texts: AVR program behavior incorrect after disabling reset fuse

texts:
I am using an ATtiny13 to drive 15 LEDs from five I/O pins (Charlieplexed). I am using ADC0 (pin1) as input from a voltage divider to provide a speed control. In order use ADC0 properly, I need to disable the reset fuse when I write the program.

The problem is, the program behaves differently when the reset fuse is disabled. Instead of all 15 LED's lighting, only 9 are. The 9 LEDs that light involve all 5 I/O pins, in both polarities, so I don't believe I've accidentally changed any configuration to those pins.

Here is the command line I use to flash the AVR (using avrdude on wintel) and set the fuses:

avrdude -c usbtiny -p attiny13 -U flash:w:program.hex -U lfuse:w:0x6a:m -U hfuse:w:0xfe:m

And the schematic:

Before setting the fuses, the program works perfectly, lighting the 15 LEDs as expected. The input on ADC0 will reset the micro when the voltage drops low enough, as expected, but otherwise speed control works. Here is a chart to show how the LEDs are connected:

LED #    AVR PINs    I/O PINs
 1       5-6         1-2
 2       6-5         2-1
 3       5-7         1-3
 4       7-5         3-1
 5       5-2         1-4
 6       2-5         4-1
 7       5-3         1-5
 8       3-5         5-1
 9       6-7         2-3
10       7-6         3-2
11       6-2         2-4
12       2-6         4-2
13       6-3         2-5
14       3-6         5-2
15       7-2         3-4

After disabling the reset fuse, LEDs 1 through 9 work, 10 through 15 do not. There is a slight flicker detectable on LED 13. ADC0 speed control works through the full range, without resetting the micro.

I am thoroughly confused. Can anyone advise?

Edit:

In case it matters, this is using an SOIC-8 package. Previously I've used a DIP-8 and not had this problem.


texts: What is a coaxial balun and what is its construction?

texts:
I don't quite understand what a coaxial balun is.

Is it a regular balun or is its wiring is made up of coax?

Also, I need to convert 75 ohms unbalanced  to 50 ohms balances impedance using a "coaxial" balun.

How do I find the reactive impedance values if that is relevant here?


texts:
I have some connections in my single-sided PCB which could benefit from a plane especially all connections to power and all connections to ground. I can easily create a polygon for only one plane (for example to intelligently flood the remaining bare spots (areas with no copper) of the PCB with ground), however I want to also be able to fill applicable bare spots with power (vcc). I tried creating a polygon named gnd then on top I tried creating a polygon named vcc and after running rats nest, it seems that the gnd and vcc are shorting each other. If I play around with the rank values, then either gnd or vcc will fill the bare spots, but not both.

Is there a way I can have both a gnd and vcc plane without resorting to non-overlapping of plane creating and without making each plane use only a small portion of the board?


texts:
When I read articles, FPGA comes with a specification-nm.
For example, Xilinx 28nm Virtex 7 or 20nm UltraScale FPGAs.
What does -nm means in FPGA?


texts: Daisy chaining a headphone amplifier with a speaker amplifier

texts:
I want to build a small projekt for with just an Arduino, a radio receiver and 2 speakers.

I have bought a small PCB with a TEA5767 radio FM chip (ebay). The audio output is however fed directly in a headphone amplifier chip TDA1308 from NXP (datasheet). The rated maximum power output of the TDA1308 chip is 80mW.

I want to however feed the audio into two speakers. For this purpose I'd like to use the PAM8403 stereo audio amplifier (datasheet). This chip is rated for 3W output power.

Would it damage the amplifiers or the speaker if I were to connect the output of the headpone implfier to the input of the speaker amplifier? If yes, what's the best way to get the audio to the speakers? Should I convert the amplified signal to line-level again and then amplify it again? Or would be easiert to just desolder the headphone amplifier and grab the TEA5767's audio output directly?

I've searched for similiar questions on this board but nothing came up. Thanks for your help.


texts:
I have a pneumatic solenoid valve switching from IRF830 MOSFET. Solenoid valve connected to MOSFET by 2-3 feet long wire.

It's necessary to use a freewheeling diode for this?

What is the most suitable place to mount the diode ? Either near the solenoid valve or near MOSFET?

P.S.

This question about most suitable place for diode. Not about diode is need or not.


texts: What is line to line voltage supposed to meter at?

texts: I'm pretty new to this but I know that in three phase power, when I'm metering line to line its usually at 208V, but I've been told that line to line meters at 240V. I don't know what would cause for it to meter different. Does it matter whether its WYE or Delta? Or is it only 208V when there is a common neutral or ground? I refer to USA and Canada.


texts: Switching power line phases with inductive load

texts:
I have one question related to this schematic:

Scenario:

Source 1: AC source 220VAC, 50Hz, 120º
Source 2: AC source 220VAC, 50Hz, 0º

If I want to switch from source 1 to source 2 or from source 2 to source 1, which is the best moment?

When the voltage in the inductor is 0V or when the current in the inductor is 0A.

The key is to reduce as much as possible the voltage peaks, so as the load is an inductor, I don't know what will happen, because the volatage over the inductor will change due the 120º between two phases of the powerline when the switch changes the source.


texts:
Working on a RS485 IC circuit.

It is a point to point communication between two devices connected to each other via MAX485 IC and CAT6 Cable.

At 1 or 2 m length of cable, the data transfer seems fine. But above 5m the logic 0 transmission is not good. The logic 1 transmission is good.

Used Fail Safe Resistors of 10k/20k on the A & B Data lines. Also terminated the line with a 120 Ohm resistor.

Currently, I am just giving a logic 1 & logic 0 through the arduino. All common ground and other considerations checked. All fine. At 1 or 2m it works fine but above 5m the thing is not working reliably.

I just need to send some logic states over the cable. Data rate : about 10 bits per second. Length of cable requirements: 10m, 15m & 20m.

What can be done?


texts: upgrading my electric bike battery. Li ion 48v 625wh battery

texts: I have recently purchased an FLX 2020 Bandit and was wondering if there was any way I could upgrade the speed or range of the 48v 625wh battery. I understand I can buy another one online, but was hoping that maybe there was an easier way. Any help is appreciated, thank you!


texts:
i have a few 2N5064 SCR that are puzzling me. No matter how many hundreds of thousands of ohms i put between their gates and a 3.2V battery source, it always starts to conduct. I even put a 10 V zener between them, and it still turns on. Looking at the datasheet, i am puzzled. Where minimum gate turn on current is, there is just a dash. Same for minimum voltage. What does this mean? Will they activate with pretty much any current?

Thanks


texts: Why did the Tesla battery in Queensland respond to grid frequency? Why isn't this stable?

texts:
The RenewEconomy article Tesla big battery outsmarts lumbering coal units after Loy Yang trips details the recently installed Tesla battery in Queensland Australia's response to a sudden change in line frequency of the power grid.
Why would a frequency change be the thing that the battery responds automatically to?
Naively thinking, since the grid may have several different power sources operating independently but connected to the same grid, wouldn't they all be designed to remain synchronized to a stable frequency? Loading might lower the voltage, but I'm surprised the frequency would be allowed to drift.

Last Thursday, one of the biggest coal units in Australia, Loy Yang A 3, tripped without warning at 1.59am, with the sudden loss of 560MW and causing a slump in frequency on the network.
What happened next has stunned electricity industry insiders and given food for thought over the near to medium term future of the grid, such was the rapid response of the Tesla big battery to an event that happened nearly 1,000km away.
Even before the Loy Yang A unit had finished tripping, the 100MW/129MWh had responded, injecting 7.3MW into the network to help arrest a slump in frequency that had fallen below 49.80Hertz.
Data from AEMO (and gathered above by Dylan McConnell from the Climate and Energy College) shows that the Tesla big battery responded four seconds ahead of the generator contracted at that time to provide FCAS (frequency control and ancillary services), the Gladstone coal generator in Queensland.


texts:
I have been trying to build a simple induction loop amplifier. I am using TDA2040 as an output stage and it delivers 10 W (I limited it for that). I am using about 14 meters (1 mm thickness) loop.

My question is: How do I calculate a suitable resistance wattage to connect with the induction loop in series to the output of TDA2040?


texts: How to simplify ab + a'b'? Is there a gate for this?

texts:
I am simplifying the sum part of a full adder. The equation I get is:

$$x \cdot \overline y \cdot \overline {cin} + \overline x \cdot \overline y \cdot cin + x \cdot y \cdot cin + \overline x \cdot y \cdot \overline {cin}$$

How do I simplify this to get the two xor gates that make up the sum part of a full adder?


texts:
I have a fan with a shaded pole motor and I installed this PWM for speed control.

At the moment everything is working well, speed adjustment is sensitive and the fan is barely moving at about the 60% range of the knob adjustment.

Do I risk damaging the motor with this setup?  Should I have gone with a different speed control method like a triac or variac?


texts:
I am simulating time-domain graphs of a Schottky diode model.

I am expecting ~zero current at the negative half cycle. But I am seeing negative current. It's only about 3mA, but based on I-V curve, it is about 0. Does anyone have an idea what might go wrong?

diode model:(from datasheet)
Is=30e15     Rs=8     N=1.05      Tg=1e-9   Cjo=0.1e-12     Vj=1     M=0.5   Fc=0.95     BV=5    IBV=1e-5     Eg=0.69


texts: BLDC Motor and Generator, query about capacitor bank

texts:
I have 3 phase generator (believe to be Wye) which goes to 6 diode rectifier, the rpm can goes from 1000 to 5000.

The output of the rectifer (50V say) has ripple on top which goes to 100W Motor driver BLDC. The BLDC motor is being used for position control (ie CDC).

Is there guideline or equation how much capacitance necessary to smooth out the BLDC motor for reliable operation (speaking generally). I'm unclear how much smoothing it really needs.


texts: A question about Faraday’s law of induction for a closed path

texts:
As far as I understand, Faraday’s law states that a varying magnetic field through a closed path creates an E-field along the closed path. And the integral of this field we call electric potential or voltage.

And if the loop is an open at one end, I guess all the potential exhibits itself across this gap. Below I assume a varying magnetic field across the wire loops.

Above the top loop is open at A and B. If we observe 6V across A and B, and then if we replace the same loop this time closed but with 3kΩ, 2kΩ and 1kΩ resistors; can we say that 3V will be induced across 3kΩ, 2V across 2kΩ and 1V across 1kΩ?

If so, what causes the higher voltage across bigger resistors? Is there any formula which shows such a relation, which uses E-field and resistance not the current? Because in the original Maxwell equations, Faraday’s law is about the E-field created by changing magnetic field.


texts: How to keep a linear regulator cool without an actual heatsink?

texts: I want to use a linear regulator for some application, it's in a SOT-223 (not SOT-89) package. How do I keep it cool, preferably without a bulky heatsink? The regulator may be dissipating 2-3W of heat. I've heard that you can use copper traces under the regulator on the PCB to keep the regulator cool; does anyone have any references on this?


texts:
Let S1 and S2 be 2 LTI systems with responses to the unit impulse given by \$g_1(t)\$ and \$g_2(t)\$.Consider that we associate S1 and S2 .Knowing that \$g_1(t)=e^{-t}u(t)\$ (u is the heavside function) and \$g_2(t)=e^{-\alpha t}u(t), \alpha >0 \$ and real, determine the response to the unit impulse of the association of these systems. Use the Laplace transform and its properties.

My doubt: I don't understand why to use Laplace transform properties. Isn't the answer the convolution between \$g_1\$ and \$g_2\$? This should be 0 for \$t \leq 0 \$ and
\$ \int_0^t e^{t-\tau} e^{\alpha \tau} d\tau \$ for \$t > 0\$

What am I doing wrong?

Thanks!


texts: Infinitely linear torque with current in motor?

texts: I'm trying to find the maximum current my brushless DC motor can handle. If I can keep the coils and cabling cool (in a freezer right now), is there any other fundamental limit I may hit such as saturating a magnetic field?  I'm trying to plot an empirical Torque-Current curve where I measure torque with an oversized mass on a scale and a small pulley, but so far have not seen any tapering off of the torque.


texts: Setup of motor control with remote and limit switches

texts:
I have a need to setup a rig that will raise and lower at the press of a button. I have two 12v motors which run the two ends of a gantry (i am not worried about speed control - since I will add that) however I am struggling to understand how i will wire this setup.

essentially what I dont know

how to connect the limit switches
If i can reliably use a transmitter to send the "up" and "down" signal or if i should have a 777 timer in the mix also.
how to make the motor change direction for up and down buttons - it doesnt need to reverse direction at the end stops, just needs to stop.

I have created a diagram which illustrates the issue?


texts: Memory mapping in the 8085 microprocessor

texts: In the 8085 microprocessor there is 64 kb of memory available of which some are assigned to ROM while others are assigned to RAM. My question is, why is ROM always mapped to a lower region of memory map in the 8085 microprocessor?


texts: L293, L298 and SN754410 H-bridge drivers on low voltage power supply

texts:
This question is about the following three integrated H-bridge drivers: -

L293 or L293D (D = protection diodes added)
SN754410 (protection diodes included)
L298 (no protection diodes)

Time after time the same question keeps coming up - someone is using one of these devices (on a low voltage, usually around 6V or less) and they are just not performing adequately. The reasons are listed further below but my question is this: -

What H-bridge drivers are preferred when controlling a low-voltage motor?

Information

The L293 and the SN754410 are nearly identical and crucially, if you try and control a 1 amp load, you are faced with dismal performance: -

The tables tell you (typical conditions) that the upper transistor drops (loses) about 1.4 volts when driving a 1A load and, the lower transistor drops (loses) about 1.2 volts when driving a 1A load. The upshot is that if you have a 6V, 1A motor and 6V battery, don't expect to see more than 3.4 volts across the motor: -

\$V_{OUT} = 6V - (1.4V + 1.2V) = 3.4V\$

Worst case scenario is you might only see 2.4 volts across it.

What about the L298? It's got a nice big heat-sink whereas the L293 and SN754410 are regular-looking chips. Here's what the volt drop (losses) look like: -

It's the same story - for a 1A load, you can expect to lose up to 3.2 volts and, what you thought might be 6V across your motor, is at best 4.2 volts and at worst only 2.8 volts.

Clearly none of the devices listed are suitable for low voltage applications where the motor might be expected to draw in excess of 0.5 amps.


texts: how to get fractional delay in picmicrocontroller

texts:
i am using 4MHz clock for pic18f452. therefore, 250ns is 1 instruction cycle. is there any way to get a delay of 375ns?
using timers, i cant define count in fractions. using inbuit delay function delay(1)=250ns delay(2)=500ns .   if i use delay(1.5) it will be still 250ns as i can only use an integer as a passing parameter.


texts: A question about coupling differential signals safely and Input Common Mode Voltage Range

texts:
This may sound a weird question but couldnt resist to ask here.

Lets say I have a differential signalling mode floating battery powered transducer(where the outputs are mirrored) and the differential voltage across its outputs Vd at a moment is 1V.

Lets call the output wire pairs as V+ and V-. At this moment I only know the differential voltage between V+ and V- by using a voltmeter or a scope as 1V.

Below illustrates the transducer and its differential outputs:

But in the above situation I dont know the voltage across V+ and the earth ground and similarly I dont know the voltage across V- and the earth ground.

Lets say I measure the voltage across the V+ and the earth and V- and the earth and I measure them as 101V and 100V respectively keeping the differential voltage as 1V again.

Imagine I hook up this transducer outputs to a differential amplifier where its system analog ground is earth grounded. I draw the equivalent circuit as:

In this case, the common mode voltage Vcm = (100 + 101)/2 = 100.5V

and

the differential voltage remains Vd = 1V

If it is true so far so good..

But in data-sheets of the amplifiers there is something called input common mode voltage range. I think it is the max voltage an amplifier can handle with respect its system ground.

And imagine this amplifier has +/-15V input common mode voltage range.

My questions are:

1-) Would the amplifier get damaged in this case?

2-) If it would, does that mean that I have to measure the differential output pairs of the transducer one by one with respect to system ground of the amplifier each time before I couple them? Is there a common practice for that?


texts: Why isn't maximum current forced upon a circuit by a power source?

texts:
I asked a similar question here  about this, but I still don't  quite understand.

Say I grab onto two wires from a standard 120V 20A wall socket. I would fry. I would have 20A at 120 forced on my body.

But, when speaking in terms of circuits, as in my linked question, if I have a power supply outputting 100mA maximum at 5v, for some reason my device only gets exactly what it needs? Why is this?

Most things flow from an area of high concentration to low concentration, taking the path of least resistence. If you connect two wires to a power supply, why don't the maximum number of electrons want to go through your circuit?

If current behaves this way...why do you have to regulate voltage?


texts:
sorry for my english,
I am from Indonesia.

I try to make a (car) relay active - switch on, if the motor/fan is working normal,
so when the fan is out, not working or broken, automaticly the relay is off.

But it is not working.

Can someone please help?

Edited
Transistor NPN 2N3055

Motor
12 Vdc / 3 A

Car Relay Hela 12V


texts: Programs for editing Proteus gerber files to panel PCBs

texts:
I am in need of a program that lets me edit gerber zip file. I have several PCB to be sent to JLCPCB but individually ordering them will cost me quite an extra (30$). Although that may not be much to some, but I don't like spending money where it can be avoided.

All that I am looking for is for me to be able to edit the board edge of my individual projects so that I can panel them in a one big square/rectangle panel.

I have tried doing it in the program I am using to create these files (PROTEUS 8.9) but it would seem there is no feature yet to combine project files. Long story short. Something will always break if I try to combine project files.

EDIT:
I have tried the solutions from another question

How to panelize gerber files?

Both of the answers did not work for me. On the marked as correct answer, no gui opens upon executing the program, if it is ment to be that way it would be really hard for me to use it. On the second answer it does come with a GUI and a guide on how to use it. Unfortunately the gerber from proteus upon creating an instance would not show up, but the gerber viewer it came along with can open it no problem


texts:
I'm trying to create a setup where I would have xrays emitted through a photodiode (the non sensitive side). I do not want the photodiode to detect these xrays going through it, only the xrays which return back to the source.
My question is then, are photodiodes sensitive to light going through the opposite side, through the back of it? (Going through from behind it)
Thanks!


texts:
I have a project which I am using an octal driver/inverter (DARLINGTON ARRAYS) to allow a micro controller to control 4 electromechanical relays. I have been experiencing relay failure and driver/inverter failure which I believe is due to back EMF. I have attached a simplified drawing to show the layout as it is today. I need to figure the proper way to suppress the back EMF.
Adding to the problem is

All parts are external from one another. The logic board is separate from the power supply as are the relays. Therefore I have harness making the physical connections.
The power supply is not on constant (driven by logic board) which means common free wheeling diode reference is not constant either.
The octal driver/inverter outputs are all independent from one another, it's up to the microcontroller as to which outputs are low at any given moment.

Can anyone help answer the following questions to help me best make the correct decision?

Is the only acceptable placement of the suppressor across the relay coil (inductor)?
Is placing a diode in parallel with the output from the driver / inverter to +24 an option? Therefore, diode anode to output (low when "on") and cathode to +24VDC.
Is the diode the best choice? MOV better?


texts: What is the difference between a 'baseband processor' and 'baseband controller'?

texts: It seems hard to find a definition for either of the terms.  From skimming through datasheets that contain these terms, I get the impression that both refer to programmable components which control the final RF circuitry.  But what exactly is the difference?


texts: Key fob receiver reverse engineering: IC identification

texts:
I'm doing reverse engineering on a hardware of an equipment, this equipment is able to identify the presence of a RF signal from a key fob.

Unfortunately, it was not possible to identify the integrated circuit, it has a mask, a number that makes no sense to me and I was not able to find information about it.

I don't know either the exactly values of the capacitors, I cannot remove them from the circuit. So, I would like to know, based on the incomplete information of the figure below, could someone identify, or make a guess, about which integrated it would be?

Below is the image of the antenna of the circuit. The other circuit components are on the other side of the board

EDITED:
Below is the image of the IC, the code printed on it surface:

506

1403

M83

PS: Sorry for the lack of information in the question, any information or guess may be valid.


texts: Using several microcontrollers as nodes in a neural network

texts:
I recently read an EETimes article about Google's neural network experiment, where they used several processor cores as nodes in a neural network. That made me wonder: could it be possible to replicate this with off-the-shelf microcontrollers?
I was thinking using 15 to 20 ATTinys or picaxe 10f200s and then interconnecting them via their serial communication lines.

Is this a viable concept?
If not, are there alternate ways of making this kind of neural network?

In other words, is this possible and if yes, how would I go about to make it? I'm new to this area of computer science, so I need some help.

Thanks!


texts: Electronic component name & value to be traced

texts:
https://en.wikipedia.org/wiki/Electronic_component
What are the best ways to trace the electronic components value, name if the name &  value are not able to be seen on the component itself because of old printed circuit boards?
Examples : capacitor, diode, transistor, integrated circuit etc


texts: MPPT for fixed DC use, or charging multiple independant batteries at once?

texts:
I've got a set of small deep discharge lead acid batteries (7ah @ 12v) and a few larger ones that I use for running electronics in remote areas for hobby use.  I don't use them evenly throughout the day, so they end up at varying levels of charge as time passes.

I have a pair of solar panels and an MPPT charging controller designed for lead acid batteries.  This is all well and good but the charge controller can only charge one battery at a time in this situation (though the controller does support 24v operation, I can't charge batteries in series because they're either different capacities or discharge levels, and I'm not sure it's safe to try to charge them in parallel for similar reasons).

Has anyone needed similar hardware? I don't really want to run an mppt for each battery (for 7ah batteries it would practically be cheaper to just buy a new battery every time one drained) but I haven't been able to find any hardware which has independant charging functionality, even the really high end ones seem to be designed for a single bank of batteries.  I couldn't find anything designed to run a fixed dc output from which I could run a discrete charger, and I'm hesitant to run an mppt ac inverter due to efficiency concerns, and complications of tie in systems (this would need to run standalone, and most importantly, portable)

I'm also tempted to grab some LiFePO4 batteries because they're lighter and have longer livespans than lead acid, so it would be convenient if any recommended hardware could properly charge both chemistries (my current mppt does not support this).

Speed is also important to me, so anything capable of utilizing as much as possible of the output of the solar panels (200 watts total under ideal conditions) to charge all of the batteries in as little time as possible is preferable.

Can anyone make any recommendations?


texts: Receive bipolar analog signal with sampling rate of 10 kHz

texts:
I  wish to receive time-stamp data of a bipolar analog signal (analog signal that oscillates about 0 volts) from a sensor (which can only send analog data as an output) into ESP32 at Nyquist sampling rate (Fs) of 10kHz.
Also I wish to transit this data further to Raspberry-Pi for its further post-processing.
Is it possible to achieve this task with the help of ESP32 and RaspberryPi?
Is somebody who has worked on ESP32, could please let me know on how do we go about this, I would be very much thankful!


texts: Disk array power supply pinout/conversion

texts:
Sorry for crossposting this, but I've had no answers from the more specific Ggroups.

I'm in the process repurposing a power supply from a scrapped Sun Microsystems StorEdge D2 array which was working perfectly well when decomissioned.

It is a Japanese made 360W FDK PEX737-40, +5V/30A and +12V/23A.
Impressively well built hardware and in mint condition.

The final objective is to have a PS with solid +12 and +5 outputs which may eventually power USB charging ports and other assorted stuff needing quality power.

The plug at the back of the slide-in box/canister has 24 pins just like the typical male Molex 39-01-2240 connector for ATX MBs but with a different pinout and keying(?) and without all the usual ATX voltages, which makes sense as it is not a for a motherboard.

Of the 24 pins, 20 have 18AWG and 4 have 24AWG cables.
All cables have their own pin assignment, no pin is used by more than one cable like, eg: sense cables in typical ATX PSs.

With the unit plugged in and switched 'off':

Logic wire resistance readings to GND

24AWG-green  ->    0.2 Ω
24AWG-brown  ->  530.0 Ω
24AWG-blue   -> 3610.0 Ω
24AWG-red    ->   60.0 Ω
18AWG-grey   ->   90.0 Ω

With the unit plugged in and the rear switch 'on' only:

18AWG-orange -> + 0.0006V to GND
18AWG-yellow -> + 0.0028V to GND
18AWG-grey   -> + 0.0004V to GND
24AWG-green  -> + 0.0000V to GND
24AWG-brown  -> + 0.0003V to GND
24AWG-blue   -> + 5.0800V to GND
24AWG-red    -> + 0.0003V to GND

The five +5V cables are on the same rail as they show 0.1 ohms between them, same for the three +12V cables.

The remaining red cable shows 10.2 ohms to the other +5V cables.

The yellow +12V cable shows 4.65K ohms with respect to the other +12V cables and is probably destined to one of the two redundant fans the array had.

With the unit plugged in, the rear switch 'on' and green+blue shorted, the unit latches_on and I get these readings:

18AWG-red    -> + 5.11V to GND
18AWG-orange -> +12.29V to GND
18AWG-yellow -> +12.01V to GND
18AWG-grey   -> + 5.06V to GND
24AWG-green  ->   0.00V to GND
24AWG-brown  -> + 5.11V to GND
24AWG-blue   -> + 5.08V to GND
24AWG-red    -> + 5.10V to GND

So I guess that the logic cable mapping would be this:

24AWG-green  ->  GND
24AWG-brown  ->  ?
24AWG-blue   ->  PS_ON#
24AWG-red    ->  ?
18AWG-grey   ->  PWR_OK

What I would need to know is:

The 24AWG-red cable has no voltage when the unit is not latched_on, so it does not seem to be +5VSB: what is it for?

Likewise, the 24AWG-brown cable has no voltage when the unit is not latched_on.

What would be the proper use of this cable?
Are they sense cables like the ones used in regular standard ATX PSs?

Do I need to put in a dummy load (10 ohm/5w sandbar resistor) to insure stability?

I'd be grateful for any input on this.


texts:
How to interpret the hFE of a datasheet?
How should I interpret this data, the image is extracted from a PN2222A datasheet
With Vce = 10v and Ic = 150ma I can obtain an hfe between 100 and 300 I understand that depending on the base current that I apply, this is correct?
But with Vce = 1v and Ic = 150ma I only to obtain an hfe of 50 regardless of the base current that I apply, is this correct?
But with Vce = 1v and Ic = 10ma, I only get an hfe of 75 regardless of the base current that I apply, is this correct?
Thanks


texts:
I have a side-project to read temperatures from 4 thermocouples (K type, around 500F for coffee roaster data logger), and no previous analog experience at these levels.

I've identified two possible solutions, but I'd like to hear feedback / suggestions / alternatives.

The first method would be to feed the four thermocouples through an analog mux (say HEF4052, though haven't done as much research on this- is finding a mux for low-freq uV signals), and then to a typical thermocouple IC (MAX6675).

The second method would be to feed the thermocouples into a 4 channel differential ADC, probably with an integrated PGA (AD7708). Then have an on-PCB temp sensor to handle cold junction compensation. Another option'd be analog mux to a single channel ADC, etc.

Are there advantages to one approach over the other? It seems like the first would be fewer components, and a bit more reliable, though a bit more expensive then the second option.

I've also seen circuits using an RC filter on both thermocouple lines- is that worthwhile? What kind of TC would be worthwhile on these kind of signals? Something for blocking 50/60Hz? Just installation specific?

My primary concern is that this is the first time working with signals measured in uV, so I'm not sure what is and isn't important (beyond basics like keeping digital and analog seperated).

EDIT: One more question for the ADC approach: is it important to measure the signals differentially, or could the low end of all 4 thermo couples be tied to ground, then be measured in a single ended fashion? ADS1118 seems like it has alot of what's wanted, but is only two-differential channel (and the datasheet shows differential measurements at that). More plainly: what's the advantage of doing differential measurement vs. single ended with one end tied to ground? Just isolation from the rest of the system?


texts: Why ATX PSU is using separate ground wires?

texts: Why ATX PSU is using separate ground wires (black, that connects to mobo via 24pin ATX, to cpu via ESP mini-fit molex, to video cards via 6 or 8pin molexes)? Instead of just using chassis as a ground? Does ground wires create ground loop with chassis? I heard ground loops are generally bad idea.. so why?


texts:
I've noticed that if I build a Colpitts oscillator (audio range) using a transistor in the common base configuration (similar to the circuit here) I can vary the voltage on the base and get a wide range of frequencies. This is a very simple circuit, so what's wrong with it? All of the VCO schematics I see are substantially more complicated. I can think of several potential reasons for this. Can you identify which are the case and elaborate on why VCO designs are often so complex?

In an RF design, this might suffer from a small bandwidth - perhaps the frequency can't be modulated enough to be useful
Perhaps the frequency stability is poor, or the phase noise is bad
The frequency vs voltage could be highly nonlinear (although it seemed fairly linear to my ear - I do not have fancy instruments to measure these things)
It could be temperature dependent
The amplitude could change too much with changing base voltage
Some other reason?


texts: Is there a crimp tool, or something, for when you're soldering leads to leads

texts: Are there any tools or parts that help when soldering a free-floating component to another one, for example a resistor to an LED? Something that will make some kind of mechanical connection instead of just relying on the solder. I imagine someone has to make some kind of little sleeve or collar that you slide both leads into and then crush, but I've never come across anything.


texts: What is the purpose of 9th pin in ULN2003

texts:
Whenever I need to use relays with Microcontroller, I use ULN2003. I connect the GPIO from MCU to the input pin of ULN. Connect 8th pin of ULN to GND and take output from the ULN. I normally set high(5v) the GPIO, ULN inverts it(0v) and gives it to coil of relay. I connect 2nd coil to 12v so relay works. I have never used 9th pin of ULN. But I have found in few schematics that the designer has connected this pin to 12v via diode, like below:

Now if the main purpose of 9th pin is to connect it to 12v, then why this diode is used in this configuration, as it will block 12v, so 9th pin will not be connected to 12v. Am I misunderstanding something. Please guide.


texts: Shielded cable vs. unshielded in underwater environment

texts:
I know basic electromagnetic theory very well and understand why this works but I'm not sure about one thing regarding usage of coaxial (shielded) cable vs. unshielded (normal conductor) cable when using in underwater data transmission.

Shortly: What is advantage (if at all) of using shielded cable underwater vs. unshielded?

This is for further info and results of my pondering:

In underwater environment is not much if at all EMI that could interfere with the signal in unshielded cable so I think that is ok. Next thing is that does coaxial carry signal (attenuation issue) a lot better than just a unshielded cable? For example does unshielded cable radiate and therefore lose signal power into water more than coaxial that has braid cover? Does that braid help to reflect and "store" signal better in cable?

What's more here is some antenna knowledge also needed because no physical contact will be used.

About my use-case: In practice I'm planning to try littlebit same setup as in the link (http://www.outdoorsmenforum.ca/showthread.php?t=168539). I will have 10 meter cabling and just pondering if I could use underwater unshielded and change it some before air environment to shielded coaxial cable. Signal that is "assisted" through water in cable is Wifi so it's little over 2,4 GHz.


texts: I'm building a 6 channel circuit with the PAM8403 (Filterless 3W Class-D Stereo audio amplifier) and was wondering if I could make things more compact by using less components. Is it possible to combine some capacitors between the amplifiers? Which ones and how would the values change? My power supply is 5V 500mA lithium battery and I'm using a combination of 3x PAM8403. Below is my schematic:


texts: WL1837MOD SDIO Control(or Wifi module in general)

texts:
There are a number of wifi module which are controlled by SDIO(as an option). I am using the WL1837MOD as a specific example but I welcome more general answers.
All the documentation for this chip references the linux drivers which aren't my interest - I am interested in bare-metal and understanding direct control and crafting custom Layer 2 packets.
Where do I find information on low level SDIO control of this device? Or any of these WIFI modules? Pretty much every single one of the WIFI modules I have looked at don't include a data-sheet which actually goes over direct device commands. They simply reference the linux driver.


texts: Purpose of these resistors in the input of in-amp

texts:
there is an instrumentation-amp here.

there is two electrodes which in primary sensor get uv to a few mv ac induced voltage.

and also impedance of the primary sensor is too high and as i know reason of using an in-amp is having a low input bios current (high input impedance in the range of   Gohm) in order to deal high impedance of sensor.

so it seems odd to my why in this example circuit, there is two 270k resistor to the ground? do you have any idea?


texts: 2 dc-dc boost converters to create dual power supply

texts:
I'm doing a project with a Silicon Photo-multiplayer where the breakdown voltage when negatively biased is -25V. I was wondering is there anyway to connect two DC to DC boost converters to give me a virtual ground and positive and negative rails. I was looking at converters such as these.

I have access to a dual power supply but for reasons of portability it is not suitable. Thanks.

A


texts:
I have a simple question.
I'm making an audio amplifier using the circuit given in the LM386 datasheet. According to the sheet, my IC can supply max 1W of output power and recommend load is 4 ohm.
The problem is I have a 4 ohm 10W speaker.
Does the 10W rating of speaker mean that it can take maximum 10W (meaning it will work fine with lower power as well) or that it will try to extract full 10W from the IC and in doing so damage it?


texts: Voltage regulator datasheet does not specify input voltage

texts:
I am working with the TL783.

I have 2 connected in series. The input to the first is 24V. The first configured to output 5.5V (R1 = 240, R2 = 820), the second configured to output 3.3V (R1 = 240, R2 = 402). But after powering it up I am getting 3.03V on the output with no load.

My question is:
Is there a minimum Vi-Vo that is required to allow the regulator to function properly. The datasheet makes reference to Vi-Vo but never specifies a minimum.


texts: toggle 12v as high and 11v as low for arduino

texts:
a little diff question, have googled to get clues but apparently I don't know what exactly to seats for.

Im trying to turn on a led with arduino when a external source triggers 12v. basically that ext source swaps between 12v when active and 11v when inactive. I hoped for that 11v to be 0v so I could use transistor or relay with arduino but unfortunately the low state on external device is 11v.

how can I check with arduino when the ext source is at 11v and how do I tell arduino that this is the low state. I just want to light up a led with arduino whenever the ext source is 12v and kill the led light when it's 11v.
I tried with 2 1M resistors on that 11v but I got it down to 9v and I don't like the idea of chaining resistors.

is there any other possible components that I could use for this purpose ?


texts: What does the minus sign mean in measurements in datasheet footprint drawings?

texts:
I have seen this more than once where there is a measurement such as "4-0.7". In this context, it clearly does not mean 4 to 0.7 mm so what does it mean. See the attached picture:

Link to datasheet: https://www.ckswitches.com/media/2780/pts526.pdf


texts:
I am looking for suggestions to solve a Sim card problem. In my system I have a microcotroller interfaced to an Lte mode and this resides in an outdoor elevated position. I would like to put the Sim card for the modem in a location which is a couple of metres away. The link to that second piece of electronics contains Ethernet lines and potentially 1-2 extra physical cables.

Are there any existing solutions to allow me to have the Sim itself in the second indoor piece of electronics. Is there such a thing as a Sim bus range extender IC? It should translate the Sim card signals to some format which can be transferred over longer distances. On the other end of the link it should do the opposite.

Any ideas guys?

Lte<-->Sim ic<----->Sim ic<--> actual physical Sim


texts: How to properly isolate multiple power supplies

texts:
Say you have a single 110V AC supply and need to use it for a number of devices, each requiring very different characterists. For me personally these are: a direct use of the 110V AC supply for a computer, a very stable yet variable high-voltage supply (up to 2.5kV, low DC current) to power some photo-multiplier tubes, and a 5V DC supply for a DAQ board.

My question is therefore, how should one connect the respective transformers and rectifiers to ensure there was no feeback from one output to another and that the setup is as safe possible?

I guess, in other words, what I'm asking is: what are the necessary considerations and equipment one should employ to safely use a single AC supply for a diverse range of multiple devices?

By "safely" here I mean for the equipment to be placed in a commercial / industrial environment and therefore necessarily complying with 'standard' safety regulations.


texts: How does one calculate change in motor speed due to field weakening?

texts:
In field orientated control (FOC) of a BLDC motor, when applying an \$I_d\$ current, one can effectively change the 'speed constant' of the motor.
I want to be able to calculate specifically how much the motor speed will change if I apply a given \$I_d\$.   What are the equations and constants one could use to calculate this?
Or is there a better forum to ask this question?  Possibly physics?
Is it possible to derive the constant from those typically published in a motor datasheet such as the torque or motor constant and/or inductance?
My guess as to what the equation might look like:
A simple model of an unload motor has back EMF
\$V_{emf}=K_v\;\omega \$
where \$K_v\$ is the speed constant
\$\omega\$ is the rotational velocity in radians per second
For a large (negative) \$I_d\$, one could imagine total cancellation of the field created by the permanent magnets.  This would describe that behavior:
\$V_{emf} = K_{id} (I_{m0} + I_d) * \omega\$
where \$K_{id}\$ is the constant I think I need
\$I_d\$ is the non-torque producing component of current in FOC
\$I_{m0}\$ is the equivalent current that would create the magnetic field resulting from the the permanent magnets.
Since we could replace \$K_{id}\,I_{m0}\;\;  with  \;\; K_v\$:
\$V_{emf}=(K_v + K_{id}\;I_d) * \omega\$
TIA


texts: Going from Transistors to Gates to.....IC's?

texts:
So I am trying to understand I guess what is probably a basic concept of computers.
I was taking a look at this previous question:
From Transistor to Gates

And it's accompanying link:
http://www.cs.bu.edu/~best/courses/modules/Transistors2Gates/

So let me get this straight, we use Transistors to build logic gates correct? Are these all usually Bipolar Junction Transistors? I also see that we also stuff multiple gates into an IC like so:
http://www.kpsec.freeuk.com/components/74series.htm (Btw most of these have like....4-6 logic gates within them....is there such thing as a SINGLE gate you can buy, or would you have to build that single NOT/AND/OR/Whatever gate out of other transistors)

So...like for example, the IC's above....are those built using CMOS technology or TTL? Im a bit confused at what the difference between a TTL built transistor and a CMOS transistor.
Like is this a TTL transistor or a CMOS transistor? (it is a biopolar one correct?):

I know this is a lot of questions, but Im just trying to understand how we go from Transistors to Gates to IC's. I mean.....the IC's I linked above (like the 74 series Logic IC's) are built from gates.....which must be built from transistors (CMOS or TTL?) But how come we never see like SINGLE gates being sold.....and if that's so then why do big transistors such as the one above exist if we can fit 6 logic gates in a small IC.

And do FET's come into play in Logic Gates at all....or not so much.

Whew....

edit: ALSO any books/websites that talk about this is a HUGE help as well.


texts: Why does this give me a red wire in Logisim?

texts: Why does this gives me a red wire? Is it a bug? I'm pretty sure my wirings are correct.


texts:
I am using the STM32F3 Discovery development board which has an STM32F303VCT6 mcu. I am also using the STM32CubeIDE. I am trying to set up the DAC to perform one-off digital to analog conversions when I update the DAC output register, however, I have been unable to get anything other than 0V out of the output pin.
According to the datasheet, the channel 1 DAC output pin is PA4. From my (obviously incorrect) understanding, the only register edits that I had to perform to get the DAC up and running were:
Change the PA4 mode to "Analog": GPIOA -> MODER |= 0x00000300;
Enable the channel 1 DAC: DAC -> CR |= DAC_CR_EN1;
and write the output voltage: DAC -> DHR12R1 = 3000; (3.3V * 3000/4096 = 2.42V output)
All of these are within the main() function. I use the STM32CubeIDE device configuration tool to initialize the clocks. However, When I run the program on the mcu, I don't measure any voltage on pin PA4. What else needs to be configured to get an output voltage?


texts:
I have built the 4 layers of 4x4 LED's and connected them up.

My question is what transistor should I use. I know that only one layer will be on at a time and the max current draw will be 16*20mA = 0.320A

I want to use a NPN as my layers are common cathode so the transistor will connect the layer to ground.

So what specs should I be looking for, I know Ic needs to be greater than 320mA

I am looking at a 2N4401 at the moment. Would this suit? If not why

I will have the Anodes driven by 2 74HC595's. An AVR will be doing all the hard stuff.


texts: Precision voltage reference divider vs. constant current source to drive an RTD sensor

texts:
I need to measure temperature with an RTD between 0-300 C.  I believe I have two options to make this work:

A constant current source feeding the RTD
A precision voltage reference and a resistor forming a voltage divider with the RTD.

It seems like I could use a precision voltage with an op-amp constant current source circuit to complete option 1.  I could also use something like an LT3092.
This approach seems more complicated than option 2, where I could connect an ADR02 5V reference in line with a 5k 0.01% resistor to form a divider with the RTD.
I plan on using a 1k platinum 2 terminal RTD.  Which is the better option, and why?
I've come up with this circuit after reading through the various suggestions.

Does it look like this will work?  Should this reduce noise reasonably well?
The 10V clamp is for protection of the ADC.  I think I also need an inline resistor on the output before the clamp, but not sure how to size it.


texts: Why are two 1 kΩ resistors used for this additive stereo to mono conversion? (For audio inputs to an amplifier)

texts:
I'm trying to convert a stereo signal to a mono signal. It would come from a 3.5 mm stereo audio jack. The jack could be from just a dollar store headphone, where I'd cut out the ear pieces, only leaving the 3.5mm jack and the wire that will be stripped, exposing the left, right, and ground wires.
If I wanted to combine the left and right signals into a mono signal to be fed into an amplifier, I'd use the circuit represented by the following diagram:

The above diagram is the most commonly suggested approach to combine the two signals into single signal.
Notice that before both the left and right signals join into a mono signal, a 1k Ω resistor is used in each of the left and right inputs.
What are the 1k Ω resistors for?


texts: How were the first microprocessors made?

texts:
I have this question. Since microprocessors were first made, the technology has developed very much. I'm asking this because i would like to try to make a simple microprocessor, something like Intel 4004. I know the files for the Intel 4004 are available online.

So, how where the first made microprocessors made, like the Intel 4004, what machines they used to built them, and can an ordinary guy try to make one?


texts: Measurement and characterization of a non-linear capacitance

texts:
Background

I am studying a device that is a non-linear capacitance.  In fact, structurally it is two parallel plates with a charged fluid in between the plates.  The charged species of the fluid can move around within the cell according to the applied voltage and in doing so affect the capacitance of the system.

In other words, the capacitance of the system has some diagnostic ability, in that the capacitance is an indirect measure of the location of charged species within the cell.

Various components of the fluid react to applied electric fields in different time scales and also react differently at different voltages.  In fact the cell looks (electrically) like a capacitor and resistor in parallel with both the capacitor and the resistor being non-linear.

What I am interested in is seeing how the system's capacitance changes with different bias levels, changes in bias (and settling over time), edge slew rates, capacitance over frequency at fixed biases etc.

Calculations show that there should be a null at 1 -> 10 MHz (but it is not known at this point).  Tests show that if you slew the system hard (high \$ \frac{dV}{dt}\$ ) that the instantaneous capacitance is very different than slower edge rates.

All these give interesting insights into the system and also will help verify the physical model of the system.

What I've done

I've built a system that uses \$ I=C\frac{dV}{dt}\$ by stimulating the system with a ramp waveform (constant \$ \frac{dV}{dt}\$ up to a max voltage, constant negative \$\frac{dV}{dt}\$ to a negative voltage, repeat).  Of course you can increase the \$ \frac{dV}{dt}\$ by increasing \$ dV\$ or decreasing \$ dt\$. When I do that the capacitance results vary.

One of the problems with the ramp technique is that the bias swings too much and it's hard to separate out the different time scales and voltage levels.  It gets all mixed together.

I will be renting a LCR meter to characterize the system better to guide building my own probe setup.  I will be performing sweeps of frequency from DC to 2 MHz (limited by eqt.) at various DC biases, amplitudes of probe waveform and also then measuring the R & C with a fixed high frequency as I slew the system with different \$ \frac{dV}{dt}\$ values.

However, I do know that the the lower cost LCR's don't go to a high enough frequency (which is what I'll be renting) and that the more capable LCR's (like a SMU - source measurement unit) are far too expensive.

Other thoughts

Using a fixed ~ 10 MHz oscillator and I/Q demodulator I should be able to generate a Sine and Cosine waveform, and then probe the system with the Sine waveform and demodulate (synchronously) the return signal to get amplitude and phase (and thus derive the complex impedance of the system).  Injecting a signal into the driver should allow for the system to be probed with various (slower) waveforms.

The design challenge

What other techniques or improvements on the above approaches can be used?

C ~ 0.165 uF
variance in capacitance appears to be (from testing) at most +/- 0.1 uF
Voltage range is from -10 V to +10 V
Response times of the system are ~ from 400 ns to 250 ms (for settling)
Inductance is very minor and need not be considered.
Measurement of C and R is important

I'm sure there is a clever solution out there.


texts: How does a "mains priority circuit work"?

texts:
Dometic makes a series of DC refrigerators and one capability is to hook the fridge up to both DC and AC and it uses a "mains priority circuit" to prefer the AC source to the DC source, if both are present. This can be either built into the fridge or come as a separate accessory that they call a mains adapter. Unfortunately, they do not supply detailed schematics for either their fridges or their adapter, so I cannot tell how this circuit works.

How does this type of circuit work?


texts: What is the purpose of this extra PCB pad?

texts:
I am looking to use this crystal in an upcoming design and I am a little bit confused by the datasheet.

The datasheet is available here:
CMR200T Datasheet

This is the image in question:

Question:

What is the purpose of the large pad on the left? Should this be connected to my ground plane? I assume the two pins for the crystal are on the right.

Any help would be appreciated, thanks!


texts: How to route signals across to a breakoff tab?

texts:
I have a small circuit board that will be paneled with a breakoff tab that allows for easy handling during assembly.

Currently we just V-Score the square breakoff tab, but we're trying to find a way to route signals across the divider to a programming header on the tab. Is there a way to create a snap off tab that has about 8 thin signal traces routed across to it?


texts:
I'm making an AC to DC power supply that connects to mains. There's an AC to DC converter, buck converter and a smoothing LDO that outputs a DC controlled with pots.

I'm verifying the supply, and have been trying to get efficiency measurements. Due to limited equipment, I can only measure input Vrms, input Irms, output DC voltage, and output DC current. However, if I just do the Vdc * Idc/(Vrms * Irms) calculation, my effeciency goes above 100% at the higher loads, which is obviosuly wrong.

I know there's apparent vs real power when driving reactive loads with AC, but when I'm measuring the Vrms and Irms that goes into my circuit, that is the real power, is it not? Adding a power factor would mean my circuit becomes even more unphysically efficient.

Is there anything else that I haven't taken into account?


texts:
I have circuit where the input can be 12-48V AC or DC. This is fed to a bridge rectifier.

I plan to put a fuse and got a bit confused, what is the best place to put a fuse?

before the bridge
after the bridge on +ive line?


texts: Current limiter for fixed voltage output

texts:
I need to design a current limiter for a circuit. I haven't started to design it so I cannot show the schematics, but I'll try to explain it.

It consists just in 2 light sensors. These sensors send a value to an MCU. The supply voltage is 12V but is lowered to 5V for the electronics. The important thing is here:

Depending on the values of the sensors (This corresponds to de programmable part of the MCU) I'll need to have a -1.5V, 0V or 1.5V output value. This is, -1.5V and 1.5V will supply the load, and 0V just won't do anything. The maximum Amperes value must be around 200mA or a bit lower.

So, I ask if you know any component-circuit that could suit this requirements.

UPDATE --

According to the comments, I'll update the post with few more data.

The functionality must be like, if sensor1 < sensor2 then output is -15V, and if sensor1 > sensor2 output 1.5V.

But I still have some things in the air that I need to define:

I could use a voltage regulator to low the voltage from 5V to 1.5V, but then, I'll need to define how I generate the negative voltage.
I need to set how the MCU tells if the output is negative or positive
I need to define the current limiter. I found components like this, but this one has reverse-voltage protection so maybe for this purpose is not the best option


texts: How many excess electrons are in a modern SLC flash memory cell?

texts:
A colleague told me that in a modern SLC flash memory cell there are about 400 electrons.
However, I can't find any reference to this.
Flash memory cells can be thought of as little buckets of electrons on the floating gate of a transistor. When they have enough excess electrons, the transistor switches. The gate floats, so the transistors don't drain away.
I'm looking for a reference to how many electrons are in a modern SLC flash memory cell.
EDIT: More references:

bunnie's DRAM FAQ from 1996: http://web.mit.edu/rec/www/dramfaq/DRAMFAQ.html
Wookhyun Kwon's PhD thesis from 2011: https://people.eecs.berkeley.edu/~tking/theses/whkwon.pdf


texts: Why don't piezo buzzers require resistors?

texts:
I'm new to electricity & electronics and am fumbling my way through some Raspberry Pi tutorials. One in particular has caught my interest, which hooks an RPi up to LEDs, pushbuttons and a piezo buzzer.

On page 2 of that PDF, you see the main wiring configuration for the project:

The one thing that caught my attention was that all the LEDs, as well as the pushbutton, all use resistors. The only component that doesn't use a resistor is the buzzer. It seems to just be wired directly to the breadboard/RPi. I'm wondering why?

Is there something special about buzzer that allows them to not draw too much current, and hence prevents them from needing resistors of any kind? Thanks in advance for any clarification!


texts: Is the phantom touch issue present in resistive touch screens?

texts: Do  phantom touches (ghost touches) occur in resistive touch screens, or are they only present in capacitive touch screen displays?


texts: Why the start bit and the stop bit(s) are necessary?

texts:
I am learning about serial communication, and I just can't understand why the start bit and the stop bit(s) are necessary.

I mean say I have two devices connected via serial ports, and the bit 1 is represented by +15V and the bit 0 is represented by -15V.

So for device 1 to send the 4 bits 0110 to device 2, device 1 should send the following voltages: -15V +15V +15V -15V.

What am I missing here, because it seems like it can work without the start bit and the stop bit(s)!


texts: Does Solder selection affect signal quality?

texts: I've been wanting to design some circuits for audio processing. I am curious if solder plays a part in retaining signal quality. Is an exotic material or high end lead based solder worth it? Does it even make a difference? How would I objectively measure this?


texts: What's the most efficient way to derive negative voltage for a bench power supply?

texts:
I’m building a bench power supply based on two LM317 with the following specs:

Input: 127VAC (from mains)
Output: adjustable from 1.25VDC to 15VDC
Current: limit adjustable from 100mA to 1.5A

In the LM317 datasheet from On Semiconductors there is a reference for the “current regulator” circuit that requires a negative voltage (below -1.25V) in the FET (detail #1 in the figure).

Since my power supply is not handling negative voltages I was wondering on using a 24VAC center tapped transformer (127VAC to 12-0-12) ignoring the center tap to power the whole circuit (detail #2 in the figure).

So, my question is how to derive the negative voltage necessary for the FET?

Also, If I decided to use the center tap of the transformer, changing it to a 48VAC one (127VAC to 24-0-24), I’ll use the full rectifier bridge between +24VAC a 0VAC and I’ll try to extract the negative from the -24VAC of the trafo. Since I only need something around -1.5V isn’t that a waste of cooper on the trafo (detail #3 in the figure)?

What is the best approach to power the power supply and also provide the necessary negative voltage for the current regulator circuit?


texts:
Is there a way to make an LC oscillator that works in most circumstances?
Which is able to start up an keeps oscillating for a wide range of inductors?

I'm asking this because I made a LC oscillator which can switch between several capacitor values (with analog switches) for operation in different frequency ranges.

In the simulation (falstad) is working for every possible capacitor combination. But in reality it is only working when both capacitors are enabled.

I don't need a perfect sine wave, but I do need a frequency dependent on the external inductor and adjustable in frequency range.

So I'm looking for an oscillator that starts in most conditions and is able to keep its oscillation going.
Might this be possible by over-sizing the amplifier gain or using other components like opamp's. The frequency will be used to measure the inductance of the external inductor. Or any tips on how to dimension all the parts to make it more stable?

Update:

The transformer is used to provide galvanic isolation from the external inductor which will be placed in the pavement as a vehicle detector


texts: BQ24618 not charging (LiPo Battery managment IC)

texts:
I have been trying to build a LiPo charger based on the IC BQ24618 (Texas Instruments). I already have the PCB design based on the datasheet's schematich and I double checked all the layout recommendations. Nevertheless, the circuit is not working properly.

The specific problem is that the charging MOSFETs seems to fail (somehow). I have the suspicion that they get triggered simultaneously when plugging in the battery. I tried to prevent this with a series RC snubber network but they still failing.

does anyone have experience with this kind of ICs?

EDIT n°1:
I think I made it work. For some reason, the previous high-side MOSFET was bad. So I tried new MOSFETs and I added a slightly bigger gate resistor. This time they managed to charge the battery! but I am not completely sure about the triggering of the gates (regardless the IC did charge the battery):

The yellow curve is the High-side MOSFET's gate voltage. Bootstrap make it 6V above the source voltage, this works great. But the blue curve is the low-side MOSFET's gate voltage. The ugly shape of low-side gate right after the triggering is due to some poor response of my oscilloscope's channel 2 (it would look much better if I measure that gate with channel 1 only) My question now is: Why low-side gate is only triggered for a short while and not along all the low-state of the high-side MOSFET?

I expected a push-pull alternating triggering.

Vin voltage is 18,4V and battery voltage is around 11,8V (not fully charged). Charging current is set to be 1,2Amps.

Best Regards


texts: Generating electricity: Does wire thickness for magenetic induction matter?

texts:
I know that the strength of the magnetic field and the speed by which the conductor passes the magnetic field have an effect on magnetic induction for the voltage output on a generator.
I also know that when conducting electricity from a source to and end user that the longer the distance the thicker the wire needs to be or else eddie currents and resistance will cause the wire to overheat (and thus either melt or cause a fire hazard.)
What I want to know is that when building my DIY generator, do I also need to adjust the wire size to the length of wire? Will using a thicker wire or thinner wire make an impact on efficiency of magnetic induction to produce electricity?
For example, if I want to be sure I have a greater voltage output or whatever (with less resistance or impedance,) do I increase the thickness of the wire or decrease the thickness of the wire?


texts: Max number of logic units / gates per logic-unit-output wire: FPGA

texts:
I couldn't find any info about this. Is there a general rule or does it change for all vendors(altera or xilinx)?

Lets assume I have a flip flop and I want to wire 10 flip-flops to its output. Normally, in my university lab using cheap (1$-2$)  ICs, 10 was max value. Maybe same for FPGA? Or can it carry heavy loads like 2000 flip-flops wired to same output? Is this related to "drive strength" mentioned in verilog/vhdl? They dont mention a constraint.

In future, when I have an FPGA, I will try some floating-point compute accelerator that need to broadcast a variable to all cores.

As "Dave Tweed" commented, it must be "fanout" and he says its an implicit control by design tool. Any more info? How many gates are dedicated if it is implicitly driven?

I'm addressing inner (dynamic) parts of fpga which I will build some cores. Not the outer parts.

Thank you for your time.


texts: Meaning of AC15, DC1, AC1, and DC13 in relay durability curves

texts:
In the datasheet of the relay OMRO G7SA from the durability curve they specify the number of operations as a function of the contact current.
Each curve is for a specific current and voltage. The curves are labeled DC13, AC15, DC1 and AC1. Can anyone tell me the meaning of these labels?

Here's the graph:


texts: Is it possible to wire a DPDT switch so that each position creates an output? (3 outputs)

texts: I am controlling three LEDs, and need to be able to toggle between them individually with a switch. Is this achievable with a DPDT switch? I'm not sure where I can find a switch that has one input and three possible outputs.


texts:
I am trying to determine the correct batteries required for my Arduino (Atmega 328) project. I have components which have both voltage and current ratings. I am adding up all the maximum current specifications from the components to determine the ideal mAH.

I am currently stuck on the Atmega328 chip. I read the datasheet, but I cant seem to find the specific current draw of the chip. My understanding is that the operating voltage is ~5V, and the current draw of the chip would be ~40mA. But if I am using 6 pins (3 analog, 3 digital), assuming they all output 40mA at the same time (which is unlikely as the 3 analog pins take in x,y,z values from an accelerometer), would it be safe to assume the current draw of the chip would be 240 mA? (this sounds wrong)


texts: Killing an Arduino and I2C device with a relay?

texts:
I destroyed* an 5V 16Mhz Arduino Pro Mini and a PCF8574 I2C port extender and I wonder how. Obviously it can be many things (ESD, overvoltage, etc.). But I suspect the problem lies in my driving a 24V relay, so in order to keep this topic narrow, that's going to be my question.

Background: There's a Pro Mini, powered by one of those XL4005 power supply boards you find all over China. Power supply is dialed to 5V. The Pro Mini is connected using I2C to four PCF5874A extender boards. The boards too are powered from the same source.

I hooked it up to a NPN transistor (2N3904) in order to switch a relay (Fujitsu FTR-K1CK024W). The relay coil is 24V, and according to its specs draws 17mA (1440ohm coil).

Is there a way this schematic could destroy the PCF and connected I2C device?

*) Pro Mini is unresponsive, boot loader LED not blinking on start. On a fresh Pro Mini, all extender boards, except the one destroyed are being recognised.


texts: Build remote wireless Wake-Up with Attiny85

texts:
I'm building a ultra-low-power system (mainly composed by an attiny85) that's in sleep state most of the time in order to extend battery life.

I was wondering if there was any hack to wake up the attiny85 with a wireless signal. I know there are several interrupts in the attiny and I started searching a wireless (ultra-low-power absolutely needed) solution that triggered the interrupt and forced the microcontroller to wake-up, but I didn't find anything.

So, finally, my question: are you aware of any solution that could suit? The current needed should be under 100 uA. The least, the best.


texts: Normalized and denormalized floating point numbers

texts:
Regarding the normalized and denormalized representations of binary floating-point numbers (as described in the book by Patterson), I want to know how a denormalized number is really shown.

See the table below which is saying that \$e=0\$, \$f\neq0\$ is a denormalized number.

(Image source)

Consider the number \$1.10\cdot2^0\$. Isn't that normal?


texts: Flyback converter role of diode in parallel to primary windings

texts:
I am trying hard to remember the role of the Diode labeled "D1" and marked with a red circle in the following schematic of the flyback converter below:

Why do we need a diode there?

I know the RLC circuit left to that is for damping the oscillations.


texts: Controlling the base of a N-Channel MOSFET on the high side of a circuit

texts:
With the help of some other members of the site, I was recently able to construct a gate driver circuit for some MOSFETs. I was operating N-channel MOSFETs on the "low side" of a circuit. Meaning that the source was tied to +0 VDC or ground of the circuit. I used an emitter-follower pair constructed from 2N3904 and 2N3906 bipolar junction transistors.

Assuming I want to build a circuit that switches an N-channel MOSFET on the high side of a circuit, I believe I can also use an emitter follower pair to control the gate of the MOSFET. The first obstacle is getting a voltage that is high enough to control the gate. Since the source of the MOSFET is at the supply voltage, I need a voltage that is higher than the supply voltage. For most MOSFETs, a Vgs of +10 VDC is sufficient. There are lots of ways to do this, in my schematic I'll just assume +10 VDC over the supply voltage is available.

The bases of the emitter-follower pair must be driven to voltage that is present on either of the collectors. So that means Vs or Vs + Vgs for an emitter-follower pair controlling a N-channel MOSFET on the high side.

Assume that my supply voltage is something high like + 100 VDC. I'll call this Vp for simplicity.

Any control signal I generate for the MOSFET will be at microcontroller logic and current levels. Either +5 VDC or +0 VDC at no more than 40 mA.  Driving the bases of the emitter-follower pair with this signal would not produce the desired result. So, conversion of this logic level signal is necessary.

The easiest way to do this is to tie the bases of the emitter-follower pair to the gate-drive voltage via resistor. Then, another transistor can be used to pull the bases to low to toggle the state of the gate.

simulate this circuit – Schematic created using CircuitLab

The capacitor C1 is just for filtering

This circuit should result in the Vgs being +10 VDC or 0 VDC no matter the state of Q1 and Q2. However, the bases of Q1 and Q2 could wind up seeing a voltage difference equal to the supply voltage or greater when Q3 is driven into saturation by the clock. In particular Q1 would see a voltage difference of 110 VDC between the base and the collector. At the same time the base-emitter voltage of Q2 would wind up being 110 VDC due to the charge in the gate.

To prevent this I added R4. When the clock is low there is not enough current in R4 to matter. When the clock is high Q3 is saturated. The combination of R2 & R4 now form a voltage divider. This seemed to be the most obvious solution.

Questions

Is the voltage potential between the bases when Q3 is saturated even an issue? The resistor R1 would limit the current and the charge of the gate is not very large.
Does the presence of R4 limit the switching speed of the circuit?
Should I just replace the transistor Q3 with an optocoupler? The optocoupler would be tied to the collector of Q2 and the source of the N-channel MOSFET. What values on the spec sheet do I compare between my MOSFET and the optocoupler to make sure it is not the limiting factor?

Update 1

It seems like this circuit might be safer, but uses an additional PNP transistor. I'm unsure if R3 is necessary, but might reduce the total current needed by the circuit without affecting the performance.

simulate this circuit


texts: Alternator power factor on load and its effect on output power

texts:
Almost all alternator manufacturers test the alternator at 0.8 power factor. But when installed at a site for power generation, the working power factor will be around 0.9 to 0.95, due to the power factor regulators used by the users. The manufacturers provide a data sheet that specifies how much is the maximum current at different power factors. It is observed that the current decreases as power factor improves. If so, will the output power also decrease?
         In case of a 3 phase 750KVA, 415 V,50Hz alternator, rated current is 1043 A at 0.8 pf. At unity pf,  the full load current is 835 A as per the alternator manufacturer. If so, the output power at this condition is 600KVA i.e., 600KW. Is this calculation true??
If true, does it means that we can never load 750 KW load(without over loading) on a 750 KVA DG ???


texts: What type of LCD backlight does this screen have?

texts:
We are in the very early stages of developing a new product and are attempting to identify the type of LCD screen backlight we want to use.  We are using a regular segment LCD glass screen, the type that connects to the PCB via a zebra connector.  We have identified a screen on another product that is absolutely beautiful and we're trying to determine what type it is.    We suspect it's the backlight that is making the different, that is giving in the high quality look.  It appears that the backlight is a solid sheet of light rather than a few single LEDs on the perimeter of the glass.

Here are two example photos and I'm hoping someone here can give some additional information on what kind of screen this is:

Here is another example:

It's the uniform distribution and blue-gray color that we find appealing.  I've read that there are three common backlight technologies used:

LED
EL
CCFL

Of those 3 options I suspect we're wanting a LED backlight.  Furthermore there is edge layout and array layout.  I'm sure there are even more options.  I'm hoping that given the two above images you will be able to determine what backlight technology is used.


texts: BJT NPN transistor as low side switch: Use voltage divider or in series resistor?

texts:
I want to use a PMBT3904,215 transistor as a switch on low side. My question is, which technique is the best and why? To drive the base of the transistor using a voltage divider like so:

simulate this circuit – Schematic created using CircuitLab
Which I think ignores R2 when the base is 5V, since all the current flows from the base to the emitter of the transistor.
Or a resistor in series:

simulate this circuit
I think a voltage divider would be a better idea to avoid my transistor's base "floating," but would there be another reason? After all the signal from the MCU can be 0V and it is not actually floating, so I can "save" some money throwing away that extra resistor (when we are talking about many products being produced.)


texts:
we are trying to built Electronic Locker Which is Controlling by a specific Combinational Password but we have a Problem with
(4x4 Switch Matrix Numbering Order)

In the Circuit Diagram the numbering order is Following ,

By default the The Password is Set (0,1,2,3)

But we have a different Numbering order Switch Matrix

In This Switch Matrix How do i use X OR Y Axes Pins According by Circuit Diagram ?
Means That i want to set 0123 input from Switch Matrix.


texts: Ethernet: Why is the link status "down" when there is a speed mismatch?

texts:
For any networking (ethernet) equipment, the link status (layer 1) is down when there is a speed mismatch between two ethernet interfaces (say: one is 10 Mbit and another is 100 Mbit). Is it impossible that communication happens when the speed is mismatched? If yes, why? Is there any change of signaling when the speed is different?

What are the differences in the networking hardware that prevent a link from being established?

Note: I have never encountered link status=up when the speed is mismatched.


texts: Similar books to "High Speed Digital Design: A Handbook of Black Magic"

texts:
I am really enjoying reading this book, "High Speed Digital Design: A Handbook of Black Magic", in particular the more in-depth material covered than in undergrad courses and the practical approach the author takes instead of being bogged down with endless theory.

I was wondering if there were such similarly good books but in the field of say RF/Microwave circuits or say... analog design?


texts: Relative Humidity Sensor with M8 Connector - Connect straight to Arduino?

texts:
Hello stackexchange friends,

I am looking to purchase this relative humidity/temperature sensor.

http://www.michell.com/us/documents/PCMini52_97176_US_Datasheet_V5-1.pdf

It has 0-5 VDC output option (as well as 0-1 and 0-10), which is perfect for my application because I am using an Arduino Mega to measure my other VDC output sensors.

So, if you look at the datasheet, this sensor has an M8 connector. Would I be able to use an M8 connector with the ends stripped, and then connect those ends to my Arduino?

I understand that the wire sheath protects from EMI and such, so I wouldn't strip it until the very end.

I've never used an M8 connector before, so please let me know if I need to pull out the dunce hat!:)

Thank you for your time.


texts: Voltage Range Mapping/Conversion from [-12V, +12V] to [0V, 4V]

texts:
I have a similar problem as javier acha already described here
Convert from a specifc range to another one which is to map a (AC, 100Hz) voltage range from [-12V, +12V] to [0V, 4V]. I am currently trying to solve it using the OpAmp approach.

This is why I have (a very basic) question concerning Spehro Pefhanys suggested circuit (see link):

What do I actually need R6 and R7 for? Can I also just leave them away?

Thanks Cristobal


texts: How can I detect which arduino board (or which controller) in software?

texts: I have a project that I want to work on either a Uno or a Mega (or even a Due) and it would be nice if I didn't need two versions of the software. For example, on a Mega, to use SoftwareSerial, you have to use different pins than the ones on an Uno. See the docs on Software Serial. Anyway, it would be nice to detect that I'm using an Uno so I can just use pins 4 and 5 for TX/RX and if I'm using a Mega the software will detect and just use pins 10 and 11 (and of course, I'll have to wire it up differently but at least the software will be the same).


texts: Feeding negative voltage to LM338 ADJ pin, what is the voltage?

texts:
In below schematic circled point tied to ground too, so the voltage on that point will be 0V or -1.2V?

The schematic is from LM338 datasheet. as a beginner things like this really confuses me, sorry if it's too basic.


texts: I'm looking at a height constrained application, that's making it difficult to find the power inductors I need.   What's wrong with say using 4 inductors in parallel to get more current?   I know the new total inductance will drop, but what other things will go wrong.  Since I intend to space them closely together will the magnetic fields interfere?   Is this a bad idea?   I've never seen it done before, but then I've never been this space constrained either.   Oh and I'm looking to do 1V 10A from 3.3V, under 1.3mm.


texts:
I am using LPC1769 micro controller and planning to use one of its serial (UART) port for PC communication.

It has 4 UART ports (UART0,1,2 and 3)

For PC communication purpose, can I use all ports or there is limitation on specific port?

How to check which is suitable for PC communication?

Thanks in advance.


texts: Are there any dangers to consider when replacing a permanent AA NiMH battery?

texts:
The battery in my electric razor has failed to charge for several years. It does not turn on unless I leave it plugged in for 20 minutes and it turns off immediately if I unplug it. To save some money, save the world, and have some fun... I decided to take it apart instead of throwing it away.

Inside I found a black NiMH battery without much of a description. Is it safe to replace this with any old NiMH battery with any mAh capacity? The electric razor seems to work fine with the new battery... but charging it might be an issue if it is made specifically for the built in battery. The charger says the output is 15v DC at 420mA. Is there anything I should consider in replacing this battery?

Edit:

I let the bad battery charge for an hour. It got up to 1.46 volts. After half an hour of letting it sit, its now at 1.39 volts.

I measured voltage of the batteries as they were attached and detached from the charger.

The good battery is charged to 1.41 volts and goes to 1.42 volts when attached.

The bad battery is charged at 1.39 volts and goes to 1.4 volts when attached.

I did something dangerous and discharged the bad battery with a paper clip. It's now at 1.21 volts and the voltage went to 1.33 while attached to the charger.

In any case, the voltage is in the right range for the new battery. I'm still not sure if its doing smart charging since it seems logical that the voltage difference will become less as it gets closer to the chargers voltage.

When I disconnect the battery and just measure the voltage across the battery connectors inside the razor, it measures .05 volts (while making a high pitched ringing noise). I'm guessing its doing some sort of smart charging if I haven't broken it yet.


texts: Design help for switching a 5V-supply: FET or BJT, relay or not?

texts:
Background: I've used BJTs before, but never FETs. Been reading the short intro at https://oscarliang.com/how-to-use-mosfet-beginner-tutorial/ and that's about everything I know about FETs (i.e, not a thing really).

My scenario now is that I have a voltage monitor for a 5V-rail. The monitor, well, monitors the rail and if/when it hits 5.5V I get a signal for that, and I will react (cut the supply) upon it.

The "cut the supply" part is where I am now. The easy way - i.e. the way I know how to do - is a BJT controlling a relay that cuts the rail. This works, but my concern is that 1. The BJT is slow on reacting, and 2. The relay is slow on reacting.

Finding a real fast BJT will solve 1, but finding a relay with reaction time not within milliseconds is harder, so 2 is unsolved. Here's where I thought of a FET. A real world scenario is a better incentive for me than just playing with numbers.

I could use a rapid FET + relay, but that will still keep the bottleneck of the responsetime for the relay.

So, here's the idea that just popped my head: what if I crap the "transistor + relay" idea and simply let a power-FET act as a rail-switch? No more than 2A will flow through the rail.

Questions:

Will a single FET be able to make or break the power rail? I'm thinking that a BJT has the Uce_sat drop of about ~0.4V, would a FET have this drop as well? (0.4V-drop from 5V is very bad in this scenario, that's why kept trying with the relay, to avoid the drop)
Similiar to the above question, how would an AC-rail work through a FET? Let's say I want to switch 12VAC, will there be a voltage drop / loss, or will the full 12VAC come out clean?


texts:
Recently I tried making an XBOX controller adapter for my PC as per these instructions. As I have very little electrical knowledge, immediately I ran into problems.

Connected everything as shown and using the code provided, nothing works, it doesn't turn on.

While using my own code, it works (somewhat):

int sync_pin = 2;
int data_pin = 3;
int clock_pin = 4;

int led_cmd[10] = {0,0,1,0,0,0,0,1,0,0};
int anim_cmd[10] = {0,0,1,0,0,0,0,1,0,1};
int sync_cmd[10] = {0,0,0,0,0,0,0,1,0,0};

void setup()
{
    Serial.begin(9600);
    Serial.write("Initializing..");
    Init();
    SendData(anim_cmd, 7000);
}

void loop()
{

}

void SendData(int data[], int delay_ms)
{
    pinMode(data_pin, OUTPUT);
    digitalWrite(data_pin, LOW);

    int prev = 1;

    for (int i = 0; i < 10; i++)
{
        while (prev == digitalRead(clock_pin)) { }

        prev = digitalRead(clock_pin);
        digitalWrite(data_pin, byte(data[i]));

        while (prev == digitalRead(clock_pin)) { }

        prev = digitalRead(clock_pin);
    }

    digitalWrite(data_pin, HIGH);
    pinMode(data_pin, INPUT);
    delay(delay_ms);
}

void Init()
{
    pinMode(data_pin, INPUT);
    pinMode(clock_pin, INPUT);
    digitalWrite(clock_pin, HIGH); // SOMEHOW IT NEVER WORKS WITHOUT THIS LINE!!!

    SendData(led_cmd, 0);
    delay(50);
}

It turns on not every time. It syncs - at times.

The biggest problem is that whenever I touch the RF module or Arduino, or even when I wave my hand near it, the whole thing goes nuts. It starts blinking, turning on or off, and the Arduino restarts.

As I've mentioned, I'm new to electronics, so I've probably connected something wrong. All I did was directly connect the RF module to the pins on the Arduino. No resistors or diodes. Nothing. One thing I could think of was to shield the wires with some foil. :)

So if I didn't yet destroy my equipment, maybe somebody knows what could be done.


texts: What are some good tools which will simplify the process of designing and modeling analog signals? I am currently using Mathematica for modeling signal behavior, but that requires me to define a new model for every new piece of functionality (e.g. a low-pass filter). Are there any tools that could help me out?


texts: Why do fluorescent lamps buzz/hum? I have one above my desk right now and it is constantly humming/buzzing. Does the bulb need to be replaced? Do I have to take the light fixture apart and replace something in it?


texts: Voltage drop over jumper cable near SN74LS173AN

texts:
I have this circuit running on 5v from a USB charger. When I measure the point on the power rail just before it is connected to the row on the breadboard that power the SN74LS173AN I measure a little more than 5v. When I measure at the other end of the jumper cable that is connected to the same row as pin 16 (Vcc) of the IC I measure less than 5v. If I remove the IC there is almost no difference.

The jumper cable is measured to be 0Ω and has 0v difference if fed with 5v and measured directly at both ends without the rest of the circuit.

I do not have a diagram of the circuit and I suspect that it is not necessary
in order the explain the behavior.

Question: why does the power rail and the Vcc rail not show the same voltage?

Screenshot from an ocsilloscope, CH1/yellow is plugged into the power rail, CH2/blue is plugged into Vcc rail of the IC

Photo of both probes plugged into the breadboard

Photo of the complete circuit

Photo of the circuit from another angle

Photo of the circuit from yet another angle


texts:
Can you guys tell me if it's okay to hook up my HV prove to my CRT oscilloscopes? And what about a multimeter, what kind of precautions do I need to take with using that? I read somewhere that it's possible to damage a multimeter this way...
Thanks all.


texts: What is the effect of larger dopant concentrations in a pn-junction diode?

texts:
When we increase the concentration of dopants on both the sides of a pn-junction diode, how do the I-V characteristics change? In particular what is the effect on breakdown voltage and forward knee voltage?

I guess that breakdown occurs earlier and the knee voltage is also reduced.


texts:
I am  trying  to simulate a Dual Active Bridge DC-DC Converter in Matlab / Simulink

So, I need to design a High-frequency Transformer with these characteristics:
Vin = 350 V , Vout = 800 V, Pmax= 10 KW ,f= 250 KHz

In order to have an accurate simulation, I have to know the Winding Resistance as well as the leakage and magnetizing inductance.

My first thought was to choose a commercial High-frequency Transformer and then search in the datasheet in order to find the parameters that I need.
Unfortunately, although that I found a lot of transformers suitable for my application, these parameters were not included in the datasheet.

So is there anybody that may have these parameters for a High-Frequency Transformer with Vin = 350 V , Vout = 800 V, Pmax= 10 KW ,f= 250 KHz)

If no , is there a way to calculate the parameters that I need using the Vin, Vout, Pmax and f?

Thanks in advance.

EDIT: I add a schematic of the Dual Active Bridge Converter


texts: Help using transistor in active mode as a current limiter

texts:
Brief context:
I have a small solar panel, nominal properties are 0.6W, 6V, 100mA.  In given conditions I want to measure the maximum power it can produce - I do not want to do anything with this power, simply measure it (I am actually using it as an estimate for the amount my main panels could be producing).
The idea I have is to vary the load on this small panel and calculate the power at each load setting - again the actual load that produces the maximum power isn't important, simply to be able to change it.

How I thought I could do this:

So I thought that varying Ib would allow me to effectively vary the load on the solar panel.  I can then measure the current flowing by the voltage difference across R1, and the voltage 2xV1 would then allow me to calculate the power. (I realise the current through my potential dividers could be over 1mA each, and I will be increasing those resistor values when I can provide a buffer for the ADC inputs).

To control Ib I have been using the circuit:

Currently I'm using the 50k version of the digital pot.  The spec says the limit is 1mA.  So (3.3 - 0.6) = 2.7V across the digital pot + limiting resistor, and the 2.7k resistor therefore limits the maximum current to 1mA.  If the transistor (currently a 2N2222 - but I'm open to suggestions) has an hfe of ~100 then this would allow for upto 100mA current for the solar panel (this should be fine to get a profile in weak sun conditions, though I will need to increase this limit to get a full load-power profile in strong sun).

However, it's not really behaving as I had hoped / expected.  I suspect due to my failure to quite understand transistors in their active mode.

I would have thought the correct circuit would have pin B of the digital pot tied to pin W.  However when I try this, I simply get a random variation of 0 to 0.03V at V1, and I also get a mix of +ve and -ve currents of the order of ~0.01mA - ie in this configuration I simply get noise surrounding V1 = V2 = 0V - as if the transistor is saturated regardless of the setting of the digital pot and therefore regardless of the current provided to the base of the transistor.

If I tie pin B of the digital pot to ground, so it's now acting more like a potential divider, then I measure (eg, in the weak indirect winter sun at the weekend) 2.5V for V1, 0 mA, up until the digital pot gets to ~1/5 of it's range (ie 3.3 / 5 = 0.66V) at which point V1 drops to 0.  It seems like despite the limited current supplied to Ib at this setting ((3.3 - 0.66) / 42,700 = 0.06mA) the transistor is still simply turning completely on and providing no current limiting function to the solar cell circuit.

Any pointers about how to correct my circuit / understanding would be greatly appreciated!  Alternatively any suggestions for a better (preferably simple) circuit to achieve what I'd like is equally appreciated.

Unfortunately I'm a little limited - I have internet at work only, and daylight to drive the panel at weekends only (an LED headtorch does a poor job!)... so that doesn't help with the trial and error approach I've tried so far!

----------- Later edit (14-12-2015) ---------

Well, this weekend I tried out user44635's suggestion.  Unfortunately the sun did not want to come out to play, so with very gray skies I got this:

which is the sort of thing I'm looking for.  A little surprised at quite how little power was produced but I'm hopeful that this may work - just need to await a sunnier weekend to get some different profiles and see if I get meaningful max power values.

I am also going to get the parts for the circuit suggested by Martin.  Hopefully then I'll have two functioning circuits and I can see which'll work best for me.  Thanks all.


texts:
So I am having trouble comparing values in Verilog for a counter module. I have a 16 bit reg 'd' that I use to assign to a output wire count. In the conditional statements, I have an 16 bit input that I use to compare 'd' to. When I use this input, all works well, but I want to use another reg to compare d to. I think I am having trouble understanding how comparing works in Verilog, can I compare two reg variables?
module counter(input clk,
input [15:0] load,
input reset,
input up_down,
input [15:0] TBPRD_SHDW,
input [15:0] TBPRD,
input [1:0] mode,
output wire [15:0] count,
output reg CTR_eq_PRD,
output CTR_dir,
output reg CTR_eq_MAX,
output reg CTR_eq_ZERO,
output reg global_load);
reg [15:0] d;

reg [15:0] TBPRD_SHDW_reg;
reg [15:0] TBPRD_reg;
initial d = 0;
initial TBPRD_SHDW_reg = TBPRD_SHDW;
initial TBPRD_reg = TBPRD;

assign count = d;
always @(posedge clk or posedge reset) begin
    if(mode == 2'b00) begin
        if(d < TBPRD)
            d <= d + 1'b1;
        else if(d >= TBPRD)
            d <= 0;
    end

This works.
assign count = d;
always @(posedge clk or posedge reset) begin
    if(mode == 2'b00) begin
        if(d < TBPRD_reg)
            d <= d + 1'b1;
        else if(d >= TBPRD_reg)
            d <= 0;
    end

This does not


texts: ATMEGA328P: Can I re-use PB4(MISO) w/ a pull-up resistor w/o interfering w/ SPI?

texts:
I have a Freetronics Eleven with their Ethernet Shield and I would like to add a DS2502-E48  to the circuit to provide the hardware MAC address. This nifty little gem from Maxim uses the Dallas 1-wire bus, and if possible I would like to reuse one of the pins already tied up on the Arduino/Shield rather than reducing the pins available for prototypes.

The SPI pins (11, 12, 13) are already claimed by the shield, but I only need to talk to the DS2502-E48 for a few ms during initialization, so I am wondering if I could use pin 12 (MISO) briefly as the 1-wire data line. With no CS line active for any SPI device, they'll be ignoring the bus, so there shouldn't be any interference there. But the 1-wire spec calls for a pull-up resistor connected to +5V… Would that interfere with SPI activity later?

Alternatively could I get away without the pull-up resistor in this case? I am vague on all theory, but it seems like the pull-up is there so that parasite devices get power. If I use the internal pull-up to power the pin for a few ms, then talk to the DS2502-E48 long enough to get the data I need, can I just let the line revert to it's normal SPI function afterwards?

Note that I don't currently have plans for more 1-wire devices… If I need 1-wire for a prototype I would dedicate a different pin.


texts: How to produce digital pulses using 555 timer IC for stepper motor?

texts:
I need to run bipolar stepper motor with 555 timer IC.

Is there any simple circuit to produce the pulses to rotate the stepper motor clockwise, anti-clockwise with the desired speed?

If there are lots of 555 IC models please mention the type or model number also..

And I also eager to know what is inside the IC  and its workings.

Can I use the above circuit?


texts:
Now I have a homework question that isn't quite clear to me.

"Construct a finite state machine that accepts a base 2 value entered one bit at a time with the most significant bit first. The machine output is 1 if the number entered so far (i.e. current state) reflects 2 mod 3 else the output is 0."

now I would have to build a truth table as well as a logical circuit.

I'm confused at where it says 1 bit at a time with the most significant bit first. So the most significant bit would be 1 in base 2, but would I not have to use more than one bit per cycle to structure this? So would this be an error in the question, or am I missing something.

Thanks in advance


texts: I need help identifying a component and how to check if itd faulty

texts:
I have a power supply that only works when the room is very warm. I narrowed it down to one green component with a 15 on top by heating and cooling. When this component is heated the psu works and when cooled it doesn't.

What is the component and how do I test it to see if its faulty?


texts:
I am really struggling with where to start to analyse this.
Using the Shichman Hodges Model and the small signal equivalent circuit, the voltage gain can be equation can be seen to be vo = -gmvgsr0. But how can two be joined together? I have looked online and can not find anything similar which has explanation.

Thank you for your help.

Here is my attempt at trying to analyse the first circuit:

1: https://i.stack.imgur.com/1yvbl.jpg


texts: How to detect when an antenna is not connected

texts:
I have a GPS receiver module connected to an AVR microcontroller and need to detect if it doesn't have an antenna properly attached. Some time ago I found a reference circuit but now that I need it I couldn't find it in my computer neither with a Google search. Could someone point me to any resources for this, or give the guidelines about the basics?

NB.: it's an active antenna.

Thanks!


texts:
I am trying to connect ATMEGA328p as master to X25020 EEPROM as slave.

here is my code

void spi_master_init()
{
   DDRB = ( (1<<PB2) | (1<<PB3)  | (1<<PB5) );   // /SS as output, MOSI and SCK as output
   SPCR = ( (1<<SPE) | (1<<SPR1) | (1<<MSTR)); //SPI Enable, fosc/64, Master mode
}

void spi_slave_init()
{
   DDRB = 0<<PB4;     //MOSI as input
   SPCR = 1<<SPE ;
}

void SPI_Tx(char data)
{
   SPDR=data;
   while( !(SPSR & (1<<SPIF)) );   //wait until SPIF flag is set, to indicate transmission is complete
}

char SPI_Rx()
{
   char Rx_char;
   while( !(SPSR & (1<<SPIF)) );
     Rx_char= SPDR;

   return Rx_char;
}

void write_to_slave()
{
   PORTB|=1<<PB2;    //take /CS on slave LOW
   SPI_Tx(0x06);  //WREN write enable command
   PORTB&=0<<PB2;    //take /CS on slave HIGH

   PORTB|=1<<PB2;    //take /CS on slave LOW
   SPI_Tx(0x02);  //WRITE instruction
   SPI_Tx(0x20);  //Address to write data to
   SPI_Tx(0x01);  //Data to be written
   PORTB&=0<<PB2;    //take /CS  on slave HIGH
}

char read_from_slave()
{
   char recvd_char;
   PORTB|=1<<PB2;    //take /CS on slave LOW
   SPI_Tx(0x03);  //READ instruction
   SPI_Tx(0x20);  //Address to be read from

   recvd_char = SPI_Rx();
   return recvd_char;
}

int main (void)
{
   DDRC=0xff;   //PORTC as output

   char recvdchar=0;

   spi_master_init();
   spi_slave_init();

   write_to_slave();

   recvdchar=read_from_slave();

   if(recvdchar==0x01)
    PORTC=1<<PC0;
}

The idea is to write 0x01 to address 0x20 on the slave chip, and read it back, if successfully read light up an LED on PC0.

Somehow i cant see why it does not work, I checked connections of slave chip, seem to be fine.

followed datasheet instructions to talk to the slave chip.

http://pdf.datasheetcatalog.com/datasheets/70/290256_DS.pdf