Micro robotic tweezers

A micro-robotic gripper for people with hand disabilities to perform fine work.

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Tweezers are essential in many fields, from medicine to PCB populating, but people with hand disabilities can't use them. The Micro robotic tweezers remedy this.


The following diagram shows the general design of the micro-robotic tweezers. It is clear that the control button plays an important role. My first thought was to use a thin film pressure sensor. The more pressure you apply, the wider the tweezers open. It would thus function similarly to cross tweezers, which, however, due to their design, allow too little control over the object held. Of course, you could also control the gripper by electromyography or a foot pedal.


Before I start with 3D modeling, I decided to build a handmade prototype first. To do this, I sacrificed one of my tweezers, cut it into two pieces, and drilled 3mm mounting holes with my drill press.

A corresponding wedge was cut out of a 10mm thick glass-fiber reinforced plastic plate, and ground, then four M3 threads were cut and an axial hole was drilled to accommodate the M3 motor spindle. The two halves of the tweezers were then screwed to the wedge using four M3 x 8mm stainless steel screws.

Here are some more parts I want to use for the prototype:

Unfortunately, I could not find a micro gearmotor with an M3 spindle and rotary encoder. I bought another motor with a rotary encoder, which I have to exchange.

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This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

  • Motor and encoder test

    M. Bindhammer05/16/2023 at 17:10 0 comments

    It took me a while to figure out the wiring of the encoder PCB. It is as follows:

    After soldering pin headers to the motor wires, the rotary encoder was tested with an Arduino Mega.

    I took the test code from the Arduino project hub.

    int counter=0;
    String dir="";
    unsigned long last_run=0;
    void  setup() {
      attachInterrupt(digitalPinToInterrupt(3),  shaft_moved, FALLING);
    void shaft_moved(){
      if (millis()-last_run>5){
        if (digitalRead(4)==1){
        if (digitalRead(4)==0){
    void loop()  {
      Serial.print("counter : ");
      Serial.print("  direction : ");

    The rotary encoder has a resolution of six counts per revolution of the motor shaft. A motor driver with a break function is certainly required, plus PID control.

    Finally, I changed the motors, which is absolutely no problem. For this, only two screws have to be loosened with a small Phillips screwdriver.

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