texts: Diodes - minimum forward conduction current

texts:
I've been working on a GPS tracker which is intended to run/idle on a battery for an extended length of time (2+ years). The tracker uses an accelerometer (LIS3DH) and remains in a sleep state until it is awoken due to movement. While the tracker is asleep, current levels need to remain as low as possible to help preserve the battery. The accelerometer is capable of running on 2-3uA in a sleep state but can only tolerate a voltage input of 1.7 - 3.6V. As I will be powering this from a single cell LiPo (3.7V+) I need to ensure that the accelerometer VCC doesn't exceed 3.6V.

Using either a SMPS or a linear regulator would achieve this but would consume too much current to be practical. I would like to know if I can use a diode's forward voltage drop to ensure that the input voltage isn't exceeded.

In a more conventional setting where a reasonable amount of current is being passed through the diode, I assume this would work. However, I am not certain 2-3uA will suffice. Is the voltage drop of a diode tied to the level of current passing through it?


texts: shunt current measurement with less voltage

texts: Are there shunts available in market which can measure current of more than 200A but with voltage less than 50mV?


texts: Will two AC devices in same socket share same low voltage in there DC circuits?

texts:
I have a 230v AC to 180v DC circuit with a MOSFET inline that I want to control via a PWM signal from a microcontroller (the load is a salvaged treadmill motor). To power the microcontrollers board I was thinking of using a usb wall charger and tying the negative reference of the two circuits.

Is it safe to assume that if two AC devices that are connected to the same house wiring circuit (they will share an enclosure) will have zero or negligable difference between there negative referances?


texts: What is the difference between disturbance and noise for dynamic systems?

texts:
In most references from dynamic system theory, the following linear continuous dynamic system is considered.
$$\frac{\text{d}x(t)}{\text{d}t}=Ax(t)+Bu(t)+Dd_{1}(t)\quad (1)$$
$$y(t)=Cx(t)+Ed_{2}(t) \quad (2)$$
where \$x\in \mathbb{R}^{n}, y\in {{\mathbb{R}}^{p}},d_{1}\in
{{\mathbb{R}}^{m}},d_{2}\in{{\mathbb{R}}^{q}}\$  represent the state vector, measurement output vector, process disturbance and  measurement disturbance vector respectively.  \$A, B, C, D, E\$ are constants matrices of appropriate dimension.

Again, the following linear discrete dynamic system is mostly studied in references.
$$x(k+1)=Ax(k)+Bu(k)+Dw_{1}(k)\quad (3)$$
$$y(k)=Cx(k)+Ew_{2}(k)\quad (4)$$
where \$x\in \mathbb{R}^{n}, y\in {{\mathbb{R}}^{p}},w_{1}\in
{{\mathbb{R}}^{m}},w_{2}\in{{\mathbb{R}}^{q}}\$  represent the state vector, measurement output vector, process noise and  measurement noise vector respectively.

My questions are:

Are the disturbance \$d\$ and noise \$w\$ the same thing? If not, why in continuous system, only disturbance is considered, and only noise is considered in discrete system?
In the continuous system, when the disturbance \$d\$ is stated as a certain function, can the disturbance \$d\$  be assumed to be differential?  Is this assumption reasonable?
In the continuous system, when the disturbance \$d\$ can be stated as a stochastic process such as Gauss white noise, can the disturbance \$d\$  be assumed to be differential? Is this assumption reasonable?


texts: Can someone please explain how this circuit works

texts: It's s simple transmitter for light modulating certain sound we input to it. But i can't seem to know how this modulates the input signal.


texts: I measured the AC resistance of my customized inductor with network analyzer of core E70. I got 23mohms AC resistance and 2.3mohm DCR for 14uH inductor with 8 number of turns using litz wire(1400) of 4.3mm diameter. I also got 30mohm AC resistance and 11mohm DCR for 54uH inductor with 16 number of turns using different litz wire(1050) of 2.8mm diameter. Both measured at same frequency. I am confused now, on which factor AC resistance depend upon. I thought I should have gotten more AC resistance for 54uH inductor. Is it depend on the type of litz wire we use? or number of small wire? How can I reduce the AC resistance? Please let me know. Thank you


texts: Which power factor is better in an industry -0.21 or -0.94 and why?

texts:
In the electrical panels , when i switched on-off the capacitor bank then
power factor gets shifted from

0.89(lagging/during OFF condition) to -0.87(leading/during ON condition)    ,

similarly on switching on-off the capacitor bank power factor shifted from 0.87(lagging/during OFF condition) to -0.31(leading/during ON condition)

Now i want to know which power factor transition is better 0.89 to -0.87 or 0.87 to -0.31  and why ??


texts: What is the power spectral density of a DC signal?

texts: I am trying to find the Esd and psd of a pure DC signal, but I am stuck at integration of a square of Dirac delta function.


texts: Does capacitance per unit length change with change in loss tangent of surrounding medium?

texts:
I am running an electromagnetic 2D solver (Q2D extractor) for finding RLGC parameters. I have a microstrip as shown below

I am varying loss tangent of the surrounding medium, keeping the relative permitivity of the medium constant. I am getting a capacitance per unit length value that is same for any non-zero value of loss tangent, but different when loss tangent is 0. How is this possible? The graph below should explain my doubt clearly.
Note: I have taken hypothetical values for loss tangent values.


texts: How to solder a connector when spacing of PCB pads is not equal to spacing of component pads?

texts:
After delivery of my PCB, I realized that the spacing of PCB pads is not equal to the connector pitch (the PCB footprint is bigger than the OLED connector)! (sad)

Look:

Any idea how to solve this problem?


texts: Should circuit breaker be installed before hand switch?

texts:
I am a student of mechanical engineering so I am not very familiar with electronics. Recently I started working on a project where I am researching a control system for a motor which does some work. The system is powered by 3 phase AC electricity + ground + neutral which comes from 5 pin socket. The 3 phases then are directly connected to a hand switch (ON/OFF) and then to a circuit breaker. My question is as follows: as a standard or following safety requirements, would it be better, if phases are first connected to a circuit breaker and then to a hand switch?

Thanks in advance.


texts: 5V regulator circuit with MOSFET. Will this catch on fire?

texts:
I have a circuit that takes a 5V output from a USB bank with 10000mAh and supplies MOSFET1, whose drain (5Vgreeni) then goes through a fuse to a 5V regulator circuit.
I don't have any heat sinks or fans.  The power supply needs a capacity of 2amperes but will most likely regularly consume about 700mA.
Based on this I don't think my MOSFET1 (FQP47P06) needs active cooling or a heatsink, but there is another MOSFET in the circuit that is a bit smaller and I am not so sure about it.  With the ambient temperature in the box exceeding 100F at times I am concerned that this may be a fire hazard.
Should I be concerned about DMG2305UX-7?

Edit here is another diagram of the circuit:


texts: Enhancement and MPP of a basic Al-air battery with saline electrolyte

texts:
I created a simple Al-air battery in oceans using Aluminum and graphite electrodes with ocean water as the electrolyte. There is no electrical separation between the electrodes due to design constraints (the electrodes do not physically touch each other but are present in the same saline solution)
The open-circuit voltage of the system is ~1.1V and the short circuit current (max) is approximately 30 mA. When a load is added, the voltage drops and current flows through the load. The current, however, decreases slowly while the voltage increases slowly if sufficient water flow is absent. Thus, measuring the maximum power point (MPP) of the system is quite difficult due to variable parameter values.
What is the usual MPP of such batteries? I wanted to find this out because I am using a BQ25570 energy harvesting IC for power management and it has MPPT options.
Also, if I use Al-Zn alloy instead of Al for the anode and activated carbon fabric with MnO2 electrocatalyst at the cathode, will this improve electrochemical performance?


texts: Low or high side switching for ZVS Mazzilli induction circuit?

texts:
I'm trying to teach myself electrical engineering as a hobby and have been studying zero voltage switching induction heating circuits. I'm learning about electronics and designing a circuit as I go along.

Let's say I have a ZVS Mazzilli flyback driver (not even sure exactly what to call this, there are many names out there like Royer etc.) like this, operating on a 12V 8A power supply:

I want to switch this circuit on with an IC but I'm not sure if it would be better to do high or low side switching with a MOSFET.

Would high or low side switching be better? (High side with a P-channel MOSFET and a driver? Or would low side with an N-channel be preferred? And why? I want to learn more about the considerations in a high frequency circuit like this, on a basic electronics level.)
Are there any considerations for the ground plane and return paths? Considering the IC and additional components? Can everything share a common ground plane or pour on a PCB?


texts:
How do I set up a Woodward 2301A load sharing device when operating generators in parallel?

Currently, when running two generators in parallel, the first generator takes too much load, and the second generator trips on reverse-power protection.

PS: We used SPM-A for synchronizer

Woodward 2301A Speed Control

The Woodward 2301A Speed Control controls the speed or load of diesel or gas engines, or steam or gas turbines.
The unit provides control in the isochronous mode, with droop available through an externally wired
potentiometer. The isochronous mode is used for constant speed of the controlled prime mover as long as it is able to provide power to satisfy the load.
The -  2301A Speed Control is compatible with Woodward SPM-A synchronizers, load sensors, and other power generation controls. These controls can be added to the system at any time, using the auxiliary or SPM inputs to the 2301A Speed Control. The 2301A Speed Control is available for forward- or reverse-acting applications, and can be used with single or tandem actuators. High voltage models accept 88 to 132 Vac or 90 to 150 Vdc, and low voltage models accept 10 to 40 Vdc supply for control power.


texts: Re-attaching Tablet Lithium Ion Battery With DC Power Pigtails

texts:
Complete electrical newbie here. Please forgive my ignorance.

I have a tablet that gets "circuit locked" or something. It refuses to detect the charged battery. It seems to charge the battery, but won't turn on thinking there is no battery or the battery has no power. The battery is (was) soldered directly to the circuit board. I detached the battery and hit the power a button a few times to possibly flush out capacitors locking the circuit (if that's how that even works, again, I apologize for the ignorance). After that, and re-attaching the battery, it worked fine. I assume this will happen again, so I want to use DC power pigtails (example: http://amzn.com/B00PZVDPTM ) to attach the battery in a way that can more easily be detached and re-attached.

I'm playing with a lithium-ion battery circuit here. It seems simple, but I'm concerned that I may be overlooking something. Will this work? Does it make sense? Would the DC power pigtails provide the same back and forth charging/discharging circuit that the direct solder to circuit board connection had? Is there a greater short circuit risk using the pigtails?

Thank you for your time and expertise.


texts:
I wanted to make a switched capacitance resistance, like shown in http://en.wikipedia.org/wiki/Switched_capacitor#The_switched_capacitor_resistor. Is it possible to make such circuits on breadboards? If possible is there any IC with we can directly make such circuits?
For what range of resistance values will I get a reliable results? Is there a restriction on what values of capacitance I use.

Thanx..:)


texts: Voltage, Ampere and and Ohm of a DC motor

texts:
This might be a quite simple question. I have a small DC motor (it seems to be this one). This webpage suggests that it needs 6V. I have a power supply which outputs 6V and writes "0.6A". But when I connect to the DC motor it does not turn. Neither with 12V (with the same power supply set to 12V). I tried a power supply with 24V and "600mA". The DC motor works with the 24V power supply, but it turns really fast (probably too fast).

Is it possible that 7,2VA from the 12V-power supply are too few? So the voltage is ok, but it needs more power? Can measure the resistance of the DC motor and use Ohm's law to calculate the amount of Ampere the DC motor needs?

Update: The motor writes RS-54ORH DC491509, that's why I suppose it is the one I linked above. And it actually needs a few Ampere to run! But 6V seem to be ok.


texts: Is there a configuration where a circuit acts as Bandpass filter in one direction and Bandstop in other?

texts:
I am not an expert in electronics. Hence, I am looking for a broad conceptual answer.

Is it possible to a directional Bandpass/Bandstop filter i.e. Bandpass in one port and Bandstop in another.


texts:
Exploring into harmonics this post explains very nicely about the odd and even harmonics with their individual importance. But what comes to my mind is:

What are the sources of harmonics? Why are they generated?
Here is the document from National Semiconductor giving explanation about different terms of ADCs and DACs. And on page 19, it talks about symmetrical non-linearities are responsible for odd harmonics and half rave rectification is responsible for even harmonics(specifically ADC and DAC). But when I tried to search about half rave rectification on Google, I didn't get anything useful. Anyone please explain about the terms symmetrical non-linearities and half rave rectification and how are these responsible for harmonics generation.


texts: EMC2, Arduino & stepper motors - Have I got this right?

texts:
I'm building a CNC mill based on Patrick Hood-Daniel's machines

I'm also playing with Arduinos, and I'm beginning to wonder if I have this right:

I have 5v 1A steppers.

I'll be using EMC2 (Linux-based CNC) to run the whole thing and I had intended to feed the output from the Ubuntu box that's running EMC2 into an Arduino that then splits the data and sends it to three stepper drivers, probably built with sn754410ne h-bridges.

I had thought of possibly building the controllers with an ATtiny2313 per motor.

Is this overkill? Is the Arduino even required or can I feed the h-bridges directly from the EMC2 output?

My main worries are that the Arduino won't be able to control three motors concurrently, although there is a new library available: http://www.open.com.au/mikem/arduino/AccelStepper/ that purports to achieve this, and also that I won't be able to get half-stepping (or finer) with this setup.


texts: How to look at the emitted assembly code of MPLAB X IDE

texts:
I'm using MPLAB X IDE V5.05 to generate the code to program a PIC32MX470F512L.

It happens that i'm having some problems in the code and i would want to take a look at the assembly code.

To program the pic i'm using an ICD 3.

I'm not finding where the assembly code is.

Can anyone help me find it?


texts: Common anode RGB LED lights going out one color at a time

texts:
I have a project involving 4 reed switches and an RGB LED. They are all connected to an Arduino and the code basically says each time a magnet touches a reed switch it lights up with a specific color.  I have a 220 ohm resistor in between each of the three cathode legs and it’s respective digital control pin.
It was working fine and then the red
Light stopped working. And then the green light stopped working a short time later. And then the blue light stopped working about a week later.
The switches are still working fine so it’s definitely something going on with the LED’s.
I have tried other LED’s and am having he same problem.
Has anyone seen this before and maybe have an idea for a
Solution for me!
Thanks!


texts: Can I use a voltage divider and a multiplier to power a 12V component from a 5V supply?

texts:
My idea was to use a the two points in a voltage divider circuit (5V and let's say 2.4V), feed those through a multiplier to power a 12V component. Is this possible? Any problems that may be encountered?

EDIT: I am limited to a 5V supply.


texts:
Consider this circuit.

We apply a unit impulse \$\delta(t)\$ that is \$v_{IN}(t) = 1 \delta(t)\$ volt-seconds. That is, \$v_{IN}\$ is a unit impulse at time t = 0. Since this circuit is driven by an impulse and there is no other source of energy, the capacitor voltage and inductor current at \$t\$ = 0 will be zero.

The problem asks value of \$v_{R_1}(t)\$ at \$t=0^+\$ and \$t=1ms\$ also value of \$v_C(t)\$ at \$t=0^+\$ and \$t=1ms\$

Since a huge current is applied should we assume inductor behaves an open circuit for a short period of time.

If there was only \$R_2C\$ part of the circuit \$v_C(0^+)\$ would be \$\frac{V_{IN}}{\tau}\$ right. And \$v_C(t)\$ would be \$\frac{V_{IN}}{R_2C}e^{-t/\tau}u(t)\$

How should I calculate the value of components asked in the problem.

Also should these kind of problems solved using heaviside operator.


texts: Which electro motor to use for steering a kite? (guestimation marathon)

texts:
I'm doing a pet project in which I want to fly a kite from my computer. For this to happen my plan is to build a little box hanging under the kite which includes a raspberry pi (connected to my laptop by wifi), a battery, a motor controller and an electromotor to pull the cords. I am now in the quest of finding a suitable motor.

In reading around and asking previous questions here on stackexchange I found I would need a basic DC motor including a transmission because they have a high torque-to-weight ratio and are easy to control. Furthermore, I will attach a little wheel (diameter == 3cm) to the motor so that the rope can be hung around it and the motor its force can be translated to rope motion.

Some requirements:

== Minimum Revs/Minute ==

I want to be able to change the rope length about 40cm in 2 seconds. Since the wheel has a circumference of ≈ 9.4cm (π * 3), it has to be able to have at least 4.24 revs per 2s or 2.12 revs per second, or 127 RPM.

== Minimum Torque in Kg/cm ==

I haven't got the kite as of yet, but I want to fly a "very small kite-surf kite" in "moderate wind". This means that at full force it will be able to pull me off my position, but not lift me in the air. So I estimate the maximum rope pull at about 50Kilograms, divided by 4 ropes equals 12.5Kilogram/rope. Since I line the two steering ropes in a loop, pulling one will release the other. This means that the rope being released "helps" pulling the other rope in. Seeing that the rope pulling force will vary between the two ropes and I also have to overcome inertia I guestimate the power needed to adjust the rope lengths at 40% of the total force, or 5 kilograms. Since we're using a wheel with a radius of 1.5cm (diameter == 3cm) we take 5 kilograms times 1.5 which results in a minimum needed torque of 7.5Kg/cm.

So I searched around on websites and found the motors below. All sites are in Dutch, so I just translated the info below.

https://iprototype.nl/products/robotics/servo-motors/metal-gearmotor-50-1

Free spinning:        200 RPM, 300mA, 12 kg-cm
Average force:        1A
Full force:           5A

http://www.conrad.nl/ce/nl/product/227552/Transmissiemotor-RB-35-150

RPM on force          104 RPM
Max. torque           9 kg/cm · permanent 3 kg/cm
Free spinning at 1,5 V    120 RPM (why 1.5 volt if its a 12V motor?!?)
Max. Current          2.1 A

http://www.conrad.nl/ce/nl/product/244023/Igarashi-transmissiemotor-150-type-33G

Max. torque           0.6 Nm (doesn't this equal 0.06 Kg/cm?)
free spinning at 1,5 V    110 RPM
Continuous RPM:       85 RPM
free spinning current:    0,10 A

The problem I have now is that the information is so different (RPM in free spinning vs. with force attached to the motor) and varies so much (12 vs 0.06kg/cm?!?) that I'm kind of unsure of my whole train of thought.

So my question: does it make any sense what I'm writing here, or do I make mistake upon mistake upon mistake? What advice would you give me here? Is the first motor clearly the best, or am I overlooking things?

All tips are welcome!


texts:
My circuit has 3 sections. The supply is 9V.

This goes to a regulator (5V), another regulator (3V) and the 9V is connected directly also to a BLDC. Now, when I start the motor (this is done in brake with braking action), I see some curves, something like capacitor charging up. I have 2000μF aluminum electrolytic cap in the voltage rail as well.

Even when I remove that, I see these spikes. So there must me some parasitic caps that seem to be charging and discharging. I then inspected the regulator o/p. Both the regulator o/p inductor showed immense noise (the voltage transients was almost 1.5V, and it was existing throughout the motor operation).

The circuitry:

The regulators are:

The images in order are:

9V- 5V regulator
5V to 3.3V
LiFePo4 charger chip
Controller to BLDC circuitry

How do you want me to show the layout/PCB? How can I sort this out? Is the motor action causing spikes back into my circuit to make the ground noisy?


texts:
After making the PCBs, we decided on some bodges and implemented them on the PCBs. What's the standard way to document that on the schematics?

For now, I hand drew with the mouse, paint style, on the schematics PDF files, to convey the idea that it's a bodge, but is there a better way?


texts: How to implement this design in ADS(Advanced Design System)?

texts: I was trying to implement this design in ADS. I have used coupled lines with all the dimensions but didn't get the expected result. Can anyone instruct any better way.


texts: Turn off circuit using microcontroller signal

texts:
I want to turn off this circuit using micro controller signal to base of Q4 transistor. Can I use the same transistor model for Q4 as for Q3? I'm attaching the picture of schematic from Proteus Simulations. The SPST button above latches the supply to turn on or off when pushed momentarily. The below given SPST button will be replaced by micro controller which will give signal to base of Q4.

The circuit will be driven by 9V battery or AAA battery cells. The output of this circuit is feeded to voltage regulator and then to micro controller.

I want transistor model for Q4 which will be able to absorb current from above circuitry and the base resistor value also?

The schematic is given below:


texts:
I tried hooking up a Raspberry Pi (+Hifiberry needs 12 V to 18V input voltage) to my classic car (to be used as music player, radio, BT speaker, no screen, only 2 rotary encoders to navigate through spoken menu). It functions great when connected to an AC/DC convertor connected to the mains, also built in the car when connected to the car battery with the engine off, but with the engine on it starts to behave strange (cutting out music, not responding correct to the rotary encoders). When I turn off the engine all problems dissapear.
As a test I tried it built in the car, with running engine but with power from the AC/DC converter from the mains (so not connected to the car battery/ground at all) and then all is OK.
I already had a buck/boost convertor in my configuration to provide a stable 12V during start and charging from the alternator. I measured the voltage with running engine and its stays at 12V so the buck/boost convertor is working ok. I also did an additional test with a higher output voltage from the buck-boost to 16V and let the Hifiberry regulate it from there, but that also didn’t solve the problem.
So my guess is that the DC power from the car with running engine is not clean enough for the Pi and electrical noise caused by the engine is messing things up and apparently the buck/boost isn’t correcting that either. At the moment I do not have an oscilloscope to measure the signal to see what is going on.
My guess is that I have to put a capacitor in my system to filter out the noise. I thought about making a low pass filter with a resistor in the positive and and a capacitor in between the positive and the ground but as the audio system pulls about 36W max it could draw 3A causing a massive voltage drop over that resistor so I don’t think that would work.
I did find this wiring scheme suggested to use in a car environment (other type of voltage regulator):

I think I will try to use the large capacitor this way but I’m wondering why there is no resistor in series with the capacitor (both in between positive and ground) to limit the charge current. Wouldn’t this scheme lead to a very high charge current at t=0, blowing the fuse? Or would the time be too short for that?
Any other suggestions what could be causing the issues with the audio system?
Thanks for your time.


texts: Why does my MOSFET only allow current when it is switched polarity (drain to GND)?

texts:
This circuit acts strangely.
I think the MOSFET is correctly placed. However, whenever I connect it to the power supply (1V 0.1A for initial testing) it doesn't let any current through - unless I switch its polarity, as in the drain connected to ground and source to positive side of the battery. I then get 1A of current and around 0.6V. I am not sure why this is. How can I fix it?
This is the code:
int FETPin = 6 ;

void setup(){
  Serial.begin( 9600 );
  pinMode(FETPin, OUTPUT);}
void loop () {
    analogWrite (FETPin , 255) ;
    delay(500);
    analogWrite (FETPin , 0) ;
    delay(500);}


texts: How to distinguish between voltage resolution and bit resolution

texts:
One might way that an ADC has a resolution of 12-bits. One could also say that it has a resolution of 1.22mV (5v/4096).

Is one of these uses of the word 'resolution' incorrect?

Is there a word to replace one of these uses of the word 'resolution'?

Context: I am trying to write a datasheet. In the electrical properties table, I wish to describe the properties of the DAC outputs.

However, I seem to have used the word 'resolution' twice. This seems wrong to me. Is there a better word I could use for one of these?


texts:
I am building a vaping mod box. I am using two LG HG2 18650 LiPo cells in parallel1, 2P, and require low voltage cut out, of around 3.8V2. The current draw will be up to 10-15 A (max).

I have looking for a solution for about a week now, and have looked at most, if not all, of the questions posted here, related to LiPo protection circuits, and most of the answers don't really seem to fit my requirements or seem overly complicated - by including over charge protection, reverse polarity, dealing with cells in series, etc. I will not be using this circuit to charge the cells in-situ, as I will charging them using an external charger.

The question that came closest to what I what is Circuit to protect against undervoltage? and endolith's answer, which uses a TLV3012, seemed to most succinct and simple, until I got to the comment about hysteresis being required for battery protection.

This is the circuit in question, suggested by endolith (this circuit shows a 2S configuration, but I am using 2P):

To achieve the 3.8 V cut-off:

R1 = 2.06 MΩ (or 1.98 MΩ for 3.7 V)
R2 = 1 MΩ

I can obviously change this ratio as required, and lower the cut-off if need be. However, I am less concerned by the cut off voltage (which can be another question topic all by itself) than I am about the suitability of the circuit. The output of the comparator goes to a PFET to switch the current to the coil, and the rest of the circuitry:

My question is two fold:

Where would the resistors for hysteresis be added?
As that question was eight years ago, is this still the simplest solution, with the lowest component count? I realise that this second question could be considered opinion based. I know that there are a number of ready made PCBs out there, but I want to avoid using something like that3.

1 Although I may consider using just one cell if the safety aspects so dictate, or the required circuitry gets overly complex. However, I can't see why it should, because there is no need to monitor individual cell voltages of cells in series, as I am using a parallel configuration.

2 I have chosen a 3.8 V cut off as that is the highest value that I have seen suggested in some RC forums and vaping blogs. However, I could chose another value, if that would give a better life cycle. I have heard of people recommending a range of values between 3.2 and 3.8 V  and don't know which value is correct, or who to trust, so I took 3.8 V to be the most conservative.

3 I have also seen a voltage detector, NCP300, but the NCP300 seems to be more of a solution to inhibit the triggering of the coil firing FET. I am looking for more of an electronically triggered "master ON/OFF switch" type behaviour based on low battery voltage


texts: NFC antenna connection to ground midway through loop

texts:
I'm designing a PCB etched NFC antenna. I'm confused about a design element I've seen in several production boards. I haven't seen this element explicitly discussed in any app notes or design guides.

On many of these nfc readers, there's a connection to ground on one of the loops in the antenna. On the pictured board, the next-to-outermost loop has a ground connection. What is this? In antenna design calculators basic loops are always implied, and I'm hoping to use these calculators to assist in my design. How will this ground connection affect my calculations for the matching circuit, etc?


texts: How to calculate amp for a power supply?

texts:
I know zilch about electrics.
Basically we have a power supply that my cousin has, and for some reason she wants to know what the amp is. The information I'm being given is:

INPUT: 230V~AC 50Hz 100mA
OUTPUT: 9v~AC 900mA 8.1VA

I don't know what this means. Can one of you kindly tell me what the amp is? I've Googled but we don't understand the jargon.
Edit: the power supply is for a regular alarm clock and it's meant for use with UK electrical outlets if that helps. As far as I'm aware, 230V is standard and safe in the UK. My cousin just told me she's using an extension lead with 4 power outlets and it'll take a total of 13 amps safely. She already has a couple of other things plugged into it. She wants to know the amps of the alarm clock to be sure it's safe to plug into her extension.
TIA


texts:
I'm trying to add the mmbt3904lt1g model to LTspice.
- I've copied its data from the MMBT3904LT1.LIB.txt in the standard.bjt library.
- I've added an NPN to my schematic then I've changed its value to mmbt3904lt1g
- through the Edit->spice directive I've pasted the path to this library
I thought it was all to use this device but no simulation is achieved.. I get only:
Can't find definition of model "MMBT3904LT1g"

where I'm doing wrong ?


texts: What temperature should a LiPo battery reach during charging?

texts:
I was attempting to charge a LiPo battery using a bench power supply as described by Dave Jones.

The battery is a PowerTech 18650 2600 mAh 3.7V model SB2308. The datasheet appears to be here.

The relevant part of the datasheet is:

I didn't quite understand the charging rate of 0.2C5 A - would that be 0.25 C (650 mA)? I thought that, if you used the units symbol in the middle of the number it would be at the decimal position (ie. "0C25 A").

To be safe I charged at 0.2C (520 mA) with the supply configured to switch to constant voltage at 4.18V.

I charged for almost 5 hours, monitoring the voltage, like this:

However at the end of that time I noticed that the cathode was about 75°C, and the anode was about 95°C. This seems somewhat hot to me. The datasheet says the charge temperature should be 25°C, but I took that to be the ambient temperature, not the battery terminal temperature.

My questions are:

Is a terminal temperature during charging of 95°C too high?
If so, what should it be?
If so, why would this have happened to a new battery? In other words, what is wrong with my technique?
Is it possible that charging at a lower than recommended rate be the reason?

The battery had been discharged at 520 mA rate to 3V before charging commenced.

  How did you measure the terminal temperatures, and what temperature did the main body of the cell get up to?

I had been periodically touching the cell body with my finger, and it seemed to stay at room temperature.  I accidentally brushed my finger against the terminal and got a mild burn. At that stage I tested the temperature with the temperature probe from my multimeter.

  But maybe the heat is coming from the charger or a poor connection at one of the terminals is heating up, etc.

I didn't think of that, but perhaps a slightly poor connection between the battery holder and the battery terminal, carrying half an amp for hours, would heat it up.

Some comments and answers have suggested that there was a poor connection between the battery holder and the battery. Below are images of the terminals in question:

The cathode in particular seems to have a blob of plastic or something on top of it. Measurement with a multimeter seems to indicate that there might be a resistance of 10 ohms depending on where the contact is made.


texts:
With a couple of friends I am designing a synthesizer on an altera FPGA (cyclone II, the one on the DE2 board). We almost wrapped it up nicely but there's a problem that bugs us.
The synth can generate four kinds of sound waves: sinusoidal, square, triangular and sawtooth. The user (the player) can change the wave while he's using the synth of course. In our first solution the perceived volume changed greatly between the various waves, square being the loudest and sin being the lowest.
We calculated the normalised power of each kind of wave and added a corrective factor for the amplitude:
$$\sqrt{\frac{2}{3}}\rightarrow \text{sine wave}\\
\sqrt{\frac{1}{3}}\rightarrow \text{square wave}\\
1\rightarrow \text{triangular wave}\\
1\rightarrow \text{sawtooth wave}$$

The problem is that the volumes still don't seem right, the sine wave seems still way lower than the others. We were a bit unsure about the power of the triangular wave, but our calculations should be correct. We then thought that our first assumption was wrong.

Question: is it correct to assume that the perceived volume of a sound wave is proportional to its power intended as the power defined in signal theory books, i.e.:

$$P_x=\frac{1}{T}\int_0^T|x(\alpha)|^2d\alpha$$
of course \$x(t)\$ must be periodic of period T.
If that is true: did we miscalculate something? We are listening to the produced sounds through a guitar amplifier so the band probably is not that wide, but that would lead to a lower square wave and a louder sinusoid if total power is the same.


texts: Why do my compact fluorescent lamps keep dying?

texts:
I know that this question may be off-topic here, but I'll ask it anyway since they do have electronics inside.

I've noticed that my fluorescent lamps keep dying after only couple of months of use. When they die, they die in groups of 2-3 and as far as I can see, both new and old lamps may die during such events. As far as I can see, electronics inside dead lamps look normal to me, but then again, I don't have much experience in electronics, so I could be wrong.

So I'm asking you people what could be the cause and how can I prevent it? I'm thinking about bad electricity supply, because I have frequent brown-outs, but as far as I can see, deaths of lamps aren't more frequent during times when I have brown-outs. I'm thinking about connecting lamps over a UPS or "power conditioner".

UPDATE:
I did some investigating and I think that I've found source for my problem. As I mentioned, I had brownouts. I noticed that nobody in my area had brownouts, so I the problem was probably with my installation. Then I noticed that voltage for two phases was between 220 V and 230 V, as expected, but one was between 190 V and 200 V. The main cause for that seems to be a 35 A DIAZED DIII fuse which is connected to the phase which powers my lamps. It turned out that the tip of the cartridge and fitting element of the fuse case were corroded and were sparking and overheating (the cartridge was so hot that I had difficulties removing it). It also turned out that when power company replaced my electromechanical meter with solid state meter, they installed new circuit breakers in such way that fuses are serially connected to breakers and are "downstream" from them. I talked to few electrical engineers and electricians and they all believe that since circuit breakers are installed, fuses should be removed. I'll get an electrician to remove them will report back how that effected lifetime of my lamps.


texts:
I am looking for a motion sensor device that can track person/animal walking by it and record time/date of the event(s).  It needs to be able to run on a small battery or two (maybe 2 AA's or a 9 volt).  It does not have to have a screen, just an input connection for a screen to hook up to in order to read the information and set the device.

Total cost would be only like $10 to $15.  My initial research on the internet points me to look at a pyroelectric infrared sensor or some kind of passive infrared sensor.

Is it possible?


texts: Help understanding PIR amplifier analog circuit

texts:
I found a PIR amplifier circuit and would like to understand better how/why it works. The purpose is mostly to learn more about analog electronics.
I found the following circuit here: PIR motion detector circuit electronic project.

The raw PIR sensor (not one with built in circuitry) outputs approx 1v and has swings in either direction from this by approx 10mV depending on motion. The signal is quite noisy though.
This is the raw output of IRA-E700 (without lens) with R1, C1 and R2 from the schematic. If i move my hand over it i can see the average voltage rising or dropping by 5-15mV.

My assumptions from the schematic:

IC1D is an amplifier, IC1C & I2CB comparators and IC1A compares the results of IC1C & IC1B

IC1D is configured as an inverting amplifier with a gain of -29.6x. This gain is set through (R6+R4)/R3.

C8 adds a low pass filter. C2 + R3 add a high pass filter. Together these give an active band pass filter.

With VCC=5v the voltage at pin 12 of IC1D is 1.544v through the voltage divider R7, R8, R9, R10:
$$5 \times \dfrac{R9 + R10}{R7 + R8 + R9 + R10}$$

IC1C has a bias of 1.674v (set by the voltage divider R7, R8, R9, R10). Any voltage above this will have the op amp output go to GND, otherwise VCC.

IC1B has a bias of 1.413v. Lower voltages make the output go low.

IC1A compares the outputs from IC1C and IC1B to 1.413v. A low on either op amp before will cause the output here to be low, in effect giving us digital logic out (active low).

VCC can be anything within the limits of the PIR sensor and op amp (no values would need to be changed for 3.3v operation for instance)

While I think I understand the general circuit I have some questions about the details:

What does R2 do?
What is the purpose of R5 & C4? I guess the capacitor would charge over time, adding another low pass filter?
What is the purpose of D1?
C3 is another low pass filter?
How would i calculate the frequency response of the whole system?
Anything i missed or overlooked?

Potential changes I could do (?):

Change R3 to a 50k resistor and 50k pot in series. This would allow me to change the negative feedback and set the amplifier from 22x to 44x, effectively affecting sensitivity (for instance to avoid pets).
Change R5 to a pot. This would allow me to change the frequency response so it wouldn't immediately react but instead trigger only if movement has been present for a while. No idea how or why this would work though. Are there other ways of doing this?

If you have other examples of PIR circuits (preferably with explanation) that would be greatly appreciated too!


texts: Three Phase Power (Delta Source connected to Delta Load)

texts:
simulate this circuit – Schematic created using CircuitLab

Will the magnitude of the current through the delta sources always be equal to the magnitude of the current though the delta loads?   I have searched online, read the textbook but cannot get a definitive answer.  The circuit displayed is more for visually purposes only.  I do not want to know the values.  The loads are the capacitors (which could be anything as long as the same) and the sources are the sources.


texts: What are the available solutions for a 8-input OR function that is 74xx compatible?

texts:
I need to implement an 8-input OR function that is compatible to IC chips of the 7400 series.

I already found a few solutions, but none of them is perfect. A perfect solution would be an OR-gate chip of the 7400 series with 8 inputs and a reasonably low propagation delay (<30ns).

The only 74xx OR-gate with 8 inputs is the 744078 (OR/NOR multifunction). The only versions of it that I could find in stores was the CD4078BE by Texas Instruments, but unfortunately it is horribly slow (300ns @ 5V).

Another solution is to use a 8-input inverter with open collector like the SN74ALS762N and then simply connect the outputs to an inverter. The chip is also quite fast, but unfortunately not available in the store of my choice.

Yet another solution is to use two 4-input NOR-gates like the CD74HC4002E combined with a NAND-gate.

I could also invert the inputs and then use a 8-input NAND-gate.

Are there any better solutions that I'm not aware of? Are there other fast 8-input OR, NOR or buffer/inverter gates (with open collector) than the ones I mentioned?

UPDATE:
I found another chip, SN74BCT756N, an open collector inverter with 2 x 4 inputs. For whatever reason, the 74756 and 74757 are not listed in Wikipedia's "List of 7400 series integrated circuits".


texts:
I am modeling LDO using ZXCL280 Datasheet. By understanding datasheet dropout voltage of the PMOS is seen as 1.46Ω(From page 5 Ron=Vdrop/Id = 220mA/150mA ). I assumed this Ron is including Rs and Rd (Source and Drain resistance). So while calculating Kp value using this formula

Ron=1/Kp(Vsg-Vt)

Considering maximum current as 150mA dropout voltage is 220mV from the dropout vs drain current plot

Vsg-Vt= Vsd = Vin-Vout = 220mV

I am assuming Vout to be 1.8V so Vin will be 2.02V

By substituting values to find Kp

Kp=1/1.46*(220mV) =3.24A/V^2

I began to simulate dropout test case schematic and waveform is as below

I this can be corrected by adding Rs and Rd in the model card to add up to Ron(Rds)
But i should have got 1.46Ω without adding. Is there anything that I am missing or wrong?

Second Method:

I rearranged Id equation to find Kp (this is the only value that i get to set Ron in PSpice model card)

Kp=W*Id*2/L*(Vsg-Vt)^2

W and L is 1 default so,

Kp= (150mA)*2/(220mA)^2 = 6.198 A/V^2

But even this method didn't attain any joy

Is this the right way of setting Ron(Rds), if Vsg(Vgs) is not mentioned or given ? If Vsg is provided  how should I proceed and If not provided how should proceed ?
How shall I look at output and Input characteristics relation with Ron?


texts: Are the currents that travel on the outside of coax really "common mode"?

texts:
Consider a ladder-line transmission line. Given any currents on the two conductors, we can describe those currents as the current on each conductor individually, or:

currents that flow one way on one conductor, matched by exactly equal and opposite currents on the other (differential mode)
currents that flow one way on one conductor, matched by exactly equal and like currents on the other (common mode)

That is, the common-mode currents are common to both conductors. This is neat, because I can reject the common-mode currents and measure just the differential-mode signal with a transformer or a differential amplifier:

simulate this circuit – Schematic created using CircuitLab

But, consider an ideal coaxial transmission line. The currents are:

currents flowing on the inner conductor, matched exactly by equal and opposite currents on the inner side of the shield (differential mode)
currents that flow only on the outside of the shield

I've heard it said that "common mode" currents flow on the outside of the shield. But are they really common? They aren't flowing on both conductors. Therefore, I can't reject these currents with a differential amplifier or transformer:

simulate this circuit

Therefore, is it really proper to call these currents "common mode"?


texts: Confusions on FFT of a square-wave in theory and in scope and simulation

texts:
Below is an ideal square-wave in time domain, and its harmonic components in freq. domain:

As you see above a square-wave is composed only of its odd harmonics as spikes nothing in between.

And below is an oscilloscope's FFT of a square-wave:

Here we see two things are different. First of all the above FFT is not composed of spikes but widened curves. Secondly it is continuous not discrete.

Maybe scope may involve some noise and the non-zero rise time of the square-wave might effect the FFT results.

So instead of scope lets look at what LTspice shows the FFT of a square-wave(pulse-train in this case) with the following setup:

Here is the FFT:

This doesn't look good either. So I set the rise times much shorter than LTspice's default as follows:

Now the FFT became better:

Now I can see one of the problem when viewing FFT of a square-wave or a pulse in a scope the rise and fall times are never zero. The other problem is there is some noise involved.

Here is my question:

Here is what I don't understand.. At the beginning I provided a spectrum of an ideal square-wave which was discrete odd harmonics as spikes. But both in scope and in LTspice the FFT is continuous.

I'm confused at this point. Let me give an example. In my last plot above, the pulse frequency is 100Hz. So I would expect it is composed of its odd harmonic sinusoids of 300Hz, 500Hz, 700Hz,.. so forth and so on. I wouldn't expect it would have 130Hz component for instance or 102Hz. In fact according to the last FFT plot there is component at 102Hz and it is even greater than 300Hz component.

Any idea which one represents reality here? What am I knowing wrong?


texts:
I have created 2 different PWMs using timer 1 and 2 on ATmega8, that is used to control a linear motor. I'm using a hall effect sensor to detect changes in voltage as the linear motor moves left and right. This change in voltage I feed into a ADC pin in the ATmega8 in order to convert it to digital. Then I basically use the USART functions of the ATmega8 to display the voltage the hall effect sensor basically detects.

I'm running the ADC in free running mode with interrupts to continuously detect a hall effect value.

The problem im having at the moment is that as soon as the interrupt is called to read the adc value i have a function in the interrupt that involves transmitting the adc value to the screen.......

Currently what happens is that as soon as I do that the PWM stops working, its as if the program is stuck in the interrupt in an infinite loop.

However, if I remove the serial transmission function, the PWM starts working again which confuses me?

//TRANSMISSION FUNCTION

 void USARTWriteChar(uint8_t data) {            //Wait untill the transmitter is ready

    while(!(UCSRA & (1<<UDRE)))
      {
    //Do nothing
      }

     UDR=data;
  }

//Main function containing PWM

  while (1)
   {
    OCR1A = Push1;                                  // Output compare register A Time 1
    OCR1B = 0;
    _delay_ms(400);                                 // set on time A

    OCR1A = 0;
    OCR1B = 0;
    _delay_ms(400);                                    // set dead time B

}

 //Interrupt function

  ISR(ADC_vect) {
   read = ADCH;
   USARTWriteChar(read);
 }

I am running the ATmega8 at 8Mhz clock frequency with BAUD of 9600.

However when I take off USARTWriteChar(read);  (still keeping rad = ADCH ) from the ISR the PWM works meaning the ADC interrupt is not causing problems but USART is for some reasons.


texts:
I was reading into Electromagnetic Compatibility Engineering by Henry W. Ott about ESD protections and I was interested by the following part.

  First, a series resistor (or ferrite) added in front of the
  diodes to limit the magnitude of the ESD current, and second, additional bulk
  capacitance (5 to 50 mF) added across the power supply rails. Both of these
  approaches are shown in Fig. 15-18B

This picture reminded me of the schematics seen inside a TVS Diode. The TVS diodes I am using up till now are the TVS DIODE (würth 8240116)

Can the shown figure actually be compared to a TVS diode?
If so, can the functionality of TVS diodes be improved by adding the
current limiting series resistance and a bulk capacitance?
Why aren't any of these improvements suggested in the datasheet just
like decoupling or bypass capacitors are recommended in every IC
datasheet?


texts:
After reading the Oscillator design guide for STM8AF/AL/S, STM32 MCUs and MPUs pdf, I have found very little information available for me to make a decision on which oscillator will best fit my project.
I am looking to for an 8 MHz oscillator that will satisfy the requirements on the guideline, however it is pretty difficult to determine all the requirements if you still don't know the C_s (Stray capacitance) of the crystal leads and pcb traces on my board (I still haven't printed/designed the PCB).
So, knowing just a minor number of requirements what do you have suggest I do? I need to find an 8 MHz that will be a good fit for an STM32F446RC for audio applications.
EDIT: Documentation: https://www.st.com/resource/en/application_note/cd00221665-oscillator-design-guide-for-stm8afals-stm32-mcus-and-mpus-stmicroelectronics.pdf


texts: can we achieve signal compression by reducing the sampling rate?

texts: Does the reduction in sampling rate causes compression of the signal? If yes, can you please provide me some specific example?


texts:
I am a total electronics noob trying to start out, so I purchased a small solar panel, of 110x80 mm, of 5V and 200mA.
However, when I tried it this morning and connected it to my multimeter, I only got a reading for the voltage (around 5V, regardless of whether or not there was any light shining on it). I could not get a reading for the current (only 0), even though I put it in direct (altugh very faint, for it is morning in the winter) sunlight. These are two pictures of front and back side.

I thought that I should get some current every time there is any light, even though it could be very small. Why is this not so? Also, I thought that the voltage would be less if it is not on direct sunlight. How come this is not so?

EDIT: Here is the setup I use for measuring the current. It isnot under direct sunlight at the time of the photo, but same results occured when it was.

And this one is for the voltage:


texts: Can anyone indentify this SMD component?

texts:
I'm trying to identifiy this component. I assume that it must be some kind of mosfet or bjt. Can someone point me to a Manufacturer Part number or datasheet?

The component is used in the circuit to blow a fuse. Its basicaly a 1-bit memory to permanently store an error condition.


texts: Are the MUX with 3 inputs and AND with 2 inputs gate the same?

texts:
I have a MUX with 3 inputs, a, b, and reset. The b input is always low. Is this the same as an AND gate with 2 inputs, reset and b?

I used the truth table to figure out this question, and I thought the answer is no, but my friend said "yes". So i am confused now, can anyone tell me the truth?


texts: Microcontrollers - disconnect I2C and Serial lines after loading from EEPROM

texts:
I am using a P8X32A (Parallax "Propeller" microcontroller) in many of my hobby projects.  It has no NV RAM internally on the chip so it loads its program code from either a serial port TX/RX pins or from an I2C EEPROM (24LC256) on SDA/SCL pins.  This loading is entirely handled by the silicon on the micro and cannot be altered.

It takes no more than about 2 seconds or so for the code loading process to complete, after which time those four pins become fully general purpose IO in the 4 MSBs of a 32bit GPIO port!  That's a pretty great feature, but it does mean I need to treat those 4 pins as a special case, which is not ideal.

From the P8X32A Manual v1.2 (page 17).  The jagged red line indicates the 4 signals I want to redirect after booting has completed.

For a future project I'm planning I would like to use all 32 pins of this GPIO port for high speed IO but I do not want to still have the top 4 pins connected to the serial port or the I2C bus.

My question:

What would be a robust, minimal part-count method for automatically severing the I2C and serial port lines from the microcontroller a fixed time after coming out of RESET state?

I can think of a few ways initially, but they have disadvantages...

Have an I2C controlled 4 pole 2 throw digital switch IC that shares a reset line with the microcontroller.  At startup the 4 signals are connected by default to the I2C bus and serial and then the first thing that the program code does is to send an I2C command to that switch to toggle away from the I2C bus.
Use an externally generated signal (basically a dumb timer or a cheap secondary microcontroller that can respond to the reset pulse) to toggle a "normal" logic-level activated switch.
Put a second small microcontroller (e.g. ATTiny2313 or similar) in between the Propeller and the EEPROM, then simply have it count the number of bytes that passes through it and then shut down it's own IO completely until the reset pulse.

I don't like (1) because I'd need to implement the small bit of I2C in my program code, which is annoying but doable, but the main problem is finding a suitable I2C switch in a SOIC/SOP package.

I don't like (2) because it adds some potential for glitchiness or timing issues to creep in.  Or if I go with a second microcontroller (ATTiny5 for instance) I'd have to have either a programming header on the board or have the chips pre-programmed off board.  A hassle either way.

I don't like (3) because it's alot of work and adds a second set of fairly fiddly firmware to the project, which I'd rather avoid.

I suspect I'm over-thinking this, is there a better way to disengage an I2C bus completely after I've finished using it?

The "high speed IO" I want to have all 32 GPIO pins involved with will be 3v3 digital logic running anywhere between 1MHz and 40MHz.


texts: Connecting an analog temperature sensor IC to an ADC input of a microcontroller

texts:
I am trying to connect an analog temperature sensor LMT84 (http://www.ti.com/product/lmt84) to a micro controller (3.3VDC) using its ADC pin which is 1.4V tolerant (max).
My Vcc is 3.3V, ADC max input is 1.4V and temperature IC minimum voltage is 1.5V. Two options I could think of is, either to place a voltage divider at the input of temperature IC source or at the output of temperature IC. Schematics shown below

Option 1 Schematic

simulate this circuit – Schematic created using CircuitLab

Option 2 Schematic

simulate this circuit

Can someone please help me with choosing the correct schematic (considering the pros and cons) and calculate the resistance values of R1 and R2 (internal input impedance of the Microcontroller ADC is high i.e 200K approx).


texts:
I try to simulate an RLC circuit depicted in the annexed file. I have noticed that ngspice is not able to compile two capacitors which are connected in series. The netlist is written as follows:

    * The global plasma model
    VRF 0 1 SIN(0 100 0.275732
    CBC 2 1 5.25154
    Cs 3 2 0.1407107F
    RB 4 3 5.25154
    LB 5 4 212.692
    VG 0 5 dc 10
    .END

This circuit can't be solved transient. I get the following error or warning message :

Warning: vrf: no DC value, transient time 0 value used
Warning:singular  matrix: check nodes 2 and 2

I would be very grateful, if somebody can give me a Hint on what went wrong. best regard
Nina


texts:
I made a module with EAGLE's 'module' feature.
Layout of multiple instances will be almost the same so is there a way to assign a layout to the module so that I don't have to do the layout for each module manually?


texts: I would like to ask about the volt-ampere (VA) rating of UPS. Is there any effect of this value in terms of the time period that the UPS can supply the power?


texts:
I am going through this datasheet of a photo-transistor from Fairchild Semiconductor.

Problem-1:  I cant figure out the gain of the photo-transistor (like in other normal BJTs). There is something mentioned Current Transfer Ratio which I guess has something to do with the gain of transistor. Not sure though.

Problem-2: Why does the manufacturer mention two different values for "Collector- Emitter Breakdown Voltage" and "Emitter-Collector breakdown Voltage"? If one says 100V, should't the other say -100V? If the collector is forced 105 V with respect to emitter, the breakdown occurs. This also means my emitter is at -105 V with respect to collector. So why not just the reversal in sign for these two parameters?


texts:
With my firm we're trying to get the CE certificate for our device and one of the tests is the protection against power surges. For this, the test company is using a device that's connected to our device's 12V power input and gives +500V surge for 1.2 microseconds. For this test, we included a TVS diode parallel to ground to our schematic, and the final schematic looks like this:

D18 is an 18V TVS diode, SMBJ18A-HT. U12 is the voltage regulator,

In its datasheet, it's stated that SMBJ18A has a surge current of 20.5 Amperes, and a clamping voltage of 29.2 Volts. This looked satisfactory to our circuit, as our voltage regulator works between 5-36 Volts.
In the actual test however, the TVS diode failed and shorted out, causing the power wires to burn and melt.

Is there any error on the choice of TVS diode for this purpose or should we use a different sort of protection for the 500V surge?

Regards,
Alp.


texts:
I am designing a four layer board in which a patch antenna is used for a GPS receiver.The antenna's feed  is a through hole and  reaches the bottom of board, where it meets a  50 ohm transmission line. The bottom of patch is filled with ground  but the layer adjacent to the ground filled layer is a power plane.

Should the layer adjacent also be ground or will this influence the performance of patch?


texts: How do utility companies treat voltage deviations in distribution networks?

texts:
I live in a region where nominal mains voltage is 220 volts and state standards permit deviations within 5 percent continuously and within 10 percent for short periods. So if I measure the voltage in a wall outlet in my apartment and see it is 180 volts or anything else out of range I can file a complain with the utility company and the company is expected to somehow treat that voltage anomaly.

My question is - how do companies actually treat voltage deviations? What equipment do they have on the distribution grid that can be adjusted so that the voltage in my wall outlet gets back to permitted range?


texts: Implementing a counter in VHLD with edge triggered clear

texts:
I'm still giving my first steps learning VHDL and after a couple of days I could not yet find a solution for this problem.

What I'm trying to do is to implement an LCD controller on an Altera MAX II CPLD that will receive signals from an existent device.

One of the signals is the frame signal that is high while a frame is being received and low otherwise. I also have a clock signal that changes state from low to high for each pixel data available.

On my CPLD I have a line and a column counter that need to be reset on the first rising edge of the clock, after the beginning of each frame and the column counter needs to be incremented on each rising edge of the clock.

What I'm trying to achieve is represented on the following diagram.

The problem I'm facing is that if I try to reset the counters on the rising edge of the frame signal and increment them on the rising edge of the clk signal I get the following error:

Error (10821): HDL error at AddressController.vhd(116): can't infer register for "line[0]" because its behavior does not match any supported register model

I think that should be an easy way to do this but I'm having trouble to figure it out.


texts: Linear regulator using emitter follower and operational amplifier

texts:
I have understood that you can create a linear regulator using a high-current BJT power transistor in the emitter follower configuration and one operational amplifier (and a voltage reference, which can be a voltage source or some kind of Zener diode or similar).

How does such a circuit work?

What is the minimum supported voltage drop of such a circuit? Is it worse or better than dedicated linear regulator ICs?

Are there any reasons to use such a circuit in the modern days where adjustable-voltage linear regulator ICs are widely available at a very cheap price?


texts: I am working with an RGB LED. For my project I need just green and red light but I don't want to add two separate diodes cause they need to be at the same place. I don't have so much space on MC so I was thinking of not connecting blue wire. Is that ok? If not I should extend MC?


texts: What does high fault coverage digital vector at an IC module mean?

texts:
I'm reading some specification docs on some integrated circuits and I came a cross this definition which I'm trying to understand.

  This provide the capability of running high fault coverage digital
  vectors at IC module


texts:
I'm designing a circuit to detect presence of AC line voltage. It's actually a very simple device with AC side made up of a 200Kohm 1W resistor and an optocoupler and a protection diode.
There will be sufficient gap between AC line side and output of the optocoupler. Entire board will then be covered with resin or silicone compound to permanently secure it inside a case. I am having hard time to interpret clearance distance in this case. Do we consider ONLY air gap when determining clearance distance? Would it be reduced if we have filler like in this case?


texts: What would it take to rebuild an appliance for 120v

texts: I want to purchase an appliance (it's a shirt ironing machine called a Tubie) that is made in Germany. It is designed to work with the 250v electrical system used there.  The appliance is, basically, a heating coil and a blower fan attached to an inflatable torso.  Would it be possible to replace components in this appliance in order to make it work on our power system here in the US?  If so, what would that entail?


texts: How can I protect a microcontroller from memory corruption due to buffer overruns?

texts:
I have recently been working on what I believe is a buffer overrun problem in a microcontroller with software that I wrote. I'm using an Atmega328PB, so it has no such thing as a MMU or address space isolation.

Every once in a while, some bug is causing many of my in memory values to get overwritten with a bunch of garbage. I have enabled the watchdog timer and it seems that what usually happens is a total crash of the microcontroller and the watchdog takes over.

However, what seems to have happened sometimes is it overwrites a bunch of memory values and then happens to set the flag byte I have internally for "write this to the eeprom". The microcontroller keeps running happily with these "new" configuration values. Even a power cycle won't allow this to be fixed, since the "new" values are read from EEPROM.

Is there some way I can protect my microcontroller against accidental buffer overrun and underruns? I have had a few ideas such as

Add a sentinel byte that should always be some number. Check this all over the place and if the number is wrong, just go into an infinite loop. The watchdog resets eventually.
Store a checksum of everything that is kept in global memory. There is practically no way random memory corruption would update the checksum to be correct. This has severe performance implications as every write to a global implies updating this checksum. The checksum needs to be validated periodically
Store each value with its own checksum. Each read needs to validate the checksum.

Option 1 is simple but likely not to actually work for all cases. Options 2 & 3 are likely to work but have severe performance & memory implications I think.

Is there an industry standard way to protect a microcontroller from memory corruption in the absence of an MMU?

Clarification:

None of this has anything to do with dynamic allocation or null terminated arrays. All the C-strings I use are stored in the program memory, thus corruption of them would involve and extremely unlikely set of circumstances. Almost every single variable is at a static scope or
is globally shared across the program. I don't use the dynamic heap at all. I can't prove that stack corruption is occurring, but I know that my global values are being corrupted.


texts: How to safely use TRRS socket in order to transfer signal

texts:
In order to build a split keyboard I want to connect the two pieces with a four wire cable. Among the keyboard enthusiasts forums I have seen often the use of a trrs cable which is used as V,Gnd,TX,RX or V,Gnd,SDA,SCL depending on the communication protocol.

Yet, many people have mentioned the problem of short-circuit when the male pin enters or leaves the female socket, because the tip of the pin may contact to the tip, rings or the sleeve of the socket.

Is there a safe way to arrange the voltage, ground and signal pins of the socket in order to avoid any damage due to accidental contact?


texts:
I'm a newbie at designing at the nanopower level, hence my question. In this circuit, I have plastic fiber optical inbound signal that drives D1 photodiode, whose dark current is extremely low (tens of nanoamps). It will be an RS-485 like signal up to 56Kb maximum.

With no fiber optic signal, I need the quiesce current of all components to be as low as possible to maximize battery life. The N-Channel enhanced mode MOSFET BSS138 is used as a switch to drive two outputs: 1) a fiber optic LED used as a repeater, and 2) a UART RxData and external interrupt line into a PIC16LF MCU. R10 was chosen as a Very Weak Pull-up to minimize quiescent current at around 600 nA.

I'm also unsure if my attempts to use the single BSS138 for dual purposes like this is going to work. The MCU UART needs a high signal (RS-232 mark) with no optic signal present. The IF-E96E datasheet suggests it requires many mAs to conduct, so unsure how that's going to factor in.

So, am I on the right track here or heading into the ditch? If it's the ditch, how can I keep component costs and quiescent power at a minimum here?

In particular, when JP2 is not installed, taking the photo LED out of the circuit, will 600 nA be enough current to create flow and voltage drop across the BSS138? How low can I realistically go with R10 and still expect reliable operation?

Many thanks.
Rick


texts: board-to-cable connector type for high-frequency (100-500 kHz), high-current (less than 10 A)

texts:
What would be possible options for board-to-cable (litz wire) connector types for high-frequency (100-500 kHz), high-current (less than 10 A)?
The aim is to have a minimum contact resistance as possible.
I am currently thinking of something like (this connector pairs), but there is no information available on the contact resistance in the datasheet.

Is there any recommended type for this kind of applications?
I am not asking any brands or specific models, but I am interested in different kinds of connector types, e.g BNC, SMA, Banana connectors.


texts: Finding Failed Component in broken florescent lantern circuit

texts:
Recently, I burned out the circuitry in a florescent lantern by accidentally reversing the polarity of the volts in. The circuit seems pretty simple, a transformer, 3 resistors, 3 mono capacitors, a 100uf electrolytic capacitor, a 5609 transistor (it exactly says 5609   5C C  EBC) and a small diode. I am wondering how I can test the components on this and identify which one to replace. I know the transformer works because I put a power supply on one end and a neon bulb on the other, and the bulb flashed when I added power for a second. I also tested the diode with a digital multimeter and got 620 ohms one way and insulating the other, so i am guessing the diode works. So this leaves the transistor and the capacitors. I am most likely sure that the transistor is the failed component, but I have no idea how to test it, and see what is wrong with it. I am guessing that the transistor is used as an oscillator for the transformer to get the right voltage for the bulbs and thus no oscillation means no light. So how can I test the remaining components (especially the 5609 transistor) so I can see what to buy and replace so I don't have to buy a whole new Lantern.

I know I was stupid messing with it and burning it out, and I should have just kept it to its 6 D battery power supply, but I am only 14 and any information will help!


texts:
I've got a project that involves lifting a heavy weight a few feet, holding it there mechanically, and then letting it down safely.  (Assume I'm raising 6000# up 3 ft)

Could the same AC motors I use to lift the weight be used to slow the decent of the heavy weight when it is coming back down?  (The weight should hit the ground at no more than 1 ft/sec, slower is better)

Assume the motor is geared so that 2000 stator rotations would take things from fully up to fully down, and no worm gears are involved.  (You might notice that the max-allowable speed going down would drive the stator well above it's forward speed going down, so in free fall, the motor would act as a generator that could potentially regulate the attached load to control the descent rate.  Plus, driveline friction is your friend during the descent.)

Summary:

Could a heavy-duty AC motor safely produce braking torque against it's stator that is rotating backwards?  (Either by applying voltage or by loading it and using the generator effect)
If #1 is plausible, how would I wire/control it?  (Ideally, could the generator effect self-stablize the decent by creating a terminal velocity of the motor?)

Details, if you care:
If I had a big budget and no pre-existing hardware, a single-acting hydraulic cylinder would work nicely.  (A single acting cylinder pushed in one direction only, and relies on gravity (or similar) to return it to it's starting position)  However, in my parts bin, I have a couple of 1HP A.O.Smith AC120V Farm-Duty motors (Similar to this) that have enough power for the lifting.  Using them instead of buying hydraulics would save $4-700.


texts: How to synchronize current from an AC and DC current

texts: I'm trying to make a battery less solar grid in which energy from the solar panel will be directly given to home appliances and will be complemented by current from the grid. I'm thinking of passing the current from solar panel to an inverter and amplifying it but the problem is that the phase, frequency, etc. will have to matched with the AC current from grid otherwise many problems such as back-voltage will occur.


texts:
I've been trying to repair my lecroy 9314l for the past couple of days and i've sort of run into a wall. out of ideas. The power supply started to fail a while ago. It wont turn on when i connect a regular 3-pin (L-N-E) power pplug to the wall. But a non-earth referenced 2-pin plug works. Obviously this is unusable, since the probe ground leads leak heavily and the scope turns off immediately as soon as i connect the probe to any circuits ground. I initially thought it might be a faulty x/y class cap on the primary side. But after initial troubleshooting i realised that the primary side is working fine. No shorts anywhere. I have attached the circuit schematic here for reference.

circuit schematic pdf

Then i started with the secondary side and straight away discovered a short on the DC output lines. -5.2v,+5v lines are all shorted to the ground. Hence the power supply wont turn on when earth is connected. I have so far individually removed all the rectifier diodes to check if they have failed. All the diodes are fine and within their stated tolerance levels. I have replaced all the capacitors which were fine anyways. Both the optocouplers U1 and U2 used for feedback for voltage and current regulation are working fine.

The problem i am running into is that my knowledge of a/c and smps circuits is basic and i cant figure out how to proceed or what further steps to take in order to isolate the problem further. Could the transformer be at fault here? But then the scope works when earth is removed. If the transformer has shorted any of its secondary coils then the failure should be persistent isn't it?

Any advice or suggestions would help.

Regards


texts:
How do I make a counter that goes from 1 to 6? I have a 555 Timer connected to a 74LS390N counter which is connected to a 7 segment display module.

I can't figure out how to make the counter's output start from 0001 and end at 0110 and then go back to 0001.

Currently:

DCBA     Number

0000     0

0001     1

.

.

.

1001     9

0000     0


texts:
I want to connect an "Adafruit Feather M0 Adalogger" to an acceleromter (IIS3DWB/ STEVAL-MKI208V1K).
IIS3DWB (Sensor): SPI, ODR: 26.7 kHz

Is the µC compatible for this sensor?

In general, at which specs do I have to look at in order to know if a sensor is compatible to a certain µC?

Product page Adafruit Feather M0 Adalogger

IIS3DWB Datasheet

STEVAL-MKI208V1K Datasheet


texts: Micro switch that closes circuit twice, on press and on release

texts:
I need to implement a switch that closes a circuit twice for a short time - when pressed and then when released. The switch needs to be really small (should fit inside a 3.5mm TRRS headphone jack, meaning that the male jack would be the button itself, no wires will come out of it).

The jack itself only needs to connect the top ring and the sleeve (when pressed), and doesn't need to transfer audio in the other rings (so it can be hollowed out to fit the electronics inside).

I have a few about mechanical solutions, but thought that maybe an electrical one could be more reliable.

Any suggestions how to implement that?


texts:
I have some routing like this;

I would like this pad/wire connection to print solid black with a small hole in the middle. After I etch with toner transfer, I'll need to see where to drill.

I can use drill-aid.ulp, but the resulting white donut's hole is obscured by the wire.

Surely this is not a unique problem. What's the trick?


texts: Is an op amp voltage follower better than one made with discrete (MOS)FETs?

texts:
Is there any advantage of the following op amp based voltage follower:-

over one made with discrete MOSFET components such as:-

other than component count?


texts: Do "solid polymer" capacitors really have a longer lifespan than electrolytic?

texts:
Many motherboard manufacturers use "Low ESR Solid Organic Polymer" capacitors instead of electrolytic caps and put great effort into marketing and advertising this fact. (For example, this FAQ by Giga-Byte.)

In addition to "lifespan" do these type of capacitors have other advantages such as greater tolerance for out-of-spec voltages or temperatures?

Do these capacitors have a significant advantage over electrolytics? If so, is it advisable to use them instead in hobby projects?


texts: Using an array of resistors to give priority on a bus

texts:
I remember that the ZX Spectrum used an array of resistors to let the output from one chip override the output from another chip (on a bus) when both had the ¬oe pulled low.

 +--------+    +--------+
 | 74HCxxx|    | 74HCxxx|
 +--------+    +--------+
  ||||||||      ||||||||
  ||||||||      RRRRRRRR
  ||||||||      ||||||||  8
 -------------------------/----...

I understand that this is power-inefficient as current will flow from logic 1s (on one chip) to logic 0s (on another chip) through the resistors.

What value of resistors should be used for 74HCxxx chips, so that there is enough of a voltage difference between the 0s and 1s to still register as a 0 or 1 when both chips are outputting conflicting bit values?


texts: Effect of duty ratio on buck converter with battery load

texts: Will the battery charging circuit be able to supply charging current if the duty ratio is adjusted to 0.1?


texts: About how to extract back EMF from SMO(sliding mode observer), maybe I need a doctor for this question

texts:
The equations of PMSM on alpha-beta frame(2 ﬁxed coordinate systems) are like this,

The sliding mode observer (SMO) is like this,

then we use Z to denote the sliding mode control terms,

when the observer has reached sliding mode surface, back EMF can be extract from Z by using a integrator or a LPF(low pass filter), and finally we can calculate theta e which is PMSM's electrical rotator angle.

but this whole thing is wrong!
the actual equation that calculates the theta e is,

so I want to ask where is my wrong?


texts: Gain of Inverting Active Bandpass Filter

texts:
For the filter below

I calculate the transfer function
$$H(j \omega) = -\frac{R_2C_1 j \omega}{(1+C_1R_1 j \omega)(1+C_2R_2  j \omega)} $$ and thus calculate the gain  $$A= \sqrt{ H(j \omega_o) H(- j \omega_o) } = \frac{R_2 C_1}{\left(R_1 C_1+R_2 C_2\right)}$$ where \$\omega_o^{-1}=\sqrt{R_2 R_1 C_1 C_2}\$.

Question: Please suggest as to why this is not the Voltage Gain, \$ A:= \left|\frac{V_o}{V_i}\right| \$ as many colleagues and sources over the internet claim the gain to be \$ \frac{R_2}{R_1} \$, for instance see here. Is there a way to derive this result of \$ \frac{R_2}{R_1} \$ by defining the Gain to be something else ?

EDIT: Here is one way I can justify the approximation to be \$\frac{R_2}{2 R_1}\$hold only for Narrowband Filters. For bandpass action we would need \$\omega_1:=(R_1 C_1)^{-1} < \omega_2:=(R_2 C_2)^{-1}\$. Now this allows us to write the gain as $$A=\frac{R_2}{R_1} \frac{\omega_1^{-1}}{\omega_2^{-1}+\omega_1^{-1}}.$$
This can also be expressed as $$A=\frac{R_2}{R_1}\frac{1}{1+\frac{\omega_1}{\omega_2}}.$$ Assuming the ratio \$\frac{\omega_1}{\omega_2} \to 1 \$ we get \$A \to R_2/(2 R_1)\$. This ratio approaching 1 signifies Narrowband Filters.


texts: How do I connect this piece of electronics to show the digit display? (from satellite decoder)

texts:
I have the following piece of board/electronics:

Link: http://i.imgur.com/jwomLz8.jpg

Link: http://i.imgur.com/4BCKU21.jpg

Now, I recently bought an arduino, so I want to connect the digit display to show digits,

I already have blown out an IR receiver so that's the reason I disassembled an old satellite decoder, and I pulled the IR receiver out from this.

But now I am curious, I cannot find any datasheets for this (maybe they are closed source?).

I am wondering how I can connect this to work with an Arduino?


texts: What is the PPM of the clock oscillator in a smartphone?

texts:
Is there a way to know the ppm of the clock oscillator in a smartphone?

For example, in the Android documentation on System Clock, there is a function elapsedRealtimeNanos, which guarantees a monotonic clock. However, I would like to know how much drift may occur when compared to an atomic clock. Even using NTP won't reveal any intuition on what is an expected amount of drift given the current hardware in phones.

If it's possible, can you share where you found the ppm information and how to calculate the error (in seconds) after x seconds have passed?


texts:
I am using below circuit to differentially drive ultrasonic transducer.

It works almost as expected. However, I notice strange phenomenon if i observe the output at the transducer with dual gate driver with inverting/noninverting output.

Blue wave is supply voltage(15V) and yellow wave is transducer side of R1. I measured both of them with respect to ground.

I understand that the supply voltage is not doing a good job since it drops almost the same with amplitude of output waveform causing HIGH voltage of the waveform to drop accordingly.

However, I don't understand why the Low(supposed to be 0V) level of the wave form keeps rising? and how i should fix it?

[Addendum] I have added picture showing PCB traces below.

One that is highlighted as white is power rail. The thickness is 0.4~0.5mm and total length is about 70 mm.

Bottom layer is basically ground plane with some traces going through via.


texts: Seamless switch to-from batteries with relay involved

texts:
I seem to have the same issue 'Ali One' asked about a few years ago
(How to create automatic dual battery changeover/switching circuit for uninterruptible power?), except I have a twist that a relay is involved too. So the answers to that question don't fully apply.
There are two supplies involved

4 x 18650 batteries
an external power supply

When on the power supply, the batteries are configured individually and each has its own charger.
And, thanks to Olin's suggestion, the supply goes through a Schottky diode to power the load.

When the power supply disconnects, the relay configures the batteries as a 2S2P set to power the load at 7.4V.
I can switch TO the power supply without incident - the diode is quick enough.
Going the other way though, I can't find a way to hold the voltage whilst the relay switches.
The load is typically about 1.5A. I tried a cap on the end, but I am up to 11,500uF and it still won't hold.

Does anybody have a more elegant answer?
P.S. I am just a mess-about hobbyist with this stuff, so I could easily have missed an obvious solution.

As requested, I have added the diagram for the relay, you will have to imagine this as one 5PDT relay - the drawing tool won't allow any annotation!  The empty boxes are  'TP4056 Lithium Battery Charger Modules'.
The final output is nominally 7.4V feeding Arduino (which is very forgiving) and +5V to a Raspberry Pi3B (which is very finnicky)

27 Dec
I have a solution to my problem - it works, but I am not confident enough to say that it is safe so would appreciate any feedback.
I acquired some high current super-caps. They are low voltage, so by the time I string a few together in series, it comes out at 5F.
Way over the top, I know, but as a hobbyist you work with what you can lay your hands on.
I have moved this 'voltage-holding-device' into the power supply rail only and isolated with an additional diode as shown.
My reasoning is ....
At the moment, there is no inrush current regulation to the capacitors as the bench power supply can do that nicely.
At power-on, the power supply will be dragged down until the capacitors have some charge (I have set the power supply to 9V 4A) and during this time, the batteries can continue to power the circuit.
Eventually (several seconds, if caps are completely discharged) the voltage can maintain 6V at which time:
a) the relay coil will pick - flicking the batteries to charge mode
b) there are enough volts in the cap to supply the circuits without reboots.
At power-off, the relay will be dropped instantly (the extra diode prevents the cap from holding the relay picked).
The capacitors will continue to power the circuits until their voltage drops below the battery voltage when the batteries take over (after about 20sec) .
All taken care of by the fast switching Schottky diodes
Is it safe/prudent/good practice to leave the caps charged?


texts: Find the power at the output of a random input + noise?

texts:
Problems on Linear Systems with Random Inputs

In this problem I don't know how to start.

the answer might be long. so it  would be really helpful if you help me with the concept and the idea how to start


texts:
I explain:
I have a screen that I want to use as a monitor. I have purchased an LCD controller board and a LVDS cable
I need someone to help me to rewire the LVDS cable. I have the input terminal pin assignment for the monitor and also the pinout for the controller, but the outputs/inputs are completely different in each. I hope maybe someone could help match them. Once I know what goes where, I can rewire the 30-pin cable.
The images are from the controller on the left and the monitor on the right.
How do I configure the wires in the LVDS 30 pin cable?
Thanks.
Edit:
OK, I did it the way Natsu Sake told me. I added a new picture with the results.


texts: Inverting Op Amp: Why does current flowing into output seem to magically reappear at ground?

texts:
I'm trying to understand the flow of current through the inverting op-amp circuit. I've created a simulation:

The thing that is baffling me is: How come the values of PR1 (op-amp output) and PR2 (ground) are the same? How can the current flow INTO the op-amp output, and then OUT of ground??? Are they somehow connected internally?

Edit 1:
I added the resistor between output and ground.

Edit 2:
Added the current probes for power supply. Now I'm even more confused...


texts: STM32F4 (Discovery board) universal delay (milisecs) function

texts:
On the net, I have found following function for delay in miliseconds for STM32F4 (Discovery board MCU:

void delay_us(const uint32_t us)
{
    us*=STM32_DELAY_US_MULT;

    /* fudge for function call overhead */
    //us--;
    asm volatile(" mov r0, %[us] \n\t"
                 "1: subs r0, #1 \n\t"
                 " bhi 1b \n\t"
                 :
                 : [us] "r" (us)
                 : "r0");
}

Inside this function, constant STM32_DELAY_US_MULT is used, but not declared and it does not compile, but this is not current problem. How does one get current STM32F4 clock and set this constant according to it? If I ask in another way, how do I write delay (milisecs) function for STM32F4 proc, that is clock independent?


texts:
I am designing a color organ and am having trouble with my pre-amp stage. My circuit so far:

For low frequencies, my system works pretty well. My input voltage is about 200mv pk-pk, and my output voltage from the emitter amplifier is about 4v pk-pk.

My problem is that when I increase the frequency, the gain is reduced drastically. When I reach the cut-off point of about 3KHz for my high pass filter, the output voltage from my amplifier is only about 800mv pk-pk and is not enough to turn on the mosfet.

I am still learning about most of this stuff, so what am I doing wrong? Perhaps there is a better way to do this?

Any help is appreciated, thanks!


texts: Please help me identify this SMD component

texts:
I've got a motor driver controller, I found an SMD component that is the same component shown in the picture.
I need help identifying this component. I've tried to google the part number, but no luck.


texts:
I've come across this in a seemingly undated power supply. I know it's bad, but I can't seem to find a replacement, or even a datasheet.

It had a resistor in parallel with it's outer two pins.

Here's a picture, as it should be the most descriptive.

This is all I know or have available. If there's anything else that would be helpful, just ask. If I could get any help with finding a datasheet, it would be great! Thanks much!


texts:
For a student project, I need a Hall Effect current sensor.
What I am going to do is to charge 8 rechargeable Li-Ion batteries of 3.7 volts in series with 34 volt supply and the buck circuit frequency is between 5KHz to 10KHz. My concern is finding the right hall-effect sensor for calculation of the input current to adjust the current flowing to the batteries.

The batteries are 4000-6000 mAh and I am going to use AVR to sense the output of current sensor. So, I need a sensor with 5 volt output. I am thinking about finding the right current sensor for this circuit. ACS712ELC-05B is an example however, it senses 5A which is too high for this circuit and reduces the sensitivity of my measurement. I need something in safe range but not too far. Could anybody help me with finding a better option?


texts:
I have below configuration:

                |---------|------- LED1
                |         |
24V, 350mA------|Switcher |------- LED2
                |         |
                |---------|------- LED3
                      |
                      |
                      |
                MCU to select the line

I need to route the input (24V, 350mA) to one of LED string at the output (1,2,3) by a MCU to turn on/off the LEDs. It is required that all LEDs may be turned on at the same time. ( I can dedicated a GPIO per led string on/off)

What is best to use as a switcher considering 1) small size 2) low cost? It should have long product life (>10 years). I couldn't decide if I should prepare something with 3 transistors and each transistor is controlled by a MCU or a signal relay or a multiplexer.. What would you be your suggestion?


texts: Any li-ion battery metric or test that could correlate with its past usage?

texts:
I am trying to find any metric or test method that I could use to get information regarding a battery's past usage.
Suppose a battery 'A' has been used in good conditions in the past and battery 'B' has been used relatively poorer in the past.
Is there any test I can perform on a battery cycler and use that data to correlate its usage history?
Any research article would be highly appreciated.


texts: Would it be possible to use a solid state relay as a dimmer switch?

texts: I wanted to make a smart switch with a dimmer using an arduino and a solid state relay. I was wondering if this would be possible and if their would be any problems if I tried to do so. Also, the switch would be controlling 6 light bulbs.


texts: 4 pin microphone SMD pinout indentification

texts:
Is there any way to "guess" what's the pinout for microphone without damaging it?

Better yet do you know what's the pinout for this? (I have searched on the web but most no site provide schematics. (My guess is there is: Vdd, Gnd, In, Out)
Forgot to add that the part in question does NOT have any reference mark (like it is shown in the picture)


texts: Looking for a good freeware/open source PCB design software equivalent to Altium

texts:
I am familiar with Altium PCB design software in my workplace.
But thats an expensive suite to maintain. Is there any decent enough free software which I can use at home for my pet projects? I have tried ExpressPCB but not satisfied with it. Any suggestions are much appreciated.
I usually design upto 4 layers of PCB for my home projects.


texts: XBee Pro Antenna Options - do the U.FL antennas have better range than the chip or micro pad antennas?

texts:
Logically the U.FL dipole antenna will have better range than the other two options, as it's a larger antenna, but is this actually true? How do the three antennas perform in relation to each other for a long-range non-LoS link outdoors?

Here's a link to the page with the different options for the XBee PRO boards, and here's a link to an application note about the antenna options. The application note only compares whip and PCB antennas and doesn't go into any detail on the typical performance of a dipole antenna.


texts: Concept of "resistance" and "power dissipation" in a transistor - Explanation?

texts:
Ok, so I've got way more experience with mosfets than BJTs.  I'd become very accustomed to the idea of mosfets having a specific 'on' resistance, which would allow me to calculate actual heat generation and operating conditions for the mosfet quite easily.

I understand a BJT doesn't have an actual 'on' state.  Instead, it has a diminishing gain as you raise base current further and further.  What I'm wondering about is how to get an idea of how much resistance there is in a BJT -or- how much it will heat up when I operate it in various conditions.  I'm guessing that if I have a resistive load that allows 5 amps (for instance) and I am switching it with a BJT, then biasing the BJT on as high as possible will minimize heat generated in the BJT because you open the channel as wide as possible.  But what I find awkward is the fact that the gain approaches zero once you get above a certain 'grey area'.  So how do I figure out what is practical?  Do I just have to look at the gain curve graphs on the datasheet and pick some reasonable range?


texts: Value of Drain Current in BSIM3v3 in triode region

texts: Here the value of drain current has been given as per the BSIM3v3 MOSFET model, but is there any reference where it has been shown how this value was calculated and what is the meaning of the symbols such as IDSAT0?


texts: My PCBs etch all bad! (sodium persulfate)

texts:
I've recently started having problems with etching my PCBs.

I use a permanent marker to do the traces and  etch them in a stainless steel cup, heated with a tea light (small candle.)

The PCBs come out very badly, the traces have holes in them and some thinner ones have completely disappeared.

Pictures:

It's before removing the marker, BTW.

I also sandpapered the board before.

This is my setup, the tea light goes in the can under the cup:

What can be the cause of it coming out so badly?

Should I use some different etching compound? I'm thinking about either ferric chloride or vinegar (or bleach?) + peroxide.


texts:
I'm working in an embedded space, where I need to keep voltages on a bunch of capacitors (RC circuits). Currently, I have an EEPROM with some data value for each capacitor. There is 1 DAC that feeds a bunch of multiplexers. The multiplexers are selected and enabled such that only 1 capacitor is connected to the DAC output at a time, which charges that capacitor up to its desired value. The MCU loops through the EEPROM data and selects each capacitor to be charged in turn, thereby maintaining charge on all the caps.

My issue is that I want to scale this system up. The charge on the capacitors cannot droop below a certain threshold, so I need to run this loop fast enough to prevent that from happening. With on the order of 50 capacitors, I'm fine. But with on the order of 1,500 capacitors, I will not be able to maintain all the charge.

So how can I maintain the charge on all these caps? My first thought is I need to parallelize. Adding another DAC (or DACs) would allow me to charge up 2 (or more) capacitors at once, which would effectively double (or more) my refresh speed.

Can this be done in some other way? Maybe other different hardware? I'm looking for advice on how to solve this issue. Use an FPGA possibly?

The problem would be solved with one DAC for every output, but I don't want 1500 DACs on my board.

EDIT:

Goal: I need to maintain charge on 1,500 capacitors.

Problem: The existing board (a 50-capacitor system) works, but will not scale up. Using the same methods, I will not be able to recharge 1,500 capacitors quickly enough.

Potential Solution: Add more DACs to the system to charge capacitors in parallel.

Desired Assistance: A solution that will maintain the charge on all the capacitors without letting them droop too low OR a suggestion of another variable that I can tweak to make the system work OR some reassurance that this is actually a good way to solve the problem.


texts: Differences between inductor and electromagnet?

texts:
This seems like a very stupid question but I have to clear my doubts.

When we connect an inductor of like 6-7 turns to a DC battery, the battery gets shorted out. But when we make an electromagnet of like 50-60 turns, and connect it to a battery, it works fine. Is it because in the case of electromagnets, the resistance is high due to a larger number of turns?

Also, when we disconnect the inductor from the DC source, its magnetic field collapses and a high surge of current is produced. So for that, we connect a diode (flyback diode) across it. Basically an electromagnet is nothing but an inductor with many turns. But why is this diode not used when we make an electromagnet?

Even on YouTube, all the electromagnet DIY projects are made without the diode. They just simply connect and disconnect their electromagnets without getting any minor shocks. Why is this?


texts:
I have a scenario, where device A provides 24V, device B converts 24V to 3.3V and feeds it back to device A. Both devices communicate with TTL (@3.3V), so we have 2 signal lines as well. What circuit is required so that I can safely plug device B in or out while device a is powered and so that I'm not limited to connector types that are hot-plug-safe.
Also there is no requirement to limit inrush currents, because all inputs have low capacitances and the 24V rail may drop. I know there are ICs for hot swap circuits, but they are quite overpowered and I prefer a circuit consisting only of passive components.

Does something like the following circuits make any sense (using diodes like for esd protection)? From my understanding, the act of connecting two devices is simmilar to an electrostatic discharge in some way.

Version 1:

Version 2:

Edit: as desired, the DCDC-circuit:

Block diagram of TPS54240 :


texts: What is the purpose of fifo in serialize of HDMI?

texts:
I'm trying to understand and study about HDMI. currently I'm referring with here (https://www.fpga4fun.com/HDMI.html).
But I'm confused that why does that fifo need for higher resolution?
in case of 640x480,  they don't use the fifo in example. but why does the fifo need for higher resolution?


texts: What are the differences between rand() function and RNG (Random number generator) peripheral?

texts:
I'm wonder for RNG (Random number generator) peripheral in STM32F4XXXX MCUs. look in this Reference Manual (page 748). On the other hand, we have the rand() function in stdlib library that do the same task. Now I have two questions:

What are the differences (advantage and disadvantage) between rand() function and RNG (Random number generator) peripheral?
Look at this part:

Please explain about these both option (especially second option).


texts: trigonometric expression in phased array

texts:
i have tried to develop the angles in the diagram bellow.
there is not triangle where we have 90 degrees phi and theta together.
why phi=90-theta  ?
Thanks.


texts: Can I use a transformer to drop a DC voltage?

texts: Can I use a transformer to drop down the voltage from a generator? Or should I just use a regulator? The generator outputs about 9.3 V and I need about 5 V, and I want to conserve power.


texts:
What is the recommended plug on the battery?

The male or the female XT60 and why?

XT60 connector