Fried my controller - WHY???!!

[declanhalpin]

Hello all,

I was helping a friend get his machine up & running and fried his board. Luckily he has another, but I want to double check everything before my 2nd attempt...

Overview:

Controller: Toshiba TB6560
BiPolar Chopper Driver
Microstepping Full, 1/2, 1/8, 1/16
15-35 Volts input

Machine: Hermes 3-Axis Gantry Style
(3) motors: 1.8 deg/step
3.3V, 2.5A

Power Supply: 25 VDC output (checked with mulimeter)

Ok, the controller has dip switches that control Current (100%, 75%, 50%, or 25%), Buffer Settings (Fast, 25%, 50%, Slow), and Microstepping (1/1, 1/2, 1/8, 1/16). I think my main problem has to do with the Current (?), as the first board literally exploded .

With the computer disconnected from the board: I plug in the power supply, LED lights up, controller comes to life and fan spins.

*unplug PS, Connect computer *

Plug in PS and LED is super dim, fan may or may not come on, and there is little to no motion from the machine.

Any ideas? I am familiar with Mach3 and have set all the port/pins properly..... Any help is greatly appreciated.....

[neilw20]

Show some photos of the all the wiring.
How the supply wiring is done is very important, as high currents in the wires can induce spikes above 5 volts.
If any the logic circuits see above 6.5v for micro seconds they can be fried.
It is easy to get the smoke out, but hard to get it back in again.
In particular photos of all the power wiring to the drivers and the power supply.

[hub]

Using Mach3 the controller would be the PC?
But you said board so I'm guessing the bob (break out board) fried?
What are the drivers' current set to? And psu current?

[declanhalpin]

Attached are photos of the setup.

Hub - The dim switches set each axis' current to 75%. What is PSU? if you mean Power Supply it's 25VDC.

Thanks again for any feedback!

d

[neilw20]

Nothing obvious from photos.
1. Ensure the motor spec (inductance in particular) is suited to the driver.
2. Loose connections, poor crimps, bad stepper connectors can fry things

[hub]

Attached are photos of the setup.

Hub - The dim switches set each axis' current to 75%. What is PSU? if you mean Power Supply it's 25VDC.

Thanks again for any feedback!

d

Yes I meant power supply Thanks, but I need to know the currents (Amps).
- How much current can your PSU supply @ 25V?
- The 75% setting of the driver doesn't tell me anything because I don't know the current. How many Amps would 100% be?
- How have you wired the motors? Bipolar paralell, serial.. ?
- Also, as suggested what is the inductance of the motors (mH)? (Note it will be different depending on how you connected the motors)

I'm sorry for no answer but more questions My point is, trying to understand if you have blown the board because of overload.

[declanhalpin]

How much current can your PSU supply @ 25V? 6.5A
- How have you wired the motors? Bipolar paralell, serial.. ? I'll have to check on this....
- Also, as suggested what is the inductance of the motors (mH)? (Note it will be different depending on how you connected the motors) How do I check this?

Thanks so much,

Declan

[hub]

You can find the inductance on the stepper motor's data sheet.
Also how many amps are the drivers set at? And how many amps are the stepper motors rated at?

I'm not familiar with that Toshiba.. Does it include "everything", or do you have separate drivers? I mean, what components are between the computer and steppers? Only 1 board?

[declanhalpin]

You can find the inductance on the stepper motor's data sheet. hmmm...that may be tricky but I'll look into it...

Also how many amps are the drivers set at? That's part of my question. Am I correct in thinking this is the formula?:

PS = 6.5A
6.5A / 3 (it's a 3-axis board) = 2.16 A
2.16A x 0.75% (from Dip Switches) = 1.63A per axis

And how many amps are the stepper motors rated at? 2.5 A

I'm not familiar with that Toshiba.. Does it include "everything", or do you have separate drivers? I mean, what components are between the computer and steppers? Only 1 board? yes, Only one board with 3 chips (similar to xylotex).

[neilw20]

The driver settings, set the current.
The steppers must be able to withstand the current.
The power supply must be able to supply all of the current required.

If a driver is set to, for example 2A, that is 2A per winding, and when micro stepped halfway between the phases, that will be 2.8A each axis.

The current setting is purely a function of the driver, the stepper must not overload the driver, by not having enough inductance,
and the power supply must supply a voltage within the voltage rating range of the driver.

At initial switch on the driver will draw almost no current, so the power supply MUST NOT exceed the driver voltage rating, when unloaded.
Also at the full current required by the driver, the power supply voltage must drop below the minimum rated voltage of the driver.

Any specs outside of the driver specs will cause malfunctioning, and or destruction.

You must observe all driver specifications, including bypass capacitors right at the supply terminals of the driver.

Intermittent, loose or switched stepper wiring will usually destroy a driver.

Rotating stepper motors generate voltage. Rotating a stepper motor rapidly with no power on the driver can destroy some drivers.

The bottom line. To do it properly, you need to refer to the driver specifications, and application notes.

[hub]

No i don't think that formula is quite correct in real life.. Yes, if all 3 motors run at the same time the current is equal for all 3 motors. But, for example if only 1 motor is running (for example only X axis moving), the PSU will supply all it can to that 1 motor (if current setting is high), the other 2 are in "rest mode", usually using much less power.
The driver current setting limits the amount of current to the motors.
If you have a multimeter, measure the amps from the psu:
1) at "rest", 2) when running only one motor.

If you can't find data on motors & board etc. Then I would start with the lowest setting (25% in your case?) and see if enough torque is produced with that. If not, go step by step higher.

[neilw20]

hub,

Stepper motors may draw reduced current when stationary IF the driver facilitates reduced current when stationary, and if this is the case then the driver usually has the option for power reduction.

It would appear that from the initial symptoms of the failure that the power supply has sagged, and the voltage has gone below the minimum spec for the driver. Usually causes significant heating, and may cause failure.

The safest way to test these things is to get ONE axis going, and do measurements to ensure specification are not exceeded.
Then multiply the worst case current measured by 3.
The worst case supply current will be when microstepped between steps, with equal current in both windings, and at this point will be 1.414 times the current when only one phase is fully on, and the other off.

Refer to the specs if 100% confidence and reliable operation is needed, and why should it be any other way?

Making assumptions, about the specs, often causes unexpected results. Microstepping drivers are quite complex, and everything has to be right so that switching device specifications are not exceeded.