Removing Weight from Small Cellphone Vibrator Motors

Robots nowadays are getting smaller and smaller. I wanted to make a very small mobile robot. I found out that cellular phone's vibrators are tiny motors but with unbalanced "weight" at its end rotating. These tiny motors have strong torque and just fit for my purpose. But removing the "weight" is difficult.

I wondered how to remove the "weight" on small cellphone vibrator motors. Forcing it may damage this fragile motors. I tried to search the net and using Google and found this site Tiny Motor. Now I can start building my tiny bot.

Embedded Programming and Electronics Blog

I have created a new Embedded Programming and Electronics Blog. This site is for my day to day adventure as a technology geek featuring my findings or work to share to other geeks.

Robotic Muscle

There have been many attempts made to re-create human anatomy through mechanical means. The human body however, is so complex that it is very difficult to duplicate even simple functions. Robotics and electronics are making great strides in this field, of particular interest are limbs such hands, arms, and legs.

In order to reproduce human extremities there are a number of aspects that must be considered:

• The gripping force required to manipulate different objects (eggs, pens, tools)
• The motion capabilities of each joint of the hand
• The ability to feel or touch objects (tactile senses)
• The method of controlling movement within the limb
• Emulating real human movement (smoothness, and speed of response).

Many different solutions have been proposed for this problem, some include using "muscles" controlled by air pressure, piezoelectric materials, or shape memory alloys. Shape memory alloys mimic human muscles and tendons very well. SMA's are strong and compact so that large groups of them can be used for robotic applications, and the motion with which they contract and expand are very smooth creating a life-like movement unavailable in other systems.

Creating human motion using SMA wires is a complex task but a simple explanation is detailed here. For example to create a single direction of movement (like the middle knuckle of your fingers) the setup shown in Figure 1 could be used. The bias spring shown in the upper portion of the finger would hold the finger straight, stretching the SMA wire, then the SMA wire on the bottom portion of the finger can be heated which will cause it to shorten bending the joint downwards (as in Figure 1). The heating takes place by running an electric current through the wire; the timing and magnitude of this current can be controlled through a computer interface used to manipulate the joint.

There are still some challenges that must be overcome before robotic hands can become more commonplace. The first is generating the computer software used to control the artificial muscle systems within the robotic limbs. The second is creating large enough movements to emulate human flexibility (i.e. being able to bend the joints as far as humans can). The third problem is reproducing the speed and accuracy of human reflexes.

The wires in such robotic hands are modeled through simple experiments. The first link takes you to a video clip showing one of these simple experiments in action. The next link is demonstration of how the interactive applet modeling this experiment works, while the third link goes to the applet itself. Finally, the fourth link is to a game involving an SMA wire in the context of the experiment you have just seen.

Micro Swimming Robots

Micro Swimming Robots for medical applications

Goal: Developing a microrobot which can travel to currently inaccessible parts of the body and perform user directed tasks such as highly localized drug delivery and screening for diseases that are in their very early stages.

Approach: For such a miniature device to be injected into the body, it has to be 800 µm or smaller in diameter. Miniature, safe and energy efficient propulsion systems hold the key to maturing this technology but they pose significant challenges. Scaling the macroscale swimmimg mechanisms to micro/nano length scales is unfeasible. It has been estimated that a vibrating-fin driven swimming robot shorter than 6 mm can not overcome the viscous drag forces in water. The objective of this fundamental research effort is to explore swimming mechanisms at small length scales and develop a biomimetic swimming robot inspired by micro-organisms motility mechanism. We propose a new type of propulsion inspired by the motility mechanism of bacteria with peritrichous flagellation, such as Escherichia coli, Salmonella typhimurium and Serratia marcescens. These robots are intended to swim in stagnation/low velocity biofluid. Potential target regions to use these robots include the urinary system.

Current Status:Prior to fabrication of the microrobot, the perfomance of the propulsive systems is predicted by modeling the dynamics of the motion. The motion of the moving organelle along with the body is simulated and key parameters such as velocity, force distribution and power requirments for different configurations are determined theoretically. In order to validate the theoretical result, a scaled up prototype of the swimming robot is fabricated and characterized in silicone oil using the Buckingham PI theorem for scaling. The results are compared with the theoretically computed values. These robots are intended to swim in stagnation/low velocity biofluid and reach currently inaccessible areas of the human body for disease inspection and possibly treatment. Potential target regions to use these robots include eyeball cavity, cerebrospinal fluid and the urinary system.

Benefits: We envision this robot having the capability to swim to inaccessible areas in human body and perform complicated user directed tasks such as diagnosis of diseases at early stages and targeted drug delivery.

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DIY Robot :Solar-Bug (Fred)

2 Transistors 2N3904
2 pager motors, high-efficient motor
1 solar panel, 3 volts
2 Transistors 2N3906
2 pager motor holders
1 capacitor, 2200uF, 16V
2 blinking LEDs (green or red)
2 resistors 3.3k Ohms, 1/4 watt, 5%
copper wires & heat-shrink tubing
2 tantalum capacitors, 0.22uF
2 resistors 30k or 33k Ohms, 1/4 watt, 5%

1. 2N3904, bend the base lead (middle lead) toward you.
The labelled flat-side facing you and the leads are pointing downward.

2. 2N3906, bend the collector lead (the third lead) away.
The labelled flat-side facing you and the leads are...



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Bipolar Stepper Motor Controller

Here's a little circuit that simplifies interfacing to bipolar stepper motors. It's similar to a common unipolar design available on the internet. However, I modified it to use a pair of MOSFET-based H-bridges. In addition, I added an enable signal so that the motor windings can be disabled to save power. Since there are diodes embedded in the transistors, there's no need to add flyback current protection across the motor windings.

A couple of notes: ORCAD does not explicitly show the power connections for the logic devices so be sure and connect the flip-flop and XOR gate packages to...



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Tiny Threads - Tiny Multitasking Threads for Microcontrollers

by: Regulus Berdin

• Idea based on http://www.chiark.greenend.org.uk/~sgtatham/coroutines.html.
• Only 1 byte RAM needed per thread.
• Very small overhead context switching.

Limitations:

• Maximum 254 lines per thread.
• Thread context switching will not work within a switch block.

Usage example:

     TT_DEF(1)
    {
       TT_BEGIN(1);
     while (1)
       {
          ...
          TT_SWITCH(1);
          ...
          ...
          TT_WAIT_UNTIL(1,keypress);
       }
       TT_END(1);
    }
   
    TT_DEF(LED_TASK)
    {
        TT_BEGIN(LED_TASK);
        while (1)
        {
            LedOn();
            delay=DELAY_1_SECOND;
            TT_WAIT_UNTIL(LED_TASK,delay==0);
            LedOff();
            delay=DELAY_1_SECOND;
            TT_WAIT_UNTIL(LED_TASK,delay==0);
        }
        TT_END(LED_TASK);
    }
    
    void main(void)
    {
        ...
        ...
        while(1)
        {
            TT_SCHED(1);
            TT_SCHED(LED_TASK);
        }
    }

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nBot Balancing Robot

David P. Anderson


I've been working on a two-wheeled balancing robot, nBot .

This robot was featured as NASA's Cool Robot of the Week for 19 May 2003. Thereafter Scientific American's online website, SCI/Tech Web Awards, honored the NASA page as one of the top 10 engineering and technical web sites for 2003, referencing nBot in its text. nBot is also featured in a new O'Reilly book spun off from Make Magazine in 2006, called The Makers.

The basic idea for a two-wheeled dynamically balancing robot is pretty simple: drive the wheels ...

The robot hardware was built in my home machine shop. Here as some exploded views of the motor platform and drive components, as well as the castering tailwheel, now removed, which was used for testing and calibrating the motors and encoders before nBot was able to balance on two wheels. The robot uses the HC11 robot controller developed for the M.I.T. 6.270 Robotics Course, the same robot controller used on the LegoBot and SR04.


Rev 1. This began as an experiment to learn to control an inverted pendulum. I began with a three wheeled robot with a ball-bearing pivot used to attach a 3 foot wooden pole topped with an orange Nerf Ball. The pivot has a low-friction 5k potentiometer used for measuring the tilt angle of the pole. I moved the battery pack over the rear wheel to give more stability. Here is an mpeg movie (10 Meg) of the robot balancing the pole in my office. Here (3.3 Meg) is a shorter version, and here (3.7) is another.



Rev 2. After learning to balance the pole, the robot was re-built as a two-wheel version, with the battery mounted directly above the wheels. The ball-bearing pivot was attached to the bottom of the robot with a short aluminium feeler touching the floor. In this way the robot can sense it's angle to the floor and, assuming the floor is level, to gravity as well. The aluminium feeler has a teflon pad on the end to help it ride over cracks and joints in the floor.


Rev 3. For the third version a third deck was added and the batteries moved to the top deck. This allows the robot to generate more torque without having to tilt over as far. The side view of the platform shows the battery and user interface on the top deck, the microcontroller and h-bridge on the middle deck, and the motors...

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