[Phife]

Hello, Im needing some help. I have 4 Gecko G320's running 4 Servos. The power supply I am using is the Keling 65V 20A. Servos are rated 72V 12A max.

I tried to follow the DC Brush type Servo diagram posted on Gecko Drives website https://www.geckodrive.com/upload/El...nicalEStop.pdf

Everything works correctly, estop cuts AC power to the power supply, But im not sure if I have the wiring right for the "Load Dump Resistor"

I have a 25w 8.2ohm resistor that is connected to the NC side of my DPDT 120v relay. When power is cut by estop the relay connects the resistor to the +DC and -DC side of my power supply. I tried this a few times, then noticed a spark in the relay and upon closer inspection the relay contacts have melted!!

With the resistor disconnected everything works fine, but the servo would hold position for about 30 secs after power was removed, then the Gecko would let out a quiet high pitched whine and quickly stopped.

Can someone help me with the resistor, i think I have it connected wrong..

Next problem, are my ground connections. Im a little confused as to what is "Earth Ground" and what isnt. I dont have anything but the electronics enclosure case and the servo ground connected to AC earth ground. Am i supposed to connect all the -DC to ground aswell? Where does the gecko get its -DC power from? I have the common pin on the G320 connected to +5V


Last problem,

I did a bench test and had a servo turning from MACH3, I have since built my enclosure and I redid all my wiring, but I cant get the G320s to turn on, I dont seem to be getting +5v Power to them. With motor and encoder connected the G320 does nothing. No fault light. With encoder disconnected motor will turn at a constant speed.

G320 has its DC+,DC- and its +5v connected and the motor and encoder connected. It also has Err/Res jumpered to ENC+

Im sure im missing something, if anyone can clear up some of my questions that would be great. Im not very experienced with electronics but I learn very quickly.


And help would be greatly appeiciated!

[TOTALLYRC]

Hello, Im needing some help. I have 4 Gecko G320's running 4 Servos. The power supply I am using is the Keling 65V 20A. Servos are rated 72V 12A max.

I tried to follow the DC Brush type Servo diagram posted on Gecko Drives website https://www.geckodrive.com/upload/El...nicalEStop.pdf

Everything works correctly, estop cuts AC power to the power supply, But im not sure if I have the wiring right for the "Load Dump Resistor"

I have a 25w 8.2ohm resistor that is connected to the NC side of my DPDT 120v relay. When power is cut by estop the relay connects the resistor to the +DC and -DC side of my power supply. I tried this a few times, then noticed a spark in the relay and upon closer inspection the relay contacts have melted!!

With the resistor disconnected everything works fine, but the servo would hold position for about 30 secs after power was removed, then the Gecko would let out a quiet high pitched whine and quickly stopped.

Can someone help me with the resistor, i think I have it connected wrong..

Next problem, are my ground connections. Im a little confused as to what is "Earth Ground" and what isnt. I dont have anything but the electronics enclosure case and the servo ground connected to AC earth ground. Am i supposed to connect all the -DC to ground aswell? Where does the gecko get its -DC power from? I have the common pin on the G320 connected to +5V


Last problem,

I did a bench test and had a servo turning from MACH3, I have since built my enclosure and I redid all my wiring, but I cant get the G320s to turn on, I dont seem to be getting +5v Power to them. With motor and encoder connected the G320 does nothing. No fault light. With encoder disconnected motor will turn at a constant speed.

G320 has its DC+,DC- and its +5v connected and the motor and encoder connected. It also has Err/Res jumpered to ENC+

Im sure im missing something, if anyone can clear up some of my questions that would be great. Im not very experienced with electronics but I learn very quickly.


And help would be greatly appeiciated!

It sounds like the resistor is connected properly.
Make sure your relay has at least 15amp contacts like the gecko document suggests and I would go for a heavier relay if possible.

Also remember that this is an E-STOP circuit and not a day in and day out contact. The relay is under a lot of stress because of what you are doing to it and it will take a beating. It will work great but I don't think it will survive hundreds of contacts when switching in this application, but I could be wrong.
I think the contacts will initially see power supply voltage which is 65v dc in your case. Make sure the contacts are rated for this kind of dc voltage.


The drive ground is on Pin 1 and comes from the dc power supply negative terminal.

I would open the gecko manual and go thru all of the setup steps again. It is very easy to make a wiring mistake.
I would also do the ohm meter check listed on the gecko site to determine if you have cooked a drive.

Mike

[Phife]

ok, so I will check the rating on the contact, I was pretty sure it was rated to handle 15A.

The pin 1 im assuming you mean is the high power (65V DC) ground, Does the +5V get its ground from the same place as the +65V?

This whole grounding this is confusing me. Can someone clear up what it "Earth ground" and whats just a Ground return?

Do i want to connect both the -65V and the -5V to "Earth Ground"

I think my problem is in the grounding, 5v is not reaching the Geckos.

It sounds like the resistor is connected properly.
Make sure your relay has at least 15amp contacts like the gecko document suggests and I would go for a heavier relay if possible.

Also remember that this is an E-STOP circuit and not a day in and day out contact. The relay is under a lot of stress because of what you are doing to it and it will take a beating. It will work great but I don't think it will survive hundreds of contacts when switching in this application, but I could be wrong.
I think the contacts will initially see power supply voltage which is 65v dc in your case. Make sure the contacts are rated for this kind of dc voltage.


The drive ground is on Pin 1 and comes from the dc power supply negative terminal.

I would open the gecko manual and go thru all of the setup steps again. It is very easy to make a wiring mistake.
I would also do the ohm meter check listed on the gecko site to determine if you have cooked a drive.

Mike

[Al_The_Man]

As pointed out in this article that unfortunately the term ground has become to be used for any supply common regardless of whether it is at earth ground or not.
If using the term Ground without reference to the supply it is relative to, creates misunderstanding.
http://www.ese.upenn.edu/rca/instrum...round/grd.html
Al.

[TOTALLYRC]

ok, so I will check the rating on the contact, I was pretty sure it was rated to handle 15A.

The pin 1 im assuming you mean is the high power (65V DC) ground, Does the +5V get its ground from the same place as the +65V?

This whole grounding this is confusing me. Can someone clear up what it "Earth ground" and whats just a Ground return?

Do i want to connect both the -65V and the -5V to "Earth Ground"

I think my problem is in the grounding, 5v is not reaching the Geckos.

Rereading your original question I can see were we are having trouble comunicating.

You have +5v hooked up to the common terminal. The negative part of this comes from the step and direction signals.

If I remember correctly the case of the gecko drive is at ground potential which is connected thru the enclosure to earth ground.

When you say -65v you are incorrect as far as the gecko is concerned. There is +65v and 0v, not +65v and -65v.

Mike

[Phife]

Rereading your original question I can see were we are having trouble comunicating.

You have +5v hooked up to the common terminal. The negative part of this comes from the step and direction signals.

If I remember correctly the case of the gecko drive is at ground potential which is connected thru the enclosure to earth ground.

When you say -65v you are incorrect as far as the gecko is concerned. There is +65v and 0v, not +65v and -65v.

Mike

hmm, interesting.. If the case of the gecko is supposed to be at earth ground then that may be my problem, I have the geckos mounted on heatsinks and the geckos are just floating in the air, not really connected to the chassis. But I get no continuity through the case of the gecko, i thought the coating prevented conduction?

regardless im gonna go read that link on grounding..

[Hellpit]

Re your bleed down resistor, I have the same issue. I'm going to try a larger value resister to try and lower the current during drain. I'm using a 30 Amp contact relay, and it still looks like a welding machine in my enclosure.

Re your grounding issues, I had the same issue as well. I've since tied all my power supply grounds to the chasis. No more issues.

[Phife]

Re your bleed down resistor, I have the same issue. I'm going to try a larger value resister to try and lower the current during drain. I'm using a 30 Amp contact relay, and it still looks like a welding machine in my enclosure.

Re your grounding issues, I had the same issue as well. I've since tied all my power supply grounds to the chasis. No more issues.

Thanks for your reply, Im glad someone else is having trouble with that resistor estop system.

An electrician friend of mine asked if I was using DC rated contacts in the relay and When i looked it didnt say DC anywhere on it.. Im going to look for DC rated contacts, but if i cant find it I will probably do what you mentioned and go with a higher value resistor.. what do you think would be a good value to go for?

And I am going to chassis ground the - side of all DC supplies.. I noticed the 5V was already chassis grounded when connected to the BOB.

But that brings up another question... Do the Geckos need to have their case chassis grounded? I got them mounted on heatsinks and the heatsinks are just hot glued to the case, no real chassis connection there, but I dont think that the Geckos can get a connection through the anodizing? anyone know for sure?

[Hellpit]

As far as I know, the G320 is grounded through the Power Ground terminal, not the chasis of the drive. (I could be mistaken though)

I'm not sure what value to use for the bleed down. I'm just going to try somthing that will bleed at about 5 amps rather than the 10 amps that mine is currently at.

[thosj]

Phife/Hellpit, did you solve the DC dump circuit melting your relay contacts? I have been fighting this same thing for two weeks using the same Geckodrive schematic!! I've tried all kinds of things, putting estop on the hot side so no switches on AC common, having one relay just switch another relay and have that relay do the dumping. I still have the same issue. I have 15 amp rated relays. I have tried 3 different relays. I have 7.5 ohm 25 watt wirewound resistors. It burns the NC contacts on the dump circuit, the contacts that should be OPEN when the relay switches!! Impossible. It burns them when the momentary start switch is pressed. Is the big DC voltage not allowing the contacts to open, or is it jumping the contact, or....??

My PS is Keling KL7220, 72 volt 20 amp, but it has 2 outputs so I am using a 3P2T relay to dump the two sides, which I ASSUME are 10 amps each, correct? For 2 weeks, nothing but 3 burnt up relays. I/we need to solve this thing!! I've posted elsewhere with no answers. I thought it was my electrical noob position, but I guess I'm not the only one. I have a pretty competant electrical guy stumped by this, too. And another looking at it next week.

What's the solution to this?

[Al_The_Man]

There is a great deal of energy when dumping a large charged capacitor, this is the basis behind steel stud welding.
You may want to look at the principle used by VFD's etc for dumping back EMF voltage by switching in a large solid state device like a HexFet.
Al.

[Phife]

No answer yet. My next option is to try a contactor, I am also going to go up to something like 20-40ohm resistor, see if that helps.

I too tried the resistor in various arrangements and went through 3 relays. That Estop diagram needs to get updated. Seems alot of people are having this issue.

Just waiting for my local electronics store to get some more stock in.


I did get the ground and no power figured out, Im connecting all my DC grounds to a separate bus and using chassis and earth ground for actual earth grounding.

Also my no power problem was that i had the encoder wired wrong, I was using some CAT5e cable for my encoder wiring and had some crossed wires at the RJ45 breakout. Motors would turn on their own when encoder was disconnected, no faults, no power to enc+ or err/res. Rewired encoders and now everything is good.

[keebler303]

The relays you all are using are probably rated for 120/240 AC. For DC, they are probably rated at 12-24 V. The contacts arc when they open or close, the AC arc is extinguished every half cycle of the AC. The arc in the DC circuit is sustained and therefore acts just like a welder and fuses the contacts. This can cause meltdown because when you turn it back on the circuit remains closed and your whole power supply is feeding your dump resistor. As Al mentioned, you need a solid state device which does not have the arcing problem. I used a DC SSR on one project and it seems to work well. I got it from www.futurlec.com If I remember correctly it was rated to 200VDC and 40A. You need some way to turn on the SSR when you shut the power off, but it should not be too difficult to find 5V somewhere to use to turn on the SSR.

Matt

P.S. Power supply common (ground) and ENC- are internally connected on the G320.

[thosj]

No answer yet. My next option is to try a contactor, I am also going to go up to something like 20-40ohm resistor, see if that helps.

Definately keep me posted on this. There is something about this that doesn't seem right. The DC contacts burn when trying to switch them OUT of the dump circuit, NOT when they are switched IN and dumping. Mine worked a few times and dumped just fine, maybe 1/2 second as mentioned in the circuit PDF. But, it burns the contacts before they can disconnect or jumps them. I've torn relays apart and can SEE this, the NC contacts of the DC dump circuit burn when you press the momentary START button and the relay should be switching OUT the DC dump circuit.

I use a latching estop, not momentary as the schematic shows, and if you do that, and you press the momentary start button before unlatching the estop, you energize the powersupply without energizing the relay and having it switch out the dump circuit, so it's attempting to dump while it's making lots of amps of 72vdc!! I thought this might have been my problem, pressing start before unlatching estop, burning the contacts, then they wouldn't switch out. I put the estop in series on the hot side of the AC to eliminate that possibility. I think there's some 'rule' about not switching the common side of AC anyway, but in this case it really wouldn't matter IF, IF, you had a momentary estop.

Phife, is yours burning when it's actually dumping, or when you turn it ON? If so, that's way different from my experience.

Anyway, we need some electrical guru to A) explain this, and B) recommend a solution. This has had me laying awake for over two weeks and I've consulted one guy that's way more of an electrical guy than me and he's mystified, too.

[thosj]

The relays you all are using are probably rated for 120/240 AC. For DC, they are probably rated at 12-24 V. The contacts arc when they open or close, the AC arc is extinguished every half cycle of the AC. The arc in the DC circuit is sustained and therefore acts just like a welder and fuses the contacts. This can cause meltdown because when you turn it back on the circuit remains closed and your whole power supply is feeding your dump resistor. As Al mentioned, you need a solid state device which does not have the arcing problem. I used a DC SSR on one project and it seems to work well. I got it from www.futurlec.com If I remember correctly it was rated to 200VDC and 40A. You need some way to turn on the SSR when you shut the power off, but it should not be too difficult to find 5V somewhere to use to turn on the SSR.

Matt

P.S. Power supply common (ground) and ENC- are internally connected on the G320.

Oops, didn't see this until I replied to PHIFE above. This is the first explanation of this I've seen even though I've somehow 'suspected' this to be the issue. Your explanation of this is EXACTLY what seems to be happening to me!!

I have to check into this DC SSR thing and see if I can figure it out. When I go to look up this electrical stuff, I'm mostly mystified because I don't really understand what I'm looking at. If you have an actual device model or something we could use, please recommend. I'll checkout your link and see what I can learn.

I have $80 worth of wrong relays into this already, I guess!! Cost is no object at this point. This is my first CNC home project and this had put a serious dent in my confidence with regard to this electrical stuff.

[thosj]

The relays you all are using are probably rated for 120/240 AC. For DC, they are probably rated at 12-24 V. The contacts arc when they open or close, the AC arc is extinguished every half cycle of the AC. The arc in the DC circuit is sustained and therefore acts just like a welder and fuses the contacts. This can cause meltdown because when you turn it back on the circuit remains closed and your whole power supply is feeding your dump resistor. As Al mentioned, you need a solid state device which does not have the arcing problem. I used a DC SSR on one project and it seems to work well. I got it from www.futurlec.com If I remember correctly it was rated to 200VDC and 40A. You need some way to turn on the SSR when you shut the power off, but it should not be too difficult to find 5V somewhere to use to turn on the SSR.

Matt

P.S. Power supply common (ground) and ENC- are internally connected on the G320.

I've checked out the SSR thing and think I understand them a bit. So.....I would use my original relay to latch the power supply is as originally designed, then use another set of contacts on that relay to switch 5v that I can get most anywhere in my box to switch the SSR, which in turn would switch the dump circuit in and dump the capacitors in the power supply which has now been switched OFF by the original relay? Does this sound right?

I'll attach Geckodrive Mariss' original PDF of this circuit just so you guru's know what we're talking about and can suggest any other solutions.

And for those electrically challenged like me, these Solid State Relays seem common. Digikey has much the same things as the ones in the link in keebler303's post quoted. My PS is 72 volts, 20 amps, so 100v 40 amp SSR would do this, right? Will I need to heatsink these seeing as they're only draining capacitors, or will having them screwed down on my aluminum cabinet backplate be enough sink?

[thosj]

The relays you all are using are probably rated for 120/240 AC. For DC, they are probably rated at 12-24 V. The contacts arc when they open or close, the AC arc is extinguished every half cycle of the AC. The arc in the DC circuit is sustained and therefore acts just like a welder and fuses the contacts. This can cause meltdown because when you turn it back on the circuit remains closed and your whole power supply is feeding your dump resistor. As Al mentioned, you need a solid state device which does not have the arcing problem. I used a DC SSR on one project and it seems to work well. I got it from www.futurlec.com If I remember correctly it was rated to 200VDC and 40A. You need some way to turn on the SSR when you shut the power off, but it should not be too difficult to find 5V somewhere to use to turn on the SSR.

Matt

P.S. Power supply common (ground) and ENC- are internally connected on the G320.

Here's the pdf. It is Mariss Fremanis schematic from either Geckodrive site, or Yahoo Geckodrive group file section, don't remember any more, but hopefully Mariss doesn't mind my posting it up.

[Al_The_Man]

Relays that switch high DC voltage/current have arc blow-out or arc suppression arrangement.
This is often done with a permanent magnet adjacent to the contacts.
I use one made by P&B Tyco in one application I manufacture where a high current DC is switched.
In the PDF in the previous post, why do you have a stop PB in the neutral? This goes against normal code practice where the Neutral is not normally switched.
You can just as easily put it in series with the cycle start PB in the hot side.
Al.

[thosj]

In the PDF in the previous post, why do you have a stop PB in the neutral? This goes against normal code practice where the Neutral is not normally switched.
You can just as easily put it in series with the cycle start PB in the hot side.
Al.

Al, that is not MY pdf, it is Mariss Fremanis (sp?) of Geckodrive's PDF, as I credited in my post I think. But in a previous post I mentioned that I did EXACTLY as you said and put the estop switch in series on the hot side, not the neutral side. We're CODE now, but still burning relay's!! I'm buying SSR's to do this switching of 72VDC.

[Al_The_Man]

I did EXACTLY as you said and put the estop switch in series on the hot side, not the neutral side.

Sorry, I must have missed it.
Also there is the practical benefit, as often the e-stop is next to the start PB, this only needs three conductors to them instead of 4.
Probably going S.S. will be cheaper than a blow-out relay, The ones I use are around $70.00.
Al.