Phase control for triac using daqmx

[willnage]

I'm trying to design a phase control circuit which can be controlled by a daqmx card. The daqmx card has a 0-10V output capability. I need someway to control the phase angle of a mains supply voltage (230V AC) using the daqmx card. I have looked at numerous circuits using a basic triac circuits for light dimmers, but I want to be able to control the phase angle (time/degrees within sine wave at which triac fires) using the daqmx card. The major problem is synchronising the mains and the controller of the triac or SSR. Any help would be greatly appreciated.

 

[Hero999]

I designed a circuit to do this a few years ago, just for curiosity's sake. I've never built it though.

Bear in mind that it's inverting, higher voltages result in a dimmer light so you'll need to add an inverting amplifier and you probably need a regulated supply as the 0 to 10V will be regulated.

This circuit is by no means finished but it's a start.

**broken link removed**
https://www.electro-tech-online.com/threads/power-control.21816/#post140389

 

[willnage]

Thanks a lot for the quick reply Hero999. What supply are refering to? The supply to the full bridge rectifier or the supply to V(control)? I would also like to know how much phase control a person will get in each half cycle? Is it possible to fire the triac in a band between 3% (2.7degrees) and 97% (87.3 degrees) of the sine wave half-cycle? If its possible can you maybe elaborate on how the 555timer sends out a pulse dependant on V(control)?

 

[Hero999]

Silly me, it does use a regulated supply so ignore my comment on regulation.

The 555 is triggered every time the AC signal passes through 0V.

The control voltage sets the time delay before the TRIAC is fired. The higher the control voltage, the later the TRIAC will fire, causing less power to be sent to the load.

The calculations for Ct and Rt can be found on the datasheet for the 555 timer and will depend on the control voltage.

The comparator performs the zero crossing function, it can be replaced with a transistor to save money but it won't work so well because the trigger voltage will be 0.6V rather than near 0V.

 

[Ubergeek63]

a card? why?

a schmidt trigger to sense the AC - diode, 1 meg, diode to power rail loads a counter. serial port loads a register with a count value, counter stops at 0 and fires traic.

solder the logic together or use an 8 pin micro.