Electronic Basics #24: Stepper Motors and how to use them

isn't it a pleasure to listen to the neurotic sounds of stepper motors while they're creating a 3d print well not really but why do we use them then I mean a brush DC motor rotates as well and it's way quieter so in this video were in order to find an answer to the question I will show you how a modern stepper motor works and how easy it is to control one with and without a microcontroller let's get started first off let's inspect the insides of the stepper motor that a salvaged from an old 3d printer by simply unscrewing the four screws on the back and applying a bit of force I remove the back which we wield a rather commonly known structure of a so-called hybrid synchronous stepper motor there also exists permanent magnets types and variable reluctance types but since the hybrid ones have more advantages and are more common nowadays let's focus on those it's removable rotor consists of four permanent magnets with alternating polarity one off and southport agava from a pole tool which has exactly 50 teeth per sprockets but the tip of the sprockets of one pole shoe are not aligned perfectly there upon offsets which means that if we look at the front we can see north-south north-south and so on magnetized teeth this data of the stepper motor also possesses such teeth but there are not magnetized yet in order to do that the motor consists of eight physically separated coils but since we only have four wires to work with they're basically just two coils which are spread out will be half of a multimeter I asserted that red blue and black with green former coil and by powering those bubala bench power supply it was pretty easy to declare which coil pair is positioned where inside the model and while the opposing coils will create the same magnetic polarity the other two will create the reverse magnetic polarity now with those information in mind let's try to experiment and find out how this motor works firstly I connect black to VCC here and green to ground which creates a South Pole at zero degrees this attracts a north polar I Steve which now aligned with the South Pole next blue connects to VCC and Retta ground now we have a North Pole at 45 degrees which the South Pole or I Steve will follow then we connect green to VCC and black to ground this time we have the South Pole at 90 degrees again the reversed polarized T follow we can move on to the last step by hooking up red to VCC and blue to ground to create a North Pole at 135 degrees which the thief will once again follow with those four steps want to move exactly to the location of the next tool and if we multiply the 50 teeth by four steps we get a total of 200 steps per rotation which actually makes sense since the type ylabel gives us a step angle of 1.8 degrees that is 360 degrees per rotation divided by the 200 steps but because turning on each coin mechanically is kind of impractical we need a driver for that I created a relic route but functional one which consists of foreign Channel and for p-channel MOSFETs to form 2 H bridges and not we know to control the 4 gate Paris an H bridge can basically let current flow in either direction through the coil by turning on either the top left and the bottom right MOSFETs or the top right and bottom left MOSFETs after connecting the motor and creating a bit of simple codes the four steps were repeated over and over again which makes the rotor spin perfect and because I can exactly control how many steps the road or should perform this step a motor is suitable for positioning applications like 3d printers another advantage is that when current flows through the coils in only one way the road or does not spin but it keeps its position persistent with a so called holding torque which is sometimes given on the type label along with the required coil current but let's go back to my driver circuits what I used here is so-called wave driving in which only one coil is active there also exists full step driving in which both coils are active and thus create a higher torque next is half step driving which combines all the previous driving States and thus increases the resolution from 200 steps to 400 steps per rotation this madness then continues to one-quarter steps 1:8 that's 116 steps and so on which is also known as microstepping but in order to implement that we don't want to use a constant voltage apply to our coils like I did it with my driver instead we need a constant current which we can vary in its strength to create the different steps an easy solution to this problem is this a 4 9 8 8 microstepping IC which is basically a more advanced h bridge I connected the setup pins like it's shown in this schematic hooked up the MS pins up to 5 volts in order to enter the 1/16 step modes connected my 12 foot power source and finally the motor which does nothing yet what is missing is a circuit that creates a variable frequency square wave like this 555 timer circuits by connecting the outputs to the step in the motor rotates one step when out of the square wave changes from low to high and if we take a look at the voltage and current of one coil we can see that the chopped-up voltage creates a variable constant current which ultimately forms a sinus audial shape at this point everything works fine and the advantages of microstepping are quite obvious not only is the movement of the rotation much smoother but the loudness of the motor also decreased drastically of course you could also use not reno to control the a of 4-9-8 a driver IC but for now you already learned quite a bit about stepper motors I hope you liked this video as always don't forget to Like share and subscribe stay creative and I will see you next time

Channel: GreatScott!

Views: 1,908,244

Rating: 4.9227962 out of 5

Keywords: stepper, motor, tutorial, basics, how to, drive, driver, 555 timer, A4988, a4988, arduino, µC, hybrid, synchronous, permanent magnet, variable, reluctance, angle, step, microstepping, electronics, greatscott!, basic

Id: bkqoKWP4Oy4

Length: 6min 46sec (406 seconds)

Published: Sun Sep 11 2016

Reddit Comments

[u/Wacov]

Thanks, that was interesting!

[u/TheFox30]

Lost him on the micro steps....

[u/VeteranKamikaze]

Great video! I doubt I'll ever be applying this knowledge to my 3D printing tasks but it's very interesting to know more about what makes my printer tick.

Edit: pun unintended, but imma leave it there.