texts: PWM speed controller with rectifier as voltage regulator?

texts:
I was looking around for a voltage regulator when I thought of this, so it might be completely crazy.  And I'm sorry if it is.

BUT...

Could I use a PWM speed controller as a voltage regulator if I were to use a cap to "smooth" out the voltage, and a simple four diode full wave rectifier to make sure the voltage never goes negative?

And I apologize if this is a ridiculous question.  I don't know much about PWM or voltage regulators.


texts:
Say I have the following three phase wye configuration:

Source

Let’s also assume that all three loads have the same constant resistance, therefore in this case the system is balanced and the neutral wire is not carrying any current.

The line to neutral voltage is 230v and the line to line voltage is 400v. The loads are purely resistive, they have no reactive components. Let’s say they each have \$1k \Omega\$ of resistance.

In this case we can calculate the power by simply doing \$P = \frac{V^2}{R} = \frac{230^2}{1000} = 53W \$ .
Since we have 3 loads on three different phases, we can multiply 53 by 3 to get the total power; \$53 \cdot 3 = 160W \$

Now instead of wiring up three loads with 4 different cables (even though the neutral isn’t needed in this case) why don’t we try to connect one load in between two lines, i.e, connecting a load using the line to line voltage which is 400v. If we do this the total power is: \$P = \frac{V^2}{R} = \frac{400^2}{1000} = 160W \$

We seem to have the same power as our other configuration.

This of course is no coincidence due to the fact that line to line voltage is \$ \sqrt3 \cdot V_{phase} \$.

So the question is, why always use a 4 wire system (L1, L2, L3 and neutral) as opposed to using a two wire system since both systems deliver the same power? Isn’t it cheaper and easier to wire up some power hunger appliance with 2 wires instead of 4?

I’m aware that 3 phase ac motors require 3 phase in order to function and probably other appliances can’t handle 400v but they can 230v on three different sections.

So what is the main reason why this two wire line to line voltage system is practically never used?

Thanks


texts: How is etalon important to tunable lasers?

texts: Tunable lasers utilize some kind of feedback in order to maintain the same optical intensity. I've read that there is some kind of etalon trans-impedance amplifier that works in order to generate the output necessary for this feedback. I'd like to know how the reflecting surfaces of the etalon generate the analog signal that is necessary for feedback.


texts: Should I ground my 5V USB dc output for user safety? - Product design

texts:
The project consists of a metallic bench that can be placed outdoors, with a couple of USB outputs to charge your mobile on the go.
The bench is grounded (bonded with our internal connection box, which itself is connected to the electric ground conductor). So we are protected against any AC fault. Also the equipment would be connected only to GFCI outlets (as mandated by NEC on outdoor applications).
The USB 5V output is provided by a small switch mode power supply, the output is "floating" or isolated from the AC Ground.
So, would it be advisable to ground the V(-) output to the electrical ground?
As our female USB connector is metal and connected to the metallic structure, we are naturally bonding with ground since said structure is already grounded. If we don't insulate this, we already have a V- grounded, since most of the USB chargers have the SHIELD coupled with V-. If we want to ground V-, should we leave that to only the USB Female casing connection? Or would it be better to attach a cable from ground to the V- directly at source? In this way, we would have 2 layers of protection, but I'm not sure if we can go into trouble by having something that could be considered a "Ground loop".

Additional comments:

Why do this? We fear these failure modes that can make the product dangerous.

Failure modes to USB output:

Failure on the insulation of primary / secondary of transformer, connecting 120V to the output. Maybe this could go unnoticed if the AC voltage goes only to the (+), and it would never touch any grounded surface.
Failure of the internal insulation of the USB charger. The 120V AC phase runs close to the enclosure of the USB male connector. If for some reason the insulation melts or we have moisture, we would have 120V directly on the case of the USB and V- of the output, since they are generally bonded in these devices. Having the (V-) or shield grounded would protect against this.

Why wouldn't we want to do it?

Maybe we can have ground loops? Since we have 2 ways to earth, from USB female enclosure to metallic case of product, and from there to ground. And also the V (-) that would be attached to ground.
Some people advise against it
Any ground interference or stray voltages that maybe can affect our outputs or the internal circuits of the power supply?

Why we are using an USB outlet for this?. (Leviton T5632)
The scope of the project can afford a personalized PCB board design at the moment. We have tested multiple USB chargers, but find that the wall USB designs are good:

They have a degree of NEMA protection.
They are designed to work in enclosed spaces and not so "ideal" situations.
Leviton device has protection against both shorts and over-current. Many don't have this!
Good charging rates, around 3A.
The output is sightly higher (5.15V), so that's ideal to correct our voltage drop by the extension cable.
Easy to get, good pricing, UL certification, not bad quality as the thousands of Chinese USB chargers.


texts: How to send ethernet frames with RJ45 on STM32F107 board?

texts:
How can I configure and initialize the ethernet connector (RJ45) and send/receive packets with the ethernet connector of the STM32F107 evaluation board (ARM Cortex-M3). I searched for tutorials, but I found nothing. For example, for the RS-232, USART and LEDs there are a lot tutorials, but there aren't such tutorials for sending/receiving ethernet frames/packets.

Can anyone explain how to do that or suggest tutorials and papers?


texts:
I am trying to design a low-pass filter for a 24V, DC, 10A power line to suppress EMI, RF interference and noise in a bus. There is no ground(chassis). I am trying to simulate this filter that was tried in the bus and worked (the audio amplifier was noise-free). This filter is the filter on my previous question.

I couldn't calculate the cutoff frequency because of the common-mode chokes. Could you help me calculate?

I am trying to simulate it, however it doesn't seem right. Am I simulating it right?

Here are the schematics and graphs from LTSpice:


texts: Why relay module occasionally switches by itself ON?

texts:
I am using this common relay module from Ebay (image below). It works very well 99.9% of time. It's controlled by ESP8266. It's in the plastic box with some AC wires (which are obviously plugged in these relays).

What happens is, that sometimes (approximately once in a few days) it switches itself on for a very short time. I know this, because when my garage doors opened few times in night, I stopped trusting this module and I have unplugged garage doors from it. Instead, I have plugged ESP8266 +5V and input in it, so I could see if relay really switched itself and by itself. Because I have also completely commented out code, which controlled this relay in ESP8266.

So now I know for certain, that the problem is inside this relay module. Because relay module is using optocoupler which is switched by connecting data pin to GND, I think it shouldn't be electricity induction problem from AC wires around.

So the last thing which comes to my mind, is that the electricity is inducted directly in relays coil, if this is even possible ? Or I have no idea :-)

Can someone shed some light on this and try to come up with reason why this is happening and mainly how to solve this problem ?

The only thing which I have ready to do right now is to use 2 relays in series and hope, that this "glitch" doesn't happen in both of them in the same time. It's more probable that I win lottery than this happening, however, I wouldn't feel very happy about this obscure solution.

Thanks everyone for your time reading my question.


texts: circuit programming using a SPLD or CPLD as a 16 bit (addressable memory) microcontroller

texts:
SPLD Reference

https://www.arrow.com/en/categories/programmable-devices/programmable-logic-devices/splds

CPLD Reference

https://www.arrow.com/en/categories/programmable-devices/programmable-logic-devices/cplds

I am trying to learn how to make a cpu, but am still far away from college. So I thought I would ask here since I got alot out of it last time. Could someone help me make a basic cpu from a CPLD, 64K-bit-SRAM, EEPROM, Basic logic gates (AND, OR, NOR, NAND), MUX, DEMUX, and a program counter, or point me in the right direction?

I know about ben-eater and that's what i'm going for but I want to make a cpu that uses programmable logic.


texts: 380V Wye on motor nameplace,VFD manual requires 220V delta. Will it work?

texts:
I removed a motor (nameplate attached) from an eddy current drive. My intention was to replace the controller with a VFD and remove the clutch assembly. The motor obviously ran at full speed with each coil connected to 220V 3 phase in star config.

As you can see on the nameplate the motor is rated at 380V star. There is a terminal box with 6 terminals for star/delta configuration but does the nameplace suggest the motor only runs on star config?
I want to use this VFD but the motor needs to be rated for 220V delta and my motor is rated at 380V star.
Thanks in advanced for any assistance.


texts: ~150 WS2812b LED's with Pi Zero and SN74AHCT125N

texts:
I'm planning to control about 150 WS2812b LEDs with my Pi Zero and a 5v 11a power source (PC molex connector). Following this guide: https://www.thegeekpub.com/15990/wiring-ws2812b-addressable-leds-to-the-raspbery-pi/ I want to use a logic level shifter (SN74AHCT125N). There's a 400 pin breadboard used in the guide, but I need to use a 170 pin breadboard because of the limited space the controller will be in. Here's a picture of what I'm planning to do, can anyone verify that it will not go up in fire and destroy all my LEDs?

I'm really for the messy sketch, it's my first time using fritzing, I hope everything is clear to understand.


texts: Dominant Pole Approximation for loop gain

texts:
I have the following loop transfer function for a unity feedback system:

I understand that the \$(s+2)\$ term becomes \$2\$, but what happens to the \$s\$ ?


texts: How is the quiescent current and emmiter resistor determined on the driver and pre-drivers of a class-AB audio amplifier output stage

texts: I am reading online about discrete audio amplifiers. I have learned about the input differential pair, the voltage amplifier stage, and now I'm learning about the output stage. I have learned that you want to bias the output to have about 25mV to 26mV drops across the emitter resistors as this will reduce distortion. But I have not found any information on how to bias the drivers and pre-drivers that come before the final output transistor pairs. I'm not refering to using Vbe multipliers, I'm asking how do we select the emitter resistor and current for the driver and pre-driver transistors? I was thinking that maybe the quiescent current through the driver should be the max current of the output divided by the beta of the output transistor but I can't find info on this. Maybe I'm looking in the wrong places or doing the wrong search keywords. I have attached an image I found online as refenrence where you can see the resistors in question. In this case they are 62 ohms for the driver pair and 300 ohms for the pre-driver. Any info would be helpful thank you.


texts: Will leaving 4 batteries in parallel and series drain them?

texts: I am making a big project soon, a spider robot, and I will have a total of 4 batteries. 2 batteries will be wired in parallel and 2 in series, and then those 2 packs of 2 each in parallel.I don't want to have to disconnect them every time I use it, but I will if it drains. So my question is straight forward, will leaving the spider off, but the batteries still connected in the circuit, drain the batteries? I can't find it on google. I noticed the batteries get hot when I tested both volts and amps with my multi-meter. So I figured, it is draining. Is it? I hope this isn't a stupid question.


texts: What conditions could be expected to occur if one or both inputs of an op amp are left floating?

texts:
Question 1: Can an op amp work with both of the inputs floating?

I assume that due to the input offset voltage if both the inputs are floating, the output would be +Vsat/-Vsat. Am I wrong?

Question 2: Can an op-amp work with any one of the inputs floating?

In both the cases there is no feedback to the op-amp.


texts:
The more I get into TFT arrays, the more I'm lost.
I know what it does, but how does it look like? Can you split a display and just hold a TFT? Can you buy a TFT on glass, without the rest of the display?
How is it made? It seems to be a circuit, but more like a special one.
I can't find this information anywhere.
I was also wondering if the TFT array design in AMOLEDs can be the same as in LCDs?


texts: Expressing dependent current source voltage using KVL

texts:
I am reading about mesh and node equations, and the book says that the voltage between \$V_1\$ and \$V_2\$ can be expressed as:
$$
10\cdot I = V_2 - V_1
$$

How is this possible? And is there a general formula for expressing the voltage across the dependent current source? It says that the controlling current is expressed as:
$$
I = \dfrac{V_s - V_1}{R_1}
$$

(which I do understand as per ohm's law). But for the dependent source, there is no resistance. I know if you are using mesh analysis, you can assign an arbitrary resistance, say Ro, which will factor out of both mesh equations that contain a current source and it is therefore not an issue.

Also, if I applied KCL to the supernode, would it look like:

$$
I = \dfrac{V_1}{Z_1} + \dfrac{V_2}{Z_2}
$$


texts:
I have seen many zero ohm resistors which says that maximum resistance is say 50 mOhm. But, the maximum current rating will be only 1 amps. 0603 package. Power rating they mention as 1/8 watt. Can anybody comment on this differing I^2 * R and power rating?

Edit: My purpose of question is to clarify doubt in a datasheet which has both current rating and power dissipation. Which one should i consider?


texts: Form factor for a large LED array on a small board

texts:
I am designing a fairly simple board with an 5x8 LED matrix. I plan to drive it with an LED driver I haven't chosen yet, probably on a separate board connected by a ribbon cable.

My question is: what are the best practices for arranging tightly grouped LEDs on a board? If they're laid out like so:

x      x      x      x      x      x      x      x
x      x      x      x      x      x      x      x
x      x      x      x      x      x      x      x
x      x      x      x      x      x      x      x
x      x      x      x      x      x      x      x

you can see that the channels are going to be pretty tight. Anyhow, this thing just seems like there's got to be a standard solution already worked out ("arranged in a Hofstadter configuration", or something like that).

Also, is there a standard ribbon cable with 41 pins?

TIA.


texts: Problem with demodulation system, LTspice

texts:
First of all, I'm sorry if my English isn't perfect, that's not my natural language.
I'm trying to simulate an electronic system for my project and I want to demodulate a sinusoidal signal.
To do that, I use a demodulation system with AOP and Switch. You can find a screenshot of my system attached at this post.
I add an complementary module, which create a square signal to command my switch. But, when I simulate my system, the AOP does not demodulate my signal and it outputs a sinusoidal signal :/
My objective is to demodulate my sinusoidal signal and use a low pass filter to have a signal centered on 5V +/- 4 V DC at the output.
P.S :
Ue and output are the same on screenshot.
Schematic:

Simulation result:

In pink, UE and switch_Output
In light green, Output system
In light blue, switch command


texts: Why can't a Wheatstone bridge measure resistance of very high value?

texts: The answer is from google but I don't get it. Can someone explain in more simple way?


texts: What is this Venn-Diagram-looking symbol?

texts: So I am looking at the datasheet for the LTC4416, and there is this Venn-diagram symbol after the op-amp, but I don't think it is supposed to be an inverter. It is also used for these currents, but what do they physically represent?


texts: Series RLC bandwidth independence from C

texts: Why is bandwidth of series RLC circuit independent of the value of C ? Reason without derivation


texts:
The problem that I have is that I can't understand the working of PWM in Arduino, even though I totally understand what PWM is.

Like the Arduino has a 980hz refresh rate (~1ms clock speed) on two of its PWM pins and 490hz refresh rate (~2ms clock speed) on the others PWM pins.

Then there is Arduino's internal crystal oscillator which works at 16Mhz (~62ns clock speed).

And then I came across this answer:

Why change microcontroller's PWM frequency?

In this the accepted answer gives a little overview on how PWM works.

But I can't seem to understand how does PWM wave fits inside the input window of PWM pins.

As PWM pin take input in every ~1-2ms how are PWM waves formed inside that input window? Can someone explain by showing an example of working like the above answer did.

And does the clock speed of crystal oscillator have anything to do in this process?

*I am totally new to electronics


texts:
I'm a .net developer, and it bothered me that I didn't have a good enough knowledge of how the computer actually runs the programs I write.
So I started reading on various subjects and came across some questions.

For example, I read that transistors are used to build logic gates since they can operate as an electricity controlled switch.
These, in turn can be used to build memory (as in an SR latch) and to perform computational tasks (as in a half adder).

What I don't understand is, how is the controlling voltage (the one applied to the gate) controlled if not by another transistor?
I read that the benefit comes from controlling a high current by applying a small one, is controlling a small current an easier task?

I know this is a novice question.
Thanks to those who answer!


texts: Common resistor for pulling up unused pins of ATmega2560

texts: I am designing a PCB with ATmega2560 MCU. I have 50 unused pins in my design. I was wondering if I can pull up these 50 pins using 5 resistors such that 10 pins have a common pull up resistor. Is that recommended?


texts: Determining Dynamic Resistance of TVS Diode from Datasheet

texts:
I'm trying to determine the dynamic resistance of TVS diodes so I can calculate clamping voltage and peak current for a given input pulse (automotive load dump).

This app note(1) from ST provides a formula for finding Rd with pulses longer than 1ms but the variables it requires are not published by manufacturers. Littelfuse suggests calculating it from two clamping voltage values in this app note(2), but only one clamping voltage value is provided in most datasheets.

The product datasheets I am primarily looking at are littelfuse TVS diodes(TP5KP Series) and Vishay TVS diodes(5KP8.5A thru 5KP188A Series).

How can I determine dynamic resistance for TVS diode products?

(1):
http://www.st.com/content/ccc/resource/technical/document/application_note/1f/d7/fc/6d/2e/27/48/98/CD00181783.pdf/files/CD00181783.pdf/jcr:content/translations/en.CD00181783.pdf

(2):
http://www.littelfuse.com/~/media/electronics/application_notes/esd/littelfuse_selecting_an_appropriate_esd_device_application_note.pdf.pdf


texts: Relay Circuit Interfere with RF signal - How to improve?

texts:
I am building a BLE Motor Controller Circuit and I have some problem with connection dropout when switching the relay.

Here is the relay circuit

This is the active high circuit.

This is the relays block. If I connected the board without hooking up the motor, the relay can toggle just fine without any issue. However, when the motor was present, there was a problem with connection drop-out.

My initial inspection was that when the relay under load, switching the relay had a ~200ms delay, it might have built up charges on the Anode side of diode D1 and D2 so when the coil engaged and released, it spiked and pushed a large amount of voltage return to 5VDC rail. The 5VDC rail is connected to 3.3 LDO, so I think it caused disturbance to the MCU, and Oscillators, those are sensitive so it dropped the RF connection. Question is, wouldn't the LDO suppose to isolate the input voltage so the 3.3VDC is stable?

Propose fix:

I am thinking of instead of connecting the Cathod side of D1 and D2 to 5VDC rail, I will connect it to the 180VDC rail. so it won't cause any disturbance on the 5VDC rail. Do you think it would work?
Move 5VDC to the emitter and ground to the collector of Q1 and Q2, so diodes D1 and D2 would suppress spikes to ground?

Please advice me what is the good way to solve this issue.

Thanks


texts: Replacing usb speaker circuit with LiPo battery & Bluetooth. Not sure what watt audio amp to use

texts:
I have a set of Logitech usb speakers which I wish to convert to bluetooh speakers. A usb has the the power, ground, data+, and data- connections. Which i believe cannot be simply replaced with a battery & bluetooth data connections(no drivers etc). So I intend to build a chip myself but the the tutorial is for 3W audio amp chips BUT the newegg specs for my speakers show total power of 1.3W.

Is 1.3watt the correct value I am looking for? or would be that the power prior to an amp chip in the original circuit
I currently intend to build this circuit for each amp chip I need (2)

Is there some way i could test for the correct wattadge without breaking the speaker?

Edit:

Thanks for the advise I will try my best to apply it tomorrow.
And for the images here it is.. ( will update with part numbers at a later time )


texts: Connecting to pins on USB to Serial module (contains FT232RL chip)

texts:
I have this module:

My question pertains specifically to the RX and TX pins shown (sorry for having it upside down, only way I could make it look clear.)

I don't understand why there are 4 pins, for 2 signals. I would like to use this module to send information to my FPGA (DE0-nano), using an IP core that implements UART-RS232. However I do not know how to connect the two.

If some of those pins are ground, how do I know which ones? It is not labeled.

This thing was originally used to program a PIC through the computer, by the way.

Thanks.


texts:
I have a thermistor which I believe is a NTC 3950, and which I suspect does not work properly.
It is from a 3D printer extruder/hot end. The displayed temperatures and the ones I measure using a meat thermometer differ by 50% or more, and I can feel with my hand in the vicinity (not touching) that it is cooler than it used to be.
The normal operating temperature is around 200 deg C. The resistance of the thermistor at room temperature, measured by a multimeter, is 108k Ohm, which seems to be normal.
Any other things I can do to test the thermistor before replacing it? I do not have an electronics lab, only basic stuff. Can it even be the thermistor that causes the problem, ie is it normal/not unheard of for a thermistor to give normal values at room temperature and be off by 50% at higher temperatures?


texts: Equivalent Resistance in a short circuit

texts: Find the equivalent resistance across terminals a and c. I don't know how the current flows in this circuit so I can't find the equivalent resistance.


texts: What determines what type of short-circuit current is highest?

texts:
I'm doing a short-circuit analysis of a system, and started wondering about the following: What determines which type of fault current is the highest (and lowest)?
The screenshot below shows the result for 4 different switchboards. As can be seen, for the two first switchboards, an LG-fault results in the highest current, while LLG and 3P-faults result in the highest currents for the two last switchboards.
I know that in an isolated system, the LG-current will be (close to) zero, but other than that, I'm not really sure what makes up the differences. The results below is for a solidly grounded system, where the zero-sequence impedances are 3 times the positive sequence. None of the switchboards are connected (only through a high voltage distribution bus).

Does anyone know why it differs from switchboard to switchboard? I would think that for a solidly grounded system, one of the types would always be the largest. Are there any system characteristics that could tell me (before I run an analysis), which of the types is most likely to be highest?
Thanks!
Update:
As Li-aung Yip (thanks) points out, the zero sequence impedance is normally a bit lower than the positive sequence in a transformer. I see the question text above is not completely correct: The zero sequence impedance is 3 times the positive sequence for lines, while for transformers, it looks something like this (this data is used when achieving the results above):


texts: Why can a single sine wave signal be used to send digital data but a composite signal is needed to send human talk,etc.?

texts:
I can understand the following text (Data Communications and Networking: 4th Edition, Berhouz Forouzan, Ch.5, page 179) which says that a property of a single sine wave carrier signal (phase, frequency or amplitude) can be changed to represent the pattern in digital data:

But I fail to understand why something like human voice (as in a telephonic conversation) can't be similarly mapped onto a single sine wave signal by changing one of the characteristics of the wave (Frequency for example). Doesn't at any instant of time, human voice has a particular frequency and amplitude. Why can't that be represented by modulating a single sine wave? I am asking this because the same book says that in order to transfer human voice etc, we need a composite signal having many constituent sine waves of many frequencies:

Please explain this to me in simple terms why it is so. What's different between transmitting something like human voice on one hand and a digital data pattern on the other?And what are other "stuff" like human talk which necessitates use of a composite signal?

NB: I will appreciate if you can also tell IF human talk can be sampled, converted to a digital pattern, and THEN transmitted over a SINGLE sine wave signal. Thank you.


texts:
I model an photovoltaic inverter in simulink.

The Inverter has a PWM, a current control and MPPT.

The PWM pulses are generated by comparing the reference sinus signal with a triangular signal. The modulation index describes the ratio of these two signals. The reference sinus signal is dependent on the current control and the power output of the PV module.

So I was wondering how real inverters work.

Do they have a fixed modulation index or do they have a fixed amplitude of triangular signal?
And how do you choose the value of it?


texts:
I am using a comparator Model TLC372CP in following setup:
As the TLC has two comparators included, I am just using one of them.

If I am using the potentiometer, I can measure a dropping resistance at 1IN- so that depending on the poti position, sometimes 1IN+ is higher than 1IN- and sometime the other way around.

So I would expect 1OUT to change from LOW (0V) to HIGH (5V).
But I can not detect any change on 1OUT.

What is wrong? Any suggestions?


texts:
I recently got my hands on a sn74ls83an 4 bit adder adder chip.I made my own circuit and  it doesn't work.Here is the circuit diagram(sorry for the messy wiring:

I used a 4 switch dip switch instead of the slide switches in the diagram.The exact chip name is:SN74LS83AN from texas instruments.

I am powering the circuit with a micro usb wall wart with an output of 5v at 500mA.

Here is the datasheet for the chip:http://pdf1.alldatasheet.com/datasheet-pdf/view/80346/TI/SN74LS83A.html


texts: Why isn't this single pushbutton on/off circuit working?

texts:
I built this about four times, replacing the transistors every time, carefully measuring all resistors and capacitors and putting a .1uf cap from the output to the positive. The LED light goes from the output to a 470 resistor, and to positive like the circuit called for. When I power it on, the LED just stays on, and if I press the button, nothing happens whatsoever. The LED is just ON.

Just two notes so as to not get confused with the picture:

the 2 10k resistor wires aren't touching and the 470 ohm that may look like its grounded is to the positive.
Also, the middle is the BC557, and the two outers are the 547'

Edit:

When the button is pressed, the voltage across the LED drops for 2.5Ms from 2.4 to 2.0 volts


texts: Reading about FPGAs, if I understand correctly, they are basically fully configurable logic gate circuits. Being this, one can design anything with them. One can design everything in the most customized way possible and hence, meet the same ends in a vastly more efficient manner which can be get using a microcontroller. Having this, it looks like an FPGA beats a microcontroller any time, any day. So my question is, if FPGAs are really this awesome, what keeps them from being much more prevalent than microcontrollers? From this point of view, to me it seems like FPGAs should have wiped out microcontrollers a long time ago. So why is this not the case? Is it the cost, difficulty to program an FPGA, or entirely something else?


texts: Implementing 1000BASE-T (Twisted pair) over PCB backplane

texts:
Problem:

We are designing a small payload which will contain several ethernet capable devices connected via a backplane we must design.

All guidelines concern the scenario where the PHY is connected to an RJ45 connector, but in my case I am connecting ethernet accross a backplane.

The Major Components in payload enclosure:

Embedded Gigabit Switch (Example: Embedded Switch) (includes Ethernet
Magnetics)
2x Embedded Computer & Expansion module (Example: COMe-mAL10 (includes Ethernet Magnetics)
Interface Board to connect to enclosure connectors. Industrial connectors with/ twisted cables)
Backplane connecting all the above boards

Note:
Both the computers and the switch have integrated magnetic and are designed for 1000BASE-T so implementing 1000BASE-KX is not really an option.
I realize that 1000BASE-KX is made for back-plane connection but the PHY transceiver needs to be modified to support that (and magnetic removed)

Usual PCB PHY to RJ45 Guidelines:

The usual guidlines are for PCB routing between the transceiver (PHY) and the magnetic, some common ones listed below:

Signal after magnetics should be above chassis ground plane, no overlap with board ground plane.
Signal should be routed as differential pairs (100Ohms controlled impedance)
The use of vias is to be minimized. If vias are used, keep them to a minimum and always match vias so the differential pairs are balanced.
ideally the magnetics are included in RJ45 connectors or that the RJ45 connector is very close to the magnetics.

Example Guideline Documents

LAN7500/LAN7500i Layout Guidelines (Section 5)

Gig PHYTER V 10/100/1000 Ethernet Physical Layer Design Guide

Similar Questions:

Ethernet Pass Through over PCB

Answer: Small PCB section, wont have much effect, follow general layout guidelines.

Are there any special internal Ethernet connectors other than RJ45?

Answer: Implement backplane ethernet (1000BASE-KX)

How to route Gigabit Ethernet, remote PHY or remote RJ45 connector?

Answer: If the correct reference plane is under the signals the PHY<->Magnetics or Magnetics<->RJ45 then longer length can be run, else keep as short as possible.

Ethernet Without Magnetics?

Answer: Use capacitors and implement 1000BASE-KX.

Questions:

From all of the above my take home message is that I can successfully connect my different devices directly via back-plane using 1000BASE-T as long as I have the separate ground below each signal and the traces are of controlled impedance, is this correct?

If the above is correct, The impedance controlled trace on the backplane will be run above a ground plane which is only capacitively coupled to the center tap of the magnetic at each end? I guess this is the equivalent of the shielding in shielded cables?
Does anyone have a link to a document/guideline describing how 1000BASE-T can be implemented on backplanes?


texts:
I'm new to EMIF (external memory interfaces) and I ran into kind of a dumb question about DDR3- not super important but mostly me just wondering if there's an answer I'm not thinking of. Basically I'm wondering- if you need to send 12 bits for both the row and column addresses, why is there only one 12 bit address bus?

Is it because the row address needs to arrive first (side question, does it need to arrive first or is that just convention)?
Or is it a due to physical constraints of the number of pins?

Any help or documentation or references would be really appreciated.
Thanks!


texts: How to check if my multimeter's fuse is damaged?

texts:
I recently bought a cheap multimeter. I played around measuring stuff on simple circuits and I think I managed to damage it as I don't seem to be able to measure current anymore (always get zero amperes, although voltage, resistance, and the rest work just fine). I googled around and found out that it is not uncommon for beginners to blow their multimeter's fuse when trying to measure current the wrong way; I think I've fallen in this category.

Though I would like to confirm, so I took out the fuse from the multimeter. I'm not sure how a damaged fuse should look like, yet it doesn't look broken, it is nice and clear and a very fine wire is visible. It is around 2cm long and on it is written F200mAL250V which I guess means that it is a fast glass 200mA fuse rated for 250V.

Can I use my multimeter to find out if the fuse is broken? What metering mode should I use for this particular fuse and what should I look for?


texts: do we only use pull-up resistor or pull-down resistors when dealing with switches?

texts:
I have heard people state that if your micro controller is not reading the signal properly, then we need to use a pull-up resistor. Which I don't get?
It makes sense when switch is involved because you don't want a floating signal.
What I don't understand is why do my friends mentions the pull up resistor help in better voltage reading??


texts:
I'm having problems using HEF4051 as an analog mux. I'm using it to switch between different audio toslink signals. Right now I'm only testing it with one signal and it works for 1-2 seconds when I connect power and then the sound cuts out. I can repeat this over and over again by reconnecting power.

Vout is the "input signal" and Vin is connected to "output signal" in the schematic below. I've narrowed the problem down to the mux since it works constantly without the mux in between (Vin and Vout connected directly to eachother).

The datasheet is confusing to me since it labels y0-y7 as both inputs and outputs so I'm not sure I'm using it correctly when I'm using Y0 as an input and Z as an output. Also I'm not sure if Vee is connected properly

I connected a multimeter to see what Z is sending out and for the period of time where I get sound Z is outputting 1.6V. Then Z drops to 0.9V and I get no more sound.


texts: Is 55ns SRAM fast enough to drive low resolution VGA?

texts:
I can't seem to wrap my head around the math.

Assuming I want a 640x480x256 VGA signal, and I had an FPGA or fast micro-controller to drive it, would 55ns be able to handle it?

Meaning each byte of the 8-bit memory would translate to one pixel.  Also assuming my R-2R ladder was setup to something like RRRGGBBB.

I have a very specific reason to use DIP SRAM.  I can find speeds down to about 15ns but small sizes.  The 512k I want to buy tops out at 55ns.

If someone could give me examples of how the bandwidth is calculated, it might help me decide to use the 512k or maybe do something different with multiple 15ns chips.

Thanks!


texts:
I am trying to find a safety sensor for a machine. The sensor should be safety rated as it will be used to detect if a cover is removed and will shut down robotics and uvc bulbs which is harmful to the service engineer (users will not have access to remove covers).

My issue is that I need one that is compact and small and also isn't ridiculously expensive as 4 of these are used per machine.

I had looked at limit switches though my main concern with them is that the contacts could fuse together over time as the switch will be pressed in the down position for about a year before a service engineer will be removing the covers.

Another type I had looked at was magnetic switches, however I was haviing issues finding one small enough.
I also looked at inductive sensors.

Does anyone have any recommendations? Or any experience in safety sensor systems who can advise on the best types of sensors for my application?


texts: Maximum ringing due to inductive coupling

texts:
Consider a bundle of wires carrying binary data and the worst case (or almost-worst case) scenario of them switching all at the same time. The wires with their partial mutual inductances would be aiding one another.

It can be found that if the currents are the same, then the magnetic fields are the same and if the currents have the same direction, these are aiding inductors.

The loops are very independent, each wire forming its own LC circuit with some conceptual capacitance on the other end of the wire. Simulating this with 5 mutual inductances (expressed with coupling coefficients) in LTspice or PSpice yields a ringing peak of about 1.4 V instead of about 1.07 V with no mutual inductance.

From the simulations, no more than 1.4 V of peaking can be obtained maybe because they weren't intended for such a large number of mutual inductances. PSpice at least supports a maximum of 6 mutual terms.

However, it can also be found that, considering the mutual inductances, there is a very large matrix of the form:

Then, wouldn't all the mutual inductances add up to the self inductance to yield a very large ringing peak for every wire in the bundle?


texts:
I am trying to understand the I2C data format of a 24 bits ACD (LTC2485).

The data sheet says it returns 4 bytes (32 bits integer), but is unclear as to where the 24 bits I seek are located.

Here is what I do not understand :

The role of the bits 31 and 30

The two most significant bits (30, 31) are used to indicate over range or under range conditions. They are also used to tell in which "quater" of the full range the signal is located.

The documentation says: If the bit 31 is set, then the signal is between 0V and +Vref otherwise, the signal is between -Vref and 0V.

I understand this as: if the signal is between 0V and +Vref, the code is between 2^23 and 2^24 and if the signal is between -Vref and 0V the code is between 0 and 2^23.

A similar reasoning can be used for bit 30, and Vref/2. That's how binary number works. Both bits can be used to tell in which "quater" of the full range the signal is.

Form this, I guess that bit 31 is bit 23 of the signal, bit 30 corresponds to bit 22, and so on. Thus, the three first bytes should be my 24 bit code.

However, the documentation later tells:

  The second bit is the most significant bit (MSB) of the result.

Which would indicate that the result is shifted by one bit. But later on:

  The function of these two bits is summarized in Table 1. The next 24
  bits contain the conversion results in binary two’s complement format.
  The remaining six bits are Sub LSBs below the 24-bit level.

Which would indicate that the result is shifted by two bits, and that bits 31 and 30 are redundant (see my explanation above).

And last, the example code provided, uses ... 32 bits instead of 24.

signed int32 x;
// Reading X
x ^= 0x80000000;
voltage = (float) x;
voltage = voltage * 5.0 / 2147483648.0;// Multiply by Vref, divide by 2^31

As a result, I feel lost. Given the 4 bytes I get (let's call them bytes 0 to 3 by order of retrieval) how do I get the voltage measured by the ADC ? What is the role of "The remaining six bits are Sub LSBs below the 24-bit level" ?

Thanks for reading me. The documentation of the part is available here. Explanations on the I2C data format are page 15.


texts: How to best estimate power consumption for a system?

texts:
I'm not an engineer, I'm a software guy getting into hardware - so bear with my ignorance!

I'm in the process of building a system with many components (e.g. a computer, many sensors, a few motors, a servo, etc). These will all be powered by a bank of batteries (size and composition TBD).

I know the operating voltage and current of all the components of the system, and am looking to make an estimate regarding the power consumption of the entire system. The highest device voltage is 7V, the lowest is 3v. The battery bank will likely be a collection of smaller batteries rather than a single large battery.

If I have a battery bank capacity of say "x"Ah, how can I go about estimating how long the power supply will power my system?

Can I simply just sum the wattage of the individual components, divide by the hypothetical battery voltage and then use that result as the system current [amps]?, or is it more complicated then that (I'm assuming so!).

Thanks in advance!


texts: Which DC-DC converter power supply to choose for a 6A motor from a 7.2V battery?

texts:
I'm looking to build a motor controller where I want to have consistent motor performance.  Normally you have a 6v DC motor and you can plugin a 7.2v battery pack directly and be fine, but the motors start out running really hard and slowly fade as the battery level drops.  So I was thinking of building/buying a DC-DC power supply so the motors would get a consistent 6v but still be able to draw a lot of current. Digikey has a 10A 6V Murata OKR-T/10-W12-C DC-DC converter for $10.  While I can buy one, I always like learning to build my own and would like the ability to have a final product have both the motor controller and DC converter in one.  The motors I'm working with have a stall current of 6A each.

My questions:

1) Is a DC-DC converter a good solution for my situation?

2) Would that Digikey DC-DC converter work in this situation?

3) Are there better alternative solutions?

Any pointers in the right direction would be much appreciated.

Here are some TI components I'm going to experiment with:

LM3150 - SIMPLE SWITCHER® CONTROLLER, 42V Synchronous Step-Down

PTN78020W - 6-A Wide-Input Voltage Adjustable Switching Regulator

LM2587 - 5A Flyback Regulator

TPS56921 - 4.5V to 17V Input, 9A Synchronous Step-Down SWIFT? Converter with VID Control


texts: Rotary Decoder circuit for high PPR Encoders

texts:
I am working on a project that uses a rotary encoder,
 I am using a locally made encoder of 200 PPR(pulses per revolution), The encoder has 2 inputs wires (0-5 volts) and 2 output wires (output pulses). I have connected the output wires of the encoder to GPIO ports of raspberry pi and am using this library to get output. It works great.

Now I need to do the same with 4000-5000 PPR encoder: http://uk.rs-online.com/web/p/rotary-encoders/2914349/  like this one. the raspberry pi is unable to gauge the output of this encoder using the above library.

Issues I need help with:
1)Should I use or design a decoder circuit and then feed output to pi?

2)Is is possible to solve this problem programmatically ? how ?


texts:
I am using LM2902 as a unity gain voltage follower to isolate measurements of a sensors voltage.
 ( datasheet: http://www.ti.com/lit/ds/symlink/lm2902.pdf )
The sensors i wan to measure operate at a voltage of 0 - 5V , for one of them, this voltage is inputted into pin 3 of the op-amp, pin 1 and 2 are connected together and also to the analog pin of a ATmega328p to measure it (or so I thought).
I messed up and wired pin 1 and 2 together and also to the 5V pin of the Atmega 328p instead of A7, pin 3 was connected to the sensor. this op-amp is used on 3 sensors, and they all gave junk information when this happened.
I am a mechanical engineer, and this sort of situation is out of my league ATM. can someone explain to what ended up happening when I miss-wired the op-amp to the Atmega? Can I wire it properly and run it, or is the op-amp fried?


texts: How much self induction would each coil of a transformer of one to one ratio be if the kVA rating for that transformer is 160?

texts: Assuming a current load of 80 A, and a voltage load of 1600 V, the straightforward kVA rating would be 128. But adjustments are made for power factor correction and other considerations raising the actual purchase of which transformer to take care of the situation to 160 kVA designation. My question is concerning one feature of 160 kVA transformer, namely: What would be the self induction on either of the two coils if they have the same self induction?


texts: Flip flop with load/set, reset, clk, and input

texts:
I'm not looking for a hardware language description of the flip flop, but the logic gate level to implement.

In verilog, the equivalent I'm looking for is

always@(posedge clk or negedge reset)
begin
    if(~reset)
      Q <= 1'b0;
    else if(~load)
      Q <= D;
    end

I've looked at: http://reviseomatic.org/help/e-flip-flop/4013%20D-Type%20Flip%20Flop.php
and
http://www.csee.umbc.edu/~squire/images/dff.jpg

the problem with the above implementation is that after I set a value to Q (D=0,Q=0,load=0) with load(set in picture) = 0, then when i set load high load = 1 on the next clk cycle, i get (D=x,Q=1,load=1). In order words, changing load from true to false will change the value of Q, but I want Q to hold it's previous value.

What is a flip flop that would hold it's value on Q after it has been set and enable is set high?


texts: Human Powered Bicycle Lighting System: Is this feasible for an enthusiast?

texts:
So, I was doing some reviewing over on bicycles stack exchange, and I realized the Cygolite Metro line of reusable chargers would fit my budget - AND be USB rechargeable!

Alas, I've been told constant charging is bad.

The idea was to hook a dynamo up to a battery and have the battery in turn charge it... I guess I can just plug unplug it manually.  I was gonna waterproof the battery, probably with some kind of project enclosure.  I suppose I could use something like this to save me some build time.

I expect my load to be 7 to 10 watts. Does any one have a sense of how much resistance that would add to my ride?  (Hypothetically, let's say I build my own.)

Also, I do giant hills.  If I do roll my own system, what can I do to make sure I don't surge too much power into the battery coasting down a hill?

Will generators generally make fixed volatages with varying amperages, usually?  (Ie, is that how power fluctuates?)

I survived the first half of Engineering Circuits one (drop related drop.)

I'm a bicycle commuter.


texts: Does my Arduino-based device need FCC certification?

texts:
I've built a small consumer device that contains an Arduino Nano. It's coupled to a custom daughter board that allows it to pulse a 12V electromagnet at about 1 hertz as well as inteface to some sensors. It does not intentionally produce any RF emissions like wifi or bluetooth.

I'd like to sell my device in the US, and I'm trying to determine what certification I need to legally sell it. From what I've read about FCC certification, including similar questions here, it's needed by nearly all electronic devices that oscillate above 9 kHz.

So, if I understand this correctly, my custom daughter board wouldn't require FCC certification? The Arduino Nano contains a clock that oscillates at 16 MHz, but I believe it already has FCC certification. Does my composite device constitute something that needs to be re-certified by an FCC approved testing lab? I'm not sure how much I'll be able to sell the device for, and don't expect to make much money, so if I can avoid wasting $10,000 on worthless certification for an unintentional emitter, I'd like to do so.

I'm not sure if this is an appropriate question for this site. If it's not, where could I find an answer to this? I've checked the FCC's website, but aside from vague FAQs, I can't find any way to contact anyone with a clue. I've seen some test labs offering to give me a quote to answer this question, but since they have nothing to gain by telling me "no don't bother paying us thousands to test your device", I'm hesitant to trust a response from them.


texts: I am using M3 screws on a PCB, I need to know the considerations needed to specify the minimum clearance between screw hole and traces.


texts: Most of the circuits that I have seen,  MOC3021 or similar opto-isolator is driven from Micro-controller. I want to do the opposite - Can I drive the opto-isolator from mains supply and use the other side as INPUT to Arduino.


texts: Power consumption in watt for fluorescent lamps

texts:
I live in Egypt where the AC voltage is 220v.
Yesterday i bought two fluorescent lamps (60cm and 120cm).

I toke the following photos for the what is written on those lamps:

Please have a look to the lamp at the top it claims 19w and 0.35A although 0.35 * 220 = 77w

Then have a look to the lamp at the bottom it claims 38w and 0.41A although 0.41 * 220 = 90.2w

My question is: are those two lamps 19w and 38w or 77w and 90.2w ?


texts:
What is the best way to implement a timeout, written in VHDL?

The purpose of this is to reset a state machine to an IDLE state if a certain amount of time has passed (a few seconds at most), to avoid a deadlock.
The only thing that come to my mind is a nasty clock counter with a big integer range but my concern is LUTs usage and optimization here. And I'm assuming my FPGA might have trouble fitting the logic of a 16 bit integer counter at full speed

Thanks for your help


texts: What kind of wattage for soldering small electronics?

texts:
I am just starting out in Electronics and I am looking for a Soldering Iron. (Obviously it would make no sense since I'm starting to get a SUPER expensive iron.)

What kind of wattage should I be looking for? 30-40 watts?

I've seen the name Weller thrown around a lot. Are they a good reliable brand?
edit: Also side question, when looking for multimeters I see a lot of "ranges" like 29 range, 39 range etc.  How do I know exactly which one to get?

I saw something like this one,

but I don't know if that's "good".  I don't figure I need a HUGELY expensive kit just to do small electronics/robotics.


texts: I was testing an old power supply(didn't work!) which have EMI filter caps on the inputs, when I disconnected the power source (220v AC), I touched the plug metal parts and I got an electric shock.so,what does that mean? Are they charged by the ac input ? Do the caps need a parallel resisor to discharge or there is a fault in the circuit that doesn't provide a path for that current?


texts:
I want to develop a product to make Wi-Fi to connect PC <-> MCU <-> MCU. I started looking for Wi-Fi modules with the stack that I need already implemented and some kind of AT commands interface in order to configure it, but those are a bit expensive.

Next idea it's to use a 2.4Ghz transceiver and a MCU with the stacks implemented. That will be a lot cheaper, but I don't know where to start.

My goal it's too have this module connected to something (an analog sensor, a remote UART, whatever) and, by sending a command over my PC or another MCU, get the data present in the sensor.

Could ypu help me through the first steps? I'm worried about the stack to choose.

EDIT

I don't know if I can do this here, but I've found Carambola a few months ago and right now they have an even cheaper module, the Carambola 2, I guess that it's a good module for projects that require Wi-Fi.


texts: What Is This PCB Component? (Sonos Play 5 Gen 1 Speaker)

texts:
I have a Sonos Play 5 Gen 1 Speaker and everything is working on it perfectly except that it makes this constant whistling / buzzing sound whenever the power supply is plugged in.
Dug into it and isolated the component making the noise. I am not experienced with electronics but would like to know:

What is this part?
Is it possible for me to fix it myself within reason?
What do you think is a fair price to have someone else repair it?

Any help is greatly appreciated.


texts:
Is there any easy way to continuously, slowly fade (dim) in and out a couple (5 at most) 12v monochrome LEDs (5050)?

A wild guess would involve a large capacitor (for the fades to be slow) and a MOSFET, but I have no idea where to start designing such a circuit.

Since my project won't need any smarter logic, I wanted to try to avoid using a µC for it.


texts:
Assuming VCC is +5V, why would the input pin receive +5V, and not a reduced voltage (as controlled by the resistor)?
When the circuit is closed (button is pressed), why doesn't the input pin have the same current as it would when the circuit is open? Isn't this effectively a kind of parallel circuit? If current flows through all available paths, why not through the input pin?


texts: How can I obtain the transfer function of an unknown circuit from its bode plot?

texts:
I have the following bode plot of some unknown circuit:

(The lines denote the -3dB frequencies, f_low and f_high.) I'm guessing it's a high-pass resonant filter. I don't have phase information, other than that:

theta = -135 deg at f_low

theta = -80 deg  at f_0 (resonant frequency)

theta = -31 deg  at f_high

I know for certain that it contains between 2-3 circuit elements including inductors, capacitors, and resistors, and I know that it's passive. My guess is that it's a second-order high-pass filter. I've worked out that the transfer function for such a circuit should be:

H1(s) = (A*(s/w_0)^2) / (s^2 + s*(w_0/Q) + (w_0)^2)

where w_0 is the resonant frequency in rad/s, Q is the quality factor, and A is the high-frequency gain. In this case, A = 1, w_0 = 2*pi*f_0, and `Q = (f_0)/(f_high - f_low)'.

From here, I should be able to come up with a predicted transfer function given what I believe the circuit to be, which will contain R,L, and C as coefficients, and use the transfer function H1(s) to find R,L, and C. A fitting circuit, by my guess, would be:

which would have transfer function:

H2(s) = (sL) / (R + 1/(sC) + sL)

which I could rearrange to the form of H1(s), and from there I could  match the coefficients in each transfer function H1(s) and H2(s) to find appropriate values of R,L, and C.

But that gives me

R/L = w_0/Q

and

1/LC = w_0*Q

Is there any way other than plugging in values and using guess & check to find specific values of R,L, and C?


texts: How and why is impedence matching done for a CAN bus?

texts: What is that termination problem? Could anyone explain in detail?


texts:
I've learnt that for resistors with 5 rings, the first 3 rings indicate the digits of the value.

But here we seem to have (from right to left): brown, violet, silver, gold, green. (The gold ring is not crystal clear on the picture, but it's definitely there.)

So no matter in which direction I read, the 3rd ring is silver -- which does not correspond to any digit!

Am I reading it wrong?


texts: Linear regulator GND pin MUST be connected to common ground?

texts:
I'm trying to make a constant current source of 2.1A which will operate around 1.7V.

I did some web searching, and I decided to use linear voltage regulators; simply put a adjusting resistor between the voltage outputs, and connect my load between the cathode and the ground:

TPS757 constant current source with output voltage of 1.5V. Note that GND pin would be at 1.7V with respect to input ground terminal, which is response voltage of my load near 2A. This means there is 3.3V different between VIN and GND, as long as my load keeps constant voltage across.

However, I found that some regulators have GND pin, while others have ADJ pin; I believe that the output voltage indicated in data sheets refer to the voltage difference between OUT pins and either of those pins.

For those which has GND pins instead of ADJ pins, must I connect GND pin to the same ground of the input voltage? I've seen some examples with regulators with ADJ pins that had the ADJ pin voltage above the common ground voltage (ex LM317), but I'm not sure it would apply the same to regulators with GND pins.

If so, how would I make a constant current source out of them?

Thanks in advance!


texts: If two hot resistors are touching each other, will their temperature rise as opposed to not touching?

texts: Consider I have two resistors next to each other both at 165°C. If they were touching each other, would this cause both their temperatures to rise? Or would the temperature stay the same?


texts: Why are GND pads often only connected by four traces?

texts:
I have seen this everywhere but cannot figure out why it would make sense to essentially compromise the quality of the ground connection. Is this done for visual reasons?

Here is an example:


texts:
I'm trying to program an ESP32-WROOM-32 on my own PCB. I'm an amateur.

I asked a related question about how to program an ESP32 using an Arduino a few days ago. I've been experimenting with it and no matter what I try I always get "Timed out waiting for packet header".

I hook everything up like the @jurag suggested in my other question. It's the same process you use for an ESP-8266. I've tried many different combinations (EN disconnected, EN connected to 3V3, EN connected to ground, IO0 connected to 3V3, etc). To be clear though I followed the instructions in that article by default.

3V3 -> 3V3
GND -> GND
IO0 -> GND
EN -> 3V3
TX -> TX
RX -> RX

I checked my connections by hooking up 3V3 to RX, TX, IO0, and EN and checking the voltage on the ESP32 itself. It's good. The 3V makes it to the ESP32. The only one of note is EN. I've carefully inspected my board and soldering and there are no bridges yet when I give EN 3V I see 3V show up on some of the other pins. I am guessing it's supposed to do that.

What I am saying is I think I have it wired right. Also, I have a USB microscope and I don't see any bridges anywhere when I do a visual inspection. To make sure I could get it to work I tried a few things:

SUCCESS - programmed an ESP-8266 using the same technique

SUCCESS - programmed an ESP-32 dev board using the same technique

FAILURE - hot glued a spare ESP32-WROOM-32 to a spare PCB of the same design

I'm not sure what the next step I should take is. It never works when I try it with my PCB using the ESP32-WROOM-32 that I solder (or hot glue) on. If I open the serial console there is nothing (it doesn't print wifi networks).

I do have pins 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, and 25 hooked up to different things but none of them are doing anything.

I've spent 5 hours trying various combinations. I'm pretty sure I even hooked 3V3 and GND up backwards at some point. ...The LEDs on the board still light up but idk, maybe I fried the ESP32. In any case I probably tried each scenario 5 times before I made that particular mistake.


texts: AVR- state change of a pin to generate an interrupt

texts: I need to produce external interrupt whenever there is a change in state of a pin. When the pin goes from high impedance state to ground or from ground to high impedance state, an interrupt must be generated. What is the possible way of doing it in AVR?


texts: What does the following Verilog code realize

texts:
I was learning verilog hardware description language. I was confused a bit with the blocking and non-blocking statements. Can someone tell me what the following verilog codes realize and simple hints how

always@(posedge clk)
begin
   q1=d;
   q2<=q1;
   q3=q2;
end

always@(posedge clk)
begin
   q1<=d;
   q2<=q1;
   q3=q2;
end

These are two different codes implemented separately. I think FF comes into the picture because of edge detection. But I don't understand what it realizes as it has a intermix of blocking and non-blocking statements


texts:
I did a pcb mount for a stn1110 "Multiprotocol OBD to UART Interpreter" and followed exactly schematic from datasheet.
The issue I have is that after is starting, there is a sequence of flashing the 4 leds, I can see on SerialtheStart Prompt "ELM327 >". Sometimes I am able to send ATZ and I get answer, but after few seconds something is happening and LED1 just keep flashing rapidly and I can't get a serial connection.
Can someone tell me what means that flashing? Where I should look for the issue? I am sure should be something related to my pcb mount probably but have no idea how to debug this.


texts:
I want to connect 4x4 keypad to nodemcu, but some of the pins on board are already in use. For LCD I have used I2C backpack, and have an extra lying around. Can it be used to connect keypad to nodemcu board?

From what I have read, a 8-pin I2C gpio extender can be used for keypad. But isn't the LCD backpack same as 8-pin extender? (Just having more number of pins).


texts:
What is the range of currents that I can safely draw out of a 9V battery without damaging it?

I am planning to design an experiment and I don't want to draw too much of current out of a battery and damage it.


texts: Attenuation - two stage RC low‐pass filter

texts:
I am having trouble with finding the attenuation and bode diagrams for this circuit below.

This circuit is two stage RC low-pass filters. I have been trying to find resources on how to do them with operational amplifiers (it is my first time using them). Any help is appreciated.


texts: USB 2.0 480 Mbps and USB3.0 5 Gbps galvanic isolation

texts:
For my project I'm searching for chips specialized in USB galvanic isolation.
It looks like there is no real product on the market. I found Silanna and AdvancedPhotonics that respectivly have products for USB2 high speed and USB3 superspeed.
However, Silanna stopped the production in 2019 and there is not much information about AdvancedPhotonics reliability.
Do you know chips that can do isolation for such speed? Any idea to achieve the same with discrete components?


texts:
Assuming we have a USB (1.x or 2.0) device and know what pins are for +5 and GND, is there a general way to detect which of the other pins is for data+ and which for data-?
There's no old schema so I can't make it live then measure/oscilloscope the real signal.
Also, how danger it is to swap data+ and data-?


texts: How do you set the reference voltage for a comparator?

texts:
I know this is certainly a beginner's question but am a first year student so hopefully I can be forgiven.

I was looking through a electronics booklet provided by IKES website, and it's talking about comparators:

Now, am very confused, I know that with voltage dividers you set the output voltage via series, as it cannot be dissipated equally without equal resistors. Yet with parallel circuits my understanding is that you have equal voltage, no matter the resistance for either resistors.

To me it seems that it holds true for the comparator too, why should there be an exception to the rule with unequal distributed voltage? Surely it would be set up like a voltage divider circuit right?

Or can you have it set in parallel as shown? If so, why is this an exception to the rule?


texts: A rather big (28 ports) USB hub design consultation

texts:
I have to design a big USB-hub that only full- or low-speed USBs will be connected to the downstream ports.

I've already made it with FE1.1 and four FE2.1. The first one converts 1 USB to 4 USBs, and each output will feed four FE2.1 converters, making 4*7 = 28 ports.

I did not use all the ports but it looks fine for the 8 ports I tested.

My questions are:

Has anyone ever designed such a big USB hub? What kind of ICs did you use?
I used these two cheap ICs. Does anyone here havr experience with a better IC?
How important is MTT selection versus STT? I feel the 1 to 4 converter which will feed the other 4 converters plays the key-roll.


texts: Why would a CD4060BE produce a copy of an input clock signal?

texts: I am making a CMOS logic clock and I have a problem with the 1Hz signal generator (see schematic below). When I connect up the CD4060BE chip to a crystal the output on Q8 of the second chip does not blink an LED at 1Hz, but rather the LED stays permanently lit (I don't have a scope to test the frequency). I connected up a 3Hz CMOS clock to the clock input on the second CD4060BE chip and Q8 blinks the LED at the same rate as the input frequency. Why would this happen? Surely the input frequency should be divided down by 2^8 and the LED blink should be extremely slow. Am I doing something wrong?


texts: SIM800l keeps disconnecting after I send at+sapbr =1,1

texts:
I have confirmed my sim card has data and can connect to the internet on my smartphone. The SIM800l also is fed with enough power and the LED does blink every three seconds.
I notice that after I setup my SIM800l module with the basic AT commands:
AT

AT+CFUN=1

I then enter the APN settings for my sim card as follows:
AT+SAPBR=3,1,"CONTYPE","GPRS"

OK
AT+SAPBR=3,1,"APN","Internet"

OK

Now as soon as I enter this code:
AT+SAPBR=1,1

OK

My SIM800l led starts blinking every second. When I started the module it blinked every 3 second (connection was made).
When I then enter this command:
AT+SAPBR=0,1

My SIM800l led then goes back to blinking every three seconds. This is very strange. Can someone assist me with this error?
My application is to post a URL link.


texts:
I have the following questions about my design shown below for a cheap low bandwidth current probe:

The probe uses a split-core current transformer and is intended for simple checks on mains-powered motor control circuits.

The part numbers for the LEDs and Zener are placeholders.  My questions do not concern the low battery indicator but I would be glad to learn whether it can be done simpler. LM324 and LM358 will be used for the opamps. Because the schematic is from a simulation, I have not included decoupling capacitors for the ICs but I understand the need for them in practice.

U1 buffers the output of voltage divider R2 R3, providing Vsupply/2. The CT
output, modelled here with I1, will be referenced against this value.

U2 buffers the input from the CT, modelled with I1.  I think this buffer is
needed for accuracy, in order that the burden R1 be the only loading on the CT.

U3 and U4 amplify the signal in order to yield 50mV/A or 500mV/A outputs, depending on R8 which is selected by a switch.  Because the probe is not expected to be super accurate, 1% resistors will be used without trimmers for R8, but a trimmer will be used in series with R5 to set the initial scaling value.

U5 buffers the output of the divider R14 R16 R18 R15. R16 and R18 are a 10k
potentiometer. This is fed to a summing node together with the output of U4
to allow small dc offsets to be added to the output.

Now to my questions about the design:

Is my understanding correct about the need to buffer the CT output and avoid
loading it with anything except the burden R1?  If so, am I making a mistake
in tying it directly to the output of U1, the split rail?
I have researched unity gain buffers in connection with what I am doing with
U1, U2, and U5. This has led me to understand that having no resistor in the
feedback path will not be a problem for this low bandwidth device.  I believe
a feedback resistor to match impedance with the input is used in high speed
design?
I realize that I have nowhere quantified 'low bandwidth'.  Even a very
low value like 10kHz would be sufficient for my needs from this device. Am I right in understanding that I can use an LTspice ac analysis to find the 3dB point for the circuit (from I1 to the output) and regard that as the bandwidth?


texts:
I have repaired this circuit from a fridge but the soldering that I have marked in red seems to have pulled away from the copper track. That is because when I tried to replace the capacitor that was there, I had to pull and that was the problem. I have almost cut the track.

The circuit is now working, but I don't know if I can repair this in some way.


texts: What do they mean by "short-circuited" here?

texts:
"Short-circuit inductance is the inductance when one of the primary winding or the secondary winding of the transformer is short-circuited and measured from the other winding."

I can't understand the part of the sentence in italic. What do they mean by "short-circuited" in this context? Even the image given in the Wiki page doesn't make much sense.

As far as I know, if an inductor is short-circuited it means there is connecting wire across it (i.e. the potential at both ends of inductor is same)

Source: https://en.wikipedia.org/wiki/Short-circuit_inductance


texts:
Can anyone give me a rundown of the various licenses that are well-suited to open hardware?  I've designed a few circuit boards and would like to make them available for others to use, so I need to choose a license for them.

Things I'm concerned about:

Attribution.  Are others required to credit me?  If so, how?  I know this turned out to be a big issue with some BSD licenses for software.
Commercial use. Can folks copies of my work, or not?  I don't really care if they do, but I'd like some credit if so :)
Can others take my work and make "closed" derivatives of it?  Similar to #2, but for when people start changing things.
How "strong" is this license?  2 lines made up by a random hacker can constitute a license, but I'd prefer someone with legal training to have looked at it.


texts: How to find gain and phase margin from transfer function without Nyquist or Bode plot

texts:
Given transfer function L(s) as a ratio of polynomials of s, I know that we can find gain margin (GM) and phase margin (PM) by using a Nyquist or Bode plot.
From a Nyquist plot:

Find a point where the Nyquist plot of L(jw) crosses negative x axis, then GM=1/|L(jw)| at that point.
Draw a circle from origin with radius 1, and find an intersection of Nyquist plot of L(jw) with unit circle. PM is the smallest angle that is required for Nyquist plot to be rotated clock-wise in order for that point on intersection to touch -1 on x axis.

From a Bode plot: here is an answer.
Question: Lets say I am not able to plot Nyquist and Bode plots, but I need to find GM and PM.

Is there any way to find exact GM and PM?
Is there any easy way to approximate it?


texts: USB 3.x to Ethernet then Ethernet back to USB 3.x IC a.k.a usb over ip

texts:
Hey all I’ve been looking around a lot for a company that has a type of USB 3.x over IP. The ones I only see are not ICs but full blown products. These products cost $250+ so I’m looking to see if I could crate one myself for much less.
There are many USB 2.0 to Ethernet then Ethernet back to USB 2.0. Mostly known as a USB 2.0 over IP. Unlike the USB 3.0 variant, these USB 2.0’s are quite cheap. Some can be had for even under $20. I’m able to find ICs for those just fine but still nothing for the 3.0.
The IC I have found for USB 2.0 over IP:
Elite USB-OVER-GIGABIT
ETHERNET CHIP
The product I found that’s USB 3.x over ip is this one:
Digi The dual USB 3.1 Gen 1 Ports, single 10M/100M/1G Ethernet.
I’m beginning to think that all of these USB 3.0 over IP products are proprietary to that company and only they can produce it. AKA closed source/distribution. Even DigiKey can not find any chips for doing this.
The reason behind this is that I am needing at least 45ft from my server room to my office. I’m already running hdmi over fiber from there to my office and I installed a 35ft active USB 3.0 in wall when building the office. Once completed I hooked everything up and it was just too long of a distance because it would go off and on constantly. This even happened when I placed both power injectors on both ends.
There are also USB 3.x over fiber but I’m sure I could not build one of those since it deals with fiber optic converting and everything else that goes along with creating that. These also flux a lot in from from $150+.
Spetra 2 Port USB 3.0 Multimode Fiber Extender
It would be great if anyone knew of an IC that can do 3.x over IP.


texts: Will changing my capacitors for ones with higher voltage but same microfarad allow me to use higher voltage batteries

texts: I have a r/c car that I'd like to use 8 of the 3.2v AA batteries instead of the typical 8 1.2v AA. There are two capacitors one is 2200uf 10v the other is 220uf 16v, if i replace them with 35v of the same capacitance will that work.  Thank you


texts: Diode selection for truck wiring light application

texts:
I need to know what diode I need for a light set up I am working on.

The main current flow through the diode is going to be 9v going to power a 55watt roughly ??? amp bulb.  There will be ocassional burts of 12 v power for when the light is flashing however I am going to wire up a seperate switched line to provide constant power to the same light on demand with 12 v power and wanted to keep that from back feeding up the line that supplies the 9v power.

simulate this circuit – Schematic created using CircuitLab

Above is the schematic, I need help figuring out what diode I need to get so I do not fry the electrical systems in a 2012 sierra


texts: 18650 battery pack. Current distribution

texts:
I'm creating a 20s6p li-ion pack from 18650 cells. Here is the design

I am are using 8 by 0.2mm nickel strips rated for 6.5A. With 6 parallel branches that's 6*6.5 = around 40Amps. But since we doubled nickel strips we get 80A flowing in and out of the battery.

My question is about the current accumulation on each terminal of the battery which contains 6 cells in parallel. I'm thinking that the 80A current going to the battery cable will have to pass through a single point on the battery which can currently only handle 13A (1 parallel branch)

So I'm not sure if we should have 6 wires connected to each parallel cell to distribute the current before connecting to the main battery cable. Or could we just triple or quadruple up on the nickel strips at the terminals.

Thanks!


texts:
How can I generate a inverted signal of a 20MHz Clock signal synchronous to the original signal? (At least, very close to the original)

With a typical HEX INVERTER the propagation delay is already too high (5-10ns).

Should I use a single-ended to differential IC? Couldn't find any references on the internet.


texts: Why use a "load switch" and not just one transistor as a switch

texts:
I am trying to understand the advantage of using a 'load switch" for switching applications.

The load switch (like the one below), has two transistors to do the job. Why can't I just use one transistor (bjt/fet) for doing the same thing?


texts: Is it possible to increase amperage and voltage?

texts:
I have an input of 5V and 2 amps from a USB battery pack. Using this voltage and amperage, could it be possible to increase both values?

Here is an extremely simple representation of my idea.


texts:
Can anyone explain why the two capacitors (C8, C9) in the CLC input filter are set up the way that they are? The screenshot is from this reference design:
https://www.ti.com/lit/df/tidryx8a/tidryx8a.pdf?ts=1610621203568&ref_url=https%253A%252F%252Fwww.ti.com%252Freference-designs%252Findex.html
I will provide some more context to my question:
I understand that there needs to be a smoothing capacitor on the output of that full-wave bridge rectifier to smooth rectified DC voltage. A rule of thumb of 2 - 3uF per watt of input power yields a value of 135uF - 405uF for Cin.
I also know that there needs to be an LC input filter to help mitigate differential-mode EMI.
According to TI's AN-2612 (linked below), the LC values are chosen based on equations outlined in section 4.2.
I cannot for the life of me figure out how we end up with those capacitor values (or inductor values for that matter) in that configuration. Can anyone offer their expertise?
https://www.ti.com/lit/an/snva489c/snva489c.pdf


texts:
If I apply a unit step input to a linear system and get the following as output:

$$(1-e^{-4t})u(t)$$

does that mean the transfer function is then:

$$T(t) = (1-e^{-4t})$$

My friend seems to think so but I disagreed. I proceeded otherwise to find the transfer function.

$$Laplace((1-e^{-4t})u(t))= \frac{1}{s} - \frac{1}{s+4} = (\frac{1}{s})\frac{4}{s+4}$$

I can then take out the unit step input (1/s) to get the transfer function so:

$$T(s) = \frac{4}{s+4}$$

$$T(t) = 4e^{-4t}$$

Which of us is correct?


texts: Why no virtual ground in schmitt trigger?

texts: In the above inverting amplifier, we assume -ve node to be at 0V approx (virtual ground), because the open loop gain Aol is very high and hence the differential voltage (Vd = V+ - V- = Vsat/Aol) has to be 0V approx. But why this concept is not applied in the below schmitt trigger ? Should not the differential voltage Vd be = Vsat/Aol here too, despite the positive feedback ?


texts:
Reading a paper regarding a power amplifier based on HEMT technology, the following statement in made:

'The circuit was designed in WIN 0.1 μm GaAs process on a 2 mil thick
substrate,has power density of 850 mW/mm and its breakdown voltage
9V. According the process power density, a 4×25 μm device should
generate a saturation power of 85mW (19.3 dBm), so aiming for 0.5 W
(27 dBm) requires a combination of 8 devices.'

I don't understand how from the given power density and dimensions (which I suppose to be 'channel lenght x channel width' of the transistor), the saturation power ( 85mW ) is found.
Thanks to who can give me a hint


texts: Why do some logic gate chips have a reversed pin layout?

texts:
I am using some logic chips by Texas Instruments, namely SN74HC02N, SN74HC04N, SN74HC32N and others.

When I connected them in my circuit, the SN74HC02N NOR-gate didn't work as expected, so I searched for a datasheet. It showed that the pin layout for the chip was reversed: It was Y, A, B instead of A, B, Y.

The other chips from the same family and manufacturer that I have are all A, B, Y.
This is very counter-intuitive and doesn't make much sense.

Why does this one chip have a different pin layout?

Is there an alternative version that has a A, B, Y layout?


texts: For an induction motor that runs with negative slip value, is it true that the plugging operation occurs when an induction motor runs with negative slip value?


texts: Opamp input offset voltage...common mode?

texts:
Looking at the datasheet for an OPA197 opamp, I see this:

What is the circled expression trying to tell me?

The common mode voltage is equal to the voltage at the non-inverting input minus 1.5 V which is equal to plus or minus 10 µV?  I can't follow that.

Where does the 1.5 V come from?  What is the point of this section in the datasheet?


texts: How does the distance between two antenna count in Friis Equation?

texts:
The scope of this question may sound weird.
Let's say there are two very giant weird-shaped antennas (imagine they are both 50 meters long): one for transmission and the other for receiving. On a flat surface, one antenna is placed towards the other one while the other is set point to the sky. In this case, how can I determine the distance R in Friis Equation? (Or how to find the distance of arbitrary antenna pairs in 3d space?)
The example picture is shown as below. Don't mind my drawing, as I just want to show an uncommon case where the tiny distance difference is not negligible.


texts: Coupling factor and Leakage inductance/magnetizing inductance

texts:
I have so trouble to understand how the leakage/magnetizing inductance is defined in function of the coupling factor. Here is the first definition that I found. It mentions that the secondary is open circuited.

"It therefore". That's not explicite to me ... If someone can show me how they obtain the coupling factor. Or inversely base on the coupling factor how they can say the leakage/magnetizing inductance is function of the coupling factor.

I understand that it depends on the coupling factor and the formula makes sense to me but I m not able to demonstrate it...

Here is a second definition but this time, the secondary is short circuited. If I do not do mistakes when the secondary is short circuited, the primary inductance is equal to the leakage inductance.

The source is the following https://en.wikipedia.org/wiki/Leakage_inductance.

Also here is the definition from LTspice :

Thank you very much and have a nice day :)


texts:
Before starting the question, a reminder of the difference between on how a baud rate and a bit rate relate.

  Two people are standing 1km apart and they want to exchange a 8 bits of
  data. Beforehand they decided that each will be given flags that have
  digits from 0-3 printed on them. They also agreed that they will change the
  flag every 1 second. They also agreed on the following symbol to bit
  mapping:

  0 - 00

  1 - 01

  2 - 10

  3 - 11

  They will be exchanging the information at a rate of 1 symbol per
  second. The baud rate is 1 symbol per second. The bit rate is 2
  because one symbol carries 2 bits of information.

To connect to a serial console of an embedded device we physically connect the device with a cable similar to this one. After specifying the correct baud rate we get a terminal and are able to communicate with the device through our PC.

My question is whether there is a standard UART mapping between the symbols and the bits?

Is the UART symbol to bit mapping a one on one relation? Voltage level low -> 0 Voltage level high -> 1?

If not, what kind of carrier for bits is used?


texts:
I am finding it very strange what is the role of R1 in this circuit, and what would happen if I would just remove R1 along with its connection, i.e., remove the connection inside the pink box:

Wouldn't both leads still get amplified?

No matter how much I read about it, opamps are still not intuitive for me.

Another strange highlight, is that this diagram looks exactly the same as the following, but the author now calls the "non-inverting amplifiers" by "voltage follower":


texts: Capacitor and Inductor Filters, no resistor?

texts:
Often in circuit diagrams capacitors and inductors are used to either pass or attenuate high or low frequency signals. For example a choke is an inductor which can be used to limit the passage of high frequency signals and sometimes bypass capacitors will be used to "short" or "shunt" high frequency signals to ground. Sometimes such elements appear seemingly "by themselves". I understand that inductors present high impedance and high frequency and low impedance and low frequency and the opposite for capacitors so I have an intuitive sense how they can be used as high and low pass filters. However, if I want to get more quantitative I might want to know what constitutes "high frequency" or "low frequency" for a given configuration. For that there need to more details. Single pole filter cutoff frequency always involve a resistance.

For example, I'll look at capacitors or inductors chosen for circuits and wonder "why was that value for the capacitor or inductor chosen?" In my mind it must have been so that the filter has the appropriate cutoff. But what sets the resistance to determine the cutoff?

My main guess based on some recent reading I've done is that these elements (inductors or capacitors) have some amount of inductance and capacitance as they are specced, but they also have stray inductance and capacitance as well as some stray resistance. It is all of these stray features which set the ultimate technical limit for the use of some device as a filter. In that case, you would have to look at the data sheet for whichever choke or capacitor or whatever that you are using and ensure that it has the appropriate frequency response in whatever band you are concerned about. Is this correct?

The other possibility is that the resistance must come from the rest of the circuit. For example, maybe the input or output impedance of neighboring devices must be considered in series or parallel with the capacitor or inductor to determine the cutoff frequency. Or maybe it's just the resistance of the wires. I'm not sure, maybe it can be any of these.

I realize it is probably hard to give an answer to this question without me presenting a specific circuit that has confused but perhaps someone can give me some general direction anyways.


texts: Can spike voltage transient at input gates during control signals switching be avoid?

texts:
I have to say that this circuit is mounted over a protoboard. This is a probe scenario.

I have a logical circuit where Vin = 12V and sometimes this control signals must switch to 0V and from 0V must switch to 12V. This Vin nodes are the logic gates inputs (AND, OR, NOR, etc..) from Texas Instruments families: CD40xxB.

This is not about my doubt but I explain this for having a general scope: The logic gates outputs will connect to a driver and this one drives current to relay's coil. Driver has its own internal flyback diodes, etc.

simulate this circuit – Schematic created using CircuitLab

During switching, I have a transient from 12V to 16V at every point of the circuit where any control signal switches from 12V or from 0V to the opposite value. Logic gate inputs and outputs are getting this transient:

I think 12V to 16V maybe is not a danger neither a too much big spike. But I'm trying to minimize it as much as I can. Because I don't think this spike will be good for gates inputs that have input protection diodes that can be forward biased during transients.

I'm not totally sure if it could happen, even if there could be something wrong.

Is it normal?
How can it be avoid?
Have you seen something wrong?


texts: Independently scaling the max/min readings of an analog sensor?

texts:
I'm currently working on a project that entails reading an analog signal with an AVR microcontroller and using it to control the brightness of some string LEDs. The signal is generated by a photoresistor whose resistance varies between about 10kΩ when illuminated and 200kΩ when dark, so connecting one end to my 5V power supply and the other to a 10kΩ pulldown resistor gives a signal between about 0 and 2.5V.

The Problem:

What I'd like to do next is scale/offset the signal from the photoresistor to constrain its range to some subinterval of 0 to 2.5V, with the new maximum and minimum controlled by a pair of 10kΩ potentiometers. The end goal is to allow the user both to manually clamp the signal either high or low (regardless of the signal from the photoresistor), or to set the desired range and allow the photoresistor to vary the signal between those reference points.

Ideally, I'd like a setup where one potentiometer sets the maximum and the other to sets the minimum, making the controls as intuitive as possible, but I'm open to any solution that accomplishes a similar end result. I only have one analog pin to work with, so reading signals from the photoresistor and potentiometers separately and handling everything else inside the microcontroller isn't an option; I'm also aware of multiplexing, but the behavior I'm looking for seems simple enough to achieve with an analog solution.

Any tips?


texts: How does / can this radar wave detector circuit work?

texts:
I have difficulties to understand how the below circuit can detect radar waves by only using C1 and the lengths of its wires to IC1. Can this work? And if yes, how? What is the physics theory behind this?

This circuit uses a 1458 dual op-amp to form a radar detector. C1 is the detector of the radar signal. The first op-amp forms a current-to-voltage converter and the second op-amp buffers the output to drive the piezo transducer. R5 sets the switching threshold of the second op-amp; normally it is adjusted so that the circuit barely triggers on background noise, then it's backed off a bit. The response of the circuit may be tuned by adjusting the length of the leads on C1. For typical road-radar systems, the input capacitor's leads should be about 0.5 to 0.6 inches long.

("Radio-Electronics" Magazine, Jul,86 issue (C) Copyright Gernsback Publications, Inc., 1986)


texts: Is the GND-pin of an USB-port connected directly to common ground?

texts:
(source: usb3.com)
Is the pin on the left connected directly to the ground-plane of the motherboard? Just a wire, without any resistance?


texts: What is a Reacto Tester unit and are there any projects in which I can use it?

texts:
I was given an old piece of electronics. It is a Reacto Tester made by Antronic Corp from Chicago. After a quick glance at the manual it seems that its a tester for tube display units such as television (color and black).

I am wondering if there is any actual usage for stuff like that these days? Who would have been most likely to use this kind of electronics?

Anyone has any idea how old this thing is? What was its value back then? What its value these days?

 -->
 -->

Here are some pictures.


texts:
I'm have a low cost (<2$) soldering iron, similar to the one shown in the image, except that it has 3 plug terminals.

Suddenly something got me thinking about safety, out of curiosity I cut the wires, to find only 2 wires (I was expecting 3). I was wondering why I'm not getting a shock? I touched the metal heating rods and tips, nothing happened (with a tester first, of course). I don't find any isolation between the heating element and me. I'm guessing the neutral is wired on the outer side (which should be very close to ground potential).

The overall circuitry is just a diode and an led with 100k series resistor.


texts:
I'm configuring I2C on a PIC18 using the built-in functions of the C18 compiler as described in section 2.4 of the documentation:

void OpenI2C2( unsigned char sync_mode,
    unsigned char slew );

I'm not sure what I should do with slew. I can choose from two options, defined in i2c.h:

SLEW_OFF: Slew rate disabled for 100 kHz mode
SLEW_ON: Slew rate enabled for 400 kHz mode

In the datasheet in register 15-1, page 257, the two options are explained in a bit more detail:

1 = Slew rate control disabled for standard speed mode (100 kHz and 1 MHz)
0 = Slew rate control enabled for high speed mode (400 kHz)

I don't understand it though - I have a couple of questions:

What is slew rate?
For me, the two options don't make sense - what if I'd want to disable the slew rate for 400kHz and enable it for 100kHz? Why is this?
When should I choose SLEW_OFF and when SLEW_ON?


texts: What is the purpose of the 6k2 pulldown resistor in the GPIB interface?

texts:
Ie:

Dedicated chips exist, but older equipment use discrete components for this, where the output is often an open-collector gate/inverter. The purpose ofthe pullup is something I understand, but what is the purpose of the 6k2 pulldown? Is it to terminate the bus with a certain impedance? Just curious.
The GPIB control-lines are a type of wire-or, so that any or all devices can hold down (assert) say NDAC to control the bus speed. Thus the slowest device controls the speed of transfer.
Image is taken from here: http://bitsavers.org/pdf/hp/hpib/TutorialDescrOfHPIB.pdf


texts:
I'm designing a basic GPU in Verilog. However, there are going to be pins that should read/write RAM. Problem is, I can't know how many bits of data the RAM can take at a time ahead of time (since it's supposed to be general purpose). The only thing I know for sure is that there is at least 32 bits of address bus.

If I send too much data, some RAM chips may not support it.

If I send too little data, there may be alignment issues and other problems when sending odd bytes.

What do I do?


texts:
I am trying to invert the output of a shift register using an open-collector TTL inverter with 33K pull-up resistors.

The inverter works fine when input=HIGH, but when the input is LOW, the output is LOW. I tried using some bypass capacitors at the inputs but that didn't seem to work. See included figure.

The square oscillations seem to be coming from my clock somehow.

Any suggestions for getting output to be high when input = low?

Here is my schematic (constructing a 4-bit successive approx circuit).

I realize that there are a bunch of double-negatives, but that is because I only have NAND gates and inverters to work with, and my flip-flops come with ~CLR and ~PRE inputs instead of S and R.


texts: Do all inductors produce 1 weber after one second when 1 volt DC is applied?

texts:
A definition of magnetic flux (the weber) is stated here as: -

  If you take a loop of superconducting wire, and apply 1V to this wire during 1s, then the magnetic flux inside this loop will have changed by 1Wb. Note that this is true regardless of size or shape of the loop, and regardless of the matter that's inside the loop! In practice it holds true enough even when the wire is not superconductive, as long as its resistance is low enough to cause only a negligible voltage drop at resulting current.

I believe the above definition is true but I'm prepared to have this belief reset. As an aside this is a basic form of Faraday's law i.e. voltage = rate of change of flux.

So, a big coil (or a little coil) both produce the same flux after one second when 1 volt DC is applied. But what about when the coil is two closely wound turns?

With closely wound turns, the coil inductance is proportional to the square of the number of turns so, 2 turns produces 4 times the inductance and accordingly the rate of rise of current (when voltage is applied) reduces by 4.

This is embodied in the other well-know formula, \$V = L\dfrac{di}{dt}\$.

Given also that the definition of inductance is flux per amp, we can re-arrange this so that flux = inductance x current and, because inductance has risen by 4 with current reducing by 4, it appears that the flux produced by a 2-turn coil (after one second) is exactly the same as the flux produced by a single-turn coil.

You could extend this to as many #turns as you want providing these turns are closely coupled so basically you could say (as per the title): -

All inductors produce 1 weber after one second when 1 volt DC is applied

Now Faraday's law states that \$V = -N\dfrac{d\Phi}{dt}\$

And this is where I'm starting to have a contradiction.

Faraday's law is about induction i.e. the rate of change of flux coupling through \$N\$ turns produces a terminal voltage that is \$N\$ times higher than that for one turn. It works the other way around also; if one volt were applied for one second then the total flux produced by a two turn coil would be half that produced by a single turn coil.

Where am I going wrong in my thinking?


texts: Mesh current method problem with voltage controlled current source

texts:
I'm signed up recently to this site but i need help for my Fundametal of Electrical Engineering course.I need to find power of the current source. Thank you.
Note: (y is equal to 2)


texts: Is there a 16 to 4 one-hot simple encoder IC chip?

texts: I'm looking for a chip that has 16 inputs where if only one of the inputs go high then it encodes the data to a 4 bit output. If one doesn't exist what would be the simplest way to build such a circuit?


texts: Texas instruments C1101 RF1100 module Schematics

texts: does anyone got schematic from this module. I tried searching around but didn't get anything except main header pin-out. There are also 2x2 pin on each corner, but there is no info about them.


texts:
okay so my situation is that i am working an avr chip which is the atmega 328p and what i want to do is i want to lets say have a user input in python lets say the user types in a string and from there i want my avr c code to interpret the code.

The reason i am doing this is because i am making a basic cnc gui so the user will input a stepper motor axis like x y or z then the direction "-"  or "+".

Then a distance which is a number into python and then from python i want to send this info to the avr-c code which will then use the info to control steppers.

I want to avoid using the default serial communication thing in avr c because it will be harder to do since the user will input  strings like "x-20 y+10" and etc.

It is much easier to use python to interpret the text  then to use avr-c so how would i go about doing this
////////AFTER SOMETIME//////////////////////////
okay so after much confusion and researching I came up with a code based on the syntax of pyserial as well as the struct modules, here is the code:

            import serial
            import struct
            import binascii

            #Function to Initialize the Serial Port
            def init_serial():

                global ser       #Must be declared in Each Function
                ser = serial.Serial()
                ser.baudrate = 9600

                ser.port = '/dev/ttyACM0' #com port of avr

                ser.timeout = 10
                ser.open()          #Opens SerialPort
                # print port open or closed
                if ser.isOpen():
                    print 'Open: ' + ser.portstr

                    init_serial()
                    values = (1)
                    s = struct.Struct('I')
                    packed_data = s.pack(*values)

            ser.write(packed_data)    #Writes to the SerialPort

            while 1:

                bytes = ser.readline()  #Read from Serial Port
                packed_data = binascii.unhexlify(bytes)
                s = struct.Struct('I')
                unpacked_data = s.unpack(packed_data)
                print 'You sent: ', unpacked_data      #Print What is Read from Port

            #Ctrl+C to Close Python Window

Please inform me if I am doing something wrong or right, or if this code work actually work at all, if so this is the python side of the transmission of python data to avr-c, how would I then handle the avr-c side of this communication with python over serial communication?


texts: Meaning of marking on LCD CCL power connector?

texts:
What does this marking mean on a cable connector for two wires:

Edit
The connection comes from the LM170E03 LCD Screen from Phillips. It is the connectors for the power source for the backlight in the LCD screen.