texts: Convert a device that is powered by a 12V 2 amp ac-to-dc SMPS to a battery powered device

texts:
I have looked up my requirements in all possible sources (Google, StackExchange, DiY boards, etc.) but I have not been able to find a clear answer to my problem.

What I have is a device that needs 12V 2Amp DC Current and is currently powered by a AC SMPS which provides that. What i need to do is convert it to a battery powered device as where I am going is off grid but I have easy access to both Sealed Lead Acid Batteries and Li-On batteries that provide DC current well over 12V (13V-14V). I have been able to run the device by replacing the battery of an old UPS and running it off that but the size of the Unit becomes too large especially with the transformer (which is not such a big issue) and I need the device to be as effecient as possible.

What I have found out is I need a DC-DC buck-boost SMPS (nobody has written this directly, but it is what I have gathered so far) to regulate, be effecient and to be able to handle the variation in voltages etc without harming the device (Please correct me if I am wrong here.)

So basically the question(s) is:

Is it possible ? (my current knowledge says, it should be)
How would I go about it?
What kind of a circuit (with components) am I looking at to do the job?

PS: I humbly request all of you knowlwgable guys to be as forgiving as possible, as this is only my 2nd project involving power related stuff and 1st if u consider battries.


texts: How to drive P mosfet gate to ground in half bridge synchronous DC buck/ boost converter

texts:
The diagram shows the totem pole driver circuit for the Hi Side P channel Mosfet driven from PIC pin PWM output. This is part of a buck boost circuit running at 250KHz.
The biased totem pole transistors drive the gate of the P channel mosfet approx 6.5 volts below Vin to turn it on. The Mosfet gate threshold is 2-4V.
This works well if Vin is above about 8 volts but when Vin is only 5V then the gate is driven at 3V only 2 V below Vin. Instead of using the level shifter (or as well as) is there a way to drive the P-MOSFET gate to ground that allows the gate to charge up and then discharge quickly when connection to ground is removed.
Thanks


texts:
I'm using the C18 compiler and need to get the three bytes of a short long from MSB to LSB. I'd say I could use this:

void theFunction(unsigned short long input) {
    doSomething((input>>16) & 0xff);
    doSomething((input>>8) & 0xff);
    doSomething(input & 0xff);
}

But now my code isn't working (does compile, but doesn't run as expected). I do not know where the problem is, so can anyone confirm that this code works?


texts: Is it possible to add several plots to the same PSpice simulation?

texts:
I'm using OrCAD Capture/PSpice 16.3 to simulate a MOSFET circuit. One of the difficulties I'm facing is plotting a timing diagram of several voltages. If I simulate the project and choose which voltages I want to plot, they all come out on the same plot.

Now, I can add a new plot to the simulation and move each of the values I want to measure to the new plots, but having to do it manually every time I simulate the circuit becomes tiresome and I was wondering if there was any way to set up multiple plots for a simulation without doing it manually every time.


texts: switch debouncing - would toggle switch still bounce

texts: I'm having the classic debouncing headache with the Arduino. The switch is meant to turn an led on and off. So if I use a toggle button (SPDT) would it still bounce? Maybe it won't since it not a push button. How much more would it cost to use toggle? It's just that it's a project I've been asked to do for my local Fabrication lab.


texts: Can I expect a probe thermometer to still work if I cut it short?

texts:
I have a kitchen probe thermometer, a bit like this one

It's overly long for my purposes, and takes an annoyingly long time to record a stable value. I assume this is because it takes a while for the heat to travel up the shaft.

I have no idea what the electrical properties of the metal shaft are, or if there is any internal structure at all. If I simply cut the probe short (to a couple of inches or so), can I expect it to still read an accurate temperature?

(I guess the electrical resistance/resistivity of the metal might matter, or it might not, depending on how these things operate? Or maybe there's internal structure which could easily be short-circuited?)


texts: Is it safe to use a Peak detection circuit on a 200 V AC sine wave ?

texts:
I have an AC waveform of which I wanted to detect a peak. The application is to find when the AC signal is above some amplitude. The amplitude I want to detect is around 200 V.

I intend to use a peak detection circuit. Something like this:

Will it be fine as long as I use a ceramic cap of a high voltage rating, and a power diode ?

Thanks for looking.


texts: CAN Bus with RS485 CAN HAT for Raspberry PI

texts:
I have set up a CAN bus between 2 STM32 Nucleo's, where one is only sending messages and the other one is only reading them. This works, I have also validated this by connecting them to another CAN Bus to receive messages.
Now I also want to read CAN messages on a Raspberry Pi. I have bought the Waveshare RS485 CAN HAT for Raspberry Pi (https://www.waveshare.com/rs485-can-hat.htm) and followed their instructions to get started.
I have connected the CAN H and L to my STM32 Nucleo CAN Bus to read the messages, however I cannot get this to work. I tried their demo code to send and receive messages (https://www.waveshare.com/wiki/File:RS485_CAN_HAT_Code.7z) and I have installed can-utils to use candump can0. Both methods don't seem to work, because I am not receiving any message from the Pi and the receiving Nucleo is also not receiving any message from the Pi.
When I run ifconfig can0 to check the CAN connection the Pi gives me the following:
can0:    flags=193<UP,RUNNING,NOARP>    mtu 16    unspec 00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00
   txqueuelen 10    (UNSPEC)
    RX packets: 0    bytes 0 (0.0 B)
    RX errors 0    dropped 0    overruns 0    frame 0
    TX packets: 0    bytes 0 (0.0 B)
    TX errors: 1    dropped 1    overruns 0    carrier 1    collisions 0

I am not really familiar how to read this, but I guess no messages have been sent or received and there is a transmission error (don't know why that is, maybe because it cannot connect to a CAN Bus?).
Can anyone help me to setup the CAN Bus on Raspberry Pi with the RS485 CAN HAT correctly? Thanks in advance!
P.S. I would like to add the tag rs485-can-hat to this question for users with the same problem, but of course this is not a 'popular' tag and I don't have enough reputation to create a new tag. Can anyone do this for me?


texts: LTSpice - Printing resultant parameters based on expressions

texts:
I'm designing a circuit but I'm computing the values of components based on a set of design values. For example,

.param Vi=120
.param Po=100
.param Ro='(Vi*Vi)/(2*pi*pi*Po)'

where Vi and Po are design parameters and Ro is being computed from the design values. This is convenient but I don't know the value of Ro unless I compute it by hand, spreadsheet, etc., which is inconvenient.

Is there any way in LTSpice to automatically display/print out the value of Ro when I run the simulation?


texts: Basic ternary circuit to light three LED’s?

texts: I need to design a circuit that can light three different LED lights to simulate a traffic signal using two inputs. The first input is either -12v, 0v, + 12v. The second input is always on and it’s just +12v. Thinking as the ternary input as the control the  other as the main power, the following truth table needs to be met. We currently have a circuit working using relays and diodes but I want to try and simplify it (I didn’t design it). Thank you for any help and feed back.


texts:
I have looked up a few things regarding rectifiers but there is still something that bothers me:

If we put aside half-wave rectifiers or things like tripler and stuff, there is apparently two kinds of full wave rectifiers: the Full Wave Center Tapped Rectifier and the Full Wave Bridge Rectifier.

Full wave center tapped rectifier:

Full wave bridge rectifier:

Main thing between these two is that the second one uses more diodes (hence twice the voltage drop) but the other needs a center tapped transformer. This kinds of sums up (very roughly I agree) what I have read for the pros and cons of these two.

However my question is about something different, this kind of rectifier:

AC output on the left and DC output over the R1 load. (Please don't mind the different values given here).

So where I need help understanding is why I can't find anything about this "sort" of rectifier. Am I looking wrong or is there some king of problem with it that I have not cornered? Because if I am correct (and am surely not I think), this would combine the advantages of the two previously quoted rectifiers i.e. no center tap and a single diode voltage drop.

This should also act as a voltage doubler which maybe puts it in a different category...

Anyway there are things that I can't really explain to myself about that so I'm really looking for some clarifications from anybody.


texts:
I'm using the popular DIY motor:

Which his operating voltage is claimed to be between 3-6V.

I'm using a battery of 7.2V. I know that running the motor outside the recommended voltage range might shorten it's lifespan. I'm planning to use it for the next couple of months, about 10 hours of total usage. Will it be safe to say that the motor will still be able withstand this voltage?


texts: Reverse current blocking on switching regulator

texts:
I was thinking what is the best solution to add a reverse current blocking on switching regulator. My first thought was to look for an ideal diode circuit but all of them were too much expensive. The cheapest solution was to put a simple diode but they've got significant amount of voltage drop. I thought to hide the diode's voltage drop inside the switching regulator. Connecting the feedback pin of regulator at the diode's cathode the Vo would be maintained to just at the desired set point.

What are the pros and cons of this circuit?
Is there a better solution?


texts: How can I use an ARM chip to read & write 4164 DRAM?

texts:
I have an idea I'd like to pursue and partly because of their speed and partly because I'd like to begin ARM development I think a Cortex based board might be a good fit. I'm quite a proficient programmer (30 years experience) but my electrical knowledge is just a bit beyond basic but improving. I have done quite a bit of Arduino projects previously.

My question is what would be the best way to read/write to 8-bit 200ns RAM? The RAM in question is dynamic and is refreshed by another system so this would purely be 16-bit addressing with an 8-bit data bus. There are some bus contention signals to take into account (video chip access gets priority). I was thinking that FSMC might do it (by reading answers to SRAM addressing questions) if I assume it were possible to introduce enough wait states but I'm finding it hard to locate the documentation on this.

Any ideas on how to achieve this would be helpful to get me started. I am fully aware that I might be asking the impossible but I'm sure there must be a way.

Edit: As I've had a couple of requests for more information I will add some more detail. What I would like to do is perform DMA to a Commodore 64's internal memory which is a supported function of the computer. The 6510 CPU can be halted and its bus lines put into a high impedance state so that an external device can access the memory. The external device must respect the video chip accesses which are indicated by a signal line. The 16-bit address bus and 8-bit data bus are available to connect to. The memory is constructed from 4164 DRAM chips of varying speeds the slowest of which are 200ns parts hence the requirement.


texts: Does the ground line in a DC circuit carries current?

texts:
I'm confused a little bit about whether or not a DC return line carries any current. the reason is that in our design we have 2 batteries 24V and 8V, they supply ~4A and ~2A respectively to different parts of a circuit. Both (-) terminals are tied together on the PCB on a plane which acts as the system ground or reference. this PCB is coneected to the rest of the circuit thru a connector. The design allowes 4 pins for the (+) terminal of each battery, and 2 pins for ground (whcih connect to the PCB ground plane)
The connector manufacturer specs each pin to withstand 1A current. I think 1 pin for ground should be enough but added a 2nd pin for redundancy because the ground should not carry any current. also I thougth it would be better to have less gound paths to eliminate ground loops. My question is am I write or wrong? and we should add more ground pins?
thanks in advance!!


texts:
I am using external CT to measure Current parameter. I am using PIC16F1938 to measure analog . Now here i am looking for circuit and calculation involved to get proper current rating

datasheet

Min Current : 0.8A
max Current :30A
Primary Current 30A nom., 75A max
Turns Ratio 1000:1

I have 10 bit resolution ADC.
Kindly suggest me the circuit how we can choose the value. I got article with arduino
Energy meter reading with ac-1030

Let me know best circuit to be achieve better accuracy. Some forum recommend to use amplifier circuit . Let me know which is best


texts:
I know there is already a lot of questions about this but I just need a quick confirmation before I solder this on my device.

I use the three resistor setup to change the range. However since it's a mapping of maximum +/-5 to maximum +5 I only need two resistors.

signal -5to5 ---2k2---2k2--- +5V ref

The new range from 0 to 5V will be measured between the series resistors.

Correct?

Thanks in advance :)


texts: Micro-controller 3.3v power supply from 115v/230v AC

texts:
I'd like to build a power supply for a micro-controller - likely 3.3VDC using 'household' current (ideally same design for either 115VAC or 230VAC). From a safety standpoint, I'd like to come up with an efficient, low-heat approach.

Have done quite a bit of work from the micro-controller down, but have no experience with power supplies...

Can anyone point to a schematic or two to help jumpstart my learning process?

What does the list of major gotchas look like?


texts:
I'm trying to replace some old leaky capacitors for this radio I'm working on and in the data sheet they have this rating of cycles for the large capacitors near the bottom of the sheet here:

What does this mean? Should this be taken into account when I go looking for the capacitors? I've done some research and been to a few stores but it seems none of them post the "cycles" of these larger capacitors. Could this be some specification for older technology that isn't used any more? I'm pretty sure all these capacitors in this list are films with the exception of the bottom two -- they'll be electrolytic I presume.

If anyone here with experience in older components wouldn't mind letting me know a thing or two I'd be very thankful.


texts:
I'm trying to switch P-Mos given that:

Vcc > Vgs max
Enable_output is 0V or 3V
I'm switching both GND and VCC on purpose.

4. 8.4VR at 2uA !

The questions:

When Q2 is off, what is Vgs at Qsp1?
Is it going to be Vcc or Vcc-10v?
Will the Mosfet turn on and off with this schematic?


texts: LM339N - Comparator #4 not working as expected (always low)

texts:
I've designed a circuit for a battery indicator for my 18V Li-ion battery pack, based off this example here:
https://www.electroschematics.com/8347/24v-battery-level-indicator/

I have it laid out on a breadboard, and it works as expected for outputs 1-3, but 4 seems to always be low, unless Vin (18V) goes very low, as below:

LED 1: Red - always on

LED 2: Green - on >3V     ***This should be ~13.5V, which is my problem

LED 3: Green - on >14.8V

LED 4: Green - on >16.1V

LED 5: Green - on >17.5V

If I move the wires for 4IN- and 4IN+ to 3IN- and 3IN+ LED3 works properly, switching LED3 on >13.5V but off under that, but LED4 is still always on. So I don't think its the wiring, it just seems like comparator 4 doesn't work?

I've also put a new LM339N in, but it makes no difference.

Any obvious errors or thoughts?

Thanks

Edit/additional info
Vin should hopefully never be below 12.5V, otherwise my battery pack is toast!
I'm happy with how it currently works, with the current thresholds and LED brightness, except that of comparator 4.
The power for this circuit is through a switched input, so it's not always on and current draw isn't really a concern, but I will look into improving it anyway.
This will be used on a device outdoors, so I need the LEDs to be pretty bright.


texts: Measuring parallel resistor without current

texts:
I am trying to read the temperature sensor in a car with a Raspberry Pi. The temperature sensor's resistance changes as the engine temp increases however the temperature sensor would be in parallel to the voltage divider that runs to the ADC I would read from and since the temperature sensor grounds in the engine block I am unable to read anything after the sensor.
How would I find the resistance of the temperature sensor and read it from the ADC?

simulate this circuit – Schematic created using CircuitLab


texts:
I always wondered how ear phone wires acted as antenna giving input to the connected device and also acted as the output driving speakers... Does the the frequency of these has to do something with such operation ? MHz and KHz....  Even thought how could something act as both input and Output ? i.e. Output given corrupts the required signal(input)....

Andy Thanks for reminding that filtering ckt has higher impedance concerning input signal thus... both can be done... This is what I have understood... Nice.. If there any mistakes please correct....


texts: What power adapter do I need to charge a 7.2V 4000mAh battery that I made?

texts:
I made a Ni-CD 7.2V 4000mAh battery. What power adapter do I need to charge it?

How many volts and how many amperes should the adapter output?

Each battery cell is 1.2 volts.
I have a 9V 500mA power adapter.Is this adapter suitable for charging my battery and how long it will take?The adapter will automatically detect if the battery is full to stop charging it?


texts: Major causes for routing cut residues on a PCB board and how to prevent it

texts:
I am not sure if it is the appropriate to post this question here. I have a question regarding PCB SMT process. We found some PCB board after de-paneling using router cut, some of its residues being deposited over the PCB board.
What would be the root cause of such issues and how can we prevent it from happening again.You can refer the below picture that I have enclosed.


texts: What are these banana plug connectors used for?

texts:
These mate with one another (in the obvious male-to-female chain). They seem to be male-to-female banana plug adapters. Maybe I am being naive, but these seem useless. What are these useful for in practice?

EDIT: They do not come apart, i.e. they are not banana plugs waiting to be soldered to wire.

The only thing I can think of is that they're intended to be connector savers.


texts:
enter image description hereI am building a small project and I used an inverting amplifier to amplify AC signal.

When R2= 220R and R1= 33k, It can work with input signal of upto 600mV but when I reduced the R2=100R and R1= 15K the maximum input voltgae (AC) I can input is 60mV. I am giving an AC signal from a frequency generator(Can there be an impedance issue between the freq gen and my input opamp).

I want to reduce the resistor because of input noise. I can see a good input noise when I reduced R2 to 100R but I don't understand why its clipping the input voltage when I increase the input.

Appreciate if you can help me understand this phenomenon.

I attached the image when R2=100R and when input is >60mV ch1=input signal ch2=output signal, Capacitor value is 10uF


texts: Computing the gain on a small signal model

texts:
[The small signal circuit]

(https://imgur.com/a/ztAlABR)

I want to find the gain on the first transistor so i wrote the small signal model in the second pic.It is said to consider D1 open.

Can you guys give me any tips on how to find Vout?


texts: Wire multiple protective earth conductors together

texts:
I'm currently designing a circuit that will use a microcontroller and several relays to switch multiple loads connected to AC mains, and the connections to mains will be inside the enclosure. I'm considering using a plastic enclosure for the circuit. Each load has a protective earth conductor.

Is it good practice to wire together the protective earth conductors of each load inside the enclosure using a terminal block?


texts: What is "Two in hand" coil winding ? How does it affect the inductor?

texts: Having to wind an inductor, I was advised to do it "Two in hand". I understand it means using two wires connected at both ends. Do I need the same amount of turns ? Is the inductance affected (same question) ? Why isn´t the result two inductors in parallel connection ?


texts: FT2232H current consumption at 3.3V calculation

texts:
I would like to estimate the current consumption of the FT2232H chip
and I have some unclear issues with it.

In the chip's datasheet, it says the current for each voltage rail(except VCCIO).

In Digikey and a reference design that I have found it says that the chip current supply is 70mA at a supply of 3 - 3.6V - I think it might be a mistake.
because the datasheet says the same current supply for the VCORE voltage rail (Icc1)

Also, the datasheet doesn't mention VCCIO's current supply.
Is it possible to calculate the current consumption without this parameter?

How did Digikey calculate it?

I would like to calculate it by myself.
How can I do it?

Thank you very much!


texts:
I am struggling with moving average model of dc-dc converter as below. The image is my modified version from the lecture here (page 18).

My question is written in the image. Can anyone explain that?
  Sorry for the bad writing.


texts: Why is my DC power supply voltage decreasing when I increase my function generator amplitude?

texts:
In lab, we are constructing a power amplifier. We built it first in Multi Sim, ran a transient analysis (picture below), built it on a protoboard and then ran it through an oscilloscope to make sure it ran as intended.

We set it up exactly as pictured in our schematic, we checked it a million times. For some reason, when we increase the amplitude from the function generator passed a certain voltage, the output of the DC power supply starts to decrease and seems to stop at around 6 volts. The problem with this is that it is now biasing it at 3 volts, instead of 6, at the base. And now is causing it to distort.

Does anybody have any idea as to why the DC Power Supply output would decrease when we increase the function generator amplitude?

Thank you very much.


texts: If I have an FCC certified BLE module, can I use it in a product destined for Europe and CE mark the product with no additional (intentional radiator) testing?


texts: Step a motor from a slow charging power source

texts:
I'd like to design a circuit that can power a stepper motor from a very weak power source such as a solar cel. Physics will of course make that a problem, but in my case I have no need to power the motor quickly, or at a consistent step rate - even just one step per 1-2 hours would be enough, so I'm hoping there is way to do this.
My general thought was something like this:

Use a step-up converter to convert the low voltage from the solar cel to something higher with lower current
Use the stepped up voltage to charge a capacitor
When the capacitor reaches a sufficient voltage disconnect the solar cel and use the stored energy in the capacitor to power a microcontroller & stepper motor for long enough to make one step cw/ccw based on some logic in the MC
store the current step phase in the microcontroller's persistent memory
disconnect the motor and microcontroller and wait for the capacitor to reach the voltage threshold again

My question is whether this logic would really work? And whether it's possible to do in a closed loop way that doesn't rely in an external element checking whether the charge is high enough to trigger the motor step?
I'm very early on in my electronics learning but to me this looks like a behaviour that could possibly be achieved with a flip flop that's used to alternate the power between charging/discharging the capacitor. But, my understanding is still loose enough that I'm not sure if my understanding is wrong, or simply my attempts at implementation.
Also as a side note. I've chosen a stepper motor in the use case as it has a fairly strong passive holding torque. A DC motor would definitely be simpler to control, and possibly remove the need for storing state in the microcontroller memory, but wold be less stable when the motor was unpowered.

Edit
Here's my attempt at a version that's using a DC motor. In theory, when a bank of capacitors charge reaches a potential of 15v, then turn off when it drops back down below 5v.

It's not functioning currently, I think that's down to the SR latch, but I'm at the edge of my understanding and having a hard time diagnosing.
The 20V power supply is coming from a step up converter attached to a solar cel. The 50K resistor is there to slow down the capacitors charging speed in simulation.


texts: Using a TIP120 Darlington transistor to control a 12V fan from an ESP32 board

texts:
I plan on making a version of this circuit to control a 12V PC fan using an ESP32. The ESP32 GPIO pins are 3.3v logic level.
https://imgur.com/a/iqOfcME

You can ignore the lower part of the circuit in that diagram. That part is stepping down 5.5V to 3.3V because he wants to use only one 5.5V power supply to power both his board and his LED strip. I don't have that problem, my board has its own power supply, and I plan to use a separate 12V wall wart to power the fan via the TIP120
Here are my questions:

Will the 3.3V logic level at point (1) from my ESP32 board be sufficient to switch the TIP120?
What is the purpose of the resistor at point (2)?
Is combining the grounds of the 3.3V and 5.5V sides of the circuit at point (3) intentional, and is that a best practice? If so, why is that done? Should I also do that with my 3.3V/12V circuit?


texts: Ultrasonic transducer actual bandwidth for filtering

texts:
I have a pair of ultrasonic transducers with a "Thick Resonant frequency" of 975 kHz ±30kHz according to the data sheet. I did a frequency sweep test where I could see that they performed best at a frequency of 1 MHz (peak) as shown in the picture below:

I wonder what the actual bandwidth of the transducer model is:

975 kHz ±30kHz

or

1000 kHz ±30kHz ?

I am asking this because I am designing a bandpass filter where I need to define the bandwidth of it, and I am not sure what frequencies to choose as the transducers performs better at a forced frequency.


texts:
I am a software engineer .

I am working on a project based on raspberry pi and sensors, I am using sensors to get data and I am using an ADS1115 ADC to convert sensor analog data to digital.

I am concerned about the ESD for raspberry pi so i have used a metal case for this project. Also, I am using a MEANWELL Net 35-b power supply .

Question:
I read on a blog that the simplest way to have ESD protection is to use a metal case and connect the metal case to the ground of the power supply also ground of raspberry pi and power supply are connected. Is this the correct way to protect circuit and raspberry pi?


texts: Valid ranges for the source follower circuit, MOSFET?

texts: I'm trying to follow the solutions for a circuits book but I'm stuck in one area. I know in order to stay in saturation \$Vgs \geq Vt\$ and \$Vds \geq Vgs - Vt\$. But, I got confused with \$Vin - Vout \geq Vt\$. Why is this true?


texts: Beginner circuit multimeter reads strange current

texts:
I have constructed the following very simple circuit.

I would like to measure the current running through the circuit with my multimeter. I break the circuit as follows and connect the red lead to the jack that says 10A max. I turn the dial to 10 amps.

When I connect the multimeter, I am reading -0.01 amps or -10 milliamps.

The following simulation screenshot shows that I would expect to get 65 milliamps.

What am I doing wrong here for there to be a difference between my multimeter and the simulator?
EDIT:
Here is the result using the 200m setting. I am unable to get the led to light up and the multimeter reads 0.0


texts: How to simply this 2 to 1 mux boolean expression

texts:
I am going through this tutorial for a 2 to 1 mux.
They create this circuit:

They then derive this boolean algebra expression and simplification:

I'm confused how they made the simplification though.  I see that the expression can be simplified to \$I_0*I_1 * (\overline{A} + A)\$ by simplifying the double negatives, but I don't see how they got any farther than that


texts: Where did I miscalculate ohms law in my experiment?

texts:
I thought I finally had a grasp on how ohm's law works but when I set up an actual experiment, the numbers don't match up.
To keep a long story short, I converted a computer power supply into a lab power supply and I need a dummy load of some kind. I decided to try to build one. My first attempt was a nichrome coil at roughly 12ohms inside of a pvc pipe which I filled with plaster. It became dangerously hot after just a few minutes so back to the drawing board. As a temporary solution I decided to try electrolysis  in an electrolyte solution of baking soda and water. This is where I must be calculating or doing something wrong. To test this load I used a laptop charger (19v). Using a multimeter I checked the resistance of the solution through the carbon rods I had suspended in the solution and got a reading of 4500 ohms (4.5 on 20k setting). When I wired the multimeter into the circuit to test amperage it showed roughly 3.3 amps...
If V=I*R, the 19 volts divided 4500 ohms should only be .004 amps. How did I get 3.3 amps??
As I'm writing this question, I'm starting to think the laptop charger works on constant current, is that why? Or am I using ohms calculations wrong? Or what else is happening here?

Image 2 is the ohm reading. It shows 4.84 on the 2000k setting.


texts: How do I implement a simple finite state machine with 2 T flip-flops?

texts:
The following Finite State Machine (FSM #1)

can be implemented with 2 T flip-flops like so:

This makes sense because you have 4 different states {00,01,10,11} and flip-flip TA handles the left bit while flip-flop TB handles the right bit.

However, if you have a finite state machine (FSM #2) that has 3 states:

how do you encode the states? Do I simply say "A = 00, B = 01, C=11" ?

Also, the inputs are {x,y} while outputs are {0,1} for FSM #2 whereas FSM #1 both inputs and outputs are {0,1}.  I'm not sure if this is a notation problem I'm having, but how do you represent FSM #2's three states, inputs, and outputs in a table like the first diagram for FSM #1?

Would appreciate all / any advise!


texts: Understanding the PN-Junction Built in Voltage

texts:
I don't like asking duplicate questions but I couldn't find one that was quite the same. I apologize if it is similar to another.

TL;DR: How can a charge neutral substance have a potential? Why would measuring the voltage across a pn-block read 0 despite the built in voltage being present? Feel free to get as technical as necessary.

My question is one that I have been unable to find a satisfying answer for even in my microelectronics class. I understand the basics of the PN-junction. P-doped material connected to N-doped material through some process that maintains their crystalline structure and allows electrons to freely flow between the two. In equilibrium there is a balance between drift and diffusion currents which results in a depletion region of negative charge on the Pside and positive charge on the Nside. This creates an electric field which is the main idea behind the PN diode.

  Now I have two questions... we were taught that at some level of
  doping, a semiconductor has a potential. It can be found using a
  logarithmic relationship which I don't want to type here since my
  question is more conceptual than anything. How can there be an
  inherent potential in a doped semi-conductor if it is charge neutral?
  The way I understand potential is that it requires some sort of
  charge. The equation I mentioned before comes from the Boltzmann
  relations between concentrations of particles at different potentials.
  If a piece of silicon is placed in a potential then an imbalance in
  the number of holes vs electrons is created based on the strength of
  that potential. So artificially creating the imbalance of holes and
  electrons creates a natural potential. However, it is still supposed
  to be charge neutral... but it has a potential... does my confusion
  make sense yet?

Ok! I now understand this! I misunderstood something I read and that was causing my sadness. Basically, the concentration gradient of charge carriers between the Pside and Nside has to be continuous (no weird deltas or steps). The levels concentrations of these carriers are entirely determined by the doping of the Pside and Nside via the law of mass action. \$ n_i^2 = n_0 \times p_0 \$ where n_i is the intrinsic amount of charge carriers in a substance at room temperature. This quantity is conserved even under doping so we can see that the concentrations of minority carriers can be determined easily thank to this law. Now, we use boltzmann relations to determine the potential difference that the Nside and Pside will have relative to each other. The equation for that can be found here.
We use the intrinsic concentration and 0 potential as our reference voltage. This allows us to determine the potential difference due to the concentration gradient.

  My second question is about the PN junction as a whole. We know in
  equilibrium there is no current flow... but there is a built in
  potential. That's fine... diffusion current opposing drift current
  explains that. However, I don't understand why we can't measure the
  voltage drop across the PN block with a voltmeter. I've read that,
  again because the whole thing is charge neutral, as far as the
  universe is concerned it doesn't have a potential associated with
  it... but there is one INSIDE it? I don't understand.

I think I have isolated the issue with my understanding here... something weird happens with contact potential... can someone explain exactly what? When metal makes contact with the PN-Junction there must be some sort of "infinite" electric field

If you took the time to read this wall of text, thanks! I would love an answer to this question.


texts: Battery size to power a 240v 35watt fan for 12 hours and what size/ power solar panel to recharge it?

texts:
I'm a real novice when it comes to electrical engineering. Like a fish out of water. I want to create a self-sustaining fan for summer.

I'm trying a fan that's 240V, 35W. If I was going to run it for 8 hours, what size or power battery would I need? What would be the most efficient size/power solar panel to recharge it?


texts: How to connect Uart to serial data output?

texts:
A small DAQ converts some sensor value to digital outputs.
Since we need analog output, it has an analog converter. DAQ serial output
will go the analog converter. But Im confused with wirig DAQ and the analog converter.
The thing is Im kind of confused with the terminology of serial
connections.

In my diagram which pin will wired to where?


texts:
Consider the following situation

We have two capacitors, C1 and C2, both with a value of 10μF. The capacitor C1 through some switching action now has a voltage of -Ain + Vref across it whereas C2 has just -Ain across it.
My understanding is that, current will flow from C1 to C2, redistributing the charges and the circuit will settle to a steady-state in which both capacitors have a voltage of -Ain + Vref/2 across them as shown below:

My question is, what would happen if C1 had a value of 10μF but C2 had a value of 50μF? I understand that V = Q/C, so in order to equalise the voltage, it would take a lot more charge on the plates of C2. With the conservation of charge in mind, does that mean the final voltage across both capacitors would be -Ain +Vref/10?
In that case, we are missing (8/10)*Vref - where did that voltage go?


texts:
I want to adapt a 40 pin SMD (0.5mm pitch) for usage on a breadboard. Are there any adapters available that I can use together with a simple soldering iron?

Already I found the SchmartBoard adapters, but they only are available up to 2 × 14 (28 leads).


texts:
I have the following signal:

$$\cos(2\pi t) + \cos(2\pi t)*\cos(20\pi t)$$

How would I find the amplitude spectra of this? I know how to find the amplitude spectra of a signal of the form like so:

$$\cos(2\pi ft)$$

But what about a product of 2 cosines?


texts: Why do our electrical utilities use transformers way over their rated KVA?

texts:
My parents' house and my house have different electric utilities, but both are rural electric cooperatives. We both have 120/240V (60 Hz) split-single phase service (this is in the United States state of Tennessee). My service is sized 600A. My dad's service is currently sized 200A, but it's getting upgraded to 400A because his property has outgrown 200A.

My understanding is that transformer sizing should be fairly simple. Volts times amps equals volt-amps. Size your transformer for the volt-amps. I also get that utilities tend to under-rate things and run them "hot," but this just seems extreme.

(Related question: I was never clear whether the "volts" in this equation should be 120 or 240. Is the transformer rating based on the combination phase voltage, or the split phase voltage?)

My transformer has "37.5 kVA" stamped on the side of it. 600A x 120V = 72 kVA. My transformer is 52% the size it should be. Not terrible, but still seems very under-sized.

My dad's transformer (before this morning) had 1.5 kVA stamped on the side of it. They "upgraded" it to prepare for his 400A service upgrade. Now it says 2.5 kVA. 200A x 120V = 24 kVA. 400A x 120V = 48 kVA. His old transformer was 6% the size it should be. Now his new transformer is 5% the size it should be. That's even worse, by a huge amount. That's just ... crazy small.

This white paper backs up my calculations. What am I missing here? This can't possibly be correct.


texts:
I have a Sparkfun EL sequencer board, which uses the FTDI interface to connect to a USB cable. I would like to hook up a MakeyMakey via USB and communicate between the two. I have not had any success by hooking the two via a USB hub.

Is it possible to communicate between the FTDI/USB cable to another USB? Do I need to wire these together directly via USB? Are then even compatible?


texts:
I've been playing around with the well-known slayer exciter, and trying to make a tesla coil.

The standard 1 transistor setup works fine for me, but the arcs I'm getting are pathetic, and it can only light up about half of a CFL bulb.

I tried replacing the transistor I was using (BC548) with a larger power NPN (BUL310PI), which stopped the circuit working altogether.

Since the circuit worked with the smaller transistor, I thought it was either to do with the larger transistor being too slow or having too low an hFE value.

I thought if I used the BC548 to drive the base of the BUL310PI, I could overcome the gain problem if there was one.

The LED I was using for a diode lit up when I did this, so I had oscillation working again, but the coil couldn't light a CFL or make arcs. The LED also dimmed whenever I brought my hand close to the topload.

The transistor on the left is the BC548, the one on the right is the BUL310PI.

I've used 8 turns for the primary, ~300 for the secondary, and a large cardboard circle covered in aluminium foil for the topload.

I'm running the circuit off of 5V from an L7805.

I've tried all the usual slayer exciter troubleshooting gubbins, i.e switch primary connections, add/remove turns, etc.

What else can I do to make this work?


texts: Can some pins of the same port on AVR MCU's be declared as inputs and some as outputs?

texts:
Can some pins of the same port of AVR MCU's be declared as inputs and some as outputs?

If yes, then I am not able to understand how this works since we have to compare the pins of the port and also assign the values to output pins. It would be very nice if you provide even a simple program for this in C.


texts:
I have an approximately 1 meter LED strip in "warm white" running from a 2 amp power supply for some time now with no problems. I want to add another strip, of about 2 meters, to this same power supply. This second strip will have a switch on it, so sometimes the power supply will power 3 m of LEDs, sometimes just 1 m.

Should I up the amperage? Is it better for the amperage to on the high side or on the low side?


texts: Design considerations for low-current SMPS application

texts:
I've got a project I'm working on that is powered by a single Lithium-Ion battery (let's say design range is 2.5V to 4.2V), and a nRF52832-based MCU. I've decided to design a power topology that goes from raw battery to a "system" rail of 2.5V, and then feed that to all devices + the nRF52's internal DC/DC regulator.

My design target for "sleeping" power consumption here (i.e., idling until event occurs) is around 300uA or so. I don't expect peak currents on the rail to ever go past 20mA or so as well -- going by the nRF datasheet numbers (taken with grain of marketing salt), they claim ~15mA or so of current consumption.

So, I've obviously got a concern about the quiescent current (Iq) of my chosen regulator, which I'm basically stuck with based on the manufacturer. But, I also have a concern about a buck controller going into pulse-skipping or similar mode and giving me a great EMI/EMC problem to deal with.

The largest possible voltage delta (4.2V - 2.5V) gives me some pause using a LDO/linear part (~55% efficiency). I've looked at the AP3401, primarily because it is incredibly cheap. The datasheet is very light on the details, but it mentions pulse-skipping once. I imagine running at very low currents relative to the 1A number is going to put me in that range.

This TI TPS62740 naturally has a better datasheet, and seems like a "better" part for this / intended for these low-currents, but it also appears to quite literally be 8x the cost of the AP3401.

Summing up:

Recommendations / literature on very low-current switching regulator applications?
Experience with / stories about dealing with EMI-related issues with a regulator that is basically always pulse-skipping?
Suck it up and go with a linear regulator? Some kind of scheme that switches based on the system state?
Recommended solutions from previous experience? Target volume I believe is around 10K units/yr.


texts: Effect of shorting DC positive pin (Vin+) to Ground (GND) pin on Arduino Uno

texts: What effect would shorting a Vin+ pin to GND have? Assuming no DC power has been fed and the board is not connected to power. Would damage the board or has no effect?


texts: TPS61240 Boost converter IC is not working at all?

texts:
I am currently using TPS61240 as a boost converter for my project. As i did not have any sample previously so there was no way I could test it. I ordered the IC and placed it on my final PCB directly. PCB layout and external components are according to the datasheets. I ran continuity and input voltage measurement test. There is no problem in PCB and Input voltage. But I am not getting 5 volts from the IC. I am in great trouble. Any suggestion would be appreciated. Thanks in advance.

Here is the PCB layout.

and here is the Schematics


texts:
I'm plugging TV signal cable directly into an oscilloscope. TV cable looks like this:

First I connected outer shell of TV cable connector to GND of oscilloscope BNC cable and center to the center of BNC cable and observed no signal as shown in this little video:
https://www.youtube.com/watch?v=QZ4LjM1p2pA&feature=youtu.be

And then I connected 'only' the center of TV connector to center of the oscılloscope's BNC cable and I observed many signals fluctuating with a maximum around 20V. And when I adjust trigger level I see only 1 signal. Here is the little video recording:
https://www.youtube.com/watch?v=tET0UnLCc04&feature=youtu.be

I'm confused at 2 points:

1) Isn't any signal must be in a loop? Why I see no voltage when I connect inner and outer shell as in 1st video. And why I see a signal when I only connect the center to the center or oscilloscope? I mean to me it is like reading voltage from a voltmeter by only connecting 1 pole of a battery. I couldn't figure out why it is like that here..

2) Why am I seeing many signals (in 2nd video) and when I trigger I see only 1 signal? I couldn't show in the video but when I change the time scale I see a kind of sinusoid as well. Is that the carrier signal?

BTW the scope I'm using is an analog 10 MHz Oscilloscope.


texts: What is the correct supply voltage for LEDs?

texts:
I have a 5V supply power, three 5mm red LEDs, and each LED has 47-ohm resistor.
Two LEDs are bright but soon as I connect the third one all of them become dim.
Where am I going wrong? I'm new so a simple explanation will be appreciated.

simulate this circuit – Schematic created using CircuitLab
Edit: This might be a terrible schematic but I just started to learn about these things a few days ago.


texts:
So my two PV panels giving me an output of 40v, 1.5A.
I am sensing both current and voltage of the PV output to give an MPPT duty cycle pulse.
I want to boost the 40VDC to at least 400VDC and controlling the duty cycle of switching.
I looked for multiple boost proposed circuits diagrams. some have transformers which I would not prefer to use in my design, I want the design to be a simple one but it has to do the job of stepping 40VDC to 400VDC.
can you please provide me with the information or at least help me with the attached paper design

http://gistworldconpro.com/uploads/3/5/1420914303_313-_al_muzahid.pdf

Thank and regards, looking for your help please


texts: Why is Bob Smith termination for Ethernet recommended if it's wrong?

texts:
I came across this article today (more detailed paper), which claims that the widely recommended Bob Smith termination (75-ohm resistor + 1000pF to chassis GND) may not be ideal (or correct).  If this is the case, why is Bob Smith termination still recommended in Ethernet design guides from Intel, TI, etc?

Is the author of the article incorrect in his analysis?  Or do people just not care that the return loss could be improved with a proper choice of resistor?


texts: How do I properly ground DC and AC in the same enclosure (DIN rail)?

texts:
I am building an electrical panel with AC and DC supplied power. My AC ground wires connect to a green DIN rail connector which has metal on the bottom of this terminal and connects to the DIN rail itself (which then is connected to the overall enclosure via back plane).
2 questions:

For DC ground, should I use the same green DIN mounts as I am using for AC? OR should I use the standard gray terminal blocks as the "-" terminal block that all PSUs can share (use jumpers across several of these blocks)? I am using 12V and 5V PSUs(see schematic).

If I should use the gray blocks, do I need separate "-" blocks for the 12V and 5V PSUs

Schematic attached.


texts: In the pictured schematic, is there a band pass filter in place? I’m having trouble understanding the function of R4, R6, C3 & C4.  Any help or resources would be appreciated.


texts:
I am using PIC18F46K80, at a baud rate of 115200, a Stop Bit of 1 and no parity. I am sending data from a C# application(Baud Rate 115200, Stop Bit-1 and No Parity) to the PIC. After send some bytes of data, I get an over-run error in the PIC. I have inserted delays before receiving the data in the PIC.

T_UINT8 UARTReceive(T_UINT8 *t_ret)
{
    *t_ret = 0;
    T_UINT8 temp;

    while(!PIR1bits.RC1IF)
    {
        /* Wait till the data is received   */
            if((RCSTA1bits.FERR) || (RCSTA1bits.OERR) )
            {
                temp=RCREG1;
                temp=RCREG1;
                temp=RCREG1;
                temp=RCREG1;
                temp=RCREG1;
                // EUSART1 error - restart
                RCSTA1bits.CREN = 0;
                asm("NOP");
                RCSTA1bits.CREN = 1;
                *t_ret = 1;
                return 0;
            }
    }

    if(RCSTA1bits.OERR==1)
    {
        k=30;
    }

    /* Return the received data  */
    Delay100TCYX(0);
    asm("NOP");
    asm("NOP");

    return RCREG1;
}

Even after inserting large delay, I am getting an over-run error, on maintaining the same baud rate in C# application . How do I avoid over-run errors while receiving data in my PIC?


texts: How to calculate access time for a cache simulation?

texts:
We're simulating a MIPS cache with a program called MipsIT. We've reached a point where we should set access time for the memory.

But I don't understand how to calculate this setting. It says in the spec

  Reset the simulator and make sure that I-cache and D-cache are enabled. Set a reasonable access time for the primary memory. Let the other parameters have the standard values.

But I don't understand how to calculate a "reasonable" access time.

It says in the spec:

  To get real values at the simulation you must calculate the average of miss penalty. That average you set in as access time in the simulator.

But how to make out a formula and a calculation from it?


texts: Z parameters to Input and Output Impedance Conversion Question

texts:
I have to design a matching network for BGA7027 at approximately 870 MHz. My understanding goes that I should convert the S-parameters given in the datasheet to Z-parameters, from which I find Zin and Zout of my device, and then match those to 50 Ohms. The datasheet gives this table:

I tweaked values for 900 MHz a bit to get closer to 870 MHz so at the frequency of interest we get:

S11 = -0.893 + 0.223i ; S12 = 0.011 + 0.017i

S21 = 0.880 + 3.810i  ; S22 = -0.744 - 0.091i

I converted those to Z-parameters to get:

Z11 = 0.0113 + 0.0684i ; Z12 = 0.0029 + 0.0051i

Z21 = 0.1684 + 1.1423i ; Z22 = 0.0624 - 0.0205i

After that I try to find Zin and Zout using:

The main question is: is the ZL and ZS normalized impedance or its actual value? In other words, if S parameters have been characterized using 50 Ohm impedance, and my source and load impedances are the same, should I input 1 in place of source and load impedances in the equations above, as opposed to 50? I'm leaning towards it being normalized but haven't been able to find the exact mention of it anywhere. The other question is, if this approach to find Zin and Zout correct, or are there any fundamental mistakes in my reasoning?


texts: Circuit Board Design...Getting Rid Of A Relay and Adding a Choke and Capacitor Filter?

texts:
simulate this circuit – Schematic created using CircuitLab

Figure 1. Original Schematic

Is there any way to get rid of the relay in this circuit?
And would it be wise to add in a power regulator? If so how?

simulate this circuit

Figure 2. Edited @Transistor's schematic

Changed Transistors to PNP
Changed Bottom Proxy to NO 2 wire proxy
Changed Top Proxy to NO 2 wire proxy
Added 2nd Digital Counter signal

simulate this circuit

Figure 3. Choke and Capacitor Filter

If I did my research correct this should do the trick... Or is my research wrong.? @Transistor

Thanks


texts: trying to understand erratic LEDs behavior

texts:
I have a small PCB that holds 6 LEDs (model, fV 3.2V, 30 mA), 2 parallel lines of 3 LEDs in series. The PCB has wires soldered onto it that go to a connector about 10cm down the line.

In an installation with several of those PCBs, I've experienced that after a while a few of them only light up half the LEDs.

In the proper setup those LEDs are driven with a LED PWM chip. Outside the setup, i test them with a 9V power supply.

What I now want to understand is the behavior I observe when debugging those faulty boards:

I test connect 9V in connection A (at connector) and only half the LEDs work
Then I test connect 9V at connection B (directly on the solder joints on the PCB) and now all LEDs work
I go back to connect the 9V in connection A (at connector) and suddenly all LEDs work from here as well

There is no visible sign of a broken solder joint or lose wire connection. (Obviously, there could be, as the boards are handsoldered. Also, most connection points are covered with conformal coating and I am now suspicious if the coating puts stress on some of the solder joints)

What makes LEDs sometimes turn on and sometimes not?
Does this behavior indicate that either one or more of the LEDs are actually damaged, or is it more likely that there's a lose connection somewhere?


texts: How do i convert a boolean expression to NOR expression?

texts:
Ive got a boolean-expression

(~a and ~b or ~b and c)

And now i will convert that expression to a NOR-Gate

I tried it many times. I know the solution but i dont know how do i get this.

my last solution was: (~(~(~b (~a + c))) => (~(b+~(~a + c)))

solution: (b nor(c nor(a nor b)))

Thanks for help


texts: holding wiring in place for a small child busy box

texts:
Seeking advice on wiring and rewiring a busy box for my young son (switches, lights & 5mm stereo jack).

All the wiring and batteries go inside a box, along with a breadboard so just the switched and lights are exposed.

I've been using tape and bluetac to secure the wires in place which is ok, but they fall our fairly frequently.

Are there any suggestions for other ways I could hold the wires in place that still allows me to rearrange the box for him from time to time?


texts:
I'm programming an STM32F4 Discovery board to push a sequence of 12 bit values into the DAC data register. This works well using timer interrupts: inside my IRQ handler, I have code that looks like:

phase += phaseIncrement;
DAC_SetChannel1Data(DAC_Align_12b_R, function[phase]);

and the output of the DAC looks like I think it should. Note that phaseIncrement doesn't have to be 1 - if I want a high frequency output, I can skip points in function[], sacrificing the accuracy of the signal for a bit of extra speed.

Now, I am reading about DMA. It looks like the STM32F4 can only increment by one of three amounts - 1 byte, 2 bytes, and 4 bytes, depending on the size of the variable being transferred. Is this correct? Is there a workaround that will let me skip some of these memory addresses so that I can emulate my current output without less CPU usage?


texts: I have recently acquired an Arduino and LCD display, I have been experimenting with it and I have made it work, and had it working for a few days on a few different sketches. This morning, I uploaded a new sketch to the unit and all of a sudden it comes up with a line of solid blocks on the top row on the LCD (Freetronics 16x2). This happens even if I upload a new blank sketch, it stays with the top row of solid blocks.


texts:
There is a lot of fake products in the market, and sometimes the original products fail to protect electronic components from ESD.

My question is how do I test my gloves "with simple equipment" if it protect from ESD or not?


texts:
I have this schematic:

I had to replace T1 transistor with a MOSFET (because D4 on an ESP8266 has to be high at boot time and the transistor reduces the pin voltage, so the ESP doesn't boot - see my previous question).

So I replaced it with a IRF3205 MOSFET datasheet (I know it is  total overkill) base = gate; source = emitter; drain = collector.

The LED works (i.e. it turns off and on) but the LED in the "ON" state is really dim. What is wrong? It has to be something elementary, but I can't figure it out.

The LED is inside a button (12 V with internal resistor). D4 is the ESP8266 pin (3.3 V logic)

Thanks.


texts:
I'm reading through the datasheet of the TPA311x family.
I'm looking for the input range for pins INPR and INPL but I cannot find this information. I see the absolute maximum ratings, but it's not what I need. I'm interested in the maximum recommended input range for the audio signal.

I also measure an offset of about 2.90V on those pins, but in the ds I can't find this value neither.

If it's not declared, is it safe to use all the available swing, i.e. 2.90V ±2.90V? It means the input signal might swing from 0.00V to 5.80V.


texts: Properly controlling a 6V servo motor from a microcontroller?

texts:
Regular old 5V hobby servos can usually be safely connected directly to a microcontroller without any issues. When it comes to 6V servos (that also might be drawing sizable current), there doesn't seem to be as much information.

I've read that you can simply provide 6V to the + and - pins on the servo from a separate source and then provide the regular 5V control signal, but I doubt that this is the ideal solution.

What's the right way to control a (potentially high current-draw) 6V servo from a 5V microcontroller? Should the 6V supply just come from a voltage regulator and a couple of caps or is it important to have a more sophisticated voltage source?

Thanks!


texts: How do I make a voltage switcher using transistors?

texts: I have a 12V battery connected to an electromagnet. I need to be able to change the input voltage from 12V to 9V using a transistor. I was thinking of something that changes the voltage path to a more resistive one. I am just starting out with electrical engineering, so if someone could help clarify this problem it would be great.


texts: Could someone answer my questions on a transformer with regulator circuit in LTspice?

texts:
The circuit itself is a UK mains power supply turning 230Vac to 20Vdc.

The first section is a transformer. The second part is a bridge rectifier, it then moves onto a voltage regulator by the name of LM317.

Questions:

Considering that this is a UK mains power supply what transformer resistances are usual?

I understand that this requires more in-depth knowledge of the core and windings, its resistances and reactances, however choosing a resistance of 1 seems to be a bit too “simple” should I say. Upon changing resistances, it mostly only affects the negative voltage. I.e reaches a positive peak of 20V but does not reach a negative peak of -20V, like 0.01 out.

I understand for LTspice to determine the ratio of voltage, is to use the equation (V1/V2)^2 = L1/L2. Which is why the inductances are 2640 and 10 respectively as this produces a 20V output.

However, to simulate such a thing in ltpsice is this the correct way of doing so? (Youtube videos really don’t help much.)

Also, the inductance coefficient is 1, what is a more reasonable value?

The bridge rectifier (i.e changing 20Vac to 20Vdc) is easier to understand.

But I’m lacking understanding of how I could reduce the voltage lost? For this the peak voltage loses about 1V.

The diode used is the default diode for LTspice, which I have some sources claiming to be the 1n4148

Are there better diodes to use as bridge rectifiers?

I’m most confused about the voltage regulator.

C1 is important to reduce noise and upon adding more capacitors the noise reduces.

Is adding more capacitors before the voltage regulator good?

Is adding a polarised capacitor better?

C2 is there just for the voltage drop, otherwise it would be zero. However changing C2 to a resistor say, the input signal to the voltage regulator has a lot more fluctuations.

Why is this? I didn’t think it would have such an effect.

The input voltage into regulator is ~19V and output is 12.5V with fluctuations in the 10^-5. I do not understand how there is 6.5 voltage drop and regardless of the input voltage into the regulator the voltage is 12.5V.

What is the cause and how could I reduce this?

I guess the most important question here is, is this a good power supply circuit?

What could be done to make this better?

I understand that this is a long question, I appreciate your time for answering.


texts: This is something I do not understand correctly about transistor polarization

texts:
Suppose the following audio amplifier configuration:

Suppose that Vc is correctly configured to be in the middle of the rail.
So, at rest, Vc = 4.5V, Ve = 0 and Vb = 0,6V, right?

Suppose I inject a 1Vpp audio signal at the base.

As the signal rises from 0 to 0.5V, Vb increases from 0.6 to 1.1V. Because Vbe > 0.6V, the transistor will conduct. Ic will increase. As Ic increases the voltage drop on R1 increases, forcing Vc down. So, we see that Vc and Vb are 180 degrees out of phase.

What I do not understand is how will this occur on the negative cycle of the audio.

As the audio starts going from 0 to -0.5V, Vb will reduce from 0.6 to 0.1. Because Vbe will be less than 0.6 the transistor will cut off. No current will flow from collector to emitter.

In my mind, as the transistor cuts off, Vc will be 9V but this circuit is mentioned on the web as being an amplifier. It seem to me more like a half cycle rectifier...

What am I missing?


texts: How can I determine the voltage the resistive load in this relay?

texts:
I am hoping someone can help me understand something. I'm an engineering student trying to analyze this circuit, but am finding myself not understanding and going in circles somewhat. I've searched as much as I can but am still stuck.

The circuit is a relay. I did not design it, only analyzing it. The only part of the analysis I am getting hung up on is the voltage across the mosfet (Vds). I feel like I have a good understanding of mosfets and their operating regions. I understand this mosfet is a switching mosfet and must be operating in the linear region. I can confirm this when I measure the voltage in simulation software and get Vds << Vgs - Vth. For the load, I am using a 24V DC LED strip light. The lights dissipate ~3.36W, so I = 3.36/24 = 140mA and Rl = 171 omhms.

Here is my hangup: I want to calculate Vds to determine the current through the mosfet, as well as determine the operating region. The source voltage is 0V, but how can I calculate Vd? I don't know the current through the mosfet, because that is determined by Vds, and I don't know Vd because it depends on the current through the load. I feel like I am missing something.


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I'm trying to measure the current through a  1 milli ohm shunt resitor, I need a resolution of at least 250mA but I only have some op 07,  I'm from Venezuela an here its pretty hard to find components, the best I could find was the op07 and the 1milli ohm shunt, it's feasible to do wthat I need? the resistence of any wire is bigger than the resistence of the shunt so I can't use the op as an non inverting, the wire resistence will give me an offset of what I have any control, I'm thinking to use three amplifiers to get a diferential input. There is a better way to approach this problem? I would do it with regular 5% resistance, I can allow an error of about 10-15%
I have already tested the circuit suggested by Spehro Pefhany, I have to use potentiometers to get the values of resistors.

EDIT

I have already tested the circuit suggested by Spehro Pefhany, I have to use potentiometers to get the values of resistors.

The first two values are quite far from each other , I'm thinking in take the median and used to calculate the current, any better sugestion?

The resistance is supposed to be of 1miliohm

Edit:

I have made more measurements and get very different values, the red ones are with a small load connected between the shunt and ground, I think there is a problem with common mode voltage.


texts: Simple question on high bandwidth Opamp reproducing low frequency signals

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So if one were to use a high bandwidth Opamp, at say 10GHz, and use it to reproduce a much lower frequency signal, say in 1GHz or 700MHz, would there be attenuation or degradation  of the signal?? Or, would they be indistinguishable?? Assuming also that we ignore power requirements and price of the hardware...

This is not for a power supply design.


texts: Why do tube amplifiers have such (relatively) small reservior capacitors?

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In learning about guitar amps, I've been studying the schematics for solid state and tube amplifiers, and I found a pattern that I've never seen an explanation for.

If you consider any of the main styles of tube amplifier, you'll usually find a reservoir cap of a value of ~ <100 uf @ ~500V - regardless of brand.

Even on a fairly meager solid state amp however, I regularly see values in the 5-10k uf @ ~50V range.

Obviously, these amps don't run at the high voltage that we see on tube amps, but I'm not sure how that effects this.

The only theory I've so far come up with is that because mosfet's are so fast, the power supplies need more reservoir capacity compared to tubes.


texts: How do I protect against an automotive load dump?

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A load dump occurs when the load to which a generator is delivering current is abruptly disconnected. In automotive electronics, this applies to disconnecting a battery while it is being charged by the alternator. It is apparently well-described in this $65 SAE document; Wikipedia claims it can be "as high as 120 V and may take up to 400 ms to decay". This document claims a 12V system dump can be as high as 87V and 400ms long:

       12V system      24V system
Us     65V to 87V      123V to 174V     // maximum voltage
Ri     0.5Ω to 4Ω      1Ω to 8Ω         // source resistance
td     40ms to 400ms   100ms to 350ms   // pulse length
tr     10ms??          5ms??            // rise time

The last linked document also has a table listing TVS (Transient Voltage Suppressor) energy absorption, as follows:

  Table 2 - Energy [J] absorbed (Vclamp=45V)

td [ms]   source resistance [Ω]
     0.5    1     1.5   2     2.5   3     3.5   4
 50  18.57  9.62  6.26  4.50  3.41  2.68  2.17  1.80
100  37.15  19.23 12.51 8.99  6.83  5.36  4.34  3.59
150  55.72  28.85 18.77 13.49 10.24 8.04  6.51  5.39
200  74.30  38.46 25.02 17.98 13.65 10.72 8.68  7.18
250  92.87  48.08 31.28 22.48 17.07 13.40 10.85 8.98
300  111.44 57.69 37.53 26.98 20.48 16.08 13.02 10.77
350  130.02 67.31 43.79 31.47 23.89 18.76 15.19 12.57
400  148.59 76.92 50.05 35.97 27.31 21.44 17.37 14.3

Now, I want to clamp much lower than 45V (say 20V), and would like to recalculate these values. The author writes:

  Calculated using the method given in Annex E.1.1.(e)
  where Ri=RL (for maximum power transfer).

This reveals the formula:

  We = (Us)2 x td / Ri / 4.6

... And updates the table as follows:

Energy [J] absorbed (Vclamp=20V)

td [ms]   source resistance [Ω]
     0.5    1      1.5    2      2.5    3      3.5    4
 50  97.59  48.79  32.53  24.40  19.52  16.26  13.94  12.20
100  195.17 97.59  65.06  48.79  39.03  32.53  27.88  24.40
150  292.76 146.38 97.59  73.19  58.55  48.79  41.82  36.60
200  390.35 195.17 130.12 97.59  78.07  65.06  55.76  48.79
250  487.93 243.97 162.64 121.98 97.59  81.32  69.70  60.99
300  585.52 292.76 195.17 146.38 117.10 97.59  83.65  73.19
350  683.11 341.55 227.70 170.78 136.62 113.85 97.59  85.39
400  780.70 390.35 260.23 195.17 156.14 130.12 111.53 97.59

This gives a maximum value of 781J. Did I do this correctly? My TVS system must absorb up to ~800J, passing nearly 30A? It seems like a heck of a lot, though it will be for up to 6 parallel semi truck batteries (~100AH each) in addition to its 130A+ alternator. (Could the source resistance be even lower than 0.5Ω?) What combination of TVS elements can effectively pass 800J without violating its clamping voltage by much, and what makes it more effective than other solutions?

I am protecting low-voltage digital and analog circuitry, which also have their own power filtering.


texts: Why smartphone IR system uses an IC instead of GPIO?

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I have an android based embedded system, and I would like to command ir controlled devices, such as tv, air conditioner, sound system...etc. I need both rx and tx.

When I see examples on internet, most of them use lirc over gpio.

However, when I see most mobile phones with IR function, they use an IR encoder-decoder IC with an IR transceiver.

Why don't smartphones use gpio directly to control IR ?


texts: Conceptual question about Frii's equation

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That's a pretty basic one but for some reason I am stuck now:

Suppose I have a transmitter that transmits Ptx=4W_EIRP with an ideal, omni-directional antenna. The power applied to the antenna terminals is 4W.

Now Frii's equation states that the received power is Prx=Ptx * Gtx * Grx * L (Gtx, Grx antenna gains and L path loss).

Now assume a transmission 1m at 950MHz, the path loss is about 32dB. Assuming lossless components, I would receive 2.5mW ... enough to power a micro controller, sensors etc.

Now I assume I have perfect line-of-sight and create super high gain antennas like Gtx=20dBi, Grx=20dBi. Then the received power would be 4W * 10^((-32+20+20)/10) = 25W ! This is higher than the transmitted power and hence unphysical.

Where is the mistake?


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I'm using below things to make cnc plotter and cnc lathe :

  3x Nema 17 Motor, CNC shield v3, 4x DRV8825 driver, 3x Endstop, Arduino UNO

Some where in the post I read that if there is a CNC with 3 motors for 3-axis than at a time only one motor is active.

Q.1 Is this true if I run the program with GRBL using Ardunio UNO? And need the power supply of one motor for running 3 motors?

Q.2 How can I calculate the required power supply?


texts: Controlling RGB led strip each color with a switch

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I am creating a picture frame that will have RGB led strip surrounding the frame. There is no room for controller.

Is it possible to wire  a switch between every color cable so I can manualy turn on and off each color.
I would drill the 3 switches into the frame and there the user can assign the desired color.

Do switches need to be rated for higher current?
The total lenght of the led strip is about 1.5m so it doesnt take much.

Only problem i can think of is that, when I turn multible colors on, the  power/voltage  will split and the strenght of light will decrease.

Is it true?


texts: opamp circuit for amplify up from 1.1V to 5 V

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I am doing a DDS　function generator with AD 9850

,because of the charactericts of DAC converter http://www.analog.com/static/imported-files/data_sheets/AD9850.pdf, page 9 figure 5, the output of amplitude of waveform is decresing when increasing frequency, due to my requirement of DDS function generator
 a) operate within range 0 to 40 MHZ with 5V amplitude

So any opamp circuit can be suggested? as I am newbie to opamp device.


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This is a follow up to the question about I posted last night, Converting a schematic into a graph. From some of the answer, I was able to re-work how the graph is done -- with components as edges and connections and nodes. This has been a bit difficult to wrap my head around as normally, I think the inverse:

"Mark" is friends with "John" ==>
    - Mark, John are the nodes;
    - Mark<->John is the edge

But with circuits:

"Resistor1" is connected to "Resistor2" (in series) ==>
   - R1R2 is now the node (connection between the two)
   - R1 is an edge, R2 is another edge (assuming a complete circuit)

Anyways, I've updated it based on some of the feedback, and now have:

I've also added the voltage at each of the nodes (though here there is really just one non-trivial node). Does this seem like an improvement on the previous approach, and a better understanding of circuits? What parts still seem to be lacking in this updated diagram? [And thanks to everyone for their encouragement/feedback on previous approaches.]


texts: Most of the pipelined CPU, that I can find, is either an accumulator or general purpose register based ISA but is there a CPU with Stack Based ISA that is pipelined?


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This is the pass band that I'm using to filter some EMG signals through electrodes.

When I test it with multisim it works really well as you can see, but when I test it with real equipment (osciloscope and function generator,) the active low filter works fine and the active high filter doesnt work, conversely it shows up -11.8V (around 12V) which comes from the supply voltages. Any thoughts?

The output wave frequency was also distorted. When the input wave was like 5kHz the output wave was like half of 1kHz or less.

EDIT: I had checked the schematic a couple times and already replaced the opamp 3 times.

EDIT #2: The parts that I'm using are the uA741 op-amps.


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Possible Duplicates:
  what do I need to make 230V AC fan spin slower?
  220v AC Fan regulator

I have an old fan with a relay made for 4 different speeds. Currently, they are all shorted together, so actually it works in the fastest speed only, no matter what I select on the relay.

What should I do to make the other speeds work right without making fire?

At this post I saw that probably the answer is connecting a capacitor in series. What does "in series" mean in this case? What parameters of capacitors should I choose?

Motor params are: 220V 0.6A 75w


texts: High freq. response of op amp using Miller

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I am trying to find the -3dB freq. denoted \$f_H\$ in the following circuit, where \$R\$ has been replaced with a capacitor \$C\$. I tried doing that in two ways which yielded different results. I'd appreciate some feedback on which of the two is correct:

Applying Miller's theorem:

\$G_v=(A/sC)/(1/sC + R_{sig}(1-A))\$

First method:

\$f_H=1/(2\pi R_{sig}C(1-A)) = 1.58KHz\$

Second method:

I tried to determine the frequency at which the voltage gain decreases by a factor of \$\sqrt2\$, hence:

\$(A/sC)/(1/sC + R_{sig}(1-A)) = A/\sqrt 2\$

Substituting \$s=j\omega\$, yielded \$f_H=4.1KHz\$


texts: Can I add an LED light to an existing device?

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I apologize in advance if this question is nontrivially stupid, but I'm not sure how else I would find this out without a theoretical background that I don't posess...

What I want to do is add an LED light to this watch winder.

What I don't know is: is it possible to wire up a small low power device like an LED light so it 'taps into' the existing power supply without screwing up the device itself?

I suspect that if I tried to attach say, an electric lawnmower or a hairdryer to the same power supply, things would go wrong. But would something like an LED be within the tolerance so that it could draw power while the device itself still gets the power that it needs to operate?

Or would I have to resort to hooking it up to a 9v battery and hide the battery as best I can?

Please assume:

That I've found a way to mount it, etc. - I'm just asking about whether I can power it;
That we're dealing with only one of the watch-winders (I dont want the fact that they can be plugged into the power base to be a confounding factor, so if that complicates things, assume I'm only using one of them and it's plugged in directly which it can be).

Again, apologies if this is very obvious or stupid to any of you - I legitimately don't know.


texts: Modulation technique's effect on Active Sensor

texts: Knowing that Bluetooth and ANT+ use FH-SS and ZigBee uses DS-SS, I would like to learn of the modulation technique's effects on a wireless point-to-point connection if I am implementing the wireless active sensor prototype (measurement sent from device to terminal, with the terminal sending back infrared LED intensity to the device to adjust the settings. It would be great to hear from you about it. Thanks in advance.


texts: max Discharge current of li-ion battery (temporary)

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Is my assumption correct that the main limiting factor of maximum discharge current of a Li-ion battery is that the cell heats up too much due to its internal resistance/the current flowing through the cell? Does cooling the cell (for example in a Tesla battery pack) increase the max current that the cell can provide without overheating? Or is it merely to increase the longevity of the cells/their lifespan by keeping them relatively cool even under high loads and is it never permitted to discharge the cells with more amps than what they are rated for regardless of how well they are cooled?
I was wondering if 18650 Li-ion cells can be temporarily discharged at a higher discharge current than their max rated discharge current? (provided the battery is adequately cooled/temperature stays below 50 degrees celcius)
For example take the following cell:
Sanyo NCR18650BL (3350mAh, 7A discharge current)
Could you discharge this cell at for example 10Amp for duration of 1 minute? (provided cell is properly cooled)?
How much impact on the discharge efficiency will this discharging of 10Amp have approximately? (since more energy will be converted to heat efficiency should be lower)
Provided the cell is properly cooled (meaning no part of the cell reaches too high a temperature during the discharge)... is there a limit to the max discharge rate the cell can handle? Is this directly linked to the amount of "surface area of active cell materials" (as mentioned on battery-university's website; https://batteryuniversity.com/learn/article/discharge_characteristics_li?
Thank you!


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I want to use a peltier element to power some small test LEDs. The power source should be a TEC (thermal energy converters) or A TEG (thermal energy generators) element.
I see a lot of people that don't know what they're doing and it I want to ask this because it seems also like a frequent idea in the maker community (to power wearables, Arduinos, even wearables).
Since there is an order of magnitude difference in pricing - can I make this work with a TEC? it's an indication light, it doesn't have to work always, blinking would be fine. In fact, as a maker project/experiment this should be kept low cost.
Here's what I know and plan, keep in mind I'm a bleeding noob:

Since TEC1 elements are not intended to be used as power generators, these specs are unclear. From random videos I gather, sillily: A warm hand on a TEC1-12706 will give you ca 0.08V with unclear current. Assuming (sillily) linearity and avg. body temperature, it'd be in the range of .1V / °10C with unknown current.
from other semi related sources I gather I can use some current to increase the voltage (current to voltage converters), I'm assuming that I can transfer all overproduced current to voltage at some cost
Jule thief circuits let you access lower voltage output by collecting and then releasing it all together and is described more precisely here
TEG modules are described to be about 3x more efficient. The SP1848 module seems to give very roughly 1V/200mA per 20°C, a hand on the module on YouTube displays .5V (so roughly matches, not an order of magnitude difference but 5x)
a common LED uses ca 20mA and 2V. The SP1848 seems more affordable than any other TEG I found and may be an alternative.

My prediction is, using a TEC-12706, even with all the tricks in the world - I won't be able to light one LED using a candle, let's assume 40°C difference (.4V, unclear current).
Questions:

Is this a waste of time and effort and one should rather spend more money on a more expensive TEG element (not listed here)?
Is it advisable to start any experiment of this sort with the SP1848 module rather than the TEC1-12706?
How much can I rely on current to voltage converters and joule thief circuits/modules to help me out, practically?


texts: Controlled impedance/coplanar wave design

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We're using Diptrace at work which has no support for controlled impedance tracks.
I'm making a small 2 layer pcb for a TDR pulse generator, and would like to make one track about 50ohms impedance.

Using the Saturn PCB Toolkit, I get the following parameters for a 52ohms track on a FR4 board: 63 mils to groundplane (matches the pcb thickness specification), 40 mils conductor with 10 mils to the track surrounding it.

I've manually drawn a copper pour around the target track, connected it to the GND pour at the bottom layer using plenty of vias and defined the pour clearance at 10 mils. See screenshot:

Should this suffice? I realize this would probably not be sufficient for UHF/SHF/... work, but that's not what I'm aiming for at the moment.


texts: Does the polarity of this crystal matter?

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I am using TXC 7B 16.0 mghz crystal for my design. I just received photo proofs from my PCB assembly house and it appears they soldered this crystal 180.0 degrees reversed.

https://www.digikey.ca/products/en?keywords=887-1104-1-ND

Edit:
the real datasheet


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I am building a custom board for CC1101. Basically I only copy the schematic from the datasheet.

I understand SI is the MOSI, SO is the MISO.
However what is the SCLK pin? Is it the CLK or SCL?
And is CSn the SS pin? If not, which one is the SS pin?


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I am working on a project that involes an inverter made with IGBTs. The device I selected for builing the H bridge is this: STGW60H65DFB. One of my roles in this project is also to select a suitable heat-sink for the transistors.
I have done all the calculation needed for the power losses and I found that a single device (STGW60H65DFB) dissipates about 60 W, in particular about 50 W are dissipated on the switch and 10 W on the antiparallel diode.
About the thermal data, looking at the datasheet, it says:
RthJC Thermal resistance junction-case IGBT 0.4 °C/W
RthJC Thermal resistance junction-case diode 1.14 °C/W
Now my questions are: should I do the thermal calculations separately for the switch and the diode? Or can I assume an "average" thermal resistance of both?
If I should do separately, should I consider separated powers for diode and switch or use in both the cases the same power (the sum, so 60 Watts)?
Thank you.


texts: How to calculate size of capacitor for microcontroller that has changing loads on its 5V supply

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How do I calculate the size of a filter capacitor to reduce the ripple when I have a microcontroller on the same regulated power supply as a high current load like a motor?

My parameters:
Motor:  DC 5V; 0.82W;  180 mA (with PWM up to 200 mA)
PWM with 70%-100% Duty Cycle
Vdd = 5V = Vmax
PWM: 20kHz
f = 1/20kHz = 50 μs
The load requires a burst of 0.2A without reducing the voltage across it than 4.9 V for 50 usec
Vpp = Vmax - Vmin = 5V - 4.9V = 0.1 V
C1 = (I*f)/Vpp = (0.2 [A] *50 [μs]) / 0.1 [V] = 100 μF
All the searches I've done lead me to articles about filtering ripple on AC power supplies. However, I'm not trying to smooth ripple from a rectified AC supply. I'm trying to smooth out variations in an already regulated 5V supply as the load to the supply changes.
How do I calculate the rating of a filter capacitor to put on the 5V rail that feeds the microcontroller to smooth its input voltage as the load to the power supply changes? Maybe my calculations are correct?


texts: I am doing my own development board using LPC1343.I gone through the application note AN10986.I noticed the topic "Automating USB ISP".In that they described about USB softconnect. Now I am designing the board,a question arises whether is it necessary to use that softconnect or manual working is enough?....and also how much voltage(minimum) should be supplied to the VUSB pin to detect as USB ISP.


texts: Is there a device to control the current in a solenoid

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I want to control the current in a solenoid using a microcontroller. Ideally, I would an IC which can do PWM with per-cycle current limiting, with an SPI input. Something like the Allegro A3972, with only a single FET, rather than a dual H-Bridge.

I've also looked at LED drivers, which have the right kind of drive, but do not allow the current to be controlled by an MCU.

Does anyone know of such a device?


texts: How do I find out whether my switched-mode power supply is galvanically separated from mains?

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This question is a follow-up to Does switched-mode power supply feature galvanic separation? : Over there, stevenvh says:

  "... a mains connected SMPS, and most of those do have galvanic separation."

How do I find out whether a given SMPS (say, my cell phone charger or a similar device, so something without a datasheet readily available) features galvanic isolation?

If there is no third (earth) connection on the mains plug, is that enough to conclude that the DC output is separated from mains, i.e. do regulations like CE require isolation for non-earthed devices?
If that's not enough - is it sufficient to test both plaugs on the AC side against both contacts at the DC side with a multimeter, or are there designs that are not separated despite having no connection when turned off?


texts: pwm half bridge inverter- split capacitor voltage alternating

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In the half bridge inverter shown below, when driven by a PWM signal, the voltage Va (the voltage in-between the two capacitors C1 and C3) is a sine wave. I was expecting it to be a constant voltage at a value half of the rail voltage.

The second graph is the graphs the pwm is formed from and ho is the pwm signal driving the high side mosfet

Can anyone explain why the voltage here follows the sine wave of the pwm in terms of the switching and voltage and current in the circuit?


texts: Building a Shunt Active Power Filiter Using

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I am trying to built an experimental setup of a shunt active power filter to validate some Matlab simulations, I am using a SEMITEACH B6U+E1CIF+B6CI. (Here is the datasheet) and picture of the device :

The SEMITEACH module contains an 3 phase uncontrollable rectifier that i am using to power DC motor to form a nonlinear load.

The SEMITEACH also contains an IGBT 3 phase inverter connected internally to an internal capacitor, I want to use that VSI as and this capacitor into the shunt active power filter that will compensate for harmonics caused by the non linear load. Here is the schematic I followed :

So far, I was able to generate the compensation current, my problem is the injection of this current into the PCC, honestly I never tried injecting power into the grid, and I am afraid of damaging an equipment because I don't know if I am doing it right, so here is my question :

Once the compensation currents generated using the VSI, am I supposed to just shunt the output of the VSI directly to the PCC? Or should i use a device or something to inject this power?


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I want to produce a symmetric square wave of about 3 kHz with a high of 5 V and a low of -5 V.
I've been trying to do this with a 555 timer (Mouser P/N: 474-COM-16473), which I wasn't sure was the way to go. My understanding is that the 555 timer can only oscillate between a high voltage and 0 V, so I've been using that as a compromise.
I've been getting confused, though. I can't get it to go to 0 V on the low. Instead, the low voltage is 400 mV and the high is 8.2 V.
Here is my circuit.

C    is 2200 pF
R_A  is 100R
R_B  is 4K
R_L  is 4K
V_CC is a 6 V battery

How do I make this circuit produce a low output of precisely 0 V or preferably below 0 V?
What am I doing wrong or this the best that a 555 timer can do?


texts: How can I transmit a TTL signal to a computer?

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I am designing a data acquisition system including a sensor that outputs a TTL pulse signal (3 wires: power supply, common, and signal). I am trying to determine how to send this signal to a program like LabVIEW, and was wondering if an FTDI cable would be able to do this? If not, what should I look into in order to connect this sensor?

It is a Monarch Instruments Optical Tachometer, ROLS-W, data sheet here: http://monarchserver.com/Files/pdf/1071-4851-114_ROLS_Instruction_Sheet.pdf?1815445338784657948


texts: Measure Li-ion battery voltage with an arduino 328p

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I try to monitore the battery capacity once every minute by reading the voltage with the ADC.

The arduino is powered by the battery through a boost converter (5V). I put a mechanical switch between the booster and the Vin so I can easily turn on/off the arduino.

I assume that wiring the input pin (Batt sense) directly to the battery (at 3.7v before the booster of course) will damage the arduino when I switch off Vin, so I decided to put a N-MOSFET switch controlled by the arduino which I activate just before measuring the voltage.

Can this work ? Am I doing something wrong ?


texts: Is hardware handshaking not available when using a USB to RS232 adapter?

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As far as I understood there is two type of hand shaking. Hardware and software.
For hardware handshaking other pins of RS232 connectors used.
Does that mean of we us a USB converter we cannot employ hardware flow control?


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I am trying to feed the cosine wave from the DDS compiler to the multiplier and multiply with another cosine wave. The output of the multiplier is then feed into a CIC compiler as shown below.

I have directly wire the tvalid of the dds compiler to the cic compiler (bypassing the multiplier) since tvalid has to be '1' in order for the transfer to be initiate. The multiplier has introduce some delay and caused the output of the CIC compiler to be act like this:

The sudden drop of output data at the beginning of the startup/ every time I change the phase of the cosine wave (it takes 4 times output sampling period) to be stable.

However, if I eliminate the multiplier, the sudden drop in output doesn't exist so I am guessing it is the multiplier delay.

I have tried the AXIS FIFO with asynchronous clock and also just wiring the tvalid of cic compiler to constant 1. The output is the same.

How can I delay the tvalid so that tvalid is rise to 1 only after the multiplication complete?
Thank you!


texts: If I use the concept of virtual ground in a basic op amp circuit I end up with zero gain

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Since no current flows in a op amp,therefore no current flows via resistor$$R_c$$,which implies that $$V_+ =0$$Using the concept of virtual ground we can say $$V_-=0$$.Now using the fact that $$V_0=A.(V_+-V_-)$$and $$V+ ,V_=0$$ we get that the $$V_0=0$$ which is incorrect.
I can't understand where I'm making a mistake. I will be thankful for even a hint.


texts: Is there a resource to look up widely in-use/standard connector styles?

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I'm working on rebuilding a design that currently uses obsolete parts. I'm taking the opportunity to increase reading accuracy. In doing so, I will have to replace our current connector to go from a 2 wire resistance measurement to a 4 wire resistance measurement for a group of devices under test and increase max DuT capacity to fill the remaining multiplexer card slots. That will takes the design to a 96 pin connection. If I go to digikey and look up a D-sub connector that has 96 pins there's only 3 active parts. That doesn't bode well for longevity of the design, but then again I'm quite new to this so I'm not sure if that's a good indicator. Maybe it's as simple as large pin connectors are uncommon in general, but I'm trying to keep this a 1 connector design to reduce risk of operator error, wear and tear, and time loss.
Is there a place I can go to gage the popularity/longevity of a connector?


texts: Understanding amplitude-time peaks in one dimensional reflection and transmission of sound waves

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There is a one dimensional system of interfaces with a transducer sending and receiving sound wave (Plane wave) normal to the interface boundary. The system consists of two mediums, medium 1 & medium 2, with acoustic impedance of \$Z_1\$ & \$Z_2\$, thickness of \$D_1\$ & \$D_2\$ and sound speed \$C_1\$ & \$C_2\$, respectively. The arrangement of the system is as follows:

The arrangement has a transducer with the mediums lined in the order as in the image and at the end there is an absorber. This system can be treated as a transmission line problem/ model.

The amplitude vs time graph of the sound pulse is shown in the image below:

How are these peaks in the image marked with the respective reflection and transmission factors?

As per my understanding: The first peak (Blue) in the first (A vs t) graph is the amplitude of the pulse generated in the transducer, which is the biggest peak in comparison to others. Second peak that follows after time \$\frac{d_1}{c_1}\$ is the transmitted pulse with the transmission factor of \$\frac{2Z_2}{Z_1\:+\:Z_2}\$ between interface of medium 1 & 2. Similarly, between medium 2 & 1, after time \$(\frac{d_1}{c_1}+\frac{d_2}{c_2})\$, the transmitted pulse has a transmission factor of \$(\frac{2Z_2}{Z_1\:+\:Z_2}*\frac{2Z_1}{Z_2\:+\:Z_1})\$ which is the product of the transmission factor from 1st interface (incident pulse) and transmission factor in medium 2.
what about the last peak and the peak in second graph?

In third graph, I suppose the peaks represent the refection coefficients with the second peak inverted due to phase shift as \$Z_1 < Z_2\$.


texts: Input offset voltage transimpedance amplifier

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I am currently creating a transimpedance amplifier for a small-area photodiode that creates around 0.15mA, 0.00015A, from it's associated laser diode at it's nominal operating point.

I am currently looking to use the transimpedance amplifier configuration with a feedback resistor for a gain of 10,000, by using a 10,000ohm resistor, therefore creating a voltage output of 1.5V.

However I am looking at sources of error and one significant one seems to be the input offset voltage. Even with an extremely low input offset voltage, say 10microVolts, is this offset voltage not multiplied by the closed loop gain and therefore creates a theoretical offset of 6% of the voltage output, at 1.5V?

Furthermore even if the gain is reduced it still creates a 6% theoretical deviation as they are proportional to each other? Is this a problem that is required to be fixed with the use of the offset null pin on op-amps?

I have simulated this in LTspice with the use of an op-amp and a voltage source in series with the positive input terminal, however this only adds the 10microVolt different to the output. But this seems contrary to what I have read/understand the concepts to be?

Any help would be greatly appreciated!

Regards


texts: SMPS shuts down momentarily during relay switching

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simulate this circuit – Schematic created using CircuitLab

I have a micro-controller based relay switching circuit, powered by AC/DC SMPS module based on THX203H controller. The module is isolated flyback type. They circuit is powered from 220V/50Hz outlet.

The phenomenon I see it that sometimes the module shuts down momentarily when they relays switch a 220V load, even very light one (such as indication lamps). The phenomenon never happens when no load is connected. After experimenting, I came to conclusion that the switching noise on the lines is somehow able to destabilise the SMPS:
1. If I add a ferrite bead on the A/C phase, the phenomenon diminished significantly.
2. If I power the AC/DC from 220v/120v transformer and the load switching phase directly from 220V outlet, the phenomenon disappears completely.
Unfortunately, I have not been able to measure the hot side yet to see what actually happens.
Analysing the module compared to the reference design in the datasheet (attached) I have found that X and Y capacitors as well as varistor and input choke are missing. Also the input reservoir is much smaller than recommended (I tried to double it - no effect). The rest seem to follow the recommended design.
Did somebody have similar experience before? Any suggestions about what can cause the issue and how to resolve it ?
Datasheet of the controller:
https://lib.chipdip.ru/030/DOC001030452.pdf

Thanks!


texts: How does an ADC read non-constant voltage?

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I have a somewhat slow ADC the ADS1115 with a measly 860 SPS (about 1ms per sample.)

Assuming perfect conditions, I would like to know what would this ADC spit out:

Here we have a saw wave of 1 volt peak to peak (forgot to place units on y axis, assuming the low peak is 0C and high peak is 1V).

If the ADC starts reading at millisecond 2 what would it read?


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I have this project where I'm meant to design a changing frequency circuit using schmitt triggers. It cycles between 2 frequencies. In the below circuit, pretending the not gates are schmitt inverters and ignoring the resistor and capacitor values, and letting not1 be of much much lower frequency than not2, should and output connected to not2 cycle between 2 frequencies.

IE, while not1 is low, not2 undergoes normal frequency oscillation based on it's charging capacitor C2 through R2, but while not1 is high, not2 charges at a faster rate via the added voltage through diode and R3.

Obviously buffering and whatnot would still need to be done on the output, but is the general design workable with tuning the resistor and capacitor values or not? If not, what improvements can be made? Thanks for any help.

simulate this circuit – Schematic created using CircuitLab


texts: Calculating resistance in a circuit where relay is controlled by microcontroller

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I've been asked to calculate the theoretical resistance of R1 in the shown circuit. The information that I've been given is that the relay needs 60 mA and 12V. I've also been told that the transistor's hFE/Beta value is 20 and that the voltage drop between the base and emitter is 0.7 V. I've tried calculating the resistance of R1, but when I do I don't seem to use all of the information given which leads me to believe that I am doing it wrong. Furthermore, I am a bit confused as to what is meant by the term theoretical resistance of R1.

If anyone could lead me in the right direction I would greatly appreciate it.