Read in phase controlled AC voltage using a daq

[maltrap]

Im all new to labview and DAQ, but have been experimenting.

I am creating a temperature control with labview 8.5 and an Arduino. 

Labview sends a signal to the micro, (o - 5v) the micro is then uses this signal  along with a zero cross detection signal (comes from anther circuit) to determine the firing angle of thyristor, and hence a changing the power of the heater.

(this all works)

Now, I want to read this phase controlled  230v AC ,  into labview and view it on the graph. I am using a USB 6008. I was thinking of using a voltage divider circuit ?

Would this be safe ? ( I checked the data sheet of the USB 6008 and it says it can take -10 to V AC)

[johnsold]

Due to grounding issues, the only safe way to do this is to use an isolation transformer.  If you can get one with a 230 V primary and 5 V secondary and sufficient bandwidth to accurately reproduce the firing step, you could use that. You could also use a 1:1 isolation transformer and a voltage divider but this has a higher risk of shock to users and damage to equipment if it is not packaged correctly.

Also remember that the voltage ratings of the DAQ device are instantaneous voltages to AI Gnd, not RMS voltage of a sine wave. So you much allow for the peak voltage of the sine wave and any transients which may occur on the power line.

Lynn

[maltrap]

Cool Thanks, Ill look into that...:)

I was thinking also i could also write a vi that simulates the phase control. 

Will post once i get it up 🙂

[johnsold]

Simulating the phase control waveform should not be too difficult.  It might be a good exercise for someone new to LV.

I wrote a simulation of a phase control waveform with a distorted input sinewave in the late 1970s (in a text-based language of course). It ran over a weekend to calculate the RMS value of one cycle with and without the distortion. Computing power has certainly changed!

Lynn