LED

Feit SHOP/4/HO/CCT/AG Teardown

The SHOP/4/HO/CCT/AG shop light is a 10,000 lumen light with tunable white light (3000K – 6500K) with a NEMA 5-15P connector that plugs into a standard 3-prong outlet.

It can be found in the US on Amazon and in retailers such as Costco for about $60 (as of the time of publishing). It’s an interesting design (in my opinion) because it’s a smart light that supports on/off, dimming, and CCT color. But at the flip of a switch you can use it just like a standard, dumb LED light.

Lights

The light module contains 6 rows of LEDs (84 LEDs/row), each row alternating between cold and warm, for a total of 504 LEDs.

Major Integrated Circuits

In addition to your usual collection of resistors, capacitors, and diodes, there’s three inductors which I couldn’t figure out P/N information for. I think there’s also a thermistor or fuse of some kind (magenta circled item on top side of of PCB). I’ve highlighted the major ICs below and provided some information based on what I could find:

Top side
Bottom side

WB2L (BK7231T chip)

Manufacturer: Tuya

P/N: WB2L (BK7231T chip)

Function: Low-power embedded Wi-Fi and Bluetooth LE module. The chip is on a daughter board which is solder to the main board perpendicularly through a thru hole. There’s a switch that overrides the WB2L (and removes power from it!) and sets the light to cool white (not cold) color.

Pin No.SymbolI/O typeBK7231T FunctionUse
1PWM2I/OHardware PWM pin; P8/BT_ACTIVE/PWM2 (Pin24)Dimmer
2PWM1I/OHardware PWM pin; P7/WIFI_ACTIVE/PWM1 (Pin23)Color Temperature
3PWM0I/OHardware PWM pin; P6/CLK13M/PWM0 (Pin22)No Connect
4PWM5I/OHardware PWM pin; P26/IRDA/PWM5 (Pin15)Unknown
5PWM4I/OHardware PWM pin; P24/LPO_CLK/PWM4 (Pin16)No Connect
6GNDPGround pinGND
73V3PPower supply pin (3.3 V)3.3 V

For this light, here’s what my probing found:

  • PWM1: 0% duty cycle is full Cold and 100% duty cycle is full Warm
  • PWM2: 0% duty cycle is off and 100% duty cycle is full brightness.
  • PWM5: Unknown if this is an input or an output. With the stock Feit firmware:
    • Logic 0: when the light is on
    • Logic 1: when the light is off

BP2525

Manufacturer: Bright Power Semiconductor

P/N: BP2525

Function: Non-isolated step-down type AC/DC Constant Voltage chip…power for the LEDs that is then current controlled by the BP2929 (for color temperature) and BP5012 (for dimming).

BP2525_ENDatasheet

BP5929

Manufacturer: Bright Power Semiconductor

P/N: BP5929

Function: Dual-channel PWM color matching chip1

This is an interesting chip, and I’m not quite sure why they’re using it. Normally, the microcontroller would output two PWM signals: one for Cool White and one for Warm White, and they would each drive a MOSFET and then dimming is handled algorithmically by the microcontroller. This chips seems to offload that functionality (sort of; this chip doesn’t actually handle dimming itself, but rather in combination with a separate current control method — which I believe is the BP5012 in this design), but I’m not sure why…the microcontroller can do all of this easily. My one thought is that maybe this method reduces flicker because it’s relies of constant voltage instead of using PWM to vary the voltage.

Pin NumberNameDescription
1VHHigh-voltage side power supply terminal
2VSHigh pressure side floating
3OUT2Output GATE signal 2
4OUT1Output GATE signal 1
5NCNot Connected
6PWMPWM Signal Input
7VCCLow voltage power supply
8GNDGround
Google translation of datasheet…so may not be exactly accurate
BP5929_ZHDatasheet

BP5012

Manufacturer: Bright Power Semiconductor

P/N: BP5012 or BP501 (maybe)

Function: PWM dimming interface converter (probably)

I couldn’t find a datasheet for BP5012 or BP501. There is a BP5011 though, which is a 2 channel PWM dimming controller. So I suspect it’s related to that.

BP5011_ZHDatasheet

JW1606

Manufacturer: Joulwatt

P/N: JW1602

Function: Non-isolated switching regulator with dimming

The package is marked JW1606, but JW1606 doesn’t exist. I’m assuming this is related to the JW1602, which I was able to find a datasheet for.

The JW1602 has dimming function, so I’m not sure why the duplicate functionality with the BP5012. The BP2525 is also a non-isolated switching regulator as well. So my theory is that there’s two completely separate control circuits on the PCB, one to provide variable control of color temperature and intensity when the microcontroller is active and another circuit that provides fixed color temperature (probably just 50/50) and a fixed dimming level (set by a voltage divider).

JW1602_ENDatasheet

GBU 4J

Manufacturer: onSemi

P/N: GBU4J

Function: Bridge Rectifier. Probably for input to both of the non-isolated switching regulators (BP2525 and JW1606).

GBU4M-DDatasheet

CRJF380N65G2

Manufacturer: CR Micro

P/N: CRJF380N65G2

Function: SJ-MOS N-MOSFET. I think this is used only when the unit is in “dumb” mode and provides the variable current control for all 504 LEDs.

CRJF380N65G2Datasheet

SVF4N65F

Manufacturer: Silan Microelectronics

P/N: SVF4N65F

Function: N-CHANNEL MOSFET. There’s two of these that are directly connected to the LEDs themselves, one for each color temperature. These are probably driven by the BP5929 to control the current for each set of LEDs.

SVF4N65FMMJD-Datasheet_3.7Datasheet

7002

Manufacturer: CT Micro

P/N: CT2N7002E-R3

Function: N-Channel Enhancement MOSFET. I think this is somehow related to the mysterious function of PWM5.

CT2N7002E-R3Datasheet

Disassembly

Remove screws and cable clamp
Slide out PCB

BK7231T is pretty straight forward:

  1. Remove two screws from cord side (red circles)
  2. Remove cord clamp (green circle)
  3. Slide the the PCB out from its slot
    Note: this might require scrapping some of the potting compound used to the secure the PCB into the slot. Pushing gently from the end using the switch usually pops it out

Flashing

I flashed the unit with OpenBK7231T/OpenBeken, which now supports this light. I followed the UART instructions, which requires using https://github.com/OpenBekenIOT/hid_download_py.

I used a USB to Serial USB to TTL CH340G to program the chip. Once the PCB is removed, make the following connections:

  • Connect computer TX to U1_RXD (Top side: red arrow)
  • Connect computer RX to U1_TXD (Top side: green arrow)
  • Connect a wire to the RST (Top side: magenta arrow), when you’re ready to program you’ll briefly connecting this to ground to reset the chip.
  • Connect 3.3 volts to 3V3 (Bottom side: red arrow)
  • Connect ground to GND (Bottom side: black arrow)
Top Side: Connect TX, RX, and Reset
Bottom Side: Connect 3.3V and Ground

Outstanding Questions

  • What does PWM5 do?
  • Does power get cut to WB2L when switch is activated?
  • What are the other chips?
  • What chip is used for LED control?
2

  1. This is a Google Translation…so may not be exactly accurate ↩

Cost of Christmas Lights

A friend of my had a concern as to the cost to keep the Christmas lights on during this holiday season. As it so happens, I have a specialty in electrical systems. So, how much does it cost?

Let’s assume 5 strands of 150 lights each, for a total of 750 lights. We’re going to be old school and use the regular “white” Christmas lights, not LED’s. Christmas lights use “about 25 watts per 50-bulb strand”12. 750 lights is electrically equivalent to 15 50-bulb strands, or 15 \: \text{50-bulb strands} \times 25 \: \text{watts} = 375 \: \text{watts}. The base rate for electricity in Seattle3 is 3.86¢4 per kWh5.

Thus, 375 \: \text{watts} \times \frac{1 \: \text{kW}}{1000 \: \text{watts}} \times \frac{24 \: \text{hours}}{\text{day}} \times 60 \: \text{days} \times \frac{\$0.036 }{\text{kW} \times \text{hour}} = \$19.40

Remember, that’s if you left the lights on all the time for two straight months. If you left them on for 8 hours a day instead of 24 hours, that would be $6.48.

Similarly, if you only used 2 strands of 150-bulbs each for 8 hours a day, that would be $2.59.

Or, if you used 2 strands of 50-bulbs each for 8 hours a days, that would also be grand total of 86.4 cents.

Point being, it doesn’t cost all that much to run your Christmas lights. It costs an order of magnitude less if you use LEDs, which use about 0.05 to 0.07 watts per a bulb. Move the decimal one place to the left on the above costs and you have a pretty good idea of what it costs to run an equivalent6 LED string of lights.

And that’s how engineering works, folks.

NB: I’m experimenting with using \LaTeX to display equations. It’s really quite spiffy.0

  1. HowStuffWorks ↩

  2. GreenOptions reports consumption for each mini-light at about 0.5 to 1 watt ↩

  3. http://www.seattle.gov/light/accounts/rates/docs/2009Oct_rsc.pdf ↩

  4. assuming you’re a residential user and use less than 16kWh/month ↩

  5. kWh is a funny measurement and is actually not time based. For example, a 100 watt bulb that is on for one hour uses 100 watt-hours of energy. Similarly, a 100 watt bulb that is on for 30 minutes uses 50 watt-hours of energy. ↩

  6. by number of lights, not output of light ↩

787

boeing-vs-airbus.png

The 787 will make its official public debut in a couple days on July 8th, 2007 (that would be 7/08/07). It’s going to be pretty spectacular.

If you haven’t had a chance yet, you should take a look at NewAirplane.com and then click on the “Launch 787 Dreamliner Site” button. A video has been released every day since last weekend showcasing a different aspect of the new 787.

There is some really cool stuff going on.

Everybody knows that the 787 is the new composite-fiber airplane.

But there is so much more.

Some of my favorite features include electronically tintable windows, sawtooth pattern of the engine chevron makes for a quieter flight, the main cabin is pressurized to 6000 feet (compared to 8000 feet of current airplanes), LED lighting that can emulate earth cycles, huge windows sizes, and so much more.

I’m having a 787 launch party at my house if anyone is interested. Show up around 3pm on Sunday. The fun starts at 3:30pm local time!

“Save: Buy Boeing / Buy: Save Airbus“: © Chappatte/International Herald Tribune, Jun 22, 20070