texts:
I have a custom made PCB that has an AtMega328p MCU and 4 MLX90614 IR Sensors that are being interfaced by a TCA9548 I2C Multiplexer.

When I first got my hands on the board I had 10k pull-up resistors on all I2C lines but the output was unpredictable (sometimes it worked and others it didn't). I then swapped them all for 4.7k and at first everything worked fine. Upon reboot all hell broke loose.

If I run i2c_scanner from the Wire.h example the chip is detected at its correct address. But if I upload another sketch to scan each of the ports, the Wire.endTransmission() function hangs.
I have coneccted only ports 2-5 due to constraints in my design.

Does anyone have any idea what the problem might be ?

P.S. If it is not suitable for this thread, point me where I should post it


texts:
Anybody have some sure to work 4-bit interface C code for a PIC 18f4685 to Hitachi LCD 2-line display? I'm using a Northmicro proto board with a LCD module which is Hitachi 44780 compatible.
Using MPLab V8.x with C18 compiler.

Lower nibble on PORTB to D4-7

E:RA4

RS:RB4

RW:RB5

Backlight:RA5

I've looked all around Google land and have found stuff that should get me through the process but none have been written for my particular configuration. I've gone through and think I've tweaked them for my uses but I can't even get the LCD to initialize. Timing delays seem to be okay when I run it through the MPlabSim.

I've tried to use the libraries in the mcc18 src folder too but that didn't work either.

I'm looking for code that is known to work so I can troubleshoot if it's my crappy coding or the board. So far I've only been able to turn the backlight on and off but that doesn't really count as it's just a pin connected to a mosfet and has nothing to do with the onboard mcu of the LCD.

I've been at it for a few hours each day for the past week... 16 hours is a long time to spend on a silly project like this so I'd love it if I could get a helping hand with it please.

Thanks in advance.


texts: Circuits that take advantage of tolerances in components

texts:
Bit of a wordy question title...

I was trying to simulate an astable multivibrator the other night and the simulation refused to run. I eventually realised that because the simulation assumes perfect components, therefore there is no way for the multivibrator to get going hence the failure.

So this means that the reason the astable multivibrator works as it does is only because of manufacturing defects/tolerances of the components used (You can use different values of resistors etc., but assuming identical components are used).

Which leads to the question, are there any other circuits out there which incorporate the manufacturing tolerances of components in their operation?

Edit:

I've attached an image of an astable multivibrator. Whenever you look up any explanation, that explanation starts "Assume TR1 is OFF" or words to a similar effect.

Now I understand in the real world how this circuit starts and works, this question is not about that.

Assume that the circuit is initially powered up and all components are perfect and our traces have no resistance. This circuit would have no way to 'start'. Therefore, from this we can say this circuit only works they way it does because of imperfections that exist.

What my question is: Are there any other circuits which only function due to imperfections?


texts: Laplace transform rotational mechanical system

texts: I have a system with an input torque Te and output angular velocities w1 and w2. I have defined the outputs relative to the system however cannot seem to work out how to find GM(s). omega2 is the output from velocity w2 (all shown below):


texts: Why no resistor is connected in open collector TTL logic?

texts:
What will happen if we connect it internally in IC itself?
Why do we need to manually connect it outside?
Is there any advantage of doing so?


texts: 8085; Why RET doesn't require a 6 T-states Fetch cycle?

texts:
The CALL instruction, requires 5 machine cycles, namely, OPCODE-FETCH, MEMORY READ, MEMORY READ, MEMORY WRITE, MEMORY WRITE. The OPCODE-FETCH cycle of CALL has 6 T-states to take care of the decrements of  the Stack Pointer.

RET instruction requires, 3 machine cycles, OPCODE-FETCH, MEMORY READ, MEMORY READ, even here, the microprocessor's got to increment the stack pointer twice, as before, to pop. But, the OPCODE-FETCH cycle only has 4 T-states, Why is that?

I've got a vague idea, as to why; in CALL and PUSH the SP has to be decremented first, unlike RET or POP. This first decrement alone is taken care in the last two T-states of FETCH cycle. But why would that require two T-states. Again, I'm really not sure about this. Kindly help.


texts: Approaches to a few thousand individually addressable widely dispersed LEDs

texts:
I'm trying to come up with the best design for a project requiring between 1000 and 5000 individually-addressable LEDs, not in a strip, grid, ribbon, pegboard, etc. configuration. There is a lot of information about LED strips and arrays, but those don't seem directly applicable to my project.

What I want to do is similar to a "pick to light" system seen in warehouses, if you're familiar with that. I will have a room with many storage locations (various sizes) in it. I will have software that keeps track of what is in those locations, and when a user searches for one (either to remove or add one), the LED above the bin will light.

I need to support having an arbitrary set of the LEDs on at any given time -- it's not just one at a time (though realistically I'd expect well under 1/4 would ever be on at once). The bins will range from 3 inches to several feet apart, and the room will be on the order of 15 feet square, with storage locations spread throughout.

Reliability, a nice clean installation and ease of setup are more important than cost. Of course, all things being equal, lower cost is better -- it's just not the top priority.


texts: Custom Jetson Nano Carrier Board 4A trace width connections

texts: Hi I'm designing a custom Jetson Nano Carrier Board according to Jetson_Nano_Carrier_Board_OrCAD_Schematics file. And as may you know, from DC Jack you can supply 5V 4A to the board. The problem is, trace width for 4A literally 50mil while rest of the connections are 6mil. So I try to keep it minimum as possible but according to this schematic file, which traces carry 4A and should be 50mil width? We assume VDD_5V_In carry 4A in here. We can't decide right now, I really need help thank you.


texts: Understanding the behaviour of a spectrum analyzer

texts:
I performed in the lab some experiments regarding a spectrum analyzer and I have a few questions about its behaviour. The analyzer used was this one

At first I had to determine the spectrum of a 4kHz sinusoidal function. I obtained the expected spectrum (one stripe at 4k). I chose a sweep velocity of 0.5s/div and pass-band filter bandwidth of 100 Hz. Now I then varied the velocity, coming to the conclusion that a velocity that was less than 0.5s/div would not produce the correct spectrum, but any slower velocity would do it. At the time I didn't fully understand what the bandpass filter bandwidth meant. I just tried 100 Hz and it worked, while 300 Hz would produce a spectrum with a not so narrow stripe and 30 Hz wouldn't work. After the lab I did some research and understood that even if ideally the bandwidth of the bandpass filter is as narrow as possible, it is limited by the sweep time. Therefore, my question is: if I had increased the sweep time (less velocity), would I be able to produce correct results with a narrower bandwidth? Also, is there a mathematical expression that relates this two?
Then I did the same work but with a rectangular pulse of 400 Hz, 20% duty-cycle. I had the same bandwidth but now with a sweep of 0.2s/div. This was the minimum sweep time I could define and again, 30 Hz bandwidth still not works. My question is the same as before but with a new factor: how does the frequency of a signal relates to the sweep time. Because now I could define a sweep time smaller than my previous case, so my guess is that obviously the frequency of the signal matters. A signal with a smaller (fundamental) frequency can be swept with a bigger velocity. Again, is there any expression that relates this two?

Thanks in advance!


texts: HSpice Manuals/Handbooks. What does Þ mean in the equations?

texts:
I'm working with the HSPICE MOSFET Models Manual for a university project.
In some equations there's this \$Þ\$ symbol. For example from an equation regarding the Shichman-Hodges Model:
$$
W_\text{eff}=M\cdot \left( W_\text{scaled} \cdot WMLT + XW_\text{scaled} - 2 Þ \text{WD}_\text{scaled} \right)
$$
It appears in numerous equations. What does Þ mean there?


texts:
Forgive me if this is a noob question, this is my first MCU project.

After reading a few tutorials here and there, I've set up my MCU circuit and programmed a simple program in Keil μVision 4 and compiled it to HEX-80. However, I'm having problems with attempting to flash the program to the MCU.

Fundamentally I am kind of lost in how to connect the devices (PC->MCU) up. I was under the impression a simple USB->TTL (Serial)->MCU UART input was going to do it, but apparently not.

After 5 hours of search, I only found articles relating to AVR or PIC with no mention of anything remotely related to 8051. I understand the AT89S2051 has ISP functionality so I don't need a dedicated chip flash programmer. I also found that the MCU does have serial flash capabilities.

Can anyone point me in the right direction here?

Additional Details:

MCU: Atmel AT89S2051 (on breadboard)
PC: Win 7 x64 (Shouldn't matter but here it is anyway)
USB->TTL: PL2303HX (on-board chipset)

Wiring:

The RXD (TTL output) is wired to the TXD (Pin 3.1) of the UART
The TXD (TTL output) is wired to the RXD (Pin 3.0) of the UART
The GND (TTL output) is wired to the circuit ground
The +5V (TTL output) is wired to the circuit +5V
The +3.3V (TTL output) is not connected.

Programs I have tried (and failed to use):

AtmelISP
PonyProg
IspPgm


texts: What will be the time to charge a capacitor if there is no resistance?

texts:
A capacitor charges to 63% of the supply voltage that is charging it after one time period. After 5 time periods, a capacitor charges up to over 99% of its supply voltage. Therefore, it is safe to say that the time it takes for a capacitor to charge up to the supply voltage is 5 time constants.

Time for a Capacitor to Charge = 5RC

simulate this circuit – Schematic created using CircuitLab

Charging a Capacitor
One time constant,

$$\tau=RC=(3\text{k}\Omega)(1000\mu\text{F})=3\text{ seconds, }5 \times 3=15\text{ seconds}$$

So it takes the capacitor 15 seconds to charge up to near 9 volts.

I don't understand: what if I don't attach a resistance in between? What will be the time to charge the capacitor?


texts: Schneider EGX100 Gateway with AB PLC 5 series

texts:
I was investigating hooking up Modbus devices to an AllenBradley PLC 5/40E using a Schneider Electric EGX100 Ethernet gateway.

I can access the web server on the gateway device and monitor the slave devices. However, I couldn't figure out how to write values to the devices.

I would assume that this configuration is useful for monitoring only but that would sort of defeat the purpose. Any idea what I'm doing wrong or resources that I could look through?


texts: Direct frequency measurement with two hw timers

texts:
In what modes would I set two timers to directly measure frequency on an STM32F303 microcontroller?
Right now I set up one timer in ETR mode and gate it with systick software interrupts, but I would like to have a second timer gate it directly to increase the precision.


texts: Eagle - Router does not understand wire jumpers?

texts: I am using Eagle 7.2 - is there any setting which allows me to make Eagle understand wire jumpers? Neither the auto router nor the "show" button seems to be able to recognize that 2 wires connected by a wire-jumper have the same electrial potenial. Maybe I am missing any setting?


texts: USB-C How to detect an Audio Accessory with Charge Through

texts:
Given the scenario in the USB Type-C Specification Figure A-2 "Example 3.5mm to USB Type-C Adapter Supporting 500mA Charge-Through"....

How does the USB Type-C Receptacle know that a USB Type-C plug with audio-jack is connected, and still get charge through the VBUS?

According to the Figure 4-14 "Connection State Diagram: Sink with Accessory Support", a Sink will loop through the states Unattached.SNK and Unattached.Accessory until either a DFP Connection is detected or an Accessory Connection is detected. But what about the case where an Audio Accessory must be detected without losing power, this state machine doesn't seem to address such a scenario.

I am guessing that the Rd and the Ra would interfere with each other, getting an equivalent resistance smaller than Ra. In this case, how will VBUS still know that it needs to provide power to a sink and not an accessory? How will the receptacle enter the state to identify an accessory if its CC lines are being pulled up by Rp? Am I missing something?

Let me know if I can do anything to make this question clearer.


texts: Oscilloscope displays the derivative of the signal instead of the actual signal

texts:
I have a Tektronix TDS 2024B Oscilloscope. For some reason it displays the derivative of the signal. It cannot be the "Math" feature as it only computes addition or subtraction of 2 signals supplied through CH1 and CH2. I even tried to restore the factory settings but it didn't solve the issue either.

Do you have any suggestions on how to make it display the signal itself instead of the derivative?

The signal I am supplying: (A square wave with 25% duty cycle.)

The measured signal:

As suggested by Spehro Pefhany I connected the probe to probe comp and this is what I got:

Then I did the same with a different probe, and this is what I got:

I guess this result validates your hypothesis that the initial probe/cable is broken.

Andre, this is a picture of the initial probe I was using. I am not sure if it has any shielding at all as it is thinner than a regular coaxial cable. Let me know what you think.


texts:
The figure below is from Analog-Digital Interface Integrated Circuits course here (page 14/25).

I am curious about the red question in the picture below. From the Bode plot, the answer would be yes. But I don't think it is correct here. The professor may want to talk about something else.


texts: How can I calculate low and high frequency in my circuit? I have used an 8-ohm speaker.


texts: Area under voltage vs time discharge curve

texts: Will the area under a voltage vs. time graph of a battery discharge curve (with a constant current load) give the amp-hour capacity rating of the battery?


texts:
I was working on a PCB design and I am stuck on a question over SPI communication over different voltages.
I am using some 74HC595 and 74HC165 shift registers to expand number of GPOIs, running on 5v DC. This will be controlled by an STM32 (STM32F103R8T6), running on 3.3v DC, connected over SPI bus. I read in STM32 datasheet that the GPIOs are 5v tolerant.
I was wondering, if I can have different voltages across these GPIO expansion chips and the μCU. Or is there anything I need to take care of?
I saw similar questions, but in my case, the STM32 seems to be 5v tolerant:

controlling SPI devices using the Arduino - different voltages


texts: Inherent exploitability and power state machines

texts:
I'm working on understanding power state machines in regard to mobile computing devices. Most of the information on this subject seems to stem from this article. It's not particularly important to the question, but I figured I would provide some context of where my information was coming from.

Here's the question: With a power-state machine, the Ttr (total transition time) can be calculated as: Ttr=Ton,off + Toff,on where Ton,off is the time it takes to transition from on to a lesser power state.

To calculate the the total power consumed during a transition the formula:
Ptr = (Ton,off * Pon,off +Toff,on * Poff,on)/Ttr is used.

My first bit of confusion has to do with the Pon,off, Poff,on variables. I am assuming these are power on and off states accordingly, so for run->idle->run the power states would be 400 and 50?

The next part has to do with inherent exploitability. Given an idle period, using this formula will calculate the energy you will save: Es(T-idle) = (T-idle-Ttr)(Pon-Poff)+Ttr(Pon-Ptr)

So, using this formula for an idle time of 1000 micro seconds I got: Es(1000) = (1000-20)(400-50)+20(400-225). - The result of this if over 3.5 million mw, which is obviously absurd. Where am I going wrong here? It's difficult to find information on this subject outside of the paper I referenced, besides other sites - referencing that paper. Thanks!


texts: I know that the Arduino Nano can handle 12 volts, and it says it is recommended to power it between 7 and 12 volts. So I am wondering do I just hack together a 12 volt adapter to a Mini-B or is it possible to power it through the ICSP header?


texts:
I want to know how the analog supply regulator from the HX711 chip works. I try to search on Google and read the datasheet but I still need to figure some things.
I want to know especially what its used for, what role has the Vfb, base and Vsup pins from the module.

Thanks a lot.


texts: What is the difference in storage of a usb flash drive and sd card?

texts:
So I am working on a usb mass storage driver, but I am using a sd card to test it.
I don't know if the same driver will be able to fetch the data from a USB drive, as the theory about usb flash storage I am unable to find.
For e.g SD card have some registers, which tells about its capacity and other parameters to the host, i.e PC, but is it same way in USB storage?


texts: What is the outer metal casing of an alkaline battery made of?

texts:
I'm doing an experiment for school which involves measuring the temperature of batteries. I'm measuring the temperature using an infrared thermometer, and in order to get an accurate result I need the emissivity value of the surface that I am using the thermometer to measure. To be more specific, I am using a 1.5 volt Duracell battery with the plastic label taken off.

What type of metal is the casing made of? For example, if it is steel, is it galvanised, oxidised, sheet, buffed, polished etc?


texts: How do I re-wire this pop corn popper to isolate

texts:
I am taking apart an electric pop corn popper in hopes of isolating the fan motor from the heating element. I'm wondering how to re-configure this so that the following would be true.

If the heating element is on, the fan is on
The fan can be on even when the heating element is off

Ultimately I want to wire in two relays to control the two elements separately. Also, I would potentially like to control the fan speed, what would be the best way to do this .... A rheostat?

I've taken a closer look at this, and I'm having some trouble understanding how it works, I know that it's been said that the motor and the secondary heating coil are in series, but from my tracing of the wire it looks to me like they are in parallel, pleas see image below ... does that look like a series connection to you?

UPDATE

Ok, So I got another $15 popcorn popper, one that is very common and it seems to be wired in a similar but slightly different fashion, but It's still not quite clear whats going on please see bellow for new photos and diagram.

From what I can tell, it seems like both of the coils and the fan would switch off when the thermostat reaches temp ... this is not how it functions however, the fan stays on the whole time.


texts: What is the most power-efficient way to generate vibration in a small area?

texts: I'm trying to generate a perceptible vibration (as felt against skin) in a roughly 4x4mm area.  What's the most power-efficient way to do that?


texts:
I want to build a little gadget which must use BLE to communicate with a smartphone, but should run for at least 24h using a 500mAh battery. So I think to achieve this, I should be able to switch off WLAN, but still use the BLE radio.
Is there any way I can achieve this with an ESP32?
Thx


texts:
I need a DC-DC convertor to bring a 5V input up to 160V DC output. Does anybody know off any of the shelf parts that would manage this? The high output needs to supply minimal current (uA) we really just need it to supply a potential.

We have a part for this currently but it's going out of production.
We'd need the replacememt to have a similiar foot print (60mmx30mm).

I know linear tech have a good range of DC-DC controllers such as the LT3757, one of these may do the job.

Has anybody used these for something similiar?

Also I read an application note which which suggested it's possible to stack voltage references which may be another way of doing it as we don't need current. Has anyone tried this?

I'd be grateful for any suggestions.


texts:
Y'all will have to forgive my ignorance of electrical components, but what is the name of the electrical component that acts like a rotary potentiometer but when you release it, it pops back to 12 o'clock.

It can go both clockwise and counterclockwise from the 12 o'clock position to control a motor forwards and backward and then return to 12 upon release.


texts: Battery Life Calculation, Sleeping and Wake modes

texts:
I have a circuit that consumes 1.6μΑ during sleep mode and 40mA during awake mode. The awake period lasts for 3 seconds and the circuit is on awake mode every 30 minutes. The circuit is powered by this battery (the link leads to the datasheet).

I used this battery life calculator because i do not have the knowledge to do the maths on my own.

I know that as the circuit working the capacity of battery is decreasing as well as the voltage. But as the battery voltage is decreasing there are a few components that cant work under 3.0 volts.

I am trying to say that there is point where the battery will be capable of feeding power the circuit but some components are not going to work because the voltage will be lower than their voltage threshold.

For example, if i have a battery at 8500mAh 3.6V and at 2.9V are still left 1000mAh i dont care because my circuit doesn't work at 2.9V.

Is the rest capacity "wasted"?

Is that thought wrong?

Does the attached calculator take care about that too?

Because i didn't see in the equations nothing about voltage.

Many thanks


texts: 220V IGBT welder model ZX7 inverter welder has no earth case ground

texts: I would like to add an earth case ground to the unit.  I am unsure where to connect the wire. One end to the earth pin on the connector but where inside the unit? Some of these are manufactured with a case ground but mine isn't. This is a really small unit.  I want to be sure I connect the wire where it won't damage or cause a malfunction. It is from China and uses the ZX7 PCB template.


texts:
I'm trying to drive a 12v (14W) solenoid and have problems figuring out the components for the driving circuit.

The solenoid draws about 1.166A and the MCU is being operated at 3.3V.

I've seen many driving circuits and they all look something like this:

simulate this circuit – Schematic created using CircuitLab

My questions:

What datasheet parameters should I look for when designing this circuit?
Is the IRF530PBF-ND a suitable MOSFET for driving this solenoid?

Also, how do I calculate R1's value?

I don't want to blindingly copy a circuit that may or may not work, I want to understand it.

Thank you so much in advance!


texts:
I'm thinking what would be the better option to get fixed 5v output from car when car is running. I want to have fixed 5v for my Atmega328p and some other parts of the circuit, and the max current drawing will be around 150-200mA.

I saw on some forums that LM7805 dissipate more heat than LM2937, but I didn't have a chance yet to try it.

I know that SMPS solution would be the best option, but for linear solutions, where I can easily just use any of these two since even the pinout is the same, which one is better \ safer to use?


texts:
I am not concentrating on a Specific MCU as UART of most controllers has similar architecture. They have FIFOs for Both Tx and Rx.

Most common errors generated by UART are:-
1. Framing Error
2. Parity Error
3. Over-run Error (Overflow of Tx/Rx FIFOs)
4. Receive Break Error (Some Error with Stop Bits)

How one should handle these Error Conditions to maintain communication properly?

I do understand it's a vague question but most of the time people get confused about what one should do when such errors occur and end up in just clearing the error bits.


texts: How protective diode protects transistor from breakdown?

texts:
Please, explain the process of breakdown; how exactly this protective diode protects the transistor?

In a Horowitz & Hill book, "The Art of Electronics", 2nd edition, in "Chapter 2 - Transistors" (page 68), i read the following:

  Always remember that the base-emitter reverse breakdown voltage for silicon transistors is  small, quite often as little
  as 6 volts. Input swings large enough to take the transistor
  out of conduction can easily result in breakdown (with  consequent  degradation  of  hFE unless  a  protective diode is added
  (Fig. 2.10).

Can't figure out how this diode protects the transistor from breakdown if the current goes only in one direction in this diode.

simulate this circuit – Schematic created using CircuitLab


texts: Am I damaging my induction cooker by putting piece of metal under aluminium pan?

texts:
Moved from SE Physics

I have bought induction cooker and to use my old cooking pan I have placed a sheet of metal and it seems to work ok...

However it is making hissing noise... am I damaging my induction cooker by doing this...

Am I damaging my induction cooker by putting piece of metal under aluminum pan?

P.S I already got a proper metal pan this question is just for educational purposes


texts:
Make a BCD to Excess-3 Code Converter by using a binary to decimal encoder and 4 OR gates.
I know how to make a binary to decimal encoder, but how do I proceed from there?


texts: Correctly Using the Chan model in LTSpice

texts:
I am trying to use the Chan model to better simulate a transformer in my design. When I am making an equivalent transformer circuit, where does the Chan inductor go?

On the LTWiki it is implied that inductors based on core properties go on the center 'node' of the expanded transformer, but other sources say it should go across any one of the windings.

My next question is, wherever it does go, does it model both hysteresis AND eddy currents or do I need a parallel resistor as well for correct modeling?

Finally, is the N parameter the total number of windings of the transformer(what the core would see), the number of turns of the specific winding the Chan core is across, or just N = 1?

I have tried looking through the manual and the Yahoo group but if anyone has any experience with the Chan core I would appreciate any advice.


texts:
As part of a project, I need to evaluate a clock distribution system involving transmission lines. As part of the system, we need to design a voltage controlled delay element consisting of a CMOS current starved inverter.

Does anyone have any resources or tips for working out the output delay as a function of the control voltage? Thanks!


texts: Drive 50 SPI oled displays with a single ESP32

texts:
i need for a logistics project to use A LOT of Oled Displays in the mezzanine warehouse to show some details about the items.

Now, i want to use this base hardware and build around them the needed electronics in order to make everything work, so, i have:

1x ESP32
50x 74x40 dot matrix SPI oled display

At this moment, don't care about the power consumption, i need some advices in order to manage the logic of the SPI bus and the relative CS of the 50 displays.

What are your recommendations? keep in mind that i want to use a single CAT6 cable and his estimated lenght is about 10/15 meters.


texts: Should I be concerned when loop gain rises back above 0dB on simulation?

texts:
Interim update

Okay, I just realized I screwed up on the simulation. When I added \$C_{bp}\$ I upset the "break" in the feedback loop necessary to get the loop gain. The left-side lead has to go to the FB node leaving the INV node the only thing connected to the inverting input. I just fixed it and now the plot looks like one would expect (and my phase margin is all gone :). I'll work it through and then may take the question down since I'm not sure it happens when one doesn't screw up like I did :)

I'm finally getting a handle on methodical frequency response compensation for op amp circuits. I got LTspice set up to show loop gain, and have compensated this circuit in a fairly conventional way. I'm not sure what the name of this compensation strategy is, if it has one, but as I understand it, after "isolating" the gate capacitance with \$R_{iso}\$ it adds a zero to the feedback circuit at the frequency determined by \$\frac{1}{2\pi C_{bp} R_f}\$, about 1MHz in this case.

The feedback circuit frequency response looks like this:

The phase margin is a healthy 64 degrees, which I'm happy about because I'd prefer this circuit to be overly stable rather than get every last bit of speed out of it.

My question is: Should I be concerned that the gain rises back above 0dB at about 1.5MHz?

Also I'm a little bit concerned that the phase drops so precipitously in that neighborhood, wondering if I should be looking to add another pole somewhere or perhaps relocate one I already have.


texts:
I am trying to monitor an incoming signal and get some properties from it. The signal is a sine wave +-5V at 900Mhz. I am trying to measure the amplitude and the frequency of the signal. I will probably also have to buffer the input but that shouldn't be to much trouble.

I have been able to use schottky rectification for a couple of Mhz but eventually the diode cant recover fast enough. If anyone has any suggestion of small signal diodes that might be able to keep up with this that would be great. I have also looked at some switchable pre-scalers but unfortunately I loose the ability to feed my RC network.

As far as measuring the amplitude goes I am feeding the rectified circuit into an RC network.


texts: Designing a safety circuit to ignite a pyrotechnic device

texts:
I have been given a project to design a circuit which will ignite a pyrotechnic flare after a certain sequence of events has been detected. The events which must be detected are:

A specific signal transitions from a short circuit to an open circuit.
A short pulse signal from a separate detector is received.
A 5V logic signal transitions from logic 0 to logic 1.

Additionally, the sequence in which these events occur is unknown.

I have a massive interest in electronics but only a limited knowledge which I have gained from my university course (Physics), so I'm struggling to know where to begin with this project.

I need advice on which components the circuit should contain in order to detect these events and if wiring them in a particular way may work better than others. I'm kind of viewing this as a learning experience, any suggestions or explanations offered will be thoroughly appreciated. I will do my best to try to understand!


texts: Driving an LED with a low amplitude square wave as an input of MOSFET switch

texts:
I am trying to drive an LED with a square wave.
I've made a circuit like below:

The problem is, an equiment can generates a square wave with a limited amplitude up to 1.7 V.

After some experiments, I realized that the LED D1 becomes bright enought if the amplitude of V1 is higher than 2.5 V.

I guess this is because a drain current I_D isn't large enough according to the transfer characteristics of M1, STD12NF06L-1.

simulate this circuit – Schematic created using CircuitLab

I think D1 can be brighter if BJT is used even though the amplitude of V1 is not high enough:

simulate this circuit

The circuit right above is a circuit I imagined by some googling. (I have little knowledge about circuits)

By making a such circuit, a square wave V1 can only act as a trigger signal, and the LED D1 can receive enough current by the BJT.

In short, I want to provide a sufficient current to D1 no matter how the amplitude of V1 is large or small.

Is what I think ---using BJT to provide a constant current--- correct?
If the first is right, which BJT Q1 and resistor R3 can be used?
If the first is wrong, can it be solved by using voltage amplifier near V1?

PS: My final goal is to drive the LED with frequnecy up to 2-4 MHz. Are parts and circuit I am using too slow to achieve such a goal?


texts:
I have this relay and the ratings are quite confusing - 10A 30v and 10A 28v, I'm confused as to why there are two. Could anyone please explain it to me.

Thank you


texts: Simulating a DC motor with a constant friction torque

texts:
I'm trying to simulate a DC motor with simulink. The problem is that I don't know how to take a load torque into account. If the DC motor drives a wheel with constant velocity, there will be a constant frictional force working against the DC motor. How would this be implemented in a DC-motor simulink simulation?

I have tried subtracting a load torque in between the two transferfunction blocks but then the simulated motor speed is always goes negative.


texts: What power is measured by a spectrum analyzer?

texts:
Is the signal level that is shown in a spectrum analyzer power of the signal being measured.  If yes then what power is it: average power, true power or peak power?

Also when using a power meter for measurement of power, what is difference in its measurement of power with respect to that of a spectrum analyzer? I mean, what is the requirement of a power meter if a spectrum analyzer is capable of measuring the power itself (assuming same level of signal being measured by both)?


texts:
I have gotten some help from the community here and thus I have reached this.

This is part of the circuit that I  want to find the impedance

simulate this circuit – Schematic created using CircuitLab

and as a result of the Fourier Transformation looking at the circuit we have the following.

My confusions are how did we come wit those three results for the three cases. Is there a way I can plot into a calculator those three cases of ω.

Just trying to prove the results


texts: Role of Coax Cable in bringing TV signal to our TV sets

texts:
We know that we receive the programs/shows of TV Channels from the producers of programs through

CATV Service providers (almost obsolete, just wanted to  get clarified on its working process)
DTH Service.

Consider that a TV Channel produces programs and wants its programs to be telecasted to a wide audience. It will request a CATV Service provider to telecast its programs. After an agreement, the producer/channel will send his programs to the service provider. The service provider will then allocate a unique number to that channel. Transmission of the programs produced by the channel will be enabled through a Coaxial Cable.

Now, a single RG-6 coax cable can carry multiple channel programs with the concept of Frequency Division Multiplexing whereby, each channel will be allocated a bandwidth of 6-7 MHz. Typically 166-200 channels will be transmitted through the same single RG-6 cable.

My queries are

Will the Service provider transmit an AC of radio frequency for all the channel programs into the cable, which gets converted to EM waves and reaches the 3-way splitter?
Is it just an assumption that the two currents in the coax conductors need to be equal and opposite in order to not radiate outward?
Provided that each channel can occupy only 6-7 MHz band, is it obvious that each program produced by the channel will be transmitted at frequencies within this band? And, if 0-6 MHz is allocated for channel A, 7-12 MHz will be allocated for channel B? To avoid overlapping of frequencies?


texts: Can someone explain, in detail, how this circuit function?

texts: This is supposed to provide over voltage protection for a system placed in a car.Can anyone explain the functionality of each component? I know that this is basically 2 switches; but when will the switches be triggered ? Usage of BZT585B33T is confusing due to its break down voltage at 33V; while battery voltage is typically 12V


texts: Cannot use particular pins in SAMD21 as Digital Output

texts:
I have moved to Atmel from a run I had with MSP430 series and a tad bit confused at the moment as the pin setup seems quite different.

While handling an SPI device I needed a general IO pin to control the RESET functionality of the external SPI radio module and noticed that from bunch of the pins I am using for similar purposes some do not function as they should.

I have picked some empty pin on the SAMD21 Explained demo board and in this particular case they were,

Ext3_PIN_3, 4, 5, 6

here is the pin defs from samd21_xplained_pro.h

//name Extension header #2 pin definitions
#define EXT3_PIN_3                PIN_PA02
#define EXT3_PIN_4                PIN_PA03
#define EXT3_PIN_5                PIN_PB30
#define EXT3_PIN_6                PIN_PA15

Hooking Ext3_PIN_4 (which is PIN_PA11) to a CRO and executing the commands below right at the start for testing, I get no toggles between 3.3 and 0 unlike the other 3 pins.

int main(void)
{
    struct port_config pin_conf;
    port_get_config_defaults(&pin_conf);

    /* Configure the pin as outputs */
    pin_conf.direction  = PORT_PIN_DIR_OUTPUT;
    port_pin_set_config(EXT3_PIN_4, &pin_conf);
    port_pin_set_output_level(EXT3_PIN_4, 1);
    port_pin_set_output_level(EXT3_PIN_4, 0);
    port_pin_set_output_level(EXT3_PIN_4, 1);
    port_pin_set_output_level(EXT3_PIN_4, 0);
}

I got break points on each pin_set line and toggling manually by advancing a single line as I didn't want to initialize the delay_ms etc.
Is there anything obvious that I am missing here?


texts: measuring from ground to an open wire = 0 volts?

texts:
On a car, if you connect your DVOM to battery neg and connect to an open wire you read 0V, why? A DVOM reads differences in potential. Does the open wire have potential in it?
Thanks


texts:
I have a car active subwoofer, 550w RMS, 1600w peak, which I would like to use in my home, and power it from 220v mains.

~133A is a fairly large ask from a transformer, I think, and even 46A seems quite high. I have a couple of computer PSUs knocking about, and I was wondering would it be possible to use a pair of these to supply the power required? Would it be as simple as connecting the transformers in parallel, to supply the subwoofer, or do I require something more complex?

Edit:
 Ok, when I say power, I'm talking about the feed used to operate the sub/amp. The +12v terminal on the unit. I'm not talking about the signal input. The two wattage values, are whats printed on the underside of the sub. (as well as 4Ω impedance & 12v DC input)

The figures I was pulling out, in regards to current draw, were 1600w/12v = 133A and 550w/12v = 45A, perhaps I'm well wrong with these though?

Added:

As people seem to be having trouble understanding this material. and as it's not clear why they are, here is a summary.

A piece of equipment is usually operated in a car and powered from the car's 12V battery supply.
The equipments purpose is to deliver audio energy into a load - usually the very low frequency end of 'music'. (It's a powered amplifier and is usually called a "subwoofer" but that tends to confuse people - think of it as equipment that needs 12V power.
The equipment's rating plate says that it's maximum power output level is 550 Watt RMS and that peak power output is 1600 Watt. The Watts is expressed in RMS power as it's an amplifier but we can think of this as DC load with fair chance of approximate correctness. Music ratings being what they are the true power MAY be lower or far lower, but start at the stated levels initially.

As M. Ohm says that I = Power/Volts, this suggests that
 at  550 W the current is P/V =  550/12 = 45.8A = 46A and
 at 1600 W the current is P/V = 1600/12 = 133A

The questioner wants to know how to power this equipment directly from an AC mains powered supply.


texts:
Need to connect remotely to a device using cellular GPRS gateway.

Device supports RS-232 and USB. It boils done to two options:

1.- Serial Over TCP/IP (Serial to Ethernet - to GPRS, or Serial to GPRS)

2.- USB Over TCP/IP (USB to Ethernet - GPRS, or USB to GPRS)

Note that there are gateways that allow transparent communication from TCP network communications to serial port. Example: Serial to GPRS Gateway.

End goal is to have a virtual serial tty port. Tools like Socat in Linux allows this.

So application programs will think that the device is connected locally to the computer.

Which one should I use? People tell me definitely Serial over IP due to USB latencies issues...

P.S. I'm talking about Virtual Serial Port.


texts: Rated current vs peak current in connector

texts: I'm looking at panel connectors and I'm not sure about the current capacity. One connector is rated at 25A continuous, which is above what I expect my device to be driving, but during startup, peak current gets to 30.8A. The specifications on the connector say nothing about peak current so how do I know if I can use this connector?


texts: Was Benjamin Franklin wrong (about conventional current)?

texts:
I am starting to see a lot of people claiming that convential current is 'wrong' because Franklin made an error when he first started investigating electrostatics, and that later scientists didn't bother correcting the mistake, but preferred to keep the 'convention' (here is a classic example: http://www.allaboutcircuits.com/vol_1/chpt_1/7.html)

I always thought he didn't get it wrong. He said that current is positive in the direction that positive charge flows, and vice-versa. He of course had no way to know which side of two sticks behind rubbed actually gained or lost mass. So he wasn't wrong. What were you taught?

P.S. I can't help but feel we are lucky that he got it 'backwards', because clearly many people are confused about electrostastics (including the author of that text book!) and believe electricity has to involve electrons (an unfortunate name... why couldn't they have been named negatrons...)


texts: Control Circuitry in the Buck Converter Design

texts:
In this question, the last line of the accepted answer states that - That's why the text suggests using 1/5 or 1/10 of the switching frequency as an upper limit in terms of how fast you should design your control circuit to react in order to keep the output voltage constant.
In the above answer, can someone please tell me what components constitute the control circuitry in a typical buck converter circuit (consider a TPS54260 IC)? is the output inductor and capacitor constitute the control circuit or the internal Op-amps present inside the buck converter IC constitute the control circuitry?
What is the control circuitry that the answer is referring? Either the outside output inductor and capacitor or the internal Op-amp and other components present inside internal to the IC?


texts:
I understand the difference between a semaphore and a mutex (I think). Only the task that acquired the mutex can release it.

What if we had three identical ports that are shared amongst tasks and tasks don't care which port they use? We could initialise the counting mutex to three. And we could make sure that only a task that acquired one of these keys returned a key (just like we do with an ordinary mutex).

I must be missing something because, though it seems to make sense to me, I've never heard of a counting mutex.


texts:
I am designing a PCB footprint for this part: https://www.meanwell.com/productPdf.aspx?i=685
On page 4, the pins diameters are indicated as:  diameter:1ψ and  diameter:2ψ
Also, on the quotes, they are using 2-1ψ and 2-2ψ
I searched the web for answers but could not find anything useful..
What is ψ? Why is it used instead of millimeters?
How can I convert this to metric? How large are the diameters of these pins?


texts: Code Composer Studio 6.1.0 debugger is not acting as it should

texts:
I am learning to code on a microcontroller from Texas Instruments, MSP430FR6969 (link), using MSP-EXP430FR6969 launch pad (link).

I am also using an IDE CCS 6.1.0 (link).

I am doing a simple odometer, where the program counts from 0 to 99,999 and then resets again.

code below

#include <msp430.h>

#define DEVELOPMENT 0x5A80
#define ENABLE_PINS 0xFFFE

int main(void)
{
    WDTCTL = DEVELOPMENT;//disable WDT
    PM5CTL0 = ENABLE_PINS;//this is needed in order to enable pins

    P1DIR = 0x01;//P1.1 is output
    P1OUT = 0x00;//port 1 = 0x00

    unsigned int tnth, thou, hund, tens, ones;

    unsigned long km = 0;

    while(1)
    {
        for(tnth = 0;tnth < 10;tnth++)
        {
            for(thou = 0;thou<10;thou++)
            {
                for(hund = 0;hund<10;hund++)
                {
                    for(tens = 0;tens<10;tens++)
                    {
                        for(ones = 0;ones<10;ones++)
                        {
                            km = 10000*tnth + 1000*thou + 100*hund +10*tens+
                            ones;
                        }

                    }
                }
            }
        }

        P1OUT = ~P1OUT;//I added a breakpoint there.
        km = 0;
    }

    return 0;
}

I added a breakpoint at P1OUT = ~P1OUT;, build it and debugged it like in the image below.

When the debugger reaches the breakpoint, I see in the variable watch window ones, tens, hunds, thou, and tnth all equal to 10, which is what I expect.

But I also expected km = 99999, instead I have km = 34463, which doesn't make sense as km is an unsigned long

Also.

When I modify the code and change unsigned int tnth, thou, hund, tens, ones to signed int, put a breakpoint at P1OUT = ~P1OUT build it and debug I get   km = 4294936223 in the variable watch window.

I asked the question in TI forum (link), and a member said that in my build

  "../main.c", line 16: warning #552-D: variable "km" was set but never used

Kindly help me on this matter, and sorry for the long post.


texts: The voltage across all points in this circuit seems to drop once an inductor is added

texts:
I'm at the end of my wits after spending the last few hours trying to work this out, so bear with me. I have the following circuit:

My resistor is a 47k resister, my D1 and D2 are UF4007 diodes. My transistor is also a TIP31C, while my L1 has about 8 turns and my L2 has about 400 turns, with a 9V battery. However, what I am finding is that this circuit simply does not work -- most of the time, when I measure voltage across L1 and L2, I get a value that makes sense -- L1 is about ~0.02V and L2 is maybe ~0.6V, meaning that I am multiplying by the ratio between the two, so I know that something's happening.

I have, however, gotten it to work once, briefly, for about a half second, where it lit my 13W CFL lightbulb.

But now I'm finding a much bigger problem.
My voltage has dropped. Everywhere.

I'm using the 9V battery -- the voltmeter reads 8.3v across the battery, but ~0.6-0.7V between ground and any position on the circuit, including, but not limited to the topload, either end of L1, either end of the resistor, and directly between the positive wire and ground.

Yet I can also return the voltage to normal -- if I remove L1, then voltage across the circuit returns to normal.... But then the circuit won't work anymore because... Well it needs L1 to work.

So now I'm stuck -- L1 seems to drop my voltage down from ~8.4V to ~0.6V, everywhere.

I'm stuck, and google isn't helping.

Other information:

L1 is wound clockwise, L2 is counterclockwise
Topload is a styrofoam ball with aluminum foil around it
L2 wire is 30AWG and L1 wire is 24
L2 is wrapped around a 1/2" PVC pipe and L1 is wrapped right around L2.

So yep, Google isn't giving me anything on this. Any help would be appreciated, as I've been working on this circuit for the last week, and I'm hitting a dead end here.

Thank you.


texts: I am creating an application that uses standard function that sets bitrate. The parameters required are BTR0 and BTR1. But the user of my application will enter the standard value of the Baudrate (eg. : Bitrate = 125000). How can i calculate BTR0 and BTR1 from the given value?


texts: Can I charge multiple devices from one transformer?

texts:
I am getting tired of bringing 3-4 power cables with me every time I travel and am thinking about building a multi-device power charger. In other words, this charger will have one transformer (and one wall cord), but will have multiple adapters for my devices (macbook, ipad, iphone, kindle, etc).

My question is whether or not this is possible. Assuming the transformer is outputting enough Amps/Watts, can I just run a serial (or parallel?) circuit between the devices and allow the 'overflow' to go to the next device?

Thanks in advance.


texts:
I made the circuit. like this paper,

But It's not working.

When you insert the AC input, a square waveform should appear.
I can not interpret the circuit well.

If you know anything, please answer me. Thanks for reading.


texts: How to generate complementary PWM signal using an IC (integrated circuit)?

texts: I am outputting a PWM signal, but the problem is that I can't generate a complementary PWM signal with dead time because this timer channel doesn't support it. So I want to use/buy an integrated circuit (IC) that generates a complementary PWM signal if I feed the PWM signal into it (with dead time). Is there such an IC available on the market?


texts:
I want to design an current protection circuit with current sense amplifier. I have to work with 220V 50Hz AC bus voltage. I could not find any IC or any design for this topic. Can someone give me some hints about this?
*I just find IC that ACS709 but I could not be sure whether it is okay or not.


texts: I am communicating between two esp32's. Can the UART at a baudrate of 512000, work fine over a distance of 1 metre? . The data will be sent at 10ms intervals. Wires are standard 24 awg.


texts: Joysticks for PCB design that are better to use than classical mouse

texts:
I suppose there are some tools (joysticks or something) that professional PCB designers use instead of mouse for PCB routing.

Would you be so kind to share with me your experience in that sense ?

Thanks,

Bojan.


texts:
I thought of making a 12 LED light with input power of 48v and 20 mA.  Is there any circuit using only transistors to act as a switch running on the above inputs. I intend to use the above circuit with LDR which should activate the above 12 LEDs when it is dark.

Kindly help with the circuit diagram. I am already using the above circuit with a switch and now, out of curiosity, I intend to use it in my bedroom for lighting purpose.


texts: How to design a two-stage synchronizer with a clock divider in Verilog?

texts:
I have a very fast clock called CLOCK_50 which I would like to slow down through the use of a clock divider. The output is clock. I also want to use a two-stage synchronizer for an asynchronous reset port reset0 which should output reset into the core. However, I'm not sure how to get these to work across different clock domains.

This is what I came up with. It generated several errors when compiled.

logic clock, reset1, reset2, reset;
logic [13:0] countCLK;

always_ff @(posedge CLOCK_50) begin
    reset1 <= reset0;
    reset2 <= reset1;
    reset <= reset2;
end

always_ff @(posedge CLOCK_50 or negedge reset) begin
    if (!reset) begin
        clock <= 1'b0;
        countCLK <= 14'b0;
    end

    else begin
        if (countCLK[13])
            clock <= ~clock;

        countCLK <= countCLK + 14'b1;
    end
end

And the warnings:

Warning (308040): (Medium) Rule C104: Clock signal source should drive only clock input ports. Found 1 nodes related to this rule.
    Warning (308010): Node  "clock"
Warning (308027): (Medium) Rule R105: The reset signal that is generated in one clock domain and used in another clock domain should be synchronized. Found 1 node(s) related to this rule.
    Warning (308010): Node  "reset"


texts: How to measure small currents using current to voltage converter?

texts:
The battery voltage = 12 volts.

In the first circuit The op amp works as a current to voltage converter and its output equation is:

Vout = - I * R

I choosed R to be 20 ohm so that each 50 mA will make -1 volt drop.

I put 240 ohm across the 12v battery and I closed S1 switch to make sure that the current passing through it is 50 mA.

Then, I opened S1 and Closed S2 and the output voltage of the op amp is -1 volt.

The equation works well yet.

In practice, I don't have a supply that can produce negative voltages, so I have to build a bias for the op amp which is in the second circuit.

The positive input of the op amp is now 6 volts.

When I close S2, I would expect the voltage to be 6 - 1 = 5 volts.

but the result is 5.5 volts !!

Why does that happen? and What modifications should I make to get correct results? can I add a buffer or something like that ?

If I can not modify the circuit, What is the best way to measure small currents without using multimeter or ammeter?

Thank you very much,


texts: How to program multiple STM32Fs on same PCB

texts:
I work in a management roll and only have a very limited electronics knowledge (enough to make simple arduino projects etc).

We are working on a product at the moment which has 3 STM32F303s and 2 STM32F103s and the main processor being a AM5718.

I was just wondering how you would go about uploading and upgrading the firmware and bootloader one each processor including the AM5718.

The 5 STM32s are connected to the AM5718 via UART and all are on the same PCB.

I would like to get a good idea about how this would be done after the PCB is produced and the product is in the field.

I would obviously ask the electronic engineer working on the project but we have finished for xmas.


texts: Aren't non-polarized plugs a little dangerous? Why still use them?

texts:
Sorry if there is an answer for this kind of question somewhere. I can't find it anywhere.

Take a look at obvious toaster example:
If you live in Europe and have non-polarized plug and a toaster (a bad one without double-pole turn off) - you have a 50% chance of touching the hot wire (via the heating elements or even bread if you're unlucky) if you plug it in the wrong way, so that the off switch turns off just the neutral wire. You will be shocked if you somehow connect your body to ground (through another device for example).

I understand that these conditions are not very likely to happen, but why do many countries still not even think about doing away with non-polarized sockets and adopt polarized?
I'm sure even in Europe the light-bulb sockets are wired to be neutral-shell polarized, so why not wall sockets?

Sure it is not a cheap thing to do, but 10 years later it will be even more expensive since more stuff will be produced without a polarized plug.


texts: NPN Transistors Not Working When Emitter Is Grounded

texts:
I'm trying out transistor logic for the first time using PN2222 transistors that came in a kit that I got from Amazon.  I've been running into some problems with making a basic NOT Gate (as shown in the schematic below) and I haven't been able to complete it.

I believe that I have faulty transistors, but so far I've tried them all (as well as troubleshooting with a meter, checking for continuity, and changing all components for new ones) and have come to the same outcome every time.

Schematic

simulate this circuit – Schematic created using CircuitLab

The Problem

When I put my LED on the collector-side of my BJT with a resistor hooked to +5V without anything attached to the BJT's base or emitter I get what I expect, the LED lights up as the rest of the BJT has nothing to do with that LED circuit. However the moment I attach the emitter to ground, the LED shuts off.  Applying any kind of input (logic high or low) provides no change.

I tried to connect an LED from the emitter pin to ground, replacing the wire I had used previously, and I found that the collector LED stays lit and the emitter LED is on, but barely.

I can provide pictures of my breadboard circuit if need be.  Any help and advice is appreciated as I did say this is the first time I've messed around with REAL transistors, not ideal or simulated ones!

Update (Edit)

R = 1k ohm, R2 = 220 ohm
Here are some pictures of my circuit:

(sorry for the bad quality, my camera is terrible and the LED is quite bright)

The top two photos are of the emitter being directly grounded, the next two are with an LED connecting the emitter to ground.  The first picture of both sets are with the switch off, then the second pics of both sets are with the switch pressed.

Notice that the LED connected to the emitter and ground lights up a little bit.


texts: Why solenoid valve when a liquid pump can be electronically controlled?

texts:
In some quick research online, I'm often seeing configurations where a liquid pump is used in tandem with a solenoid valve on the same liquid path.

So, let's say I have a very simple scenario: a standard pump transporting liquid from one container to another container (at a higher position).

If I wish to electronically control the flow/no-flow of liquid, I can simply switch on & off the power supplied to the pump, perhaps using a relay.

So then, what does adding a solenoid valve to that system achieve -- isn't it redundant?

EDIT: Example of a drawing I saw (although I suppose the valve here is a manual one for easier access):


texts: measuring time between extremely fast laser beam breakage using LDRs

texts:
I am conducting a scientific experiment to approximately measure the entering velocity and the leaving velocity of a magnet through an electromagnetic coil.

Beside the coil are two lasers and two LDRs as depicted by the figure below.

I expected this circuit to generate a rising edge and a falling edge, but I realized only after testing on the oscilloscope that I was not able to receive a square waveform to input to my MSP430 MCU as interrupts. My plan was to calculate the time between these two interrupts.

However, the waveforms I observed were as below.

Then I thought that I could use an LM358 in front of my voltage divider. This is described in here. But looking at my practical waveforms I observed from the oscilloscope, I am doubtful how I can tune the comparator. Is there a better way to achieve my task using better electronics? I am not limited by component costs, however, I am not willing to buy a ready-made apparatus for this purpose. My intention is to develop one.

Thank you for your views and help.


texts:
I have created a wav file (sampling rate of 44.1kHz at 32-bit floating point precision) consisting of 44.1k samples at 0.0 followed by 44.1k at 1.0. After which the file is played out from line-out using Media Player Classic and looped back into line-in. The resulting waveform is captured and inspected using Audacity.

The output waveform goes from 0.0 to 1.0, holds it there for a number of samples and some how "decays" back to 0.0. What is going on? And how do I recreate the desired step waveform where it will persist at 1.0 for the second half of the waveform?

The brand of the sound card used in question is Realtek, PC is an Acer TravelMate 4720.

PS: This may seems like a PC question but I suspect it has more to do with sound electronics used on sound cards.


texts: Relation between the impedance of speaker and amplitude of sin wave?

texts:
I have an oscillator producing a sine wave with amplitude 3 V (so it oscillates between +3 V and -3 V). The oscillator is at about 500 Hz. I connected this to an 8 ohm speaker and I hear the sound from the oscillator. I noticed that on the speaker is written 0.5W, so I assume that this speaker can handle at most 0.5 W.

I am not sure that I understand how speakers work, but applying Ohms law I see that at 3 V and 8 Ohm, the speaker would draw a current of 3/ 8 = 375 mA. This would mean that the power consumed is P = UI = 3x 0.375 = 1.125 W.

The speaker is only rated for 0.5 W, so I assume that I should reduce the amplitude if I don't want to damage the speaker.

My question is simply: Did I calculate this correctly?

(One of my concerns is if I can apply Ohms law since the voltage isn't constant. Could I possibly just add a resistor in series with the speaker to increase the impedance?)


texts: Help on identifying a component (marked 8C609)

texts:
after having plugged the power-adapter with inverted supplies (19.2V +/- swapped) into the ASUS U5F notebook of my wife (you'll understand the severity of the problem), it has burnt a little bit and since then the USB (maybe the 5V supply) seems to not work correctly anymore (the rest seems to be ok).

To investigate the problem until now I found out the following:

the schematics of the mainboard are not available
the device seems similar to the Asus U5A (no schematics available either)
at least one component has burnt (as pictured below)
I'm unable to identify what this component is doing exactly, so I can't replace it
the components is of probably packaged using "SOT-223-4"
the marking code is 8C609 (I could read it before cleaning the section, now there is only "8C6" left)
I suppose it is a LDO-regulator, but I don't know the exact reference

EDIT: The question now has a follow-up.


texts: why these AND gates are getting no output. I confirmed all the connections. The first and gate is getting 0 and 1 as an input but there is an error in output. Can someone help? Urgent


texts: DSP - Voice Activity Detection: what are my options?

texts:
In a performance sensitive environment, I have an audio stream. I need to classify each frame as speech/non speech.
For this purpose, only "clean" voice should be classified speech. Voice with substantial background noise (maybe music) should be classified as non speech.

What features/methods could you suggest?


texts: Gerber - is my understanding of solder mask layer (GTS / GBS) correct?

texts:
I've just had a PCB manufactured for me, but it seems like the solder mask is only applied to where the copper is.
I'm trying to figure out if it's my fault or not.

According to my understanding there supposed to be solder mask everywhere on the board except the places in red (pads/vias ect...).
Am I correct ?

Here is how the GTS layer file looks like:

EDIT:

Note that yellow solder mask was chosen. I haven't seen the PCBs in person but it sure looks like no solder mask to me.
But perhaps I'm just stupid/blind.

Here are photos the pcb:


texts:
I need to coarse control the frequency of oscillation on a parallel resonant tank. The frequency band is in the 500kHz-1Mhz range, so the small capacitance of varactors doesn't suit the task.

Another way of doing it is by switching a capacitor branch with a MOSFET

simulate this circuit – Schematic created using CircuitLab

The problem is that the tank is floating, thus the source is not fixed biased and that makes it difficult to control the conduction on the MOSFET.

I've not considered adding a PLL or another stage because it's the coil where I need the output to be and the current in the tank is already pretty high.

A second problem is that even if I can switch the capacitor on and off, the amplitude of oscillation will vary according to the impedance change, and I need to get as stable amplitude as possible.

¿Are there any solutions for this specific arrangement or is it better to use a grounded tank so I can switch the then properly biased MOSFET?

Thanks in advance!

Note the values in the schematic are somewhat random


texts: transmission line theory, complex conjugate matching

texts:
Referring to the below output matching network of an amplifier ,in which gamma_out is chosen as the complex conjugate of gamma_l (in the figure Γ and Γ*) in order to achieve maximum power transfer from the output of the amplifier to the network.
Why in this particular case of conjugate matching Γ1 turns out to be 0 ?
Can somebody carefully explains me this perhaps trivial thing?
thank you in advance.

simulate this circuit – Schematic created using CircuitLab


texts: Analysis of BJT RC Phase Shift Oscillator

texts:
I have designed an RC phase shift oscillator and it works in LT spice but i want to know if the analysis i have did on this circuit is correct or not. I want to calculate the "gain" as well as the "input impedance". Please guide me where i am wrong because i am a beginner in electronics. It oscillates at around 500Hz.

AC analysis

\$|Z_{in}| = |(X_{C1}||R3)| \approx 315\Omega \$
\$|Z_{in_{base}}| = |(R1||R2)||\beta*Z_{in}| \approx 13K\Omega\$
\$|Z_{out}|= |Z_{RCnetwork}||R4| \approx 8K \Omega\$
\$\text{Voltage Gain} = Z_{out}/Z_{in} \approx 25.4\$

DC analysis

\$ V_{b} = 1.62V \$
\$ I_e \approx 0.4mA \$
\$ V_c \approx 5V \$
My questions are -

Why is there sustained oscillations even when the voltage gain is around 25. Shouldn't the voltage gain be around 29. Where am i wrong in my analysis.Is my AC analysis correct?
Is my Dc analysis of the circuit correct since i want the signal to swing around the midpoint i.e 4.5V


texts: Are all the pins from a USB3.0 micro-B connector necessary

texts:
I'm designing a system that has a camera (Ximea: MQ042RG-CM) that uses a female USB3.0 micro-B connector. I could connect to my computer through a male end, but I want to minimize the number of connectors I use in my system. I see that the USB 3.0 micro-B has 10 pins. Are some of them not crucial? I read that 5 of those pins are only there to make the port backwards compatible, but if I attempt to connect my computer to the camera using only the other 5, will it be enough? Does it depend on the camera? My computer supports USB 3.0.

I essentially want to know which of the pins in this table, if any, I can do without:


texts: Design considerations for LED strip PWM dimming

texts:
A note on my background: I'm a programmer in an electronic design company, starting out with hobby projects.

I'm planning to design a PWM LED strip dimmer and colour controller for an RGB/RGBW led strip (yes, this is a hobby project). Before I start picking parts and drawing the schematics I want to ask if I'm not missing anything.

System overview

Led strip

A common anode configuration. The LED strip will be up to 5m in length, with 14.4W/m for RGB or 18W/m for RGBW - that's up to 90W, or 7.5A drawn from a 12V power supply. With some overhead it comes out to a nice 3A per channel.

PWM and MCU

PWM switching frequency will be around 6kHz, everything will be controlled by an MCU (STM32F0 family).

What has been taken into account

Power supply

A 12V one with sufficient power, most likely a modified ATX PSU or a dedicated LED one
To make sure the PSU handles large switched load well there will be a few large electrolytic capacitors - most likely on the order of a few millifarads, rated for at least 25V with low ESR
Inrush current protection - an NTC
The MCU will be powered with an LDO, it has undervoltage protection so it will not boot until the logic supply is in it's operating range
The 12V rail will be monitored by the MCU and it will only turn on the LEDs if supply voltage is ok
According to an online calculator using 35um copper I will make the traces at least 12.5mm wide for common power (anode and current return) and 1.5mm wide between cathodes and drains

Driving the LEDs

Low side switched with a single NMOS per channel, Rdson under 20 mOhm
To keep Rdson in spec the MOSFETs will be driven using a dedicated driver, like the MCP14A0153, supplied by 12V
With 200mW power dissipated in transistors with a larger package (DPAK or Nexperia's LFPAK56) it should not be a concern

PWM

As per an article on Digikey I plan to have a frequenct of roughly 6kHz
The MCU will run with a 48Mhz clock which is available to the PWM peripheral, giving 13 bits of resolution - probably more then enough

What I'm not sure about and will research

Protection - overvoltage and overcurrent, do I need it and how to implement it
ESD protection on the terminals
Any (magic to me) effects like parasitics, inductance, ringing and what not
The relationship between the emitted light and PWM duty cycle is almost linear. What is the relationship between emitted light and perceived brightness?

What I'm asking

Apart from the points I listed is there anything more I need to consider? Also I will be grateful for any comments regarding the points above.

Update

I've noticed from comments and @Tony's answer that I should underline that the strip is a ready-made one - I'm not in control of it's schematic. It is a stock one with resistor-limited LEDs in parallel made to use with 12V source, like this one, schematic from Adafruit below. From what I understand you cannot use constant current dimmers with such a setup.


texts: Help identifying a strange device in an SMPS PSU

texts:
I had 4 SMPS PSUs blow up after PGE power resumption on our fileservers.
I opened it and found this strange device. Since its broken I pulled
it apart and its basically just a straight thick lead (1.5mm or so)
with some white stuff around it and encased in a black plastic cylinder.
So it would look like a rectifier, except it isn't. The resistance
across is zero in the working and blown ones. The two vias on the PCB
are for the transformer that was removed.
One end of the lead is connected to one end of the windings of a
 transfomer in an SMPS PSU.
It has spread this white powder onto surrounding devices. The lead
itself is not burnt. In fact its unlikely it will melt as its pretty thick.

What purpose would it serve to vaporise the outer coating and leave the
thick lead. Just to be clear this device is a straight continuous lead with the white stuff around and encased in a black plastic cylinder. So there's no resistance across the leads.

I checked another PSU and it also had blown the same way. The working
one shows a crack on the surface casing, but continues to work.
View of blown device next to transformer

I found another similar device that is intact. The blue sleeve is loose around the lead:


texts:
I want to use universal motor as a DC generator. The motor specifications are

180 Watt
230 V
10000 rpm

When I supply the motor with 3000rpm it gives 1.5V. I thought it was rpm problem but when I supply 10000rpm it only gives 4V. While exploring its theory I figured out that a universal motor is a DC series motor. As for DC series generator there must be load connected to its terminals in order for field circuit to be energized otherwise the circuit will be open (if I am not wrong).
But when I connect load (incandescent bulb of 100Watt and 220V) it give me even less than 1V. I do not understand what is the problem. If someone has good undestanding of universal motors please provide guidance.

Thankyou.


texts: Solving a circuit using superposition (strange case)

texts:
My professor gave us a problem that we are free to do by ourselves that is a typical exam problem. I was wondering if half of my solution can be verified (the other half I am fine with). The circuit, along with the half that is of concern is attached below.

If there is anything of concern please let me know. The problem statement in case it is not clear is solve for Vo using superposition; in this case I only am wondering if I found Vo1 correctly.

EDIT: More neat work.

$$
Vo = Vo1 + Vo2\\
Va = -Vx \\
$$
Nodal Analysis at Node A

$$
Therefore: \\
{(-Vx-Vc)\over R1} + {(-Vx-Vc)\over R2} - {Vx\over 2} = 0\\
-{Vx\over R1} - {Vx\over R2} - {Vx\over 2} = 0\\
Assuming: {1\over R1} +{1\over R2} + {1\over 2} ≠ 0\\
Then\\
Vx({1\over R1} + {1\over R2} + {1\over 2}) = 0\\
Vx =0\\
$$
If Vx =0, the dependent current source acts as an open circuit as no current flows through it; also, there is no current flowing through the loop with Vx, that is, Ix =0, therefore the dependent voltage source has no voltage across it and is thus short circuited. The circuit therefore now can be simplified to:

$$
Vo1 = (-Is)(+R3) = -IsR3
$$


texts: Upgrading an Arduino Duemilanove from ATMega168 to ATMega328

texts: I have purchased an ATMega328 from SparkFun with the Arduino bootloader pre-programmed.  My intention is to replace the ATMega168 I currently have in my Duemilanove.  Is this as simple as swapping the chips, or will I need to take any additional steps?  As I recall, I am currently at Arduino 13 but am planning to upgrade to 17 (current version) concurrent with the part swap.


texts:
I'm about to simulate a voltage mode buck-boost converter. To stabilize this converter, it is well known that we should use a type 3 compensator. The configuration of that compensator is given below with the components values computed in matlab with the following specifications:

The switching frequency is 100kHz.
DC Bias (Output voltage from power stage to error amplifier) is 12V
We place a double zero at 600Hz
A first pole at 7kHz
A second pole at 50kHz

The circuit I have simulated is shown below:

When I simulate the transfer function of a type 3 compensator in matlab, I get the bode plot in the figure below (as expected):

But when i simulate the circuit in Simetrix/Simplis, I get something different and has nothing to do with the well known frequency response of Type 3 amplifier
The frequency response I got is shown below:

If we compare what I got in matlab and Simetrix/Simplis simulator we notice a huge difference between the two. I have changed many parameters, like the gain of the error amplifier but I did not get the expected response of a type 3 amplifier!
Could anyone help me to figure out what may be the problem ?


texts:
I want to use a LiFePo4 cell as a supply for the msp430. For this purpose TI developed the TPS61221. I'm wondering if that's really needed if I can guarantee that the cell voltage is between 2 and 3.6V? Is it a problem if the supply changes its voltage? I know the frequency probably changes linearly with the voltage, but apart from that, are there any other problems?

I'm aware that it's probably a good idea to use this IC but I also want a very cheap solution for my msp430. Could you elaborate a bit on this topic? (For example: I want to measure the voltage of a cell using the same cell also as a supply, is there a ground problem if I don't have this IC?)

Thanks


texts:
I am trying to implement a system where I have to use Touch Sense Controller(TSC) with LPC2138 controller, through SPI interface.

As per my consideration,

MOSI line of LPC2138 --> Din of TSC

MISO line of LPC2138 --> Dout of TSC

Is these consideration correct for SPI interface? Thank you.


texts:
I want to match RF power amp to aerial. There is no 50 ohm or 75 ohm transmission line inbetween.

So, I consider my aim to be matching certain load-reflection coefficient (Γload) to a short circuit (no transmission line).

Can I do it using a Smith chart? I'd appreciate an advice.

UPDATE

I guess I do not need to do any matching here whatsoever. What I need is to calculate load-reflection coefficient, mount proper components and then connect an antenna. Am I right?


texts:
process

  variable vGoodRead      : boolean := true;

  while (vGoodRead = true) loop         -- read till end of line.

      hread (vLineIn, vInData, vGoodRead);
      ........
  end loop;

  vGoodRead := true;  -- cos at End of line, it turns false

end process;

I am using this code, to read in Hex values.
There are multiple (and different no of) hex values on a single line.

This code works, provided all hex values on the line/s are correct.

My problem is, I have not been able to figure out, how to detect a case, when there is an incorrect input value, somewhere within the line.
I.e. there is FO (f, cap O) versus F0 (f, zero). The latter being valid, while the first is invalid.

Thanks for your help.


texts: Connecting 3v digital output to Arduino using bi-directional level shifting (mosfet)

texts:
I have a digital output from a 3.3v device that I would like to make 5v tolerant - i.e be able to connect it to either a 3.3v OR 5v MCU.

I could technically connect the output directly to the Arduino Uno (or a 3.3v MCU) without any problems. The problem with the output is that the VOH minimum is 3v, while the VIH for the Arduino Uno is 3v - so there is no margin for error.

So I will need to shift this output up to 5v (if so required). I have considered 3 options:

1) a part like this - MC74VHC1GT125 - would do the trick.
2) Use an optocoupler - like the HCPL-181
3) Use a bi-directional level shifter using a MOSFET and 2 resistors - like in this Philips AN97055 note

Takes a wide variety of input voltages (3v in our case), and translates it to the Vcc reference voltage (which may be 3.3v or 5v depending on our MCU of choice)
The output from the optocoupler can be tied to the Vcc reference voltage, so it will work with either 3.3v or 5v MCU
The output side of this (connected to the MCU input) can be pulled up to the Vcc reference voltage, and so is again tolerant of 3.3v or 5v MCU and will pull up to the appropriate level

3 looks very attractive as I am already using a couple of MOSFETs (BSS138) in my design (for the I2C lines), for simplifying the BOM.

However, I see that it seems to be mainly used for open drain/collector configurations like I2C pins - a digital output pin is not an open drain/collector type.

My question is - can the bi-directional level shifter shown in the Philips note above be used in the uni-directional case of a digital output pin with no ill-effects?

If so, what does say, the MC74VHC1GT125 or another specifically designed level shifter IC, offer in terms of advantages over this approach? And how does the optocoupler approach compare?

I have scoured the internet quite a bit, but am left deeply yearning for more clarity and understanding!

Thanks!
Sridhar


texts:
could someone please do for me the calculation of total throughput of PCI-E? The best material I could find was a Xilinx pdf that mentioned 2.5Gbps as reference value and somewhat awkward formula that didn't utilize clock speed. You see, I had no problem just memorizing this thing until someone said 100Mhz and now I want to know how does 100Mhz become 2.5 Gbps.

EDIT

Both answers are very good. Thank you. Unfortunately, I can only mark one.


texts: I am looking for an ARM, preferably with an MMU, that is not in a BGA package so hobbyists reflow it at home.


texts:
I am making a amplifier with darlington Pair with 2N3904. In input i used my mobile phone & additional supply of 5 volt. It simulates well in Multisim11 BUT in real the second transistor gets so hot. When i open the power supply mobile shows audio connected but when the power supply connected it lost connection from mobile from but i can hear sound in my amplifires speaker as well as my mobile phones speaker.
*** Second transistor gets so hot....!!!


texts: What are the differences between a gyroscope, accelerometer and magnetometer?

texts: What is the difference between a 3-axis gyroscope, 3-axis accelerometer and 3-axis magnetometer? How do these sensors work? Why are all 3 used in some devices like smartphones, tablets, quadcopters etc.?


texts: Is it dangerous to use an ungrounded USB C charger to charge a laptop?

texts:
I have a laptop (with an aluminium case) that charges via USB C. The original power brick is 95W (but uses 60W charging in standard mode if I don't enable fast charging in software) and it has a standard CEE 7/7 plug.
When I travel or am in another room, I use a small unofficial multiple-output charging brick, rated 60W on the usb C output, which doesn't have grounding, only the standard 2 pin plug (CEE 7/16 Europlug).
[After a few weeks] I noticed that I get very small electric shocks when touching the corners of the laptop case with the forearms and also the touchpad had weird responses and ghost touches when using it but only very rarely. Today I realised this only happens when using the other, non grounded charger so I pulled out the digital multimeter and I get around 20V AC between the laptop case and my hand (with small jumps to 40V). DC reads are almost zero, probably within reading error (~0.4V). This doesn't happen with the original charger so my guess is that it's related to the lack of grounding, is this correct?
My main question is: is this dangerous for the device? Should I stop using the secondary charger completely? Should I only use it when not touching the laptop? Or is this normal for a low power device and grounding is not needed/mandatory?


texts: Power source for 12V PWM controlled light

texts:
I'd like to build a PWM-controlled light circuit. Since I'm not an electrician, I want to avoid working with 230 V as much as possible. I imagined an Arduino (fPWM = 460 Hz) controlling a MOSFET which controls a 12 V LED or halogen light circuit.

However, I want a decent light intensity, so I'd need 60 - 120 W depending on chosen bulbs.

The problem is that when looking for 12 V source, I found out that some of them require certain minimal load (around 10-15 W). I don't know if the frequency of PWM is low enough for the power source to "see" two states or if it could damage the source.

So my question is: do I have to care specially about the power source or will any power adapter work?


texts: I have this transformer I have 240 going in and only 56 coming out should be 110. Is that jumper correct for 240? On other transformers for 240 i have two jumpers on the outside and when it’s 480 one jumper in middle.


texts: Capacitor selection for LM3940 LDO regulator

texts:
My project requires 3.3v for operation. For the simplicity I want to power it with USB sources and this makes me to add step-down converter/regulator to get 3.3v from 5v line (let's omit input power filtering for a moment).

I've chosen LM3940 low-drop regulator because of the following:

works with 4.5v to 5.5v input range;
can handle up to 1A, however, power consumption of my scheme unlikely exceeds 100mA.

According to the datasheet (section 8.2.2) I should add output capacitor no less than 33uF but there is also one more requirement: the ESR value.

They give some advises in section 8.2.2.1.2 for proper capacitor selection but I'm not very familiar with ESR yet and want to get it right.

According to the plot above I should be pretty safe (let's get the very minimum) if output capacitor ESR value lies within [0.10; 0.32] Ohms range (if I assume only 0.1 Ohm and middle value between 0.1 and 1 on the plot).

Also one thing to note: my device will always work at room temperature (15-30 degrees) so now ESR oscillations should occur; with this understanding I want to use only one electrolytic output capacitor without messing up with tantalums.

So I've found some electrolytic caps (series K50-35) in local store and checked datasheet to find info about ESR. However, they only gives tan δ value and tells no about testing frequency (but it seems to be 120 Hz, as stated in Accuracy subsection). So I used this formula to calculate ESR for capacitors:

$$ ESR = \frac{\tan \delta}{2 \pi f C} $$

For given f = 120 Hz I've found that only following caps are suitable to be right for LM3940:

1000uF / 6.3v, 10v, 16v, 25v, 35v, 50v, 63v
470uF / 50v, 63v, 100v
330uF / 63v, 100v

However, I'm somewhat confused with so large voltage/capacity values and suppose that there is some kind of error in my calculations.

Could you please say if I'm right or not in selecting proper capacitor or I've missed something? Thank you!


texts: which is the best circuit simulator for my purpose?

texts: hi all i want to know the the limit of my circuit,upto which it can withstand,so that i can select or change the components accordingly.When i tried simulation in NI MltiSIM, it works fine,but the issue is when you apply 50A directly to an LED, it'll still work fine,I am wondered how is that possible??I would like to know which other simulators can show "when my circuit will get fried?"


texts:
On page 2 of this PDF, a voltage source \$V= |V| e^{0}\$ is connected to a load \$Z = |Z| e^{j\psi}\$. Then, the apparent power is described as
$$
P + jQ = \frac{ |V|^2 }{2|Z|} e^{j\psi}
$$
However, I think the power should be
$$
P + jQ = \frac{|V|^2}{|Z|} e^{-j\psi}
$$

Where did the extra factor of \$2\$ and the positive \$j\psi\$ come from? Is this is a mistake in the PDF, or am I missing something?


texts:
I have a momentary push switch connected to my mbed microcontroller. The switch is used to trigger an interrupt which changes a setting on the device.

At the moment the button works around 70% of the time. But every now and again when I press it it triggers the interrupt twice?

Is this a problem with my code or do I have a floating switch? And how would I fix it?

I have tried changing the resistor (I initially had 1K and it worked even less of the time)

Thanks!


texts: Interfacing Microphone amplifier with MATLAB A-weighting filter

texts:
I am working on a project that essentially would be used to measure the Noise produced by ceiling fans and regulate the speed if the noise interferes with speech levels.

For the first phase of this project I have to sense the noise levels. I have used an Electret Microphone Amplifier MAX4466 to detect the sound and have written a sketch in arduino to measure peak-to-peak amplitude and calculate the voltage. I am looking to provide this signal as in input an a-weighting filter (attached as example.m) on MATLAB. I have downloaded the MATLAB Arduino support package. I somehow can't figure out how to incorporate the analog output of the mic-amp into the matlab a-weighting code.

i'll attach the code (example.m) for reference. (it's an open source code for a generic A-weighting filter response with AWGN )

http://www.mathworks.com/matlabcentral/answers/uploaded_files/46634/example.m
http://www.mathworks.com/matlabcentral/answers/uploaded_files/46633/filterA.m

If there are any suggestions as to a better or different technique to solve this problem, I would appreciate that too.


texts: Parabolic dish focus microwave into mouth of feedhorn, how can wavefront be in phase

texts:
I have a parabolic dish 80cm, offset feedhorn, so section of parabola.
Fix 1cm mirror squares at centre and 4  points near edge.
Sunlight brought to common overlapping point at feedhorn.
 Distance further edge to horn mouth 73cm,
 distance centre to horn mouth 60cm,
 distance lower edge to horn mouth 52cm.

I have made telescope mirrors, the parabolic shape ensures a parallel wavefront is focussed to a point. The curve is so shallow in comparison, the software does all the correction calculations. It never occurred to me the geometry would seem to introduce a wavefront 'phase' error.
At 12 GHz, wavelength is about 3cm.

Have I missed something with my understanding here?
Or is this dish totally warped out of correct shape?


texts: ESP32: how to keep a pin high during deep sleep (RTC GPIO pull-ups are too weak)?

texts:
I'm using an ESP32 in a battery-powered device. The ESP spends most of the time in deep-sleep to save power. The device also has some 5V-powered sensors which I'm feeding from a MCP1640 step-up converter, which is on during the brief active part, and powered off via its "ENABLE" pin during deep sleep. The relevant part of the schematic is:

simulate this circuit – Schematic created using CircuitLab

So, I need to hold pin #4 high during sleep.
Due to sloppy testing of this part, I didn't know that the ESP32 shuts down its GPIOs during deep sleep, so pin #4 isn't kept high, and the sensors remain active. This drains the battery at a much faster-than-expected rate.

I'm wondering whether it's possible to workaround this blunder by a software patch (of course, it's easy to just add an external pull-up resistor to pin 4 - but I have a few devices on the field, which I would hate to have to travel a few hundred kilometres just to solder a resistor to! And the people around aren't tech-savvy to do this themselves; on the contrary, remote software patching is easy and well-tested).

For example, I tried the RTC's pull-up resistors:

gpio_num_t pin = (gpio_num_t) PIN_DISABLE_5V;
rtc_gpio_set_direction(pin, RTC_GPIO_MODE_INPUT_OUTUT);
rtc_gpio_pulldown_dis(pin);
rtc_gpio_pullup_en(pin);                     // set the pin as pull-up
esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH,
                    ESP_PD_OPTION_ON);       // keep the RTC IO domain powered

Executing this just before entering deep sleep almost worked, but it turns out the weak pull-up is too weak: probably ~38k if it is a resistance, or 90µA if it's a current source. This is insufficient to drive the ULN2003's pin. I also tried RTC_GPIO_MODE_OUTPUT_ONLY + rtc_gpio_set_level() too, but this didn't seem to increase the drive capability. Another possibility is light-sleep, which I'd avoid as it was buggy some time ago and I don't want to get my devices bricked.

So my question really is: have I exhausted all software options (since the hardware ones also require burning a tankful of gasoline)?


texts: Altium - Simulation of different circuits in the same project. What's the better way?

texts:
I'm working on a circuit simulation to understand the effects of the presence or absence of a determinate schematic parts. For example, I have one section with an high-pass and a low-pass filter

After I simulated this configuration and made my various analysis, I'd like to see what happen if I remove the high-pass filter

so my first thought was to remove phisicaly the components. But I have many channels like the one in the picture, so it could be frustrating to remove and add, remove and add again if I want to make many simulations.

What's the proper way to menage this situation?

Maybe:

I could use parameter in the values of the components (C1 and R3 in the example) and set them at C1 = 1T and R3 = 1T to inhibit their effect. But I think that they contribute anyway in the simulation. Isn't it?
I could create different sheets whit different circuits. But how can I tell to the simulator to take care only of that sheets in particular? I don't even want to remove and then add sheets from project, it remain intricate for me but it could be the only solution.

What do you think about it?


texts: ds18b20 temperature sensor data changes with additional lead wire

texts:
I've been working with some ds18b20 temperature sensors and I noticed something funny which I can't wrap my head around. For starters, I know the ds18b20 sensors are not "top of the line" and I've also read there are "many knockoffs" found in the market. These facts are not the focus of this question and the sensors fit my application. On to the question...

There are numerous resources out there which tell you how to wire up the sensors, so I'm pretty sure I got this right. I'm taking readings using a Raspberry Pi, which again, there are many resources which tell you how to interface the 1-wire device in software. In summary, the sensor is connected to a 5V pin on the Pi with a 4.7K pullup resistor between the 5V and data pins (also grounded of course). I'm able to read the sensor data via a Python script and the values are certainly within the ballpark. Again, this is not the issue, I'm just painting the full picture for completeness.

I have the Pi + sensor in a small box about 10cm^3 which is enclosed for the most part (i.e. no direct light, wind, etc.) and I've been running some tests indoors (consistent ambient temperature). I run the software for about 5mins until the temperature stabilizes in the box at 31.687 C, which is very close to what other temperature sensors (multimeter and infrared gun) are reading. Now to be very clear, I'm not trying to calibrate the sensors...I'm just trying to see if they're in the ballpark of other sensors.

The wiring for the temperature sensor uses 22 AWG solid core with lead wires about 5-7cm in length. Again, the initial temperature stabilizes at 31.687 C. I then added 26 AWG stranded core lead wires about 20cm in length between the Pi and the previous 22 AWG lead wires (basically, an "extension cord"). The temperature now stabilizes at 30.437 C. This is where my question comes in.

I get that the sensors have a +/-0.5 C rating, but I'm using the same sensor in the same box under the same conditions. I've repeated this test probably 10 times and I consistently get the same difference of about 1C. I don't understand why adding the "extension cord" would cause a difference. As a sanity check, I also swapped out the sensor and repeated the experiment. I found consistent behavior, but a difference of about 0.5 C. Overall, it seems the conclusion is that an "extension cord" will reduce the temperature readout (in my case 1/0.5 C respectively).

I don't know how to explain this "conclusion" and I'm hoping for insights. I initially thought it would be related to the "added resistance" of the "extension cord", but it is only about 20cm long, which from what I gather is "negligible" (I could very well be wrong here). I don't know...at this point I'm grasping at anything to understand why the sensors would give a different reading with the addition of the "extension cord".


texts: How to split or join an inout bus in the Verilog top module?

texts:
I try to simulate a multi-IC system consists of a MCU (or CPU or FPGA it does't matter) and a couple of memory ICs on the Modelsim with Verilog models of ICs. The MCU has 8-bit bidirection ports.
Memories has 8-bit bidirection data buses. I add to the testbench module 8-bit inout buses then connect them to the MCU and memories.
module testbech(bus0, bus1);
    inout [7:0]bus0;
    inout [7:0]bus1;
    mcu mcu (
        .port0(bus0),
        .port1(bus1)
        //something else inputs or outputs
    );
    mem mem0 (
        .data(bus0)
        //something else inputs or outputs
    );
    mem mem1 (
        .data(bus1)
        //something else inputs or outputs
    );
endmodule

Suppose I change a couple of 8-bit memories to a single 16-bit memory (or I change the MCU with 8-bit ports to a MCU with 16-bit ports).
How can I split or join an inout bus on the Verilog top module?


texts: Measuring transconductance of any circuit

texts:
May I know if the following transconductance measurement test circuit is correct because I am getting quite small Gm values ?

I suspect that I need to use some derivative function because changing the mosfets width by a large factor does not change the gm result much at all.

However, my test circuit is simulated in AC, not DC, therefore I really confuse if I should use derivative function or not ?

Note: X1 is a CMOS inverter


texts:
I have to make a digital filter with a dsPIC30F4011 (I'm completely new to microcontrollers). I was reading the documentation about the DSP Library to figure out how to use it. I created a simple C program based on a piece of code I saw in the documentation:

#include <stdio.h>
#include <stdlib.h>
#include <p30F4011.h>
#include <dsp.h>
#include <xc.h>

int main(int argc, char** argv) {

    fractional *dstV;
    fractional srcV1[2] = {Q15(0.2), Q15(0.2)};
    fractional srcV2[2] = {Q15(0.5), Q15(0.5)};

    dstV = VectorAdd(2, dstV, srcV1, srcV2);

    int n = 1;

    return (EXIT_SUCCESS);
}

But when I build it, I get the following messages:

build/default/production/main.o(.text+0x22): In function `_main':
: undefined reference to `_VectorAdd'
make[2]: *** [dist/default/production/test-dspic.X.production.hex] Error 255
make[1]: *** [.build-conf] Error 2
make: *** [.build-impl] Error 2
nbproject/Makefile-default.mk:135: fallo en las instrucciones para el objetivo 'dist/default/production/test-dspic.X.production.hex'
make[2]: se sale del directorio '/home/adrian/MPLABXProjects/test-dspic.X'
nbproject/Makefile-default.mk:90: fallo en las instrucciones para el objetivo '.build-conf'
make[1]: se sale del directorio '/home/adrian/MPLABXProjects/test-dspic.X'
nbproject/Makefile-impl.mk:39: fallo en las instrucciones para el objetivo '.build-impl'

BUILD FAILED (exit value 2, total time: 1s)

It says that the function VectorAdd isn't defined. Is there something wrong or missing?


texts: Arduino Uno with Ethernet shield is not working

texts:
I recently purchased an Arduino Ethernet shield, plugged it on top of my Arduino Uno and loaded up the WebClient/WebServer sketches that comes with the Arduino 0022 IDE, but I could not get it working.

I've tried a number of IP address configurations, played around with the router, etc., but to no avail. I can't ever ping the device, and never see it appear on the router.

If the 'link' LED on the Ethernet shield is not lighting up when I plug into the Ethernet jack, is this a sign of a faulty board? Or is there some other diagnostic test I can try to verify the board is OK?

I'm thinking the board is the problem and will try another one.


texts: I have a 4 pole DC mobility scooter motor but no controller. I want to use it to run a small mechanical hacksaw.  The motor on a 12 volt battery is powerful enough but is too fast. I have seen plenty of reducers on the net, but will these work with a 4 pole motor?


texts: Can I use a 3-wire AC adapter in a DC circuit?

texts:
I am reading through the excellent book Make Electronics and am in a chapter that suggests getting an AC adapter, cutting off the connector at the end and stripping the rubber outer coating back to expose the two conductors inside. When I did this with an AC adapter that I had laying around in the house, I found three wires inside instead of two. One was black, another red and the third yellow.

After googling a bit, I am guessing that the black is negative, the red positive and yellow neutral? I could be wrong, though. But, can I use this 3-wire setup to feed DC power into my circuit? And if so, do I use all three wires?


texts:
I have the circuit below.
Now my question is: why the rise time and fall time measured on Vout are the same as in a circuit using only one inverter gate?

I know the propagation delay is the sum of the delays, but can someone help me with a good explanation? Thank you!


texts: Where can I find beginners electronics project schematics online, for free?

texts:
I have bought the following books in order to start learning basic electronics:

Electronics All-In-One Desk Reference For Dummies
Robot Building for Beginners (Technology in Action)

My desire though, is for a good book that has a lot of projects in it that starts from the basic level, such as; from a few LEDs and a battery, to more advanced circuits such as making dot matrix displays for around the house and even up to robotics.

I really am serious about this and have even purchased a learn to solder kit which i aced well.

I have searched online, but since I am inexperienced, I don't know what is good.