texts:
I'm a software engineer so not very good at electronics. I have a similar issue as resolved here, namely when I heat the board below it works. This is a remote key module for my car. It stopped working recently my guess was because it's cold now it being winter and the car being in my cold garage. I tested my theory by removing the unit heating it to about 100-120F and reinstalling it and viola! it worked again, but only for a minute or two until it got cold again.

As mentioned in the answer linked above looks like when some resistors go bad they're affected by the cold weather only, which seems to be my problem. The issue is I'm not sure how to test that or even which components to start with. I do have a multimeter. By looking at the board can you tell which components are most likely to be the issue here and how I can go about testing them? Is there a voltage regulator in this circuit and is that the area I should probably focus on? Do I need to unsolder and remove from the board the components that I want to test with the multimeter? If the ICs are the issue are they replaceable or do I need to reprogram them? (which would be beyond my capabilities most likely)
I tested the heat theory multiple times and I'm very certain that it does make the circuit work again for a short period of time. I have a Fry's Electronics store kind of nearby if you think I need new components are these parts I can get from there? I don't care of they don't look the same or are bigger, etc.
So no one asks, yes, I have checked the 20A fuse right in the middle and it looks fine.
Here is the back of the board:

Here is the pinout description for the main white connector (this is the main connector to the module, other connections/sockets are not used):

Pin 1 Blue (goes to central tunnel panel lock/unlock)
Pin 2 grey white (Goes to power window module in 2002-03 cars not used in 04)
Pin 3 yellow 12 volts Key on (fuse 3)
Pin 4 red battery 12volts constant (Fuse 14)
Pin 5 black GND
Pin 6
Pin 7 black/blue GND
Pin 8 Starter crank start signal from key in crank position)
Pin 9 orange/ white (Door microswitch) (input)
Pin 10 green (Goes to both MED fuel solenoids)
Pin 11 black GND
Pin 12
Pin 13 Green/white (Flashes signal lights) (outputs)
Pin 14 Green/Red (Flashes signal lights) (outputs)
Pin 15
Pin 16 Red/ Green (Central locking switch) (inputs)
Pin 17 White/ green (Central locking switch) (inputs)
Pin 18 Blue/red +12vdc to starter relay while the key is in the crank position. (output)


texts: How to use a graph of a wavefunction (psi) to create an approximate graph for potential (U)?

texts:
I don't understand how the top graph was used to approximate the bottom graph, could someone please explain to me what was going on?

I know that in regions 1, 3, 5, 7, there is no oscillation and therefore E<U, but I don't know what other information I can extract from the top graph.


texts: Change a symbol of a component on LTspice

texts:
I have downloaded the PA107 microtechnology component library. The symbol is displayed like this:

However I want to change that symbol to be the symbol of an amplifier. How can I do that on LTspice?


texts: Build AND logic gate with 74'00 ICs (NAND) in negative logic

texts:
I am not sure how negative logic affects the Boolean algebra derivation and the gate schematics.

I know that if I want to derive AND with NAND in positive logic (using De Morgan), I'd do something like this:

$$
y_{target} = x_0 \land x_1 \\
y_{src} = \overline{x_0 \land x_1} \\
y = \overline{\overline{x_0 \land x_1}} \\
$$

Now I've read that in negative logic all AND's become OR's and 0 become 1.
http://www.dsm.fordham.edu/~moniot/Classes/CompOrganization/boolean-outline/node11.html
Does that mean the NAND acts like a NOR?

Question:

How would the algebra expression for AND using NAND looks like in negative logic?

Is that the way to build a AND from NAND in negative logic with gates (thats the way i would build it with NOR gates)?

simulate this circuit – Schematic created using CircuitLab


texts: Very thin, flexible wire for LEDs -> Arduino inside cramped space?

texts:
I'd like to fit an Arduino inside of a metal broomstick, and use it to drive groupings of LEDs that poke out of the stick. It's a light toy. The Arduino fits, so do the AA's, but I need wire that's flexible enough to work in tight spaces, and that I can solder to both the Arduino and LEDs. Once it's all packaged inside, it shouldn't have to flex at all.

Can anyone recommend wire for this?


texts:
When a PN junction is formed, free electrons from the N type diffuse into the P type material.
Now books say that the same applies for holes, which diffuse from the P type material to the N type one. However, everyone knows hole movement really is a reaction movement of adjacent valence elctrons wanting to hope in the holes(incomplete covalent bonds of Silicon/Germanium for example). Does this mean, that the hole diffusion from P to N realy is a diffusion of valence electrons from N to P, in addition to the diffusion of free electrons from N to P?. Am I understanding this correctly? if yes, that means that after the depletion region is formed, we cannot tell which electrons in the P type material originate from valence bonds from the N type material and which electrons are free/excess electrons from the N material.


texts: Calculating the power supplied by the current and voltage sources

texts:
simulate this circuit – Schematic created using CircuitLab

I have attended one exam where I was asked to solve this Question. Generally the Power is nothing but the product of current and voltage in a network. But here the question is to calculate the power delivered by current and voltage source individually. So how can I proceed to solve this?


texts: Cheap, low-quality constant-current sink over wide voltage range

texts:
I'm looking for a cheap (as in: low component count, low PCB area, low component cost) way to put >= 1mA of load on a voltage that may be anything from 1.2 to 17 volts (minimum required load on a LDO output).

The easiest solution is a simple 1.2kOhm load resistor, but the power consumption becomes enormous at higher voltages (240mW at 17V, which leads to a huge package size).

A JFET-based current-limiting diode seems ideal - but I can't find a vendor that actually sells one.

So my idea is to use a BC817-16 NPN transistor, which has current gain between 100 and 250, send 10-15µA flowing into the base from a nearby 3.3V rail via a 220k resistor, and just watch 100 to 250 times that (1mA - 4mA) flow from the collector to the emitter, no matter the collector voltage:

simulate this circuit – Schematic created using CircuitLab

The circuitlab simulation indicates a current of about 4mA for 17 volts, which gives a more than acceptable power dissipation.

However, one of my (much more experienced) colleagues strongly advises against this technique, claiming that there will be runaway effects and the transistor will blow, so... will this circuit work reliably? Any other suggestions?


texts: Standard Relay vs SSR vs TRIAC for Switching CFLs

texts:
I'm confused weather I should go for a standard electromechanical relay (EMR) or a sold state relay (SSR) to switch CFLs @ 220V with 100W max load. This is for a commercial product with the following objectives:

Have at least 7 years of life (of continuous use)
Resilient to short-circuits at the outputs of it's switching device (SSR, EMR or TRIAC).

The main concern here is the failure of the device: SSR will provide an extremely long life (if other components are up to it) whereas a EMR will have a relatively shorter life-span. However, it seems EMRs are more rugged to a short-circuit (till the circuit breaker or fuse pops, at least). A failure mode of CFLs I've found is that they sometimes short-circuit - either the internal wiring insulation fails or some other type of fault due to sub-standard components).

I suppose the question becomes: how long can I expect an EMR with a resistive electrical contact life of 100,000 cycles to work if the relay is switched 10 times a day?

Alternate approach that I had in mind: use a large TRIAC (rated for 30+ amps continuous) and a resettable fuse, rated for 500 mA, in conjunction with it. The fuse interrupts the current flow thereby saving the TRIAC from damage. Since the TRIAC is a heavy-duty one it has a higher likelihood of surviving such a failure.

Will the TRIAC allow me to have my cake and eat it too?


texts: Migration from multimode to single mode fiber

texts:
In my company we are using custom measurement systems with multimode fiber optic transmitters and receivers for synchronization between different devices. We are thinking of migrating our multimode fiber optic technology to single mode to extend the reach to 20 km. The problem is that I have certain doubts about the single-mode fiber technology.

At the moment, our synchronization system consist of emitting synchronous pulses through the optical line from a base generator, and receiving and replicating said pulses from first equipment on the line to the next ones, cascade connection. The pulse synchronization system has the following characteristics:

Type of fiber = Multimode 62.5 / 125 um
Wavelength = 850 nm
Optical power = 0.17 mW (for 1 m fiber)
Front delay < 5 ns
Pulse duration = 40 ms
Pulse Distortion <1 ns
Reach = 2.5 km

Therefore, I want to migrate this multimode system to a single-mode in which to reach distances of optical fiber of synchronization up to 20 km., but I have some questions:

Will our synchronism methodology continue to be compatible with this kind of pulses? I need to know if at such distances this kind of sync pulses suffers some distortion or deterioration. I know that the new pulse generated on single-mode fiber will have different characteristics but I am concerned about possible phenomena that may interfere with the operation.
In any case, could I implement a system of synchronism using a bit string, for example?
What type of optical transmitter and receiver can I use? I have seen some single-mode fiber optic transducers with wavelength of 1310 nm that manage to transmit at 30-40 km. Are there other options? Some kind of single laser emitter/receiver?
Do you know some good evaluation kit for this technology?

Would appreciate If someone can give me some help.


texts: Simulation not working for my custom module on top of openMSP430

texts:
Creating a new project in Vivado and importing the core openMSP430 (https://github.com/olgirard/openmsp430) files, I could easily test everything out by setting tb_openmsp430.v as the top file in the simulation and by using the pmem.mem file generated by compiling "core/sim/rtl_sim/src-c/sandbox".
I have created my own modules "tb_openMSP430_fpga.v" and "openMSP430_fpga.v" in order to simulate and later synthesize the project for an fpga.
// *File Name: tb_openMSP430_fpga.v
https://pastebin.com/xvtdBz9R
And for synthesizing:
// *File Name: openMSP430_fpga.v
https://pastebin.com/PrcTpF6S
Setting tb_openMSP430_fpga.v as the top file and trying to simulate the project does not seem to produce meaningful output and the register values remain the always the same during the simulation.
What is my mistake in the two _fpga.v files that I created (in practice altered from the existing ones that Oliver created)?


texts: Op amp only getting half wave output on dual power supply

texts:
In my project I'm putting together a H bridge circuit which uses the N Channel type MOSFETS only and it is controlled by my amplified Arduino square wave signal that is operating the MOSFET Gates which is connected to the outputs of my dual op amp setup (the op amp IC I'm using is the LM1458). The first op amp is the inverting op amp circuit and the second op amp is non-inverted.
So far the build is nearly all complete and both the non-inverted and inverted output signals are amplifying the Arduino PWM square wave signal the way I want however I'm only getting getting a half wave signal from both outputs and as a result only Q1 and Q4 are turning on and off as those N channel MOSFETS are receiving the positive signal while Q2 and Q3 are only receiving the negative signal which results them being switched off all the time. I definitely know there is a fault in regards to how I've setup the dual supply for the op amps as for some reason it is behaving like it is a single supply. And my code in the Arduino is definitely making a full square wave signal too. I've already tested with my oscilloscope on both outputs from the op amps and both of them have half wave signals so the fault I believe is the dual Supply for the op amps, just that I'm a bit confused as to why my dual power supply is not powering the other cycle and how to fix it.
The reason why I'm posting this is because I find there isn't much clear information out there in regards to setting up a dual power supply properly on a dual op amp setup and it is probably something small I've overlooked when building this circuit. I've also already did this same circuit in a simulator and it worked (but as we all know simulators are not always completely accurate).


texts:
Suppose I have a rechargeable 70 kWh battery , and I use 120 V rms from my house with a 10 A RMS circuit.

To find the max power of this circuit, is it just P = VI, since both the voltage and current appear in RMS?

So in this case P = 120 * 10 =1.2 kW?

Furthermore, suppose the battery was drained, in order to find out how long it takes to fully charge this battery, is the following correct?

70 kWh / 1.2 kW = 58.33 hours?


texts:
This circuit signals an MCU via OU lead. I am not interested in the MCU side. I just show the concept.
My question is very simple: How does the surge protection(actually ı meant detection) part work?
By the way, I have basic knowledge of TVS, MOVs, opto-couplers and RC theory (phase etc.)


texts: Why isn't my transistor outputting enough voltage when switched?

texts:
So, I'm a software guy, and this is a bit out of my element. I'm working with a Raspberry Pi, and I want to power one of an LED button, a push button with a pair of integrated green LEDs wired in parallel with 1K resistors each.

For max brightness, the LEDs should be supplied with 5V. However, since I'm using a Pi, the GPIO pins output at 3.3V levels. So, I wanted to use a 2N2222 to switch the 5V rail on the Pi. Because I don't want to risk damaging the Pi (since nothing is more dangerous than a software engineer with a soldering iron), I've instead connected a test PSU with a 5V rail and a 3.3V rail to opposite sides of a breadboard.

So, my circuit arrangement for testing is as follows:

5V connected to leftmost pin on 2N2222 (collector).

3.3V connected to the center pin (base), in series with a 1K resistor. I have a loose jumper connected here as well that I am using as a switch by plugging/unplugging one end.

LEDs connected to the emitter (rightmost) pin, running to ground.

When I connect the base line to the 3.3V rail, the LEDs light, but very dimly. Connecting this wire to the 5V rail lights the LEDs fully. Interestingly, touching the LED to my jumper to my finger lights it somewhere in between the two. Now I'm really confused.

I suspected it was because I did my calculations for the base resistor wrong, so I tried a few other values, including 220, 330, and 2K. None of them made any (noticable) difference in brightness, as far as I can tell.

What is going on here? How do I get this to work as intended?

Note each GPIO pin has a max current draw of 16 mA, but I'd like to keep that below 8mA really. Not sure if that information is relevant here.

I don't have a multimeter available to me for the next few days, so I can't easily test to see what's going on.


texts: Is it possible to drill through a peltier?

texts:
I want something like this:

But I don't want to pay 30 bucks (USD) for a single peltier. Can I just drill a normal one?


texts:
In terms of semiconductor integrated circuits, is there any difference between an accelerometer or a gyroscope? are they the same part?

Can I get a IC recommendation  for something with 3 axis?


texts:
I am using this in my Arduino board to transfer data via Bluetooth.

I wanted to know, how is it poosible to receive data sent by this BT on the PC using C#. What sort of a communication would it be?

Because Serial data is transmitted by this BT, how am I going to receive this data in a C# application.

Please help. I'm a newbie

Thanks


texts:
I am checking out for dual-inline packages for my chip (which I want to insert in DIP) and I came across some products from Analog Devices, Texas Instruments and NTK Ceramics. However, NTK Ceramics have dimensions for the chip Die. But Analog devices and the Texas Instruments doesn't have any information about the Die for DIP.
Are the DIPs from Analog Devices and Texas Instruments just only programmable without any option to ınsert our own chip into the DIp?
You can find the picture of the datasheet of 24 pin DIP of Texas Instruments (İt doesn't have any picture of the Die)    and Also  you can find the other picture of DIP from NTK Ceramics which has die information shown clearly


texts:
When using kirchhoff with a loop with resistors and current source, how should I use kirchhoff voltage law?

for example in this circuit:

simulate this circuit – Schematic created using CircuitLab

I can not use kirchhoff voltage law


texts: DC-DC Up-Conversion without Switching Electronics

texts:
I have a project where I am trying to find a means of powering a sensor with the following requirements: 24-30 V and a regulated constant current of 2 mA (about 60 mW). The latter requirement I will handle with a constant-current diode.

The source power will come from a USB port (5V up to 200 mA).

My problem is that I need a low-cost method of DC-DC up conversion with very low EMI characteristics and was looking for something more novel than a traditional switched-mode converter. Also, low heat generation and light weight would be desired.

I am not an electrical engineer and wondered what my options were.

I have some crazy ideas such as electric-light-electric conversion (such as LEDs wired in parallel sandwiched with photovoltaic cells in series), but was hoping there might be a conventional way of doing this.


texts: How can I test the maximum safe current I can put through an electrical switch?

texts:
Firstly, apologies as I'm very new to electronics!

I'm converting an old broken Atari 2600 to be an enclosure for my ODroid UX4 single board computer.  I thought it would be nice to  be able to run the odroid's power wire (5.0V/4A DC) through the Atari's original power switch (https://console5.com/store/atari-2600-slide-switch-power-difficulty-color-new-old-stock-c010373.html) so it actually works as a power switch but not sure if this would be safe- if the switch would handle that kind of power?  Can't find any details about the switch or what it is rated for?  Is there anyway to test this or are the voltages/ amps so low that it's not a concern?


texts: Adjustable brightness for IR remote signals

texts:
I'm using and Arduino, an IR Led, and a transistor to for sending RC5 signals (36khz).

For the next step I need to be able to adjust the brightness of the signal, basically changing the range. The value could be set by an analog signal, spi or i2c or anything basic.

I thought about using a digital potentiometer, but they are not taking enough current for the LED - should be up to about 250mA (for a short time).
Searched the web but really not sure how to approach this. How do I create a circuit to adjust brightness for IR remote signals?


texts: Shield ground to metal body or signal ground?

texts:
I have a question about grounding.

I will have two short shielded cables with signal wires inside, located at the top of a tower. The cables have a grounding wire inside shorted to their foil shields to prevent the foil from building a charge.

I have two choices for terminating the grounding wire. (I only plan to terminate it at one end to avoid ground loops.)

A) I can attach it to the metal at the top of the tower. Let's say this metal body is ungrounded but it's decently big.

B) I can attach the grounding wires to signal ground which has to travel down long wires of 75 ft before it reaches its source.

Is there a clear better option for this? Does it even matter which I pick? I would appreciate any insight.

Thanks


texts:
I am trying to build a very simple amplifier type device to power a 4ohm 150 watt piezo tweeter.  I am getting my signal from an mp3 player and then want to use a voltage source, 9-20 volts, to amplify the signal to as much as possible and as simply as possible.  The goal is 120db.  I have talked to a few people and all give me different ways of doing it.  The simplest way I was told is using a basic transistor amp circuit and it would work.

Can I use this very simple circuit and just replace the small transistor with a larger mosfet and apply my 9-20 volts?  Will anything back feed into my mp3 player and destroy the output?

I don't really care about quality sound since it will just be constant tones coming out.  I just need them to be amplified as much as possible and very simple.
Thanks


texts: How to identify whether given motor is permanent magnet AC ie sinusoidal back emf or permanent magnet trapezoidal back emf motor. I am confused as motor I am having seems sinusoidal back emf and control strategies in literature for the two are different


texts: Do I need a resistor when controlling an ESC with an Arduino?

texts:
I am planning to connect one of my arduino's PWM pins to the input pin of an esc and the GND pin to the GND pin of the ESC, which in conjunction with the servo library should allow me to control the ESC. See below for an idea of what I mean.
esc http://api.ning.com/files/QYxylXSaas588I6jwxcoAJR8lBXneWApDBFHGCoOMg7Ge975QGTPeT0Qinw4ffnFDRoWYf7TcktkQRYX--0YwbQT05HgK*zp/arduino_esc_lucaszanela_com.png

I have seen guides on the internet that just connect everything without a resistor, like pictured above. Is this safe to do? I am not sure what sort of current the signal line would allow and whether it would be in the safe zone of a digital pin?


texts:
I'm currently working on a fun PCB project and have this circuit built that will input into an ATmega328P.
What I'm looking for is what you guys think of this and if you think it will work.
Does the op amp look okay for being in single ended mode?
Unfortunately I've been told that an LM386 is mainly designed for driving speakers but I feel as if my schematic should work, shouldn't it?
Otherwise, I was told to look at using an MCP6002 op amp.
Despite my "killer" design below, I'm really not great with op amps. Does anyone know what a microphone schematic with an MCP6000 series op amp might look like?

Edit: I was trying to mimic this design but KiCad's implementation of op amps is a bit funky so my schematic above is upside down compared to the  conventional implementation.


texts:
I have tried breadboarding a simple Colpitts oscillator, just to see how it works (and to get to use my 'scope for something more interesting than measuring static voltages).

I have been following this example, specifically the second circuit design:

A Colpitts oscillator http://www.play-hookey.com/oscillators/lc/images/colpitts_oscillator_cb.gif

I'm feeding it 5 V, the resistors are all at 1k, L is a .22 µH fixed inductor, Q is a 2N4401, C1 and C2 are .001 µF ceramics and the unlabeled cap at the base is a 220 pF ceramic (maybe way too low?), and I'm probing between emitter and ground.

Now, admittedly, these values are more or less randomly chosen from my component drawers. In this case I am not interested in obtaining a specific frequency as long as it's low enough for me to measure it (50 MHz), so I figured I could just throw in any values for the caps and the inductor, as long as they were high enough - I've read that this can actually be a pretty accurate method of measuring capacitance and inductance respectively, based on the frequency you get.

Questions:

Why is the circuit not oscillating? I'm measuring a DC voltage of 1.87 V at my probe point.
How do you calculate the proper resistor values (or ratios)?
What's the base cap used for? Just power decoupling?
Am I probing in the right place?


texts: Range of unsigned fixed point division in VHDL

texts:
I was thinking about the range a result signal should have to acommodate an unsigned fixed point division. Suppose we have:

SIGNAL a : UFIXED (3 DOWNTO -3);

SIGNAL b : UFIXED (4 DOWNTO -2);

am I wrong assuming:

SIGNAL y <= a/b should have

y'RANGE = (a'LEFT - b'RIGHT DOWNTO a'RIGHT - b'LEFT +1)

to acommodate any resulting y from this division?


texts: Why can't large batteries (such as the one by tesla) be charged in parallel

texts:
Tesla has many small individual battery packs. Why can't the output from wall outlet be taken and be distributed on each individual pack to be charge independently and hence faster, because many packs will be charged in parallel?

Wouldn't the charging take minutes instead of hours?


texts: Using Webpack from the command line, but without a project file?

texts:
I recently got Webpack to sorta work for me on my Linux system... but I tried using ISim for simulation of my designs and got hit by a problem. And from what I can tell, this problem isn't Xilinx's problem, since I'm not using a supported OS(Arch Linux)... and I can't figure out how to fix it... so I'm going to do something that hopefully is easier in the long run.

Anyway, I want to use ghdl/gtkwave for simulation, and then use Webpack's tools only for when I need to generate a bitstream for uploading to my FPGA... And I want it all to be run easily from a makefile. Of all the makefiles I've seen for using their command line tools though, they all require a project file. I'd really rather just specify files manually somehow in my makefile. I'd rather not have to, every time I add a file, change the project and my makefile. Is this possible?


texts: What's a good spectrum analyzer to learn with?

texts: I'm trying to learn more about building RF circuits and I want to buy a spectrum analyzer. I've looked around on ebay, and a lot of them are really expensive. I'm a student, so I don't have a lot of money to spend on it. What's a good model to buy since I'm just starting out?


texts: Class A Emitter follower instantaneous power

texts: I don't quite understand the explanation given in the book I'm reading. Why the maximum instantaneous power dissipated by Q1 is P=2Vcc*I at RL open? Also, why is the current ic1 constant I? Wouldn't the varying input signal will cause it to vary as well? As you can see in the graph below when vce1 = 2Vcc the current ic1 = 0. This confuses as to why it is maximum at that point? Thanks!


texts: Safety rules for DIY projects involving 220V

texts:
I'm planning to add some home automation to my home, using a 5V relay and most likely an ESP8266.
This will be used, for instance, to control the lights or the heaters, certainly through Home Assistant. I have experimented a lot with 5V DIYs, but this will be the first time that I will touch to 220V (domestic voltage in France.)
I read a lot of tutorials before even thinking of reproducing this, as I have very little knowledge of electronics. For instance, I'm considering a circuit like this one. (source [fr]).
However, most DIY tutorials do not dare to address all the possible security issues. Some are just mentioning "be cautious for fire hazard due to high voltage", but nothing more specific.
In such a relatively small project, what is the worst that can happen and what should be done to prevent it?
Any source of noob-friendly documentation would be very welcome.
EDIT:
Reading the comments, I could refine my search keywords and find some resources.
For instance, you could consider this circuitbasics tutorial (and especially the comments). It certainly doesn't seem to require an electrician but it would be very interesting to be proved wrong here. If they actually teach something wrong I think it is essential to notify it.
Electrical experts should really be aware that DIY is a thing and that telling people to seek qualified persons instead of teaching themselves is useless: they will do it anyway.
However, teaching what should be done in the right context might make some aware that they cannot do all the required things. In this case, they will stop by themselves and ask a qualified person.
EDIT2:
I live in a concrete building, as there are almost no more homes made of wood in France, especially in big cities like the one I live in (unlike in the USA I think). This might be important to consider regarding the fire hazard.


texts: Fail Safe for circuit, when input is removed

texts:
I have built a circuit which inverts the signal of a ULN2003A, it is in turn connected to a relay. It is possible for the ULN2003A output to be disconnected from the external circuit as it is remote from the driver. I have tried different methods to try and make it that the circuit defaults to an off state, making the relay go to NC, yet retain normal operation.

I have been trying to work out he circuit for the whole day, to no avail. I have been trying to keep the circuit as simple as possible in that I want to use transistors.

My current circuit:

simulate this circuit – Schematic created using CircuitLab

When the driver is active it switches the relay to NC.

The way in which it is supposed to operate is that while the driver is active the relay is contacts are NC, when the driver is OFF it should activate. Then the important part, if the driver line is removed it should then default to NC.

The last part is what has been troublesome, I need help in figuring out the circuit to achieve that.

I have also noted 0.6V on the ULN2003A pins when its is attached to the circuit, or not.


texts: Place a component on specific height above the PCB

texts:
what I have as a big issue is the following layout with two connectors. The problem is that the connector K201 (in right bottom) is very close to the frame. This frame will the attached to a device so there is a maximum 10 mm height of metal and insulator. If I put it the connector so close to the frame then it is impossible to plug any cable in. Then the question is - is there a way to lift the connector up on a fixed and defined during the design height?

I exclude the use of another small PCB, which is not very rational and cheap.

UPDATE

The connectors are for side-montage, meaning that the cable plugs in parallels to the PCB area. A solution with perpendicular connectors is already known, but not preferable. Thru-hole is not an option, because the upper layer must be perfectly flat.

Thanks!


texts: Can you use an iPad battery with an Arduino?

texts:
I'm looking to power an Arduino based project with a sufficiently large lithium battery so it can run for hopefully a week or more of constant use (ultrasonic based traffic counter). For large capacity lithium batteries, the usual advice is to use 18650s which seem to cost around $10 each for a 3400mAh Panasonic. However, I run a phone repair business and so through my connections with suppliers in China I can pick up an iPad3/4 battery for just under $10 which is around 11000mAh or an iPad mini battery for around $7 (~4000mAh). Once you get around the connector on these batteries, they seem to offer insane value in terms of mAh per dollar spent, plus it seems difficult to find batteries of that capacity in general.

My question, and it seems to be unanswered anywhere before, is how feasible would it be to use an iPad battery in place of any other lithium battery when powering an atmega328 based system? Ideally I'd also like to be able to recharge these batteries either with solar trickle charging in the device itself or a stand-alone charger. So far I believe this would involve a couple of points:

Are the batteries protected? Are their overcharge/low voltage cutoffs implemented in circuitry inside the battery which would mean they can be safely used outside of an iPad?
Is the fact that the iPad 3/4 battery contains multiple cells going to cause problems with load balancing during use and charging? If this is a problem, the iPad mini contains just one cell and so may be a viable alternative.

I am hoping that it is possible to use these batteries as on the surface they appear to be an excellent, untapped source of power for many embedded projects.


texts: Replacing a 1200v 8A fast switching diode that is obsolete

texts:
In order to evaluate (power up <1hr) and aircraft power converter. There are 2 leaky of 8 "Stealth Diodes" That are rated 1200v 8A and are hi-frequency switching diodes in a TO-220 PACKAGE, obsolete.

question: What in my extensive parts bin could I temporarily cross these diodes with? ie TV horizontal barrier diode etc

Data sheet link  http://www.alldatasheet.com/view.jsp?Searchword=Isl9r8120p2


texts: Methods for batch populating PCBs without a pick and place

texts: What are some good methods to populate moderate numbers of pcbs (20-100), without the aid of a pick and place machine?


texts: How to change get positive value on my weighting Scale?

texts:
My weighting Scale is working fine when I keep weight after the start. But I am getting stuck when I keep weight before starting my weighing device. When I do this auto-calibrate with available weight.
I am going to explain the whole experiment with pics:

I am sharing my code also:
#include <LiquidCrystal_I2C.h>
#include "HX711.h"

int button1 = 9;
int press1 = 0;

LiquidCrystal_I2C lcd(0x27, 16, 2);

HX711 scale1(4, 5);

#define MAXFLT 8

void setup() {
  //lcd.clear();
  lcd.init();
  lcd.backlight();

  lcd.setCursor(0, 0);
  lcd.print(" Weighing Scale ");
  lcd.setCursor(0, 1);
  lcd.print("----MakerMan----");
  delay(3000);

  lcd.setCursor(0, 0);
  lcd.print("--Place Weight--");
  lcd.setCursor(0, 1);
  lcd.print("   ..... kg      ");

  scale1.set_scale(-56);  // BUG: calibrate the scale (higher number, lower reading)
  scale1.tare();

  pinMode(button1, INPUT);
  digitalWrite(button1, HIGH);

}

void loop() {
  float r;
  char buf[MAXFLT + 1];
  r = scale1.get_units(5);
  Serial.println(dtostrf(r, MAXFLT, 3, buf));
  lcd.setCursor(0, 1);
  lcd.print(dtostrf(r, MAXFLT, 2, buf));

  {
    press1 = digitalRead(button1);
    if (press1 == LOW)
    {
      scale1.tare();
    }
    else {
      ///
    }
  }
}

Here I want that if I placed the weight before starting the machine. and when I start then it should calculate the exact weight. How i do this?
I want to solve this, please help me.


texts: I was wondering what kind of damage a 350V, 6000uF (link to capacitor) electrolytic capacitor could do. will this kill me if it blew up next to me? I have never blown capacitors before, but I definitely would not want to blow this one. Has anyone reading this blown a capacitor this large before? If so, what could I expect to happen, and how could I take precaution against it?


texts: Powering a Raspberry Pi using 15A supply

texts: I'm trying to power a Raspberry Pi off a 5V, 15A power supply. Measured with a multimeter, the voltage is actually a little more than 5 - ~5.25V. I've never powered a Pi with anything more than 2A, so will this be a problem long term?


texts: I want to know whether it is necessary to clamp UART signals when they are crossing to a different power domain. For example, in my design, a UART in one power domain is talking to a UART in another power domain. Is it necessary to use level shifters or clamp cells?


texts: For obtaining high selectivity, all natural modes should be complex conjugates (except for odd ordered filters). Why this condition? Thanks.


texts:
I need to pass high current on some part of my circuit. I used an online PCB track width calculator to see that required track width is about 5mm and minimum clearance is 1mm, which makes it about 7mm width at total just for one track. I need several of these high current carrying tracks on my PCB which will consume too much space to afford.

I am thinking of soldering copper wires on the top side of the PCB which will be parallel to the thin and symbolical tracks on the bottom side. But I would like to know if there is a more professional way of overcoming this problem.


texts:
I made a custom library for a 1x3 header with 5mm pitch on Cadsoft Eagle. Since I had to make the pins in metric, I'm having an issue now connected to the 0.1 inch grid that the rest of my schematic is in.

Picture 1 - It's two pictures combined. Top picture shows the pin and ground, bottom shows that they don't match up "exactly" on the grid.

After scurring around on the web some, I found several posts generic posts saying to just change the grid to a very small size (0.001/0.0001 inch) to make a bunch of connections then throw a Junction over top and it will work out fine. If I do this, then the ERC will have many more errors about overlapping.

Unfortunately, after looking at the ERC Errors, it still says it's not connected.

Notes:

The ground is only so close that the junction is covering so I could get a good close picture. In reality, I would move it to the right more.

I took pictures after saving and restarting Eagle. I know that can be problematic at times also. I'm also using Net's, not wire.

My questions:

Will using a tiny grid and having a Junction still count/pass as a connection when I go to have the PCB made? I know the ERC can be sketchy at times. I have the same issue with Pin 2 but used the grid change/Junction method also.
I made the part library using 5mm to inch conversion, then placed the pins at (-0.19685 0), (0 0), (0.19685 0 ) so they were technically placed on the inches graph. Is changing the grid to 0.19685 then connecting the net's an effective solution?
Is there a proper way to make metric components to fit on the 0.1 inch grid? I know it's a general rule to keep the 0.1 inch grid.
I've read/seen Youtube video's that says to take the ERC with a grain of salt. Should it be taken "seriously"? IE correct all of the errors?


texts: Flickering LED on BP3106 based LED Driver

texts:
I have got a LED fixture with a flickering problem. As I am unable to check the output due to lack of equipment I would like to research and gather some information first. The switch used is not dimmed, it is an usual mains switch.

It blinks at around 2 Hz. LED driver is based on BP3106 chip with a similar circuit as per image (taken from datasheet):

Visual inspection does not show any damage on output capacitors or any other part. I must say that this lamp worked at least 1 year before it started failing. See photo below:

I presume it is a problem with output capacitors but due to lack of experience and equipment I cannot find anything. I could try to check at work in a week time but meanwhile may I get some enlightment regarding this? What part(s) is/are more likely to fail after a year? Bear on mind this looks like a generic LED driver (no manufacturer information attached on housing). Specs are:

LED Driver: Constant current, Model LF02/25-30*1W, input 180-260V 50/60Hz, output 285-315mA, 75-100V.

Lamp: 5x 12V/5W connected in series.


texts: How does an inductor generate back emf equal to a source driving it?

texts:
I have a question about the way inductors fundamentally work. How can an inductor be modeled as accurately as possible?

I tried to approach this problem from the basics of electromagnetic fields, but I am still having some problems understanding the matter

When we connect the ends of a inductor across a battery:

The end at lower potential pushes the electrons in the inductor by applying electromotive force on it
due to this push the electrons gain acceleration
because of this acceleration a change in current with respect to time di/dt occurs
because of this di/dt an electric field is developed in the inductor to oppose it
now there are two forces acting on the electrons that is the force due to battery and the force due to induced electric field in the battery
now we see that under these two opposing forces the net acceleration of electrons has decreased and there is anew value of di/dt at that instant now since the di/dt has reduced the induced emf this time  will be less compared to previous now again under the influence of these two forces a new acceleration will come and according to it will come a new di/dt
and so there is a jerk like increment as well as decrease in the di/dt so the problem is what is happening inside because in textbooks they write that in simple inductor and battery circuits the di/dt is constant?

Another question I have is about the induced emf to be equal to the external battery if the induced emf(opposing emf induced in loop) is equal to the external battery then how in the world is di/dt not equal to zero because if there is are two fields exactly same in magnitude and in opposite directions then how come the current increases with time?

If external emf and induced emf are same then the energy given to electrons in completing the circuit is equal to the energy taken by the inductor from the electrons then how is their kinetic energy (current) increasing?


texts: How internal capacitor stud finders work?

texts:
I don't understand how can a non magnetic object like wood be detected using a stud finder

For instance, stud finders find wood from dielectric constance, but I don't understand the princible.

The basis of my question is to understand how sensors can detect non-magnetic objects in order to build a paintball ball counter.


texts: Looking for a replacement part; need help finding from photo

texts:
I blew out a part in my dad's Fender Chorus guitar amplifier several years ago. I didn't ever get around to fixing it for him, no clue why, but I really should.

Problem is I can't find this part or an equivalent replacement anywhere.

So I'm turning to you guys. Help is very much appreciated!


texts:
I have to interface a uc to a ADF7020-1 and I want use adf7020-1 as master and uc as slave in 3-wire spi mode. adf7020-1 have txrxdata that interfacing with uc(it has mosi and miso pins). how did connect 3-wire SPI into uc?
do need isolate mosi and miso pins with diod?
Can i Short MISO and MOSI?
please help me
thanks

short miso and mosi to interface with uc


texts: Do electrical devices "take what they need"

texts:
One concept of electronics I have a hard time understanding is if things like motors, actuators, solenoids etc. use as much power as they need or what you give them.

If a motor needs 12 volts and 500ma and I supply it with 12 volts and 3000ma will it only consume 500ma? Also, if I supply it with 15volts and 500ma what will happen?

It seems logical that an LED and a DC motor are way different when it comes to requiring/using electric where as an led has to be completely regulated and (I assume) a DC motor doesn't.

Is my understanding wrong?


texts: Motor-side of BLAC supply goes into overvoltage when regenrative braking using an LM5060

texts: I am currently using an LM5060 for protection of the motor supply on my BLAC motor driver. Everything works well until I decelerate the motor quickly, this makes the supply voltage peak above the OVP and cuts off the power. What are best practices when it comes to protecting the motor supply? Should I consider only using reverse polarity protection? Or should I increase the OVP threshold? Thanks!


texts:
I bought my first LED strip and was a bit surprised that resistors are used to limit the current.
When connecting only one or two LEDs it is an obvious solution, but when ther are several hundred LEDs, why don't they use the voltage drop per diode to construct a resistor free setup. After all, LEDs may be efficient components, adding resistors just consumes energy, and worse, add heat to the strip.


texts:
i need to regulate the speed of a noisy kitchen FAN from a microcontroller (arduino board), i have been looking around and checked a lot of websites and schematics, and i think the solution should goes to a TRIAC regulator I think...

The point is that i have no knowledge in power electronics and i don't know witch circuit is going to be good and reliable. I have seen some circuits that use only a TRIAC and others that uses a TRIAC and a DIAC... Why is the difference? and the DIAC function?

Could you provide me with some good schematics or recommendation form my situation?

thanks you very much :)


texts: How sound waves travel for reverse parking sensors?

texts:
Looking at (ultrasonic) reverse parking sensors, they're all installed with a (plastic?) cover like this:

Traditional ultrasonic sensors are installed with a mesh:

Since plastic reflects sound waves, how do reverse parking sensors work?


texts: ISA efficiency code compaction and memory traffic

texts:
I'm having issues understanding this problem and am new to ISA's. Here's a problem with 3 questions and my biggest question is, what is supposed to happen? Specifically, the HLL Code at the bottom.

Assume four ISAs

accumulator-based
stack-based
memory-to-memory (operands located in main memory)
register-based (pure load/store)

Instruction / data size

all data operands 4 bytes
all memory addresses are 16 bit
all opcodes 1 byte
memory address fields 2 bytes wide
register fields in load/store machine are 4 bits wide (16 32-bit registers)

Additionally, all memory addresses are 32-bits long and all instructions and data are fetched in one single memory access in the case of memory-memory architecture, no need to use additional memory location.

Compile code for four ISA's and determine the metrics: 1) code size 2) data memory traffic, including addresses, 3) instruction traffic, including addresses.

HLL code:

 A = B + A
 C = A - C + D


texts:
I'm currently working with a small SPI Flash Memory chip attached to a microcontroller.

After having some problems interfacing with the memory, I took a closer look at the datasheet and realised that the RESET and WP (write-protect) pins are Active Low.

In terms of circuit design, am I right in thinking that if there is never a use for resetting or enabling write-protect, I should wire these to VCC (or in the case of a PCB, the power plane)? If so, is it better to have a resistor on these pins as well?

This is the pin description table

SYMBOL     DESCRIPTION
CS#        Chip Select
SI/SIO0    Serial Data Input (for 1 x I/O)
SO/SIO1    Serial Data Output (for 1 x I/O)
SCLK       Clock Input
WP#        Write Protection Active Low
RESET#     Hardware Reset Pin Active low
HOLD#      To pause the device without deselecting the device or Serial Data Input & Output (for 4xI/O read mode)
VCC        Power Supply
GND        Ground


texts:
I've been using TIP120 darlington transistors to drive various motors, I apply a 5V Base-Emitter voltage, that I sometimes modulate with PWM and a resistor on the base, this works great, but is there a same type of transistor for 3.3V?

More generally, what is the best way to look for transistors?


texts: modify schematic to work at 5V (solar panel sun tracking system)

texts:
I have this schematic and I want to know:

if it will work at 5V (my solar panel is 5V-6V)
modifications required to command (clockwise/anticlockwise rotation) the motor directly with the final transistors (without relay).

The motor is very small one. 11mA at 2V (minimum voltage at which it still starts spinning) running without load. Once I install the solar panel I expect to suck no more than 50mA.

Another requirement is to power this circuit directly from the solar panel, not from the battery hooked to the solar panel. So, the circuit needs to safely shutdown when the voltage provided by the solar panel is too low. In other words it should not start to randomly spin the motor when the voltage drops way below 5V.

from: https://www.electroschematics.com/8019/diy-solar-tracker-system/


texts: I need help in fast charging lithium ion batteries

texts:
I am building a college project for a national level competition. In my project (which is similar to a drone), I am trying to charge the lithium-ion battery pack quickly.

I am using a 10000mAh Li-ion battery pack but would like to feed as much current into so as to charge 50% of the battery in under 10 minutes.

Most of the battery packs that I came across usually accept 2-3A input current.

I am using a DC-DC converter to increase the current but would it be feasible?

And how can I achieve such quick charging? Can Tesla's supercharging technology (that's used to charge up entire vehicle in 40-50  minutes) be somehow applied to charge up Lithium ion batteries in a model drone?


texts: Why are stepper motor phase currents a sinusoildal waveform?

texts:
I don't know if this is a really dumb question or not, but I've seen all kinds of torque, peak-current and RMS discussions related to current drive output for stepper motors. I acknowledge that for a 2-phase Hybrid stepper motor to run smoothly the phase currents must be two sinusoids one advanced 90º in relation to the other, like the image below

https://www.researchgate.net/figure/Sampled-currents-in-2-phases-of-stepper-motor-in-500-ms_fig4_275460011 But I really don't know why is that. I've read in a book ( Stephen D. Umans- Fitzgerald & Kingsley's Eletrical Machinery) that the torque as a function of the rotor angle is a sinuisoidal curve when phase A or B are excited, but why phase A and B should also be a sinuisoidal current is not clear to me. I'm a grateful in advance for anyone who can explain for me this correlation between current sinusoidal waveforms and torque

(https://www.researchgate.net/figure/Sampled-currents-in-2-phases-of-stepper-motor-in-500-ms_fig4_275460011)


texts:
I'm trying to design a simple level shifter to read the digital output of a sensor into a beaglebone GPIO. The sensor output is either 0V or the 24V supply voltage, although a different supply voltage might be used (5-30V).

The line from the sensor is also used for serial communications (IOLink) which I don't want to interfere with in this circuit.

Will this design work well or am I missing something? It seemed to work in circuit simulators but I'm quite new to this.

Thanks!


texts: Large capacitors with very high series resonance

texts: I am trying to build a high frequency amplifier board with the Mini-Circuits GALI-S66+ InGaP-Darlington RF amplifier. I am trying to resemble the evaluation board layout and there they use 2.4nF capacitors to block DC. However I am struggling to find any capacitors that are free of resonances up to 3GHz (as stated necessary in the reference design) and have a large enough capacity. I did find the muRata ULSC series, which seems to be free of resonances up to 20 GHz, but those are some very costly capacitors (~7€). On the other hand a voltage capability of more than 30V would be beneficial. Am I missing something here?


texts: Why do I measure 5V in this circuit when I should measure 3.3V?

texts:
I have an audio processor board that has a 5V -> 3.3V LDO. For some very strange reason, when I measure the voltage of the output of the LDO, I read 5 instead of 3.3V -- which by the way is a lethal voltage to the chip that's on the board, but for some reason, it doesn't seem to mind it.

So here's some background information, this is the board:

And this is the full schematic:

https://drive.google.com/file/d/1OV1CHaihA_eIsqDjlkCkUZPVncHjFkQO/view?usp=sharing

It's a very simple board, just an audio DSP chip and an eeprom, designed for quick prototypes and DIY solutions.

The DSP chip is ADAU1452. For it's "IOVDD" rail, it asks for 3.3V, and absolutely no more than 3.6V. The way this board achieves this voltage is using a typical 1A linear regulator.

The regulator that came shipped with this board was AMS1117, apparently, a very popular choice for Chinese made designs.

When I power the board using a 5V supply, it seems to work just fine. Here's the problem: when I measure the voltage between output pin of the LDO and the ground, I read 5V. Input is 5.1V, output is 5V. How can this be?

The multimeter I am using is Fluke 115, a reputable name brand multimeter, so I know it cannot be lying to me. Why would I possibly be measuring 5V instead of 3.3V like I should?

As a step to debug, I took the original LDO out, soldered jumpers to its pins, and supplied it a 5V input out of the circuit, without any caps. And lo and behold, I read on my multimeter that it was outputting the correct 3.3V! As soon as I put it back into circuit, I read 5 V again...

I thought maybe there is some problem with stability related to input or output caps, so I swapped the part with a brand new pin campatible LDO ADP3338. And again, when I measure, I read 5V at the output.

What am I not understanding here? When I plug my multimeter in this board by connecting the ground probe to the ground lead of the LDO and positive probe to the output lead, why shouldn't I read 3.3V? Is this a measurement fault, or is there some other components in the circuit that can change the voltage of the LDO output? When I look at the schematic, I can't pinpoint a possible cause for the output voltage of the LDO to climb back to 5V. I simply don't understand what's going on.

By the way, ignore that weird, backwards looking Q1. The board came shipped like that. Somebody must have made a blunder when designing the board and later realized oops, gotta put the part backwards. That transistor doesn't seem to be the culprit though.


texts: How does the microcontroller read potentiometer resistance as integer without regard to potentiometer value?

texts:
When I hook up a 5k rotary potentiomoeter to the analog input pin of a microcontroller it will read values from the pot as integers 0-1023.

If I switch the 5k out for a 500k the microcontroller will still read values as 0-1023.

How is the system able to abstract the reading from the potentiometer down to the same range and distribution of integers when the max value of the potentiometer changed?


texts: Why are wifi antennas covered in plastic?

texts: Couldn't it be like a radio antenna (wifi is radio after all), telescopic and without any encasing?


texts: Utilizing both TTL and RS-232 level signals from transceiver

texts:
In the past I have used Maxim's MAX213CAI part as my RS-232 transceiver with FTDI VCOM chips. In our application we utilize both, the TTL level and the RS-232 level signals, depending on which device we attach to our board. This means I have both signals routed to the connector:

Where TXD1/RXD1 are the TTL level, and TX1RS232/RX1RS232 are the RS-232 level signal, for the same COM port. This works just fine with Maxim's MAX213CAI.

However, due to the high price of the MAX213CAI and the very attractive price for EXAR's SP213EHCA I decided to switch. I got new boards for testing some other changes and included this new Exar part, and lo and behold, it doesn't work.

I tried with a lookback and it just doesn't work. The EXAR part pulls the line high and the FTDI part (in the loopback), or the device attached to the connector, can't pull it low enough to receive data.

I took this screenshot from my scope:

As you can see, the RXD1 line doesn't drop bellow 3.5V, not enough to detect a "LOW". This is not the behaviour of the MAX213CAI part.

The 2 parts are 100% pin compatible, and this is how I have them hooked up:

PIN 24 is the ENABLE pin, if set to HIGH, the outputs are "Enabled", and if set to "LOW" the outputs are set to "Tri-State". The problem I described above is when the EN pin is set to HIGH. If I set the pin to "LOW", then the TTL level signal works just fine, but the RS-232 signal stops working.

Any ideas why the Maxim part has no issues with this, but the Exar part does?

EDIT:

These are the traces for the charge pumps:

PIN 15 (C2+):

PIN 16 (C2-):

PIN 144 (C1-):

PIN 12 (C1+):


texts:
Hi,

I'd like to understand the context in between an oscillogramm and the resulting FFT. My example is a full-wave rectifier and I am try to calculate some harmonics.

Because the function is symmetric I only need to calculate the an-values:
$$
A_n = a_n = \frac{2}{\pi}\int_0^{2\pi} \! f(t) * cos(nt) \, \mathrm{d}t \\
a_n = \frac{2}{\pi}\int_0^{2\pi} \! |sin(t)| * cos(nt) \, \mathrm{d}t
$$
dividing up for integrating
$$
a_n = \frac{2}{\pi} \left( \int_0^{\pi} \! sin(t) * cos(nt) \, \mathrm{d}t + \int_{\pi}^{2\pi} \! (-sin(t)) * cos(nt) \, \mathrm{d}t \right) \\
$$
result of the integral
$$
a_n = \frac{2}{\pi} \left( -\frac{cos(\pi n) + 1}{n^2 - 1} - \frac{cos(2\pi n) + cos(\pi n)}{n^2 - 1} \right)
$$
My question is whether my way was right up to here and how I have to transfer this into the fft?


texts: How can I make a phantom power mic popless mute switch?

texts:
I want to make a phantom power (PP) mic mute switch with an indicator led powered by PP. I already did it based on the following circuit. It works but, with the led included in the circuit, I get a pop when turn On-Off the switch. Without the led it work fine and silent.

simulate this circuit – Schematic created using CircuitLab

Is it possible to prevent this pop keeping the led being powered by the PP? Or there any contraindications of powering the led with PP?

Please, help me. I'm not electronic engineer.


texts: Battery in parallel with main power source

texts:
I have a system that is powered by a main voltage supply and I want to connect it to a battery for backup, in case of power outage.

I need to know what would happen if I connect the system with the battery in parallel with the source and both the battery and the source give 5 V. Where from will the load take its power? From the source or the battery? And how can I isolate the battery from the system if the source is working? And will the battery power the system when the source stops providing?


texts: STM32F4 - CMSIS & Board Specific Libraries

texts:
I recently purchased a STM32F4 board to learn the ARM architecture. I am fairly comfortable with embedded programming having worked with AVR series for about a year.

I was going through this tutorial at here

In this the author has mentioned that usually in the ARM boards world, you have 2 set of libraries:

Cortex M Software Interface Standard (CMSIS) - general HAL layer/interface for Cortex M specific features
STM32 libraries - specifically for the onboard peripherals on the STM development board (I2C, SPI, CAN etc)

The author also mentions that just like any HAL layer, the purpose of these is for one to quickly develop rather than waste time on setting things up.

Coming from AVR side where I am using minimal/no libraries and setting up everything by hand (for example spi configuration, rx and tx interrupt driven functions etc) I find this bit strange. By using the STM specific libraries, wouldn't one be constricted to using their microcontrollers only? Then in future if I use some other vendors chip, I'll have to learn to use their specific library

I would like to get an opinion that if this is the right way to go. Being new to ARM should I just use these libraries for now till I become more comfortable or should I from the start get into the habit of doing everything myself?

The idea is to lean ARM independently of any vendor specific board or microcontroller.


texts: Implementing a programmable variable resistor

texts:
The R-2R network can provide digital-to-analogue conversion of arbitrary precision using resistances of only two values. Is there a corresponding circuit architecture that switches resistance values to provide a variable resistance?

I want to implement a digitally programmable resistance.  The dream solution would be something that could produce all of the E24 series over 5 decades, i.e. 100, 110, 120, ... 82M, 91M, 100M, but I would settle for a proof of concept - a design (scalable) that could accept say, a 4-bit digital input and give 16 exponentially or linearly increasing resistance values.  The unit needs to be a two-terminal fully isolated unit and would probably use reed relay switches to provide isolation and minimize switch resistance losses.

A trivial solution to this would use a resistor of every required value, a corresponding reed relay switch, and a whole heap of logic to turn on the appropriate switch.  I'm hoping there is a circuit that uses one switch per bit and fewer resistors.


texts: Analog Devices Footprint issues: ADP7156

texts:
I have designed a circuit with a voltage regulator(ADP7156) from Analog Devices in KiCad. I have chosen the package type as 8-lead SOIC since I am planning to hand solder it to the PCB. While creating the footprint, I found the dimension of datasheet a little confusing.

From the picture, I figured out basic footprint as follows(drew in paint for clarification purpose)

X=0.41mm,

Y=1.05mm (=(6-3.9)/2 mm), here 6 is median ,

C=4.95mm (=Y+3.9),

E=1.27mm

2.29mmX2.29mm for exposed pad

Am I good to go draw the footprint in KiCad Footprint editor with these information I collected from Data Sheet. I usually find the recommended pcb layout on other manufacturer's datasheet which helped a lot to draw the footprint easily. Please guide me.


texts:
Every op-amp has error. We all know that. So logically, the more op-amp used, the less accuracy we will have, right?

In the circuit ,there are 2 parts: first is the current to voltage converter, second is the voltage amplifier. So let start by assuming that the current through LED as detector is -1 nA, variable resistor is 10 kOhm, so the final output should be 10V.

But I wonder: does that really need for the second op-amp? I mean, if we replace 1MOhm resistor with 10Mohm resistor (so that we wont need the second Voltage amplifier part) we will get the same value, and because fewer elements are used, the accuracy is better. Is that correct?

Also, I tried to read a lot but I still don't understand. The capacitor here acts as a filter or in order to stablize? What if we don't have capacitor?


texts: OP-AMP circuit for voltage to current conversion

texts: It is required to design a circuit for voltage to current converter to have a current output with 4-20mA. So, I wonder if the above circuit will work. Suppose that the input ranges from 1 to 5V.


texts: Why does my multimeter use increments of 2?

texts:
I bought a cheap multimeter (etek 10709 if you are curious) from Walmart the other day to just check out a few readings on my cars ignition system.

While I have no problem getting the reading (in ohms) I noted that all the increments were in 2s, 200 2k 20k and so on.

Does this mean whatever readings I received must half to accommodate for this?


texts: Curious state transitions in state machine RTL simulation

texts:
I have a simple state machine as part of my Verilog module:

localparam State_IDLE = 3'b000,
           State_WRITETOLANE1 = 3'b001;

reg [2:0] currentState;
reg [2:0] nextState;

always @(posedge TxByteClk) begin
if( rst ) begin
    currentState <= State_IDLE;
end else begin
    currentState <= nextState;
end
end

always @(*) begin
nextState = currentState;
case( currentState )
    State_IDLE: begin
        if( TxSync ) begin
            nextState = State_WRITETOLANE1;
        end
    end
    State_WRITETOLANE1: begin
        nextState = State_IDLE;
    end
endcase
end

TxSync is an input signal. The bizarre behavior I'm seeing is that at the positive edge of the clock when TxSync is high, currentState is set to State_WRITETOLANE1 and as a result nextState is set to State_IDLE. But nextState was never set to State_WRITETOLANE1 in the first place! Why is currentState getting a value that was not even present in nextState? Doesn't the line currentState <= nextState; imply that currentState is the delayed version of nextState?


texts:
I'm doing a project that can draw an analog clock on the XY mode of an oscilloscope using the Atmega88-20PU with the default clock frequency of 1MHz. To display the image I use a PWM signal applied to a low-pass filter (working as a DAC) for channels 1 and 2 of the oscilloscope.
The problem I'm facing is that, even though the PWM signals are being generated correctly, the output of the low-pass filter isn't working correctly. Just for testing purposes, I tried drawing a simple rectangle (4 vertices) but it only displays 1 vertex.
My intuition tells me that the problem might be that the clock frequency is too low, or that the values of the RC low-pass filter are not the most appropriate (R = 4.7KOhm, C = 100nF).
After some research, I found another similar project where the creator used the same RC values, but the code was running on a 16MHz µC (https://www.youtube.com/watch?v=nlCADL5_g-I).
Here is some of my code:
void Clock::display() volatile
{
    for(uint8_t i = 0; i < 4; i++)
    {
        display_point(points[i]);
        _delay_us(point_delay);
    }
}

void Clock::display_point(Point point) volatile
{
    OCR2A = point.x;
    OCR2B = point.y;
}

void Clock::calc_points() volatile
{
    points = (Point *) malloc(4 * sizeof(Point));
    points[0].x = 20;
    points[0].y = 20;
    points[1].x = 100;
    points[1].y = 20;
    points[2].x = 100;
    points[2].y = 200;
    points[3].x = 20;
    points[3].y = 200;
}

clock.display() is called every frame of the main loop.
clock.calc_points() is called every 1 second (on an ISR).
EDIT #1: I have already slowly tested the code and the PWMs generate correctly accordingly to the points I tell it to run. Therefore the problem must only be on the low-pass filter.
EDIT #2: The frequency of the PWM waves is f_clk / 256 = 3.9 kHz. What should be the value of the cutoff frequency of the filter?
EDIT #3: I added a 20 MHz crystal oscillator (PWM frequency of 78 kHz) and changed the filter to have a cutoff frequency of about 200 Hz and got the following output (channel 1 shows one of the PWM outputs and channel 2 shows the filter of that same PWM):


texts: What is the capacitor's functionallity in a Simple oscillator where it is conntected to same terminal through both sides?

texts:
I was reading the Wikipedia page about the applications of capacitor, when I saw an example there for a simple oscillator circuit :

Yet I noticed the capacitor seems to be connected to the (-) terminal from both sides.

How can this circuit function when the capacitor is connected in such a way ? am I missing something here?


texts:
I'm sending two complementary PWM signals from a control board to a separate power board via a ribbon cable (along with some other signals, 20cm or so).  The PWM signals control a MOSFET driver on the power board which, in turn, switch two MOSFETs as part of a half-bridge.  I've noticed that as soon as I plug in the PWM signal there's up to ~100mV of noise on the 3.3V rail of the control board (checked with a scope).  Since I'm using the 3.3V as a reference for ADC on the control board this is leading to substantial error in the ADC readings.

Is the wiring itself responsible for much of this noise?  Wondering if this design is even feasible and whether it would make much difference to move the MCU, etc. from the control board to the power board in order to avoid wiring.

Schematic of the power board:


texts:
I am trying to make simple switch pedal. I need 3 pole switch to toggle between two left inputs for each right output. Inputs and outputs are mono jacks connecting guitar pedals. Is this schematic correct? Is my wiring drawing correct?

Last third set of input and outputs is missing on drawing but I will probably need it as well.


texts: I need to program an EPROM/EEPROM with the code for an 8085. I do not have a programmer. I can't buy one. But I have access to an 8085 kit. Can I use it to program the EPROM/EEPROM via an interface? What difficulties may I expect if I do it this way?


texts:
I have been given the task of designing a 12-bit pipelined adder:

There are 4-bit adders connected by latches.
Why are latches used between the 4-bit adders? Is it for synchronization?


texts:
I'd like to control 3 status LEDs with two different PCs:

an OrangePI-PC, using the GPIO pins as power source (same pinout of a RPi2);
regular desktop PC, using the parallel port as power source.

Both PCs can be powered at the same time and shall share the same LEDs (there is no need to enforce a priority between them in case of conflict).

This is the wiring scheme i am thinking to use (sorry if it is a bit confusing, this is the first one i've made with fritzing):

My ideal solution should rely only on discrete component (diodes, resistors, etc.). I'd like to avoid using ICs, Arduinos, etc.

UPDATE: i've made the circuit and it works pretty well.
I've also experimented with other interfaces, but in the end i've settled with the GPIO pins and the LPT port.
Here it is the driving script in Python.


texts: Why, when providing FM radio designs, do people use physical parameters instead of electrical? I.E. 2 turns, 20awg, 2cm dia.


texts: Using the UBT-12HC Serial Bus Motor with Arduino

texts:
I recently bought this motor and am trying to figure out how to use it. I also need a driver as this Bus Servo uses omnidirectional Serial communication. That is why I also bought this TTL board.

I, so far, have tried LewanSoul libraries and PC software, and many
Python scripts with no success. They all just say that the incoming
packet is invalid.
I also tried Feetech's PC software and it picked up this motor as
150 of them connected to the controller.
I know the motor is responding because as soon as I unplug the
motor, there is no response from any scripts and the Feetech tool
detects nothing.

After researching, I found out that this motor is really similar to the "UBTECH Alpha Servos UBT-12HC". But they don't have much documentation on how to use them. I found tutorial this tutorial that shows you how to get it to work. There is a plugin for a program but I don't know how to use that program. So how do I use such a motor? Are there any steps I can take to figure out how to use it? Perhaps looking at the chips inside? Any help is truly appreciated.


texts: When the transformer is operating in rated apparent power, the voltage and current at the secondary side(is it the secondary side, please verify) is the rated voltage and current. My question is what is the rated load?


texts:
I have been coming across so-called "band switching diodes" recently, but I can't figure out what they actually are. Is this some type of RF switching PIN diode?

I came across these while I was searching for a cheap alternative to step recovery diodes. Someone recommended using the BA682, which is a band switching diode.

BA682 link


texts: Charging a USB C device with fixed voltage / No Power Delivery/ Fixed dedicated Source

texts:
I have a lenovo yoga 730 13-ikb without a charger, it uses TYPE C usb charger with PD

specifications for the charger in online stores are:
AC Input: 100-240V ~ 1.5A 50-60Hz DC Output: 20V 3.25A   (65 watt charger)

Laptop Specs sheet say:
AC adapter            65W USB Type-C AC adapter

I was thinking of creating a DIY charger with 20V power pins and 65w from some other source.

Can I damage the USB C port or the laptop at all if I don't do it with the Power Delivery specs, I mean does it need it to be PD compliant or giving it the required power as the spec says be good to go without worrying that it will only work for this laptop and nothing else?

I don't care if it does not work for my phone or any other lower consumption device, I don't want it to be a universal USB type C charger, just want t to charge this specific laptop.

is Power Delivery supposed to be switching voltages once it is powering the laptop , maybe for powering different parts of it, or once negotiated it continually delivers settled voltage until disconnection?

Can I Bypass the negotiation of power by bridging some pins or somehow modify it so it just goes with single power available, is negotiation mandatory?.

I have seen more questions with answers in but apparently all talk about a charger compliant with PD, my goal is not to create a PD charger, just directly be able to charge the laptop.

Update
While checking the service manual I found this
so apparently it always has the 20V to start with, does anybody know if PD chargers output by default the maximum power?


texts:
as my primary thing with electronics is hardware, I am having some difficulties learning programming. Unfortunately, my college where I study offers no such course so for my project this year I decided to incorporate some, to force myself to learn it, however, I am struggling to understand some of it! I have been building up separate parts of my code and most of it is working, however, I am trying to display a count on an LCD, and each time a button is pressed, I want it to increment by 1.

I managed to do this successfully on an Arduino (as there are many example sketches out there) but I want to do my project using an STM Nucleo (F103RB). I tried to transfer the example code over, and edit it using commands the online mbed IDE would understand, but it would not work. I then found a few different examples and each gave me different results. I eventually came up with my own code following a guide in adding/subracting in the book 'C Programming: A mordern approach'. The code I have come up with is here:

#include "mbed.h"
#include "TextLCD.h"

DigitalIn ip(D7);
TextLCD lcd(A0, A1, A2, A3, A4, A5);

int i =0;

int main() {
    lcd.cls();
    lcd.locate(0,0);
    lcd.printf("COUNT:");
    lcd.locate(0,1);
    lcd.printf("%d",i);
    while(1) {
    if (ip ==1) {
    lcd.locate(0,1);
    lcd.printf("%d", ++i);
        }
    }

And finally, the count started responding when I pushed the button. However, the issue I am having, is that the count increments all the time I have the button pressed, so even a small press will increase the count by 50-80 (depending how quickly you press it) and I want it to increment by 1 each press.

I have tried structuring it differently, having the 'while' statement at the beginning etc, but that just caused the LCD to oscillate strangely.

I've been stuck on this for about 6 hours now before getting to this point! Would really appreciate if someone could give me some pointers in the right direction!

In case anyone is needing it, my (simplified) schematic is here:

simulate this circuit – Schematic created using CircuitLab

So you can see it really is very simple. But I have just zero knowledge of C programming and have never been taught how to do it properly, so any solutions will need to be explained!


texts: Which AVRs are pin-compatible with the ATtiny2313?

texts: Until the 4kb upgrade to the ATtiny2313 is available, which AVRs can I substitute when the ATtiny2313 is too tiny?


texts: What solutions, if any, are there for visible light transmission (VLC)?

texts:
I want to know what ways are there to transmit data using LED's that are available to us today.

I currently can find only one reasonable resource for this topic, which is this:
http://www.siemens.com/innovation/en/news_events/ct_pressreleases/e_research_news/2010/e_22_resnews_1002_1.htm

Is there any other information about this or resources I can use?
What is the highest frequency can you blink a under $5 led at?
What about a photo diode or photo transistor that can respond at such frequencies for under $5?

My aims are to have anything above 10KB/s but under $5 or so, with range that includes line of sight and it would be no more than one or two feet away. Am I just going at this entirely wrong and should instead use a RF solution? I am gearing towards visible light because it seems cheaper, does not give me the headaches of RF, and most certainly looks far more interesting than a RF or IR design, since you can actually see the process. :P


texts:
When I was reading the datasheet for these relays (http://www.mouser.com/ds/2/357/105A_117SIP_107DIP_171DIP-6475.pdf), it says to put 1/2" spacing between two adjacent relays. Why is this?

As the relays are fully insulated, why would I have a problem by putting them right next to each other?


texts: Using an MCP23008 IC with a 4X4 matrix keypad on a Raspberry Pi

texts: I want to be able to free up the native GPIO pins on my Raspberry Pi Zero. I know the MCP23008 gives me 8 extra pins, but I can't seem to find any resources on using the additional pins with a 4X4 matrix keypad.


texts: Why is high voltage AC more common than high voltage DC?

texts: Why is that high voltage AC is more commonly found than High voltage DC? Example my battery powered fly swatter and fluorescent lamp both use high voltage AC. Why can't these devices increase the DC voltage from battery and directly use the High voltage DC?


texts: How to multiply voltage of a pulsating positive only source?

texts:
Total newbie here.

I'm trying to multiply the voltage of a positive only pulsating source. It variates from 0v to 500v.

All voltage multipliers I found explain how they work with a AC source, varying from +V to -V. I can't get my head around an schematic for +V to 0V.


texts:
new to electronics here, so bear with me...

What I'm trying to do, is use a single momentary switch to act as both power and input for an arduino. The schematic pictured is a basic layout of what I'm trying to do (I know what's pictured is missing a lot, it's just for simplicity).

The way the operation would work is pushing the button would allow power to turn on the arduino, then pin 13 would get set HIGH, keeping the gate open the IRLB8721, allowing power to continue to flow. Pin 9 would be read as input for button presses, and when turning the unit off, pin 13 would be cut.

I've found similar schematics, but I can't get anything to work. I've tried reversing the power (running (-) through the IRLB8721), a multitude of resistors (pull down in there as well), voltage dividers to lower the voltage before entering the switch setup, etc.

The best result I can get is if I disconnect pin 13, and press the button to power on, the arduino powers up (gate open) and stays on. As soon as I touch the gate wire to anything (plug it in to any arduino pin), the arduino shuts off. I can't seem to actually control the gate properly.

I've borrowed this schematic from another post: (Using a momentary push button as a latching on-off toggle switch).

I've recreated this schematic (with a voltage divider pushing in 5v from a 9v battery), and still can't control the gate (but if I disconnect pin 13, the gate stays open after powered on).

Any advice on how to properly control the gate on my mosfet? (https://www.digikey.com/products/en?keywords=IRLB8721PBF-ND)

*****UPDATE*****

@royc, I tried your schematic, but was unable to get it to work properly. It was late and I was in a hurry, so I very well may have mis-wired something. I'll try again this weekend.

Earlier, I got to try this, and it works spectacularly:

Using the above setup, I'm able to turn keep the arduino on and turn it off in software. However, I can't seem to find a take off point to get a reliable read for the button press, while it's on.

If I plug in anything with voltage to an arduino input pin, the unit stays on (or powers on) regardless of the switch or output pin. I also can't see a way to apply voltage to a pin when the switch is pressed. And, it seems to be a little questionable to apply more than 5v to an arduino input pin.

So, here's what I've come up with:

The thinking is that once the circuit is powered on, voltage from the battery will be applied to the base of Q2, keeping it open, allowing 5v to flow from the arduino to an input pin. When the switch is pressed, that leg will ground out, the base will close the path, and the pin will read low (software logic will detect a button press when it reads low).

Haven't tried adding the input leg yet, but does anyone see anything wrong with this or have any better ideas?


texts:
I am testing a transformer with a center tap on its secondary winding and I am pretty sure it is broken. Never the less I cannot explain to myself the reason behind some of the values I read with a digital multimeter.

The transformer was the only component inside a Yamaha PA-20 power (AC-AC step-down) adapter.

Input: 230V~ 50Hz 42W
Output: 17.5V-X2 0.94A

This is the schematic (labels on the connector are written in purple):

simulate this circuit – Schematic created using CircuitLab

Measurements of windings resistance values:

P1-L2: inf
P1-(A or B or C): inf
L2-(A or B or C): inf
A-C: inf
C-B: inf
A-B: 0 Ω

Given these results, I suspected a broken primary winding and a detached tap (C).
If I give an input line voltage, though, I can measure these AC voltages on the output.

A-B: varies 0.000 - 0.015 V
A-C and C-B: varies between 3 V up to 5-6 V, with asymmetric values.

And this is the behaviour I cannot explain, given that the primary winding seems broken.
Can you please shed some light on this?

Thanks.

After @Mattman944 suggestion, I have added resistive loads on the outputs. With a 10kΩ resistor between A and C and another 10kΩ resistor between C and B, all output voltage readings are near zero (AC, AB, CB).

The purpose of my original question was to understand the strange measurements I had with a broken primary. I did not think about adding a load on the output.

Thanks to @Transistor's answer, I was able to restore the transformer, something I originally did not expect to be able to do.


texts: Low-power "killswitch" until power reset

texts:
I have a specific design issue and do not know how to start. We have a supply of about 9-13 VDC, battery-powered. The circuit I'm looking for acts as a power switch for this supply voltage. By default, it should be closed. When a 3.3 V "kill" signal is asserted, however, the switch should sever the connection and latch this "killed" state until all power is removed (then at next turn-on it should be default closed again). It is critical that the power consumption in the "killed" state is as low as possible (ideally less than 10 µA).
My thought on this so far: I'm looking for a P-channel MOSFET to do the switching, with a large resistor pulldown on the gate (1 MOhm between G and GND). MOSFET S goes to power in, D goes to power out. I need some sort of low-power "latching" circuitry now that overrides the "default on" state, probably by using bipolar transistors (to ensure they don't accidentally fire on power up, i.e., driven by current not voltage). Once engaged, they would pull the G to S. But I do not know how start this, any hints?
Edit: I have put a draft of my idea in LTspice, but power consumption in the "killed" state is way too high, about 11 mA:


texts: Infrared Filtering from Laser Modules and Wattage Considerations

texts:
I have come across a project which used this Chinese laser module. Apparently from someone who worked with the mentioned laser, it emits IR light (noise) even though it's a green laser. While I was browsing for alternatives on Digikey, I have a hard time finding an alternative that has an IR filter built in to get rid of the noise. Here are my questions.

From your experiences working with the laser modules ordered from Digikey, have you encountered any issues with IR noise?
Should I be looking at lasers with similar wattage to ensure similar brightness?

Thanks in advance for your help!


texts: Why is RS422a more immune to electrical noise than RS232?

texts:
I have read that

  RS-422a cable uses a 20 mA current loop instead of voltage levels.
  This makes the systems more immune to electrical noise, so the cable
  can be up to 3000 feet long.

I do not understand why having a current loop will provide more protection against noise. Can someone please explain? Also, does that mean RS422a uses current to turn ON/OFF instead of voltages?


texts:
It's theoretical and stupid question.

In my example Master and Slaves have 8-bit shift registers. I can't understand how to receive data from second slave.

Is the below algorithm right?

Master lowers /SS signal.
Master writes 16 zero bits to MOSI (Slave 1 and Slave 2 will contain 8 zero bits,  data from Slave 2 will shift to Master).
Master have to high /SS signal.
Read received data from Master.

I was embarrassed that SPI is full duplex interface. I thought that Master must to send only valid data to slaves (not zero or trash).


texts: How do I scale a 0.5-4.5v signal to a 0-3.3v signal?

texts: I am trying to scale down the analog value of a pressure sensor to an analog value that my mcp3008 analog to digital converter can read. The pressure sensor outputs a voltage between 0.5v and 4.5v while the mcp3008 takes in analog signals between 0v and 3.3v. I have read about voltage dividers, but it seems to me that in this case that would be really imprecise. If I just divide the max voltage of 4.5 down to 3.3 aren't I losing a lot of resolution due to the range of the pressure sensor output starting at 0.5v?


texts: I am  understanding a rc network shown in the above image . I need to calculate the Value Vc after i give 24 volts step input for 16 μs. i used capacitor charging equations Vc=Vinput(1-e^-t/rc) equation for outer loop but how do i take inner loop into calculation. Laplace method  gives very  huge polynomial . Could you please tell me if i can use time domain equation to calculate the value of Vc ? i am stuck on this problem for last 2 days . Kindly Help me out folks .


texts: What does polarization mean in "polarized cap"?

texts:
Question emerged from my last question about small caps' markings, better to open new question so not become bloated.

Heard term polarization in the context of light but not with caps. Googling revealed the effect: Dipolar Polarization. Not sure whether it is the right effect but at least it mentions cap.

1. What does the term "polarized" mean?

2. Why should I use "polarized" cap instead of non-polarized cap?

3. Why does the circuit need a polarized cap? http://en.wikipedia.org/wiki/File:RC_Filter.png


texts: What does this overlapping ADC symbol in a block diagram mean?

texts:
I am wondering what multiple overlapped ADC symbols in a block diagram mean.

My best guess is that it either represents multiple channels but I am not sure and each of the datasheets that I have seen do not provide a clear answer as to what the meaning is.


texts: Arduino - Controlling 8 RGB LEDs (beginner question)

texts:
First time poster here.
I have an Arduino Uno project that will require 8 RGB LEDs to be controlled. They will be turned on and off with pushbuttons, cycling through red, then green, then blue, then turn off. Multiple LEDs will have to stay on together at times, too. It's going to be part of an electronic lock, so basically a keypad that, instead of having keys, has coloured LEDs as a password input. However I am not using a physical Arduino, I'm doing it in the 123D Circuits environment (made by AutoDesk), so I'm limited as to what parts I can use.
I ran across Charlieplexing and Multiplexing, as well as using transistors and shift registers, as possibilities.
The problem is that I haven't had any electronics classes yet, so I have no idea which is better/more suitable/even possible, specially regarding wiring the parts together, and how they communicate with my project, so that's what is making it difficult for me to understand, or even begin to code.
I followed this guide to try wiring 4 RGB LEDs.
However they're common anode LEDs, and mine are common cathode, and as I've said, I have no idea how to figure the electronics (I can't even read schematics without getting lost at what am I supposed to be reading there).
Here's how I tried wiring it: http://postimg.org/image/gu4cwdv0n/full/ following the guide's instructions.
(it may be absurdly difficult to see what is happening due to the awful graphic interface for wire jumpers in the platform there)
It didn't work with the code provided, so I assumed it's my wiring that is the problem.
EDIT -- I have 8 pins that can be used to those LEDs. Also, if there is no alternative to Charlieplexing, could someone explain or compare how it is different in RGB LEDs to normal LEDs? I believe I could understand it better that way, since I think this is what is troubling me: the common cathode, as opposed to 3 cathodes in 3 multi-coloured LEDs.
Thanks in advance.


texts: Issue on charging current while switching two power sources

texts:
The circuit is to switch the voltage for battery charging circuit and not allow the solar power to 'other load' circuitry.

The charge current is set to 1A where in this configuration it draws only 125mA. The diodes D1, D2, D3 are SS34A.
When removed D2 and applied supply voltage to solar source it works fine.
When I replace all the diodes to 1N4004, the circuit draw sufficient charge current.

As I have tried this simulation using SS34A and 1N4004, I get no issues but practically for which property of SS34A I'm getting the problem.


texts:
What are some ways to prevent hacking a circuit? Of course no circuit can be completely obfuscated. Here are some suggestions I've seen:

1) Scraping the serial numbers off of parts

2) Tainting the components with something? Black ink?

3) Are there any materials that would corrode circuitry when exposed to air?

The purpose of this would be to conceal a proprietary design from competitors.


texts: Determination of region of operation for pmos

texts: Given the value of Vgs, Vds and Id for a pmos, how to determine the mode of operation and its Vt


texts: Low-Pass Filter Selection and Placement in Active Noise Cancellation

texts:
This continues in the same vein as my previous question - I'm working on an Active Noise Cancellation circuit to get rid of highway noises in my bedroom.  Based off an ANC circuit pictured below, I intend to modify it in the following ways:

Replace the simple op-amp inverter with a phase controller

This will involve modifying the phase controller circuit to have an active range of 32-4096hz, discussed in the previous question linked above

Add in a low-pass filter

Some of the notes on the website where I found the circuit mention that it's not as effective above 1kHz, and I also recall reading about a hiss.  Accordingly, I want to be able to eliminate this in a controllable way - so I want a variable low pass filter.

Step 2 is where I'm stuck - I'm not sure on A) component selection (High C, low R?  High R, Low C?  Variable R? Variable C?... I mean, probably variable R, but still) and B) filter placement.

I have 3300pF capacitors on hand, so I calculated that 1MOhm potentiometer would give me a range from 48hz to as high as I want for the cutoff (I mean, I imagine 10kHz would be more than enough).  I was thinking of placing it immediately before the volume control (after the phase control) in my circuit, but I don't know how well that will line up with input characteristics of the op-amp I'm looking at using - or if there's a better place to put it?  For the op-amp, I'm considering NE5532 (the datasheet I found said it had an input resistance of 30kOhm (min) and 300kOhm (average)).

I guess my question(s) (is/are), then:

What should I use to judge the component value selection for this particular application?  I'm still new to audio, and while I understand some of the selection criteria I'm not sure how it applies.
Where should I place the filter?  Will immediately prior to the volume control work, or should I look elsewhere for better results?
Will my chosen op-amp work for this, or should I consider alternatives?

The diagrams I'm using are provided below, as well as links to where I found them.

ANC: https://web.archive.org/web/20110813221708/http://gilmore2.chem.northwestern.edu/projects/showfile.php?file=noise_prj.htm

Phase Control: (All-pass filter) https://sound-au.com/project103.htm


texts:
Finally bit the bullet and considered getting help with a simulation I'm looking to get right. Just a heads up, I have limited experience with SMPS simulation in both LTSpice and Multisim. The circuit I'm attempting to simulate is an interesting ZVS and ZCS flyback I found in an IEEE report. It utilizes a resonant clamp along with a half bridge voltage multiplier to achieve the zero voltage and current switching.

Here it is in multisim:

I first attempted to follow along with the report's calculations and use my own parameters for fun, but the waveforms looked nothing like the expected or tested waveforms they presented. I then went back and plugged in the component values listed in the report to try to get the correct waveforms with no success. Here's the theoretical waveforms for the primary side:
And here's what the simulation gave me:

The voltage waveform looks clipped because the IRF250 has a breakdown of 200V. Not intending to operate at this level. The characteristics of the transformer are 9:30 turns ratio, 22 uH magnetizing inductance, and a 2.4 uH leakage inductance if anyone's interested. The gates of S1 and S2 are driven by 15V signals opposite each other and at 60V a duty cycle of 40% gets it close to a 340V output (370W).
My question is, is there anything glaringly wrong with the simulation? If not, what could I be doing wrong?


texts: Value of FNOSC in the configuration of my code

texts:
I am using PIC24FJ64GA002 and I have configured my setting for PIC as following.

_CONFIG1( JTAGEN_OFF & GCP_OFF & GWRP_OFF & COE_OFF & FWDTEN_OFF & ICS_PGx3)
_CONFIG2( FCKSM_CSDCMD & OSCIOFNC_OFF & POSCMOD_HS & FNOSC_PRIPLL & I2C1SEL_SEC & IOL1WAY_OFF)

I would like to know how my FNOSC value is equal to 32 MHz and how I can change it to 8 MHz. My external oscillator is 8 MHz one.


texts:
I am trying to create an integrator op amp circuit for a lab, but Spice is not happy for some reason. The error message: "Analysis: Time step too small; time = 0.006, timestep = 1.25e-018: trouble with lmf1:qx-instance q:lmf1:1"
When I change the capacitance to 0.01uF (Which is not what the lab wants) it runs fine with no error.
Here is the screenshot of the schematic and waveforms:

I would greatly appreciate some help figuring out what's wrong


texts: What do engineers think about the application of control theory? Is it exaggerated? Is the math too overwhelming for real life application?


texts:
I have a question about proper grounding while measuring low voltage signals meaning how can the noise be minimized? The following schematic shows the setup:

simulate this circuit – Schematic created using CircuitLab

Short description:
A carrier signal is generated in an FPGA eval board, is sent to a connected DAC board which produces an analog signal which is then sent via a SMA connector to a PCB I'm designing. The PCB consists of some analog circuitry (mainly opamps) and generates a modulated signal which is sent back via SMA connector to an ADC connected to the FPGA.

The FPGA and ADC/DAC eval boards are connected to a separate power supply. I'm using an additional power supply for the analog circuit which is regulated by LDO's to provide a dual supply (+-5V) to power the opamps.

The frequency range for the analog circuit is about 0.5 - 1.5MHz.

The first problem is, that I'm creating a ground loop, don't I? Also, how can I separate the PGND and AGND? Or should I just use a common ground instead?
I'm using a 2-Layer PCB. Also, where should I connect the grounds? Can I just use the top layer for signal and power routing, fill the free space with ground and use the bottom layer as low impedance ground layer? If yes, where should these grounds be connected?

Also, how to route the power traces and signal traces? Do I have to care about that?

The goal is to minimize the noise coupled into the signal path.


texts: Confusion between Faraday's law and Kirchoff's circuit law

texts:
Consider a voltage source V connected to a coil. By Faraday's Law e=-(dƛ/dt). I don't understand the direction of the induced voltage e making v=-e

However, if we treat the coil as a circuit element and use Kirchoff's law, v-e=0(since v is seen as a voltage drop) so v=e

Can someone explain what am I missing out on between the two(more specifically Faraday's laws).


texts:
While trying to change the analog reference voltage in ATMEL Studio for ATSAMC21 I found no way to configure this in ATMEL start and in the higher level drivers.

So I searched around the ASF a bit and found, that this function is only implemented in the HRI drivers.

However the usage of these drivers is not well documented (or I don't find the right document).
The documentation gives these drivers just a general description, mostly on how the functions are named and what are available.

After some searching I found the HRI driver file HRI_SUPC_C21.h.
In it there are several functions for changing the VREF register such as

static inline void hri_supc_write_VREF_reg(const void *const hw, hri_supc_vref_reg_t data)
{
    SUPC_CRITICAL_SECTION_ENTER();
    ((Supc *)hw)->VREF.reg = data;
    SUPC_CRITICAL_SECTION_LEAVE();
}

What confuses me, and also what the documentation does not explain, is:

What is the "onst void *const hw" pointer?
When I call this function, what value do I use here?
If there is some initializing function for this "hw" how do I find this? (I'm asking in general, because most functions in the HRI driver files require this "hw" pointer
If it is some constant value or address, how do I find this?

As this question is kind of related to my other question, for good measure here the link ATSAMC21 - Change ADC reference voltage


texts: Best way to select a hall-effect sensor and a magnet that work well together

texts: What is the best way to select a hall-effect sensor and a magnet that will work well based on the constraints of a specific project? Say, I want the sensor to detect a relatively small magnet positioned at 1/3 of an inch, what are my options for which sensor and magnet to pick?


texts: Why does Intel's Haswell chip allow floating point multiplication to be twice as fast as addition?

texts:
I was reading this very interesting question on Stack Overflow:
Is integer multiplication really done at the same speed as addition on a modern CPU?
One of the comments said:

"It's worth nothing that on Haswell, the FP multiply throughput is
double that of FP add. That's because both ports 0 and 1 can be used
for multiply, but only port 1 can be used for addition. That said, you
can cheat with fused-multiply adds since both ports can do them."

Why is it that they would allow twice as many simultaneous multiplications compared to addition?