Thanks Santa!

A mystery Newark package appeared on my doorstep this past week. I wonder what it could be? 

It’s a gift from the wonderful dychen and my secret Santa!

Remote controlled wireless touch lights!

A gift where batteries are included. Look at how many alkaline cells are included in this package:

With 18 AA and 2 AAA alkaline cells, this kit weighs several pounds. I love the fact that the batteries are included.

The lights didn’t come preprogramed for the RF remote, but pairing them is simple. You enter pairing the pairing mode by inserting the final battery with the front cover switch depressed. Then just press on of the remotes buttons and the light is paired to the remote. Here are the lights all powered up:

Teardown

Here is a look at one of the lights up close:

Each light has a twist lock back panel that is indented to be mounted to a surface with double sided adhesive pads. Each light requires 3 AA cells:

Taking the front cover off you can see how the front lens is sprung with 4 plastic tabs:

Not much to see on top side of the printed circuit board…

The bottom side is much more interesting:

Only 2 zero-ohm jumper links were needed for this single-sided PCB.  The solder mask is noticeably misaligned to the copper pads in many locations. Overall, a pretty nice little 2.4 GHz remote controlled touch light.

 Here is a rough schematic of the touch light.

Mostly mystery parts, but the Holtek LDO specifies a typical quiescent current of 2 uA, which is nice to see in a battery powered product.

Secret code

I probed the I2C bus while pairing the RF remote. The MCU stores a value of 0xE0 into the 2kbit serial EEPROM at address 0x00.

Subsequently, when the light is powered up normally, it reads this magic code from the serial  EEPROM:

Plus an additionally byte, not sure why. 

Power Consumption

With the light turned off, the quiescent current is approximately 300 uA. So, even if you don’t ever use these lights, you would deplete 2000 mAh rated AA cells in less than a year. With light running the LEDs at full intensity and a 4.5V battery voltage the operating current is 138 mA. The dim mode current is 76 mA.

The MCU wakes up and listens for remote commands at approximately 5 Hz:

The MCU and RF module are only listening for RF packets for approximately 2 ms before going back to sleep:

I didn’t end up getting a real-time spectrum analyzer (or SDR) for Christmas, so the 2.4 GHz signaling will have to be left as a mystery.

Never the less, this is an extremely thoughtful gift and really nice wireless touch light. And, will make a great addition to my closet .

Best wishes to all who make e14 wonderful.

Update: RF Remote

Here is a photo of the internals of the RF remote which operates on 2 series AAA cells:

The interesting observations here are:

• There is a 12 MHz crystal in a 2mm x 6mm cylinder can (similar to 32 kHz tuning fork crystals)  
• They used silkscreen as solder mask to route traces between the pads of the SOIC-14 MCU