[H.O]

Hi guys, and welcome back Kreutz!

After experiencing the exact same as Jozsi did, where the motor was stiff in one direction and sluggish in the other I replaced U9 since that fixed Jozsi's drive up. However, mine is still behaving strange.

Background:
Replaced C28 with 4.7uF/25V tantalum cap.
Replaced R54 with jumper wire
Placed 1N4148 between R54 and GND, cathode facing GND
Replaced R21 with 4.7k resistor.

Ref1 voltage measures to 2.96V, Vref set to 80mV, VrefOC measures to 180mV.

1) 60V powersupply, everything seems normal, motor feels and sounds the same in both direction - slow limit LED does not come on, no matter what though.

2) 90V powersupply, motor stiff in one direction sluggish in the other, slow limit LED never comes on. Vpp across sense resistor seems to match VrefOC when turning the shaft one directiona and Vref when the turning the shaft in the other direction - VERY noicy though.

3) 120V powersupply, motor stiff in one direction sluggish in the other, slow limit LED never comes on. Measurements as with 90V supply.

4) Backing off the powersupply voltage to around 60V and it's back to "normal" again. That is peak-current all the time.

I've desoldered and checked the Schotky diode and I've replaced U9 a second time but the results are exactly the same.

All ideas appreciated!

/Henrik.

[kreutz]

Hi
I just bougt a set of UHU controllers and one of these is supposed to drive a motor rated 130V 1A.
Can i just replace the IRF540 with IRF640 Fets since I'm not talking very high currents? Of cause all capacitors would also nee to be replaced with higher voltage rating.

Regards
Chris

I would try it before saying it won't work, you don't have anything to lose, if possible get a variac and increase the power supply voltage little by little to see if it does not smoke.

Kreutz.

[kreutz]

Hi guys, and welcome back Kreutz!

After experiencing the exact same as Jozsi did, where the motor was stiff in one direction and sluggish in the other I replaced U9 since that fixed Jozsi's drive up. However, mine is still behaving strange.

Background:
Replaced C28 with 4.7uF/25V tantalum cap.
Replaced R54 with jumper wire
Placed 1N4148 between R54 and GND, cathode facing GND
Replaced R21 with 4.7k resistor.

Ref1 voltage measures to 2.96V, Vref set to 80mV, VrefOC measures to 180mV.

1) 60V powersupply, everything seems normal, motor feels and sounds the same in both direction - slow limit LED does not come on, no matter what though.

2) 90V powersupply, motor stiff in one direction sluggish in the other, slow limit LED never comes on. Vpp across sense resistor seems to match VrefOC when turning the shaft one directiona and Vref when the turning the shaft in the other direction - VERY noicy though.

3) 120V powersupply, motor stiff in one direction sluggish in the other, slow limit LED never comes on. Measurements as with 90V supply.

4) Backing off the powersupply voltage to around 60V and it's back to "normal" again. That is peak-current all the time.

I've desoldered and checked the Schotky diode and I've replaced U9 a second time but the results are exactly the same.

All ideas appreciated!

/Henrik.

Henrik,

We live a little far away, otherwise I would like to take a close look at your drive. Can you please e-mail me some photos of the power part of the board?. You already have my e-mail address.

What is the measured voltage and maximum current spec of the +15 v power supply you are using?

I suggest bypassing the slow limit as in the modification instructions a couple of posts back. Then tell me the results when doing the same tests. Remember to re-adjust the potentiometer to the maximum continuous current of the motor after the modification.

Eliminating the Slow/Fast operation by replacing C28 by 470 pf ceramic capacitor, eliminating R20 and soldering a jumper wire across R54, while applying a 1N4148 diode across the potentiometer with the anode connected to the R54 jumper wire and cathode to ground, and replacing R21 by 4.7 Kohm 1% 1/4 watt resistor. After that modification, the current limit circuit will work like in the original UHU circuit.

Voltage measured at the sense resistors is normally noisy, a lot less noisy when measured at the D16 cathode.

Is this the same pcb that had the copper bridge in one of the Mosfet driver's chips? I suspect something funny with the PCB. Do you have the chips mounted on IC sockets? If they are; Disconnect the motor power supply cables, take out U9 from the socket, turn on the 15 v power supply. Does the Current limit LED light up? Are the pin# 2 voltages on both U7 and U8 at a LOW logic level?

Thanks,

Kreutz.

[jcdammeyer]

Is this the same pcb that had the copper bridge in one of the Mosfet driver's chips? I suspect something funny with the PCB. Do you have the chips mounted on IC sockets?

Thanks,

Kreutz.

Hi,

These types of problems appear to be somewhat similar to the problems I've had with the Embeddedtronics.com version of the UHU servo board. In my case, in one direction I had torque and the current limit light came on but twisting the motor shaft in the other direction caused the UHU Atmel processor to reset most often also destroying all the EEROM parameters.

I've ordered a more standard board from Manjeet which he tells me is on it's way and I've been trying to pay Paul for an HP UHU version but I think he's really busy at the moment.

I've read previously that the Atmel processor is very sensitive to noise. My guess is that somewhere along the line one of the processor input (or output pins) is going above 5V which makes it seem as if the processor reset has been brought to ground causing my dramatic reset and damage.

It may be worthwhile to examine layout etc. to see if ground bounce is causing some of these other good/bad torque depending on direction.

John

[kreutz]

Hi,

These types of problems appear to be somewhat similar to the problems I've had with the Embeddedtronics.com version of the UHU servo board. In my case, in one direction I had torque and the current limit light came on but twisting the motor shaft in the other direction caused the UHU Atmel processor to reset most often also destroying all the EEROM parameters.

I've ordered a more standard board from Manjeet which he tells me is on it's way and I've been trying to pay Paul for an HP UHU version but I think he's really busy at the moment.

I've read previously that the Atmel processor is very sensitive to noise. My guess is that somewhere along the line one of the processor input (or output pins) is going above 5V which makes it seem as if the processor reset has been brought to ground causing my dramatic reset and damage.

It may be worthwhile to examine layout etc. to see if ground bounce is causing some of these other good/bad torque depending on direction.

John

Thanks, John;

I use the same Atmel processor on my unipolar and bipolar stepper drives, so far had never had any problems losing EEPROM parameters or resetting themselves, they both work at 39Khz a little over the 23 Khz PWM frequency of the UHU chip. Ground noise or noise picked up by the 5 volts power supply could be responsible for the bad behavior. On the original UHU there was cross conduction even at low voltages, that could explain a lot of ground noise on the board.

In our case, I can not rule out something similar yet, but I doubt it is cross conduction induced noise because the HP design uses a 1 usec dead-time (Unless there is less than 100K to ground at pin#4 of U7 or U8). I also took good care when designing the ground planes, but it might be worth investigating further into the problem...Don't know yet if the UHU chip is resetting because of brown-outs, that is why I asked for the specs of the 15 volt power supply. It would be pretty obvious because of the LEDs changing status during reset.

Henrik's suspicion on the current limit circuit seems to be more plausible, I still want to know why it is failing/misbehaving in one direction and not on both directions since the current limit circuit should be indifferent to motor direction or to which side of the H bridge is active.

Regards,

Kreutz.

[HJozsi]

Hi,

These types of problems appear to be somewhat similar to the problems I've had with the Embeddedtronics.com version of the UHU servo board. In my case, in one direction I had torque and the current limit light came on but twisting the motor shaft in the other direction caused the UHU Atmel processor to reset most often also destroying all the EEROM parameters.

I've ordered a more standard board from Manjeet which he tells me is on it's way and I've been trying to pay Paul for an HP UHU version but I think he's really busy at the moment.

I've read previously that the Atmel processor is very sensitive to noise. My guess is that somewhere along the line one of the processor input (or output pins) is going above 5V which makes it seem as if the processor reset has been brought to ground causing my dramatic reset and damage.

It may be worthwhile to examine layout etc. to see if ground bounce is causing some of these other good/bad torque depending on direction.

John

Hi John,

I built two Embeddedtronics UHU board and they work well with my small servo motors ( Elektrocraft E240) I like them, they are Gecko size, small. I had no torque difference problem in the different directions... I had only problem with bigger motors: processor reset and EEPROM parameter damage like your experience... But I can tell you that the same problem had with original UHU pcb on higher voltage and current ... Just read back Kreutz's post and you will find some of the reason for that... Man can consider to try some signal isolating complements with additional components and boards it might help. My recommendation would be ruther a HP UHU board. Kreutz and the HP UHU team made exellent job, I can tell you based on my tests ( 1kW 85V 15A servo motor with 137V 1kVA power supply )
there are some videos in the previous posts... On the HP UHU board the Amtel UHU chip is rock solid, NEVER happened a reset or EEPROM damage, NEVER! Not even when I set the current limit too high, and the load of the lathe as well and then I had to replace two Fets ... I've just made the change in the current limit according to Kreut's advise and now it is running again...

The Embedded board is good for the range they specify and they tested. If you look at the board, you can see the Amtel chip is only 1mm(!) distance from the power stage. Even it is gnd, there are interesting signals (waveforms ) running ...

Regards,

Jozsi

[jcdammeyer]

The Embedded board is good for the range they specify and they tested. If you look at the board, you can see the Amtel chip is only 1mm(!) distance from the power stage. Even it is gnd, there are interesting signals (waveforms ) running ...

Regards,

Jozsi

Hi Jozsi,

I disagree about the Embedded board being good for the range. I'm running a 2.7A 24V motor and even with the current set way back, I'm still having issues. I agree about the layout. My other gripe is it's almost impossible to service the board because of the way the components are installed and the way the layout is done.

But, I suspect, perhaps like the original UHU board, that the UHU hardware design might also be a bit component tolerence sensitive. i.e. The first 5 prototypes work perfectly in the lab. The next 1000 in the production run all exhibit the same problem... what in the world is wrong????

The HP UHU board with other different driver may be a large part of the improvement. What I like about the UHU is that at the moment it's a nice black box with a proven track record. If something goes wrong for now we can lay the blame on the harware or the layout. Having been on the receiving end of the "it must be the software" this is kind of a nice change.

John

[cnc2]

################## Newbie here ! ######################

Hi every body on the forum !

I'm about to build a 3 or 4 axis machine & i wanted to drive it with servos, i was thinking about the UHU controller but i didn't know where to find the official info about the latest version, so, my quetions are :

1) If someone can tell me where to find the latest version files for making the UHU controller & tell me the differences between the different versions(power, building price, PCB ...etc) ?

2) Which step/dir parallel interface are you using ? is this one suitable for UHUs http://pminmo.com/4axisopto/4axisDIYopto.htm i'm not sure because the board function is stated "4 Axis fast OptoIso interface" & it's current limiting is stated "DB25 to IDC with High Speed Opto Isolators" & there is no user's manual, does it include all what is needed for a milling machine (limit switches,spindle ...etc) ?

3) What do you think about the Ametek 38vdc servos from surpluscenter ?(if you are using them please let me know about the performance they are reaching & their rear shaft diameter) or if you know a better performance to price ratio let me know ?

4) What encoders are the best & cheapest (or salvaged) for UHU & what is limiting the resolution to 1000 line encoder on UHU (assume the motors are 1200 rpm max) ?

Thanks !

cnc2. (if there's something wrong with my english please let me know !)

[contactirfu]

################## Newbie here ! ######################

Hi every body on the forum !

I'm about to build a 3 or 4 axis machine & i wanted to drive it with servos, i was thinking about the UHU controller but i didn't know where to find the official info about the latest version, so, my quetions are :

There is probably no new version, the version being discussed is the high power version redesigned by Kreutz.

1) If someone can tell me where to find the latest version files for making the UHU controller & tell me the differences between the different versions(power, building price, PCB ...etc) ?

Read thru the thread and you will get all the leads.

2) Which step/dir parallel interface are you using ? is this one suitable for UHUs http://pminmo.com/4axisopto/4axisDIYopto.htm i'm not sure because the board function is stated "4 Axis fast OptoIso interface" & it's current limiting is stated "DB25 to IDC with High Speed Opto Isolators" & there is no user's manual, does it include all what is needed for a milling machine (limit switches,spindle ...etc) ?

I tried building the board u mention, but did not find success in it. I went on to buy a candcnc.com board.

3) What do you think about the Ametek 38vdc servos from surpluscenter ?(if you are using them please let me know about the performance they are reaching & their rear shaft diameter) or if you know a better performance to price ratio let me know ?

i have no idea, probably some one else might answer!

4) What encoders are the best & cheapest (or salvaged) for UHU & what is limiting the resolution to 1000 line encoder on UHU (assume the motors are 1200 rpm max) ?

Most use US digital, its usually simple to buy them direct! i use 250cpr encoders

Thanks !

cnc2. (if there's something wrong with my english please let me know !)

[contactirfu]

Hurrah ! reached 150 pages today!

[H.O]

We live a little far away, otherwise I would like to take a close look at your drive. Can you please e-mail me some photos of the power part of the board?. You already have my e-mail address.

Will do when I get home later today. Anything in particular you want to see?

What is the measured voltage and maximum current spec of the +15 v power supply you are using?

It's a bench type lab supply, same one I've been using all the time. Voltage is set to 15.0V and it can supply 3A.

Is this the same pcb that had the copper bridge in one of the Mosfet driver's chips? I suspect something funny with the PCB. Do you have the chips mounted on IC sockets? If they are; Disconnect the motor power supply cables, take out U9 from the socket, turn on the 15 v power supply. Does the Current limit LED light up? Are the pin# 2 voltages on both U7 and U8 at a LOW logic level?

Yes, this is the same PCB as the one with the copper bridge. It didn't behave like this from the beginning though so something happened. I just can't find what and why the heck it's different depending on direction.

Originally I didn't have the chips in sockets but as I've been changing them I've put in good quality sockets with machined pins so I'll remove U9 and see what happens. I'll get back with the results later on.

Oh, I'm pretty sure that the uC is fine, no indication of brownout resets or anything like that.

Thanks!

/Henrik.

[rokag3]

hello.
looking for a good cheap encoder

http://catalog.digikey.com/scripts/d...me=102-1307-ND

it works perfect and gives you the opportunity to change the resolution with 4 microchips

also the axe system is very smart and it cost 30 us$ for 48 to 2048 lines !!!

on my hp board
Replaced C28 with 4.7uF/25V tantalum cap.
Replaced R54 with jumper wire
Placed 1N4148 between R54 and GND, cathode facing GND
my motor is 180v 8Amp cont. should I replace r21 also ?

[rokag3]

it works perfect and gives you the opportunity to change the resolution with 4 (microchips) MICROSWITCH

[kreutz]

hello.
looking for a good cheap encoder

http://catalog.digikey.com/scripts/d...me=102-1307-ND

it works perfect and gives you the opportunity to change the resolution with 4 microchips

also the axe system is very smart and it cost 30 us$ for 48 to 2048 lines !!!

on my hp board
Replaced C28 with 4.7uF/25V tantalum cap.
Replaced R54 with jumper wire
Placed 1N4148 between R54 and GND, cathode facing GND
my motor is 180v 8Amp cont. should I replace r21 also ?

Yes, It won't hurt to have it replaced. Is your current limiting circuit working fine?

I still need to find out why my prototype works perfectly fine with the original values. It might be because I use a low voltage low current motor, but on the tests done with Tenmetalman's motors it behaved good too even at 185 volts...

Hmmm, EUREKA!, I think I've got it....Will make some tests as soon as possible...nothing to do with U9, the PCB, motors or currents....it should be the recovery time of the Slow limit circuit...

Kreutz.

[H.O]

rokag3,
Glad you got one going too!

A couple of questions if you don't mind:

1) Does your fast slow limit work properly?
2) Can you make the Limit-LED light up by loading the motor?
3) Is you current limit set to 8A?

If the answer to any of the above is yes:
4) If you set the current limit lower than 8A, say 4A, does it still work?

Thanks!
/Henrik.

[rokag3]

hey,

i am going to start my trial today
so i cannot answear
but i will tell you as soon as possible

[H.O]

Hi,
With U9 removed the current limit LED turns ON as soon as the 15V powerspupply is turned on. It's quite dim though but that's probably due to the 1k series resistor. Put U9 back in and it behaves as before.

rokag3,
Sorry, I didn't mean to rush...take your time, let us know what you come up with, thanks!

/Henrik.

[LZ1TWB]

Hello
I want to know if the output transistor of the power dump circuit needs any additional cooling and how much it heats after some long period of operating?
I am designing my own PCB and need to know if I have to leave some place for a cooler to mount the FET on. Even not for a cooling purpose I will use some aluminum elbow because it just doesn't look good having this size of transistor waving alone in the air only on its legs. I could also bend it 90deg and bolt it on the pcb.
I may post some pictures when I am ready with the design later.
Todor

[HJozsi]

Hello
I want to know if the output transistor of the power dump circuit needs any additional cooling and how much it heats after some long period of operating?
I am designing my own PCB and need to know if I have to leave some place for a cooler to mount the FET on. Even not for a cooling purpose I will use some aluminum elbow because it just doesn't look good having this size of transistor waving alone in the air only on its legs. I could also bend it 90deg and bolt it on the pcb.
I may post some pictures when I am ready with the design later.
Todor

Hi Todor,

I had it tested only short period of time and open air not in a box. The dump activates itself only on higher rpm... While the 3 * 50W dumpresistors become warm a bit ( 30 - 35 C) the fet remained cold... For just safety reason I'll use a cooling plate. The fet must be totally off when inactive the circuit. If slightly open, it could heat... The foot of the fet are quite strong, in a closed box can't be any problem, the smaller parts have far weaker foot...
Waiting for your solution!

Regards,
Jozsi

[cnc2]

There is probably no new version, the version being discussed is the high power version redesigned by Kreutz.



Read thru the thread and you will get all the leads.




I tried building the board u mention, but did not find success in it. I went on to buy a candcnc.com board.




i have no idea, probably some one else might answer!



Most use US digital, its usually simple to buy them direct! i use 250cpr encoders

Thanks for the reply !
I asked about the UHU's latest version because i saw different PCB versions of the UHU & was lost, is the one in the servo.zip(2.39Mb) file up to date ?
Thank you !
cnc2