# All Questions

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### Eagle library for MCP2551

I need to make a PCB, and the only software I have is EAGLE. All the other parts are listed in my libraries, but where can I find a library that has MCP2551 (CAN transceiver)?
4k views

### Most reliable Flash memory for an embedded Linux system?

What would be the most reliable Flash memory hardware to use for an embedded Linux system? I.e. one that has the least chance of losing data or getting corrupt when the power goes down? The Flash ...
356 views

### Accurate -2V reference

I have an old Keithley 175A multimeter that has been suffering from a bit of drift lately. Internally it uses a 6.35V zener and a couple of resistors to create a -2V reference, but the zener is ...
427 views

### How does this shunt regulator work?

I'm investigating battery monitors and I'm looking at TI's BQ76930 to take care of an 8 cell 24V LiIon. They provide the datasheet for their evaluation module (PDF warning) which includes the board ...
218 views

### Computational complexity of current netlist matching algorithms

I understand that the problem of matching two netlists could be reduced to the graph isomorphism problem which is NP-intermediate. Apart from that what are the complexity results of some of the ...
411 views

### Guitar Tube Amp RC Filter frequency fluctuation

In a simple LP or HP RC filter, is there a scenario where the centering frequency can fluctuate? So say the filter is a low pass and its set to pass everything up to 800hz, is there a situation where ...
3k views

### Maximum frame sequence number in sliding protocols

I am reading about sliding protocols and in almost every book its written this: Frames have sequence number 0 to maximum $2^n - 1$. Why is the maximum $2^n-1$?
490 views

### Regarding miniature solar panels

I am a bit confused. I want to buy a miniature solar panel like this. The problem is that all the miniature solar panels online in their specifications they give the peak voltage and peak current. ...
699 views

### Charge a Lipo with only Constant-Current Stage?

I'm following this standard algorithm: http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries Algorithm for charging LI-PO batteries? but am wondering if I can get ~80% of the ...
891 views

### How to get a pseudo-equivalent circuit for a 2N3904 transistor?

I'm trying to analyze an FM transmitter circuit, but it has a 2N3904 circuit. I have just basic circuit analysis tools; how could I get a circuit that does similar things to this transistor using just ...
2k views

### How does this antenna match work?

I had a matching technique described to me by a professional broadcast engineer. Here's the problem: you have a vertical antenna with a low resonant impedance1, let's say $38\Omega$, but you need a ...
2k views

### How do I invert a signal without deforming it, and without using a logic gate?

I have an IC which outputs pulses over an open collector pin. I need both these pulses and their inverses in my circuit. I want to do the inversion by using as few as possible transistors and without ...
2k views

### Build simple wireless door (open/close) sensor with Arduino or Attiny84/87

I have a spare Arduino uno, a few Attiny84 and a few Attiny87. In my Raspberry PI I have installed a RFM12Pi and have a spare RFM12b to use with Arduino. Last piece I have in the drawer is a sonic ...
269 views

### Series and Parallel Circuit

In the following schematic, if R1 = 42ohm, R3 = 33ohm, VT = 220V, and IR2 = 1A How do I find R2? simulate this circuit – Schematic created using CircuitLab
470 views

### Thermoelectric cooled Avalanche Photodiode sensor PCB

I'm designing a small PCB (max 5x5 cm) to bias and readout from an Avalanche Photodiode. Since the APD response varies greatly with the temperature, I want to use a cheap 12706 TEC together with a ...
885 views

### ADXL 335, lack of resolution for short angle inclination?

I am currently working on a project where I would like to measure X/Y inclinations changes, without worrying too much about the acceleration. I decided to use ADXL335 accelerometers in order to ...
180 views

### Designing an efficient PSU

I am designing a PSU capable of producing 5 watts @ 5V 1A. The design will power about 12 RGB LEDs (totaling about 400mA @ 5V) and a audio class D 1.4 W amp. Space is no issue but efficiency and cost ...
153 views

### Calculating phase angles from symmetrical components

I'm getting the following values from a meter: ...
1k views

### Sharing DDR3 memory between two sources

I have an FPGA and a powerful ARM processor both support DDR3. I am an experienced designer for smaller more embedded designs with less powerful CPUs but this is my first rodeo with a powerful ARM and ...
914 views

### 12 V relay instead of 9 V?

My RC car uses 2 relays (9 V, SPDT) for it's forward/backward movement, as image below indicates: However, RC car isn't able to be driven anymore. Specifically, servo works fine but motor can't spin. ...
351 views

### How should I understand this twin coil relay pinout? (Screenshot)

I'm currently looking on an automotive twin coil relay. The Datasheet gives me following schematic: My Question is: How could I test this relay? In other cases I put the corresponding Voltage on the ...
3k views

### Using RTOS support in OpenOCD

I can see that OpenOCD is RTOS aware and it supports FreeRTOS, which I'm using at the moment. I have looked at various sources and cannot seem to figure how to use this feature.
1k views

### Header plastic melts while desoldering

While I was trying to desolder a 6-pin header, the plastic holding the headers together melted. Now, that is fine, because I can pull out the individual pins that way, my question is, will the plastic ...
1k views

### How do I use an adjustable LDO regulator to power devices with USB that usually use AA/AAA batteries (or should I)?

I want to use USB to power devices designed to work with one, two, or three AA/AAA batteries. Three seems to be the trickiest, because it involves dropping the voltage only ~0.5 V from 5±0.25 V to 4.5 ...
1k views

### LM2575 switching regulator - ideal inductor and COUT sizes

I'm developing a PCB in Cadsoft Eagle as seen in the brd and sch files as per the links below: Eagle schematic file Eagle board file See the images below for screenshots of the schematic and the ...
893 views

### Current Division

The answers are : i2 = 8.15 i3 = 3.06 i6 = 1.02 i8 = 2.04 I understand how to get i2 For i3 : Combine R6, R7, R8 (Req1) (R6||R7) + R8 ...
14k views

### Voltage increases speed/ current increase torque?

I don't understand how current reduces speed in an electric motor,while voltage increases it. Wouldn't a stronger magnetic field mean there is a stronger "force" thus should be a higher acceleration, ...
2k views

### Connecting ON/OFF switch

Forgive me for the simplicity of this question but I am a microelectronics/very low voltage guy, and I have only 1 switch so I want to get it right the first time. Better safe than sorry :) I have an ...
3k views

### How important is the number of cores in RJ45 jacks with magnetics

While searching for RJ45 jacks with magnetics (MagJacks) in Digikey, we found that there is a selection criteria which says "Number of cores per jack". Though we have been using MagJacks previously, ...
326 views

### Can batteries conduct from their sides?

Back when I was younger, I used to take apart the old disposable cameras I'd take to camp to have fun playing with the parts and doing a bit of exploring. One year I ended up with a camera with a ...
301 views

### Standard doping concentrations for Si and GaAs Solar Cell (as well as other standard values)

I am doing a MATLAB project where I need to plot the current of a Silicon and GaAs Solar Cell under Air Mass 0 and Air Mass 1 conditions. I have used solar irradiance data to calculate their ...
1k views

### Designing a test instrument to be connected to an oscilloscope

I'm working on a piece of test equipment that is intended to be hooked up to an oscilloscope to measure the waveforms it produces. Since that's its reason for being, I figured it made sense to provide ...
348 views

### Power Transformer Rating Question

I am trying to understand power transformers practically. I have an inverter that outputs 12V AC. I want to step this up to 120V AC. My load will just be a resistive load that takes no more than ...
6k views

### Flyback NE555N driver and mosfet overheat

I have built a small and very simple flyback SMPS based on NE555N IC. The circuit exactly I did built from is shown below: It works nicely for small loads. However I have some issues with it: ...
596 views

### Identifying a bluetooth development device

This is some kind of bluetooth development device and I want to find out if this can be used with BlueLab software suit, but cannot find more details on it The main chip is BlueCore BC358 The ...
2k views

### DC or (AC + DC) coming out of a full wave rectifier

DC or (AC + DC) coming out of a full wave rectifier Is there a truly correct answer to this? Considering the representation as a waveform I would say its an AC wave form offset by some DC amount. ...
30k views

### Astable 555 timing circuit (0.5 Hz and 50% duty cycle)

I am trying to build a timing circuit to generate a 0.5 Hz 50% duty cycle signal. In other words 1 second on, 1 second off, and so on... I have searched a few places and found the following ...
122 views

### Software timers using hardware interrupt

I have to implement a counter for upto 30 minutes on my microcontroller. However the hardware interrupts maximum time is nowhere close to this. So I think I would be using the interrupt and increment ...
828 views

### Pros/Cons of using a Power MOSFET vs. a standard MOSFET

I recently sought (and received much great help) help with a brake light project from this site. That project went well and I installed it a week ago. Everything seems to be working as intended thus ...
411 views

### Please correct my understanding of “how electric works”

Being in Information Tech, I'm good with programming languages, processor logic, and the such. It's only natural I got curious about that outlet I plug my servers into. Here is where I am: I tried ...
171 views

### Best possible specs for a MEMS mic in 2014?

I want to use the best MEMS mic that's on the market today (June 2014) in terms of audio quality. Since I know that "shopping" questions are forbidden, I'll phrase it like this: What are considered ...
1k views

### Set a constant high signal to low

I have a keypad circuit, when I press and hold a key, the signal "key_pressed" is always high, as long as I keep the key pressed, which is normal, when I leave it, it gets low again. But I don't want ...
4k views

### “Halt and Catch Fire” BIOS cloning scene unrealistic?

The first episode of the TV series "Halt and Catch Fire" (inspired by the early days of Compaq) has two characters starting to clone the IBM PC BIOS in 1983 by creating a circuit that would display ...
808 views

### Protection against audio output shorting

I built a little USB powered audio amp (op-amp based) with 3.5mm audio jacks as an output. If I plug something to the audio jack, then during plugin moment there is a small period where the amp output ...
808 views

### Which schematic should I use with CNY 70?

I have tried this three schematics (pictures below), and they all seem to be working mostly the same. So I can't choose which one to use, and what are the advantages/disadvantages. Any ideas ? P.s. I ...
548 views

### Custom 'flex copper' ribbon cable

I am trying to learn more about what I believe is called 'flex copper' ribbon cable. This is the cable that you often see connecting CD drives to main boards in laptops etc. where the cable 'curls' ...
3k views

### Capacitor exploded - why?

Recently I had an explosion on my desk. A 220uF 25V electrolytic capacitor just blown up shortly after attaching a load. The high-level connection was: Phocos CA08 (solar charger controller) -> 12V-3....
270 views

### Small-value current sense resistor value changes after assembly

I'm using a small value (~60milliohm) and small-package (0402) resistor to measure current. When I probe the resistance with a (nice Agilent) DMM, the resistance is more like 100millohm though and it'...