Need Help in SCR/TRIAC Project

[MiZZi]

Hi! I was wondering how should I isolate my low power components from my SCR/TRIAC which controls high powered loads. We currently have a project which entails controlling high power loads using Triacs/SCRs; however, I am not sure on how do I isolate the microcontroller (which we should use in the project as the controller of the SCR/Triac) from the SCR/Triac. Is there an electronic device that is specially made for that isolation? Thanks!

 

[KrisBlueNZ]

Yes - optocouplers. There are several types. If you give us more details of the type of control you want (firing angle control? Cycle-by-cycle control? SCR or triac? What type of load? What voltage?) we can make some more specific suggestions.

 

[MiZZi]

Yes - optocouplers. There are several types. If you give us more details of the type of control you want (firing angle control? Cycle-by-cycle control? SCR or triac? What type of load? What voltage?) we can make some more specific suggestions.

thanks for your reply. Hmmmm, Optocoupler. I'll definitely check that one. I'd like to control the firing angle. I'm still not sure whether I am going to use an SCR or a Triac but I would be using a motor as a load. It will be operated @ 220 V. Well, what can you suggest? Thanks!

 

[KrisBlueNZ]

If you want to control the firing angle, use an optocoupler WITHOUT zero crossing circuitry inside it. Your optocoupler will also need a high output voltage rating (350V or more) unless you use it to control some other circuitry that actually fires the SCR or triac. Start with a Google image search for schematics, choose the ones that look appropriate, and visit the pages. http://www.google.com/search?q=triac+optocoupler+circuit&tbm=isch

 

[MiZZi]

If you want to control the firing angle, use an optocoupler WITHOUT zero crossing circuitry inside it. Your optocoupler will also need a high output voltage rating (350V or more) unless you use it to control some other circuitry that actually fires the SCR or triac. Start with a Google image search for schematics, choose the ones that look appropriate, and visit the pages. http://www.google.com/search?q=triac optocoupler circuit&tbm=isch

This is too much to grasp right away. Hehehe! Anyways, thank so much Kris. I'll definitely update you with it. THanks!

 

[BobK]

There are also triacs with built in optocouplers. And some Solid state relays are basically that.

Bob

 

[KrisBlueNZ]

There are also triacs with built in optocouplers.

That sounds interesting... can you suggest a part number for me to check out?

 

[BobK]

Here is a link:

http://www.mouser.com/ProductDetail/Fairchild-Semiconductor/FODM3012R2V_NF098/?qs=sGAEpiMZZMteimceiIVCB6I5k3wqkA2zIyaVFd2K9yc=

The biggest one Mouser has can handle 2A, so probably not good enough for the OP.

Edit: I used one like this to pulse a laminator motor for toner transfer.

Bob

 

[KrisBlueNZ]

Ah, I see what you mean. I thought these devices were designed to control larger triacs - at least, the ones with zero crossing circuitry in them are. I guess I assumed that because they're described as optcouplers with triac outputs, not triacs with optocoupler inputs! They're like an MOC3063 with a bigger triac. But sure, they can be used on their own for fairly low-power applications.