texts: How do I protect analog circuit from relay switching noise?

texts:
I'm making a thermocouple based temperature controller. The thermocouple voltage is measured by using cold junction compensation IC LT1025 and precision opamp LT1050.

The measurements are read by ADC and the relay is switched on by a MOSFET controlled by microcontroller.

The device will be a separate "shield" containing cold junction compensation, opamp, MOSFET and connectors for thermocouple and relay.

I want to avoid noise on analog part as much as possible and I'm using separate ground for analog part - grounds for analog and digital parts will be connected on power supply (which might cause some problems in ADC reading accuracy as these grounds will be at different potential, but I will compensate that in software) and I'm running a trace, separate from analog ground plane, for relay ground return.

I've put a reverse protection diode across relay terminals and decoupling capacitors of values 10uF and 100nF on MOSFET Drain terminal. What else should i do to avoid spikes from relay in my analog part? It might be not too critical in this particular application, but I'm willing to learn.

Circuit diagram that Olin is slightly less liable to complain about:


texts:
I've have a system consisting of a Raspberry Pi Zero W, a usb2422 USB-hub, a CP2108 Uart-to-USB converter as well as another USB device (lets call it device 2, it doesn't matter which one I plug in).
Starting the circuit up, i have access to device 2, but not to the CP2108. In the dmesg kernel output of the raspberry I can't find any errors. It just does not recognize the CP2108.
After some debugging, I found it working. Following scheme is reproducable 100% (tried it about 10 times);
I found it working if I turn off power to the circuit and then turning it on again. After tuning it off, the 5V supply voltage of the Pi (where the 3V get generated from a switching converter at Pi) drops down to 1V immediately, then slowly further. If I turn the power on again before beeing lower than 20mV, the all devices work.
Following information gathered during debugging:
The CP2108 has a reset pin. When i have no access, resetting the device via this feature has no effect. I do not see any log of this event in the dmesg output. However, it disables the pullup on the data line, as it is supposed to do, as long as the reset is pulled.
When I have access to the device (measured quarz Voltage at startup), a reset causes the expected error message in kernel, seen at the dmesg output.
Plugging and unplugging device 2 always causes the expected kernel messages.
The usb2422 as well as device 2 are always visible to the Raspberry, no matter the state of the CP2108.
Additional info:
CP2108 and USB2422 are on 1 pcb, the design is my own. I can share it if you want.
device 2 is connected via a usb connector.
I posted it in this forum as the whole thing with measuring the quarz making it work pointing to a electrical mistake, but thats only a guess.
Thanks for any help!
(edited after further debugging findings)


texts: Smartphone ribbon connector identification

texts:
I need to replace this 78-pins connector on a smartphone PCB (Galaxy A40) but I can't find its name (dimensions in cm):

Here is the ribbon cable:

Many thanks


texts: Why it is preferred to use PNP and PMOS for pull-up, and use NPN and NMOS for pull-down

texts:
I have noticed that when I was designing universal logic gates like  CMOS NOR gate  that uses PMOS for pull-up and NMOS for pull-down.

Then I faced it for second time with
the H-bridge circuit, but in this case the upper part of
H-bridge was PNP and the lower part was NPN (I don't know if I can call it pull-up and pull-down ) this  circuit works perfectly.

Even though there is  a circuit which is composed of all NPN but it doesn't work properly.


texts: The unit that is written between parentheses alongside the dB

texts: What is the meaning of the unit that is written between parentheses alongside the dB unit? For example 2 dB (mW) or 2 dB (uW)? What exactly does this unit refer to? Does it refers to the unit of the reference value, the measured value (P2), or both?


texts: Relay seems to fail (sticks on) when a load is present, but not otherwise - does that make sense?

texts:
I'm repairing my stove.  The control board has a relay (G2RL-1A-E-HA DC12) for the oven element.  When turning the bake function on, the element heats, but it won't turn off when bake is turned off.

My question is, is it possible for a relay to switch on/off properly when no load is attached, but fail (latch on) when a load is present?

The board is hard to get to, and operate the controls when it's live - so to enable testing I desoldered the relay and connected it to 2 wires running to the board.  This enabled me to test continuity on the load side of the relay, without any load attached.  The relay worked properly.

I'm reluctant to solder it back on, and try to test it live, because moving the control around exposes high voltage/current terminals.

Should I just assume the relay is a dud and order a new one?  The $ cost is minimal but I have to wait for it to get here, which would be less than ideal if it isn't the problem.

EDIT: Pictures, please forgive the goofy wiring, the red and white wires are just parallel because I didn't have more suitable wire for the task.

I don't know if there's a flyback diode because I don't know what a surface mount diode looks like.

EDIT: More pictures as requested

I found that relay P11 (P1 is the relay I've been talking about) is a DLB for the element.  DLB means double line break, so I believe the heating element circuit goes through P11 and P1 in series, both can turn the element off.  Which is more baffling because it means they'd both have to fail.  That would make you think that the logic coming from the chips is wrong, but remember when I tested the relay it was opening and closing properly when the oven was turned on/off by me, but I didn't have load on it at the time.  Can I test a relay for continuity while there is load on it?


texts: MOSFET Gate Charge dependance on temperature at HOT, to determine charge needed to design driver?

texts:
i am designing this push and pull driver for external NMOS in my buck topology circuit.
i am well aware the gate charge ( based on Cgd) i need to turn FET ON and OFF at room temperature based on datasheet. But i do not know how much charge i need at 125 C in the design ?
all the spice models i have works only at room temp.
Gate Charge Q_GD =  Slew Current x Rise Time  or there are many other formulas. also data sheet shows how much minimum charge i need to turn on the FET
but my question is should i worried about gate charge at 125 C ? will it increases ? how to find it from datasheet?
AT hot RDS ON of the FET is increases , bigger RDSON more static power dissipation..but since i am switching the FET at 300 KHZ I am more interested in switching power dissipation.
My thinking is VGS of the FET will be hanging at 125 C so i think gate charge shold increases too.. how much that will be ?


texts: What is the typical 230 VAC power line RLC characteristics?

texts:
If we take a typical 2- or 3-wire power line how do I estimate its parasitic capacitance, resistance and inductance?

I tried to find this information at internet sites of wire manufactures but looks like nobody needs this information except me.

Mostly for power lines using cables with 3 copper single wire conductors with 1.5 or 2.5 mm2 section:

Line, protective ground and neutral wire respectively.


texts: Hall-Effect Current Sensor Output Voltage Difference (26.4 mV/A)

texts:
I am using a hall effect current sensor. Its part number is ACS781LLRTR-050B-T from Allegro MicroSystems. In my circuit, I'm reading its output voltage to calculate current with MCU.

With no load, I read output voltage of current sensor as 2215 mV and use this value as zero current value. When the load is connected, it draws 2.3 A which means the output voltage of the current sensor must be 2286 mV, because the sensitivity of the sensor is 26.4 mV/A. However, in the MCU the voltage read is 2331 mV, which is higher than the expected 2286 mV.

What is the problem? What might be the solution?

Hall effect sensor datasheet


texts:
I have a series of 1 ohm/ 4 Watts that each theoretically takes up 2W. It got pretty hot while in the circuit, and when I plugged off the power they kinda gave out some "tearing sound".
Does anyone know why that happens?


texts: Why does the MCP1650 datasheet give such a low value for the inductor in a boost converter?

texts:
I'm currently designing an SMPS around an MCP1650. In the datasheet (see page 4), the recommended value of inductor is 3.3uH. However, all the inductor size calculations I've come across (here and elsewhere) give a much greater value:

Inductor frequency ~= 750kHz

Vout = 12V

Iout = 0.1A

And using the 10% rule of thumb (i.e. ripple current = 0.1*output current), this should give a first approximation of 1.6mH. Why is there such a large discrepancy here? I'm assuming the designer is using a decent value of ripple current of course, I think with the inductor specified the ripple current was approx. 35% of output current, but to my mind this is excessive. What gives?


texts: Choosing wattage for current limiting filament bulb

texts:
I am building a fully featured breadboard/prototyping box for audio circuits and would like to include a current limiting light bulb that will be in circuit when I apply power to the box and then I can switch it out if everything looks OK. I am wondering how I can calculate an appropriate wattage bulb to use.

Theres four main components to my prototyping rig, two power supplies and two circuits:

One linear +/-12V power supply that feeds the breadboard and what
ever circuit is on it which will not exceed 100mA (if everything is
hooked up properly)
One linear +15V power supply that feeds a 2.5W audio amplifier

With that said, how can I calculate the wattage of a bulb that will limit enough current to prevent damage to any components but still allow everything to power up to idle state?


texts: How to evaluate the assembly Storage temperature?

texts:
Question about the Storage Temperature after soldering in general.

If the components were all specified with, for example:

Storage Temperature Tstg :  -65...+125°C;
Operating Temperature (or Junction temperature, anyway) TJ :  -40...+85°C

What shall we consider for specifying the storage temperature of their complete PCB assembly?

For a simple start, let us assume:

there are no CTE issues
we are having very small components/semiconductors
we are not cycling the environmental temperature


texts: What type of power supply to use for a 4-20 mA loop? SMPS or Regulated?

texts:
I am planning to use an instrument that gives a 4-20 mA analog output. I am not sure whether to use a SMPS based power source (which is cheaper) or a regulated power source for the DC power supply? Any ideas?

Regards,
Abhishek


texts: Arduino RGB ledstrip control 2 separate power supplies

texts:
Please ignore the 2 green and orange lines in the middle and consider the transistors to be IRF mosfets instead.

First of all looking at the setup on the picture: is there any issues with using 2 completely separate power supplies here one supplying 5V to the Arduino and the other supplying 12V to the RGB led strip (the supplies are not connected on any way)?

Second Question:
When using 1 single 20v 10A power supply with 2 buck converters connected to it one of them providing 5V and the other one providing 12V I have noticed the following (without using any Arduinos): if I connected the GND of the 2 buck converters which went to the MOSFETS as well and I used the 5V rail to control the mosfets I could measure 0.5-0.7A flowing through the 5V buck (which would ruin the arduino). Why is this happening? When I disconnected the 2 GNDs, aka the 5V rails gnd and + went into the arduino the 12V rails only to the LED strip I did not see any significant power draw on the 5V rail yet all of these guides recommend you to connect the GND of the 12V and 5V rails in case of using 1 power supply, why?

Thx


texts: RC filter infront of Analog port pins in pic microcontroller

texts: What is the use of RC filter in front of Analog port pin while using port pin for analog to digital conversion in pic 16f877A and in most pic controller the RC filter is advised to be used?


texts: I'm building a double stage Common Emitter preamp and I'm wondering about the order of amplification. I want a voltage gain of 30 coming out of the second stage; would it matter if I had x10 in the first stage and x3 in the second as opposed to x6 and x5?


texts: Electrical behavior of holding magnets when you pull them apart

texts:
I'm going to buy a holding electromagnet and a strike plate to hold some things, and I want to design my circuit (arduino-controlled) not to fry like bacon.  I'm aware that since a holding magnet is an inductor, I should use a flyback diode and possibly a capacitor to handle the back EMF for when current is interrupted.  However, what happens if the holding magnet is physically forced away from the strike plate?  Work is being done to overcome the magnetic force, so I figure the energy goes somewhere, but how does that momentary change manifest in the circuit?  Do I see increased current through the coil?  Decreased current?  And for that matter, what happens in the circuit when the magnet meets and locks to the strike plate?

Basically, I'm trying to determine if I need to handle a forward EMF spike as well as a back EMF spike, and my research hasn't taught me enough about magnetic fields to figure it out on my own.

EDIT

I'm currently using this circuit:

simulate this circuit – Schematic created using CircuitLab

L1 is the magnet; I don't know its inductance, but it has a series resistance of 20 Ohms.  D1 is the zener that protects against overvoltage; R1 is there because the only zener I had was exactly 12V and I wanted some safety margin to avoid a short in case the power supply went high for some reason other than L1.  D2 is the flyback; it protects against voltages less than -1V, which hopefully aren't enough to ruin the cap (a schottky would be better, but I don't have one lying around).

I operate this by turning the power supply on and off.  In the future I'll put a Darlington between C1 and V1.  It SEEMS to work and not damage anything even when I force the plates apart, so that's good, hopefully I'm not doing anything nasty to the power supply.  I still need to look at this with a scope to make sure.

I did have the idea of putting my own inductor in series with L1.  This would act to limit current changes caused by L1's inductance changing.  Not sure if I'll do that.


texts: How to attach an electronic enclosure to glass?

texts:
I'm developing a very small PCB that I'll put inside a small case that will be attached to glass, let's say for example in a car. Once you attach this to the glass, it should stay there for a long period, but should also have the ability to be detached and attached again without too much effort.

At first I considered using a sucker also known as a  suction cup but this is maybe a too bulky solution, and I need something more discreet. Also the distance between the glass and the case should be minimal, and using the suction cup this distance is considerable. So do you know something that could do the job for this application?


texts: How to set text layout in a custom component in a different angle in Altium?

texts:
I'm wondering how to set the text of a parameter in a component in a different angle, so different angles have different layouts when you press spacebar? Like what a standard component does in Miscellaneous.IntLib?

This is what I have accomplished so far the text is positioned at the far left always and when I press space it autorotates. Though the position remains in the far left. I want to define the layout to be in the vertical middle position of the component whenever the component is in a vertical position. Like what its done in the native components.


texts: Making accelerometer sense nonconventional gravity

texts:
I am working on a project of finding the bevel angle of a worm drive blade. To find the angle, I have decided to use 2 accelerometers. One of it being my reference and will sit on the footplate, the other one will be on the housing and moves with the bevel pivot.

I want the accelerometer sitting on the footplate to be my reference. Hence, whenever it moves, gravity will be perpendicular to the accelerometer. This is of course impossible to create because gravity is always pointing DOWN!! Is there a math equation or algorithm such that it would take the G values of the footplate accelerometer and create a " nonconventional, pseudo" gravity ?

Please let me know if there is any clarification needed. I am using the MPU6050 accelerometer.


texts: How to install Altera USB master driver for Windows 8 (64 bit)?

texts:
I am trying to connect Altera Stratix 4 board with my PC in which Quartus 11.0 is per-installed. But my PC is not detecting USB JTAG connection from the board.

What I am guessing is that, this problem is because drivers are not supporting window 8 64 bit version. Am I right ? How can I rectify this problem ?

I tried Googling, but nothing is helping me. Help me please.

Edit: In list of drivers\others USB Blaster is showing, I right clicked and tried to install driver for the same. But it is not working. I think the problem is that USB Blaster driver is not working. How can I rectify this problem?

Edit 2: Error window


texts: Differences between bulky vs compact AC Step Up & Step Down solutions for high power loads?

texts:
So, I was considering buying an Electric pressure cooker to use through my global movement. The following advise was given to me. WHY?

  For safety reasons (meaning, if you want to be certain that you won't
  burn out your cooker or start a fire in a hotel room), you'll want a
  converter/transformer that is rated for continuous use at a power
  draw that is at least 50% higher than that of the device (the
  IP-DUO60 is rated at 1,000W, so 1,500 is correct). The small,
  inexpensive voltage converters like this are not rated for
  continuous use and would be risky to use with the Instant Pot.

Some possibly relevant Q&A/ information from another Adapter on amazon:

  CAN NOT USE, Use this converter only with Non-Electronic control
  heating devices that have a power rating from 26-2000 watts, such as
  hair dryers. For example: pressure cooker CAN NOT use this converter,
  because the pressure cooker has a timer function and LED screen, The
  pressure cooker require electronic control turned off or insulation.
  Before using the converter/adapter, check the product you intend to
  use has the proper voltage and wattage rating to run your devices.

Additional information ascertained about product. Also, Product Manual / Tech Specs. http://instantpot.com/benefits/specifications-and-manuals/

  It looks like the Instant Pot FAQ page addresses this question. Here's what they have to say:

  The US/Canada version of Instant Pot
  models are designed to work only with 110~120v. It doesn’t work with
  220v without a voltage converter. A few users have tried it and
  reported that the cooker works well, in UK, Italy, Australia and
  Malaysia with a proper voltage converter that is able to
  accommodate up to 1500 Watts.

I'd like understand what are the internal technical/ electrical differences between such power/ voltage transformation devices?
How are they operationally similar/ dissimilar under different loading scenarios?
Why was the above advise given?

I have an Electronic & Compter Science background (who has moved on to business side of life) but I'm not an expert on Power Engineering like my dad, so I'd love to understand this better.

Bonus: If not allowed as part of this question, my next DIY solution build question would be something on the lines of,
"Would there by any electrical/ electronic solution way to make the larger ones smaller/ more compact for travel?"

Maybe relevant information online:

https://www.quora.com/Is-it-possible-to-build-a-light-weight-step-down-transformer
https://en.wikipedia.org/wiki/Capacitor_voltage_transformer
http://wikitravel.org/en/Electrical_systems


texts: How to calculate if I need to buffer the input to my ADC?

texts:
I am putting the output of a current sensing IC (ACS70331) into an ADC (LTC2373).  I am that a buffer on the input to an ADC is often required if the output of the source is high impedance. However, I am not sure how to find the cutoff where that becomes necessary for the ADC and I do not see the impedance on the current sensor data sheet.
I have some guesses that you could look at the source current (0.4mA) of the current sensor and calculate the dV/dt of the input capacitance of the ADC input. I am looking for confirmation if that is the proper approach for this type of problem.


texts: I'm working with an Atmel SAM4 ARM Cortex M4 microcontroller and every example I've seen using USB CDC mode bridges a UART channel, and it looks like checks the UART's registers to read the data. Is it possible to have a USB CDC that doesn't interact with the UART so I can actually use that UART channel separtely from the USB CDC as a UART on the separate pins of the MCU? Is this usually how USB CDC is implemented or am I missing something?


texts: SPI device act as a Master and as a slave

texts:
We developing embedded device that contains 2 MCU(A and B), both of them can act as master or slave.

The device can run in 3 cases:

1- A + B + eeprom, A master B slave eeprom slave, no problem with that.

2- A + eeprom, A as master eeprom slave, B removed from the circuit, no problem with that.

3- B + eeprom, B as master eeprom slave, here is the problem, B act as slave becouse A control B(in case 1), but now we need that A act as control to control the eeprom, did it's possible to combine this kind of think?

Thanks.


texts:
I am using this level shifter spark fun breakout board: https://learn.sparkfun.com/tutorials/using-the-logic-level-converter

My goal is to interface a 5V logic SPI LCD with a 3.3V logic micro controller. To start I have been testing the level shifter board to make sure I can get the correct levels. I apply 3.3 V from the micro controller to the TXI pin and get 5V on the TXO pin no problem. The issue is when I apply 0V to the TXI pin. This results in a 1.4V on the TXO pin. From the spark fun board schematic I see that it is using a MOSFET to apply the conversion and from my understanding when one side of the MOSFET is pulled low it enters into a conducting state and this should result in both sides going low. I don't understand why I'm seeing the 1.4V as opposed to just 0V.

If I'm stuck with the MOSFET going to 1.4 V for low-level logic should I expect my SPI LCD to treat 1.4 V as low-level logic and then operate correctly?


texts: Nintendo Game Boy emulation using Cortex M3

texts:
I am planning to build a Nintendo Game Boy simulator using ARM Cortex M3 processor.

I have no idea how to interface with the game cassette. Could anyone give some hints about it?


texts: Confusion regarding diode rectification circuit graph

texts:
I have this question:

This is how I went about answering this question:

In the above question, it's telling us to presume the ideal diode model. Therefore the D4 (diode 4) is in forward bias when Vs is negative. So this would mean that D4 is on when Vs is negative. But according to the diode model, when the diode is on doesn't this mean that although it allows an infinite current, the voltage through the diode is 0?
Therefore, during the region that Vs is negative Vd4 is 0.

When Vs is positive, D4 is is the negative bias state (i.e. "Off state"). Therefore, voltage in the direction of anode to the cathode of D4 is negative.

All in all I'd get a graph like the following:

However, I believe that the actual solution is:

Could someone please tell me where I am going wrong in my logic?

Thank you


texts: How do I switch over between 2 AC power supplies with circuit breakers

texts:
I once saw a diagram where a house was supplied by a generator or from the grid by using 3 trip switches only.
It must be manual so I can select as preferred, and not a automatic system.
I also prefer circuit breakers over a common 3-stage switch-over because the setup can also be used in other applications.


texts: How do I properly earth this voltage regulator that only has a two-prong plug?

texts:
I have this automatic voltage regulator (AVR) that powers some audio equipment.

The problem is that it only comes with a two-prong plug so it isn't properly earthed.
This means that the people who are using the equipment like microphones will sometimes get an electrical shock to their lips.
Other AVRs available in my country also don't have the third ground prong either so purchasing a new one isn't an option.
It seems to me that the terminal on the lower left corner of the back of the AVR is a ground terminal that I can theoretically connect to earth.

My question is that since my mains electrical outlet has an earth, can this terminal be connected to that hole by some sort of cable? Or should I just connect the terminal with the pipes under the sink?


texts:
Anyone here using FTDI's FT_Prog?

At first I wanted to re-program the E²PROM of my FT232H to use it as a JTAG device but if I click Scan and Parse the program crashes after a few seconds without any kind of error message (only program stopped working from windows).
Even if I disconnect the FT232H from my PC I get the same behaviour.

Did anyone here use the program? Did it work?


texts: Transfer function of full bridge inverter using mosfet and LLC circuit

texts:
I'm new at deriving transfer function and trying to derive the same for following circuit. It contains full bridge inverter circuit with input as 50 Vdc (50% duty cycle used to drive MOSFETs). Output of inverter circuit is given to LLC circuit. I've derived transfer function of individual LLC circuit but not able derive for full bridge inverter. Can any one describe how to derive transfer function of full bridge inverter circuit or combine transfer function of full bridge and LLC circuit?

Note : Input is 50 Vdc supply and output of combine circuit is voltage across 100E resistor.


texts: What is phase ripple and how is it measured?

texts:
Whilst reading up on phase response, I came across a reference to "phase ripple". Specifically, I was reading this article by Keysight, on phase measurements. From my understanding of the article, phase shift and phase response are two terms for the same measurement, but please correct me if I am incorrect. Towards the end of the linked article, the concept of "phase ripple" is introduced. The article states that:

  the number of ripples which occur per unit of frequency

are taken into account when making the group delay calculation. My question is, what exactly are these ripples and what causes them? Were I to look at an S21, or whatever s-param measurement, phase data, would I be able to identify the number of ripples?


texts: Use Darlington instead of multiple transistors? If so which one?

texts:
Using the example half way down a web page titled "Using the BBB to turn on a transistor" I wanted to know if a similar layout could use a Darlington to drive multiple LEDs instead of individual 2N3904 transistors? I'm thinking based on other forum posts I can and this is what I would need. Can someone please confirm?
I believe to mirror the examples layout of the LED after the transistor this Darlington would work.
OR
I could put the LED before the transistor and use something like this?


texts: How to read data from Agilent 34401a using GPIB-USB-B connection

texts:
I want to read data from an Agilent 34401a DMM directly into python or matlab so the data can be automatically recorded. However, I can't seem to make the connection. On my computer the device is listed as an unknown device without drivers, matlab doesn't list it as available in the instrument control toolbox, and when I used pyvisa's resource manager to list connected devices, it came out blank. I've installed pyvisa to try to get python to work, and in matlab I have the instrument control tool box along with "Instrument Control Toolbox Support Package for Keysight (Agilent) IO Libraries and VISA Interface", "Instrument Control Toolbox Support Package for National Instruments VISA and ICP Interfaces", and "Agilent 34401A Digital Multimeter - Driver".
I'm not sure why the device won't recognize any drivers. Is there a step or software that is needed for these to run?


texts: On a transmission line, why are voltage and current waves reflected at a short circuit?

texts: I do not intuitively understand this. A short circuit simply means there's no impedance. If there's much less impedance than the transmission line, the waves should simply move through the short-circuit, uninhibited. The voltage and current waves being reflected back do not make sense to me.


texts: GPIO signals from Raspberry, read by Arduino

texts:
I'm working on a program on Arduino to control the Raspberry. My plan is using a button to make Raspberry Pi 4 switch on by pressed button (if i pressed a button for 3 seconds, raspberry will switch on). I want to use a Python script and use GPIO's to send status signals to Arduino, but when I was reading the GPIO signal from Raspberry on Serial Monitor on Arduino I have been able to see this:

A 0 and 1 party, how can i use a 0 or 1 stable signal from Raspberry? GPIO is imposible?
Thank you so much!


texts:
I am really confused with the block diagram of 4017 IC. Here's the dataheet.

I really can't wrap my head around the way they have taken the output for each count. They are just taking two flip to choose the state. Shouldn't they take all four?

The outputs of flip-flops go through the AND gate (NAND+NOT).Let's take the count of 3 for illustration here. For this, the counter should have 0011 (Q4-Q3-Q2-Q1) in the flip-flops. In the block diagram, they have chosen only Q4' and Q3. This means the LED connected to count three should light up when the Q4 is low and Q3 is high ie. (01XX). But that't not what the flip-flops are holding.

Also there are 4 cases where the Q4 is low and Q3 is high. Counts of 4,5,6,7 have their 4th bit 0 and 3rd bit 1.

What is going on exactly inside the counter? You may take any count for the illustration.

I have attached the portion of datasheet for convenience:

Here's a decade counter that I have studied:

Cropped by Irfanview ^Y then copied ^C and pasted here ^V


texts:
Let's say I have a square. I also have a device that has an emitter of some sort. I need to detect when my device is pointing at my square.

Here's my question:
What emitter and receivers can I use to detect like this without anything visible?

Things I've thought about trying:

Lasers - No. Clearly visible on object
IR - No. Not accurate enough.

Any suggestions would be appreciated.


texts: Which ground plane connection will perform better in terms of EMC?

texts:
In figure 12 of these EMI Design Guidelines
for USB Components, I can see that VBUS and Gnd signals from
the USB receptacle are bypassed with ferrite beads and then connected to their respective power and ground planes, while the USB receptable itself is tied to the ground plane at its connection points.
Following this guide, my design should look like the one below:

However, after reverse engineering the PCB layout of a simple wired Razer mouse, I saw that they implemented the filtering of the ground signal slightly differently. Specifically, the ground signal from the USB cable is tied to the ground plane (no f.bead) while the USB shield* connects to the ground plane through a ferrite bead.
*Noted that in this case the USB cable is not connected to the PCB via a standard micro-B USB receptable like in the first case, but instead through a permanently attatched vertical 2mm pitch 5-pin header. So when I say shield for this second case I mean the 4th pin of the Razer USB cable which is the extension of a  bundle of thin copper wires (acting as a shield) that are wrapped around the other 4 wire signals (V, D-, D+, GND). In the first case, where a USB receptable is used, the 4th pin is the ID pin meant for something else , unrelated to this question.
My question: Are those two methods of connecting the gnd signal to the respective ground plane similar in terms of EMC performance, or should I expect to see my board fail at the test house after following one design over the other? I would be inclined to follow the design guide had I not seen an actual product designed in a different way.


texts: How do moving iron meters work on AC current?

texts:
I read on the internet that an iron vane is attracted to a coil and the vanr is attached to a pointer. Thus we get the reading.
The article also said that we can measure both AC and DC using it.
How is that done? Won't the vane keep oscillating when connected to AC?


texts: Finding the Current I1 using Polar Notation

texts:
For the circuit in Figure Q3. Convert all voltages and currents to the form X sin(t + φ ). You need
only find the stead-state solutions.

Solution

My Steps

...

It seems that I am going along a wring direction...
How to obtain the answer?

Thank you for your help.


texts: How to simplify opamps in circuits for limit analysis

texts:
I know that when simplifying electronic circuits for limit analysis you can e.g. replace capacitors with closed lines and coils with open lines.
e.g.:

the equivalen at high frequencies would be:

simulate this circuit – Schematic created using CircuitLab

But what about opamps?

e.g:

What would be the simplified version of that at lower and higher frequencies?

simulate this circuit


texts:
How do I turn a high negative DC voltage into a positive DC voltage around -88v?

I need to do this to be able to measure this across a sense resistor using an LTC2992


texts: What is the best way to balance supercapacitor cells at 700mA peak charging current

texts:
So I want to charge a stack of six series-connected super capacitors from a small 10W solar panel.

The part number of the capacitors is TPLH-2R7/12WR10X30.
https://www.tecategroup.com/products/data_sheet.php?i=TPLH-2R7/12WR10X30

The part number of the solar panel is TPS-12-10W.
https://tyconsystems.com/documentation/Spec%20Sheets/TPS-W%20Solar%20Panels%20Spec%20Sheet.pdf

Like most super-capacitors, the cells are rated at 2.7V each.  I want to limit the voltage one each cell to be in the range of 2.0V to 2.5V max.  At first glance the cells could be mismatched in value by at least 60%.  The solar panel looks like it could supply 500mA to 600mA in full sunlight.  Unless properly regulated, the open-circuit voltage would rise to 21.95V.

Given the above, what is the lowest part count and lowest cost way to ensure that the voltage on each cell doesn't exceed 2.5V when the stack is charged at 700mA peak.

What I want to do is stick some sort of device in parallel with each cell to regulate their voltages.  When all cells are charged I want the total voltage to be between 12V and 13.5V.  The voltage on each cell should not exceed 2.5V.

I have looked into various options.

Advanced Linear Devices Supercapacitor auto-balancing (SAB) (ALD8100xx / ALD9100xx).  These are just precision threshold MOSFETs.  It seems that a lot of people are using and recommending these.

They are limited to 80mA max drain current.
The datasheet shows that the drain-source voltage typically crosses 2.7V at around 9mA.
This would seem to require that the capacitor cells are either well matched, or that the charging current is very low.  None of which are true in my case.
They have a 500mW power limit per part so I would need a separate regulator to take any excess power from the solar panel to keep the load voltage in regulation.

Zener-diodes.

I don't seem to be able to find 2.25V zener diodes with the 1 ohm or less output impedance required in this case.
Zener didoes tend to have a lot of leakage as you approach the threshold.  In my case I want the leakage to be less than 100uA worst case at a cell voltage of 2.0V.

TL431 or similar.

Very low leakage below threshold.
Precise, adjustable threshold.
Limited to 100mA.  In my case I probably need to be able to shunt over 800mA to be safe.

TL431 + power BJT.

Very low leakage below threshold.
Precise, adjustable threshold.
Can sink multiple amps of current.
Uses at least four components per cell (so 24 total for the design).  I was hoping for something simpler.

Ideally there would be some sort of two terminal device that had < 50uA of leakage below 2.25V but would sink at least 1A in the 2.25V to 2.5V range.  I have looked quite a bit but have not found such a device.  This actually surprised me because the vast majority of super-capacitor cells are rated at 2.7V.  The cells usually have very high tolerances, and it is not uncommon to want to charge them at currents beyond 1A.  The only viable solution I see right now is the "TL431 + power BJT" option, but it uses 24 parts when I would rather be using six.


texts: What happens to an electron when he returns home after doing his job?

texts:
When an electron turns on a LED, a lamp or moves an engine, I guess the electron is not lost, what happens is that it loses energy

What really happens, "returns home" in an orbit lower than he had before doing his job?

Thanks


texts: How to determine SNR required for adding AWGN noise to clean IQ samples?

texts:
I'm doing an experiment w.r.t PSD output. I have generated some 11a  IQ samples and checking its PSD output in MATLAB using pwelch and comparing with the PSD output obtained using hardware.

Here are the block diagram  and output snapshots

wfm from VSG is transmitted at -10 dBm

I realized that VSG---> loopback cable ---> VSA   adds noise to the samples which results in noise floor whose level is at -90ish dBm/Hz . And when I was using pwelch function , noise floor goes down to -140ish dBm/z

To Make it more similar , I am adding some AWGn noise before I input to the pwlch function using MATLAB

iqSamples = awgn(iqSamples,SNR,'measured')

I was doing some trial and error for SNR value and using SNR =50 dB gave me the following output

Few questions here

1)  In this case ,On what parameters does SNR depends?
2)  I' guessing this value might change with hardware and also loopback cable ? But what if I don't change the hardware , loopback cable used and VSG tx_power_level ?

Thanks for going through my simple question. Still trying to learn communications/DSP.


texts:
A brief introduction to this problem:

I have a STM32F767 which is configured for USB Device FS. USB interface is used to transmit a large array of data from MCU to computer. If, by any chance user closes the Virtual Com Port (USB) of MCU, next time user opens Virtual Com Port (USB), MCU will send remaining data it was transmitting to computer, creating a lot of troubles.

I want to flush TX buffer of USB Device mode or abort transmition progress whenever VCP is opened/closed in the computer. I've to mention that I use HAL libraries.


texts: Parasitic spikes on the primary side of a relay

texts:
I'm building a system that will measure current through a current clamp. To maximize accuracy, several rounds (100) are done around the clamp (see picture of early prototype).
The system is powered by a 220V / 6v transformer connected to sector (50Hz).

There may be a 0 to 25 Ohm resistor in the circuit (I will have several relay modules that will commute different resistors). The wire rounds around the clamp on the picture provides ~1 Ohm of resistance.

The system is commuted via this relay module. It contains an optocoupler, a free wheel diode and a transistor.
The relay module is controlled by a microcontroler.

The problem is that when commuting on or off the relay, I observe voltage spikes up to +/- 60 volts on the primary of relay module (basically VDD).

The microcontroler and the relay are powered from PC USB. I tried to power the relay with a bench power supply but the result is the same.

What can I do to filter this?

Thanks

Julien


texts: LTspice: Plot energy efficiency in the same window with volt and amp graphs

texts:
I am trying to draw energy-efficiency in the wave-plotter. Like what you get using .meas and .param commands (as seen in the schematic), but plotted.
I want to have the efficiency of the circuit together with the other waves in the same windows because I want to quickly change components and see how that changes the efficiency. (Theoretically)

Circuit:

 https://drive.google.com/drive/folders/1WAiPilCNFHLMNI6gvyyoom95Kz3YYDTR?usp=sharing

The .meas commands use the average of the whole waveform as the basis of the calculation of efficiency:
pin: AVG(-v(vbat)*i(staticbattery))=0.0487199 FROM 0 TO 2
pout: AVG(v(vled,vled2)*i(led))=0.0305857 FROM 0 TO 2
efficiency: 100/pin*pout=62.7785
I could plot or look at this in a separate window - with an irritating amount of clicks everytime I change a component - sure. But I want a line or wave together with the other measurements in one window.

So I was trying to put battery-milli-Watts in relation to LED-milli-Watts, to get a factor in %, in the plot window.
Why isn't it as easy as (100 / BATmW) * LEDmW? It seems like wave peaks and troughs interfere and put the calculation off.
For example, this calculation doesn't work: (100 / (V(VBAT)*-I(StaticBattery)/1mW)) * (V(VLED,VLED2)*I(Led)/1mW) (I use /1mW to get rid of the unit)
That gives me a graph that could be useful if clicking it with CTRL WOULD show the correct average - But it shows a value of 241.52. The waveform has peaks in the ten-thousands, pointing at interference. So it's useless.

How do I create the same behavior as 100 / averageIN * averageOUT = efficiency in the plot-view window? Since the "AVG" command does not work in there, unfortunately, I need a different solution.

Thank you very much!


texts: Why do most Passive Buzzer Modules for sale online use PNP transistor?

texts:
At first I have made a simple circuit to make tones with a passive buzzer. I have used a buzzer, 1K resistor on base and a NPN transistor (8050). This is working nicely. The circuit is similar to what you can see at https://startingelectronics.org/beginners/circuits/arduino-buzzer/ except that I have a passive, not active, buzzer. The transistor is on the low side.

I am generating the square wave with Arduino's tone() function.

Next I wanted to replace the individual parts with a module. I got a module that is similar to this one: https://www.aliexpress.com/item/New-Electric-3-3-5V-Passive-Buzzer-Module-PCB-Dimension-3-3cmx1-3cm-For-Arduino-9012

When I started using it, I discovered that it has a PNP transistor connected on the high end and that when the I/O pin is low the transistor and buzzer are passing current and wasting energy.

It makes sense to me that designers understand that default for off is LOW, right? Why would somebody make the module this way with off requiring a HIGH signal on the I/O pin? Any advantages to PNP transistors over NPN here?


texts:
I was trying to repair a battery-powered electric razor when I suspect there was a short-circuit.

The device started heating and it began smoking a bit so I took it and put it in a bowl full of water.

I guess this wasn't the best idea but now I'm stuck with the device still working, sunk into water as on the picture and I have no idea what to do. I know it may not be the best place to ask but I'm really stressed right now.

The device has a non-removable 5V / 5W battery.

I would appreciate any help on what to do.


texts: Low Side Reverse Protection Diode + Wide Battery Input Range

texts:
Quick background:

I'm working on a very wide input range for a battery powered application (capability for two different types of chemistries). In the original design, a low side NFET was used as reverse polarity protection. This works, of course, at higher battery levels but when it starts getting lower, Vgs is just simply not high enough to sustain the in-rush currents from the devices being powered.

So I was able to find a low Iq charge pump from LT and was using it somewhere else in the circuit but I thought.. "why not use it to drive the gate of that low side FET as well!" See what I'm talking about below.

So the big question is, any gotchas here that I'm not thinking of? I'm going to have it prototyped up shortly but I figured it would benefit the community if I share my concerns here!

Thanks y'all


texts:
I want to create a shift register using d-flip-flop as basic structural element,
code:

dff:

  module dff(d,q,clk,rst);

  input d,clk,rst;
  output reg q;

  always @(posedge clk)
     begin:dff_block
        if(rst==1'b1)
          q=1'b0;
        else
          q=d;
     end
  endmodule

shift register:

  module shift_register(s1,d,clk,s0,q);
  parameter n=3;

  input  s1,clk;
  input [n:0] d;

  output s0;
  output [n:0] q;

  genvar i;

  assign d[3]=s1;

  generate
  for(i=0; i<=n; i=i+1)
     dff U1(.d(d[i]),.q(q[i]),.clk(clk));
  endgenerate

  assign q[3]=d[2];
  assign q[2]=d[1];
  assign q[1]=d[0];
  assign q[0]=s0;

  endmodule

test bench:

  module tb();

  parameter n=3;
  reg [n:0] d;
  reg s1,clk;

  wire [n:0] q;
  wire s0;

  shift_register UUT(.s1(s1),.d(d),.clk(clk),.q(q),.s0(s0));

  initial begin

  d=4'b0000;
  clk=0;
  end

always
begin:clok
#10 clk=~clk; s1=1;

end
endmodule

I think test bench has the problem.I have tried to give s1 values for every #10 while clk=1 but again does not work.

This code does not give me waveforms for q and s0.
I cant find whats wrong. Any ideas?


texts:
A little backstory for those not in the know. Model trains used to be, for the most part, controlled by varying DC voltage, usually in the 12V range. Over the past 30 years, systems have been developed to use "Digital Command Control", a bipolar AC signal (9-16V, depending) that contains packets in pulse waves. These are decoded by on-board decoders on the model locomotives.

Over the past decade, sound decoders have become more popular with a small on-board speaker. Now, I'm in N scale (1:160) and many of those speakers are as small as 11x16mm and 8 ohm. They have exactly the bass response you'd expect.

What I'd like to do is record the output from this. The last thing I want to do is fry one of these $120 decoders, so I want to figure out how. Can I hardwire the speaker output directly into a 3.5mm mic in on a computer or audio recorder?

Decoder manual is available here: http://www.esu.eu/uploads/tx_esudownloads/51972_LokSound_V40_ESUKG_EN_User-Manual_Edition-4_eBook_03.pdf

If more technical info on the decoder is needed, let me know and I'll try to get it.

Thanks!


texts: Powering 36V motor with 48V LiPo battery through a motor controller

texts:
I am planning to use 36V BLDC motors from a hoverboard, (this one)
with this  motor controller.

The controller mentioned can handle up to 50V, 60A continuous. I would appreciate it if someone can enlighten me on whether using a 48V LiPo battery to power the 36V motors using this motor controller is feasible.

The reason why I am not going with a 36V battery is that somehow it's not available around, only 48V. I guess business and market demands.


texts: Protecting a microcontroller powered from a 1500W 12V supply

texts:
Im building a quadrocopter, so that's why im going to be using such a big power supply (for the tests, autonomic power supply will be a LiPo 3S - my 4 motors draw up to 20A current each).
What kind of countermeasure should I include on my PCB to protect it, in case i make a short while soldering, or there will be a design flaw. The uC+step down regulator+gyro+esp wifi module shouldnt require more than 1 A (probably even less than 500mA).

Varistors and transils wont work because its not voltage thats going to be too big.
Fuse/circuit breaker will probably be too slow.

So what should I use in this case.


texts: I have the following circuit setup to feed a sine wave into a microcontroller. This converts the sine wave into a square wave so I can measure the frequency. The output of the opamp (U1 - OPA4830) looks perfect until I connect it to the level shifter (U2 - TXS0108E). Then, it develops "bounces" on the rising and falling edges. This is a problem since these bounces can trigger my interrupt controller. Why does introducing this level converter cause this noise in the system?


texts: I am working with a oscilloscope GWINSTEK gds-2074a. As per the time resolution is concerned, turning the dial all the way down, it shows that it can go down to 1 ns.  There is a Delay function in the oscilloscope and I have to use the FRR function. Can any one guide how I can find its resolution? The pulses which I want to study is expected to have a time difference of 2 ns. I checked the manuals and could not find it anywhere. Any resource in this matter or guidance would be very helpful.


texts: Why does body biasing (i.e when \$V_{bs}\$ is less than 0 V) leads to increase in threshold voltage? I am looking for an intuitive explanation.


texts: Gain of particular op-amp circuit (A combination of inverting, non-inverting and differential configurations)

texts:
I have a following circuit with an operational amplifier. It is a configuration I haven't seen before and I am not quite sure how to calculate the gain in terms of its inputs A and B.

The input B is just the configuration of Inverting Amplifier
$$Gain_B = -\frac{470}{240}$$
Then I am puzzled by the 4k3 resistor. If the resistor wouldn't be there, the configuration would be similar to the differential amplifier and the gain would be
$$ G = \bigg(\frac{240+470}{240}\bigg)\bigg(\frac{3k6}{3k6+510}\bigg)A-\bigg(\frac{470}{240}\bigg)B$$
However, that is neglecting the 4k3 resistor, which somehow changes the gain - it reminds me of the non-inverting amplifier configuration, which would have gain of $$G_\text{part} = 1+\frac{470}{4k3}$$ and the two resistor in front of it would just act as a potential divider \$\frac{3k6}{3k6+510}A\$
The correct solution should be $$G \approx 2.687A-1.9583B$$
Just to clarify, I am assuming and ideal op-amp here (i.e. infinite gain, etc.). This should not be a hard problem, however, I have failed to find even after a hour of googling (it might be caused by the fact that I do not know how to call this circuit configuration).


texts: Is it necessary to allocate multiple channels at the same time window?

texts:
Let a channel allocation system is to be deployed to allocate unlicensed frequency spectrum to a set of access points.

The system performs channel sharing in time-domain.

Let an access point, say N1, demands 2 channels (frequency slots), say C1, C2 to operate.

I need to ask, is it possible for the system to allocate C1 and C2 to N1 in different time-window? In other words, is it ok if the system allocates C1 in time T1 and C2 in time T2? where T1 and T2 represent some time window in a scheduled repetition period.

I am asking such a question because someone said "it is not practical that you schedule an access point in different time window." He said, "if an access point is allocated multiple channels then it needs all those channels at the same time to operate. We cannot schedule it in different time window"

I need your help to clear this concept. Moreovre if there is no such compulsion can you please tell me some reference so that I can use that reference in the argument.

Thanks,


texts: Hooking up a loop-powered 24V NPN/PNP sensor to Arduino

texts:
I have a 24V pressure switch that is loop powered.  Here is the manual/datasheet.  I'm trying to figure out how to read the sensor with an Arduino.

Obviously, the Arduino can't handle 24V, so I got some optocouplers (manual/datasheet)

The original schematic looked like this:

This, however, didn't seem to work.  When I measured voltage across ports #1 and #2 (from the schematic), it measured between ~13V and ~20V (when the sensor was engaged vs not-engaged).

I'm not really sure how to fix this.  I tried using a voltage divider (instead of an optocoupler), but, in my ignorance, I burned up one of my small resisters.

Thanks for any help!

UPDATE:
New Schematic (the one above is old)


texts: Filter w/ seemingly higher output voltage than input?

texts: I'm working on a simple LC filter as part of an AM radio project. I was intending to use a ferrite antenna (modeled roughly by the voltage source in series w/ inductor which is then connected to a capacitor that will be parallel to the rest of the circuit), but according to my simulations and calculations the output voltage not only peaks at w0, but peaks higher than then input voltage which seems conceptually impossible to me. Is this right or am I missing something?


texts: Do you know what type of environment is this? I didn't find any information on Google.


texts:
How do I determine battery manufacturers/companies whose batteries that have met UL 1642 certification?

I am asking because I want to determine other companies whose products have successfully passed the UL1642 standard.

I look forward and appreciate your help.


texts:
I'm currently interested in following this tutorial which explains how to create a homebridge (ESP8266) controlled 12v RGB strip which is exactly what I've been looking for. However, whilst I do believe this project will work perfectly for an RGB strip up to about 5m, I am aware that lengths larger than 5m require additional consideration when it comes to powering them.

For my project, I wish to make a 30m RGB LED strip to be placed around the perimeter of the ceiling in my living room. My question is; what is the best way of powering a 12v RGB LED strip for 30m whilst keeping just 1 controller as linked above (ESP8266)?

Whilst researching this question online, I was unable to find any definitive answers for exactly what I needed. For example, in this image:

Whilst the idea presented in the second figure down makes sense (injecting 12v periodically) makes sense; it raised a few questions for me.

Do I only need to inject just the voltage at these intervals, or do I also need to include the R, G and B lines in the 'blue' wire pictured in the diagram?
Do the amps matter in this case? Correct me if I am wrong, but a 5m RGB strip will usually run fine off 2A. So, do I only need a 2A supply if I am 'injecting' at 5m intervals? Or would I need a 12A supply (30/5 *2)?
Is this even the correct approach for what I am trying to achieve? I.e. would this process of 'injecting' at 5m intervals work for a full 30m trip? If so, could I stretch the intervals to 10m for example in order to reduce the amount of wiring round my ceiling?
If it's not the right solution, would using an RGB amplifier at 5/10m intervals be a better solution? Or, would something like this work:

Would the diagram shown above help in any way, or is it completely the wrong approach for what I'm trying to achieve? If it is kind of the right approach, could I ignore the method of 'injecting' 12v at intervals by supplying a higher voltage 24v at this first 'junction' so that 12v would be supplied to either side, or is that not how it works?

P.S. These are the RGB LED strips I am looking to use (RGB, no waterproof).


texts:
I am building an evaluation board for ATmega32, I am designing an embedded USBasp programmer (The programmer will be also in the board and they will be a micro-usb header to connect the board to PC).
Here is the programmer I'll be using. (Note that it will not be separate like it appears on the image, it will be within the board, this is just to show you the components of the programmer)

I am wondering how I will be able to burn the first firmware for the programmer inside the programming chip above. I don't want to take out the chip, program it out then solder it back, I want to program it in board.
How I will be able to do so? (I have an external programmer but how I will be able to connect it?)


texts: Power loss due to mismatch impedance connector in coaxial line

texts:
Not being an electronics professional but face the following problem I hope you can help me.
I would like to estimate the losses due to an impedance mismatch of connector used in wall-crossing of a coaxial transmission line.
Unfortunately, I do not have the experimental resources for testing the connector (with network analyzer).
Is it possible with analytical formula or with simulations?


texts:
I'm currently building my own Bluetooth Box and need a portable power supply.
For that I use two 18650s LiPos and a PCB Protection board.
PCB Protection board:
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.de%2Fulk%2Fitm%2F253581817900
For charging I will need an extra charging board.
I found this on eBay:
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.de%2Fulk%2Fitm%2F112195812078
Will my two Lipos charge when I connect the outputs of this board to the p+ and p- pins of the PCB or am I missing a component?
The output voltage of the batteries is stepped down to 6.5 V. Can I use the bt Box while charging?


texts: Push button debouncing circuit without extra IC? Possibly RC based?

texts:
I have a push button that I would like to debounce. I only care about the first rising edge of the signal which is connected to an Arduino's GPIO. After reading on the web about hardware debouncing, I understand that to truly debounce a push button, I would need a latch or a logic gate to keep a sharp edge that the Arduino could read correctly. But I don't have any and it takes a month to order anything from where I am.

So, I came up with this circuit attending to avoid using extra parts:

I would like someone to help confirm the following assumptions:

When the button is pressed, C1 will charge almost instantly because there is no resistor to slow it down. When the button is released, C1 will slowly (0.1s) discharge thru R1. This should debounce the rising edge of the button as after the initial rise, R1 prevent C1 to discharge thus keeping the GPIO high.

I don't own a oscilloscope to test this. So this is just what I'm assuming will happen.

My questions are:

Is it safe to charge C1 so fast?
Is it safe for the GPIO?
Are my assumptions correct?


texts: How do I get a low impedance current output from this circuit?

texts:
I am learning about the VI characteristics of diodes, specifically nonlinear resistor applications.  The circuit in this question is used as an example, but the question applies to any high to low impedance current buffer requirement.

I simulated a circuit to "brute force" an approximation to the equation y=(2^(x-1) )/100000 as a way to create a linear voltage to exponential current converter where 0 < x < 5 volts and 0 < y < 1.6 milliAmps.  The blue signal represents the triangle voltage source 'x' between 0-5volts, and the red signal represents a current 'y' (0-1.6milliAmps) taken between the triangle voltage source and the rest of the circuit.  The non-linear properties of the current are determined by the resistive attenuator circuit.  Here is the circuit below working as expected:

Question: How do I buffer the current 'y' (red signal) in order to drive other circuits (such as the bias current pin of an LM13700) or simply convert that non-linear current to gain a non-linear voltage?  I tried to add a resistor to ground to convert the non-linear current 'y' to a non-linear voltage along the top path of the circuit, but that removed the non-linear properties of the current.  I think that creating a buffered current would solve the problem.  I could then connect a resistor to ground and convert the current to voltage.

I've gotten the hang of op amp voltage followers, but don't have a strong understanding yet of current buffer/followers.  I tried employing a current buffer using a BJT in common base configuration based on some research googling "current buffer circuit".  I don't think I am using it correctly though (see circuit shown below with current buffer added).

If anyone else is interested in V-I characteristics of diodes, I have been following the IIT Madras lecture series on Analog Electronics.  This is one of the first videos in the series on diodes:
https://youtu.be/qEg3DrBe-3U


texts: Beginner struggling with first time PCB etching - advice

texts:
First time hobbyist here.
Is it a common issue for closely placed track lines to end up touching each other during the toner transfer process (I'm assuming this is the correct term)? If so, are there any quick fixes I can do to my process to fix it? I'm just trying to avoid redesigning the PCB layout (unless that's the only option).

Please see attached pics -  Yes some of the tracks are too close, but what I don't get is this - when I print it on paper, the lines are thin and the gap is reasonable. But when I use nail polish remover and place the paper on the copper board, at least 1-2 lines end up getting closer or nearly touching - see area marked in blue, bottom left. Track width is 0.25mm and gap is 0.5mm which I would think is reasonable. In the first two iterations I tried, these lines didn't end up touching, it was other lines. Is there anything I can try aside from redesigning the layout?

The process I'm following:
I printed the layout on glossy paper on a laser printer. Cleaned the copper board and poured a really small amount of nail polish remover on it. Spread it evenly. Placed the layout paper on the wet surface and gave it about 5 seconds. Then using a paper towel, applied vertical pressure (not horizontal) for about 30-50 seconds. Then took the paper towel away and waited for the thing to settle for another 2 minutes. Finally dunked the board in water for another 2 minutes and tried peeling the paper. The toner transferred better than my previous attempts where  I didn't give the process any time and also applied horizontal pressure/swipes.

Two major issues on this third iteration:

The paper is stuck in some nooks and crannies. Trying to scratch it with my nails was clearly not a good idea because it erased away some of the track lines. Is there a better way to remove the paper bits?
Two track lines at the bottom ended up touching each other. Yes I accidentally scratched them later, but they were reasonably apart pre transfer, but touching aftewards. Is there a way to prevent this from happening? does it just take practice?

For track lines that didn't fully transfer, can I just use a black pen and write over it? if so, any particular type of pen/marker to use?

Also, here are the variable I think I could change to make this better. Experts, please share your thoughts:

Use a different printer, but laser is supposed to be the most precise option from what I've heard. Not sure if I should be trying a different tech (e.g. digital printer) or just another better laser printer.
Use a wood block instead of hand pressure directly over the paper. Maybe I inadvertently did a horizontal swipe thus causing the ink to smudge
Fix the PCB layout design (most obvious but want to make sure the mistake isn't elsewhere in my process)
Change the concentration of my nail polish remover. I don't even know how to do this. The one I have doesn't have any ingredients or concentrations listed on it.


texts:
I need a floodlight for a large yard.

I want to build one using 100 white LEDs (e.g. 10x10).

The input voltage is not important for me (220v AC , 24v DC ,12v DC all are OK)

How the schematic should be?


texts: Are the digital pins in this schematics shown wrong?

texts:
The output from the phase detector H11AA1 going to Dig Out and the Dig In goes to the input of optotriac in the following circuit:

Image Source

Shouldn't it be the other way around?


texts: My Solar PV system correctly shuts off power during a blackout - I want to safely override that

texts:
For obvious safety reasons my residential PV system disconnects from the grid if it notes the grid is down. The thing is it also shuts itself off so that during a grid blackout rather than providing me power but detaching from the grid the inverter disconnects itself from both the grid and the panels leaving me without power. I want to safely defeat this safety feature that is to say I want to be able to use solar power when the grid is down without frying the guy in the cherry-picker working on the lines to fix them.

Edit to add: I was hoping I could do something more clever along the lines of : 1) manually throw knife switch to disconnect grid from my home. 2) turn on little liar circuit that puts out a drip of 240vac (powered by say a motor cycle batter) to make my inverter think the grid is live and then uses the inverter power feed to keep the 240vac liar circuit powered (as well as the battery charger for the motorcycle battery). Seems safe for the line workers and simple enough to build assuming the inverter will be fooled.

Note that SolarCity now sells a battery pack along with the switch setup I was looking for.


texts: How to dump M50747 (6502 derivative) ROM

texts:
I've recently picked up a Canon ES 3 Personal Typewriter, and have of-course popped the cover to reveal this PCB (bottom). On board I find a chip marked as "Canon NH4-0338 D52 039100", not very helpful, but the silkscreen right next to it is marked "M50747" [datasheet]. This is an 8-bit 8 MHz 6502 derivative chip with an 8 Kb ROM and 256 bytes of RAM.

I wish to gain access to the firmware, a seemingly impossible task until reading through the datasheet and stumbling across the "Eva-chip mode". This mode seems to configure the chip to use an external ROM to run code for the purpose of evaluating a mask ROM. Is there any information on this being done for other devices that might prove useful (a blog post with a how-to or details from another chip)? (I've seen this is how the Tamagotchi firmware was dumped, as well as a printer for the Atari and the keyboard in the AppleII)

The purpose of dumping this ROM would be for hacking the typewriter, namely interfacing some other micro-controller and use it as a teletype. There is a much simpler option for interfacing through the keyboard port, which seems to be a scanned and multiplexed column affair, but working out which key combinations correspond to what is proving difficult (21 lines with 4 modifier keys and no data-sheet for the keyboard).

Any ideas as to how I should best go about modifying this typewriter?


texts: Is there a method to provide physical stimulus to design inside FPGA like we do in VHDL test bench?

texts:
Basically I need to find out if there is a feature that allows one to enter stimulus into an FPGA without using things like signal generators. Altera FPGAs have a feature implemented via Quartus called signal tap II. This allows requird signals to be tapped, stored in internal memory and then streamed via JTAG into Altera Quartus II and viewed on screen. This is similar to how one would use a logic analyzer. So, the idea is like this:

Is there a way to have "signal tap in reverse" i.e I provide a simulus that is stored in memory blocks in design and not part of actual design, as soon as the FPGA goes into user mode it shall read from these memory blocks (it contains all signals including reset) and uses the standard system clock that also goes into the memory blocks. The stimulus is read out when the end of stimulus is reached, the reset signal is asserted again and the stimlus reading starts over again and this continues in endless loop, or could be setup to run only once after configuration.

Does such a feature exist?


texts: Boosting speed of data on GPIO line between microcontrollers

texts:
I made a circuit in which the data bus P0 of an AT89S52 is connected to the P1 of an AT89C4051 and both clocks are each driven by their own 22.1184Mhz crystal.

I have used a 10K standard pull-up on each of the port pins, but due to the high speed of the crystals, I'm starting to think the resistor value is too high.

I looked at both datasheets and the AT89S52 states maximum current per port pin shouldn't exceed 10mA. This suggests I can get away with a 500 ohm resistor but that would kill my batteries in no time.

Both data sheets state each pin has a 10pF capacitance if Ta = 25 degrees and test frequency is 1Mhz, but my test frequency is more like 2Mhz because many instructions on these microcontrollers execute at 1/12th of a clock cycle. and if I keep executing commands to read data from a port, I want to read quickly.

Sure I can get away with this:

Mov A,P0
nop
nop
nop
nop
nop
...
Mov A,P0
nop

But as you can see, those nops waste clock cycles.

Given that I have a capacitance and resistor value, I did some math (10K * 20p) and I got 795774.71545948 Hz which is the max speed? or I did something wrong? I used this tool: http://sim.okawa-denshi.jp/en/CRlowkeisan.htm

I picked 20p for the capacitance because I assume when the pins are connected, the capacitor values are added (capacitors in parallel).

So how do I calculate the max speed on the wire between the GPIO lines and if I'm on the right track, just how low can I go with the resistor without causing significant battery drain? should I use 1K? 4.7K?


texts: Multimeter fails to measure forward voltage

texts:
I have a MS8233D Multimeter and wanted to measure the forward voltage of some LEDs.

I connected the leads directly to the LED and used the Diode Testing Mode.

However the multimeter just displays Ol and the LED does not light up.

I was also unable to measure continuity with this multimeter. No beeping sounds.

simulate this circuit – Schematic created using CircuitLab

As an alternative I used this circuit and measured the voltage by touching the anode and cathode of the LED. Using the V DC setting.

simulate this circuit

The lowest readings I got were around 1.9 V for my green and yellow LEDs. 2.9 V for the white ones.

The manual states 1.48 V open circuit voltage.

Does this mean the multimeter does not supply enough voltage to effectly power the LEDs and thus cannot read the forward voltage? Is my technique of measuring even correct?


texts: How do I go about powering appliances from solar energy

texts:
I would like to learn how to power some house hold appliances from solar energy.

I haven't had any experience with electronics but am eager to spent time reading and experimenting.

I've done a little Googling which has been interesting for a start but has also raised some more questions.

I've seen a wide range of specifications for small solar systems, batteries, converters and inverters but haven't been able to work out the best combination to use to power say, a TV, a caravan fridge, a laptop and a microwave.

Is there a formula that I can use to calculate the specs required for the solar panel/inverter/batteries and inverter?

A description of a working system with examples of what the system is powering and the sunlight hours required to keep it alive would be very helpful.


texts: LM2937 Replacement/Upgrade Thermal issues

texts: We are using an LM2937-5v LDO regulator in an SOT223 package - currently flowing approx 150mA with a 14V input (9V drop over it), and, as you can imagine it gets quite warm: 70degC (though from my rudimentary datasheet checking it seems to be in spec). My question is, can anyone recommend a replacement 'higher efficiency' part, of the same footprint (up to 24V input, 5V output, nominally its 14V input, around 500mA max loading, but typically sub 200mA) that would do a better job thermally?


texts: Can I connect transistors to GPIO2 and GPIO15 of my ESP8266 in order to control LEDs?

texts:
Is it possible to connect transistors to GPIO2 and GPIO15 pins of my ESP8266 and to control LEDs using these transistors?

Something like this:

If yes, then how to calculate values of the resistors for the bases of the transistors and pull-up/pull-down resistors of GPIO2 and GPIO15?


texts: PNP load switching circuit that uses opposing PNP transistors

texts:
Background: This circuit uses two input signals to create a 0, 2.5, or 5V output signal that switches ON/OFF periodically to control for example an LED.

I saw a transistor circuit example that had opposing PNP transistors. What is the point of Q3?


texts: 8V AC signal into 3.3V digital input pin

texts:
I'm a noob and I'm doing this to learn, basically.

I have a typical old-style door bell with a transformer that outputs 8V AC, the wire the goes through the push button on the door and finally hits a solenoid-based ding-dong thingy.

I'd like to tap into this circuit and extract a signal that I can safely feed into one of the digital 3.3V input pins of my very delicate Raspberry PI.

I have a few diodes, capacitors, resistors, a couple of transistors and a lot to learn.


texts: Electronic circuit analysis: Find V_out with several MOSFETs

texts:
I have a question about an exercise from my electronic circuits class, number a): Find an expression for the large signal V_out at DC.

Since it is DC, we can ignore the capacitor, it will act as an open circuit. We are dealing with MOSFETs, so now current will flow into the base. That means I0 will flow up into from S to D. Now I am confused. If there was no battery, it would just flow to the right, divide 1:2 through M2 and M3 (since they are identical"), and recombine. Then, I_L would flow into the load, and I_0 - I_L would flow into R_0, which would give V_out = (I_0 - IL) * R0. Unfortunately, there is the battery V_bat. Some current will also flow in the battery right? So my way of solving it seems to be incorrect, but how else to I tackle the problem?

Thank you very much! :)


texts:
I have to design a 4 relay or 4 triac switch.

First would control a 12V solenoid for water flow.
Second would control 230V for a complete device which contains a small boiler as well.

After reading this:
Triac versus Relay

It is still not clear to me if triac circuit like this:

http://www.instructables.com/id/Small-Triac-Switch/

are safe to use here. I read that triacs can break then let current flow (which would be catastrofic in my case at controlling the solenoid). This can never happen to relays, if the relay broke then that only means it wont turn the device on.

So can I rely on triacs for long time period (years)?


texts:
This is a battery pack for a 1992 cordless phone. The cells shorter and thicker than a AA cell, I have no idea if they are regular cells. The original charger was replaced by someone with a 14V/500mAh one giving out 18V when no charging/ 5V when charging. I have to replace the cells because they are dead. What min/max specs should the voltage have?
Thanks.


texts: I am making a homemade capacitor for a science project. I have a 5 volt power source that I need to charge the capacitor with. If I cut out two 10"x10" slips of foil and 1 10"x10" piece of paper, and I put the paper in between, what would the capacitance be? Please keep in mind I need to have it charge to 5 volts. If this model doesn't work, can you please direct me to a better model. I cannot just buy a capacitor, though.


texts: How do I use a hit and hold circuit with a solenoid?

texts: Solenoids burn power when turned on and get hot, what is a way I can reduce the power while keeping the coil actuated?


texts: Recharging 14v battery straight from 18v supply?

texts:
I am recharging a 14v LiFePo4 4s8p battery from a Phillips wall transformer from scrap. The phillips wall transformer is rated 13V 400ma on it, but it measured 18V on the multimeter.
I put it on anyway. The voltage when it is charging is 0.5 volts higher when connected to the transformer, rising from 11.7V to 12.3V in about an hour.
What damage can incur from charging a 14V battery on a small 18V power supply? until it reaches 14v? I know that some chargers limit the charge current to 0.5V over the battery current, does that also make sense for lithium chemistry?


texts:
I tried to experiment with boost SMPS with multiple supply rails and I almost burned myself when touching parts when running.

Here is the circuit and the part getting hot:

simulate this circuit – Schematic created using CircuitLab

I am trying to kick the 8.8V from my regulator to 15V. The PWM comes from Arduino, assuming near perfect regulation from the regulator powering this experiment.

In my first experiment with 600Hz PWM and 10mH the inductor is very noisy and gets hot. I get 10V across R1.

In my 2nd attempt running 31.5kHz PWM and 100uH inductor at L1 the MOSFET start to get extremely hot. I am also getting 53V (!!!) across R1. I probably damaged the diode.

Can anyone tell me what did I do wrong in this?


texts:
In fmcw radar rather than sending a signal at constant freq. we are sending a chirp which goes e.g. from 6-GHz to 6.1-GHz in 5ms.
What i cannot fit in my mind is this:(Nmbers are just for example)
The rf signal is moving at speed of light so while we are changing the chrip freq. linearly e.g. we start from 6Ghz and waited like 500us then increased it to 6.01 (this goes up to 6.1 ghz with sometime between each freq. change) and we already received the 6ghz signal from receiver without completing 5ms chirp period. So up to this point we have nothing to do with other frequencies of chirp (6.02,6.03...6.1). How is this generating IF like 5-10kHz based on distance. If so then by applying the formula in the picture we can find the distance, why we are changing the tarnsmitted signals' frequency since we already had a IF for a constant 6ghz part of signal chirp signal.
Shortly should i just simultaneously change chirp from 6to 6.1 and 6.1 to 6.0 back and forth and at the same time a/d convert the upcoming signal and save it somewhere until it makes 5ms then plot the fft of the whole 5ms block.
I hope i am clear. Please show me what i am missing here:)
LATER UPDATE:
Everyone was trying make me understand the theoretical background where i already know but thank you guys for your time.I had a moment of enlightment and now i understand :)
I am teling this with examples so people who have same problem in future can understand. While sending a chirp we start sending with a fix freq. as a start point like 6ghz. While it is traveling to the target and coming back a little bit of time passed and during this time our TX chirp signals freq. changed a little bit linearly like 6+X GHz so multiplexer difference is X Hz. Therefore this change depend on the distance of the target since let say target is so far far away we will maybe receive the first signal which was at 6GHz while our chirp is at its halfway of 6 to 6.1 GHz cycle. So the difference will be like 6.05-6=0.5GHz.
Another way of saying, for stationary object nothing happening on the transmitted signal(doppler effect says reflected data is radited with same structure if object is stationary) but until the transmitted signal come we changed the transmitted signal so the upcoming signal will be multiplexed with different freq. signal and based on this change we are telling this is object at this much distance. Thank you


texts: What is causing - The target device is not ready for debugging?

texts:
I am trying to debug code on PIC16F677 using MPLAB X IDE (v3.10) and Pickit 3 and result is this message - The target device is not ready for debugging. Please check your configuration bit settings and program the device before proceeding. The most common causes for this failure are oscillator and/or PGC/PGD settings.

Code looks like this.

#include <xc.h>
#include <stdbool.h>

#pragma config FOSC = INTRCIO
#pragma config WDTE = OFF       // Watchdog Timer Enable bit
#pragma config PWRTE = OFF      // Power-up Timer Enable bit
#pragma config MCLRE = OFF      // MCLR Pin Function Select bit
#pragma config CP = OFF         // Code Protection bit
#pragma config CPD = OFF        // Data Code Protection bit
#pragma config BOREN = ON       // Brown-out Reset Selection bits
#pragma config IESO = OFF       // Internal External Switchover bit
#pragma config FCMEN = ON       // Fail-Safe Clock Monitor Enabled bit

#define _XTAL_FREQ 8000000

void main(void)
{
    IRCF0 = 7;
    IRCF1 = 7;
    IRCF2 = 7;
    HTS = 1;
    SCS = 1;

    while (true)
    {

    }
}

I am not sure about those IRCF. Just tried out some things. I have tried without configuration bits in main function as well.

Do I need external oscillator for this? This poster http://ww1.microchip.com/downloads/en/DeviceDoc/50002010B.pdf says - Target device must be running
with an oscillator for the debugger
to function as a debugger. What does that even mean?


texts:
I have a question when designing a circuit.

I want to power two sensors with a 3.3V LDO.
My question is the following, in the LDO datasheet they recommend me to place a 10uF capacitor at the output of this one, but in the datasheet of each sensor, they recommend me to use 10uF and 0.1uF capacitors.

My question is, do I have to use as many capacitors as each datasheet asks me, or can it be solved in another way?

The same happens with the LDO input, it is recommended to use a 10uF bypass capacitor, but that same input that goes to the LDO, goes to another IC that advises to place a new capacitor.

Do you know which would be the best solution to these cases?


texts: External power to WEMOS mini using 3.3V 1W Zener diode

texts:
I'm using a 12V DC 2A power source to power a 12V LED strip, and controlling it using a WEMOS mini and a relay.

Yes, I know there is a power shield for WEMOS, but  I tried to regulate the 12v input to power the WEMOS as well, which did not succeed.

First I tried with a 3.3V Zener diode via 3.3V pin on WEMOS- with no success.

Later I tried with a 5.1V Zener diode, and 5V pin on WEMOS - and again no succees.

See schematic (please ignore diode's catalog number.) Circuit yields voltages as expected.
Measuring current, using a multi-meter, shows a draw of only 10mA, when I guess a 200mA is needed at start.
Since it is a 1W diode, at least P=VI should yield a nominal of 200mA when using a 5V diode.

simulate this circuit – Schematic created using CircuitLab


texts: How does oscillation of reactive power take place between source and load?

texts:
I have come to read that reactive power is that power which is constantly oscillating between the source and the load.

Can anyone please explain this to me?

Suppose an AC source is connected with an inductor. The power is reactive in inductor as we know but how will oscillation of reactive power take place between the inductor and the source?

I need intuition on all this process?


texts: Understanding VFD speed control input using a potentiometer

texts:
I am working on hooking up a potentionmeter as a speed control input to a variable frequency drive.
Here is are the diagrams from the VFD manual:

(Its a Lenze AC Tech SMVector ESV112N01SXB; full manual)
The potentionmeter I have does have 3 terminals and appears to go up to 10 kOhm.
Based on the definitions of terminals 2,5,6 I find it confusing to understand what is required. Especially #2 "analog common" (common what?)
Since a potentiometer is basically just a resistor, I had the impression that it would only need the pot center and one of the other two, not both.
If I do not actually need to wire all three, which of 2, 5, 6 actually should be used?
Possibly I could just try it various ways and experiment ... but I'd prefer not to risk damaging the device (assuming that's possible with these connections).
I hope to come out of this actually understanding how it should work, not just wiring tips. Thanks!


texts: Designing a car steering wheel interface, need to distinguish between two resistor ladders on the same ADC

texts:
I am designing an interface for my car steering wheel to a Android head unit, using a Sparkfun Arduino Pro Micro to handle the USB side of things. The steering wheel buttons use three wires and a resistor ladder for the buttons, as shown in this diagram from the service manual:

Each resistor in the diagram is the same value. My current solution is looks like this:

simulate this circuit – Schematic created using CircuitLab

Which works on my PC, but causes two problems in the car

Pressing "Power Switch" or "Mode Switch" causes a brown-out on the micro controller and resets it, most likely due to exceeding the USB current.
The car is a much noisier environment and the "Volume Switch" buttons are not distinguishable reliably in the car, no matter how much smoothing i do in code.

Ideally what I need is to know which line (L or W) is being pressed when the ADC reads a value. This would make the noise far less of an issue and I could then probably apply some sort of current limiting to eliminate the brown-outs without worrying about compressing the ADC range of values too much (and lose the diode).

Is there a simple way I can read the value at the ADC and use a digital pin to figure out which line was pressed (hopefully without too many components)?


texts:
I have some doubts about the Scattering Matrix of a transistor seen as a 3 port devices. Precisely, I read (for instance here) that we do not have 9 independent S parameters since there is this relation (6 equations):

So there are only 4 independent S parameters, and this is correct because generally transistors are described as 2 port networks. But I do not understand the proof of these relations. It is shown in these pictures:

First question: is the fact that the sum of current = 0 always verified? Is it a sort of Kirchoff Current Law?

Second question: we are applying equal voltages to the ports, why should this procedure be general, valid for each case?

Third question: why applying equal voltages = each current is 0 ?


texts: Slayer exciter 2N3055 to 2N3716, what can explain these behaviours?

texts:
I built a slayer exciter with a 2N3055 from which I can pull 1.5" arcs at ~30V (tried base resistors ranging from 20-30kohm). I was planning to run it at a higher input voltage than the 2N3055 can tolerate, so I was looking for a comparable transistor to swap in. I tried the 2N3716, but arcs are practically non-existent at 30VDC.

I also noticed on my oscilloscope that the 2N3055 runs at around 530kHz while the 2N3716 runs at around 930kHz for the same circuit and input voltage.

What parameters on those datasheets should I be looking at to explain these discrepancies?


texts: What PCB components typically require hand assembly or are associated with difficult assembly?

texts:
With regard to PCB design for manufacturing (DFM), I've come across a guideline of 'Avoid selecting components that need to be hand placed'. However, this guideline didn't go on to state what components generallyrequire hand placement.

So my question: What component types typically require hand placement? And maybe a bonus question, what components can almost always be automatically placed?


texts: Why can't you divide a series + parallel circuit into branches to get total current?

texts:
Suppose we have a circuit like this where \$R_1 = R_2 = R_3 = 1\$

simulate this circuit – Schematic created using CircuitLab

Why can we not divide this into two branches, \$ B_1, B_2 \$ and then do the following to find total current?

$$
I_t = \frac{V_1}{R_1+R_2}+\frac{V_1}{R_1+R_3} = 1 A
$$

However, when we get the equivalent resistance and use it to find the current in the usual way like so, we get a different answer.

$$
I_t = \frac{V_1}{R_1 + \frac{1}{\frac{1}{R_2} + \frac{1}{R_3}}} = 2/3 A
$$


texts: Protecting equipment submerged in water against earth fault - RCCB vs MCB

texts:
I would appreciate help understanding the difference between an RCCB and MCB in the context of the situation I'm sharing below.
I have a mini fountain pump in my pond which doesn't have any earth pin (i.e. it has only 2 pins) and it connects directly to the electrical socket. Let's say the submerged portion of the electrical wiring somehow gets cut and exposes the copper wires to the water. An RCCB would immediately cut off the electricity. But an MCB would perhaps take a few seconds to kick in (or would it not kick in at all, given that the pump consumes low current/power?). Is my understanding correct?
Based on the past hour of reading articles and watching videos, I understand that RCCB's work by monitoring outgoing current vs incoming current. When there is a difference (domestic ones seem to kick in at 100mA), the RCCB shuts off the circuit.
But then, wouldn't an MCB do this too? Going through some data sheets, it looks like an MCB needs a much higher current, i.e. 3x the house load. So is the difference that an RCCB kicks in at a very low current (100mA) vs 18 Amps for an MCB?
and what about the reaction time - how long should the current flow for each device to kick in?
I'm in a rural place so don't really have alternates than the 2 pin (ground wire missing) mini fountain pumps. I plan to put about 3 of them into my pond. The house electrical panel already has an RCCB. Is there any reason to install one more RCCB at the electrical outlet next to the pond that's powering these pumps?


texts: Why are infrared LEDs used in optocouplers?

texts:
I read that optocouplers and optotriacs use infrared LEDs with infrared sensitive transistors.

What is the idea behind using IR frequency but not visible light freq. LEDs inside a completely closed dark chip?


texts: Powering 4.6 V with 5 V USB power supply

texts:
I need an output of 4.6V 900mA from 5V USB power supply. The smaller the better, what is the best way to achieve such conversion.

I want to mod Nintendo DSI XL to charge it using USB micro. Case says input power is 4.6 V 900 mA. Google doesn't recognize any ICs near power input so I don't know what's the maximum voltage I can provide (although when I measured the voltage from original power supply (while plugged in) I got 4.8 V).

I tried using these buck converters: Link  but I managed  to fry two of them for no apparent reason, so I don't trust them anymore. Unless you have an idea how I could do it please don't suggest them.


texts:
So I had a circuit to analyse and I needed to find the equivalent resistor and then I arrived to a confusion. Are R1 and R3 in parallel?
Here is the circuit.

simulate this circuit – Schematic created using CircuitLab


texts: Learning the Art of Electronics - keypad schematic

texts:
The image below is an extract from the schematic for the keypad referred to on page 620 of LAoE.

What does the symbol connecting switch S4 to pin 11 of U7 and connecting pins 6 and 11 of U7 mean in terms of how to wire it up? Does this just indicate direct connections between S4 and pin 11 and between pin 6 and pin 11, with the three unfilled circles and the solid and dotted curved lines indicating the function of S4 as toggling between 10Hz and 20Hz?


texts: Can Pulsed DC be used in a radio transmitter?

texts:
I'm building a small radio transmitter based on a 555 timer.
In my circuit a 555 timer in astable mode is used as an oscillator.
kind off like : http://www.instructables.com/id/555-AM-Transmitter/

From what i understand a 555 Timer in astable mode outputs a "Pulsed DC" signal (HIGH LOW HIGH LOW, but never goes negative).

And a "AC" signal is needed to drive an antenna for electromagnetic radiation to occur, Is this correct?

Or can a "Pulsating DC" signal just as well be used for radio transmission?
In the instructables project the "Pulsed DC" is directly used to drive the antenna. How does this work?

thanks in advance,


texts:
I am having trouble simulating Right Leg Driver in an amplifying circuit of eeg signals.

The schematic of the circuit:

The instrumental amplifier circuit has a gain of about 2 and E1 have 10m amplitude and 10Hz.Then the output of the circuit should be:
10mV * 2 = +/- 20mV

When I use the RLD circuit, the output I_E1 is:

However, when I do not use the RLD circuit, the output I_E1 is:

The output with RLD is correct?
The simulation is like that or am I doing wrong?


texts: Weird output on 16X2 JHD162A LCD display

texts:
I am learning interfacing of Atmega 16a with 16X2 LCD.
I have a written a header file for routines which will used frequently and every time I want to interface with LCD using Atmega 16a I use this header file.

here is my LCD header file:

#include<stdlib.h>
#include<avr/io.h>
#include<util/delay.h>
int cx=1;
int cy=1;
void LCD_Send(unsigned char c,unsigned char DC)
{

    if(DC==0)
    {
        PORTC=0x0F & (c>>4);
        PORTC=PORTC|(1<<5);
        _delay_ms(1);
        PORTC=PORTC & (~(1<<5));
        _delay_ms(1);
        PORTC=0x0F & (c);
        PORTC=PORTC | (1<<5);
        _delay_ms(1);
        PORTC=PORTC & (~(1<<5));
        _delay_ms(1);
    }
    else if(DC==1)
    {
        PORTC=0x0F & (c>>4);
        PORTC=PORTC | (1<<7);
        PORTC=PORTC|(1<<5);
        _delay_ms(1);
        PORTC=PORTC & (~(1<<5));
        _delay_ms(1);
        PORTC=0x0F & (c);
        PORTC=PORTC | (1<<7);
        PORTC=PORTC | (1<<5);
        _delay_ms(1);
        PORTC=PORTC & (~(1<<5));
        _delay_ms(1);
    }
    return ;
}
void LCD_init(void)
{
    DDRC=0b11101111;
    LCD_Send(0x01,0);
    LCD_Send(0x0F,0);
    LCD_Send(0x28,0);
    cx=1;cy=1;
    return ;
}
void LCD_Send_String(char* s)
{
    for(int i=0;s[i]!='\0';i++)
    {
        LCD_Send(s[i],1);
        if(cx==16)
        {
            cx=1;cy++;
            LCD_Send(0xC0,0);
        }
        else
        cx++;
    }
    return ;
}
void LCD_GotoXY(unsigned int x,unsigned int y)
{
    if(y==1)
    {
        char addr=0x80;
        addr=addr+(x-1);
        LCD_Send(addr,0);
    }
    else if(y==2)
    {
        char addr=0xC0;
        addr=addr+(x-1);
        LCD_Send(addr,0);
    }
    cx=x; cy=y;
    return ;
}
void LCD_Print(int data,unsigned int x,unsigned int y)
{
    char string[10];
    LCD_GotoXY(x,y);
    itoa(data,string,10);
    LCD_Send_String(string);
    return ;
}

Here RS,R/W and E are PC7,PC6 and PC5 respectively, DB4,DB5,DB6,DB7 are PC0,PC1,PC2,PC3 respectively. I am using 4 bit mode for input.

here is my main.c file (the code which will be run on the microprocessor):

#include"lcd.h"
int main(void)
{
    LCD_init();
    char s[20]="1234567890123456789";
    LCD_Send_String(s);
    return 0;
}

When I flash the memory with the HEX file then reset the LCD is displaying fine

Then when I reset later it displays random variables(infact I can see that the second line doesnt change at all, it means that the screen is not cleared but a command was written to LCD_init() to clear screen)

I am pretty sure that nothing is wrong with board and the connections because it works with other header files, I am pretty sure that it is a fault in my code.
I would really thankful if anyone help me fixing this code
If i reset again it displays the correct sequence as in first image


texts:
I'm trying to use a pair of RF switches (SKY13421-486LF) to switch two channels between the circuit output and a matching resistor: I have two inputs and want to pass one to the output and dump the other. I'm using a 3.3V supply, and this problem appears on all the devices I've checked. The signals in question would be in the order of 100-150MHz.

However, instead of acting as a switch both devices act more like a splitter, passing the input to both outputs equally, regardless of the control voltage. That is, a signal input to either U6 or U7 appears on both R7 and C10.

I've tried changing the matching resistor value and placing DC blocking capacitors on the outputs without success. Searching around hasn't led to anything, but that might be because I have no idea what search terms to use.

Has anyone seen anything like this before, or have any suggestions on how to stop them acting like splitters?

EDIT:

@Bimpelrekkie: I've tried placing capacitors by cutting and strapping on the outputs with no success. The input of U7 is DC blocked at the origin of the input signal.

@Andy aka: Powering on, yes. It does occur to me that powering off is done by just cutting the power, so that C98 and C99 might hold the voltage at the VCTL pin higher than VDD for however long it takes to discharge. The datasheet doesn't seem to specify the tolerance of the device for this, so I'll email Skyworks and ask.

EDIT again:

Contrary to what I wrote above, placing capacitors on the output pins of both switches does work. It may have been a layout issue or an accidental short while cutting and strapping. Note that putting caps on one set of outputs is not enough.


texts: My HP laptop battery charger's input is 1.7A. Can I replace it with one that is 3.5A. Every other spec is the same on the input and output. Thank you for your assistance.


texts:
I'm investigating a noisy output of a Femto DHPCA-100 high speed transimpedance amplifier (http://www.femto.de/en/products/current-amplifiers/variable-gain-up-to-200-mhz-dhpca.html). The final application is to amplify the signal of a PMT tube - however, the bulk of the noise can be reproduced without the PMT.

The test setup is shown below. The TIA is powered and the output is connected to a scope with a 50ohm terminator. The output of this amp is specd at +/-1V @ 50ohm load. The amplification level is set to 10^4, low noise setting. With the input left disconnected, the noise level is around 4mV pk-pk.

When a 6ft BNC cable is connected to the input - but left open at the other end - the noise level jumps to around 40mV pk-pk. This is plenty enough noise to conceal small input signals.

I assume that the BNC is "acting as an antenna" (for lack of a better technical phrase) and picking up ambient noise, such as wifi or AM/FM and the like.

My question is as follows:

Is this standard behavior for a TIA?
What can be done, if anything, to reduce this kind of noise? Perhaps a shorter or better shielded BNC? I have tried a 12ft BNC cable and the noise levels are about the same
Is there any glaring error I am making with the configuration of the instrumentation? Are there any best practices to reduce noise of this variety?

I have read several sources on TIA noise and stability, but most refer to creating your own circuit rather than using an off the shelf product. I've also tired many different configurations of this test setup, such as terminating the input, terminating the output just with the 1M res of the scope, etc. None produced any useful knowledge. I am baffled as to what to do here.

Thanks in advanced.