texts: 4 - 20 ma current loop, Short circuit isolator

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I am trying to design a short circuit isolator, for 4 - 20 ma current loop based intruder alarm system.The below system,identify short circuit in sensing line and sensor activation(closing 1 k in line) as same signal.I tryed to make, fast isolator, that opens sensor line, before intruder panel, detect  a short circuit across the sensor zone terminals.

system block schematic.

Brief about system.

Working voltage  for zone 24 volt dc.

3.9k end of line resistor for minotoring line break.Line Resistance go higher than 3.9k reports fault.connected in parllel to zone terminals working in 24 volt dc.

1k resistance or less for fire/intruder detection resistance.Cinnected in parllel to zone, working in 24 volt dc.

System has its own fire and fault relay operates, in case  1k resistance appears across its zone or fire reported, if line resistance goes higher than 3.9k across tetminals.

Currently, any
short circuit across , intruder alarm zone, turns system to alarm mode, instead of a fault.

For the above requirement, below shortcircuit isolator with mosfet and external power supply designed, and its not functioning as expected

Design assumption:

Normally mosfet will be in on and powering optoisolator, any short circuit across terminal turns voltage across gate to source voltage zero.Turning off the optocoupler transistor, by isolating sensor and system postive terminal, thus a open circuit in line is reported instead of a over current situation.

I used, n chanel Mosfet(Irf z44n),  connected(Gate and drain) across intruder alarm zone  terminals in parllel, to sense,  short circuit and its feed back activating a series optocoupler working in 12 volt.

After connecting, isolator  circuit is not working as expected, once a short circuit simulated across,  current loop terminal, opto turns off, and isolating line, to limit short circuit current.

Experts,Please advise

1)whats wrong in my approach  ?
2)How, can i correct  the design error, in my circuit ?
3)Other  simple solutions for, fast  short circuit isolator for 4 - 20 ma current loop?


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I use an Orange Pi platform for flashing SPI chips soldered directly to the board. Chips are packed in an SO-8 package so I have to use 5250 pomona clip. There are no problems with flashing platform but there are issues when it comes to boot the platform. I want to boot my platform without removing a pomona clip. I've used a TXS0104E logic level converter. This chip features a tri-state buffer as well but it hasn't solved my problem.

Sometimes I need to unplug the MISO cable only and my platform starts but it is not repetitive.

I'm thinking of another solution. What do you think of building a buffer based on 4 relays? Maybe it's controversial a bit because of using the mechanic elements but I think I would have a certain disconnection the SPI interface?

A
Of course, I will make sure if the chosen relays handle such frequency.

Or maybe you have another proposals of solution? What do you think?


texts: Detection of object movement & rotation in magnetic field

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I need to develop solution for monitoring movement & rotation of components in 3D space (integrated logistical and production workspace). Components have a size of circa 0.5 x 0.25 x 0.25 meters. Both movement as well as rotation of components need to be measured. Workspace where components are being moved & rotated is circa 10 x 10 x 4 meters. Total number of moves and rotations to each component can be high, counted in hundreds. Frequency is high as well, a few movements or rotations per second. Required precision: +/- 3 centimeters (movement), +/- 2 degrees (rotation).
I am thinking about system consisting of two modules:

few (3?) dedicated “stations” emitting electromagnetic field with specific signature;
a detachable, small magnetic field sensors, which could be attached to each of the components in question.

Rough idea is following:

each of the “stations” is located in different corner of the workspace (at least one of them has to be on height different from the other two);
a to-be-monitored component is introduced to the workspace; a small magnetic field sensor is attached to the component and “calibrated” at place we can call “position 0”;
with each movement/ rotation of the component, the sensor detect change in magnetic field of each of the “stations”; information from the sensor is send via wi-fi to a dedicated computer;
based on information received, computer determines position/ rotation of the component in the production workspace.

A few questions to the above:

Does the general concept make any sense?
What type of magnetometers would be suggested for sensors (e.g. Hall? Reed? Any particular solutions/ models?)?
What components could be used for the “stations” emitting electromagnetic field?


texts: Can a current be induced in an HDMI cable that runs parallel to a 120v AC cable for 15 feet?

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I just went to go unplug an HDMI cable and got shocked from the end of it! The only possible causes of this that I can think of are that the receiving or sending end of the long (50ft) HDMI cable is introducing a live current into the line, or that an electrical current is being induced in the HDMI cable because it runs side by side (parallel) to a 120v AC extension cable for 15 feet.

Should I be concerned? What are the first steps I should take to diagnose this?

For reference, there was a Sony PS3 connected to one side, and an HDMI Splitter to the other end (http://smile.amazon.com/dp/B00B46XUQU)

If you need any clarification, please don't hesitate to ask!


texts: sample input signals and check their values VHDL

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I have 2 input signals - ID_1,ID_2 which sampled into id_vec.
LEDx_GRNn are output.
In this point, only one of a,b,c,d should be '1' and the others '0', which after should make only one led on and the others off.

For some reason all the leds are on so I'm guessing I do something wrong.
Waht am I missing?
ID_1,ID_2 have the constants values.

signal id_vec :std_logic_vector (1 downto 0);
signal flag :std_logic;
signal a:std_logic;
signal b:std_logic;
signal c:std_logic;
signal d :std_logic;

id_vec(0)<=ID_1;
id_vec(1)<=ID_2;

a <='1' when id_vec<="10" else '0';
b <='1' when id_vec<="00" else '0';
c <='1' when id_vec<="01" else '0';
d <='1' when id_vec<="11" else '0';

LED1_GRNn <=  not (a);
LED2_GRNn <=  not (b);
LED3_GRNn <=  not (c);
LED4_GRNn <=  not (d);


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From the results given by power analyzer, I find that the Xilinx FPGAs always have a high static power consumption no matter what your design is, although it will vary if your design utilize different number of resources.

What are the components consuming the static power on Xilinx FPGA reported by power analyzer?

My guess is:
interconnect (wires and switches) + slice used + IOB used + memory used + ASIC component used (multiplier, adder, etc)


texts: How would I connect very fine wire (0.005") to a PCB?

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Let's say I have very fine gauge wire of 0.005" (0.127 mm) diameter.

This wire is completely exposed (i.e. no insulation). What are available methods for terminating this to a PCB? Searching through Digikey and Mouser, the smallest gauge terminal blocks I could find were only 30AWG.

I'm thinking that there must be some type of PCB 'post' in which I could wrap the wire around to make the termination. I'm thinking something like this exists, but my searches yield no results.

Any thoughts?


texts: I tried soldering cables to the female XT60 connector but no matter what I did, my solder did not stick to the metal part of the connector. I had no problem with the cables though. Any idea about what I might be doing wrong?


texts: How do I get rid of switching noise from these types of DCDC converters?

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I am using a lot of these types of isolated DCDC converters for measurement circuits.

The problem is they introduce so much switching noise. I try to put filters on the output and even put the recommended 220 µH and 0.22 µF filter on from that datasheet but the noise is always there!

How do I get rid of noise from this type of DCDC? It is really annoying. There is always this short period of ringing and oscillation happening at like 50 kHz or 100 kHz (presumably at the switching frequency of that particular DCDC) of up to 20mV sometimes and this destroys my measurements unless I take averages.

DCDCs like these ones are even more noise, 100mVp-p!

Noise looks like the yellow waveform here (not my image):


texts: Timing diagram of circuit involving switch debouncing

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I have a push button switch (single-pole double throw) connected to a latch as follows:

I was thinking about the timing diagram of the circuit above (above image is the default state of the circuit when the switch hasn't been pressed down).

Would this timing diagram sufficiently describe the output given the signals below?

I would just like clarification of my diagram before I implement this circuit on a breadboard as an example of switch debouncing. P is basically Q.


texts: what is the voltage across the diodes when placed across 5V, as forward biased and reverse biased

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here two diodes are connected in series, one is forward biased and the other is reverse biased, are connected across 5V. thermal voltage is given as 26mV.
the voltage drop across each diode is asked.

since one of the diode is reversed biased the current through the circuit will be reverse saturation current of the diode.
 so by applying shocley's equation we can find the voltage across each diode.
but that doesn't add upto 5V

is there any mistakes in my method


texts:
I'm trying to drive a brushless motor (BLDC) with an ATMEGA328p
I use Timer0/1/2 to generate 3 different PWMs @ 62Khz.
First I tried (only absolute values)

$$A = \sin(T)$$

$$B = \sin\left(T + \frac{2\pi}{3}\right)$$

$$C = \sin\left(T + \frac{4\pi}{3}\right)$$

But the angular speed was "pulsing" so I tried to generate 3 triangular signals
$$\text{space by} \frac{2\pi}{3} \text{ also,}$$
but it's still "pulsing".

Any idea how can I achieve it?

I'd like to be able to control position/speed, but for the moment I'm just trying to make it rotate constantly.

Code : http://pastebin.com/yAfqzVSu

Video : https://youtu.be/ksYnc2J_IFU

BLDC has 12 poles, the PWM has a 62Khz frequency, but the values are updated @ ~20hz


texts: Solder bridge in schematics and 0 resistors

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I came across solder bridge in the schematics for STM32F4 Disocvery board and I don't think I fully understand the design here. For example in schematics they have a lot of solder bridge symbols like this(SB18, SB19 and SB20):

But for example R56 is just 0 ohm jumper resistor.
On the board solder bridges are either not connected or have component(0 ohm resistor?).

My original idea was that solder bridge means that for different revisions they can leave it unconnected, but this idea is probably wrong since there are a lot of R## resistor footprints without component meaning that they could have simply use 0R symbol instead of SB.
The question is - why use SB symbol instead of 0 Ohm resistor and why use 0 Ohm resistor in SB locations instead of you know... solder bridge? And if it is not 0 Ohm resistor as I guess - what is it? There is no markings and I don't want to desolder it from board.

Or even better question - why not just have a traces? Especially for example in 8MHz crystal connection to uC pins(like on example above), why not just connect it with copper?


texts: Is there an electronic reason to make micro USB cable without data wires?

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When buying electronic products that use a microUSB plug for powering, we often receive a male USB <--> male micro USB charging cable that doesn't include the 2 DATA lines (Data + / Data -).

It's extremely annoying for the end-consumer, because :

at the end you have a big amount of USB-µUSB cables at home that you cannot distinguish visually (no distinctive symbol on the cable): some of them are "power only" (won't work to transfer files from phone to computer for example), some others "power+data"  (will work for file transfer).
it can lead to ambiguous situations like "My device X doesn't work anymore. I plugged it to my computer and it's not recognized as an USB device". In fact it's just that the cable is not a real USB cable, but only a charging cable.

Question: Is there an electronic justification to produce micro-USB to USB cables that don't include the data lines, except for saving 0.00001$ per cable for the maker because they can avoid 4 soldering points for the soldering robot?


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I'm working on a little project in my physics lab.
We would like to create a photon coincidence counter. We were thinking to use the Pi GPIO pin to monitor a couple of photo diode which produce a 15ns 5V TTL signal (I know the Pi can handle 3.3V maximum).
I asked on the RaspberryPi stack exchange (here) if the board could detect such short pulse and they suggested to use "GPIO Asynchronous Edge Detect" (they also suggested to ask here because it seemed a more specialised question).
I think this could work but I would like to know if the pin has some kind of "down-time" after being triggered where the pin doesn't register anything and if it doesn't at wich rate can it count?
I also would like to know if the board can read multiple signal of this type in short delay one with another (or even better simultaneously).
To make it more clear we are not trying to measure the duration of such pulse but only if two pulses from two different photo diode arrive on the Pi simultaneously.

I'm pretty new with the Pi and I hope i explained clearly the problem. This is more a proof of concept to see if it can be done, even if we need to go "bare metal".
Thanks


texts: Are jumper wires just wires with insulation cut off on both ends?

texts: Is there a specific purpose for jumper wires like these where they have female pins at the ends?  I'm assuming they are mainly useful when you want to chop a wire into something like a breadboard, but the wire is too thin or flimsy.  If the wire is thick enough, I'm assuming a wire with the insulation cut off on both sides is equivalent, right?  Seems like a common sense question, but I haven't really seen wires with female pins attached on both sides before.. :)


texts: Diode Array for Full-Wave Rectifier for PoE

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I was looking for SCHOTTKY diode for designing Full-Wave Rectifier for PoE. I was searching for the diode but came across the term Diode Array. After applying filter for my specification, I found the one. The diode that I found considering cost and specification is over here. Is there any preferred configuration of diode array like independent, common-cathode or anode, maximum number of diode in single package?

I would like to know what are advantage and disadvantages of using diode array over normal diode. Which one is preferred for Full-Wave rectifier for PoE application? Is there any standard?

EDIT:

My Specifications are:

Reverse Voltage Protection: Atleast 40V (Considering Full-Wave bridge-Rectifier)

Average Current: 500mA

Forward Voltage Drop at 500mA pr above: As less as possible.


texts: Altium PCB Parameter Live Updating Issue

texts: I have two PCBs open at the same time... one of them live updates parameter strings (i.e. '.Print Date') as soon as I place them, the other just shows the meta text. However the 'broken' one still outputs to PDFs/Gerbers correctly. I've hunted furiously for a solution but Google has failed me this time. Any ideas?


texts:
This circuit provides 30dB gain to a 100kHz signal with a 10k input impedance. Is capacitor C2 necessary to suppress DC gain or is it redundant with the AC coupled input?

I would also like to make this circuit single-supply and I don't see how include the C2 effect. I also need to minimize noise around 100kHz.

EDIT: The bandwidth required is 100kHz ± 5kHz and it may be driven by an inductive source with C1, R1 tuned for a 100kHz resonance.


texts: Design dilemma: Are frequency counting methods better than voltage sensing when detecting ppm signals

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I'm trying to design a precision spectrophotometer that only uses three wavelengths of light. The high level design involves using three laser diodes that pump photons of the three wavelengths. This light passes through the sample and is detected by three photodiodes.

I am using the AD9833 DDS chip to enable me to generate sine/square waves as need be. These are then fed to a current generation circuitry that forces currents resembling these waveforms to flow through the diodes.

I'm in a fix deciding what method to use for the detection circuitry(photodiodes) as the signal I'm trying to decode is in ppm/sub-ppm level. I have thought of two schemes:

1) Generate a sinusoidal light pattern of a frequency(say 1kHz). If I use an integrated package like TSL257, I should be able to read out the voltage with a precision ADC, then demodulate the received signal at the transmit frequency. This synchronous mod/de-mod should give me good accuracy/resolution.

2) Generate a square wave light pattern(0 to high) and then use a package like TSL237 to convert the light energy to frequency and use frequency counting to get the accuracy/resolution. With a base frequency of 1Mhz, a ppm of signal would cause a frequency shift of 1Hz while the noise floor is in 0.1Hz. This made me think this method could also work.

Which one is a better way to sense ppm-level signals?


texts: How can I know the phase shift or phase delay of the SMA connector and RF port?

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I am now doing a project to measure the phase difference in my circuit. Figure 1 is my circuit. My target is to know the phase difference between the output of the DAC and the input of the ADC. I have known the phase of the output of the DAC, phase shift of the analogue circuit and that the modulator has no phase shift. And the output signals from the DAC is lower than 20kHz.

My questions are:

what phase shift would the SMA connector cause normally?(SMA connector is 5-1814400-1 from TE connectivity) And

How about the RF port?  What phase shift would it cause?

Does anyone have idea about my questions or idea about how can I solve the problems?
(I will try my best to update all information in need)

Thank you very much!

simulate this circuit – Schematic created using CircuitLab

Figure 1.

More information:

The cable between the SMA and RF port is about 30cm long. But I can`t find any more detail about it. The modulator and analogue circuit are connected through fibre and PD. The analogue circuit, SMA connector and MCU are inside one PCB board.


texts:
I have programmed my ATtiny1616 to output the clock on a pin.
Here is my reading:

Why is there all that ripple?
How might I reduce it?


texts: Multiple sensor circuits connecting to one counter and a 555 timer IC

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I have to use a 555 timer in a context where I have multiple sensor circuits connecting to one counter circuit.
The idea is that the counter should indicate how many activated sensor circuits are there.
How do I even begin to approach that? I have no idea how to translate the number of activated inputs into a tangible value that I can display. And how to use a 555 in that context.

Also, Arduino/micro-controllers are NOT an option.

Any tips?


texts:
I was building an ESC. Motor V=22V max current I=90A Battery max current I=60A. My controller is a MIC4607 (Datasheet:http://ww1.microchip.com/downloads/en/DeviceDoc/20005610B.pdf)
The PWM f=16kHz but i will try to get 20kHz later.

As you see there is a RSNS resistor, which is conected to the Source of the MOSFETs and to the MIC4607, where ILIM+ and ILIM- is a comparator which would trigger if the voltage rises above 200mV and turn all High-Side MOSFETs off. I want to use this function to protect my Batteries and Motor from overcurrent.

My Question is how do I do that. I would need a SHUNT resistor but they are very bulky. I found SMD shunts https://www.mouser.it/ProductDetail/KOA-Speer/PSJ2NTEB1L00F?qs=sGAEpiMZZMtlleCFQhR%2fzfOI4xHs7IDUutBqgYbi4Il52bsccUJZvA%3d%3d this one has 1mOhm resistence and could withstand the amps P=I^2*R would be 3.6W. Is this possible? The Voltagedrop over it would be only 60mV but i could amplify it. An other solution would be the measure the current at the Battery with the currentsensors of Alegro, up to 100A bidirectional and just apply a voltage to IlIM+ if the current excides the max allowed current, that would instantly switch off the MOSFETs.


texts: Phase-frequency detector not used in a PLL

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My application: I need to output a voltage based on a phase difference between two input signals (a voltage and a current). It seems that a phase-frequency detector will do exactly this but I have hardly seen any examples where people have used these outside of Phase locked loop applications.

What else do I need to consider before trying this out? Are there any pitfalls to using a PFD for my application or will it work? I need both positive and negative output voltage based on the sign of the phase difference.


texts: How to use an op-amp (that only uses ground and positive voltage to operate) to create a sawtooth/triangle wave generator?

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The design I have in mind will be battery operated, so I have found the TL972 (Datasheet Here) which only operates from 0 - 12 V.
What I want this op-amp to do is to create a sawtooth/triangle wave generator to drive a VCO, namely the POS-535+ (Datasheet here). The frequency we want the VCO to output is around 300 - 400 MHz, and according to the figure named "Frequency and Tuning Sensitivity" in that datasheet, 2 - 7'ish volts will cover that output range of frequencies. (For the design, I want 1 - 8 V just to be on the safe side.
. . .
I have researched all over the Internet, but the only op-amps I am seeing that will generate the desired waveforms swing and operate from negative voltages. I have tried those circuits, to no avail.
Technically, I could use an LDO voltage regulator to output a negative voltage for an op-amp, but this will add more complexity/cost to the circuit and will be considered as a last resort.
So designing this circuit isn't too easy as first we have to make the first portion of the op-amp create a square wave, and then the other will create the ramp. I'm not entirely sure how to do that and would like help/pointers on doing so. Unfortunately, I have no schematics thus far for reference as all the schematics I have seen are for op-amps that operate between negative to positive.
. . .
Also, to generate a ramp wave of 1 - 8 V is pretty dang broad. If there is a better VCO that operates no more than 12 V and covers 300 - 400 MHz, please by all means recommend one to me if that is more convenient than designing a ramp wave that sweeps 1 -  8V.
Any help, guidance, or pointers is greatly appreciated!
(Forgive my terminology if I misused some terms. Engineer in progress here.)


texts:
For a new project I need to build an RF amplifier for continuous-wave with about 500 mW (27dBm) output at 170 MHz.

It doesn't need to transport data, it is only for measuring purpose.

The input comes from a signal generator, that can go up to about 15 dBm output, so the amplification needed is about 12 dB. The circuit should run with 5 V supply voltage.

The output of the RF amplifier is directly connected to an antenna, that is matched to 50 Ohm at 170 MHz.

A simple solution without big matching effort would be preferred, as I don't have much RF measuring equipment, only a cheap chinese network analyzer (NanoVNA).

So far I tried some ADL5535, but always when the output comes up to 500mW (14Vpp) they got killed.

The same experience I had with a BFQ790. It was drawing about 500mA, when the output was OK, but then also died.
Heat dissipation should be no problem, as I'm using the PCB (with heat sink compound) of a former destroyed amplifier module for my experiments, see picture

I'd really appreciate some help, how to design a simple circuit, that is more robust against mismatching of the antenna. I know some theoretical basics about T or Pi-Networks, but I'd rather need some practical support.

Maybe someone has an example circuit (with components, that sill are active and available).


texts: SelectMap accepts FPGA image but does not enter the startup sequence

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I am loading the image of my Spartan 6 and it seems that it cannot go to the final step of the process: the "Startup Sequence". After I load the image byte by byte, and add a lot of extra clock cycles at the end, the status register of the FPGA reveals that there have been no errors, and GHIGH STATUS status being high means that:

  The device has properly received its entire configuration data stream. The device is ready to enter the Startup sequence.

I have checked that the INITB and PROGRAMB are not pulled low preventing the startup sequence, and in the status register everything looks very promising.

Why is my Spartan 6 not entering the startup sequence after it received and is happy with the image?

(Below is the status register after configuration.)

[0] CRC ERROR                                                              :         0
[1] IDCODE ERROR                                                           :         0
[2] DCM LOCK STATUS                                                        :         0
[3] GTS_CFG_B STATUS                                                       :         0
[4] GWE STATUS                                                             :         0
[5] GHIGH STATUS                                                           :         1
[6] DECRYPTION ERROR                                                       :         0
[7] DECRYPTOR ENABLE                                                       :         0
[8] HSWAPEN PIN                                                            :         1
[9] MODE PIN M[0]                                                          :         0
[10] MODE PIN M[1]                                                         :         1
[11] RESERVED                                                              :         0
[12] INIT_B PIN                                                            :         1
[13] DONE PIN                                                              :         0
[14] SUSPEND STATUS                                                        :         0
[15] FALLBACK STATUS                                                       :         0


texts: calculating port address from base address in 8255

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if the 8255A has a base address of FFF9H. then how will I calculate the address of PORT A,B,C and control register?

I have made a calculation as the following. adding 1 each time with the base address to generate the rest others:

PORT A:FFFAH
PORT B:FFFBH
PORT C:FFFCH
Control register: FFFDH

is the process ok or have I made anything wrong in the calculation?


texts: 12v Power adapter IC circuit design High voltage AC

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So this question is a follow up to my previous question. Here is the story. Few days ago, while installing a 12v LED strip, I found out that the 12v AC-DC power adapter actually carries a high voltage AC in it. My question was marked as duplicated, and the answer from there states that the high voltage AC is from the capacitance between two inductors in the transformer. It really doesn't satisfy my curiosity because I have many AC-DC power adapters -- who don't? -- , and not all of them have this problem. So yesterday, I finally managed to open up that problematic 12v power adapter, and found out that there is a 222 2kv capacitor connected between the two inductors in the transformer. This is probably the reason to the HIGH voltage AC, but my question will be what is its purpose?

0, what are the purpose to the 222 2kv bridge capacitor?

Other than that, I have few more questions about this circuit design.

1, what is the unmarked IC used in this unit?

2, what are the purpose of the 3 parts: 100k, 222j, and diode on the high voltage side? ( red in the paper)

3, Why the IC is not connected to V+? Pin 8, 7 should be the drain to switch the transformer, and Pin 6 should be the feedback, and Pin 3 is the ground, Pin 1, 4, 6 are not connected to anything.

4, how reliable is this circuit design? any faulty?


texts: MSP430 launchpad's bypass capacitor mystery!

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I've been looking into MSP430 launchpad's schematics and saw something that can't quite understand: the bypass capacitors for the reset button and for the P1.3 are different (1nF and 100nF respectively).

Since the noise frequencies generated from pressing any button would be (I assume) the same, wouldn't the value of the capacitors be the same?


texts: Power bank design, Lithium Ion vs Lithium polymer, single vs series

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I'm working on prototyping a power bank, to be used for charging mobile devices, smart watches, ect.. It needs to be 10'000mAH.

My initial thought, since this is just a prototype and doesn't have to be in a final manufacturable state, was to use a single lithium polymer pack, 10'000mAH and at 3.7v. I would then use a boost regulator, to boost it to 5v, and use the 5v to charge the devices.

This approach is the simplest approach, and should work in theory.

I started looking at existing models, and >90% of power banks use cylindrical lithium ion cells, used in parallel and in series. The <10% that do use lipo's use them in series, at 7.4v or even higher. I assume they are doing this, because it is more efficient to reduce the voltage, than it is to increase it.

My thought with multiple cells, is that it will make it difficult for me, not controlling my battery sources, getting cells which match enough to use together.

Is my initial approach that wrong of an idea, and if so, what are your suggestions to use multiple cells (lipo or lithium ion)?


texts: Doubt about current direction in CircuitLab

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I'm not sure how to interpret the current value in this basic schematic. If you simulate it, CircuitLab will plot a value for the current flowing through the Output node. Why is it a negative value? What convention does it use?

simulate this circuit – Schematic created using CircuitLab


texts: LED strip appropriate for fiber-optic cables

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A project will use 20 fiber optic side-glow cables, 3mm-thick, with one controllable LED each. A WS2812 LED strip or similar would be perfect for the ease of controlling the LEDs, however all that I've been able to find seem to be difficult to attach the fiber optic cables to. Using a "regular" diode, I could just attach it with heat-shrink tubing.

What would be a convenient solution to this problem?


texts: Connecting battery cells in series VS using boost converter

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I need a dc output of 12V 60AH through 18650 li-ion battery cells to use with a 1000W AC inverter to power a 650 Watts computer ( each cell 3,7 Volts 3500 mAh )

One way would be make 17 packs in parallel ( each pack is 4 cells connected in series 4x3,7v=14,8 volts, 3500 mAh ) so the outcome would be 14,8 volts and 59,5 AH ( from total of 68 cells )

How about using a DC-DC step up converter? ( I know Boost converters are not 100% efficient )

Connecting 68 cells in parallel ( 68 x 3500 mAH = 238 AH and 3,7 Volts ) and using a DC-DC Step up converter to convert 3,7 to 12 volts? What is the downside?


texts:
I'm having trouble with a circuit I'm building using WS2812b LEDs. The 41 LED pixels are connected to the D3 pin of a Wemos D1 Mini. They are powered by a sufficient strong power source, with a power injection after 20 LEDs.
Actually, they work great. At least, they do when they're supposed to show a single color at full brightness. But when I dim them, even just one or more, they start flickering at random places. Same when I light a few leds instead of all of them.
I'm using the FastLED library. I've had succes before without using a level shifter.
Any idea on what's going on?
t.


texts: Can I use one battery to power up two circuits?

texts:
I 'm planning to use a zinc–carbon 9 V battery to power up two circuits (the one that battery belongs and one more). I 'm thinking of using a breadboard in order to achieve this.

The second circuit is BeagleBoard-xM (5 V, 300 mA), that will be powered up, via buck converter LM2596S-ADJ.

My question is:

Is this possible or there will be voltage drop? I think that I can do this, but this way battery will last less. If I am not correct, please let me know.


texts:
I am using ATmega32-A micro controller, coding in C language and compiling using CodeVisionAVR compiler.

I want to display current time, I have tried with "time.h":

int main(void){
 time_t now;
 time(&now);
 printf("(percent)s", ctime(&now));
}

but it seems this compiler and hardware won't support time.h. I know that all AVRs don't have a RTC/calendar in them.

Is there any other way to display current time. I am very new to programming micro controllers. Can any one help me with some examples.

I don't want to add external hardware to the existing board now. I am displaying information on the PC (hyperterminal) using USART communication. Is there any possibility that I can get current time from PC? if there can you explain about it a little bit?


texts:
Below is my circuit which drive LEDs using 555 timer. ( Total 20 LEDs are connected in parallel to D20, I have shown only one here)

I am getting ringing / overshoot for the current flowing through LED as below.

Is there anything that I am missing here. I would also like to know why is it coming there.

When I added 1uF capcitor after R3 (470ohm), it disappears.

Thank you.


texts: How to add in this circuit a Vbe multiplier?

texts: I would like to see this circuit working with a Vbe multiplier, together with the ci LM833N at its entrance, is it possible? How would that look?


texts:
I'm in the process of getting ready to build a car PC running Linux. One of the features I'd really like to incorporate is the ability to record car statistics from the sensors live using ODB2.

Due to the location of where the ODB2 port is on my car (in the dash where the door opens), it'll be pretty difficult to close the door while the cable is plugged in. Therefore, I'd like to split the line further back a bit and route an ODB2 cable to the back of my car to the machine.

I've never done stuff like this before, but I have done a bit of electrical work (ie: switching out switches, plugs, rewiring things). I'm assuming that what I'd need to do would be to cut the existing cable and basically solder all of the internal wires together to both plugs, the one available in the door for mechanics, and the one running to the back for my computer.

Is this what I need to do? How can I put the wires back together again in a nice, insulated fashion?


texts: What does this RC network do in this audio transformer output stage?

texts:
This is a relatively well known ABY circuit available on the internet.

CLICK HERE, REMOVED IMAGE FOR COPYRIGHT REASONS

I have two questions about this circuit :
1) What does the RC network (in the secondaries) do in the output of the transformer?
   My guess is that it's some sort of filter.
2) what is the point of the two resistors (on the opamps driving the primaries) on the opamp. They don't seem to be providing any gain?

Below is my attempt at an isolated buffer.
The aim is to provide a potentiometer giving attenuation (not to silence, just to allow adjustment based on the output differences of various guitar pickups) in one direction and some gain in the other (about 2x gain).

As you can see I've just added some gain to the opamp, and a pot on the output.
LTSpice shows this working perfectly.
I've left the original RC network in place. What effect on that will the POT I've added have?
Is there a better way to do this?


texts: 500v generation with 24V, request for current limitation

texts:
I am generating 500V from a 24V source. Attaching schematics. This circuit is generating stable 500V.

I am attaching a load of 7 kohm. In the schematics the buck regulator is supplying 19V to the transformer. What happens is at no load, the current sunk from buck converter is 0.6Amp, but at loaded condition the current becomes 3.2Amp and voltage of buck convertor drops to 2V and still the 500V output remains stable.

I need to limit the current because I am not allowed to sink 3.2Amp.

Please have a look at the schematics and suggest if there is any technique to reduce losses of this circuit?


texts:
I'm interested in flash detection, what would be equivalent to 1000 FPS. High speed cameras that do this are too expensive and too heavy and provide too much information. In the long run I'm going to have probably 30 of them attached to a half dome with the goal of approximate direction finding.
What are the options for a photoreceptor?


texts: is this possible: Amps feed joining a Regulated V line

texts:
As we all know linear regulators cannot handle a lot of amperage and tend to waste a lot of energy, so I was thinking if it is possible to create a regulated output then put the amperage after the regulation...

A slight demonstration of a schematic to show what I mean:

Is this possible? If yes is there a schematic I can look at? What should I look for?

sorry for the bad picture, I tried to make it better but failed..

--Edit--
I'm not trying get my circuit to work, just to convey the meaning.. I know this circuit won't work the way I want it, it is just an illustration.


texts: I am recently doing a project on robotics.And am following (societyofrobots) 50$ robot tutorial for that purpose.But i can't find ATmega8 chip anywhere as they told but i did found atmega8L instead.Now,is it possible to replace atmega8 by atmega8L though it has low capacity than atmega8?


texts: Voltage controlled current line driver for PLC

texts:
We are designing a power line communication system using FSK. We are working in narrowband with a carrier frequency at 87.5kHz.
For this system a line driver that increases the available power from the modulator is needed. It should then drive the current of the transformer, which couples it to the power line.
The main requirement is that it should be able to convert a voltage at the input to a current at the output. Summarized it has the following further requirements:

The input voltage is a sine wave that oscillates around 2.5V coming
from the oscillator circuits. About 3V pp.
The output needs to be a current with a sine wave with an amplitude of 160 mA (rating of the
transformer).
The output needs to be differential or the topology should be such that it can be connected to the transformer (no DC currents present)
It should be linear.

We found that for the 3rd requirement a differential op amp could be used but these were very hard to find for the given current rating, and we wouldn't know how to design a voltage to current converter structure with it.
Another option we thought of was to use a single voltage controlled current amplifier configuration and connect the other side of the transformer to a virtual ground. But we would have some difficulty implementing this and weren't quite sure whether this would result in a good circuit.
Do any of you have any suggestions on topologies or where to look for information regarding this amplifier design.


texts: How do I generate the following statements in SystemVerilog using a loop?


texts:
I was revising my notes and I stumble across this problem. In my notes, it says that a feedback circuit required some feedback elements to works. Let's take the integrator op amp as example: The feedback mechanism used is negative feedback, right? So inside this circuit, are the feedback elements R1 and C2? Or is there no need for any "feedback elements" for a feedback circuit to work?

simulate this circuit – Schematic created using CircuitLab


texts: Passing through/blocking a high voltage dual polarity signal

texts:
Good day. The question I have is regarding a device the function of which my employer asked not to discuss in too much detail. But I believe the engineering problem itself is general enough and I will try to give as much engineering data as I can without disclosing any commercially sensitive info. The device I am designing at the moment has to switch the following waveform on or off:

This is a high impedance differential signal (10kOhm) with voltage of 72 Vpp, that can reach 400 Vpp. The load for this signal is also high impedance (I am using a 1 MOhm resistor as a model). I am trying to achieve a switch-like functionality in my circuit that will be controlled by a microcontroller. In one state it will pass the signal to the load, in another it will block the signal.
I was thinking about different approaches from primitive to more complex:

Mechanical relays - Pros: easy to operate. Cons: bit expensive at the voltage specification, have a clicking sound that might not be suitable for the product, wear out
SSR - Very expensive at the specified voltage
Optocouplers - Pros: also easy to operate, cheap, solid state. Cons: usually has a low reverse voltage limit
Discrete transistors (BJT, FET)- This might be a solution but most of the components I've looked at also have a low reverse voltage breakdown. Maybe I'm missing some specific type?

I have experimented a bit with optocouplers in a simulator as well as on a breadboard.
Here's an LTSpice setup with an MOC205 (datasheet):

According to the simulation the circuit works just as I intend it to:
Voltage across the load with 5 volts at the MOC205 input:

Voltage across the load with 0 volts at the MOC205 input:

I couldn't get my hands on MOC205 in the current state of lockdown, so I used K1010 (datasheet) that I had on hand.
The result was quite a bit different.
With 5 Volts at the input the signal was identical to the first picture in the question, so it was completely passed through.
With 0 volts at the input:

I guess this result should be expected due to the nature of the transistor in the optocoupler.
Both MOC205 and K1010 list their reverse voltages to be 6V, so I'm not sure I can trust the result of the MOC205 simulation either. So the question is: are there any optocouplers, or other devices that would be able to pass/block such high voltages? Or maybe I should change the topology? I thought of connecting two optocouplers back to back but the result wasn't perfect either (still was passing some negative voltage pulses), plus it seems like there should be a more elegant solution. Or maybe I should ditch the idea of optocouplers alltogether and work with a different device? Any help would be highly appreciated!
EDIT from the comments:
The rise time of the signal is 500ns.
The output impedance of the device is about 10k, which I guess is not too high an impedance.
Load is not returned to the ground but I guess, I can ground one of the differential signals, grounding the voltage.
If 90% of the signal goes through in the on-state, I would call it acceptable for the application. Inversely of 10% goes through in the off-state, that is also acceptable.


texts:
I need to measure the red or green or blue component of a light source. Are there any resistor or diode with this specific capability? I found some diode with rgb filter, but i'd want to know if there are something more specific.

thanks


texts: Low Power Switching application With N-Mosfet

texts:
In my application I need to effectively switch on or off a very small load, around 0.5W to 1W. Also, I need to ensure that power loss is kept to a minimum. The voltage levels of my application will not exceed 5-10V. Correct me if I am wrong, but I think that the main consideration when looking to optimize the mosfet's power losses would be for it to have the minimum Rds(on) possible (of course considering that it meets the application's other specifications). Let me also add that The switching on will be occurring for a small amount of time every other hour or so, so I thing that the turn on-off characteristics of the mosfet would not play a significant role here.

Based on that, after looking at the available options, I found out that the mosfets that have the lowest Rds (on) are designed for very high power applications and can withstand very large voltages (STP55NF06L for example), which is completely unnecessary for my application.

On the other hand, smaller mosfets (like BSS214N for example) that can withstand much lower power, have a significantly larger Rds (on).

Overall, am I missing something in the above-mentioned thoughts? What else should I consider for my application


texts:
I've been working on crating a simple PWM fan driver for my Raspberry Pi. To simply explain idea - I get 3 pin input (1 - PWM, 2 - 5V, 3 - GND), then using RC filter I turn PWM signal into voltage and feed it into positive side of OpAmp. Then output drives MOSFET which in turn works essentially as variable resistor controling fan speed (M1 motor on schematic).

My (newbie) questions are:

PWM signal is 3.3V, is there a way to make OpAmp output do full 0-5V without adding additional OpAmp to scale it up?
How should I protect circuit from effects that fan might have? It's an inductive load after all.
And probably most important - am I missing something obvious to people who know what they are doing?

On the side note, speciafic OpAmp and MOSFET I will choose later, but I was thinking about rail to rail opamp that works in 0-5V range and for MOSFET I will use some TTL level one.

Also, C1 is planned to be 1uF


texts:
I was looking to get a delay in a pulse output.
Is there some IC I can use to be able to change the time of the pulse output?


texts: How does Mains Isolation work with the ACS71020 IC?

texts:
In the datasheed for the ACS71020 IC, it shows the typical application of the device in which current is passed through the chip and voltage is measured on the opposite side.

I do not understand how the voltage measurement pins can be placed on the same side of the IC as the low voltage connections.  Doesn't this ruin the mains isolation from the low voltage side?

https://media.digikey.com/pdf/Data%20Sheets/Allegro%20PDFs/ACS71020.pdf


texts:
I try to simulate different MOSFET's for wich a spice model is provided by the manufacturer as a .lib file containing a subcircuit. In my schematic, the subcircuit is included with a .inc <fname> statement and used by changing the Prefix of a NMOS from M to X and setting to value to the name of the subcircuit.

All of this works, however, as I want to compare different MOSFETS, I want to step through a list of different models.

I tried to use the same method as found here:

Define numerical models: .model 1 ako:<FET Type>
Step over the numerical models

However, this does not work. A error "Unknown subcircuit called" is returned.

Is there another way of stepping over different subcurcuits?


texts:
Hi anybody know how to get ATMEL unique ID from Atmega microcontroller?

I read this question but the code in answer not work in Atmel Stadio.

Edit:

Because we produce about 1000 board per week I want to a way that find our board in a project with broadcast a message to them and they replay a Uniq code that we could identify them.


texts: How to properly wire a five color RGB LED strip?

texts:
I've worked with common anode and common cathode RGB LEDs either 12 volt or 5 volt using PWM mostly to change color.  Usually then these products that I work with have the typical four color wiring where color may differ a little bit depending on being common anode or common cathode.  I haven't yet worked with RGBW, but I think the white seems to make use of yellow wiring in most situations I've seen.
I often get products given to me that I eventually put to use.  I received a light bar that I believe is RGB, but I don't know if its addressable.  The person that gave it to me doesn't know where they got it from so they cannot look the product up to identify it or get tech specs for it.  I'm puzzled as to what it is with the wire colors and markings inside the light bar.
I did take a 12 volt battery and hooked up black to negative and white to positive and got red led color.  Other than that I'm unable to get any other color to reveal, but at this time I'm afraid I may burnout something through trial and error.  I could not find any other markings on the strip's exterior or on the short wiring it came with either.
I placed an AA battery next to the light strip just to give size perspective.

The wires have five colors coming out Black, White, Red, Green, and Blue.  I have no idea what role each has.

Inside the led bar I see markings where the wire is soldered to the LED strip.  It shows GND, L, 12, and +12 from top to bottom.  There is potting covering the solder connections so I can't make any positive identification of where the colored wiring is going.  I've also never seen these labels before so I'm stumped!


texts: Is it normal for LM317 to give a higher voltage without a load?

texts: I just built a small 5.1V regulator with LM317, using 220 and 680 ohm resistors. However, I measure 8.6V at the output without a load connected. Is this normal, i.e. under a load (about 120 ohm) it would drop to 5.1V? The input is a 9V/300mA unregulated wall wart, which reads about 13V without a load.


texts: I am making a modified sine wave inverter. The PWM wave is generated, switched using transistors, and then passed through a transformer. What is the PWM frequency required to generate a modified sine wave of 50Hz?


texts: What are the dangers of making an extra wall socket on a circuit?

texts:
Given that one has a basement room on an apartment complex running a single set of cables to power a quite noticeably dim lamp. Given also that the cables do provide 220v, what are the risks of cutting the cables and creating an extra wall socket and running just one of these appliances (there is no wall socket at all, the cables were just "meant" to power the dim light):

-Fridge (small spikes on current)

-Microwave

-Desktop computer (stable current withdrawn)

I imagine that the danger here is on how many watts (i.e. how much current) the cables can support before over heating, right?


texts: Possible to use 7447 to drive common-cathode 7 segment display?

texts: I know that the 74(LS)47 is designed to drive common-anode displays. However, is it possible to make it drive a common-cathode display? What is the simplest (in terms of components) way of doing this?


texts: how to read the dimensions phi A,D,E at the pins 1+ / 1- /2+/ 2-


texts: Programming of ADC in PIC12F675: Not Working Properly

texts:
I'm new to embedded systems and I want to program a PIC12F675 for a project.

So, the idea is that there is a switch. If the switch is off, the microcontroller normally outputs a clock signal, which its frequency is controlled by a potentiometer. And if the switch is on, there is another button that I can push to output a pulse that lasts for 500ms and goes low again.

I wrote the code, but it seems to not be working correctly.
Also I didn't code the potentiometer part because I don't know how, so it outputs a clock that it's frequency can't be controlled.

The problem:
When the switch is off (mode = 0), the clock doesn't work. However, when the switch is on (mode = 1), the clock works. It should be the other way around. Also, the pulse button doesn't work in either modes. Lastly, as I said before, I didn't code the potentiometer part because I don't know how.

So, could someone help me with this?
Thank you.

Here's the config:

#pragma config FOSC = INTRCCLK
#pragma config WDTE = OFF
#pragma config PWRTE = OFF
#pragma config MCLRE = OFF
#pragma config BOREN = ON
#pragma config CP = OFF
#pragma config CPD = OFF

Here's the code:

#include <xc.h>
#include "config.h"
#define _XTAL_FREQ 4000000

void dClock(int delay){
    GPIO2 = 1;
    __delay_ms(delay);
    GPIO2 = 0;
    __delay_ms(delay);
}

void main(void) {
    TRISIO2 = 0; //output
    TRISIO3 = 1; //mode
    TRISIO5 = 1; //pulse_button

    char pressed = 0;
    GPIO2 = 0;

    while(1){
        __delay_ms(50);

        if(GPIO3 == 0){
            int delay = ADC_Read(); //Supposed to read analog value here
            dClock(delay);
        }
        else{
            if(GPIO5 == 1 && pressed == 0){
                GPIO2 = 1;
                __delay_ms(500);
                GPIO2 = 0;
                pressed = 1;
            }
            else if(GPIO5 == 0 && pressed == 1){
                pressed = 0;
            }
        }
    }
    return;
}

Edit: I edited the code and config, and everything is working fine. Now, I'm just still missing the analog input of the potentiometer.


texts: Indicator LEDs on Arduino current blocking

texts:
So I just inherited a project. I am designing a board for a mega32u4 smd microcontroller that has indicator leds on 8 input and output pins (4 digital (3pwm) and 4 analog) that light up green when a pin is set high and yellow when a pin is set low.

I want the circuit to light up yellow when an input voltage from 0-1.4V is applied or outputted from a pin, not turn on (or rather both LEDs are not visible) when 1.5V-3V is applied or outputted at the pin and light up green when 3-5V is applied or outputted.

This is the circuit I inherited:

This is the part of the schematic that has the circuitry for the indicator LEDs:

Where the pin numbers are the pins of the microcontroller. I am using the following surface mount components: schottky diode, zener diode, green led, yellow led

I chose the resistance values based on another circuit that used the same LEDs. We want around 1-4mA running through each LED as they seem to be bright enough when that amount of current is running through them.

So to my understanding: When 0V is inputted into one of the pins (ie the circuit) 5V is dropped 3.6V by the diodes and then the resistance should be changed to around 1.4V/4mA~350 ohms. And when 5V is inputted the potential difference at the input point is 0V because of the 5V so the circuit doesnt or shouldn't source any current from the arduino as the zener is supposed to block it and the potenial is 0. Which would give us a resistance value of 5V-2V (LED)-.5V (diode)/4mA ~625 ohms which I am gonna maybe call 2.5k because the green LED is much brighter then the yellow and on another cirucit I was handed with the same LED I calculated the current and it was around 1mA running through it.

The problem is when I use any of the resistance values (the ones in the circuit and the ones I computed) when nothing is applied to lets say pin 11 (ie its left floating) the green LED is turning on enough to be visible. I measure the current and around 4uA is going through the green LED (wow! are LEDs that efficient). Is this because the zener diode is leaking 10uA at 1V drop according to the data sheet. I am not measuring any current flowing through the yellow LED and resistor when nothing is applied at pin 11. But I am still seeing the green LED turn on. I bread boarded the circuit out with the smd componenets soldered to jumpers and am still getting the issue so I don' think it has to do with my circuit

I think my understanding is wrong. Please help I am new to circuits and I want to understand the math before I start ordering a bunch of wrong parts. Or perhaps I am going about this completely wrong. If anyone could give me some insight how they would get the problem solved I would be super grateful :)!


texts: What causes, and can you fix "stuck" gpio pin?

texts:
On my LoLin "V3" NodeMCU the GPIO pin 5 is stuck on high. It was working before, but have been doing a lot of prototying.

It can be either in INPUT mode, or OUTPUT mode set to HIGH. Do not know electrically how to tell the difference. All I know is that it drives an LED no matter how it is set.

Is this like a bad pixel on those older LCD screen where you just have to live with it, or is there something I might be able to do to salvage the pin.

All other pins alive and well.


texts: Decay Modes - Stepper Motor related Query

texts:
I'm trying to understand something fundamental about Decay Modes.It is widely accepted on the internet that a slow decay mode shorts the Back-EMF of the motor and in essence stops the motor instantaneously. Hence the torque generated is higher when slow decay mode is used in comparison with Fast Decay Mode. I have a few queries regarding this

When slow decay mode is used, the motor is shorted to ground through the Rds of the of lower MOSFETs, this doesn't imply that the voltage across the coil has to become zero, a high enough current can flow to maintain a high Back-EMF.
When the Back-EMF is zero the current through the coil is still present, doesn't the coil current dictate the torque generated? Why does the Back-EMF have precedence over the coil current when it comes to the torque.
Please help me clear any misconception I have regarding this

Thank you


texts:
I'm looking to add an audio amplifier to a circuit, in this case the TPA0211 in 5V mode for a full 2W of output.

My rather dumb question is this: I should expect at least 400mA of current draw from the amplifier, given the 2W output at 5V into a 4ohm load, correct? I don't see current draw listed on the DS, other than the supply current of 6mA, so I'm wondering if its amperage draw is implied given the output power and input voltage are stated.


texts: Most stable internal microcontroller clock

texts:
According to the research I have done so far it appears that the stability of the internal clock of a typical microcontroller is approximately 1% (calibrated) to 10% (uncalibrated). Do you agree with these numbers? Which microcontroller has the most stable internal clock?

Thank you!


texts: What does "a.u." mean in the scale of a graph?

texts:
Please refer to the X-Y labels of image posted here, showing the I-V characteristic of a memristor. What does this abbreviation "a.u." stands for?
Atomic units/arbitrary units?


texts:
I am trying to control speed of a DC motor using PWM. To reduce coupling of motor noise onto my electronics, I am using a separate power supply for both(LED and Phototransistor) and am planning to interface PWM pin from µC to motor using 6N137 optoisolator. Speed of PWM is about 20KHz as recommended by motor manufacturer.

When I try to test 6N137, when I use a single supply for both input and output, i.e LED and phototransistor everything works according to truth table listed in the data sheet. When I use two different supplies(with or without isolating ground) output is always high irrespective of the input. Can anybody point out my mistake for this behavior? Find attached the schematic and output waveform.

Regards,
Ani


texts: How I can find a practical value of CIO barrier capacitance (primary to secondary side) in digital isolators?


texts: How to profile the communication protocol of my Microsoft Arc wireless keyboard?

texts:
I bought a new keyboard for windows, datasheet, and I would like to sniff the packets between the keyboard and the pc / USB transmitter.

The datasheet is useless and there is nothing informative for this purpose as I see it.

Firstly to see what protocol they use I have to see what is transmitted, I prefer not to open the keyboard and be in the middle between the computer and the keyboard.

I thought to build some RLC circuit around 2.4 Ghz and see the Voltage changes according to the keystrokes. Is there any smarter and better way to do it?


texts: On/Off latching circuit with a raspberry GPIO 3.3v

texts:
I'm currently failing solving my problem. Of course if I would good better in electronic, I would not post my question here but that's life, and any help would be appreciate.
Context:
I have around 50 bulbs (not LED) to switch on (and keep on) or off (and keep off) at different times (20V max, 6 volts used, 1/2A consumption)
I have around 10 coils to switch on (and keep on) or off (and keep off) at different times (60V max, 24V used, unknown consumption)
I have a raspberry pi 4 with GPIO ports
I wanna use GPIO port(s) to do the switch on/off of bulbs & coils and because of GPIO limits (maximum of 16mA per pin with the total current from all pins not exceeding 50mA) then several bulbs can not be kept on for a long time thus I need a latching circuit so once it's on, it's kept on and one it's off, it's kept off until next signal.
I believe there are 2 approaches:

use 1 GPIO pin per bulb/coil combined with an on/off latched electronic. In that case I need GPIO extended board since raspberry does not have 60 GPIO and 50 time the same circuit for the bulbs & 10 time the same circuit for the coil.
use several GPIO pins for driving an or several IC(s) in an electronic circuit that would provide the latching expected behavior, so less GPIO pins but a more complex electronic circuit and probably less circuit to repeat because the IC may handle more than one switch on/off.

Notice that I would prefer to build an electrical circuit for cost reason, rather than buying an all-in-one circuit that would cost me 8$ each around (50+10)x8$=420$ total and that having a circuit dedicated to bulbs and another one for coils is acceptable for me.
From an electronical & financial point of view, what's the best way to go ?


texts:
I'm trying to come up with a simple way of sharing a USB peripheral between two USB hosts (computers) so that the host that is currently turned on controls the peripheral. I'm targeting low-speed USB1.1 devices. Full-speed devices would be nice. High-speed (USB2) devices are not really needed.

My first stab is the circuit below, made up of two diodes and some MOSFETs. I only show Vcc and D+ for clarity. D- gets the same treatment as D+, and the grounds are connected together. You can play with the circuit using the falstad simulator applet. I added two 10k loads to make sure the outputs don't float. When the circuit is part of a USB connection, the resistors in the host and in the device should take care of that.

Questions

Is the basic idea of switching USB signals with MOSFETs sound? I understand that the channel in saturation mode behaves like a resistor, and that the resistance can (depending on gate voltage and device) be in the order of milliohms. Is this correct?
The output Vcc will be a full diode drop lower than the input Vcc. I think this will put me outside the tollerances of the USB standard even if the input Vcc is 5.00V. What can I do to prevent/lessen this drop?
In this circuit, if both PCs are switched on, the results are all messed up. Specifically, if both Vccs are high and one D+ is high while the other is low we get into a short circuit situation. Is there an easy way (with little additional circuitry) to shut everything down if both Vccs are high? Should I just bite the bullet and put in a small micro-controller to act as a gatekeeper?


texts:
Recently my water heater's thermostat failed. It's just a simple mechanical one, with a piece of metal that "pops" and connects or disconnects the heating element.

I would guess that what made it fail was arcing in the contacts. How would I calculate a capacitor (or RC snubber) for this application?

The heating element is 1500W 220V.

I remember I used to have a small space heater with a similar thermostat and arcs were pretty spectacular whenever it switched on or off.


texts:
On the above picture, VAB is 380 V, balanced loads.

The right answer says power on Wattmeter A is 0 and power on wattmeter C is 7240 W.

This question came from a previous admission test from a power company

I need help understanding why the zero.

Also, why do I have to ignore the phase of the source ?

The following was edited. See edit history if necessary

I tried:

VAB²/(2*Z)

380<0² / 2*10<60

Which results in 7220 (not 7240, but I believe it's an approach error).

Also, kindly answer another question I made, which I believe is related:

Relation between phase angle and current direction

The answers there don't seem, to my eyes, related to the question. And they came before I enhanced the question.


texts: Feedback on current transformer signal limiting with zener diodes

texts:
I have read enough to build a simulated circuit and it seems to do what I need:
https://everycircuit.com/circuit/6423598925086720
Did I miss anything?
(purpose below)

Purpose:
Building an ESP8266 based controller for a 100W to 200W pump.
Controller will include a current transformer to monitor the state of the pump.
Pump is plugged into a regular 120V wall socket. ESP relay switches on the socket.
It is desirable to have more resolution in the < 5A range.
But someone can plugin anything into the socket and draw the maximum from the 15A breaker.
This circuit is intended to protect the ESP8266 ADC which can take 1V max.
Also that ADC has only 1024 values so mapping the entire 15mA range may not provide very interesting results.
The simulation does not have a current transformer, so I used a "voltage controlled current source".
This is just to simulate CT producing its' mA.
CT "zmct103c" is 1000:1 and rated for 5A. I tested it to be linear enough until 6 or 7A. Above 8A it curves and looks like will not reach 15mA.
Secondary question: anything wrong with measuring half the wave?
I suspect that -0.5V to 0.5V biased to 0-1V is not any better than 0 - 1V with half the cycle missing. The software can take care of reading for max V over some number of samples and mapping the max to what I can measure with a KillAWatt (I only have mA meters :(  ).
Thank you.
Edit:
removed one of the zener diodes, it seems unnecessary
Added a 1uF capacitor to make sure the ADC never encounters even the tiniest negative voltage. The peak signal got lower a bit, but easy to tweak with the divider.

Another question occurred: is there any downside to this arrangement vs this What is the purpose of the capacitor in this current transformer to arduino interfacing circuit?
where the ac signal is given a DC offset to make it positive?
Thanks again


texts: Precaution and Rules to Paralleling Power MOSFETs

texts:
I'm going to use a Full Bridge Inverter for my application.

The problem is that the current which flows through the MOSFETs when they are ON can reach 70A RMS and the power dissipation is too high. In fact using a IPW65R019C7 MOSFET (home page, datasheet) one obtains:

Pd = Rdson*Ieff^2 = 0.019*50^2 = 47.5 W

I would like to reduce this power loss by using two MOSFETs in parallel. In this way the current is divided by 2 and one obtains:

Pd = Rdson*Ieff^2 = 0.019*25^2 = 11.8 W

The question is: Are these calculations correct? Do you know the rules and precautions to ensure that the current flows half in one MOSFET and half in the other one?

I thought to use an L6491 (home page, datasheet) as a MOSFET driver. Can I use just one MOSFET driver to drive both of them or do I need one driver for each MOSFET?

Thank you.


texts: How can I tell the full spec of my step motor just by looking ati it?

texts:
I have a retro CNC machine (EMCO F1P) in my garage that I am currently tinkering with. I would like to replace the old motor control but use the existing step motors. Unfortunately the documentation is scarce, and so I decided to pick one motor apart to see if I could learn anything from it.

Turns out it has 10 wires going into it and 10 windings inside. Each winding pack looks like it has only two wires coming out of it. The wiring diagram is the PCB visible in the picture:

So with my limited understanding of step motors I could need some help determining the parameters for this motor. Is it unipolar or bi-polar? How many steps per revolution does it have? How can I find a driver that will work for it, and how would I know which wire goes where?

Thanks!


texts: How to get MicroBlaze running on Papilio Pro

texts: I am new to the FPGA world, and there seems to be gazzilions of boards and FPGA vendors. I just bought the Papilio Pro, which is based on the Spartan 6 LX9, and although I can already bitstream basic VHDL designs, I was looking to install the MicroBlaze soft core; but there doesn't seem to exist a top-level component for the LX9. Thoughts?


texts:
I tried out the the BBB with the Adafruit python library.

I was connecting a Voltmeter to the right Pin and run the following program

 import Adafruit_BBIO.GPIO as GPIO
 import time
 pin = "P8_10"

 GPIO.setup(pin, GPIO.OUT)

 for x in range(0,5):
     print("High")
     GPIO.output(pin,GPIO.HIGH)
     time.sleep(1)
     print("Low")
     GPIO.output(pin,GPIO.LOW)
     time.sleep(1)

 GPIO.cleanup()

Unfortunalty it was always on high, I did try a 1kOhm pulldown resistor to the ground. Still the same always high.

I did try the it the other way using this code:

 import Adafruit_BBIO.GPIO as GPIO
 import time
 pin = "P8_10"

 print("Setup " + pin)

 GPIO.setup(pin, GPIO.IN)
    for x in range(0,5):
            if GPIO.input(pin):
                    print("High")
            else:
                    print("Low")
            time.sleep(0.5)

 print("end")
 GPIO.cleanup()

Connecting it over a 1kOhm resistor to ground. I did still stay High all the time.

The OS on my BBB is Ubuntu. Any suggestions what could be wrong with the setup?


texts:
I'm a complete amateur at electrical stuff, although I can solder and make some basic electronics with Arduino.

I'd like to wirelessly charge a battery in the rotating part of an astronomy dome. The battery is for lights and eventually a motor to open/close the dome hatch. I know about slip rings, but I'm wondering about wireless because, well, it would be cool.

So could I wire up ten 5 V 1 A Qi wireless chargers to get 50 V and then step down to 12 V to charge a 12 V battery at maybe 10 amps? When the dome is "parked", the chargers would line up and provide power. I would have to find a battery charger that takes DC instead of AC but those exist, no?

If this idea is terrible, does anyone have other ideas?


texts:
I have an h-bridge I have setup using transistors. The transistors I'm using are TIP120 (NPN) and TIP125 (PNP).

simulate this circuit – Schematic created using CircuitLab

They both are supposed to run at a max of 60V with a 10V max base. I am supplying the circuit with 25V at 4.5A and controlling the gate with a 9V battery. This setup was fine when I using 40V transistors rather than 60V. However, the current setup is only letting through about 0.2V. While with the 40V setup up, I was getting well over 8V using a 12V input supply.


texts:
When I search for 1N34 on Mouser I get nothing, and when I search for 1N270 diode I only find a note that it is obsolete. What is now used in place of this part?

I am using Ronald Quan's book on building AM radios and he specifies it in several projects. For example, he uses it in his two-transistor reflex radio project. It appears to be in the "detection" part of the circuit.


texts: Calculations for building a mixer circuit

texts:
I have been tasked with building a mixer.

\$V(output) = 1/2*V1 + 1/6*V2\$

Thinking in terms of superposition, I assume I can hook up \$V1\$ and \$V2\$ to the circuit separately, and then sum the results up to achieve \$V(output)\$.

I start by connecting the circuit to V1 and ground, and add two equal resistors to each side of the output. Since the resistors are equal, V splits in half, and the first half of the task is done.
I replace V1 with ground, and hook up V2 to where ground was. I change the relationship between resistors from \$1:1\$ to \$1:5\$ to get the 1/6 relationship. \$1/(1+5)\$.

But now I don't understand how to proceed. I can't simply add the values of the resistors together, as that will yield neither of the right relationships. Please note that this question is tagged with homework.


texts:
I have created a system to plug my studio mic (MXL 990) into my MacBook's 3.5mm headphone jack that consists of the following system:  Mic -> AC Power supply for the mic -> 3-Prong microphone cable to 6mm headphone jack transformer -> 6mm to 3.5mm converter. The system, however, doesn't work. I have tried diagnosing the problem myself with the following:

Using a different mic
Skipping the transformer in the line
Skipping the AC Power supply in the line
Hooking up to a different mac, and directly to a speaker.
Checking the output voltage of the AC power supply


texts: I have a variable resistor as a load that want the current to remain constant by changing the voltage, This circuit also has polarity switching (like H-bridge). Each time the circuit is turned on, user set new  current and Auto transformer that Rotates by ac motor set voltage To keep the current constant. V=0-20v, I= 20-200A!, I found IRF1404 and parallel them (for H-bridge). if there is better circuit please help me!


texts: Single cell Li-Ion battery - cascaded double protection?

texts:
I have an application where I have a battery protection circuit (overcharge, overdischarge, charge overcurrent, discharge overcurrent) containing BQ29700 on the main board separate from the raw battery pack (which I guess is very bad practice). The circuit is the exact same as the example given in the datasheet, except the MOSFETs are CSD17527Q5A. The circuit is the following:

simulate this circuit – Schematic created using CircuitLab

This design choice was made to be able to use cheaper, unprotected battery packs in the prototypes of the product when comparable protected ones were too expensive. Now what we want to do is to be able to accommodate protected batteries without modifying the existing boards, if possible. Namely, it will look like the following:

simulate this circuit

My hypotheses are:

Charge/discharge overcurrents are measured by the voltage across the MOSFETs, i.e V- to Vss (datasheet says so). Therefore, the two cascaded protections should continue to work correctly in the presence of each other.
Overcharge/overdischarge voltages are measured by the voltage across BAT to Vss (datasheet says so). Therefore, the protection circuit inside the pack should continue to detect these conditions correctly, turning off one of the MOSFETs. When the battery pack "disconnects itself" like this, the onboard protection should see the pack as an open circuit, equivalent to no battery present.

My questions are:

Is it reasonable to assume that no matter the battery brand, a single cell battery protection circuit that comes with the pack will have a similar topology, namely two MOSFETs back to back (to measure charge/discharge currents and open them on fault) on the return current path and an RC low pass filter over (to measure and be supplied by) the raw battery pack voltage?
We will be connecting the battery packs directly to our circuit which contains a charging circuit as well. What we experienced so far is that when the unprotected battery pack is first connected (none of the fault conditions apply), the discharge MOSFET never turns on. Charging must first be initiated so that discharge becomes available. This is noted in the datasheet, however, there are no more details on this. When two protection circuits are cascaded, the onboard one will experience this at every fault condition detected and treated by the one in the pack (if my hypothesis 2 is correct). I'm guessing that this condition (i.e first time voltage across BAT to Vss, apply charging voltage across VDD to VSS) is detected by the voltage across BAT to V-, is this a reasonable assumption?
Would charging be required every time a fault condition arises in order to enable again the onboard circuit?
Are there other foreseeable conditions that would prevent the MOSFETs of one of the circuits to never turn on, even in the absence of fault conditions, no matter what?
If there are such conditions, we imagine simply bypassing the onboard MOSFETs with a thick wire would be the fastest solution with the least modifications (of course this would prevent unprotected raw packs to be safely used with these boards unless the wire is removed again). Is this correct/safe?


texts: How to make equivalent circuit diagram for 150 kV Lattice tower transmission?

texts:
How to make equivalent circuit diagram for 150 kV Lattice tower transmission.
I need to make a EMTP simulation for lightning strike and see the effect to backflash over.


texts:
What is the (minimal, usual, maximal) AC frequency of petrol engine ignition (at the spark plug electrodes)? I'm interested mainly in cars and garden machinery.

Also, I found that dielectric strength of air under normal conditions is higher than of mixture in the engine cylinder at ignition point. Is it true?
Thanks.


texts:
I'm very new to Eagle so please bare with me. I'm hoping to check and change the properties of the holes on a PCB, but I can't seem to right click them. I've removed all layers except for the hole and drill ones.

The biggest issue is that, after converting to gerber, the drill file blows up the area by almost 100x (from 0.5in^2 to 70in^2), so I wonder if my holes are problematic.

Thanks


texts: Is there a "standard" way to verify HDL of a state machine?

texts:
State machines are a pattern that is used very often in writing synchronous designs. They serve as the controllers in the design. So, is there a standard way to verify them if they are written using VHDL or Verilog/SystemVerilog? Or is it better to use some GUI to draw them and then generate code from the GUI instead?
By standard way I mean a pattern of code used to verify them. There are always different ways to "skin the cat" but perhaps there is a method that is very popular.
The thing is that state machines can be quite big and one would have to write code to verify each branch in the state machine which leads to a lot of code in the testbench.
Edit:
I am only taking about verification of the fsm itself on its own, to verify that it matches the fsm state diagram and no errors in rtl coding exist.


texts: What is a common mode signal in a layman's language and why do we care for it while studying Differential Amplifiers?

texts:
I searched on the topic 'Common Mode' on the internet but what I found is the application of common mode and without any simple explanation. Well, one needs to have a master's degree in order to understand what the internet says about common mode signals.
Can anyone help me with the basics of common mode signal and its use in the differential amplifier, assuming that I am a 5year old kid and does not know ABC of electronics?


texts: Is reed switch sensitive to DC magnetic field?

texts: How would I know if a reed switch in parallel to a DC wire in which is flowing current can be closed by the magnetic field produced? If yes, what's the minimum current required?


texts: Safely probing low voltage isolated DC/DC converter rails with an Oscilloscope

texts:
Lets say you have a flyback with a 20V dc input and 2 secondary side outputs, 5V and 12V. The 20V power in is provided by a benchtop power supply. What is the safe way to measure the input and output sides of the converter?
Can you connect to the secondary side rails using a single ended probe only or would this cause ground loops through the bench equipment? Can you connect primary using a single ended probe and secondary using a differential probe using the same oscilloscope?


texts:
Good day everybody.
This is my first question on this site so bare with me :) .

I am working on general purpose driver using TBD62083 (replacement of darlington array ULN2803). As you can see the circuit is realy simple:

The only problem that I foreseen is reversing polarity on POW1 connector.
Analysing the internal diagram of the driver I came with this solution:

Of course that on 24V the resistor must be rated to at least  5W. I don't have room on PCB for such big resistor so I was also thinking to add a resetable fuse in series with resistor.

So, my questions are:

Will this setup affect in normal operation (in case of using an inductive load) the clamp diode?

Did anyone tried a better solution?

Is this device suitable for paralleling the outputs (no reference found in datasheet)?

Thank you in advance for your answers.


texts:
I am assigned to do lab that is allowed to ask other people for hint.

I am given an uncompressed PCM WAV file that has signal like following image:

And this is question:

determine the sequence of bits that were transmitted. Hint: the remote control transmitter contains a sticker inside with a number 50325 printed on it. The number is transmitted somewhere in the signal given, in binary.

Does that transmitted bits mean 3 bit representation which I can obtain after sampling and quantization? (as explained in the bottom of following webpage -
 https://courses.engr.illinois.edu/ece110/su2017/content/courseNotes/files/?samplingAndQuantization)

So somewhere in signal has 1100010010010101 (50321 in binary) as 3-bit representation? so there is a sequence of bits that contains ... 110 001 001 001 010 1.... ?


texts: Final voltage of two parallel (switched) capacitors

texts:
I am trying to obtain a resistance-circuit equivalent to a switched-capacitor circuit. It is the first stage of a ladder filter.

simulate this circuit – Schematic created using CircuitLab

Two switched capacitor C2 and C3 are charged (during the current semi-period of the clock) to different voltages: C3 is charged to - say - $$V_2 - V_{in}$$ (V2 is the output of the following stage), while C2 is charged to V1 (V1 is considered as the output of the actual stage).

But during the successive semi-period of the clock, the switches put the capacitors C2 and C3 in a parallel configuration. Do they discharge themselves until an intermediate and common voltage?

And does ground play some role? The left terminal of C2 always remains connected to ground.

The circuit above should be the switched capacitor realization of the following first stage of a ladder filter.

The op-amp is a differential inverting integrator, with unity resistances as its inputs realized by the switches and C3. It is used to realize the relation

$$V_1 = \displaystyle - \frac{1}{sC_1} (I_2 - I_{R_1}) = - \frac{1}{sC_1} \left( I_2 - \frac{V_{in} - V_1}{R_1} \right)$$

(I2 is the current exiting from V1 towards the second stage, which contains an inductor, L2)

simulate this circuit

I have read the consideration in this question and I agree, but here the problem is more conceptual. That is: how can I correctly draw the first circuit by substituting all the switched capacitors with their equivalent resistances?


texts:
I was wondering if someone could recommend a textbook or some online resource on batteries- working with lifepo4 for the first time and I was wondering what all I should be worried about and what all I need to be testing.

Tried to find stuff online but it was difficult to find anything that went into depth.

Thanks


texts: Improve 3D printing via distance detection

texts:
3D Printers are now "auto-leveling" via a limit switch contacting the surface that is swung into place prior to printing and height of the bed is checked in 3 places.  Software then continually adjusts the print head on the Z Axis throughout the printing process to travel the printing head in the same plane as the printing bed.

Are there not electronics that can simply measure such a short distance (<2") accurately (ultrasound, infrared??? to accuracy of .1mm likely) and instantly without the need to lower the print head until a limit switch is engaged?

It would seem likely this measurement of the printing bed's plane could be accomplished quicker and cheaper than by a limit switch swung down into place via a servo motor and moving the print head down to have it engage...


texts: Digital input ports of the dsPIC30F4011/4013 not working on the dsPICDEM 2 Development Board

texts:
I have a Microchip dsPICDEM 2 Development Board with two microcontrollers on it: a dsPIC30F4011 (Motor Control Family) and a dsPIC30F4013 (General Purpose Family). I'm programming in C using the MPLAB IDE.

What I want to do is read the a digital input signal with TTL levels (0-5 V), but the reading of the ports is always 0.

If I set the port to be an output using the corresponding TRIS register and then write to the corresponding LAT register, it works fine. For example:

TRISBbits.TRISB0 = 0; // set RB0 to be an output
LATBbits.LATB0 = 1;

works perfectly.

However, when I set the port to be an input, I keep reading 0 both from the LAT and the PORT register. So, neither of the following code excerpts work:

// This doesn't work:

TRISBbits.TRISB0 = 1; // set RB0 to be an input
value = LATBbits.LATB0;

// This doesn't work either:

TRISBbits.TRISB0 = 1; // set RB0 to be an input
value = PORTBbits.RB0;

My program is as simple as this:

int main(void)
{
    TRISBbits.TRISB0 = 1;
    TRISBbits.TRISB1 = 0;

    while (1)
    {
        int rb0 = LATBbits.LATB0;
        LATBbits.LATB1 = rb0;
    }

    return 0;
}

so there's no other possible error source in the program.

These are the documents I've used for reference:

dsPIC30F Family Reference Manual
dsPIC30F4011/4012 Data Sheet
dsPIC30F3014/4013 Data Sheet

What am I doing wrong?

EDIT: After the corrections pointed out by Tut (see accepted answer), the code of the program looks like this:

int main(void)
{
    TRISBbits.TRISB0 = 1; // set RB1 as input
    TRISBbits.TRISB1 = 0; // set RB1 as output
    ADPCFGbits.PCFG0 = 1; // set RB0 as digital input (i.e. disable analog input)

    while (1)
    {
        LATBbits.LATB1 = PORTBbits.RB0;
    }

    return 0;
}


texts:
High-level survey of this question is fine:

After reading https://en.wikipedia.org/wiki/Laser_diode I still can't tell if the electronics that enable a diode to lase are different from those that enable it to emit light. So, in general, is a laser diode a LED plus some sort of optical resonator or cavity?

Or are any laser diodes themselves electronically distinct from non-laser LEDs, meaning they don't look like a LED plus some extra physical structure to allow them to act as a laser?


texts: How to correctly calculate Coss and Cstray capacitance in Full-Bridge LLC?

texts:
To select the correct value of the magnetizing inductance Lm, it is necessary to observe the equation:

This allows the selected Lm to completely discharge Coss and other parasitic capacitances during the dead time and reach ZVS (zero voltage switch).
Coss - transistor (Mosfet) output capacitance, consists of Cds and Cgs. Specified in the datasheet of the transistor.

Each transistor has its own Coss capacitance. At the moment of time, only two transistors (Q1, Q4 / Q2, Q3) are operating here.
Questions:

What is the Coss value used in the formula? The capacity of one transistor or the capacity of two transistors? (there are two transistors in one arm).
It is also recommended to take into account the value of the parasitic capacitance of the printed circuit board and the interturn capacitance of the transformer. I don't have a printed circuit board yet.
Is it possible to guess the value of parasitic capacitance? Or do you need to check on a breadboard?
Perhaps by choosing a value of Lm slightly below the equation, then we can discharge stray capacitances.

UPD: To make a reserve for discharging Cstray, it is worth reducing the Lm value by 0.5–0.8 from Lm_max (in the upper formula).


texts: How to connect Onion Omega relay board to AC110V Electric Solenoid Valve

texts: I am a electronics newbie who wants to connect a Onion Omega to a AC110 V Electric Solenoid Valve (such as this one for example) with their Relay extension board. Do I need any capacitors/transistor/etc?


texts: Transmitting power and PWM signal through the same cable

texts:
I am working on an Arduino based project, which required to supply 24VDC at 2A and 3 PWM outputs from the main board to the other board. The 24VDC is for powering the LEDs, and PWMs are for dimming control. To make wiring simpler, instead of running 5 separate wires (3 PWMs, 24VDC, and GND), I plan to use a multi-conductor cable like this and circular connectors like this
 for this purpose.

Is this a proper way of delivering both power and signal through the same cable? What other methods are recommended?


texts:
First of all, I would like to tell you that this is my first question on this forum and I found your topics and your answers very useful during my academic years so thank you all. At the moment I have the following problem:

I am trying to implement a transfer function for a rotary encoder to link the position of my mechanical system with the encoder measured position. This is a classical problem of model design to run a Simulink system.
Exactly I would like to have a transfer function in the Laplace domain where the input-output relation is something like:

$$
    \frac{angle_{measured}(s)}{angle_{real}(s)} =\frac{1}{1+s*T_{tv}}
$$

I found on some books that this approach is the easier and got a good approximation and the terms are equal to:

$$
    T_{tv}=\frac{1}{\omega_{tv}}
$$

Where Wtv is the bandwidth of my encoder and s is the Laplace operator.

Then here comes my question, how can I find the bandwidth of a rotary encoder?
I just have the specification of this which are linked here:

http://www.contelec.ch/fileadmin/user_upload/contelec/Downloads/Datenblaetter/Englisch/Vert-X/Vert-X%2028/Vert-X_28_24V_0.1-10V_e.pdf

Thank you for the help guys.


texts: How would the input impedance of the instrument affect my measurement?

texts:
I have an instrument (a Lock-In Amplifier, a spectrum analyzer, etc.) with some input impedance, 1 M Ohm. I use these to measure a sample of a much higher resistance, 100 M Ohm.

What is the affect of having the input impedance of the instrument much smaller than that of the load?


texts: Keep potential difference fixed for transformer's output

texts:
I have a source consisting of V1, R1, L1, and L2 to which my load R2 is attached:

For the load, I have 10 or 100 Ohms.

1) R2 = 10  Ohms: Vrms = 315 V, irms = 32 A, P = 10 kW

2) R2 = 100 Ohms: Vrms = 788 V, irms = 8  A, P = 6  kW

How do I adjust the circuit in such a way that for R2 = 10 Ohm, I still have 788 V across R2? I suppose, I have to match impedance in such a way that the supply sees R2 like if it is 100 Ohm instead of 10 Ohm.

I am not allowed to change V1, R1, L1, and L2. That is to say, they should be treaded as a power supply that I can't adjust in any way. I am free to add components across the load R2.

Here are the waveforms:


texts: Understanding Touch Switch with BJTs and Relay

texts:
We worked on this circuit today in one of my labs and it had my groupmates and I puzzled. We had a 1k resistor in series with an LED on the NO side of the relay.

I searched for the circuit online and found this website explaining, but his explanation does not make any sense to me. He says that when you activate T1 and then T4, this "energizes" the relay, thus activating the other circuit. This part makes sense, but the following has me confused. When you let off of the touch switch for T1 and T4, the light continues to stay on. By my understanding of relays and transistors, this doesn't make sense. The transistor is acting as a switch, providing ample current to the relay, but should it not then cut off when let off of the switch?

Secondly, T2 and T3 are activated to turn the relay off. This part makes a but more sense as the high current from the darlington transistor would draw all of the current from the relay, I believe.


texts: Free multiplatform oscilloscope with custom oscilloscope support

texts:
I have a USB oscilloscope (works with command line) and I want to have a oscilloscope GUI to see the samples and preferentially have options that most oscilloscopes have (e.g. trigger, frequency calculator).

Do you know any software where I can create custom oscilloscopes in order to use the GUI with values readed by my own (by creating an adapter)?


texts:
I have a tiny PCB that I've been working on and off of for a while now. I received it with leaking batteries, and it had corroded some of the traces off the board. Most recently, I tried redrawing the burnt traces with conductive paint, but to no avail. I actually popped batteries in it last night and had activity for the first time ever, though it was short. I then scraped off the paint and decided it might be time to try a jumper wire.
My question is: there used to be a trace pad that completely came off the board, do I need to worry about that? Is it possible to skip the pad entirely and make a bridge between the two sections of trace?

The missing pad

The two points I would bridge

I'm familiar with soldering, but not with specifically making a jumper wire. Mostly I'm trying to find the right kind of wire to do it with and where to purchase it.


texts:
I am looking for a simple 3d software solving the drift and diffusion model
for a diode in equilibrium. (Very simple abrupt p/n-junction - even without contacts. Purpose: teaching).

I know Silvaco Atlas and Synopsis. However, their licenses are far too expensive
for my very simple experiment.

Is somebody aware of shareware that I could use?

Many thanks in advance.


texts: Irregular output from DC Motor used as a generator?

texts:
I was trying to make a generator out of a DC motor inrunner by following this video by following this schematic:

I made this structure and started testing the phase voltages. A-, B+, C- are combined together and made as the neutral wire.

While testing the voltage outputs from A_neutral, B_neutral, C_neutral, V_ab, V_bc and V_ac, I am getting non-uniform outputs and I am getting problems troubleshooting this issue.

Voltage_cb

Voltage_ab

Voltage_ac

Voltage_a_with_neutral

Voltage_b_with_neutral

Voltage_c_with_neutral (almost no voltage, dont know why)

Why is the voltage_cneutral almost nil compared to the other voltages? I checked the copper coil winding and they are all same.


texts: Phase difference between resistor and inductor voltage in an RL AC circuit

texts:
In my textbook, it is given that \$\mathcal {E} = -L\frac{\Delta I}{\Delta t}\$.
The graph of resistor voltage (\$V_R\$) and inductor voltage (\$V_L\$) in a series RL AC circuit is given similar to below:

Where the red wave is \$V_R\$, and the blue wave is \$V_L\$.

It justifies this by implying that since \$V_L\$ is a multiple of the rate of change of current (\$\mathcal {E} = -L\frac{\Delta I}{\Delta t}\$) and current is proportional to \$V_R\$ (\$V_R=IR\$), then the graph of \$V_L\$ is simply the rate of change of \$V_R\$ multiplied by some constant.

The problem I see is, wouldn't the negative sign in the induced emf equation mean that the \$V_L\$ should have a negative amplitude (i.e. be flipped)?.


texts: How did handheld video games from the 70's and 80's work?

texts:
I'm curious about how the early handheld video games from the 70's and 80's worked. You know, those small games with a LCD display with "fixed elements" meaning it was hard wired for one (or a small number of) specific games(s). For instance,

this one:

or this:

Specifically, what type of micro controllers did these games use? As I recall, there was usually one big epoxy "blob" at the center of the board which probably controlled everything. So my question is, what was inside this blob? Was it a small standard microcontroller with a ROM running the actual game, or was it a custom CPU/controller for every design? Or maybe it wasn't even a CPU but more like a simple state machine hardwired for the game in question? I realize the answer may depend on the particular game.

Has the design/schematics for any of these games been released or is there any good books/references about how they were made? Finally, what tools were used to design microcontrollers like this? Was it based on something like VHDL/Verilog synthesis, or was it a more low-level approach with wiring the individual elements?


texts: Why does the LCD impede the ESP8266 NodeMCU initialization?

texts:
I have  a very  simple setup on  a breadboard  that connects
a  Lolin  v3  NodeMCU  ESP8266  with a  16x02  LCD.  No  I2C
communication, I'm doing with  directly with Arduino IDE and
the LiquidCrystal library.
For some reason when I  disconnect the LCD Vdd and connect
it after the MCU has  booted everything works fine. My power
supply indicates it draws ~70mA  during boot and then lowers
the current. However  if I leave the LCD  connected and turn
on the power  supply, the MCU won't boot and  the circuit is
stuck drawing 40mA with the  LCD showing blocks on the first
line at 50% contrast.
How can I fix this?
Here's how I setup my wiring:

And my code:
#include <LiquidCrystal.h>

LiquidCrystal lcd(D8, D7, D6, D5, D4, D3);

void setup(void) {
  lcd.begin(16, 2);
}

void loop(void) {
  lcd.setCursor(0, 0);
  lcd.print("hello, world!");
  delay(10000);
}