Triac ? - Page 1
Forum section: electronics / projects

author: tekman11
author_rank: Contributor
timestamp: December 15, 2014, 04:44:44 am
content: Hi all,For a AC power (220vac) show a triac placed on the high side.Can it be used on both high and low side of the AC?Thanks

author: Zero999
author_rank: Super Contributor
timestamp: December 15, 2014, 11:22:41 am
content: It depends on the circuit. Generally the switched is placed on the high side.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 15, 2014, 11:34:53 am
content: It's noteworthy that, in the US, both lines are hot, so it doesn't matter. The consequence is, even when the switch is off, you must still treat both lines as potentially hazardous -- because they are!Tim

author: tekman11
author_rank: Contributor
timestamp: December 15, 2014, 01:12:58 pm
content: Quote from: Hero999 on December 15, 2014, 11:22:41 amIn reference to earth gnd.208vac, both lines(L1 and L2) are hot a triac conducts in both directions, should work120vac(USA power), the neutral and earth ground are at the same potential, is where I'm stuckthanks

author: MrAl
author_rank: Super Contributor
timestamp: December 15, 2014, 02:42:03 pm
content: Quote from: tekman11 on December 15, 2014, 01:12:58 pmHi,I would connect MT1 to neutral and use MT2 for the load. That way the gate common also connects to neutral.The load connects between the 'not' and MT2.However, you can not always trust the wiring in the house or other because sometimes the black and white (hot and neutral) wires are switched inside the electrical outlet box. This means MT1 might get connected to the 'hot' wire in some cases.The wiring accuracy has gotten better over the years as everyone starts to understand this better and with the introduction of the three wire and two wire plugs with wider and more narrow prongs, but there is still the possibility of a swap inside the box.If you need to test for this with your circuit, test for voltage between the supposed 'hot' wire and neutral wire which should show the full line voltage, and from the other wire (white usually) to neutral which should slow only a small voltage or zero.

author: madires
author_rank: Super Contributor
timestamp: December 15, 2014, 02:51:56 pm
content: ...and take care about Q4 operation mode. Some TRIACs can't be triggered in Q4.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: December 15, 2014, 03:06:36 pm
content: Quote from: madires on December 15, 2014, 02:51:56 pmYes. No worries if you're going to use something like the usual MOC3011 or whatever, standard circuit, of course.Tim

author: David Hess
author_rank: Super Contributor
timestamp: December 20, 2014, 05:13:42 am
content: Quote from: T3sl4co1l on December 15, 2014, 11:34:53 amAll of the US wiring I have worked with is split phase 240 VAC so there are two hots and a neutral with any 120 VAC circuit having one of the hots and the neutral. Mis-wiring happens of course with hot and neutral swapped so devices should be designed to handle that.

author: tekman11
author_rank: Contributor
timestamp: December 21, 2014, 02:58:40 pm
content: Hi,I would connect MT1 to neutral and use MT2 for the load. That way the gate common also connects to neutral.The load connects between the 'not' and MT2.A triac would be placed above and below the load, the gate common for the triac above the load would not be connected toneutral. Is this a problem?

author: MrAl
author_rank: Super Contributor
timestamp: December 21, 2014, 08:47:57 pm
content: Hello,If you mean you are connecting the load between 'hot' and MT2 that sounds right.MT1 then goes to neutral. Gate pulse between gate and MT1.I dont know what you mean by, "the triac goes above and below the load". Do you mean you are using two triacs?

author: tekman11
author_rank: Contributor
timestamp: December 26, 2014, 04:32:12 am
content: Quote from: MrAl on December 21, 2014, 08:47:57 pmthe plan is to use 2 triac's one above and below the load. is it mandatory that MT2 be connected to the load when switching neutral (load connected to hot, when off)?thanks

author: Zero999
author_rank: Super Contributor
timestamp: December 26, 2014, 12:21:18 pm
content: Quote from: tekman11 on December 26, 2014, 04:32:12 amWhy?I hope you're aware that TRIACs are not an effective way to isolate a circuit and protect against electric shock? They tend to fail short circuit and have a nasty habit of being turned on by EMI.

author: dannyf
author_rank: Super Contributor
timestamp: December 26, 2014, 02:34:31 pm
content: QuoteSince it is AC, there is no "high side" or "low side".