[pminmo]

if IC8 pin 2 changes state and pin 1 doesn't, you have a problem. Your statement "most items seem fine" troubles me, are there other differences other that IC8 pin 1?

[foxgarden]

Good evening to all.

This is my system. I think that is correct.

I have tried for approximately a week the 3axis with ballast resistors feeding to 13 VDC and all was OK (only the speed was limited to approximately 1000 step/sec), therefore I have decided to construct the chopper (current setting resistors = 0.32 ohms for my steppers).

I have made a simulation without the 3AxisBoard and have applied to the escape of every axis a 10ohm resistor.
I have measured a current flow of approximately 2.6A.

Question #1: the current flow is fixed or varied to varying of the load applied?

Therefore, verified the corrected operation of the chopper I have connected it to the 3AxisBoard like from outline.

As usual I have opened TurboCnC and acts in manual jogging.

I have connected the 3 motors and verified current on the "Y" axis .
The current, with motor detention, is approximately 0.6A, Q1 and Q4, Q5 and Q8, Q9 and Q12 (IRLZ44) are very hot and the motor loses steps also to the speed of 1000 steps/sec. When I have tried to 13 VDC without chopper with ballast resistors all the IRLZ44 were nearly cold!

Question #2: can I make a test replacing the motor with two 3 ohms resistors in order to verify the current?

I am trying to resolve this problem, but I'm sure to find in this forum a great aid! Thanks to all!

Fox

[foxgarden]

Sorry! I wanted to write:

"Question #2: can I make a test replacing the motor with two 1.8 ohms resistors in order to verify the current?"

Fox

[pminmo]

I goofed on the Estop latched BOB on my website. Led2 needs to be removed an a jumper installed in it's place. My bad, sorry.

Phil

[slp_prlzys]

Estop seems to be working tho the LED is not
lit when the button is pressed, the reset works too.
I'll take off the LED then.

[pminmo]

I suspect there are two states to LED2 bright and dim? No real off, correct?

Phil

[tachus42]

Foxgarden I can't see from your diagram wether you have the earths of the two power supplies connected together - they need to be. Testing with just a resistor will give uncertin results the circuit needs the inductance of the motor to work properly.
Is your 12volt supply regulated? What value did you use for the timing cap?
Can you power up the chopper without a motor attached and post the circuit diagram of one channel with the voltages at each point. I'll be able to see if there is any thing wrong then.

[slp_prlzys]

Phil,

the LED is off not even a slight glow, before I can't
make the Estop button to work,but the LED lights up
when I press the button then turn off when the button
is not pressed. I found out that I had the button on the
wrong connection on the board, now the Estop is working
but the not the LED, I'm expecting that the LED would
be lit when I pressed Estop and stay lit until I press
reset, but not.

[tachus42]

Foxgarden - i looked at your diagram a little closer. The problem might be your 30 volt power supply. 30 volts is right on the limit for 60 volt z44's some z44's are 55 volts and this would cause a problem with a 30 volt supply. The motor acts as a autotransformer and the off mosfet sees twice the power supply voltage when the current flows in the other half of the winding. There is a 60 (or 55) volt zener in the fet and when this conducts lots of heat will be generated.
Can you post the full part number of your mosfets and the exact voltage of the 30 volt supply?

[foxgarden]

Thank you Tachus

I answer to your questions:

"Is your 12volt supply regulated?"
Yes it is. But now I returned back to 13.5VDC regulated (for both OSUNI-3 and Chopper)

"What value did you use for the timing cap?" Timing cap = 4n7

"Can you power up the chopper without a motor attached and post the circuit diagram of one channel with the voltages at each point"

V PSU = 13.46
X chopper out: 13.46
Y chopper out: 13.46
Z chopper out: 13.46

Current (digital multimeter), with motor connected (Y axis):
Not rotating = 1.14A (couldn't it be 3.4A?)
Rotating at 1,000 pulse/sec = 0.86A (???)
Current setting resistors = 4 x 1.2ohm (1.1/3.4=0.32)

The motor seems to resonate between 600-700 s/s

Now with 13.5VDC the IRLZ44's are pretty warm, but the IRF9540 are hot! Do they need heatsink?

Fox

[tachus42]

Nothing should be getting hot. So you have gone to the 13.5 volt supply for the chopper board now?. What voltage exactly was the 30 volt supply? What value are you using for the power supply resistors? (the ones in series with the zener diode ). What is the voltage across the 10 volt zener ? it should be 10 volts. I suspect that the chopper circuits supply is to low causing the 9540 to get hot.

There is no way to easily measure the actual current which is flowing in the windings so don't worry to much about you current readings.

[pminmo]

Tach,
I'm thinking outloud here, what about changing the the unipolar driver mosfet to:
http://www.irf.com/product-info/data...irfs41n15d.pdf 150V Fet could run higher voltage ps.
Running the logic at 8vdc, and changing the 74hc14 to opto couplers 6N135's for the pc interface. Thoughts?

Phil

[foxgarden]

Yes tachus!

I forgot to change the zener resistors. When I was with 30VDC they was (330+68=398ohms) --> (30-10)/.05=400ohms

Now, with 13.5VDC I bridged the 330 resistor, so Rzener =68ohms -> (13.5-10)/.05=70ohms (only on Y axis)

- Voltage across Y axis Zener = 10.0V +/- .05V (on X axis and Z axis, with 398ohms, same value...?!?)

The 30VDC was exactly 30 +/- 0.5V

When the motor rotates the IRF9540 is warm, but when it stops gets really hot!

About speed: probably my motors are not designed to rotate beyond 500-600 s/s: at these speed they not resonate.

Fox

[tachus42]

Fox Somethings not right. On my prototype running at the same current the 9540 runs cooler than the z44s. Can you post the voltage at each lead ( B C E ) of each transistor on one channel? Check with board powered but no motor. Also what is the voltage at the motor common with the motor connected but not stepping.

[tachus42]

Phil it should work ok. I haven't looked but are higher voltage Logic level mosfets a rarity? A transistor / zener preregulator would be needed for the 7805. A transistor level shifter or a schmit trigger made from transistors could be used instead of the opto's but the isolation would be a nice feature to have.

Take a look at the attached files for a quarter stepping bipolar driver. It's far from finished and I need to think through it a bit more to see if I have missed anything, No component values yet.
The driver board compares the output current to a analogue input voltage centered about 2.5 volts and switches the bridge to bring the current back to the target. The control board uses the Analogue switches and the 4 bit binary up/down counter to gernerate two 2 90 degree phased stepped sine waves. The 4030 adds 4 to the count for the 2nd phase. There is also a charge pump for the high side drivers.

[foxgarden]

Tachus,

"what is the voltage at the motor common with the motor connected but not stepping"
1.90Volts

Voltage on the schematics = with board powered but no motor

R4+R5=68ohms

Fox

[tachus42]

1.9 volts at the common seems about right and the voltages look ok. How hot is the 9540? I built the prototype as a single channel and there was more copper on the board - which might have kept it cooler.
Can you parallel the timing cap with another in the 4n7 to 22n range as a test. If it's chopping you should be able to hear a high pitched noise from the motor.

[foxgarden]

Thanks tachus.
Yes. It's chopping.

Fox

[tachus42]

Sounds like it's working ok then but might need a small heatsink. Do you know what voltage your z44's are ?

[pminmo]

Tach,
Couple of questions. The parallel 244'd driving the FET gates. To overcome gate capacitance? Is the voltage reg on the charge pump necessary? The discrete voltage reg on the input, what was your thinking instead of using a adj 3 term reg?
Man you sure can get some milage out of one side of a pcb!
Phil