Post by phervier on Feb 19, 2016 16:05:04 GMT
There is two main reason to change them :
First mounting same precision 1/16 step :
The example pictures are for the X axis driver it is the same thing for all the drivers.
it is done ! you may now use your motor at full power without too many heating.
Second mounting 1/32 step :
It is done !
- the DRV8825 is more efficient, it may deliver a 1.5A constant current to the motor without the need of active cooling
- it offers 1/32 microsteps vs 1/16 for the A4988 allowing more precision in the positioning. But keep in mind that smaller microsteps means less torque and more CPU needed for computation. As the delta printer are already very demanding in cpu power, it may speed down the printings.
First mounting same precision 1/16 step :
The example pictures are for the X axis driver it is the same thing for all the drivers.
- Remove the A4988, and remove the ms1 and ms2 jumpers (see photo).
- Put the DRV8825 in place, the IC is on the opposite side of the board compared to A4988.
- switch the power on (the motors should be connected) and set the appropriate voltage.
In my case I have 42SHD0217-24B stepper motors, it is writen on the back of motors but not really readable. On the Geeetech site they are given for 1.5 of nominal amperage so the reference tension should be 0.75V
you should measure the voltage on the side of the potentiometer (see picture), It is quite difficult to have a precise reference voltage as the overall range is very large.
it is done ! you may now use your motor at full power without too many heating.
Second mounting 1/32 step :
- Replace the A4988 by the DRV8825 without changing jumpers
- set up reference voltage (see higher)
- In your firmware change the number of steps by unit. In marlin it is the DEFAULT_AXIS_STEPS_PER_UNIT array constant, in configuration.h file. You should double values for the axes you change (in this order X Y Z Extruders). Update your firmware.
switch on the printer connect it on your computer and send the following commands :
M502 ; to take into account new constant values
M500 ; to save the values in the EEPROM
It is done !