On 9/13/06, John Waters <john_fm_waters@hotmail.com> wrote:
> Hi All,
>
> I'm experimenting the MOC3023 Triac Output Optoisolator.
>
> In the first experiment, I connected a 4.7K resistor (as load) in series
> with the output Triac and used a signal generator to provide a 3V ac (peak
> to peak) as power source. I then applied a 6V d.c. to the input LED through
> a 1K resistor connected in series. There was current flowing through the
> load immediately.  When I connected the input to 0V, the triac cutoff and no
> current flowed through the load.
>
> In the second experiment, instread of using the low voltage ac from the
> signal generator, I used a 10V ac (rms) stepped down from a power
> transformer as power source for the load. I also changed the pure resistive
> load with a small ac motor that consume very little power. This time, when I
> applied a 6V d.c. to the input, the triac would be turned on immediately,
> however, if I applied a 0V to the input, current would continue to flow
> throught the load, the triac would only cut off when I manually disconnected
> the ac power source.
>
> I want to know what causes the differences between these two experiments. In
> fact, my application requires to use the input alone to turn on/off the
> triac (like what was doing in the first experiment), is there any way to
> achieve this?

  The triac is turning off only when the current flow through
anode1-anode2 is lower than the sustaining current. As long the power
sourced by the motor is too small, will be no zero crossing in the
load current. Add a resistive load in parallel with your motor (or
create a resonant LC circuit on your motor) and repeat the experiment.

Vasile
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