[H500]

Are you certain the sense resistor is .05 ohms? Are you sure it's not .5 ohms? Can you post a scope trace of the sense resistor waveform?

[Dzeus]

thanks for the reply, yes I'm using two 0.1 ohm 1W (brown/black/silver/gold) in parallel this should give me 0.05 ohm (2w); unfortunately I don't have a scope so I can't make such as probing :/ but I'll try with different resistor (I have 0.22 ohm )to see if there's any difference, Also I forgot to mention that I'm using 1µf TANTAL cap for STBY (C7 in your schematic) and for RESET too

[H500]

The tantalum caps should be fine.

I still suspect the resistors. Can you put an ammeter in series with one of the coils? Single step until the maximum current is reached. What current do you get? Note: do not connect or disconnect the coil when power is applied. It will kill the fets.

Can you post a photo of your board and power supply? I might be able to spot something.

[Dzeus]

Please H500 when you say in series do you mean one lead to A output and the second one attached to the ground ? or one lead to A and second one to A|
for The power supply the one I'm using is a generic chines (switching mode 24v/15amp). C12 is also tatalum (all 1µf are tantalum) btw
I'll change the sense resistor tomorrow and make the measurement after your confirmation about multimeter connexion and I'll take a better photos
Thanks

[H500]

Connect the meter as follow

driver A+ ----------- ammeter-------------stepper coil--------------- driver A-

[Dzeus]

I killed 4 fets before making the amp test (tried to run the driver without the diode in the mosfet gate) now I replace them and did the test; the Amp-metre show 0.74 amp to 1.11 amp when motor is running (jog) and various value with few step, I've got upto 7amp while the motor is in hold and when I turn on the driver, Also there's a difference in the value that I measured depending in which direction (clockwise / counter clk) . The resistor to set the current is 3.3k actually

[H500]

Be sure the ammeter is set to DC during the hold current measurement.

Is the holding torque much higher than the running torque?

If you are reaching 7 amps, then the driver appears to be working properly. It sounds like you have very high inductance motors. 24v power is not enough. As soon as the motor turn, the inductance prevent the current from ever reaching the set value. That's why the torque is so poor. Try a higher voltage power supply, 40-60v. For testing , the current rating only needs to be 1 amp or higher. See if it works better.

[Dzeus]

Yes the ammetre is set to DC and the Holding torque look much higher then the running torque, I'll buy a 48 volt power supply and test again.
The motor inductance is 6.8 mH /resistance 0.58 ohm and they are rated 5 amp
I'll test again and with different power supply and let you know
Many thanks

[H500]

6.8mh is very high. Your power supply voltage should be closer to 80v. I tested up to 60v, but 80v is theoretically still OK for the 100v fets. You might want to double check the calculations on the voltage sensitive components.

[Dzeus]

I bought some irf640 too, they are rated 200v but they are 18amp only , I'll try them with the 2nd driver (I need to recalculate the gate resistor) and I will build a power supply with transformer to get more then 60v and enough current for the 3 motors
Thanks

[yngndrw]

Well I'm really late to the party, but I thought I'd have a go at this.

I'm using a slightly different approach - I have a Spartan 6 FPGA dev board and have made separate generic H-Bridge boards for each phase.

Here's the board I've made for the H-bridges:
H-BRIDGE | Projects | CircuitMaker
https://oshpark.com/shared_projects/rcGSS2kY

The op-amp and related circuitry is done on stripboard. The current sense connections are done using thin coax and everything else uses small stranded wire.

It's not without its issues of course. There is likely some coupling between the signal wires, there are definitely some ground loops and I was an idiot who decided to use a 10k potentiometer with no buffer for the 0-3.3v current set reference, which obviously gets pulled down by the rest of the circuit. My op-amps are powered from the 3.3v rail as this wasn't specified and I'm using the FPGA's internal PLL to generate the 5MHz clock from a 100MHz crystal.

Aside from that it kind of works. With the corrected code, the correct waveforms are seen on the ASIN outputs, but when connecting the step input to a signal generator I've noticed that the motor steps slowly in one direction and then jumps back to its full-step. I've been struggling to work out what's best to trigger on but thinking about it the output of G05 is probably best. (It's the reset gate in the sine / cosine generator) Does anyone have any suggestions on what I should start looking at in order to help diagnose my problems ? I've confirmed that the APH and BPH outputs are the correct quadrature waveform and corresponds with the ASIN / BSIN outputs.

Also what does the potentiometer on the original circuit that's connected to a HV feed do ? I've noticed in one of the circuits in this thread the 330K resistor is replaced with a 1K resistor and it's connected to the current set reference instead of HV.

I really wish my oscilloscope had the MSO logic analyser option, but sadly I have to use a separate Saleae Logic 8 which isn't correlated with the analogue waveforms.

Edit: G24 confuses me, the diagram and text suggest that it should be "~QB[7] & ~QB[6] & ~QB[5] & ~QB[4]" but the code listing shows it as "QB[7] & QB[6] & QB[5] & QB[4]" - Which is correct ? I think my problem may be related to the standby / recirculation mode but I'll confirm that tomorrow.

Thanks,
-Andrew.

[yngndrw]

Quick update, I've tried the 10-microstep code from this thread and have tried disabling the standby functionality with no luck.

I just tried switching the two H-Bridges over and somehow blew them both, as well as damaging my Nexys 3 FPGA board as the H-Bridges now output 12V down the control lines - Hopefully it's just the protection diodes which have failed on the Nexys 3. The H-Bridges are now also driving both MOSFETs at the same time with no input.

Attached is a PDF with the schematic for the H-Bridge so that you don't need to register with circuit maker. Have I missed any important details which could make these fail ? My MOSFETs are from DigiKey but the drivers are from Ebay so it's possible they are fakes, they did seem to work before hand though.

My spare H-Bridge board (With the same Ebay drivers and Ebay MOSFETs) is still working fine with no voltage being output down the control lines so I'm not sure if it's a design fail or a part fail.

[Mariss Freimanis]

The way you have the 100K resistors connected is what's blowing up your bridge. R5 should go to the half-bridge output terminal, it must not go to the Q1 MOSFET gate! Get rid of R4, it is doing nothing useful and move R5 from Q1 MOSFET gate to its source (or to Q2 MOSFET drain).

Here's what happens when it's connected the way it is in your diagram:

When the bottom MOSFET Q2 is on, C4 charges to 12V through D1. C4 is a boot-strap capacitor that will supply 12V to Vbb for the 12V needed on HO to turn on Q1. The way you have it, R5 drains the charge on C4 when top MOSFET Q1 is turned on. When R5 drains the 12V volts on C4 down to 3V (in about 0.05 seconds), MOSFET Q1 goes into its linear region and quickly destroys itself (shorts) if a load is present. Look at your MOSFET SOA curve and you'll see how little current it takes to kill it in the linear region. For example, a 33A, 100V rated IRF540N is killed in 10 milliseconds with 1A drain current and 60V drain to source if it's allowed to go linear.

Mariss

[yngndrw]

Thank you very much Mariss.

I must have misinterpreted the your response from a few years ago when I showed you my last revision and then added R4/5/6/7. I'll get that change made and replace the drivers, fortunately I still have 4 spare driver ICs. Oddly the drivers are definitely dead, but the MOSFETs seem to have survived. (Or at least a far as I can tell with the diode test on my multimeter.) This error would also explain the issue I was having, where phase B would receive the B0 signal but never drive the coil.

I'll update the thread once I've made the fixes and re-tested.

[Mariss Freimanis]

I think what got misinterpreted was where R4-R7 go. The IR2104s have a 'peculiarity' that is addressed in a deeply buried application note. That ap-note says VS (pin 6) must be at ground potential when the IR2104 is initially powered up. VS connects to top MOSFET source / bottom MOSFET drain which forms the half-bridge output. The resistors insure VS is at ground potential and are sized to prevent them from burning up while the half-bridge is operating. 100K is scaled for 1/10W surface mount resistors and 100 VDC. Use Ohms = Volts^2 / Watts if you want to re-scale the resistors (60V^2 / 0.25 Watts = 15K).

Mariss

[yngndrw]

Everything was correct in your original post, for some reason I just misunderstood. It didn't help that I couldn't find the app notes that you were referring to in order to confirm the change, but nevermind I've now replaced the blown drivers and made the resistor changes. (See attached) Thankfully my soldering skills are better than my designing, debugging and reading skills !

I'm waiting on the replacement zener pack to fix my FPGA board, Digilent were very helpful by providing me with the correct part number but sadly I could only order it from America and will therefore have to wait. Once I fix that I will re-test, I think this fix might resolve the odd stepping issue I was having.

Thanks for your help Mariss - This tutorial is a much better way of learning about gate arrays and motor drives than anything else I've found.

[yngndrw]

Success ! I just received the diode pack I needed to fix my FPGA board from Digi-Key (Really impressed with their international shipping) and made the repair. SOT−323 packages are hard to solder even under a microscope, but fortunately I only had to replace one.

The drive works great with the correction that you mentioned Mariss so thank you for that - I'll publish the fix to the H-Bridge designs incase anyone decides to use them. The motor's a little noisey but I'm going to put that down to the wires I have running all over the place, there's probably quite a lot of noise on all of the signals. Now I can have a play with the Verilog code and carry on experimenting.

Update: New board design completed, complete with improved track isolation: https://oshpark.com/shared_projects/NTc0L6wF / H-BRIDGE | Projects | CircuitMaker

[tivoidethuong]

my 2 hbridge mosfet desgin, incluce hv regulator to 12V and 5V for logic control


thanks mariss

[websrvr]

my 2 hbridge mosfet desgin, incluce hv regulator to 12V and 5V for logic control


thanks mariss

Is it possible to get all of your eagle files?

[tivoidethuong]

Is it possible to get all of your eagle files?

what are you use for?