texts:
I'd like to switch a boiler on and off electronically.
It is now connected to a thermostat.
The first thing I did was measuring the current flowing, closing the circuit with a multimeter set to DC. It is 0.44mA.
Then I switched to voltage and measured 90V.
I didn't expect such a high voltage.

I was wondering if I could use BC547 transistor, but I saw that limit on collector voltage is 50V. So I think it will not fit. However the current is very small so I don't know.

Do you have any suggestion ? May I still use this transistor, or you have another kind of transistor to suggest?  I would use NPN transistors because they are the easiest to use.  Would in this case be needed a different kind of transistor?

UPDATE
@ Dave Tweed: Good point the AC. I closed the circuit with my multimeter set to AC. I got 120V and 0.6mA.  Now I don't know any more if it's DC or AC.

@  markrages: NPN transistors, as long as I have read are easier compared to PNP.  What do you mean when you say they are not easy? Compared to what? I'm afraid I don't get the sense of your sentence.

@ George Herold and @ Peter Bennett: A relay is easy to intall and certainly working for my project.  This is why I'm asking about transistors. However, I didn't consider the circuit isolation point, which I consider very valuable information, since I really don't know anything about the remote circuit.  I just have 2 cables and I know that if I connect them the boiler powers on.
The reason why I am asking about transistors as an alternative to relay are the following
Relays are more expensive, more noisy (chatters), larger, more power demanding.

So I renew my question:
Does it make any sense to use a transistor to electronically turn on and off a remote circuit with the current characteristics outlined above?
In case nobody has any suggestion for this question I'll certainly use a realy as suggested.


texts: Communication between FPGA and OMAP 3530 using GPMC

texts:
I am working on a project which requires communication of data between Xilinx Spartan 6 FPGA (XC6SLX45T-2FGG484) and OMAP 3530, I have a ULK dev board on which

The 32Kx8 (256Kbits) serial electrically erasable PROM (24AA256-I/SM) from Microchip is used to interface with OMAP processor through I2C interface.
The same 32Kx8 (256Kbits) serial EEPROM (24AA256-I/SM) from Microchip is used to interface with FPGA through I2C interface. The I2C is common to both processor and FPGA.
The GPMC bus of the OMAP3530 processor is used to communicate with Spartan-6 FPGA for register read/write and for programming the FPGA. here GPMC controller signals of OMAP3530 Processor will be Configuring in address/data non-multiplexed mode. As well as Chip select signals (CS0-4), SPI3, I2C3 and GPIO signals will be connected to FPGA for misc communication. To generate interrupt from FPGA Processor two dedicated GPIO signals are used.

Now I am not sure where to start,

what is the choice

a. can I use the EEPROM as like shared memory into which processor and fpga perform r/w operations. what would be the feasibility and speed implications of such an implementation.

b. can I Use GPMC misc communication part..? how shall I go about it?

which of the two would be more appropriate?
and how shall I move ahead, kindly forgive  my ignorance,if I made some mistakes or interpreted data wrongly.


texts: Why isn't the BIOS' ROM chip made using CMOS technology?

texts:
After reading a computer hardware course on BIOS/CMOS, I'm still unable to determine the reason why the BIOS' ROM chip isn't built using CMOS technology, and why it is connected to a separate chip called "CMOS" for storing the configuration information.
This is from the lecture note:

Programs are stored on the system BIOS chip, while the changeable data
is stored on a CMOS chip
CMOS Group of Hardware: Hardware that is common, necessary but may
change – RAM, hard drives, floppy drives, serial and parallel ports

I know that the BIOS is stored in a flash memory, and that CMOS MOSFET technology dissipates less power compared to other implementations.
Why is it only the BIOS ROM that doesn't use CMOS, like other storage devices - what exactly is the advantage? And why can't the BIOS configuration information  be stored in its own ROM chip instead of the "CMOS chip"?


texts: Implementing a filter with an LDI integrator why this phase jumps

texts:
So I have a continuous time filter that I implemented in discrete time using an LDI Integrator. This what I obtained for the filter phase:

In green there is the phase for the continuous time filter and in black for the discrete one. What are the weird phase jumps? Is it because of sampling?
EDIT:
I'm implementing a 4th order Bessel filter using an MF10 and here is my schematics:


texts: how to implement Pic18f97j60 with PoE Ethernet

texts:
I am a beginner when it comes to mcu and electronics design, I did some projects on Arduino and other ready made microchip boards. However this is my first time building something from scratch.

I want to design a water tank level sensor using ultrasonic sensor and then sending the data to MySql database using Ethernet. After my research I decided to use Ethernet over Wifi or Radio frequency because of interference(if there was more than one tank with each having the same sensor) and range issues(needs to be at least 10 meters and concrete walls and stuff)

After my Research for components I selected PIC18F97J60 because it has integrated MAC+PHY and I can use Microchip IP/TP protocols.

My question here is do I need something else other than RJ45 Magjack
https://www.robotshop.com/eu/en/rj45-magjack-breakout-board.html

because in the pic18f datasheet it says I need to have this circuit, so is Magjack enough, if not what more I need and how can I power it through Ethernet if possible?

Thanks for your time in Advance


texts: I am in the process of selecting a N channel MOSFET for switching purposes and thus, tried out this simple circuit in Multisim. But it seems that the MOSFET conducts in the cut off mode and remains off in the saturation mode. Can you tell me where I might be going wrong?


texts: How to create a circuit for this signal? Transistor?

texts:
today I measured a signal with my oszilloscope. Its a pressed button of my robotic vacuum cleaner. The strange thing for me is, that in idle mode (button not pressed) the signal level is at 3.3 volts. But if I press the button the voltage goes up to 4.5 volts and drops than to 800 mV. This repeats until I release the button.
Its a SPST button like you find on a keypad.
The button starts the robot. I don't want to press it every time manually, I want to "press" the button remote via the GPIOs of my ESP.
I measured the voltage on the mainboard. There is a pin header where the button is connected directly to the mainboard.
What I want to do is now, I want to trigger the button via the GPIO of my ESP32. Do you have clue what kind of transistor-circuit I need? I need to raise the current somehow to 4.5 volts...

Thanks


texts: Solar Panel Cellphone Charger - Not Enough Current?

texts:
The Materials :

1) 3 X 1.5W 6V Monocrystalline panels @ 320mA

2) DC-DC Variable Voltage regulator

3) 3 X 1N4001 Diodes

The Problem : -

I have connected the panels (which give about 203 mA realistically) in parallel wiring with an 1N4001 diode at each of the positive terminals to prevent reverse flow of current. The entire array generates around 7.09 V at 610 - 720 ma in ideal conditions. Now using my multimeter, when I measure the current (used the positive and negative leads of the multimeter ----> 10 A unfused) at the breakout board it displays 0.61 A which is enough to charge any sort of USB Devices since the typical USB 2.0 current output ranges from 250 mA to 500 mA. On measuring the current from the ends of the voltage regulator (5V output) it displays 0.98 A. It charges devices with no charge protection and doesn't charge the ones with charge protection.

At this point I'm really confused. Is there a problem with the wiring, a problem with how I measured current or is the current too low? because according to my calculations there should be plenty of power for charging phones. Please help me out here.

Thanks in advance :)


texts: Transformer impedence-question about problems

texts: I'm given this transmission line problem in which I have a 3-phase transformer and I'm also given its impedence. I usually solve these problems using only one phase. So what should the impedence value be in the equivalent single phase circuit I make? More specifically , if it is correct to say it this way, is the 'phase' impedence different from the 'line' impedence?


texts: Implementing a Boolean function using NOR gates with maximum 4 ports

texts:
I need to implement a Boolean function using NOR gates only. The minimized function written as PoS is:

f(a, b, c, d) = (a+b)(a+c+d)(b+c+d')(a+c'+d')(a'+c'+d)

I used double negation and DeMorgan's laws to make the following (unfinished) circuit in the Hades simulator:

Now, the problem is that Hades has NOR gates that have a maximum of 4 ports, and I have 5 separate sums I need to input in the NOR gate. Any ideas how to solve this problem?


texts:
Here is schematic that provides polarity inversion and switch off motor if it reaches one of its two end positions:

SW1 is On-Off-On DPDT switch with the center position Off. SW 2 and SW 3 are limit switches.
Motor voltage is 12V and it will consume max. 2A. I will build power supply for it consisting of transformer and rectifier bridge. Should I add back EMF protection and, if yes, how can I implement it in my case?
Here is one schematic:

I can't do this in my case because of polarity inversion ability (first schematic), right
?


texts: What are the differences between these Darlington-like circuits?

texts:
I built these two circuits. Both of these are Darlington-like circuits, using two NPN transistors in conjuction with each other to generate a much higher gain.

simulate this circuit – Schematic created using CircuitLab

Looking at the circuit on the left, the resistor R1 limits the current in D2 to avoid damage to the LED. The resistor R2 turns on Q2 normally. The combination of Q2, R3, and SW1 act to turn off Q1 by pulling the base low. I don't actually have a switch so I just touched the wires together. The gain of Q1 is 100, which is typical for a 2N3904. But when Q1 and Q2 are considered together the gain is 1000. This circuit seems to work fine.

Here are some scope traces from the base of Q1 when SW1 is open and closed. I am just using a scope here because it has a good display and is much better quality than any other measurement tools I have.

Here is the circuit working. The LED is just some random ugly one I had in my box of parts.

The second circuit was made by rearranging the first. It also seems to work, but R5 means the LED never turns off completely. Here are the measurements from Q3

I couldn't really measure any difference between the circuits.

Is there a name for these circuits? Like an inverted Darlington or something?

This test was performed at DC. Would this work if SW1 was toggled at a high frequency such as 30 kHz or would I run into issues?

The current through Q1 and Q3 was not higher than 5mA. Would this circuit work at currents closer to the maximum current values for a 2N3904? Such as 150 mA.

Is there a name for the circuit on the right hand side with Q3. My idea behind it was if R5 is properly sized, the load (D3 and R6 in this case) dictates the current in the base. For high impedance loads, the current in the base is small. For lower impedance loads the current in the base is larger. This should theoretically prevent a condition where the current in the base-emitter junction of Q3 exceeds that of the collector-emitter. Is this possible or am I just imagining this?


texts:
I've heard this term many times from many different sources, but none of them gave me a definition.

Here is my understanding: "coupled" means "connected together". If two circuits are "capacitively coupled", that means they are connected with capacitors between them.

However, one question remains: What is an "ac coupled signal"? I know circuits can be coupled, but how can we couple a signal?


texts: Proper way of storing a register address on ARM Cortex M4?

texts:
I am writing a program on STM32F4 Discovery where I have to store address of Timer's CCR register into a pointer and then change register via this pointer, ie

volatile uint32_t* tim_ccr_reg = reinterpret_cast<uint32_t*>(TIM4_BASE + 0x34);
// 0x34 = offset of CCR1 register
*tim_ccr_reg = 1999; // Set CCR1 to 1999

When I test this alone in an "empty program" it works, but when I use my entire program (along with all other features I implemented) it causes hard fault at one of those assignments. Now Im figuring out whether its my other code which displaces something in memory or I'm saving register address the wrong way and it only shows when more complex program is loaded. In documentation I read

  The simplest way to implement memory-mapped variables is to use pointers to fixed addresses.

#define PORTBASE 0x40000000
unsigned int volatile * const port = (unsigned int *) PORTBASE;

  The variable port is a constant pointer to a volatile unsigned
  integer, so we can access the memory-mapped register using:

*port = value; /* write to port */
value = *port; /* read from port */

  This approach can be used to access 8, 16 or 32 bit registers, but be sure to declare the variable with the appropriate type for its size, i.e., unsigned int for 32-bit registers, unsigned short for 16-bit, and unsigned char for 8-bit.
  You should also ensure that the memory-mapped registers lie on appropriate address boundaries, e.g. either all word-aligned, or aligned on their natural size boundaries, i.e., 16-bit registers must be aligned on half-word addresses (but note that ARM recommends that all registers, whatever their size, be aligned on word boundaries.

http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka3750.html

Then I went to see documentation for CCR registers for timers and it says

so now I'm not certain, is the register always 32-bit and only 16-bits are used in some timers or is register in some cases 16-bit only and I have to use 16-bit pointer to write to it?

In any case, I would like to know what is the proper way of saving timer CCR register to a variable. If I second click on CCR1 in following command

TIM4->CCR1 = 1999;

and click "go to definition" it takes me to some weird chunk of code

/** \brief  ITM Send Character

    This function transmits a character via the ITM channel 0.
    It just returns when no debugger is connected that has booked the output.
    It is blocking when a debugger is connected, but the previous character send is not transmitted.

    \param [in]     ch  Character to transmit
    \return             Character to transmit
 */
static __INLINE uint32_t ITM_SendChar (uint32_t ch)
{
  if ((CoreDebug->DEMCR & CoreDebug_DEMCR_TRCENA_Msk)  &&      /* Trace enabled */
      (ITM->TCR & ITM_TCR_ITMENA_Msk)                  &&      /* ITM enabled */
      (ITM->TER & (1UL << 0)        )                    )     /* ITM Port #0 enabled */
  {
    while (ITM->PORT[0].u32 == 0);
    ITM->PORT[0].u8 = (uint8_t) ch;
  }
  return (ch);
}

Im (very) confused.


texts: FPGA multiplication using DSP hardware, signed vs. unsigned

texts:
I'm using the DSP unit (just a fancy name for the multiplier/accumulator unit) of the Gowin GW1N devices to do some fairly simple math.  These units accept two 18 bit inputs for the multiplier adding the 36 bit result into the 55 bit accumulator.  It also subtracts a 54 bit input from the 55 bit accumulator at the same time.  I was planning to use 18 bit data in Q1.17 format.  Then someone asked me if these units were signed or unsigned...  I don't know.  Seems that unlike addition, multiplication hardware is different for signed and unsigned numbers.
It is hard to imagine the multipliers are not signed, but I'm not sure.  I guess I'll have to test them to see.
The documentation on this DSP unit is truly abysmal lacking much detail at all.  However, I think I may have gleaned a bit of insight from a comprehensive block diagram in the main document combined with the simulation source code for the block in the mode I will be using.  The code shows signals named ASIGN and BSIGN.  Initially I had hoped they would be to control if the inputs were complemented to allow for subtraction and such, but they are for controlling the use of the sign bit.
I see logic that clearly control the sign extension of the 18 bit multiplier inputs to 36 bits.  These 36 bit numbers are multiplied using the VHDL operator defined in
use IEEE.STD_LOGIC_UNSIGNED.ALL;

assigning the result to a 72 bit signal which is then truncated to the 36 lsbs.
    mult_out_tmp <= ina * inb;
    mult_out <= mult_out_tmp(35 downto 0);

It is late and my brain hurts.  Is this controlling the multiplier to allow it to be used for either signed or unsigned numbers?  Unsigned would be great!  The subtract input allows me to subtract values without complementing them and the accumulator feedback allows values to be added through sequential load and accumulate steps.  Doesn't matter how many steps it takes really.  We have maybe 100 calculations to do and 167772 cycles to do them in.
Yeah, I think I need to write some test code.  Is this the customary way to design FPGA multipliers, with a control to indicate if the inputs are signed or unsigned?  Do I understand this correctly?


texts: Difference between multiple pipelines and superscalar?

texts: I have read some threads and the wiki articles, but still don't seem to understand what exactly the difference is between having multiple parallel pipelines and the superscalar architecture. I know that (in case of dynamical superscalarity) out-of-order-execution is used to fill the pipeline optimally and avoid hazards. But what keeps you from using such a dispatcher in combination with multiple independent (except for the instruction fetcher and dispatcher) pipelines? What is the difference then?


texts: How does erasing a NAND-Flash memory work?

texts: I am trying to understand how the NAND-Flash memory works and I think I understand how programming a page works but I don't see why inverting all the voltage would not lead to erasing the page. So, why is it that the whole block has to be erased (instead of a finer grained page-erase)?


texts: Impedance matching of a RF power amplifier based on the s2p file

texts:
I'm designing the input/output impedance matching circuit for a RF power amplifier, based on the vendor supplied s2p file. I designed separately the input/output matching circuit at the given working frequency. But when I connect the input/output matching networks and the model based on the s2p file and do simulation in ADS, the matching frequency point went away from the designed frequency.

In the diagram, SnP is the model based on the s2p file, the left is the input network, the right is the output network. It seems the output network will change the S11. So the input matching network designed based no load no longer matching at the given frequency.

So, what's the correct way to do a matching based on the s2p file? Do I need matching them in order, that is, first output, then input?


texts: Basic Electronics - I want to learn the "why", not just the "how"

texts:
I have been looking for a very basic book on electronics, but many of them explain what the components do (and how they are made) and then go into designing circuits that do stuff.  They tell you to put the components in various parts of the circuit to make it do what it's supposed to do.

However, they don't tell you exactly why it does what it does.  For example, a circuit with a transistor, a couple capacitors and resistors, and a transformer causes a speaker to warble.  Logic tells me that there is an oscillation going on in the circuit, but I need to know why the components are placed where they are placed for the circuit to work.

Please direct me to a book that explains the 'why' very clearly.


texts:
my circuit is a capacitor multiplier. I want to generate some noise (200mv) at 100Khz and 500Khz (input V) and want to see the attenuation on the output

How can I generate specific frequency noise in SPICE/LTSPICE ?


texts: Mesh to block or reduce wireless cell signals

texts: I want to block or reduce the amount of wireless cell signals coming into my house through my window(s) by using some type of mesh (screen).  I could use a sheet of metal but then I wouldn't be able to see through the window.  I am initially planning on standard window screen made of aluminum (not fiberglass), and I would ground the screen to an earth ground outside my house.  The wireless signals are from a new cell tower across the street from my house.  It has 3G, 4G and is supposed to get 5G.  So the frequencies I believe would be 850MHz-1.9GHz for 3G, 700MHz-2.6GHz for 4G and 2.5-30GHz for 5G.  What would be, or how would I calculate the maximum hole size to block these signals?  Does the thickness of the screen matter?  Would I be trying to interfere with the frequencies or the amplitudes of these signals?  PS: My house has metal siding but the roof is asphalt.  My EMF meter typically has higher readings throughout the house the higher it is to the ceiling.  Any other suggestions would be greatly appreciated.


texts: How is it decided what modulation is used during an 802.11 communication?

texts: I understand, that 802.11x protocolls can use different type of modulations. BPSK, QPSK, 16-QAM, 64-QAM... I also understand that the used modulation depends on the quality of the channel, I guess on the SNR. But how does the actuall process look like? How does the transmitter decide what modulation should be used?


texts: How the slew-rate and drive strength affect the output signal of the FPGA?

texts: Can someone describe the difference between the drive strength and the slew-rate preferences in Lattice FPGA?


texts:
Today suddenly the voltage increased too much in our area and many people's TV, Lights and Others things get damaged ( mine too). What happened and what to do?
What to do in future to be safe so that none of my electric item get damaged?


texts: Analog 4-20 mA Output module for Process Control

texts:
I am reading a spec sheet for an 8 channal analog output module for process control that says this:

  Because all current is sourced from within the module using the 24 VDC
  excitation, current outputs cannot be used with an external loop
  supply.  Current outputs are self-sourcing and cannot be used in loops
  that are loop-powered or already have a self-sourcing device in the
  loop.

I'm having a hard time interpreting this warning. This is how I understand a typical 4-20 mA control loop:

In my case the transmitter / sensor 4-20 mA input goes to an input module, gets acted upon by say a PID algorithm coded into the "brain" module & the output 4-20 mA ought to come out via the output module to then drive some valve / actuator.

So what's an "external loop supply"? Or a "loops that are loop-powered or already have a self-sourcing device in the loop"

http://www.opto22.com/site/pr_details.aspx?cid=4&item=SNAP-AOVA-8


texts: Will my deep cycle battery protect itself from full depletion?

texts:
I have a 12 V, 55 Ah lead acid deep cycle battery that I am using to power a small cooler/fridge that will hold medicine for a community project that I'm working on. The goal is to provide continuous power to the fridge despite any power outages caused by natural disasters, and there will eventually be a solar system connected to lessen the load on the battery and increase the uptime. The full system will also have a switching module that will automatically detect when the grid (wall outlet) stops working and will switch to this battery (it will also do this in the other direction), like a UPS but much cheaper due to budget constraints.
Now, I am going to do an experiment where I run the 12 V, ~48 Wh cooler directly from the battery and log the voltage vs. time across the terminals so that I can tell how long the battery can power the cooler before it turns off and compare that to the expected result.
I have found plenty of tables from google that showing the depth of discharge percentage vs. battery voltage, and it says it shouldn't drop below 12 V until the battery is about 60% depleted. This is desirable because I do NOT want to completely deplete the battery and reduce its lifespan.
Here is what I am unsure of, the fridge operating manual does not provide any information about the lowest operating voltage. Can I assume that the lowest operating voltage is close to 12 V, and that the fridge will shut off once the battery reaches, say, 11.5 V? If yes, then I am good to go. If not, then what is an average operating voltage range for a system that is designed for 12 V?
(I know that it is likely very dependent on the system, but I am looking for more of an anecdotal answer. If an answer is not obvious, then I can attempt to use a variable power supply in the lab to find out the voltage at which the fridge stops drawing current, though I am asking here because I'm in a bit of a time crunch to assemble the first prototype and would like to be able to run this experiment as soon as possible)
Edit: for reference, here is the only information I could find about the cooler https://secure.img1-fg.wfcdn.com/docresources/0/156/1564815.pdf


texts: If I use PA13,14 pins for flashing my MCU via ST-LINK programmer then can I also use these pins as GPIO in the same circuit? Will that not disturb the ST-Link if some analog or digital circuit is connected with these pins? Also if I use these pins as GPIO inputs then how will the MCU know if the input signal is for GPIO or for flashing the MCU from ST-Link?


texts: Specs for an AC Power Bank as an Outlet Replacement

texts:
I've been seeing cheaper and cheaper power banks on Amazon, and have even started to see them in hardware stores.

My impression is that most people will use them to tailgate or to power batter pack rechargers on a job site while playing a radio.

What interests me is if they can be used to actually power tools. For example, a electric edger, leaf blower, or circular saw.

I imagine the peak wattage has to be quite high, there has to be some issue with the simulated sign-wave and the motors, not to mention the frequent on and off of the device. Insight into this or even side effects for the tools would be very interesting, but is not the core of the question which is...

What specifications should be labeled to imply that the Power Bank would be able to handle that kind of punishment?


texts: What are the prerequisites to understand how FPGA Zboard works?

texts:
I have a computer science background. For my intern purpose I need to work with FPGA Zboard. I don't have any idea how it works. I have some knowledge on logic gates, not more than that.
It will be helpful if anyone let me know what prerequisites I need to cover, what fundamentals I should have knowledge on?
I was planning to buy some kits like:
kit1, kit2 to get use to with this field. Will it be worth it for me as a starter or there are more better kits to get started with electronics world?


texts: RFID: Why is inductive coupling used instead of EM waves for LF and HF systems?

texts:
Is it because of antenna sizes? At 900 MHz a 1/2 dipole has a size of around 15 cm. That would be far higher for 125 kHz, so instead we use coils to power the transponder and use load modulation for the reverse-link.

Does the low frequency have any effect on reflection? Reflection is dependent on frequency, low frequency waves tend to "go through" materials easier so we would have a harder time reflecting those through the transponder antenna?

Are those the two main reasons?


texts: Any truth behind "multipole" technology in audio signal transmission?

texts:
After reading this question about ultra-expensive audio cables, I was reminded of a product that we sold at a company I used to work for.

MIT Cables makes these "audio interfaces" which go a step beyond mere audio cables, adding little electronic circuits that are claimed to transform (for lack of a better word) the audio signal. Primarily, "Multipole" technology.

Is there any truth behind these claims whatsoever?

Edit: I'm looking for either a debunking or validation of the claims, from an electrical and audio stance.

(Related question: What's the best cable to transfer audio signal?)


texts:
It is a snapshot from an AC/DC converter. do I need to consider "dist. 1" or "dist. 2 at" the below image to measure the correct clearance space.The caps are both Electrolytic that have an aluminum body.

If I need to refer the dist. 2, isn't there an issue on the below reference design on the marked part?


texts: When to use a special high frequency PCB material and not Fr-4? Rogers

texts:
Based on this article, fr-4 can usually be used up to 7 GHz. Above 10 GHz losses become too high and a special high frequency (HF) material should be used (e.g. Rogers).

Advantages of a special material:

control of Er over a broad range of frequencies and from batch to batch,
lower dielectric losses at HF.

Can anyone please share experience (give a broad guidance) at what frequencies an HF material should be used and when it is a must? Rogers, as a most common, is of a particular interest.
How much is approximately lost due to dielectric losses (leakage) in Fr-4?

Appendix 1

Figure: Comparison of losses FR-4 vs Rogers. Source - the same article.

Appendix 2

My particular situation is a PCB with a 1 GHz square signal (thus, 5 GHz harmonics and higher should be present) and I am contemplating whether to buy an expensive Rogers or not. I can tolerate an insertion loss not greater than 10% (~0.5 dB) per inch within the 1-5 GHz range. The FR-4 the foundry provides does not have specs above 100 MHz - so, I can either use it at my own risk or use Rogers (which has specs in the needed range).

Appendix 3

Answer like "see the datasheet" are not very welcome. I've already done.


texts: How to program DSP inside ADAU1772 codec?

texts: I have read ADAU1772 audio codec datasheet but there is no information about internal DSP's instruction set and how to program it. There is a guide for evaluation board with ADAU1772 but I do not have that board. What is more pins of my ADAU1772 are permanently connected to FPGA so I have to program it using FPGA. I just need information which registers inside audio codec I should write and what are possible instructions. Unfortunately I can not find any information on Analog Devices website.


texts: High permeability core material at high frequency

texts:
I am trying to design a transformer with 1 turn at the primary and 10 turns at the secondary. For application purposes, I need a long wire at the primary and a large conductors at the secondary, which makes it difficult to consider a higher number of turn at the secondary. I do not care about losses as the transformer is not use during a significant time. It works at 500 kHz.
So I have a large leakage inductance at the primary and to not loose a lot of voltage due to the voltage divider between the magnetizing inductance and the leakage inductance, I need a large magnetizing inductance, so a high permeability core. It will also reduce the peak current at the primary if I have a high magnetizing inductor value and then it will reduce the effect of the leakage inductance. I need also to have a high density flux saturation Bsat
I am looking for a graph which shows the permeability of different magnetic materials in function of the frequency. Does anyone know a material that have a good permeability at those frequency and a high Bsat? Better than ferrite?
It is said that ferrites is good material for high frequency, i.e. that the permeability is still high for high frequency. But I know that the Bsat of ferrites is very low and the permeability is not very high compared to supermendur.

Have a nice day!


texts: How to detect mains outage for 12V SLA battery charger

texts:
I'm wanting to use a 12V SLA battery and off the shelf mains charger as an uninterruptible power supply for an Arduino or similar device (via an appropriate 12->5V regulator) as also described here and here.

The battery voltage can be monitored using a voltage divider and one of the analogue i/o ports, but I also want to be able to detect from the Arduino software when the mains is off. I think what I'm after is an electronic version of something similar to this (to use for sensing rather than switchover). What is a way to do this with minimal additional components?


texts: Are these results normal: 5M led strip, only 1 A

texts:
I just bought a cheap LED strip from China. The used LEDs are from the SMD5630 type. Each meter has 60 LEDs, so 300 LEDs for 5m. The voltage is 12V.

From what I found, the current for 1m should be around 1A (12W / meter). I connected 5m on a power supply that is rated 120W (10A x 12V).

I wanted to make sure that everything is okay. So, grabbed a multimeter and measured the voltage wich is around 11V. Then I measured the current as following: 1 wire from the power supply to the multimeter, from the multimeter a wire to the LED strip, and the other wire from the LED strip to the power supply. This gave me only 1A.

This would mean a power consumption of only about 11W. This sounds very strange to me, as the LEDs are quite bright.

I guess there is something wrong. Any suggestions?


texts:
I am new to electronics and the use of an oscilloscope. I have read several threads about the dangers of floating an o-scope. I own a  Rigol DS1052E o-scope. I've noticed that the BNC ground on the two channels are tied together (no resistance), however, there is 4.2k ohms between the channel clips and the earth ground lug.

Is this o-scope floating?

Would it be permissible to probe the AC outlet with this o-scope?

I assume it would be dangerous to do so with an o-scope that is ground referenced (as you might clip the ground lead to the hot wire)?

Is it counter-productive to wear an anti-static wrist strap while working with an o-scope regardless of the type of o-scope?


texts:
I want to know whether the two circuit given are equivalent? Explicitly I want to know when can we use Norton's transform for dependent source?

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to substitute the obsolete NAND chip in this circuit (part of an audio synthesizer) with a standard CMOS one (for example CD4011).
The original NAND chip is a DTL chip by Motorola, MC846.

datasheet: http://pdf1.alldatasheet.com/datasheet-pdf/view/130532/MOTOROLA/MC846.html

The pinout is different but I don't care about that, I'm only worried about electrical differences.

I don't think I can just put the CD4011 in place of the MC846, I'm not sure about that but I may need pull-up resistors, and then I read on the MC846 datasheet that it contains "wired OR" and I don't know what that means.

Also, what I'd like is to remove the 5V supply and only use +/-15V.
The LM301 comparators are indeed powered by bipolar 15V, but as you can see their outputs are forced to 5V since the MC846 can only be powered up to 5V (is this the purpose of the 2 diodes on the pin 8?)
The final output of the NANDs network is going to a normally closed electronic switch

Can anyone help me figure out how to do those mods?
thank you

UPDATE

what do you think of these mods? I've added diodes on the output that goes together, and then pullup resistors.
Would this work now with CMOS NANDs?

If yes, now I need to understand how to remove the 5V supply (not needed anymore since the CMOS chip can withstand 15V.


texts: How do surface mount components withstand heat of reflow while through hole components can not?

texts:
I have read some online tutorials about soldering through hole components which say that transistors and ICs are delicate components and can be easily damaged by heat. So they recommend to keep the soldering iron in contact with the leads not more than 2-3 seconds and also to use heatsink while soldering.

Here is a quote from one of the tutorials

  Some components, such as transistors, can be damaged by heat when soldering so if you are not an expert it is wise to use a heat sink clipped to the lead between the joint and the component body.The heat sink works by taking some of the heat being supplied by the soldering iron and this helps to prevent the component's temperature increasing too much.

But when it comes to soldering surface mount IC and components, some prefer to use a reflow oven which heats up the entire board as well as the delicate IC to a temperature above the melting point of solder.

SO why don't those components get fried?

What makes the tiny components survive such temperatures while big through hole components can't even if they have larger surface to dissipate heat?


texts: How are the connections made to the driver module as shown in the figure below

texts: How are the connections made from the Arduino, the battery, and the motor to the motor driver module? I am not able to make these connections.


texts: How do I calculate the hysteresis losses of a straight line inductor?

texts:
In using a particular type of conductor for an antenna in AC frequencies between 3MHz and 30MHz (HF), it was suggested that magnetic hysteresis losses may be significant if the permeability of the conductor was high.

How do I calculate the hysteresis losses for a straight line inductor carrying an AC current?


texts:
I have to select a WiFi chip for IoT device that basically has the following features:

battery powered (non rechargeable)
acquire sensors using I2C and analog lines every 5 minutes
connect to an access point and send the data on a TCP socket (HTTP GET)

The battery should last at least for 150,000 connections.
I need to roughly estimate the capacity of such a battery...

All the peripherals (sensors, ADC, RF ecc...) are powered ONLY during the acquisition. Hence, during the stand-by, the power consumption is below few tens of uA.

The critical phases are of course connecting to the AP and transmit the data to the server. The devices should first check if the AP is available, otherwise they return to stand-by immediately. And if the AP is available it will be VERY close, so the transmitting power should be kept to the minimum.

Thus I'm looking for a WiFi chip/module which should have this (ideal characteristics):

wide power supply range: 2.7V - 4.1V
very fast power up and shutdown

What might change the time required to connect to the AP?

I'm reading through the documentation of ESP-WROOM-02 but I'm wondering if there are more suitable modules for this application.


texts:
For a project, I am using the following circuit to detect the load3 change. With an 16-bit coulomb counter ADC I am measuring the current I. Using onboard Arduino Uno ADC I am measuring votage, V at node A.
With the equation R = (OCV - V) / I; where OCV is the open circuit voltage at no load condition, R = 10 mΩ + Load3 + Source (3.7 V) internal resistance if it is a battery, I am measuring the change of load3 in the figure. By changing load3 I mean initially there is no load3 (shorted-indicated by blue line) and then I introduce a 10 Ω load3. But the problem is when there is no load3 the code reports it almost correctly (R = 14 mΩ) but with the 10 Ω load3 I found it reports only 80 mΩ instead of 10 Ω.
My questions are:

Why is the measurement mismatch so huge? If it is because of the ADC (both V and I measurements are from coulomb counter and Arduino ADC), how can I address that it is for the ADCs?
What are the possible ways to improve the measurements accuracy?

Thanks!


texts: How can I add a signed vector with an unsigned one in VHDL?

texts:
I would like to know how can I add an unsigned vector with a signed one. The reason is that I am creating a MIPS processor and I would like to add the program counter which is unsigned with the immediate field of I-Type instruction which is signed. Below you can see the datapath and the addition of those 2 vectors.

I've already tried the following resulting in error:

-- Signals used
PC_BRANCH_DEC_OUT   : out std_logic_vector(31 downto 0);
PC_PLUS4_DEC_IN     : in std_logic_vector (31 downto 0);
signal signed_imm_s : std_logic_vector    (31 downto 0);

-- Addition of the signals above
PC_BRANCH_DEC_OUT <= std_logic_vector(unsigned(PC_PLUS4_DEC_IN) + signed(signed_imm_s));

The aforementioned addition works only if both are unsigned or signed.

Is there a workaround to make this addition possible and how?


texts: dsPIC33E ADC with external voltage reference

texts:
I am using dsPIC33EP64MC202-I/SP to read analog inputs with the code shown below. It is using a 2.5V voltage reference on pin5 (VREF+) as ADC reference voltage. When I connect 1.1V to pin3 (AN0) ADC1BUF1 (CH0) reads 0x1F5, which converts to 1.223V (501*(2.5/1024)). AN3 (CH0) reads 0x3FF, which seem correct. What is causing the error in reading AN0?

To test the voltage reference, I changed the code to use AVDD (connected to 3.3V) as voltage reference by setting AD1CON2bits.VCFG = 0. Then AN0, ADC1BUF1 reads 0x155  = 341*(3.3/1024) = 1.099V, which is the correct answer.

So I am wondering why the 2.5V reference is not working as expected?

void initAdc() {
    ANSELAbits.ANSA0 = 1;       // set AN0/RA0 as analog input
    ANSELAbits.ANSA1 = 1;       // set AN1/RA1 as analog input
    ANSELBbits.ANSB0 = 1;       // set AN2/RB0 as analog input
    ANSELBbits.ANSB1 = 1;       // set AN3/RB1 as analog input 2.5V
    TRISAbits.TRISA0 = 1;       // set AN0/RA0 as input
    TRISAbits.TRISA1 = 1;       // set AN1/RA1 as input
    TRISBbits.TRISB0 = 1;       // set AN2/RB0 as input
    TRISBbits.TRISB1 = 1;       // set AN3/RB1 as input
    /* Initialize ADC module */
    AD1CON1 = 0;
    AD1CON1bits.SIMSAM = 1;     // Simultaneous sampling
    AD1CON1bits.SSRC = 7;       // Auto convert
    AD1CON1bits.ASAM = 1;       // auto sample
    AD1CON2 = 0;
    AD1CON2bits.CHPS = 2;       // all four channels
    AD1CON2bits.ALTS = 0;       // Always uses channel input selects for Sample MUXA. MUXB not used
    AD1CON2bits.VCFG = 1;       // External VREFH = VREF+, VREFL = Avss
    AD1CON3 = 0;
    AD1CON3bits.SAMC = 0x1f;    // Auto-Sample Time for 31 TAD
    AD1CON3bits.ADCS = 0x0f;    // TAD = 16TP

    AD1CON4 = 0;

    /* Assign MUXA inputs */
    AD1CHS0bits.CH0SA = 3;      // Channel 0 Positive Input Select for Sample MUXA bits
                                // Channel 0 positive input is AN3
    AD1CHS0bits.CH0NA = 0;      // Channel 0 negative input is VREFL
    AD1CHS123 = 0;              // CH1 = AN0 (voltage FB), CH2 = AN1 (I_OUT), CH3 = AN2 (temp)
    /* Enable interrupts */
    IFS0bits.AD1IF = 0;
    IEC0bits.AD1IE = 0;

    /* Enable ADC module and provide ADC stabilization delay */
    AD1CON1bits.ADON = 1;
    __delay_us(20);
} //initAdc


texts: Confusion regarding Fixed-Biased configuration of JFET

texts:
This is the picture of a fixed-biased JFET, taken from a book :-

This is written in the book, relating to the above pic :-

I am unable to understand why \$ V_{GS} \$ has a different polarity than \$ V_{GG} \$ in the first place. Shouldn't they be of the same polarity according to the connected terminals ?


texts: How to convert raw radar sensor data into custom compressed data format for efficiently storing and archiving on file system

texts:
The binary raw data from the SAR sensor is processed in fpga and outputted as hex. Now, this data we currently store as ASCII in .txt files. However, it takes lots of space in storing.

Is there an efficient way to store these hex data so that it consumes less space and we can efficiently retrieve it for processing using a python application.


texts:
I have a PCB with documentation. In the documentation, there is referred to specific pins of several jumpers and connectors. On the PCB however, there isn't a label or so for which pin has what number. I need to figure out which pin has which number, so that I know the function of each physical pin.

I noticed all connectors have all pins with a rounded tin pad, whilst one pin (either the first or the last when counting from right to left) has a square tin pad:

Is it some kind of convention which number this pin has? After that, how to count the other pins?


texts: Scanning simultaneously across 2-dimensions electronically (like a "3D oscilloscope")

texts:
I have a laser that has sensitivity to two electrical inputs (that can be input simultaneously). Of course, I can easily add an electrical signal with an input of a "linear sweep", and observe the output intensity of my light (retrieved from the voltage outputted by a photodetector). [this photodetector does not have any spatial resolution, and simply gives me a simple DC voltage value representing the intensity of my light field]

By looking at the output as I "linearly sweep" through one of my two inputs, I can see how my output behaves with respect to that degree of freedom.

But this just gives me a 2D slice of the entire 3D picture if I were to consider all possible values of both of the two inputs.

I would think that this is something many people would have already been intersted in having, just for practical reasons. (If I want to find the optimal value right now, I have to move one of the two inputs manually, as I look as I sweep the other degree of freedom)

I'm interested in if there is already a pre-built protocol that I could use to set up a "3D imagining system" where one dimension is the output voltage, and the other two dimensions are the two input voltages.

I have a digitizer card I could send into my output (converting my signal from analog to digital ). Does anyone know of any pre-built programs that might be able to perform such a "3D oscilloscope" feature?

I'm looking for something to save time, so ideally I don't have to write things from scratch or have to set up some entire programming enviornment to implement this.

EDIT:

If there is some confusion over the fact that a laser is involved, please ignore that completely. The fact that there's a laser in the setup has no relevance to answering the question (I guess I shouldn't have even mentioned it). Additionally, although I'm asking for a three-dimensional representation of my data, it has nothing to do with "spatial" dimensions or some sort of representation of something you could see with your eyes.

Putting it strictly mathematically:
I have a system that returns a voltage output as a function of two (electrical, DC) inputs.
$$V_{out} = unknownfunction(V_{input1}, V_{input2})$$

I could look at the output as I "scan" through one of the two inputs (while holding the other input constant). So for clarity, let's say I hold V_input2 = 0. Then I could plug a linear voltage into V_input1, and plug my V_out into an oscilloscope. This would produce a "2D graph" that I could see on my oscilloscope.
If I collect each of these 2D images for EACH fixed value of V_input2, I can line them up such that it forms a 3D graph (where each 2D graph is a "slice" or "cross-section" of the bigger 3D graph).

To me this is a very simple "algorithm" that I can make on my own, but I would prefer if I could just load a prebuilt program that can perform this type of reconstruction for me. I was interested in what types of implementations of this protocol already exist so that I can not waste time reinventing the wheel.


texts: protection device on power line and io lines

texts:
I have seen many design to protect nput circuitry from surge , EFT and ESD
Mov's for surge protection, Choke for Conducted emission TVS for ESD. still i am confused on below point

Q1) If surge is applied to both input power line and all I/O lines then why most of design only had mov on Power lines but not on IO lines.

Q2) TVS diode on IO line will protect from ESD or EFT or both.

Q3) Mov is for surge protection but what device protect circuit from EFT on power lines.

Q4) what protection device used for power lines to protect from ESD.


texts: Protecting electret mic amp from 25mA current spikes on power rail

texts:
I'm looking for some advice on how I might protect an electret mic amplifier from picking up noise from 25mA current bursts that will be happening on the same power rail.

My setup involves 3 major components:

ATTiny1614 mcu
W25Q32JV flash IC
Electret mic w/MAX6644 amp (schematic)

The issue is that whenever I execute a write command to the W25Q32JV module, the temporary higher current draw (~25mA) is being picked up and amplified by the electret mic amp, creating a noticeable "tick" in the mic output.

I've tried adding various bypass caps (0.1u - 100uF) at the VCC/GND pins of each of the components, but it hasn't created a noticeable difference. The mcu only has a single GND pin (no AGND) unfortunately.

Using a separate power supply for the W25Q32JV and the mic/amp isn't an option, although in testing this does significantly improve the mic output.

Does anyone have any suggestions (general or specific) that I might consider?

I'm happy to provide a detailed schematic if it would be helpful, but it's basically just the 3 components listed above with a 0.1uF bypass cap on the ATTiny.

Thank you!

[EDIT 1/1/20]
Thanks for the comments everyone!

@Brian Drummond do you mean placing a low pass RC filter on the VCC input of the mic/preamp board? Do you have any recommendations for RC values to try?

@skvery the flash writes need to occur at the same time as the mic input unfortunately.

@JRE I am using the Adafruit module for the time being. Just using breakouts I have around but I'll be putting together a custom PCB soon.

@Drew agreed, although I'm trying to keep the cost really low so this might not be an option. Just out of curiosity, I tried powering from another 3.3v source I have that uses a AP2112-3.3 and it produced less noise. I may have to play around with a few different regulators.

@Andy aka are you referring to the two 1K resistors (R1, R2) pulling up the mic output?


texts: 45 Ohm volume control on 8 ohm speaker, what would happen?

texts:
A friend of mine was asking me to splice a 45-Ohm intercom speaker volume control between his speakers and receiver, at 6 or 8 Ohm.

Obviously it's not ideal, but what would happen? Would the speakers be damaged? Or just be reeeeeeal low?


texts: Current mirror circuit across a MOSFET: Help needed in understanding the working

texts:
Below is the circuit in which a PNP Current mirror circuit is used to control a P- channel Mosfet. What is the intended operation of this circuit? V2 acts a  power supply voltage for many devices  down  the line.

Is the MOSFET intended to be in ohmic region or saturation?

What will be the voltage at V2?

Does this still work as current mirror?

simulate this circuit – Schematic created using CircuitLab

Edited section:
I have read about ideal diode and understood the following:
If V2 < V1 (10V), it implies
i) Vbe(q2) < Vbe(q1) => Ic(q2) < Ic(q1) => Vc(q2) < Vc(q1)
ii) Q1 just acts like a diode clamped to 0.7V, Q2 acts like a transistor in active region
iii) Some sort of regulation happens with Iq2 and V2. As V2 dips ( say due to a load increase), Q2 conducts less=> M1 is driven harder=> V2 increases.
Iam unable to find to what voltage it gets regulated to? If it has be an ideal diode, somehow it should get regulated very close to V1.
iv) As V2 dips further , Q2 enters enters in cutoff and MOSFET M1 is fully turned ON. After that V2 =V1- I*Rdson
Iam not sure whether the body diode would ever conduct. Also Iam not seeing any current mirroring happening here. May be I correlated this to current mirror wrongly?


texts: One voltage regulator (varistor?) instead of dozens of current limiting resistors in an LED array?

texts:
I am trying to be smart with a breadboard that runs dozens of TTL lines together, and which are monitored with LEDs. All the chips I am using are inherently current limiting enough so I won't burn my diodes, but the LEDs are a load on the TTL lines and some of these dozens of lines drive only a single TTL input high, but some drive more than one, especially data/address bus lines are driving up to 10 inputs, the limit for TTL. So, I want to use the highest possible resistor(s) in my LED array to keep the light visible (not glaring bright anyway) yet suck the least amount of current from the bus to allow all the inputs to be reliably driven high.

simulate this circuit – Schematic created using CircuitLab

Now I am lazy and prefer to be smart rather than soldering together some contraption of LEDs with built-in resistors. Yes that would be ideal and maybe in the USA I could buy it, but I'm not there now and I can't buy fancy LED arrays with common cathode and in-built resistors.

So I thought about what if I use a single variable resistor on the upper ground bar on my breadboard. If I use the usual 220 Ω resistor I can see the LEDs OK until 4 light up, after that it gets too dim. I never have all of them light up, say, at a maximum 8 data / address bits (0xFF), 8 control lines that are active low, and perhaps 4 control lines that are active high. So, that's about 20, two dozen. Not a small number.

So if the number of LEDs that are on is about constant, I could just use a small resistor, like 10 Ω, and I believe I should be OK. But the number is of LEDs lit is of course not constant.

simulate this circuit

So I wonder, what if I replace that single fixed resistor R_com with some smart variable thing? In this case, what about a voltage regulator? Wouldn't a voltage regulator ensure that the "output" voltage over it stays constant so that as more current goes through the diodes, raising the voltage from all the TTL lines being high, it would reduce its effective resistance to ground to keep the voltage level constant? Or even a varistor?

simulate this circuit

Does anyone know of a trick like that?

PS: I know I can solder it fixed on a board and don't have to fuzz so much about number of components. But this is all still prototyping, I will experiment with ergonomics, figuring out which colors and brightness type of LEDs works best, adding more lines or removing some lines, until I have something that works. The best I can think of without the trick would be to solder resistors on the feet of the LED, but that is a lot of work, clutter, and prone to breakage as the resistor wires are so fine these days.


texts: Is it possible to use a MOSFET for Li-ion reverse polarity protection when protecting a charger?

texts: I've made a simple charger out of 4 TP4056 modules and 4 18650 sockets. These modules have overcharge, undercharge and overcurrent protection included, but I also want to know how simple it would be to make it also reverse-polarity protected since that condition is much more likely as the above 3 combined, given that I'll swap batteries often and am bound to be mistaken once in a while. I'll also likely build some chargers for other people for their needs and this could be a nice feature. Could I just use the MOSFET trick to make reverse polarity protection for the charger or is there something I'm missing?


texts: I am making a DAC circuit with uses an AD7541A chip which is going to be connected to another board with a microcontroller on it. Now the AD7541A gets fried if someone turns it on while all the pins are floating. So I want to ensure that even if someone accidentally turns on the circuit with pins floating, the chip does not fry. So what can I do to ensure that?


texts: How do the TX/RX/CTS/RTS/DSR/DTR/DCD/RI/GND signal monitor LEDs on these odd FTDI-based USB-RS232 converters work?

texts:
While searching for a "decent" USB-RS232 converter, I turned up the following two fascinating creations which have status LEDs for all the signal lines:

This concept really appeals to me from a debugging/verification point of view (although I do NOT get what the GND signal LED is expected to do... stay on all the time?). My only problem is that the blue one is $25 and the black one is $35 (despite the fact that they both appear to be identical - they're probably based on the same reference design). In my opinion, that is way too much for a device I can essentially go and grab the barebones version of off eBay for less than $3 shipped. Thus, my question is, how do these LEDs work, and would it be possible to mod the same kind of functionality into a cheaper converter (perhaps one of the FTDI breakout PCBs on eBay)?

I'd like to make the point that while I am likely to wind up with a small collection of USB converters as time goes by, this is something I see I'm only likely to need one of any time soon, so I don't mind having to put a bit of effort into building it, although I don't (yet) have the tools to work with SMT componentry; I also have no need for the end result to be compact/self-contained - [premade] PCB-based solutions are fine.


texts: Designing glue logic circuit for 16 bit data input to 32 bit data output with half the input clock frequency

texts: I need to design a 16 bit parallel data in and 32 bit parallel data out synchronous sequential  glue logic circuit with output clock frequency half the input frequency.Can anyone please provide me an insight on its implementation..?


texts: How to interface a C64/Atari joystick port with the ESP8266 (level shifting from 5 to 3.3V)?

texts:
I'm working on a device based on an ESP8266 (Wemos D1 Mini) that shall be connected to a C64 or Atari 8-Bit computer's joystick port. At the same time, a normal joystick could be connected (signals are passed through).
The device should then both be able to listen to the joystick movements as well as also be able to simulate a joystick.

In my current setup, I have taken the risk of hooking up the ESP directly to the joystick cable, despite the fact that the ESP should not have 5V as input on the pins. So far it has been running for a few days now without a problem, but I want to make it right and apply the correct voltage. If possible, this should be a voltage divider done with resistors because I want people to be able to build this device on a bread board.

My problem now lies in the fact that the joystick port constantly delivers 5V on the direction pins. For a voltage divider to work, I would have to have, say, a 1k and a 2k resistor leading from 5V to GND, and then tap the signal between the resistors and connect the resulting 3.3V to the ESP.
However, the joystick only connects the corresponding wires to ground if it is moved to that direction. If I understand things correctly, that would mean if the joystick is in idle position, none of the 5V pins are connected to ground and thus there is no voltage division. As a result, the 5V from the joystick port would then again be applied directly to the ESP's pins.

On the other hand, if I make a bypass after the two resistors to GND for the voltage divider to work, the C64/Atari would detect that the direction pin has been connected to ground and thus interpret this as the joystick's move in that direction.

If my thoughts are correct, what other way could there be to bring down the joystick port's current to 3.3V?

Thanks in advance for any ideas!


texts:
A stm32f407vet6 module route DP (PB15/Pin54 of LQFP100) and DM (PB14/Pin53 of LQFP100) of one USB full speed port to two separate header connectors which are 7cm from each other. The module designer doesn't consider this USB port to be used (there is another USB port on PA11/PA12).

Since the MCU is placed in the center of the module, the trace length should be 3~6 cm each. It is possible the traces have via too. The board should be 2 layer to be low cost.

Will the USB full speed port work fine? Does the trace length need to be matched to some precision (like < 1cm) on the carrier board?

I'v read this How critical is the layout of USB data lines / how does my layout look?, but I'm still not sure about this specific case with separated trace that is routed without considering USB at all.

Update: This two wires are routed as non USB wire separately on the module, and are separated by 7cm, then also need to be routed by ~3cm each on the carrier board to go together again. The question is about how long can USB full speed traces be routed separated? If based on frequency and wave length, differential cable won't be needed for USB full speed - any to wire will work.


texts: Why do DC motor controllers have minimum voltage?

texts:
I'm trying to build an H bridge to rapidly toggle between a variable voltage from 0 to ±30v.

When I look online for pre-built motor controllers, the lowest voltage they go is around 1v.

This is strange because when I look at a simple four chip MOSFET H bridge design, I don't see any reason why there should be a lower limit on the voltage that actually hits the motor?  I understand there needs to be a minimal voltage to activate the MOSFET.

Sample spec sheet:

Here is another one that goes from 5v to 12v.

What I expect the circuit to contain:

Four of these chips (863-NDDL01N60Z-1G) should be able to achieve a similar effect, but lets you get low voltage across the "motor" terminal?

Why can't these shields output a small voltage across the motor? For example, 0.2v?


texts: Multiple two pin multi-color LEDs pattern - how does this work?

texts:
I'm quite blank when it comes to electronics, but am trying to learn...

So I bought a DIY Learning Kit from Banggood to get some solder practice.

As you can see from this video, the leds will change color and turn on and off in different patterns.

This question already establish that two pin RGB leds most likely contains some kind of micro chip, but it doesn't say anything about how they can be controlled.

The chip on the board is a STC15F204AE, and I guess that's the one responsible for creating the patterns. But again - how?

Is it just a fixed sequence pattern in the LED, and then the chip ensures that each LED receives power right after the previous, or is the LEDs addressable some how?


texts: Designing a 4-bit binary number divider circuit

texts: I was given homework to design a 4-bit binary number divider which divides four bits by 5 (101 in binary). I tried looking at a lot of solutions without success. All I can use are basic gates, no registers and no sequential circuits. I have studied multipliers, adders and substractors but can't make a divider. Any help?


texts: Working Principle of Amplifier in INA290-Q1

texts:
I'm looking at TI's current sense amplifier specific to INA290-Q1.

Their method for amplifying the differential voltage over the shunt resistor is shown in the image below:

I am familiar with a standard differential amplifier where we have resistors in the feedback loop and an additional resistor on the + terminal of the op-amp going to GND.

My question is how this amplification circuit works and the advantages it has over a standard differential amplifier.

For reference, this is their datasheet.


texts: Op-amp inductive output impedance oscillation

texts:
In Learning the Art of Electronics pg.362, the author presents an op-amp follower driving a long cable. I don't understand the explanation given for the cause of oscillation. In particular, the author claims that the inductive output impedance of the op-amp (caused by weakened feedback due to op-amp dominant pole gain roll-off - not actual inductance) combined with the cable's capacitance reduces the phase margin to zero at a frequency where gain is greater than unity, causing oscillation. However, I don't understand how the closed-loop output impedance can cause oscillation.

I was under the impression that stability is determined entirely by the loop-gain, not the closed-loop gain. For instance, to analyze stability, the loop is broken (say, at the inverting terminal of the op-amp), the op-amp output is loaded with the impedance seen looking into the break point, the non-inverting input is grounded, and a signal is applied at the inverting input. The loop gain is then the negative of the gain measured at the break point. But no-where in this analysis does the op-amp output impedance appear inductive because this is not a closed-loop analysis.

How can the inductive output impedance of the closed-loop circuit (which becomes entirely resistive when the loop is opened) affect phase-margin if phase-margin depends solely on the loop-gain and not on the closed-loop gain?


texts: What are the effects of self-inductance in a DC armature?

texts:
So, I just stopped to think that, for the armature coils, the current passing through them varies with time due to commutation.
The voltage applied to different conductors in the armature varies abruptly, and I'd expect it to respond similarly to an inductor fed with a square wave voltage, presenting an impedance that's greater than it's DC resistance (and also distorting the current wave form a lot).
So, to test that, I fed only the armature of a DC motor,while leaving the field winding open.
I had to use a resistance in series to limit the current, it was a 21.5 ohm resistance.
With the armature stationary, the current was 950 mA DC. Then I wound string on its axis and spun it the fastest I could, the current dropped by 100 mA at peak speed.
Considering the series resistance and the voltage, this means the armature impedance rose from 4.6 ohms while stationary to 7.7 ohms while spinning.
I also tested doing it with the field winding shorted, it didn't make any difference.
Also, It's interesting to note that, while there's no DC voltage being induced on the field winding, there is a high frequency AC voltage with considerable magnitude being induced on it.
My multimeter measured up to 7 V RMS induced in the field winding, with a peak frequency of 1.5 kHz when I spun the axis the fastest I could with the string (which I consider to be probably under 2000 rpm, this isn't a small motor).
Anyway, it looks like self-inductance in the armature is reducing the DC current on itself a lot.
I also tried to measure AC current on the armature while spinning it, but the greatest value I got was a mere 10 mA in peak speed, and obviously zero while it was stationary.
Anyway: How do I take this in account?
Previously I considered that the armature total impedance depended only on its resistance and the back-emf from the main field, but seems like there's also self-inductance here.


texts: Is it possible to connect arduino pro with an android phone with a usb cable?

texts:
I would like to read some potentiometers into my android phone. Is it possible to connect an arduino (ideally the arduino pro w/ USB-Serial-FTDI) to an android phone*? Other than the software part, I'm also wondering about the physical connection. I can't find a micro-b to micro-b usb cable on the internet.

*I have an Android phone that runs version 4.x and another that runs 4.4.4.


texts: How the frequency of oscillation is determined in a multi-resonance oscillator circuit?

texts:
If we have a self-oscillator with multiple resonant frequencies, what are the criteria for the preferred frequency of oscillation?

For example, a push-pull oscillator with parallel-compensated two coupled inductors will have two resonance frequencies at the high coupling i.e \$f_{\rm{resonance}}\approx f_0/\sqrt{1\pm k}\$.

How do we determine the frequency of oscillation in such cases?


texts:
I'm new to electronics and I'm trying to reverse engineer the circuit board in an R/C car. I've come across a diode and it is labelled...

C3V3
 5T

1) I assume 3V3 means 3.3V, but what do the C and 5T mean?

2) Is the black stripe on the input or output side?

3) Is there a dead giveaway letting me know this is a "zener" diode? I ask because I've been web searching and all results turn up as a zener diode.


texts: Please help identifying this SOT-23 part from a vehicle sensor

texts:
What is this encircled part in the picture? It is labeled "WB2" and "62".

This is a vehicle sensor.


texts: Drain/Source Voltage -- Logic Level N-Channel Power MOSFETs

texts:
I'm using the following MOSFET:

https://www.sparkfun.com/datasheets/Components/General/RFP30N06LE.pdf

I have 5V going into Gate, and source is connected to ground. My understanding from the datasheet is that, this would be enough to allow Vds.

My multimeter does detect the Vgs of 5V, but does not detect any voltage between drain and source.

Why is there no voltage between drain and source even though i've met the threshold Vgs?


texts: Compute the minimum number of 120Ω resistors to get 80Ω of resistance?

texts:
I recently had to take test in basic electronics. I didn't get one question right, but I don't quite understand why.

How many 120Ω resistors are at minimum required to get a resistance of 80Ω?

The possible answers to this question are 2, 3, 4 and 6. The only answer I can come up with is 6, with the resistors arranged as seen bellow. But 6 isn't the correct answer.

Question:

How many resistors are required and to arrange them?

simulate this circuit – Schematic created using CircuitLab

I only know the very basics of electronics, so I hope my thoughts are correct.


texts: CE Amplifier Small-Signal Equivalent Circuit model confusion

texts:
The following CE Amplifier Small-Signal Equivalent Circuit and nodal equations are from this site.

I'm completely lost how they form the above KCL Equations for the nodes B, C and D.

For example, for B node the currents \$\frac{v_i}{R_s}\$ and \$\frac{v_e}{r_{\pi}}\$ does not make sense to me for a KCL equation at node B. \$\frac{v_i}{R_s}\$ is a current when \$V_i\$ and \$R_s\$ is shorted. What is that to do with the KCL?

Similarly for node C what is the current \$\frac{v_e}{r_o}\$? Again this equation doesn't make sense to form a KCL for node C.

What are the current directions in these cases? And in this model \$R_C\$ is shorted but why \$V_i\$ is not shorted to ground?(as done in a any small signal analysis) Can someone explain how these equations form a bit in more detail?


texts: Trying to understand negative voltage generation with capacitors and diodes

texts:
I want to generate a negative voltage from a possitive rail. To do so, I'm reading this article. Here is the schematics it is depicting, assument the input step is +10V:

I understand that when the capacitor is charged, there will be a potential difference of 9.7V, since the first plate is at 10V and the second one needs to be at 0.7 because of D1.
However, the text also says:

When the positive plate drops rapidly from 10V to 0V, this 9.3V potential difference must be maintained due to coupling. Therefore, the negative plate drops to -9.3V.

I don't get that. My understanding is that if the voltage in the first plate drops sharply to 0V, C1 won't discharge through D1, because D1 won't be forward biased when its anode goes below 0.7V. Therefore, those 0.7V should discharge through the former C1 positive plate, which is now at 0V (so GND).
How is that the negative plate drops to -9.3V? how is that possible if D1 is supposed to force its anode to be at +0.7V with respect to ground?


texts: How to make such a scheme in an electronic workbench

texts: This is a transistor circuit with a common collector


texts:
What I want to do, re my question of a time shifted resistor, is to analyze the input of a switching regulator consisting of the input capacitor with its ESR and the inductance of the trace maybe with or without the resistance of the trace.  I am interested in the regulator switch-off transients where the load current is 5A, the regulator takes 15nsec (a SWAG) to turn off and the regulator is represented in the circuit as a 3 ohm load resistor.  I am assuming a 24V DC input;  C is 15uF with 1 ohm ESR; L is 0.05uH; I ignored the 7 mohm trace resistance.  I can't figure out how (if possible at all) to set up a Laplace transform circuit that runs the 5A steady state for a short period, and then the 5A abruptly drops to zero.  I want to understand the transient at the LC node.  At the basic level about 8v reverse EMF is produced across the inductance, but instant voltage change is not allowed with a capacitor.  Or if the high dv/dt is assumed you get current through the capacitor in the millions of amps.  But then if current flows through the capacitor, the abrupt current drop through the inductance no longer exists removing the back EMF;  and the dog keeps chasing its tail.
In any event I am unable to come up with a Laplace transform that accounts for the abrupt drop to zero of the load current through the inductance, and opens the load resistor.  My first idea was the change the load resistor from 3 ohms to 10^12 ohms time shifted, but that fell apart.


texts: Why does a capacitor block DC and not AC?

texts: If someone can explain why a capacitor blocks DC, but not AC, with some math, I will understand all of that much better. I know that there are picture animations illustrating this, but I really want to know this a little bit more detailed.


texts:
I have a scenario that implies measuring 2 inputs:
- voltage through a resistive divider
- current through a hall sensor followed by opamp for offset, direction and scaling

In my software, each channel has it's own average factor. I plan to use a simple 2 points (MIN/MAX) calibration technique on each channel.

The problem is slightly more complicated since my sensor use a opamp that (may) have it's own gain offset errors. Moreover, the sensor itself vary with Vdd and for this effect I use ratiometric measurement: ADC and sensor share the same Vref.

For voltage measurement I use a simple resistive divider which isn't perfect (measured ratio it's quite different from calculated) mostly due to un-precise resistors used. But even when I'll use 1% will be some errors which I compensate with 2 point method above.

The question is where should I measure / apply the calibration data?

Calibrate once raw ADC data (offset and gain) and use for all channels
Use separate 2 points for each channel on entire paths:

hall sensor -> opamp -> adc -> average for this channel -> apply calibration
voltage -> divider -> adc -> average for this channel -> apply calibration


texts:
I am using a MJH6284 (Acting as a switch) to power 15 BXRA LED's (Max i = 1000mA, V=9.5) How do I find out the electrical conditions under which the transistor will power the LED, i.e - the supply voltage- Vcc, resistance and voltage at the Base??

Thanks.


texts: FCC rules for wideband / spread spectrum devices

texts:
I'd like to clarify how the FCC measures power in a frequency band (both for intentional and unintentional radiators).  There are devices which either frequency hop (output is a sine wave, but center frequency may jump quickly) or which have modulation that broadens the frequency band (eg FM); for an ultra-wideband example, the output could be a single Gaussian pulse or half-sine wave.  A lot of the FCC regs describe field limits in terms of the field in uV/m at a frequency, or at all frequencies within a range; but obviously devices like this don't have a single operating frequency, and the rms field value depends on the time interval used for averaging as well as the bandwidth of the instrument.
An example of this type of regulation from 45 CFR 15 is here:

How exactly is the field strength measured for FCC purposes?  Is there some specification like "the meter will measure RMS power using 100ms averages of each 1MHz wide band in 1MHz steps over the whole range of interest" (or something like that)?
If the device radiates quite a lot of total power, but spread evenly across frequencies (near the limit in uV/m at each single frequency), would it pass?  What if the power comes in pulses which are much above the limit, but the rms values are very low?
I'm interested in both Part 15 and Part 18 type devices.


texts: Why, where and how we use envelope detector in AM demodulation?

texts:
I have studied AM modulation and demodulation. But i can't understand the purpose of envelope detector in demodulation. So my question is:
Why, where and how we use envelope detector in AM modulation?


texts:
With the recent Cortex-M rage, there seems to be a lot of 8bit bashing going around.

I was wondering what specific use cases engineers encountered where 8bit MCUs were the preferred choice over 32bit, and what decisions informed their choice.

I think this information proves useful as an aid for others who need to make a similar choice between 8/32bit.


texts:
One design of light rail electrification is:
1. AC from a power company is rectified to DC
2. In the train the DC is inverted back to AC for use by trains AC motors, etc.
3. Then changed back to DC to return to the substation.

Why would a design like this be used?


texts: How can I detect angular movements and disregard lateral movements?

texts:
I'm working on a project that involves a flat platform that a user can tilt from side to side and forward and back. I'd like a sensor that can monitor the angle difference between the platform's original position on and its current orientation.

Do I want a tilt sensor, an accelerometer, a gyro or IMU?

To provide a little more background, this is supposed to be a game that the user will play by holding the plane with both hands and tilting it in the two axes. I wouldn't expect it to move around a lot, but the user might move the platform if they start walking around (translation as opposed to rotation). Can any of the above devices distinguish between lateral movement and tilting? I only care about rotation and would like to ignore any incidental translation.


texts: What certifications are needed for GPS/GSM devices in AirPort?

texts: I am kind new in industrial engineering my company has order for several devices which would be used in airport Technics cars. Do I need some kind of special certification for devices that I create to be allowed used in airports?


texts: Is there any difference between pin 13 and the rest of the pins?

texts:
Pin 13 has a surface mounted LED on it. Aside from the fact that it makes something light up, is there any non-negligible difference between this pin and a general digital pin?

For example, if I analogWrite() on pins 12 and 13, will the output on 13 be significantly less?


texts: Negative recommended intensity on read of logical 1 D-latch octal register

texts:
I am very new to electronic design, even if I do have some bases in electric design.

For an hypothetical circuit I'm designing, I need some D-latches to operate as 8 bit registers. Searching for chips suited for this,
I found this datasheet :  http://www.ti.com/lit/ds/symlink/cd74ac373.pdf

While reading the specifications, something struck me : the "High level output voltage" entry on the recommended operation conditions table suggests by it's test conditions, that the current on the pin be negative when reading a logical 1.

While this may also be misinterpretation of the table causing this nonsense, if it's not, how to design circuits such that they do accept the negative current (maybe shift it to 0 mA ?)

Sorry again if my question is dumb.


texts: Common-Emitter NPN Transistor Amplifier Simulation Failed

texts:
I'm trying to simulate a simple common-emitter transistor amplifier presented as an example in Practical Electronics for Inventors in Qucs.

The circuity is identical to the one presented in the book. To investigate the behavior of the amplifier, I feed a 100 mV square wave at the input.

It shows the voltage on the DC-blocking capacitor - it gets charged and starts output a stabilized AC signal, but unfortunately, it failed to show any voltage from the output side.

I've attempted various output levels and frequencies of the square wave generator, from 1 volts to 20 volts, but none of the simulations showed the switching or amplifying behavior of the transistor.

I also tried to use an AC-signal source, but in this case, the simulation takes forever to complete. This particular issue has been discussed by the developers from the official project, who explained that Qucsator, the simulation engine, is more suitable for RF circuits simulation in frequency domain, and is known to have problematic behavior running simulation in the time-domain.

Following the suggestion of the developers, I tried to run the same simulation in Qucs-S, which instead uses NgSPICE as the simulation engine. Qucs-S generated the following netlist,

* Qucs 0.0.21 /home/gaizi/qucs/trans2.sch
.INCLUDE "/usr/local/share/qucs-s/xspice_cmlib/include/ngspice_mathfunc.inc"
* Qucs 0.0.21  /home/gaizi/qucs/trans2.sch
R2 0 _net0  1K
C3 _net1 in  0.32U
R3 in 0  110K
R4 0 in  10K
R1 out 0  10K
V1 0 0 DC 20
R5 _net2 _net0  74
C4 0 _net2  16U
QT_2N2222_1 out in _net0 QMOD_T_2N2222_1 AREA=1.0 TEMP=26.85
.MODEL QMOD_T_2N2222_1 npn (Is=1e-14 Nf=1 Nr=1 Ikf=0.3 Ikr=0 Vaf=100 Var=0 Ise=0 Ne=1.5 Isc=0 Nc=2 Bf=200 Br=3 Rbm=0 Irb=0 Rc=3 Re=1 Rb=10 Cje=2.5e-11 Vje=0.75 Mje=0.33 Cjc=8e-12 Vjc=0.75 Mjc=0.33 Xcjc=1 Cjs=0 Vjs=0.75 Mjs=0 Fc=0.5 Tf=4e-10 Xtf=3 Vtf=0 Itf=2 Tr=1e-07 Kf=0 Af=1 Ptf=0 Xtb=0 Xti=3 Eg=1.11 Tnom=26.85 )
V2 _net1 0 DC 0 SIN(0 1 1G 0 0 0) AC 1
.control
echo "" > spice4qucs.cir.noise
echo "" > spice4qucs.cir.pz
tran 0.000990099 0.1 0
write trans2_tran.txt v(in) v(out)
destroy all
reset

exit
.endc
.END

But in this case, the simulation doesn't even run.

$ ngspice netlist.cir
******
** ngspice-30 : Circuit level simulation program
** The U. C. Berkeley CAD Group
** Copyright 1985-1994, Regents of the University of California.
** Please get your ngspice manual from http://ngspice.sourceforge.net/docs.html
** Please file your bug-reports at http://ngspice.sourceforge.net/bugrep.html
** Creation Date: Sun Jan 20 13:41:46 UTC 2019
******

Circuit: * qucs 0.0.21 /home/gaizi/qucs/trans2.sch

Doing analysis at TEMP = 27.000000 and TNOM = 27.000000

Fatal error: instance v1 is a shorted VSRC
doAnalyses: operation not supported

It says the voltage source v1 is shorted, which doesn't make sense.

My question is,

The circuit doesn't output anything in the original Qucs simulation with a square wave signal source, why? Is there something wrong in my circuity, or that I've hit some known limitations of the simulation?
Why can't the netlist generated from Qucs-S be simulated by NgSPICE? I've heard using multiple ideal voltage sources at the same time in a SPICE simulation may be problematic, then, what is the appropriate way to simulate the behavior of the circuit under a signal source?

Thanks.


texts:
I have made the following astable circuit in Multisim:

However, it didn't work (oscilloscope reads 0V as an output.)

I think the problem is because of VDD and GND pins which are hidden in Multisim.

Does anybody know how can I make them visible? If I have another mistake please tell me.


texts: How do I understand the effect when the load current is over the inductor's saturation current?

texts:
Got a question about the effect after the current over the saturation current in a buck DC-DC regulator.
I'm thinking of a theory that due to the fact that the inductance will be downgraded if Isat was reached and exceeded, and by the equation V=Ldi/dt, since the V is kept the same(assume Vout is in steady state? not sure why....), and L is now degraded, so (di/dt) is increased, and that's why we can see a ramp up in the current waveform (at the end of a cycle), instead of a linearly go up current in normal operation.
Not sure if my understanding is correct, but I need a more intuition explanation to explain why the inductor would act like a wire(or something else?) after the current exceeds Isat, and chances are that it will damage the component (inductor or the MOS?).
Can someone help me on this with some fundamental equations?
Thanks a lot!


texts: Is it possible to convert 3 Phase 220V to 110V without use of a transformer?

texts: I am living in an area where line voltage is 220V. If I have access to all 3 phases, is it possible to create a "socket" with output voltage of ~110V, without use of a transformer? This is primarily a thought experiment, rather than a project with definite scope.


texts: Fan not working on motherboard even if same voltage works with batteries

texts:
First of all I want to mention that I have no knowledge electrical field, so please forgive me if I will not be explicitly enough or I lack some terms, but I know no one with knowledge about electricity and spend a lot of time trying to figure out what is going on using google.

I bought a 5V/100mA fan for my Odroix XU4Q single board computer.
(full fan specs: http://noctua.at/en/nf-a4x20-5v/specification)
When I connect it to 2 pins socket on Odroid XU4Q board, fan is not working. That socket is supposed to
provide 5V/200mA and it is designed for and sold along with a CPU
fan of 5V/120mA

(full CPU fan specs: http://www.hardkernel.com/main/products/prdt_info.php?g_code=G146727436639 )

(full Odroid specs: https://dn.odroid.com/5422/ODROID-XU4/Schematics/XU4_MAIN_REV0.1_20151202_LOT1606.pdf , page 4 for FAN)
If I connect ground(black) and voltage(red) to USB or 3 x AAA 1.5V
batteries, fan is working.
I measured voltage on the board, but it seems fine. On 100%
load, voltage is ~4.10V
(fan intensity is based on voltage which is controlled by cpu temperature)
I measured the 3 x AAA batteries and it is the same voltage: ~4.10V.
Current while fan is mounted on batteries is oscillating pretty much, between 15mA to 65mA, but tends to stay more around 60mA
Current with fan mounted to the board, it is almost 0. I am assuming electricity is not going through my fan's circuit.
mounted the fan to the USB port of the same Odroid board and stressed CPU to 100% load to consume as much power as it can. Fan still starts. Measured voltage in USB port is ~4.90V
added 1 AAA battery in series with the board to create higher voltage,
which measured ~5.25V (black wire coming from the board went into "+" of the battery and another wire from the "-" of the battery went to the fan black wire input). Fan not starting.

So, what I know:

I=E/R (I=current, E=voltage, R=resistance)
R should be the same (because same circuit is used: fan, cables)
Voltage is the same

What I don't get it:

Why the current is 0 if E and R are the same between batteries use and board use?!
What may be the problem?
What do you suggest me to do/check?

Thank you for your time!


texts: Lowest possible latency, 1-way RF transmission

texts:
I am working on a wireless telemetry project with a bit of a twist.

I have a CC3220 inside of a rotating shaft connected to an AMS board collecting pitch readings from a magnet mounted inside.

The data is being sampled at 20 MHz and stored locally on the MCU.  After 5 seconds of collection, the data is wirelessly transmitted (over Wi-Fi) to my computer where some software crunches the results to display graphically.

Along with the pitch measurements being collected inside the shaft, I am also gathering other metrics with sensors connected directly to my computer.  I would like to see how the pitch affects these other readings, so I need to stitch the data together after I send it over Wi-Fi.

The problem is with lining up the data.  Because the MCU is separate from the rest of the sensors, it doesn’t start at the same time that I start the others because of the delay induced by using Wi-Fi, so I don’t know the initial time of the first pitch reading to line up with the rest of the data I collect.

I started looking into other RF solutions, including Bluetooth and Zigbee but had to rule those out because of the latency (3 seconds and 15 milliseconds respectively.)  This got me wondering if there was ANY wireless protocol that has a latency of less than half a millisecond.  The transmission would only have to be one-way.  A simple pulse meaning “GO!” to start sampling; then using Wi-Fi to send the data back.  If there is no RF solution then I will have to re-engineer the housing to allow a laser diode to have line of sight, but this will cause the cost of this project to skyrocket… which I would like to avoid!

Do you guys have any suggested reading on RF latency?  Have any of you had to overcome a similar problem?  If you need any more info let me know, I’m not very experienced yet, but that’s why I’m here trying to learn!


texts: DIY mixer - use diodes to prevent input potentiometers influencing each other

texts:
I've builded a simple amplifier (just stereo audio in, two speaker outs) and I'm building a mixer for it.

There are some audio inputs, which goes through stereo potentiometers (volume for each input) and then all into main potentiometer (master volume). It looks like this:

EDIT: The schematics is wrong. To wiper is connected output, not ground. To resistive strips is connected ground and input.

But when I connected, I find out how stupid this is. The potentiometers are influecing each other, so when I lower one of the outputs by turning potentiometer, other inputs's volume's are also lowered.
I tried to solve this by putting diode after each potentiometer, before the wire are joined, but this extremely lowered audio quality (the speakers were just buzzing the melody).

How to solve this? Is there any diode made for audio?

And my second problem is, I have mono wireless microphone with mono outpout (output from lm741 based preamplifier) and I want to make it stereo, but if I will connect the output to both L a R signals and joining them, as far as I know, the stereo inputs will no longer be stereo.

How to make mono signal (one input) playing on both, L a R signals, without destroying the stereo on other inputs?

Thanks.


texts: Amplifier humming when no source is attached

texts:
I've got a little problem with an amplifier board.
When no audio source is plugged in, there's a loud hum or buzz (rather low-frequency, I unfortunately don't have the proper measuring equipment). As soon as I plug in a source, my smartphone for example, the loudness of the hum decreases dramatically, and when I turn on music (hence sending an audio signal) it disappears completely.
I had a look on the internet, but all i could find was about the amp humming if there was something attached.
This looks like the board I'm using.
I would be glad if anyone could help.


texts: Design a circuit in Ltspice based on the input and output

texts: I need to design a circuit that takes a sinusoidal input with peak of 8V and generate an output such that the positive peaks remain the same and the negative peaks get inverted and have a peak of 4V.


texts: Why aren't antenna signals inside smartphones stopped by the metal case?

texts:
Our smartphones or other device are surrounded by metal, yet there are plenty of antennas inside it (NFC, 4G, Bluetooth, ...).

How can it work ? Isn't the metal supposed to block RF signals ?


texts:
We have ordered from a supplier some high power leds - 20W RGB.
They dont have any data sheet , and so we where thinking that we would try and find quickly how to connect them .

Everything we tried failed, we even checked a few of them, and nothing worked.

Well, what happens is that sometimes it flashes for a second and then never turn on again, and sometimes we see a very low green light from it .

We have the right voltage and current supply for it (600mA,32V) , but i guess we still had not guess the right configuration.

Please check this image :

We tried also to switch the vcc/gnd, we also tried to ground the body and then give ground to one of the rgb pins, but nothing ...

I guess it works in low, so that you give it a vcc, then you ground the r/g/b to get the right color .

What are we missing here ?


texts: How do bitshifts work on the electrical layer?

texts:
I'm a software developer and I understand how arithmetic and logical bitshifts work in principle.

But how do they work on the electrical layer?

I might have a completely wrong imagination;

Let's say we have the binary value 0000 1011 and left shift it by 2.
The outcome is 0010 1100, nothing special.

But how do the bits "jump" to their second neighbors?

Edit: Fixed a slip, where I wrote "right shift" while doing a left shift.

Edit: Added ALU and DIGITAL-LOGIC tags


texts: Can I connect 2 power supplies for 16 meters LED RGB strip?

texts:
I've bought 2 sets of 10 meter LED RGB strip (7.2w/m) for a room. Then I've cut them to around 8 meters each to get 16 meters. Everything seemed fine but one thing, because it's 2 separate controllers, sometimes color cycling can get out of sync and to fix that, I was thinking:

If I'm going to buy a new 144W controller, can I save a buck by not buying new power supply? Because both of the power supplies are 12V 6A (72W), can combining them make it 144W? I really feel dumb for asking this, but I'm on a tight budget.

Or is there another way of fixing that "out of sync color cycling" problem?


texts: Low-pass (band-pass) filter for op amp circuit

texts:
I have a circuit that amplifies a one-shot inductive trigger pulse of about 1.3Khz (@780 micro sec period) from about 10-200mV to about 3-4V.  Between C1 and R3 there is a 0.13uH inductor coil with 11 ohms resistance that is being triggered externally (magnetically) and eddy currents are created as a result. I did not know what symbol I should use for the inductor coil which is actually that IG1 sine-wave source in my circuit. So there is no ground there, just a coil between C1 and R3.

I am using the op amp as a non-inverting amp. The inverting amp (using the negative input of the amp) was too unstable. It basically acted like a comparator and with every tiny imbalance between the + and - it fired the Output. The circuit is single supply 3.3V, and only the op amp's power pin is powered.

It works good, but seems to have problems with weaker signals. The oscope shows either a lower amplitude first square wave of the pulse-period, or a lower amplitude second square wave.  From the 3-4V it goes to 1-2V.  Weaker, not only means lower mV amplitude, but it seems that at frequencies lower/higher away the signal is being cut off...by the circuit's inherent low/high-pass (band-pass)?

I used Texas Instrument's online program to design an op amp circuit with the correct band-pass I need.  It's 500Hz-10Khz (a range of about 100 micro sec - 2000 mico sec periods).  I used a single stage op amp, for now.

But, I hope to see were the problem is with my current circuit before I make this other one suggested by TI.  The TI circuit is designed to cut-off at about -40DB by default as part of the TI design.  Is that minimum recommended cut-off for band-pass filters?

Here is the TI-designed circuit:

And here is the one I built that seems to have intermittent cut-off(?) issues:

This is the oscope when reading a strong/good signal:

Reading a weaker signal.  Seem like the first wave is spiked instead of being more like a square:

Reading a weaker signal.  Seem like the first wave is spiked instead of being more like a square:


texts: USB to TTL (CH340G) and maybe Logic level converter to program chips

texts:
Since i have a bunch of Atmega328p-pu(5v), Attiny85(1-5v), ESP8266(3.3v) & Raspberry's(3.3v) it was time to get:

A USB to TTL
Logic level converter

Now before buying that stuff i read about those USB to TTL converters.There are alot of them. Some need special drivers, some destroy chips if not original and some cost alot.
I found that one CH340G, i read good things about that USB to TTL. People are happy with the product and so i buyed it.
Like i said i need it both for the Atmel chips but also for the ESP8266 wich is 3.3v. It works on the ESP8266 with a minor problem. Some sources say that it needs drivers for older win OS's or OSX. I'm on win8.1 and it works out of the box apparently, even if i tried to install & uninstall the special drivers.
First Problem:
I can't get it to work with Atmega328-p pu. I only get "device not wroking correctly unrecognized".No COM port is listed in the arduino ide.
As the device CH340G only has TX RX 5v(also3.3v) & GND and NO DTR & RESET i gueess i need to put the (Atmel)chip in some sort of connection mode & pullup/down something. What?
Second Problem:
Like i said it works with the ESP8266. But i got a little suspicious after various transmission errors and measuring the TX & RX. In fact the voltage was 3.65v and dropped right after a sec to 3.58v. Now the Datasheet of the ESP8266 says it's limit is 3.6v and so i tried both of my logic level converter (One based on the PCA9306, one on mosfets). They both don't work. Device unrecognized. Is 3.65v ok if the max should be 3.6v? if not why do those logic level translator not work?
note:To test the logic level converter i used a AMS11117 3.3v regulator on the ESP8266 side and set the CH340G to 5v. basically if you want 3v logic you bridge the 3.3v pin if you want 5v you bridge the 5v pin to the VCC PIN.
Extra info:
Actually i got the logic level converters only to control a WS2812B Adressable led strip(5v) from a raspberry(3.3v). I read that those self made mosfet/transistor Logic level converters don't work properly. I also tried with some BSS138 mosfets(one of the first sparkfun's logic level converter), no luck. And so i got "expensive" ones. One is based on the PCA9306. I just noticed now that the second one is also just an array of mosfets. So basically the only "good" logic level converter is the PCA9306. i don't get why it does not work with USB2TTL.
EDIT related to questions in the comment.
The 328p-pu chips have an optiboot.. the default one (Arduino IDE). And yes i would like to program them on a breadboard. Thats why i got myself a usbtottl. It's frustrating to remove the chip everytime you have to upload something new.
Atm i'm using 2 original arduino UNO to program attiny's and atmega328p-pu.. but like i mentioned above its alot of work to remove the chip every 2 seconds.
To program the Attiny85 i made my own "shield" with the relative capacitor.
and connections to the UNO board.Also a simple blinky led to see if the bootloader is programmed correctly the first time.. or if i change the frequency.But that uses different pins.. not tx rx.
EDIT2
Solved second problem

It works on the ESP8266 with a minor problem.
To test the logic level converter i used a AMS11117 3.3v
regulator on the ESP8266 side and set the CH340G to 5v.

I added an additional external powersupply only for the ESP8266. Always using the AMS11117. but this time powered by a normal phone charger powersupply.
Looks like when programming it needs alot of power.There are no more transmission errors. So i guess this 0.05 overvoltage has nothing to do. And should not harm the mcu.
the main problem remains unsolved.


texts: Explanation of touchpoint density in touchscreens

texts:
I'm looking at touchscreen supplier specs such as this one.

What does the specification "touchpoint density" expressed as touches/sq.cm sq.in or mean? The value given is "> 100,000 touches/in^2". Does this mean it can differentiate between pinpoint touches at 100,000 points at every square inch?