advertisement
from the Forum department...
Triac or relay cards as output
PLCs and related questions. topic
Posted by Jeffereson Shield on 1 December, 2008 - 2:41 am
I want to know about the difference in the Triac and relay-based cards used in PLCs. Also, a brief about their application and effectiveness.


Posted by Muthukumar.M on 2 December, 2008 - 3:27 am
Relay Output: Relay output is a potential free contact. That means you can connect any voltage such as AC or DC.

Triac Output: Triac output is a constant output voltage. It's not a potential free contact. If potential free contact is required you must use the Relay Board.


Posted by Roy Matson on 3 December, 2008 - 12:58 pm
To add to previous poster, the Triac is only suitable for AC, it would not switch Off on DC.

Roy


Posted by Muthukumar on 4 December, 2008 - 6:40 am
Dear Mr. Roy,

Thanks for your valuable information. We can say Transistor Output module as a DC channel output module.


Posted by Gerald Beaudoin on 4 December, 2008 - 12:07 pm
They also only work properly with loads greater than a minimum value. If the current draw is too small, you can run into problems where they won't want to turn on.


Posted by jjchopp on 9 December, 2008 - 7:02 pm
I have only found two advantages to triac outputs. On the design and construction side, they are easier to wire in that they only require one power source which usually supplies all outputs as opposed to two power sources or a jumper wire in the wiring arm. This does not reduce the number of wiring points because they require a neutral as well, but it does put a neutral for voltage checks right there for you. The main advantage is reaction time that can be critical in high speed applications. On the down side, triacs don't handle spikes or hard grounds very well and have a tendency to take out the entire module rather than one set of dry contacts. For higher current draw devices, an isolation relay has to be used anyway. Most important in my experiences is dealing with a lost or lifted neutral in the triac circuit as it can cause the output indicator on the card to turn on even though it is not on in your ladder logic as well as cause false voltage readings while trouble shooting. If at all possible, avoid using them in non grounded systems that are common in the automotive and foundry industries.

Your use of this site is subject to the terms and conditions set forth under Legal Notices and the Privacy Policy. Please read those terms and conditions carefully. Subject to the rights expressly reserved to others under Legal Notices, the content of this site and the compilation thereof is © 1999-2014 Nerds in Control, LLC. All rights reserved.

Users of this site are benefiting from open source technologies, including PHP, MySQL and Apache. Be happy.


Fortune
"Nondeterminism means never having to say you are wrong."
Advertise here
Advertisement
our advertisers
Help keep our servers running...
Patronize our advertisers!
Visit our Post Archive