Using the MOC3010 In a light dimmer circuit application - Page 1
Forum section: electronics / beginners

author: jwhitmore
author_rank: Regular Contributor
timestamp: January 19, 2020, 11:44:53 am
content: I'm not sure I understand things well enough to formulate a decent question, but here goes...I'm trying to make a Mains AC light dimmer circuit using the MOC3010 . I decided that there might be some inductance in the lights so I opted for the example circuit in figure 12 of that datasheet . I used a BTA16 as the TRIAC I did forget to put a current limiting resistor between my micro-controller and the MOC3010, but I'd have thought that the dimmer part of the circuit should still function. At present sending a square wave to the MOC3010 doesn't dim the light/load at all. The datasheet  does have both a high side switch arrangement (Figure 13) and the low side switch (figure 12). Should I have used the high side switch example?I should maybe say that I have a zero crossing circuit using a H11AA1 chip, so my micro-controller is detecting the zero crossing but I'm not using a full bridge rectifier in the circuit at all. I didn't think I needed it as the light bulbs are AC bulbs anyhow. I've a small module which converts the Mains AC down to 5V DC to supply the micro-controller and that's all there is. I've been sitting on this for a week trying to find some clue as to why the circuit in the datasheet doesn't function, perhaps I have to wrong TRIAC chip?On that thought it is a 'logic level' TRIAC so possibly I should not be using the MOC3010, but rather a simple opto-coupler with the BTA16 and forget the MOC3010. Aragh is that it I've put two devices together which don't match up?http://www.farnell.com/datasheets/2287694.pdfhttp://www.farnell.com/datasheets/1699992.pdf

author: Andy Watson
author_rank: Super Contributor
timestamp: January 19, 2020, 12:23:33 pm
content: Could you provide a circuit/schematic of what you have made?Quote from: jwhitmore on January 19, 2020, 11:44:53 amSo there's a chance that either the micro or the MOC, or both are damaged ? Can you test the operation of the micro's output? Can you test the LED in MOC ? - it should "bleep out" like any other LED would with DMM.QuoteDo you mean the light is on and does not get any darker, or that the light is off and doesn't get any brighter?

author: wraper
author_rank: Unknown
timestamp: January 19, 2020, 12:32:30 pm
content: QuoteDoes it stay ON all of the time even without triggering signal or does it not switch ON? What is your mains voltage? If it's 230V MOC3010 will fail to work properly.QuoteDoes not matter.QuoteDid you actually check zero cross and output signals with oscilloscope?

author: Andy Watson
author_rank: Super Contributor
timestamp: January 19, 2020, 09:22:38 pm
content: If you have followed fig 12 on the datasheet, have you allowed for the fact that the MOC will be activated by the output of the micro being LOW? I.e. the signal sense is inverted.

author: Yansi
author_rank: Super Contributor
timestamp: January 19, 2020, 09:27:03 pm
content: Also note that MOC3010 is only suitable for 115V mains applications. Not suitable for 230-240V mains.(good to note, as you do not have a flag displayed in your profile)

author: jwhitmore
author_rank: Regular Contributor
timestamp: January 22, 2020, 11:35:17 am
content: Thank you all for your help, and thanks for pointing out that the MOC3010 does not work in 240V Mains AC Voltage. Yes I am in 240 V land and I've looked at the datasheet again and again. I see that the figures I was using to have to AV Supply Voltage specified, but I'd looked at the 'Off-State Output Terminal Voltage' of 250V and wrongly assumed that meant the MOC3010 could handle 240V AC. Reading Datasheets is something I'm still struggling with so many parameters and obviously not all of them fully understood.I've relaid out the circuit with current limiting resistors in place and I'll order up the MOC30120 part.Thanks again for all your help, sorry I got that so wrong

author: wraper
author_rank: Unknown
timestamp: January 22, 2020, 03:12:09 pm
content: Quote from: jwhitmore on January 22, 2020, 11:35:17 am240V AC means around 340V peak, not including increased mains voltage and transients. I also don't suggest using even optocouplers rated for 400V. That's too small margin and I've seen countless troubles with them, like when they are starting to randomly switch on, especially at elevated temperatures. Much safer to use optocouplers which are rated for 600V.