texts: Open termination, signal propagation, transmission lines

texts:
I'm inexperienced with transmission line theory so I have a question about implications of signal travel time. Most of what I've read so far has been on lossless transmission lines, not sure how relevant that is.
Suppose you have a dc source connected to some transmission line with an open termination:

Here the wave travels down the transmission line and is reflected back at the end. Depending on the impedance matching between R1 and the line there might be more back and forth reflections but eventually the voltage at either end of the line will stabilize at the value of the source voltage and no more current flows.
Now the same thing but with an ac source:

In this case the end of the line will always oscillate since the line is being driven with a changing velocity, so it can't settle to a single value. Because of the presence of the transmission line, this diagram implies a source driving a load whose physical dimensions are comparable to wavelength of waves launched by the source, meaning that the voltage and current varies with position over the line. Also, the propagation speed of the waves is independent of the length of the line or the frequency of the source. As an example say the waves propagate at \$c\$ and that it takes the waves 100 ps to make a one-way trip from the source end to the open termination end. So the load is approximately 3 cm long and the source wavelength is on the order of 3 cm at most, so the frequency is approximately at least 10 GHz.
So now suppose you use the same ac source to drive a load whose physical dimensions are much smaller than the source wavelength:

This could happen either because the load circuit was made smaller or because the frequency of the source was reduced, thus making the wavelength much bigger than the dimension of the load. Considering the second case, say the load is still about 3 cm long, but the source wavelength is now increased to 300 cm, or a frequency of 100 MHz. However, changing the source frequency hasn't changed the wave propagation time, so it still takes 100 ps for any electrical signal (or any information at all since the wave travels at \$c\$) to reach the open termination and then another 100 ps for any "response" information to come back to the source.
Lumped circuit theory says that the voltage at the open circuit will follow the oscillating source (instantaneously) and there will be 0 current in the branch at all time. In reality the open termination needs at least 100 ps delay between a "new value" being presented at its input (due to changing ac source) and that value having any effect on the open terminated end. Since the load is driven by a constantly changing ac source it seems that there should always be a nonzero current going "into" the load. This seems incorrect so I think I'm missing something.
I think the answer might be that the period of the new source is 10 ns, which is 100 times longer than the one-way travel time of an electrical signal through the load (or there are 50 reflections from open end that make it back to source in one period). Each returning reflection "tells" the source to decrease the amount of current going into the load since the reflection has information about the open circuit. So I think that the low frequency source input changes very slowly relative to how quickly reflections make it back and reduce the amount of incident current. So if you hook up a low frequency source to this kind of load, although the current is not actually zero it is very small since reflections make it back to the source and "dampen" the incoming current at a rate much faster than the input current increases/decreases.
Is this an accurate description?


texts:
I am trying to connect the STM32F103 (blue pill) with the specific w5500 module via the SPI bus. The physical connection I made was

SCS  -> PIN14
SCLK -> PIN15
MISO -> PIN16
MOSI -> PIN17

Uploaded a sample sketch from Ethenet 2 library, but nothing works.
It seems like the processor or the module itself, keeps resetting.

I have connected successfully the Ethernet module previously on Arduino nano, with out any issues.

With the blue-pill, I cannot even find the device on the network while port scanning.

So two questions arise:

Have I connected correctly the pins?
Should I make any changes to the code to enable SPI at the bluepill, since it may serve two different SPI's?


texts:
im designing an ESP32 system with three haptic drivers.
Description of the system:
3 Drivers:

3.3 V
15 mA
ESP32-pico-D4:
3.3V
Sleep mode: 50 mA
Active mode: 150-300 mA
Antenna: Compact Reach XtendTM Bluetooth®, 802.11b/g WLAN Chip Antenna

It's powered by a Lithium Battery of 400 mAh, and i'm using a LDO TPS7A20 with a Voltage Drop Out of 140 mV low current consumption. With a current output of 300 mA.
The question is the next, i should use a LDO with that especification or maybe it's better to use a Buck Converter. I know that the efficiency of the Buck Converter is better but it maybe has EMI signals that can interfere with the Bluetooth signal. The key of the question is that it's true if with this signas and the size of the board (25 mm x 20 mm) I'll have some EMI's of the Buck Converter. Or some tips for design it. Or maybe use another kind of IC regulator (for example PMIC)
Note: Im new in designing batteries circuit and power management. I read a lot about LDO and in first place i took it because it hasn't got noise that produce EMI in my board.


texts: How can I estimate the Rds(on) parameter of MOSFET in PSPICE LEVEL 3 model?

texts:
Recently I was designing a DiffAmplifier model, whose gain is obviously gmRout. However, I can't get the Rout parameter of my MOSFET, which is MbreakN3 in OrCad. I have checked the Pspice Model and I only got a RDS parameter, shown as below.

But we know that Rds varies with bias current. So how can I get the actual Rds parameter in my circuit?


texts: How does electrical devices consume power?

texts: I'm curious to know how does an electrical device can consume any amount of power it is required? Suppose the voltage here is 220V. How can you get any amount of electrical power say. 1000 watts out of it? Please tell me what I'm misunderstanding.


texts: Writing the Nodal and Mesh equations for large circuit and large supermesh

texts:
Here's my circuit:

simulate this circuit – Schematic created using CircuitLab

I have defined the node 'voltages' and the mesh current directions and the currents themselves. What I want to do is calculate the nodal and mesh equations for this circuit given the information above.

Here's my work at the nodal analysis:
$$KCL\;\;V_1:\;\;{ {{V_1-V_2}\over R_2} +{{V_1-V_3}\over R_1} + {V_1\over R_3}= 0}$$
$$KCL\;\;V_2:\;\;{ {-I_b} +{{V_2-V_1}\over R_2} -I_a = 0}$$
$$KCL\;\;V_3:\;\;{ {{V_3-V_1}\over R_1}+I_a +{{V_3-V_4}\over R_4} = 0}$$
$$KCL\;\;V_4:\;\;{ {{V_4-V_3}\over R_4} +{{V_4}\over R_5} - I_c = 0}$$
As far as I can tell, those should be correct.

My next problem is how to get the equations for the mesh currents. What my issue is, is at the super mesh(s?) formed by Ia and Ib. I'm not sure how to get the mesh currents if those are there.

To summarize, I'm pretty sure my voltage/nodal equations are correct but I'm not 100% sure about that. I don't know how to get the mesh current equations if those independent sources are in this particular configuration.

If anyone could help I would greatly appreciate it. Thank you!


texts:
I am trying to solve the following question related to cascode circuit. Where T5 has Vbe=0.7V

I have answered the questions as follows.

- Explain how the circuit works?
The circuit has a DC operating point which gives the AC parameters of the transistors such as the transconductance. A AC current will flow through the transistor and the output voltage will be given by the voltage dropped at R4. The input impedance of the circuit is high but it's not depending on the bias current due to the gate current is really small, thus the rd can be regard as infinite.

- Explain the FET T3 is biased at the red point in figure 3 characteristics.
how do I explain this, does this has something to do with calculating the Q point in the load line?

- Calculate the value of R3 using the data from figure 3.

Vgs = Id * R3 there fore,

R3 = Vgs/Id = 0.4V/10mA = 40 ohm

**- **Determine in a graphical way from  the characteristics from figure 3
   the transconductance of T3?****

gm = delta Id/delta Vgs (keeping Vds constant)

gm = (13.8-6.3)/(0.2-0.6)

gm = 7.5mA/0.4 = 18.75 mA/V

- Calculate the voltage gain of the circuit?

Vout = R4 * id

We know, id = gm * Vgs = gm*(vin - id*R3) = (gm *vin)/(1+R3*gm)

Replacing the value of id we get,

Vout = (gm*R4*vin)/(1+R3*gm)

Vout/vin = (gm * R4) /(1+R3*gm)

Av = (18.75mA/V * 3.9K ) / (1 + 40*18.75mA/V)

 = 41.78

- Judge the power supply rejection of circuit 3?
 This is a small signal analysis so i think,

PSRR  = 20log ((delta Supply / delta Vout)*AV)

but i don't have the supply voltage and Vout so how can I calculate PSRR?


texts: Is it safe to apply voltage to buffer output?

texts:
I want to design a SDI-12 interface and I am using this schematic as a starting point. In receive mode, the 5V SDI-12 data signal will reach UART RX via the transistor Q1, but will also reach the output of the buffer U1 (I my case, it is a 74LV1T126GVH).
So, is there a risk of damaging the buffer when applying the RX voltage on its output? If so, what solution is there to this problem?


texts:
I am hoping to put together a simple 12V circuit whose load is a digital voltage meter. The circuit will have two 12V inputs and the goal is to have power to the meter when only one of the leads are hot, then turn off when both 12V leads are hot.
Seems like it would be fairly simple and might utilize a single transistor. Or maybe there is a small device that I can use to accomplish this?


texts: Passive Attenuator + Level shift simulation slightly off from hand calculations not sure where mistake is

texts:
I am trying to take a +/- 3.5V signal and shift it into the 0.65V to 2.65V range for input into an ADC with common mode of 1.65V. I have calculated the attached circuit by hand but when I simulate it on LT Spice I am just slightly off. I also have the constraint that R1 = 50 ohm in the circuit.
At -3.5V I want an output of .65V but I am getting about .5V. At +3.5V I want an output of 2.65V but I am getting only 2.05V. This is my first time simulating on LT Spice so I am not sure if my calculations are wrong or maybe it is my simulation.
Here is simulation at 3.5V

And this is simulation at -3.5V


texts: Reasons and assumptions behind the use of per unit length quantities in the telegraph equations

texts:
I am working out the derivations of the telegraph equations of a transmission line

$$\begin{gathered}
  \frac{{\partial V}}{{\partial x}} =  - L\frac{{\partial I}}{{\partial t}} - RI \hfill \\
  \frac{{\partial I}}{{\partial x}} =  - C\frac{{\partial V}}{{\partial t}} - GV \hfill \\
\end{gathered}$$
where I is the current, V is the voltage, R is the resistance per unit length, L is the inductance per unit length, C is the capacitance per unit length, and G is the conductance per unit length.

Working into the derivations, two questions arose: Why do we express the parameters on a per unit length basis? What are the assumptions underlying the transformation from total values to per unit length (e.g., linearity, isotropy, etc.)?


texts:
I have an interesting project and I don't know whats the best solution.

Basically I have a charger (charges one battery at a time) and 2 batteries.

What I want to do is to have the charger charging battery 1 (while battery 2 is feeding clean power to an audio system)

With a voltage sensor (when battery is low) , I want to switch the charger to battery 2 and have battery 1 power the audio system. (the voltage sensor its not the question)

My question is : The battery that feeds the audio system must be completely isolated from the charger and ground (so no power noise is present).

Is there a way (except SSR) to do that ?
PCB is quite small and space is at a premium. Also take in consideration and charger is 3A 5.5v and batteries are 5.4v


texts: I know a signal initialisation in VHDL is an event. But, what about a signal elaboration without assigning an initial value?


texts: 2bit asynchronous binary counter in Multisim

texts:
I'm trying to simulate 2bit asynchronous binary counter using D flip flops in Multisim. Here is schematic (I didn't show clock signal):

Problem is, one of flip flops is not reset (5V on Q output).
When flip flops are not connected, like on schematic below, both flip flops are reset (0V on Q output).

For asynchronous counter to work properly, all flip flops should be reset before we apply clock pulse to LSB flip flop. Can I do something in Multisim for all flip flops to be reset when connected like on first schematic?


texts:
I have a circuit (from a RC car) that uses a 5610 transistor, which can't find in store.

Is there any equivalent transistor?

Here are pictures of the board (click here for high resolution images):


texts: Is there a hardware only way to read a digital pin on the STM32 at a given frequency?

texts:
I'm using an STM32H7 and looking to sample a digital signal at ~6MHz directly into memory with periodic interrupts? I've seen an approach using a DMA read from the GPIO ODR address but this would seem to sample as fast as the DMA can read from the peripheral. Using a timer interrupt its possible to achieve 2MHz+ but these interrupts are costly from the perspective of CPU time as they are occurring at the sampling rate.
Is there another approach I'm missing or not understanding, such as abusing I2S, that could permit a ~6MHz sampling frequency into a memory buffer in batches of hundreds of samples? This would permit the CPU to crunch on the bitstream while the hardware continued to fill the next samples buffer.
It's possible to change to other chips in the STM32 family or another SoC all together if it helps solve this problem.


texts: Questions about RS-232-like naming and standards

texts:
1. Is official RS-232 (EIA-232) standard open and free available? I couldn't find it in Internet.

2. Does "RS-232 with TTL levels" is covered by some standard?

3. Does "synchronous RS-232" (via USART) is covered by some standard?

4. Is there general name for RS-232-like protocols with different voltage levels?


texts: How can I use PWM to power a 1.5v dc motor with an 5v board Arduino UNO?

texts:
I tried to calculate the value for analogwrite which is 77 but that doesn't work. I also tried a bunch of other value but none of them spin the motor. Is this possible and am I missing something? the motor is a FF-N20ta-2232 and i am using pin 13 on the Arduino uno.

simulate this circuit – Schematic created using CircuitLab


texts: Mirror-inverted and wrong-colored display

texts:
I'm trying to address a (cheap chinese) ILI9320-driven 320x240 LCD display from an Arduino Mega 1280. I've got it to work via the UTFT library. Well, not fully; something is shown, but the colors seem a bit faded and wrong, and the display seems to be mirror-inverted (the letters printed on the screen by the example programs from UTFT library at least are).

Supposedly this is the documentation of the display I'm having.
I'm running it from an Arduino Mega 1280, the example given on the documentation page is for the Mega 2560; could that be the reason for my problems?
I connected all the pins (RST, RS, WR (actually called RW on my display board), RO, and DB0-DB7 according to the above documentation:

RS -> D38
WR -> D39
CS(pin6) -> D40
RSET-> D41
RD -> 3.3V
DB0->DB7 to D22->D29

Double-checked all these connections so they should be connected where the docs say they should.

I first had 5V and Gnd also connected; but since the above pin mapping doesn't mention them at all, I tried without them, and noticed they weren't needed - the display also shows something without them connected, although disconnecting Gnd makes the image a little darker. Could I have blown the screen circuits somehow by that? Should I connect 5V?

Here are some example images of how it looks like:

From the demo program (Bitmap from UTFT): Supposed to be properly colored Tux'es and happy faces in various sizes I guess:

Supposed to be a red rectangle with the text "Hello World" across, shown via the same method as in the "Bitmap" demo program from UTFT):

Any ideas what I'm doing wrong here?

Something I forgot to mention in the start (but which might be very important!):
In the example code, I tried to use myGLCD(ILI9320,38,39,40,41) for initialization as mentioned in the documentation, but ILI9320 does not seem to be defined in the version of UTFT I'm using (and also isn't mentioned anywhere in the comments in UTFT.h, only ILI9325D), so I tried ITDB24D; I played around with the possible value there a little but haven't tried all possible values, maybe I just haven't found the right one yet? Anybody knows what the proper value to use is, or where ILI9320 is defined?


texts:
I'm trying to chose correct stepper motors to drive 2 wheeled robot. I started with geared DC motors, but found they are too fast (I have 27:1 geared), and they provide little torque at low speed.

Therefore I'm looking at stepper motors that will give enough torque at low speed. The criteria are:

Motors need to be small. Top are Nema 17, Nema 23 are going to be too large
Need to be driven from low 12V accumulator
Need to output 1Nm torque, to move 5kg dolly on potential 5 degree slope with 10cm wheels
Need to use as less current as possible
Need 30RPM on output shaft

I researched this topic a little and found that low inductance motors will need less volts but need more amps. As the setup doesn't require very precision movement I think I can get more torque if I go for geared stepper motors.

I found 2 identically geared motors on ebay, one having 34mH and another having inductance 2.8mH

http://www.ebay.co.uk/itm/DE-Ship-27-1-Planetary-Gearbox-Nema-17-Stepper-Motor-0-4A-DIY-CNC-Robot-Camera-/231657603766?hash=item35efde82b6

http://www.ebay.co.uk/itm/DE-Ship-27-1-Planetary-Gearbox-High-Torque-Nema-17-Stepper-Motor-DIY-CNC-Robot-/231657805043?hash=item35efe194f3

If anyone had experience with geared stepper motors and can advice on the selection, I would really appreciate it. 27:1 is not set in stone, I can go for 5:1 if it provides enough torque, or higher if not. I can even use bare motor without gearbox, but I'm afraid it will be either too weak (even at low speed), or will have to be too large to give enough torque.


texts: What mode of SPI is the standard if nothing regarding the mode is mentioned in the slave datasheet?

texts:
I am trying to bit bang SPI for a SD Card, I went through this SD Card datasheet and I couldn't find any information regarding the mode that needs to be used. If I missed, please point it out.

Else what mode would be standard if nothing is mentioned? What CPOL and phase should I use?


texts: Confusion between Input/Ouput Impedance and Thévenin's theorem

texts:
I'm bit confused about what Input Impedance or Output Impedance is. I tried to read Wikipedia's page (https://en.wikipedia.org/wiki/Input_impedance)  but I find it hard to follow.

Is the Input Impedance of a circuit (defined between two terminals A and B) the same as the equivalent impedance obtained by applying Thévenin's Theorem? What is the Output Impedance instead?

I'm interested in the general theory, an example (with the diagram of a circuit showing input and output Impedance) would be really appreciated


texts:
]2

I tried KVL, KCL and the standard stuff (My knowledge goes up to Super-nodes and Super-mesh) but I have no clue what the 4V source is actually supposed to do? Sorry if the answer is obvious, but I'm stuck on this.

Edit: I've added some labels and added an image of what I came up with.


texts:
My question is how much Amperage can I draw in DC using this kind of setup. I have a 3055 and it's rated at 15A. Is that my max draw then? Power systems aren't my thing, so I'm out of my element with this stuff. Equations are also appreciated too! Thank you so much!

EDIT: Also, how efficient is this kind of circuit?


texts: Setting optimum base current for saturation and power dissipation of a BJT

texts:
Regarding the following circuit example, I want to find the optimum current for saturation of Q1. By saturation I mean the safe one. For simplicity I didn't bias the transistor and I'm assuming beta is very very stable.

I sweep Vb from zero to 5V and obtain the following plots:

[left-click to enlarge the plots]

Green plot is the power for the Q1 with respect to Vb.

So by using a cursor I find the minimum point(after cut-off) for the BJT power. This is where the saturation regime begins. At this point Ic is maximum and I find Ib is around 26uA.

So if this transistor needs to be in ON OFF mode for long time, does it make sense that I set Ib as 26uA to obtain the optimum saturation? Or should I do some overshooting as common practice? I'm wondering how would it be safe set in common practice.


texts:
I have a surface acoustic wave based separator device built on piezoelectric (PZT) substrate and this is mounted on a PCB for the external connection as you can see from the picture.

When I was working with this device in Norway, I used wire bonding to connect the PCB and the metal strips on the PZT substrate.

As I moved to new place I don't have this wire bonding machine available here.

So I was thinking can any of you brilliant people please give your insight about how to do the connection without the wire bonding?

I have some ideas like connecting with conducting tape or conductive epoxy glue pen but I am not sure.

This device works with 13MHz frequency.

So I am not sure if the conducting tape can withstand this frequency.

I can't use soldering because the most common tin solder will remove my thin gold layer from the PZT device.

Please see the attached image.


texts: Can you explain contact rating of this toggle switch?

texts: I'm looking at the datasheet for TE Connectivity Gemini Series switches and contact rating is given as:  5A @ 125VAC or 28VDC resistive; 0.4VA @ 20V AC or DC. I want to use this switch for DC application and the first part of specs: 5A @ 28VDC seems inconsistent with the second one 0.4VA @ 20VDC, which suggests 0.4W/20V = 0.02A current. Can someone explain discrepancy between 5A in the first part and only 0.02A in the second one?


texts: Designing an op-amp circuit to generate a digital pulse from LDR

texts:
I am trying to design an op-amp circuit to generate a digital pulse when an LDR is quickly obscured from ambient light (like when you pass your hand over it). This is the circuit I built - a differentiator:

And here is the output when I pass my hand over the LDR:

Is this the right approach? What should I do to get a cleaner digital pulse output? Should I use a comparator at the output stage?

NOTE: R below LDR is 10k.

Update:

Just wanted to mention that Microchip has a "Tips 'n Tricks Comparator PIC MCU - Microchip" document with a section on the "Data Slicer" circuit mentioned by @Andy.

ww1.microchip.com/downloads/en/DeviceDoc/41215c.pdf


texts: Calculating parallel resistance of a rated bulb

texts:
I have a bulb rated 110 V, 60 W and is in series with another bulb which is 110 V, 110 W. It's being powered with a 220 V source. Now, what would be the resistance of the resistor to be added in parallel to the first bulb so that each bulb will get the rated power?

The way I approached this is first get the resistance of each bulb, then get the voltage drop of each bulb via current divider principle. After that, I'm stuck.


texts: According my book, which I think it might be an error, Q1 is a D-MOSFET, and the behavior of the circuit is shown in the following picture. But it seems to me that according to the behavior this should be an E-MOSFET. Because if it was a D-MOSFET it would be normally on and an increase in duty cycle would mean a shorter T off and thus shorter time the MOSFET is on and thus less V out. But the Waveforms show and say that a larger duty cycle with more T on produce an increase in V out


texts: Does using HVDC for distance transmission make theft of electricity easier to detect?

texts: In particular, if you were going to try to steal power from HDVC transmission lines you'd need one cable attached to current going in 1 direction and the other attached to current flowing in the opposite direction. So this would create a branch current and if there are meters measuring the current flow, the utility companies could detect an unexpected drop in current and locate where it is coming from.


texts: Question about a charge injection compensation network for analog switches

texts:
I'm studying this kind of CMOS switch:

With the switch in Fig. 2.17 in the on state, after a transient, we have Vout=Vin hence the drain to source voltage of M1 goes to zero. The MOS enters the linear region and its on-resistance is approximated by

Assuming that the gate voltage is driven by a clock signal, we have the problem of the charge injection: when the clock goes down, the transistor M1 turns off and the charge of the channel splits approximately into two. Half of the charge goes toward left (i.e. the low impedance path), instead half of the charge is deposited on the top plate of the capacitor, thus causing a voltage drop at the output (which, as a consequence, becomes smaller when the switch M1 is off). When M1 turns on again (i.e. high level of the clock), the output voltage returns to be equal to the input voltage.

The book on which I'm studying proposes some solutions to alleviate the charge injection; among these, the following circuit is reported:

The problem is that I don't understand how this circuit works: the author of my book just explains how this circuit behaves with the charge injection problem (when M1 turns off, half of the channel charge goes to the inverting terminal, causing an offset at the input of the op-amp; but at the same time also M2 turns off, thus half of the charge of the channel of M2 goes to the non-inverting terminal and, thanks to the high CMRR, no problem occurs at the output), but he does not explain how this circuit works as a switch. I assume that the working principle of this circuit must be more or less the same of the "original" switch of Figure 2.17, but then why do we have an integrator circuit? Does M1, when it is on, work in the linear region (and thus is equivalent to a small resistor) as in the "original" circuit of Figure 2.17?
In the "original" circuit of Figure 2.17, when the transistor is on, vout=vin; in the circuit of Figure 2.24, when M1 is on, we have an integrator circuit and thus a linear output voltage (and thus vout cannot be equal to vin).

Thank you


texts: why is noise always a high frequency signal ? what then is frequency of a noise?

texts: while designing signal conditioning circuits for sensors , we design low pass filters to remove high frequency noise. why can't noise be a low frequency signal or what will its frequency be ?


texts: A question on 4-20mA precision current measurement

texts:
Sometimes I need to calibrate devices which have current outputs.
Typically the devices output 4...20mA currents and I have been using a calibrated 250Ohm precision resistor(goes to a single-ended data acquisition channel) to measure current output( measure of course as a voltage and then divide by the resistor value).

This is very common way of measuring such current loops. But my concern is that none of the current sourcing devices I encounter have specified output impedances in their manuals/datasheets.
Here is an example device.

As you see there is no output impedance mentioned in the manual.
So I was thinking to be on the safe side maybe it is better to use an active circuit to minimize the possible error due to the current source's output resistance and the 250Ohm shunt combination:

I also see some noise time to time.
So my aim is to measure the current as precise as possible and the error should not be more than 1%.
In this case I'm not even sure if it would be waste of time to make an active circuit.
The problem is I don't know these device's output impedances so that I could estimate the error when shunted with 250Ohm.

What is output impedance of such current output devices roughly? Is it worth to worry about precision here and to use an active circuit? I would appreciate any ideas.


texts: Can the high current motor change the ground potential level in the H-Bridge?

texts:
I'm planning a half-bridge driver with bootstrap IC-s. My motor runs on 12V, with 50-60A. I linked the schematic. I supply the bootstrap from an other battery (7.2V). Due to the big current, can the ground potential level change? In this schematic the ground of the batteries is connected to each other.  I fear that the potential level increase/decrease can damage the other part of the electronics, that is supplied from the 7.2V, too.
I found a datasheet: http://www.irf.com/product-info/datasheets/data/ir2184.pdf, where two types is introduced, a coupled (IR2184), and a decoupled bootstrap IC (IR21844). What are the advantages/disadvantages both of them?


texts: What is 8 pin tssop packed component?232/485 ethernet converter

texts:
-size =    2.9mmx3.1mm
-GND pin = 1,6,7 connected
-7.pin 4.7uh connected


texts: As in the question title. Is it possible to generate basic dual rail power from two bridge rectifiers? I tried wiring one forwards and one backwards in a simulator, but I found that it did not work. Does anyone know if it's possible? Instincts say no, because it would require doubling the supply voltage, and that's tricky with just diodes.


texts:
There are circuits for constant controlled voltage, and constant controlled current as shown below:

Voltage controlled constant current source

Voltage controlled constant voltage source

simulate this circuit – Schematic created using CircuitLab

What if I wanted to create a circuit that was a voltage controlled constant power source? Here is the basic idea, I'm wondering if anyone has used a circuit that does this sort of thing, or if there are circuits that do this. I have not found any yet. I would like to control the power going into a load.

simulate this circuit


texts: Stepper motor causes voltage drop when running

texts:
I am a bit new to the electronics hobby so I am trying to understand what is going on with my circuit. I am using a pic microcontroller to control a stepper motor, an LCD and an RTC using USB to provide power as shown my circuit diagram below

I am using a power bank or USB phone charger for power, both can supply 5V and 2.4 amps. What I found out is that when the stepper motor runs, the voltage in the circuit drops down from 5.2 volts to 4.6 volts, causing a dim in the LCD and sometimes it caused a hang in the PIC or the RTC.
The stepper motor is NEMA 17 HS4401 which has phase voltage of 2.6 volts and phase current of 1.7 amps but I am limiting the current to less than 1.2 amps
After adding a 100 uf capacitor in parallel with PIC and increasing the motor capacitor from 100 uf to 220 uf, things became better. Getting the motor power wires (VMOT and GND) closer to the power supply somehow reduced the drop, voltage now drop to only 4.9 volts.
So my questions:
1- Why is this voltage drop happening? as far as I understand, it should not happen as long as I am drawing below the 2.4 amps the power source can supply
2- Is there any way to eliminate that drop? would using a bigger capacitor for the motor make any difference?
3- The motor completes a cycle, stops a bit then moves again, which keep changing the voltage between 5.2V and 4.9 volts, is there a risk that the constantly changing voltage would damage any components?
Any help is appreciated


texts: If you were to add "DC offset" with a clamp, can you easily remove it afterwards?

texts:
I don't have a circuit right now, but let's say you wanted to add DC offset to a signal (ex. to prepare a signal for an Op amp stage) but then afterwards center that signal on 0v.

Is this possible with a clamp for adding offset, and then using a high pass filter for removing offset?


texts: I'm having trouble finding an available switch to match a schematic. Is it possible?

texts:
I'm having trouble finding a 4P3T switch for the circuit below, credited to David Mikeska, which I believe to be described as follows in a contact configuration table you'd commonly see on a datasheet. Is this table correctly described, and are there any recommendations about the switch configuration itself? This doesn't seem to be a commonly available configuration when compared to catalog offerings.
L             C             R
X             O             X
O             X             X
X             O             X
O             X             X
Thanks
EDIT: I am seeking an industrial selector-type solution, such as a 23 or 30mm panel mount switch. Here is a link to an example product sheet to show how their configurations are published. On page 22 of this document (Cat Pg #741) you'll see the available configuration of a 4NO contact Selector switch with operator positions listed. These positions don't quite match what I need, the configuration listed above. I think I may be overcomplicating this, but I can't seem to figure it out. I don't seek a specific product recommendation. More value would be added in understanding how to reconstruct the switch design, if necessary, to accomodate the more generic modular solutions offered by manufacturers.


texts: What's the difference between these diode symbols?

texts: What's the difference between these three different ways of symbolising a generic rectifier diode: solid, outline and outline with connection between anode and cathode?


texts: Wiring up a current limiting resistor with an IR LED burns of the LED

texts:
I have a 5V DC supply and i am trying to wire an IR led with a resistor in series to it. I have wired it up to a bread board as shown in the pic

The current limiting resistor value is ~ 216 Ohm.
Using a multimeter's diode setting, i found out the forward voltage for the LED is 1.18 V
Wiring the circuit as shown in the pic, blows up the LED!

Could you please point out where am i going wrong?


texts: Why does my multimeter report a tiny current through a shunted 9-V battery?

texts:
Why does my multimeter report a tiny current (microamps, if that) through a shunt resistor (e.g., 1.5 kΩ) or even a short placed across the terminals of a new 9-V battery?
The multimeter and all components are connected in series.
Edit: Answer
It is likely that neither multimeter probe is connected to the common (COM) terminal of the multimeter. Note that the placement of this terminal (black) relative to other terminals (red) varies from multimeter to multimeter. Important: DO NOT retry the dead short test, especially after correcting the mistake or on µA/mA measurement ranges, to avoid blowing a fuse.


texts: Will forced air on PCB improve current capacity of trace?

texts:
If a trace can carry 3A for a temperature rise of 20°C, will adding forced air over the board increase current capability (by any factor)?

Is the current limit defined by the heat or is it the properties of the material (geometry, type, etc..)?


texts: Node analysis with voltage source, How to solve with matlab?

texts:
So i have this matlab homework where i need to find voltage on Y2 and Y3 using node analysis. Arrows indicate direction of current flow in branches.

simulate this circuit – Schematic created using CircuitLab

With LTspice i got:

  Y2=17.158V and Y3=11.297V

Also solving this system i got the same results:

  KCL on Y2 { (Y2+E1)/(R1+R2) + (Y2-Y3+E2)/(R7+R6+R5) + (Y2-Y3)/R8 - 9 = 0;
  KCL on Y3 { -(Y2-Y3)/R8 - (Y2-Y3+E2)/(R7+R6+R5) + Y3/(R3+R4) = 0;

The problem starts when i try to solve this system as matrix in matlab. I think i have written the matrix wrong, but i cant figure out how to write it properly. Got confused at E1 and E2.

My incorrect Code:

E1 = 5;
E2 = 10;
J3 = 9;
R1=1;R2=2;R3=3;R4=4;R5=5;R6=6;R7=7;R8=8;

G1=1/R1; G2=1/R2; G3=1/R3; G4=1/R4; G5=1/R5; G6=1/R6; G7=1/R7; G8=1/R8;

G = [G1+G2+G5+G6+G7+G8 -G5-G6-G7-G8;
     -G8-G7-G6-G5 G8+G7+G6+G5+G4+G3];

E = [-E1*(G1+G2)-E2*(G5+G6+G7)+J3; E2*(G5+G6+G7)];

U=G\E;

Y2 = U(1)
Y3 = U(2)

Later i will switch E1 and E2 with functions.

Thanks!


texts: Enhancement type MOSFET - channel formation

texts:
In an enhancement type MOSFET (an n channel one assumed here), when a positive gate to source voltage is applied, the holes of the substrate near the gate move deeper into the substrate away from the channel, and the electrons of the source and drain region accumulate near the gate to form the channel.

At the same time, the minority carriers of the substrate (electrons) should also be assisted by the electric field to accumulate in the channel region.

The book by Sedra and Smith mentions that only the source and drain electrons form the channel, while Boylestead's book states that the minority carriers of the substrate are involved in channel formation.

So, can I assume that both these mechanisms are involved in channel formation?


texts: SPI data lines look identical, but results are different, how is that possible?

texts:
I have a golden sample system which consists of 2 devices communicating via SPI.
I swap one of the devices and bit bang the SPI to make it similar to the golden sample.
However the bit banged device doesn't receive the correct data in the MISO line.
If the signals are the same, then what could be the issue?

More info:
The devices are the Yellow/Redbeet carrier-board-h and Raspberry Pi, and NanoPi Core.
The devices are connecting with jumper wires, less than 10cm in length.
All devices get power cycled before doing this test.
Edit
As a second part of my experiment, I now do bit banging on the golden sample to ensure my bit banging method is correct.
I also tightened the CS because of the comments below. The output from MISO is looking correct even with these changes, so I don't believe the issue is CS.
Is there something more to SPI that I'm not aware of here?
Bit banged golden sample (with tighter CS timing), still works:

Update 2
This is what the signal looks like for the NanoPi Core (the device that's not working as expected) when using the driver to control the SPI:

And loosening the CS pin (still no good data):


texts: ESP8266-01 pull GPIO2 down only after boot

texts:
the specific TTP223B I have doesn't have jumper to change "active high" to "active low". This is the answer that is usually given to my problem
I am currently working on a touch-activated wall-mounted light switch.
I am using an ESP8266 ESP-01S (specific one) module programmed via ESPHome in Home assistant. GPIO2 is used to read the switch state.
I am using a ZHITING TTP223B Capacitive Touch Switch Module for the switching action.
note: this schematic doesn't include any resistors because I'm currently doing testing using a curent-limited desktop PSU and kept it simple for development purposes

simulate this circuit – Schematic created using CircuitLab
ESPHome config file (for those not used to ESPHome, it basically generates templated programs to flash on the ESP based on yaml config)
api: ~
binary_sensor:
  -
    name: "Test ESP8266 binary sensor"
    pin: GPIO2
    platform: gpio
captive_portal: ~
esphome:
  board: esp01_1m
  name: wall_mounted
  platform: ESP8266
logger: ~
wifi:
  ap:
    password: REDACTED
    ssid: "REDACTED"
  password: "REDACTED"
  ssid: "REDACTED"

My current circuit looks like the above schematic. It works well as long as GPIO2 is not connected to the IO during the ESP8266's boot sequence. If I connect them after the ESP has booted, the circuit works well.
The problem seems to come from the fact that, to boot in "normal" mode, GPIO2 must be high on the ESP and the TTP223B pulls the IO low when in "open" state.

I tried using a weak pull-up between the IO-GPIO2 and VCC. Didn't work
I tried using GPIO0 (which has an internal pull-up) as the VCC input for the TTP2223B but all I ended up doing with that is pulling GPIO0 low ... which prevent "normal" boot again

I thought of using some kind of transistor or relay setup to keep the TTP223B's GND line open during boot but I find that solution overcomplicated ...
QUESTION: How can I use the TTP223B with an ESP8266-01S without having to disconnect the IO line during boot time.
notes:

The *-01S version of the ESP8266 only has two accessible GPIOs, both must be pulled high for normal boot
I would like to avoid switching to an other declination of the ESP. I only need one IO pin and am looking for the smallest possible form-factor.


texts:
I work on the book "Make - Electronics" doing some experiments. One of these is working with a relay. The simple schematic is this one:

The circuit that I build works to 95%..... The left LED is lighting up when connecting to power, which means the relay is passing through the current. When I press the button, the left LED is turning off correctly, but the right one doesn't light up. I tested both LEDs by switching their places and got the same result. So I know that both LEDs are working. But i do not find the error... So I would think the relay is working, right?


texts: What is the role of ISA (Instruction Set Architecture) in the comp arch abstraction stack.

texts:
I have programming background, and I recently started taking computer architecture course. Most of the lectures I see use the some sort of the layering as described in the following diagram explaining what will be covered in the course.

The question here is compiler (System software) takes care of converting high level/assembly code to machine code that can be understood by the processor. OS executes this code by managing the resources such as processor scheduling, memory management etc.. so what's the role of ISA layer here

What is the input interface to this layer (Machine code from OS)?
What is the output interface to this layer?

Image courtesy: http://theembeddedguy.com/2016/05/15/layers-of-abstraction/


texts: Gain Resolution after delta-sigma (ΔΣ) analog-to-digital converter (ADC)

texts:
Is it possible (effective) to do oversampling and apply extra Moving Average Filter with a delta-sigma (ΔΣ) analog-to-digital converter (ADC)?

More detailed: The ADC (ADS1258) I chose has an effective resolution of 19.5 Bit at a sampling rate of 23.7kSPS/Channel. I need that high sampling rate for a feedback; however the final output can be at data rate of 500 to 1k Hz and must have more effective Bits (22 – 24 Bit).

I know that the ADC applies internally 5 cascaded windowed moving average filters which make it very inefficient to gain further resolution Bits (The noise is than correlated). But then there is the down sampling applied at the end of the ADC.


texts: Can I use this power supply DC output terminals to create a dual power supply?

texts:
I have this power supply.
And here is the photo:

I named the DC outputs as A, B, C, D in red color to ask my question.

I saw in some bench power supplies they create dual supply.

Can I make a +24V -24V dual power supply by tying B and C together and making this joint as GND. So lets say I tied B and C and this is called BC. Im expecting A to BC voltage will be +24 and B to BC will be -24V.

1-) Can I do that in this case safely? Or tying B to C short the supply and damage it?

2-) If I can do that, do you recommend this way of powering a dual opamp for a good performance or do you recommend another IC solution to obtain dual power supply for opamps?


texts:
I have Electronic board with power supply , control board etc. I wanted to conduct noise test . Is there any standard procedure available.
I wanted to check if i induce the noise into power line or controller line microcontroller will operate normally or Reset every time. The device work fine in normal condition. when it goto Control panel it may affected with other device

We have EMI/EMC test facility to take of it. But is there is simple way to conduct noise test where we could induce particular frequency of noise and check its functionality.

Test should meet IEC standard.


texts: Is the LED-like device in the front of an Arduino flame sensor a photo transistor?

texts:
This is a common Arduino flame sensor found in the Elegoo 37 sensors kit V2.
Is the led in front of it a photo transitor?


texts:
I wanted to use this function generator IC as a voltage controlled frequency output especially to obtain low frequency sine waves. But unlike many implementations, I wanted to control the frequency not by a using potentiometer but instead by applying a voltage directly to its inputs. For powering the chip, I use a ±15 V dual power supply with 133 mA rating.

From the 8038 datasheet there is a section about sweep shown below:

Above the sweep voltage is shown between the V+ and pin 8.

But instead, I tried the following scheme where I apply the DC voltage signal between pin 8 and GND. Here is how I use it at the moment:

As you see above Vin is coupled directly to pin 8, and in my case the component values are Ra = Rb = 47 kΩ; C is selectable 4.7 μF or 100 nF; RL = 15 kΩ and pin 12 is directly connected to V-.

And here is a photo from the board:

Since I couldn't find a similar implementation I have couple of questions regarding my implementation:

In my case  I apply the input voltage(call it Vin) directly between pin 8 and the GND, and to get sine wave output the Vin must be such that 6.5V < Vin < 15V.

I can observe on a scope that the output frequency can be varied by varying Vin.

But since I couldn't find an exact example for the input I'm not sure what I'm doing is correct for the input.

Is it proper to just apply DC voltage Vin to pin 8 as in my case?(What confuses me is that the sweep voltage is shown between the V+ and pin 8).
Okay in my case it is inversely proportional i.e. the output freq. is increasing with Vin decreasing which is not a problem for me but I'm wondering whether it is fine to use it this way.
In almost all examples there is a resistor between pin 12 and V-. But in my case I get the least distortion when I connect pin 12 to V- directly. Indeed whenever I introduce any resistor between 0 to 100k sine wave gets distorted.

Again since it is counter to examples I'm wondering is it  proper to use this pin without resistor and directly connecting to V-?
How can it be known how much current would pin 8 sink at 15 V DV? It is because of I supply lets say 15 V to the pin 8 through an opamp, the opamp might not source enough current if "pin 8 input impedance" is low,

Note: I have also came up with this document but couldn't find any answer to my doubts.


texts:
I am trying to sample sinusoid signals using AD7928, which is a 1 MSPS ADC. It is connected to an Altera Cyclone V FPGA, and runs at 20 MHz master clock. Data rate is 1.25 MHz and that's due to the fact that the ADC outputs a new sample every 16 cycles. Using SignalTap Logic Analyser, I monitor the output of the ADC, and it is clocked with the same data rate frequency (1.25 MHz) to meet Nyquist criteria. Input is a 440 Khz sine signal (under Nyquist's frequency 500 KHz), however, it looks distorted in SignalTap, figure below depicts it.

If I apply a higher frequency signal like 1019 KHz, it looks like a regular sinusoid signal.

As I change the frequency, signal dilates and contracts.

What do you think is the reason?


texts:
I need some help identifying these SMD . 23ALB7  with 6 pins.

They are found on a laptop TOSHIBA SATELITE L650.


texts:
Just want to make sure that I understand how the current sense resistor works in this circuit:

Basically, we want to monitor the current through the primary side of the transformer, so we know when to switch the MOSFET on and off.
Rcs creates a voltage based on the primary side current and the value of the resistor (V = IR), and the CS pin of the flyback controller measures that voltage.
We have to choose an exceptionally low value for Rcs because we need to be able to generate a high enough current through the primary winding to achieve the output voltage that we desire.
What I do not understand is why can't we just monitor the current directly? Why do we need Rcs at all?


texts: STM32F769 Change/Update IP Address Issue

texts:
I have a problem. I am working on STM32F769 TCP/IP ethernet protocol. I can send data to arm and send data back to pc / terminal . Problem is that I don't know which function or functions need to change IP address of device. I can get 4 byte data when user send.
Thanks.


texts: What is the Global Descriptor Table memory type?

texts:
What type of memory type is used for the Global Descriptor Table in an Intel Core 2 CPU?

Is it just EEPROM or does the CPU normally use another type of NVRAM?


texts: 4G LTE: Is it possible to make a high gain antenna that resonates well for two frequencies, where one isn't a close harmonic of the other?

texts:
I want a high gain antenna for Verizon LTE data to my JetPack 7730L but don't really see one as high as say this MIMO parabolic antenna that's probably design for 2.4 GHz WiFi. From all I know it's only possible to make an antenna that's turned well to one frequency but could also work at harmonics of that frequency like 1/4, 1/2, 5/8 (not sure of the gains for these).

For instance a 1/2 wavelength antenna for 2 GHz could also double as a 1/4 wavelength antenna for 1 GHz based on the equation...

\$\lambda =\frac{c}{f}\$

But is it possible to create an antenna that is tuned to a different frequency outside of the near natural harmonics? Like say

These frequencies I am interested... all the Verizon Wireless bands and I'm not sure if it's helpful at all the have the fraction of wavelength... but that's just the thought that first came to mind.

 Frequency   Fraction of Wavelength
-----------|------------------------
 2100 MHz             1.00
 1900 MHz             0.90
 1700 MHz             0.81
  850 MHz             0.40
  700 MHz             0.33

PS: I'm not sure if all these frequencies are used for Verizon Wireless 4G LTE data, but at least these are frequencies they use in general.


texts: Tool to test analog phone line connection quality

texts:
An ancillary job of mine is to support an analog phone line for our credit card machine. From time to time AT&T changes out hardware in the core which causes the machine's modem to not connect over the phone line.

Testing the line by plugging in an anlog phone is not rigorous enough. Often the phone will have a dial tone and place calls, but there is too much noise for the modem.

I am looking for a hardware tool I can plug into the RJ-11 jack which will evaluate the line quality. I have a budget of up to a couple hundred dollars if necessary. I need to know if the line quality is degraded and unable to carry a modem connection.

I appreciate any recommendations of a tool to do this job.


texts:
If a ideal inductor of inductance L is connected to dc voltage say,V. How does the current change across it?
I tried writing kirchoff's law

\$ V = L \cdot \dfrac{di}{dt} \$

I got

\$ i (t) = i(at \text{ } t=0) + \dfrac{V \cdot t}{L} \$

is my try correct?


texts: Is there a good place for human help identifying parts?

texts:
I have a part that I have not seen before, and that has no identifying information on it that I'm trying to replace in a piece of critical equipment.  Being a semi-common design, and being a non-semiconductor, I thought it would be fairly easy to find (it's a stacked USB-A to through-hole connector), but because of a unique stair-step outline at the rear of the part, it turns out to not be very common.  I have been over and over the common distributor sites (Digikey, Mouser, Allied, Newark) but can't find a replacement.
Is there a place on the web, maybe not here, but maybe a related stack exchange, or another site, where one could find assistance from other people with potentially identifying unknown components by image alone?


texts:
Preamble
Due to the super-secret nature of commercial GPU, I didn't find anything interesting yet.The best thing I can do is asking that to someone which has more experience than me (everyone). It's quite a huge question, I hope it'll fit the rules.
Also because GPU aren't directly related to this network, but there are many others, so I tried.
Because quotes parallel processing and because older GPUs (from retro console and other) uses architectures very different from the modern one, this question is about recent GPUs (the ones supporting GPGPU). To semplify the question, think about NVidia and AMD ones.
Question
My idea of GPU is quite confusing: I know it's a particular piece of hardware, which primary components are tons of cores working parallel, used to elaborate images or general signal, and a quite high amount of RAM used to buffer thing and make elaboration faster
Too much "Wikipedia" for me
These are some of my thesis and information I got (HELP section says to share your research), feel free to confute them:
Point 1: What happens when data send form the CPU enter inside the GPU?

You can't write GPU programs in it own assembly: a program written in, for example, Cuda is PTX, an intermediate language that is elaborate (compiled? interpretated?) internally by the GPU. If there is an internal language, a sort of assembly (maybe a microcode like architecture?), it is super-secret
There are no official open source drivers. May you want to find something reversing the drivers? Good luck. But there is a good news: some GPU has a quite good doc.

Point 2: Pipeline and shaders
What is a shader? Difficoult to answer. But someone tried. However, shader should be a piece of software that is elaborate by the GPU to render all the beauty 3D scenes. There are more type of shaders, each one is elaborate in a particular step of the GPU pipeline.
But what's that pipeline? Seems to be a sequence of step that goes from receving input from the cpu to the render in output. DirectX and OpenGl should give an astraction of that implementation, but each model/family has a different implementation? Is that a super-secret or it's freely shared with us, poor community? (Or maybe with NDA?)
Point 3: Metaphore
I want to avoid something like "This question is too long. We hate you. Question closed" Probably you are right, but I still try to save my question.
The faster way to answer this question is making an example: can the GPU look like another piece of hardware? Maybe one not conceptually sophisticated.
In my opinion, it can be viewed partially like an FPGA because of the parallel execution. Many cores = many IP = FPGA? Maybe. But obviously that is a completely different hardware, much more flexible and suitable for different scenarios.
Can you make other examples? Any help is really appreciated from the bottom of my hearth. If you want, you can also post any resource-book-readings you think it's related to the topic. I really like to go in depth


texts: Transistors why does increasing base current increase collector current?

texts:
I am new to this area so please can you keep your answers simple, thanks.

From what I know for an npn transistor in the common-emitter connection the base-emitter junction is in the forward bias and the base-collector junction in the reverse. Electrons flow from the emitter to the base where some leave the base as they recombine with holes, forming the collector current and some pass into the collector forming the collector current. If we increase the base current we get an increase in collector current, why is this?

My first thought would be that the collector current would decrease since more electrons are are flowing into the base electrode rather then the collector electrode. I really am at a loss of how to explain this.


texts: How to step down analog sensor signal voltage using voltage divider

texts:
I am trying to work out how to use a voltage divider to step down the signals from an analog sensor, powered by a standalone XBee.

The XBee provides 3.3V power to the sensor, which has 3.3-5.5V operating voltage. The output voltage of the sensor is 0-3.0V. This info is taken from the sensor datasheet.

I'm using an XBee Pro S3B. The S3B ADCs have a configurable reference voltage of either 2.5V or 1.25V. So I need to step down the 3V output signal from the sensor to 2.5V for the ADC using a voltage divider circuit (any alternative ideas are more than welcome). However I'm finding that only tiny voltages are being sent to the ADC pin when everything is hooked up as shown below.

When I disconnect the sensor from the VD circuit and test with straight 3.3V VDC, I get ~2.7V out as expected. So it seems connecting to the sensor is the problem.

Here's my setup. The resistors are 10Ω and 51Ω. The sensor shown is a resistive soil moisture sensor for illustration's sake, but I'm using this capacitive sensor instead.

Does anybody have ideas on how I can get a correctly stepped-down voltage out of this sensor? Thanks!


texts: How to sort Pin 1 (Passive) of 'xx' component is not driven - KiCad ERC check

texts:
In DRC KiCad (4.0.7, release biuld), after doing ERC, there is error: 'ErrType(3): Pin connected to some other pins but no pin to drive it. Pin 1 (Passive) of component C5 is not driven (Net 49).'

How to solve this issue?

In my case C5 is connected to Atmega32 AREF pin.


texts: Obtaining printed serial number of MIFARE NFC card

texts:
I am working on a project that involves MIFARE 1Kclassic cards. The goal is simply to be able to identify each card when scanned based on the printed number on the front of the card.
For example, on one card the printed S/N reads: 0002868279
But the UID for this card is: 16:44:E0:43
Is there any relevance between these two values?
Or is it common for MIFARE cards to have unique numbers printed on the front that bear no relevance to the hardware UID?


texts:
I have a situation which I'm not sure how to handle. I've purchased an appliance from US. This appliance is powered by electric motor (175W) and then I realized I cannot use simple step-down converter because they usually convert 220v 50hz to 110v 50hz, but in electric motors the frequency matters. Of course, such voltage/frequency converters exist, but they usually in kW range industrial grade converters with price tag ten fold of the price of the appliance. So, I'm thinking about taking 220v 50Hz AC to 12v DC converter and connecting it to 12v DC to 110v 60Hz converter, like pure sine or something. Does it make sense? Would it work? is there any better solution which wouldnt break a bank?

In case my solution is good to go, how to calculate the wattage of each of parts I will use? For example, 175W it is nominal power draw of the motor, but it has spikes, so I guess, 300W output will be ok, maybe 350W. Then what wattage AC to DC I have to use for the DC to AC converter to produce 350W output given the power efficiency is not 100%?

EDIT001: The appliance is WorkSharp Ken Onion Edition Knife & Tool Sharpener, hope it helps


texts:
I have a new custom built PCB circuit incorporating an atmega256rfr2 chip. I really can't program the chip using AVRISP MK11 based programmer (Olimex brand). But it can program the Atmega328p DIP chip on breadboard.

Been trying for weeks with zero results. It writes "unable to enter programming mode". i am using Atmel Studio 7.

Connection is follows:

MOSI--------------->PDI(MOSI)
MISO--------------->PDO(MISO)
SCK---------------->SCK
RST---------------->RSTN

Help will be appreciated. Thanks in advance.


texts:
Assuming I have a working solar panel system, all the things such as inverter, charge controller and battery are in place.

The state of battery will obviously change, some times it will fully charged and sometimes it wont be fully charged depending on my usage.

Now, If I try to charge my laptop with this solar-panel-battery, Will the charging time of laptop be dependent on charging state of solar-panel-battery, that is will there be a change in the way laptop is being charged if solar-panel-battery is 80% charged or if it is 100% charged?


texts:
Staying within an op amp's specified output voltage range, how does a difference in output swing affect the op amp's noise applied to the output signal? Obviously by increasing gain, we amplify the op amp's injected noise as well, but in practical applications, is this a perfectly linear increase?

For context, I am looking at designing a transimpedance stage for the differential current-output DAC PCM1794A. At the output, it sources between 2.3mA and 10.1mA, with a center current "zero" of 6.2mA. I'd like to minimize added noise, and I will need two identical transimpedance stages to bring to a differential summer in order to receive a single-ended signal at the circuit's output (snip from the datasheet below).

Why would the reference schematic's designer not maximize the gain of the transimpedance stage? Conversely, why would it not be lower? From other posts and articles I've read (here for example), assuming identical noise figures from each op amp (which will never happen, but assume I at least plan to use identical op amps for all stages in my circuit), it seems like it would be best to try and form the circuit such that each amplifier's gain is the same to achieve the desired output voltage (in this case 4.5Vrms). To add to my confusion, there is another example in the datasheet that, among other things, replaces R3 with a 560-ohm and R5 with a 270-ohm (in addition to R4 and R6), negating the desire for a differential summer with input coefficients being 1.

Also, would there be any benefit to biasing the transimpedance stages such that the "zero" output of the DAC resulted in 0V at the output of the transimpedance stage? Seems to me that this would be unnecessary since both signals go through the differential summer together. I would also think that this would produce more noise as a result of deriving the bias voltage, but they do just this in TI Application Report SBOA237.

Thank you, I'm just trying to wrap my head around the "practical theory" here.


texts:
I have the following MOSFET driver circuits for high side P-Channel MOSFETS. The circuit works for supply voltages up to 20 volts. It gives some satisfactory results for it's range, but I would like for it to work up to 80 volts. Assuming I have selected a P-Channel MOSFET that can withstand the voltage, what considerations should be made to the driver? What ratings should I select for the transistors?

I want the circuit to only draw current when the gate is actually being charged and discharged. My current setup draws current when the gate is held low (on) indefinitely, which I would like to address, but am not quite sure how. The input for AH is 5v btw.


texts: UART Blocking Mode and Non-Blocking Mode

texts: I want to using RS485 communication between two or more device using stm32 + tranceivers, I need to request-response type communication so RS485 bus will have many data. Which one would make sense to use for a communication blocking mode or non-blocking mode, and why ? Which one is more healty for the systems running ?


texts: How to read from multiple channels of the ADC on an STM32F407?

texts:
I am working on a project wherein, I need to read the Analog outputs from 4 sources and convert them to a digital value using a single ADC module on the STM32F407 microcontroller. I want to sample the ADC values every 50ms and therefore have decided to use it in polling mode and have a timer Interrupt every 50ms to trigger the ADC reading. I am using the STM32 CubeMX software to generate initializations for me.

Here are the ADC initializations:

hadc1.Instance = ADC1;
hadc1.Init.ClockPrescaler = ADC_CLOCK_SYNC_PCLK_DIV2;
hadc1.Init.Resolution = ADC_RESOLUTION_12B;
hadc1.Init.ScanConvMode = DISABLE;
hadc1.Init.ContinuousConvMode = ENABLE;
hadc1.Init.DiscontinuousConvMode = DISABLE;
hadc1.Init.NbrOfDiscConversion = 0;
hadc1.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
hadc1.Init.ExternalTrigConv = ADC_EXTERNALTRIGCONV_T1_CC1;
hadc1.Init.DataAlign = ADC_DATAALIGN_RIGHT;
hadc1.Init.NbrOfConversion = 1;
hadc1.Init.DMAContinuousRequests = ENABLE;
hadc1.Init.EOCSelection = DISABLE;

And in my main function:

while (1)
{
/* USER CODE END WHILE */
g_ADCValue = HAL_ADC_GetValue(&hadc1);
}

Now this works when I have one ADC channel enabled, but how do I read from more than 1 channel at the same time? How does the GetValue() function return the ADC value of a certain channel? Also I know I do not want to use ADC interrupts for this as I want to sample the ADC at particular intervals of time (every 50 ms), but should I be using DMA? If so, how would I do that?

Thank you very much for all your help!


texts: How do I make a small sample solar cell?

texts: I want to know how to make a sample solar cell which can generate power of a very small magnitude.  What material is required and how would I assemble it to make a simple solar cell?


texts: Why need more aperatures in microphone array?

texts:
I am tring to achieve delay sum beamforming with microphone array, for that I bought playstation eye camera which has 4 microphones in it.

For locationg the angle of the sound I need to find exact time delay which gives the max output.

Now I take the FFT of the data from channels and apply cross correlation on them.I found the time delay between two channels.  But I realize  I can do this with just two channels,I don't see the point of calculating the same value with other channels.

My question is I can calculate the time delay with data from channel 1 and 2 , what is the benefit of having more than two channels in delay sum beamforming?


texts:
I have a display that has six white LEDs in parallel (common anode) as backlight.

The LEDs' forward voltage is 3.2V, the current per LED is 20mA, so 120mA in total.

The available voltages in the circuit are 3.3V and 5V.

Of course I could use 5V and a serial resistor for every LED, but that is not very efficient, and the device which contains the display is supplied by a battery.

PWM control should also be possible...

Most small LED boost driver ICs need their LEDs in series.
Using small DC-DC converter to create a voltage between 3.3V and 5V, and smaller resistors would be better, but PWM should probably be done with a MOSFET, not with the EN pin of the DC-DC converter.

What is the best solution to power the parallel LEDs?


texts: Please explain negative bias and "a stronger field to sweep carriers out of depletion"

texts:
I want to understand what a comment means, and I couldn't ask in a comment. In this question, someone asked why use an op-amp with a photodiode rather than just a resistor. The answers and comments were great, and in a particular a comment by @john-doty said, "For further improvement, put negative bias on the diode's anode. This reduces the capacitance while providing a stronger field to sweep carriers out of the depletion, for better speed and linearity. – John Doty Jul 17 at 14:52"
Would someone please expand on that? Specifically, what changes to the circuit schematic does this imply, and what does "... providing a stronger field to sweep carriers out of the depletion ..." mean? I have taken college physics, so please dig right in. I want to understand what's going on so that I can fine-tune with less guessing.
Thank you!
The circuit in discussion:


texts: What does quiescent power mean and how I can find how much current the chip consume

texts:
I was checking this datasheet about a multiplexer. It says:

  This device handles rail-to-rail analog signals and consumes less than
  4μW of quiescent power.

Checking the tables below it says that Off-Leakage Current is about a couple of nA.

Because of I will use it with 3.3V and an Arduino to control the digitals A0 AI EN, how I know how much the chip consumes and what does quiescent power mean?


texts: Cheap easy way to test for RF power output

texts:
I have a need to remotely confirm output power on a radio.  However I'm poor and want to do cheaply.
All I need is a confirmation that it's pumping out in excess of 75 Watts and then have a contact closure that indicates it worked.

When I search online I usually get an over wroked solution that gives me a display of the power out and of course they cost a small fortune.

What could I make or buy that would just sense that the RF output has gone from nothing to >75 Watts?

One solution I came up with was a current sensor that would trigger when the radio starts pulling huge current but I'd rather trigger on the RF out.

Any and all ideas would be great!

Edit:  VHF frequency 152-162MHz

I guess I left stuff out, sorry about that.
Yes needs to be left attached.  The radio is part of a paging system and I want to know its going off.
I can't distrupt the transmission.  A Bird wattmeter does some sort of coupling with the coax like the diode detector idea.  However the parts for a Bird cost an arm & leg and for that much cash I might as well just pay the full price and have the full meal deal.


texts:
This question was put on hold, citing the fact that any answer would be based on opinion. I can't really argue that point, but I do believe that in this case the point is irrelevant. I am asking for basic information, where to start from. Because different people started from different locations the answers will be based on opinion.

However, I feel that the "primarily based on opinion" rule exists to discourage trolls and avoid arguments. Neither of those points are the case here. The answer to my question is advice; it is opinion. Not to be overly dramatic, but putting this question on hold, without suggesting another source for the information, is stifling the search for knowledge. It is essentially saying that "you need to already know how things work" to participate.

Please reconsider.

I have been a programmer since the early days of the PC. I have now decided that isn't nerdy enough, so I am teaching myself circuit design.

I have picked up a few kits, and have gotten pretty good at soldering, following directions and reading a schematic. But, I'm not picking up basics I need to be able to design my own circuits. I have hit both Google and YouTube looking for starter tutorials but they miss the sweet spot. They are either assuming complete ignorance describe what the basic components do, and spend no time describing how they work together. Or, they assume you already grok the topic and start soldering things, again, without any description of how and why.

I am aware of "The Art of Electronics" and it is on my list to pick up when the new edition hits hater this year. Collin Cunningham did a great little series in YouTube for make magazine. Unfortunately he only did a couple of dozen videos and they mostly stopped short of explaining how things worked together. In addition to sound references such as TAoE I am also on the hunt for a video channel to pick up where Collin left off.

The goal is to be able to sit down and design a circuit that brings my idea to life the same way that I can sit down with a compiler and write a program that brings my ideas to life.

Here is what I think I need:

i need to understand how the components interact. Book, video channel or website, any source of info would be good. However since this isn't my day gig, a video channel would be ideal. I need to know when you add a LED
to a circuit how do you know what resister you need to use to keep
from blowing it out (this is asking a deeper question then pointing
me at a website with a LED calculator). How do you know when you
need a capacitor, transistor, resistor, diode, or any other
component. I need the basics, but not the very basics. I know what
the components do, just not how they dance together.
Parts. Where do I get cheap parts en-mass,  what would be a good selection to start
out with, and does anyone sell a kit like that (hundreds to start, not dozens). I know ebay is a good source, but what should I pick up
as a good starting selection?


texts: Switching a Step Up Converter with Mosfet

texts:
Im trying to switch this common converter:http://www.ebay.com.au/itm/281807832840?_trksid=p2060353.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

With: https://www.fairchildsemi.com/datasheets/2N/2N7000.pdf

Connected direct to battery it works fine and does not pull a great deal of current.

But when switched with a mosfet, loads, such as an LED, cause the voltage coming out and into the converter to drop and the current consumed by the converter to increase to compensate. (I figure with these things the larger the voltage gap to get up to 5v the greater the current it pulls)

The reason I need to switch (eventually with a micro) is to get around its idle current because running off batteries.

Direct to batteries, measurement at Step-Up:

No load: 3.7mA, inV: 2.48v outV: 4.98v
With LED: 7.4mA, inV: 2.48v outV: 4.98v

Via Mosfet:

No Load: inV: 24mA, inV: 0.38v outV: 4.34v
With an LED: 24.4mA, inV: 0.36v outV: 3.44v

As far as i can tell this mosfet should be suitable for this sort of voltage and current range. But I am new to mosfet, so not sure how to work out what the problem is.

output voltage of mosfet at turn on

Eventually I want to drive a 5V sensor that pulls more current than an led ~ 10mA idle and a 3v3 voltage regulator that drives a rf module (~20mA). But the more load i add the worse this situation gets very quickly to the point that the step up is pulling like 80mA and only putting out about 3V.

simulate this circuit – Schematic created using CircuitLab

**Update" From the data sheet would this be the graph of interest to me, showing that with the voltage range i have i cant pull much current ?


texts: Different options when generating gerber/ drill files after PCB designing/ layout

texts:
I am generating gerber files for manufacturing of my PCB. I have completed my PCB layout.
When generating gerber files/ drill files I am getting several options. What are they? I have highlighted the options in below image in red boxes. See below image:

I would appreciate answers explaining any/some/all of the above options (highlighted in 4 red boxes). Let me know if any more clarification is needed. I am using KiCAD.


texts: Small piezo buzzer with low voltage, low current

texts:
I am designing a board which communicate wirelessly with a smart phone. When I send a specific command, I want it to sound an alarm to the user, making it able to be found when lost. My board runs on a coin cell 3V battery, which has a current drain which should not go above 15mA. The sound unit should not exceed 10mm in diameter. I struggle to find any speakers or buzzers which can operate within these conditions, so my question is:

What methods and/or components can be used with 3V, max 15mA circuit to notify a user using an audio signal around 70dB SPL?


texts: Voltage Mode Buck Converter Output Voltage

texts:
I am trying to design a simple buck converter. But it doesn't work as expected. Output voltage should be 19V but it is very close to input with value 48.5V. Also there is a problem with pwm generator.
If anyone could help,I will appreciate for it.Thanks.

With this configuration pwm generator (comparator LT1001) doesn't work well, but seperately it works.

And the Output:

feedback goes through differential opamp:


texts: Interfacing 16-bit SRAM/MRAM with Arduino Mega

texts:
I a looking to interface a MR2A16A 4Mb 16-bit MRAM with an Arduino Mega. I am new to interfacing with memory chips and would like some advice from someone more experienced than myself. I am not looking for speed or a permanent implementation, I am just wanting to be able to read and write to the chip for testing purposes.

From the datasheet it seems as the MRAM uses the exact same timings and interface as a similar SRAM chip.  I looked at the pinouts and I should have enough for the 18 address pins and the 16 data pins of the MRAM plus the 5 control pins.

Please let me know if :

This is possible.
What advice/tips I need to proceed
I would need any additional circuity to interface the chip?

Thank you.


texts: I am working on making a flyback driver with a 555 timer. The only part I need is a MOSFET power transistor. I am wondering is it possible to substitute a triode vaccum tube (14GT8) for the MOSFET?


texts:
I've been playing around with some LF RFID tags and want to create a EM powered sensor tag (ie, a normal passive tag). Ideally the tag should power up for a couple of mS, take a sensor reading (which requires more power than I got out of the test circuit), send it to the reader and power down.

What I've found was that the capacitor in the parallel LC tuned circuit affects the power delivered to the tag considerably. Even when the capacitance was changed to move the resonant frequency away from the carrier, very little power was delivered to the tag as the impedance seen by the reader was fairly high (opposed to extremely high when in place).

When the capacitor was removed from the parallel LC circuit completely I got the required amount of power out since it was acting just like a transformer. My question is this, how do I switch a capacitor out of a parallel LC circuit completely? Since the current and voltage in the LC circuit changes polarity I haven't been able to use a simple transistor. Any ideas?

Perhaps I should clarify, RFID tags work something like this:

With the FET switch not engaged, the impedance seen by the reader is high and only a little power is transferred to the tag, this is enough to power most tags however. With the switch engaged, the LC stage moves away from resonance and even less power is delivered to the tag. By switching between these two stages data can be transferred.

Instead of using the FET switch I want to switch in and out the capacitor. This would have one state where the tag acted like a transformer, delivering maximum power to the micro, and another stage where it presented a maximum impedance to the reader and little power was delivered. This would enable the use of sensors that requires more power.

I either have to change the capacitance by a large amount to make it fall out of resonance completely and present a low impedance to the reader, or switch out the capacitor, which would work better. Due to the polarity of the LC circuit I haven't been able to come up with a way of switching out the capacitor. Any ideas?


texts:
I am confused about the photodiode current voltage diagram.

According to this diagram the current at zero bias is down->reverse current.How is that even possible?
At photovoltaic mode isnt the current forward?


texts: Help me calculate spectral irradiance of an LED from a LED spec sheet

texts:
I am not a physicist or engineer, and that is why I turn to you for help. This is a new post from an old topic. This is a repost because important information was absent from my first post on this topic. I have an infrared LED that emits light at 940 nm, and the manufacturer claims it's about 1000 mW/sr. While the light is not visible to human eyes, light of this wavelength can damage human eyes if it is strong enough. The following equation can help me determine if this LED represents a hazard. I recognize that the LED is probably not a hazard but I need science to back that statement.

Equation One:

  E_IR_only (W/m^2) = SUM (from 770 nm to 3000 nm) E_lambda x delta_lambda

Equation One, Definition of terms

  E_IR_only = irradiance in W/m^2;
  E_lambda = spectral irradiance (W * m^-2 * um^-1);
  delta_lambda = spectral bandwidth (um);

  Note: manufacturer reported spectral bandwidth = 30 nm.

Step One:

I first calculated the energy of a single photon of light at 940 nm. I am not being careful with my significant figures...apologies to the community.

  E940 = hc/lambda = (6.626e-34 Js)(2.998e8 m/s)/(9.4e-7 m) = 2.113e-19 J

Step Two:

From the spec sheet I believe the radiant power of this LED is 40 mW or 0.04 W, and from that I can calculate the flux, phi.

  phi = radiant power/E940 = 0.04 W / 2.113e-19 J = 1.893e17 photons/m^2

Step Three:

The next step is where I get confused. Every source of information I can find says that spectral irradiance (E_lambda from Equation One) is defined as:

  F_lambda (W * m^-2 * um^-1) = phi * E940 * (1/delta_lambda)

In my case that would simplify to F(940) = radiant power / delta_lambda.

  F(940 nm) = 0.04 W / 3e-8 m ~ 1.33e6 W m^-3 or 1.3 W * m^-2 * um^-1.

Question:

I feel my calculation is incorrect because if I apply the equation I need, E_IR_only = E_lamba x delta_lambda = 1.3 x 30 nm I just end up with radiant power again, or 0.04 W. Clearly, 0.04 W is not SOME_NUMBER W/m^2. Am I supposed to used the spectral bandwidth (delta_lambda, 30 nm) in the calculation for spectral irradiance, or am I supposed to use the specified wavelength (940 nm)?

I've made an error somewhere, and I keep going in mathematical circles. Any help the community can provide is very welcome.


texts: Does air flowing over a bulb affect the amount of lumens produced?

texts:
If a bulb is cooled by air flowing over it, would that change the way light is emitted?

I see contradicting evidence that air cooling bulbs changes how much light is emitted because the cooler air outside the bulb changes the chemical reaction temperature inside the bulb.

But then there are other sources stating that inside the bulb there is a vacuum that maintains a certain temperature, so it has nothing to do with its surroundings (obviously to an extent, not like we're in the Arctic).


texts: Successive Detection Logarithmic Amplifier

texts:
let's consider this logarithmic Amplifier:

I do not understand why at the terminal LOG OUTPUT there is a current which is proportional to log(Vinput). The current flowing on each diode is equal proportional to exp(-qVouti/KT), where Vouti is the output voltage of each stage.

Each stage is a limiting amplifier: it has a transfer function like this one:

References: https://www.analog.com/media/en/training-seminars/tutorials/MT-078.pdf


texts: Where can I find the EEPROM memory in STM32 Nucleo F401RE?

texts:
I'm looking for to store and read values on STM32 Nucleo F401RE and I need to find which sector and begin address to start with.

I did watch a tutorial how to do, but he's using another STM32 board.
https://www.youtube.com/watch?v=RmRRPtxhCZE&t=500s

So I begun to download the data sheet
https://www.st.com/resource/en/datasheet/stm32f401re.pdf

And now I found this in chapter 5. Can anyone tell me which is the EEPROM sector and the start memory?


texts: Audio playback design issues with WM8731

texts:
I am using WM8731 Audio Codec taking hints from the Audio Board PROTO with a 1 W Audio Power Amplifier LM4889 to drive a speaker from CUI INC: CDS-13138-SMT. The setup works but not as expected. I am using the recommended circuitry given in LM4889 Datasheet for high gain amplifier.

My application requires a speaker to output frequencies in 17 to 20 KHz. But when I pass a wave audio of pure 19 KHz(from here) to it, the speaker outputs a frequency at around 9KHz and 15 KHz.(Why?) The playback is slow too.(I tried playing a song. It ran in slow motion)(can't understand Why?)

(I am using Spectrum Analyzer. It shows the two peaks at 9 and 15). The whole setup is interfaced with Raspberry Pi through I2S.

I don't have much experience with audio applications. Is my approach wrong? Am I using a wrong speaker for my application? Can anyone provide any alternative? What all can be improved in the design? I am sorry if I come across as a complete noob.

Thank you.


texts: What does grey dots represent in Proteus and why I am getting those

texts:
I am using a 5 by 32 decoder to implement a certain sequential circuit. However I am getting strange results. Here is the Snapshot:

I don't understand why doesn't the decoder change its output when q0=1 as shown by the separate LED flashing alongside the main circuit. Instead, I am getting grey dots along q0 in the main circuit (as shown in the picture)  which I do not understand at all. This happens the instant I provide the clock to the Flip Flops, perhaps this has something to do with the undetermined states of the Flip Flops at initial stage.

Here q0 is the state of third Flip Flop from left and t2 t1 and t0 are separate combinatoric functions which depend on the outputs of the Decoder. I think their circuits are unnecessary in the context of this problem. If it helps debugging, I will be more than happy to attach those circuits as well.

PS: The ground in the first picture has nothing to do with the circuit.


texts: I2C and separate power source affects SDA signals

texts:
Despite the fact that I2C devices should be able to operate with different power sources I'm having problems with my setup. Specifically, it seems that when I have separate power sources the SDA signal becomes sloppier (as viewed by a scope).

I have an I2C sensor which includes an ADC. I've been getting suspicious readings so I reached out to the the manufacturer. He specifically pointed out that the voltage should be 3.35 - 3.45 as "that's what's used during calibration" (Vdd minimum, according to the datasheet, is 3.3v). This snesor hooked up to the I2C ports on a raspberry pi via a circuit board I made, a jack, about 3 inches of cable, another jack, and another circuit board. I measured the voltage at the sensor at 3.293v. Other than the suspicious readings, I've never had an issue communicating with the sensor. Definitely no I/O errors from the Pi.

Due to the manufacturer's advice, I want to test the sensor at 3.4v. The RPi is being powered from a dual adjustable buck converter, so I decided to set the 2nd output to 3.4v and connect GND and 3.4v directly from the converter to the sensor, and only connect SDA/SCL from the sensor to the RPi. I got a lot of communication issues from the software, and I found that the voltage was reading a little bit different than expected. I decided (possibly incorrectly) that this was due to floating grounds*, so I then wired the sensor's ground to the RPi and only the + 3.4v from the converter. The setup looks like this:

I'm continuing to get frequent I/O communication errors so decided to bring out my cheap scope. (Note that I'm a scope newbie with a cheap DS212, so take the following with healthy skepticism.)

When the sensor is wired directly to the Pi, including power and ground, the SDA signal looks reasonably straight with perpendicular lines and 90degree angles.

When I had the sensor Vdd wired to the buck's power output the SDA line was a bit sloppier. Less 90 degree angles, and an occasional blip. For what it's worth, Vdd looked stable on the scope.

I thought that maybe the cable I built to connect the sensor to both the RPi and the power supply might be bad, so I then disconnected the +3.4v wire from the buck converter and connected it directly to the RPi's 3.3v pin. After doing this the SDA signal looked clean again.

FWIW, the sensor has configurable pull-ups. I normally keep them disabled because the RPi has its own, but after seeing the SDA signal I tried enabling the sensor's pull-ups and it didn't make a difference.

So, what could be causing the sloppy SDA signal? How do I address it?
My long-term plan is to send 5V to the sensor board and then use an LDO to convert to 3.4v. Will this approach solve the problem I'm seeing?

*I measured a voltage difference between the Buck's output ground and the Pi's ground somewhere around 50mv.


texts:
I want to control shutdown pin of this IC MAX9920 using digital output of arduino.
https://datasheets.maximintegrated.com/en/ds/MAX9918-MAX9920.pdf
My question regards to this:
In the datasheet page 6 says shutdown input current max 10ua. So if digital output of arduino when is high is 5v, do I have to put a 600k or 800k between this pin and the ic shutdown pin?
I ask this for 2 reasons:
Because I don't want to damage ic when digital output pin of arduino is high.
To understand logic input current definition.


texts: How do i varying high voltage(80-100v) control using Arduino, PWM and Mosfet?

texts: How can I control(Varying) high voltage (80-100v) using PWM and MOSFET? Basically, I want to control the LED light's brightness using Arduino which generates the PWM signal and control MOSFET.


texts: Integrating an Altair module with an Arduino

texts:
As a disclaimer, I have experience with Arduinos and Raspberry Pis, but I know embarrassingly little about electrical engineering and anything beyond the basics. Most of my previous projects consisted of attaching/soldering pretty big high-level components rather than tinkering with the small pieces.

With that being said, I am working on a new DIY project: A small LTE-M-connected device that, when pinged, turns an LED on or off. I have been researching LTE-M modules and was impressed by this one by Altair.

However, I am confused about how to integrate it in terms of hardware and software into a simple Arduino. I am aware of other options such as LTE shields or modules built into an Arduino, but I am curious about using this module in particular, in part for its tiny size.

I couldn't find any documentation online and was wondering if I'm missing something pretty basic about how this kind of stuff is done. Is there something simple I am missing or anywhere I could find guidance on how to use this module?


texts: Replace 12V 5A power supply with battery

texts:
I am buying a rgb led strip with the following technical details:

Voltage: 12 volts
Wattage: 60 watts

I want to connect this strip to a battery and don't know what will be the right one. I need the battery to last for 2 hours.

I been doing research and this are my assumptions based on what I have researched. Please let me know if I am wrong.

I know that volts * amp-hour = watt-hour If I plot the technical details into the formula then I know that I will be needing 5 amps per hour.
I now need a battery of 12 volts that can output 5 amps per hour. When looking into the internet I see a lot the term Ah which means amps per hour. Based on this needs I found this battery: Elk ELK-1280 12V 8Ah Sealed Lead Acid Battery.

  I read that if a battery has a capacity of 2Ah then if you discharge
  it at 2 amps per hour it will drain in one hour. If you discharge that
  same battery at 1 amps per hour (half of that) then it will last
  twice. If you discharge it at 4 amps per hour then it will last 30
  minutes.

I assume that 8Ah means that if the battery where to use 8 amps in an hour it will drain in that hour. But because I will be using 5 instead of 8 then I know that I will be able to have the battery last longer about 1.4 hours.

All the batteries with this capacity that I am looking for are often big and heavy. Then I came across Hiyadeal Portable 12V 9800mAh Li-ion Rechargeable Battery Pack. That battery is only 1 pound! That battery claims to deliver 9800mAh or 9.8 Amps per hour. That means that if I where to use this battery because I only need 5 amps then it will last for about 2 hours?


texts: Using an internal pull-down resistor on a microcontroller

texts:
I am using an STM32 microcontroller.

If I configure a pin as input with a pull-down resistor for use with a button, do I also need to put a resistor between the input pin and VDD?


texts: Why do we assign our outputs to signals first in VHDL?

texts:
I saw in many VHDL codes that data/control outputs are first assigned to signals and then to output ports, and not instantly to the output ports.

I'll give an example:

entity ex is
port (clk, rst : in std_logic;
      ....
      data_out : out std_logic);
end entity;

Architecture ex of ex is
signal data_out_sig : std_logic;
Begin
    process(clk,rst)
    begin
       ....
       data_out_sig <= some_data;
       ....
    end process;
data_out <= data_out_sig;
End Architecture;

My question is, why do we not assign some_data instantly to the data_out port? Why does it "have to go through" the signal data_out_sig?
Does this have anything to do with synthesis? Is it common practice?

Thanks!


texts: Difference in cut-off point when powering camera from 24v output vs 14.4v output

texts:
I work in the film industry and my question relates to powering our cameras.

Our cameras are generally powered by block batteries that provide either 24v or 14v power - an example here (VCLX). Some cameras only accept 14v whereas others accept 14v and 24v power. The Arri Alexa Mini is a common camera that accepts both (Alexa Mini)

My questions is this; when powering from 14v a full battery will generally show on the cameras as 16V and the common cut off point for changing the battery is about 12.5v (varies depending on exact camera and configuration).

However when power the same camera with the same battery from the 24v output the general reading from a fresh battery is approximately 26v, the common cut off point is about 21.5v. Why is this?

Why for example can you not run the battery down to 12.5v when powering from 24v?

As is probably evident, my understanding of electronics and power is basic and I'm trying to improve it.


texts:
I want 4 bit digital input for presetting of counter 74ls192.How can I do such task using Analog to digital converter? Is there any specific IC available for 4 bits ADC? Or do i need to design ADC using comparator and resistors?
THANK YOU!


texts: What are the metallic loops on the sides of a connector for?

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I'm designing a device that involves the 24-pin GPIB / IEEE-488 connector interface.
I’m trying to find the ideal panel-mount female receptacle, but I'm not fully confident I'm even sure what I'm looking for because the socket puzzles me.

I see a lot of receptacles of this and similar kinds, that feature these metallic loops on the sides that I believe are called spring-locks. What are they for?

I failed to find any assembly guides or example images where I'd see those loops in action.

Here's a typical example:


texts: Mosfet Td(on) and Td (off) must be equal

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I am having a mosfet CSD13380F3

The problem I am having is that I need the Td(off) and Td (on) to match. In the datasheet they are specified at 4ns and 11ns

I am trying to make the 2 timings equal (needed for my design)

While researching I have found a formula :

Ig = Q/t

where Q is the gate charge in Coulomb (nC from the data sheet) and t is the switching time (in ns if you use nC).

So my calculation is I=0.082A . Is this formula correct ?


texts: I'm trying to reduce the voltage of a power supply for a certain load without affecting the current the load draws. Since the op-amps I could find were not able to provide sufficient current, I added a NPN transistor to the output of the op amp as can be seen in the figure below. I simulated the circuit and it worked perfectly. Would such a circuit function as desired in practice?


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I'm doing a project with an Arduino.

I read a voltage from a tachometer connected to a generator.

The nominal max output is 21V at 1000 rpm. The generator is managed so that the maximum tachometer output is 2.5V maximum. Therefore the signal voltage should NORMALLY be bounded from -2.5V to 2.5V, depending on the rotating direction.

But, as I said, I can have a spike and I want to prevent the Arduino's ADC converter from dealing with such a large voltage.

Here are some over-signal that I want to saturate:

Also everything should be translated to be within 0-5V:

So, summarizing, I need to clip the signal and then add 2.5V to it.

Searching online, I found some solutions using photo-couplers, but they address only half of my issue.


texts:
I need a tiny oscillator circuit for testing an application. Now I haven't much experience in creating oscillators so I would like to use this Collpits-circuit:

I only need the carrier wave so I deleted the parts needed for modulation (I hope):

So I want to ask, if this is ok and might be oscillate?


texts: MOSFET on condition - Relationship between drain-gate voltage and drain-source voltage?

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I am trying to learn the relationship between drain-gate (VDG) voltage and drain-source (VDS)voltage?
From one of the QA readings in StackE, I understand that drain-gate voltage is less than drain-source voltage at MOSFET on condition. I am not sure how is it possible. At this on condition, drop across drain-source voltage would be so small. With that much of small drop, how (VDG) < (VDS) can be true?

Image is taken from here


texts:
I've been going through my third soldering iron this weekend. I already bought two and took one back to the shop. I'm in the middle of a project and the tips keep failing: the lead-free solder won't stick to the tip despite cleaning them with sponge, metal sponge and tip cleaner/tiner. I bought the latest iron yesterday (25W Antex) and it was already useless after a few hours. I don't know if I should return this one again? What am I doing wrong? I can't keep buying soldering irons every day... I use to have one that lasted for years and the tip was usable even after months.

edit: when using the tip cleaner, blobs of solder form on the tip like pearls. In other words, nothing will stick to it.


texts: How to meassure a high frequency dirty current?

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I'm interested in a way to accurately (about 10 % accuracy) meassure a sinusoidal current that has a 25 kHz frequency and has A LOT of higher harmonics. Voltage is unknown but is supposed to be around 300 V.

What instrument can I use?


texts:
I found a couple of old battery packs from an RC boat.

when measured using a multimeter they currently have a voltage between 5V and 6V.

is there any way to find out what type they are (NiMH, NiCd, etc.)?

What would be the charging voltage for them?


texts: I have broken open a few circuits of some electronics (DVD player, handheld game device) and I can see the microcontrollers in them. However, I have no idea how they get their programs onto them! There is no micro usb or usb plug anywhere on them! How would they have gotten their program onto there?


texts: I am working with automation using pH and EC sensors. Both are of 4-20mA communication standard. When at a time single sensor is placed in liquid(in 1000 litre tank) then everything works fine (correct value is given). But when both sensors are placed in liquid and reading is taken simultaneously from both sensors then value is unacceptable (large variation as compared to actual result). Both sensors are supplied power (24V DC) from single point and also grounded at common point. What is wrong when both sensors are placed in same liquid ?


texts:
Im working on a AC triac motor controller for universal motors
 For this I want to measure the motor current and the speed. For the speed the motor provides a tacho-signal. To isolate the measurement I will use a current sense transformer for the motor current before feeding the signal to the ADC. But what I am not sure about is wether an isolation of the tachometer signals are necessary. I do not have any documentation of the motor but i guess it uses a hall sensor for providing the tacho signal. So in my opinion no isolation is needed and I can feed the signal directly to the ADC but I want to make sure I am right.

So my question is:

What is your opinion? Do I need an Isolation for the tacho signals?

thanks in advance