The theory, the research and the tallies.

Ever since I had my first Oculus Quest 1(which I unfortunately had to part with, RIP - thing was great) I wanted to find an affordable full body tracking(FBT) solution. At the time of me using the Q1, solutions were either Vive Trackers or janky projects still in their infancy, so the dream of an affordable FBT was put to bed until a later date.

And now, with a recent acquisition of my Oculus Quest 2(review of this will come at a later date, stay tuned!) SlimeVR trackers being very affordable yet offering a full body tracking with extensible track points, with their official kits starting as low as €200? Sign me up!

Now, with the SlimeVR project being open-source, this means people are free to make their own out of the parts - and I must admit, there is beauty in simplicity; It is literally an ESP8266-based microcontroller combined with an IMU - for those not in the know, IMUs are intertial measurement units, and they’re essentially responsible for tracking their position from an origin point. These modules, combined with Wi-Fi ESP8266 boards, and a battery turn out to be quite decent positional trackers, all without base stations!

Estimating that I’d want to have a go at this project, I decided to undergo the research in order to acquire parts and assemble these trackers myself. I figured, ‘by putting the parts together myself I’d be able to make them for cheaper!’

Oh, how naive I was.

Yeah, it turns out some IMU’s are stupidly expensive. For example, the BNO085 IMUs used in the official SlimeVR trackers - they cost €12 a pop! If I were to go for the full body package of 10 trackers(getting 15 under the assumption some would be DOA, Dead On Arrival) - I’d be €120-€180 out of pocket just for the IMUs!

Thankfully however, there are cheaper alternatives. For example, the BMI160 IMU manufactured by Bosch is a much cheaper alternative and can be found for around €1.20-€1.50 a pop, which is a much cheaper alternative, which in theory shouldn’t affect performance in anyway since allegedly the magnetometers found on the BNO085’s are disabled by default in SlimeVR’s firmware, in order to prevent some enviroments from causing the trackers to crap themselves.

Then, the topic of the microcontrollers themselves came forward. Ideally, I’d get a load of ESP-32 based boards for their better performance, however the ESP8266-based microcontroller devboards like the Wemos D1 Mini are still quite affordable on your local Chinese suspects like AliExpress, going for around €2 over there, so that one was a no-brainer.

Now, the topic of the batteries! For the charger boards, there was no contest - the TP4056 USB Type-C charger boards were an absolute requirement from me, because over the past year or so I have slowly phased out Micro-USB(only survivors are my budget earbuds and my Logitech G933 headset), and if I wanted to charge them all up it’d be wise to go with a widely supported connector vs the one that’s slowly being phased out. As for the batteries themselves, I decided to NOT fuck with Chinese batteries and went for domestic sources - thankfully, there is an electronics store named Lemona that operates in major Lithuanian cities, so I was able to locate some 1200mAh LiPO batteries on there for €7.80 a pop.

This is something I really wanna drive home - Never EVER use cheap or unknown brand batteries. Please. I have seen and heard of so many horror stories of them going belly up, causing fires, explosions and whatnot, that I cannot under good conscience even suggest it.

Welp, that makes the four major components sorted out. With some knick-knacks(like diodes for protecting the battery while charging, a resistor for each battery to track it’s current charge, and a switch to turn the trackers on) out of the way, we’re left with only one big dilemma.

The cases.

This one had me genuinely stumped for a while - where on earth is one to get cases(short of purchasing some from official channels) in order to store the trackers?

And this is where I turned to… Power cable distribution boxes. This solution does make sense on the paper - they’re plastic, so lightweight, weather-proofed(and in some cases, water-proofed, too!), and they’re cheap! So after some research, I had settled on some distribution boxes that were small enough to fit. That still leaves the issue of strapping them to my body, however. But, since most distribution boxes do have screw holes to wall-mount them, I could utilise them to sew them onto some nylon elastic bands.

So, with all of the requirements mentioned, what would be the estimated tally of creating such trackers, myself? Excluding the soldering gear, of course - I have that on hand myself.

Item Amount Cost per Total Cost Delivery Link Notes
Wemos D1 Mini ESP8266 devboards 7 required* - get a lot of 10 ~€2.10 ~€21.14 Free AliExpress Main board - required, but perhaps other ESP8266 devboards go for cheaper?
BMI160 IMUs 10-12**, get 15 ~€1.40 ~€21.15 Free AliExpress The go-to IMUs for DIYers, because BNO085’s are too much $$$
TP4056 charger boards 7 required* - get a lot of 10 ~€0.71 ~€7.10 Free AliExpress Must-have if using batteries.
LiPO batteries - 1200mAh 7 required* €7.80 €54.60 Free - local pickup Lemona Don’t mess with Chinese generics.
1N8517 diodes 50pcs/generic set       AliExpress I already had comaptible 1N8519 diodes on hand, so can ignore this.
180kOhm resistors 100pcs/kit   €1.15 Free AliExpress May not even need these if I locate enough in my personal stash.
0.32mm²(28AWG) gauge wire 60-pin, 2 metres €11.48 €11.48 €5.43 AliExpress I might have some laying around… or I might just go for local purchase.
75x75x34mm distribution boxes 7* €1.16 €8.12 Free Moki-Vezi  
75x37x39 distribution boxes 5* €0.89 €4.45 Free Moki-Vezi  
5-pin JST connectors(both male/female) kit, they have like 10 €1.95 €1.95 €2.83 AliExpress  
Nylon elastic straps 2 kits, 5pcs each ~€5 ~€10 €4.05 AliExpress Maybe get different sizes, some for IMU extensions vs main assemblies?
Note: all prices are estimates. Don't take these literally, as your delivery costs/domestic prices may vary.
* Only 7 main trackers need to be present - other IMUs can just piggyback as extensions!
** 10 IMUs are used for FBT in SlimeVR, but additional 2 can be used for elbows.

And as such, this brings the final estimated price of assembling this thing myself to… around €140! For a full-tracking solution, that is genuinely not bad! Granted this is a pessimistic estimation, in reality I expect the price to be slightly higher; but considering the fact the entire kit would cost me less than a lower-body basic kit from SlimeVR themselves(around €200), this is a really enticing way to tackle this project in order to achieve FBT!

Anyways, thank you for reading this build log part 1. I will try to begin ordering parts over my paychecks, and once I acquire them I will write up a second blog post, documenting my assembly experience, with hopefully more pictures. Take care!