Switch High Voltage (~220V) Appliances with BTA16 and ILQ74 - Page 1
Forum section: electronics / beginners

author: Shark Bate
author_rank: Newbie
timestamp: July 25, 2013, 04:16:21 pm
content: I have got a couple of BTA16-600B and ILQ74's and want to switch some home appliances like lamps and fans on and off.I would like to know the proper and safe way to interface these two to serve this purpose.Also the ILQ74 will have a micro controller pin or a Arduino pin as it's input.So, can anyone help me on this as this my first post.Here are the data-sheets if anyone needs it.http://pdf1.alldatasheet.com/datasheet-pdf/view/22033/STMICROELECTRONICS/BTA16-600B/+Q214WUORlHDyRHOIpa/1XXyxeoPiRHxyPKlZ+/datasheet.pdfhttp://www.vishay.com/docs/83640/ild74.pdf

author: C
author_rank: Super Contributor
timestamp: July 25, 2013, 09:03:59 pm
content: I would guess that the BIG reason that you have not got a reply yet is thisAC POWER LINE CONNECTION IS DANGEROUS.There are really no safe ways, just less dangerous ways.Life & DEATH are involved. Even the experts die at times.Not knowing what you do know,leaves us here atNOTwanting to assist in your or others Death.May be harsh, but this is true.You could tell us what you do know to try to change this

author: Zero999
author_rank: Super Contributor
timestamp: July 26, 2013, 01:49:45 pm
content: I agree the mains is dangerous but I'm quite sure the original poster is aware of the risks.It is an interesting problem because the transistor is only rated to 20VDC, yet it has to control 310VAC which I think is what is really being asked here.You need to make sure there's enough clearance on the PCB between the mains and control voltage: 10mm should do.Try the circuit below. The emitter will need to be briefly activated at the start of every cycle. C2 should be enough to provide a nice trigger pulse.

author: Shark Bate
author_rank: Newbie
timestamp: July 26, 2013, 04:00:45 pm
content: Ok C, thanks for your "reply".Here's what I know.The ILQ74 is a optocoupler so it isolates the microcontroller output from the triac and hence the mains. The BTA16 is a triac that can handle upto 16A.When I said safe I meant less dangerousand I was looking for good design practices. Oh and I will be careful regarding the ac part.and Hero999 which value should I look for the voltage that can be switched through the triac? because I think it could handle upto 600V.also when you say clearance between mains and control voltage do you mean the distance between the optocoupler and the triac or the microcontroller out to the whole optocoupler+triac combination.Thanks for the circuit I may try it out.

author: David_AVD
author_rank: Super Contributor
timestamp: July 26, 2013, 11:53:59 pm
content: Maybe check out some more suitable opto couplers like the MOC3041.

author: C
author_rank: Super Contributor
timestamp: July 27, 2013, 01:47:00 am
content: Some things AC line connected may not like a triac based switch.The Snubberless? trac should do better with more loadsAS David_AVD suggests one of the many opto trac drivers makes it a lot easer.One side of Opto is connected to AC line & AC curcuit, the other side logic The closest point between the two sides should be the opto pins every other point should be greater. even the pc board can cause safety problems between the chip pins.much Safer and easer choice would be using a Solid State Relay.C

author: Paul Price
author_rank: Super Contributor
timestamp: July 27, 2013, 10:37:18 am
content: Always Make a "Guard Area Gap" between the Hot AC Mains Circuitry and the MCU circuitry (shown here as the left copper area) where there is no copper or wiring or components except for optocouplers bridging the gap.

author: Paul Price
author_rank: Super Contributor
timestamp: July 27, 2013, 11:28:46 am
content: To control many TRIACS with safe isolation and solid triggering, always use a negative trigger voltage.I take apart a cheap discarded Cellphone Charger power supply and re-mount it on the AC Hot side of the control PCB to supply up to 500mA at approx 4 to 7V DC to use for triggering TRIACS through isolating optocouplers.Hero999 circuit would be troublesome: Firstly triggering is best with a NEGATIVE trigger, so D1 and optocoupler should connections should be reversed. R3 is paralleling the internal shorted-gate junction of the TRIAC that is about <50 ohms and so a 1M resistor has no effect.R1 resistor value in this circuit also seems too high and likely not suitable to create a bias supply for continuous cycle to cycle triggering. The TRIAC you are using requires a 50mA short pulse width to trigger reliably with the positive trigger circuit shown.This circuit may work with "sensitive-gate" TRIACS, not the type you are using.If you to control fans, a 33-ohm resistor in series with a >250V RMS .01uF capacitor circuit should be in parallel from MT2 to MT1. This is called a "snubber." but a MOV to protect the TRIAC may also be prudent or required for TRIAC control of some motors and fans and other transformer circuits that are "wet switched."

author: Zero999
author_rank: Super Contributor
timestamp: July 27, 2013, 02:21:18 pm
content: Quote from: Paul Price on July 27, 2013, 11:28:46 amI see your point about negative pulses being more effective at triggering the TRIAC but that's easy to fix: reverse D1 and the transistor collector and emitter connections.QuoteI'm not sure what you're getting at.R3 is required to pull the gate down so the TRIAC can't be triggered by the transistor leakage.You don't need to trigger the TRIAC continuously. There should be enough energy stored in C2 to trigger the TRIAC (don't forget you only need a short, sharp trigger pulse) providing the TRIAC is switched off for long enough to allow C1 to charge sufficiently.It has the advantage of only needing two mains wires. You're right, it's easier with three but wouldn't a transformerless PSU be easier to implement than a using a mobile phone charger?

author: Paul Price
author_rank: Super Contributor
timestamp: July 27, 2013, 03:40:07 pm
content: Hero999Shorted-gate TRIAC's have built-in Gate-MT1 shunt resistances approx. 33- ohm, but a 1Meg resistor would be outrageously high anyway for almost anything, a value <1K for non-Sensitive Gate TRIACs>1K for Sensitive Gate TRIACS.This is not a Sensitive Gate type of TRIAC. BTA16-600BFor a single TRIAC to trigger your circuit may be practical for Sensitive Gate TRIACS, but as the OP said, many things to control, then this trigger circuit has to duplicated for each TRIAC to trigger, making a fixed power supply (Cellphone P/S) attractive.You would need to trigger the TRIACs continuously if the MCU didn't have a fixed zero-cross reference for phase firing of the TRIACs, otherwise the results will be unexpected, chaotic, on-the-blink.

author: Zero999
author_rank: Super Contributor
timestamp: July 27, 2013, 04:00:15 pm
content: Oh I see what you mean, you need a lower pull down resistor value for a, non-sensitive gate thyristor, I must've only ever worked with the sensitive gate variety.Yes, I was assuming he intended to use zero-crossing which is pretty standard.He could use another opt-coupler to provide a nice pulse train for the zero crossing.