Query : PWM based AC LED Brightness adjust

[Dhaval Varia]

Dear Sir,

I need to  setup following type of configuration :

1. IOIO PWM signal vary from 0 to 100% duty cycle

2. As a result of step 1, AC Supplied LED (used for home lightning) should adjust its brightness accordingly. 

I need some kick-start.Please help me to setup above mentioned configuration.

Please NOTE that this is not direct LED interface to PWM pin.

Thanks & Best Regards.
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Dhaval varia

(9924343883)

[Ytai Ben-Tsvi]

Do you have a certain specific driver you plan to use? Can you share the datasheet?

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[Dhaval Varia]

Sir,

you know i am new to electronics..

but yes i can do well if you suggest some kick start..

I have search following : 

http://www.supertex.com/pdf/datasheets/HV9925.pdf

http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/zhu_dimmable_sslmiw2011.pdf

http://www.digikey.com/Web%20Export/Supplier%20Content/NS_14/PDF/National_power_designer126[1].pdf?redirected=1

But not getting any thing fruitful here.

I got some tutorial/datasheet for 6v to 30V variable control driver.

but we are having 0 to 3.3V PWM signal from IOIO.

What should do i do??

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[Jeff Eberl]

I can't open your pdfs for some reason. My advice for dimming leds is to do it in dc. Switching ac is harder, and more dangerous. At some point, the power is going to be dc, so I would switch it there.

[Dhaval Varia]

Thanks for reply jeff.

but here i need LED,which would provide brightness for whole Room.

1. is it possible to achieve same thing using DC?

2. Is it possible to make PWM'd duty cycle vary for such higher DC volts by the lower one [3.3V] which is provided by IOIO. If yes and if you know some arrangement please help me to know.

[Jeff Eberl]

First, I'm not an expert, but I'll speak to my experiences

1) My understanding is that "AC" LED lights are really just DC LEDs powered by a AC->DC power supply. Even the LED light bulbs. For example, the long "under the counter" LED light strips often have a "wall wart" style AC-DC power supply, and a cable that transmits that DC power to the strips. This cable is a good place to put your switching electronics to control and dim the lights.

2) I bought some 12V DC LED strips from ebay, and used a darlington controller package (https://www.sparkfun.com/products/312) to control them. It was very simple. The package I used has a 500mA limit, so I had to cut up the strip into <500mA lengths. The darlington controller has near instant switching time, so the PWM looks just like a dimmer. You can achieve a similar effect, with larger voltages, and larger currents with an opto isolated solid state relay. They are more expensive. They are hard to find, but there are SSRs for AC switching as well. A regular relay will not be useful for you because the switching is mechanical, and won't switch fast enough for dimming. You'll probably want the PWM frequency to be around 100Hz.

[Ytai Ben-Tsvi]

Jeff, you're over-thinking this. The DC case is super-simple: a single power MOSFET should do it. If you go crazy voltage or current, you may need gate drive, which is yet another MOSFET or a driver chip.

Dhaval, I recommend you to either go DC or have a qualified Eng/Tech build this for you if you want AC.

What you really want to start with is finding the LED you want to use. Once you have its specs, we can figure our what the proper driver circuitry is.

To view this discussion on the web visit https://groups.google.com/d/msg/ioio-users/-/kqiThE1F3iEJ.

[Dhaval Varia]

Ok sure sir :)

Thanks for help

[Dhaval Varia]

Sir i got one thing for AC driver.

I don't know how much reliable this.

Please find attached PDF,which has whole schematic.

Here in place of switches,i would add Transistor to make switching possible using IOIO.

Please correct me if something is wrong.and please let me know,will it work in reliable way for market product?

[Ytai Ben-Tsvi]

Is this related to your original question on LEDs?

[Dhaval Varia]

Yes it is.

In place of fan,i am going to use LED bulb

[Dhaval Varia]

In above question by AC, i means Alternate currunt

[Ytai Ben-Tsvi]

This looks way over-complicated for dimming an LED bulb, and being designed to drive motors, it is probably not suitable for driving LEDs.

The first link that you originally sent (supertex) seems much more sensible, and possibly there are similar products from other vendors.

This goes back to the question: what are the LED specs?