texts: How is it possible for voltage to exist when only a single voltage source terminal is connected?

texts:
Please take a moment to look over the circuti below:

As you can see, the circuit is nothing more than a 10 volt power supply and a diode. Note that the power supply negative terminal and the diode anode terminal are not connected to anything. Also note that a multimeter is connected across the diode with the purpose of measuring voltage.

Based on the circuit above, what voltage amount would you expect the multimeter to measure? Zero volts? Well, as it turns out, the multimeter actually measures around 850mv. This is puzzling to me because the circuit is not complete so no current should be flowing through the diode therefore the voltage drop on the diode should be zero right?

Could someone explain this phenomenon?

Thanks.

EDIT:

Per user request, here is a picture of the setup:


texts: Power Mosfet Information Mismatch: On Region Characteristics vs Total Charge Graphs

texts:
I'm dealing with Power N-Chanel Mosfets and, while looking at the data sheet of several units, I noticed that the information about the On-Region (\$ I_{D}\$ vs \$ V_{DS}\$) and the Gate Charge (\$ V_{GS}\$ vs \$ Q_{G}\$) does not match. Before going any further I think it would be useful to mention the assumptions I'm making while interpreting this data:

The Gate Charge graph is obtained by supplying constant current to the DUT while switching (see section 2 in this app note from IR or figure 13 in this data sheet from ST).
The constant current switching operation is done in 4 steps. First, \$ V_{GS}\$ rises until the threshold voltage is reached. Then \$ I_{D}\$ starts rising until the current set by the constant current source is reached (the Plateau begins). Thirdly, \$ V_{DS}\$ decreases until the device enters the Ohmic region (Plateau ends). Finally, \$ V_{GS}\$ keeps rising until the final value is reached.
All the graphs in the data sheets are given for the same Junction Temperature values.

The point of conflict is that, in the Gate Charge graph, the Plateau voltage for the given test conditions (i.e. \$ V_{DS}\$ and \$ I_{D}\$) is frequently much higher than the one you would deduce using the On-Region characteristic. Here are a couple of examples:

On Semiconductor NTMFS5C426N:

The Gate Charge graph shows that, for an \$ I_{D}\$ of 50A the Plateau \$ V_{GS}\$ is 4.74V. The \$ V_{DS}\$ at this point should be very close to 20V.

Checking the On-Region graph shows that for, the same \$ V_{DS}\$ and \$ V_{GS}\$ values, the \$ I_{D}\$ should be clearly higher than 160A.

It is my understanding that these figures should match. I would highly appreciate if you could help me understand why this is not the case. I have tried contacting the manufacturers but so far none has replied.

This behavior can also be seen on further Mosfets. I won't put the images in here but here are the links to their data sheets if you are interested in checking them out:

On Semiconductor NTD5805N
ST STL260N4F7

This is not always the case, there are some devices where the values match:

Infineon IPLU300N04S4


texts:
So I'm reading through the Tab Electronics Guide to Understanding Electricity and Electronics, and I'm literally at the first few pages of the introduction and he mentions electronics databooks.
The author describes them as such:

The manufacturers and distributors of electronic components publish data books, containing cross-referencing information and individual component specifications. A few examples of such books are NTE Semiconductors, The GE Semiconductor Replacement Guide, and SK Replacement Cross-Reference Dictionary.
Your first project in the field of electronics is to obtain all all of the electronics data books that you can get your hands on ... They are that essential.

After reading the whole section on this (about ~3 pages), I still don't really understand what they are, and why / if I need them.
Also, this book has a 2000 copyright... has anything changed (e.g., have these things gotten digitized and become free?)


texts: Step up SMPS with unrealistic voltage output with a 100W LED COB load

texts:
I got some 100W LEDs to make a lamp, realized with a boost converter I could use an old ATX power supply and bingo I'd be fine.

It worked at first, until I didn't like the color so I decided to order a full spectrum LED, it turns out to be purpleish in color but looked great when mixed with the white light.

The specs on the purple LED said 30-36V, 3.5A, so I gathered if I went with 36V @ 2.7A, I'd probably be Okay(higher voltages provide better lumen per watt efficiency), but I went with 30V anyway, just to be safe because my meter can't exceed 2A. I

The boost converter failed on the purple light, I did notice that the converter was getting kind of hot on the MOSFET side so I replace the boost converter and add a fan, that worked for about 2 weeks and the MOSFET dies again on the purple light.

That got me angry and I started researching boost converters and how they're made, thinking maybe I could just replace the MOSFETs. After killing a dozen or so MOSFETs, I decided to make my own boost converter. I ended up having the same hot MOSFET and voltage drop issue( I forgot to mention there was always a voltage drop over the purple LED on any boost converter I attached it to).

Through experimentation I find I get a better voltage output if I attach the legs of the diode to either side of the inductor, but still not getting the output I want and a very hot MOSFET, so I remember the autotransformer and think eureka and came up with this

EDIT: This is actually an Update of the original schematic that worked quite well once I added the MOSFET driver. However there should be a shunt resistor between the source pin and ground to measure MOSFET current and a comparator with a reference voltage at one input with the secondary comparator input tied to the source, to shut down the oscillator once the desired current has been achieved to avoid inductor saturation as well as the destruction of the MOSFET. This was a cool, basic, (yet can be DANGEROUS) experiment to see how a boost converter operates, but there should have been be a bit more regulation implemented.

At this point, I wouldn't design such a simple circuit to power a load of any real value. Though it did operate well for months as a desk lamp until I retired it.

No more nasty voltage drops, MOSFET stays a lot cooler loaded with a white LED it came up at 35V (32.3V on purple), but wasn't so bright, so I turned it up and it got brighter, but it was running at 37V.

It seems I was getting the opposite of a voltage drop? I replaced the MOSFET for one better suited for the job STP80NF70, that one let me go as high as 45V with a 60% duty cycle. I like the MOSFET, decide to test it with a 20N60S5.

I went with the auto-transformer because I figured if I was only charging a portion of the inductor during the on cycle I could send some of that stored energy in the other direction, and what is a boost converter really? If you add a secondary winding attach the diodes there and its a flyback supply. So I figured Id make a step up auto-transformer flyback.

At 50% I get a semi dim light at 33V but when I turn up the duty cycle marginally, the light gets extremely bright and I get a reading of 150-180V this freaks me out. The light is extremely bright, the crappy heatsink on it isn't getting hot at all, but the MOSFET gets hot. that mosfet can handle 20A I have a 10A breaker switch on the line, so what gives? why the freaky voltage and the hot mosfet?

One more Question, how do I stop the thing from literally desoldering connection from the drain pin and killing the FET when there's no load?


texts: Does a PC need pure sine wave? Need to test using 1000W, 120VAC 60HZ input, 240VAC 50HZ output

texts:
I need an OTS (Off The Shelf) solution to test PCs before they ship to Europe and beyond. I need to provide up to 1000W of 240vDC 50Hz power from a 120vAC 60Hz outlet, because I want to make sure the (not Brand X, but from quality manufacturers) off-the-shelf PC power supplies which are specified to work with both 120vAC@50Hz and 240vAC@50Hz we build into the PCs behave OK with EU current.

Specific power supplies which come back with customer complaints of noise or other bad behavior will be tested. The power supplies in question will be tested outside of a PC with an artificial load, and then tested in a open chassis before going into a PC chassis of the type used by the customer.

Why? We've gotten complaints of power supply buzzing and crackling noise from our customers which we want to resolve expeditiously.

What are your thoughts about a 120VAC to 12VDC converter wired to a 12VDC to 240VAC power supply, both rated to handle 1000W or more?

Does a PC need a pure sine wave, or is a 'modified' sine wave adequate?


texts:
Is it possible to use a Smartphone audio jack as MIDI output?
My plan is to use a standard TRS to MIDI cable, like the one Arturias Beatstep uses, to connect a Smartphone/Tablet to a MIDI device.
I want to make a step-sequencing software that uses as simple of a connection as possible.
As far as I've read, MIDI needs to hold 5V, and I'm not sure if that's even possible to do.
I also don't know about AC or DC. I'm assuming though that MIDI is using DC, while the audio output uses AC? I might be wrong on that, but that would completely negate my plan in any case.
For devices that use USB-C, I don't know if I can do something with that. Probably only with audio as well, but might have the same problems as the TRS version.


texts: How much clearance through air is required for 10 kV DC?

texts: Suppose I have two uninsulated connectors with 10 kV DC between them. How much clearance through air should I have between those connectors? What table is this found in?


texts: Disconnecting the load from a synchronous generator

texts: How is the terminal voltage of a synchronous generator affected when we disconnect the load ?


texts: Zero Voltage in a power semiconductor chip

texts:
In an ON-mode silicon IGBT chip operating within a real power module, is the collector contact fixed at 0 V or emitter?
What about Power SiC MOSFET?
enter link description here


texts: Is it possible (with reasonable effort) to use ethernet hardware to provide point-to-point digital I/O bridge?

texts:
I'm interested in designing a "simple" circuit that would bridge digital inputs or outputs over a distance with relatively low latency. The idea is to take several pins from a GPIO bus like Arduino or Raspberry Pi and reproduce their status remotely - let's say 8-bits in each direction, rather than freely configurable, and up to 30m distance and shoot for <1us latency (ideally no overhead that could cause non-deterministic behavior).
I like the idea of trying to leverage ethernet hardware to provide decent noise immunity, cheap standard cabling, and the possibility of providing remote power. The devices I find (and older questions on stack exchange) seem to always circle back to a fairly complex packet exchange and highly integrated ICs (or is that "highly ICs"). Most industrial solutions (e.g. Modbus or profinet) also stick to the packet model. I'd be happy to just use a clock and some 74-series shift registers, etc. to generate a serial train and decode it on the other end - just wondering if there's a "middle-bit" that would manage the level shifting and signal processing without getting into all the more complex ethernet layers (I suppose there may be some clock recovery - although I'd be happy to use part of the cable for a clock signal, or force the serial speed to be a standard ethernet speed and a start/stop bit if needed). I don't care about running through standard ethernet hardware (switches, etc. - those would all tend to introduce significant latencies), but would like to preserve the magnetics to obtain better isolation and power injection.
Thanks for any suggestions or references to existing hardware solutions or perhaps better suited protocols.


texts: I have grip warmers on a bike.  basically just heat tape.  I would like to reduce the supply voltage from lithium battery from 18 vdc to 12 vdc.  My goal is to reduce warmer element temperature and increase battery life.  What is the simplest way to do this?   thanks!


texts: Why would a BMS (or other circuit) have reduced voltage after a short?

texts:
I have this 9Ah 42v battery pack protected by a BMS wrapped in a shrink which I would rather not disassemble (so I don't currently have access to BMS' circuit). It has two wires for charging, and two for load. Both showed 42v.

I then accidentally shorted the ones for charging for a moment (my probe melted instantly). After this incident it showed 37v. But the load wires still had 42v.

Now BMS's job is to protect battery from such occurrences. If it had a fuse, I assume it would blow thus breaking the circuit and showing 0 volts. Which must mean it doesn't have a fuse.

The battery must be okay since it still has its voltage. And its voltage reaches the charging wires in some way. But how can it change from full 42v to mere 37v? Did it have a resistor which momentarily burned thus increasing its resistance and therefore voltage drop on itself?


texts:
Hi I would like to fit a (motion sensor/IR sensor) sensor switch to a machine in my catering van. The machine is a 12v machine.
I would like to start the machine using the sensor switch and would like to work for 60 seconds. Once 60 seconds have passed, I’d like it to turn off.
however, it gets a little more complicated,I would only like it to turn off, if there is no power going to compressor (again 12v). If the compressor is getting power, I’d like to leave the machine on.
so once the sensor switch start, the machine would turn on:
it should only turn off if 60 seconds have passed and the compressors is NOT getting power.
If the compressor is getting power, the machine should stay on, until it (the compressor) stops getting power.
....And it gets more complicated...
Above a certain temperature inside the machine, I would like it turn back on, the compressor will automatically kick back in.
Any ideas, and knowledge in how to set this up will be much appreciated. Ideally it will be a reliable system and have minimal circuit boards as I need something that’s I can rely on and will work in hot weather.
I will also have a bypass switch so I can control the power to the machine and compressor manually.(This is how I currently control the machine.)


texts: What device should I buy to cool liquids in a container

texts:
Basically I have a large Evaporative Cooler (one of those fans that you can put water in the bottom of). It has a really large container so it can last a day or two. The problem is once the water gets hot its doesn't work as effectively.

I was wondering if there's some type of cooling element I can purchse that could be rigged up in the water? I'm just not sure what I should be Googling for, does something like this exist?

Using a  commercial refrigerator would be too big and too expensive.
Is their some form of electronic device which can be used to apply refrigeration or cooling to reduce the water temperature, and how well would this work ?


texts: I am writing an essay about LCDs. None of the websites I've used mention anything about the dates and eras that newer technologies were used in LCDs, so wondering, does anyone know whether TFT is still being used in LCDs these days?


texts:
I have seen that most of RF printed board circuits have a GND plane which is connected to the power supply ground terminal and serves as a return path for current from different components on the board.
Something like this:

What I have seen in many datasheet is also that this plane is assumed as reference potential for the output ports and indicated with the symbol:

like the classical GND terminal of an Op - Amp or other simple circuit.
What I do not understand is: How can be this plane represented by a single node?
How can it be a reference voltage?
At high frequencies it is a transmission line, so its voltage will have some spatial oscillation, so it will not have a constant voltage. How can it be considered a reference potential for output ports?


texts: How can I achieve cm accuracy for x,y,z outdoors positioning

texts:
How can I achieve cm or less accuracy for x,y,z outdoor positioning contained inside a 100 meter cube (bigger the better but this is minimum). I do not care if I need external beacons/sensors or internal beacons/sensors I just want accuracy.

I suggested 100m cube to make the problem hopefully easier to solve. I can place beacons etc inside the cube.

Any ideas?

Thanks!


texts:
TL;DR: Go to the bulleted list below.

As a weekend project I tried to design a simple power supply (without sofisticated switching mode ICs, since they are very hard to find where I live). So after some calculation and study, I came up with the following circuit, it is supposed to be a 7V 4A power supply for small projects, enough to power some microncontrollers (5/3.3V 100mA), small DC motors (5V 1A), and charge a li-ion battery :

I am aware of the nonidealities of these components, so extreme precision is not a important role here, since I don't intend to replace my good ol' bench supply. I will wire a digital voltmeter/ammeter to the output for calibration.

That said, I would like to ask some questions:

About the resistors R3 and R6, is it correct to pull up a MOSFET gate for such operations? Should I pull it down instead? Or remove the resistors? I am concerned about LM324 output sink/source capabilities with those resistors.
Also, in my output circuit, should I add other components to improve safety and stability?
And last but not least: is it safe to charge a li-ion battery with this circuit? (Considering a 2200mAh battery, with 4.2V max voltage) If not, how could I improve this circuit to achieve this?

Any help/advice will be very apprecieated!

Datasheets:

IRF540 - https://www.vishay.com/docs/91021/91021.pdf

LM324 - http://www.ti.com/lit/ds/snosc16d/snosc16d.pdf

1N4732A & 1N4737A - http://pdf.datasheetcatalog.com/datasheet_pdf/bkc-international-electronics/1N4728_to_1N973B-1.pdf


texts: Microcontroller timers and their applications

texts:
Hi I wish to understand more about the timers of the micro-controller(AVR) because I find it difficult to basically understand them. So what I am really asking is that: a)when you try to control for example, a stepper motor(unipolar) speed, how do you set the timers in order for the MCU to generate output pulses and change the pulse speed of the pulses in order to turn the stepper motor at different speeds? b) Is there any other algorithm which can be used beside timers?

Thank you.


texts: Why are contacts missing on some of these M.2 modules?

texts:
I want to replace a preinstalled Qualcomm Atheros WiFi/Bluetooth M.2 2230 card on my motherboard (ASUS Maximus VIII Impact) with another that has better driver support. This is what the card I want to replace looks like.

As you can see, its edge connector has all of its contacts. I want to swap this card with an Intel 8265 M.2 2230 card that looks like this.

But this card seems to be missing contacts. Here's another card from Intel with model number 7260 that is missing the same contacts on the edge connector.

Both of these cards have fewer contacts. Why do these cards have fewer contacts than the preinstalled card and will this cause problems when I swap the old one out for the new one?


texts:
Given the truth table for a 3-input XOR, how come the output is 1 when all inputs are 1? This doesn't logically extend from a 2-input XOR where output is 0 when all inputs are 1. Is there a way to understand this intuitively, or do we need kmaps etc?

xor http://www.electronicshub.org/wp-content/uploads/2015/07/3-IP-TRUTH-TABLE2.jpg


texts: (schematic) Using a micro controller to drive Opto-coupler > 555 timer > MOSFET

texts:
I'm trying to use a micro-controller to activate an opto-coupler connected to 555 timer which is connected to a MOSFET. The circuit will drive a solenoid which draws 2amps at 12v. I'm new to circuit design but have combined a few schematics I have found to come up with the one below. I think I have some resistor values wrong, and I'm unsure if the 555 can drive the MOSFET directly???

5ms pulse fom micro converted to .5 second pulse by monostable 555

R1 470 ohm 1/4 watt) (R2 2.2k 1/4 watt)  (R3 470 ohm 1/4 watt)  (R4 45k 1/4 watt)   (R5 2.2k 1/4 watt(Micro controller to opto =5v)
(555timer, MOSFET, Solenoid =12v)

(MOSFET=1PP096N03L) (555= TLC555) (opto=PC817)

IPP096N03L
Solenoid is 130ft. of 30AWG magnet wire. 13.4 Ohms

The solenoid in this circuit is coupled with another solenoid, connected to an identical circuit as this one, except their polarity is reversed. So one circuit magnetizes the core in one direction and the other circuit magnetizes it in the reverse. Since they are coupled, one circuit will create current in the other right? Does that cause any problems, or will it be shunted by the diode (BY229)?

Another thing I was thinking about is having an H bridge connected to the 555 and using the same solenoid, instead of having two. I'm trying to keep the cost down as I need a number of these circuits, and an H bridge design seems to be more expensive from what I can find. Thanks


texts: I was wondering what the output of capturing flop looks like, if there is a hold time violation from capture flop. Can anyone explain with a timing diagram?


texts: RS485 transceiver supplied with 3.3V. What voltages can I receive?

texts:
I'm designing a print for RS485 with the LTC2854 transceiver, but I don't know in what exact situation it will be placed in. So I don't know what voltage levels the other devices will communicate on. I will supply the transceiver with 3.3V and communicate on 0V and +3.3V.

Does this mean I can still receive the full range of voltages -7V - +12V of other devices on the bus? Or does this mean that it can only be implemented on 0V - +3.3V level systems?

In my understanding I should be able to detect difference between a zero and one, as long as the difference a-b of the transceiver is at least +/- 200mV. I won't be using biasing and the termination resistor can be turned on or off with LTC2854. Could you explain if my understanding is correct?


texts: Circuit Analysis Schematics Conventions in Voltage Divider

texts:
I have searched high and low for a diagram similar to this in order to help me understand what little I do know (in an intro college electronics course) but I cannot find anyway to understand this. So am hoping I can find some help.
Everywhere I search for an answer or guide I get nice, beautiful complete circuits (A nice obvious loop so I know how to follow along with Ohm's Law, KCL, KVL, Voltage Divider equation, etc. (Like this, this, this, etc)
The actual assignment question is different than this - but if I can understand what is happening here than I will be able to proceed. I just can't follow because I don't know what is implied here?
What I've been told is that Va and Vb are not ground, and for my purposes I need to know what is happening at Vo.
I know in this case that Va and Vb are 'sources' - so they are 'pushing' 'towards' each other and 'meeting in the middle' (that is my description of it, since I'm new to this thats best way I can describe it)

So my intuition tells me that since Va and Vb are in opposite directions, that theres something like a Va - Vb going on here. I'd love to use KVL but this doesn't look like a loop to me - so no idea what can do. Because it also don't look like a loop, I don't know what the current would be. It seems intuitively wrong to have two currents (in my head it seems like there would be a current from Va across R1 and a current from Vb across R2 - and in the middle they'd "meet" - but that doesn't make sense (I still see current using Ohms law as \$\frac{V}{R1+R2}\$, but there are two sources here so no idea whats really going on.
Basically am lost on what this diagram means, and I'm sure it must be valid (it's not a trick question - idea is to find Vo) - but I just don't know what to make of it since every other example has a nice complete circuit. This thing must be like a complete circuit in some way? Like closed in some way? There must be something happening between Va and Vb implied?


texts: Are analog planes necessary for my circuit?

texts:
I'm working on a Raspberry Compute Module 4 carrier PCB with an USB 3.0 controller.
This controller (TUSB7320) needs 3.3V supply and 3.3V analog supply.
Is it necessary to add an analog ground? This would be annoying because the place of the inputs.


texts: Is it safe to control a DC motor's RPM with rapidly turning on/off?

texts: Would it safe (no overheating or equipment damage) to control a DC motor (gear head in particular) by rapidly turning it on and off? For example, if I have a 500 RPM motor and I was 250 RPM, could I turn it on for 1 ms then off for 1 ms, repeat? If possible, this would be a cheaper alternative to roughly controlling non-stepping motor RPMs than controlling voltage.


texts:
I am getting a synthesis error when reading this line of code:
a <= '1' when x > y else '0';
b <= c when a = '1' else B"000";

The error is:
   xxx:    b <= c when a = '1' else B"000";
                       ^
[Error] Read error: trying to read port of mode OUT

a is the read port.  How can I avoid reading a and still accomplishing what I need ?


texts: I'm trying to heat up a steel wire of d=0.05mm with a specific current. The length of the wire is about 5cm. By measuring the voltage over the wire, how can I find the temperature?


texts: Calculating the Gain in an Amplifier circuit

texts:
Having some issues calculating the gain in circuit below, it is apparently 1802, but I can't seem to arrive at this answer. If anyone could help explain how to get this answer I'd be very appreciative!

Edit: My Working


texts: Effect of the horizontal magnifier control on the sweep speed, sweep time and number of cycles observed?

texts:
What is the effect of the horizontal magnifier control on the sweep speed, sweep time and number of cycles observed?

Sweep speed increases by ten times for a 10X magnifier, sweep time reduces by the same and the number of cycles observed will be more.

Is that right?


texts: Can I use Eclipse CDT to debug a PIC18 using PICkit3?

texts:
I'm curious and interested in buying a PIC18 micro and a PICkit3 to do some programming on a breadboard, to learn a bit. I like using Eclipse CDT for C development quite a bit.

Is it possible to use Eclipse rather than MPLab X, the Netbeans version?


texts: Why are there so many signal grounds for PCI Express?

texts:
PCIe connections have one to two ground contacts per differential signal pair.  Why is this the case?

On the boards that I have been studying, all of these pins are tied together onto the same ground plane on the board (at least as far as I can tell), so does it really make a difference?  They should all be at essentially the same potential, right?

Are there just ground pins interleaved with the signal pairs in order to absorb any potential crosstalk between adjacent pairs?  If this is the case, why are you supposed to remove any (internal) ground plane in the contact area?


texts: What is the relationship between a step input and an integrator?

texts:
While trying to understand control engineering from first principles I came across the following which I cannot yet explain intuitively or mathematically.

What is the relationship, between a step input and an integrator?

Why are they identical to each other?

I kept on seeing \$1/s\$ being used to both represent a step input and an integrator.

The Laplace transform of the unit-step function is \$1/s\$.
An integrator symbol is also \$1/s\$.

Step Function:

Integrator Block:

Multiplication by s in Frequency (Laplace) domain is differentiation in time.

Dividing by s in Frequency (Laplace) domain is equivalent to integration in time.

Is a step input equivalent to integrating in the time domain, or is it purely coincidental that they both have a spectrum that falls as frequency increases?

Why the Laplace transform of the integral is 1/s?

\$\int\$ in Time Domain = \$ 1/s\$ in Freq Domain

AND

\$\mathscr{L} \{1/s\} = 1\$

EDIT:

If I am understanding the answers correctly, there is not relationship between a step INPUT and an integrator, but there is a relationship between a step FUNCTION and integrator, as explained below.


texts: What determines the frequency of the oscillator?

texts: I want to understand what determines the frequency of this ring oscillator and how to lower the frequency.


texts:
I am was wondering if an IC like the PCA9685(Datasheet) that generates PWM signals can be used in a PID controller for controlling a heated bed on a 3D printer.

My understanding of PWM is that it will be to fast for a normal relay but that it might work with a Solid State relay.

Even if it can bring down the number of times I have to check the Temperature it would be useful.


texts: Saturated Transimpedance Amplifier Issue

texts:
I am using a transimpedance amplifier with a BP104 Silicon PIN photodiode to receive incoming pulses from an infrared LED with a frequency around 100 kHz. Here is the relevant part of my schematic:

I have not included specific values for the feedback network, as it occurs for all values I have tested. Now here is the issue: this receiver only works beyond a certain distance between the transmitting LED and the photodiode; this distance is dependent on the gain, which is the value of the feedback resistor. If I have it too close to the IR LED then the output just saturates to my supply voltage (+10V). Any ideas on why this this happening? I know that it is not simply the capacitor charging up, as it also occurs without that. My best guess is that when I have the LED too close I am generating too much current, which is trying to pull up the output voltage beyond its maximum limit, thus causing it to rail and affecting it internally. I am having trouble convincing myself of this though, because my transmission is a 50% duty cycle square wave, so during half of the period there is no signal at all, and yet the output continues to hold at a steady +10V. Is such an intense amount of irradiation on the photodiode causing a current to persist through the LOW portions of the signal? This it the first time that I am using a transimpedance amplifier in a serious application, so this may be obvious. Many thanks in advance for any insight or tips.

Edit: Here is a plot showing the resistance values that I have tested. More specifically, it shows my maximum transmitted distance vs. the resistance value (gain). The blue curve is my theory prediction, and the red points are my data.


texts: How to export the milling layer properly with Eagle 8.0?

texts:
I've got one of those jack power plugs with the thin rectangular pins on one of my PCBs.

The milling layer in Eagle shows the "slits" to be drilled as expected (in cyan).

I export the .drd and .mil files with excellon.cam and gerb274x-mill-drill.cam respectively (job files). However when I upload my gerbers to Eurocircuits, the "PCB Visualiser" thing does not display the slits but only the dot holes.

How can I make sure Eurocircuits got the right information? Using a gerber viewer on my computer I do see the slits from the .mil file.


texts:
While learning the Lumped Circuit Abstraction (and the Lumped elements discipline), an inductor was considered a lumped element. But I fail to see how it fits the requirements of LCA:

For it, the \$\frac{d\phi}{dt}\$ is not zero.
In a circuit with an inductor, (in AC supply), resistances would not be the only irreversible energy loss, owing to the inductor's em waves.

Although there are various ways to put in the restrictions after which LCA is rendered valid, but these two requirements are commonly cited.


texts: Driving a flyback with pure AC sine wave

texts:
I am quite confused about flyback drivers. I have a high frequency (up to 50 kHz) AC sine wave generator, and I would like to use it to generate some arcs on a flyback. So I thought I could just wind a primary coil around the flyback core and get some arcs between the secondaries. Is that correct? Do I need to rectify my generator output?

P.S.: If my generator couldn't be used for this project, I will build the Mazzilli ZVS flyback driver.

Any help would be appreciated :).

My flyback is the same from the picture below.


texts: Loadcell strain gauge with 10 V excitation

texts:
I am designing loadcell (spec) measuring using 24-bit adc (MCP3561) with excitation 10 V. But I couldn't find the reference design for 6-wire loadcell that its sense pins connect to ref+ pin of ADC. Most design usually use excitation 5 V.

What I am trying to accomplish here is to still use 10 V excitation and still compensate excitation voltage drop with both sense pins of loadcell.

If I use voltage divider for put down voltage to 1.2 V (according to the spec of MCP3561). I am not sure if this is going to work due to the resistance might change.

If there is a better solution, please let me know.

I have added the reference design that I find here

As you can see the sense+ and sense- pin is connected to excitation voltage and Ref pin of ADC.

So when the excit. voltage drop due to the loadcell your measurement value is compensated.

This is actually work when your excit. voltage is 5V or 3.3V. But mine is 10V. ADC ref pin can receive only AVDD max, which is 5V.


texts: Why does a buffer op-amp need two feedback paths?

texts:
I am designing a linear voltage source. I have a precision volatge reference (REF5050 by TI), and before I do anything with its output I buffer it. However, the datasheet of the amplifier I use (OPA197) suggests the following:

This brings up the question - why are there 2 feedback paths and why is the isolation resistance needed? A unity gain opamp should have only 1 feedback path, as I understand.

Thanks in advance!


texts:
I found below schematic from LTC1150 datasheet (PG11) I want know what is the purpose of 10R resistor to ground.

when I add this resistor to my circuit it reduce the noise (or peaks).how?

After some research I found Out they call this t network   base on this website

but how this help the noise


texts: Do LEDs Need UVLOs (Undervoltage-Lockouts)?

texts: I'm currently working on a project involving (I think 3mm, 1.5VDC) Infrared LEDs. However, due to my photoresistor, I think the current, voltage, or whatever (forgot) will vary greatly to minuscule amounts. So, do these LEDs need UVLOs? They are very, very sensitive and I've already wasted half the pack.


texts:
Since an 8-bit MCU can't read the whole 16-bit timer in one cycle, this creates a race condition where the low-word can roll over between reads.  Does the community have a preferred method of avoiding these race conditions?  I'm currently considering stopping the timer during reads, but I'd like to know if there's a more elegant solution.

FYI, this is for a PIC16F690.


texts: Direct coupling Biasing of Two stage amp

texts:
General question. I see a lot of two stage amplifiers with a diff pair input and a cs second stage. In IC design these two stages are always directly coupled ie. the dc bias of the second stage is fed directly from the output of the first.

The question is then how does one properly bias the second stage? The usual method of having a current mirror acting as a current source works great at typical; however over PVT either the CS fet or the mirror fet will go into the triode region.

I see it as a two high impedance sources fighting each other. Is there a way to get around this?

Edit: For instance M8 and M7. M8 is the input device to the second stage and M7 is the mirror biased transistor.


texts: Is it possible to drive 120 solenoids from 120 outputs of shift register 74HC595?

texts: I want to drive 120 solenoids from 120 shift register outputs. I am driving solenoid by using TIP120 Transistor. When i connect all the solenoids Shift register circuitry heating.


texts: Choosing capacitors for a full swing oscillator and an ATmega328P

texts:
I am relatively new to embedded electrical engineering. Iam attempting to rebuild the Arduino Uno PCB for learning. I am familiar with the Pierce oscillator and LC circuits and some of the math around them.
I noticed on the ATmega328P datasheet that while the Arduino uses a low power crystal oscillator (as shown), to get a more robust clock signal you can use a full swing oscillator

I found the following 16MHz full swing oscillator.
The ATmega328P datasheet suggests that 22pF caps should be used:

It is not clear to me how (if at all) capacitors would be applied. The full swing oscillator data-sheet states that it has a maximum output load of 15pF, however I am unsure how this works into the problem.
Below is a tentative attempt at how one might connect the components. What is the correct configuration and why?


texts: What are some causes of amp clipping aside from those related to exceeding the rail voltage

texts:
I often encounter problems where an amp may exhibit clipping despite the input signal being well below the rail voltage. I understand that there are numerous problems that cause this.

However, what are the some common reasons as to why such clipping may occur? I am not looking for specific circuit designs but rather mistakes/problems such as inputting a signal that exceeds the common mode range.


texts: Where is the official RS-232 specification?

texts: Searching with Google returned only 3rd party documents (i.e. from chip vendors or university lectures). Is there a main document of such specification, similar to USB?


texts:
I designed a current limiter in a sim and it works perfectly in the real world. It gives me an output of 0-5v for 0-50 amps in one direction.

The problem however is that as soon as the direction of the controller is changed, the voltages goes much higher in the other direction.
So the op amp doesn't match both ways if I've made it clear?

I've included my circuit below. I am a little stumped as to what do really do... I could always make it so that the limit output voltage are matched to the higher side, but then as soon as the direction is changed again the readings will be too low on the lower side.

So the reading from one direction of the h-bridge is 5v at 50A which is perfect, but then if the direction of the h-bridge is changed the voltage at the output of the op-amp is 5v at only 10A.

Any help is appreciated!

I've abandoned this project as it's flawed by induction issues


texts:
I have a PCB from a control box for a machine. It's conmected to the machine via a DB25 cable, and gets power over the cable. How can I identify the power and ground pins on the cable?

If it helps, here are pictures of the DB25 connection on the PCB: back front.


texts:
I'm using an Atmega328P running at 16Mhz (similar to an Arduino UNO). to control a 433Mhz Superheterodyne RF receiver (WL101-541) and two TowerPro SG90 analog servos.

Everything is working except for the situation I describe here.  In the event a servo is under a load, such that it is remaining active trying to hold position, RF cannot be received.  I believe that the motor activity is causing some sort of interference.  I have been unable to track it down or work around it and am looking for ideas.

Some details:

A single switching power regulator capable of 3A (far more than is
being used).
Power and ground split at the power regulator with one
path going to and from the servos, and another going to and from the
MCU and RF receiver.  My understanding is that this will minimize
any ground loops.
The servos currently reside behind 3 220uF capacitors to handle startup current needs (There are 3 because I had no larger ones available).
I have tried a variety of other capacitors across the    serve power and ground to try to filter any feedback to no effect.
I    have tried twisting the servo cable.  This had no effect.
I have    tried placing Ferrite around
the servo cable (both straight through    and 3 loops).  This had no
effect.

I'm not sure how to proceed identifying the issue or fixing it.  Thanks.

Update: 1/23/18:

Running with the theme that it is likely the power, here are some additional findings.

The issue does not occur when powering with 5V from my Tekpower
TP3005T variable linear power supply.
Issue does occur when powering
with a L7805CV Voltage Regulator to supply the 5V
with 10uF capacitors on both the input and output lines.
Issue does occur when powering using an LM2596 based buck converter.
I need to confirm this again, but I believe the issue occurs using the L7805CV and LM2596 whether they are powered using a battery or the Tekpower.
Using two L7805CV regulators, one to the receiver and another to the servos, from the same power source appears to greatly reduce, if not resolve the issue.


texts: I am making a Halloween costume for my son and it needs some light. Basically he's a character from the Mario Bros universe that carries a traffic light on a fishing pole (Lakitu in Mario Kart). I am trying to figure out a way to light the traffic lights red, green, and yellow lights using leds in a single circuit that would turn them on and off independently. Just something simple that goes red, then yellow, then green, then back to red over and over. Is there something to build or a circuit diagram? I really have never done any wiring like this ever, so the easier the better. Thanks for your help.


texts:
I am a developer using languages like C++ and .NET.  I am trying to understand how computers work at a lower level.

Say I have a hard disk that is 7400RPM and 150MB read/write speed.  My book implies that these measurements are independent of each other e.g. you can have a hard disk that is 5200RPM and 150MB read/write speed as well.

Are these measurements independent of each other? What physical factors determine the read/write speed? e.g. bus width?


texts: How to isolate a PCB circuit from a high noise source in the nearby

texts:
I am designing a circuit that will sense an electric fence shock generator.

In my first prototype, it worked very well, except in the time the shock generator creates a spark, when it produces a lot of interference in my sense circuit. It seems to me that the wires that connect my circuit with the generator are carrying a lot of noise inside my PCB and I am looking for advices for how to reduce it. More details about my circuit below:

Schematic

simulate this circuit – Schematic created using CircuitLab

Real picture:

The PCB has two pairs of wire connections: The power supply, a 12V sourced by the shock generator circuit and the wires that came from the electric fence, with are connected to an optocoupler.

The signal generated by the optocoupler is processed by a digital circuit, which is experiencing a lot of false clocks and triggering in the moment a spark is generated in the fence.

I tried to start an investigation about what was happening and I almost concluded that the noise has been carried by the wires, because I put a scope probe with both terminals shorted together in the nearby of the wires and I found this:

I have repeated this test far away from the wires, but I did not obtained this results.

The image below is the noise in a track which work as a clock in the digital block:

As the image above indicates, the circuit has a lot of false clock that are may causing the erros I have mentioned. However, I feel I can not trust 100% in my scope in such high frequency. As a counter test, I tried to watch the voltage in the supply pins of the microcontroller of the shock generator (this part is working very well) and I obtained the following image:

If this was the real voltage across the supply pins of the microcontroller, I think it would burn in less than one second, as its maximum voltage was 5.5V and it has spikes grater than 8V (maximum values not shown in the scope snapshot).

Anyway, it seems to me that I can trust that I have a lot of noise inside my PCB, but not generating so much voltage as it is showed in the images above.

Finally, the questions:

Am I right to think that the noise is propagating via wires and not via the air?
If yes, how could I workaround it and decouple it in a proper manner?
--> In the second version of the prototype, I am planning to use ferrite bead in the PCB entrances; RC low pass filters in some sensitive tracks (dont care about slowing down the signals); isolate the High Voltage block in one corner of the PCB and put a guard ring around it; What is your opinion about it?

Information that can be helpful:
Voltage rating of the shock generator: 10kV;
Distance between High Voltage block and digital block: 3cm;

EDIT
Waveform of the HV pulse generated in the fence (the maximum amplitude is around 10kV);

This pulse happens once in a second. But this was captured in the case when the spark does not happen. I don't have the waveform of this case, but I believe that the dV/dt will be much greater in this case.


texts: How to tell which side of a Meanwell Encapsulated is AC and which is DC?

texts:
I received an AC/DC Encapsulated PSU from Meanwell.
The datasheet Meanwell IRM 60 5ST seems to suggest that the the terminal block with two screws is for the AC while the terminal blocks with 4 screws are the 5v outputs.
However it looks to me as if the plastic chassis has been swapped, perhaps when they fitted they made a mistake? I have used the same model in the past, but this is the first time I see this.
Can anybody help me figure out which one is which? (AC or 5v)
Thanks!


texts: I2C with 1.8V levels without level shifters?

texts:
I have problems detecting an MPU-6050 I2C device on the Intel Edison Mini breakout board (it only supports 1.8V levels). According to the thread here, it might be possible to get the sensor working with 1.8V levels:

  "The MPU-6050 also supports different supply (VDD) and I/O interface
  (VLOGIC) voltages.  If your board allows you to make separate
  connections to VDD (on pin 13) and VLOGIC (on pin 8), leave VDD on
  3.3V and connect VLOGIC to 1.8V.  Connect the pull-up resistors on SDA and SCL to 1.8V.  The MPU-6050 will then speak I2C directly at 1.8V,
  eliminating the need for a discrete level shifter."

Anyone can suggest how this setup might work (i.e. make a drawing) ?

Thanks!


texts: LDO vs Switching Voltage Regulator for Drone Application

texts:
I have been designing a drone flight controller and currently have been using LDOs to regulate the voltage to 5V.

As I have started to use higher voltage batteries the LDOs have started to overheat. I know that switching regulators are so much more efficient which is definitely a plus with battery-operated devices, but heat is not my only concern when considering which power supply to use.

When the drone's motors are on, the voltage supply becomes very noisy, and I have RF ICs on the board that are incredibly sensitive to power supply noise. Would a switching regulator be better for this application, or would it generally perform worse?

TLDR: When comparing LDOs and switching voltage regulators, which are generally the better performing option in terms of output voltage noise when considering an already noisy power supply?


texts: Powering a low current device from a mosfet N

texts:
I have a question regarding a circuit providing low current capacity voltage for device powering, that goes down from a lot higher voltage:

How does it exactly work? I understand that the Q1 gate is biased at 5.6 V no matter what is the voltage level on the Q1 drain (because of the zener diode). But how come there is around 4V at Q1 source? The Vgs of the Q1 is around 2.5 V (2N7002-7-F). The voltage at Q1 drain can vary and the voltage at source stays around 4V. This schematics is a part of circuit found in the BQ34110 datasheet.
I would appreciate all hints.


texts:
I'm trying to get the ATtiny13A to run on 3.3V which, if I'm not wrong, would be possible.

I've programmed the chip using an Arduino Uno. I'm doing a simple blinking LED example and when I power the ATtiny with Arduino's 5V pin it works without any problem. If I power it with Arduino's 3.3V pin it does not light the LED.

This is my Arduino IDE's config when programming the ATtiny:

I've tried other configurations also.

Am I doing something wrong? Do I need to program it in a different way or do something else?

Edit to add more info:

I'm using this guide (or a similar one, don't exactly remember if it was that one).
This is how the connections look like:

Red LED connected to pin 4 with a 220ohm resistor.
Also, I've measured voltage on that pin 4 of the ATtiny when connected to 5V and it's outputting ~6V but 0V when connected to 3.3V.


texts: Using a DAQ with a programmable power supply floating input

texts:
I have a programmable power supply (Sorensen DCR300-16T) that requires a floating programming voltage.  From the manual:

  (3.9.1)  In selecting a signal source, the following should be considered:

  The source must be capable of sinking approximately 1 mA (the Programming Current).
  A floating (ungrounded) source must be used.  All signal programming voltages will, however, have a common return.

I would like to use an analog voltage (ground-referenced) output of a NI PCI DAQ card for this purpose.  (e.g. PCI-6713)

In tests, the power supply programming inputs float as much as +/-75 V with respect to the building ground.  I suspect that the solution here is to insert something between the DAQ and the power supply input that converts a ground-referenced signal to a floating signal.

What is the conventional advice for how to do this?


texts: Updated. Extending Range of a microstrip antenna with a SMA 2.4GHz Omni Direction 20db wifi antenna

texts:
Dear all I have the bellow A2DP bluetooth module which has a zigzag microstrip antenna. I want to extend the gain in the antenna with my 20db wifi antenna.

I know as far as that I need to scrape the majority of the zigziag antenna off. Then solder my antenna extension to the remaining bit.

Which of the two 2.4GHz antenna wires do I connect to the remaining zigzag microstrip antenna (the inner wire or the outer wire?).

Is a ground plane necessary? If so where is the ground plane on this circuit board and how would I connect the two 2.4GHz wires to this board to achieve the best gain?

This is quite new to me, thank you for all your help!

Update

I have cut off the microstrip antenna and soldered on the SMA central wire to what remained from the microstrip antenna. I have also cut the on board copper connections where I have shown in the close up with a sharp knife .

Whether I leave the coax outer shield 'F' disconnected or soldered to what I think is ground, point 'G' I can't pick up this bluetooth device on any of my devices (it used to work before attaching the new antenna).

Also I have noticed that the point 'G' which is what I think is ground is the same potential as the (-) black power wire and also the same potential as the central SMA antenna wire which I have soldered to the board.

So they must somehow be connected. Not sure if this is meant to be like this? So if point 'G' is the same as potential as the negative power wire, should the middle of the coax wire be also the same? Have I shorted a connection somewhere?

What have I done to make this bluetooth device stop being received. Added note it still powers up and lights up.

Full size image


texts: Emitter follower/Common collector confusion

texts:
I'm in the need of a buffering circuit for a project and I would like to use a common collector amplifier or emitter follower for this purpose. Above is a schematics of the circuit I'm looking into.

However, I'm having slight trouble understanding this circuit, specifically why the voltage at the output is the input voltage minus the base-emitter voltage drop (around 0.7 volts). Doesn't the capacitor C1 cause  a voltage drop? It has capacitance, therefore it has impedance. If this circuit is used as a unity-gain current amplifier (buffer), I want only a small amount of current to enter at the input. Therefore, C1 should be quite small capacitance (because current is the voltage divided by the impedance, which in turn is inversely proportional to the capacitance). But if it has large impedance, I think it would have a larger voltage drop across it, and the output voltage would be input voltage minus the capacitor drop minus the diode voltage drop.

Somehow I think I'm thinking about this circularly, and I can't really make sense of what's happening. Can somebody explain to me why the output voltage is (almost) the same value as the input, and how the capacitor values are chosen?

EDIT: What if there is a load across the output? Say, a small-ish resistor. If the input capacitor is also small impedance, would there now be a quite large current through the circuit from input to output, defeating the whole purpose of the buffer?


texts: How to derive the Tf of an amplifier from its datasheet?

texts: I am designing a control system, where the forward path has an amplifier in Howland's current pump configuration. I want to derive the TF of the current pump, and also take into consideration the Poles and zeroes inherited from the used amplifier. My approach was appointing Vo = A(V+ - V-) and after i derive Io/Vin i replace the Gain A in the equation with (A/(S + Wp)) but till now i am failing miserably, so any help would be appreciated.


texts: Why are input MOSFETs in Laptop power supply always in pairs?

texts:
For example, on https://youtu.be/CW87dyYIimE?t=340 (and related work on motherboard), it says the managment chip uses two MOSFETs as a switch (as overheat protection, emergency poweroff on 10-second powerbutton press etc).

While the story makes sense and I can understand how it would work, I'm wondering why such MOSFETs need to come in pair?
To my (begginers) view, it looks like one MOSFET should be enough to act as switch for mentioned purposes. So why are there two MOSFET connected in series? What else am I missing?


texts: Best way to protect a MOSFET from overcurrent

texts: I'm trying to build the circuit in picture above. unfortunately the load on high side of the step up transformer is unpredictable and the input impedance of transformer is very low so I'm guessing the current through the MOSFET is going to be very high, basically the power supply will be short circuit to the ground while it's on. Should I add a resistor to the source of the MOSFET? If so, how big? How do people usually protect these kind of circuit? I can't add a high power resistor due to space constraints, so what's the smart way to do this?


texts:
So copying a little bit of what this guy showed on youtube, I tried to get my HD74LS86 ic. Here's what I tried to do:

Edit: I forgot to draw a resistor between the led and ground.

I put switches in-line for the B3 and A3 ports. And I used an Arduino to power it with 5V.

I hardly know anything about integrated circuits (but I've read on transistor and diode logic gates), so I'm not surprised it didn't work.

Here's the datasheet if it helps


texts:
In the checklist for USB 2.0 compliance there is a requirement for maximum droop at a load inrush current of 7.5 A. What I don't understand is how to test this. I might be blind, but the standard only seems to mention a capacitive load with lower currents (100 mA / 500 mA). Is there a load waveform which shows how the load should actually behave?

Here is what the test procedure says about it:


texts: Why would an IR remote circuit use one resistor/transistor pair for each LED?

texts:
I've done some reverse engineering work on the protcol for a remote that... sucks.  I'm replacing it with one of my own design, but while I've improved on the interface, the range and view angle of my system are terrible.  I'd like to complete this as soon as possible... I, uh, fried my original remote while trying to debug my own.  =]

So, like any good geek, I thought I'd borrow from someone else's successes and pulled up the circuit diagram for the TV B Gone:

My question is, why have one resistor and transistor for each LED, instead of chaining the LEDs in series and controlling them with a single transistor which is controlled, in turn, by the arduino pin coming in through a single resistor?

I have no qualms about implementing the same way (frankly, I'm tempted to use about 32 LEDs, resistors, and transistors just for the hell of it,) but I'd like to understand why it was done this way.


texts: Hot-swap controllers vs load-switch circuits and bidirectional current flow

texts:
We've got a battery of 50V connected to a load that may regenerate power, hence a bidirectional current could be present. We'd like to be able to switch on and off the load. We're looking at load-switch IC's such as shown in the figure.

Another suggested option is a hot-swap controller such as https://www.ti.com/lit/ds/symlink/tps2490.pdf?ts=1588751913165
Or this one: https://www.analog.com/media/en/technical-documentation/data-sheets/4226f.pdf (in here it says bidirectional current limiter, does this mean bidirectional current is possible too?)
The latter is what we know of that keeps the mosFET in a SOA but of the load-swith IC we are not sure about that. And about the latter, we have no clue whether it will support bi-directional currents.
The main reason we'd like to keep the mosFET(s) in SOA is because we expect high inrush currents and
on our old designs, the FET has broken down multiple times. See figure for our old design.

Now, I'm quite curious about the differences of a hot-swap vs load-switch circuit and suggestions on how to keep a load-switch circuit in SOA such that we can have bi-directional currents in our system.


texts: Selecting active RC integrator values such that the circuit properly integrates

texts:
I'm designing an active RC integrator, using the multiple feedback low-pass filter topology (working using the same principles) and I'm having some real trouble understanding why sometimes the thing does not integrate.

I do all my calculations and simulate, it does not integrate the signal. I have kind of sussed out that the feedback capacitor has to be <10nF to start integrating. I find the better the thing integrates the more out of wack my phase angle goes. My frequency of interest is 50/60Hz and the device should work from 10-10kHz* @ 3 degree phase error at 40-70Hz and 15~degree for the rest.
The input voltage is being fed off a buffer opamp supplying for about 30uV (worse case) to about 1V .

I calculate the time constant for the frequency of interest and design the RC filter accordingly. If the RC is much lower it does not integrate and if its any higher the phase angle goes wacky the integration is not clean.

Any advice on how to tackle this - should I set the RC time constant much higher than the frequency of interest, and how do I fix the phase angle?

Circuit im using is below:

simulate this circuit – Schematic created using CircuitLab

p.s
Im using the following links to aid in my development if anyone is intrested
http://sim.okawa-denshi.jp/en/OPtazyuLowkeisan.htm
http://www.analog.com/media/en/training-seminars/tutorials/MT-220.pdf


texts: Can we give a bipolar signal to ADC of ATmega88?

texts:
Can we send a bipolar signal to the ADC of ATmega88?

We know that an analogue signal has a positive value as well a negative value. So can an ADC take a negative value or does it just take the positive value of a bipolar signal?


texts: Can I communicate with a STM32 over SWO?

texts:
Currently, I can program/debug a STM32 over a Raspberry Pi 3 with OpenOCD and also want to receive and transmit data to/from STM32.

Can I use STM's SWO trace pin to transmit and receive data? Or is SWO only for debug purposes (read-only)?


texts: Via in PCB - Why not go for a solid copper filled via than a plated via?

texts:
If a via is meant to carry current why not go for a solid copper filled via than a plated via (which is hollow/nonconductive at the center)?

After all in electrical engineering, we dont go for a hollow conductor saying it will be cheaper. We just change the conductor size ( or use more no: of conductors) as per the current.

Why cant we follow the same approach to via?


texts: Selecting OpAmps for Transimpedence Application

texts:
Hi I am working on an application that will use a PIN diode to detect very small light intensity changes. Looking for low noise, single 5V rail operation, and high gain. Cost is a secondary consideration. All other metrics such as bandwidth, slew rate are not as important. I am trying to decide how to build my circuit but could use some advice - I realize there is no one answer in analog design but some advice would help me move beyond the simple circuits we were taught in school.

1) How do you select the first stage for a transimpedence amplifier such as this? I have found several parts that seem to match the application well but I am not sure how I should chose between them.

http://cds.linear.com/docs/en/datasheet/62689f.pdf
http://cds.linear.com/docs/en/datasheet/624012fe.pdf
http://cds.linear.com/docs/en/datasheet/624678fa.pdf

2) Is it better to build a CMOS buffer 1st stage with a discrete CMOS like so? Or just feed it straight into one of the other Op-Amps?

3) If my currents will be on the order of pA the how do I chose subsequent stages for the amplifier? Should I use the same amplifier again, just anything that will give me the right gain or are there other gotchas I need to anticipate?


texts:
There are many different power amplifier classes for transistors, like: A, B, A/B, C, D, etc. But as I searched through the internet and I only found those classes referring to BJTs.

What about JFETs, MOSFETs, IGBJTs, etc., does the same thing applies for them?


texts:
This is more of the technical, i would try to test it via trial and error but i don't have extra equipment. Anyways, firstly if i set the SPI.setBitOrder(MSBFirst) transfer the command, for example 0b11110000 the "1s" are to be sent first, right? MSB is supposed to be transmitted on the first clock cycle based on the datasheet.

Does it comply both ways? if i were to receive the data 0B11110000 then store it in a variable, would the position change? the device sends the MSB first.


texts:
I want to use the TPS65070, the power solution for DSP to power the OMAP L138, but i read in the errata sheet of the OMAP L138 OMAP L138 Errata page 25 that the 1V8 power supply can pull up to 2.7V when using Dual-Voltage at 3.3V.

One of the proposed solution in the errata document is to use additional shunt regulator (page 27) TLVH431. But the problem is the leakage current into the DVDD18 supply is 140mA and the regulator provide 70mA ? So, the use of two regulators can resolve the problem, or can anyone suggest any other regulator which provides 140 mA?

Thanks


texts: I'm going to buy a PIC32 which has inbuilt USB support. What is the difference between "FS Device", "FS Device/Host/OTG", and "HS Device/Host/OTG"? Am I right in thinking that the "OTG" aka "on the go" means that the USB can be plugged in and out at anytime?


texts:
I work on a project that need 36 PWM signal to drive 36 MOSFETs.
Can I use a microcontroller with  a limited number of PWM and configure all pins as PWM output or do I need to find a microcontroller with 36 PWM pins?


texts: gain of opamp circuit with current output

texts:
I'm designing a current source using a MOSFET driven by an opamp. The opamp controls the gate by comparing the voltage on a shunt resistor to the input reference. You could say that the fet replaces the feedback resistor in the standard non-inverting configuration.

I know the bandwidth I require, but how do I work out the gain of this configuration so I can choose an opamp based on GBW and phase plots?

My output is current, and I can't work out how to translate the units of amps per volt into dB. Simulations show many opamps are unstable, and the compensation I've tried reduces the bandwidth too much.

update:

a simplified version of the schematic im using is the following:

simulate this circuit – Schematic created using CircuitLab

main differences are that i've been experimenting with cascoding the output FET, and adding a push-pull bjt stage between the op-amp and the output.

in teks answer, he assumes a resistor in paralell with Rf and Rsense, which can be modified to adjust the gain - i cannot easily put one in this position because it will introduce an error which i would like to avoid (this should be high precision)

in general, i want to achieve a reasonably high bandwith for the current, in the MHz range.

what i've done so far is to model this in LTspice, - grounding Vref and using the "loopgain" source as excitation for AC analysis. plotting V(fb)/V(-in) should give me the loop gain and phase margin, which i believe will tell me about the bandwidth and stability - which is where my issue is.

i've modelled the output stage on its own (no opamp), and the phase is pretty flat up to and above the bandwidth i require, so reasoned that the poor phase margin was connected with the op-amp.

compensation techniques worked, but reduced the bandwidth to below what i need. therefore i would like to choose an op-amp which has a good enough phase margin at the bandwidth i need. however in order to do this, i need to know the gain since the datasheets show open loop gain graphs.

the Answer from sixcab seems to imply that the gain is 1, if you take the output as Vsense, however this didn't seem to work as an opamp that had a good phase margin for a gain of 1 at the frequency i need didn't perform fast enough (leading me to believe that the gain figure i should use is higher)

i suppose my question is: how do i read the open loop gain/phase plots for an op-amp to determine if it will work in this circuit.

Thanks very much


texts: Arduino Yun not starting after connecting DC Power (from time to time)

texts:
My circuit Consists of:

Arduino Yun: http://arduino.cc/en/Main/ArduinoBoardYun?from=Main.ArduinoYUN
Arduino Motor Shield rev3 : http://arduino.cc/en/Main/ArduinoMotorShieldR3
12V Lead-Acid Battery like this one http://gnarlyparts.ca/images/040-BATT1-2_w450.jpg
Step Down regulator 12V -> 5V: ( http://www.robotshop.com/eu/pololu-step-down-voltage-regulator-d15v35f5s3.html )

Output of voltage regulator (5V) is connected to motor shield screw terminal (Vin,Gnd) and motor shield passes the power to Arduino. Both Arduino and Motors are powered with 5V.

After connecting power to input of voltage regulator Arduino Yun flashes green LED and shuts down. This happens about 50% of the times. In other cases Arduino starts up properly and circuit is working as expected for hours.

What could be the cause of Arduino shutting down fraction of a second after connecting power? When I powered separate Arduino Yun witch micro USB phone charger this problem didn't happen, but with motors and shield I need too much current for powering with microUSB. The voltage regulator I use is quite reliable i think.

UPDATE:

I attached capacitors for decoupling, but it didn't help. the circuit looks like this:


texts: Neutral wire diameter and phase wires diameter (3 phase current)

texts:
I have nothing to do with electrical engineering so this may be lame question.

According to Kirchhoff's law sum of currents of L1+L2+L3 should be same as current of neutral wire. What puzzles me is why neutral wire has the same diameter as phase wires in a cable. Can anyone explain or point what may be stupid about this question?

ADDITIONAL INFO
L1/L2/L3 do not have to be equal. I know a building with say 3 flats can be connected to "outer world" with 3 phase cable and each phase is connected to different flat. In such scenario phase currents differ but neutral is common.  Doesn't neutral wire conduct sum of all 3 phase currents then?


texts: How can I make a very temporary "backup battery"?

texts:
I have a project where I am driving a car horn that is rated for 12V@8A.  I have a pack of NiHM batteries rated at 9.6V (usually get's up to about 11.3V) total and their spec'ed out to 10A for 8 minutes.  I also have an Arduino mega and a Beefcake Relay kit.

There is a point in my program where the car horn sounds off 3 times (ON 500ms, OFF 500ms).  However, when the car horn starts, it usually gets through 1 whole sound, then resets the Arduino.  Both the Arduino and the car horn are being powered off the same 9.6V batteries.

My theory is, the Arduino is being starved of voltage when the horn goes off, then resets.

I want to know if it's possible to make a small (in physical size) capacitor bank that I can use to keep the Arduino alive while the car horn is being used in short 0.5sec bursts.


texts: Where can I find out what language a MCU would use?

texts: I have looked through the data sheet for, ATSAM4LC2BA-AU but found nothing regarding what language it uses, I was hoping to code C onto it, also any thing on the necessity of a boot loader?


texts: Help identifying pinout of LTM-0436M multi-segment LED

texts:
I've got following unique segmented LED display module from local store. It has 8-pin (physically similar to common 7-Segment display), the marking on body of the module is clearly printed as "LTM-0436M", thus it seems a LED display module produced by Lite On Inc. Its display is driven by built-in PTC PT6961 IC (a LED Driver IC), so it's clear from PT696 datasheet how to drive the display, if only we know which pin of the module is connected to which pin of the controller IC.

The problem is, I have no idea about the pin configuration of this module. And since it's command-driven, I can't simply connect +3V/GND wires to test the pins (they are not simple anode/cathode terminals).

I've search Lite On Inc. website with no luck (their website seems incomplete, a lot of product pages remains empty), the product (LTM-0436M) is not even listed. I've also tried google with any possible search keyword I can imagine, also with no luck.

The PT6961 itself requires 4 serial input pins for interfacing (Din, Dout, Clock, and Strobe) plus 3 input pins for key scanning (K1-3). It also needs to be connected with an external oscillator which I believe has been there inside the module (it's resin-protected, so it's impossible to see the inside without damaging it), so no need to break this pin out. Other than 4+3 input pins, this module needs power supply (VDD) and ground (GND) for total 9 pins, but it only has 8 pins.

Do any of you have experience with this module? Thanks in advance for your care.


texts:
From Bartlett's bisection theorem. Common-node.

So I don't get, shouldn't \$ i_{b1} \$ be:

\$  \frac{V_{ic}}{r_\pi + 2 R_{ee} }    \$

?

\$r_\pi\$ is in series with \$2 R_{ee}\$, so they have same current. No?

I also had shown in red what the current is across \$2 R_{ee}\$


texts: How to connect IRF 630B N-Channel MOSFET on 220VAC?

texts:
Here is datasheet: http://pdf.datasheetcatalog.com/datasheet/fairchild/IRF630B.pdf

From my wall is 220 VAC, but from datasheet I think this MOSFET alow just 200VAC (I am not sure please check).

Should I just connect drain and source to the AC wire?


texts: Is gapped core required in Two switch forward converter

texts:
I want to design a Two switch Forward Converter. So is there Gap required in this topology like a  Flyback converter or not.
My second question is, can I calculate the transformer turns ratio of the   2 switch forward converter like a single switch flyback converter or it is a different procedure. Thanks


texts: What does it mean when "Adoption of MBIT processes" is listed as a feature of a component?

texts: What is the "MBIT processes" and what does it mean when it's a feature of a transistor like below?


texts: I have an outlet adapter that is clicking at 260bpm. What is happening?

texts:
I plugged this adapter, GE Grounded Adapter-Spaced Six-Outlet Tap, into my outlet the other day. I noticed a clicking noise in my apartment, and it's coming from the adaptor. I used an online app to measure its BPM. 260 BPM. But 260 isn't an even multiple of 60 or 120 (I live in the US).

Can anyone explain what might be happening?


texts: How to vary the range of a potentiometer...is this even possible?

texts:
I am a total noob so apologize if this doesn't belong here but I haven't had any luck finding an answer to this...

I have a simple circuit with two 555 timers...similar to an Atari Punk Console. I have a switch in my circuit to switch between a headphone jack and a built in speaker (I know there's switchcraft plugs that do this. I just don't have one yet).

Anyway, the problem is the audio level/volume range is great through headphones  with a 50k pot, but switching to my small 8 ohm speaker the output isn't loud enough unless I switch to a 2k pot. But then with the 2k pot, audio level through my headphones is deafening.

I guess my question is, is there any (relatively simple) way to have the same pot utilize one range when running through one output path and a different range when going out another?

Does this even make sense?

Or am I thinking about this all wrong?

Incredibly grateful for any input.

Thank you!!!


texts:
So i was working on JFET networks and in the calculation of The output impedance (Solution from the book) I am stuck in the solution
My question is How can Vrd = V0 + Vgs ?

The solution picture


texts: I want to measure battery level within my circuit with an ADC. I've been said to scale the voltage to Vcc and use it as Vref of the ADC. I've thought of two options for doing it: a voltage divider with resistors or an op amp. I want to know which one is better and why.


texts:
I know this question was asked before, But couldn't understand properly the datasheet reading.
I would like to control water pump via RPI.
Wanted to make sure Im reading the datasheet correctly + Im connecting everything properly.

So if I understand correctly, on the worst case, the water pump will need 6v. so the calculations will be according to Ipump(max)
Ipump(max) = 1.8w/6v = 300mA
Ipump(min) = 0.6w/4v = 150mA

According to 2N2222 data sheet, figure 11:

When Ic=300mA, Vbe(sat)=0.9v and hfe=10.
So:
Ib = Ic/hfe -> 300m/10 = 30mA
R1 = (Vrpi - Vbe)/Ib -> (3.3-0.9)/30m = 80ohm

In order to make sure the water pump will get the current it needs, we will limit Ic to higher value:
R1=50ohm
Ib=(3.3-0.9)/50= 48mA
Ic=Ib*hfe= 48m*10 = 480mA

So R1=50ohm
Wanted to ask :
1. Do I read the `hfe` correctly? is it the right value to make sure the saturation?
2. There is a need to connect a diode in parallel to the water pump? resistor in series to the water pump?

Thanks for the guidance.


texts: What causes a transistor to enter into the saturation mode?

texts: I'm looking into the construction of logic gates, and am wondering what conditions are need across emitter-base-collector in terms of both voltage and current to enter the saturation mode. For reference, I'm interested in npn type Bipolar Junction Transistors. Any help, and links, that you can give would be most appreciated, as I cannot find a unified answer to this.


texts:
I'm developing the PCB of my L297-L298 stepper motor driver, but I have a doubt about the SENSE pins of the L297 I.C.
I understand that the pin 13 and 14 of the L297 are used for controlling the voltage on the two resistors(0,5 ohm), but since the current that flows on the resistors can reach 2A, does not this current flows on the pin of the L297, burning out the I.C.?

The schematic:

Datasheet:


texts: Using a DP3T Toggle On-On-On to switch between two devices and then have them both on

texts:
I have a DP3T on-on-on switch that I would like to use to switch the power from my bicycle dynamo hub to front light on position 1, rectifier/regulator on position 2 and then both light and rectifier/regulator on position 3.

The positive and negative leads would go directly to the switch but I don't know which pins to connect them to nor do I know which pins to bridge.

I am using this switch https://uk.rs-online.com/web/p/toggle-switches/7109876/ by TE Connectivity which has six pins to connect to. If you can provide a diagram that would be very helpful to me. Thanks


texts: Raspberry Pi ver 2.0 UART connection with PC and Xbee

texts:
I am trying to connect Raspberry Pi ver 2 with my PC using UART.

Connection of my board is

Raspi  Tx  -> Rx RS232toUSB PC

Raspi  Rx  -> Tx RS232toUSB PC

Raspi  GND -> GND PC

Problem I am facing with this is while I send "+" using picocom on Raspi it gives me output "j" on teraterm

Also I want to connect it to Xbee S2C module

Connections are

Raspi  Tx  -> Rx Xbee

Raspi  Rx  -> Tx Xbee

Raspi  GND -> GND Xbee

Raspi 3.3v -> Vcc Xbee

With using it on Picocom giving input of "+++" for 3 or 4 times it gives Output of "K".

While using with Breakout board og Xbee it works normally.

Please help me to determine problem with Raspi UART

Is max3232 IC required between interface?

Thanks in advance


texts: Mezzanine Plug/Receptacle on PCB or FPC?

texts:
I'm about to use a Mezzanine connector from the SlimStack series with 0.35mm pitch by Molex.
One side will go on a FR-4 PCB (rigid), and the other will go on a flexible printed circuit board (FPC).
Does it matter if the "plug" or "receptacle" goes on the PCB(rigid) or FPC(flexible)? I would assume that by convention the "receptacle" goes on the rigid part but.. does it even matter? (My hunch is that it doesn't matter for my application but.. I figured I'd ask)
After assembly, the part will remain static.
This is the "plug":

And this is the "receptacle":


texts: Can Grid Dip Oscillator (GDO) detect WiFi, Bluetooth and NFC?

texts: Can I use GDO to detect those waves? Can I buy one somewhere or I need to build one? I would to have digital one, that will just show the frequency of the waves.


texts: Altium Desinger: Collect harness instances into bus

texts:
I'm working on a larger project involving Altium Designer 13 and Multi Level Design.
The problem: I have numerous instance of the same Harness and I want to collect them into same bus and output them trough single bus port:

When I compile the project, I get the following error:

Can anybody help me how to correct it?
Maybe, my idea was wrong to collect numbered harness instance into one bus?


texts: Currently using two car batteries in series as filter for 24v power supply. Is it possible to connect 12v power supply to one of those batteries?

texts:
I am currently using two 12V car batteries connected in series connected to a 24V power supply (SMPS), so they act as a filter.
I need to do the same with a 12V power supply and I am not sure if to:

Connect the power supply directly to ONE of the batteries (the same batteries that are connected in series to the 24V power supply.)

If just connecting the load to one of the batteries will behave as a voltage divider and the 24V supply will act as a 12V supply (without having to connect the 12V power supply.)

If I can't mix things and I need to use a separate battery.


texts:
I Have started making my 1st PCB, as per my other question (Located Here) and have been looking at the datasheet for the MAX7219CNG and studying the library to run it on an Arduino (Located Here)

Now my question is from what I can see in the library, there is a method called spiTransfer that sends the data to the IC to turn on and off the various LEDs. This is done by shifting data containing opcode and data bits. The opcodes are at the top of the .cpp file. For example
#define OP_SHUTDOWN 12

I can't find where the related information is in the datasheet to say that 12 = Shutdown.

Am i reading the datasheet wrong or understanding the library wrong. I want to learn how to read a datasheet and implement code to run an IC with out relying on code written by others.

And guidance would be great thanks


texts: 4 layers PCB stack - (signal, signal, power, ground)

texts:
I've developed a board for a project and the company that is going to assemble it in a pluggable module has just asked me a weird modification.

Currently it's a 4 layer board: top signal, ground, power, bottom signal. Pretty standard.

They want me to swap the ground plane with the bottom signal layer.
This way they can easily contact the mechanical case (that has a big heatsink) to the ground plane with a thin graphite layer. They aim to improve the heat dissipation of some critical components, already contacted to the ground plane through the component exposed pad.

I'm trying to figure out if this is a bad idea or not. Here are my considerations:

The signals that are routed in the board are not HF, 10MHz at most, and there are no squarewave clocks in the board.
The fastest edges of some signals have a settling time of few um and come through a connector from a different board, so they will be probably already filtered by the connectors parasitic capacitance.
Having the reference layers so far from the signal layers seems a bad idea for the return paths. A better stack could be: (top signal, power, signal, ground).
On the other hand, increasing the distance from the reference planes of those critical components (some very low noise TIAs) reduces the parasitic input capacitance (currently at about 0.5pF), thus reducing the output noise of the TIA configuration.

What are your thoughs?

Some answers to your comments:

  Would it be possible to just add polygon pours on the bottom layer?

It might be, but there are a bunch of signals in an area that cannot be rerouted. Since the graphite is conductive, I would only rely on the soldermask to avoid short circuits, an the isolation on the vias could be a problem (I cannot use tented vias).

  Are the signal layers flooded with ground?

Currently no. Mainly to reduce the input capacitance to ground of the TIAs, but there are some areas that I can definitely fill.

  Can the hot components get moved to the bottom of the PCB?

No, they must be on the top layer due to other assembly and routing constraints.

  Do they actually care where the power layer is, or do they just want the ground on the bottom?

They just asked for the ground to be on the bottom. That's why I considered the alternative stack (top signal, power, signal, ground).

  Graphite is electrically conductive. If your vias aren't fully tented / filled, you will be in a whole world of problems.

I'm also very concerned about that. Furthermore, if I don't completely clear the area from signal traces I'm just relying on the isolation given by the soldermask, that can be easily scratched.


texts: Advice on battery powered ESP32 with NFC Design

texts:
I'm new to PCB design (First one) and I want some advice and tips from more knowledgeable people in regard to basic design elements and especially the power consumption part. I want to make the hardware consume as little as possible during sleep. I spent a lot of time researching, but would like some expert proofing before I pull the trigger.

I'm trying to design a battery powered esp32 that will turn on the motor when the NFC breakout board connected through SPI is reading the correct code. It only wakes up by a built in touch sensor and is in deep sleep most of the time. I choose the ESP32 to add some IoT capabilities. I'm using low quiescent current LDO voltage regulator (4uA) for 3.3V. I have connected ground of the motor, voltage divider for battery measurement , and the NFC module to N-Channel logic level (>1.8V) MOSFET to operate and save power by turning off NFC module and the divider constant drain. This specific MOSFET has a low 1uA leakage IDSS.

Capacitors are the same as the data sheets suggest. Motor current is not more than 1.4A for 5 seconds. Batteries will be 2x2 lithium-ion (~6V-8.4V). The NFC module will be connected by male 2.54 1x6 header on the back side of the board (GND to SCK). Also note that the pcb and breakout board's top,left, and right sides are meant to match. Only the bottom side on my pcb is shorter. There are external UART connectors. Also I'll be soldering all components by hand.

Old Schematic:

Old PCB:

Project link on EasyEda for PCB and Schematic for close up inspection

Feel free to request any info that I could've missed.

Update:
I've reworked the voltage divider/motor circuit. It Now it uses a pmos connected to battery in both drain and gate (Motor is a 6 Ohm resistance so the gate is connected to VB) If my theory works, the traces have so little resistance in relation to the motor (about 0.1 Ohm to 6 Ohm of the motor) the voltage at the gate would be still much lower than the drain (1V vs 8-6V if my calculations are correct, threshold is 1.2V difference) so pmos will be turned on. There's no direct connection between any pin to VB when the circuit is off.

I divided the schematic into smaller parts. Added a diode for reverse voltage protection, reworked the SPI lines to make them adjutant since they were just software SPI. Made battery traces slightly thicker.
I've decided to not put any terminations resistors. UART have one internally, while the breakout board have resistance for each line. Of course, ideally you would put the resistors at the sender, but given that they seem to work fine with 20cm of ribbon cables, I think I could skip it? Also used smaller caps for 100nf values. I've bought separate BMD for my Li-ion so I don't have to fiddle with that.

Ver0.2 Schematic:

PCB:

Link to new

If you have any tips, questions, or corrections, feel free to leave them in an answer. I'll mark Umar response as the correct answer for now.


texts: Understanding Minimum Output Voltage of Cascode Current Mirror

texts:
I guess that I have some serious trouble understanding how to get the saturation equation for the cascode current mirror right which is known from all the textbooks as

$$
V_{out} = 2 V_{DS, sat} + V_{th}
$$

It's quite intuitive to get to the point that the gate voltage at Q4 needs to be

$$
V_{G, Q4} = 2 V_{DS, sat} + 2 V_{th}
$$

Now when looking at how a MOSFET is saturated we use \$ V_{DS} \geq V_{GS} - V_{th} \$. So applying this to Q4, why do we just simply do

$$
V_{D, Q4} = V_{out} = V_{G, Q4} - V_{th} = 2 V_{DS, sat} +V_{th}
$$

? That doesn't work for me because we look at \$ V_{G, Q4} \$ with respect to ground, so for me it makes sense to write

$$
V_{out} = V_{G, Q4} - V_{S, Q4} - V_{th} = V_{G, Q4} - V_{D, Q2} - V_{th}
$$

But we don't know \$V_{D, Q2}\$. When assuming \$V_{D, Q2} = V_{D, Q1}\$ we get

$$
V_{out} = 2 V_{DS, sat} + 2 V_{th} - V_{DS, sat} - V_{th} - V_{th} = V_{DS, sat}
$$

which obviously is nonsense... So where did I get stuck or where did I go seriously wrong?
Any help is greatly appreciated!


texts:
I want to switch on 5V when switch is connected to 12V. I have been using relay to do this, but I am wondering if I can use NPN transistor or something similar that is cheaper and smaller than a relay.

This is the logic i am going for:

Version 2:


texts: I'm currently working on a little project using a Raspberry Pi and an Ag9000-S. I've got it working using Mode A (phantom power over the data pairs) and Mode B (direct power over unused pairs), but when using Mode A I can't use the data pins for Ethernet communication because they're cranked up to ~48V, and Mode B isn't implemented on some of the switches I have around. Is there a way to bring the voltage back down to a normal ~2.4V for Ethernet communications? I know I'm not exactly an electrical engineer, but any information would be useful!


texts:
I'm having a bit of a problem figuring out how this sample and hold circuit works.

I am to calculate \$V_\text{out}\$ if (a) \$A\$ is infinite and if (b) \$A\$ is finite. \$A\$ is the open-loop gain of the OpAmp, and \$V_\text{DAC}\$ is a DC voltage.

What is \$V_\text{out}\$ in the two cases (a) and (b)?


texts: 2N2222 NPN Transistor, no current flowing through collector

texts: I have a 2N2222 NPN Transistor wired up in the most basic common emitter setting (emitter grounded, base hooked up with a 1k resistor to 5V, collector connected to load and load connected to +12V). Ground is common with the two voltages, but when i try to do anything, even short the collector with the +12V, i get no current flow. I measured with a multimeter, and there's indeed 12v between collector and +12V, but i can't even power an LED. I'm a beginner so i honestly don't know anymore.


texts:
I have a full bridge SMPS and I am measuring the voltage across the output´s diodes on the secondary side.

As you can see the voltage spike changes by changing the output current, for example at zero output current the spike is arount 32V,

while at 14A it is around 41V.

It means the poles of the transfer function of full bridge SMPS are moving.
So the question is: Which part of the circuit or PCB depends on the output current?

Thank you in advance


texts: Why accessing the SRAM is slower with AVR XMega load instructions?

texts:
The AVR XMega has 16 GPIO registers in I/O space in addition to its internal SRAM. Interestingly the timing of LD instructions differ to these locations: Accessing the (rather large) I/O space is faster than accessing the internal SRAM.

This can be observed more or less in the instruction set documentation:
http://ww1.microchip.com/downloads/en/devicedoc/atmel-0856-avr-instruction-set-manual.pdf (from Page 22)
(Rather "less" as it is quite ambiguous).

Not being sure on how the timing works I made tests with actual hardware, measuring the timings of various instructions.

Accessing the SRAM:

                    Mega   XMega
LD reg, ptreg       2cy    2cy
LD reg, ptreg+      2cy    2cy
LD reg, -ptreg      2cy    3cy
LDD reg, ptreg+imm  2cy    3cy
LDS reg, imm16      2cy    3cy
ST ptreg, reg       2cy    1cy
ST ptreg+, reg      2cy    1cy
ST -ptreg, reg      2cy    2cy
STD ptreg+imm, reg  2cy    2cy
STS imm16, reg      2cy    2cy

Accessing the I/O area (tested with GPIO and UART registers), the loads are one cycle faster:

                    Mega   XMega
LD reg, ptreg       2cy    1cy
LD reg, ptreg+      2cy    1cy
LD reg, -ptreg      2cy    2cy
LDD reg, ptreg+imm  2cy    2cy
LDS reg, imm16      2cy    2cy
ST ptreg, reg       2cy    1cy
ST ptreg+, reg      2cy    1cy
ST -ptreg, reg      2cy    2cy
STD ptreg+imm, reg  2cy    2cy
STS imm16, reg      2cy    2cy

Anyone could provide some insight on why it could have been desinged in this manner? The performance difference is rather significant for memory intensive tasks, and the 16 GPIO registers are not much if someone needed some faster RAM (while the I/O space is huge in comparison, apparently wholly capable to operate by the faster timing, which is a design choice I can't really understand if this faster access required more costly hardware).

A particularly bad case is the 3 cycle displacement loads which are very frequent, and even AVR-GCC seems to lean towards using those rather than trying to walk through memory areas with post-increments when optimizing.


texts: Isolating power for an infrared receiver

texts:
I am using this IR receiver in a circuit, and I have noticed that sometimes the unit generates an oscillating output when it is not being activated by a remote - I am guessing that this is due to the USB power supply.

I have seen other threads talking about 'filtering' the power supply with a cap and a resistor
- however, could somebody explain how they come about calculating what size cap and resistor are required - and how they actually achieve the 'ripple filtering' effect?

For examples sake, my IR receiver is powered by 5v, directly from a netduino - and generates output pulses (when activated by infrared) in the 0.5-4.5ms range (see image: I dont know if that information is required, but there it is).


texts:
I am working on an Arduino controller project with a few attached components returning data e.g. GPS and mini camera.
All works fine with USB power or 9V battery.
I tried using button cells in parallel creating approx. 9V (to save space) but the resulting battery does not seem to be able to power the components.
Is it a maximum current problem?
The button batteries are in three pairs connected in parallel.
Any ideas?


texts: 4-pin-momentary button replacement with 2N2222A

texts: I want to replace the switch with an arduino trigger. this is my attempt with a 2n2222a, but somehow it triggers the switch not with the HIGHs of the PWM but with a completely other frequency I can't track.


texts: Help required regarding Cypress 4200 coding

texts:
I am a newbie when it comes to Cypress chips. I am developing a capsense keypad.

I recently started with CY8kit049. I can code into the chip on board. How can I code other PSOC 4200 chips too using it? The bootloader accepts bootloadable programs directly. But when the chips will be new, they won't have any bootloader loaded in them.

Any kind of help would be highly appreciated.


texts: Convert reed switch disconnection or SPST off to single "LOW" pulse

texts:
I'm trying to wake up my Arduino and run some code when a reed switch or SPST switch connected to an interrupt is opened. If my Arduino is in powered off mode, only LOW interrupts are accepted (not changes, which would make things much easier).

Is there a simple hardware way to send a single LOW pulse when the switch is disconnected? I'm trying to avoid the interrupt continually triggering my Arduino to wake up while the switch is open; I only need the code to run once, and then I want my Arduino to power back off until the switch is eventually closed and then reopened again.

I've been exploring using a 555 timer in monostable mode, perhaps with a transistor inverter to make the pulse low, but it appears that that solution will eventually trigger again (more than once) if the reed switch remains open for a prolonged period.


texts:
This data sheet (linked from the product page of Rapid p/n 61-6211) covers an adapter for LVDS displays, that can provide various different voltages. This includes a 'VGL' signal that is set at -6.8V.
The datasheet helpfully includes a schematic, but having never designed a -ve supply, I'm hoping someone can help me to understand how the part of the circuit that creates this -ve voltage works:
.
The part we're interested in is on the right hand side, but the rest is included for context.
The MIC2289 is a switching regulator; VOut (AVDD) is ~10V.
The zener D2 is rated at 6.8V, so it looks like changing this value changes the -ve supply, but I would really like to know the 'how' and the 'why'?


texts:
I have been looking into homemade PCB etching, since ordering PCBs takes longer than I would like.  I have seen PCB stencils for applying solder paste, and I am wondering if it is possible to use a stencil instead of using an iron to transfer the trace image to the copper board.

I assume the steps would be as follows:

Order a stencil with all the traces and pads cut out (basically everywhere you want copper
Secure the stencil to the copper board
Use a permanent marker to color in all the traces and pads, using the stencil to keep the lines neat
Remove the stencil
Etch the board

Would this be a reasonable way to make PCBs at home?  I thought that this would be a better way to transfer the trace image to the board because based on what I've seen, the iron-on method isn't always that easy to execute.  It also seems like the stencil would take less time to use each time you needed to make a new PCB.


texts: 5V/2A Fixed Output Buck Boost Converter Design

texts:
I am trying to build a fixed 5V buck boost converter with input voltages ranging from 3-7.2V (which is from a battery) and maximum output current with 2-5 A. My use case for this converter is to power up a micro-controller and a servo motor. I have found an online design that closely matches my requirements which is linked below.
Buck Boost Converter
The design looks as follows,

I was unable to find the IC for this design which is XL6009.I also wanted this circuit to work with the input range from 3-7.2 V.So I am planning to replace that chip with LT1171CT. Will this work with the same design? Datasheet is linked below,If you have better suggestions please do.
Replacement IC
I am really new to power electronics so I only have very small knowledge about it. So I looked up how to design buck boost converters and found the following post on electronics stack exchange.

Buck Boost designs

I tried to go through the data sheets in buck boost converter chips but they either have step up or step down seperately. I cant seem to figure out how to combine them together and make a buck boost.
If you can direct in the right direction it is appreciated. I want to learn how to use the datasheets to design circuits but I am confused right now.
Thank you!


texts: Powering 12V 35W halogen bulbs with a constant current supply

texts:
I'm revisiting an old project, and I want to see if there is anything I could have done differently, or if I missed any important details or considerations.
Basically, I used a constant current driver (designed for LEDs) to power and dim a halogen bulb. The driver is a MeanWell HLG-100H-20AB, and the bulb is 35W, 12V halogen. This constant current driver can be controlled via variable resistance (10kOhm at min. brightness and 100kOhm at max. brightness), and its max current output can be adjusted as low as 3A. I calculated that the bulb needs 2.917A to shine at its maximum, so I set the max current on the MeanWell to ~3A and arranged my potentiometer and resistors such that the max resistance delivered would be ~97.5kOhm, meaning, theoretically, that the Meanwell unit should not output more than 2.917A.
Here are my questions:

This worked well from what I saw. The light dimmed as I expected,
and the bulb didn't burst. But, I'm wondering if there's anything
crucial that I could have missed. I don't generally see people
dimming halogen or incandescent bulbs with constant current devices,
and there must be a reason for this. Any ideas?
I'm assuming that if I had used the MeanWell to output, lets say 4A,
the bulb would have failed, since my understanding is that the
MeanWell unit is capable of "force feeding" current. Is this
actually true? Or, does the unit just modulate voltage to indirectly
control current?
I noticed that the spec sheet has a "constant current region" listed
between 10V and 20V. I don't understand what this means, or how it
would affect the halogen bulb. For instance, when running only 1.5A
to the bulb, for example, its a safe bet that the voltage across the
bulb's termninals is less than 10V. Yet, the MeanWell unit still
supplied steady current. What gives?
Am I correct in thinking that this setup negates voltage drop
considerations for the bulb over a long cable?

Thanks!