MechMate CNC Router Forum

Go Back   MechMate CNC Router Forum > After Building the Beast - Operating , Troubleshooting and Maintenance > Troubleshooting
Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Reply
 
Thread Tools
  #1  
Old Sat 10 November 2007, 14:49
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Contactor does nothing when powered? - Correct terminals for coil

Can someone please help me? This weekend, I began the process of wiring up my control box but things aren't working correctly. I can't get the contactor to latch. I've checked and rechecked everything several times. I hope I'm doing something wrong but I believe the coil in the contactor is bad. Shouldn't there be an audible click when power is applied to the coil? I don't hear anything. Just now, I connected a temporary power cord directly from the wall to the coil on the contactor and checked for continuity across the terminals but there is none. However, when I manually press down on the center of the contactor, I achieve continuity.

I'm using the recommended TECO contactor.

Before someone asks, yes, there is power coming from the wall. When I press the on button, which is mounted on the control box door, the "on" light stays on until I release the on button.

Any ideas?
Reply With Quote
  #2  
Old Sat 10 November 2007, 15:24
Tom Caudle
Just call me: Tom
 
Texas
United States of America
Doug: Take a DVM set of ac volts 200 scale and measure across the coil of the contactor. With the button not pressed you might get a few volts of AC. When you hit the button the voltage should go to your line voltage. If it does and the contactor does not pull in you have a bad contactor (not very likely). IF it the voltage does not go to full AC then something is hooked up wrong. I suspect you have both sides of the contactor coil wired to the same side of the AC circuit. Coil needs Hot and Neutral across it to activate. The pushbutton should put it across the coil to pull in the contactor then one set of contacts are used to "hold" by being in parallel with the pushbutton. It shuts off with another NC switch to break the current flow at the coil.

Another thing to try if high voltage makes you nervious: Unplug the AC cord and put an ohmmeter across the two line wires (not safety ground). Low ohms meter setting (2K). Take the lamp out of the Start button or disconnect one side of the lamp from it's connection to the AC. When you push the button the ohmmeter should register a few hundred ohms (of the AC coil). Measure across the coil with no power and get a reading. You should see close to that when you hit the button out at the two AC line cord pins.

Use your meter with one side to one leg of the AC cord (unplugged) to tack it through the circuit. Then do the other one. If you go through it methodically you will turn up the bad/wrong connection
Reply With Quote
  #3  
Old Sat 10 November 2007, 16:59
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Doug, if you remove all wires from the contactor, then put your temp. mains wires direct to A1 & A2, you must hear a satisfactory "clunk" when you power up.

Before that you could measure the resistance across A1 & A2 to make sure the coil is present. Don't know how much it should be, but there should be something of less than 1000 Ohm for sure (I think).
Reply With Quote
  #4  
Old Sat 10 November 2007, 17:23
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Thanks Gerald and Tom.

Gerald: I just checked the resistance across A1 and A2. There is 0 continuity until I press the button. After I sent my last email, I connected one leg of my temp power cord to A1 and the other leg to A2 and no clunk.

Tom: I'll try your suggestions in the morning when I have better light.
Reply With Quote
  #5  
Old Sat 10 November 2007, 20:51
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Doug,
I just took a new LS Industrial Systems GMC-18 120VAC 60 Hz contactor right out of the box. With nothing connected to the contactor, I read 108 ohms across the coil. (Other brands of contactors and coils designed to work at other voltages will show different amounts of resistance.) Start with Gerald's suggestion, disconnect everything from the contactor and then connect power directly to the coil. (Be sure that you know which contact points go to the coil. Some contactors have a lot of screws and it can become really easy to confuse the coil connections with the auxiliary switch connections.) When you turn the power on, the contactor should activate. When you turn the power off, the contactor should de-activate. If the contactor's coil doesn't work properly, try another contactor.

If the coil works, then use Tom's suggestion as you rewire everything and carefully trace each connection to verify that everything is connected properly. To make things easy, print out the schematic and color each line with a red pencil as you verify connection points. That way you'll be able to tell at a glance that you've thoroughly checked each and every connection.

Just for the record, whenever I've had a problem when using commercial grade components, the problem has always been the result of a bad connection. I've never had a fresh-out-of-the-box component failure. (Obvisiously, I don't count as component failures the times that I goofed and fried things. Those were all operator errors. The sight and smell of the magic smoke let me know that I'd made a mistake.)

(Soap Box Time: One of the things that everyone is going to have to do when they build their own control boxes is to have spares of everything on hand. When you build your own box for 10% to 25% of the cost of a ready-made box, part of that price difference is the spare parts that the dealer stocks - just in case the box he sold you has a problem. When you become the manufacturer, you'll need to stock the spare parts. The good news is that even if you have a spare of everything, your cost will still be just a fraction of what if would be if you bought the controller ready-to-go.)

Above all, don't feel badly if it takes a few tries to get things working. After a while, building and troubleshooting electronics will become easier. If you want to see something really funny, just watch me attempt to do anything mechanical. You'll think that you're watching the three-stooges with me playing all three parts at the same time.
Reply With Quote
  #6  
Old Sat 10 November 2007, 21:44
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Tom, this type of thing has happened to me when I purchased a contactor with the incorrect coil voltage. If the rated coil voltage is too high, nothing happens, but there will still be a some Ohms measured. If the rated coil voltage was too low, it would clunk once, burn out and no Ohms measured after that, but the burnt smell would be there. And, for some contactor brands the coil is purchased as a seperate option - there is no coil in the case and nothing happens.
Reply With Quote
  #7  
Old Sat 10 November 2007, 22:05
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Thanks Mike. I read and reread all of the posts dealing with the contactor and am sure I know which terminals to use so I think I'm using the right ones. However, the door switch and e-stop circuit could have had a mistake in it although I checked and rechecked it several times too. I'll perform Gerald and Tom's tests as soon as I get up in the morning. Then I'll disassemble it to see if there's a coil present and try to determine if I burned it up or something. The box discusses coil replacement but I believe the brief instructions were translated from Chinese to English by a computer so they weren't much help. At least I know it's possible to look inside it.
Reply With Quote
  #8  
Old Sun 11 November 2007, 11:10
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Moron Obviously Needs More Supervision

Dang it. I had rather be shot than have to write this email.

The problem was my stupidity. I had the temp power cords hooked up to the NO relay terminals. I hadn't even noticed the coil connections on the back of the contactor. When I disassembled it and started trying to figure out how it works, the coil connections were staring me in the face. Heavy sigh. I apologize for wasting everyone's time but maybe some other dummy like me can learn from my stupidity.

Gerald, we need to add a smiley face with egg on it.
Reply With Quote
  #9  
Old Sun 11 November 2007, 11:17
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Doug,
We've all been there and done that. It's part of the price that we all pay to get an education in electronics.
Reply With Quote
  #10  
Old Sun 11 November 2007, 11:45
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Doug, we have all been there and done that.

Close up photos of that relay will help the next generation. . . . (please )

Even those that havn't wired their Teco's yet can give us photos - don't leave it all to Doug.
Reply With Quote
  #11  
Old Sun 11 November 2007, 14:21
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Not wasting my time here in florida....your just helping me not make any mistakes!
Reply With Quote
  #12  
Old Sun 11 November 2007, 19:23
Doug_Ford
Just call me: Doug #3
 
Conway (Arkansas)
United States of America
Thanks guys. Attached is a photo. I've circled the terminals in red. Notice that they are are low on the back and that's why I overlooked them.
Attached Images
File Type: jpg Teco Contactor.jpg (30.9 KB, 74 views)
Reply With Quote
Reply

Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 02:40.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.