A4988 Arduino Uno AC Power Adapters

Through Pololu I bought the Arduino Uno, the A4988 and the stepper motor. I bought the variable AC power adapters at Radio Shack. I wired it via the video on You Tube by Ignacio R. I set the AC power adapters at 7.5 dcv and 4.46 dcv. I cut wires and twisted them and put them through the tiny holes and looped them around and twisted them nice and tight. I used Arduino stepper motor software (stepper_oneRevolution). My first time at programming. I’ve always wondered how they convert script to mechanical movement. It’s done with two mouse clicks. The stepper took big steps in one direction, paused, continued, reversed, paused, repeated but never made a revolution. Just erratic jerky movements. Then it wouldn’t stop or turn off. I killed the adapters. Tried again and got the same results. Not exactly the smooth movements displayed by some of the many YouTube videos. I messaged the video creators and they never wrote back. YouTubers usually post the videos and forget about them. Some are years old. The stepper motor didn’t heat up at all. I’m looking for success. I’m looking for complete control over my stepper motor. The more success I have with components the more I buy. I’m having fun, yo.

[quote]I cut wires and twisted them and put them through the tiny holes and looped them around and twisted them nice and tight.[/quote]You really need to solder connections, especially to a motor. Radio Shack also sells soldering pencils.

Avoid changing the motor wiring with the circuit powered, or you will probably destroy the electronics.

Assuming connections and acting stupid were not the issues what else could be the problem, oh Smartest Kid In The Room?

I’m having fun. I have a headache and I’m crying. Weee. I just pluggd the four wires from the stepper motor into the Arduino Uno and ran the Arduino script (can I say ran the script?) And the stepper worked. Worked erratically. It kinda worked better. I stay away from breadboards because they inherently have a resistance problem that can effect your project. I would solder but that means hauling out the homemade fume evacuator. But given a fool proof plan I would.


Just wrapping wires around the through hole pads on the driver is probably not making a good electrical connection. With stepper motors, it is particularly important that you have good connections. As Jim mentioned, if one of the leads of your motor looses connection while powered, the driver could be damaged.

I also noticed that in your first post you mentioned using a 7.5V source and a 4.46V source. The A4988 requires a motor voltage of at least 8V.

Lastly, you mentioned connecting “the four wires from the stepper motor into the Arduino Uno”. I do not expect an Arduino to be able to drive a stepper motor directly well, and controlling it that way could damage your Arduino.


Sorry for the delay. Arduino website said to place the four wires in the header: “stepper_oneRevolution Stepper Motor Control - one revolution.This program drives a unipolar or bipolar stepper motor.The motor is attached to digital pins 8 - 11 of the Arduino.” So that’s what I did. I plugged in the USB and a Radio Shack voltage converter set at around 4 volts into the Arduino Uno R3 and the stepper motor purchased from Pololu began to rotate a little smoother than the former set up I used: -

That video, which is written in spanish but very simple to follow actually contradicted the stepper motor wire attachments as described in the Pololu A4988 literature. But even when I reattached the wires the Pololu way the stepper motor did not change its erratic movement at all. It functioned in the same manner. When I attached the four stepper wires to the Arduino, also purchased from Pololu, I did so by just inserting the four wires in the order that is on the stepper motor.And it worked better than the wiring uncorrected/wiring corrected video set up.

As far as contact is concerned I twisted the wires very tight so that contact was assured. In fact it’s almost impossible to not have good contact.

I am stumped when it comes to the Pololu A4988 diagram that mentions “logic power supply 3-5.5V” and the “motor power supply 8-35V”. Where is VDD (aka “positive”) on my Arduino? I see three gnd (aka “ground”) on my Arduino board. “Logic Power Supply” powers the “chip”? But why the variation in the two “power supply”, aka “3-5.5V” and “8-35V”? I assume that I can use my Arduino Uno R3 as the “microcontroller” mentioned in the black box. YouTube videos on stepper motors, except for that one I tried, take the first minute telling you the video’s name and purpose and then just show a stepper motor purring along like a well tuned V8. Then the video maker disappears into cyberspace and never answers my pleas for help. Pleas for help on Arduino are answered with more confusion. If Polou’s A4988 diagram specified by name and model a “microcontroller” and specified by name and model the two “power supply” and some kind soul would told me where “VDD” is on the Arduino then I could have a stepper motor functioning in perfect manner.

Ok, some kind soul provided a .png with text and I located the VCC on the Arduino Uno Revision Three but it ain’t VDD…or is it? :open_mouth:

you dont need to worry about solder fumes (‘hauling out homemade fume extractor.’) It is bad, in quantity or over time, not horrible for small time hobby work. Worse case you can just use a fan blowing away from you (sucks air in vicinity and blows away.)

You do need to worry about making your posts more coherent. It’s very hard to follow what you’re writing, and what you’ve done, and therefore it’s very hard to help you. I also don’t have the sense that the confusion is due to ESL, I think you’re just not laying things out clearly and carefully for your readers. If it is english as a second language, I apologize, and understand it’s reasonable for readers to take more effort reading in that case.

I can say this more directly because I’m not a pololu staff member and I don’t need to be as nice :p.

As for some of your most recent questions:
(1) twisting wires is possible to be ok, but it’s still very foolish. you will blow up your driver at some point if they disconnect momentarily. it will be hard to diagnose unless it blows open circuit and you can tell because your driver chip gets hot in all conditions.

(2) The a4988 diagram mentions logic supply and motor supply as two different ranges, because they are powering essentially two different parts of your circuit, controlling two different components. Some driver chips manage this internally (e.g, DRV8825), but not the A4988. My guess the motor supply has a higher minimum voltage (8V) due to something relating to the mosfets used internally.

Vdd, aka positive, is found on your arduino with a pin called “5V.” It’s usually close to at least one of the Gnd. It’s not the same as “Vin” which I am pretty sure is the input (unregulated) voltage of your arduino.

Bottom, next to two grounds, “5V”. That’s Vdd of your microcontroller.


I think you are confused about VDD because you are looking at the minimal wiring diagram from our A4988 product page which shows a 3-5.5V source being used to power both the VDD pin on the driver and the microcontroller:

However, in the case of a standard Arduino, power is usually supplied through the external power plug, USB port, or VIN pin, and the “5V” pin will output 5V. If you are powering the Arduino in one of those ways, you should not connect a supply to the 5V pin; this could damage the Arduino.

The 5V output pin on the Arduino can be used to power the VDD pin on your A4988 carrier.


Claire, I’m not confused. I just am the victim of misinformation. It’s like your diagram was never tried by anyone. Claire, 2+2=4. But I’m getting ?+?=4. Claire, you are withholding information. Give me a fish and I eat for a day, teach me to fish and I eat for a lifetime. Same stuff. You’re there to push Pololu product. Emily was great but she’s gone. Claire, we have to be specific. Electronics is specific, exact and precise. “Standard Arduino”? Nay, sister! I bought from Pololu an Arduino Uno revision 3. My stepper motor that I bought from Pololu says it rates “4.5 volts” Not 5 volts. I must use the Arduino USB port for data exchange. VDD is voltage drain drain but now is the acronym for positive. The diagram indicates that I must buy an “AC Adapter” from Radio Shack that is one amp and is variable so I can set the DC voltage somewhere between 3 volts and 5.5 volts. The diagram indicates that I must create a split with the “AC Adapter” from Radio Shack on the postive pole and connect them to the VDD on the Arduino Uno R3 and the A4988. The diagram then indicates that I must do the same thing with the negative terminal on the “AC Adapter” from Radio Shack.BUT, ground and negative are not the same thing. I rewired my house, so I should know. You got the hot, the not hot and the ground which ultimately is attached to a copper rod you bang into the GROUND. Claire, I’m not powering the Arduino, I’m simply following the little lines on the diagram you posted. The diagram says nothing about “5V”. Claire, why don’t you draw a diagram using the stepper motor I bought, the A4988, the Arduino Uno R3 and any external power source and name a product that will fill the bill such as a Radio Shack AC adapter or one that Pololu sells? I mean why post the Pololu diagram and then say it won’t work and that I’m confused. Enlighten me. Draw me a circuit that will cause my stepper motor to work in beautiful progression when I bring up the Arduino stepper motor code and make that mouse click.

I DO need to worry about solder fumes as they are toxic. I built a double fume extractor using two bathroom exhaust fans and drier vent duct that vents out the plexiglass half window I created.Your photo is not my Arduino Uno R3. (1) Twisting wires is an effective method of contact. I use magnification to ascertain contact. Just make sure you strip at least two inches of insulation so the length can prevent unraveling. (2) The stepper motor that I am using and BOUGHT FROM POLOLU rates @ 4.5 volts. The term “logic” refers to the chip to be energized. Your advocacy for use of the 5V “pin” is contradicted by Arduino member “Robin2”, a “Tesla member”, who wrote, “What power supply are you using? I hope you are not trying to power the motor from the Arduino 5v pin.” So you see how I suffer. Bits of information scattered about and one person contradicts the other. Woe is me, I say.

Hello, solder123.

Your tone and attitude are not appropriate for this forum. Here are some examples:

We let this behavior slide initially because of your history here, but it looks like you are moving in the wrong direction since making this forum post two years ago:


Thank you for your reply. I am very new to this and I have a limited understaning of electricity and no knowledge of programming. I do not intend to regard Pololu as a tutor. Good information is found in your product descriptions. It is time consuming to sit down and take a question and write an answer that will be easily understood. And who has got time on their hands? I’d like to try to answer some questions posted by forum members and it is plain to see my limitations. Thank you for the professional way you handle my purchases. Everything is done quickly and thoroughly.[/quote]

If this is how you feel:

maybe you should find a more appropriate hobby. If you want us to continue to tolerate your presence here, you will have to soften your approach. You are asking experts to volunteer to help you, and mocking them and complaining as you have been is not advancing your cause.

- Ben

Just answer the question instead of being obtuse. If you don’t know how to make your own stepper motor, A4988 and a microcontroller work then say so. Don’t hang back in silence. Just say I don’t know. Don’t say I’m confused etc. You are masking incompetence and ignorance with belligerence. You go back two years? What you said two years ago will probably sound funny, too. I asked for a turtorial on the maestro and the jrk and you people said we are engineers and we are too busy to help you. Why is Hartnett gone? You give her a gutfull too? And by the way, I bought a horn from you and it never worked. I called about Pololu about it and some jerk giggled and said that he was going to charge me a $20.00 restocking fee. Delete my accounts. I’ll take my money elsewhere and it’s a lot of money but then Pololu employees can’t count in the dark since you’ve got your head up your ass.

You’re a total troll and being mean. Pololu offers incredible support on a high value product. You seem not to understand what you’re doing. I really like that you were called out, and am interested by the contrast between now and the clear and calm writing you had two years ago. There was nothing “funny” about what you wrote two years ago, it was simply more clear and reasonable.

Pololus information is well within the minimum a hobbyist without formal background needs. I’ll say that additionally as personal verification, because I’ve been using their products since two years ago when I first touched a microcontroller.


Everyone’s been at the point of extreme frustration because your project isn’t working how you expect it to. Troubleshooting is hard work that requires a lot of concentration and thought to determine what tend to be meaningless small mistakes that are often hardly satisfying in consideration of the work needed to find them. So, really, if you just want to be more reasonable everyone would be happy to still help out.

By the way, your stepper motor is 4.5v rated, but the pololu driver is a chopper driver. You need more than 4.5v to run a 4.5v stepper in any case. You will need to set the current limit to the driver board, and that is more key than the voltage you run it at.

For example, I was running last week a 3v motor with 42v and had no problem. Remember the danger is your motor overheating, since its not a semiconductor device and below 200-400v doesn’t have insulation problems. So power lost is related to iir, that is the current through the windings squared times the resistance of the windjngs. So you can see the key detail is the current through the windings, since resistance is held constant. Since the drivers limit the current based on how you set the potentiometer, you’ll be all set.

Hope its ok to say on pololus forum, but when I was starting I needed everything I could get. So its good to check tutorials both on adafruit, pololu, and sparkfun, even when the product you get is from pololu. I believe the main tutorial I used on steppers wasn’t any of those three anyway, though they used a sparkfun board for the tutorial. I like pololus more, though

The bit about semiconductor devices was just meant that with semiconductor devices you usually also have a strict voltage limit and if your system goes above that it blows. I assume because some semiconductor barrier is shorted? Not sure. But with more mechanical systems you tend to be more limited by heat, though voltage can often indicate a power source (but not always. Like elctrostatic shock will almost never kill a plain electronicless motor, but it can destroy a motor driver board electronics)