Triac Dimmer  - Page 1
Forum section: electronics / beginners

author: Jbliss
author_rank: Regular Contributor
timestamp: December 26, 2015, 09:41:15 am
content: Here is the Circuit I have built however its not working can some one please help explain what I'm doing wrong

author: Simon
author_rank: Unknown
timestamp: December 26, 2015, 10:07:53 am
content: The resistors feeding the triac gate should come from the power directly and not through the load.

author: Jbliss
author_rank: Regular Contributor
timestamp: December 26, 2015, 10:17:08 am
content: all the circuits i have seen show the Resistors after the load ?

author: Jbliss
author_rank: Regular Contributor
timestamp: December 26, 2015, 10:23:25 am
content: Just tried it and made no differences

author: SeanB
author_rank: Super Contributor
timestamp: December 26, 2015, 10:38:25 am
content: Triac connections are wrong.. The triac gate has a reference, in this case pin 1. Using the other way round it likely will either be on always or off, depending on the capacitor charging.http://www.nxp.com/documents/data_sheet/BT136_SERIES.pdfNote the gate is referenced to MT1, thus you must always apply the trigger with reference to this.Read this golden rules as well, will help you understand more.http://www.nxp.com/documents/application_note/AN_GOLDEN_RULES.pdf

author: Jbliss
author_rank: Regular Contributor
timestamp: December 26, 2015, 01:20:04 pm
content: so it show be connected around the other way so MT2 is connected to the positive

author: MagicSmoker
author_rank: Super Contributor
timestamp: December 26, 2015, 07:19:59 pm
content: There is no "+" terminal on the mains, but judging by the naming of one terminal as "N" it seems you are in the USA, yes?The RC values are more appropriate for a 230VAC/50Hz dimmer circuit - try reducing the fixed resistor to 3.3k and the capacitor to 100nF (note that it should be a high voltage film type for safety reasons). Other possible problems are: bad or miswired pot (center and right terminals, with knob facing you); 10k resistor not really 10k (too high or open circuit); diac breakover voltage too high (needs to be around 30V); bad triac; shorted capacitor; insufficient or missing or highly inductive load present - this dimmer circuit will not work without a predominantly resistive load (like a... wait for it... incandescent lamp!).Quote from: SeanB on December 26, 2015, 10:38:25 amIncorrect. Triacs can be triggered by any combination of gate polarity with respect to MT1 (T1) or MT2 (T2) polarity. See relevant excerpt from the BT136 datasheet you posted:

author: Jbliss
author_rank: Regular Contributor
timestamp: December 27, 2015, 12:17:48 pm
content: Not america in australia Mains voltage is 240

author: Jbliss
author_rank: Regular Contributor
timestamp: January 07, 2016, 01:30:23 pm
content: ok came back to the circuit today still not working any help out.ty

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 07, 2016, 09:52:50 pm
content: You might want to take a look at this page:http://www.circuitstoday.com/simple-lamp-dimmer-fan-regulator

author: Paul Moir
author_rank: Frequent Contributor
timestamp: January 08, 2016, 02:02:56 am
content: A 10k pot and 500k limit resistor seem backwards. Like the pot should be a much higher value and your current limit much lower. In your original schematic, it looks like you have a 500k pot, but your symbols are not clear. 500k likely prevents the TRIAC from ever turning on. 10k probably isn't enough adjustment range to notice.PS - probably helpful: is your load always off or always on? What TRIAC?

author: SL4P
author_rank: Super Contributor
timestamp: January 08, 2016, 03:32:40 am
content: Also assuming you have aDIACin position D1 (DB2)Anything else will have unexpected consequences.