texts: Current-voltage characteristics of silicon carbide luminescence

texts:
I am currently studying the textbook Light-Emitting Diodes (3rd Edition) by E. Fred Schubert. Chapter 1.2 Henry Round's demonstration of the first LED says the following:

The mechanism of light emission in forward-biased and reverse-biased Schottky diodes is shown in Figure 1.4, which displays the band diagram of a metal-semiconductor junction under (a) equilibrium, (b) moderate forward bias, (c) strong forward bias conditions, and (d) under strong reverse bias where avalanche multiplication occurs. The semiconductor shown in the figure is assumed to be lightly doped (n-type); the semiconductor can even be insulating (i-type). Such diodes are frequently called metal-insulator-semiconductor (MIS) Schottky diodes.

Under strong forward bias conditions, minority carriers are injected into the semiconductor by tunnelling through the surface potential barrier. Light is emitted upon recombination of the injected minority carriers with the n-type majority carriers. The forward voltage required for minority carrier injection in Schottky diodes is larger than typical p-n junction forward voltage. Round (1907) reported operating voltages ranging between 10V and 110V.
Light can also be generated in a Schottky diode under strong reverse-bias conditions as shown in Figure 1.4(d). At a sufficiently strong reverse bias, the avalanche effect occurs in which high-energy carriers impact-ionize atoms of the semiconductor, that is, a valence electron is excited to the conduction band. In this process, holes are created in the valence band as well as electrons in the conduction band, which will eventually recombine thereby creating light. Additional light-generating processes in Schottky diodes under reverse-bias conditions have been reported by Eastman et al. (1964).

Chapter 1.3 Oleg Lossev's research on SiC LEDs says the following:

Oleg Vladimirovich Lossev (1923, 1924a, 1924b, 1928), a brilliant Russian experimentalist who worked at the Nizhny Novgorod Radio Laboratory in the former Soviet Union, reported the first detailed investigations of the electroluminescence phenomenon observed with SiC metal-semiconductor rectifiers. Born in 1903, Lossev published his first paper on electroluminescence at the age of 20 years, in 1923, when he had not yet a formal degree. In the 1923 paper, Lossev reported seeing green light with the "naked eye" when reverse-biasing a SiC metal-semiconductor rectifier. In his 1924 paper published in the Wireless World and Radio Review, he showed the first photograph of SiC emitting electroluminescence. It is shown in Figure 1.5.

For forward bias, the current was higher but little or no light emission was observed. The main use of these rectifiers was in solid-state demodulation radio-circuits that did not employ vacuum tubes. Oleg Lossev found that luminescence occurred in some diodes when biased in the reverse direction; subsequently he found that in some diodes luminescence occurred when biased in the forward and reverse directions. A detailed current-voltage characteristic revealing Lossev's the high degree of scientific rigour is shown in Figure 1.6.

Chapter 1.3 claims the following:

For forward bias, the current was higher but little or no light emission was observed.

But based on what is claimed in chapter 1.2 and figure 1.4, it seems that forward bias should result in light emission. Am I misunderstanding something here?
Furthermore, I am unsure of how to understand figure 1.6. There are two points where it is stated that "Beginning from this point the luminescence is observed", where the bottom-left statement seems to be in the "(-) carborundum (+) steel wire" area, and the top-right statement seems to be in the "(+) carborundum (-) steel wire" area. So what is figure 1.6 showing?


texts:
In the following circuit, my understanding is that when there is a spike or rise in the data line higher than Vcc, the top diode conducts and the voltage flows into the path to protect the downstream IC/circuitry.

But how does that voltage flow into the top Vcc, which is a probably a power supply? Or am I missing something?


texts: Reading hundreds of inputs with a single atmega32

texts:
I have 128 inputs (push buttons) in a single row in a project and I want to read them using a single atmega32. Of course there is not enough pins in an atmega 32 for this purpose and I know the solution would be using some kind of multiplexer but I don't know which one suits the best.

What I'm thinking is to have some kind of multiplexer that have 128 pins as input and have 7 pins for output that represents the result of inputs into binary (as an example if all inputs were 1 (UP) and output pins will be 1111111 (all UP)). But I'm not sure if there is any multiplexer doing this ?

I have to mention that I need a cost effective solution. Becasue I have to extend this solution to maybe 1000 or even 10,000 inputs in the future (which we have to use several multiplexers to read all of them)

Any help would be appreciated. I need to know which multiplexer I need to use ? (probably part no. or any other suggestion)

Update:

Only one single button will be pushed at the one given time AND it update rate won't be fast. maybe 10-30 times per second or much less.


texts: Differential voltage measurement on shunt resistor

texts:
I trying to build a simple differential measurement circuit to feed a analog to digital chip to monitor current consumption of a board with an Arduino. So I decided to go with a "traditional" differential amplifier with op-amp in front to get a nice high impedance for this improvise differential probe. Here's a simple schematic of my circuit: (Op-amp have 12v supply)

To my surprise, the reading on the 5 ohm shunt resistor is way off the real reading (measure with a multimeter). Instead of having 2.02V which correspond to a 404mA consumption (which is what is expected), I got 43mV!? I used this probe (pin 3 & 5) to check voltage around others components on my board and the reading are correct. But on the shunt R1, it's completely off. I tough that since it's a really low resistance that my high-impedance will be ok be it seems not. I look around on the net and the solution seems to go with this approach but that's not working for me right now... Any suggestion?


texts: Is this the correct truth table to determine whether or not to execute an interrupt in a RISC V system?

texts:
I'm working on implementing the privileged RISC V ISA, which can be found here.

I'm looking at the bottom of page 20, and the interrupt conditions are stated very confusingly:

  Global interrupt-enable bits, MIE, SIE, and UIE, are provided for each
  privilege mode.  These bits are primarily used to guarantee atomicity
  with respect to interrupt handlers in the current privilege mode.

  The global x IE bits are located in the low-order bits of mstatus, allowing them to be atomically set or cleared with a single CSR instruction.

  When a hart is executing in privilege mode x,
  interrupts are globally enabled when x IE=1 and globally disabled when
  x IE=0. Interrupts for lower-privilege modes, wx, are
  always globally enabled regardless of the setting of the
  higherprivilege mode’s global y IE bit. Higher-privilege-level code
  can use separate per-interrupt enable bits to disable selected
  higher-privilege-mode interrupts before ceding control to a
  lower-privilege mode.

With this description, I have made the following truth table which determines whether or not a certain interrupt will be execute based upon the  MIE, SIE, and UIE bits, and the current privilege mode. This is confusing because it seems like while execution as a user, the supervisor won't take interrupts of a higher privilege level... Is that correct?

is this truth table correct?


texts: Help with Motor encoder connection with motorcontroller

texts:
I am new to building drones and bots. I started out using motors without encoders with my Roboclaw Motor Controller for my pet project. Here is the controller's link. Connection seemed simple and it was working the way it was supposed to. Now I got these new motors with encoders for better control. There are 6 pins from the encoder. on top of that, I can see two metal prongs (marked M+ and M-), much like my earlier motor, connected to the motor itself. And I am confused about the connection. I don't know which pin goes where.

I tried contacting customer service to no avail. I am not super confident about trial and error either. Can anyone please explain the connection details? Thank you.

Sorry if this question seems too naive. Also, if this is not the appropriate place for this question, any pointer to where it should go will be highly appreciated.


texts:
The setup is a 240V 50Hz AC transformer outputting 60V 50Hz AC. Connect this power supply (with a push button) to an old telephone and it rings the bell on command, but unrealistically fast.
I need to take this 60V output and reduce the AC frequency to 25Hz so the phone sounds more realistic. As per what I've read about the signals for making phones ring (here in Australia anyway).
Any advice on what I can put inline between power supply and phone to achieve this?
Thanks.


texts: What clear plastic stripping is used to wrap a toroidal power transformer?

texts:
I'm partially rewinding a toroidal transformer just for the pure thrill of controlling the output voltage. I'm sure I'll get over it, but for the moment that prospect is pretty exciting for some reason :)

I'm leaving the 120V primary in place (I removed a second 220V "extension" primary winding) which is good because it's about 1500 turns. I'll wind a new secondary or two and then wrap it back up.

On the outside and between the primary and secondary windings, the transformer is wound with a clear plastic tape (no adhesive backing) that is 12mm wide and 3 mils (0.003") thick. I'm sure it performs a mechanical protection role and given its inter-winding appearance an electrical insulation role as well.

I notice the tape is pretty stiff (not floppy or stretchy to speak of) and holds the kinks from its original winding position pretty clearly. It occurred to me that it might be some sort of heat-shrinkable tape that stiffens and holds bends once it's been shrunk. That would make some sense I suppose because the shrinking would insure the winding underneath was tightly bound and less likely to become noisy or whatever.

Does anyone know what this stuff is and whether it's available in modest quantities for prototyping purposes etc.? Or perhaps whether it's okay to reuse it?


texts: Safe to turn variable speed AC motor on/off via wall switched outlet

texts:
I have a (high velocity air) dual AC brush motor pet hair dryer (details). (There is no heating element.) It's rated at 120 Volts 18.5 Amps. It has a rotary knob (listed on the parts page as a "Variable Speed Switch and Circuit Board") that clicks on & off and then rotates to set the motors' speed. It's a bit of a pain to click it on and then find the desired speed setting each time. Plus it's wall mounted and a bit hard to reach. I'd like to plug it into a switched wall outlet and use that to turn it on and off, and leave the speed setting at the typical use level (about 90%). It that safe to do? Or can doing that cause damage to the motors  or electronics?

[edit/update]
It's currently on a 20 amp circuit and I would have an electrician install a properly rated wall switch for this.


texts: What concepts in programming are useful in Electronics Engineering?

texts: I am studying Electronics Engineering. I only took two 3 programming courses. The first 2 are in c++ and I learnt up till pointers, classes and the basics of data structures. The third is mips Assembly language. I need to know if learning more about data structures, Algorithms and discrete mathematics will help me in the field of Electronics Engineering. I will not have the chance to study these topics in my university, so if they are important I can self study them.


texts: What do 3-digit reference designators mean?

texts:
While looking at many circuit boards and schematics, I often notice that 3-digit designators are used, for example R101 instead of R1.

What do these digits actually mean? The numbers are not in sequence, for example only a single relay, K101 may be present, still numbered 101.


texts: In DSP for audio, I understand what Aliasing is (fixed with an anti-aliasing filter), but there is also something called Imaging (fixed with a reconstruction filter). Aliasing is when a higher frequency mirrors DOWN about 1/2 the Nyquist frequency, but Imaging is when a lower frequency mirrors UP about 1/2 the Nyquist frequency. It has something to do with the DSP reconstruction of the signal the consequences of "zero padding" and so forth. Can someone give me a good explanation using detailed examples on why Imaging happens and what it is exactly?


texts: Schematic review for simple LED circuit?

texts:
I'm pretty new to circuit design, I am trying to make a small board with a few LEDS that uses a toggle to turn on and another toggle to either show the LEDS always on or to blink the LEDS.  I believe that this circuit will work as the CD74AC14 schmitt-trigger IC is low power (1.5 - 5V) and the LEDS are being driven at about 1.7V.
For 11 LEDS @ ~20mA each its about 385mA-hours.

I am thinking a coin cell rated at 3.0V , probably a Panasonic BR-2477A/FBN ?

If there are any pointers or critiques please let me know.

Datasheet for Switch : http://www.ckswitches.com/media/1422/js.pdf

EDIT : Updated schematic to fix switch issue. LEDS left as is.


texts:
I'm confused again about electricity. There seems to be two types of resistance, a dissipative and a restrictive one. Everything I've read, however, says there's only one type of resistance.
Let's assume, for instance, you have current supplied to a heating coil (nichrome wire in a coil) in a circuit with a potentiometer in series. The heating coil converts the current energy into heat via the resistance of the electrons. The potentiometer, on the other hand, can equally resist the same amount of current flowing to the coil, yet it doesn't dissipate much heat at all. It appears the heating coil's resistance works by dissipating the excess current into heat, while the potentiometer restricts the current flowing through it. Is there really two types of resistance?  Why doesn't the potentiometer heat up as much as the coil?
Notes I made a small but potentially important edit. When I used "coil" in my example, I meant nichrome wire formed into a coil used as a heating element as commonly found in soldering irons, space heaters, etc. A poster clued me in that "coil" might be interpreted as an induction heater.
Btw, I've had nothing but excellent experiences with this community. I am deeply touched by all of your efforts and assistance! While it maybe off topic, I cannot allow such good deeds to go unappreciated. Thanks for all the help!


texts: Power spectral density on the output of frequency modulator?

texts:
Is there a formula with which we would be able to calculate the power spectral density on the output of a frequency modulator?

The information we know is that we have a receiver working in 180MHz that receives signals with bandwidth of 200kHz and the receiver is comprised of an antenna, the frequency modulator with amortization of 0.1dB and an amplifier with bandwidth of 9.9MHz and 10.1MHz, gain of 4.5dB and noise figure 2.5dB .

We also know that the temperature is 27 degrees Celcius. The noise temperature of the antenna is 100 degrees Kelvin and the SNR fraction at the input is 12.5dB

What would a voltometer show for the voltage on the output?


texts: How to make MSM photodetector more selective?

texts: I got a question, how can I make Metal-Semicondutor-Metal photodiode more selective in terms of wavenlength spectrum. I need to mention I cannot use Bragg reflectors like in RCE photodetectors. All I can use is quantum wells and p, n doping layers. To be more precise, I need to narrow the absorption spectrum below 1300 nm, let's say to 1250-1350 nm. In general the upper range (1350 nm) is just limited by bandgap of active material, so that's not a problem for me


texts: Why are the wires of thyristors always twisted in pairs?

texts: I have always been told that you should never untangle the wires of a thyristor or subset of thyristor (such as TRIAC and SCR). Why is this? Is this just for convenience or is there a use for the wires being twisted?


texts: Can a decoupling capacitor be too large?

texts: For my project containing an ATtiny85 running at 32.768 kHz using an external watch crystal I thought I'd include a 1 uF decoupling capacitor near the MCU power pin for good measure. However, reading up on it it seems that most people recommend a 0.1 uF capacitor. Can using a too large value cap (e.g. 1 uF) do any harm or would it work alright?


texts: Convert a wired headset to a wireless one

texts:
new to the board and not caught up with current technology, but I can handle myself when it comes to soldering and small electrical appliances. I have a headset that I really love, but the wire snagged on something and snapped. I could wire the headset back together, but I thought I'd do something a bit cooler. I'd like to fit a wireless transmitter as well as a cell phone battery inside the headset to convert it into a wireless headset. The battery is already installed and working, and now I have a bit of a puzzle in front of me:

Do I solder the remaining points back into USB female port, then stick that into the headset and use an out-of-the-box wireless USB data transmitter / USB Bluetooth transmitter? Or is there a compact wireless board I can easily use to send the audio data? The soldering points I'm dealing with seem to be left speaker, right speaker, and a data point. I've tried looking for wireless USB data transfer kits, but the ones I can find are bulky. On the other hand, I can't find a Bluetooth setup out of the box because any USB plugins for Bluetooth seem to assume the port you are plugging into should be broadcasting audio, not receiving it. Suggestions welcome, pictures and a walkthrough if I am successful.

EDIT: I found a Bluetooth SMD Module on sparkfun.com, I think it can do what I need it to: https://www.sparkfun.com/products/11678
My only question is, is this a solder and go or do I need to make my own drivers for it?

EDIT 2: Hacked a Bluetooth headset and wired it all up, works great. I wasn't confident I'd be able to use the breakout board for the module I linked without writing my own drivers, so now my Razer Banshees are recognized as a Verizon headset, but the sound quality is good and I had the spare cell phone batteries. If anyone can give me insight on using breakout boards in the future I'd be grateful.


texts: ATmega168 versions for low power applications

texts:
I am interested in using an ATmega168 for a simple application, which has however very strict power limitations. As a result, the important thing for me is to find the version with the least power consumption. I checked several versions' datasheets, and this is what I found:

ATmega168: Active-250uA | Power Down-0.1uA
ATmega168P: Active-300uA | Power Down-0.1uA
ATmega168PA: Active-200uA | Power Down-0.1uA
ATmega168PB: Active-350uA | Power Down-0.23uA
Bonus: ATTiny24A: Active-210uA | Power Down-0.1uA

I expected that the "P" in the uC's name would mean lower power, which apparently is not the case(?). Apart from that though, I am very confused with the 168PB version, which mentions in the datasheet about the utilization of PicoPower Technology, but is the worst in terms of power consumption. Also, the fact that ATTiny consumes more than the ATmega168PA, really makes me think why one would pick ATTiny.

I would really appreciate it if you could give me some info if the above facts are right or I am overlooking something, and recommendations about which version I should choose after all. Also any info on the naming of the uC's would be welcome.


texts:
I'm trying to understand the Arduino design.

LM358 and FDN306P is connected in between USB input and primary source input. In presence of USB and primary supply the Arduino mega board is drawing current from both of the sources. If it is used for power switching then why is the load sharing happening?

Here is the schematic. Is this mosfet used for allowing one of the power source at a time or for load sharing?


texts: Is state machine based sequence detector easier to verify than shift register based one?

texts: Suppose I have two versions of sequence detectors: one is based on let's say Moore machine and the other one is based on simple shift register & comparator. Which one among these is easy to verify and scalable?


texts: What is the difference between Ground and Low?

texts: What is the basic difference between sending a LOW signal vs GND to a circuit? What If I ground instead of sending LOW? Or similarly what is the difference between Vcc and HIGH?


texts:
Consider the below schematic

simulate this circuit – Schematic created using CircuitLab

How would we find the current flowing across the short circuit?  I know what a short circuit is (no voltage) and I know how to find the current across all the resistors using kirchoffs laws.  However, applying that to the circuit doesn't seem to add up.

Is there a trick to this?


texts: How to scale audio signal from PCM data to a dB SPL value?

texts:
0
I've got a set with MEMS microphones that measure audio signals at ultrasonic frequencies. The MEMS microphones have a PDM output which is then converted into PCM (this is necessary to allow for a microcontroller to do certain processing on the sampled audio data).
I'm trying to come up with a method to convert the PCM samples into dB SPL and the best resource I've found on this is this link: https://curiouser.cheshireeng.com/2015/01/16/pdm-in-a-tiny-cpu/. I understand how they calculate a RMS value from 977 PCM samples (this is called an SPL value in internal logarithmic units in the article). They relate this RMS value to a dB FS value by using the microphone datasheet (where the maximum possible PCM value/RMS value for a square wave will be equivalent to a known maximum value of dB FS of +3 dB FS ). I don't understand how the author then creates a linear relationship between dB FS and dB SPL (akin to the classic y=mx+b). The specific paragraph from the article discussing this is listed below:

To relate the finished SPL value in internal logarithmic units to dB SPL, we have to note that the microphone data sheet claims that a 1 kHz tone at 94 dB SPL will typically register as -26 dB FS, where 0 dB FS is largest amplitude sine wave that can be represented in a PCM sample without clipping. A full scale square wave is then +3 dB FS, and which would measure as 8 * log2(8192) or 104 which can be rescaled to dB by multiplying by 20 * log10(2) / 8 or about 0.75 to get 78. Subtract the 3 dB for a sine wave, and we find that the offset is about -75 dB to dB FS, or +19 to dB SPL.

Putting this all together, if we wanted to output true db SPL we would need the following expression in terms of our computed variable spl: dB SPL = (3 * spl / 4) + 19

I'm not understanding how the coefficient of 0.75 or the intercept of +19 is justified. Does anyone have any ideas or some additional resources I can consult on this?


texts: How to determine Audio Transformer Ratio of 1:10 at Digikey?

texts:
I'm just starting to work with Transformers and while doing electronic experiments I found that I didn't know much. I'm trying to find an Audio Transformer with a ratio of 1:10 or 1:20 with an inductance of about 670 Ohms. After searching through the DigiKey website on Audio Transformers everything appears to have a ratio of 1:1. But there are specifications like 3.4kCT Primary, 4/8/16 Secondary.

What does the CT mean? And How do I calculate based on these numbers what the ratio would be or to find this type of transformer I suppose it's not a Audio Transformer any longer.

Can I find this transformer http://www.conrad.com/ce/en/product/739679/670-Audio-Transformer-110 at Digikey?


texts: Powering down parts of a pcb to conserve power, is it possible? Any caveats?

texts:
I'm building a USB 2.0 bus-powered STM32F429-based audio device that is able to run in a stand-alone mode from a phone charger, or running as a USB device when connected to a computer.
To comply with the USB spec, the device should not consume more than 2.5mA when in suspend mode.

I want to be able disconnect power to the led driver (25 mA idle), a SDRAM chip (also 25 mA) and a oscillator using MIC94070 high side switches, as well as disabling the boost-regulator that powers the analog part. This will leave me running only with the MCU and USB PHY.

Are there any ceveats to this approach?
I can think about avoiding back-powering the chips by pulling the gpio's low first before disabling the switches, but that's about it :)

To help conserve power, I've already optimised the number and values of pull-down resistors and chosen low-Iq regulators.


texts: Opamp positive feedback circuit problem!

texts:
The opamp being in positive feedback with Vn @  4V has an output of 0volts and when the input is a pulse of sufficiently large magnitude that the positive terminal goes high above refernce voltage  and output remains at Vcc even after the pulse is removed!

The question is :
But,when the pulse is not high enough but still appears positive terminal of opamp , i still see a postive pulse at output in millivolt range, Why does that occur ?
Also when i vary the resistor values ,the output pulse magnitude varies and at some point i see positive feedback dominate and take output high forever!! Why?

Here is a pic of output :


texts:
I have an old design, since 1999 approximately, with an old FPGA XCS30XL and old MCU6840 MCU. They are connected together via a parallel bus peripheral and both utilise and power off 5V. But there is an oddity which is that some of the control lines between the two (IRQs, CSs, R,W,etc) are pulled to 3.3V instead of 5V (Address/data are a mix pulled to 5V or no pullups). All other pullups in the system are generally 5V,

What could the reason/benefits be for pulling a 5V signaling system (at 16Mhz or so) to 3.3V instead of 5V in push/pull logic when the chips actually use 5V signaling?


texts: due to attenuation the signal has loss in power, but not frequency, so why here in EDFA optical amplifier use the pump since the amplification medium ist the Eribium ?


texts: Need suggestion on 2 channel transceiver 5V to 3.3V level shifter

texts: I need to Interface multivibrator output to control input of the analog switch. Where the maximum operating voltage of analog switch is 3.6V. So I need voltage level shifter from 5V to 3.3V. And the output of the Multivibrator is a timing data so I need a transceiver 5V to 3.3V without affecting the pulse width(I can accept ~15nSec tolerance)


texts: What are primary and secondary sides of PCB?

texts:
I am designing a 2 layer PCB with components on both side of it. SMT components are one one side of PCB, but TH (through hole) components are on both sides. I have to go for mass production of say 300 pieces and for assembly. So, I was reading about component placement and minimum spacing. I need to understand something mentioned in guidelines (Dave Jones and Spirent) called primary and secondary sides of PCB and secondary side components needs more spacing.

Also some very good source of guidelines for volume production will be very useful.


texts: Level shifting 3.3v to Rail Voltage(up to 36V) using a bi-directional level shifter

texts: I have the above circuit which is able to convert Vin to 3V3. Any IO pin of the MCP23S17 can be connected to D_OUT on the level shifter. D_IN can be used for either input or output signals. The MCP23S17 is able to detect inputs and outputs logic levels correctly when used with a power supply. However, when I connect the pins to a device that has some proprietary circuit at its input pin the voltage on the level shifter output drops to 3V3. What would be the best way to implement isolation at the output of D_IN so that it can still be bidirectional. I have looked at CD4050BNSR but am unsure if it will be bi-directional. I will be very thankful for any recommendations.


texts: I'm learning about power management in OMAP35x and I came across these terms. I can't seem to find a good explanation anywhere. What do they mean?


texts: Calculating symbolic input impedance of Multiple Feedback Low-Pass filters

texts:
I am trying to design a filter and I am Following this guide. The second step is determining the input impedance of the circuit.

The filter is a MFB Low-Pass type:

And its transfer function in s-domain will be equal to:

For calculating the symbolic input impedance, I recon that I have to use Thevenin Equialent of the circuit as seen by the input (voltage source). Will this be the calculating the resistor in prallel and series and then adding the series resistance of capacitors to the result? what will happen to the OpAmp, will it have effect on the input impedance calculation?

Hints and tips are pretty much welcome!

Thanks.


texts: What is "foldback short circuit protection" in a power supply?

texts:
I am looking at buying a 24V power supply. Two of the options are these:

PSP24-060S 24 VDC 2.5A (60W) power supply
PSB24-060-P 24 VDC 2.5A (60W) power supply

The first offers "foldback short circuit protection" and "overvoltage protection," but it is $85 dollars. The second is much cheaper but does not mention these.

What are these types of protection, and how important are they? Are they worth an extra ~$50? Thanks!


texts: Controlling IRL2703 with 3.3V (Reading MOSFET datasheets)

texts:
I have an application where I want to switch on/off a resistive load (24V/300mA) from a 3.3V MCU GPIO pin at a rate of 1 HZ or slower. I also have some IRL2703 MOSFETs, and I wonder if they would do the job. Or generally, how to read a MOSFET datasheet to find out if it would do the job.

Looking at the datasheet, I find/interpret

Drain-to-Source Breakdown Voltage 30V -> sufficient for the to-be-switched 24V
RDS(on) only specified down to Vgs = 4.5V, so it does not tell me about my 3.3V.
For completeness, the Gate Threshold Voltage is min. 1V (no typ. or max. value listed), but that does not tell me if 3.3 V will work correctly.
Fig. 1 "Typical Output Characteristics" shows Id = 2A @ Vds = 24V @ Vgs = 3.0V @ Tj = 25 °C @ 20 us pulse-width
Fig. 2 "Typical Output Characteristics" shows Id = 4A @ Vds = 24V @ Vgs = 3.0V @ Tj = 175 °C @ 20 us pulse-width

I'm assuming that 20 us pulse-width refers to a PWM signal with 20 us HIGH and 20 us LOW, i.e. 50% duty cycle. Because I want to drive the MOSFET steadily, I guess that I can only drive half of Id, i.e. Id = 1A @ Tj = 25 °C.

Is my understanding correct?
The graphs are typical characteristics. How do I obtain the minimum guaranteed/worst case Id?

How can I estimate the RDS(On) (and thus the dissipated power) in my setting?


texts: 9V to 5V regulated or 6V to 5V regulated? Which one is more efficient?

texts:
I have a choice of choosing 1x 9V Duracell battery or 4x AA Duracell batteries. I want to regulate the voltage to 5V with a 7805. From what I understand, the voltage regulators just converts the unwanted energy into heat to reach the regulated voltage.

My best guess for efficiency is using the four AA batteries, less wasted energy and higher mAh. Should I be looking into the drop off voltage for these different power sources?

My application is to power a MCU while data logging without having to change the batteries often. It would be best to have the highest mAh option, but with a maintained voltage.

Is there somewhere I can look to obtain more information on this? Or could I be enlightened?


texts:
Alright, I was wondering how this is currently done in the industry. Usually, when we produce some hardware, we have a few testing options available (Automatic Optical Inspection, Flying Probe, In-Circuit-Testing, Function Testing, ...). Usually the customer will ask us what the advantage of one over the other is and we have a document explaining those which is fine. The next question usually is, if his board can be effectively tested using the one or the other method. What he usually would want to hear is: Using this test method we are able to find 75% of all errors, using the other one we can reach 90%. If you did this up front, we could reach 95%.

Now for the (engineering) question: How do you create such numbers? Have you done this in the past already? Do you require such numbers from your manufacturer. I know there is no universally available answer to this question but I would like to get some insight how this is handled in other companies. We simply want to provide a reliable and dependable source of information to our customers. Any insight is highly appreciated.


texts:
I want to design a high side variable current source:

Power source (Vacc) is an accumulator whose output varies between 9V and 7V.
I need output DC current values between 10mA and 100mA.
I need it to be high side, so the load (RLOAD) is referred to ground.
RLOAD is between 1 ohm and 60ohm
Precision in current should be 10%.
Maximum output voltage should be as high as possible, ideally up to 6V.

To control the output current value I'm using a micro-controller powered at 5V, so I can have either a PWM, or a number of ports set to 0V / 5V. I can produce a control signal Vctl:
 - ground referred.
 - between 0 and 5V.
 - With a 1% precision.

I would like to have it built with basic components, if possible.

I tried this schema:

simulate this circuit – Schematic created using CircuitLab

The idea of the circuit is that the PNP transistor is providing current to the source so the voltage drop in R4 plus the Vbe is equal to Vc. Vc is the voltage drop in R2, which is supposed to be proportional to the current driven by the NPN transistor. I need this to translate the Vctl input, which is ground based, into a high-side reference. In the end it doesn't work because an uncontrolled amount of current is leaving the base of PNP transistor.

Can someone help-me?


texts: Single Phase Energy Meter using Atmega32

texts:
Version 1 :

We are trying to measure the input voltage from the AC mains (which theoretically should be 230 V). The circuit to measure this is a simple resistor divider network as shown below.

The values of the resistors are chosen such that it will generate corresponding step down voltage across 20k resistor which is fed into the micro controller.
EX. When the AC mains voltage is 240 V then the output voltage across 20k resistor should be 2.4V.

Before connecting the resistor network to the single ended ADC input of atmega32 - 2.4V across 20k
After connecting the resistor network to the single ended ADC input of atmega32 - 1.56V across 20k

The input impedance of the ADC of Atmega32 is high as mentioned in the datasheet. Hence there is no scope of loading effect.

Version 2 :
To remove the ambiguity of ground in version 1 we gave differential input across 20k to the adc on pin0 and pin1 as shown below. But still we are getting the same results.

NOTE:
All the voltage levels are measured using both CRO and DMM.


texts: Safety Rule: Sum of wire lengths over two phases may not exceed X. What is this for?

texts:
Everybody knows various flavors of the rule "don't connect too long electrical lines to an outlet / generator / whatever". They sometimes come in the form of "don't chain your extension cords". As far as I know, the main reason for this is that you might raise the wire resistance to a level that prevents fuses from blowing if you create a short-circuit.
Now, at the German THW (Federal Agency for Technical Relief), there's an additional rule when working with (non-grounded) generators: You may connect anything up to 100m, measured over any pair of two phases. So, connecting 50m cords to all three phases is fine. Connecting 75m to L1 and 25m to L2 and L3 is fine, too. Connecting 75m to L1 and L2 would not be okay.
I wonder what's the reason for this? We sort of suspect that it's because the generator is not grounded, i.e., your neutral is "not really neutral". It would be great if somebody could elaborate on this in terms I understand. I'm not an electrical engineer (obviously, otherwise I should probably figure this out myself…?).


texts: Switch to connect/disconnect 7 lanes (maybe 7pdt?? switch)

texts:
I'm looking to take a 6s Lipo Battery balance lead  (7 pins), and run them to one of two sockets.  One with a charge meter, and the other with a charger.

I want a switch that will toggle between the two sockets.

I've searched for various switches or ways of doing this, but cannot find anything (short of having 4 dpdt)

Is there any way I can achieve this with a single switch?


texts:
Is this correct to connect 5v outputs and 3.3v inputs ttl logic via an open drain transistor and an internal pull-up resistor on the digital input?
I suspect the 5v part can influence to the 3v part through base -> collector -> pullup -> 3v power line.

(the transistor comes as a part of existing device, so doesn't cost anything for my solution).

simulate this circuit – Schematic created using CircuitLab


texts: Identify component in 1970s vintage video game from photo

texts:
Can anyone identify these two components, marked "SKY 4433" and "2.000000 K.D.S", respecitvely? Are they capacitors, crystals, or something else?
They are from a vintage 1970s ball-and-paddle-style video game (Parat Game by Technigraph) based around the AY-3-8500 chip.


texts:
We need to magnetically shield a solenoid that activates this valve (shown below)

Just slipping a mild steel cap over the end does not do the job, nor appears to have any screening effect at all. Any suggestions for a practical way of doing this? Or any explanation of why a mild steel cap is not working?


texts: How to store the electric energy produced by solar panels properly?

texts:
I am building some solar panels from 6" cells (4W, 0.5V, 8A). At the moment I have two 1x2 panels and one 2x2 panel. So there are 8 cells in all panels and the added voltage is up to 4V.

Now I want to store the energy somewhere. I have a laptop with the input of 19V DC 2.1A (40W) and I'm also planning to buy a 12V 12Ah battery. As far as I know if I will provide voltage that is too high/low for the laptop/battery, it may cause some problems or even damage, so I need to control the voltage. But what about the current? What happens if I provide a current that is too high/low for the battery/laptop (since there are many models out there, I'm asking about usual situations if there are such)?

So I need to control the voltage and I assume that I also need to control the current. Since I'm on a low budget and have lots of time, I decided to build my own voltage/current controler circuits (one for the laptop and one for the battery). When building a controller for my laptop, it's pretty clear (?) that I have to provide 19V DC 2.1A. But what about the 12V battery? The only parameters given on the battery is 12V and 12Ah (in the catalogue of the shop that i'm going to buy it in), so what input current should I provide for that battery?

I want the circuits to be as simple as possible, with less components, since my knowledge in electronics is very narrow (for now). I would appreciate if you would give me advice, links to information or even suggest your own circuits for this application.


texts: How to increase thermal shock resistance of the electronics components?

texts:
How to increase thermal shock resistance of the electronics components assembled on the PCB? Is there any material (or method) for increasing the thermal shock resistance of components?

Best Regards,

EDIT1 : Correct term is Thermal Shock Resistance. (Credit : comments)
EDIT2 : Procedure is seen below. T1 is -40 celcius, and T2 is 85 celcius. Is this enough to be able to find a solution ?
EDIT3 : This is an interview question comes to me for a position about the electronic design. So I have not conducted a test for observing a specific electronics component and interface fault.


texts:
I am reverse engineering a LCD (this is a raw bit of glass, i.e. no controller) and trying to understand the signals... there are 16 lines of which 4 are backplanes and 12 are segment lines.

The backplanes are driven, in a 60 Hz repeating 8-step sequence, at 4 levels... 0, 1v12, 2v24 and 3v36.

I took the output from one segment line and subtracted the individual backplane signal to get 4 different signals (effectively the demultiplexed signal)..

The average voltage for these signals is zero (i.e. no DC bias), the segment that is illuminated has a signal with a RMS of 3v, the segment off signals have RMS 1v.

Why does a segment off signal have an amplitude, could it not just be fed with zero or is that impossible in an LCD multiplexing scheme?


texts: I have a 12V DC mini air compressor that has a cigarette lighter fitting, now I want to use it for an airbrush kit, can I someway attach a wall plug and use it that way, please excuse my ignorance of this matter it's way out of my field, thankyou.


texts: What's the simplest Linux capable board I could make at home?

texts:
I'd like to make a single board computer capable of booting Linux, with my low-tech garage tools (2 sided PCBs, reflow skillet, no plating through holes).

What's the simplest hardware design I could choose?

Are there any microcontrollers with enough onboard flash/RAM to run Linux/uCLinux?


texts: How should I connect the TVS GND in a metal enclosure?

texts: I am using a TVS diode for ESD protection.  My device has a metal enclosure and I wonder if I should connect the TVS GND to the metal enclosure or system GND.


texts:
I don't know how the output expression for each output produced from the truth table. Can someone please explain how this output expression was dervied from the truth table?

Problem: Design a combinational circuit with two inputs and four outputs. The output binary number should be the square of the input binary number.

Truth Table:

Output Expression:

S0 = B
S1 = 0
S2 = AB'
S3 = AB

P.S. Apostrophe is for Prime/Complement.


texts:
The drain current is related to gate to source voltage by the following equation:

\$I_d = I_{dss} (1 - \frac{V_{gs}}{V_p})^2\$

Now, with changing \$V_{gs}\$, I think \$V_p\$ also changes. I am studying Electronic devices and circuit theory by Boylestad and Nashelsky where they are using \$V_p\$ defined at \$V_{gs}=0\$ for calculation of \$I_d\$ at all levels of \$V_{gs}\$ though it is nowhere mentioned that \$V_p\$ is going to be constant with changing \$V_{gs}\$. Is it the case or am I mistaken somewhere? Please clarify the doubt.


texts: Inductor & Led, In series or in (reverse) parallel?

texts:
I am using a YX8018 IC. It's a basic switching boost design meant to boost a single AA rechargeable (1.2V) to a white led (3.3V), with solar panel charging. According to the data sheet (Chinese, not very detailed) and this breakdown by Analog Devices this is the internal setup. A simple oscillator paired with an inductor. A typical DC-DC switcher for Solar Lights, nothing special. This I get.

It has two recommended setups. The First has the inductor and led in series. Inductor is charged by the battery, switched with LX, and dumps through the led back to the battery.

But the second has the led across the inductor.

From the Analog breakdown:

In figure 2 the current pulses from the inductor return to the battery through the LED to the ground side of the battery. We can also connect the LED across the inductor so that the inductor current returns directly to the inductor.

This I don't get.
I'm assuming the point is to dump the current back into the inductor so it boosts again (a cycle of diminishing returns but better than wasting it?) or charges faster?
Which of these two setups are better? Or do each have their own pros and cons? If so, what are they?
One thing I noted in the IC's data sheet, is that the second is preferred when you have 2 batteries in series (2.5V) compared to the first which is for 1 battery (1.2V)


texts: How do I select the transistors for this circuit?

texts:
I have no background in electrical engineering at all, and only bought my first breadboard this week.  I'm still completely new to this and just trying it out.
I'm trying do drive an 12V actuator, where flipping a switch reverses the polarity.  Eventually I'll be replacing the switch with a raspberry pi, so the signal (is that what it's called?) is limited to 5V.
I've managed to create a circuit on my breadboard that does this using 2 SPDT relays (I don't have DPDTs), but this obviously isn't ideal.
My primary question is

how do I select the transistor to replace these relays?

Specifically,

Should I use FET or BJT?
What sub-variety of transistor should they be (npn/pnp?,  JFET/MOSFET?, enhancement/depletion?)
Can This circuit be constructed more simply? i.e. with fewer components?

More generally,

Does it matter that the signal and power channels are different voltages?
What type of transistors should a new hobbyist stock up on?
How does one generally go about selecting a transistor for a given application. e.g. What is does the flowchart of transistor selection look like?

Diagram of functional circuit with relays.  A simulation of the circuit is available here.


texts:
I using Xilinx FPGA and need to use its PLL (MMCM or Clk Wizard)
I have on my board LVDS 200MHz clock with 50 ppm frequency jitter,
I took this and go to some converted I can find on the internet and I can see that 50 ppm from 200 MHz is a frequency variation of 10 kHz:

OK so I look at my PLL and there I need to insert the jitter value in units of PS or UI.
How I can convert it to these units? I can't find it in the PLL documentation from Xilinx.


texts: How to read the text printed on top of every IC?

texts:
I find very difficult to read part numbers. I haven't figured out how which kind the ideal amount of light and inclination would help me.

I also wonder why chipmakers don't paint the numbers in white for a better contrast.


texts: Can i use DC Voltage (5DCV or more?) to trip the Gate of a Triac BTA series Transistor to connect Terminal 1 and Terminal 2 completing the circuit?


texts: Does higher impedance speakers generate clearer voice?

texts:
I have a PAM8403 based amplifier module and going to build a small portable speaker, mostly to listen to lectures and audio books. The module looks like this:

First I attached two 4 ohms 3 watts speakers and it worked fine. But I've read that it would make a clearer sound with 8 ohms speakers. And in the module properties it is said it can work with 4-8 ohms speakers.

A clear sound would be a benefit for me, but will I loose power (loudness) with higher resistance speakers?
How is the sound quality related to the speaker resistance? What is the theory behind it?

All the speakers I am going to use would be the same diameters.

Here is the efficiency chart from the PAM8403 datasheet:

As far as I know, efficiency is about delivered power, not quality of the sound. Please correct me if I am wrong.


texts: Bias current and offset voltage, op-amp 741 DC imperfections

texts:
Can the effect of the bias current counterbalance the effect of offset voltage?

I am asking this question because today in a lab it occurred to a couple of groups.

Is there a reason for that?


texts: Using only a part of Bms's balance leads

texts:
i was serching for a 100Amps bms and i saw one that said: 6S-28S and i was wondering if it's possible to use only a few balance leads and how to do it.Any other 10s bms is either not capable of enduring 100A or too big for my usage.Thanks in advance for your answers.

edit:here's the part


texts: External VCC for USB cable while keeping data connection

texts:
I want to connect my android phone and arduino to create a fast and reliable serial connection. I've read that it is possible with USB OTG but i will need to charge my phone eventually. So i was wondering if i can use another USB cable to feed VCC for both cables while maintaining data connection between arduino and android. I created this simple schematic. Will this work for what i wanted to do? (Sorry for mistakes. English is not my native language.)

Thanks


texts: Stability of Buck Converter when output capacitance is variable

texts:
I am designing a buck converter for an application that has several different loads. Depending on what devices are connected, the capacitance seen at the output of the buck converter can vary significantly (200-500uF). This makes designing a consistently fast and stable ac performance very tricky.

This answer suggests adding an LC filter to decouple the bulk/load capacitance from the control loop. I would like to use this approach, but how can I determine a value for the inductor? Some applications I've seen use a very small value (100-200nH with a capacitance of 100uF), others larger (470nH to 2.2uH (see section 2.3 of this application note (PDF)), but don't specify how they arrive at this.

(I'm not so concerned about noise suppression, which most of these app notes are tailored for, just transient performance.)


texts: How to modify D-FF Setup/Hold Times using Verilog?

texts:
I am new to Verilog. I need to find a way to modify setup/hold-time and clock to output delay timing parameters. Why I need this is to simulate a problem that changes the timing parameters with some value.

So, let's say in some reason the setup time of a flip flop has changes which resulted in incorrect behavior. But the designer has not considered such a timing change.

How can I modify the D-FF setup time in Verilog so that I can see the real-world problem?


texts: How can I program an SOC without a hardware kit?

texts:
I am new to the production side of electronics. I was wondering if I can directly use a DA14683 to implement a size-constrained project. I have a few queries in mind

Is interfacing a SOC similar to interfacing a microcontroller like Atmel or ARM?
What does electronics product development look like? Do people directly buy SOCs to implement their idea?
What all pre-requisites will I need to be equipped with before using raw SOC for my project?


texts: Why the current across a diode is zero when the forward bias voltage is less than barrier potential?

texts:
In the I-V characteristics of diodes under forward bias , I have seen that the current starts increasing from zero only after reaching the barrier potential , say 0.7 for silicon. As far I understand , the formation of barrier potential is somewhat like this : when the diode is just formed, due to the carrier concentration differences, diffusion of carries starts to take place. But this creates a depletion region and an opposing electric field. The opposing electric go on increasing, and a potential is generated which increased from 0 to 0.7 for silicon, as time elapsed. At 0.7 V,the diffusion current and drift current due to this 0.7 v gets into equilibrium and net current become zero.

So my question is this : if I apply a 0.1 V as forward bias, won't it reduce the barrier and make it 0.6 V? As the 0.1 V bias continue to exist, I think the voltage barrier should now remain at 0.6 V. At this 0.6 V diffusion component of current should overcome the drift current and a net current flow should be there. This net current should go on increasing continuously on increasing the forward bias, rather than abruptly start increasing at 0.7 V only (no current till 0.7 V). Why isn't it happening?


texts: Current sink - work in simulator, doesn't work in real

texts:
I've built current sink to drive wheatstone bridge. I've counted that I must reach current ~0.2mA to properly working whole measure system. Picture below present my current sink (I use MCP6001 op amp):

Before constructing whole device I've simulated it in LT-spice, and simulation looked good.

Op amp is powered ofc. MCP6001 is low power amp with Rail-to-Rail Input/Output feature.
When I measure voltage on opamp output I've got zero volts...
Is it possible to reach 0.2mA with this current sink based on MCP6001?

Thanks in advance!


texts:
I have a problem understanding one thing in op-amps, namely - when the cycle of stabilizing ends?

For example, when we have simple non-inverting amplifier, firstly the difference equals the amount of voltage we supply. It is amplified and through the feedback loop it goes back to the second input of the op-amp, and the difference changes.

It goes on until we reach 0 difference on both inputs. But then the output should become zero, as it can be also expressed as the product of common mode gain (0) and the average of both inputs.

If output is zero now again the difference between inverting and non-inverting terminal is not zero, so it starts to stabilize and so on.

Then when this cycle stops? How the op-amp manages to maintain any constant output if it tries to make voltage at both terminals the same, but by making it it creates output voltage that makes these voltages different.


texts: What could happen if a lightning strikes a car with a battery connected to the chassis ?

texts:
I was wondering today what could possibly happen if a lightning strikes my van where I have a 12V battery negative connected to the chassis. Could that destroy the battery or start a fire?

In order to prevent it should I disconnect the battery negative during the storm?

Thanks


texts: How to determine if this filter is stable

texts:
Hi I have a filter which has the following transfer function:

H(z) = (z^2 + 0.04)/(z^2 + 3.24) for which i need to determine whether this is stable or not. I'm not sure how to attempt this, but I'm thinking it has something to do with the poles and zero's (just taking a guess here).

Any ideas?

Thank you


texts: Having problem in blinking the LED on Nucleo-L073 board, through HAL library

texts:
Could you please advice me where I make the mistake, the LED is on but it does not blink.

#include "stm32l0xx_hal.h"

int main(void){
    HAL_Init();
    GPIO_InitTypeDef GPIO_InitStruct;
    __HAL_RCC_GPIOA_CLK_ENABLE();

    GPIO_InitStruct.Pin = GPIO_PIN_0;
    GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
    GPIO_InitStruct.Pull = GPIO_NOPULL;
    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
    HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

    while(1){
        HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_0);
        HAL_Delay(100);
    }
}

This is the bare metal code which works.

#include <stdint.h>
int main(void)
{

volatile uint32_t *RCC_IOPENR = 0x0;
RCC_IOPENR = (uint32_t*)(0x40021000+0x2C);
*RCC_IOPENR |=0x1;

volatile uint32_t *GPIOA_MODER=0x0, *GPIOA_ODR=0x0;

GPIOA_MODER = (uint32_t*)0x50000000; //MODER BASE ADDRES
GPIOA_ODR = (uint32_t*)(0x50000000+0x14); //ODR BASE ADDRESS
*GPIOA_MODER = (*GPIOA_MODER & ~0x03) | 0x1; // SET MODER BIT TO 1,

while (1){

//GPIOA PORT, PIN 0 BLINK (PA0) by changing ODR register bit
*GPIOA_ODR = *GPIOA_ODR | 0x1; //ON
for(int i=0; i<50000; i++){} // DELAY
*GPIOA_ODR = *GPIOA_ODR & 0x0; //OFF
for(int i=0; i<50000; i++){} //DELAY

}
}


texts: Monoshot oscillator with a opamp level shifter gives huge oscillations

texts:
I am trying to level shift the output of a LTC6993-3 using a THS4631 based level shifter.
I get a 0-5V output which I want to level shift from -5V to 0V.
I get a clean output from the monoshot but, the output has huge spikes after the level shift stage.
Below is my schematic and outputs.
Can someone please explain why this is happening?


texts: Design a Circuit with Zero-Order Transfer function H(s) > 1

texts: I know that if I do 2 1K ohm resistors in series, I can just do a voltage divider to get Vout/Vin = R2/(R1+R2) = 0.5. But if I want to get a transfer function of 3, what components would I use?


texts: is the resistance in ten meters of copper wire too high to use in a circuit powered by AA batteries?

texts:
I have a wireless security system at home, and the wireless node is too far from the receiver. I was thinking that I could splice about 10 extra meters of wire into the existing line to move the node close enough to the receiver.

From my university days, I remember the I = V / R equation, meaning that with a fixed voltage (from the two AA batteries), if I increase the resistance, the current that gets through will be smaller - possibly not enough to power the wireless node.

How do I determine the resistance of the wire? Is there a standard calculation I can use?

I haven't picked up the wire yet, so I can use another type of wire and a small gauge if that would help.


texts: I've noticed that CMOS delays are only up to 50% of output instead of 100%. Why do some people use 50% delay? Is there an advantage as opposed to 100% delay?


texts: Am I mistaking this component for a 1000F capacitor?

texts:
I'm organizing some capacitors I acquired over the years in my parts bin. There's one large disc capacitor that has me perplexed. It has the markings:
 **ERIE 1000F 10KV 7634**

While it's quite a large capacitor, measuring ~13/16" or 21mm, it's doesn't appear to be large enough to hold 1000F (farads) of capacitance. I tested it with my multimeter and only got 1.260nf which seems more likely. The 10KV (kilovolts) also appears to be very high but seems probable given its size. I searched for it using the numbers on the marking but it yielded no pertinent information.
Am I mistaking this for a capacitor when it is actually another similar looking component, such as an MOV or voltage suppressor?  If so, what does the 1000F and 10KV mean?


texts:
Let's take an example:

extern volatile __bit TRISB0 @ (((unsigned) &TRISB)*8) + 0;

I believe this is pointing TRISB0 to the appropriate bit address. But I don't understand why __bit is used instead of bit, the XC8 data type.

I've tried to find an explanation for __bit in the XC8 User's Guide and elsewhere, but to no avail.


texts: Adding a DC bias to an AC signal for amplification and measurement

texts:
I am trying to add a DC bias to this AC signal, but for some reason the schematics I found online for this do not work. The AC coupling is not happening.

I have simulated the circuit here: http://everycircuit.com/circuit/5315107213279232

Or screenshot here:

simulate this circuit – Schematic created using CircuitLab


texts:
I have a problem with a sbc that I am repairing, the sbc is controlled by an 8-bit OTP microcontroller which I think is broken.
I only get 200 ohms between pin Vcc and Vss, specifically the chip is COP87L84BC and is out of production.

What I try is to read the registers of the microcontroller with a cable ISP and any similar software WinPic800 but for this chip.
I never used the COP8 OPT from National Semiconductor so I wanted information about this MCU or web sites where I can find information.


texts:
I am making a stir plate out of an old PC fan, variable resistor, and DC power supply from this tutorial.

I have two power supply's to choose from, their outputs are:

PS1 = 12Vdc, 2A

PS2 = 12Vdc, 300 mA

Question #1: Which power supply should I use?

Question #2: What size potentiometer should I select given the power supply such that I can control the speed of the PC fan?


texts:
Here is the following assertions from "Section 4 – Power Transformer Design" written by TI (https://www.ti.com/lit/ml/slup126/slup126.pdf) :

From the Faraday's Law, the current across the primary winding or the primary inductance is proportionnal to the duty cycle and Vin (volt-seconds product) and is inversely proportionnal to the switching frequency (and the inductance). Nevertheless, it is true by experience that the primary current is higher when Vin is low... It implies that the volt second product is higher at low Vin... I have some troubles to find the physical relation that prove it ! Could you please help me ?

Thank you and have a nice day :)


texts: Franctional-N PLL spurious emissions/harmonics

texts:
I have a very rudimentary understanding of PLL frequency generation. I've heard from people that Fractional N PLL synthesizers generate a lot of spurious signals and harmonics on the output if unfiltered.
This Youtube video was linked which apparently demonstrate the phenomenon. Additionally, I've found mentions of this in a technical brief by TI (Pg 34 § Fractional Spurious Signals and Compensation), however it's mostly above my comprehension.
I thought the VCO would generate a single frequency and the PLL would compare against reference frequency and adjust tuning voltage so the output is a desired frequency. What part of this system generates the harmonics?


texts:
Some 16 bit ADC's specifications has "No missing code: 14 bits min", like ADI's AD7656. I want to know where the 14 bits locate in the 16 bits. Does it mean the high 14 bits?

According to the definition of 'No missing code', the missed code can be one or more of the possible 2^n binary code. Assume a 16 bit ADC with 1 bit missing code, no matter where the missed code locate, i can safely use it as a 15 bit ADC, right?

And i want to know the relation of DNL and 'No missing code', i think if a 16 bit ADC specified with DNL = +/-4 LSB, i can assume the no missing code is 14 bit, right ?


texts: Closed circuit vs low resistance resistor

texts:
I'm learning electronics and this confused me.
In this circuit it shows that current flows through both wires with resistors and lower only through one wire where there's no resistor (even though one is with really low resistance). I thought current should still flow, what's happening here?


texts: Keysight's Advanced Design System users, what's wrong with this simulation?

texts:
For those of you that uses Advanced Design System (ADS), from this circuit:

Fundamental Frequency for transient simulation tool is set to 1GHz.

Yet, I'm getting this output:

Main question:

Since this is Common Drain, VOUT should at most have the same amplitude as VIN. Probably even negative shift, since I didn't change the voltage threshold (I haven't got to tweaking parameters yet). So what's up with the positive DC bias?? Why is the amplification significantly less than unity?

Other questions:

1.) Also, what's that Transient Response at the very first cycle of VOUT? Why would a semiconductor have a Transient Response? Is it because of the "inductance" on the drain and source of a MOSFET?

2.) Lastly, why is it that this simulation does not work on very low frequencies? I first started with 1Hz scale for everything (just change all units from 1GHz below to 1Hz). The M1 just acted like a 1kOhm constant resistor.

UPDATE:

Because of recent response, I bothered to simulate this in the 1kHz scale (replaced all units from GHz in the pics to kHz, did the same with Fundamental Frequency) -- really should've done that in the first place (stupid me). This is the output:

Even here, the DC bias is nearly the same and the amplification is much, much less. It also lags by 90°. Why?

I'm starting to think it's either just using the wrong component or there was a set of parameters to fill-in for this component to get this to work.

UPDATE:

the continuation of this discussion:

Keysight's Advanced Design System users, what's wrong with this simulation - II


texts: Connect multiple devices to one power cord

texts: I have one Canon power cord (below I have include an image), for connecting one camera directly to power and not using a battery. I want to connect two or more cameras to it. This power cord has output 7.4V and  2.0A. For connecting two devices (doing the suitable soldering of course). Are 7.4V and 2A enough or do I need to buy a different cord with more Amperes? Is the formula like 4 ampere for 2 devices 6 ampere for 3 etc or am I wrong? I think I need to keep the voltage untouched.


texts:
I am designing a circuit that has a nominal 24VAC input. This circuit is protected by a 4A Fast-Acting fuse. I would also like to insert a transient voltage surge protection. For achieving that, I am willing to add a 26VAC varistor between the input terminals.
I am well aware that a long duration over-voltage may lead to a catastrophic failure in the varistor. However, for this voltage there is no TMOV device available, not even THT. My question is: is the only solution to insert an extremely ugly, huge and Thermal Cutoff near the varistor terminals?

Edit 1:

As suggested by Dwayne Reid, I think it would be better to use a TVS Diode instead of a varistor. Besides, he pointed that the 26VAC rating is underestimated. I agree, and think that a 11% variation in the mains 230V as well as a 25% voltage regulation from the transformer should be considered. A 35VAC rating makes much more sense.

Edit 2:

Well, I have finally decided to use 2x 1812 35VAC varistors in parallel. The TVS diodes are a good option, but can only withstand much lower surges. As far as I have read, the fast acting fuse at the input should protect the varistor against catastrophic failure.
Another worry with the TVS Diode is that most manufacturers do not specify failure condition. It could only damage the P-N junction in a way it appears to be an open circuit. In that way, the user would never notice that he is currently unprotected against surges.

Thanks.


texts:
I'm using an NAU7802 ADC which has a built in amplifier. I'm trying to use it to read a strain gauge but it keeps giving me weird readings.

Eventually I resorted to shorting the two differential inputs together so that it should read 0, however these are the readings I actually get (at 80 Hz, gain = 128):

As you can see, most of the time the reading is correct, but every 0.4s or so it has a burst of nonsense.

I am pretty sure that my code is correct (I can't post it, sorry). Note that I am polling the device for DRDY (data ready) rather than interrupting on it. That shouldn't make a difference but I'm kind of at a loss as to what is causing this.

Does anyone have any suggestions? I've added capacitors to just about everywhere I can and put everything in a metal box so I don't think it is EMI.

I am going insane.

Update, it gets weirder

So I changed my code a bit so that it uses the DRDY interrupt, like this (I couldn't get I2C to work within the ISR for some reason, hence the boolean):

    // In setup()
    attachInterrupt(1, adcIsr, RISING);
}

volatile bool dataReady = false;

void adcIsr()
{
    dataReady = true;
}

loop()
{
    if (dataReady)
    {
        Serial.println(adc.readADC());
        dataReady = false;
    }
}

And now I get this graph. The magnitude of the triangles is independent of the gain!

I seriously have no idea what is going on now. It seems like some kind of timing issue but the data sheet says whenever you read the ADC output it latches and gives you the last one.


texts: Why rotor copper loss in induction motor doesn't change with slip

texts:
Why air gap power is consumed in R2/s but rotor copper power loss only in R2?
Transformer Equivalent circuit of Induction motor: https://drive.google.com/file/d/1g37XlYaLSb9sbIHuVYDUP1XuDgW_h8TS/view?usp=drivesdk


texts: Drive in movie speaker via bluetooth and mini amp

texts:
I need some technical help that I believe a site like this could answer. I bought some drive-in movie speakers which I restored by cleaning up and replacing the old 4" drivers.The 2 drivers are 4" in size, 4 ohm and 5 watts. (See pictures)
I bought a mini bluetooth amplifier to hook up these two speakers so that I could play 50s tunes from my phone via bluetooth cast out in mono.
It worked great for the short test runs I did but yesterday I lost all output from the mini amp (see picture of mini amp) which had an output of 50 watts per speaker. I put both speakers onto just one output on the amp so it would be 10 watts on that output leg. The amp company through a very broken English email is telling me that the speakers are not large enough and it backed up the amp and overheated it. That may be true but the amp was only on for less than 15 minutes and it was not hot when I went to see what was up with it.
The only advice from the amp company (they say they wont warrantee my purchase) is to buy another amp but hook bigger speakers up to it. I can not do that due to the nature of what I am trying to do with the drive in speakers.
My question here is: Is there a way to put some kind of circuit/resistor???? in this mix somewhere that could fool the amp into thinking there are larger speakers and thus dissipating any output power that might otherwise back up and blow out the amp?
Please note with this request that I know NOTHING about wiring and circuitry so your answer would have to be very specific of what I should buy and where to place it in the mix (a drawing would be helpful). If any of you with a more technical side would wish to help me I would be so appreciative. I was supposed to show off this system at the end of the month at a drive-in which no longer uses real speakers. I was going to blue tooth the radio broadcast of the movie onto my speakers. Thanks for reading
-John


texts: What does the number of parallel lines in a relay symbol imply?

texts:
Some relay cores are represented by two parallel lines and others by three. Does the number of parallel lines have any significance?

Saw this symbol in Tiny cad. What does three parallel lines in the picture imply?


texts: MSP430 JTAG, read flash content / Chip ID

texts:
I am very new to MSP430 programming, I only have experience with Atmels AtMega and the Atmel Studio.

In Atmel Studio I have the possibility to read the Chip ID, and Flash.
How can I accomplish this with the MSP430? I am using CCS at the moment, and can't see any method.

I have a commercial hardware, where a MSP430F2252 is used, I would like to try if the chip is accessible via JTAG, and if it is, I would like to read out the content, if it is not, I would like to erase the whole chip and write a new program for that.

Is this somehow possible with CCS or another Software?

Thanks!


texts: Power losses in long wires with multiple loads

texts:
I need to calculate power losses in long wires. I managed this for the case of constant currents. But in the real world, my loads are DC-DC regulators.

The load draws 11W of power, network voltage is 24V. So in ideal world DC-DC will draw about 0.5A from the network. But further from power supply voltage drop will increase -> voltage at load will decrease -> current have to increase. But voltage drop depends on current flow. And for me it looks like recursion.

Can somebody point me how to calculate such case?


texts: An SRAM cell uses 6 CMOS transistors to store 1 bit of information. A DRAM cell uses 1 transistor and 1 capacitor to store a bit. So one could guess that for the same amount of information (say, 1GB), SRAM would be around 6 times more expensive than DRAM (if capacitors were free). In the real world, however, this difference seems to be much larger than a factor of 6. What's the reason for that?


texts: Can I use pushbuttons with pull-updown driven by a gate?

texts:
I have a digital circuit, which generates a signal passed to another part (let's say a flip-flop) and I want to be able to force this signal 0 using a pushbutton. Do I need to use any additional logic ICs? Or will this be fine:

simulate this circuit – Schematic created using CircuitLab


texts: Why does the signal MOSFET keep failing in this circuit?

texts:
The following is the power control part of the circuit I use in my car to control the wing mirror folding motors, the idea is that the whole circuit can power itself off after its done its job to prevent even minimum battery drain.  (full circuit here)

The power goes through the P-channel power MOSFET and there's an N-channel signal MOSFET to drive the power MOSFET's gate low.  The signal MOSFET's gate has a pull-down resistor to keep it off and may be driven on either from a 5V arduino signal or a 12V car signal, through diodes.

The N-channel MOSFET is failing every few days or weeks.  I have tried using a 2n7000 small signal MOSFET and I have also tried the way overkill RFP50N06 power MOSFET in its place but both eventually failed.  In both cases I believe I have stayed well within the maximum absolute ratings from their specs.

This is my first direct use of MOSFETs but as far as I've checked a MOSFET will burn mostly if the gate is kept on at a voltage below the Gate-Source Threshold voltage because part of the Drain-Source current dissipates at the MOSFET.  In this case the threshold voltages are 2-4V and the gate is driven at 5V to 12V minus the diode's voltage drop, so it should be fine.  In any case the Drain-Source current should be so small it shouldn't even matter.

What else could be the problem?

(I have also once tried a BJT NPN transistor in this place and I was surprised it didn't work, haven't investigated further)


texts: Replace 3 X LR44 battery requirement with a single AAA or AA battery

texts:
I have a rowing machine that requires ("eats," more like it) three LR44 batteries. I'd like to replace that battery requirement with something more common and rechargeable. I've made a career from writing very complex software, but am seriously in the dark about electronics so I do not know where to start with figuring out how to make this conversion.
Where can I go to learn the basic knowledge I'd need to figure this out? Even better, if someone has done this before and can share notes?
Many thanks...


texts: Does Ground Voltage Need Lowered As Well?

texts:
I am dividing voltage of a 9V battery to 3V for a Rasperry Pi GPIO. I have the ground connected to the end of the resistors, so it is back to 9V when I connect it to the Pi's ground pin. Is it ok to have the ground at 9V?

simulate this circuit – Schematic created using CircuitLab


texts:
I am a novice and are working on a project . I need to get a view point of if im heading in the correct direction. My question is:
Can I put two 115 volt 2 hp motors through a step down out of a 240 volt 16 amp house point?


texts: Why does this magnetic relay max DC voltage rating is much less than its max AC voltage rating?

texts:
Below is a specifications of this magnetic relay:

For AC and DC the max switching current is given same as 10A.
On the other hand, max switching voltage for DC is drastically lower than its AC counterpart as 40V and 240V respectively.
Now here is my confusion. For instance, let's say we apply 1V DC across a 1 Ohm resistor and the power becomes 1 Watt. Now if we want to apply AC voltage across this 1 Ohm resistor and we want to obtain again 1W it means we should apply AC 1V rms voltage across the resistor. This means in this case max AC becomes sqrt(2) V. So for the same power dissipation the instantaneous AC voltage can be sqrt(2) times higher than max DC.
But in the relay example it is not that simple. Why is the difference in max AC and DC voltages not close to sqrt(2) but much greater?


texts: How to calcuate thevenin voltage with two voltage sources

texts: In the following problem, calculating Thevenin's resistance is simple enough , 0.1 ohms. However I cant seem to calculate the Thevenin's voltage when there are two voltage sources? How could I apply KCL or KVL to find the Thevenin's voltage in order to solve the problem?


texts:
I am making a set of speakers using 34.5 AWG magnet wire, and neodymium magnets to make a voice coil.

For my wire gauge and required length I should have ~3 Ω (DC), 4 Ω (AC).

The issue is when I went to check the resistance in the wire after I cut it from the spool, my multimeter didn't pick up any readings. I went and bought some alligator clip test leads and tried again; still nothing. I've used the multimeter before, the cables are plugged into the right ports, and I’ve tried all the range settings for DC resistance.

I'm trying to avoid winding the coil and gluing the whole unit together, just to find that it doesn't work.

Any suggestions to get the multimeter to read the resistance? It should be about 3 Ω for the length I cut.

Cheers


texts:
This is mostly a Microchip centric question.  I'm very new to Microchip world.  So any info beyond my questions is most certainly helpful to me...

I purchased one of these demo/break-out boards from Microchip:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en024149

I tried plugging in the supplied dsPIC33 module and programming by connecting to the header my PicKit2 programmer.  I wired up one wire for the Vss, one for the Vdd, one for the PGD, and one for the PGC lines.

The PicKit2 programming software and MPLAB both complain that the Vdd voltage is measuring zero (as if to say the voltage supply has a short?).  Then I noticed the PicKit2 getting very hot!

I quickly unplugged it, let it cool down, and verified that it still worked on other circuits I have & it did.

This particular demo board has a jumper marked 5v and according to the manual, I can power the board with 5v or 9v.  So I pulled the jumper and put 9v on the board and reconnected my PicKit2 and still got same results.

Questions:

Do all the Vss lines need to be wired to ground?  I only wired one Vss to the PicKit2
Do all the Vdd lines need to be connected to the 3/5v supply line?  I only had one.
Is it even possible to program via this demo board, a socketed dsPIC33 chip (see link above).

I have other dsPIC33s I can program external to this demo board.  They are mounted on a circuit board that was not designed by me.  This board has a header I can connect the PicKit2 directly too.  I don't have a schematic for the board either so I'm not sure if the Vss and Vdd lines are tied together or not; I just know I can programm the same dsPIC33 chip on this board with my PicKit2.

I'm considering purchasing their MPALB ICD 3 programmer?  What benefits does the MPLAB ICD 3 programmer offer over the PicKit2 programmer?

My goal is to simply be able to program socketed dsPIC33 Microchip micros and have access via header break-out to various signals for quick prototyping.

Based on the comments so far, come clarifications:

I forgot to mention above that I did have the MCLR pin wired as well.
I should add, that I checked, double checked, & triple checked that non of my jumpers were touching, chip was oriented in the socket correctly (pin-1 aligned with PCB pin-1 and checked written documentation for the board), and jumper wires were on the correct pins.  Why it got so hot is puzzeling me.  I will look to connect a RJ11 type jack to the J3 port into the PicKit2 to see if that makes a difference but have my doubts.  I used purchased jumper wires with molded ends for connecting to headers so, for example, pins 11 & 12 are the Vss and Vdd pins, there is no way the wires could have been touching each other.  Their header connectors are insulated and such...


texts: Which logic families interpret a floating input as a definite value?

texts:
From what I remember, from decades ago, 1980's 5v TTL chips would see a floating input as a zero (because they switched on current, rather than voltage).  Update: it seems they were interpreted as ones.

Are there currently any families of discrete logic which interpret a floating inputs as a zero or a one, rather than a non-deterministic value?  (AC, ACT, HC, HCT, ALS, AS, AC, CB, CBT, F, S, LV, LC, etc.)


texts: What could cause 45FPS limit for SSD1306?

texts:
I'm porting U8G2 display library to ESP32 microcontroller (no suitable tag) with ESP-IDF (its official platform) as the platform, I2C protocol for now, using SSD1306 display for testing. After all improvements and optimisations FPS got stuck at 45. I tried:

Changing bus clock (no difference on 800KHz and 1MHz)
Disabling waiting for ACK (150+ FPS test do so, but no difference for me)
Changing ESP32 processor frequency (160MHz and 240MHz give the same result)
Commenting out all delay functions (they probably aren't called at all)

What is likely a critical link in chain here?


texts:
Having investigated producing my own audio attenuators, how are commercial (off the shelf) passives produced? Namely how are an individuals I/P - O/P characteristic requirements matched by these commercial units?
I know my device input Impedance but not the feed device output, therefore am struggling to "get it right".

Thanks to all concerned, this info is what I needed but still beggars the question of how, if input/output impedance (of devices) values are essential, are the values of commercial devices (Typically Rothwell) made if they have no starting point reference too end users I/O impedance values. It can only be assumed that they are marketed on the basis of guesswork.
I digress, Thanks for the clear instructions I can now forge ahead with the project in the knowledge that they will be what I want in the end.


texts: How to use SYSTEMConfigPerformance on a MPLAB X project

texts:
I started a new project for a pic 32 (pic32mx470f512l) with MCC.

And now i want to use the function SYSTEMConfigPerformance to optimize the performance of the pic.

It happens that i'm not able to find the library that has it.

The main of my code:

#include "mcc_generated_files/mcc.h"
#include "xc.h"
/*
                         Main application
 */
int main(void)
{
    // initialize the device
    #define GetSystemClock() 60000000
    SYSTEM_Initialize();
    SYSTEMConfigPerformance(GetSystemClock());
    while (1)
    {
        // Add your application code
        IO_RD5_Toggle();

    }

    return -1;
}

Maybe that function doesn't work with MCC


texts:
I am implementing an all digital PLL system on an FPGA using VHDL. Now, I have not yet closed the loop, instead I have modelled a sinwave(simulating an input) at 22kHz and also modelled a cosine wave(simulating the NCO(numerically controlled oscillator)) at 24kHz. This means that I am simulating an sin input with regards to a cosine reference. I am then multiplying them (phase detector) and passing the output through a 25kHz LowPass Filter. I am expecting to see a DC output realted to the error at the input, however I am seeing an oscillatoy reponse. Attached is a screenshot of my work so far.

Any help would be greatly appreciated as I am quite stuck here..

Thanks.


texts: Are ideal op-amp characteristics redundant for solving ideal op-amp circuits?

texts:
I have found that for solving problems with ideal op-amps, you need two rules:

The potential at A is the same as that at B
No current flows into or out of A or B

I have also come across a third rule:

No current flows into or out of C

I know this obviously not how an op-amp works in reality, and I have found that it is a redundant rule (i.e. all problems can be solved without considering it), but so far I  have not found an ideal op-amp circuit where this rule cannot be true. That is, I haven't found a circuit where the consideration of this rule changes the answer that you get.
My question is: can you find a circuit where this rule physically cannot be true?


texts:
I bought a cheap china tablet and it worked fine for a few weeks. Yesterday while charging and using at the same time it got warm.
I opened it and recharged the battery manually and it worked again.
But it is not accepting any change through the USB port.
Today I took a more closer look and found one IC was burned. The tablet is a BS109.

Is is possible to know what this chip could be? I'm guessing some voltage regulator, since voltage at battery +/- should be 4.x Volts and now only is 2.5 Volts.
I see only a 4 then a burned hole and a 0 and a 3 (4?03). On row 2 I guess it is year and week.
On another picture I think I see 4C03

Update. On a similar tablet I found that the chip is marked 4603


texts: What is this component (is it a rectifier?)

texts:
I'm currently reverse-engineering an air conditioner inverter circuit.
I have stumbled upon a weird package.
The thing is I can't de-solder this component, so I can't read the letters on it.
Do you know what this is?
Since it's connected to the capacitor, it might be a full-bridge rectifier, but I couldn't say for sure. A part number or a datasheet would be very helpful.
edit - hey guys, I think it's time to let it go. You can't possibly reverse engineer everything you see. I've learned it the hard way. But also I've learned so much more about power electronics along the way. I guess that what actually matters.
Search for "Intelligent Power Module" for to learn about this "inverters" and "High efficient BLDC motor Drivers" if you interested. I have lost so much time because I didn't know that particular Word. Thanks everyone.


texts: Confusion with peak and RMS values when calculating the torque of an electric motor

texts:
For electric 3-phase motors with a efficiency of 100% (assumed here for simplicity) the following equation holds:

$$P = \omega T = 3 U I$$

where \$U\$ and \$I\$ are the phase RMS values of the voltage and current respectively (phase to neutral RMS voltage and phase current when a star connection is used). I can calculate the torque with this expression. So far so good. Now I want to use an approach which is better applicable for data from e.g. FEM analysis. The torque can also be calculated like:

$$T=\frac{N_p}{2} \vec{\Psi} \times \vec{i}$$

where \$N_p\$ is the number of poles and the 3-phase values are transformed to vectors with a power invariant transformation like:

$$\vec{a} = \sqrt{2/3} (a_a + a_b \exp(j 2 \pi /3) + a_b \exp(j 4 \pi /3))$$

as a power invariant transformation was used, the torque formula from above doesn't need another factor. At least this is how I understood it. When a symmetric 3-phase system is assumed, \$\vec{a}\$ can also be rewritten as:

$$\vec{a} = A \exp{j \omega t}$$

where \$A\$ is the RMS phase-to-phase value (if everything is assumed as ideal, hence, sinusoidal flux density and MMF distributions). But this means, that I'm combining two phase-to-phase values in the second equation but two phase values in the first equation. And like for the flux, flux density and so on, normally there isn't something like a RMS value because the iron and so on doesn't care about RMS values, it is only 'interested' in peak values. So I don't really get the connection here. It would be great if someone could give me some hints what I'm not getting here.


texts: Are there consumer ALUs in the GHz range?

texts:
When browsing consumer ICs, I struggle to see parts that function faster than a few hundred MHz, let alone in the GHz range. (Mostly the chips I want are ALUs or something similar.)

Obviously computer ALUs function well into the GHz range, so If I wanted an ALU with comparable performance, is there a way to get one? Would I have to commission a company for a wafer?


texts:
I am trying to simulate this Photoplethysmography circuit in Pspice.But I am getting the following errors:
ERROR -- Convergence problem in transient analysis at Time =  .193
         Time step =  296.9E-15, minimum allowable step size =  1.000E-12

I am trying to give a sine input and expecting a sine output.
Is it possible to create a noisy signal in pspice and see the output.
How do i visualize the filters.

Thank You very much

Anupam


texts: how does this log-periodic serpentine antenna work?

texts:
I'm used to seeing log-periodic antennas, the classic "TV antenna" that one can still see on the tops of houses or older buildings. There is a long row of transversely-mounted elements, connected in some way along the center axis, whose length and spacing vary in a log-periodic fashion.

From: https://www.scannermaster.com/CLP_5130_1N_Log_Periodic_Antenna_p/40-541274.htm

But when I was doing research before writing this question I came across this log-periodic antenna.

Does this design have a name? It's one continuous conductor, and serpentine with each successive element connected in the opposite direction than the previous. Why? is the serpentine nature important for the way that it functions?

above: Cropped detail of "Log-periodic shortwave antenna besides the old Varberg Radio Station, Sweden" From here. Right click and open in a new window for larger view.

above: "Log-periodic shortwave antenna besides the old Varberg Radio Station, Sweden" From here.


texts: Calculating the period, frequency, and confirming multimeter readings

texts:
I have some readings from an Oscilloscope that I want to take info from and calculate the period, frequency, and then confirm some multimeter readings I took.

For the 1st:

The function generator had these settings:

Vlow = -8V and Vhigh = 8V

125KHz square wave

Multimeter reading of 258.9mv AC

Next,

For the 2nd:

The function generator had these settings:

Vlow = 0V and Vhigh = 5V

300KHz square wave

Multimeter reading of 2.430V DC

To summarize, I want to calculate the period, frequency (Only using the pictures), and then confirm that the multimeter readings I took are correct.

The reason I ask these things is that I do not understand how to read these pictures correctly.

Thanks for any possible help.


texts: Using Electricity and Magnetism to Lift non-ferromagnetic Copper Pennies

texts: Is there any way (If you pumped a lot of current through a copper penny by shorting a circuit out through it with leads on either end) to create a magnetic field in the penny and lift it with a (very strong) magnet positioned right above the penny- say neodymium?


texts: How do you model acoustic waves underwater that are generated by an Nd:YAG laser?

texts:
In this paper on page 84 they show the following experimental setup:

The array of receiver hydrophones are set up to record sound pressure waves sent by the transmitter hydrophones.

In Figure 6.13 on page 87 shown below, you can see the relative sound pressure decreases with increasing relative distance.

I would like to essentially duplicate this experiment with one difference : use an Nd:YAG laser to focus a beam at a single point on the water surface to form a plasma under water.  This laser would be 20 ft above the surface of water and some arbitrary angle from the normal vector to the water surface.

This plasma will undergo thermal expansion.  This expansion will then generate sound pressure (or acoustic) waves that the hydrophones can detect.

Two questions:

Does it make sense for me to use the exact same hydrophones they use in the paper (i.e. now that I am using laser pulse to generate underwater sound pressure waves, how do I decide the best hydrophone to use?)
Before purchasing a hydrophone, is there a way I can simulate this experiment to get a better idea of what I need? For example, how do you model a laser beam focused at a point on the water surface that forms plasma underwater? And separately, given a particular plasma shape, how do you model the sound pressure wave that gets generated?

Obviously I don't expect complete answers to my questions, but if somebody could even point me to other papers that might have answers, then I would greatly appreciate it.


texts:
I have a bunch of electro-mechanical relays on a board intended to switch 220VAC for CFLs. The maximum load on the relays will be 100W with inrush currents of upto 2A (lasting for less than a second). The relays do survive short-circuit currents, briefly, as long as a 10A circuit-breaker kicks in.

The relays is Omrom  G5LE-1A DC5 - a 240VAC 1200VA relay. I am also considering the G5LE-1A-E-DC5 which is the 16A version of the above relay with 4000VA switching power - link to datasheet.

My question is, is it safe to rely on this for a commercial product? We won't be installing this anywhere that does not have a proper breaker system anyway. I don't want to include a fuse for two reasons:

The product is intended to be mounted on a wall. The board will not be easily accessible.
The board has live voltages and if possible, I would prefer that the user does not have to replace the fuse very often, unless there is catastrophic failure like the circuit-breaker failing as well. I'm not counting a short-circuit as a catastrophic failure because some (poorly made) CFLs end up failing as a short-circuit and this could be a annual occurrence or more frequent - the user would probably get fed up of the product.

I think some sort of backup protection should be there but resettable fuses seem to be too slow, at least for mains voltages. What are my options here?


texts:
I’m looking at installing a zwave system in the UK. The relays I want use require a 3 wire system. They say most of the uk is wired via a 2 wire system

This is the product

http://www.vesternet.com/z-wave-fibaro-relay-insert-2-1-5-kw-3085

My question,  can a 3 wire system be created from a 2 wire system?

I’m confused by this and welcome any explanation.

David


texts: Basic formula for calculating required cable area

texts:
Trying to do a spreadsheet to figure out how much cable of different dimensions I will need for a low voltage DC electrical system, but got stuck on the formula for converting current draw, distance and acceptable voltage drop into the minimum cable area required. At the moment I have

((distance * amps * 0.04) / ((voltage * %drop) / 100 )) * 100) / 100

Which I copied from http://www.solar-wind.co.uk, but I have no idea where they got the 0.04 magical number from, and I suspect the results may be inaccurate. What is the correct way of calculating the (minimum) required (copper) cable area, when voltage, current, distance and acceptable voltage drop is known?


texts: Raspberry connected to adhoc and wifi simultaneously

texts:
Currently I am working on a project where we have to connect multiple cameras to a Raspberry.

Our idea is to buy multiple Raspberry PIs with a connected camera.

These raspberries connect to a master raspberry with an adhoc network, the master raspberry is also connected to the internet (wifi), so the photos can be uploaded to a remote server.

Is this the best way to do it?

Is it possible to have a raspberry manage an adhoc network and be connected to wifi at the same time?

How would I do this?


texts:
Could you please explain me about pipelining in FPGA and how is it done in xilinx system generator design by adding registers and delays in a particular system design?
I have a system design in xilinx system generator. That design meets the timing constrain with 20ns (takes 50MHz clock frequency). However, the FPGA board I use is Virtex 4. It offers 100 MHz (10ns) clock at pin B15. I set 20ns as the FPGA clock period and pin B15 in the System generator token. I was able to generate HDL netlist without any error. However, I wasn't able to get any outputs from the FPGA after I downloaded the bitstream from xilinx ISE. I was wondering it would be the issue with the frequency of the FPGA borad and my design as my design meets only 50MHz NOT 100MHz.

Update with more information

My design:

I was not able to upload the picture. I designed a system to generate UWB signal.

For this design I only managed to reached maximum of 50MHz(20 ns) of clock frequency by adding registers and delay blocks in between the inputs and outputs. I was not able to reduced the time constrain below 20 ns. Because when I tried to reduce it to 10 ns (attempting to reach 100MHz) by increasing the amount of delays I ended up with an error "Resource overmapped", as shown below (Figures are not the same,but similar).

elected Device : 4vfx12ff668-10

Number of Slices:                     6690  out of   5472   122% ()
 Number of Slice Flip Flops:          20567  out of  10944   188%
 Number of 4 input LUTs:              10072  out of  10944    92%
    Number used as logic:              9969
    Number used as Shift registers:     103
 Number of IOs:                           7
 Number of bonded IOBs:                   6  out of    320     1%
    IOB Flip Flops:                       2
 Number of GCLKs:                         2  out of     32     6%
 Number of DSP48s:                       33  out of     32   103% ()

However my Virtex 4 FX12FF668 only offers 100MHz clk at pin B15 (i.e. FPGA clock period (ns) = 10 and Clock pin location = B15 ). I'm clueless for how to change it to 50MHz to suite my design and set it in the sys gen token.


texts: What actually is MIDI and how does it function in a system?

texts:
Sorry for the primitive question but this is a topic where I'm completely blank and has been a mystery for me until now. I had some readings on the net but couldn't get a clear picture. All say MIDI is an interface.

I thought about it and maybe a short brief journey of MIDI music from a MIDI file in a PC to the computer speaker would help to see the bigger picture.

I have some midi files aka music files in MIDI format and when played by a media player you can hear the synthesized music. Here as an example can be downloaded and listened to an example "Confutatis" from Mozart's Requiem.

So what happens right after the program runs in terms of the information transfer?

Here is what I guess:

The program code(midi file) executes ---> The CPU and RAM sends the digital data in the program code to the sound card via a MIDI interface ---> The soundcard probably knows the MIDI coding converts the digital data to analogue audio----> This audio is amplified and sent to the speaker. ???

The above might be completely wrong and I cannot find a flow chart or any circuitry about it on the net. An example with an electronic keyboard and MIDI also would be fine.


texts: How to avoid infinite on/off loop of a voltage controlled (with a photoresistor) switch?

texts:
I have designed this circuit to switch on a light (R2) when it gets dark. The circuit works fine, however I have a small problem.

simulate this circuit – Schematic created using CircuitLab

As you can probably guess, when it gets dark the voltage at the gate drops and the mosfet is turned off, the relay is turned on and the light is turned on as well. Now as you might have guessed, the light shines on the photoresistor, makes its resistance drop, turns on the mosfet, turns off the relay and turns the light off. This is pretty much an infinite loop...

Of course I could put the photoresistor in a place that cannot be reached by the lamp's light, but I was wondering if one could devise a circuit to avoid such an infinite loop, perhaps a circuit "with memory". What possible solutions could I try?

I thought of a timer that prevents temporarily the mosfet to change state after it has just changed its state, say for the next 12 hours, but I'm not sure how to do such a thing or if simpler options exist.

Then again I might be overthinking things and I could just put the photoresistor in a place not reached by the light of the lamp...