You should not measure the waveform on those pins, they are the gate drive outputs, have different reference potential, and it could be as high as the motor power supply voltage + 15V for the HO pins. Look at the waveforms I posted on the original UHU thread while troubleshooting the overheating snubber issue.
If you want to see the driver waveform look at U7 pin 1 and U8 pin 1 respectively, they should be measured with reference to P3 (GND test point), they will be 23.5 khz pulses U8 pin 1 inverted regarding U7 pin 1 waveform.
Hello from a very happy old man,
Thanks to the guidence and advice from this
forum i've just finished a totally successful test on my first hp-uhu
board.
thanks everybody.
mick.
HI Mick,
We should thank you and many others for taking up and trusting this relatively new design. Do elaborate on the tests you have done and the parameters you have set.
RGDS
IRfan
Hi,
A look at the kit -
Thank you Paul for the Picture.
RGDS
Irfan
Irfan,
i was hoping to upgrade my power supply to around 100 voltsbefore posting a reply but hav'nt managed it yet,
[/LEFT]The only parameters altered from the defaults are H 4000 and E 30,
the 70 volt motor has massive torque in both directions.
The only testing done was with a small Gcode subrutine varying speed
and distance, this was running for about an hour,no o counts.
The standard encoder 200 cpr is connected with the SN75115 removedand jumpers from the socket to j1 j2.
MACH3 is running at 25 kc,steps per mm 630, velocity 2164 mm the
acceleration was lowered until there was no error tripping.
rgds mick.
Is there a schematic available somewhere for the "power dump" circuit ?
You can find it in this post
/Henrik.
Hello,
I have just blown the output on my hp-uhu board,after weeks of being
meticulous, switching the logic first and then the power.
i connected both logic and power to the same toriod and BANG.
when the irf264's and thier drivers have been replaced what else
should i replace.
thanks.
mick.
can we have pictures mick.
rdgs
Irfan
Irfan,Kreutz,
Thanks for coming back,here are 3 shots of the damaged board.
hope you can see the burnt track around Q4, I hope to repair
this with copper wire hammerd flat.
this is the third time the mosfets have been replaced,and the
board is starting to look iffy!,already the small tracks to Q2 are
replaced with wire.
so i think just one more try before the Z axis on my lathe goes
back to steppers.
thanks for all the help and advice,
rgds mick.
Hi Mick,
I'm sorry to hear you've blown the MOSFETs.... You said you connected both logic and power to the same toriod. What exactly did you mean by that?
I'm not sure exactly what the UHU-chip does during "boot up" but you really should have the logic part powered up before applying the motor power supply.
The other times this happend, was it with the same motor, perhaps you have short in that motor...
/Henrik.
Is this one the only board with that problem?, Do you have other HP_UHU boards?
Maybe there is a defective component on the dead-time circuit (100K resistors) going from pin4 of the Mosfet drivers to GND. check also R22 and R28 (10 ohm) and D4 and D5. Check the PCB traces too.
Best regards,
Kreutz.
Hello Henrik,
The first time the mosfets blew was due to my ignorance,
not switching logic on first.
2nd time the 15v supply and powerside were wired from the
the same socket,i thought they would both come on together,
the drive worked until it was switched of,but the next time it
was turned on there was smoke!.
after the repairs i went back to manual switching logic and then
power,for weeks the z axis on my lathe ran ok.
but then i got hold of a toroid able to supply 70v ac there is
also a winding 12v ac which i used for the 15vdc supply,
the results were tragic,
if and when the board is ok after repairs,is there need to
fit a delay off timer to the logic supply as well as a delay on
timer to the power side.
rgds, mick.
Hi Mick,
I really can't tell you what is strictly neccessary. All I can tell you is what I've done: I have my motor powersupply switched on and off by a large contactor, this contactor is controlled by the E-stop circuit which gets its power from the low voltage powersupply. So, I can't turn on the motor power supply if the low voltage power supply isn't already on.
When I E-stop the system the contactor switching the motor power supply switches in a resistor across the capacitor bank that discharges it around 1.5second.
Obviously, if I get a power failure both the low voltage supply and the motor power supply will be switched off at the same time - I have no idea what happens then.... :-/ Hopefully there's enough capacitance in the logic supply to keep the drive alive long enough to prevent terminal damage....
Again, I've never had any problems like this myself but judging from others it seems it's a bit too sensitive this power sequencing thing :-/
I hope you can get it going again!
/Henrik.
cheers Henrik,
mick.
Merry Christmas!!
Kreutz.
Hello;
It's being a long time and in a last few days I have been exchanging e-mails with Henrik (H.O.). He has been involved in this little project since the beginning and I really appreciate his contributions, creativity and knowledge.
Resulting from our e-mail exchange is a modification to the HP-UHU current limit circuit that will make it a lot more reliable. The modification includes only an extra diode (1n4148) and resistor (2.2k 1/8W), as well as desoldering one lead from another resistor and reroute +15V to that lead. Integrator Capacitor (C28) should be a film capacitor rated at 25V or more.
Enjoy!!
kreutz