[H.O]

OK, I'm glad you solved that part of it. What type of breakout board is this?

I'm not sure what kind of sugestions you are looking for.... The numbers doesn't mean anything to me since I don't know you steps/inch, gearing, leadscrew pitch, maximum motor speed etc.

If you have 60ipm set up in motortuning it doesn't matter if you go above 100% feed, it won't go faster than 60ipm...

/Henrik.

[ahmedrehan]

OK, I'm glad you solved that part of it. What type of breakout board is this?

I'm not sure what kind of sugestions you are looking for.... The numbers doesn't mean anything to me since I don't know you steps/inch, gearing, leadscrew pitch, maximum motor speed etc.

If you have 60ipm set up in motortuning it doesn't matter if you go above 100% feed, it won't go faster than 60ipm...

/Henrik.

I was seeing your HP UHU circuit in which 1r21844 is conected directly to mosfet gate through 22ohm resistor but in my pcb there are these 12volt surge protection diodes which are not preforming well should i also drive mosfet directly with ir2184 removing extra parts.

Ahmed

[H.O]

Ahmed,
I'm not the designer of the HP-UHU and I'm no expert on mosfets etc but I guess the idea with the diodes is to make the MOSFETs turn off faster than they turn on. (If they are connected in parallel with the resistors which I think they are from your description?). I can't tell if it will work better if you remove them - I guess one way to find out is to try it or ask the designer of the circuit you are using.

It seems to work fine on the HP-UHU but as you've notices it uses the 21844 with adjustable deadtime while the 2184 has a fixed 500nS deadtime - I don't know if that is part of the puzzle.

[contactirfu]

a very interesting reading as usual - continue folks - very informative too.

[ahmedrehan]

Ahmed,
I'm not the designer of the HP-UHU and I'm no expert on mosfets etc but I guess the idea with the diodes is to make the MOSFETs turn off faster than they turn on. (If they are connected in parallel with the resistors which I think they are from your description?). I can't tell if it will work better if you remove them - I guess one way to find out is to try it or ask the designer of the circuit you are using.

It seems to work fine on the HP-UHU but as you've notices it uses the 21844 with adjustable deadtime while the 2184 has a fixed 500nS deadtime - I don't know if that is part of the puzzle.

I will test 2184 without diodes as the data sheet also show direct drive. will post the result.

also to your previous question:

My setup for motor is

steps per inch = 2500
velocity= 60 ipm
acc=2 i/s/s

Ahmed

[chrugel]

Ahmed,
I'm not the designer of the HP-UHU and I'm no expert on mosfets etc but I guess the idea with the diodes is to make the MOSFETs turn off faster than they turn on. (If they are connected in parallel with the resistors which I think they are from your description?). I can't tell if it will work better if you remove them - I guess one way to find out is to try it or ask the designer of the circuit you are using.

It seems to work fine on the HP-UHU but as you've notices it uses the 21844 with adjustable deadtime while the 2184 has a fixed 500nS deadtime - I don't know if that is part of the puzzle.

H.O is very right here, the gate diode is to create faster turn off times since the discharging of the internal gate capacitance of the mosfet is done faster.
The original 1n4007 diodes here is way to slow to make this happen, replace them with high speed ones. 50nS or less to get the desired effect.
I have successfully used the original design (with some modifications) at 140V flawlessly.
see this thread for more information.

regards
chris

[ahmedrehan]

H.O is very right here, the gate diode is to create faster turn off times since the discharging of the internal gate capacitance of the mosfet is done faster.
The original 1n4007 diodes here is way to slow to make this happen, replace them with high speed ones. 50nS or less to get the desired effect.
I have successfully used the original design (with some modifications) at 140V flawlessly.
see this thread for more information.

regards
chris

hi chris

what were the modification you used? can you post the changes

regards
Ahmed

[ahmedrehan]

Hi Henrik,

Should i isolate the computer ground from UHU ground and machine ground? as again there are some Ocounts also do i need to reduce the voltage of servo motor? or increase the capacitor Bank.
Ahmed

[H.O]

It's really hard to say as each system is different but you should aim for a single ground point - called star ground.

Take the -ive of you motor powersupply to this point, take the -ive of the logic supply (12v) to this point. Take the the two GND connections on the UHU to this point. Connect the motorcable shield (if you have) to this point as well. Use shielded cable for the encoder and connect the shield to the same ground-point.

The UHU has opto-isolators on the inputs so you shouldn't need to do anything in particular with the PC GND.

And don't forget to check the capacitors on the SN75115 that I mentioned earlier. If you have them mounted, try removing them or replacing them with 22pF or something like that.

[ahmedrehan]

It's really hard to say as each system is different but you should aim for a single ground point - called star ground.

Take the -ive of you motor powersupply to this point, take the -ive of the logic supply (12v) to this point. Take the the two GND connections on the UHU to this point. Connect the motorcable shield (if you have) to this point as well. Use shielded cable for the encoder and connect the shield to the same ground-point.

The UHU has opto-isolators on the inputs so you shouldn't need to do anything in particular with the PC GND.

And don't forget to check the capacitors on the SN75115 that I mentioned earlier. If you have them mounted, try removing them or replacing them with 22pF or something like that.

Hi Henrik,

Today i made the the single ground for 12volt uhu motor supply and encoder sheild. Thank GOD the problem for o counts was solved. But another problem in x drive started as i gave command to x servo the uhu chip strarts to reset many times any sugestion but the z drive works fine.

Ahmed

[chrugel]

hi chris

what were the modification you used? can you post the changes

regards
Ahmed

Hi Ahmed,
Really sorry for the late reply.
What i changed was the Snubber circut at the output, replaced the original R C snubber with the configuration used on the HP UHU. I also changed the output transistors form the IRFP260 to IRF640 to get lower turn on and off times. Also replaced all the diodes with high speed ones. And I also placed 100k resistors from the output to Motor supply +.
If you have any questions feel free to ask.

regards
Chris

[ahmedrehan]

Hi Ahmed,
Really sorry for the late reply.
What i changed was the Snubber circut at the output, replaced the original R C snubber with the configuration used on the HP UHU. I also changed the output transistors form the IRFP260 to IRF640 to get lower turn on and off times. Also replaced all the diodes with high speed ones. And I also placed 100k resistors from the output to Motor supply +.
If you have any questions feel free to ask.

regards
Chris

Thanks for your reply i have done the same changes except the mosfet i used irfp264 same as in HP-UHU.

[H.O]

Hi Ahmed,
It sounds like you still have a grounding issue somewhere that causes noise to get into the circuit resetting the UHU-chip. I've read about this happening with the old design so if you search the UHU threads here perhaps you can find some pointers. Make sure you have solid low resistance, low inductance ground connections, also try placing an extra 100nF cap right across the power pins on the UHU chip. You could also try lowering the value of the pull-up resistor on the reset-pin of the UHU controller.

Please note that this is just ideas, without being able to see (with a scope) what is happening it's really hard to say. But, again, I've read that this can happen with the old desing so look around and perhaps you'll find a solution.

/Henrik.

[chrugel]

Thanks for your reply i have done the same changes except the mosfet i used irfp264 same as in HP-UHU.

Just be aware that this device has a very high gate capacitance so you could get cross conduction at high voltages since the driver has a fixed delay of 500ns. In the HP UHU design they use a variable one that is set to 1000ns i think.

regards
chris

[kreutz]

Thanks for your reply i have done the same changes except the mosfet i used irfp264 same as in HP-UHU.

That is the problem, you are having cross-conduction problems, that is why your UHU chip is resetting. That is also the reason of the HP_UHU modification.

[kreutz]

Just be aware that this device has a very high gate capacitance so you could get cross conduction at high voltages since the driver has a fixed delay of 500ns. In the HP UHU design they use a variable one that is set to 1000ns i think.

regards
chris

You are right.

[chrugel]

That is the problem, you are having cross-conduction problems, that is why your UHU chip is resetting. That is also the reason of the HP_UHU modification.

If you dont need the high current capabilities of the HP UHU design ahmedrehan you could use the IRF640. This devis has seriously low gate capacitance and should give you the possibility of up to 160 V and maximum 3-5 amps without cross conduction.

regards
chris

[kodalo]

Hi Ahmed,

Here's a screenshot of the UHU terminal software. I added some text to it.... The motor is an Indramat PMDC servo rated at 19A continous, 150A peak. Drive is HP-UHU with current limit set to ~20A. Encoder is 625lines (2500 counts/rev). I wish there was some kind of scale in the software so you could see just how big the error actually is.....oh well....


The motor is still on the bench so it's not driving anything. I suspect that actually driving a load will dampen the small ringings a bit but will most certanly require retuning.

I had Mach3 loop thru a simple test like this:
G0 X25
G4 P1.5
G0 X0

And here's a screenshot of the motor tuning dialog in Mach3:

You can see that I have the steps/unit set to 2500 which is the number of steps in one revolution and the speed is set to 1800rpm. It accelerates to 1800 in roughly 0.25 seconds.

When running with the UHU-terminal active (ie the Analyzer is turned on) I get some O-counts at this speed but not if I turn off the analyzer.

Hope this helps.

/Henrik.

Hi,
I have the old layout (20/10/2005) and problem with position error. I am using encoder with 500 lines. There is no O-count, but motor always go left. More precisely, if I have started from 0 and G01 X100, G01 X0, (several times)…. G01 X0 after some period it finished at X -2 or similar, not at 0. Analyze shows that left point (X100) has smooth sinusoid (only few oscillations), but changing direction at 0 has more and bigger amplitudes.

It looks like that:

 
                        0 --------- 100
                        --------- 
                      --------- 
                     --------- 
                    ---------

I have tried various paremeters, but without success.
Motor is "pancake" type, and table with specification is damaged, but I think is has 3000 rpm and 90V. I have tried various voltage, but only 16V and slow rev gave acceptable result.
A also have tried with other motors with known specification (24V) and try with voltage up to 30V (115% of nominal) but simptoms are the same.

Why my controller alway run left?

[ahmedrehan]

Hi,
I have the old layout (20/10/2005) and problem with position error. I am using encoder with 500 lines. There is no O-count, but motor always go left. More precisely, if I have started from 0 and G01 X100, G01 X0, (several times)…. G01 X0 after some period it finished at X -2 or similar, not at 0. Analyze shows that left point (X100) has smooth sinusoid (only few oscillations), but changing direction at 0 has more and bigger amplitudes.

It looks like that:

 
                        0 --------- 100
                        --------- 
                      --------- 
                     --------- 
                    ---------

I have tried various paremeters, but without success.
Motor is "pancake" type, and table with specification is damaged, but I think is has 3000 rpm and 90V. I have tried various voltage, but only 16V and slow rev gave acceptable result.
A also have tried with other motors with known specification (24V) and try with voltage up to 30V (115% of nominal) but simptoms are the same.

Why my controller alway run left?

Which breakout board you are using ? try to bypass the optocoupler on breakout board . if you are using laptop then check the result with desktop pc
else your left side circuit of uhu has fault maybe faulty ir2184 or some diode.
check the waveform on oscope at the input / output of bridge circuit.

Ahmed

[kodalo]

Which breakout board you are using ? try to bypass the optocoupler on breakout board.

There is no additional BoB. Only optocoupler on main (UHU PCB CNCECKE from http://www.gertronik.de/cncecke/servo.zip)
What is suggestion for breakboard?

if you are using laptop then check the result with desktop pc

No I am using desktop, but I can try with laptop.

else your left side circuit of uhu has fault maybe faulty ir2184 or some diode.

I have two identical boards and both of them has similar symptoms, so I think components are OK.

check the waveform on oscope at the input / output of bridge circuit.

I will see it.