# Questions tagged [velocity]

Velocity is a vector quantity referring to the rate at which an object changes its position.

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### In theory, is the position derived from accelerometer absolute?

I recently found multiple research papers that say that in theory double integral of accelerometer data gives a position of the device. Does that refer to absolute position (like the one given by a ...
2k views

### Most small / cost effective way to detect changes in altitude?

I want to make a device, which when placed on someone skiing or snowboarding, will be able to tell whether that person is sliding down the slope. The problem is two-fold. I must first detect whether ...
4k views

### How to measure propagation velocity through a trace on a pcb?

With a pcb in hand, how to measure the propagation velocity of a path from point A to point B, with accuracy in the picoseconds range?
528 views

### Doppler shift velocity sensor

Any reasonable priced (sub 20\$/100) ways to directly measure indoors velocities between around 0.1 and 15m/s? Its main purpose would be to reduce speed drift for a 9DOF device (acc/gyro,magnetometer)...
902 views

### Estimation of swimmer's velocity from IMU sensor

I am dealing with the problem of estimation the swimmer's velocity. In the same time data from IMU sensor and tethered system are acquired. Data from tethered system are reference data. From IMU ...
173 views

### How do I determine the curve of the transmission output on a torque-angular velocity graph for a DC motor?

I'm doing a homework problem that involves motor characteristic graphs. For this problem, I have a motor with stall torque of 8 N-cm and a no-load angular velocity of 80 rad/s. The motor powers a 4-...
606 views

### A speedometer like chip

Is there a device which acts like an accelerometer but only measures absolute velocity? I could integrate the accelerometer's output but errors quickly accumulate and cause problems. Preferably the ...
603 views

### Confused on MOSFET terms (velocity limited, mobility limited, constant mobility)

So we're learning about transistors, but we don't much of the physics behind how they work (yet) so these terms are quite strange to me. The models we've used are "velocity limited", "mobility limited"...
1k views

### Brushless DC motor problems at high velocities

For a project we use a brushless DC (BLDC) motor. Everything works fine until we tried to reach high velocities. I will first explain my setup, and than explain our problems using some graphs. ...
47 views

### How is Gyro drift error related to error in velocity and position?

While reading about IMU on wikipedia I found this about its disadvantages: "A constant error in attitude rate (gyro) results in a quadratic error in velocity and a cubic error growth in position." ...
395 views

### Which hardware to measure velocity via string/wire wheel attatchment?

This is a broad question but I want advice on what type of hardware I should look for to make a device that could measure the velocity of an object attached via a string/wire to some sort of rotary ...
306 views

### How to choose the correct graph

This is a question based on electromagnetism. Screenshot of the question and all the necessary stuffs are given below, This is the figure , And the choices that are given, First choice Second ...
68 views

### How to choose proper power supply for 8 servos on Adafruit shield with Arduino Uno controller

I use Adruino Uno micro-controller powered with USB 5V from PC and Adafruit 16-Channel 12-bit PWM/Servo Shield on it with 1000uF capacitor, powered with 6V 2A power supply. Seems like it is not ...
74 views

### current speed/flow [closed]

Note my questions are in form of explaining. its because I've scattered information (or assumptions) and it want to link them. that's probably why you can see me explaining to much? Question part: ...
127 views

### Looking for a circuit switch operated by velocity

I'm not at all electronically minded, but am looking for a small electronic circuit switch that is operated by velocity. Many years ago, I used to have a Casio watch that had some sort of switch for ...
38 views

### Is there a limit for voltage a PM generator gets to based on RPMs?

I build different small PM handcrank generators for fun, Recently I built a single phase generator and printed myself a couple transmissions. Now as far as I know 3 things affect voltage, speed of ...
40 views

### Detecting velocity in a specific threshold [closed]

I have three velocity sensors that are axis in 3D. I would like to know the best method to do basic ON/OFF trigger.. I'm thinking of a hystersis control, is there a method that can detect if the ...
884 views

### Electron speed in resistors

What affects the speed of electrons in a resistor? If two resistors are connected in series, they both have the same current ; same amount of electrons passing at a point per second. Then if one ...
116 views

### Methods of measuring speed of anemometer

I enjoy DIY, but to keep things simple I purchased an anemometer cupset (3 cups). I feel that a magnetic reed switch would get "bounce" at higher speeds and I was thinking of a disk with a slot, and ...
76 views

### Required velocity of each wheel in 3-wheel omni bot [closed]

I'm using a 3-wheeled omni bot which can move in any horizontal direction (example: https://www.robotshop.com/en/3wd-48mm-omni-wheel-mobile-robot.html). Given an object velocity (velocity at which ...
46 views

### Coordination of mechanical and electrical power in electric drives

I want to ask a question to respected specialists in electric drives. It is known that the mechanical power of an electric motor is determined by a simple formula: ${P_{mech}}= M {\omega}$; ...