texts:
As I understand it, a 32-bit barrel shifter takes about five thousand transistors.

Suppose you built a shifter that is like a barrel shifter in providing an answer instantly without iteration, but only allows shifts in 8-bit increments. How much cheaper with that be in transistor count, gate delays, power consumption? Would it be dramatically cheaper, or just slightly?

(And, what's the right name for that kind of shifter?)


texts: Is this diagram wrong as the congruent circuit?

texts:
Given the below diagram.

The 2 identities are given.
$$
V_{1}=AV_{2}+BI_{2}
$$
$$
I_{1}=CV_{2}+DI_{2}
$$
$$
A,B,C,D~\text{are constant coefficients.}
$$
As \$V_{2}=0~\$
\$V_{1}=BI_{2}\$
\$I_{1}=DI_{2}\$
the above circuit is congruent with the below diagram.

Hence,
\$V_1=r_3I_2\$
\$V_1=r_1(I_1-I_2)\$
These statements are given from the textbook.
The problem for me is that why the pre position of \$r_2\$ was shortened in the second diagram.
I think that as \$V_2=0\$ then any current doesn't flow between the endpoints of \$r_2\$ so this part must be opened,not be shortened.
Is the second diagram incorrect?


texts: triggering a solenoid valve from batteries charged by hydroelectric system

texts:
I'm providing a slow-closing solenoid valve for a hydroelectric system in a village in the Philippines.  I need to have the normally closed valve activated to open when the batteries are drained to a certain level.

The current system (without a solenoid valve) is a mile-long pipe descending from a small pond.  During the operational season, it runs 24/7 and the system for bleeding off the produced energy keeps getting fried.  So we are thinking the solenoid would prevent that problem and decrease wear and tear on the hydro system.

I'm out of my league here and could use some ideas asap.  Thanks.


texts: Connecting power supply to fan? Does it work?

texts:
I'm all new to electronics and I was wondering whether or not this work.

That one, as you can see it has a black + red cable, can I connect it to this Brushless DC Cooling Blower Fan 12V 50mm x 40 mmx10mm 4010 2 pin Wire?

And as you see in the 2nd picture, it has a white thing on the cables, can I cut that off and connect all the cables together and then, would the fan start working?


texts: Alternate uses for Gate Driver - Driving a Load without External IGBT or FET

texts:
What issues would one encounter by using a gate driver IC to directly drive a load instead of using it to drive transistors?

For consideration would be the very affordable Infineon 2EDN752x series dual low-side gate driver capable of 5A source and sink. The load would be inductive -  a Wurth 732-2909-ND flyback transformer stepping the voltage up from 12v to about 140-180v. The transformer will be driven at a frequency range between 20kHz and 80kHz and a 25% duty cycle of 1s (250ms on 750ms off). Current draw will average less than 300mA.

What would be the issues of utilizing such a device as a full-bridge "in-and-of-itself" by connecting the outputs in series with the load and adding appropriate external protection such as flyback diodes?

This is specific to the Infineon 2EDN752x series of gate drivers, but it can just be considered as a starting point for this discussion. Click here for the datasheet.

The transformer is a Wurth Electronics 750845240 - Click here for the datasheet.


texts: Missing low frequency tones from bluetooth audio output

texts:
Currently I'm working on a project which uses a bluetooth module (Bluegiga WT32i) to get audiostreams from my iphone to a 3.5mm stereo jack input for a car AUX input.

The problem now is that I have very little experience in analog circuitry and ran into some problems when playing songs with quite some low frequency bass tones. All the low bass tones are somehow filtered out of the output.

I used the exact circuit from the dev-kit from the bluetooth module.
Basic simulation in LT spice shows a clear filter behaviour on both low and high frequencies 40hz and 20KHz.

Is the filter output required at the output of the bluetooth module, or can I adjust the circuitry to prevent the low tone signals from being filtered out?

I just measured the output of the bluetooth module when playing a frequency test stream which goes from 20Hz to 20Khz.

I matched the output amplitude to the same gain of the smartphone direct output (±750mVpp) The bluetooth module puts out a audio stream based on the AAC codec.

Both directly from the iphone as from the bluetooth module the complete frequency response is clearly measured by the scope.

Now the complete frequency band comes out of the bluetooth module with the same amplitude I am not sure why the low tones are missing.

Has anyone an idea where to look next to find the cause of the missing low frequency tone when playing music?

I measured at the end of the audio cable to make sure I measured with all the potential connector and cable losses.

EDIT:

Further testing shows some additional results:
when a laptop is connected to the bluetooth module the audio is like described above, missing the low frequencies.

if I disable either the left or the right channel in the windows audio properties the other channel together with the LOW frequencies is active! I still measure the same amplitude at the output. this effect happens for both the left and right channel.

When I now play a test tune of 40Hz it is not at the output when both channels are active and decreasing one of the channels enables the low frequencies more and more. that's right both the left and right channel are out of phase by 180 degrees! (I should have seen that earlier in the scope view!)

Which means of course the lower frequencies are resulting in no output at all.

Question now is how is it possible that both channels are exactly 180 degrees out of phase?


texts: Can I use I2C bus or GPIOs as I2C to connect I2C devices?

texts:
This question is regarding use of I2C Bus/GPIOs as I2C.

My application processor has three I2C controllers. Is it preferable to connect all I2C devices (obviously we can not connect more than 128 devices on I2C) on these buses?

Or, is it preferable to use GPIOs as I2C? (My application processor also has GPIO lines which I can use for I2C purposes.)

When is it preferable to use I2C controllers and when it is preferable to use GPIO lines for I2C interfacing?


texts: Analysis of the effect a opposing voltage source has to a buck-converter's output?

texts:
I have two voltage sources Vps and V1 connected in series:

simulate this circuit – Schematic created using CircuitLab

There is also Load(1) connected which I believe is in series as well, and there is another load(2) that would require a a higher current and lower voltage(less than Vi which I believe is V1 + Vps), hence the use of a buck-converter. What would change if I've introduced another voltage source opposing the output voltage like so:

simulate this circuit

V2 is opposing the output voltage (Vo < V2 < Vi) and reducing the output current(Io), how would V2 affect the output and input variables(Vi,Ii & Vo,Io)?

I could not analyze this circuit, and think of the net voltage to load(2), or how the input voltages would be effected(Vps&V1).


texts: How to increase voltage of induction detector

texts: I've built a project from the design here, however the voltage is far too low to light the LED. Using a multimeter, I've measured only up to 0.33 volts across the LED and only while my phone was charging on a Qi charger. How can I either increase the voltage or find a low-voltage LED?


texts: Charging a USB device with ac connection

texts: I have a device that charges via a USB connection. Can you also connect that USB cord to AC adapter and charge it safely?


texts: Fixing a transformer inside a metal case

texts:
I want to fix this transformer inside the case you see in the picture.
It doesn't matter if it lands on the bottom, walls or the ceiling of the case, I just want to learn how to fix an element like this on a plain metal shell.
What mechanical methods and strategies do I have to follow?


texts: Power Kinect from laptop (or another mobile power source)

texts:
First of all, I'm passionate about electronics, but that's just like a football fan saying he's passionate about the sport but can't actually play. I'm a programmer, so since I'm on the tech side I can get pretty ambitious, but I do need your help.

I have the Kinect with the crazy proprietary cable and no adapter. I can hack it or just buy the adapter from Microsoft to use it with my laptop, but I want to be able to use it without keeping the Kinect plugged in a socket in wall.

The Kinect needs 12v, 2A. Some people reported it should work with 1.5A as well. I found this question that should sort out the voltage problem, but there's no way I can get 1.5A, is it? Get 12 volt power supply from Dell Laptop

Ideally I'd like to be able to power the Kinect from the laptop (I realize that would drain the battery very quickly) but alternatives are welcomed. I suppose a battery pack would do as well, but it would be great if I could avoid paying $40 for one...

How do you think these guys pulled it off? http://www.kinecthacks.com/navi-%E2%80%93-a-kinect-powered-vision-aid/

Thanks,
Claudiu


texts: Identifying the "Preset" Component in this 555 Monostable Timer PCB

texts:
I have a PCB for a 555 monostable timer circuit as shown below:

For the most part, the components are clearly labeled (I think the round circle with a + inside denotes a capacitor, but please correct me if I'm wrong).  The only component I can't quite identify is the one called "Preset"...

It has 3 pins, one on top and two on the bottom.  The top pin is connected to R1 and eventually connects to the VCC and Reset pins on the 555 timer as well as the positive voltage source.  The bottom left pin of the so called "Preset" component connects to the Discharge pin of the 555 timer.  The bottom right pin of the "preset" component does not seem to connect to anything at all, so it surprises me that it's even there to begin with....

What should this "Preset" component be and what is it's role in the circuit?  How does its value affect the behavior of the timer circuit?

UPDATE

Here is a look at the backside of the PCB.  I flipped the image horizontally so that the left side of the image of the back PCB aligns with the left side of the image above.  Hopefully, this will help to identify how the circuit is layed out:


texts: Ultra low noise power supply for pre-amp

texts:
I have designed the following power supply smoothing circuit for my turn table preamp. This will be powered by a 24V 'wall-wart' type adapter.

I tried to combine a transistor/zenner diode voltage regulator with a capacitance multiplier, the 0.1uf caps are for RF suppression.

As far as I can tell this works really well, but I'm not quite sure how well it will work in real life.
My question is will this work well for ripple/noise rejection?
What improvements can I make here?
'pwr_out' directly powers the collector resistors of the amplifying transistors at only about 2mA total draw (per channel) as its only driveing an amplifier with a 47k input impedance.

My full circuit:

Thankyou.


texts: Wondering if this could be simplified even further. Feels like I can do more with the 1000 ohm and the 2000 ohm resistors on the righthand side.


texts:
First of all, I can control Arduino from iPhone by using Processing and TouchOSC app.

But my task is to achieve a control wirelessly "without using a PC" in between. I need to control Arduino directly by iPhone via "wifi". I should only use an Arduino, a shield, an iPhone and the wifi network. This is the task i am given.

I am really confused which way to use and which shield to buy.

I would be so glad to have your opinions.

Regards,


texts: Effect of load resistance on inductor current for a boost converter?

texts: Is it the same as buck converter? when a  decrease in load resistance , more current will flow through the inductor


texts:
Today I was burning bootloaders on a fresh batch of four ATmega328-PU (the slightly cheaper non-picopower version, not to be confused with the ATmega328P-PU), and was surprised with the following message from avrdude:

avrdude: Device signature = 0x1e950F
avrdude: Expected signature for ATMEGA328 is 1E 95 14
Double check chip, or use -F to override this check.

Then I changed the chip type on my Arduino IDE to ATmega328P-PU and avrdude burned the bootloader without complaints.

So, my question is threefold:

1) Is this MCU just a mislabelled ATmega328P-PU?

2) How rare this event is (i.e., getting a mislabelled MCU from the factory)?

3) How can I be sure the chip is really an ATmega328P-PU?


texts:
total newbie here.
I was reading this post:
http://dduino.blogspot.com/2012/02/trigger-buttons-with-arduino.html

It is basically trying to trigger a button in an IC from an arduino(green) pin.

I understand how the second method works, it just bypasses the button from one side to the other using the transistor as a switch, although not sure what the resistor is for.
I am not sure if I understand how the first method works. I understand that the action gets triggered when the IC pin is connected to GND.

Now, I think that the arduino pin is connecting the diode to a pin as an Output Low( 0V? GND?) and that triggers the IC pin to GND so that the action gets taken.
To switch it off it sets the arduino pin to Input and it just works? How?

Will this work if the IC and the arduino are connected to different power sources?


texts: What FET can I substitute for PF5102 or J305?

texts:
I want to build this microphone: https://www.instructables.com/id/Modify-a-cheap-LDC-Condenser-microphone
I am able to find all of the parts except for the FET. The schematic says to use PF5102, and the text of the instructable says that the author used J305. Neither of which are stocked by digikey, and from what I can tell they are not manufactured anymore.
I'm considering using J113, but I don't know enough about FETs to be confident that it would be a good substitute.
Here are the relevant datasheets:
https://www.onsemi.com/pub/Collateral/PF5102-D.pdf
https://www.onsemi.com/pub/Collateral/MMBFJ305-D.pdf
https://www.onsemi.com/pub/Collateral/MMBFJ113-D.PDF


texts: How to preview the full content of a PcbLib on Altium?

texts:
I have a PcbLib that includes hundreds of footprints with 3D models and I would like to create a gallery including the 3D isometric view and the name of the footprint.
Is this possible?
Why do I want this? I made this library 10 years ago and I totally forgot what it contains.


texts: Will the relay break if the disconnected end voltage is too high

texts:
I'm trying to create a simple overvoltage protection circuit.
In brief, there are times when my mains voltage goes well over 250V (normally 220) and I want to switch off the whole thing connected to this circuit.
Mains goes to the Common contact and the load to NC contact.

I currently have this relay.

Question: I'm not quite sure what the rated contact voltage means (on connected end or disconnected end or just when switching or all), but if the mains goes to something like 300V will the relay break?
The relay will only be switching if the mains is around 250V and if it rises to 300V it will just stay disconnected, but I'm the sure if this is allowable


texts: Difference between UART and USART and the essense of oversampling on STM32F4

texts:
USART is an asynchronous transmission whereas UART isn't (unless there's more to it).
As shown in the photo below, USART being synchronous doesn't need start and end bits since clock is used to sync the data, whereas, in UART, you do need start and stop bits; for rx and tx to talk, they need to be on the same baud rate so when the tx sends out a start bit, rx receives it right away, yeah?

But in STM32F4, I see they use the term USART but the implementation does seem to have a clock. Is there any specific reason? what am I missing?

Also, is oversampling at the RX mainly done to detect errors? I see it samples 3 bits in the center, and if all of them are the same, there's no error otherwise there is. And you can select the oversampling (8,16) based on your baud rate I guess. What about parity check then?


texts: What do all of these symbols mean on an old power factor meter?

texts: "cos. phi" is OK, it's a power factor meter. Apart from that; from the top left, I understand "Klasse 1,5" to mean max. 1.5% measurement error, 5A to mean maximum 5A I guess. On the right, I understand 110V to mean expected voltage 110VAC. Can anyone help with the rest?


texts: Counteracting pull up resistors in a MAX15162 to prevent turn on until the system stabilizes

texts:
I am planning to use the new MAX15162 smart circuit breaker / eFuse to turn on and off a circuit and protect from short circuit / over current. Problem is I failed to notice that the enable pins have internal pullup resistors which means that it will immediately turn on when the system is turned on rather than waiting for an enable pull up from the system MCU.
My idea was to use a pull down resistor to counter and effectively sink the internal pullups which can then be overcome by the MCU.
I can't see why this wouldn't work but was hoping for some perspective as I am new at this.
A little more about the system, it is a midpoint device that can provide 24v or 48v on two different rails and the 24v or 48v could come up before the MCU 3.3v signal in some situations so I don't want both of the IC's to turn on both of their outputs at the same time.
R20,R21,R26, and R27 are the resistors that I am proposing and I guess don't know for sure how to calculate.

https://www.maximintegrated.com/en/products/power/protection-control/protection-ics/MAX15162.html


texts: Is it possible to get a Raspberry Pi zero to wake a computer over a USB connection?

texts:
I would like to wake up my desktop computer (Mac or PC) from sleeping using a Raspberry Pi Zero.

Is it possible to get the Zero to wake a computer over a USB connection? I can wake my Mac up using the mouse or keyboard so it seems possible that if I could configure it to send the same signals then I could.

I have read that one can turn the Pi into a 'USB gadget' - this may be the right approach or unnecessary.


texts:
I have a question understanding the exact commutation of the sensorless BLDC motors.
My motor has 7 pole pairs. Let us assume that the 3 phases are $U,V and W$ ( so that's \$U+,U-,V+,V-,W+\$ and \$W-\$ from the MOSFETS). Now, the back EMF (BEMF) of the floating phase, is the indicator to be measured. Now, the BLDC motor datasheet states \$1000 \;RP/V\$. So, as I increase the voltage the rotation speed increases. This voltage is increased via the PWM duty cycle. Now, if the PWM duty cycle is increased, we also increase the current through the motor, thereby increasing the thrust. So, if we want the speed to remain at, say \$3000 \; rpm\$, and increase the thrust from, say \$400\;g\$ to \$500\;g\$, we increase the current through the motor. We do this by increasing the PWM duty cycle. But, this means the speed will also increase from \$3000\;rpm\$ to a higher value, right? How can the speed be maintained while increasing the thrust?
Next, I was operating my BLDC in a stepper motor like action. The disadvantages being that, it loses thrust as I am not firing my MOSFETs at the right interval. Now, I was studying the BEMF waveform for this stepper motor action in the BLDC. The BEMF is measured in the floating phase of the motor. For example, say \$U\$ and \$V\$ are supplied and \$W\$ is floating. The duty cycle is \$40%\$. I observed the following points in this stepper motor action.

The BEMF (at the bottom part of the PWM) on the floating phase shows a distinct sine wave action.
This sine wave keeps repeating (almost 3 complete cycles) with 3 peaks and 3 valleys.
The speed is directly proportional to the amplitude of the BEMF. So, from point 2 I understand that the speed keeps rising and falling.
After a series of rises and falls the control goes into the next state.

In the 1st cycle, when the speed is max (highest amplitude of BEMF), will commutation to next state ensure no loss in speed? I think that would be fine.
Regarding thrust. I need the thrust to be constant. Would proper commutation as stated in point 1 above ensure smooth thrust?
For greater thrust, I increase the PWM duty cycle. This will increase the speed and hence give me a higher amplitude BEMF. In my code via the ADC, I measure this amplitude and then commutate to next state at the highest ADC value. This will increase speed as the slope and amplitude will be greater with increased PWM duty cycle.

Have I understood the points correctly and am I on the right track please?


texts: NPN transistor energy drain from base to emitter?

texts:
I have the following example circuit:

I do not understand why this lights the LED. For my main project I am building a circuit that has a button connected to an output as well as the collector of the transistor as shown in the diagram. The circuit works as expected when I put the LED on the collector instead of the emitter, but this solution will not work for my overall setup. Even a 1M Ohm resistor allows current through. Am I just using transistors wrong?


texts:
Hello I have been working on this for many months, many parts, circuits, etc. I dont know if its even possible. I have a 24V A/C source lighting fixture that uses two SCRs in anti-parallel for dimming. Im trying to use this phase angle (and power/current) to drive a LED either directly or with PWM with the same amount of brightness, so the LED replaces the incandescent. The original fixture lamp was 24V/250Watt Halogen so there should be plenty of power for LED, however the LED I want is 100W, 30-35V, 3A constant current driven, so i'm concerned how to get 30V minimum if phase angle is very small.
I tried single diode, works but flickers at 60Hz, dimming is nonlinear due to the power requirements of all LED's.
I hired electrical engineer from Fiverr who built this circuit

After many back and forth with parts, It finally arrived and didn't work at all.. Changed Resistor R3 to 1K and it began to kind of work. I believe this circuit is supposed to rectify, smooth, and regulate a DC output and somehow a 555 timer is in there to generate PWM.. But instead U4 heats up to 126C, max output to LED is 27VDC, low dimming flickers (but almost seems to work) as the LED does light up, just with reduced voltage, flickering thats worse with lower duty cycle.
Any ideas how I can fix this circuit, or use the parts to make a simpler one? The end goal being not using an external power supply as im hoping to get enough juice from the lamp output.
For your info I also include the source dimmer circuit from 25 year old fixture.


texts: can we use supercapacitor in filter circuits?

texts:
Supercapacitors combine the advantages of a battery and a capacitor, i.e., faster charging, slower discharging.

We also know that however good a filter circuit is, there remains a ripple when converting an a.c voltage to d.c.

So my question is, can we use supercapacitor instead of capacitors, to minimize, or even diminish the ripple factor, and obtain a superior DC voltage?


texts: why fork- join is not supported in ISE Webpack?

texts:
I am using the newest version of Xilinx ISE Webpack(v14.7). every time I try to use fork-join statement ( in Verilog ), I receive this error:

ERROR:Xst:850 : Unsupported Fork Statement.

Is this block type unsupported in Webpack or I am missing something?  Here is a very simple example:


texts:
I wanted to buy an opamp for experimentation. I ended up with LM324. I searched the web and they come in different packages.

For example, take a look in these two pictures.

(source)

(source)

What's their difference? The one is through hole and the other SMD?

Now with more search I came up with so many different terms. DIP, SOP, SMD...

When you want to take your project from the breadboard to PCB, what do you use? What is what and which is which?

Is there a tutorial for reference for all the different parts, when to use each, advantages/disadvantages etc.?


texts:
I am working on a module (based on ATTiny) that will be plugged and unplugged onto a MCU systems. This MCU system powers up the ATtiny module and when this module is removed, the MCU system has to notified.
I though of tying the power from the module to the MCU so that a removal provoked a falling edge but I am not sure that would work.
Another option would be using a switch but I think I'll face problems when the gate is floating (the device remains closed)
A relay/optocoupler drains too much current and the only reliable solution I come up with is using an RC network.
Which one of these do you think it could work best?
Thanks


texts:
My inverter 12 to 220 v  3000w
Should drive my deepwell pump 700w condensator 13 mf
2 x120ah Batteries are full and loading
Pump motor works  properly on the 220v 50hrz from the net, but with the invertor ,motor does not rotate smoothly at all.
Someone suggested a low pass filter .( What is that)?
What is happening ?and how can i resolve this problem.?
Willem.


texts: Calculation of base current and what decides the current through collector-emitter branch

texts:
I have the below circuit. Its not a homework material. I am understanding how to analyze the transistor circuits.

Below are my questions while trying to analyze :

If I am given the below circuit, how to determine whether the transistor is operating in active/saturation/cut off region?
How is the base current determined in the below circuit when there is not base resistor given? The voltage at the base is calculated to be 1.4V. But how is base current calculated?
What determines the current through the collector-emitter branch? Is is the emitter resistor or collector resistor?

To determine the current through the collector-emitter branch, we need to find the region of operation of the transistor, right?
How to find Ib and Ic?

Can someone help.


texts: Lattice iCECube2 cannot find clock in .sdc file

texts:
I've tried a zillion different ways to get the lattice iCECube2 tools to find a generated clock.
How do I specify the .sdc file to see the output of baudgeninst, which is used as a 115,200 baud clock to the test junk register?  I think this is causing problems later in the design where the tool can't place a not-very-complicated block of logic.  I've removed the larger block from below code.  The code below happens to build, but it still can't find the clock.  When I include the larger block, the code fails at placement.  I suspect not knowing about the baud clock is the reason.
top.sv:
module drotop(input  rstb,
            input  clk,  // board clk
            input  dclk, // dro clk
            input  ddat, // dro in
            output dclkout,
            output ddatout,
            output tx,   // uart out
            input  rx,   // uart in
            output debug,
            output [7:0] dbus,
            output [7:0] led
            );

    logic [7:0] junk;
    logic baudclk;

    baudgen baudgeninst(clk, baudclk);

    always @(posedge baudclk, negedge rstb) begin
        if (!rstb) junk <= 8'h0;
        else if (baudclk) junk <= junk + 1;
    end
endmodule

module baudgen(input clkin, output clkout);
    // From https://www.fpga4fun.com/SerialInterface2.html

    parameter freq = 12_000_000; // 12MHz
    parameter baud = 115200;
    parameter width = 16;
    parameter incr = ((baud<<(width-4))+(freq>>5)) / (freq>>5);

    logic [width:0] acc = 16'b0;
    always @(posedge clkin)
        acc <= acc + incr;

    assign clkout = acc[width];
endmodule

prj.sdc:
# Clocks
create_clock -period 83.333    [ get_ports clk ]  ;## 12.0 MHz

# I've tried various versions of this type of thing with get_pins, get_nets, get_ports,
# identifier names in top level, identifier names between modules, net names inside the
# the module as found in reports, vertical bar '|', slash '/', curly braces, etc.

# Error looks like:
# "c:/lattice/constraints/prj.sdc":11:0:11:0|Clock source [get_nets {baudgen|acc_derived_clock[16]}] not found in netlist: create_generated_clock -source [get_ports clk] -divide_by 104 [get_nets {baudgen|acc_derived_clock[16]}]
create_generated_clock -source [ get_ports clk ] -divide_by 104 [get_nets {baudgen|acc_derived_clock[16]}]
create_generated_clock -source [ get_ports clk ] -divide_by 104 [get_nets {drotop|baudclk}]
create_generated_clock -source [ get_ports clk ] -divide_by 104 [get_pins {baudgen|clkout}]
create_generated_clock -source [ get_ports clk ] -divide_by 104 [get_pins {baudgeninst|clkout}]


texts: How are voltage dividers useful? I can't seem to get enough current for them to be useful

texts:
I must be doing something wrong here, because when I make my simple voltage dividers and do the math, the most current I could draw through my voltage divider would be 33.3mA. Here are my factors:

Vin = 5V

R1 = 100Ω

R2 = 200Ω

Vout = 3.33V

Now, using ohms law, i=v/r, so 3.33/100 = 0.0333, 33.3mA.

Am I doing something wrong here? Thanks :)


texts: What are the units of RSSI, noise and SNR as defined by IEEE 802.11?

texts:
I'm a CS graduate, but to my shame have very limited knowledge of electrical engineering and especially antenna theory.

As far as I understand, RSSI determines quality of how measurer "hears" the object being measured. Noise determines environment conditions that affects measurer. And SNR is simply how much RSSI is better than Noise. This theory (assuming I got the basics right) raises only single question:

How is it even possible for a single fixed measurer to determine both RSSI and Noise?

Now some practice. Let's say measurer is my Macbook Air running builtin Wireless Diagnostic tool. And the object being measured is my WiFi Router. Observed values are −60 dBm for RSSI and −92 dBm for Noise. Therefore SNR is 32 dB. What I completely cannot understand is:

Why both values are negative and measured in dBm?

As far as I understand, −60 dBm means 10−9 W while −92 dBm means 10−12 W. But who radiate that power? Maybe that theory represents Noise as another "antenna"? But why is its value so small then? Or I miss some very key points here? I'll be thankful for an intuitive explanation of this stuff.


texts: How to use 200 mil DIP components on solderless breadboard?

texts: I recently got my hands on some miniature DIP relays, and would like to prototype a circuit with them on a solderless breadboard. Unfortunately, these relays have standard 100 mil pin spacing, but 200 mil between rows, rather than the more usual 300 mil. Obviously I can't just put them in at a right angle... is any adapter available to deal with this? Or any cute tricks?


texts: Altium error: "Could not find closed shape" when creating region from primitives

texts:
I have imported a dxf onto mechanical layers, and want to use this to create the pads for a component footprint.

My approach is to select the whole outline of the would-be-pad on the mechanical layer, use "Tools -> Convert -> Create region from selected primitives", change the region's layer to the top layer, and then place a pad inside the region to assign the designator.

When I click "Tools -> Convert -> Create region from selected primitives" I get the error message:

"Could not find closed shape using primitives centerline due to the following error:
Multiple paths found from location: (-0.15, 0.15)
Would you like to try finding closed shape using primitives external edges instead?"

I have checked the position of (-0.15, 0.15) and it is a point where an arc meets a line. There appears to be no overlap and no duplicates at this point.

I am using Altium Designer v15.1.

Edit: This is what it looks like when I select the area around (-0.15, 0.15).


texts: Calculating the correct BAUD for the ATMEGA168A

texts:
What is the correct way to set the BAUD when programming an ATMEGA168A?

The code below works fine, however I don't know exactly what to do in case I decide to work with a higher BAUD such as 9600:

//CPU clock
#define F_CPU 1000000UL
//Baud
#define BAUD 1200
//Baud rate
#define BAUDRATE ((F_CPU)/(BAUD*16UL)-1)


texts:
I am new to the forum and the EE world so forgive me if technical terminology is a bit off.

I may be thinking about this too much, but what is the procedure for calculating SPI clock speed for a bus that needs to transmit large amounts of data (28Mb/s) in real time? This is for a large number of slave whos' output data rate is 200Hz each.


texts: How do I check the functionality of a 4511 x 7 segment display?

texts:
So this may sound so stupid but I can't find whats the problem. I have created 7 Segment display with BCD and my 4511 Decoder Driver is getting too hot.

I checked if I have short circuited but I have not. I don't have (yet) a voltage tester so I used a LED and after some tests the volt turned out to be as expected. I tried different breadboards but it was still overheating.

How do I check the functionality of the display? What should I check first?


texts:
I am trying to build a circuit which is controlled from an analog input signal Vin to produce a -24V signal with >50mA output. My analog card can only produce ~10mA, therefore I generate the signal using an Op-Amp. I used the analog simulation tool from Microchip (MINDI) and the simulation result differs from my hand calculation.

The circuit represents the standard layout of a inverting amplifier. I removed most of filter capacitors and other resistors from the design guideline.
Building a non-inverting amplifier with the same principle gives the correct results.
Is there a bug in the calculation of the simulation or does my circuit has a significant error?


texts:
I am studying for an exam in my course, and I will certainly have a question of the kind:

In what base is the equation written, for example:

42-3=36

Another example:

(8*5+11)/4=12

I am wondering how to approach this kind of exercises, and how to solve them. I know how to convert from one base to another, but is there a method to solve these equations?


texts:
I am working on a project that needs to convert a high input/output voltage into a TTL signal.
The box I am working with has a parallel port output that was supposed to send out a TTL signal when a button was pressed. Instead the voltage reads 9V before the button is pressed and 14V when you press the button.  The problem is I need the voltage to start at 0V and go up to 5V when the button is pressed.  Is there a simple way to do this?  Thanks for any help.
-M


texts: Silicon Labs USB Debug Adapter and other MCUs

texts: Recently a friend donated a Silicon Labs C8051F devkit to me. It has this USB Debug Adapter. For me this device looks like a JTAG adapter or I'm wrong? Is it possible to debug other MCUs like ARM (Raspberry Pi rev2 specifically) or AVR with this USB device? And if possible which software to use with GNU/Linux or Mac OS X?


texts:
I am new to AVR programming and have tried couple of tests on assembly language and were successful.

However, I would like to try out programming in C with Atmel Studio.

Could somebody tell me where I can find the complete documentation of what is available for C language in Atmel Studio?


texts: Modding an old Sony Ericsson W205a phone to work on car

texts:
Good day, I hope this is the right place to ask this question.

To provide context:
A few days ago I found an old Sony Ericsson W205a Phone, it can be used to speak and receive text-messages, but it's unable to reproduce any sounds unless external speakrs (through headphones/usb/bluetooth) are used. I tried with my car radio (that has bluetooth), and it works perfectly fine with it.

However, I keep on forgetting to turn the cellphone ON every-time I get on the car, making it's presence there kind of useless. Leaving it always ON would be a good solution, but the idea of wasting electricity in something I am not using makes me feel bad.

The question:
I am kind illiterate in what regards electrical engineering (I'm actually a programmer), but is there any way to modify my SEW205a to turn ON when receiving electrical current (coming from the car), and OFF after 10/15 minutes of complete inactivity?
Do you think there is an easy way around this, or is the task is so hard that's beyond my skills?

Thank you.


texts: Interfacing with a truck's internal CAN bus system

texts:
I'm currently exploring different ways by which I can communicate with a truck's internal CAN bus system and would like some advice on the most appropriate solution for me.

I have overviewed the CAN and J1939 protocols used in trucks. I would like to take CAN (J1939) messages from the truck and decode them into human readable data.

I'm thinking of connecting a Linux-based board to the system with a CAN transceiver and a CAN controller then make an application with Python and SocketCAN to decode the data. Can this work be done with a microcontroller only? Without having to use an OS-based system.

I know about the ELM327 for example. What is the difference between the frames that I would get from it and those that I would get directly from a CAN controller (MCP2515 for example) through SocketCAN?

Would programming a PIC microcontroller with the Microchip J1939 library be of any use to me here?


texts: Using LED's to track the sun with ESP32 analog inputs

texts:
I am trying to automate single-axis tracking of the sun for solar panels on my RV. I have a 10mm LED mounted on each side such that if the panel is aimed directly at the sun, both LED's get full sunlight. As the sun moves, one will become shaded. With my multimeter, I get ~0.5VDC shaded and ~2.0VDC in full sunlight. For an Arduino or similar as a controller, this should be perfect.
However, I'm not getting valid values with the LED's connected to the ESP32. Putting an LED in the shade changes my analogRead() value very little. I am getting around 1,600 - 2,000 shaded or not.
const int analogPin36 = 36;
const int analogPin39 = 39;
int analogPin36val = 0;
int analogPin39val = 0;
void setup() {
  Serial.begin(115200);
  delay(1000);

  pinMode(analogPin36,INPUT);
  pinMode(analogPin39,INPUT);
  int res = adcAttachPin(analogPin36);
  res = adcAttachPin(analogPin39);
}

void loop() {
  analogPin36val = analogRead(analogPin36);
  delay(500);
  analogPin39val = analogRead(analogPin39);
  delay(500);
  Serial.print("\t36: " + String(analogPin36val));
  Serial.println("\t39: " + String(analogPin39val));
}

If I connect my multimeter to an LED while it is also connected to the ESP32, I do not get a full voltage reading. This leads me to believe the LEDs are not putting out enough amperage to drive both the meter and the analog input. Additionally, I'm wondering if there is simply not enough power to reliably drive the ESP32 analog inputs.
I could parallel more LEDs or swap the LEDs for tiny solar panels to increase power but I'd rather build an amp that ups the power without increasing voltage above the 3.3 limit of the ESP32.
Two hours later, it's dark outside. To my surprise, I'm still getting readings from the ESP32 so I put the voltmeter on. 0.2vdc. How can this be? I disconnect to check just the LED and 0.0vdc. I connect to the analog port and I get 0.2vdc. I've set the ports as INPUT. So confused... Why do I have any voltage on an analog input port?
I see elsewhere that many recommend using a photoresistor or LDR. This is not an option as they go bad after being in direct sunlight for a while.
UPDATE: Thanks to @Mattman944 I've figured it out. The issue is that the LEDs are not able to drive the ADC. In other words, the input resistance of the ADCs is too low for the LEDs The solution is to add a unity gain buffer between the LED and ADC. I've completed the circuit and bench tested it. Now to get it installed and write the code so it intelligently aims the panels.


texts: When an independent voltage source is expressed as: 50e−tV What does that mean?

texts:
When an independent voltage source is expressed as: \$50e^{-t}V~~\$ What does that mean?

How do you solve this exercise?

If p(t) is expressed as \$p(t) = 2.5e^{-4t}W~~\$ How do I calculate i(t)?
Here's what i've tried, not sure if it's correct.

If t = 250 ms

\[i(t) = \frac{p(t)}{v(t)} = \frac{2.5e^{-4t}W}{50e^{-t}V} = \frac{919.699 mW}{38.940 V} = 23.618 mA (t)\]

So if that's i(t), how do I get just i? divide? \[i = \frac{i(t)}{t} = \frac{23.618~mA~(t)}{250~ms} = 94.472~mA\]

This is how I tried to calculate the charge :
\[q = i·t = 94.472~mA \times 250~ms = 23.618~mC\]

But 23.618 mC does not match the correct answer which is 8.8 mC. So where did I go wrong?

It's very difficult to find a meaningful result when searching for this type of problem on google, because the results are not really related.

This exercise is in page 15 of the textbook, and pages 1 - 15 do not explain what \$50e^{-t}V~~\$ means. In fact page 15 is the first time this notation is used.

If we had an independent voltage source that was 50V, then it should maintain 50V regardless. So if the voltage is expressed this way \$50e^{-t}V~~\$ does that mean it depends on time? Then should it be drawn as a dependant voltage source, with a diamond shape, instead of a circle?


texts: Understanding op-amp circuits with extra capacitors in the feedback path

texts:
When looking at circuits like this one

(source: prohosting.com)
I often find (see U6-A in linked schematic) extra capacitors in the pF range slapped in parallel with the feedback resistors, although the op-amp has a buffering or gain function:

Doesn't that make it a low-pass filter instead? Is it supposed to filter out high frequencies or what other role does it play?


texts: Why not reflow a PCB before placing parts?

texts:
A standard reflow method for low-volume assembly is:

Method A

Apply solder paste (using stencil or syringe)
Hand-place parts (using vacuum pickup pen or tweezers)
Oven reflow

-

But what happens if one does the following instead? Are there any potential disadvantages?:

Method B

Apply solder paste
Oven reflow first time
Hand-place parts
Oven reflow second time

-

I see no disadvantage to Method B, and one rather convenient advantage:

The solder paste will have already solidified during the first reflow, so after that, part placement cannot disturb/smear the solder paste any more; so, it's easier to get a high-quality finished board (fewer solder bridges or missed solder joints). In contrast, Method A demands greater hand precision, especially for fine-pitch ICs, and really gives you only one shot at the part placement.


texts: What are the .NET Micro Framework ready systems available?

texts:
Once I heard of Netduino I began to wonder which other systems would provide the same features:

Processor and Memory Micro .NET Framework ready
USB interface
Cheap
Portable


texts: I'm new to electronics and have a question about oscilloscopes, if I understand this correct when attaching probes, one of the leads of the probe needs to be grounded, my question is why? Can't I use a oscilloscope just as a voltage-meter to measure the potential difference across the two leads ? What would happend if I attached the "ground" lead to something non-ground ?


texts: Is my DIODE in PARALLEL with the Relay (to protect input)

texts:
this is my circuit (the path / "read" is from 1 row to N row):

The GREEN wire (from 17 row) is the DATA from a Raspberry (ANOTHER GREEN wire enter in 11 row - resistor in serie - and is connected to the base of that transistor) that actions the relay.

RED wire is the POSITIVE and BLACK negative/ground (from the Raspberry).

The circuit performs very well. My doubt is: the DIODE is correctly put in PARALLEL with the relay?

I did read that is better put a diode in parallel and not in series at the POSITIVE, to minimize // eliminate his voltage drop...

Thank you to all!


texts: Calculating voltage drop across capacitor

texts: Generally, i have no idea how to solve it. I thought about doing superposition method on every source, but i guess there have to be some method to do it faster.


texts: Is there a type LED with adjustable wavelength? I need a light source with variable wavelength between 400nm and 700nm


texts: Why LM358D and LM358ADT differ in price a lot?

texts: I was trying to find a significant difference between the LM358D and LM358ADT (datasheet). They seem to be pretty much identical, but the price for SO package in Mouser differs in 5x. Could anyone point out to me what I am missing here?


texts:
I am using a Lego DC motor with a 9V battery which can provide up to 1A of current. I called Lego support and they said the motor draws 300mA of current. What does that mean? If I plug the motor to the battery will it use 300mA of current or will it use as much as my battery can provide and damage itself?

I know a motor has an internal resistance that's why I make this question: if is has na internal resistance it can control the amount of current that will consume without any external resistor, right? Am I right?


texts: Help with identifying a PCB header connector

texts:
I have scoured the Internet trying to locate what this is - I'd appreciate any information if someone recognizes this plug/socket combination. It is currently used to carry 5V DC power of about 1A.

The only identification is on the plug. There are two strings of characters on the plug: 5284 and MK136.


texts:
I bought an ExpertPower EXP-1270 12v 7Ah battery, and I want to know how to charge it.
I don't have a battery charger, but I want to do it with my variable power supply.
I had already set it to 13.8v, but after charging for an hour or two the battery had only reached 13.2v. Am I doing something wrong?
I want to use the battery for general purpose where I can charge it, disconnect, and then use it for whatever I need to. When I'm done using it, I will recharge it again.
The battery has several specifications, including two voltages:

Standby voltage 13.7-13.9v

Cycle voltage 14.6-14.8v

Current limit 2.1A

Constant Voltage Charge

12v 7Ah

20HR

How should I charge it?
I'm used to charging lithium batteries that don't take long to charge.
I'm just looking for what voltage and current I should use, and how long to charge for.


texts:
I'm working on a spectrophotometer for a physics project. I've figured out the monochromator already, so for the detector I decided to try a photodiode circuit. This being my first experience with circuitry and arduinos, I put together the following:

I'm using a 10k pot, 22pF ceramic capacitor, UA741 op-amp and OPF432 photodiode.
Not sure if I connected things wrong but when I run a sketch reading pin A0 it just reads as noise (converges to 1.11). Anyone have any ideas?


texts: Recommend how to use .spl files from "CAD Star"

texts:
Hello I am a software engineer with no experience in getting PCBs created. My friend has designed a PCB in CAD Star and we are ready to get it manufactured, however the files are .spl format and I am struggling to find a company that supports .spl files.
How can I output files that PCB makers can use?


texts: Connecting an external switch to my circuit

texts:
I'm pretty new to electronics and kicad.
I would like to understand how to add a physical switch to my circuit using molex connection.

I'm adding my initial schema.


texts: Altera/Intel FPGA Interfacing External Memory

texts:
I am in the process of making a prototype PCB with an Altera Cyclone IV or V FPGA and 2 channels of external memory, one channel for a softcore CPU and one channel for a 2d graphics accelerator. I would like to use DDR1 or DDR2 memory but at this point in the design I can use any form of DRAM, This is just a hobby project; there are no real constraints on the design. If I have to use slower memory, I will just run a lower screen resolution. I have a some questions about interfacing with external memory that I need to have answered before I can finalize my design.

I have looked at a few reference designs to get a feel for what I need to do. These designs use DDR1 and DDR3 memory, the boards didn't seem to have any termination resistors besides the ones on the differential lines. Is this normal if the traces are short and you program the FPGA and memory with the correct drive strengths and the traces are properly impedance matched? Or are they using on chip termination?
As far as I know, DDR1 doesn't have on chip termination, Is it safe to wire it directly to an FPGA without termination resistors as other designs have done?
Are you required to supply a voltage reference to the FPGA Vref pins and the DDR Vref pins or just the DDR Vref pins?
If you are required to supply a voltage reference to the FPGA, how many Vref pins per bank do you need to drive?
When doing my initial routing on a test board, all of my DDR1 traces are close to the same length, Is it ok to just length match them all to the exact same length or is some requirement that doesn't allow that?
If all of this turns out to be too complicated I can fall back to old fashioned SDRAM. I assume that with SDRAM you can just use any I/O pins, not just the dedicated high speed memory interface (DQ/DQS) pins on the FPGA?


texts: Why is MSI and MSI-X enabling at the same time prohibited?

texts: The PCIe spec says that only one of MSI or MSI-X can be enabled.  Else system behavior is undefined.  What is the reason behind this?  What is the problem if both are enabled for a PCIe function?  Thanks.


texts: How do I get Ad and Acm for a BJT differential amplifier?

texts:
In a practise exam question I am given a circuit of a BJT differential amplifier and told to show that these equations are true:

I am told to do it using the hybrid-pi model.

Here is a picture of the circuit:

I know how to replace the transistors with the hybrid-pi model, but am not sure how to analyse the circuit from there.
I've been having a great deal of trouble with this. Could somebody please show me how to get Ad and Acm?

Edit: I've received some responses but am still confused so will update my question to give a clearer picture of what I understand so far.

Here is the circuit I get when I replace the transistors with the hybrid-pi model.

I also understand that in common mode V1 = V2 = Vcm,
and in differential mode V1 = Vd/2 and V2 = -Vd/2

Some of the things confusing me:
When I tried to research problems similar to this on google some websites told me that the output would be Vo = Vo2 - Vo1,
Yet in this question it looks like I'm supposed to just consider one output at a time, choosing either Vo1 or Vo2. I am also confused by Vpos and Vneg - should I be considering them in my calculations or ignoring them?


texts: Using a voltage divider with buried zener voltage reference

texts:
My plan in the below circuit was to use a voltage divider from a Max6225 2.5Vref, to get 2V and 1V from it in order to use the full 16bit bipolar scale of the ADS1115s, but I'm getting strange resistance readings from a DMM across the resistors - can I use a voltage divider with the Vref like this?

EDIT: Apologies for the drawing - not sure how to do the buried zener vref part, so I've marked the connections instead OK.

EDIT 2: Please ignore the test resistor in the bottom picture - this was just to test if the same thing happened however I connected a resistance from Vref out back to ground, rather than a short or something on the board


texts: What design decisions must I make to select a suitable P-Channel MOSFET

texts:
I need a PFET with a logic level gate to trigger a power connection to a hobby servo that pulls more current than my MCU pin can handle.

The requirement is simple but I'm trying to understand how to go about designing the circuit so I can then choose from available devices that meet my need and can eliminate those that don't. At present I can see there are (literally) thousands of MOSFETS that are available and I don't know what is required to choose ones that will meet my requirement.

The reason for the PFET is to kill power to the servo during sleep mode so that I can get longer battery life.  In idle mode the servo pulls 3.58 milliamps and I am trying to use just a single 18650 battery connected to a 5v boost converter to power the project.  In testing, with the servo always pulling current I get about 27 days out of a single battery.  When I remove the servo from the constant current plan and only calculate the current draw when it rotates (50-100 mA), I can get more than a year from a single battery.  Problem is I have no idea what an appropriate PFET is for this project.  I went to this site but the sheer number of choices is staggering.

Can people please advise what I need to do to establish a tighter requirement for the MOSFET I require?

Project components:

5v 16MHz ATmega168 Arduino Pro Mini
5v boost converter (quiescent current 130 microamps) (used to boost the 3.7v LiPo battery to 5v; actually boosts to about 5.27v)
Knock-off Clone Futaba S3003 servo (4.8v - 6v operating range) (idle current 3.58 milliamps; with a normal load (50-100 milliamps)
LDR sensor with 10k resistor
LED with 220K resistor for low battery warning


texts:
I'm using LM386 with my guitar and currently I power it with 9v battery but now I want to switch to 5v power supply because I don't want to use a battery.

I want to use a 5v usb wall charger + sparkfun usb mini-b breakout but it doesn't work, it haves a lot of noise/static.
If I use a 7805 with the 9v battery it works flawlessly.

What's wrong?

Thanks!


texts: PIC does not restart in case of power off and then power on

texts:
I am using PIC18F26K83 and everything works great.

But when I close the power source (no source voltage for PIC) and then I open it again, PIC does not restart.

I do not what does it do but it looks like it continue from where it was when I close the power source. Is it normal? Is not it supposed to be restart from the first line of the main?


texts: Verifying an existing Micro chip RF component range with my calculations

texts:
I'm trying to understand how the microchip RN4871 chip range is calculated. I know the chip Antenna used in this module.

According to its datasheet, RN4871 has a range of 10m. So my calculations should yield this result. Else
I did something wrong.

I put all the parameters in a range calculator I found online (link below) and the result doesn't match up.

https://www.rfwireless-world.com/calculators/Antenna-Range-Calculator.html

Transmit Antenna gain = 0.45 dB mean effective gain(Antenna Datasheet fig 5), also tried 0.1 dB (RN4871 datasheet fig8-2)
https://www.digikey.com/product-detail/en/yageo/ANT3216LL00R2400A/311-4590-1-ND/9360410

Transmit power = 0 dBm (RN4071 data sheet) https://www.digikey.com/product-detail/en/microchip-technology/RN4871-V-RM118/RN4871-V-RM118-ND/6130476

Operating frequency = 2.45GHz

cable loss = -27.3 dB (Antenna datasheet at 2.45 Hz, figure 4)

Receiver sensitivity = -70

I get a range of 815 m which is not the case (it's 10 m).

But if I change the cable loss to an acceptable estimate of 10 dB, then I get the correct range of 10.26 m. Is the Antenna return loss graph (Fig 4) incorrect? Or did I understand it wrong

which is more likely. Can you please explain?

Also, the gain is highest (5.5 dB) in certain directions. So is the range of more than 10 m in those directions? and range 10 m is mean effective range?

Thank you


texts:
What are the general rules of filling / pouring traces? What traces should I pour?

I assume ground is poured most often.
Should I pour other traces? Supply/Signal or something else perhaps?
What are the advantages/disadvantages of pouring?

If specifics are needed then assume an analog low-power audio circuit.


texts: Why are there more than one RF amplifier in a TRF receiver?

texts:
In literature TRF receivers are said to be hard to tune because they have many RF amplifier stages in reception. They all need to be tuned each time for a different broadcast which makes things hard.

My question is why one RF amplifier is not enough in a TRF receiver? I must admit that I don't understand from the short answers like selectivity, interference ect. I would like to picture why is that so? Do TRF receivers have many variable capacitor knobes for each RF amplifier stage? I cannot find any clear explanation in internet.

Note: This question comes from my previous questions' comments. I needed to make this as a separate question.


texts:
I often see schematics of basic buck converters. The majority of these schematics use a P-Mosfet as high side switch.

Why is this design preferred over a low side, N-Mosfet buck converter?

simulate this circuit – Schematic created using CircuitLab

Would this design work?
The load is a 12V Fan, 3.6W
The Mosfet would be driven directly from the microcontroller in PWM, 5V logic, 32 Khz carrier frequency.


texts:
The first Green bit is a thermistor out of a fluke 374 clamp meter, but cant find the manufacture from the logo or what the number means.

The other is a socket pin from a single wire connector, its very close to molex but it only has one retention tab  11mm long barrel, 18.5mm oal, and 2mm pin bore

More images.


texts: What is the difference between narrowband and wideband?

texts:
Im a bit confused between the difference of Narrowband signals and Wideband signals.
Is there a specific value of bandwidth which classifies a signal into Narrowband or Wideband?
What values of bandwidth would be considered as Narrow?


texts: How would I power a circuit and charge its battery simultaneously?

texts:
I have a circuit powered by a rechargeable battery. When a USB cable is plugged in, I want the battery to charge through a separate charging circuit and for the main circuit to be powered through the USB cable and not the battery. I know there are dedicated ICs for this but am curious if it can be done otherwise.
Here's what I have so far. VSUPPLY (below the battery connector) is the voltage input to the main circuit. VBATT+ is connected to VSUPPLY through solid state relay K2 unless VCHARGE (i.e. VUSB) is present, in which case VCHARGE is connected to VSUPPLY instead. VCHARGE is also connected to VBATT+ through solid state relay K1, under normal charging conditions. D2 is to ensure nothing powers the charging circuit when the USB cable is not plugged in.
Does this effectively prevent the battery from powering the main circuit while it's charging?


texts:
First off, I searched for this question and while I found other similar questions, none had an answer for this.

I've got a serial cable from a (Linux) PC supplying data to a PCB (AVR XMEGA). I'm trying to monitor the data sent across this serial cable using a Bitscope.

I've got CHA connected to pin 3 of the serial port DB9 (FWIW, this is a UART-backed serial port, not a USB "serial port")and GND connected to pin 5 of the DB9.

No matter how I change the Bitscope settings, I can't get anything resembling a square wave, whether data is being transmitted across the serial port or not. The attached image is all I can see.

Sorry to be such a n00b, but if anyone can tell me what I'm doing wrong, I'd appreciate it.


texts: Arduino Nano - Multiple 5v Power Sources

texts:
I am planning on building a small device that sits inline for a SNES controller to allow remapping the buttons. My initial idea is to use an Arduino Nano, but I'm a bit unsure about how best to do it.

The console itsself has a 5v line going to the controller. My plan is to use this to power both the controller and the Nano. As far as I can tell, connecting this to the 5v line and backpowering it should be fine, but not ideal. I could also just connect it to the USB 5v port.

However, the plan is also to have input reading capabilities, which requires using USB to connect it to my PC.
I believe this may cause a bit of an issue, since the 5v from the SNES and the 5v from the USB connection could potentially conflict.

Is there any easy way round this?
What I really would need would be a diode on both the SNES 5v line and the USB 5v line, but I don't believe there's a way to do that.


texts: Why single ended signal line is not immune to noise in RS232?

texts:
In single ended signal line the measurement is the difference between the signal and the ground. Isn't this way of calculation make it differential?

Almost all the resource I have read says that noise (unwanted signal contamination) is added only to the signal line (they don't even mention ground line picking up the same noise) because signal wires act as aerials, picking up environmental electrical activity making them sensitive to noise errors. Just like in the differential signaling the ground line here can also pick up the same noise as the signal wire and because the receiver is only looking at the difference it should make it immune to noise. But it doesn't why?


texts: determining sensitivity of carbon monoxide sensor

texts:
i'm working with a alphasense CO-AF sensor & i need to find out the CO quantity in ppm . i referred to the data sheet of the device and i dont know how to convert the given sensitivity
specification to ppm.here is the link to the DATASHEET.can anyone help me out.


texts: How to convert 8-bit information containing MIDI note, to square wave signal using basic chips and components?

texts:
Using basic electronic components (capacitors, transistors, etc) and/or chips (555, 74 series, etc) how do I convert from:

Input: 8-bits containing the binary representation of a MIDI number "m", example: 0b1001000 (72) for the note C5

Output: A square wave with frequency corresponding to that note "f", example: 523Hz for the note C5

I'm intending to build this on a breadboard to connect to a basic computer also on a breadboard.

My initial approach was for the output to come from a 555 chip configured in an astable state, with the input somehow manipulating the capacitance/resistance of the components used with the 555. The part in particular I'm struggling with is the fact that f is proportional to 2^(m/12) and I can't think of a way to combine the input in a non-linear way to get this exponential behaviour.

Edit: Clarification on the nature of the connected computer and the project: I've been following along with Ben Eater's 8-bit breadboard computer series on youtube, so the computing capabalities are very primitive (I can load/store 8-bit values, and add and subtract them).

As an extension of this project, I had the idea to store MIDI value notes in memory, and output them to some module that will create a square wave that makes a peizo/buzzer produce the note. The goal of the project in general is not to "cheat" by using chips that I don't fully understand the inner workings of, so limiting myself to basic chips. In some cases the project uses more complicated chips where the underlying principle is understood but would be laborious to implement (e.g. using a whole chip is a register, when I already understand and know how to build flip-flops; or programming and using a CMOS SRAM chip for the 7-segment decoder etc).


texts: Do AC transformers (particularly the 60 hertz ones) generate an Extremely Low Frequency (ELF) wave at 60 hertz or is it just a plain oscillating magnetic field with no electronic part 90º out of phase like normal RF waves.


texts: The output of the household outlet is AC. But when repairing one of those, I found that there was a LED (used as indicator) in there. Since LED is a diode, it must switch on 60 times and switch off 60 times in a second, since frequency is 60Hz in my region. But I saw that the LED is constantly on. Is the LED really constantly on or is it my inability to see it switching on and off regularly?


texts: Strange amplitude fluctuation in video signal

texts:
I am reading a video signal from a CCD array. For some reason I get this extreme vertical jitter. I use decoupling and bypass caps everywhere possible. But it does not seem to be the noise issue. Any one has an idea of what could be the reason of such jitter? The yellow clock signal is just for reference. Here are superimposed frames of the video:

TRIED:

Different illumination intensities - the fluctuations present in the dark too.
Tried different light sources: flashlight, diode lamp, luminescent lamp, laser.
Tried running the microcontroller with the internal clock (no external oscillator).
Tried running the setup from a 12V battery (no mains).
Tried using electronic switches DG642 and EL7156 instead of direct connection to the microcontroller.
Tried switching/interchanging the probes (as you can see, the TTL signal looks just fine).
The oscilloscope and the power supply seem to be grounded since the power sockets have the third 'ground' pin.
Tried three different kinds of CCD arrays.
Do not seem to have any high power electromagentic devices around me.
When I measure a signal from a waveform generator, no fluctuations are present.
I use bypass and decoupling capacitors everywhere I should.

I am seriously stuck. Please, help!!!

Perkin Elmer RL1024PQ sensor

Vishay DG642 video switch (pin driver)

Intersil EL7156 pin driver


texts: I wanted to see if i could use a BJT to power a small pc fan. I have a potentiometer into the base but how would I wire the fan so that depending on the base current it would adjust the current to the fan?


texts: How would one go about using an arduino mega ADK to emulate a USB hub with a mouse and keyboard attached? I found oodles of information from vusb and this related project, but nothing about emulating a USB hub.


texts: 20 3.2v - 3.8v LEDs in a line on a 12v circuit

texts:
What do I need to know? Such as, how would these be best wired up? And what resistance would I need?

It's for a computer case modification I'm planning on doing in the near future, Will be powered from a single 12v source (Computer Powersupply).


texts: Create a low frequency oscillator with CPLD TTL input and output

texts:
I have 2 available pins on a CPLD which is a 5V TTL device (ATF750C-10PU). The inputs are just regular logic not Schmitt trigger. One pin is an output, while the other is an input.

I would like to have a very simple external circuit that makes an oscillator at around 500Hz to drive internal circuitry. The rate is very non critical; it's just to drive a counter and multiplex some LEDs, but I don't want it be higher than 1kHz.

You can make a reliable RC oscillator with inverter but only with a Schmitt trigger input. There's no Schmitt trigger option on the device I'm using. I don't mind if there is an external transistor or other semiconductor devices as long as the external parts are cheap and the component count is low.

I was wondering if I can make some kind of RC oscillator using those two available pins on the CPLD.


texts: Is there a "canonical work" for radio amateurism?

texts: My friends and family have been radio amateurs and I'm not very familiar with radio technology. I know basic mathematical physics but I only know the X25 and the As400 (or what's its name) by name and nothing more. as a computer engineer I have found that there are "canonical works" that are referred to e.g. for computer engineering, for computer science, for hobbyist electronics, so now I wonder if you can tell me about whether there is a good recommendation how to not get started in practice with radio amateurism, but rather how to gain a knowledge about how it works.


texts: What values of components to use in this 30V-2V, 3A(max) current limiting circuit?

texts:
I'm looking for a current limiting circuit for my lab bench PSU, and found this one.

What are the values for the components? Is R_sense the pot?

Thanks in advance!


texts: Is this way of sizing the load correct for this PNP output sensor?

texts:
A proximity sensor has the following specs:

It is PNP output and the specs say 100mA at 30VDC.

Does that mean the resistor/load between the sensor's PNP output and the GND should be more than 30V/100mA = 300 Ohm?

How come 35mA supply is enough if the output can source 100mA?


texts: What is wrong with this LCD backlight boost converter circuit

texts:
I have been working with a dev board with the LCD backlight circuit shown below. The boost converted used is the TPS61041. On page 18 of the datasheet, there is an example of the backlight circuit configuration.

I am trying to drive a NHD-4.3-480272EF-ASXN# 4.3" TFT. The TFT backlight requires 40-50 mA at ~25 volts. To make the circuit compatible, I have replaced R2 with a 27 ohm resistor for ~45 mA regulation. I have also removed DZ1 to prevent it from clipping the output at ~16 V. The TFT backlight still does not power on. I have checked all of the TFT connections and they are correct. I also have the EN pin set high. Where am I doing something wrong?


texts: How much voltage does a green LED need to be supplied? Will it handle 5V?

texts:
I’m supplying 9v through a 5v regulator. This regulator powers five IC quad gates. This is all for a 4 bit ripple carry adder.

With that aside, could I just power the LEDs (which will visualize the 4 Sums and the last Carry) with the 5V, connecting GND to an LED to a Sum output on the IC, for example? I think that's what this guy (Ben Eater) did in this video:

Video

I'm really novice to electronics so this question may sound silly to the more experienced.


texts: Find the Resistance between Two Terminals

texts: Let's say R = 49 ohms, and we want to find Req between a and d, how do we do that? Do we have to find Req for the whole circuit?


texts: Using an op amp as a switch for audio (Dual supply +-12V)

texts:
I'm wondering if the below circuit would be a reliable bipolar analog swtich. I'd like to be able to disable signals from certain circuits and I'd rather not have to bias and normalize the signal in order to use a typical analog switch. What issues might arise and how could they be corrected?  The op amp is a modern rail to rail jfet input device.

Note: cost is of critical concern, I'm trying to keep cost below $2 per complete setup @1000 units, also assume at least a quad channel op amp, need to control all signals at the same time, ie a quad signal from a set of audio inputs and assume another circuit would be used for another set of signals. Signals are line level.

One more edit: voltage input is line level, but I would like the flexibility to go higher if necessary

Edit: The output doesn't need to go high impedance, but it would be better if it did. Assume V_out will be feeding into a resistor of at least 2kOhms before connecting to other parts of the design.


texts: How to design the frequency response of an analog filter when I get the transfer function?

texts:
I am not trying to design a filter. I just want to understand the theory of laplace transform and s-domain.I read an example from the book The Scientist and Engineer's Guide to Digital Signal Processing

I know that I can change the value of the resistor, the capacitor and the inductor . Respectively , I can change the position of the zeros and the poles. So how to design the frequency response from the position of the zeros and the poles?
For example , if I want to design a notch filter with the narrow stop band at Pi/4. How to choose the positions of the zeros and the poles? If the zeros and poles are moving around. How would them affect the frequency response(the fourier transform along the jw axies)?


texts: How does USB Power Delivery work with voltages above 5V without damaging 5V peripherals?

texts:
I have a Qi wireless charging pad for my phone, powered via a micro-usb port. The markings on it indicate that it will accept the typical 5V that nearly every USB port provides, or it will accept 9V for "fast charge".

I was under the impression that USB standards allowed for no more than 5V.
My research shows that USB Power Delivery has several profiles (up to 20V), and Revision 2.0 Version 1.2 includes a 9V profile.

Now I'm wondering: How can voltages above the usual 5V be provided without worry of damaging an expensive phone when connecting them directly (no wireless pad)? If things are running at different voltages, wouldn't that cause an issue?

In this example, 9V is used for fast charging, but could that 9V be sent to my phone? Do phones have a safeguard for this? The USB standard allows for up to 20V. That's a lot when expecting only 5V. Some "dumb" devices are powered directly off of USB, like cheap LEDs and fans that have no IC. Surely they would blow upon 20V!

I'm guessing there is data exchanged between the power source and the peripheral, ultimately telling the power source whether or not it's okay to provide more than 5V. Some USB charging cables don't have data pins though, which can allow for faster charging. In this case, it seems that not having data pins would be a restriction. Maybe the power source would have to default to 5V?. Unfortunately I cannot find an explicit protocol/explanation of how the different potentials are managed.


texts: Wiring a switch to a BlueTooth transceiver

texts:
Please note: Because this question is concerned with integrating a BlueTooth chip to a PCB and a remote device, I do believe this is an electronics question at heart.

I have an experimental/hobby project where I want to use a momentary switch like this one to communicate to an app running on either my (Android) Samsung Galaxy as well as my iPhone 7+. Anytime the switch is pushed down, I want my app (regardless of whether its running on my iPhone or my Galaxy) to be notified and react accordingly.

Unless anyone has any better idea, I'm thinking about using BlueTooth for the communication link, because iPhone's have now deprecated the use of 3.5mm audio jacks, and so BlueTooth appears to be the only platform-agnostic way I can send signals from my momentary switch to my app.

So I'm looking for a BlueTooth transceiver that would fit the bill here:

Will likely solder the switch and the BlueTooth transceiver to a PCB and power it externally (battery, not sure what the needs are there yet)
When powered on, I need the BlueTooth chip to start attempting to connect to any other devices (such as my phone) that are listening for a similar connection
Once a connection is made and the app (running on the phone) is listening, then when the switch is being pushed (closed), I want it to fire "a signal" to the BlueTooth transceiver/chip which would in turn then fire "a signal" on to the phone; the app would then respond accordingly

So my question: is there a BlueTooth chip (maybe such as these ones?) that can be integrated with a switch, and be used to scan for -- and connect to -- my phone in keeping with my needs above? Are there any "tricks" to configuring them or getting them to work with Android vs iOS devices?


texts:
I know that SMD components are smaller in size compared to their through-hole equivalents. They enable a designer to reduce overall pcb size.

Is there any other advantage of using SMD over through-hole components ?
By other advantage i mean benifits in parameters like power dissipation, noise immunity, stability etc.


texts: Using magnetics for single board Ethernet routing

texts:
I have two SoCs that are mounted on a the same carrier board using SODIMM connector. The two SoC are mounted very close to each other, the entire carrier board is smaller than 15x15 cm
I need to connect the two computers to each other using cross over Ethernet so they can talk back and forth. Given that I am not using any RJ45 or any sort of cables and the Ethernet pins of SoC-A is being directly connected to the Ethernet Pins of SoC-B using traces on the PCB, do I need to use any magnetics? Can I just directly connect the SODIMM pins to each other ?
Distance between the two SODIMM pins are about 1 or 2 cm


texts: This LDR is said to have Peak voltage rating of 400V in the description. Does this equal the voltage drop, meaning that I need to supply at least 400V or is it the maximum voltage value?


texts:
I am designing a hi end SMPS and I have 1 CMC on the input (ac line) and a second on the DC output.

My question is where to place this  second CMC.

Usually its best to place  filters right at the source of noise. I assume that source of CMN is the secondary output of the transformer . Of course I cannot place it after the transformer , so I am thinking to place it after diode + pi filter and Cout.

Is the above better or I should place it at the cables (DC output) ?


texts: Parasitic noise after boosting opamp output current

texts:
I'm coming back to you with the same circuit again. I "upgraded" my circuit by turning it into a more powerful one (using a more powerful opamp and adding an output current boost with 2 BJTs).

I'm almost satisfied with this circuit (although i should add more protection because it is high voltage now...). Last problem with it is the fact that i see some "parasitic" noise in the current passing through my capacitor "Cact1" (which is not a capacitor in reality, it is a piezoelectric actuator but electrically the same as a capacitor, which is why i need more current in the real circuit).

I see that it happens exactly at the voltage peaks so basically when the current changes direction. This didn't happen when i didn't have the transistors stage wired.
So my guess is that the BJTs are the culprits for this noise and that it happens when the transistors switch in order to make the current change direction. Do you have an idea how this can be fixed ? I really need an almost perfect sine for the current, my application heavily depends on that.


texts: If \$\vec A=3\hat a_r+2\hat a_{\theta}-6\hat a_{\phi}\$, determine the vector component

texts:
If \$\begin{aligned}\\
\vec A=3\hat a_r+2\hat a_{\theta}-6\hat a_{\phi} \text{ and } \vec B=4\hat a_r&+3\hat a_{\phi}\\
\end{aligned}\\\$ determine a)\$\vec A.\vec B\$, b)\$|\vec A\times\vec B|\$, c)The vector component of \$\vec A\$ along \$\hat a_z\$ at \$(1, \pi/3, 5\pi/4)\$
I have calculated a) and b) but I can't understand how to do c). Please anyone give me some hint.


texts: '1011' Overlapping (Moore) Sequence Detector in Verilog

texts:
I'm designing a "1011" overlapping sequence detector, using Moore Model in Verilog .
The FSM that I am  trying to implement is as shown below :-

Verilog Module :-
`timescale 1ns / 1ps

module seq_detector(
input x,clk,reset,
output reg z
);

parameter S0 = 0 , S1 = 1 , S2 = 2 , S3 = 3 , S4 = 4;
reg [1:0] PS,NS ;

    always@(posedge clk or posedge reset)
        begin
            if(reset)
                PS <= S0;
            else
                PS <= NS ;
        end

    always@(PS or x)
        begin

            case(PS)
                S0 : begin
                            z <= 0 ;
                            NS <= x ? S1 : S0 ;
                            $display(PS);
                        end
                S1 : begin
                            z <= 0 ;
                            NS <= x ? S1 : S2 ;
                            $display(PS);
                        end
                S2 : begin
                            z <= 0 ;
                            NS <= x ? S3 : S0 ;
                            $display(PS);
                        end
                S3 : begin
                            z <= 0;
                            NS <= x ? S4 : S2 ;
                            $display(PS);
                        end
                S4 : begin
                            z <= 1;
                            NS <= x ? S1 : S2 ;
                            $display(PS);
                        end

            endcase
        end
endmodule

Testbench :-
`timescale 1ns / 1ps

module testbench;
    // Inputs
    reg x;
    reg clk;
    reg reset;
    // Outputs
    wire z;
    // Instantiate the Unit Under Test (UUT)
    seq_detector uut (
        .x(x),
        .clk(clk),
        .reset(reset),
        .z(z)
    );

initial
    begin
        clk = 1'b0;
        reset = 1'b1;
        #15 reset = 1'b0;
    end

always #5 clk = ~ clk;

initial begin
        #12 x = 0;#10 x = 0 ; #10 x = 1 ; #10 x = 0 ;
        #12 x = 1;#10 x = 1 ; #10 x = 0 ; #10 x = 1 ;
        #12 x = 1;#10 x = 0 ; #10 x = 0 ; #10 x = 1 ;
        #12 x = 0;#10 x = 1 ; #10 x = 1 ; #10 x = 0 ;
        #10 $finish;
    end

endmodule

Simulation Output :-

The issue is that, the output 'z' is staying low always, even when I've applied an input sequence which has three '1011' patterns in it . What's the possible modification that I'd have to do, so as to eliminate this error ?


texts: How can a 8-bit CPU calculate big numbers?

texts:
I'm trying to design an instructable 8-bit CPU in Logisim. Is it possible to calculate big numbers with an 8-bit CPU?

In a 32-bit computer, you can calculate numbers bigger than 32-bit, I think it's a software trick but who can explain to me how it works?


texts:
To calculate what value of capacitor suit for ripple,
we can use this formula:
Cmin = Load Current / (Ripple Voltage X Frequency)

It seems higher value of capacitor will get better performance for suppress of ripple.
Of course, higher value of capacitor will also be more expensive. So as title,
if cost can be ignored,
is higher capacitor of ripple always a good choice?


texts: Why would you use a feedback resistor on a logic buffer?

texts:
Please excuse my poorly drawn photo-interrupter circuit.  It is used for external home sensing where a flag will interrupt the light source, turning off the phototransistor.

I'm just curious as to why somebody would include the feedback 47.5k resistor here.  From my understanding, it is parallel to the 20k resistor when the home signal is high, and is in parallel with the phototransistor when the home signal is low.  This would increase the current when the phototransistor is off and have a negligible effect when the phototransistor is on.  The 74LVC1G17 already has hysteresis so I am just asking what the benefits of this resistor are.


texts: Why a system is causal if the impulse response is zero for \$t<0\$?

texts:
I was reading a definition that

  Suppose \$h(t)\$ is the impulse response of any system \$Y\$, then the system is causal if and only if \$h(t)=0\$ for \$\forall t<0\$

I know what a causal system is, but I don't understand it in terms of the impulse response. And I was wondering why is it causal here?


texts: Are transmitters always required for industrial sensors (4mA-20mA)?

texts:
I am designing a device that takes in various types of industrial sensors.

Initially, I had a transmitter to take the PWM signal and convert it to 4mA-20mA.

After reading lots of articles about the subject, it is still unclear if these sensors use primarily PWM signals or output a value between 4mA-20mA.


texts:
I am making a project on water level indicator. I've completed the circuit like this:

The circuit is closed through the water.

The problem is even before switching on the circuit, and with terminals not immersed in water, LED glows feebly when connected across 5 VDC source powered from AC source, but not with a 9 V battery.

I want to use the circuit powered from AC, for a long run. I want to know where I am going wrong.


texts:
I want to remote control (WiFi/Zigbee) a water pump AC motor, 1 phase or 3 phase depending on the case, with the smallest board size possible.

I have used large motor AC contactor in past, it works fine but it is also very heavy, bulky, and it has significant "bump" when activating, it also need a relay to control the coil which is in 240V AC, I cannot use that here for these reasons.

The load is a water pump AC motor, 240V AC 1 phase or 3 phase (so 240V between a phase and neutral or 400V between phases), the maximum power of the pump is 3.5HP, but if I can handle 3HP it would be OK too.

As of now there are two options I can think of, either a circuit based on three triacs (for example BTA41-800B) with MOC3083 to drive them, or a circuit based on 30A relays (model SLA-05VDC-SL-A).

The triac solution looks good but I have two concerns with it, first is heat, I don't know how much heat to expect from the triacs, I can add a small heatsink for the 3 triacs tabs (tab is insulated), for example 70*20*10mm but not very much bigger. The second concern is what will append when the capacitor on the pump motor fails and the triac will see pretty much a short circuit, I plan to add some high power (130A) hall current sensors in the circuit for monitoring so I could use that to stop the triac within an half wave in case of short but sadly I also know the triac cannot be turned off elsewhere than zero current cross, which will not append with a short, I also think a fuse will not help since the triac will likely blow before the fuse has a chance to melt.

The second option is 30A relays, 1 per phase, they are given for 30A @ 240V AC. They are rated 1-1/2HP, which to my understanding mean 1.5HP, now I wonder if I use one relay per phase on a 3 phase motor what is the total power it can handle? is it still 1.5HP total or 4.5HP total?

Does it look like a good plan to use such relays? Any advice would be very welcome.

EDIT

After more input it looks like triac or back-to-back SCR is not really an option since for 20A each phase will have to dissipate 30W, which is too much for the heatsink surface I can provide here.

Now one question remains about the 30A relay, with one relay per phase, each relay rated 1.5HP / 30A@240V, should I consider the system capable of driving 3.5HP or only 1.5HP?


texts: how to position precisely the cursor in a bode diagram with LtSpice?

texts:
I'm using Ltspice, and when I have a bode diagram, I have a cursor.

I'm able to move the cursor over whatever value I'm using. However, sometime I need a precise frequency. When I try to enter it in the box, it appears to be locked.

As a side question, would it be possible  to make the cursor go to the maximum peak?


texts: Is using a transformer at reduced voltage a bad idea?

texts:
My Google is failing me.

I want to make an isolated AC voltmeter capable of working at 120 or 240 VAC.

I've found a suitable 240 volt to 5 volt transformer to use (current capacity doesn't matter - the measurement will be at very high impedance).

What would it do if it were fed 120 volts? Ideally the transformer would simply output 2.5 volts, but I have a memory of transformers getting very cranky when fed the wrong voltage.


texts: Reasons of delayed damage signs to AMOLED touchscreen

texts:
I had the misfortune of dropping my cellphone (couple of feet). It was working perfectly right away but throughout the day the screen started displaying a darker spot in one corner that overtime expanded to the upper half of the screen, the remaining became discolored turning to a purplish hue and becoming less and less responsive to touch and finally the day after was completely black.
It seems im not the only one seeing this happening after a fall.
Why there can be such a delay to complete screen failure?


texts:
I have a PCB where there is mounted a microphone, on page 17 in the datasheet, there is a PCB landpattern with broken GND ring.

I have used this landpattern and routed traces through the opening.

But the microphone has an pad there, so directly above the traces there is soldermask and then the pad.

I was thinking if this could be a problem, that the PAD might short with the traces, or should the soldermask be able to keep the isolation ?

Below is a picture of my routing, the grid is 0.1mm.


texts:
I am trying to show a visual representation of a few cycles of a 50Hz and 60Hz sine wave at 400 Volts overlapping and trying to find out how to create this as a chart in Excel.
Does anyone know how to do that?


texts: How to work to find the values of the components that should be used in a project

texts:
My question is somewhat general but I will try to narrow it down.

I want to build a project for which I have all the necessary components and the knowledge as to how I should connect them but I don't know what their values should be.

In order to make myself clear I will use a simple "project" as a reference.

Let's say that I want to build this simple NOT gate:

simulate this circuit – Schematic created using CircuitLab

How do I find the values of the components that I should use when I only have that schematic?

Keep in mind that my question is not focused in that particular "project". I ask generally how should I work in a case when I know the way to connect the components but not their values.


texts: Substitute for permalloy core for power transformer

texts: I want to build an 220AC/22AC transformer to use in PSU for 90W amplifier. The problem is that I can't find permalloy plates for it. What material would be reasonable substitue for permalloy plates for use in such transformer?


texts: Why does the ISDN S0-Bus require terminating resistors?

texts:
It is a well-known fact that ISDN S0-Bus must be terminated with 100ohm resistors to match the transmission line. This is the case even for everyday household installation with cable runs shorter than 50m. Why is this so?

Some back of the hand calculations:

According to this, ISDN has a bandwidth of 80 kHz. Assuming propagation in vacuum, it follows from c=f*lambda that the typical wavelength is about 3.8 km. Reducing this by a factor of two to account for the shorter wavelength in copper wires gives 1.9 km.

Assuming that interference due to cable reflections is non-deleterious for path differences below lambda/10, this would mean that for cable runs of less than 150m, no terminating resistors should be necessary.

This is clearly not the case however. Where is the mistake in above reasoning?


texts: Calculate average current draw for instantaneous loads

texts:
I have a battery powered project with the following statistics:
sleep current: 1.5uA
activity A: 500uA average in 10ms interval (peak current is 1mA)
activity B: 1.2mA average in 20ms interval (peak current is 5mA)
Activity A happens at 1Hz, and B at 0.5Hz. I would like to calculate average current consumption for entire operation, so I did the following computation average current in uA:
1.5uA + (0.5mA * 10ms)/1s + (1.2mA * 20ms)/2s

I think my calculation for Activity A and B is okay, but I am not sure if I have accounted for the sleep current correctly. Should it not have the time instants of A and B subtracted from it to be fully correct?


texts: Why don't I need to consider trace width for a high speed oscillator crystals?

texts:
I have followed some reference designs that uses crystals like 40 MHz for the MCU, and I have not considered the trace width to do impedance matching. The result is that the boards works fine (I kept the track as short as possible). I have not seen any note anywhere that one should consider trace width to have an impedance matching (or at least get closer to it) as above 3 MHz is considered high speed signal. I wonder why one does not consider the wave reflections on the crystal's traces? I don't see any note about it on crystals' datasheet neither.

Even if the reflected waves does not change the frequency of the oscillation, it should cause more noise in the board am I wrong? Even if one would not need to use extra L-C matching circuit for it, but at least wouldn't it be better to use a little bit thicker or thinner line width to improve the reflection depending on the crystal and MCU?


texts:
It's been years since my undergrad work as an EE. I am a physicist and medical researcher now, but, as a startup, we all take on anything we can.
Let's face it... 12VDC high current PSU's are cheap. But when we need a different voltage we don't want to buy custom (expensive) and typical bucking isn't high enough in current.
Right now, we need to take the two 12VDC @ 150A supplies we have and make one 17 VDC and the other 34 VDC.
Off the shelf, what is available? Could we build SIMPLE circuits with MOSFETS (if so, what is the circuit diagram?)
We've also read that inverters (DC to AC mains) can generally be used in reverse. IE, supply 110/220VAC to the output as an imput, and the input with output the designed VDC input. This would be simple and cheap enough if true.
In all honesty, why can't we crack open a PC PSU and up the output voltage?
Many questions here. IE we are open to ideas to get non-standard VDC at high current.
Thanks,

J

____________________________________
From comments:
The output current is currently 15.4A . VDC needed currently is 17 and 36.


texts: What is this IC from a Polar chest band? Top markings: TR06-3 7B227 VP712

texts:
from

I need to find this IC datasheet, but I could not find any details on Google. It's from ST Microelectronics. Top markings: TR06-3 7B227 VP712

It's from the Polar chest band. The full PCB image above came from here.


texts: Correct version of PWM speed control of BLDC

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Different sources shows different versions of speed control:
https://youtu.be/b5J5qkR7msc?t=418

In upper source output (duty cycle) from PI controller (that takes as input difference between desired and actual speed) is provided directly into PWM block.
https://www.researchgate.net/publication/273634792_Speed_Control_Analysis_of_Brushless_DC_Motor_Based_on_Maximum_Amplitude_DC_Current_Feedback?enrichId=rgreq-f79af632138101a2bb06fcf1df0fd5a5-XXX&enrichSource=Y292ZXJQYWdlOzI3MzYzNDc5MjtBUzoyMDc4MTIxNjU2NzI5NjhAMTQyNjU1NzY4OTkyOA%3D%3D&el=1_x_3&_esc=publicationCoverPdf

Here, we have two PI controllers, where first is the one that takes as input difference between desired and actual speed, and second that takes as input difference between output from first PI divided by mechanical constant and Imax.

what is difference between the two versions?
is Imax maximal value from ia, ib, ic or sum of them or something else?
several sources shows scheme where output of first PI controller (whose input is difference between desired and actual speed) isn't divided by mechanical constant. Should I divide output from first PI controller by mechanical constant or not?
PI controller gives output from 0 to 1 (the smaller difference between desired and actual value controled by the PI controller the bigger value in output). But if output from PI controller is duty cycle, then that mean that small difference between desired and actual speed should give PWM signal with very large duty cycle, and then provide more current to phases of bldc motor by switches. Shouldn't be that that PWM closes switches (provide current) when its signal have low state?
should pwm signal on low state reverse direction of current in phases similarly to this movie (link to specified fragment) https://youtu.be/b5J5qkR7msc?t=482 ?


texts: Why does my guitar pre-amp lose it's offset?

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I found a guitar preamp on the web after trying to build one myself and having no luck. This one works for a bit, but the offset part of the OP-amp slowly depletes. It's like C1 is charging up really quickly then just discharging over time.
The only differences from this circuit is that I'm using a gain of 10K/4.7K and a 100 uF electrolytic for C3, bypass capacitor. I'm also using a MCP6002 at 5V which isn't a FET Op-amp. Can someone please explain to me why it's not working?


texts: Can someone help me complete this Verilog code for this sequential circuit?

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I'm still pretty new to Verilog and all and could use some help completing/fixing my code for this problem. I have made the state diagram, state table/assignment, minimized the equation, and even have some of the Verilog done, but I'm just not too good at understanding Verilog.
Here's the prompt:

Derive a sequential circuit with one input (w) and one output (z)
using D flip flops that detects an input sequence of 101. Use a Moore
model, and show all of your work including the state machine, state
table, state assignment, state assignment table, and the final
circuit.

PS, I also don't know how to fully draw the circuit. But other than that, here's the progress I've made:
(I don't have a high enough rep to embed images if someone can do that for me, thanks)
State Diagram:

State Table, Assignment, and Minimal equation

Besides the circuit diagram, I have the first part done. Now I have to implement this as a Verilog program.. even though I'm not quite sure where I'm going with it. I've looked at some examples and this is what I've got so far:
Verilog code so far
module my_circ(Clock, Resetn, w, z);

    input Clock, Resetn, w;
    output z;
    reg [3:1] y2, y1, Y2, Y1 //not sure about this line.. probably throws the rest off
    parameter [3:1] A = 2'b00, B = 2'b01, C = 2'b10, D = 2'b11;

    always @(w,y2,y1)
        case (y2)
            A: if (w)  Y2 = 0;
                       Y1 = 1;
               else    Y2 = 0;
                       Y1 = 0;
            B: if (w)  Y2 = 0;
                       Y1 = 1;

    /////////// I don't think this is right at all :(
            default:    Y1 = ...

    always @(negedge Resetn, posedge Clock)
        if (Resetn == 0) //something :/
        else //something else :/

    assign z = (...); //something :/

endmodule

After trying to write that Verilog, I realize I'm just about clueless when it comes to implementing this :( I tried following different examples but all of the ones I can find use 3 states instead of 4 like this one. I think I should have multiple cases? And ugh idk where to set which variables and what to set them to.
Any advice will help me. Thanks.


texts: UWB circular antenna: input impedance (Zo= 50 Ω)

texts: I'm having difficulty with the line input impedance of the circular planar antenna signal. Its impedance is 117 ohms and the correct is 50 ohms, I am not able to lower the value. I made modifications to the input increasing the line width and also made an impedance transformer. When I get it down, the whole process on the antenna I made is impaired. Example: reflection coefficient is lost, surface current loses efficiency and also its power and directivity. Please can someone help about this.


texts: Charging supercapacitors with Buck converter. Do I need to cut power once charge is reached?

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I am trying to build a supercapacitor charger, and as I don't particularly have a good handle on the risks of such a thing, I'm hopping on here to give some information.

I am using a buck converter connected to a 12v power supply to feed my 2 2.7v supercaps (in series, 5.4 is what I want to cap the charge at)

I have the pot on the buck converter set at 5.4v.

What's the risk in actually not having a cutoff? It's not like caps on a computer motherboard have a cutoff, right? They're constantly receiving a charge.

Once the cap is charged, the amp draw should be close to nothing, right?

If I felt compelled to cut off power at 5.4 volts, what would be an easy way to do so?