360bot - Stepper motors are cool!

So far just a Stepper motor hooked up!


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Strange, some Google videos are down. Link to the one down now when writing this, here.


So I thought; With 360 degrees overview, I am unbeatable, I can navigate anything. I took an old toy-tractor and in amazingly short time got everything fitted onto it. That tractor was made for this, I thought.

I knew that it would be crap at steering, as the wheels where big, and the rear wheels (or front sometimes, this is 360!) where locked to each other, giving no differential steering, and slow turns.

But after a short while I got really tired of it; It is turning not on a plate, but on a big football stadium! :)

So it is going to die now, 360bot will not be on a tractor. Still I thought it looked cool :D And so I took some snaps just before I now go back and tear it apart. Click on image for more images..






I wanted to transfer power and signals to the moving part. I tried all sorts of stuff, but did not relly manage. So in the end I just gave up and used a 3.5mm jack-stick. Simple and easy.. but only 3 lines open.. So i had to give up on my first thought of having several LED's spin around. The thought was that they should sort of draw a rotating "radar image": Closer objects would make LED's closer to the axle light up.

However, I really like the sound of it spinning, and I will make something up! Added new video with the jackstick-trick. The LED on it is simply using the Sharp signal directly - that is actually quite a nice hack in itself :) I will always add a LED on the sharps from now on, nice indicator!

For a long time I wanted to hook up a stepper motor, and finaly I got to it!

Wow, these are cool! I enter this as a robot because I simply have to make a robot with this. I do not have much time, but now I have told you all that I am going to make a robot with a stepper motor, and so I will have to find the time :)

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I've never tried this, but what are the merits of the sequence





In the case of a 4-coil motor this means that two of the coils are pulling against each other, but would there be any torque benefit?

Here's another thought: You could compromise with a mix'n'match of torque and accuracy:









When the two coils are energised you have more torque (not double the torque, just "more"). You still have accuracy with the single coil steps, but the step might not be fully complete under high torque. 

I'm pretty sure the first step sequence wouldn't work....i think it would just cause the motor to jitter and vibrate....servos aren't as versatile as you think!


the second step is a text-book approved stepping sequence...i believe it's called 'double-stepping'....not sure though.

Don't give up! You are sooooooo close. cut eh back axle and mak teh stepper power only one of teh wheels. Get a brass gear servo instead of aplastic one for the steering. This could be so cool.

BTW - I love the video. Specially the bit at the end where the pile of sticks falls over and the small child laughing. 

PS - why does everything you make have to beep and fart? Next I suppose it will be bashing stuff and recording the sounds it makes? 

I absolutely LOVE the idea of the jack plug!!!


makes wonder why i never thought of that myself and always tried to consider complicated (high-noise) bearing and brush connections!


I'm really starting to love this site....a true testament to KISS ;)

(The last "S" would be me :) But I try to use it to my advantage :D

And you are not the only one to consider brushes etc. I got this far before quitting :)

The "grab bag" sounds very fair. I think I gave $25 for one. And I think you want as few amps and ohms as possible unless you want to drive something with it - I just like it to turn. Apart from (and including) this, I have no clue.

I just hooked it up to a standard 28 picaxe board, no special H-Bridge or anything. It says 12V, but I give it 5, and do not feel much difference if I give it more. It has 4 "signal" that I feed 2 by 2 with pause between, and 2 "Volt", that I have just short circuited and give both 5V.

I may learn some more and tell about it. For now I am looking into making some sort of cool radar with it. I think :D

In work, my colleague and I have just completed a stepper driver. It drives a 4-wire motor 50 steps per rev with 64-microsteps per step. Get this: it has feedback using a Rotary Variable Differential Transformer. My colleague did the electronics (three H-bridges: two for the stepper and a third for the RVDT excitater. I did the software (including PID) in an FPGA. It took us nearly 8 months, but it's a sexy piece of kit.

Guess what? He's one of the ones who couldn't explain FETs ina language I understand. Maybe I'm just thick?

I don't understand why you'd need an H-Bridge for the steppers.  Can't you just reverse the firing pattern on the steppers' input pins?

Indeed. The H-bridge is used for controlling the currents through the coils in both direrctions while micro-stepping.

Rather than pulsing each of the coils on and off in sequence, they are actually fed with a pair of out of phase sinusoidal currents . This means that even though the stepper only supports 50 steps per revolution, we can microstep, giving us a resolution of 0.1125 degrees!

Told you it was a bee-atch! 

So you are saying that you first atract the thing like "normal".. but instead of atracting in a row, just in between each attraction, you push away from the one leaving?