texts: Combining multiple capacitors to make up required value

texts: I'm doing a project and have one small problem.  My project calls for two 2.2uF capacitors, I only have one. I have plenty of 1uF capacitors, three 10uF capacitors and two 100uF caps. Can I use three 1uF caps in series or can I use one of the 10uF caps instead?


texts: How to find RPM from the square wave of a MSD box

texts:
I am trying to make a tachometer for my car. I am using a MSD6Al-2. The box outputs a 12 volt square wave at a 20 % duty cycle

I talked to someone at MSD and they said you'll get a signal every time it sparks.

The problem is it can spark up to 10 times per cylinder up to 3000 rpm. Now when  tried to figure out the RPM if I just don't account for the muti-spark the numbers are better.

I am having trouble trying to figure out what RPM it is turning at.

Here is what I was doing:
number of sparks in the purple area divided by the number of cylinders (6) then doing that mutiplied by how many times that would happen in one minute.

Here are the images of the waves I got from my scope:

Idle RPM

Higher RPM

If anyone know how to find the RPM from this please let me know.

Also, what does the negative wave mean and should I count those too?


texts:
Anyone have any details on how to make a programmable capacitor?  Is it some fancy op amp trick?

EDIT: I suppose I should be more clear.  The new iPhone 4 is having severe antenna problems, because the antenna is exposed to the user's touch, and some users are bridging two ends of the antenna while holding the phone, altering the capacitance of the antenna so significantly that calls get dropped with even 4 bars.

Allegedly, the iPhone 4 also uses programmable capacitors, and there is some noise about whether the iPhone OS 4 will be able to tune the caps to compensate for the user's hand grip.  When I heard this, I was not sure exactly how one might create a programmable capacitor...


texts: non-linear characteristic of image sensor

texts:
Let me ask a stupid question. It might not be a well specified question, but since I'm a newbie in this field, I'd like to ask it.

The question is this. Why the pixel counts from CMOS image sensor is not linearly proportional to exposure time?

I took images under dim, uniform and stable illumination on object. My object was a clean white paper. In order to avoid making any shadow and non-uniformity on object. I removed everything near the paper and it looked really uniformly white paper. Now I captured lots of RGB565 format data with picamera (OV5647 sensor). Since I'm studying how CMOS image sensor works, I plotted the average sensor counts versus exposure time. The maximum exposure time for the picamera is 6s so I set the time from 0.01s to 6s. But the result was somewhat surprising. The average number that one pixel reads is not linearly proportional to exposure time, but was a log function. It increases rapidly between 0~3second, but then the slope comes down. at 6 second it's slope is so small that it's lower than 1/2. I confirmed that the counts are distributed uniformly and also the maximum value was less than 200. With the RGB565 format maximum brightness corresponds to 255. So there wasn't any saturated pixel among the 5 million pixels.

Could you please let me know how it occurred? I searched some papers describing non-linearity of photosensor. But non of them clearly stated something about this non-linearity between exposure time and sensor count(or electron or voltage)

I'm not dare asking full explanation. But it would be very helpful to me, if you let me know whether this non-linearity is an coincidence or if it means my sensor has been defected. And if it is genuine characteristic of image sensor. I would really appreciate to whom gave me some informations(article, webpage or just keyword) how I can learn the phenomena.

ps: I plotted it for various ISO, but for all ISO settings the sensor counts showed a graph of log function. Papers just mention that there would be some values higher or lower than the linear fit line. However my picamera showed just decreasing derivative. I mean, it goes up rapidly and then goes up slowly.


texts: 240v dc connected to 24v dc battery bank

texts:
1.I connected my 3 phase ac pma generator/hydro turbine to a 600vdc rectifier. As I opened the water nozzles the generator produced from 38vDC to 213vDC.How do I connect to my 24vDC battery bank without it over charging. I then will connect to a 2500 watt inverter.
 2. Would it be better to go from the 3 phase AC to 1 Phase 120v. I have 3 wires coming out of the 3 phase generator


texts: Finding resistance and how many appliances can be connected

texts:
A household electricity system can be modelled as a fuse in series with appliances, all of which are in parallel across the 240V mains supply.

In one household there is a 16A fuse in series with the parallel arrangement of appliances.

What is the resistance of a 1 kW toaster connected to a 240V supply?

How many 1kW appliances can be connected in parallel before the fuse wire blows?

What I attempted:

Can anyone verify I did it correctly?


texts: Convert 8 bit Parallel output from ULN2003 to serial without any Microcontroller

texts:
I am hobbyist only with some basic idea about electronics..
I am trying to measure rooftop watertank water level and to display it on a small led bargraph. So by googling I thought about to proceed with ULN2003 darlington array.
Here is the circuit I'm trying.

But my challenge is it's little far from tank to the bargraph at room. So taking 7 wires from rooftop is not sounds to be a good approach. Is there is any encoders or something like that to convert this 8 output (in my case 6) to a single serial output and to decode it?
I thought about shift registers but it does require some mcu to control it and also some voltage restrictions.
So which is the best way.
I have one more confusion, which is the best metal to use as an underwater probe. Or how can I eliminate the risk of corrosion or oxidation issue after some period.


texts: Protect output of op-amp from overvoltage

texts:
I'm working on a circuit I have a buffer amplifier with a low value pull-up on the output. I need to protect the op-amp because there could be high voltage on the pull-up pin.

The circuit normally works at 5V but there is a possibility that the output of the op-amp can see up to 15V. The op-amp would get damaged. I can't simply use a diode or other common techniques because this over-voltage could last minutes plus because of the low pull-up on the output, I need very low output impedance. Any suggestions would be appreciated.

What I need is somehow to detect an over-voltage on the op-amp output (I'm thinking of using a zener or comparator) and then disconnect the op-amp circuitry from the output.


texts: Place(s) for ground (PE) and neutral (N) connections in TN-C-S

texts:
Where is/are the correct place(s) where PE (ground) and N (neutral) should be connected in a 230 V TN-C-S network? One or multiple times?

In the fusebox of my rental apartment (several apartments per house), the  thick "inward" cable contains yellow-green (PE, ground), blue (neutral), black, brown (and possibly gray, hard to see because it is very tight, phases L1-3).

Within the fusebox, the metal bars with all the subsidiary wires for (a) blue and (b) yellow-green going to kitchen, bedroom etc. are connected by a thick short yellow-green wire, essentially creating an (additional?!) connection between N and PE, or - on other words - render the PE and N "before" my apartment a common (double) PEN wire.

I believe I had learned that the "outdoor" TN-C with "connected" PE-N should be separated to TN-S (with separated PE and N) at the place where earthing is placed (there is obviously no direct earthing for PE in my flat), usually at the mains entry to the whole house and the main brakers (cannot find original description, but in line with the answer of this post). The incoming already separated blue and yellow-green suggest they have in fact been separated before.

=> is it correct (allowed, or maybe even necessary?)  to have such additional connections between N and PE?

Edit: I re-checked, it turns out that we have different "shades of blue" (which I deem not very intelligent): big wires from house to my fusebox: yellow-green is PEN (not PE), and 3 phases are black, brown and blue (live! - very old convention). Smaller wired from fusebox to sockets etc.: PE, N (blue! - new convention!), and phases (only black is used). => PEN is separated into P and NE in my fusebox, i.e. distant from central earthing point. Is this ok?

Schematic drawing:

Photo of equipotential bonding busbar and wires (purple circle in drawing above). What are the 4 wires plus solid metal bar ging downwards?


texts: Interfacing microcontroller with external circuit - detect LED and simulate and detect button press

texts:
This is my first question on here. I am good at programming but am a little stuck when it comes to electronics and connecting two circuits together.
I would like to interface a spa controller with 3 basic elements - increase temperature button, decrease temperature button and “currently heating” LED.
The MCU I am using runs on 3.3V and the physical controller runs on low voltage (12v I think).

I can access the back of the PCB on the physical controller and can see the 2 push buttons pads behind each button.
I also have access to the + - controlling the red LED.
The voltage reading is 0.45v when the LED is turned on and -0.29v when the LED is turned off.
Logically to me there is a voltage change detected on my multimeter so there must be a way to interface this to an input of 1 or 0 on the micro.
Also not sure if it helps but I got a reading of 135mA across the two pads while the LED was off.

The button pads are joined when I hit the key on the front of the controller unit.
I would like the ability to simulate a button press from the micro (so I can change the temp up and down from the micro).
I would also like the ability to sense if someone has pressed the physical button so I can update the current temp stored in the micro to keep them in sync.
I realize this would require 4 pins (2 for input to the micro and 2 for output from the micro).

I have researched other questions here and on the net and am having trouble finding anything to do with interfacing with external circuits.
I have found some information on 4N35 optoisolators and also reed relays.

Thank you

Horatio


texts:
I'm not too versed in EE so I apologize for my duncitude -

My thought is that you can precisely control a stepper motor, but can you inversely get precise readings out of a stepper motor?

For example: if you have an xy plane controlled by stepper motors, you can say "navigate to 0,0 by moving x motor 40 times and y motor 30 times". If you manually drug both axis in position, could you get a reading of x: 40, y: 30?


texts: Connecting flowmeter via USB to a computer

texts:
I have a Swiss flowmeter sf800 which generates 5v pulses if liquid passes through it. I want to connect it to a computer and count pulses via USB. I realize that I need some kind of converter to do so.
I thought TTL to USB converter would just work, so I've got this one https://www.adafruit.com/product/3309 and tried to connect the signal wire to RXD pin. I cannot read any messages from the USB device.
What am I doing wrong? Is any other way to do this?


texts: How to compute current given voltage in a particular RC circuit with a voltage source and a current source

texts: I have troubles solving this simple circuit: I'd like to express \$I_b\$ in terms of \$V_{sig}\$ but I don't know where to start (\$V_{sig}\$ is AC, \$I_b\$ is DC). Could somebody give me a hint ?


texts: Whenever I seach for radar implementations, independently of application (weather, military, autonomous vehicles, speed limiters, etc) it always comes in many flavours: huge antennas, small antennas, high power, low power...but never low frequencies. They are offen in the GHz area. Why one’s not able to create a radar using some MHz? Is it related to directivity? If so, why MHz cannot be as directional as GHz?


texts: Magnetic power connectors (ie. "dots") for slim power supply connection

texts:
This may be more of a mechanical question, but does anyone know what these magnetic power connectors are called?  You see these on Fitbits and other IoT devices.

I'm building an IoT board, that has a waterproofing requirement so a USB connector is out.

Typically there are these magnetic "dots" insert molded in a plastic enclosure, and then the DC adapter has a custom molded connector with matching "dots" that magnetically link to the unit.

Here is a image from a device that has the "dots" I am talking about.

Is there a name or manufacturer/s that are selling these pieces off-the-shelf, for designing electronics with these magnetic "dots"?

I'm thinking someone must sell a premade cable, like USB male end to "dots" on the other end, that you can put in a USB female end wall wart.


texts: Get 48V -> 5V efficiently, mostly low current but occasionally 1 A

texts:
I have an off-grid PV system with a 48 V battery. I'd like to remotely monitor the battery voltage. For that purpose, I have an Arduino plus GPRS shield.

I want to build the monitoring efficiently, so that the battery would not be drained during the Finnish winter, about 5 months. The solution must work in a sub-zero environment, down to -25 °C (-22 °F). Measurements are taken with a CAN module (connecting to the MPPT) and a DHT-22 (for temperature/humidity).

I plan to measure and send data via GPRS eg. every hour, or measure more often and send eg. once a day, depending on what's feasible.

Arduino uses something like 25 mA @ 5 V when idle. The GSM transmission will take about 30 seconds and will momentarily pull up to 1 A.

I've considered these options:

A) just a DC-DC converter to run Arduino. I'm not aware if DC-DC converters would give reasonable efficiency with low currents, i.e. when Arduino is sleeping. One I tried draws 20 mA @ 48 V when giving 25 mA @ 5 V, which is a bit high. I'd like to stay well under 1 W average consumption, since the MPPT also takes something.

B) control the Arduino with an external 3 x 1.5 V battery-powered low-current Atmega 328 (eg. 70 µA), driving a relay that would periodically connect the DC-DC converter and thus switch the Arduino on and off. Besides added complexity, I'm worried about the battery life of those 1.5 V cells in the cold. When on, the relay would draw something like 0.2 W. (I'm a bit worried to use a bistable relay in case the 1.5 V batteries die when it's on.)

Are there other approaches? Or, are there ways to improve these?


texts: wire gauge for solderless lithium batteries in series?

texts:
I am making a prototype lithium battery of 2kw / 40 amps.

it's 8p14s, and every bank of 8 parallel is joined with copper sheet in solderless contacts.

I have bought some 0.1mm thick copper sheet and i have measured that it can be maximum 70mm of trace width to carry the current.

It is too thin to carry 2000 Watts even if it's 7cm wide, and very short in length, as it's equivalent to a 1mm wire?

Even if the connections in series are very short, say one inch each, having a 1mm equivalent copper sheet connecting them is a no-no?

Is this true?

Furthermore, by using copper sheet instead of round wire, the surface area is about 20 times larger, so heat dissipation should be at least twice as fast, so i can use thinner wire?


texts: I found this circuit that I wanted to quickly implement. He is using an optoisolator and feeding back the output using it. I understand that the optoisolator is isolating the sensitive circuit from noise but if I didn't care about the noise, would the circuit function reasonably if I replace the optoisolator with a large resistor (say 10M)?


texts: Multiple ESP8266-12E's with multiple touch sensors

texts:
I'm looking for some advice, and I'm not sure I'm barking up the right tree by using ESP8266 NodeMCU CP2102 ESP-12E's.
I am currently using Arduino IDE to program the 8266's. I have two 8266's that I want to use for my cabinet lighting. I have different strands of 2811/2812 strands to try (RGB, RGBW and just W), but all I want to use is white light. I have no desire to have a web page where I can control the color. I want them to communicate to turn lights on an off based on touch sensor inputs. (I use relays to control the power to the strips.)
Module #1 will have two strings of LED's as well as two touch sensor inputs. (either sensor will control both strings.)
Module #2 will have one string of LED's as well as one touch sensor input.

Is it possible to have these modules send commands to each other that basically trigger a status check and command? Is Arduino IDE the right environment to be using, or should I be looking at Visual Studio/Platform IO  - It seems that different LED libraries want you to use different IDE's?
The basic touch switch code I am using is this: (It turns the LED's on at first power up, which I don't like. But changing the initial states around hasn't fixed that. Not sure why.)
const int relay = 5;
const int TOUCH_BUTTON_PIN = 16;
int switchStatus;
int switchStatusLast = LOW;
int RelayStatus = LOW;

void setup() {
  Serial.begin(115200);
  pinMode(relay, OUTPUT);
  pinMode(TOUCH_BUTTON_PIN, INPUT);

}

void loop()
{
  // Read the state of the capacitive touch board
  switchStatus = digitalRead(TOUCH_BUTTON_PIN);

  // If a touch is detected, turn on the LED
  if (switchStatus != switchStatusLast)
  {
    if (switchStatus == HIGH && switchStatusLast == LOW) RelayStatus = ! RelayStatus;
      digitalWrite(relay, RelayStatus);
      switchStatus = switchStatusLast;
  }

}


texts: Instruction Register? Whats it's purpose/how is it connected? (And what happens after)

texts:
So im learning the SAP 1 Computer Architecture. Most things I get pretty well, but from what I understand: (Lets pretend it's an 8bit and address is 4 bits and opcode is 4bit)
http://www.instructables.com/id/How-to-Build-an-8-Bit-Computer/step8/Program-Memory-and-RAM/

^^ is the guide im? kinda going through)

The Program Counter gets the next ADDRESS for the program which it STORES in the MAR (Memory Address Register), (So the last 4 bits), so MAR only needs to be capable of holding 4 bits(1/2 byte) correct? (Or does the MAR store an entire byte......)

It then stores this in RAM (via a multiplexer), in the guide here 16 bytes, so the multiplexer chooses what Address it will be stored at. (Is it storing 4 bits or 8 bits.....It seems like it'd only store the 4 bits from the MAR). If so....why does the RAM even exist? Couldn't the MAR just store everything. But the Website above shows the RAM outputting 8 bits?

From there the Instruction Register is storing the 4 bits of ADDRESS and then the 4 bits of the OPCODE Correct? So the 4 OPcode bits go into the Control Matrix which tells it what to do and the other 4 bits (the address) go where? Whats the point of the 4 ADDRESS bits? Whats our next step?

Would it go into the Accumulator? What for?

As you can tell im a bit stuck at what happens next? I really want to understand this but im just stuck.


texts:
Sorry for the long post, but I've been trying to work this out in my head.

The circuit I’m working on is based on EEVBlog's dummy load. The circuit works by using an op amp to set the voltage at a current shunt resistor and burning rest of the voltage across a mosfet.

The voltage is set at the op amp by filtering a PWM signal from an Atmega328P. This is my first mixed analog-digital board, so it seemed like a useful design to start with; not too surprisingly I’m having issues with it. In short, I have a lot of noise in the lines connected/near the op amp.

Screenshots of the relevant schematic and pcb layout areas are in this imgur link. (I don't have enough reputation to post them all here.) When I built it on a breadboard all of the signals looked good. The oscope screenshots of the breadboard post-filter voltage (net N$2) and the feedback voltage (net N$1) show mean voltages within 3 mV of each other, so everything seemed in order.

Noisy feedback voltage (net N$1) on pcb with load present: -

When I assembled and tested the PCB, the post-filter and feedback voltages have extreme amounts of noise (see the feedback pcb with load image). The noise increases when the post-filter voltage increases as well. When the load voltage is removed (but still with the post-filter voltage set) the noise disappears; see the post-filter pcb no load image.

My first thought was that the PWM signal (net ISET) was causing the problem, so I turned off the PWM and applied a constant voltage to the input of the op amp (net N$2). This still resulted in the same noise problems. I then checked the load voltage on the pcb and found it was noisy as well. When I tested the load voltage on a breadboard with a power resistor, it's not noisy with a Vpp of only ~30 mV (it's a genuine Apple iPhone wall wart). Also keep in mind there were no issues with the breadboard implementation, so the load source shouldn't be the source of the problems.

My next thought is to cut the the feedback voltage trace (net N$2) and use a jumper to route it away from everything, but that would require destruction of the pcb. So before I do any permanent alterations, does anyone have any suggestions or thoughts as to why the pcb version doesn't work when the breadboard does? Does it have to do with the trace routing? Thank you for any help!

Here is some relevant information:
Op amp: Microchip MCP604 (DIP for breadboard, SOIC for pcb)
Mosfet: NXP PSMN022-30PL
PWM: 15.6 kHz, 0-5V
Load voltage: Apple iPhone wall wart, 5V, 1A

EDIT 1

I implemented some changes Andy suggested. The feedback voltage originally had a pk-pk of 680mV with a mean of 130mV! After decreasing the gate resistor to 50 ohm, the Vpp was 650mV. Reducing if more had no effect. I then removed the feedback voltage follower buffer. This further reduced the Vpp to 450mV. I have an updated schematic in the imgur link that I will try next.

EDIT 2

The oscillations were fixed by adding the inline resistor and capacitor between the op amp output and inverting terminal. I also increased the gate resistor to 300 ohms per the op amp data sheet.


texts:
Can't get my headphones replaced in warranty during COVID lockdown so I am forced to fix the old ones.

I have a pair of old headsets that have this volume potentiometer that I would like to bypass entirely. And keep the volume full at all times.

Could anyone tell me which pins I would need to manipulate?
I have numbered the pins and shown which direction the potentiometer goes for volume increase.


texts:
Is it safe and not harmful to run a preamp tube filaments at 5v?  The tube is ECC85.  I built a tube preamp in a DIY portable guitar amp. It's very similar to Matsumins valvecaster with a few slight changes so the anode voltage is only 12-13v depending on the battery charge level.  It's a starved-cathode design but I really dig the warm slight distortions it gives to a guitar.

My schematic is very similar to matsumin, capacitors I believe are a little different and the gain pot is replaced with 50k resistor and R3 is 270k  (works a lot better for some reason).

I am considering this because right now I'm using LM317 but it wastes a lot of power from the battery and also I want to put a USB charger (yes, that's quite silly)  so 5v 2A would be really useful.

And if it's safe would the output level be somewhat lower or I should worry about more distortions from the tube as it is a starved-cathode design.

What's your advice and perhaps you have some recommendations on chips that have quite good efficiency of providing 5v.  Again, the main part of the question is still whether this would harm tubes and how to get better efficiency for heating them.


texts: How to construct a LTI system with a specific impulse response function, say \$h(t) = \delta '(t)\$?

texts:
I want to ask the question on a generic basis, but using \$h(t) = \delta '(t)\$ as my example.

I have Mathematical knowledge on the LTI system, but no hands on experience. In real life, how can we construct a LTI system with specific impulse response function? Say for \$h(t) = \delta '(t)\$, I know it is a differentiator, so I would search for "differentiator" (e.g. this one) regarding how to construct it.

How about the other form of \$h(t)\$? Is there a generic way to construct LTI system for a specific family of \$h(t)\$ (say the family of linear combination of \$sinc(t)\$, \$\delta (t)\$, \$\delta '(t)\$ and other common functions)? Or I need to construct it in an adhoc way for every different \$h(t)\$?

Many thanks!


texts: I am building a portable speaker and I am looking for a decent amp for my two 15W Phillips speakers. It is tough to find an amp that is efficient and cheap so I was wondering if there is something wrong with buying an amp that is rated for 50W*2 while my speakers are only 15W*2. Thank you in advanced.


texts: What is the lowest voltage that a microcontroller can successfully read on the analog pin?

texts:
I'm testing the Seeeduino v4.2 board with the ADCInOutSerial code in the Arduino IDE and the lowest voltage the board can read is 18 mV, showing an equivalent ADC of 4 on the serial monitor.
The chip that the board uses is the ATmega328P. It works on a 5 V power supply and has a 10-bit ADC (1024 levels), so the voltage that I calculated for an ADC level of 1 is, 5/1024 = x/1, where x is the equivalent voltage for the ADC level of 1, which comes to 5 mV.

But the board fails to read anything below 18 mV. Is this normal for the chip to be unable to read an ADV value below 18 mV or am I going wrong somewhere?

I tested the voltage using a multimeter.


texts: Equivalent circuit to use when calculating the impedance of an electrical cable from its datasheet parameters

texts:
I'm trying to work out the impedance of a cable (specifically a single twisted pair of Lapp Kabel 0035836). The datasheet quotes the following information:

Mutual capacitance:
C/C: approx. 120 nF/km
C/S: approx. 160 nF/km

Inductivity:
Approx. 0.50 mH/km

Can I assume the equivalent circuit is something like this:

simulate this circuit – Schematic created using CircuitLab

and can I assume the impedance follows the following equation?
$$Z_{total} = Z_{R} + Z_{L} + Z_{C}$$

where

$$Z_{R} = R$$ is the resistance (calculated using the resistivity of copper, the conductor material);
$$Z_{L} = i \omega L$$ is the "inductivity" above multiplied by the length;
$$Z_{C} = \frac{1}{i \omega C}$$ is the "C/C" value which I assume is the "core to core" capacitance, multiplied by the length.

Is my logic correct, or have I misinterpreted the datasheet parameters and/or the equivalent circuit to use?


texts:
I would like to model a condenser microphone in LTSpice. This kind of microphone has a variable capacitance dependent on the incoming pressure. I know how to vary a resistor with time, but unfortunately these methods don't work for capacitors. I know this has been asked a couple years ago, but this soultion ist not satisfactory for me. So I'm hoping there is some better method available today.

The capacitor has a constant capacitance and a smaller linear variabled capacitance (modelled by a sine function or whatever). When I try the methods from above for a capacitor, It get the folowing error:

Thank you already in advance!


texts: Is there such a thing as rubber band resistor?

texts:
I'm doing a project with some tight requirements, in which I need to measure the distance between two points, which might not be in direct view of each other, and on parts that are too small to mount anything on them.

An elegant solution would be to tie some kind of conductive rubber band between them, which would change resistance as it stretches, and then measuring the resistance, but all I've got from Google is stuff about physical resistance of exercise bands.


texts: how to increase the speed of a solenoid?

texts:
I'm working on a prototype of a small electric appliance. The part I need help with is a small box in which the floor needs to move up and down quickly to repeatedly bounce an object against the top (approximately 60 times per 30 seconds). I've built the box out of plexiglass, and it's approximately 1 1/2 inches wide, by 2 inches long by 4 inches tall. The solenoid I'm currently using is rated at 12V DC, 2.5A, 15mm travel, and 45N. I'm powering it with an adapter with the same rating. The object in question (it's about the size and weight of an unshelled almond) is not striking the top of the box hard enough. I think it needs to move faster. Any suggestions would be appreciated.

-Bob


texts: Can't solve the math related to power factor improvement

texts:
Image source - Fundamentals of Electric Circuit by Alexander & Sadiku, Practice problem 11.15.
I tried to solve the math in the following way.
\begin{equation}
S_{old}=140000\angle cos^{-1}(0.85) = 119000+j73749.576\\
S_{new}=140000\angle cos^{-1}(1.00) = 140000+j0.00 \;\;\;\;\;\;\;\;\;\; \\
So, Q_c = 73749.576 \\
And,\; C=\frac{Q_c}{2\pi f {V_{RMS}} ^2} = \frac{73749.576}{2\pi 60 (110) ^2} = 0.0161675\;F
\end{equation}
Which is a wrong answer. Can anyone provide me the correct way?


texts: Specific solar circuit setup recommendation?

texts:
For a setup which uses:
a 100Ah 12V battery (Absorbed gel mat Lead acid), with an MPPT solar charge controller,
a 12V 12-55A DC electric motor as the primary load,
additionally some 12V LED lights and electronics,
and a solar panel array of about 1kW STC-rated power as a kind of a target, to cover for losses of operation at NOCT, to have (on average) more than 350W power input from the panels on a sunny day;
—— what kind of cell number / voltages should the panels have to organize this circuit?
is it possible that the charge controller has a way to directly feed the motors when they operate, to keep the battery without load at most times in a (sunny) day?
Thank you very much


texts: How do I get this 4-bit synchronous up/down binary counter to work?

texts:
I'm trying to get this circuit using a SN74HC191 chip to work but it's producing no output to the LEDs.

My current setup so far is:

What makes this more difficult is that the datasheet for the SN74HC191 has no truth/function table so I'm not sure which switches needs to be high/low. Please could anyone provide some help?

Thank you!

Edit: This is the datasheet.

I have now actually found another datasheet with a truth table. However, even with the same H/L settings for "Count up", it still does not produce any LED output.


texts:
This diagram from a lab assignment is not making sense to me...any help would be greatly appreciated.

I don't understand what \$I_{C_\max}\cdot R_e\$ is and why it appears on this diagram. Even if it should be on the diagram, why is it only \$R_e \$ and not \$R_{DC}\$? Shouldn't \$V_{CE_\min}\$ be from \$0\mathrm{V}\$ to \$\sim0.3\mathrm{V}\$?

When calculating \$R_e\$ and \$R_c\$, this equation is used

I've tried leaving the term I don't understand out (probably a bad idea lol), which causes either \$R_c\$ or \$R_e\$ to be negative and I have tried calling it \$I_{C_\max}\cdot R_{DC}\$, which results in two negative resistances...

Side question:

 For a Common base amplifier, would \$R_{AC}\$ include \$R_s\$ (the signal resistance)? Thus should be \$R_C\parallel R_L + R_e\parallel R_s\$?

Thanks a ton!


texts: Which battery chemistry to use in a project

texts:
I'm wondering what type of batteries to use on a project I'm building, it's a wireless temperature data logger.

It spends 15 mins asleep drawing 15 microAmps of current.
And about 10 seconds awake drawing between 70 and 200 milliAmps of current.
The board is tolerant between 2.5v and 3.7v.

I've currently got it running off 2 primary Zinc Chloride Dry cell AA's as they were to hand and it's been on a month so far and it's down to 2.70v now, but I'm wondering what would give the longest life.

I don't mind if it's rechargeable or disposable batteries but I want to get the longest life span between having to change them as it won't be in a convenient place to do so.

I realise using C or D cells would give more life than AA's but this is more of a question about chemistry and self discharge rates, high current discharge rates etc. Once I have decided on the most appropriate battery chemistry I will choose the largest capacity that I can to fit the solution.

I also don't want to have to have any additional regulation circuitry to keep the complexity down and also the standby current low.

I'm concerned about using a LiPo as it's over 3.7v after initial charge plus needing cut off circuitry to prevent damage to the battery, also some NiMh & NiCd can be 1.4v after initial charge so 3 of those would 4.2v

Anyway any help appreciated.


texts: Length measurement of a moving hot deformed bar with a sensor

texts: In a hot rolling mill moving deformed bars are cut according to the desired lengths, which sensor is suitable to use for measuring the length of the moving hot bar and sending the instruction to the shear cut to apply the cut, e.g. 40 feet length is desired from a 240 feet long bar, keeping in view the temperature factor.


texts: Efficiently regulating primary cells for a long-life IoT device

texts:
I'm working on a long-life IoT sensor device which spends probably about 99.99% of its life asleep, waking up every 15 mins to take measurements and send data. I'm sure this is a problem that many people face as IoT becomes more popular.

I've figured out a few things to start: To get the longevity I require from the system the sleep mode current has to be tiny. Combined with this the primary cell has to be a high-capacity, low-self-discharge cell (Lithium Thionyl Chloride 3.6V battery, for example).

For example's sake, lets say the current requirements are typical of my typical wireless IoT device varying as follows, depending on the mode of operation over a period of 15 minutes:

Sleep mode: <10uA (99.99% of the time)
Measurement mode: 0.5-10mA (~10s)
Transmission mode: up to 50mA (2-5s)

Ideally I'd power the device straight from the cell, but a couple parts I'm using have a max input voltage of 3.6V, and a few LiSOCl2 cells I've seen will sit at 3.7V before settling into their nominal voltage of 3.6V.

I'm aware the cell voltage may droop when under heavier load, so to be safe, 3V seems like a reasonable level to operate without being affected by the droop.

What is the best way to go about efficiently regulating this sort of primary cell to provide around 3V? The regulator would also have to consume very little current itself.


texts: High/ Low level output voltage in gate driver datasheet

texts:
Gate driver datasheet mentions about VOLL and VOH with test conditions Iol=100mA

I am testing this using this setup by calculating value (ron of pmos is 7.05 ohms) of load to be placed, Is this the right test setup to check this parameter/ what is the functional meaning of this?

I am also testing peak pullup and pull down current which i got approximately proper result and mentioned in datasheet(dc and transient analysis) LM5102 figure 6.


texts: How can I decouple two 555s from each other?

texts:
I have two 555s in astable mode producing two audio tones that are sent to a speaker. The idea is to mix the tones. The power source is a single 9V battery. The problem is that the two 555s interfere with each other.

I added some decoupling capacitors across the VCC and GND pins of each 555 but it looks like I will need 1000uf to separate their signals perfectly. Small capacitors in parallel seem to have no effect.

Is 1000uf excessive? It feels excessive.
Are there any other common methods for decoupling?
Could I avoid the problem entirely if I used an LM358 op amp as an oscillator instead?

EDIT: More information

I have not tried the CMOS 555s but that is probably the easiest solution.
I am using a summing amplifier (op amp) which sums the signals but does not stop the 555s from interfering with each other.


texts: I'm starting to learn about antenna theory, feedlines, and different types of matching. I can build antennas etc from plans but I would like to be able to design my own and understand their characteristics.  What software could I use to get started? Any tutorials? I'm interested mostly in high frequency and would like to venture into V/UHF, especially for amateur radio satellites.


texts: Maintaining phase continuity of LO when switching from Tx to Rx mode

texts:
I am building a two-way communication setup based on software defined radios.

Setup: The Tx needs to send a sinusoid to the Rx, and the Rx - after some processing - sends its own sinusoid in return. It is basically a ranging problem.

Problem: What I want is to keep the Tx LO running during this time (without any transmission) so that its phase can be compared with the phase of the incoming signal from the Rx later.

Equipment: Currently I am using HackRF SDRs but I can get USPRs if needed. If a specific hardware is required for this purpose, I would be glad to hear about that as well.

EDIT: I just thought of a simple way to pose the question again. Does a typical LO (in HackRF for example but in other devices as well) maintain phase continuity when switching from Tx to Rx mode?


texts: Can floating op-amp input pin destroy op-amp?

texts:
As a follow up to my question (see circuit diagram there), I am thinking further if I may be a cause of the problem. My idea that the second part of op-amp and another op-amp chip may have been damaged because, at some point in time, I did not connect their positive inputs, and was "hot-" connecting these inputs to the signal source on the same board.

I think it is very low probability, as initially, when things did not move properly, everything was connected, but anyway worth checking.

I saw this and this. My chips did not heat (I was checking it almost every time when operating them), no smoke and no craters up to physical damage. All op-amps were configured as voltage followers all the time, thus, as I understood, must drive output to some specific level, not saturate or get to "latch-up" situation.

Am I correct?

Update: op-amp is AD8512A (this info is available in my original question).

@PlasmaHH: looking to datasheet I see

  The AD8510/AD8512/AD8513 have internal protective circuitry that allows voltages as high as 0.7 V beyond the supplies to be applied at the input of either terminal without causing damage

No word about unconnected input pins, or floating input pins.


texts:
Does anyone know of a good basic Cortex-A9 design? Something with just enough to run with power and ethernet? I'm looking for something as a starting point and maybe with eagle files.

edit: While this isn't my first time designing something. I do think I'm in way over my head still. I'm looking for something with a lot of horsepower, +1GHz. I really like the Panda board, and this would be my first choice. The only problem with it is the extras, the video, sound just use extra power and won't be used. The M3 is close in design, ie loadable via USB (SD card would be nice too). I really just looking for horsepower. I also didn't have a chip picked out, I wanted to leave that open, but was looking at the OMAP4430.

Thanks for all the input. I will likely just use a panda board unless some knows of a better design. I think the cost of eagle (full version) will put this project out of my range to prototype.


texts: I've made several small tesla coils, however I wanted to buy one that was compact and powerful, so I bought this one. I'm assuming it is a drsstc, since it has a half bridge of mosfets or igbts, which switch power to the primary. It is fairly powerful, and can make arcs that jump several inches. It has a bluetooth feature where it can play music, however it doesn't work very well, and only works well using a function generator online. I assume it is some sort of interupter circuit; is it possible to use the midi files that something like the oneTesla uses? Why do drsstc's use midi files instead of just regular mp3's? Can't all music just be made into a square wave?


texts: I am quite new to electronic engineering. I have a circuit and I have calculated the input resistance to be about 0.65 kOhm. To verify the calculation I would like to simulate the circuit. Is there a good sophisticated method to simulate the input resistance.


texts:
I am using a DCP010505DBP with this configuration

I supply it with 5V and I obtaining:

10V between the pins 6 and 5
-10V between the pins 7 and 5

I am using a fixed 5V output of my power supply and I am using an multimeter between pins 6 and 5 (+Vout) and 7 and 5 (-Vout).  The schematic I am using is on the datasheet http://www.ti.com/general/docs/lit/getliterature.tsp?genericPartNumber=DCP010505B&fileType=pdf

What am I doing wrong? If I take a look at the datasheet I should have 5 and -5V at the outputs.


texts: Current pulsing circuit, troubleshooting

texts:
I was not sure what to title this question.

What I have two version of the following circuit, that I have built and modelled.

The application is to create a pulsed magnetic field, by pulsing a current through the coil.

I would like to be able to measure the current through the coil, it was initially suggested to me to move one of the 1 Ohm resistors R7, and then measure the voltage across it, and with V=IR, as R = 1, V = I. This change is represented by the change from the left side diagram to the right side diagram.

While this way to measure the voltage and hence the current does work, I now have a much smaller current through my coil. The general idea was the current limiting resistance of the line would be the same with the resistor moved further down the line, but something else is happening too, and I have not yet been able to figure out exactly what it may be.

I am hoping someone with more experience may be able to offer an explanation as to what is happening.

Additionally, I think my MOSFET, M2, blew in the actually circuit, when I moved R7, I need to pull it out and confirm, but there was a large spark from it while it was running, so I suspect it has gone. I will update when I am sure.
I've tried probing the model to figure out what may have happened, but I am still unsure.
If someone could make a suggestion as to what occurred based on the circuit, I would appreciate any help.

I do have what I think is a reasonable fix for my current measurement, and that is to put R7 back (left side diagram) and instead add a 1 mOhm resistor to the just after the source of M2, and then the each mV is equal an Amp of current.


texts: Can I use a 0.5 ohm power resistor along with a 13.6V regulated power supply, to current limit a 12V battery charging circuit?

texts:
I have a 13.6V 10A continuous rated (12A peak rated) regulated power supply, that I use as a charger (and trickle charger), for a 12V AGM battery bank for an inverter setup that powers a shallow well pump during power outages.  What I don't want to happen is when the grid power comes back on, the 13.6V 10A power supply gets overloaded, cuz the battery bank is down around 12V and wants to draw more than 10 amps.  So I was wondering if I use a 0.5 ohm power resistor, if that will do the trick.  I can position it in front of a large fan so excessive heat should not be an issue.  So assuming the charger (power supply) and batteries plus wires already have maybe 0.5 ohms of total resistance, by adding 0.5 ohms more (thus making it perhaps 1 ohm total), is it safe to assume that I can just take 13.6V - 12.0V = 1.6V differential, and assume that at 1 ohm total resistance, the current would be limited to about 1.6A?  F.Y.I., the battery bank I am using is currently 12V and 300Ah rated (but will be getting larger in capacity).  It is ok if the bank takes up to 72 hours to recharge after being drained to 50% SoC, but the thing I want to avoid is drawing close to 10A from the power supply cuz it will likely get stressed out and get hot.  Also, does it make any significant difference if I put the 0.5 ohm power resistor on the + or - side of the DC?
The 300Ah rated battery bank consists of 4 identical 12V 75Ah rated AGM batteries, all in excellent health (checked individually on a 100A load tester).
Also, the power supply has an overload light indicator, so I am thinking it is possible to overload it based on that (not having the datasheet for it).


texts: Why might a rectifier circuit not behave as expected?

texts:
I'm building a power supply for a guitar amp in order to replace the poor quality PS/amp circuit that it had initially.  And after much deliberation and simulation this is what I designed:

Output is to be taken from the zeners, such that the amp will receive the 16V across ZD2, and the other parts of the amp receive the 32V across both.  The RC network C1R2 is supposed to smooth the output as well as prevent voltage doubling, and the PI filter after that should ensure that the final output is as clean DC as possible (this may be a little over-engineered, but I was given this to remove a noise issue in the first place).

The trouble is that instead of the expected output, the voltages across the capacitors is reading the RMS voltage for double the input AC voltage, and ZD2 is dropping nearly no voltage.

Why might these be so?

There are no obvious shorts around that particular zener, or at the receiving end of that 16V. The readings are as follows:

IN: 48.6VAC
D1: 22.4V D2: 22.5V D3: 21.8V D4: 21.9V
R1: 62.0V R2: 7.5V R3: 33.7V
C1: 62.0V C2: 54.5V C3: 54.2V
L3: 0.29V
ZD1: 20.5V ZD2: 8.0mV


texts: Impact of Transmitter Noise on Link Budget

texts: I am having trouble finding resources on how the noise/SNR of the an RF transmitter impacts receiver design / link budget. I know that sometimes the NPR of a power amplifier is given as a figure of merit, so there must be some utility in understanding the SNR of transmitted signal. Could someone briefly explain the significance of transmit SNR, or point me to a resource that elaborates on the topic.


texts:
I am trying to interface a PS/2 keyboard to a MSP430 for a toy. The PS/2 keyboard runs off 5V, but the MSP430 microcontroller runs off 3.3V. So I have a 74LVC245 level shifter to convert between the two.

Now I have this, however, I have discovered that the PS/2 keyboard interface uses open collector signals, so that they can be driven from either end, and apparently using a 74LVC245 with these is complicated. This is the first time I've met such a thing; I'm mostly a software guy.

I'm not interested in sending commands TO the keyboard, only in receiving commands FROM the keyboard, so I never need to drive the data and clock lines from the microcontroller end. Is it sufficient simply to tie the keyboard signals to Vcc via a (large) pullup resistor, so that they stay high when the keyboard's not driving them (this is required by the protocol; if they're not high, the keyboard won't send). But this means that when the keyboard tries to bring the lines low, it's driving against the resistor, and I don't know what the implications of this are. And I don't know whether the 74LVC245 itself has its own pullup/pulldown resistors in the inputs.

Is this a good idea? If not, why, and is there any way I can make this work without having to build a proper driver circuit with resistors?

The 74LVC245 datasheet is here, for reference: http://www.adafruit.com/datasheets/sn74lvc245a.pdf


texts: Is it possible to know the output Amps from a big power transformer?

texts:
I have big power transformer that's used in an old-style arc welder; it is just this huge thing, which can be connected to 110VAC or 220VAC and has four output tabs: one is ground, the others (I got told) are "low", "mid" and "high" output. But it is a home made transformer, so it doesn't have any specs.

Question: is it possible to find out the Amps it would yield, without running it?

Remember it is an arc welder, I guess the amps are like 40 Amps up, right? It works nice, I'm just curious what are the real approximate amps output, so perhaps I can pick the right rods.


texts: Getting floppy drive stepper motor to work

texts:
I want to learn how a floppy stepper motor works so that I can latter control it with my arduino.

What I did was to test if the motor in a floppy worked before pulling it off. I used a 5v from my power supply and tested the motor while still connected to the floppy circuit. And so it did. I even figured out the sequence required for it to go forward. So, I took if off the circuit.

The problem is that when I tried to make it work again (off the floppy circuit this time) it won't turn. And now, when I connect the 5v to the terminals that worked previously, this time all I get is that I'm short-circuiting my power supply.

Any thoughts? this probably has a simple explanation, but since I'm just learning electronics as a hobby I don't know much about it yet.


texts: How to suddenly stop stepper motor without vibration?

texts:
I first send continuous pulses to the stepper driver to make the motor run at high speed(fixed speed), then I stop sending pulses, I know the motor will stop quickly, but will it cause great vibration?

In my application, I need to stop the running motor suddenly, then start running the motor(not so quickly), then stop it quickly... again and again. I do need to use stepper motor for its small size, and I don't want to use electro-mechanical brake due to its limited life time.

Do you have a better way to stop the running stepper motor quickly with minimal vibration?

Thank you.


texts: KiCad mouse cursor freezing in schematic

texts:
I've begun to make a transition from EAGLE to KiCad (wasn't particularly familiar with EAGLE either).

I've installed KiCad  4.05 just because it seems there were more tutorials and info available out there than KiCad 5.0 yet.

I've encountered an annoying issue of my cursor freezing quite often in schematic.  I've googled around a bit to resolve this issue. I've tried different DPI settings, to no avail.

I have a workaround where I would just click on my google chrome icon below and then go back to the schematic. I would like to have a permanent solution though if there is one.


texts: Understanding common terminal in common collector/emitter amplifier

texts:
I am beginner in electronics and trying to understand some basics. One thing that confuses me is transistor configuration with common terminals. Since transistor has three terminals then we must use one terminal as common for both input and output actions.
But when looking at some of the circuit schemes for common collector I can't see clearly how collector is common for both input and output circuit? Take this scheme for example (taken from: allaboutcircuits.com):

I don't understand how is collector common here and not emitter? As far as I can see the emitter is part of both input and output loops. How is this collector common?
On the same page they explain it like this:

It is called the common-collector configuration because (ignoring the power supply battery) both the signal source and the load share the collector lead as a common connection point as in Figure below.

Common collector: Input is applied to base and collector. Output is from emitter-collector circuit.

But I still don't understand it.
What I see from this scheme is that the input loop is (according to Kirchhoff loop law): V_in - V_BE - V_load = 0 and output loop is: V_cc - V_load - V_EC  = 0. So the common for both loops is V_load that belongs to emitter terminal and not to collector's.


texts:
I have interfaced a Nokia 5110 LCD to a PIC. It displays characters using a font table.

Is there a way to plot ADC data on the LCD with ADC data on Y axis and time on X axis?
I do not want to use a library as my code space is limited. I'm using Microchip XC8 compiler.


texts: Code misbehaviour when linear actuator to the circuit

texts:
I have a circuit meant to operate an actuator in function of the temperature.
The code has been tested and, as long as the actuator is not connected, it does what it is meant to do (tried simulating temperature with serial monitor, and checking the answer of the system), without any error.
When I plug the actuator (a 12V DC with Max load 1000N/push from eco-worthy.com), the program starts showing random behaviours (some line of code are executed twice, some other never, finally the behaviour is KO)
The circuit looks like that

The battery used for the prototype is taken from my moto, it is a 12V 8Ah 110A EN FTX9-BS
I started reading about decoupling capacitors then, and tried to add some of the 10nF I had here and there, trying to do it well, but no effect...
I see I should dimension the capacitors, and place them wisely.
Reading on the web, I've got that:

there should a minimum capacitance:

But I don't really know how to exactly measure the amount of current needed by the actuator. Any help?

Anyway I hoped that using 10nF would cover the minimum need

They should be placed as close as possible to the sensitive IC

I placed a 10nF between the two rails on the top of the breadboard in picture, the 5V (output of the voltage regulator) and ground.

Often, a big and small bypass capacitor are used, in this case (Big power supply + voltage regulator) the big before the voltage regulator, and the small after, close to the IC

I placed then also 1, then 2, 3 and 4 in parallel (I was trying...) between the two rails on the bottom of the breadboard in picture, the 12V from the battery (from which also the actuator draws current) and ground. But nothing changed

Where and how to use decoupling capacitors here?
Does someone of the community here know how to help me? Any contribute and discussion will help
Thanks!


texts: If I am charging a battery from a solar panel, how do I switch the current away from the battery when the battery is completely charged?


texts:
I want to get some knowledge in RF PCB design. Therefore I have some questions about this, in order to make some clarification.

What is the purpose of the golden ring around the PCB, often seen on RF designs, like this?

Image source

I suppose it is used as some kind of shield. But, what is it protecting - the board from the external EM sources or the environment from the board's EM radiation? Why is it golden and not masked (painted)? Are there some rules for designing such rings (e.g. ring width, shape, via mechanics, ...)? And, finally, in some cases, there are rings that are not completely golden, like around the CC3200 in the following image below. What is the difference?

Image source


texts:
I am new to Eagle having just returned to my hobby after many years and decided to use Eagle.
I need a 1v8 supply net, and so followed the guidance and created my own supply line in my own library.
BUT.... no matter what I do, I can not see the device in the schematic, or in the device preview but I can see the symbol - I have no idea what I have not done, or done incorrectly.
I wanted to define my own PSU symbol rather than just use VCC and VDD as this is recommended practice.
What have I done wrong? Here is a link to a copy of my lbr file that has the symbol and package in it... Eagle Library file
Library file
I have also added the screen shots of the eagle library manager


texts: High-side driver IC use of diode in the npn transistor BE

texts:
I would like to know why is used a diode between the BE of the npn in this circuit. The npn is used to boost the current to deliver to M2 gate in this bootstrap circuit.
Is it maybe needed to get rid of the accumulated charge during ON operation of the npn itself? (conductivity modulation)

Here another high-side and the diodes are still present


texts: Confusion with the relation between SNR, voltage divider and amplifier concepts

texts:
Imagine you have an input signal s(t).
And the signal of course has some noise n(t).
So lets say the SNR value is x.

Now if we attenuate this signal by a voltage divider by 100 lets say, will the SNR of the attenuated signal remain same or?

Consider the following two scenarios:

1-) I log voltage data of a signal varying between -100mV to +100mV.

2-) And in the second case I log the voltage with same resolution "after amplifying this signal by factor 10" which means I log as -1V to +1V.

Neglecting the amplifier's noise contribution, which way is better in practice? Why?


texts:
Can I use the aluminium enclosure of my mains powered product as a heatsink?

I'm thinking about mounting TO-220 transistors pressed against the enclosure, to get away with passive cooling by using the large surface of my product's aluminium enclosure as a heat sink. I'd use transistors with insulated tabs.

However, I worry this isn't really safe. The IEC-60950-1 stipulates that the product must be safe even under a single fault.

I believe this requirement would be fulfilled on paper. If the insulation between the transistor and the housing fails, the product would be short circuited to ground which would immediately blow a fuse. I can arrange to have the resistance in the ground much smaller than the resistance through the rest of the product, so even the transient voltage of the housing should be safe.

However, I worry that it might be hard to get the aluminium box properly grounded. I'm thinking that a grounding wire would be attached to the housing using screws. But how reliable would such an connection be, electrically? Could aluminium oxide accumulate over time, increasing the resistance to unsafe levels?

Edit: I might need to clarify that of course the housing of the product is earthed. It is the reliability of this earthing bond that worries me.


texts: Issue for TCXO through frequency multiplier (PLL) for STM32 I2S signal

texts:
I try to use TCXO (KT7050A24576KAW33TAD) at 24.576 MHz through frequency multiplier (PLL) x4 (NB3N511DG) to clock the I2S bus (SAI domain) at 98.304 MHz on a MCU (STM32L4R5VIT6). Signals are not what I expected. Can someone help me to understand what I miss ?
1 - SCHEMATIC

(I remove R15)
2 - IMPLEMENTATION

3 - TCXO OUTPUT SIGNAL

Take on pin 5 of KT7050A24576KAW33TAD probe x1 with short ground spring
I expect a "CMOS" signal from KT7050A24576KAW33TAD but it look like more than "Clipped Sine Wave". Page 77 of the Kyocera Catalog I expect the following signal

4 - PLL/MULTIPLIER OUTPUT SIGNAL

Take on pin 5 of NB3N511DG probe x1 with short ground spring
I use CubeMX for quick test, I think STM32 pin "CLK_SAI" is well put in alternate function as "SAI Ext Clock". I expect a "CMOS" signal too on NB3N511DG output (square with lower min and higher max). (CLK_S0 and CLK_S1 are pulled low from the STM32)
5 - LACK OF UNDERSTANDING THE DATASHEET
When i bought the TCXO I see it's a CMOS output from supplier :

But friend of mine caught my attention on KT7050A24576KAW33TAD datasheet  and suggest it can be use in both mode :

But I don't understand how to change mode from "Clipped Sine Wav" to "CMOS" mode...
This is the first time I play with TCXO and multiplier, I probably don't understand something (or more), can someone help me to find my issue ?
EDIT 1 : MEASUREMENT PROBE
I use 1x probe with short ground spring like this :

EDIT 2 : NEW MEASUREMENT PROBE x10
Many BIG THANKS to Justme and Tom Carpenter
Ok, with x10 probe (set on probe and oscilloscope) i got :
Output of TCXO :

It's look like a CMOS signal :)
Output of PLL :

This is a sinwave :( I
So the input of PLL seem good now, but the output is not what I expected. The NB3N511DG datasheet say :

Phase−Locked−Loop  (PLL)design  techniques  are  used  to  produce  a
low  jitter,  TTL  level  clockoutput up to 200 MHz with a 50% duty
cycle.

TTL/CMOS Output with 25 mA TTL Level Drive

The logic diagram show a TTL/CMOS output buffer

And caracheteristics tell me :

Does CMOS not implied square signal ?
Can someone help me to understand why I don't get a almost square signal at NB3N511DG PLL output ?
EDIT 3 : NEW MEASUREMENT PROBE x10 @50MHz
Many BIG THANKS to Justme
Pff... Don't forget Shannon-Niquist theorem... Don't try to look at 100MHz signal width 100Mhz bandwidth oscilloscop...
So I change the PLL multiplication coefficient to x2 to go lower than FS/2.
I can go to 49,152 MHz, here is the measurement :

It's look like what I expected !


texts:
Why is a capacitor a linear device?

One property for linearity is that the capacitance or some such parameter must not change with voltage or current. Is this enough to make a device linear?

A few sources say that the \$Q=CU\$ has a linear characteristic with voltage and so it is a linear device but wouldn't there be at least one such parameter in a MOSFET/diode that does change with respect to voltage or current in a linear manner - for example the voltage of a diode decreases linearly with the temperature.

So what should I exactly consider for linearity?


texts: capacitor placement: series or parallel with IC?

texts:
I have doubts about capacitor placement near ICs,
It's a good place for it?

----EDITED: IMAGES CHANGED TO SCHEMATIC -------------------------------

Thanks in advance!


texts:
I'm having trouble understanding the percent error from the following closed loop feedback equations. \$w =1\$ is the road grade change and \$r=65\$ is the speed control input, and given closed loop output speed \$Y_{cl}\$ and closed loop error \$e_{cl}\$:
$$ \ Y_{cl} = \frac{100}{101}r-\frac{5}{101}w\
$$
$$ \ e_{cl} = \frac{r}{101}+\frac{5}{101}w\
$$
My question is why is the correct percent error equation as follows:
$$ \%error = 100\frac{\frac{100}{101}r - (\frac{100}{101}r - \frac{5}{101}w)}{\frac{100}{101}r}
\
$$
and not: $$ \ 100\frac{e_{cl}}{r}\
$$

thank you


texts: Creating an Arduino-based Gameboy cartridge?

texts:
First off, I am not sure if this question fits here, so sorry for any inconvenience, mods!

I've looked over the internet, and I found this pretty little thing called nanoloop, and I've been wondering if I can make something like that myself. As I am pretty familiar with Arduino, I thought that I could make an Arduino somewhat of a Gameboy cartridge, and probably someone on the internet has done it, right?

Wrong. I haven't found a thing in people trying to use Arduinos as Gameboy cartridge processor. So, here comes my question: Is such thing possible? If so, where would one start?


texts: How to set a positive and negative current from arduino?

texts:
I'm designing a PID temperature controller for a laser diode with arduino. The laser gives me the value of its temperature, which I compare with my reference and then, through the controller implemented in arduino, I'll obtain the proper output values in volts.

The way the laser increases or decreases the temperature is by a peltier cell. So applying a current through this cell it will change it (to the correct value if the PID is set-up properly).

The thing is that the current has to be positive or negative, depending on if we want to heat the laser up or cool it down. I don't know how could I get those currents from the voltage values obtained in arduino.


texts: What does this resistor do in this RTD wheatstone bridge?

texts:
The question is in bold at the bottom, the following is background.

I am going to measure air flow with a hot wire anemometer using the FS7 sensor from Innovative Sensor Technology (IST). They provide an application note for the sensor linked below.

https://www.ist-ag.com/sites/default/files/AFFS7_E.pdf

The application note includes a wheatstone bridge circuit to use with the sensor on page 11. The schematic is recreated below.

simulate this circuit – Schematic created using CircuitLab

I believe I understand the operation of the circuit, excluding R5 and R6.

One idea is that R5 is there for startup. If the circuit turns on and both amplifier inputs are at 0 volts, the bridge is balanced, Q1 stays off, and nothing happens. R5 ensures that current flows through the bridge so that the amplifier inputs move away from 0V and then the op amp can balance the bridge.

A guess is that R6 is for startup too, ensuring that the non-inverting input has some positive voltage to turn on the transistor and start current through the bridge. I don't see why it is necessary if R5 does the same thing.

What is the purpose of R5 and R6? If they are for startup, are they both necessary?


texts: How to calculate overall propagation time for circuitry

texts:
Below is circuitry including a 2-input NOR gate, a 2 input OR gate with 2 inputs inverted, and an finally going through an AND gate.

Through experimentation I measured the propogation delay of each logic gate:

AND - 14ns,
NOR - 4ns,
NOT - 8ns,
OR - 12ns,

How do I estimate the total propogation delay of the circuit above?
Do I simply add up all the logic gate times? here's my solution:

4ns + 8ns + 12ns + 14ns = 38ns

Is this correct?


texts: Are power systems that rely on batteries limited to 25% efficiency?

texts:
In a system involving a power source that charges a battery, and a load that subsequently runs from the battery, are we limited to 25% efficiency at best?

Since charging a battery (or capacitor) loses 50% of the power transferred to heat, and by the same logic, another 50% while discharging into a load...does that not imply that battery systems of this type cannot be more than 25% efficient?


texts:
In this schematic example they are using a 0 value resistor for R3 on the right side. Why should I do that?

Is this only because of the TP? As I dropped the TP for my design I would think of dropping the 0 resistor also.

Datasheet


texts: How simulate trick htc wildfire charger (get max current)

texts:
I have an HTC wildfire phone and I'm looking for way to trick this HTC to think it's connected to the original charger. I don't have original so i can't open it to measure. Right now for charging I'm using the USB port built inside a power inverter for solar installation. I also tried a car charger, rated as 2A, but still charging is very slow.

The problem is I notice the charging is very slow. I have took up it almost all night to get fully charged.

When I play music on phone and display stays on, it discharges faster than it charges.

I set up my little test experiment installation

For test's i got female usb plug, and i hook it up into my work bench psu, set to 5V.

Current draw  390mA
(hmmm, it's looks like safe USB current draw)

I start search internet, and found information about shorting data lines together.

I do, this but current not changed. Still 390mA.

Shorting both data lines to GND also won't help.

Does anyone have similar problem, and found way to make my htc think it's being connected to fast charger and took >1A charge  ?

best regards


texts:
So I was looking through the MAX713 datasheet and came across the schematic below. In short, MAX713 is a NiCd battery charging IC and below is shown the schematic for it in the the switching mode. The DRV pin is a 30mA current sink PWM output. Sinking the current turns the PNP Q1 on and the NPN Q2 transistor off, thus pulling the P-channel M1 transistor gate to the power and turning it off, so in a way it inverses the output.

I have two questions about this schematic.

1) Why is the Q1-Q2 pair needed after all? Won't just the R2 resistor be enough?

2) Can the Q1 and Q2 be just switched places to put a much more common N-Channel MOSFET instead of the P-Channel M1?

3) Is there any reason to use a P-Channel MOSFET here after all?


texts:
I studied electromagnetics and with that understanding when I recall the Working of DC Series motor I stumbled upon an inherent negative feedback action in the DC series motor during starting as follows:

  Considering the DC Series Motor is started with No Load:

  1) At the instant of powering up the motor armature current is low (Transient)

  2) Implies the current in the field coil is low

  3) So the flux due to field coil in the air gap is low

  4) The armature starts rotating because of Lorentz force

  5) By faraday's law- the Back Emf is low as the air gap flux is low

  6) So the armature current increases as per KVL

  7) This, in turn, increases the torque on the armature.

  8) However simultaneously the current through field coil also increase(since Ia =If )

  9)The FEEDBACK action ----Because of Step 8 the flux increases and thus back EMF induced increases which in turn reduces the armature current. Thus the Torque on armature also reduces and so the speed also inturn reduces!!

Isn't this a negative feedback action? Won't this stabilise the DC series motor at some operating speed?

Why it is said that motor speed increases drastically and reaches un-stability when started with no load?


texts: Asynchronous sequential circuit - state table reduction

texts:
Welcome! I got trouble in assignment like this (I got stuck):

  Solve using the optimal number of rows in reduced program table. Use
  sr flip-flops to implement the circuit.

I got stuck in part where I should reduce state table. I can't get it and also I can't understand things like race, so I can't solve this task.

Could you explain it to me in simple words?

My started solution is:

1) find how many states are in (completed)

2) draw state table (completed)

3) fill state table (completed)

4) reduce state table (?)

5) reduce as Moore or Mealy machine (?)

6) what next? (?)

7) get K-maps? (?)

8) draw circuits from boolean functions (?)

Solution:

State table:

Filled state table (stable states are in circle):

Any hints in simple words how to solve this exercise?


texts: Best methods for long term position tracking?

texts:
I am in the beginning stages of development for a project where I need to continuously track the position of an object for long amounts of time. The object will not move very much, but when it does I want to track it to see when it moves 10 meters from its initial position.

I looked into IMU tracking as I have some past experience with IMUs but they seem to have huge problems with long term position tracking due to bias buildup.

The object will be in an area where people can walk, so something like ultrasound won't really work because someone can get in the way of the sensor and make it look like the object is closer to the wall than it used to be when in reality someone just stepped in front of it. The object in question is a large chair that will be stationary most of the time and can only be moved by humans but it can be lifted up. I am mainly concerned in tracking its location on a 2D surface which is the floor its on, but it CAN be lifted off the surface.

Triangulation has been mentioned but I do not know what technology is involved. Do I need to mount reflectors on the object? There will be other things present and moving in the room like people and furniture so how do I account for that and only focus on the object I am interested in n?

The response to the object moving must be somewhat short, preferably less than 30 seconds but closer to 5-10 if possible (and of course lower is always better).

What are the most common techniques used for long term position tracking? When I say "long term" I mean months preferably but right now I'm just trying to figure out what's possible with current technology.


texts:
I need to supply a uC from 42V power source (battery). The uC controlls a buck converter to 12V output which will drive some Leds (0.5A). If the whole device will not be used (no Led driving), a months maybe, the uC will be in sleep mode draining as little power as possible.
A uC will be supplyed from a buck, but i need to start it from 42V battery directly and then switch to supply from a buck. It is because supplying a zener diode from 42V is too lossy, so i will have to disconnect a 42V supply after buck powers on.
I designed two different legs for driving buck also , one "light" for sleep mode and another "heavy" for Led driving.
Does anyone see some possible improvement, simplifying? Or do you see some problems in design?


texts:
I cannot get my toner etch resist on to my copper board. I'm doing with the iron, but each time I try the ink does not transfer completely.

I've tried many things - applying some water on it, different paper type (regular glossy and magazines), etc. I do not own a laser printer so I get the design printed somewhere at Staples.

I sand my board, and clean it with 99% alcohol, and leave it soak for an hour after I'm done so the paper gets fully dissolved, but still I cannot manage to get the ink to transfer correctly on the board.

What do you think and what are the other easy ways to apply etch resist on a copper board?

Here is my etch resist design:


texts: MCU: Strong interference/ripple when touching a wire connected to a GPIO

texts:
I have a microcontroller (ESP8266) which has one GPIO pin configured as "INPUT" with enabled internal pullup resistor.
If I check the voltage of this pin using an oscilloscope I can see that it's near VCC (3.3v) with very low ripple/noise.
A 10cm wire with open end is connected to this GPIO pin. Once I touch the open end of this wire, the GPIO pin "goes crazy".
The oscilloscope shows very high noise (peak to peak approx. 2v) and this behavior continues as long as I'm touching the wire.

This also causes an interrupt (which is enabled on this GPIO) to trigger continously, which is my problem I need to solve.
I need to "harden" my circuit, that even touching the open end of the wire does not bring any (or very low) interference into the circuit.

I tried to solve this by putting an 100n capacitor across the GPIO pin and GND. The oscilloscope showed, that there is no more interference.

I would like to know, is the approach (fixing it with a cap) correct? And why does touching the open end of the wire cause a pulled-up GPIO pin to go crazy? Is this an EMI issue or whats the explaination for this?

Btw: The microcontroller is powered by a switching power supply. Schematics of the power supply are available in this document on page 2:
Schematics

Any comments are greatly appreciated!
Thanks


texts:
I have built two custom Ardunio Micro's. One works perfectly, while the other will not connect via USB. After much testing, I have figured out that it seems to be a poorly routed PCB on my part (I used the auto-router). I think there is a crossed connection somewhere, but after poking at the board with a multi-meter for an hour, I cannot seem to find one.

The schematic for each board is practically identical, with no changes to the layout of the processor. Just to make sure that one of the processors isn't bad, I switched them. The same board still works fine, while the bad board will not work. So I know it is something with the PCB.

When I plug the bad Arduino in, nothing happens. The computer does not even say that there is USB device failure, or one plugged in at all. The other is recognized just fine.

I have checked resistance between the D+ and D- pins of the USB port and the pins on the processor, and there is resistance between them with no crossed connection between each other.

I do not understand USB communication enough to try and figure out what is wrong with my second board in compared to my first. Any thoughts? I would like to try to nail down the issue before I redesign the board and hope it works.


texts: Why there is no high voltage repeater / voltage translator ic (like max232) for I2C

texts: why I2C don't work  don't work with long wire, for UART we have 10 volt translators like max232, for I2C why there is no high voltage repeater ic?


texts: Simplifying a boolean expression to not need a or gate

texts:
Hi I'm a student and I got stuck on a problem.

I need to create a logic circuit only using AND gates or NOT gates. But the question in boolean form includes the OR operator and i'm having difficulty figuring out how to get rid of the OR in the expression.

The boolean expression is
ABC + A~B~c + AB~C

I know I'll probably have to use the boolean properties to expand/simplify, i've been trying different things but I have no ideas and completely lost.


texts: What is the purpose of everything to the right of the proton exchange membrane in a microbial fuel cell?

texts:
A standard microbial fuel cell looks like:

And my question is, why is the cathode and bascially the entire right chamber necessary for electricity production if the load (or the multimeter) can be attached to that area that says "electricity" and can produce electricity?

Would there be an actual problem if one were to leave the hydrogen cations just floating in the anionic chamber?


texts:
I have a differential signal which I want to measure with a differential probe.
While reading the specification of the probe, I got confused with a few terms.
Can someone what the highlighted terms mean:

On page 7, we have a specification table from which I have taken a snapshot.

What does "DC Input resistance of 200kohm differential" mean? Suppose I am measuring a LVDS signal which is 100ohms terminated. How can I measure using that probe itself because it is mentioned to have a DC input resistance of 200kohms? What is 50kohms as common mode?

Why do different tips have different differential impedances? Won't my LVDS signal (which is terminated using 100ohms) be measured inaccurately because all these tips have different impedances than the 100ohms which is necessary?

Please help me understand what the "DC Input resistance" and "Impedance" terms mean in the above table.


texts:
Are there common sources of 434MHz noise or interference in a residential/household environment? I've been playing with some radios, and they seem to be behaving flakily at my friend's house even at close range, and working flawlessly at my house... I'm a bit stumped.

I suppose another possibility is some kind of crazy noise on the wall power at my friend's place, but I'll have to try out a battery power source on the receiver to rule that out, and can post back once I do.

Unfortunately, I don't own or have access to a spectral analyzer either.


texts:
I need help to recognize a dead component from a lab instrument control board. It is part of a TTL-serial interface, arguably a logic gate or some level shifter, in a TSSOP-14 package.

You can see the picture below: manufacturer is easy to recognize as Fairchild, now OnSemi, while part of the code has been blown up.

If you know the component, a good search engine or just have good hints, please help!


texts: One power supply, two loads, fuses and current sense

texts:
I have a project where I need to power two 5V 40A loads. To save space, I'd like to power them off a single power supply module, something like this
power supply [pdf].

The PSU supports remote sense to detect voltage drop. I don't know how I would connect the remote sense across both loads - so I guess it would just go across one?

The power supply has short-circuit protection, but 5V 90A is still quite a lot of power. Should I include a 50A fuse in-line with each load? Or is the short circuit protection enough?

If I have a fuse in-line with each load, and the fuse blows, this article makes it sound like the current will flow through the remote sense lines, but doesn't suggest any solutions. How should I prevent this?


texts: Probable heat probe malfunction, how do I test it?

texts:
Disclaimer
I'm not very sure about the stack where I'm suppose to post my question (between here and "Home Improvement" stack.)
Question
A few days ago my oven started beeping repeatedly when it was powered on.
The beep is the power-on bit.
After taking the oven apart I noticed that what I am assuming to be a heat probe had a burnt wire.
This probe is supplied directly from the current input (brown wire), this same wire then continues to the oven control console. If I unplug the probe the oven does not work (which makes sense.)
I have two question:

How can I test this probe to be sure that it is not the one causing the problem?
Can I find this part on the internet if I have to change it?

Pictures


texts:
I read that current enters an appliance through live wire and leaves through the neutral wire.Consider the appliance to be a light bulb.Now my question:

1.Shouldn't the current first travel to the appliance though the live wire,become zero,and then flow from neutral to live? Because AC reverses direction?

2.The current is alternating in magnitude.But why is the bulb glowing with the same power?
Should not the bulb first glow very brightly,then dim and finally gets off and then again starts glowing??


texts: Why such specific resistances in the TL431 datasheet examples?

texts:
I was looking over the TL431 datasheet, and a few examples, particularly figures 33 and 34 (page 28) in there use what seems to me like needlessly specific values for resistors. I've attached an image of them below:

(In the interest of saving space, part of Note A is cut off in this screenshot, but it's not relevant to this question. The full note, if you must know, is "\$R_b\$ should provide cathode current ≥1 mA to the TL431.")

Why would one use 243 Ω or 27.4 kΩ resistors, when in these cases it's theoretically only the ratio that matters, and the absolute value can be anything reasonable? Why not go with nearby standard values, like 220 Ω or 22 kΩ?

As an aside: Isn't 243 Ω (or 220 Ω) a bit low for a voltage divider anyway? Why didn't they use a larger resistance for that circuit? That's a fair bit of current for that feedback network.


texts:
I'm talking about a simple solenoid train as shown in below image that works on the same principal as a homo-polar motor. It consists of an electric cell (AA or AAA type) whose terminals are fitted with neodymium disc magnets. This setup is called a train. When this train is placed inside a copper coil, the train moves. The working principal is explained in this YouTube video.

Now how do I determine the speed and efficiency of a solenoid train?

For determining efficiency, I think I could divide the product of displacement of the train and the Lorentz force by the output power of the battery, neglecting the friction between the train and coil as given in below equation:

μ=  (Power of train) / (Power of battery)  =  (D × IBL) / (I × V)

Where,
μ is the efficiency of the train.
D is the displacement of the train.
I is the current in the coil. Which is the same as the output current from the cell.
B is the magnetic strength of the neodymium magnets.
L is the length of the portion of the coil acting as a solenoid which is equal to the length of the train.
V is the voltage of the cell.

For calculating veleocity of the train can I use Newton's second law of motion:

F = m x (v/t)

From which,

v = (F x t)/m

Where,

v is velocity of train.
F is Lorentz force driving the train.
t is the time taken by the train to displace itself.
m is the mass of the train.


texts:
I'm trying to understand how conductance that is measured in Siemens is equal
to Amperes/Volt.

The SI units of Siemens is given to be in $$ kg^{-1}m^{-2}s^3A^2 $$ (link).
I am not sure how this is related to A/V.

Could someone explain?


texts: Why do embedded systems need to be programmable?

texts: According to my understanding, certain types of embedded systems are dedicated to a particular task. Why, then, do engineers not transfer all the burden of processing onto the hardware in the form of Application Specific Integrated Circuits (ASICs)? Surely, this would make the controllers more efficient? This approach should work for all embedded systems that don't need to run application software, right?


texts: How can I power four devices each having different working amperages?

texts:
I want to power four devices with different working amperages.

1st device: 0.015A, 12V
2nd device: 1A, 12V
3rd device: 1A, 12V
4th device: 3.5A, 12V

Power supply: DC 12V 6A Power adapter

I'd connect all four of them to power source in parallel, to make the voltage stay the same in each branch (correct me if I'm wrong)

Would a power supply with an output of 6A be enough to properly power them all? Because 1A+1A+3.5A+0.015A=5.515A≈6A= Output of the power supply (Is that correct?)

So how can I provide different amperages to devices with single power supply?
Here is a simple scheme if it helps:


texts: How to light a bulb from an audio signal?

texts:
So this is my first post, hello everyone. :D

Well, I am trying to make my computer/synthesizer light up a bulb - Reacting to the voltage. Right now this is working with an LED: (I using a 2n3904 and some random LED)

But when I am using an incandescent light bulb (12v, 30mA) it does not work. I have removed the 1k resistor from the supply, and tried different lower value resistors for the transistor base. I even added another transistor to make more gain, but with no luck.

Maybe I need more energy to light it up? A capacitor? More gain? Or am I totally forgetting obvious (Diode vs. bulb)?

Please enligthen me wise people. :D


texts:
It occurs to me that, beyond my current problem, I ought to ask, "What should I know when making a library for the Arduino?"

First, what I am doing:

I'm using Eclipse as my editor and writing code in C++.  I have written a simple Arduino application that includes my header file and am working through errors.

First problem: how do I do a 'build clean'?  I am seeing errors that I think I've fixed, almost as if the header file were cached.  (Yes, quite likely I am doing something stupid [edit: I was], but I'd still like to know how to clean the library, and don't know where the object files are).

Secondly: what conventions should I be aware of?  I haven't used the Arduino as much as I'd like, and it feels so good to be programming in C++, but I know the intent of the libraries is to keep things nice and simple for the users.  Are there conventions for function names?  Creating constants (it looks like the global namespace is polluted with #defines)?  And so on.

Lastly, is there anything else I should know?

I should mention that I've looked at the Arduino Library Tutorial, which is good, but doesn't go very far.  I've also peeked at some of the libraries that are installed on my system.


texts: What to look for when selecting an RF detector diode

texts:
I'm currently diving into the topic of RF detectors and I ask myself which are the key criteria  when choosing a diode for a given frequency range.

I have a simple detector using a 1N916, which works up to 1 GHz as I would say without confirming this on a professional meter.

On 2.4 GHz it does not work as expected so I want to replace the diode; but what are the key criteria to look for?

Of course breakdown voltage and so on but I want to know which parameters allow higher frequencies to be measured. I guess low capacitance?


texts: Does triac used for on/off purposes need RFI suppression?

texts: I noticed that in dimmer circuits using a triac there is a need for chokes to suppress RFI, Do on/off only circuits need the same?.. Please I need a detailed explanation or references to understand (not a yes or no answer)..


texts: Synthesising a circuit when \$Z_{21}\$ is known

texts:
I have a \$Z_{21}\$ parameter of a circuit which is given by $$ Z_{21}(s) = \dfrac{s}{s^3 + 2s^2 + 2s + 1}$$

I would like to synthesize as an L-C ladder network with \$ 1 \Omega\$ resistive termination. There is a relation
$$Z_{21} = \dfrac{z_{21}}{z_{22} + 1} = \dfrac{\dfrac{s}{2s^2+1}}{\dfrac{s^3+2s}{2s^2 + 1} + 1}$$

Using this, I can synthesize the L-C network using partial fraction expansion of \$z_{22}\$.

Method 1: I pull out an \$s\$ term first.
$$z_{22} = \dfrac{s^3+2s}{2s^2 + 1} = \dfrac{s}{2} + \dfrac{\dfrac{3s}{2}}{2s^2+1} = \dfrac{s}{2} + \dfrac{1}{\dfrac{4s}{3} + \dfrac{2}{3s}}$$

Using this expression, the overall circuit can be synthesized as

simulate this circuit – Schematic created using CircuitLab

Method 2: I rewrite \$ z_{22}\$ in the below fashion and pull out \$\dfrac{1}{s}\$ term first.

$$z_{22} = \dfrac{s^3+2s}{2s^2 + 1} = \dfrac{1}{\dfrac{1+2s^2}{2s+s^3}} = \dfrac{1}{\dfrac{1}{2s} + \dfrac{\dfrac{3s^2}{2}}{2s+s^3}} = \dfrac{1}{\dfrac{1}{2s} + \dfrac{1}{\dfrac{4}{3s} + \dfrac{2s}{3}}}$$

This can be synthesized as

simulate this circuit

I would like to know which of the above synthesis of \$Z_{21}\$ is correct?


texts: If you only have an Ethernet MAC without higher layer, what happens if packet is lost?

texts:
Does an Ethernet MAC have a built in ack/retransmit scheme or is this the job of a higher layer of network protocol?

In other words, if you have only the Mac layer and an Ethernet packet is lost ... what happens without the higher layers?

I was just curious if you could take a 40G full duplex MAC, reverse the phy transmits lanes into receive lanes and get a half duplex that runs 80G and only receives packets...  the problem here is if Ethernet sends any kind of ack at Mac or phy levels...

It seems like it would work if you had UDP riding on top of Mac... and only needs to transmit packets from source to destination...


texts: GPS accuracy problems outside vs inside with repeater

texts:
I have an interesting problem testing GPS receivers:
While working inside our lab, we get reasonable results. We have a GPS repeater, as shown in the picture.
Inside the lab, I get good accuracy (between 3m to 5m error). On the roof, I get more than 10m errors. I am using the Trimble C1216 (MTK3329 chipset) with an SMT antenna. Our building is in an urban environment, however, the roof is quite clear with other buildings more than 30m away.

How can I explain the differences in accuracy between the roof and the lab? Can the repeater mitigate the multi path effect?

Edit: Some more information:
GPS repeater antenna is the Trimble bullet antenna
GPS distribution antenna is the Alliscom PA175S
The amplifier gain is 26dB maximum GPSNetworkink LA20RPDC


texts: Would Arduino be an appropriate platform to teach high school students?

texts: To teach students about electrical engineering, would the Arduino be a good fit? Or would it be more appropriate to teach them the theory with simulators, or something else completely?


texts:
We have a water level monitor attached to a water tank. The water monitor has an hydro-static (output 0-5V) water sensor that goes to the bottom of the the tank. (See figure)

In most cases this works OK, but for some of our clients, the water sensor seem to be getting burned out repeatedly.

We think is that this is caused by and ESD issue. By analysing the situation of these water tanks, it seems that this occurs in Zinc tanks that have an internal plastic coating on some really dry and dusty areas.

Our hypothesis is that wind blows dust on the tank, which makes it build a potential with respect of the water (given that the water is separated from the metal by a plastic layer) and this difference of potential gets discharged into the water sensor...

To solve this problem, we were considering switching to 4-20mA water sensors, with ESD protection in the sensor, but we are not sure if this will be enough to solve the problem...

Additionally, we are considering grounding our device to the water tank, to prevent electric charge from building between the tank and the water... The idea is that the charge would flow with low resistance through the ground of our device and the probe...

My question would be: Would this approach be correct? Wouldn't conducting the electrostatic charge to the tank create galvanic corrosion in the tank to device contact areas?

Also, maybe it is not ESD... could it be that the probe cables are acting as inductors, and creating a big potential on changes of current to the probes?

Thanks in advance,


texts: Equivalent resistance and circuit reduction of an "8"-shaped circuit

texts:
I am having trouble reducing a specific "shape" of circuits resembling the figure 8 like this one:

I can't figure out what is in parallel and what is in series. I want to reduce the circuit and find an equivalent resistance. I just assigned arbitrary values to the resistors in MultiSim. I'm not looking for an answer to this specific problem, rather I'd love some help as to how I can reduce circuits that look like this one.


texts: Quick and easy question - if you know the answer. I can't find it mentioned in the documentation. What do the icons circled in red mean?


texts: TI Application Report - What are those additional resistors in the low pass filter

texts:
I was searching some documents and tutorials online for filter design. Then I stumbled upon this TI application report. The following is referring to section 2, figure 7 and figure 8 of the paper. I added a picture of the circuits below for convenience.

Comparing the circuit with this electronics tutorial I am not able to figure out, what the resistors R3 and R4 are supposed to do. And why are R3, R4 and Cin, Cout not needed for the circuit with +/- supply?


texts: Voltage Divider producing unexpected voltage

texts:
I am attempting to create a voltage divider that create 4.5 volts from a 9v battery.

Using the voltage divider equation  4.7k / (4.7k + 4.7k) ) * 9v = 4.5v, I decided to use two 4.7k resistors.

When I tested my circuit in a simulator, the voltage produced from the voltage divider was not 4.5 volts.
(the led is just for testing purposes)

I got the same result on a real breadboard. I tested the voltage across R2 in addition to the led. Both voltages were 1.83v


texts: Stability measurement of Operational Amplifier

texts:
All,

I am trying to simulate as well as measure the stability of an op-amp with high gain (~50dB).  The gain is necessary to boost a low level signal.  I am struggling to understand if I am making the measurement right as well as if I am simulating it right.

I am using OrCAD for the simulations and an AP Instruments model 300 for the measurement.  Page 78 in the user manual indicates the test setup, and you can find the manual at http://www.apinstruments.com/files/Model300.pdf.  I have used the supplied transformer and a parallel leaded 10 ohm resistor for reference.

The Op-Amp is a texas instruments TLV316 component in a non-inverting configuration.  I am having trouble taking screen shots for some reason so I will describe the circuit.  It contains an AC coupled AC source to half supply voltage (say 2 volts), and the amplifier is configured as a non-inverting amplifier.  The feedback is a 113k resistor in parallel with a 100pF capacitor.  The inverting input is 3.3k in series with 0.036uF capacitor.

I've tried employing the 3 techniques outlined in the article below but I have convergence problems unless I AC couple the audio through.

http://electronicdesign.com/print/analog/use-pspice-verify-feedback-amplifier-stability

My question is:  Is the stability measured by plotting the difference of the magnitude and phase of the output versus the negative input OR is it the difference between the positive input and negative input such as open loop gain?  Further, if the former is true, am I supposed to measure the difference across the 10 ohm resistor in the lab and across the high 1000H inductor in my simulation, or do I measure from the output terminal and the negative input terminal?  Also, what is the phase supposed to be at near DC?  180 degrees, -180 degrees, 0 degrees?

EDIT:  The schematic is shown below.  The non-inverting node has an AC source connected and is AC coupled as mentioned, however in the screen shot I removed the source and directly connected the left side of the capacitor to ground.

I think I may be getting hung up on the affect of the capacitors on the phase.  I am going to retry the circuit but with just resistance.  For reference, I don't have any reason to suspect the circuit is unstable and no, it is not oscillating.


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I need some help to figure out what this NPN transistor circuit do, how it works and why it's needed in order to make the CSR64215 bluetooth chip work. Here's the schematic:

And here's what MFB stands for in CSR64215 chip (took it from the datasheet):

I'm asking all these questions because I'm about to use this bluetooth chip in my car and the problem I'm facing right now is that when I'm cranking the engine it turns off and back on quickly, but after that it unables to connect to my phone automatically and it's very frustrating as you have to do it manually after all. So basically I'm looking for a fix for this issue.


texts: understanding data semantics and diagram

texts:
According to http://www.auto-diagnostics.info/pdf/ford_eectch98.pdf page 10, "The 8361 ROM chip contains 8k bytes of program memory plus 128 bytes of additional RAM."
I found two diagrams under different names "81C61 RAM" and "8763 EPROM".

It seems to me that the 8763 EPROM has 16K*8 = 128kb of memory while the 81C61 has 8kb of RAM.
Are they related to the 8361 chip or are the values just a coincidence? Any suggestions to further explore? (opening the microcontroller etc?)


texts:
I am building a custom box from wood (around 14 inches by 10 inches by 10 inches) to encase 3 high energy Metal Halide Bulbs (400+ watt each). The box will be opened and closed intermittently, automatically. It will be closed for a maximum of 60 minutes straight. When the box is closed, the lights will remain on.

This will of course generate a lot of heat when the box is closed and I understand that I need to some take precautions to filter out the heat from the box.

Right now I can think of having a few holes in the back of the box and using a powerful fan to "drain" out the heat.

Furthermore, I am thinking of treating the walls of the box with a flame proof liquid.

Are there any other / more efficient ways to drain the heat from within the box?

Thanks


texts: Decoding Signals from an Unknown Port on Spectrometer

texts:
We have a Thermo-Nicolet Nexus 670 FT-IR Spectrophotometer, made in the USA around 2000. It was the work horse of the infrared spectroscopy community. The instrument sends out signals to a proprietary card in the computer for data processing, mainly FFT, I suppose. It looks like this, with a large Xilinx FPGA chip, a Zilog processor, some memory chips and a PLX PCI controller. I could not identify U1 and U2 sfter a quick search. They are probably quite important for communication.

On the instrument side, there is a 20-pin connector that sends signal to the card.

My question is, based on these information, would it be possible to decode the signal passed between the card and the instrument? An FT-IR signal is basically an array of intensity vs. mirror position. Doing an FFT on the array one backs out intensity vs. wavelength. So the computer needs to send signal for driving the mirror and getting back digitized signal from the instrument.

A plan B would be to chop most of the existing electronics and tap out the analog signal directly from the detector while find a way to drive the mirror by oneself.