texts:
The Early voltage is a definition rather than a real existing and measurable quantity. It can be found using the slope of the output characteristics \$I_c = f(V_{ce})\$.

However, there are two basic alternatives: constant \$I_b\$ or constant \$V_{be}\$.

Question 1: Which of these two alternatives can be used to find the EARLY voltage?

(a) Constant \$I_b\$,
(b) Constant \$V_{be}\$, or
(c) Both?

Background: Some books use definition (a), some others use (b) and some do even not specify if (a) or (b).

Question 2: If (c) is correct - how can we theoretically prove that both alternatives give us the same (correct) value for the Early voltage?

EDIT:
For my opinion, my problem is not yet solved; therefore some further remarks:

I am aware that my question is not too relevant for circuit designers - and that is the reason I was looking for some corresponding - theoretically oriented - contributions from Universities.

Here are the results:
One lecture note from Berkeley Univ. defines the Early voltage VEA for IB=const., but in another contribution VBE is held constant.

Papers from Stanford Univ. are defining VEA for VBE=const.

Lecture notes from the Columbia Univ. define VEA also for VBE=const.

Even more confusing is a contribution from the Georgia Inst. of Tech.. Here, the Early voltage VEA is definde for IB=const. However, in the same paper this parameter is used in the equation y22=IC/(VEA+VCE). And - as we know, y22 is the output conductance for VBE=const.
Can somebody explain these contradictions?

Here are corresponding links:

http://www-inst.eecs.berkeley.edu/~ee105/sp04/handouts/lectures/Lecture22.pdf
Georgia IT:  http://users.ece.gatech.edu/~alan/ECE3040/Lectures/Lecture20-BJT%20Small%20Signal%20Model.pdf
http://www.ee.columbia.edu/~bbathula/courses/SSDT/lect07.pdf
http://www.eecs.berkeley.edu/~hu/Chenming-Hu_ch8.pdf
Stanford: https://www.coursehero.com/file/7827746/ho3BJT/


texts: Build an OR gate where the output is fed into the input B

texts:
I want to make this logic gate.

It is basically an OR gate where the output is connected to input B. I want to make it using transistors and a breadboard.

The images show my attempt.
The problem is the output doesn’t stay on high if I stop pressing the button. I really don’t know what the problem is.
Maybe you can help?
Edit: I hope the schematic will help.

Thanks to all of you who tried to help me. I guess the way I imagined the oa to work isn’t right. So maybe I should start from the bottom.
I saw this circuit at a YouTube video from Ben eater about sr latches. He uses a 74LS32 chip, which contains 4 or gates. One of them is used in the circuit. I thought I could just build a standard or gate from resistors (the circuit is from the video „logic gates using transistors“ from Ben eater) and then act like it is the or gate from the chip. This was my try. Can anyone explain why this didn’t work? Are there differences in t or gates or something?
(https://i.stack.imgur.com/0bs1R.png)


texts: Practical ESD protection without latchup

texts:
My understanding has always been that any CMOS I/O pin needs external ESD protection - since the on-chip protection diodes are only there to guard against ESD events during manufacture handling.
However, I've taken apart a fair few devices over the years which directly connect CMOS and NMOS I/O pins to the outside world via DIN or D-sub connectors - with no protection at all. This is not just hobbyist gear - I've seen it routinely in high-priced commercial gear (£1000+). This is especially true of older equipment (the late 80s to late 90s).
So, am I going overboard with trying to protect every I/O pin with external components? Or could it be that these commercial designs are actually seriously flawed? Could it be that output-only pins are less vulnerable to ESD than I/O or input pins? (although I have seen inputs exposed in this fashion too)
More specifically, I'm embarking on a project where I will need to connect eight MCU I/O pins to a D-sub connector - without any series resistance. I considered using eight TVS diodes for protection, but this appears to be inadequate - even if the TVS clamps at 6 volts, that's still one volt higher than the power supply. A heavy current will therefore flow through the ESD diodes in the MCU. This could destroy the I/O pin, or latch the chip up.
My fallback position is to use 16 external Schottky diodes to clamp to the power rails, but that's a lot of parts on a small board. It's my understanding that it will completely guard against latch-up - an external Schottky can have a much lower voltage drop at several amps.
I considered the use of a 74S1053 Schottky diode array since that can clamp 16 lines. But unfortunately, the device is designed for bus termination rather than ESD protection. It has a rather high forward voltage drop at significant currents. Assuming an ESD event could see currents in the order of several amps, the voltage across the diode will rise to a couple of volts. This would force current to flow through the MCU's internal protection diodes, with all the ill effects this could cause. But is there something I'm overlooking here? Could the 74S1053 be a viable option?
Like a lot of CMOS chips, the MCU datasheet specifies that the inputs should not deviate outside the supply rails by more than 0.3 volts. The clamping diode current is limited to 20mA. I've seen first-hand a CMOS chip latching up and crowbarring the supply due to the current flowing through the protection diodes - so I'm very keen to avoid this happening.
What are the "best practices" in a situation like this? Would adding an RFI filter component to the I/O help? I've heard it said that series resistance sometimes guards against ESD since it creates a lowpass filter with the I/O pin capacitance - but I can't really afford any extra series resistance. I'd also like to guard against a 5V input being applied while the device is powered-down - so it looks like I'll need diodes to Vcc at the very least. But the device only draws a few mA so it could probably survive being powered through the internal diodes. But there could be a current spike when first connected, while the decoupling capacitor charges up.


texts: Is it a good idea to omit HSE in favour of HSI?

texts:
I'm considering using stm32 L412 chip that comes with a 48Mhz HSI with +/- 0.25% accuracy. On the datasheet it says HSI can be used to drive usb fs peripheral. I will also using SPI peripheral.
https://www.mouser.in/datasheet/2/389/dm00481909-1799148.pdf
My question is, Is HSI reliable and can it be used in production examples?


texts:
I want to make a Bench power supply unit based on:

For initial AC to DC conversion - ATX PSU (Enermax EG365AX-VE 350W) capable of providing 12V 26A
Internally Step up module for powering the below - one of below:

400W unit 15A input, 10-60V 12 A output
150W unit 10A input, 12-35V 6A output

PSU output adjustable and provided by RD DPS5020 (input 6-60V, output 0-50V 0-20A)

For up to 10V application I would like to omit the step up module and power the DPS5020 directly from ATX.
For higher voltages I want to manually switch to use step up module.

My first idea was to use 3P3T switch, but I could not find one that can safely handle 12V DC and 26A.
Then I wanted to use the switch that would control 2 relays, but high current relays are very expensive.
The third idea was to use high side switching with two Power MOSFETs.

N-channel MOSFET configuration:

Link to the editable source

or alternatively P-channel MOSFET configuration:

Link to the editable source

What MOSFETs should I choose? Are the following criteria safe:

Vds  = min 75V 24V (12*2) (or should it be much higher?)

Id= min 30A (what if the mosfet would become warmer)

Vgs = +/-20V (I will ensure that the mosfet is fully open with Vgs=12V) - However as I have the ATX psu, I could easily use 5V or even -12V, - 5V.

To minimize the power loss (heat) the Rdson should be low.

Each mosfet won't switch frequently (and most probably not under load), as it would switch its state only when SW1 is flipped.
Can I disregard then the switching power losses, so I should care only about conduction losses, witch would be P=IIR_dson.

How about:

IRLB8314PbF (30V, 130A, 2.4mOhm, 125W)
IRFB3607PBF (75V, 80A, 9mOhm, 140W)
IRFB4410ZPBF (100V 97A, 9mOhm, 230W)

How about the power dissipation and safe operation area?  The conduction losses even for 26A would be max 6-7W.

To make sure that when then M2 is providing the 12V and the Step up converter is off there is no voltage on the + output pin I added the D1 diode, is it sufficient protection?


texts: Convert High voltage output ( 15V ) to 5 V

texts:
I want to use : DSD 70 Dual Channel Hall Effect Speed Sensor and integrate it with an MCU ( arduino ) atmega , so I have to convert the output of the sensor to 5V to be able to read it by the MCU.
Any one can suggest a chip to do that ?
The sensor is : https://www.te.com/global-en/product-CAT-SPS0020.html#:~:text=The%20DSD%2070%20series%20speed,a%20frequency%20of%200%20Hz.
and the output spec is :
2 phase shifted square wave signals, minimum edge shift with an involute gear
wheel: minimal phase shift of 20° for gear of the defined module between output 1
(S1) and output 2 (S2)

Push-pull outputs : Imax = ± 30 mA
o Output voltage HI (for I = Imax): UHI > Usupply - 1.5 V
o Output voltage LO (for I = Imax): ULO < 1.5 V


texts: What connector can be used for dimmer output?

texts:
I have some poorly designed PCB board (LED dimmer), through-hole mounting. The output is in the left corner, it have 8 x 0.1" pitch pin mounting holes for connecting line-in, power, and output (H,M,L,+). Signal input is placed right near the power pins, which is simply wrong. The worst thing is that place with mounting holes in PCB is too small for standard 0.1″ (2.54 mm) Screw Terminal Blocks.
The exact pad size for this 8-pin output connector is only of 20 x 6 mm.  For this tight header, I can only use 0.1″ (2.54 mm) male header pins, which it not suitable to use in LED Dimmer.

Can anyone advice what connector can I use in this case?


texts: What makes the data to scroll in LED matrix display?

texts:
I am not able to understand what is making the data to scroll in LED matrix display.

http://www.npeducations.com/2011/11/simple-led-message-scrolling-display.html

Is it the shift registers? This site mentioned that the shift register are used to reduce the no of pins needed.


texts: Is there an "additive manufacturing" method to make an ASIC?

texts:
Reading questions like this one "How much does it cost to have a custom ASIC made?", I was wondering if there's some sort of equivalent to additive manufacturing that would lower the cost to getting prototype chips made. For example, can you "write" a chip with an electron beam or something? Carve it out with an AFM?

If not then why not, and who's working on this?

What if we restrict ourselves to analog chips / large geometries, are there any methods that then become feasible?


texts:
I encountered signal ground symbol while studying 555 IC
Please explain why isn't a simple ground connection used and how does signal ground differ from normal ground. I am a first year undergraduate, kindly explain the most basics.This inverted triangle symbol


texts: What is the best solder type in terms of health?

texts: Hi im thinking of picking up a soldering iron and im wondering what type of solder is the best in terms of health


texts:
Atmega328P provides logic signals to the AQH1213 solid-state relay to control AC load (contactor).

Task:
Protect the Atmega328P in case the solid-state relay fails and supplies high voltage to the low voltage part. Although the technical data sheet shows insulation up to 5000 volts, I would like to provide additional protection measures.

What I use now:
- TVS diode (600W) between the relay control line and ground. Theoretically, if suddenly 220 V falls on a low voltage circuit, the TVS diode turns off, the 220 V fuse blows, and the microcontroller does not receive a high voltage.

What I found:
- Digital isolator.
Example: TI ISO7220ADR

The datasheet says about using separate power supplies (VCC1 / GND1 and VCC2 / GND2). I have one line with a voltage of 5V on the board.

Question: Will the digital isolator work if I use one power line on both sides?


texts: led chaser with non-mechanical shut-off option

texts:
I've seen thousands of standard led chaser circuits online but I haven't seen one in which I can shut off all LED's in a non-mechanical way.

I'm wiring one pin of my chaser up to a microcontroller so that it controls whether or not the LED chaser operates or not. In the schematic, the pin is labelled as GPIO.

The reason I'm not using a micro for the entire chaser design is because I'm doing a major project with someone else and they don't know coding, so I want the other person to adjust the speed with control knobs. That part I have no problem with.

My circuit is a modification of the circuit found at: https://electrosome.com/wp-content/uploads/2016/09/LED-Chaser-using-4017-and-555-Timer-Circuit-Diagram.jpg

Here I'm just showing one LED and one stage.

Assume that one LED with one resistor is actually a set of 30 LED's with 2.0V voltage drop and 30 330 ohm resistors connected in parallel

Here's my question. Is the NPN transistor with emitter connected to ground in the right position to switch off a large array of LED's and are the resistor values to the NPN base correct?

And could I also copy the transistor to LED arrangement (circled in green) and apply it to each Q output of the 4017 and tie the NPN emitters in the LED arrangements together and to the NPN collector of the grounded emitter transistor?

In the end I want to make 5 sets of 30 LED's bright and have each set light up one at a time in sequence and have the option to shut the whole thing off without manually disconnecting power.


texts: I am using a DAC form analogous devices viz - AD565A. Now, according to Nyquist theorem the minimal sampling rate for a decent reconstruction of a signal twice the rate of its highest frequency component. Now, the Max sampling rate of different DACs are given in rates ranging from ksps to Gsps. I an not seeing any such sampling rate info on this data sheet. Also, DACs are given a clock input. The sampling rate (Max) is a factor of this clock. Henceforth, if the DAC is given a clock of 10MHz, the max sampling rate (decent) is 10Msps, right ?


texts:
Is there any reason to not use a UF2008 as catch diode on a DC relay, solenoid, or electromagnet?  IN4001 costs $0.07 and UF2008 costs $0.03 and seems to be better suited in all ways

simulate this circuit – Schematic created using CircuitLab


texts: Gate biasing of common source MOSFET amplifier

texts:
I am trying to fully understand the following circuit and have some questions about it. Some preliminary info is that this is an audio voltage amplifier specifically for guitar use. Now overall, it looks like a run of the mill common source amp but it has a variable source resistor and also the gate is biased via a divider being fed the drain voltage. The DC drain voltage of course changes as the source resistance is changed thus changing the gate bias voltage.

What is the benefit of biasing the gate like this? Wouldn't feeding the gate voltage divider the 9V supply to keep the gate at a constant 4.5V work just as well? It seems the FET would still remain in saturation this way.

simulate this circuit – Schematic created using CircuitLab


texts: Leaving NiMH and LI-ION powered devices (toothbrush) at charging station

texts:
So I have 2 sonic toothbrushes, one powered by NiMH the other by Li-ion batteries (waterpik & philips). The base stations (with charger in them) look so convenient and just lure me to store devices on them.

I've studied the manuals and could not find whether device is designed to be kept on base station indefinitely or device should be stored off the charger until 'battery-low' signal.

So the question is: does it degrade the battery considerably if the device is stored all the time on the charger station?

Charge time for them is around 12-24 hrs. They use inductive charging method (I mean there's no port/plug you physically connect charger to, you just place device at or near charge station).

UPDATE So I've contacted customer supports of both companies, and asked is brush designed to be stored on charger and how long the battery is to serve.

...and basically they both said brush is designed to be stored on the charger. Phillips says there's 2 year warranty for the battery, Waterpik support mentioned it should last 3-5 years.

While this is a great battery life (longer then on my ihpone 5s lol) as @BillDubuque and @FakeMoustache mentioned they might serve even longer if stored off charger.

Would still be interesting to know what difference two charging strategies make on the battery life.

UPD could anyone please un-close this question? I'd love to accept answer from @BillDubuque as the man provided lots of useful info in comments, I'd like him to get his reps.


texts: How to achieve a block of Z^(-0.5) in Simulink?

texts: I'm doing simulation in Simulink of Matlab, but don't know how to get a Z^(-0.5) cell like this:


texts: Should I ground my body when working with 200V+?

texts:
I was working on a project converting 220V AC to 5V DC and I accidentally touched the underside of the transformer which gave me a big shock and I was wondering if it's a good idea to ground my self like with a wrist band or something like that to the ground too if this happens again, I protect my heart, etc.
Is this something I should do or what precautions should I take to protect my self?


texts: What's the proper track to learning PCB Design?

texts:
I am a Computer Science guy. But recently I became interested in designing PCBs. I have done a few designs on Eagle. But they are quite basic. I tried to move forward, but PCB design just seems to be vast. There are books on High Speed Digital Design, and PCB Standards etc etc.

My first question is do PCB designers exist for separate domains ? If so, what are those domains?

Second, if I want to pursue a Design career in this, what kind of study track exist. I mean is it a masters level course in Electronics?  Or a masters level course in CAD/CAM ?

How do people start out ? I am having trouble with charting out a study track for designing PCBs.


texts: CS Amplifier without load or signal resistance

texts:
So I came across this interesting MOSFET question and thought I'd give it a try. I seem to be stuck on a couple of parts however, hopefully someone can see something I'm not seeing. Here is the circuit:

Here's my attempt at a solution for it and where I've been getting stuck:
(a) In the low frequency regime, capacitor CL becomes an open circuit. Performing a small signal analysis on M1 results in the following gain equation: Av=(Vo/Vsig)=gm1*Req, where Req=(r01||r02) since there is no load resistor RL at the output. gm1 is calculable since ID1 can be determined from the current mirror formed by Mb and M2 and the provided value of ID3. But the question specifies that r01=r02=infinity, however. Would this mean that the low frequency gain is indeed infinity?
(b) We can consider the high-frequency regime to determine the 3dB freq and therefore must consider the internal capacitances of M1. Since there is no signal resistance (Rsig=0), you can use the amplifier output to determine the 3dB freq. In particular, fH=1/(2pi(CL+Cgd1)*Req), where CL includes the relevant capacitances from the other transistors. But the result is fH=0 since Req=(ro1||r02)=infinity.
To me, these answers don't seem correct, but I cannot figure out where I am going wrong. The fact that this circuit doesn't contain a load resistance and neglects channel length modulation is puzzling.


texts: Nonlinear circuit v(i) function for I-V plot

texts:
I'm trying to understand how to theoretically derive the equation that could be used for plotting the I-V graph. The points of interest are Out + and Out - and the current that would flow through that branch if different loads were applied.

simulate this circuit – Schematic created using CircuitLab

I know that the graph should roughly resemble the image below:

After learning that Thevenin can only be used on linear circuits, I got left without ideas.

Is it possible to theoretically approach this and have a function u_out(i_out) as a result?


texts: Matching line driver output impedance over wideband

texts:
I'm designing a high impedance line tap for 10-10GBASE-T ethernet signaling. In the AFE I have a JFET LNA for high input Z which goes to a var. gain amplifier that is a fully differential ADC driver. I'm looking to have a flat passband from DC to 800MHz. The ADC has 100 ohm differential input and I'm controlling the characteristic impedance of the traces to match 100 ohm differential. The output impedance of many of the ADC drivers I've found all increase to 100-1k ohm at around a few hundred MHz. Surely this is going to cause reflections for the higher frequency components of the signal? Should I look into some passive impedance matching network? Even if I move the two chips close enough together I'd still have a large voltage divider past a few hundred MHz

I forgot to add that there is an anti-aliasing filter after the var. gain amp. I am a current student and don't have too much access to simulation tools, but I do have LTSpice, MultiSim, and a full Altium Designer seat


texts:
I want to know if there is any way to read Eeprom from an 68HC05 with an Arduino. I've been reading other SPI and I2C EEPROM's. Thanks for your help and have a nice night.

Sorry for my bad English if I write something bad but I'm still learning the language.


texts:
I'm working on I2C master driver for interfacing a particular peripheral.
The problem I have, is that when the 9th clock arrives, the slave device doesn't pull down the SDA line.

I checked the signals with a scope, and everything looks like fine. the address is fine.
I'm not using external pull-up resistors, I'm using the internal pullup capability of my MCU (EFM32GG).

I'm not an electrical engineer, and my experience is from the software side, so this question may be silly, but is there a chance that the device can't pull down the line because the pull up drive is too high ?

Can there be another explanation for this problem (except for the obvious one, that the slave chip is dead)?


texts: Are spacecraft electronic systems built in a modular way that allows astronauts to switch identical cards in case of damage?

texts:
In Mars episode 1, the astronauts find a damaged electronic card in a system. They decide to replace it by another card used by another system and that is supposedly identical to the damaged one. It suggests that the electronic is designed in a modular way and that the different systems use a set of generic cards to carry out their task.

Is it possible to build such a system in a way that makes it viable in space (reliable, with a reasonable amount of spare and complexity)?


texts:
Can we calculate the total harmonic distortion of an oscillator directly from ezwave?
If yes, then please tell how to calculate it.
Else what are the approaches to calculate THD of an oscillator.


texts: Reverse engineering LCD module pinout and finding a replacement

texts:
I trying to reverse engineer an LCD module with no useful markings (datasheets etc). It is for sure a 128 X 64 LCD matrix of some sort, as I counted the dots in a closeup picture of a working one.
There are 12 pins on the cable going into the LCD display module. The backlight is a separate thing.
The LCD display module is fed by a ROLAND R8A02021ABG, but I do not have the schematic for this particular unit. What I do have is a schematic for another Roland unit (integra 7) that uses the same R8A02021ABG. In this schematic I can see that there looks to be 18 pins that feed the LCD display of that unit.
What I am after is how this 18 pins listed below may also work for a 12 pin LCD.
These are the names of the LCD associated PINS as far as I can tell.
NOT PIN NUMBERS, ONLY FOR THIS REFERNCE

GDB_RXD
GDB_TXD
SSC_IO1
SSC_IO0
SSC_RXD
SSC_TXD
UOVCD
UVBON
SSC_IO2
LCD-CS
LCD-CD
LCD-SO
LCD-CLK

MAY or MAY NOT Be associated with LCD function

XRST
DGND
CP1.2V
DGND
DGND

I'm trying to understand these pin functions by name and see how these "names" may also be able to feed a "12 pin" version of a 128 X 64 LCD display.


texts:
I have a challenge at work to build a device to monitor the health of ceramic cartridge heaters, similar to this. It operates with an AC transformer and there are 5 heaters I'd like to monitor independently. The transformer operates on our 120V mains and is estimated to provide 1A to the heater.

First I picked up a non-invasive current sensor but in the limited testing I've done so far, I think the < 1A current and the gauge of the wires won't provide the necessary field needed for useful monitoring. Additionally I'd have to scale the device's 0-1V output to 0-5V logic of my microcontroller.

Then I thought about sticking an LED indicator inline with the heaters, like this one. This brings me to my main question: if I put this LED in series with the heater, as in Transformer > LED > heater, will the current drawn by the heater just burn out the LED? Would a resistor in the circuit allow the indicator to work properly without also limiting the heater and/or just melting?


texts:
I need determine if a cable is connected to a wall-socket (230V) on the other end with a timer in-between.

230VAC---TIMER---CABLE

Depending on how the timer is plugged in, it can either cut the phase or the neutral.
If the timer is "ON", then it's quite simple by just putting a relay on the 2 AC-cables that shorts/closes another circuit. However, if the timer is "OFF", then it can cut either the phase or the neutral.

In case of timer cuts the phase, then there should be connection between zero and ground (making a continuity-test will show if cable is connected to the socket or not)

In case of timer cuts the neutral, the phase should provide voltage if cable is connected. To detect voltage I would simple use a "non-contact voltage detector".

Brown is phase
Blue is neutral
Yellow/green is ground

My main problem is how to detect which wire at the end of the cable that is the phase or the neutral. Until that I can not perform a continuity test on the correct wires (neutral and ground) and not a voltage detection on the phase.

My first thought was to rectify the AC voltage and when given DC+ and DC-, I would make a continuity-test between ground and DC-, and a "non-contact voltage detection" on DC+. If one of them is "true", then the cable is connected. If non is "true", then the cable is not connected.

I know how to build a "non-contact voltage detector" and a "continuity-tester", but when I made a simple rectifier-bridge with 4x 1N4004 diodes I measured voltage around 100V between ground and DC- and I don't want to continuity-test on that!

So what am I missing? How can I safely make a continuity test between zero and ground on AC voltage?

Best Regards
Niclas Rådström


texts: Automotive alternator: zero crossing detection (frequency)

texts:
I need to detect voltage frequency of an automotive alternator (before rectification). Alternator is a 3-phase generator, I will be looking at one of the phases. The voltage frequency never exceeds 1.5 kHz.

I was thinking of taking OPA340 OP-AMP. I would connect non-inverting input to one of the phases and leave inverting input at ground, while supplying OP-AMP with 3.3V (ADC takes 3.3V max). This will give me 3.3V on the output during positive half-period and 0V during negative half-period. However, I am worried about noise around zero-crossing. Output voltage is just a 3.3V logic signal. Accuracy within 1 Hz would be nice.


texts:
I am normally pretty good with wiring up stepper motors and having a step pin which can be pulsed with a gpio output and a direction pin that can be set to high or low. Also using servo motors that can be wired into a PWM 16 channel output board and can be easily controlled with python because of its libraries (from adafruit_servokit import ServoKit). However, this motor is giving me trouble. It has an S pin and a GND pin that i would hook up to my PI and simply pulse it, but that doesnt help with direction. If anyone has hooked this up to a PI before and can give some insight before i kill 8 of these it would be much appreciated. I need it to go forward and backward and have some what of a control of the speed (which should be the delay in the pulse).
UPDATE: Using signal pin and ground from PCA9685 does not move the motor. Tired using a DAQC plate to set the voltage to high and low with a digital output pin and still no movement any ideas?


texts: Common base circuit with zero supply voltage

texts:
Consider a bipolar junction transistor (either PNP or NPN). Which output would produce this circuit for various input (\$= V_{\mathrm{BE}}\$) voltages?

It is common base, but without a voltage supply for the collector.

The resistor is assumed to have resistance on the order of \$V_{\mathrm{BE}}/I_{\mathrm E}\$ with \$V_{\mathrm{BE}}\$ typical for this base–emitter junction when forward biased.

Of course, Ī̲’m aware it’s no amplifier. The question arose from conditions considered in Why does the collector current direction remain the same in saturation and active region? and Transistor working with unusual biasing threads, but particular formulation of the questions hinders learning these specific things. Namely, Ī̲ seek arguments against the “two diodes model” as an universal answer for any question about BJT saturation.


texts:
I'm trying to understand what each of the 10 data input pins of a DAC mean. The datasheet for the AD9761 I am using is available here.

The pins' description is given as follows (see page 10):

  Each DAC consists of a large PMOS current source array capable  of
  providing up to 10 mA of full-scale current, IOUTFS. Each array is
  divided into 15 equal currents that make up the four most significant
  bits (MSBs). The next four bits or middle bits consist of 15  equal
  current sources whose values are 1/16 of an MSB current  source. The
  remaining LSBs are binary weighted fractions of  the middle bits’
  current sources. All of these current sources are  switched to one of
  two output nodes (i.e., IOUTA or IOUTB)  via PMOS differential current
  switches.

I am confused about a few things here.

"Each array is divided into 15 equal currents" -> Why 15? The four MSBs have 2^4 = 16 combinations.
"equal currents" -> Why are the currents equal? Does it mean that 1000_0000_00 is the same as 0100_0000_00? Why do that?
"The remaining LSBs are binary weighted fractions" -> What is a binary weighted fraction?


texts:
I'm designing a system including a 3 V coin battery.

I am looking at a catalog of coin cell battery holders / sockets.

Their cost varies from 0.25 to 2+ euros (single item), so we can say there's an order of magnitude in difference (it's quite a lot!).

From the datasheets they all seem mechanically robust enough for your typical pcb application, irrespective of the price.

They also have basically the same footprint.

So why choose a more expensive one over the cheapest one?


texts: Electriconically controlled variable resistor

texts:
I have a wire whose temperature I will change. This will change its resistance, but I want the same amount of current flowing through. I was thinking of having some kind of variable resistor in series with this which would detect the current flowing through the circuit, and adjust its own resistance accordingly so that the current remains constant.

I was thinking of somehow using an Arduino or raspberry pi, but I wasn't able to find any way to do so. Any tips?


texts: maximun number of inputs on a opamp adder circuit

texts: With 4 timers of a mcu I am generating 4 square signals , each of them have an amplitud of 3.3v and are generated at diferent frequencies (8KHz 9KHz 10KHz and 11KHz), to generate a multitone signal I am adding them with an op amp adder circuit, everything is OK, but I would like to try with more of 4 signals if it is possible, What would be the maximum number of input signals for an adder circuit?, the op amp is working with 3.3 volts (ad822).


texts:
I was having a problem with one of my circuits in CircuitLab, and traced it down to my sources always enabled, even if I switch them off by connecting to an open switch.  This seems to be so simple, but I can't figure out it.

Here is a simplified circuit showing the behavior.  I have a 5v voltage source V! on the left, disconnected from ground because switch SW1 is open.   I have a second 5v voltage source V2 on the right, connected to ground because switch SW2 is closed.

When doing a DC simulation, I would expect node "off" to be 0v, and node "on" to be 5v.  But they are both 5v as shown in the simulation window.  Why?


texts:
Because I am a software dude, I would like some help verifying this minimal Arduino based circuit which I designed with some changes.

It is single AAA cell operated (NiCd or Alkaline), needs to be very energy efficient.
Both ATMega and the DC Booster can be configured to any voltage between +1.8v to +5.5v, so I can go higher than +2.2v.
Input: 4 push buttons, each can wake it up from sleep using Pin Change Interrupt on port D (All switches are pulled up internally).
Once awake the circuit should read which switch woke it,
A visible light Phototransistor whose analog value can be read.
A tact switch whose on/off value can be read (pulled up internally).
Output is done by blinking an LED using PWM.
The software (including Arduino boot loader) needs to be burned over SPI using USBTinyISP.
The FTDI port is for Arduino IDE debugging.

Are there errors in the attached design? Anything missing? Anything can be improved?

I ultimately built the circuit, and now have a problem with serial communication as described in this link.


texts: Can I use USB to power a flashlight that runs on 3*AAA or 1*18650 battery?

texts:
I am thinking of buying this UV flashlight.

It runs on either 1 18650 battery (4.2v) or 3 AAA batteries (4.5v). Since the flashlight can already take 4.5v, will it be safe to run on 5v USB?

I found this image of the circuit board inside the flashlight in the reviews if that helps.


texts: Efficient current drive with arbitrary waveform

texts:
I need to drive a defined, arbitrary current waveform into an output with a load impedance that may not be constant.

Currently, I am using this:

The 100V is created from 9V dc using a standard boost converter circuit. Peak current is 0.2 A.

Questions:

Is there a more energy efficient design that avoids dropping all that voltage in the transistor that does not break the bank from a component count standpoint? Is there a clever way to merge the current control with the DC-DC voltage boost circuit? (I am thinking class D amplifier or transformerless Cuk converter.)
What would be a good design/approach if the output had to be galvanically isolated?


texts: stm32f103: a timer triggering DMA to update another timer's CCR using libopencm3

texts:
I'm playing with the blue pill.
Here I run TIM2 and enable the DMA on its update event, according to Table 78 of RM0008, the DMA channel I should use is channel 2 on DMA1. Then I want the DMA to update TIM1.CCR1.
But I cannot get it working around DMA part. Here is the code:
#include <libopencm3/stm32/rcc.h>
#include <libopencm3/stm32/gpio.h>
#include <libopencm3/stm32/timer.h>
#include <libopencm3/stm32/dma.h>

#define PHASE_SIZE  10

const unsigned short PWM_phase[PHASE_SIZE] = {
  1, 11, 21, 31, 41, 51, 61, 71, 81, 91
};

int main(void) {
  // setup TIM1 as the main output
  rcc_periph_clock_enable(RCC_TIM1);
  rcc_periph_clock_enable(RCC_GPIOA);
  rcc_periph_clock_enable(RCC_AFIO);
  gpio_set_mode(GPIOA, GPIO_MODE_OUTPUT_50_MHZ, GPIO_CNF_OUTPUT_ALTFN_PUSHPULL, GPIO8);
  timer_set_mode(TIM1, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
  timer_set_oc_mode(TIM1, TIM_OC1, TIM_OCM_PWM1);
  timer_enable_oc_output(TIM1, TIM_OC1);
  timer_enable_oc_preload(TIM1, TIM_OC1);
  timer_enable_break_main_output(TIM1);
  timer_set_oc_value(TIM1, TIM_OC1, 30);
  timer_set_period(TIM1, 120);
  timer_enable_counter(TIM1);

  // setup DMA
  rcc_periph_clock_enable(RCC_DMA1);
  dma_set_peripheral_address(DMA1, DMA_CHANNEL2, (uint32_t)TIM1_CCR1);
  dma_set_memory_address(DMA1, DMA_CHANNEL2, (uint32_t)&PWM_phase[0]);
  dma_set_number_of_data(DMA1, DMA_CHANNEL2, PHASE_SIZE);
  dma_set_priority(DMA1, DMA_CHANNEL2, DMA_CCR_PL_MEDIUM);
  dma_set_read_from_memory(DMA1, DMA_CHANNEL2);
  dma_set_memory_size(DMA1, DMA_CHANNEL2, DMA_CCR_MSIZE_16BIT);
  dma_set_peripheral_size(DMA1, DMA_CHANNEL2, DMA_CCR_MSIZE_16BIT);
  dma_enable_memory_increment_mode(DMA1, DMA_CHANNEL2);
  dma_disable_peripheral_increment_mode(DMA1, DMA_CHANNEL2);
  dma_enable_circular_mode(DMA1, DMA_CHANNEL2);
  dma_enable_channel(DMA1, DMA_CHANNEL2);

  // setup TIM2
  rcc_periph_clock_enable(RCC_TIM2);
  timer_set_mode(TIM2, TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP);
  timer_set_period(TIM2, 100);
  timer_set_dma_on_update_event(TIM2);
  timer_enable_counter(TIM2);

  while(1) {
    //__asm("nop");
  }
}

I can read through openocd that the TIM2 is ticking. But when the RCC_DMA is enabled, I cannot read DMA registers anymore (may be they are busy?).
Is there something wrong with DMA setup? Thank you!
And there is no libopencm3 tag yet?


texts: I'm currently trying to implement the MIPI RFFE (As master) protocol on a simple AVR microcontroller, the specs says that the clock frequency can go down to 32 kHz, so I guess this it should be possible to implement it this way. However it does not seem to work, in the figure below, a picture of the waveform is shown which seems to be matching the specification. Does anyone have any experience implementing RFFE on an MCU or some reference code?


texts: Can I use a 12V 70A source to convert/boost to 24V 5A supply?

texts:
I have a self built custom made computer that is using a Ultra X3 1000 watt power supply. Over the years I have been reducing the power needs by adopting more energy efficient hardware. My computer is now using about 200 watts at any given time and can jump to a maximum of 360 or so when gaming or folding. So the PSU is overkill by 60% minimum.

I also have a 2560x1440 LG S-IPS LED monitor I built myself (63 watts max typical) using parts I sourced from around the globe and on eBay. The LG electronics that powers the monitor only needs a 24V 5A power brick for which I do not have yet. It is only $23 on ebay. However, I am wondering if I could use one of the empty +12V modular connectors on my PSU to supply the voltage/current to the monitor as well?

The PSU is a 85% efficient model with 70 amps on the +12V rail. I need to boost it to 24V, but I only need 5A according to the original power brick these come with.

Would a cheap DC-DC boost module work for this? Such as this boost converter.

The PSU I am using is connected to a very nice and conditioned power strip.

I am concerned that this boost converter says "Input current ：16A (MAX) (more than 10A please strengthen heatsink)". I thought current is only determined by the load draw required? Thus if the device I am powering only needs 5A at max, then why would I be concerned with the Input current of 70A? Isn't the input current just the maximum my PSU can supply, but draw is determined by the device using it?

My goal is to try and avoid using a cheap power supply, and saving a few bucks, and since my PSU is/was very expensive I consider it a much higher quality supply.

So can a boost converter do what I need to do safely? Or is this dangerous?


texts: What is the main difference between registers, bit fields, and flags?

texts: In school I was accustomed to programming various registers when working with microcontrollers to manipulate their behavior.  At my job registers are now referred to purely as bit fields.  The word "register" is only used to refer to a hex value, which I'm guessing is the address location.  The words "bit fields" are used to indicate the portion of the register which pertains to a certain functionality of our product. Looking at the Atmel documentation here (page 3) they indicate that 2 smaller registers make up one larger register.  This wiki document indicates that bits are referred to flags.  I guess I am confused on the nomenclature.  Is there an industry standard for defining what the differences between the terms are or when they should be used?


texts: Use one 12V 30A timer for two separate 12V inputs?

texts:
I'd like to use the following timer, rated 12V 30A, but for switching two different 12V inputs at the same time and not having to buy and program two timers. But the timer only have one channel.

One input is 12V 14A and the other is 12V 16A, coming from a PC power supply. It will be used to power two separate LED strips.

What would be the solution?


texts: File system to use with NAND Flash and 32 bit microcontroller

texts:
I am searching for a file system, suitable for NAND flash memory chips.
Currently I use a Micron 256MB SPI NAND flash memory where I write and read raw sensors data but without a file system and error correction.

So I decided to move to a file system but I don't know where to begin with.
I use the PIC32MX274F256D microcontroller

Now that I also need error correction I decided to move to a suitable file system for NAND. After searching I realized that  it is more dificult than I thought.

If someone has prior experience with NAND flash memory file system or where  to begin with please give me a few hints.

If there is something that I forget to mention please let me know

Thank you


texts: What determines how narrow a radio channel can be?

texts:
As an example: We used to have analog TV broadcast but now we're switched to digital. With digital we're able to pack in more data into a smaller frequency range. I assume that it is our advancements in digital signal processing that has enabled these "modern miracles".

Question: How narrow can a channel be? What determines channel width?


texts: High voltage high speed low current amplifier

texts:
I want to design an amplifier that can take an 8MHz signal (even square) with an amplitude of only a few volts (1-3V) and amplify it up to 160V but I only need it to deliver about 60mA. I also want to avoid using a high voltage input voltage.

Does anyone have any ideas where to start? I was thinking of a small class A amplifier in conjunction with a transformer. Would the use of a transformer be impossible due to the high frequency? Or should I just use a boost converter and then use it to supply my class A/class AB amplifier?

Any ideas are welcomed.


texts:
How many clock cycles will take execution of this segment on the simple pipeline without forwarding or bypassing when result of the branch instruction (new PC content) is available after WB stage. Show timing of one loop cycle in Table below.

This is the question and here is the answer in the second photo however I didn't understand how we got the number of clock cycles for segment execution on pipelined processor. My doctor solved it in this way:

Number of cycles in the loop = 15 c.c.
Number of clock cycles for segment execution on pipelined processor =
= 1 c.c. (IF stage of the initial instruction) + (Number of clock cycles in the loop L1) x
Number of loop cycles = 1 + 15 x 400/4 = 1501 c.c.
Speedup of the pipelined processor comparing with non-pipelined processor =
= Number of Clock cycles for the segment execution on non-pipelined processor /
Number of Clock cycles for the segment execution on simple pipelined processor =
= 3005 c.c. / 1501 = 2 times

Can you please explain me from where did we get the 1? What is the formula he used?


texts: When I was at work the other day, one of the techs showed me a delta connected power supply in which the phase to phase voltages measured 120Vrms. What didn't make sense to me was when he measured the phase to ground voltages and got 65V, 65V, and 77V. I asked him how the ground was connected to the delta system in order to measure these phase to ground voltages, but he didn't give me a satisfactory answer. It can't be a high-leg delta because the numbers don't work, so does anyone know what type of delta connection this could be?


texts: Alternating between charging two solar cells

texts:
I am designing a boat that is operated by two solar cell banks which in turn charge two separate batteries. I would like to run the boat with one bank while the other is charging, and once the one running is below a certain voltage, the other bank comes on and the cycle is repeated. I have tested my set up and each bank provides enough power separately to propel the boat at a slow speed(1-1.5 m/hr).

Any ideas about the hardware set-up particularly switching from one battery to the other.

Thanks in advance for all the help.


texts:
I have a 415V compressor with a 3-phase Commando plug in the configuration 3P+E, however my wall socket is 3P+N+E. Is it possible to change the plug on the compressor to a 3P+N+E without connecting the neutral? As I understand it isn't needed so shouldn't cause an issue, but could this have potential impacts on RCDs/other circuit breakers installed in the circuit? If it helps the device is in the UK so conforms to that wiring specification.

Thanks in advance!


texts:
I have asked here a month ago regarding measurement of very low current.
I was told that Amper-Meters today has this resistance in series that will cause a voltage drop, hence you can't measure a very low current.

So what happened with my Fluke is a very strange thing. If I put it on the scale of 2mA, or even 20mA, and try to measure current in my PCB, I get many resets of the MCU because the voltage is dropping.

But I discovered something else, if I put the scale on the Ampere meter to be in 20A, then the PCB is working and I can measure the current (!).

So my questions are:

Why is it working only with a scale of 20A ?
Are the measurements good? Can you count on them? I can tell that the LCD shows a curent of 0.03 in this scale, that means its about 30uA? (that's what I expect)


texts: NTC Thermistor selection for high temperature where beta value needs to be > 22000

texts:
We would really appreciate some help with finding a thermistor (and accompanying resistors) in order to do some current limiting in high-ambient temperatures. The circuit comes from the LT3741 datasheet (below).

http://cds.linear.com/docs/en/datasheet/37411ff.pdf

Options A, B, C and D show different methods of use, some which would allow better linearization of the R-T curve, but it's still not exactly what we want.

The problem is that most NTC thermistors have the largest resistance differential at a temperature lower than our application. This means that we can't get a large enough range of resistance to be useful.

Vref is 2V, and CTRL2 should be 1.5V at 80°C, falling to ~0.075V at 100°C.

For example, if R2 was 120k, then the desired resistances of the thermistor would be 360k at 70 degrees C and 4.6k (or lower) at 100 degrees C. I can't seem to find any thermistors which such a great resistance differential at that range. By my calculations this is about a 28000 beta value. Most thermistors don't go above 5000.

Do I need an op-amp to increase the voltage change?

I would welcome any advice on how to manipulate a standard thermistor such that we get a large resistance differential at these temperatures, or are there known thermistors which operate around this range for the resistance change we require?


texts: Whether a battery stores energy or simply it converts chemical energy into electrical?

texts: A battery is a simple thing but I'm afraid, the concept just doesn't work in my mind. The confusion is basically that whether it stores energy or simply it makes it by converting chemical energy into electrical energy.


texts: Obtain a Transfer Function from Bode Plot shown

texts:
I want to obtain a transfer function from the Bode Plots

I already got the corner frequencies (approximates) and all the terms for my T.F.

Then when I try to check my results in MATLAB my plot drops to -40 dB instead of -20 dB like in the original plot.


texts: Are there side effects to using too much resistance for an LED?

texts:
I have a 9v battery and a standard red led from reference 1.7v drop and I want it to draw 20 ma also from reference. so id need a 365 resistor. to my understanding if i have too little resistance then the led will eventually burn out or worse.

But I have tried 1k and 10k resistors and the led still gives what to me is just as much light.(1/2 watt resistors)

What are the downsides of using higher resistances instead of a calculated 365 by ohms law?

If there are none, are there any advantages?

Or will it make no difference?

Any help would be greatly appreciated, Thanks.


texts: Repair (fixing back) lifted power thru hole pad+trace

texts:
Attached pictures are a lifted power pad+trace of a 1000W PSU of a commercial subwoofer. Caliper showed 0.42mm thick, which if correct gives about 12oz copper trace!

In this particular pad was the source of a mosfet after rectifier bridge, transformer and capacitors bank.

Pad+trace are intact, I just need to reliably fix them back to place.

What are the best options? Epoxy? Maybe araldite? I am not sure if it will ever corrode copper or sensitive electronics.


texts:
I recently borrowed an Arduino Inland Basic Starter Kit. It includes an active and passive buzzer. What is the difference? I can hear a difference in sound when I use the tone() command. Anything else?

How can I identify which one is which? Are there any specific commands for each one?


texts: Is it possible to have an universal RF receiver and transmitter (Wifi / Bluetooth)

texts:
First of I should make clear that I'm not an engineer. My friends who are helping me with this project are. But me.. well lets just say I know the basics.

Problem

I have to be honest, it's a first world problem but nevertheless a problem.
Most of my devices that are connected to my tv are in my livingroom(groundfloor). I have a setup which allows me to send the image of all my devices to my bedroom which is on the firstfloor approximately 30ft (10 meters) away. the problem is that some of my devices are not receiving the bluetooth/wifi signals from the remote/controllers (bluetooth/wifi). Offcourse that's not very surprising.

Solution

We have been searching the web for quite some time but we are unable to find a bluetooth range extender/repeater.

To put in layman's terms; we thought that it might be possible to create a device that has an antenna which receives all RF signals (bluetooth and wifi are RF signals) and sends all received signals to a base unit which stands next to the equipment or extend/repeat the signal so it reaches the devices on the groundfloor. This device will not alter the signals in any way. Just transfer it back and forth as it is.

Are we completely crazy or is this possible. And if so, what do we need.

Thanks for reading and even the smallest push in the right direction is much appreciated!


texts: Question Regarding Series and Parallel Circuit

texts:
Stack Exchange members, I am new to this stack, so please allow any formatting errors. My question is that what is a 'bank' in the following statements:

'3 out of 12 resistors in one parallel bank'

'2 resistors in a bank that is series with 1 resistance'

I personally think that it is a synonym for a branch in a parallel circuit, but what are your thoughts?


texts:
Is there any possibility to use smartphone camera modules without their smartphone?
     those modules are relativity cheap and provide good results,
     can someone explain how to do it?


texts:
Hey guys. I'm building a 9 RGB LED chaser, using an ATTiny2313 to drive it. The cathodes are connected to all of PORTB and pin 6 of PORTD. I wrote some code to drive them all, but for some reason it's really slow. If red is set to 200 and blue to 100, you can see the red staying on for twice the amount of time, and you can almost time it. This should be happening many, many times a second but it's going very slow.

#include <avr/interrupt.h>    // Defines pins, ports, etc to make programs easier to read
#define F_CPU 1000000UL       // Sets up the default speed for delay.h
#include <util/delay.h>
#include <stdint.h>
#include <stdlib.h>
#include <math.h>

#define bit_get(p,m) ((p) & (m))
#define bit_set(p,m) ((p) |= (m))
#define bit_clear(p,m) ((p) &= ~(m))
#define bit_flip(p,m) ((p) ^= (m))
#define bit_write(c,p,m) (c ? bit_set(p,m) : bit_clear(p,m))
#define BIT(x) (0x01 << (x))
#define LONGBIT(x) ((unsigned long)0x00000001 << (x))

#define RED 1
#define BLUE 0
#define GREEN 2

void delay_ms(uint16_t ms) {
  while ( ms ){
    _delay_ms(1);
    ms--;
  }
}
struct LED {
    uint8_t r;
    uint8_t g;
    uint8_t b;
};

volatile struct LED strip[9];
uint8_t x;
uint8_t y;

int main(void)
{
DDRD = 0xFF;
DDRB = 0xFF;
for(x = 0; x <= 8; x++){
    strip[x].r = 0;
    strip[x].g = 0;
    strip[x].b = 255;
}
while(1){
    PORTB = 0xFF;
    PORTD = (1 << 6);
    for(x = 0; x <= 255; x++){
        for(y = 0; y <= 8; y++){

            if(strip[y].r > x)
                bit_set(PORTD, BIT(RED));
            else
                bit_clear(PORTD, BIT(RED));
            if(strip[y].g > x)
                bit_set(PORTD, BIT(GREEN));
            else
                bit_clear(PORTD, BIT(GREEN));
            if(strip[y].b > x)
                bit_set(PORTD, BIT(BLUE));
            else
                bit_clear(PORTD, BIT(BLUE));

            _delay_us(1);
            if(y == 0){
                bit_clear(PORTD, BIT(6));
                PORTB = 0xFF;
            }else{
                bit_clear(PORTB, BIT(y-1));
                bit_set(PORTD, BIT(6));
            }
            _delay_us(10);
            PORTB = 0xFF;
            PORTD |= (1 << 6);
            _delay_us(1);
        }
    }
}
}

Any help would be greatly appreciated :)


texts: Is it okay to mix different versions of Xilinx IP in a single design

texts: Suppose the IP repository contains two versions of the same IP. Does Xilinx Vivado allow instantiating both versions in the same design, or can that conflict in some way?


texts: Change the speed of an induction motor with an additional capacitor

texts:
I have a three phase induction motor (a fan motor) that get power from a two phase power line. To start the motor I have a start capacitor.
I need to change the speed of the motor to reach the 70% of the nominal one, a colleague of mine said that I can use the scheme of CASE 2, so I have to add an additional capacitor. I was not aware of this configuration, so I seached on the internet. I find some example:
Speed control on a ceiling fan induction motor
I understand that the additional capacitor produce a phase shift to reach the desired speed.
My question is related to the sizing of the two capacitors to reach the target speed. If I know the motor data how can I size the additional capacitor C2 to reach the desired speed value? Do I need to use some equivalent motor circuit?

simulate this circuit – Schematic created using CircuitLab


texts: The Blue LED of ESP8266 glows continuously when connected to 5V relay output

texts:
I am a newbie. Need help on my project.
I am building a project which controls a 5V relay from ESP8266 ESP-01. Since the GPIO2 gives the output of 3.3V, I am using an N channel MOSFET 2N7000 to control the 5V relay.
The circuit is shown below:

However once everything is connected and I switch on, the ESP-01 Blue LED glows continuously, and the LED after R1 continues to glow and I get garbage On serial port from ESP-01. The standalone ESP works absolutely fine.
Kindly help how to solve this issue. Thanks in advance


texts: I’m replacing a transformer on hot tub. Markings on original were obliterated from rust. New transformer is marked as follows. 0 v blk wire, 115 v white wire, 230v red wire. The transformer receives power from a plug on a pc board. I’ve measure the voltage on the board as follows. Blk wire Socket 110v, 0 white wire socket 110v red wire socket. My question is do these corresponding board voltages need to match the transformer input voltages? I was reassured this is the correct transformer.


texts:
There's quite a bit of math to be done when you need to calculate a size for your heatsink.

As there are many options to choose from if you don't know the size yet, is it just better to pick the largest one? (assuming you have unlimited space for it);
Example

The other option would be to use a smaller one but with a fan for forced airflow like this one.

So is it more efficient if I put a small heatsink with a fan or just use a large but not 100x bigger heatsink?


texts: How to implement polar codes on MSP430 in CCS?

texts:
I am working on error correction codes. I want to know, is it possible to implement polar codes on MSP430FR5994?

Actually, I wanted to confirm its feasibility for small devices, namely sensor tags cc2650 and MSP430. I want to use the polar codes for constructing the SRAM based PUFs. Polar codes will do the error correction and after that AES and/or hashing will be employed for generating a shared secret key. For polar codes, the block size will at least be 1024 bits and the operation needs to be fast, in 5 - 10 milliseconds. So I was concerned if all these objectives are achievable on MSP430FR5994 launchpad?


texts:
Just a basic question... For arduino/avr/ATMega328 I find lots of examples using Timer1 (there's even a whole library for it) but rarely any that utilize Timer0 (or Timer2).

Now, I know that using any of these timers to control an ISR method will disable the use of PWM on it's associated pins, but is there a specific reason that people seem to stay away from Timer0? Is it used for something else internally that one should not mess with?

My current application is fine using Timer1, I'm just curious if I'm missing something about these other often neglected timers.


texts: I recently dismantled an old treadmill and removed the electric motor. I was wondering how I could power this and control it safely and preferably with a battery. There are three wires coming from it. A red one a black one and a green/yellow one. Pictures are below


texts: Why does this part of an OLED filter light only when orientated correctly?

texts:
Note: The screen is an OLED screen. I had assumed it was LCD, therefore the post mentions it as such.

I was disassembling a Samsung phone (GT-I9305) and was able to seperate the LCD into two sections.

The top section consists of the top glass surface and a tinted film wedged between the surface and another piece of glass.

The bottom section includes all the other layers of the LCD with a bronze glass layer on top with a very fine grid like pattern, barely visible to the naked eye. When light it shone on it, a colourful, but distorted reflection is produced. Below this is a black film-like layer with fairly clear and thin light grey horizontal and vertical dashes, similar to those seen in a segmented LCD. Each of the dashes, consistent in size are approximately 1 mm in length.

Based upon this Samsung website, I'm assuming that the layers, from top to bottom are as follows:

Top section

Glass surface - Top chassis
Tinted film - Top polariser
Glass layer - Glass substrate

Bottom section

Bronze layer - Color filter (RGB)
Black film - Common electrode

When the top section is placed on the bottom section is acts as a filter, blocking a significant amount of light. This filtering occurs as long as the top section has the glass surface facing up.

If the top section is flipped, such that the glass surface is facing down, no filtering occurs and is only darkened to the extent that the tinted layer is normally.

I initially thought that the glass surface had an effect on the filtering, so I removed a small section of the tinted film and observed the same effect. If the glass is orientated how it was designed, it filtered, if it was flipped, it wouldn't.

I thought polarisation should work either horizontally or vertically no matter if the film is flipped or not. That's what I've experienced with sunglasses, so, clearly something else is going on.

If the molecules were orientated along the z axis, that would explain how the top section can be rotated without a change to the filtering, but it doesn't explain why it only works in one direction.

So my questions are:

Have I correctly identified the layers?
How does the tinted film only filter in one direction?
What is the name of this effect?


texts: Design for a small shop 240-volt induction heater?

texts:
I am interested in finding a design for the electronic/electrical components of an induction heater for a small shop using a 220V 60Hz input.

I do not need designs for the coils and cooling system, I can handle that.

There is an interesting web page describing a simple design for a small induction heater. In another question on this SE a reader complains about getting this design to work. From the discussion there it is evident that getting a good quality induction heater design is a non-trivial problem. The circuit on this page is advertised as being 300 watts.

I have the book "High-Frequency Induction Heating" by Frank Curtis (1944), but this book mostly focuses on coils and only has one sample circuit which is old has a lot of tubes. I also have the circuit in the Encyclopedia of Electronic Circuits vol III. The key component of that circuit is the MTM15N45 power FET, but it appears that component is still being made so this might be a viable circuit since it can be with a 220V line. This circuit is advertised as being 500 watts.

(Also, according to my initial calculations my types of applications would require a 20,000 watt system, so that would be 90 Amps at 220V. Basically I would have to divert the entire power of the house to the heater while it was in use. So, the Encyclopedia circuit may be too low power.)

Is there a better circuit than this, or a more detailed resource that would be appropriate?

Maybe this is too complex and I should just buy one?


texts: MOSFET as a VCCS or an variable resistance

texts:
I am a bit confused. In saturation region, sometimes, an MOSFET is called voltage-controlled current source and sometimes it is called variable resistor where its resistance is controlled by the gate-source voltage.
Are the two concepts equivalent?
I meant MOSFET operates in saturation region not triode.


texts:
So for whatever reason I'm having a little bit of a problem understanding why every dc motor explanation says the current switches after every segment in the armature.

I mean the current is going to flow the same way since the power source isn't being reversed right? So when they say it switches after the break between segments is it because the armature is just at a different position in relation to the magnets or is the current really reversing?


texts: Why are the IV curves of capacitors and inductors ellipses?

texts:
I don't really know what the difference is between a regular diode, a zener diode, a schottky diode or an LED. Neither do I knoe the difference beetween a DIAC, a TRIAC or even a NPN transitor.

The way I see it, the difference lies on the IV curves, how the component behaves at different voltage values, so I decided to buy a curve tracer from China like this one:

But before testing it, I wanted to make sure to understand the theoretical basis behind the IV curves of some basic components:

Resistor

Let's suppose I have an adjustable voltage dource called Vs, and some kind of black box for electronic components called BBEC. In this black box you can place an unkown electronic component, and by changing the voltage values of Vs, you can trace the IV curve of that component, and this way, see what kind of component is.

So, let's place a resistor, the IV curve must be a straight line. There is an equation to model this and it is called "Ohm's Law":

$$ V=RI $$

In its differential form, it can be written as:

$$ dV=R dI $$

It is a linear relationship, if the resistance is higher, the slope of the IV curve decreases and if the resistance is smaller, the slope increases

The gray zone marks off the limit of the operating zone.  If you cross the gray zone, you are going to have a burnt resistor.

From the resistor case it is possible to obtain two special cases:

Open circuit

No matter how much you increase the Voltage, the current is going to be zero.
Short circuit

By just increasing the voltage a little bit, the current is going to increase and go to infinite. You're also going to have a burt wire.

My problem comes with the next components:

Capacitor

The capacitance is described by:

$$ q= CV   $$

In differential form:

$$ dq= C dV   $$

and this gives:

$$ i(t) = \frac{dq}{dt}= C \frac{dV}{dt}   $$

So, in words, the current is equivalent to the derivative of voltage with respect time multipled by some factor C.

How does this relate to an ellipse?

The equation of an ellipse centered at the origin with width 2a and height 2b is this one:

$$ \frac{x^2}{a^2} + \frac{y^2}{b^2} = 1  $$

I was thinking that the relationship can be seen with the parametric equation of an ellipse

$$ x = a cos t    $$
$$ y = b sin t   $$

But I have no clue, I don't understand why a capacitor can be modeled with that equation.  What physical basis does it follows that makes it arrive to the equation of an ellipse?

Also, if you cross the gray zone, you are going to have a burnt capacitor, but I am not sure if the limits are correctly placed.

Inductor

An inductor is described by this equation:

$$ v(t) = L \frac{di}{dt}   $$

It is very symmetric to the capacitance rquation.  By just changing v(t) to i(t) and L to C, you arrive at the same equation, so why is this one also an ellipse?

The difference on ellipses is that if the capacitance incresses, b increases and a decreases. In the case of the inductor, if the inductance increases, b decreases and a increases.  I guess it is due the symmetry of the equation.

You might be asking, How do I know they are ellipsis if I have never seen an IV curve by myself?  Well, I don't know, but that is what curve tracer sellers say on the internet:


texts: What programmable board should I use for my project?

texts:
I have a small project going on, you can call this a research project that I needed to pass a certain class。 But the thing is, I don't know what I should use Arduino? Raspberry Pi? Im a complete beginner so please help me.
Here is my project:
I will make a device that does some web scraping stuff where it will collect necessary data on a site and for the collected data, there will be a certain condition where, if that data passes that condition, an action will occur like sending a SMS message or activate an alarm or something.
So I need help on where I should start and I'll probably handle the rest through the power of internet. I'll probably take care of the coding stuff. I need to know what electronics I should use and if it's possible, recommend a cheap and affordable one. Thanks


texts: Blocking DC without blocking any frequencies?

texts:
Is there any practical way of blocking DC without blocking any AC frequencies (or as few as possible)? Suppose I wanted to block DC and let through all frequencies between 2Hz and 10Ghz with minimum resistance.

The first methods that spring to mind would be to either use a very large capacitor or many capacitors in parallel with different values adjusted for different frequencies.

Is there something blatantly obvious I've missed?


texts: Negative components appearing in total gate capacitance in nanowire

texts: I am using sentaurus tcad simulator for simulating a gate all around nano wire and nano tube mosfet. I have to extract the total gate capacitance Cgg and its components like Cgs, Cgd etc wrt gate voltage. I have done ac simulation at 1 MHz. The total capacitance Cgg is a positive value, but while looking at the different components like Cgs, Cgd their values are coming to be negative. Even for reverse polarity capacitance like Csg, Cdg their values are different compared to Cgs and Cgd and negative also. Is the negative values possible and which components should I see for gate-to-source capacitance and gate-to-drain capacitance in the simulator?


texts: analog automatic gain control design issue

texts:
I am trying to create automatic gain control circuit(AGC). I am newbie with not much experience

Basically input to the 1st stage amplifier is form sensor based on that I want to control the gain of second stage. So I fed the output of 1st stage amp. to peak detector. Then to LPF so that the signal detects follows peak.
In the figure,
White is the signal after LPF(node before 1uF)
Till this point I have circuit working right.
But now I have to remove the offset after LPF so that the signal at gate of PMOS is 0-1V only. So when I connect output of LPF to HPF the signal before 1uF changed completely as bellow(the blue signal). What exactly am I missing or doing wrong?


texts:
How can I debug I2C in Atmel Studio (latest)?

I have enabled it as shown inside the I/0 View with TWEN and TWIE bits enabled. However, after sending a START condition, I do not see the TWI-interrupt routine being called.


texts: Is there a glitch / race condition at the output of this circuit?

texts:
The input rising and falling edges occur at time t = 0. The propagation delays of the respective gates are 3 and 4 ns, as shown.

According to my analysis, the waveforms are as below:

As I've drawn above, I don't think there's any glitch in the final output Y2, since both the inputs i1 and i2 have a transition at t = 0; and if there was to be a glitch, it would have been at t = 4 only if the 2 inputs to the AND gate were High before t = 0.

But since Y1 is Low before t = 0 and turns High only after t = 3, and by the time Y1 goes High, the other input i2 is already at Low. So there is no glitch in output Y2.

Is this correct? Or am I missing something here?


texts: How to Increase RF Amplifier Efficiency?

texts:
I've inherited another engineer's RF design and I would like to increase the transmitter efficiency.

It's a 406 MHz radio that is using 14W to send out 5W (36%). The amplifier in use is http://www.rfparts.com/pdf_docs/RA/ra07m4047m.pdf

  "The RA07M4047M is a 7-watt RF MOSFET Amplifier Module
  for 7.2-volt portable radios that operate in the 400- to 470-MHz
  range."

In general, I'm wondering,

What is a good way to accurately measure the efficiency of amplifiers?
How feasible is it to obtain higher efficiency?
Where should I start my search?
Are there any nonobvious things I should be aware of?

I'm new to RF design. Thanks for any suggestions.


texts: How does an Intel processor "talk" to an I2C device?

texts: I don't come from an Electronics background, so please bear with me. Assume an Intel processor wants to talk to a temperature sensor over the I2C bus. How does the underlying communication look like? So far I understand, Intel processors use specialized CPU instructions (IN/OUT) to communicate with peripherals. Also, I believe an Intel doesn't have an on-chip I2C controller. So, we need an I2C controller, isn't it? If so, does the processor treat the controller as a peripheral and use IN/OUT CPU instructions to talk to it? Is the controller mounted on the motherboard? What bus connects the CPU and controller?


texts:
Hi I want to bypass an Inrush Limiter Thermistor. It is between the rectifying bridge and the smoothing capacitors, I was considering using a solid state device.

After the rectifer current only flows in one direction, so I considered using a mosfet because I have good quality ones lying around. However, would the charged capacitors maintain a reverse voltage on the mosfet when the AC wave goes down? In such case would a mosfet be unsuitable?

Then my next choice would be an SCR/Triac right?

p.s.: voltage is 12V to 15V AC, 4A max, I have 6600uF of capacitance.


texts: 2 Ethernet jacks on a Device with ENC28J60 chip in with switch

texts:
Have a ethernet device that works with Microchips ENC28J60 chip perfectly. So if I want to connect a cable from a switch/controller, to device 1 (that has 2 RJ45 jacks), then have device 1 second port connect to device 2 1st port, then device 2 2nd port to device 3 1st port so communications will be communicated to all 3 devices.
Kind of like a RSTP network with daisy changed devices with their own separate IP addresses.
.
I found this thread for a 3 port passive HUB..
Also another reason is to not have to run cable from each device back to a central switch in a large warehouse or building. Each device can plug into the next device closest to it and so forth.
If I need to add more detail, please let me know. But I think what I want to achieve is noted.
Thanks for anyfeed back or threads I missed.
EDIT: Added basic diagram

EDIT: Clarified body for active switch since no parallel passive mode is available.
So if use just ENC28J60 chip... I would need to figure out how to preform the connections from ENC28J60 to a Micrel un-mangaged mode chip, so not having to add another MCU chip with more over head.
Found this Application note from Microchip
For using • Configuration Straps for basic/auto configuration without MCU
Also searched hear more and found the right topology - simple topology based on link aggregation, up to 200 Mbps of overall system performance is hypothetically reachable
High speed data from microcontrollers to pc using daisy chain


texts: What trace length is considered short in case of buck voltage regulator

texts:
I'm working on LM2596 based voltage regulator circuit that will be printed on PCB.

According to LM2596 datasheet some traces should be kept as short as possible. However no numbers are given.

This is my design (with ground plane hidden), from left to right:

LM2596S voltage regulator
SS54 Diode
12.5mm 100uH Inductor
2x Low impedance 300uF capacitor

First attempt:

I'm a little bit worried about C In (capacitor on the right between input voltage and ground) connection with regulator. The trace length is about 35mm.

Next attempt:


texts:
I am using the Altera Quartus II PinPlanner to enter all my pin details for my FPGA design. Some of the pins are connected to the SPI configuration bus of this ADC.

As can be seen on page 8, the 3 pins SCLK, SDATA, and SEN must be driven at 3.3V. Now the pin planner gives me three different 3.3V options:

3.3V LVCMOS
3.3V LVTTL
3.3V PCML

Which of these I/O standards should I use for my ADC?


texts:
In my textbook, there are two interrelated equations.
 1. wb = wt / (1 + R2/R1)
 2. wb = wt / Ao

where
 wb = break/cutoff frequency
 wt = unity gain frequency
 Ao = DC gain
 R1/R2 = standard resistors

These equations were derived from a simple and standard closed-loop inverting amplifier.

From: https://electrosome.com/wp-content/uploads/2016/11/Inverting-Amplifier-using-Opamp-Circuit-Diagram.jpg
 G = - R2/R1

I understand the derivations of these equations separately, however cannot define the semblance between them.
For voltage gain G, isn't Ao = G? And from that, the +1 becomes an issue. I hypothesize that there is an assumption involving a << or >> I am overlooking.
Update: Upon further research, I have come across "feedback factor", often denoted by β. My logic follows for the non-inverting configuration given:
 Ao = G = 1 + R2/R1

However, the fact remains that I am unsure as to accounting for the +1 for the inverting configuration.


texts: How to detect a Bluetooth low energy device or IBeacon without a smart phone?

texts:
I am putting together a simple project where my ibeacon (or a small BLE device) causes the receiver to trigger an alarm when inside the range of the receiver (5 ft max). The receiver will not be smart phone/app based.

The examples I've seen online are almost exclusively based on a cell phone app detecting the beacons. I'd greatly appreciate any suggestions on what hardware to use as a receiver and the BLE beacon.

Would an Bluetooth Module for Arduino detect the sticknfind beacon?

Thanks!


texts: How do I fix the ngspice warning "Can't open viewport for graphics."?

texts:
I'm trying to see some waveform plots for SPICE circuits with ngspice. As far as I can tell, the plot command is supposed to raise a window with a nice chart in it. But I keep getting this error message:

ERROR: (internal)  This operation is not defined for display type printf.
Can't open viewport for graphics.

I'm on linux mint 17.3 (ubuntu 10.04 lucid?).

I've tried:

Installing libxaw-dev as per https://askubuntu.com/questions/461466/cant-open-viewport-for-graphics-in-ng-spice/575866#575866
Compiling from source as per https://sourceforge.net/p/ngspice/bugs/263/#27fb
compiling with --enable-xgraph
xhost +, just in case

But I'm still seeing this error message. Any ideas?


texts: How to terminate switching transistor for level change?

texts:
For a typical driver, I would add a series termination resistor to terminate the line.

But what would be the correct way to terminate when a transistor is used to level shift a 3.3V/5V signal to some arbitrary voltage ?

Consider a simple circuit, V1 is some higher voltage to which I am switching to. Could be 12V, 15V, or 30V. R2 is a pullup. The pullup value would be most likely greater than Z0, otherwise, the power loss at high frequencies could be pretty big. 30V and say R2 is 50 ohms, thats 18W, when the transistor turns on and 600mA through it. So I would imagine that that the pullup would be much higher to combat that.

I've never seen in any book, app note, or any reference that speaks about this.


texts:
I'm trying to make a working can bus example sending and receiving frames.I managed to test this library using loopback mode
https://github.com/UBC-Solar/Firmware-v2/tree/master/Peripherals/CAN
it seems to be working fine. but since I'm not very familiar with STM32 (coming from arduino IDE) I couldn't find how to set Extended id. and also in datasheet I couldn't find anything about it.

here is the main code:

uint8_t data[8] = {0, 0x1, 0x2, 0x3, 0, 0x4, 0x5, 0x6};
CANInit(CAN_250KBPS);
CAN_msg_t CAN_rx_msg;
CAN_msg_t frame;
frame.id = 0x1801234;
frame.len = 8;
frame.data= data;
CANSend(&frame);
if (CANMsgAvail())
  {
      CANReceive(&CAN_rx_msg);
         if (CAN_rx_msg.id == 0x1801234)
             printf("Good");
         else
             printf(CAN_rx_msg.id);
  }


texts: I'm trying to understand why certain CPU cache memories are faster than others. When comparing cache memory to something like main memory, there are differences in memory type (SRAM vs DRAM), and locality issues (on-chip vs having to traverse a memory bus) that can affect access speeds. But L1 and L2 are generally on the same chip, or at least on the same die, and I think they are the same type of memory. So why is L1 faster?


texts: INA125P Strain gauge amplification problem

texts:
I'm using the INA125P to amplify the strain of a 350 ohm strain gauge in a self-built Wheatstone bridge circuit for measurement. I'm testing using a 351 ohm resistor to mimick a strain gauge under maximum strain.

This is the basic circuit I have (modified circuit from http://www.mechtechplace.net/mech-tech-electronics/building-a-low-cost-strain-gage-load-cell-amplifier/):

With my current calculation I would be feeding in a 1.78mV signal, with an amplification factor of 1004, I should be seeing 2.5V+1.87V= 4.29V Output.
I understand that I would be hitting the maximum output, but currently I'm measuring about 50mV at the output.

I've checked the other pin voltages to be correct, and Vin+ and Vin- are both close to 1.3V.
Any ideas on what could be happening?

EDIT: edited calculated estimation numbers.


texts: Whenever I am given a system type with a certain transfer function, I am always asked to proceed to find out the 1. impulse response and 2. step response of the system. My question is, what is so special about these two response types that other responses, like for example parabolic response, is not what I am asked to find out?


texts: Average power dissipated as the heat in the resistor

texts:
I’m trying to calculate the average power dissipated as the heat in the resistor.

A 12 V amplitude sinusoidal signal is applied across a 500 ohm resistor.

I have determined the current amplitude to be 0.024 A and the root mean square to be 16.97 mA.

I use P = I x V = 0.024 x 12 = 0.288 W

Where P is the power, I is the current and V is the voltage.

Is this correct ?


texts: How does this blinking LED circuit work?

texts:
I found a circuit that has an led that is blinking in it.  I was interested to see how it works so I took it apart and found that there was no capacitors in IC's in it (here is a picture):

I think the thing under the white circle is a spark gap, but I'm not positive.  My question is how does this LED blink without any capacitors?


texts:
I'm about to buy components for my first Arduino project: Reed contacts for my model railroad (H0 scale) to detect track usage. I don't want to use special shields, but use as few components as possible to directly connect the reed switches to the Arduino.
To make good use of the Arduino Nano, I'd like to use an input matrix. Let me summarize, how I understand the matrix (here it's 4 by 4, but with 14 digital IO pins, I could have a 7 by 7 matrix, right?):

To see the closed contacts, I switch on the one of the inputs at a time (I, R1, S1, T1) and read all of the outputs (N, O, P, Q). If R1 is active and I receive a high on O and P, then both of the middle contacts would be closed.
Since I'm a real newbie here, I'm unsure about the specs I should look for in the reed switches and the diodes. Also, do I miss any components (resistors?) or are switches and diodes enough?
Thank you!


texts: how to calculate equivalent resistance of a circuit

texts:
R2=100 ohm , R3=150ohm  , R4=220ohm  , R6=330ohm

I calculate equivalent resistance like this

150*100/150+100=60 ohm

220*330/220+330=132 ohm

60+132=192 ohm

can you tell me whether it true or wrong?


texts: I turn on the oscilloscope, work a little, then I remove the cables and after a while when I want to use it again, I notice the ground has moved 0.4 or 0.6 V upper or lower than it was half an hour ago. What could cause this problem?


texts: Why does wound rotor IM have the belt leakage but the squirrel cage rotor does not?

texts:
According to the description on page 159 of Prof. Lipo's book "Introduction to the AC Machine design":

It is important to mention that the harmonic leakage is important only for wound rotor machines. When the induction machine is equipped with a squirrel cage the
harmonics in the air gap produced by the non-fundamental components of MMF will
each induce a component of rotor current which will tend to “short” the harmonic
inductance. Although belt harmonic fluxes still remain in the gap, they are now very
small, being the summation of the harmonic stator fluxes and the opposing harmonic
rotor fluxes.

However, I could not understand why such induced higher order harmonics rotor current, which cancel out the effect of higher order stator MMF in the case of squirrel cage rotor, cannot happen for wound rotor. After all, the current in the wound rotor is induced by the stator MMF, just the same as squirrel cage rotor.


texts:
I am trying to amplify an audio signal generated by a hydrophone. I am trying to work from this (very general) circuit diagram I have found online and in an electronics textbook I own.

simulate this circuit – Schematic created using CircuitLab

However, I am confused about what input and outputs correspond to what. The hydrophone is attach to a coaxial cable, which is diagrammed as such on its data sheet.

As of now I am using a connecter to break out the coaxial cable to a "positive", and "negative" wire. So, currently, my circuit is as such, with ground representing the 0v terminal on the bench top power supply I am using.

simulate this circuit

When I measure my Vout with an oscilloscope with the power supply turned on, I get a randomly oscillating garbage output, so clearly I am doing something wrong. Are all of my input and outputs correct. Should I be completing the circuit by connect Vout to gnd, or the + terminal of my hydrophone?


texts: Replacing a transistor in a CCFL inverter circuit

texts:
I have a DC-to-AC inverter circuit that isn't working. It takes 12V DC input and is being used to power a CCFL. The circuit looks remarkably similar to the one labelled "Conventional CCFL inverter" on https://en.wikipedia.org/wiki/CCFL_inverter .

As far as I can tell with my limited electronics skills, the problem was in one of the transistors. I have unsoldered it OK, and measuring it with a multimeter, I'm seeing a short between two of the pins, which I assume isn't supposed to be the case. Before I removed the transistor, I was seeing a short across the two DC input pins, which I assume is due to the dodgy transistor.

So I need to source a replacement transistor, but I don't know enough about transistors to know what to look for. The dead transistor has written on it:

H.   A
3669
89(something)Z

Web searching for HA3669 I find http://www.hsmc.com.tw/pdf/HA3669.pdf which sounds like what I have.

Does anyone know an equivalent transistor that I can obtain easily in the UK, e.g. from a Maplin store, or online.


texts: I'm wondering about alternators used in automobiles and the mechanical load that they present to the engine. My question is: what is the relationship between the mechanical load presented by the alternator and the electrical load presented by the car's electrical system? Similarly, if I were able to reduce car's need for electrical power or provide a supplemental means for energy harvesting, what potential increase in performance or fuel economy might I see?


texts:
I am going to use rectifier circuit (attached in below) for consumer application (mobile). I tried this schematic design in virtuoso (cadence). I consider rectifier input voltage=1V and based on this voltage, i recieved output voltage=200mV.

In my project (Energy harvesting), this rectifier circuit output is giving to the DC-DC converter. Through this rectifier & DC-DC converter circuits, finally i recieved less efficiency (because, i received rectifier output voltage is very low).

So i need to increase rectifier output voltage (≃3V). Please anybody give solution to my problem.


texts:
I am controlling a 6x6 matrix of LEDs using a PLC with sourcing outputs and sinking outputs (24V). However, there is an issue with current leaking through to other lights.

For example, in the schematic below if I turn ON L25 (Source) and L30 (Sink), LED 16 will illuminate, but LEDS 4,10,22,and 28 will also slightly illuminate. Additionally, LEDs 13-18 will slightly illuminate. It appears that current could be using the open sinking as a ground or that the LEDs are not acting as perfect diodes.

The leakage LEDs are very dim and initially, I could not observe the problem. However, since running the matrix over several months, the leakage lights have become brighter. I checked using a multimeter and found that 1-3V are leaking across to other LEDs.

My question: what is a possible issue here? How can I resolve this most easily as I do not want to make significant changes to the matrix.

Thanks in advance.


texts: Are bacteria on integrated circuits problematic?

texts: Considering the scale of IC's using sub 50nm technology, I would think that even thought fabs are incredibly clean, there would still be a substantial amount of bacteria. Do they prove problematic in leaking current/shorting parts of the circuit?


texts: 2 Capacitor induction motor Humming troubleshooting

texts:
I have a single phase cutting SAW , 3 years old , yesterday i was cutting thick material it stalled as usually happens , but when i turn it off and then On again now it doesn't rotate , it just makes a humming noise .

motor type :

1-AC single phase 220v 2KW motor .

2-it has 6 wires coming out of the motor 2 red 2 black and 2 green wires .

3-Capacitors 200uF 250v and 35v 400v .

steps that i have done :

1- tested capacitors using FLuke , 200uF measures 220uF , and 35uF measures 22uF.

2- tried rotating motor by hand , i runs smoothly and freely ( no bearing problems and such)

3- i disassembled the motor , it is surprisingly very clean from inside , the centrifugal clutch seems OK , the contacts are clean , i wiped them and re-oiled them and continuity test seem OK ( the 2 green wires ) .

Question :  and what could be the problem ?  is it a shorted winding and how to know exactly

thanks in advance ...

EDIT :

As advised by the commenter , i made some tests using an LCR meter ( with 100hz lowest frequency) it appears that the stator coil from black wire 1 to black wire 2 has 30mH inductance . BUT from Red to red which is supposed to be the main Coil there is very high inductance (3000 Henry) and resistance is in the Mega Ohm range.
 I donot know if this is an indicator of short coil or open coil maybe the connecting wire is broken ?? does anyone has know how to fix this ?


texts: how do you link components between them on a protoboard

texts:
I have the following protoboard (see picture below)

Each hole has a distance of 0.5mm

I want to link components between them. I found a few ways to do that:

1) Use tiny wires to connect the components

2) Solder the part of the board I'm using. However, issue is the dots between them are tiny (very actually) and my iron is kind of unfit for precision work.

Any insights would be great.

Cheers

Update:

Please find the size between holes of my protoboard and the the size of the tip of my iron (size in mm and cm)


texts: Separating / Isolating the circuit blocks

texts:
I was designing the circuit of a superhet receiver, block by block. Needless to say, my concern is how would I separate the various blocks. In other words, how would I interconnect the blocks ( not just this circuit, but any circuit) so that one block does not affect the other. For my purposes, how would I separate / interconnect :

1) Local oscillator ( Hartley or Colpitt) from a Frequency Mixer ( Ring diode type)

2) The Mixer from active bandpass filter

3) The bandpass filter from the oscillator ( Hartley or Colpitt )

4) Amplification stage from the Mixer

such that each circuit block does its own function without affecting / getting affected ( or getting minimally affected ).

Is there a uniform strategy to adopt ( or a strategy which works in most of the cases ) or does it depend upon the circuit elements involved ?

Will just adding a very high resistance / buffer amplifier between the stages work, or is there more to it ?


texts: cant understand this OPAMP configuration

texts: i am working on CAN_bus capacitance sniffer meaning take the 2 data line and without cutting the wire to recrate the signal. and i came across this configuration. i can’t undusted it, can anyone help me?


texts: Meaning of an arrow in the control scheme

texts:
I cannot understand what the arrow that goes through "internal model" block mean? how can I interpret what does it do? What is the difference from any other "normal" arrow?

(source: cam.ac.uk)


texts: Wire Length Restrictions on Simple Battery Powered Circuit

texts:
Right now I am setting up a simple circuit with a switch at one end and a LED on the other. Basically it is going to be used for someone on one end to get the attention of the person on the other. The distance from one end to the other is approaching 50 feet.

I would like to set it up on an AA battery, or two if needed, but I do not know if the distance would be prohibitive. If necessary I will add in an RF transmitter and receiver but would rather not, since it would add to the bulk on the end with the button and I want to build it to be small and easily hidden. I can route the wire out of sight without a problem.

So being an amateur with electronics I thought I would ask here. Is that length going to be a problem? If so can I increase the size of the battery to overcome it? What gauge wire should I use? I am a Network Admin so I have boxes of 22 gauge CAT6 kicking around that I could use, is that heavy enough or is it too heavy?

Thanks in advance


texts: Intuitive Question - effect of capacitor on this common-source stage

texts:
I was watching one of Razavi's videos
https://youtu.be/oC2otEX3i0I?t=553
Minute 9:13

He has this circuit

He says that at higher frequencies, the effect of the capacitor becoems more pronounced and that the capacitor will be providing some of the drain current and hence the resistor Rd will have less current through it. The resistor has less current through it, thus a smaller voltage drop across it. Then, he says that because of that the Vout will drop. That makes no sense to me.

My reasoning:
$$V_{out} = V_{DD} - R_DI_R$$

Now surely, if I_R decreases as Razavi said it would, then of course the voltage drop across the resistor would decrease and hence we would be doing Vdd minus a smaller number, so Vout should increase and not decrease

So which is it, would Vout increase or decrease at higher frequencies where capacitor has an effect?


texts: PID algorithm: how to account for fast input value changes after a long delay

texts:
I am trying to implement a basic PID algorithm on an Arduino Leonardo to mix hot and cold tap water using servo-controlled valves.  The goal is to hold the temperature as close to a setpoint as possible.  Especially important is preventing the output temperature from overshooting the setpoint to protect the user from burns.  Secondarily important is getting the temperature near the setpoint as quickly as possible.

For small changes in temperature, a standard implementation of the PID algorithm seems to work OK.  But I don't know how to account for the long delays that may occur when waiting for hot water to reach the valve, since these delays are much longer than standard delays after changing the valve positions.

Obviously depending on the length of the hot water line and time since last use of hot water, it can take multiple tens of seconds for the hot water to reach the valve, so during this time, the water temperature remains fairly constant at a low temperature and the hot water valve soon opens 100%.   The integral component begins to accumulate a large error value.

When hot water finally reaches the valve, the detected temperature rises very rapidly to the max hot water temperature.  Due to the large integral error, the hot water valve is held at 100% for a long time after the temperature exceeds the setpoint, due to waiting on the integral value be reduced to normal levels.  Thus the result is maximum-temperature water for several (tens) of seconds.

I'm not sure how to account for this possible long delay.  In such a case, would it be wise to set an upper (and lower) bound on the integral error value, in order to limit max response time?  This seems to defeat the purpose of the integral component, and would also still impose some lag after reaching the setpoint.

Or is there a better way to handle fast input changes after a long delay?

Thanks for any advice!


texts: I having troubling understand what other interrupt firing besides TMR2 on PIC18f4550

texts:
I having troubling understand what other interrupt firing high_isr besides TMR2 on PIC18f4550.

Way I detect it I set pin MY_DBG_PIN toggling everytime high_isr is activated, and from what I try to do, only TMR2 I have activated and nothing else.

My code looking like:

#include <p18f4550.h>

#define USE_OR_MASKS

#include <pwm.h>
#include <timers.h>

#pragma config PLLDIV = 10
#pragma config FOSC = ECPLLIO_EC

#pragma config PWRT = OFF
#pragma config BOR = OFF
#pragma config MCLRE = ON
#pragma config PBADEN = OFF
#pragma config ICPRT = OFF
#pragma config LVP = OFF
#pragma config WDT = OFF,DEBUG=OFF

/* Sets the PWM value on CCP1 to 50% duty cycle*/

#define MY_DBG_PIN        LATBbits.LATB1
#define MY_DBG_PIN_TRIS   TRISBbits.TRISB1

#pragma interrupt high_isr
void high_isr (void)
{
    //* Comment to notice toggling of MY_DBG_PIN at 0.7Mhz
    if(PIR1bits.TMR2IF)         // Timer 2 interrupt
    {
        MY_DBG_PIN = 0;

        PIR1bits.TMR2IF = 0;
    }
    //*/

    // Are some other interrupts also firing? Why?
    //MY_DBG_PIN = 0; // If uncomment, toggling at 0.7Mhz
}

#pragma code high_vector=0x08
void interrupt_at_high_vector(void)
{
    MY_DBG_PIN = 1;
    _asm GOTO high_isr _endasm
}
#pragma code /* return to the default code section */

void main (void)
{
    TRISC=0;
    OpenTimer2(TIMER_INT_ON | T2_PS_1_4 | T2_POST_1_16 );
    OpenPWM1( 149 );
    SetDCPWM1( 300 );

    MY_DBG_PIN_TRIS = 0;    // make it an output

    PIE1bits.TMR2IE=1;           //enable Timer2 interrupt
    INTCONbits.PEIE=1;          //enable peripheral interrupts
    INTCONbits.GIE=1;           //enable glogal interrupts
    INTCONbits.GIEH = 1; /* Enable global Interupt */

    while(1)
    {
    }
}

As can see, only TMR2 possibly fire ISR, but then do you notice high freq. update of debugging pin if you uncomment the line?

If I specify TMR2 interrupt flag in ISR and then toggle debugging pin, then expected update freq, as current active code is like.

What other thing can be triggering ISR and how I check that without checking flags of all interrupts?


texts:
I have designed a circuit to keep the heating element at a constant temperature. The digital part of the circuit is being feed from a 5V LDO which is powered by two 18650 batteries in series and the heating element is directly connected to the output batteries. Also heating element wire(approximately 2ohm) is controlled with an N channel low side mosfet by the microcontroller.

What i noticed is that the LED and the seven segment display(connected to 5V output of LDO) seems to flicker when controller toggles the mosfet because of the voltage drop on the supply. Is there anything i can do to isolate these rails so that current draw for the load does not affect the 5V components?

The highest supply voltage for the system is 8.4V and currently the load roughly uses 2A. The problem is becomes more significant when the supply voltage gets lower. I don't think that any inrush current situation occurs because voltage continues to stay below 5V at the output of LDO when the load is on after few seconds. Also i tried with both batteries(which i am sure that can supply a lot more than 2A) and a lab bench power supply with no luck. I read that bulk capacitors can fix instant voltage drops but can they prevent constant voltage drop? If so where should i place these bulk capacitors?

Here is my schematic and pcb:


texts: I recently designed a circuit board, but now I'm looking and I believe that once the diode and capacitor are connected, they might be shorted. Thank you for your feedback.