Synchronization PWM on ZeroCrossing

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Hi I want make a device with 2 incandescent lamp dimmer 230Vac 50Hz and display, keyboard and I2C for memory and RTC and RS485.
But is very important the dimming fase with low ligth.
Can I synchronize the PWM hardware with the zero crossing for start the triac.
What kind of micro I can use?

Thanks in advance.

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Dear Infoxrs,

Two cents regarding mains side - zero crossing has not much to do with chip choice. Shall You use anything as indicated in a link:
http://www.eng-tips.com/viewthre...
Once You poll zero crossing it's up to You how to synchronize with PWM or whatever.
IMHO You shall choose a chip specific to Your requirements for interfacing; two PWM's and zero crossing poll shall be present in mega of Your choice.

Good luck,
kp

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Use the compare features of the timer not the pwm.

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I agree with Kartman. It helps if you do NOT think of synchronizing, but triggering.

1) Start the counter on a zero crossing with the pulse width set in a compare register

2) When compare occurs, turn off the output, stop the counter, and reset it.

3) Repeat on the next zero crossing.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Hello and thanks for all user. I made 3 or 4 years ago a dimmer for incandescent lamp,but I used a PIC 18F.. and I charge the value in the counter ( for the delay ) and when compare interrupt counter I make the trigger for the triac and repeat on the next zero crossing.
But I viewed the at90PWM and I want use it for triggering (thanks ka7ehk ) on the ZC But whit HW resource use as PSC.
Can you help me?

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Don't think you need AT90PWM.

The PSC is really designed for switch-mode power supplies and motor controllers. Extra high speed PWM. Dead-time. Plus fancy DAC.

For a triac dimmer running at 50/60Hz, virtually any AVR with an ADC (to read the power level from a potentiometer, probably) and one ordinary timer/counter will do just fine. Might not even need to be 16 bits!

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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Thank's, I think use a simple uC for the two triac dimmen and another uC for : I2c, polling RS485, keyboard Display.

Thank you very much.

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Trying to use PWM to trigger a triac is a waste of time. the very first pulse from the PWM system will trigger the triac. Once triggered, it will remain on until the next zero crossing, ignoring both the width of the pulse and any further pulses it may be sent. Since the triac cannot be turned off by the CPU once triggered, trying to use any sort of high speed PWM will not work. The zero crossing detect followed by a timer delay is by far the easiest method of doing triac dimming.

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Thanks Chris-Mouse.
It's rigth, of course, but I want use HW resource I think use ATXMEGA whit 4-DMA