# All Questions

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### What is the difference between a PT3 and a PT4 power lead?

I want to know the difference between a PT4 and a PT3 power lead. Can I use them interchangeably? http://www.cctvcamerapros.com/CCTV-Accessory-PT4-p/pt-4.htm http://www.cctvcamerapros.com/Power-...
8k views

### Which is the best, clean way to join wire together

I am installing CCTV cameras and I'm using a 3A adapter to supply power to the cameras, but I have very messy results when trying to join together very small wires with electrical tape. Is there any ...
43k views

### How to have an Arduino wait until it receives data over serial?

So I've wired up a little robot with a sound shield and some sensors. I'm trying to write a sketch that will let check the sensors. What I'd like for it to do is print out a little menu over serial, ...
9k views

### Arduino backup power supply

As a complete beginner in the field of electrical engineering, I am trying to build an alarm system on an Arduino board. I want to power my board using an external 10V power supply. In case of power ...
1k views

### How to Increase RF Amplifier Efficiency?

I've inherited another engineer's RF design and I would like to increase the transmitter efficiency. It's a 406 MHz radio that is using 14W to send out 5W (36%). The amplifier in use is http://www....
724 views

### Wireless Sensor to Internet

Looking for a low cost implementation to post ambient temperature readings from a sensor to servers via a COTS router. 1) Have a temperature sensor connected to a micro controller which sends data ...
887 views

### Does solder being or not being uniformly thin and shiny really indicate reliability of the circuit?

I'm currently reading an article (in Russian) and the author compares two devices (hard disks) of the same model one manufactured by Company A and the other manufactured by Company B. One of the ...
1k views

### Can I transfer data wirelessly to the inside of an aluminium can?

My problem is that I have to control (turn on and off) one LASER that is placed inside an aluminium can (not like soda can, but one 2 mm thick). So the question is if there's any way to do that ...
64k views

### Understanding motor constants Kt and Kemf for comparing brushless DC motors

So for a practical definition, the torque constant Kt specifies how many Nm of torque you'll get from the motor at a certain current? Is a bigger Kt always better? I am more confused about the ...
1k views

### Using Mic from 10 feet away for voice recognition

I'm trying to use a mic from 10 feet away. Background: for my senior project I would like to talk to a computer to run scripts, but I want to talk to the mic throughout the house. So I need to be ...
32k views

### Simple and safe solution to control a power plug with Arduino or PC [closed]

What solutions are available to control a power plug (or even if possible a light socket), i.e. turning it On and Off? I have looked for xbee/zigbee solutions but there doesn't seem to be a solution ...
11k views

### how can I read the serial port from arduino when I enter the chars and 'enter' in the keyboard

I want to make a arduino program which can wait in the loop, until I input some sentience and enter the 'Enter' in the keyboard, so the program can then read all the chars in the serial port and ...
2k views

### USB port and bench power supply ground difference

So I recently coughed up the \$250 for a semi decent bench power supply, the thing that got me though is when powering a circuit from this unit and connecting the BusPirate via USB is that the ground ...
29k views

### What is the difference between emitter and collector for BJTs?

the (surely simplistic) model of a bipolar junction transistor one is taught in foundational physics course appears to be symmetric. - So, what is the difference between the collector and the emitter ...
18k views

### What does it mean to “assert a pin”?

From the XBee/XBeePro product manual page 24 (link to pdf): Sleep Modes enable the RF module to enter states of low-power consumption when not in use. In order to enter Sleep Mode, one of the ...
536 views

### Will the constant voltage appear across the capacitor?

Could you please help me with this question? (Because I'm new here, it seems that I couldn't post an image.) The circuit diagram is the first picture from this lecture Voltage Vg is the node voltage ...
241 views

### Is there any wire with many small wires which i can use for multiple video signal

I have 6-7 cameras at one location. The problem is i don't want to have separate cable for 8 different cameras comming to my room. I am looking for one big wire in which i can have small 12-14 wires ...
8k views

### Choosing a relay to control outlets from Arduino

I'm working on a project that involves an Arduino Uno and some external electronics. I have a 12 V power supply that will connect to an outlet, and I want to be able to control this power using a ...
655 views

### How to connect MP3 player to TV using RCA? [closed]

I have a personal MP3 player with 3.5mm stereo socket for output. I have made a 3.5mm to RCA stereo cable by connecting the shorter inputs to the centers of each of the Left and Right RCA jacks and ...
2k views

### Could a bad hdmi cable be the cause of 60hz speaker hum?

I was at a friend's house trying to help him get his computer/tv/stereo connected in his new apartment. We had some difficulty getting the tv to acknowledge the video signal. The hdmi source option ...
9k views

### Power consumed by a CPU

I think the power for a CPU with current I and voltage U is I · U. I wonder how the following conclusion from Wikipedia is derived? The power consumed by a CPU, is approximately ...
1k views

### Explain the HIP 4082 pwm input from the datasheet

I'm trying to use an H bridge driver ic, namely the HIP4082 from Intersil. My question is about the pwm input shown on the "Typical Application" diagram from the datasheet. From the functional block ...
2k views

### Power supply with opamp and BJT transistor

I am studying for my EE exam but I couldn't quite get how this circuit works. Source Assume R1 = R2, Vout = 10V Vref = 5v. This is stable as it is, and when Vout decreases for a reason below 10V, - ...
680 views

### Converting a battery powered pocket heater into a portable 5V power source

I bought the attached pocket heater. The elevated element seems to be heater spirals so the red cables seem to lead to short circuit - capable circuitry. Background: So I built this tight case for my ...
592 views

### Oscilloscope time base

I am working on a personal project to make an remote oscilloscope using a PIC32 with wifi module for Android phones. So far I have did a lot of things, like connecting the wifi module of the PIC32 to ...
5k views

### Cell Phone as Microcontroller

I have a couple of cell phones laying around, one of them being this one: http://www.gsmarena.com/sony_ericsson_elm-3057.php Is possible to clear the flash memory and replace it with a bootloader and ...
9k views

### How to rebuild Ni-Cad battery pack for power tools

I have some cordless power tools which all require a certain 12V nickel-cadmium battery pack. My battery packs are dead, but the good news is they're held together with screws, so I took them apart to ...
141k views

### How to compare mAh and Wh

When looking at consumer electronic devices with batteries I sometimes see the battery capacity listed in Wh (watt hours) and sometimes in mAh (milliamp hours). I would like to be able to compare the ...
3k views

### Soldering a wire to a small MOSFET pin

I have this small mosfet with pins that are about 1mm in length that I need to solder to wires that are maybe 3 times larger than the pins. Should I just drop blobs of solder on it or is there a ...
1k views

### How can I determine the peak power consumption of my office

how can I determine the theoretical peak power cost per hour for my computer? What is the formula I can use to calculate this? Do I need to know amperage? My current cost per hour is ...
2k views

### Simple pn junction / diode question

Lest assume we have the setup presented in the image. What would be the potential difference (not voltage drop) between points A and B? Why? What effect will the pn junction barrier potential have ...
10k views

### With shielded twisted pair cable, do you ground one end, both ends, or neither ends of the shield

I've got a project coming up that's to be doing RS-485 communications over shielded twisted pair cable. The project will involve cable length runs of many 10s of ft and the cables will probably have ...
6k views

### Tracking Sun with Solar Panel - Need Photosensor

I'm trying to build a structure onto which I can mount a solar panel where the structure will be able to turn and track the sun - to maximize solar energy input. Can anyone suggest a photosensor that ...
294 views

### AC control coil relay

Is there a type of relay where the control coil can operate from a 220/240 VAC signal? I don't want to convert my existing signal from AC to DC. Are there any special search techniques to find parts ...
2k views

### Current regulation - oscillation problems

I'm playing around with opamps trying to build power supply for lead acid battery charger, but in general I want to learn a bit about opamp based design. I'm stuck with constant current mode. I'm ...
871 views

### Roomba - IR LEDs

I was wondering if it was possible to create a DIY virtual wall for the iRobot roomba. Can anyone explain how I'd go about figuring out how this works?
407 views

### Total resistance of circuit

Hi I'm struggling a bit with obtaining the total resistance of this circuit, I know it's an easy one I'm just a bit confused on how the resistors are merged using parallel and series operations, here'...
38k views

### How can I power my 6-pin PCI Express card without using an ATX power supply?

One of my older computers has a 365-watt power supply that, for various reasons, cannot be replaced with a new power supply. I would like to upgrade the graphics card in that computer, but all the ...
527 views

### Crosstalk on PCB

I am currently working on a PCB with DDR2 on it. We are bringing out the DDR2 CLK, DQS signals using pogo pins to make some timing measurements. The length of the pins are about 5 cm. The problem is ...
1k views

### What is the typical range of a nRF24L01+ module with PCB antenna?

I have seen the nRF24L01+ ( http://iteadstudio.com/store/index.php?main_page=product_info&cPath=7&products_id=53&zenid=qa08tp07o8bn54mjpo155e5o1 ) module linked before as a solution for ...
2k views

### What type of LED lights are needed for detecting retro-reflective markers for motion capture project?

I've a project in which I want to add 10-12 led lights around webcam's lens so that the camera can detect retro-reflective tape in it's viewing area. How this process works is something like this. I'...
246 views

### Options for object tracking

Say a company has a parking garage for its employees, and they want to track the traffic in and out. So they require that all employees put some kind of tag in their car window, and they have some ...
575 views

### remake PCB hole

I was soldering some components on a PCB and suddenly i realized that i soldered a wrong resistor (i should solder a 10k ohm and I did solder a 1k ohm). I tried to remove it, with iron solder (it wasn'...
8k views

### Why do Arduinos ship w/ 16MHz crystal instead of 20MHz?

Why do Arduino boards ship w/ 16MHz crystal instead of 20MHz? They are spec'ed for operating at 20MHz, after all. I guess there are a few advantages to running more slowly (lower power consumption, ...
4k views

### Microprocessor schematic symbol

When drawing a circuit a resistor looks like this. How would a Microprocessor look? Microphone? Webcam?
267 views

### battery management IC - duracell alkaline

I'm trying to monitor the health of my duracell consumer battery. Is there an IC that can do this? I've come across the MAX6775, but it appears that you have to use a voltage divider. Isn't this ...
19k views

### Why isn't it dangerous to put finger in light socket?

This is in reference to "Why three prongs?". Why does this hold true: "Curious kids might still stick their finger in a light socket and receive a shock, but the unwanted current was directed through ...
2k views

### What action is responsible for speed changes in a brushless DC motor?

Hi and thanks for looking! Background As a hobby, I enjoy tinkering with basic circuit building (often using Arduino) and lately I have mixed this hobby with another hobby of mine: building RC ...
When we build op amp circuits that use negative feedback, like so: ... we can analyze the circuit very easily, by assuming that $$v^- = v^+$$ due to negative feedback (when also assuming the op amp ...