texts: Control a switch with headphone output jack

texts:
So I recently finished my boombox project, but ran into a minor problem. The boombox is powered by a blue wrapped lithium ion battery and using a ta 2021 chip amp from parts express. If I plug the aux cable into my phone BEFORE turning on the power, everything works perfect. If I turn on the power then plug in the aux cable to my phone, the speakers make a pop as it is being pressed into the phone and then the battery goes into protect mode.

My thought is that the pop is essentially a transient signal which exceeds the current limit of the battery and throws it into protect. My thought to fix this is to create a circuit that leaves the mute and ground on the amp connected until a signal is seen at the aux input and THEN unmute the amp. My problem is I'm not sure where to start to come up a circuit to do just that. Any help is appreciated. See the picture to hopefully make things as clear as possible.

Basically I need a way to trigger a switch to disconnect mute to ground using the iphone headphone jack output signal.


texts: Firing Triac strategy for motor phase control

texts:
I try to design a replacement potter's wheel motor controller for an old potter wheel. I have solve some problem and I am able to control the phase standard of filament light.

Now I try my board on a real motor and oddly the board does not work as expected. Yes I (re)discover the current phase angle effect. I see a lot of motor phase control only use a VOLTAGE zero crossing detector of the main supply and do not take in account the current, I don't understand how they work properly.

To try to understand, I try to plot voltage and lagging 90° current phase at the load. I use main voltage zero crossing detector event to trigger TRIAC between >0 to <10 ms. (for 50 Hz supply voltage)

1. TRIGGER AFTER ZERO CURRENT

With long delay (~6 ms) after voltage zero crossing, I expect to put a little power on the load (like on the filament light) but if I take the current in account, I see the TRIAC is ON during almost all the period

2. TRIGGER BEFORE ZERO CURRENT

Now with short delay (~4 ms) after voltage zero crossing, I expect to put a more power on the load (like on the filament light) but again, if I take the current in account, I see the TRIAC is ON just a small time until current cross zero.
I can generate pulse train to "pass" the current zero crossing but in this case TRIAC will be OFF AFTER the next pulse, so he will be OFF during to much time before the next (next) pulse, signal will be unbalanced.

So here is my question:

How does motor phase control do without knowing the phase of current to be able to control light AND motor? (In other words, why not a single dimmer use a current zero crossing detector?)
Do I need to add a CURRENT zero crossing detector to my board or measure the current phase to be able to shift my pulse delay to current phase. (ex: 1: Wait voltage zero crossing, 2: wait 5ms (90°), 3: Start my delay timer, 4: generate gate pulse)?
I read somewhere the phase of current move on a motor depending speed and torque, how to do without current zero crossing detector?

As you see I'm completely lost on the inductive load triggering TRIAC strategy, take a step back. Thanks in advance


texts: Simple voltage regulator circuit with 7805c outputs very low voltage

texts:
I am trying to make simple voltage regulator circuit from my 9V battery to 5V using 7805c voltage regulator. The schematic looks like this:

simulate this circuit – Schematic created using CircuitLab

My question is - why the output voltage is so low? Did I fried somehow IC or I messed something with values.

One more extra question: Checking a lot of different schematics to build my circuit I found a lot of different values for each of C. So how they should be chosen? Is there any formula for that, or something?


texts: Use Arduino to Plot the balance of my airplane propeller using optical sensor and reflective tape

texts: I would like to use an arduino to determine how out of balance my airplane propeller is.  I've seen a production device that uses an optical sensor and reflective tape to plot this.  Can this be done with an arduino, and if so, what would I need to do it?


texts: I have two lithium battery packs with separate BMS, Can I connect the packs in Parallel?

texts:
I have two lithium battery packs with separate BMS, Can I connect the packs in parallel, will the BMS get damaged or will something happen?
12v 10ah battery pack, I have three in total and each has it's own bms and for now I want to connect two packs in parallel, I'm confused whether the bms will get damaged or what will happen? will it work?


texts: Builiding a catapult that runs continuously with a motor

texts:
I need some ideas for designing a catapult that runs on a motor. Basic requirements:

able to launch a cookie 30m,
capable of continuous operation,
fits within a 0.4 m × 0.6 m × 0.4 m high box,
allows 2 seconds minimum between each launch to load,
self-sufficient (once the motor is turned on it can't be touched)
made of steel,
springs, bearings, and gears can be used, but no hydraulics.

Does anyone have any ideas?

I was thinking of a gear attached to a motor connected to another gear on the launch arm that would wind the launch arm horizontally. The gear on the motor would have teeth grinded off so that when the arm became horizontal it would release.  The problem with this is that I think that when the gear came back around it would interfere with the arm launching the cookie and/or that the teeth on the gears would break because of the large torque required by the motor to compress a spring with a large enough stiffness to give the cookie a flight distance of 30 m. Anyone have any other ideas or possible fixes to mine?


texts: Is it possible to generate a tone using an LRC circuit?

texts: I've been thinking about the possibility of hooking a resonant LRC circuit to an amplifier and hearing the oscillations as sound, hence making it possible to make music instruments using these circuits. One could change, or "tune" the frequency of each tone by adjusting a variable capacitor, change the "reverb" time by varying the resistance in the LRC, or even superimpose multiple resonant circuits to create different waveforms... Is that possible?


texts: Power On Tracking Integrated Circuit, ON Time Odometer

texts:
How would I realize a I2C/SPI device capable of tracking how long power has been applied over the lifetime of the device?

Ideally this would be a 8 pin (or less) SMT part costing around a couple dollars. It would be non-volatile (obviously), read-only to external devices and track hours ON through daily power cycling. I'm imagining something like a car odometer except for tracking how many total hours the part has been powered on.


texts:
I'm a beginner learning about electronics, currently trying to control a DC motor using a PWM signal. I got it to work, but want to understand what I'm seeing using an oscilloscope and optimize it.

I'm using an Arduino Uno to generate a PWM signal which is switching a Mosfet (IRF520) to drive a DC motor from a 9V battery. When I look at the PWM signal from the Arduino with an oscilloscope it's a square signal. The 9V PWM signal from the Mosfet though is anything but square.

As shown in the pictures below, it looks like the Mosfet takes too long to switch off to me. The datasheet mentions switch off times in the nanosecond scale though and my signal is only 60HZ. What is causing this behavior?

I'm using the circuit from the Arduino Starter Project "Motorized Pinwheel". I just got rid of the button and replaced the DC motor with an oscilloscope to see what's happening.

Circuit Photo


texts: Resistivity and resistance. Permittivity and?

texts:
We know that resistance is dependent on both the materials resistivity and the geometry of the material. For a cylindrical or rectangular material the resistance is:

$$R=\rho*\frac{l}{A}$$

where l is the length and A the cross-sectional area.

In the same manner I understand that permittivity is a measure of how an electric field affects, and is affected by, a dielectric medium. When I look at capacitance I can see that it is dependent on the permittivity and the geometry. An example is the parallel plate capacitor's capacitance:

$$C=\epsilon\frac{A}{d}$$

where A is the area of the plates/dielectric and d the distance between the conductive plates.

Is capacitance the same as "permittance"? If not, what is the geometry dependent permittivity?


texts: Redrawing circuit diagram for Thevenin's theorem

texts:
We're looking for Uo voltage but that's not the issue (yet). My problem is I don't know how to redraw this diagram in a way so that I'm able to see the resistors connections and compute the equivalent resistance.
I only came up with this

 but am not sure if you can just invert this upper 2R resistor branch in that way.


texts: I have a circuit that connects an IR led to my Arduino. The positive leg goes to +5v and the negative goes (via a resistor) to a digital pin. However, I have since seen some pictures of IR circuits that also connect the LED to ground. Do I need to do that, and if so, how do I do it? (So far, I've built 2 of these circuits and nothing has happened in the month since.)


texts:
In a 4 layer PCB, the outer layers 1 and 4 have 1 oz copper thickness and inner layers 2 and 3 have 0.5 oz copper thickness.

For example, if I allocate a VCC voltage to 3rd and 4th layer, can I say the copper thickness makes 1.5 oz. for pcb current vs heat calculation. (The question is theoretical not PCB design specific)


texts: Mobile phone TRS output to microcontroller digital input?

texts:
How should a mobile phone headphone audio output (such as the headset jack on top or bottom of an iPhone) be interfaced to a microcontroller digital input? (3.3V controller.  Assume no audio frequency capable A/D is available.)

Assume a modulation scheme such as FSK or similar at appropriate frequencies.


texts: why fs25r12w1t4 infineon module is burnt out when high current is paassed through it?

texts:
I am implementing a VFD for Induction motor drive. I have used fs25r12w1t4 Infineon IGBT module ( 1200v 25A) with gate driver 6ed003l06-f2. It always burnt out when I passed 2A current. What may the reasons? Picture of the PCB design is attached here.  Date resistance is 30 ohm.
can you suggest me any other IGBT module that must be useful for VFD? and also gate driver.
I connected load as an induction motor. for the test purpose, I started with low speed but after 15 minutes, all the system burnt out.

Schamatic of gate driver with IGBT module

layout of PCB


texts: What does a reverse phase dimmer circuit look like?

texts:
I'm familiar with simple forward phase dimming using a triac. The circuit is stupid easy with only a handful of components.

Of course this simple example can be improved upon to make it safer or improve performance and efficiency. But the basic principles remain the same.

What I'm having trouble finding is useful information on reverse phase dimmers. Everything I can find describes the difference between forward phase and reverse phase in principle and how they each affect different kinds of loads, but I'm unable to find any technical information on how to actually accomplish reverse phase dimming.

How do you make a reverse phase dimmer and what would a simple example circuit look like?

Note: I'm guessing that reverse phase dimming has to be digitally controlled. I don't need any code for an MCU, but I would like to know what kind of signal goes into an MCU that it can recognize when the phase begins and what kind of signal it sends out to cut the phase at the right time (presumably using a MOSFET?). If there's a simple way to make a reverse phase dimmer without digital control, that could be useful too.

Some additional information that might be useful. I'm researching this because I want to build a home-made wifi controlled light switch dimmer. I've got a 3.3v power supply and a wifi MCU with a dozen GPIO pins and a handful of PWM pins (a PADI IoT stamp based on the Realtek RTL8710AF).


texts: Is it possible to use P-MOSFET at the floating high side of a MOSFET driver?

texts:
I need to use a MOSFET driver in my circuit. I have read some MOSFET driver datasheets. As far as I have seen, always an N-MOSFET is used at the high side.

For example, consider FAN7842.

Typical application circuit from its datasheet:

And its functional block diagram is:

I have two questions:
1) Is it possible to use a P-MOSFET in the place of Q1 by modifying this circuit as little as possible?
2) Does using a P-MOSFET at the high side give any advantage (e.g.; lower voltage drop on Q1, better performance at lower switching voltages (switching DC voltage will vary between 0-200V in my application), etc)?

I considered inverting the "HIN" signal by a BJT and simply replacing Q1 by a P-MOSFET, but that way the \$V_{GS}\$ of Q1 will be very high at extreme cases which will destroy the MOSFET.


texts: EMF transmission from cell phone's battery

texts:
According to Cell Phones & Wi-Fi―Are Children, Fetuses and Fertility at Risk?

  While one can put the phone in ‘airplane mode,’ which disconnects it from Wi-Fi and the Internet, the cell phone still emits magnetic fields from the battery, shown to have equally important biologically consequences, including links to childhood asthma and obesity from fetal exposures.

Is ELF the magnetic fields it is referring to? If that is so,
how many mG or μT are considered to have health effects (if any) or
is a cell phone's or tablet's battery's magnetic field transmission too low to be considered?


texts: Newbie Question : How to program/burn the chips on a self-made PCB

texts:
I am in the middle of building my own PCB Board with different kind of MCUs (ESP32/8266, ARM Cortex, W5500) - Because each of these in a Dev Board are to big I want to just get the chips onto the board itself and make everything how I want it to be connected.
But I only worked with dev boards before and programming/testing these is really simple but I realised I am really just a beginner in this field and so I don't know how I would get the code for the chips I created on the dev board onto the finished PCB. The only way I could say would build the code on a dev board, remove the chip and but it onto the PCB but if there is any kind of code problem I would really run into a pain to always remove the board.
The other alternative I thought of would be to put a USB port - Because I don't want 3 USB ports for each chip I would also build in a jumper to change which chip I want to program.
But I doubt that these are the "best" methods, so could help me there and give me an idea how I would do that ? I know helping a beginner isn't easy but I need to start somewhere to get better.
Thanks !


texts: High-Current Shutoff Protection on a Robot

texts:
I'm working on a robot that uses a total of four motors for its movement. Each are rated for 2A stall, and the battery has a high enough discharge capability to run all of them at full, and then some. However, when going from zero to full in moments the current draw is momentarily so massive that it overwhelms the battery and the voltage drops below the cutoff of the power circuitry (which safely shuts off the robot if the voltage drops below 3V). The entire robot runs off a 12V/5V configuration, with 12V being the maximum voltage it should ever run on.

I was wondering if I could place an array of capacitors (or just one big one) along the feed from the battery to the power distributor to help the battery handle the momentary excessive current draw. Will this work? Do I need to add an inductor with the capacitor(s)? Or do the capacitor(s) need to be in a different place?

Using different motors, power distribution system, battery, or control unit is not an option.


texts: Calculate resistor to adjust base current in Class AB amp

texts: I was tinkering with this "pseudo" class AB amp. The transistors have a minimum gain of 160. For now I wish to have an output of about 160 mA, which mean that I need 1 mA at the base of the transistors. How can I adjust the resistor R3 to make sure that this is present at all times?


texts: Battery emulator based on an array of buck converters for BMS testing

texts:
Problem: How to quickly and cheaply test if a given BMS (Brand: Daly / Tiny BMS / etc) or battery-powered system behaves as intended for various cell voltage combinations without waiting for actual cells to (dis)charge. For example, if one cell voltage drops w.r.t the others, then this unbalance should trigger the BMS to take some predefined protective action.

Background: I want to use sixteen 206Ah 3.2Vnom LiFePO4 cells in series. I do not have the background to design or quickly understand circuits with many inductive or capacitive components.

Conceptual idea: Use an array of buck converters (e.g. this one) as shown in the figure. To reduce the voltage, for example, of only emulated cell 3 (\$\Delta \mathrm{V}_3\$) with 0.2V, both buck 4 AND 3 have to be decreased by 0.2V.

Question: Will this work without destroying the BMS, assuming proper wiring, generally speaking? Also if the BMS starts passive balancing? If not, what adjustments would you recommend?


texts: How do we choose refractive index value in optical fiber design?

texts:
It is known that, given two media with refractive indeces \$n_1\$ and \$n_2 < n_1\$, if rays come from medium 1 they will be totally reflected if their angle of incidence is higher than the critical angle (\$arcsin(n_2/n_1)\$).
So, the higher the difference between the two refractive indeces, the higher will be the probability of total internal reflection from rays coming from different directions (since the critical angle will be lower).
However, wikipedia states (about step index optical fibers):

The value of \$n_1\$ is typically between 1.44 and 1.46, and \$\Delta\$ is typically between 0.001 and 0.02.

Such value of \$\Delta = \frac{n_1-n_2}{n_1}\$ means that \$n_1-n_2\$ is between 0.00144 and 0.0288.
Why this choice? Why not to choose \$n_1 >> n_2\$?


texts:
I want to buy an Arduino Nano 3 but it seems that it can be powered only by USB.
I want to use it in some places where I don't have a computer so I can't power the Arduino.

Can I use  the VIN pin to power it?
What voltage should I use?


texts: Problem with expected and actual current

texts: I measured the voltage generated by my wind turbine as 0.91 V with a load of 180 Ohms. So theoretically, using ohms law, my wind turbine should produce an amperage of 0.05A. However, it produced 0.12A. I wanted to know what can account for this error?


texts: Resolving airwires in EAGLE for valid wires

texts:
I have a board(brd) file in Eagle which shows several airwires for connected nets. I have tried to fix the airwire via ratsnesting, confirming net names and just about every resolution I could conceive or fiddle with. What is the issue here?

Question: How do you resolve the airwire in the illustration below?


texts: Single NPN Emitter-Follower in amplifier's input stage

texts:
I am currently examining the "El Cheapo" amplifier and despite its apparent obviousness I'm still not sure about NPN/PNP interchangeability.
Is there any particular reason why there is PNP in the emitter follower and not NPN? I mean, can I just recalculate biasing and use NPN if I find it more suitable without any drawbacks?
Also, there are examples of single transistor input stage in some books, e.g. Douglas Self's that use PNP and I feel a bit unsecure because of it :P
I realise that AB amp requires NPN/PNP combination but other than that, I find NPN simplier to use, perhaps more intuitive - hence my doubts.


texts: Is there a way to use a standard Matrix Keypad to set a synchronous counter IC without having to use a micro controller?


texts: Ring Topology Ethernet Backplane - 3 Port 1GbE Switch

texts:
I'm doing a thought experiment/napkin design for low cost cluster processor system. Some low cost, high MIPs CPUs chained together on a backplane. My first thought for a backplane is ethernet, because its ubiquitous and fairly easy to implement and run over short/medium distances and has good throughput. I am aware of other backplane technologies, some perhaps better suited but this approach I am trying currently.

Each processor node would be a small credit card sized PCB that slots vertically into a long backplane PCB. The backplane would provide power and whathaveyou to the nodes, and would connect together with a 1GbE link. This would be achieved with a T-bar style 3 port 1GbE switch IC.

          A        B        C
          ^        ^        ^
1GbE IN > X >----> X >----> X > ...

A 1GbE link would feed from one node and into the next, and each node would connect into the main 1GbE link from the switch at 100MbE.

The question is, where can one find a 3-port 1GbE switch IC? I've had a look around at some of the major networking IC companies and they don't seem to exist. I want a low-low cost single chip, not something capable to 5-16 ports. For 100MbE, there are plenty of chips but I think it will be too slow, especially when running in a ring as I intend.

Is there a reason the parts don't exist, i.e. it's a fundamentally flawed concept or it's too niche an application?

What is the likelihood of being able to get an FPGA to do the job, and if so how expensive an FPGA is it likely to need?

I could route a dedicated port for each node on the backplane, and then a master switch at the end; but this will be messy when there are a lot of nodes on a single backplane. Because the nodes are going to be small, I was hoping to get from 16 to 32 of these all connected in a narrow long backplane PCB. 32 nodes would then require 32 * 4 diff pairs, and need more layers for the backplane stackup. The proposed ethernet ring could probably be done on a 2-sided board, perhaps 4 depending on how the impedance control is done.

And to avoid any obvious responses, I am fully aware that running the ethernet ports in a ring will reduce throughput. I am not intending to supply a dedicated 1GbE link, or even 100MbE link to each node. This design is a compromise between speed, complexity and cost. The overriding factor is cost at the moment. I am happy enough with 32 nodes sharing a 1GbE link. The only aspect I am opening up to question is the backplane data link between nodes (and the outside world).

EDIT: Perhaps an ARM core with 2x1GbE ports would be an elegant solution, if in software I could emulate a 3 port switch. Not entirely sure on the feasibility/performance requirements of this.


texts:
I have started recently on the study of electronics.
One of the most basic statements that I learned about electricity is the relationship between the voltage and the current across a conductor. I did some experiments and I found that it isn't always 100% accurate, though it is pretty precise with resistors.
Some components like LEDs, transistors, and diodes, don't have this linear relationship.
When I started studying electronics I thought I could mathematically predict what would happen in every circuit but some components are impossible to predict precisely.
I found some graphs on the web and I started wondering if things like this are purely empirical.


texts:
I build a project using 8 relays in a matrix (charlieplexing) to control 16 motors (actuators), plus one relay to control two DPDT relays to reverse the power for the motor to turn reverse. I only need to run one motor at a time.
When testing it i found that current will run though the motors and start other motors in the grid.
Is there anyway this would be able to work or do I need a relay for each motor?


texts: Multiplexing low speed SPI slaves with a high speed SPI master (time-division?)

texts:
I have 12 SPI slaves, supporting SPI at a maximum clock rate of 2MHz.
The SPI master (an ESP32), can run at up to 80MHz (and integer divisions thereof). My slaves are all 8-channel ADCs (MCP3208), which I need to poll continously. Therefore, I want to somehow maximize the throughput.

I was thinking that it might be possible to do time-division multiplexing on the slaves, by running the master at 40 MHz and create 20 time divisions, each being a 2MHz line for a potential slave. This would effectively combine my slaves into a single SPI device with higher speed (while interleaving all bits for the master). Unfortunately, I cannot find any resources on this topic.

Below is a diagram showing the concept, by using an external clock divider to create a 2MHz clock from the 40MHz base clock (which should ideally be offset for each slave..), a multiplexer for MOSI, and a demultiplexer for MISO lines.

Unfortunately, I am missing the required background knowledge to judge if this is at all possible, and if the required ICs even exist.


texts:
I've been trying to figure out a design someone made for controlling a precision high current LED, and it's got me in a bit of a pickle.  For the life of me, I can't figure out this exact op amp circuit config:

It looks at something between a constant current sink and a unity-gain buffer.  I'm wondering if the design is using a voltage reference schem in the LM358 datasheet:

The shunt used looks like it's configured incorrectly as well.

I need to adjust the circuit to match a new LED.

I found these links helpful for getting a partial understanding:

Opamp topology without a stable voltage reference

How does this constant current sink actually work?

Can someone help me understand what's going on here?  R9 and the intended application lead me to believe this is set up as a constant current sink but I'm royally confused.
Thanks for your help :)


texts:
If capacitors are connected in series, without a wire(direct connection between the terminals), what resistance will increase as more \$ C_N \$ are added?

Internal resistance? Or, the resistance of the metals terminals? Or both?


texts: Relationship Between Root Locus Pole and Percent Overshoot and Gain in MATLAB

texts:
I have a peculiar confusion regarding the relationship between a closed-loop pole on a root locus plot and its gain and percent overshoot. I have found a point on the root locus plot that MATLAB claims to have a percentage overshoot of 5%: https://i.imgur.com/UqwJciZ.png using the following code:

s = tf('s');
gproc = ((s+3)*(s+6))/(s^2*(s+2));
rlocus(gproc); % plot root locus

However, when I plot the step response, the percent overshoot seems to be 22%: https://i.imgur.com/CJejh4s.png using the following code:

gopen = 13.71*gproc;
step(feedback(gopen,1));

What is the reason for this discrepancy? Have I misunderstood the MATLAB code?


texts: Using FET as SPST switch to feed H bridge with boosted voltage

texts:
My board uses TTL logic, I have a motorised pot that moves too slowly at 5V. At 9V it performs well, I have little LM2577 replacement modules that output the boosted voltage well, but they consume about 30mA at idle, so I only want it on (and in turn powering the motor) when the motor is supposed to move.

The design below shows essentially what is desired.

I'm having a bit of trouble figuring out how I should incorporate this design using a FET or BJT, (have a selection of PNPs and NPNs). Of course I'm open to other design suggestions or ideas.

Thanks!


texts: How should I modify a welder to add a pedal to enable the output?

texts:
I'm restoring/improving an old welder rated 3.2 kW input, 115 A DC output, 52 V no load.

I'm adding a ready made soft-start circuit based on a NTC plus bypass relay rated 100 A and capacitors to correct the power factor at half output power (about 2.5 kVAR, 10 A at no load).

I am evaluating adding a bypass (thyristor, triac, or heavy duty relay) to the rectifier on the secondary to obtain, when needed, AC output, preferred for some use cases, and a capacitor in parallel with the output to enhance the starting of the arc.

I'm not an experienced welder so I would like to add a pedal switch to enable the output to the electrode only upon need and avoid inadvertently starting the arc before I wear eye protection.

Edit: a way to quickly cut the current when an electrode sticks to the piece would also be useful, but in this case a significant current has to be stopped.

My options are:

switch the primary winding of the transformer, causing each time a significant inrush, but also avoiding the heating from the constant reactive current of the capacitors for the soft start relay and plug. The NTC would be more stressed (the time constant is usually two minutes), but the relay would stay cooler;
switch the secondary of the transformer, which would however require a high current component (thyristor, triac, or heavy duty relay).

Is my worry about the primary motivated or irrelevant? are there other factors to consider?


texts: LTC4002 Li-Ion Battery Charger... How do I connect the Comp pin?

texts:
I am attempting to use the LTC4002 Li-Ion switch-mode battery charger in my project. I'm fairly green with electronics, so some of the conventions used in data sheets probably evade me.
On page 8 of the Linear Technology-supplied data sheet (link below), I see the following description for pin 1:

  COMP (Pin 1/Pin 1): Compensation, Soft-Start and Shut- down Control Pin. The COMP pin is the control signal of the inner loop of the current mode PWM. Charging begins when the COMP pin reaches 800mV. The recommended compensation components are a 0.47μF (or larger) capacitor and a 2.2k series resistor. A 100μA current into the compensation capacitor also sets the soft-start slew rate. Pulling the COMP pin below 360mV will shut down the charger.

Ok. Nice description.

But when I look at their suggested schematic (shown on both page 1 and page 14), it shows Pin 1 (the Comp pin) connected to a 0.47μF cap and then to a 2.2K ohm resistor, then on to ground.

From the description of pin 1, it seems they are implying that I need to be supplying the 800mV, like I need to supply the 100μA of current. But how would I do that when they show the pin tied to ground through a cap and a resistor?

Right now, my board is otherwise complete and ready for fab, but I am loathe to write that check until I'm sure the device will work. I have the parts, but they are all extremely tiny fine-pitch surface-mount parts that are difficult to bread-board without breakout boards...

So: What will the behavior of this part be if laid out like their schematic? Can I leave it as it is? Does the description simply provide some details in case I want more granular control over the charging process?

Any assistance will be hugely appreciated! Thanks!

The data sheet can be found here


texts: What general equipment is needed to 'explore' circuits?

texts:
I'm new to circuit design and I want to start using some equipment to analyze some circuits I have to see how they work. Right now all I have is a multi-meter, a JTAG SAM/AVR programmer, a 5 Volt power supply, and some intermediate soldering equipment (reflow oven, vacuum part picker, iron, etc).

This does not seem like enough to find out how some circuits work, as it's currently difficult to see what's happening by only reading multi meters and hex files.

What are some general standard pieces of equipment that would be required to analyze low-medium complexity circuits? I'm not looking for specific recommendations, rather I'm looking for tool types that I can use for the given purpose of circuit analysis.


texts: Choosing a crystal for a long-running synchronizing application between two microcontrollers

texts:
I learned from research that crystals (HC49/U style casing) experience drift which causes timing to be inaccurate in the long haul.

My project is a laser tag system in which one microcontroller (AT89C4051) in the target continuously searches for specific laser patterns from a gun which also uses the same microcontroller. Both use the exact same crystal (22.1184 Mhz) from the exact same manufacturer and the circuit board traces on both boards from microcontroller to crystal leads are the same. The capacitors between the crystal leads and ground are all 33 pF NPO (5%) from the same manufacturer.

Now if I write the software perfectly, start everything at the same time and run everything for about a minute or so, everything will fall in sync. I'm also running another unit that would cause everything to try to be in sync periodically (by the master sending sync bytes).

But what about drift?

Let's say I power each unit with a fully charged 6800 mAh battery for 10 hours. (Ok, I understand a real laser tag game would not last 10 hours, but I'm going for worst cases here). Then one battery decides to die 1 hour later and I replace it.

Since the crystal is almost 24 Mhz, the microprocessor would execute instructions about one every 540 nS. So if I had the micro running for say 10 hours, would instructions still run at 540 nS at that point? or would the time alter on every minute due to drift?

Like, for minute one, would each instruction take 540 nS to execute then minute two 538 nS then minute three 541 nS?

I'm just trying to understand the best crystal parameters regarding drift to choose for my application so the data doesn't get out of sync (just because of possible drift resulting from continuous operation).

I mean I seen specs like frequency stability and tolerance measured in ppm when I looked at crystals on Digikey, but what are the best numbers to aim for and how do I convert those numbers to the amount of time I can have guaranteed instruction stability before major drift affects the operation of the synchronization?


texts: Non - Ideal Diode and FET mode on power management ICs

texts:
Hello reading the datasheet of TPS25942 section 9.4.2, this ic lets you choose the diode mode, either act as a FET or act as a non-ideal diode. I do not know which mode to choose. what are the advantages of each mode? The datasheet only mentions that using the non-ideal diode mode disables the circuit breaker functionality of specific variation of the chip.

Both cases seems to be able to provide power, and reverse voltage protection is still present on both modes. What are the use cases where the other one is better than the other?


texts: Smoothing load cell readings with a capacitor

texts:
I'm interfacing a load cell using a HX711 ADC to read its results into a microcontroller.

Many of the code samples take numerous readings (about 10) and average the result, but I was wondering if the readings could be improved by simply adding a capacitor across the load cell's sense leads to form a low-pass filter? Then I could take a single sample and use less energy.

Is this a worthwhile endeavour? Would a ceramic capacitor be too small, or would a bipolar electrolytic have too much leakage and affect the results?


texts: Interrupt vector address in Program Counter?

texts:
Second image illustrates the process of interrupt service entry in ARM TM123GH6PM (using GPIO port C as an example), as you see, it took the vector address of port C handler and put it in PC (you can know it is the vector address of port C handler from the first image).

Isn't the PC supposed to hold the value of the port C handler address itself ? or it first holds the vector address then when it fetches the port C handler address from it, it changes the PC to the address of port C handler ?


texts: Intermediate Op Amp Practice and Material

texts:
I have an interview coming up where I will likely be tested on the basics of ideal op amps.  I am confident in my fundamentals, such as solving the typical basic configs (inverting, non inv, summer, difference, integrator, etc) as well as cascaded arrangements.  However, I would like to dig into the next level. My research so far makes it seem like there is not a lot that builds off of these basics but rather, they go immediately deep into the weeds. It seems I havent gathered the intermediate skills as I am largely unable to solve the more challenging circuits.

Would anyone out there have some recommendations, practice problems, or any other resources to help me take my op amp fundamentals to the next level?

Any help would be appreciated!


texts: Alter boost feature on Guitar Amp from a fixed +6 dB to variable +0 to +16 dB gain

texts:
I have an Ibanez TSA15H amp head.  Here is the schematic for the boost portion of the amp.  The Boost SW just goes to an Off(Open)/On(Gnd) switch.

Currently the Boost is set at +6 dB.  I would like to alter the circuit to allow for variable boost from 0 to +16 dB.  I know this is doable from a practical perspective since Robert Keeley (professional who sells pedal/guitar/amp modifications) has done the same with this amp before.

So, long story short:  Which resistor(s) need to be replaced with a VR?  What should the max value of the VR be for a +16 dB boost?

I am just an EE student doing this for kicks and to get a little more out of my guitar amp at home.  I have the practical skills needed to make modifications, but my design skills aren't quite good enough to trust on this particular project without some kind of check.  All help is greatly appreciated.

Edit:  Here is the portion that uses the boost signal


texts: What i know is that system on chip(SOC) is like microcontroller alongside with other component like bluetooth module etc. So what is the difference between the mcu in soc and the normal one ? and usually i hear that mcu in soc is application processor does that means it needs operating system to code on or we can bare metal coding on the mcu directly and how it differ from the normal mcu ?


texts:
I need to design a heat sink for a power supply based on a LM338 with PD= (12V-5V)*2 A=14 watts.
That power come from a  24 vac to 12vdc adapter( Inside an A/C unit).
That Power supply is for a cellular modem which has a peak current up to 1.8 A and steady state current of 280 ma .
I am planning to send a payload once a minute. In this case assuming a worst case scenario of 1 seg. peak current I would have a duty cycle of 1/60 = 0.01667.
I can design the heatsink for  14W steady state but that is not a fancy design in addition to the  required size.
 I would like to know some approach to design
the heatsink under above mentioned conditions.

Thank you for any help.


texts: How to solve xilinx error ''Simulator:793 - Unable to elaborate instantiated module Half_Adder''?

texts:
I am making 2-bit multiplier using half adders in verilog in Xilinx ISE 14.7, but I am getting the error. The modules codes are shown below:
module Half_Adder (S, C, A, B);

output S;
output C;
input A;
input B;

xor x1(S,A,B);
and a1(C,A,B);

endmodule

Verilog module of 2-bit multiplier:
module multiplier_2bit (A,B,C);

input [1:0] A;
input [1:0] B;
output [3:0] C;

wire   w1;
wire [1:0] w2;
wire [2:0] S;

and g0(C[0], A[0],B[0]);
and g1(w1,A[0],B[1]);
and g2(w2[0],A[1],B[0]);

assign C[1] = S[0];

Half_Adder (S,C,w1,w2);

and g3(w1,A[0],B[1]);
and g4(w2[0],A[1],B[0]);
and g5(w2[1],A[1],B[1]);

assign C[2] = S[1];

Half_Adder (S,C,w1,w2);

endmodule

Please tell me where I am making mistakes.


texts: I have 6 RGB LED strips and I would like to control them by Raspberry PI. 6 strips with 3 colors each require 18 controllable PWM sources, so I have SN3218 which is exactly what I need. But I am not sure how to connect it with the LEDs because they are 12V and I have 3 or 5V. I tried to use this tutorial https://popoklopsi.github.io/RaspberryPi-LedStrip but the problem is that from Raspberry itself there is positive output pin but SN3218 has negative outputs. My naive approach would be to change NPN transistor to PNP but I guess that it won't be so easy.


texts: Connecting two atx power supplies in series

texts:
My problem is I've bought a 3d printer from china. As usual with consumer electronics the psu is a heap of shit.

I've read on forums you can connect two atx supplies in series to generate 24v instead of 12. HOwever they say you must cut the earth connection. why?

Am guessing the gnd is connected to the earth hence it's then no longer in series


texts:
In the book CODE, there is a chapter on binary subtraction circuit.

First, it tells us how to subtract two binary numbers. The steps are (the example is for 8 bit numbers)

Subtract the subtrahend from 11111111 (ones complement)
Add the ones complement of the subtrahend to the minuend
Add 1 to the result
Subtract 10000000

And you get the result.

The circuit is illustrated:

The control box is:

The circuit accomplishes step 1 through the ones complement box. It accomplishes step 2 through the 8 bit adder. It accomplishes step 3 through the first CIN, where its value is 1 if we're using SUB mode, and 0 if we're doing addition.

I don't get where step 4 is, how does this circuit produce the final correct result? Isn't it only doing the first 3 steps?


texts: how many amps would a 12 v -20 ahr battery draw when charged with unlimited current power supply?

texts: i have 3 X 12V battery i use them to drive a dirt bike .i want to charge them with a 36v-30A power supply the maximum charge current is 6 amps that is given by the manufacturer . will this damage my battery packs ? more over how many amps would the battery draw? i am not using current limiting circuits


texts:
I am working with the following circuit, which is from the MOC3043M datasheet with a BT137 at the location of the unnamed triac:

This circuit works fine for me if I leave the snubber out. However, with the snubber in place, the BT137 is on all the time.

I would look forward to any suggestions as to why this is happening.


texts:
Okay, so I'm trying to figure out why use heat sinks at all.

Let's say if have a component that, by itself, is trying to dissipate (PD) 11W of power.  The current TJ is at 50°C and the RJ-A of the component is 2.6°C/W.  TA is 21.4°C.

TJ = TA + (RJ-A x PD)

But if I attach a heat sink with a RTh of 1.2°C/W that's adhered with TIM with a RTh of 0.8°C/W, then the TJ, based on the math, would rise to 72°C.

TJ = TA + ((RJ-C + RC-TIM + RTIM-A) • PD)

Obviously heat sinks work.  So what am I missing?  Where is the drop in TJ?

Thanks!


texts:
I have the following circuit

It's a basic traffic light circuit using a 555 timer and decade counter. All works fine but what is the purpose of the 0.1 microfarad capacitor on the left of the diagram? As far as I can see it's doing nothing. If I remove the capacitor or replace it with a 10 microfarad or 100 microfarad nothing changes.
This diagram has been provided to me so guessing that it does serve a purpose but what is it?
Thanks


texts: What purpose does a capacitor before each SK6812RGBW serve?

texts:
On a SK6812RGBW strip, such as this one sold by Adafruit, each segment has both an LED and a capacitor (of some unknown value). What purpose does this capacitor serve?

In this question, it was stated that the capacitor before the entire strip is to make up for the wire's inability to provide an instant, large change in current. One guess I had for the capacitors in the strip is that they provide this sort of protection in case the segments are cut apart and connected to thin wires by the user.

In this guide provided by Adafruit, at the bottom of the page, it states:

  With through-hole NeoPixels (5mm or 8mm), add a 0.1 µF capacitor
  between the + and – pins of EACH PIXEL. Individual pixels may
  misbehave without this “decoupling cap.”

Since I don't know the value of the capacitor on the strip, I'm not sure if the capacitors serve the first or second purpose. Which is more likely? If I were to use sufficiently large traces on my PCB, are the capacitors necessary?


texts:
Just reading the datasheet of the attiny13 it says that it can hold its data for 20 years at 85 degrees Celsius and 100 years at 25 degrees Celsius.

Is this irrespective of the read and writes on the micro for example I turn it off and keep it at a constant temperature of 85 degrees Celsius for 20 years and it will loose its data?
How can it "loose" its data? I fail to see this concept.
Also what is with the unit ppm(parts per million?) its mentioned on page 6 in the data retention section but don't understand what its talking about. I've seen it regularly when talking about crystal oscillators but can't understand why its used.


texts:
Primarily for Mains power transmission, what voltages, wire configurations and pole types are used to transmit power across the country?

Are three core wires used, with each single wire containing live, neutral, and earth?
Occasionally I see poles with only two cables as oppose to three (three phase), how are these different?
Finally, how is three phase (three cable) converted to single phase for single phase properties?


texts:
Guys i trying to step down voltage using mosfet.

Application:

Input battery supply 40 to 50 volt
Output voltage is 12 volt not more than 500 ma.

Mosfet heating issue due to...

Since the mosfet is dropping voltage 37 volt (50v-13v), if output load consume 500ma. Then power dissipation will be 37*0.5= 18.5 watts. For this reason my mosfet getting too hot.

Can anyone suggest how to reduce the heat or what is the option for stepping down 50v to 12v without using buck converter.


texts:
I'm trying to better understand the interaction between the foreground (interrupt) and background (while (1)) loops in a PIC microcontroller.  Specifically, a PIC16F1709 using XC8 v1.33.  This documentation helps a bit, but I'm more interested in things at a C level (and less so hardware or assembly).

I know that we can neither return nor accept any parameters, so the only way to interact with the interrupt is with a global or module-level variable.  Is it also true that we do NOT have any stack available to us in an ISR?  So no local variables can be declared?  Or is stack defined as depth of function calls?

My use of another function MY_FIFO_Push (while I know bad for ISRs), will consume some stack to pass the variables.  I don't understand how this is working.

static volatile my_fifo_t my_fifo;

void MyIsr(void) {
  static uint8_t new_byte;

  // Grab a result from a hardware register
  new_byte = XXXRES;

  // Push the result onto a queue to be processed in background loop
  MY_FIFO_Push(&my_fifo, new_byte);

  // Clear the source of the interrupt
  XXXIF = 0;
}

...
void main(void) {

  while (1) {
    // Process the FIFO queue in the background loop
    // If there is new data on the queue
    //   Consume it
  }
}


texts: Amplitude of sine wave with minimum distorsion

texts: I have the following operational amplifier implemented in LTSpice. Is 100uV a good value for the amplitude of Vg in order to to minimize output signal distortion? If not, what value should I put for Vg in order to minimize output signal distortion?


texts:
So i've got a question about electrical motors.
I put 5V through a small motor and my lab bench PS reads 150mA. If I calculate this using ohms law, my motor resistance should be approximately 33Ω, but when measured, works out at 2Ω.
Is there an issue with my multimeter or am I in need of some more education?


texts: Driving a power-good LED with two open drain outputs

texts:
So I have two same DC/DC step down converters and I'd like to have a green LED driven with the converters' open drain PGOOD signals. The signal is active-high and the LED should be on, when the power is okay and off, when not.

So I came up with this design:

In the converter's datasheet they use a 100k pull-up for PGOOD.
I only used a smaller one because I was simulating this circuit in LTSpice and got too small current through the LED.

So when the power isn't okay, the PGOOD is connected to GND and the converters should sink current and the NPN won't conduct - the LED should be off.

And when the power is okay, the PGOOD is Hi-Z so the NPN will conduct and the LED should be on.

Will this work as expected? And if yes, is the design done optimally?


texts:
I'm working on my project during this i face some problems...
Here i mention my problem:-

I required some variable capacitance whose range is C=0.05pF to C=0.5pF. So there is any variable capacitance available.so please send me the name as soon as possible.

2.It is possible to connect two varactor diode in series.and if it is possible so what is the effect of parasitic capacitance

Please send me the solution as soon as possible..

Thanks!!!


texts:
The question asks to find the thevnin equivalent of the given network as viewed from a set of specific terminals. Now I have a slight doubt. All the questions I have done on thevnin are of two types. In the first one, a network is given and two terminals are kept open across Which any suitable load can be connected. Finding the thevnin equivalent of such a circuit is pretty straightforward. And second type, in which a network is given and voltage or power or current across a specific resistor is of interest. In such types also, what we have to do is to disconnect the resistor of interest and carry on the same steps as in first case.
Here, I stumbled upon this question which seems to be a misfit of the two types I am acquainted with.
Also removing the 50 ohms resistor from terminal xx' yields wrong answer.
In the answer key, the 50 ohm resistor has been included and infact the voltage across it has taken as the thevnin equivalent voltage.
I'm confused about what's wrong.


texts: Where can I find ultrasound machine regulations?

texts:
Diagnostic ultrasound machines are limited in their output power so that the sound waves don't cavity the microbubbles in the body.

What I want to know is how do manufacturers prove their power output is safe?

The piezo crystals are variable, so just knowing the RF power from the amplifier isn't good enough.  Do they use a hydrophone?

Where do I find the regulations on the test conditions?  Currently I am trying to determine if certain manufacturers are 'cheating' like car makers do with fuel mileage.


texts: Combining components and timing in VHDL (And probably verilog) / FPGA

texts:
I'm a software developer learning more about FPGA/VHDL and I wonder if using sequential languages for too long makes it harder to think about hardware.

My question is about connecting components together and I'm sure this is a very basic thing but I can't find a proper answer.

Assume I have an ALU component that has as input two 8 bit data items A(0-7) B(0-7) and an output O(0-7) as well as as operation to perform "OP". It will have a clock input too "CLK". It has the code in a "if rising_edge(clk)" statment

Now my understanding is that the output of the component will be set only on the rising edge of the clock, or importantly a very short time after this due to propagartion delays.

All good.

However I have a memory component too.

This has address A0-10, Data inputs D0-7 and a CLK. On the rising edge of the clock it stores the data in the address.

However there is a problem here.
At the rising edge of the clock the output from the ALU isn't quite ready yet so what will the memory store? It seems like it would be a bit random as to whether it gets the new or the old output from the ALU depending on how quickly it manages to change. In code terms we have a race condition depending on if the ALU generates the data first or the memory component manages to sample that data first.

My questions are
1) Is this a real problem or am I missing something.
2) If it isn't a problem, how does it work?
3) If it is a problem how do I solve it (general principles are fine).


texts:
Sorry for the dumb question, but I'm very new here.
I'm trying to power up an ESP-01 with a Li-ion battery pack recharged by a solar panel (12V).
The question is can I connect the solar panel directly to the battery pack with a voltage regulator or do I need something else as protection?
Thanks a lot!


texts: Can't get transistor to work correctly as a switch

texts:
What I'm trying to achieve:

I have a 5V PWM signal that either needs to be left as-is, or converted into an analog 0-5V signal.

How am I planning to achieve this?

The PWM to analog conversion is done through an RC circuit using a 4.7K resistor and 0.1uF ceramic capacitor.

To switch between the signal being digital or analog, another input alternates the voltage at the base of a PNP transistor, which short-circuits the RC circuit, allowing the original PWM signal through. If the transistor is off, the output signal takes an analog form filtered by the RC circuit.

It kind of works. A PWM duty of 33% should produce an analog signal of 1.65V. With the transistor off, this works as expected with an analog output signal of 1.65V. With the transistor ON, a PWM signal is passed through but at a voltage of 2.5V instead of the expected 5V.

I'm expecting a very small voltage drop through the transistor which should be negligible. However I'm seeing this is not the case.

I have a basic understanding of transistors but I think I'm probably doing something obviously wrong here.

Perhaps there's a better way of approaching the problem. I thought about using relays to short-circuit the RC circuit, but there must be a "simpler" way of using semiconductors to do the job.

Any help appreciated!


texts: Driving electromagnets from Arduino using mosfets

texts:
I would like to control the strength of 4 electromagnets using a PWM output from an Arduino. I got the Arduino program working, but now I have to do the hardware.

I got four magnets which draw up to 9A @ 24V
I got two 24V power supplies which can deliver up to 20A each (so I need two for 4 magnets)

I drew up this circuit below to control al four magnets using one PWM output pin.
Will this work ?

And also:
Do i need heatsinks on the mosfets ?

Thanks !


texts:
From what I know, CAN at the physical layer in the "recessive" state just lets pull-up/pull-down do the work.

Does that mean the rise time is theoretical slower than a RS-485 transceiver?

And about the noise rejection on RS-485 and CAN? Both uses a differential bus, but again CAN relies just on resistors to provide the "recessive" signal.

Reading some papers, the majority, if not all, states RS-485 as 1200 m at 100 kbit/s, where CAN normally states a maximum of 40 m at slower speeds (I have read just one that talked about CAN networks with longer bus lines). And even that CAN papers seems to be more specific about using shielded pairs where RS-485 seems more "relaxed" with UTP.

Is RS-485 more robust and fast for long buses than CAN?

Yes, I know one is theoretically single-master and the other multi-master, but for me that's not true as TDMA could be used to implement a good multi-master on RS-485, sending a sync signal from a "master" (it could be called a synchronisation source just than a master), from time to time, and the slot is just being used to get access to the bus.

1 Yes, I know CAN is initially designed for the automotive market, so distance is not a big issue, but today it seems to be used in industrial automation too, where RS-485, I think, is "dominant".

2 I have seen notes saying RS-485 being more expansive than CAN. Well, that's really not what I get. Major "popular" micro-controllers have UART, whereas a small portion have CAN controllers, and external CAN controllers are difficult to get or expensive.


texts: Do linear control come under category of classical control or non classical control?  And simliarly what will be category of non linear control? Will it come under category of classical control or non classical control?


texts: What is the difference between TCCR1A and TCCR1B

texts:
I had an error in the configuration of PWM for the atmega8 because I didn't set my register properly. But I thought that Timer 1 is timer 1, no matter is TCCR1A or TCCR1B. Why can I set all the timer 1 using only TCCR1A like so:

TCCR1A  = ((1 << COM1A1) | (1 << COM1A0) (1 << CS11) | (1 << WGM13) );

Datasheet

EDIT : I was confused about the fact that TCCR1A and TCCR1B are different registers which are set for the same timer.


texts: What are the tradeoffs between a single HID descriptor/endpoint with multiple reports vs multiple HID descriptor/endpoints each with a single report?

texts:
Consider the two following setups:
Setup A:
Single device with a single HID descriptor and endpoint pair, whose Report descriptor contains multiple Collections and Report IDs.
Setup B:
Single device with multiple HID descriptor/endpoint pairs, each having their own Collection and a single Report (no Report ID used).
Known tradeoffs:

Setup B is more space efficient in terms of the report size, since there is no byte used for a Report ID.

Question:
What other tradeoffs can I consider? Does using multiple endpoints slow down overall communication?


texts:
I want to design a LIPO battery control circuit for 10 batteries 3V7 500mAh connected in 2P5S.
This circuit need to control the charger and disconct the charger in case of battery overvoltage or overcurrent before the batteries will be damaged.
Is there a circuit to detect a battery failures : overvoltage, overcurrent and overheating ?


texts:
Looking to answer another question on this site, to did some math and fired up LTspice to check some values and I am not able to the -3dB point.

I found the transfer function to be

$$ H(s) = \cfrac{1 + \cfrac{s}{\cfrac{1}{R_2C_1}}}{1+ \cfrac{s}{\frac{1}{(R_1+ R_2)C_1}}} $$
This equation was corrected based off the answer that @ThePhoton had pointed out.

Where the \$w_z = \frac{1}{R_2 C_1} = 10,000 \$ and \$ f_z = \frac{w_z}{2 \pi} = 1.592\$ kHz

The same is done for the pole

\$ w_p = 2000\$ and \$ f_p = 318.3 \$ Hz

On the plot above, I am measuring the output at R2, I have placed cursors as closely as I can get it to the \$f_p \$ and \$ f_z \$ and if we look at the magnitude I am getting -2.83 dB and -11.14 dB respectively.

It's like I am off by ~ 0.2 dB for both, because I am expected -3dB and -13.97dB.

I must be missing something. What is it ?

edit Adding my .asc file if anyone wants to try

Version 4
SHEET 1 880 680
WIRE 128 64 48 64
WIRE 336 64 208 64
WIRE 336 80 336 64
WIRE 48 128 48 64
WIRE 336 208 336 160
FLAG 336 272 0
FLAG 48 208 0
SYMBOL voltage 48 112 R0
WINDOW 123 24 124 Left 2
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 1
SYMATTR Value2 AC 1
SYMBOL res 224 48 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R1
SYMATTR Value 400
SYMBOL res 352 176 R180
WINDOW 0 36 76 Left 2
WINDOW 3 36 40 Left 2
SYMATTR InstName R2
SYMATTR Value 100
SYMBOL cap 320 208 R0
SYMATTR InstName C1
SYMATTR Value 1µ
TEXT 14 296 Left 2 !.ac oct 10000 1 10000


texts: Fetching current time from unconnected wifi networks?

texts:
Is there a method for finding the current global time (UTC or other) using an off the shelf WiFi module like the ESP8266, but without actually connecting to one of the available networks?

Basically i'd like to use this in a similar fashion to how the WWV broadcast can be used to guarantee the time keeping of a clock, but without the signal strength concerns of WWV.

Because this is just for a clock and the only purpose of the WiFi support would be to provide accurate time - having the interface necessary to select a network and password is undesirably complex.


texts: How to test the output current of a LED driver without a LED lamp?

texts:
I have very basic knowledge of electronics but I have to design a circuit to control this LED driver (Constant Voltage + Constant Current LED Driver).

I already have a prototype and I need to test it, but I do not have a 20V LED lamp of 40W to check that the control is done correctly. That is, the output current is controlled by PWM or by 1-10V.

Instead of using the LED lamp as a load, could a 10-ohm 25W resistor be used? Or, is it enough to connect the ammeter directly to the output of the LED driver? Thank you.


texts: Charging my 4V battery with a lab bench power supply isn't working, any ideas why? The battery voltage decreases

texts:
I'm charging a 4V GAMA-SONIC RB420E 2.0AH Lead Acid battery.
Standby use 4.5V.
Max charging current 0.6A, I used 0.5A just to be on the safe side.
For some reason the battery voltage isn't increasing but instead decreasing, the power supply is a MCH303A power supply, 30V 3A.


texts: Voltage proportional comparison (division?)

texts:
I'm looking for a circuit that produces an output voltage which represents the voltage between A-B compared to B-C here. IE if AB is 10V and BC is 1V, the output is 10V, and if AB is 10V and BC is 2V the output is 5V.

Essentially what I want is an output voltage that represents the resistance ratio between R1 and R2.

The absolute output values is not important, as long as I can derive the current value of R1 from the known values R1(cold) and R2.

The reason is that R1 will change value as it warms, and I want to track that with a microcontroller. V1 will vary too fast to sample A and B separately, but I can use a single channel differential ADC if required.

I don't think this is possible without a very complex circuit having gone through it this morning but I thought I would throw it out there in case I am missing something.

EDIT:
Thanks for both answers (and thanks for the 3rd but I don't really understand your suggestions). Firstly I think I can see that the result for me is that 'no its not possible to do it the way I hoped'. IE bridge like resistor networks.

The op amp idea is nice and probably the closer to my aim as I wanted a mathematical approach, but the result is that high currents need to go through linear devices which will lose considerable power and produce considerable heat. Also during fault conditions (which I will encounter) I won't be able to clamp the 200Aish currents fast enough to protect the devices I think.

The multiplier approach is also nice as I didn't realise a multiplier could be configured to divide. This one is more practical I think - but I don't think I can use it as I suspect I need greater accuracy and stability than I can get from relatively standard components, and the cost as you say is high.

So the result seems to be that I need to find another way to do it. Its hard to know who to award this to because I think both answers are equally excellent. Any help 'choosing' the most stack exchange 'best' reply would be appreciated.

As for my problem, I guess its either a sample and hold (I was thinking a homebrew with a 4066), or I will search for the controller mentioned that does simultaneous conversion. None of the ADCs I have seen seem to sample and hold the Vref voltage at sample time which is a pity as it seems to me that if I could feed A into Vref, B into ADC in, and C to gnd, that would work perfectly. Any further comments on that would be great if anyone had them.

Edit2:
Since no one has commented as to the 'best' answer I think I am going to choose the op amp one, because of the algebraic approach and principle behind it which is kind of what I wanted (even if I wanted a non active type). Thanks to both.

Thanks, Pete


texts: Why would this h-bridge driver circuit include capacitor across MOSFET's?

texts: In the typical connection diagram for the IRS2007 Half-Bridge MOSFET driver taken from here and shown below, what is the function of the capacitor in parallel with the two MOSFET's (is it just to stabilise the power rails) and if critical how would an appropriate size be calculated?


texts: NAND gate that outputs 0 when all inputs are 0

texts:
I'm trying to work out a piece of binary logic and this is essentially what I am trying to achieve:

A B C | Output

0 0 0 | 0

0 0 1 | 1

0 1 1 | 1

0 1 0 | 1

1 0 0 | 1

0 1 1 | 1

1 0 1 | 1

1 1 0 | 1

1 1 1 | 0

I am attempting to implement this using logic gates and I have tried playing around with the NAND and NOT gates to somehow combine the two, but I am failing to get the exact logic that I am after. Any tips here would be very appreciated.


texts:
I have what I believe to be an electret microphone on a 3.5mm jack.  This kind:

I also have a socket that provides access to the three lines:

Finally, I have several microcontrollers and a heap of miscellaneous resistors, capacitors, etc.  My intent is to have the microcontroller read sound from the microphone.  HOWEVER, I'm having trouble finding information on how to do this.  I keep finding explanations of how to wire a bare 2-pin electret microphone - which is not what I have.  Or, it's not clear that's what I have - perhaps inside the mic housing there's a tiny transistor and/or resistor etc, or maybe it's just the electret piece.  I've found like 5 images all showing how you should wire a bare electret, and none depicting how a consumer microphone IS wired.
How is this device to be used?  What voltages and currents are provided to it, and what comes out representing signal?  Is left used for power and right used for signal?  Are they both wired together?  Is one entirely unused?  I assume I need to provide some amount of voltage to one or more lines?  On which of the three lines do I listen for a signal, and how?  Do I apply some combination of resistors and capacitors?  Is it a sub-millivolt signal, or more like 500mV?
One of my assumptions is that at the jack, these microphones all operate the same, since they all get plugged into the same computer.  It COULD be that the computer has some kind of autodetection mechanism which like, switches on different circuitry when you connect different mics, though.
Can anybody provide some guidance, here?


texts: Why would Discontinuous Conduction Mode be desirable for an LED driver?

texts:
I saw this press release where DCM was listed as a feature for a new Infineon driver chip.

Source: led-professional.com

I'm involved in LED driver design for Horticulture where DCM is undesirable.

In what case would DCM be desirable for any LED lighting application?

Or is DCM in reference to something other than the output to the LED? Still, if so, why is DCM desirable in any LED driver?

UPDATE:  Why DCM is used in the power stage was answered in the comments.  I still wonder if DCM is ever desirable in the output to the LEDs? This secondary question is not related to the linked AC powered LED driver.

Datasheet defines operating modes on Page 11 and has an appendix with definitions of related terminology.

Section 3.1.8.5 Other PFC Protections, mentions CCM.
Section 3.2 Flyback Controller Features, mentions DCM.

Datasheet:  XDPL8221 Digital PFC+Flyback Controller IC


texts: Unable to program and debug ST BlueNRG-M2SA Bluetooth module

texts:
I would like to ask you for help with programming and debugging the BlueNRG-M2SA module.

I am just not able to get started and successfully connect to the module using ST-Link v2 over SWD. Neither using USB-UART chip (PL2303SA) to communicate with embedded bootloader.

I prepared this adaptor to DIP for the module to make it easier for breadboard tests:

When I try to connect to the target using BlueNRG-1 ST-Link Utility, after checking that VIN, GND, SWDIO, SWDCLK and #RESETN pins are connected correctly, I get this error messages in the trace.log file:

cErrLog::SetLogTraceOn
STLinkUSBDriver.dll loaded
ST-Link/V2 device detected
Target voltage detected: 3.227749
Driving NRST low
Driving NRST high
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode
ST-Link/V2 device detected
Target voltage detected: 3.235602
Driving NRST low
Driving NRST high
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode
ST-Link/V2 device detected
Target voltage detected: 3.235602
Driving NRST low
Driving NRST high
W at 0xe000edf0: 0xa05f0003
R at 0xe000edf0: 0x03030003
R at 0xe000edf0: 0x00030003
Activating vector catch system
W at 0xe000edfc: 0x00000001
Sys reset req
W at 0xe000ed0c: 0x05fa0004
Error (0x12) after target cmd F2 35 0C ED 00 E0 04 00 FA 05
Error (0x12) after target cmd F2 36 F0 ED 00 E0 00 00 00 00
Driving NRST high
ST-Link/V2 device detected
Target voltage detected: 3.234031
Driving NRST low
Driving NRST high
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode

Or sometimes I get this different error log messages:

cErrLog::SetLogTraceOn
STLinkUSBDriver.dll loaded
ST-Link/V2 device detected
Target voltage detected: 3.228777
Driving NRST low
Driving NRST high
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode
ST-Link/V2 device detected
Target voltage detected: 3.230347
Driving NRST low
Driving NRST high
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode
ST-Link/V2 device detected
Target voltage detected: 3.238195
Driving NRST low
Driving NRST high
W at 0xe000edf0: 0xa05f0003
R at 0xe000edf0: 0x03030003
R at 0xe000edf0: 0x00030003
Activating vector catch system
W at 0xe000edfc: 0x00000001
Sys reset req
W at 0xe000ed0c: 0x05fa0004
R at 0xe000ed0c: 0xfa050000
R at 0xe000edf0: 0x03030003
Driving NRST high
R at 0xe000edf0: 0x00030003
W regId 16: 0x01000000
W at 0xe000edfc: 0x00000000
Error (0x12) after target cmd F2 3E 00 00 00 00 00 00 00 00
Error (19) in ReadMemory_32Bit (4 bytes from 0xe000ed00)
Error (0x12) after target cmd F2 3E 00 00 00 00 00 00 00 00
Error (19) in ReadMemory_32Bit (4 bytes from 0xe000ed00)
Error (0x12) after target cmd F2 3E 00 00 00 00 00 00 00 00
Error (19) in ReadMemory_32Bit (4 bytes from 0xe000ed00)
Error (0x12) after target cmd F2 3E 00 00 00 00 00 00 00 00
Error (19) in ReadMemory_32Bit (4 bytes from 0xe000ed00)
Error (0x12) after target cmd F2 3E 00 00 00 00 00 00 00 00
Error (19) in ReadMemory_32Bit (4 bytes from 0xe000ed00)
R at 0xe000ed00: 0x00000000
R at 0xe000ed00: 0x00000000
R at 0xe000ed00: 0x00000000
R at 0xe000ed00: 0x00000000
R at 0xe000ed00: 0x00000000
R at 0xe000ed00: 0x00000000
W at 0xe000edf0: 0xa05f0000
Error (0x12) after target cmd F2 35 F0 ED 00 E0 00 00 5F A0

Similarly, using the BlueNRG-1_2 Flasher Utility, after connecting required power and UART pins and setting the BOOT pin high and trying to read flash memory, I get error messages in the log. Selected baudrate is 115200.

18:56:56.542: Device COM19 -> Read Board Started
18:56:57.719: Device COM19 -> Exit readBoard: Exception ID1: auto baudrate functionality failed

Sometimes reading seems to start and then stuck at about 5%, with error message that I should perform Mass erase, but checking that box doesn't help.

Thank you for help!


texts: Using serial-input latches from Pi to drive 24V load (LEDs)

texts:
TL;DR: LEDs when 'on' are great, however, they're too bright when they should be 'off'.

I'm trying to build a custom, large 7-segment LED display driven by a Raspberry Pi.
I'm a coder so the bit twiddling is the easy bit (although I'm very willing to believe I've screwed that up too :)), electronics ... not so much.

I'll eventually be using 21 LEDs per segment of the digit, split into 3 strings of 7 LEDs, so I need about 24V DC to power the LEDs.

I thought of using an MIC5891 in each of the digits because it promises latching, easy serial input with 5V logic supply, chaining and 'will sustain at least 35V in the on-state'.

Here's what my test board looks like:

simulate this circuit – Schematic created using CircuitLab

All 'off' and the LEDs are very dim (about 1V) but acceptable.

If any of the 'segments' are lit, the ones which should be off are showing and I can record about 6v across them, so they're pretty bright :(

Just for my sanity here's the 21 LED segment setup.

simulate this circuit

I wonder if there's a grounding issue here, I keep seeing mention of pull-down resistors but always in the context of inputs.

Any advice very welcome -- it's driving me nuts :(


texts: Measure propagation velocity through finite transmission line

texts:
I'm currently trying generate a wave in a circuit but am running into the issue of figuring out exactly how to measure the propagation velocity. The circuit diagram is below L1=L2=L3, C1=C2=C3, R1=R2=R3: I have a finite transmission line setup as such:

I understand the theory which would suggest v = \$1/\sqrt{LC}\$, but I'm having issue figuring out how to precisely measure this.

I thought that I should be able to send a pulse and measure the time it takes for the signal after the last L to reach maximum voltage, then divide by the number of RLC blocks to get RLC blocks per second. But I'm not 100% certain this is correct or the best approach - especially since the theoretical v is much larger. I suppose on the oscilloscope I could be seeing the response at the end from an earlier pulse.

Below is the measurements I am taking, The blue is the pulse and green is measured after the last L component.From this it would seem v = 500 blocks / sec while the calculated v = \$1/\sqrt{LC}\$ = 7502 blocks / sec.


texts:
What could be a near rail-to-rail opamp with very low voltage for this use?
LM386 seems to be out of limits for my needs.

How do I choose it from datasheets? What values are important (of course limits & power) but what else? Is there something more important than power inputs & current limits?

simulate this circuit – Schematic created using CircuitLab

on this schematic I did not calculate component values yet.

I want to make a very light and portable mic amplifier on 2 batteries.
It should consume very low power and have medium/high amplification.

What could be a near rail to rail amp with very low voltage for this use?

I tried from this datasheet to guess that the LT1494 would fit this need. Is this correct? (If not, why?) LT1494 datasheet

For audio, will 100nF be ok for C1 & C2?

mic will be an electret
connected device may be another amplifier or why not a speaker


texts: Making USB power supply out of 5V 60A LED DC power adapter

texts:
first of all please sorry if my question would sound dumb, I'm new to electrical engineering I've did my first soldering of two wires just yesterday. So here goes the question: I have 5V 60A LED DC power supply (also I have lab. i.e. variable voltage dc power supply which I use for testing things).

I'd like to adapt my 5V 60A power supply to a general purpose USB charger station with multiple USB docks, I have several female USB wires. And I guess that making a USB charger out of 5V supply is something more than just soldering plus to plus (red to red wire) and minus to minus (black to black), which I already did and it didn't worked.

What has to be done in order to make a USB charger out of 5V power supply and a female USB cable.

Thank you in advance


texts:
I have used PIC18F45k40 device for RS485 communication. I have 2 ckts one is isolated and another non isolated RS485 design. I have schematic & placement for reference. I have connected multiple slave device independently isolated and non isolated product , its working well. There is no issue with poll mismatch
Now i am combining isolated and non isolated module in parallel.during this stage, after hour isolated module stop communicating but isolated version product working well.
difference i found in both device i found is voltage level during operation isolated version if measure voltage across A& B w.r.t gnd is 7V-9V respectively i.e for ADM2483(Isolated ground)
where as SN75176 non isolated IC voltage level across A &B w.r.t ground is 2.5V-5V respectively.
i would like to why my communication of isolated version get disturbed when non isolated version is introduced.
which one is better to use to make solve this kind of problems
sn75176


texts: Converting Audio File to Digital Voltages

texts:
I am beginning a project where I am using a microcontroller (TI's MSP432) as a sequencer in an electronic drum machine. I have already written code that successfully samples the output of a few drum circuits, via ADC, and I have a few audio samples that I would also like to integrate into the project.

Currently, I am wondering how to go about converting these audio files (.WAV files specifically) into digital voltages that I can combine with my ADC results to form drum tracks.

Any assistance that anyone can provide would be greatly appreciated. Thank you!


texts: drone power distribution board on a perf board

texts:
I have seen some PCBs dedicated to being a power distribution board but the drone that I have has some connections for an in-frame power distribution board.
only thing is that it may be difficult to make good connections so I was thinking of making my own on a perfboard and strapping it on the frame.
is it possible to make a simple PD board on a perf board? i know the more complex PD boards have voltage regulators and capacitors but how important are those exactly?
from the way that my drone frame implied that the PD board can be on the frame itself tells me that all the power distribution can be done through simple wires. my understanding is that the PD board just allows connections in parallel to be made from the motors to the battery.
so that is something i can set up on a dedicated perf board (and perhaps add regulators and capacitors as needed) but i am not sure if it is a good idea since i haven't seen it very often and 30 amps from the battery may not be suitable for a prototyping/perfboard
edit: this is the frame and motors i am referring to. this is the battery that powers the motors and their ESCs.


texts: How to Calculate Op-Amp Level Shift for differential amp and gain of 2

texts:
I struggle grasping circuits, especially Op-Amps. In my research, I was able to put together this inverting op-amp circuit in LTSpice that takes the input and level shifts it by +1.5V. I understand it has a lot to do with the voltage divider located at the non-inverting input, but I cannot fully understand why. This voltage divider turns the 5V to 0.75V and I could see by doubling that, it becomes 1.5V and the shift that I want appears. I believe there is a greater mathematical significance here than simply that. Leaving R1 and R2 equal means the gain will be 1(or -1?), so I'm happy so far.
However, if I wanted to alter the values of R1 and/or R2 to add in gain, the gain appears in the simulation, but my +1.5V shift changes. I understand this change is possibly due to the summing of voltage at the op-amp's inputs, and by changing the resistors R1 or R2, I am changing the math of the entire system. I don't know what that has to do with the level shift though. I can change the shift and not the gain, but I can't change the gain without also changing the shift.
Additionally, if I wanted to provide a gain of 2(or a gain at all) in addition to this +1.5V level shift, how can I figure that out? Would it be better to separate my goals here by creating two op-amp circuits that achieve both individually?
Also, for clarification, the green wave is the signal at the sine wave voltage input. The blue wave is the output "Vout."
Thank you.


texts: Calculating the damping ratio, \$ \zeta \$, and the undamped natural frequency, \$ \omega_0\$

texts:
I'm confused on where I went wrong finding  \$ \zeta \$ (zeta) and \$ \omega_0\$. I think its where I originally did nodal at Avx. Any help would be appreciated.

-thanks


texts: Glue used to adhere cellphone / laptop components (not screen)

texts:
What type of glue is used to adhere cellphone (or laptop) components (excluding the screen which has its own speciality glue)? I'm talking about the sticky, but not too sticky glue used to hold things like the antennas, nfc flex, camera, battery etc. in place... when a firm but non-permanent hold is desired.

It seems to be a super thin double sided tape? What is it called and where can it be bought? (Searching phone glue yields just the very strong ones for the screen.)

I suspect it's not a fancy type of adhesive...

Some example images from iFixit:


texts: XTR116 4-20 ma Transmitter Measuring Problem

texts:
I have created the following circuit :

On the DAC side,output in the range of 0-4.095V,VREF = 4.095 and VCC_ISO = 5Volt. Totaly normal. But XTR116, I cannot control less than 16ma current. Between 16-20ma ıs normal. But ı have never seen less than 16 ma. Vcompliance > +7,5. (So no problem.) I can not fıgure out .anybody have an idea ?

Original Circuit : https://medium.com/electronza/4-20ma-current-loop-arduino-tutorial-part-i-hardware-bb50935da42e


texts: Kelvin "4 Wire" Resistance PCB Design Questions

texts:
I am designing a PCB that will utilize 4 wire measurement for 40 or so test points.

A little background here - day to day I troubleshoot PCB's to component level, I'm an electronics technician and not an engineer and I'm okay with that. 95% of the time I can find an issue with a circuit based off of how the DVM measures resistance and it's behavior. My boss wants me to automate my process using LabVIEW; so I need to make a PCB that does just 4 wire resistance testing. I have an existing pogo pin block and a PCB that mounts to it, I just need to re-spin the PCB board and write the LabView program.

Are there any special PCB design details I need to consider when doing this very basic design?

Please be gentle; this is my first engineering project.


texts:
I generally work with 12V standard and simple DC wiring. Awhile back I put a bunch of LED lights on a bicycle for a Youtube video, though I ran them off of a single 9V battery. I would like to run two 9V batteries, but seeing as how this will result in 18V, I'd rather not blow out my lights.

Where and what size resister should I use so that everything works as it should?

Here is pretty much how the bike is set up now, if this gives you any idea:
https://www.youtube.com/watch?v=iNgIvaooP88


texts:
I am planning to communicate from my dsPIC33FJ64GS608 Microcontroller with a HEF4894B IC.
Because of the Microcontroller is running at 3.3V I want to drive the IC also with 3.3V.
According to the data sheet this seems to be ok.
But there is something I am not sure about.

Is it safe to connect the output of the Microcontroller directly to the input of the IC so can I omit R1-R4 or because of the capacity of the IC inputs I should always put a resistor in between to limit the current flow?

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to include a DC jack on one of my PCBs. I am just setting up the footprints now, and I am not quite sure which pin is which. What do the symbols on the drawing mean?

I have included a snap of the schematic below, it has been taken directly from the datasheet.


texts:
I have been assigned to design a kind of programmable power supply. Can't decide on a way to make it. Need help with this.

This is a high level block diagram of the required system:

How it works (How it should work)

The system will be given 0 to 10 Volt variable input, which decide output voltage. The output should be proportional to the input. So that when input is Min, output is also Min (i.e. 0v), when input goes to Max, output also should be Max (i.e.24V). Simply, if the input voltage is V_I, then the output voltage should be (24/10)*V_I

The output is drawn from the systems power supply, not from the input voltage. (Actually input and output should be isolated.)

I hope that part is clear.

Then there is another input (input 2). Let’s think about it as a Potentiometer. So that its value can vary between two values, for the sake of explanation, lets say it changes between -10 and +10.

Its role is like this. (I’ve mentioned it as tolerance.)

Output value is decided from the input 1. That value is changed a bit around the original value by this input 2. For example, if output is 10V now, I can increase it a bit by rotating my preset clockwise. Or decrease it a bit by rotating it counterclockwise. Maximum change, lets say, will be 10% of the set value.

That’s it. I tried to explain the thing to the best I can. If any clarifications are needed please ask.

This is the requirement. I’m very good at microcontrollers, But not much experienced in electrical side. I thought a lot to make this using microcontroller. May be there is, but can’t figure out.

But it doesn’t need to be microcontroller-based, this is an actual requirement. So if there is any way to achieve this, then I’ll move to that.

Please share your knowledge. If anyone can point me in an exact direction that will be much appreciated.


texts: How to design a sharp 200kHz band pass filter

texts:
I have made an a fm communication system to send audio through power lines. The center frequency is 100khz or 200 khz and maximum frequency deviation is ±10khz(with no IF stage).

The modulator and demodulator work fine when connected directly with wires. Now I want to use 220v power lines as transmission medium.
If the receiver board is connected to the input and powerlines using a small ferrite toroid as an isolated transformer.
 The powerline-side is 2 turns series with a 100nf capacitor and the receiver-side is 12 turns paralleled with a capacitor(the resonant frequency of 12turn side paralleled with capacitor was 200khz) I tested the filter in lab with a spectrum analyzer, unfortunately the Q factor was too low. The spectrum analyzer was 50ohm input/output put a 1k resistor in series with the input port of the analyzer to enhance Q with little effect.
The transmitter device was already off, I connected the output of the above BPF to an audio amplifier directly (without fm demodulator) and I was surprised with an irritating noise in the frequency of 4-6khz range.
After some time I discovered that the source of the noise is a nearby CFL lamp powered by the same powerline! I designed a 3 stage RC HPF with cutoff frequency of 50khz but it couldn't eliminate the 4khz noise completely and the noise power was still high.
There are multiple choices with this design:
1-I can use an active filter. I designed it using nu-hertz filter solution program.but it needed some 4.7pF or 6.8pF capacitors to which I think opamp's parasitic capacitances are comparable and I worried it may cause error in center frequency and filter response.
2- I can use 455 khz ceramic filters(and change system frequency to 455khz). but unfortunately they are hard to buy for me.another problem is that most of these filters have low BW (less than 20khz).

3- I can use a crystal filter as used in SSB communication circuits , but they are hard to design for low frequency.

Can you please help me which one to proceed?


texts:
I am really new to hardware design but have a fairly good knowledge of analog and digital circuits. I have only built one automated car using an Arduino board for a lab. However, I have really good knowledge of computer science.

I am trying to build a device with an operating system in it that will be turned on through a USB port. I want the processor to be ARM based and handle FLASH memory of a minimum of 16GB, have a multi touch display and be a really small device. I don't really know how to find any information about even getting started with it.

So, my question is:

Can a USB port output enough power to run an ARM Cortex M series?
How can I find out how much FLASH memory an ARM Cortex can access? Or does it even matter for microprocessor design?
How can I find prices for the microprocessors?

I would really want someone to guide me on my work. If you want me to clarify anything please let me know.


texts: Convert 1kHz PWM signal to 0-10V DC with minimal ripple

texts:
For my application, I want to control the position of a valve which takes 0-10V input voltage. For the determination of the position I need to use a digitial 5V 1kHz PWM signal from an Arduino Nano. What is the best way to convert the 5V PWM signal to 0-10V DC?

I have thought of a lowpass-filter and an OpAmp with gain 2, however, the DC voltage should change within <1.0s (better <0.5s) after a one-resolution-step of the PWM (which has 8-bit). On the other hand, the DC voltage should also be as stable as possible over larger times (>1s) once it reached its nominal value. I am not sure if both requirements can be met with a low-pass filter.

The other option I thought of is a PWM-DAC and an OpAmp. What do I have to look for there?


texts:
I'm tinkering with an Arduino with more knowledge in software than hardware & seeking clarification that I understand specifying a resistor on my project correctly?

I am using an Adafruit Feather Huzzah ESP8266 (https://cdn-learn.adafruit.com/downloads/pdf/adafruit-feather-huzzah-esp8266.pdf) microcontroller.  This reportedly provides a peak output of 500mA at 3.3v.  The manufacturer recommends that I keep the draw less than 250mA.

I plan on connecting an LED (multi colour) http://uk.rs-online.com/web/p/visible-leds/6194943/ to the pins, which will then have a resistor connecting the LED to earth.

This LED has a forward voltage of 2-2.5v, a DC forward current of 25-30mA & a peak forward current of 140-160mA.

On this basis, I've ended up at this site, specifying the right resistor to use: http://ledcalculator.net/

I've inserted 3.3v as the Power Supply Voltage, 2.5v as the LED Voltage Drop & 25mA as my LED Current Rating.  This suggests a 33Ω resistor.

The item that I'm looking to clarify is, what would you consider to be the correct forward current to specify?  Would you specify the lowest amp draw specified or the draw at spikes (i.e: 160mA)?


texts: Is there a sensor that is equivalent to a dry toothpick?

texts: For the non-cooks in the audience the dry toothpick test is used in baking (cakes, banana bread, etc.) to determine when the item is done baking. The procedure is to stick a toothpick into the food, pull it out and look at it, If it came out moist, you are not done cooking. It is simple and effective, but you can't do it from a chair with a cellphone. Any Ideas?


texts: How does a camera pixel accumulate charge (colour)?

texts:
I refer to the Wikipedia entry for a CMOS camera sensor's individual pixel. There is a schematic like so:-

and a statement that:-

  The read-out transistor, Msf, acts as a buffer (specifically, a source follower), an amplifier which allows the pixel voltage to be observed without removing the accumulated charge.

Where is this charge accumulated /stored?


texts: Output impedance for microcontroller minimum 5kOhm

texts:
So I'm looking into the stm32f469 series of chips (datasheet here), and see if I can play good audio with one with the build in DAC. To my knowledge, the built-in ones on chips usually aren't that great, but with 12 bits of resolution, I'd like to give it a shot. The problem comes in with if it can drive headphones or not:

Down on page 163/219, it says that with the built-in buffer (reportedly included to be able to drive loads) the minimum impedance is 5 kOhm, which seems extraordinarily high. I'd be using it with earbuds, and I've never seen cheap earbuds listed with any more than 50 ohms impedance. With the buffer disabled, it reports a maximum of 15 kOhm, but I'm worried that if it's meant to be in the kOhm range it might not handle earbuds too well.

Am I reading this completely wrong and it can drive a set of earbuds or will I be looking into an external audio chip?


texts:
I am looking to detect, if battery is connected to board or not, by adding optoisolator to a battery and connect it to micro controller, before reverse polarity protection circuit. (Which is MOSFET with LM74700)

I want know if below added circuit (diagram) will be safe from reverse polarity from battery since I am sharing the ground on Phototransistor.

I know the TVS will protect from reverse polarity but will micro controller be safe of reveres polarity

simulate this circuit – Schematic created using CircuitLab


texts: What is PT1 on a 232 Watt AT PSU and how to decode it?

texts:
I recently wanted to repair an old computer of mine. I found a part in the PSU (Phihong PSA-2054C) which falls apart.
Nonetheless the PSU works, well worked until I recently decided to desolder the item. With a web search I could only find documents for the PSU which showed the dimensions of it but I could not find the circuit diagram of it.
Now I have this part desoldered and have trouble decoding it. If i read it correctly it could be like 50 or 850 nF. But this does not seem very widespread.

Sadly there is nothing on the back of it, and what is left is degrading.
It seems to be a circular capacitor of kind, like the field on the PSU reads PT1.

Maybe you can help me find out how to exchange this particular part. And as this is the first kind of project for me, any help to help myself is very much appreciated.
Edit: Added a picture to show the back of the particular place.

Kind regards


texts: Use a PWM LED dimmer to crossfade between 2 different sources?

texts:
I'm wanting to build an LED light panel using this PWM dimmer. However, I'd like to have 2 different LED light strips that can be faded between using the pot. I need one light strip to take the power provided from the board and the other to use the remaining power (50/50, 90/10, etc). Is this at all possible, or is there a separate board I could search for (what terms could I use)? Would I simply need to use two different boards and control them separately?

Thank you.


texts: Where can I find Micro-USB B feedthrough adapters?

texts:
Perhaps I am missing something, but I am finding it virtually impossible to find Micro-USB type B receptacle to Micro-USB type B receptacle feedthrough adapters. As I understand it, this is effectively the same as Micro USB type AB.

The application is plastic enclosure, which needs USB to power a Raspberry Pi.

This is the only product I have found so far that meets these specifications.

Perhaps this confusion is a result of my misunderstanding the USB standard. In any case, I appreciate the help.


texts: Design a circuit that takes a 3 bit binary and makes it (x^2 - x), using a decoder of your choice

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i tried making the circuit for each output on its own then make the final circuit
but i have a feeling that wrong
     any thoughts ?


texts: How to safely charge a 200v 330uf capacitor?

texts: I have a 200 volt 330uf(not sure what that means) capacitor i pulled from an old tivo power supply. I was wondering how i can charge this and use it, and what i can use it for. Iv charged some smaller ones in the best by directly connecting to battery but read somewere you should use a resistor. Iv also only ever run a christmas lightbulb off a capcitor for a few secondsWill a 19 volt laptop charger work with this? If so do i connect it directly? How long do i charge it? What can i power? Thanks!


texts: J/K to D type flip flop strange behaviour

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As a student, I have been tasked in one of my assignments to design a traffic light system using D-Type flip flops, simulate it on Proteus, then build it on breadboard. This was simple enough, and after a half hour, the process was complete, and my circuit was working.

simulate this circuit – Schematic created using CircuitLab

In this case, the Flip Flops were D type, not T! (The schematic editor didnt have a D type with both Q and inverted Q output). I got the required output, which was to make the traffic lights go in the following order: R - R/A - G - A - R where R=RED, A=AMBER, G=GREEN, R/A=RED and AMBER

The next task seemed to be very simple too. It was to do the same thing, but use J/K flip flops instead. As far as I am aware, to turn a J/K flip flop into a D type, you place an inverter between the J and K pins:

Again, seems simple enough. I built the circuit on Proteus, and the circuit worked fine. It done exactly as I had asked. I then built it on breadboard, and it didn't work correctly. The lights went in the wrong order. It went R - A - G - R/A - R. So the RED/AMBER combination was in the wrong place.

I changed my proteus simulation to use the 74LS76 (the IC we were given) and to my surprise, the simulation started acting as my practical circuit, with the LEDs in the wrong order (I was originally using a generic J/K on Proteus). The only difference between the 2 was the 74LS76 has an inverted clock input, so I did a new simulation with an inverter on the clock input of the generic J/K and shared the clock line with the 74LS76 and when running the simulation, both flip flops acted exactly the same. So why would they be acting differently when put into the full circuit? I have been trying to figure it out for the best part of an hour now and no idea!


texts: Centre contact clamping in coaxial barrel connectors

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Barrel connector plugs seem to have two different methods for keeping the centre contact under pressure.  Some plugs have a rigid circular inner contact which relies on the socket to have a split pin which can press outwards to maintain contact (eg., the non-yellow plugs below).  Others have a pair of clamps within the plug itself, which (I assume) press against a solid pin in the socket (eg., the yellow ones below).

I need plugs like those yellow ones, but with solder tags.  When searching, how do I refer to them in a way that distinguishes them from the plugs with a rigid inner contact?

They don't have to be yellow.


texts: Need help understanding and interpreting IGBT datasheets

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When it comes to motor control, I understand that we have the option of using discrete MOSFETs or IGBTs. Also, there are some products in the market where 6 IGBTs are placed in one single package, such as GB25XF120K. (Here's another example part, from Infineon: FS75R06KE3)

However, I don't know how to compare and contrast this solution to using 6 discrete MOSFETs, in terms of:

Switching speed
Power dissipation (static; what's the IGBT equivalent I2 * RDS, on?)
Power dissipation (switching)
Cooling (Why isn't there any junction-to-ambient thermal resistance published?).
Gate drive circuitry

Also, all the sources I've read on the subject "recommends" IGBTs for high voltages (> 200V) but they don't really get into the details. So I ask the question again, perhaps a bit differently: Why wouldn't I want to use an IGBT for -as an example- a 48V brushless DC motor?


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I tried to repair a device and these two film capacitors were broken. I can read "393K 250V" on one cap but can't recognise the manufacturer logo due to the scratches.
Could you help me identify the manufacturer? Otherwise I guess any cap can work.


texts: neutral conductor in a three phase system

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I do not understand the answer of the following question :

A three-phase power in the lab have symmetrical three-phase voltages 400 / 230V and
terminals marked L1, L2, L3 and N. A 60W bulb is connected between phase L1
and N. Another 60W lamp is connected in the same way, but the phase L2
and N.

Calculate the current in the neutral conductor N.

The answer is 0,26 A.

Why it is 0,26 A , should not it be 0,26 A + 0,26 A (from the both lamps)?

Thanks


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Today I was looking at STM32F205 datasheet. this MCU has a feature. except 20 × 32 bit backup registers, it has 4 KB Backup SRAM. and due to datasheet:

And look at this:

Does "Backup SRAM" get erase after reset?

Well, so far "Backup SRAM" is bigger than "backup registers" and "Backup SRAM" can do everything which "backup registers" do(except remaining after reset?). is there any difference between "Backup SRAM" and "backup registers"?
Why didn't they put a bigger "backup registers" instead of "Backup SRAM"? isn't it faster? doesn't it consume lower power?