Reciprocating autuator with time delay at extremes of stroke (required wiring)

[Syncro5]

Hi all,

I'm currently designing a system which requires a electronic linear actuator on a reciprocating cycle. I have been informed it would be relatively easy to use a latching DPDT relay with 2 micro switches positioned at each end of the actuator's stroke. However, I require a time delay at each end of the stroke so the actuator remains at full stroke / zero stroke for 2 / 3 seconds before moving in the opposite direction.

Can anyone help me with this one?

Cheers,

Joe.

 

[Skogsgurra]

Use a "programmable relay". It is a little PLC that is perfect for the job and costs less than a handful of relays plus two timers and you get a neat solution without much of the wiring you would need if you go the relay-and-timer road.

I use the Siemens LOGO! for that. Lots of examples in the application libraries if you are unsure how to implement your function. There's probably also a User Group that can help you.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

You beat me to it Gunnar.

Bill
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"Why not the best?"
Jimmy Carter

 

[Syncro5]

Sounds ideal! I'll look into that. Thanks for your help

 

[Skogsgurra]

Sorry Bill

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

If your actuator is pneumatic they also have pneumatic logic that would probably do that with no electronics.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Consider the skill set of your maintenance guys when deciding on the solution. Most electricians can find their way around a discrete relay circuit, but many would walk away from a smart relay. The cost saving of the smart relay could be eaten up pretty quickly if a machine is down because for a shift until engineering can get in to repair it.

 

[itsmoked]

Excellent point Scotty.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Don't agree.

A pre-programmed spare unit should be available if the machinery is critical. If not so critical, then wait till someone can fix the system comes along.

Finding lose wires and failing limit switches is something an electrician should be able to do. The relay as such seldom fails.

Do electricians shy away from PLCs?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

Do electricians shy away from PLCs?

Yes. Like they were a spitting cobra, or poison electric acid shark lava.

I think needing a PLC where two timing relays would work might be on the verge of over-kill. Now if more tasks can be found to use the PLC for...

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Keith - you got a photo of one of those critters?

Skogs - Yes, some do. It depends on the industry. The lads at my previous employer (power generation industry) would have had no problem. Where I am now (in the oil industry) the electricians have yet to discover the circular wheel.

 

[DRWeig]

There are simple time-delay relays too, the OP could use one of those and keep a spare too. To set them up, all you need is maybe a photo of the switches and dials and stuff, which might ease the stress of an electrician. Perhaps it would only be poison electric acid shark lava without the spitting cobra part.

Some have different model numbers for different functions, so the replacement would only have a dial or switches for the time setting.

Here are examples.

http://www.kele.com/relays-and-contactors/821td10h,-tdrsoxp,-tdrsrxp.aspx

http://www.kele.com/relays-and-contactors/rte-series.aspx

http://www.kele.com/relays-and-contactors/438usa,-438usa-int.aspx

Disclosure: I am on contract with Kele, and was chief engineer for many years there. The relay(s) shown are available many other places.

Best to you,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[Skogsgurra]

What morons do you have on your sites? Same as the management?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[ScottyUK]

Management are actually not a bad bunch. It's an old site with old ways of doing things: there are a lot of outdated and outmoded practices and a lot of resistance to change, largely driven by a handful of trade union die-hards who don't want to move with the times and still think it is 1974. The younger generation are generally more receptive to change, and guys who are fresh to site from other places. I guess that means I'm still still part of the younger generation at heart.

 

[waross]

I'm with Scotty on the capabilities of electricians. In the sawmill industry in Western Canada, it is common in many mills to see some electricians capable of designing control systems and programing PLCs and trouble shooting PLCs to the extent of discovering design flaws in the program. In the part of the oil industry that I see these days there are some very good electricians but a knowledge of ohms law is not a prerequisite to be a construction electrician in the heavy oil industry.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Skogsgurra]

Scotty,

I have done some work in the UK. On one site, there was a guy working on a manual lathe producing little pins with chamfers at both ends and two grooves for retaining rings. On another site, there was a paper machine with drives from late sixties up to modern days. There was a "slight" problem with the speed setpoint chain and also with drives being of so differing character - old DC drives via old scalar drives to modern vector drives - that it was almost impossible to change speed with out having a web brake.

My remarks that it might be a good idea to do something about both these situations were not received well. Charming, in a way. But a problem.

I can understand that a programmable relay, how good and reliable and easy to replace it ever may be, can be looked upon with the deepest doubt in some locations. I still maintain that it is a good and simple way of getting the work done.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.