Hi Rick,
Sorry for the delayed response.
We are using mixed decay mode. With fast decay also we are seeing same behavior.
I am not understanding why channel 2 is going to negative voltage. This waveform is not similar to actual pump signal. This is what we want to understand.
Please help me if you have any idea on why both waveform are different with simulated load and with actual pump.
Best Regards,
Raju
Part Number: DRV8825
Hi,
We are using DRV8825 IC for driving Peristaltic Pump which is having stepper motor. We designed one fixture to simulate the motor with equivalent inductor and resistance.
When we tested both actual motor and simulated loads with DRV8825 IC, we found current waveforms for both scenarios are different. I am attaching the waveforms with actual motor and simulated loads here.
Can someone help me in understanding what is the difference between these two setups?
Thanks in advance.
Best Regards,
Raju
With Actual Pump @ 20 rpm:
With Zoom:
With Simulated Load @ 20 rpm:
with zoom:
Part Number: DRV8305
Hello Everyone,
We are using DRV8305 for driving a BLDC motor in 1-PWM mode with a 200kHz PWM signal. We have observed sudden changes in motor speed in specific ranges of PWM duty cycles. There is a drop and then a sudden rise in motor RPM with increasing PWM duty in these regions. DRV8305 is operated with the following settings;
PWM FREQ: 200kHz
PWM MODE: 1-PWM
COMM OPTION: Active Freewheeling
DEAD TIME: 52ns
TDRIVE: 1780ns (for both high and low sides)
MOSFET: http://www.ti.com/lit/ds/symlink/csd18540q5b.pdf
MOTOR: http://www.maxonmotor.com/medias/sys_master/root/8825427656734/17-EN-241.pdf
Following plots are obtained by slowly increasing the PWM duty cycle and logging the motor RPM,
Especially the drops near the 17000 RPM region are problematic as we are operating the motor in this region.
Lowering the PWM frequency prevents this behaviour. However, as the R/L ratio of the motor is quite large (i.e. small electrical time constant), we prefer using high PWM frequencies.
Best Regards.
Hello Will-san,
Following is latest customer request.
Please give me any response today, because they have meeting with their customer at tomorrow night.
1. 2nd Stage Gain Drift vs. temperature.
1-1. Datasheet has 2nd stage Gain specification as follows.
Does this specification include temperature drift?
If this specification includes temperature drift they can use this specification to estimate system gain error because customer performs only initial offset calibration.
1-2. If datasheet specification does not include temperature drift please supply statistical drift data (mean, sigma, and min/max).
2. Shift Buffer Offset Drift.
2-1. Datasheet has Shift Voltage Offset (+/-5mV) of Shift Buffer.
Does this +/-5mV include temperature offset drift?
2-2. Please supply statistical offset drift data (mean, sigma, and min/max), because they perform initial offset calibration and need this data to estimate offset error when temperature is changed.
Best Regards.
Hello again,
I've lowered the TDRIVEN and TDRIVEP values but the response is practically identical to the above plots.
Best Regards.
No Updates?
Part Number: DRV8711
Hello,
we are using the DRV8711 driver IC in an application with this stepper motor: Nanotec ST8918M6708 (https://de.nanotec.com/produkte/566-st8918-schrittmotor-nema-34/).
The schematic is nearly the same than on the eval board, only other FETs were used. We use CSD19532QB5 (http://www.ti.com/lit/ds/symlink/csd19532q5b.pdf). The supply is 48V
The motor is specified to run until 2100/min, but when we reach about 1200/min the current regulation cannot hold the current on the desired value and then the overcurrent protection stops the driver. Here you can see when this happens:
In detail: The desired current is 2.6A (the orange line) but neither slow nor fast decay can decrease the current.
To config the driver I do the following:
Stepper.Driver.Ctrl |= STEPPER_CTRL_ENBL;
Stepper.Driver.Ctrl |= STEPPER_CTRL_EXSTALL;
Stepper.Driver.Ctrl |= STEPPER_CTRL_MODE_HALF_STEP;
Stepper.Driver.Ctrl |= STEPPER_CTRL_ISGAIN_20;
Stepper.Driver.Ctrl |= STEPPER_CTRL_DTIME_450;
Stepper.Driver.Torque |= TORQUE;
Stepper.Driver.Torque |= STEPPER_TORQUE_SMPLTH_50;
Stepper.Driver.Off |= 20;
Stepper.Driver.Blank |= 50;
Stepper.Driver.Decay |= 100;
Stepper.Driver.Decay |= STEPPER_DECAY_DECMOD_ALL_AUTO;
Stepper.Driver.Stall |= 60;
Stepper.Driver.Stall |= STEPPER_STALL_SDCNT_4;
Stepper.Driver.Stall |= STEPPER_STALL_VDIF_8;
Stepper.Driver.Drive |= STEPPER_DRIVE_OCPTH_500;
Stepper.Driver.Drive |= STEPPER_DRIVE_OCPDEG_2;
Stepper.Driver.Drive |= STEPPER_DRIVE_TDRIVEN_250;
Stepper.Driver.Drive |= STEPPER_DRIVE_TDRIVEP_250;
Stepper.Driver.Drive |= STEPPER_DRIVE_IDRIVEN_300;
Stepper.Driver.Drive |= STEPPER_DRIVE_IDRIVEP_200;
I tested all decay modes and modified all other settings, but it always is the same result. When reaching a specific rpm value (maximum around 1200/min) this behavior happens.
Does anyone has an idea what I am doing wrong?
Cheers,
Christoph
Part Number: DRV8844
Hi,
What is the reference for V3P3OUT, is it VNEG or LGND?
I couldnt find that information in datasheet.
Tool/software: TI C/C++ Compiler
Hello,
I am using Delta Connection Stator in BLDC Motor and it has 5 pole pairs. How could the commutation pattern be done for this configuration? I will be grateful if anyone helps me.
Thanks
Part Number: DRV8303
I am experiencing what appears to be a DVDD fault condition, but am unable to observe any problems on the DVDD output pin. The behavior is as follows:
1) fault pin is asserted by DRV8303
2) Read of SPI status registers indicates NO fault conditions, but shows that all configuration parameters have been reset to defaults.
According to the datasheet, this behavior is indicative of a DVDD fault. However, no change on the DVDD pin can be observed on oscilloscope.
At this point, the workaround is to read the status registers on a fault pin assertion and to send new configuration parameters if they have been reset. Needless to say, this workaround is not ideal.
Does this sound like an actual DVDD fault? If not, what else could be causing this behavior?