texts: Reading dynamic resistance values over a wide range

texts:
I'm trying to measure a material which might fluctuate between 500-100k Ohms with an ADC (e.g. an Arduino or Raspberry Pi with something like the MCP3008). I'm a novice with electronics, and my go to strategy was simply what I knew already: voltage dividers. The problem I'm running into is the wide range. My setup is like so, where I want to know R1:

3.3V -- R1 -|- R2 -- GND
            |
           ADC

I conduct the following simple calculations to get it:

v_out = ADC * 3.3/1024
R1 = R2*(3.3-v_out)/v_out

The problem as many of you likely know, is that highly mismatched values for R1 and R2 make for poor resolution, so the output looks very "steppy." Here's a simulated plot of a range of R1 values (what we're measuring), and the value calculated using the formula above using some common resistor values for R2:

The 1k and 4.7k are great for the low end, but they really flatten out at the high end where a 10k would be much better.

Is there a reasonably simple and low cost circuit/method to read a dynamic resistance that might swing several orders of magnitude?

Dreams/wish list:

lost cost (say, $25)
works with hobby-level hardware (Arduino or RPi)
measurement error of <= 1%

Ideas considered

Given the above, the dream seemed to have a variable resistor! I learned that digital pots exist and thought I could idea to use one. With some great answers there, it turns out I can, but the accuracy is poor (~5% vs. <1% with fixed resistors) and somewhat unrepeatable.

I also thought of having several R2 resistors connected to separate pins on the ADC. As the value of R1 changes I could switch which pin I read from. With this circuit, all candidate R2's will be connected to the output of R1 and analog inputs... I don't know what that will create with respect to a circuit. Are they floating? Can I sort of disconnect the unused pins so I don't get a weird multi-voltage-divider? That might be what this question gets at, just for the purpose of stopping power drain.

Sorry if this is a dumb question. I can find plenty of confirmation that this problem is real, such as from this article on making an Arduino Ohmmeter:

  The accuracy of the Ohm meter will be poor if the value of the known resistor is much smaller or larger than the resistance of the unknown resistor.

I just don't find much on what people actually do in this situation in the real world. Many thanks.


texts: Can anyone explain this USB ESD protection circuit?

texts: Also what are these diodes? I haven't came across them in any book yet.


texts:
I am looking for a open ALU to compute several equations like these:

y1 = e^((constant1 - x)^2/(2*x))
y2 = constant2/y1
y3 = y2*constant3 + x*constant4

Where x is the input of my system and y3 is the output.

I would prefer that the ALU supported floating-point operations.  Where can I find an open or free floating-point ALU?


texts: Invalid inputs in a SR Latch & Enabled SR Latch

texts:
Lets consider a SR Latch built with NOR gates. The invalid inputs are S=1, R=1. With enabled latch [gated latch], the invalid inputs are same, S=1, R=1.

Now, lets consider, NAND gates, in SR Latch, the invalid inputs are S=0, R=0. But in enabled SR latch, the invalid inputs are S=1, R=1 :

Why is this so? Is it because the latch getting inverted inputs, i.e. S'R' (as in the image)?

So, can I say, invalid inputs with SR Latch with NAND are:

S=1, R=1
If enabled, then S=0, R=0


texts: What should I buy to test whether my DC power supplies are able to provide their rated power?

texts:
I recently bought an aftermarket AC-DC power supply for a laptop which was woefully defective. When connected to a Chromebox, a boot message appeared indicating that the supply could not provide enough power. Although it was enough for a Chromebook to boot, the battery charge was indicated at 22 hours. Both instances were alleviated by using the original HP-branded power supply.

What what I buy that will allow to put a load on these laptop power supplies to both generate a load and also to test the voltage and amps it provides? A readout similar to my bench power supply would be nice such that I can see a digital readout of these values and to see if the voltage drops below spec as the amps increase.

I believe that what I need is a "load tester" but I don't know enough about this kind of equipment to know what it is I'm buying.


texts: What does the triangle look like in this diagram?

texts:
Using my intuition, I would assume the triangle in this simple circuit to be an inverter, but does that look correct?
What is this symbol?


texts: Why are my LED string lights not working with an adapter?

texts: I have a string of led lights that runs on two 3V batteries.  When I measure the voltage on my multimeter it comes to about 6V as expected.  I would like to use an adapter to avoid using batteries, so I took a USB phone charger and exposed the two voltage wires. The voltage output from the adapter is exactly 5V.  When I connect the adapter to the lights, the lights get hot and shine too bright as if they have too many volts going through them.  But there is only 5V as compared to the 6v coming from the batteries.  Why is it that the adapter is making the lights do this?  Thanks.


texts: 'reserved for future' bits in microcontrollers

texts:
Why some bits in microcontroller registers are marked as reserved or for future pupose? I have seen some address spaces also marked as reserved for future expansion.

Are these bits result of a 'plan for future'? Or are these 'useless but may be we can use in future' bits?

Do the manufactures usually implement functions for these bits in their future release microcontollers?

Example:

Screenshot from this document.


texts:
I'm currently doing a project that consists of:

Arduino Nano.
Battery.
Buck Boost converter.
GPS module.
TSL2561 light sensor.
BH1750FVI light sensors.
LSM6DS3 Accelerometer.
HDC1080.
MicroSD shield with microSD

All of the sensors are I2C based, GPS is UART and SD card is SPI.

My question is:

I'm planning to place the components inside a wooden box and mount the box to the top of the car roof with neodymium magnets so it is movable around the vehicle roof top for the measurement.

Will the wood box be sufficient to stop the magnetic fields produced by the neodymium magnets (for mounting) from interfering (if there is going to be any) with the components that are connected to the PCB board?


texts: Monostable Transistor Circuit not stable

texts:
I am just learning electronics, and bought a rather cheap oscilloscope (DS0138). Although it is not much, it is sufficient for my present needs. I am trying to use it to learn more about electronics.

I put together a Monostable Transistor Circuit

It works just fine when R6 is 10k

But when R6 is 100K, it is not stable.

I have tried to figure out what is going on, but I cannot.

Any insight would be much appreciated. Thanks in advance.


texts: How can I layout these regulators to minimize board size and EMI?

texts:
I have three switching regulators. A 12V, 5V(green box), and 48V(purple box). The plan is to supply both regulators through -/+12vout pours.

If I am trying to minimize board size while also minimizing EMI, what is the best strategy for laying out these regulators?

If I pack the components as much as I can, what will the consequences be?

A professional perspective on how power should be routed to the green and purple regulators would be highly appreciated. Lastly, any criticism of current design is extremely valuable to me.

*Board stack up is 6 layers with L2 & L5 as GND Layers.


texts: SPI signals show overshoot and ringing - does that affect reliability?

texts:
Here is MISO in yellow and MOSI in purple. I thought I would use a ferrite bead in series of each signal to filter out the noise.

I will be making hundreds of these boards. I'm not sure it is worth fixing, but I wanted these boards to be reliable as possible.

Here is an updated photo:
1. yellow CS
2. light blue sclk
3. purple MISO
4. dark blue MOSI
I used 4 probes on 10x with close grounds. I am running SPI at 2Mhz. The under and overshoot (see  ringing) on MISO is 1V magnitude. It seems the ringing couples to MOSI. How can I mitigate this? Would a series 33ohm resistor help?


texts: What is this white circle on this circuit?

texts: I found this circuit inside a LED reflector that turns on and off at regular intervals, and there is this white circle in it. I am guessing that it somehow keeps time of the intervsle, but can someone explain it to me? Also, I found this same circle on another device with 3 LEDs that turn on and off in regular intervals.


texts: Is charging current shared between Separate LiPo batteries wired in parallel?

texts:
I have two separate 2000mAh LiPo batteries (not RC type the standard 2 wire DIY component type https://coolcomponents.co.uk/products/lithium-polymer-battery-2000mah) Which I want to wire in parallel to achieve a combined 4000mAh. The specs say max charge current for one battery is 0.5C or 1A. If my charger charges at 2A is that shared between each battery so they are ok with 1A max or do both get 2A?
Many thanks in advance.


texts: stm32 timer synchronization between output compare and timer interrupt

texts:
I need to have timer output compare synchronized with timer global interrupt
,they start separately with two lines below

HAL_TIM_OC_Start(&htim3,TIM_CHANNEL_2);

HAL_TIM_Base_Start_IT(&htim3);

but i see 2us difference between them, what I have to do?

thanks in advance


texts: How can I control a 120v, 1amp fan with a Nest thermostat?

texts:
I have a fan (hot, neutral, ground) that requires 120V and uses 1amp max. I'd like to be able to control this with a thermostat so that the fan turns on when the temperature is above a certain set point. The thermostat I'm looking at, Nest, requires 3 wires ... 24VAC, a neutral, and a switch wire. When the thermostat activates the circuit, it connects the neutral to the switch wire.

How can I control the 120V circuit with this low-voltage thermostat? And is there a way to pull 24VAC power at the same time to run the thermostat?

I was thinking I'd need a 120V to 24V transformer, but I'm not sure how the switch circuit would look.


texts: How do I calculate the correct resistor, capacitor for a low pass circuit?

texts:
I'm looking through an article on www.allaboutcircuits.com and www.electronics-tutorials.ws in an attempt to learn more about how low pass noise filtering on for example a circuit that needs to supply 3.3V would be designed.

I don't have an oscilloscope, and I am most certainly not a mathematical or electronics genius, this stuff is all to make these weaknesses stronger, by learning.

So in a circuit like the following:

...how does one calculate the correct capacitance to use, determine which direction they need to be hooked up, and whether to use polarised or non-polarised caps?

Would I rather need to hook up the Vin supply to determine what noise there is in the first place, and decide from there, what I want to make my cut off frequencies?

I tried simulating this in iCircuit, but with some capacitor values, the frequencies fluctuated, and the voltage on my circuit increased in a stepping sinusoidal wave manner, so i clearly have no idea what I am doing. ;)


texts: Simulation of OCC, for a 3 phase Alternator using MATLAB/Simulink

texts:
I was wondering if there was a way simulate a 3 phase alternator on MATLAB/Simulink and obtain its Open Circuit Characteristics by conducting an Open Circuit test.

Also is there any other possible software tool,on which it could be simulated if it cannot be done on MATLAB/Simulink?


texts: Bypassing Capacitive Touch Sensor on Wemo Insight

texts:
I have a WeMo Insight plug that I'd like to use to monitor the power consumption of my networking devices but unfortunately if the power goes out, the WeMo device will not come back on automatically.  I can mechanically press the button to turn it on, but thought ideally I could control it with a little a microcontroller.  After doing some research and checking out some teardown articles, I couldn't find anything definitive on how the capacitive touch sensor works.
I opened mine hoping to find out more but cannot figure out how the touch sensor works or what controls it (I understand it's the metal piece coming off the circuit board, but not what it connects to).  I was hoping someone might be able to point me in the right direction as to how it might be working so I can continue on with this project.

If this weren't the device controlling my networking equipment, I could easily toggle the device on/off via an API.  My back up is to just use a stylus and servo to mechanically trigger the touch sensor...though it wouldn't be as clean.
Edit: I've been testing continuity to narrow down how this works.  Apologies for the low quality MS Paint quality markings. The IC only has 127DIK printed on it with pin 1 being at the bottom right.


texts:
This question is in regards to the EL817 Opto-coupler(http://www.everlight.com/file/ProductFile/EL817.pdf).

I'm trying to choose a suitable resistor to lower the current/resistor of the Opto's LED. With a source of 3.3v, an LED forward voltage of 1.2v at 20ma, I've calculated the resistor value to be 105ohms. Is this correct?


texts: How do I avoid interference in 433 MHZ RF transmission (in my case)

texts:
I suppose to do remote keyless entry (RKE) for door opening as a commercial product, there is DC motor which drive the door to open or close (receiver side), on transmitter side (remote) three button for 'OPEN' ,'CLOSE' and 'STOP'.

I'm new to RF, but I completed this project using a cheap 433 MHz transmitter and receiver model, and made compact size remote with that tx module, both tx and rx module is interfaced with ATmega88PA SMD package. For data processing I used the USART protocol for data transmission.

I'm using 3 V coin cell battery so it has a low range of transmission, but I overcome this with the antenna set, and now I'm getting the expected range (not bad).

The problem comes here: It is interfering with other 433 MHz. There is a water level controller in my company, and it will transmit data continuously for 30 min from the water tank to motor control room. During that time my receiver is not taking my signal since my remote is powered with 3 V, and that water level controller is powered with 9 V using HOLTECH encoder also.

So it's not good idea for selecting modules for commercial products. I want an RF IC for overcoming these problem. It should have its own protocol, since I wasted a month with these modules. It should be easy to configure.


texts: Op amp to supply current to 3 thermistors and an ADC voltage reference input

texts:
I have 3 thermistors in parallel that I need to measure.
These thermistors will be fast changing - think up to 100C in under 1 second.

I want to do this ratiometric measurement, so I want to supply the ADC reference from the same voltage which the thermistors are excited by.

Is it OK to do this using 1 opamp follower from the voltage reference? The LT1499 says it can supply up to 30mA, and there will be lets say max 2.5mA for each thermistor when it heats up (total 7.5mA), and a few 100um for the ADC reference pin.

Is this a normal technique? It would mean I can use just a quad package of opamps (+3 for buffering the thermistor output to the ADC input channels)

These thermistors are fast moving temperature, so will go from 10k to 500 Ohm in under 1 second, and with the current needed to maintain the 2.5V going up 20x accordingly. So this is effectively a variable load for the op amp? and I may have to put some 10n or 100n caps in parallel with the thermistors


texts: Looking for a particular solution to a wiring problem

texts:
I don't even know what such a part would be called, but here's my problem: I have a bunch of electrical equipment (sensors, relays, etc) on one side of a piece of stainless steel sheet metal. I have a data acquisition card on the other side of said sheet metal. I need to connect the equipment to the DAQ through the sheet metal. I would like to use screw terminals, if possible.

Does a thing like that exist, and what would it be called?


texts: Adiabatic CMOS circuits in low power design

texts: There are several techniques to reduce dynamic power consumption in low power design, but I could not understand the basic concepts of Adiabatic circuits and how will it reduce the dynamic power consumption in the low power design. Any help is appreciated


texts: Building an inverted peak voltage detector

texts:
So I am trying to build a detector that will find the lowest voltage dip of a DC source.

So for example, if I attach a load I can see what the voltage drops to.

I have built this peak detector in LTSpice

But I can't manage to get it to work to stick at the lowest voltage reached.

Do you have any tips?


texts: The schematic on the side of a Panasonic cassette deck is (-)-(o)-(+) where the brackets are actually a circle.  Does that mean that the negative is the sleeve and the + is the tip?


texts:
Is there a standard that all DC power jacks follow? More specifically, I plan to use 5.5/2.1 mm barrel, and I've found a bunch of these components on eBay, but they all lack drawings (not to mention 3D models).

I've found a 3D model, but it does not fit to a footprint of one commercial component that I've managed to find. And that is why I'm asking for a standard.

For example, this component

http://www.gravitech.us/poja2x51.html

does not have a drawing, they only state that it follows the IEC 60130-10 Standard, but I wasn't able to find drawings for this standard.


texts: Single Board Computer with no hardware memory for firmware

texts:
Im looking for a SBC that has

Completely no hardware memory for the firmware (e.g BIOS,  ,etc.), i think raspberry pi has that, except the bootloader which is ROM

OR

All firmware memory on the board is ROM and or EPROM, no EEPROM

Raspberry pi is a perfect example, but i need a bigger range of selection, so im looking for some keywords here. Or are there even any keywords for this or is that thing that you always have to look at specs, components etc.?

My question is are there already given knowing names for these devices that correspond to this?

Very beginner form

There are microcontrollers on the board, microcontroller stored
firmware (software), there are what i know ROM, EPROM, EEPROM. The
EEPROM you can theoretically reflash/hack via a digital
attack/physically attack, i only care about digital attacks. ROM, EPROM you only can hack when you have it physically.

ROM, EPROM = Safe from digital attacks.
EEPROM = Not safe from digital attacks.

No memory footprint SBC, ...?


texts: Setting up Norton Equivalent of RLC circuit automatically?

texts:
I'm trying to gain a better understanding of how the internal SPICE solve works, and for the most part I understand the basics of DC analysis and transient analysis when it comes to RLC networks. The big issue I'm running into is how to handle circuits with voltage sources instead of a current sources. Dr. Mitcheson's Lecture notes suggests converting voltage sources to a Norton equivalent current source. However, I am having a hard time figuring out how to automatically calculate the Norton equivalent circuit params in code.

Current strategy (no pun intended):

Resistors have a basic 2x2 elemental conductance matrix.
\begin{equation}\boldsymbol G =
\begin{bmatrix}
\frac{1}{R} & \frac{-1}{R}\\
\frac{-1}{R} & \frac{1}{R}
\end{bmatrix}
\end{equation}
Capacitors are converted into a simple numerical derivative:
\begin{equation}
\frac{I_c^{k+1} + I_c^k}{2} = c \frac{V^k - V^{k-1}}{\Delta t}
\end{equation}
Here k is the current time step and k-1 is the previous time step. Can easily be converted into a 2x2 elemental conductance matrix.
Inductors are approximated with a numerical integration (trapezoidal rule).
\begin{equation}
I_L^k = \frac{\Delta t}{2 L} \left ( V^k + V^{k-1} \right ) + I_L^{k-1}
\end{equation}
Here k is the current time step and k-1 is the previous time step. Can easily be converted into a 2x2 elemental conductance matrix.
Currents should be known for all nodes at the previous time step and current time step.
Superimpose all elements together to get linear system which can be solved with any matrix solver. Repeat for each time step.

From the above capacitor and inductor approximations I can create an equivalent resistor model which is valid at that time step only and work only with a pseudo-resistive network for calculating the Norton equivalent, which would be quite simple by hand.

Is my strategy at all valid? If so, how would I take the next step and make a computer perform the same calculation?


texts: Reasons for choosing a transistor instead of an op-amp as a buffer

texts:
I have often seen circuits for guitar pedals that use an emitter-follower configuration as the input and output buffer (see example below). If an op-amp can provide a greater input impedance / lower output impedance, why are they not used instead?

Is it simply the case that a single transistor circuit is cheaper to mass produce? Some people (audiophiles) say that transistors sound better, claiming that op-amps have a more "clinical" less warm sound. I am quite skeptical about this since there is no obvious difference in the frequency response at audible levels.

If I'm not trying to mass produce a pedal and I'm looking to build something of quality, is there any reason not to use an op-amp as a buffer? In your experience, do op-amps have any intrinsically negative effect on the sound?


texts:
I'm trying to determine the most effective layout for a 2.4GHz chip antenna on my PCB. I';ve read through a few application notes and Datasheets but none really clarify which antenna setup is most efficient or will allow the best range.

Right now I have looked at two options, but I'm no closer to knowing which might be best. I'm using a discrete Balun network and a pi-network for later tuning.

The two options I'm toying with right now are the horizontal orientation routing:

Or the Horizontal routing, diagonal antenna:

So which one would give me the best range?

I'm also completely uncertain if I've set up the feed-line correctly, so any tips or advice on setting that up correctly would be greatly appreciated too!

Antenna I'm using:
http://www.johansontechnology.com/datasheets/antennas/2450AT18B100.pdf

Schematic of set-up:


texts:
I am trying to simulate the same IR code coming from my Heater remote control, but it seems like is not a standard code transmitting.
I have took a part the device and I discovered there is a CHIP BEC5104S which is an IR generator which has poorly documentation.

I am using Arduino to recreate the pulse with IRremote library which allow me to read the raw timing and play it back. The result is that with my DVR and TV everything works fine but as soon as I try to record my heater remote, it doesnt transmit correctly.

I tried to simulate the IR with a simple schematic like this https://cdn-learn.adafruit.com/assets/assets/000/000/550/medium800/light_irremotetest.gif?1447976110 ( I double checked with a phone camera that was transmitting ) but still didnt work.

I was thinking that my IR led wasnt the right specs, then I replace on my remote and it did work.

I have hooked it up to the Oscilloscope to understand if the signal was 38khz and it is.

I am not sure how to translate the timing from my oscilloscope as it seems to have ON and OFF timing the same.

How can I make sure I can match the 6 codes of my remote? Should I just hook it up to my arduino with an interrupt and trying to record it?


texts: High failure rates after pcb coating using DC 3140 RTV

texts:
We have been protecting PCBs using Dow Corning 3140 for many years now without any problems. Last couple of months however, one board after the other is failing after coating. We can't think of any other possible solutions. Hopefully one of you can point us in the right direction.

What do we do?
The boards I am referring to are control boards for a specific type of machinery. They come in different types for different machine capacities. The boards are all very much alike. The problems only occure with the "professional" range of machinery.

To make sure the boards are in good condition when delivered to us, the machine with the board is tested completely. No problems so far.
In the next step, the board is removed from the machine taking all possible ESD measures. The board is never touched without the necessary connections. Transport is only carried out using the pink bags. Consequently, the DC 3140 is applied using a 30 ml seringe. The boards are cured at room temperature. We do not use any cleaners, primer or whatsoever, the silicone is applied directly to the board. After coating, the boards are mounted to the same machine again and we end up with a failure rate of more than 80% ...

We have discussed this issue with the OEM but without any probable cause. To make sure that the problems are not ESD induced, we have invited an ESD expert to our workshop to check and measure anything that could be measured. Conclusion: all measures are in place, co-workers are using the equipment properly, nothing to improve.

The last possibility we could think of is the DC 3140 itself. Could this be the cause of all this trouble. As stated before, we have been using this silicone for many years now without any problem whatsoever.

Do you have any suggestions on a probable cause for our mysterious failures?


texts: Potting microSD card inserted in slot with epoxy resin

texts:
I would like to know whether it is possible to completely cover/pot a microSD card inserted in a slot (which is soldered on a pcb) with an epoxy resin. Will the sd card continue working properly? Will the card's contacts work without problem with the epoxy? If this could be done but not with epoxy, please suggest other potting compound or technique.

My reasons for doing this are to prevent microSD removal from the slot and also waterproofing.


texts: How to control 0 to 110 of AC with microntroller rms output of 0 to 5 v

texts:
Is it possible to control high current with small rms voltage?

UPDATE

Do you think that this is gonna work?


texts: Indicated vs. true RMS value of sawtooth waveform

texts:
A sawtooth waveform is fed to "Average reading (with full scale rectification)" ac electronic voltmeter. This voltmeter is calibrated for RMS value of pure sinusoidal input. What will be reading displayed on voltmeter? Also find percentage error in the reading. Take amplitude as 10 volts and time period of 1 second.
The given answers are:

RMS indication = 6.5 V
error = 12.7%

Here's what I have done so far
\$V_{RMS}\$ of sawtooth is 5.77 V and average is 5 V. \$V_{RMS}\$ of sinusoid is 7.07 V and average is 6.37 V.  So the ratio of \$V_{RMS}\$ to \$V_{avg}\$ is 1.11 and 1.154 of sinusoid and sawtooth respectively. But the question here is that voltage of sawtooth waveform is being measured by sinusoidally calibrated voltmeter and I don't understand how to find the value that will be measured and what will be the error.


texts: Use ATX power source to power Raspberry Pi

texts:
I'm setting up several Raspberry Pi's and Arduinos connected together, and I'm looking for a way to power them.

Would it be possible to adapt an ATX stock power source with female USB plugs using the 5 V wires to provide more than 500 mA?


texts: The results of my magnetic flux data from voltage recorded

texts: For my electrical engineering senior design I created an experiment to test magnetic flux (more voltage) through a receiving coil. There is a large sending coil with A.C. voltage and a small receiving coil with an oscilloscope measuring voltage_pp. Its wireless power. I ran three tests. One with the two coils, and two experiments with different metallic materials in the center of the receiving lens. Sort of a wireless transformer. I have results. I found online that flux has a 1/r^2 relationship. My results show a 1/x at almost the entire range of distances. When the two lenses are close I think mutual inductance comes in and stops the constant increase of voltage measured. If I plot voltage against 1/distance I definitely get a straight line. This would mean a 1/x relationship right? But online everywhere its 1/x^2. Also my large sending coil has a big radius which I'm wondering if that matters. If i take my slope from the straight line its voltage/(1/x) = voltage*x which is a weber? Or flux? I was really happy to see the slope is units of magnetic flux but I'm unsure. (its cm so not exactly weber but i can change to meters later) Big takeaway is why my results are 1/x and am interpreting the results of my slope correctly? I'm all on my own on this experiment, my group mates have done nothing lol and my prof has admitted to not knowing what wireless power transfer is about. Any help would be appreciated. (I have a capacitor on my receiving coil so the voltage induced can have zero impedance by sending the ac voltage at its LC resonant frequency. The tested material would change resonance but everything was in the range of 190kHz - 210kHz.)


texts:
I am new to the field of electronics engineering as I'm originally an electrical engineering graduate (Read Power Systems, machines and HV engineering) so I studied only 'basic electronics' in my undergraduate.

Having said that, I am currently working on a project developing a disk array controller. My question is: Do I call this an ASIC or a SOC? I thought it was an ASIC till I read this article.


texts: What is the best way to layout a PCB with crystal oscillators and MCU?

texts:
I have heard that the clock circuit is a noise source and that the clock circuit is also sensitive to noise. I believe that keeping the clock circuit close to the MCU and keeping other routes or circuits far from clock circuit is always better.

In my design, there are many wires on a four-layered PCB. The layout of the MCU（STM32）with crystals is shown below, without routing. The MCU is placed on the right of the image and the two crystals are placed on the left. Crystal 1, Y1, is 32.768 KHz, and placed on the top left corner. The Crystal 2, Y2, is 8 MHz and placed below Y1.

The second image shows all routing of this part of the PCB. The thin green lines across Y1 are responsible for communication between the MCU and the CPLD. Signals up to 72 MHz will go through these lines. The thick green lines below Y2 connect the ADC module of MCU and analog signals will go through these lines. The thick yellow lines on the bottom left corner are responsible for analog power and the analog reference of ADC module of the MCU.

What a mess it is. I am concerned about the functionality of the PCB, especially from EMC problems. Can anybody give some suggestions on how the PCB can be improved?


texts: Selecting Appropriate TVS Diode for protection against Load Dump

texts:
I am working on Bike Flashing lights. I have used 7805 as the regulator to supply +5V to the controller, also have 1N4007 in series at the input with capacitors.

I don't want to add any expensive components which may increase the cost. I was looking for TVS diode, but having the hard time to select the appropriate one for my application.

Load Current is 100mA (Max)
Voltage source is 12V battery

7805 Maximum Input Voltage is 30V.

Questions :

What should be the minimum breakdown voltage we should look for in a TVS?
What should the TVS maximum clamping voltage be in order to best protect the L7805 from Load Dump?

Supply Circuit :-

Below is the screenshot of some of the TVS Diode which is low cost.


texts:
I'm currently programming a pic16f18323. I'm using MPLAB X. And XC8 as the compiler. I just want to ask if pragma configurations can be shown as ('110' is the binary representation of 3 bit RSTOSC configuration in Oscillator configuration register. Page 50 in 'PIC16(L)F18313/18323' datasheet) :

#pragma config RSTOSC = 0b110

instead of

#pragma config RSTOSC = HFINT1

I tried using the first expression instead of the regular(second) one. It didn't give me any compiler error, but it didn't work properly neither. When I program the pic with simple blink code, with 'HFINT1' configuration it works well. But when I use the binary number, the frequency of the blink increases largely.

It makes me think that it is probably about the syntax, but still I'm not perfectly sure. It doesn't affect my work directly, I encountered this problem by coincidence and I just became curious. If someone knows about this I would be glad.


texts:
As far as i understand eddy current direction is determined by lenz's law.
But the following example -

describes the currents and magnetic field direction when the current in the coil increases -

but when the current decreases -

the magnetic field also decreases, so according to lenz's law the eddy currents are directed so they induce a magnetic field in the same direction as the magnetic field of the coil - which is counter clockwise (unlike the clockwise eddy currents in the image).
how can that be?? eddy currents are supposed to stay in the same direction!


texts: Changing reference planes from AGND to DGND. Should I put a stitching capacitor near the via?

texts:
Based on my experience and reading, I would generally put a stitching capacitor between power and ground (for example) if my signal was changing reference planes.

http://www.hottconsultants.com/techtips/pcb-stack-up-6.html

Do I need a via or stitching cap when I transition between physical reference planes of the same potential?

Let's say for the sake of argument that I have a situation were I absolutely need to run this signal from DGND to AGND briefly. Normally, I would put a stitching capacitor....but I also would tend to keep as little coupling as possible between AGND and DGND.

Assuming that this signal (SPI speeds) does need to briefly cross AGND, should I put a stitching cap there?


texts: I am switching 5V relay with an Arduino Nano. When using USB cable as power source, everything works as it i supposed to. When using external source in form of batteries,(First I tried 9V battery, then 4xAA 1.5V batteries) when I switch relay, the voltage drops to 4.7 V from 5V pin to GND.Battery voltage at input stays at 6V. What might be causing this?


texts: Simple methods for switching a boost converter, to get a stable output voltage?

texts:
I've made a boost converter circuit, with a MOSFET as a switch, and a (7)555 timer operating as an astable oscillator, and it's output goes directly to the MOSFETs gate pin. The problem is that the input voltage for the boost converter is unstable (solar panels). When the input from the solar panels is high the output from the boost converter is also higher and when input's low, the output is also lower. That is because the 555 is operating at a constant frequency and duty cycle.

What can you suggest for controlling the 555, so its output would switch the MOSFET at such frequency/duty cycle, so that the output voltage of the boost converter would be stable? I need it to be around 14.7V, minimum 14.4V and maximum 15V for my CSB GP 12120 battery.

I've played around with 555's control voltage (5) pin, tried to use op amp to compare the batteries voltage to the solar panels voltage and apply the result to the 555 in a couple of ways (the fifth pin and the supply voltage). There were cases, where the output was more stable, but still, that was not even close to what I need. Maybe I just didn't do it right, or maybe 555 is just not what I need.

So in case you think I should use something else than a 555 timer, please suggest it. And please give me as many details as possible.


texts: Does it always make sense to constrain an I/O port?

texts:
I am following an Altera online course on their timing analyzer software called TimeQuest. In it, their recommend that, at the very least, all clock and I/O ports be constrained.

In my FPGA design, I am generating an output clock pin to an ADC by muxing various clocks (some generated internally). As far as I know, the way to constrain output ports is to use the SDC command set_output_delay, by specifying setup and hold constraints with respect to a clock.

In my case, there does not seem to be any meaningful clock to base the set_output_delay contraint upon. How should my output clock be constrained? Does it even make sense to try to constrain this specific output port?


texts:
I have created a circuit that can basically make a motor run in both directions using an on-off-on SPDT rocker switch and two relays.
Here is the circuit.

The catch is that this motor is 30 A at 12 V. That little rocker switch can only handle 5 A. I have highlighted the high current paths that the motor uses in red.
Could I use small gauge signal wire for the relays and switch, and thick high current wire for the motor current path without using a second power supply?


texts: EEE-INST-002 Wire Derating - Single Wire vs. Bundle/Multi-Conductor

texts:
We have an aerospace application and are having trouble defining EEE-INST-002's current derating guidelines in regards to wire.

The issue that I have isn't about stranded versus solid. MIL-W-22759 does seem to classify tinned, copper strands as one wire so long as the outer diameter of said wire is of its declared gauge. Similarly, we don't have any cause for concern when it comes to multi-conductor, shielded, jacketed cable in the sense of, say, Ethernet or something similar.

What I'm having trouble understanding is what exactly does NASA consider to be a "wire bundle," and when should we use the derating guideline for bundled wires/multi-conductor cables?

Consider this portion of our application:
We need a power input of something like 85A @ 70V. INST-002 would dictate that we need 8x 12AWG wires since, according to the derating table, 12AWG wire is rated at 25A, and 4x would cover the positive bus and 4x the negative (with some margin to spare).

But wait! We just tie-wrapped these wires inside of our box, making this a harness (bundle) of 8x wires. So....if these are now part of a bundle, did our derating of each 12AWG wire in this bundle suddenly drop to 11.5A according to INST-002? Why?

I found an article titled "Derating Standards and Thermal Modelling Tools
for Space Harness Designs" which boils down to "why in the world do multi-conductor cable ratings vary so widely between different space agencies?" But I was not able to glean any sort of reasonable answer from it regarding my own application.

Any thoughts? And more importantly, are my boss's fears that we suddenly need to double the current rating for every cable in our unit unfounded, or at least able to be allayed?


texts: I am using ESP12F to drive LED array circuit for dimming and other functions. Supply from LED driver is constant current for LED array. What does ESP12F requires? Constant current or Constant voltage? And what should be minimum amp I should take into consideration. I am considering 3.3v, 1A supply.


texts: Use NRG sensors - Anemometer (low level AC sine wave) and Wind Vane (analog DC voltage) with ESP8266 or ESP32

texts:
I have set of sensors

NRG #40C Anemometer:
Output signal:

Signal type: Low level AC sine wave, frequency linearly proportional to windspeed.
Output signal range: 0 Hz to 125 Hz
Output voltage at 60Hz: 12 V (peak-to-peak) typical.

NRG #200P Wind Vane (page 3):
Output signal:

Signal type: Analog DC voltage from conductive plastic potentiometer, 10K
ohms.
Transfer function: Output signal is a ratiometric voltage
Output signal range: 0 V to excitation voltage.

What I need to use this with ESP8266 or ESP32 - preferably on GPIOs not on analog input?


texts:
Can't find the 'design' menu on the toolbar anywhere. I am looking for the 'update template' form.

I am still learning altium so I have no clue what I am missing. I opened an existing project and want to update the sheet information section.


texts:
While going through the text, the author says that when \$R_1\$ is shorted \$V_B=10, V_E=9.17, V_C=9.2.\$
I understand that \$V_B\$ is \$10\$ but I am getting \$V_E\$ as \$9.3\$ and I have no idea how to get \$V_C.\$

Edit: Since there is a slight confusion in my question I'm including one more image with the introduction by author.
" Let us discuss troubleshooting voltage-divider bias because this biasing method is the most widely used. Fig 8.16 shows the VDB circuit. Table 8.1 lists the voltages for the circuit when it is simulated with MultiSlim. The voltmeter used to make the measurements has an input impedance of \$10M\Omega. \$"


texts: What are the steps needed in finding capacitance from this circuit diagram?

texts:
Can anyone please point out the steps needed (not the final answers!) in finding the following things from this circuit diagram?
It's difficult to find resources regarding complex circuit problems online.

1) Overall capacitance of the capacitors in series?
I'm aware that in series charge is less in total, and would be found like this: 1/C tot = (1/C1 + 1/C2 + etc). The issue here is what on earth does the resistor do to affect this value?
2) Overall capacitance of the circuit?
So here the total series capacitance is just added to the capacitance of the parallel capacitor. But what does the resistor do?
3) The max charge in the circuit?
Charge = Current X time. But what does the resistor do? How do I factor this in?
4) The max energy in the smallest most capacitor?
Now this bit I'm pretty lost on.
Thanks!


texts: When does Direct Source-Drain tunneling become a problem?

texts:
Because of the probabilistic nature of quantum mechanics, direct source-drain tunneling is bound to happen as a result of CMOS scaling. The smaller the transistors become, the more tunneling occurs.

My question is: Assuming that CMOS scaling continues, when does the tunneling become a serious problem? At what size (minimum feature size/gate length etc.)?


texts: Why does my Inductor Get Warm? (Inverter Output Filter)

texts:
I have a H-Bridge based Inverter that modulates a 350VDC source into 220V RMS @ 50 Hz. Right now I'm working at just 70VDC but my output inductor is getting quite warm. Here is a schematic:

The output inductors, L1 and L2, both get quite warm when the DC source is at 70VDC. I haven't gathered the courage to go higher voltages. The switching frequency for my PWM is 16KHz. I have no load on the inverter. By adding a 1.95 Ohms shunt resistor I was able to measure the RMS (I assume mostly reactive) current, which was approximately 400mA. Note that the output waveform looks extremely good and relatively free of ripple, even under some load.

The particular inductor I'm using is 2320-V-RC. The DC Current rating is 3.8A. I don't have enough experience with filters meant for power to know if I should be using a different type of filter or a different sized inductor.


texts: What is the purpose of a capacitor to ground?

texts: I have here a filtering circuit from a microwave. What is the point of the capacitors to ground. Another answer in a previous question of mine said they were used for filtering however I don't understand why. The inductors by the way are part of a common mode choke.


texts: Change layer to a raster image object in Eagle

texts:
I have a project in eagle cad with an image in bmp which I imported some months ago.

I have it in the top layer and I want to move it to the bottom one, but I can't find the way to change its layer.

What should I do?


texts:
I have an MPU-9150 which uses I2C address 0x68 by default, but I'd like it to use address 0x69. This is possible by desoldering the 3-way AD0 "Jumper" on the breakout board. By default there are 3 solder pads and pads 2+3 are connected, so that pin AD0 is defaulting to "ground".

So as I understand it, I need to "desolder" the connection from pads 2+3 and then I can connect VCC to pin AD0 which will switch the I2C address to 0x69.

I tried desoldering, but it looks like this won't "break" the connection even if I get rid of all the solder. It looks like it'll still be connected due to the little "circle" and the edges around it (see images). I haven't done such tiny connections before yet either - so any tips on how to best proceed ?

Also, I'd like to understand better how this 3-way jumper works. So assuming pads 2+3 are desoldered, can I "manually regulate" which address is going to be used by putting "high" or "low" on pin AD0 (or is it then going to be fixed to 0x69)? ... and not connecting anything to the pin now would probably be "bad"?

What happens if I'd solder AD0 jumper pads 1+2 together?

Will it then always be using the higher I2C address (0x69)?

For future reference: Following the suggestions of SamGibson, cutting the connection between pads 2+3 using a hobbyknife + loupe - and then connecting 3.3V to AD0, it now indeed reports I2C address 0x69, see image :


texts: Air circulation and condensation in custom enclosures for outdoor project

texts:
I am designing 6 custom enclosures in mild steel to be placed outdoors for 5 months in London UK.
They will be interconnected, only one will contains 4 power supplies, all with conformal coating and keeping cool (don't overheat after numerous testing). There will also be two Raspberry Pis inside.
Up until now I thought I would use Gore vents to avoid condensation.

Unfortunately the enclosures won't be perfectly sealed, and the enclosures will be painted with a dark colour.
What type of fans (or else) should I install in order to:
- provide decent air circulation
- avoid condensation (fan heaters?)

Should I add vents?

Also, as the boxes will be connected with holes through which I will run cables etc, should I install such vents in each one of them or just in one of them?


texts:
I was wondering what energy efficient protocol should I use for a FSK modulation in a steel conductor. My limitation is on the number of continuous bits I can transmit due to the charging and discharging of the capacitor, and the circuit is battery operated. From my testing I can only transmit a byte at a time with a delay of 200us before a transmission of the next byte.

For a byte communication, the protocol I was considering is to use start, data bits and send it in byte chunks. The packet is going to be fixed length to reduce the packet size. I am not very sure would I need preambles and a stop bit as that would increase the data size, and the start bits and fixed length would determine the start and end of the data transmission.

Paul


texts: Adding an Obstacle Avoidance Sensor to a PIC

texts: I have a PIC16F917 microcontroller that is used to operate a robot. I would like to add a sensor to it that will allow me to detect obstacles. How can I determine what sensor I should be using for this? Are there any special protocols I should be looking for to work with my PIC?


texts:
In automobile industry, while some of the sensor & valves were connected with electronic control unit, short to battery & short to ground test conditions are taken care against the loads.

What is the reason for this test condition?


texts:
How can I wire this 4 pin webcam from my old HP Pavilion DV6000?
I can't find any website that can help me with this 4 pin webcam.
As you can see it the image below, the wires black and blue are tangled together while the red and greenish or metallic like color wire are not. I don't have a multimeter right now because I don't need it in my course in college which is I.T. but we are focusing on programming.
I want to connect it to a USB cable so I can use it.


texts: Simulating a tranfer function with opamps

texts:
I am asked to simulate the following transfer function using operational amplifiers:

Obviously what it evokes is a second order filter, my question is what kind of filter should I use (Butterworth, Biquad, etc) and how should I calculate the components?


texts: What fuse to use for a AC/DC buck converter

texts:
I want to make this 8 channel DMX Splitter. Instead of the transformers I will use 9 AC/DC Buck Converters, 5V/3.5W. According to the explanation 1.5W is enough so that should be ok.

The description also shows a slow blow 0.1A fuse to be used. However, I checked that these are relatively expansive, so I wonder if I can use e.g. a 0.25A or 0.5A fast blow fuse. I never used a fuse before, so I'm not sure if this could cause a problem (like sometimes for resistors/capacitors it also doesn't matter much, as long as the value is high/low enough). Or is a fuse not needed anyway because a buck converter has already safety within?


texts: Trying to replicate the behavior of an smartcard without sucess. What I am doing wrong?

texts:
Background: I am a software engineer and I am starting to research security hardware in my free time. The one I am starting with are contact smartcards, which are defined by the ISO 7816 standard.

I managed to create a hardware to probe into the signal between a smartcard and  a smartcard reader and here is what I got:

In this probe, D4 is RST (Reset), D5 is (I/O) and D6 is CLK (Clock). D2 is VCC and D0 is GND. The reader has D5 with pull-up transistor to VCC. THis is because, according to the standard:

"When  both  the  card  and  the  interface  device  are  in  reception  mode,  the  electrical  circuit  shall  be  at  state  H".

The first part of the image above shows the activation phase of a card, which is:

RST shall be put to state L
VCC shall be powered
I/O in the interface device shall be put in reception mode, see 5.2.5.
CLK shall be provided with a clock signal, see 5.2.3

The second part of the image shows the cold reset phase:

"By  the  end  of  activation  (RST  in  state  L,  VCC  powered,  I/O  in  reception  mode  in  the  interface  device,  CLK  provided  with  a  suitable  and  stable  clock  signal),  thecard  is  ready  for  a  cold  reset."

"The  clock  signal  is  applied  to  CLK  at  time  Ta.  The  card  shall  set  I/O  to  state  H  within  200 clock cycles (delay ta) after the clock signal is applied to CLK . The cold reset results from maintaining RST at state L for at least 400 clock cycles after the clock signal is applied to CLK . The interface device shall ignore the state on I/O while RST is at state L."

At the end of the reset phase, the card replies with an ATR (Answer to Reset)

On the far right of the image, you can see the RST sinal being pulled up, and the clock is stable. The ATR is sent as an array of characters (which are represented by character frames:

"a character (frame) consists of ten consecutive moments numbered 1 to 10. Each moment is either at state H or at state L"

**This is the part where I enter experimentation phase and most of the stuff I am doing might be wrong **

I tried to reproduce this behaviour using the most off-the-shelf device I know: an arduino.

First, I created a timer where I sample the IO and RST signals. inside the timer handler, I created some kind of machine state where I determien in which phase I am at, and try to write the bytes accordingly.
Here is my result:

As you can see, in the end, the smartcard reader try to reset it again, since, for some reason, it is not receiving the reply I sent:

At this point, the signal created by an arduino and by an actual smartcard are very similar. However, the smartcard reader still replies with "card absent or mute"

My circuit shares a GND between the smarcard reader and the Arduino, which is plugged in an USB in the same computer the smartcard reader is at. The I/O signal is generated from one if the IO arduino pins to the smartcard reader.

Is there anything that might be wrong in the electrical part? Is there any problem in sharing a GND with the Arduino and then driving data from it?

simulate this circuit – Schematic created using CircuitLab


texts: Path for a child to learn electrical engineering

texts:
What are some paths for a child (7-year-old) to learn electrical engineering (in a safe way)?

I do not want to saturate (or frighten away) the child with lots of concepts, I want that my son learn playing with the basic and core of electrical engineering.

Or is 7 years not an age to learn electrical engineering? Or is it dangerous? I will always be by his side.


texts:
Is it possible to inherit some properties from the scope that we invoke a function? A code snippet might help more to explain:

typedef enum logic {
    RESET    , IDLE   ,
    STATE_A  , STATE_B} states;
//as you see above I don't define the width or the values of the states

states current_state, next_state;

  always_comb begin
    assign next_state = next_state_func (
      curr_state,    reset,
      modportA.some_signal_a, modportA.some_signal_b);
  end

function next_state_func (
      //THIS IS THE BUG ZONE:
      //Can I inherit the caller's signals properties? I mean I don't have specific width available so what do I do?
      ref curr_state,    ref reset,
      ref some_signal_a, ref some_signal_b);

  endfunction


texts:
I'm trying to discover a circuit that will produce a voltage which is some factor of the square root of the input voltage. I.e. \$V_{out}(t) = K\sqrt{V_{in}(t)}\$. The factor K is irrelevant.

I looked at the circuit at the bottom of this page. The problem is it uses a MOSFET and the formula predicting the output requires various parameters \$\mu_n, C_{ox}, V_{th}\$ (some of which I imagine vary greatly even among devices of the same model, and some of which I wouldn't know how to find from the data sheets)

I'd like to find an alternative circuit which has a consistent and predictable output, before I purchase the necessary components.

When I say K is irrelevant, I just meant that I can later amplify the output by a constant factor if needed. It needs to be consistent and predictable though.


texts:
I am designing a power stage using LMZM23601V3.

In normal condition there is no 5VUSB but only +15V, during programming there is no +15V and just 5V from usb, I want to protect the only component using 5V from +15V and that's why I am using a diode.
Is it a good approach or there are others solutions?
Thanks


texts:
I'm trying to make a N.Peak Detector with reset functions. I've tried various modification to the classic peak detector without any success.
What I'm trying to accomplish is:

Detect the negative peak of the output [Red arrow]
Output a Low signal
Keep signal to Low till,
Output crosses above zero [White arrow]

Is there a specific name for that kind of circuit?
Thanks in advanced.


texts:
I am currently having problem with the Analog to digital conveter IC ADS1230. It used to work perfectly fine on the PCB, but now I am not getting any data. So I was wondering if there is any method to check whether or not that ADC is fine. By check I mean, how can I check that IC without placing on the PCB with simple instruments like multi meter. Any suggestion would be appreciated.

Sorry to ask this question.


texts: Wiring RGB Vandal Switch as PC Power Button

texts:
I'm trying to wire up a Schurter CPS16 capacitive, multicolour (RGB), anti-vandal switch to my PC for use as a power button.

The switch function is momentary and normally-open.

Tech Sheet

I'm just not sure what needs wiring up, and to where:

I can get 5v or 12v (and Ground too, I suppose) from a Sata Power connector
Obviously I need to connect the motherboard power button pins
I have a free RGB header (and an RGBW currently in use)

I'm keen to learn what's involved! Any assistance is appreciated :)


texts: 'Missing subcircuit' when creating a Pspice library part from the OPA188 Spice file provided by TI

texts:
I created a Pspice part using the Spice file provided by TI. When simulating, I get the following error:

ERROR(ORPSIM-15108): Subcircuit RNOISE_FREE_0 used by X_U1.XR101 is undefined
ERROR(ORPSIM-15108): Subcircuit RNOISE_FREE_0 used by X_U1.XR105 is undefined
ERROR(ORPSIM-15108): Subcircuit RNOISE_FREE_2 used by X_U1.XR104 is undefined
ERROR(ORPSIM-15108): Subcircuit RNOISE_FREE_0 used by X_U1.XR103 is undefined

Some of the lines with the offending subcircuits are as follows:

XR109_3 23 9 RNOISE_FREE_0
XR109_4 41 9 RNOISE_FREE_0

Would 'RNOISE_FREE...' be circuits recognized by TINA (TI's software) but not by PSPICE?
Could I replace them with an equivalent?

Thanks!


texts: Black bar and red / green swap in OV7670 image

texts:
I´m working on my OV7670 interface and I have some issues with the color / image settings. I use the color bar settings of the sensor to check my logic and the color bar looks good:

But I´m unsure if the order of the colors is correct because I have green / red swapped in the camera image. It doesn´t make any sense to me that the color bar from the camera has the correct order, but the camera image has green and red swapped.

And the camera image contains a black bar on the left side of the image (live image only) - check the photo. I have checked the data with a logic analyzer and it seems that the camera transmits some black pixels and the beginning of the frame (see the signals OV7670_D_Out and OV7670_HREF_Out which are the input signals from the camera):

I use the following settings for the image sensor (the first byte of an element is the register address and the second is the register value):
static uint8_t OV7670_Config[][2] =
{
    {0x11, 0x01},
    {0x0C, 0x00},
    {0x12, 0x04},
    {0x3E, 0x00},
    {0x40, 0xD0},
    {0x70, 0x3A},
    {0x71, 0x35},
    {0x72, 0x11},
    {0x73, 0xF0},
    {0xA2, 0x02},
};

Do I use the wrong configuration for the sensor or where does the black bar in the live image and the red / green swap in the live image come from?


texts:
I'm teaching myself CPLD programming using a development board with an Altera MAX II EPM240.

After learning how to make a 4-bit digital counter in VHDL using clock/reset inputs, I'd like to use the onboard 50MHz oscillator wired to pin 62. I understand it is fed to the Global Clock Network, but how do I wire it to an input of my VHDL design? (in my case CLOCK)

entity Foo is
    port(
    CLOCK: in std_logic;
    LED_0: out std_logic
    );
end Foo;

architecture rtl of Foo is
begin
    LED_0 <= CLOCK;
end rtl;

I know I can assign I/O pins to my design with the Pin Planner tool in Quartus II 13.1. I tried assigning pin 62 to the CLOCK signal, but I see no visible output to LED_0 (one of the onboard LEDs). I'd expect to be half-lit, but it's always on. I suppose it's because I'm now trying to use pin 62 as a regular I/O, which is not what I want.

The datasheet mentions LAB column clocks, and signals like labclk1 or labclkena1, but I have no idea how to reference them. As far as I can tell, the signal names I define in my VHDL design aren't related to any internal signals of the chip it will run on.

How do I tell (either in VHDL or with the Quartus tools) that I want one of my input signals to be connected to one of the Global Clock Network clocks?


texts: So as seen in the graph, the voltage was varied firstly ascending and then descending. So, is the difference in field currents between the two curves due to hysteresis in the machine ?


texts: Potentiometer as Voltage regulator 12V to 6 - 12V range

texts:
I am new to electrical engineering and I would like to build simple circuit with potentiometer as voltage regulator.

I have simple circuit, as you can see in attached picture below.

I have 12V/1000 mA DC source connected via potentiometer to LED strip (unfortunately I don't know the resistance of this component, strip is about 1.5m long - type 5050 if it will help somehow)

I would like to know what kind of POT should I use to regulate source to range 6 - 12V. At the moment I have chosen 1k Ohm POT and it dims LED strip only in first 10% of range then nothing happens at all because strip barelly shine.


texts: What would be the cause of measuring AC voltage across a LM7805?

texts: This is my first time here so I apologize if I don't provide enough information.  I am trying to repair a centrifuge that is giving an error on its LCD display.  Though the service manual doesn't say what this error means, (other than its an electronics issue) based on my online research it is due to high/low Vout on LM7805.  Others who have encountered this issue with the instrument recommend to replace the electrolytic caps by the LM7805 (circled yellow in photo below).  I successfully replaced those (circled green = 50V 47uF and circled blue = 25V 220uF) but it did not resolve the issue.  I tested the Vin and Vout with a multimeter and received 3.0 VDC and 0.7 VDC, respectively. I heard somewhere that the voltage regulator could be full of 120HZ notches due to an upstream capacitor going bad so I decided to measure AC voltage for Vin and Vout I got 5 VAC and 0.9 VAC, respectively.  I still haven't replaced the 250V 560 uF power supply filter cap but I have ordered a replacement.  I was just wondering if anyone might know if there are any other potential faulty components upstream that could cause AC voltage to be detected on the LM7805 (bad bridge rectifier, LM7805 itself, etc)?    Unfortunately I could not find a schematic for this instrument.  But here is a photo of the PCB below.  Any help would be greatly appreciated!


texts: What will cause if I put a larger inductor to a step down converter like MP1584 or MP2307?

texts:
For example my calculation for MP1584 inductor is 10uH, but i could put only 47uH to it. It is a problem?
I'm doing this wrong?


texts: How to route power in split-plane layout?

texts:
I'm working on a sensitive analog measurement board.  The design currently has split ground planes for analog and digital which are tied under the ADCs, as described in Analog Devices note MT-031.  There are several ADCs.  While this seems like a good way to handle ground, I'm not sure how to distribute power to the analog sections.

This is for a relatively low-frequency (< 1kHz) but very high precision (ENOB > 18) analog application.

Here are sketches of three possible layouts.  Black is ground ties (connecting the split planes), red is power distribution traces.  You can assume each domain is appropriately decoupled, nothing crosses the gaps in ground planes, there is a power plane in each domain, and the digital outputs from the analog section go directly over the ground tie (and are as short as possible).  Analog and digital power are produced by separate LDO regulators.

Layout 1: Power to the analog domain goes through the digital domain and enters next to (or over) the ground tie.  While power is kept as far away from digital signal traces (and on the other side of a ground plane), there may still be some noise pickup.

Layout 2: Power goes from the power domain to each analog domain directly.  This necessarily crosses some of the splits in ground planes.

Layout 3: Power goes from the power domain to each analog domain directly, and is paired with ground connections for the return current.  This necessarily creates some loops in the ground.

Layout 4: Each analog domain has its own LDO regulators for power, located within it.  These are fed from the unregulated power (battery) in the same way as in 1.  Obviously less preferred since that increases the number of power components by a lot.

Which of these is likely to produce the least noise, and why?


texts: Understanding basic photoresistor circuit

texts:
I'm new to electronics, so I just can't wrap my head around how this photoresistor circuit works.

I understand the following:

the photodiode can be understood as a variable resistor (i.e. works in principle the same as a photoresistor)
I want to measure the difference in voltage, that is caused by that variable resistor

Intuitively, I'd like to take a voltage measurement before (source: 5V) and after the diode. Can someone explain, maybe using an intuitive analogy (e.g. water current?), why this only works with an additional resistor (like below, copied from here)?

I built a working sensor using the arduino starter kit photoresistor (datasheet) using a 10kOhm resistor and a 5V source but want to understand it better.

Edit: afer helpful comments, this question is basically:
 a) what is the difference between a photodiode and -resistor
 b) why does a voltage divider need 2 resistors


texts: I'm using a 6s Lithium Polymer battery in one of my projects, and I'd like to make it more consumer friendly. This means that I should probably get rid of the need for a balance charger (which few consumers have) by including the balancing and charging mechanism in the project then simply have a power adapter plug into the project. However through many google searches I haven't been able to find a correct term for this or even where to get started. My electrical knowledge is fairly basic, so whatever knowledge and or resources that can be offered are greatly appreciated!


texts:
Assuming square law model, transconductance of an npn transistor in saturation mode can be found as gm = Kn'* (W/L) * (Vgs-Vth) which can also be written as gm=2*Id/(Vgs-Vth).
Now, while simulating a particular Si-technology file, I am using a very simple circuit (W/L=1), which I have attached. The DC analysis on LTSpice gives:
Id=1.58 uA , Vgs = .5 V, Vth = 0.469 V, and gm = 2.73e-5
However, 2*Id/(Vgs-Vth) is 10.19e-5 . Can someone please explain the discrepancy? Because the difference is too big to be attributed to non-ideal effects.

The technology file I am using


texts: How do I determine mosfet capacitances (Cgs, Cds, Cgd, ...) in LTSPICE?

texts:
I am simulating a 2 stage miller opamp in LTSspice. I'm using the standard models provided by my uni. I can simulate the operating point, but in the operating point data, all capacitances are 0. I assume this is because LTSpice just sets all capacitances as open in the operating point analysis but I'm not sure. However, since I need to have an idea about these capacitances, I was wondering how I can get to them after doing the simulation. In the uni labs we use a tool (JMOSCal, designed by someone in our department a few years ago) that will give all these values, but it requires hSpice, which I don't have access to at home.

LTSpice clearly does calculate these values at some point, since my opamp doesn't have infinite bandwidth.

EDIT:
I would like to mention the following: The reason I'm using LTSpice is because it's the best I have at home. I don't have access to the fancy Cadence or Mentor tools. LT spice is a good simulator in terms of accuracy. However, it's license does not permit the use of technology models from fabs. Predictive technology models do not fall under this clause, and hence can be used.

I would also like to point out that this is not a standard simple model, but a high acuraccy and advanced predictive technology model. We are talking about 200+ parameters per device type. They are available from this website: Arizona State PTM models page The one I am using is the "PTM High performance 45nm metal gate, High-K, strained-silicon".

I need to do high-accuracy simulations. The accuracy I can achieve with hand-calculations is not enough. Even if I could manually calculate them to any decent level of accuracy, I would not be able to just "add them" - LTSpice clearly does model them internally, because I can see poles and zeros that would not be there if no capacitance were modeled.

How do I find these values?


texts:
I came across a page which explains bipolar transistors which are used to implement wired-and logic. It says

Another feature of DTL is its ability to implement a "wired AND" function. For example, if we wired several DTL NAND gates together, we would observe the following behavior. If any one of the NAND gates had a logic 0 as its output, the whole output function would also be at a logic 0 voltage. All the output functions would have to be at logic 1 for the output to be 1. See Figure B.9, which shows the internal wiring and the equivalent logic schematic for the wired AND function.

Looking at the figure, I see that, it all inputs (three gate inputs) are logical 0, then the output is logical 1 due to the pullup resistors. On the other hand, if any of the inputs (or all) is (are) logical 1, then the output will be zero because there is a connection between output and ground. So, it it actually implements wired-nand!
Any explanation for that?


texts: Voltage sources in parallel Kirchhoff volage law

texts:
Can somebody please tell me how can I apply Kirchhoff voltage law in the following circuit??
Is there a way to find an equivalent circuit for the sources V1,V2 and resistors R1 and R2??

simulate this circuit – Schematic created using CircuitLab


texts:
Why does the time constant of the capacitor with ideal op amp, is independent from R1 and R2?
If I put test voltage source, it clearly does depend on it,because V+ is function of R1 and R2.
therfor, The output voltage is also function of R1 and R2, and therfore the current of the capacitor is function of them.


texts:
From linear systems theory, self-excited sustained oscillations are only possible by means of a marginally stable system, where poles are located exactly on the imaginary axis. However, such a situation is a impossibility in the real world, as tiny parameter deviations would cause the system to go either stable or unstable.
And if it goes unstable, than I assume that it would reach any kind of physical limitation (for instance, saturation) that would make it lose its linearity property.

However, reading about oscillators circuits using opamps, I don't really know where is the non linearity. For instance, is this phase-shift oscillator non linear (taken from Opamps for everyone)? How can I know it?

Thanks!


texts: Explain me, please, what "loop response" is, to help me translate this term into other language

texts:
English in not my native language.
I've tried to find full definition of "loop response" in English, but I failed.
Here is an example of using the term "loop response":

As a working example of SIMPLIS time domain simulations, the Self Oscillating converter from the What is SIMPLIS? topic is pictured below. This converter oscillates at a frequency dependent on the load current, which prevents the easy derivation of a small signal averaged model. Using the SIMPLIS POP analysis, the steady state behavior is quickly simulated, then the SIMPLIS AC analysis simulates the loop response on the same time domain model. The simulation results for this converter have been compared to hardware measurements. For information on how SIMPLIS simulations compare with real hardware measurements, see the Accuracy of PWL Models topic.

I need to translate this article into other Russian language.


texts: What's the difference among these static protection bags?

texts:
I have some old modems & other cards stored in plastic static bags and noticed that a few of them were distinct... these are all from the 1990s or maybe early 2Ks.

Here's a sampling:

From left to right, there are:

Opaque and mirror-like
Translucent (this is what I thought of as "normal" and most the ones I have are like this)
Hexagonal pattern on less-shiny clear plastic
Grid pattern

Do the patterned ones have some special function? Do these all do the same job and equally well?

More detail on two:

PS: I can't really find any relevant tags... please suggest if you know.


texts: Why are accelerometers (and other MEMS devices) so rarely integrated into components?

texts:
With the way things are headed, more and more functionality moves into a single chip each year. However, one thing that seems to remain completely untouched by this is MEMS devices like accelerometers and gyros.

Despite many device classes practically requiring accelerometers, integrating MEMS into chips seems astonishingly rare, except for a few expensive (and weak) outliers by ST and Bosch. I assume the reason is technical.

In particular I'm interested in the following questions:

What makes them so rare?
Do process differences have an impact on this?
How do the components that do exist circumvent these problem(s)?


texts:
I'm multiplexing 32 LEDs in a 4:8 configuration on an ATMega328 and am trying to dim them with what is probably a completely naive understanding of PWM. Note: I'm multiplexing them directly with 12 pins from the ATMega, no other chips are used at all. Basically, out of every 10 cycles of refreshing the whole display (which takes 8 of the ISR interrupt) I am just turning everything off for 2 of them if I want to show it at 80% brightness. But, in practice this just gets me a bunch of pulsing LEDs.

At first I thought I was just not calling ISR enough so I changed the prescale for 8 to 1, but that made no change.

Rough code is below. Any suggestions appreciated. I'm sure I'm doing this COMPLETELY the wrong way :P The multiplexing works fine and I'm getting a full display refresh rate of 244Hz I believe, which was seemed good enough. Just can't seem to dim.

Note: "data" variable is being changed in the (not shown) loop() method.

uint8_t pwmStep = 0;
uint8_t pwmMax = 10;
float pwmLevel = 0.8f; //range 0.5 - 1.0 (50% - 100%)

void setup()
{
  //port inits and other stuff here...

  // timer 1 setup, prescaler 8
  TCCR1B |= (1 << CS10);

  // enable timer 1 interrupt
  TIMSK1 = _BV(TOIE1);
}

uint8_t col, row = 0;
ISR(TIMER1_OVF_vect)
{
  //Turn all columns off
  PORTB |= (_BV(PB0) | _BV(PB1) | _BV(PB2) | _BV(PB3) | _BV(PB4) | _BV(PB5));
  PORTD |= (_BV(PD6) | _BV(PD7));

  if(pwmStep < pwmLevel*pwmMax)
  {
    //set the 4 rows
    for(row=0; row<4; row++)
    {
      if(data & (1UL << (row + (col * 4))))
        PORTC |= _BV(row);
      else
        PORTC &= ~_BV(row);
    }

    //Enable the current column
    if(col < 6)
      PORTB &= ~_BV(col);
    else
      PORTD &= ~_BV(col);
  }
  col++;
  if(col == 8)
  {
    col = 0;
    pwmStep++;
    if(pwmStep == pwmMax)
      pwmStep = 0;
  }
}

*Update: * Trying to do this with an ATTiny85, but not quite getting the results I suspected. It does dim it, but only a very small amount.

See code below. Even with OCR0B set to VERY small, I only get a small amount of dimming.

#define PRESCALE_1 _BV(0)
#define PRESCALE_8 _BV(1)
#define PRESCALE_64 (_BV(0) | _BV(1))
#define PRESCALE_256 _BV(2)
#define PRESCALE_1024 (_BV(2) | _BV(0))

void setup(){
  DDRB |= _BV(PINB0);

  PRR &= ~_BV(PRTIM0); //Enable Timer 0
  TCCR0A = 0x00; //Outputs disconnected

  // turn on CTC mode, 64 prescaler
  TCCR0B |= _BV(WGM01) | PRESCALE_64;

  OCR0A = 200; //~1200 Hz
  OCR0B = 50;  //~4800 Hz

  //
  TIMSK = _BV(OCIE0B) | _BV(OCIE0A); //Interrupts Enabled
}

ISR(TIM0_COMPA_vect){
  PORTB |= _BV(PINB0); //Set PINB0 on
}

ISR(TIM0_COMPB_vect){
  PORTB &= ~_BV(PINB0); //Set PINB0 off
}


texts: Lattice iCEcube2, error synplify_pro 321

texts:
I just made a fresh install of iCEcube2, first time i'm using it, and whatever design files I use I've got this error when I try to synthetize :

/opt/iCEcube2.2017.01/synpbase/bin/synplify_pro: 321:
/opt/iCEcube2.2017.01/synpbase/bin/config/execute: Syntax error: "(" unexpected (expecting ";;")

I'm using ubuntu 16. No idea what happens, and I don't know what I could do knowing that it's a fresh install. I tried to launch the software in sudo with same result.

Thanks


texts: Energy subtracted from a capacitor for a given voltage drop

texts:
I am trying to estimate, from a total energy of a capacitor (which is the output of a charge pump circuitry), how much energy do I have to power up an LED before the voltage goes below a certain threshold.

At first, I guessed is the $$ E = \frac{1}{2} C (dV)^2 $$ where dV is the voltage drop I can allow to happen before I turn off the LED and keep the remaining energy in the capacitors (and allowing them to charge again).

But I have the feeling is not that simple. For example, I was forgetting what was analyzed here in this question, and made me suspicious on my simplistic view. Or can you confirm mine is correct?


texts: What would be the effect of adding small (~<10mm) lengths of conductor between a CPU's contacts and socket

texts:
[I am interested specifically in the case of state of-the-art consumer processors and motherboards]

To clarify what the setup might be in practice, imagine wires running vertically between each pair of contacts on the CPU and socket.

I don't have much expertise in this area, but these are the potential issues I am concerned about:

The additional length of the conduction path from the processor slows down the speed of processing.
The change in length of the conduction path means that the processor won't work at all as the devices are designed to operate with a specific length of conduction path.
There is interference of some sort between the conductors running from the CPU to the socket.

In each case I am wondering if this is a problem and, if possible, what sort of effects would be observed.


texts:
I realize connecting two different voltage sources in parallel is a contradiction (in an ideal circuit). But if I were to connect this in practice and measure the voltage across points A and B, what value of voltage would it show?
And how much current would be sunk by the 5V battery? (Non ideal conditions)


texts: Can anyone identify this connector? Found inside a Panasonic fan.


texts: Maximum rate between ADC-FPGA link for Igloo 2 vs Max 10

texts:
An ADC has a source synchronous output interface and is to be interfaced with an FPGA. The ADC can communicate using single ended CMOS, DDR CMOS and DDR LVDS. How do I know what is the fastest rate that I can run this at with the FPGA I have, assuming that the FPGA is the limiting factor.
These two FPGAs are being compared:

Max 10

IGLOO 2

I believe that I just need to look at the fastest rate that the FPGA I/O pins can be run at. But, obviously the FPGA fabric will also need some attention. How can I find a ball park figure?


texts: What are different battery capacity algorithms used?

texts:
I need to implement an algorithm to know the capacity of a battery. I don't want to use any external gauges which are available on the market.

Can you suggest which algorithm(s) is/are popular?
Can we implement any algorithm ourselves?


texts: Is the configuration in startup.s file generated using KEIL IDE directly putting the Fcpu @ 60 MHz?

texts:
I am using LPC2148 for learning purpose and I was trying to mess around a lil bit with the startup.s file and understand it. In the Keil's Target option for the project it is assuming the XTAL frequency to be 12Mhz. I have this section of code

; Phase Locked Loop (PLL) definitions
PLL_BASE        EQU     0xE01FC080      ; PLL Base Address
PLLCON_OFS      EQU     0x00            ; PLL Control Offset
PLLCFG_OFS      EQU     0x04            ; PLL Configuration Offset
PLLSTAT_OFS     EQU     0x08            ; PLL Status Offset
PLLFEED_OFS     EQU     0x0C            ; PLL Feed Offset
PLLCON_PLLE     EQU     (1<<0)          ; PLL Enable
PLLCON_PLLC     EQU     (1<<1)          ; PLL Connect
PLLCFG_MSEL     EQU     (0x1F<<0)       ; PLL Multiplier
PLLCFG_PSEL     EQU     (0x03<<5)       ; PLL Divider
PLLSTAT_PLOCK   EQU     (1<<10)         ; PLL Lock Status
;// <e> PLL Setup
;//   <o1.0..4>   MSEL: PLL Multiplier Selection
;//               <1-32><#-1>
;//               <i> M Value
;//   <o1.5..6>   PSEL: PLL Divider Selection
;//               <0=> 1   <1=> 2   <2=> 4   <3=> 8
;//               <i> P Value
;// </e>
PLL_SETUP       EQU     1
PLLCFG_Val      EQU     0x00000024

That is defination of Registers for the generation of CPU frequency from the low frequency oscillator

; Setup PLL
            IF      PLL_SETUP <> 0
            LDR     R0, =PLL_BASE
            MOV     R1, #0xAA
            MOV     R2, #0x55

;  Configure and Enable PLL
            MOV     R3, #PLLCFG_Val
            STR     R3, [R0, #PLLCFG_OFS]
            MOV     R3, #PLLCON_PLLE
            STR     R3, [R0, #PLLCON_OFS]
            STR     R1, [R0, #PLLFEED_OFS]
            STR     R2, [R0, #PLLFEED_OFS]

;  Wait until PLL Locked
PLL_Loop        LDR     R3, [R0, #PLLSTAT_OFS]
            ANDS    R3, R3, #PLLSTAT_PLOCK
            BEQ     PLL_Loop

;  Switch to PLL Clock
            MOV     R3, #(PLLCON_PLLE:OR:PLLCON_PLLC)
            STR     R3, [R0, #PLLCON_OFS]
            STR     R1, [R0, #PLLFEED_OFS]
            STR     R2, [R0, #PLLFEED_OFS]
            ENDIF   ; PLL_SETUP

This section of the startup.s File seems to be directly setting the clock to 60Mhz. Is what i understood from the startup.s file correct?

LPC2148 User Manual

Why is this startup.s file directly taking the CPU frequency to 60 Mhz?
If I need to change the CPU frequency should I do it in the Startup.s file or in the main section of my program ?

NOTE : I just switched from the AVR Microntrollers to ARM and I am more familiar with #define F_CPU (Frequency of the XTAL) hence the question.


texts:
Can a switching regulator deliver more current than the input side can provide just at a lower voltage?

For example if I have a 10V 1A (10W) input source going through a switching regulator (100% efficient) can I have a 5V 2A (10W) output? Or will the switching regulator be limited to 5V at 1A and 50% duty cycle?


texts:
I'm trying to make this as non-opinion-based as possible.

There are a lot of textbooks and resources for how transistors, and various things that are made of transistors, work. However, in all my searching, the only tutorial I've ever seen for actual IC design is this one. In my initial perusing, however, it seems fairly "off the top of my head"-ish, as in, "I think I'll talk about this, now."

Are there any other such IC design tutorials? I'm not even asking for a ranking, just if they exist in the first place.

Edit: in college, I took a course called "Analog & Mixed-Signal Integrated Circuit Design"; most of our time was spent talking about different types of op-amps and their different merits and limitations. The final project was to design an op-amp, using one of the four types mentioned in the class (two-stage, telescopic, folded-cascade, and current mirror) to meet one of four different sets of design specs. But it just seemed like we were thrown into the deep end with an understanding of what swimming was but with no idea how to do a breaststroke.

Essentially, in IC design, there are a lot of knobs to twist to accomplish your goal; so many knobs, in fact, that it gets a little overwhelming at times, and I don't know where to start. I was just wondering if there were any resources out there, not for how these IC and IC blocks work, but how to design them and use them effectively.


texts: Bypassing refrigerator door alarm piezoelectric buzzer

texts:
My appliances keep beeping at me. How can I deactivate or bypass this refrigerator door alarm buzzer without affecting the rest of the circuit?

I thought I could just cut/connect the wires at the momentary door switch, but then I'd lose the interior lights. When the door and (I assume) switch is open, the lights (and eventually alarm) activate.

Can I just swap it out for a piece of copper wire and solder; or are there other properties/attributes to consider?

  Piezoelectricity is the electric charge that accumulates in certain
  solid materials in response to applied mechanical stress. The word
  piezoelectricity means electricity resulting from pressure and latent
  heat.

https://en.wikipedia.org/wiki/Buzzer#Types

  A piezoelectric buzzer/beeper depends on acoustic cavity
  resonance or Helmholtz resonance to produce an audible beep.

https://en.wikipedia.org/wiki/Buzzer#Piezoelectric_2


texts:
What is the Atmega8 input impedance. I want to add a push button to an Atmega8 and my configuration would look something like this:

A +5V source, resistor, push button not pressed goes to Atmega8, pushed goes to ground.

From my understanding Atmega8 is a CMOS and therefor the input impedance would be very large, most likely in the 100MOhm. For a logical high the Amtega8 need 0.6Vcc, my Vcc is 5V, therefore a high will be considered for anything above 3V. Assuming that my assumption of very high input impedance is right, the resistor can be:

3V = 5*100M/(100M+R) ==>R = (500-300)/3 = 66.66MOhm.

Would that be the correct theoretical highest resistor value that I can use?

**The actual resistor used will be a 47kOhm but I really want to know how to find the maximum theoretical value.


texts:
The code below flashes some LEDs in order: pin 1, pin 2, pin 3, pin 4.

After this sequence has completed I would like to reverse direction and show pin 4, pin 3, pin 2, pin 1.

I wrote the code below but it's not working in reverse order.

What might be wrong?

#include <htc.h>

__CONFIG(1,OSCSDIS & HSPLL);
__CONFIG(2,BORDIS & PWRTDIS &WDTDIS);
__CONFIG(3,CCP2RC1);
__CONFIG(4,LVPDIS & STVREN);
__CONFIG(5,UNPROTECT);
__CONFIG(6,WRTEN);
__CONFIG(7,TRU);

#define _XTAL_FREQ   40000000

void delay_sec(unsigned char seconds)    // This function provides delay in terms of seconds
{
    unsigned char i,j;

    for(i=0;i<seconds;i++)
        for(j=0;j<100;j++)
            __delay_ms(10);
}
void led_display(char a)
{
    switch(a)
    {
        case 0: PORTB=0x01;PORTD=0x08;  break;
        case 1: PORTB=0x02;PORTD=0x04;  break;
        case 2: PORTB=0x04;PORTD=0x02;  break;
        case 3: PORTB=0x08;PORTD=0x01;  break;
    }
}

void main()
{
    TRISB=0x00;
    TRISD=0x00;
    char a,b;

    while(1)
    {
        led_display(a);

        a++;
        delay_sec(1);
        if(a==4)
        {
            a--;
        }
    }
}


texts: Why don't we have wireless charger in every portable device yet?

texts:
Today I found Texas Instruments announced a circuit for wireless charging - Ti BQ51013 Qi receiver controller - all the materials emphasis how tiny, lightweight, portable, efficient and otherwise cool it is.

While I of course like the idea I don't get one thing. What's so hard in implementing such circuit in just all cell phones allready? Every other company introduces so-called "charging mats" that also require en extra gadget attached to the wireless device to make it receive power from the "charging mat" and I guess different systems are incompatible with each other, but there're almost no devices with built-in wireless charging (except maybe shavers and toothbrushes).

It's year 2011 and we have microchips with millions of transistors on them - why don't we have such simple thing as wireless charging in every applicable device yet? What's the technical difficulty here?


texts: A question on thyristors and phase control

texts:
High schooler here reading on thyristors.
Videos online and books say they can be used as light dimmers. I assume that's because we can control the amount of current that can enter a load. But what got me thinking was: won't the light bulb continuously flicker because there's this part in the output signal where the voltage is just zero?
Or do text books assume that the frequency is so large that you hardly notice the lightbulb flicker? I've been searching for an answer everywhere in the internet, but none of them mention anything about it.
(I made a drawing here showing the normal signal. There's this tiny moment when it's flat zero, and I wonder if that is noticeable when connected to a light bulb)


texts: What makes a high speed USB cable high speed?

texts:
I was shopping around for USB 2.0 cables.

Some manufacturers claim their cables are "high speed".

My understanding is that the electronics on the device determine the speed, not the cable.

I understand that the length of the cable has an effect on the speed (but probably negligible, like nanoseconds).

So, what makes a USB 2.0 cable, high speed?
(One can search the internet for "high speed usb 2.0 cable" to find instances.)

What is the average speed difference between a high speed cable and a cable not high speed?


texts:
I understand that, for an ideal opamp, Vo is bounded by Vee and Vcc (i.e.; Vee < Vo < Vcc).

But, what about the input voltage range? What is the allowed input voltage range in which opamp works normally? Can we apply Vn and Vi voltages which are below Vee or above Vcc? For single supply opamps, can we apply negative input voltages?

Does opamp being ideal, practical, rail to rail change the answer of this question?


texts:
I'm looking to implement a phase lock in an FPGA without using any external components (other than the ADC). For simplicity locking to a simple binary pulse is adequate. The frequency of the signals is ~0.1-1% of the clock. I can't use the onboard clock PLL's because they are typically:

Not configurable (set during synthesis).
Jittery.
Don't support the frequency I need.

I've been sorting through the literature and found a few binary phase locked loops. Most notable a "pulse steal" design that I can post a link to if desired. I have implemented and synthesized with some success, but its jitter and lock range was not as good as advertised. I've also had success using a external DVCO, but I would prefer if I can implement everything on chip.

A digital circuit design or even a hint in the right direction would be helpful (I've been banging my head against this for a while), a proven FPGA implementation would be wonderful but not expected.

ADDED 10-27-2010

The actual DPLL design that I used has a "Random Walk Filter" as the loop filter (not the "pulse steal" described earlier, going through my notes that didn't work to well), which then drives the clock pulses to the DCO. The lock-in range is set via divider in the DCO. The sensitivity of the loop is established by varying the length of the random walk.

The paper in which this is found is cited at the end of this post. After implementing parts of it myself, I found that it was actually already implemented on OpenCores, however it turns out that in the last few months the project was deleted but I have the Verilog files saved if anyone wants them.

Yamamoto, H.; Mori, S.; , "Performance of Binary Quantized All Digital Phase-Locked Loop with a New Class of Sequential Filter," Communications, IEEE Transactions on , vol.26, no.1, pp. 35- 45, Jan 1978

doi: 10.1109/TCOM.1978.1093972

URL: http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1093972&isnumber=23895


texts: How do protection circuits deal with instantaneous voltage?

texts:
For protection components such as Varistors and Diodes, when an instantaneous fault voltage is applied - how to do these devices protection before the device has time to conduct. For example, a Voltmeter rated to measure up to 1kV, if an instantaneous 5kV voltage is applied at the input terminals, will the overvoltage just smash everything if the input circuit is protecting. If the voltage applied is truly instantaneous, is the circuit designed to have a certain amount of inductance/capacitance to limit the speed the 5kV moves through the circuit?

simulate this circuit – Schematic created using CircuitLab


texts: AC analysis of a circuit including variable resistors

texts:
I have a problem concerning the AC analysis of a simple circuit, containing variable resistors (each variable resistor is a pressure sensor). I am sure this is quite simple, but I have never worked on variable networks and I cannot find answers by searching on the web.

Goal
R1, R2, R3, and R4 are the variable resistors, each one corresponding to a pressure sensor. Their resistance varies with the applied pressure, which is a stochastic process (trackinf of the hand pressure). My goal is to track in 1D the pressure along the sensor, thanks to the multiple pressure areas.
I know the circuit is bad, poor dynamics, etc. but I need a very compact and cheap circuit that can find the value of the resistors R1 to R4 by measuring output voltages via an ADC. The simplest way I have found is this one, where I put equal resistors R between the ground/power voltage and each variable resistor. By doing this way, I can measure the output voltages V0 to V4 and find the resistors by a quick circuit analysis.
As a result, I just want to measure the pressure with not so much noise to be able to conclude if the work I am doing require more investment or if this is useless to spend more time on it.
Problem
The resistors R1, R2, R3 and R4 are variable. I want to filter the output voltages (V0 to V4) as they don't see variation in voltage higher than the nyquist frequency of my ADC converter. I can sample at 50kHz, but sending my data to the computer take time and I need to filter out frequencies above 500 Hz. For this purpose, I would like to use a passive filter to remove frequencies above 500Hz and then use a digital filter to remove everything above 500Hz.
So I have two ways of doing this passive filter:

Finding the matching R and C that will reduce the impact of the variable resistors and filter close to 500Hz in any case. I think it is problematic as R1 to R4 are time-varying and are a stochastic process;
Finding a way to reduce at max the output impedance of each output and use a RC filter in cascade with each output. I would like to not use an Op Amp;

AC Analysis of the circuit
Can I consider the circuit as multiple two-ports networks in cascade (simple RC filter)?
Vd is my power voltage, all resistors R and capacitor C are equal.
I thought it will be possible to model the circuit like this, since the charge of the capacitor provoked the transient. Note that I didn't include V3 and V4 to clear the scheme, but I obviously should.

Do you have any idea on how I am supposed to perform the AC analysis? How can I find the bandwidth of each output Vx in response to the change in pressure at each pressure sensor Rx?
How do I tell Spice that, say, R4 changes between resistance Rlow and Rhigh in a square wave that ramps up in frequency from 10 Hz to 10 MHz?
Thank you so much for your help!


texts: Wiring 4+ 12v led ring switches from one 12v supply

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I am new to electronics and general electronic circuits. I have 4+ led ring switches (from here: follow link)

The website says that the rating of the switch contacts is 5A 250VAC with an illumination voltage of 12V

I am unsure as to how to wire the switches together from one socket.

I currently have a 12V DC plug adapter that I am using to power one single switch.

As the switch requires the power to turn on LEDs, would it be that the high amperes would damage the components within the circuit?

The adapter I am using gives this information:

input: 230V~50Hz 300mA
output: 12V 1500mA

Since each switch will require 12V (as stated on the product page) will I be able to wire the switches as such in the image below? (with red being positive and blue being negative) Or will I have to use multiple power sources to power a few switches at a time?

The diagram below shows the adapter (bottom left) with the 4 12v switches, the wires go to the positive and negative terminal on each switch


texts:
Another question I asked about Power Supply Noise pushed me to ask this question.

The background is as follows: I have a design with PD (Photodetector) and Opamp at medium frequency (couple hundred KHz). I am trying to test my design when it come back. I am looking at power supply noise, opamp supply noise and opamp output noise. I realized, there is more to it than just touching the probe. People talk about power loops, having special cables etc.

I will spin another board in two weeks and I wanted to ask, if you are designing your board now, what type of test points or elements you place on your board so that you can measure the noise accurately. We are talking about <20mV type signals.

Bonus question: The output of the opamp is connected to an ADC of the processor. Could I simply run the ADC and plot that to gain a deeper understanding of the noise compared to connecting my cheap scope?


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I bought an iPad with dead battery (it’s bulged). When I connect it to a charger, the only result is a boot loop (Apple logo, blink, Apple logo, blink…).

I want to use it as a kind of picture frame, which would necessitate constant charging anyway, so I’m reluctant to buy a replacement battery that will be of no use and dead again within few months because of constant charging.

I am thinking that it should be possible to solder a charger into battery circuit (disconnecting the battery, of course) to trick iPad into thinking it actually has a battery connected.

Do you know any examples of this?


texts: Tips and cases to avoid when singals acts like antenna

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I want to ask an explaination about when a signal may act like antenna creating EMI, for example with wrong grounding design. I understood that a main ground should be compact without any signal crossing it. What about Top and Bottom grounds in a 4 layer?

For example, should I avoid second case(ex of wire jumping another)?

There is other tips? (like avoid L shape wire or T connections that acts like antenna).

EDIT:

I also want to ask, if I place a component that is in a position where I'm unable to place power vias near decoupling caps on Vin of the component, can I wire a Vcc wire of 10-15mm lenght form the most near Vcc via to decoupling cap and Vin? Or Vcc are particolar wires that should be as short as possible?


texts:
I have a few questions, namely:

I aim to charge a 220 VDC battery pack with solar panels producing 240 VDC when open circuit using an MPPT charger. Where may I get such an MPPT charger?
I'd like to charge a 220 VDC battery bank with a 220 VAC generator used as back up power. Then I need to convert a 220 VDC power supply back to 220 VAC to power domestic appliances. How is this done?


texts: I want to charge a 7.2V-2000mAh NiMH battery. I have many solar panels and a voltage regulator but I do not know what voltage is required to charge it. I've heard people say that as long as it is any voltage higher than the battery peak voltage it is good. So I can use a 12V panel or even a 24V panel. I understand that low current is important for trickle charging, like 10%. I have an LM317T to limit current to 200mAh. I just don't understand the voltage requirement.


texts: How to make a preamp that is ON when input is a MIC but OFF when a LINE level?

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My question is very simple:

Is there a way to create a "preamp" circuit that is automatically ON when there is a MIC connected (for example, a desktop PC microphone) but OFF when there is a LINE connected (for example, some mp3 player?)

By the way, here I found some "preamps."


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On my Atmel SAM4E-EK I have a USB composite device setup (MSC + CDC over USB), hooked up to a Windows 7 PC. Sometimes I want to disable the MSC and let the CDC class be, is this at all possible given the USB 2.0 specification?

I imagine a solution to my problem would be to discard all the MSC USB packets in conjunction with a forced enumeration (by the host but issued from the device).

This situation is similiar to this question as I have a FATFS filesystem on the SD card which gets exposed to the PC over USB MSC and I want to have some kind of mutex over the filesystem so that it does not get corrupted from simultaneous accesses.