texts: Making connections to coin-cell batteries

texts:
I'm working on a project that will be using several coin cells in parallel to a flex PCB.  The product will be disposable with non-replaceable batteries, so I'm looking for ways to attach the batteries to the PCB without the cost and size of battery holders.  Putting contact pads on the PCB is usually a workable approach for rigid boards, but I'm doubting the reliability on a flex circuit.

It is possible to get metal tabs of the appropriate size spot-welded to the cells so that they can be soldered, which may be the best route.  Are there any others I should consider to make reliable connections?  Conductive epoxy?


texts: How to drive high powered LEDs as efficiently as possible

texts:
I have come across some very high powered LEDs.

Datasheet for LEDs
http://www.cree.com/led-components-and-modules/products/xlamp/arrays-nondirectional/xlamp-cxa2011

My question is: for these high powered LEDs how can I create a driver circuit that will be energy effiecent or is there a driver for high powered LEDs that I'm just not finding.

The LEDs will eventually be used in a grow light for an aquaponics system so effiecency is essential.


texts: Triode preamp with TL072 phase inverter buffer?

texts: Wondering if anyone can advise on this tube triode (12ax7) preamp stage followed by an Op Amp buffer stage to correct the inverted signal. I wired it up and did not work. Before tho, I wired it with 22K resistors instead of 220K. Perhaps signal was overloading OpAmp? Also, should the impedance output from the OpAmp be essentially the same as if it were from the triode, just inverted?


texts: Wire to board connections; turret terminals

texts: Are turret terminals robust for wire to boards connections as shown below? Are there other/better ways to implement this? It might depend on the application I think. I've seen these types of connections used for transmitting power instead of signals.


texts:
The diagram below shows the control circuitry of a heating system. I am trying to understand why the wiring depicted here caused the fan relay (PC90-360Q) to 'chatter' constantly when powered on.

Like many HVAC systems the controls operate on a 24 VAC signal which is produced by a transformer stepping down from 120V. Various equipment such as pumps & fans run on 120V also and so relays are used to mediate between the controls & the devices.

The seemingly relevant part of the intended operation was as follows:

System is powered on
Thermostat detects heat is needed; closes its internal switch

Red / green path is energized through the fan relay coil
Water pump relay is also energized (via one of the zone sections on the bottom, all actually wired as in the blue example)

Fan relay closes its 120V contacts, energizing fan motor

Now what actually happened was that when the thermostat switch would close, the fan relay would 'chatter' seeming to switch on/off fairly rapidly.

The problem was not the thermostat itself - replacing it with a jumper wire produced the same result.

Notes:

The control voltage was actually about 26VAC, but that seems to be within tolerance as far as I am aware.
The controller ZVC406 is a self-contained board which normally just operates thermostats, valves, & pumps. Controlling the fan was an additional requirement necessitating the addition of the relay in question.

FYI I have actually solved the issue by instead wiring the relay between the switched output of the thermostat and the return pole of the transformer (i.e. a parallel path instead of series). So this question is really just for my own understanding.


texts:
This has been bothering me:

If I am told \$v_1 = -36\,\mathrm{V}\$ and \$v_2 = 18\,\mathrm{V}\$, how am I meant to find \$i\$?

I figured since \$v_1\$ is giving off a negative current it would be flowing in the opposite direction of \$i\$, and wouldn't the equation to find \$i\$ then become \$18-(-36)=i\$?

I thought about loop or nodal analysis but then I realized there aren't really any nodes, just loops.


texts: Why the distribution network have 4 wires ( not neutral)?

texts:
In a real network the distribution lines were 3 lines (ABC). At one pole the lines became 4 lines which are ( ABBC) the phase B split to two lines . Could you please illustrate why they split them to ABBC configuration.

Thank you


texts: SPI Interrupt Handler delay in STM32F303?

texts:
I'm working with an STM32F303 microcontroller configured in slave mode running at 72 MHz, and I've come across some strange behavior that I'm trying to track the origin of. The master first sends across ~40 bytes and clocks them at ~300 KHz. After a 6 ms pause, the master then starts to transmit ~20 bytes at 5 MHz and repeats this behavior indefinitely. Since I have a logic analyzer, I've been using it in conjunction with some debug GPIO pins to find out approximately when the SPI ISR is firing.

During the first set of bytes, the Receive Buffer Not Empty (RXNE) interrupt takes ~0.52 us to trigger after the last bit of the first byte has been clocked in. I would expect that I would see similar behavior for the other set of bytes, but instead, it takes 1.3 us to trigger for the faster clocked bytes.

This is a problem for me, because by the time the 1.3 us has passed, the second byte has already been clocked in when I should have had data ready for it to clock out with it. I've checked my code and it doesn't seem like any other interrupt is firing, and I've also given my SPI handler the highest priority, so it shouldn't be preempted by any other ISR to begin with. I'm positive that speed isn't an issue, because even though the SPI peripheral I'm using is actually clocked at 36 MHz, it should be plenty fast to address a master clocking in bytes at 5 MHz.

My only guess is that it's something hardware related with the STM32? Has anyone seen behavior like this, and or do they know the origin of this? Also any possible workarounds?


texts:
I am looking for circuits used to measure or monitor the current charging of a battery (Li-Ion or NiMH), microchip has proposed the following circuit:

My concerne is about the selected circuit in RED

I did not understand how does this ciruict works!
*Why  have we used R24=1.2M? Especially in case we remove R21 (As it is noted by DNP)

*What is the contribution of R16, C12 and R18 in measuring the current flowing through a parallel resistors R4 and R5

*What about C15, is it used as a filter or just for optimization?


texts: Can't upload to SAMD21 over SWD port. Tried Black Magic Probe and Atmel-ICE, Arduino IDE and PlatformIO

texts:
I must be missing something here. I’m unable to upload to a SAMD21 microcontroller with either a Black Magic Probe (v2.1) or Atmel-ICE. I have tried using both Arduino IDE and PlatformIO and haven’t had any success. I am mostly hoping to program an Adafruit Trinket m0 using a pogo pin fixture which connects to the SWD and SWC pads on the bottom of the Trinket m0. I have been able to program these Trinket m0s over USB, but my application requires the USB port to be removed. I have also tried to program an MKR 1000, and a custom SAMD21 PCB (that someone else was able to program on their computer) using the 10 pin jTag/SWD interface and gotten similar results.
I have tried uploading with PIO and the Black Magic Probe both with and without the upload_port option specified, using both ports that appear when the Black Magic Probe is connected. I have looked for how to use the Black Magic Probe with Arduino IDE, and I have found examples of them being used together, but haven’t found instructions on how to add the Black Magic Probe to the list of programmers supported by Arduino IDE. I have tried the normal upload option with the Black Magic Probe by specifying either of the COM ports that appear when it is plugged in.
When I connect Atmel-ICE and look in the device manager it says the drivers are not installed. I have tried searching automatically and manually online and have not found them.
I am including pastes of the uploader output for both Arduino IDE and PIO using both the Black Magic Probe and Atmel-ICE, uploading to the Trinket m0:
PIO, Atmel-ICE: https://pastebin.com/mcKLt0kU
Arduino IDE: Atmel-ICE: https://pastebin.com/4S1VY0mG
PIO, BMP: https://pastebin.com/XByDshRh
Arduino IDE, BMP: https://pastebin.com/RJtMKQhx


texts:
I would like to vary the value of the inductance in function of the current flowing through it.
Here is the simulation :

I have some troubles to make the current at t = 0 to be equal to 0 without adding an inductance (L3). Also, I do not know how to "measure" the current through the inductance without adding a voltage source (V3)
Above all my simulation has a problem of "timestep" too small, but I do not know how I can do a simpler simulation ... Is impossible for LTspice to evaluate the inductance each time with the formula given by the arbitrary voltage source (B1) ?

Version 4
SHEET 1 1208 680
WIRE 336 192 112 192
WIRE 112 256 112 192
WIRE 336 304 336 192
WIRE 112 384 112 336
WIRE 336 432 336 384
WIRE 320 464 224 464
WIRE 224 512 224 464
WIRE 336 560 336 496
WIRE 224 624 224 592
FLAG 112 384 0
FLAG 336 560 0
FLAG 224 624 0
SYMBOL voltage 112 240 R0
WINDOW 3 -369 62 Left 2
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR Value PULSE(5 0 0 1e-3 1e-3 0.5 1)
SYMATTR InstName V2
SYMBOL AutoGenerated\\VARICOIL 336 464 R0
SYMATTR InstName U1
SYMBOL bv 224 496 R0
SYMATTR InstName B1
SYMATTR Value V=(-0.204*ln(I(V3)*34/0.01273)+1.1283)*350e-6
SYMBOL voltage 336 288 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V3
SYMATTR Value 0
TEXT 48 536 Left 2 !.tran 1s
TEXT 48 480 Left 2 !.ic I(L1) = 0
TEXT 56 440 Left 2 ;Ix(U1:1)
TEXT 496 184 Left 2 !.param l_wire = 0.01273 N = 34 a = -0.204 b =1.1283

Thank you very much ! :)


texts: Powering 12V 2A device from high-power USB portable charger

texts: I'm in the middle of a project and I've recently bought a 26,000mAh portable charger with 4 USB ports on which can each deliver 5V and 4.8A max. In my project, I'm using an amplifier which needs an input of 12V 2A. What can I use to get 12V at 2A from the USB ports on the portable charger?


texts: How to cheaply build a latching relay system to disable a circuit until power is cycled?

texts:
This is my first post here. I have an aftermarket backup sensor that needs to be disabled when I back a trailer. I want to be able to push a button to disable it, but have it be automatically re-enabled when the ignition is cycled. Right now the buzzer is powered by the reverse tail light, but I want the disable device to be controlled by the ignition. Reason being is when I've got a trailer, I may put it in R and D many times (cycling power to the unit), but I'll want the system to be silent until the next time I start the vehicle. So whatever controls it controls the power is NC until I press the button to open the circuit, but then it goes closed when ignition is OFF (or off then on).
I looked for a simple NC latching relay, but it doesn't seem to exist. All latching relays I found required a signal to toggle them between open and closed. The push button will give it the signal to open, but how can I give it a momentary signal to close once the ignition cuts off?
I suppose I can also use a timer relay, but I am hoping to do it the way I described.


texts: Twisted-pair wire's effect on Common mode noise

texts:
In another answer here on the SE, this statement was made:

  Usually, my goal is to have all EM noise appear to a good amplifier as common mode,
  and use twisted pairs to achieve this."

(emphasis added)
This seems to suggest that using twisted-pairs vs independent, single wiring will change how EM noise will alter a signal.
My question is in regards to the part I've highlighted.  How does twisted-pair wiring affect noise on the signal?  Is there something special about the twisting that facilitates this effect?  Or is it just the proximity that's important.  At which point, could I just bundle the individual wires and zip-tie them (or similar) together?

(see here) for the answer from which I'm quoting. Taken from 2nd paragraph.


texts: I wanted to design a circuit where the LED turns on when the voltage is in the range of 4.9 to 5V and same to that of charge with the range of 0.5 to 0.52. Can anyone help me with a basic circuit?


texts: Is it possible to design cascaded LC filters with inductors sharing the same core?

texts:
I want to design an higher order LC filter for filtering out a power signal. In the theoretical design, the inductors are supposed to be on separate cores. But in practice, it will be very costly and space consuming. Is it possible to wind the inductors on the same core (e.g.; a toroidal core)? If it is possible, what must be the proper dot-convention between these inductors?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm new to embedded programming and looking for advise on a couple things:

I'm developing two "projects."  One is based on Microchip's dsPIC33 series of micros and the 2nd project involves Freescale iMX515 processor much like the pandaboard.org system.  I may purchase a pandaboard to get up and running quickly.

So with my two projects based on the above core components, I was considering this board by MikroElektronika:

http://www.mikroe.com/eng/products/view/669/uni-ds6-development-system/

And was looking to hear feedback from anyone who may have purchased this to do some simple POC(Proof Of Concept) type work.

My 2nd question:
2.  With the Linux on iMX, I plan to make use of Freescales ATK, LTIB, and GCC to build up the software but for the dsPIC, what C compilers do you use?  I understand Microchip has one that installs with MPLAB IDE but I'm not sure how full featured it is yet.  MikroElektronika offers a full IDE & C compiler that looks/seems impressive from reading about it but I'm interested in any feedback from those of you in the trenches with it.  Particularly, I'm looking for anyone who has experience with both compilers (Microchip and MikroElektronika) to give me some advise.

Thanks....


texts: RGMII - Origin of RGMII and does a standard exist?

texts: I'm implementing an Ethernet system on a Xilinx FPGA, and I've been reading IEEE 802.3-2015, but nowhere have I found mention of RGMII which is the interface to the PHY.  After extensive searching, I have been unable to find a source for where RGMII came from and whether a standard exists, I've just been able to find manufacturer's specs for the interface.  So my question is how did RGMII come to exist and is there a common standard out there?


texts:
I need to create a current sensing switch and am looking for ideas. I have very little experience with op amps / comparitors (as you'll see) but this seems to be the way to go.

I am monitoring 24VDC motor and if current is > 2.6A, I need to signal to a microcontroller to disable the motor.

I have a 175-R10-JBW (.1Ω) shunt resistor and an LM311 comparitor.

My testing shows that when the motor current = 2.6A, the voltage drop across the shunt resistor is ~.01v. When current is 1.3A the voltage drop is ~.005v.

My question is how do I use the LM311 to to state if "-" is .01v > than "+", send low output of LM311?

Of course I do not want to be shown exactly how to do this, just some direction on where to go. I've seen a lot of writing on current monitoring and op amp outputting an analog voltage proportional to motor current, that is just way overkill and would like to simplify.

Below is where I'm at and I know it's not close to where it needs to be. Any input would be greatly appreciated.


texts: Do latching relays controlled by two different open/close pushbutton exist?

texts:
I need to control a latching relay but I don't need to change its state alternatively with one single input. I need to control its state with two separate pushbutton: "open" and "close". Does it exists?

If the relay is open and I push "open" nothing should happen and the same for "close".


texts:
If I want to draw this type of picture
which program should I use?

Just for drawing not for some technical things.


texts: SPI flash chip failing without a 1M resistor from power pin to ground

texts:
Why would an SPI flash chip stop working after a short random period of time but work fine with a 1M resistor from the power pin to ground?

I'm debugging a problem with an SPI flash chip (W25Q80) driven by Atmega 328P at 765 KHz SPI clock stopping to work after random small intervals of time (200ms-5s) or not working right from the power up. This failure is seen as the chip stopping to respond on the MISO line (the line is floating) where it was responding to the same command just before that (the same power up cycle).

I've tried ceramic through hole capacitors of 100nF, 100pF and 15pF from power pin to ground and this doesn't help.

Then I connected a scope to the power pin of the flash chip and it started working.

Connecting a resistor of 1M from the power pin to ground also makes it work.

What could be an explanation here? Am I using wrong bypass capacitors with wrong ESR and the resistor acts as a small but sufficient bypass cap with high enough ESR?

This is reproducible with 2 chips so this makes it less likely that this is because of a faulty chip.

The datasheet for the flash chip doesn't give any recommendations about bypassing.


texts: Does anyone know what this component could be?

texts:
I am currently working on an already fully assembled PCB. I want to get into Hardware Reverse Engineering and my first step would be to identify all important components.
I found most of the components via a simple Google search but there is one that I simply can't identify.
I even tried to search for the company logo (the thing in the left upper corner, I guess that's the company logo, at least I don't know what else it could be) but I can't find anything helpfull.
This is why I am asking here, maybe someone of you knows what this can be or even knows the company :)

My suggestion btw is, that it could be the NAND Flash but I am not sure.

Picture description (in case you can't read the characters):

FP1545

5F1GQ4UCYIG

H8K094


texts: what kind of tape is used in electronic devices

texts: I repair quite a few devices and one thing that bothers me is that when I remove some of the tape pieces they never go back down right. I was looking for some replacement tape and didn't know what to search for. In the image of a samsung note tablet I highlighted some of the pieces. Is this just a version of capton tape? what should I be searching for on digikey etc. ?


texts: BTA16 triac snubber and operation quadrant

texts:
I am working on a dimming circuit to be operated by an ESP8266.

I have read a lot on this over internet and got a working circuit as well. But myself I am not satisfied with my understanding of TRIACs.

This question is not related to the dimmer directly, but more related to the operation of the TRIAC. I am not holding any electronics degree from any university, rather its my hobby and I am a self taught guy (thanks to internet).

The circuit is really simple. I am detecting zero-cross with the help of 4N35 and driving the TRIAC through MOC3012 using a GPIO of ESP.

Now today I got some free time and I was reading more about TRIACs and specially the datasheet of BTA16.

Here is the datasheet from farnell:

http://www.farnell.com/datasheets/1699992.pdf

Now as I am operating AC load (can be resistive or inductive load. Eg. operating bulb or fan) using the TRIAC.

The MT2 is connected to gate through a current limiting resistance and isolation side of MOC.

So the first question is, am I ever operating the triac in IV quadrant?

What I undrestand is, when the gate is positive and M2 is negative with respect to MT1, the triac is operating in quadrant IV.

Now as my gate is connected to MT2, and when MT2 is negative (compared to MT1), my gate is also negative. So I am never in the IV quadrant.

Please correct me if I am understanding something terribly wrong.

Now I am asking this question as the snubberless part (I want to use because of possible inductive load) of BTA series (BTA-600BW) does not operate in quadrant IV. I am saying this as I don't see any gate current specification for quadrant IV for the snubberless part (in the datasheet).

Also, in some reference circuits, I see people specified connect MT2 to HOT (phase) and other point of load to COLD (neutral).

I don't understand why does this matter for AC current. Please explain if that really has got a meaning.

Can someone please let me know, if I have learnt things in the correct way?


texts: Energy dissipation in RC circuit given AC sinewave input

texts:
I'm implementing a low-pass RC circuit that as an input will have an AC sine wave voltage input. How can I calculate the average power dissipation in the resistor, given R, C, peak (or RMS) voltage applied, and frequency?

Edit: Please assume no current draw from the output of the RC circuit. (However would be interesting to see the formula given an impedance across the output)


texts:
This schematic appears in a recent question. The triangle may be an op-amp or a comparator, because they both have the same connections. (Why) isn't there a separate symbol for a comparator? The functions of op-amp and comparator are very different.

Or from the document @boardbite writes about in a comment:


texts: op amp oscillation problem during chip measurement

texts:
I had an oscillation problem when testing my fabricated chip. As shown in these figures, the transient waveforms of the op amp outputs got severe oscillations. Ch1 and Ch2 are the two output nodes and the red curve is differential output after math operation.

the oscillation frequency for the two channels seem to be different, the lower one is around 20KHz and 133KHz for the higher one.

More about the op amp, it is a fully-differential class AB power amplifier designed for audio applications, it is connected with a closed-loop gain of 2. It is driving a 16 Ohm + 200 pF load and is supplied by a power supply of 1.2V

I suspects the amp is not stable. But during the pre-layout simulation, I checked the stability conditions of the amplifier and ensured it has good phase margin (>60 Deg) and gain margin (<-20 dB)

Please advice me on any possible source for this problem or any diagnostic test needs to done. Thanks in advance!


texts: Capacitor Storage Circuit Having Lower Voltage Than the Simulation

texts:
I designed a circuit to store a pulse of 8 volts and duration of 40 micro seconds. When I simulated the circuit it reached 3.5 volts and discharged.The circuit and the simulation is given below;

In real life, I have just made the circuit and when I test it, the output voltage reached at most of 387 millivolts then discharged.
What may be the reason for that?

Thanks in advance.


texts: How can I sense a signal on a 12v automotive wire non invasively?

texts:
I'm working on a project where I need to sense if a circuit is in operation on a wide range of vehicles. My plan so far is a current sensing clamp, and an Arduino micro listening for the current draw on that wire to be above 0ma. (or a more reasonable threshold to be determined)

I've looked into the normal clamp meters for AC applications, but they dont work on DC. I also need this to be non invasive, and able to be quickly attached to and from various wires - so must be a split loop pickup or similar... These types of current sensors wont work, as they are invasive.

I'm thinking some kind of a coil on an Arduino analog input, that is clipped onto the wire to monitor - but I'm at a loss as to what this coil needs to look like - and I'm not getting anywhere trying various random coils hooked up to an Arduino and looking for any change in analog read...

Can anyone offer any help on this?


texts: Component / Circuit for variable resistance (0, 5K, 100K) at 110V and 1.5Amps @ 0Ohm

texts:
I am searching for a circuit or component, lets call it IC1, which can deliver varieieng resistance with zero capacitance for a power output.
When IC1 has 0 Ohms, there will be 110V and 1.5AmpsMax pulses (capacitive load).
5K and 100K should be possible.

simulate this circuit – Schematic created using CircuitLab

Currently I am thinking of a relais and digital potentiometer. But are there potis which have 0Ohms and can hold 1.5Amps@110V?
The Tolerance can be 20%. But up till now, I found no poti which has the 0Ohm, or when f.e. LSB = 0.6 and wiper is 400 Ohm, I can assume that I have 0.6*400 Ohms at input == 0V?

Are there simpler solutions, or other ICs which can do that?

To add, the circuit will be controlled by an IC, so a normal poti is no option.


texts: Admittance inverter realisation in filter design

texts:
I read some theory about lowpass prototype filters in the "Handbook of Filter Synthesis" by Zverev and in "Microwave Filters for Communication Systems". I read these two because I want to understand how the coupling matrix of a filter works and how a filter with a given coupling matrix can be realised. However, there is some part which I don't understand. It concerns the lumped element implementation of a filter. First consider this filter.

It is a classical low-pass filter. No special things about it. However, we now insert admittance inverters. This allows the series inductors to be replaced by parallel capacitors. This is nothing special either. Now comes the interesting part. If we do a bandpass transformation, all the parallel capacitors are replaced by LC parallel resonant circuits, as follows:

So far I don't have any trouble to understand the math. Now comes the realisation of the filter. An admittance inverters equivalent circuit consists of two negative parallel capacitors and one positive series capacitor. So, if each of the admittance inverters in the middle of the filter is replaced by its equivalent circuit, the LC resonant circuits are coupled by positive capacitors and the negative capacitors of the admittance inverters are absorbed by the parallel capacitors.

But what happens to the two admittance inverters at the load and the source, J0 and J5? How can these be implemented, especially when lumped elements are considered? There must be a solution, because there is a paper by Seymour B. Cohhn, "Direct coupled resonator filters", where he also has LC parallel resonant circuits coupled by capacitors. Unfortunately, the paper doesn't give a derivation of the circuits.


texts: How to find/make a latch that reacts to 0 / 1 inputs and keeps the last state while in high impedance

texts:
The title basically states what I want, but to detail more: I have a microcontroller that has some outputs directed to a TXB0108 level shifter. Basically it's an 8-bit bidirectional level shifter that has a control port (OE) that can be used to enable/disable the 8 data ports. When OE is low, all the data pins are in high impedance.
What I want to do is to set one of the outputs from the microcontroller (that goes to the TXB0108) to 0 or 1 while OE is high, and then set OE to low and have the last state of the corresponding output of the TXB0108 preserved. Any ideas?


texts: LTSpice sim with PWL data from multiple files

texts:
I want to run an LTSpice simulation with data acquired from an actual, real circuit. I have multiple files containing data from different scenarios and I need to consider them all. Is there a way to run the simulation multiple times, using data from a different file each time?
Here's a simplified schematic to illustrate what I've tried - it doesn't work (I get an error: Could not open file "c:\data" in PWL):

The folder C:\Data\ contains ten files, named 10.txt, 20.txt, ..., 100.txt. The sim works fine if I specify an actual file name in PWL file.
Any suggestions how I can make this work? It would really help my task to see the data from the various scenarious (different motor speeds) in one diagram.
Thanks a lot!
merendo


texts: How does an ideal op amp amplify a voltage input when the voltage difference is 0?

texts:
I am a first year Electrical Engineering student. Next week I have my exams on Op Amps and their applications and such.

While looking at the op amps, there was always this one this that was confusing to me: in a non inverting amplifier, the inputs of the op amp are both zero, since the one at the +-pole is grounded. But when they are both zero, how can there be any amplification? I would think that you can just draw the line of the circuit, without writing down the op amp, since no current flows in the inputs of the op amp.

I really hope anyone can help me, since my teachers only really gave me how to solve it. I know how to solve op-amps, but not the logic behind them.


texts: How to implement HD74HC32 (quadruple 2-input positive-OR gate)?

texts:
I'm struggling to implement the HD74HC32 (quadruple 2-input positive-OR gate) package:

My breadboard looks as following:

Notes:

1.8 volt power supply, sufficient according to the HD74HC32 datasheet
1A is located at the left bottom
Vcc connected to [+] and GND connected to [-]
1Y connected to LED Anode
LED cathode connected to [-]

I tried every possible combination, with and without resistors, but I cannot get the gate to work.  The LED even stays on while 1A and 1B are disconnected.

How do I get this OR gate to work as expected?

The following question looks alike, but I just can't get it to work :(
Connecting AND Gate Chip to an Integrated Circuit

My reputation is too low to embed images, that's why linked directly, sorry!


texts: Need help designing an operational amplifier circuit

texts:
I am trying to design an operational amplifier with a gain of more than 200000. My first stage is a differential amplifier with an active load. I am getting a gain of about 1900 from it. Second stage is a common collector amplifier with unity gain just to minimize the loading effect on the first stage. Until the output of the 2nd stage (common collector amplifier), it all works well.
Problem arise when I try to connect a common emitter amplifier to the output of second stage to increase the overall gain. From what I can see, the BC junction of transistor 10 is forward biased so the CE amplifier doesn't work as an amplifier. I have tried many things like changing resistance values and biasing current. Nothing works.
Would really appreciate if anyone can help. I am stuck.


texts: Tracing a mobile phone's location without GPS

texts:
Without GPS, one way to locate a phone could be through trilateration. However, this would require the phone to be connected to 3 (or maybe even 4?) base stations to accurately obtain the phone's location.

In the case that the mobile phone is not connected to a sufficient number of base stations, trilateration would not work. Is there any way that the location could still be obtained from the base station? Would internet access help in any way?

I have often observed how a phone's location can be obtained by tracing a call made to the phone (in several TV shows and movies, which I agree is not a very reasonable or accurate source of information) and by having the call last for a certain duration, during which the location can be obtained. My primary doubt is: what additional information can be obtained in the packets transmitted between the base station and mobile phone, when compared to the case that the phone is idle (not communicating with the base station)? I was wondering if these packets might contain the needed location information.

Assuming that this technique actually works, how would it? How can tracing a call provide location information, unless the phone is connected to a sufficient number of base stations?


texts: Magnetizing current in switching converter

texts:
I have a question about the magnetizing current in a forward switching converter (image from "ON Semiconductor: Am improved 2-switch forward converter application").

From the picture it looks like there is a finite current in the primary, when the switch Q1 is off. My question is, how is that possible, since the primary is made out of a single wire ? How can you physically have a current in an open wire ?


texts: How do I check the stability of Multiple pole feedback Bandpass filter?

texts:
Is it possible to find stability measures like Phase Margin or Gain Margin for Multiple feedback Band Pass Filter?

The circuit is as shown below,


texts: What ist this component on early network cards with a slit in its package?

texts:
Early PC network cards (10BASE2, with a BNC connector) often had a two-pin component, typically yellow, with a slit in its package, close to the connector (image source):

What is this component, and what is the purpose of the slit?


texts: implementation of a large number of outputs (1024+)

texts:
I want to control 32x32 (or even 64x64) pieces of electroluminescent or electrochromic film with a microcontroller.
Film itself will be driven by supertex hv816. Planned refresh frequency 2-4Hz.

There are two variants:

simple, where piece has only two states, turned off and turned on
more complex where there are some intermediate states

For the first variant I think I can use shift registers, and digitally controlled pots for the second variant.

Is it possible to control this drivers using matrix approach? I hope there is  way better then one output-one piece of film implementation.


texts: Why Vds starts to decrease after Id reaches limit?

texts:
I've come across several articles and application notes regarding MOSFET switching, gate charge, Cgs, Cgd capacitances etc.

Power MOSFET Basics: Understanding Gate Charge

Power MOSFET Basics: Understanding the Turn-On Process

Q&A: Why is the gate charge curve (Miller plateau) of MOSFETs dependent on Vds?

These articles explaining the switching process, that Drain-Source Voltage (Vds) will only starts decrasing (at t2 - beginning of the Miller plateu) after Drain Current (Id) reached the limit:

I've created a simple LTSpice circuit to simulate the turn on process of a IRFZ44N.

Simulation result:

Simulation shows Vds starts to decrease as Id increases. Thinking in conventional current this actually makes sense to me, as Id can only start to flow (through R2) if there is potential difference between the 44V voltage source and the drain terminal.

Why is the LTSpice simulation differs from the "theoretical" Vds-Id behavior shown in the application notes? What am I missing here?


texts: I need to transmit my measured data of torque and temperature (measured using RTD and strain gauge) from a Rotating shaft running at 7500 rpm through IR communication. Is it possible? does line of sight become a problem?  Does the device (transmitter & receiver)needs to be stable for IR data transfer? Will the fast running shaft be a problem? how to accomplish this?


texts: What happens when I connect low ohm resistor to arduino I/O?

texts:
I would like to know what should happen when i connect low resistance to arduino output.

People say it will get damaged because it cannot supply the current. But I cannot understand this because the transistor can never exceed his max current.

Lets say, we can to drive the output low. This is done by activating typical one mosfet inside arduino pin. Schematic overview is shown here under. Rd is in this example 100 ohm.

After activating the transtor, it will conduct. The current that will flow can be found by using loadline.

The lower the resistor, the highter the slope of loadline, the more current will flow. BUT, if the resistor is very low, also the voltage over the RD will  discrease and the current will not increase anymore because the transistor is in saturation. This means that the transistor will never exceed the maximum current? So very low resistance can be used on I/O to draw max current. It will just give the max possible current.

So can I connect 100 ohm to arduino I/O or not?

I also wonder, IOL = 20mA, and VOL= 0,9 in TABLE. But when I check that graph VOL is about 0.3-0.5 when IOL is 20mA. This is for arduino. Please check answers below


texts: How to solder the 4-pin battery connector back to phone's motherboard?

texts:
One wickedly hot day the battery of my old Nexus 4 swelled up.  I use that phone as Android development platform, so most of the time it was plugged into the computer for USB debugging.  It's been like that over a year without incidents, but this day it cooked the battery.

I ordered an OEM replacement, got excited seeing it is quite fresh, and popped the "trunk":

"What can be easier?" - i said.  But i didn't know what was ahead..

Unscrewed 2 tiny Phillips bolts on the connector's metal top plate (marked with "V").
Had to apply some pressure to pop the connector up from the motherboard.  I used one of the plastic hook-tools conveniently included with the new battery.  Didn't know about the 2 side hooks (Phillips bolts weren't enough?!);  but even if i did - everything is so tiny and hard to get to..
Original battery was glued to the case, but not permanently.  So again carefully i pried it off with another flat plastic tool.

All seemed wonderful, i was about to put the new battery in, when i noticed that its connector looks different..  Huh??  That's when i saw that 3 pins and the connector's piece, which was soldered (not too strongly) to the motherboard, got ripped off of it, leaving one pin on the mobo (i took that photo not yet realizing what happened):

Now after studying the difference between battery connectors, i figured what happened and took the mobo's piece off the batt's one.  Then while trying to fit it in place the 4th pin got unsoldered from the mobo too..

Here's what i have now:  the plastic piece is intact with all 4 pins.

I'm gonna try to just attach it and see if 2 Phillips bolts make enough pressure to make contact for the 4 pins to touch the mobo.  I can certainly superglue it back..

But i'd like a solution which is more robust electrically.

Is there a way to solder it back?  Please, help!


texts: Can Toroidal-core Transformers be mounted with bolts going directly into the core?

texts:
I realize that the most common way to mount a toroidal-core transformer is by sandwiching it between two rubber-padded plates with one long screw holding them together and to the case (or whatever it's mounted to).

But I was thinking of another way to mount a toroidal core, in particular the kind that's made of a roll of iron alloyed with silicon (which is the best for low-frequencies, such as 50hz/60hz power transformers).  What if I were to drill and tap 2 adjacent holes into the core (perpendicular to the laminations), and then use screws to connect it to a case.  If the case is the perfect width, I could even put another screw into the opposite side of the core to attach it to both sides of the case.

This would also effectively ground the core.  That's a good thing, right?  Doesn't it somehow add stability to the transformer?

The only problem that I can see is that the screws would electrically link the plates together.

Other than that, I cant see why toroidal cores aren't ever already mounted this way.

Edit: Note that I am referring to the toroidal cores that are made of a roll of silicon steel (notice the spiral shape in my pictures), mostly for sizes ranging from 4-15cm in diameter as in mains transformers. Not the ferrite or iron powder cores used for higher frequencies, which tend to be too small for much benefit from this method anyway.

I also changed a sentence that used to say "Doesn't [grounding the core] somehow reduce problems when the core is getting saturated?"


texts: I am using a Sensor to measure barometric preassure. It states an extended range. What exactly is this ? And how can I read from this range ?


texts: Difference between Inphase/Quadrature (I/Q) Mixer and I/Q Demodulator

texts:
I wanted to know the primary difference between an Inphase/Quadrature (I/Q) Demodulator and an I/Q Mixer.

My requirements are as follows:
My input signal is a 500 Mhz bandwidth signal centred around 4.25 Ghz. I need to obtain the I and Q components of the baseband signal with respect to the Local Oscillator( of 4.25 Ghz ).

Previously a Hittite chip [HMC620](http://www.hittite.com/products/view.html/view/HMC620I/Q Mixer) which has been described as a "mixer" in the datasheet. But I am unable to find an I/Q "mixer" from big companies like Texas Instruments or Analog Devices (the companies that are easily available). If my understanding is correct, an I/Q demodulator (TI and AD ics available) should also do the job I require.Is this correct?

UPDATE 1 :

The TI I/Q demodulator chip i am talking about is TRF371135 . while the Analog Devices one is ADL5380. They do not exactly satisfy my 500Mhz bandwidth requirement, but they are the closest I could find on Digikey.

Are all I/Q demodulators I/Q mixers ? Or am I going fundamentally wrong somewhere ?

Thanks


texts:
I've made an arduino circuit for my high school physics project. It uses an ultrasonic and an infrared detector to sense distances and operate a Servo and Leds and I am having troubles with the circuit diagram.

Can someone explain to me how I can represent an ultrasonic sensor, an infrared sensor and a servo in a circuit diagram? The ultrasonic sensor has 4 pins. Echo, trigger, ground and Voltage. The infrared and Servo have 3 each. The block diagram is as below


texts:
I have seen some examples of schematics with page numbers in the filenames of the sheets. e.g. [01] sheetNameforSheet1.schdoc
Do does one do it, manually or is there more elegant way of doing it? How does one do it for hierarchical design. If you shift/add/remove any page, seems like you need to change all following filenames.


texts:
The definition of I2C is - "A multi-master multi-slave serial bus used for communication between low-speed devices".

However, I have been searching the web for a concrete explanation for this but can't seem to find any, and other search results are troubleshooting tips for related errors. The closest I got to a definition was these restrictions listed in the explanation for how USB works:

The maximum packet size for data transfers is 8 bytes
They cannot use Isochronous nor Bulk Transfer pipes
May only have 2 endpoints other than the zero endpoints

What are some examples of low-speed vs high-speed devices and what exactly does "speed" (speed of data transfer?) mean in this case?

My guess was that low-speed devices use serial transmission whereas high-speed devices use parallel transmission, but I am really unclear about this.

I am a newbie with regards to electrical engineering and would appreciate if a less technical/guided explanation could be given, thank you!


texts: Can anyone recommend characteristics for a low power (< 1W) 1:10 step up transformer for driving a piezo crystal (1nF capacitance) at 200kHz?


texts:
I saw a thing on my GDS-1052-U oscilloscope: if I set the time base to 25mS/div there appear a delay of the signal on the screen. So, when I rotate the knob for the time base to 25mS/div, there is a delay until the trace appear on the screen. If I set the time base to 5mS/div there is almost no delay. If I set the knob for 10mS/div the delay is smaller than the delay for 25mS/div. This happens on both channels. The probe is not connected to any signal source while I do these things. The voltage/division is 20mV/div.
Is that normal ?


texts:
This is my first question here, and my english is not the best, so i am sorry if i miss some community rules :)

I have a microprocessor MIMXRT1064DVL6A from NXP, and I am having a bad time figuring out the basic things to get this thing working. I need to be able to power and program this microcontroller.

Since I am using this to control a beamforming system for my master thesis, I need to made my own board with my SMD components (buy a evaluation board is not a option).

Someone with experience doing this can help me?

Is it OK if I replace the following circuit with a 7805 regulator, for simplicity.

Can someone explain me the following circuit? is it needed, or can i replace or ignore some parts of it for simplicity? i understand some parts of it, by reading the datasheets, but overall i miss some steps.

I take this from evaluation board schematic, in order to get some advice to start. Can someone help me, getting the basic stuff to get this thing working and ready to program it?


texts:
I'm looking to configure a Xilinx Zynq-7000 custom board with LVDS receivers according to the following diagram.

In my setup, the 'IOB' on the left represents an LVDS driver from a radar receiver and the IOB on the right represents the Zynq board that receives and processes the data. My concern is with the 50 ohm cable connecting the LVDS transmitter to the LVDS receiver. Standard 50 ohm coaxial cable is not going to work because there are actually many such connections that all need to fit within a single shielded cable that plugs into the Zynq board. I'm having a tough time finding higher gauge wire that specifies a characteristic impedance and I don't feel like putting two lengths of 100 ohm ethernet cable in parallel to make a single connection.

I was considering using MIL-C-27500 22-awg wire because we have a bunch lying around, but I can't seem to find any datasheet that specifies its characteristic impedance. The cable will be up to 3.5 feet long and will be used to transmit 10 MHz SPI data. A quick calculation using 100 ohms and 50 pF (completely made-up number approximating cable + receiver capacitance) gives a rise-time of 5 ns, so BW = 70 MHz. At 70 MHz, the electrical length is 14 feet so my 3.5 foot cable is starting to look like a transmission line (of course, these are extremely ballpark numbers).

Anyways, I don't think I can get away with using regular old 22-gauge wire (please correct me if I'm wrong) given that signal integrity is fairly important in this application. Where should I be looking for higher-gauge, 50 ohm wire for this LVDS application, or is there a better solution?


texts: How can I use Charlieplexing with common anode RGB LEDs?

texts:
I've an ESP32-based dev board (LoLin32) which has 26 digital I/O pins. I want to connect 25 common anode RGB LEDs to it. Connecting them in the 'normal' way would require 75 I/O pins, which I don't have ofcourse. I've heard that you could use Charlieplexing to connect n*(n-1) LEDs to n pins, but I don't quite understand how I could use Charlieplexing with common anode RGB LEDs.

Edit: it doesn't neccessarily have to be Charlieplexing, other solutions are welcome too. I know about WS2812-ish things, but that's something I wanted to avoid.


texts: convert Unsigned Int to array of chars (String)

texts:
EDIT: I am using this for programming a pic, so the C will be quite limited. The compiler is XC8.

Following function expects me to pass a string:

void OLED_string(char* str, short x, short y) {

    short pos = 0;
    char character = str[pos++];
    short startx = x;
    short starty = y;
    while(character != '\0') {
        OLED_char(character, startx, starty);
        if(startx >= 123) starty++; //wrap around
        startx += 5;
        character = str[pos++];
    }
}

I would like to display a value I have in a unsigned Integer. This value should be converted to Float and then divided by ten. Since float is very slow I would prefer to convert the integer to a string, and then simply add a point before the last character. I tried to pass directly the integer to this function but it does not work.
Thanks!


texts:
I'm writing a code to enable and disable the watchdog timer in ATmega32. I'm using the function in the datasheet that disables the wdt. Also, I'm toggling led in the beginning of the code to know if the uC resets or not. The led keeps toggling which means that wdt is not off and the uC resets over and over.

This is my code

typedef unsigned char u8;
typedef unsigned long u32;

#define DDRA    *( (volatile u8 *) 0x3A )
#define PORTA   *( (volatile u8 *) 0x3B )
#define WDTCR   *( (volatile u8 *) 0x41 )
#define MCUCSR  *( (volatile u8 *) 0x54 )
#define SREG    *( (volatile u8 *) 0x5F )

// delay about one second
void
delayOneSecond( void )
{
    u32 i;
    for( i = 0; i <= 70e3; i++ )
    {
        asm("NOP");
    }
}

// toggle PA0 pin
void
toggleLed( void )
{
    // PA0 direction output
    DDRA |= 0x01;

    // PA0 high, delay 1 sec
    PORTA |= 0x01;
    delayOneSecond();

    // PA0 low, delay 1 sec
    PORTA &= ~(0x01);
    delayOneSecond();
}

// disable watchdog function (from datasheet)
void WDT_off(void)
{
    // clear global interrupt
    SREG &= ~(1<<7);
    /* Write logical one to WDTOE and WDE */
    WDTCR |= (1<<3) | (1<<4);
    /* Turn off WDT */
    WDTCR = 0x00;
    // set global interrupt
    SREG |= (1<<7);
}

int main( void )
{
    MCUCSR &= ~(0x1F);      // clear reset flags
    toggleLed();
    WDTCR = 7;              // watchdog prescaler
    WDTCR |= (1<<3);        // watchdog enable

    WDT_off();

    while( 1 ) {}

    return 0;
}

I have tried many things to disable wdt and none of them worked. I've read that wdt is affected by the fuse bits and the bootloader, but I don't know much about them.

uC: AVR ATmega32, toolchain: AVR-GCC, IDE: Eclipse.

Any help would be appreciated.
Thanks in advance!


texts: How does a Low Power Factor draw more current?

texts:
In the course I'm reading, there's this example to show that a low power factor leads to more current being drawn, and thus more power lost in the transmission lines.

Assume a certain load requires 1 kW to function correctly.

If the power factor were 0.9, and the power supply gives 110V, we would need 10A.
If the power factor  were 0.6, and the power supply gives 110V, we would need 15A.

However, something here just doesn't make sense. If we consider the power supply as an ideal voltage source, then the current has nothing to do with the given power.

It seems that he just assumed the load would draw the required power to function properly no matter what.

On the other hand, it seems to me that the current would stay the same, being affected by the impedance of the load, leading to a lower real power and thus a malfunctional load.

Where did I go wrong?


texts: KIndly advise if Class 1 BLE 4.0 -20dBm input or/and output sensitivity?

texts: i am building a class 1 BLE 4.0 100m but not sure if the -20dBm specfication is an output or receiving standard? Please any one with this information. Regards!


texts: Can I use X9C102 digitally controlled potentiometer on AC voltage?

texts: I am working on a project to make a dimmer using the triac and a photocoupler, and I want to know if I can use a digital potentiometer to regulate the intensity of the light. I know it works for direct current, but will it work for AC?


texts:
I'm currently in the process of getting MIDI input to my Raspberry PI through UART, and in order to follow the standards, I should optically insulate the MIDI cable from the RPI by using an optocoupler in such a way that then there is no current flow, I get logic HI, and when there is current flow, I get logic LOW, so probably the optocoupler is also inverting the signal.

Please note I'm kind of a layman here. I'm currently studying physics, and have always been very interested in electronics, but have never dug deep into this realm. However, I'm interested not only in getting things to work, but understanding why and how they work.

I'm currently planning on using the 6N138 optocoupler. In the diagram provided in the datasheet, there is a diode which I don't get the usefulness of.

The diode in question in the one that connects the base of the phototransistor to Vcc. If I understand correctly, the diode is in reverse bias when Vcc is at a higher voltage than the base of the transistor.

My guess is that this diode allows the base to discharge when there is no longer light arriving from the LED between pins 2 and 3. This, of course it just a guess, but it certainly seems that I'm missing something big here.


texts: Charge time capacitor in a BJT collector with a parallel resistor

texts:
Hello, Given that circuit that has a constant current(let's say 3mA), How do I determine the charge time of that capacitor? since in t=0 the capacitor would have all the current but later it will split, so I can't use the usual formula(Vc=Vi(1-e....), but also can't use I=C*dV/dt since I would vary with time. How can I model the behavior of the charge time through the capacitor?
and how does I do it if instead of a resistor I would have a diode? thanks a lot.


texts: Does changing PWM frequency in arduino affects SPI and I2C communication and helps controlling DC motor?

texts:
I'm using L293D based motor shield for controlling two dc-motors from Arduino Mega 2560.
I use 5 and 6 PWM pin for setting speed of each motor. I have two questions:

Does increasing frequency of PWM (from default 500Hz to maximum 31KHz) will make the motors more sensitive? With default frequency (apart from noise) the motors are working  above 130-140 PWM level. Below 130 they are not rotating, only giving the "BEEP" noise. There is also little difference between 130 and 255 level. Does increasing pulse frequency will make them more sensitive, so I could run them at like 32 level (1/8 max speed)?
If so: Does changing the divisor in timer0 (as described here http://arduino.cc/playground/Code/PwmFrequency and here http://www.mythic-beasts.com/~markt/ATmega-timers.html ) will affect SPI and I2C interface? Will (and how) it affect the pulseIn function? (I know it will affect the delay function, but I guess it I will need to rescale function argument).


texts: 10 volt power source for field recording gear from two 5 volt usb lithium battery packs?

texts: Can I join the two usb outs from the batteries in series to make 10 volts? This is not running from a computer and I will charge each pack separately. The device draws very little power but needs 9-16 volts to run. I will be using a hirose connector at the device end and a fabricated y cable with dual usb (male) plugs that are wired in series? Possible?


texts: Please help me perform DC analysis of the attached circuit and derive equation for VB (Q1)

texts: I am designing a differential pair with single supply source (Vcc), and I am very particular about not using split supply. I am using discrete current source for setting the tail current, and biasing the Q1 and Q2 using R4 and R5. To determine their values, I must know VB at Q1, which is sum of Vbe(Q1), VR1 and Vc(Q6) (w.r.t. GND). I am finding it difficult to calculate Vc(Q6) in such an arrangement. Please help me with this difficult arrangement.


texts: Should we include Source and Load Impedance while calculating two port parameters?

texts:
While calculating the \$Z\$, or \$Y\$ or \$h\$ parameters of a two port network, should we include the source impedance and load impedance or not? In other words, for finding \$Y_{11}\$, we short the second port, my question is should we short the \$V_2\$ or replace it by its internal impedance?
For example, in the following question,

  the h parameters of a two port network are given below: \$h_{11}=1\,;\, h_{12}=2\,;\, h_{21}=2\,; \,h_{22}=1\$; O/p Power is \$100\,W\$; The network is excited by a voltage source, \$V_s\$ of internal resistance \$2 \Omega\$ Calculate \$V_s\$

Are the h-parameters given in the question, found out by including the \$2\Omega\$ internal impedance or without including it? Rather, how those specified parameters would've been found out initially?
Does one two port network have only one fixed parameter (for Z, Y, etc)?


texts: Why does this datasheet specify 12 100nF capacitors?

texts:
I am learning to make my first PCB with an MCU and looking at the Power Scheme, it asks for 12 x 100nF capacitors. My question is why have 12 of them rather than 1 x 1uF, and 2 x 100nF (I see that there is limited value selection, but these are popular values too)? This would save space, and manufacturing costs. I also assume these are in parallel to add up the capacitance, is this a wrong assumption?
Thank you for your help.
EDIT:Thank you for all the good advice, due to request, here is the datasheet:
STM32F446xC Datasheet


texts: positive edged and negative edged D flip-flops

texts:
I want to know that my understanding about D flip-flops is right or not.

We have different types of D flip-flops:

Some of them are positive edged (0->1) and some of them are negative edged (1->0)
All of them take two inputs: an enable (clock) and another D input
They give two outputs: Q and Q'
For all of them, the output equals to the D input ( but they differ in the time of showing the correct output)
The Master-slave D flip-flop is a negative edged flip-flop.

Is this all true?

If not, what parts are wrong?


texts: Can I use the oscillation frequency equation for this circuit?

texts:
I'm not really sure if this is a question that can be answered so I'm sorry in advance if it isn't. I've just started doing electronics on a breadboard and I'm making a "Mini Strobe Light" from Jaycar's 'Short Circuit 2':

The book says that the first IC 555 (IC1) is a basic oscillator and that the second IC 555 (IC2) is a monostable multivibrator. I was going to use an equation for oscillation frequency (1.44/((R1 + 2*R2)*C1) to determine the flashing frequency of the LED. However, the book said that the potentiometer (circled in red) is not R2 and makes up R1 with the 33k resistor and that the circuit does not have a R2. On top of that, I'm not really sure if this equation is relevant as I thought that the LED flashes because of the output it receives from IC2. So I was just wondering if I could use the previously mentioned equation?

I'm really sorry if this is extremely longwinded but thank you to anyone who tries to help!! Please tell me if I haven't explained anything enough.


texts: I want to make a 4x4 set of cups which have holes in the bottom and lead into a chamber at the bottom of the base. The user will throw a ping pong ball and try to make it into one of the cups. If the ball successfully falls through the cup, it goes into the chamber. In my basic plan, I am planning to connect 16 sensors (1 for each cup) and 16 LEDs (again 1 for each cup) to a raspberry pi which will update a web server on which cup caught the ball and then light up the corresponding cup. My question is, what type of sensor would be the best to recognize whether a ping pong ball fell into a cup or not? Any suggestions would be appreciated, thanks!


texts:
I'm at best a hobbyist EE and could use some help reading a schematic. I'm trying to test a chip (TI BQ76920) I found that will read the voltages from a multiple cell (1-5 cells in series) Lipo battery that can be accessed via I2C. I have plenty of practice with reading device registries from breakout PCBs but bread-boarding from a bare IC is new to me.

Anyway I have a schematic from the datasheet and it has values for some of the resistors and capacitors but not all. I highlighted the values in the image. There are 6 resistors called Rc on the left, next to them are 6 caps named Cc, on the bottom left toward the middle is a resistor called Rsns, then at the top to the right is a resistor called Rf and below that is a cap called Cf. Not sure what these are or how to calculate what they should be. Are these standard values that show up a lot and I should know what they mean? Any and all help is much appreciated.

Here is the schematic in question:


texts: Single power supply replacement for LM741 op amp?

texts: I'm trying to build a twin-T oscillator for synthesising drum sounds. The LM741 heats up pretty quickly and the circuit hardly oscillates even when the feedback is at 100 per cent. Even with an LM386 amp I hardly get anything (though I can see some oscillation on the scope). The circuit gets 10ms 5V pulses from an Arduino. Does the TL071/2 run from single supply? Can it replace the LM741?


texts: Error-Detecting Code and ASCII Character Code?

texts:
As ASCII character code uses seven bit to encode 128 characters and most computers manipulate an eighth-bit quantity as one byte and ASCII characters are stored one per eight bit, and an additional bit(most significant bit) is taken zero for ASCII characters and other 128 bytes with most significant bit 1 are used for other types of characters e.g. italic etc.

But when even parity is created let's say for example for T (ASCII 1010100)
 for error detection when transmitting it becomes T( even parity 11010100) with 1 as most significant bit but this code is for another character (from those which have 1 as MSB).

Will it not be overwritten?
How this happens?
Or what I'm lacking in my concept?


texts: Port full register file from/to a verilog modue

texts:
How can I port out/in a register file with Verilog (synthesis-able code). At this specific code a generate loop code is not viable due to the architecture of an existing code.

A test code, trying to port to/from my module a dynamic register file, with size based on a parameter.

module mux_test (/*AUTOARG*/
   // Outputs
   ro,
   // Inputs
   clk, rst_n, ain, v, din, bias
   ) ;
   parameter D_WIDTH=8;
   parameter A_WIDTH=2;
   localparam N = 1 << A_WIDTH;

   input wire clk, rst_n;
   input wire [A_WIDTH-1:0] ain;
   input wire               v;
   input wire [D_WIDTH-1:0] din;
   input wire [D_WIDTH-1:0] bias[N-1:0];
   output reg [D_WIDTH-1:0] ro[N-1:0];

   wire [D_WIDTH-1:0]       d2s    = din + bias[ain];

   integer                  i;
   always @(posedge clk, negedge rst_n)
     if (!rst_n)
       for(i=0; i<N; i=i+1)
         ro[i] <= 0;
     else if (v)
       ro[ain] <= d2s;

endmodule // mux_test

The model-sim gives me the following:

  -- Compiling module mux_test

  ** Error: ..../mux_test.v(3): (vlog-2110) Illegal reference to memory "ro".

  ** Error: .../mux_test.v(5): (vlog-2110) Illegal reference to net array "bias".


texts:
This question is linked to this one:

Octave rlocus: format ploles and zero

I am using the Octave command pzmap but the size of the markers of the poles and zeros by default are very hard to see on the computer screen. I have looked at the pzmap.m file and changed the line:

h = plot (pol_args{:}, zer_args{:});

to

h = plot (pol_args{:}, zer_args{:},"markersize", 20);

but there is no effect.

and putting the markersize parameter in an actual code is not valid:

num=[1 3];
den=[1 5 20 16 0];
sys=tf(num,den);
pzmap(sys,"markersize", 20) %not valid

Any suggestion?


texts: Using TBD62083 to drive LED array from CPLD

texts: I am looking for a cost effective way to drive 6 seven segment LEDs and 20 discrete LEDs from an Altera Max V CPLD.  The CPLD has I/O voltage of 3.3V and 4mA drive and the Common Anode seven Segment display has Vf=4.0V and If=20mA.  After considering Fets, transistors and other options I have settled on the Toshiba TBD62083AFG 8x DMOS transistor array with a 39ohm resistor between it and the LED.  At $0.52 ea it seems the most economical and I have room for the rather large 18SOIC pkg.  Does anyone have any experience with this part in this application or have a better part in mind?


texts: What is the simplest possible circuit for a wireless on-off switch

texts: On one side I have 5V DC powering an LED, and on the other side I have a button (switch/latch/whatever). What's the simplest circuit for this button to control the state of the LED (hopefully without OpAmps)? Range is not important, just the principle. Not including electromagnetic induction...


texts:
Analog CMOS layout finger size
I am doing analog CMOS layout in under 65nm processes.
What is the "rule" on the finger size I use for layout? Is there a rule of thumb for this?
For example, say I have a simple 2 stage opamp with an NMOS differential pair with PMOS active load and a second stage which is a common source stage. So I have three stacks to layout - a PMOS stack, and two NMOS stacks if you include the biasing for the NMOS differential pair.
You have a total width of a transistor but you can have transistor fingers each with their own width and then the amount of fingers*finger width = total width.  So how to pick the finger width is the question.


texts:
I recently bought this product from Amazon, but need to get a splitter for the 20V output. I need to know what to look for though, and cannot identify what kind of cable this is / what to search for.

The print on the cable is

  (UL) SPT-1 2X20AWG VW-1 105°C 300V E307922 WL

  C(UL) SPT-1 2X0.519²(20AWG) FT2 105°C 300V WL +LF+

Please let me know what kind of cable / splitter to look for. Thank you!


texts: 5V 1A Solar panel only delivering low power

texts:
So I bought this 5V 1A solar panel that can be used e.g. to charge your smartphone accroding to the product description.

When I measure the voltage using a multimeter I measured 6.9 V. A little bit higher than my expectations. However, when I measured the Amps it was ~0.3 A, less than I expected at blazing sun.

I decided to add a 6 ohm resistor and measure V and A again. To my surprise I measured to voltage to just 1.6 V and the current to 0.2 A. Later I read that I/V ratio for solar panels is not trivial...

My question: How should this solar panel be suitable to be used for charging a smartphone when a smartphone clearly needs 5V?


texts: Formula for BJT common emitter output characteristics curve

texts:
I collected experimental data of input and output characteristics of a BJT NPN in Common Emitter configuration. I need to find the right function to fit the Ic vs Vce, but I'm not finding it. I've used the Shockley Equation with no luck. I have tried the Early model and it worked fine on the linear region, but I need to fit the whole curve. Could you help me finding the right formula?
Thanks, Alberto.

Note:
this is the function I've used with no success.

Ic = a+bx+c(1-exp((x/(d*e))) Where x is Vce

Update:
My bibliography is Jacob Millman's Analog and Digital Circuits.


texts: Safe operating area for different types of battery chemistry?

texts:
I'm trying to find the safe operating area for various types of batteries; in particular I need minimum and maximum termination voltages, although information on temperature / power / current is also desirable.

For example, I know Li-Ion typically has a safe charge window of about 3.0V to 4.2V, and I've heard that NiCd / NiMH should never be discharged lower than 0.8V / cell.

Are there any authoritative resources that list the safe operating area for a majority of battery chemistry types?


texts: Arduino UNO and ADXL345 getting 0 0 0 OR -1 -1 -1 outputs with SPI communication

texts:
I have EVAL-ADXL345Z evaluation board from Analog Device hooked up to the Arduino UNO R3, the code complies and runs fine. At first I could still get the output values, but after sometime the output values i get is either  0 0 0 OR -1 -1 -1. Is it any problem with ADXL345 or Arduino UNO? Did I damage the sensor?

Connection:

ADXL345 --> Arduino
VIO     --> 3.3V
GND     --> GND
CS      --> Pin 10
VS      --> 3.3V
SCL     --> Pin 13
SDA     --> Pin 11
SDO     --> Pin12
INT1    --> Pin 8

Code:

#include <SPI.h>
#define PINNUMBER

int CS=10;
char values[10];

int x,y,z;
double xg, yg, zg;
char ff=0;
long line = 0;

#define   DEVID      0x00   //Device ID Register
#define   OFSX      0x1E   //X-axis offset
#define   OFSY      0x1F   //Y-axis offset
#define   OFSZ      0x20   //Z-axis offset
#define   THRESH_ACT   0x24   //Activity Threshold
#define   THRESH_INACT   0x25   //Inactivity Threshold
#define   TIME_INACT   0x26   //Inactivity Time
#define   ACT_INACT_CTL   0x27   //Axis enable control for activity and inactivity detection
#define   THRESH_FF   0x28   //free-fall threshold
#define   TIME_FF      0x29   //Free-Fall Time
#define ACT_TAP_STATUS   0x2B   //Source of tap/double tap
#define   BW_RATE      0x2C   //Data rate and power mode control
#define POWER_CTL   0x2D   //Power Control Register
#define   INT_ENABLE   0x2E   //Interrupt Enable Control
#define   INT_MAP      0x2F   //Interrupt Mapping Control
#define   INT_SOURCE   0x30   //Source of interrupts
#define   DATA_FORMAT   0x31   //Data format control
#define DATAX0      0x32   //X-Axis Data 0
#define DATAX1      0x33   //X-Axis Data 1
#define DATAY0      0x34   //Y-Axis Data 0
#define DATAY1      0x35   //Y-Axis Data 1
#define DATAZ0      0x36   //Z-Axis Data 0
#define DATAZ1      0x37   //Z-Axis Data 1

void setup(){
  SPI.begin();
  SPI.setDataMode(SPI_MODE3); //configure accelerometer for SPI connecttion
  Serial.begin(9600);
  pinMode(CS, OUTPUT); //set chip select to be output
  digitalWrite(CS, HIGH); //set chip select to be high
  writeRegister(DATA_FORMAT, 0x03); //put accelerometer into 16G range
  writeRegister(POWER_CTL, 0x08);  //Measurement mode
}

void loop(){
  readRegister(DATAX0, 6, values);

  x = ((int)values[1]<<8)|(int)values[0];
  y = ((int)values[3]<<8)|(int)values[2];
  z = ((int)values[5]<<8)|(int)values[4];

  line  = line + 1;
  Serial.print(line);
  Serial.print('-');
  Serial.print("X: ");
  Serial.print(x, DEC);
  Serial.print(',');
  Serial.print("Y: ");
  Serial.print(y, DEC);
  Serial.print(',');
  Serial.print("Z: ");
  Serial.print(z, DEC);
  Serial.print(',');
  delay(100);

  //convert accelerometer value to G
  xg = x * 0.0078;
  yg = y * 0.0078;
  zg = z * 0.0078;

  //Print the results to the terminal
  //so that i can monitor the reading using the serial monitor.

  Serial.print("xg: ");
  Serial.print((float)xg,2);
  Serial.print("g,");
  Serial.print("yg: ");
  Serial.print((float)yg,2);
  Serial.print("g,");
  Serial.print("zg: ");
  Serial.print((float)zg,2);
  Serial.println("g");
  delay(100);

}

//  char registerAddress - The register to write a value to
//  char value - The value to be written to the specified register.
void writeRegister(char registerAddress, char value){
  //Set Chip Select pin low to signal the beginning of an SPI packet.
  digitalWrite(CS, LOW); // to signal beginning of SPI packet
  SPI.transfer(registerAddress);
  SPI.transfer(value);
  digitalWrite(CS, HIGH); // to signal end of SPI packet
}

void readRegister(char registerAddress, int numBytes, char * values){
  // to perform read operation the most significant bit of the register address must be set
  char address = 0x80 | registerAddress;
  if(numBytes > 1)address = address | 0x40;
  digitalWrite(CS, LOW);
  SPI.transfer(address);
  for(int i=0; i<numBytes; i++){
    values = SPI.transfer(0x00);
  }
  digitalWrite(CS, HIGH);
}


texts: How do I safely drive a 500W inductive load with a computer power supply and suppress voltage spikes from switching?

texts:
I need to find a safe and reliable way to power a DC hobby motor off mains supply. The motor is large (i.e. 500W) 14.4V. Therefore, the current requirements are large i.e. 35A for a 14.4V supply.

I can't find such a power supply to purchase and my budget is small. Therefore, I thought I could use an ATX power supply from a computer. They typically have a high current 12V line that can deliver the required current, 42A in this case.

I will be using a power MOSFET to regulate the power going to the motor by switching it on and off using pulse width modulation PWM. There should be some huge inductive spikes created. I need a way to protect the power supply from these.

I was thinking of using several layers of protection just to be safe as long as they are compatible with each other. There location in the order that I mention them is arranged starting closest to the motor and moving towards the supply. The first line of defense is a freewheeling diode put in parallel with the motor forward biased from 0 to the positive supply direction. In addition, perhaps an RC snubber also in parallel. Then a 12V standoff TVS also in parallel in case the other two fail. However, this will short the power supply if it is triggered. If the supply doesn't have over current protection it will kill the supply. I need some sort of fast acting fuse or polyswtich to at as a current limiter in series with the supply. I've noticed that a the polyswitches are very slow. like 9 seconds to "disconnect" the line and I don't want to use a fuse that I have to replace when this happens. Is there a good solution to this problem, or is this all too much? That is, should I just leave the TVS and polyswitch out of the design?


texts: Why do I get less power from cheaper batteries?

texts:
This is something I ran into when testing a small heating coil with 9V batteries.

I tried an Energizer battery that was previously used so it only had 9V remaining. The coil heated up a weak red, but still noticeable.

I next tried a freshly opened Sunbeam 9V battery from the dollar store. Nothing. No heating at all. The battery measures 10V from my multimeter.

Even though it's at a higher voltage, its seems to provide less power?

I have two hypotheses on this:

Higher internal resistance. Perhaps cheaper batteries have higher resistance. But I don't think it should be that big of a difference.
It can't reach the same level of current. P = VI, so if less power given more voltage should mean much less current. I'm not sure how batteries work, but does the battery have a limit on much current it can produce? So the cheaper battery might have a shallow limit.

Which is correct? Or am I completely wrong?


texts: EM78P156 pins description? How does it work?

texts:
How does it work?
After research on its pin description in the internet, could not find the exact pins.

What controls the delay time about 2 seconds or about 5 seconds of the outputs between 2 output pins?

What controls the output or routine to repeat itself again when output reached by pin?

When input is supplied either with A3 or A4, the IC outputs 5V from 0V at B1 for about 5 seconds, and again drops to 0V from 5. After a gap of about 2 seconds, another 5V is output at B2 for the same time period, and so on until till B4. As B4 drops to 0V, the output repeat for another cycle starting again from B1 to B4. Then the cycle is complete.
If input is retriggered by A3 or A4, the same routine is executed.
Values of B6 to B9 remains same whether the IC is triggered or just at idle.


texts: Problems amplifying mV potential differences

texts:
I am trying to help my daughter with her science fair project of measuring efficiency of different types of household lighting in various heating conditions.  Since she doesn't have the electronics experience I volunteered to make the current data logger.

In order to measure the current going into the light I am using a poor mans toroidal coil (see picture).  I am getting a potential difference between the two ends of the coil of around 2-4 mv AC when a typical lamp is turned on.  I am trying to amplify this potential difference so I can feed around 2-5V analog DC into an Arduino for data logging.

So far I have tried just strait diode rectification (that didn't work as the input voltage to Ardunio isn't enough I suspect).  I then tried to use an 741 op-amp to amplify this potential, however that is also failing (see circuit below) as I get no output voltage (not sure why).

My question is: can anybody point me to a simple circuit to boost these potential difference in my coil to something I can rectify and log?  OR is there a simpler (non-expensive) way to accomplish current level datalogging?

EDIT:

I supplied +/- 5V to the 741, since that is the max V that the Aurdino can handle. The Toriodal coil was made from a piece of steel pipe 2" (3/4" dia.) long covered in electrical tape. It had 200 turns of 20 ga magnet wire. There is a slit down the side of the pipe. R1 was a 10 ohm resistor and R2 was a 1500 ohm resistor. I figured that should have given me several hundred millivolts AC, but I got no output at all on the 6 pin. If that had worked I was planning on going from a 10 ohm resistor for R1 to a 1 Ohm resistor. If there is a better op-amp to use I can switch out the 741 .

I attached one end of the coil to the 741 input (3 in the diagram) and the other I attached to the ground.

Edit:  figures for recommending Op Amp in comments.


texts: Where might the noise be coming from in this speaker driver circuit?

texts:
Well, it will be a broad schematic. To summarize, there my approach is:

Yellow part is for oscilations at three different freqs(around 0.8 - 2 kHz, different for each of the three signals), sinusoidal, I can get nice 6 Vpeak sine waves, observed with oscilloscope, no noise, smooth.
In the orange part, I use classical potentiometers to change the amplitudes of the signals. For this part, I suspect from the potentiometers, I know they are very unstable but I somehow have to use them.
Then, red part, adds the signals together, nothing fancy.
Finaly, the green part is my design to drive an 8 ohms speaker.

Now, when I connect the speaker, I get a noticable noise on the speaker output. It is both understandable from sound and also checked by oscilloscope. I have heatsinks for transistors, and I suspected from them for the reason I explained in my other question.

  when I inspect the signals in the circuit via oscilloscope, I see there is some noise on waveforms, while trying to understand where it comes from, I have touched the heatsink (...) It becomes much smooter.

However, then, I thought it might be resulting from something else and wanted to get your opinions about it. What can I do to minimize the noise ? Would soldering things on something like this solve things?

Things to note:

I got satisfying results in simulations, everything was as I wanted. However the reality spoiled me.
I implement the circuit on a breadboard for now, while prototyping, I suspect it may be bad in terms of noise.
I don't know it is relevant or not but the noisy parts are mostly in the upper parts of sinusoidal waves.

Thanks in advance.


texts: Scaling analog signal before ADC: A low cost, low pin and component count solution

texts:
Extending the question: Scaling Voltage for Arduino Analog In, Beyond Voltage Dividers

Making a simple digital thermometer. Ideally, my circuit will only need a 3.3v supply. The sampling will be by a PIC 8 bit ADC. I'm hoping to achieve full scale accuracy by scaling up the output voltage from the thermistor potential divider, using an  easily obtainable, cheap op-amps or alternative.

Perhaps someone could recommend low voltage single rail op-amps, (not op-amp circuits) or any really clever transistor circuits or similar that only use one or two cheap components to get better accuracy measuring a thermistor in certain ranges than just a potential divider fed straight to the ADC.

Thanks

Edit: Thanks for the response on the LT1677, however I'm having real trouble finding a retailer for one-offs! It's a little bit on the pricey side as well, so I'm still looking for alternatives.

I'm thinking of adding a 5v rail to my scaling circuit, so I can use LM2904N instead and get approx full accuracy, it's a cheap dual with full swing on the lower rail and just 1.5v less than full swing on the upper rail. Not ideal tho.


texts:
I'm here with yet another problem. This time I can't figure out what the question wants. I've calculated the Thévenin equivalent, however I can't work out how I should calculate the RL.

Is the load resistance the same as the Rth?

Here is my Thévenin equivalent schematic:

simulate this circuit – Schematic created using CircuitLab

This is the original question:


texts: Variable Frequency PWM to Analog Circuit?

texts:
I need to convert a PWM to analog signal. But the issue is, frequency of PWM may change. So, RC-filter option is not preferred. What kind of circuitry would be appropriate for this?

There exists an IC named LTC2644, which operates exactly as I want, but not meeting my frequency requirements.


texts:
I'm repairing a Tenma PS (straight forward 12V 4A linear) and I noticed
a couple 103Z ceramic caps on the bridge rectifier, however one cap goes
from ~AC to + and the other goes from the other ~AC post to -. What's the point on shunting those two diodes with .01s?


texts: When working with logic gates and transistors, which is more important to pass through them for them to work, a high current or a high voltage?

texts:
So I was wondering, if, say, I'm getting a current from a transformer where the current is very low but the voltage is very high. And there's a diode to turn my circuit into a DC circuit. And I'm using an AND gate to turn on my transistor.
For the gate, we need the two inputs to be high, but do we mean by the high input a high voltage or a high current. And to turn on the transistor do I need a high voltage or a high current or both?
I wrote this question in the physics community but I was kindly told that it should be posted here and that there are so many kind of different transisors but I was wondering what kind of transistors should I think of in my level (highschool igsce OL physics)
This confusion got into me when I was solving this question

and there were parallel and series connection—which contrary to normal questions where the high resistor would prevent a high voltage from reaching the other parts and it won't matter wether we think about voltage or current because they will always be low in the same time— here it was different. Even though it won't really matter which way I think about it here because in the end it's an AND gate but I still want to know.
PS: this isn't a hw question, I've the answers of the question already and understand how the circuit work, I'm just curious about how I should think about it.


texts: For what reason(s) is it not desirable to have the amplifier gain depend on the β of the transistor.


texts: Knock Sensor using 555 Timer with a timed light

texts: I have seen a few Knock Sensors using the Piezo Speaker and the Arduino. I am wondering if there is a way to eliminate the Arduino and utilize a 555 Timer and other simpler components so that when the Piezo sensor detects a Knock it triggers a Relay to illuminate a light either in three successive pulses lasting 3 seconds or a continuous on time of 3 seconds then off again until the next Knock? ie: (Knock: Blink Blink Blink, or Knock Light on(3 seconds)off) I apologize, I have just started learning some of this.


texts:
The book (Principles of Electric Circuits by Thomas Floyd 9th edition, International edition) says it's 1.955k Ω.
When I calculate I get (R1 || R2) + (R3 || R4) + R5 = 3.38k Ω.


texts: power pin to ground impedance- Short(0.3 Ohm)

texts: I am designing a board and the problem I am facing on the board hardware is that the core power supply and ground has very low impedance of around 0.3 Ohm. This is leading to a conclusion of two nets as if these are shorted together. Although the current drawn for that particular assembly for core power supply is 9A the impedance would be low(may be around 4-5 Ohm).But is 0.2 Ohm a correct value. We have done the x-ray analysis of BGA, and no solder bridging is observed. Can anyone suggest what could be the issue?


texts:
Im verilog beginner and I'm encountered some unknown syntax:

wire       slip_lock;
reg        fslip_lock;
wire [1:0] dslip_lock;

assign slip_lock = &{fslip_lock,dslip_lock};

What this code does? is it containment? or bitwise AND operand?


texts: Little torque of single phase asynchronous motor

texts:
I have a single phase asynchronous motor rated 230V, 500W. It has three terminals labeled U, V, W. I connected L1 to U and N to V (other way round makes no difference though). Between V and W is a 500V 18µF capacitor.

Without load the motor starts spinning and reaches top speed within two seconds. However when I put light load it starts rotating very slowly and is accelerating only slowly too. Once it reaches maybe ~ 2/3 of it's top speed of 2340 RPM (labeled, not measured) it get's much more torque.

Is there anything I can do so the motor has more torque when starting, without affecting torque at top speed? Maybe replacing the capacitor but to what value?


texts: Electrified Vertical mounted rotary joint questions

texts:
Hey all, continuing my PhotoBioReactor project. :)

Need some assistance determining not only what kind of rotary slip ring I need to use but where to get it as well.

Basic overview:
I plan on oscillating a vertical shaft 360 degrees over a varied timeframe. This shaft has some aquarium lights vertically mounted to it. I need to power these lights without the cords getting tangled up, hence the idea to use a rotary slip ring to pass the electricity needed through the rotating shaft's axle housing and have a stationary cord to the base unit and an automagical electrified light pole. Of doom.

Needless to say, finding a slip ring supplier (or even someone who knows WTF I'm talking about) has been... challenging. Help?

I need the rotating joint to be able to attach to 1/2" thick transparent lexan, support at least 30 pounds of weight on it (likely need ball bearings), pass enough electric-juice through to power (at full peak power) four fluorescent 24" T8 light fixtures that suck down 120v~277v 50/60Hz each, allow a geared servo or stepper motor to effortlessly rotate the shaft, and preferably not be a pain in the arse or wallet. :P

A work-in-progress Google Sketchup shot of the light-shaft:

Eagerly awaiting enlightenment,

-- Daerk


texts: High Voltage Linear Regulator Output Not Staying Constant

texts:
I'm trying to use a 3-terminal linear regulator LR8 (Also tried TL783 and saw the same problem...) to regulate 180V from a fixed PSU down to 116V, to power some very light loads < 1mA.

But when I power this thing on, the output voltage is all over the place!

Currently, I have the rheostat adjusted to 0, so the resistance from Adj->GND is 16K. This means the nominal output voltage should be ~97V. I put a 24K load at Vout... depending on output voltage should set the output current to single-digit mA range. (EDIT: And similar current range through the set resistor R6).

It looks exponential, but the output cap is directly connected so obviously the time constant isn't minutes.

At 120V, the load dissipates ~0.6W, the set resistor dissipates 0.9W, and the LR8 dissipates 0.75W. The regulator is definitely hot to the touch, so I was thinking temperature effects? But with thermal resistance of 81C/W, this only brings the temperature up to maybe 100-105C, within the operating range. I'm not sure how to measure the actual temp.

Also, if you have ideas for a better regulation alternative to this circuit, please leave a comment! Thank you.

VOUT drift:

The circuit is stupid simple:


texts:
The question is:

The answer is:

My question is how did he get the 100 (highlighted)?
Source:
PPI PE Power Reference Manual, 4th Edition – Comprehensive Reference Manual for the Closed-Book NCEES PE Exam
Publisher : PPI, A Kaplan Company; Fourth edition (January 31, 2021)
ISBN-10 : 1591267838
ISBN-13 : 978-1591267836
by John A. Camara PE


texts: Converting clock radio from 60 hz to 50 hz

texts:
I have an old clock radio that works fine, except for one detail. The clock is made for 60 hz mains but I would like to use it in a country where 50 hz is the standard. As the clock directly relies on the mains frequency to keep track of time, it slows down when used with 50 hz mains power, making it useless as a clock.

Is it likely that it is possible to modify the clock to work with 50 hz mains power? The clock radio is a Panasonic RC-6030. I have not been able to dig up schematics for it.


texts:
I'm having trouble to identify this (presumably broken) part for replacement:

It was used in a broken LED power supply, with 220-240 V AC on the input and 120-200V DC on the output. I suspect this part is broken, because there is always 230 V across it. One side of it is attached directly to the mains input. Its resistance appears to be infinitely high (measured resistance up to 20M, max. range of my Ohmmeter).

It looks like a resistor, but wikipedia tells me it could be a capacitor as well (source: http://en.wikipedia.org/wiki/Electronic_color_code#Capacitor_color-coding)

I have tried to figure out the value and I came out at a 1000V - 0.05 Farads capacitor, but I find this hard to believe. Can anyone confirm?
Thanks!


texts: STM32F4 Cube HAL UART. Is it a bug or am I missing something?

texts:
I am using interrupt based UART IO (no DMA).

HAL_UART_Transmit_IT function sets EIE bit in CR3 register. According to STM32F407 datasheet (and real behaviour), this generates interrupt only in multi buffer mode (when DMAR bit is set). EIE enables interrupt generation for frame error (FE), overrun error (ORE), noise error (NE). This error, as I understand, only for receiving.

Part of HAL_UART_IRQHandler function:

tmp1 = __HAL_UART_GET_FLAG(huart, UART_FLAG_ORE);
tmp2 = __HAL_UART_GET_IT_SOURCE(huart, UART_IT_ERR);
/* UART Over-Run interrupt occurred ----------------------------------------*/
if((tmp1 != RESET) && (tmp2 != RESET))
{
  __HAL_UART_CLEAR_OREFLAG(huart);

  huart->ErrorCode |= HAL_UART_ERROR_ORE;
}

if(huart->ErrorCode != HAL_UART_ERROR_NONE)
{
  /* Set the UART state ready to be able to start again the process */
  huart->State = HAL_UART_STATE_READY;

  HAL_UART_ErrorCallback(huart);
}

HAL_UART_IRQHandler checks for each error. If error occurred and EIE bit is set, it resets UART state, but doesn't reset interrupt enabling bits, so TXE interrupt will be always generated, but UART_Transmit_IT function treats state HAL_UART_STATE_READY as invalid and doesn't do anything. Infinite loop.

Part of UART_Transmit_IT function:

static HAL_StatusTypeDef UART_Transmit_IT(UART_HandleTypeDef *huart)
  {
  uint16_t* tmp;
  uint32_t tmp1 = 0;

  tmp1 = huart->State;
  if((tmp1 == HAL_UART_STATE_BUSY_TX) || (tmp1 == HAL_UART_STATE_BUSY_TX_RX))
  {
  }
  else
  {
    return HAL_BUSY;
  }
}

Is it a bug in Cube HAL?


texts: Deriving the Integral Voltage-Current Relationship of a Capacitor

texts:
I am having trouble understanding the derivation of the capacitor voltage equation in my circuits textbook.

Here is the process they followed from the textbook

My confusion is: when the initial voltage across the capacitor is not able to be discerned, that it is "mathematically convenient to set t0 = −∞ and v(−∞) = 0"

Why would t0 be set to −∞ and wouldn't v(−∞) = −∞ not 0?


texts: How to calculate the resonance frequency of a parallel LC circuit with L having a DC resistance?

texts:
Here is the parallel LC circuit with inductor having also r:
http://img842.imageshack.us/img842/4858/resonancelc.jpg http://img842.imageshack.us/img842/4858/resonancelc.jpg

How can I calculate the resonance frequency?


texts: Understanding capacitor usage in the Sparkfun arduino

texts:
In the schematic for the Sparkfun Arduino mini pro 3.3v https://cdn.sparkfun.com/datasheets/Dev/Arduino/Boards/Arduino-Pro-Mini-v14.pdf
there's a 0.1uF capacitor (C3) just left of the atmega ground pins going from vcc to gnd.  In the upper left corner on the power regulator there's also a 0.1uF (C10) cap from the output vcc to gnd which should be essentially the same thing.

What is the design rationale here?  I assume they're doing this for power smoothing but why not have a 0.2uF cap or two parallel 0.1uF caps on the regulator output?  Are they trying to say that the other one should be closer to the atmega?


texts: How is a diode used to regulate voltage?

texts:
Hi all, I was wondering how a diode is used to control the voltage here? Assuming the voltage coming in from the left is greater than the reference voltage provided by the potentiometer, the diode is somehow acting to ensure the voltage going out is equal to the reference voltage. How does it do this, and if I tried to create this in real life what should I watch out for when choosing a diode part?
Thanks


texts:
I have researched about PDM Data and I have seen this sentences on wikipedia:
In section of Digital-to-analog conversion

"The process of decoding a PDM signal into an analog one is simple: one only has to pass the PDM signal through a low-pass filter. This works because the function of a low-pass filter is essentially to average the signal" *

Then, I have tried this situation with MEMS Microphone which microphone has PDM Data output and I have seen low pass filter(RC filter) has able to  converting PDM Data to analog data clearly.
So, my main interest is about this 2 terms; "average the signal" and "low pass filter".
That are the questions:

How can the low pass filter do that?

What is the theory of behind the low pass filter can  average of signal? Can you explain this situation with mathematically through RC Low Pass Filter?

Can we say this "Low pass filters filtering almost (not clearly) all harmonics except Fourier first coefficient?(Note that ı assume  fourier first coefficient corresponds average of signals.)

Note thats:
*Wikipedia link is below
https://en.wikipedia.org/wiki/Pulse-density_modulation
*Yes, ı have research about this questions on the website but ı haven't found clearly answer...
and thank you for your interest...


texts: leakage inductance on three winding transformer

texts: I have a toroidal 3 winding transformer. It's a step up, lets say 1:10 ratio, the secondaries are identical. If I measure the leakage inductance, shorting 1 secondary at a time, I get about the same leakage for both secondaries. If I short both, I get about 10% smaller than the individual leakage. Anyone know the reason or have an idea of what the equivalent circuit would look like?


texts: Why does this resistor network simulate differently from the physical package?

texts:
I am trying to simulate a Bourns 4310R-R2R-104 dual terminator 104 circuit resistor network.

According to the datasheet, the circuit looks like this:

When I read the resistance between pin 1 and pin 2 on the physical package I get 200K ohms:

I built an equivalent circuit in Circuit Wizard and measured between the same pins but get a different result:

Why is this?


texts:
i want to build a constant current source to drive an LED like the one in the image below. I want to use a BSS138 N-mosfet transistor which is mainly used in logic level shifting. My question is if i can use a transistor like this or is it used only for level shifting? Will this be able to dim the led according to the potentiometer voltage? In simulation it worked just great but i wanted to get a second opinion.

Thank you


texts: Altium parts management in a small startup

texts:
I recently joined a small startup as the only HW designer (working in Altium 18) and am looking for ways to optimize my design time without having access to a full-fledged CAD team. In my previous jobs there was always a dedicated team of people who would manage libraries and design parts upon request. In my current situation I have had to design a lot of the parts myself, which isn't a huge problem but it is not optimal, especially because a lot of the parts are fairly common and I'm sure someone else has had to have done the same already. What I do not understand is why Altium's little brother - CircuitMaker has access to extensive libraries and it is possible to pull virtually any part that I have needed from there but Altium uses the much more limited Vault, which they seldom seem to update. My question is two-fold - 1. What do people in similar positions to me usually do? Do they just end up biting the bullet and designing all of their own parts / libraries? 2. Is there a way to bring Octopart libraries like the ones in CircuitMaker into Altium?

Thanks in advance!


texts: Can somebody please help me in understanding the fuse specifications. Actually i went through many fuse parameters. I am getting cofused between the hold current and the cut-off current since there is a large gap between the two.


texts:
I'm working with in RF system with the same RF coil for transmitter and for  receiver.  I wait 100us microseconds while the coil is discharged to change the transmitter mode to emitter mode.

If I open the circuit quickly, the current storage disappear and I don't have to wait the 100 microseconds.

I would use the MOSFET but the Mosfet has V threshold between Source and Drain to drive. The voltage aplicate in gate I don't mind but the
minimum voltage between Source and Drain yes because my signals received are of microvolts.

The TRIAC is the same because between in the MT1 and MT2 there is a voltage threshold. Do you know some switch or discrete component that I can use? switch without voltage threshold?

I use the same circuit to transmit and receive, but in receive mode the signals are microvolts and cannot exceed the voltage threshold between Drain and Gate.

I think in an example it would be clearer. For example, if I use the Mosfet irfz44n as in the following image.

I connected the 20V battery with a 100 ohm potentiometer, the mosfet and the DC motor. If I measure the voltage between Drain and Gate when the potentiometer is practically 0 ohm, the measured voltage approaches 2v. I cannot lower this value because the datasheet shows that this is the minimum.

My question is: do you know of a Mosfet, TRIAC, SCR ... that when in drive mode, the value measure between Drain and Gate (MT1, MT2 ...) will be 0v?


texts: Permanent circuit board jumper - I have a RTC chip that kills soldered battery before clock set

texts: If I wave solder in the battery, it begins draining rapidly until the RTC chip (clock) is set. So I installed a jumper. Now I manufacture without the jumper, and then in the bed of nails testing, I set the clock and install the jumper before I package it and put it in stock. I never EVER want the jumper removed, but it is happening. Is there a way to make a lockable jumper or other ideas for a solution?