Hi all,
I want to control 28byj-48 stepper motor without the use of any drivers like uln2003
ie directly from the Arduino board
FYI I am using Arduino mega 2560 r3 board
Hi,
Sorry, Won't work. Arduino outputs can not handle the current needed by stepper motors.
- Current : 92mA
- Resistance : 130 Ω
- Voltage : 5V DC
See the details HERE.
I want to control 28byj-48 stepper motor without the use of any drivers like uln2003
What you want is one thing, what is technically / physically possible the other one.
I think, @terryking228 already fed you with the right information.
Curious, what if you put a resistor on it to reduce the current? Definitely would reduce the power of the motor, but assuming it turned would that work? Say the shaft only has an indicator needle on it... Flyback? Cap
capricorn2:
Curious, what if you put a resistor on it to reduce the current? Definitely would reduce the power of the motor, but assuming it turned would that work? Say the shaft only has an indicator needle on it... Flyback? Cap
If you did get it to turn, it would not be able to stay in that position.
Paul
Thanks Paul for the response. I'm sure it's a long shot, but I do not quite understand why it would not be able to stay in its position. It only moves when there is input doesn't it? Cap
Stepper motors need current to hold their position. If you reduce the current with a resistor you also reduce their holding torque.
It would still not be sensible to connect a motor directly to an Arduino because the movement in motors can generate brief high voltage spikes that can damage an Arduino.
It's not as if a ULN2003 is very expensive?
...R
Thanks Robin, that's what I figured (flyback). It would have been nice to avoid the darlington and extra wiring is all, that would have been cool, but oh well, I guess I knew it wouldn't fly.
capricorn2:
Thanks Robin, that's what I figured (flyback). It would have been nice to avoid the darlington and extra wiring is all, that would have been cool, but oh well, I guess I knew it wouldn't fly.
Actually, that unit looks like the one that was part of my Arduino instruction kit I bought about 3 years ago. The data sheet is: robocraft.ru/files/datasheet/28BYJ-48.pdf.
The kit and software drove the stepper directly from the Arduino pins and used no "libraries". Worked fine running the whole thing from a 9 volt battery. I did not run it for a really long time, but it did turn, step, both directions.
So, you will not hurt anything by using it, but it will tie up a lot of Arduino memory.
WELL! I had to go out to the shop to get the Arduino lesson manual and I was TOTALLY wrong about the stepper motor lesson!!!!!
It uses the ULN2003a chip which is a transistor array with built-in diodes to suppress the inductive reverse voltage when the stepper motor windings are switched off. So, you can't use the Arduino directly.
Paul
Darn! You had me for a moment. Oh well, thanks for looking. Cap
Hi,
DISCLAIMER: Mentioning stuff from my own shop... (which I understand ) 
At $2 I really like these little "Stepper Motor Drivers"...
They are made for those little 28byj-48 steppers, but I use them for other stuff often. This is a general-purpose ULN2003 breakout board, with LEDs showing active bits. This can be used to drive small DC motors (one direction), high-power LEDs, incandescent lamps etc. up to 500 mA and 50 volts. The Data Sheet is here: http://www.arduino-direct.com/Photos/uln2003.pdf
I just bought over 1000 of these (and the stepper motors) for Arduino-related educational kits I make. Having the LEDs on them helps people figure out the actual step/winding sequence.
The factory we get them from usually sells them to Air Conditioner manufacturers who use them to control those little moving flaps on room air conditioners. They are also used in some air duct vane controllers. When I was looking for low-cost steppers and drivers for education these were the perfect hit.
Millions of these are made every year and that is why they are so cheap. But the factory is fine with selling us "Only 1000 at a time". They come 50 in a layer, 500 to a box:
Then they go into kits like this:
I love playing with these little things...
Terry, thanks, I think you got me, cheap as the chip itself and ready to go. I really like the cheap motor too, they work well, nice that they have a gearbox built in too. Nothing wrong with pointing to your site IMO.
Since I've got you, do you know of a place to get tiny bipolar steppers? Fairly common again I think, about 10mm dia with stretched thread shaft. I didn't see any on that web site. I'm trying to miniturize.
Not sure how much you know about servos, I don't really like them but they are much simpler, I'm looking for "micro" servo with anything from 270 deg rot and up. I don't think they exist. Probably too many $ for me anyway. There are a few "360 deg", but those are misleading, they are continuous rotation, no pot.
eBay usually has a variety of miniature steppers, the sorts from optical drives and autofocus lenses
I believe.
Thanks Mark, Those are the ones, for cameras I think. I've seen them before, I can find them again. Thanks for the repsonses. Cap
And if you want free-wheel diodes for a miniature stepper, this single device has all 8 in one package!