[JakeHappiness]

Hello Tom,

I am installing a KSnap with dual SnapAmps.

I have Both X, and Y axis going with step response.

I have been fighting with power supplies trying to use the old one..

In the meantime, I have a 10 Amp 30 V supply that I have been using to power the amps one axis at a time.
When I look at the Analog screen for the X and the Y, Channels 0 and 2, on SnapAmp0 I see the 30V displayed as expected.
When I have the power hooked to SnapAmp1 Channel 4 for Z, I am only seeing about 19 volts or so and the unpowered axis on SnapAmp1 shows 2.9 or 3.0 V instead of the 1.1-1.6 that normally displays when there is no external power.

It is possible that SnapAmp1 saw 100V briefly on its input connector when old power was first hooked up. Could that have blown something and be the cause of this?

Thanks and Happy Holidays!

Jake

[JakeHappiness]

Additionally, when I run the program to set Amp limits the voltage for both amps on KFLOP1 go to 1.6V. They stay at that until KFLOP is rebooted.

More background info. Motors are 8 wire steppers wired as two series sets. They are rated I believer for 80V 8Amps. (Anyway that I can set amp limit to 9.5 for 8 Amps?)

Happy day,

Jake

[JakeHappiness]

Here is the init code for the motors:
// peak current limits

WriteSnapAmp(SNAP0+SNAP_PEAK_CUR_LIMIT0,10);
WriteSnapAmp(SNAP0+SNAP_PEAK_CUR_LIMIT1,10);
WriteSnapAmp(SNAP1+SNAP_PEAK_CUR_LIMIT0,10);
WriteSnapAmp(SNAP1+SNAP_PEAK_CUR_LIMIT1,9);
// clamp supply to 40V
WriteSnapAmp(SNAP0+SNAP_SUPPLY_CLAMP0 ,SNAP_CONVERT_VOLTS_TO_ADC(40.0));
WriteSnapAmp(SNAP0+SNAP_SUPPLY_CLAMP1 ,SNAP_CONVERT_VOLTS_TO_ADC(40.0));
WriteSnapAmp(SNAP1+SNAP_SUPPLY_CLAMP0 ,SNAP_CONVERT_VOLTS_TO_ADC(40.0));

// enable supply clamping
WriteSnapAmp(SNAP0+SNAP_SUPPLY_CLAMP_ENA0 ,1);
WriteSnapAmp(SNAP0+SNAP_SUPPLY_CLAMP_ENA1 ,1);
WriteSnapAmp(SNAP1+SNAP_SUPPLY_CLAMP_ENA0 ,1);

[TomKerekes]

Hi Jake,

If you applied 100V to SnapAmp it might have been damaged especially if a lower voltage clamping was enabled.

With the 30V applied to SnapAmp #1 and it is displaying only 19V what is the actual voltage of the supply? Is something getting hot?

Stepper Motors usually have a rating of a few volts (not 80V). Even though a much higher voltage supply is normally used to drive them.

Regards

[JakeHappiness]

HI Tom,

Perhaps I am mistaken about the motor voltage. I am an ME and have worked my career around brushed servo motors.

I do not think there was any voltage clamp applied at the time, as I was just first hooking it up. My supply had been putting out a really nice 75Volts. After my first hook up, I measured, and one of the three was 100 and two were 32 or so.

Have been fighting with the supplies since. About ready to give up. Are there supplies that you recommend?

Is there a diagnostic test that you might recommend to tell if I have ruined the SnapAmp?

It measures 30V at the connector pins.

Thanks,

Jake

[TomKerekes]

Hi Jake,

No specific recommendations on a supply. Either switching or linear as long as the peak voltage is less than 80V and with enough power to meet your requirements.

If you disconnect everything from SnapAmp (except KFLOP) and apply only the Motor Supply then power up (without configuring anything) the reported voltage in Kmotion.exe should be within several volts of the voltage you measure with a voltmeter at SnapAmp. If not most likely SnapAmp has been damaged.

Regards

[JakeHappiness]

Tom,

It looks like one SnapAmp is damaged.

Is it repairable or do I need to buy a new one?

If repairable, can you estimate time frame and tell me where to send it?

Happy day, Happy holidays,

Jake

[TomKerekes]

Hi Jake,

Sorry to hear that. If you send us the board we can test it and try to analyze what the problem is and if it can be easily repaired. However in many cases it isn't cost effective to repair if it isn't something simple. Testing will take ~1week. There is no charge if the board is not repairable. Contact our support email for an RMA#

Regards

[JakeHappiness]

Hello Tom,

Is it possible to have current limits between 6 and 10 Amps? The motors in my machine are rated for 8.2A so at 6 I am at 3/4 power at best. At 10 I risk blowing them out right?

Thanks and happy day,

Jake

[TomKerekes]

Hi Jake,

Is it possible to have current limits between 6 and 10 Amps? The motors in my machine are rated for 8.2A so at 6 I am at 3/4 power at best. At 10 I risk blowing them out right?

SnapAmp has both low side current control and high side peak curent fault detection. The high side peak current fault is only designed to protect things like a "screwdriver" short to GND. Set that to the next highest level than needed for normal operation.

KFLOP+SnapAmp will use the low side current control to provide sinusoidal currents to the coils with an Amplitude of 8.2Amps using the Microstepping Amplitude parameter. The Microstepping Amplitude parameter has a range of 0 - 1023 which corresponds to a current from 0 - 35 Amps. So for 8.2A set the parameter to:

8.2 / 35 x 1023 = 239

BTW as a side note you may find that the overall performance (and motor power) is the same regardless of the current setting of 8.2 vs 6.0 Amps. The higher current setting will have higher holding and low speed torque, but that is a zero to low power situation and not usually an issue. At higher speed (and power) the motor current will drop regardless of the setting because the available supply voltage, motor back-emf, and motor inductance will limit the current flow.

HTH
Regards

[JakeHappiness]

Hi Tom,

I shipped the board back to you. Looks like it almost got there but no one was home?

https://tools.usps.com/go/TrackConfi...99300460573679

[JakeHappiness]

Hello Tom,

Quick summary of my project. Old Bridgeport CNC. Old 8 wire steppers wired as unipolar. Open loop.

I finally have a good clean stable 60V supplies for my 3 axis. I have both X, Y Moving with step response and jogging with KmotionCNC.

A few more questions that I have not been able to find answers to searching the forum.
-I assume that I will need a few lines of code to tell the KFlop what pins my limit switches are hooked up to. How do I do that.
-Does all scaling happen (so that CNC knows what 1 inch is) with the inverse distance per cycle parameter?
Happy day,

Jake

[TomKerekes]

Hi Jake,

I'm out of the office this week, I should be able to get it next week.

Regarding Limit Switches see the Limit Switch Options on the Config/Flash Screen.

Scaling is performed in the Application - either Mach3 or KMotionCNC. Do not use the invDistPerCycle Parameter.

Regards

[JakeHappiness]

Thanks!

[JakeHappiness]

Hi Tom,

I have all three axis working nicely with KmotionCNC (I have substituted 3rd axis into first board to test while you fix the blown board). Calibration is dead on for all three.

Next question. Limit switches and homes.

Two of my axis have mechanical snap type limit switches that act as a limit at each end of the axis. When tripped it is just a closed contact.

A few question about these.

Is JP7 on the KFLP board pins 19-22 the best place to connect these?
Or should I use the JP7 Connector on the SnapAmp?

Is the correct way to connect these NO switches is to connect with pull down Resister (1M Ohm??) to 3.3V on JP7 Pin 1 or 2 and then connect switch across sense pin and ground?

Last, can I use the same bit for + limit and - limit? Will KFLOP understand the direction it was driven into, to use "Do Not Drive Into Limit"??

Thanks,
Jake

[JakeHappiness]

Hi Tom,

With the 1Mohm, I get lots of noise on the limit switch pins on the KFLOP board JPIO7. I tried 1Kohm instead and it is much improved but I didn't want to go farther without checking with you.

I am considering running shielded twisted pair to the switches to reduce noise. Do you have other suggestions? Should the ground on the KFLOP be tied to chassis ground of the machine (earth ground?)

Made my first chips today!

Thanks,

Jake

[TomKerekes]

Hi Jake,

I don't understand the description of your limit switch wiring (pull up or down?). 1K ohm would be a more reasonable value.

But SnapAmp has 12V opto isolated inputs. So it would be better and simpler to use those. They will provide some noise filtering as well.

Use an isolated 12V supply and connect the +supply to the opto plus, the opto neg to your switch, with the other side of the switch to the -supply.

Grounding is very complex but It usually not a good idea to connect the KFLOP DC GND to Earth GND.

To use Disallow Drive Into Limit mode it is simplest to have separate inputs for both ends of travel.

HTH
Regards
TK

[JakeHappiness]

Hi Jake,

But SnapAmp has 12V opto isolated inputs. So it would be better and simpler to use those. They will provide some noise filtering as well.

TK

Optos worked great. Used a 12V Wall wort. (12.3V)

Thanks!

Any idea when I might see my SnapAmp that you have in for repair?

Thanks and happy day,

Jake

[TomKerekes]

Hi Jake,

We received the SnapAmp back. We can't find anything wrong with it. What exactly were you seeing? We did notice you had the SnapAmp #1 JP5 jumper in it. To operate a single SnapAmp it must have the jumper removed to be SnapAmp #0. Did it work at all for you? I thought you said the Supply Voltage readings were incorrect?

Regards

[JakeHappiness]

Hi Tom,

I had this as the second SnamAmp. #0 is still working fine.

I subjected the motor power in to about 100V DC.

After that when I had 30V hooked up for motor supply voltage it would read 18V or something weird like that looking at the analog screen. SnapAmp #0 read very close to the supply voltage.

Thanks,

Jake