strange behaviour with ULN2003 mini.....

[terryb22160]

Hi,
I've built the ULN2003 with 28byj-48 stepper mini version. It all connects ok, but only gives 500 steps per rotation. If I change to 1/2 step, it stays the same, and checking step rate, controller returns Stepmode:1. The other problem that I have, is that it only moves in one direction, no matter which of the + / - step buttons I press.
I'm using latest arduino code.
cheers
Terry

[brownrb]

Hi terry
from document https://sourceforge.net/projects/arduinoascomfocuserpro2diy/files/DRIVER%20BOARDS/BOARD%20OPTION%20ULN2003.pdf/download

Half-stepping is not supported at present using the ULN2003 driver. So changing step mode has no effect.

and also
Another advantage is that the 28BYJ-48 stepper includes a gearbox, giving an effective 2048 steps per revolution

If motor only moves in one direction this is wiring issue.
See diagram here

[brownrb]

ULN2003 driver board ONLY supports full stepping

[terryb22160]

Hi,
thanks for the reply. The controller board that I have is one of the ebay board and motor kits, with pre-wired connectors. Ok for the steps, but I'm only getting about 600 steps per rev....any ideas. The movement is nice and smooth.
terry

[brownrb]

Hi Terry
U are using the L293D motor shield?
You have changed the line of code that reads
const int stepsPerRevolution = 1036; // NEMA17-PG5 motor

to the correct value then reprogrammed the controller? For you I think you said 8192?

Set focuser position to 0.
Then enter 8192 as focuser position and click GOTO position
At full steps when things are right the stepper motor will go one full rotation

then switch to half steps
repeat - set focuser to 0 position
Then enter 8192 and click GOTO position
half steps then motor will go half rotation

You have motor now moving in both directions?
Robert

[terryb22160]

Hi Robert,
I'm using the ULN2003 board, with 28byj-48 stepper motor. I have movement in one direction only, no matter whether I use + or - steps. The output shaft does 1 rotation in about 600 steps..
Terry

[brownrb]

Hi Terry
Bad news. The stepper motor you purchased is not recommended one, the one you have is an eight step motor not the 4 step one that is recommended.

Thus it does not work with the published code.

Step Angle (8-Step sequence: Internal Motor alone): 5.625° (64 steps per revolution)
Step Angle (4-Step sequence: Internal Motor alone): 11.25° (32 steps per revolution)
SO: it takes (6464 = 4096 steps per output shaft revolution.. In 8-step sequence.
SO: it takes (3264 = 2048 steps per output shaft revolution.. In 4-step sequence.
NOTE: Arduino "Stepper Library" runs in 4-step mode only

8STEP = HALF STEP = 5.625 degree per step, 64 steps per rev, 64:1 = 4076 steps per rev
4STEP = FULL STEP = 11.25 degree per step, 64 steps per rev, 64:1 = 2038 steps per rev

So what to do?
Let me see if I can make some code changes for you to try - ignore other code for time being. I will see if that is possible. If not, then you may have to purchase different motor - but let me make some code changes first - maybe 2-3 days at most.

Cheers
Robert

[brownrb]

Hi Terry
Please try attached version. Let me know what happens
Robert

[brownrb]

Simple test program should work with your stepper motor

[terryb22160]

Hi Robert,
code works great. I also have a 35BYJ-412B which is a similar motor, but 12v with 4080 steps.... great!!!!
All checks out with APT...
If the modification to the firmware is easy, would it be possible to add to the other versions, as later on I'd like to build one of the more complete versions.
Next projects are your dew buster and the sqm.
many thanks
Terry

[brownrb]

Hi Terry
Yes, that is possible. Just let me know when the time comes. You can email me direct. For the email address, look in Control panel for the myforcusepro2 windows app - in win10 it listst the support URL when highlighted - which is the email address

Cheers
Robert