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Halogen Lamp driver circuit with Triac T1235H: Test circuit with 12Vac

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Member level 3
Jul 3, 2008
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I have developed an Halogen Lamp Driver circuit based on Triac T1235H of ST Microelectronics.
This circuit have to work at 220Vac.
The gate of the triac is driven from a GPIO pin of STM32L152 microcontroller.
The triac firing pulse generated from the STM32L152 is based on ZVC circuit that sense the zero voltage crossing on the main line and than process the firing pulse with a variable time delay.
I have designed the circuit with a negative voltage regulator (-5V) for te STM32. The schematic diagram is similar at the application note showed at this link http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/USER_MANUAL/CD00268175.pdf .
I would like to test two important factor:
1. The Zero Voltage Crossing circuit;
2. The Firing Pulse generated for the triac.
I have thought that to test this two important aspect of the circuit is mandatory to use a low voltage power line derived with a 220vac/12vac transformer where I can connect the triac and the load (12v lamp for example).
With a 12vac how power line, I can use an oscilloscope to see the waveform without any problem.
Than I have to connect the evaluation board of the microcontroller (STM32L-Discovery) at this basic circuit and the USB cable from the evaluation board to the computer (to evaluate the firmware).
I think that it is important this connection becouse an error in ground and power can do a fault at the evaluation board or at the usb port of my pc.
Can sameone help me to understand the best connection that I can use?

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