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How to drive a triac from a 16c54?

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Junior Member level 1
Jun 3, 2002
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Drive triac with a pic.

How can i drive a triac from a 16c54 with only a resistor to drive a selenoid working 220 volt 50 Hz.

Thanks advance.

You crossposted this message to several sections! I will not delete message because you already got several answers but next time your points will be substracted and thread deleted!


You can use a optoswitch to isolate the triac from the circuit.
I think this is the safest way and easy.


Thanks BoNe

I already drive triac succesfully. It is possible. But I want to learn new ideas.

Thanks again.

the common way is the cathode of triac connected to 5V and the gate at I/O port with a serie resistor (330 ohm or less), the triac is drive with negative pulse


Read application notes of ST and Phillips, you have many examples there.
For low power microcontroller applications and use of sensitive gate triacs, cheap nonisolated supply is usual, so optoisolation is not necessary.



First you have a great book that give you all the options and theory
from motorola that called: MOTOROLA THYRISTOR DEVICE DATA.

If you can get it that will great for you ,you will have all the method.

Second try at
use search text for triac run it then cose the option appication notes only
and run the search again you will get a lot of info interfaces for traics.
**broken link removed**

Warning you can use the mirco without otocupller(RECOMMENDED OPTOTRIAC) but
all your design will be must isolated.

Best regards.


I don't trust 220v 50 hz triac/resistor to common DC elektronic/Processor.
If I where you use the optoswitch, to isolate AC/DC!!!
Thats just mine opinion. I'm sure there is another way.
But I think this way is simple and secure!!!!

That's just my words..


Please dont do it without opto or tranformer isolation. It may work, but could be very dangerous. After all what does an opto cost!.

Just curious, what is an optoswitch, and how it works..?
I cannot imagine it as an actual optical device that will help isolate the two circuits...

Thanks in advance...

Yes it is exactly that. A led (or 2 inverse parallel for AC) on the input side. Use series resistor to supply about 10ma. Output side is photosensitive Transistor/FET/SCR ect, depending on type. Isolation is usually at least 2000v. I you give me more details of what you are trying to achieve, maybe I can assist further.

Just a further thought. There are speciific types of optos to directly drive triacs out there. If you do a web serch for opto triac drivers you should be able to find one that fits the bill. BTW if you using a PIC on 5V you should be looking at an series opto input resistor of around 330 ohm to 1K

Re: Drive triac with a pic.

can help me the way to use a optoswitch to isolate the triac from the circuit?

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