02/04/2021

RESEARCH: Sunglasses & Attenuation of UV/WHT Light

This project is part of the "why am I jumping to other projects before finishing off my old ones" series...

I have always wanted a compact UV capable flash light and last week got the JETBeam MINI ONE SE (it's surprising how much they managed to cram into this thing...). Well after playing around with the UV light I soon found that I am quite sensitive to it, which would explain why I tend to get headaches after spending a good portion of the day outside

To help with these headaches I have some clip on polarizing sunglasses, and now that I have a UV source I was curious how well they attenuated UV (365nm) & WHT light. So I used my works spectrometer to get some cool spectra plots


Ambient Light

Here is the ambient light spectrum after the spectrometer was zeroed (below is a roughly overlaid humanly visible spectrum)


UV Light (365nm)

0.42W/m² → 0.05W/m² (~89% reduction)

NOTE: 365nm is a bit too close to the spectrometer limits, so there is a bit of clipping happening


WHT Light

75.31W/m² → 22.12W/m² (~71% reduction)

27/03/2021

PROJECT: Turnigy Accucell-6 FW Update & Calibration

This project is part of the "why am I jumping to other projects before finishing off my old ones" series...

Many moons ago I tried using my Turnigy Accucell-6 battery charger to log charge/discharge data via DataExplorer, though sadly I could never get it working properly. Well it turns out that the Turnigy Accucell-6 (along with a bunch of other 4 button chargers according to my colleague) is basically a rebranded SkyRC iMax B6 mini, which is fully compatible with DataExplorer :D

So here I attempt to flash the iMax B6 mini FW and calibrate the charger


FW Update (v1.12 → v1.14)

The FW on my charger was changed from:

  • Turnigy Accucell-6 v1.12 (this would have been the original FW charger came with)
to
  • SkyRC iMax B6 mini v1.14

Interestingly the product page for SkyRC iMax B6 mini shows v1.13 as the latest FW, however only v1.14 has calibration functionality. Also updating the FW is super simple, you just need to connect your charger to the PC (via USB) and run the flash utility "B6mini_SK1.14.exe"


Calibration

This step is a bit more tricky, luckily SkyRC have a video describing the whole process:


Things you will need to run through calibration:
  1. A charged 6S LiPo battery. Since I did not have one on hand I tried "simulating" one by pumping ~4.2mA into 6 1K resistors in series, but this did not work as the load/resistance (and thus "cell" voltage) changes as soon as you connected it to the charger; meaning you will need to have a voltage source at a minimum. So again my colleague was kind enough to let me borrow his 6S LiPo battery
  2. A calibrated multimeter. I used my trusty EEVblog 121GW which I verified against a calibrated multimeter (Keysight U1241B) at work


From then you basically record the voltage of each cell (remember cell 1 is the one closest to GND) with the multimeter, and then calibrate the charger by going into "BATT METER" and holding "Enter". At this point you enter the voltage (in mV not V) you read with the multimeter for each cell via +/- keys, and once you are happy hold "Enter" again to save & exit the calibration menu


Here is how my charger performed before/after calibration:

Cell # Volt. 121GW, [V] Volt. before CAL, [V] Err. before CAL, [%] Volt. after CAL, [V] Err. after CAL, [%]
Cell 1 4.1865 4.18 +0.16 4.18 +0.16
Cell 2 4.1910 4.19 +0.02 4.19 +0.02
Cell 3 4.1879 4.17 +0.43 4.18 +0.19
Cell 4 4.1909 4.18 +0.26 4.19 +0.02
Cell 5 4.1966 4.19 +0.16 4.19 +0.16
Cell 6 4.1958 4.17 +0.62 4.19 +0.14

So running the charger through calibration reduced the error range from 0.59% to 0.17%, and given this is a hobbyist-tier piece of equipment I am quite happy with the <1% accuracy

A couple of extra points about calibration results:

  1. It looks like the charger ADC/MCU likes to round the voltage down in a curious way. For example:
    • 4191mV will be rounded down (as expected) to 4190mV (4.19V on charger)
    • 4188mV will be rounded down to 4180mV (4.18V on charger, not 4.19V)
    • 4197mV will be rounded down to 4190mV (4.19V on charger, not 4.20V)
  2. If you perform calibration more than once you might notice that the mV reading is not quite the same as the multimeter value. Lot's of other people (see video comments) report the same "issue", which I suspect is totally normal for this hobbyist-tier piece of equipment
  3. I will be mainly using this charger for LiFePO4 batteries which are typically charged to 3.65V ± 0.05V per cell. Knowing that at worst the charger error is +0.19% this means when I charge to 3.65V the actual cell voltage will be more like 3.6569V, which is well within the ± 0.05V limit

Data Logging

As expected DataExplorer now talks without any issues. Here is me charging and discharging a 2S LiFePO4 battery:

NOTE: You can plot fancier looking graphs by exporting the data as .csv and plotting it in your favorite package 

07/03/2021

PROJECT: Woodworking & 3D Printing

Sometime in late 2018 my wife and I decided to upgrade her workspace. The initial plan was to tackle this in several sections:

  1. Build the left (self-contained) shelf
  2. Build the right (self-contained) shelf
  3. Bridge the two with a desk

Well we managed to complete left shelf within a couple of months, as for the last two... they basically took us till late 2020. Surprisingly we have COVID to thank for that, as being locked inside with nothing to do gave us a wee boost :D

An interesting aspect I wanted to try with this project is merging woodworking with 3D printing, as I felt the two could complement each other reasonably well especially with smaller fittings. So below I document such 3D printed items:


Small Drawers

Probably the only exception to the "smaller fittings" description. The larger drawer measures 320 x 300 x 70mm and both had to be split into several parts. The only things not 3D printed with these was the metal rods running through the body (for extra support), and the MDF base. Also the body is printed in PETG and fastened with Loctite Control Gel Super Glue


Drawer Handles

Wife wanted something flush yet accessible, so came up with this simplistic design


Drawer Supports

A while back we found a bamboo tray (on the street!) which we decided to convert into a drawer. Initially we were going to mount the drawer slides onto another piece of wood, but after realising how much work would be involved (and how uncool it would look) we decided to 3D print the supports instead


KVM Switch Bracket

Couple of brackets that hold a KVM switch (Unnlink 2 port). Side note, the switch makes it incredibly easy to jump between the laptop & desktop


HDMI Splitter Bracket

Couple of brackets that hold an HDMI splitter (CABLETIME C355). Again super useful for changing between the TV and monitor


Cable Holders

Super simple cable holder. Initially this was twice as tall (so you could cram more cables) but someone wanted a more flush design...


Outlet Bracket

Couple of brackets that hold an 8 way outlet (HPM D105PA8CC). The cylindrical cut-outs act as a cable runway (unfortunately the outlet mains cable was on wrong side...)


Wood Spacer

This one is probably the most "pure" merger of woodworking and 3D printing, a simple 7mm thick spacer that allows the desk and shelf surface to be level 


EXTRAS

Fern Pot Brackets

Don't recall the exact plant pot & saucer combo, but suspect it's something like this & this


Laptop Stand (ゴ ゴ ゴ ゴ ゴ ゴ...)

Simple Metabox Alpha N850HJ stand, same one shown here


Desktop USB & HDMI Bracket

Makes USB (2.0 & 3.0) & HDMI ports more accessible, again same one shown here

16/01/2021

PROJECT: PC Upgrade & Benchmark Results

Since 2011 I have been rocking on an Intel i5 2500K (man this thing should go into a museum for how well it has aged...), and only a couple of years ago did I "upgrade" to a Intel i7 3770K. I did this primarily for VR, as my old motherboard did not support the correct USB 3.0 specification... 

Well early this year I decided to do a proper upgrade, but before doing so I ran some benchmarks to compare the old/new PC. Turns out the new hardware is at least twice as fast, so I am a happy camper :D


Old/New PC Specifications

  Old PC Specs New PC Specs
CPU Intel i7 3770K Intel i7 10700KF
CPU Cooler Hyper 212 EVO be quiet! Dark Rock 4
RAM Kingston HyperX Beast 2x8GB 2133MHz DDR3 Team T-Force Dark Z 2x8GB 3200MHz DDR4
GPU ASUS GTX 1060 6GB Gigabyte RTX 3070 Gaming OC 8GB
SSD Samsung 860 Evo SATA III 250GB SSD Kingston A2000 M.2 NVMe 1TB SSD
MOBO Gigabyte GA-Z77MX-D3H Gigabyte Z490-GAMING-X
PSU Corsair HX650W 650W Gigabyte AP850GM 850W


Benchmark Results

  Old PC New PC
3DMark CPU ("Time Spy" test) 4398 9857
3DMark GPU ("Time Spy" test) 4162 14086
Steam VR Score 7.1 11.0
SOLIDWORKS (_AR2_Assembly.SLDASM) 17sec 12sec
Altium (Solar-heart_MAIN_v11b.PcbDoc) 12sec 3sec


Benchmark Results (Extra)

20/12/2020

PROJECT: Prusa i3 MK3S Extruder Heatsink

It may come as a surprise but some 3D printer extruder stepper motors tend to run quite hot, like +25°C above ambient hot. This is not too bad when your ambient/room temp is ~20°C, but boy do the summers in Australia get toasty... and if things get toasty enough the heat can creep through the shaft/driver gears and warm up the filament surface, making it that much harder to feed in controllably

Now as far as I am aware I have not run into this issue with my Prusa i3 MK3S + MMU2S, however I was curious to see:

  1. What is the typical temperature rise of the extruder stepper motor
  2. If installing a passive (no fans) heatsink could help lower the above temperature


The Setup

I tested the extruder stepper motor of my Prusa i3 MK3S under 3 scenarios:
  1. Original (no heatsink)
  2. Dense fin pattern heatsink (ATS-FPX040040025-05-C1-R0)
    • Single fin dimensions are 0.8 x 8.5 x 22.2mm and there are 50 of them
    • Weight 29.6g
    • Thermal resistance 8.7°C/W (unducted flow)
  3. Light fin pattern heatsink (ATS-CPX040040025-116-C1-R0)
    • Single fin dimensions are 0.9 x 8.5 x 22.2mm and there are 32 of them
    • Weight 21.4g
    • Thermal resistance 4.1°C/W (unducted flow)
    • Suspect this will be the winner due to the spread fins 

In each case I logged the stepper motor & room temperature, from which the temperature rise (above ambient) value was calculated. I should point out that comparing the Δ/change in temperature is more suitable here instead of say comparing the absolute peak temperature in each scenario 

Also to make sure I was testing the heatsink performance (and not how well it coupled to the stepper motor) I used a crazy high thermal conductivity pad. The EYG-A091202DM, which is graphite based and has a thermal conductivity of 1850W/m·K! (two orders of magnitude higher than your typical thermal pad)
NOTE: To mount the heatsinks I had to change the M3 screws from 30mm to 35mm

Finally, for those curious this is the model I was printing for the test:


The Results

As I suspected the lighter fin pattern heatsink (ATS-CPX040040025-116-C1-R0) gave the lowest temperature rise, reducing it by a cool 7°C compared to no heatsink

On paper this may sound surprising, as this heatsink has a lower thermal resistance (4.1°C/W vs 8.7°C/W) which in theory should mean worse performance. BUT what one must realise is that we are extracting/exchanging the heat from the heatsink via convection currents (not forced air flow), and in this case it's easier for the air to couple into a less dense fin pattern

23/10/2020

PROJECT: Half-Life 2 AR2, Update #7 - Receiver Progress

LINK TO PREVIOUS POST


With this update I though I would show what a typical evenings worth of SOLIDWORKS looks like, and what better way to do it than a cool timelapse video: 

Here I am working on the AR2 "Receiver", the part that hold all things relevant to the "firing pin" as well as trigger. In the video you see me fix up small issues (like unexpected collisions), as well as figure out how each part will fit and fasten together

Once that stage is complete then plan is to then figure out how on earth I am going to find the space to fit all the extra components/electronics...


27/09/2020

PROJECT: Half-Life 2 AR2, Update #6 - Now with Sound

LINK TO PREVIOUS POST


Quick update... I have the sound part of the AR2 prototype working :D

To give you a quick rundown. Initially I went with a VS1000 based dev-board but soon found that this chipset does not support polyphonic playback, as in a sound must finish playing before another can be played. Well this is where the WAV Trigger (a crazy flexible WAV player designed by Jamie Robertson) comes in, as this STM32 based dev-board allows you to play up to 14 tracks at the same time! Which is perfect for blending the firing/reloading sounds the AR2 makes 

Also with the current prototype I am using a Class AB amplifier to drive a 4Ω 3W speaker. I did have a quick play around with a Class D amplifier, but found that it slightly distorted the firing sound


With all that said, the next step is to fix up the 3D model (note all the black marker markers...) and start thinking about combining all these dev-boards into one (as in put my Altium hat on)