I am working on a project which requires six stepper motors to be operated in conjunction with one another to form something of a prototype braille machine. My setup involves 6 28BYJ-48 stepper motors, all run by ULN2003 driver boards. They are connected to an Arduino Mega 2560 and powered by a 9 V 800 mA power supply plugged into an MB102 board. Which is in turn connected to the motors via a breadboard. Now, if I have one or two motors, they run like a dream. However, once I go up to three motors, the MB102 gives out, with its power LED fading and flickering for a short time before eventually completely going out. From what I've read, it seems the MB102 is only able to provide 700 mA of current to the circuit, so I'm assuming I need something with a bit more oomph to it to drive this many motors? Or am I way off base here? According to what I've been reading, the motors and the driver boards seem to have a combined current draw of 150 mA or so, so why would a 700 mA power supply give out with only 3 motors connected, which would presumably have a current draw of 450 mA? Any help would be greatly appreciated, and I am happy to provide any additional information/clarification necessary.
Know that steppers consume quite the same power all the time, moving or not moving.
Check the spec for Your stepper, what current they can use and multiply by the number of motors. 800mA sounds really bad to me, way too little.
ULN is a poor driver board. Use a board where the windings current can be set.
Apologies if this is a dumb question, but what exactly is a winding current and how can I tell if a board allows for it to be set?
If 800 mA is much too low, how much would be a good starting point? Having a hard time finding information as to the current needed for these motors and ULN.
Get hold of some stepper basics theory. If You are going to work with steppers You really need to know. Use Google or the magnifier symbol to the right of the menue bar in this window.
Steppers have their specifications telling maximum current per winding. Look that up! Max is seldomly needed but using, say some 75%, gives You a well running stepper.
ULN2003 is just an array of power transistors, Darlingtons.... You might make tost of the steppers if the pwr supply is strong.
Search for stepper driver boards and look for current controlling boards.
How much pwr You need? Read the specs for the steppers and multiply by the number of motors used.
You can't be having any hard time. I used Google and got this: 28BYJ-48 - Sök
Thank you. I must be very bad at googling because trust me I've been looking all over for answers about this for a week now. Finally found the current draw for the motor in question (240 mA), so I guess I will need to provide about 1.5 A for the motors. Now it's just a matter of figuring out how to accomplish this safely.
Google often lists a number of pages listing sellers, I know. Digging in the Google list for data sheets is the trick.
If You go for a pwr supply of some 2 amps or more You will be safe. 12 volt will sure do.
Search for stepper driver boards. Google Arduino stepper board. I am using a Protooner V3 board and it handles 3 independant steppers and it has current setting, like the 240 mA (small motors?) You told. I use heat sinks, acomosnying the driver board bougjt from Ebay.
What do You think?
If you use a stepper driver board you can also power the steppers at 9V or 12V, maybe even higher voltage. The stepper driver sets the current regardless (subject of course to the maximum voltage the board can handle).
Those stepper boards also make control of the steppers a lot easier - most take just two pins, STEP and DIR. A pulse on STEP makes the stepper move one step (or microstep, depending on the board setting), DIR gives the direction of rotation (CW or CCW).
Use a 5V buck converter or separate 5V power supply for the Arduino (in the latter case remember to connect the grounds).
Railroader:
ULN is a poor driver board. Use a board where the windings current can be set.
The ULN2003 is the standard driver for 28BYJ-48 stepper motors. It works fine - there is no need to change it. Most 28BYJ motors are sold as a package that includes the ULN2003.
If the performance of a 28BYJ + ULN2003 is not sufficient then a different motor (and driver) should be selected.