GN4 Car Dock rev2

Galaxy Note 4 Car Mount Rev2

For Christmas I got a new Otterbox case for my Galaxy Note 4.  Since the Otterbox is significantly bigger than my old case, it forced a a revision of my car Galaxy Note 4 Car Dock.

Rather than simply increasing the size of the Car Dock, I set out to add several new features:

Wireless Charging

To add Wireless Charging to the Galaxy Note 4 all you need is a QI Sticker and a QI compatible wireless charging pad.

The QI Sticker I chose includes a separate antenna for NFC.  This is important because many cheaper QI Stickers render the NFC inoperable.  The QI Sticker installs inside the phone between the battery and the back cover.

QI Sticker
QI Sticker

The QI charging pad I chose is pretty much the cheapest one out there.  It is a single coil design so the phone placement is critical.  I found that the phone has to be in the exact perfect spot or else it will not charge at all.  Despite perfect placement, I find this charging pad to be extremely slow.  Hopefully it will keep up with my in-car entertainment and GPS usage during long trips.

QI Charging Pad
QI Wireless Charging Pad

Back to the Drawing Board

My original Galaxy Note 4 Car dock was designed in Solidworks, revising the 3d models was easy.  For the second revision I simply measured the new Otterbox case with my calipers and revised the dimensions for the Galaxy Note 4 model I had created previously. Thanks to the equation based design constraints,  the brackets automatically scaled to fit the new phone dimensions.


GN4 Car Dock rev2
GN4 Car Dock Rev2 Solidworks Assembly


4G Signal Amplifier

I’ve found T-Mobile reception to be pretty spotty, so I wanted to add a signal amplifier to help improve the range.

The signal amplifier kit consists of three parts:

  • Amplifier
  • Exterior Antenna
  • Interior Antenna

The Wilson amplifier kit I chose supports 4 signal bands and appears to actually have some clever design features including feedback-loop detection.  I was pleasantly surprised by the build quality.

The product seems to work fine, and the number of bars on the phone definitely goes up.  Unfortunately, if the phone is only getting 2G/3G, then after amplifying it still only gets 2G/3G.  I suspect this may be because some of the cell towers don’t actually support 4G LTE.  I wasn’t expecting miracles, however I’m not sure its worth the price.

Cellular Signal Booster Kit
Wilson Electronics Mobile 4G Vehicle Cellular Signal Booster Kit
Signal Booster Antenna
Signal Booster Antenna
Signal Booster Exterior Antenna
Signal Booster Exterior Antenna

Final Assembly with NFC

I printed and assembled the new car dock design on my Ultimatker 3d printer and had the new assembly up and running in just a few hours, not including the shipping time for the various products.

NFC was added using a Samsung Tectile.  Using the Xposed NFC LockScreenOff Enabler” module I was able to configure the phone to automatically unlock when placed in the dock.

On its own, the NFC works great, but since NFC and wireless charging use similar frequencies, the charging pad drowns out the NFC signal.  The next revision of the dock will use a bluetooth connection to determine the lock status instead.

GN4 Car Dock Rev2
GN4 Car Dock Rev2

Galaxy Note 4 Car Mount

Galaxy Note 4 Car Mount

I just got a new Galaxy Note 4 and its so big that after a week the spring in my old car mount couldn’t hold it anymore

Complete Galaxy Note 4 Car Holder

3d Modeling

Using Solidworks I designed a new bracket that would mount on the blank plastic insert that fills the gap where my car stereo should be. 

3d Model of the final assembly
Simulating the phone insertion
Side Profile of the bracket with the phone installed

3d Printing

Two copies of the bracket were printed using Cura software and my Ultimaker 3d Printer.

Printing with Cura Software
Ultimaker printing the Galaxy Note 4 bracket


The brackets are mounted to the blank stereo insert using 3M Command Strips for easy removal.  Some black foam was added to create a snug fit and prevent the phone from sliding side to side while driving.

Brackets mounted to the blank stereo insert.

Final Product

The final bracket installed in my Honda Civic where the stereo should be


Bad Power Source

Bad Power Source

I created this bad power source for my workbench to aid in debugging and validating some of the high
voltage projects I’ve been working on.   The goal is to be able to simulate various line faults while also providing a slightly safer environment for debugging.


  • Toggle Switches to break Hot, Neutral, Ground
  • Polarity switch to swap Hot and Neutral
  • Short Switch to short Neutral to Ground
  • Indicator light showing voltage differential going to the outlet. This acts as an on/off indicator.  Also, if this light is on but the GFCI light is off then the GFCI breaker must be tripped.  This also helps you quickly find out if another breaker upstream has been tripped.
  • GFCI Outlet.  With the toggle switches in nominal positions the GFCI outlet will provide additional safety when probing around my high voltage projects. Note: this GFCI outlet will not function properly when the toggles are configured for a fault condition.
  • I like to keep one of my outlet testers plugged in to show the line configuration.

 Pictures of the Build

    An Old-Work Junction Box is the enclosure

    Right Toggle Switches
    Left Toggle Switches


    Stuffing it all together

    Other Accessories

    Here are a few other DIY accessories I use with my Bad Power Source. 

    NEMA 5-15 Plug to Banana Jacks
    Split-Rail Extension Cable for Current Monitoring

    My Full Test Bench

    Connected in the following order:

    1. Bench Power (Conditioned, surge protected, breaker)
    2. Bad Power Source
    3. Variable Transformer with 3way outlet for voltage monitoring.
    4. Split-Rail Extension Cable with current meter
    5. Device Under Test. (I used a lamp in this picture)
    Complete Bad Power Test Bench

    Future Ideas

    • Add a Hot to Ground polarity toggle switch.
    • Add an indicator lights before the hot switch to indicate incoming line voltage.
    • Full isolation transformer so it is safe to probe with my oscilloscope.
    • Step up transformer for 220V verification.


      Network PDU-S: RevA Complete!

      Here it is!



      The final product turned out pretty great.  I’m glad I followed through and turned RevA into a fully functional product despite the constant desire to redesign every time I ran into issues.

      • Silkscreen text too small.
      • Instead of 22uf Ceremic caps switch to 47uf electrolytic for cost savings
      • Shink size of SOIC pads so they get less solder
      • Use 4mil stencil
      • Add stencil alignment tooling holes to board and stencil 
      • Reduce BOM.  Since I’m used to working on high performance RF devices I tend to use too many bypass caps for such a low speed design.
      • Use smaller microcontroller.  The ATMeega2560 was too large physically, feature wise, and cost wise.
      • Use smaller vias
      • Figure out how to use interrupts with wiznet to cut down polling
      • Reduce board size.
        • Switch to using 2 boards: 1 for relays+ drivers, and the other for the main circuitry.
        • This will allow changing the relay board for some NEC UB2-12NJ relays if I want to do a low-voltage version.
        • This will allow the main RJ45 jack to butt up to the back panel.
      • Add the Wiznet reset line to avr so I can reset manually if watchhdog timer fails.
      • Test points!
      • Bottom size copper keepout around relays to avoid arcing
      • Add an LED per relay.
      • Add power monitoring per outlet
      • Finish zero crossing detector to improve relay lifetime.
      • Switch the Power button LED to a port with PWM output so I can do the “breathing” LED effect.
      • Make the power-monitoring module an addon (CT, Zero crossing, Vsense)
      • Mirror RJ45 differential termination so they stay coupled better.
      • Enclosure cutout for the IDC power inlet was the wrong size.  Had to file it down a bit.
      • Need a rear on/off switch with integrated 15A breaker for power cycling the logic.


      Network PDU-S: Wiring it Up

      Enclosure Arrived

      The enclosure arrived.  Of course I jumped right into assembly.  The only design defect with the case turned out to be the IDC connector.  I must not have used the right 3d model because the radius on the corners is a little different.  A few minutes of filing and we are up and running.


      The Button

      I created a sub-assembly of some rainbow wire, a 4pin Molex connector, and of course the beautiful button.
      Adding the Connector

      Completed cable

      Completed Button

      110VAC Wiring Harness

      When I originally designed the PCB I assumed that if I had receptacles and relays that both had quick connect terminals that cabling would be easy.  I was wrong.  Cabling up the 110VAC lines turned out to be one of the more difficult tasks.

      Wiring only had a few requirements:

      • Functional
      • Clean routes
      • PCB must be able to be removed
      •  Safe enough to pass UL listing.

      Once again, choices made early on in the design turned out to be based on invalid assumptions.  For example, i thought for sure i would be able to find a 11AWG Fully Insulated 90Degree Flag crimp connector with a tab width of .187″.  Nope.

      After much deliberation, I made the painful decision to soldering the Neutral and Ground wires directly to the outlets.  I also soldered the load wire to the relay terminals.  So much for “quick” connects…
      Finally, I ended up repositioning the PSU to keep the wiring tidy. For now I’ll just tell myself that RevB will have better wiring.

      Everything will be better in RevB.

      Fully Insulated 90degree Flag Quick disconnect Crimp Connectors
      Load, Neutral, Ground All Routed.  Just need to connect PSU

      Network PDU-S: Enclosure Design


      When I first found out about Protocase from a Midi Workstation project listed on Hack A Day I couldn’t wait to design something to take advantage of their service.

      The Protocase website has a template generator that will create a complete assembly for use in your CAD program so you can get started right away.  I chose Solidworks since that’s the software I’ve been using.

      Engineers at Protocase were very helpful and were able to use the 3d Solids directly which was great.


      Original assembly from Protocase

      With the Protocase assembly generator I was able to start with a model that was 90% complete.

      I attempted to import my VRML 3d PCB model directly from Kicad.  Unfortunately, I never quite got that working so I ended up making a simple model of the board outline and mounting holes in Solidworks.

      From the various manufacturer’s websites I was able to find 3d models for the PSU, IDC Connector, and the RJ45 pass-through jack.  This not only saved time but also gave me confidence in the design.  I couldn’t find any model for the NEMA 5-15 outlets so I made one using the suggested panel cutout drawing.

      Completed Assembly Isometric

      When I designed the board I included 8 relays, however when it came to designing the case it became obvious that 8 switchable outlets can’t fit on the back.  I thought about making the front outlets switchable, but it didn’t really fit any of my use cases.

      In the future I will need to spend more time on a top-down design of the project before jumping into the sub-assemblies like the electronics.

      Exploded View

      Network PDU-S: Hello World

      Debug Environment

      This is what real work looks like

      In order to debug I used the following:

      • ICSP Programmer. I use the UsbTinyISP programmer from Adafruit.
      • Network Serial Port.  I use a BrainBox ES246 network serial adapter so I can access the serial console while on Wifi since I like to debug while lying in bed.
      • Current Limiting Bench Power supply
      • Fluke 87v DMM
      • Rigol Oscilloscope



      Arduino Environment

      Before I could even get started debugging, I needed to create a custom boards.txt and pins_arduino.h files so the Arduino programming environment would know how to map things like the friendly “LED_BUILTIN” to the actual I/O register.

       To keep thing simple, I started with the timeless “Led Blink” sketch. 

      Wiznet W5100 Debug

      Programmer, Serial Port, and Ethernet Hooked Up

      I discovered a short on the 1.8V LDO output of the W5100.  After some rework with the hot air and some solder wick I managed to repair the short.  It looks like I made the pads extend under the device a little too far making it very difficult to clear a solder bridge under the IC.

      After that, it was smooth sailing…well not exactly. The 3.3v and 1.8Vdd and 18.Vda rails all were outputting the correct voltage, and much to my surprise the Link and Activity lights on the RJ45 mag jack were lit, so at least the chip was alive.

      Oscilloscope and Hot Air Rework Station

      I probed around the SPI bus a bit, I discovered the SlaveSlect signal was not toggling.  It turned out that the SlaveSlect pin was hard coded in the Arduino Ethernet library.  Having it configured with a header or constructor would have been much better.  Nevertheless, another quick hack and the Arduino Ethernet tutorial I was using was fully operational.  Hello World!


      USB Charger

      USB Charger Assembly

      I created this USB Power supply to try out one of the reference designs in the RT8288AZSP SMPS. It was also an opportunity for me to try SMD reflow soldering with a stencil and hot plate.

      Solder Paste Stencil

      The Solder Paste Stencil came from OSH Stencils.  It was pretty easy to use, but the blue tape didn’t really hold it tight against the board so i got a bit of solder paste bleeding outside the pad boundary.

      Reflowing on my Mother’s hotplate

      Almost all parts have reflowed
      The SMD soldering was perfect.  The only problem turned out to be the through holes for the USB-A jack.  Somehow I ended up with the drill diameter set too low.  After some careful work with a flush mount side cutter and soldering Iron I turned the through hole jack into a surface mount one and managed to make contact with the board.
      Completed board with through hole jacks installed