Help me select triac or relay for switching 230VAC devices

[kekon]

I always have many doubts on what would be better: triac or relay. These would be used for switching 230VAC devices such as flourescent bulbs (with "electronic transformer"), inductive loads and heaters. The first idea that comes to mind is to use relays as they can withstand surge voltages and currents better than triacs. When it comes to triacs only ones with zerro-crossing detect circuit are taken into account. The main issue with triacs is over-current protection. As one knows very fast fuses are desirable to protects triacs. However, there is no guarantee that the fuse will blow faster than the triac will be destroyed. Tracs have one advantage in comparison to relays which is much longer life span (if working conditions don't exceed maximum ratings). So, i'm confused what to use: triac or relay ?

 

[IanP]

tk using triac

It sounds like a poll ..
I would say this: if you can, always use a triac with a proper snubber circuit around it, whether it is driven by a zero-crossing circuit, or just simple on/off logic ..

Regards,
IanP

 

[kekon]

triac fail safe

There is also another issue: power dissipated in the triac. If, for example there is 5A current flowing through triac there will be about 6W of heat dissipated in the triac. In case of a relay the power will be much lower.

 

[narbeh_rob]

how to use a triac instead of a relay

Hi

if u want to switch a system with low-medium power the best choice is triac, instead if your system use large power u can use relay.
if u have trouble with Relay EMI , u can isolate it using optocuplers.

if there is a troble yet i can help u.

 

[yousafzai]

triac fuse protection

Each has its own advantages as given below:

Relay:

(a) no need of zero crossing detector circuits
(b) no "ON" resistance
(c) A fast blow fuse can be used.
(d) Driver circuitry required if it is to be controlled by a programmable device

Triac:
(a) need a zero crossing detector circuit
(b) Has some ON resistance
(c) can be used for fast switching of load
(d) no driver circuitry required

 

[yogi]

relay vs triac

go for relay. That is better. IT is easy drive.
But only speed of switching is less for relay compared to triac. I think ur application don't require much speed.

Bibin John
www.bibinjohn.tk

 

[mtl]

triac or relay

Relay is better for simple circuits, but
Triac, is very fast and very acurate.

 

[polymath]

Re: Triac or relay ?

chalk and cheese!

can't blow up relay with a spike!
simple isolation
can't phase control with relay
can NEVER use triac as fail-safe relay
relay is generally idiot-proof

different tools for different jobs
Polymath