texts: What will be the output ripple current per capacitor buck regulator?

texts:
I have a existing buck regulator design. Converter part number: TPS54340Q1.

Input voltage = 5 V.
Output voltage = 3.3 V

RMS ripple current is calculated as = 108 mA. (Don't worry too much about value. Conider the value for mathematical analysis)

I have two decoupling capacitors at the output:

a) Cout1 = 1 uF, ESR1 - 110 mOhm

b) Cout2 =  4.7 uF, ESR2 - 120 mOhm

Switching frequency = 500 kHz.

  Question 1

I just need to calculate how ripple current will be split between Cout1 and Cout 2. I mean how will be ratio.

Can we do the current splitting just as we do with two parallel resistors for ESR1 and ESR2?

  Question 2

Assume we got the value for each capacitor ripple current. How can make sure that the existing decoupling capacitor is enough to withstand the ripple current passing through it.
( I checked for rated current value in capacitors datasheet, there is no such parameters with ceramic capacitors but yes, there is rated current for tantalum capacitors. My output capacitor is ceramic type)

Done some research on internet from my end,but there was not much I could not find.

EDIT:

Cout1 Capacitor link

Cout2 Capacitor link


texts: AC dimmer- triggering triac using moc3041. lamp always remain on, and does not change its intensity

texts:
Below is schematic.

1) Problem is lamp always remains on,even if i haven't provided the Anode A terminal with power through micro controller.

2) Also please explain me the need for R7 resistor.

3) Is it because the  triac remains always triggered from AC through resistor R7.

Thank you


texts: How do I determine the power rating of a stepper motor?

texts:
I have in my possession two stepper motors that are clearly marked as 50 ohm, 22V motors. They have six leads each, which I believe makes them unipolar stepper motors.

It is my understanding (and experience) that unipolar stepper motors can be driven as bipolar stepper motors by ignoring the center lead, and that is what I am doing. When I measure the resistance between leads to determine which lead is the center of each winding, however, I find that the resistance between each "edge" lead and the center lead is 50 ohm, and the resistance between the two "edge" leads is actually 100 ohms. It is my guess that this is because when driven by a unipolar driver, current is never passed between the "edge" leads, and only ever from the center lead to one or the other "edge". This arrangement would make the 50 ohm rating make sense. Is this correct?

Because I am driving these motors as bipolar motors, however, I see double the resistance that a unipolar driver would see. I am also using a "chopper" driver, or constant-current driver, and I have the ability to select the maximum current for the motor. How do I calculate this? Is it a simple question of ohm's law, using the 100 ohm value I measured between the "edge" leads?


texts: How to replace a switch with a NJK-5002c hall sensor?

texts:
I'm building a 3D printer, and I want to replace my endstop switches with hall sensors instead. I've bought some NJK-5002c hall sensors from Ebay, but am unsure how I can hook them up to replace the switch.

The previous setup that I have, which works, is that each endstop uses a simple two-pole switch. When the 3D printer reaches the top it hits the button on the switch, and connection is made. The two wires from the switch is connected to two pins on a RAMPS board.

The NJK-5002c doesn't have a lot of documentation, but I've found that if I connect the brown wire to V+ (12V), and blue wire to V- then the black wire will toggle between V- and V+ when a magnet comes close to the sensor.

Now, I'm unsure how to hook this up to replace the passive switch. I'm worried that the RAMPS board will be damaged if I hook up V- and the black wire directly to the two pins on the RAMPS. What do you suggest?

EDIT:

Link to the item I bought.

Schematic of RAMPS 1.4 board

Actually, it seems like the RAMPS 1.4 board has three pins for the endstops, and thus matches the hall sensors perfectly. The passive switches I'm using are connected to the "Endstops" pins between signal and GND, and I think that I can just plug in the NJK-5002c sensors directly to the three pins. I've connected it, and think it might work. Just need to reinstall some software tomorrow to confirm that the software detects the triggering.


texts: Capacitance multiplier with voltage regulator

texts:
I am trying to make a low noise voltage regulator.

My concept is to use a symmetrical regulator using LM338 followed by capacitance multiplier (ESP version).

According to Rod Elliot from ESP, the capacitance multiplier is able to source around 2.5 amps whereas the LM338 can source around 5 amps.
My question is, if I follow the scheme like this,
(Rectifier--->Capacitance Multiplier--->Voltage Regulator)
and if my load draws more than 3 amps, will it put too much pressure on the capacitance multiplier?

If so, is there any other way to achieve more current handling capacity from the capacitance multiplier circuit by paralleling output devices?


texts: Set the Gain of an Opamp Accurately Using a Potentiometer

texts:
I want to set the gain of an opamp accurately using an potentiometer, with low thermal drift and good long-term stability. From what I've read, there are three basic ways of doing it, but none of them performs really well.

Configuration 1

The first way is simply using a potentiometer as a variable resistor. Unfortunately, it means the uncertainty and drift of the potentiometer's end-to-end resistance is fully incorporated into the gain equation.

Configuration 2

The second way is using the potentiometer as a real potentiometer (divider).

In this configuration, as it's only a voltage divider, only the relative position of the wiper matters, the absolute end-to-end resistance of the potentiometer is not important, thus a much higher accuracy is possible. Thus, it's recommended that a potentiometer should be always used as a potentiometer if possible.

Unfortunately, because how the potentiometer is connected here, the gain of the amplifier's adjustment is highly nonlinear, and probably unsuitable for most applications but audio.

Configuration 3

Source: Analog SEEKrets, by Leslie Green, fair use.

It's possible to linearize the gain in Configuration 2 using two additional resistors. However, the gain is, again, depends on the absolute magnitude of the end-to-end resistance of the potentiometer, making it less useful.

Question

Are there better ways to make use of a potentiometer, without purchasing a more expensive one with better tolerance?


texts: EMI Issue: Ringing in switch mode power supply layout (5V -> 3V3)

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I am working on a device which is undergoing testing to pass FCC part B (CSRR 22) emissions. At one angle and polarization (Vertical) the device fails as it has emissions in the 100-200Mhz range which breach the threshold.
The test result shows two characteristic peaks at 145Mhz and 128Mhz. One source of wider band noise is ringing. The ringing has multiple harmonic components.
Problem
The PCB has 2 Switch Mode power Supplies (SMPS) These are Semtec TS30011/12/13 series chips. (DATASHEET) Upon closer inspection, there is a ringing on the power output (before the inductor stage) SMPS 1 has a ring at 145MHz while SMPS2 has a ring at 128Mhz. It is worth noting that they have different loads on them. Their schematics are identical their layout is some what different but 80% the same.

What layout options do I have to reduce the EMI noise?
I am busy adjusting the trace thickness going into the inductor to reduce stray capacitance

Note there is a GND pour which is not seen in the layout which ties all the Caps together fairly well
I am at a loss for how to adjust the filter components to reduce the ringing.
Test Results (3M, Vertical Pol.)

Schematics and Layout of 1

This can be solved by placing a ferrite core onto the power supply cable going into the device, however this is a non-optimal solution for various cost and aesthetic reasons.
Pre inductor measurements

Layout of Both SMPS next to each other
The all run reference to GND which is hidden, the power layer below supplies Vin at 5-12V they each are fixed to output 3V3


texts: Is a diode an effective way to replace a resistor in an application where heat should be avoided?

texts:
Currently with my project where I removed some christmas lights from a string, I used a resistor in place of the removed bulbs successfully.
(Note: Skip down to "Diode as replacement?" section for the question. Below are the details for reference)

Here is what is going on currently:

R1 is a 150 ohm 10 watt resistor, and
R2 is a 220 ohm 10 watt resistor.
The whole string has these specs:

120 volts (outlet)
0.34 amps
40.8 watts

This means each bulb is:

2.4v
0.17 amps
14.11765 ohms
0.408 watts

Here is what is running through R1:

38.4 volts
0.17 amps
225.88 ohms
6.528 watts

And here is what is running through R2:

26.4 volts
0.17 amps
155.29412 ohms
4.488 watts

(note: calculations calculated via online calculator)
It works.
However, the downside of using a resistor is that it gets very hot, and according to the heat chart, in order for it to be cool enough even to not burn to the touch, it would need to be at 15% load.
See an earlier comment I made:

... about 44C is the threshold for pain in touching a hot surface, so
around 42C (108F) is safe to touch... according to the chart, the
safe-to-touch threshold is at only about 15% load!

You can see from the chart (thanks @Bort), the limitations of using a resistor in this case:

This chart is for the 220 ohm 10 watt resistor. (part number and datasheet)
In other words, I would need a very high wattage resistor in order for it to run cool, which isn't practical. Or, I would need to string together many resistors, which also is not practical.
I'm worried that something like a leaf could land on the resistor and catch fire. So as a result, I have unplugged the lights for now (still have a lot of time before christmas!).
Even though for example the R2 resistor is running in the safe zone for the resistor at 65% load, still that is 165°C which is actually a very very hot 329°F!
Over 300 Fahrenheit is very hot, and as such it is not practical nor safe to use a resistor for this project, even though it works and is running in the correct range and is used correctly.
Other options are build a heatsink, but for $3 or even $10 string of lights, that makes no sense. And attaching a large piece of metal (for heat dissipation) could work but would turn the christmas lights into an eyesore.

Diode as replacement?
So I was thinking about if there could be an alternative to using a resistor, since it doesn't make sense to use a resistor in this case due to the reasons described above.
Someone suggested that I could use a rectifier diode in place of the resistor in order to step down the voltage.
This makes sense, by stepping down the voltage, it would subsequently reduce the wattage and hence possibly remove the need for a resistor as the whole string would have a lower wattage due to the formula for determining wattage from amps and volts.
So that means that to replace R1 with D1, we would need to step down the voltage by 26.4v, and to replace R2 with D2 we would need to step down the voltage by 38.4v.
See this new schematic with diodes instead of resistors:

So if that is right, it would mean that for example on the D1 string, the remaining voltage going through the remaining would be 93.6v.
Assuming the diode does not affect amperage, then that means that going through the remaining 39 bulbs on that string are:

93.6 volts
0.17 amps
15.912 watts

15.912w / 39 bulbs = 0.408w through each bulb
This is the original wattage going through each bulb, which is perfect.
So I have a few questions about this:

Would this work? If not, what can you do instead?
Would the diode not get hot?
Are my calculations correct?
Any other variables to consider?

Thanks in advance!


texts: Can I change the voltage (12V) input into my optocoupler to 24 V?

texts:
simulate this circuit – Schematic created using CircuitLab

I have an inductive sensor (LJ18A3-8-Z/BX,) normally open 6V to 36V 300mA. It is connected to a 12V 80kHz single channel opto-coupler. At the moment it is connected to a 12V DC power supply.
The positive wires (brown) from the power supply and sensor are screwed into one terminal on the opto-coupler board, the negative (blue) wires between the power supply and sensor are directly connected and the final wire from the sensor (signal?) connects to the second terminal on the opto-coupler board. According to the specification sheet for the sensor, it operates at 12V 8mA or 24V 15mA.
Can I change the supply voltage to 24V and if so, would I need to change or add a resistor to the opto-coupler board?
Between the terminals on the board and the opto-coupler chip is a 1Kohm resistor and a red LED on the other side. My thinking is I've essentially increased the power in the circuit by a factor of 4, assuming I should also increase the resistor by a factor of 4 as well?
optocoupler link data on the optocoupler link to supplier


texts: So for the following circuit, the lowest the output voltage is -Vcc + Vce(sat) according to my textbook. However why can't we assume a lower value than Vce(sat) at the collector-emitter junction of Q2? Is it because the current mirror would not work at a collector-emitter voltage less than Vce(sat)?


texts: I am a beginner wanting to know how to interface the spartan 3e board with the pickit2- PIC16F887. I have so far connected j2- pin a6(spartan) to port a Pin1 on the PIC, the ground Pins and j2 pin e7 to output port RD 1 on the PIC. I'm trying to configure a code that will run an elevator and I am also having trouble putting the pull-up resistors for the pushbuttons on the spartan board- they seem to be super-sensitive. Any advice would be great or if you know of some tutorials that involve interfacing the two boards. Thanks ahead


texts: Turn a LED on and one off, with a single Reed switch

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I would like to create a circuit in which a Reed switch is able to switch current between two LED. Is this possible without any IC or others components?

One led is on and one off, until the Reed switch is activated. I saw this working with 2 different load (led and lamp / led and motor) and I'm thinking If the same is possible with 2 LEDs.

5V used in the circuit.

I know there are 2 kind of Reed switch, and I do not care about which to use if it solve the problem. I anyway prefer to use the NO one.


texts: PCB surface mount alternative for JST-XH connector

texts:
I am having a very hard time finding an answer to this, most likely because it is rather difficult to search for items without knowing the acronyms or names for the connector types.

I have a PCB that contains what I believe to be a JST-XH connector with an accompanying female cable:

What I would like to do is make a new PCB that would contain the female connector so the boards would essentially plug into each other - stacking the boards. My problem is that I am having a very difficult time finding a female PCB surface mount JST (or whatever it is) connector.

Does anyone know if such a thing exists? If not, I see a few alternative options:

  Remove the connector on the board and replace it with something like this

  however removing existing components is typically a tricky business so
  this is not ideal..

  Connect the two PCBs with standoffs and use ribbon cables between the connectors; or
  Strip away the wire housing and treat the wire like a pin to solder to the second board, which is less than ideal and will most likely be unreasonably messy.

Does anyone have any ideas for a scenario like this?


texts:
So a few of my buddies and I (all undergraduate Electrical Engineers) were discussing FM signals. We found we all understood the modulation and signal profile itself, but none of us could think of a good circuit example for how the carrier wave and modulating wave are combined.

I could instant think of how to code an MCU and then use a filter to generate the FM signal so we all accepted that possibility.

But knowing how long FM has been used and that the rise of modern, cheap MCUs is relatively recent in electronics, there must be a host of way to accomplish this modulation scheme.

I'm just wondering if any of you know of any easy ways to do FM? Simple circuits would be great! But I'm also interested in any and all more complex methods (explanations would be appreciated!)


texts:
I am currently in the process of building a sensor-less 3ph axial flux BLDC with concentrated windings. I’m thinking 12s10p but have not yet decided. It’s just for a project - not for real world applications. And by no means and I am expert in this subject. However I am trying to gauge what size power supply I will need to drive it. I know that the speed I want it to operate at will also impact this to some degree. However is their a rule of thumb which will help take this into consideration. If I know the parameters of 1/12 of the coils.
Below are the estimated results I get when using a solenoid calculator for one coil. (They are air coils)
Coil Parameters |
Wire Diameter -     .321 (mm)
Number of Turns - 2000 (turns)
Bobbin Length - 40 (mm)
Bobbin Diameter - 31 (mm)
Rated Current  -  1amp (I)
Gap Distance -  1 (mm)
Results
Turns per Layer - 124 (Turns per Layer)
Number of Layers - 16 (Layers)
Coil Diameter - 40 (mm)
Cross Section Area - 970 (mm²)
Total Length of Wire - 220 (M)
Total weight of wire - .159 ( Kg)
Resistance/(M) - .213 (Ohm/M)
Resistance - 47.063 (ohms)
Inductance  - 88549 (uH)
Voltage at Rated Current - 47.063 (V)
Power at Rated Current  - 47.063 (W)
Electromagnetic Force   - 1776 (N) 399 (Lbs)
Cross Section Area - 706  (mm²) (A)


texts: Voltage Multiplier: step by step explanation

texts:
I do not understand how this voltage multiplier circuit works:

wherever I have read (also Wikipedia), I have not found a step by step explanation. I do not understand if the voltage drop across the diodes in conduction is negligible or not, and in general I need to understand the temporal trends of the voltages at the ends of the capacitances. Moreover, I do not understand what happens when the input AC voltage is different from its maximum value.

Can you give me a detailed explanation on what happens?


texts: Options for 2 or 3 band active audio tone control circuits with quite steep frequency response

texts:
I'm trying to roughly replicate the sound of the per-stereo-channel 3 band equaliser conttols of an old Citronic Pro-8 / Pro-10 DJ mixer. If I'm correct had a fairly steep curve so bass and treble controls didn't affect middle frequencies much, and were very effective at cutting bass/treble as required.

As long as the sound is all flat when tone controls are centred and there are no odd peaks /resonances.

What type of filter might it have used? Googling 3 band audio equaliser brings up circuits that I don't think would do it? Technically they all seem to be first order if Im correct? OK I should try it first but in principle something to try next anyway? Second order filters? Or even a half way house of technically easy in analogy circuits?

My mixer wasn't parametric but I guess a single parametric tone control (not thought this out at all mind you) could give the same effect on top of a simple first order set of tone controls.

Ideas:

http://rane.com/pdf/acceler.pdf


texts: how to understand the capacity in binary symetric channel (BSC)

texts:
According to the wiki about the BSC (binary symetric channel),
given the bit flip rate p,
the capacity is derived as :
H(p) = -p*log2(p) – (1-p)log2(1-p)
C = 1 - H(p).

the error probability p should be with [0, 0.5].
I am little bit confused about this condition.

For example, when p =0.2, H(0.2) = 0.7219280948873623, and the capacity is:0.2780719051126377.
However, when p=0.9, H(0.9)=0.468996, and the capacity is :0.531004.
Why the larger bit error probability results in a larger capacity?
And I can not understand why and how to swap the output (interpret 1 when it sees 0, and vice versa) just as the BSC says.

Actually, the ber, H(p) and  capacity is the following relationship:

p=0.100000, h:0.468996, c:0.531004
p=0.200000, h:0.721928, c:0.278072
p=0.300000, h:0.881291, c:0.118709
p=0.400000, h:0.970951, c:0.029049
p=0.500000, h:1.000000, c:0.000000
p=0.600000, h:0.970951, c:0.029049
p=0.700000, h:0.881291, c:0.118709
p=0.800000, h:0.721928, c:0.278072
p=0.900000, h:0.468996, c:0.531004

Any one could help me understand it?
Any hints would be appreciate!


texts:
I'm trying to understand system stability basics. Let us say I have a system
$$
    G(s) = \frac{500}{s^2 - 500}
$$
Since it has two poles in the right half s-plane, it is unstable.
How can I stabilize it? I have read that a simple pole-zero cancellation would mostly be unreliable.


texts: What will happen if motor requirement due to more load is high(lets say 5A) and we limit current with current limiting circuit to lets say 2A. what will happen.. will it work without anything getting damaged?If not what should i do? Thanks..


texts:
I want to provide 12 actuators from a microcontroller (Particle Core) over I2C. The problem is that the drivers for the actuators have all the same I2C addresses. So I'am considering to use I2C multiplexers. However I only have found a 1 to 8 channel I2C multiplexer like the TCA9548A from Texas Instruments. The idea now is that I have 1 multiplexer connected directly to the microcontroller. This multiplexer is connected to 3 further multiplexers and each of them is connected to 4 actuator drivers.
My question now is, if it is possible to nest such I2C multiplexers?
Thanks in advance!


texts:
I want to make a simple electronic circuit to make some LED lights of Christmas 3 volts cause fades, phases, flashes, etc. How can I do this circuit without Arduino?

Thanks for your responses.


texts: How to combine multiple transistor logic gates without gigantic voltage-drop?

texts:
In follow-up to my previous question: Resistor values in transistor logic gates

I've breadboarded all common types of transistor logic gates:
XNOR, NAND, INV, NOR, XOR, AND and OR.
The two yellow wires are input A and B. The white wire is the inverter input.

Input A=0 + B=0 + inv=0 gives:

Input A=0 + B=1 + inv=0 gives:

Input A=1 + B=0 + inv=0 gives:

Input A=1 + B=1 + inv=1 gives:

All logic works perfect, but the voltage-drop differs significantly between the gates. For example, the XOR gate is created from AND, NAND and OR gates and each transistor increases the voltage-drop. The LED barely lights up!

My goal is to build a 4-bit calculator from transistors (using CMOS chips I did not encounter this problem). But if each logic gate results into significant voltage-drops like these, how can I ever combine 10 logic gates behind each other? I've played around with many resistor values, but most combinations render the logic gates useless. How to adjust the XOR gate above to match the voltage drop in, for example, this simple AND gate?

EDIT (response to answer by JIm Dearden)

I learned a great deal and can't stress enough how much I appreciate your answer!!!
The drawings are really clear, I'm sure many people will benefit from them in the future!

Though really obvious, I never realized:
- NOR = NOT (with two inputs)
- OR = NOR + NOT
- NAND = AND + NOT

The "base everything on a simple inverter circuit" does indeed the trick!
All logic gates, including the combined gates like XOR, output the same :)

Best wishes!


texts: SIM7000e what are the two bottom keep out areas

texts: What are the two bottom keep out areas shown in  the docs: 2.4 Footprint recommendation  for SIM7000 module? How should I adrress them in the footprint? Screenshot with markers:


texts:
I'm currently trying to power both a motor connected through a relay. And an Arduino.

I just connect the power with the Arduino Vin, and create a circuit through the relay with the motor.

This works, but only when the motor is not running. When the motor starts, the Arduino restarts. I suspect this is because the motor is taking all the available current.

I'm probably missing some piece between the Arduino and the power source. Is what I'm trying to do possible? And what am I missing?


texts: How the lw (load word) instruction works on the MIPS Unicycle (Implementation)

texts:
I'm reading the Computer Organization and Design book from David A. Patterson and John L. Hennessy. Specifically, I have a question about the implementation of a MIPS Unicycle.

So, in the book, they show how to implement the MIPS Unicycle using this architeture:

My question is: How is possible to the load word instruction (lw) to work using this architeture? This is not well explained in the book, so let me explain to you what it's not very clear to me.

The load word instruction has this format:

6 bits for OPCODE
5 bits for the Rd
5 bits for the Rt
16 bits for the offset

Rt <- Mem(Rd + offset)

So, in a simple way, it is possible to say that the load word instruction works this way using that architeture: The instruction is decoded and the Rd goes to the Read Register 1 port of the Registers Bank, while Rt goes to Write Register port. Then, the ALU sums the Rd with the offset and send the result to the address port in the memory. The MemRead signal is activated, so the corresponding word is passed to the output. This word goes directly to the Write Data port in the Registers Bank. Now, the RegWrite signal is activated, so the word is stored in Rt.

This seems ok, but my question is: How this is done using only one clock cycle?

Specifically, I'm talking about the memory reading and the register writing. In my understanding, both of this operations are clock-sensitive. You can only read the memory or write in the Register Bank if there's a rising edge.

That said, how is it possible to the memory reading to be made in the middle of two clocks edges? This must be done this way, otherwise on the next rising edge the Mem(Rd + offset) value will not be in the Write Data port of the Bank Register and trash will be written.

I hope you guys could understand me. Thank you very much


texts: Rubik's cube solver (help required for hardware)

texts:
I am very new to this. I have only done a "introduction to programming" course where I learnt C. I once worked with arduino. My program in C language prints the solution of the given rubik's cube combination on the screen. Now I want to make hardware for it and I have to use 6 stepper motors for 6 faces.

MY QUESTIONS

1)Is there a platform such as arduino which can accommodate 6 stepper motors.

2) Do I need 6 drivers for 6 stepper motors

3)which stepper motors should I use?

4)what is estimate costs for that?


texts: Switch battery usage off when jack 3.5mm is not inserted

texts:
I have an ongoing project where I'm using a condenser microphone to record various stuff, it's powered by a CR2032 battery and the output of the microphone is directed to a TRRS jack connector (3.5mm), and I'm looking for a way to save the battery life since it's for a light usage (around an hour per week, and letting the battery power the microphone non stop would drain the battery in about a week).
Kinda like a switch off battery when jack is not inserted.
But to be honest, I'm a bit lost on that part.
My current schematic is the following one :

I hope someone can guide me to some ressources or answer, and I hope my post is comprehensive !


texts: 1V Overshoot and Undershoot on Power Rails of LTE Module

texts:
I have designed a PCB (four layer) having SIM7600I LTE Module. The Stackup is:

Signal & Component Layer with Ground Pour
Internal Ground Power Plane
Internal Power Power Plane (3V3, 4V and 1V8)
Signal & Component Bottom Layer with Ground Pour

The datasheet says:

I have followed the datasheet guide and included approx. 700uF capacitors (considering the load transient response of AP6503 as it can handle the transient with 200mV voltage drop):

I have been using AP6503 Buck Converter to step down from 5V to 4V. The schematics of power design specially for LTE module is given below:

And I have placed 700uF capacitors near to Module's Power Pin.

The Power traces from Buck Converter to LTE Module is on Internal Power Plane (Layer 3).

After assembling the PCB and testing it, I found out it is working perfectly but after few days, I put probe of my oscilloscope to the power pin of LTE module and saw weird undershoot and overshoots. I am not sure the culprit behind it. The spikes are of 1V. I want to resolve this issue in my next iteration but I am not sure who is the culprit. I have been using these capacitors near to power pin of LTE Module.

470uF Aluminium Polymer 11mohm 16V X 1
100uF Tantalum 100mohm 16V X 2
100nF Ceramic Capacitor X 1
33pF Ceramic Capacitor X 1

The pictures of the noise on power pins of LTE Module are:

I want help in understanding what I did wrong. I think I have followed the datasheets and took measures to avoid any problem after PCB fabrication. Please help.


texts: What is the term for this construction of ADC?

texts:
The following description from GBATEK explains the implementation of a low-cost ADC that was used in a video game from the early 2000s. It contained a solar sensor in the cartridge:

A/D Conversion
The cartridge uses a self-made A/D converter, which is (eventually) better than measuring a capacitor charge-up time, and/or less expensive than a real ADC-chip:
It contains a 74LV4040 12bit binary counter (clocked by CPU via the I/O port), of which only the lower 8bit are used, which are passed to a resistor
ladder-type D/A converter, which is generating a linear increasing voltage,
which is passed to a TLV272 voltage comparator, which is passing a signal to
the I/O port when the counter voltage becomes greater than the sensor voltage.

Feeding a ladder DAC with a binary counter and comparing the (increasing and then resetting) output voltage to the voltage from some analog source and recording the binary counter's state when they match sounds like it would be a very simple, low-cost ADC. It looks like it is a good fit for situations that require fairly low resolution (this one is 8-bit), low sample rate (this one has a 666Hz clock), and where the source is expected to be relatively steady (like sunlight). Does this design have a name?


texts: Can any one identify this component or tell me a way to do so?

texts:
Can anyone identify this component or tell me a way to do so?

Unfortunately I do not have access to a circuit diagram.

The component burnt out when I reversed polarity by mistake...

Thanks in advance.

UPDATE ----

The board is from a MEI Cashflow 330 coin validator.

Link to product www.norpay.se/pdf/cf3xx_4xx/330_dg_gb5_142799044.pdf


texts:
Would the following Verilog be synthesize (in Altera's Quartus) to a bus of 1024 tri-state devices connected to one wire?
Will it be faster (clock latency) than a binary tree of 1024 or-gates?

`

module TriBus #(parameter N = 1024)(inb, enb, outb);

  input inb, enb;
  output outb;
  wire [N:1]inb;
  wire [N:1]enb;
  wire outb;
  wire [N:1] orbus;

  genvar I;
  generate
    for (I=1; I<N; I=I+1) begin
      assign outb = (enb[I])? inb[I] : 1'bz;
    end
  endgenerate
endmodule

`


texts: What is the specific function of a triac inside a soldering station?

texts:
I'm trying to understand the different parts inside a soldering station. One of the components i found was a Triac.

I've tried to find an explanation for the use of a Triac inside the soldering station. Can someone explain me this?


texts: Finding out power requirements for plug replacement

texts:
I bought a inverter for arc welding that is imported and comes with a CEE 7/7 plug (I guess it goes to the European market). In Brazil we have two types of plugs one for 10A and another for 20A (they differ in plug diameter).

Now the manual for the inverter says that the Imax is 27.8A. In the power supply specification section it says that the cables are 1.5 mm2 and the line current is 10.8 A. The plug that came with the inverter was rated for 16A.

Now, I would rather use a 10A brazilian plug, as it is more ubiquitous and convenient. Can I do that or should I step up and use the 20A plug, and thus limiting the places where I can plug the inverter?


texts: Charge 3.7 Li-ion Battery with 5V battery charger?

texts:
Is it possible/save to charge a 3.7V Li-ion Battery with a 5V battery charger like this one: https://www.amazon.de/gp/product/B0191EVW0C/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Additional question: Would this be sufficient for an Arduino Pro Mini 5V using the VCC Pin?

Thanks!


texts: Why can't we read voltage between just one pin of a loaded capacitor and any ground?

texts:
I know that we can only read voltage across a capacitor if it's two pins are connected to the voltmeter or can't talk about any potential difference between totally different systems if they do not have a common ground. But as I think about it more, I started getting confused and can not understand the physical reason why this is the case. Let me introduce a case;

simulate this circuit – Schematic created using CircuitLab
First I charge my capacitor via battery. Numbers are trivial. Then;

simulate this circuit
Then I measured the voltage to be sure that its charged. After that;

simulate this circuit
Than I connected the negative probe to any universal ground(earth, a big copper plate etc.) and from common knowledge I know that I could not measure any voltages but I could not understand the physical reason of why. If voltmeter is measuring the current across its probes than why the charge carriers do not flow from the capacitor plates to ground? If voltmeter measures the electric field like an electroscope than why a plate with charge carriers and a ground do not create an electric field? Thanks for reading and sorry for trivial question.


texts: Professor said no current flows to ground

texts:
According to the professor, adding the ground at 0V has no effect on the current flow and current flows in this circuit as if the grounding point did not exist so the answer is E.
How have people died from touching powerlines?


texts: Need to power two or more UPSs to a common battery details follow)?

texts:
I wish to design a system that allows multiple Uninterruptible Power Supplies  to operate from a single 12V battery while ensuring that there are no unexpected undesirable consequences.

I already have multiple Uninterpretable Power Supplies that must only supply power for less than 20-25 seconds, normally, since the LP fueled back up generator normally supplies all connected devices / circuits within 14-17 seconds of AC - utility failure.  The total is comprises 3-4 sec. sense (loss of voltage), generator starts within 5 seconds, and RPM sense (up to speed) and load transfer occurs within 7 - 8 seconds.

Since power loss, sense, start, & transfer are not (cannot)" be instant <1 sec. not just the computers, but the DSL modem & 2 set top boxes (need 3+ minutes to boot), the professional VTRs (used mostly as play sources) - DVD recorders when being used, ect. have to have continuous power.

Over the years I've gone through hmm 3 or 4 sets of two each 12V UPS batteries X four or five UPS X $19 - $26 batteries = a LOT of MONEY!

I realize/understand each UPS has it's own battery voltage sensing and charging so using a single (with sufficient ampacity/capacity) and therefore only one UPS can be allowed/used to charge the single battery.  Unless someone can recommend a BETTER blocking diode yet one that has sufficient forward current capacity than the NTE 6087 Si. Schottkey Barrier Dual rectifier (diodes).  They have the following characteristics-specifications:
Prv - 45V Max, Ifsm - 150A, Ip - 30A, and Vf .82@ 30A
I'd place the cathode on the B+ comming from the UPS(s) which will NOT be maintaining the battery.

Unless the backup/standby generator FAILS to start, no UPS should/would 'ON' longer than 30 seconds.  To keep the 12 V DC leads from the HEAVY duty battery I will be using #8 wire <4' for one and #6 >8' for the other combination of UPSs supplied by the second EAVY duty battery.  I plan to use standard #14wg Romex and standard AC plugs-receptacles to route the AC (line and/or UPS) to the location nearest the equipment needing UPS backup until the generator can take the load.

Cautions, suggestions, corrections, etc. invited and WELCOME.


texts: Protections against spikes in the design of AC and DC electronics?

texts:
Assuming that you are focusing on the choice that will give the best protection against spikes, would you go for an AC or a DC powered piece of electronics? Could you explain why and if this is your choice only in some given intervals in input (like only in X to Y Volts from a maximum of Z volts of tolerance)?

For example, an electrical engine that is out in the open and subject to bad weather (lightning) should be powered by...?

EDIT:

Following the clarification in the comments below, I would like to limit the discussion to devices and hardware that are used in aviation or that have similar properties and applications, like being able to function properly even without a ground connection.


texts: 2D parity code error detection/correction?

texts:
If we assume the following: the received bits were encoded using a 2-D even-parity code, what is min #of error is there.

I am a little bit confused , it is clear that the third column has an error and ( second , fourth and sixth ) rows have errors.

For example, If we change the bit location(2,3) the third column and second row will indicate there are no errors and we lift with only two rows (fourth and sixth) with no column. What can I say about this , the minimum # of error in this case?

Can someone help me with this? Thank you


texts:
Is there a way to reset the atecc508a from Microchip Technology to default?
The configuration zone was already locked.

I would appreciate any help. Thank you very much.


texts:
I want to replace the onboard AMS1117-5.0 (broken) with a LM7805.
However, the pinout is different between the two voltage regulators; AMS1117: Gnd, Vout, Vin vs LM7805: Vin, Gnd, Vout.

I would like to know what is the best practice of how to approach this? Line-up the Vin and cross the Vout and Ground pins and add some insulation so they dont make contact. How do the experts at EESX do this?

Follow-up: adding the lm7805 using jumper wires works fine with the 12v DC input i have. It is a temporary fix until replacement ams1117 arrive.


texts: When untied inputs are necessary, what is the technology to use for an OR gate?

texts:
What is the best technology to implement for an OR gate when there will be an open input?  I would prefer a common IC.

I wired a quadruple 2 input positive OR gate, HD74LS32P.  I have a PWM signal coming in the 1A input.  The 1B input will have another PWM signal coming in when it is powered on.  But there may be the case when it is not powered on.  Unfortunately for me, when powered off, the signal line 1B becomes high and thus the output 1Y is high.  I need 1B to be low when the 1B device is powered off.

I read on this site that I should tie the unused pins to something, and can implement that.


texts: pcb design: how to route through hole connectors with tightly fitted pins?

texts:
I'm new to all of this but I'm trying to make a breakout board to a 51 pin micro-d connector. There's a lot of pins like so:

The breakout board is used too check continuity so no current actually passes through. I don't need to worry about traces being too close.

Below, I tried the auto-route feature on multisim, since there's so many points that it would be too difficult to manually route. As you see, the inside pins all are deemed unreachable. I tried to lower my trace width and clearance all the way down to 5mil and that made no difference.

What is the correct approach to tackle this problem?


texts: Can you connect multiple photodiodes in parallel and treat it as one?

texts:
Im working on an IR sensor based off of the Texas Instr. particle sensor (TIDA-00378). They use just one photodiode in their design. I would like to use multiple photodiodes, lined up with multiple emitters, to cover a larger area. In my current design using phototransistors, I was able to connect multiple phototransistors in parallel to achieve this, as shown in the second image. Will this work similarly with the differential amplifier if I use multiple photodiodes in parallel?

Thanks!


texts: Problem with ideal LED diode with much higher voltage than its minimum

texts:
I have an ideal LED diode with Vγ (minimum voltage)= 0.7 V that supports a maximum current of 5 mA. And I want to connect the diode and use it directly polarized with a voltage source with value Vg = 5 V, but my question is what problem can occur if we connect the diode directly to the voltage source?

As far as I know, the diode is supposed to not work if voltage is less than 0.7 and work as a short if is higher so it should work fine. But I think that this problem wants me to answer something like: The LED will burn. So what will happen?


texts:
I think I may have bricked my IMU or seriously damaged it earlier this week. I have the Adafruit 9-DOF IMU Breakout - L3GD20H + LSM303 (link: http://www.adafruit.com/products/1714) which has an accelerometer, gyroscope and a magnetometer all rolled into one. I had it connected to my Arduino Uno over i2c and was successfully using the provided Adafruit sensor libraries to read data from each of the chips. As far as I could tell, the accelerometer was working except for a slight (1m/s^2) positive bias in the Z direction and both the gyroscope and magnetometer seemed to be working alright.

I was demonstrating use of the chip to some of my students and one of them mentioned that they wanted to see what would happen to the magnetometer's reading if it was exposed to a magnet. Normally the highest reading from the magnetometer is around 60-70 uTeslas. With a stack of rare earth magnets placed within a few centimeters of the chip, the reading spiked up to between 1000-2000 uTesla. I thought nothing of it.

However, my accelerometer's outputs are now constant values of between 10 and 20 m/s^2 no matter what orientation it is or if it is being moved around. The sensor library reports  "Oops ... unable to initialize the L3GD20. Check your wiring!" for the gyroscope and the magnetometer's readings seem to have been shifted, although I'm not sure if they're completely terrible. The following picture is from continuously gathering sensor readings while rotating the IMU for about 20 seconds.

They appear to be an ellipsoid. I've read some things about hard-iron and soft iron offsets, but I'm not exactly sure what I'm seeing here. I looked online for how magnets affect IMUs, but none of them had anything about something this... stupid. heh Thanks for anyone who can shed light on this issue or how to troubleshoot. The IMU is relatively inexpensive (~20), so luckily that's not the issue. I'm just wondering for my own knowledge at this point.


texts: Secondary voltage referred to the primary

texts:
I am studying transformers and I am not completely understanding a basic detail, but it is annoying me.

When we draw the equivalent circuit of a transformer, why is the secondary voltage referred to the primary written as \$V_{2}'=\frac{N_1}{N_2}V_2\$ ?


texts:
In Table 11-3, p180 of http://ww1.microchip.com/downloads/en/DeviceDoc/70000657H.pdf, there is no way to map any spi1 pins?!

I've gotten spi2 pins to work, but I need two buses and the part was specifically chosen because it had two spi peripherals.  Is the documentation lacking?  Is there something simple I'm missing?  Part of me is tempted to just guess every binary combo of 6 bits.

The errata here seems to have no helpful mention either: http://ww1.microchip.com/downloads/en/DeviceDoc/80000533g.pdf


texts: Using NAND gates to construct OR/AND gates

texts:
I have this Boolean equation

B'*C'*D'  +  A*C*D  +  C*D*E'

and I was just wondering how to use nand gates to express this equation.

With the schematic the inputs are

NAND1 it is  B'*C'*D'

NAND 2 it is A*C*D

NAND 3 it is   C*D*E'

This schematic shows me converting the first AND inputs to NAND then the OR to NAND and I was trying to build a circuit with this logic.

simulate this circuit – Schematic created using CircuitLab


texts: What are the 49.9 ohm resistors for in this circuit?

texts: I was wondering what do the 49.9 ohm resistors do in this circuit? Are they absolutely required since I don't have any that size.


texts: USB3.0 OTG SSTX/SSRX crossover confusion

texts:
I am having some confusion with creating a USB3 connection between two boards. I have two UltraZed+ EG boards, each sitting on a carrier card. Both boards have a USB3 Micro-B receptable that is internally connected according to the pinout shown here. The boards can be configured to act as host, OTG, or device.

I want to use one of the boards to act as a USB3 host and the other board to act as a device. I set several jumpers so that the power on one board works according to host mode and the other according to device mode. However, I have some fundamental confusion regarding the SSTX/SSRX pins.

I have obtained a USB3 Micro-B to Female-A OTG cable together with a standard Male-A to Micro-B cable which I connect via the A-plugs so I have a long cable with male Micro-B connectors on both ends. When I measure the connections of the combined harness, I would expect the SSTX and SSRX wires to be crossed so that the host SSTX lines connect to the device SSRX lines and vice versa. However, this is not the case. The cables create a 1:1 connection and hence connect SSTX to SSTX and SSRX to SSRX. There seems to be no way to swap the lines either via switches on the board (they seem are routed directly into the FPGA) or in the FPGA itself (it uses special PS-GTR transceivers that are hard-wired).

This makes me wonder, is there a fundamental flaw in my approach? Do I have a faulty USB3-OTG cable? Apparently there are some that cross the wires but others that don't (see here) and I have not found a USB-OTG cable specification in the standard and, according to 4, OTG isn't really standardized. Can someone more knowledgeable in all matters USB3 shed some light on this, please?

UPDATE

I did some measurements on the OTG-part of the wiring and I've found that it connects as follows:

Micro-B Pin 10 (RX+) - A-receptable Pin 9 (TX+)
Micro-B Pin 9  (RX-) - A-receptable Pin 8 (TX-)
Micro-B Pin 7  (TX+) - A-receptable Pin 6 (RX+)
Micro-B Pin 6  (TX-) - A-receptable Pin 5 (RX-)

Since, according to the standard, a Standard-A to Micro-B cable also does a crossing, this explains what is going on and according to 4 this would be a bad OTG cable. I still wonder why those are sold so often and get solid reviews on Amazon and co. Is most hardware able to detect this and then just swap the TX and RX lines internally?


texts: Create differential signal from single ended encoder

texts:
I have a problem with the output of an DC motor encoder feedback. I have an 5v single ended encoder (AB signal), but my control needs an differential signal. I am not sure how to do this as I have no experience working with "negative" voltages. I have multiple optocouplers based on the EL817 available and initially thought that I could just hookup a positive and a negative voltage to the output collector of the optocoupler, but I am not quite sure if the phototransistor would allow a negative voltage on the collector / have then a negative voltage on the emitter, as I am still kind of unclear how transistors handle negative voltage input. Can somebody enlighten me / help me out or has a good background site available about this transistor behaviour?
Also, what would happen if you put a negative input into a photocoupler (e.g. hook up a negative voltage source to the anode and put the cathode against mass)? In theory the LED should also only see a total 5v, right? Only important thing is the current limitation here as the led drop voltage is reached by the negative potential also? Or do I misunderstand LEDs completly?


texts: Redundant power supply for mini-pc using mosfets

texts:
I'm rather green when it comes to electronics (so please pardon obvious and glaring mistakes).
I have something like the following in mind:

Basically I have two 12V switching PSUs (off the shelf units) and I'd like to make sure that the Load (a mini-pc) stays powered on in case one of the PSUs dies and/or goes offline.
I read a bit about the problems with voltage difference between V1 and V2 and I thought that diodes might fix this (at the cost of some voltage drop). But I was surprised to learn that a diode that could withstand 12V and 2A seems hard to come by (or is rather expensive).
Hence I thought of using MOSFETs instead (they do have a "diode" in reverse, right?):

Now my Q is, has this any chance of working, and reliably at that?
And if yes, how far from a real circuit is the second picture?
As in, what other crucial parts of the circuit am I missing? In plenty of real circuits there are flyback diodes, various resistors in different places. And I'm not sure what applies here (and what doesn't).


texts: How to calculate the output impedance of this circuit?

texts:
This is a hybrid-pi model of a BJT, and I want to know its output impedance:

simulate this circuit – Schematic created using CircuitLab

I know that I should short the input ports, place a voltage on the output ports, calculate the consequent current and finally apply Ohm's law, but I have no idea how to deal with that CCCS.

According to the key, the input impedance is Rc. Does this implies that the CCCS can be seen as a ideal current source, and thus considered as open circuit?


texts: Where is the return path for electrostatic discharge (ESD)?

texts:
Typically ESD diodes are placed at the input, output or external contact points for product to prevent product being damaged by ESD.
What I don't understand is where the return path is for this ESD shock on the battery operated device. Since battery positive and negative are relative terminals, battery negative connected to the ground net is just relatively the lowest potential in that circuit.
Where does the current go since it has no way to actually go to earth?


texts:
So I was doing a bit of research on the AVR controllers and came across this schematic for programming the chips.

After doing research on the 74 LS 254, I realized that either this design is overkill or I am missing an important point. Notice in the schematic how the DIR pin is tied high. Consulting with the datasheet for this IC informs that this state is such that information is transferred through the chip from bus A to bus B (or left to right in this schematic).

If the only purpose of this chip is to pass the information through itself, what is the point of including it? I thought that perhaps the inclusion of the IC was to prevent overloading of the PC, but considering that the chip will itself be powered by the PC this worry seems impractical.

What is its purpose?

/--------------------------------------------------------------------------------

Also, the pins for the DB-25 connecter seem strange too.

According to the schematic we have several digital out pins tied to ground and many other important pins left floating.


texts: What is the drawback of a high-value resistor for positive comparator feedback / hysteresis?

texts:
I'm building a simple circuit which has an LM211 comparator at its heart. The positive input is connected to a 10k-10k resistor divider across the supplies, stabilized by a 1uF capacitor. Hysteresis is provided by 1.8MOhm from the output to the positive input.

The signal on the SENS line is a slowly changing resistance hooked up to +5V on the other side.

Everything works perfectly on a breadboard, but I wanted to check a few things before finalizing the board layout, and came across a TI application note which says in paragraph 6:

  It is a standard procedure to use hysteresis (positive
  feedback) around a comparator, to prevent oscillation,
  and to avoid excessive noise on the output because the
  comparator is a good amplifier for its own noise. In the
  circuit of Figure 2, the feedback from the output to the
  positive input will cause about 3 mV of hysteresis. However,
  if the value of Rs is larger than 100Ω, such as 50
  kΩ, it would not be reasonable to simply increase the
  value of the positive feedback resistor above 510 kΩ.

However, it doesn't say why a high value feedback resistor is "not reasonable". I built up my circuit on a breadboard, and it seems to work fine, I can definitely see good hysteresis behaviour with the 1M8 resistor as compared to without it.

So, what is the drawback?


texts: How does mouse keep working when the battery is drained?

texts:
When battery is drained with time it provides less voltage. Which makes me wonder - how does appliance (like a mouse) keeps working with lower voltage?

Is it because electrical components inside can work with different levels of voltage?
Or there are components that lower the voltage when the battery is full?
Or maybe vice versa - some how the voltage is amplified when the battery is drained?

Or something else?


texts: Seeking means of maximizing energy use from LiIon battery supplying a 3.3V load

texts:
I have a device that operates with 3.2 V MAX, and I wish to power it from a standard 3.7 Li-Ion battery. A fully charged battery=4.2V.
I used a simple LM317 circuit to drop voltage to 3.2V and it worked perfectly.

Now the problem is as the battery starts to drain, the output voltage starts to become lower, so subsequently the LM317 output voltage will be lower as well, for example

Batt=3.7V,
   LM317=2.5V

In which this case the voltage is not enough to keep the device up and running.

So what I need is some sort of dynamic regulator to keep the output voltage fixed at 3.2V until the battery voltage drop to 3.2V as well.
Advice on good ways to achieve this would be appreciated.


texts: ADC STM32L476RG : Why do I have an offset when connected to 0V?

texts:
I'm working on a software solution which set the Pin PC2 to "reset state" if my input signal (connected to ADC) is above 2V.

I testing my code with STM32 Studio to watch in real time the digital output of my ADC.

Here is how i configured the ADC1 :

  hadc3.Instance = ADC1;
  hadc3.Init.ClockPrescaler = ADC_CLOCK_ASYNC_DIV6;
  hadc3.Init.Resolution = ADC_RESOLUTION_12B;
  hadc3.Init.DataAlign = ADC_DATAALIGN_RIGHT;
  hadc3.Init.ScanConvMode = ADC_SCAN_DISABLE;
  hadc3.Init.EOCSelection = DISABLE;
  hadc3.Init.LowPowerAutoWait = DISABLE;
  hadc3.Init.ContinuousConvMode = ENABLE;
  hadc3.Init.NbrOfConversion = 1;
  hadc3.Init.DiscontinuousConvMode = DISABLE;
  hadc3.Init.NbrOfDiscConversion = 0;
  hadc3.Init.ExternalTrigConv = ADC_EXTERNALTRIG_T1_CC1;
  hadc3.Init.ExternalTrigConvEdge = ADC_EXTERNALTRIGCONVEDGE_NONE;
  hadc3.Init.DMAContinuousRequests = DISABLE;
  hadc3.Init.Overrun = ADC_OVR_DATA_PRESERVED;
  hadc3.Init.OversamplingMode = DISABLE;

sConfig.Channel = ADC_CHANNEL_1;
  sConfig.Rank = 1;
  sConfig.SamplingTime = ADC_SAMPLETIME_2CYCLES_5;
  sConfig.SingleDiff = ADC_DIFFERENTIAL_ENDED;
  sConfig.OffsetNumber = ADC_OFFSET_NONE;
  sConfig.Offset = 0;

I can proper retrieve the output number of my ADC with DMA but I've an electronic problem I think :

In Nucleo STM32L476-RG, the ADC1 Channel 1 & 2 are connected to the pin PC0 and PC1.

When I connect the pin PC1 to the STM32L4 GND and the pin PC0 to the 3.3V, i can retrieve the 4095 value from the ADC, that's good.

But, when I connect the pin PC0 to GND or a 0V source, the ADC should return me 0 value but it don't, it return 1981 value.

For resume :

Input of ADC1 : 3.3V | Output of ADC1 : 4095 | Config : PC1 on GND ; PC0 on 3.3V
Input of ADC1 : 0V   | Output of ADC1 : 1981 | Config : PC1 on GND ; PC0 on 0V/GND

I don't know why i've got this Offset. I've read the datasheet a thousand of times, STMicroElectronics mention a 0V Reference which called VSSA or VREF- but i don't understand how to connect my Pins.

The only pins which i use is the PC0 and PC1. Should I connect other PIN to a ground or anything? Someone had this problem before?


texts:
In my board it may happen to power only one side of the ADuM140x. All the pins on the other one will be completely floating.
When the user plugs in a connector also the second side will be powered at 3.3V and the signals pins will be connected to the device too.

I cannot find in the datasheet is such a scenario is allowable.
Anyone has any experience on this?


texts: I've been looking at Molex's website for hours and I can't identify this connector.  It's the motor connector on a cheap quadcopter.  Does anyone know what connector it is?  Thanks for your help.


texts: Multiplexer CD4051B gives strange readings

texts:
I'm trying to multiplex an analog input port on an Arduino Uno.

Datasheet

simulate this circuit – Schematic created using CircuitLab

I've connected the input to 5V for testing stability of the reading. I've programmed a small routine that checks for consistency of the signal reading.

I'm using a breadboard of questionable quality.

The CD4051B Output is grounded via a 500k resistor, so that unconnected ports read 0.

If I read only port 4 for 30 seconds, it starts to read correctly and stable.
If I start reading random ports (between 0 and 7), it reads correctly for about 10 seconds, then suddenly starts reading zero.

I've tried changing the pull-down resistor. It still goes to zero.
I've tried removing the pull-down resistor. The value then starts reading randomly.
I've also tried adding a 1uF capacitor.
But it changes nothing.

I'm using digitalWrite on three pins to select the input port, and then waiting (delay) for 30ms before doing an analogRead on A0. I've experimented with various delay times, and 30ms seemed to improve things a lot when reading sequantially (0, 1, 2, 3...), but when reading randomly, it doesn't work at all.

I'm a bit lost to what the problem could be. I imagine it could be something with capacitance on the ports, but I have the impression that the multiplexer is actually supposed to support very fast switching?

Update:

I saw a comment on the 'arduino' board which said that "the for loop repeatedly cycles count from 0 to 7, so [selector pins] will average 2.5 V". Is this realistic? Wouldn't the digital pins be able to sink fast enough that the IC would mux correctly?

The IC has internal protection circuits. Is it possible that they are getting triggered? But this happens even with 1k resistor on Input 4.


texts: Why is BJT scaling not as significant as MOSFET scaling?

texts: When reading about integrated circuits, MOSFET scaling comes up very often, however BJT scaling is never discusses. What's the reason for this?


texts:
This is probably a basic electronics question, but I'm a self-taught hobbyist and I can't seem to find a direct answer to this.

I have a host device that I want to connect to that supplies 100mA at 5V.
The module I'm connecting runs on 3.3V and peaks at 200mA.  I will have a voltage regulator and level shifters in between.

My question is, does running at 3.3V make any difference with the amp draw on the host?  Or is it 200mA no matter what the voltage, meaning I will need an external supply.

Is there a general principle I can follow in the future?


texts: Anyone knows how X86 platform set the PCIe bifurcation at boot up?

texts:
I got a question about the PCIe bifurcation setting when booting up in X86 system.
Normally, we can set the PCIe controller to be X16, two X8, or four X4 in the UEFI shell menu.  However, there is an auto detection way to do the same thing automatically. For example, if I put four X4 devices on the riser card, and put this riser card to the X16 PCIe slot, the system can automatically detect that the PCIe controller should be configured as a four X4 host controllers.
Does anyone know the detail procedure to implement this function?
I think it's not specified in the PCIe spec.
Using PRSNT# pins hard wired to the PCH may be a way, but is there any other (or real case) way to achieve this goal?
Thanks.


texts: Buck using discretes - Driving p-MOSFET using n-MOSFET

texts:
We are designing a buck using discretes. I have a problem with OFF time of Control MOSFET(U1) and driver(T1). In OFF time, Gate of U1 is rising very slowly to 12V which makes U1 always ON. Which in turn makes output to 12V always.

I have seen few BJT Totem pole drivers for p-MOSFET. But, i want to use this same circuit. any modification suggested so, that we can make U1 gate to rise faster.

VG1 is 1.8V,100K, 50% duty cycle square wave.

I tried to change the R1 2K to 500 and VG1 1.8V,90K,50% and found.

How to still make the Turn OFF of T1 fast, so, that Vgate of U1 rises to 12V very quickly.

Edit:

I have changed the 2k to 0.5k and i am getting FET swtiched OFF and getting 5V output as intended, but Switching frequenxy is very less close to 80K and it is not following Buck formula Duty cycle ~ Vout/Vin. As OFF time has notches and slow. Any tweaks we can do on the same circuit to make it more faster. ....


texts:
I will try to explain my situation as simple as possible :)
In my house, one side of telephone installation cable (it has few wires inside) comes from wall and I have access to it. I know approximately where other side of that cable is in house, but I don't have access to it because it is in wall. I need to find exact position where it ends in wall. Is it possible to trace that cable from one side of it (which is accessible to me) to other side (which is not accessible because it ends somewhere in wall)? If yes, which tools I need?
Thanks in advance.


texts:
I use these toothbrushes: http://www.amazon.com/Oral-B-Advanced-Toothbrush-Vibrating-Bristles/dp/B00336EUV8

They tend to run out of battery quite quickly. I'm happy to keep buying more because regular toothbrushes just don't get the job done in comparison.

However I've stumbled upon a neat little trick.

I've been taking them apart to insert 10440 size Lithium batteries in place of AAA cells.

As you can imagine this gives a boost in power which is quite amazing. I'm reasonably certain that it's not too much power, I'll ask my dentist about it next time I see her, but I am pretty much hooked on the extra power. More gum stimulation is healthy right?

Anyway, the real issue is that after a short amount of time (a few days of normal usage) the motor eventually gets more and more sluggish. It would start out going quite fast, then gradually slow down. Pausing for a while, then restarting sees it regain some power.

I can of course do some more controlled tests to better determine what's going on but the behavior seems like a temperature dependent effect to me. When I perform this modification to a "new" (i.e. its alkaline cell it came with has been exhausted and I put my lithium cell in it) motor it runs nice and powerful for a few sessions of brushing before this pattern of rapid loss in performance starts to set in. I check the voltage of the battery and it is above 3.8V (not depleted).

Whether it's the battery or a degrading motor that is limiting the vibrating power, I think I should be able treat it by limiting the current in the circuit. As it is, there is no circuitry for regulating current: the battery is directly connected to the tiny DC motor.

What modifications could I make?

I have very little space to work with so it seems like I'll only be able to insert one or two small components (diode, resistor), and the circuit must remain small.

My hope is that a well adjusted modification can keep the current supplied by a lithium cell to within a range that does not degrade the motor. This way I can make the circuit once within the assembly and I can transfer that into new toothbrushes (because these need to be replaced as they are worn out).

I'll be back to post measurements of current, battery internal resistance, and maybe temperature when I get around to doing this.


texts: Can I use 1 mm² wire for 24 VDC / 15 A load?

texts: I am currently using 1 mm2 copper wire for a my application of driving a 360 watt motor, haven't caused any problems for me yet. The total wire length is around 3 meters. a voltage drop of 0.5 V ~ 1 V is acceptable with 5°C rise in cable temperature. Should I change the cable to 2.5 mm2 or is the 1 mm2 safe?


texts:
I want to use THis buck regulator and i was wondring what is the function of the capacitor between the Boost and the SW pin ?
And What happen if i choose to not add this capacitor ?


texts: How to fully shutdown a boost converter?

texts:
I've been working on a boost converter based on an LM2733-Y integrated circuit, as follows:

My question is, how to shut it down completely?

If the SHDN pin is in low state, I get the input voltage on the output.

I want to add a switch between a battery and a PIN 5. What should I use?

The converter must be controlled by a microcontroler unit (0 - 3.3V). I mustn't use any mechanical element e.g. relay. I'm thinking of an SSR, but it requires a lot of power to control it and it is relatively expensive.

A PNP transistor is not an option as well. Could you recommend me any solution?

What do you think of using this solution?


texts:
Hi am currently looking at creating an IR remote control for a robot but i need something that i can use to monitor the signal so i was think that a wii remote has a IR cam in it so i can use that to report back to my pc the signal that my remote is generating.

anyone know if this is possible?


texts: D-domain vs Time-domain (Digital Linear sequential ciruits)

texts:
I wonder if anyone could give my a short explanation of the D-domain and T-domain in linear sequential digital ciruits.
Got an exam in about 3 weeks. Last chapter is very theoretical. I got a hard time visualizing why I should use the D-domain. I can calculate it but I have no clue if someone asks me....."why do you use this"?

To those people telling me to ask the prof. and his minions : They are all on X-mas-leave

Formal question:
What is the purpose of the D-domain? What is the diffrence between D and T-domain?

EDIT:
Accordning to my book; D-domain is a domain where you are calculating with delay-operators.
In other words; the use the Huffman D-transform.
They are talking about "The delay of a Laurent series" and so on...


texts: Is there an electrostatic equivalent material property to magnetic retentivity?

texts:
Consider the following thought experiment:
I take a chunk of some material X which contains atomic dipoles., not free charges, and subject it to an external electric field. We know that the dipoles will align themselves to the field, this is analogous to atomic scale magnetic dipoles in a ferromagnetic aligning themselves to an external magnetic. The question is about what happens when the field is removed.

Is there any material which exhibits some kind of electrical retentivity, i.e. the dipoles do not all rotate back resulting in a remnant electric field?


texts:
I know how to connect potentiometer, but to be honest I don't know why. I would really like to understand what I'm doing.

From what I have read the input voltage and the ground should be connected extreme terminals and the output to the middle one.

Now few questions:
1) What would happen if ground was switched with the output?
2) Why do we need all three terminals? Can't I just use two of them?

Edit 2014-07-11 9:47

So basically potentiometer is something like this.
Few thoughts about potentiometer:
1) The total resistance of R1 and R2 is constant but we can split it as we want.
2) If we use just extreme terminals then it would behave like normal resistor.
3) It doesn't matter whether ground in connected to middle or extreme terminal.

Please correct me if I misunderstood the concept.

simulate this circuit – Schematic created using CircuitLab

Edit 2014-07-11 10:49
Basically what I'm asking in question one and thought 3 is whether following circuit is correct if I want to measure voltage in analog input?


texts:
Given these waveforms:

and the first difference system:

there are discontinuities at omega = 0 ,2pi, ...  I know that there is a DC component, but how is the DC component at omega=0 removed from the system?  Can anyone please help me?


texts: Can undervolting damage my laptops fans?

texts:
so I started reading a lot about undervolting etc. and tried it myself. I use a lenovo yoga 920 and I dont do any hard workloads, but the fan noises annoyed me as lenovo is known for its loud fans. I wanted to do smth about the noise and came to the conclusion that undervolting could help to decrease the cpu's power use and therefore the noise of the fans. I use Intel XTU and did a few stress tests with undervolting up to -0.100V. Now my laptop runs at a core package temperature of 45C on average and max is 90C during the stress test. My problem is that, just now the fans totally stopped making noise even when the cpu is under heavy demand. When i did a stress test the temp. of the cpu went up to 93C but i couldn't hear any fan noise. Just yesterday I could still hear it. Are my fans damaged? is that even a possible result from undervolting? How can I check if the fans still work (speedfan doesn't work as it does not support new laptop models) and what should I do next?

thanks in advance!


texts: Electrical braking a stepper motor (revisited)

texts:
My question is similar, but not identical, to an older question about electrical braking a stepper motor: Can I use electrical braking with stepper motor?
In my application I do not need to brake the motor, but rather hold it steady at its present position. I know that I can do this by keeping the proper coils energized, but for long durations this impacts my battery drain. Empirically, externally shorting the coils makes the motor "harder to turn."
What I'd like to do is actively stop the motor, then (carefully!) remove the driving voltage, and short the coils. Ideally the shaft position should hold within one full step, but some slip may be acceptable. [To re-start the motor, the process should be reversed.]
I'm having difficulty calculating how well this scheme could actually work, and if there are already existing driver controllers and bridges implementing this. Stepper motors sometimes specify open circuit detent torque, but I've not found numbers for different resistive shorting. Also, I'd expect the timing details and circuit transients could be rather intricate, and would hope they have already been incorporated into commercial IC's.
Summary:

How much would resistive shorting improve detent torque?
Are there any commercial drivers that implement this?


texts: Having trouble in GPIO output, 220 V to 5 V signal

texts:
I'm not an electric guy, I'm just trying to build a small circuit to sense 220 V  with my Microcontroller (RPi). But I'm getting either 5 V or 1.3 V on a GPIO wire.

I can't understand the problem. I want 0 V or 5 V on GPIO.


texts: Why does CMRR degrade in an instrumenation amplifier when the feedback resistor is increased?

texts: Why does CMRR degrade in an instrumenation amplifier when the feedback resistor is increased, keeping all other resistances constant at a fixed value? What mathematical relationship links the feedback resistor and CMRR?


texts: Output characteristics curves do not merge in LTspice

texts:
I wanted to plot the output characteristics curves and Early effect of a transistor in CB arrangement. In LTspice I made a DC sweep along with parametric sweep as follows where I sweep the Vcb from -24V to 5V and for each fixed emitter current from 0 to 100mA with 10mA increments:

In the plots below -I(V1) is the collector current and -V(C) is the collector-base voltage.

Even at around -24V these curves do not merge. Is the simulation setup wrong?


texts: CAN communication between mcp2551 & tja1050 transceivers

texts: I am trying to have 2 arduinos one connected to mcp2515(controller)& mcp2551(transceiver) , the other is mcp2515(controller) & tja1050(transceiver). I tested the setup by sending CAN messages from one arduino to other. But the message stopped sending after I received 3 messages! Can anyone please help ? Is there any problem connecting 2 different transceivers to communicate on different ends?


texts:
A batch of questions here really (if it helps I'm operating at 433.92MHz):

How should I orient a helical antenna with respect to my board (i.e. my "ground plane") to get the best range performance?

What should the dimensions of my ground plane have to be in order to get good performance / how much does this matter compared to orientation?

I'm also wondering what effect (if any) the relative orientation of these types of antennas between the transmitter and receiver has on link quality (due to polarization?).

Is the antenna pattern directional for these types of antennas (related to 3), and if so how narrowly?
Sorry if this question is a little bit all over the place - I've got an EE background, but RF can be kind of mysterious (if you know what I mean)...

Regards,
Vic
[Edit] 3-d visuals would be really helpful in helping me get my head around this as well [/Edit]
[Edit2]
5. Going to attempt some ASCII art here - what's the best way to mount my antennas? slashes (/) are the helix orientation, underbars (_) are the ground plane, and vertical bar (is the feed point):
    Transmitter                             Receiver
**A**
         /                                     /
         /                                     /
         /                                     /
         /                                     /
     ____|____                             ____|____

**B**
      ////////                              ////////
     _|_________                           _|_________

**C**
      ////////                              ////////
     _|_________                           ________|__

**D**
         /
         /
         /
         /                                  ////////
     ____|____                             _|_________

**E**
         /
         /
         /
         /                                  ////////
     ____|____                             ________|__

[/Edit2]


texts: Bias headphone audio signal for use with digital potentiometer?

texts:
I am attempting to control speaker volume via a digital potentiometer, the problem being that audio signal goes both above and below 0V, for regular potentiometers this is no problem but for digital they cannot handle a signal below ground.

How can I shift the signal up to always be above 0V? I believe this is called biasing, so instead of -2V to 2V it'll be 0V to 4V. I have seen example circuits for this. So for me the more important question is do I have to shift it back down for the speakers to "understand" the signal again?


texts: Are there specific microwave antennas for digital and analog signal transmission?

texts:
I'm supposed to do a class report on microware antennas. The report said we have to present 1 microwave antenna that sends digital signal and another that sends analog signals.

Do you know such specific antenna ? (I'll then work on googling their technical specifications)


texts: Arduino How to improve laser detection on photodiode?

texts:
I am building arduino laser transmitter.

I have modulated laser blink, however the photodiode detection is not really sensitive to the beam (I would need to spread detection at higher range). I tried to use photoresistor, but it was slow discharging making bits in graph unreadable.

How can I increasy sensitivity of the photodiode (and possibly reduce effect of daylight)?

currently using arduino circuit with PP75 photodiode and 10 Mohm resistor (there was no detection when using lower resistors..)

Maybe I have badly connected circuit? Or do I have to use some MOSFET? (but I am not sure how to use it properly...) thank you for advice. Photos shown bellow

EDIT:

here is my previous result of using circuit with photoresistor. The only problem with this was that the values was dropping slowly, making the output unreadable at higher speed. I thought a photodiode would fix this, but the responsivity is not hight enough.
How can I improve my circuit with photodiode to get a simillar result as if using photoresitor except I would get these values changed quicker as on img2 ?

The deviations at bottom of the graph is a lamp switching on and off so its good because it doesnt affect the laser blinks.


texts: Current zero cross detection circuit off of triac

texts:
I need help modifying the circuit below.

The assumption in this circuit as it stands is that AC Hot would be common to GND and then MT2 of the triac would go through a light source to AC Neutral. P_IRPT pulses high when there is no current flowing between MT1 and MT2 of the triac T1, which occurs at every zero crossing

The modification I need is for my case where AC_HOT is common to the 5V rail rather than GND (my power supply has a negative output).

I know there are other ways to detect zero crossing but this circuit gives the me assurance that I am definitely detecting the zero cross after it has occured so I never run the risk of firing the triac prematurely.

Thanks!

This was taken from page 16 of this TI app note:
http://www.ti.com/lit/an/slaa043a/slaa043a.pdf


texts: MSP430 interrupt issue with the MSPFET Emulator connected

texts:
I'm using the emulator MSPFET Flash to program the MCU MSP430F5507. There is a peripheral interrupt subroutine that should receive an external interrupt every 1 second.
I have a problem that the interrupt doesn't work until I disconnect the emulator.
The interrupt is active low, and a pull-up resistor is connected to the pin.
If the emulator is disconnected, the interrupt signal is by default high and a low pulse is coming every 1 second and is watched on the scope.
But, once the emulator is connected the interrupt signal is low and doesn't go high even though the pin is pulled up in hardware.

Anyone have a suggestion for this issue??


texts: How to IR LED as half-duplex transceiver or just receiver?

texts:
I'm i need to capture IR signals in their raw form from IR remote to analyze them. Currently I'm doing it by connecting logic analyzer directly across led on the remote. I want to skip that step and make a universal receiver that does not demodulate a signal and use IR led as receiver instead of photo-diode or photo-transistor.

I know that it's possible to use single IR led as both receiver and transmitter but not at the same time(which is logical) because there are TV remotes that have programmable buttons and you just point the original remote to the IR led at the top(I'm sure that led is used as receiver because there is no other optical component).

Can someone explain it to me how to use IR led for receiving raw IR signal and provide me with basic schematic?

It needs to have fast rise and fall times(probably simple to do, leds have fast response time).


texts: Connecting diodes to a motor in H-bridge

texts:
I'm attempting to design a three wheeled toy that is controlled by a remote connected with it via a cable. I first designed it with relays, however I had to change to transistors due to contrast between low power required by the toy itself and a high power demand of relays.
I know that if there are vulnerable components in the circuit with a coil such as a motor, you should connect a diode in parallel with the coil in the reverse bias direction.

Here's a problem, in my H-bridge, current will flow both ways through the motors and I'm confused as to how to connect diodes to my motors to protect the transistors.

simulate this circuit – Schematic created using CircuitLab

Also, if you have any idea how the design could be improved further, I'm all open for criticism.
Note that on the schematic there are no specifications of the devices as these are liable to change with the choice of components available.


texts:
Here is sequential circuit I want to simulate in Multisim:

Pay attention to AND gates which I labeled with red numbers.
Inputs to first gate are X and Q1, to second X and Q2 and to third X and complemented Q1. To simulate this circuit, I would connect all those flipflop outputs (Q1, Q2 and complemented Q1) to and gates.
Question: Is it possible to label Q1, Q2 and complemented Q1 like on schematic I posted on some way so they represent Q1, Q2 and Q1_complement outputs of flipflops, WITHOUT CONNECTING THEM WITH WIRES?
Why I ask this? Imagine we have some really complicated schematic. It would be very time consuming drawing that schematic in Multisim and, moreover, schematic would be very confusing with all that wires...
Thanks in advance.


texts:
Every circuit diagram of a relaxation oscillator says I have to put a 100 ohm resistor between the capacitor and the voltage source like this:

simulate this circuit – Schematic created using CircuitLab

But I think it would be better to use an 1000 ohm resistor instead of a 100 ohm resistor. This would discharge the capacitor at a slower rate and give me a lower frequency.

What do you think?

simulate this circuit


texts: Timing diagram question of an EL-display

texts:
I am having a hard time interpreting this timing diagram of a Planar electroluminescent display;
datasheet: Planar EL320.256-F6  pages 10-11 in the browser pdf viewer.
If i read this correctly,
it states that "T9 HS period (tHS)" is 51 µs. This means that the minimum "T7 HS Low Time", which is 4 tVCLK + the minimum "T8 HS High Time", which is 320 tVCLK, takes 51 µs. A little calculation gives us about 157 ns for one tVCLK. But in the "Setup and Hold Timing" section it states that the minimum "tVCLK", the "VCLK period" is 40 ns.
How does this add up?
If i'm completely in the wrong please correct me, the other question i have is, what does the "setup" and "hold" times mean in the diagram table descriptions?
I was able to try its test mode (just giving power to given pins), the goal is to drive it with an fpga using a state machine, but to do that i need to know, and present the correct signals at the correct time, if someone gives a deep explanation about timing using this datasheet i linked, i would be impressively thankful.


texts: Convert [-24V,24V] range analog signal to [0V,3.3V] range for ADC

texts:
I need to realize a circuit that converts an analog signal from [-24V,24V] to [0V,3.3V] before sending that signal to an ADC "MCP3208". I found the circuit in the picture below and it works perfectly in simulation, but I am still not sure if can I use it to send the signal to an ADC input or not. I use the capacitor as a bypass to avoid AC noise if it exists but normally the input signal is DC.

Will this circuit work? If not, what different circuit would work?


texts: Single Phase Induction Motor Working Principle

texts:
It is often said that the main stator winding of a single phase induction motor provides zero torque, if so what is its function? How does it help in keeping the rotor rotating?
How could one using electromagnetic theory, and the geometrical parameters of the motor determine its rotation speed?
Why does the motor yield zero torque at a maximum rotation speed? What causes the back-reaction? I am guessing this is due to the dissipative impedance in the windings, correct?


texts: Increasing output voltage of a fixed linear regulator

texts:
I'm using a AMS1117 fixed 3.3V linear regulator and I want to increase its output voltage to about 4V.  The input voltage to the 1117 is in the range of 9-10V.

Wikipedia suggests that it's possible to put a zener or resistor on the ground terminal of the regulator to change its output voltage but it provides no citation or reference.  Anyone know how this works?


texts: New here, self taught, been working with tube amps for a while. Currently working on my 64 Deluxe Reverb that I have restored to stock, with some of the original ceramic and film capacitors. Just received an ESR02 to test capacitors. I still cannot wrap my mind around exactly what ESR affects in these old circuits. The ceramics are used for coupling, electrolytic's for bypass and filtering. My question is what does the ESR affect. If I find say 1.5 ohms ESR on a component, what exactly does that affect? Obviously in a grounded cap, 1.5 to ground would not be too good, so how should I view ESR, the way it gives up it's capacitance, or passes voltage in the coupling, lowered voltage to the next? These parameters change the tone, feel, and response of the amp as I have tried substitution. Still a bit hard to comprehend.  To me capacitance is the most difficult thing to understand, and yes I have read much about it.


texts: Half-Bridge Gate Driver Circuit Question

texts:
I got two questions about Half-Bridge Gate Driver MP1907 circuit on brushless motor driving.

MP1907 chip's eveluation board uses 1uF for bootstrap capacitor. However the 20A brushless motor ESC i have uses 4.7uF. Does the value matter? Should I use a smaller value like 1uF for fast charging in fast switching applications? The application is brushless motor driving around 20-30A max current. The voltage is around 16V.
The ESC I have uses 47 Ω resistor between gate of the MOSFET and the DRVH, DRVL pins of the MP1907. Is this necessary? What good is in there to use them since again eveluation board does not use any resistor and connects the Drive pins of the MP1907 to gate of MOSFET directly?


texts: High/Low Input Voltage Atmel At90USB128 Microcontroller

texts:
I am working with Atmel's At90USB128 and wanted to figure out what the input high/low voltage was for the SPI communication. In the spec sheet , I noticed that there seemed to be two conflicting information. Under the "electrical characteristics" section of the spec sheet, I saw this:

And under the "typical characteristics" section of the spec sheet, I saw this.
.

Clearly, the numbers are conflicting on the table and the graph. With the table giving a much higher input high voltage, and much lower input low voltage. What exactly is the difference between them?


texts: Why is the data rate a function of the length of the transmission line?

texts:
The length of a transmission line is limiting the highest possible data rate on that line.

Why are faster signals more likely to become corrupted on long transmission lines than on shorter ones, with focus on frequency-BW of the signal, raise time, etc... ?

Would appreciate any explanations.


texts: Bluetooth low energy multi peripheral topology

texts:
We are trying to read data from 8 BLE peripheral.
When using single peripheral, the peripheral device was sending notify to the central side(this fire a callback on central), ensuring lossless data transmission. How can central read 8 devices simultaneously?

How should central's data reading policy be? Notify based or write/read based?
Peripherals are asynchronous to each other. Should they be synchronous?
Is there a setting that needs to be applied to the ble stack that about the BLE parameters itself.
Do peripherals have to give up by reducing their speed?

NOTE: simultaneously meaning in central's connection interval to peripheral. Not exact same moment in time domain.
Best Regards


texts:
I couldn't find the explanation for this query of mine.
Why back emf in dc motor is nearly equal to the applied voltage on no-load?
I tried to search on the internet but all in vain.


texts: Noise generated in 2nd stage of active bandpass filter

texts:
I'm breadboarding a two-stage inverting amp/filter to amplify a radar signal, using the TLV2464 opamp. My first stage has a gain of 45dB, the second stage 35dB. The input will be a radar signal which I offset to 2.5V so I get a positive output signal after the second amp stage that I feed to a comparator after which it will be fed to an STM microcontroller.
There are two major problems that I can't figure out how to solve:

When I add 0.1uF decoupling caps to the PWR pins the output signal disappears - it just stops working and starts again when I remove the cap,

Without any input (or even when tied to GND), the signal after the first stage is quite clean and stable. The output of the second stage however looks like high frequency noise with an amplitude larger than 0.5V, so the signal swings from below 2V to almost 3.5V. There seems to be a ~62Hz component in there (16ms period).

I power and  scope the breadboard with an AnalogDiscovery2 USB scope which of course isn't the best tool around but it should be plenty good for this kind of job. Anyway, the first stage works just fine.
The TLV2464 ICs I have are 4CH versions; I've tried using two channels of one IC for both stages and I've tried using a different IC/package for each stage: same result.
So there must be something very basic wrong with my schematics I guess.
Any advice is welcome
This is with the input signal floating. Blue is after stage 1, yellow after stage two:

This is with the radar module connected to the input line but there's no movement in front of the radar. Blue again is after the first stage, yellow after the second stage:

Adding a cap to the bias reference line like @DAS suggested indeed seems like a good idea, but when I tried a 0.1uF or a 1uF I'm getting a signal with a weird bliep almost every second. Not sure what I'm looking at here...:

UPDATE:
After the detailed response by @analogsystemsrf I looked at it again. I don't really understand the entire reasoning but not wanting multiple return paths is clearly a good design guideline! How I changed my circuit: Instead of using one voltage divider to create the bias at both opamps, I took the output of the voltage divider and fed it into two followers/buffers, each one which will be providing its output to each of the amp stages. The intention is three-fold: (1) controlling the impedance, (2) taking out the multiple return paths (not sure if that happened!), and (3) not leaving the 3rd and 4th channels of the package (4 opamps) unused; they have to be properly terminated or used. This is what it looks like:

Anyway, these well-intended changes did not improve my amp/filter: after the second stage I still get crazy noise with a large amplitude (V).
Another issue that hasn't been resolved: there's still a very consistent signal in the noise around 60Hz. I have no idea where this could originate from!


texts: Question about Z-Diode circuit and measurement

texts:
I am currently diving in in embedded development using ATMega Microprocessesors. I have now a question regarding Z-Diodes. My circuit is powered by a 9V battery that gets through an IC7805, thus getting a constant 5V power supply. Now I have a part that requires to be used at 3V. I made my thoughts how to achieve that and two things came across my mind: 1. Use an LM1086, which I felt is a but overpowered for just one part needing 3V or use a Z-Diode.

I build a little prototype on my breadboard using the IC7805 as supply and using a 3V Zener Diode to go down to 3V and power a LED with that. It so far works fine, but when I measure the power at the LED, I always only get 2,3V and if i measure the diode, i get 2,7V.

Here is the circuit plan I use:

(I just saw I forgot to add a value to R1, which is 100 Ohms)

Am I really getting just 3V at the diode? If yes, why cant i measure it with my multimeter.

Thanks in advance!


texts: Could you please find the Laplace transform?

texts:
I can use the table directly, but I am struggling how to make the combination. This equation will help me to work on my gyroscope sensor equations ( magnetic based ) , My pain point is at the combination.
$$ t^n\mathrm{e}^{-at}\sin\omega t $$


texts:
I am looking for a chip which will convert CAN messages to an SPI message.

Is there any chip available as such?

Until now I have found MCP2515. But this chip does not serve the purpose, because SPI transactions need to be triggered in this chip. The master has to request for data from MCP2515. This is not my purpose.

I want a converter such that it will immediately convert CAN to SPI, without any help of the trigger.

Is there a chip which can work like this?

Alternative ideas to serve this requirement will be appreciated as well.


texts: What is a pinout of TOP side of Intel Core i7?

texts:
Here is a core i7 cpu

It has some contact pads on the top side, some grouped in 4 or 6 and two big groups.
Is there a pinout of these pads? Where are the JTAG connection pins?


texts:
I have a IPB011N04LG N channel MOSFET configured as a switch in the following circuit:

It works, but doesn't turn fully on.

If \$V_{\text{BAT}}\$ is \$23\$V I get \$11\$V on the load side
If \$V_{\text{BAT}}\$ is \$16\$V I get \$7\$V on the load side

Did I make a mistake? How do I drive this MOSFET properly to fully switch on the load?


texts: Run *.net files with python sequentially

texts:
I work for a project in which we use Pspice and *.net files.In my code I use a button which is selecting *.net files and it returns back their paths in the Entry.The following code doesn't work for the paths which they should have ran from the pspice solver(psp_cmd.exe).I want my *.net files to execute from the pspice solver(psp.exe) sequentially,so I can create *.out files.The below code is running regularly without any error,but the *.out files doesn't generate in my folder..What are you suggesting?
file_path= []
def selected():

    file_path= tk.filedialog.askopenfilenames()
    print(file_path)
    myEntry.insert(tk.END,file_path)
    filepath2=('\n'.join(map(str,file_path)))
    print(filepath2),str
    Pspice="D:/tools/bin/psp_cmd.exe "
    for f in file_path:
        subprocess.call([Pspice ,"-r",f])

```


texts:
Any Lithium battery experts here?
My concern is that there is a lot of work and specialized chips on BMS systems that specialize in balancing battery cells for large batteries.
Lets say I have a lifepo4 battery with 480 cells for 76.8V and is configured at 20p24s.
Why do they configure it that way instead of lets say all 480 cells in parallel for a 3.2v and then a boost converter. I'm exaggerating here with the 3.2 volts, but why not 12v and then put a second stage for boost?
Max current draw seems to continue to increase due to new cell designs.


texts: Why does the Collector-Base Junction need a lower magnitude voltage to be forward biased compared to the the Emitter-Base Junction?

texts:
We are learning about the different modes of BJT transistors currently and something that is a bit odd to me is that our textbook states that

"... an npn transistor whose EBJ is forward biased (usually, VBE ≃ 0.7 V) will operate in the active mode as long as the collector voltage does not fall below that of the base by more than approximately 0.4 V. Otherwise, the transistor leaves the active mode and enters the saturation region of operation."

My question is why the Emitter-Base Junction needs the 0.7 V we're all familiar with to become forward biased, but the Base-Collector Junction (\$V_{BC}\$) needs to only be 0.4 V to become forward biased? My line of thinking is that the collector is less doped than the emitter, so there is a smaller barrier voltage to overcome.


texts: Why this point in this schematic will begin at 2V at 0ms?

texts:
I have ask this question in here before:Simulation is the same as my thinking,but different from the pape r(charging loop) ,and @a concerned citizen showed his\her simulation and schematic to me.However,everything,except the diode and switch,is the same as his ,but our simulation are different.By the way,his simulation is right,that is,the same as paper.

Our simulation are different,here are our difference:

1.His positive half wave or negative half wave start from a positive or negative voltage,but mine start from 0V.

His schematic information and simulation

2.At the 0ms,his voltage is about 1.4V,and at this moment,all switch is opened,that is ,the equivelent circuit should be like this.And i think that is very strange,because at 0ms,the sine current source just ready to produce sine wave,and the capacitor,which initial condition is 2V ,did't connect that C1 with their positive pin ,why is there a 1.4V in the 0ms?

simulate this circuit – Schematic created using CircuitLab

@a concerned citizen told me that You're probably using something similar to uic (initial conditions), I let the solver determine the .op. If I had used with uic, it would have, most likely, started from zero (everything).However,the simulation still start from 0V when i don't use the UIC.What is this mean by using .op?does anyone know that?


texts: Can someone how to find this voltage gain neglecting r0

texts: I'm trying to figure out why my professor starts off the way he does when trying to find voltage gain. How he starts off is shown in the last picture. Any explanation would be appreciated.


texts: Ideal Op-Amp obeys virtual ground principle without negative feedback?

texts:
I was reading this book - 'Fundamentals of Electric Circuits - Alexander, Sadiku'. I came across this:

They say that a characteristic of an ideal op-amp is that v1 = v2. I was taught that this is only true when the op-amp is set up in a negative feedback configuration. Is that not true? Is this v1 = v2 'virtual ground' principle always true?


texts: Uses of a silicon semiconductor and why its resistance at different temperatures

texts:
We conducted an experiment in which we found the variation in the resistance of a fairly pure silicon sample between temperatures of about 400K to 600K, and we found a value for the energy gap of silicon of our sample. We were comparing the resistance variation with the model:

\$ R=R_0e^{\frac{E_g}{2k_BT}} \$

Firstly, does anyone know what the name of this model is? I have spent several hours trying to find out about this model (unfortunately it is not possible for me to ask my practical demonstartor) to no avail. This model also predicts that this relationship will only be followed when the temperature of the semiconductor is sufficiently high- within the 'intrinsic region'. However all of my searches about the 'intrinsic region' of a semiconductor simply come back with intrinsic and extrinsic semiconductors. Nothing about the 'intrinsic region'.

Also, I am trying to figure out why such information may be important. I know silicon as a semiconductor has many applications for example in detecting the temperature, however I have not come across any examples of devices that would use the properties of silicon at such a high temperature.


texts: Why is JSN giving error readings when powered with Buck converter 12v to 5v different power source?

texts: When I power my esp32 with an USB cable and check the readings of JSN-SR04 it shows correct and consistent readings. But when I connect esp32 and jsn with 5v from LM2596 12V input errors are not correct and sometimes consistent. Can anyone help me with this?