Triac Breakdown in Dimmer circuit, Help!

UroBoros · Oct 21, 2005

triac dimmer circuit

Hai

I have done a light dimmer cum fan regulator circuit using PIC.

regulation by varying firing angle.

Using optocoupler MOC3021 to drive the triac BT136.

It is working ok,But the triac becomes leeky frequently. triac starts conducting slightly without any drive .So the load wont be completly cut off and I have to replace the triac.

What may be the cause of such triac damage?

Is this has anything to do with inappropriate firing angle I am delivering to triac?

Please ..
Thanks

Picstudent

IanP · Oct 21, 2005

triac dimmer

This is sensitive gate triac ..
Maybe you should consider adding L and C around this triac and additional resistor between Gate and L/MT2, as you can see in this publication: https://www.epanorama.net/documents/lights/lightdimmer.html#advanced
(goto "professional voltage controller" section)
Regards,
IanP

UroBoros · Oct 21, 2005

triac circuit

Hai

Thanks for the link and info.

I have to make this device so compact so that it can fit in a switch board assembly.So I will be happy if I can avoid bulky inductors and all,if possible.

If this is a sensitive gate Triac do we have any other triac options to replace so that we can have a compramise at ,least for small loads like fan.

Primarly I am using this Triac to regulate the speed of a ceiling fan.

regards

picstudent

IanP · Oct 21, 2005

pic triac dimmer

There is nothing wrong with sensitive gate triacs .. they just need less "power" to trigger them .. you may consider increasing the value of resistor in series with MOC-Gate loop ..
As you work with inductive load make sure you don't overheat it; small heatsink, small inductor in series and 100nF/400V may help ..
Regards,
IanP

rauol · Oct 21, 2005

triac driving

you can try high di/dt rated triac from SGS thompson (BTA series)

Humber555 · Oct 21, 2005

inductive dimmer circuit

1)You didn´t tell us the main voltage (220 or 110V) you are using.
2)BT136 is the generic name of the TRIAC but it should have a capitol letter following this number.
This letter has a direct correspondence with the repetitive peak off-state voltage.
BT136A, BT136B, BT136F, BT136M, BT136S, BT136X, etc. Read the corresponding voltage in the data sheet.

Try with another TRIAC with higher allowable voltage.

humber555

UroBoros · Oct 21, 2005

triac damage

hai

BT136 600D is the name and my supply voltage is 230V .AC

600D is 600 volts I belive.
Locally no high voltage Triacs are avilable .High current is available .

Can anybody guide me regarding the part number of available high voltage Triacs here in INDIA?

With regards

Picstudent

IanP · Oct 22, 2005

dimmer triac circuit

Here are some types available in India from RS-Components ( www.rsindia.com ):
TIC225M and family ..
BTA08-400B and family ..
BTB10-600BW and family ..
Regards,
IanP

rauol · Oct 22, 2005

dimmer circuit

Go to any elctronics shop in india You will get BTA16-600 BW (W stands for snubberless) generaly general purpose BTA 16 is available for less than 30 rupees.
even you can try BTA12 series which is a bit cheaper.
Dont ever try to buy from RS components, he will charge you ten times the price for
even easily available components.

hjamleh · Oct 23, 2005

triac driving circuits

I did such a dimmer light circuit using PIC and I mention some of important information about how to make it:

1- You have to use the external Interrupt, INT0, to detect the zero crossing from the outlet after stepping down it from 220 to a suitable voltage, don't foret to put zener diode on the PIC input for more safety because there are internal diodes entire the PIC on the input, so after that you can select a suitable delay time, i.e. if the frequecy is 50Hz--> T=20ms; 10ms + 10ms, so you have to choose from 0ms to 10 ms.

2- Use the hardware interrupt, TMR0, to make the delay.

3- you have to make some LC circuit to save it from the noise..

4- Have fun

UroBoros · Oct 25, 2005

triac dimmer pic

hai

Thanks for all the guidelines.

My system is working now (in principle!)

But I would like to get few more guidelines.

Now the main objectives I have to meet is

1. protection of triac without huge hike in cost.

2. Reduction of size of the Whole unit to maximum possible extend that it can be fitted in a switch case.

BT136 is cheep here .(only 10 IRP) .So this triac with a snubber circuit (.1uF and some 100R is series) across the it can give reasonable life for driving a ceiling fan? Otherwise I will go for some snubberles versions.Your opinion?

for size reduction, what is the drawback of driving the triac directly from the I/O of MCU? In case of isolation point of view my unit ia already having no isolation because it is working on a transformerless power supply. can we expect more failiure rate if we drive triac directly from MCU without optocoupler?

With regards
Thanks
Picstudent

IanP · Oct 25, 2005

bt 136 600d testing circuits

I assume PIC's 0V=Neutral, so you can control triac's gate "almost" directly from PICs pin. I said "almost" as I would put 5.1V zener diode between this pin and 0V and use small, say 22-47Ω, resistor between PIC's pin and Triac's gate ..

In this case load will be connected between Active and MT1 ..

BT136 should work well with inductive loads such as fans but I would mount it on a small piece of metal (heatsink which fits inside a switch box) ..

You should test this circuit thoroughly before trying to "squeeze" it into a switch box ..

Regards,
IanP

UroBoros · Oct 26, 2005

moc3021 bta16

IanP said:
I assume PIC's 0V=Neutral, so you can control triac's gate "almost" directly from PICs pin. I said "almost" as I would put 5.1V zener diode between this pin and 0V and use small, say 22-47Ω, resistor between PIC's pin and Triac's gate ..

In this case load will be connected between Active and MT1 ..

IanP

Hai

I am about to construct the Optocoupler less version.

But one thing . In the present opto version I am serially connecting the triac in the load circuit. Just cutting the load circuit and inserting the triac without any consideration for live or neutral or on which side the load is etc...it is working in that way.

But in the opto -less version I think the load side will be critical . As you mentioned should load be between active (Phase ) and MT1?

with regards
picstudent

IanP · Oct 26, 2005

triac driving microchip

If you want to keep one common pole as 0V reference (Neutral) for both MCU and Triac then you have to "move" load from Neutral to Active (phase) side of the triac ..
Regards,
IanP

iova · May 28, 2007

triac circuit for fan

Hi people nice forum!! Im trying to do AN236 microchip aplication but for a ceiling fan and having the same problems commented before...dont know exactly what moc to use with what triac (snubberness or not) ..at first thought about moc3021 and a btb04-400 ...i live in Arg (220v....50hz) does anyone have the whole proyect finished at least to start using the same components you used for the speed control part??? Is there anywhere i can download this information?? see ya online!!!!

sajal1975 · May 28, 2007

triac dimmer filter

may be use of filter in both input-output can serve your problem.

johnbharath · Aug 16, 2007

dimmer bta16

For the microchip Application moc302x canbe used and for triac i used BTA12 still having some problem ,i wll upload when i finish fully.

Karin · Nov 15, 2010

hi

if your dimmer circuit works well now, can you upload the circuit and the program for the PIC , im trying to build a digital dimmer to dim a lamp , i think my zero crossing is working fine but i have too many problems trying to fire the triac BT136-600E , its giving weird results , so i need a little help

thanks

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