relay motor and valve control

[angryman]

I created a 220vac circuit where I'm using relay contacts to swtich on/off a valve and a motor contactor. Is there a way I can effectively 'debounce' the contacts using a small inductor or something? The coils of the relays are 'controlled' by other switches. I will gladly put the schematic up if someone will tell me how to get it in here...

 

[xnuke]

Debouncing isn't typically done unless the device receiving the input can read the bounces, e.g., a microprocessor. There shouldn't be any need to debounce the two devices you mentioned unless the bounce is actually causing operational problems.

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[angryman]

I use the word debounce loosely...I would like to prevent chatter from teh contacts. If DC, I could use a capacitor circuit...I'm not as familliar with ac circuits..

thanks....

 

[xnuke]

Why? Is chatter a problem?

xnuke
"Live and act within the limit of your knowledge and keep expanding it to the limit of your life." Ayn Rand, Atlas Shrugged.
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[angryman]

the control switches will be actuated by very large heavy metal plates...if they should hit the switch and bounce a little upon getting to their rest position, there could be a bouncing like action on the switch. I could always use a timer relay, but I was looking for a more simple way....does this make any sense?
Do you know how I can insert a pdf here?

 

[jraef]

Now your description makes more sense, but what you are wanting is to debounce the control input devices, not the relay itself. Yes, one method to debounce control inputs is to use a timer, but if the timer cannot stand the "bouncing" input you are just shifting the problem. The best way is to use a sensor with a hysteresis in its own action if possible. Another option is to use a "seal-in" type of circuit, where the relay gets energized by one input and seals itself in with one of its contacts, then another input drops it out. You can also use a seal-in that uses a timer to deactivate it if you cannot come up with a way to use another input device.

These are all good reasons to use a PLC or Smart Relay by the way.

Regarding posting pdfs, it is the same as posting an image. Read this FAQ for instructions, although a pdf file will post the same as a jpg. The problem with doing that is that is embeds the image of the pdf into the forum thread and increases bandwidth usage, which is especially problematic for those with slow access. Better to follow the instructions but just post a link URL to the website that contains the pdf rather than embed it.

faq238-1161

JRaef.com
Eng-Tips: Help for your job, not for your homework Read faq731-376

 

[angryman]

Thanks Jraef....i wanted to keep the number of relays down, and a PLC is not really an option....yet ....

Actually I've got the relays wired up to latch, however, if the coil input is not solid, it still effects the contacts....I set up a test circuit and blew breakers and threw sparks and soforth when hitting the swtich a few times....So if i want to 'debounce' the switch, there isn't some sort of simple little RL circuit or something I could throw in there?

I do not have a URL to post the dwg to.....it's very small, 26k I htink.....hope it won't cause too many problems...

Thanks,
Mark

 

[angryman]

stupid question i'm sure, but how might I convert pdf to jpg or other?

 

[itsmoked]

angryman; There is no quick way to use a few tidbits to "debounce" an AC circuit.

The professional way to fix this would be to purchase a $30-$60 "delay-on-break" relay. This is a relay that, once closed, stays closed, until the signal to it goes away for a certain period of time you set. So if you set it for say, two seconds the contacts can open and close over and over but the relay's output will stay closed until the input 'stays open' for a full second.

Here is an example: You must determine for yourself if it is the correct function etc.

http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611769667

There are others that have separate inputs and outputs which may make more sense in your application.

http://www.grainger.com/Grainger/wwg/itemDetailsRender.shtml?ItemId=1611769668

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[angryman]

ok....I've played with this all day for 2 days now...I got it working, but I have one unanswered mystery...when the down limit switch is depressed quickly, the motor will run as if building pressure, however, pushing the down ls again starts the piston moving....

Not sure I filled you in on the scenario...I'm running a motor with a hydraulic pump on it that has a pressure up gravity down cylinder.. The load on the cylinder is just weight now, seems to overcome gravity at around 80 pounds.

So when I hold the down swithc until the motor starts moving the cylinder, no problem. However, the test I want to do, I need it to fall down on the switch and start the motor to push it back up and soforth. I am having trouble figuring out a way to maintain that switch for a second or so....I can't spend $50 on a cool timer relay, but foudn that using a 2-pin helped. with the overcurrent problem....

After about 3 ups and downs, it would trip the 15A breaker, when I put a delay timer in line with the motor, that stopped, but I started getting my original problem of the "start" or down limit swtich not latching.....here's the dwg I've got hooked up now.....hope this works...please let me know...

http://i9.tinypic.com/446680y.jpg

I really don't understand what's going on...I'm fairly certain it's due to my ignorance of ac and of inductive properties....

 

[angryman]

???