texts:
I've to constraints an Lattice Semiconductor FPGA and I've some doubts about the multicycle constraint described here. I've the following RTL :

Basically it is a counter that is driven by a rising edge detector. Each times that a signal rise from 0 to 1 an impulse is generated and the counter increases. This is also the VHDL code, just to be clear :

type COM_PACKETS_COUNTER is array ( 7 downto 0) of std_logic_vector(31 downto 0);
signal capture_com_tx_packet_counter : COM_PACKETS_COUNTER;
signal capture_com_rx_packet_counter : COM_PACKETS_COUNTER;
signal capture_com_tx_data_reg : std_logic_vector(7 downto 0);
signal capture_com_rx_data_reg : std_logic_vector(7 downto 0);

signal capture_com_tx_start_byte_reg : std_logic_vector(7 downto 0);
signal capture_com_rx_start_byte_reg : std_logic_vector(7 downto 0);
signal capture_com_tx_start_byte_reg_delay : std_logic_vector(7 downto 0);
signal capture_com_rx_start_byte_reg_delay : std_logic_vector(7 downto 0);
signal capture_com_tx_start_byte_reg_edge : std_logic_vector(7 downto 0);
signal capture_com_rx_start_byte_reg_edge : std_logic_vector(7 downto 0);

..........................

COM_COUNTER_PROCESS :
    for i in 0 to capture_com_tx_data_reg'length-1 generate

        process(clk_i, rst_i)
        begin
            if rst_i = '1' then
                capture_com_rx_start_byte_reg_delay(i) <= '0';
                capture_com_rx_start_byte_reg_edge(i) <= '0';
                capture_com_tx_start_byte_reg_delay(i) <= '0';
                capture_com_tx_start_byte_reg_edge(i) <= '0';
            elsif clk_i = '1' and clk_i'event then
                capture_com_rx_start_byte_reg_delay(i) <= capture_com_rx_start_byte_reg(i);
                capture_com_rx_start_byte_reg_edge(i) <= not ( capture_com_rx_start_byte_reg_delay(i) ) and capture_com_rx_start_byte_reg(i) and CAPTURE_COM_RX_SELECTED_FILTER(i);
                capture_com_tx_start_byte_reg_delay(i) <= capture_com_tx_start_byte_reg(i);
                capture_com_tx_start_byte_reg_edge(i) <= not ( capture_com_tx_start_byte_reg_delay(i) ) and capture_com_tx_start_byte_reg(i) and CAPTURE_COM_TX_SELECTED_FILTER(i);
            end if;
        end process;

        process(clk_i,rst_i)
        begin
            if rst_i = '0' then
                capture_com_tx_packet_counter(i) <= (others => '0');
            elsif clk_i'event and clk_i = '1' then
                if capture_com_tx_start_byte_reg_edge(i) = '1' then
                    capture_com_tx_packet_counter(i) <= capture_com_tx_packet_counter(i) + 1;
                end if;
                if capture_com_rx_start_byte_reg_edge(i) = '1' then
                    capture_com_rx_packet_counter(i) <= capture_com_rx_packet_counter(i) + 1;
                end if;
            end if;
        end process;
    end generate;

I have several counter in my design. Now I want to relax the timing, so I'm wondering if I can use a "Multicycle constraint" between the source register ( capture_com_rx_start_byte_reg_edge ) and the destination register ( capture_com_rx_packet_counter ) because I don't need that the counter is updated after the rising of capture_com_tx_start_byte_reg.

My only concern is that the generated impulse could last more than a clock cycle that could be a problem because the counter could be increased more than 1 unit.


texts: Electrical Motor filler metal for laminated stacks

texts:
Looking at several cores from failed motors some will have a filler-type material that is inside the stack of laminates. This material is almost always silvery, and it does melt relatively low, leading me to believe it is aluminum (and thus recoverable for casting parts purposes). However I haven't found anything to indicate what it is, other than not Magnesium for obvious fire-testing reasons.

In the found photo below, the metal in question is at the top and bottom of the core; runs through the core (thin lines), and can be extracted through application of heat. It is not extremely shiny nor is it extremely dense (like zinc might be), and I'm unfamiliar with the different grades of 'pot metal' if I could determine that with testing.

Thanks-


texts: Problem when using MOSFET to switch on/off voltage regulator

texts:
I initially designed a circuit with a P55N06 MOSFET that would be used with a LM7805. The drain is fed by 9V, the source connects to the 'in' pin of the LM7805 and the gate is fed by 3.7V. The simulation results for this are:

I expected to get 9V on the source, but as you can see it's only 2V. Any ideas on what I'm doing wrong here?


texts: Could someone please explain me what is the 0.4Ω resistor at the Vcc pin (yellow color)? Why it is surrounded by a dashed rectangle? Should I add such kind of resistor when I design my circuit?


texts: How to know if the ESP8266 has been manually reset?

texts:
I try to entirely rephrase my problem.

On the ESP8266, the RST pin is always HIGH (+3.3V), and you need to put it dow to 0-1V to reset the chip.

I will plug two push buttons on the reset pin, "button red" and "button green". My objective is to know which button has been pressed to reset the ESP.

The overall idea is to put a Resistor-Capacitor circuit on the green button. When green button is pushed, I will measure a low voltage if t=RC is high enough. If the red button is pressed, then I will measure a high voltage.

The schema with only the green button is:

simulate this circuit – Schematic created using CircuitLab

Sorry I don't know how to draw it, I insert an image of the voltages when green is pushed then released:

Then I need to plug the red button so the U(RC) stays high when pushed, but U(reset_pin) still a "rectangle".

Is this schema the right thing to do:

simulate this circuit

I cannot test the circuit right now, but is it OK in theory?

And am I in the right direction, or am I missing a trivial solution?


texts:
I am in process of hiring a freelancer to develop a PCB which will incorporate Wiznet W5500 ethernet IC.
Some have suggested a 4 layer PCB, but some are saying it is possible in 2 layers.
As the board has many buffer IC's and other connectors which don't require 4 layers.
I am skeptical to take this decision and need help.
Please advice. Thanks!


texts:
I'm trying to be this part separately but I don't really know its exact name therefore I couldn't find it.

It's the black separators highlighted in the red rectangle that I'm looking for.

I tried looking for pin separators and pin spacers but that didn't result in anything.


texts: Peak detector and amplifier for electret microphone

texts:
I've designed a circuit for detecting peak levels of a electret microphone.

I've tested the circuit before manufacturing 100 units and it worked nice. After testing the 100 PCB I've received, only 32 of them works as it's supposed to.
The units than worked perfectly shows 0 when it's not sound and 3.3 V when a loud sound is adquired by the microphone. The other units has noise at "SOUND_LEVEL" output when no sound is on the microphone. The noise is variable, some units have few millivots of noise, others have almost 1 V.
I'm sure that I had a mistake with this circuit and, depending on, maybe, the noise of the 3.3 V rail op amps oscillate or something like this.
Please, can someone help me?
Thank you in advance
Update:
I've attached switching converter schematic.

Update 2:
I've added some oscilloscope capture of SOUND_LEVEL signal when there is no sound on the microphone.

Update 3:
Today I've received a new design of this circuit. As analogsystemsrf, electret microphones have no PSRR rejection, so I've change it to a MEMS microphone (SPH1642HT5H-1) to try if it helps. SOUND_LEVEL signal has more or less the same level of noise that with electret microphone.

I think there is some kind of problem with operational amplifier stability, but I've been able to find it out.
May someone help me please?
Thanks!
Update 4:
I've replaced 3.3 Mohms resistor with a 150 Kohms one.

The signal is with almost no noise but sound pressure should be quite high in order to produce something on SOUND_LEVEL.
What do you think about TLV9062 and TLV6742 as a replacement of TLV9002?
Really, I can't understand why in some units there is dc offset on the output (apart ot the ripple). On 30% of my units, there is no noise on SOUND_LEVEL. The main problem, for me, it's dc offset on the output.
Thank for you help!


texts: Differential amplifier circuit, problem with saturation

texts:
I have a homework problem regarding differential amplifier.

  We have a differential amplifier with symmetric supply (i.e. \$V_{CC}=-V_{EE}\$).
  Emitters are connected to a perfect current source \$I_{EE}\$. T2's base is connected to the ground. T1's base (circuit's input) is connected to a sin wave generator, \$V_{PPUIN1}=2mV, \ \overline{V_{IN1}}=0V\$.
  We also know that \$\overline{V_{OUT2}}=8V, \ V_{PPOUT2}=400mV\$, where \$V_{OUT2}\$ is "wy2" in the image below. \$R_C=5k\Omega, \ V_{CESAT}=0.2V, \ V_{BE}=0.7V\$

Calculate \$I_{EE}, \ V_{CC}\$
\$V_{IN1}\$ was changed to \$-1V\$. Calculate \$V_{OUT1}, \ V_{OUT2}\$
Draw the transfer characteristic for both outputs for \$V_{IN1}\in<-1V;1V>\$

Since \$U_{IN}=U_{IN1}<2\varphi_T\$, then we assume that both transistors are active. Hence we can use this formula (I am not familiar with English naming convention, so pardon me, if my guess is incorrect):

\$G_{DIFF2}=\frac{g_mR_C}{2}=\frac{I_{EE}R_C}{4\varphi_T}=\frac{V_{PPOUT2}}{V_{PPUIN1}}=\frac{400mV}{2mV}=200V/V\rightarrow I_{EE}=4mA\$

The average value at the second output is \$\overline{V_{OUT2}}=V_{CC}-\frac{I_{EE}R_C}{2}\rightarrow V_{CC}=18V\$

And now let's calculate for what \$U_{IN1}\$ T1 becomes saturated:

\$V_{CC}-I_{EE}R_C-V_{CES}=V_{IN1}-V_{BE}\\
V_{IN1}=-1.5V\$

so.. it seems like our assumption was wrong and both transistors are not active. But from the other side, if T1 is saturated, then T2 must be cut off... which does not make sense, since we were given the information, that there is a sine wave at the second output. At this point I don't know what to do next


texts:
Hardware:

I have an asic-"sensor" which sends me 32-bit packages (serial). I need to detect this packages with an FPGA.

When I start the readout, the sensor is sending me data-packages until I stop the readout. There can be idle-times (no specific length) between the data-packages. If the asic is sending no package (idle-time), I receive 0xA3 as idle-data.

The sensor is sending LSB first (of one package). That means that I get the data first. I receive the header at the end of a packet transfer.
In my FPGA I want to detect these packages. Is there a general way to do this?

I already managed to format the serial bit stream in 8 bit parallel data.

Demonstration of the problem that I have:

The general problem is that there can be data that looks like idle or data that looks like a header. Which is not bad when it is not the last data byte of the packet, like in the 2. Example:

I -> 0xA3 (idle-data)

H -> 0x6 (header of the package)

D -> 0x00 - 0xFF (data in package)

ID -> 0xA3 (data that looks like idle)

HD -> 0x6 (data that looks like a header)

1. Example (Sensor is sending LSB first):

 MSB
| packet 2  | packet 1  |
 H  D  D  D  H  D  D  D  I  I

these 2 packages are easy to detect because there is no "ID" or "HD".

2. Example (Sensor is sending LSB first):

 MSB
| packet 3  | packet 2  | packet 1  |
 H  D  D  D  H  D  D  HD H  D  D  ID I

Hard to detect. The first package starts with an idle sequence and the second package has data that looks like a header.

Is there a general way to detect this?
I thought about convolution, but I am not sure how to implement it here.
I am using VHDL.


texts: BJT Constant Current, Resistor Equations

texts:
I am looking to design a simple constant current circuit to draw a precise load from a variable voltage rail.  The voltage rail (V+) should be 10V-20V in normal conditions, but it is possible for V+ to be floating.  The control signal (CTRL) is to be driven from an MCU on 5V rail.  I am looking for 150mA from V+.  Note that I am sizing resistors such that R1 and R3 will drop majority of power when V+ is 10V.  The transistor would then handle the additional power as V+ goes to 20V. (So T1 will be rated for >1.65W to handle up to 11V at 150mA).

I understand that normally, R2=0ohms so I'd have a constant 4.3V at the emitter (assuming Vbe of 0.7V).  That provides the easy formula of R1 = 4.3V / 0.15A.

My concern with R2=0 is that if V+ is ground or floating, there's nothing to limit the base current except for the MCU's output driver.
When I add R2 to solve this concern, I'm not sure how to set the current in the circuit as it will be dependent upon base current, which I assume is going to be based on transitor's Beta.

Is there a way to create a constant current while protecting the base in my situation?


texts: I am attaching the screenshot of differential op-amp with positive feedback(TLV9062),i am having the doubt ,is the output is same as input with all the same resistor values or any effect with positive feedback,can anyone explain? here i need differential to single ended output.


texts: Components on both sides of one side PCBs

texts:
I'm in preliminary stages of designing a PCB for my project which will have a PIC18F4680, an PCF8583 RTC plus some logical circuits and transistor arrays (exact components are to be decided) for driving 210 LEDs (six 5x7 matrices), all in through-hole technology. The PCB will be home-made which at this time limits me to a single sided 10 cm by 16 cm board plus jumper wires.

To keep the noise as low as possible and to deal with small board size (since the LED displays are going to be 52 mm tall), I'm planning on having the LED displays (and perhaps some of the logical components driving them) placed on perf-boards connected via jumper wires to one edge of the PCB and place the PIC close to that edge.

I've read in the datasheet and manual that in order to get as much accuracy as possible, I should place the RTC in a quiet part of the board (so opposite side of the PIC) and pour Vcc under the RTC, its crystal and trimmer capacitor and solder the crystal can and one side of the capacitor to Vcc (yes, I know that the usual procedure is to use GND for this, but the datasheet explicitly calls for Vcc with this model).

On a two sided board I expect that this would be done by having the top, component-side, layer be Vcc and have it go under the chip and in case of a PTH components, have a plated-through hole connected to the Vcc for RTC's power supply. Unfortunately, I don't have the luxury of having plated-through holes and multilayer boards, so I'm considering my options.

The simplest option would be to just pour a Vcc layer under the RTC, capacitor and crystal with the two of them on the component side and give up on soldering the crystal can to Vcc layer. I'm not sure how good (or bad) results would this produce.

The second option would be to put the crystal can under the RTC and solder it to the Vcc pour and RTC pins with RTC being on the component side. That would look something like this (the location of decoupling capacitor for this question isn't important):

Right now, I don't see any problems having the crystal on the bottom side of the board and it would be very easy to solder it to the RTC. This, I think, should provide me with greater immunity from noise than the first option.

The third option would be to place both the RTC and the crystal on the bottom side of the board and maybe only leave the trimmer capacitor on the top side (depending on the type of enclosure I manage to find). The problem here is that I'd have the pins of RTC sticking out of the board on the component side and that I'm not sure how I'd actually solder the RTC. I could perhaps solve the problem by using an SMD version of the RTC, but I'm not sure that I could make PCB which would be precise enough to fit the component on it.

So what I'm asking is: Are there any negative side effects that I missed and in particular are there any negative side effects if I decide to go with option 3?

Also, in case anybody here worked with this particular RTC, what can I expect if I decide to go with option 1? Am I over-thinking this whole issue? I'd like, if possible, to keep the whole thing within ± 5 minutes a year, as far as accuracy is concerned.


texts:
I am working on a clone of a Vox guitar amp and wanted to use thermal flow simulation to assess the 60's cab design and orientation of the amp chassis.

In the particular Vox amp the tubes face down (like many amps) inside the amp head. I am not sure how to apply a heat source value for the tubes/filter caps etc in the chassis. I can input a solid or surface value as a temp or in Watts.

The tube data sheets dont show a working temperature range and capacitors only show a max temp rating.

The flow simulation should show if the heat convection to the components in the chassis is better or worse depending on its orientation, which is the aim of the study.

Some people have added fans to their old amps as they have a concern about heat, and some swear that the hotter an amp runs the better it sounds. However there must be an ideal temp range or at least max that tubes and capacitors should run at before their life span is dramatically reduced.

I can also use the simulation to see if adding a fan will improve the air flow and therefore heat dissipation.

There is also transfer of heat through the chassis from the tubes to other components on the turret board and I have often wondered if the chassis is better off in an 'upright' config whereby the heat from the tube rises up and out of the head, without passing over the rest of the components as apposed to the 'upside down' config. Although in the amp I want to build the chassis would dissipate heat, however I have seen pics of this amp where it clearly has become so hot it has darkened the chassis around the tube sockets, (see photo below).

I am unsure what temp to apply to the various components as Heat Sources in the simulation.

As an e.g. in a typical push-pull amp, the maximum plate dissipation of is 30 watts plus about six watts for the filament and a couple for the screen so I could model a total as 40 watts. The temp runs around 400 degrees F for a tube. Is there a direct relationship between the dissipation in Watts and the Temp of the tube under normal operation?

An amplifier like this is about 50% efficient (or a little less) should I double the rated output to be somewhat in the ball park of the power (and heat in watts) as input to the amplifier.

Of course, after a few hours, the transformers get hot along with everything else including the capacitors and resistors in the circuit.

In my model there is a 300-0-300 V@120mA max and 6.3-0 V/4A secondary mains Tx, and an Output Tx . Again I am not sure what average heat these components would generate.

The amp will have 1 x EZ81 rectifier tube, 1 x 12AX7, 3 x 12AU7 and 2 x EL84 tubes.

The DC filter caps are 2 x 32 uF in a can; 2 x 16 uF as a double axial and one single axial 16 uF caps to produce 300V DC filtered B+.

My schematic also shows the input V at the tubes after the first V drop resistor and the Voltages at the Cathodes of each tube.

Thus with all that said, do I have enough info to set up a Flow Sim study in Solidworks to assess the best chassis orientation, cab ventilation and need for a fan??

Thanks

PS Here is a partially completed model of the amp. Only 3 filter caps shown so far. Most of the other caps are on the turret board and actually soldered above a resistor


texts:
This is probably a marginal mistake.

This circuit, a current regulator:

simulate this circuit – Schematic created using CircuitLab

Works fine on simulation.

However, it does not once built. I built it twice, once on a PCB once on a breadboard, using different components, and both behave the same.

The OA2 output is either at High or Low, depending on the V1 but is not regulating anything.

I also observe some kind of schmitt trigger behavior, current is 0 and V1 is 0, then slowly increase the voltage, it suddenly switch to the max output. Then I have to reduce V1 to almost 0 to stop conducting.

There is no oscillation or anything like this. it's either fully on / off instead of regulating.

At this point I do not believe it's a mistake on the build.

Opamp are single rail supplied at 10V.
V1 is 0-1V to control 0-1A.
I tried with BA2902 and OPA227


texts:
I want my circuit to be fail-safe. The requirement is that a signal from the processor should be able cut the power supplied to the processor. But when the power is switched back on, it should be able to power up normally.

I've been thinking whether to use relays, but it doesn't make sense. I am stuck on the part where I have to switch the power back on.

Any ideas on how to implement this on a circuit?


texts: Is it safe to rebuild my laptop battery pack?

texts:
this is my first question on this website, so please excuse me if I did not follow the guidelines correctly.

I have an Alienware 17 R1 (2014) and have been looking into rebuilding its laptop battery that has been dead for a while now. I have read up quite a bit into battery chemistries etc., but I would appreciate advice from the experts here regarding my little project.

I am a computer enthusiast, but rebuilding a battery pack is something I have never done before. My laptop battery uses a 4S 2P configuration of 18650 cells for a total of 14.8V and 5.6A. I want to replace these cells with higher capacity ones, but am unsure of what cells to buy (unprotected or protected), and if directly soldering onto these cells is really a good idea. What I am worried about the most, however, is if this modification will result in a battery that is unsafe and might result in my house burning down.

One last question that I feel is relevant to this topic. I was also thinking about replacing the optical drive bay of my laptop with more 18650 cells for more battery life, I read about another guy doing this in this forum: https://www.overclock.net/forum/158-laptops-netbooks/1528118-guide-tutorial-upgrading-your-laptop-s-battery-life-without-wasting-existing-battery-capacity.html. I was wondering if I can do the same safely. I know for a fact that the batteries will fit (took the measurements).

Please feel free to inform me of any equipment that you feel I should have when building the battery. I already have a list, but I am open to more advice and suggestions.

Thank you so much for your time and advice, I will select the best answer in a week.


texts: Why do the polarities of the capacitor change while discharging?

texts:
I was going through the working of class D commutation and the article said:

  As soon as the capacitor completely discharges, its polarities will be reversed but due to the presence of diode the reverse discharge is not possible.

Why does the polarity of the capacitor reverse as soon as it completely discharges? Is it because it immediately ( at the speed of light) starts to charge?

Moreover, what does reverse discharge mean?


texts: In building an electronic load with a mosfet and op amp. It adds some benefit to use a mosfet driver IC?

texts:
I´m building an electronic load following this schematic.

My op-amp is an LM358 or LM324.
My mosfet can be an IRFZ44N, and STW45NM50 or a IRFP460.

Those are the parts that are in my bin.

My question is that if adding a mosfet driver IC TC4420 between the output of the opamp and the gate of the mosfet will improve the switching response and reduce heat dissipation. Or in this application will be the same using or not the mosfet driver.

Thanks


texts: Can I use the same electrical ground for everything in a van?

texts:
I have the following setup in my van .
BAT1 is the battery in the front of the van which was build in. It is being charged by the alternator while the car engine is running. This also turns on the 12V 70A relays which usually means that it also charges BAT2.
I ran this for a while. But then BAT2 basically died. This could be because I overdischarged it, but makes me worry.
Sidenote: The two appliances FRIDGE1 and LS1 are examples. In reality there are more.
Today I checked and with mild sunshine at an okay angle, the 2x(12V 100W) solar panels were delivering around 15V 0.1A. So there is a problem. Do you have any idea how I can figure out what that problem is?
The ground is the hull of the van. Is that an issue that everything is connected like this??
EDIT
More information was requested.
The black image between the labels Bat and Load depicts a solar charge controller (30A max). I attached a bluetooth reader to it. My readings come as information from the charge controller and a multimeter. I used the multimeter only to measure voltage.
Solar
-15.5 V (can be more sometimes, but not significantly)
-0.1 A
-set up in series as depicted
BAT2
-14.4 V max (while car engine is on), 12.2-12.9 V otherwise
-the 160Ah hour Calcium Battery is still good enough for making a coffee☕, but the voltage drops significantly when doing so.
-I plan to exchange it with a lithium battery. But before that I want to make sure that my setup doesn't break it.
BAT1
-60Ah Lead battery under the hood
-12.39V (single measurement with multimeter yesterday)
To precise my questions:

Is it okay to connect everything to the same ground like that?
How do I "debug" my solar setup to figure out what's wrong?

If there is anything else missing, please clearly tell me what that is.


texts:
The usual circuit (found widely across the internet) for a true random number generator's (TRNG) entropy source is a reverse biased transistor like so:-

Q1 is typically a 2N3904 as it has been found to be quite noisy the wrong way round running in breakdown mode.  +ve is typically in the order of 11V. This topology works well initially.

I came across someone who had build a TRNG and experienced problems whereby "after about 3 months of use the noise signal would drift".  I've seen other references to long term degradation of such a  topology but can't seem to locate them at present.  I have the sense that continuously shoving electrons the wrong way up a transistor might be detrimental, but have not found any references to prove this one way or another.  After all, this is not the principal use case for a transistor.  Could the junction suffer gradual and irreversible damage thereby altering it's noise characteristics?  Zener diodes are another situation altogether as breaking down is their modus operandi.

Three references on E.SE discuss reverse biasing, but not long term stability:-

Understanding reverse biased PN junction

Does a reverse-biased P-N junction create quantum noise?

Is my avalanche noise “random?”

Is a reverse biased transistor stable in the long term?


texts: Working with current feedback opamps [CFA]

texts:
Before entering in to problem:
My application is a laser pulse detection. In this process, when a laser pulse falls on a photo diode, it generates current. Later stages include a I-V conversion, gain, difference amplifier and comparator.
My current problem with I-V conversion can be seen here.
My pulse characteristics:
pulse width min: 10 ns max: 150 ns rise/fall time: 2 ns - 5 ns pulse to pulse width:22 µS
How I selected the opamp for gain and difference amplifier stages
Key parameters: BW - bandwidth and SR - Slew Rate
From this literature I found my BW can be calculated by the formula:
BW = 0.35/(rise time) = 0.35/5 ns = 70 MHz
Now the slew rate is to be calculated:
SR = 2 * 3.14 * BW * Vp = 2 * 3.14 * 175 MHz * 4 V = 2198 V/µs
So matching both these parameters is a CFA AD8003 from Analog. When I go for high slew rates and high BW almost all opamps avaliable are CFA's!
What is worrying me?
Without any notion when I used CFA for my difference amplifier stage, with unity gain using a 500 ohm resistor for Rf and Rb, the results seemed stable, but it is this statement from Texas Instrument technical literature, clearly saying:

the first difference between voltage feedback and current feedback—the
input impedance of current feedback op-amp inputs is very different.
Because the inverting input has low impedance, current feedback
amplifiers are not good for balanced systems such as differential
amplifiers

CFA as difference amplifier

So my results are like this for a difference amplifier followed by a comparator. The pulse here is 10 ns width and 1 ns rise and fall times and repeating at a 150 ns rate.

Why is the pulse quite expanded? Which capacitor stage has done it I didn't understand.
CFA as amplifier with gain

The results for the above circuit are also not as desired (I just see 0 V output), why so?


texts: How to prevent electric arc on a precision contact

texts:
I'm not native English speaker. I hope I can be clear enough. Sorry.

My scenario is me trying to convert a 3D printer into a CNC PCB mill and as the bed and I need to use the drill as a probe to work as Z axis endstop. So the printer circuit has a pin with a pullup resistor (12v) and it being driven to ground marks the z=0 height. So I connect the PCB to ground and the drill to that pin and that's it.

But I observed electrical arcs between the drill and the PCB and I think that reduces the precission. And I need that precission. I think the board is "sensed" before actual contact is made. 0.05 mm is enough error to reduce que quality of the result as I am milling 0.16 mm with a cone drill.

So, Is there a simple way to prevent that arc? My first thought was to put a resistor but there is already one there, the pullup, so I think it might be useless.


texts: I am trying to make Decimal to binary encoder using IC 74147 in Proteus. But Led's are not lighting up. What am I doing wrong?


texts: Linearized state space model of PM synchronous motor

texts:
I intend to implement field oriented control of PM synchronous and Induction motor in Simulink. I started with the synchronous motor and was trying to find its linearized state space model.

I read that I should equate the following three equations to zero and find an equilibrium point.

(di_d)/dt=Vd/Ld - (Rsid)/Ld+(weLq*iq)/Ld = 0

(di_q)/dt=Vq/Lq - (Rsiq)/Lq-w_e(Ld*id+ƛ_PM)/Lq = 0

J*(dw_m)/dt=T_e - B*wm

where T_e = 1.5*Pƛ_PMiq

Since, there 5 unknowns, namely Vd, Vq, id, iq, and wm (we=p*wm, p= pole pairs) and three equations, I am unable to solve the above equations.

I tried to read few papers online but they did not explain it properly.
If you have any tips or suggestions to proceed further, it would be great!

Thanks,


texts: What’s the proper soldering iron temperature for standard .031" 60/40 solder?

texts:
I recently purchased a Weller WES51 soldering iron as my first temperature controlled iron and I'm looking for recommendations on the best default temperature to use when soldering.

I'm using mainly .031 inch 60/40 solder on through-hole components.


texts:
I'm using arm gcc (CooCox) to program an STM32F4discovery, and I've been wrestling w/ an endian problem

I'm sampling with a 24 bit ADC via SPI.  Since three bytes are coming in, MSB first I had the idea of loading them into a union to make them (I hoped, anyway!) a little easier to use.

typedef union
{
int32_t spilong;
uint8_t spibytes [4];
uint16_t spihalfwords [2];} spidata;
spidata analogin0;

I load the data using spi reads into analogin0.spibytes[0]-[2], with [0] as the MSB, then I spit them out via USART at a megabaud, 8 bits at a time.  No problems.

The problems started when I tried to pass the data in to a 12 bit DAC.  This SPI DAC wants 16 bit words, which consist of a 4 bit prefix starting at the MSB, followed by 12 bits of data.

Initial attempts were to convert the twos complement the ADC gave me to offset binary, by xor-ing analogin0.spihalfwords[0] with 0x8000, shifting the result to the bottom 12 bits, and then adding the prefix on arithmetically.

Incredibly frustrating, until I notice that for analogin0.spibytes[0]=0xFF and and analogin0.spibytes[1]=0xB5, analogin0.halfwords[0] was equal to 0xB5FF and not 0xFFB5!!!!!

After noticing this, I stopped using arithmetic operations and the halfword, and stuck to bitwise logic and the bytes

uint16_t temp=0;
.
.
.

// work on top 16 bits
temp= (uint16_t)(analogin0.spibytes[0])<<8|(uint16_t)(analogin0.spibytes[1]);
temp=temp^0x8000; // convert twos complement to offset binary
temp=(temp>>4) | 0x3000; // shift and prepend with bits to send top 12 bits to DAC A

SPI_I2S_SendData(SPI3,temp); //send to DACa (16 bit SPI words)

... and this worked fine.  When I peek at temp after the first line of code, its 0xFFB5, and not 0xB5FF, so all is good

So, for questions ...

Cortex is new to me.  I can't recall PIC ever byte swapping in int16's, even though both platforms are little endian.  Is this correct?
Is there a more elegant way to handle this? It would be great if I could just put the ARM7 into big-endian mode.  I'm seeing many references to Cortex M4 being bi-endian, but all the sources seem to stop short of actually telling me how.  More specifically, how do I place the STM32f407 into big-endian mode, even better if it can be done in gcc.  Is this JUST a matter of setting the appropriate bit in the AIRCR register? Are there any ramifications, such as having to set the compiler to match, or math screwups later with inconsistent libraries??


texts: Negative Voltage Reference For Instrumentation Amplifer

texts:
I'm trying to measure a variable resistance, RX, creating an AC voltage  with two PWM and applying it to a wheatstone bridge. The PWM goes from 0 to 3.3v and to measure the voltage differential i'm connecting each arm to a InAmp to read after with a ADC. My problem is that my circuit is unipolar (+3.3v) so i'm looking for solutions to create an negative voltage source (-3.3v) to power the opamp in the negative rail to avoid saturation. I read about charge pumps, is there any other better solution ?

Thank you in Advance.


texts: KiCAD: Why is ERC throwing errors on apparently connected pins?

texts: I've reconnected several of these (C1, U1 GND) more than once, even redrawing entire wire segments, but I still get errors about unconnected pins. Is there something I'm doing incorrectly?


texts: How to go about determing the System Type of my setup?

texts:
I have a small project where I am PID tuning two servo motors. Something very similar to this:

I am interested in finding the system type of the above setup, which includes the PID loop I have tuned. I know that the system type can be very generally described as the number of integrators or poles at the origin in the system.

- I know that I am dealing with a cascaded control system.

Loop 1: Standard DC motor closed loop system (for both servo motors).
Loop 2: PID tuning of that servo motor such that when I want a 90 degree rotation, the servo motor does not actually overshoot.
Loop 3: PID that I have created myself on top of the whole system.

Below is a Simulink block diagram of what I predict the cascaded loops would look like.

How would I be able to estimate accurately or work out the number of integrators in such a system?


texts: Why is my shift register circuit not working?

texts:
I would like to capture the state of some push buttons with a shift register (CD4014B). I am trying to troubleshoot and identify if the problem I'm having is hardware or software.

Printing the byte to the serial monitor I can see 11111111 when no buttons are pressed.. The expected result.

The problem I'm having is no matter which button I press all bits remain 1... Except button 'D'. When 'D' is pressed all bits are 0.

Here is my schematic:

(Side note: I don't currently have actual push buttons installed. I'm simulating a button press by connecting the pin header to ground)

int dataPin = 8;
int clockPin = 9;
int latchPin = 10;

void setup() {
    Serial.begin(9600);
    pinMode(latchPin, OUTPUT);
    pinMode(clockPin, OUTPUT);
    pinMode(dataPin, INPUT);

    digitalWrite(latchPin, LOW);
    digitalWrite(clockPin, LOW);

}

byte shift() {

  byte data, i;

    /* first clock pulse gets parallel load */
    digitalWrite(latchPin, HIGH);

    data=0;
    for(i=0;i<8;i++)
    {
        /* clock low-high-low */
        digitalWrite(clockPin, HIGH);
        digitalWrite(clockPin, LOW);

        /* if this is the first bit, then we're done with the parallel load */
        if (i==0) digitalWrite(latchPin, LOW);

        /* shift the new bit in */
        int temp = digitalRead(dataPin);
        if(temp) {
            data = data | (1 << i);
        }

    }
    return(data);

}

void loop() {
    byte buttons = shift();
    Serial.println(buttons, BIN);

    delay(10);
}

Is my schematic wiring correctly, and is my code error free? And in either case, why am I not getting the desired results?


texts: If two BJT bases are shorted, where does the voltage come from?

texts: While trying to understand the circuit below in this question I got the idea that PNP base current is going into NPN base terminal. This way, you drive 2 transistors with only one base current. With R3 and R2 you prevent the ringing from dis/charging base capacitance. Simulating this I could get voltages all across the circuit. But how to manually calculate the voltage at PNP and NPN h bridge's bases? My thought is, if transistor are voltage switches, although BJT are current driven, where does the voltage base to saturate they come from ?


texts: What happens to the output voltage in CS Amplifier when signal source is large enough to drive the transistor into cutoff and triode regions?

texts:
simulate this circuit – Schematic created using CircuitLab

Given this circuit of a common source amplifier with a resistive load, I know that as long as the signal source $$A\sin(\omega t)$$ is small enough and the operating point lies in the saturation region we can do the regular small signal analysis to find Vout. There will be a negative incremental gain. Similarly, based on what I understand , if the operating point were in triode region the output voltage will still show some negative incremental gain but much lower than the gain in the saturation region. Please correct me if I am wrong.

I would like to know what happens if the operating point is in the saturation region, but the signal is large enough to drive $$v_{GS}$$ to cutoff and triode regions(each on either half cycles). What will the trans conductance look like then?

Here is what I thought about it:if $$v_{GS}$$ were to be driven to the cutoff region, $$V_{GS}+A\sin(\omega t)$$ should become very low. So this should obviously mean this occurs below some point in the negative half cycle of $$A\sin(\omega t)$$. In the cutoff region, no current flows through the MOSFET, so no current must flow through R3. Therefore, $$V_{out} = VDD$$. Similarly, triode region must occur above some point int the positive half cycle. In the triode region gain will be lower. So I arrived at the following graph(attached), which is obviously wrong because it has discontinuities in it, but I don't understand why it is wrong.
For the trans conductance part, I am totally confused. Are we supposed to consider the signal source also to plot it because it is not "small enough" anymore or is it a constant straight line at $$K_n\frac{R_1}{R_1+R_2}V_{DD}$$.


texts: What will be voltage drop across 1N4007 Bridge wave rectifier at 24 volts AC?

texts: Actually... I'm finding the response of 1N4007 Bridge Wave Rectifier at INPUT Voltage 24 Volts AC with 2 Ampere Current taken from a Step down Transformer which provides us output of 24 volts AC. So please show me that what will be voltage drop across 1N4007 Bridge Wave Rectifier at 24 volts AC?


texts:
I have read that the inductors are imbedded in asphalts in small cities and this is how the traffic light detects if a car is approaching.

I have two question.

1- So if they are embedded would the magnetic field be strong enough to pass the asphalt without attenuation?

2- The cores of the inductors remain the same and what is changing is not the magnetic filed inside, but outside. From the basic physics we know that
the change in inductance depends on the permeability of the core, area of the core and the length of the wire. So nothing in core changes when a car stops on top of an inductor. So the question is how would the voltage changes in this case?


texts: What kind of capacitor is this in the image?

texts:
The power supply of my model railway got broken.

I think the problem is the capacitor shown in the image. So does somebody know which kind of capacitor this is?


texts: Raspberry Pi stereo camera frame synchronization/genlock (video or still image)

texts:
I need to frame synchronize a stereo camera for a computer vision application. The synchronization should the best possible, hopefully on a millisecond level. I would like to get about 10 FPS either as video or still images. Resolution requirement is around 2 Mpix.

The application will be mobile stereo road/terrain scanner from a passenger car moving up to say 100 km/h during daytime (thus good lighting conditions). Rolling shutter should not be an issue with Pi camera at FullHD according to this and this video.

My current hardware search has ended up with a Raspberry Pi solution. I think basically I have 2 options with it:

Get two standalone Raspberry Pi units each with a camera on it. Synchronize them via an external GPIO trigger. Cost is 2x25+2x16 = £82.
Get the new Compute Module Development Kit and connect both cameras to the single board. Couple the two cameras for a simultaneous release with software. Cost is 126+16+16 = £158.

Will both options have similar sync results? Also I would rather like still image output than video output, because I will need to extract given frames from the video anyways. The still images would preferably be uncompressed not to loose image detail, but JPEG is OK too. I am not sure how many FPS can do the GPIO external trigger with still imaging.

Cost is an important factor for me. Using USB webcams probably wont work since USB devices cant be synced easily (see link below). I will be happy with another hardware recommendation if someone knows better stuff within a similar price range.

The origin of this question is on Video Production SE site in a post titled Creating synchronized stereo videos with 2 cameras at low cost. This link can reveal some more background.


texts: Dc Motor giving ac as well as dc voltage when used as generator

texts:
When I rotate the rod or the moving part of motor and probe its output through a multimeter (set on ac measuring) it shows around 0.50 volts.
When I set the multimeter on dc measuring, it still shows 0.50 volts. How is this this possible?.i have a mextech multimeter. When i slow the rotating of the motor the voltage falls in both the ac voltage and the dc voltage


texts: Why does capacitive loading occur when using passive oscilloscope probes?

texts:
I was recently reading an article written about oscilloscope probing. And at one paragraph there is a comparison between active and passive probes as in the below quote:

"For high-frequency applications (greater than 600 MHz) that demand precision across a broad frequency range, active probes are the way to go. They cost more than passive probe and their input voltage is limited, but because of their significantly lower capacitive loading, they give you more accurate insight into fast signals."

What does "capacitive loading" means in this context? Why are passive scope probes more prone to it in high frequencies?


texts: Charging a battery from both solar panel and wind generator

texts:
I am a complete newbie to electronics. I have taken up a project that basically aims to generate power using solar and wind energy due to personal interest and have done research but I seem to have hit a dead-end.

I have a 10 watt solar panel, 17.28 V (Vmp) that gives me current in the "AC" form DC.

I have used a stepper motor with the following features:

2 Phase
Rated Voltage : 12V
Rated Current : 0.33A
Winding resistance: 32.6 Ω
Winding inductance: 48 mH

UPDATE: I just went over the specifications again of the stepper motor, and it is a DC motor.  The DC motor is 12 volts output, The solar panel as mentioned before is also the about the same. I know how to produce electricity using the motor as well after a bit of research, i used a propeller that turns the motor to produce power now. The question now is, i have two DC sources and I want to charge one battery with it that will store the energy produced. How do I do it safely and connect both to one battery ? Thanks for putting up with me, although i sound very stupid i am still trying to learn. Thanks and merry xmas !!


texts:
I am ready to perform a BGA reballing operation on my ps3's CPU and GPU chips. Should i take into consideration electrostatic discharge or is it not needed?

How can i protect from these dangers? Are there special gloves to buy? Or i saw in a pic a guy wearing a bracelet, maybe one of these? Do these work in isolation?


texts:
I am designing a PCB Board for Altera Cyclone III EP3C5E144. However, I cant find any library for this device in Eagle.

Is there anyways I could create the library and symbol for this device, based on this bsdl file?

http://bsdl.info/view.htm?sid=599926c619a107a388ca59b002289d77


texts: Why do most textbooks use the inverse formula 1/rtotal for parallel resistance?

texts:
I was calculating the parallel resistance for a circuit, but just couldn't get the correct answer despite several attempts. I felt incredibly dumb when I watched a video on how to calculate parallel resistance and realized I forgot to take the final inverse after summing all the terms:

For example, suppose we have a parallel circuit with resistors of
30 Ohms, 60 Ohms, 20 Ohms and 10 Ohms. Then the total resistance

$$\frac{1}{R_t} = \frac{1}{30} + \frac{1}{60} + \frac{1}{20} + \frac{1}{10}  = \frac{2}{60} + \frac{1}{60} + \frac{3}{60} + \frac{6}{60} = \frac{12}{60} = \frac{1}{5}$$
$$R_t = 5 $$

I realized my answer was 1/Rt, not Rt. I kept forgetting to take the final inverse! I became furious when I recalled this wasn't the first time I made this mistake. The video lecturer said it was a very common error.

Why do electronics textbooks and teaching materials use this error prone formula instead of the simplified (variable isolated?) form:

$$ R_t = \frac{1}{\frac{1}{R_1} + \frac{1}{R_2} +\frac{1}{R_3} ...} $$

You rarely see other formulas expressed as a non-isolated variable in an equation. Consequently, it's very easy to overlook the final inverse operation. Why is this form so commonly presented? I suspect it is used for pedagogical reasons to help students understand the underlying concepts, but unsure.


texts: How to limit Inrush current from a DC motor?

texts:
I'm new to this platform and knows very little about electronics. Please forgive if any of this is dumb.
I wish to create an inrush current protection for my L298N Motor Driver, which drives a 7.5V DC motor.
The Motor draws nearly 2.5A (Please see waveform) during start which according to L298N Datasheet is above maximum.

waveform under no load

waveform when loaded
To prevent inrush, I came up with a circuit as given below. The capacitor would be charged at all times and the IRF740 MOSFET is set to turn on when the motor starts. The capacitor would discharge through the mosfet to provide the initial current requirement. Diodes prevent reverse current.

I don't know if this would work or if this has any problems. Please tell me whether this circuit would work. If it has any problem, suggest a good method to prevent this inrush.


texts: What is the significance of Common Mode Signals?

texts:
I don't understand the physical significance of Common Mode Voltage.

It is arbitrarily defined as the average of two voltages and is expected to be rejected by a differential amplifier. Why? What is its physical significance?

EDIT
my question was specific to differential amplifiers. Both inputs to the differential amplifier need not be equal and opposite. What would be the meaning of common mode voltage in such case?


texts: OpAmp choice and circuit configuration for DAC amplification to speaker

texts:
For a school project we're using a uC with a DAC which outputs values between 0V-3.3V, which we want to amplify and feed into a speaker.

We haven't settled for a particular speaker but considering it would be mounted on a PCB it should be assumed to be a small 8~16Ohm one.

Now the DAC needs a minimum load of 1kOhm and it obviously can't be fed directly to the speaker so we were juggling a few options.

The first one was to use the widely available LM386 in the following configuration:

Blue signal is the DAC's output, green signal is the LM386's output, red signal is what reaches the speaker after the filter.

This seemed to be the easiest way but, it has a huge problem in that the DAC's output has to be limited to +-0.06V in the example, which cuts down the DAC's resolution and we assume introduces a lot of noise. Even with such a tiny signal the LM386 seems to be saturated on the top too, as it's cutting off the signal's peaks.

A second idea was to use an LM4811, which... we haven't even been able to find so we're not optimistic about even being able to get it, but it would work in a voltage follower configuration, letting us cut the DAC's output down to just 0V-1V. The problem here is I don't have a good LM4811 component model for the simulator so I'm not 100% sure of whether we need to alter the circuit's design further.

The question then, is: is there some way to get a better signal conditioning using the LM386 in our case, or any other widely available audio opamps we haven't considered? We don't need an amazing signal/noise ratio nor high specs at all since it's a project a bunch of first-timers should finish in a month, but we're not really experienced enough to tell exactly what we need here.

Thanks a lot in advance!

EDIT:

DAC electrical characteristics:

EDIT 2:

We're using an EDU-CIAA board (Spanish language link) which has an LPC4337 as its uC.


texts: Switching a 12V AC current from a microcontroller (no magnetic relay)

texts:
I need to commute on/off a coil feeded with 12 Vac from a microcontroller output (5V).

I've found a cheap Solid State Relay but the datasheet and a forum says this doesn't work with less than 75 Volts ac.

G3MB-202P SSR

https://www.electronicasannicolas.com.co/productos/index.php?id_product=3099&controller=product&search_query=rele&results=10

Others models operate in a high dc input.

What can I do? (in a cheap way).

Solved:

thanks to Jack Creasey.
the circuit work perfect.
adding a triac in the output I can drive the voltaje like this image.


texts:
I would like to get some help with the calculation and modeling of the attached circuit.
this circuit is supposed to generate a 159.15 Hz sine wave(according to formula), i want to connect the output of the circuit to a transformer with minimal losses of voltage, for that i need that the output impedance of the circuit(which is also the output of the op-amp 741) would be as low as possible.

I know that ideal op-amp output impedance is 0, but how do i calculate the actual impedance of the circuit(Rout) ? and how to i model the opamp in the circuit ?

if i suppose to model the opamp according to the pic below how do i calculate the inputs?(v±)

when solving these circuits i usually start with KCL from a voltage source summing up all elements until i get to ground but how do start the calculation if it is a feedback circuit like this.

frequency formula: 1/2*pi*R1*R2*C1*C2 while C1=C2=0.1*10^6 [F], R1=1K[ohm],R2=100K[Ohm]

the impedance of C1 and C2 is 1000 [Ohm],

Thanks for your help


texts:
I am looking at a Smith Chart tutorial on the antenna-theory.com website. Unfortunately, I'm confused by one of the examples given...I don't get the same answer, so it's safe to say I'm doing something wrong. I was hoping someone could point me in the right direction.

It's example 2 on that page. It assumes a reference impedance, Zo = 50 Ohms. It provides a reflection coefficient, Γ = -0.3 + i0.4, and calculates the corresponding load impedance, Zl = 20.27 + i*21.62 Ω using the equation below:

Zl = Zo (1+Γ) / (1-Γ)

However, I don't get the same result for Zl. My working is:

For the real component of Γ, Zl = 50Ω (1+(-0.3)) / (1-(-0.3)) = 26.9Ω

For the imaginary component: Zl = 50Ω (1+i0.4) / (1-i0.4) = 116.67 Ω

Giving Zl = 26.9 + 116.67 Ω, which is miles off their answer. I'm obviously misunderstanding something, so any help would be appreciated!

Thanks in advance


texts: Why does flash size depend on target hardware?

texts:
I've been writing an application for AVR microcontrollers. I intended to burn it on ATtiny13A (because it's cheap, and I wouldn't use complex functions anyway), but at that time I had only ATmega328P available, so I used it to develop code. Knowing that flash size of ATtiny13A is only 1kB, I spent quite a lot of time optimizing code for size, making it 910B. Today, my ATtiny13A's arrived. However, when I recompiled code for this hardware, the code took just 772B - a 15% of difference! If I knew this before, I would wait with those optimizations. I don't use any advanced library functions - the only files included are: avr/io.h and util/delay.h. Thus, I wonder what caused the size difference - were those some additional assumptions the compiler could use knowing the target platform? If yes, what were they? Or maybe the included files themselves contain some boilerplate code varying betweeen platforms?

Note: I'm using avr-gcc 4.8.1.


texts: Calculating core length and question regarding B-H curve

texts:
I understand the problem and all (or so I thought), but my answer was way off. Looking at the solution, I realized that I calculated the core length wrong.

I don't understand how though. Shouldn't \$l_c= 2 \pi(r_o+r_i)/2 -g\$? In the solution, they gave  \$l_c= 2\pi(r_o-r_i) -g\$ How does this make sense? What am I missing?

Also, if I want to find \$\mu\$ from B-H curve, do I take B/H or dB/dH?


texts: Understanding instruction pipelining speedup calculation

texts:
I was solving the exercise problem 4.17.6 of chapter 4 in the book Computer Organization and Design by Patterson and Hannessey (4th edition):

  Percentage occurrences of the instructions are as follows:

  and following are the clock cycles sizes for different stages:

  We can convert all load/store instructions into register-based (no offset) and put the memory access in parallel with the ALU. Assume
  that the latency of the new EX/MEM stage is equal to the longer of their latencies. This change requires many existing LW/SW instructions
  to be converted into two-instruction sequences. If this is needed for 50%
  of these instructions, what is the overall speedup achieved by changing from the
  5-stage pipeline to the 4-stage pipeline where EX and MEM are done in parallel?

The solution given is as follows:

  The latency of the pipelined datapath is unchanged (the maximum stage
  latency does not change). The clock cycle time of the single-cycle datapath is the sum of logic latencies for the four stages (IF, ID, WB, and the combined EX + MEM stage). We have:

  The number of instructions increases for the 4-stage pipeline, so the
  speedup is below 1 (there is a slowdown):

Doubt
I feel this is pretty wrong. The solution simply seeks to first find the increase in the number of instructions and then compare them. $$\frac{1}{1.15}=0.87$$However it neglects the increased clock cycles (from 200ps to 215ps) and decreased stage count (from 5 to 4). I feel it should be $$\frac{5\times 200}{4\times 215\times 1.15}=1.01$$
So there is indeed little speedup. Am I right?


texts: Why does my phone pull less current from power bank when the screen is on?

texts:
While charging my phone (a Samsung Galaxy S5) with a power bank that displays the power output with 0.1 W resolution, I turned the screen on. To my surprise, the power pulled by the phone went from 7.1 W to 5.0 W instantly.

I repeated the experiment many times. Screen on, 5.0 W. Screen off, 7.0 W.

I would have expected the phone to either pull more power to both charge at full speed and power the sceeen, or to pull the same amount, and simply charge the battery at a lower rate.

But I find the drop in power when turning on the screen counter-intuitive.

Does anyone know why this would happen?


texts: Is it possible to build DRAM out of discrete transistors and capacitors?

texts: Is it possible to build DRAM out of discrete MOSFET transistors and capacitors?


texts:
I was practicing for the exam suddenly I found this question the professor solved, but I think whether he or I made a mistake.

Part (III) in the image. His calculation is on the image he added the two current claiming that it is I of the source which is not true for me. What I have done is adding them together subtracting the value of the current moving in the resistor with Vx getting 26.5 but I realized that the voltage across the resistor with 4ohms is (-)....(+) So the current moving also to the node which is no true due to KCL.

Believe me it's not a homework but I'm solving this problem for practicing that is why I want to understand.


texts:
Hi there,
Im just starting out electrical stuff. And for the life of me I can't figure out why it works this way. So I'm trying to wire two pull-up buttons on an ESP32. I understand why the second figure does not work, i.e. pressing one button triggers both. But why does the first figure work, i.e. pressing one buttons does not trigger the second?
When I press one of the button, shouldnt the entire circuit complete and all the electrons flow to the ground through the one switch that is completed? Thus putting the state of both GPIO pins to low?


texts: Is there a way to place all parts of a connector at once in Altium?

texts: I have a part with 50 pins and currently it only allows me to place one pin at a time. Is there a way to do that quicker? Currently I have to place one pin and then right click it to change it to part 5/50 and so on.


texts: Why did a trace blow in seemingly low current application?

texts:
I recently designed a board around the D12F200A buck converter; I use it to convert from 5V down to 1.4V. Earlier today, I increased the load on the converter beyond what I had ever done (still well below its limits), and a trace blew almost instantly. However, the trace that blew was a signal trace-not a power delivery one.
I have attached photos showing where the trace blew and the current path. The trace is 20mil and the board was manufactured using 1oz copper. Could a crack in the trace or a manufacturing defect have caused this? I have used this board for a total of ~20 hours across the past few weeks.


texts: Where can I search components according characteristics, not model?

texts:
I'm 2 years disconnected of electronics, and i don't know how i get and know the components i used, and i want to get and know few more components, but i can't get to know them... and well i was wondering if there is some search engine or database where they are classified according characteristics... i never got to know anything like that, only the books... but if there are books, they certainly are some sites of it... i just can't find them...

Is there a Component search engine where i can search according the characteristics of a certain component?
For example, gain and power of an OpAmp?, or an integrate circuit for ADC and DAC,
certain gate current of a FET, etc etc etc...


texts: Polarities when expressing currents in terms of node voltages

texts:
This question is specifically about node voltage method. In this example I subtracted the nodes (Vth - V1) / R2 in order to express the current over R2.
It seems to have worked out as my calculations matched the multisim simulation.
But this leaves me questioning:
Why not V1 - Vth instead? How does one to about choosing their polarities when expressing currents in terms of node voltages?


texts: What is "VESA standard" PCB mounting pattern

texts:
In hirose's LVDS connector datasheet, I find there is a "PCB mounting pattern : VESA standard", but I can't find out what is special for this mounting pattern. May someone give some clues.
Thanks.


texts: Debugger connection fails when using UART2 in DMA mode in Nucleo-401RE

texts:
I am trying to build a simple communication between my PC and a Nucleo-F401RE using UART over the USB connection.

I am able to do this successfully using a “polling” or an “interrupt” configuration.

However, when I configure the UART2 of my F401RE as using DMA (I use the CubeMX tool in CubeIDE to do the configuration) and then try to run the program in run or debug mode, I get the error messages:

“Debugger connection lost.
Shutting down...”

Is it not possible to use DMA of UART2??

Many thanks in advance!


texts: Component selections for the ETA3406 DC/DC converter

texts:
I was browsing Seeed Studio's Open Parts Library and found the ETA3406, which is a 1.5 MHz 1.2 A Step-Down Converter.

It's pretty cheap, and looks very useful for something I want to build, but the datasheet only shows it using a 2.2 µH inductor, which curiously is not in the Open Parts Library.

The datasheet also doesn't provide any guidance when it comes to selecting the inductor, all it says is:

  If much smaller values are used, inductor current rises, and a larger
  output capacitance may be required to suppress output ripple.
  Larger values than LIDEAL can be used to obtain higher output current, but typically with larger inductor size.

I assume LIDEAL is that 2.2 µH value, but it's not very clear. Anyone have any tips on how to make the selection, given the scarcity of data?


texts: Do I need a feed network when used two port (coax probe) for Circular polarization?

texts:
I used two coax probe to feed my patch antenna on CST; they're perpendicular to each other. There's no connection between the probes. For axial ratio, two broadband simulations I got, one 'farfield broadband [1]' and other is 'farfield broadband [2]'.  Their gains are same. (So sounds circular to me). However, Axial ratio vs freq plot is same with when the only one port used and simulated. Highly suspected that CST only considers the one port, not both.  In such a case, do we usually need a feed network? Or any way possible to browse both monitors since it only browse 'farfield broadband [1]' or 'farfield broadband [2]' at once.
Hope that explained well. Appreciated in advance for any kind of help.
Regards


texts: Is charging an empty Li-Ion cell to 50% more or less efficient than charging it from 50% to 100%?

texts:
Many devices that are powered by a Li-Ion battery can be recharged over 5V DC supplied by a USB connection.

Is the 5V voltage internally converted by the charging logic to something lower, and is that process energy efficient (e.g. by using a DC-DC converter), or is some of the power dissipated as heat (e.g. by simply using a resistor to reduce the voltage)?

If so, is there a difference in efficiency when the battery is empty vs. when it is almost fully charged?

My practical reason for asking is that I am using a portable USB battery pack to charge my devices and I want to use the energy stored in it as efficiently as possible. It would be useful to know whether charging from 50-100% is more or less efficient than charging from 0-50%.


texts: How to obtain the transfer function of this sensor?

texts:
How can I obtain the transfer function(voltage to RH(%)) of this ratio-metric sensor by using the following data?:

The Vsupply might drift so I also need to include it in the equation.


texts: Solution for unconnected GPIO extender pin

texts:
I have a situation like the one below

The GearN is either GND or not connected. I don't have control over those states (it's a motorcycle gearbox sensor). When the pin is not connected I reach 7.5V on the MCP-A0 point (it's a MCP23017 GPIO expander pin). Way more than I want to. I would like it to be in a low state when that happens.

Just wanted to ask how can I go about it?

Is this solution better? My reasoning: current flows constantly (that part worries me a bit) so the MCP23017 sees high state on it's pin (the GearN is in unconnected state). When GearN connects to GND current will flow directly to it and whole 12V will drop on R1 which will make MCP23017 read low state.

Is it sound? Is there any better way to do this? I don't feel comfortable having 6 lines (that's how many gears there are) constantly draw current (even though it can be minimal).


texts: Do I need a level shifter with an open drain output

texts:
I'm currently doing a schematic that has an IC that operates at 3.3V (HDC1000 for those curious), and the rest of my digital operates at 1.8V. I have a level shifter for the I2C lines, but there is an active low data ready pin that is an open drain output that's used as an interrupt on the MCU.

My question is, would I need a level shifter on this line as well, or since it's an output, can I just pull this line up directly to 1.8V  and have it sink the current to interrupt the MCU?


texts: Can someone suggest to me how to select a three-phase common-mode choke with self and mutual inductance in LTSpice?


texts:
I have this evil thought that building a fly zapper with a counter every time it works.

There are two ways in my mind, first one is hacking a bug zapper product which I already have (hand grip style, will use 9v adapter instead its battery). But my question is, how do I put a counter on its high voltage end. Is there any way to limit a proportional voltage at the output for safe arduino reading?

Other way is the capacitor voltage multiplier path, which is easy to read for me but I don't know which would be easiest to make.


texts: Flash memory SPI MISO line unresponsive, using PIC

texts:
I am interfacing a flash memory component (M25P16) to a PIC microcontroller (PIC18F14K22) using SPI. However, I am unable to see any data come through on the slave output line at all (literally nothing, as if the chip wasn't even in the circuit).

Attached is a logic analyzer trace and circuit diagram. The logic snapshot is in attempt to read the device ID with command 0x9E, followed by some empty clock cycles to read the data. As you can see, SO line is dead.

I believe I have set the clock polarity and phase correctly (data is output from PIC on the rising edge of the clock, and the clock is idle-low/active-high. Also, my chip select pin is being held high (via pull-up) during startup and then driven low for the transaction. Clock speed is 500KHz, well below the maximum speed. Write protect and Hold lines are tied to Vcc, which  is 3.3V. I have pull down resistors for the data and clock lines to bias them low when idle. Although, I have tried letting the MISO line float, as well, to no avail.

Any ideas? Thanks!

simulate this circuit – Schematic created using CircuitLab


texts: Is it possible to use Ultrasonic sensor HC-SR04 in continuous power-on mode

texts: I will be using Ultrasonic sensor HC-SR04 in water level measurement. I will be triggering the US sensor and getting back the time-pulse from it at very slow rate maybe once every minute. I want to know is it OK to keep the US sensor module powered-up at +5V using 7805 regulator continuously 24/7? Will it heat-up the sensor or its electronics and cause accuracy problems after few days of continuous operation?


texts:
I'm trying to understand the specifications of a brushless motor which I would like to buy for making an E-bike. Here are all the specs if have about the motor I'm interested in (copy-pasted from the product page):

         Voltage: 60V
           Power: 2000W
     Rated Speed: 5800rpm
      Max Torque: 4-5 N.M
Electric Current: 40A

So let's assume I have it connected to a controller which is powered by an unlimited power 60V power supply. Can the motor consume more than 2000W of power if I vary the load I give to the motor or is it the maximum that the motor is gonna pull? Thanks!


texts:
If we have a transfer function that shows no peaking in the magnitude bode plot (Starting from a flatline and then rolling off). Does this mean that there is no resonant frequency? Or do we consider the point at which the curve begins to roll off the resonant frequency?

I understand that resonant frequency is the location at which we have the maximum value so I'm assuming that there isn't a resonant frequency in this case but I wanted to be sure.


texts: Why doesn't this battery voltage measurement circuit work?

texts:
So, I built this simple circuit for measuring voltage from a battery pack to an Arduino.

The thing is, I want to measure the first cell and then the voltage from the whole battery pack: using two transistors for changing the voltage divider input (check the image so that you know what I mean.)

I do not want to apply a constant load to the battery, that's why I'm using transistors to turn on and off the voltage divider circuit.

Here's the circuit:

I'm using a simple calculation when reading from pin A0: 0-1023 (analog range) reading to 0-25 volts (as the voltage divider is at a 5:1 ratio.)

My question isn't about the code. Here's the situation:

When both transistors are off, I get a 0 Volts reading (as it should).

When the first transistor is on, and the second is off, I get a ~4.2v reading (as it should.)

The problem is when the second transistor is on (and the first is off). I get the SAME reading (~4.2v) instead of 8.4v (the whole battery pack voltage.)

Adding diodes between each collector and the voltage divider for protection didn't alter my results.

I'm really confused about this.

UPDATE
Note: Each battery cell is rated at 4.2v.

Real Schematic:


texts:
I am using an Analog Devices ADM483E RS485-chip to build a device with RS485-capability. Datasheet here: http://www.analog.com/media/en/technical-documentation/data-sheets/ADM483E.pdf .

The finished apparatus is supplied with 24V DC, and now I'm looking to design it so that it isn't destroyed if a technician accidentally connects the supply 24V +/- to the RS485 inputs (which are connected to the RS485 input/outputs on the ADM483E).

The ADM483E is specified for +/- 14V applied to the RS485 inputs/output.

It would be perfectly adequate for the apparatus to simply short-circuit the power supply in order to protect itself. The power supply is 24V DC and I can arrange for it to have a fuse of 2A.

I can't use reverse biased diodes to ground, since -5V is perfectly acceptable RS485 signal level.

I've considered using transient suppression diodes, but the typical ones are only rated for 1-2 joules of transient energy, and I haven't found any 2A fuses that will reliably break at such low energy.

Do I have to build my own crowbar device, or is there some best practice for what I'm trying to do?


texts: LXE-HX2i decrease battery voltage, step-down converter

texts:
Hello,
I got this battery and I want to decrease it's voltage output. Can I just use cheap step-down converter with LM2596 onboard?


texts: SPICE model library component for IG17 photodiode

texts:
Where can I find a SPICE model for this photodiode regular InGaAs photodiode IG17? Here is the datasheet:
https://www.lasercomponents.com/de/?embedded=1&file=fileadmin/user_upload/home/Datasheets/lc-ingaas/ig17-series.pdf&no_cache=1


texts: Custom LCD glass with ST7066: Can it display 8x8 characters?

texts:
I'm redesigning a product that has a custom LCD glass with a rather strange organization. It uses 22 segments with 14 commons. It's a little bit like the display in the picture below:

Since this is a cost critical product, I'm looking at the extremely common ST7066 LCD controller, which is used to drive alpanumeric LCD displays.

My approach would be to run the ST7066 in two-line mode (16 commons, 1/16 bias) and configure the first four characters of each line to be custom characters. I would use the 64 x 8-bit character generator RAM to define the patterns for those characters thus allowing me to lit up the segments individually as I please.

Now here comes the tricky part: I need 22 segments to control individually. And we're temptingly close with the 8 programmable characters. I need 14 commons, so I must set up the controller into 2-line mode. So I have 4 characters per line. If the characters are 5 pixels wide, that gives 5 x 4 = 20 segments, just short of 22. However, the CGRAM has 8x8 bits per character.

So the question is can the ST7066 / KS0066 / SED1278 be configured to actually display 8x8 characters? Or are the "extra" bits in the CGRAM just don't cares in any configuration? With 8 pixel wide characters, I would have 32 freely controllable segments and I would be home free.

Finally, do you think this approach is viable at all? The segments in the display have hugely different sizes. Does it affect the drive capability of the controller; would larger icons have worse contrast than the small ones? Also, the ST7066 drives 40 segments; since I only use 22, does that play a role in the contrast or the required panel bias voltage?


texts:
I appologise if this seems like a dumb question, but is it possible to get a Xilinx FPGA (specifically, the Artix-7 35T) to run Linux without the use of Xilinx's EDK? I have found some tutorials like this one but they seem to require the EDK (of which there is no free version I believe).

I am currently using Vivado and the Xilinx SDK and I can get a simple C "Hello World" program to run, but I am having problems with trying to get it to run Linux. Can I implement Linux using those two tools? Is there a good guide anywhere on how to do it?


texts: I've this transfermodel, my controller is a PID-controller and my sensor is this, how can I find the Tranfer Function of the sensor?:


texts:
I'm running a Microchip dsPIC30F6012a. I have this chip on several PCBs, all running the same software, and observe the same problem on all of them. This implies a systemic problem, not a one-off production issue. The problem is also reproducible, implying I should be able to kill it if I know where to look. But I'm still having surprising difficulty debugging the application.

The board under test accepts 24V, which gets stepped down to 5V through a V7805. The chip runs on its internal oscillator, with a 16x PLL, giving an operation speed of ~29.5 MIPS. The relevant code on this board is essentially very simple: wake up, read data from EEPROM, then enter an infinite loop. Interrupt every millisecond, observe some environmental data, and write an updated value to EEPROM. There's other stuff going on, but the problem still occurs even if the unrelated code is commented out, so I can be reasonably certain it's not relevant to the problem at hand.

In general use, 95% of the time the board wakes up with the correct value in memory, and goes on about its business. The other 5% of the time, though, it wakes up with an incorrect value. Specifically, it wakes up with a bit-flipped version of the data it's supposed to have. It's a four-byte unsigned long that I'm watching, and either the upper or lower word of the long can get flipped. For example, 10 becomes 2^16-10, which later becomes 2^32-10.
I can reproduce the glitch by manually cycling power several dozen times, but that's not very consistent, and my switch finger gets worn out.

In order to reproduce the problem in a controlled fashion, I built a second board which drives the 24V supply to the board under test. (Another dsPIC driving a darlington optocoupler.) The tester board turns the 24V off for 1.5 seconds (long enough for the 5V rail to drop to essentially 0 and stay there for one second), then turns the 24V on for some configurable length of time. With an on-time of approximately 520 mS, I can reproduce this EEPROM glitch within five power cycles, every time.

The 5V rail is behaving reasonably. It settles at 5V within 1 mS of turn-on, with perhaps .4V of overshoot, assuming I can trust my scope. At turn-off it decays to 0V exponentially, reaching 1V within 50 mS. I have no build warnings that seem relevant, just unused variables and missing newlines at the end of files.

I've tried several things:

Enabling/disabling the MCLR
Enabling/disabling the WDT
Enabling/disabling code protection
Enabling/disabling/changing brownout detect voltage
Enabling/disabling/changing the power-on timer
Different PLL settings on the main internal oscillator
Connecting/disconnecting my PICkit 3 programmer
Adding 470 uF of capacitance to the 5V rail
Adding/removing .1 uF across the 4.7k pullup on my MCLR pin
Disabling all interrupts in the code and leaving nothing but EEPROM updates in the main loop
Adding a 1.5 second delay to my startup routine before I start reading EEPROM

I've also written separate test code which does nothing but continually write values to EEPROM and then read them back, making sure that the value has not changed. Tens of thousands of iterations gave no errors. All I can conclude is that something goes wrong with EEPROM read or write, specifically at powerup/powerdown.

I've been using the same EEPROM libraries since 2007. I've seen occasional glitches, but nothing reproducible. The relevant code can be found here:
http://srange.net/code/eeprom.c
http://srange.net/code/readEEByte.s
http://srange.net/code/eraseEEWord.s
http://srange.net/code/writeEEWord.s

I've seen EEPROM errors before in other applications, but always as one-off glitches, nothing this reproducible or consistent.

Does anyone have any idea what's going on? I'm running out of things to try.


texts: Why three-phase power? Why not a higher number of phases?

texts:
Is there a reason, beyond historical reasons, that three phases has become the dominant number of phases?

I am aware of the advantages against one phase and two phase, namely the reduced amount of conductor needed, and that motors can provide torque when stalled (and less pulsation).

Is this solely due to diminishing returns, with only a small increase in smoothness of torque application, at the cost of increased complexity (increased number of wires (albeit of smaller CSA)).

To be clear, the phases are all evenly distributed, that is, five phases separated by 72 degrees.


texts: Choosing the right voltage divider by load

texts:
I'm using an Android IOIO board to detect simple digital pulses from a 12v source.

The input pins are 5V tolerant. Would a simple voltage divider work in this situation? I guess my concern is whether or not the IOIO would have much if any load pull when used as a digital input sensor.

I would say and I don't know this for sure that the max load would be 20mA??

What considerations do I need to make in selecting the correct resistor value ratio to go from 12v to 5v?

I also have these resistors available:

0Ω, 1.5Ω, 4.7Ω, 10Ω, 47Ω
100Ω, 220Ω, 330Ω, 470Ω, 680Ω
1kΩ, 2.2kΩ, 3.3kΩ, 4.7kΩ, 10kΩ
22kΩ, 47kΩ, 100kΩ, 330kΩ, 1MΩ

I've calculated that I can get 3.84V by using a 10k and a 4.7k. Will this be too much resistance?


texts:
So this feels like a silly one but I'm absolutely stuck. I'm trying to balance the power between a 3 phase source and two 3 phase loads in parallel. One is a Wye and the other is a Delta:

So I figured out that the single phase source current is 5A per branch, so the source complex power is (3*120V*5A) = 1800 W and 0 var.

The problem comes when I try to find the load draw. It's easy enough to find the delta line-to-line voltage and the current going through the phases of the loads:

When I go to sum the powers, though (including line impedance), I get a strange answer that doesn't balance:

Does someone see my obvious mistake?

Thanks!


texts: I have to calculate the symbolic transfer function of this bandpass filter. I tried to do the calculations, but I would like, if it were possible, to check them out and let me know if the transfer function is well calculated.


texts: Quiescent current of 12v brushless water pump

texts:
I couldn't find the datasheet to my Quioran QR50E water pump and I want to estimate if I can run an arduino and 4 of those on a battery for longer than a month.
I don't know the quiescent current of the pump and I think it could be much more than the arduino's.
It is a 12V DC, 5W water pump with a Qmax of 280 liters per hour.
What is it's quiescent current?
If no one knows, could I astimate it?
What are normal values for such small pumps?


texts: Are the AVR GPIO registers used by AVRGCC?

texts:
Most (all?) of the AVR family controllers provide some special GPIO registers.

  4.8.1 General Purpose I/O Registers
  The lowest 16 I/O Memory addresses is reserved for General Purpose I/O Registers. These registers can be used for storing information, and they are particularly useful for storing global variables and flags, as they are directly bit-accessible using the SBI, CBI, SBIS, and SBIC instructions.

Q: Are those registers actually used by compilers, especially AVRGCC? Or would one be free to use those registers in some inline ASM for example without messing things up? After some digging, I haven't found anything conclusive.

Background:
Controller: XMEGA128A1
In a recent project, I discovered that an uninitialized pointer to a struct (size = 9 bytes) was dereferenced (and "written" to), potentially corrupting data at address 0x0000. This address is located in the I/O memory section instead of the SRAM area.

The first 16 bytes are used by the 16 x 8-bit GPIO registers available for this controller.

As I discovered this bug (that has actually been present for some time) the question came up, why there were no noticeable ramifications. So it would be interesting to know, if those registers are used at all or if we just got lucky so far.


texts: Do I need a wire connected to the negative terminal for led light bars and if so can I use the negative terminal as ground for the relay

texts: I'm not sure if this will work can someone help me out


texts: How to calculate the shannons channel capacity and the bandwidth, for a desired BER and EbNo value?

texts:
I understand that, for BFSK modulation scheme, to achieve BER of \$10^{-5}\$, the required Eb/No is 12 dB, and this is theoretical value of the required Eb/No predicted from the graph below:

According to shannons theorem, wkt:

$$c = BW \cdot log_2(1 + SNR) \; bps$$

So how do I calculate the values of SNR that I can substitute in the shannons equation? And how to calculate the BW?


texts: Determining when a serial connection is opened

texts:
I have a PIC24FJ MCU with an FT232RL USB to UART controller. My design has end users opening a serial connection to my MCU to set parameters and get debug information.

My question is: How can I tell when the end user has opened screen/PuTTY/etc to my device's COM port?

From what I have read, the DTR signal is not a good way to go about this as the OS decides when to raise DTR.

My use case is that I would like to display a banner with help commands as soon as the COM port is opened.


texts: Why are engine spark plugs w/o resistor so potent killers of electronics nearby them?

texts:
I've recreated the ignition coil part of a small Honda ICE (typically used in lawn mowers or single-digit kW gensets).
I use an electric motor to turn a flywheel taken from a dead engine, and I've placed the ignition coil unit  just like in the real engine, with a spark plug and all. I get sparks when the flywheel runs faster than 500 RPM.
Physically, it looks like this:

I've also attached an Arduino-like device, like this:

simulate this circuit – Schematic created using CircuitLab
The ignition coil is meant to be operated like this:

The coil's body (laminations) is electrically connected to the engine block (chassis).
One well insulated wire runs to the spark plug socket. The circuit is completed through the chassis.
There's an engine kill switch: when you want to turn the engine off, you close the switch, which shorts some signal of the ignition circuitry. Again, circuit is completed through the engine chassis.

In my setup, the engine chassis is this strip of metal where the spark plug rests on, and I don't have a kill switch (I don't need one).
The signal to the kill-switch is much lower voltage (25-100V) and has some strange shape, but with some dividers and low-pass filters I've conditioned it for a digital input pin of an Arduino. The signal conditioning circuitry shouldn't matter much (see below), but I'm including it for completeness:

simulate this circuit
My device is powered by a Li-Ion battery + a 3.3V LDO.
I'm observing the following results with engine at 1000 RPM and a non-resistor spark plug:

Arduino device not electrically connected to the engine, but physically close to the spark plug - unaffected
Arduino electrically connected to the kill-switch signal, but otherwise far away from the spark plug - reboots continuously, essentially on every spark
Only the grounds connected (the blue wire) - same thing, reboots furiously

If I swap the spark plug for a resistored one (Denso W20EPR-U), I'm observing

Device close to the spark - unaffected
Connected to the kill-switch signal - unaffected (I can read the engine RPM)
Only grounds connected - unaffected (but of course I can't read the engine RPM)

I also have a GPS chip connected to the Arduino. It shows similar behaviour (it reboots furiously when the non-resistored spark plug is used). All chips are duly bypassed by caps. Scoping on the power rails do not reveal any glitches. The GPS, of course, has a sensitive antenna, which I guess picks up a lot of noise.
Question
What mechanism causes the Arduino's MCU to reboot furiously when I only have the grounds connected? And why the change to a resistored spark plug fixes it so well?
Also, how to protect against the non-resistored spark's nastiness? Is opto-isolation a must?
EDIT:
Answering clarifying questions by @glen_geek:

the device is powered through a Li-Ion battery and a 3.3V LDO
nothing else is connected to it
I've included the signal conditioning circuitry
I've added a photo of the actual setup (the device itself not shown). As you can see, the thinner wire coming out of the ignition coil goes through a couple of bullet connectors, and into a 4-wire cable. The GND from the laminations (blue wire) is in the same cable. The other 2 wires of the cable are unused. So it's not twisted pair, but it's not flying wires either.


texts:
I recently purchased addressable RGB LED strips based on the WS2811 chip. These strips have a single data + clock line that uses NRZ style encoding to distinguish between a 1 and 0. The datasheet for the strip can be found at https://www.adafruit.com/datasheets/WS2811.pdf

Since the timing is strict for these strips, I am trying to use assembly code to drive the strip (my first attempt with assembly).

Using Atmega168 @ 16Mhz (1 clock = 62.5ns), I call the following assembly code (which I expect to set the LED color to WHITE).

asm_pin_toggle:
sbi DDRC, 4

;reset the led strip data line ~50us
ldi R19, 255
loop:
    nop
    dec R19
    brne loop

ldi R19, 23 ;loop 24 times - all 1 bits
loop_all_1:
    sbi PORTC,4
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    nop
    cbi PORTC, 4

    dec R19
    brne loop_all_1

ret

However when I run this I get the color GREEN. Any ideas what am I doing wrong?

There are many version of the WS2811 timing floating on the internet. The one I have used is

T0H - 250ns
T0L - 1000ns
T1H - 1000ns
T1L - 250ns
RET - >= 50us

any help will be much appreciated!


texts: Current flow stops at battery's positive terminal?

texts:
So let's take this circuit:

To find voltage across \$ V_1 \$, you do KVL in loop 1 to find \$ V_1 \$

you say:

\$ 5V +  V_1 + V_3 = 0 \$

correct? But why is it assumed that current flows through the 5V supply? Aren't the positive and negative terminals of the battery (5V supply in this case) separated? Current direction defined as flowing from the positive terminal to negative terminal, but let's ignore that, and talk about what happens in reality. Physically, electrons will go from the negative terminal of the 5V supply around the loop to the positive terminal of 5V supply.

So, the 5V supply is really an open circuit, isn't it? Whenever you do KVL or these loop equations, why is it assumed that current flows seamlessly between voltage supplies?


texts: Can you deal esd damage to an internal PCIe solid state drive while it is inside an anti-static bag?

texts: I apologize for the paranoia, but my mind refuses to rest. I have recently been working on a laptop. While doing so, my SSD (internal, it's a PCIe board) was inside an anti-static bag (the very cheap kind, my idea of sealing it was folding one edge) and I was frequently gripping a light metal pan. The SSD was never removed from the bag, but as I was working, the frequent touching caused the metal pan to move across my work surface until I discovered that it was on top of the SSD which was inside the bag. Presumably, the metal pan will have rubbed against the outside of the bag at some point, over the part containing the SSD. Could this have damaged the component inside the bag?


texts: Diode: reverse and forward bias current and voltage

texts:
The question asks :

"Assume that diodes have voltage of 0.7 V and resistance 4Ω. Find the current through the forward and reverse bias of diodes. Draw the characteristic of diode through the given values."

My question is that how do I approach these type of questions and what "diodes have voltage of 0.7 V" means. Does that mean "the voltage drop" of each diode in the forward bias(I presume not in reverse bias)? Also, why do I need to know the resistance of the diodes since we know the voltage drops, and aren't the 4 ohms negligible compared to 1.5 K ohm?

In addition, can I thread the two diodes as one diode in reverse bias?


texts:
As per my knowledge the purpose of All Pass filter is to add phase shift (delay) to the
response of the circuit. The amplitude of an allpass is unity for all frequencies.Then why it is called as a filter??


texts: What is the most efficient way to increase the frequency of a waveform?

texts: More specifically, I have an electric induction kettle. From what I understand, it heats the water by sending a high frequency (voltage?) signal around ~24kHz. This high frequency signal causes a rapidly changing magnetic field that induces many eddy currents into the material. The bottom of the pot becomes hot and heats the water through conduction. My question is, how is a high frequency signal created from the 120V AC current in the wall in such a small area (the induction device is roughly the size of a large hand).


texts: I'm playing around with a BD179 transistor, trying to get my LED bulb to light up but without luck. My mistake is probably something very simple but I'm learning so bear with me.


texts: What is the easiest way to monitor a 120v line via software?

texts: I'm wanting to count how often a water pump turns on, how long it's on for and when it turns off for an extended period of time. My plan was just to monitor the pressure switch, which is at 120v on 1 leg and write the data into a MSSQL database. What's the best way to get this data safely?


texts: Difference between shunt resistant measurement circuits using op amps

texts:
I've been trying to measure the current going through a motor controller and basically succeeded in obtaining the same values from two different circuit configurations:

simulate this circuit – Schematic created using CircuitLab

and

simulate this circuit

I don't understand exactly why both these circuits work and would be very grateful if someone could explain why!


texts: Can differential USB traces be routed relative to Power (not Ground) planes?

texts:
I would like to route my USB 2.0 (12MHz) signal on the bottom layer of a 4-layer PCB.  However, the edge-coupled microstrips would then be referenced to the power plane, not the ground plane.  The signals are going to the USB pins of an STM32F105 microcontroller.

The signal path should be 90-Ohm differential, but I don't know how important the characteristic impedance is since I won't be using the High-speed (480MHz) rate.

My board's stackup is:

Top (signal, components)
Ground (unbroken)
Power (3.3V, unbroken)
Bottom (signal)

I have radio transceivers on the top layer, using differential, edge-coupled microstrips for the rf signalling.  All the IC's are decoupled fairly well.

I see a few options:

Route the traces relative to power plane.

I would prefer this.  Will it work?  Does it couple noise onto the rest of the PCB's power plane?
Remove a section of power plane, exposing the ground plane underneath the microstrips.

The ground plane is now so far away that my traces would be quite wide...
Isolate an area of copper in the power plane under the microstrips, and stitch it to the ground plane.  Kind of a "ground mezzanine" :)

I think this would work well, but the top layer is too thick with traces for me to do a good stitching job.  I don't want to use blind or buried vias.  Would this solution require good stitching?
Don't concern myself with the characteristic impedance.  The traces will be about 600 mil long, and I'm only signalling at 12MHz...

Here's the section in question. I intend to run the traces to the far left, underneath the microcontroller, then bring them up to the top layer.  For scale, the small components are 0402 (1005 metric).

(those traces aren't actually crossing on the same layer; it just looks like it because I highlighted them in red)

Are any of these good options?  Is there anything I'm missing?

Thanks.


texts:
I want to create an adjustable power supply for my electronics projects, and the cheapest/fastest option seems to be using an LM317.
However, I do not want to blow things up by doing something wrong (what is pretty possible, considering my little knowledge in electronics), so I want to have a few questions cleared:

What power should R1 be able to handle, considering a maximum drop of around 30v (from 32v to 1.25v) and, let's suppose, 1A of current (I have no idea of how much current I'll use, but I'm setting the value high to make sure)? If the calculation I did are correct, the power dissipated by the LM317 is of around 30w (I have a huge heatsink, heat on the LM317 shouldn't be a problem), but what should be the rated power of the resistor? 30w resistors aren't cheap, and the store I buy components from only offers resistors up to 10w (that are also very expensive).
Do I need a capacitor between the input of the LM317 and ground? If I don't use one, what could happen?
If I wanted to put a LED to indicate if my power supply is on, how could I transform my input voltage of 32v in the voltage of the LED without having to dissipate a ton of heat, and without expending much?
How can I protect my circuit from a short circuit, so I don't blow everything if mistakenly connect something wrong?


texts: I am replacing a small DC motor that powers a Santa mobile using single AA battery - the only thing I could find was on Amazon, by "ajax" - listed as 1.5-3.0 V. The motor spins the propeller a little too fast, and it seems like reducing the voltage to 1.0 V or so would give the correct RPM. If so, what is the best (easy) way to reduce it?


texts:
I'm designing a product powered by an alternator with a DC regulator that will provide me with 24 V DC and something like 100 A rated consumption. Do RCDs protects against earth leakage current in DC circuits or only in AC systems?

If not, how should I protect my system agains current leakage?

Thanks!


texts:
First time posting on this, so apologies if I mess anything up. I'm having an issue with my circuit that I'm having difficulty figuring out. I am using a TIP120 transistor to turn an LED on/off. The LED has a max operating current of 1A. I'm using a 1A buckpuck LED driver to power the LED, and this is a diagram of what my circuit looks like (wasn't sure what to do with the Arduino, sorry, so I just subbed in a voltage source):

The LED turns on and off when it's supposed to (I'm using an Arduino output pin connected to the TIP120 base through a small resistor). However, the brightness of the LED will sometimes start off very low, and over time (30s to a couple minutes) ramp up in brightness. I'm not sure what is causing this delay- I've tried with multiple LEDs and the behavior is the same, so I don't think it's that. My guess is that somehow I'm messing up the transistors?

I've linked to the product info for the buckpuck I'm using: http://www.luxdrive.com/content/3021-BuckPuck.pdf

And the LEDs: https://www.ledsupply.com/leds/luxeon-rebel-color-leds

I'm also powering the buckpuck with a 12V 4.20 A DC power supply.

Hopefully I didn't miss anything, would appreciate any advice. Thanks!

Edit:

This is the buckpuck configuration I'm using, with an external pot and a switch to control intensity. Without the transistor, this circuit works as expected. However, as soon as I add a transistor in the configuration posted above, the LED intensity becomes unreliable. The LED- terminal of the buckpuck is grounded, while the LED+ terminal of the buckpuck leads to the anode of the LED, and the cathode of the LED is connected to the collector.

If it helps, this is a screenshot of my Eagle schematic showing some more of the connections. I will try to make a more complete diagram once I have a mouse again. The LED560 label on the base connects to an Arduino GPIO pin via a 330 ohm resistor.

Edit 2:

Thanks everyone for the quick answers. Configuring the circuit as in Figure 13 of the buckpuck datasheet works, and I now understand why it was a bad idea to use the TIP120, especially since the buckpuck driver already allows for logic-level control.


texts:
I want to use LIS3MDL magnetoresistive sensor for Parking Vehicle Detection project. I compared this with HMC5883L. LIS3MDL 's Full Scale range is +16 Gauss but HMC5883L 8 Gauss.

But I did not understand what is detection range. Do you know anything about it ?
Can these sensors detect vehicle from 1meter.


texts:
I've just got Altium Designer, and while I was searching for some components I discovered that I only have two libraries:

MiscellaneousDevices.IntLib
MiscellaneousConnectors.IntLib

Is there any way I can add the default libraries to Altium?


texts: What is the maximum voltage for MPPT/PWM to charge a X volt battery?

texts:
I currently have a PWM 12/24v (auto commute) with ~18V as input and a 12V battery in the output.

I wanted to switch to 24V battery and I thought about going ~36v solar panel. (18V * 2)

Then I saw online some examples of putting more in series for a higher voltage, like this one:

These solar panels are 100W and can go up to ~22V. So if I'm correct this schematic will send about 66V to the PWM/MPPT to charge a 24V battery. (two 12V in series.)

Can a charge controller handle whatever amount of voltage? And is there on this aspect a difference between MPPT and PWM?

And is there a difference in efficiency between sending 66V or 33V?