Triac number

**loopyloo** · 20-12-16, 12:44 AM

I want to modify a couple of 4 or 6 outlet power boards to become master/slave .
I might use a MOC3020 or similar to trigger them though PC USB on state. (off during sleep).
Can someone please give me the number for a common triac say 20amp or more ?

**bob_m_54** · 20-12-16, 11:14 AM

**loopyloo** · 20-12-16, 07:54 PM

Thanks. I went for SMT BTB24-600BWRG and Lite on MOC3020

**TVguy** · 23-12-16, 09:02 PM

Originally Posted by loopyloo

Thanks. I went for SMT BTB24-600BWRG and Lite on MOC3020

Be aware that the in BTB series of triacs the metal tab is not isolated. So if you plan on mounting it to a heatsink, you will need some serious isolation washers unless you want a live heatsink.
I came unstuck many years ago when repairing an enormous Christmas Tree Light controller for the Darling Harbour site in Sydney; used BTB devices instead of BTA (insulated tab). Let an awful lot of smoke out from that thing!
The other concern is the MOC3020 which does not have zero crossing detection. Conceivably, the triac could be fired at peak mains sinusoid and cause great distress on the device.
The has zero crossing embedded and can be driven easily by low voltage/current. A few dollars difference may make for a more robust design?

**loopyloo** · 24-12-16, 07:55 PM

Originally Posted by TVguy

Be aware that the in BTB series of triacs the metal tab is not isolated. So if you plan on mounting it to a heatsink, you will need some serious isolation washers unless you want a live heatsink.
I came unstuck many years ago when repairing an enormous Christmas Tree Light controller for the Darling Harbour site in Sydney; used BTB devices instead of BTA (insulated tab). Let an awful lot of smoke out from that thing!
The other concern is the MOC3020 which does not have zero crossing detection. Conceivably, the triac could be fired at peak mains sinusoid and cause great distress on the device.
The has zero crossing embedded and can be driven easily by low voltage/current. A few dollars difference may make for a more robust design?

Yeah I was going to go for the BTA triacs but would have had to wait for stock.
Not sure if I would need a heatsink, I figured I'd just try it and see. It will only be supplying a monitor and a stereo.
How many watts do you think before it will need a heatsink ?

**loopyloo** · 27-12-16, 12:54 AM

I found some BTA's I can get in a couple of days so I ordered a couple of them.
They will be easier to handle.

**loopyloo** · 19-01-17, 06:17 PM

Photo taken during assembly and testing.
It works nicely.
With a 60W lamp the BTB stays at ambient temp.
Non zero switching shouldn't be a problem in this case since both the monitor and the stereo system turn on in standby mode before the monitor is triggered by the computer and the stereo is triggered by a home made auto turn on device.

**TVguy** · 20-01-17, 07:38 PM

Originally Posted by loopyloo

I found some BTA's I can get in a couple of days so I ordered a couple of them.
They will be easier to handle.

They are much easier to handle, got some very bad bities from those metal tabs over the years.
I learned the very hard way about the "Wattless Dropper" to generate non-isolated, LV DC from the mains without a transformer. Sat me on my arse and almost saw the bright light from beyond!
Live tabs are very unforgiving; an inadvertent brush with bare skin has left me with some scars and bad memories.

**BCNZ** · 21-01-17, 05:23 PM

I remember Silicon Chip did a project for this not that long ago. A system that switches on and off slave devices when the main is switched.
Could be worth digging it out, they've done all the hard work already!

**PAFMelb** · 24-02-17, 06:54 PM

Originally Posted by loopyloo

I want to modify a couple of 4 or 6 outlet power boards to become master/slave .
I might use a MOC3020 or similar to trigger them though PC USB on state. (off during sleep).
Can someone please give me the number for a common triac say 20amp or more ?

Responding to an old post, I know, but someone may find this useful.

A 20 Amp triac is way too huge for anything to do with a plugboard. Most plugboards with between 4 and 8 sockets are rated at 1000 watts (occasionally 2000) over all the outlets. That means at very best you could reasonably pull 10Amps on a single socket (and nothing on any of the others).

I assume you want one socket to have current sensing and when it is drawing load all the remaining sockets become live?

If the load(s) is/are light as I saw somewhere else, consider using an SSR instead of a triac. There are some very cheap SSRs around rated at 2Amps and selling for around $2.00AUD. Even a 40Amp SSR is under a fiver. The reason for using an SSR instead of a triac is that all the packaging, heatsinking and trigger isolation is already taken care of. All you need to is mount the SSR (with or without heatsink and in your case probably no heatsink) and drive it with a few tens of mA.

As wisely noted by others, a naked triac has issues of insulation mechanical mounting and wiring to T1, T2 an d Gate. An SSR (which of course IS a triac, but all packaged up) has none of those issues, aznd as a bonus many come with zero crossing built in. May not be relevant for this application but for many others could be a nice touch.I recently used just such a package to slave the main garage lights to the timed light built into the door opener.