Jump to content
Electronics-Lab.com Community

Triac help


Recommended Posts

I am trying to use a triac to replace a broken relay in a circuit I made. A 555 is setup to flash on and off about every second. The positive pulses go to a relay, which controls a 60W 120VAC light bulb. I have bought a triac to replace the relay, but I don't exactly know how to use it.
Coil: SPST 12 volt, 20mA, 250 ohm
Contacts 0.5A @ 125 VAC
VRRM: 300V
IGT(I & III) 30 mA Max
VGT 2.5 V Max
IH 30 mA Min

How can I use this triac?
Do I need to heat sink it?

Link to comment
Share on other sites


Not so fast! If you look at the datasheet you see that you need a few more parts to make it work. First a series resistor for the input (or you blow the led inside). And also a snubber circuit to help the triac get the correct gate current and such you can see an example of this on page 4.

Link to comment
Share on other sites


The filament is not very inductive, consider it as an resistive load. You can omit the extra gate at pin 2 just connect pin 2 to neg on your timer circuit. The capacitor should be rated 250VAC. I understand why your relay is broken, a one second on off time will kill any relay quite fast. This new circuit will not be worn out.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Create New...