All right, I've done it now! - Page 1
Forum section: electronics / beginners

author: Leuven
author_rank: Regular Contributor
timestamp: March 10, 2013, 03:39:42 am
content: So I have this bench grinder I was trying to clean and I've managed to mangle some of the wiring while connecting the switch back on. In retrospect, I should have been a lot more careful and write down a diagram but here I am now, and sure enough, it makes a hell of a screeching noise and no go when I turn it on now.Any ideas what I've done wrong? I sure hope I didn't fry it. The switch is a KEDU KJD11 no-volt release.

author: G7PSK
author_rank: Super Contributor
timestamp: March 10, 2013, 06:22:22 pm
content: Does the grinder turn at all, screeching noise sounds like bearings or other mechanical noise such as rubbing guards.

author: Leuven
author_rank: Regular Contributor
timestamp: March 10, 2013, 07:38:35 pm
content: It looks like an electrical fault. Bearings are perfect, turns smoothly by hand. It's actually more like a very loud buzz rather than screeching, and it's not turning at all when power is applied.I just replaced the capacitor and still the same.

author: IanB
author_rank: Super Contributor
timestamp: March 10, 2013, 08:36:16 pm
content: Seems like you have probably connected some of the wires to the wrong terminals on the switch. You'd better trace the wiring, make a schematic diagram and then determine where the wires really ought to go...

author: Leuven
author_rank: Regular Contributor
timestamp: March 10, 2013, 10:27:53 pm
content: Took the time and drafted a better diagram. It looks like I've switched pin 2 with pin 4. I've measured the motor windings (values on the diagram), and also against the chassis (OL as expected, no short).

author: Leuven
author_rank: Regular Contributor
timestamp: March 17, 2013, 05:16:28 pm
content: I haven't got any further with this, switching pins 2 and 4 has no effect - still buzzing, except that the start button is not latching now. So I don't think that's the answer.I tried to turn the spindle while having it on and it's completely locked up! It unlocks as soon as I turn it off.This is wearing me thin, any ideas folks?

author: IanB
author_rank: Super Contributor
timestamp: March 17, 2013, 05:57:04 pm
content: If the motor shaft is locked while power is applied it would indicate that the two motor coils and the run capacitor are not wired up correctly. The motor is seeing a stationary magnetic field that is locking it in place.If you didn't take a photo of the wiring before you disassembled it and you don't have the skills to determine how to reassemble it this is going to be hard. I imagine if I had it on my workbench with the opportunity to test it and analyze it I could figure out how to put it back together in working order, but doing this remotely with limited information is more complicated.Can you find a similar unit to compare to, or can you find an electrical engineer nearby who can figure it out for you? Maybe you can find a wiring diagram online somewhere for that particular model?

author: ignator
author_rank: Regular Contributor
timestamp: March 17, 2013, 06:07:38 pm
content: Forgive my ignorance: Is this a run capacitor or a start capacitor? Run would be a metal can. Start would be a plastic package. When it was working properly could you hear a switch noise from a centrifugal start switch? If not I would assume this is a run capacitor.The .1 ohm is confusing in your measurements.

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 17, 2013, 07:31:38 pm
content: Quote from: ignator on March 17, 2013, 06:07:38 pmLooks like a metal can, you can just see it in the bottom of the picture.By looking at what it should do, I think you have to swap pin 4 and pin 6, but don't blame me if it burst into flames...

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: March 17, 2013, 07:46:48 pm
content: It's a 4 pole relay with a1 and a2 being the 240 volt coil, where does the start stop switch connect? Is it integral with the relay? I don't see any wires for it.The start switch should energize the relay and one of your extra contacts should act as a holding contact. The third wire on the motor is probably for a higher speed.

author: Leuven
author_rank: Regular Contributor
timestamp: March 17, 2013, 08:59:37 pm
content: Quote from: IanB on March 17, 2013, 05:57:04 pmNothing similar that I can compare with, and the shop who sells these units not very helpful. No luck with the diagram for the switch either.Quote from: ignator on March 17, 2013, 06:07:38 pmIs is a 8uf plastic capacitor, so it's maybe a start one? I don't remember any switch going off as I've only powered it once before taking it apart. It was one of those ebay bargains, definitely working though. I had the casing apart and couldn't see anything that looked like a centrifugal switch, I would assume that it doesn't.Quote from: PA0PBZ on March 17, 2013, 07:31:38 pmCapacitor is plastic. I tried switching pin 4 with 6, still the same buzzing.Quote from: 4to20Milliamps on March 17, 2013, 07:46:48 pmStart/Stop buttons are built into the relay. I've noticed the switch does not latch on if there are no motor wires connected, just acts like a momentary switch.If there's any help, I've measure the resistance between the capacitor wires and the other 3 going into the motor.black capacitor wire:to black - 0 ohmto red - 0 ohmto blue - 13 ohmwhite capacitor wire:to black - 47 ohmto red - 47 ohmto blue - 37 ohm

author: notsob
author_rank: Frequent Contributor
timestamp: March 17, 2013, 09:10:32 pm
content: AND next time you take something apart - before you DO anything - use your phone - it takes PICTURES

author: Leuven
author_rank: Regular Contributor
timestamp: March 17, 2013, 09:18:25 pm
content: Quote from: notsob on March 17, 2013, 09:10:32 pmOh boy, don't I know that now!Anyway, there are another 3 permutations I haven't tried on the motor wires (from top to bottom):black-red-bluered-blue-blackred-black-blueI'm tempted to just press on, what's the worst damage I can do?

author: Monkeh
author_rank: Super Contributor
timestamp: March 17, 2013, 09:51:13 pm
content: Quote from: Leuven on March 17, 2013, 08:59:37 pmNo, it doesn't latch because it has no neutral connection. If you disconnect the motor and connect A2 to 4, it will latch.Try red-blue-black.

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 17, 2013, 09:55:29 pm
content: It looks like these KDJ11 switches are made for 3 phase switching. I wonder if there is anything in the motor that controls the latch, like an overcurrent situation or something like that. Maybe you killed it by wiring it the wrong way, there's only that much ways to connect it and it looks like you tried all the sensible ones.

author: IanB
author_rank: Super Contributor
timestamp: March 17, 2013, 10:08:12 pm
content: First I would try to make the motor run without the switch in the way. That way you can figure out the required motor connections.This page may help you:http://www.allaboutcircuits.com/vol_2/chpt_13/9.htmlSince you have a low power application you most likely have a permanent-split capacitor motor (scroll down to that section). Using that diagram and a bit of experimenting you should be able to determine what connections to make to get the motor running and turning in the right direction.Then you come to the switch. The switch is being used as a latching relay with momentary on and momentary off pushbuttons. The momentary on push button feeds power to the motor and simultaneously feeds power to the AC relay coil which keeps the relay closed. Once it's on it stays on. The off push button momentarily interrupts power to the relay coil and thus causes the switch to turn off. You should be able to make the switch operate by itself without the motor connected.Once you have both pieces figured out you can join them up and get the whole thing working.

author: IanB
author_rank: Super Contributor
timestamp: March 17, 2013, 10:16:16 pm
content: Looking at your diagram:If you disconnect all the motor wires from terminals 2, 4 & 6 you have the switch by itself.Now discconnect the wire from terminal 5 and connect it to terminal 4 (in other words connect terminal A2 to terminal 4). When you press the start button a mains voltage should now appear across the relay coil between A1 and A2 and this should keep the switch latched. The relay coil current will flow from the live on A1, through the coil to A2, through the wire to 4, through the switch contact to 3, and back through the neutral wire.With these connections the switch should click on and off. Try this and see what happens. After that we can figure out where to connect the motor wires.

author: IanB
author_rank: Super Contributor
timestamp: March 17, 2013, 10:21:55 pm
content: In fact, going by the diagram above, it looks like you just need to swap the motor wires between terminals 2 and 4, leaving everything else the same. You have tried this and it doesn't work?

author: IanB
author_rank: Super Contributor
timestamp: March 17, 2013, 10:31:19 pm
content: Reading earlier posts, I believe the following.Of the wires coming out of the motor, the two black wires are the red wire are internally connected, and should be connected to mains live. The blue wire goes to the other side of the motor windings and should be connected to mains neutral.How many wires did you originally disconnect from the switch, and which wires are still in their original locations?

author: IanB
author_rank: Super Contributor
timestamp: March 17, 2013, 10:37:43 pm
content: In fact, scrub what I said above. The more I look at the diagram the more I believe it should work the way it is shown. So I don't really know what is going on.

author: PA0PBZ
author_rank: Super Contributor
timestamp: March 17, 2013, 10:38:53 pm
content: Quote from: IanB on March 17, 2013, 10:37:43 pmWelcome to the club

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: March 17, 2013, 10:40:01 pm
content: I should have read his description more carefully, the no voltage relay is a protection device to prevent the grinder from re starting if power is lost, both a1 and a2 should be on the same side of the relay as the motor leadsA1>2A2>4Mains connected to 1 and 3Push the momentary start button it should close contacts between 1&2 and 3&4 energizing the coil and maintaining the power to the motor, when power is lost the start button must be pushed to re start the motor.The third wire on the motor must be to reverse the motor? or for a higher speed?

author: Monkeh
author_rank: Super Contributor
timestamp: March 17, 2013, 10:46:09 pm
content: Quote from: 4to20Milliamps on March 17, 2013, 10:40:01 pmAnd just where do you suggest he connect the motor? You've now got no terminals free for the line and neutral connections. It's also clear from the wiring present that it was never wired up in this manner.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: March 17, 2013, 10:53:34 pm
content: motor on Terminals 2 and 4I wasn't aware that his schematic was correct.....isn't that the problem?

author: Monkeh
author_rank: Super Contributor
timestamp: March 17, 2013, 10:55:22 pm
content: Quote from: 4to20Milliamps on March 17, 2013, 10:53:34 pmThere's only one blade connector for each terminal. It has insulated non-piggyback connectors. You cannot do this, it was not wired this way. Please try again.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: March 17, 2013, 11:05:17 pm
content: I really can't see how many terminals it has from that picture, either way the relay coil should be on the motor side.

author: Monkeh
author_rank: Super Contributor
timestamp: March 17, 2013, 11:11:30 pm
content: Quote from: 4to20Milliamps on March 17, 2013, 11:05:17 pmNo, it just has to be switched.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: March 17, 2013, 11:36:02 pm
content: You're probably correct, so if this schematic from the manufacturer doesn't do it I will rest my case.http://www.kedu.cn/PDF/8/p47-48.pdfsurely one of these ways will have to work

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 12:23:50 am
content: Quote from: IanB on March 17, 2013, 10:16:16 pmI moved A2 to 4 and the switch latches on. So far so good.I switched around 2 and 4, still buzzing.Quote from: 4to20Milliamps on March 17, 2013, 10:53:34 pmMy schematic should be close. I did write down a rough diagram so if I've got something wrong, which I did, it shouldn't be that far off.

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 12:28:56 am
content: Quote from: 4to20Milliamps on March 17, 2013, 11:36:02 pmI came across this diagram too, I think that's my switch. The problem is it looks like I have to completely re-route all wires. I would do it but I'm pretty sure it wasn't like that to begin with.

author: IanB
author_rank: Super Contributor
timestamp: March 18, 2013, 12:35:25 am
content: If you have the switch tested and working, the next step is to ignore the switch and consider the motor. If you disconnect all the motor wires and have the other wires connected according to your diagram, you will have a mains voltage at terminals 2 and 4 when you press the green button. The switch won't latch, but that does not matter right now.What you should do is try connecting pairs of motor wires to terminals 2 and 4, press the green button and see if the motor runs. Try the following pairs:2 : blue4 : black(red floating)2 : blue4 : red(black floating)Do not connect red and black to the mains or you will blow a fuse (these two wires seem to be connected internally).If the motor does not turn when you connect a mains voltage across the blue and black or blue and red wires, then the motor could be faulty.

author: ignator
author_rank: Regular Contributor
timestamp: March 18, 2013, 12:40:32 am
content: Quote from: Leuven on March 10, 2013, 03:39:42 amSo how is the stop button shown in any diagram? It needs to have a contact in series with the hold coil. Did I miss this somewhere in one of the diagrams. Also how is the start button in this circuit, I'm going to guess it's a mechanical closing of all the contacts. I agree with Ian it's a Permanent-split capacitor motor configuration, as you indicated there is no centrifugal switch in the motor. And this makes sense as the starting torque for a grinder is minimal (mainly just the inertia of the motor rotor and grinding wheels).

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 12:49:03 am
content: Quote from: IanB on March 18, 2013, 12:35:25 amI've done that and it's buzzing both ways. I can't believe this, I haven't done anything to it but giving it a good clean inside, no wire pulling or anything rough.I will try again and bypass the switch completely, least I could do before I scrap it.

author: AlfBaz
author_rank: Super Contributor
timestamp: March 18, 2013, 12:53:25 am
content: have you tested the cap for a short cct?turn auto ranging off on your meter, place it on the highest ohms reading. Disconnect and short the cap terminals. place the meter across the cap terms, you should see the ohm reading climb to OL

author: AlfBaz
author_rank: Super Contributor
timestamp: March 18, 2013, 12:57:39 am
content: Oh and 13ohms between blu/blk and blu/red should yield 26ohms across red/blk.Disconnect everything from the relay and ensure it meters as expected, at the same time re-measure the motor leads, including the cap leads with the cap disconnected

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 01:11:53 am
content: Quote from: AlfBaz on March 18, 2013, 12:57:39 amQuote from: AlfBaz on March 18, 2013, 12:53:25 amI connected the motor directly to the mains, blue/black and then blue/red as advised. Same buzzing on both, with spindle lock.I have 2 caps here, the original and a replacement. Both measure as expected - climbing up to MegaOhms.However, Ido notget 26 Ohm across red and black, I get 0.1ohm. Does that mean short in the windings?

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 01:33:28 am
content: Further measurements:across the 2 cap wires (cap disconnected) - 49 ohmblack cap wire to motor wires:black - 0.1 ohmred - 0.1 ohmblue - 13ohmwhite cap wire to motor wires:black - 49 ohmred - 49 ohmblue - 36 ohm

author: AlfBaz
author_rank: Super Contributor
timestamp: March 18, 2013, 01:46:51 am
content: for completenesswhats the resistance between wht cap to blk cap wire?

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 01:53:48 am
content: Quote from: AlfBaz on March 18, 2013, 01:46:51 am49 ohm, cap disconnected.Edit: I mean across bare black and white wires, not the connectors on the cap.

author: 4to20Milliamps
author_rank: Regular Contributor
timestamp: March 18, 2013, 02:04:03 am
content: I know i'm whipping a dead horse, but you did say you had this thing all apart and there is no centrifugal switch on the motor?This thing seems like it should run, your windings aren't open, they're not shorted, and your capacitor seems to be o.k.What else is there?

author: IanB
author_rank: Super Contributor
timestamp: March 18, 2013, 02:08:46 am
content: Take a look at the permanent-split capacitor motor schematic in the link I posted before:http://www.allaboutcircuits.com/vol_2/chpt_13/9.htmlCapacitor black, motor black, motor red are the lower left terminal, all connected together. The 0.1 ohms is just meter lead resistance.Capacitor white is the top of the capacitor.Motor blue is the upper left terminal.If you measure between capacitor white and motor blue, you will see one winding. If you measure between capacitor white and motor black you will see two windings (higher resistance).It seems like everything should be good. No idea why the motor is not turning.If you connect the mains between motor black and motor blue with the capacitor in circuit, the motor ought to turn.

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 02:13:32 am
content: Quote from: 4to20Milliamps on March 18, 2013, 02:04:03 amYes, I did take the 2 ends apart to replace the bearings, the 5 leads go into a bundle directly into the windings. They go into a sleeve before they get to the windings so I can't tell which one goes where but there is nothing else out there. A centrifugal switch is a big thing and I haven't seen anything remotely like that.

author: ignator
author_rank: Regular Contributor
timestamp: March 18, 2013, 02:31:07 am
content: Quote from: Leuven on March 18, 2013, 02:13:32 amTake the motor apart again, and look to see if any wires got pinched to the chassis ground. I've had this happen to me. Don't scrap this yet. Trace all the wires through to windings, and see how the capacitor is connected.Your going to make this run again. Quick ohm meter check the ground wire to any of the motor wires, for a short.

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 02:34:32 am
content: Quote from: IanB on March 18, 2013, 02:08:46 amI think your theory of how it works is as good as it gets.Is there something that could have compromised my measurements, such as using a standard multimeter (a Fluke nonetheless) instead of a megger?

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 02:40:22 am
content: Quote from: ignator on March 18, 2013, 02:31:07 amI've checked all motor wires against the chassis ground - all sound, infinite resistance.I will take the ends apart again and split the sleeve to see where exactly these wires go.

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 03:13:22 am
content: Photos with the motor open. There are strings that hold the windings together and will have to be cut in order to get at the sleeve.

author: AlfBaz
author_rank: Super Contributor
timestamp: March 18, 2013, 03:45:15 am
content: Quote from: IanB on March 18, 2013, 02:08:46 amI agree completelyLeuven, don't cut the strings, with the motor out you should have something like the attached picHave you tried running it as Ian has proposed?

author: Leuven
author_rank: Regular Contributor
timestamp: March 18, 2013, 04:44:20 am
content: Quote from: AlfBaz on March 18, 2013, 03:45:15 amYour diagram checks out exactly! I will connect to the mains again to squash out any doubt.

author: ignator
author_rank: Regular Contributor
timestamp: March 19, 2013, 02:03:29 am
content: Quote from: Leuven on March 18, 2013, 04:44:20 amDid you make it go again?

author: Leuven
author_rank: Regular Contributor
timestamp: March 19, 2013, 11:22:43 pm
content: I've got it working, the wiring was correct all along!There are 4 long screws that keep the ends together and what happened is all this time I kept testing it without the ends screwed on. On the other hand, the ends are held together by the bearings to begin with. Even without the screws, the rotor is perfectly centered - the aluminium stator frame has no radial play and very little axial play (maybe half a millimeter) so it didn't even cross my mind it might affect the way the motor works.Anyway, lesson learned and a big thank you to all of you that chimed in to help. The reason I put the screws on is it was the very last thing I could do, since everything else checked out.

author: AlfBaz
author_rank: Super Contributor
timestamp: March 19, 2013, 11:55:43 pm
content: I once worked on a large series DC traction motor that when ever it was powered up it made a terrible knocking noise. Turned the power off the motor was still spinning at roughly the same speed but no noise. The 2 stator coils were bolted to the carcase with 3 bolts each, one of them didn't have a nut on it. The armature's magnetism pulled it in whenever it was energised