# All Questions

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### Why do we have exactly three parameters to describe relationship between current and voltage in linear elements?

I was simply pondering over everything I learned about circuits and electricity and there was this one question I couldn't give a simple answer to. Why exactly do we need only these three parameters ...
295 views

### Capacitor's energy(J)=F•V²/2 Why divided by two?

So if use these two equations: $$J=C\times V$$ and: $$F=\frac{C}{V}$$ I get: $$J=F\times V^2$$ Then why is it divided by two? Is it always like this or only for capacitors?
8k views

### Hexagonal resistor circuit (equivalent resistance ) [closed]

I've already find the equivalent resistance between A en B by Star-Triangle transformation , but can someone just explain how can i handle it by Symmetry,asymmetry network analysis ? all the resistor ...
173 views

### 555 Timer duty cycle changing formula

I am making a PWM motor speed controller. I used the Astable mode thinking it would work; it did not. Using an oscilloscope I noticed that I am only changing the frequency not the duty cycle by ...
103 views

### I need to know what diode to use to protect a 9V battery when connected directly to a 12V battery ( +to+ and - to -) [closed]

When connecting a 9V battery to a 12 volt battery what diode do I need to protect the 9V battery?
179 views

### Electric potential in a cicuit

Look at the image at (http://sub.allaboutcircuits.com/images/00082.png). Ignoring all the resistors in the diagram and assuming that the charged particles flow as arrows show, why does the electric ...
342 views

### Integrate residential hardwired alarm zone with modern wireless sensor

I have an old alarm system in my house that I would like to integrate with a modern system. The old system has hardwired circuits where multiple reed sensors in series monitor a zone with as many ...
62 views

In the circuit below, I want to measure the voltage going to the ADC (output from the voltage divider consisting of a fixed resistor and photoresistor) using an MSP-EXP432; however, the MSP-EXP432 "...
121 views

### What does "LB" out mean in a DC-DC buck converter?

Teacher gave me a schematic,and it includes a DC/DC buck converter with "LB" input and output,but i have no idea what the "LB" is,so i want to ask that does someone know what may the "LB" be?
758 views

### Most efficient way to power a LED (with 2 modes) using CR2032?

It's new for me to actually ask a question here instead of only reading which I did appreciated a lot in college. I have a background in mechanical engineering and do have some (low level) experience ...
5k views

### Bluetooth Interference with High Pitched Tone

i'm building a portable stereo system and am having some unwanted noise from the bluetooth receiver. the noise is typically a high pitched tone. please see the attachment for my chicken scratch ...
464 views

### Switching from battery to usb power source [duplicate]

I'm currently creating a small device to operate on a CR2032 battery when it is disconnected and a USB power when it is connected. I want the device to be powered by USB when it is connected, without ...
496 views

### Peltier cold temperature does not transfer when a heat sink is attached

I am trying to build a peltier cooler. It works. Cold side temperature is about 10C on cold plate of peltier. I want to blow this cool air out. But the cold temperature goes up as soon as the ...
3k views

### Finding proper motor for lead screw lifting?

I need to lift amount 0.6 kilogram up to 20 cm in 2 second with Permanent Magnet DC Motor with PWM speed control driver ,for this device: So i have one PM dc motor with 300 RPM MAX,12 V and 2 Watt ...
5k views

### Twin T active notch filter [closed]

So I know that this a band reject filter with the quality factor of Q I have two questions: 1-Why in one T the resistance is half the other resistances in the second T. 2- How would adding a ...
184 views

### Why are VOL and IOL seperately defined in I2C and SMBUS?

What is the point of defining VOL and IOL separately in I2C and SMBUS?
234 views

### MOS Current Mirror

I was investigating a MOS current mirror on the photo however i could not understand how the equation (3) was obtained from equation (2). I put a question mark also there on the photo. My second ...
5k views

### Max discharge rate of Alkaline AA batteries?

I'm in a bit of a tight situation, as I need a new battery pack for an upcoming competition, so I've tried to make my own. I put 7 of these: http://www.amazon.com/Rayovac-Alkaline-AA-Batteries-36-...
124 views

### BJT current distribution

I asked a similar question here a few days ago. I'm asking this question here again because the answers were ambiguous. Consider the first picture, no collector battery, only a base voltage is given. ...
2k views

### Op Amp output range

Consider the following scenario: The supply voltages of op amp (rail to rail) is 5V. Amplification factor of the op amp is 100. Which means if the input is 0.01 volt, the output will be 1V. If the ...
98 views

### How to design a transistor voltage divisor amplifier with a load resistance of 100 ohms?

I am trying to design a transistor amplifier with a load resistance but I have a lot of problems because the load resistance is very low. I can't change the value of it. I have read a lot about it but ...
774 views

### Can a secondary transformer winding output too much current? [closed]

Most household appliances operate with a step-down transformer if I'm correct where they decrease the voltage. Consequently, the current will be relatively high in the secondary winding, but this is ...
72 views

### Oscilloscope and probes [closed]

What effect , if any, has using a x10 probe on: Voltage reading of oscilloscope with resistance box set to zero ohm? Voltage reading of oscilloscope with the resistance box set to 900k Ohm? And what ...
116 views

### Identification question - tiny SCR & colorful Zener? [closed]

Update: The transistor with 3D marking is really an NPN, not a PNP. I found the exact model at https://www.google.com/search?q=pnp+3d+transistor&tbm=isch&source=univ&sa=X&ved=...
1k views

### HDB3 Waveform: Determining the bit sequence

I was asked to determine the bit sequence of a given HDB3 waveform. I understand that if there are three consecutive 0's then the fourth in that sequence must be a violation pulse. In this example ...
323 views

### Buck-Boost power supply I_ripple calculation

I'm not looking to get torn apart, just looking for a hand. I can't remember exactly how to calculate the RMS Current required from the output capacitors or a Buck-Boost power supply and I was hoping ...
510 views

### My first transformer causing safe fuse to go out

I found a fairly big, old transformer. I unwinded all the coils and winded them again. My primary coil has 20 turns, and the secondary coil has 200 turns. I didn't use any tools while doing this, so ...
202 views

### Using a laptop to communicate with an MBED module

I'm using an external power source to power an MBED module. I have the UART transfer and receive ports connected to a MAX232 level switcher in order to make the signals compatible with RS232. From ...
210 views

### Is there a full list of the names & abbreviation of electronic components [closed]

I came by a few electronic components that I don't recognize them from their shape nor their letters printed on the PCB. Is there a full list of the names and abbreviation of electronic components? ...
3k views

### BJT characteristic curves -- generating them

I know that the relationship between the base current $i_B$ and the base-emitter voltage $v_{BE}$ is given by the Shockley equation. $i_B = I_S (e^{v_{BE} / V_T} - 1)$ This is the input ...
108 views

### Which load resistance is connected to generator U2?

I have this op amp and one of the questions says Which load resistance is connected to generator U2? This is my attempt but I can not confirm if it right. No it's not homework, it examples I'm ...
1k views

### Can C547B transistors be used to build H-Bridge?

I've collected many C547B transistors from an old UPS, Can I use these to build h-bridge to control DC motors from Arduino?
546 views

### Can you connect a microcontroller to USB without USB built into the chip?

I have a microcontroller that I don’t know if it has USB capability built in but I don’t have the money to get one that does. Is there any way of either software to directly read an IO pin or use ...
179 views

### What's the thick wide aluminum tape used for in last mile grid transformers?

This YT video (scrolled to 0:45) shows the process of fabricating a pole mount transformer. At 0:45 the following is shown: there's a wooden brick used to hold everything together, it's covered in ...
674 views

### Converting a square wave into a sine wave

I have been researching methods for converting a square wave into a sine wave, but I cannot seem to reach a conclusion. Is it possible to preserve the amplitude and frequency of a square wave when ...
162 views

### Voltage regulator and Kirchhoff current law

In a linear voltage regulator like a TO-220: does Kirchhoff current law apply? What is the equation for the three currents flowing? In other words, what is the relation between I1, I2, I3 in the ...
192 views

### Is a ferrite sleeve better than a low-pass filter in order to protect a PCB from EMI caused by lightning

Follow up from previous post. This post is different because I am now focusing on the power cable and thus the power input of the PCB. This post is related to the EMI produced. I wrote a different ...
127 views

### Voltage regulator current and heating

Many texts I read take (Vin - Vout)*Iload i.e the current Iload is I3 in the below figure when calculating temperature of a regulator: But I3 is not exactly same with I1 there is something called "...
538 views

### How to reduce maximum power rating of dishwasher for use with photovoltaics inverter? [closed]

I have a photovoltaic power system and an inverter with an overall power rating of 1500 Watts. I want to connect a dishwasher which consumes 2200 Watts when heating the water. Question: What is the ...
232 views

### Arcade stick PCB not working as expected

I am using Logitech precision PCB to make an arcade stick. I am having a problem in button 1 (green) area. While I try to solder button 1 via R2, I had a great difficulty - R2 resistor moved every ...
138 views

### Can I control 6-7 devices of 12v max (each) with Arduino Uno?

I have to control following devices: 2 × Gear motors (each 12V, 200mA, speed & direction) 1 × Motor (12V , 1.2 A, on / off) 1 × Motor (3V, 110mA, on / off) 1 × dc pump (...
147 views

### Can synchronous data transfer be used for transferring large data in case of computer architecture and organization? [closed]

I am learning computer architecture and organization. I have this confusion, can synchronous data transfer be used for transferring large data in case of computer architecture and organization? I ...
297 views

### Can I safely ground myself by clipping an anti-static wristband to a half-inserted plug?

I'm having some trouble grounding myself for laptop repair. I cannot get the crocodile clip of my anti-static wristband in to my plug socket (I'm in the UK, so our sockets are a bit difficult) and I ...
145 views

### Basic audio amplifer circuit with transistors [duplicate]

Possible Duplicate: Simple Audio amplifier Using Transistors I'm looking for a basic audio amplifier(1w - 0.5w) circuit which is designed with transistors. Could you help about that?
113 views

### DC DC converter

I am newbie trying to build a circuit, please help me out. I am trying to build a DC-DC converter whose input will be 24V and output would be 5V 3A. I have picked AP63301WU-7 DC DC converter from ...
966 views

### Using a digital potentiometer with a SMPS?

Is it possible to use a digital potentiometer with an SMPS, to adjust the voltage? I'm looking at one with a 2 MHz -3dB bandwidth. What does this mean for a 300 kHz switcher?
178 views

### Design of carry chain -- Problems with clock's in design

I am trying to implement carry chain on FPGA and i want that resault from each block is written in register. Each block is 10 bit adder with following code: ...
866 views

### How to find the frequency of any device? [closed]

Are there devices which can figure out at what frequency every device transmitting radio frequencies operate at precisely? Say from a high of 2.4 GHz microwave to a low of 402 Hz pacemaker.
According to here the resistance drops liniar along the path. In scenario 1 at the start of R1 the resistance the current encounters is 100$\Omega$ and at the ...