Energizer Wiimote Induction Charger

An inductive charger is a type of wireless energy transfer system, it can also be called an air core coil transformer. It works by passing alternating current into the coils and air acting as a medium between them, the interacting electromagnetic field helps to induce inductive coupling. Wikipedia does a much better job of explaining it: Inductive Charging.

In this teardown, I’ll be featuring the Energizer Wii Inductive charger (model # PL-7581) and try to figure out how it works internally. This will be a challenging on-going project since some key IC components have been blackened for a reason to keep their functionality secret. I would like to add that throughout this teardown, I have come to appreciate the complexity of this device and commend Energizer for a job well done, they did their homework.

Now, this inductive charger works in the same way as the wireless charging toothbrushes. This schematic of the Interplak Model PB-12 electric toothbrush (although rough) is a good example of a simple inductive charger, and yes, it does indeed work nicely. Here is another example of a toothbrush induction charger at the picaxeforum.co.uk. Hack a Day has featured this technology in the past, “Inductive charging going mainstream“.

Readers are encouraged to help with this project, I’ll need information on capacitor values (since I do not own a capacitance meter) and help identifying any unknown IC’s and passive components (would the bus pirate help while cycling through charge on/off modes?).  Alternate uses for this project have been posted at the bottom. Also, clarification or explanation of the theory and operation is also encouraged. Posting comments or emailing (teamubermodder(*at*)gmail.com) us works.

I should first explain the various operational modes that are noticeable upon using the device. Placing the Wiimote and connected Energizer battery pack onto the charging dock, the red symbol lights up, when charging is complete, the symbol turns green. If the battery pack is not connected to the Wiimote and placed onto the dock, the red symbol flashes red in error and will not charge the pack. Just the charge peak detection through inductive fields alone is noting some incredible built in intelligence circuity.

To start, I removed the myriad of screws holding the bottom cover, then I opened it up and went straight to the good stuff.

Let me backup to the wall-wart transformer. It’s a 100 to 240 VAC 0.3 Amp 50/60 Hz (model # JSD-2710-050200, energy star rated device), quite capable since they only need to make one model to support the European and American markets.

As expected there are two inductive coils taped to the underside and a magnet resides in the center. The magnet appears to help the WiiMote stay on the charging dock since the accompanying battery pack also has a magnet. If designed properly, ferrite magnets can also improve the inductive coupling of the electromagnetic field between the coils, however I don’t think Energizer had that in mind for this application. The planar inductive coils appear to be wound in one layer (rectangular shaped) with about 16 windings. There are also two rectangular weights to keep the charging base properly weighted.

Top side of the circuit board exposed. The circuit board is basically divided into two, a side to manage each inductive coil. Model # shown on circuit board: HC-Q-0712 V4, built on 2009.09.01. Two large red ceramic capacitors reside in the middle (154J), 0.15 uF 250 volt. Various resistors and capacitors reside below the large capacitors. Note that the circuit board is double sided and the inductive wiring connected on the right and left.

Bottom side of the circuit board exposed.   I’m assuming that the IC, SO14 package, in the center is a microcontroller to manage the charging modes and various functionality. Could the IC be a Microchip or an Atmel product? Maybe the readers can help! The other two IC’s, SO8 package, have to be some COT’s (commercial-off-the-shelf) based devices, maybe power managment IC’s like battery chargers or current/voltage monitors to help the microcontroller judge battery charging characteristics. The large black capacitor is a 470 uf electrolytic, used to condition the dock’s power source coming into the black connector. There are two SOT23 6 pin IC’s towards the center of the board, I can’t find an explanation for those at the moment, these may be measurement IC’s of some sort. Two SOT package transistors, both are beside the SOT23 IC’s, the markings on them are illegible.  Beside each of the red capacitors is what looks to be a Zenier diode. Scattered around the board are various passives like capacitors and resistors, all surface mount. Lastly, note the indicator LED’s on either side.

The inductive charger comes with two battery modules, each are rechargeable. The rechargeable batteries are Nickel Metal Hydride AAA, 500 mAh in series to produce 2.4 Volts overall (but the voltage was not measured through a multimeter, so it must be connected through a power management circuit board). Here what’s inside of them…

Each module has an inductive coil taped to the backside and a magnet resides in the center. The planar inductive coils appear to be wound in two layers (rectangular shape) with about 17 windings per layer. Also, the coil is backed with stainless steel foil, this must help reduce the inductive field that would normally be absorbed by the batteries and the wii-mote. The coil is somehow connected to the + and – of the 2.4 series battery setup (noting again my theory of a connected power management circuit board).

Upon turning over the battery module, I noticed that the shell can be popped off. The two AAA batteries can be easily removed as they aren’t even soldered in, this may open the door for higher capacity NiMh AAA batteries! Where the batteries previously resided, there was masking tape covering up wiring and a small double sided circuit board. I carefully removed the tape, let’s take a look…

The circuit board have a few noticeable features, a small black bead temperature sensor monitors the temperature of the batteries during charging. There is a small SOT-23 6 pin package off to the side, looks to be the temperature sensor receiver (reads LM75 variant, check out Maxim IC’s information on these variants), the only SOT23 packed temperature sensor information that I could was at Maxim IC’s website (MAX6625). What looks to be a red Zenier diode nearby. Also, the typical blackened IC with no legible identification, I really think this is a microcontroller, same as what is in the base. Four diodes on the right hand side to turn the AC component of the inductive field signal into DC (Wikipedia: rectifier), they look to be 1N400X series diodes (rated for low voltages, small signal rectifier, 1N4001 would do). Four SOT package transistors, the two beside the IC have the same marking (431), the other two different markings (KL3P0) and (A1SHB). Lastly, the two wires from the inductive coil is in parallel with a small surface mount capacitor, leading into the diode rectifier circuit.

For the sake of my time on this project I’ll have to leave you here for now. To conclude, here are some of the things I’d like to look into:

• Measure all pins on the nameless blackened IC’s in both the base and the battery module. Monitor record all waveforms while invoking various charging and on/off modes, post pictures. Try to produce an IC pin diagram with functional pin descriptions. It would help us understand what’s going on here.

• Figure out what activates the charging dock into battery charge mode, if it’s a waveform from the Wiimote, more simply a resistance measurement or current draw prerequisite. If this is solved, the charging station can be used for alternate projects.

• Alternate uses for charging station:

1. Roomba or robot charge dock, the Let’s Make Robots! community would be interested in this.
2. Mousepad charger for wireless mouse.
3. Cell phone/Ipod charger (although li-ion charging characteristic must be taken into consideration, risk of fire!).
4. Or contribute with your own idea, let us know!

This will be stamped as a reader contributed on-going research project, stay tuned!

Tyco Fast Traxx

Add a Tyco Fast Traxx, WRT54G router, tons of batteries, web camera, gps head, and user control via a laptop. What do you have? A wicked homemade wireless tank-like rover!

While it may not look like the mid 90’s commercial boasting the original Fast Traxx, it has taken on a whole new dimension of geek-like excitement Übermodder has to offer, (batteries sold separately).

I have to give credit where it’s due, if it wasn’t for JBProjects this rover system would be a lot harder to implement. I will be using some their code and hardware to jump start our rover in the beta stages, then later revisions of the project will upgrade with our own code and programming structure. I might go as far as minor autonomy to help the rover navigate in tough situations, stay tuned…

Goals

I wanted to build a rover that was capable of:

• Trolling around in mildly rough terrain, like grass and gravel.
• Expanded battery life of greater than an hour.
• Sport a real time camera system with a gimbal to view objects that aren’t directly in front.
• Laptop control with an easy to use interface.
• Wireless radio that has large bandwidth capabilities and decent range (150 yards).
• Low cost, low power micro-controller system.
• GPS tracking device.

So you may ask yourself why? The better question is, why not? The experience learned from a systems integration standpoint is priceless. Also the obvious fact that robots are cool!

FastTraxx

Here we have a virgin Fast Traxx, perfect for what I need. It sports twin mubachi 370 motors, tank tracks, and lots of space to cram electronics into.

Chassis Mods

Here comes the worst part, chopping and cutting into the poor thing. Terrible huh? Choke up those childhood memories and get going. The first goal was to increase the number of 9.6V batteries stored within the chassis. The extra plastic parts were stripped to make way for the components that will be fitted on top and to make space for the electrical wiring. I did this by cutting the inside housing and bending the plastic with a heat gun.

After the modifications, the battery capacity was increased to three, two in the midsection and one underneath where the previous stock housing is located.

Drivetrain & Motor Controller

Seen in the picture above, the stock motor controller board was moved up front to clear up some space. The wires leading to the drive motors were lengthened to accommodate the modifications.

Motor Controller

Rather than starting from scratch and building a new motor controller board, why not use what was supplied in the first place? Here the stock controller board has been modified to accept signals from the proposed controlling system. The TAIYO 88-R IC chip that I soldered to only responds by setting the pin low via the controller board ground, see the pinout picture below. That way I can activate the motors to perform Forward Right/Left and Reverse Right/Left from the soldered control wires. I’ll be isolating the control wires from the controlling system by use of an opto-isolator because the ground potentials are different.

Also, be sure to disconnect the antenna and disable the antenna input filter circuit to keep out stray interference. I did this by removing the two capacitors at the input of the antenna. The antenna hole can be seen on the lower right side in the picture below.

Back of the Fast Traxx stock controller board

TAIYO 88-R IC pinout

Drivetrain

Since it was working well the drive system was left stock, other than some minor plastic weld epoxy repair work.

Camera

JBProjects found that the best network camera for this sorta setup was a Panisonic BL-C1A (detailed specs here). The nice things about about it is that it supports low voltage operation, hassle free setup/easy to use, and serves up a streaming url that is perfect to integrate into the basestation software. Just plug it into to the WRT54G router. I paid about $40 US for it on E-bay.

Specifications at-a-glance:

• Color Video
• Video Resolutions – 640 x 480, 320 x 240, 160 x 120
• JPEG image compression & video streaming
• Frame Rates (Max.) – 7.5 fps @ 640 x 480; 15 fps @ 320 x 240; 15 fps @ 160 x 120
• Motion Mode available
• 9VDC at 750 mA operation
• Green light indicator lets you know that you didn’t burn up the controller

(Courtesy, panasonic.com)

Basestation Control

I’ll be using a standard issue Dell laptop with a linksys 54g wireless card as a suitable basestation control center.

Software Interface

Ugh VB! Fine. I’ll use it for now. =)

Wireless Radio

WRT54G Router

Operating system

OpenWRT WhiteRussian v0.9 (Linux) for the WRT54G.

Sofware Contol

Hardware Interface

Rover Microcontroller

Hardware Inferface

(to wrt54g)

Safety features

Schematic & Circuit Board

GPS Tracking Device

GPS-500

Shown previously in the Budget USB Enabled GPS post, this tiny gps unit is perfect for tracking the location of the rover. The gps unit was connected in via the RS-232 chips on the rover microcontroller board and sent to the RX pin of serial port 0 (S0). For now, I was able to Cat the NMEA data output and show it on the screen in real-time.

Power Delivery

Power Consumption Estimations

Battery Packs

Linear Regulators

Camera’s 10V 750mah  linear regulator with three diodes to step down the voltage to around 9v.

Wireless router’s 12v 1.5A linear regulator.

Rover microcontroller 5v 750 mA linear regulator.

Schematic & Circuit Board

Testing, testing, tes..t..ing…

Breadboarding

Systems Integration

Smoke and broken mirrors

Mismatched grounds caused a small fire, I’m okay.

It works!

Making it all fit

For beta, just to proof-of-concept, I didn’t care much how it got there, just as long as it stayed. That’s when good ol’ masking tape came in handy.

Bear with us, this is a work-in-progress project. =)

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