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Project Help and Ideas » driving 150 watts AC ~ with microcontroller

January 27, 2011
by mrkvickasteve
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I am trying to drive flood lights with 115v 150 watts off of each channel pc1-pc5 I want to stay away from relays but unfortunately that is all I know how to use but am afraid the switching speed will not be quick enough.

Does anyone have any other ideas of how to switch the bulbs with just the outputs from the micro-controller

the c code is actually a modification of the led_blink project and the program is running on my controller with the led's doing what I want them to do.

January 27, 2011
by rajabalu21
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You could possibly use a Triac and optically isolate the controller and the 115V AC circuitry. Something similar to this.

-Raja

January 27, 2011
by 6ofhalfdozen
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You mentioned you are concerned about the switching speed being too slow. How fast are you trying to switch them? And do you know if the bulbs can take it?? some of the higher wattage bulbs don't like being switched on and off rapidly. If you wanted to get fancy you could try running an SCR, after you optoisolate it, that might give you more control.

January 27, 2011
by mongo
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There are also SSR's that can handle the job. (Solid State Relay) They are relatively cheap and can be driven directly from the outputs.

January 28, 2011
by mrkvickasteve
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I have not made up my mind in the floods yet, its either slow switching of traditional floods or fast switching of led floods but the primary purpose is strands of christmas lights.

February 07, 2011
by mrkvickasteve
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I am not real sure of how a ssr works. I get the concept but the website I found is not real informational and since I'm not real sure of what the microprocessor will support, I am kind of in the dark. I want to switch the 150 watts max but not sure what ssr to chose and does any other components need to be used with the ssr like resistors between the chip and ssr? any detailed help is greatly appreciated.

February 08, 2011
by Rick_S
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If Christmas lights are what you have in mind, I'd recommend researching the sites for those such as the Do it yourself Christmas Forum.

Here is a link about a homemade Solid State Relay from the Christmas in Shirley wiki. You'll also find a bunch of other useful info there. A few years back, I built a dimming circuit with an ATMega8 driving 4 triacs each at an independant brightness level. I could send a command via serial to change any given channel from full on to full off. The key with dimming is to have a zero-cross circuit so the micro-controller can turn the triac on at the correct point in the AC phase to create an AC - timing based PWM.

Rick

February 08, 2011
by Rick_S
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If Christmas lights are what you have in mind, I'd recommend researching the sites for those such as the Do it yourself Christmas Forum.

Here is a link about a homemade Solid State Relay from the Christmas in Shirley wiki. You'll also find a bunch of other useful info there. A few years back, I built a dimming circuit with an ATMega8 driving 4 triacs each at an independant brightness level. I could send a command via serial to change any given channel from full on to full off. The key with dimming is to have a zero-cross circuit so the micro-controller can turn the triac on at the correct point in the AC phase to create an AC - timing based PWM.

Rick

February 09, 2011
by mrkvickasteve
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that was very helpful rick. I did some research and never used a triac or ssr but the concept is awesome and exactly what I was looking for. I found some good help with those links. I cant wait to share the finished product,

steve

February 09, 2011
by mongo
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Triacs are the heart of the SSR's. The only difference is how they are driven. Triacs are the basic part and needs a drive circuit to isolate the PC outputs. SSR's only need to be wired in, as they have that circuitry built into the package. Most are optoisolated and have built it current limiting so anything from about 5 to 30VDC will work.

February 09, 2011
by mrkvickasteve
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mongo,

I was basically under the impression that I had to stay strictly within a few mV of the SSR stated voltage to achieve the desired operation without blowing the microprocessor.

I really love this forum and have figured out my code so far with what I want to do on the output side.

Now all I have to do is figure out how to use crossovers and use a trigger from audio to start and stop routines on the outputs with an input from the audio source.

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