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9:34

As others have commented, a very clear explanation and a very soft pleasant speaking voice ( which many Northern accents have ), so you're ideal for youtube videos. However is the overlay at 4.24 correct ? At 100mA x2 the torque is apparently 6x the base 5v test of 32mNm, but torque is given as 117mNm. This is the same torque value of 50mA x2 at 3.6x the base torque value ( 3.6x 32mNm = 115.2mNm ). I haven't a mechanism to test the torque against at present and therefore don't know what torque I require, so it's all theoretical. But if I needed a bit more torque than a 5v bi-polar stepper offers, I presume a 9v PP3 battery source could be an option ( I need a battery source that anyone could buy ). You haven't carried out tests at 9v, but do you think the respective values would be midway between 5v - 12v ? For example, at 50mA x2 would the torque be ~ 75mNm ? I've a 9v rechargeable battery which is 200mA. Would that be capable of 100mA x2, and what torque could that translate as ? Obviously these 28BJY-48 motors come as 5v or 12v. Would I still need to use current limiting to pair the 5v motor with 9v ? I've read online that 12v with a 5v motor does generate heat build up after a few second of operation. A 9v battery would still turn a 12v motor I presume with reduced output.

Nice video, congratulations and thanks for it. I have found that with current limiting at 12V, the modified motor, if we want to keep it stopped but with the coils powered so that it is not possible to move it by hand (it will handle a flap), the voltage chopper makes the motor vibrate. I am using the MP6500, I have ordered a DRV8825 to test as well. I think there is no solution for this and when it has to be stopped you have to disable the controller and trust that the gearbox prevents the flap from moving.

THe more they say IK the lower their IQ. Proven fact.

You may not have a arbor press but I am guessing you have a vise? You can design and print jaw extensions that you can use as your tool.

can i have the codes plss

Thank you. This is better than many videos out there . cheers

i thought inverse kinematics was extremely hard. no fear any more! thanks for the video

Mine has no curcuit....:( I really don't suggest anyone take apart these unless youplan on not using em after....

Love you man, You're so funny :D

What is the name given to this inverse kinematics method? I would like to research further

Wtf did you do to it, though? Did you just cut the common, converting it from unipolar to bipolar? Well, no shit a bipolar motor will outdrive an identiacal unipolar one. But a bipolar requires TWO H-BRIDGES, i.e. 8 transistors and additional circuitry to at least create dead time between phases, so you aren't getting away with just 4 pins; whereas a 28BYJ you can drive with just 4 N-MOSFETs or NPNs. Oh, you've got a DRV8825? That costs as much as 2-4 of these motors, and can drive much more powerful stuff. Perhaps get a proper bipolar motor, then? I mean, even if there is a situation where this "neat trick" may come in handy, what have you even achieved with this modification? You're pushing current through twice as much wire, which, I have to idea how this would affect the magnetic flux density, but I know that twice the wire is twice the resistance, so half the current... Have you tried just running an unmodified 28BYJ at twice the voltage?

I would use a bolt to go inside the yet to be formed loop/circle area area and a mandrel bender style hinge to wrap around the bolt on the same axis so the metal will wrap around the bolt as it swings around look up mandrel bender for an example. then make a 3d printed stamp to get the steps in it . That metal also looks like stainless and is harder to form as it wont stretch well and will have lots of spring back try aluminium a non hardening version is a good place to start

Question. When stalled these motors will or will not strip thier gears? I wish to use them with a vent flap where I drive them until the vent closes and they stall. I don't need extra torque so I do not plan to make your modification. Great video otherwise.

what are the libraries used in the code?

Awesome project! I am so impressed you were able to get those plastic servos working for this project. For me, those servos break when I look at them wrong.

I am new to the use of stepper motors and understanding them. I thank you for your content. I just accidentally found you on RUclips and I’m grateful for that. I have a few questions about heat being generated on a low maintenance project that I am working on and what your suggestions would be, please let me know if you’re willing to help. Thanks again for the video.

Isn't it refreshing to watch an educational video with no "pointless verbal garbage". Thanks so much for your time, making this video.

Hi there! I really enjoyed your video on the 28byj-48 motor. Do you have the 3D model available for download? I'm interested in creating a new internal reduction for the motor and would find it super useful. Also, do you know if the sizes in the model are accurate? Any insights would be appreciated!

Thank you very much for your information and I have taken your information to study and adapted it into python for learning. If anyone is interested, you can follow and test and try it at this link. colab.research.google.com/drive/1tpKsER2IazlSDh9AVQmRVnxvxA4uU8Hm?usp=sharing

Really? 5V for your unmodified stepper, and 12V for your modded stepper? G... I wonder why. 😂😊

could i ask you sir. we kinda have problem when it comes to writing j3 and j2 arduino. we use your formula but the output show nan. we are not missing any single information for video even though it only one mistake. so pls help us this for high school project.

Superb!!!

should the angle really be negative? depending on the value, the J3 is negative

why were these values added? const double Y_Rest = 70.0; const double Z_Rest = -80.0;

Hello, great video! Will you please share your wiring schematic with the DRV8825 and controller board?

does it matter if J1 has offset away from J2? I see there are many designs of 3 dof leg in this way.

Hexapod with Parkinsons 😂. Good effort. Try using better servos

very cool! thanks for the explanation (and the take apart), very helpful in understanding the motor

Hello, can you give me your e-mail address? I need to consult you about a few issues.

Hello, there. Good hacking video. My only doubt is: how the comparison between a 5V motor and 12V hacked should be interpreted... I mean, using a higher voltage wouldn't affect the results?

I want ask something, in minute 3:25 . Are L variable is range between servo 2 and the lowest point of foot point can be?

can you post your sketch as a comment or something? It is hard to read in the video. Thanks for posting!

03:11 that's where i lost track, cool work btw might get into robotics sometime in the future, thanks

The 5 volt test, the motor did not seem to sound correct and the shaft did not move smoothly. You might have to drive them at a different frequency to find the sweet spot.

i believe that your plastic pieces has a deforming factor greater than metal so dispite your theory about scale is corret you need a better deforming factor material, in first stage you can easily bend the metal sheet because is not plastic that is deforming it but that metal rod. If you apply 90% plastic but just the tip of some metal you can achieve better results i believe

Id say cast the tools out of pewter

Interesting to see strength and durability comparsion with eSUN ePLA-CF, they claim 15-20% carbon fibers, while Bambu makes PLA-CF and PETG-CF 5%, and only PA6-CF, PAHT-CF (PA12) and PET-CF is probably 15% (MSDS says 12-20%) Printed some parts with Bambu PLA-CF 5% and I'm disappointed, it negligible stiffer than eSUN PLA+ but doubles the price and will wear AMS unit faster

You know you might be able to finish the hinge roll by using the 180 bend jig first and also giving the "sharp" end a

@07:00 Classic... Imagine doing your CAD on like a 77" Screen like I occasionally do which totally ruins ANY and ALL sense of scale of a part 🤣

thank you very much for your prompt answer, you are a genial teacher, now i understand the code… please keep on going!

this is a great work, congratulations! I built it too, but i do not understand the code, in special the arrey with the moves. can you please link the example for writing, so i can learn the movements? thank you very much!

I do enjoy a good side quest! The unexpected plastic metal press was a bonus! MORE BEEF REQUIRED!

Does a Part 3 for the Hexapod comes? with Controller Control?

so cool! good work

Love a good side quest 👌

Hello I would like to use WiFi, but the servos are controlled via GPIOs that support ADC2 and that is not recommended. So I had no choice but to use a PCA9685. In the original code, the servo values are transferred directly; for the PCA, these must be converted into PWM signals. I can proudly say: it's done. with a few additional functions. but this example code already works. I also integrated an IMU straight away. #include <math.h> #include <Ramp.h> #include <Wire.h> #include <Adafruit_PWMServoDriver.h> #include <Adafruit_MPU6050.h> #include <Adafruit_SSD1306.h> #include <Adafruit_Sensor.h> Adafruit_MPU6050 mpu; Adafruit_PWMServoDriver pwm = Adafruit_PWMServoDriver(); #define USMIN_J1 500 #define USMIN_J2 400 #define USMIN_J3 750 #define USMAX 2400 #define USMAX_J1 2500 #define SERVO_FREQ 50 // Debug #define DEBUG #ifdef DEBUG #define DEBUG_PRINTL(x) Serial.println(x) #define DEBUG_PRINT(x) Serial.print(x) #else #define DEBUG_PRINTL(x) #define DEBUG_PRINT(x) #endif // MIDDLE LEFT LEG // x // ^ // | // | // y <------o // Servo pins const int J1Pin = 0; const int J2Pin = 1; const int J3Pin = 2; // Variable für Servo-Positionen int pi_pos = 45; int ya_pos = 45; // Vorherige Werte für Gyrodaten float oldPitch = 0.0; float oldYaw = 0.0; float offset_ = 0.35; // Constants const double J2L = 57.0; // Length of J2 (57 - 2.35)mm const double J3L = 110.0; // Length of J3 110mm const double Y_Rest = 70.0; const double Z_Rest = -80.0; const double J3_LegAngle = 15.4; // Joint Variables double J1Act = 0.0; double J2Act = 0.0; double J3Act = 40.0; rampDouble J1Tar = 0.0; rampDouble J2Tar = 0.0; rampDouble J3Tar = 40.0; // Command Variables bool started = false; bool ended = false; uint8_t commandStep = 0; // Commands const double lines[62][4] = {{0.0, 0.0, 40.0, 1000}, {-30.0, 40.0, 20.0, 200}, {-30.0, 40.0, -20.0, 200}, {60.0, 40.0, -20.0, 1600}, {60.0, 60.0, 20.0, 200}, {-30.0, 30.0, 20.0, 200}, {-30.0, 30.0, -20.0, 200}, {60.0, 30.0, -20.0, 1600}, {60.0, 50.0, 20.0, 200}, {-30.0, 20.0, 20.0, 200}, {-30.0, 20.0, -20.0, 200}, {60.0, 20.0, -20.0, 1600}, {60.0, 40.0, 20.0, 200}, {-30.0, 10.0, 20.0, 200}, {-30.0, 10.0, -20.0, 200}, {60.0, 10.0, -20.0, 1600}, {60.0, 30.0, 20.0, 200}, {-30.0, 0.0, 20.0, 200}, {-30.0, 0.0, -20.0, 200}, {60.0, 0.0, -20.0, 1600}, {60.0, 20.0, 20.0, 200}, {-30.0, 40.0, 20.0, 200}, {-30.0, 40.0, -20.0, 200}, {-30.0, 0.0, -20.0, 800}, {-30.0, 20.0, 20.0, 200}, {-20.0, 40.0, 20.0, 200}, {-20.0, 40.0, -20.0, 200}, {-20.0, 0.0, -20.0, 800}, {-20.0, 20.0, 20.0, 200}, {-10.0, 40.0, 20.0, 200}, {-10.0, 40.0, -20.0, 200}, {-10.0, 0.0, -20.0, 800}, {-10.0, 20.0, 20.0, 200}, {0.0, 40.0, 20.0, 200}, {0.0, 40.0, -20.0, 200}, {0.0, 0.0, -20.0, 800}, {0.0, 20.0, 20.0, 200}, {10.0, 40.0, 20.0, 200}, {10.0, 40.0, -20.0, 200}, {10.0, 0.0, -20.0, 800}, {10.0, 20.0, 20.0, 200}, {20.0, 40.0, 0.0, 200}, {20.0, 40.0, -20.0, 200}, {20.0, 0.0, -20.0, 800}, {20.0, 20.0, 0.0, 200}, {30.0, 40.0, 0.0, 200}, {30.0, 40.0, -20.0, 200}, {30.0, 0.0, -20.0, 800}, {30.0, 20.0, 0.0, 200}, {40.0, 40.0, 0.0, 200}, {40.0, 40.0, -20.0, 200}, {40.0, 0.0, -20.0, 800}, {40.0, 20.0, 0.0, 200}, {50.0, 40.0, 0.0, 200}, {50.0, 40.0, -20.0, 200}, {50.0, 0.0, -20.0, 800}, {50.0, 20.0, 0.0, 200}, {60.0, 40.0, 0.0, 200}, {60.0, 40.0, -20.0, 200}, {60.0, 0.0, -20.0, 800}, {60.0, 20.0, 0.0, 200}, {0.0, 0.0, 40.0, 200}}; // Funktion zum Begrenzen des Werts auf ein Maximum int limitToMaxValue(int value, int maxLimit) { if (value > maxLimit) { return maxLimit; } else { return value; } } // Funktion zum Addieren von altem und neuem Wert float addValues(float oldValue, float newValue) { if (newValue > 0.2 || newValue < -0.2) { oldValue = oldValue + newValue; } return oldValue ;// + newValue; } void setJ1(int servo, int pos) { //This first bit of code makes sure we are not trying to set the servo outside of limits int sendPos; if (pos > 179) { pos = 179; } if (pos < 0) { pos = 0; } sendPos = USMIN_J1 + ((USMAX_J1 - USMIN_J1) / 180 * pos); if (servo > -1 && servo < 16) { //only try to move valid servo addresses pwm.writeMicroseconds(servo, sendPos); } } void setJ2(int servo, int pos) { int sendPos; if (pos > 179) { pos = 179; } if (pos < 0) { pos = 0; } sendPos = USMIN_J2 + ((USMAX - USMIN_J2) / 180 * pos); if (servo > -1 && servo < 16) { //only try to move valid servo addresses pwm.writeMicroseconds(servo, sendPos); } } void setJ3(int servo, int pos) { int sendPos; if (pos > 179) { pos = 179; } if (pos < 0) { pos = 0; } sendPos = USMIN_J3 + ((USMAX - USMIN_J3) / 180 * pos); if (servo > -1 && servo < 16) { //only try to move valid servo addresses pwm.writeMicroseconds(servo, sendPos); } } void setup() { // DEBUG #ifdef DEBUG Serial.begin(9600); #endif if (!mpu.begin()) { Serial.println("Sensor init failed"); while (1) yield(); } Serial.println("Found a MPU-6050 sensor"); pwm.begin(); pwm.setOscillatorFrequency(27000000); pwm.setPWMFreq(SERVO_FREQ); // Analog servos run at ~50 Hz updates delay(10); UpdatePosition(0, 50, 30); delay(5000); } void loop() { // Update position J1Act = J1Tar.update(); J2Act = J2Tar.update(); J3Act = J3Tar.update(); CartesianMove(J1Act, J2Act, J3Act); if (ended == false){ // Check if command finished if (started == false | J1Tar.isFinished() == true){ commandStep++; if (commandStep > 61) { ended = true; } double xMove = lines[commandStep][0]; double yMove = lines[commandStep][1]; double zMove = lines[commandStep][2]; uint16_t duration = lines[commandStep][3] * 2; J1Tar.go(xMove, duration); J2Tar.go(yMove, duration); J3Tar.go(zMove, duration); started = true; } } } void CartesianMove(double X, double Y, double Z){ // OFFSET TO REST POSITION Y += Y_Rest; Z += Z_Rest; // CALCULATE INVERSE KINEMATIC SOLUTION double J1 = atan(X / Y) * (180 / PI); double H = sqrt((Y * Y) + (X * X)); double L = sqrt((H * H) + (Z * Z)); double J3 = acos( ((J2L * J2L) + (J3L * J3L) - (L * L)) / (2 * J2L * J3L) ) * (180 / PI); double B = acos( ((L * L) + (J2L * J2L) - (J3L * J3L)) / (2 * L * J2L) ) * (180 / PI); double A = atan(Z / H) * (180 / PI); // BECAUSE Z REST IS NEGATIVE, THIS RETURNS A NEGATIVE VALUE double J2 = (B + A); // BECAUSE 'A' IS NEGATIVE AT REST WE NEED TO INVERT '-' TO '+' UpdatePosition(J1, J2, J3); } void UpdatePosition(double J1, double J2, double J3){ // MOVE TO POSITION setJ1(J1Pin, 90 - J1); setJ2(J2Pin, 90 - J2); setJ3(J3Pin,J3 + J3_LegAngle - 90); //DEBUG_PRINT("J1: "); DEBUG_PRINTL(J1); //DEBUG_PRINT("J2: "); DEBUG_PRINTL(J2); //DEBUG_PRINT("J3: "); DEBUG_PRINTL(J3); }

Enjoying the content and your process through making stuff. Subbed.

Excellent video clear explanation. I build a hexapood myself. One question if I have a J1L=60 how does this affect the code?

i like a lot the design and i'd like to print. it semms like the STLs files are not there. Unlikely I'm not capable of setting up the plate with those files..