Plc Output devices. solenoid and a solidstate device.

[Rpowelll]

Hi, ive recently just started studying Plcs as a topic within my engineering course. and im finding it extremely hard to find information about these 2 questions given to me by my tutor. so if you would be so helpful to share any knowledge you can help me with it would be appreciated.

I need to be able to explain the construction and the operation of a 24v dc solenoid with a stroke length of 20mm. and how it is interfaced to aplc?

A solid state device for switching a 240v 10A ac load?

and the construction and application of opto-isolators in plcs?

if some one could shine some light on me for this, please as i am really struggling to find some straight forward answers online.

 

[rkukl]

http://www.wisegeek.com/what-is-a-24vdc-solenoid.htm

http://en.wikipedia.org/wiki/Solid-state_relay

maybe a web search would help?

 

[gclshortt]

DC Solenoids can be the worse culprits for electrical surges on your PLC system.
http://accautomation.ca/get-rid-of-surges-that-are-destroying-your-plc-outputs/
Some additional information on wiring.
Regards,
Garry
http://www.accautomation.ca

 

[CapinWinky]

Most PLC digital inputs use optical isolation to protect the PLC from voltage spikes or improper wiring. The input comes in and turns on a little LED and a receiver sees the light from this LED and tells the PLC the input is on. All of this is inside the IO module.

High speed inputs don't have time for optical isolation, and so try to use other methods, like fusing to protect the PLC.

VDRs (Voltage dependent resistors) are another way to protect the IO from voltage spikes. High voltage causes the resistance to drop to nearly nothing and shunt the current to ground.

 

[rdrast]

High speed inputs don't have time for optical isolation, and so try to use other methods, like fusing to protect the PLC.

What, Light is slower than electricity?

 

[CapinWinky]

What, Light is slower than electricity?

Switching times for LED and Optical pickup are, which is why VDRs tied to ground are getting very popular. I actually looked at a spec sheet for IO that I know used to use optical isolation and they've switched over to VDRs, and raised the maximum switching frequency. It may be that optical isolation is on the way out?

 

[rdrast]

What is a VDR?

 

[Bit_Bucket_07]

What is a VDR?

Sounds very much like an MOV.

 

[locotumbler]

http://www.resistorguide.com/varistor/

 

[locotumbler]

Hi, ive recently just started studying Plcs as a topic within my engineering course. and im finding it extremely hard to find information about these 2 questions given to me by my tutor. so if you would be so helpful to share any knowledge you can help me with it would be appreciated.

I need to be able to explain the construction and the operation of a 24v dc solenoid with a stroke length of 20mm. and how it is interfaced to aplc?

A solid state device for switching a 240v 10A ac load?

and the construction and application of opto-isolators in plcs?

if some one could shine some light on me for this, please as i am really struggling to find some straight forward answers online.

What i'm trying to grasp is what does the stroke length of the solenoid have to do with it? If you are caring about reaction time never use a mechanical relay. On the same note I strongly reccomend against ever using your PLC's outputs as relays for solenoids. Just my 2-bits

 

[Lancie1]

What i'm trying to grasp is what does the stroke length of the solenoid have to do with it?

The solenoid stroke length would control the type and size of equipment that could be operated with that solenoid. The solenoid stroke length has to match the required stroke length of the valve, pusher, brake, switch, and so on (the equipment to be operated).

 

[rdrast]

http://www.resistorguide.com/varistor/

That was all I came up with as well, but it's not a switching device

 

[CapinWinky]

The input has a VDR to ground that shunts over voltage current (resistance drops to near zero as voltage rises):

https://imgur.com/aPyolvE

 

[Lancie1]

A solid state device for switching a 240v 10A ac load?

Search for a 240 volt 10 Amp triac (transistor AC). There are plenty to pick from. Here are 5 from RS-Online.com in the UK:

http://uk.rs-online.com/web/c/semic...4858495&lastAttributeSelectedBlock=4294956796