switching mode power supply in lightbulb?

[danjel]

I have these large plastic lightbulbs that you can unscrew the bulb part and you are left with access to the threaded part that goes into the light socket.

I want to build a really small switching mode power supply that can fit inside the bulb so that it converts the 120VAC into 9VDC so I can power an arduino or led controller.

I have little experience with power supplies except building a simple linear one.

The current requirements of the load devices will be relatively small (9-10W max.) and I would like to make the power supply as small as possible but also efficient (and not running hot).

Any tips???

 

[smanches]

Can you run at 5V? You can find some really tiny SMPS wall warts from cell phone chargers.

 

[danjel]

yes I could probably go down to 5V. I would like a schematic so that I can create a pcb that will physically fit.

 

[blueroomelectronics]

Just buy a small UL approved switchmode supply, bypass the regulator on the Arduino and you can feed it 5V directly (more efficient)

9W at 9V is 1A would require a very large capacitor and get pretty hot. Plus transformerless supplies are a hazard and pretty much a very bad idea for powering something that may be touched.

 

[danjel]

Just buy a small UL approved switchmode supply, bypass the regulator on the Arduino and you can feed it 5V directly (more efficient)

That should be pretty straight forward given the abundance of cell phone adapters. However, it will need to be dissasembled so that I can wire it to the mains.

9W at 9V is 1A would require a very large capacitor and get pretty hot.

I think I should drop this down to 3W (it will be powering RGB leds so I can limit them to 1W each color)

Plus transformerless supplies are a hazard and pretty much a very bad idea for powering something that may be touched.

oh really? So is there no safe way to integrate this into the lightbulb structure? What makes it more dangerous than a linear supply?

 

[ronsimpson]

Design idea for driving LEDs with out isolation.
https://www.electro-tech-online.com/custompdfs/2009/06/di186.pdf
Power Integration has many applicaiton notes. Welcome To Power Integrations | Power Integrations

 

[danjel]

so I should clarify that inside the lightbulb will be the following:

power supply
arduino/uP
wireless transceiver (e.g. xbee)
rgb led driver

The more I can integrate all of these onto a single pcb, the better.

 

[ronsimpson]

Also see https://www.electro-tech-online.com/custompdfs/2009/06/di92.pdf

 

[ronsimpson]

Joke?? If not, I am looking at TI's eZ430-RF2500 developement tools. I think it could happen. I know two groups here that are working on something simular.

 

[danjel]

Also see https://www.electro-tech-online.com/custompdfs/2009/06/di92-1.pdf

I looked at this but I don't see how this is going to help me. I need pwm control of the RGB leds via the uP so that I can change the colors.

Joke?? If not, I am looking at TI's eZ430-RF2500 developement tools. I think it could happen. I know two groups here that are working on something simular.

why would this be a joke? I am sure there are other people developing simmilar things but I have some specific features that I want to implement (in terms of software and physical form).
For now I need to get the internal electronics down in size and safe.

 

[ronsimpson]

>At one company I work fore, we have a PWM and a micro inside a flash light bulb.
>I did not see anything about RGB untill your third post. Most people cannot get from 120 volts to 9 volts so I sent information on that.
>TI has low power RF in the 300-900mhz and 2.4ghz range. My ZigBee is too big but I see TI has one with a 16 bit micro that will fit in a light base. I think you can get an 8051 + 900mhz RF in one part, if size in number one.

 

[danjel]

the bulb part of this project will be bigger than a typical lightbulb and made of plastic.

For prototyping purposes I thought I could stuff a Funnel I/O in there with an xbee module on it:
funnel.cc | Hardware / FIO

later I would just make a pcb with the led drivers and arduino part integrated.

I'll take a closer look at TI stuff you recommended. I have done a lot of uP based projects but they have all been arduino based so far. This means there will be a bit of learning curve for me to jump to a new platform at this point.

 

[Hero999]

Why not use a mains powered LED driver and omit the switched mode power supply?

There's very a common IC for this but I can't rememebr the part number at the moment, someone else here will certainly know.