desired brightness, maximum battery life, as well as greatly extends the life of the led. ideally you’d have some sort of dc-dc converter to ensure led brightness throughout the life of the battery, but if you aim for the voltage level at which the batteries are 50% drained or so you should be fine. msg me if you want further deets.

    • Chris Weghorst

      you don´t need one! a simple white LED has a normal working voltage of 3,4Volts at 20mA. since the led only gains 3 volt it will not even burn out or something like that. And to increase the lifetime isn’t necessary, a basic LED will keep up 20.000 hours or way more. about the battery, a basic battery from Duracell or so will contain about 2500mA so they will be empty after 125 hours or so. thats long enough.

      • Clonkex

        Actually you most certainly do need one. Unlike normal incandescent light bulbs, which are voltage-controlled (more voltage = more brightness), LEDs are current-controlled. They will draw as much current as they can regardless of the voltage applied, and if there’s no current-limiting resistor, they’ll draw as much as the battery can supply and burn out very quickly or even instantly.

        tldr; you absolutely do need a current-limiting resistor.

        • Chris Weghorst

          your wrong, trust me, where did you get this information?

          • Clonkex

            Wtf? It’s common knowledge. The only two times you don’t need a series current-limiting resistor with an LED is when the battery itself has sufficient resistance (such as in certain coin-cell battery-powered keychain lights), or if the LED has a built-in resistor (usually to save space on PCBs).

            You need only google any LED how-to or look at Wikipedia to learn this…

            Try simply powering an LED from an unrestricted power source and tell me that it doesn’t instantly burn out.

          • rg33

            I had always used a resistor with LEDs, so I just tried an experiment, feeding 3v to a white LED with no resistor while measuring the current using a voltage & current controlled power supply. If the voltage was between 2.75v and 3.0v, the LED drew a limited amount of current (~15ma), but as the voltage increased above 3.1v, the current climbed dramatically.

            At 3.3v it almost doubled to 35ma. At 3.5v it almost doubled again to 60ma.!

            I inserted a 200ohm resistor at 3.3v and it fell to only 3ma. Brightness was still good, and battery life would soar. It also stayed below 10ma even feeding 5v to it. (5v w/o resistor gobbled as much as 100ma.)

            Conclusion, if your battery voltage stays below 3v, current isn’t bad, but battery life will be significantly shorter than with a resistor.

            As far as LED life is concerned, it lasted at least an hour of testing! :-)

          • Clonkex

            Interesting! So it seems that you _can_ use an LED without a resistor, but it depends greatly on the particular LED and battery you have (i.e. the inherent resistance of the battery), and relies on very specific voltages.

            In my previous tests of running LEDs without resistors (at 5v), some of them just flickered once and died, and others burned extremely brightly for a second or so then died. Never thought to take it further and try lower voltages.

          • sorbustenherra

            In 99% of cases you should still use a resistor for this kind of circuits. You are essentially creating a short circuit if you just strap a led onto a battery without a resistor :D

          • Clonkex

            Exactly.

          • Gamie1543

            both right i have some 9v leds here you could just connect to 9v battery they come in different voltages

  • Bla

    u can use kinoconsol. Ten time better than running through splash top and actually made for streaming pc games to a smartphone for VR