Android App for Blackmagic Pocket Cinema Camera 4K

Android Wear

I've just written an Android app that is capable of starting and stopping a recording on the Blackmagic Pocket Cinema Camera 4K  (BMPCC4K) and the URSA Mini Pro
(no wireless focus supports on the EF mount version).

It can
  • Start/Stop a recording remotely
  • display a live timecode and the most important parameters
  • pull live focus via touchscreen
  • change some parameters - codec, resolution and frame rate (some values not offered yet)

That this app does not yet offer much functionality.
I am still adding features.
I plan to
  1. allow starting and stopping the recording via Android Wear smartwatch (for Vloggers)  
    • making great progress here
  2. allow syncing the GPS-time of the phone to the camera(s)
  3. allow changing more settings on separate screens 
    •  work in progress
  4. allow to start/stop recording on multiple cameras e.g. for multicam interviews. (No idea for a good user interface yet. Proposals?)
  • My idea to also display audio meters will not work because the camera does not seem to send these via Bluetooth.
  • DCI 4K and 4.6K resolutions can not be selected because Blackmagic forgot to define the values in the protocol (support ticket DEV-144. Will be fixed in a future firmware) 
  • Also the camera does not seem to report the selected storage medium correctly.
  • I have not figured out how the iOS app gets the remaining time on the storage media yet.

Stable Releases: https://play.google.com/store/apps/details?id=biz.wolschon.bmpcc4krecord
Open Beta Test :
https://play.google.com/apps/testing/biz.wolschon.bmpcc4krecord (early access to improvements)


Yes, I did put a reasonable price tag of 10€ on it.
That's 20% the price of a power-cable set or 14% of an original Canon-battery or a meal at McDonalds.

Privacy Policy

(This is required by Google Play Store.)

This app does not collect, use or distribute any kind of personal data.
End of story.



Problem with optical input switches

The situation:

I'm trying to replace my microswitches as end-stops + homing sensors with an optical sensor for homing. (and keep the mechanical switches as end stops.)

I'm using a TCST2103 photointerruptor.
On the Emiter-side I use a 220 Ohm resistor to my common +5V to limit the current.
On the Detector-output side I use a 10 KOhm pulldown.
Emiter and Detector -inputs are on +5V.
Between the Detector-output and the 10KOhm I get my signal.

I meassured my VCC to be between +4.78V and +4.80V with allother loads connected to it.

The signal goes into an AKZ250 USB motion card that works with MACH3 to run my CNC milling machine.

(The sketch also shows the internal logic from the schematics of the USB board. It uses a TLP521-1 photocoupler, a 330Ohm resistor, the mentioned LED and a 4.7Kohm resistor on each input pin.)

 The problem:

When I hit "reset" in MACH3 with the photointertutor not interrupted, everything is fine. The input-LED on the USB board is off and the diagnostics page in MACH3 says the input is not active (high).

When I interrups the photointerruptor, the input-LED goes off and MACH3 says the input is active (low).

HOWEVER: When  I chease to interrupt the photointerruptor, the LED goes on again BUT MACH3 says the input stays active.
Until I tell MACH3 to reset.


I found my 220 Ohm resistor on the (E)mitter side too low.
180Ohm should have been used to reach the nominal 20mA on the emitter LED. 
This way we only get 15mA.

The graph "Fig. 8 - Collector Current vs. Collector Emitter Voltage" in the TCST2103 data sheet shows that this means only about Ic=2mA instead of about 4mA on the (D)etector output side.
(Apparently enough to still light up the red status LED just as bright as the others. These red ones nominally want 16mA but do work with less.)

The TLP521-1 inputs recommends 16mA (max 25mA) but gets 4mA.
This means only 4 instead of more then 10mA on the TLP521-1 output. (The recommend 16mA input would result in 40mA)
So I *guess* from studying just the data sheets, that way too little current get to the digital input that is behind the optocoupler on the AKZ250 USB motion control board.

Update 2:
I found THIS mention and it seems that may pull down resistors may be too large.

Update 3:
Or my 10K pulldown may be too large (correct for 3.3V) for 5V.


Building a rotacy CNC milling machine

Project history

  1. Previous project: TravelCNC
  2. current posting
  3. next step: TBD
  4. Next project: TBD


At the moment I have a heavily modified Carving-CNC/OmioCNC 6040Z+S80 machine from 2012 with an automatic tool changer and an 80mm 4th axis.

However the 80mm chuck and the 150mm clearance below the gantry of the 600x400x150mm machine has proven to be quite a limitation.
Even if you could make your part just barely fit...the next largest standard size of stock material would not.
If the stock could fit, you would not be able to raise your cutter high enough to reach the outher diameter. At least not the electronic 3D touch probe (that is much longer then most cutters).


So the idea was to build a special purpose CNC mill just for parts on the rotary axis.
It does not need a Y axis at all but a chuck with a large diameter on the 4th axis.
I was inspired by the Rotary CNC (movable tailstock) and the Farm OX (horizontal spindle)

  • Use a chinese 130mm chuck with 1:20 gears as a 4th axis.
  • No automatic tool change needed because it doesn't do general purpose work.
  • Use Openbuilds C-Beam with trapezoidal spindles (you can't buy these with ball screws off te shelf).
  • paired with high powered stepper motors for acceleration.
  • Add some end-stops and an electric touch plate for tool-length.
  • Use the existing stepper drivers, Mach4 USB breakout board and power supply of my old, mobile 400x300mm CNC machine.
  • Use either the 2.2KW water cooled chinese spindle with RS485 controlled VFD (left over from the ATC upgrade) or a 200W DC spindle (lightweight and easy to accelerate).

Since the C-beam is trivial to assemble and all the other parts are already here,
this SHOULD be a fairly quick and straightforward build.


...more soon


  1. The long X-axis uses a 1m C-beam ACME assembly with the XL gantry plate and a huge 4.2A stepper motor for maximum acceleration and thus direction-changes.
  2. There is no Y axis.
  3. The short Z-axis on top uses a 250mm C-beam ACME assembly with the extra-long gantry plate.
  4. A secondary X guide-rail in the front with a custom, 3D printed, extra-wide but not extra-long gantry plate stabilizes the Z axis and keeps it square to X.
  5. A 300W DC spindle with ER11 collets is enough for the soft materials this machine will encounter. It is also sufficiently silent. (a major consideration)
  6. Custom, 3d printed mounts for spindle, A-axis and tailstock complete the setup.

Lessons learned

  • Keep the oil-release screw accessible when designing a mount for a gearbox.
  • Openbuilds gantry plates can rotate slightly when presented with some force on a long, sideways lever. So a second, guiding rail and custom wide plates are needed to make the machine stiffer.
  • The Openbuilds ACME screws are performing surprisingly well compared to ballscrews.
  • The worm gear I used was of very bad casting quality and gets very loud in constant rotation. So instead of machining parallel to the A axis, I need to do it parallel to the X axis. This way X moves all the time but A only every few seconds for a short step.
  • Helical toolpathes in my version of Deskproto 7 seem to not render. The issue is being investigated and should be fixed soon.
  • I need to finish the custom mount for the tailstock quicker then I anticipated.
  • During an accidental plunge the modular Z axis proved surprisingly durable and very easy to dismantle, readjust and assemble again.
  • Always check for loose wires to your stepper drivers when things start to vibrate for the first time. ;)
  • My Z axis is too long but I could not get C-beam assemblies shorter then 250mm.

Next steps

I'm currently finishing the soundproof enclosure.

I'm currently adjusting my existing 4th axis, inductive homing sensor to the new 4th axis. At this time I only have home+limits on both linear axis.

I already ordered brushes to separate the axis from the machined parts and keep shavings out of the horizontal Z-axis.

I already ordered a proper guide-rail to replace that silver Openbuilds -contraption. This is fine for some first test-cuts but I don't want to re-tighten the wheels every few weeks.



Trying and walking away from Slack


The local FabLab (sorry, they still haven't managed to roll out basic SSL support for their website) had a very limited, internal forum for members.
That was replaced by Slack. A corporate chat enriched with features commonly found in forum software.


Aparently they thought, they could use it as a moderated, persistent forum instead of the temporary chat it was.
I tried it for a few month and looked at the dynamics of how it could be used and how it was used.
In the end, I found it too slow and organized for a sensible chat and too temporary and feature-limited for a forum.
So I decided to deactivate my Slack account again.

Why not a chat?

Many channels for different areas of the FabLab break up the (already very limited) audience into tiny sub-groups.
Conversations (answers to postings are grouped below that posting and no longer apear in the main feed) hide many things.
Being able to edit postings and being moderated reduces the number of new lines in the feed to almost zero.
It was the slowest going chat I've ever seen.

Why not a forum?

Conversation make it work much like a forum. However most features the initial poster has (such as images) are not possible in answers to that posting.
These features are not even allowed when editing your own posting. So e.g. adding a images that failed to upload is impossible.


More dust collectors

Project history

  1. Previous project: Testing the Kreg K5 Master System
  2. current posting
  3. Next project: ...

After I had designed the dust collector adapter for the Kreg K5 Master System
to Kärcher and Festool 36mm hoses, I had to go on and make some more:

Kärcher/Festool to Makita PJ7000J Lamello/Biscuit Joiner router


The local FabLab had a Makita biscuit joiner that didn't fit the local Festool shop-vacs.
So I quickly adjusted the diameter and labeling.
(Hooray for parametric CAD.)

Kärcher/Festool to Bosch GKS 12V-26


The new 12V battery operated circular saw is making quite a mess.
So for it's cute, tiny dust-collection part I made an adapter too...



Testing the Kreg K5 Master System

Project history

  1. Previous project: ...
  2. current posting
  3. Next project: More dust collectors



 Pocket holes?

I plan to build some pieces of practical furniture that does not need to look pretty.
As the local FabLab is just next door, I have easy access to a Lamello milling cutter and other eqipment. Apart from dovel pins, these "biscuit joiners" seems to be the prefered joining technique in Europe.

The preference in the US seem to be pocket holes.

Now the strongest joint for particle boards is of cause to glue it. Since it is made of glued particles anyway, this maked it one solid pice.
But to glue something you need two things. alignment and pressure. 
Lamello -type Biscuit joiners provide great alignment and the limited ability to slightly correct that alignment in one axis but they need clamps for pressure.
Pocket holes provide no alightment but a lot of pressure.
So combining these two should allow me to build very strong furniture without having to use clamps and wait for effectively the next day for the glue to set because the screws in the pocket hole will clamp it down no matter where I take and put the unfinished piece.

After reading a lot about the topic, I decided against buying the cheap 30€ Wolfcraft Undercover Jig that is sold everywhere around here and get myself the big Kreg KregJig Master System in the current K5 version.
It's the big set. I just can't resist good tools. It's not the real big one that has the drill built-in.
It was a good decision because
  1. the dust-collector is a godsent,
  2. the side-extensions (with storage space and easily available screw-size table on the inside) are very useful,
  3. having the lever on the side you are on make working with it a lot of fun. (As opposed to the older K4 version with the lever on the wrong side of that large piece of wood.)
The only downside was that the vacuum cleaner attachment had a different diameter then the auto-start/stopping Festool workshop vacuum cleaners we have in the local FabLab.
...but a few minutes of CAD and <40 0.5mm="" 3d="" a="" aesthetic="" br="" did="" for="" height="" layer="" me.="" minutes="" mm="" needs="" no="" not="" nozzle="" of="" part="" printing="" qualities="" stop="" that="" time="">

Festool vacuum cleaner adaptor


Results I

Obviously the first on I build was would be crap.
So I got myself some 1€ pieces of leftover material of the same type I wanted to use but wrong thickness and  with a lot of defects and got working.
Without a plan I made some mistakes in judgement, some logical mistakes (forgot to subtract the thickness of the back wall,..) but not many mistakes in craftsmanship. Apart from working with too thin a material.
Access to proper tools made sure that the work was quick to do, quick to fix things and everything was square and how it was supposed to be.

Results I

So here I am, ready for a real piece of furniture that will actually be used. (In a place where nobody but me will ever see it.)

What I learned:
  1. Combining "Lamello" biscuit joiners and Pocket Holes is not worth the effort. Just skip the Lamello, meassure twice and double up on your clamps.
  2. You can not clamp down the K5 Master System onto a workbench.
  3. The dust collection is sow worth it.
  4. Use some kind of physical spacers for anything that needs to be clamped "in mid air" unless  you have a second pair of arms.
  5. SPAX backpanel screws are stronger then the Kreg screws and they have a standard Pozidriv crossed slot. I would have prefered Torx here to have the screw on the driver and reach to a far away hole this way.
  6. You need to clamp down everything for fastening the 4.0x25mm or 4.0x30mm SPAX backpanel-screws in the pocket holes. They tend to bend onto the side with the hole with a LOT of force.
  7. The tiny Wolfcraft "ES 22" (3051000) are much stronger then they look.
  8. The Kreg clamps open up way too wide and are a pain to work with unless you have giant hands.
  9. The Kreg clamps are very strong but you need to adjust them first.
  10. Sawing melamin coated wood is hard without damaging the surface. I'll have to do more experiments here. 
  11.  You will want a very strong screwdriver with replacable batteries even for small projects such as this. Preferable 3 batteries and 2 chargers.
  12. While I only ever see pocket holes in solid woods, they works like a charm in particle board. Just limit your screwdriver to 8-10Nm to not outsight squash the board.
  13. Update: For Melamin-coated wood, pre-drilling through the pocket-hole makes sure the screw doesn't push the 2 pieces apart when threading inside the first part but not having penetrated the coating of the second one yet.

I had the chance to try the Bosch Professional GSR 12V-15 FC screwdriver+cordless drill with replacable heads and  I think it's the perfect tool for this. 20Nm is plenty. I can't use more then 10 without destroying the wood. The excenter+90° head combines reach into the back of cabinets and to screws close to a wall. I have not switched between drill and screwdriver yet but I imagine it to be a godsent for pocket holes.

Sadly there is no Sortimo L-Boxx for the Kreg. Only some Kreg case made for Husky Boxes.
So I will have to build that myself to combine both cases into one stack.

I asked SPAX about Torx backpanel screws because the Pozidriv bit can't hold on to the screw when reaching far into cabinets.

Sehr geehrter Herr Wolschon,

vielen Dank für das nette und freundliche Feedback. Es freut uns sehr, so etwas zu hören.

Die Rückwandschrauben führen wir nur mit Pozidrive Antrieb, nicht mit Torx. Der PZ-Kraftangriff ist vor allem bei der maschinellen Verarbeitung besser geeignet.

Mit freundlichen Grüßen / with kind regards

i.A. Christoph Hessel, Dipl. Ing. (FH)
Product Manager
SPAX International GmbH & Co. KG



Bonaverde: testing Henry Hück

Project history

  1. old posting: 'roast only' on the Bonaverde - Familia Alfaro
  2. current posting
  3. next posting:

This time I tried
Bean Type:  not specified
Process "natural"
Grown by Henry Hück
of Nicaragua
Store: Bonaverde Store entry for these beans

This is one of the larger bean packs I got from a coffee delivery for my Bonaverde Berlin roast+grind+brew coffee machine.

Results I

I used: roast+grind+brew via the alpha version of the "Coffee Concierge" Facebook Messenger Chat bot.
No extra time after roasting for CO2 could be released.

I used  600ml of freshly filtered water.

filter coffee

At first I got the same, distinct sour taste along both sides of the tongue,
that I seem to get with all coffee I try. I can't get rid of it.
After a while I cleaned my mouth with filtered water. Used a fresh glass and tried again.
The sourness is only very faint and in the back of the mouth
but sadly it's the only taste I can find apart from the obvious.
Given the horrible results I had before, this however is a great success.
I will have to find out wether to attribute it to the green beans, the roasting profile belonging to these beans, the slightly cool glassware I used instead of my regular earthen coffee mugs or whatever.

PS: Obviously it still gets sour quickly when it has cooled down. Like any coffee.

Henry Hueck | Coffee Producer from Bonaverde on Vimeo.