texts:
I am new to electronics and trying to understand how a "warm/hot start" works.

I am currently working with someone to design a PCB schematic for the SIM928A, a GSM/GPS module. In the hardware design PDF for the SIM928A you can see that it shows 12.5 for an A-GPS cold start (I assume this is no power at all, and then suddenly full power) and just 1.5s for a "warm" start. Am I right in assuming this means that there is some form of power to the device before it is fully powered with the recommended voltage?

In order to achieve this much faster time to first fix, would I need to have a battery running the unit in order to warm start the SIM928A module?

Also, I notice for the time to first fix using a standard GPS antenna, the hot start is <1s and a warm start is 26 seconds. I would really appreciate it if someone could explain why this is and the difference between hot starting the module and warm starting it.


texts: How to plot the phase response of a transfer function

texts:
I am trying to plot the phase response of a box with an unknown transfer function by by measuring the phase difference between the input and output at different frequencies but I am not exactly sure of how to plot the phase response with the data obtained.

So I have added a table below with the data that shows the phase shift at different frequencies and whether it is the output or input that is leading. If anybody knows how to plot the phase response using this information their help will be very much appreciated.


texts: What type of motor can provide smooth motion at low speed around 0.1 to 1 mm/s

texts:
I am building a stage for tissue cutting and the motion of the stage should be very slow and smooth. The speed range is 0.1 to 1 mm/s. I got a stepper linear motor from PI (M230.10s), I test its speed at 0.1 mm/s and the chatter is 3 times of the setting value.

I hope the motor can motor can move very smooth with chatter around 1%. Is it possible?


texts: What is the true representation of voltage and current for the sinusoidal wave?

texts:
In the Circuit Theory, the book said  the representation of voltage and current in the sinusoidal wave should be

\$v(t)=V_m\sin(\omega t)\$, and \$V_{rms}=\frac{V_m}{\sqrt{2}}\$

\$i(t)=I_m\sin(\omega t)\$, and \$I_{rms}=\frac{I_m}{\sqrt{2}}\$

However, in the Power Transmission and Distribution, the book said  the representation of voltage and current in the sinusoidal wave should be

\$v(t)=V_m\cos(\omega t+\theta_v)\$, and \$V_{rms}=\frac{V_m}{\sqrt{2}}\$

\$i(t)=I_m\cos(\omega t+\theta_i)\$, and \$I_{rms}=\frac{I_m}{\sqrt{2}}\$

So I want to ask, what is the exact representation of voltage and current in the sinusoidal wave? \$\sin\$ or \$\cos\$? Or we can represent them in both \$\sin\$ or \$\cos\$ ?


texts: Are DIP sockets against overheating worth the cost?

texts:
Sockets allow easy replacement of a device and eliminates the risk of damage from overheating during soldering. [Wikipedia]

I personally never (ever) replace these ICs. For programming microcontrollers (as a hobbyist) I use a dedicated pin header. So the only reason for me to use DIP sockets is to prevent overheating.

Now I'm a cheapskate (student) so I would not want to buy any of these sockets if they are not absolutely necessary. However, I find it hard to decide whether I need them.

Given that my DIP-packages cost around €2.50 each, should I protect them with DIP-sockets?


texts: Why does this EPROM have comb-like structures around the wire bonding pads?

texts: I took some pictures of a Microchip EPROM die from the late 80s / early 90s (I can't recall the exact part number). The wire bonding pads are surrounded by a comb-like structure. What is the purpose of this structure?


texts: Why is the initial current in this capacitor not continuous?

texts:
I am working on this circuit:

Basically, \$V_1\$ is on all the time, and \$V_2\$ turns on at \$t=0\$. For the conditions at \$t=0^-\$ (the time just before zero), I can see why the voltage across the capacitor is equal to \$V_1\$. The current through the resistor at \$t=0^-\$ is zero, as no current would flow.

After the second voltage source turns on, my sources tell me that the current flowing through \$C\$ is equal to \$V_2 / R_2 \$. That is, the current instantaneously goes from 0 to \$V_2 / R_2 \$ at \$t=0\$.

What is going on here?


texts:
I asked similarly before, but I really have to do this soon. Please help me. ı have signals that are received from sensors (seismometers) are usually noisy and of very small amplitudee. The frequency
range of these signals varies between 0.01 and 1000 Hz.A high-gain band-limited amplifier is needed.
1)The amplifier should be able to provide a dynamic range of over 60 dB.
2)Maximum output voltage is 10 V p-p
3)The amplifier bandwidth should be limited to 1-200 Hz, such that high-frequency noise is
blocked. Low-frequency noise (1-200 Hz) usually has amplitude of up to 100 nV p-p, with
input impedance of 4 k ohm.

I can't decide which type of transistor to use.at the same time I could not adjust the gain and bandwidth of the transistor please help


texts:
I have a VHDL module in which several block RAMs are inferred. Now I would like to place these block RAMs into a certain region of my FPGA (close to some IO pins).
How do I do this using Xilinx constraints (UCF file)? Can I group the block RAMs and define a single LOC constraint for the group or do I have to constrain every block RAM individually?

The main hurdle to me is that the number of block RAMs depends on a generic, which is why using one individual constraint for each block RAM seems not possible.

EDIT: The reason I am trying this approach is that my timing constraints can not be met. The timing errors are all related to the block RAMs of one module. Looking at the PAR result I can see that the critical block RAMs are scattered across the center of the FPGA, instead of being placed close to the relevant IO pins. Therefore I want to try to guide PAR into the direction where I think the block RAMs should be placed. The timing results should then tell me if my advice to PAR was helpful or not.


texts: Why does the \$ Q\$-factor depend on the resonant frequency?

texts:
The \$Q\$-factor is defined as $$Q=\frac{\omega_{0}}{\Delta \omega},$$

where \$ \Delta \omega\$ is the bandwidth around the resonant frequency \$ \omega
 _{0}\$. For a series RLC circuit, $$\Delta \omega = \frac{R}{L}$$

and $$\omega_{0}=\frac{1}{\sqrt{LC}}.$$

\$Q\$ is supposed to measure how sharp the frequency response is. And so a higher \$Q\$ means a smaller \$\Delta \omega \$. But we can clearly see above that for a series RLC circuit, the \$Q\$-factor can be increased just by increasing \$\omega_{0}\$, alone, by decreasing the value of \$C\$, without even changing how narrow the response curve is, i.e. without even changing \$\Delta \omega \$.

So why a higher resonant frequency implies a higher \$Q\$-factor, which is supposed to measure how sharp the frequency response of our resonant circuit is? In other words, why should the resonant frequency have anything to do with the  the \$Q\$-factor?


texts: Calculate impedance in time and frequency?

texts:
I'm characterizing the impedance of a system. To get the impedance I apply a sum of sinusoidal voltage waves that basically looks like noise.

I recorded the output current from the system. As you can see there seems to be some time dependence on the output.  I was wondering how to get the time and frequency dependence of the impedance.


texts: What is the difference between "medical" grade and ordinary AC-DC power supplies?

texts:
Background

My wife and I are expecting a baby soon and a family member has given us their previously-used, thoroughly cleaned electric breast pump. The pump came from the vendor with a "medical grade" 120V AC to 9V DC power supply (i.e., a "wall wart") that powers the pump's motor.

Based on the size and weight of the power supply, it appears to be a transformer-based linear power supply. It is marked "120V only". This is a problem, as my wife and I now live in Europe were 240V AC power is the norm.

The pump itself is fairly simple and does not seem to have highly sensitive electronics: there is an electric motor powering a peristaltic pump and a potentiometer that varies the pumping speed. My multimeter indicates that the internal electrified components are isolated from the user and the fluid being pumped, as expected.

I've tested the pump with an off-the-shelf regulated 9V switching power supply (UL-listed and CE marked) that operates on 120/240V power and which can supply more than adequate current for the pump and the pump works normally.

Question

What is the difference between a "medical grade" AC-DC power supply and a more common, non-medical one like one would find accompanying an ordinary piece of consumer electronics?

Would a medical-grade power supply offer additional voltage stability, less ripple, greater isolation, and/or greater reliability than a standard wall wart meant for electronic devices?

While I understand that higher-grade power supplies would be important for critical life-support systems, is there any reason why a common, non-medical-grade power supply that meets the voltage/current needs of the pump would be inappropriate?


texts: Problem calculating resonant frequency [series RLC]

texts:
I try to link/prove the theory of resonance in practice. So for test I connected in series 1mH inductor, 1k Ohm resistor and 2.1 uF ceramic capacitor.

Calculated resonant frequency -> \$ f_{r} = \frac{1}{2 \cdot \pi \cdot \sqrt{LC} } = \frac{1}{2 \cdot \pi \cdot \sqrt{1*10^{-3}*2.1*10^{-6}}} = 3473 Hz
\$

Okay so, to prove calculated resonance I pluged 4Vpp sinusoidal signal from function generator to my RLC circuit and monitored resistor voltage on my oscilosope. I went from 1Hz up to the point at which I observed change in signal amplitude. From my calculations I expected resonance to happen at 3473 Hz but surprisingly something started to happen at frequency of around 0.5 Mhz. How is that possible? The amplitude went from 3.3V to 330 mV. I started to blame inductor value, since there is no code/indicator on it's body. I got rule for inductance:

\$ L=\frac{\sqrt{\left( \frac{V}{I}\right)^{2} -R^2}}{\omega} \$

and to calculate it I conncted in series resistance of 1k Ohm and my "1mH" inductor. Powered it by 1Khz sinusoid. Therefore I calculated that inductance is 15.8 mH instead of 1 mH.
So, in my resonance calulations I changed 1mH with 15.8 and got resonant frequency equal to 873 Hz...not even close to what I observe on my scope.
So to summarize here are my questions:

Why in my series RLC circuit I only see decrease in amplitude instead of sharp rise?
Why I don't see any change in resistor voltage at calculate resonant frequencies?


texts: How can I effectively drive multiple LEDs with multiplexing?

texts:
I am interfacing my microcontroller (AVRmega32U4) to a 4x4 LED array. There are 2 control lines to operate columns (passed to a 2 to 4 demultiplexer) and 4 control lines to operate rows. I bring a column high and a row low to illuminate a specific LED. I pull either the column low or the row high to turn off an LED.

This design works fine for around up to 4 LEDs at once. However, when I try to light all 16 at once with this strategy, the LEDs are noticeably less brighter (they're on a 1/16 duty cycle after all!).

What are some ways to more effectively light larger numbers of LEDs in this array? Say, 10+?

I am considering writing a lot of code to handle the different situations, but that will consume more space on my microcontroller than I am comfortable with. I was considering adding another micro with 16 control lines to manage these LEDs, one at a time, but this seems like a lot of overhead to introduce.


texts: Using PSPICE model of gate-driver from manufacturer

texts:
I have found a PSPICE model for a part I'm interested in.

ISL55110 Datasheet:
https://www.mouser.com/datasheet/2/698/isl55110-11-1302115.pdf

Manufacturer PSPICE Model:
https://www.renesas.com/cn/zh/www/software/simulation/isl55110_spice_model.txt?key=7c34d7bf3964f39e34346fc510d75e83

In the past, when I needed to use manufacturer models of components in PSPICE, I would simply find a part that was already defined and had the same number of pins/parameters and copy-paste the code into the spice model editor.

For example:

Vishay - BZT03C200 PSPICE model copy-pasted into D1N4467 from the DIODE library.

Which gives me the desired result.

I've looked through all the gate drivers in the MFET_DRVR library, but there are no components that have the number of pins shown in the above datasheet, which is 9.

How can I go about using this model in PSPICE? I have looked into how to make custom components with specific numbers of pins/parameters/etc., but I was unsuccessful in making one work. Also, doing a google search has come up with a few forum posts, but many of them are amibiguous to me since I am unfamiliar in using Cadence.


texts: Safety precautions when making a commercial electronic product

texts:
I have designed and fabricated an electronic device. High level explanation for this device is as follows:
The device designed scans the environment for RFID tags and when a tag gets too close to the scanner it triggers and alarm and then sends out an SMS using the SIM800l module.
The device pulls at most 2.5A and is connected to 5V supply. The scanner device takes 5V while the SIM800l takes 3.8V. Therefore a buck converter was used to step down the voltage from 5V to 3.8V.
The power supply contains a variety of safety features such as Short circuit / Overload / Over voltage. The main supply also has a surge protector. Hence the plug outlet and therefore my device is safe from any sort of surges.
The scanner is connected to the SIM800l using Veroboard and some resistors. These resistors are used as a voltage converter. The scanner output 5V but the SIM800l needs 3.3V.
The entire project is encapsulated in a plastic housing. The circuitry (scanner and SIM800l) does not produce a lot of heat, in fact, it does not even feel warm after 14 days of testing continuously.
My question is therefore what else saftey measures should I employ if I want to take this product commercially?


texts: DC Relay Module for Switching ~200 VDC @ 1.4A with Arduino Controller

texts:
The context of the problem is that I am trying to switch a ~200 VDC Meanwell Constant Current Supply @ 1.4A, to selectively  power on a number of COB LEDs connected in series. My initial approach was to switch the power using a 30 VDC 10A optocoupler relay module.
I understand that this will certainly cause arcing during switching if the line is hot. However, I can cut off the mains input to the power supply right before the switch, and prevent any arcing since the relay would switch on a cold line. I'm sure that would work for mechanical switches, but is my understanding correct when we are talking about optoisolators?
I know this would be a risky way of implementing this, and I'd certainly go with a properly rated relay module for 200+ VDC, but being a newbie in this field I'm not well equipped to research for the most cost effective option here. If there's anyone here who can provide a recommendation for a SPDT relay at these ratings I'd really appreciate it. Thanks in advance!


texts:
Reading through OnSemi's application note AND8173, I'm having a hard time understanding the voltage swing level of AC-coupled CML (Current Mode Logic).

It says VoutputH/L=Vterm+/-200mV which means there's 4mA flowing through RT1 and RT2. But how can there be a current through C1 and C2?

Image source: Figure 7 from On Semiconductor application note AND8173


texts: AVR Timer1 OCR1A controls TIMER1_COMPB_vect interrupt!

texts:
I was struggling with timer interrupts in my project. I couldn't make it work properly. So I decided writing a simple code and I saw a very interesting case.

ISR(TIMER1_COMPB_vect)
{

        PORTB ^= (1 << PORTB5);

}

int main(void)
{
    cli();          // disable global interrupts
    TCCR1A = 0;     // set entire TCCR1A register to 0
    TCCR1B = 0;     // same for TCCR1B

    OCR1A = 10000;
    OCR1B = 100;

    TCCR1B |= (1 << WGM12);

    TCCR1B |= (1 << CS10);
    TCCR1B |= (1 << CS12);

    TIMSK1 |= (1 << OCIE1A);
    TIMSK1 |= (1 << OCIE1B);
    DDRB= 0xFF;

    #define F_CPU 16000000
    sei();
    while (1)
    {

    }
}

Here is my code. When I change OCR1B value, nothing happens, but if I change OCR1A value then blinking gets faster. Is there a logical explanation for this?


texts: Circuit to keep two LEDs on when buttons are released

texts:
I am trying for the first time to build something on my own. I am pretty n00b when it comes to electronic so, please, bear with me.

I'm trying to build a "simple" schematic that goes like this: there are two buttons (SW1 and SW2) normally open, and 2 LEDs (D2 and D3) associated to each button. When a button is closed, the relative LED turns on, but when button is released, the relative LED shall continue to stay on.

One button shall not influence the other LED.

In addition, there is a third button Reset button which is used to turn off both the LEDs: while it's pressed, the Reset button will turn off the LEDs.

To do this (apparently) simple circuit, I am using some gates:

a NOT gate which inverts the reset button: when button is not pressed, the gate shall be high and enter two AND gates.
two AND gates which take the reset as one input. When reset is pressed (+Vcc), the NOT gate should go low, making the AND gates to go low in output. The other input of the AND gates is the output of two OR gates (one-to-one).
the OR gates (OR1, OR2) use a feedback mechanism to keep high the signal once it goes high. Each OR has SW1 (SW2) and the output of the AND gates (AND1, AND2) as input. When reset is pressed and no button is pressed, the OR goes low, but if one button is pressed and no reset is pressed, then the output is high, which goes in the AND port, which shall output high and thus keeping the OR gates high.

I realized on a breadboard the circuit below

simulate this circuit – Schematic created using CircuitLab

Sorry, in the image some resistors are wrong:
R5 = R3 = R1 = 5.6k Ohm
R6 = R7 = 10k Ohm

I used 74LS04 for the NOT gate, 74LS08 B1 for the AND gates and 74LS32 for the OR gates.

Being LS, I connected all the unused input to ground, while every other input shall be connected, because I tried to use pull-down resistors on the inputs.

Now, this is the first time I try something this complex: I know this is conceptually simple, but I just don't have the tools and knowledge to deal with the hardware fabrication.

In fact, this circuit is not working as I was expecting: even if the reset button is not pressed (or even if it is pressed), the NOT gate will always produce an output voltage of 0.75, which is (I think) low. In fact, the SW1 and SW2 buttons will just turn on the LEDs when they are closed.

If I remove the link that goes from the NOT gate to the AND gates, leaving only the D1 LED as output, the NOT gate works as expected.

As additional input: the chips are connected properly to Vcc and GND (+5V and 0), and I am using, as a power source, a stabilized power supply (that is actually a recycled computer PSU).

Well, that's all for now... Can someone give me an advice? I can't really understand what's happening (and why).


texts:
I am trying to develop a digital data link based on FPGA (spartan 3E) where the transmitter serializes 8 bit parallel input to single channel. At receiver side I want to get the data back by de serializing. I am not adding clock recovery complexity at this point.
I can serialize the data at transmitter side where the 8 bit input can be multiplexed using a simple counter.
I want to understand how to demultiplex the signal at Rx side.
How can I control the Rx when to start demultiplexing data, so that I can get exact 8 bit parallel output as sent at Tx input side.
Please let me know if you need any other information.


texts: nrf51822 BLE beacon not always discoverable - how to choose the correct flag?

texts:
I have some BLE beacon modules (Radioland Beacon) using the Nordic nrf51822 and I want to make an indoor positioning system with them.

There is a problem with my beacons that they are not always discoverable (when scanning with an Android app) and I can't get the beacon RSSI which is needed in my app.

I have searched the web for this problem and I found that every beacon has a 5-bit flag indicating the behavior of the beacon (you can check these flags with scan section of Beacon Simulator Android app).

I think the problem is the that "LE Limited Discoverable" mode is set instead of "LE General Discoverable", so the beacon went out from scanning app after some minutes. So my questions are as follows:

Is the problem caused by "LE Limited Discoverable" flag?
If yes, How can I change it?


texts: For using an inverter, what determines the power usage?

texts: Say I have a 12V battery hooked up to an inverter (assume no inefficiency). I guessed that if a 1A, 120V draw was placed on it, because 120W was pulled from the inverter, it would pull 120W, and therefore 12V/10A from the 12V battery. Is this assumption flawed?


texts: Voltage across LED and source when LED is floating from one end

texts:
Refer to these pictures and can you explain why is there 3.335V coming across LED and the LED isn't even turning on. Also to note is that changing the resistor value does not change voltage at D2(A2) when switch is open. (I am using the D2(A2) point as an input for a microcontroller).

(This is also the same voltage coming in my real life circuit)

Addition!!!

Extra Points:
Also is it safe to use the point D2(A2) as input to a micro-controller (PIC18F46K22) with it being brought to 0V when SW1 is closed and being brought to high logic level when the SW1 is open.


texts:
Is it possible to build a circuit to make a fluorescent tube flash on and off for use as a lighting effect? If so, how?

Also, if the above is possible, can it be used to flash more than one tube at a time without having to repeat the control circuitry for each tube?


texts: Are capacitors and inductors capable of absorbing positive power?

texts:
A resistor is capable of absorbing positive power.
Why wouldn't this be true for capacitors and inductors?


texts: How to calculate Li-Po battery discharge time?

texts:
I want to calculate the time for a Li-Po battery (7.4 V, 2200 mAh, 30 C) to discharge. Battery powers up an embedded device, that requires 5 V, 147 mA.

For this reason, I use a voltage regulator, in order to regulate voltage from 7.4 V to 5 V.

I haven't chosen a battery yet and as a result I cannot provide any datasheet. I 'm looking for an approached disharge time and what is the way to calculate from a discharge graph.


texts: How is the frequency for a CR Filter acting as a Differentiator Determined?

texts:
The CR filter looks like:

It is a High pass filter, so can the frequency be calculated by using the following equation?
\$ f_{0} = \dfrac{1}{2\pi CR}\$


texts: I want to know what the symbol for a button switch is. It's the kind that if you push it, the circuit is complete, and if you release it, the circuit is broken. Also, it has four prongs, two on each side, which are connected in pairs. How do you draw this symbol in a diagram?


texts: Current sinking with PC13 on STM32F103C8T6

texts:
I recently started playing around with a "Blue Pill" board that uses the STM32F103 MCU. The board has an onboard user LED, that is driven by sinking current into the PC13 pin. This is done because the PC13 pin should not be used for sourcing current higher than 3mA. This is a known property of the BP board.

However, while reading up on the MCU manual, I discovered this:

  The GPIOs (general-purpose inputs/outputs) can sink or source up to ±8mA, and sink or source up to ±20mA (with a relaxed VOL/VOH) except PC13, PC14 and PC15 which can sink or source up to +/-3mA. When using the GPIOs PC13 to PC15 in output mode, the speed should not exceed 2 MHz with a maximum load of 30 pF.

Form this, it seems, that PC13 (along with PC14 and PC15) can not sink current above 3mA.

My question:
Is the "Blue Pill" violating the STM32F103 spec by sinking more than 3mA into the PC13 pin?


texts: Is this definitely common-mode interference and how can I model and filter it?

texts:
A test device which can output voltage between 0 to 10V by a knob is powered by a DC adapter which converts 220V rms(meaning 311V amplitude) 50Hz AC to DC. Device is not a commercial and its adapter looks like a two prong laptop adapter.

When I use this device with any data type of acquisition(either single or diff-ended) I see significant amount of 50Hz noise. And when I put a very large cap like 47uF between its output terminals the 50Hz noise was mitigating but still annoyingly exists.

Then I do the following test with a multimeter's voltmeter settings:

When I connect either terminal of the device to one lead of the voltmeter and connect the other lead of the voltmeter to the earth I read 80 VAC. Figure 1 and Figure 2 illustrates that. This 80V AC the voltmeter shows must be rms so the amplitude is around 113V.

If I connect the voltmeter leads to each terminal of the device as in Figure 3 for lets say 1V DC setting I read 1V DC and 0 VAC.

And there is also another multimeter which has a low impedance setting. So if I set the voltmeter to low impedance those 80 VAC in Figure 2 and Figure 3 almost disappears to zero.

So I'm almost(?) sure that there is common-mode voltages on each terminal probably caused by the leakage through the power supply.

I measured the output resistance of the device between 20 Ohm to 100 Ohm.

The input impedance of the voltmeter I used is 10Meg Ohm.

First of all I wanted to model this in a circuit before I ask my question as follows:

I've chosen the parasitic capacitance as 250pF such that to make the Figure 1 and Figure 2 voltmeter measurements 80 VAC rms i.e 113V amplitude sine. I also add the output resistance of the device as 40 Ohm to see the effects.

Below are the plots for Figure 1, Figure 2 and Figure 3 situations:

As you see above as the red plot the common-mode noise is not rejected well because of the unbalance above due to the source output resistance, there is 50 Hz noise on the 1V DC voltage.

My questions are:

1. Is my circuit model for the situation correct?

2. I tried to add some resistor Rx on the other line to match the balance in real but as long as the difference Rout-Rx is not zero I think there will be common-mode noise. In sim it is easy to match. I actually couldn't manage it in real since I only have fixed resistors.

So is it normally/practically done by using a potentiometer leads and adjust it very delicately? I heard about common-mode chokes but those are only for RF frequencies or still can be used for 50Hz common-mode coupling?


texts:
I'm transmitting coax level S/PDIF over an SMB connector, and I'm wondering if the "body" pins (all pins that aren't the center) should be left floating, or if they should be connected to ground.

As I understand it, RCA Coax S/PDIF does expect the ground to be connected, rather than floating, which leads me to believe that the "body" pins should be connected to ground.

I'm using this Molex 73100-0259 connector, FWIW.


texts: Will a USB port be able to power a series of LEDs?

texts:
I'm planning on having a set of blue LEDs connected in series. I'm looking at having about 30-40 LEDs in series. The power supply will be from a USB 2.0 port mounted on my television. Reading up on the specs for USB 2.0 it has a pin for 5v and ground.

If I used this as my power supply, will my LEDs light up as much as they should or would they be really dim.

The specs for the LEDs are:

Material : Semiconductor; Light Color: Blue
Head Dia.: 5mm / 0.197"; Forward Voltage: 3.2-3.4V
Luminous Intensity: 2000-3000MCD; Wave Length: 460-463
Size: 24 x 3mm / 0.9" x 0.1"(L*W); Package Content: 50 x Light
Emitting Diode

And a link to amazon where I purchased is this


texts: PIC32 - Jumping from application to bootloader without a software reset

texts:
Because I need to maintain some GPIO output states when transitioning from the application to bootloader, I'm jumping back into the bootloader instead of using a software reset to get there (which results in the GPIO tri-stating for ~200ms).

Before I make the jump, I disable interrupts and clear interrupt flags.  After the jump, the bootloader starts working through its initialization, but once it gets to INTEnableSystemMultiVectoredInt(), the MCU resets...

I tried overridng _DefaultInterrupt to catch an interrupt that might have been left on by the application for some reason, but this doesn't seem to be working.  The MCU just resets and I'm left scratching my head.

Any ideas to what could be causing this?  I'm essentially mimicking the behavior of jumping from the bootloader to the application (which works) and so I don't know why it's not working the other way around.  Anyone ever able to jump from a PIC32 app to the bootloader without a software reset?


texts: I bought this USB to TTL converter and it came with the option to switch between 5v and 3.3v. I want to use it at 3.3v, but I'm not sure where the (grounder?) should be placed? Thanks, see image below. (5v and 3v3 option is on the side upside down).


texts: Calculate output power of sine and triangular wave

texts:
What is the mathematical expression to calculate the power dissipated by a load crossed by two separate electrical signals representing two specific mathematical functions knowing:

Load resistance
Frequency and period of the function
The time when the function starts
The time period in which calculate the power dissipation
Starting voltage and peak of the function
Assuming that voltage and current are in perfect phase

Specifically, I need to calculate the total power that crosses the load over time from 0 to T (the red part), of two mathematical functions: the sinusoidal one and the triangular one.
The image is for example only, I need a generic formula to apply to various voltages and times.


texts:
I'm trying to generate a modulated UART signal from the standard Tx coming out of my microcontroller. What I'm trying to accomplish is to have a 100us wide pulse generated on every edge (rising/falling) of my UART signal.

My plan was to send the UART out over the Tx pin of the STM32 I'm using, and loop it back into a GPIO. Then I could trigger an interrupt on the rising/falling edges of the GPIO and generate a pulse on an output pin for each interrupt.

My questions are:

Does this make sense?

Is there a better way to do this?

What's the best way to generate the clock (2* Baud Rate) for the modulation?

**Looking for software solutions only if possible.


texts:
I solved this circuit for the current in the 3 ohm resistor and I thought that the current would be continuous but it's not.
The circuit is first at stable state, then we turn the switch off and the question asked us to find the current through the 3 ohm resistor as a function of time.
I wonder why the current is different before and after turning the switch and how to find current after that.
Please explain what happens exactly at that moment?
Thank you.


texts:
I am testing the green LED of my RGB LED, and I am confused about its behavior on my DMM.
In the following picture, I connect the black lead to LED's cathode and the red lead to LED's anode, and get an open circuit reading. However, I was expecting something that tells the forward voltage.

In the following picture, I connect the red lead to LED's cathode and the black lead to LED's anode, and get 750mV reading. I was expecting an open circuit though.

I wonder what the implications are from my DMM readings. Why 750mV? Thanks so much everyone!


texts: In a CPU, does the speed of a calculation affect the heat generated?

texts: Take as an example a CPU that is capable of changing its clock speed, like a modern computer CPU (Intel, AMD, whatever).  When it does a certain calculation at a particular clock speed, does it generate the same amount of heat as when it does the identical calculation at a slower clock speed?  I know that heat dissipation and heat buildup are different issues, so let's just talk about raw heat generated.


texts: Why is my loudspeaker not working? From Make: Electronics

texts:
I am a complete beginner in the world of electronics and I am following the amazing book by Charles Platt, Make: Electronics (second edition). I am stuck at Experiment 11, when I need to connect an oscillator to a loudspeaker.

The picture shows the circuit I am trying to make. It's an oscillator. It does work with a  LED, but not with the loudspeaker. I do hear a very faint click when the capacitor discharge, but no sound. The loudspeaker is a 8ohm as indicated in the book.
This is a picture.
I know it's not super clear, but consider that the top part works as it should, it's the part with the speaker that possibly has something wrong.
To check that everything was working I also added a LED and made a video (and a switch to control it), here: https://youtu.be/UkEZzxmkfes
It shows that the oscillator works ok, but the loudspeaker doesn't.
Am I connecting the loudspeaker the wrong way? Is it possible that the loudspeaker is broken?
More generally, since I am a complete noob, how would I go debugging this / giving people the proper information in order to help them helping me?
Thanks!


texts: How can a pot allow variable off times in a time delay relay

texts:
I have a pellet stove motor that cycles on when an external potentiometer is dialed on. The run/on time period for the motor is always fixed--about 5 seconds, and then it pauses for a period controlled by the pot.  But how? The "off" time varies, according to the pot dial position. I'm a learner so I cannot visualize what is happening inside the timer. From the symbols on the face of the timer, there appears to be two TDRs at work in the timer. I understand a pot changes the R, but how does this translate to shorter or longer "off" periods.
  Could it be that greater R means less current to pull a relay, thus delaying its ultimate closure?
      All thoughts most appreciated. Scott


texts:
Can an IC 741 op amp can be used with an input voltage of +5 and -5 V?
If not so, what are the commonly used opamps that can be used 5 to 12 V?


texts: Metal Detector using IC 555 Timer project

texts: I want to build some project about metal detector using integrated circuit 555 timer. I already made a schematic in proteus 8 application. I made some change with the original schematic i found on internet. I added some LED on output and resistor 220k. I think my schematic wrong because when i made it in breadboard the project doesn't work. Also, when i run simulation on proteus, led not on.I need help, thank you for your attention.


texts: Changing BaudRate in both sides simultaneously

texts:
Through the C# interface i want to change the baudrate, to do that ofcurse i have to change the baudrate in the other side which is MSP430 using CodeCompserStudio and to send an Ack to PC then I implement the changes also in C#, but when i change the baudrate in CCS i cant then send the Ack message properly because the baudrate does not match! and because of that I get a non-sense message instead of the "Ack" which prevents changing the baudrate in the other side (PC) because it was waiting for the "Ack".
I'v tried to send the "Ack" message before changing the baudrate in CCS, but it did not help.
This is my pseudo code:
Initially in C# i just hit a button which sends a proper command to CCS to change the baudrate.
Then in CCS after or before changing the baudrate we have to send "Ack":

while(!(UCA1IFG & UCTXIFG));    // in this case we send the Ack msg before changing the cnfgs.
UCA1TXBUF='*';           // '*' indicates "Ack"
UCA1BR0 = 3;                 // 9600 baudrate (32k ACLK)
UCA1BR1 = 0;
UCA1MCTL = UCBRS_3+UCBRF_0;

in C#:

private void SerialPort_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
   string receivedData = SerialPort.ReadExisting();
   if (receivedData == "*") // BaudRate Acknowledge
       SerialPort.BaudRate = Convert.ToInt16(BaudRate.SelectedItem);
}

any ideas?


texts: What is meant by power well in IC terminology?

texts:
Intel PCH Datasheet refers to power wells: Core well, Suspend well, Active Sleep well. Is power well same as power rail/power plane?

Does it have any connection with p-well or n-well in IC fabrication process?


texts: Connecting multiple loads to an extension cord

texts:
We have a garage at our house and whilst there is electricity going to it, it's basically just one outlet connected to our second fridge/freezer via a 15A extension cord.
I was wondering if it would be okay to plug the refrigerator (not sure what wattage it is), my soldering iron (90W and has a 500mA fuse), one 24 inch monitor and potentially a laptop charger?
Basically i am not allowed to solder inside the home and was hoping to have this as a set up. It's only temporary as i will hopefully move out this year. What can i do to make this a-little safer?
Edit: The Fridge/Freezer is 800 Watts, the soldering iron is 90W, the monitor is 25W, charger 90W and i'd like to connect a usb hub which is 90W also).
So considering my load is approximately 1100W. My extension being able to supply 230V at 15 A = 3450W. Does it mean it's adequate? Thanks!


texts: Reusing/linking component groups in kicad schematics

texts:
I just started playing around with KiCad, and still try to get my head around proper hirarchy management.

Let's say I want to create a simple and-gate with transistors, but need to use this gate multiple times in a schematic.

Is there a way to define the and-gate schematic once, and reusing it multiple times?

Ideally including changing of referenced sub-schematics. e.g. if I spot an error in a gate, I can change it once, and it gets fixed everywhere it was used.

It's somewhat like components, but actually using a circut instead of just a single component.

I know I can copy&paste a sub-sheet, but that copies annotations as well and removes the possibility to change a whole schematic later on


texts: Can I convert my 175.4Mhz radio microphone receiver to pick up a signal from a mobile phone?


texts: Is there application note or white paper with an in-depth explanation or best practices for how to size PCB bed of nails test points?

texts:
Ideally a reference for small boards: The board that will be tested is 10 x 20 mm, and it's crowded. It doesn't have a lot of real estate left for test pads.

All I know is to look up IEEE papers:

Conformal surface lenses from a bed of nails
https://ieeexplore.ieee.org/document/6901743
Bed of nails: fine pitch wafer-level packaging interconnects for high performance nano devices
https://ieeexplore.ieee.org/document/1614483

The best resource so far, was an article in Printed Circuit Design & Fab, which recommends 0.9 to 1.0 mm test pads.

For this specific case, six signals will be exposed to the bed-of-nails: power, ground and four digital signals This is to be able to change firmware after the board has been assembled. Two of the digital signals are not exposed on any connectors.


texts: 370 V, 400 mA stablilized power supply with variable load

texts:
I need a power supply that can deliver stable 370 V DC voltage, while load resistance is variable.

Average load current(assuming stable 370 V supply) is 200 mA, however it may rise to 400 mA. Input voltage(DC) is 40 - 60 V higher than 370 V, but it's unstable.

I was expecting that I would simply buy something like LM317, but rated for 370V and 400mA. It quickly turned out that nobody sells such things.
Closest to what I need was this stabilizer: Microchip LR8K4-G, 1.2 → 440 V Linear Voltage Regulator, 30mA, 1-Channel, Adjustable, ±5%.
It meets my voltage requirements, but it can only handle 30 mA.

This fragment from its datasheet caught my attention:

  The output voltage can be adjusted by means
  of two external resistors, R1 and R2, as shown in the
  typical application circuits. LR8 regulates the voltage
  difference between VOUT and ADJ pins to a nominal
  value of 1.20V. The 1.20V is amplified by the external
  resistor ratio R1 and R2.

So if we can just amplify the voltage difference, then perhaps there is a way to use lower voltage stabilizers for higher voltage? Can somebody point me in right direction?


texts:
I'm using the ADC module of a PIC16LF15355 MCU.  When I initiate the ADC conversion after setting the ADCON0bits.GOnDONE bit, I loop and wait for the bit to clear.  It never clears, even when running the setup time out to several milliseconds.  I have successfully implemented the same code (except for setup) on a PIC16LF15344 without any problems.  I included the relevant code below.  So what can cause the ADC to not complete a conversion?

#pragma config RSTOSC = HFINT32 // Reset oscillator set to internal HF
#define _XTAL_FREQ    4000000   // 4 MHz oscillator freq for delay functions
#define NUM_ADC_CHANS 9

uint8_t spiOutBuf[10];

int main( void ) {
    OSCFRQbits.HFFRQ = 0b010; // Set internal HF oscillator frequency to 4 MHz
    WPUA   = 0b00100000;      // Disable all weak pull-ups on port except RA5
    WPUC   = 0b11000000;      // Enable weak pull-ups on RC6 & RC7 (switch inputs)
    TRISA  = 0b11111111;      // Set all port A bits as inputs
    ANSELA = 0b11011111;      // Set all port A bits as analog except RA5
    TRISC  = 0b11000011;      // Set port C RC0, RC1, RC6, RC7 as inputs (analog & switches)
    ANSELC = 0b00000011;      // Set port C RC0, RC1 as analog (flex sensor inputs)

    // Initialize ADC
    ADCON0 = 0x00;            // Clear ADCON0 to default settings
    ADCON1 = 0x00;            // Clear ADCON1 to default settings
    FVRCONbits.ADFVR = 0b10;  // ADC FVR buffer gain 2x (2.048V)
    FVRCONbits.FVREN = 1;     // Enable Fixed Voltage Reference
    ADCON1bits.ADFM = 0;      // Left-justified results in ADRESH
    ADCON1bits.ADPREF = 0b11; // Vref+ is FVR
    ADCON1bits.ADCS = 0b101;  // Fosc/16 conversion clock selected
    ADACTbits.ADACT = 0b00000; // Auto-conversion disabled
    PIE1bits.ADIE = 1;        // Enable ADC interrupts
    PIR1bits.ADIF = 0;        // clear ADC interrupt flag
    INTCONbits.GIE = 1;       // Enable global interrupts
    INTCONbits.PEIE = 1;      // Enable peripheral interrupts

    while(1) {
        for ( uint8_t chan = 0; chan < NUM_ADC_CHANS; chan++ )
        {
            spiOutBuf[chan + 1] = ADC_read( chan );

            // Write the SPI buffer to the device...
        }
    }
}

uint8_t ADC_read( uint8_t chan ) {
    const uint8_t ADC_port_map[NUM_ADC_CHANS] = {
    0b00000000,   // RA0
    0b00000100,   // RA1
    0b00001000,   // RA2
    0b00101100,   // RA3
    0b00010000,   // RA4
    0b00011100,   // RA7
    0b00011000,   // RA6
    0b01000000,   // RC0
    0b01000100    // RC1
    };

    // Set the ADC channel using the register mask from the port map.
    if ( chan < NUM_ADC_CHANS )
    {
        ADCON0 = ADC_port_map[chan];
    }
    ADCON0bits.ADON = 1;         // Turn on the ADC
    PIR1bits.ADIF = 0;           // Clear the A/D interrupt flag
    __delay_us( 20 );            // Delay for acquisition time
    ADCON0bits.GOnDONE = 1;      // Start an A-to-D conversion
    while (ADCON0bits.GOnDONE == 1);  // Wait for conversion to complete
    PIR1bits.ADIF = 0;           // Clear the A/D interrupt flag
    ADCON0bits.ADON = 0;         // Turn OFF ADC
    return ( ADRESH );           // Return higher 8 bits of the ADC result
}


texts: Altium: Create library part from a schematic symbol

texts: I have a schematic but not its associated library. All symbols in the schematic have proper details such as description, manufacturer, part #, etc... Is there a way to extract all this information and create a library using the symbol found in the schematic?


texts: Why would running the coil cable straight for ~10 inches affect metal detector sensitivity?

texts:
Metal detecting enthusiast here.

I have been reading various posts pertaining to sensitivity of metal detectors.  It is has been suggested that instead of immediately wrapping the coil cable around the stem to instead run the cable straight up the stem for about ten inches and then begin to wrap.  What affect would this have on the detecting characteristics of a detecting coil?  Would that really do anything?  I don't know enough about EE to really understand what's occurring.  Can someone explain it?


texts: Why is Rds(off) never listed on MOSFET datasheets?

texts:
I can always find the Rds(on) values for the MOSFETs I use, but the Rds(off) value is hardly ever listed. Is there a special reason for this?

In the datasheet listed, the Rds(on) equals 0.54 ohms but Rds(off) can't be found.

http://www.vishay.com/docs/91015/sihf510.pdf


texts: RFID reading / sniffing demonstration at a live-event

texts:
In the context of a live-event, we want to demonstrate how easy it is for someone with the right equipment to sniff RFID devices, including clear-text information.

Our idea is to hide a RFID reader with an antenna (up to 40cm) inside a common object such as a coffee machine or a trash, and to invite people to come by, then at the end of the presentation we would show what the reader has found, hopefully containing a bunch of personally identifiable information (e.g. name, address, ID).

Please note that everyone attending this event will be told beforehand we are going to do something like that, and every one will have the possibility to "opt-out" for this demonstration. At the end of the event, the data gathered will be completely wiped.

The device would have to understand the most common protocols used for every day RFID tags (as far as I understand, that would be MIFARE and a couple ISO standard protocols), to increase our chance to collect visible (i.e. clear-text, demonstrable) information.

I'm used to programming (C/Python mostly), but I have a very little electronics experience, and more importantly, I won't have time to go for a DIY project. I need a ready-to-use solution (although I already plan to code a bit in order to extract the results and put them in shape automatically so that I can directly present the results with a nice layout).

My question is: which hardware would you recommend for this project ? I have parsed hundred of products, online shops and forums, but I can't get a clear idea of what I need. And, from your experience, what are your recommendations for such an event ?

PS: If my question is too "vendor-oriented", please answer with generic devices requirements I have to check, like the protocols it must support, type of antenna, etc.


texts:
I built this voltage multiplier today.
I hooked it up to my 10kV AC power supply and it worked just fine. It even lit up electronics from far away (from the EM waves generated.)
There was just so much coronal discharge and the capacitors were arcing so I decided to get olive oil to insulate it.
After doing this, the voltage multiplier stopped working and I don't have the faintest clue why.
Did the capacitors blow or did something else happen? Can someone help me out? I can provide more information if needed.
The capacitors are 20kV 470 picofarad and the diodes are rated 20kV as well.


texts: Power supply modulator using op-amp and BJT -Output is not coming properly at 1Mhz

texts:
I am designing a power supply modulator using an op-amp. I have a DC voltage of 1.6 V when the clock is LOW the output should be at 1.6 V and when CLK is high the output should be at 3.6 V. I am using the below circuit to implement this functionality. Please find the attached circuit.
When the input frequency is low (say 100 kHz) output is coming as expected when it goes to 1 MHz the output is weird.
My op-amp (TLV9062, datasheet) has a BW of 10 MHz and BJT(MMBT2369ALT1) has an ft of 700 MHz.Please find the attached circuit diagram and output obtained at 100 kHz and 1 MHz.
May I know where I Went Wrong?


texts: Would proximity to water affect a magnetometer

texts:
I'm using an InvenSense MPU9150 as a tilt-compensated compass in an autonomous sailboat. I'm trying to decide where to put the the control board, with options being in a dry box on top of the "deck," or inside the hull, potentially below the waterline, encased in urethane foam.

My question is - will the proximity of the magnetometer to the water level impact the readings / soft/hard iron offsets in an appreciable way?


texts: Voltage drop from PCB ground plane to motor driver

texts:
Note: Feedback has been addressed and the circuit has been updated, however the same behaviour still applies
I'm new to creating circuits but have designed a PCB and made it with Eagle, however, the BD6210F that I'm using doesn't want to allow me to run the motor due to the voltage only being input at 2.5v.
According to the datasheet for the BD6210F, there are two important steps to getting this device to work:

Choose the operating mode (Page 10 attached at bottom has a table of
choice of which I chose b and c)
Based on B, C I need to have VREF Connected to VCC

To do this with Arduino I'm doing the following with an ESP32:
  if (is_open) {
    digitalWrite(LEFT_PIN, LOW);
    digitalWrite(RIGHT_PIN, HIGH);
  } else {
    digitalWrite(LEFT_PIN, HIGH);
    digitalWrite(RIGHT_PIN, LOW);
  }

I've used a multimeter to confirm that 3.3v is going into RIN and low voltage is being applied to FIN, and the reverse given either situation, however, the motor is only receiving 2.5v of power due to the source voltage (VCC) being 2.5v.
I've isolated this down to one section of the board which is the ground plane since when I measure any voltage with it grounded to that there's a drop of 0.8v, so my 5v input measures 4.2v while my 3.3v input measures 2.5v even though if I ground to the battery source directly it measures 3.3v and 5v respectively.  I'm not sure why this happens though or what I need to do to stop this from happening, any advice or pointers would be great since I'm stumped!
References

Update After Modification Edit
After redoing the schematic to use enable and printing out a new circuit board, I realized the voltage drop only occurs with batteries and is still present even with the extra capacitors. On top of that I've discovered more of its behavior:
Measuring the voltage to the voltage regulator this is what I'm given:

With no battery connected 0v (obviously right?!)
With battery connected the voltage jumps to 3.6 and then immediately starts dropping
Voltage hits 2.5v and stops dropping
Disconnecting the battery and there is now ~0.7v in the circuit that begins discharging slowly till it reaches 0

I'm not sure why this would happen or why it's acting as a battery storage!
New Schematic


texts: Best way of jumpering high current traces on PCB?

texts: I am designing a 4-layer PCB on which I have a trace that carries around 40A of current. The board will need to be tested at 125C. I need a way to physically disconnect this trace when needed. What's the best way to introduce a jumper on this trace?


texts:
My exam is tomorrow and there is something I don't understand in the material, so I really hope to get some help with this.
Giving the following circuit:

And giving that both FF are connected to the same clock but FF2 gets it after a positive delay (t_skew after clock goes up) my professor said that this helps us in T_setup.
I understand this point since FF2 has more time to prepare itself for a new input to be processed, but what I don't understand is that why t_skew will be "harmful" when talking about T_hold?


texts: Any Way of Converting Several 2-Port S-Parameters Measurement to 4-Port S-Parameters

texts:
I have a bi-driectional coupler and attenuator (att) in which I would like to capture its s-parameters:

So I measured 2-port s-parameters between ports 1 & 2, 1 & 3, 1 & 4, 2 & 3, 2 & 4, and 3 & 4.

Now I was wondering if there is a way in which I can combine the 2-port s-parameter measurements to come up with the 4-port s-parameter data for the network.

I found an article on doing so but this seems to be for coupled differential line systems. Any thoughts on how I can attack this problem?


texts: Flexible Layout/Autorouting with GPIO Pins (Eagle)

texts:
I have a MCU board with a number of GPIO pins that I'm connecting to some peripherals, sensors, etc. I would like to place and autoroute these in Eagle.

In firmware, it's easy to re-assign any pin to any purpose. However in the Eagle schematic, I must "hard-wire" each connection. The Eagle autorouter then gets tied in knots trying to connect the exact pins I specified. (Whereas in reality, switching GPIO "4" and "5" for example, is an equally valid route, just a small software change.)

Is there any way to give Eagle a set of GPIO source pins and destinations, and let it route 1-1 connections between any two pairs such that it gets an optimal solution? Hack solutions welcome :)


texts: Am I interpreting power supply current limit function correctly?

texts:
A bench power supply has one variable and two fixed voltage outputs. Below are the related specs:

I highlighted the 5V output specs to focus on it for simplicity of the question.

Regarding 5V fixed output the nominal output current is given as 1A. The limited current is given lets say 1.5A. It says it can be between 1.2 and 1.6 but lets say ours is 1.5A.

Now what I understand from these is: if I connect a 5 Ohm load across 5V output the current will be 1A.

If I vary the load to 3.333 ohm the load will see 5V and pass 1.5A.

But if I vary the load to 1 ohm the load will pass 1.5A but the voltage across the load will be 1.5V.

Are my above conclusions based on the specs correct?

(I’m trying to verify whether this supply has such functionality and whether I understand constant current compliance concept.)


texts: High-Voltage Pulse Measurement Using Just Resistors for oscilloscope measurment

texts:
I would like to measure a High-Voltage pulse (20kV) with a duration of a few tens of nanoseconds using an oscilloscope and a simple 1000:1 Resistor Voltage divider.

Is it possible to do this without capacitors, considering that it is a simple pulse and not high-frequency?


texts: What's special about "unity-gain stable"?

texts: As mentioned in opamp datasheets, like this one. I would think stability is a problem at higher gains, due to oscillation. What are the problems with unity-gain?


texts:
I was experimenting with a low watt boost converter,12V to 100V,50mA using the venerable MC34063A and an external MOSFET switch..I calculated the inductor value to be about 100uH.So I made two inductors using a drum core and toroid ring,both of which are 100uH.The drum core works well,but under load the toroid drops to 60V or so.
Is the toroid saturating? If so ,should i use a larger toroid to overcome this problem?
TIA.


texts: Maximum transfer rate of USB mass storage device using micro-controller

texts:
I plan to design a NAND flash disk using STM32F415RGT6 (168 MHz Cortex-M4) micro-controller. Using USB3300 PHY enables the microcontroller to connect in High-speed USB 2.0 mode. Therefore, the transfer rate of the physical layer should not be an issue. There are two requirements:

Transfer rate of the disk must be over 1 MB/s (both read operation and write operation).
A specific algorithm must be performed on the data before transfer it to/from the NAND chip (about 1100 cycles per 16 bytes = at least 70 MHz considering the 1 MB/s rate).

1) Is is possible to achieve such transfer rate using this micro-controller? The micro-controller supports DMA enabled data transfer for its USB connection.

2) How much processing power will be left for my algorithm? Has anyone measured their idle cycles after implementing a mass storage device in a micro-controller?

I know it is possible to implement such application using FPGA but I really like to avoid it if it would be possible.


texts:
I want to use an FPGA to generate quadrature modulated signals for use with an RF transceiver (something like MAX2828 ).

I am confused specifically about how the digital to analog modulation should be done.

Please correct me if this is not accurate, but the symbol rate will be the same as the frequency of the IQ waveforms, so 1 symbol per Hz? so 1 amplitude change per oscillation of IQ.

Assuming I am generating the quadrature cos/sin waveforms from the FPGA via a DAC, if I wanted to modulate the amplitude of I/Q from the digital data, the clock rate the the digital bit will be the same as the frequency of the IQ waveforms.

If this is the case this would surely lead to abrupt changes in the amplitude of the IQ waveforms. Am I meant to digitally low pass filter the output such the the DAC outputs a smooth continuous waveform, or is there meant to be some low pass filter after the DAC to smooth out these abrupt changes?


texts: Individual cell balancing on multiple packs

texts:
UPDATED: I edited my question to clarify
I'm building a 4s4p pack with 18650's. What is the best method to achieve on a per-cell balancing & protection if that makes sense? Most of the 4s BMS I looked at cannot achieve this, I concluded this by looking at the wiring diagram of most of them, example below shows the BMS working on each individual cell however this would only work on a 4s1p not a 4s4p.

The only other method I thought about is to forget about the 4s4p and instead go for 16s1p, with that arrangement the BMS tends to be on per cell basis if I'm not mistaken?
My only objective here is to ensure each individual cell is protected and well balanced, I don't know if I'm being over cautious here. The cells I am using are brand new Samsung 35E.


texts:
I have been attempting a modified star topology for my SPI bus. In my application I have my SPI bus split to several ports. These ports have 1 to 3 slave devices connected in series to each other. Is there anything wrong with this type of SPI format?

Also is it okay for the SPI bus to loop around a PCB like it is below?
I am asking this since my microcontroller is on a motherboard which talks to several daughterboards. Each of these daughterboards has one slave device. Some of the daughterboards are connected in series with other daughterboards.


texts: Serial port monitor for Arduino in Eclipse (on Linux x64)

texts:
I like to program my Arduino using Eclipse. However, I still need the Arduino IDE to use the Serial port monitor.

This is very inconvenient and breaks my work flow

I tried to use RXTX but this would cause Eclipse to crash. I also tried to use a workaround using a SSH-Server but I didn't succeed.

Has anyone managed to monitor an Arduinos output from within Eclipse on a Linux x64 machine (I use Debian Testing), who could give some detailed instructions?

Thank you in advance!!!


texts: How does less cable impedance, source/termination impedance, lead to longer cable length for higher data rates?

texts:
This question is about high speed digital transmission on a transmission line,
I need to know about how does the

(1) impedance of the transmission line and the
(2) source impedance and
(3) termination impedance,

effect the (1) cable length when we want to transmit a fixed high data rate,
and also
(2) effect data rate for a fixed length cable.


texts: PCB via, increase annular ring or increase hole size?

texts: I have to use via to route small analog signals. If I want to minimize the effect of via on the signal, should I increase the annular ring size or hole size. Lets say the total via diameter is same in both cases.


texts: How do I solve this? Can someone give an explanation?

texts: I don't understand how to calculate the timings for trigger and reset. The answers are 394.1ms & 11.3s respectively. But I don't know the explanation behind it.


texts: Help identifying cyan three lead component marked 270S

texts:
I'm trying to identify a component I salvaged off a projection TV PCB. It's blue or cyan with three legs marked 270S. Unfortunately I can't figure out where I pulled it off the board from so I don't have the board marking or location to help.
I didn't see continuity, capacitance, or diode drops between any of the three legs when I checked it with a multimeter.


texts: why we are using 2 wired connections in can bus

texts:
I am software engineer student and I am doing researching about electric cars also how communication works in electric cars. So I was trying to find answer for,
why everyone using 2 wired connections ( CAN High & Low ) for can bus. Can we use only CAN High or CAN Low? and why we could use Can High and Low.
I was doing some researching but can't find exact answer. So I want to ask here.
For example I was reading this informations.

Easy Steps for Detecting Permanent Shorts in a HS-CAN Bus
Practical tips: CAN-Bus
CAN high / CAN low

Thanks in advance.


texts: Verilog: Escape non-printable characters in string initialisation

texts:
I am trying to escape non-printable characters in string initialisations in Verilog.

In C, one can escape non-printable characters as described here. In Verilog, there is an escape mechanism, but strangely seemingly only for printable characters:

  2.7.1 Escaped identifiers

  Escaped identifiers shall start with the backslash character (\) and
  end with white space (space, tab, newline). They provide a means of
  including any of the printable ASCII characters in an identifier (the
  decimal values 33 through 126, or 21 through 7E in hexadecimal).

  Neither the leading backslash character nor the terminating white
  space is considered to be part of the identifier. Therefore, an
  escaped identifier \cpu3 is treated the same as a nonescaped
  identifier cpu3.

Can I escape non-printable characters in string initialisations in Verilog? I'm looking to do something like:

reg [6 * 8 - 1:0] test = "Hello\x01";
// Here, \x01 would be replaced by the SOH non-printable ASCII character


texts: Are there gate-level ways to produce the min or max of two binary values?

texts:
Some basics of digital logic are the half-adder and full-adder.  We know how to produce the sum of two binary values at the level of AND/OR/NOT gates, in a straightforward way presented in many textbooks.  (Never mind any advanced tricks used in real-world high performance chips.)   A few tweaks, and we can subtract.

What I don't recall ever seeing is gate-level ways to produce the minimum or maximum of two binary values.  Is there such a thing?  If so, do any microprocessors use it?


texts:
I would like to know what is the fastest SiC FET greater than or equal to 10A in a TO-247-3 package.
Currently I am using a C2M0280120D. My switching speed is 7 MHz. I want to know if there is a faster FET.
Maybe the C3M0280090D would be better?

So, if I understand correctly, what I should be looking for to determine the speed of switching should be:
Lower RDS on.
Lower input capacitance.
Lower rise time? Turn on delay time?

Is that the idea?


texts: Can you safely use a lower voltage on a DC motor?

texts:
I have some pepper seedlings I'm starting indoors and I'd like to set up an oscillating fan for ventilation. I found an old one in my garage meant to plug into the cigarette lighter of a car. It's rated 12VDC 0.8A.

I cut off the end and wired it to a 12V 3A LED power supply and it works, but it's very powerful and there's no speed adjustment. I have a box full of power supplies and the two that I think might work are a 6VDC 1.66A adapter and a 7.5V 2.1A adapter (I couldn't find a 9V one powerful enough). I know a the motor can draw much more than .8A at startup, so ideally it should be double, but I wanted to know two things:

1) Can I run a 12VDC motor on 6V or 7.5V without burning up the motor (or my home).

2) On an unrelated note: if I had a 9V 2A and a 9V 3.5A power supply, they'd act the same in regards to the motor, right? It just draws what it needs?

I've tested both supplies on fan and both start it fine. I tested a 12V 1A power supply and it failed to start the motor.

Thanks for any assistance you might be able to provide on this project.


texts:
The the NXP LPC17xx Cortex-M3 family has internal pull-up resistors on some important pins such as the JTAG, NMI, Bootloader-select pin etc.

While reading the data-sheet I learned that the pull-up is internally connected to a voltage source of 2.3V to 2.6V. The core itself runs at 3 to 3.3V.

I see that 2.3V is good enough to give a reliable logic high level, but why didn't NXP just pulled up all these pins to VCC instead?

What is the advantage in doing so? NXP clearly didn't did it that way just for fun..


texts: Noise immunity of single ended analog voltage signal

texts:
I want to use a sensor with analog output in my design. The output of the sensor is a low frequency traingular wave (less than 300 Hz) and voltage vetween 0 - 5V.  I need to carry the sensor signal to the controller through a cable, approximately 400mm in length. The sensor supply voltage and ground line also comes from the controller. I have following questions

There is a strong noise source (motor windings) close by. How can I improve the noise immunity of the signal carried to my controller?
The literature I have gone through suggests approaches like shielding, single ended to differential conversion or conversion to current signal. Is there any other approach available for this kind of situation?


texts: How can I calculate the total capacitance of a pair in this cable by using data-sheet?

texts:
Below depicts a 100m 3-pair STP cable, where my focus is the pair 1 on the top:

simulate this circuit – Schematic created using CircuitLab

If I know the output impedance of the source Rs, and if I want to calculate the LP filter effect of the cable on the V1 signal; how can I calculate the total capacitance C1 for the Pair 1.

How can I calculate the total capacitance of the pair from the data-sheet like this one? Which parameters should be taken into account?

(Consider the signal frequency V1 is low like 100Hz(sinusoidal), I guess we can neglect the transmission line effects)


texts:
Recently, I was asked in a final exam how to do this. I tried to apply superposition but I think I am not understanding something in here.

Does anyone know how to calculate the transfer function of this configuration? The question is to obtain the output at the exit of U1.


texts: Rotary Switches - 4 Positions, Two Outputs - How to determine the selected "mode"?

texts:
My apologies for not such a great description.. so I will clarify here.

I have a rotary switch from an old aircraft panel that has 4 positions and two outputs.

Using my voltmeter's resistance mode I can see the following on the outputs:

OFF
OUTPUT1: OPEN  OUTPUT2:  OPEN

ALIGN
OUTPUT1: CLOSED  OUTPUT2:  OPEN

NAV
OUTPUT1: CLOSED  OUTPUT2:  CLOSED

ATT
OUTPUT1: OPEN  OUTPUT2:  CLOSED

I am just beginning into transistors and associated ICs, so let's say I am quite green in this area.

What I want to do is run +5V into the switch and then somehow determine which of the four modes is active and then pass that back to one of four pins (or really 3 due to the OFF condition) on a microcontroller so it knows which one is selected.

Would I use some kind of logic gates for this or some kind of transistor array?


texts: Why is a lower switching frequency more efficient?

texts:
I'm designing a 10V to 3.3V step-down converter. Looking at the LT8610, the applications example shows two similar circuits that have different switching frequencies.

The Efficiency vs Frequency plot shows that a lower switching frequency is slightly more efficient. Why is this so?

Alternatively, what are the advantages of a higher switching frequency?


texts: I was soldering a magnet wire with a normal copper wire, and while doing that, i burned a small part of the magnet wire, so will this affect the conductance of the wire??


texts: What is the difference/relationship between electron current and hole current in MOSFET?

texts:
When I read MOSFET applications notes, i see term of hole/hole current many times. What is it exactly and what is the relationship between them when a channel is created by the gate in enhancement mode?
Other hand, what do these equations say?


texts: Could I install 4 pole RCCB for unbalance 3phase load (like residential building) ? How does 4 pole RCCB work? Thank you.


texts: Effect of zero order hold on gain and phase margin in continuous analysis.

texts:
I heard a rule of thumb this morning indicating that modeling a discreet system as continuous using a second order padé approximation for the zero order hold will result in a 2Db loss of gain margin, and a 7° loss of phase margin, provided the sample rate is sufficiently faster than the bandwidth of the system.  I have found no mention of this in my textbooks.

Has anyone else heard of this rule of thumb?

If so, is there a reasonable set of limitations for it's application?


texts: Understanding the workings of an ultrasonic sensor

texts:
I am trying to simulate an ultrasonic sensor using a ray-based approach. For that, my current process can roughly be described as such:

approximate wavefront using rays that mimic the shape of the sensor's beam form
subtract angle-dependent SPL loss for each ray
calculate sound pressure level that gets reflected back to the sensor at each hit point, track Δt the ray needs to get back to the receiver
subtract angle-dependent transmitter SPL loss
aggregate SPL at the sensor given tuples of SPL and Δt from each ray (e.g. overlaying different echos arriving at the same time)

My calculated SPL always refers to the reference sound pressure of 20μP.
My problem is as simple as it is impossible for me to understand: I now have SPL values at the receiver ("measured" at 30cm distance from the sensor, as in most datasheets like here). However, I'm not sure how to determine whether the receiver can register an echo or not, which is where the sensitivity comes into play. As far as I understand from here and here, that value from the spec sheet describes how the receiver can translate sound pressure into a voltage.
This is not what I need, I just want to decide whether an echo is registered or not - can I just assume that the sensor can pick up any sound pressure impulse above the reference, i.e. 20μP or an SPL of 0dB? I feel like I am missing something very obvious here, but I cannot seem to be able to figure it out. Any help would be greatly appreciated!


texts: Measure impedance of PCB antenna with very small ground plane

texts:
I have recently been designing different PCB antennas with very small ground planes due to design restrictions. I use a VNA to measure the impedances, but am having trouble measuring them correctly.

I know that the error in the impedance measurement is because the cable to the VNA is relatively large compared to the ground plane area. Therefore the cable is electrically a part of the antenna.

The design in the picture has a radius of 15mm. The cable has a diameter of 1.37mm.

How do I measure the impedance of such a small design?

Note, the question is not meant specifically for the design below, but more in general on how to do this.


texts: How to do a cut in the middle of the polygon on Altium Designer 19?

texts:
I'm wondering how to do a cut in the middle of the polygon using the Altium. It seems it has the tools just for making the cutouts and splitting the planes, but not making the cuttlines in the middle of the plane. Tried various methods to achieve this, but unsuccessfully. It would be great if someone could explain how this could be done. Thanks!

Btw this is just an example what I'm trying to achieve


texts: Should I get a multimeter to check size of voltage to avoid damaging a logic analyser?

texts:
I am looking into getting a Saleae logic analyser for a project to reverse engineer an electronic display and buttons for use with a RaspberryPi.

I think it should be OK as I would doubt, by my own assumption, that the voltages involved come anywhere close to the max +/-25V allowed for the Saleae.

I'd like to be 100% sure though, so you you think it would be standard practice to get a multimeter as well? I have been researching the specs as I'd need something that can show me the peak value of the voltage as the voltage outputs I am analysing will vary because they will have a voltage for 0 and 1 and there will be analogue outputs for audio too.


texts:
Essential Question: Which Peltier is the most Efficient for reaching coolest temperature, and is the 6V 2A peltier inefficient?

I was looking into more efficient Peltiers for my project and tried to test the amperages of certain Peltiers on a 5V power supply.

Here are the results I have up with:

Using a 5V power supply,

TEC-12704 (12V 4A standard draw) drew 5V 1.4A.
Peltier TEC-12705 (12V 5A standard draw) drew 5V 1.36A.

I don't understand how a Peltier rated higher than the previously mentioned runs at a lower power, and furthermore, when converting 12V -> 5V current output using ratios, (12V/5A = 5V/XA, where a 12V 5A Peltier should draw 5V 2.083 Amps? Why is this happening!

Lastly, I tested a 6V 2A Peltier which ran at 5V 2.2 Amps, more amperage at a lower voltage? - so does that mean this is inefficient compared to the last 2 Peltiers?

Currently I am using the 6V 2A Peltier, trying to find a more efficient Peltier and need to figure out: are these weird numbers due to one Peltier being more efficient than the other (critical to my project) or something else?


texts:
Hi I saw several datasheets from servo that use kg-cm units and other that use kg/cm I think that is a misspelling error, this is not my problem I assume that the unit most be kg-cm in units of torque force times distance.
Ok, so when the units are in N-m there not problem by when they use kg I'm not sure if they are talking about kg in terms of mass or kg in terms of force, because one is about ten time bigger than the other.


texts:
Im working with an ATMEGA328P, making a bit of USART code.

I used asm linked with C, with no less than 7 building errors.

All those were same "Number must be positive and less than 64".

Yes, I have defined __SFR_OFFSET to 0 and _SFR_ASM_COMPAT to 1. I don't have problems while accessing the PORTs, but when I try this line

#define __SFR_OFFSET        0
#define _SFR_ASM_COMPAT     1

#include <avr/io.h>

#define PORT                PORTD
#define LSB                 0
#define XCK                 4

.macro Blank
CBI PORT, LSB
.endm

.macro Black
SBI PORT, LSB
.endm

.org 0x13

    //*Emulated DMA*
    //R18 <-- [Z], Z++
    //USART <-- R18
    //if Z=0, Z=1024

    ld r18, Z+
    out UDR0, r18
    cp ZH, r1
    cpc ZL, r1
    brne Normal
    ldi ZL, 0x00
    ldi ZH, 0x02

    Normal:

reti


texts: Circuit for driving a 5 wat led via 18650 battery

texts:
Recently I got a hi power LED (3.3v, 1500mA) and few tp4056 modules and i would like to build a rechargable flashlight with it.

At first I tried connecting it directly to a 18650 battery and ... well it burned.

I tried to find available 3.3v led drivers for powering it, but all of them either work with 220v ac, or at least 5v dc (buck converters).

Is there a way to do this? For example by simply adding a resistor or any other diy friendly way?


texts: Increase input impedance of an amplifier to be the same as other amplifier

texts:
I have two different power amplifiers (on PCBs) and I want them to produce the same output volume. Both already have the same gain (26db) but their input impedance is different. One has 100k and other 20k.

Does adding a single 80k resistor to the line in of the 20k amplifier increase its input impedance or it has consequences to the design? I don't have its datasheet because I bought it assembled, but it's basically a Gainclone.

If the resistor doesn't solve it, what should I do to match the impedances?


texts:
I have an embedded application that wakes up every 15 minutes and performs some specific function for a period of two minutes.

I need to log the current consumption of this specific function on the embedded board say for a period of two weeks and see if there was any unwanted current consumptions caused due to some unknown software cases.

I am thinking of buying a cheap NI DAQ. I would like to have some suggestion on how to go about this task.


texts:
I'm looking into this reference design: https://www.ti.com/lit/pdf/tidrlf7
When U1 turns on the pin 5 outputs a 32 kHz PWM signal which is supposed to turn Q4 on and subsequently turn Q3 off during startup. When Q4 turns on D20 should be shorted, right? I'm doing some tests in a design like this and generally speaking it works, I get stable output voltage. However, what I don't understand is the voltage across D20. When Q4 turns on I should read nearly zero at D20, but I always read 24V even when U1 is running. Am I misunderstanding something?


texts:
Two circuits are equivalent if you provide a certain voltage to the terminals the current through the terminals will be the same and and vice versa; i.e. if you let flow a certain current through the terminals, the voltage across the terminals will be the same for both circuits.

Now, I have these two circuits:

I solve the second circuit and I find the voltage on R23, then usually in exercises I use that voltage in first circuit to compute current in R2 and R3 in first circuit. My question is: why the voltage in the second circuit can be used for the first (I want a rigorous proof)? Is there a theorem concerning equivalent circuits (in this case R23 is equivalent of R2, R3 in parallel) embedded in other circuits?

Important:
I gave that picture only for example, I want a proof that it is true in general.
I want to prove that if I have two equivalent circuits A, B respect to a pair of terminals and I plug them to another circuit C so we have C+A and C+B, plug using the terminal in which A and B are equivalent, then the voltage on A is equals on B in both the circuits on the terminals.

In substance starting from my definition of equivalent circuit I would like prove that: Given A and B equivalent in my definition we have that the voltage across the terminals and current flowing through terminals will be the same, when placed in the same context.

Update
To give an example for proof I would like to see, we can take the substitution theorem which similar but not equal to my question (as you can see this theorem seems obvious and has a rigorous proof)

Taken from
Circuit Theory
T. S. K. V. Iyer

I have insert this update only to say that my question seems obvious like substitution theorem and as you can see substitution theorem has an detailed proof and I think that my question maybe should have similiar proof in which are involved considerations on KCL, KVL and v-i equations.
In my question KCL, KVL and v-i equations are not exactly equals in C+A and C+B (like in substitutions theorem) but equals in C and more we have that A is equivalent to B (in sense of my definition).


texts:
I'd like to know if this LCD display is a common one like the HD44780. Sadly there is no model number on it, only the brand(?) "onv" or maybe it should be "auo" when you read it upside down. It's part of a car radio. It has a 40 pins connector.

connector:

whole display:


texts: How can I measure voltage in range -15 V to 50 V with an ADC in a microcontroller in a single circuit arrangement for scaling?

texts:
Possible Duplicate:
How do I measure a negative voltage with a ADC?
How do I sample a -2 V to +2 V analog signal with a PIC microcontroller?

I want to measure the negative and positive DC voltage with a microcontroller.
If the voltage is not in the range 0..5 V then I will need some divider circuit or the scaling circuit to measure the voltage. In measuring positive voltage, the voltage divider circuit is useful, but for measuring the negative voltage I need some circuit.
What would be a scaling circuit which will scale -15..55 V to 0..5 V.


texts:
Is it OK if I use 100K linear potentiometers to input values to Arduino?

The documentation specifies 10K should be used and I suppose that would translate to 0.5mA power consumption which would be well within spec of maximal 40mA per pin.

The question is, would it be fine to use 1K or 100K potentiometers because that should translate to 5mA and 0.05mA power consumption?

What is the advantage/disadvantage of using higher or lower value potentiometers?

What are the upper/lower values pots which are OK to use?


texts: Thermal protection effectiveness against short circuit

texts:
I'm using the L6201PS H-bridge to drive a 48V DC motor and I broke one of the H-bdridges (when I drive it in the forward direction now, both OUT1 and OUT2 are 48V instead of OUT1 at 48V and OUT2 at GND. When I drive it backwards, it's still working properly) by accidentally using a faulty connector that had the motor terminals +/- shorted together. There was a popping sound as soon I tried to drive the motor.

I was a bit surprised since this chip has thermal shutdown as one of its selling points: "A thermal protection circuit has been included that will disable the device if the junction temperature reaches 150 °C".

My thought was that as the H-bridge starts to short circuit, the junction temperature would rise very quickly and then it would go into thermal shutdown, saving itself from permanent damage - however based on this recent experience I'm starting to wonder if this is not true. Does thermal shutdown not provide protection against short circuits ?


texts: 1000 watts, 220 volt, 52" length, Coiled Nichrome wire

texts: I need to use Nichrome wire for heating purposes. My heating temperature could be among 200 Celsius, voltage should be 220V, wattage should be approximately 1000 Watts, and length should be 52 inches for this. How can I identify the nichrome wire gauges, and since I am going to use coiled wire in what diameter should the coil be?


texts: Accessing RS232 Rx Tx instead of OTG on stellaris LM4F232H5QD evaluation board

texts:
I am asking two related questions here:

I can see a program uart_echo for stellaris lm4f232h5qd . What I want is that  I need to access this data on teraterminal using PA1 and PA2 pins instead of OTG.  I have a RS232 to USB converter that I connected to PA1 and PA0.

PA0 is connected to the Rx of the converter  and PA1 is connected to the Tx of the converter. The Vcc of the converter I connected to 3.3V pin  adjacent to PA7 (near temperature sensor). I connected  the ground of the converter to the GND pin on the same row where PA7 is located

The board is powered by a 3.7V battery. The +VBUS is connected to + terminal of the battery and the negative connected to GND pin near the SD card.

Then I plugged the  USB end of the converter to the laptop,, and the smoke started coming from the converter!

The converted is useless now but fortunately the board is not having any issues.

Where did I made mistake in the above connection?

What is the correct procedure to access PA0 and PA1 pins of the board?
I want to get the Accelerometer data on the teraterminal.  There is a pin on the board Ax, Ay, Az. I checked using a multimeter that if I move the board the values changes.

How do I get this data on the teraterminal?

Kindly help me resolve this.


texts:
I have read here and here that nichrome of a certain gauge requires a certain amount of amps to reach a certain temp. e.g: 30awg nichrome requires 0.92Amps to reach 205 Degrees Centigrade. With 1 foot of 30awg wire. 12V will get the wire to 583 Degrees Centigrade.

Question: How long does it take to reach from room temp to the final temp? i.e. What is the temp velocity of Nichrome wire?


texts: Temperature-dependent leakage current in IGBTs

texts:
On one hand, the leakage current of power electronics modules such as IGBTs depends on the temperature. On the other hand, the temperature distribution on the IGBT chips is significantly non-uniform in high current and high voltage power modules where the chip center often suffers a maximum value while border edges and/or corners have a minimum value.

Which temperature of the chip below does affect the leakage current?

maximum,
minimum,
area-weighted average temperature,
the temperature of the active area or
termination area.


texts: Art of Electronics ground noise treatment puzzle

texts:
With respect to how to reduce the effect of ground currents on sensitive analog portions of a circuit, Art of Electronics (3rd Edition) chapter 8 includes this suggestion:

My question: what is the purpose and effect of the 10 ohm resistor connecting the two grounds?
I understand how this allows the low-level section's ground to float a little separately from the high-level ground, which might come about if the two sections were each attached to different external systems (not shown in the diagram), each  with their own disparate grounds, while still allowing the high and low level sections to receive power from the same PSU.
However usually the low-level section will need to communicate signals to the high level section (or vice versa), and, for those signals, any current in the 10 ohm ground resistor produces a voltage that adds unwantedly to the analog signals between the two sections.  After all, this excerpt follows a discussion of reducing the impedance of ground networks (along with deliberately designing the current paths) for just that reason, not increasing them.
For example, the 10 ohm resistors in the positive and negative rails will split the voltage drop attributable to the current consumption of the low-level section, thereby adding that half amount to any signals from one section to the other. That's already an issue, and made worse if that current consumption fluctuates (more of a problem at low frequency, since higher frequencies are absorbed by the reservoir capacitor.)
No doubt there are techniques that ameliorate the mentioned problem, such as communication between the two sections using an analog optocoupler or differential signals. But for plain old individual analog signals, I'm at a loss to understand how that 10-ohm ground resistor helps, or in what scenarios, compared to a zero resistance connection.
Thoughts?


texts: I am trying to charge a 3.7v 200mah 10c E-Cig battery with a 3.7v 380mah 25c Li-Po battery and a TP4056. For some reason my TP4056 is burning up when connected to the 380mah battery. I did some research and calculated that using a 15k resistor would get me around my target output of .24 amps to charge the E-Cig battery. Would this be correct and if so, would it help cool down my TP4056?


texts: Mux switching one leg of differential signal

texts:
I found the schematic below for a muxed thermocouple circuit from this web page.  This circuit uses a mux to switch just one leg of the thermocouples.  While I am sure that this works fine I have a feeling that its causing a couple problems with the noise immunity that one would normally get with a differential signal.  First, each leg now has a different impedance to ground which could cause different voltages to be induced on each cable when interference is present.  Second, all cabling of the disconnected thermocouples will behave as an antennas inducing noise on the negative input for all of the other channels.

Is this a correct assessment?  And, besides using a differential mux, is there a reasonable low complexity, low component count way to accomplish this (muxing thermocouple channels)?


texts:
I saw that many of nfc reader/emulate based on PN53x chipset of NXP.

But the disadvantage of this chipset is , you can't emulate ISO14443-B

why is PN53x chipset can't do it? what is so special on this iso?
i looking for another nfc reader that can emulate this iso
why many of nfc reader based on this chipset?


texts:
can you make a lithium battery pack with protected batteries?
I know there is a protection chip put on lithium battery packs, which makes protected batteries in a battery pack unnecessary, but are there any limitations, or dangers of making a battery pack with protected batteries?


texts: Why bipolar encoding such as AMI is called bipolar?

texts:
In bipolar encoding, we use three levels: positive, zero, and negative. The voltage level for one data element is at zero, while the voltage level for the other element alternates between positive and negative.

I understand the idea but don't know why it is called "bipolar", because in my understanding, polar means we can use positive and negative value(+,-), and for AMI, we use zero value as well, so a total of 3 values (+,-,0). And "bi-" mean twice/double, so a bipolar encoding should mean it use 4 values (twice of polar ecoding's available values), so I feel that "one and an half polar" is more suitable in this context?


texts: Can't understand Frequency and Bandwidth

texts:
I just don't get it. How bandwidth is the factor that the data rate and the capacity are based on?
Let's say we're using Amplitude Modulation. The main factor here is the ability to change the amplitude! The difference between the maximum and minimum frequency can be 0. Who cares? How can Niquist come and say that Capacity=2*B*n?
Just tell me how bandwidth states the speed and the capacity, please.
Thank you!
Oh, Please use understandable English :)


texts: Will my step-up converter module burn if I connect a power hungry device to it?

texts:
I recently bought a step-up converter module. It is rated to work at 24 volts and output MAX 28 volts and 2 amps. I will connect it to a source that outputs 5 volts and 20 amps. If I connect a power hungry device to the module which draws more than 2 amps, the module will limit it or it will exceed the limit and burn?

Here is the module:
https://grobotronics.com/dc-dc-converter-step-up-5-24v-2a.html

It says that the output current does not exceed 2 amps but the input current can exceed it.


texts:
I have a TB6612FNG motor driver module. Here is the manual of the module: http://www.nex-robotics.com/images/downloads/tb66fng%20dc%20motor%20driver%20module.pdf

I am trying to control one DC motor (toy DC motor) via Arduino. When I try to run this setup using a 9V battery the motor runs as expected (albeit really slow). But when I change the power supply to a 9V DC 1A AC-DC adapter the motor controller IC gets super hot. When I check the current from the adapter to the circuit, it shows 1.5A, and the voltage across the supply is 4.5 V. The motor runs for a second or two, then it stops. I guess it is because the supplied voltage dropped below the Arduinos operating voltage.

So, my questions are:

Why does the IC become hot when powered by the adapter? (I guess I burnt one chip already. Shouldn't there be a thermal shutdown?)
Why does the voltage drop? I guess probably because the adapter is unregulated, but I am not sure. Do I need to get a different adapter? If yes, what should be the specs? (When I bought this adapter, I did not know about regulated vs. unregulated. The Arduino website suggested 9V 1A, so I got that.)
How can I avoid overheating of the IC when running with an adapter?

FYI: I am a hobbyist and a newbie in electronics. Please feel free to suggest alternatives and point out the mistakes. I need to control 4 DC motors.

Thanks

EDIT 1
Sorry for inadequate details.

The motor specs are as follows:

RPM: 60 at 12V
Voltage: from 2V to 12V

The voltage applied to pin 13 is 5V, from the Arduino 5V pin. There is no load/torque applied to the motor.

See the product page: http://www.nex-robotics.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=535&category_id=84&option=com_virtuemart&Itemid=45


texts: Is it practical to make home-made membrane switches in low quantities?

texts:
I'd like to custom-make membrane keyboard switches as a replacement for the cheap push buttons I am currently using. You have all seen these kinds of buttons. If you have experience making these membrane keyboard switches, can you shed some light on that? Or if it's really something that should only be done in a large manufacturing environment, let me know. Alternatives are just as well - I appreciate it.

EDIT AFTER ANSWERS
i am considering capacitative switches after review of methods used to make membrane switches,  as i am not sure whether the membrane switches i can produce are of professional quality. as an alternative, there is a capacitative switch in my lamp ( these act as a proximity sensor almost.. detecting the capacitance change , from the human body, interacting on the switch) i hover my finger over a solid transparent plate where the switch is under and then it switches. This may be a more consistent, quality way to switch the power.

the switch uses a transparent solid plate.. then a decal over it, then another transparent solid plate. Where the switch (sensor switch) detects my movement is left transparent.


texts: Limit drawn current but not voltage (LED driver for 100W LED)

texts:
So I have serial connected 8 LiPo's with corresponding controllers to monitor the battery pack. Now, they deliver 32 volts which is precisely what I need but they deliver way to much amperage compared to what the LED can handle.

The LED specs for input is 32-34V and 3500mA.

So I got reccomended to build/buy a "Buck driver" which looks promising, but I don't know how to calculate the different components and I'm way to much of a beginner to figure it out on my own, so i found a calculator that points me to a list of items that might be suitable.

Problem here is, non of the datasheets mention the range of the amps the circuit can limit within. I would feel much more confident if they mentioned it somewhere before I go about my "learning by doing" quest.

I have no clue where to begin or if the products are correct, I've read up a bunch on buck converters, Constant-current diode's and what not.

I got an example to me saying something like "Lets say you have a car. To maintain the speed you need to have a car that can go fast enough, and a cruise control to set the correct speed", I assume the car is the LED and the circuit I'm looking for is the cruise control. However, this confuses me since the power supply and the LED is already agreeing on the voltage, I don't need a cruise control I need a fan for the bloody engine so it doesn't overheat?

I need help, in any shape or form so I'm turning to the guru's of stack-exchange!

Edit: I've Googled for 4 days and asked engineering friends, and just as I post this I find: http://homemadecircuitsandschematics.blogspot.in/2011/12/make-hundred-watt-led-floodlight.html

Not sure that works for my setup either tho.. I'm so confused by now..


texts: 2nd order Sallen-Key low pass filter frequency response

texts:
I am trying to implement the following circuit in LTspice for studying the frequency response of the 2nd order Sallen-Key low pass filter for a project.

Why am I getting a negative peak in the frequency response curve at higher frequencies?
Why is the maximum gain not occurring at the theoretical undamped natural frequency?


texts: Are my calculations wrong for the capacitance?

texts:
In an earlier post i discussed about the effects of voltage derating on a capacitor. From here i measured the output with DC and AC applied to a highpass filter and found the cutoff frequency with the applied voltage and calculated the capacitance change from these results.

Now i wish to calculate the capacitance from my input and output with a known resistance. I know the formula for the reactance of a capacitor, and if i recall correctly a Highpass filter is a voltage divider, where it attenuate lower frequencies. With this knowledge i was able to solve for the capacitance.

What seems to the issue with my calculation is, the capacitance calculated from this seems to be double or even more than its normal value. I am not sure if my measurements are wrong, since the results are the same on different measurement equipments.

Edit:
So i tried another approach at this, but the results still seems to be the same as before:

Any suggestion on what might could have gone wrong?


texts: How to enable serial emulation through USB in a STM32F4 Discovery board?

texts: I've been searching for this and still haven't found anything about it. This board connects directly to the host PC with a USB bus. Is it possible to emulate a serial port in this case?


texts: Recipe for Stepping Down DC Voltage from 19V to 12V w/ Low Inrterna Resistance

texts: I need a good 12V power supply from time to time. There are a lot of good laptop power supplies around that can give out about 5A. Is there a good, proven recipe out there that can do the voltage conversion from 19V to 12V? I don't want to use a resistor-based voltage divider, or a string of 10 power diodes.


texts: How do I convert an inductor into the dq0 reference frame?

texts:
This is what I want to convert to DQ0 from ABC:

VG_ABC - VT_ABC = jwL*IG_ABC

So basically its two voltage sources (VG_ABC and VT_ABC) separated by an inductance L.

I know how to convert it to dq0 if it was written as follows:

VG_ABC - VT_ABC = L*d/dt(IG_ABC)

But when the inductance is written as an impedance I don't know how to work with the "j" thats in there.


texts: Can BLANK pin of TLC5952 device be permanently connected to ground or does it need to be toggled (once at the startup or each cycle...)?


texts:
Due to the base current, in a common emitter circuit the emitter current is a bit higher than the collector current:

\$ I_e = \dfrac{1+\beta}{\beta} I_c \$

I was wondering how this is for a phototransistor, like in an optocoupler. I would expect emitter and collector current to be equal because there is no base current. But a photodiode can create a current with zero volt across it, so it seems the photons can create electrons. So is \$I_e = I_c\$ for phototransistors?