Hi Everyone,

I'm having a few problems getting my triac to turn on through an
opto-triac. More specifically, the opto-triac is turning on and putting
mains voltage at the triac's gate, but the triac won't start conducting.

A schematic:

+5vDC                                       240vAC (live)
|-R1---LED1---|     |------R2-----|------------|
              |     |             |
             LED2  TR1           TR2
              |     |            | |
--------------|     |------------- -------LOAD-|
Gnd                                           Neutral

R1     200 Ohms
R2     5.6K
LED1   Red indicator LED
LED2   MOC3041 opto-triac
TR1    MOC3041 opto-triac
TR2    BTA16-600 Triac (16A, 600V)

My LOAD is a 60W table lamp I'm using for testing.

I'm a bit nervous of experimenting too much with this because I've already
welded my meter probes together and flipped the house electrics off
yesterday, and if it wasn't for my (now black and sooty) safety goggles,
I'd be very unhappy.

TR2's data sheet says it needs a max 50mA of gate current to turn on,
and 240/5600 is 42mA. From the datasheet's graphs, it looks like the
minimum Igt is 16mA. I've tried it with a 9.6K resistor in there and a
fresh triac, but still no light.

I've read up as much as I could find on interfacing to triacs, and (to me)
mine looks OK.

Any ideas of what I'm doing wrong?

Cheers,

Tim

PS Hope everyone's having a good Christmas :)

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