texts:
I've the following setup based on a Sonoff basic flashed with the Sonoff-Tasmota firmware.

I've connected a wall switch (not push button) to the GPI14 and GND pin header of the Sonoff in order to be able to control the state of the lamp not only with the WIFI but with physical input has well.
The the Sonoff-Tasmota firmware allow to sense the change of the Input (ON->OFF or OFF->ON) of the GPIO14 an reflect this input change to the status of the LAMP.

This setup has worked perfectly for weeks. But since a couple of day the the lamp is flickering (ON->OFF, OFF->ON in intermittence).

Bug reports are available which are describing the same issue but all off them conclude that the issue is not software but hardware related. The following remediation are proposed:

Install an extra restore (5-10KOhm) between GPIO14 and 3.3V headers
Aditionally to step one (pull-up restore) install a capacitor between GPIO14 and GND

Questions:

What is really happening (the logs clearly showed a change of the GPIO14 input ON->OFF / OFF->ON) ?

There are already pull-up resistors available on GPIO14 according to this, why would add an other solve the problem ? What about the capacitor ?

Is there an other way to address this issue ?


texts:
I am trying to repair the power supply of my PS4. It looks like the fuse has blown out with the TVR 10561 varistor. I can't find this varistor online and I am looking for a replacement.
The TVR 10561 data sheet is here: http://www.konkurel.ru/thinking/en-TVR.pdf
The best replacement I could find is https://in.element14.com/littelfuse/v56za3p/metal-oxide-varistor-35-vac/dp/1612088
Does it look like a good replacement? Did I miss some important value?


texts: Amplify sinusoïdal signal with op-amp with V- = 0V

texts:
I have a small sinusoidal signal, with an amplitude of 10 mV (the signal goes from -5mV to 5mV) that I'd like to amplify.

I'd like to use an op amp, but my problem is that I only have +3V and GND voltages to supply the op amp. Which means the classical amplifying circuit would not work:

Any idea how I could amplify my input signal?


texts:
I built a simple circuit to produce -5V from regulated +5V but it doesn't work unless the voltage is at least +6.5V as input.

The LT1054C shoud work ok from 3.5V but I measure 0V at output with my multimeter when Vin is +5V.
If I raise Vin to +6.5V, the Vout is -6.5V and my circuit works normally. Seems that 6V is the minimum to get the negative voltage output.
from the datasheet, the switching frequency of the DC DC step down LM2596 is 150 KHz while the LT1054C can be configured between 15 and 35 kHz. So it impossible to sync both. I think the issue could be here maybe?
I use tantalum capacitor (marked "Ta"). Other are Al standard cap. I followed the LT1054 datasheet. I tried Cin=Cout=100uF (tantalum) too.

(I bypassed the problem by using 7805 and 7905 regulators in each corresponding inputs but it's ugly)

Why can I get directly the -5V from the +5V?

LT1054 datasheet

The buck regulator I use (12VDC to +5/+6.5VDC):

I will be using 12V unregulated input and regulation to -5V.

It is still not working. I measure Vout = +0.4V with Vin=+12V. It's curious that Vref=+7V while it should be +2.5V (internal reference).
I tried a second chip (LT1054C N8 by Linear Tech.), same thing.
Both chips work fine as simple inverters (no resistors, Vout=-Vin if Vin>+6.5V)

I tried a LM336-2.5V reference as external reference instead of using the reference pin, same thing.

Breadboard circuit: [link]https://drive.google.com/open?id=1Rgna1OPtDUJwWGj8AU4rmA7glmsUp6G5


texts: What causes horsepower and torque to remain the same in a dual speed (single winding) motor?

texts:
Below is an extract that I've found but don't fully understand... What actually causes the horsepower to be the same at both speed? And for the second scenario, what causes the torque to remain the same?
Also, how do I distinguish one from the other just by reading the nameplate?

"If the motor is wound in such a way that the series delta connection gives the high speed and the parallel wye gives the low speed, the horsepower will be the same for either connection. If the winding is such that the series delta gives the low speed and the parallel wye gives the high speed, the torque will be the same for both speeds."


texts: Output Pin of Burleigh PZ-150 Amplifier Driver Analog High-Voltage Power Supply Unit

texts: I have found a Burleigh PZ-150F Analog Amplifier Driver. However, I could not locate the manual. What connector cables are compatible with the output port of this amplifier? It seems there are two male pins and two female pins.


texts: VHDL: Optmize signal comparisons for synthesis

texts:
As a preface, there are certain coding styles used in VHDL/Verilog which help the synthesis tools infer different hardware(some better in perfomance than the other). For example using an if-else-if ladder would infer a series of mux'es whereas a case statement would infer a single wide multiplexer. These coding styles are not significant when doing only functional simulation, but substantial when targeting the RTL for ASIC or FPGA implementation. In case of FPGAs the CLB(configurable logic block) architecture defines the capabilities achieved using RTL(like the LUT input width).

Coming to the Question, I have seen many instances where two n-bit wide signals might have to be compared in VHDL. And I need some advice on the hardware inference. I will use the following code snippet to further narrow the question.

signal counter_a: unsigned(31 downto 0);
signal counter_b: unsigned(31 downto 0);
signal clk, trigger_en, count_b_en : std_logic;

counter_a_gen: process (clk) begin
    if(rising_edge(clk)) then
        counter_a <= counter_a + 1; -- free running counter
    end if;
end process;

counter_b_gen: process (clk) begin
    if(rising_edge(clk)) then
        if(count_b_en = '1') then
            counter_b <= counter_b + 1;
        else
            counter_b <= (others => '0');
        end if;
    end if;
end process;

-- compare the counters to generate some logic
trigger_gen: process (clk) begin
    if(rising_edge(clk)) then
        if(counter_a = counter_b) then
            trigger_en <= '1';
        else
            trigger_en <= '0';
        end if;
    end if;
end process;

The above snippet has two 32 bit counters counter_a and counter_b, which have to be compared in a sequential block. If I consider a 4-input LUT in an FPGA, the comparison would need multiple levels of logic. Such a path would be make it hard to meet timing because of the huge combinatorial delays. So my question is how do we make it optmized? In this case to increase the perfomance?


texts: Is it Safe to Plug an Extension Cord Into a Power Strip?

texts:
Just a bit of context, I am a technology enthusiast. I love everything from software to hardware, Windows to Linux, Computer to Phone, and everything in between. So, I wouldn't be surprised is my electrical usage exceeds 50% of the entire household (8 people). To power all of the equipment I use, I use a pretty expensive surge protector, with 12 outlets on it. Recently, I have been very plain and simply, running out of outlets.

I have an extension cord with 3 outlets on it. Maybe, I thought, I could plug some of the things on my surge protector into the extension cord, and then the extension cord into the surge protector. I know, it's pretty dumb of me, but I went and did it, without checking to see if it was safe first. But I did, and everything seems to running fine. It's been running for about a 30 minutes now, and neither the surge protector or the extension cord are overheating.

However, after the fact, I am reading on websites about weather or not this is safe, and they're all saying it's not, even though everything is running perfectly fine. Thoughts? Something I'm not understanding?


texts: Multiplying 3 bit number with 3 bit number using 4 bit full adder

texts:
ive been trying to do this for hours to multiply 3 bit number with a 3 bit number ,
can some here tell me whats wrong here ?


texts: Why do push button telephones use dual-tone for signalling?

texts:
Here is a related information from wikipedia:

  For touchtone service, the signal is a dual-tone multi-frequency
  signaling tone consisting of two simultaneous pure tone sinusoidal
  frequencies.

Above shows that if one pushes number 1 he sends the mix of 697Hz and 1209Hz to the telephone station/center through a wire.

My questions are:

What is the practical reason or advantage to mix two signals instead of a single pure tone?
Is there a reason to use such frequencies like 1209Hz which do not belong to any music tones(modern western twelve-tone equal temperament)?


texts: Switched mode Battery Charger CC/CV operation

texts:
Shown below is the internal block diagram of a switched mode battery charger IC (LT1510). The LT1510 is a current mode, PWM (pulse-width modulated), positive buck switcher that operates in one of two states: constant current or constant voltage.

From the design note

Iam having difficulty understanding the operation and internal block diagram of IC (especially the highlighted sections). Kindly excuse my beginner level knowledge on current mode control and op-amp compensation.

Can somebody explain  how 'constant voltage- constant current' mode happens here?
The current mode control employed is peak current mode control. In peak current mode control inductor current is sensed ( along with slope compensation) and compared with a control voltage derived from the voltage control loop. What is the purpose of current amplifiers CA1 and CA2 here?

Design note of LT1510


texts: Pulse train profile generator for stepper drive step/dir input

texts: All, I am trying to create a circuit to control a stepper drive step/dir input.  I'd like to generate pulses starting at 1kHz and ramp up to a 10kHz peak, then decelerate to 1kHz until motion is stopped.  I.e., a ramp up/down pulse profile.  I know there are great motion control units on the market to accomplish this, but I am running my application on a Rasperry Pi 3 B+ and interfacing to those products is tedious (and more expensive).  It seems that adding a secondary RC circuit to a 555 astable circuit might accomplish this.  Anyone have a solution?  Thx!


texts: Turning on LED when input voltage has desired frequency.

texts:
I want to design a circuit that turns on an LED when the frequency of the input signal is between 950-1050 Hz using only passive elements and op amps aside from the actual LED.

I have designed the band pass filter but I am stuck on the best way to make the LED turn on only when the input signal has the desired frequency since an input of 925Hz wont be attenuated significantly more than 950Hz. I should note that I want the input signal to have a DC offset of 2V and an amplitude range between 2 and 5 V for the sinusoidal portion.

My initial idea was to use an op amp with no feedback to turn the LED on however I also want the input signal to power the LED so it can then be detected by a photo transistor.

Is there a better way to do this?


texts:
In DC circuits, we say that the negative terminal of battery is considered as ground(0V).
But in AC circuit, the polarity of votage change continuously but what is ground in AC circuits with respect to which polarity changes?
Please also explain the concept of ground in circuits in little bit more detail. In books, this concept of ground is not taken into account.


texts: Working out AT28C16 LED output from datasheet

texts:
I'm trying to work out how to connect some LEDs so I can view the value of the value stored in the AT28C16 (pdf) chip.

I'm actually following a youtube series. In the video he chose a 330Ω resistor but I'm not sure how he would work this out given we don't know the maximum VOH value.

My LED's are rated at

  1.8v - 2.2v 20mA

Please could you explain how to read the datasheet to calculate the resistor value required.

Thanks.


texts:
I have on my board two PISO shift registers in series, giving an output train of 16 bits.
The problem is that the order of the bits is reversed compared to what I need. That means, the last input of the second PISO shift register is the first of my serial train (as usual), while I need it to be the last one.
I cannot change my PCB and I cannot find any PISO-FIFO (sort of) component able to do what I need.

Do you have any idea?
Thanks


texts: How to confirm whether a device was fried by higher voltage

texts:
After a move, I inadvertently hooked up a 15V/3.42A adapter to a device—an X99 (RK3399) Android TV box—which I later found out (when it didn't turn on again)—on the web, as it's not indicated on the box—was rated for 5V/2A (or 3A, depending on the page). I then tried other fitting 5V adapters I had at home—one 1A and one 2.5A—and still no pulse (the box has a digital display). Is there a way of confirming whether I indeed fried the thing (like hooking up multimeters, or somethin')?
(Yes, I did search through the forum, and have read all cautions against using higher voltage adapters on electronics, but still... just wanted to know if there is an easy way to confirm before going about replacing it.)


texts: Why bode plot of cascade system is not the sum of subsystems?

texts:
I have two subsystems which the transfer functions you could see below as g(s) and h(s). According to some references show below, I found that the bode plot of a cascade system should be the sum of subsystems. Then, to comfirm that I implemented code as below in Matlab, but the result seems violate with the reference. So, where I went wrong?
Subsystem transfer functions:

Matlab code:
den = [0.3352 0 209.8621 0];
gs = tf(num, den);

num = [1 3];
den = [21 2 10 40];
hs = tf(num, den);

c = gs*hs;

figure
bode(hs,gs,c)
grid on
legend('subsystem1','subsystem2','cascade system')

Result:

Reference:


texts: Kirchhoff's laws with current source in a circuit

texts:
Here is a circuit with a resistor, current source and a voltage source. I need to apply Kirchhoff's laws on it (both current and voltage), but I get confused with the current source. What do I do with it, how do I handle a situation with a current source in a circuit?

Thanks


texts: Pin letters not shown in circular connectors D38999 series

texts:
I'm working with military circular connectors of the D38999 series and I've discovered that when the connectors have their pins designated by letters instead of numbers, some letters are not shown.

For example, in this image, the letter "O" is not shown:

I've done about 10 different Google searches and I can't find any information on this. Does anyone know which letters are not shown (both capital and non capital)? If anyone has some site/pdf file about this it would be great too.

Also, somewhat related, is there a part in Orcad that is a connector that has pin names in letters and not numbers?

Thank you!


texts: Altium: Change part designator from Letters to numbers

texts: I am creating a new component with several parts in Altium Designer. When I place the component in a schematic page, each part get a unique letter like (IC10A, IC10B, IC10C ... etc). How to change these letters to numbers, like (IC101, IC102, IC103 ...etc)


texts: Reasons for using separate sets of wires for the solar controller and the loads to the battery vs using a bus-type configuration

texts:
This has been discussed a few times, both here and on other sites, but the justifications given are usually very light. Here are a few examples that say that you should run separate sets of wires to the battery for the charge controller and the loads:

Would splicing existing wires (from charge controller to battery) to connect an inverter work, and is it safe?
Connecting the charge controller
Connecting multiple loads - straight to charge controller/battery, or need separate..

The question is basically about these two configurations:

simulate this circuit – Schematic created using CircuitLab

simulate this circuit

The reasons given are:

Any extra voltage drop (due to connectors, etc) on the battery side of the charge controller can confuse it, resulting in undercharged batteries.
Additional noise introduced by the charge controller into the voltage seen by the load that would otherwise be remedied by the battery impedance.

Are there any other practical considerations against doing it one way or another?

EDIT: To add a little more detail on why you wouldn't just always go with separate sets of wires, suppose that the battery compartment is only accessible via an 8 feet pipe that's 1 inch in diameter (my exact situation right now). That means you can either run four 4 AWG wires through it or two 2 AWG wires. When the charger and the load are pushing/pulling 30 amps (not at the same time) to/from the battery, the wiring drops 0.12V with the 4 AWG wire, while it only drops 0.075V in the 2 AWG case. When the charger is powering the load directly, the current doesn't have to travel the length at all and there's no drop.


texts: Can I use a MAX232 to communicate between a PIC and a Raspberry Pi?

texts:
I would like to send serial data at 9600 baud between a PIC and a Raspberry Pi.

Both circuits are powered by a 5V wall charger. The distance shouldn't exceed 15cm. They don't currently share a common ground, but I could change that if necessary.

Can I use a MAX232 for this? Are there other (better) options?


texts:
Seriously confused about the behavior of a circuit. See below schematic.
What we see is this: The output of the first LMC6081 (left side of R2) acts as expected: a simple voltage follower whose output matches its input. After R2, however, (at TP1) the node is always 0 V, regardless of input before R1; TP2 always reads roughly +1V. This is relatively simple circuit so it's unclear why the follower works but neither of the inverters do (also, to preempt the discussion, the purpose of the two inverters originally was to buffer an offset which was being added to the buffer output previously).
We thought initially that we had just blown the second and third stage during testing, we replaced those LMC6081's with AD820's because we had them on hand. The common mode requirement for each stage  should be safely beyond our inputs, since our Vcm should never have been above 0.5 to 0.6 V while testing. Our only clues are:

the fact that the circuit behaved identically with either 3 LMC6081's or 1 LMC6081 and two AD820's
the benchtop supply providing the +5V rail and the power for the negative regulator (switching MAX1681 gives -5V) is having significant current flowing from it (up to 40 mA) while this circuit is powered

Any thoughts?
EDIT, 8/26
Per the first answer, we ran some tests on the circuit with minor alterations. Final circuit shown below:

With R4 disconnected the buffer LMC still worked as intended and TP1 was still zero. Checked that no pins were shorted to GND or to the power rails and they were not. Installed the capacitors as shown above and now the output of the first AD820 (node between R3 and R4) worked properly (value was the inverted version of the input to R2). Replaced R4 and the same was true; the node between R4 and R5 was zero, the node between R5 and R6 was the inverted version of the node between R3 and R4. Also, the draw from the benchtop DC supply has dropped to ~10 mA. So there was some kind of oscillation problem and that has apparently been fixed.
However, there is still some problem with the chain: at TP2, we now always see 0 V. We have already checked: that TP2 does not have continuity to GND; the R6 and R7 are the values they say they are; the voltage divider and TP2 are actually isolated from upstream paths (upstream circuitry not drawn for simplicity).
Edit, 8/27/20
Per the discussion below, ran extensive measurements of stage 3 and the voltage divider. Below is a list of those measurements (several are redundant, just for sanity) followed by a graphic showing those (in schematic form, so admittedly a little nonsensical):

Vout of stage 3 does not have continuity to output of R6. Node between R5 and R6 does not have continuity to TP2, but the output pad of R6 does. The output pad of R6 has continuity to the input pad of R7; resistance between them is 0.1 Ohms.
R7 reads as almost exactly 82 kOhms on the meter, whether meter leads are placed on either solder pad or between the input pad and a separate ground.
When resistance is measured between the R5 and R6 nodes (at the R6 input pad) and a separate ground, almost exactly 282 kOhms are measured; if the node lead is moved from the R6 input pad to the output pin of stage 3 (separated by only a few mm of trace), the reading is ~5+ MOhms.
Similarly, measuring resistance between Vout of stage 3 and the R6/R7 node yields ~3.5 MOhms and rising (indicating capacitive charging) but moving the Vout lead to the input pad of R6 yields almost exactly 200 kOhms.
Measuring resistance between the output pin of stage 3 and the input pad of R6, however, yields 0.1 Ohms.

There are a few other checks done (as seen in the image) but the strange impedance readings around the short trace connecting R5, R6, and stage 3 Vout make no sense. Moving the meter lead a few mm changes the resistance significantly, despite the fact that the R between those pads is 0.1 Ohms.


texts: Op-amp Forward biased or negative biased?

texts:
simulate this circuit – Schematic created using CircuitLab

I came across this question and just want to know whether my answer to this question is logically right.
The question is- Is the opamp forward or reverse biased. Also tell the value of V?
Now using Circuit Lab simulation I know it is reverse biased and the value of V. Now logically solving the question-
If I increase the value of V+, the output of opamp V will increase. This increase in V will cause the value of Ve to increase and hence the emitter current of BJT will increase and thus the collector current. This increase in collector current will bring down the value of V+ and hence we get a stable output and thus it is reverse biased.
Now is my reasoning right or am I going somewhere wrong here?


texts:
I searched on SO, and on web, no where found the ans.
I have following code, where It success fully parsed `define and generate expected results, but if number of times calling of macro is large then, Can we using Looping Construct?.

`define myreg(name) \
   addr_``name

`define para(i) \
  parameter `myreg(i) = i

module register;

`para(1);
`para(2);
`para(3);
`para(4);

initial
begin
  $display("ADDR1 = %d, ADDR2 = %d", addr_1, addr_2);
  $display("ADDR3 = %d, ADDR4 = %d", addr_3, addr_4);
  #100 $finish;
end
endmodule

Simulation Result:

// # Loading work.register(fast)
// # run -all
// # ADDR1 =           1, ADDR2 =           2
// # ADDR3 =           3, ADDR4 =           4
// # ** Note: $finish    : reg.v(18)

Now, when I use for loop, like in below code,

`define myreg(name) \
   addr_``name

`define para(i) \
  parameter `myreg(i) = i

module register;

genvar i;
generate
  for (i = 1; i<=4; i=i+1)
  begin
    `para(i);
  end
endgenerate

initial
begin
  $display("ADDR1 = %d, ADDR2 = %d", addr_1, addr_2);
  $display("ADDR3 = %d, ADDR4 = %d", addr_3, addr_4);
  #100 $finish;
end
endmodule

In that case, It shows an error while displaying or using it,
Simulation Result:

// # vsim -lib work register -c -do "run -all; quit -f" -appendlog -l qverilog.log -vopt
// # ** Note: (vsim-3813) Design is being optimized due to module recompilation...
// # ** Error (suppressible): (vopt-7063) reg.v(24): Failed to find 'addr_1' in hierarchical name '/addr_1'.
// # ** Error (suppressible): (vopt-7063) reg.v(24): Failed to find 'addr_2' in hierarchical name '/addr_2'.
// # ** Error (suppressible): (vopt-7063) reg.v(25): Failed to find 'addr_3' in hierarchical name '/addr_3'.
// # ** Error (suppressible): (vopt-7063) reg.v(25): Failed to find 'addr_4' in hierarchical name '/addr_4'.
// # Optimization failed
// # Error loading design

It is asked more times but proper solution is not given by any one, any help appreciated a lot.


texts:
I've designed a PCB for small scale production; currently I'm hand soldering them in batches of 20 at a time. This PCB uses an ATMEGA168 microcontroller which I program before soldering to the board - this method works well for me at the moment.

I'm looking at having a batch of 200 boards manufactured and assembled for me as the product I've designed seems to be quite popular. Would it be better practice to either include an ICSP header onto the board or keep on pre-programming the ICs myself? Re-programming of the board after manufacture or assembly isn't an intended or required feature.

I'm unsure of how this is done in a larger scale production environment? Adding an ICSP header would increase the cost of manufacture slightly so is pre-programming a standard practice?


texts: What is the gold-coloured area on this circuit board and what is it for?

texts:
The below PCB belongs to a wireless access point.

Could anyone explain what are the golden-like part of the circuit that is indicated by the red circles(ish)? What material is it? What is the the functionality/use of it?

The left two circles have the same layout on the other side of PCB, and nothing is placed on top. The right circle is just under the wireless chipset.

P.S. I could not come up with a good title as I don't know the proper name or technique that is used on the PCB, please feel free to edit it.


texts: My amplifier is rated at 8ohms for my surround sound but my speakers are 6 ohms. The owners manual says that if the speaker resistance is too low the power protector will blow and that is exactly what happens when I raise the volume on my amp. I want to increase the resistance on my 5 surround sound speakers and my subwoofer by 2 ohms from 6 to 8.  I was thinking about inline resistors. My question is do I use 2 ohm resistors to take 6 to 8 and do I put them on both the positive and negative speaker lead or just one of them. If both would I put 1 ohm on each lead to get 2 ohms total?


texts: What determines the speed of a homopolar motor?

texts: What determines the speed of rotation of a homopolar motor?


texts:
I can't find the purpose of IC ( which is power sourced by VConn) inside the EMCA.
Source/Sink can communicate with EMCA via this IC. But what is exactly function of this IC in Power Delivery ?

P/S: IC means : Integrated Circuit inside EMCA( Electronics Mark Cable Assembly - a type of cable which complies with Type-C connector). This IC is powered by Vconn signal.

Thank you!


texts:
I have an STM32F2 (reference manual here) which is connected to a GPS receiver through 5 pins. One of these pins is a power supply pin for the GPS.

All pins on the micro-controller are GPIO pins that need to be configured. (E.g. configure as input, output, floating, open-drain, push-pull, etc.) The ARM reference manual does not discuss GPIO pins as power sources.

What GPIO configurations do I need to apply to a power supply pin?


texts:
I have a circuit that uses a TRIAC that controls when 120VAC passes to the output. Never really had any problems until recently when I noticed that I had continuity through the TRIAC without any power going to the gate. I have 100 other boards that don't have this problem. So my main question is, is it normal for a TRIAC to fail closed and if so, how does this happen? Manufacturing error perhaps? My knowledge on TRIACs is pretty limited. The only reason I am so concerned is because I use this TRIAC to control power to a heating element. Without any control on the gate the temperature just skyrockets.

Oh, the TRIAC I'm using is: MAC4DLM.

Schematic: https://ibb.co/f4QPAk

Thank you!

Derek


texts: Reducing reactive power by using a resistor

texts:
I have a school exercise that goes like this:

Voltage is 230V. Frequency is 50Hz. Inductor is 400mH.

How big of a resistor should be added with the inductor (in a series) to reduce reactive power by 75%? (The correct answer is apparently 218 ohms.)

How do you calculate this? Is this even possible? I know only of capacitors reducing reactive power.
I can only figure out that 25% of the reactive power is be 105,24 var. Also sorry, I don't study in English, so the terms might be a bit strange. Thank you.


texts: Energy wastage in wireless charging rotary toothbrushes?

texts: I'm not going to change my habits based on the answer, but I did wonder from a theoretical standpoint. I get idea of wireless charging. I still have flashbacks to my power generation & electric motor courses in undergrad (3 phase systems, lossy magnetic field circuits, etc.).  So basic intuition, I have a vague sense of.  What I don't know is whether today's wireless chargers for rotary toothbrushes are made with enough monitoring and control logic to be aware of when a load (i.e., a toothbrush) is docked and drawing power, so that it dials down the EM field when there is no toothbrush.  As a related 2nd question, does the toothbrush switch loads when full charged so that the charger can tell, and dial down the juice?


texts: Ground plane directly underneath physically large 100 µH inductor?

texts:
I plan to use a physically large ferrite core inductor (Murata part "1410478C", 100 µH at 1 kHz) in a 12 V, 7 A DC filter circuit. It will be mounted on topside of a four-layer PCB (from top down: top routing, split GND plane, split PWR plane, and bottom routing).

It will be filtering typical DC input from a car's 12 V system, which can be a fairly noisy environment. The circuit has transient suppression and reverse voltage protection nearby.

I am not sure what to do with the ground plane directly beneath the inductor's physical location. My instinct is to back-off the perimeter of the GND plane so that it is not close to the EM field surrounding the inductor.

There are two GND planes on layer 2, one called "VEHICLE_GND", which surrounds all the input filtering components, and another called "0V" and provides GND connections for the 3.3 V digital systems which are unrelated to the filtering. The two GND planes are connected at a single point by a through-hole zero-ohm link. Star grounding has been used throughout the design.

Is my instinct right in this instance or would it be better to allow my VEHICLE_GND plane to cover the area underneath the inductor? I would be concerned that ripple from the car's electrical system might be directed through the inductor and cause the VEHICLE_GND plane to exhibit the same ripple probably at a slightly lower amplitude.

Any guidance would be welcome.

Inductor datasheet: http://www.farnell.com/datasheets/1697186.pdf

EDIT...

I have accepted Oliver Street's excellent answer and have decided to remove the GND plane beneath the inductor (also suggested by Peter Smith) as it does not form a hole in the plane in my case due to the inductor being crammed into the corner of the PCB. However had the removal caused an enclosed hole to form (and quite a large one) I would be less inclined to perform the removal. The PCB has not yet been manufactured, and I still have an opportunity to perform some measurements on my selected components, now that I have some idea what to look out for.

Here's a rough sketch of the position of the GND plane and the inductor for the curious.


texts: Why does the VNA show negative gain(S21) for a high power RF amplifier?

texts:
I am a testing a high power amplifier IC(RF6886) for its s-parameters(gain and impedance matching) at a frequency of 145MHz. I have designed the board using eagle for this IC and got it manufactured through power PCB. The IC operates on a DC supply of 3.3V.

When I give supply to the board without connecting the vector network analyser, the IC draws a current of 0.3A and when I then connect the VNA, the current consumption increases to 0.9A and the supply voltage is observed to drop to 2.9V. Also, the VNA shows the gain as -15dB though the gain in dB of any amplifier should be positive. I have ensured multiple times that the IC and all the DC  components as well the RF components have been soldered perfectly. What could be the cause for this to happen?


texts: Dendrites (ionic contamination) on home-brew PCBs

texts:
I've been making PCBs myself for 5 years already.

I use UV curing
develop in NaON (SodiumHydroxide)
etch in Na2S2O8 (Sodium Persulfate)
clean finished PCB with acetone

Recently, I've noticed variety of weird glitches with newly made PCBs - hundred kilo-ohm resistance across separate tracks, power leaks, self-resetting MCUs and self-flashing LEDs or self-turning FETs.

When inspecting PCBs under volates (up to 12V) i've noticed weird spots growing in front of my eyes. Absolutely clean PCB gets dirty in approx. 60 seconds.

Further inspection led to a single conclusion - DENDRITES (or ionic contamination).

I've thrown away all my chemicals and ordered a new set of blank PCB material.
I've event replaced standard water with the distilled-one as well as bought new welding Flux (Weller).

I do still get the same effect.

What else should I try?

ps: PCB in the photos below was crystal clean 60 seconds before powering it up with a 12V rail.


texts: What is the bluetooth library for Adafruit CLUE? Does one exist to download?

texts: I couldn't find any information on Adafruit CLUE's bluetooth library or even examples of code. Could someone tell me if Adafruit CLUE even has a bluetooth library and where I can find it?


texts: Self-made Arduino pushbutton bank not working

texts:
So I'm trying to make a 5 key keypad like circuit, but with increased tactile feel, so I forwent actual store bought pushbuttons. I rigged up keys with some aluminum foil and pieces of plastic and connected that to 5V. All of the buttons share this 5V. Then, I made some contact pads of aluminum foil that has one lead sandwiched between two layers. This lead had two wires, one that connected to one of the digital I/O's and one that connected to a resistor that then connected to ground. All of the contacts share the resistor( and therefore ground). So when the plastic piece connected with the sandwiched piece, it becomes a button. This works, I've tried it. What I can't fix is that if I only connect the pin for Digital 2, then push down any button, not just the one connected to pin 2, it registers a push.

Here is the code I use to check for presses :

int ledPin = 13;
int val = 0;

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  for(int x = 2;x<6;x++){
  pinMode(x, INPUT);
  }

}

void loop(){
  /*for(int x = 2;x<6;x++){
  val = digitalRead(x);
  if (val == HIGH) {
    digitalWrite(ledPin, LOW);
    Serial.println(x);
  } else {
    digitalWrite(ledPin, HIGH);
  }
  }*/
  if(digitalRead(2) == HIGH){
    Serial.println("2");
    digitalWrite(ledPin, LOW);
  } else {
    digitalWrite(ledPin, HIGH);
  }

}

The commented part was intended to check for all 5 connections, while the uncommented part only checks for pin 2.


texts:
I have some doubts to interpret the CISPR standards, one of them is in relation to the test environment for EMI conducted (150kHz up to 30MHz). The minimum size indicated for the vertical or horizontal ground plane is 2m x 2m. Would it be constructively possible to join two planes of 2m x 1m to form one?
Some with this knowledge could help me?

Thank you.


texts: Inverse Fourier Transform of transfer functions

texts:
I want to find the inverse fourier transform of the following transfer function :
$$
H(iw) = \frac{10 + (iw)}{4 - w^2 + 4(iw)}
$$
So my first idea was to replace \$iw\$ with \$s\$. Then convert this into some euler formula. This gives me :
$$
h(t) = \frac{10 + s}{4-w^2 + 4s}
$$
But I can't really factor the denominator since there are 2 different variables. So how exactly do I proceed?

I know the inverse fourier transform formula is \$0.5(pi)\$ * integral of \$h(t)*e^(st) \$ from negative to positive infinitiy.


texts: Instantaneous Current (Inrush) Calculation

texts:
How is the instantaneous (inrush) current calculated for the capacitor in this circuit?

Both Falstad Circuit Simulator and LTSpice give the same answer for inrush current (500 uA).
LTSpice

Falstad Circuit Simulator

How does this get calculated?


texts: The TI quad-XOR gate acts as it is short circuit

texts:
I have a TEXAS INSTRUMENTS CD4030BE Quad Exclusive-OR gate. I have an electronic board of

simulate this circuit – Schematic created using CircuitLab

using this and this refrence. According to the XOR data-sheet:

I should have A ⊕ B = J. However, what I get is that when I press any of the pushbuttons all three LEDs are on:

I would appreciate if you could help me know what is the problem and how I can solve it.


texts: how to calculate the power of the energy harvester

texts:
this is a tough question for me.looking for your guys's help.This energy harvester use DC motor to collect the energy.And an external electrical load R is connected to the generator,i got an oscilloscope to to record the curve of voltage.Then the power of output is

is it right？ and i tried the resistance of 200ohm,the curve likes this

but i tried the 1Mohm the curve is almost keep the same.
If you can help me with this i wll be really really grateful for you kindness.


texts: When do I choose to use a rosin based flux or rosin-free flux?

texts:
What are the general guidelines for determining when flux should or should not have rosin?

Thanks


texts: High-voltage cutoff for battery charger necessary?

texts:
I'm trying to build a treadle-powered general purpose USB charger.

Internally, the treadle spins a motor which feeds through a diode bridge to charge up a storage battery. The battery then discharges through a voltage regulator to power a USB port (with some capacitors scattered around to smooth out noise).

As far as I understand, I need to worry about three potential modes of failure:

Battery overcharge
Battery undercharge
Regulator overheating.

The latter two are easily handled in a loose way by a couple of LEDs and a thermistor, the former is more complicated.

My immediate thought is that it might not be necessary. As the battery becomes overcharged, it seems to me that the current necessary to charge it farther increases, so the treadle would quickly become very difficult to move.

Failing that, it seems as though the simplest solution would be to put a Zener diode in series with an LED or some other indicator, so that when the voltage of the battery increases past a certain point the Zener diode turns on.

The problem with this is that the range the Zener diode should act over is pretty small, and I don't think that I can know what it will be before putting everything together. Also, it may just mean that the Zener explodes before the battery does.

Third and most complicated solution is to have the Zener diode turn on a transistor or relay shorting out the motor. This probably avoids the problem of the Zener exploding, but leaves in the one about deciding what range to use and makes for some very noisy behaviour when the battery is on the edge of being overcharged.

The motor is a simple DC motor. There are a couple of options for the battery, though the best one at the moment is a ~4.5 Ah 6-V Lead Acid. Do I need to implement one of the latter two solutions, or was my initial thought correct?


texts:
Sorry for what might seem like a really simple question. I came across a LED bulb that has the following specs:

It is rated for:

120VAC (which I assume is just because the wall voltage in the US is 120VAC @ 60Hz)
14W power
14mA current

However, I don't know how they calculated 14W if according to the power law equation:

P = I * V

I should get something like

16.8W = .14A * 120V

So my question is, where does the 14W come from if the power equation is 16.8W?

Thanks in advance!


texts: Instantaneous vector sum of three phases 120 apart is not zero?

texts:
Vector sum of equal 3 phases 120 degree apart is zero and serves as a neutral. However, while drawing instantaneous vectors of the three phases, they summed up all together to give a vector. I have attached the animation which shows: "An ordinary three phased system in both vector form and in sinusoidal form. The black vector is the resultant space vector; a vector sum  obtained by adding the three vectors. As can be seen, the space vector's magnitude is always constant".

Kindly explain the difference between the two approaches.

The source of the animation and text is this page on three-phase power conversion.


texts: Is this the right convention for SPI modes?

texts:
The table shown here, under "Clock Polarity and Clock Phase" doesn't agree with my conclusions from table for SPI modes on Wikipedia.
I'd like to distinguish between whether the one on the first like is another convention, or is it just just that 11 and 10 are mistankely swapped, I'm working on a school project and the document provided is from the first website.


texts:
I want to amplify a weak pulse train lets say from 0-0.2V to 0-5V pulses.
The reason I'm asking this question; when amplifying I also want to sharpen the rising falling edges of the pulses. Original pulses to be amplified should be sharpened in case of bad shape.


texts:
I need to magnetize a 1/16" x 4" cobalt steel ( drill) rod to its maximum strength. I plan to heat the rod past its curie temp before magnetizing for maximum effect.

Can I do this with straight DC ( car batteries ) or should I construct a capacitor discharge system?

How would I calculate the coil wire size needed, and number of turns?
How would I confirm success?

Thank You For Reading,
Bill


texts: What are these components in green white and orange colour on this PCB?

texts: Got curious about these components because they seem very different from what I've used till now.


texts: Capacitor and resistors at t=0 and t after long time

texts:
I’m pretty sure my answer is wrong because I forgot to include the capacitor in the calculation and I don't know how I'm supposed to do that.

Find the current for each resistor and in the capacitor at t=0 and after a long time.

simulate this circuit – Schematic created using CircuitLab

\$
\mathrm{I_1} = \mathrm{I_2} + \mathrm{I_3}
\$

\$
\begin{aligned}
\mathrm{R_{eq2,3}} &= {\left(\frac{1}{\mathrm{R_2}}+\frac{1}{\mathrm{R_3}}\right)}^{\displaystyle-1}\\
&= {\left(\frac{1}{3300}+\frac{1}{5000}\right)}^{\displaystyle-1}\\
&= 1987.95\Omega
\end{aligned}
\$

\$
\begin{aligned}
\mathrm{R_{eq}} &= \mathrm{R_1} + \mathrm{R_{eq2,3}}\\
&= 1000 + 1987.95\\
&= 2987.95 \Omega
\end{aligned}
\$

\$
\begin{aligned}
\mathrm{I_1} &= \frac{12}{2987.95}\\
&= 4\!\times\!10^{-3} \mathrm{A}
\end{aligned}
\$

\$
\begin{aligned}
\Delta\mathrm{V} &= \mathrm{I_1} \cdot \mathrm{R_1}\\
&= 4\!\times\!10^{-3} \cdot 1000\\
&= 4 \mathrm{V}
\end{aligned}
\$

\$
\begin{aligned}
\mathrm{I_2} &= \frac{8}{3300}\\
&= 2.42\!\times\!10^{-3}\mathrm{A}
\end{aligned}
\$

\$
\begin{aligned}
\mathrm{I_3} &= \mathrm{I_1} - \mathrm{I_2}\\
&= 1.58\!\times\!10^{-3}\mathrm{A}
\end{aligned}
\$


texts:
Hello, I just need a little guidance on if I am analyzing this circuit correctly using Node Voltage.

Mesh and Thevenin Theorem resulted in Vy= 36V
If i leave the ground where it is, the node after the 2A current source would be Vy.
If i do KCL at the node where the 9A is, I get -(Vy/4)+9=0 thus, Vy=36V

I just want to make sure that I am allowed to do that instead of working with the dependent source and the super node.
Thank you!!


texts:
I have an SSR that takes 3-32V as an input. The trigger current is 7.5mA/12V.
Can I use two 4K resistors as a voltage divider to allow a 14V to 55V power supply to be connected?
The load side of the SSR is a 12V drop down regulator.
Alternatively is there a better option to switch everything on/off?
https://cdn.sparkfun.com/datasheets/Components/General/SSR40DA.pdf Data Sheet for the SSR.
https://www.aliexpress.com/item/4000262700918.html the drop down regulator.
Answer:
After the answers in the question. I have ended up going with a proper voltage regulator


texts: VHDL: case when using constants constructs

texts:
I'm having some trouble with the following statement

if spi_ctr = 9 then
            case spi_op is
                when spi_op = op_get_r_count => spi_reg_out <= ref_count_i;
                when spi_op = op_get_s_count => spi_reg_out <= sig_count_i;
                when spi_op = op_get_g_limit => spi_reg_put <= gate_limit_i;
            end case;

Quartus sinthetizer spits the following errors

Error (10500): VHDL syntax error at spi_iface.vhd(93) near text "=";  expecting "!", or "=>"

Error (10500): VHDL syntax error at spi_iface.vhd(94) near text "=";  expecting "!", or "=>"

Error (10500): VHDL syntax error at spi_iface.vhd(95) near text "=";  expecting "!", or "=>"

i don't see a syntax error around however, i also tried using the following

spi_reg_out <= ref_count_i when  spi_op = op_get_r_count else
               sig_count_i when  spi_op = op_get_s_count else
               gate_limit_i when spi_op = op_get_g_limit;

and it spits a similar error

the constants are defined as follows

-- read operations
constant    op_get_r_count: std_logic_vector(7 downto 0)    :=  "00000001";
constant    op_get_s_count: std_logic_vector(7 downto 0)    :=  "00000010";
constant    op_get_g_limit: std_logic_vector(7 downto 0)    :=  "00000011";

spi_op is as follows

signal  spi_op:         std_logic_vector(7 downto 0);

is there something obvious i'm not seeing or you need to use literals in these kind of statements?

--- Edit

after following the recomendations from @Oldfart i changed the code to this

case spi_op is
                when op_get_r_count => spi_reg_out <= ref_count_i;
                when op_get_s_count => spi_reg_out <= sig_count_i;
                when op_get_g_limit => spi_reg_out <= gate_limit_i;
                when others         => spi_reg_out <= (others => '0');
            end case;

and voila! it Almost works

however it outputs quite a weird error that really caught me with my pants off

Error (10344): VHDL expression error at spi_iface.vhd(102): expression has 31 elements, but must have 32 elements

?! shouldn't the last statement take care of that?

--- edit again

actually that error was from an other line, dumb me

Oldfart post your answer if you want the kudos :)


texts: What is a "solder mask opening" in a footprint?

texts: In the Luxeon LED datasheet under Solder Pad Design section there is a diagram with 3 crosses around the edges of the LED. They are identified as "4x Soldermask Opening (hatched area)" but I am not entirely sure what it is exactly or why it is used. What are they, what do they achieve and how should they be drawn in Eagle or other software?


texts:
I'm new to electronics and trying to understand the difference between analog and digital ICs. My understand of analog and digital signals is up to scratch but I am struggling to categorize ICs into either analog or digital based on their function.

After digging around in datasheets and looking around online I am becoming more confused! I'm hoping someone can point me in the right direction or re-align my thinking so I can figure out what these ICs are without having to ask about individual components.

My confusion mainly comes from looking at functional block diagrams in datasheets.

For example, if we look at this Half-Bridge Gate Driver,  http://www.ti.com/lit/ds/symlink/ucc27211a.pdf the schematic on pg 13 shows a diagram containing logic gates (digital signals) and what seems to be amplifiers of some sort(?), a diode, Schmitt triggers buffers (?), which are analogue components, so is this IC a digital or analog IC?

There are also some functional blocks; level shift and UVLO, I'm not even sure where to start with these!

Also, I seem to have been convinced that transistors are analogue components, but these are then use to create a logic gate. The line between analog and digital is becoming ever more blurry, any help is greatly appreciated.

Thanks in advance.


texts: Elaborated difference between static and dynamic EMF

texts:
I have seen two sources have contradicting takes on static and dynamic induced EMFS.
One source says that Static EMFs are produced by the circuit and magnetic field both being stationary. Dynamic EMFs meanwhile are produced when figuratively either the circuit cuts through the magnetic field or the magnetic field cuts through the circuit. Now I know what they actually say is change in flux but I'm just putting out a simple concept and in no way am claiming that it is near to what is actually happening. It is just a concept.
This idea is what I almost always get when I search in Google.
Another source says that both Static and Dynamic EMFs have either of the magnetic field or the circuit being moving. Which means there is no case where both the magnetic field and circuit are stationary. Static EMF is when the magnetic field cuts the circuit and Dynamic EMF is when the circuit cuts the magnetic field.
https://www.youtube.com/watch?v=JN1Z5mgbORY
https://www.youtube.com/watch?v=dbtp6bOn4WQ
These are my reference for the second ideas.
I just want a clear cut explanation on what they really are and a way to easily distinguish the two. I mean, I can totally elaborate what magnetic field cuts circuit and circuit cuts magnetic field are but my problem is distinguishing the two and how the applications really work. Sources do mention examples like transformers, self inductance and mutual inductance but because I am confused with the right idea, I don't really want to base it on the examples and leave it at there. I hope someone is able to explain and also relate those common examples.


texts: Can anyone explain to me how to calculate the voltage between A and B in this circuit please?


texts:
I'm looking for a simple circuit that uses only a comparator (or an opamp) to detect the presence of a small current through a high-side current resistor. The idea is for a microcontroller input to go high when the current through the resistor exceeds a predefined value (of let's say 200mA).

This is to detect when a phone is actually pulling power from a +5V source. The circuit below illustrates my intent, by I feel that it is missing something, mainly that the comparator may not reset when the voltage across the sense resistor reaches zero. I'm not aiming for precision, but rather a rough "there is current" and "there is no current" type of circuit.


texts:
I'm looking into sampling a signal into a micro-controller, the ADC will be sampling at ~38.5 Khz with 8 bit depth.
The dynamic range is given by 6.021*N + 1.763 dB, so in this case I'm getting ~49.92 dB which means I need to attenuate the signal about that much at the Nyquist freq. of 19.25 Khz.

After some experimenting with TI's filter lab I got the following implementation of a 4th order LPF:

I was wondering about the input impedance of the circuit so I quickly entered it into Multisim and got the following:

At 20 Hz the input Z is about 750 KOhm which is good enough for me, however as we move towards 1 KHz that figures goes down to about 16 KOhm. At 4 KHz (passband) the input Z is only 4 KOhm.

Questions are:

How can I improve on that? Is there anything I could do without adding an additional op-amp buffer stage in front of the filter?
Since the ADC is single supply I'll need to bias the signal to VCC/2. How can I do that without killing the filter response? Looks like adding a cap at the output and a voltage divider will have a very dramatic effect on the low freq. response.

A passive filter also possible (but low input Z):

simulate this circuit – Schematic created using CircuitLab


texts: Which relay switches can be activated by the parallel port?

texts:
I'm planning on controlling some external circuits using the parallel port by switching on relays that can switch on the external circuits.

Am I right in thinking the pins have a voltage of 3-5V when high and a maximum current of 50mA? The most sensitive relays I can find require 5V and 1A (eg, http://www.maplin.co.uk/dpdt-1a-miniature-relay-37494)


texts:
I have some related questions here and I hope I get better understanding thru this forum.

ATX SMPS has Over Voltage Protection. Does it mean that it will shut itself down in over voltage situation or will it attempt to regulate the output voltage within limits and still remain on?

Motherboards interact with SMPS thru PWR_ON line Pin#16 on 24 Pin ATX Power Connector. It’s pulled to active low to start the SMPS and open circuited to put it in standby mode. So there’s a circuit on motherboard that controls this.

So if the SMPS has capacity to shut itself down, does it practically override this motherboard circuit, if the need be?

Can OVP kick in if I attach a different load to SMPS instead of a motherboard e.g. a Car Audio system?


texts: What is the best way to interface ST7066 lcd controller with Atmel SAM4E

texts: I am trying to interface ST7066 LCD controller with Atmel SAM4E MCU, but is quite confused about the best way(Least no. of pins used) to interface them together. Should I use GPIOs or Should I go for Static memory controller. Do it needs any chip select or SPI.


texts: I'm designing a board that works with 300 VDC peak. I understand that there are rules for trace to trace PCB clearance. But what about Pin to ground pour clearance? I have not seen any standard specify this kind of clearance. This is one of the pin that I have on my PCB design. What should be the minimum pin-to- ground pour clearance to use?:


texts: Simple capacitor use for buffering a battery?

texts:
I have a simple application where a 6V, 2A DC power supply is driving 4 hobbyist-grade servos.  In most cases this is adequate, but there are cases (when all servos are suddenly loaded) when I think the power draw will exceed 2A for a short period of time.

It was suggested to me that I should use a capacitor between my power source and the servos in order to handle this kind of transient load.  Unfortunately the suggestor didn't know how this would actually be implemented.  I tried the University of Google, but mostly came up with videos of giant capacitors being used to dramatically explode things.

Could someone point me in the right direction, or give me a simple circuit example of how I would do this.  Is it as simple as wiring a capacitor onto the positive lead?

What calculations should I make to determine the appropriate capactitor size?  For example, if I wanted to sustain a peak of 3A for 5 seconds.


texts: Controlling a high voltage relay by a PC USB

texts:
My 2.1 speaker's transformer is consuming active power even when the PC is off. I know it because it is always warm. Thus, I want that only when my PC is operating the transformer will get the AC power from the gird. So I need to put a relay between the L1 from the grid to the correct pin in the transformer.
I have managed to configure in my BIOS that when the PC is off the USB will not have output voltage, so I am planing to use a USB port (5V) as control pin for the relay.

I saw that there are relays which have a second level of isolation by using a LED.
Is it too dangerous to use only 1 level of isolation between my PC (USB port) to the grid?
I mean that the 5V from USB will output the current for the relay's coil.

Thanks!


texts: What's an analog way to measure only the on-time of a servo PPM pulse?

texts: Hobby radio control receivers typically output a 1-2 or 0.5-2.5 ms pulse every 50 milliseconds, and only the duration of the high pulse matters. Now the best way to decode this signal is probably with a microcontroller. What would be a good way to convert this signal to a voltage without a micro? A sample & hold or track & hold amplifier latched on the falling edge?


texts:
This is the datasheet of the driver IC I am working on (LM5112).

Following is the application diagram of the module.

Basically this is the GATE driver circuit for the MOSFET with PDM signal as the input.
I am looking for how to calculate value of the MOSFET input resistor (R3) ?

MOSFET input voltage (VDS) = 10V
Output power required is 200W.

Questions:

1) How to calculate the MOSFET input resistor?

2) What are the factors affecting the MOSFET input resistor calculation?

3) What will be the maximum, minimum resistor value possible and effect in the circuit if the resistor value is changed (Increased or decreased) ?

Please let me know if any further info is required.


texts: Paralleling mosfets to handle more current while driving a DC motor?

texts:
I would like to drive a 180W, 24VDC motor with a PWM signal using mosfets such as follows:

simulate this circuit – Schematic created using CircuitLab

The motor is inside a control loop with negative feedback which regulates the speed of rotation by acting on the PWM output. Given a mechanical load, the speed of the motor can be regulated by varying the applied voltage. The variation in the voltage supplied to the motor is achieved by varying the duty cycle of the pwm output. So far all my efforts have been focused on designing the control system with the analogue PID controller.

Suppose the motor is rotating at a speed w which requires a 10V voltage and a current of around 2A. In this case I can see at least two problems with this approach:

The mosfet is dissipating 14 * 2 = 28 W. Not acceptable unless using a heat sink
The diode is dissipating 1.8 * 2 = 3.6 W.

As for the first problem, my solution would be use more mosfets in parallel in order to share the motor current. The number of parallel mosfets would be designed to handle the worst case scenario. However, I have never used mosfets in parallel and since I know that no two transistors are the same, I am afraid the current will not be shared equally (as in a resistor current divider) resulting in a possible overload of one/two mosfets. What are the critical points to consider while paralleling mosfets for this particular application? Furthermore, in case the "current sharing dilemma" is solved, should I put a resistor in series to each gate when sending the PWM signal to each mosfet?

As far as the diode is concerned, I would look for a diode that can withstand more current within the worst case scenario current for the motor which should be around 10 A. Is there a better way to do this?

If you think there is a better way to achieve the same goal, please do provide your solution. This is a hobby project and I need some constructive feedback/critics.

PS: when I talk about worst case scenario current I mean the nominal current under (a heavy) load. In case of high currents due to blocked rotor or short circuit, I plan to add a fuse for protection.


texts:
I have a transformer with dual input 115v and dual output 9v and rating power 1.15va.

My goal is to connect it in parallel to produce single input 115v, single output 9v and rating power 2.3va.

The primary doesn't have a Center Tap, but the secondary has it and it confused the hell out of me.

The secondary has 5 connections.

How do I achieve the 9v and 2.3va on the secondary ?

Thank you


texts: How to connect 2 devices to single USART?

texts:
I have GPS receiver connected to ATMega328 USART RX/TX pins. However, I also need to use RX/TX pins for ATMega firmware upgrade through bootloader, so RX/TX is connected to FT232.

How to properly connect both GPS Receiver and FT232 to ATMega RX/TX? I can't use jumper solution, because user doesn't have access to PCB.

Update:

No software UART, please.
The more simple solution, the better. I need to maintain the cost and PCB size.


texts: How do I apply Thevenin theorem in this problem?

texts: Can't find the answer to this question. Am I supposed to get the voltage in the 4 kilo ohm resistor? Really appreciate it if anyone can solve this one! Here's the circuit:


texts:
I came across this circuit for a high-side current sense using BJT current mirror, and I am trying to derive a formula for how I could calculate the sense voltage output (going to the FB pin) in terms of Isense and the resistors used. I am having a hard time understanding how they derived their formulas. Firstly where does the 1.25 come from to calculate their \$R_\mathrm{FB1}\$, and when it says suggested bias current of 1mA, is this talking about base current, and why 1mA?

  Resistor \$R_\mathrm{B}\$ sets a bias current through the right-hand transistor. The suggested bias current for the PNP
  transistors is 1 mA. \$R_\mathrm{B}\$ is selected by dividing the typical output voltage minus one diode drop by 1 mA.
  $$
R_\mathrm{B} = \frac{V_\mathrm{O} – 0.6}{0.001} = 32.6\mathrm{k}\Omega\label{1}\tag{5}
$$
  $$
R_\mathrm{B} = 32.4\mathrm{k}\Omega\pm 1\% \label{2}\tag{6}
$$
  \$R_\mathrm{FB1}\$ is set to bias the left-hand PNP at 1 mA, using the following expression
  $$
R_\mathrm{FB1} = {1.25 \over 0.001} = 1.25\mathrm{k}\Omega \label{3}\tag{7}
$$
  $$
R_\mathrm{FB1} = 1.24 \mathrm{k}\Omega\pm 1\% \label{4}\tag{8}
$$
  \$R_\mathrm{FB2}\$ is set to amplify the current sense signal to equal the feedback voltage:
  $$
R_\mathrm{FB2} = \frac{I_\mathrm{F} \times R_\mathrm{SNS} \times R_\mathrm{FB1}}{1.25} \label{5}\tag{9}
$$
  $$
R_\mathrm{FB2} = \frac{1.0 \times 0.2 \times 1240}{1.25} = 198\Omega \label{6}\tag{10}
$$
  $$
R_\mathrm{FB2}\text{ is }200\Omega\pm 1\% \label{7}\tag{11}
$$
  Texas Instruments Application Note: AN-1696

Now using "1" for left transistor and "2" for right transistor:

From my understanding the base of the two transistors will be at \$V_\mathrm{O} - V_\mathrm{BE2}\$ (forward drop of right-hand transistor). Doing KVL around the top loop, you have
$$
R_\mathrm{SNS}\cdot I_\mathrm{SNS} +  V_{BE2} = V_{BE1} + R_\mathrm{FB2}\cdot I_{E1}.
$$
For a matched pair, where \$V_\mathrm{BE1} \sim V_\mathrm{BE2}\$, this gives
$$
R_\mathrm{SNS}\cdot I_\mathrm{SNS} = R_\mathrm{FB2}\cdot I_{E1},
$$
so \$R_\mathrm{FB2}\$ has the same potential across it as \$R_\mathrm{SNS}\$, and for a given sense resistor and load current, \$I_\mathrm{E1}\$ is set by \$R_\mathrm{FB2}\$ as:
$$
I_\mathrm{E1} = \frac{R_\mathrm{SNS}\cdot I_\mathrm{SNS}}{R_\mathrm{FB2}}.
$$
Since \$I_\mathrm{E1} \gg I_\mathrm{B1}\$, then \$I_\mathrm{C1} \sim I_\mathrm{E1}\$, so \$V_\mathrm{SNS}\sim I_\mathrm{E1}\cdot R_\mathrm{FB2}\$.
So:
$$
V_\mathrm{SNS} = R_\mathrm{SNS}\cdot I_\mathrm{SNS}\cdot\frac{R_\mathrm{FB1}}{R_\mathrm{FB2}}.
$$

So is this a correct formula to use for the \$V_\mathrm{SNS}\$ output?

I think I'm not understanding something correctly, because I don't get what effect \$R_\mathrm{B}\$ actually has on this formula? The formula I derived above does not include \$R_\mathrm{B}\$, but I think the base current of both transistors is set by \$R_\mathrm{B}\$, and the collector/emitter current should be related to base current as an approximation:
$$
I_\mathrm{B} = \frac{I_\mathrm{E}}{\beta},
$$
where \$\beta\$ is the current gain - but if I try to derive a formula that way I can't seem to get the same result.

So where should base current and \$\beta\$ come into these calculations?

Could you not just replace the transistor pair (emitter diodes) with two regular diodes OR'd together and connected to \$R_\mathrm{FB1}\$, and arrive at the same formula, and functionality?


texts:
Is it possible to export vector values or other data from ngspice to a file?

It would be nice to use the data in other programs such as octave or gnplot for prettier plots.

Thanks


texts:
I want to convert DS18B20 temperature (4-bytes code from datasheet) to string with accuracy 0.1°C (like sprintf %.1f). AVR. C language (avr-gcc). I need for small code, so sprintf, floating-point types and round from math.h is bad idea. My following current code is bad also:

void reverse_string(char *s)
{
    char *p, c;

    for (p = s + strlen(s) - 1; s <= p; ++s, --p) {
        c = *p;
        *p = *s;
        *s = c;
    }
}

void ts_to_string(uint16_t ts, char *s)
{
    int8_t n = (int8_t)(ts >> 4);
    uint8_t neg = n & 0x80;
    char *p = s;
    float f;

    if (neg)
        n = -n-1;
    do {
        *p++ = n % 10 + '0';
    } while ((n /= 10) > 0);

    if (neg)
        *p++ = '-';

    *p = '\0';
    reverse_string(s);
    *p++ = '.';

    f = (float)(ts & 0xf) / 16.0;
    if (neg)
        f = 1.0-f;
    *p++ = (char)round(f * 10.0) + '0';
    *p = '\0';
}


texts:
I started learning control systems and I have a question about system identification.
Let's say I want to identify DC motor. I want to control speed using a PID controller. I can model my system based on physics equations and then compare to my real system. I measure my speed periodically in discrete time (microcontroller). Should I compare my real system with the model in continuous time and then transfer it into discrete model with my sampling frequency and design discrete controller? Or how can I identify a discrete system? Thank you.


texts: Any way to duplicate the behavior of this device? Or another one similar for commercial use?

texts:
I'm having problems hot swapping a powersource to my board due to the input capacitance, I have a big inrush current (around 80A peak) and hence I see arching (sparking) on the connector when I power my board. I believe this could lead to damage down the line so I want to avoid it.

I tried NTC Thermistors to limit the inrush, they worked, I managed to get down to around 30A peak but still there is sparking.

http://www.youtube.com/watch?v=qmf1HL4CYJM

This device limits the inrush current in a unique way, by creating a slow transition on the output voltage. But alas this is a very specialized device for military use, and hence must be very expensive, and also looks quite bulky.

Can you recommend a similar device but for commercial products? Or any other way to duplicate the behavior of this device?

Input source: External Power Supply Brick. 24V DC
Steady State Current: 3A
Max Peak Current under normal load (momentary): 8A
Max Inrush Current: 80A


texts: Is it safe to use MG Chemicals Nickel Conductive Pen on a surface exposed to hand/skin touch?

texts:
I'm currently working on a project i.e. making a custom controller for my own game. I've to make a glove like controller. I'm currently using wires for making the controller work but I've listened to this new conductive pen thing (I thought it would be better if I get rid of wires on glove controller for a better experience) and I ordered one (MG Chemicals 841AR-P Nickel Conductive Pen). This conductive pen has a lot of warnings and danger signs which state it can cause skin cancer or eye irritations etc. I want to know that does it cause any problem when the ink is dried (or these are just the dangers when ink is not dried yet) as I've to use it on the glove-like controller which will be in direct contact with skin.

Did anyone use Nickel based conductive pen on bare surfaces?


texts: A triple voltage supply from a dual supply

texts:
I have build a dual power supply for an analog synth (see image below).

The input source is a 12 VAC - 1.7A adapter. It is based on the Wall Wart power supply from Music from Outer Space.
Now I would like to include a 5V output to drive one or more Arduinos. If I expand the power supply with a voltage regulator (LM7805) in parallel with the LM7812 regulator, would this work?

I expect that the LM7805 regulator will be less efficient as it has to bring the voltage down from 12V to 5V and will produce more heat. Therefore, I've attached all voltage regulators to heat sinks.
Might it be better to exchange the LM7805 linear voltage regulator with a switched voltage regulator? The advantage being that it is more efficient and produces less heat, while the noise might increase. I do not intend to use batteries, so efficiency is less important, and I expect that the Arduino will not take much current.
An additional question: Have I placed the fuses F1 and F2 at the correct position in the circuit?


texts: Transformer based digital isolator vs Capacitor based digital isolator

texts:
Nowadays, digital isolator vendors all argue digital isolators are more superior to optocouplers. And they also argue their product is more superior to others in some aspect. Like TI (produce isolators based on transformer) and ADI (provide isolators based on capacitor), in their appnotes or data sheets, they even compare their products directly with the products come from their competitor. These comparison confused me some. So, anyone can give a comparison fairly and objectively? Or in what situations we must choose one and abandon the other.

Update:

TI says their products have better Magnetic-Field Immunity, and ADI says their products have better CMTI. Anyone has experienced the differences?


texts: Shimming loose AA batteries with aluminum foil... Will this cause corrosion?

texts:
If you folded up a piece of aluminum foil and put it between the nickel plated terminal of a AA battery and the nickel plated contact in the battery holder....

Would galvanic corrosion cause either the battery or contact materials to become damaged?

Does it matter whether you put the aluminum foil on the positive or negative end of the battery?

Are there any other risks such as safety risks, exploded batteries, or as I've mentioned, any expected corrosive effect that might ruin your device contacts after a period of time?


texts: SMD diodes with mark YR103, WX104, and RZ102

texts: I'm trying to identify the SMD components on a contactor control circuit.  They are from General Semiconductors and have the labels: YR103, WX104, and RZ102.  I think they are diodes, but I'm not sure what kind.  Can I get some help with identifying them?


texts: Use Current-Loop Transmitter as voltage controlled current source

texts:
Yes, I understood, this is very strange idea from newbie, but whatever...
I want to make sawtooth waveform generator, based on capacitor charging by constant current. With specified frequency, capacitor will be short-circuited, producing sawtooth on the output.
So, voltage controlled constant current source is needed. Yes, I understood that there is more convenient solutions, like Howland current pump. But! I have found XTR115 - current loop transmitter.

As I understood, this IC could supply constant current in range 0.25-25mA depending on input voltage Vin.
Is this extremely silly idea to use this IC as voltage controlled current source?


texts:
I am thinking about a project that has need for various different complicated wiring connections. I would like to make a single board that would make it as easy as possible to make arbitrary connections between signals. My thought is something like this:

By putting the signals in a configuration such that they all cross every signal from the opposite side at some point, then I can use the vias to make connections by soldering a thin piece of wire in the appropriate hole.

I made this image in Eagle to demonstrate my point, but vias will not work, because they will be always connected all of the time. What I want is the copper on top and bottom but not in the through hole part. Is this possible to do in Eagle? Can most fab houses deal with things like this (I generally use ITead)?

In my final design it will be much larger than this (64 in - 64 out).


texts: How to connect 120V to a relay on a prototype board?

texts:
I'm designing a microcontroller controlled switch.  I idea is to have a 120V outlet controlled by time of day, or a motion sensor, etc.  The plan is to have a lamp plugged into the outlet.

I will switch the 120V with a relay, which I plan to have on the same board as everything else.  Since I have the 120V anyway, I thought I would use a Recom AC/DC Converter to provide 5V.

My questions are more mechanical than electrical, but important to the design:

How do I get the 120V to the board?  Can I use a lamp cord with a standard plug on one end, with the other end connected to a terminal block?
Can I use a 2-conductor cord (i.e. no separate ground) ?
If I use a terminal block, what gauge wire should I use to connect from the block to the realy?
Let's say I decide to make a "real" board out of this...can I put 120V through traces?


texts: Using a DC Electronic Load vs power resistors (dummy load)

texts: When setting up a test to evaluate a DC power supply, would using a power resistor suffice? I have a 5 V power supply hooked up directly to a 5Ω 20 W resistor to pull a constant current of 1 A. When probing the 5 V line for charger noise (high frequency oscillation), I see voltage spikes on my oscilloscope which don't match up to the max variance in the data sheets. The vendor uses a programmable DC Electronic Load with a 1 A load and doesn't see the same spikes as I do. Would this be because of load I am using?


texts: How prevent discharging static electricity when touching metal case of sensitive circuit?

texts:
I have made a metal box including raspberry pi, touch screen and lcd screen. my problem is when i touch the box static electricity cause arc and shock to device and cause software failure also. i tried to connect all grounds to earth but:
1. it cause touch screen act weird
2. the earth connection is not available everywhere

i have an idea to connect metal box to ground using following circuit but i dont know if it would work or what part numbers should i use.
In my theory when the voltage rises more than 5v the zener diode should pass the current then resistor should convert electricity to heat. please correct me if i am wrong.


texts: Input voltage of LM317 drops when lead acid battery is connected on output

texts:
I have built a voltage regular circuit with LM317. Its input is connected to my solar panel.

As in many circuit examples, there is a voltage divider to bias the adjust pin. Also, I have connected a diode on output to prevent backward current flowing into voltage divider.

When no load is connected on output, I measure the output of my solar panel, it is also the input of LM317. It is generally over 18V. I set the output voltage to 8V by using a pot, and it works perfectly. In this connection, due to the voltage drop on diode, I get about 7.2V at the end.

Now, when I connect my 6V lead acid battery (it says 7.20V - 7.50V for charging), I measure the input of LM317, and see that it drops to about 4-5V and stays there. I don't have much experience with lead acid batteries, but some days it works perfectly, and output stays really high, other days, battery doesn't charge at all and above situation is seen. What is causing this? Is it normal?

P.S. After charging batteries, I use it to light hallway with white LEDs.

.. After a while ...

I used a 12V power adapter last night as substitution  of solar panel, and measured voltage at different points. I saw the same effect. That means this effect is not about solar panel.


texts: Make sure this equipment can do what I want (infrared decoding)

texts:
I'm CS but took a digital electronics physics class at my old university and found it really interesting so I wouldn't mind having my own small EE workshop. For my main project I just want to decode infrared signal for a gated community gate clicker so that I can write an Android app to retransmit it from my S5.

I just need this list of components checked over to make sure if this is all the equipment I will need for my main project.

Breadboard & Micro: Arduino Starter Kit
Oscilloscope:
http://www.amazon.com/Huhushop-TM-Digital-Storage-Oscilloscope/dp/B00GD6BYDM/ref=sr_1_53?s=electronics&ie=UTF8&qid=1398097080&sr=1-53&keywords=oscilloscope
IR demodulator:
Digi-Key part # TSOP57238TT1TR-ND

This is the tutorial I want to follow:

http://www.eevblog.com/forum/blog/eevblog-506-ir-remote-control-arduino-protocol-tutorial/


texts: Can current flow to earth in TN-S Earthing system?

texts:
The above illustration of a TN-S Earthing system shows one shared connection to earth between neutral and protective Earth.

Assuming a short circuit occurred, in the brief second before detected by a circuit breaker, I would think that the current would flow back to its source, and not into the earth, as current must flow in a loop (and current cannot flow in both directions simultaneously).

In reality, are there multiple independent connections to earth back at the generator/transformer, which would provide the necessary loop?

If not, what is the purpose of the physical connection to earth in such a configuration?


texts: Does the constant current mode in power supplies correspond to short circuit?


texts: Calculating resistance for 50% duty cycle

texts:
I am planning for simple standalone LED flashers to fill the ceiling of a room. Planning to fix at least 60 of these and they will be flashing randomly at about once a second.

I'm using this circuit. Rb of 100K and Cb of 10microfarads are chosen to give the required timing. By experimenting with various values, I can decide what to use for Rc to achieve the 50% duty cycle. Rc must be matched to the current in the LED to achieve the 50% duty cycle?

What I want to ask is, is there any other more straightforward method to estimated the Rc?

I haven't order the LEDs yet, so I need advice on that too. It will be the standard size of 5mm plastic cased LEDs.


texts: Order of writing variables at the top left of a K-Map

texts:
[Beginner here]

I was studying from AAC and I've reached till here. On this page, they've this example:

My confusion is NOT in how to make pairs, quads or octets or how to fill gray codes. I'm good at that. My only confusion is:

  How do they decide - in the top-left square of the map - whether CD comes to the right of the diagonal or AB does?

Like in the above example, I put AB to the right of the diagonal and got this answer instead: $$(A+\bar{B}+C)\cdot(A+\bar{B}+D)\cdot(\bar{A}+B)$$ which happens to be the same answer with A,C and B,D swapped. But it's still a drastic change in the answer.

Hence, my question:

  How do they decide - in the top-left square of the map - whether CD comes to the right of the diagonal or AB does?


texts: I saw this circuit in an answer to temperature controlled water bath but didn't understand the working and how the temperature would be controlled

texts: I need to understand how this circuit will work and how will the temperature for water bath be controlled using this circuit . The link to the question where i found this is : Building a temperature-controlled water bath


texts:
The accepted way for implementing a sequence detector is with a state machine. why implement a SM when (it seems) any sequence detector can be implemented with logic demonstrated below (ASIC and FPGA)

 module detect_1011;
       input bit in_bit;
       output bit detected
       bit [3:0] in_seq;
       always @(posedge clk);
          in_seq <= (in_seq<<1) | in_bit;
       assign detected  = in_seq == 4'b1011;
    endmodule


texts: Switching power supplies with a relay, how to account for delay between connections?

texts:
this is my first post on this site (but I will have more, have no doubt), so if I have posted in the wrong section or something please forgive me.

Anyway, I am currently doing a battery powered pc build and I have wired up a DPDT mechanical relay to automatically switch between a battery and a 12V regulated powersupply. The problem I have run in to is that the amount of time when the relay actually switches over from one pin to the next is too long and it will shut off my dc-dc powersupply for the computer (it is an M4 ATX PSU). My first thought was to try to find a make-before-break relay but those seem scarce and may damage my lithium battery. The other idea that I had was to maybe use a capacitor bank to supply the necessary 20A at 12V for about 10-50 milliseconds, but I have honestly no idea how to find the right size of capacitors for the job. I might have to deal with the shut-down when plugging it in if the capacitor bank is too large because space is tight in the case I'm building.

Thanks for your help,
Kevin


texts: Given hardware specs: How do I calculate the data bandwidth [bits/s] of this system?

texts:
I'm currently trying to buy a hardware that is supposed to extract your brain waves. In other words, a data transmitter.

I am looking at the hardware spec and I am uncertain as to how I should calculate the data bandwidth i.e. how many bits the system is able to send per second.

https://emotiv.com/product-specs/Emotiv%20EPOC%20Specifications%202014.pdf

I'm primarily confused between sampling rate and the resolution. What does resolution mean in this context?

Thank you for your help!


texts: What are the Pros/Cons of using an OTP vs a masked chip?

texts:
I work for a toy company and to date all of our electronics have used masked chips. This incurs a chip masking charge and a lead time of 45-60 days to mask and manufacture/program the chips.

Recently one of our vendors offered us an OTP (one-time programmable chip option). No chip masking charge, shorter lead time to get chips programmed (~30 days). The one downside is the cost of the chip is higher.

Besides a cost analysis of when using an OTP chip will be better than a masked chip (based on volume produced) to help me decide which option to go to, what are other pros/cons of using  a masked chip vs an OTP chip?


texts:
I'm building a chronometer for high speed projectile speed measurement. Currently i'm in the process of designing the projectile detection gate. It needs to be able to detect obstructions in light for a duration of just under 1 μs.

The design is supposed to work as follows:

The reverse biased photodiode will be lit by a stable light source (battery powered led)
If the path of light is blocked from the light source the voltage on MP1 will rapidly fall.
The voltage on MP2 is slightly negative biased to ensure it is below MP1 under normal conditions
Since MP2 has a RC circuit it's voltage will change slower than MP1
If the voltage on MP1 gets lower rapidly the gate will output 1.

So far so good, it seems to work with simple tests of breaking the path of light.
The problem i currently run into is noise, for some reason the signal at MP1 (measurement point 1) is very noisy, it seems irregular (for as far as my equipment can tell) and it measures over 20mV peak to peak, which renders the sensor unusable.
The following is measured with an ADC of an arduino (atmega328p) @ 200Hz +/- 1mv per unit.

Blue line is MP1, Red line is MP2, Output is not drawn cause it will offset the scale too much and is jumping up and down like crazy as you can imagine.
The gradual fluctuations are caused by changes in light (probably by my hand) and are intended. However the irregularity in the blue line is causing the problem. As can be seen the noise is higher than 20mv and also higher than the offset voltage and object detection limits. This causes the output to constantly bounce up and down.

Is this amount of noise normal for an Photodiode (SFH213)? and thus should i just deal with it?
Is there anything obvious that i'm missing that could cause this noise?
Could i filter the noise in a way that would still enable me to see dips in the light of slightly under 1 μs?


texts: How to program an ATmega32 in C++ to control a LCD?

texts:
I'm electronics student. I'm a newbie in programming. I have loved C++ after watching some videos on C++. Am using Atmega32 uC, WinAVR GNU GCC compiler programming tool, 16*2 Hitachi HD4478OU LCD for my project.

I have connected 3 switches to PA1, PA2 and PA3. LCD connected to PORTC, PD6 and PD7. I want to write C++ program that will display on the LCD "SWITCH 1 IS PRESSED" when switch on is pressed, "SWITCH 2 IS PRESSED" when switch 2 is pressed and "SWITCH 3 IS PRESSED" when switch 3 is pressed and if no switch is pressed it should display "WELCOME" swinging from end to end. Each switch press should light a corresponding LED connected to PA1,PA2 and PA3.

Please somebody help me as this is my school project and I have only few months to submit it, the circuit is already built. I can write for the LED, but don't know how to write for the LCD and how to combine the two programs.


texts: What is this chip? Labeled "Atmel MC3G-04KI78-5"

texts: I am unable to find any detail nor a datasheet about this component... Any idea? Cheers


texts: How to remove turn on ringing/overshoot in MOSFET output for 1 MHz and 70V Switching?

texts:
I have to make a pulse generator square wave for ultrasonic transducer with frequency 1 MHz and 70V for the amplitude, the input is function signal generator with 10V VPP output and 1 MHz. I have made it and it works, but there is a problem. There is always a ringing or overshoot in turn on or rise time but not for the fall. It happens for all frequency, not just in 1 MHz, in 100 KHz for an example, the overshoot is so tight or narrow. this is the circuit that i made

and this is the result of the output

what i have done
1. try to add resistor 1M or 10K in gate of MOSFET, the result : no output signal
2. Add Decoupling capacitor, the result : no effect

UPDATE

how i add up the resistor

So, how to fix the overshoot or the ringing of the output?

Thank you


texts: Charging of Li-ion battery fails after voltage was cut-off

texts:
I designed a charging PCB using this Li-Ion charger IC:
https://datasheet.octopart.com/BQ24072RGTT-Texas-Instruments-datasheet-5404322.pdf

In my tests, the charging works as expected when using unprotected batteries. However, when I try to charge a battery equipped with an undervoltage protection circuit that was discharged to such an extent that the voltage was automatically cut-off at 2.5V, the charging process fails. The charger IC doesn't provide any charging voltage (to be more precise, it provides only a charging voltage of 0.7V). Does anyone know a possible explanation for this?

I used this battery:

https://lygte-info.dk/review/batteries2012/Keeppower%2018650%203120mAh%20P1831R%20(Black)%202017%20UK.html


texts: Can I wire the secondaries of 2 high-voltage transformers in series safely?

texts: I have two 6kV, 30mA Neon Sign Transformers, and I want to get 12kv or higher at 30mA or less. I know you can wire in series to get that effect, but is it safe for the transformers? Obviously, you can put batteries in series without harming them, but can you safely do the same with transformers? By the way, these are AC output.


texts:
I'm trying to get a reading from a Digi-Star load cell.
I'm using the INA122 instrumentation amplifier, the schematic is attached.

Nothing complicated, I connect the cell output directly to the ina122 inputs, and I use a low gain (10K Rg).
Single power supply, 5V, to power the amplifier.

The problem is that at the output I have about the supply voltage.. about 4,8 V.

I used the same schematic as the one in the datasheet..
I don't understand why this behavior.. Any idea?
Thanks

EDIT: problem solved!
I used the same voltage for the amplifier and the load cell, and I added a potentiometer to control Vref. Thanks to Andy for his advices!


texts:
So here is the deal, for the 2nd time in less than a year, my halogen bike light on the front has popped due to cold. This is rather bothersome and I can't find any nice inexpensive LED alternatives in my country.

So I set out to do it myself, I have possibly gathered a list of components, but I am somewhat new at building electronics that doesn't just hook up to a pre-made micro controller prototyper.

So I would like to ask you kind people if my current assumptions and hardware list is correct or if I am totally in the woods and if I am, how I should go about doing it instead?

The list:
1*3W 650~700mA Constant Current Regulated LED Driver (8~40V Input),
1*2W 160-180LM LED (Rated voltage: DC 3.0V~3.2V - Rated current: 600~650mA),
1*6.3V 3300uf Aluminum Capacitor

The dynamo is a 10 year old AXA HR Traction, possibly without power control (rated at 6 Volt/3 Watt).

I was thinking I open the housing of my bike light, take out the old stuff, connect the wires to the current regulator, connect it's output to the capacitor (for power at intersections) and then hook up the LED and run it back to the regulator?

Will this actually work?
The numbers seem right to me, but again I have no actual education in electronics.


texts:
I´m having trouble with this circuit. Is it possible to get Q2 --> saturation using the VI voltage?

When VI = 0; the VCE2 = 14.457 V.
By calculations I know that Q1 and Q2 cannot be on saturation at the same time.

Is possible to get Q2 saturated with the VI voltage?


texts:
I must do this task:

Short translate:
Picture presents modified sine signal. I must calculate F(k) using Fourier Series, next draw amplitude spectrum and phase spectrum.

I have 2 problems:

Is this proper way to calculate F(k)? (T-period (2pi/w), w-angular frequency)
Can anyone explain how should look amplitude and phase spectrum?

Thanks for any help/


texts: Can I use a 220v engine to build up a RC car?

texts:
sorry for the noob question, but I'd like to build myself a small RC car. I've found this motor in a blender, which runs at 220v.

Can I power it with a lower voltage? What should I use?

Thanks a lot, I'd appreciate some good help :)


texts: How CRT allows use of ligh-guns or pens etc?

texts:
While reading about CRT on Wikipedia, an information (CRT Allows the use of light guns/pens;  https://en.wikipedia.org/wiki/Cathode_ray_tube#Advantages_and_disadvantages) suddenly triggered a a vast lots of memories.

Around early 1990's when I was a toddler,  in a local "mela" or fair each year, there was a stall for video games .

They had several big boxes (maybe CPUs), several tiny to large sized, portable monochrome televisions with a mesh of cables.  They provided any 1 of  2 kinds of input devices, 1. a game-control with arrow-keys & fire-key etc; as-well, 2. a toy Gun-shaped device.

(The above diagram drawn completely based-upon memory.)

In the game, to destroy the enemy (a rocket, or an octopus, or a ghost etc), the tip of the toy-gun were almost-touched on that object on screen, and on pressing the trigger, the selected rocket were destroyed.

It was, specifically surprising to the kids, because that was a pre-touchscreen era. The television set, acted quite like a touchscreen.

Now I want to know, how that systems  worked?

Which-one is acting as the sensor (of the particular place where the rocket was fired)? the toy-gun or the CRT? What is the mechanism to identify a particular spatial-position (of target-object such as rocket) out of many-other objects (other rockets)?


texts: How fast can a Li-Ion battery be charged?

texts:
So far I've seen many Li-Ion battery chargers that do the full charge in about 1,5 hours or more. There're also NiMH battery chargers that claim they charge a NiMH battery in 15 minutes and then the manufacturer follows to say that it reduces the battery lifetime compared to recommended 6-hours charging.

What's the limit to how fast a Li-Ion battery can be charged? Will the fastest charge affect its lifetime?


texts: + and - meaning in Tx+ and Tx- in cable pairs?

texts: Tx and Rx are required in Computer networking, used in Cat5 or Cat5e or Cat6 cable? What does +(plus) and -(minus) sign mean in cable pairs for  RJ45


texts: What's the name of the thing that creates electricity if you add hot things to one side and cool to the other?


texts: This question involves finding the transfer function for the system, but I first need to get the differential equations correct. Have I set up the gearbox correctly?


texts:
Using a 32MHz pic processor, and over sampling the demodulated analog output of an RF receiver (instead of the data slicer output) is it possible to use averaging to reduce increase the SNR of the system? The data is NRZ OOK at 4.5kHz.

Update
I found this article from Chipcon on the subject, but it addresses Manchester encoding, though somewhat applicable to NRZ.


texts: Time Reversal of a signal and convolution sum

texts:
Why do we often time reverse the impulse response of a signal while performing convolution sum?It can be done even without time reversing the impulse response.

By time reversing the impulse response how does it really helps us,what are the advantages of it?


texts: What is the proper way to preserve solder iron tips?

texts: My question is should you turn off a solder iron to preserve tip when not in use. I am currently working on a project which requires sometimes a lot of soldering and sometimes occasional soldering to reroute wires or just tin wires to use as jumper cables. I work 8 to 12 hours a day and most of the time I am programming but sometimes I need to change things on hardware when I solder. So when I am programming should I turn off the soldering station or should I just leave it on or should I minimize the tempreture to preserve the solder tip?


texts: Can an eight ohm speaker produce ultrasonic sound?

texts: I am currently making an ultrasonic dog repellent circuit using a 555 in astable configuration generating a frequency of 30khz. Most circuits that I saw use a piezo buffer. I was thinking that since a speaker connected to computer can generate ultrasound, why not  connect the same to a 555 output. Would my speaker burn out?


texts:
I'm designing a gate driver for my SiC MOSFET SCT3160KL using gate driver UCC21732-Q1 from TI. I am using overcurrent protection, active Miller clamping, UVLO and also overvoltage protection by using a TVS diode between the Gate and Source of the switch.
I'd like to know if there is some rule governing the need of more levels of overcurrent protection. Like, say I want to add cycle-by-cycle overcurrent protection. From what I read, I understand this is mostly used in buck/boost converters, but I think I can implement it here for overcurrent protection.
My idea is to detect the current by the "AIN" pin of gate driver, but I'm not sure how to add the cycle-by-cycle part with counters etc. Any views pointing me in the right direction are appreciated.


texts: Out-of-band communication between two PCs

texts:
I'm working on a little project.  In the project, data must be sent from a PC to another device.  Initially, I used a Raspberry Pi and life was good. I could communicate Python between the RPi and the PC via a USB to serial interface as the RPi has serial I/O pins. Eventually, my application out-grew the RPi and I needed more processing power. I am considering moving up to something like a NUC (chromebox).

I really DON'T want to use typical TCP/IP comms, I'd like to use something like a serial connection.  Something like USB-A to USB-A would be great but from what little reading I've done, that doesn't seem to work. If you had to use something other than a NIC to talk between two computers, what would you use?


texts: What type of transistor would be required?

texts:
I am trying to turn on a 12V LED, whenever power is applied to a 3.5V LED.
I want to use a switch transistor instead of a relay.
With the relay, 3.5V+/- on the switch activates 12V passthru; what switch transistor
could I use to achieve this?

Great with old school (relay) but need the help of the pros here to use a transistor
instead.
Not sure that this will work, but I'm assuming it can. Any help or advice would be
a great help.

The 12v LED uses 20mA (.24w ~ 1/4Watt) of power to run thru the transistor. Be a Newbie in the transistor world, what am I requiring for a transistor. Can 2 different voltages run thru a transistor, the same way it would with a solid state relay?

I was trying to light the 12v LED on a circuit that has an LED on it. When I connected it, I was extremely dim. Upon metering the circuit, I realized it was 3.5V. I have to run this 12v LED, so I'm trying to do this with a relay style of switch. I want to use a transistor, because I have been reading it's quicker switching and doesn't use much of the 3.5 draw to remain open, which the relay would do.

Help! not sure what to use or how to arrange this with a transistor.


texts: How to detect pinout of trackpoint (probably ps/2) module?

texts:
I have following trackpoint module of recent thinkpad x390.
There are some info about older modules, most useful(combined) one is: https://deskthority.net/wiki/TrackPoint_Hardware
However, i found no info about this trackpoint module (which seems  most of newer thinkpads use).

IC has label "33306B 3900 1851 BG18CK2" (no datasheet on internet)
On the backside: pcb has label "PSG8E8-Rev.2 AD19021218" (no results on google)

Current findings:

I'm only guessing 2nd pin of 8pin FPC connector is the GND. I have no idea what are the others.


texts: Looking for feedback on my microcontroller-controlled boost converter

texts:
Title is pretty self-explanatory. Here's a boost converter I've layed out:

Instead of being driven by a chip, to save cost, I'm driving it from a micro. This micro has nearly no other tasks (some basic button checking), and runs on a 48MHz clock. So I think having a 1MHz PWM channel controlling this isn't too far fetched.

Was just looking for some feedback, particularly:

I've spec'd a BJT instead of a FET as the switch. I did this because the BJT will definitely turn on, whereas I'm not sure even small FETs will even turn hard-on @ 3V gate voltage for high-currents. Is this okay? I rarely ever use BJTs in a design unless it's an FPGA, so I'm a little hesitant.
I think I'll add a zener in parallel to C15 in the feedback path, to ensure protect the micro. It has internal ones obviously but these are just for ESD, extra never hurts in case the thing fails and the voltage goes higher than expected. I've also put in a pretty hefty (100n) feed-forward cap, since the load is a motor and could have some pretty sharp load changes. Any other parts worth adding?
The supply is for 12V @ 200mA, input is 4V. Do you think my cap and inductor values are within reason? Obviously I'm starting with pretty boring 10u/10u ballparks, but who knows - I could need heaps more, or heaps less with my demands. I've never found "consistent" or "standard" equations for determining the required capacitance or inductance of power supply designs, so I always just base off reference designs.
Depending on EMC performance, I'm thinking its worth a ferrite bead on the output and a capacitor to ground after R7 to smooth the PWM edges coming out of the micro
Any other comments? It just seems very...lacking. Obviously the firmware required compensates for the lack of hardware but. I have veraboarded it and it worked fine, but this doesn't guarantee performance over a long time.

Thanks. Appreciate your comments.


texts: Can a case act as a shorted turn for a coil?

texts:
If you put a bolt through the middle of a toroid power transformer, then attach a metal strip back to the chassis, you create a "shorted turn" which does all sorts of nasty things. Shorted turns can be spectacular on power supplies, but are also bad for signal transformers.

Question: What about the "metal can" found around IF coils? Is there an "air gap" I can't see? Do ALL metal cases, RF shields, etc act as shorted turns?

I want to put a ferrite core AM radio coil in a metal cylinder [cigar tubes, or flashlight cases] as a portable crystal radio. The actual "antenna" wire will dangle outside, of course. Should I add an air gap, by adding a groove down the side of the cylinder [and re-filling with epoxy]?