Gecko Slayer

[CAM_MAN]

Please help anyone. I have managed to destoy 4 geckos in a month. I have followed all the wiring schematics that have been posted on cnczone and basically they all follow the same principals. I have checked to make sure that I dont't have any frayed wiring or shorts. I am using a toroidal transformer with 50V 20A output. I am running the output thru a 125V bridge and a 10000 MFD cap. My output off the cap is abot 78.5V. I have the + input going thru 3A fast blow fuses. I have fired up my machine and done some motor testing and have managed to completely smoke three drives and wound a fourth. The first three all died at different times. They would be working fine and then I would hear a sharp pop and smell smoke. The power resistors would split in half and yes the fuse was toast too. It is almost like a surge of power so fast that the fuse isn't fast enough to save it.The fourth has just slowly faded away to wear it just stutters the motor. I have got to the point that I can't afford to be going thru drives like kleenex. The only thing I know that I have done different from some that I have seen others do is to run the +5V to terminal 10 from a 5V power supply and not from the PC. Please someone help.

[ger21]

Are these G201's? Do you have them heatsinked and fans? You're awfully close to the Max rated voltage.

[CAM_MAN]

Yes they are G201's. And I am running them on heatsinks with fans. I also have been checking the baseplate temp on the drives with a laser temp and they have never got over 120F. The motors barely even get warm. I did just pull apart my power supply for the millionth time and remove the transformer bridge and cap and set them up alone and tested the voltage. I was suprised to see that the voltage was at 87.9V. When I first tested them I was only getting about 78V to 79V. This possibly could be that I just paralleled the transformer to double my current. Right now I am totally dazed and confused and about 7G's in the hole on my project. Could you give me some insight so I may be able to regain focus. Thanks.

[2muchstuff]

88 volts is pushing it, I think somewhere in a previous post by the Gecko guru he mentioned that they could be taken to 80 volts, don't quote me though. You might be experiencing a back EMF or spike as the motor slows down or stops. Try reducing your voltage out of the torroid by removing several turns or inserting several diodes in series with the positive wire coming out from your capacitors. The current rating should be the same as your bridge. Each diode will have a forward voltage drop of .707 volts each. 10 doides =7.07 volts dropped.

[ger21]

I believe Mariss at Gecko is currently on vacation. I'd try to get ahold of him when he gets back, in a week or two. It sounds like a combination of too much voltage + back EMF pushed it too far. I believe the back EMF has to be accounted for in the 80V max. Mariss has stated in the past that running Geckos at their max ratings leaves little to no room for error.

[CJL5585]

It sounds like a combination of too much voltage + back EMF pushed it too far. I believe the back EMF has to be accounted for in the 80V max.
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I agree. I think this is most likely the problem.

Jerry

[pminmo]

I also think you pushed the power supply voltage to high.

[Bloy2004]

As I understand it, The Geckos come apart around 100VDC. but if your line voltage changes (as mine does here) the combination of and increased line voltage with back EMF, along with 80+VDC(when line voltage is low) output can easily exceed the limit.
I think the recommended max voltage applied to the Geckos is 72VDC. This is considered safe pending any line voltage increases or other surges from decelerating motors.

[CAM_MAN]

You guys are all right. I did a little test to see waht the back EMF would be by having my wife push the gantry while I had test leads across the motor outputs from the geckos and I was getting between 7V to 9V. Also when I did my initial testing breadboard style I did it in my kitchen at the table. In there I was getting 78.5V. When I tested it in my garage last night I was getting 88.7V I then brought it all back in my kitchen and plugged back in to the same place as my initial test and low and behold 78.5V. Now it is hard to believe that I can walk 15 feet form my kitchen and get a 10V rise. So between the rise in voltage from one receptacle to the next and the back EMF I think I have found my culprit. I am definitely pulling some windings off the transformer tonight. I am not going to split any more power resistors if I can help it (crosses his fingers). Anbody got any suggestions on what vaoltage I could safely run and still get some good performance out of my steppers. Here is a link to the motors I have they are the 1200 ozin. http://www.tormach.com/document_libr...34-xxx-STD.pdf BY the way my router is a 4 x 8 CADCUT.

[swarfmacdaddy]

You should also fuse each run from your power supply with a fast blow fuse if you havent already. 5 amp fast blow.

[CAM_MAN]

I have fast blow 3A fuses inline and always have from day one. It still didn't save the geckos. I talked to Mariss about this a while back and he said he thought that I was getting some form of voltage spike that was doing it. It suprised me that the fuses have never blown even though the drives have.

[2muchstuff]

Murphy's Law says that the $1000 piece of equipment will blow protecting the 29 cent fuse.