texts: Simple parts to stop "phantom power" from entering circuit

texts:
I have a circuit here which can sometimes program a microcontroller.
I think a big problem here is that "phantom power" is introduced in the circuit because when I'm ready to program it, I plug the unit into the parallel port of my computer and it may give off 3V into the entire circuit which could power both the microcontroller (AT89S52) and the tristate latches (74HC125.)

One idea was to use optoisolators but that means a lot of tiny chips on the board with an extra gate because one setting is meant to raise the reset line and enable the remaining gates to allow programming.

Someone on another forum suggested replacing the part with another IC of almost the same family (74AHCT125 I think) or use one where the input voltage doesn't use VCC as a value. I'm not sure.

I have also thought of making voltage dividers between the input (PC parallel port) and the output (microcontroller programming input pins) so that the voltage is too low to power the ICs but not low enough to make the ICs think the input is always logic 0.

The board itself is powered with a regulated 5.5VDC supply and I apply that power after the board is plugged into the parallel port.

So without making my board look crazy, what would be the best solution? Buy a series of optoisolators (4N25?) and use them, change the IC family, or make voltage dividers?

Another idea that popped into my head now is applying a reverse-based diode between each parallel port connection and the respective IC input and adding a resistor from the anode to the board VCC (+5V.) But 5V wouldn't damage the port would it? The parallel port I'm using is on my laptop. Is my last idea wise?

I want to know the best way to eliminate the phantom power.


texts: Downshifting binary signal from higher to lower voltage using an LM339 comparator

texts:
I'm working on an experiment where I'd like to shift a 24V on/off signal down to 3.5V or 5V (i.e. suitable to use with an Arduino or Raspberry Pi).

For simplicity and safety - I really don't want to fry the equipment I'm working with - I decided to use an comparator rather than some sort of voltage divider. The ship I bought was a TI LM339N (datasheet here: http://www.datasheets360.com/pdf/4687091707087477802), as I have to eventually sense multiple signals.

As an experiment, I'm testing this with a 9V signal downshifting to 3V connected to an LED.

The wiring looks like this:

Pin 1: 1OUT: connected to Resister & LED. Tested separately to make sure it works
Pin 3: Vcc: 3V+
Pin 12: GND: 3V-
Pin 6: 1IN-: 9V-
Pin 7: 1IN+: 9V+

So I'm pretty sure I'm on the right track here. But I'm expecting the LED to be lit up, the logic (in my mind) being that there's a 9V difference between pins 6 & 7, so pin 1 should be and be showing 3V.


texts:
I have a small SOT-23 (3 pins, transistor-like) device that burned out (shorted between 2 pins). I need to identify it so i can replace it.
It belongs to an Asus mainboard and after it burned down the SSD1 interface (on the left) 1 stopped working (no damage to the HDD).
The marking on it seems to be 018 ⊃
Any help would be apreciated.


texts: pci express bifurcation - clock fanout buffer needed to split reference clock?

texts:
I am designing for a motherboard with a single PCIe x16 slot which can be bifurcated into 2 logical x8 slots with jumper settings.  I am designing a board to handle the physical splitting of the port.

The manufacturer of the motherboard has told me I can't just split REFCLK (100Mhz HCSL) to 2 cards, but rather need to use a clock buffer.  This adds a decent amount of extra complexity to my adapter board which would otherwise have no active components on it.  Is this really necessary?

I'm told the original REFCLK is generated by Intel PCH C216 chipset, and the C216 datasheet says it supports multiple PCIe slots.  If I was just designing a motherboard with C216, would I need to add a fanout buffer to support multiple slots?  Wouldn't the C216's clock be able to drive multiple PCIe cards directly?

Are bifurcation adapters like this one completely passive?


texts: Constant or variable current when using a solar charger?

texts:
I am looking at the CN3083 chip to charge a LiPo battery using a small solar panel (5V 0.15W).
To set the charging current, the pin ISET is used with a fixed resistor, to set the constant charge current (max charging current = 600mA).
In which case woud I need a BJT to control the charging current rather than a fixed resistor?
Is there an advantage to have a variable charging current rather than a fixed one?
For example, if my solar panel is outputting 4.2V or 5V, wouldn't it just be better to keep the charging current as high as possible? (600 mA)
Here is the schematic of the IC I am using (CN3038).


texts:
simulate this circuit – Schematic created using CircuitLab

The circuit is simplified like above to solve the thevenin voltage.The solution says that \$V_{AB} = 14 V\$. I couldn't understand that, i used Kirchhoff's Voltage Law using counter clockwise loop: \$V_A + 2V - 16 V = V_B\$ which is \$V_B - V_A = -14 V = V_{AB}\$. Could you tell me what's wrong ?


texts: Finding the capacitor value for power factor correction

texts:
I know the formula of how to find the capacitor value but id need to find the supplies value first and I don't know how to do that. I have the Is=21.60A and phase angle=43.95.
question:
A recent malfunction in a factory has led to a decrease in its power factor, it has dropped to 0.72 when drawing 30A from the supply.


texts: Sensors to detect vehicle height from the side

texts:
I am looking for a way to determine vehicle height measured from the side. The application is for a drive-through ATM, the sensors being mounted inside the ATM enclosure.

Some ATMs have a roof as well, in those cases the solution would be straightforward - ultrasonic sensor (emitter and detector) mounted in the roof, measuring distance to vehicle roof, and with a known distance to ground, the height could be calculated. But I need a solution that works in all cases.

I want to preferably avoid any detectors or emitters outside the ATM enclosure, such as an ultrasonic sensor on a pole sticking out the top of the ATM, or a detector on the far side.

One solution is to have an array of ultrasonic sensors arranged vertically inside the ATM enclosure. This will require experimenting with the spacing between sensors, and knowing the overlap in each sensor's 'field of view'.

The application is outdoors, with large temperature variations, which is why I looked at ultrasonic sensors first. I'd like to know if something else may work better in a cost-effective manner.

If someone one wants to see what a typical drive through ATM looks like:


texts:
Let me start by saying that I am a newbie on this, trying to do some hobby stuff. I am a  software professional trying to interface with hardware (maybe getting into Arduino).

Using this information I was able to build an IR transmitter for an audio device (like my Samsung Galaxy Ace).

Using this information I built a receiver for the computer, captured some input from my TV's remote and built the .wav file to play it in my phone with my transmitter.

It works. Kinda. The range is very short (maybe 3 feet).

Also, I have read somewhere of people adding a resistance because there is a risk of burning the sound card.

I have an old set of computer speakers that have their own amplifier. I am considering connecting them to the output of my phone, and connecting my transmitter to the output of the amplifier. I wouldn't mind if the amplifier died in the experiments, but I am trying to prevent my cell from getting killed in the process.

So the question is, how do I protect my laptop (when recording with the IR receiver) and my cell phone (when playing back with the IR transmitter) from getting burnt?

Thanks.

Note: I know I can just buy the transmitter for the cell phone, but there is no fun on that. This is a hobby project.


texts: multiple arduino communication (1 master, n slaves)

texts:
I would like to develop a master/slave network that consists of:

1 Arduino master that reads sensors and generates velocity ramp profiles based on the sensor signals and then sends those ramps to slaves
3 (or more) Arduino slaves that control the velocity of 12V servo motors following the ramps sent by the master

What is a good communication protocol to achieve this? Serial (SPI)? I2C? Something else? If it is serial, is the new Arduino Leonardo a good choice? What issues should I be considering in selecting a protocol?

I'm imagining something like:

Master:

void loop() {
    update_ramps()
    for(int i=0; i< num_slaves; i++) {
        send_to_all(i, ramps[i]);
    }
}

Slave 1:

const int id = 1;
int recived_id, recived_value;
void loop() {
    read_data();
    if(recived_id == id) {
        do_motor_step(recived_value);
    }
}

And serial communication in which RX/TX from the master is sent to all slaves.

Does this seem like a reasonable solution?


texts: What is the purpose of putting a capacitor on the primary side of a step-down transformer?

texts:
I'm looking at this design

For a split supply. I get that the thermistors are there to limit the inrush current, but I don't understand the purpose of C9 and how its value was chosen.


texts: Will a 2A 12VDC PSU harm a 3A OnHub wifi Access point?

texts:
What's the risk of using PSU that is underpowered?
Is there risk to the device drawing the power?

I have a TPLINK AC1900 Onhub Router. It is missing the PSU (12VDC, 3A)

I have a 12VDC 2A. I think the only risk is that I'll blow the PSU ( I guess it might heat up as well. Perhaps dangerously??).
The PSU is a leftover, so I don't mind the risk of blowing it.

But... perhaps there's some risk to the OnHub as well?
-Clay


texts: Charge protection thermistor proximity to battery

texts:
I am working on designing a low power wireless sensor intended for permanent installation outdoors. Since this device will be used outdoors during the winter months I need to leverage the temperature protection features of my charge controller(TI bq24074). I understand that what really matters is the temperature of the battery, but am having a hard time finding sources for LiPo batteries with built-in NTC thermistors. I assume the next best thing would be an external NTC taped or glued to the side of the battery, but this adds complexity to assembly. Would an SMD thermistor on my charging board be adequate? The board and battery will be in close proximity in a small weather resistant container, so there shouldn't be much variance in temperature, but have yet to see mention of how accurate this temperature measurement has to be.
TL;DR, With the bq24074 and similar battery chargers, is it good enough to measure the temperature with an SMD thermistor if the board and battery are in close proximity?


texts: I made this circuit, and it is working fine. But didn't understood the theory in it. How is it putting a frequency in the coil? It did not match with any of the oscillator circuits. And also it is not working in LTSpice.


texts: I want to set up a system such that wherever a user of VHF presses the PTT button the coordinates from a GPS receiver will transmited to receiver and stored in a computer. Is that possible ?  Where should I look around for something like that?


texts:
Suppose I have the following RF mixer circuit-

How does placing two AC voltages of differing magnitude and frequency directly in contact with one another not create a short circuit condition in a circuit like this?  By short circuit condition, I mean placing two different voltage potentials directly in contact with one another.  I realize this circuit works in reality when built and tested, but this question has always bothered me from a theoretical perspective, even beyond encountering circuits like this (e.g., DC biasing transistors with AC inputs as well).  I know that at least in the case of DC biasing transistors, superposition seems to be the correct answer.  But it still seems intuitively like you are directly combining two different potentials, and therefore creating a short circuit condition.


texts: Ceramic vs. Film Capacitor: Which one is preferred in audio circuits?

texts:
I'm considering building an amplifier following instructions from a MAKE magazine article.

However, as I was reading the circuit schematic, I noticed that the author denotes that the capacitors C101, C104, and C105 are supposed to be "film capacitors."  Is there a reason as to why one would use film instead of ceramic capacitors in this application?  Also, if a website denotes "metal film capacitors", is that the same as a "film capacitor"?

Right now, the only difference I know of in types of capacitors is that electrolytic capacitors have a polarity, while ceramic ones don't.  I was wondering if film vs. ceramic has a similar differentiation.


texts: Guitar pedal works by itself but not in a signal chain

texts:
I just built a clone of an LPB-1 pedal, as my first ever guitar pedal project. It works great between my guitar and amp with no other pedals in the chain. When it is placed in a chain with pedals before or after, though, it doesn't work properly. When it shares a power supply with other pedals, it completely blocks any signal from passing through. With its own power supply, though, it works, but also generates a loud 100hz hum. I don't know too much about electronics but I'm confused as to why the pedal would work by itself, but not in series with other effects. What could be causing this to happen?

I am powering the pedal using a standard 9v power supply. I also added a DPDT footswitch, wired as a true bypass switch connected to the input and output jacks.


texts: Using arduino and transistor for motor control

texts:
I am currently a computer engineering student trying to build a simple circuit to vary voltage by using a transistor and a arudino uno. The motor draws between 12v and 28v with a current of about 280mA. I want to control the voltage using the arduino thru the use of PWM from the arduino.
So in theory a 50% duty cycle of the arduino will give me half the voltage from collector to emitter. I tried using PWM without any capactiors and it ended up making the motor whine and might end up damaging it.

The BJT that I will be using is the TIP120 with a beta of 1000.

Here's the schematic,
I originally tried using a 1nF capacitor across the motor to try to smooth out the voltage during the off cycle of pwm.
But that still made the motor whine so I tested a bunch of different capacitors and about 10uF made it quieter but both the power supply and the motor both whined.

At its current configuration the signal across the motor looks something like this (when using a 50% duty cycle)

How would I be able to get a consistent line at 12v? or any other voltage as set by the duty cycle.

PS the inductor is the motor and the values are not correct. Just used as a reference.


texts: What are these connectors called? (Often found inside of Smartphones)


texts: Suggestions on board designing, ground plane and layers - PCB images

texts:
I'm designing a board (with EAGLE) for my first time and, before posting here, I've read some topics and documents on how to design a board, but I still need help since I'm a beginner.

My board should power and control 9 solenoids (12V, 2A) and a servo.
I will use a board with two layers and 90um.

Two proportional solenoids use PWM at 120Hz.
The oscillator for atmega328p is 16Mhz.

The board is powered by 12VDC with 12VDC, 200Ah AGM battery and I'm using an isolated power supply (+5VDC) to power up the microcontroller (atmega328p). The atmega328p isolation is made by optocouplers which drive the MOSFETs.

This is the schematics made in Eagle where GND5 is the ground for the 12V circuit and GND is the ground for 5V system
(sorry if the schematics is not very clear, EAGLE does not allow me to remove some junction points).

I don't know if I need to create two ground planes (one for GND5 and another one for the GND) or if I only need to create a ground plane for the GND5.
The +5V system powers only the atmega328p and a RC receiver, may be, it does not need a GND plane? So I can only create the GND5 plane?

It is better to put only the ground plane on a layer and all the other connections traces and +12V traces on the other layer?

Could it be a good idea to create a "+12V plane"?
What are your suggestions for the designing of this board?

I'm following these guidelines:

place the decoupling capacitors C22, C23 very close to the microcontroller
place filter capacitors close to the drivers (MCP1406)
place diodes close to the connectors for the solenoids P_OUTx
large traces for +12V (or a +12 plane??)
only GND5 ground plane (??)

[EDIT: The schematics is now correct and clearer]

EDIT1:
These are the board layout, the upper and the bottom layout.
I placed a ground plane for GND5 (the ground for 12V) and a power plane for +12V. Do you think it is better to place also a ground plane for 5V?

EDIT2:

This is the second version of the layout. I separated the 5V circuit from the 12V circuit by using the optoisolator and the isolated power supply as a "moat".
I also placed the ground plane for 12V at the bottom layer and the ground plane for the 5V circuit on the upper layer.
Is it OK, now?

EDIT3

This is the third version of the board layout. I removed the +12V connector which was at the bottom of the board since it wasn't really useful and I tried to separate the two circuits (12V, 5V) in a better way.
I also fixed the errors with some traces which were connected to a wrong source.
Are they Ok, now? Anything to fix?

EDIT4

This is the version #4 for my board layout as suggested by @ThreePhaseEel. Now, I think all the traces are in the correct area and the optocouplers work as a "barrier" between the two circuits. I hope everthing is Ok, now! :)

**

VERSION WITH MOUNTING HOLES

**

EDIT5

This is the version #5 with the diodes flipped and wider traces for the diodes.
I also tried to remove the acute trace for the 12V connector.


texts:
I'm trying to extract data from a 4x14 segment alphanumeric display controlled via 2*595 in series and 4 transistors. Serial data is fed from STM32f103, its firmware should not be changed.
Problem is that Atmega running 16MHz can't cope with 2.2MHz SPI clock from ARM. And it is a 16bit continuous word, Atmega has only 8bit SPDR buffer.

Is there some one-chip solution that would allow me to store data from dataline, and read it on slower clock as master between transitions?
I don't have enough pins to do it in parallel.
Will or-wired (diodes) clock on 595's work?


texts: How to calculate a circuits efficiency with the help of LTspice

texts:
Note that this is not a question for circuit critique (and lots of things could be said about this circuit) but this circuit is only the base for the discussion of further points.

Here it is (an NE555 based PWM driving a buck):
(.asc file can be found here)

I want to measure the efficiency of such converters and similar circuits, along with the contribution of single parts to the dissipated power (in order to pinpoint components that could be optimized to dissipate less).

Now to measure the efficiency, I should simply do \$ \eta=\frac{P_\mathrm{out}}{P_\mathrm{in}}\$. And for DC and simple loads, it is rather easy to calculate the dissipated power as \$P=V_\mathrm{drop}\cdot{}I\$. For a sine wave and ohmic load, its also not hard, you seem to either do \$P=rms(V_\mathrm{drop})\cdot{}rms(I)\$ or when you have a tool like LTspice you can make it plot \$V_\mathrm{drop}\cdot{}I\$ for sufficiently small timesteps and then just take the average of it.

But what do we do for more complex/unusual waveforms? Take for example LTspices plot of \$V_\mathrm{drop}\cdot{}I\$ for L1:

Although not surprising from the fact that the voltage drop reverses over the inductance, the plotted negative power dissipation confuses me. So this leads me to the first real question:

  What does this negative Power mean, intuitively, and how does it relate to the power dissipated at heat (i.e. how to use it to calculate that power)?

Now this circuit has a bit ripple at the load (diode+resistor together) but that shouldn't hurt calculation of \$P_\mathrm{out}\$. But now lets look at the plot of what I want to calculate \$P_\mathrm{in}\$ from:

This is not anywhere near a sine curve, so my question for this is:

  Is taking the average of this (and similar) plot (assuming sufficiently small step sizes) still a good approximation of the total disspiated energy (heat)?

For completeness, here is the output of the .measure statements:

avwin: AVG(-v(in)*i(b1))=1.74212 FROM 0.002 TO 0.009
avx=0.007 FROM 0.002 TO 0.009
avwout: AVG(v(inductor_diode,diode_resistor)*i(d1)+v(diode_resistor)*i(r2))=1.27344 FROM 0.002 TO 0.009
avdloss: AVG( v(from_mosfet)*i(d4))=-0.0478017 FROM 0.002 TO 0.009
avlloss: AVG(v(from_mosfet,inductor_diode)*i(l1))=0.0946656 FROM 0.002 TO 0.009
avlloss_a: AVG(abs(v(from_mosfet,inductor_diode)*i(l1)))=1.14626 FROM 0.002 TO 0.009
avcloss: AVG(v(inductor_diode)*i(c1))=0.00312184 FROM 0.002 TO 0.009
aveff: (avwout/avwin)*100=73.0969
xloss: avwin - avdloss - avlloss - avcloss - avwout=0.418698

This would indicate an efficiency of ~73% which does seem reasonable, but looking at the individual losses I have no idea since all have plots with negative values, and as per above question, I am confused as to how to interpret them or use them to calculate heat dissipated.


texts:
Im using a transformerless capacitive power supply with this simple circuit:

C1: 3.3uF 400V
R1: 480K
D1-D4: 1N4007
Z1: 10V 1W
C2: 470uF

But it burned some my microcontrollers sometimes when I plug it to AC source ( I saw a small spark at plugging zone ).
I've used my scope to check its voltage at plugging time and I saw some high voltages (about 40V) on positive output with about 10us duration.
Also I saw negative voltage (about -30V) on it at plugging time.
I used a voltage regulator (AMS1117) and measured the output voltage of it , but the noises were still appear on scope.
But why ? How voltage can be negative after the rectifire diodes? Also I used 100nf ceramic cap but nothing changed . Why capacitors and zener would not affect these noises?
How can I protect my microcontrollers against this plugging noise ?


texts: Reduce current flowing into a switch by using XL6009 enable pin

texts:
I have an XL6009 powered circuit that draws about 2 Amps at steady state. Actually, the ON/OFF switch is connected near the source input and before the DC/DC converter but, in this way and by design, the 2 Amps current must flow through the switch.

I would like, instead, to use the ENABLE pin on the XL6009. Connecting the switch to the EN pin would drive the circuit ON/OFF without requiring the same amount of current flow through it.

The problem is that I've noticed that EN pin left floating or driven to Vdd enables the circuit and to power off it should be driven to ground.

How, using simple components (like a resistor) use a simple ON/OFF switch to drive the EN pin on the XL6009?

simulate this circuit – Schematic created using CircuitLab

Thanks in advance for all your suggestions.


texts: How safe is parallel wiring two ATX PSUs, if they weren't explicitly sold as dual PSUs?

texts:
Pages such as this discuss wiring ATX PSUs in parallel, in what seems to be a sensible manner, with links to various projects showing details.

Companies with a decent reputation for ATX PSUs, sell cables specifically for that purpose, and many others sell them on Amazon.

I'm interested in running two PSUs in parallel but would like to know how safe it is, if done right.

I'm running a large (20+) HDD array on an underpowered but extremely high quality 750W PSU. I need to upgrade the PSU to ideally get around 5v @ 35-40A and 12v @ 115-130A. Dual PSU with as second 750W - 850W PSU seems to have a lot of advantages over replacing with a 1600W or higher PSU, and perhaps no disadvantages. Both would be same brand, possibly same model, single rail, and very high quality build+output.

(OP updated: image added as recommended by comments/replies)

Electrically it looks simple enough. Give them both the same shared "soft start/stop" feed, and crosswire 0v to give them a common ground plane. I'd have a stability advantage over the mining users in that I don't want extra power for PCIe graphics cards, my need is extra 5v/12v power with a common ground plane just for external HDDs. So I'd have one PSU handling the baseboard and 1/3 of the HDDs, and the other PSU handling the other 2/3 HDDs.

Parallel PSU also beats a larger monolithic PSU in other ways that benefit me: I need disproportionate 5v, more than even a 1600W PSU would provide (5v @ up to 36A needed for HDDs but not used by PCIe/graphics cards which large PSUs target, so max on even a 1600W PSU is about 24-30A while dual gets me 48A). It doubles my HDD connector sockets so I can reduce current/heating in any given string (5-6 HDD connections per PSU, so only half the number of HDDs on each). It also spreads heat dispersal between them. I don't have resources for a formal dual-PSU case of the kind I'd need, so it's either dual high quality standalone PSU or large PSU. So I'd like to do it if I can.

In theory I'm guessing there shouldn't be much scope for problems due to current loops.  Also, unlike wiring in series (see this question), their 0v planes would be connected so even if both PSUs were earthed, I guess the earth would be in common for both anyway, which might help avoid earth loop issues.

In theory, provided it works electrically, I use very high quality PSUs from the same brand/model range (which I would), and I double check the crosswiring and junctions on any crosswiring cable before using it, dual PSU is a far more efficient solution, gives several electrical benefits, and costs 1/4 the price of a monolithic 1600W PSU while guaranteeing that both 5v and 12v peak current capability are met.

But electrically, the PSUs weren't explicitly intended for dual use so I don't know. How risky is it? How safe if done right?

Is this pretty much how any dual PSU works?

Am I missing any other important safety/setup issues that I have to know/do, to dual PSU safely and not imperil my equipment?


texts:
So I designed this Half-Bridge Mosfet Driver for 48V.
Since I'm pretty new to this type of circuit I would like to ask if there are going to be any problems with this circuit. (eg. speed, power loss, voltage limit)
The target frequency is going to be at about 60KHz, PWM modulated and 2 of those circuits are going to be configured as a H-Bridge, driving a resistive load.

The 2 Transistors marked with ULN are going to be 2 ULN2803A stages.
CLK is the signal input.

If you see any problems, please let me know.
Thanks.


texts: Unused GPIO pins shall be configured as pull up or pull down

texts:
I have recently started working on Embedded Systems. I am configuring GPIO pins for MCU. But I'm bit confuzed whether I should configure them pull up or pull down. Is there any configuration rule to be followed to minimize current consumption or these configurations are MCU Specific.
Pls note that I have left unused pins as Input GPIOs.
I am currently using ARM Coprtex M0+ MCU


texts: Altium: How to hide silkscreen designator for specific components

texts: In Altium, how can I hide the component designator for a specific component, without hiding the designators for all components?


texts: Standards used for indoor telephone cabling?

texts:
Which standards/specifications (IEC, ANSI, etc.) are normally used for PE insulated indoor telephone cables?

I've scoured the internet looking for the right standard, but can only find ones applicable to PE OUTDOOR (IEC/BS 60708) and PVC INDOOR insulated standards. Is PE not a commonly-used insulating material for indoor telephone cables?

I've also noticed that most telephone cables use the British Telecom CW standards, but I haven't found anywhere online where the standards can be purchased. Any help with this would be greatly appreciated


texts: Is it safe to use a bus buffer as level shifter?

texts:
I am currently using SN74ABT5402ADW as a buffer and level shifter for my ADC, however, the datasheet does not explicitly say that it can be used as a level shifter. I provide it with 5V power, but the input signals (out of the ADC) are 3.3V. The performance is bad: when I scope the signal on the output pins, the signal is not even close to look like binary HI/LOW. It does have rise/fall edges, but HI/LOW values seem to float, especially at xxx1111 to xx10000 transitions. I suspect that it does not convert the signal from 3.3V to 5V properly. Could anyone tell me if I am misusing it as described, and what can I do to make it work?

I use BNC2110 and CB-68LP connector blocks that connect to three PF50 connectors shown on the schematic. The bloks, in turn, are connected to NI PCI6259.

Measured signal at the input (yellow) and the output (blue) of '5402A when it is not connected to the NI connector blocks.

Measured signal at the input (yellow) and the output (blue) of '5402Awhen it is connected to the NI connector blocks via 8" unshielded wires.

Power at the power pin of the '5402A:

All ground pins on both NI connector blocks are interconnected internally.

Cable 1-3: Digital lines
Cable 4: trigger signal and GND wire
Cable 5: GND wire


texts: Controlling MG946R servo with 3.3v PWM signal

texts:
For a project we're building a robot arm, using three MG946R servos and one MG90S servo. Now I was wondering how to control those since I've been tasked with acquiring the hardware.
I think the MG90S takes a 3.3v PWM signal since I've worked with its 'brother', the SG90, before. Can we use a 3.3v PWM signal for the MG946R servos too? Seeing that they use 6V for power.
Also, what micro controller would you recommend? I assume it would need four pins with PWM to control the four servos
Thanks for any help!


texts:
I have a part in Eagle that has two pads for VDD (pad 1 and 2) and two pads for VBAT (pads 9 and 10). The pads must be tied together on the PCB so I have designated a single pin for each pair of pads.

With the pins set to show both the pad and pin names, I expect to see VDD as a pin name and 1*2 for its pad name as well as VBAT as a pin name and 9*10 for its pad name. This works fine for VDD but not for VBAT. For some reason, VBAT is showing 9*2 as if it were connected to pad 9 and 2; however, that is not the case.

I am relatively new to Eagle so I'm sure its a simple mistake but I can't seem to figure it out. I have attached screenshot snippets of the relevant information.


texts: Why is there a voltage drop in a twisted pair wires of an UTP cat.5 cable?

texts: I put 12V DC through a pair of twisted wires of a 50 meters (~160 feet) UTP cat.5 cable and noticed that there was a voltage drop at the other end of the cable. It only had 5V. If I'm feeding the same 12V through two wires that aren't paired (twisted), I don't get that voltage drop. What's the phenomenon that causes the voltage drop?


texts:
I'm having some trouble getting any reading from an I2C ITG-3200 Gyroscope breakout I'm using from Sparkfun. Here is the product: https://www.sparkfun.com/products/9801

I have a feeling this might be to do with my addresses, as I can't get my head around how the hex address should be written, and how I should be formatting my addresses. I've read the datasheet and sparkfun's tutorials. I am using an Electric Imp, with code written in Squirrel.

I have just been trying to get raw data so far, but can't even read from the WHO_AM_I register without a null: 0x0x0 error. Has anyone else worked with this module, and would you be able to provide me with any help at all?

Thanks a lot!

EDIT:

Currently I'm using this code:

local gyroAddress = (0x69<<1);

hardware.i2c12.configure(CLOCK_SPEED_400_KHZ);
imp.configure("Gyroscope", [], []);

function startTest() {
    server.log("WHO_AM_I ID: " + hardware.i2c12.read(gyroAddress, "0x1D", 64));
    imp.wakeup(3, startTest);
}

hardware.i2c12.write(gyroAddress, "\x3E\x80");
hardware.i2c12.write(gyroAddress, "\x16\x18");
hardware.i2c12.write(gyroAddress, "\x17\x05");
server.log("Written to Register");
imp.wakeup(2, startTest);

All this is doing is writing a byte to the device and changing a few parameters in the register, then calls a function which reads from the Gyro_X data and prints to the console every 3 seconds. So far, the best I have achieved is the ouput below. The jumbled characters appear when I tilt the device, so I know it's working in some way, but it appears to be acting strangely.

5/12/2013 8:18:53 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:18:56 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:18:59 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:19:02 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:19:06 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:19:09 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:19:12 PM: WHO_AM_I ID: ���P��O����� (8��wD^�����D���R�R�r��Fͼ�
5/12/2013 8:19:15 PM: WHO_AM_I ID: :ؑĀ%%U\��~�,^��d���������5T��l�͆V���B��Df��
5/12/2013 8:19:18 PM: WHO_AM_I ID: u���H�@x�� �� �FQCȄ#g7�ޜ�����́�/�R΋��8��F�Nx
5/12/2013 8:19:22 PM: WHO_AM_I ID: �^��"&���C�"O_��sS �����F`c{�v^���gCA`b�w}M�,����
5/12/2013 8:19:25 PM: WHO_AM_I ID: ��F! ��b/mlk:�!�ư���-J���� (8��� wD^�
5/12/2013 8:19:28 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:19:31 PM: WHO_AM_I ID: (null : 0x0x0)
5/12/2013 8:19:34 PM: WHO_AM_I ID: (null : 0x0x0)


texts: Harmonic voltage source, how to calculate it

texts:
I have this scheme.

I have all the parameters:
L1=110 uH

C1=160 nF

C2=5 nF

Rt=1.2 kΩ

ω1=45290 rad/s

ω2=162089 rad/s

ω3=238366 rad/s

ω4=276982 rad/s

But I dont understand how to calculate the voltage source. I have this formula for it:

So my job is to calculate \$ i_{2}^1 \$ in harmonic \$w_{1}\$, \$ i_{2}^2 \$ in harmonic \$w_{2}\$,
\$ i_{2}^3 \$ in harmonic \$w_{3}\$, \$ i_{2}^4 \$ in harmonic \$w_{4}\$.

QUESTION:
I don't get how to calculate this voltage source. I'm not sure how to replace sin(wt), what's the the time(t)?


texts: What is the reason/benefit of using vector potential of magnetic fields?

texts:
Especially in antenna theory books, they employ magnetic vector potential.
Why is the vector potential concept used?

For example the  magnetic vector potential is written as:

And the magnetic field in terms of this potential:

But what is the motivation or need to introduce the vector potential concept here? And is the magnetic vector potential derived from Maxwell equations?


texts: Best practice for paralleled four leg shunt resistors connection to a shunt amp, and best placement

texts:
I am using three WSK12161L000FEB paralleled together on a four layer PCB for a three phase motor controller (9 shunts total in design, 3 for each phase)

From my understanding, a kelvin connection to just one of the three WSK12161L000FEB shunt's measurement leads is the best practice. Is this accurate, or should I make a kelvin connection to all three shunt measurement leads? It feels like a waste of a high quality shunt to just use one shunt for measurement when they all have measurement leads. My thought is it would be more accurate to use all leads.

I am using an INA240-Q1. one of the features it offers is PWM rejection. Is it best practice to place this amp next to the shunts, or place the amp near the microcontroller reading the signal? Placement next to shunts is also near the MOSFETs, a noisy spot, but sending the 20x amplified signal past the MOSFETs to controller (I think this is best). Placement near microcontroller would make the two shunt leads extremely long, which will likely pick up more noise going past MOSFETs considering this signal is not amplified. In the datasheet it does not mention which practice is best but shows the INA240 next to the shunts.

WSK1216 datasheet
INA240-Q1 datasheet
Edit: added reference PCB, shunts are far from amps. Note this device was destroyed from water damage, not poor PCB layout


texts:
We have a new LED roof-lamp at our home and I ordered a matching dimmer-switch to replace one switch in a 3-way-switching. To have matching wall-elements, I also ordered a replacement for a normal toggle-switch (for another roof-lamp) and a normal power-outlet in the same "wall-group".

I was able to replace the topmost toggle-switch without any problems, but when I wanted to replace the 3-way-switching switch in the middle with the dimmer, I got stuck because there were four cables instead of three as indicated in the dimmer instructions circuit-diagram. I know when to better stop, so I will not temper around with the installation and let the rest be a job for the electrician.

However, since I turnred off electricity for the room circuit, I wanted to at least connect the old switches again and have everything work as usual in the meantime. I failed (and I honestly don't know where), since the GFCI kicked in.

My question now is: Until an electrician installes everyhing correctly it might take some days or weeks - is it okay to have all cables loose and unconnected (with the ends protected against touching, off course) in the meantime? Or is there any danger from NOT connecting cables? I would like to use the other wall-outlets and lights in the room that are not directly related to this wall-group.

Thanks in advance for your support!


texts: Would a heating element have a very high resistance, or a very low resistance? (All comments in this post are based around the fact that the voltage is the same for each situation) I would have thought that a higher resistance would have resulted in more heat loss, but I've been taught that the higer the current, the more energy is lost to heat. Therefore, a lower resistance would release more heat.


texts: Via tenting when solder masking an entire layer on Altium?

texts:
I am trying to remove most of the solder mask on my bottom layer so that I can mount a large heat sink on the PCB. I don't have any traces or any components. So what I did was I did a polygon pour on the entire layer and changed the layer to bottom solder and have it as a GND net.

However, for some reason Altium will not tent VIAs that are not GND that are in the polygon pour.

As you can see all VIAS don't have tents any more. So when I install my heatsink  I will short.

I tried to do a solid region but that didn't work either. I even tried to play around with the keepout but had no luck.

What is also weird is that when I check the box to remove dead copper on the polygon I created for the solder mask, it removes all of the solder mask. It is like the solder mask is not connected to my GND. Which doesn't make sense to me.

I don't want to manually route the solder mask layer because this is a pretty big board and I am just showing a subset of it.

Any ideas? Thanks


texts:
I need the following simple device (to make or to find):

It will have bluetooth connectivity, one pushbutton and, obviously, batteries.

What it has to do is to send a message over bluetooth (the target will be a PC or a mobile phone) when the button is pressed.

Are you guys aware of a similar device? If not, can you recommend me the right components to build in a simplest possible way?


texts: How many LUTs are needed to implement a CPU?

texts:
I am looking to start my first FPGA based project, but as I am a complete beginner, I have very little idea how big an FPGA I need to implement my idea.

My project will be something similar to a CPU, so in order to get a sense of how big an FPGA I will need here is my question:

How many LUTs are typically required to implement a simple CPU? Is it hundreds, thousands, tens of thousands?  I have seen a few open CPU cores online (e.g. The J1 and Opencores), but none of them seem to mention how many LUTs they might need.

All I need is a very rough idea of how many LUTs a CPU might need, or one or two examples to help me decide if this is worth further investigation.

The FPGA I have in mind is the Lattice Crosslink which contains 5936 LUTs. Would it be possible to implement any kind of CPU on that?


texts: Should a ferrite bead be placed close to the MCU or close to the power supply?

texts:
I am trying to design a PCB based around the STM32F446RE microcontroller. I looked at the schematic provided by ST for their Nucleo-64 board, and physical placement of the ferrite bead on the board.
The ferrite bead they use is a Taitec FCM1608KF-601T05. Which is placed on the VDDA line (pin 13). They do not have a ferrite bead anywhere else.

I have seen a few designs done by others, and they seem to place the ferrite bead at the input side of the their 5V linear regulator.
In other words, ST seems to concerned primarily with noise coupling on to analogue measurements and have placed the bead after the 3.3V regulator to the MCU.
Other designs seem to be concerned about noise getting into the overall circuit.

What are the pros and cons of each approach?
I am considering putting my ferrite bead at the input stage to the 5V regulator, with the thinking I can filter out at everything right at the beginning - but get a feeling that this may introduce other issues.

The ferrite bead I would be using is Würth Elektronik 74279265 which has better DC resistance and impedance characteristics over a wider frequency range.


texts: Need help identifying cable in old boombox

texts:
I'm planning to replace the radio part of my old boombox with a 3.5mm jack so I can connect my phone. The cable that leads from the main pcb to the radio pcb has four lines, labeled L, G, R and +B. I assume L is left, G is ground and r is right. But what is +B? Do I need it for the headphone jack?

Thanks.

Edit: Here's a picture


texts: Wiring a simple 24v DC light on an output terminal on a PLC

texts:
I am using a Micrologix 1100, part number 1763-L16BWA. I have been able to get the input side working, but can’t seem to figure out the wiring for the output side. I also have an 1762-IQ8OW6 extension.
I have some simple lights that “light up” when I connect them to the DC+ and DC- terminals so I know the lights work.
I have created a simple ladder program that has one rung for each output on the PLC and each output on the 1762-IQ8OW6 extension. Each rung has a separate bit that turns on or off that output:

All the outputs on the PLC and the extension are activated:

However, no matter how I have tried to wire it, I can’t get the light to turn on using the output terminals. I have connected the VAC/VDC terminal in the output to DC+ and then connected one end of the light to the other output terminal and the other end of the light to DC-. I have also tried the reverse.
I have tried wiring all 12 of the output terminals.
I have watched lots of videos, but they are all doing more complex things. It seems like everyone knows how to do this but me.  How do I wire a 24v DC light to an output terminal on the PLC?
Please help.
Thanks.
[EDIT]

AC Input connect to 110V.

D+ and DC- power from PLC.  DC- is connected to one end of the light.  Second end of the light is free so I can connect to various terminals.  Two wires out of DC+ - both connect to the 1762-IQ8OW6 extension VAC/VDC terminals.

There are two VAC/VDC terminals on the 1762-IQ8OW6 extension.  Each has 3 separate output terminals (0, 2 and 4) and (1, 3 and 5).

Touching the free end of the light to either VAC/VDC terminal in the 1762-IQ8OW6 extension illuminates the light.

Wiring Diagram.


texts:
This is what I am talking about (click to enlarge):

It is from an old (1990s) telephone system. There were multiple lines, some digital, some analogue, and in the output stage these modules (double sided) were standing (in a slit) on the main PCB and soldered to it (with the pins you can see).

There were a couple of other sub-PCBs on this thing, but only those were of this ceramic type. So the question is: Why are those printed on ceramic?

It seems that the traces will have higher resistance and the overall building cost for unusual PCBs is often higher than for established processes. On the other hand, this looks like a multilayer, and the other side is a multilayer too, which made me think if this is cheaper than a "real" four-layer PCB (since it has no vias). But then some of the modules (unfortunately I cannot remember anymore which of those was for digital and which for analogue lines) only had one side populated.


texts: How were the first microprocessors programmed?

texts:
This has just dawned on me that if you're writing an operating system then what are you writing it on? I ask this as I am reading a microprocessor fundamentals book from 1980 and this question popped in to my head:

How was the first microprocessor chip programmed?

The answer may be obvious but its bugging me.


texts: Suitable wiring for very low current mains equipment

texts:
I'm building an interactive portrait gallery with seventy portraits, each back-illuminated by an LED lamp. The lamps draw less than 30 mA at 230 Vac, and each is switched using a small optocoupler/phototriac, under microcontroller, er, control.

Given the very low current draw of the lamps, standard 3-core mains cable seems to be considerable overkill.  (All of the wiring will be hidden within the gallery structure, out of the way of prying fingers; we have a mains bus, from which I can tap the connections for each lamp.)

Would a three-strand section of ribbon cable be up to the job?  Some specs I've unearthed are rated to 300 Vrms (and up to 1 A), which would seem to be suitable.  But what consideration would I have to give to voltage spikes?

I want to build something safe, but a lighter cable would make construction much simpler.


texts: DC Power Line Communication (PLC) low pass filters

texts:
I've seen many times that a low pass filter needs to be implemented before a switching power supply in DC power line communication transceiver boards.

Why is that? I assume that the switching power supply absorbs the modulated signal, right? Would it be the same if it was a linear power supply?

Also, do all the devices that are connected to the same DC bus need to have a low pass filter?
I uploaded a schematic. Would DEVICE1 and DEVICE2 need a low pass filter as the transceivers PLC1 and PLC2 do?

PLC1 and PLC2 are two devices that contain power line communication transceivers and they have a low pass filter. Device1 and Device2 are devices that might exist on the bus, for example head lights on a car, the audio system etc...

simulate this circuit – Schematic created using CircuitLab


texts: I2C reading sequence head-scratching diagram

texts:
I am using MPU6500 accelerometer in I2C mode. Datasheet explains the reading sequence on page 33.

It may seem easy for someone who is an expert but it is my first time using the I2C interfaced device. I have written a function but It doesn't read register values like WHO_AM_I etc.
    uint8_t Accelerometer_Read(uint8_t reg)
{
    uint8_t read;

    HAL_I2C_Master_Transmit(accelerometerhandle, 0x68|0x00, &reg, 1, 100);
    HAL_I2C_Master_Receive(accelerometerhandle, 0x68|0x01, &read, 1, 100);

    return read;
}

This is the function that I wrote, I have connected AD0 to GND so that I2C address is 0x68. How can I implement this sequence?


texts: How to determine the nominal current of an LED?

texts:
I salvaged the LED disk from a defunct LED light bulb. (The problem was an arced transformer, the LEDs are intact.) It has several unmarked white SMD LEDs soldered on it: 5 lines parallel, with 3 LEDs in series on each line.

I want to use this disk in a strobe. My aim is to get the maximum brightness out of it without damaging the LEDs. Is there any way I can determine (vaguely) its nominal current rating, rather than guessing it?


texts: What's a good set of PWM values to make sine waves for a 3 phase motor?

texts:
I'm building a synchronous rotating spark gap for a tesla coil. I have a working mcu (Kinetis K64F) driving a 230volt inverter board and it spins a 3 phase synchronous motor. The motor is a synchronous type itself, and the power I give to it must be as well: synchronized to the ac line. That's why I chose to build my own hardware. I can compare the performance of my running drive with a commercial one and I see that mine is underpowering the motor.

The store bought 3-phase inverter kicks the motor right up to speed, into a sync that slowly shifts to one side with no way to control it. Whereas my drive takes more than a minute of wobbling sound to come up to speed and then it's dead steady with the line frequency. I can move it to either side one degree at a time. That's what I need.

So I think it must be the data I'm sending to the 6 pwm channels. My naive solution for this has been to fill an array with sine values at startup. I make 2 positive half cycles like this:

int angle;
   double param;
   extern double hold[370];

 for (angle=0; angle<=179; angle++) {
   param  = 255 * sin (angle*PI/180);
   hold[angle] = param;      // fill first half of the array
   hold[angle+180] = param;  // fill second half with duplicate data
 }

Then in a periodic interrupt I read out that array of sine values like this:

    if (angle1 < 180) { PWM1_SetRatio8(hold[angle1]); }
    else if (angle1 == 180) { PWM1_SetRatio8(0); }
    else if (angle1 > 180) { PWM2_SetRatio8(hold[angle1]); }
    if (angle1 >= 360) { angle1 = 0; PWM2_SetRatio8(0); }

    if (angle2 < 180) { PWM3_SetRatio8(hold[angle2]); }
    else if (angle2 == 180) { PWM3_SetRatio8(0); }
    else if (angle2 > 180) { PWM4_SetRatio8(hold[angle2]); }
    if (angle2 >= 360) { angle2 = 0; PWM4_SetRatio8(0); }

and so on for angle3, all of which are 120 degrees apart from each other. I see now that 180 per half cycle is too many so I divided it down to as low as 20 but with no change in the motor output.

I lock my 360 value internal array with a precision zero crossing pulse from the outside to keep them in sync.

So I read up about Magic Sine Waves and that sounds good. But I would have to rewrite a lot of code to use it, and I need to cover speeds from 58 to 62Hz which is what the power companies present me with. If I filled an array of Magic Sine values I think I would get crossover distortion when I shifted to the different line frequencies.

Then I read about triangle wave modulating the sine values and adding in some extra 3rd harmonic to get more power. That sounds like the way forward. I can read in a bunch of pre computed values at run time and away I go. Does anyone have experience with building a data set like this? Or can give me some pointers on how to do it?


texts: MCU clock drift and radio frequency drift - are they the same?

texts:
Let's assume that I have two sensor nodes, one with crystal oscillator running at 24 MHz frequency, the other at 24 MHz + 10 ppm frequency.

To my understanding, in system-on-chip (for example, Texas instruments CC2650) based sensor nodes this single high-frequency crystal (MHz range) powers both the MCU and the radio (where GHz range is needed). I mean, the "local oscillator" component in RF diagrams that generates the 2.4 GHz sine wave is calibrated by using the MHz oscillator as the source (through PLL).

Assume that on both nodes the radio is configured to use the 802.15.4 channel 11, which has 2405 MHz center frequency. Is it the case that one node will communicate using 2405 MHz and the other 2405 MHz + 10 ppm?


texts: What back-end and front-end are in hardware design?

texts:
I saw these two terms in context of chip-design.

what are Back-end and Front-end?
what are the differences between them?


texts:
Good day,

I have built a H-bridge as in the image below. The NPN transistors are TIP102 and the PNP transistors TIP107. The bottom NPN transistor is connected to the PWM pulse of the MCU. When I close one of the switches (MCU pin HIGH), the corresponding PNP transistor overheats and the motor is turning very slow. I measured a voltage at that transistor at about 1.8V and strangely at the opposite PNP only about 5V. So it seems to me the transistors don't saturate properly. I also tried smaller base resitors, but it didn't work. With further testing however, when I connected the switch to the 12V rail, the the PNP doesn't overheat and everything is working correctly. Is there a flaw in my design?


texts: Which parts of this U.FL laptop wifi antenna need to be exposed?

texts: I got these wifi antennas for use in a small metal computer case. I'm cutting some holes in the case to give the antennas exposure, but I'm not sure what parts of the antenna need to be exposed. As you can see, there is a circuit board portion, and a "flap" portion. Do both of these need to be exposed, or can one or the other be inside the metal case? Thank you!


texts:
I am connecting up my PHY to an RJ45 with magnetics and was wondering what I do with some pins on it.
Here is the circuit for the Rj45 w/ magnetics.
My questions are:

do I connect pin 10 to the chassis GND?
What do I connect 4,5,7,and 8?

Thanks!


texts: I am using a processor which operates at 5 V and a MUX with 3.3 V. If I want to give selection lines from the processor, I have step down the voltage level. how can i do this by simply placing a resistor across it. How can I find the value of the resistor?


texts: Actual Assembly Yields -- 0402 vs. 0201 / 01005

texts:
I've been designing boards mainly using 0402s.  I can hand solder 0402s all day with a microscope and some tweezers.  Our passive supplier (a random Chinese passive company) has told us to get ready to switch to 0201s.  They are going to phase out 0402s, in a year.

We are starting work on an IoT device, and this device is going to be going in front of venture capital folks to drum up investor money.  This seems like the kind of device we need to look at 0201s and GULP 01005s.

I understand more expensive chip-shooters are rated for smaller components, but that is no guarantee of real world results, 01005s are soo tiny...

Ignoring any cost differences, has anyone noticed a significant decrease in board yields when moving to smaller parts?

Can anyone who has moved boards over to 0201s and 01005s provide any anecdotal evidence on how their production yields were affected by moving to such small pats from 0402s?

Get ready to replace those 01005s by hand, fun times...!


texts: Calculate simple NPN transistor circuit Arduino 3.3V

texts:
I am trying to control a 3v latching relay (single coil) using an Arduino @ 3.3v [SPST-NO PCB Mount Latching Relay, 16 A, 3V dc] rs-online.com/web/p/latching-relays/8276283/
  The relay requires a 3v positive to latch one way, and inverse to latch the other way.

I think this is the circuit I need to implement:

However, I cant get the relay to switch because the voltages in the coil are not high enough (should be 3v and I am getting +-0.49V when using 3.3v supply).
(using transistors: BC558 and also tried BC548)
(relay coil Coil Resistance: 16.8ohm)

I have done a simulation using livewire which shows pretty close what I am measuring in real live.

I have been suggested to use an H-bridge, however I would like to know if having a 5V supply, I can make this circuit work and make the design simpler.

Could I get some help on how to make this work and understand it?

I have set variable resistors in the simulator and tried different values but cant get 3V.


texts: Vrms, Vpk-pk, Vpk, Vavg for AC signal with DC offset

texts:
This might be a dumb question, but what values change when applying a DC offset to an AC signal?

Does Vpk represent the maximum voltage of the signal, in which case it increases directly with the DC offset?  Or is it 1/2 the value of the signal Vpk-pk, in which case it would stay the same?

And in that case would Vavg change too?


texts:
I'm building a DIY tablet with Orange Pi & A20 SoC (maybe I will change for LeMaker Bass) & Android 4.2.2 (v.5 with Bass).
This is a 17.3' screen tablet. I already have a IPS screen, and all works, 4h30 autonomy

Anyway, now I'm looking for a cheap but quality solution for a touch screen. So, multitouch, and easy interface: USB is the better choice for me.

I have seen the "HP ENVY TouchSmart 17 t" touch screen. The others touch screen are about 180$, because not a serial manufacturing...
Here a pic of the PCB:

It seems that the chip is eGalax (so no problem for the driver: /drivers/input/touchscreen/usbtouchscreen.c), and the interface looks USB (CN1 ref VDD, D+, D-, Ground).

But, because of norms of USB which is VDD, D-, D+, Ground:

Here, D+ and D- are inversed... It distrub me a little.

So, my question: Does somebody can confirm this is really an USB device ?

Thanks

Edit: Here a second pic, but the PCB is a little different:


texts: I have a very simple question regarding what resistor to use

texts:
Hi all i have a very simple question which i'm sad to say is past my skills.
I've spent all day trying to work this out but it's past my skill level.

can someone please advise what i need to buy from ebay for the following.

I'm using 6v to power a the Led.
The only information i have on the led is below:-

10W High Power LED PCB Grow light Aquarium Heatsink White
Certification: CE,RoHS
Power Dissipation: 10W
Chip: Bridgelux
Life: 50,000h
Forward Voltage: 2.0-3.6V
Forward Current: 700mA.

Can any tell me exactly what resistor i need to buy on EBay please as the listings are hard to work out and don't make much sense to me. the link below is the best i've found for what i think i need (could be wrong)

Cement Resistors 5W - 2.2Ohms

http://www.ebay.co.uk/itm/152114730196?_trksid=p2055119.m1438.l2649&var=451314342967&ssPageName=STRK%3AMEBIDX%3AIT


texts: Why MAX232 works without any capacitors?

texts:
I was playing today with a very simple setup of pic16f876 and max232 connected to the COM port of a PC running a terminal emulator. I was just testing (the uc simply echoes anything it receives) when I decided to try using smaller capacitors for max232. For my amazement after I removed from the breadboard ALL FIVE capacitors (C1-4, Cbypass) it turned out that the communication was still working just fine! It works at 9600 and 28.8k (couldn't test with higher speeds because the 4MHz crystal I use is not suitable for generating the higher baudrates).
But anyway, so far everything I tested works just fine. I even tried another analogous chip ST232CN and it also works without caps.

So my conclusion is that max232 already has inside all it needs for the generation of +/-8.5V. Until now I thought that the chip DEPENDS on the external caps to work. But it seems that they are not critical to max232 operation but ... I don't know, only provide extra stability? And yet with all my tests I never observed corrupt data transfer so I wonder what kind of interference do the caps actually protect from, what would the drawbacks be if I continue to use this setup with no caps at all?

PS: Since I didn't expect max232 to work without caps, at first I thought that I was mistaken and that I was observing some local echo at the terminal. But then I programmed the uc to echo not the same byte but byte+1. As expected, the incremented ASCII symbols were observed arriving at the terminal, so the local echo possibility was eliminated.


texts: 5VDC and 10VAC on the same PCB - what happens on 10V goes to 5V ground?

texts:
Me and a colleague (we are both EE-trainees) had a chat the other day about mixed voltages on the same PCB. She pointed out an interesting question that I was not able to solve.

Imaging having a PCB that use a ground plane for the 5VDC and the 10VAC/50Hz somewhere else on the board (not interconnected with any 5VDC-part whatsoever). That is, they are two completely separate voltage lines on the same board. The 5VDC is not derived from the 10VAC in the power supply, everything is separated.

Now, my colleague blurted out this one:

  Imagine I make a mistake when soldering, so that one of the two 10VAC-cables also gets attached to the ground-plane (for 5VDC). Nothing will happen to the 10VAC-circuit since only one of the cables is misplaced, but how will this single cable affect the 5VDC-ground?

After two days I am still not able to answer that question. I cannot grip this question theoretically and I do not have any equipment to try it out practically.

I'm thinking on the one hand: 5VDC will be unaffected since there is no path to the second 10VAC-cable, so there will be no short or anything like that.

And I'm also thinking on the other hand: Will the 10VAC induce noise to the 5VDC-ground, making all 5VDC-circuits unusable?

What will happen?

EDIT: added pseudo circuit schematic

simulate this circuit – Schematic created using CircuitLab


texts:
I am interested in knowing what is the max amps that I can use to safely (ensuring the battery doesn't get too hot, and maximizing battery life). The battery is Panasonic LC-R127R2PG (12V,7.2Ah/20HR) Valve Regulated Lead Acid. I googled and found the spec sheet http://www.farnell.com/datasheets/1674772.pdf and it's listed as: "Charging Method - (Cycle use) Control voltage: 14.5 - 14.9V; Initial current: 2.88A or smaller. And Trickle use Control voltage: 13.6 - 13.8V; Initial current: 1.08A or smaller."

That seems to be super small and will take a while to charge at only 2.88 amps.

Also I am looking at solar to recharge the batteries as back up/emergency. Does anyone have a particular solar panel that he/she would recommend for this application.


texts:
I have used PartSim for discrete circuits but when I wanted to add a 555 timer chip there was nothing available in the list of components. I read about creating my own project models from spice text, which I tried but it makes no sense to me.

Is it possible to make circuits with chips like 555 etc.?


texts:
It is known that it is possible to get 2Vcc output voltage in a BJT Common Emitter amplifier by using an RF Choke (instead of a simple resistor) connected to the collector.

Precisely, we will get at the output terminals a signal with VCC mean value and a VCC peak voltage (with a total value equal to 2VCC).

(there is VCC connected to the collector, although it is not written in the image)

With this configuration, we will have this following graph:

With a precise load resistance RL it will be possible to get 2VCC, because the slope of the dynamic load line depends on it. But I was told that, regarding the output current dynamic, the maximum current peak is equal to IQ (= 0.5 Imax). Why?


texts:
How exactly do buck converters work under no load condition?

The capacitor voltage will try to charge up to the peak input voltage, with no load connected across it to discharge. How to avoid this problem?

** I've included the simulation result. The output voltage (green curve) reaches 12V (peak input) slowly. I don't understand why the input voltage to filter has spikes.

Even if the controlling circuit alters the duty cycle, wouldn't the output reach the peak input value if there is no load?


texts: How to design mechanical switches to an arduino controlled circuit

texts:
I have desined a circuit with a motor that controls an opening\closing door (of a
Skinner box). Below attached a figure of the circuit.

The switches are for the door, not to keep moving when it is already in desired position. (i.e., not to continue openong when it is already open, and not to continue closing when it is already closed). When the door is fully open, the Op_switch is pressed and when it is fully closed, the Cl_switch is pressed.

The problem is, I want the switches not to be controlled by the arduino. I want them to be mechanically connected to the circuit.

  If the Cl_switch is pressed, I want the door not to be able to keep closing
  (but to be able keep opening).
  If the Cl_switch is pressed, I want the door not to be able to keep closing
  (but to be able keep opening).

Is there a way to do that without the arduino?
(I attach also my arduino program).

Thank you!

Here is the full arduino code:

int IN1=8;
int IN2=9;
int IN4=4;
int ENA=7;
const int IRLEDpin = 3;
const int PhotoPins = A1;
int thr = 0;
int temp;
int numPorts = 1;
int PhotoSensor = 0;
int swtch_open=2;
int swtch_close=1;
int swtch_stat=0;    // 0 means pressed 1 means not pressed
int motor = 2;

void setup() {
  Serial.begin(9600);
  initPorts();
  reset();
  pinMode(IN1,OUTPUT);
  pinMode(IN2,OUTPUT);
  pinMode(IN4,OUTPUT);
  pinMode(swtch_open,INPUT);
  digitalWrite(IN4,HIGH);
  //pinMode(swtch_close,INPUT);
}

void loop(){
  analogWrite(ENA, 250);  // motor speed
  readmyPorts();
  if (PhotoSensor == 1) {
    motor = 0;
  }
  if (motor == 2){
    OpenDoor();
     }
  if (motor == 1) {
     readswtch();
     if (swtch_stat == 0) {    // 0 means switch pressed
      motor = 0;
     }
  }
  if (motor == 0) {
    StopDoor();
  }
  //delay (3000);
  //motor = 2;
}

void OpenDoor() {
     motor = 1;
     digitalWrite(IN1,HIGH);// rotate forward
     digitalWrite(IN2,LOW);
}
void CloseDoor() {
     motor = 1;
     digitalWrite(IN1,LOW);// rotate backwards
     digitalWrite(IN2,HIGH);
}
void StopDoor() {
     motor = 0;
        digitalWrite(IN1,LOW);// stop motor
 digitalWrite(IN2,LOW);
}

void initPorts() {
  pinMode(IRLEDpin, OUTPUT);
  digitalWrite(IRLEDpin, HIGH);
}

void reset() {
    thr = 0;
    for (int j = 0; j < 5; j++) {
      temp = analogRead(PhotoPins);
          if (temp > thr){
        thr = temp;
      }
    }
    thr = thr - 20;

}
void readswtch() {
  if (digitalRead(swtch_open) == HIGH)
  {
   swtch_stat = 1;
  }
  else if (digitalRead(swtch_open) == LOW)
  {
   swtch_stat = 0;
  }
   }
void readmyPorts() {
    int value = analogRead(PhotoPins);
    if (value < thr) {
      Serial.println("object in the way");
      PhotoSensor = 1;
    }
    else {
      Serial.println("clear to go");
      PhotoSensor = 0;
   }
}


texts:
I have this DC socket:

Which I intend to wire up to a circuit to provide power.

I have a DC power supply which has a positive tip polarity.

I'm good to go and wire up the socket but I am a little stuck as there are 3 pins on my socket.

From the look of the socket it's fairly obvious which pin is for the center pin (which I will wire pos) so I assume the other two are for the outside (which I will wire neg).

Is this assumption correct? And if so why two pins instead of one?


texts: Using IR Emitter and detector incorrectly

texts:
So I bought this from radioshack and tried to set it up following this tutorial.
The problem is, the red LED lights up and when i try to interfere with the connection, nothing happens. When I remove the black one, everything still works fine. How do I properly use these ir diodes?


texts: How to use arduino nano to switch an 230V AC motor on/off?

texts:
I want to switch on and off an 230V AC motor with a relay what is controlled by an arduino nano.
The on time and off time would be able to set by a 3-position slider switch. So would be 3 different on-off time available. I want a status led for the relay to show if the relay is activated.The Arduino nano will be powered by a 5v mobile charger.

schematics:

the motor:

the relay module

program code:

const int switchPin1 = 2;    // D2
const int switchPin2 = 3;    // D3
const int switchPin3 = 4;    // D4
const int RelayPin = 5 ; // D5
const int ledPin = 6;      // D13 status led

int switchState1 = LOW;
int switchState2 = LOW;
int switchState3 = LOW;
int mode = 0;
int timeON[3] = {30000,60000, 60000}; // 0.5 min, 1min, 1 min
int timeOFF[3] ={30000,60000, 120000}; // 0.5 min, 1min, 2min
int relayON = timeON[0];
int relayOFF = timeOFF[0];

void setup() {
  pinMode(switchPin1, INPUT);
  pinMode(switchPin2, INPUT);
  pinMode(switchPin3, INPUT);
  pinMode(ledPin, OUTPUT);
  pinMode(RelayPin, OUTPUT);
  digitalWrite(switchPin1, HIGH);
  digitalWrite(switchPin2, HIGH);
  digitalWrite(switchPin3, HIGH);
  digitalWrite(ledPin, LOW);
  digitalWrite(RelayPin, LOW);
}

void loop() {
    switchState1 = digitalRead(switchPin1);
    switchState2 = digitalRead(switchPin2);
    switchState3 = digitalRead(switchPin3);
    if (!switchState1 && switchState2 && switchState3) { mode = 0;}// mode selection
    if (!switchState2 && switchState1 && switchState3) { mode = 1;}
    if (!switchState3 && switchState1 && switchState2) { mode = 2;}
    relayON = timeON[mode];
    relayOFF = timeOFF[mode];

    digitalWrite(RelayPin, HIGH);
    digitalWrite(ledPin, HIGH);
    delay(relayON);
    digitalWrite(RelayPin, LOW);
    digitalWrite(ledPin, LOW);
    delay(relayOFF);
  }

Will this work or is there something that I didn't take into account? Any advice is appreciated.


texts: Identify an Accelerometer in an Xfinity XR11 Remote

texts:
part identification question here. It comes from an Xfinity XR11 Remote. It’s used to detect acceleration when picking up the remote.

The footprint and part/trace placement heavily matches what I’d expect for an STM accelerometer but the register map just doesn’t fit. Specifically one of these.

The package reads 31UHQ and is a 2mmx2mm LGA package. It seems that the 4x3 pin layout has a standard pin configuration of two interrupt outputs and I2C/SPI pin locations.

It has registers starting at 0x00 and some of the reads and writes I see from a logic analyzer are to addresses that the datasheet claims are “reserved”. For example, bits 0, 1, and 2 on register 0x17 enable the X, Y, and Z axis. I can provide a full register dump if needed.

If it helps, here are the ins and outs. All resistors are 0ohm bridges.

R11 = SCL
R20 = SDA
TP50 = VCC (2v5)
TP1 = Interrupt (not sure if INT0 or INT1)
TP26 = Unknown
TP27 = Unknown

Start-up sequence: (Op, Reg, Data)

W 17 07
W 19 02
W 25 04
W 26 06
W 36 07
W 20 08


texts:
It appears that either all the people over the internet have either not thought about this question or that I am mistaken in my thought somewhere:

Confusion appears when I try to apply ohms law to the power supply coming to our homes. Taking it as simply as it can be, why and how a thicker/longer resistance element of a 100W bulb draws more current than a thinner/shorter element of a say 60 W or 0W bulb when ohms law suggests something else, that current through smaller resistance would be greater. I know that the system tries to keep its voltage constant and hence has to feed more power into the load as it demands but Im not getting the result which I should on paper.

Now some or most people would like to suggest that a 100 W light bulb has a smaller resistance than a 60 W. Please think again....have you seen a heating element room heater, one which burns a hole in your pocket? or better try to visualise putting many 100 W bulbs in series...resistance increses with each light bulb introduced in circuit as well as the current!how does a load draw power from the system


texts: Help me understand EM Field behavior around Ferrite sheet

texts:
I designed an NFC reader board that reads and writeS to tags. Some of the parts with NFC tags have metal frames inside them (think of cup holders with NFC tags, but the object in the cup holder can be metal.)
In order to keep the induced eddy current that creates interfering magnetic field which block the incident (from Reader) EM Field; i taped a ferrite sheet on the cup holder and stuck my tag right on it (see below.)
It turns out the reader can't read the tag unless there is some gap between the ferrite sheet and the tag (space.)

I'd like to understand why this space between the ferrite sheet and the TAG is required.


texts: Selecting low-power managed flash storage?

texts:
I've been trying to find a low-power flash storage solution. It needs to have built-in management (finding bad blocks, wear leveling, etc), so I've been looking at eMMC chips. But the specs on almost all chips in this family seem to be hidden behind some kind of barrier. With the good manufacturers, all you have to do is sign up for an account to view the datasheets. Some manufacturers (like Samsung) make it seemingly impossible to view any information on the chips, other than throughput.

How do designers normally find information about these sorts of chips? Is there any hope for someone looking to only produce a few thousand units or less? Should I call it quits and just use a microSD / microSD slot assembly?

EDIT While I am asking this for general advice about sourcing managed flash, I want to mention that my specific application currently only uses about 120mW. Additionally, only reading will be performed on the flash.


texts: Test automation framework/software for hardware applications

texts:
I am an Electrical engineer so my background on software testing is limited. My application is not a software testing issue. I need to develop a software package in python to interact with a RF electronic board to do various test procedures and measurements. I want the software to be general enough so in future adding new test cases and changing parameters etc. be very easy and don't take time so we focus on results.

As far as I read through existing test automation tools that are available found they are for software tests, not for hardware applications.

I was wondering if you have suggestions or come across a framework/tool/arch. that fits hardware applications.


texts: Mismatch between Input Power and Output Power in a typical Power Supply

texts:
Here are the data attached on a Switching Mode Power Supply :
Input : 230 V - 2.5 A PF = 0.95 ( Hence the power can be obtained as 230*2.5*0.95 = 546 W )

Output : 300 + 103 + 3.6 + 12.5 = 419.1
And at the line bellow the table it has mentioned 330 Watt as the Total wattage.
How can this be possible ?


texts: Removing unnecessary fuses from 12V DC car plugs

texts:
I have a 12V DC car socket is connected to a car battery and cable with 12V car plugs on each end.  The socket and each of the plugs has its own fuse, which seems unnecessary.  If I were to blow a fuse, I wouldn't want to check 3 places.
I'd like to keep the socket's fuse since it's directly connected to the battery and remove both fuses from the male-male cable.  However, since a fuse is part of the spring-loaded mechanical structure for a 12V car plug, I can't just replace it with a wire.  Is there any kind of placeholder that I can use?  Will I need to disassemble a glass fuse and wire the ends together?  Is this all a terrible idea?


texts: How do I determine the maximum amp output of a battery pack?

texts:
How can I determine the maximum amp output of a battery pack?

Some background: I've got a 5-AA battery pack hooked up to a microcontroller and some continuous rotation servos, but there's current weirdness when everything is drawing their maximum amounts. The microcontroller randomly restarts itself, and the servos stutter and jerk around instead of rotating smoothly. Suspiciously, everything runs fine, just a little more slowly, when hooked up to my laptop's high-speed USB port, despite that being lower voltage. This makes me suspect that I'm exceeding the current output of my battery pack at 7.2V.

How do I determine how much current my AAs are capable of pumping out? Do different battery materials have different output ratings?

(I know that LiPo batteries of the sort used in RC cars have a "C" rating that represents the discharge rate, but I've been unable to find a similar rating for household batteries.)


texts:
I'm trying to charge 3 NiMH/NiCd AAA cells from USB. I've already got an atmega32u4, so I can use that to read battery voltage and stop when battery reaches 4.2V. I'm not sure about the capacity, but 100mA seems a safe charge rate. Board space is limited so I would like to use as few components as possible.

I can't use an LM317, the voltage drop is too high. Is there another voltage regulator that I can use with current limiting?

Alternatively, the atmega32u4 can do about 100mA total on it's io pins. Can I just use a few pins, add a diode or 2 in series for the voltage drop, and use that to charge the battery?


texts: Input Bias Compensation Resistor Calculation for an Integrator

texts:
I have been reading the following tech note from Analog Devices that discusses designing an op amp circuit to compensate for the input bias current: https://www.analog.com/media/en/training-seminars/tutorials/MT-038.pdf

The example they provide to calculate the input bias current is an inverting op amp.

I would like to understand how to better calculate the value of a compensation resistor in an integrator op amp design:

As I understand it, input bias currents are what can lead to op amp saturation when nothing is connected to the input of an integrator. Is this correct? Is an input bias compensation resistor necessary in an integrator?


texts:
I have read several explanations with respect to how grounding works but I am fundamentally confused with this diagram.

Why would I be electrocuted in the "Shocked" image
Shocked
Why would I not be electrocuted in the "Not Shocked" image
Not Shocked

Shocked:

Not shocked:

Wouldn't there still be a path? I don't understand why only after the load I won't be shocked.


texts: Minimize Two bit Multiplication in Binary function

texts:
the input are X=(x1,x0), Y=(y1,y0).

the output is Z=(z3,z2,z1,z0).

the component: Z=X*Y  .

I got these simplified expressions by Karnaugh maps:
(* = AND / + = OR / ~ = NOT )

z3=x1*x0*y1*y0

z2=x1*(~x0)*y1+x1*y1*(~y0)

z1=x1*(~y1)y0+x1(~x0)*y0+(~x1)*x0*y1+x0*y1*(~y0)

z0=x0*y0

now I want to minimize these 4 expressions with the less number of component using (AND/OR/NOT/NOR/NAND/XOR) every component have only 2 inputs.

z0 I am sure that it's minimized (it has only one component) and I think also z3 minimized.

can someone show me how to minimize z2 and z1 ?

this the best that I found but I need to minimize it for 7 gates or less (not 8)


texts: I came across an N20 motor, and couldn't find anywhere what N20 actually tells us about the motor, and where the designation comes from.


texts:
So I was tasked with creating a function "transitions" that takes as input a value of type std_logic of arbitrary length. The returned value should be an integer that records the number of transitions (0 → 1, or 1 → 0) as you scan the binary bit pattern from left to right (or right to left). For example, the value 0110010011 would return 5; the value 001 would return 1. In my simulation, I need to display the first 100 ns, with t2, t4, t6 and t8 all shown as either signed or unsigned decimal and data displayed as binary.

Here's what I came up with but keep received an error having to do with going out of my index range in the loop I created. How would I go about limiting the loop to clear the error?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity TransitionFunction is
end TransitionFunction;

architecture Behavioral of TransitionFunction is

  function transition(signal data: in std_logic_vector) return integer is
    variable count: integer := 0;
  begin
    for i in data'range loop
      if data(i) /= data(i+1) then
        count := count + 1;
      end if;
    end loop;
    return count;
  end transition;

  signal data: std_logic_vector(7 downto 0):="01111100";
  signal t8, t6, t4, t2: integer;
begin

  tt:   process
  begin
    wait for 10 ns;
    data <= data+1;
  end process tt;

  t8 <= transition(data);
  t6 <= transition(data(5 downto 0));
  t4 <= transition(data(3 downto 0));
  t2 <= transition(data(1 downto 0));

end Behavioral;

Error message:


texts: How did static charge ruin my control board?

texts:
We have a Thermia geothermal heat pump that was working fine up until we had a particularly bad thunderstorm.  Lightning took out the power for a while and burned up a DSL modem, a router, and a IP Cam.

After the storm I noticed that the heat pump registered the outside temperature way too low.  This is a water based system with radiators in the house and no thermostat.  It works by knowing the outside temperature and you can adjust the curve of how much heating you need.  After diagnosing it and finding some documentation I found the values the thermistor should be registering.

It checked out correct and the wiring was not causing a problem.  When I shorted the two terminals it was reading 9° which from this chart is about 250Ω too much.  There are 3 other thermistors reading other values that are still working properly but they use a much higher resistance (1-70kohm).

The pins marked in red are other thermistors that have a much higher resistance. The blue ones are for a thermostat that I don't have but I would love to understand if anyone knows how it works.  All of the thermistors are connected to pin one which I suspect is ground.  The outside temperature is read on pin 6 marked with an arrow.

My big question is how can I get the values to start reading correct again?  What should I check or replace?  I have started by checking all of the resistors and they seem to be ok.  I would like to fix this so I don't have to spend $500 for a new board if they are even possible to buy.


texts:
I have a basic question about the linear regulators (eg.MC7912CT).
If the output current of the regulator is 1A, what would be the input current? Is it still 1A or less?


texts: Should there be solder mask under this QFN-16 chip?

texts:
The layout for a QFN-16 packaged chip (FXOS8700CQ) I am using is shown below.

I'm confused about the solder mask opening. Should it be everywhere inside the green outline or just rectangles around the pads? The first method results in exposed FR4 in the middle.

Will it matter either way?


texts:
I have a preamp rescued from an old stereo: BA3308

It has a pin "ALC" and the data sheet keeps going on about how splendid this ALC is and how it has a built-in ALC diode and such.

Nowhere does it tell you what ALC is, or how you should use this ALC pin.

I have looked for meanings of ALC online, and I have found 2 possible meanings that would fit this device:

Automatic Level Control
Audio Limiter Control

There may be others...

What is it?  How should I connect it?  is it an input, or an output?  It's a major feature of this chip, and I guess it's assumed you know what it is as you chose the chip.


texts:
I have a 2.1 PC speaker system and I would like to know what are the disadvantages and advantages of extending both satellites cables using RCA cable extensions.
Each satellite has 16W. The amplifier is located in the subwoofer and each of the satellites are connected using ~150 cm long cables with RCA connectors on the subwoofer. I don't know the AWG of the satellite cable, all I know is that the cable is about as thick as a PC mouse or PC keyboard cable.
Later edit: The extension cables that I want to use are 150 cm long, which means that the entire cable from each of the speakers to amplifier will be ~300 cm long.
Also, would soldering a normal 2 wire cable (not shielded) with one end to a male RCA connector and the other end to a female RCA connector be a good way to make an extension for the speakers? In a photo I saw that the original cable is not shielded.


texts:
I am creating a package for Molex's MicroAB USB 47590-0001 component because I could not find one for Eagle. My question is will this work to create the custom slots as seen in the datasheet? I've not had to mess with slots yet. How would you handle the slightly oval G4 and G5 holes, or are slightly larger circular pads good enough?

The blue is the milling layer, where the board will be cut. I see OSH Park has a page about this and they say use that layer too. The green is a via pad, which I extend with the red pad on the bottom. I opened up the green layer on the red pad as well. From what I understand, the blue should take care of the hole and the pad also creates a hole (as it does for G4 and G5) but the blue will make the custom shape.

Below is the data sheet for the connector.


texts: Are transformers used in moving the AC signal from the antenna to the TV? I am asking this because the electromagnetic waves must hit the entire antenna for voltage to be produced . Also how some types of antennas convert the sinusiodal wave to square signal?I haven't really understood it yet.


texts: 230VAC dimmer MOSFET failure at surge test

texts:
Our dimmer prototypes work fine, but fails surge test, as per 61000-4-5, 1/50us.

Circuit is isolated dimmer for 230VAC different types of bulbs. It uses 2x N MOSFET as switch. V503 detects zero crossings. N504/N505 are isolated drivers, in parallel to provide more power=faster switching.

Mains side passes test for 0,5kV, 1kV and 1,5kV L-N, tested in OFF and ON states. Bulb side fails for 0,5kV L-N @ ON state (because of peak current), passes 1,5kV @ OFF state (voltage suppressor works). 50% dimming is not tested yet.

What I tested, but not helps: protect each transistor with separate varistor, without LC filter (L503/C503), without CMChoke L502 on mains side, additional gate-source capacitors 2n2, additional gate-source TVS 15V bi-dir, moving output N before L502.
Most often only one of FETs gets broken (but not always the same) with almost shorted 3 terminals, no smoke or package holes. Load is 60W tungsten bulb.

I have limited space on PCB and components prices, can't add second CMC.

L503 is 470uH/2A


texts:
I am an EE student and my final project was giving to us without explaining what power amplifier are or how to design them. After researching and working on designs for about 40+ hours, I have come up with Oscillator and the amplifier circuit. The one issue I'm having is my oscillator circuit voltage is unstable and biasing it is quite difficult.
The final problem I have is the one I don't understand is why I has such low power. There is a resonator that is storing and creating the power to the load resistor, but I can’t change the resonator for 10 mhz and if I put more in parallel my impedance goes all over the place. I know that the BJT is supposed to be dissipating less power due to having such low on time. Then what would limiting factor be for supplying more power(the goal is 20w with 50 ohm load impedance)?
Any guidance would be appreciated.
Thank you.

The project outline said only passive components (aka no opamps).

 plan was mosfet)]2]2[]3
[]2


texts: Will a transformer with no output overheat

texts: I have replaced my old doorbell with a wifi model.  Because of renovations to my home over time I cannot access the transformer of the old doorbell to disconnect it.  If I just remove the old doorbell and push button, will the transformer overheat with no output load?


texts: Deriving admittance matrix for shortened quarter-wavelength transmission line

texts:
For Reduced-size branch-line and rat-race hybrids for uniplanar MMIC's , how to derive equation (2) ?

and is the imaginary constant j needed in equation (1) ?


texts:
For a PCB design, the longer the track length the greater the parasitic inductance right?

But why would this be a concern if I'm working at low frequencies (e.g 50-60Hz) because it'll behave similar to a short circuit right?


texts: Why are there not more incompatibilities in 3.5mm audio jacks?

texts:
I use 3.5mm audio jacks for my boom box, laptop, android phone, iPhone, iPod Touch, portable personal analog FM radio (no external speakers), and my classical sound system on a shelf.  I assumed that the signals were standardized, but Wikipedia says there isn't a single standard, though there do seem to be a bunch of standards followed by different companies.

When I google audio headphones with 3.5mm jacks, they typcally don't specify the conductor assignments.  It seems like it should be the luck of the draw whether a headphone is compatible with a given device.  Why are there not more incompatibilities devices and headphones with 3.5 mm jacks?


texts:
I'm going to use spring loaded pins (https://www.digikey.com/products/en?keywords=811-SS-004-30-002101%20) for interconnection between miniPCIe and base board. They are going to be mounted on base board under miniPCIe board - we are using high connector so there is enough space for them - but I have no clue how to shape pads on miniPCIe board! Should I just make pads without solder mask?

Thanks in advance!


texts: College Computer/Electrical Engineering Circuits - Modulating Signal DC offset based of modulating index question

texts:
Here is an image of the question.

I am stuck at part a, which asks to find the DC Offset based of a modulating index of 0.7, or 70%. So essentially, you will transform the maximum and minimum, yes? How do you know the minimum and maximum values?

I know that m (modulating index) = (max-min)/(max+min). Should the Vpp value be preserved and stay the same as original after the transformation?

How do you do this? Would you do trial and error? Or am I using the wrong formula?


texts: Digital to Analog Conversion with STM32F7 Discovery Board

texts:
I am a mechanical engineer interested in Data Acquisition and Closed-Loop Control projects. As a beginner who wants to work with STM32 microcontrollers, I have a specific question about the STM32F7 DISCOVERY board: How can I perform Digital to Analog Conversion (DAC) using STM32F7 DISCOVERY board.

According to the user manual, the PA4 and PA5 pins of the STM32F746NG microcontroller are dedicated to High Speed USB and DCMI Camera connector. These pins are not directly available to the user (such as in Nucleo-F746ZG, in which the PA4 and PA5 pins are directly accessible through the morpho connectors). Do I need an extra board to perform DAC with STM32F7 DISCOVERY board?

What should I do to access the PA4 / PA5 pins for DAC operations that are essentially required in closed-loop control projects?
Regards
Mohsen


texts: Retro computers and "jail bars" on the screen

texts:
I have tried to eliminate "jail bars" on the screen after UHF mod to video out (based on that: http://zx81stuff.org.uk/zx81/ts1500_video.html) by adding 460uf 16V capacitor between +5V and GND but it didn't do anything to reduce them.

Any thought on that?

This is how it looks on the screen:


texts: Y matrix (admittance parameters) and Transfer function

texts:
I have the following two port network:

for which the Y matrix elements are:

\$y11(s): (2+3s)\$
\$y12(s): -1\$
\$y21(s): -1\$
\$y22(s): 1.5\$

I need to get the value of \$ZL\$ in order for the transfer function of the circuit to corresopnd to the following Bode plot:

From the two port network:
Based on the equations of the network,

and the fact that \$V_2 = -I_2*Z_L\$, writing the following equations system:

I get the transfer function \$H(s)=\frac{2*Z_L}{2+3*Z_L}\$

On the other hand, to find the Transfer function of the given Bode, I proposed:

num. of decades between two frequencies:
$$log\frac{\omega_x}{10} = \frac{4}{20} \implies \omega_x = 10^\frac{4}{20}$$
In \$\omega_0\$ there is a single pole.
In \$\omega_x\$ theres a single zero.

Therefore: \$H(s)=k\frac{(\frac{s}{\omega_x} + 1)}{\frac{s}{10} + 1}\$

Where \$k=0.5\$

With all that, I get the following value for \$Z_L\$:

which has absurd numbers, and therefore I suspect I'm doing something wrong, although I'm not seeing where.

Thanks in advance for any help you may give.


texts:
I've been trying to set up MCU (STM32 L432KC) as an I2C slave device. I have previously tested it as a master device to interface with a port expander(MCP2307) and it works perfectly fine.
The following is the code I am running. The master sends 1,2,3 every 500 ms and the slave device is supposed to a glow a common anode RGB led (rgb led program works fine too, tested as SPI slave device before)
#include "stm32l4xx.h"                  // Device header

#define RED_ON (GPIOB->ODR &=~(1<<1))
#define RED_OFF (GPIOB->ODR |=1<<1)

#define BLUE_ON (GPIOB->ODR &=~(1<<6))
#define BLUE_OFF (GPIOB->ODR |= 1<<6)

#define GREEN_ON (GPIOB->ODR &=~(1<<7))
#define GREEN_OFF (GPIOB->ODR |= 1<<7);

void i2c1_init(void);

int main()
{
    i2c1_init();
    uint8_t c;

    RCC->AHB2ENR |= RCC_AHB2ENR_GPIOBEN;

    GPIOB->MODER &=~(3<<2 | 3<<12 | 3<<14);
    GPIOB->MODER |= 1<<2 | 1<<12 | 1<<14;

    GPIOB->ODR |= (1<<1 | 1<<6 | 1<<7);

    NVIC_EnableIRQ(I2C1_EV_IRQn);

    while(1)
    {
    }

}

void i2c1_init(void)
{
    RCC->AHB2ENR |= RCC_AHB2ENR_GPIOAEN;
    RCC->APB1ENR1 |= RCC_APB1ENR1_I2C1EN;

    GPIOA->MODER &=~(3<<18 | 3<<20);
    GPIOA->MODER |= 2<<18 | 2<<20;

    GPIOA->AFR[1] &=~(0xF<<4 | 0xF<<8);
    GPIOA->AFR[1] |= (4<<4 | 4<<8);             //PA9, PA10 - AF i2c

    GPIOA->OTYPER &=~(1<<9 | 1<<10);
    GPIOA->OTYPER |= (1<<9 | 1<<10);            //configure as Open Drain

    I2C1->CR1 &=~(I2C_CR1_PE);

    I2C1->TIMINGR = 0x00400D10;         //100khz, 1000ns tr, 100ns tf

    I2C1->OAR1 |= 0X40;     //own address
    I2C1->OAR1 |= 1<<15;    //enable own address

    I2C1->CR1 |= I2C_CR1_RXIE | I2C_CR1_ADDRIE;         //enable addr match and RXNE interrupts

    I2C1->CR1 |= I2C_CR1_PE;

}

void I2C1_EV_IRQHandler(void)
{
    uint8_t c;

    if(I2C1->ISR & I2C_ISR_RXNE)
    {
        c = I2C1->RXDR;

        switch(c)
        {
            case 1: GREEN_OFF;
            BLUE_OFF;
            RED_ON;
            break;

            case 2: RED_OFF;
            BLUE_OFF;
            GREEN_ON;
            break;

            case 3: RED_OFF;
            GREEN_OFF;
            BLUE_ON;
            break;

        }

        I2C1->ICR |= I2C_ICR_ADDRCF;

    }

}

I've tried configuring Slave Byte Control (SBC) in CR1 and NBytes in CR2 registers too, but it didn't change anything. From the reference manual, the only step to configure as slave is enable Own address. Are there any other steps or event interrupts I need to configure too?
By the way, I've tried using polling too instead of interrupt previously and had no luck either.
PS: TIMINGR value was generated through xls file by ST (and verified in cubemx) and I've tried different clock frequency and different timing values too, just in case that comes as a suspicion. And I'm using external pullups on SCL and SDA lines.


texts: What is digital Termination and when is it used?

texts: I have heard transmission line termination but today I came across this "Digital termination" but couldn't find out why is it used and what effect does it have on digital signals?


texts: Pads reflecting in controlled impedance strip?

texts:
Background

I'm designing a controlled impedance line for a 1900MHz signal travelling between SIM7000A cellular chip and an antenna.

Question

Tuning circuits are recommended for antennas with series and shunt passives to correct their impedance to 50 ohms by using a Smith chart. These are soldered to pads on the PCB (obviously). When the signal transitions from the controlled impedance copper trace to the pads the tuning components are mounted onto wouldn't it be reflected? How can we assume the characteristic impedance of a pad is 50 ohms?


texts: I am using ADA4937 as the driver circuit to my 14 bit high speed ADC. A term in the datasheet is Low Input Voltage Noise is used which is 2.2nV/√Hz. Please explain the importance of this term and unit used(nV/√Hz)in ADC driver. How lower or higher value of Low Input Voltage Noise will affect the overall performance.


texts: MC68000 Modern Equivalent (or can/should I use NRND/EOL chips)

texts:
I am designing a SBC that will feature the Motorola 68000 (or one of its descendants) but am having trouble finding new chips. The only chips that I have been able to find on Mouser or Digi-Key are the MC68SEC000AA10 and MC68SEC000AA16, both of which are NRND.

My questions are as follows:
1. Is there a modern (and non NRND) replacement for the MC68000? If so, what is it.
2. Should I (as a hobbyist) even worry about NRND/EOL parts for a system that I will build (at most) a handful of?


texts:
I'm making the circuit depicted here.

I already have the shift registers I require, but I can't find any UDN2981A ICs in the stores I have available to me. Unfortunately, I don't have time to wait for shipping from an online store.

1) Are there alternatives to the UDN2981A I could try? (I've already checked UDN2981A, UDN2982A, UDN2982LW, and A2982SLW, none of them are available)

2) Can I use discrete transistors to substitute the UDN2981A? Which kind do I need?

3) Are there any completely different circuits I could try finding parts for and building?


texts: Solar charger behind heat-reflecting windscreen

texts:
I am looking for help as my knowledge of solar charging (and apparently physics) is limited.
I have a solar charger that plugs into the 12 V socket in the car. It's intended placement is on the dashboard (although I do consider placing it on the roof and threading the cable the sunroof).
My car has a heat reflecting windscreen (I believe it's a metallizing layer laminated in the glass), which I presume would reflect IR light.
Would this also reduce the energy generated by the charger, compared to a conventional windscreen?


texts: How to increase QSPI flash clock frequncy in Zynq ZC702

texts:
I am working on Zynq ZC702 board. The board has a QSPI flash.  I want to increase the clock frequency of QSPI, so that I can read/write at a much faster rate.

The closest I found is this :

EDK-14.3,Zynq-7000 - What is the default QSPI interface clock frequency used in the FSBL and how do I speed it up?
Search

But reading this it is not clear to me exactly where do I make changes, DIV/8 to DIV 8 etc, are these parameters in FSB.elf file? I remember I was not able to open this file, as it is a binary file.

Any idea how to approach this?


texts: Start a teensy sketch after USB handshake has completed or upon a button has been pressed

texts:
I have an issue in starting a sketch on my Teensy at the right time.

I work in a school as an IT technician and over the summer I go through all the computers on site, log-on and check if they're behaving correctly.
To avoid to log on more than 500 workstation. I thought that emulating a keyboard with teensy was the best way to make this process faster so I wrote some code to help me doing so...unfortunately there's a problem with timings.
To solve this issue I'd like the teensy to start the program after the usb device on windows has been installed correctly or after a button as been pressed.

Below is the code, please would it be possible for some of you gurus to help me out?

int count = 0;
const int buttonPin = 5;
int buttonState = 0;

void setup()
{
    pinMode(buttonPin, INPUT);
}

void loop() {
   buttonState = digitalRead(buttonPin);
   if (buttonState == HIGH){
      Keyboard.set_modifier(MODIFIERKEY_CTRL);
      Keyboard.send_now();
      Keyboard.set_modifier(MODIFIERKEY_CTRL | MODIFIERKEY_ALT);
      Keyboard.send_now();
      Keyboard.set_key1(KEY_DELETE);
      Keyboard.send_now();
      Keyboard.set_modifier(0);
      Keyboard.set_key1(0);
      Keyboard.send_now();
      delay(2500);
      Keyboard.print("Administrator");
      delay(1000);
      Keyboard.press(KEY_TAB);
      Keyboard.release(KEY_TAB);
      delay(500);
      Keyboard.print("XXXXXXXXXXXXXXXX");
      delay(500);
      Keyboard.press(KEY_TAB);
      Keyboard.release(KEY_TAB);
      delay(500);
      Keyboard.press(KEY_ENTER);
      Keyboard.release(KEY_ENTER);
}

else {

     Keyboard.print("No Button Pressed!")
     }

}

Many thanks in advance.