# All Questions

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### Could use some help on what should be a simple LED wiring scenario

First off, I'm new here - found this site while researching to figure out why my circuit isn't working as I expected. I appreciate any help you can provide... The picture is the wiring diagram for ...
14 views

### help with QT1070

I am using AT42QT1070 touch IC in comms mode with I2C communication.I have used 10k pullups with SDA and SCL line and 47k pullup with CHANGE line(active low) as mentioned in datasheet. The CHANGE ...
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### What does the “phase margin” parameter of an opamp imply?

I was reading datasheet of MCP6072. I saw a parameter namely "phase margin" (table 1-2, page 4). As far as I know, "phase margin" is a control engineering term, and implies the phase difference ...
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### Power supply noise caused by external heat pad

I have a circuit that switches a 50W Sunbeam heating pad via a relay (for regulating temperature). My circuit is driven by a 5v AC/DC switching converter. The AC input to the power converter is shared ...
27 views

### NPN BJT Relay Circuit will not turn off

I'm applying a 3.3V signal with my Raspberry Pi to the base of an NPN transistor to activate a SPDT 6V relay (relay data sheet, model G2R-1-S-DC6(S)). The relay pickup/dropoff voltage is 4.4/0.9V. ...
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### What is the ALS and BLS pin for on the ISL83204A full-bridge driver chip?

The datasheet for the ISL83204A full-bridge driver chip documents "low sense" pins that connect to the source of the bottom N-channel MOSFETs. As those are typically connected to ground, what is the ...
32 views

### Circuit for a DC motor with 2 microswitches reversing direction

So here is what I am trying to do... have a DC motor wired to an on/off switch and 2 microswitches. Each switch will reverse the direction of the motor, so one switch tells the motor to go forward, ...
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### How do I direct input/output to correct circuit module. (2 bit calculator circuit)

I am designing a 2-bit four function calculator. With separate modules for division, multiplication and add/subtract. Subtraction is performed by adding 2’s complement to input. So I have 3 modules. ...
36 views

### Identifying DC electrical power connector

I have here a PowerFilm 10 Watt F15-600 Solar Panel, and attached to the panel is this connector: The male end attached to the panel has a little green rubber gasket on it and the female end ...
20 views

### Find four current mesh

I have to find the 4 current mesh in this circuit V1= 12V R1= 1/12Ω R2= 1Ω R3= 1/3Ω I1= 6A R4= 1/3Ω R5= 1/2Ω R6= 1/13Ω I2= 6A I tried a source transformation and got this I3= 144V R1-2= ...
21 views

### Conductance in a transmission line

I'm just trying to clarify the transmission line concepts in my head. Now wikipedia (that great source of always reliable information) defines the conductance in the transmission line as ...
42 views

### Is it possible to increase voltage without changing the current?

If we have a certain power applied to a circuit, and we would only like to increase the voltage applied by large factors... can this be done? Maybe by increasing only the resistance? Or maybe by ...
40 views

### Using a motor as a generator: How fast does it need to rotate?

I have a dc motor with the following specifications: ...
23 views

### Biasing resistors for RS485

I know I should have a terminating resistor but do I need biasing resistors on the +/- lines of an RS485 differential signal?
26 views

### Current limiter for NiMH battery charger

I am trying to learn about electronics by making my own MCU controlled battery charger for standard AA 1.2V NiMH and NiCd batteries. The supply voltage is 5V from a USB battery pack. I did a lot of ...
16 views

### Simple sound pulse (or frequency) to voltage for switch

I am building a tiny project using an android phone -- it simply has to drive a transistor switch on and off. Instead of going down the route of trying to interface to a micro controller via ...
42 views

### PC as USB Target? [on hold]

I would like to experiment with creating novel devices that act as USB targets. I want to start by using an existing old-PC to prototype my software. are there PCI boards that I can install into an ...
32 views

### Supply voltage of stepper motors

I'm going to use the following stepper motor drive chip: http://www.st.com/web/en/resource/technical/document/datasheet/CD00255075.pdf And I have choosen the following AC/DC converter: ...
76 views

### PCB design consideration for a SMA antenna

I am designing a PCB with the transceiver SX1231 (868MHz) with a SMA connector for the antenna. I don't know much about antennas. I would like to know if there is some parameters I need to be careful ...
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### Could a missing segment of a fan result in hardware failure [migrated]

I'm using an example that I have just encountered, but it involves a more general question regarding computer hardware and airflow. For some reason my NVIDIA 9800 GT fried, I've actually no idea why. ...
32 views

### How to deal with asymmetrical slew rate in 2-stage op-amp?

I made sure to take slew rate into account when designing this op-amp, but the slew-rate appears to be asymmetrical, as apparently the fall time is much slower than the rise time. How do I rectify ...
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### Faradays Law: How Does Curl E Change Over Time In a Coil? [migrated]

I think I am currently making a mistake regarding my interpretation of Faraday's Law. $\vec{\nabla}\times\vec{E}=-\frac{\partial\vec{B}}{\partial t}$ Assuming we have an electric field $\vec{E}$ ...
60 views

### What is the difference between Vss and Vs?

I know the difference between Vdd and Vcc and all the other ones,but I cant figure this out? Whats the difference between Vss and Vs?
35 views

### What is each pin's output voltage of an ATmega328P?

I would like to operate an ATmega328P in 3.3V supply alongside some other 3.3V non-5V-tolerant-peripherals. I looked up in the datasheet but I couldn't find an answer as to what is the output voltage ...
31 views

### Arduino Serial connection

I've written a small program for Arduino, in which it receives a two digit number from serial, for example ""26". Then it set's HIGH voltage to pin 2 with the duration of 6*100. That works fine, ...
57 views

### Battery chargers that can recharge disposable batteries. How do they work and are they safe?

A few years ago a product called SecondWind appeared, which claimed that it could recharge disposable batteries. To a layman like me that sounded like a great idea, but does such a product really ...
34 views

### L293D Problem- cant run both motors together

I am making rf based metal detecting robo and i had used 8051 for controlling the operation. The rf is fine and programming is also i think okay as i am getting desired outputs at 8051 output pins and ...
62 views

### How to choose optimum length for op-amp design?

I've heard that minimum length is discouraged in analog design due to matching problem but what's the drawback of using very long transistors apart from the size and resistance? Based on the ...
61 views

### How these circuit diagrams in the datasheet was made? [on hold]

I've seen so many IC datasheets, and so appreciate the elegant reference circuit diagrams they've made. I'm not meaning the 'function' of the circuit, but the 'beautiful' schematics itself, such as ...
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### how much time it will take to charge a 48v 35amphr battery using a solar panel of 20w

please help me out with this problem.I have tried several sites , but i didnt get a specipic method.please kindly include formulas used also.
34 views

### Testing a transformer

I have a 3-phase transformer with primary and secondary windings both star(neutral connected). When connected to 3-phase source whose line volts is 415V, I got the following readings at secondary ...
32 views

### Loss of speed on error-free aDSL line [on hold]

Is there such a thing as an old telephone line? Does a POTS cable deteriorate over time? I am talking about lines in area where no one lived 75 years ago. Sometimes a customer using an asymmetric DSL ...
42 views

### AVR SPI slave with interrupt

For a project I want to have two microcontrollers talk to each other via an SPI interface. I wrote the following code for the slave: ...
24 views

### Circuit with coupled inductors, need help with mesh equations

Are the mesh eqations in the image below correct? It gets a little tricky with the mutual inductance and my textbook gives no solution (American textbooks..). Click the image below for a larger view. ...
77 views

### How this circuit works?

Recently, i see such a circuit in a board schematic, but can't figure out how it works, why the first Op Amp has positive feedback ???? Thanks.
40 views

### doubt about using both watchdog timers in pic

I want to use the conventional WDT and deep sleep WDT. I will be using WDT to prevent any code lock cases if any. And the other after entering deep sleep mode.? My question is whether the WDT ...
51 views

### Aluminum winding in inverters

I am planning to buy inverter. I finalized one model; however, I was told that it uses aluminum windings whereas the other model has copper windings. They recomended I should buy the one with copper ...
28 views

### Q3.24 (d) Signals & Systems 2ed by A. Oppenheim

3.24 (d) Determine the Fourier series representation for the following signal: a_k = 1 (k is even), 2 (k is odd) The solution (see attached) breaks down the answer to two components: y(t) and z(t). ...
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### Communication between FPGA and OMAP 3530 using GPMC

I am working on a project which requires communication of data between Xilinx Spartan 6 FPGA (XC6SLX45T-2FGG484) and OMAP 3530, I have a ULK dev board on which The 32Kx8 (256Kbits) serial ...
406 views

### What is Overmodulation?

The Wikipedia article is very short and doesn't explain the concept very well, and there aren't any other sites that I can find that give a simple explanation. What does it mean by 100% modulation? I ...
49 views

### Help understanding switching voltage regulator (OKR-T/1.5-W12-C)

Looks like I need help understanding how to use the OKR-T/1.5-W12-C DC/DC voltage converter, b/c I just burned two of them. I am obviously doing something wrong, but I don't understand what. Here's ...
36 views

### Any good resource for MOSFET op-amp design? [on hold]

I've been trying to design a two-stage op-amp for a week, but I haven't been progressing much. Does anyone know good resources that teach you how to design an op-amp (transistor level), preferably ...
30 views

### Meaning of control pins: CE, OE, WE

Just understanding some syntax. On my Ram (6116) and Rom (27C64) it has a asserted low CE and OE pins. These I believe are control pins. I'm assuming to use the RAM for example, chip enable (CE) has ...
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### Scrapping conponents from an iphone

I have an iphone 4 that no longer works. I know that selling it is always an option, but i'm curious if i can scrap spare parts from it instead (especially sensors). I've looked online, but haven't ...
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### Is an AB amplifier feedback like this (image inside) possible?

Whole question in the title, don't know what more information is possible: Is an AB amplifier feedback like this possible?
49 views

### Transistor for 4-20 mA voltage drop resistor connection?

This is for converting a 4-20 mA current loop signal to a voltage. Is it okay to connect the resistor for measuring voltage drop with a transistor to allow for switching between voltage and current ...
53 views

### 8x40 led matrix [on hold]

I am building an 8x40 led matrix for a project and have run into some trouble coding. I have been using an arduino and I cant seem to get the code to run properly. I have been to several other sites ...
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### How do you calculate ICMR?

Let's say the Vdsat = 0.2V for M1 to M4, but 0.5V for M5. VT is 0.5. I think it's: ...