WIP: Galaxy Note 2 Car Dock Part 3 (Video)

At the end of Part 2, I had a semi-functional dock for the Note 2. It was able to retract and extend, but the wireless charging portion did not function properly and was constantly disconnecting and reconnecting every time I shifted into reverse or braked.

In this part I try to solve some of the problems and improve on other aspects of the dock.


The first thing I tried to do was to solve the problem of the charger constantly disconnecting and reconnecting to the phone. I thought that it was due to the magnets embedded in the wireless charger not having a strong enough pull on the phone cause it to move in and out of the charger's range when I braked.

To solve that problem, I drilled some holes into the moving platform and embedded some more magnets into it. These magnets were rare earth magnets which could hold up to 3 lbs, which would be more than enough to hold the Note 2 in place, even upside down. I then placed a metal plate in the back cover of the Note 2

The rectangle is where the metal plate went and the circle is where the Touchstone charger coil is.

The magnets held the phone firmly in place but when I tried it in the car, the charger would still disconnect and reconnect. Thinking that the charger and the phone was too far apart from each other to charge reliably, I placed the phone directly on the charger without everything else and held it firmly while I shifted into reverse, the still caused the charger to disconnect and reconnect. I tried a spare Touchstone charger I had as well as the other 12V socket but it produced the same results. Plugging the USB cable directly into the phone was the only way for the phone to constantly charge so the problem must be in the Touchstone chargers.

The next thing to do would be to try it in another car, as I suspect when shifting or breaking, the voltage across my 12V sockets drop enough to disconnect the Touchstone chargers. The Touchstone chargers are already picky in the 12V to USB adapter used so it must contribute to it. Even if it does work in another car, it wouldn't work for my Genesis, so what I will likely have to do is try using a Qi charger, which should not be as picky about the 12V to USB adapter and have a further charging distance.

*EDIT* Another culprit could be the weather and temperature, as the Touchstone charger worked perfectly fine when I was testing it with the foam core holder I made and used back in early December when it was warmer.

While I wait for the Qi chargers to arrive, I also thought of an improvement to the extending and retracting mechanism. Currently, with the 5 spring loaded pen mechanisms, one or two of the mechanisms would not trigger, causing some to be extended and some to be retracted and end up slanting the base. Other times, some of them would jam, making me have to wiggle them around a few times for it to work and not look very professional.

I decided to solve this by using a new mechanism that would be electrically powered and automatically extend or retract based of whether the car is turned on or off. I wanted the base to retract in to make room for the Note 2 when the car was turned on, but extend out so I can take the phone out when the car was off.

I decided to use a servo to do this as I had many spares laying around from my humanoid robot project (sorry for the lack of updates on that! the batteries were back ordered so I have to find a new place to get some) I found a schematic for controlling a servo using an inexpensive 555 timer IC (http://www.555-timer-circuits.com/servo-tester.html) and a potentiometer so I based my circuit off of that.

The circuit is very similar to the one found on the site, except I replaced the potentiometer with a relay and 2 sets of resistors. The potentiometer was in the original circuit to move the servo all 180 degrees but for my use I only needed it to move to 2 specific positions. I only needed the servo to move to the 0 and 90 degree positions, so I used a 1k resistor (close to 0) and a 56k resistor (half of the original 100k potentiometer for 90 degrees) attached to a relay so that it would go to one position when power was applied to it and the other when there was no power. The other modification was the addition of the 0.1uF and 1000uF capacitors to help reduce the noise from my power source which would reduce the amount of servo "twitches".

The 5V from the car would be from a USB port attached to a 12V socket in the car. The socket only provides power when the car is turned on, which would change the connection of the relay which in turn changes the resistance to the 555 IC and the servo position. I also needed a power source that would still be on after the car was turned off. I didn't want to tap directly into the car's power in case something goes wrong with my circuit and ends up draining the car's battery. The perfect power source came from a dash camera in my car. It powers itself and turns off a few seconds after the car turns off which would be plenty of time for the servo to move into its off position extending the phone and base back out.

Most car dash cameras have IR LEDS for night vision, which does not really serve a purpose as the IR LEDS only project a very small distance, so I unplugged the IR LEDS and tapped into that for power. The IR LED ports provided me with 5V, which would be enough to power the servo.

Here is a video of the circuit working. When the power bar/car is off, the servo pushes the platform out and when the power bar/car is on the servo reverses allowing the platform to retract in.

Next is to install the servo into the holder and connect the circuit to the camera and a USB port in the car while I wait for the Qi charger to arrive from Hong Kong.