Convert headtracker from battery to USB power

[Raven_Morpheus]

Hey all

 

I've got a homemade IR LED array that is powered by 2 AAA batteries (3V) with the LEDs in a parallel circuit but I'd like to convert it to USB power as I'm kind of fed up with the batteries running low on me and causing tracking problems.

 

The plan is to chop the battery holder off (it's one of those black cases with a switch on the outside), attach a JST connector and use a USB lead with a JST connector (and maybe put one on the battery holder so I can still go wire free if I wish).

 

Not having much knowledge of electrical circuits, I don't know if it's possible to do this.

 

Would anyone here be able to give me some advice on this?

 

TIA

[Dami]

Interesting. I have seen a lot of people struggling to become wireless, but not so many wishing to revert to cables and stuff. :)

 

I'd suggest to visit the Freetrack site to get some basic assembly instructions. And you can google the rest - basically, everyting about it was discussed long time ago.

 

However, I see at least two problems in your case:

 

1) Your LED clip is designed to run on 3V. USB power provides 5V. You probably will need to replace resistors or else you will end up with fried LEDs :)

 

2) If you have no knowledge about electrics/electronics at all, I'd suggest to refrain from messing with USB power - inadequate LED assembly plugged into USB port may permanently damage your motherboard.

 

UPD I would suggest one more alternative - why not just try to improve your power capacity and still stay wireless?

I personally prefer inertial trackers nowadays, but long ago when I created my clip, I just used two 18650 batteries (or similar, I sold that thing long ago) in a case plus a long wire (like 40 cm or so). The battery case had a little clip to fix it on clothing, but most of the time I just had it in my breast pocket.

 

The capacity of industrial-type elements is A LOT higher than those AAA puppies. ) The only backbone is that they are pretty heavy and require special charger (they are pretty cheap, though).

 

To make things even more exciting - why not use LiPoly like these? Using this small board you can receive a fully working and quickly rechargeable battery.

Edited October 17, 2016 by Dami

[Len62]

Visit the Freetrack site as Dami mentioned. You can determine what size resistor you'll need to run off of 5 volts. You may want to use an external USB power supply to avoid the issue Dami mentioned. I use an old 5 volt phone charger, or you can wire in a fuse to protect your motherboard.

[Raven_Morpheus]

Interesting. I have seen a lot of people struggling to become wireless, but not so many wishing to revert to cables and stuff. :)

 

Yeah, I was keen to go wireless from day 0 of using head tracking, but I've found it's not quite as good as a wired connection (I've used both wired and wireless) - because the LEDs dim as the batteries drain. I often don't have a spare set of batteries fully charged either. At least with a USB powered clip I can just plug it in and go and never have any tracking issues due to dim LEDs. Although the ideal solution would be a dual power source clip, battery and USB for those times I just get fed up with a cable.

 

It's always the case that when I go to use my LED array the batteries are low...

 

I'd suggest to visit the Freetrack site to get some basic assembly instructions. And you can google the rest - basically, everyting about it was discussed long time ago.

 

Thanks. I wasn't aware the freetrack site was still going, considering the software (afaik) is no longer in development.

 

However, I see at least two problems in your case:

 

1) Your LED clip is designed to run on 3V. USB power provides 5V. You probably will need to replace resistors or else you will end up with fried LEDs :)

 

Yes I considered that. I think I could put a LED driver between the JST plug and the USB cable, that will negate the need for changing resistors as it will output only the required power.

 

But if at all possible I'd like to avoid rebuilding the internals (i.e. the resistors and LEDs), as I've already rebuilt it twice due to wires coming loose - I'd rather not have to completely rebuild it again (or build a new one).

 

2) If you have no knowledge about electrics/electronics at all, I'd suggest to refrain from messing with USB power - inadequate LED assembly plugged into USB port may permanently damage your motherboard.

 

Yep, I considered that also, I'd use one of those USB power blocks you plug into a wall socket. Wouldn't dream of putting something like this into my USB ports on my PC.

 

UPD I would suggest one more alternative - why not just try to improve your power capacity and still stay wireless?

I personally prefer inertial trackers nowadays, but long ago when I created my clip, I just used two 18650 batteries (or similar, I sold that thing long ago) in a case plus a long wire (like 40 cm or so). The battery case had a little clip to fix it on clothing, but most of the time I just had it in my breast pocket.

 

The capacity of industrial-type elements is A LOT higher than those AAA puppies. ) The only backbone is that they are pretty heavy and require special charger (they are pretty cheap, though).

 

To make things even more exciting - why not use LiPoly like these? Using this small board you can receive a fully working and quickly rechargeable battery.

 

I have considered batteries like 18650 but as you say there is a weight issue - I have the entire unit velcro'd to my headset (Creative Soundblaster Tactic3d Rage wireless) as it was the only way to attach it without doing it permanently, thus the reason I chose AAA batteries, I originally considered AA batteries but found them to be a little too heavy. And I've tried attaching strong neodymium magnets, but they don't stay attached to the plastics too long...

 

Have considered LiPos, I have some 3.7v ones for my RC micro helicopters I could use (they're only 240mah though), but again high Mah LiPos tend to be rather big and heavy, not to mention the fact they can be a lot more volatile than normal batteries.

Edited October 17, 2016 by Raven_Morpheus

[Demon_]

 

Connect the battery in series (use one resistance to drain less current). http://led.linear1.org/led.wiz