Wireless TrackIR with a TrackClip Pro

[Milopapa]

I finally mustered enough courage and determination to convert my TrackIR to wireless - here to show how I did it.

 

TL:DR - I cut and soldered the USB cable of the TrackClip Pro unit to the internal battery pack of my wireless headset.

 

Background:

I have a wireless headset, so the extra cable needed for the TrackClip Pro has become a nuisance and a trip hazard. Since the cable is only needed for the +5V that the USB port can provide, I started looking for alternative power supply to drive the clip. I looked at various solutions (extra Li-ion battery strapped to the headset) but I didn't like the idea of having to charge the clip separately, plus not knowing how that battery's doing in terms of remaining charge.

My headset has a standard micro-USB port for charging and it starts giving warning beeps when the battery is becoming low, so I decided I would use its internal battery to power the clip - with a bit if hacking and soldering :)

 

Result:

• no cables at all coming to my head
  
• headset functionality completely intact
  
• switch on TrackClip unit to minimize battery usage
  
• cable flexes so headband can be adjusted freely
  
• headset warns me when battery's low
  
• charging headset also charges the TrackIR clip
  

 

Materials needed:

• Wireless headset
  
• TrackClip Pro (somewhat broken already so I could sacrifice it without too much to worry about)
  
• inline DC switch (I salvaged it from one of those annoying plastic dolls that cries or laughs when you press on its tummy - my daughter basically forgot about this so no harm done)
  

Total cost: $0

 

Solution steps:

 

Cable routing and soldering:

1. removed the cushion from the left speaker cup to reveal screws and began disassembly

2. unscrewed 3 layers of components (including speakers)

3. found main PCB

4. measured various points with a multimeter to find +5V or similar - came to the conclusion that I need to use the battery output (4.2V) directly as none of the others were close enough (closest was 3.9V). This also meant I needed a switch to shut off the infra LEDs when not user, otherwise they'd be always on, even when the headset is switched off - and would drain the battery quickly.

5. drilled a hole to allow the USB/power cable to go into the speaker cup

6. inserted cable

7. removed cable, drilled an even bigger hole to enable tight assembly

8. fought hard to insert cable through the rotating axle alongside the original cabling

9. soldered cable to battery endpoints on the PCB

10. played with routing the cables for a while, decided the remove outer cable covering to save some space

11. re-assembled whole earcup only to find while testing that one of the speaker signal cables snapped from the PCB (no sound from left side) so I had to take it apart and re-do that soldering

 

Adding the switch:

1. removed switch from the doll

2. found the right place it could go on the clip unit

3. cut, sawed, hacked, chipped and cursed for an hour to remove the appropriate amount of plastic to create a slot for the switch

4. inserted switch into the slot (needed some padding to make it tight)

5. cut and re-soldered red wire to the backside of the switch

6. tested the switch

7. rejoiced immensely to find it working

8. went to bed at 4am

 

Attaching some photos:

 

Removing the layers:

 

The main PCB (connection points on the backside)

 

Soldering completed (this was taken before I removed the rubber cover of the extra cable to make some space):

 

Showing the new hole (I first drilled it too close to the joint, couldn't fit it back together with the cable inside):

 

And here's the new switch:

[Rabso]

This is amazing work Milopapa, I liked the idea and indeed I will try it in feature!

 

(somewhat broken already so I could sacrifice it without too much to worry about)

Mine is new this why for sure I will be worry to do it now :huh:

[Goblin]

Nice hack!

[Tone71]

Awesome. Good work.

[Rogue Trooper]

A very nice, well thought out and executed mod.

[agrasyuk]

very clean.

 

how do those kind of mods affect headset battery life?

[Milopapa]

how do those kind of mods affect headset battery life?

 

That is a really good question - and I don't know, to be honest. I haven't used it long enough to be able to tell.

 

I don't even know how long the headset lasts - never measured it. I'd estimate it to have at least 8 hours of charge.

I got into the habit of charging the headset frequently (almost daily) to make sure it doesn't start giving out in the middle of a gaming session.

 

I'll try to make some measurements - run it through the night or something.

[Sporg]

Maybe you could get an extra battery to mount inside the headset.

 

Try to find the battery inside, so you can get a second one with the same specs.

[Milopapa]

You got me thinking there - as I'm into flying RC helicopters, I know a bit about LiPo (lithium polymer) batteries and now that I know how to open the headset :), I might just go and upgrade the original battery with something more powerful.

 

Someone already opened a similar model and found that the battery is a single-cell 3.7V LiPo with 900mAh capacity.

 

I'll do some research and see if I can find something more juicy that is not too much heavier (the trackclip on the other side should compensate for a little more weight and still keep it balanced).

[Milopapa]

Maybe you could get an extra battery to mount inside the headset.

 

Try to find the battery inside, so you can get a second one with the same specs.

 

OMG - that is creepy :)

See my post just below yours...

[Sporg]

OMG - that is creepy :)

See my post just below yours...

 

Posted at 10.13... :)

[Sporg]

You got me thinking there - as I'm into flying RC helicopters, I know a bit about LiPo (lithium polymer) batteries and now that I know how to open the headset :), I might just go and upgrade the original battery with something more powerful.

 

Someone already opened a similar model and found that the battery is a single-cell 3.7V LiPo with 900mAh capacity.

 

I'll do some research and see if I can find something more juicy that is not too much heavier (the trackclip on the other side should compensate for a little more weight and still keep it balanced).

 

You could also consider two batteries in parallel so you can distribute the weight, if there is room enough.

[Milopapa]

You could also consider two batteries in parallel so you can distribute the weight, if there is room enough.

 

Well, the left side is pretty cramped with the electronics... I'll open up the other half and see how much wiggle room I have there.

 

Offtopic:

My biggest worry about this headset is not the capacity but that it's prone to radio interference that I could not so far identify. I rarely hear it but my buddies complain about it all the time - apparently it also affects the microphone input. I tried moving the dongle, disabling wifi on my router - no joy. Strange thing is, no-one else with this headset seems to have this problem - must be something unique in my home.

[Milopapa]

You need a voltage booster for strong lights

 

OK, so things were not as rosy as I thought. What other similar mods failed to mention is that the voltage provided by a LiPo battery is not enough for this setup to work reliably. I found that out the hard way - as soon as the voltage dropped below 4V, the lights would dim and the TrackIR image would start to flicker... moving closer to the camera and increasing the light filtering threshold would help (for a while), but it wasn't what I could call a working solution.

 

Here's a little crash course on LiPo batteries and LED circuits for those of you interested:

 

 

Even though the nominal voltage of a LiPo cell is 3.7V, in reality it is more of a range between 4.2V (fully charged) and 3.65V (almost discharged).

This presents a problem for LED applications where there is a strong correlation between voltage, current and light intensity.

In essence an LED is a diode (remember, Light Emitting Diode) which has a forward voltage (also called voltage drop), below which it will not let current through (or in other words, light up). There is an almost linear range of input voltage where the light intensity is directly proportional to current, this is the useful range. Anything above this range, and the LED will be damaged and eventually burn out. To avoid this, most LED circuits use in-line resistors to control the current.

 

Here is a typical voltage-current diagram of an LED chip:

 

And here is how the TrackClip Pro is built:

 

I've been trying to find the exact specs of the LEDs used in the TrackClip Pro, but I haven't been able to get a definite answer. It looks like its forward voltage is either 1.45V or 1.5V. Since there are 3 of them in series, this translates to a total voltage need of 4.35-4.5V to reach the useful range.

 

Now you can see why we have a problem with a LiPo power source which provides 3.65-4.2V.

 

I've found a resistor in the clip (43 Ohms) which I tried replacing with lower and lower resistors (as low as 5 ohms) to increase the current and it kinda worked but again, as soon as the voltage started to drop, the lights would dim dramatically.

Another trick I did was to replace the battery with a higher capacity one (670mAh to 2000mAh) to increase the time when it was above 4V, but again, this was just buying time.

Oh, by the way, the headset had an original battery with a temperature sensor (to be precise, a negative temperature coefficient (NTC) thermistor). This is an extra wire on top of + and -, which regulates the charge/discharge cycle through a resistance reading. Without this, the built-in circuit thought the battery was disfunctional and refused to use it. I had to get one with the thermistor built in (see, 3 wires!):

 

 

 

 

The ultimate solution was to use a voltage booster, which would not only boost the input voltage but also regulate it at a steady 5.2V. The one I used from Adafruit works in any LiPo to USB environment and fit perfectly into the earcup (just below the PCB).

 

 

After connecting this between the power source and the clip's input lines, it worked like a charm. Strong, steady lights which remain operational throughout the entire discharge cycle of the battery - which incidentially is now 3 times as much since I upgraded the battery :)

[Econ]

http://www.aliexpress.com/promotion/diy_18650-diy-promotion.html

[Milopapa]

http://www.aliexpress.com/promotion/diy_18650-diy-promotion.html

 

What the heck is this?