texts: How to chose right lens for concentrating IR signal?

texts:
I am looking for the right acrylic lens. Since will be buying at least 1000 pieces I don't want to make any mistake.
I want to concentrate the signal from IR LED in a 1cm diameter tube at one point 20cm in diameter. From what I know, IR LEDs disperse the beam too widely, hence the need for a lens. What shape of lens should I buy? Are there any online resources that could help me
The distance between wall and led is 5-10m. Size of LED is the standard one I guess 5mm.
Wave length is 970nm.


texts: Best practice to get several voltages from a wall adapter via buck/boost adapters

texts:
There are two battery operated devices connected to the garage door in my house. One is a bought solution which opens/closes the garage door, the other is a self-made module which detects whether or not the garage door is open, and communicates this with a receiver in the house.
Both are running on batteries, and both eat through batteries like crazy, so I want to power them both with a wall adapter.
I wanted to use a single wall adapter and two buck/boost modules to power them both, but was wondering which was the best practice. One device needs a coin cell (3.2V), the other an MM21 12V battery. The way I see it, there are three options:

Use a 3.2V wall adapter, connect device one directly, and use a buck/boost module to power the 12V device
Use a 12V wall adapter, connect device one via a buck/boost module, and power device two directly
Use a wall adapter with a voltage in between (say 6V), and use a buck/boost module for each device

Which option is best practice, and why?
Thanks!


texts: How to calculate the speed of AC signal in different mediums?

texts:
Most wires will have a speed of travel for AC current of 60 to 70
  percent of the speed of light, or about 195 million meters per second.

  Read more at:
  http://www.epanorama.net/documents/wiring/cable_impedance.html

I also read here that the propagation speed depends on the wire material and its surrounding. What is the mathematical equation that allows me precisely calculate the speed of an AC signal given the physical parameters of the wire and its environment?

For example:

Printed wire using silver paste on plastic, surrounded by air.


texts: Can lead acid battery be used as a capacitor between power supply and equipment?

texts:
I have a lead acid battery from an old broken ups.

And I have a WIFI router with power adapter.

Can I connect the battery directly in the middle between the power adapter and the wifi router like a capacitor, so wifi would still work when there's power cuts?

I assume my idea is too naive. What should I consider if I want it to work as I imagined?


texts: Can probing an EEPROM with a multimeter corrupt the data?

texts:
Say there's an EEPROM on a board and you happen to try probing the pin one by one with a multimeter, is there a good chance that the sequence of probing the pins must have overwritten (thus corrupt) the data?

I always thought it was fairly safe as for EEPROMS, from what I've skimmed through, the writing happens in hundreds of kilohertz or above.

I was using the continuity tester in my multimeter that tests at around 0.4V.


texts: power 12v fan using laptop charger while running laptop

texts:
I have a laptop with partially damaged internal fan. Dont want to buy new one. I am thinking of swapping the internal fan to a 12V fan. The 12V fan I have can fit as it is small. Internal fan is 5V.

Most solution out there

uses external power supply to power 12V fan
uses 5V from usb to power 12V fan
uses laptop charger to power 12V fan but laptop is not connected

What I want

power up 12V fan using laptop charge WITH laptop connected. 12V voltage level will be achieved using a step down converter with 19V laptop charger as input. OR connect in parallel to an existing 12V connection in motherboard circuitry.
5V usb is good idea but I want to operate the fan at its full power using 12V.

Point of doubt

Laptop charger is already used to supply power to laptop. External load (fan) will definitely drain current but will it interfere with the normal laptop operation?

Question

can i use buck converter to step down voltage to power up 12V fan safely?
is laptop charger capable of giving more juice even when it is already used on laptop?

Do please share your knowledge. Much appreciated. Thanks!


texts: How to find a way to detect if a device was open or not

texts:
I'm making a device which is inside in an enclosure and at this point of the project it's relevant to understand if the enclosure/box was open. I was trying to understand if I can try to figure it out with a magnet and a ReedSwitch but if someone open my device without the power plugged in, I have no way to realize if it was open or not. Or do I have?

So the device should be easily opened by me if wanted but if someone decide to open without my consent I should receive a warning by the system remotely.

Relevant point: There's no battery as backup.
Can someone give me a tip to prevent this issue


texts: How much Energy is Stored in this Capacitor?

texts:
This is a followup to my previous question: A capacitor stores half the energy when charged from a battery each and every time?

This is a real world circuit with losses. The losses are in the resistance of the battery, the switch, the capacitor, and the inductor.

The inductance value of the L1 inductor has been left out because it was not known or measured. It's not a value of 0 however as it has some inductance.

The capacitor starts out with an initial energy of 0 Joules as well as an initial voltage of 0 Volts.

The switch is closed only one time and left closed. The capacitor charges to the same voltage level as the battery of 12.33 V therefore it now has 76.014uJ of energy in it.

The question is:

Does the 50% loss of energy that normally occurs when charging a capacitor from a battery (without the inductor) still apply to this circuit, even with the L1 inductor in place?

In other words, the capacitor will charge up to the same voltage level as the battery of 12.33 V as confirmed with an actual physical circuit. Has only 50% of the energy been transferred into the capacitor than what came from the battery?

The actual physical circuit has actual inductance in the inductor, but it is unknown, but it's not 0.

Summarized and to the point:

In this circuit, how much energy is transferred from the battery and into the capacitor when everything comes to rest and all processes are completely done? 50%?, 99.8%?, how much energy was transferred from the battery to the capacitor?

simulate this circuit – Schematic created using CircuitLab


texts:
It is my understanding that, in an electric circuit, voltage is divided amongst components in a ratio determined by their various resistances. That is, for example, if a 5Ω and a10Ω resistor were placed in series across a 12V power supply (assuming negligible resistance in wires), then the voltages across the 5Ω and 10Ω resistors would be 4V and 8V respectively - that being the EMF of 12V being divided in the ratio 2:1 as defined by the resistance values, correct?

However, some components aren't like this, and I'm interested to know why. Take for example the base of a transistor. The base is said to 'drop' around 0.7V between itself and the emitter, rather than being described as having a resistance value. It's easy enough to work with just by using a voltage divider, but it still seems a weird concept and I would very much like to know how this works.

Thanks in advance.


texts: openOCD flash 'erase_sector' command NOT erasing lpc1768?

texts:
I am trying to debug LPC1768 using a JTAG debugger and openOCD(version 0.7.0). My os is Win7 .

I'm connetced to the openOCD via telnet(port 4444)
commands like halt, flash info, resume etc do work peoperly.

Now when I do

flash erase_sector 0 0 0

I get the follow reply

erased sectors 0 through 0 on flash bank 0 in 5.705326s

then I do

mdw 0 7

and it returns

0x00000000: 10001ffc 1fff0081 ffffffff ffffffff ffffffff ffffffff ffffffff

What are those first two words?
Should it not be all ffffffff?

UPDATE

flash write_bank too has no effect on flash.

I then uploaded the same binary using H-JTAG and it got programmed. So that means my chip isn't bricked!

content of my openocd cfg file

interface parport
gdb_port 3333

gdb_memory_map enable
gdb_flash_program enable

source [find board/mcb1700.cfg]

contents of mcb1700.cfg

# Keil MCB1700 PCB with 1768
#
# Reset init script sets it to 100MHz
set CCLK 100000

source [find target/lpc1768.cfg]

interface parport
parport_port 0x378
parport_cable wiggler

global MCB1700_CCLK
set MCB1700_CCLK $CCLK

$_TARGETNAME configure -event reset-start {
    # Start *real slow* as we do not know the
    # state the boot rom left the clock in
    adapter_khz 100
}

# Set up 100MHz clock to CPU
$_TARGETNAME configure -event reset-init {
    # PLL0CON: Disable PLL
    mww 0x400FC080 0x00000000
    # PLLFEED
    mww 0x400FC08C 0x000000AA
    # PLLFEED
    mww 0x400FC08C 0x00000055

    # CCLK=PLL/4 (=100 MHz)
    mww 0x400FC104 0x00000003
    # CLKSRCSEL: Clock source = internal RC oscillator
    mww 0x400FC10C 0x00000000

    # PLL0CFG: M=50,N=1 -> PLL=400 MHz
    mww 0x400FC084 0x00000031
    # PLLFEED
    mww 0x400FC08C 0x000000AA
    # PLLFEED
    mww 0x400FC08C 0x00000055

    # PLL0CON: Enable PLL
    mww 0x400FC080 0x00000001
    # PLLFEED
    mww 0x400FC08C 0x000000AA
    # PLLFEED
    mww 0x400FC08C 0x00000055

    sleep 50

    # PLL0CON: Connect PLL
    mww 0x400FC080 0x00000003
    # PLLFEED
    mww 0x400FC08C 0x000000AA
    # PLLFEED
    mww 0x400FC08C 0x00000055

    # Dividing CPU clock by 8 should be pretty conservative
    #
    #
    global MCB1700_CCLK
    adapter_khz [expr $MCB1700_CCLK / 8]

    # Do not remap 0x0000-0x0020 to anything but the flash (i.e. select
    # "User Flash Mode" where interrupt vectors are _not_ remapped,
    # and reside in flash instead).
    #
    # See Table 612. Memory Mapping Control register (MEMMAP - 0x400F C040) bit description
    # Bit Symbol Value Description Reset
    # value
    # 0 MAP Memory map control. 0
    # 0 Boot mode. A portion of the Boot ROM is mapped to address 0.
    # 1 User mode. The on-chip Flash memory is mapped to address 0.
    # 31:1 - Reserved. The value read from a reserved bit is not defined. NA
    #
    # http://ics.nxp.com/support/documents/microcontrollers/?scope=LPC1768&type=user

    mww 0x400FC040 0x01
}

contents of lpc1768.cfg

# NXP LPC1768 Cortex-M3 with 512kB Flash and 32kB+32kB Local On-Chip SRAM,
set CHIPNAME lpc1768
set CPUTAPID 0x4ba00477
set CPURAMSIZE 0x8000
set CPUROMSIZE 0x80000

# After reset the chip is clocked by the ~4MHz internal RC oscillator.
# When board-specific code (reset-init handler or device firmware)
# configures another oscillator and/or PLL0, set CCLK to match; if
# you don't, then flash erase and write operations may misbehave.
# (The ROM code doing those updates cares about core clock speed...)
#
# CCLK is the core clock frequency in KHz
set CCLK 4000

#Include the main configuration file.
source [find target/lpc17xx.cfg];


texts: Transimpedance amplifier simulation acting weird

texts:
So, I have been trying to simulate this low input current transimpedance amplifier, but I am just not getting results I was expecting. So to explain the circuit in short, I will be working with photocurrents ranging from 0 to 100 nA and I want those currents to be translated to 0 to 5 V range signals on ADC. On the left from opamp you have equivalent circuit of a photodiode, north of opamp you have feedback capacitor and resistor (I have chosen 50 MOhms because 5V = 100nA*50MOhms) and to the right there is a DC blocking capacitor and input impedance of my ADC of choice.

While the input current(first graph to the left) is exactly what I have expected it to be, the graph on which i plot output voltage on ADC versus time is completely unexpected, as the minimal and maximal amplitudes are way too low, and it is hard for me to grasp this specific error, because the waveform looks as I would have expected it, but the amplitude is off, like the current sees a smaller resistor and not 50 MOhms.

EDIT: I have connected non-inverting input directly to the ground, and now the results make even less sense to me.

Any help, tip or info would be greatly appreciated.


texts:
I recently bought a LM35 Linear Temperature Sensor off littlebirdelectronics.com (as well as other Arduino stuff) and everything all worked fine when I had the temperature sensor attached up to the Arduino using just short wires (10cms). It was reporting a stable 20 degrees and was nice and happy.
However after I setup the system fully, the LM35 was connected to the exact same PINs but using a 4 metre shielded cable. Using the same code, same PINs and everything the reported temperature now jumps all over the place. It will be -31, 30, 1, 15 degrees all within the space of 10 seconds!
I'm assuming the problem is that the 5V power line is interfering with the analogue data line, thus messing with the results.
My question is, am I doing something wrong, or is this the accepted performance of the LM35 temp sensor? (ie it will only work at small distances)
Also, if I purchase this 18B20 Temperature Sensor instead, will I end up with the same results or should the fact that it's digital allow it to transmit over longer distances?
Thanks!


texts: Using digital pot to control gain of hi-fi audio op amps

texts:
I'm looking to use a digital potentiometer (AD5206) to control the op-amps on the hi-fi audio XMOS board (schematic can be found at bottom of document). I'm wondering what would be the best way to go about implementing it:

Keep the fixed gain at the opamp itself, then use the digital pot to 'attenuate' the input. So the digital pot would be placed at the input to vary the level of the output signal.

Advantage - Allows me to fairly accurately control the upper limit avoiding clipping; any capacitance in the digital pot itself would be AC coupled to the opamp input anyways and not going to matter at the output.

Disadvantage - ?
Use the digital pot in the feedback loop controlling the gain of the opamp.

Advantage - ?

Disadvantage - Any capacitance caused by the digital pot is going to affect the high freq roll off; If the digital pot is a break-before-make type, it'll cause the loop to open up for a sub-fraction of a second causing the output to saturate and from which it'll likely need another fraction of a second to recover from; lower limit isn't easily controllable.


texts:
I have 2 power banks:

Anker 20,000 mAh powercore.
Mophie 20,000 mAh

The Anker has 6 of the 18650 cells and
the mophie has 8 of the 18650s. What I'm am trying to do is combine these cells to make a 40,000 mAh battery and be able to use effectively.

Is it possible to combine all the cells to the motherboard and charge all as one battery?


texts: Can a H-Bridge be driven using Rasberry PI 3.3V GPIO Pin

texts:
I have designed this circuit to operate based off of the fact that when a transistor is in saturation mode it will behave as a switch when a voltage is applied at its base. The base voltage is greater than the emitter voltage, but the base voltage is greater than the collector voltage. The H-bridge is supposed to allow a path for a motor to be operated in one direction when a 3.3 V gpio pin is activated and then also to reverse the polarity when another gpio is activated on the second set of switches. This motor is being powered by a lithium ion battery of 3.7V. This circuit is not operating as it should and I am unsure as to why it isn't working. The green circuit shows the path for the top LED and the blue one shows the path to the bottom one. I used these LEDS to show the reverse polarity as you cant simulate a motor moving. I am unsure as to where I have gone wrong in this design. The top two transistors are in their forward active mode. VB is greater than VE but less than VC. With the VBE Junction in forward bias with the VBC junction in reverse. The bottom transistors that supply the path to ground are in saturation however as the VBC and VBE junctions both being forward biased. I would think that since these top two transistors are in active mode they would still allow current to flow, just current that is proportional to the base current. Is there a reason that I am overlooking that is causing this to not function as expected. I am trying to use these switches to provide power to a load in both polarities. It would be nice to have all of these transistors in saturation as active mode will limit the power to this load somewhat. I have tried using a voltage divider and sending the split voltage to the collector node and this still doesn't cause the circuit to operate as I would think it would. Any help or suggestions would be appreciated.

I tried this implementation with pnp transistors and I cant seem to get it to work this way either. Is this the correct implementation?

My third attempt adding pull down transistors


texts: 7 Segment LED - What is the difference between driving 1-digit and driving 4-digits?

texts:
I read a few threads explaining how to drive a 1-digit (7-segment) LED correctly. After all, most threads recommend that I should connect 1 resistor for each segment (which make it the total of 8 resistors) rather than using only 1 resistor for all of them.
Now I agree with this view-point, as the characteristic of each LED is different and therefore using only 1 resistor may result in uneven brightness and other issues.

However, when I think about the case of driving a 4-digit (7-segment) LED. The problem seems to repeat itself.

With the above 4-digit LED, each segment is connected to one common pin. For example, all 4 A-segment are connected to pin number 11. Since I can only wire 1 resistor to this pin, this turn out to be the case of 1 resistor for 4 parallel LED again!

So I wonder how can I drive this 4-digit LED correctly without causing uneven brightness in any segment at all? Moreover, I exclude the case we use 4 separate 1-digit LED because that results in too much pinouts and resistors.


texts:
The LED in question is described as 0805 dimensionally. However, the footprint in the PDF is different from that described as being suitable for a resistor. For example, the gap between the anode and cathode is a recommended 1.1mm while that between resistor electrodes is typically 0.65mm

Can I put these LEDs onto 0805 resistor footprints?


texts: PI control Implementation for Buck Converter using Arduino

texts:
I am implementing current control on my synchronous buck converter using ARDUINO UNO. I designed my control via "Symmetrical Optimum" method and calculated the values for Kp and Ki (not Kd since i am implementing PI control). I am implementing the control using the Arduino's PID Library. I have the following two questions regarding this:

(P.S : it is my first time implementing control, so i might be asking some really basic things)

1) When using this PID library, if i only want to use the PI, i will pass the value "0" to the Kd parameter, and this will do the job, right ?

2) My Buck converter switching frequency is 62.5kHz, so i calculated my sampling time to be 16us from this. And i have used this value of sampling time i.e 16us in my PI design method to calculate the value of Kp and Ki. And also we are supposed to multiply this value (16us) with Ki while implementing the control in the micro-controller (this is done in SetSampleTime() function as well).
 Now i am supposed to pass this value of sampling time to the SetSampleTime() fucntion. But i am confused here, and the confusion is that i dont want my controller to be very fast (i.e work for 16us) as i will be charging a battery using this controller, so getting values (updating the controller) at 1 second interval may be also good enough. So is it okay for me to pass some other value of sampling time, like may be 100ms to the SetSampleTime instead of 16us ? I mean can i just pass this value in my current scenario ? or shall i again calculate the values of Kp and Ki using the 100ms as sampling frequency, and then only i can pass this value of sampling time(100ms) to my  SetSampleTime() fucntion ?

To explain my confusion a bit more, the value of "Sample Time" is being used at two places in the PID library : one, it is being used to tell the controller when to update it self, and two, it is being multiplied by Ki parameter. So i am confused that i want to sample slowly than 16us, but i have calculated the Kp, and Ki using 16us as the sampling time. So what would be the right way to go if i want to sample slowly than 16us ?
I hope i am able to make myself clear on the second point.

You helpful suggestions and comments would be appreciated.

Thankyou


texts: Minimum specs before a flyback diode is needed for a relay?

texts:
Given a low power signal relay, 3V 140mW coil, controlled by a 2n3904 npn transistor, is a flyback diode required? At what point is a flyback diode needed for any given inductor? Is it total power, voltage, current, henries?

simulate this circuit – Schematic created using CircuitLab


texts: How to draw the stick diagram of a JK flip flop

texts:
Recently me and my friends have been tasked a project to design a frequency divider using a JK flip-flop (divide by 4).

After drawing the transistor circuit, I noticed that it was complicated for me to draw the stick diagram of one JK flip-flop let alone two. We were only taught to draw simple stick diagrams for for simple equations.

I can draw the stick diagrams for 3 and 2 input NANDs just fine, but I don't know how to connect them to each other in the stick diagram.


texts: Wireless communication between more than two Microchip PIC microcontrollers

texts:
I would like to create wireless communication between Microchip PICs for my simple project.
It's actually an one way communication but there is one server and more than one client (about 2-4, all client needs to the same number at the same time, so they are identical). I have to push through very few bytes.

Im absolutely beginner with wireless communication, or almost any hardware communication at all.
So please help me, what kind of wireless transceiver should I use?

I have some conditions:

It must be relatively cheap.
It must be easily available.
It would be nice if it easy to use.
about 10 meter range (at least)

Firstly I found "Serial Bluetooth RF Transceiver Module rs232" but I can't find any info about how to use. (I guess, it's too simple?) And I also don't know is it capable to connect to more clients.
And I also saw ZigBee, but I found it a "little" overpowered for my needs. (And also complicated.)

So what kind of wireless transceiver do you recommend me?


texts:
I am building a hand held portable raspberry pi. I have just plugging the battery in and using the thing, but I want to make the battery completely part of the unit without the need to unplug it when i am done. so here is what i want to do completely:

Have a switch to be the master on/off switch.
when the unit is plugged in to a dc power source (wall wart), you will have a switch that will let you to select between powering the unit or charge the unit
Have led indicators for charging, unit powered by battery, unit powered by external

here is what i have come up with already

let me know where i need to go from here

Clarifications:

the 7.4 v battery has a output of 2 A and it has a charging PCB built int the battery (which is why i bought this one)
I have been using the pi with this setup less the switched for about a month no issues. Since i wanted to add in switches and led indicators AND i am just a novice on building circuits, i don't know if what i have the switches right
I am using a variable switching regulator that will work down to 5.5 v and it works perfect with little current usage.


texts:
I'm curious about one thing. Can a switching power supply with 24V - 4.5A output can kill you if you touch its outputs directly?

As I know, just a 100mA may kill you too, so is it safe to use switching power supply without using any safety equipment or what should I care about?


texts: Regulate high current LED light with potentiometer (voltage regulator or voltage divider)

texts:
Can someone help me with designing a schema to regulate voltage to dim an LED light? I have 3 LEDs connected in parallel. One LED has following specification:

Forward voltage = 2.75 V (max. 3.4 V)

Forward current = 1000 mA

Power consumption = 3.4 W

Reverse voltage = 1 V

So, if I understand it correctly, I need output of 2.75 - 3.4 V and 3 Amps to power them.

My goal is to regulated voltage to these LEDs to be from 2 V to 3.4 V (or 0 V to 3.4V if not possible to limit the low voltage) and constand current of 3A. I also prefer the schema to consist only of necessary components and to make it as small as possible to fit it in the flashlight housing. I read about source voltage to be as close to the output voltage to minimize the heat dissipating. My 18650 battery, fully charged, gives me about 4.1V (I understand that the battery has to be capable of delivering 3A - in case I can connect more in parallel too), but some of my voltage regulators I have at home just won't provide as much as required 3.4 V. Then I read about low dropout voltage regulators (LDO) and did some research too, but have none at home to try it. I thought that you electrician geeks would probably help me out instead of me trying by errors to figure this out. Also, I have few 10K or 1K potentiometers laying around that looks like this, but I am afraid that they may not be suitable for my purpose, perhaps because of the high 3A current I need? Perhaps, it can be designed, so it could be used? It perfectly fits hole of my flashlight housing. Can you please provide schema, either for voltage regulator with some LDO or voltage divider schema, please?

I looked this forum for similar posts, but it doesn't answer all my questions, e.g. if my potentiometer will work or not as it is not heavy-duty.

Your help is very appreciated and that you in advance for your eventual help.

PS: Of course I have only some basic knowledge about this, so please bear with me. Thank you.


texts:
Every time I use hal_delay() the program hangs just before the call to hal_delay().
I have gone through few comments where it is told to add HAL_IncTick() to SysTick_Handler in stm32f4xx_it.c file. However, I don't have any file with this name in my project. Can anyone please help as to where exactly I need to add HAL_IncTick() for it to increment uTick.


texts: We tend to identify systems more often by using the step response. Why? Especially when the impulse response is directly related to the transfer function?


texts: Control voltage to heat resistor using PID

texts:
I have a question about PIDs. I have a 2.2 kW heat resistor powered from 220 Vac. I would like to control the resistor using PID.
As I can see the most PID based control systems are using a Solid State Relay (SSR). Therefore, I conclude that these systems produce a smart on/off sequence based on PID parameters.
I would like to ask you if I can control the voltage across the heat resistor with a PID system i.e. not just on/off control. This will control the power and therefore the heat produced. Do you have any proposal?
Excuse me if the question is trivial.


texts: Creating identical 'copies' of circuit elements?

texts:
I have a circuit comprising of 3 identical nodes connected in a loop i.e. output of 1st node is input of 2nd, output of 2nd is input of 3rd, and output of 3rd is input of 1st. Circuit diagram of the node is below.
Now, each node has a potentiometer which I wish to vary (\$R_3\$ in the circuit diagram). As all 3 nodes are identical, I need to vary all 3 potentiometers identically. However practically, this is, of course, unfeasible to do by hand.
So, is there any way I can only use 1 potentiometer, and redesign the circuit such that I effectively get 3 'copies' of the potentiometer, with 1 in each node? If so, then I could effectively vary all 3 of them identically.


texts: How to find the cutoff frequency using Simulink (from the scope)?

texts:
R=1000 ohm
C=0.1uF

I need to find the cutoff frequency from the scope and to show it matches the theory \$f= \frac{1}{2pi*RC}\$

In this case it's 1591Hz.

How do I measure it?


texts:
I am using the DigiX board and trying to connect a DS18B20 (one wire temperature sensor).
One of the issues with the DigiX is that it can only tolerate 3.3V on the I/O pins.
I have been trying to look through the data sheet to try and find out what the max output could be.

Which, if I was powering with 3.3V would be too much? 3.3V +0.3V.
Is this the correct way to asses if there compatible and that I do in fact need a level shifter of some sort?
Thanks for your help, I just feel im missing something and it should be fine but I don't want to fry my board.
edit- I'm aware I could try measuring it with a multimeter but do not have access to one for a while and would not be confident in when or how t produce the max output current.


texts: Jump starting a motorcycle behind a fuse? (slow blow atc fuse?)

texts:
I have a motorcycle with an SAE 12v 10ga lead for charging that I'd also like to occasionally jump-start the motorcycle with, I need about 90amps for about 1 second, which is fine for the 10ga wire, but not fine for the 30amp inline ATC fuse.

Do they make slow-blow fuses for ATC that would allow momentarily 90amps, but break on sustained 30amps?  I don't want to risk of fire and I don't want to bypass the fuse entirely.

Must I go Direct?

Edit, I found "Flosser Micro FMM Mcase Fuse" that are slow-blow 30Amp fuses, but cannot find an inline holder, that may be the answer I need but still unable to source the parts.


texts: Transistor gain, what if there is not enough current?

texts:
I understand that a transistor will amplify current by a certain gain factor if it is below saturation.

But what if there is a resistor that reduces current?

So let's say there is 1mA between base and emitter and a gain of 100x that means there will be 100mA between collector and emitter?

But what if there is a 5v supply voltage and a 1000ohm resistor between supply and collector, it will be impossible for this much current to flow.


texts: Opinions on an oscilloscope suitable for hobby electronics on a budget

texts:
I'm thinking about getting an oscilloscope as my next tool purchase but I don't really know what I should be looking for or what the options are. Ideally I'd prefer something that was stand alone, but I expect a device that hooks up to a PC for the display would be cheaper and offer more functionality. Right now my projects are reasonably simple but I'd prefer to buy a tool that I wont outgrow too quickly.

Thanks for all the answers so far, that's a lot of information to look at!


texts: I am working on a small Raspberry Pi cluster that I am going to use for web hosting, home automation, cloud storage, VPN, and so on. I plan on using the 3D printer and laser cutter/engraver at my high school to make a small "server rack" for the cluster using rather thin plexiglass, and PBA plastics. Instead of using up many wall outlets or using a power splitter, I would like to develop a small PCB that has one wall plug, and splits in to 4 USB female ports, and one or two 3 Pin computer fan ports. What I'm not so sure about, is can I just split the 5V input to 5V and GND wires on the USB ports or is there other components that need to be integrated such as resistors, ICs, capacitors an such? I have seen many boards like what I'm looking for, but they all seem to be complicated which leads me to believe it cant be as simple as I think this is.


texts:
There is this exercise in my book said to make a mod 6, mod 4, mod 3, mod 12 counter using 7492. I can do mod 6, 4, and 3 but there is a problem when doing mod 12.
The circuit counts to 5 then skip to 8, how can I fix this problem?


texts:
I need help to identify this diode, mark "AC C"
I attach photos of it I think there are SOD123.The caliper said 3,2x1,64

This is how they are in the PCB.

They are connected in this way.


texts: I'm designing small DSP device, currently I've been using stm32 development board but now I need to move to dedicated PCB. I can make footprint for uC myself, but I believe it should be available somewhere and  I'm just looking wrongly.


texts: Split Audio lineout into two different amps

texts:
I am using a 3116d with a lpf and a 7498 for the mid range.
The audio signal comes from a common source. The cables are split and soldered, so that both amps receive the same input.
However, doing so distorts the right channel on the 7498 and the left channel ist maybe half as loud as when the 3116d is disconnected.
The 3116d on the other hand works just as expected.
Do I need a 3,5mm splitter?
I am an absolute beginner in audio electronics.
Regards.

EDIT: Here is a "kind of" schematic. I use two amp boards from china, so the actual circuitry of both amplifier chips is hidden inside the boxes:

eventually, this may help a bit.


texts: Battery charging circuit using 12V dc generator

texts:
This is a project work of power generation from speed breaker.I am using an IBL-100SW dc motor in my project as a generator to produce power.I am getting a voltage from 3V to 18V and current of 0.1mA to 6.8mA.The rpm varies from 1100 to 3000.But the time duration is very small like 2 to 6 milliseconds.
Now I want to store it in a battery.I am a noob in electrical circuit design.Can anyone help me with the components and circuit diagram?Any type of readily available battery type will be good for me.


texts: Simple Interconnect circuit to simulate crosstalk in ltspice

texts:
I want to implement a very simple interconnect circuit to simulate crosstalk in ltspice because I am new to this area of crosstalk. Where can I find such a design? I have searched in the net but all the circuits seem complex and they are from different research papers.If anyone suggest me or give me a simple circuit to simulate crosstalk in ltspice then it would be very helpful.

Thank you.


texts: Simpler ways to generate a negative voltage?

texts:
I was in need of negative voltage to generate a ramp signal. But I am using the single supply. I tried to generate negative voltage using the DC-DC converter, but I felt it is quite an expensive solution. So are there any simpler ideas to generate negative voltage with a single supply?

My specifications are:

Power: 1W
Regulation: 5%


texts: Speed control of a DC motor using variac

texts:
I have a offset printing machine and it's original electrical design uses a
variac device to control it's speed (RPM) value of the main motor drive.

I don't have access to any electrical wiring diagram, so I need to find it's typical
wiring diagram from variac device to motor.

bellow picture is the front side of the variac.

I got four wires going into DC motor. And above is the backside of the variac device
and it seems to me that, it goes through a inductor depicts as in bellow figure.
What is the original purpose of that inductor? Is that a interpole motor which used to
reduce the spaks on amateur brushes? Or is that for another purpose?

I need to know it's typical wiring diagram. How could I simply connect a DC motor
to a variac?

--Thanks in advance--

EDIT: I confirm that this is a DC motor, there are 2 rectifiers like these.


texts: Op-Amp / In-Amp (INA826) as voltage divider

texts:
We're trying to buffer (for safety, ruggedness and scaling reasons) the input of a µC via some instrumentation-amplifier : INA826
We had our eyes on a schematic in TI INA826 datasheet
The only problem is that we only have access to a asymetrical voltage supply (+5V) and also, we'd like to scale the op-amp output from 0-10V to 0-5V.
As I undestand it, we can just supply it with 0 / +5V and the output would be scaled to 0 / +2,3.
The one thing I don't understand though is that I thought the way to do it would be just to do a voltage divider followed by a unity op-amp circuit but that is not the case there...


texts:
So if I have a batter that says it can produce a max of 2000mAh and a device that says it uses 3.6 mA does that mean I can run the device for 2000mAh / 3.6mA ?

How does the voltage get factored into this?

Here is the battery I am referencing
https://www.sparkfun.com/products/8483

Here is one of the devices I am referencing https://www.sparkfun.com/datasheets/GPS/SL1204%20Product%20Specification_v2_10_2009.pdf


texts: How can a SerDes based link be used to replace the age old UART?

texts:
UART is great to transmit log data from a DUT to a PC. However, it is not fast enough. There are many newer things like USB, PCIe e.t.c that can transfer a lot more data and also use serial transfer. This brings me to the question. How can one use the SerDes to replace the UART? SerDes is just a serializer-deserializer. Usually SerDes would be used as a component of a much larger design that has more components like 8b/18b encoding e.t.c.
If one wants a really high speed but simple replacement for UART to send characters to a PC screen for log data, what methods should one go for? The SerDes exists on FPGA here.


texts: What happens if I connect two lead acid batteries in series, one fully charged and one half charged?

texts: I am interested in several things: What happens right when I connect them? How does this behavior affect the batteries, both short term and long term?


texts: What is the correct term and schematic symbol for a bar "connecting" multiple toggles together?

texts: This has driven me mad, I've searched for this on google and am now going to the world to find out what the part is called. I've tried things like "Gang bar", "shared cover", did a google image search of the two images I have, and anything else I could think of, but without knowing what it is I cannot accurately search for it. It's a part that can connect multiple toggles together for an action, usually to "off", sometimes allowing for individual "on" activation. Attached are two pictures to assist. It's the Black bar on the brass switches image and the two Chrome bars on the other image. Any help is appreciated.


texts: Alternating between two LEDS using BJTs and SPST Switch

texts:
I made a circuit based on this post, Alternating between two LEDS using BJTs.

It seems to work in the simulation just fine but when I'm connecting it with real components, I get funny behavior. Here's my circuit:

simulate this circuit – Schematic created using CircuitLab

In my real world circuit, when the switch is closed, the green LED comes on just fine and the red is off, just like it's supposed to do.

simulate this circuit

When the switch is open, both the green and red LEDs and both are faint. I tried adding a pull down resistor at the base of Q13 and it does nothing.

Any ideas? It's definitely hooked up right on my bread board.


texts: Should I attempt to add a capacitor to a power supply for outage stability?

texts:
I have a network device that runs on a power supply rated at 48v about 1.2a. it plugs into a 120v diy ups (a power switcher from an rv with a battery and an inverter). This seems to work fine on other devices but with this particular device when the power switches to the inverter, the device resets.
I'm thinking the power dips just a little too long and I might be able to put a capacitor either inline with the 48v cable or maybe by opening the power adaptor and replacing their capacitor with a bigger one.
Are either of these feasible and how do I know whether it will solve the problem?


texts: This is the phase frequency detector circuit that I am using in my pll design. How do I find the gain of the PFD when all the blocks are digital and the input and output waveforms are pulse waveforms?


texts: Vpp voltage listed with a division symbol?

texts:
I'm reading a spec sheet of an intercom and it lists the electronic call signal with the following notation:

8÷12 Vpp

I get that Vpp is Voltage peak-to-peak. However I cannot figure out what exactly the min and max amplitude are.

This is the part on the actual sheet. From what I understand it's a Spanish manufacturer:


texts: How to find voltages of a node using commands in lt spice?

texts: I am simulating this circuit, how do i find the voltage of the diode through the error log in each step of the the voltage source through a command? I tried using the .meas command but it just shows nothing.


texts: Can it be proven that running a GPU at high temps is bad for the card?

texts:
If you continuously run your graphics card at between 80°C and 90°C (176°F and 194°F) is it actually bad for the graphics card? I.e. does it reduce the life of the card? Can this be proven? Or is it just assumptions?

I understand that the safety shut off for GPUs is normally 90°C (194°F).


texts:
I am currently using two 8-wire ribbon cable to connect 2x8 pins on the Arduino to 2x8 pins on a board. This makes plugging/unplugging very tedious are the ends are not glued together like in a connector

Question: How can I create my own ribbon cables with connetors for 2x8 pins? After some researched I found IDC connectors somewhat suitable, but the connectors appear to have additional plastic like the clips which will obscure the 2 pins to each side of the 2x8 pins I'm plugging the cable into.

What other options do I have? I'm hoping for a 8x2 version of the following cable, what are such cables called?


texts: How to determine the resistor value when I want to use this op amp circuit?

texts:
I want to know how to determine the resistor value when I am using this op-amp circuit.

Any theory I need to follow? How to determine the gain with diodes? If possible, please explain with an example.

This circuit is from here.


texts: Name for two pads intentionally adjacent but separated to be solder optionally

texts:
I have seen some boards that leave small adjacent pads that the user can solder in order to connect the two tracks attached permanently.
Is there a standard name for that?


texts: I can't get a through hole diode to work on mechanical keyboard PCB key

texts:
I'm not experienced in electronics or soldering.
I find myself soldering the components of a PCB from a mechanical keyboard, all right and smoothly, except for two keys.
When I use the multimeter in V mode over the diodes, they all return values like ~1.628 V. When I do it over the two ends of the hot-swappable switch, the value amounts to ~2.794V.
However, on these two keys that don't work, neither the diode nor the switch gives a value, so I take it for granted that the problem is in the diode.
I have tested the diodes individually using ohm mode, and the value in all is ~66.1, including those that give apparently error, so I can conclude that the diode works.
The diodes are through hole type. Each key shares section for the holes diodes and for SMD diodes. In my case, I bought the through hole parts.

I have several questions:

How can I corroborate that the problem is the board connector for the through hole diodes?
Can I use, in this particular key and only and SMD diode?
Can I solder a through hole diode on the board for SMD?

What is the best solution?


texts: My JTAG connection with Cyclone IV is not working

texts: My FPGA board is not programming. I think I have followed all the guide lines for JTAG connection. Can you see any problems with this connection?


texts:
I'm trying to replicate the effect of this LED panel I found at Home Depot with a different set of LEDs and use a differently sized panel. It's basically just a diffused light that mimics a window or skylight.

It's 2x2ft and produces 4250 lumens and has selectable color temps (daylight white, bright white, soft white) with a switch-based color temp selector.

Upon inspection, I realize that it uses some type of edge lit material, but I'm not sure what. My goal is to diffuse light through the panel uniformly using an RGBW strip, maybe something like Philips Hue. I'm not sure if the panel should be clear with a backing or frosted.

What are the best materials to use for this?

Edit: I found a teardown of the panel on youtube. No identification of where the material is from exactly, but maybe will aid the answerers.


texts: How fast we can change direction of rotation of a stepper motor

texts:
I want to do the following of a stepper motor with following characteristics which has 100 RPM

change DOR(direction of rotation) every alternative rotation in the opposite direction
control the speed of change
control the angle of rotation i.e 30 degrees or 40 degrees after which it will change the DOR
Ability to lock at any position

this is to try flapping wing orinthopter we cannot control wing beat angle and to implement gliding with current idea of using normal DC motor with crank mechanisms because we cant determine the mid point of wing beat.

can we do this?


texts: How well do reflowed connectors self align?

texts:
I am thinking of using some Hirose DF40 PCB stacking connectors to stack together a bunch of PCBs. Each pair of PCBs would be connected by two connectors for mechanical stability.

These connectors do not have locating pins, so they rely entirely on the self-alignment effect during reflow to pull them into the correct position. Now, I can imagine that these connectors, being 0.4mm pitch, will self align pretty accurately in the X axis, but surely not so well in the Y axis.

This might not be a problem if only one connector was being used, but two connectors have to be lined up fairly accurately between the two PCBs. How well will they self align in the Y axis?

Does anyone have any experience with similar connectors in a similar situation?


texts: Why is there a spec for min fall time in I2C Fast Mode?

texts:
Why is there a spec for min fall time in I2C Fast Mode but not in standard mode?
Is it fine to use I2C standard mode with a fall time of 5n?


texts: Does anyone have code to emulate a 16-bit input shift register with an ATtiny2313?

texts:
I would like to use an ATtiny2313 to emulate a Super Nintendo controller because I have an ATtiny2313 but I do not have an input shift register and I don't feel like soldering wires onto an existing SNES controller board.

This application requires 12 inputs (bits 13-16 are always 1) and a latch, clock, and data out pin.

Do you have this code lying around? It can't be more than 20 instructions.


texts: Multiplexing battery voltages with high precision

texts:
I would like to multiplex battery voltages used for impedance measurements. The battery cells are not connected. My idea is to have one multiplexer chip for the positive poles, and one chip for the negative poles. Then the outputs are compared to get the battery voltages.

Is it OK to multiplex floating voltages like this, and then compare them afterwards? What factors might affect the measurements? Are there better alternatives?

I am planning on using the mux MUX506IDWR. The outputs of the muxes will go to a measuring device (Gamry Reference 3000) which I assume has high impedance and will not draw current in the voltage measurement. I don't really know what goes on inside of the Gamry device. All I want is to deliver the battery voltages without distorsion, as if a battery is directly connected to the Gamry.

4-point measurement is used, with a relay multiplexer used for the current cables. Relays are used for the current wires, since 3 A will be used in the measurement. Using mux ICs for the voltage measurements are used in order to save money and space.


texts: Can Linear Feedback Shift Register be used to generate pseudo radnom numbers with uniform distribution and zero correlation?

texts:
I need to implement a circuit inside the FPGA that generates pseudo random numbers with uniform distribution and zero correlation. To make the repeat period of the sequence long, it would require a moderately big shift register. I think 64 bits is sufficient.

As far as I am aware, it is important to wait N clock cycles before reading the state of the LFSR to get Pseudo-Random Numbers. In this case N would be 64. However, I am not sure what is the simplest way to create a uniform distribution zero cross correlation pseudo-random number generator using linear feedback shift registers inside an FPGA, or even if it is at all possible. What can be done to reduce the cross correlation drawback of LFSR?


texts: How does the resitivity of different material add up?

texts:
I have material A (e.g. carbon) which is a poor conductor with a resistance of around 700 ohm. what would happen if I melted some high conductive material (B) on it (e.g. copper).
Would the resistance of the combined product be the summation of both resistance or ould be a value less than material A?


texts: I2C: Trying to read multiple registers, getting first register repeated instead

texts:
I´m trying to read registers 0x28 through 0x2D from the L3G4200D (gyroscope, datasheet), which is part of the GY-80 board, using the esp32 (I2C info) as a master, which is part of the LOLIN32 board. But I am getting the first byte repeated eight times instead and I can´t figure out why. I do get the right result when reading the registers one by one.
The registers are found in the datasheet here:

This is the I2C packet seen trough my oscilloscope (picoscope):

Zoomed in on the write part:

Zoomed in on the read part:

I´m using this code to send the packet:

//I2C init:
  i2c_config_t conf;
  conf.mode = I2C_MODE_MASTER;
  conf.sda_io_num = GPIO_NUM_16;
  conf.sda_pullup_en = GPIO_PULLUP_ENABLE;
  conf.scl_io_num = GPIO_NUM_17;
  conf.scl_pullup_en = GPIO_PULLUP_ENABLE;
  conf.master.clk_speed = 400000;
  i2c_param_config(I2C_NUM_0, &conf);
  i2c_driver_install(I2C_NUM_0, conf.mode, 0, 0, 0);

//function call:
  uint8_t gyroData[6];
  getWireRegister(GYRO, OUT_X_L, &gyroData[0], 6); //GYRO = 0x69 , OUT_X_L = 0x28

//function:
bool getWireRegister(uint8_t device, uint8_t reg, uint8_t * receiveData, int amount){
  i2c_cmd_handle_t cmd = i2c_cmd_link_create();                           //create command to tell device what to send and read the registers
  i2c_master_start(cmd);                                                  //startbit
  i2c_master_write_byte(cmd, (device << 1) | I2C_MASTER_WRITE, 0x1);      //send device address and tell it that the master is writing , ack check is enabled
  i2c_master_write_byte(cmd, reg, 0x1);                                    //tell it what register to send , ack check is enabled
  i2c_master_start(cmd);                                                  //repeated startbit to tell it to send stuf to the master
  i2c_master_write_byte(cmd, (device << 1) | I2C_MASTER_READ, 0x1);       //send device address and tell it that the master is reading and it needs to write , ack check is enabled
  if(amount > 1){
    i2c_master_read(cmd, receiveData, amount-1, I2C_MASTER_ACK);          //give the device space to write
  }
  i2c_master_read(cmd, receiveData+amount-1, 1, I2C_MASTER_LAST_NACK);    //give the device space for its last bit and tell the device it is done writing
  i2c_master_stop(cmd);                                                   //stopbit

  i2c_master_cmd_begin(I2C_NUM_0, cmd, 10000);                            //send first I2C message

  i2c_cmd_link_delete(cmd);                                               //delete first message

  return true;
}


texts: Help identifying connector type on Nissan TV Tuner

texts:
Can anyone identify the grey (24 pin) and white (6 pin) connectors on the Nissan TV Tuner pictured below.

Don't currently have a pair of calipers. I have measured as best I can with a ruler.
The 20 pin grey connector is 35mm x 14mm
The 8 pin white connector is 15mm x 14mm
The workshop manual suggests connector type is TK but that's not entirely helpful without a manufacturer.
Mating half below, in case that helps.


texts: What is the difference between "reverse stand off voltage" and "breakdown voltage" on a TVS?

texts:
On a transient voltage suppressor, let's take a unidirectional Fairchild P6KE11A for example, what is the main difference between reverse stand off voltage (\$V_{RWM}\$) and breakdown voltage (\$V_{BR}\$) as shown on the chart on page 2?

In my experiments with this part in reverse bias, it begins to conduct just at 10.65V. This is within the \$V_{BR}\$ range of 10.5 to 11.6. I think I understand that the \$V_{BR}\$ range is what I might expect from one particular P6KE11A to another, but of what use is the reverse stand off voltage?


texts: Number of logic gates for counter with each type of flip flop

texts:
I am designing two synchronous counters one mod 21 and the other one mod 30. Is there a way to know which kind of flip flop (D, SR, JK, T) will use the smallest number of logic gates?
I know we can build all of them and then check for the answer but that will be a lot of work. I am just wondering if there is a simple way to know that before design.


texts: Working with borrow save signed digit arithmetic output mismatch

texts:
I am working with OLA adders the borrow save module for signed digit addition
I implemented the added in vhdl modeling the following picture

I have run the following example as given in the table and got the same result but with a glitch on the first Zp since it has 2 registers and stays unsigned output for the first 2 cycles

I have did the subtraction manually using basic sub and got different results I do not understand why

manually I did:  0010000110100001 - 1000010010010100
the result i obtained is : 01001110100001101
which is different of the result obtained in the table

EDIT: I tried the simulation of fig2 diagram with the following

X = 01 00 10 10 and Y = 00 10 11 10

as 74-46
the obtained result is Z : 01 10 00 00

which is not equal to the hand made calculation of 00 01 11 00

the following is the simulation and I added 2 cycles of 00 00

library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.std_logic_textio.all;
use IEEE.std_logic_arith.all;
use IEEE.numeric_bit.all;
use IEEE.numeric_std.all;
use IEEE.std_logic_signed.all;
use IEEE.std_logic_unsigned.all;
use IEEE.math_real.all;
use IEEE.math_complex.all;

entity sD_adder is
port ( clk,rst : in std_logic;
         x_p,x_m,y_p,y_m : in std_logic;
         z_p,z_m : out std_logic
        );
end sD_adder;

architecture cSadd of sD_adder is
signal sig_xm : std_logic;
signal sig_zp, sig_zm : std_logic;
signal n_sig_xm, n_sig_ym, n_sig_w2m,n_sig_g2p,n_sig_g2m,n_sig_g3 : std_logic;
signal sig_g3, sig_h2, sig_w2m : std_logic;
signal sig_g2p, sig_g2m, sig_w2p : std_logic;
signal sig_z2p,sig_z2m : std_logic;

begin

    n_sig_xm <= not(x_m);

    FA_add1: entity work.add_sig
    port map( a => x_p,
                 b => n_sig_xm,
                 cin => y_p,
                 sum => sig_g3,
                 cout => sig_h2);

    reg_ff1: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>y_m,
                 q=>sig_g2p
                );

    reg_ff2: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>sig_g3,
                 q=>sig_g2m
                );

    n_sig_g2p <= not(sig_g2p);

    FA_add2: entity work.add_sig
    port map( a => sig_g2m,
                 b => n_sig_g2p,
                 cin => sig_h2,
                 sum => sig_w2p,
                 cout => sig_w2m);

    n_sig_w2m <= not(sig_w2m);

    reg_ff3: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>sig_w2p,
                 q=>sig_z2p
                );

    reg_ff4: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>sig_z2p,
                 q=>z_p
                );

    reg_ff5: entity work.d_ff
    port map( clk=>clk,
                 rst=>rst,
                 d=>n_sig_w2m,
                 q=>z_m
                );
end cSadd;

EDIT 2: Added a question regarding the overflow

How can i detect the overflow of such adder when adder two unsigned numbers in the range of 0-255 if I add:
01 01 01 01 10 10 00 11 + 01 00 01 00 10 00 10 10 = 228 + 149 = 377...with the output being 01 00 11 11 10 11 11 01 = 121 I should add an extra digit which is the 256 therefore I will have 9 digits of 8bit pairs but if the result is in the range i do not need to set the 256th digit what is the indicator of overflow in SD MSB adder?


texts: 1 Byte Register broken into 2 Nibble outputs not working VHDL/ModelSim

texts:
I have made a 1 byte instruction register in VHDL.  Instead of having a 1 byte output, I have created an upper nibble output and a lower nibble output.  The lower nibble output is special because it uses a tri state buffer.  It has this because it connects to the main bus.  The upper nibble does not as it feeds directly to the control circuit and does not need high impedence.  For some reason, I can't get the lower nibble to output anything.  The upper nibble seems to work fine.

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.NUMERIC_STD.ALL;   --This is required when doing additions to STD_LOGIC_VECTORs

ENTITY INST_REG_SAP_1 IS

    --LiN is the load signal.  It is active low
    --Clk is the clock for the register
    --Din is the register input bus
    --EiN is the enable signal for the low nibble.
    --HighNibble is the high nibble output
    --LowNibble is the low nibble output

    PORT(
    LiN, Clk, EiN: IN STD_LOGIC;
    Din: IN STD_LOGIC_VECTOR(7 DOWNTO 0);
    HighNibble: OUT STD_LOGIC_VECTOR(3 DOWNTO 0);
    LowNibble: OUT STD_LOGIC_VECTOR(3 DOWNTO 0));

END INST_REG_SAP_1;

ARCHITECTURE Behavioral OF INST_REG_SAP_1 IS

BEGIN
    PROCESS(LiN, Clk, EiN)
    VARIABLE tempLowNibble: unsigned(3 DOWNTO 0);

    BEGIN

        IF(rising_edge(Clk)) THEN

            IF(LiN='0') THEN
                HighNibble<=Din(7 DOWNTO 4);
                tempLowNibble:=unsigned(Din(3 DOWNTO 0));
            END IF;

        END IF;

        IF(EiN='1') THEN
            LowNibble<=(OTHERS=>'Z');
        ELSIF(EiN='0') THEN
            LowNibble<=Std_logic_vector(tempLowNibble);
        END IF;

    END PROCESS;

END Behavioral;

Here is the testbench

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity TB_INST_REG_SAP_1 is
end TB_INST_REG_SAP_1;

architecture test of TB_INST_REG_SAP_1 is

--create time constant
constant CLOCK_PERIOD: time:=2 us;

--create signals for every port
signal Clk: std_logic;
signal LiN: std_logic;
signal EiN: std_logic;
signal Din: std_logic_vector(7 DOWNTO 0);
signal HighNibble: std_logic_vector(7 DOWNTO 4);
signal LowNibble: std_logic_vector(3 DOWNTO 0);

begin

dut: entity work.INST_REG_SAP_1
port map(Clk=>Clk,
    LiN=>LiN,
    EiN=>EiN,
    Din=>Din,
    HighNibble=>HighNibble);

--simulate the clock
ClkSimulation: process
BEGIN

    FOR count IN 1 TO 32 LOOP
        Clk<= '0';
        wait for CLOCK_PERIOD/2;
        Clk<='1';
        wait for CLOCK_PERIOD/2;
    END LOOP;

END PROCESS ClkSimulation;

--simulate the load (LiN)
loadSimulation: process
BEGIN

    LiN<='1';
    wait for  4 us;
    LiN<='0';
    wait for 4 us;
    LiN<='1';
    wait for 4 us;
    LiN<='0';
    wait;

END PROCESS loadSimulation;

--simulate the Low Nibble Enable (EiN)
enableSimulation: process
BEGIN

    EiN<='0';
    wait for  20 us;
    EiN<='1';
    wait;

END PROCESS enableSimulation;

--simulate the Din
DinSimulation: process
variable temp: unsigned(7 DOWNTO 0);
BEGIN
    Din<="10000000";
    temp:="10000000";
    wait for 4 us;

    FOR count IN 1 TO 8 LOOP
        temp:=temp+1;
        Din<=Std_logic_vector(temp);
        wait for 4 us;
    END LOOP;
    wait;

END PROCESS DinSimulation;

end architecture test;

Here is the output.  Notice no output from the lower nibble.


texts: Can a failed write to Read/Write partation on SD card cause corruption of a Read Only partition?

texts:
I have a project that uses a raspberry pi zero where the power will be cycled unexpectedly, so I configured the filesystem as Read Only. I also have a small amount of data that I want to update every few minutes, which I don't mind losing if it doesn't happen often.

I would like to create another partition on the SD card that is Read/Write for this extra non-critical data, with the expectation that if power fails during a write it will only corrupt the one partition.

I know that SD cards have their own controller build in that remaps addresses to the actual flash cells. So, are partitions on an SD card treated independently at the card level or is there some internal process on the card will cause data from both partitions to be modified, thus allowing potential corruption of a read-only filesystem?


texts:
I am working on a school project: a robotic arm controlled by an Arduino Mega board,

6 servo motors:
https://hobbyking.com/en_us/power-hd-lw-20mg-servo.html?___store=en_us
1 PC power supply (450W),
Arduino board 12V input
ServoMotors 5V input

Ever since the beginning I had problems with my robotic arm, it keeps twitching (every servo goes to different random angles ) when I start it up and sometimes when its doing something.

I tried modifying the code, changing the wires, and after a few weeks I just got frustrated.

But today I tried something new, I disconnected the Arduino, disconnected every signal cable from every servo and left only + / - from the PC power supply, I started the power supply , for a few seconds nothing happened and then ... again the servos started twiching, every servo just goes to random angles, end moves in every direction.

I`m studding IT so engineering is only a hobby, can you please explain this behavior?

Can the servo motors run without signal cables connected to something?

When I am testing with the Arduino board, the robotic arm works but at random moments it does the things i described before.

Another strange thing is that I replace the power source with a new one,

I changed every servo, before this I had another type of servos , they were behaving in the same way.

I also changed all the wiring.


texts:
I'm experimenting with capacitive sensors acting as switches and want to actually give my circuits some practicality. I've been researching how to use relays with microcontrollers (in my case, an Arduino) to control lamps, but I still have a few questions.

Based on this guide (specifically under the "The Setup" section), I should wire my relay into the live wire. How safe is this? Is the only thing separating wandering hands from live wire just the screw terminal? If so, what would be a good way to house the relay (maybe some sort of project box?)?
Could I not forgo the plug altogether and just power the bulb from my Arduino? What would be the characteristics of a lamp that could be powered solely from the Arduino? I have a lamp labeled with MAX 12 V 50 W. Is this even close to possible?


texts: How do I read digital input on ATmega16?

texts:
What do I have to do to read a digital input (pushbutton) on ATmega16? Do I have to enable pullup-resistors or can I use a 10 kohm one? What would some simple code be be? Just a simple 'Turn the LED on when it's pressed thing'.

Is there a beginner's tutorial? I have tried googling and AVR Freaks, but everything just evolves into a fight there and I don't get my answer. I really haven't found any tutorials about this stuff. Tons of specific things but nothing simple about my AVR microcontroller...


texts: Karnaugh Maps - What is the purpose of a "don't care" condition?

texts:
I've got a problem and was stuck for whole day..

I'm designing an octal to 7 segment common cathode decoder which only octal digits 2 to 7 are applied to the inputs of the decoder so combination for digits 0 and 1 are never applied.

I understand that X don't care conditions can be 1 or 0

For my input A

But When i tried to set input A, it lights up when 1 is switched on?

I just wanted it to show 2,3,4,5,6,7 digits only

What's the purpose don't care conditions?


texts: How do I limit the current supplied to a DC motor?

texts: I am designing a robot and my motors are taking up too much current when the robot runs into a wall or has the motors forcefully stopped. How do I limit the amount of current I give the motors?


texts: How does Magic Sky Control work in the new mercedes-benz?

texts: I came across this new technology implemented by Mercedes Benz that allowed windows to be tinted just at the pressing of a button. I figured out that some voltage applied at the actual window would move some particles that would do the job, but I was unsure how this system deeply worked and what exactly was going on. Even after googling around, answers like this from the official Benz website, seemed to be rather vague.


texts: Potential hardware solutions to detecting which string/fret is being played on a guitar?

texts:
I'm aiming to translate sounds played from the guitar to guitar tabs (accurately).

I've had a look at solutions for detecting which string is being plucked:
Detect string plucking in electric bass guitar?

Problem is that the sound waves won't reflect which fret the strings are being played from as different tabs could produce the same sound frequencies. So I concluded purely relying on sound frequencies won't do the job (accurately). I can't have any hardware that interferes with the string touching the fret board as it could effect the performance of the guitar. But I need a solution around it, a way to detect when the string has touched the fret board (and which fret on the board as well) + how long the string has been on the fret (for accurate tabs generated).

I think the ability to detect all of those would allow me to generate accurate tabs. Does anyone have solutions as to how I can achieve this? I don't think a pure software solution would work and would be great to hear your ideas.


texts: Connection between RF output to the source for minimum loss and maximum power transfer

texts:
The bottom device in the left image is an RF generator with ratings 230V, 15A (max), 13.56 MHz and variable controllable output power up to 1250 W. The top device is an auto match.

The metal strip with holes is the output of auto match, which has to be connected to one of the plate (shown in right image) of parallel plate capacitor made of aluminium. The dimensions of plates are 12 cm diameter and 1 cm thick with adjustable gap between both from 1 cm to 10 cm.

My problem is: How to make a connection between the output of auto-match and the plate of capacitor, so that there are minimum power losses? Somebody suggested me to use short wide flat copper strip and fasten it using nuts and bolts on both ends. Is it a good idea or are there any standard connectors available that can be used here?


texts: What do these symbols in ac connectors stand for?

texts:
I'm trying to use a relay to control my house lights with a electronic circuit. I'm familiar with 5V DC circuits, but I've never played with AC before. My relay has three connections, which I assume are ground and the two wires that will be connected when the thing is on.

However, I can't find any datasheet or information about it, my only clue are these symbols:

Using pure logic I would guess that the "bottom" (in the picture) and the middle one are the connectors, and that the other ("top" one) is the ground. So when it is on the relay connects bottom to middle, and when it is off, connects the top to middle. Is that it?

And one more thing: my house is not grounded (yeah...). So is it safe to not connect anything in the ground terminal (leave it unplugged), or for this specific case I'll have to use some quirk to make it work?


texts: Help with identifying characteristics of elements power supply S040SN2400167

texts:
I've faced with overvoltage issue for my hue lamp.
I found that a power supply(Model:S040SN2400167) of that lamp :

was burnt a bit:
Could you help with identifying characteristics of elements in red area?

ps: was able to make a photo for RT1 element:


texts:
How can I reduce or supress the in-rush current for an inverter?

I have a pair of 100 watt solar panels feeding into a solar regulator (TPS 1230) which is connected to a 12v 100 Ah lead acid battery and a 2Kw inverter connected to a 50watt fridge.

The solar regulator claims to be ’10 amp’ and the inverter draws 4-5 amps when the fridge is on. So, in theory the two ought to be compatible. In practice whenever the fridge switches itself on and the inverter kicks in then the solar regulator trips out and needs to be manually reset.

To cure this I tried upgrading to a 30 amp regulator (MPPT30 like this), the good news is that this one only trips out 50% of the time, the bad news is that it still trips out 50% of the time.

How can I cure this? My guess is that the regulator is tripping out due to a large in rush current when the inverter is switched on, I can measure the steady-state current (about 4-5amps) with a multi-meter, but have no idea what the in-rush current might be.

I know that I could connect the inverter directly to the 12v battery (I’ve tried doing that and it works fine) but by doing that I loose all the battery health and charge status information that the solar regulator gives me (with the load going via the regulator I get to monitor the inverter current and the health of the battery, I lose this if I connect the load straight to the battery)

Is there anyway to suppress the initial current surge of the inverter and prevent the regulator from tripping?

Thanks.


texts: RF transformer design for a capacitance variation sensor

texts:
So I`m trying to design a variable capacitance vibration sensor and the best implementation I came up with is a capacitance-to-phase converter.

I used:

a PIC16F15323 NCO peripheral to control the input frequency to compensate for large stray capacitances
a simple RLC circuit like in quadrature detectors to measure the capacitance
a XOR gate to measure the phase shift
an active low pass filter to amplify the audio signal

Maximum capacitance delta is 1.5 pF, maximum oscillator frequency is 11 MHz but I plan to decrease it to 7–8 MHz.

The results are satisfactory but recently I stumbled upon condenser microphone cicruits which use transformers for phase detection. I think they have much better performance compared to my setup since transformers, unlike XOR gates, add no jitter and are capable of noiseless voltage amplification, thus allowing to get rid of a noisy op-amp amplifier.

The problem is, I`ve never worked with RF transformers and I`d like to know how to choose the right parameters for a target transformer. Here are some circuits I`d like to use; see below.

My questions are:

how do I choose a proper transformer?
how do I interface a CMOS oscillator to it?

(source)


texts: Exponential amplifier thermal stabilisation

texts:
I am currently trying to build a DIY analog synthesizer. I've looked at a lot of different designs and I am quite stuck on understanding how some exponential amplifier designs work.

In analog synthesizers an exponential amplifier based on a BJT transistor differential pair is used most commonly. The problem is it's thermal stability. While most of the effects cancel by using a differential pair, an effect related to the thermal dependence in the Ebers-Moll equation will be still present. A solution that I understand completely is using a tempco resistor, just as shown on the first image.

However, I've seen also an another solution (in Arturia minibrute, for example) that I do not understand at all. It is shown on the second image - the exponential amp without the tempco resistor next to R5 is on the left and a weird "thermal stabilisation" part is on the right.

The question is: how does it work? I don't see any connections with the left part at all beside the fact that all of the transistors shown are on a same CA3046 chip.

And which solution will be more stable?


texts: Reason why an inverter will drop the battery voltage from 24 to 10V after turned on and then immeadetly shut down?

texts:
I reacently modified an off-grid solar system, nothing fancy just included an automatic "turn on" switch for the Victron Phoenix 24/220 1200VA inverter.
Then I connected the loads (2 computers, internet and phones) and it worked for about 2 seconds before shut down. This happened before when to many equipments was connected, we have printers, lights and other stuff that I manually disconnect to use the inverter, this usually was fixed by turned the inverter off and on again.
I restarted it, and now it will show the blinking red led with no green led showing low battery voltage, it wasn't obvious untill I disconnected the solar panels and the voltage droped to 10V (24 voltage system) if I try to turn on the inverter.
I know something went wrong, the only variable is that some phone guys were working yesterday and they changed the modem and a phone that I didn't disconnect, this because I thought it would not be a  problem.

The inverter for itself will show blinking red light and the nothing, if I turn on the solar panels the battery voltage will somehow "stabilize" and allow the inverter to acctualy run, however 50% of the times it will fail and will show again the blinking red light. If I succeed and the inverter starts, it will shut down if I connect a load bigger than 200W, after that it will also show the blinking red led again.

According to Victron, blinking red lights and no green light is indication of low batery voltage, however the inverter itself is the cause of the low battery voltage, as soon as I disconnect tehe inverter the battery voltage will recover to 25 volts.

I am an electrician and not an electronic thecnician however I can perform replacements and identification of components, what should I be looking at in the inside of the inverter to fix it up?

Thank you for your help.


texts:
I'm trying to automate LTSpice using the command line. I have tried the following command several times:

test.asc -run  -b

However, it only opens my schematic in LTSpice and does not run it! I have no idea whats wrong with it. The schematic is a very simple circuit which should be run in less than a second. Does any one have idea? How should I resolve this issue?

Thanks


texts: How does full wheatstone bridge with strain gauges work?

texts:
I have gone through a number of tutorials on Wheatstone bridge and how to use it to sense load using strain gauges. I have also gone through the calculations where one of the resistors of the Wheatstone bridge is a strain gauge and how the voltage we measure across a Wheatstone bridge is proportional to the change in the resistance of the strain gauge. But when we use the full bridge, the calculations do not go through, i.e, the output voltage is not proportional to sum of resistance change in all the strain gauges. How does the full Wheatstone bridge where all the four arms are strain gauges? Consider the following circuit from the tutorial page:

\begin{equation}
    E_a = \frac{E \times R_3}{R_1 + R_3}
\end{equation}
\begin{equation}
    E_b = \frac{E \times R_4}{R_2 + R_4}
\end{equation}

\begin{equation}\label{eq:diff}
    E_{ab} = E \left(\frac{R_3}{R_1 + R_3} - \frac{R_4}{R_2 + R_4}\right)
\end{equation}
Let us assume the change in the resistance in each of the resistors is given by $$r_i, i \in \{1, 2, 3, 4\}.$$ Then above equation becomes,
\begin{align*}
    E_{ab} &= E \left(\frac{R_3+r_3}{R_1+r_1 + R_3+r_3} - \frac{R_4+r_4}{R_2+r_2 + R_4+r_4}\right).
\end{align*}
If we further assume $$R_i = R, \forall i.$$ Then above equation becomes,
\begin{align*}
    E_{ab} &= E \left(\frac{R+r_3}{R+r_1 + R+r_3} - \frac{R+r_4}{R+r_2 + R+r_4}\right)\\
    &= E \left\{\frac{(R+r_3)(2R + r_2 + r_4) - (R+r_4)(2R + r_1 + r_3)}{(2R + r_1 + r_3)(2R + r_2 + r_4)} \right\}\\
    &= E \left\{ \frac{2R^2 + Rr_2 + Rr_4 + 2Rr_3 + r_3r_2 +r_3r_4 - \left( 2R^2 +Rr_1 +Rr_3 + 2Rr_4 + r_4r_1 + r_4r_3\right)}{4R^2 + 2Rr_2 + 2Rr_4 + 2Rr_1 + r_1r_2+r_1r_4 +2Rr_3 + r_3r_2 + r_3r_4} \right\} \\
    &= E \left\{ \frac{Rr_2-Rr_1 - Rr_4 + Rr_3 + r_3r_2 +r_3r_4 - r_4r_1 - r_4r_3}{4R^2 + 2Rr_2 + 2Rr_3 + 2Rr_4 + 2Rr_1 + r_1r_2+r_1r_4  + r_3r_2 + r_3r_4} \right\}\\
    &=E \left\{ \frac{R(r_2-r_1 -r_4 + r_3) + r_3r_2 +r_3r_4 - r_4r_1 - r_4r_3}{4R^2 + 2R(r_2 + r_3 + r_4 + r_1) + r_1r_2+r_1r_4  + r_3r_2 + r_3r_4} \right\} \\
    &=E \left\{ \frac{R(r_2-r_1 -r_4 + r_3)}{4R^2 + 2R(r_2 + r_3 + r_4 + r_1)} \right\} \quad \text{assuming $r_ir_j$ is very small}\\
    &=E \left\{ \frac{(r_2-r_1 -r_4 + r_3)}{4R + 2(r_2 + r_3 + r_4 + r_1)} \right\}\\
    &=E \left\{ \frac{(r_2-r_1 -r_4 + r_3)}{4R} \right\} \quad \text{if $r_i \ll R \forall i$}
\end{align*}
The final equation is not just a simple  $$f(\sum_ir_i)$$ which means the signal we get need not be directly proportional to the weight applied.


texts: What is the output voltage range of computer headphone ports?

texts: I made a simple microphone with amplifier which outputs 9V max signal. It's biased in the middle somewhere around 4.5V. I hooked the output of the circuit to the computer speaker audio in. I was wondering how much it can take or what is the recommended input and output voltage ranges of computer headphones and speaker ports?


texts: acquiring conductivity through curl of magnetic field density and Ampere's circuital law

texts:
I have some question.

I want to acquire conductivity and I used Ampere's circuital law.

The problem is

A solid conductor of circular cross section with a radius of 5mm has a conductivity that varies with radius. The conductor is 20m long and there is a potential difference of 0.1V DC between its two ends. Within the conductor, H = 10^5 * p^2 (A/m)

But the solution(I'm solving Engineering Electromagnetics 8th edition W.Hayt) solved that problem through curl of magnetic field. To be specific, it gets current density(J) from curl of magnetic field density and put it in to

'conductivity = J / E(electric field)'

Yes I understand that is solution. But my question is that can't I use Ampere's circuital law.
I solved like this.

2pi * p * H = pi * p^2 * conductivity * E

thx for all advice.


texts:
I wrote down these lines intentionally avoiding to reset the output o when rstb is asserted:

module top_trial (
  input        clk,
  input        rstb,
  input        a,
  output reg   o
);
reg ff;

always @(posedge clk or negedge rstb)
  begin
    if (!rstb)
      ff <= 1'b0;
    else
      begin
        ff <= a;
        o  <= ff;
      end
  end
endmodule // top_trial

By using Real Intent's Ascent I retrieved this schematic:

The question is: do you think the multiplexer has a chance to be replaced by a latch (with enable) during the synthesis phase or by using another schematic tool?


texts:
Please forgive the long question. I have split it into 2 parts.

I am very confused about how harmonic suppression is measured in RF system (in my case, ham radios). I have picked up a couple of the Baofeng radios: The UV-5R+ and the GT-3, and I am keen to understand how bad the harmonics are whist using them.

I have read the following 2 blog articles that do measurements on these devices:
http://hamgear.wordpress.com/2013/01/30/baofeng-uv-5r-spectrum-analysis-revisited/
http://hamgear.wordpress.com/2014/01/24/review-baofeng-gt-3/

Also, referring to the EU standard EN-301-166-1 Section 7.4.3:

  "The power of any spurious emission, occurring more than 2,5 × CSP
  from the centre of the channel on which the  transmitter is intended
  to operate, shall not exceed [0,25 µW (-36,0 dBm)]"

Part 1

When doing these experiments, you configure a certain attenuation on the Spectrum Analyser. However, by applying different levels of attenuation, doesn't that mean that the measured harmonics will vary?? Does this mean that to obtain the absolute dBm value coming out of the radio, you need to add the attenuation figure onto any measure figures? For example, if you are applying 20dB attenuation, and you measure -50dBm on your analyser, does this mean that your radio is actually putting out -30dBm?? Or have I got this all wrong?? Also, what does reference dB mean? Is that simply the top line on the graph?

Part 2

I don't have a spectrum analyser, but I do have a very cheap RTL-SDR dongle (DVB-T stick hacked to act as a wideband receiver). Using the program SDR-Sharp, this gives about 50dB dynamic range (i.e. the amount I can see on the FFT display). The FFT display in SDR-Shaper has a y-axis of dB (not dBm, unfortunately). With the absence of any calibration equipment, I had to make do with relative measurements, rather than absolute values...

Using this dongle, an experiment I did, was set my radio to a certain VHF frequency (144.500Mhz), and by way of adjusting the SDR gain and moving the radio closer/further away from the USB dongle, made sure that the main frequency was just touching 0dB on the SDR-Sharp FFT display. I then went on to measure the harmonics, up to the 7th one.

The values I got from the UV-5R+ radio, from the 1st harmonic (main frequency) up to the 7th harmonic were as follows (in dB): 0, -55, -47, -45, -48, -52, -54

Have I measured anything useful here? And can I relate these figures to the EU standard at all?

Any help is appreciated.

Many Thanks


texts: mosfet gate different voltages along trace

texts: I have a N-mosfet connected to an led through a resistor at 5V at the drain, a voltage source coming from another board through a board-to-board header and the source at ground.  Regardless of the voltage sent to the gate (0V or 3.3V) the led is on.  When probing voltage at the header (a direct connection to the mosfet gate) the voltage is near 0V (4mV).  When probing voltage at the gate, the led turns off and the voltage remains at the unconnected multimeter voltage of ~200mV.  What could be wrong with this circuit?


texts: Replacing brushless motor (starting) capacitor with one of a higher capacitance

texts:
My kitchen hood vent is malfunctioning, the motor driving the fan is buzzing at different intensities depending on the speed I select.
I took down the unit and if I give the fan blade a spin, it starts just fine and maintains it's speed.

I have figured out that the starter capacitor has run dry (we've had the unit for over 10 years, and it's rated for a max of 10000 hours at 420V)

Now I want to replace the cap, which has the following characteristics printed on it:

  AV arcotronics 1 .27 .6CA2 MKP

  3.15uF +- 5%

  420V ~ 10000h/CLASS B

  470V ~ 3000h/CLASS C

  25/85/21

  PO

  CE 3.15 09340433

  B X4

I've tried to find a capacitor rated for 470V/420V at 3.15 uF but I haven't had any luck.
The only capacitors I can seem to find within my region (the Netherlands) have a rating of 450V, and either a capacitance of 3 uF, 5uF, 8uF or 10uF.

Since this capacitor is used to give the motor a bit of a boost at startup, I'm wondering if I can just swap in a higher value capacitor (I have a brand new 10 uF 450V capacitor lying around) without causing damage or it becoming a hazard.

Another thing is that the capacitors I manage to find all have 4 terminals instead of the two terminals that the capacitor that was built into the unit seems to have, any idea what that would be about?

The motor is being driven by mains AC (european mains)

To summarize my questions are:

Can I replace the capacitor with one of a higher capacitance?
What's with the 4 leads on the newer capacitors?

The built-in cap:

The 4-lead capacitor:


texts:
Maybe this is a stupid question, but here goes:
I just got a piezo buzzer and on the top there is a sticker that says "Remove After Washing".

My question is why would I ever want to wash an electronic part? I have no idea. Is there some manufacturing step where this makes sense?


texts:
I have a single-side ifa antenna design to which I wish to solder a coaxial feed. Now, I only have this female SMA connector with 5 pins on the otherside that I wish to solder to my PCB.

This may seem like an odd question but: will it function if two of the 5 pins are on the dielectric plate and the bottom two are on a conductive plate (copper)?

Fifth one is on the middle and on the feed point.
I did consider moving the feed point a tad lower but making the feed point longer would require me to change all the other parameters to compensate it, which I couldn't find a way to do.

The antenna is designed to work at 2.4GHz frequency.


texts: Source for a 6-pin DIL "stackable" header (for Arduino ICSP header)?

texts:
Does anyone know of a source for a "stackable" 6-pin DIL header? I would like to use one on an Arduino shield I am designing, in order to carry the ICSP header from the Arduino up through the shield so it's usable with the shield still installed.

I found this article where a more industrious / patient man than myself managed to fabricate a suitable part by cutting up an 8-pin SIL pass-through header with a Dremel tool and a diamond blade. I do have a few of those about, but they're matched in sets for making shields and I don't really want to start cutting them (and probably myself) up.


texts:
I'm developing on a small modular computer system using the Z80 just for fun. The backplane is a prototype PCB with five DIN41612 connectors wired in parallel, running about six inches from the first connector to the last. (This one: http://www.busboard.com/BB3U)

The CPU card I've made is composed of 74HCT-series logic and CMOS components (for SRAM, Flash, Z80, UART, etc.) all running at 5V. What kind of termination on the backplane would be ideal for a system like this?

The fastest signal on the bus is a 20 MHz system clock, everything else is in the 5 MHz range. The signals are mostly unidirectional, a few bidirectional for the data bus, and then some open drain signals for reset and interrupts inputs to the CPU card.

I've read about the VME bus which used Thevenin termination and it required strong drivers (74F-series to sink/source 24mA) over a very long backplane so that seems inappropriate here. But I'm not sure what else is appropriate.


texts: System Generator: a block to change sign of a floating point

texts:
I´m working with floating point numbers in System Generator. I need to perform this arithmetic operation y = x*(-1) . I think it could be done by using the mult block, but I don´t like this way because is very expensive in terms of FPGA demanded resources.
So I was wondering if there is any block to perform some kind of data conversión. The only thing is needed to do is to change one bit.
Does anyone know how to change the sign a floating point number using a reasonable way?
Thank you so much.


texts:
So, I am trying to fully understand circuits without the use of analogies like "voltage is like a waterfall" or "a battery is like a pump," since I've heard that those analogies break down when we get to more complex circuits. I am looking to understand EXACTLY what is happening on the atomic and subatomic levels. So, I have a few questions.

When voltage is referred to as "potential difference," does that just mean a difference in potential energy per charge between two points?
What exactly causes a voltage?
(This is more of a series of questions) What exactly are the electrons doing as they are moving? The Drude model treats electrons and atoms like solid objects, with the electrons hitting the atoms like a game of Plinko. But is that what ACTUALLY happens? Furthermore, are electrons ripped from their atoms and hop around from electron orbital to electron orbital, or are they freely spread out in the metal? When moving, do they physically hit the atoms? I can't imagine they would hit the nucleus of the atoms if the nucleus is extremely small and far away from the electron cloud, so how could it be possible that they actually hit the atoms? My textbook shows this photo, which is the cause of my confusion. If the electrons DON'T physically collide with the atoms, what accounts for heat in a wire? If heat is a measure of the kinetic energy of the atoms, and if the electrons do not in fact physically collide with the atoms, where do the atoms get their extra kinetic energy that we feel as heat?

With regards to Kirchoff's Voltage Law, I understand that all voltage drops = all voltage gains in a loop. That makes perfect sense as the law of conservation of energy. However, what I don't quite understand is when it is applied to a loop with just resistors, like the one below. If we go in a loop and sum up all the voltage gains and voltage drops, we should get 0. But I thought resistors only dissipate energy, thus the voltage gains should be 0 in the loop since a resistor can not provide voltage, and therefore, the voltage drops should also be 0, but they are not.

Why does V = IR? If, for example, I were to use the analogy of water moving downwards through a hole in the bottom of a tube, moving that tube up and down in space should not increase the rate at which the water exits the hole. The gravitational "voltage" is increasing since height is increasing, but the current should (I think) stay the same in this scenario. So, why does more voltage mean more current?

I know these questions are basic, but I really want to fully understand EXACTLY how this stuff works.


texts: What is the zero-sequence equivalent of a YNy0 transformer?

texts:
The zero sequence equivalent network of a YNy0 transformer with grounded primary is shown below (source).

It looks like there is no connection between the primary and secondary side of the transformer. This means that, if a line-ground short circuit occur on the primary side of the transformer, there won't be a fault current from the transformer.

From several simulation tools, I've concluded that this is not correct. I've included a screenshot from one (Paladin Designbase). As you can see, by running an short circuit analysis (using IEC 61363). Running an analysis using standard IEC 60909, there is no line-ground fault current.

What I'm wondering is: What is the zero sequence equivalent of a YNy0 transformer, and how can I use it to calculate the fault current?


texts: Would it be safe to use a 1.5 volt motor with the adafruit motor shield? It is rated for 4.5 to 36 volt motors so I am unsure what will happen. Also, what would be a good way to determine the voltage of a motor if you have no information on it at all?


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I need to PWM control six 24 V DC fans with a total load of 10.6 amperes. That's easy, right? Just PWM to a few MOSFETs. However, my system voltage is 28 V.  At 28 V I'm out of specification for the fans and looking at a 36% increase in power (watts). I'm guessing I probably don't want to PWM the raw 28 V to the fans, right?

I'm in a power-draw sensitive scenario, so I don't want to just stick some big power resistors in line to reduce the voltage to them. I've also looked into RC low pass filters to smooth the PWM voltage to be within specification for the fans, but I'd need a very small resistor and basically a bank of 10 µF ceramic capacitors.

What is a good solution in this scenario? Is there one?


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I want to write program with " MPLAB IDE v8.50>>Pic18f452 " by 1) low level pulse & 2)Rising edge . but, how?(without interupt & micro C,maybe!)
I wrote this program with falling edge.
Thanks a lot.

This is my circuit in proteus 7.7 .


texts: Replace AMS1117 5V-3.3V LDO on NodeMCU for LiPo with low quiescent current

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I want use my NodeMCU to drive a SIM808 Module with integrated LiPo Charger.
https://www.itead.cc/wiki/SIM808_GSM/GPRS/GPS_Module

There are two problems. First of all the SIM808 Module just provides the LiPo Voltage, no steady 3.3V or 5V output. The NodeMCU needs 3.3V (or 5V with LDO).
The internal LDO has a high quiescent current of >1mA. So the idea would be to replace the onboard 5V to 3.3V LDO with one with a low quiescent current (<0.1mA) for direct LiPo input (3.7-4.3V) and 3.3V output which is pin compatible to just replace it direcly on the NodeMCU.

The MCP1700 would be an option as TO92 to make the PINs fit because VIN/VOUT is reversed.

This would be my easiest idea. Do you have any different ideas?

More about the NodeMCU and the AMS1117 position on the board
https://tinker.yeoman.com.au/2016/05/29/running-nodemcu-on-a-battery-esp8266-low-power-consumption-revisited/


texts: Reducing the number of expensive capacitors in an audio opamp circuit

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I'm designing a guitar effect (simple booster) which uses a CD4053 cmos switch as outlined here (http://www.geofex.com/Article_Folders/cd4053/cd4053.htm)

As you can see from the second diagram, RG suggests using the "existing in and out capacitors" of the effect itself to properly ensure that the CD4053 does not experience any DC offset (which cause clicks).

Notice however that the link between 2 and 12 (the bypass link) does not have capacitors. So RG clearly assumes that there is no need for them in a simple link.

Now... This is the boost circuit I'm trying to implement (I like it because it also an attenuator, it has a volume knob, which is fundamentally a problem in this case)

Firstly, because RG has no caps on his bypass link, do we think it's safe here to omit the boost circuit input capacitor as long as I properly bias the input to 4.5v?

Secondly, what do we do about the output potentiometer, could I just use 4.5v instead of ground, then I don't need to re-bias the output to 4.5v?

In short what do we think about the booster circuit here :

LTSpice seems to indicate that the circuit works, but I have no idea what it would be like in an actual application.

s you can see here :

Whilst I have enough space on a PCB sized for the hammond 1590B to implement a Booster with a few more capacitors, I'm quickly running out of space so I couldn't use this design as a template for other effects. I'm pretty stuck on using the WIMA caps.. What is the point of making your own circuit if you don't use the best bits?

Does anyone have any suggestions as to how I can improve the booster circuit generally? And particularly how I can do that without using up much more PCB space?

EDIT :

See below same thing but with JFET switching as per the tube screamer :

Here's the swtich.. notice a nice ramp up in volume caused by the capacitors on the JFETS.. Much better than the rock hard (but instant) switching of the cmos chips.


texts: Approaches to creating better mouse pointing hardware for absolute input?

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I play the video game osu!. Osu! is a game that requires the player to quickly move the mouse pointer to different areas of the screen in a precise manner.
A game such as osu! lays out unique requirements for an input device:

It should be absolute (1-to-1 correspondence between position on screen and position of input device), unlike most computer mice. This is to avoid a problem known as "mouse drift", where the mouse drifts away from the central position of the mousepad after some time of gameplay.
It should have low latency, ideally less than a millisecond.
It should have high refresh rate, ideally around 1000hz.
It should have high (spacial) precision.

Such an input device only needs move the mouse cursor. Any mouse buttons or anything of that sort are not used.
Most top players today use a graphics tablet such as the Wacom CTH 480 and XP-PEN G640, normally used for drawing digital art. See this video as an example. Graphics tablets offer absolute input with high precision. However, most graphics tablets suffer from worse latency and refresh rate than conventional computer mice, and need to support things like pressure sensitivity and button presses—functionality that goes unused. I have not seen a graphics tablet that refreshes more than 240 times per second, while most have a refresh rate closer to 120hz. That's 4.16 and 8.33 milliseconds of latency respectively, on top of the "constant" latency.
My question is: What would be a feasible approach to creating a DIY input device that meets all four of the aforementioned requirements? And additionally, are there any reading materials that I should look into? For context, I'm an electronics newbie coming from a computer science background, who is quite comfortable with embedded development.
I have thought about three different possibilities. Perhaps the people here could envision more?
Conventional Graphics tablet
The best explaination I could find regarding how these work come from two Scanlime videos:

Graphics Tablet Primer for Hackers - scanlime:012
Wacom Teardown and Schematic - scanlime:013

Perhaps some of you have better reading material? From what I've gathered these use a set of coils to sense changes in the magnetic field when the pen moves across the tablet surface. I wonder why these can't be made to refresh faster? Perhaps it's just because the pens need time to collect enough energy from the tablet for it to transmit back the button presses and such?
Magnetic tablet (grid of hall effect sensors)
These would use a grid of hall effect sensors to sense the presence of a magnet embedded in the tip of a pen's stylus. Examples projects using hall effect grids include:

The paper GaussBrush: Drawing with Magnetic Stylus.
Multiplexing A3144 hall sensors with an Arduino/AVR
Imaging Magnetism With A Hall Effect Camera and High Speed Imaging Of Magnetic Fields

Is my understanding correct that the refresh rate of this approach, along with conventional graphics tablet, is limited by the fact that you only have so many bits that can be fed to the microcontroller from the ADCs, resulting in the need to do time multiplexing where only certain subset of sensors are sampled at each time step? If so, couldn't the refresh rate be increased by using a larger microcontroller and multiple ADCs so that more sensors can be sampled at once?
Optical approach using laser pointer
I recently came across this video where a person which used a laser pointer combined with a web-cam to control the mouse. Thus I have the question, does there exist some kind of surface which can detect the position of a laser pointer, similar to a camera, which operates at high refresh rates and low latency? I'm imagining some kind of graphics tablet where the pen is replaced with a laser pointer.


texts: Overcurrent Protection for COB Leds wired in parallel powered by Const Voltage Mean Well Driver

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Roughly this is my current wiring diagram.

The Mean Well driver that I am using is the HLG-185H-36B.  Output 36v DC, max current 5.2A.  The Cobs are 36V and have a max operating current of 2.76A, however, I am running them at around ~1.44A (Max).  The Mean Well driver has the ability to adjust volt/current which I do have setup to a 100k ohm Linear POT.

What I am worried about is if a COB fails.  I'd like to add overcurrent protection at the nodes that I marked with (NODE#) so that no more than 1.7A-2A could be drawn.

I also am concerned about thermal runaway, details more here (there is a section that talks about it more in-depth) http://ledgardener.com/constant-current-vs-constant-voltage-drivers/

What are my options to protect the circuit so the COB LEDs don't overdraw current in either the event of 1 or more cobs failing and/or thermal runaway?  Thank you!


texts: Thevenin equivalent of circuit with no voltage sources

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I need to find the Thevenin Equivalent left of the >> symbols.
Due to the lack of voltage sources I tried finding the Norton Equivalent first and came up with \$Rn=R_O\$, \$v_{th}=i_S \cdot R_O\$. Is that correct? If not how does one handle this case?