Lukas Henkel @QVHenkel Twitter profile

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Lukas Henkel

8 months

I am in the process of getting the production version of the open-source Raspberry Pi CM4 compatible module based on an iMX 8M plus up and running. If you are interested in this module, check out the Crowdsupply pre-launch page 😊

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Lukas Henkel

@QVHenkel

3 months

I've set up a simulation of a Rotman lens to drive a phased array in Elmer. The matching of the ports is poor, causing lots of internal reflections, resulting in unwanted side lobes and poor channel separation. Nonetheless I think it still demonstrates the principle nicely 😊

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Lukas Henkel

@QVHenkel

2 months

Testing another rendering pipeline in Blender. The simulation shows an airflow for forced convection over a circuit board

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Lukas Henkel

@QVHenkel

2 years

Murata DCDC converter with embedded ferrite core. The VIA aspect ratio is pretty high. These seem to be 0.2mm VIAs in a 3mm thick board

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Lukas Henkel

@QVHenkel

3 years

So many layers like an onion and the price also makes me cry 🙃 This is a 14 layer PCB (top and bot not shown) for a planar transformer assembly. Copper thickness is 2oz

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Lukas Henkel

@QVHenkel

5 months

Many ferrite beads are surprisingly susceptible to external magnetic fields. Even laminated ferrite beads can easily couple noise for example from a nearby switching regulator into the net that they are meant to filter. I recently observed this problem with a low noise design

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Lukas Henkel

@QVHenkel

23 days

The SiP design I´m working on could fit nicely into a tiny USB stick. I´m sure there are no malicious use cases for a tiny Linux USB stick with 4GB RAM and 128GB storage 🙂

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Lukas Henkel

@QVHenkel

10 months

Do not run high-speed signal lines underneath a stainless steel stiffener 😅 I have to remember to change this stiffener to FR4 or break out the CSI signal lines on the opposite side of the board with the GND plane facing the steel stiffener. I will still have to change layers

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Lukas Henkel

@QVHenkel

2 years

Well that took long enough 😅 Routing and length tuning finally done 🙌

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Lukas Henkel

@QVHenkel

7 months

Today's progress, slowly getting crowded🙃

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Lukas Henkel

@QVHenkel

2 years

Open-source vs. commercial simulation tool. While the setup time for the open-source tool was much longer, the output accuracy for a DC PDN simulation is on par with the professional tool. Comparison with real world measurement will follow

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Lukas Henkel

@QVHenkel

6 months

The 3D models from Würth are very detailed. This micro-SD card connector for example contains the entire leadframe geometry. Some 3D models of USB-C connectors also include the entire internal structures. I would like to do an EM simulation of one of their connectors in the

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Lukas Henkel

@QVHenkel

7 months

These buck converter modules are getting ridiculously small 😅This one is 2.5mm X 2.5mm and can output 1.2A. I´m interested to see how the thermal performance looks like.

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Lukas Henkel

@QVHenkel

5 months

BVTKnodes for Blender allows using predefined or arbitrary geometry as stream tracer source to visualize magnetic fields

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Lukas Henkel

@QVHenkel

9 months

I´m experimenting with using ultrasonic surface waves on the trackpad of the laptop project to enable multi-touch haptic feedback. This should make it possible to generate haptic feedback under individual fingers for multi-touch gestures. @elmerfem is a really helpful tool to

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Lukas Henkel

@QVHenkel

7 months

Sometimes VIAs are the biggest source of length mismatch 😅

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Lukas Henkel

@QVHenkel

1 month

Fully open-source AI enabled vision system featuring the PiMX8 module. The enclosure that I´ve designed for the crowduspply campaign can be transformed into a vision system with just two 3D printed parts. The system uses the Raspberry Pi HQ camera module.

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Lukas Henkel

@QVHenkel

2 years

I´ve received the first prototype PCBs 🙌 Assembly is going to be fun 😅

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Lukas Henkel

@QVHenkel

7 months

Another interpretation of flip-chip that I wanted to try since I got my new SLA printer😁I have 3D printed this small component holder as an assembly aid. The PCB with solder paste already applied is flipped onto the component holder, which has a fixed distance of 0.15mm to the

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Lukas Henkel

@QVHenkel

2 months

I wanted to see where the hotspots in my ultrasonic cleaner are and which water levels to avoid to get the most even pressure distribution 😄

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Lukas Henkel

@QVHenkel

1 year

Assembly is done 🙌

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Lukas Henkel

@QVHenkel

3 months

I'll use all the pins I paid for 😄

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Lukas Henkel

@QVHenkel

8 months

For the manual assembly of fine-pitch components where no pins are visible, I usually place small copper rectangles on at least two corners of the chip in the PCB design. This makes it very easy to align the components independently of the silkscreen, which is often offset.

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Lukas Henkel

@QVHenkel

2 years

Raspberry Pi CM4 compatible compute module using an iMX 8M Plus SoC. I´ll have a lot of testing to do with this design. Let´s hope there are no major errors on the board. 😬

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Lukas Henkel

@QVHenkel

8 months

I used @elmerfem to visualize the mechanical stress in a PCB that is mounted on an aluminum heat sink. The material stress is caused by the different thermal expansion coefficients. This is why we should not place ceramic capacitors close to mounting holes 😬

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Lukas Henkel

@QVHenkel

2 months

New company website online 😊 As well as showcasing the engineering services we provide, we are planning to publish more in-depth blog articles on the open source projects there soon. We will also be adding some simulation articles.

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Lukas Henkel

@QVHenkel

1 year

If the turntable in your microwave is broken, grab your favorite EM solver and pinpoint the best position for your coffee cup to the millimeter 😄

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Lukas Henkel

@QVHenkel

2 years

If you want to analyze the DC drop of a simple power delivery polygon you can do so in 2D with the freeware tool FEMM. You can import the DXF contour of the polygon you want to analyze and assign fixed voltages and load currents.

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Lukas Henkel

@QVHenkel

6 months

I'm currently working on a couple of concepts where SemiFlex might be a good option. I'm interested in trying out SemiFlex to see how reliable this approach is and how important it is to maintain the minimum bending radius during assembly. Perhaps a bending tool will be needed...

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Lukas Henkel

@QVHenkel

1 year

I´ve started to describe how I use open-source simulation tools to model the cooling system for the open-source laptop project. In the next update I´ll be modelling the heatsink itself 😊

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Lukas Henkel

@QVHenkel

10 months

I was a bit too generous with test pads and series resistors for testing purposes in this display interface 😅 Unfortunately, I didn´t use voids in the ground plane underneath these components. The resulting impedance mismatch cause quite a few reflections that degrade the

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Lukas Henkel

@QVHenkel

2 years

I´ve assembled the i.MX8 PCBs. Couldn’t find tombstone components at first glance 🙌

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Lukas Henkel

@QVHenkel

2 years

Routing is ~75% done. It´s getting pretty crowded, but I think I have enough room left for length matching

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Lukas Henkel

@QVHenkel

2 years

Routing of the signal layers is done 🙌 I still have a little work to do on the PWR layers but I should be able to order the PCBs soon

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Lukas Henkel

@QVHenkel

4 months

Assembled the top side of the open source Pi.MX8 board. After assembling both sides I noticed that the stencil I´ve used was 100um thick instead of the ordered 80um, which explains the excess solder...

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Lukas Henkel

@QVHenkel

1 year

0.48mm pitch, that will be fun to solder 😬

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Lukas Henkel

@QVHenkel

7 months

I'm making progress on the inner layers. That is approximately 50% of all nets routed

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Lukas Henkel

@QVHenkel

9 months

I've just realised that in this tiny 5A buck converter layout, the PCB itself takes up most of the volume 🫣

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Lukas Henkel

@QVHenkel

5 months

I'll be designing an open source system-in-package for an upcoming project. The module will be based around an NXP i.MX8 ULP and will include the SoC/DRAM/eMMC and PMIC.

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Lukas Henkel

@QVHenkel

1 year

The lid prototype for the open-source laptop is now almost finished. I am currently waiting for the updated aluminum tray which will allow me to install the touch sensor board above the screen. Once that is verified, I'll move on to prototyping the rest of the laptop case.

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Lukas Henkel

@QVHenkel

5 months

I'm doing some comparisons of different planar transformer cores. While the shown core type is the most cost-effective choice, the fact that the centerleg is not pulled back from the edges and therefore the windings are not covered by the core, it performs worst in terms of

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Lukas Henkel

@QVHenkel

7 months

Fanout is done ✅ Only 500 unconnected nets missing 🙃

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Lukas Henkel

@QVHenkel

10 months

The antenna design used on the CM4 module is patented. For the Pi.MX8 I will have to use chip antennas. I´m currently testing out several antennas in simulation to see which one should work best. I will use the same setup to optimize the antenna cutout in the heatsink for the

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Lukas Henkel

@QVHenkel

2 years

Transient simulation data from my last post, rendered with NVIDIA IndeX in Paraview

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Lukas Henkel

@QVHenkel

3 months

Playing around in Blender with adding overlays to images

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Lukas Henkel

@QVHenkel

2 years

Following up on my last tweet for comparing open-source to commercial simulation tools – The real world measurements match pretty good. The OS tool calculated 53.2mV drop at 5A and the commercial tool 53.7mV at 5A. The measurements show 52.8mV drop at 5A

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Lukas Henkel

@QVHenkel

2 years

The aspect ratio of these traces is pretty high

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Lukas Henkel

@QVHenkel

6 months

For the next iteration of the open-source CM4 compatible module I´ll probably use stacked blind and buried VIAs. Most manufacturers I have talked to have quoted a price difference compared to staggered VIAs that is not too large and with only two micro VIA sequences reliability

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Lukas Henkel

@QVHenkel

1 year

Blender can import IES files provided by most LED manufacturers to describe the radiation characteristics. Using these files can provide a good initial estimate of light homogeneity as a function of distance from the LEDs

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Lukas Henkel

@QVHenkel

7 months

I love (almost) mirror symmetrical routing 😄

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Lukas Henkel

@QVHenkel

10 months

I´ve created a tutorial video on how I use free and open-source simulation tools for the laptop project. Take a look if you are interested in this topic 😊 Link in the comments

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Lukas Henkel

@QVHenkel

1 year

The keyboard for the open-source laptop is taking shape 🙌 I´m currently prototyping the keycaps and stabilizers. The keyboard itself will be easy to swap/replace. I´m also working on a machined aluminum case to use the keyboard standalone.

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Lukas Henkel

@QVHenkel

1 year

Having some fun using blender to visualize simulation output. I´m using the BVTKNodes addon for blender to directly import the solver output. Shown are the convection current that form above hot components.

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Lukas Henkel

@QVHenkel

1 year

Visualisation of magnetic field lines with Blender and BVTK Nodes. A plane source is used to generate stream tracers that follow the magnetic field strength. The position of the plane source is changed within the BVTK node tree.

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Lukas Henkel

@QVHenkel

11 months

I have designed a simple enclosure that allows the keyboard module of the laptop design to be used stand-alone. I left enough space so that I could later think about adding a USB Hub, SD card interfaces and a Bluetooth module.

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Lukas Henkel

@QVHenkel

9 months

One has to be very careful with these Hall-effect current sensors not to route any current carrying traces close to the IC. Even the angle of the load current traces can have an impact. Having a ground plane underneath the IC that can potentially carry return current can cause a

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Lukas Henkel

@QVHenkel

2 years

I’m always fascinated by the perfect silicone lenses on these LEDs. Does anybody have details on how these are manufactured? Is this the result of a highly polished mold or just surface tension?

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Lukas Henkel

@QVHenkel

10 months

I finally got my 3D printer up and running and printed the LED diffusers for the lid of the open-source laptop. I assembled the whole lid with the display panel and the display glass and I'm pretty happy with how it turned out 😊

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Lukas Henkel

@QVHenkel

2 years

I´ve finished routing and ordered the PCBs. Now I´ll have to wait 3 weeks

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Lukas Henkel

@QVHenkel

5 months

What you can see here is an unnecessary visual representation of where I have a short on my board😄 For sensitive PCBs where I don’t want to inject high currents to see which component lights up under a thermal camera (or low resistance short circuits) I usually apply a small

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Lukas Henkel

@QVHenkel

1 year

I received the LCD panel for my laptop project. Unfortunately something went wrong during shipping of the panel, so I had to send it back. This gave me enough time to quickly put together a DP to eDP testadapter.

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Lukas Henkel

@QVHenkel

2 years

A Pi.MX8 in the making

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Lukas Henkel

@QVHenkel

7 months

The preliminary placement for the second revision of the Pi.MX8 board is done 🙌 This was the easy part 😅

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Lukas Henkel

@QVHenkel

6 months

The carbon polymer used for PCB switch contacts can also be used to some extent as a strain gauge. This method has its drawbacks in terms of accuracy and sensitivity, but with the right track geometry it's good enough to detect a hard button press for example.

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Lukas Henkel

@QVHenkel

10 months

These diffusors were my first ever print on an SLA printer. They are certainly not perfect but for the first try I´m quite satisfied. Due to the small size, I was able to fit 600 pieces on the build plate. With a print time of 10min and overall handling time including

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Lukas Henkel

@QVHenkel

3 months

I'm experimenting with solving the capacitance matrix in Elmer FEM to calculate and optimize the sensitivity of the trackpad design

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Lukas Henkel

@QVHenkel

5 months

For the design of the SiP I'll be using 80um laser VIAs with 200um pads. This will allow me to design in 300um pitch WLCSPs. One picture shows a comparison between a 0.4mm 325pin footprint and a 400pin BGA with 0.8mm pitch. Actually seeing the difference in person makes me a bit

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Lukas Henkel

@QVHenkel

1 year

Playing around with interfacing LTSpice and Blender through wav files. I´ve simulated a load switch that is switching a 5V rail onto an FPC. The stray inductance of the FPC coupled with the bulk capacitance on the other side of the FPC causes a significant overshoot at the load

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Lukas Henkel

@QVHenkel

4 months

The PCBs before cleaning. There are some soldering defects, but nothing that would cause problems during testing.

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Lukas Henkel

@QVHenkel

9 months

Today I´ve learnt that Altium Designer can directly export very detailed .OBJ files 🙌 These can be imported into Blender for stylised renderings without having to use a CAD tool for file format conversion

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Lukas Henkel

@QVHenkel

6 months

We are currently in the process of debugging the first prototypes for the second revision of the PiMX8 module. We´ve encountered some problems but were able to solve most of them by now. Pictures of the assembly process and PCBs will follow soon of course 😇

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Lukas Henkel

@QVHenkel

4 months

Let´s assemble new prototypes of the open-source PiMX8 compute module😊

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Lukas Henkel

@QVHenkel

9 months

I'm trying to create some graphics for my new company using Inkscape and Blender. I personally find Inkscape much more difficult to learn than Blender. Just a few simple lines and a bit of text took me far too much time 😅 Still need to practice a bit on that…

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Lukas Henkel

@QVHenkel

9 months

The keyboard for the laptop will be based on the RP2040 and use QMK. Sourcing the Kailh switches I wanted to use turned out to be much more difficult, so I'm going to switch to Cherry mx ulp instead. Thanks @PCBWayOfficial for sponsoring the PCBs for the keyboard 😊

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Lukas Henkel

@QVHenkel

4 months

I had some fun reverse engineering the DF40C connector used on the Raspberry Pi CM4 to create an open-source FEM model. Since I have a good representation of the geometry, I've calculated the permittivity from a capacitance measurement between the pins. I'll probably just use a

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Lukas Henkel

@QVHenkel

1 year

The 3D models of inductors provided by Würth electronic are detailed enough to model the eddy currents that form in the copper planes under the component. I use the Elmer FEM transient magnetic solver to simulate the eddy currents under an inductor at 100kHz

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Lukas Henkel

@QVHenkel

2 months

I have added some objects to the renderings to give a sense of perspective for the size of the SiP. I think I´ll pass on manually assembling this one😅

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Lukas Henkel

@QVHenkel

2 months

You can simply copy and paste Altium schematics or layout selections into MS Word as scalable vector graphics. It's a pretty neat feature for documentation. Also works with Inkscape to prepare DIY solder paste stencils for example 😄

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Lukas Henkel

@QVHenkel

2 years

I´m using a through-hole-reflow process for the HDMI, USB-C and industrial ethernet connectors. Since no solder bump is generated on the opposite side of the board with that process, I can utilize the space to place the SD-Card connector (plastic insulated bottom side) there.

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Lukas Henkel

@QVHenkel

1 month

Prototyping of different assembly variants in progress 👀

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Lukas Henkel

@QVHenkel

8 months

I have started to clean up the schematics for the PiMX8 module. I decided to color-code the ports that leave a schematic page according to the voltage level of the interface. This makes it much easier to keep track of the ~12 voltage domains of the iMX8. I also love the fact that

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Lukas Henkel

@QVHenkel

3 years

Some manufacturers: Fill out this form below with your contact information. A sales representative will get in touch for signing an NDA. After that you can download a simplified 3D model. Würth elektronik: Click download to setup your own fab for this part

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Lukas Henkel

@QVHenkel

12 days

I'm currently testing the PiMX8 with various baseboards. Timebeat sent me a beautiful Open Timecard Mini with an interesting interposer approach to create more space underneath the compute module.

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Lukas Henkel

@QVHenkel

2 years

I´ve used the same layerstack for these two projects to save some cost in low volume. Assembling this panel will take a few hours 😅

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Lukas Henkel

@QVHenkel

4 months

I´m testing a few materials for the sealing gasket that I plan to use on a more vibration resistant stack for the PiMX8 module

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Lukas Henkel

@QVHenkel

2 months

To reduce component count and decrease PDN inductance at higher frequencies I´ve swapped the 0201 decoupling capacitors on the core supply rails for the SoC to 0402 feedthrough capacitors. Even though these caps are larger the mounting inductance is lower than on the two terminal

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Lukas Henkel

@QVHenkel

1 month

Got a new stencil printer 🙌 Still need to dial in some adjustments but first tests look good I think

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Lukas Henkel

@QVHenkel

3 months

Looking forward to the design of the open-source SiP using UHDI micro-VIAs 😁

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Lukas Henkel

@QVHenkel

18 days

I'm using 5000 laser VIAs on the SiP design. Due to the ELIC construction, a single "through" VIA consists of 9 laser VIAs, resulting in the high total VIA count. Fortunately laser VIAs are fast and therefore cheap to manufacture.

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Lukas Henkel

@QVHenkel

2 months

I´m currently trying to figure out what a good allrounder base configuration for the first batch of the PiMX8 module might look like. In order to keep the cost down I´d like to manufacture the first run only with two variants: base configuration / base configuration + coral

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Lukas Henkel

@QVHenkel

8 months

I am currently experimenting with 3D printing keycaps for the Cherry MX ULP switches that I will use for the open source laptop. I'm trying to optimize the geometry so that the caps can be removed more easily without damaging the switches themselves. I can print and post-process

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Lukas Henkel

@QVHenkel

3 years

I´m familiarizing myself with openEMS for antenna simulation. I want to model wifi antennas for my laptop project. So far setting up the simulation and generating output data works fine. Next step will be some benchmarks and optimization.

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Lukas Henkel

@QVHenkel

1 year

How great is the influence of the placement of decoupling capacitors on the impedance spectrum? Not as great as it is sometimes portrayed in various design guides

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Lukas Henkel

@QVHenkel

3 years

Coilcraft has built an inductor specifically designed for placing components underneath it. That will come in handy for my SoM project.

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Lukas Henkel

@QVHenkel

1 year

The boards for the laptop lid arrived today 🙌 I really like the look of the black FPCs from @JLCPCB I printed out a little assembly guide showing what goes where and will now have fun putting it all together 😊

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Lukas Henkel

@QVHenkel

9 months

The redesign of the Pi.MX8 is in full swing 🙌 I will use a standard JLC PCB stack-up with filled and capped VIAs. I plan to release the data and start a small campaign Q1 24 for anyone interested in getting a module

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Lukas Henkel

@QVHenkel

8 months

I´m using Elmer FEM to model the effects of the aluminum housing on the radiation pattern of the integrated antenna. I´ll have to adjust the enclosure to achieve a more omnidirectional pattern. Unfortunately, I won´t be able to use a dual resonant cavity antenna as part of the

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Lukas Henkel

@QVHenkel

2 years

PCB sandwich 😋

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Lukas Henkel

@QVHenkel

2 months

I´ve received the SoC for the SiP design. It is difficult to capture the size correctly in an image. This chip is tiny with 512 pins on less than a square centimeter 🧐

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Lukas Henkel

@QVHenkel

1 year

Today I did a few tests with the anti-glare etching of the cover glass. Personally, I'm a fan of the matte look. Thanks to the anti-glare etching, there are no unwanted reflections between the panel and the glass even in direct sunlight. I think optical bonding won´t be necessary

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