texts: Current splitting in nA,pA range till 100 kHz frequencies

texts:
This relates to my previous question of current splitting. Current splitter/divider in nA/pA range possibilities

I read about some circuits on current copying (current conveyor). However, the circuits operate less than around 10 kHz.

https://www.researchgate.net/publication/263076351_Current_Mode_Techniques_for_Sub-pico-Ampere_Circuit_Design_Special_Issue_on_Current_Mode_Circuit_Techniques
https://pdfs.semanticscholar.org/42ae/6752d1f2656aeddcf34519702c289dc8d653.pdf

But my requirement is to copy currents at a high frequencies (100kHz).

Therefore, I wanted to know if circuit in Current splitter/divider in nA/pA range possibilities 's answer or any current copying circuit would work at high frequencies with a high linearity? or is it something impossible?


texts: What happens when you connect a 16bit analog device to a 10bit adc

texts:
Can someone explain  what happens when you hook up a 16bit analog device to a 10bit ADC (like the one on the Arduino).Will it still function?Will the 10bit ADC normalize the values with a lower resolution?

Also how would i go by interfacing 16bit analog device to the Arduino.

thanks in advance.

link to the device im looking at. measuring frequency is at 2kHz


texts:
I'm looking for a .1" pitch female-female or female-male header with common pins, i.e. all the pins are connected. I'm sure it exists, I'm just having trouble coming up with the right keywords to find it on google.

I want to use it as a cheap way to expand the ground and 5V terminals on an arduino without needing a whole shield.


texts:
I am using the ATtiny861a and have made it so that the SPI connects to a Radio and an external memory source VIA two different chip select pins but sharing the same MISO/MOSI/CLK line.

Correct me if I am wrong, but are there two different ways that I could wire ISP programming into the circuit? The first way being that I need to put a resistor in each MISO/MOSI/CS/SCK line before the 'Slave' and the other way is that I put a Pull-up/Pull-down resistor into the CS lines. I found this on another site. ( http://www.societyofrobots.com/robotforum/index.php?action=dlattach;topic=10394.0;attach=4420;image )

Which way of programming the circuit would be better(more energy efficient during non-programming/easier installation)? The circuit will be a wireless node so it will not be "functioning" when we are programming it.

(from the link above) If I am using 1.8V to power my circuit, would I change the pull-up resistors to be connected to 1.8V? Is there any downside(more power consumption) to use Pull-up versus Pull-down? Are Pull-up/Pull-down resistors interchangeable or can they only be attached to certain pins? If power consumption is important, what resistor values should I use?


texts:
I have the following digital plant:

\$G(z)=\cfrac{z+1}{(z-0.3)(z-1)}\$

I want to use root locus to design a system with:

(1) position error=0;

(2) overshoot \$\leq 10\%\$

(3) settling time \$\leq\$ 5 seconds

(4) rise time as small as possible

I made the design manually:

Calculations done so far:

The overshoot requirement leads to \$ \zeta \geq 0.6 \$,

\$t_s=\cfrac{4.5}{|\sigma|}\Rightarrow |\sigma|\geq \cfrac{4.5}{5}=0.9\$

Unitary circle centered in the origin with radius of \$e^{-0.9T}\$. If T=1, the radius is \$e^{-0.9}\approx 0.41\$.

\$-\cfrac{1}{h}=\cfrac{z+1}{(z-0.3)(z-1)}\$

Zero: z=-1

Poles: z=0.3; z=1

Break point:

\$N'D-ND'=0
\Leftrightarrow -z^2-2z+1.6=0\leftrightarrow z\approx 0.612 \vee z=-2.612\$

I need to determine \$h\$, so I have to determine \$z_h\$. How could I determine \$h\$ in Scilab?


texts: make a 2 wire voltmeter w/led bulb display

texts:
So I've been working on a project for a while now and I'm looking to create a specific feedback for the user. What I want to do is to make a 2-wire voltmeter that operates similar to this one. (Click the link for tech. specs)

The major difference I am looking to make, is that I would like the feedback to be with LED bulbs in a bar-graph style.

I think the chip on the back is the LM3915, but the rest is totally unrecognizable to me, can someone help me to understand how this circuit is working, and how to to adapt it to output in a bar-graph style.


texts: Choosing a voltage regulator for a 1.3V to 1.0V drop

texts: I am looking to power a 5V system at roughly 600mA from a 6V AGM lead acid battery (voltage varies from 6V-6.3V). My main concern is finding a regulator that is tolerant enough to deal with the battery at full charge down to 50% charge without too much heat being generated. A quick search on linear technology's website yielded the LT1086, but the 1.5V max dropout has given me pause since I am unsure if the the NOCO Genius G750 Charger might bring the battery voltage higher. I am mainly looking for reliability with people that don't know much about electronics, so suggestions you have on picking a regulator would be appreciated.


texts: How to deal with start sequence in payload of communication packet?

texts:
Basic serial messages are being transferred between an embedded device and a PC app.

MCU UART Peripheral -> FTDI cable -> PC USB Serial Library

The messages are currently fixed-length (32B) and being transferred in the format:

start_low_byte start_high_byte payload_0 payload_1 ... payload_(n-1) end_low_byte end_high_byte

Where not all of the payload bytes are necessarily being used.

Now I know there are many tradeoffs that are application dependent (fault-tolerant, bandwidth => overhead/payload ratio limitations, range of the values in the payload, etc).  In this case, I'm trying to transfer an arbitrary payload which makes me wonder:

If needed, how can I ever transmit a start or end sequence?  And is there any advantage to having a separate start and stop sequence, or is a single delimiter sequence OK?

If I escape the start/stop sequence, then my message seems as though it can grow up to twice as long.


texts: I'm working with these two MOSFET CSD18504Q5A and CSD18510Q5B. With Altium I need to design their PCB footprint, but their datasheets in the section "Recommended PCB footprint" for each dimension they provide a minimum and a maximum. How can I draw the footprint using max and min? Which are the design criterias?


texts:
I have disassembled Parts of something (I think it was an old TV or RC controller).
There I found an IC with this printed on top of it: "Futaba Japan FP2108T 9175K". I am not good enough that i can understand the circuit/datasheet so I want to ask you out of curiosity what it does. Its enough for me to get a rough Idea, of what its purpose is.


texts: Replacing a Wired Controller with an Arduino Uno: Relay Alternative

texts:
So, I have a simple robotic arm that has a wire controller you plugin into it. The controller has 8 pins. I haven't played with it too much but I know that the far ends are power sources and the middle pins are to the motors. When a connection is made with one side to a middle prong a motor runs. The motor runs in the opposite direction when the opposite side's prong is used with the motor prong. Because the controller is made completely up of switches and no other components I figured it'd be relatively simple to create a circuit to replace it with the Arduino Uno. However, I'm unsure how I could replicate the switches with a circuit. I don't want to fry the Arduino by plugging the robotic arm right into it so I was considering using relays. But 10 relays would be kinda pricey and I'm not sure if there is an easier way. Does anyone else have any good ideas/advice?

I FOUND THE ROBOTIC ARM ONLINE: Link

EDIT: This is what I am replacing with my Arduino. It will plug right into the arm.


texts: Electric heating for glass melting furnace

texts:
Some furnaces use electricity for glass melting. Low voltage and high amperage power is passed through the molten glass through 2 molybednum electrodes dipped into the glass. The molten glass acts as a resistor (when current passes from electrode to another) and heat is generated which heats up the glass to the required temperature. A scott transformer and a thyristor control panel is used to control the power to the electrodes. I am trying to replicate this process in my glass melting furnace.I have little electrical knowledge. My question is
 1. Why does this (glass) heating process have a requirement of low voltage and high amps. Although I am not sure but some users have suggested that a 9kVA load would be running at 60 volts and 150 amps.


texts: Using VBUS instead of the USB port to power a MCU

texts:
I'm using an EK-TMC123GXL, for now powering it from the PC. I have found some problems with some pins (ADC, PWM) that doesn't arise if I power it up applying 3.3V to its VBUS pin instead of connecting it to my PC.
However, in its user manual (part 1.5) I have read that apparently the only way to power it up is through either of the two USB ports it has, specifically 4.75 to 5.25 V. As explained above, I have been using it by aplying 3.3V to the VBUS pin, can this damage the board? How can it work with only 3.3V if the minimum stated is 4.75?
What I have investigated
I have seen the schematics and the VBUS pin is connected to a 3.3V regulator. The name of the regulator, according to the schematics, is TPS73633DRB, which I haven't found. I have found this one though TPS763, which matches the beginning of the reference in the schematics. Below in the datasheet, I have found that the model TPS76333 has an output of 3.3V, so I suspect this is the regultor my board is using. Don't understand very well the schematics reference. The thing is that this voltage regulator, according to the datasheet, admits a maximum input voltage of 10V (part 7, Absolute Maximum Ratings). Then, can I power up my board with a 9V battery safely?


texts: I currently have Arduino 1.0.1 and I want to upgrade to the new version. However, do I just replace the old files? How do I know if I need to update the drivers for the boards? Does Arduino even release new drivers? I admit, I have been putting this off, but I think it's time to update. Also, should I be wary of deleting anything stored in the Arduino files? I like how it has all the sketches in the file menu, does this regenerate when Arduino is opened?


texts: Different footprints for different surface mount Resistor packaging?

texts:
When using the same surface mount package size (0402) for all my resistors on a board, but using resistors from different manufacturers or with different resistance values, should I create a different footprint for each manufacturer?

In other words, are all 0402 resistor footprints the same?


texts: Cortex M0+ MemManage Fault on first PUSH instruction

texts:
I have an example program compiled for the ATSAML21E18B, which uses an M0+. The project was generated using the default Atmel START settings for this device. I initially uploaded the .bin to the device using JLink's software, the command is as follows:
loadfile /home/azimuth/example-l21/gcc/AtmelStart.bin,0

Stepping through this shows two LDR instructions executing successfully, and then a PUSH which causes a HardFaultMemManage, causing the device to interrupt into an exception handler where it hangs on an infinite loop. The offending instruction is on line 453 here. The fault jumps to the "Dummy Handler" directly above on line 445.
https://pastebin.com/08uENS29
I am lost as to why this exception can occur here, the stack pointer is pointing safely into SRAM as shown by the value of SP below. My initial suspicion was that I was perhaps loading the .bin to the wrong address, but everything ive seen of this upload method shows images being uploaded at address 0.
J-Link>r
Reset delay: 0 ms
Reset type NORMAL: Resets core & peripherals via SYSRESETREQ & VECTRESET bit.
J-Link>s
00000240:  11 48              LDR       R0, [PC, #+0x44]
J-Link>s
00000242:  12 49              LDR       R1, [PC, #+0x48]
J-Link>regs
PC = 00000244, CycleCnt = 00000004
R0 = 00000324, R1 = 20000000, R2 = 3F3D0002, R3 = 86082820
R4 = 58617C18, R5 = 25D4819D, R6 = 02D6011D, R7 = 513170AB
R8 = 7F081161, R9 = 431A11A1, R10= 43910040, R11= 08A04DB3
R12= 41801210
SP(R13)= 20002020, MSP= 20002020, PSP= 98216104, R14(LR) = FFFFFFF9
XPSR = 11000000: APSR = nzcVq, EPSR = 01000000, IPSR = 000 (NoException)
CFBP = 00000000, CONTROL = 00, FAULTMASK = 00, BASEPRI = 00, PRIMASK = 00
FPU regs: FPU not enabled / not implemented on connected CPU.

The second output is the regs after the exception has occurred.
J-Link>s
00000244:  70 B5              PUSH      {R4-R6,LR}
J-Link>regs
PC = 0000023C, CycleCnt = 00000000
R0 = 00000324, R1 = 20000000, R2 = 3F3D0002, R3 = 86082820
R4 = 58617C18, R5 = 25D4819D, R6 = 02D6011D, R7 = 513170AB
R8 = 7F081161, R9 = 431A11A1, R10= 43910040, R11= 08A04DB3
R12= 41801210
SP(R13)= 20002000, MSP= 20002000, PSP= 98216104, R14(LR) = FFFFFFF9
XPSR = 11000003: APSR = nzcVq, EPSR = 01000000, IPSR = 003 (HardFaultMemManage)
CFBP = 00000000, CONTROL = 00, FAULTMASK = 00, BASEPRI = 00, PRIMASK = 00
FPU regs: FPU not enabled / not implemented on connected CPU.


texts:
I have been assigned a project of designing a cache memory with some advanced features (using efficient cache algorithms) and implementing it in VHDL.

I know the required theory for carrying out this project and am trying to implement a 4-way set associative L1 and 8-way set associative L2 cache, but the problem is implementing the code in VHDL and simulating it in Xilinx ISE.

The main problem lies here: even if I implement the cache in VHDL, won't I require an MPU to simulate it? And even if I design an MPU, what exactly would I have to do to simulate the cache (for simulation, as I know, would require to run some sort of program on the system)?


texts: What Amplifier for Piezoelectric Ultrasonic Transducer?

texts:
first post here so feel free to point out my shortcomings.

I am interested in building an Ultrasonic device utilizing two Ultrasonic piezoelectric transducers to create a standing wave between them in order to 'float' droplets of water and other small objects. I am attempting to better understand the nature of focused compression waves in regards to electronic propulsion.

I've purchased these:
LYWS High Conversion Efficiency... https://www.amazon.com/dp/B01LXMWLGE?ref=ppx_pop_mob_ap_share

I am attempting to use my laptop as an arbitrary waveform generator using the output of my audio jack. It is a Windows based machine, using MATLAB or similar software outlined in this post "https://www.allaboutcircuits.com/technical-articles/how-to-use-your-computer-as-an-arbitrary-waveform-generator/".

My question is this, what type of amplifier should I use to get the amplitude up to the 50W required to power the transducer? I am thinking of using an audio amp but am unsure if the line voltage will be off or if I'll even be able to reach the 50W. I'm looking to achieve minimal distortion without having to create a special amplifier that only works on specific signals, since I am trying to create something that is adjustable in order to experiment with different materials caught in the compression wave. I'm assuming that there is a range of voltage in the Ultrasonic frequency that this device can use but I'm unsure as this is my first attempt to create something with these devices. Should I just purchase an arbitrary waveform generator? Will that still need some sort of amp?

This whole project is a bit advanced for me and I'll admit that I dropped out of electrical engineering school, but we never really covered analog waveform generation anyway.

Any feedback is much appreciated


texts: Why would doing the "outlet challenge" cause notable damage to outlet and wiring?

texts:
WARNING!!! WHAT "PRANKERS" IN THE VIDEO DO IS MOST LIKELY VERY DANGEROUS AND MAY CAUSE DEATH, INJURY, FIRE OR OTHER DAMAGES AND IT SHOULD NOT BE TRIED IN ANY ELECTRICAL SETUPS WHICH ARE NOT DESIGNED SPECIFICALLY FOR DOING SUCH EXPERIMENTS

The video at the bottom shows how young people plug a phone charger into a generic USA fashion (two flat prongs) outlet but don't push the charger until it touches the outlet surface and instead leave a small gap between the charger and the outlet surface. Then they drop a coin onto the charger prongs which causes a short circuit condition because now most of the current flows through the prongs and the coin. The short causes a flash, a pop sound and some smoke. The short also causes the circuit breaker to disconnect the outlet.

On 01:09 the video shows the outlet internals burnt and melted and it's attributed to causing the short as explained above. Why did it get so much damage? I was under impression that the purpose of a circuit breaker is to promptly disconnect the circuit when a short develops. So a pop sound, a flash and maybe some smoke are no surprise but a melted outlet is rather unexpected.

Why does a short cause so much damage in a circuit protected by a circuit breaker.

https://www.youtube.com/watch?v=C5XJ1RThaVw


texts: Can't secure supply of 32mhz Automotive grade oscillator - why is this?

texts:
This is my first automotive PCB. I designed in a high temp crystal from Digikey. Stock then went to 0 with big lead times, and then my alternate went EOL. I then spun the board with a TCXO. All three parts I had picked went to 0 stock. I then sourced from a manufacturer, and then this went EOL.
Isn't a high temp 32Mhz oscillator a common thing in automotive just like a 32Mhz oscillator is in a consumer product? It sounds like it isn't. I never had trouble in consumer. Can someone tell me what I don't know about sourcing this part and not having to re-source it every 3 months?
It is hard without a mentor, or experience in automotive, to find who knows what I need to know. So far the buyers don't know the answer, and the manufacturers are not responding (if they know).


texts: Are there any problems with this simple Arduino LED Wiring?

texts: Is it ok that the resistors aren't connected directly to the positive? Any advice, warnings, or rule of thumbs?


texts: Calculate zero sequence voltage and current in a HV network with one source and two feeders

texts:
My goal is to prove the direction and magnitude of Uo and Io seen by the two protection relays during a single phase to earth fault in LINE 1.

By my understanding this can be done by setting up a sequence network diagram and using symmetrical components to calculate it.
Unfortunately I have not found any text book or websites covering this exact problem in detail.
To make it easier, we can assume that the current and voltage measuring transformers are ideal.
The most interesting part is the values in the high voltage network itself at the points where the CTs and VT are connected.
What is the best way to attack this to meet my goal?


texts: Linear antenna: with electromagnetic coil, trap circuit

texts:
I am trying to understand the concept of the linear antennas.
I have read that the linear antennas are the simplest form of the antenna in the case of asymmetrical (coaxial) feed.

what happens if I add the coil?

or circuit?


texts:
I want to ask you about this please how I can edit Component DECAL already placed on PCB file ? the idea is I found that some chips may be the same but different pin numbers like if BGA has 160 pins I want to make it 200 and save it !
like this

is there a way to create and import my new DECAL to the PCB PADS ? please help me

Regards


texts: Solving nodal analysis equations using matrices- gives a full rank matrix

texts:
I am trying to solve for node voltages in a circuit using nodal analysis. I am using the fact that the sum of the currents into each node must equal 0.
I have a system of equations which can be represented in matrix form as [G][V] = [0] where [G] is the conductance matrix, [V] is a column vector of node voltages and [0] is a column vector of 0s. I already know one of these node voltages since it is the value of the voltage source and I have been able to find a solution by rearranging the equations in terms of this known source voltage so the RHS is no longer 0.

However what I do not understand is why I am able to find a unique solution in the first place. The conductance matrix found is full-rank and therefore by the rank-nullity theorem, surely the only solution should be a vector of 0s.
Am I misunderstanding something?


texts: Graphical circuit simulator like Logisim

texts:
I wanted to make a CPU and then somehow measure its efficiency/speed.

Logisim is a little buggy, and I don't think it allows you to do any sort of testing/measurement. Does a tool like this exist?


texts: PID algorithm implementation using computer vision

texts:
I am constructing an automatic labyrinth maze solver, and using a webcam to control my maze.

Based on suggestions in other forums, I am trying to control maze's ball movement at least in one direction at the moment. So, I am trying to control my ball movement between two coordinates 466,288 and 466,152. The input to the stepper motor controller board is time, no of steps to rotate for each axis i.e x and y.

The stepper motor controller board that I am using is the egg bot stepper motor controller board:
http://www.sparkfun.com/products/10025

So in order to move between two points, should I create a number of way points between the two points namely 288 and 152 (say 260 240 230 ... 150) and correct my ball movement?

My image processing algorithm is not fast enough to track the ball that the ball would just spin and fall into a hole.

Some suggested that I use a standard template as shown in the following video and correct my ball movements for deviation in the path:

http://www.youtube.com/watch?v=Prq78ctJ2Rk&feature=player_embedded

I also came across an image processing tool where they solved the same problem using way points for the ball movement. Seeing too many solutions to the same problem, I am totally confused in going about solving the problem. I am aware that I should implement a PID controller. But how should I go about solving the problems in stages? I am stuck and just frustrated in finding a headstart in solving the problem.

My setup looks like this:

...and here's a screenshot of my software:

Revision 2:
I am also facing a new problem now:
Earlier I controlled the stepper motors via Arduino serial port Java applet. I am able to drive the steppers using the applet.

I have to reset the board every time I try to communicate via serial port. Also, the stepper motor energizes itself in small intervals when no command is sent to it. When the stepper motor enters this mode, I cannot control my board without resetting the board. Any assistance would be appreciated.

Revision 3:

I made some progress where I got the PID algorithm implemented. Please find the video below:
http://www.youtube.com/watch?v=MEfp7RqPmqY

Now I have a problem with the speed at which the PID algorithm is implemented. Actually my image processing finishes a cycle in 200 ms, identifies a ball and send the commands to the stepper motor controller board. Even though my serial port is sent commands to switch directions, my stepper keeps rotating in the same direction. You can find the weird behavior in the video above.

My thought is that I should restrict the PID values with a ceiling where if the calculated PID value is greater than 100, I should just send a 100. I am looking forward to hear your thoughts on this.

The way I implemented the PID controller is that I identified the starting point of the template using the template matching algorithm and identified the ball using another template matching algorithm. Now, I made the ball move to the centroid of the starting point template. How do I make it follow the straight line with the PID algorithm?

Revision 4:

I have isolated the trajectory but I am not able to find the correct function to print the correct pixel coordinates from the starting point. Any thoughts?


texts: Need to choose between 48 solenoids, trying to design a proper circuit to do so

texts:
I am in the process of designing a project that will allow a Raspberry Pi to "print" to an old (60s) electric typewriter. I have decided to have a push-solenoid for each key (24V), for 48 total keys. I have chosen a set of decoders (74VHC138M) to take a six-bit output from the RasPi GPIO pins to select the solenoids (one at a time).

I am trying to figure out how to drive the solenoids, and I think an optocoupler might be a good idea (something like this: LTV-847).

My question: can I drive the solenoid straight through the LTV-847 simply by triggering the optocoupler with the decoder? I was looking at this post and I'm wondering if will be necessary to build a Darlington (one for each of the 48 keys...). I'm hoping I don't have to do that, but if it necessary, I want to do it correctly.


texts: How to increase the size of value of X/Y axes in Simulink scope?

texts:
I want to increase the size of the value shown in the X and Y axes so it can be seen in the report.

If you look at this figure, we barely see the value:


texts: Understanding the meaning of a waveform of an alternative current

texts:
Let's say we have a simple electronic circuit with an AC power source, a resistor and wire. If the AC source can produce this kind of electric current waveform

does the peaks of this waveform corresponding to a particular position to the wire?


texts: Arduino Mega 2560 -- Ports F & K as digital outs?

texts:
I'm stumped.. I'm simply attempting direct port manipulation of the pins on Ports F and K.

// First Set the port data direction registers as "outs"

DDRF = B11111111;  // GREEN LEDS - "ARMED"

DDRK = B11111111;  // YELLOW LEDS - DISARMED OFF HOOK"

DDRL = B11111111;  // RED - "ON HOOK"

//Then drive alternating pins High/Low

PORTF = B01010101;

PORTK = B01010101;

PORTL = B01010101;

Port L works fine, the other two "no joy".

Any thoughts?


texts: Changing 18650 batteries in a laptop battery pack

texts:
My laptop is 7 years old (bought in november 2012) and I've had 1st battery ever since. Whenever I plugged it into power plug, I always removed battery.
Even though, after 7 years of use the battery lasts ~1h, while laptop works perfectly. I decided to change 18650 batteries in the battery pack, but here's the catch: Original battery's specifications are: 10.8V 4700mAh 50Wh.

I would like to remove all 18650 batteries and replace them with new, better ones, such as Samsung INR18650-35E 3450mAh. Here's the thing: Could there be a problem with replacing old (original 18650) batteries with new 18650 batteries, which has higher energy charge than the original one had? I am talking about laptop power supply, battery charger unit and anything else, perhaps?


texts: MOSFET Amplifier: Maximum Signal Swing without Clipping

texts:
I have a degenerated common source amplifier. I want to know what's the maximum input signal I can apply before the output signal begins to clip.

What I currently do is to increase the input signal  until I see in the scope that the output signal begins to clip. It's a trial an error method.

But I would like to know what's the general procedure to compute (by hand) the maximum input signal without clipping.

simulate this circuit – Schematic created using CircuitLab


texts: Do I need a decoupling cap for a line buffer gate?

texts: The data sheet does not say anything about the decoupling capacitors for this buffer gate. Would it be correct to assume that no caps needed? Please, explain.


texts: Photodiode OP-AMP circuit for UV light radiation

texts:
The project: The aim is to be able to use the photodiode to detect plasma (radiation in the UV light spectrum). The photodiode suggested for this application is the BPX65 and I currently have access to a AD622AN low instrumentation amplifier.

OP-AMP: http://www.analog.com/media/en/technical-documentation/data-sheets/AD622.pdf

Photodiode: http://www.osram-os.com/Graphics/XPic1/00181579_0.pdf/BPX%2065,%20Lead%20(Pb)%20Free%20Product%20-%20RoHS%20Compliant.pdf

Ideally, the project requires this to be connected to the 5V supply of an Arduino board in order to provide a signal on whether there is a presence of plasma or not. Accuracy is not key but quick responses are of importance.
Without any circuitry, when the plasma is active, the photodiode is able to detect a small voltage drop from 260mV to 240mV. Reading analogue values from the Arduino board with the a simple resistor to ground is unable to detect any change while the plasma is present, so I decided to add an instrumentation amplifier by following a basic non-inverting configuration as below:

However, this has made little or no change to the output values detect. Would anyone be kind enough to shed some light on this issue. Thanks.


texts:
I need to control 6 SSR inputs. These are 16Vmax rated on the control side. I need to use them with 24V control voltage out of a PCB which looks like has mosfets for output and all positives of the output are connected together. I assume these mosfets are sinking current. I thought about a simple voltage divider, which should be ok. Are there any other options?

SSR PART NUMBER: SSR-1028ZD1
DATASHEET: https://www.tme.eu/Document/b96df566ad9896bc37fe6c7e432d75ab/SSR120A.pdf


texts: Geometric mean versus arithmetic mean or harmoic mean in multiconductor transmission cable inductance?

texts:
In the Electrical Power Transmission And Distribution,if we want to know a inductance of inductor,we will use this formula

\$D_{aa'}\$ means the distance between a and a'

In the \$L_P\$.we call the formula, which is in  the numerator, GMD (Geometrical Mean Distance).

In the \$L_P\$.we call the formula, which is in  the denominator, GMR (Geometric Mean Radius).

I am curious about the  \$L_P\$, GMR and GMD,first we can find the inductor (\$L_P\$) = \$2\times10^{-7}ln(\frac{GMD}{GMR})\$

Why should (\$L_P\$)= \$2\times10^{-7}ln(\frac{GMD}{GMR})\$, not (\$L_P\$)= \$2\times10^{-7}ln(\frac{GMR}{GMD})\$. Although it seems like a definition, but I believe there must be some reason to explain why should we write \$ln(\frac{GMD}{GMR})\$,not \$ln(\frac{GMR}{GMD})\$.
GMD and GMR are both Geometrical Mean, as I know, there are three kind of mean, that is, Arithmetic mean, Geometric Mean, and harmonic mean. Why should we use the geometric mean when we want to find the inductance if inductor, but not using Arithmetic mean or harmoic mean?

Arithmetic mean \$=\frac{a+b}{2}\$

Geometric Mean \$=\sqrt{a \times b}\$

harmonic  mean \$=\frac{2ab}{a+b}\$


texts: SNM (Static Noise Margin) and DNM (Dynamic Noise Margin) confusion in digital circuits

texts:
I've found in several sites that SNM is the min between NMH and NML where NMH=VOHmin-VIHmin and NML=VILmax -VOLmax

But this paper really confuses me, because it uses the same graphics and apparently the same definition to DNM.

Can someone explain to me the difference between both concepts?


texts: Changing old batteries in handheld device and replacing the charger

texts:
I need them to power a small handheld soldering iron, which had an old battery that died.
The original battery was NiCD 1200 mAh 2.4v
I am replacing them with 2 NiMH-520rs in series
First question: Will putting the two batteries in series, allow them to be charged with 2.4v or do i have to charge them with 1.2v?

Secound: Does it make any difference that the battery in the device was a NiCD and the ones im replacing it with are not?

Secound problem is that the wall charger is broken as well. When ever i try to draw power from it, it dies and outputs 0v no matter what.
It says on the back, that it supply 3v at 600 mAh
But when i hook it up to a multimeter it says 6v...

So my first thought was that, if it could convert it to be charged via USB 5v, i would solve the problem with the wall charger.

So my next question is how to transform or drop the voltage from 5v to something i can charge the batteries with...


texts: Drain current as a function of temperature

texts:
I was working on the temperature dependence of the Mosfet and I obtained the following characteristics shown below. Interestingly the drain current decreases with increasing temperature. But  thought that temperature increases the energy of the electrons thereby it should cause a higher current is it not ? Why would it be otherwise ?
In the graph shown below Vgs was constant and the Vds was varied for different temperature values and you can see that the current decreases for higher temperatures.


texts: Why is the 8061 microcontroller described as having 256 bytes of internal memory?

texts:
According to doc (http://www.auto-diagnostics.info/pdf/ford_eectch98.pdf), this 8061 microprocessor chip contains 256bytes of internal
RAM (also referred to as register file in the doc). However, the only register file
named in this diagram is a 120x16 register file(or 960bytes?)
Hence, where is the 256bytes of internal RAM aka general purpose register
And why is there a 120*16 register file instead? What is it made of?

Is the 256bytes of internal RAM in the instruction register? (which I assume
Consists of the address and instruction register(among others as stated here https://cs.calvin.edu/activities/books/c++/engr-sci/WebItems/Chap05/ComputerArchitecture.pdf) ?
The Memory Map doesn’t show this as well.
If according to the notes on the memory map, the 256 locations are on chip and refer to the internal register file then what would be considered external?

a relative to the 8061: http://datasheets.chipdb.org/Intel/MCS96/APPLNOTS/27006102.PDF


texts: How can I use a greater USB charge current without device enumeration?

texts:
I'm designing a device with USB communications, using an STM32F105 microcontroller.  It has a LiPo battery, which charges from the USB port using an LTC4077 charge controller.  It will generally use a high-current charging port to charge the battery, but will sometimes be plugged into a PC for data communications.

To stay within the USB specification, the charge controller initially allows a charge current of 100mA. If the STM32F enumerates with an appropriate USB host, it asserts a logic line telling the charge controller to take 500mA.

I have a power switch in between the battery/charger and the rest of the circuit.  When the switch is off the microcontroller doesn't have power, and the battery will charge at 100mA.

Q: How do I charge at a higher current without microcontroller intervention?

The USB Battery Charging Spec 1.2 (found here) gives different hardware options for charging ports, to allow "Portable Devices" (like mine) to determine the capabilites of the charging port without enumeration.  For example, a "Dedicated Charging Port" (with no communications capability) puts a 200-Ohm resistor between D+ and D-.  If the Portable Device detects this connection, then it can assume the device can supply higher current.

I have found some charge-management IC's, such as the MAX77301, which handle this detection and set their charge current levels appropriately.  However, they do their own enumeration, and do not pass through the USB data.  I assume they can't be placed in parallel with the data communications path.

What am I missing?  What is considered good practice, to accomplish what I am looking to do?

Thanks.


texts:
I am trying to communicate two xbee version 2, one of them coordinator and the other is end point xbee.

I have tried to write two functions namely receive and transmit.

void receive ( string &data ) {
 // construct data format with xbee id and checksum

 // ?
}

What should I write the position marked as ? in order to take data from usb ?

Operating system : Linux

Desktop edition : Ubuntu 12.04


texts: How do PID control loop in a servo motor reverse motor direction?

texts:
Suppose the motor is set to turn to the 40 deg position. We apply a load that acts in the opposite direction (want to take the motor to the 30 deg position). A simple P(ID) controller will apply current proportional to the error. Now the motor is at position 41 deg. Still an error so the controller will reduce the current till a balance is reached.

However, in the opposite case, when the load is trying to turn the motor to the 50 deg position, you actually need to turn the motor in the opposite direction (with the same amount of current as before). But a simple PID loop cannot do that. It can only change the amount of current, but not its polarity. I understand we can somehow imply an H-bridge to reverse polarity but don't see how this is integrated in the system.

Any idea?


texts: Terminology clarification for transformer with a third primary tap

texts: I am looking over the reference design from Microchip app note 46102, page 4, that shows a reference schematic for the M90E26 energy meter.  They are using a transformer that has a series tap along the primary winding to pull 35Vrms for rectification before passing through a 3.3V linear voltage regulator.  What do you call such a transformer?  A search on digikey has yielded nothing, and the part number seems to be long out of production.  Does anyone know which search parameter you might use to find such a device?


texts:
I am using TPL5010 http://www.ti.com/lit/ds/symlink/tpl5010.pdf watchdog timer's RSTn pulse to trigger 555 timer in monostable mode with 10 sec pulse width in order to turn ON relay using transistor at OUTPUT pin of 555 timer.

1. Here problem is that during startup TPL5010 generates tREXT = 100ms RST pulse which is triggering 555 timer and which will turn ON relay. How can I neglect this initial startup pulse to avoid triggering 555 timer during initial startup.

Both TPL5010 and 555 timer is running with 5V suply . I am thinking that if I can delay the supply voltage to 555 timer for a period  till which TPL5010 finish it startup process.Is there any way I can solve this problem

All answers appreciate


texts: Finding Voltage in a Circuit with a Capacitor

texts:
I have applied the voltage division, but I am struggling to find a way to find a final answer, would I just distribute multiplication?
Thank you to anyone who helps :)


texts:
Electricity novice here. Thanks for reading!

I have a 3000 watt DC to AC inverter attached to a 12V battery bank.  The inverter has "DC ground lug" on the exterior of the inverter's case which the manufacturer says should be "tied into the DC ground of the system".

My "system", however, is a small box on wheels that I take around with me.  There is no vehicle chassis or house ground that I can tie into.

As I understand it, the purpose of the ground connection is to bleed off current in the event that the inverter's case should ever become energized, which in turn would trip a breaker.

My questions are as follows:

How much metal does the ground wire need to be connected to in order for the ground connection to work as intended?  Is it enough for me to attach a strip of metal inside of my "mobile power box" and attach the ground wire to that?  A car's chassis is massive and I see that it might conduct a lot of energy, but I'm not sure how much mass is enough.
Can the ground in a system like this be tied into the negative side of the battery bank?  The battery in this case is not tied into a vehicle chassis, so I'm not sure that would even make sense.

Thanks in advance!


texts: Decoupling capacitors - placement close to DC output

texts:
I have a general question regarding the placing of decoupling capacitors.
Example at DC Vout of SMPS or LDO regulators. Does it  really matter which capacitor out of 100nF, 1nF and 10uF is placed closest to the Vout?
Also, when both electrolytic and ceramic capacitor are used where should they be placed?
What order would be best in terms of noise/ripple considerations?


texts: TP4056 custom PCB battery reference voltage

texts:
I have a custom PCB where I implemented BMS system based on TP4056 from a 5V regulated solar power source. Everything works as expected regarding battery charging and output but I am encountering a special case when if power source isnt connected before the battery, for some reason, battery (-)ve drops  to less than ground (ie -2.8 volts currently) and battery (+) has remaining 0.5-1v. Soon as Power is connected from either solar/bench supply battery negative reference becomes the same as ground reference of PCB.
I compared the voltages to before and after power is connected and have them shown is the attached schematic as yellow and blue fonts. In the TP4056 with protection circuit I have from Aliexpress/amazon, battery negative is always the same has Circuit Ground, and irrepective of when the power is applied.
What I can see based on voltages is :

on DW01, pin 1(OC), and pin 3(OD) somehow split the total voltage of the battery between them, compared to when power is connected, and both have the same potential.

Right now I am clueless as to how to ensure battery negative reference is the same as ground reference of the PCB.
As a Side note, I have attached the later 1 and layer 3 pictures of the 4 layer pcb. Layer 2 and layer 4 are grounds.


texts: Acceptable Silk to Solder Mask Clearence

texts: I am running DRC in Altium Designer and Im getting tons of "Silk to Solder Mask Clearence" Errors. I searched for acceptable values, but without luck. Altium is set to 10mil. I have most values around 7.5mil. Sometimes its even not possible to reduce, for example with an LQFP100 package. What would you suggest me?


texts: If you have long PCB traces and want to minimize the resistance, is it feasible/viable to use through hole vias to be able to utilize copper on both sides of the board? If width of the trace is limited, what might other strategies be? Thicker copper? Looking for solutions that are most economic in scaled production.


texts: I am able to solve the question by transforming the original circuit into an equivalent circuit. However, I cannot seem to solve the question using mesh current analysis on the original circuit diagram.


texts:
I am using COG-C144MVGI. I am trying to turn it on with my Raspberry Pi.

I am not sure if I am following the "power on sequence" correctly. Does this kind of LCD modules work without backlight? I am wondering if I am supposed to get some kind of reaction on the screen even without backlight. Thank you.

Here is the datasheet :

https://www.avrfreaks.net/sites/default/files/COG-C144MVGI-08%20Full%20Spec.pdf


texts: Can I use a single SMPS instead of 4 separate transformers?

texts:
Can I connect 4 nos car halogen bulbs (12 volts 90/ 100 watts each ) to a 12 volts smps which is 200 meters away ( cable size 6 sq mm copper)
If yes, what amps rating?

Also will the bulbs get more hotter than normal?

By normal I mean generally these lights run on car batteries

What would be the difference if I connect them to 4 different soft start transformers (12 volts 100 watts each ? Temperature wise, cost durability wise ) of course these transformers have to be near the bulbs say 5 to 8 meters


texts:
I'm a beginner when it comes to electronics. So I want to play sounds using my controller and I am using a WT020-SD-16P

I connected the module to my microcrontroller like in the picture. and added a switch on pin 9, 12, 13 of the module for its play/pause, next, and previous. Refering to the forum, they it is not true that it has a 1gb memory card limitation so I used 2GB genuine SandDisk. Acorrding to the manual([WT020-SD-16P](http://e-gizmo.blogspot.com/2013/03/wtv-020s-voicewav-player-module-quick.html
)it only play AD4 sounds file, but to be sure I included both the wav and AD4 file. After setting up i tested the sample program in the forum:

#include <Wtv020sd16p.h>

int resetPin = 2;  // The pin number of the reset pin.
int clockPin = 3;  // The pin number of the clock pin.
int dataPin = 4;  // The pin number of the data pin.
int busyPin = 5;  // The pin number of the busy pin.

/*
Create an instance of the Wtv020sd16p class.
1st parameter: Reset pin number.
2nd parameter: Clock pin number.
3rd parameter: Data pin number.
4th parameter: Busy pin number.
*/
Wtv020sd16p wtv020sd16p(resetPin,clockPin,dataPin,busyPin);

void setup() {
//Initializes the module.
wtv020sd16p.reset();
}

void loop() {
  //Plays synchronously an audio file. Busy pin is used for this method.
  wtv020sd16p.playVoice(0);
  //Plays asynchronously an audio file.
  wtv020sd16p.asyncPlayVoice(1);
  //Plays audio file number 1 during 2 seconds.
  delay(5000);
  //Pauses audio file number 1 during 2 seconds.
  wtv020sd16p.pauseVoice();
  delay(5000);
  //Resumes audio file number 1 during 2 seconds.
  wtv020sd16p.pauseVoice();
  delay(5000);
  //Stops current audio file playing.
  wtv020sd16p.stopVoice();
  //Plays synchronously an audio file. Busy pin is used for this method.
  wtv020sd16p.asyncPlayVoice(2);
  delay(2000);
  //Mutes audio file number 2 during 2 seconds.
  wtv020sd16p.mute();
  delay(2000);
  //Unmutes audio file number 2 during 2 seconds.
  wtv020sd16p.unmute();
  delay(2000);
  //Stops current audio file playing.
  wtv020sd16p.stopVoice();
}

but when I uploaded it without errors, I tried to pressed the play/pause switch connected to the pin 9 of the module. When I tried to pressed the switches there is no audio output. Im using a 8ohm speaker. Did i do something wrong? But I followed all the instructions in the forums. pls help me.


texts: Can I use 1 optocoupler to drive 4 MOSFETs?

texts: I've this circuit and works correctly, now I need to control 4 MOSFET instead of 2, is the second schematic correctly?


texts: Nyquist stability criterion for positive feedback

texts:
it is known that the stability of a system with negative feedback may be analized through the Nyquist stability criterion, which is based on observing the number of turns around the point (-1;0) in the complex plane.

But, what if we want to apply the same criterion for a positive feedback system? Is it correct or should be modified in some ways?

Can we say also for positive feedback that the system is unstable if and only if there are at least 1 pole with positive real part?


texts: Sinking and sourcing switching I/O hardware configuration

texts:
This is the Siemens S7 PLC and I'm wondering what's the internal circuit of the I/O looks like?
I'm trying to design an I/O circuit that allows me to switch between sinking and sourcing I/O by connecting either a 24V or 0V to one of the inputs just like the S7 PLC and the whole circuit combination will be sinking or sourcing.
For example, in this S7 PLC, by connecting a 24V to "1M", the inputs on the PLC will become a sinking input and by connecting a 0V to "1M", the inputs will become a sourcing input. Same goes for the output, when connecting a 24V to 3L+, it will become a sourcing output and when connecting a 0V to 3L+, it will become a sinking output.
I'm trying to design a circuit like this and I'm wondering what will the circuit looks like.
Thanks.


texts:
I recently discovered the device class 'curve tracer', the kind that you hook up to an oscilloscope via BNC in X-Y mode to test components.
It appears to me as if there would be two variants.

2 terminals for diodes, capacitors, inductors, etc. This variant draws a single trace on the screen.
3 terminals for transistors. this variant draws a comb-like shape on the screen, reflecting the transistor response under stimulation of various voltage levels.

Is my understanding correct?
If yes, is there a kit or device out there that combines both functionalities in a single circuit?


texts: Is this an acceptable circuit for debouncing a Raspberrry Pi input pin?

texts:
I am trying to design a circuit to debounce an input switch on a Raspberry Pi. The switch is for a doorbell, so it doesn't need to register multiple valid presses that are close together in time. There will be at least a second between any two actuations.
I have done some research, and the thing that confuses me, is that I'm not sure if both R2 and R3 are required, or just one (and in that case, which one). My understanding is that a value of 300nF for the capacitor, and 100k for the resistor, to give a time constant of 30ms, should be ok.

(Where R1 is the internal pull up resistor)
As I understand it, removing R3 would make the switch short the capacitor, which breaks the debouncing effect. Remving R2 would mean that when the switch is released, there willl be a large inrush current from the pin into the capacitor (which might damage the pin?). The thing I don't understand, is whether the time constant calculation should reference R2, R3 or both.
(I know I could just copy this from somewhere, but I would like to learn.)


texts: Arduino project, powered by car electric system

texts:
I want to assemble an Arduino project that would be powered by car, and also it should be power-independent to some degree. This project will be a simple car alarm system, with gps reciever and will send messages by gsm network (yep, there're plenty of those, but it's just a hobby project). But I'm a beginner in electrics, so I don't know much about subject. Recently I connected new car stereo system by myself, and proud of it - that should give you some idea :) (there was no ISO connecter in my old car though, so I had to discover and sort wires).

I plan to get positive wire from cigarette lighter, and connect negative to car body.

I need a battery (I'm thinking SLA), and a charger that will be able to charge it from 12V car electrics. Since charger will be connected to lighter (which powered through ingition), it will be active only when engine is running, so it wouldn't drain my car battery.

So, can I just get any car charger, say for usb or some phone, and charge my battery with this? Which will have an arduino project connected to it at the same time?

Or I need some failsafe? I heard smth about "voltage regulator", but I don't know what it is.

Links to appropriate chargers available online will be appreciated.


texts: Which minimum tracking/spacing size is actually required for a 0.2mm gap between LQFP leads?

texts:
I am uncertain as to the manufacturing specifications that I will need for a PCB I am hoping to get produced. The most complex component is the MCU (STM32151RCT) which has a recommended footprint for the LQFP64 ordering option as shown in the figure below:

Most of the online PCB manufacturers that I have compared have ordering options for "Min Tracking/Spacing" of 4/4mil (~0.1016mm), 5/5mil(~0.127mm) or 6/6mil(0.152mm).

The recommended gap between the pads is 0.2mm which is wider than all of the above Min spacing options. Does this mean I can use the lowest tolerance 6/6mil spacing? Are there any rule of thumb design rules that are appropriate to this issue?

I have also referred to the discussion here Trace width and spacing, which suggests that it is best to avoid using the minimum size available due to quality issues that can arise.

Please also bear in mind that the cost increase in going from 6/6mil to 4/4mil is quite large, so if possible the wider spacing would be preferred.


texts:
I've been practicing some Fourier series questions and then verifying my answers by generating an equivalent graph on MATLAB and comparing it with the graph generated by PSpice in simulating the same circuit.

This is my working:

The Fourier series of the source current:

\$i_s\left(t\right)=1+\frac{4}{\pi}\sum_{n=1}^{\infty}{\frac{1-\left(-1\right)^n}{n}\sin{n\pi t}}\$

Then do a source transformation to simplify the circuit:
\$v_s\left(t\right)=1i_s\left(t\right)\$

simulate this circuit – Schematic created using CircuitLab

Then working in the phasor domain and using voltage division:

\$\omega_n=\pi n\$

\$V_{out}=\frac{Z_L}{Z_L+3}V_s\$

\$V_{out}=\frac{j\omega_n}{j\omega_n+1}V_s\$

\$V_s=I_s=\frac{4}{\pi n}\left(1-\left(-1\right)^n\right)e^{j\left(-90\right)}\$

\$V_{out}=\left(\frac{j\omega_n}{j\omega_n+1}\right)\left(\frac{4\left(1-\left(-1\right)^n\right)}{\pi n}\right)e^{j\left(-90\right)}\$

\$V_{out}=\left(\frac{4\left(1-\left(-1\right)^n\right)}{\pi n}\right)\left(\frac{w_ne^{j\left(90\right)}}{\sqrt{1+\omega_n^2}e^{j\left(\tan^{-1}{\pi n}\right)}}\right)e^{j\left(-90\right)}\$

Taking only odd n terms since evens result in 0:

\$V_{out}=\left(\frac{8}{\sqrt{1+\pi^2n^2}}\right)e^{j\left({-\tan}^{-1}{\pi n}\right)}\$

and finally in the time domain:

\$v_{out}\left(t\right)=\sum_{k=1}^{\infty}{\frac{8}{\sqrt{1+\pi^2n^2}}\cos{\left(\pi nt-\tan^{-1}{\pi n}\right)}}\$

with n = 2k - 1 for odd terms

I plot my answer in MATLAB and it seems to be the negative of what the equivalent PSpice graph shows.

Can someone point out what is wrong please?


texts: How to make a synchronous generator unstable

texts:
I was try to analyse what factors can affect the stability of synchronous generator .
Let's say  a synchronous generator working in isolation and some loads are connected to it and we have to make it unstable by various methods ,so how many different ways are there to make it unstable ?
To me one of the obvious method is to just keep increasing the torque due to prime mover and after a  value of prime mover torque, synchronous generator will be unstable.
But ,is there any other method so that we can destabilize the generator (e.g changing load or field current etc.)?
Any suggestions would be appreciated !


texts:
I'm building a circuit powered by a small Li-Ion battery.  The battery will be connected to a 3.3V LDO, which then powers the entire circuit.

Li-Ion batteries are damaged if they are allowed to drain below about 3V. There are chips to do this LVC cutoff.

But I figure the LDO will already have the pass transistor and voltage reference, so it seems wasteful to add another part.  This seems to be the kind of thing that could be easily integrated.

Does anyone make an LDO with low-voltage cutoff?  Parametric searches and Google seem to be failing me.


texts: System Generator: a block similar to a three state logic

texts: does anyone what is the xilinx block for getting a three state logic?


texts:
Complete electronics novice here - any information at all is appreciated.

I'm attempting to rig up a numitron clock.
I've used:

4 x IV-9 Numitron tube
4 x TPIC6B595N shift register (chosen based on various forum posts)
1 x Raspberry Pi microcontroller

The shift registers follow into one another such that the output of the first becomes the input of the next and so on. It is not multiplexed.

I've tested it and the logic seems to be fine - each tube displays the correct digit. The issue is that the tubes refuse to stay lit - with each refresh some tubes become dimmer and then go out altogether. However, if I place my finger on an open wire, or even an exposed metal part on the raspberry pi, all tubes instantly work fine, with no flickering whatsoever. Adding to my confusion is that if I move my hand closer to the rig, without touching, the tubes react and become brighter. I want a clock, not a theremin.

As I said, I know close to nothing about electronics, so I'm sure that there is an obvious solution to this. I just can't for the life of me figure it out.

EDIT: If I touch my finger to ground, all digits are completely stable with no flickering at all. When I release my finger, the digits fade with each refresh until they go out. What does this mean?


texts:
What is the highest maximum voltage for a high voltage FET or other transistor? I do not need to be able to buy it, just want to know the voltage it can handle.
I was searching the internet and found that I couldn't find any real high voltage FETs or other transistors. The highest I could find where between 3000 and 9000 V.
Are there actual transistors or MOSFETs for higher voltage out there for example in specialized machinery? The around 9000 V versions were experiments in universities.


texts:
I'm trying to connect an arduino with 3 sg92r servo motors on it and an RPI with and lcd and the serial of the arduino connected to it.

They are both connected to a power supply with 9v/1A and 5v/2.5A for arduino and rpi respectively.

Is this possible?

or can I just connect the arduino to the rpi without connecting the arduino to the power supply?


texts:
I'm quite new to electronics and am doing it as a hobby. I recently bought a 16x2 LCD display online to use it with an Arduino. When I received it, it noticed that there were a few components missing on the back. Is the display still functional or do i need to buy new components? If i do, which components do I need?

The back of the display looks like the display on the top in this photo.


texts: Noise in portable power supply to guitar effects pedals

texts:
I am constructing a battery powered power supply for a guitar effects pedal board.
There are 5 pedals and I am using a phone charging  battery and a boost converter to supply 9V (centre negative) to power the pedals.

The total current draw of the effects pedals is about 600 mA. Four of the pedals can be connected to the supply and cause no noise in the audio signal. The fifth pedal when connected to the same power supply causes a whining noise.

If it has an independent supply (which means another battery and boost converter) there is no noise.

Is there some way to connect the fifth pedal to the original power supply but with no noise?


texts: What are the consequences of oversizing resistors?

texts: When building a circuit to power an LED, we use Ohms law to calculate the required resistance, then to calculate the required wattage of the resistor.  Suppose this formula dictates a 1/8 W resistor, and I instead use a 1W or a 100W resistor of the correct resistance.  What will happen?


texts:
I recently bought a Transformer so that I can make an ionic lifter but it has a max 30 amp output and I’m sure that is way too much for what I need plus Since I have this plugged straight into the wall I’ll definitely need an ac to dc rectifier which at most goes to about 5 amps So my question is how can I reduce the output amps so that I don’t mess up this rectifier as soon as I get it.

Btw the transformer is a 3000W YaeCCC Auto Transformer


texts:
I've got a 5m LED RGB strip to go up the stairs and will be programming it with arduino.

eBay link.

They state 60 LEDs/m @ 18 watt/meter, thats 3.3 W per LED?

It says current rating of 3 A, so that means I can only power 9 LED's at a time wiring it from both ends?

That doesn't sound right.

By the looks of it if I wired in my 5 V, 20 A supply to both ends it would still set fire.

I've seen these questions asked with some good answers, but I don't understand how the small cables I see people use don't simply go up in flames.

So I would have to run it in batches of 9 LEDs using my calcs, which would be an absolute nightmare, surely I'm wrong.


texts: What do you mean by cross range dimension of a radar's resolution cell?

texts: I'm reading a book on radars and found this term. Any help is appreciated.


texts: Non-isolated DC-DC buck converter layout - which one is better

texts:
I'm doing a DC-DC buck converter routing, using TPS62130. As known, the key point to route a DC-DC converter is to reduce the current loop area. In my design, I have a dedicated ground plane, so I have two choices to close the current loop:

The left one, the loop is closed on the top layer.
The right one, the loop is closed through vias, and the current flows on the ground plane and return through the thermal vias back to the PGND of the chip.

In the graph, the biggest component is the output inductor, and there are two output capacitors in parallel at the right end of the inductor. The only difference is: The left one, no current will flow on the ground plane. But the right one, the current will go through vias and flow on ground plane, then return to top layer.
Which one is better?


texts: How to determine resistor value for PWM signal?

texts:
I have 8 fan modules that contain 2 fans per module. These 16 fans are powered by 12 VDC and are controlled by the PWM control pin.

The spec sheet for the fan module: https://www.delta-fan.com/Download/Spec/GFM0412SS-BL4F.pdf.

Microcontroller I am using: https://docs.particle.io/datasheets/wi-fi/photon-datasheet/

According to the spec sheet, I can output 3.3 V on the PWM pin of the MCU. This fits in the range of the PWM signal the fan reads. In the example in the datasheet for the fan, they place a 2 Kohm resistor between the MCU and the PWM pin. I believe I am reading the MCU datasheet right and it says I only get 100 mA that I can source on the PWM pin of the MCU. I would like to have all 16 fans running at the same speed.

Questions:

How do I determine the size of the resistor to use on the PWM signal for one fan?
Can I use that PWM signal to control all 16 fans? If so how do I determine the resistor value?
If I can't use the one pin to control all 16 fans, perhaps a transistor would solve this for me. If so again no idea how to figure out the required resistor.
If you figured out the resistor value(s), please explain what I should be looking for on the datasheets so I know how to do this for other components in the future.


texts: Why I can't get the desired output when simulating this dc to dc converter circuit?

texts:
I found the below attached circuit of the TPS54560 4.5V to 60 V input, 5 A step-down converter.

It is supposed to give an output of 10.8 V but when I simulate it I can't get more than 1.5V or 2V.

I'm pretty sure I'm doing something wrong here but not sure what it is.

Does anyone know what might be going wrong?

P.S. I updated the images with nodes names!

This is an updated simulation of the circuit and its obvious that I got a better results after I set the simulator to run longer time (I set it to be .tran 100m) based on the valuable recommendations from JRE and The Photon. As shown in the updated image, it took an hour and half to reach ~9V.


texts:
I used a silicon coax cable (characteristic impedance 45 ohms) and sent a square wave with frequency 1 Mhz and amplitude 5V through it. The cable was teminated openly with no end resistance. I could find a reflection in-phase with the input signal.

Now i tried to hit the cable in between with a force around 80N so that the cable is deformed. But i dont find any reflection in the area that i tried to deform in the oscilloscope. The reflections are still like before for the open end and every time i bend or squeeyze or deform the cable, i dont find any reflection for that area. Whats going wrong here and how can i have reflections on the cable during impact with an object ?

Thanks


texts:
I got the following rfid reader from a colleague
https://www.aliexpress.com/item/4000035966273.html?spm=a2g0o.productlist.0.0.4ac14adcZL3H9M&algo_pvid=af835e25-e532-4426-8714-cd80a9871169&algo_expid=af835e25-e532-4426-8714-cd80a9871169-0&btsid=0ab6d70515978825018782158e600d&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_
I have connected it to my raspberry pi 4 module b using the following pinout;

raspberry pin 2 (5V)-- reader module pin VDD
raspberry pin 6 (GND)-- reader module pin GND
raspberry pin 19 (MOSI) --reader module pin MOSI
raspberry pin 21 (MISO)-- reader module pin MISO
raspberry pin 23 (CLK) --reader module pin SCLK
all other pins left unconnected

I have followed the setup steps described in this video https://www.youtube.com/watch?v=evRuZRxvPFI
My problem is that the reader is not reading data. I confirmed that the system does power up using an LED and (a resistor) in series connected to the VDD. The reader was pulling 0.46mA using a 3.3V supply, and 0.74mA using a 5V supply (measured using a multimeter).
When I fire up the raspberry and run the code, the reader does not seem to be reading any data from the rfid chips I have. I did confirm that the chips contain data using an other reader module.
I did go through the documentation but I havent found anything useful.
http://read.pudn.com/downloads567/ebook/2333609/THM3060_UM.pdf?fbclid=IwAR1y0qh-cUdnnL9wfk-ZVLEcNVTvyHoviiM6Qsg6VQggS1zu8OVPTPRnPrU
I tried connecting pins RSTN and STDBY to ground but it made no difference.
I have no contact with the seller unfortunately(wasnt the one who made the order), so i cant get any more information about the reader. Has anyone had any luck with these specific types of readers? How else could I trouble shoot the system? Continuity tests have confirmed that there are no damaged traces on the reader board itself.
How can I get it to read/write data?


texts:
I'm quite interested in this rather simple transmitter design called the Michigan Mighty Mite, described here:

https://makerf.com/posts/mighty_simple_shortwave_transmitter

I'm familiar with resonant circuits and crystal oscillators such as these:

I know that a crystal resonator can operate in either "series" or "parallel" modes as shown in the picture above. I understand the principle behind these basic circuits: the crystal acts as a resonant filtering circuit and when a voltage is applied to it, it starts to oscillate at its resonant frequency. The oscillation is prevented from dying out because it's continuously being fed energy by the transistor amplifier.

But still I can't quite figure out how the MMM works. I'm quite confused as to whether is belong to the series or parallel class of oscillators. Here is a picture from the website:

Here it looks like the L1 and the variable capacitor form one resonant circuit,
but then there is also the crystal. I assume the crystal here is
the element that determines the frequency, so what does the
L1 and variable capacitor resonant circuit do? Also the L1 is tapped, and the tap is going into the collector of the transistor, which is also a difference to the oscillators in the above picture.

So these were my initial observations to the differences of this transmitter to simple oscillators. I tried googling but I couldn't really find sources that would explain this circuit beyond very brief overviews. I would like someone knowledgeable to explain this transmitter in greater detail. Thank you!


texts: How to remove mains hum from a BNC cable?

texts:
BNC cables are used as inputs to a data-acquisition hardware.
If long BNC cables are picking up the 50/60Hz mains hum through the air like antenna, how can I filter this? Would connecting the BNC conenctors' GNDs to the earth help? Or using a capacitor?


texts:
I know this is going to sound like a dumb question but is there a way to test a power cable?
Background: I was having issues with my 3D printer. I brought it over to a friends place and it worked fine using a 14 AWG. The power cable I was using that was causing troubles was 18 AWG. So I brought it home and replaced it with the 14 AWG power cable and it worked fine. The power cables themselves are regular PC power cables. The power cable is plugged into an APC surge protector. Some variables are -

Maybe the power supply for the printer needs a 14 AWG cable?
Maybe the cable was just went bad and it can still use an 18 AWG?

I would like to know if it is possible to (safely) test a power cable to determine if there is a fault or was made with cheap materials?


texts: Can I run a charger and inverter in parallel on solar?

texts:
Currently I have about 4.5kw in solar running to an inverter. The inverter is energy saving only, so when the grid goes out (it does frequently) I have no power. I just want to keep some basic appliances on like the network, so I don't need much. I have an idea but I'm not sure if it's possible:
The DC from the solar could go to the current inverter, but also a small 20A solar charge controller to charge two large car battery sized solar batteries.
The rest I am already pretty sure will work:

add a smaller inverter on the charge controller for when the power goes out
add an automatic power transfer that will use the wall power until the power goes out then switch to the small inverter. It will not connect to a battery charger since this will be done by the solar. (Recognizing that it won't charge the batteries at night)
if all goes well when the sun is up the small inverter will run on the solar without discharging the batteries or run on the batteries at night

Will all of this work?


texts: Find the noise figure for a receiver front end

texts:
I'm editing this question as suggested in the comments. This is indeed a homework question for an old course that I'm reviewing, and the idea is not to solve it for me, but to show me how such questions can be solved. In particular, what is the way to calculate the NF for an entire system when we have it for each sub system alone. Since I'm not sure what should be taken into account, I'm including all relevant information.
The operating frequencies of the below receiver is 1.574 GHz to 1.576 GHz, the ADC requires at least 10 dB of SNR. What is the overall noise figure of the front end?


texts: I am working on a project to detect mobile phones in a room to avoid cheating. But the airplane mode ha posed a problem. A google search told that all radiations are switched off during airplane mode. How can i detect mobile phone in airplane mode? Is there any way out? Even the faintest idea will help.


texts: i'm currently designing a device which uses GSM module. which works on 12V and if the main supply is not there, it will run on battery. right now i'm facing a problem in power supply circuit. i'm using a BLE module which works on 3.3V, the BLE module controls the GSM module switching it On and Off. the issue is the BLE module reboots every once in a while. when the BLE module reboots, the GSM module also reboots. i believe this occurs because i'm using the same supply for both GSM module and also the 3.3V regulator. it would be very helpful if some you can give me some suggestions. i have attached image of the power supply circuit


texts: Current carrying capacity of 28 AWG wire?

texts:
This SCSI cable is composed of 28 AWG twisted pairs.  According to an L-Com "tip", such a twisted pair should be able to carry at least \$3 \times 0.8=2.4\text{ A}\$ per conductor.  However, this other web site which references the Handbook of Electronic Tables and Formulas suggests that you can carry only 226 mA per conductor.  This is an order of magnitude difference!  Can anyone explain which one is correct?
The application requires the conductors to carry 1 A at 5V DC.  So the question really comes down to whether I need one pair or more than one pair.
Only one pair will be carrying this current, and 1 A is the most current I expect that pair to carry.  All other pairs will carry at most 50 mA worst case per wire, typically much less than that, and all the other pairs combined are current limited to 150 mA.


texts: MAX17205 DevName reading wrong, but other default value is correct. Why?

texts:
I am using the battery fuel guage MAX17205
through I2C bus.

The Device Name register that I read from it seems have a different value than what the datasheet states:

I am reading a 0x2a7c, but it's meant to have a LSB of 0x5.

In the Datasheet the DevName reg (21h) should be:

so for MAX17205, the LSB should be a 0x5.
however, I am reading a 0x2a7C from it.

I checked the I2C waveforms, the reading is 0x2a7c for sure.

And this is the probing on oscilloscope:

So I tried to read other registers with default value, and they all seems match the default value.

The I2C tool that I am using is working - There are a few I2C slave devices on the same bus and I can read from them all ok.

What might be the reason for this wrong reading from DevName?
Could it be a faulty one single resistor, or does it indicates that my chip has other problems too so I can't trust any data from it?


texts: Why are two transistors often used instead of one?

texts:
Many circuit designs I see with transistors use two transistors chained together instead of just using one transistor. Case in point:

This circuit is designed to allow a device with a 3.3V UART to communicate with a 5V microcontroller.

I understand that when Q2 is off, TX_TTL will be high, and when Q2 is on, TX_TTL will be low. My question is, why not run UART_TXD directly to the base of Q2 instead of using Q1 to control the base voltage of Q2?


texts: Good ways to read a 16-bit code at very short distances (~0.5cm)

texts:
I'm looking at ways to read a 16-bit code over a very short distance, through an opaque material.

The sensors might be quite close to each other (~10cm), and they'll need to read only the code that is ~0.5cm from the sensor. The form factor should be compact. The stack would be the size of a AA battery or so, being inserted into the matching socket with up-to something like 10cm x 10cm x 10cm worth of space to hold the sensor (excluding the microcontroller and other components, they can be in an adjacent space).

Currently, I'm looking at using Hall Effect sensors to read a stack of 16 washers from the side; plastic representing 0, steel representing 1. A configuration of 16 sensors could read the stack at any time, or a configuration of two sensors could potentially read the stack when it is passed by the sensors.

Another approach I'm looking at is using an inductance sensor (like the LDC1000) to measure the composition of the stack of washers.

Anyway, I'm wondering what other approaches are possible. RFID seems to be overkill and too expensive, but I am open-minded.


texts: Charging a circuit to around 10kV from 3V (two AA batteries) for discharge over 20msec

texts:
How can I design a circuit that can be charged to around 10kV (somewhere between 5 and 20kV is fine) from two AA batteries (~3V)?

I am going to draw about 20mA over a high resistance load for a short amount of time, around 20 to 50msec. It is okay if it takes the circuit a while to reach the 10kV output voltage, as to not draw too much current from the battery while charging the circuit.

When discharging, the output current will be current limited to a maximum of 20mA.


texts:
I'm working on a design  with MOSFETs and with the LT4415 device.

The MOSFETs should dissipate an average heat of 0.45 W (with peak at 2 W but just a couple of seconds with several minutes to recover).
For the LT4415, the maximum would be 1 W of dissipation (but that should be much smaller 0.2 W , I will measure it during real use, it is hard to predict for now).

I decided to have a pattern of small vias (drill 0.3 mm) on a grid of 1x1 mm2. (I talked already about it in another question.)

Now my actual question is how to choose the type of vias. I can imagine that depends how I will solder the device. For now, I think I will solder them with solder paste and hot air.

Initially, my goal was to use filled vias. I talked with the manufacturer. Like expected, the price is twice higher and that takes much longer to manufacture the board.

So I'm wondering if it is a really bad practice not to fill the vias or to have them plugged. I can understand that vias filled with copper are better for heat conduction than empty vias or vias filled with epoxy. However, does that make sense to try or that doesn't have any chance to work out ?

My guess is that vias will be filled with solder so they may have a decent heat conduction, right ?

I attached some pictures of the design (red = top layer, blue = bottom layer, the hashed area are the respective tstop and bstop layers). Feel free to comment ! Thank you in advance.


texts: Desing a PI controller for process with complex conjugate poles

texts:
I have a dual-loop control system. In the inner loop, the process is represented by a first-order transfer function. For control I use PI controller. Open loop transfer function is:
$$
G_\text{co}(s) = \underbrace{K_\text{P} \left( 1 + \frac{1}{s \ T_\text{I}} \right)} _\text{PI controller} \frac{1}{s \ \text{L}}
$$
and closed loop transfer function
$$
G_\text{cc}(s) = \frac{G_\text{co}(s)}{1 + G_\text{co}(s)} = ... = \frac{s \ T_\text{I}+1}{s^2 \ \text{L} T_\text{I}/K_\text{P} + s \ T_\text{I} + 1}
$$
Using a characteristic polynomial of the normalised second-order system, I define relative damping (overshoot) and undamped natural frequency to get PI controller parameters. I add pre-filter to eliminate zeros. Input loop transfer function final form is:
$$
G_\text{cc1}(s) = \frac{1}{s^2 \ \text{L} T_\text{I}/K_\text{P} + s \ T_\text{I} + 1}
$$

For the outer loop, I am using again PI controller. Poles are complex conjugate (\$-1.5708\pm 1.5708i\$) and I don't know how to continue...

All the examples I could find on-line deal with systems with real time constants. For example, symmetrical optimum (SO) and technical optimum (TO) methods are based on separating dominant time constant and fast time constants and calculating \$K_\text{P}\$ and \$K_\text{I}\$. I don't have two different time constants. I cannot even approximate \$G_{\text{cc1}}\$ with the first-order function and apply characteristic polynomial of the normalised second-order system. This could be a way forward, but I am not sure how to approximate the function with complex conjugate poles?!

Some methods propose using root locus approach to design controller parameters. I have not looked into it or tried it because I would like to use numerical methods and understand them first.


texts: Is this alternator W RPM input circuit ok and how can I improve it?

texts:
I need a robust and reliable way of taking a RPM signal from the W terminal of a standard automotive alternator. Most of the time the signal will come from a 12V alternator but there is a requirement for it to be compatible with 24V (28v when charging).

Here is what the signal looks like straight from the alternator:

I have used this circuit to convert it into a 3.3V DC signal:

and I then get this signal at the same RPM:

so far so good but when I triple the RPM a lot of noise is introduced like this:

the time in-between the lines here is around 928µS.

(Update) The noise however seems to be introduced at the input as this is the waveform from the alternators W output at the same speed:

I have added a 10K resistor at the output to the MCU and the output waveform now looks like this:

Red is without the resistor, blue is with.

So my questions are:

Is the noise in the last picture a problem, if so how do I get rid of it?

Is this signal (with or without the noise) suitable and reliable to feed into a MCU to read RPM?

How can I improve the circuit to make it reliable and robust for production grade products?

Starting from scratch what would be the most reliable circuit?


texts: Is the thermostat in a room heater meant for room temperature control or for heater protection?

texts:
I've an Intermatic Heatwave 1500W heater with me.The heater has 3 modes of operation: FAN, WARM(746W) & HOT(1490W).

The heater functions pretty normal in both FAN and WARM mode. But the moment I switch to HOT mode the heater activates the thermostat and turns off quickly and turns back ON after 30 secs or so.

My room temp is like 70F, in WARM mode the temp rose to 128F and in HOT mode it varied in two runs between 142F to 155F before the thermostat activates. The thermostat is a simple bimetallic one placed just behind the grill/ in front of the coil(white square shaped stuff with two wires as shown in picture).

While I could run in WARM mode, but as it becomes very cold in morning the WARM mode isn't sufficient. Does shorting the thermostat cause any issues? I plan to do this only if the response is " its just for room temperature control only".


texts: How to test conductivity of copper wire?

texts: I purchased 90 meters of 0.35mm2 stranded copper conductor wire. How can I test this wire for conductivity to ensure quality copper was used?


texts: What is the meaning of Microchip's acronym TRIS for data direction registers?

texts:
When reading/writing/talking about electronics, I like to understand the acronyms and mneumonics for abbreviations used for registers, functions, filenames, pin names, etc.  Usually, the first time the abbreviation is used, either the context or a parenthetical note sets it off, or it's blatantly obvious.

On the Microchip dsPIC parts, the TRIS register controls the data direction. I can't find a note which uses the full word/phrase that would be abbreviated or have the acronym TRIS. ('The Register Input/output Settting' is about the best I can come up with, although 'TRIS Really Is a Silly abbreviation' is a close second guess).

How do you remember this?  I've heard it pronounced as a word, but I'd like to know what it means to make it easier to remember, read, and write.


texts:
When I was about 10 years old playing with lamps, I accidentally picked up a wire completing a circuit for a lamp plugged into the wall (120 V AC U.S. standard). I'm not sure if it was the hot or neutral wire, but I had completed the wire from hand to hand. I had a shock and dropped the wire in slightly less than a second.

According to what I see online, which says milliamps can kill me, how did I survive for this long, with no burns or negative health effects? I remember immediately running up to my mother and saying I just got shocked by a house socket with a big grin on my face! (she was not happy!)


texts: I have been reading quite a lot on the subject in the past hour and I don't seem to be getting an answer, just about amps. I have a 2 watt rated ball valve, and I have a 12v dc 1 amp power supply. W = a * V. So 12 watts power supply? Would it burn out the ball valve?


texts: Why does cmos inverter consume power while discharging load capacitance?

texts: Consider a simple CMOS inverter. To calculate the switching power dissipation, we consider the case when capacitor is charged till by pmos as the current is drained from Vdd. But when it is being discharged by nmos the power supply is cut off from circuit the current simply goes to the ground. Since Vdd is not involved, so is nmos even dissipating power?


texts: Driving a 4.5V motor with PWM from an Arduino

texts:
This is a basic question but I would appreciate help.  I have:

An Arduino
A 4.5V DC motor
Various transistors, like BC337, 2N7000, 2N2222A

What I'm trying to do is very simple: control the motor with the Arduino.  I want to control it with PWM, so I can change the speed.

This is what I tried:

Connect the motor between my 5V power supply (a 500 watt PC power supply) and transistor collector (with protection diode); connect PWM pin of the Arduino to the transistor base, with a 1Kohm resistor; connect the transistor emitter to ground.

The motor doesn't spin, it just makes a little noise!  If I connect the motor direct to the power supply it spins.

What might I be doing wrong?


texts: What is the general operating principle of an AC Electronic Load?

texts:
I'm working my way through electromagnetics and in particular power (line) transformers at the moment. I'd like to be able to run tests of various kinds at different AC loads and possibly at different frequencies, say 10Hz-10kHz, to observe frequency response of cores and so on. It would need to emulate a resistive load, so for example 10A when the sine wave was at 10V and 1A when it was at 1V.

I'm pretty familiar with DC Electronic loads and designed and built one for myself that performs nicely for my needs. Details in this question for anyone interested in that.

I was inclined to do something along the same lines for an AC load. Unfortunately that doesn't seem to be a popular project and I'm finding a dearth as regards circuit ideas, general approaches, etc. The simplistic solutions like rectify to DC and then attach a DC load don't emulate a resistive load, you get current spikes of course at the top and bottom of the sinusoidal waveform and then dead zones in-between.

The best I've been able to come up with in the DIY department is to run an incandescent or heater load (hair dryer, iron, etc.) off of a Variac, which would actually probably work fairly well; but I was kind of hoping for an all-electronic solution, dissipating the load in MOSFETs or something like that.

I was able to find a commercial solution, this is one example:

http://adaptivepower.com/English/Products/AC-DC-Loads/3A-Series.aspx

There is no price quoted, nor is there for the others I found, so I'm taking that to mean: "If you have to ask, you can't afford it." :) Which is probably right. I'm not looking to spend thousands here, just get something decent that works, maybe make a nice project out of it.

Can anyone explain in broad terms how this sort of thing works?

I'm inclined to think it probably tracks the input voltage and somehow does the proportioning to track the right current value to the instantaneous voltage value of the sine wave (or perhaps other waveform too). Then from there perhaps it looks similar to a DC load, perhaps doubled, one for each "polarity" of the cycle. Maybe a peak detector that determines the peak voltage and then a variable amp that modulates the current regulating signal to follow the curve or something like that?


texts:
I recently ordered a custom transformer and under load with half of its rated current it heats up to 55 °C, and now it's started to radiate a "weez" noise.
Is this normal? How hot is too hot for a transformer?
How can I get rid of the noise? Pushing it down doesn't help!
Update: the iron core was loose (or wasn't tight enough), I returned the transformer to be fixed with a new core.


texts: I'm working on a Lattice board and I'm want to to use IP cores for my project. I have a license to a third party IP core but I have no idea how to integrate the IP  to my project. My research shows me that the info available online is specific to different design tools and I haven't found one for Lattice Diamond. My question is, are different IP cores implemented differently or is there a general method to do so?


texts: Schottky diode equivalence in RF wattmeter?

texts:
I think I may have fried D1 in the circuit below, if that seems plausible? (During my initial testing, with up to 15W of input power, I had an open circuit after R4. I really don't understand how this circuit works but I figure if half of it was missing the other half could have felt some pain.)

Testing D1 still in circuit, I do measure a 0.321V drop in the forward direction however I also measure 2.209V in the reverse direction — this seems unexpected. The other diode, D2 measures 0.320V forward and OL in reverse. So I think I should replace D1.

The problem is I'm not sure what I can replace CDSH270 with. Digikey does not find results for it; Mouser says it is discontinued with 1N276 BK as a "possible replacement" — it is also a non-stock part afaict. Even if I could track some down, how likely is it to work? On what basis would I make that call? They have the same forward voltage drop, but e.g. the replacement has only 40mA maximum forward surge current instead of 0.75A (!?).

Also, I have on hand some 1N5711 Schottky diodes. They certainly seem even more different in specs, but again I'm wondering if use as an RF power detector in the <30MHz range is all that picky?

Basically I'm looking for a pair of easily attainable replacement diodes for this circuit. This is in a recently-purchased kit, and I'm worried that if there was a more affordable component they'd have used it instead :-(


texts: LTSpice showing negative transistor power

texts:
I'm using LTSpice to model a LC oscillator, driven by a NPN transistor. When I used the power calculating function on the transistor, LTSpice indicated that during part of the cycle the power dissipated in the transistor is negative. I was under the impression that transistors always dissipate power resistively since they don't store energy in E or B fields.

So my question is, what am I to make of this? Should I take the absolute value or something?

EDIT: As requested, here's the asc file: http://pastebin.com/F1wBPXVy


texts:
I have 4 wires 10AWG stranded, that I need to connect to a PCB that I'm designing. They will be in a high vibration environment, so direct through hole soldering may not be the best solution.

I've thought about ferrules, but those are usually used with screw terminals, which are also not ideal for high vibration env.
I've also thought about crimping the ferrule onto the wire and then soldering the ferrules to the PCB, but I can't find any information on that idea, good or bad.

What other options are there?


texts: Routing one UART Tx output to multiple UART Rx using MOSFET

texts:
I have a very cost effective MCU that only contains one UART which can only be mapped to one set of pins. I am not willing to change the MCU choice. I also do not need to use the Rx on that MCU.

I was hoping to use the UART and a GPIO to send that Tx signal to multiple devices. This is a single input multiple output situation.

There are a few ways I can think of doing this so I'll list them out here:

Use two MOSFETs and two GPIOs to control them. I can't think of how to use one GPIO with two MOSFETs but this is the preferred solution.
Use a 2-1 MUX with the 1 connected to UART Tx. My hesitation is that for some reason I think the 2-1 will stop signals from flowing backward?

If anyone has advice I would appreciate it.


texts:
I have encountered a problem that I am unsure how to solve.
As shown in the image at the bottom of the question, I have an FPGA (Nexys A7-100T) that generates signal to run a motor connected to a L298N motor driver. The FPGA signals are forward, reverse and a 20kHz PWM signal. However as the FPGA outputs are 3.3V max and the L298N requires 5V inputs, I have used a BSS138 bi-directional FET level shifter board.
This system works perfect without the PWM signal connected to the BSS138. When the enable jumper is in the L298N and the forward or reverse input is high, the motor runs at full speed.
But when I try to use the PWM signal through the BSS138 to the L298N, all the 5V outputs sit at the same voltage as the PWM channel, which is around 2.5v (The PWM signal has a 50% duty cycle).
Is this BSS138 not suitable for PWM signals?
Or what is my mistake here?

EDIT 1
Below is an image of the BSS138 level shifter board used:

EDIT 2
Below is an image of the L298N board used:


texts: If I wanted to simulate keypresses over a phone line, could I just play dial tones?

texts:
I'm trying to put together an API that deals with the annoyance of minutes of pressing keys to connect with a person. "For spanish, press 4. For billing, press 1. For..."

Unfortunately, it would seem most programmable phone services won't do dial tones. But many will play mp3's for hold music. If I just made an MP3 containing the desired dial tone and played it over the line, would the other end register that as a keypress? How accurate would it have to be?


texts: VHDL does not have built in capability to read binary files, do Verilog and SystemVerilog have it?

texts: Reading and writing binary files in VHDL is not straightforward, I am not sure why this is so. I think that Verilog and SystemVerilog are more closer to C. Do they have built in capability to read/write binary files? I would expect SystemVerilog to have it since it is a high level language intended for verification. However, I am not sure about Verilog at all.


texts: Question regarding GM Tubes Calibration Frequency

texts:
My friend has has been using  GM Tubes for more than a decade now. He has been calibrating them once per year. But the calibration data reveals that his GM Tubes  would have remained within allowed error range even if he had never calibrated them after the first calibration.
Can I use this operaring experience to calibrate my GM Tubes (same manufacturer, same type, same working environment) after a decade?

I know that calibration frequency is:

Recommended by manufacturer.
Adopted by end user based on his own experience, as they might have different operating environment.

What is the correct method of defining calibration frequency without risking safety as well as keeping in view economic considerations?


texts: Can someone explain me the role of MOSFET in this circuit ? Are these MOSFET working as a switch here?

texts:
This Image is taken from the PIC16(L)F15356/75/76/85/86 MCU datasheet

datasheet- go to page number 286 for more details


texts: Discrepancy between RTL schematic and Behavioral simulation in Vivado

texts:
I'm having a strange issue with a simple Vivado (2015.3) VHDL simulation.

This code:

library ieee;
use ieee.std_logic_1164.all;

entity pulse is
    port (
        d   : in  std_logic;
        clk : in  std_logic;
        q   : out std_logic );
end pulse;

architecture Behavioral of pulse is
    signal ff0 : std_logic := '0';
    signal ff1 : std_logic := '0';
begin
    process (clk, ff0, ff1)
    begin
        if rising_edge(clk) then
            ff0 <= d;
            ff1 <= ff0;
        end if;
        q <= ff0 and not ff1;
    end process;
end Behavioral;

produces this RTL schematic:

The purpose is just to take an input pulse d, which may have a duration of multiple clock cycles, and output a single-cycle pulse q. Very basic. The simulation looks like this:

If I change the code to only use process variables instead, the simulation fails:

(note: the code below is terrible practice. It is not something I do operationally, nor something I recommend. Having two if rising_edge(clk) clauses in a single process is just something I stumbled upon - and now I am trying to understand its implications, and why it creates a contradiction between the results of the behavioral simulation and the actual synthesis.)

library ieee;
use ieee.std_logic_1164.all;

entity pulse is
    port (
        d   : in  std_logic;
        clk : in  std_logic;
        q   : out std_logic );
end pulse;

architecture Behavioral of pulse is
begin
    process (clk)
        variable ff0 : std_logic := '0';
        variable ff1 : std_logic := '0';
    begin
        if rising_edge(clk) then
            ff0 := d;
        end if;
        if rising_edge(clk) then
            ff1 := ff0;
        end if;
        q <= ff0 and not ff1;
    end process;
end Behavioral;

In the variable architecture, the variables are converted to signals since they are in separate clock condition clauses. So, the two implementations should literally be the same.

The pre-synthesis RTL schematics of both architectures are identical (as produced by Vivado, and shown above), so unless I am missing something simple, the simulations should be as well.

edit 1:

The post-synthesis schematics of both architectures are also identical. They both look like this:

edit 2:
I have confirmed that "Post-Synthesis Functional Simulations" produce identical results for both architectures.

For "Behavioral Simulations" (i.e. simulation before synthesis), my question still stands.

For completeness, here is the simulation code:

library ieee;
use ieee.std_logic_1164.all;

library UNISIM;
use UNISIM.VComponents.all;

entity pulse_sim is
end pulse_sim;

architecture Behavioral of pulse_sim is

    -- Sim component
    component pulse is
    port (
        d   : in  std_logic;
        clk : in  std_logic;
        q   : out std_logic );
    end component;

    -- Test signals
    signal d   : std_logic := '0';
    signal clk : std_logic := '1';
    signal q   : std_logic := '0';

    -- Clock constants
    constant PERIOD : time := 10 ns;  -- 100 MHz

begin

    -- DUT instance
    UUT: pulse
    port map (
        d   => d,
        clk => clk,
        q   => q );

    -- run clock
    clk <= not clk after PERIOD/2;

    -- test process
    process
    begin
        d <= '1' after 30 ns,
             '0' after 80 ns,
             '1' after 120 ns,
             '0' after 150 ns;
        wait;
    end process;

end Behavioral;


texts: Automatic switch between parallel and series connections

texts:
I need advice if it is possible to replace switches ( see drawings ) with suitable transistors and other parts.

Requirements:

Base leg voltage to "open" transistor ~0.2 - 0.3 Volts.
Transistor remains "open" until base leg voltage drops to less then 0.1 Volt.
OR duration for "open" position of transistors 5-10 seconds to allow maximum energy transfer from C1 and C2 to C3.
Amperage levels on all stages are 0-2 Ampers.

Purpose of this device is to "upgrade" energy available from very low-level sources to more useful levels.
I tried many different kinds of DC to DC up-converters. Some of them are really well made and do great job.

But all of them have very low efficiency levels (10 - 40 % ) and if more higher level of upgrade requested ( for example from 0.1 Volt to 5 volts ) lower is efficiency. Multitude of experiments show that supercapacitors ( directly connected to the source ) do much better job. Circuit on the drawing works, but need constant human intervention. I think automation of this process is possible.

My knowledge and practical experience in Electronics are very poor.
Please, help with selection of components needed for this unit from existing marketplace.


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Is this a series resitance at the IC input limiting the input current?


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My signal is between 1 and 2 GhZ.

How should I choose the value of this inductor ?
1µH is enough ??

What are the other parameters to take care about ?


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texts:
This project is on my boat which has 3 Group 27, 12V batteries in series which is my house power source.

I want to power approx. 510 LED lights from my 12V house batteries.  The lights are taken from several string lights originally part of a system consisting of approx. 100 lights powered by a rechargeable 3.2V 300mAh battery and a small solar panel.  I intend to discard the batteries and solar panels and connect these strings together to form 1 string.

My thought was to use a DC-DC Converter 12V to 3.3V, 3A max step down voltage regulator transformer (DROK 090601).

I am not an electrical engineer and am looking for concurrence or guidance on a workable design.

Thank you in advance for any advise offered.