Built a few Solid State Relays like this the other day. Once I sorted them out
(nasty stuff 240v!) they work a treat. Saves the clacking of those relays....

I'd (A) reduce R2 a lot I was using MOC3020s driving less sensitive gate triacs,
with the load on the highside. I had R2 at 360R (B) I would check I had the
triac the right way round (MT1 v MT2) (C) I split R2 and put a 0.01u 240v cap
from the centre to neutral so they could (I hope) deal with some inductance in
the load.

Here are few references which may help
http://www.hut.fi/Misc/Electronics/circuits/semiconductor_relays.html
http://www.teccor.com/web/PDF%20Files/Power/an1003.pdf
http://www.fairchildsemi.com/ds/MO/MOC3010-M.pdf
http://ubasics.com/adam/electronics/doc/triaccir.gif
http://www.epanorama.net/documents/lights/lightdimmer.html#basics

Stuart
----- Original Message -----
From: "Tim ODriscoll" <tim@STOKEPOGESWAY.NET>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: 26 December 2003 11:42
Subject: [EE:] Triac driving problems


> 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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