4 Replies Latest reply on Dec 8, 2012 9:33 PM by COMPACT

    Wirelessly Power a Low-Power (5-7 Watt) Light Bulb


      One of the products I am seeking to design involves a small candelabra-sized low-power light bulb in a small glass. The goal is to embed an electromagnetic transmitter/primary coil inside a shallow wooden shelf (a regular 120V wall plug will run out of the shelf to provide power to the transmitter) and enable the light bulb in the glass to turn on when the glass is placed atop the wooden shelf (i.e. close enough within range of the transmitter's field to induce voltage in the receiving/secondary coil in the glass w/ the light bulb).


      Obviously the TI bqTESLA setup is designed for low-power charging applications (and I have been successful in wirelessly powering LEDs using the eval models...) - but does anyone know what I would need to enable this application with traditional 120V bulbs? I already have loads of magnet wire (of various gauges), a full library of resistors/capacitors/etc., a function generator, oscilloscope, and several microcontrollers at my disposal (in addition to a Wurth charging receiver coil and the TI transmitter/receiver evals), but I am looking for the fastest-to-build solution if one does in fact exist.


      Any insight would be much appreciated.






      This picture below doesn't actually function as of yet (it's just a bulb in a glass with a handmade magnetic coil wrapped around and touching the bulb's current leads), but it would be great if the design could work out in a similar fashion...

      Bulb in Glass w Coil.JPG

        • 1. Re: Wirelessly Power a Low-Power (5-7 Watt) Light Bulb

          Hello Justin,


          The limitation of the bq51013A receiver is that the maximum continuous output power is 5W. With incandescent lighting that's about the light strength of a bike lamp (most incandescent front light bulbs are rated at 6VAC, 500mA). To let a 120V rated lamp glow you'd need to do some power conversion (boost converter, or an inverter) which reduces the total efficiency, thereby reducing the available power available at your lamp.

          There's another thing you'll have to consider: a filament as a load starts as a short (few mOhm) to your power source; only when it warms up, the resistance rises. When you draw too much power at once from the bq51013A the transmitter shuts down the power to your receiver. So however you choose to let your lamp glow, do use a measure to limit the output current at startup!


          Please share your results!

          • 2. Re: Wirelessly Power a Low-Power (5-7 Watt) Light Bulb

            Thanks so much for your response Victor. I'm guessing the bq transmitter is probably not the answer I'm looking for since it is primarily designed for low powered charging applications. How challenging do you think it would be to build my own transmitter/receiver that would work reliably (and perhaps using a wireless power xfer method other than induction)?


            Thanks again,


            • 3. Re: Wirelessly Power a Low-Power (5-7 Watt) Light Bulb

              Hello Justin,

              I think building your own transmitter will be quite challenging, although not impossible. I guess induction is the best method to do this.

              One of the things I was thinking about is: how long does the lamp need to burn? If that time is only a fraction of the time you use the lamp, you might use the low power of the TI receiver to charge a battery during the time the lamp is off, and use that stored energy to turn on the lamp when needed. I don't know the exact requirements you have, but for 'show' effect this might do the trick.

              • 4. Re: Wirelessly Power a Low-Power (5-7 Watt) Light Bulb

                QED - Just have some patience and use the upcoming 30W version of Qi wireless power.

                I would highly recommend to use the purpose designed Qi Inductors. These are optimised for efficient power transfer.


                BTW - Are you trying to replicate Telsa's technologies of wireless power?