320 and Encoder dead together

[millmore]

Hi,

I have a small CNC router using US Digital E5-250 encoders with Gecko 320 drives.

I have successfully run my machine for a couple years. Suddenly, I am blowing 320's and encoders at the same time (and ONLY on my Z axis).

I have no breakout board, never had (but it looks like I should get one)

I power the Geckos with a 5v USB tap from the computer's power supply.

I can't figure it out as this system has worked for quite some time with no issues. After my first set of 320/encoders died, I replaced with new and restarted the machine. Mach 2 finished the run of parts that was interupted by the failure. We ran a new part and again, the same problem happened half-way through the run.

I assume this must be a 5 volt supply issue as that is something the encoder and the 320 has in common? But why only the Z axis?

Any help would be appreciated.

Thanks.
Marc

[dannystooblue]

I had a simular situation but it was not the 5v supply at all. It was a wire that had worked out a straggler strand and shorted accross the encoder. When the high voltage was introduced to the lower voltage system both the encoder and the gecko were smoked. I would start by checking the wires all the way from the motor to the gecko to make sure there is not a pinch in them or any bare spots. You might make sure that everything is grounded properly as well, it may be something inside the motor sending voltage to the body of an ungrounded motor?


Danny

[Lemo]

1. Do not run low voltage/low current in the same cable as high voltage/high current.
2. Use shielded cable for the signal carrying cables and don't forget to only ground it at one end.
3. ground of the machine/motors and the PC must be the same if you use power from the PC or other switching power supply which is grounded. If they are not grounded together there can be a potential difference of quite a few volts which damage circuitry.
4. Use a break out board before the PC goes up in smoke. In the good old times all which probably died was the parallel port card, today all that jazz is in one chip together with other vitals and if that blows.... dud you need a new dell!
Lemo

[millmore]

Originally Posted by Lemo 1. Do not run low voltage/low current in the same cable as high voltage/high current. 2. Use shielded cable for the signal carrying cables and don't forget to only ground it at one end. 3. ground of the machine/motors and the PC must be the same if you use power from the PC or other switching power supply which is grounded. If they are not grounded together there can be a potential difference of quite a few volts which damage circuitry. 4. Use a break out board before the PC goes up in smoke. In the good old times all which probably died was the parallel port card, today all that jazz is in one chip together with other vitals and if that blows.... dud you need a new dell! Lemo

Thanks guys for the info.... a couple of questions...

1 - So.... The motors are attached via 2 wires to the geckos, should the black wire that goes to the gecko be grounded at the control box with a wire coming out of the gecko to a ground? Can this ground be the metal case of the control box?

2 - Ground of PC and Machine... I assume the ground on a 3 prong AC power plug is the ground wire for the PC. Is this correct? My control box is plugged into the AC and has the same 3 prong plug and the ground plug is tied to the metal casework of the control box. So that is grounded the same. If I tie the black motor wire to this same point on the control box, all will be using the same ground, correct?

3 - What about the encoders? Do they need to be grounded?

Thanks again.

[keebler303]

DO NOT CONNECT THE BLACK MOTOR WIRE TO GROUND!
This would short the gecko directly to ground as it reverses the polarity of the motor to change directions. This would probably kill another gecko.

These points should all be tied together:
The ground wire of your computer.
The ground wire of the high voltage power to the gecko.
The ground wire of any other power supply used in the system. The encoder is already grounded through the gecko.

What are you powering with the 5V USB tap?
The encoders?
The common anode for the step/dir pins?

If the encoders are powered by an external source, not hooked to gecko directly, you need a resistor across the terminals as stated in the manual.

Matt

[millmore]

Originally Posted by keebler303 DO NOT CONNECT THE BLACK MOTOR WIRE TO GROUND! What are you powering with the 5V USB tap? The encoders? Matt

OK on black motor wire

5V USB tap = Geckos (and the endcoders) get their 5 volts from the USB tap, the 5 volt tap comes from the computer with just the one wire (+5) and no matching black ground wire.

Is this a problem?

[keebler303]

You are saying the USB 5V goes to the positive wire of the encoders and to the "common" pin on the gecko?

If this is the case:

"power ground" term to encoder wire- to computer ground should all be connected.

The step/dir signals are generated from the computer so the 5V common must come from the computer (USB)

The encoder interfaces with the gecko so the encoder ground wire must be connected to the gecko enc- terminal. If you are powering your encoder from the USB tap, and not connecting to the enc + terminal, you should have a 470 ohm resistor connected between encoder + and encoder -.

If all of this is correct, you should not have a problem, I would however suggest a breakout board.

Matt