texts: Stellaris Launchpad: UART over GPIO PIN in ASM

texts:
I want to initialize and use UART on my LM4F120 Stellaris Launchpad in ASM. I found a reference code on how to to this on this site.

This works fine, however it initializes and uses UART0 (which is emulated over USB). I need to employ UART using the PIN headers. Thus, I want to use UART1 over PC0 (Rx) / PC1(Tx) following the convention in table 2-3 form this manual:

Basically, I changed the constant values to:

NVIC_EN0_INT5      EQU 0x00000020   ; Interrupt 5 enable
NVIC_EN0_R         EQU 0xE000E100   ; IRQ 0 to 31 Set Enable Register
NVIC_PRI1_R        EQU 0xE000E404   ; IRQ 4 to 7 Priority Register
GPIO_PORTB_AFSEL_R EQU 0x40005420
GPIO_PORTB_DEN_R   EQU 0x4000551C
GPIO_PORTB_AMSEL_R EQU 0x40005528
GPIO_PORTB_PCTL_R  EQU 0x4000552C
UART1_DR_R         EQU 0x4000D000
UART1_FR_R         EQU 0x4000D018
UART1_IBRD_R       EQU 0x4000D024
UART1_FBRD_R       EQU 0x4000D028
UART1_LCRH_R       EQU 0x4000D02C
UART1_CTL_R        EQU 0x4000D030
UART1_IFLS_R       EQU 0x4000D034
UART1_IM_R         EQU 0x4000D038
UART1_RIS_R        EQU 0x4000D03C
UART1_ICR_R        EQU 0x4000D044
UART_FR_RXFF       EQU 0x00000040   ; UART Receive FIFO Full
UART_FR_TXFF       EQU 0x00000020   ; UART Transmit FIFO Full
UART_FR_RXFE       EQU 0x00000010   ; UART Receive FIFO Empty
UART_LCRH_WLEN_8   EQU 0x00000060   ; 8 bit word length
UART_LCRH_FEN      EQU 0x00000010   ; UART Enable FIFOs
UART_CTL_UARTEN    EQU 0x00000001   ; UART Enable
UART_IFLS_RX1_8    EQU 0x00000000   ; RX FIFO >= 1/8 full
UART_IFLS_TX1_8    EQU 0x00000000   ; TX FIFO <= 1/8 full
UART_IM_RTIM       EQU 0x00000040   ; UART Receive Time-Out Interrupt
                                    ; Mask
UART_IM_TXIM       EQU 0x00000020   ; UART Transmit Interrupt Mask
UART_IM_RXIM       EQU 0x00000010   ; UART Receive Interrupt Mask
UART_RIS_RTRIS     EQU 0x00000040   ; UART Receive Time-Out Raw
                                    ; Interrupt Status
UART_RIS_TXRIS     EQU 0x00000020   ; UART Transmit Raw Interrupt
                                    ; Status
UART_RIS_RXRIS     EQU 0x00000010   ; UART Receive Raw Interrupt
                                    ; Status
UART_ICR_RTIC      EQU 0x00000040   ; Receive Time-Out Interrupt Clear
UART_ICR_TXIC      EQU 0x00000020   ; Transmit Interrupt Clear
UART_ICR_RXIC      EQU 0x00000010   ; Receive Interrupt Clear
SYSCTL_RCGC1_R     EQU 0x400FE104
SYSCTL_RCGC2_R     EQU 0x400FE108
SYSCTL_RCGC1_UART1 EQU 0x00000002   ; UART1 Clock Gating Control
SYSCTL_RCGC2_GPIOA EQU 0x00000002   ; port A Clock Gating Control

However, I can not receive any characters on the virtual com port. Do you see any mistakes in the code?


texts: What to study after discrete bjt amplifiers?

texts:
I am a novice interested in learning amplifier design for audio projects.  I can design simple "elementary" amplifiers such as CE, CB, and CC and can make them work with desired impedances, good biasing, and properly-sized coupling capacitors.  I am good with basics like Ohms Law, KVL/KCL, and can do simple analysis of discrete bjt circuits.  I have probably a basic understanding of transistor models like hybrid-pi.
I'd like to get to the point where I can design more useful circuits with multiple stages that would actually work to drive real-life speakers, but have struggled to find a good source.
I don't know what I'm missing, but when I look online for information on combining stages, power amplifiers, class AB amplifiers and the like it's clear that there are gaps in my knowledge.
What is the next thing I need to learn about?  And, perhaps more importantly, can you suggest a book that might meet me at my level?


texts: PCB-less prototyping with surface mount components (like DFN)

texts:
I'm expecting some interesting comments and answers on this one, mainly because I'm probably just insane for even considering / asking this.

One component I want to prototype with is the MCP73123 LiFePO4 battery management IC.  The problem is that it doesn't come in anything but the DFN package, which is insanely small and has very small contacts.

I couldn't find any posts here, and I only found one almost-useful link online that talks about prototyping with DFN components.  The problem is, it assumes that it's an option to design a PCB for prototyping.

Now I realize that it's expected that someone would create a PCB, but I just wanted to test out the IC first to see how it works.  So I figured, why not try to fly some 30AWG wires off of the chip and test it that way!  Well, even though I seem to be able to solder the wires down, they just pop right off with the slightest tug.

It looks like my first Eagle project is going to be a PCB for this particular chip (and then I still have to deal with soldering it properly, so any tips or DFN-specific PCB layout tips here are welcome), but if anyone out there has done this successfully, please provide an answer that outlines ways to do it properly.  And if it's just downright impossible, I can accept that as well.  :)

EDIT -- so far, I have ruined two ICs trying to solder them to a PCB.  :)  I received my adapters from Proto-Advantage today... would everyone recommend Chip Quik and a hot air rework station to attach the IC?


texts:
Wikipedia’s definition of DIMM says:

Most DIMMs are built using "×4" ("by four") or "×8" ("by eight") memory chips with nine chips per side; "×4" and "×8" refer to the data width of the DRAM chips in bits.

So if DRAM chips have 8 bit data width why DIMM has 64 bit data width? I mean doesn’t memory controller issue read or write request to one DRAM chip at a time? If it does what is the purpose of other 56 bits?


texts:
Connecting passive low pass filters in series and with a load, reduces the dc voltage.
Maybe it is very simple but would you explain a little bit to me about the low pass filter's effects on dc.
Filters don't reduce dc without a load by the way.

Source 12VDC(with little ripple)
Load 20 Ohm.

Filter section(RC lowpass passive)

If i take the output of the first filter,

500 Ohm 1mF (cutoff around 0.3Hz)---Out ~7VDC---

If i take the output of the second filter also current draw reduces a lot.

500 Ohm 1mF ---Out ~0.20VDC--- etc.

Thank you.


texts: Is there a right way of implementing a T flip flop in verilog wrt using reset signal?

texts:
I made a t flip flop using structural modeling in verilog.

module Tflip(input T,input clk,output Q,output Qbar) ;
wire S,R;
and(R,Qbar,T,clk);
and(S,Q,T,clk);
SRLatch srt(S,R,Q,Qbar);
endmodule

module SRLatch(input S,input R, output Q, output Qbar);
nand(Q,R,Qbar);
nand(Qbar,S,Q);
endmodule

And then I tried to make T flip-flop in behavioural modelling. It took me ages to find a neat way to initialise the flip-flop.The below code works great. Is it always required to use a reset of some kind ? Would that make the structural code above wrong?

module T_FF(input T,input rst,input clk,output reg Q);

always@(posedge clk)
begin
if (rst == 1)
Q <= 0;
else if (T)
Q <= !Q;
end
endmodule

I tried to implement a version without a reset signal, but it would only work if the test bench started off a certain way.

Every diagram of T flip-flop i looked for did not show a reset signal, so it took me a lot of time to even understand a reset input was required. It feels like structural modelling a foolproof way of creating things.


texts: How to figure the wiring of a 4 cable pc fan without frying it?

texts:
I have a 2 spare PC Fans which come with a four cable wiring and I would like to reuse them as ordinary fans (running at full speed all the time) outside a PC box, powered by a 12v source.

Unfortunately the wires have all the same color, so there is no way of guessing what is what. Is there a way I can "measure out" (using a multimeter) the correct connections?

Update: Thanks to the comments I figured out where plus and minus is and the fan is running. But although I can't be sure, to me it seems that it is not running at full speed. What would I have to feed into the remaining two cables to have it run at max power?

And I forgot to mention, that I am a beginner in this field.


texts: 2n7000 used for inductively coupled load modulation apparently latched

texts:
So I've got a fairly basic circuit set up for load modulation of an inductively coupled circuit:

A few notes on the above: LC's were designed for 1 MHz but work better at 950 kHz, thus the chosen frequency. C8 is ~2.7 nF, rectifier caps are 10 nF, noise cap (farthest right) is 10 uF. The load is a couple of regulator and oscillator IC's. Diodes are 1n4148's, NMOSFET is 2n7000. I've got a question mark drawn for the gate input since I've basically just measured a reduced amplitude version of my current Vds signal there whereas it should be zero (the output of an LTC6990 when its power is too low to turn on), so that's a bit confusing.

I'm transmitting across a ~30 Vpp sine wave from a Class E amplifier that isn't well tuned but it appears to be sufficient. The problem is essentially this: with the MOSFET removed, my inductive link is excellent (nearly 1:1 waveform shapes and amplitudes transmit across) and all my IC's turn on and do their jobs (regulators, op-amps, and the modulation oscillator work great)...

Yellow channel: Vin on Tx side. Blue channel: output of oscillator on Rx side, which goes to MOSFET gate.

...but with the 2n7000 installed I get an odd "rectification" and significant reduction in amplitude (down to ~1.6 V). You can see this in the waveforms below:

Yellow channel: Vin on Tx side. Blue channel: Vin on Rx side (or across C8, or Vds, all are the same nodes).

I thought maybe there was self turn-on occurring so I tried some caps between the gate and source (470 pF and then 1.5 nF) but there was no change. The FET does appear to be on most of the time (with the exception of the 200-300 ns where voltage can actually rise across C8), and I'm sure some of this is due to Vgs surpassing Vt when the source side is going negative but the voltage doesn't seem exactly right (datasheet for 2n7000 says Vt can be as high as 3 V but should be more like 0.8 V). The time constant of the Vin rise/fall suggests the ripple tracks more with the transmitted flux than with any kind of RC-induced decay.

I have also pulled the 2n7000 off, replaced it with a new one, and gotten the same behavior; I also tested the one I pulled off with a simple LED test circuit and it still works.

As a note, I have seen a circuit in this configuration (layout and IC selection) work, with slightly different LC's a cap values.

Any thoughts here would be greatly appreciated, feeling like I'm missing something very basic.

Edit:

Forgot to clarify what I was expecting (and how the previous iteration of this circuit worked). The Rx should like something this at the drain node:

That shows up back in the Tx due to load modulation, then I filter it and measure the modulation frequency. Ignore the numbers in the simulation, intention is just the basic layout.

Edit #2

Based on Russell and Bruce's suggestions, I attempted to make use of two series FETs in the configuration shown here:

You'll note that I left the 3.3 V oscillation since I can't do anything about that at the moment (working from a PCB and limited components so can't change regulators right now). I did include the series resistances Bruce mentioned (LTSpice doesn't show the coil series R but I did add it).

I now get a clean waveform across the Crx:

This is more than enough to turn on all my regulators and IC's and I see proper supply rails.

However, I'm back to seeing a modified Vin (Vds) at the node where the oscillator output joins the two gates:

I can tell that this isn't the oscillator output because it's the same frequency as the input AC (oscillator isn't configured for that frequency range) and the amplitude is too low (should be GND to V+, which is 3.3V).

For experimentation's sake, I tried two more things: connecting the node between the two source pins to GND (didn't change anything) and also just connecting the LTC output directly to the top of Crx (could see the modulation on the Rx side now but the load change was too minimal to be seen back on the Tx coil).

Next I'll try cutting the trace on the source side and placing a series FET there, as suggested below.


texts: Testing electrolytic capacitors from washing machine

texts:
I've removed and tested a 560uF 500V capacitor and my UNI-T 210E says it's 500 mF? Now I may be a newbie but I know m is bigger than micro!
So is this capacitor faulty and this reading is an artefact of the way the meter tries to measure capacitance?
Am I doing something wrong or will this meter simply not measure this sort of capacitor accurately? I don't have any new capacitors to test the meter on maybe that's the next step?


texts: What should I know if I want to move from microcontrollers to microprocessors?

texts:
I'm familiar with using microcontrollers, both with frameworks like Arduino and natively (PIC / AVR). I'm also familiar with the general architecture of embedded systems, in so much as I know you have a processor with discrete RAM and ROM/flash connected via various buses. However, I've never really built a project from the ground up using a microprocessor.

What should I know before moving on to microprocessor-based projects? For example, on a microcontroller, I'm used to just sending some code through my compiler and getting a binary that can be uploaded via ISP or similar - how does this work with a processor with discrete flash? And what about clock sources - do processors normally come with an internal clock like MCUs do? I'm sure there are plenty of "unknown unknowns" too - where should I look to get started?

I'm primarily interested in ARM and x86 platforms, but general advice would also be useful.


texts:
I am working with the I2S audio protocol in one of my projects and I'd like to use it in one of my final projects for a class of mine.  Quite honestly though, I don't entirely understand the MCLK line.  You'd think, "Oh that just stands for Master Clock" and you might be right but since everything has to do with audio and sampling rates, I get confused.

I'm using the CS42436 in software mode: in short it takes in 3 signals (that I'm questioning).

MCLK - Master Clock (Input) - Clock source for the delta-sigma modulators and digital filters.

SCLK - Serial Clock (Input) - Serial clock for the serial audio interface. Input frequency must be 256 x Fs

FS - Frame Sync (Input) - Signals the start of a new TDM frame in the TDM digital interface format.

Can somebody explain how to use these clock signals in reference to this picture?

I know the middle signal is the serial clock, but the other two I don't understand at all.


texts: Can a 10% resistor be used as a 1% resistor?

texts:
If my schematic calls for a 1% resistor, can I use a 10% resistor that measures to the correct resistance within 1% or is there some quality to tolerance beyond what it measures Ohm-wise?

For example, my schematic calls for a 1% 1000-Ohm resistor. I have a 1000-Ohm resistor with a silver band (10%). I measure the resistor using an Ohm-meter and it reads 1008 Ohms which is within 1% of 1000. Can I use the resistor and meet the designer's intent?


texts: Can a general-purpose AA charger be used for rechargeable AA lithium-ion batteries?

texts:
I recently learned that rechargeable lithium-ion AA batteries, 1.5VDC 3200mAh, have become available.  For instance:
https://www.amazon.com/EBL-USB-Rechargeable-Lithium-Batteries/dp/B0828KRQZ3
https://www.google.com/shopping/product/13543601031434520708
Can a charger supporting >3V Li-Ion and 1.2V NiMH batteries, be used for these? And if not, what would be the necessary technical changes?


texts:
when selecting continuity test, starts continuous beeping sound even with test leads removed. Also there is battery sign on display and no zero when it turns on.
I used it to check voltage of mosquito racket. It was beyond given rang since then its not working.
I checked circuit if it is burn some where but I did not found any thing specious.


texts: Looking for information or spec sheet on an old PROM/EPROM chip

texts:
A week or so ago I received in the mail a lot of Game Boy prototypes.  The seller threw in a "bonus" which happened to be a small box containing the following E/PROM chips, which are not for Game Boy games.

As you can see, HN27256G-25 is imprinted on these chips.  I've searched the internet but I can't find any information on them regarding size or read speed.

For more details on these chips, "One - on - One" was a Nintendo game that was released in 1988.  The original game was 128k in size and, I've been told, was small enough to fit on one typical development EPROM, so four wouldn't have been needed.  I'm curious why this game is on 4x chips rather than just one and the dates are also later than the final release, leaving me to speculate that that this is either an updated version of the software, or this was work on a port of the game to a new system or, possibly, to an arcade cabinet.  I wonder if this is specifically for an arcade version because "Rare Coin-It, Inc." was company that also specialized in porting arcade games to household console systems and vice-versa.

My end goal/hope is to get the details on these chips so that I can properly get the data dumped but so far I've had no luck finding information on these old chips.  Any information would be helpful.  Thank you guys.


texts:
I am a beginner with embedded programming and am using the IAR workbench for a project of mine using STM32F4Discovery. I am trying to compile an existing code and have a few errors at  a few places regarding the bit definitions like the following:

Error[Pe020]: identifier "GPIO_PIN_SET" is undefined

Error[Pe020]: identifier "DMA1_Stream6_IRQHandler" is undefined

I have around 100 such errors. The GPIO_PIN_SET is defined in the file stm32f4xx_gpio_hal.h and is already included in my project. In order to resolve this issue when I looked up online, I have found this solution. However, I don't have the System  tab in the General Options in my IAR Workbench. I have a full version of IAR Workbench and am not sure why the System tab is missing.

I also tried defining

#define ENABLE_BIT_DEFINITIONS

as stated in this link in my main.c file but to no avail.

Trying to set

#define STM32F4XX
#define USE_STDPERIPH_DRIVER

in the main.c file or defining the symbols STM32F4XX, USE_STDPERIPH_DRIVER in the Preprocessor tab in General Options as mentioned here also didn't help.

The solution could be very simple that I am probably overlooking but am not able to figure out what could I be missing. Any help would be appreciated


texts:
Suppose we have this circuit:

simulate this circuit – Schematic created using CircuitLab
According to the dot notation rule the current :The convention is that current entering a transformer at the end of a winding marked with a dot, will tend to produce current exiting other windings at their dotted ends.
If the windings werent coupled to each other we would have these 2 equations for currents:
I1 = If1(1-e^(-R1t/L1))  = VCC/R1(1-e^(-R1t/L1))
I2 = If2(1-e^(-R2t/L2))  = VCC/R2(1-e^(-R2t/L2))
but now there are coupled and there is a term M(dI2/dt).Which is the equation of current for that term?


texts: Can I use an amp before my voltage regulator to ensure I get 5v?

texts:
I have a 4.8v battery pack and I made a simple power supply with a L7805CV voltage regulator, which has a 2v dropout. So I'm only getting like 3.5v out. Is it possible to throw an op-amp or something like that before the voltage regulator to make sure I get at least the 7v I need to achieve 5v on vout?

If not, what is best practice?


texts:
I am using IRFZ44N for supplying current to the RGB LED strip. The current that is supplied by the three MOSFETs for the three corresponding colors  (R-G-B) is not uniform and much less than required for illuminating efficiently. Is there any other MOSFET that can supply more current? Or should I change the power source?

I am using 12V 1 Amp adapter as a power source.

Here's the schematic of what I am trying to make


texts:
I was testing something with an op-amp (TLC272CD) and multiple op-amps got destroyed. There's a short circuit between VDD and GND now.

I found out that the board I was testing it on had a loose contact to ground.
I'm using the exact same wiring as with the first tests and it's all working fine now, so I can be 100% sure the op amps got destroyed because of the loose contact to ground.

Now I'm wondering why the TLC272 gets destroyed when it's missing a ground.

Would be nice if someone could help me as im really new to this.

Datasheet to TLC.

The ground of the power supply had a loose contact.

Circuit of TLC. The second part of the op-amp had resistors with the same values too. It's just not added in the schematic.


texts: Why does an opamp buffer output voltage with no input?

texts: I have an opamp (specifically a TL072) I'd like to use as a high impedance buffer for a digital filter circuit I'm building. When I power the opamp with +5/0 on the rails configured as a unity gain buffer - with nothing connected to V_in, V_out = 1.4V~. Even if I model this in circuitjs, I'm almost seeing exactly the same behaviour - so what am I missing? Where does this floating voltage feedback voltage come from?


texts: What does Computer-in-the-loop or CIL mean related to embedded systems

texts: Im trying to learn more about embedded systems. During some of my research I have come across references to CIL or HWIL (apparently Computer-In-Loop or Hardware-In-Loop). I have not found much of an explanation in terms of CIL. Could someone elaborate a bit more on what this typically references? Is it possibly related to testing scenarios in a simulation environment?


texts: What is the mechanism by which corona discharge damages wire insulation?

texts: I understand that corona discharge can damage wire insulation over time. How? What exactly is happening to the insulation that it ceases to become so insulative?


texts: Calibrate/adjust sensitivity of a 801S Vibration Sensor Module

texts:
I have some 801S Vibration Sensor Module I want to use for a project, but I need to make sure they have the same sensitivity. The sensor module has a potentiometer which makes it possible to adjust the sensitivity. I need some help on how to calibrate these sensors.

You can see additional description about the 801S Vibration Sensor Module here:
https://protosupplies.com/product/801s-vibration-sensor-module/


texts: Powering circuit from 12V with stand-by battery + solar charger

texts:
I did some research but I haven't been able to find the information that I really want.

I am building a home made security system consisting of several IP cameras. Brownouts are very frequent so I have purchased a 12V 7Ah that I am intending to use to power my system during these periods.

I also have a 12V battery charger which runs off 220V AC.

So,

Can I wire a load to my battery if it is connected in parallel with the charger?
Are 12V devices (IP cameras) supposed to tolerate 14V coming from a fully charged battery?

I also have a 12V solar panel that I'd like to use to charge my battery during the day and have the 12V charger provide the remaining necessary power to keep up with the demand. I have a solar controller which connects to the solar panel and the battery and takes care of regulating the charge.

How can I add a solar panel + controller to the previous circuit?

Updates:

Power consumption will be less than 3A.
Battery is lead acid
I am guessing the solar controller DOES have diodes that prevent the battery from being discharged.

I am going to get some regulators but are there any other alternatives? I have plenty of resistors, transistors and the like but no regulators like that.

I am not sure what the maximum voltage for the cameras could be ( no datasheets or anything like that available ) but would it be such a bad idea to add a series diode to cause a voltage drop of about 0.7V? Voltage would be about 13.5 if the battery is fully charged ( 12% more than 12V ).


texts: Is the laptop's power adapter output negative terminal grounded?

texts: Today I find my lenovo laptop power adapter's output negative terminal is not grounded (the input ground terminal is not connected with output negative terminal, measured with DMM). But another old one is just opposite, the output grounded. Why? There is any standard for power adapter? If the laptop is not grounded, is it safe?


texts: Programming a PIC microcontroller using toggle switches and logic gates. Ideas to suggest?

texts:
I saw a guy on Youtube  programming an EEPROM using toggle switches and he would press a button to send a clock to the EEPROM for the data to be written.  Could I do the  same thing  to program  a  microcontroller?

Above is an manual EEPROM  programmer I got  from the  web.

have a nice day.


texts: If a step-up transformer increases voltage, then how current can be decreased ? is really the current in output is smaller?

texts:
If a step-up transformer increases voltage, then how current can be decreased ?

If a step-up transformer increases voltage, then how current can be decreased ?

(I'm trying to ask that, in case-of battery, if I take a battery of lower voltage (say 10 Volt), and another battery of higher-voltage (say 50 volt), and use them in  2 separate circuits (each with same path-resistance , say 2 Ohm ) ; then , in the circuit that got stronger-battery (50 V), will give much more current.

Now, instead of batteries; we're taking 2 AC sources:  an AC source of 10 V , and another similar AC-source of 10 V magnified to 50 V through a step-up transformer.

Since a step-up transformer increases voltage and decreases current; then , that 50 V AC source should give LESSER CURRENT than the 10 V (according to conservation of energy).

But common sense is telling, if there is a potential difference of 50V, then we SHOULD get a MUCH GREATER CURRENT THROUGH OUTPUT(Load) circuit, than the 10V source;  since we know from Ohm'law  (and even non-ohmic conductors with any positive resistance), that, if we apply greater voltage, we'll obtain greater current.

Then, among these 2 thoughts (assumptions) , which one is correct?  and why?

& if the first assumption is correct ( "the 50 V transformer gives 1/5 times lesser flow than the 10V  original source", then why we're telling it 50V  at all; and not saying 10/5 or 2 volt? )

And if it is really works just like a true 50V source and increase current, then how it obey at all the law of Conservation of energy?

See also: How do Step Up Transformer work? on this website (https://electronics.stackexchange.com/questions/11004/how-do-step-up-transformers-work)

and

On that page, an answer , explaining how each loop work as a battery. https://electronics.stackexchange.com/questions/11004/how-do-step-up-transformers-work/11006#11006

However I'm not a physics or math person. So please explain that way.


texts: How do I make a wire link for veroboard quickly and accurately.

texts:
I recently put together a prototype on veroboard. It was necessary to make several links from BTC to do the vertical connection between tracks.

Is there a quick way of making wire links accurately?


texts: LoRa modulation and chirp process clarification

texts:
I am new to LoRa and I would like to get some confusion on chirp-based modulation process clarified. I was reading the very good thread
Understanding the relationship between LoRa chips, chirps, symbols and bits

My additional question is: up or down chirps change frequency from Fmin to Fmax. Now, clearly all chirps in a spectrometer diagrams look the same since they (mostly) all have same frequency change (again Fmin to Fmax or viceversa). But am i correct that although is not visible in those type of diagrams, during that frequency change process is where the magic happens? Because if we'd look in detail there we would see per-symbol phase changes in order to modulate a specific code or sequence of raw-bits (e.f. 7 bits symbol)? In other terms the phase-change pattern is specific to a symbol whereas the frequency change is the same for all possible symbols?


texts: differential amplifier will cancel DC present at input

texts: In differential amplifier, it is written that "only AC signal will be amplified and DC part at the input will be canceled and hence there is no need of DC blocking capacitor". I am not getting this concept. According to me DC signal at the input should also amplify. Please explain.


texts: What are the general guidelines to configure IMU sensor parameters?

texts:
Im working on developing a Attitude and heading reference system (AHRS) for my quadcopter project.

Im working with AltIMU-10 v5, it is 10 DOF (gyroscope,Accelerometer,Compass,Altimeter) IMU board.

The gyro,accelerometer and magnetometer, have some common parameters, that are user-configurable. These include : Bandwidth of LPF, sensitivity of each sensor, output data rates(ODR), cut-off freq. digital LPF & HPF configurations after ADC processing etc etc.

Question:

1) How do I configure these parameters so that it suits my application best? (i.e quadcopter)

There might not be a definite answer to my question but general guidelines on how to work around these parameters specific to my application, would help me a great deal.

Useful Links:

AltIMU-10 v5 homepage

Magnetometer Application note

Magnetometer Datasheet

Gyro and Accelerometer Datasheet

Application note for Gyro and Accelerometer


texts:
Background

I have a small circuit that consists of a microcontroller operating on 14Mhz and a wifi module. This circuit is enclosed in a small plastic box. I am considering gluing a few magnets on this box in order to install it on a metal surface, and I was wondering how bad it could influence the circuit and the wifi connection, since these magnets will be placed really close to the circuitry.
Here are some technical details:

Magnets are Neodymium Disc 1/4" X 1/16" N32 grade.
Plastic Box is 4.22" X 3.75" X 1.21"
Wifi module is RN-XV (802.11 b/g, 2402 ~ 2480MHz, TX 0dBm to +12dBm, RX -83dBm)

I would like to know:

Should I expect bad interferences?
Are there any special considerations where to glue the magnets on the box, except from "away from the wifi module" ?


texts: Grounding for surge protection for telephone/internet/data lines

texts:
After my router broke in a thunderstrorm, I am trying to establish surge protection for power lines as well as (this question) for telephone/internet lines.

I  found devices such as Tupavco TP302, using gas discharge tubes. It is placed between the TAE wall data outlet and the router. In contrast to others, it has also a grounding cable. I thought a grounding cable would offer additional security to get rid of surges, but...

Questions:

Is this truly beneficial?  Isn't it enough to shortcircuit the 2 wires with the potential difference? Or is it simply "faster" for the current to escape via a (thicker) grounding cable? (The attached grounding cable is quite thin, I'd say less than the standard 1,5 mm for AC wiring :-(
Could it be even a disadvantage? What about surges that might possibly enter via ground, especially if the telecommunication line is not connected to the "same" ground (main grounding terminal). Could temporary transients (as explained here) between the main grounding terminal of the house ("Potentialausgleichsschiene", AC power for router) and telecommunication ground (data lines) after an (indirect) flash of lightening rather cause destruction?
Would ignoring the grounding wire of the data surge protector (i.e. not attaching it to ground) result in a disadvantage compared to a device that simply does not have a grounding cable in the first place? (I assume the grounding cable simply the center tap of the gas discharge tube(s)?)
Most important: Would it be safe to connect the grounding cable of the data surge protector to AC power ground (PE contact, e.g. via a plug where I connect only the grounding (PE ) wire?)** I am hesitating to touch AC power outlets/plugs. Commercial grounding plugs I found so far have 1 MOhm resitance (necessary for EMD protection while touching electronics), thus not suitable. Alternatively I thought of iron water/heating tubes, but would have to determine resistance/impedance to earth and possibly introduce a "third" ground potential. Better than nothing?

AC power network is most likely TN-C in Germany as far as I found out so far.

EDIT

I found the following schematic drawing (Tupavco website) of a rack-mountable version of the device (I can only guess it uses the same technique as my not-rack-mounted device), showing GDT betweeen paired lines, with the center tap connected to ground:


texts: Length matching, Routed or Signal on Altium?

texts:
I have searched some information about the diference between Signals and Routed on the PCB Tab in Altium, and I understand it, but, when you have to do a length matching, Which is the best option? The diference is not stable (2 mils, 3 mils, it depends of the trace I have done).
Thank you so much!


texts:
In a project where we use STM32 as a microcontroller, we need to record 512Mbit data. As far as I know, NAND flash ICs are used extensively in flash memories(From ISSI,Panasonic,Samsung,Toshiba.. companies). But they are very big and needs lots of pins.

  Instead this, we want to use a spi flash which is much smaller and requires 8pins.(from Winbond, macronic, micron ..) For example;

Since the device will operate with battery, it is also important to have low power.
Can we use spi flash in this project? Is there a handicap to use?


texts: High frequency relay options for 5V 20A DC

texts:
While researching for a while upon relays, I had a hard time finding out how to choose a relay that can switch high DC currents at frequencies up to 20MHZ. I found those solid state relays, but most of them seem to work only for AC. Any suggestions? Thank you very much!
I want to use this switch in an electrolysis cell, to pass pulsed DC from a lab source at various frequencies up to 20MHz (generated by a function generator). To research possible effects I need currents between 8 and 20A at aprox 3-4V.
I find it difficult to measure the cell resistance since it looks like it is not constant throughout the process.


texts:
I'm looking at creating a "specialized" MIDI over USB device for a project I'm working on and my requirements have gone beyond that of the Arduino/Pi/etc, due to limited I/O. I am very much a beginner in the world of MIDI, microcontrollers, etc. and would appreciate a jump-off point to get started.

For my project I need a MIDI Receive box that transmits the signal over USB, but I need it to be able to receive from 16 separate input devices. The Arduino Mega and Teensy 3.5/6 have the most UARTs to support this (I've decided against software serial options due to limitations), but the Teensy still only has 6 UART channels. I've come to the conclusion that building my own box would end up working best to allow me to accomplish what I need while avoiding what I don't.

I've found some UART chips from different manufacturers such as Exar and NXP that have 8 channels and also specify that they are built for PCI/PCIe applications, while the ones under the USB category list 2-4 channels. Would that mean I need to hook these 8-channels up to some sort of USB-PCIe adapter? And is it possible to combine two of these to obtain those 16 channels I mentioned? How would I get these to talk to my computer over USB? I read about using a FPGA; would this be the most straight-forward/easiest/most versatile option? Is there also some completely different approach to this which would be better suited?


texts:
I'm learning electronics (and basic electricity) and I wondered if a 1MHz oscilloscope like the DSO Nano is enough for (very) basic electrical and/or electronic circuits. I'm almost broke and I need a cheap portable oscilloscope to try various circuits (wherever I am, hence the required portable property) with resistors, capacitors, transistors, and microcontrollers (if I study hard enough). I don't thing I need a more powerful oscilloscope because I'm learning and I'm just following the exercises in various books right now. This would be my first oscilloscope and I would eventually buy a 20MHz portable oscilloscope later.

Thank you!


texts: Where do we use arithmetic multipliers in 5G technology?

texts: I have recently learned about arithmetic multiplication and the various types of multipliers used in digital circuit design. Now, having an interest in cellular technology, I am curious about the applications of these multipliers in 5G circuits. For example, I have done some research and found that they can be used in the minimum-mean-squared-error minimization in MIMO receivers. Where else would I find arithmetic multiplication being performed in cellular technology?


texts: Sampling voice and send it over cable, which A-D converter is best for it?

texts:
I'm learning electronics on my free time from zero. So I'm sorry if this question is stupid.

I want to make a system to transfer voice from one floor of my house to another, each side will have a microphone and an speaker, and both will be connected by a cable.

The first problem I have encounter is how to convert the voice to digital. My idea is to connect an opamp to the microphone and then an AD converter to make the signal digital, but this is where I don't know where to start. Searching a little, I have found the MCP3201 very cheap on an online store and reading the specs it looks like it is what I need, but I really have no idea if I'm missing something. Is that thing really useful for what I want? Is there some better converters out there for it?

I know that I can send the voice as an analog signal directly through the cable but I want to make it digital as a challenge (and in case I want to add more terminals in the future, control it with an arduino, or whatever).

Anyone can help me?
Thanks


texts: How do I stop my LED strip from getting too hot?

texts:
When I plug A 12V DC 8" LED strip into my car, it gets too hot to touch, but when I plug it into A 110V AC to 12V DC 120mA transformer, it works great; "cool to the touch".

So do I go buy a resister and put it in line? If so, what resister do I ask for and which band goes to the LED side?


texts: Does turning a light on and off quickly use more or less power than keeping them on all the time?

texts:
I just purchased 5 philips hue lightbulbs! I have a program that can do cool features (such as strobe lighting) and I was wondering if this would use a ton of power. Ie:

Will turning on and off the led lights use a ton of power, or is the same (or less) than just keeping them on straight?

Thanks.


texts:
I am new to electronics, circuits, etc. Currently I am reading I2C and synchronous serial communications. As I understand, two devices must be connected to the same CLOCK wire so that the slave knows at which rate to interpret data because it might not have an internal clock. Now, I wanted to see how fast SCL pin on Arduino Uno oscillates by connecting a LED to it and GND and expected the LED to blink fast. Of course, as I believe, I attenuated the frequency to 1 by using Wire.h library and calling

Wire.setClock(1);

as it is said here. The LED still didn't blink as I expected - once a second. What is wrong? How does SCL behave actually? Does it oscillate from 0V to 5V periodically or I must manually do this in the code?

EDIT

The complete sketch was as follows

#include <Wire.h>

void setup() {
  // put your setup code here, to run once:
  Wire.setClock(1);
}

void loop() {
  // put your main code here, to run repeatedly:

}

EDIT 2

I built a circuit. The LED is turned on but it doesn't blink. I also tried changing the frequency in the code from 1 to different values up to 100000.

EDIT 3

It blinks! But I am not sure is it actually SCL making it blink. I added Wire.begin() in setup() and started together with ending a transmission in the loop(). But it doesn't react to changes in setClock(frequency). Also I tried to put a delay or send long random text with Wire.write() between Wire.beginTransmission(0xA3) and Wire.endTransmission(). Then it just blinks once (maybe multiple times but fast) in the beginning and then stops blinking just being on. The complete code is

#include <Wire.h>

void setup() {
    // put your setup code here, to run once:
    Wire.setClock(32000);
    Wire.begin();
}

void loop() {
    // put your main code here, to run repeatedly:
    Wire.beginTransmission(0xA3); //arbitrary address
    Wire.endTransmission();
}


texts: Can HASL finish be used for castellated pads?

texts: I am designing a PCB that uses castellated edges to connect to the parent board. I would like to use HASL finish to save on costs for prototyping, but I am concerned that the non-planar surfaces of the module may pose assembly issues. Is it common at all to use HASL for castellated boards, or do I need ENIG to ensure successful assembly?


texts: Beginner Kirchoff Voltage Law in DC circuit

texts:
Why is the voltage \$ V_A = 2.5V \$ in this circuit?

I know the current in the mesh by applying KVL is:

\$ I = 50 \mu A \$

but why is

\$ V_A = \dfrac{V_1}{2} + \dfrac{V_2}{2}\$?

How do the voltages V1 and V2 end up being added together? Could you explain this to me with equations?


texts:
I can't get my home brew pic programmer to execute the factory reset sequence correctly (or rather, it's not resetting the device and I can't work out what I'm doing wrong). Other functions such as flashing program memory work fine.

The datasheet specifies the following sequence:

Execute a Load Configuration command (data word 0x0000) to set PC to 0x2000.
Execute Increment Address command 7 times
to advance PC to 0x2007.
Execute Bulk Erase Setup 1 command.
Execute Bulk Erase Setup 2 command.
Execute Begin Erase Programming command.
Wait Tera + Tprog.
Execute Bulk Erase Setup 1 command.
Execute Bulk Erase Setup 2 command

Note: All bulk erase operations must take place with VDD between 4.5-5.5V.

I think the voltage is good (measures as ~4.8 to 4.9V on the pin) and that I've executed the sequence as stated, but the chip simply does not get reset.

Has anyone else managed to get this done? Was there anything not in the datasheet that might be useful?

This is a problem because I accidentally enabled code protection so the program data is fixed until I can get this to work.

Thanks,
Charlie.


texts:
Below is a sample current mirror circuit.

I understand that If the transistor Q1 is connected in a diode connected BJT configuration and the Transistor Q1 and Q2 have identical transistor parameters,

The current flowing through both the transistors will be the same.

My questions :

What would the operating region of both the transistors - Q1 and Q2? And if there's a load connected to the collector of Q2, what would be the working region of the transistor.

My understanding is that -  The Transistor Q1 would be in saturation state and the transistor would be in Active region. Q2 will be in active region because, in order to maintain the same current (as flowing through Q1), the voltage across Q2 can vary only in the active region. Is my understanding correct?

In othercases, I have seen this below circuit :

What is the purpose of the transistor Q3 over there?

In the current mirror circuit (first figure), there is a limit to the amount of current that can flow through the transistors Q1 and Q2 right? That depends on the resistor value R1. Correct? And in the Q2 Branch, the amount of current depends on the maximum VCE voltage right? I just want to understand the parameters that control the maximum current through the transistor Q1 and Q2.


texts: noise comparions between Schottky and MOSFET

texts:
I have a circuit that uses a Schottky diode to provide reverse voltage protection.

However, the diode chosen is on a long lead time and an alternative that is immediately available is required.

I've been looking for an alternative Schottky, but due to a number of factors (e.g. a specific footprint size) I'm struggling to find a suitable device.

I was wondering whether I might be able to use a p-n junction diode, but these will likely add more noise into the system which I want to avoid.

Another idea was to try to use a P-type MOSFET instead. However, I'm not sure if these are noisier than than a Schottky. Does anyone know if there is any work comparing and constrasting the noise between these two devices? Or is there a general rule of thumb that suggests that one is generally considered quieter than the other?

Thanks


texts:
I found this circuit for an AC optocoupler:

For this circuit, what would be the criteria to choose the correct resistors and capacitors?

Why were these values chosen?

How do I select the right values for a certain application?


texts:
I want to design PCB of a GSM module. Inside a GSM module there is a place to put a (mobile  cellular ) SIM card. And then this GSM module can send SMS text messages to different phone numbers.
Basically I want to design a breakout board containing the different chips required in a GSM module. I was able to find a schematic of a GSM module (containing chip SIM900) on the following website:
https://www.itead.cc/wiki/SIM900/SIM900A_GSM/GPRS_Minimum_System_Module
Here is the schematic download link in the above web page:
ftp://imall.iteadstudio.com/Modules/IM120525010_SIM900_module/SCH_IM120525010_GPRS_Module.pdf
OK i I now have the schematic but I am unable to find the individual components (to buy) present in the schematic. Why so ? (Question 1) For example I am unable to find SIM900 standalone chip.
I want to have my own minimalist design  of a GSM module because I want to integrate this GSM module with other chips on a single PCB. How can I do that? Is it feasible ? (Question 2)
I can buy that complete GSM module from the market. The complete 'connected' GSM module breakout board containing the SIM900 chip. Yes I can do that. But actually I want to integrate the GSM module board with another different arduino board. So I will need to buy these 2 boards.
But, I want to lower the cost and have my own design of arduino and GSM on a SINGLE PCB. That is why I need to have my own design of GSM module. And thats why I am searching for it.
Let me know if you need any more clarification.


texts: Frequency of the CTC mode in the atmega328

texts:
I am trying to understand the expression for the waveform frequency of the CTC mode (p. 99 of the datasheet).

Assuming that the prescaler is 1 and that \$OCR0A\$ is a constant value, in \$(1+OCR0A)/f\$ seconds the \$TCNT0\$ regsiter restarts from \$0\$. So the frequency is \$f/(1+OCR0A)\$. My reasoning is off by a factor of \$1/2\$. What am I missing?


texts: Today, we just replaced the phone line which was damaged due to moisture and were causing a great deal of disturbance and noise in the phone. What exactly causes this noise? Does the signals gets broken by the water entering the phone line?


texts: What fan could I use to extract hot air from an oven?

texts:
I am making an reflow oven. I've decided to use the picoReflow to do the job and monitor it.

The oven is originally a lab oven, and it doesn't cool quickly at all. It has a vent at the top which I'd like to use for cooling, but just opening it is insufficient.

I'd like to mount a fan which extracts the hot air. Because I need to keep things cheap, preferably it would be some sort of computer(axial) fan (like this one: https://uk.rs-online.com/web/p/axial-fans/6688827/) but I am fairly worried about three things:

The cable might burn since the oven gets hot. It will be going around the outside.
The fan might melt, it does look like its from plastic?
It is usually rated 12V dc but I want to control it with a Rasp Pi model 3 b+, will I need an amplifier?


texts: Upper and lower bound - Digital electronics

texts:
A logic signal is transmitted in a logic circuit with positive logic, where \$V_{IL}=2.3 V\$, \$V_{IH}=4.5 V\$, \$V_{OL}=1.4 V\$, and \$N_{MH}= 1.8 V\$ . Recall that when using positive logic, the higher-amplitude range represents a 1 while the lower-amplitude range represents a 0. Use the figure to determine the lower and upper bounds of the undefined region for the output.

I calculated 0.9V for the lower bound, and 6.3V for the upper, but these are wrong.


texts: Raspberry Pi Zero 12V Battery backup to 5V - do I need the resistor?

texts:
I found this diagram on the internet which seems to divide the voltage down to 5V and still be able to deliver 1A with the 7805 just like I want.

It will use a 12V lead acid battery and a 12V IN transformator. The 5V OUT is for the RPi and the 12V OUT is for a solenoid I'll be using in my project.

My question is, why do we need the 1k resistor in this?
Also, does the 1N4007's make the battery charge from the 12V IN or what are their purpose?


texts: how to drill anti-rotation holes in enclosures?

texts: I am wondering how those holes with a flat for connectors are opened in enclosures. I'd like to know how do to it when prototyping world and in production for aluminum and in plastic.


texts:
Hello good day I been trying to build split keyboard using 2 pro micro.

I'd been following let's split keyboard using qmk firmware.

And the connection diagram of the i2c is this

When doing it on the breadboard everything is OK, until I finish writing the firmware and decide to test the connections. then soldered all the socket to use, when tried to use it, it didn't work now after 3 days of troubleshooting, I found that the coiled wire used in the pin 2 and 3 is the culprit.

When it is connected, it will work properly until I touch the coiled wire, I am suspecting that there is interference if I touch it, but I don't know how to prevent it, and the wire I'm using is YAESU MH-48A6  cable cord.

But I can reproduce the issue using a single strand of UTP wire around 1 meter in length, when it is connected and running I will slow wrap my hand to the wire, then slowly tightening my fist. Then the i2c connection on the pro-micro's gone.

BTW all the testing still done in the breadboard.

I will appreciate any advice/suggestion you give. Thanks.


texts:
I am developing a device that consists of a base station and several wireless sensor nodes. In application there may be up to 30 of these devices in a laboratory with up to 5 sensor nodes communicating with each base station. The sensors will be sampling and sending data at up to 4kHz at 12bits.

Without developing my own wireless protocol at 915MHz (to get away from busy 2.4GHz) it seems that bluetooth offers the best interference handling (using frequency hopping) of the many 2.4ghz wireless protocols available.

Has anyone had any experience with ~100 bluetooth devices or ~30 piconets operating in the same room?

I have thought about using 6LoWPAN at 915MHz but cannot find any information related to how it would handle the interference my application could cause.

Thanks!


texts: is it possible to repair a DMM which was burned by putting the leads into 230V on a frequency-measuring setting?

texts:
There is a DMM (not a cheap one, so its worth to repair it), whose leads where put into a 230V AC socket on the frequency measuring range. The meter did "bzzzt" sound and stopped showing anything.

Neither of its two fuses (1A and 10A) got blown (I checked with a resistance meter, both of them have less then an ohm).

What element would usually get fried in such situation? Is there any chance to repair it, by replacing some elements? Maybe its a common accident, so someone might know what usually gets burnt in such situation.

It was an auto-ranging DMM, the setting it had when in contact with 230V AC was:

Frequency: 100Hz - 10MHz ±0.05%

EDIT, more details:

I opened it, and it looks like there are three transistors (or maybe something else with 3 legs?) on the board fried, and nothing else looks like fried. They are however fried to the extent that it is not possible to find out what markings where on them, so I don't know with what kind of transistors (or whatever this is) I can try to replace them?

All the three fried elements are about 2.9 x 1.3 mm in size, are SMD with three legs, look exactly like SOT-23:

Two of them are next to each other, and their descriptions on the PCB are: TP1 and TP2. The third element is in a different region of the board, and is described TC on the board. These are the only discrete transistor-looking-like elements on the board.

I would be very grateful for some wild guesses with what elements, with what parameters to replace them. Are they transistors or maybe voltage reference? Its worth to do it, even if it takes me several tries to find the right one.

The DMM was a Digitek DT80000.


texts: Finding frequency of a series of pulses (3 - 60 Hz) without using a microcontroller or frequency-to-voltage converter

texts:
I came across an interesting yet challenging problem of finding the frequency of a series of pulses. The pulses can have a frequency anywhere from 1 to more than 100 Hz. The goal is to detect if the pulses have a frequency between 3 and 60 Hz. That is, raise a flag or light up an led if the frequency falls between 3 and 60 Hz. The constraints are -

Using microcontrollers are not allowed
Using a frequency-to-voltage converter IC is not allowed.
False positives are allowed but false negatives are not allowed.
(weak) The pulses can have a duty cycle less than or more than 50%, not necessarily equal to 50%.

Can you please suggest a method of doing so?

One method that I have designed and analysed is to use a counter IC and count the number of pulses, and reset the counter every 1 second (using a separate timing circuit like 555 timer). If the output number of pulses is between 3 and 60 (one can use a logic circuit to determine that) then raise the flag. The logic circuit required for this would be a bit tedious, and depends on the type of output of the counter IC.


texts: Nucleo H743 USB OTG FS not enumerating when external 3.3V source is used

texts:
Scratching my head on this one. I am using a Nucleo H743ZI2 board.
The manual claims it is recommended to use an external power source when using the USB OTG port. Up until now I was using the STLink USB as it was the most convenient when testing things out.
I am getting ready to port the project into the actual system and am using the only available power source, a 3.3V from a shield.
According to the manual (chapter 6.4.5) this is fine:

When the 3.3 V is provided by a shield board, it is interesting to use the 3V3 (CN8 pin 7 or CN11 pin 16) directly as power input (Refer to Table 9 and Figure 14). In this case, programming and debugging features are not available, since the STLINK-V3E is not powered.

However, this either fails to mention that using a 3.3V source will prevent the USB OTG from enumerating, or I must be missing something obvious.
edit: the datasheet also gives this warning in the USB OTG FS chapter (6.6.6), not sure if it's relevant to the issue though.

Warning: USB Micro-AB connector (CN13) cannot power the Nucleo-
144 board. To avoid damaging the STM32H7, it is mandatory
to power the Nucleo-144 before connecting a USB cable on
CN13. Otherwise, there is a risk of current injection on
STM32H7 I/Os.


texts: How to add part in eagle board that doesn't have corresponded in the schematic "jumpers"?

texts:
I am using Eagle to design single side board and I want to use smd jumpers to connect between some points.
So basicly I don't want to add those smd jumpers as a component to the circuit in the schematic, I just want to be able to add them whenever I need without jumping every time to the schematic window and add them.
Just add them from the pcb window directly.

I have tried to search this but couldn't find something useful.


texts: Does AREF pin of ATMEGA series consume any current?

texts:
I have a voltage reference in the circuit and I thought I can feed that reference to AREF pin of ATMEGA as well:

The current at "1.024V" tag is around 200 uA, any current drawn by the AREF can affect the reference voltage to some degree.

Does the AREF pin draw any current? how much?

Can any noise on the AREF pin (or the MCU itself) affect the reference voltage?

Can I dump that 10 uH inductor (LC filter) which is recommended and used in most designs at AREF pin?


texts: Best way to remove paste in pad footprint in Altium

texts:
I have a top only pad in a footprint. I don't need any open window on the the top solder layer so I set the tented option enable for my pad...

But even if the top solder is off (no window for this pad, it is tented), I have top paste for this pad... see picture :

So, I have to switch to manual paste mask expansion and put -999 mils into value to be sure it disappear...

For me it's a mistake/bug from Altium. Because it have no sense to have paste on a pad without any window on top solder mask on it to received. So does not a tented pad should automatically disable the associated paste for this external layer ?

Related information :
https://bugcrunch.live.altium.com/#Idea/9120


texts: Waveshaper: Amplitude changing as frequency changes

texts:
I have designed a Sawtooth to triangular waveshaper using a precision full wave rectifier.I added C1 to stop clipping and the parallel resistors R7 and R5 to get the triangle's ampitude the same as the sawtooth (5V). But as the frequency gets higher, the amplitude is decreasing. Any ideas of how this can be prevented?

UPDATE: This desing  is for a music synthesiser, so the input sawtooth will vary from 30Hz to 1Khz while wanting to keep the amplitude about the same. It is also important that the triangle wave has an average offset of 0. So that it can be again converted into a sin wave later

Without Capacitor


texts:
I have developed bad intuition and a lot of misunderstanding about how grounding works.
For example, in this thread: Will a battery connected to the Earth eventually deplete?, the accepted answer is not what I expected.  Like the person who originally asked the question, I thought that current will flow between the battery terminal and ground,
because at least one of the terminals must have a different potential compared to ground (at
least one, because the two terminals have a different potential compared to each other).
It seems that this is not the case, moreover the other answer asserts that the battery doesn't "care" about the ground and that being connected to earth carries no special significance.
I still can't understand the explanation from the link, but thinking about this led me to a host of other questions such as:

If I touch a two-terminal voltage source not connected to mains power (for example a battery
or a stun gun) does that mean that current will only flow between the two terminals that
I'm touching, and not also through my feet to the ground below?  Is this true even if the source is an ideal voltage source?
Is ground only "special" in respect to mains power, because in power distribution networks one of the wires is connected to the earth?  Is a small amount of current passing through the ground at all time (because ground and the neutral wire are like two parallel wires)?  Does that mean that during a ground fault event a large amount of current passes through the ground, so while walking on it we are not unlike birds standing on a power line?  Is this safe in all cases?
If the ground is not "special" in any way why ESD wrist straps work at all - it seems that the charge on a person's body will go to the earth, if a suitable path exists.
The same question but in relation to lightning - if the earth is not "special" why lightning
prefers to hit the earth, and not something else?
I have noticed, that after getting charged with static, the discharge is very painful if I touch a metal object that is connected to the ground.  The discharge is not painful if I touch the ground itself.  This doesn't make sense to me - if the discharge is going to the ground, and the metal pole is highly conductive and "in series" with the ground, the current should be the same.
Why birds standing on a wire don't get shocked when they land on the ground, that is, why they don't act as a capacitor that charges (on the wire) and discharges (on the ground)?
Sometimes the earth is described as a "bad conductor" - but the earth is very large, so even if it has a high specific resistance, that resistance should be lowered by the fact that it is so large (the same way a thick wire has less resistance than a thin one).  Why is this not so?
I recently read that I should just think about the earth as a "reservoir" of electrons, where I can pull or push as much charge as I want - this explanation confuses me.  If there are already a lot of electrons that I can 'pull', then 'pushing' them should be much harder.  I can't understand if the earth behaves as something positive, negative or neutral, or all three at the same time?

Anyway, instead of polluting the site with such questions (I can think of more, lol), I want to ask - can you provide me with the fundamental knowledge on how ground (earth) works, so I can answer them myself?  References to specific books/literature are welcome.


texts: A question about positive feedback resistor in a Schmitt trigger

texts:
In many tutorials when explaining hysteresis what I read that when the output is high R3 becomes in parallel with R1; and when the output is low R3 becomes in parallel with R2. Above is a depiction of the situation.

Why is R3 in parallel with R1 when the output is high?
And why is R3 in parallel with R2 when the output is low?

I could not figure out the reason.


texts: How do you add an onboard ISP for an ATTiny85?

texts:
I've taken a liking to building circuits around the ATTiny.  Typically I add 6 headers and use an AVR programmer or an Arduino to program the ATTiny in circuit.

I'm trying to figure out how move that AVR programmer into the circuit such that my device is programmable via the Arduino IDE or avrdude.

It seems like I could use V-USB and USBtinyISP, but the commercial license for the former might be cost prohibitive.

Are there any common circuits people add to AVR projects that make them programmable via USB?


texts: Isn't C1 and C2 nulling the input signal?

texts:
I am a relative newbie to electronics.

Looking at the following schematics I see something strange: C1 and C2 at the input.

I always knew that capacitors block DC signals and let AC pass. By having these caps to ground aren't them letting the signal go to ground, or in other words, grounding the signal zero or nulling it?

I do not understand them and now I see also C9 and C10 at the output.


texts: Why are high end audio connections gold?

texts: Silver has a lower resistivity than gold and is cheaper, so why are high end audio components gold plated?


texts: Is it possible to route USB 2.0 using regular traces?

texts:
In the future I will be faced to design a system that includes USB 2.0 connectivity. I've seen that there are many trace calculators, but as far as I can see, they refer to microstrip lines.
So, is it possible to route using regular traces? Maybe if the distance is short enough. Do I need to add additional resistors to the lines?


texts:
I got a DE2 board that failed so they sent me a replacement board which is the finer DE2-115. But my config file (.sof) is not forward compatible. How can I migrate existing projects that I have for the DE2 to DE2-115? I think I need to define a .sof file and I don't know how to do that, it was my university instructor who gave me a public domain .sof file that works with the DE2 but not the DE2-115. I got a spec error msg saying something like pins are different from the Quartus envirronment. Can you propose or suggest what I should do?

Related question what project I want to program with this gear
https://stackoverflow.com/questions/12872409/how-to-make-pong-for-the-nios-ii-processors

I got C code, assembly and hardware definitions that work with the DE2 already. So I want these in DE2-115 as well instead of getting started from scratch with DE2-115 I just want to move some projects but the .sof file is incompatible beteween DE2 and DE2-115. The big difference is that DE2 uses Cyclone II while DE2-115 has Cyclone IV chip.


texts:
I would like to ask you for help with identify one capacitor at photo below (can't find it). I got GTX 1080 Ti to my hand with torn out capacitor on VRM. I am looking for the identical one. Can any one point me to which one it is, or advice to closest similar one?

size is : 7,5 x 4,35 x 1,9mm


texts: I am looking for information on JTAG interface on PCI-e 1x connector. Do anyone has an informaton how to program it? I would like to use it to program microcontrollers and FPGAs.


texts:
For a project we're working on we need to detect if a car is standing on a parking spot.
We're using an ultrasonic sensor for this, SRF05. While using the correct timings we can only sense for about a range of 25cm. Even though the specs are saying a range of 3m should be possible.

How can we improve this range? Should we try another sensor? Suggestions please.


texts:
I'am looking for a circuit schema to convert 0.5V square signal from 2-6 kHz into square signal of 5V on output side. What I need is to count / measure frequency with microcontroller. I have a SEABIRS SBE3 temperature sensor (http://www.seabird.com/sbe3s-temperature-sensor?qt-product_tabs=1#qt-product_tabs)

thank you


texts: Antenna Impedance Matching, 0 Ohm Response

texts:
I'm currently trying to match some SMD antenna breakout boards. These boards have one type of SMD antenna, footprints for an SMD pi network and a 50 Ohm cable as connection to my VNA.

Now the problem is, I'm reading a real value of 0 ohms on the desired frequency of 2.45 GHz. I tried to match it, and (more a tolerance problem) got a nice result on 2.3 GHz, but 2.45 is still at 0 ohm. I'm stuck at the moment since the values I'd need are very small or very big if I try to calculate a matching network with these parameters.

This is the result with a 0ohm resistor in series with the antenna.

Also the result with a matching network (lowpass, 12nH P/N(LQP02HQ11NH02), 24.5pF P/N(GJM0225C1C120GB01) at 2.4 GHz).


texts:
I am analysing the an eval board circuit for a battery charger IC which has the following inrush control circuit.

Question 1:
I understand that C22 is used to "slow start" Q6 limit inrush current into C3,C4,C23,C24,C44.
Signal CHG_OK goes high, when a power source is detected at J1 (12V).
With CHG_OK high, Q10, Q9B and Q9A are turned on. I don't understand resistor R10 because if Q9A is on, ~12V are applied on Q6 gate, which will keep Q6 closed.
How does this inrush control circuit work?

Question 2
Why are there several capacitors (C3,C4,C23,C24,C44) and why can't they be replaced with just one large capacitor?


texts: Comparing rated, stall, and inrush current in DC motor

texts:
I see the definitions of them are:

Rated current: maximum current the motor draws (or some says the maximum current the motor can endure?)
Stall current: the current the motor draws when hold physically
Inrush current: the current the motor draws when it just starts to rotate

I have a motor and it only says a rated current. Would it be safely larger than the other two? In other words, if I make sure the circuit can stand the rated current, would it be safe enough in words of current?

Also, is there some general rule like, the stall current is larger than or equal to the inrush, or vice versa?


texts: Can I replace a complementary N&P channel MOSFET with two separate MOSFETS?

texts:
I'm wondering if a complementary enhancement mode N&P channel MOSFET like this one http://micric.ru/data/documents/P2503NPG.pdf
which is used as an inverter driver for the LCD display, could be replaced with two separate MOSFETs one N type one P type with similar characteristics?
If not why not? What is unique in having those two transistors in the same package? Also if yes but with drawbacks(parasitic effects?), then I'm also wondering what could be added to the circuit to compensate for that.


texts:
I am about to wire up some HIH-4000 humidity sensors to a project of mine.  The datasheet suggests a maximum voltage of 5.8V in (minimum 4V).

If I am using a 4AA battery pack (non-rechargable), will I have to worry about the extra .2 volts going through the HIH-4000?

I know 4 AA batteries are theorized to produce ~6 volts and I will be using the 6 volts elsewhere in my circuit to run other things.

Here are my questions:

Should I worry about resisting the extra .2V?
If so, will a simple resistor work for the long term?
Whether I use a resistor or I make a step down converter, should I step it down more, to around 5V?
Will this extend the life of the HIH-4000?


texts:
I've found a burned chip (due to DC power overload) inside the sound card Roland UA-25EX.
This is a picture of the part:

Can someone give me a hint?
I'm not an expert, I want only to find the spare part.


texts:
I just installed a solar array to charge an existing battery system. Even with full sun my charge controller is not receiving enough voltage to go into charge mode. All the system info is below.

Existing battery bank:

24 volts
600 amp hours

Solar panels:

6 panels wired in 2 series
Rated power Pr SW250
Maximum power Pmax 250W
Maximum power point voltage Vmpp 30.5V
Maximum power point current Impp 8.27A
Open circuit voltage Voc 37.6V
Short circuit current Isc 8.81A

Charge controller:

Outback FLEXmax 60
Capable of receiving high voltage and converting it to 24+ volts for charging.

In full sun the charge controller is only receiving 18.5 volts from the panels. I would really appreciate suggestions as I can't think of a starting point for troubleshooting.


texts:
Apparently this question looks better for DSP SE but I am posting it here to get answer in simple words for those EE graduates who didn't studied signal processing in undergrad.

Apparently as far as math expression is concerned, both are somehow similar but
what is difference between correlation and convolution?

I have tried to google but I also come across a term "kernel".

What is meant by "kernel" in this regard?  Is it same thing as a filter or any other entity?


texts: wav file audio samples are signed, how does DAC deal with signed numbers when it does not have negative supply?

texts:
I was looking into wav audio file specification, they may hold the pulse coded modulation data as signed our unsigned integers as well as floating point values.

How does a DAC deal with signed numbers? Do they need a dual supply to output signed numbers?

What would be an appropriate way to convert floating point numbers into integer when sending them to DAC? I assume e.g conversion onto 8 bit would be simply multiplying by 255 but I am not sure since floating point numbers are signed.

Yes I realise that there are multiple types of ADCs.


texts:
Ok so i'm hoping that someone can explain to me in basic terms: in an un-fused circuit what could actually cause an electrical component to be damaged by current flow. I'll explain the reason for my question.

I have recently fitted custom dash gauges to my Jeep. The instructions recommend fitting a fuse to avoid damaging the gauges, so that is what i have done. What i am trying to get my head around is how the gauges could actually become damaged if there was no fuse. Power is flowing through the gauges which are providing a resistance and then the power is flowing back to the battery. So what could cause the fuse to blow? I guess some kind of short circuit but i'm struggling to get my head around where the short circuit would occur that could damage the gauges (if i had no fuse). Maybe i'm over simplifying the system in my head but the way i am thinking of it is: if i had a simple bulb in a circuit, if that circuit shorted out then the wire would be destroyed but the bulb would still be ok? wouldn't it? because the short would bypass the bulb.

So in the case of my gauges what could hypothetically fail that would cause my gauges to be damaged by excess current flow? Or are the instructions wrong and what they actually mean is 'a fuse should be used in case something in the gauges fail in order to prevent a potential fire' and not 'a fuse should be used to protect the gauges'?


texts: How to put a breakpoint to after last line of a loop in GDB?

texts:
Consider the following loop:

28:  while (true) {
29:    chThdSleepMilliseconds(1);
30:    txbuffer[1] = num_zero + offset;
31:    spiExchange(&SPID1, 2, txbuffer, rxbuffer);
32:    // we want to examine rxbuffer at this point
33:  }

I want to examine contents of rxbuffer in GDB after spiExchange function is executed. The following doesn't work:

(gdb) break main.c:32
(gdb) continue

GDB doesn't hit above breakpoint (probably as expected). If I put a breakpoint main.c:31 and then execute next, context is totally changed, so there is no rxbuffer at that point.

Currently I insert an unused variable and put a breakpoint at that point:

31:    spiExchange(&SPID1, 2, txbuffer, rxbuffer);
32:    int x; // we want to examine rxbuffer at this point
33:  }

How can I put a breakpoint at that point without defining the temporary variable?


texts:
I was trying to build a passive cell phone detector this evening, and finally got one to work.

Along the way, I tried two different antennas:  a 1 wavelength loop, and a dipole.

I had the hardest time getting a signal out of the dipole, but the loop worked like a charm - hooked it up, and got a blink from my phone.

Here are the circuits:

simulate this circuit – Schematic created using CircuitLab

In both circuits, I get pulses of voltage across the 1N34.  In both circuits, the pulses across the 1N34 are several volts (varies depending on distance and phone activity.)

In the loop circuit, I also get pulses across the LED - it lights up.

In the dipole circuit, I don't get voltage pulses across the LED.  It acts like an open circuit - my oscilloscope shows 50Hz hum as though I had connected a length of wire to the probe.

The dipole will not light the LED in this configuration.

I don't understand what is different between the two that causes this.

I did find, though, that I can place a voltage multiplier across the 1N34 in the dipole circuit and get a blink.

That looks like this:

simulate this circuit

The dipole with voltage doubler works, and has about the range of the loop antenna.

Since the voltage doubler worked so well for the dipole circuit, I thought I'd try it on the loop.

That was a disappointment.  Putting a voltage doubler on the loop antenna actually makes it less sensitive.

Now it gets interesting.

I put a second stage on the voltage doubler on the dipole antenna, and drastically improved the range.

Now, down the the questions:

Why doesn't the simple dipole circuit work?
Why does the voltage from the loop circuit actually drop when using a voltage doubler?

I've decided to go with a dipole and a couple (or three) of stages of voltage doublers to finish my gadget, but I'd like to understand what is going on here.

Possible explanations:

For (1):

a.  There isn't a DC path through the dipole in the simple circuit.  The RF passes through the 1N34 and on out the opposite antenna half, passing through the LED due to capacitance.  The rectified DC, however, has nowhere to go.  The dipole is only a closed circuit for RF.

b.  Suggested by Glen Willen:  The loop is acting more like an inductor than an antenna.  It reacts differently to the voltage doubler because the load changes the resonance of the inductive circuit.

"Range" is something of a misnomer.  The dipole with a two stage voltage doubler will blink a couple of centimeters from the phone.  The loop blinks when it is almost in contact with the phone.

This is fine for what I'm doing.  This isn't a functional circuit.  It's more of a decorative thing.

The band on my hat broke, and I'm going to make a new one out of leather.  The cell phone detector goes on the new hat band in place of the original escutcheon.

A dipole is mechanically easier to use than a loop - the dipole can hide behind the band, whereas the loop can't.  And, a loop long enough to go around my head won't receive cell phone signals.


texts: 2-to-1 Multiplexer logic equation: is order of inputs important?

texts: The boolean logic equation for a 2-to-1 multiplexer is \$(A.\bar{S})+(B.S)\$, where \$A\$ is the first input and \$B\$ is the second input. Is this logic equation equivalent to \$(A.S)+(B.\bar{S})\$, given that the inputs \$A\$ and \$B\$ have the same order? Thanks in advance!


texts: Need help with software config on PIC12F629 to blink LED

texts:
I started learning PIC some days ago and have played around with different tutorials. Many of the tutorials I have read, doesn't work for me. I always have to change stuff in the code to make it work, so I actually havn't had any succes yet.

Now I have some code, that SHOULD work (if yiu ask me), but it doesn't. It builds without any errors, byt after burning it, nothing happends. No LED's are blinking or anything.

Could someone please help me figure out why this is not working and maybe explain why. I have read alot of pages on the net, but havn't found anything that could give me a solution, so now I have to ask for help. Thanks

I'm working with a 12F629 and Pickit 1

#include <htc.h>

#define _XTAL_FREQ 4000000     // oscillator frequency
#include <delay.h>           // defines DelayMs()

__CONFIG(FOSC_INTRCIO & WDTE_OFF & CP_OFF & MCLRE_OFF);

void main()
{
// Initialisation
    TRISIO = 0b111100;

// Main loop
for (;;) {
    GP0 = 1;
    GP1 = 1;
            __delay_ms(200);
    GP0 = 0;
    GP1 = 0;
            __delay_ms(200);
}
}


texts: Kid's geothermal power plant science project

texts:
I’m from Cape Town. My daughter is doing a geothermal energy power plant for her science project and we are battling to get the turbine with the DC motor to spin when steam hits it. The Dc motor is not loose enough so won’t turn to generate electricity to our small LED light. Please can you help.

We have literally tried everything (9V, 3V and 5V. The voltage is not the issue) it’s the amount of pressure needed to turn the wind mill. Is there anything you can make other than the DC Motor that will turn with the light pressure of steam? I can send a video so you can get an idea of our intentions. Anyone that lives in Cape Town. ☺


texts: what is the equivalent circuit for a Complementary Split Ring Resonator (CSRR)?

texts:
Can any one help me find the equivalent circuit and how to calculate the resonant frequency of a CSRR (not SRR) like in the one in the figure below?

Here is the S11 parameter of the CSRR obtained by CST studio

If there is any article about this I will be grateful, if you can link to it in a comment.


texts: GPU-grade memory bandwidth on low-cost FPGA solutions

texts:
I'm designing a custom FPGA board, for something low-cost like a Xilinx Spartan 6. I want to perform research about solving memory-intensive algorithms in an FPGA.

As we all know, memory bandwidth is often a bottleneck, especially in low-cost solutions like Spartan 6. However a middle-end GPU has 150+ GB/s of memory bandwidth.

Is there any way to increase bandwidth in a low-cost FPGA to near-GPU levels?

I see only few ways:

Connecting high-bandwidth memory like DDR4 to GPU chip and connecting all to the FPGA (kinda strange solution and I don't know if it's feasible and, if it is, won't the bandwidth between GPU and FPGA become a bottleneck?)
Using multiple wide and fast memory interfaces to connect off-chip memory to FPGA
Using custom controllers, connections or something else, optimized especially for this task to improve bandwidth

I care for at least 100 GB/s. On a low-cost Spartan 6 FPGA, this bandwidth would be success. Or it's impossible with this piece of hardware at all?


texts: How to calculate the induced voltage of two electrically isolated coils (solenoids)?

texts:
Suppose I have the following setup:

suppose then that:

Self inductances L1,L2, the radius R, the number of windings (turns) N1, N2 are all given.
V1 is given.
The distance between the coils (solenoids) is so small that can be neglected.
The material used for the coils is copper.
The coils are wrapped around a plastic core and a laminated core is added as displayed here.

How can I calculate the induced voltage V2?
I'm having a hard time figuring out which model I should apply. At first I thought that the flux must be the same because of the geometry of the problem, but then I get stuck when I need to write down the equations.


texts:
I need help on number one of this practice assignment. I barely learned about this so it is kind of hard me to understand it right now. So any advice or help is appreciated.

I want to determine the amount of delay in clk cycles needed to generate a PWM with a period of 0.05 ms.

What i did to determine the amount of delay was to divide 0.05 ms over the clk freq. which is 0.05ms/10^-8. The answer I get is 5000. Is this correct?


texts: I am part of a team at school that designs and builds a hybrid electric vehicle. We have chosen to use a series hybrid configuration, so we will be using a motor as a generator to charge lithium polymer batteries, which will be connected to a battery management system. We are likely going to be using a brushed DC motor as the generator, which will be connected to a small engine that will be running at a constant rpm and I'm trying to figure out if a controller is necessary for this generating motor and if not, what is the best option? Also what needs to be regulated before reaching the battery?


texts: Identification of power connector for LED panels

texts:
We bought a bunch of 32x32 (6mm LED pitch) LED panels from a Shenzen company and some of the power cables were missing, so I'm currently trying to identify them.
Attached are some images.

We think it might be Molex or JST but not sure. The Chinese company contact offers to sell the missing ones to us at outrageous shipping and toll.

Price negotiations => sudden loss of English language skills ;)

I know there are quite some possibilities out there, but can anyone help to unambiguously identify them, so we can try to find them over here (Germany)?


texts:
I have set the baud rate of sim808 module to 57600 and with a USB2TTL module connect it to my PC. Everything works fine and the module recognize the AT-Command except that constantly send the following message to the terminal

RDY
+CFUN: 1
+CPIN: READY
Call   Ready
sms    Ready

I wonder to know how can I stop sending these messages,
Is it possible that the module reset itself?

PS: Power indicator light is on and GSM Net light indicator is blinking.
PWRIN Voltage is 5V


texts:
I need to find this for a homework as an introduction to designing with flip flops. It must use only JK, D, T or SR flip flops. All the designs I find, are made with transistors or capacitors, and that's not what I need. I don't really know how to design it myself. But I wonder if this is correct: (Using D flip flops, and a 3 bit counter, although signal is not fed back)

a  b  c    a* b* c*
0  0  0    0  0  1
0  0  1    0  1  0
0  1  0    1  0  0
0  1  1    0  1  0
1  0  0    0  0  1
1  0  1    0  1  0
1  1  0    1  0  0
1  1  1    0  1  0

I need to use some simulator. Which would you recommend? I'm totally new at this =S

EDIT: Forgot to put a youtube example from 0:32 to 0:40 mark


texts: How to change component size in expressSCH?

texts:
I have a sketch with too small AND gates and too small capacitors etc.
Is there a way to enlarge them?

When I right-click the component it lets me change only the text size....

Thanks!


texts: Ri and Ro - What do these acronyms mean?

texts:
I am trying to make sense of the below circuit diagram.

What do Ri and Ro mean?

What purpose do the resistors after the Pinouts of Pin 3 and Pin 2 serve?

This is the datasheet for the sensor: http://www.ge-mcs.com/download/turbidity/920-480B-LR.pdf. It says its rated current is max. 30mA. In order to test the current in the circuit I built for this sensor (which you can see at this question: https://electronics.stackexchange.com/questions/207096/help-with-turbidity-sensor-circuit-and-reading-voltage), I would just use a multimeter between my Vcc source and Pin4 to measure the current?

I was also trying to see if I accidentally fried the sensor somehow. I used a digital camera and pointed it at the photo TR, but I could not see anything (this was to see if there was any IR light coming from the photo TR). I tested the camera first with a TV Remote to see if I could see IR light coming from the remote, and I could. I am not 100% sure if it is an IR LED on Pin 3, however. Are there any other ways to see if I fried the sensor?


texts: Do Battery Powered devices require bulk cap at power input?

texts:
I am in the process of designing a +5V power supply for a hand-held 2xAAA powered device.

When using TI's webench simulator tool to simulate a switcher power supply that I am considering, I noticed on the default schematic for the TPS61099 device that there is a very large capacitor right at the battery input (labeled Cin).  It is 150 uF, physically HUGE, and EXPENSIVE ($2.59!).  This cap is in addition to the usual moderately sized cap on the input of the switcher (15 uF)

This is my first battery-powered design, so I must be missing something.  I'm used to designing products which run off of a 12 or 24V industrial DC bus, and there was never any need for such a cap on the input.

So why is the cap required?  It seems that TI is not the only one to suggest this as a reference design, since this answer shows an LT datasheet that shows a similar setup, also for a battery powered design.

Can I safely leave that cap out of my design?  Or is there a particular aspect of battery-powered design that requires enormous input power caps?  Why can't I rely on Cinx (15 uF) as the only input cap?


texts:
I'm completely new to hardware in general. I just got a raspberry pi and was messing around trying to get an LED to light up.

I have everything wired like the picture below. I am using a 330ohm resister, which I believe is bigger therefore ok then what is required.

also (sorry this is my first time using any program to draw a circuit)

The program runs successfully, but no light comes on. I know the LED is good as I've tested it on the arduino. Anybody care to explain my wiring fault?

root@raspberrypi:/home/pi# cat test.py
#!/usr/bin/python
import RPi.GPIO as GPIO

GPIO.setmode(GPIO.BOARD)
GPIO.setup(11, GPIO.OUT)

GPIO.output(11, True)

Changing to GPIO pin 0 results

Traceback (most recent call last):
  File "test.py", line 5, in <module>
    GPIO.setup(0, GPIO.OUT)
RPi.GPIO.InvalidChannelException: The channel sent is invalid on a Raspberry Pi
root@raspberrypi:/home/pi#


texts: Why does the circuit tranconductance remain unchanged after cascode?

texts:
I have a simple cascode amplifier as follows:

The circuit transconductance remains the same as if the cascode was not there. i.e.
$$G_M=g_{m1}$$
Why is it so?
I initially think the circuite transconductance would be the product of the component transconductances, like
$$G_M=g_{m1}\cdot g_{m2}$$


texts: number of gates in carry look ahead adder

texts: In "Computer Architecture and Organization"(written by John P. Hayes), it is mentioned that in IC 74283, the number of gates grows in proportion to n^2 as n(number of bits) increases. But in the diagram, I can see that one AND gate is increasing in every step(without the second one). So, isn't the number of gates grows in proportion to n? Or, am I making a mistake?


texts: How do I make a programmable resistor for testing purpose? For example, I want the value of the resistor follow a ramp wave: 0ohm --> increase by 10k each 1ms, until reach 1Mohn and restart


texts: 433M/2.4G ISM RF signal coupling on PCB board?

texts:
thanks for reading my text.
I have an idea:
Use cheap 433M/2.4G transceivers to replace on board digital signal isolator.
Data rate is not a problem.
e.g.  Battery pack cell balancing AFE board.
But RF signal transmission though air is not acceptable.
So how to link them just on board?
STAR connection through （X）pF capacitor in each transceiver's TX pin?
And PCB track should be 50Ohm impedence?
I know little about RF micro-wave.
Advice please. Thanks !


texts: Protecting DC GND from high voltages induced on mains PE

texts:
In electrical vehicle supply equipment (EVSE) the Pilot signal GND is common with the PE conductor. An RCD (either 30mA AC, or 6mA DC + 30mA AC) is also included.
For making an external test of the RCD good functionality, a momentary short of the Live conductor to the PE, through a switch and a series resistor of some tenths kΩ to cause an AC current of 30mA is a common practice. The same applies to a DC test with a switch in series with a bridge rectifier and a resistor to cause a DC current of 6mA.
The problem arises from the momentary high voltage of the Live conductor that is conducted to the PE (and according to the signal GND) during the test, and that could destroy the sensitive electronic parts. What can I do to isolate only the AC part from the GND? And to keep a good DC coupling among PE and DC GND?
I have seen on the PCB of an industrial EVSE, on which the PE is also connected, a black SMT part without any marking that connects the PE to the signal GND, but it is impossible to find out what part it is.
One time, by mistake I got the output signal from the GND connector and not from the PE connector and the PCB damaged. In other words, I bypassed this black SMT part. I checked it with ohmmeter and shows almost 0 ohms. I checked some similar parts on the PCB and I got again 0 ohms, so I suppose this part is OK. What kind could be this part? An inductor? A ferrite bead? A MOV varistor?
Thanks for any idea.


texts: Using a Arduino Pro Mini to power more than 2 servos

texts:
I don't know very much about Arduino, but from some basic research I have read that the Arduino Pro Mini can only support two servo motors.

I am trying to create a set of reaction wheels using hard drives, brushless motor controllers and an Arduino Pro Mini. (I can get a different model of Arduino, but that's what I had lying around.)

Since a set of reaction wheels requires a minimum of three hard drives to work, I need to find a way to be able to control another servo using my Mini.

Is it possible to control more than two servos (with precision) when using an Arduino Pro Mini?

If so, how?

If not, should I look into a different model of Arduino? Since I value small size, will an Arduino Micro work?


texts:
I have recently started studying RS flip-flops. I noticed that for the SR NOR Flip-Flops most of the images online, as well as my text, have the 'Set' input attached to the NOR gate that outputs 'not-Q', some sources said that it is designed this way because we want Q to be '1' when S is pulsed '1' and vice versa.

However when dealing with NAND SR Flip Flops this rule of making Q '1' by pulsing S to '1' does not work. Futhermore some of the online images of NAND SR Flip-Flops have the 'Set' input on the gate that outputs Q and others have the 'Set' input on the gate that outputs the compliment of Q.

Please excuse my rather elaborate question but in summary, I would like to know:
1) Does the R and S inputs have to be attached to specific gates in the flip-flop.
2) If yes to '1)' can someone please explain  why this is, for both the NAND and NOR SR Flip-Flop.

Thank you in advance.


texts:
I tried to simulate the circuit given in your design note "https://www.analog.com/en/technical-articles/battery-protection-circuit.html"

According to the designer, the cut off voltage is 3V but the circuit is not going to cut off when the i/p is below 3V also.

Please see the attached simulation result. Could you please help me how to solve this issue?


texts:
Is it possible to simply add a car/truck battery to my computer's PSU output, in parallel, to make sure if there is a power outage, that the computer will seamlessly continue running, for a period of time (just like an UPS unit would do, but it's more advanced, of course)?
What is the best way to do it, in terms of battery life? I'd like to do this as a DIY project, to learn more about this topic and to create something useful out of it.
I understand the UPS units exist for a reason, but I'm also curious is it possible to do it in a more simple way, like stated above.
Thanks in advance for all the answers!


texts: I have a problem with using a voltage controlled switch in Pspice

texts:
When using the voltage controlled switch in Pspice, the current flowing on the other side of the switch is equal to the current flowing through the voltage source controlling the switch.
Why is it so?
I want to see the current source value on the other side.


texts:
Synchronization:

---------------------
Port ( ...
                  rotary_a : in std_logic;
                  rotary_b : in std_logic;
...);
...
signal      rotary_a_in : std_logic;
signal      rotary_b_in : std_logic;
signal      rotary_in : std_logic_vector(1 downto 0);
...
      rotary_a_in <= rotary_a;
      rotary_b_in <= rotary_b;
...
      rotary_in <= rotary_b_in & rotary_a_in;
---------------------

in the last step, what is the advantage of using temporary signals?
one could achieve same output using ports directly (rotary_b & rotary_a)


texts: Electron flow through the semiconductor crystal

texts:
Talking about doped semiconductors:

Atoms outer shell extends and overlaps with another ones outer shell (the conduction band), right? So when electrical field is applied to a semiconductor bar (lets say n-type) electrons start to flow in the bar, and then what happens? I know that the electrons in the outer shell/conduction band contribute to electrical current density (usually marked as "J").

But my question is: How is it done? How the outer electrons contribute to electron flow when other electrons flow by or however it is done.


texts: Appropriate charging current for parallel 18650 lithium cells

texts: I have 9 18650 cells salvaged from a laptop battery. They have all been tested to work and since they were always used together, I put them in parallel. I'd like to make a power pack, so I got some lithium charging circuits with all the protection bells and whistles, but with just 1A max output current. Now, I've been charging them with the circuit board from another old USB power pack, and it works, it's just super slow. Someone mentioned that the 1A max current simply would not work for 9 parallel cells, but I don't fully understand how it couldn't. As long as I'm charging the batteries with more current than I'm drawing from them, they should charge, right? I'm not super worried about the speed, right now it takes pretty much a full day to charge the pack. My question is, will the pack charge with a 1A total charging current (albeit slowly), or am I missing something?


texts: Does it make sense to power multiple 12V devices from one single power source?

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I have a number of devices (External hard disks, switches, router) on my desk. Each ones comes with a own power supply. This leads to a waste of space and a mess with all the cables.

Does it make sense to power all devices from a single power source?

I would simple buy a power supply which provides enough current to power all devices and would connect all the cables to this single power supply.

Are there any risks in doing this? Are there important things to pay attention to?


texts:
What's the white component? The one besides the green resistor.

It has 5 pins, the pictures are below.

Here is the circuit.


texts:
In my circuit  , I need  decoupling capacitors , but my local shop doesn't have some values like 300nf so I need to put in parallel 3 of 100nf . the equivalent CAP would be 300nf but with multiple paths to GND (each is 100nf) .
So dose the equivalent CAP would work or it must be 300nf as one piece ?

NOTE : this decoupling capacitors are needed for Vi of 7805 REG .

Also I need a 15pf decoupling noise capacitors for DP,DM for USB but I only have  (10pf , 5pf) and 12pf (dose 12pf  work as a proximately value ? or this value is critical ?).


texts: Can multiple window blind motors run on the same low voltage wire?

texts:
I have a wall of 8 windows using battery operated motors (8 AA batteries in a long tube). I am looking to run these off a DC power supply instead.

I can't get the exact specs on the motors, but a Reddit user who successfully converted his were 12v with less than 1amp peak draw.

Can I wire these in parallel using three 18/2 runs?  The longest run is 47 feet to the power supply (running them through the attic and back down into a furnace closet).  Here's a picture from before the wall was finished and the path of the three runs I would take if running multiple motors (wired in parallel):

I am looking at connecting each of these lines to this 12V 20amp power supply:

https://www.amazon.com/dp/B078RTV41D/ref=cm_sw_em_r_mt_dp_U_VbDRDbEWJGRA7

And this wire:

https://www.amazon.com/dp/B01J4E0KO8/ref=cm_sw_em_r_mt_dp_U_6gDRDbEWEBMCN

Or would I need to run 8 separate wires and connect them to an 8 channel power supply like this one?

https://www.amazon.com/dp/B0069MIBLS/


texts: Antistatic mat instead of antistatic wrist strap?

texts:
Just to make sure, before doing something silly: can i place a 2nd antistatic (dissipative) mat on the floor (along the 1st mat on the table) and stand on it with bare feet? Instead of wearing an antistatic wrist strap?

Of course, the mat is connected to mains earth thru a resistor. For safety.


texts: How do capacitors improve power factor without destroying the capacitor?

texts: Can anybody help explain in simple terms how adding capacitors to a 120/240/higher AC power circuit helps improve power factor without blowing up the capacitor? I'm familiar with capacitors in DC circuits as tanks for storing energy but it seems like that concept collides with the idea of putting a capacitor in parallel with AC voltage in a circuit - wouldn't the constant reversal of polarity destroy the capacitor? And wouldn't it be a huge waste of energy (every time the capacitor charges in one polarity it discharges and works against the AC line voltage as it swings to the next opposite polarity...)?