texts: Missing phase 3-quadrant TRIAC-based solid state relay for 3-phase engine

texts:
First of all, I'm a simple mechatronics technician student first time posting here, so please don't mind if I say something that seems completely stupid, since I consider myself to be a total newbie at this. do feel free to correct me if you find anything wrong with my thought process.

With my limited knowlege of eletronics, and in an attempt to consolidate the knowlege aquired in the course I'm doing at the moment, I've been trying to learn by studying and developing a missing phase solid-state relay for a 3-phase engine (star-delta startup), as a viable replacement for the more usual mechanical relays. The objective is to be able to handle currents in the order of 30-50 amps and small enough so that it can be assembled on top of the engine's connector box, and able to only trigger if one of the phases goes off for 1 second at most, half a second minimal.

The engines where the relay should be placed are 3-phase 400V 50hz engines, capable of developing 5bhp+ of power.

The issue here is that I've been head deep on simulators (mostly proteus) and investigating components. after extensive trial and error, I've managed to come up with the following:

3 quadrant TRIACs are mandatory, as to avoid snubbers, thus driving costs down
SCR or optocouplers as TRIAC drivers, any of these two options are fine
3 input AND gate as trigger
On the command part as a whole, to aquire the signal I've been using a simple resistor (to drop voltage down) + retctifying bridge combo, where the capacitor acts as the "sensitivity" of the trigger. The signal is aquired after the TRIAC.
FYI, the command portion is supposed to run at 5VDC at most and a consumption of about 300mA tops
there is a need of adding a small power cell to feed both the AND gate IC and to serve as a "starter".

With all this I've been spending a good part of of my time investigating components, searching datasheets and attempting to make it actually work, but after the realization that a 3-quad TRIAC is needed, I´ve hit a wall. The TRIAC needs the gate to be at negative (working at quadrant II and III), and for all that's holy, I simply can't make it work on the simulator, even if the logic of the circuit is correct, so yes I'm pretty much asking help here.

Small considerations:

Nearly all the components are overspecced for the job at hand, mainly to have enough redundancy so that it requires little to no maintenance except to change batteries.
Also, been thinking about using simple 1n4001 diodes as fuses assembled between the TRIAC and the coupler or SCR, is that a good line of thought?


texts: Why does a typical PCB always has rounded tracks? What harm can a sharp edged PCB track can cause? Please explain!


texts: Precision with opamp in transimpedance amplifier configuration with LED as photodiode

texts:
I found this circuit in searching for a circuit that uses LED to measure absorbance

What I want to ask is: in order to "accurate" the readings from \$ V_{out} \$, for example: assume that the current through LED is \$ -0.1 µA \$, \$ V_{R} = 10 kOhm \$,  then \$ V_{out} \$ should be \$ 1 V \$ but the actual reading is \$ 1.303 \$ for example. I know this is due to many parameters such as: devices, offset current, bias current, offset voltage, blah blah ...

I just wonder how can I reduce the error and obtain the result more accurately?


texts: Why battery specs are given in contextless mA·h instead of meaningful W·h?

texts:
Possible Duplicate:
  Why are deep cycle batteries rated in amp hours instead of watts hours?

I don't understand why it is so common for specifications of battery capacity to be given in mA·h, when you have no clue how much power that is and how long a given device can be powered through such a battery, or to compare batteries with different voltages (and try doing that when the voltage is conveniently omitted from the spec altogether).

Why don't everyone give out capacity specs in W·h?

Similarly, although seemingly not nearly as common as with batteries, some devices likewise only list their power consumption in mA again, where you again have no clue how much power they'd be consuming, unless you happen to know what voltage they operate on.

Why isn't consumption always given in watts instead of milliamperes?

Isn't it error-prone to be giving capacity and power consumption specs in units which cannot be directly compared without, (a), knowing the voltage of both the battery and the to-be-powered device, and, (b), having an expensive calculator or a piece of paper.

Why aren't Watts universally used here, and what kind of sense does it make to be giving mA or aA·h ratings without ever mentioning the voltage (happens all the time when you look at various specs online, apparently).


texts:
DC or (AC + DC) coming out of a full wave rectifier

Is there a truly correct answer to this?

Considering the representation as a waveform I would say its an AC wave form offset by some DC amount.

Using the standard electronics notion I would say it is purely DC.

A quick Wikipedia such on Rectifier returns, "A rectifier is an electrical device that converts alternating current (AC), which periodically reverses direction, to direct current (DC), which flows in only one direction."

I know that they both can be true but, I am curious if any consensus exists for the green waveform below.

The question originated from can you feed a, "dc voltage with a bad ripple" into a dc to dc buck converter.... At first I assumed no using the notion that DC meant constant, but then thinking about the output of the buck is frequency driven I started to have second thoughts.
Thanks,
Josh


texts: High side smart load switch input protection

texts:
I am in the process of designing an input protection circuit for my smart load switch (TPS27SA08)
This circuit is intended to provide reverse polarity protection and overvoltage protection:

The input voltage of the circuit is 12V, 8A is the maximum current.
D1 is a bidirectional TVS diode with 17.1V maximum clamping voltage at 10A and 12V working voltage
Q1 is a P CHannel MOSFET with Vgs maximum voltage +- 20V and Vds of -55V.
The smart load switch voltage input goes from 8-36V
I have 2 questions:

Do I need to add a fast blow fuse at input for an overcurrent situation or with the tvs is enough?
Will the MOSFET survive an overcurrent and overvoltage scenario? Keeping in mind the maximum clamp voltage of the TVS and the maximum voltage of Vgs of the MOSFET.


texts: How to measure ratings of a transformer?

texts: If I am given a transformer without any datasheet of it. Then how can I measure the maximum current and voltage rating of the transformer?


texts: DAC and/or output amplifier selection for a MP3 player?

texts:
I am designing my own MP3 player now. While decoding & all digital backend looks straightforward, I am only puzzled with audio output (i.e. DAC->Amplifier part). My goals are 1: sound quality 2: power efficiency. Price is not important.

My previous approach (looking for I2S DAC with integrated D-class amplifier) seems to be bad idea as for some reason there are just no low-power D-class amplifiers.

I see some DAC's have integrated headphones amplifiers (AB-class). I am scared a little, as they probably eat too much energy...

Other ways might be getting bare I2S DAC and building my own analog frontend on high-quality opamps. Power consumption is still a problem here (+all fun of having dual-rail power on battery powered device).

Any ideas? Or will I have to spend 80-100mW just to drive headphones at 40mW and have barely 10 hours of battery time...


texts:
So I’m trying to fix my blu-ray player and there are two spots where this beige stuff is. Is this there intentionally, or is this the result of some malfunction?

Could someone please explain what it is and why it happened?
Thanks


texts: Using transistor as switch with low voltage

texts:
Basically, I need to monitor a circuit's output so I can activate another system. The output voltage of active stage is 140mV.

If I am not wrong (from what I read about transistors) 140mV is not enough to put a BJT transistor into saturation (ON mode).

The end goal is turning on an LED and/or a relay, so I really need transistor in the saturation region.

I don't want to use a micro-controller's ADC to measure the voltage for such simple device (cost wise)

How can solve the problem in a simplest manner possible?


texts: What voltages are expected/can be tolerated on USB Data Lines?

texts:
I'm currently working on a project using an ATMega328P and the V-USB library. V-USB is meant to be USB 1.1 compliant, and the documentation mentions that 3.3V is expected on the D+ and D- lines by the host.

I want to run my microcontroller off the 5V supply that USB provides.  I need 5V to guarantee it can operate at 20MHz. However, this would mean that the D+ and D- lines would be communicating at 5V.

Can I do this or do I risk damaging my USB port?  If it's an issue, what would be the best method of shifting the voltage levels?  The wiki page below has some solutions but I'm not sure what would be best.

Thanks!

V-USB Wiki - Hardware Considerations


texts:
I am new to electronics and i am having trouble finding how to properly connect a DC circuit to a power suply. I don't understand the symbology used.
Do i have to connect the positive (+) terminal of the power suply to the positive (+) terminal marked on my circuit board or to the negative (-)  terminal?
Each time i see a component wich has polarity (such as diodes or capacitors), the marking of the component (+) goes to the (+) terminal on the power suply, or to the (-) terminal?


texts: How to avoid the saturation of the current amplifier?

texts:
I have to calculate current gain of the following circuit and to model it in Spice. I arbitrarily set Is = 0.0002 A:

Here are the results provided by LTSpice:

Also, in order to find an equation for current gain, my first idea was to transform Is and its parallel 5k resistor to a combination of voltage source (Vs = Is*5000 Ohm = 1V) and series 5k resistor. In this case the voltage at inverting input is Vy = Vx = 0.33*Vout, and the output voltage itself can be found according to following equation: (Vs - Vy)/5000 = (Vy - Vout)/20000.

Strangely, the results provided by LTSpice become quite disturbing when I increase the voltage to 2V (or current to 0.0004 A):

The same happens when I increase the value of 5k or 2k resistors. As you can see, I had a good luck arbitrarily choosing Is value as 0.0002 A. Otherwise, I could have very hard times.
In general, if I keep all the resistors as they are and don't increase the current above 0.0004 A, then the output voltage can be calculated following these equations:

(5k*I1 - 1/3Vout)/5k = (1/3Vout - Vout)/20k;
6R*Is = Vout;
6*5000*0.0002 = 6 V;

My question is: how to correctly select voltage/current source and resistor values in order to avoid op-amp saturation?


texts: Significance of back EMF in a PMSM motor?

texts:
How is back EMF generated in a pmsm motor and how does it vary.?
Which parameters of the motor change due to the back EMF development.?


texts: Tesla coil charging the battery with AC?

texts:
For Tesla coil, eventually the capacitor voltage becomes so high that the air in the spark gap is unable to hold-off the high electric field and breakdown occurs.

But usually from what I know DC can charge up the capacitor, not AC. What am I missing?


texts: 3v3, 12v Smps: "Design ok!" "Pcb ok!" Why not stable? Please Help

texts:
Im working on a project and i need 3v3,5v and 12V in this. I though smps circuits would be better than Linear Regulators. So i choose LM2676-adj IC. I designed schemetics for 3V3-3A SMPS and 12V-3A SMPS. Read all datasheet and get all recommended pieces from distributor. Printed the PCB and soldered on it. when i supply(16V) the Input on Pcb, i read 12.10V and 3.28V and its OK for me. But when load the circuit for get near of 3Ampere (3v3 - 1.5 ohm & 12v - 4.5 ohm) problems begin. I always read 1.2V from output of 3v3 smps and 11.90V from output of 12v smps.

Output of 3v3 smps is stabile at 1.2v but output of 12v smps is not stabile, its up to 16V and down to 6V by the time randomly.

Here is my all components list, Schemetics and Board images, What do you think about this problem, how i can handle it?

http://imgur.com/a/3DTFQ?gallery [1]

For 3v3 SMPS I use:

IC: 1x LM2676-ADJ, Inductor: 1x P0841, Output Cap: 2x 100uF (10V 1.1A(Irms)), Input Cap: 2x 4.7uF (50V 0.6A(Irms)), Boost Cap: 1x 10nF, Schottky: 1x 40V (3A), FeedBack Res: 1K & 1K74

For 12V SMPS:

IC: 1x LM2676-ADJ, Inductor: 1x PE54039S, Output Cap: 2x 47uF (20V 0.9A(Irms)), Input Cap: 2x 4.7uF (50V 0.6A(Irms)), Boost Cap: 1x 10nF, Schottky: 1x 40V (3A), FeedBack Res: 1K & 9K1


texts: Is it normal for DC wall adapter power supplies to provide voltages above the nominal ones?

texts:
When I measure a 9V DC wall adapter power supply with a multimeter it shows 11.8V. When connected to my board this voltage lowers to 10V. Is this normal? Should I be afraid of toasting my 1117CD-5.0 supplied board when using this adapter?

Edit: This regulator accepts up to 12V inputs. So that will be no problem. A second "9V" adapter yields 15V to the multimeter. Will this one burn my circuit?


texts: Non blocking communication between 2 Arduinos

texts:
I have a nema17 stepper motor and a WS2812B based LED strip (60 leds) and an Arduino Nano.
The goal is to update the brightness of the led strip based on the motor position as frequently as possible.
The problem is because of the CPU time the LED update needs, the motor will slow down and stutter.
The motor drives is A4988 based driver with step and dir pins. The lib is AccelStepper. The motor has a max speed of 2000 steps per second and the step resolution is set dynamically based on speed (lower speed 1/16 steps). I need to know the exact position of the motor at all times and the position can't drift. I only have Nanos and try to do it with them.
I now moved the LED update code to another Arduino Nano and tried to send the the ratio 0-1 (position on a circle) as a byte 0-255 with I2C. It's better but seems like I2C still blocks the motor update.
Best would be if I had 16 digital pins I would just send the number with setting them binary to that number and when the other one finishes updating could just read in the current state and go into another LED update cycle. That would not block the main code at all but I don't have that many pins.
I'm currently thinking of using analogWrite and mesuring the pulse width with pulseIn on the other but that's just 255 resolution.
Is there any better solution that I might be overlooking?
Thank You


texts:
I've built a PCB with a 7805 based power supply on it. I tested the other parts of the PCB on a breadboard before I had the PCB made, but as the power supply circuit looked straightforward, I just took it out of a local electronics catalog without testing it.

The problem I'm having is the power supply only outputs 2.8V until you put it under some load. Surely the TIP2955 should not affect the circuit in any way until the voltage drop across the 3 ohm resistor rises above 0.6V? What on earth is going on? I've even taken the components off the PCB and built them on a tag strip. Still only 2.8V until some current is drawn.

It's also worth pointing out that the 7805 is getting quite hot with the circuit at rest.  But seems fine when a load (10 ohm 5W resistor, so about 1/2A) is applied.

I'm baffled...


texts: Creating an adjustable output regulator, in LTspice

texts:
Firstly, I'm having some trouble with simulating a variable resistor in LTspice.. I am wondering if this can be done?

Also, does anyone have any advice on how to theoretically analyse this circuit? I mean, the data sheet gives a formula for Vo but I think it's a little vague, any pointers in the right direction to derive this would be great as well.


texts: Using both clock edges in an FPGA design

texts:
So, after getting some advice from some good people here, I managed to put together my first (very modest) FPGA design. It is basically just a few registers and counters, and only runs at a few MHz, but I could synthesise and implement it with no warnings, and the real signals coming out seem to do what simulation made me think they would. I learned a few things along the way.

Now I want to learn how to set timing constraints and run timing analysis. So I am reading through the Xilinx doc UG612 and I see at the top of page 205:

"Use only one edge of the clock"

Hmm. Seems I broke the law. Part of my design is a parallel load shift register - I used the negedge of the last cycle of the clock to load it (from a counter which was clocked on the previous posedge). A quick sketch:

Of course, I am not directly using the negedge here, but the load signal is derived from it. I thought that this was good - but Xilinx tells me - don't do that.

Am I wrong? If so, why? What should  I do instead?


texts: Should you place traces at right angles through a via?

texts:
I understand that right angle pcb traces should be avoided because it can cause problems during manufacturing.

But what about right angle through a via?  Will this have any negative effects?

I have a multi layer board and I don't have that much space. I have come across a point where the only place I can place a via is right next to the pad I want to connect to, and my trace is coming from directly above.


texts: Will this simple four n-channel mosfet H-Bridge Circuit work?

texts:
This is my H-bridge circuit without considering Back EMF. In the real circuit I would put four fast recovery diode to eliminate the Back EMF.Maybe schottkies?

Before I came up with this design , I googled "DIY H-Bridge". And I only found out H-bridge design that is composed of two p-channel mosfet and two n-channel mosfet , as follows. My question is: Will this four n-channel mosfet H-Bridge circuit really work? If it works. Why the 'TWO N-CHANNEL TWO P-CHANNEL' plan is more popular? I mean. It is said that N-channel mosfet can handle high current much better than P-channel mosfet.I have concerns that the top N channel Fets are not getting enough drive .Will they run hot ?My proposed circuit is simple but do you think it needs refinement? Do you think that shoot through could be a problem?

At first , I didn't know what is high-side switching.This thread might help for people who also have question about what is high-side and low-side switching.

http://www.edaboard.com/thread182857.html


texts:
Wikipedia explains the basics about the markings of capacitors, here. It lacks many markings most of which confuses me:

Ceramic brown-yellowish cap

104 K5K (small )   --- what is the end "5K"? (Cannot be 5 kelvin as operating temperature!?)
10 (box box, perpendicular right upermost corner) 35+  (Tantalum Cap, bigger variant of the last one
154 C1K  (what is C1K, some other notation to Wikipedia?)

Orange Ceramic

333 K5X   (what is 5X? X roman numeral?)

Brown Circle Slit

10n (no other marking, what is the op.temp?) (Diameter: 7.5mm)
27J 100V (what is 27J?) (Diameter: 4.9mm, blackdot on the head)

Blue Slit Square

(triangle) 104K X7R50   (What is triangle? X7R50? Operating V?) (side = 4.9mm)
104   (side = 2.6mm, op.V? Tolerance?)

Questions about the bracketed

How to know operating V without its explicit marking?
What do the symbols, such as squares, plus-sign and triangle, mean?
Can you evaluate the operating voltage from the size of the capacitor in the case when no marking or poor marking is given?


texts: Atmel AVR assembly language multiplying by 2

texts:
I'm trying to multiply a 32-bit unsigned number by 2 across registers r18, 19, 20 and 21, r18 being the most significant byte. This is my code:

ldi r18, 0x03
ldi r19, 0x00
ldi r20, 0x00
ldi r21, 0x00
lsl r18
ror r19
ror r20
ror r21

Just used 3 for an easy example so I will know the output. I can't work out whether it's ror or rol for the rest of the registers. For a 16-bit number you would use ror to account for a carry, does this also apply for unsigned 32-bit numbers?

Am I supposed to use ror or rol?


texts: What is the name/type of this DC power connector?

texts:
I would like to know the name/type of this connector:

It provides 12 DC power to a hand drill, its diameter is about 2.5mm. I would like to buy an adapter for it that converts it to a 4mm banana plug (so I can use the drill from a laboratory power supply).


texts:
A non-cyclic Gray code has the same definition as a cyclic Gray code, except that
property P3 is not safisfied (the first bit string and the last bit string in the sequence differ
in at least 2 bits). For which values of n do a non-cyclic Gray code exists?


texts: Why are Li-Ion battery so much safer than lead-acid?

texts:
Recently I asked how to charge a (lead-acid) car battery at home and looks like the answer is very dangerous, don't do it unless you really really have to.

Meanwhile people charge Li-Ion batteries of laptops and power tools in-house every day. Those Li-Ion batteries are smaller than car batteries yet still have enough chemistry inside to cause trouble should anything go wrong. I guess anyone who says laptop batteries shouldn't be charged in-house would be labeled paranoid immediately and then ignored.

So it looks like Li-Ion batteries are much safer that lead-acid batteries or at least are perceived so.

Why exactly do these two types of batteries differ in safety so much?


texts: Are these SMD aluminum electrolytic capacitors busted?

texts:
I recently bought a car radio and made a stupid mistake when I connected the radio to the car.

Apparently I reversed the polarity on the radio which made the radio go poof and smell awful.

After opening the unit I saw that one of the radial capacitors was busted (the top of the unit is not flat)

Before ordering a new one, I noticed the surface mounted capacitors, they have a visible cross on the top, while other (smaller in size) capacitors
don't have a visible cross on top.

They still look flat to me, so I can't tell if can expect them to work or not because all the surface mounted capacitors with this size (8*12mm) on this board have this cross visible.

I don't have an oscilloscope as I have read that this could help determine if the capacitors are busted or not without removing them from the circuit.

I have searched the internet for examples of busted aluminum surface mounted capacitors, but I haven't been able to find examples to compare with.

So my question is, can I expect these capacitors to still be functional?

I'm hoping I can get the radio working again by replacing the busted capacitor(s). Hoping this is the only damage made to the circuit.

** EDIT **
I really don't understand why this is a bad question?


texts: How do anti-static wrist strap alarms detect a disconnection of the wrist wrap?

texts:
Sometimes I need to disconnect my ESD wrist strap, but forget to reconnect it again. Apart from improving my discipline to work more structured and more carefully, I wondered if there was any device/circuit that could warn me for not having reconnected the ESD wrist strap.
Searching on internet, I found an ESD wrist strap with build in ground alarm

How does such a device work, how does it detect a disconnection of the wrist wrap?

I couldn't find any schematic on internet, so thought of a schematic how I think it may have been implemented.

simulate this circuit – Schematic created using CircuitLab

A (modulated?) current source causes a defined voltage drop across R_device when SW1 is open.
As soon as the ESD wrist wrap is connected (pictured by SW1), the series resistance of R_connection_wire plus R_wrist_wrap plus R_human_body plus R_shoes/floor will be in parallel with R_device, which will lower the defined voltage drop.

With a multimeter, I measured the resistance of my own wrist wrap (bad measurement, but not relevant anyway) and the resistance of the connection wire to the wrist wrap. I made assumptions w.r.t. to the resistance of the human body and other resistances in the path (shoes, floor).

Next to the question:

How does the ESD wrist strap with build in ground alarm detect a disconnection of the wrist wrap?

I'd like also to ask:

Do you have other ideas/suggestions to detect a disconnection of the wrist wrap?


texts: Sensor reading is chaotic when Arduino is powered by laptop unplugged

texts:
I have a Sharp proximity sensor connected to my Arduino (analog input). This Arduino is connected and powered through USB by a laptop.

When the laptop is plugged in, everything works fine (I get
consistent readings).
When the laptop is running on batteries, the values I'm reading are
"chaotics". I mean that they vary a lot.

I also have an Arduino motor shield, which is powered by an external battery, but that's just for the motors (sensors are powered by the Arduino). The GND of the battery and of the Arduino are connected though, maybe that's causing the problem?

Or is too much power required from the USB?

Well, do you have any idea to understand that and fix it?

Additional informations:

Sensors reading are "smoothened" using a low pass filter (see my previous question about it).
(if you need some more information, that will show up here)


texts: Using a Relay with SMPS as load leads to contact welding after keeping energized for sometime

texts:
I am using a relay SRD-5VDC-SL-C(generic module made for diy projects) to control AC current going to my SMPS(120-300v AC to 12V, 2A DC) driving my LED strip. The relay is controlled by a Lolin NodeMCU v3 microcontroller. The line from power outlet is connected to COM and the line to SMPS is connected to NO. The switching happens perfectly in the start, but if I keep the relay energized for a long time then when I turn the relay off it still lets the current flow and doesn’t switch. I checked the continuity and it is indeed between NO and COM even after turning the relay off(control pin high). Knocking the relay solves the problem.

I am fairly new to electronics. For a load like SMPS do I need some additional circuitry along with the relay to avoid this or is it a bad relay?

Thank you in advance, my iot project is on hold because of this.


texts: Multiplexed LED column driver MOSFET doesn't fully turn off without a resistor parallel to the LEDS

texts:
I have a board with a 16x10 led matrix.

The columns are switched with DMG9933 Dual P mosfets.
The rows are driven with a constant current led driver ST STP16CPC26 (similar to TI TLC5956)

I noticed this problem because there where some ghosting between the columns.
I tried to solve it in software, by adding more blank time. That didn't change anything. The blank time was longer then the on time.
Lowering switching speed didn't help either.

I made a diagram of a single LED.
Adding R1 Helped mitigate the problem. R1 needs to be added once per column, not for each LED.

Without R1:
Green is the gate and blue is the drain.

With R1:
Green is the gate and blue is the drain.

I though at first that it might be leakage current, but this transistor supposed to have that under 10na so i doubt that's the cause.
I've built 2 of these boards and both exhibit this problem on all 10 columns.
There should be very little capacitance between the LEDs and the drain.

So what is the cause of this?
Is this the fault of the led driver maybe?


texts: What is the definition of characteristic impedance of a lattice network?

texts:
We were being taught about Lattice networks in class, today, and our professor mentioned that the characteristic impedance of a symmetrical lattice network like

is given by:

$$Z_0=\sqrt{Z_aZ_b}$$

I'm not sure what characteristic impedance means in this context. I searched around the net a bit and found that the term is generally used in the context of transmission lines. However, I'm not sure how it applies to a lattice network or perhaps more generally to a two-port network.

Basically, my question is: What is the definition of characteristic impedance of a lattice network (or a two-port network)?


texts:
I am using an arduino Mega to control 4 DC motors with 2 Sabertooth 2x12 motor controllers. I am using the Sabertooth controllers in independent analog mode (1,2,3,5,6 UP.. 4 down). I have a simple program setup right now just to move the motors (Im in very early stages of making an ROV). I am just wondering what the analogWrite() value i would use to 'brake'. 255 is full forward, and 0 is full backwards. But what is just brake? lol

#define Motor1 2
#define Motor2 3
#define Motor3 4
#define Motor4 5

void setup() {
pinMode(2, OUTPUT);
pinMode(3, OUTPUT);
}

void loop() {
analogWrite(2, 128);
analogWrite(3, 128);
analogWrite(4, 128);
analogWrite(5, 128);
delay(5000);
analogWrite(2, 0);
analogWrite(3, 0);
analogWrite(4, 0);
analogWrite(5, 0);
delay(5000);
}

Thanks in advance :)

Edit:
My issue has been solved, the braking value is 128, but i had to make a low pass filter and adjust the PWM frequency.


texts: Soldering wires to a 5V-to-12V converter

texts:
I have a small project that requires me to solder some wires to a PCB that converts 5 volts to 12 volts.

Here is a picture of the PCBs:

On the PCB to the left, there is no label of "negative or positive". How can I tell where to solder the red (positive) and black (negative) wires. Furthermore, on the PCB to the right, it says the output is "5-16V", even though when I bought it the description said 5V to 12. I am a bit confused.
What is the proper way to solder a red and black wire to the output "holes".

For instance: do I put the wire through the top of hole and solder from the bottom of PCB?

... or do I solder from the top?


texts: Best way to run current for certain amount of time

texts:
I have a circuit set up that requires around 5 Amps of current to run but I need it to only run for a specific amount of time. The circuit is activated when I press a button and I want some tool to limit the amount of time current can pass through the circuit when the button is pressed. Does anyone have any ideas for a sort of timer I could use that is able to input and output 5+ A of current for a certain amount of time? Any help is appreciated.
Edit: Since someone asked, I want it to run for a short amount of time (maybe half a second) and it will have a voltage drop of around 15V


texts: What are the correct procedures when someone accidentally touches high voltage live cable and is getting electrocuted?

texts:
Suppose a family member accidentally touches high voltage live cable and is getting electrocuted in the toilet while he is installing lights. The problem with electricity is risk of conduction and trying to save him will get one killed as well.
What are the correct procedures to save him?


texts:
I want to wire a reset switch for my STM32F0 microcontroller. The datasheet suggests the following external circuity to do so:

Connected to the NRST pin is a 0.1uF capacitor and the reset switch. A pullup resistor is included internally in the microcontroller. However, when the switch is pressed won't it short circuit the capacitor and thus cause large current pulses/ interference? (Problems similar to what was found here: https://forums.parallax.com/discussion/110594/button-pull-up-resistor-reset-problem). Should I wire the circuit like what was shown in the datasheet or add a current limiting resistor?


texts: Exact recreation of Xilinx FPGA binaries from source control

texts:
I'm software developer in a small shop where there's only been one EE guy responsible for a series of FPGA designs spanning a decade, almost all of which target the Spartan line, specifically the XC3S5000.

I'm looking for the community's opinion on some of the EE guy's assertions which I find hard to believe:

1.) Many builds must be created and tested (without changing the input files) because a particular binary often fails testing due to "timing issues." (verbatim)

  Me: Is frequent failure of an FPGA design expected and this incredibly slow process considered normal? I can't imagine repeatedly compiling the same traditional software development language and hoping the output will be right *this time*. The HDL seems underspecified if this is the case.

2.) Because the creation process is subject to "random" algorithms (I assume this is placement and routing) it is "very hard" to recreate the binary from just the input HDL.

  Me: Surely there is an initial seed provided to this pseudo-random algorithm which can be queried after a successful build? The exact good binary could then be recreated using the seed later. This seed could optionally be checked in to source control.

3.) Because the Xilinx-provided tools may change (be upgraded, etc.) even if an exact recreation is possible from a known good seed and the old tools, a new set of tools may create a binary which fails testing. EE guy doesn't see any use in investigating how to find the random seed used for a build, and how to provide it to a rebuild.

  Me: How likely is a build to break upon introduction of new tools?

4.) The binary build process disallows any post-build manipulation of the bytes of the binary due to checksumming and the inability to write to a known offset into this binary.

  Me: You can't embed information into an existing binary?

5.) He insists on checking in both the final product and NGC files.

  Me: Is there ever a reason to store NGC files?

Notes:

*FPGA binaries will eventually be stored in a different place, but definitely not in a text-centric version control system.

*We use a fragile version scheme to query what FPGA is currently running in our system. It is useful for software to work around hardware bugs by checking if the FPGA is of a certain version.
We can read both a monotonically increasing 16-bit number and a build date from the FPGA, but these numbers don't sync directly with the version control system in which the binary is checked in.

*I've looked over the following questions already:
What files/directories are needed to recreate a Xilinx PlanAhead project?

List of Xilinx file suffixes (for ISE)


texts: Altium Designer - Should I place ground vias on a ground polygon?

texts:
I am migrating a design from Eagle to Altium and on the Eagle PCB there is a ground plane (polygon) and every pad has its own GND via.

So I placed the ground polygon as on Eagle, and Altium registers all ground connections as made. So I was wondering, do I still need to place GND vias on every pad just as on Eagle?

Is it so that placing the polygon and GND vias help reducing current gain in components?


texts: Driving an LED/Laser diode with a RF signal up to 20 MHz

texts:
I'm trying to design a circuit that will let me drive an LED or Diode laser with a RF signal up to ~20 MHz or so. Since the optical device will need to be biased with a DC current, a bias -t is a natural choice.
I was planning on using a GALI-84+ amplifier from Minicircuits to amplify my RF signal and then pass it into a bias-T circuit, however when I was looking at the schematic for the eval board for the GALI-84+, I noticed that the output of the amplifier is biased using an inductor and a DC supply, before it is AC coupled using a capacitor to the output.

I contact Minicircuits asking if I could remove the coupling capacitor and use this circuit to both bias the diode and amplify my signal at once, but they said:

  The GALI-84+ is an RF amplifier designed to drive 50 Ohm loads. To drive an LED,
  you will need to configure the amplifier conventionally, detect the RF output signal
  using a simple diode detector and use it to turn on a transistor with the LED in the
  collector.

They described the diode detector as, "a series small signal Shottky
diode feeding a 1K resistor to ground", and then connecting the Shottky to the base of a transistor.

So, now I'm confused:

1) Why use a diode detector?
2) Will I harm something if I use the GALI to drive a non-50ohm load directly?

Update Is there any reason I can't use this configuration to drive my LED? Since the amplifier seems to be a Darlington pair, wouldn't this be appropriate for driving a variable current? The non-handdrawn portion is the Gali-84+ schematic from the datasheet.

Update A few details on the specifics. I need to dive a diode laser, with up to 200 mA of current. The laser turns on at about 4v, with 40 mA of current, and will be driving about 200 mA by 5.5v. I need to bias the laser on (above the cut-on voltage) and drive it with an AC signal. So, bias at 4.75v and driving with a +/- 100 mA current, or +/- 0.5v. The diode is extracted from BlueRay DVD players, and as such, I don't have detailed specifics on its behavior.

Thanks.


texts: How to handle low voltage stepper motors?

texts:
So I've been looking at various NEMA-17 stepper motors, and I noticed that a most have an extremely low voltage. For example, on this page, there are NEMA-17 motors ranging from 2.8V to 5.4V, with currents from 1A to 1.7A. However, most drivers, (including this company's own page) can't drive that low. Their 'low-voltage' driver can't run motors with a low current. Ideally, I'd like to use one of the L298N drivers that I have lying around, but their minimum is 5V. Am I misreading something to do with the current and voltage of motors or drivers? Could I just use an L298N even though the minimum is 5V?

FYI I'm using an Arduino Mega. For the power supply, I've got a 12V power supply, 5V power supply, and various combinations of batteries.


texts:
So the parameter beta for a Common Emitter Amplifier is called the Current Gain and is defined as

\$\beta =\dfrac{I_{collector}}{I_{Base}}\$

\$\alpha =\dfrac{I_{collector}}{I_{Emitter}}\$

What is this \$\alpha\$ called and what is its significance?

Like for example \$\beta\$ can be treated as the amount by which a signal is getting modified.

Also maybe a question for meta but why is MathJax differently written for this site?(Answered)


texts: NPN transistor circuit connection, what determines which region it is at?

texts:
I know that for an NPN transistor to be in the active region, the base emitter should be forward biased and the base collector should be reverse biased while for the NPN transistor to be in the saturation region, the base emitter and the base collector should both be forward biased.
This appears clearly in the view of the NPN transistor as 2 diodes put back to back as in this sketch:

I can't understand the case where it is in a circuit as in this sketch:
(had to remove the link due to lack of reputation but it's just the basic BJT circuit)

Assuming there is some voltage on the base. Why do we have to assume it's active and then see if$$V_{be} > 0.7$$ and $$ I_{b} , I_{e} > 0 $$ and check if: $$V_{ce} > 0.2$$ If not then we assume it's saturated and check the same conditions except that: $$V_{ce} < 0.2$$
Shouldn't the condition for saturation or activism(if that's the correct word to use) be the biasing of the base collector and base emitter. What made me think about this is this PDF here page 2, the circuit drawn:

http://web.engr.oregonstate.edu/~traylor/ece112/lectures/bjt_reg_of_op.pdf

They're using it as it will always be in saturation mode although I see the base emitter is forward biased while the base collector is reverse biased so that suggests an active mode not saturation one.


texts:
I'm designing a relay-driver board with 15 double throw relays.

I'm using shift registers to save IO-pins on the CPU. The shift registers feed into darlington ST ULN2003A transistor arrays: http://www.ti.com/lit/ds/symlink/uln2003a.pdf .

During bootup, I'm thinking about arranging so that output-enable on the shift registers is disabled.

This should be safe, right? There's no way a darlington transistor will start conducting when the base is floating? With MOSFET I know it wouldn't really be stable, since the MOSFET gate could keep a charge for a long time. But it should be safe with bipolar transistors, right?


texts: Why can't this mixer be built with two resistors?

texts:
Disclosure: This is for the MIT Circuits MOOC on edX.

The task says build a circuit such that Vout ~= 1/2 V1 + 1/6 V2. Now I understand the solution, which uses three resistors.

However, I'd like to understand why it can't be done with two resistors.

For example, if it was modelled like this (but with the top resistor R2 and the bottom R1):

Then, by using superposition, can't you say:

Vout = aV1 + bV2 where a and b are some coefficients by reference to the resistors.

Then you could make a = R2/(R1+R2) = 1/2, and b = R1/(R1+R2) = 1/6 ? And solve for R1 and R2. I know those two simultaneous equations can't be solved, but I don't understand why and how that fits into the theory of the circuit.


texts: Circuit to protect Saleae input from high voltages

texts:
I was browsing OSH park's shared circuits when I saw this:
Logic Analyser Buffer.

Since a true 12v RS232 signal will exceed the Salese's voltage limits, something like this could be useful. The diode and resistor seem straight forward enough. The three pin device I assume has a zener in it that shunts current to ground if the voltage exceeds 30 volts.

The part in the picture is labeled 215, but I can't figure out what it is.

If I can figure it out I was going to make a version of this which plugs directly into my Saleae. Or perhaps one with a DB9 tap.


texts:
An analog video camera has this connector.

9.4mm, sting hole much thinner than in RCA (but still too thick for a copper core); has 2 bumps (or whatever they're called) on its sides (turning lock?). No screw thread.


texts: Alternative to voltage regulator S81250HG

texts:
I'm fixing a device that is using this S81250HG voltage regulator that takes 9V as input and has an output of 5V. But this regulator seems to be fried. I'm measuring and it gets 9V on the input but nothing on the output. But I don't have the same model to replace it and see if that is the only problem.
However, I have lying around a 5V voltage regulator: L7805CV. For what I see it can also take 9V and regulated it down to 5V and it has 3 pins too (even though they don't have the same distribution, but I wouldn't connect straight to the PCB).
I was wondering if I could use this L7805CV voltage regulator as an alternative to the S81250HG or it could cause any issues. At least to see if the device turns on. And then I would look for a proper replacement.
Updating with a some more information:
The device I'm fixing is a Sony Discman D-50 (D-5 in the US). Here you can find a copy of the service manual.
If you check on page 17 of this document you can see the part of the DC input and voltage regulator:
And also on page 26:
Thanks!


texts: Is my circuit analysis correct in this problem?

texts:
This is the problem:

My solution:

I'm new the delta-to-y and y-to-delta transformation, it is obvious we need to use them. I got the same answer but I'm a bit skeptical about my solution.

Is my solution and analysis correct?


texts: Why are all log amp examples with common base logging transistors?

texts:
I am not experienced with log amps, and am trying to learn about them.

Every log amp article has the base of the logging transistor grounded.

simulate this circuit – Schematic created using CircuitLab

Why not have the transistor as set up as common collector or common emitter?

simulate this circuit

or

simulate this circuit


texts: Writing extra data causing Arduino Mega 2560 to miss sensor data

texts:
I am working on a project that requires data from 3 different sensors and syncing is necessary. The first sensor(HX711) is relatively slow proving 80 samples per second. The second sensor(MAX30101) works at around 200 samples per second. The third sensor(BMD101) works at around 500 samples per second. The third sensor is the one I'm currently having issues with.

I thought of timestamping the data and syncing them up using that. The problem that I'm facing is that when I add any small serial print along with just the third sensor data, I seem to miss a lot of data from the sensor and get checksum errors.

Here is the code I used to test this,

uint8_t inByte;

void setup() {
  //Set up Serial Ports
  Serial.begin(57600);
  Serial1.begin(57600);
}

void loop() {
  Serial1.readBytes(&inByte, 1);
  //Serial.write("E");
  Serial.write(inByte);
}

The BMD101 is connected to Serial1 of the Arduino Mega 2560 and the PC is at Serial. When I uncomment //Serial.write("E");. The data I receive is missing many bytes and I never receive the complete package, only checksum errors.

I don't just need it to be able to print a single character along with the data, I would like to have it print timestamps and data from two more sensors. How would I do that?


texts: How much current is consumed by an avr analog sensor?

texts:
I'm trying to measure a small analog device that emits about a volt (I believe up to 5V, but I've not measured at extremes yet) AC.  I rectify the reading to DC, but I'm really interested in getting something a bit smoother out of it because I just want to know approximately what it's doing.

I'm looking to size a reservoir capacitor, but that requires me to know how much current is actually flowing through this circuit.  I assume it's non-zero, but must be somewhat close to that.

I can compensate by just taking a few samples and picking the biggest one, but I'd like to be able to just take any given sample and have it properly represent the current state (in practice, "current" is on the "second or so" scale).

I've seen RMS ICs, but I don't really want to add another $10 to the project when I've already got a reasonable workaround.  More importantly, I'd like to understand the stuff I'm working with a bit better.


texts: Virtual ground before or after low noise LDO?

texts:
I have two boards (microphone amplifier and speaker driver) that require +/-15 VDC. The max current required for the boards is 500 mA. Since low-noise dual power supply devices are hard to come by, I'd like to modify my system to accept a single power supply. Ideally, what I'd like to do is design the following chain:

Input from the AC mains would be via a high-end SMPS (with switching frequency in the MHz range) with an output of 36 VDC.
A virtual ground would be provided using a TLE2426. A current boosting BUF634 feedback loop to get up to 250 mA as described in https://tangentsoft.net/elec/vgrounds.html would be used. Note that this can be stacked with a second BUF634 to get up to 500 mA. This would provide +/-18VDC rails.
I would then use LT3090 and LT3045 LDO regulators to further drop the voltages to +/-15VDC rails that feed into the board. The LDO regulators are very high PSRR devices with ultra low noise outputs.

Questions:

To minimize cross-talk between the microphone amplifier and speaker drivers, each device should have their own power rail splitter and LDO regulators (this is also necessary because of the max current capabilities of of the regulators and buffers). Can they share a common SMPS, or should each have their own?
Should this setup work well for powering devices that work in the frequency range 100 Hz to 100 kHz (this is for auditory research experiments at a university, so we have to deal with frequencies above the audible range of humans as well)?
An alternate approach would be to use the TPS7A47 ultra low noise LDO (which can accept up to 36 VDC input). In this case, I could then use the following chain: SMPS -> TPS7A47 -> TLE2426 + BUF634 -> board. However, would this be OK or would there be higher noise in the circuit due to placing the TLE2426 + BUF634 after the LDO?


texts: Sensor Polling via USB-RS485 Serial Interface stuck at 16ms, even though it should be faster

texts:
I have a setup, connecting a Razor IMU sensor board, with a RS-485 Breakout board, to a USB-RS485 Serial Interface via USB-cable into my laptop. I run a software on the laptop (Max/MSP) that sends out polling messages to the sensor, waits for the response data, and on receiving the response triggers automatically a new polling message. It's a constant loop:

send out a polling message
wait for a response
on response go to 1.

I want this polling to be as fast as possible, as i'll have to hook up 21 of these sensors to the same RS485-bus. The firmware on the Razor is programmed with the Arduino IDE, and according to the code there should only be a ~2ms delay between the polling message and the writing of the response. The firmware also spends 12ms every 20ms on sensor-allocation-and-calculation. This calculation sometimes delays the response to the polling. I am aware of that and all results are accordingly.

My problem right now is that the polling of the sensor is stuck at an update-rate of average 15 milliseconds. I looked at the data with my small usb-oscillosope and made a diagram (>PDF).

My oscilloscope sits directly on the USB-RS485-interface and sees the polling go out, and the response message come in. The delay between these two lies between 2 to 13 ms. This difference is explainable with the fact that sometimes the razor is busy doing its sensor-math-calculations. The weird fact is, that even though the responses come in with different delays, the polling always seems to go out at the same interval of about 15ms.

We also implemented the same setup with

coding the firmware in C and programming the Razor with avr-dude
doing the software-polling in Python code
on Mac OSX and PC Windows 7

All possible combinations resulted in the same 15ms interval. So the problem is neither in the Arduino-code, nor within Max/MSP. I have the suspicion that the problem could be due to the USB-RS485 Serial Interface and/or the necessary FTDI driver.

Does this problem sound familiar to anyone??


texts: Please help me what the point I had wrong

texts: I want to find the power across each components in the circuit but the summary of power that I can find It’s not equal zero. I don’t know what do I wrong. I’ll appreciate if you can help me.


texts: Is it possible to solve for the values of this grid of photoresistors in software?

texts:
In this question a circuit was set up as shown:

The idea is to power the rows one at a time, and read off the voltages of each column. But there's a subtle problem. There are alternate paths to ground through other photoresistors, meaning the value of other photoresistors will affect the voltage across the photoresistor you're trying to measure. One solution is to put a diode in series with each photoresistor. I'm wondering if there's a way to solve this in software using math.
After scanning through each column and row in the above circuit, you'll have 12 measurements. There are 12 resistances to determine. Can this system be solved? If so, is it also solvable for an 8x8 grid? Would solving it on an Arduino be feasible?


texts:
Different scientific publications [1,2] mention that DDRx memory has a (data) retention time of 64 ms while on average each cell is refreshed every 7.8 us (tREFI). I want to know where this information originates and I was looking into the DDR4 SDRAM Standard (JESD79-4B) but it does not mention anything about these 64 ms. Also, I couldn't find anything about these 64 ms in earlier DDRx standards.
Where is the data retention time of 64 ms defined? For me, it looks like this is something that the DRAM vendors guarantee for their products (e.g., [3]). However, this raises the question why 64 ms and not more or less? I guess that is again due to the DDRx standard?
References
[1] Section 2.2, paragraph 1: https://dl.acm.org/doi/pdf/10.1145/2508148.2485928
[2] Section 1: https://dl.acm.org/doi/pdf/10.1145/2637364.2592000
[3] Page 1 (left column, 5th item): https://www.micron.com/-/media/client/global/documents/products/data-sheet/dram/ddr4/4gb_ddr4_dram_2e0d.pdf


texts: What's the meaning of this marking on this old transformer?

texts:
I'm studying this old power supply, and it has an odd marking on it (probably not, but it is for me).
I'm guessing it is: output in the range [-17v, 17v]
with the possility of having different input voltages, am I right?
What does the S mean ?


texts: Why does an arduino need 7V if it uses 5V?

texts: The recommended voltage for an arduino Vin is 7-12V. The Vin can't be outside 6-20V for proper operation. If Arduino uses 5V on its rails and for its logic, why is 7V needed?


texts: DC voltage at the output of push pull stage

texts:
I have an output stage. The circuit diagram is as shown:

In DC condition, the node X has a DC voltage of Vdd/2. The node Z has a voltage of about 1.26 volts. Vdd = 3.3 volts. Transistors M7 and M5 have same W/L and so is the case with M6 and M8. The current through both the branches is the same around 50 uA. Both X and Z nodes are unloaded, i.e open. Now here are my questions:

Why does node X settle to vdd/2?
Why node Z does not settle to vdd/2?

Here is my attempt at the solutions:

Considering the output branch, Id will be the same through M7 and M8, if both are in saturation then the standard equation \$ I_d = K(Vgs-Vth)^2 \times (1+\lambda Vds) \$.
Since Id is the same, Vgs for both the transistors is 1 volt, \$\lambda \$ is negligible because the channel length of both the transistors is long. What remains is the factor K and Vth. Unfortunately i cannot find the technology values hence I would like to know whether this analysis is correct so that i can blindly blame K and Vth :). If that is true then somehow all the values come together in the branch with node X to get X at vdd/2.
Second line of thought are the caps Cds of M7 and M8. they are in series and using the capacitor voltage divider rule, the voltage at node Z and similarly for ode X can be estimated. I checked the capacitance but the voltage at node Z and X do not check out with this theory.

Any help will be appreciated.

Edit:
Also if i consider the first line of thought, that since Id is the same in the output branch, therefore M7 and M8 will force the voltage at node Z such that Vds for both transistors are enough for the current of 50 uA to flow. If thats the case, then what needs to be changed (w/l, bias current) to get node Z to vdd/2


texts:
We are designed and printed the PCB of the stm32f103c8t6 blue pill board as per stm rules..
After fabrication and assembly finished, we connect the board to Keil software and device detected and the program also uploaded perfectly... we faced some problems listed below...
1.ADC value varied in the difference of ( + or - 50 ) ..total range is (0 - 4095)
2.we crossed checked the program with stm bluepill ( amazon board )..it works fine...but our pcb boardADC
value varied...it means program is good and hardware is something wrong.
3.we removed the crystal oscillator (8Mhz) in our board..ADC value works fine in our board.
Anybody kindly helps me with this problem..?
I have attached below the schematic layout image..


texts: ESD protection: clamp to 12V or derived 5V?

texts:
I have an input connector which provides 12V power, and a few 5V logic lines. The 5V Vcc is derived from a local regulator:

simulate this circuit – Schematic created using CircuitLab

What's best practice for ESD protection on this input connector? I'm thinking clamping diodes between the data line(s) and the power rails, but which rails?

clamping to the 12V rail would subject the logic to a higher voltage
clamping to the 5V rail would subject the regulator to the ESD

Alternately, do both? Or lose the 5V regulator and bring 5V and 12V in on the connector?


texts: How to protect bistable latching 2 coil relay with diodes?

texts:
I know that a revers diode is required to protect a DC coil relay.

But to protect this relay RT314F05? It has 2 coils, are 2 diodes enough?


texts:
We have designed a board for mass production . This board has a few components on it, that works with 3v3 , such as MCU, Wi-Fi, and a few more sensors.

We used to have a battery, 3.7v to power the board directly, and later on, we have decided that we must use a regulator, because its more safe .
the regulator is AMS1117

After some research, we found out that this regulator(and others) must have 1V more in its input,relative to its output .

So, using a battery pack of 3.7v lithium, will not work properly for such regulators(3.3v) , even when its charged with 4.2v .

We found out that logically ,connecting the battery directly (no regulator) to the board is much clever, because you can "enjoy" the battery power as long as it is > 3.3v  .

Our only concern is that we are not using a regulator, and its not healthy .

Is that a good thing to do- "professional" ?

do you think of more options,such a zener diode instead of a regulator ?


texts:
I have a 12-24 V dimmer for LED strips like this:
https://www.circuitlab.com/editor/#?id=c8m48y

simulate this circuit – Schematic created using CircuitLab

I want to understand a couple of issues about it:

Does it utilize only 1 channel of LM358?
Copying the schematic analogous to R4, VA1, R5, R6, R7, Q1 and MOSFET to a second channel (unit) of LM358 I can get the second dimmable channel for another LED strip? If yes - would it be also up to 8A?
I can use the same output after R2 as a negative input to the second channel of LM358?
What is the PWM frequency? \$ 1 / ( C3 * R2) \$ or \$1 / ( C3 * ( R3 + R2))\$ ?

Thank you!


texts: Can two IRLZ44N MOSFETs in parallel handle a current of 20 A without heat sink?

texts:
Can two IRLZ44N MOSFETs in parallel handle a current of 20 A without a heat sink?
The Vgs command is a square wave at a frequency of 70 Hz.
Do I need to attach two big heat sinks or not?
Will my two MOSFETs without a heat sink burn out after some time?
The duty cycle is 50%


texts: steady state voltage in capacitor network

texts:
simulate this circuit – Schematic created using CircuitLab
I have this capacitance network in my circuit and I can't figure out the math behind why the final steady-state value of Vx=0.542v when SW2 closes to the other position. Coincidentally I found out this is Vx - 1.(c2 /(c1+c2+c3))  but I would like an intuitive approach. Please ignore the absence of resistance in the circuit to make it practical.


texts: Does it matter if differential pairs have no reference plane or cross reference planes?

texts:
More specifically, does it matter on a PCB if routing differential pairs if they cross reference planes?
Do they need a reference plane?
Is there even a reference plane with a differential pair?

I don't do many high speed designs, when I have in the past, I make the routing as short as possible between high speed connectors and PHY's so I don't have to worry as much about matching, transmission line effects, ect. I have also used a continuous ground plane in all cases. But now I'm wondering...

My intuition tells me that a continuous ground plane in the case of a differential pair is not a big deal because there is little or no return current, so the only thing that matters is ensuring that the lines are matched.

A reason not to would be cross coupling of noise through capacitance into the differential pair, but noise will appear equally on both pairs (if the capacitance is the same on both pairs) and subtracted out.


texts: What should the capacitor values be for the 2n3904 transistor to operate in the mid gain?


texts: Does the size of the data bus control the maximum value the CPU can process?

texts:
I know the data bus size defines the size of the processor, but can the processor actually process data above that limit?

Would really appreciate some explanation on this.


texts: How can I find out a components voltage rating and amperage draw?

texts:
I bought a whole bunch of components for mounting on a circuit board (I'm new to electronics and I'm just experimenting at the moment) - things like LED's, small microphones, buzzers, very small speakers, motors,  displays, IC's, Op Amps, etc.

I'd like to know the method for finding out what the power requirements for each component is.  What tests can I do with my multimeter to determine the needs of each component without damaging the component?

The only method that comes to mind (with my limited knowledge) is to attach a DC power supply, such as a 9V battery or a 4.5 V battery pack and run the current through a resistor in series with each component, starting at very high resistors (MΩ) and working my way down to less and less resistance, all the time monitoring the component to see of it is operating.  This seems very imprecise and is just trial and error until I get in the ballpark of what each particular device needs.

Is there a better way of doing it?  Does it have something to do with measuring the resistance of each device?

I know I can use Ohm's Law for V/R = I where V = voltage of battery pack and R = resistance of component, but that doesn't really tell me the requirements of the component - or does it?  The motor for instance runs on 2.8V and 8.2V - just faster in the 2nd case.  Things like the displays are much more prone to damage and I can't just run some random voltage through them and hope for the best.


texts: What are the errors with using only the line from a socket to power an appliance?

texts:
In the diagram below, the image on the left shows how a plug is normally connected to an outlet.

The image on the right shows how the socket is replaced by a new configuration. One of the holes on the original socket is used and connected to a transformer, while the other plug is connected to the ground to create a circuit. The rationale for this is: when I used a voltmeter to connect the socket to the ground, I was able to read 110V. Clearly, there is some voltage you can draw from just one hole of the socket.

The voltage is run through a step up transformer, creating 220V. This is used to create a new socket. One of the holes is connected to the ground, while the other one is live.

This entire setup clearly looks incorrect to me, but I don't know the specific reasons why. I created a setup that looks roughly like this (using a voltage regulator for the new socket, and using a long line to plug the wire in cemented ground far away from me) and it was able to charge a power bank, but it couldn't drive an electric fan forward -- the blades started spinning, but very very slowly. There were no fires or electric shocks experienced by anyone.

But, I don't understand why the setup worked in the first place. It seems to me like it shouldn't have worked at all.

My question is, What is wrong with this design, and why did it sort of work?


texts:
I'm making a circuit with this PAM2401 IC to get 5V from my LiPo cell. Its datasheet calls for a low DCR inductor (on the "inductor selection" section). How much DCR can be counted as "low"? How much is the scale we are talking about?

I accept answers in general since this is a general doubt of mine too, but I actually want to know specifically for this project.


texts: Modelling differential amplifier input circuit

texts:
I'm trying to understand the behavior of a filter connected between a mixer and fully-differential amplifier. Here are the relevant portions of the schematic. The first part is the mixer output

5VF is 5V. And here's the input to the FDA.

The amplifier is the ADA4940. I was able to track down a spice model for the ADA4940, but unfortunately I'm having trouble getting Ngspice to accept it. So, instead, I'm trying to design an input circuit that looks roughly equivalent from the perspective of the filter. Here's what I've come up with:

The voltage source is the mixer output, then everything up through the 10n caps is part of the filter or mixer output bias and then everything to the right of that is meant to simulate the amp input. I've used \$50M\Omega\$ resistors for the dividers because this is the reported common mode input resistance from the data sheet (I guess theoretically since the resistors are in parallel, the 50Mohm should be the combination of both in parallel, not each individually, but this value doesn't seem to affect the simulation much). The dividers also set the common mode input voltage to half the supply voltage. The data sheet also says to use twice a single gain resistance for the differential impedance, hence the \$2\times 549\$ value.

When simulated I get the gain and phase response shown here, which is more or less what I'd expect given the desired pass frequency range (about 30kHz to 1MHz).

and zoomed into the passband

Have I correctly described the diff amp input circuitry for this simulation?

Separately, the ADL5802 mixer datasheet says to use pull-up chokes, but this design uses pull-up resistors. I tried to simulate this with inductors instead of resistors but couldn't get the simulation to work. Why were resistors chosen here in place of inductors? Is there any downside to using the resistors? Why would the datasheet insist on inductors when resistors seem to work fine?


texts:
I have this 5 V output SMPS I bought a while ago. I was wondering why there are LCRs connected to the input of my SMPS. I don't understand why it's there.

BTW, I'm an electrical engineering student, and I know the basics of LCR, but I am not sure what it's doing here.


texts: Do these fluorescents contain ballast and starters?

texts:
I will probably buy some used fluorescent lamps to grow vegetables indoors for my project.

As I am aware fluorescent lamps need ballast and starter. I don't have experience with fluoresent lamps and I don't know if these used ones contain it as seen in picture.

I need to know what else will I need to make them work except cable and digital electric switch.

Edit:

I haven't got more photos, I haven't bought them yet, just looking at them in online marketplace.


texts:
I am designing a thermistor circuit to determine if a nozzle is becoming plugged or flowing freely. My idea is to use a low resistance thermistor and resistor to form a voltage divider that when powered would become hot, and immerse that into the stream of water. The water flowing by with the nozzle unplugged would keep the thermistor cooled to a certain temperature and when the nozzle started to become plugged the flow past the thermistor would decrease and allow the temperature to rise.

I am looking into designing the circuit and buying all of the parts but I have absolutely no heat transfer experience and don't know how sensitive the circuit needs to be. To have a low enough resistance so the circuit actually heats up I am planning on using a 33 ohm bias resistor and a 33 ohm thermistor.

So my question is how do I calculate what voltage I would need to feed into the voltage divider to heat the circuit up to say 100 degrees C, and how do I calculate say how much heat there would be dissipated if the thermistor at 100 degrees C was immersed into a 3/8" diameter PVC pipe with a flow of .5gpm?


texts: Negative consequences use epoxy glue to fix lifted SMD trace/pad

texts:
What are some unforeseen side effects using glue to fix SMD pads and traces that have been lifted off from the PCB board. It was for 0406 caps, the cap is soldered on the pad but both pads are lifted off the board and hanging like a bridge. About 2mm of trace after the pad was also lifted. We rejected the boards that are damaged, but the fab house send it back to us after they fixed. They poured epoxy glue over it to fix it. Doesn't anyone know any side effects that might arise from this kind of fix??

Thanks for your help!
Ping


texts: Simple Servo Control Issues with PIC and ICSP

texts:
simulate this circuit – Schematic created using CircuitLab

I have a project in which I am controlling/trying to control a Carson CMS-1 servo using a PIC.

I have a board set up with a 7.5v 1A dc supply going through a 5V regulator to power the PIC and servo.

I have generated a software PWM at 50Hz as per specification.

I have connected the output pin - RC4 of the PIC16F72 to a transistor C547B which switches 5v to the signal line of the servo. There is nothing else connected to PIC except the 4MHz oscillator, 9k pull up on MCLR and ICSP pins.

The PIC is programmed using a ICSP interface and a Pickit 3.

The circuit works fine when ICSP is connected to Pickit 3 however when the Pickit is disconnected the PIC gets very hot and the circuit fails to run.

I have looked online and seen PIC's connected directly to servo signal line and also through a transistor.

I assume the signal line requires more current that the PIC can supply so the PIC gets hot and programme fails.

Does anybody have any ideas as to where I am going wrong? I have changed the circuit a few times to reflect different schematics I have seen and always found the same problem. Does the Pickit affect the power on the PIC? I thought the Vdd and Vss lines on the Pickit were simply to detect if the device was powered.

edit: I mentioned the Vdd and Vss lines on the ICSP connection because the circuit works when all other connections are removed except these

edit: I dont have a schematic drawn but circuit is similar to http://www.pyroelectro.com/tutorials/servo_motor/parts/schematic_large.gif

edit: power from Pickit 3 is deselected.

edit: Schematic drawn and added. (thanks for pointing me to the tool)

edit: note added to schematic

edit: image added. Same problem occurred when using a different breadboad. One link removed

edit: Circuit diagram now amended to show functioning circuit. With separate power rail +5V for servo and decoupling between Vdd and Vss.


texts: How to calculate the cycle time of pipeline

texts:
I have an 8-stage pipeline (IF,ID,OF1,OF2,OF3,Ex1,Ex2,WB) with respective stage delays as 5ns,4ns,10ns,6ns,8ns,11ns,9ns,13ns respectively. The interstage registers have delay of 1ns.

I think here the cycle time must be 13ns, that of WB stage.And since we don't need register after WB stage, we don't need to add register delay.

Am I correct in my reasoning.

I am new member here and I am preparing for an exam.I got across this question and wanted to ask about it.

Please help.


texts: Lower Voltage of 15 VDC Power Supply to 13 VDC for DC Blower

texts:
I have a centrifugal blower, model 007-A42-32D, that uses 12 VDC at 17.5 amps. The performance information provided by the manufacturer, SPAL Automotive, was acquired at 13 VDC.

I have a power supply that provides 15 VDC at 20 A. I feel that applying 15 VDC to the blower, given that it will be subject to continuous duty, may cause premature failure.

Question #1:
Is applying 15 VDC to a blower that was tested by the manufacturer at 13 VDC problematic?

Question #2:
Will someone please provide to me the simplest method of reducing the voltage of the power supply using electronic components?

Thank you to all who help for your time.

edit:
I understand Voltage is the product of Current and Resistance as in V = IR. Since 12 VDC power supplies capable of 17.5 A minimum are not cheap, if the placement of a resistor can allow my 15 VDC power supply to work, that is the most sensible choice.

Given V = IR, if I = 17.5 A, then R must equal the equivalent series resistance of the blower combined with additional resistors such that V will equal 12. Is that correct?


texts: What's wrong with this Wheatstone bridge?

texts:
I was trying to solve this unbalanced Wheatstone bridge and found that the current $i$ in the mid wire is 9A .This result was achieved by using node voltage method.

Then I rearranged the same circuit to the form shown in the second image.

and at this point I flipped the right half of the circuit so as to obtain the equal resistors on the same side.

now I again rearranged the circuit as shown.

Here, the final circuit  is a balanced Wheatstone bridge and thus the current i must be 0.

So clearly something went wrong in there.

I saw a post a quesiton before this one just to make sure that there is no mistake in rearranging the circuit in the way I have done.

It was answered by the user PhillipWood as being correct and was unfortunately put on hold.

So can someone please point out what exactly went wrong with the above method.


texts: Received a new Tektronix AFG1022 function generator, I would like to see if I could output a higher amplitude using a transformer or amplifier

texts: I'd like to operate in a 0-12 V range, I would like to see what the best option would be to increase the voltage at the output. Our maximum frequency is 1Hz if there may be an issue with attenuation.


texts:
I am currently working with few 150 W SMPS designs for industial applications with heavy transient load condition. Current design works well by mean of line/load regulation and device reliability but facing some issues regarding transient loads, say 500 Hz to 1 kHz 50% to 100% load transients. It can't maintain output voltage and faces very large voltage dip.
I had tested some reputed brand SMPS, they have very good response in such load conditions without stability issues. Only change I notice was, they use op-amps in feedback loop, while I use TL431.
My questions are:
Is TL431 have any limitation over op-amps?
If I want to replace TL431 with op-amp, on which characteristics of op-amp should I focus while selecting?


texts:
I did read several questions about safely probing high AC voltages with an oscilloscope.   I had been taught to isolate the scope, which I see now is dangerous.  So I think what I should do is then use an isolation transformer between the DUT and the 120VAC wall outlet.   My question is then if I want to measure say just the AC voltage waveform can I just connect my ground clip to the isolated neutral and my probe tip to the isolated line?   Assuming both probe and scope input can take the voltage?

Or do I need another transformer between isolated neutral and line and the scope?


texts: Properly simulating a NAND gate? (I'm building a computer in my computer)

texts:
I am about to embark on a project, enspired by Nand2Tetris (http://www.nand2tetris.org/), to fully simulate a computer, building the entire thing up from NAND gates.

I want to simulate everything from scratch, starting with a primitive implementation of a NAND gate that simulates how a NAND gate would work on the physical level, and then connect them together to build a computer.

The thing is, I don't understand enough about how a NAND gate would work on the physical level in order to write this.

To be clear, this is certainly not what I am looking for:

def nand(a, b)
  return !(a && b)
end

I'd like to implement the NAND gate as a class, so it functions more like an actual object.  I'd like it to have pins, and I'd like to be able to connect the pins together and apply voltage, etc.

Can someone show me how you might implement a proper simulation of a physical NAND gate, one that could be linked together to ultimately build a computer?


texts:
I am having this Current probe

I am using this to measure the inductor peak current.

Inductor is rated at 2.05A.

Schematics :

Input Voltage to the converter during measurement is 7.5V

I am setting this current probe to 100mV/A division and upon connecting it to the scope, I change the probe setting ON SCOPE to be 0.100V/A.

I am getting this waveform :

Could you please tell me how to perform the conversion?

Or is the peak current (upon start-up) 7.8A as shown or is there some conversion. Can someone tell me how to perform the conversion?

I am thinking that there is a conversion because the inductor would get damaged if 7.8A flows because it is only 2.05A rated?


texts:
I have setup a step down transformer to transform my 115v AC down to 5v AC. I ordered a transformer and hooked it up in parallel (there are two coils) and my oscope is showing 10v on the output side. There isn't any load on the circuit. Is this similar to show an unload DC circuit will show higher voltages when not loaded.

Thanks in advance!

Cheers,

Gregg


texts: High powered driver for 10W and 45W LEDs

texts:
I have 8 x LZ4-00B200 (14V, 700ma operating) and 8 x LZ4-00R200(9V, 700ma operating) which I would like to wire off of one power supply.

My problem is two fold. First, how should I organize the 16 LEDs? 16 in series? 8 in series in parallel with another 8 in series?  I'm not sure what is best.

Second, what driver can I use to power all 16 LEDs? I was looking at some of the LED drivers from Recom but I'm really not sure which one I need.

I successfully designed a few lights with the Recom drivers using 8 LEDs but I couldn't design one for 16. Any help would be appreciated. I actively give up votes


texts: PIC12F508 "Calibration value is invalid"

texts:
We use PIC12F508 chips by the tens of thousands.  We normally purchase from people like Future Electronics or Arrow.  However, I see that our purchasing people are now buying 12F508 chips from someone whom I am not familiar with: Technoshack in Ontario, Canada.

Most of the places where we use this PIC controller do not have stringent timing requirements.  The native accuracy of the internal RC oscillator is entirely adequate.  Quite frankly, even an uncalibrated RC frequency is adequate.

However, a few projects / products do need the native accuracy of 5% or better.  This is never a problem when we load the calibration value that is programmed in the factory.

My problem arises with the last two batches of chips supplied by Technoshack.  These arrived in sealed bags with Microchip tamper-evident seals.  However, MPALB reports that the chip calibration value is invalid.

I've checked with two different programmers: PICstart Plus and PICkit 3.  Both report the same error.

I spot-checked one chip from each of 30 or so different rails.  All have the same problem.

I'm not sure how to go about dealing with this.  Obviously, I need to get Microchip involved but I'm not sure who to talk with.

Guidance appreciated.


texts: Inject energy on a RLC circuit to mantain a sinusoidal

texts:
I want to design an ideal RLC oscillator that generates a sinusoidal voltage and current waverforms. To accomplish this I must provide the energy lost in the resistor. I want to do it from a DC voltage source as simple as possible (with a simple switch?).

How can this be accomplished?


texts: Why do I need PWMs on Arduino but not on ATMega16 or PIC16 to drive the stepper motors with L293d?

texts: Seems to me , I'm lacking some concepts here. From what I know is that PWMs pins are essential for driving the motors (as they can drive the motors at different speed with diferent duty cycle). So actually I wanted to drive 4 motors with a single Arduino uno but couldn't as it has only 6 PWMs, but with ATMega 16 looks like they don't have a condition on the PWM. Why is so ? or I am lacking some concepts here ?


texts: Determine polarity of IrED with multimeter

texts:
I have an infrared LED as part of an IR transceiver, and I want to determine its polarity. As the device is unmarked, finding its datasheet is out of the question. And, as it is infrared, seeing it light up is also out of the question.

Using my multimeter on its diode setting, I connect the positive multimeter lead to one of the device pins, which we will call pin 1. I then connect the negative multimeter lead to the other pin (pin 2). Doing this, I measure a voltage drop of ~1.3v. I then swap the leads and measure a drop of ~0.5v. Unfortunately I do not know what to do from here, as both directions give me a reading.

Based on these readings, is it possible to determine its polarity? And if so, what IS the polarity?

Thank you for your time.


texts: Thevenin equivalent in a nonlinear circuit

texts:
Is it possible to use the Thevenin equivalent of a voltage divider driving an emitter follower?

simulate this circuit – Schematic created using CircuitLab

In general, when is it safe to use the Thevenin equivalent of a source if it is connected to nonlinear components? Common exercises always imply a resistor as the load.


texts:
In my aplication I need to use a galvanic isolator DC/DC convertor. One parameter in the datasheet (of DC/DC convertor) specifies that maximum capacitve load is 220uF and maximum mA output is 200

However in my application I need about 900uF.

Can I use a DC convertor ---capacitor 100uF--- and then LDO with current limiting (at 150ma) and use as much capacitance I want after the LDO  ?


texts: Tips for reliable card edge connections?

texts:
I'm considering a redesign involving moving from maintenance-unfriendly mezzanine connectors for daughter cards to a real backplane with card edge connectors.

I like how easy and physically robust card edge connectors are. I'm a bit worried about reliability, though.

My environment should be generally sealed, but with high temperature cycling. (inside a NEMA 4 enclosure, but located anywhere from hot deserts to frozen tundras)

I've read that a thicker gold plating on the gold fingers isn't that much more expensive and adds considerable life. Is that good enough? These units need to live in the field for a long time.  (10+ years)

How about upgrades? Can I expect to be able to leave a unit in the field for years and then install an expansion card in a slot that's been unused that long? How about when replacing a card with another one?


texts:
I can't seem to find an answer to this, or the answers available are too advanced for me to understand.

I have an AC source 0VAC-40VAC.
I also have a buck converter rated at 6VDC-24VDC input, and 5V output.

To connect the two, I've soldered 4 diodes together to convert VAC to VDC. I have put a 50V capacitor at the output. But my question is, how do I convert the DC source (after the rectifier) so that it caps at 24 VDC? If my memory serves, the Vrms is what comes out of the AC source and so the DC out of the rectifier is the same as the Vrms minus 0.7 (diode) multiplied by 2? Do I add more diodes in series to drop the voltage from 29VDC (0.7 x 40V) until it drops to 24VDC?

The problem is I can't measure because the AC source is not at a constant voltage, it goes anywhere between 0 and 40 at any time.

Please point me in the right direction to figure this out.

Thanks for reading.


texts: When I turn off a servo how much do torque I need to rotate it?

texts:
I'm designing the actuation of a throttle for an engine.I thought to put a servo to move the plate.

Very interesting are the smart servos used for the robotics(for example dynamixel AX-12W http://www.trossenrobotics.com/p/ax-12w-dynamixel-robot-servo.aspx).

I need that when I push the shutdown button(for emergency) the plate of the throttle returns to the idle position.The throttle already has two return springs.

I have some ideas to calculate the right reduction to move the plate when the servo is powered on but where I can find the torque value that i need to rotate the servo when it's powered off?

If I knew that value I'll know the right spring constant.

Thanks


texts: A question about interpreting and reducing high frequency noise in a low level square wave

texts:
As a part of a circuit the output section of the circuit is as follows(C1 is actually 10u):

The input is a 1kHz 0V…5V pulse train coming from the output of a 74HC74, and the output is a square wave around 10mV pk-pk.

Here are the input signal in time domain and its FFT:

And here are the output signal in time domain and its FFT:

I have questions about interpreting and reducing noise here.

1-) The FFT of output signal has two high freq. spikes. How can we interpret it? Does that mean it has 500kHz and 750kHz high freq. noise?

2-) Is it possible to eliminate those high freq. noise by not effecting the square wave form much? The output will be sampled with an ADC less than 100kHz sampling rate. So do I still need to eliminate that high freq. noise


texts: Assign one audio input to multiple outputs

texts:
I've been interested in electronics for couple of months now so my knowledge is still very limited. I like microcontrollers so I'm trying to include them in my projects.

I'm trying to build a similar device as Millenium HP4 but with 8 channels. Idea is to have 8 inputs and to map them freely between 8 outputs (you can combine multiple inputs). There are a lot of great articles about splitting, mixing, combining etc. audio signals.

I am stuggling to find a component which can assign one signal input to 0..8 (or 0..16 if available, for stereo sound) outputs. It can be controlled with i2c or simple address inputs (I can control with for example ATMega328p and ATTiny85 slaves).

I'm looking for something like MC74HCT4851A demultiplexer but which can output to multiple channels simultaneously. Seems like I can't find one.. Any recommendations or other ways I can achive what I want?


texts:
I am a beginner in the electronics so please bear with me for this question. You can see two Voltage sources (V1 and V2) and one Current source (I3).

When we start solving the circut, we replace the Current source (I3) with the Voltage source (V3) and we draw three currents going clockwise. But, shouldn't the last current (Iiii) go counterclockwise? Thank you!


texts: Data path timing vs control store subcycles

texts:
Are two clock cycles, one at microarchitecture level (data path clock cycle) and another at control store memory address register, operating sequentially or asynchronously of each other?
More precisely, is MIR register loaded from MPC during the control signals are being set up at data path side, or does it happen before?

MPC = MicroProgram Counter
MIR = MicroInstruction Counter

– MPC: Address of next microinstruction to be fetched from memory.
– MIR: Current microinstruction whose bits drive control signals of data path


texts: Analog Devices Gyro: What are these pins for?

texts:
I am after some guidance please.

I am designing a basic PCB which includes an ADXRS646 gyro. This is the first time I have designed a circuit with a BGA package and I do not understand the purpose of the following pins, or whether I need to include them in my 'breakout' (it will be connected to an Arduino for debugging purposes):

Output Amp Summing Junction (SUMJ)
Charge Pump Capacitor pins (CP1/2/3/4)

See here.

I had ignored them (just added capacitors), but I notice that some evaluation boards from Analog Devices connect these to break-out pins.

Any guidance on their purpose would be useful please. I just need to use this gyro for basic rate-out operations.


texts: Splitting supplies with EMI filter / Ferrit bead?

texts:
Im in a project, where I will have some noisy digital IC's, and a analog sensor circuit that I want to be a little bit noise free -

Im using a buck regulator to take in some power from a Lipo battery.

For when splitting the supply to analog and digital, how /what would i select for connecting the 2 sources to the buck converter? -

Can you use one of those "EMI filter" beads, which have a built in filter, or how would I select an good ferrit bead for this application?
Thanks for your time


texts:
I got this simple wireless power mechanism:

http://dx.com/p/diy-wireless-charging-transmitter-receiver-solution-module-green-golden-dc-5-12v-194469

If I'll have the receiver end rotating at about 30 rev/sec, will this have any effect on the power transmission? Will it still work?


texts: What does PWM width control in brushless motors?

texts:
For servos PWM controls angular rotation - for example 1ms width means 0 degrees and 2ms means 180 degrees (it is PWM width is proportional to angular rotation).

I am not sure what PWM width influence in brushless motors. Of course when I set PWM width to higher value motor runs faster, but is PWM width proportional to thrust, RPM, power or maybe something else?


texts: Does the rating of an AC fuse point to the amplitude or rms value of the current?

texts: If one reads 16A on an household fuse. Does that mean that fuse can handle up to 16 ampere rms or 16A amplitude?


texts: High pitched feedback or interference in system with amplifier and Raspberry Pi

texts:
I have a system running on 12V currently provided by a current-limiting power supply. In parallel this source feeds an amplifier and a 12V to 5V transformer. The 5V transformer directly feeds a Raspberry Pi Zero, which is the USB host for a USB sound card. There is an audio cable running from the sound card to the input of the amplifier. The amplifier connects to passive speakers.

When I turn the whole thing on, disconnect the input from the amplifier, and attach a new input (from a separate system, for example from my phone), it sounds great. When I attach headphones to the USB audio, it sounds great. However, when I connect the USB audio to the amplifier as I've described, I get a pretty annoying high pitched sound in there. I figure this must be some grounding issue since the whole thing works fine without that last link, however I can't figure out why. My electronics knowledge is pretty beginner-level. I thought I might ensure that the ground is the same between the Raspberry Pi and the amplifier by connecting them directly, but that made no difference. Any ideas how I might be able to fix this while still using a single power source?


texts:
I have a PCB with 3 inputs:

Ground
5V (logic IC power supply)
User-selectable 5V or 12V (motor power supply)

There are two types of motors, 5V and 12V. If the user selects the wrong DIP switch up-stream (12V instead of 5V) the motor will blow up. The user-selectable input is directly connected to a dual voltage power supply (~10A @ 5V and 12V).

How would I go about designing a protection circuit for the 5V motor to prevent user-error (inputting 12V instead of 5V on the variable input) from blowing up the motor? I assume I can't simply place a diode between the 5V and 12V rails because it will effectively connect the two outputs of the power supply via that diode (or would this work?). And the cutoff would need to be fairly fast, so as to not immediately destroy the motor.

Any ideas how I might implement such a protection circuit? Also, the lower voltage does not harm the 12V motor.

Note: the motor is an encoded stepper motor and so this is not a current issue - sending 12V to the 5V motor will destroy the associated control electronics.


texts: How to calculate the feedback resistors for an SMPS

texts:
I have designed an SMPS circuit for my host board. As the datasheet, the feedback resistors are calculated as

As per the datasheet, Feedback Voltage(Vref) is 0.6V and I want 4V Output Voltage. Therefore, feedback resistors are chosen like below after the calculation.

R15 = 5.6K

R17 = 1K

I measured the output voltage from the board; it is 1.2V.

I also measured the feedback voltage and it is 0.6V, same as in the datasheet. So, what can be the problem? Am I doing something wrong? Calculations were done with an oscilloscope.

(I can not add the datasheet link as I don't have enough reputation. The SMPS regulator is L7986 from STmicroelectronics.)

Update1: I changed feedback resistors to get the 4V output by changing the resistors ratio. Measured output was 1.2V with initial resistors. So I changed the resistor rate by multiplying it with 2.3 (4/1.2V) to get 4V output. After this change, the output voltage is about 7.8V. I had thought that I can get the desired output voltage if I modify the ratio of feedback resistors. So, any thoughts?

Update2: I guess I broke the regulator while trying to measure the output voltage with an oscilloscope. I don't know what caused this, but now the regulator outputs the input voltage directly to the output pin. I was very careful with the connections, I just connected it to voltage supply as the same before and measured voltages from the scope.


texts: Convering bandwidth (frequency) to bit rate without knowledge of the modulation?

texts: How would i convert a bandwidth of say 30kHz to bps if I only know the number of bits per sample (4)? (and I was using a two chanel system). I am assuming it is simply 30KHz * 2 * 4 but this may be wrong


texts:
The last stage of a power amplifier to an 8 ohm speaker is usually a common collector. Now many textbooks mention that it is used as a buffer as it has a low output impedance compared to the speaker (Zout << Z speaker).
To me this is what people call voltage impedance matching as the full voltage of the amplifier is applied to the speaker.  But I always thought that what is of interest is the maximum power transfer. So what matters is power impedance matching which implies that Zout =Z speaker.
So which one is true :   voltage or power impedance matching in the last stage of a power AMPLIFIER?


texts: Help identify RJ11 pins on a relay board - No152133

texts:
I'm tinkering with my garage door motor (Marantec Comfort 220) which have a RJ11 6-pin connector (X10) for an accessory relay board. The relay board is quite expensive and I don't actually need the relays.

The board consists of three (3) relays driven via the RJ11 connector.

Solved: I'm using the following pins for the outer RJ11 connector (X10) on the board:

GND Garage light
All relays, 24 V
Close with 5
GND Door open
Close with 3
GND Door close


texts: Anyone knows what component is this? Found scavenging an old monitor.


texts: Phase-locking pixel clock to HSYNC/VSYNC

texts:
I am trying to capture pixel data going to a small B&W CRT display. The signals I have to work with are the TTL-level pixel data signal, HSYNC, and VSYNC. I know the pixel clock frequency (~16 MHz) but for my application, I have no access to the pixel clock signal.

I want to sample the pixel signal at the appropriate time (during the middle of the bit period, not during the transition), so I figured I need to generate a new 16 MHz clock with some phase relationship to an edge of the HSYNC signal and use that to sample the pixel signal.

I know how to use a PLL to multiply a clock signal and maintain a certain phase relationship between the input and output, but how do I maintain a similar relationship between a new 16 MHz clock and a signal that only occasionally has an edge (HSYNC)?

Or is there a better way to solve this problem?


texts: Verilog: including one module in another module

texts:
I am beginner in Verilog. So I am confused in coding in Verilog. Can I use one module in another module?

module pn(
  input p,
  input n,
  input clk,
  output reg q
);

  initial begin
    q = 0;
  end

  always @(posedge clk) q=(q&n)|((~q)&p);

endmodule

I want to use it in following module

module ic2323(
  input p0,
  input n0,
  input p1,
  input n1,
  input clk,
  output q0,
  output q1,
  output x
);

endmodule

Is it possible?

EDIT:

 x=q0~^q1;

this code gives error

Reference to scalar wire 'x' is not a legal reg or variable lvalue

Illegal left hand side of blocking assignment


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