Hello All,

Please help to design a circuit where I can trigger BT136/BTA12 triac using micro-controller pin directly without using any isolation. The reason for not using isolation is to reduce over all cost of the system for now. Also help me out to figure safety of appliances & triac using snubber circuits.

 

Well if you don't want isolation , just feed the gate with a series 1K resistor ,transistor buffer, and a 1K resistor between the Gate /Mt1 to suppress false pulses,.

Note if you're firing it on mains, then your circuit will be at Live Potential, ideally you need to use an opto-coupler, for the sake of £0.50 ($0.70) is it worth it!!

 

Appliance safety a lot cheaper than paying out death and injury claims.
Not to mention design quality/ruggedness/reputation effects on company.

Just a thought.

Regards, Dana.

 

As Dodgydave said, a direct connection to mains means, hopefully, that the triac cathode is connected to Neutral. That will typically mean that the cathode has several volts of noise. Otherwise it is at a dangerously high line voltage and your processor is as well.

That doesn't sound safe either way, unless the controller is out of reach and well insulated from ground. Say, for example, your product is inside a light bulb base.

 

Appliance safety a lot cheaper than paying out death and injury claims.
Not to mention design quality/ruggedness/reputation effects on company.

Just a thought.

Regards, Dana.

Before SMPSU technology fully matured, TVs etc were usually live chassis - live front panel micros weren't exactly rare.

Modern SMPSUs make mains isolation easy - but designers still usually put something between the micro and power devices like SCRs etc.

 

Thank you all for your replies.
I have decided to go with opto-triac MOC3021 for switching an array of LED Lights.

 

How can I protect my TRIAC from getting damage in case of short circuit without using fuse. Please suggest some efficient techniques that I can implement on my product.

 

How can I protect my TRIAC from getting damage in case of short circuit without using fuse. Please suggest some efficient techniques that I can implement on my product.

If by efficient you mean "cheap", I don't know of anything cheaper than a fuse for line over-current protection.

 

PCB Trace Fuse (but then you have a failed PCB when all is done) -

https://electronics.stackexchange.c...in-sections-of-copper-traces-be-used-as-fuses

https://www.google.com/url?sa=t&rct.../fusingr.pdf&usg=AOvVaw0Mumq0T2NRmurlhJL13Cvv

Regards, Dana.

 

Thank you all for your replies.
I have decided to go with opto-triac MOC3021 for switching an array of LED Lights.

Are you going with phase angle control or on/off?
As the MOC3021 is a phase angle Opto.
Snubbers attached.
Max.

 

It is false economy, and bordering on irresponsible and maybe even potentially criminal to do cheap hacks on controlling mains. You could well cause someone to get killed or start a fire.....
As crustchow says, fuses are cheap. If you budget does not stretch even that far my feeling is you should scrap the idea before someone, maybe you, gets hurt.