# All Questions

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### What's the definition of “signal to ground capacitance” of a coaxial cable? What's the difference between it and normal capacitance?

What is the definition of "signal to ground capacitance" of a coaxial cable. I know what capacitance is, but I'm not sure whether it is just the same thing.
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### Can voltage be controlled in a fixed DC circuit?

If resistance is fixed in a DC circuit, can voltage still be controlled and changed from one value to another? Imagine this circuit, that has a fixed resistance of 1 Ohm, and the desired current is ...
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### Create large Arduino powered LED sign

For a project, I need to create a large display (most likely an LED matrix) that can be controlled via Arduino. Large means probably somewhere in the neighborhood of 3' by 10". I intend to use an ...
42 views

### Cooling an MCU to boost performance

As part of an ongoing project of computers ran by microcontrollers, one of my desktop models will overclock it's main MCU far past recommended operating frequency, since the first model isn't very ...
24 views

### PWM only works after touched with oscillicope probe

I am using 2 PWM outputs from a netduino 2 to control 2 servos. One of the PWM pins work perfectly fine but the other doesn't work until I have touched it with an oscope probe. The probe doesn't need ...
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### MAR /MBR / MUX Device

How can I modify this circuit to permit loading of the MBR from either the hex keyboard or from memory. As it is, the circuit can only load the MBR from user input.
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### Routing trace characterstic impedance determination based on interface

One question.... I have seen specifying routing impedance of interfaces from Manufacturers like for USB Differential impedance of 90 ohms DDR2 Single ended impedance 50-60 Ohms, Differential ...
24 views

### Finding the Thevenin Equivalent Resistance

In this problem I'm trying to find the Thevenin resistance in the circuit below: simulate this circuit – Schematic created using CircuitLab The first thing we do is remove all sources ...
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### Pulse Detection

I have the following simple LED driver. I over drive LED much beyond its current limits in terms of current. (90mA @ 30% duty cycle with an RMS current around 30mA). In this case the circuit ...
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### milliwatt-hour meter

I am looking for a way to design something that can tell me the cumulative power draw of a circuit -- the same concept as a Kill-a-Watt, but measuring mWh rather than KWh. An added bonus would be the ...
20 views

### Microchip's XC8 Linker doesn't recognize some custom section names

Slightly related to this one: http://programmers.stackexchange.com/questions/254734/microchip-xc8-how-to-pack-code-against-an-upper-limit I can relocate code just fine, but I'm having some trouble ...
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### How many IO pins in C8051F975

I can't tell how many IO pins that are available on the C8051F975. SiLabs website, Farnell and the datasheet p. 42 says 19 IO pins, so I guess that is correct, but the according to the datasheet p. 38 ...
50 views

### Why do dual-rank DIMMs have twice the bandwidth of quad-rank DIMMs?

I'm looking at the RAM compatibility table for my motherboard: and it shows that dual-rank (DRx4) memory modules can operate at twice the speed of quad-rank (QRx4) memory modules (1600 MT/s vs 800 ...
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### Noise from switching fans nearby disrupting the I2C bus

I have a RPi controlling a solar system which uses temperature sensors on the I2C bus, the sensors are away from the RPi (20m). The problem is that I have cooling towers and cooling compressors which ...
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### Issue charging a 12V battery using solar charger

I bought a 12V solar charger for vehicle batteries, because I am usually using wall chargers and I wanted to give green technology a try. When I connect the solar charger to my battery, it shows 10V, ...
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### Elongate the power supply p4 connector

I've got pico-psu, tiny little power supply for computers. Recently I've moved onto a new motherboard, connectors on this mobo are located further than before. So I had to elongate psu-p4 connector ...
38 views

### Microcontroller information transfer to Android application [on hold]

I wanted to do a project on bus tracking (GPS) through an Android application, therefore in order to do so: I need to install GPS module in bus along with microcontroller so that GPS fetches the bus ...
45 views

### Can I determine a formula for fuse disconnection times?

This is the first time I have used this stack site so am not 100% sure this question is on topic (based on the tags I couldn't find) but thought someone may still be able to help me. For those not ...
44 views

### Video streaming from image processor

The project I'm working on involves streaming video from an image sensor to an LCD, preferably as cheaply as possible. My question is: can I get an image processor/sensor SOC (a la ...
172 views

### PCB's and designing power connections

I've designed a few PCB's now, but never put much thought into good practices. They were small boards and most of the emphasis was put into just making sure everything that needed to be connected was ...
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### 19.5V, 5.13A power supply to replace 19.5V, 7A power supply? [duplicate]

I have this laptop: http://www.newegg.com/Product/Product.aspx?Item=N82E16834233058 It came with a pretty large and heavy power supply, so I am trying to replace it with a smaller one. The reason ...
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### Designing an optimal BPSK and/or QPSK transciever in SDR

I'm currently working on writing firmware for the modem on a cube satellite for my university's satellite team. My primary goal is to implement the data uplink & downlink. The RF system, ...
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### If the depletion layer of a transistor collector/base junction is thick, why are majority carriers still collected?

In "Principles of transistor circuits, 8th edition" (top of p26) it is said that once holes have been injected in the base region by a forward biased base-emitter junction (which I understand) of a ...
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### Which kind of motor would be better for an electric solar car, geared or non-geared?

My friends and I are working on an electric solar car. We want to know which kind of motor we should use: Geared or non-geared? 1kWh is the maximum power limit for motor which we can use to drive our ...
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### Multisim database BOM report problems; alternatives?

For example, we use four parts that are all .1uF 50V capacitors, all with different footprints. They’re electrically the same, so we’d want them to show up on the schematic as “.1uF 50V”. That means ...
35 views

### Linear slider motor mount location - Pros/cons [on hold]

I'm currently designing a linear camera slider, that will be used to hold camera equipment weighing just about 15 Kgs including all of the lenses and monitors and everything else. For those who ...
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### What is the difference between Machine and Time Cycle in 8085 microprocessor?

I have search this topic but their I can not find any specific answer to this . So I need some specific answers .
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### How does this constant current sink actually work?

So I have implemented a constant current source and it works wonderfully, but I was just hoping to try and understand it a little bit more! Here is the circuit in question: I have tried doing some ...
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### OrCAD- Hierarchical Blocks - Printing issue

I am facing one issue in OrCAD 16.7 version. Please give your ideas to solve this. Here is my issue. I have created my design using hierarchical blocks. I created one Main page for the whole design. ...
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### Should I keep my notebook connected to the AC adapter all the time or “excercise” the battery for long lasting battery life [on hold]

I have a Dell 7537 and I want to keep the battery in good shape. I have not found a clear answer as to how I should treat the battery. Most of the time I use my notebook indoors and connected to an ...
38 views

### What can be the consequences of charging a lead-acid battery with an excessive voltage?

In my field-operating device I use a simple PWM step-down to charge a 6V 3.9Ah lead-acid battery from a 5W solar cell with a voltage of 7.2V. Unfortunately the DC regulator got damaged today and the ...
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### Output resistance of Emitter Follower

I have to measure $R_{in}$, the input resistance seen by the signal. It was told me, that the quickest way is measuring the voltage gain using oscilloscope, insert a resistor before $R_B$, ...
19 views

### Make a pad connect to two nets with different names in Eagle

I have a part that is an SMT 'jumper', it is unpopulated and you use it by bridging the pads with solder. I want to put a track from the pin pad to GND. But the pad pin needs to also go to an address ...
46 views

### How does a Successive Aproximation ADC Handle Negative Voltages?

First, apologies for what must seem a simple question to most of you. I do understand the SAR algorithm. And Two's complement representation. My question is algorithmic. When a negative voltage is ...
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### Truck 24V->12V DC regulator gets me 13.5 volts, how can I get it to 12.0 +- 0.5?

I am wondering whether I need a new regulator or is there something that can fix my issue. BTW, what's the deal with 24->12V regulators that all output 13.5V volts? I have quite sensitive IT ...
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### Load sharing using asynchronous motors

I am involved in the design of a system composed of: multiple asynchronous motors, each equipped with separate drive, all acting in parallel on a load, via a common rack and pinion transmission. ...
35 views

### What is the current consumed by Ultrasonic Sensors/Transducers (1-2MHz) to generate Ultrasound waves

I would like to know what is the current consumed by a 1-2MHz Ultrasonic Sensor (i.e sensors used for Clamp on Ultrasonic flowmeter) to generate Ultrasound waves. The two ultrasonic sensor ...
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### STM32F103: not working USB when I turn on the timer

In my project the USB works, if do not use the timer 2. As soon as I enable the timer, the USB is not defined on the computer with an error -71. I use libopencm3; debian; gcc arm; what is the ...
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### Need a battery OR wall wart circiut [on hold]

I am just learning electronics so please bear with me ... I have a plastic model that I will be lighting with a (for me) complex circuit. All the youtube videos (model makers that light their models) ...
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### Cutout a polygon from another in any layer in Eagle CAD part creation

I am trying to create a part with a bespoke pad. How do I cut one polygon (for where the hole will be) from the original pad polygon. I don't just want to make a dimension layer and let the PCB house ...
28 views

### Ferrite antenna receiver for 33khz detection [on hold]

I would like to design a electronic circuit using ferrite rod antenna for receiving 33khz square wave signal being sent on undergroud armoured cable for detecting the burried underground cable. Give ...
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### Using shielded cable on an ebike hub motor, what ground to use

I have been having strange issues with an ibike that I have built, in that interference keeps being generated from the motors phase wires into the RX/TX lines on the hall sensors. I have been advised ...
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### Difference amplifier schematic

I am trying to get this difference amplifier working, but it doesn't seem to be outputting what I want it to output. $$V_1 = V_{in}\qquad V_2 = -0.5\mathrm{V}\qquad R_f=R_i, \quad A=1$$ I want ...
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### Capacitive where is the touch?

I am a newbie in the world of circuits and electronics. But we all started somewhere. I have this idea about a street sign that should be used as an instrument. All most like a Theremin. Touching it ...
25 views

### Prototyping Board to collect GPS data and Connect to internet using cellular network [on hold]

I am new to prototyping products like the arduino. I am working on a project and I wanna know what could be the cheapest way to implement that. I want to collect location information from GPS and send ...
55 views

### how to choose a mic and make sure not to overcahrge it [on hold]

I'm not sure that's the right forum to ask this question but I'll do it anyway . in my project, I've to listen to different machines using an MEMS mic by fixing the mic directly on the machine , the ...
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### Advantages of splitting a single NMOS transistor into two

Can anybody explain to me why in the schematic attached below that using two transistors is better than using only one transistor that is larger (longer)? I see that these two transistors are the ...
61 views

### TRIAC turning on asymetrically by itself when it gets warm

I've got a simple triac phase angle controller which is very similar to the MOC3021 data sheet app circuit. Most of the time everything is fine. The circuit looks like this: The triac is a ...