texts: Why would the Schmitt trigger relaxation oscillator a bit unstable?

texts:
This thing oscillates from time to time. Why? (Respect part numbers, all chips from NXP)

simulate this circuit – Schematic created using CircuitLab

C14 = 74HC14D (no Schmitt trigger symbol in Circuit Lab), C06 = 74LVC1G06.

The 10uF cap is a 1206 SMT tantalum I recycled from a dead board.

All SMT parts mounted on adapter boards and entire circuit is powered from USB, with another scrapped 10uF tantalum as filter cap and a (also scrapped) polyfuse. No bypass cap used.

-- EDIT --

Added bypass caps per Spehro Pefhany's suggestion, still does not work. However by replacing the long USB lead with a Li-ion battery pack it worked. Why?

-- EDIT 2 --

Here is a picture of the actual set up. Li-ion pack shown and working, but with USB it does not work properly.

The big blue cap is a 4700uF aluminum electrolytic, the yellow square caps on boards are the 10uF tantalums, and the small leaded yellow caps are 100nF ceramic. The big chip is 74HC14, and the smaller one, sharing an adapter board with the LED, is 74LVC1G06. I am still using that buffer. The board strapped onto the Li-ion is charger/controller board, can be safely ignored.


texts: If a common mode choke (CMC) is added between PWM signal and PWM return without additional chassis return path, will it act as a common mode filter?

texts:
In this schematic a common mode choke is added between PWM output and PWM ground (return path.) There is no other return path to load (like through parasitic capacitance to chassis.) In this case, will it act as a common mode filter?
CMC is added between the output of PWM generator and LISN. DUT load for CE testing is on the right side of LISN:

This was suggested to suppress conducted emissions across supply line when tested across positive and negative lines.


texts: When to use BJT in differential configuration instead of op-amp

texts: Why would one use a BJT differential amplifier configuration such as this(these) one(s) instead of an op-amp? Are there any pros and cons to both these circuits? I would maybe assume that a BJT amplifier might be cheaper and be used by companies to reduce costs, buy I'm not even sure if that is true.


texts: Connecting many proximity sensors to a controller

texts: I need to connect many (about 100) IR proximity sensors to a controller. What are my options? Can use any sensors, for example one of those - https://ams.com/proximity


texts: Attack and Release times of the Automatic Gain Control

texts:
What is Attack and Release times of
the AGC? I couldn't find any understandable pdf on this.


texts: How to convert sensor signal to temperature from the data available from the datasheet?

texts:
I have a Pyrometer datasheet showing signal percentage (0 to 100%) with the corresponding respective temperatures (from 0 to 200 °C) and current values (from 0 to 20 mA) in the whole measuring range.

Practically, I get the Pyrometer signal output as a voltage which I want to convert into temperature by using the above data. What is the procedure to do this?


texts:
I recently took apart my camera to solder some wires onto the take video button so I could trigger taking videos remotely. The button for this was housed inside a plastic housing and all I could find was a thin fpc connector that contained lines for several buttons. I scraped off the plastic with a knife and attempted soldering on a very small wire. BIG MISTAKE.

The iron melted the plastic, but not the solder paste! It also managed to rip/melt the wires at that point in the connector.

I have two questions for the EE Community:

(1) How can I fix the connector I destroyed

(2) How can I attach wires to this connector for an oscilloscope reading and eventual automation?

One Idea I had was to use conductive paste...


texts: How does this circuit work? I can't reproduce the results in real life

texts:
I've built this circuit in Paul Falstad's circuit simulator (trapezoidal approximation is off), and I don't understand how it works.
When I switch the input from 0V to 5V and then to 0V again, the node to which the diodes connect has a voltage difference to ground of about -4.8V.

How does it work?
Why can't I replicate it in real life?

Is there something wrong with the simulator?


texts: How do I pick an inductor(s?) for an LC filter on a power rail?

texts:
I'm using a TI SN6501 transformer driver to provide an isolated power supply for a project I'm working on.  However, it is imperative that the output power rail be as clean and noiseless as possible, so I've added an LC filter onto the output of the TPS76333 (a 3.3V LDO).  The SN6501 datasheet says that it switches at 410kHz, but the switching frequency can range "between 300 kHz and 620 kHz for VCC = 5 V ±10%" depending on things like ambient temperature.  While I'm fairly certain my project will never be used outside of room temperature, I still want to make sure that I'm doing a passable job of blocking this entire frequency range.  Will the schematic excerpt shown below work?  If so, how do I best pick an inductor to block these frequencies- what specs, physical sizes, and other factors should I consider?

Edit: Added a new picture of my schematic, hopefully this one is more readable.


texts: How can I add to LTSpice the MC34063 model?

texts:
I found the MC34063 moden in the eevblog forum: link

How can I add it to the LTSpice to if I want to make a buck or boost converter it appears in for.example in the power product list?


texts:
So I am trying to assign footprints right now to all the components in my schematic. My schematic is all about a flyback converter. I have assigned footprints to most of the components such as resistors, capacitors (radial and rectangular throughholes), MOSFET (TO-247 package for example), and stuff. The only ones remaining that I haven't assigned footprints yet are the following:
1.) 2-pin terminal block (both on input and output)
2.) Holes for the transformer bobbin.

So my questions are:
1.) How do you assign footprint to a 2-pin terminal block? In my schematic, I used 1x2 CONN (connectors) for the two terminal blocks but when I am now assigning footprints via CvPcb, I can't seem to assign footprints to the terminal blocks well. What am I considering at this point is that, instead of using a 1x2 CONN on the schematic, I'd just place two 1x1 CONN instead, and assign individual wire-pads for each 1x1 CONN. And since I know that my terminal block pins has around 5mm distance, I'll just separate the two pads by 5mm on the PCB layout instead. Is this ok?

2.) Basically, same problem as the first one but instead this time, I want to assign holes for the transformer bobbin that I will be using. In my case, the bobbin that I will use is for the PQ26/20 transformer core that I will be using. The mechanical details of the bobbin is shown below.

Fig.1 Bobbin Mechanical Details

Since I know that separation distance between the bobbin pins, what I am thinking for the transformer footprint is that I'd do the same as in 1. Assign 1x1 CONN in the schematic for each bobbin pin I'll be using (transformer winding-pins). Then in footprint, assign wire-pads individually. Then on PCBlay-out, I'll just place the wire-pads based on the mechanical data that I have. Is this ok?

For extra info, a part of my schematic is shown below for the terminal blocks (CONN) and transformer core that I want. Right now, in my schematic, I placed a transformer as is, instead of six 1x1 CONN for each transformer pin. To avoid confusion, the two 1x1 CONN (P3 and P4) in the schematic are just for the fuse that I'll be using.

Fig. 2 Input Terminal Blocks

Fig. 3 Transformer (bobbin pins) and Output Terminal Blocks

Fig. 4 1-2mm wire-pad that I am considering on using


texts: Whats the minimum voltage and current to feel stimulation on skin?

texts:
What I'm trying to ask is what voltage and current is necessary in order for it to be felt on the skin when touching an electrode? And is AC of DC better for this job?

I know it depends on the distance between the electrodes and the resistance of the skin.

To put this into perspective, I'm trying to replace vibration notifications - like the ones found in smart watches- with an electric shock. I couldn't find any information on this. Maybe someone can give me some good starting values or an amperage and voltage range and I can just experiment to find the optimum.

Thanks


texts:
I am currently working on a 4-layer PCB that uses a Cypress PSOC4200 with a USB Full Speed connection. However, I am completely overextended with calculating the impedance and the resulting requirements of the traces.

I am working on a printed circuit board with the following layers:

Layer 1: Top (USB Signals)
Layer 2: GND
Layer 3: VCC
Layer 4: Bottom

I want to layout the D+ / D- Signal Lines in CADSOFT Eagle, however this program does not offer calculation. Can anyone point me in the right direction?
I have seen the PCB Saturn Software, but I am not sure what to fill in. I am planning to order the PCB from this manufacturer:

http://www.pcb-specification.com (Tag Layer Build ML4)


texts: How is galvanic isolation established in an SMPS?

texts:
I can understand how an isolation transformer can establish isolation but since SOME SMPS supplies don't have transformers and they have rectifiers instead I wonder how the AC and DC ends are isolated.
Edit: Here is an SMPS with no galvanic isolation.
Here is the datasheet which says there is no galvanic isolation.
How is that possible?
I'm asking because people here all agreed SMPS has small transformers which isolates the input and output power.


texts: Can I update the Beaglebone Black without a micro SD adapter?

texts:
I lost my micro SD card adapter, and the stores around here don't sell them (except in a package with a micro SD card). Hence, my question:

Can I update the Beaglebone Black (i.e., program the on-board eMMC) without a micro SD adapter? Perhaps it is possible to dd the flasher image from usb storage to the microSD using the BBB? Detailed instructions would be appreciated, as I am far from a Linux pro. My main computer runs OSX 10.9 (macbook pro retina 15).


texts: Use BBB analog inputs with 0..5V or 0..10V

texts:
I plan to use the BeagleBone Black analog inputs for sampling of analog data. But there are some major problems for this:

BBB allows a maximum of 1.8 V analog input voltage while I have 5 V or 10 V max
there are two lines AGND and VDD_ADC where I don't know how they are involved here and what to do with them
my knowledge in electronics is very limited

My only idea: a voltage divider with two resistors (that's within my range of knowledge), but there I see some problems:

resistor tolerances which make measured data inaccurate
in case of tolerances being at the wrong end it may be possible the maximum 1.8 V analog input may be exceeded and the BBB can be killed
when I choose values of  resistors in a way where this can't happen, I lose a part of the limited 12 bit sampling range

So...what could I do to solve this? How can I measure 0..5 V or 0..10 V ranges with the 0..1,8 V ADC range of the BBB?

It would be really nice when somebody could provide a schematic I could use for setting up my hardware (yes, soldering some components is within the range of my electronic possibilities ;-)

Thanks!


texts: Can a DC-DC regulator support a high inductive load?

texts:
Can a cheap voltage regulator (DC to DC Buck Converter Step Down) blow up when I connect/disconnect a pretty big inductor (about 9000 turns) or is it self-protected?

I am asking because it makes a pretty big flame when I connect the inductor to the power supply (15V).


texts:
I'm trying to use a BC108A (datasheet) transistor as a switch for a 12V power supply using the 5V digital out pins on an Arduino Uno board.

I have connected the collector the 12V supply, the base to the 5V pin on the arduino  and the emitter to ground via a multimeter.

Here's a picture of the setup:

Where red is multimeter to ground, blue 5V and white 12V.

I thought that this would result in 12V flowing out from the emitter when the base was high and nothing flowing out from the emitter when the base was turned low.

However my multimeter reports 6.1V from the emitter.

I think I got the pins figured out so I don't understand these results.

Can anyone explain these results? I'm new to this field so it's possible I got something basic totally wrong...


texts: When has to be used a ferrite bead in power supply?

texts:
I'm designing a PCB with a Telit GL865 GSM/GPRS module. I find this example in Internet and I am wondering why has it got a ferrite bead on 3.3V power supply line.

Some extre values from datasheet:

Vin between 3.22V and 4.5V (Extended mode) and 3.4V to 4.2V (Normal Operating Mode)

Iaverage=360 mA
Ipeak_max = 2A in 0.625ms when the module is sending a GPRS message

Two questinos about:

1) What is the sense of put a ferrite bead in DC power supply lines?
2) How can I choose the appropiate value of it?


texts: Are "ionizing" hair dryers any different from the regular ones?

texts:
I've been shopping for hair dryers and in all malls I've been to the salespeople explained how the "ionizing" hair dryers are better than the ones without that function, because it makes your hair less frizzy. I have been able to talk four of about twelve of them to come clean with me and tell me if they actually knew the science behind that, and they said they didn't really know how that works, but they were instructed to tell that to customers to sell more of these new, more expensive dryers.

Reading up a bit on how the fans and dryers work, turns out they tend to make the air passing through them leave electrons on the encasing, and the air coming out of them is slightly positively charged. So to negate that, hair dryers have negative ion generators like YFA-114 variants from Youji.

I have been drying my hair with the old non-ionizing and the new ionizing dryers and I haven't noticed any difference with my hair length (~15cm). Maybe it matters more with longer hair, but I asked girls with longer hair to try these out and they said they didn't notice any difference between them either. Maybe my hair dryer doesn't have a working ionizing element, maybe we're just not seeing the difference, or maybe it's just a marketing trick.

There's also an awkward situation when sometimes you want to get more volume in your hair, so you'd want to turn off the negative ionizer. I've seen some hair dryers on the internet stores have a switch for it, but most don't, leaving you less options. If so many people would have bought those dryers and had problems with achieving volume, you'd think it would be something people talked about, but that's not the case. Perhaps because there's no actual difference at all.

Do these fans actually ionize anything? Is it really helping reduce hair frizziness? If it doesn't work, why not, and how would it work in theory?


texts: Latching relay dual supply to coil under fault conditoin

texts:
I could use some advice please.

I am looking to use a set/trip relay as part of a safety critical circuit.  Both set and trip supplies are interlocked via other contacts but I am in the process of doing a FMEA, and was looking at what effect it would have on the relay if both coils were energised at the same time under a fault condition.

The relay is an Arteche BF-4BB latching relay with coil over voltage protection.

I believe the relay would not chatter and the circuit with the most impedance will eventually win.
The supplies to the coils are both driven by timer relay contacts and are asymmetrically off-set. (that is, the set coil is driven from a 2 second constant supply and the trip coil from a 4 second constant supply.)


texts:
so I have this diode that is under a transformer on a battery charger. I was looking for faults on it with a thermal camera and noticed the one next to it was glowing at over 120C . I removed the hot one and it is pretty much shorted as shows 0.03 in both directions with the diode test. Iv also got a peak tester dca 75 and it won't even identify it as a component.

The one next to it is marked with V21 and is just a regular looking brown / orange looking colour and is glass.
I would go on what the dca 75 says, but each time it tests the working one, the vf goes up.

It's been so hot that it's burnt 99% of the markings off it, but it looks to be paired with the one next to it.
The problem is I can't seem to find a replacement for it. "V21 Zener diode" just brings up an smd diode sot 23 package and not a through hole glass diode like this.


texts:
I'm trying to solve the following question (a):

According to the solutions manual and wolfram the answer is:

http://wolframalpha.com/input/?i=%28%285-6i%29-%282%2B8i%29%29%2F%28%28-3%2B4i%29%285-i%29%2B%284-6i%29%29

http://imgur.com/CyFHil4

This is what I've done:

I'm not getting the right answer and I don't understand why. I'm following the phasor multiplication and division rules:

http://en.wikibooks.org/wiki/Circuit_Theory/Phasor_Arithmetic

I'm using the fx-300MS for all polar and rectangular conversions.

EDIT: I've tried using exact values, but same problem.


texts:
I am designing a PCB which incorporates a LM2576 LM2576 datasheet in the T0-263 package which is a SMD with a power disputation of proximity 2W(calulated from datasheet).
I am after some help in figuring out which type of heatsink is required. For this example I have decided to use Rjc(top) (but if you could tell me the difference from top & bot that would b great)
I understand Rja=(Rjc+Rcs+Rsa)2 ,Rjc(top)=43.3 but I don't know what Rcs is? I would assume its Rjb in this case since its a PCB mounted component.
From the data sheet the following is observed.

From this point I am not sure where to go from here. I would assume that you would want a heat sink with the lowest thermal resistance possible to reduce Rja? But being pointed on the right direction would be a great help.
Thanks,


texts: How to control 1 PWM in MOSFET H-Bridge driver with current sensing IC?

texts:
How can I design a MOSFET H-bridge motor driver controlling only 1 PWM for a motor?

I also wish to use BTS50055 Highside High Current Power Switch for current sensing in the motor driver. Could someone explain more about BTS50055?

I'm just not sure if it can drive motors too because I was told that it can replace a MOSFET to simplify the circuit. I don't quite understand how.


texts: Multiple infrared proximity sensors and Arduino

texts:
I am wondering if it's possible to connect multiple infrared proximity sensors as this one
http://www.adafruit.com/products/1568
to an arduino uno. I would need to connect 5 of them pointing in different directions.

Should i use an external power supply for each of them to be sure they are all running at 5V? Should i be aware of something else or it should be just plug and play as if i was using just one sensor?
Thank you very much for your support. Any suggestion is higly appreciated!

Ok thank you very much for your answers. So a connection diagram like the one attached should work?
Thank you again for your help

!Multiple infrared sensors connection diagram
IMAGE DIAGRAM


texts: Uneven (10 dB) RF Power Splitter/Combiner

texts:
I'm trying to modifying and improve the MIT radar project

Here's the basic block diagram:

Input power is split by 3 dB SPLTR1 to transmitting antenna and LO input to the mixer. From what I understand, I don't need to input 13 dBm power to mixer, so I was thinking on putting, say, 10 dB splitter instead with relatively low insertion loss so I don't waste power.

I've searched for 10 dB RF power splitters on digi-key, mini-circuits, etc. but I can't find one. How should I search for them, or, are they impractical?


texts: Connect unused inputs/outputs on RS232 line driver/receiver Chip

texts:
What is the safest (and reliable) way to deal with unused input/output pins of serial comm. chips like MAX232, ST3232, etc..

So far i'm familiar with these three options:

Input and Output Not connected
Tie inputs toghether (ie. MAX232 connect pint 10 to 11, and 8 to 13), output not connected
Pull-up/Pull-down resistors to input, output not connected.

I've seen this setups many times and never with a proper explanation as of why it was chosen. Maybe there's another setup i'm not familiar as well.


texts: How to replace two AAA batteries with a capacitor

texts:
I am trying to replace two AAA batteries with a capacitor in a wireless mouse. The mouse pulls at 1.2V and .023 A and I was trying to find what kind/size capacitor there was a similar question posted here (How to calculate equivalent capacitance to a battery?)

But I couldn't quite makes heads or tails of the variable s he had used in his formula otherwise I would not be posting. So hopefully I can find some help.


texts: How is asynchronous reset physically implemented in a flip-flop?

texts:
In Cliff Cumming's excellent paper on asynchronous vs synchronous resets, the following paragraph about the risk of metastability appears on page 19:

  Attention must be paid to the release of the
  reset so as to prevent the chip from going into a metastable unknown state when reset is released.
  When a synchronous reset is being used, then both the leading and trailing edges of the reset
  must be away from the active edge of the clock.

The paper in particular notes that metastability is not a risk when asserting reset on a flip-flop with asynchronous reset, and explains why on page 23:

  There is no reset metastability issue when reset is asserted because the reset signal bypasses the
  clock signal in a flip-flop circuit to cleanly force the output low

How can a asynchronous reset in a flip-flop be implemented such that asserting the reset carries no risk of metastability on the output?


texts: How does a GPU/CPU communicate with a standard display output? (HDMI/DVI/etc)

texts:
I am interested in how the cpu/gpu presents (to whatever equipment that it does) video data after it has been processed.

I have been told that the video is processed by the CPU/GPU and then sent to an integrated circuit by high speed serial that converts the serial signal to an appropriate display output, but I can't confirm this by searching online.

I'm interested in the signaling and can't search for protocols/etc because I don't know what it is that I'm looking for. So does the CPU/GPU interact with video outputs directly (I can find these protocols easily) or is there a "middle man" so to say and if so what is it, type of chip/etc?


texts: Why do we need a flip-flop in this circuit?

texts:
Supposing I built some machine x3 that is capable of multiplying the input by 3.  If I want to multiply some number with 3^3 then I should use 3 instances of the machine.
My book asked for another solution using minimal hardware.  The solution appears in the image I have added, where S is 0 for the first clock cycle and then for other cycles it's 1 to allow previous result to enter and multiply it by 3.
But I can't understand why we need the flip-flop here? Why can't we just connect the output of x3 directly to the mux? What's the problem with that?
I know it's wrong because removing the flip-flop will result in using less hardware so if it was true my book would mention it.


texts: Confusion in selecting number of state variables

texts:
Generally we take no. Of state variable equal to number of independent energy storing elements ,
let's take two examples -
1.a RC circuit with voltage source as an input ,so here we can take  different State variables but we need only 1minimum state variable ,so we generally take voltage across capicitor and with the help of this state variable and input we can calculate any possible system variable.
2.A partical of some  mass  and an input force ,so same as RC circuit ,it has only one energy storing element(mass) ,so it also requires only one state variable.
But in almost every books
why in case of mass elements (or mechanical systems in 2nd example) state variables are taken as position and velocity rather than only position?
isn't we unnecessary increasing one extra variable or there are some other reasons that I'm not aware?
When RC circuit and a single mass element is analogous then why 1st require only one minimum state variable while other require two?


texts: What equation do I use for simple class AB input impedence?

texts:
I'm a novice at this.  I've done some figuring and would love to know if I've got this correct before I move to more complicated circuits.
I have the simplest Class AB amplifier and I'd like to know its input impedance.  I'm starting with the assumption that I can use \$R_{ib}=\beta(R_L+r_e)\$ to find the impedance looking into the base, as I did when I worked with Class A bjt amplifiers.  Here is the circuit:

I started by finding the dynamic resistance of Q1 with: \$r_e=25mv/I_c\$   I assumed that when \$V_s\$ is at its 10v peak the base-emitter junction will drop 0.7v and leave the emitter at 9.3v,.  This would mean my current through \$R_L\$ will be 9.3mA.  This gives a tiny value: \$r_e=2.7\Omega\$.  With \$R_L=1k\Omega\$ and \$\beta\$ of 50, that gives an input impedance of $$R_{in}=50(1000\Omega+2.7\Omega)=50,135\Omega$$
This suggests that a good approximation for such a simple circuit would be simply \$\beta*R_L\$.  Correct?
Also, do I need to account for the condition of when \$V_S\$ is nearing the deadzone (say, at 1.0v) and \$r_e\$ is higher?
Lastly, do I need to consider the second transistor Q2 even though it is off when Q1 is on?


texts: SMD footprint design: Heavy copper, pad width smaller than pin width?

texts:
I'm working on a high power board that's using heavier (4oz) copper.  I have an IC on this board in a 0.8mm pitch QFP-32 package (no other package options available).  The IC's datasheet says the pin widths will be between 0.3mm and 0.45mm, and on the recommended footprint the pads are 0.45mm wide, which leaves 0.35mm (~13.8mil) between them.  My PCB fab requires a minimum spacing of 15mil (0.381mm) for 4oz copper, so what I've done is decrease the pad widths to 0.4mm to satisfy this requirement.  This leaves the possibility for a pin to be up to 0.05mm wider than its pad.

My question is if it is ok to do what I did, or can this cause assembly errors and/or other problems?


texts: Will a CR2477 coin cell battery make a nichrome wire glow?

texts:
To begin with, my experience and knowledge in electronics are very limited. I am familiar with Ohm's law, but only in theory.

I'm developing a small device for which I need a nichrome wire to glow for a minimum of 5 seconds. It shall be powered by a battery, as small as possible. The whole device is disposable so it doesn't matter if the battery goes flat after 5 seconds. The nichrome wire needs to be at least 0.2 mm diameter and 3-5 cm long (but the longer/thicker the better).

I have read every forum covering this topic and have figured out that I need a battery that can supply enough current. I was therefore thinking of the high capacity coin cell battery CR2477 (1000mAh, 3V).

I have found this great website that lets you calculate power requirements for a given wire: http://www.jacobs-online.biz/nichrome/NichromeCalc.html

When I insert my values (5 cm wire, 32 gage, 2V) I get a required current of 1.15 amps. I inserted 2V because of internal resistance of the battery, don't know if that was correct.

Will the CR2477 battery be able to deliver this current for 5 seconds? Or will it explode or burn? In the data sheet of the battery I read a max pulse current of 25mA. But I was thinking that if a standard 9V battery could do the job, this one will also, because it's got a higher capacity (though lower voltage).

I'd like to have an idea of the risks before I start experimenting at home.

Can anybody give a hint if this will work or if it's useless/dangerous?
Thanks in advance!


texts: Considerations For Motor Cables: what are the downsides to ribbon cable?

texts:
My friend (a Mechanical Engineering student) is building machine that uses an array of motors in an application where they are under almost no load. He showed me the thin, old, ribbon cable he intends to use to power them, and it seemed like a bad idea to me.

The thing is, although I am an Electrical and Computer Engineering student, I have very little background in power systems and electromagnetism. It seems like using flimsy and thin ribbon cable to supply power to a motor is a bad choice, but aside from it possibly breaking from being a little brittle, I can't justify why. It just seems wrong.

So my question is, what are the limitations that these little ribbon cables are putting on the motors? Am I just being snobbish or is there a compelling reason beyond mechanical concerns why they are a bad choice?

Edit: The first answer to this post pointed out some of the possible advantages to ribbon cable. Thanks! In the specific case I was taking about, my friend is just using two  lines on the cable for the positive and ground of each motor, but using several lines on each cable makes a lot of sense and had not occurred to me before.


texts: In this ECL circuit, how he got the equivalent circuit for the noise voltage and what is the meaning of hib4 in the equivalent circuit.


texts: What is Vcc-2 referring to in the Texas Instruments Tech Sheet for the SN74AS138?

texts:
Total noob here.

The tech sheet can be found here:  http://www.ti.com/lit/ds/symlink/sn74as138.pdf

In the VOH parameter for the SN74AS138 on page 5, it states that it's MIN is VCC-2.

What does that mean?  What is referring to?  Is it referring to the actual VCC minus 2 volts?  So 2.5V for VCC = 4.5V?

Here's the snippet I'm talking about:


texts:
I have a TowerPro SG90 servo which matches the "JR" brand wiring discussed here where the servo's 3 wires are as follows:

Red is +
Black is -
Orange is signal

According to that article:

  The motor of an analog servo receives a signal from the servo amplifier (inside the servo) at 30 times a second. This pulsing signal tells the servo motor when to start rotating and which way to rotate.

To me this means that the signal wire expects signals that are encoded with both directional and positional information. I'm wondering where I can find the correct signal encoding for my particular servo, or any other servo for that matter. The manufacturer site does not provide any data sheet.


texts: Crossing a single-cycle spike signal from a fast clock domain to a slower one

texts:
I have a 1-bit signal coming from a part of my circuit that is running on a 40 MHz clock. The signal is mostly 0, except it is 1 for a single 40 MHz-cycle every ~million cycles.

Another part of my circuit is running on a 1 MHz clock. I would like to do some synchronous processing on the signal described above in this part of my circuit. What is the correct way to turn the single-cycle 40 MHz signal into a single-cycle 1 MHz signal?

In case that matters, both the 40 MHz and the 1 MHz clocks are output from the same clock manager driven by the 32 MHz clock on my dev board, so they should be phase-locked.


texts: Is it possible to reduce the number of capacitors in the ft232h recommended configuration?

texts:
I'm trying to design a board as small as possible. I'm trying to minimize the number of components I need.

My design is based off the self powered configuration of the FT232H chip. I've decided to use ceramic instead of tantalum caps(I'm aware of the repercussions).

http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232H.pdf

So my question is, could I reduce the amount of caps safely(why)?


texts: Iam trying to make a mini refrigerator with peltier device. I do have two heat sinks and the hot side of the device is connected to a fan. The colder side is connted to another heat sink with thermal paste and some adhesive. The question is how can i spread the temperature from the cold side to my componet?


texts:
Hello,
In this problem, i am not able to understand how I2 is getting replaced by I01. More over, will these zener diodes become ON as the applied voltage is less than Vz?

Thanks in advance.


texts:
given w be the pole of open loop what in the pole of the closed lop shown bellow?
i have found axpression for GAIN but for the pole i am not sure.
Thanks.


texts:
Ludic science light dimmer driver
I was watching this video made by ludic science and at 3:14 he said that at the maximum output of the high voltage ignition coil, the distance was 10mm/1cm which he claimed to be 10-12kv. Isn't the gold standard for the breakdown voltage of air 30kv/cm? Can someone explain?


texts: Discrepancy in I2C behaviour of two microcontrollers EFR32MG21A020F1024IM32 and MCP39F521

texts:
I am using EFR32MG21A020F1024IM32 to communicate with the energy meter (MCP39F521) using I2C protocol to read the data from the energy meter registers. I2C is used in standard mode and configuring the i2c as gpioModeWiredAnd having a pullup resistance of 2.2k ohm.
First I am writing the read command packet {0xA5, 0x08, 0x41, 0x00, 0x02, 0x4E, 0x20, 0x5E} to the slave address. The 7 bit slave address is 0x74.
At first when writing the read command packet and all the bits are getting acknowledged along with the start and stop conditions.
While receiving I gave the slave address as ((0x74 << 1) | 0x01). But we are not getting any response and the address itself is not getting acknowledged.
The same board has a STM32L412CBT6P chip on the same line. when using this board to communicate with MCP39F521 i am getting the proper responses and the register readings.
PFA the image captured while probing the i2c lines while communicating using EFR32MG21A020F1024IM32.
A
ny help or suggestion regarding this would be appreciated.
Thanks in advance.


texts: Indoor direction using wifi ESP8266 RSSI

texts:
Am trying to build a small device that is able to determine the direction of object indoor. Not the location, only direction. I bought ESP8266E wifi chip and arduino ESP8266E:

The ESP8266 is the receiver that must read the signal and specify the direction depending on the RSSI. first problem is that the ESP8266 is not directional and the access points around are not directional either . second problem is that the RSSI information takes long time to be read by the ESP8266 . each 3 seconds I can take on measurement. small measurement number make it difficult to analyze the results . I don't know if it is possible to build small directional antenna for the ESP8266E or not . and is the accuracy of the device would be reliable and maintain the device size small or accurate readings ?.


texts: 2 LEDs for a mixer, one for signal monitor and another for mute status

texts:
I'm sorry I know I already asked for the similar question but now I learned how to properly ask my question and I will detail it more on this thread.
I have a DIY mixer on breadboard right now.
It's only 1 channel for the moment and I used a SPDT switch to pass the signal on or off. The center pin of the SPDT is connected to the output. Left pin is at the input where the signal comes from, and the third pin is on ground to minimise the noise when the switch is on the muted status.
I successfully added an LED with a 3904 transistor on this channel so when the SPDT is on, passing the signal to the output, this audio signal (AC I guess) is turning the 3904 transistor on and lets the green light monitors the signal, this LED reacts to the audio signal, like a level meter LED bar graph but only 1 LED, it flickers as the sound frequencies are being played.
Now my question is I want to add another LED, a red one, that would turn on ONLY when the SPDT switch is turned off (this is the muted state for the chanel mixer.)
I tried many things already, with 3906 or other simple circuits I found online for toggling 2 leds but since all I find online is using a steady voltage instead of an audio signal like I do right now, it makes my circuit light up both leds when the signal is on.
So I guess either I would have to block some portion of the audio signal triggering both LEDs (which should trigger just the green ON LED) or convert the audio signal to a DC voltage like something 3V for on and 0V for off. If I can know how to convert this audio signal to 0V or 3V it would solve my problem because right now K can turn on the muted red LED when the audio signal is muted but I can't make it so that when the spdt switch is on it only light up the green led, not the red led.
I hope it is more clear now, I'm sure this is basic electronics but 'm new to all this so it's complicated for me.


texts:
I'm using hx711 adc module and after adc is powered on, the adc values start to increase after 1 minute adc values become stable.  how can i get stable value in less time when adc pwored on.

schematic:

adc read function:

long read_adc(void){
  unsigned long Count;
  unsigned char i;
  PORTC|=(1<<4);
  PORTC&=(~(1<<5));
  Count=0;
  while((PINC & (1<<4)));
  _delay_ms(1);
  for (i=0;i<24;i++){
     PORTC|=(1<<5);
     for(volatile uint32_t n = 0; n < 3; n++){}
     Count=Count<<1;
     PORTC&=(~(1<<5));
     if((PINC & (1<<4))){ Count++;}
     for(volatile uint32_t n = 0; n < 1; n++){}
  }

  PORTC|=(1<<5);
  Count=Count^0x800000;
  PORTC&=(~(1<<5));

  return Count;
}


texts: How do failure modes of high voltage cables play out?

texts:
I fix x-ray equipment, and here is the connector that fits into the x-ray tube.  It carries up to 150kV, and maybe 500mA during exposure.

My boss tells me if I see some black carbon deposit on the sides of the 'candlesticks', that means the x-ray tube itself is going bad.

What exactly is happening when there is carbon deposits?  Is the high voltage sending its current to the walls of the receptacle (instead of into the tube)?  Why does this mean the tube is going bad?

My boss says this has something to do with 'tube spits', where there is an arc between the anode and cathode inside the tube, resulting in much more current.  How does something inside the tube affect carbon deposits inside the connector receptacle?  Thx.

Image from Parker Medical

x-ray high tension cable


texts: Parallel resistors, why? (Basic electronics)

texts:
I'm curious as to why R1+R3 is parallel to R4 and not R2? could someone please explain this to me.
What rules are R2 violating that makes it non-parallel (and what makes R4 parallel)?
Thanks.

What i was thinking: (R1+R3)//(R4+R2)

Correct expression: (R1+R3)//R4 + R2


texts: In what cases would one need to use embedded linux or a kernel on a microcontroller?

texts:
I have already written bare metal software and used FreeRTOS on embedded devices. But I would like to understand why some people choose to use embedded linux or a kernel on an embedded device?
In what cases would it e.g. be unavoidable that you need to use embedded linux or a kernel on an embedded device. How would one come to the conclusion that he needs one of those two things?


texts:
I'm trying to use the uart on an MSP-FET to connect to a custom-made board. But I stumble on the first hurdle - getting some traffic through the uart.

I'm bridging pins 12 and 14 (TX and RX) and all other pins are disconnected. I was expecting to be able to loop some data, but I don't get anything.
I'm running Ubuntu Linux 20.4 and I get two tty's - ttyACM0 and ttyACM1. But none of them responds when I connect using minicom.
I have tested with an FTDI serial adapter, and that one works fine. (ttyUSB0)
(MSP-FET = MSP MCU Programmer and Debugger by Texas Instruments, used for developing devices based on MSP430 microcontrollers. It utilises a 14 pin connector with jtag, Spy-Bi-Wire and uart interfaces. )


texts: Why "bury" lead acid batteries in the ground?

texts:
I've heard once from a person who had installed stand alone systems in rural villages in the third world, that ideally batteries should be placed in a hole in the ground, even though it rarely happened. This should increase the lifespan. I think the reason was both to reduce/eliminate temperatature changes, but also to have them at a lower temperature in general.

Does anybody know what the effect might be of doing this, is it really making a significant difference?

Is it mainly to avoid temperature fluctuations, or mainly to keep them cool in general?

Is this a rule being followed in the industry, ie when batterybackup at hospitals are placed in basements is it because they want to keep them cool?


texts: A relay for each terminal (live and neutral)

texts:
I'm investigating a control circuit that switches a heating element. From what I can see there is a relay on both the neutral and live to the heater. The relays are controlled together and cannot switch independently.

Is this common for controlling a heating element? What is the advantage of this over just a single relay across the live?


texts: How can I make an LED glow by touching it with my finger?

texts:
I can make an LED glow very dimly in all 4 following circuits. The voltage source in the circuits is the output of an AC to DC converter fed into a breadboard. Also, one end of the voltage source is always floating, as shown on the schematics.

simulate this circuit – Schematic created using CircuitLab

What is the physics behind this? I understand that there occurs a potential difference between me and positive AND me and negative terminals of my power supply but I don't know how and why this happens. Also I understand that depending of the circuit, my electrical potential becomes:

Higher than the negative terminal
Lower than the negative terminal
Higher than the positive terminal
Lower than the positive terminal

Since the LED glows in all 4 configurations. How is this happening?


texts: Does Quick Charge have an effect on battery lifespan?

texts:
When charging my phone (a Samsung Galaxy Note 4 using a 3,220mAh lithium-ion battery) I have the option of charging it with with a standard charger or a Quick Charge 3.0 charger. Quick Charge is a:

  proprietary technology which allows for the charging of battery
  powered devices, primarily mobile phones, at levels above and beyond
  the typical 5 volts and 2 amps which most USB standards allow for. [source]

Some technical details can also be found on the same Wikipedia page linked to above. My understanding is that in addition to higher voltage / amps, Quick Charge also uses a more sophisticated algorithm to provide variations of charging speeds at various %s of battery capacity to optimise the overall speed.

Using the Quick Charge offers a noticeable improvement to charging speed. However there are often situations where charging speed is irrelevant (e.g. at night).

My question is whether or not there is any difference in battery wear and lifespan between a standard charge and a Quick Charge. If there is a difference, then in situations where speed is irrelevant, it makes more sense to prioritise battery wear.


texts: How to detect how much battery power is drawn?

texts:
I'm programming a small device using a microcontroller.  I'd like to optimize it to use less battery.  How can I detect how much power uses over time as I run it through some tests?
Based on the tests I can optimize the code to use less battery life.

If I can't get an amount of power used over time, then what's the easiest way to see if the sleep is really working and if it is using any power at all?

In laymen's (or at least programmer) terms please!  I'm definitely heavier on the software side of things.

At least what pins do I connect the voltage meter too.  Sorry for noobiness.


texts: How can I get 8V 30A power supply from a 12V 30A DC supply? I would be glad if you could illustrate on your point since i don't know much about this yet.


texts:
What's the proper way to model really long wires in circuits (18ga, ~1500 ft)?  I'm aware that over long lengths start to accrue non-ignorable resistances.  I'm wondering if they start to get other attributes as well (inductance / capacitance) and what your approaches are on modeling them for simulations?  How can you predict these features? (Resistance is really easy since it's just ohms/1000ft on a lookup table).

My first attempt is below.  I've got a long wire modeled up as a resistor and inductor in series.  Is this an appropriate way to do it?

Problem context (How I got here / why this matters to me):
I'm looking to provide ground closure on a distant relay circuit.  I want to use logic (5V) to drive a circuit that powers a relay that is very far away (maybe more than 1500ft).  My investigated options are as follows:

Electromechanical relay (with mosfet driver)
Mosfet
Transistors
Solid State Relays

I originally decided to close the circuit with a relay (yes a relay to start a relay), but am wondering if a MOSFET can do the job.  Are there any "gotcha's" to switching a very long circuit with a mosfet?  I feel like I'm not taking into account the inductance of the line (how would that affect my circuit?)  I've searched the forums and found that putting mosfets far away from their gate drivers is an issue.  Is it similar for what the mosfet is driving (drain/source?)

Additional info:

Design Considerations:

i. Very low leakage current over the line when turned off. (much less than a uA if possible).

ii. Low switching frequency (only turn these on once every week or so).

iii. Low throughput current across the switch (~40mA when turned on).

iv.  Reliability.  Can't have a switch stick on/off/be unresponsive.

I believe that #3 along makes a normal switch not a good choice (minimum current to ensure the switch turns on needs to be ~100mA usually, right?)

Here's a diagram of the circuit just in case I wasn't clear (The mosfet/resistor can be replaced with any switching/driving element):

I simulated it with LTSpice attempting the following:

Modeled the relay as an inductor/resistor pair (series).
Modeled the wire as an inductor/resistor pair (series).
Toggled the values / tried to see what changed the behavior.

I tried to get a situation where the resistance/inductance was very minimal, and then one where the inductance was on par with the relay.

So here's the general circuit modeled.

And here's all four that I ran next to eachother with different values:

And results of current and voltage drops across the relay (which is what I care about since I need it to turn on):

"Experiment" Results:

Under ideal wire conditions (no inductance/resistance) in the line, the signal snaps up to 14V when the mosfet is closed.
With resistance added to the wire, the voltage drags down as time goes on to a stable value (but it still looks okay)
With resistance and a little inductance, it behaves basically the same as 2.
With resistance and a lot of inductance, the circuit actually flips around and rises up to the stable voltage.  Weird.

Any comments on my methods?  Am I doing this right?

edit:  flipped diode (Found out very quickly it was facing the wrong direction when I simulated in LTSpice and had 220Amps flowing.  Also thanks to Mr Karas for spotting it), and added simulation results. (See above)


texts: Analyzing 24V fast PWM signal in Arduino

texts:
I am currently trying to fit a 3d printer head on a cheap chinese CNC mill. So far I have successfully been able to control the fan, heating element (including reading a thermistor) and the feeder motor using an Arduino Uno.

The CNC itself has a terminal that connects to the mill spindle motor. This produces a 24V 2MHz PWM signal meant to control the speed of the spindle motor.

After I install the printer head, I would like to be able to control the speed of the filament feeder motor by using the spindle speed setting of the CNC. For this, I need the Arduino to be able to read the output of the spindle speed terminal.

Now to my question: how is it possible to shift a 24V PWM signal down to 5V so I can read and measure the duty cycle with my Arduino?

My first thought was to use an opto coupler: this seems like a possible way, but my opto couplers (LTV-817A) have a cut off frequency of 80 kHz, so as far as I understand, they are too slow for a 2MHz PWM signal.

What alternatives do I have?


texts: An opto-coupler/triac oddity -- is it a problem, and is there a solution?

texts:
I'm using VO2223A opto-coupler/phototriacs to drive some low-current mains lighting with a PIC controller. All are working fine, but when the (DPST) mains switch is first turned on during system power-up), on 50% of occasions the lamps will briefly flash, even though the PIC control inputs on the chips are being held low. (Even grounding these inputs as a test has no effect on this flash.)

Why are the power triacs being triggered? Is there a voltage surge?  And is this potentially damaging to the V02223As?

If it is a potential problem, is there a way of softening the initial power-up, raising the voltage more gently, and preventing this somewhat disconcerting flash (of 35 lamps...)?  Many thanks.


texts:
while using MCP1630 in switch mode power supply design, in the datasheet they gave the input bias current of the "current sense pin"

what are the considerations the designer should take while choosing the sense resistor and the ramp generator circuit (in current mode control)??


texts:
I'm thinking about making a reverse polarity protection for a project, and I've came up with this idea:

simulate this circuit – Schematic created using CircuitLab

I think that if I reverse the polarity, the diode will short the supply and blow the fuse. Will it work this way?

The only weird thing is that I didn't find anything simillar when looking around the internet... so I'm assuming there is a catch.


texts: powering +5v device with usb and/or battery

texts:
I made a PCB with an arduino clone and a tiny motor driver. The arduino clone itself needs +5 volt power supply, so I decided to use a DC/DC boost converter to boost a 3.7 volt Li-Ion battery to +5 volt. Then, a battery charger comes to my mind. After some thinking time, I wired my circuit like this, sorry for bad lights and an misspelling "converter"...

I used one-cell Li-Ion charger bq24032a, according its datasheet, it can accept power from USB and/or AC( AC not used in my circuit). It can also provide power to system while charging the battery.

Some facts I discovered:

ONLY USB presented, battery absented. Bq24032a's OUT pin voltage will be +5 volt approximately( with no load).
ONLY Battery presented, USB absented. Bq24032a's OUT pin voltage will equal to battery's voltage approximately...of course...( with no load).
USB and battery presented, Bq24032a's OUT pin voltage will be +5 volt to battery's voltage. The charger is charging the battery, so the OUT voltage just lowered...

I used tps61032 for DC/DC converter, it is dedicated for one-cell Li-Ion battery boost to +5 volt, but accept input voltage for 1.8-5.5 volt.

So I have two question:

Is my circuit's block diagram just looking OK?
When bq24032a's OUT voltage is +5V( ONLY USB present), is it OK for tps61032 to boost a input +5 volt to a +5 volt output? Sounds weird...

By the time I posted, I already have my PCB in hand... But I cannot figure out the two question( and many many tiny questions...). Answers desired... thanks :)


texts:
I need a current sink that I can control from a micro-controller. Should handle 5V up to 4mA or so in at least 256 steps (more is better). I'm looking for a design, not so much a complete product, due to cost.

UPDATE #1:
Here is a working circuit using a BJT, I tried a MOSFET (2N7000) but it did not work as expected. Seems the control over the range is a bit limited. I'm going to wire up a DAC and plot the in / out values.

Update #2:
I've hooked up the circuit (100% like in the simulation) and I can get a range of between 0.7mA to 4.7mA. Not exactly according to the plan, but seems to be getting there. How can I lower the "low" range? The OP07 had a very low offset.

simulate this circuit – Schematic created using CircuitLab


texts: Looking for a way to connect wires to a breakout board without soldering

texts:
I'm looking to get a custom keyboard cable but there's a catch - my keyboard cable is currently hardwired. The solutions I've come up with are either to use a janky solution where I use solder splices to connect the wires inside of my mechanical keyboard to a USB C Female to USB 2.0 or micro USB male adapter, however this is janky as I said before. The only other solution I've found is to solder the wires to a USB type C breakout board, however I do not have a soldering iron and that would drive up the cost of the whole thing by a massive amount.
While I'm sure you guys will probably recommend that I get a soldering iron due to how undeniably useful they can be, this is more of a one time thing so getting a soldering iron specifically for this is a bit iffy. I was wondering how I could do this without soldering and still with a pretty reliable connection.


texts: How big does ground need to be? Step down from 5v10a to 1.2V 50a, do I need a 50 amp ground?

texts:
I'm just a layman. I was just thinking about CPUs in computers. They run at about 1, 1.5 volts or there about, sometimes even lower. Desktop cpus can take 90 watts, some 120 watts. That's close to 100 amps at 1 volt. How can they return 100 amps to ground? Does the voltage regulator up convert ground somehow so that 100 amps doesn't go back through the mains circuit?

What if you tied the ground of a voltage regulator to the same ground as a 1 volt 100 amp circuit? So you have 5 volts 10 amps and 1 volts 100 amps returning via the same ground. How does ground not blow up?


texts: Calculate the complex impedance, the impedance and admittance of a capacitor

texts:
Please help me out a little bit, I got really stuck here with somethings and I just can't figure it out.

So, I need to calculate the complex impedance, the impedance and admittance of a capacitor with :
C = 33 nF
f = 100 Hz
and knowing that X = -1/2*pifC.

So far I figured out that the pulsation is ω = 6,28 * 10^2
and that X = -48,2532 * 10^-3 [Ohm].

Right now I need to calculate the impedance Z. However I found more than one formulas for it and I don't know which one to use. So far I was thinking of going with Z = -jX or Zc = 1/jωC. However I don't really understand what to do with that "j". I know it shows that this is a complex number and that it represents a change of phase with pi/2. However I don't know what to do with it in calculus.


texts: Piezo buzzer giving faint clicks instead of loud buzz

texts:
Please note: Even though this question involves a Raspberry Pi, I really think its an essential electronics question at its heart, and that the fact that I'm dealing with a Pi is secondary.

I have the following piezo buzzer wired up to my Raspberry Pi 1 Model A (hereafter RPi) as follows:

When my software (which uses wiringPi under the hood) sends an output signal to GPIO output pin, which is the pin driving the buzzer, it just makes a faint clicking noise, not a big booming buzzzzzz like I expected. I'm trying to figure out why.

My thoughts:

Perhaps its not as simple as just sending a HIGH signal to the buzzer...perhaps there's a more sophisticated signal I need to send it
Perhaps the buzzer is junk, however I ordered 3 of them from DigiKey and all three produce the same faint clicking sound
Perhaps something else isn't wired correctly

I have confirmed that my software is sending an output signal to the correct GPIO pin, namely because the buzzer does click when the software sets this pin HIGH.

Any idea how I can troubleshoot here and begin diagnosing?


texts:
I have a simple circuit, powering an ESP8266, specifically the esp-12-e.

Connected to the 3.3v coming in I have a 1000uF electrolytic capacitor, to help keep things stable (suggested by the esp8266 community)

It's all working well. However when I cut the power to the board, I see my LEDs etc hang around dimly glowing for just less than a second before the board appears to loose all current. I assume this is because of the giant capacitor. I like it :), and have it behaving otherwise very stably.

I hear people talk about bleeder/discharge resistors, normally on DC power supplies. However, if my theory is right, one may help me here, so when I cut the power, everything turns off...more or less instantly.

Thoughts? If my theory is correct, how would I wire the resistor up, how many ohms should it be, and why?


texts: Setting audio output impedance for output protection

texts:
I'm building a module for a modular synthesizer, according to the Eurorack standard. So this is a module intended to be connected to other modules via patch cables.

While the above standard page does not specify an output impedance for the module outputs, it seems that in general this is in the region \$100\Omega - 1k\Omega\$. Input impedance is specified as \$100\mathrm{k}\Omega\$. As my final output stage is an opamp-based amplifier, I need to specifically drop the impedance, as the op-amp itself would give a very low output impedance. Further, since any outputs and inputs can be connected by the user, I should expect that the output may be shorted to any voltage in the range from \$-12\mathrm{V}\$ to \$+12\mathrm{V}\$ (system power rails) by the user; for example, it is possible for the user to connect two outputs together, and while that won't do anything meaningful, the modules should not be damaged.

Online, I can find two different ways to do this. The obvious op-amp circuit followed by a resistor:

simulate this circuit – Schematic created using CircuitLab

or putting the resistor in the feedback loop:

simulate this circuit

In both cases, \$R3\$ sets the output impedance.

The rationale for the latter is that since the feedback is taken from the actual output node, the output is effectively very low impedance under normal conditions, but the resistor nonetheless protects too much current from being drawn: if the power rails are \$\pm 12 \mathrm{V}\$, then at most \$24\mathrm{V}/R3\ = 24\mathrm{mA}\$ (for \$R3 = 1\mathrm{k}\Omega\$) can be drawn before the op-amp saturates (although in practice, the TL07x will saturate earlier, as it can't output that much current).

So there's two related questions here

Is the latter way indeed recommended, and safe for my module and any other (reasonably designed) module it may be connected to? The reason why I have doubts is that looking at modules in the wild, the first way seems to be much more common, so I'm thinking there's some downside which I don't realize. On the other hand, just a direct output from the op-amp seems to be quite common too...
In the latter case \$R3\$ acts really as a current limiter, so I'm inclined to actually use a much bigger resistance, say around \$10\mathrm{k}\Omega\$, so that the maximum current is set by the resistor, not the op-amp output capability. Is this a reasonable thing to do?

Update:

To answer Olin's missing spec: users would not assume that passive mixing by shorting outputs would work (and, indeed, the output impedance of other modules varies, so it is not reliable). So basically any behavior that doesn't damage the modules is acceptable.

On the other hand, since the output of this module is not really usable as a control voltage anyway (due to the nature of the module), a slight loss due to the outside-the-loop resistor doesn't really matter much; for audio that's just a small drop in volume.

Finally, reading this thread, I notice that one potential problem with the latter option is that the op-amp needs to drive any output capacitance directly. In general, modular patch cables are quite short, but there are also wall-sized modulars which may use longer patch cables.

In the end, I think I'm leaning toward the first option, primarily to avoid any problems with cable capacitance, and since the downside (small signal loss) is not really important. But any thoughts or insights are still welcome!

Update 2:

The application note linked by JRE clears things up further, when it comes to capacitive loads: the second circuit in this question is the same as the last one in the app note, except for the capacitor \$C_f\$ in the loop. The app note tells us that this configuration is good for driving a capacitive load, but only if the load capacitance \$C_L\$ is known.

So the conclusion of the previous update still holds, the first circuit is a better bet when we don't know the load.


texts: Consider a simple C-R 1-pole high pass filter.  Apply a step input.  The rising edge of the output rises up and then exponentially decays back to zero.  Integrating the output over all times yields a positive number, so the output signal has a non-zero DC component.  How is this reconciled with the notion that an HPF blocks DC with its zero at DC?


texts:
I'm trying to make an explanation for the behavior of the following RC-circuit with a diode pulled up to 12V. The input signal is a square wave alternating from -7V to 12V. My intuition is that the diode pulls up the output to 12V - Vff, and then reflects the input signal at the output offset by that voltage, so that the output is a square wave from 11.4V to 30.4V.

However, I have a hard time solving this mathematically, so help would be appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: Bridge rectifier: 4 diodes vs. single chip?

texts:
I notice (among the DIY audio enthusiasts at least) that when it comes time to design a power supply for an amplifier, DAC or whatever that the parts list will inevitably include something like "4 x MUR860 diodes" for the sake of building a full wave bridge rectifier (MUR860 is a particularly popular choice).

However, you get these all-in-one bridge rectifier "chips" that essentially include 4 diodes in the correct bridge configuration, and:

are often housed in metal casings that can be cooled if necessary
can typically handle much higher voltage/current ratings
occupy less physical/PCB space than 4 discrete diodes
often cost less than 4 discrete diodes!

Question: Are there any benefits in using separate diodes over a single bridge rectifier chip, and if not, why does it seem so popular to do so? Is this just about the satisfaction of "making it yourself", or perhaps some audiophoolery at work? Thanks!


texts: How to modify Full Adder for the addition of two 4-bit Binary numbers?

texts:
I need to Modify my Full Adder implementation to conduct addition of two 4-bit binary numbers. The new implementation should give the summation of two numbers and any overflow carry out. How can I achieve this???

Can I use two Full Adders (one 4-bit binary numbers as input for each Full Adder) ????


texts: How to identify pinouts of my transformer with (2 +3) wire on primary side and (2+2)wire on secondary side?

texts: I got a Transformer from  old DVD player. the primary sites have 2 wire for main powers and other three winding and on the another side I have 2 pair of wire.


texts: DC Motor driven by P-MOSFET stops after half turn

texts:
I have a problem with my permanent magnet DC brushed motor. I'm trying to drive it from N-Channel and P-Channel MOSFETs from STM32F100 pin (3,3V logic). I want to turn the motor on and off only, speed is controlled via step-down converter (LM2679-ADJ) and potentiometer.
At first I tried to turn the motor on by push button connected to STM pin. Every time the motor has stopped after half of a turn (it has mechanical commutator). Both transistors turned off without my input.
Later on I've put instruction in main loop of STM to constantly turn on the N-MOSFET and the motor started to work properly.
I wonder what is wrong in schematics that causing that particular situation.
I measured voltage across Zener diode and it's 12V when N-MOSFET is turned on. IRF5210 is fully turned on at Vgs=-10V according to datasheet.

Schematics in attachment. Any help will be appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: Adding a resistive path between live conductors and earth - safety issues

texts:
(Note: I am in the UK so the terms 'line' and 'neutral' refer to the two live mains conductors)

I am trying to establish a list of safety issues which I should be aware of if I decide to introduce a resistive path between either of the live mains conductors and earth in a Class I device, or to decide whether I should avoid the idea completely!

The reason for this is that I am working on a circuit which performs a number of diagnostic measurements on the mains supply to be built into a device (earth resistance, correct line/neutral polarity and AC voltage), the circuit will disconnect the supply in case of a fault. One idea for the circuit involves resistive paths between both live conductors and earth (other versions use capacitive sensing but have a number of issues) - see 'Scenario 1' in the image below for a simplified schematic. I can also think of other situations where someone might consider using a resistor between a live conductor and earth - for instance to ensure Y-capacitors in a CM filter are drained ('Scenario 2' below) - so I'm interested in getting to the bottom of the general issue here of allowing a DC conduction path between the live conductors and earth.

The earth in the device is bonded to the chassis and appears on a number of external conductors. I was initially against the idea of using a resistor between live conductors and earth as this compormises galvanic isolation, however as I thought about it more I started to sway towards the opinion that this is possible if done carefully. I have not found any sources which deal specifically with this issue, however indirectly by reading about electrical safety testing and regulations as well as using some common sense I have compiled a list of requirements, which, if met, might make this acceptable:

The resistance should be sufficiently high to minimise leakage current - most obviously so as not to trip the RCD (the threshold in the UK is 30 mA), however a much more restricting constraint is an insulation test: for instance, if I understand correctly during a PAT test 500V DC is applied between the live and earth connectors, and the measured insulation resistance must not be below 1 MOhm. From this follows that the total resistance of the resistive path must be at least 1 MOhm plus a safety margin (perhaps 2 MOhm?)
The components in the resistive path must be of a sufficient power rating to handle both dissipation under normal use and dissipation during an insulation test such as above.
The resistive path should not introduce a risk of voltage spikes on the live conductors reaching the earth conductor, so appropriate transient voltage suppression should be used before the resistive path and/or incorporated into it. In my circuit as drawn in 'Scenario 1', I would use higher-voltage transient suppression between the live conductors and earth, as well as lower-voltage transient suppression between the sense inputs and earth.
The physical construction of all resistors should be such that clearance and creepage requirements between live conductors and earth are met (e.g. use a through-hole resistor where the distance between leads is greater than 5 mm).

After coming up with this list, I'm still not confident that this is a good idea, partly because I have never seen this done - so the question is have I missed anything, or is there any other reason why resistors between live conductors and earth should be avoided?

Of course I'm aware that insulators always have finite resistance and Y-capacitors have a leakage resistance which in this context is theoretically identical to having very high-valued parallel resistors, but these resistances are much higher than the megaohm range considered here!


texts:
Could be this stack-up correct/appropriate for a 14 layer pcb?

The PCB includes a CPLD at 50 MHz and a Gigabit Ethernet transceiver at 125 MHz. Both mounted in Primary Component Side.

There are 4 different voltage.
Layer 7 is a non-splitted main power plane.
Layer 8 is a splitted power planes with three differents voltages.

Any suggestion with the prepeg thickness? IMHO, It will be better if the High Speed Signals are closer to the GND power and further between then.

Units are microns


texts: Debugging Vds exceeded in motor drive application

texts:
I have an existing motor drive circuit that uses an Allegro 4935 to drive a brushless DC motor.  The circuit has been working fine.  We've decided to change motors, now with some of the motors the 4935 stops driving prematurely and indicates a fault condition.  The majority of the motors can be driven fine however.  I can read out a 10 bit word from the fault register and it is 0x42, indicating "VDS exceeded on A phase low-side FET" and "Bootstrap undervoltage detected on phase B".  I am pretty new to the circuit but am supposing that the Vds exceeded is indicating the current draw across the MOSFET is too high?  Are there any basic tests I can do on the problem motors to try and determine what the exact problem is?

Here's the motor drive section


texts: How to select a home automatic circuit breaker?

texts:
A room contains electrical devices which has a max demand of 10A (may be more than that in the future).

The mains cable from the electric panel (distribution board) is 4 mm2 which can handle current up to 23A.

The sub-cables from the main cable to the wall outlets are 2 mm2 which can handle current up to 15A.

Each outlet is rated for 16A.

  What should be the current of the automatic circuit breaker? and Why?

If the panel contains 5 breakers and each breaker is rated for 20A.

  Is the value of the main breaker 5*20A = 100A?

Edit:

simulate this circuit – Schematic created using CircuitLab


texts: EAGLE - Singular matrix warning in RL circuit simulation

texts:
I'm studying for my electrical circuits exam and since Eagle is used for some future exams I thought I could learn it and double-check my calculations by simulating with Eagle.

I'm trying to simulate the following circuit, but Eagle is giving me a "singular matrix warning" and failing to simulate. It's also telling me to "check nodes l_l2#branch and l_l2#branch" but I don't know how which nodes those are, or how to get nodes' names.

I searched for this error and what I found concerned voltage sources in a loop (only one source here) or infinite impedance branches (there shouldn't be any). Why isn't the simulation running? Thanks in advance!

Netlist:

* SpiceNetList
*
* Exported from Main.sch at 5/12/19 12:37 PM
*
* EAGLE Version 9.4.0 Copyright (c) 1988-2019 Autodesk, Inc.
*
.TEMP=25.0

* --------- .OPTIONS ---------
.OPTIONS ABSTOL=1e-12 GMIN=1e-12 PIVREL=1e-3 ITL1=100 ITL2=50 PIVTOL=1e-13 RELTOL=1e-3 VNTOL=1e-6 CHGTOL=1e-15 ITL4=10 METHOD=TRAP SRCSTEPS=0 TRTOL=7 NODE

* --------- .PARAMS ---------

* --------- devices ---------
V_V1 N_1 0 DC 1V AC 1V
R_R2 0 N_1 4
L_L1 0 N_3 20m
L_L2 0 N_1 20m
R_R1 N_3 N_1 2

* --------- simulation ---------
.control
set filetype=ascii
OP
write Main.sch.sim
.endc

.END

Schematic:

P.S. Are there any good Eagle tutorials out there focused on SPICE simulation? Moreover, Eagle only allows simulating DC/AC sweeps, transients or at operating point. How do I simulate a constant-frequency AC source?


texts:
TMDS (Transition Minimised Differential Signalling) is a nominally differential signalling specification used, for example, in DVI & HDMI.

Today though I was reading Brooks' Signal Integrity Issues, which defines differential signalling as a mode with two conductors, one carrying a signal and the other carrying an inverted copy of it - providing the return path - so that there is no return through ground.

Looking at the diagram of a TMDS tx/rx pair in the DVI spec (pg. 33) (copied below), it appears though that this condition is not met. The transmitter sinks or does not sink current on one or the other line. Due to configuration of the receiver there appears an equal and opposite voltage across each of the two termination resistors, but only one conductor at a time actually carries current, leaving the return path I presume to be the data[x]_gnd lines that are found on a typical DVI connector (signified by the third net in that schematic between the transmitter and receiver?).

Is this assessment correct or have I missed something about how it operates?

According to Brooks' definition, is Transition Minimised Differential Signalling actually differential?


texts:
Below the 60Hz signal from the CT only with the burden resistor connected:

When I connect it to the opamp circuit, this is what it becomes:

Some points about the circuit below:

x1,x2 - z1-z2 are analog switches: SN74LVC2G66DCUR
L1 L2 are two identical secondaries from the same CT. One is used for sensing and the other is occasionally used for testing.
D12 sets the DC offset to Vcc/2

My guess is that the culprit here is related to the analog switch. Any light on this?


texts: How can the charging time of a cell phone battery be calculated?

texts:
Suppose I have a 20 AmpHour battery at 4V (as in, the actual capacity of the battery is 80 Watt hours).
And I'm using a 10V 2A charger to charge it (this is a 20 Watt charger).
How can the charge time be calculated?

Is it 4 hours?

Note: The charge time is definitely not 20Ah/2A = 20h as a lot of people state, since these numbers are close to the actual values for most fast-charging smartphones today, and the charge time should be of the order of 1 hr).

Note 2: Please explain using the fundamentals of physics, instead of obscure formulae.

Since the charger is at 10V and the battery is at 4V, how does this affect the charging?


texts: State space representation of parllel RLC circuit

texts:
I just started reading  state space representation from book by (Norman s.)
and in this book all examples of state space representation are either of series RLC with voltage source as an input or parllel RLC with current source as an input.
But
How to represent a state space model for a parallel RLC circuit with voltage source as an input ?
I tried but in this case
1.I confused about what should be order of system (because here different system variable as an output  give  different order of differential equation  )
2.how many minimum system variables require to write the state equations?
Or
3.its state representation is not possible ?


texts:
In hall sensor based BLDC motor, motor is controlled by feedback of hall sensor.
At a time only 2 stator pole pairs will be excited and 3rd pair will be ideal. So in third pair Back EMF will be generated.
In my opinion we don't need that back EMF.
So how that Back EMF is dealt with or reduced?
Do they use Flyback diodes on motor? Or that Back EMF is used in any other operation?


texts:
I am trying to produce negative voltage with this circuit:

The circuit with PMOS:

when the parameters are:

Vsw=1.1v
vin=1.1v
Cfly=2pF
CL=15pF
Ts=50nS/ f=20MHz
dead time=50pS

I can't understand why the output is around -500mV, instead of -Vin.
Thanks in advance.


texts:
I want to build a keyboard from scratch which will be illuminated as well (one LED per key/switch). Due to the fact that I don't need some fancy stuff, just turn the LEDs on/off, can I connect entire columns of LEDs per I/O port of the MC, or I should control them intividually as several schematics suggest?

The reason being, I run out of ports sould I connect them individually. I understand that the answer depends on the amaunt of current the LEDs need  and each port supports, yet I would like to know if someone has any experience on that.

To be specific, I want to connect at most seven LEDs per port on a Teensy board. I am not sure about the voltage because I haven't decided yet which exactly board to use.

By the way, are there any specific LEDs (color or type) which are brighter than others without consuming much current?

Any opinions would be appreciated.


texts: Battery Voltage Sensing Circuit (Voltage divider, buffer)

texts:
I've been trying to figure out a quick and easy circuit for sensing a battery's voltage, then translating that voltage to an 0-5v signal that could be read by a microcontroller like an Arduino.

My idea is to have the voltage from the battery divided, so that high (~13v) would come out to be 5v, and low (10-11v) would come out to be lower.  After the voltage is divided, a unity gain op-amp would be used to add current protection to the microcontroller.

Here's part of the schematic that I'm working on to give some visualization:

Would this be a good circuit for sensing battery voltage?  Even if it is, could I make any improvements?


texts:
I'd designed a USB-JTAG Programmer with FT2232D. I programmed Xilinx spartan3 FPGA 2 times yesterday and everything was perfect. But today when I connect it to my laptop I see the following message: "USB device not recognized"

I saw a post about same problem: "If enumeration is failing, something in the hardware is broken. This could be a damaged chip (make sure you always power the chip completely , so don't let VCCIO be unpowered if you power VCC)."

I've connected the VCCIO of the FT2232D to the VCC of the FPGA board with a jumper, so when the FPGA board is off VCCIO can be unpowered.

Can anyone tell me wheather my chip is damaged or not? Or how I can check it?

Here is my board's schematic:

Note: My laptop has windows XP SP3 media center edition, I've also tested it on win7 64bit but it didn't work.


texts: How can I calculate the current through an LED?

texts:
I am trying to find out if increasing current increases the brightness of an LED.
I'm pretty sure this is the case now that I have looked into semiconductor band theory physics and p-n junctions.
However, I still don't understand how I can calculate the current through an LED if I have been given the brightness and vice versa.
I'm also not sure if I understand exactly why the brightness increases with an increase in current (if it does), but this is probably too big of an ask for someone to explain.


texts: Does data rate increase with channel frequency?

texts: It is commonly said that a higher channel frequency implies a higher data rate. For example, in https://www.howtogeek.com/222249/whats-the-difference-between-2.4-ghz-and-5-ghz-wi-fi-and-which-should-you-use/ they say that 5 GHz wifi connection is simply faster than 2.4 GHz. However, Shannon–Hartley theorem states that the maximum channel capacity in bits/s depends only on the channel bandwidth and the SNR. Therefore, the data rate shouldn't really depend on the center frequency of the channel, only on the available bandwidth. Is it a misconception that higher frequency channels support a higher bit rate or is it true for some reason?


texts: Can I use same LDO for two or three outputs? Given that the LDO provides enough needed current for three devices.


texts:
I have two H-Bridge drivers controlling two geared DC motors. These are the modules I am using : https://www.handsontec.com/dataspecs/module/BTS7960%20Motor%20Driver.pdf
I have two of the above modules, sharing a common 8V power supply. I get some odd behavioir when attempting to control one of the motors with PWM. At low speeds, the other motor will turn slightly. If I turn one of the motor shafts by hand, the other motor will also turn.
I'm assuming the issue is due to the sharing a common supply. Is there anything I can use to isolate the two?
Thanks


texts: I have an LM7805CT 5v voltage regulator that is faulty.  I am unable to source a direct replacement locally but I do have a TS2940 in my parts bin that according to the datasheets should be an equivalent replacement.


texts: Proper way to monitor temperature of a surface?

texts:
I'm looking into creating a solution to monitor the temperature of a chip which has no temperature sensing available for me to use. I would like to use some sort of simple through-hole temperature monitoring component, yet I am unsure of what exactly I need to look for. It needs to be a cheap solution (under $5) and able to stand temperatures from at least 50-200 Fahrenheit. I have a few questions about this that I feel would be helpful in speccing out a component:

What are the different types of temperature sensors available?
What are ones that are low-cost and can measure the temperature of a flat surface (chip, simplistic heatsink, etc)? Would something like the TMP36 work?
Is there any go-to solution for monitoring the temperature of a chip without any accessible temperature detection?


texts: Designing a circuit to replace AA batteries with a LiPo battery

texts:
I’ve been looking at ways to replace 2 AA batteries in an older device I have with a LiPo battery and USB C charge board so that I can easily charge it up and save on batteries. The biggest barrier to doing so is that most LiPo batteries have an average output of 3.7 V rather than the 3v needed by the circuit, and start out at about 4.2 V which is far too high.

Some videos I’ve seen solve this by placing a 1N4001 diode in series with the battery which drops the voltage down to ~3 V. I guess that might mean that it starts out a bit hot for the device, but overall that sounds fine to my electronically uneducated ear. I’ve noticed, however, that companies who offer boards to do this same thing use voltage regulators (+ capacitors) and extra diodes. My question is why? I’m worried that there is something that I’m missing that could put the battery/device at risk.

Since the device already ran on AA batteries I would assume it doesn’t need a more stable voltage than the LiPo already provides (e.g. there is no reason I can see to cut the power below a certain voltage threshold). It could potentially have something to do with the low battery indicator that is triggered at 2.4 V, but I would have thought that that would work with the 1 diode circuit anyway. Or alternatively it could have something to do with not depleting the LiPo battery too much, but since the device cuts out at about 2.2 V, that’s unlikely to be an issue either.


texts: Determine the polarity of aluminium electrolytic capacitor

texts:
This question was inspired by this one: Determine Polaritry of Aluminum Electrolytic Capacitor.

I thought that the question would be on how to determine the polarity if there are no markings and the leads have already been cut. The question was different, and the curiosity remained unsatisfied.

I found this question which is also not that into electronics, but the accepted answer suggests that measuring the capacitor's case voltage may indicate the reverse polarity. It seems interesting.

Two questions:

How the polarity of an electrolytic aluminium capacitor can be determined experimentally?
Why would the voltage of the case be different when the capacitor is reverse biased?


texts:
I'm using AD8283 which is a ADC IC and has 12 bits output.
In my design I'm using two pieces of it by using Repeat() command.
My question is how to connect data buses to next level.
I thought using Repeat() for data buses might work but it didn't.


texts:
I have been reading the book of Goldstine on computers and I was wondering how ENIAC could activate a computation using numbers (the antecedent of the stored program concept).
Goldstine wrote that instructions were coded as numbers with part of the number used to identify a register with a stored value to work upon and the other half to select the "operation is to be executed".
Now, how was the operation selected? Let's say the punched card had the number 4 punched to select an operation and let's say operation 4 was a multiplication. Multiplication was carried out by a dedicated "panel" that is, a set of circuits arranged inside a cupboard that could perform only multiplication.
Would the number 4 on the punched card carry an electrical signal to the accumulator number 4 and the number stored in this accumulator send a signal to the multiplication panel? Or did the number stored in accumulator 4 had a further meaning?
Goldstine wrote that a typical order encoded as an instruction would "transfer a number from a specific location in the memory [an accumulator?] into the arithmetic organ [a panel?]; add the content of a delay lines in the arithmetic organ [?]; transfer a number from the arithmetic organ into a specific memory location". Is there a simple visualization of this process?
Thank you


texts: ADXL354 Power Sequencing Sources and LDO's

texts:
The ADXL354 with Analog Outputs include three power pins: Analog Power Source V1P8ANA, Digital Power Source V1P8DIG and Logic High Level VDDIO, besides the VSUPPLY Main Supply Pin.

According the Power Sequencing datasheet feature (p.22), when VSUPPLY is tied to ground, the Analog V1P8ANA and Digital V1P8DIG Power Sources can be supplied externally.

Which is the purpose of this feature in the ADXL354?

For which reason should I use that complex Power Sequencing instead of simply plugging in the VSUPPLY to 3.3V?

If the maximum level of these pins is 1.98V, which is finally the purpose of them? It cannot be changed into 3.3V either.


texts:
I'm making a prototype based on the W7500P reference design, the latest version (updated 6 months ago) specifies the need for a Power over Reset IC.

I do not understand the point of this component over more traditional resets, and I'm questioning wether or not it is necessary to include this.
The WizWiki W7500P developement board (made by the same company) does not include this component.

Here is the reference design :


texts: How would you find the power balance in this circuit?

texts:
I have been having some problems trying to solve the mesh analysis of this circuit to calculate the power balance throughout the circuit. Here is the circuit:

simulate this circuit – Schematic created using CircuitLab

I was unable to solve the equations simultaneously, so I was wondering if I did something wrong? The mesh's go from left to right of the circuit with mesh 1 including the Solar Panel and the LED, and with the mesh 2 being a supermesh going around and excluding the current source. Here's the equations which I've got for the two meshes:

Mesh 1:

265.5 - 52(i1) - 0.33(i1) - 66(i1) + 66(i2) - 7.7 - 0.33(i1) = 0

to

118.66(i1) - 66(i2) = 257.8 -> [1]

SuperMesh (Mesh 2):

7.7 + 66(i1) - 66(i2) - 0.1(i2) - 0.82(i3) - 12.9 - 0.1(i2) = 0

to

66(i1) -66.2(i2) - 0.82(i3) = 5.2 -> [2]

And then including the current flowing through the current source:

i2 - i3 = 0.5 -> [3]


texts: PSpice AC Circuit Simulation Showing 0 V for Output Voltage?

texts:
I am trying to run a simple Op Amp simulation. My lab gives zero instruction on PSpice, tossed us a brief manual on DC PSpice circuits (even though the class is AC), and said go forth. The circuit I am trying to build is below:

The values for components are:
R1 = 330 Ω. R2 = 6800 Ω. R3 = 2200 Ω. C1 = 0.01uF

The amplitude of Vi = 5V, and the frequency of Vi = 1000Hz.

I expect around 20V at the output V2.

My PSpice Circuit is below:

I create a blank new project. I build the circuit. I create simulation profile. When I run the simulation, The output shows a constant 0 V. Output below:

Does anyone know where I might be going wrong, in the setup or the circuit?

EDIT: New circuit schematic below after changing setting from transient to AC Sweep/Noise:

New simulation:


texts: Prevent compiler optimization for memory access in reflashable memory area

texts:
I am working with an embedded software in which part of the software(some CONST
config values) are reflashable, without modifying the application software. Consider the following code:

const uint32 Reflashable_Variable = 0;

uint32* GetAddr_Reflashable_Variable()
{
   uint32* addr;
   addr = &Reflashable_Variable; //Compiler optimizes this access to the static
                                 //fixed address of Reflashable_Variable.
   return addr;
}

The problem is that the address of Reflashable_Variable might vary later in the binary due to the change in size of some other parameters. What is the solution to prevent compiler from already assigning the address, rather to access the actual address of Reflashable_Variable during runtime? The compiler used is windriver Diab for PowerPC.

I have thought about using volatile, is it a good solution? Even if it is, it triggers lot of modifications in other parts of the software, so not the best for me. Is there a different possible approach?


texts: How to calculate a transistor response time to a square wave?

texts:
My objective is to learn how to predict the output to a sqaure wave given R1, R2, R3 and Q1 datasheet (not specifically the 2N3904) without using SPICE or any other software

I was looking on google for a good source but could not find something specific enough that regards transistor parameters to that specific circuit and hoped for insight from you guys

PS: input source is 1 ohm

simulate this circuit – Schematic created using CircuitLab


texts: how to calculate power consumption by a power transistor

texts: How can I calculate power consumption by a power transistor or what is the formula to calculate power consumption by amplifying transistor during its amplification action? That is a Vcc supply, not an input signal.


texts:
I'm getting started with XBEE S2 modules and I have a doubt I still couldn't get a clarification, hope you guys can help.

I want to have 2 end devices transmitting data to one coordinator, all of them working in API mode (escaped characters). The data should be sent "as fast as possible" so I'm afraid I will get many collisions. How XBEE deals with that?

On the the RX packets I can get the source address but I need to read many bytes before I know it. What happens if while I'm reading bytes from a packet the other end device starts to send another packet?
If XBEE implicitly uses collision avoidance, are that "per byte" or "per packet"?

Thanks!


texts: I'd like to print the top layer of my EAGLE PCB so I can check wether all the components fit as they should. Obviously, the dimensions should be the same as if manufactured. What is the best way to do this?


texts:
I have a FSK modulated signal of binary data. This I am trying to recover using PLL.

The mark and space frequencies are in the range of 1.5MHz to 7MHz.

I am struggling because, the PLL output is not stable, in the sense that the signal is varying like a sine wave and this makes the decision process difficult (Because I am not able to fix the threshold as "0" or some other value).

Here is the PLL LPF output:

I know I cant use this directly for decision making so I am using a low pass equiripple filter after PLL, which gives a pretty good signal which I can use it for decision making. But again the probelm is the signal is varying like a sine wave and not proper horizontal variation, which is what I am looking for.

Here how the LPF output is:

All I want is that, to keep the center of the signal "0" at all time instant. How can I achieve that with simulink?

Here are the PLL, block parameters:

Filter: [1]/[1   2*pi*0.001]
VCO input sensitivity: 5 Hz/V
VCO Quiescent frequency: 10000 Hz
VCO initial Phase: 0
VCO output amplitude: 10V

Important Note: I am looking for demodulation at different data rates, so I want to vary from sample time in Bernoulli binary generator from 1 to 0.00001 i,e from 1bps to 100kbps. What I have observed here is that as the data rate changes, the property of the PLL filter output changes and which makes me to readjust the PLL for every significant change in this sample time (or as I referred it as data rate). For this if someone can give me tips or solution to demodulate the signal at every rate without re-adjusting the PLL, then it will be a lot of help.


texts:
I'm using Hamamatshu s8559 photodiode to convert x-rays into it's respective energy.

I'm using a 10 bit ADC converter.

  The problem I'm facing is I have no relationship between the Photo-current and respective X-Ray Energy.

This is the circuit I'm using, leave the ADC part I'm measuring voltage across R2.

Thanks in advance


texts: What power relationship (between active and reactive powers) should I expect from a CNC machine?

texts:
I have collected loads of power data from a 3-phase CNC machine and it all looks like this:

The 3-phase active and reactive powers can be seen above, as well as the Q (reactive) - P (active) difference.

My question is, does the relationship between the 2 powers make sense? They seem to be highly correlated and the reactive seems to have a higher increase when the cutting is happening (which is correct I guess, since that's when the spindle motor is spinning, so a magnetic field is generated.)

But I would like someone with more experience to explain if we always expect to see this kind of correlation in powers when a resistive and an inductive load are present or there should be a higher fluctuation of the reactive because of constant changes in the magnetic field.

Edit: This is the previous picture with the addition of the absolute apparent power |S| and a scaled (x10000) power factor that I calculated.

Can it be that the power factor increases when the cutting is happening?


texts: Move servo relative to current position (analog)

texts:
I have 3 sensors that feed into a couple of comparators that determine whether to move the servo or not. I used to do the moving with a microcontroller but I need to free some pins badly so I'm trying to accomplish this without software.

The sensor circuit has two output pins that tell me whether to move clockwise or counter clockwise or stop. Take note that this is relative movement, so it doesn't know the current position of the servo. All it knows is whether it should move and in what direction, if further movement is not possible then it should just be ignored.

I thought I could accomplish this by using 555 timers, but I couldn't think of a solution! I reckon I could just use a stepper or an ordinary motor instead but they don't fit on the joint. Is there anyway to accomplish "relative" servo movement with just analog circuits (and without messing the innards of the servo)? Any suggestions?


texts: Is there a software program that calculates the Transfer Function for a given circuit?

texts:
I'm asking for a program (either freeware or not) where you can draw your circuit as the input, as it happens in PSPice, Multisim, LTSpice etc.., then specify two nodes of reference, say \$ V_{out} \$ and \$V_{in}\$, or \$V_1\$ and \$I_2\$ and then the program outputs the transfer function e.g. \$ V_{out}(s)/V_{in}(s) \$ (preferably in the s-plane), or some impedance function \$V_{in}(s)/I_{in}(s)\$ or any function accordingly. In my opinion this would be the perfect program to check your circuit analysis on the s-plane.

For example if you draw this Sallen-key circuit in the following picture

and specify your nodes of reference \$ V_{out} \$ and \$V_{in}\$, it will output the transfer function above (in terms of the circuit components not the values they have, just like in the picture). Thanks in advance.


texts: How can I switch a 12v line with arduino using a p channel mosfet when they have the same ground

texts:
I'm trying to turn on/off a 12v line using a Arduino and a p channel mosfet (f9540n), but if i were to connect them together using some simple schematics online, i would be sending 12v through the arduino. The supplies for the 12v line and the arduino have the same ground since im using the same power supply and a 5v regulator to supply the arduino. What options would I have to solve this? Is getting a n channel mosfet the only choice?
Edit: This is the diagram, I'm not really good at making them, but i hope it helps


texts: If a single contact in a parallel circuit shorts out, can it ark?

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I am considering stress test scenarios for solderless battery packs, to know how much destructive impact they can handle before internal arcing can happen on individual batteries.

If you have 200 volts at 100 Amperes coming from a 5p50s battery box, and you interrupt 1-2 batteries physically for 10ms, is it possible for there to be an arc, considering that the current can still pass through the neighbouring batteries?


texts: Help looking for an 220V AC transformer replacement

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My old Philips MC-M250 stereo transformer has died after a power surge. I can't find spares so I'm looking for some compatible replacement.

I found a power board circuit in the service manual.

AC is 220V. From the power board 3 wires lead to the main board. I can't find output voltage. I assume it is 12V, but I'm not sure.

I would greatly appreciate any tips.


texts: Image recognition for PCB - is this available?

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I have a populated PCB, and I want to draw a circuit diagram of it.
For printed documents, you have OCR which can recognize text in an image. Is something similar available for PCBs? i.e. I provide photos of the front and back of the PCB, and the software recognizes the components, their values and how they're connected?
I realize this would be limited (the sw can't see PCB traces covered by components, multilayer PCB etc), but is it possible at all?


texts: Inductor with high Q-Factor for low frequencies

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I am a little bit confused by the types of inductors you can buy. After looking through numerous datasheets, it seems to me that most inductors have a high Q-Factor only at high frequencies (around 100 MHz), and the Q-Factor for frequencies below 1MHz is not even plotted in the datasheet.

I, on the other hand, am looking for an inductor with a high Q-Factor for frequencies around 200kHz. Is there some special type that is designed for rather low frequencies? Or do I just have to accept that for some physical reason Q-factors are always low in the sub-MHz range? I can not really find that attribute anywhere?

Thanks,
Peter