texts: Performance of series fans on a heatsink

texts:
I have a large heatsink with fans that push air through the heatsink parallel to the fins, very similar to Fischer Elektronik LA 9 150 230 V but not identical. I know that a heatsink increases the static pressure of a fan, reducing total airflow through the heatsink, I also know that having two fans in series increases airflow for a given pressure.
If I was to add another fan to the other side of the heatsink, essentially having two fans "in series", would this increase the cooling capacity of the heatsink?
EDIT: Will performance be increased if the additional fans don't have the same performance characteristics of the first fan? At which point will adding a fan actually reduce the cooling performance of the heatsink?


texts: Core loss appearing in buck converter ripple current

texts:
I have been told (and have also seen experimentally) that an inductor with a high core loss will introduce "glitches" to the ripple current in a switch mode power supply. I have tried researching this, but can't seem to find any information. Below is an example of what I mean by "glitch". An explanation of why this is occurring would be great, and I would also love to be directed to any literature on this topic that I could research further.

Edit:
Below are two waveforms I just took. The circuit is a synchronous buck converter, and the parts are the exact same. Out of 30 inductors, 15 were purposely damaged and the other 15 were left undamaged. All 15 damaged parts exhibit the "glitch", while all 15 undamaged parts do not. The original waveform was actually from user 'gsills' while answering an unrelated question of mine "Ripple current in synchronous buck converter". I have also heard this elsewhere, not only from gsills.

The below waveforms are from the exact same circuit, only the inductors were swapped out.

One of the undamaged parts:

One of the damaged parts:

For some reason there is a little added slewing on the switch node voltage waveform. I've used this same circuit many times and that generally doesn't occur.


texts: How small could Z80 microprocessor made with modern transistors?

texts: If an 8,500 transistor Z80 microprocessor were manfactured using 7nm transistors rather than 1970s era 6µm, how small would it be?


texts:
simulate this circuit – Schematic created using CircuitLab

I have looked at several questions/answers regarding this topic on EE.SE and other forums I found with a search on google.  I am only as familiar with using a transistor as to block current flow and to allow current flow, but never really had to worry about passing a specific current.  After reading all of the questions I still can't seem to understand how to calculate the base resistor for a transistor to ensure it can switch enough current.

As an example, I will be using the following parts:
WP130WDT/EGW LED, MMBT3904 NPN Transistor, and the 74HC595 Shift Register.

With the LED operating at 3.3v and 20mA I have calculated the base resistor with the following formula:
Base Resistance = (Base Voltage - Vbe)/(Ic/Hfe)
(3.3 - 0.65)/(.05/60) = 3180

Am I on the right track/using the correct values(I know the LED will only pull 20mA even though I calculated for 50mA Ic)?

My goal is to get ~equal brightness for all LEDS.

EDITED: added schematic.


texts:
I am designing a PCB including a GPS module. I am using the Locosys LS20031 which has a antenna mounted on it. The module is mounted on the board with 1" plastic studs and a connector connects it to the PCB . The question is if it's good/wrong to lay a layer of copper on the PCB area underneath the module.
Will it reduce the antenna gain/sensitivity? It's better to put a keep-out area instead of copper?


texts: How does this circuit produce a triangular-wave output?

texts:
I came across this circuit and can't see how it works. I have never really dealt with any operation amplifier circuits that make use of positive feedback, so that only worsens the problem.

It seems that we have R1 and R2 forming a voltage divider for the input of U1A (about 1.9V). I have no idea what C1 is doing there since we are dealing with DC and the op-amp is high input impedance  and to my knowledge does not do very much internal switching (thereby demanding current spikes). If C1 were in place to filter the supply then it's in an awfully strange place.

The second op-amp, U1B looks to be like some form of an integrator.

Any intuition into this circuit? How could you analytically go about solving this problem?


texts:
I'm trying to switch 12V with an IRL540 from a 5V micro. Right now I have it a 1k resistor between 12V and the drain, the source to ground, and the gate has a 100kHz 5V square wave on it. That's the whole circuit, this was just to validate the switching.

If I go faster than this it starts to not even reach 12V before I turn on the FET and pull it down again.

As we can see from the capture there's quite a lag in rise time, I suspect by the charge needing to return to the drain of the FET. But should it really take this long? It's at least an order of magnitude longer than what's specified in the data sheet (given that's with Vdd at 50V, but this seems very slow). My square wave seems fine. What can I do to fix this?


texts: Convert 3.3V PWM of Beaglbone black to 5V PWM

texts: I have a Beaglebone Black revC. I want to use a brushless motor (EMAX XA2212/1400KV) with ESC (hobbywing skywalker 20) . Beaglebones Vpp voltage is 3.3V and ESC gives ( gives beep about 2 sec interval) "Throttle signal is irregular" trouble signal. I think this ESC accepts only 5V Vpp. How can fix this? How can i change 3.3V PWM to 5V PWM


texts: Voltage controlled current source using op-amps

texts:
I have a sensor which gives a voltage output between 0V and 5V. I need to transform this sensor output to a current suited for a 4..20mA current loop.

The thing is, the current loop doesn't have a fixed resistance, so my current circuit does not seem to work, because as soon as you change the RLOAD (pot in the schematic for simpification) the output current does not stay within the range.

What do I need to change to make this circuit funtion as a variable 'constant current source' (not sure how to call it, I want constant current based on the input voltage but the input will be changin).

I'd really appreciate some guidance to figure out what I'm missing!


texts:
simulate this circuit – Schematic created using CircuitLab

The Circuit is of 2 alternately flashing LED's (BXRA-C0402 -- max i = 500mA).
Each of the transistors(TIP120) power 15LED's (going on an off simultaneous) How do I find out if the transistors can supply enough required current to the load (15 LED's each = 500mA*15) and if not, how much current is the circuit short of?? How can I over come this??


texts:
I have an U type inductor. I'd like to calculate temperature rising on the inductor. I found a formula but the result was approximatly 350-550 celcius, I think that is not possible.
Here my formula:
$$
T_r = 450(\Psi)^{0.826}
$$
$$
\Psi = \frac{P_{totalLOSS}}{A_t}
$$ watt/cm2
At--> Total surface area of the magnetic core.
my values:
PtotalLOSS -->4.3846 Watt
At --> 4.7 or 5.6 cm2


texts: I painted myself in a corner. How to layout?

texts:
I'm a hobbyist working mostly in DC projects. For development and testing, I  use breadboards, and later a perforated board. My projects are normally low count: an Arduino Nano/Pro Mini + a few ICs.

All my works are one-of-a-kind, and making a PCB is out of question for me.

I use the ICs and physical board itself to test the layout of components on board. I have Fritzing, but it's not up to the task for planning the physical layout; it's more like an ideal vision  of the circuit where wires have no thickness and every thing fits neatly in the matrix.

My problem is that sometimes I paint myself in a corner: after soldering a few things, I found the next pin buried under other wires and components; no way to solder anything. I'd been searching for tips, found none. How is your flow work? How do you do these things?

Here some questions:

Solder all component first and wire them later?
Wire each component directly to Vcc, Gnd and shared signal or use rails?
How to layout for changes? Maybe I need to add something in the future.


texts:
Well as you know many hardware modules work with 3.3V.
Our product has a PCB with a few components which most of them require 3.3-3.6V to work properly. A little bit below that, they will not perform well anymore.

Till now our approach was to use a lithium polymer chargeable cell of 3.6V which works great with a regulator. But we want to go back to coin cell battery.

Most of the coin cell batteries are 3V. The only one that has a 3.6V is LIR2450 but its a chargeable battery with very low capacity.

I see two options:

A charged coin cell battery is usually more than 3V. Can we make that assumption and just put it in our products? Is it "not professional"?
A step up converter from 3 to 3.3V. Does it take lots of current? Are there modules that just do that?

How generally engineers approach this issue that all cell batteries are 3V and most of the hardware components are 3.3V?


texts:
Say I have some low pass filter of the form:

$$G(s) = \frac{a}{s+b}$$

How do I find the bandwidth? I know for example that with bandpass filters it's the difference between +-3dB of the cutoff frequency but I'm not sure how that would work for this example.


texts: MOSFET Constant current - Current mirror circuit

texts:
I have been reading this current mirror/constant current circuit using MOSFETs.
How does the current not change through Q2 when the voltage at Q2 increases? Ref. Fig1
Where does the excess voltage go when Vcs is increased?
Can someone explain the complete working in simpler terms?


texts: 100BASE-T two devices on a single ethernet port

texts:
I am trying to embed a SBC inside a device. Power, weight and space are very limited. The two devices need to communicate with each other via Ethernet using a crossover cable. I would like to solder wires directly from the PCBs of both devices to a single Ethernet port. By using two pairs from each device I would be able to either interface them separately by splitting the 4 pairs again before connecting to a router or allow them to communicate via a crossover cable feeding back into the same port. This would allow me to remove an Ethernet port from one of the devices and save space.
For the crossover cable:
            |----ETHERNET PORT-----|
Device 1 -> CableSideA -> CableSideB -> Device 2
1           1             7             3
2           2             8             6
3           3             4             1
6           6             5             2

Here is a diagram I quickly made that might help explain:

Legend

The crossover cable can be seen at the top left. This is an RJ45 connector (MALE) with wires crimped as seen in the diagram
Below the crossover cable is the RJ45 (FEMALE) Port that both pcbs are wired to
At the bottom there are both PCB pinouts
The right diagram shows the cable that will be built to split the connection if I need to interface either one or both of the devices.
The cable has on one end an RJ45 connector(MALE) that is split on the other end into two RJ45 connectors (MALE)

Is it possible to wire directly from the PCB's of device 1&2 to a single RJ45 port (HR911105A) using two pairs from each device (100BASE-T only utilizes two pairs) and then split this connection outside of the port?
Data Sheet of the port in question: HR911105A

(source: netdna-cdn.com)


texts:
I have searched "how to wire a MOSFET" in a few different wordings and looked at a bunch of MOSFET wiring diagrams, but I can only seem to find the more complex examples of a MOSFET wiring.

Currently I have a low voltage switch (coming from a RaspberryPi) I want to use to turn on and off some 5v lighting.

The four wires I have are the positive and negative for my switch (low voltage), and the positive and negative for the light (5V).

I'm not sure if my scenario is the right one for whatever the most basic form of MOSFET wiring is, but I'd like to start by understanding this.

What is the basic way of wiring a MOSFET?  Could someone please show me a diagram?

EDIT:  so far, this instructable is the best novice description I have found.

EDIT 2: This question pertains to a basic example of MOSFET wiring.  My scenario happens to exist in a different question, but the answer I'm looking for is not simply how to solve my particular problem, but (in the most basic case) how to wire a MOSFET.

P.S.  I know this is probably an incredibly basic question to anyone who knows the answer, but as stated above, I'm only finding answers to complex questions about MOSFETS on the internet, and the part I bought did not come with what is most likely a very simple diagram.


texts:
Section 13.4 of the STM32 Reference Manual (for my STM32F303RE board) states:

  The DMA controller performs direct memory transfer by sharing the system bus with the
  Cortex-M4 ® F core. The DMA request may stop the CPU access to the system bus for some
  bus cycles, when the CPU and DMA are targeting the same destination (memory or
  peripheral).

My question is: when exactly are 2 memory destinations the same in this context? Is it only when the 2 actually overlap (e.g. CPU accesses 4 bytes @ A with one instruction - thus accessing A,A+1,A+2,A+3 - and DMA 1 byte @ A+2) or is the memory split into larger regions and the 2 collide when they're accessing the same region?

If it is the latter, how big are those regions?


texts:
I acquired a lot of vintage electronic components at an estate sale.
The sale included a dozen of what may be variable resistors.
These components are all the same size and have the same plastic mounts.
The code on the bottom varies but the last part of each code is N4A.
Can you tell me what I have?


texts: Testing conductive RF shielding paint with a VOM

texts:
I heard it claimed that you cannot test the conductivity of conductive RF shielding paint with a Volt / Ohm meter. This was in reply to someone who had done so and claimed that the paint was ineffective because they did not detect any conductivity.

Is this true, and if so, why?


texts:
If a live wire is taken from AC and connected to a bulb, while the other terminal of the bulb is connected to ground, the bulb glows; but if I take the positive terminal of a battery (DC source) connect it to one terminal of a bulb, ground the other terminal of the bulb, then the bulb doesn't glow. Why?

(I find this pretty confusing..)


texts: How to measure telephone DTMF tones with an oscilloscope?

texts:
I have a situation where I'm trying to connect two computers via their dial-up modems. I've built a line voltage simulator (9v @ 40ma) into the line that connects them, and I've tested with a telephone to listen and make sure the modems generate DTMF tones, and by pressing keys on the phone, that the modems can receive DTMF tones.

The problem is that when I connect both the modems together, the receiving modem doesn't detect anything from the transmitting modem. There must be some difference between the tones/voltage/frequencies generated by a normal telephone, and those generated by the source modem.

I'd like to measure the DTMF tones generated by the phone, and those generated by the source modem so I can compare them and perhaps isolate the problem. But I'm not sure how to measure a telephone line with an oscilloscope.

The line is made up of a tip-and-ring pair, how can I get a nice measurement of the audio on the line?

Edit:

From what I understand it should work just hooking up the wires to the probes - at least by using the scope's math function and subtracting one channel from the other. The problem is, I never get any signal at all, except background AC noise. The main things I don't understand is what to do with the ground probe, as the cable doesn't have a ground, and if there can even be any signal without a device attached on the other side of the cable to complete the circuit between the two cables


texts: Through hole via isolation in Eagle CAD 4 layers board

texts:
In Eagle CAD, in a 4 layers board (signal-ground-power-signal) how do I avoid that a through hole via from, for example, the top signal layer to the power layer is electrically connected to the layer in between (ground)?

Do I need to manually move the ground polygon or overlay a "cutout" polygon or can it be done automatically? Can Eagle CAD place a cutout or a no-copper space around the Via on the in-between layer?

Thanks


texts: What is the best way to make an Arduino play a sound file? Is there a code library or shield I would need? How would I store this sound file on the Arduino's chip? Is isn't very big, so I would be concerned doing this.


texts:
I'm setting up my PIC oscillator frequency and I'm using a PIC24HJ128GP202. From what I've seen in the datasheet, two of my total options were to use a crystal or a internal oscillator (FRC) which would go through the PLL and scale my frequency of operation up to 80MHz.

I decided to use a 10MHz external crystal. To reach 40 MIPS I should configure correclty the PLL parameters N1, N2 and M. It all seems to be fine except that these last parameters are configurable by software. I was used to PIC's like PIC18f4550 where these oscillator settings were configurable through the configuration bits. So whenever I program the device, it would have those settings always after reset.

In this case (PIC24HJ128GP202) I can only configure what kind of oscillator I will use in the configuration bits (HS with PLL). PLL is only configurable by software. So, since the PLL default values will get my frequency out of the bounds specified by the datasheet, how can I configure the PLL by software if the software requires a correct oscillator frequency of operation? Is it the case of using IESO (start-up with internal oscillator)? Any other way around this problem?


texts:
I have got the task of coming up with a solution of individually controlling around 250 LEDs. As I would be a complete newcomer in programming an Arduino or whatever else there is, the computing platform is relatively irrelevant for this job (*). It mainly should be portable and not overly large.

The LEDs could be single colour but if there is a simple extension for RGB LEDs, this might be even better. If there is a hard limit in controlling such a number of LEDs and things would be much easier if we reduced this number, we might be able to put three or at most four LEDs on the same controller. (The LEDs will be behind a screen and not directly seen.) In that case, the number might be around 80.

The question is mostly about what would be the best platform choice in this case?

(*): I am mainly a programmer and not an electrical engineer, so diving into a C like library is my least problem. Hardware is my problem.

Edit: The LEDs should be variably positioned. There may be smaller clusters or strings of a few LEDs but otherwise it should be rather arbitrary. There should be ~< 2m between the outmost LEDs.


texts:
YELLOW- LOW IN

RED -   HI IN

BLUE - LOW SIDE OUTPUT

GREEN - HIGH SIDE OUTPUT

I have designed a H bridge circuit using FAN7392 & 25N120NDH IGBT. The voltage I want to switch for now is 24 volt DC. It’s designed for switching 400V DC.

So right now the bootstarp capacitor is 0.33 uF tantalum cap (In schematic it is 10uF). Switching frequency is 2.94 kHz. And its only driving the half bridge.

The problem is FAN7392 getting hot. FAN7392 is at 65 degree Celsius. And its drawing 0.00 to 0.80 A (varying with the PWM duty cycle). FAN7392 has been provided with 15V DC. And the logic level side has 5V DC. Shutdown pin is Grounded. And NO LOAD IS PRESENT ON THE AC SIDE (IGBT OUTPUT).

So the heat is normal for the current draw or I am doing  mistake?


texts:
I've a doubt about clock domains and synchronization FF. I'm working on a FPGA and I've two clock domains. In the firs clock domain there is a clock frequency of 125 MHz, in the second the frequency is generated by a PLL that has in input the 125Mhz and it generates a 12.5 MHz.

Are syncronization FFs, between the clock domains, needed for signals that goes from one domain to the other ? I know that when the signals are asyncronous or unrelated I must put syncronization FFs, but in this case the frequencies are related. Is it safe to eliminate the FFs ?

Thanks


texts:
If you get a capacitor that is two plates and a dielectric and next to it you put two plates close but not in contact at opposite sides and the capacitor in the middle is charged, each of its plates will act as a Leyden jar to induce charges in the outside plates.
When the outside plates are connected they will induce current because a huge potential difference is created between the outside plates.
The potential difference is created the same way the outside aluminum foil on a Leyden jar is charged, when the water inside the bottle is charged.
If I fixed the two outside plates (white plates) in one place and rotated the capacitor (red plates) at 60Hz so that the electric field is charging fast just like a magnetic generator, will it produce constant current if the capacitor itself is not discharged?

b. If the capacitance between the plates of the capacitor in the middle is 1µF and that capacitance between the plates of the capacitor and the outside plates is 5µF. If the capacitor is rotated at 60Hz will the current be generated be
Q= 5µF x 1200v =6
current per second
6 x 60Hz x 2    (2 is number of plate discharges per cycle)
=720 amperes
What do you think?


texts: How do you apply the negative feedback laws when there are two feedback networks?

texts:
I have the following circuit, which has a series-shunt feedback in the form of r3 and r7, and a shunt-series feedback in the form and r4 and r6.

How do I apply the usual steps in analysing negative feedback amplifiers, then? For example, to find the closed loop gain, I very much want to use Aol/(bAol + 1), but I don't understand what b I should use as there is a current-sampling, current-feedback and a voltage-sampling, voltage-feedback circuit.

What about the other negative feedback theorems that relate to bandwidth and input/output impedance? How do I find them?


texts: How to calculate amp hours when voltage and amperage changes

texts:
I have a Lithium battery pack.  All I know about this battery is that its no-load voltage is exactly 20.0v when charged.  I then connect a load to this battery; I have no direct information about the load, however, the load is connected through a power tester circuit which shows the following information (recorded at the specified time intervals below):

Time (initial): 18.9v, 5.6A

Time (after 1 hr): 16.2v, 5.2A

Time (after another 16 minutes, or at 1.27 hr): 12.0v, 4.4A

QUESTIONS:

What is the AH rating of this battery?
Is a voltage drop of 1.1V significant?
How many watts is the load drawing?

Thanks for your responses.


texts: How to detect that my apartment door buzzer is being pressed

texts:
I want to detect the button presses of my apartment's door buzzer. This is the button in the building lobby which, when pressed, plays a ringing/door bell sound in my apartment to alert me that someone is at the front door. I want to capture these button presses to send to an Arduino to eventually support some kind of secret morse-code like password to unlock the building's front door (note: I don't need help with triggering the door opening, just detecting the button presses).

The intercom in my apartment is a 4-wire intercom with standard door/talk/listen buttons. This is the circuit for the door buzzer as currently installed:

(terminal on central console in basement) -> (button switch in lobby) -> (intercom speaker in my apt) -> (other terminal on central console)

So there is no clean DC on/off signal for me to read; only the audio signal (kind of a vibrato tone) that goes straight to the speaker. What is the best way for me to detect when this circuit is closed? It would be especially nice if I could do this just by attaching leads on either side of the button switch, and not have to wire anything into the circuit in series.

FWIW, my multimeter reads DC 20V on either side of the switch when it is open and drops to 0V when closed. But given that there is an AC audio signal in the mix, I don't know how to interpret those numbers.


texts: How to drive a magnet with a coil from an amplifier (to test acoustic guitar resonant frequencies)?

texts:
I wish to attach a rare earth magnet to pieces of wood and to acoustic guitars and drive the magnet with a signal generator through an amplifier to a coil. In essence, turning the wood into a loudspeaker. The purpose is to find the resonant properties of wood used to make guitars prior to manufacture and then again at different stages of manufacture.

I've come across a method in principle but with no specific details. I have very poor knowledge about electronics and circuitry. If any one can tell me what kind of amplifier specifications I need, what kind of coil specifications, how to wire everything and what things to pay attention to ensure that everything I source is compatible then I would be very grateful for the help.

The signal generator will sweep over a range to cover 50Hz to 2500Hz in about 2 minutes. The computer audio output goes to the amplifier, which needs to boost the signal enough to drive the wood to audible levels.

The sound can be recorded and analysed and modes of vibration can be discovered. All of this helps to make a better grade and quality of guitar with greater consistency of final performance properties.


texts:
I'm trying to design a circuit using a zener diode but am having issues getting it to work right.

This circuit works fine and show Vout = 6.198V. However, if I swap their positions -

Here, Vout = 200.364V. Why is this happening? Why does the anode of the zener diode need to be referenced to ground? I expected it to be 200-6.2 = 193.8V


texts: Ripple voltage on output voltage of an smps

texts:
I am trying to select the output capacitors of a flyback topology (without using a second LC filter). This is a general question. My question is how evolved the ripple voltage in function of the different capacitor parameters. Apparently, it depends on the capacitance itself, but above all it depends on the ESR value of the capacitor. It seems that the number of capacitors would help for having the required ripple voltage.
Here are the following AN that I read :
https://www.st.com/content/ccc/resource/technical/document/application_note/09/94/ed/b6/59/57/43/9b/CD00004190.pdf/files/CD00004190.pdf/jcr:content/translations/en.CD00004190.pdf
https://www.ti.com/lit/an/slva559/slva559.pdf
https://www.onsemi.com/pub/Collateral/AN-4137.pdf.pdf
In the first document :

It misses some informations to me, it is said that if the output capacitor is sufficiently large we can consider that only the ESR would be a problem for the voltage ripple... Nevertheless where does this relation come from ? I would like to know this relation which allows to tell this assertion.
Some of the answer could be in the third document :

Where Vro is the reflected output voltage at the primary of the n-th output
Where Kl(n) is defined as follows :

And Idspeak is the primary peak current.
I do not understand the formula. If I took a look on it :

The part encircled in red is equal to the turn ratio. Then multiplied by the Idspeak which is equal to the primary peak current, it gives us the secondary peak current. Finally we can consider that the secondary peak current is equal to Iout plus the capacitor current. We get :
$$
\mathrm{
DeltaV_{o(n)} = \frac{I_{o(n)}*D_{max}}{C_{o(n)}*f_{s}} + (I_{o(n)}+I_{cap(n)})*R_{c(n)}*K_{L(n)}
}
$$
I some troubles to understand this relation...
Here is the relation that I founded according to my calculs it may be false ... And I think I have done some approximations that are debatable. Please bring me to light.
I have considered that the ripple voltage is sufficiently low as to consider the output voltage constant and then if Pout is constant, then the load draw a constant current. I considered the circuit at the primary MOSFET OFF time.

simulate this circuit – Schematic created using CircuitLab
Then :
$$
\mathrm{
V_{min} = -R_{esr}*I_{out} + (V_{C(avg)} - deltaV_{C(OFF)})
}
$$
$$
\mathrm{
V_{min} = -R_{esr}*I_{out} + (V_{C(avg)} - \frac{I_{out}*(1-D_{max})}{C_{out}*F_{sw}})
}
$$
Then I considered that the average capacitor voltage is equal to the average output voltage. I think it is true, but mathematically this is not clear ... So we get :
$$
\mathrm{
V_{min} = -R_{esr}*I_{out} + (V_{out} - \frac{I_{out}*(1-D_{max})}{C_{out}*F_{sw}})
}
$$
$$
\mathrm{
V_{out}-V_{min} = R_{esr}*I_{out} + \frac{I_{out}*(1-D_{max})}{C_{out}*F_{sw}})
}
$$
which is equal to :
$$
\mathrm{
\frac{deltaV_{out}}{2} = R_{esr}*I_{out} + \frac{I_{out}*(1-D_{max})}{C_{out}*F_{sw}})
}
$$
And as the first document shows, if C is large we can neglige the second term, and we see the the ripple voltage depends only on the equivalent series resistance.
Do you think my formula is correct ?
I would like to plot a graphic where we see the output voltage ripple in function of the ESR and the capacitance value (I could do a 3D plot if necessary)
Thank you very much and have a nice day !


texts: Commands and large data packets over UART to MCU

texts:
I have a question about protocols used over UART. Trying to either create or use an already defined protocol that will allow for transferring a large amount of data as quick as possible over UART. I would like to use the DMAC as much as possible on the receiving end which will be some type of MCU. With that said I'd like to be able to interpret commands as well (which may be in conflict with using the DMAC).

A few thinkgs I seem to get stuck on are:

What happens if the transmission is terminated early form the transmitting end?
Am I wasting my time trying to use the DMAC?

I'm sure there's information I've left out of this question or something I need to do to narrow it down, so I will try to do that with future edits. For now the main question is (although a bit more generic than I want), is there already accepted practices to sending big chunks of data over UART/RS232?


texts: Are \$h_{ie}\$ and \$r_{\pi}\$ the same thing?

texts:
In my proving below, \$r_{\pi}=h_{ie}\$. Why two different symbols are created? It confuses beginner. Or, actually there are something different?

\begin{align*}
  r_e     &= \frac{26m}{I_E}\\\\
  r_{\pi} &= \frac{26m}{I_E}(\beta+1)\\
          &= \frac{26m}{I_E}\beta\\
          &= \beta r_e\\
          &= h_{ie}\\
\end{align*}


texts: My oscilloscope's inputs are rated "250V DC + AC peak (10 KHz)." Does this mean it would withstand mains voltage (325V peak) or only 250V DC? I have no plans on doing this any time soon, I am only curious.


texts: Value of resistance R from the equation: \$ R = \frac{t}{C\, \ln\frac{U_0}{U}} \$ for specific value of \$U_0\$ = 300 V at time t =0

texts:
I have a question regarding the value or resistance \$R\$ at time t = 0 s, when original voltage is \$U_0 = 300\text{ V}\$ and the capacity \$C = 47\text{ nF}\$ - if the wanted resistance can be described as:
$$
 R = \frac{t}{C\, \ln\frac{U_0}{U}}.
$$
I do have table of values:

but honestly I do not really believe my calculations. To me, to get the value of resistance as teraohms seems strange.
My calculation for time t = 10 min:
$$
R =  \frac{10 \cdot 60}{(47 \cdot 10^{-9})\, \ln\Big(\frac{300}{299}\Big)} =  3,823 \cdot 10^{12} \text{ }\Omega
$$
But for value at time t = 0 s:
$$
R =  \frac{0 \cdot 60}{(47 \cdot 10^{-9})\, \ln\Big(\frac{300}{300}\Big)} =  \frac{0}{(47 \cdot 10^{-9})\, \cdot 0} =  0 \text{ }\Omega
$$
Thank you for any suggestions/ideas.... if my calculations are right or where I went wrong.


texts:
I'm learning to weld. I've realised my earth clamp is limited. The spring is weak and its contact area is small as it's tooth shaped.

Researching better clamps, I see clamps which have threaded bolts to clamp the jaws against the workpiece tightly. It is my understanding that unless you are clamping something malleable such as lead, increased clamping force wouldn't increase the contact area, unless such force is applied to leave indentations in the workpiece.

So I've been looking for clamps which have larger contact areas, and magnetic clamps seem to have large flat brass areas rather than pointed teeth which will be pressed against the workpiece with moderate spring pressure.

How does increasing clamp force increase conductivity, and is contact pressure really interchangeable with contact area size?

To be clear, I'm aware different clamp designs are more suited to different applications, but I'm specifically asking about the properties of electrical conductivity of a larger area being pressed lightly, vs a toothed (i.e, small) area being pressed very firmly.

Toothed clamp design:

Magnetic design with brass flat contactor:


texts: How to find a transformer for a dry cleaning machine?

texts:
My dad asked me to help him find a price estimate and figure out the ordering process for a new transformer for his dry cleaning machine. He's not that fluent in English and isn't too comfy using the internet, so I am on here to learn how to even start understanding what I need to do??
About the current transformer:

Italweber Elettra
Single Phase Safety Isolating Transformer
Power: 63 VA
Input: 0/208/220/240/440V S.E. (uses 220V)
Output: 9V

What he needs:

Same power of 63VA
Same input of 0/208/220/240/440V S.E.
Different output of 12V
Doesn't matter the brand if possible

I've attached a photo of the label on the transformer box he shared with me when sending me on my mission.

What I've tried:

Googling "Italweber Elettra transformer" (went to the company's website but afraid shipping from Italy to the US would be expensive)
Browsing ebay for variations of "Italweber Elettra/transformer/single phase safety isolating" but the ones I found didn't seem to be a match
Googling "single phase safety isolating transformer" and tbh just got really intimidated.
Searched stackexchange for past similar questions (couldn't find any)

Other potentially relevant information:

My dad has an electrician (I think that is his title but I feel like he did HVAC stuff for him too maybe) who is searching for the transformer with the 12V output but I guess the electrician just buys things my dad needs and texts him the price and doesn't show the bill/receipt?? (I know, I'll talk to him about this). My dad wants to know an estimate of how much a new transformer might be so he doesn't get ripped off... He also might not be too confident in the electrician's ability to find one in this small town so he wants a backup plan.

Thank you for reading through this. I apologize for not being well-versed in this realm - I hope I put enough information. I would really appreciate some guidance and hope you are safe and well!


texts:
If I have a power supply that is feeding a fully integrated voltage regulator(Lets call it VR) and so on the VR is feeding a chip.

My goal is to calculating the static icc of the chip but I dont have a physical access to that line.

I can only meassure the static icc on the power supply.

I know that the VR have some power losses so How can I calculate it?
Thanks

simulate this circuit – Schematic created using CircuitLab


texts: What is this transformer-like component with only two leads

texts: I found this while taking apart a PSU, the closest label was B1. It appears to be a transformer-like component with two leads, and the coils on the vertical part around the core seem to be connected opposite the leads. Googling the label got me nowhere.


texts: Is it possible to detect and filter noise on an earth?

texts:
I ask because I have a solar array on my house with micro inverters. The monitor (an Enphase Envoy) no longer detects the the inverters. Troubleshooting suggests noise on the earth, perhaps caused by transformers and motors. A suggested remedy is to plug it into a circuit that is not protected i.e. no safety switch - my shed is not protected and the Envoy detects all 16 panels while plugged in there.

Using the Envoy in the shed is not ideal because I can't see it daily and it's too far from my WiFi which it needs so my question is this:

Is there a method to detect noise on my earth and/or is there a device that I can use to filter it i.e. can I plug my Envoy into filter then into the wall?


texts: I'd like to build a circuit to control a 1-HP 10A motor.  To switch it on and off I was thinking of using a SSR since I could pair it with a microcontroller.  I've never used one before but thought I'd give it a go since I was having trouble finding any mechanical relays that I could pair with an UNO or Nano and feel comfortable they could handle the current draw from the motor.  A search of Amazon reveals many SSRs in the 50 to 60A range for about $15.  The voltage available is 110VAC.  When using the SSR will I need a heatsink? I'm just a newbie so any additional comments are appreciated.


texts: reflected electric and magnetic fields component

texts:
The question states that the direction of propagation of E  is +x and +z plane.
The goal here is to find the reflected component of E and H. I know that the propagation changes sign once it hits the boundary. but what i don't understand in part a) why z component changes sign not x? why not both?
Also in part b) I cannot visualize how the the sin and cosine component works here, also why these are added to reflected component of H ?
can anyone draw this out for me please and explain it? Thanks

a)
Find the reflected electric field in phasor form.

b)
Find the reflected magnetic field in phasor form


texts: What does 75A mean for this motorcycle battery?

texts:
I just bought this battery:

So what does the 75A mean? How do I get the same parameter "10hr" that appears in this question: Whats does "hr" mean among "V" and "Ah" in batteries?


texts: How to include schematic page name in OrCAD BOM

texts: I am generating BOM in OrCAD. How can I include a part's schematic page name in the Bill of Materials csv file.


texts: I am using a CT 60/5 A. I would like to know how would I select a burden resistance to convert 5A current to 400mV signal? I understand that V=IR will give the required resistance, however, for 5A even 1ohm resistance will develop 5V and hence the power dissipation of resistance has to be atleast 25W(P = V*V/R) which is huge. How should I calculate the resistance so that it remains in reasonable power dissipation level? What if the burden is rated at 1VA? Assume that the current in primary can reach close to 60A.


texts: Peltier with Mosfet - Heat Issues and Alternatives

texts:
I'm interested in using a Peltier device in conjunction with arduino as a precise temperature controller. I've followed the example below and have switched out batteries with a 12v power supply. After switching to the power supply the temperature gradient improved but the Mosfet became scorching hot. Although you might be inclined to say throw a heatsink on and all will be well, the end use would be a compact solution that would not favor the use of a heatsink. Are there any design changes that could be made so that I can avoid this heat issue?

http://garagelab.com/profiles/blogs/how-to-use-a-peltier-with-arduino


texts: Independently toggling two series switches to multiply two pwm signals

texts:
Preface

It is known that one can synthesize a signal into a train of boxcar pulses (pwm modulation), each with the same amplitude, if proper low pass filtration is applied to this pulse train before it reaches the load.

Now consider the synthesis of the product of two signals. I have found with some rudimentary matlab simulation (see below) that the average* of the multiplication of two pwm modulated constant** values is equal to the value of the multiplication of two constant signals

*I use the average because it is equivalent to passing only signal at frequency equals zero which is a low pass operation.

**Non constant values are constant across small time intervals so turn up both carrier frequencies and you're golden.

    %pwm test

    %domain
    n = 5e6;
    t = linspace(0,1/2,n); %time

    %sawtooth carriers
    %Frequencies f1 and f2 should be much different in
    %magnitude relative to eachother i.e. f1 >> f2 or f2 >> f1. Here I use
    %the case of f2 >> f1.
    f1 = 1e3;
    f2 = 1e5;
    st1 = sawtooth(2*pi*f1*t)';
    st2 = sawtooth(2*pi*f2*t)';

    %constant values
    constant_11 = -1/2*ones(n,1);
    constant_12 = 1/2*ones(n,1);

    %pwm modulation
    pwm1 = sign(st1 - constant_11);
    pwm2 = sign(st2 - constant_12);

    %multiply
    pwm12 = pwm1.*pwm2;
    av_pwm12 = mean(pwm12)*ones(size(pwm12));
    actual12 = constant_11.*constant_12;

    %visualize
    plot(actual12),hold on,plot(av_pwm12),hold off

Multiplying the two pwm modulated signals in code like I have shown is like independently toggling two series switches mutually in series with the load i.e. the load only receives current when the state of both switches are closed.

Question

If no one finds an issue with what I have said in the preface, I'd like to ask if there has been any studies done on this type of signal multiplication. If so, could you direct me to information about such study or studies?

I have tried to locate information on this topic but can't seem to dig anything up. Perhaps I am lacking the correct keyword that has been assigned to what I am looking for...Anyway, any help on this would be much appreciated. Thanks in advance.


texts: I know why DRAM is slower to write than to read, but why is the L1 & L2 cache RAM slower to write?

texts:
DRAM is slower to write than read because it takes time to either charge or discharge a DRAM memory cell. But what about the SRAM in my processor's L1 and L2 caches? It's slower to write as well but AFAIK, SRAM is latched memory based on gates.

So why the slower SRAM writing speed?

Thanks.


texts: how to import data from MATLAB to ISE XILINX testbench

texts: For a project, i need to take sine samples in MATLAB and somehow i need to call it in Xilinx ISE testbench, so that i can use them for further operations. Please tell me how to do it?


texts: Why is there a capacitor that is parallel to Op Amp inputs in this circuit?

texts:
In this application note, there is a circuit for temperature control which includes an NTC.

Why is there a capacitor (C5) in parallel with the inputs of the MC33201 Op Amp?
Is it a helper to the Op Amp as the Op Amp tries to make its inputs equal when there is a negative feedback?
Does it introduce an another negative feedback like this: When there is a sudden enough change in the resistance of the NTC that can pass C5, the voltage is then passed to the inverting input of the Op Amp and the output of the Op Amp does not need to change to compensate the small change on the non-inverting input due to the change of NTC resistance?
Explanation from the App Note:

The same 5 V supply is used also as reference voltage for the
Wheatstone bridge, formed by components R2 (NTC), R3, R6, R7 and C5
used for  low pass filtering.

If it is for low-pass filtering, why this capacitor is not connected parallel to R5 instead of where it is now? What is the advantage of it being on the place it is now compared to it being parallel to R5?


texts: LiPo Battery power monitoring with ESP-12E

texts:
I am using 3.7V LiPo battery and ESP-12E in this project. I need to monitor how much charge is there in the battery to help when battery falls below certain level and notify to charge it up again. I've red that 3.7 LiPo batteries maximum voltage goes upto 4.2V. And readable analog input voltage for ESP-12E is 0-1V.
I was planning to make a simple voltage divider to convert 4.2V to 1V and provide it to analog input of ESP-12E.
Voltage divider resistors -
Input Voltage:4.2V
Output Voltage:1V
R1: 1 Kohm
R2: 330 ohm
So as charge in the battery drops the analog input voltage to the ESP-12E drops. But I have a doubt about voltage divider wether to use voltage divider or something else for this project. Because voltage divider will consume power continuously to drain the battery and will cause the circuit inefficient. and I've also red that voltage divider is mostly used in high impedance circuits.
So is simple voltage divider suitable for this circuit or should I use some other DC-DC converter or regulator for converting 4.2V to 1V more efficiently to drain as much less possible power from battery itself to provide it to analog Input of ESP-12E?


texts:
(first question on this board - n00b alert)

I'm on a second iteration of a small autonomous project which logs changes in magnetism.  It consists of just:

Espruino board

Lipo battery

HMC5883L magnetometer

Battery and charger on the bottom, Espruino on top of that, and magnetometer soldered to the top of the Espruino.

Its all very thin and discrete, which it must remain for this project.

I have ordered some large heat shrink wrap thinking this will fine for weatherproofing it. For this iteration I am happy to rip off the wrap to get to the data after say, a month.

As I come to solder this stuff up, I am now starting to ask myself :

a) is wrapping it in heat seal going to break something?
b) will the magnetometer be affected by the surrounding electronics?
c) are there any other issues I should consider?

Thanks for any remarks, pointers - or general advice about my approach which you are willing to share.


texts: Can I use a dual primary transformer to generate isolated 110v output?

texts:
Given a transformer with a dual primary winding (generally used to step down a series 220v or paralel 110v), can I instead hook up one winding to a 110v input and use the second as an isolated 110v output?

What kind of power restrictions or undesired behavior might this cause?

EDIT: This transformer, for example: http://mouser.com/ds/2/410/media-1067445.pdf

EDIT2: Added 24v to the image secondary coil for clarity


texts: How to reduce an audio system noise in a way which is similar to a human touching one of the system's components?

texts:
I have a somewhat weird question (hopefully not too weird).

I work with an audio system. It includes a wave generator, a (33500B series Keysight) wave generator, an amplifier (2003 op-amp based circuit, will be replaced with LM1875 circuit in the future) and a speaker (H1283 Seas Prestige). I use BNC cables between the system components.

Here is my problem, I have background noises (even when the generator is on but not outputting any sounds).

I noticed, that the best thing to reduce this noise is me touching one of the  system components (not speaker but wave generator, audio amplifier or the metal ends of the cables).

I am not sure why is it so. Is it because I am a huge capacitor?

Anyway, here is my question: (Since I can not hold the boxes while applying the experiments...):

What is the simplest action I can apply in order to create a similar effect to me touching the system components?

I already tried:

Attaching a metal mesh (to create a "Faraday cage" effect).
Attaching parts of the metal mesh to components of the audio box.
Connecting the boxes to an external ground.
Connecting the grounds of all the boxes.

All these things helps a little. But nothing has the effect of me touching the boxes.

Any ideas?


texts: NPN common emitter transistor as a switch switches off as the current draw in collector falls

texts:
I am trying to switch power to a Pi Zero using an NPN transistor (2N2222) as a switch, as in the following diagram.

simulate this circuit – Schematic created using CircuitLab

The Ib is around 5mA and the pi zero draws about 120 mA during bootup and settles down to about 80mA steady state. So, when I send a Hi through the arduino digital pin, the Pi starts booting - and all goes fine. However, the moment the boot up process is complete and the current draw from collector falls, the transistor switches off. Have confirmed the same by increasing the steady state power draw of the Pi by attaching it to a HDMI display - and some USB peripherals - and the pi remains up - no problem.

I am a beginner to using BJTs - and gather I am doing something stupid to land up in this problem. Any help in helping me understand what I am doing wrong will be of huge help.


texts:
I'm working on a project that will plug directly into the wall outlet, similar to a night-light or a wall-wart power supply.

Internally, I'll use a AC-DC converter like this one.  It has built-in filters and has agency approvals.  I'll add the necessary fuse, MOV, etc.  The rest of the circuitry consists of a microcontroller and sensors, and will fit entirely inside the case.

I'm having a difficult time figuring out how to actually implement the physical power jack.  I've found one vendor with blade connectors intended to be soldered into a PCB.  However, since they are the only one I can find, I expect there must be a more common way to do this.

Also, does everyone design custom cases, or are there generic ones available? How do you handle the mechanical considerations of wall wart design?


texts: I am trying to communicate with a LIN sensor device via a PC COM port (I built a board that converts USB to UART and then UART to LIN). The board works and I wrote a simple Matlab script to grab data from it. The problem is that now I need to convert my code to LabVIEW to integrate with a larger application. However, I ran into a problem where I am struggling to find a way to transmit more than 8 zeros (for proper LIN I need 13-16 zeros in a row) since the NI VISA Write maximum data size is a byte. If I try to transmit two zero bytes in a row, I get a logic 1 between them e.g. 0...010...0. Is there a good way to generate a 13-16 bit stream of 0 with LabVIEW?


texts:
How do I increase the refresh rate of a Nokia LCD that I'm driving using the STM32F103 microcontroller?

The LCD is 132*162 and takes a 9-bit instruction/DATA with RGB for each pixel in 565 format. Since SPI on STM32 can't do 9 bits, I'm using USART (running at maximum 4,000,000 bit/s max as I'm using HSPI) in 9-bits mode to drive the LCD.

This works just fine, but the refresh rate is not that great. Right now it takes me 230 ms approx to write the whole screen.

Doing rough calculations, (132*162*2*9)/4e6 = 97 ms. Mine is higher because of overheads + the fact that I need to mirror each byte before sending as USART does LSB first only.

I am looking for some suggestions as to how can I reduce the refresh rate.

Use DMA? I am not sure how useful it would be in this case as my microcontroller is just driving the LCD. Nothing else.
Buffer the LCD display in RAM and send it out to the LCD in one go. I can't do as the microcontroller has only 16 KB RAM.
Bit bang GPIO to drive the LCD. I am not sure if this would achieve a rate more that 4 MHz of USART. Plus with this I lose the ability to use DMA in the future if required.

The LCD I'm using is used in the Nokia C100 series and use the controller SPFD54124B.


texts: Distinguish between two ultrasonic transmitters

texts: I want to have two ultrasonic transmitters emit signals to three receivers for measuring distances and relative position of the transmitters to the receivers. The distance between the transmitters is about 1ft and the distance between the transmitters and receivers is about 3ft. If there is more than on transmitter how can the receivers distinguish between the two transmitters? I heard things about encoding the signal or multiplex but I do not know what they mean or if and how they will work for this case.


texts:
I have come across some old capacitors and would like to use them if possible, but I'm not sure how to determine their values from the markings on the sides.  I understand there is some convention to these markings, but have not been able to decipher it.  Can anyone tell me the values of these three capacitors, I would appreciate if someone could break out what the various parts of the names indicate?  I believe they are all ceramic.

1) Good sized disk.  Labeled E N750 10J.

2) Square.  Labeled CK05 BX 104K 50V K 8514.
This one I could kind of decifer as 10^4=100000pF=100nF +/- 10%, max input voltage of 50V, not sure if the other numbers mean anything.

3) Tiny blue one.  Labeled 104 25E 8720.
I'm guessing the 104 also means 100000pf.

Also, are any issues expected when using old ceramic capacitors?


texts: Driving a 12v LED, substituting a PWM chip for a linear regulator?

texts:
I'm trying to reverse engineer a broken control box for some dual intensity motorcycle LED spotlights, and I note on the circuit board there is an AX 3007-50 12V input, 5V output PWM chip.

I assumed the 5V PWD output was to drive the low beam of the LED spotlight, and in a bid to simplify the new circuit I wanted to replace with a 5V linear regulator.

In my tests, this hasn't worked. I've been trying to understand why, and I'm thinking that the LED needs 12v to run, the 5V output from the PWM is 12V, but just cut up so it's only on for ~40% of the time. My constant 5v output is not enough to drive the LED, so it simply won't turn on.

Would this line of thinking be correct? I know the LED works with 12V, should I be looking to replace my linear actuator for a PWM setup like I think it used before?

Some pictures of the LED, and the PWM chip on the control board:


texts:
The lecture says that differenial biasing is easier than single ended.
Could anyone explain why differential biasing is easier than single-ended one?


texts: Dual-row connectors for ribbon cable offset one row of insulation-displacement contacts with respect to the other row so that they convert the linear pinout of the cable into a row of evens and a row of odds. Is there only one standard for which row is even and which is odd? Simply rotating the connector 180 deg doesn't change this - it would have to be a mirror image to do so as far as I can tell. Thanks!


texts: Does the fundamental frequency affect the bit rate on a wire?

texts:
This is from the book Computer Networks by Tennenbaum:

  The bandwidth is still the width of the band of frequencies that are
  passed, and the information that can be carried depends only on this
  width and not on the starting and ending frequencies.

So what I understand from this is, if I have a bandwidth of say 500
kHz, even if my base frequency is 1MHz or 1GHz, the bit rate on the same wire will be same.

However then Tennenbaum gives an example, he calculates the bit rate he can get from an ordinary phone line, first states:

  An ordinary telephone line, often called a voice-grade line, has an
  artificially introduced cutoff frequency just above 3000 Hz.

And then he gives this table:

Header definitions:

Bps = Given Bit Rate [Bit per Second]
T (msec) = Time needed to send 8 bits
First Harmonic (Hz) = The lowest frequency signal that could be made. It corresponds to byte 11110000 for examples.
#Harmonics sent = The highest multiple of the First Harmonic frequency that is lower than 3,000Hz

Well it is clear that there is a relationship between the data rate and the harmonics. It seems like (from the table), if you want more bit rates, you need a higher First Harmonic (the fundamental frequency), and upon that you can build the second, third harmonics (meaning using the frequency range - the bandwidth)...

So what am I missing here?

It is shown in the table that if I have a higher fundamental frequency, I will be able to send more data in less time, but then also Tennenbaum states that the information that can be carried only depends on the bandwidth?


texts:
In Practical Electronics for Inventors, Paul states the following as the pulse triggered SR flip flop:

Of course there are some minor issues in the truth table. (One of the \$Q\$’s must be \$\overline Q\$ and \$00\$ must be \$ Q \overline Q\$ in the hold condition.) But even after correcting them in the back of my mind, I think that the given truth table is not correct for the Set and Preset conditions for the given circuit.

I think that for the circuit shown, \$\overline{PRE}=0\$ and \$\overline{CLR}=1\$ condition is not correct in the truth table. I think it also depends on the values of \$S\$ and \$R\$. Like if \$SR=01\$ I think \$Q \overline Q = 11\$, not \$10\$ as the text purports.

Similar concerns for the other non-\$11\$ configurations of \$\overline{PRE} \; \overline{CLR}\$.

Can you please provide a correct truth table?

Edit: The following is the truth table that I came up with. Please make sure that it is correct.

\$
\begin{array}{cccc|cc}
\overline{PRE} & \overline{CLR} & S & R & Q & \overline Q\\
\hline
1 & 0 & 0 & 0 & Q & 1 \\
1 & 0 & 0 & 1 & 0 & 1 \\
1 & 0 & 1 & 0 & 1 & 1 \\
\hline
0 & 1 & 0 & 0 & 1 & \overline Q \\
0 & 1 & 0 & 1 & 1 & 1 \\
0 & 1 & 1 & 0 & 1 & 0 \\
\hline
0 & 0 & X & X & 1 & 1 \\
\end{array}
\$

Another Question: I think that this implies that Preset should be activated after activating Set; and Clear, after activating Reset, to have the outputs complements of each other. Correct?


texts: Definitive land pattern for 0603 SMD capacitors?

texts:
So, I am trying to figure out what pad size to use for 0603 (imperial) SMD capacitors. The datasheet for the particular capacitors I plan to use provides part dimensions but does not recommend a land pattern.

Googling, I found that the land pattern is typically parameterized as X=pad width, Y=pad height, C=center-to-center pad spacing.

As a first pass, IPC-SM-782A recommended X=1.00, Y=1.10, C=1.70 (all mm).

http://tinymicros.com/mediawiki/images/3/3c/IPC-SM-782A.pdf

Then, I found a document from Kemet that contains a bunch of maths and stuff to conclude that X=1.08, Y=1.05, C=1.73 would theoretically be more effective than the standard at countering possible tombstoning. But in their comparison table (pg 12) they misquote the standard as having specified X=1.2, which is incorrect AFAICT. This makes their maths and stuff seem somewhat less impressive but maybe it's just an isolated typo. I really don't want to try to understand the maths itself, "estimation of error" techniques were always a giant weak point for me.

http://www.kemet.com/kemet/web/homepage/kfbk3.nsf/vaFeedbackFAQ/2209BDBA03843BBF85256BCD004EBC11/$file/f2100e.pdf

Finally, I downloaded some component libraries for KiCad, and everyone seems to use slightly different pad sizes (e.g., "walter"'s library is close to X=0.9, Y=1.0, C=1.5).

I've soldered before, but only larger stuff w/ iron and solder wire. I've never used the solder paste + hot air method before nor handled components as small as 0603, so I am worried about the tombstoning and it seems to make sense to try and input the pad dimensions that will work best, and have the greatest chance to avoid tombstoning ... problem is, all the sources have conflicting advice.

So, the question is: what pad sizes should I use? the standard's? kemet's? walter's? an average of these? also, if you use other sizes that you have practical experience with and they work well, please share ...

I guess a pertinent higher-level question is, do the few fractions of millimeters make any practical difference at all?


texts:
Here is my problem. I built this circuit and for some reason it works. FYI, the diodes are red 5mm LED's, the transistor is 3904 NPN, and the resistors are what are shown in the schematic. Logically it should not work when you press the PBNO. The red 5mm diodes should be destroyed. According to simulating, the current is above 300mA. How is it possible this circuit physically works? The lights are dim, then when you press the PBNO, they become bright, which is what I was after.

simulate this circuit – Schematic created using CircuitLab


texts: Compatible/Equivalent/Substitute Diode for 1N5819?

texts:
I am just new to the electronics field. basically I am a software developer but currently my job profile changed and I have to teach students some electronics subject and electronics project.

Currently me with my team decided to develop the project over here.

but as shown in the part list of that project,
I couldn't find component D3 = 1N5819 here in my local area.
So could any one suggest me the compatible/equivalent/substitute for that diode?


texts: How to use the parameter in comparing the variable and constant value?

texts:
I've learned that using a parameter in defining a module is a good habit like having a default value for the parameter in C++ or other languages.

So, I've used a parameter value a lot but faced a problem when I want to compare some register variable to a constant value that has an equal size with the parameter.

For example, I declare a variable size of which is the value of the parameter and would like to compare it with a constant value sized 8bits such as 8'b0.

module top_module #(parameter SIZE = 8) (output out_top);
  reg [(SIZE-1):0] temp_var;
  assign out_top = (temp_var == 8'b0) ? 1'b0 : 1'b1;
endmodule

If I use the constant value with the specific size, in this case, 8'b, it would be problematic when I want to instantiate the module with the #SIZE = 16 like below.

  top_module #(SIZE=16) top_module_inst;

Is there any way to use the parameter in a declaration of the parameter?

Or should I change the size of the constant value when I instantiate the module with different size every time?

Can anyone please explain the differences between using Hardcoded values and parameters during Synthesis and Simulation?


texts: Switching a 5V power relay with optocoupler

texts:
I have looked at the schematics of a few 5V power relays and noticed different designs. Some use just a transistor to draw the higher current to switch the coil and some use optocoupler (surge protection) with a phototransistor.

Regarding this schematic:

Why do I need an extra transistor to switch the relay? Can I not just switch with the relay with the transistor of the optocoupler.


texts: Is it okay to leave regulators heating at higher end of range of operating range?

texts:
IC operating range -20 to 80 degrees Celsius
Regulator IC application spec 12V in, 5V 1.5A output
Is it okay to keep IC running at 70-75 degree Celsius (with heat sink) all the time, circuit will be always running.
efficiency and out stability is fine for my application @ 70 degree.
Will this damage the IC over time or reduce the reliability of regulator IC?
or do i have cool it down to somewhere around 35 degree Celsius using more temperature spreading techniques? (fan or increasing pcb thermal conductivity )


texts: What does the 25 Ω termination resistor do in a 0/180-degree hybrid power splitter?

texts:
The circuit in the picture is a 3dB power splitter using a 0/180-degree hybrid transformer/balun.

I see the impedance ratio of the transformer is \$ (14/10) ^2  \approx 2 \$, thus the equivalent output impedance of a 50 Ω input is 100 Ω into a differential load, or 50 Ω into two single-ended load, which makes sense.

But I don't understand the function of the 25 Ω termination resistor at the center-tap. I understand that the center-tap of a transformer is often connected to ground to establish a common ground reference, but what does the resistor do? How do I calculate the effect of a 25 Ω resistor to the impedance at each port of this hybrid?


texts: I was explaining a transistor to someone, and I realized: I don't really understand several key concepts at a low level. Help?

texts:
(Surplus story removed.)

I was explaining MOSFETs, CMOS, and logic gates to someone and realized I didn't grasp some concepts as well as I thought.

It culminated when he drew a single transistor, put the two inputs at the gate and source and the output at the drain, and said "Why isn't this an AND gate?"

I hesitated, then said that the truth table for that circuit would have Z (high impedance) as the output when the gate was 0 and the source is 1, and that's not an AND.

But then I realized that I don't understand Z very well.  It's high impedance, meaning little/no current flows.  But isn't that the same as the situation between two points at 0V?

So, my questions:

If current is the flow of electrons, how do they traverse the positively charged channel in the n-type?
In the p-type, the body has a lack of electrons anyway, so how does current flow when voltage isn't applied to the gate?
How are 0V and Z different?


texts: Is it essentially nothing given how small they are? I see most configurations are given 5V, but does that mean they draw amperage as well?


texts: Analog Oscilloscope Flickering Signal Problem

texts:
I am using BK Precision 2125C Dual Trace Oscilloscope (30 MHz), which is analog. I'm trying to observe signal generated by the output of microprocessor. I'm seeing flickering signal (quickly moves left and right to the sides of scope) for which I know it's most probably not flickering like that in real "life" but that is most likely some scope's triggering issue. I'm almost sure that is the case since I observed normal square wave before this one and it also flickered like current one, at some trigger setting, but after re-setting trigger, there was no more flickering.
This flickering is really annoying when trying to observe little changes in the signal or read its period.
Here is the video to measurement of flickering signal.
Just for reference, for this measurement, I'm using following setup:

DC coupled input, CH1 (get same behavior with AC input coupling)
coupling: norm (same behavior with "auto" or "TV-V" or "TV-H")
source: CH1
main mode (not mix or delay mode)
voltage/div: 2V/div
time base/div: 2ms/div

Regarding "trigger level" and "hold off", however I turn both knobs (literally any combination), I always get flickering or unsynchronized signal. Otherwise, I'm measuring at output of MCU (10k pull-up, UART transmission) with normal passive probe (in 1:1 internal divider rate).
Any ideas how should achieve the view of "standing-still" looking signal at the screen of scope?


texts:
I am unsure if a bandpass with one zero at 0 Hz and two poles above would be called a first order or a second order filter. The amplitude is rising and falling with 20 dB / decade and the phase approaches +/- 90 degrees, which indicates a first order filter. But there are two poles.
Same for an equivalent bandstop: it has one pole and one zero.
Are these first order filters or a second order filters?


texts: Does the reverse saturation current aka “Is” in the Ebers-Moll equation have any link to Iceo or Icbo

texts:
I can understand what are the leakage currents Icbo and Iceo but I don’t know and cannot find whether one of them is the same thing with the reverse saturation current in Ebers Moll equation namely Is.

Is there any relation between the  reverse saturation current Is and “Icbo or Iceo”?


texts: How to sync clock frequency to a microcontroller

texts:
I'm building a project which uses old FM synthesis chips - the Yamaha YM2612, which was the sound-generation chip used in the Sega Genesis, and also the TI SN76489, which was also in the Sega.

YM2612 has 8 data pins (D0 to D7) which are used to write to the internal registers of the chip. In order to latch a write instruction (a byte, as it were), then values are assigned to D0 through D7, and then one of the pins is flashed low, and then high on the YM2612 IC. Data can be written to specify the sound type, attack, decay, release, sustain, timbre, frequency, note duration, etc., but it's all transferred this way. The SN76489 is very similar here and also uses 8 input pins which work the same way.

I want to build a project which uses the Arduino, PIC, or another microcontroller to control one of these chips and to use it as a synthesizer, so I can preprogram sound patches and play notes through them. This, of course requires writing data to the registers as described above. The problem I'm having is this:

The Sega chip is controlled with a clock frequency of 8 MHz. If I were to use an Arduino, for example, which has a 16Mhz clock, how can I possibly provide the 8 MHz clock for the sound chip while also synchronizing my Arduino's write instructions to happen at the right times?

Optimally, I would load an 8 bit shift register like the 74HC595 with the eight data bits, and then pull the /WR pin low on the chip, and then put it back high again, so 8 bits have been written. But wouldn't this require the Arduino to operate at the same frequency as the sound chip? Also, if the Arduino executes 16 million instructions per second (nominally, or for this example) then some of the write commands will actually take several cycles, because I will have to write 8 bits in a shift register, which might require 16 instructions or something like that, PER BYTE written to the shift register. This seems to mess up all the considerations of frequency and I have no idea how to go about solving it.


texts: Why LM35DZ temperature sensor accuracy deteriorates towards the lower end of the range?

texts:
I get some curious data from my LM35DZ temperature sensor. Every minute or so I take 8 measurements 1/2-second apart and average them. The graph below shows that the accuracy of the measurements deteriorates noticeably towards the low end of the range (0°C). I connect the sensor's OUT pin to ATmega328's ADC pin directly - no resistors or capacitors - with 6 inches of unshielded hookup wire. The sensor is in the same plastic enclosure with XBee, humidity sensor, relay switching 110V-powered fan and a 12V to 5V voltage regulator.

Here's the graph illustrating the problem:

As you can see, at 20°C the accuracy is worse than ±2°C. I have a similar sensor connected to another ATmega328. With no other sensors or fans attached to it. And the accuracy is as expected (half a degree or so). So I'm positive it's my circuit (and not the sensor or the micro code).

Any ideas what could be affecting the accuracy and how I can improve it?


texts:
For a home automation project I need to source panel mounting electrical outlet sockets which are as low profile as possible and are rated at least 200 watts.

Something like a female version of these figure of 8 connectors would be perfect but they don't appear to exist:

EDIT: RE off topic. I'm not asking for shopping links, I'm trying to solve a design problem. I'll ask elsewhere, thanks to those who contributed.


texts: What is the proper term for a board that replaces a chip?

texts:
I've been working on some vintage electronics lately.  In the course of this work, I've found that in some cases it is much easier to design a circuit to replace an old DIP chip that has failed than it is to locate the old part.  (Actually, the bigger problem is that some of these parts are so old that the only replacements available are 30 years old and may not function at all)

For example, I've replaced two socketed SRAM chips with a single modern SRAM on a daughter board with pin headers aligned so that the whole circuit plugs into the two DIP sockets on the original board.

My question is, what is the actual name for this type of a board?  Daughter board?  Mezzanine board?  I'm trying to figure out how to describe it in the tech notes.


texts: How large would be the transformer for converting a lightning into useful electricity?

texts:
My dad asked me the oh-so-famous question yesterday:

  Why can't we harness the electricity from lighting?

After explaining to him the impracticalities of this as far as the amount of energy in lightning and how hard it is to get the same thing striked more than a few times in a year, I began to ponder another critical issue...

How big of a transformer would it take to get the theoretical 100,000,000 volts down to a level that could be stored in capacitors? From my understanding right now, this is a HUGE transformer! I don't know the math and EE involving fast transformers though.

When I talk big, I mean size. Like building big? Truck big?


texts: Designing Stepper Motor Drive logic in PLD?

texts:
I am doing a project which requires us to design logic in Stepper Motor Drive in SubPLD using Multisim. I designed the logic but it is not following the table below
In the question, two design are required for Stepper Motor: Half Step Sequence Driver (step angle θ=0.9°), Full Step Sequence Driver (step angle θ=1.8°).and as mentioned below these are the table and Mutltisim design given to us.


texts: Using a "quick connect" terminal for IEC inlet or just soldering the wires?

texts: I am using the Schaffner FN284-10-06 power inlet for a project. It has "quick connect" terminals, and it seems like the 3M FDI18-250Q connector would fit them. I've never used a connector like this before, and my first instinct was to just solder wires to the terminals and put a nice bit of heatshrink wrapping on them. That said, the removable terminals certainly look convenient. Are they sturdy? Can I trust the connection and the crimped wires to stay put (assume not much vibration is expected).


texts:
How can you add a tunable delay to a TTL pulse?

My understanding is that this is the job of a PPL. I am not sure if a digital PLL delays a square wave or if it can also delay a single rising edge (which is desired). I am hoping to tune the delay from 0ms to 10ms with accuracy in the microseconds.

________Rising_Edge_At_
Input__: 0,12,84,98,109,130
Output_:   10,22,94,108,119,140


texts:
Im trying to understand this basic circuit from a book.

The book said:
"The analysis is simple, if you remember your golden rules:

(The golden rules:

I. The output attempts to do whatever is
necessary to make the voltage difference
between the inputs zero.

II. The inputs draw no current. )

Point B is at ground, so rule I implies that point A is also.
This means that (a) the voltage across R2 is VOut and (b) the voltage across R1 is Vin"
So, using rule 11, we have
In other words,
voltage gain = Vout/Vin = -R2/R1

I cant understand why voltage across R1 is Vin and in R2 is Vout


texts:
For a standard basic RC Filter, the transfer function is as follows:
$$
{ V_{out} \over V_{in} } = H(j\omega) = { 1 \over 1 + j\omega RC  }
$$

However, when simulating the circuit, I find the output voltage to equal:
$$
{ V_{out} \over V_{in} } = |H(j\omega)| = \left|{ 1 \over 1 + j \omega RC  }\right| = { 1 \over \sqrt{ 1 + (\omega RC)^2  }}
$$

Why is the actual output equal to the modulus of the transfer function, not the transfer function its self? What does the original transfer function tell me, if anything?


texts: clkp and clkn inputs in Intel MAX10 FPGAs

texts:
The clkp and clkn can be used to insert a differential clock signal into the Intel MAX10 FPGA.
Intel MAX10 FPGA Datasheet
My question is, can we have 2 separate independent single ended clock signals being input into the FPGA on these two pins or just one single ended clock on either of them?


texts: Surface oxidation rates in CO2 vs Nitrogen vs Air?

texts: Is there a difference in surface oxidation and formation of electrical arcs on electrical contacts in ambient CO2 and N2 and Air? Can the surface oxidation difference be quantified?


texts:
I'm not having much luck searching this out.

I need a circuit that will allow me to select which of two parallel resonant crystals is operating with a common on-chip gate oscillator.  I vaguely remember seeing circuits like this back in the 70's.  I can't pull a single crystal far enough or accurately enough.   Fop is around 14 MHz


texts: Driving a CMOS 1.8V input with a CMOS 5V output

texts: I'm trying to drive a Telit UL865 UART 1.8V input with a ATMega32u4 UART 5.0V output.  Both of these gates are CMOS.  The datasheet for the Telit says that it has a 5K to 12K pullup on the input.  I believe that I need a voltage divider to drop the 5 to 1.8, but I can't tell if the pullup resistor is on the gate side of the CMOS or the source/drain side.  I imagine that if its on the gate side, the voltage divider will be thrown off by pull up resistor that is parallel to R1.  Where would the pull up resistor be placed in a discrete schematic of a CMOS gate?


texts: choosing crystal when tracks are very close together

texts:
This is a circuit I am having trouble with. I made 20 units with the exact same setup.

Three units with this setup managed to work with 33pF ceramic caps with 20% tolerance and a crystal from Ebay.

The remaining units are failing yet nothing is smoking or showing discoloration. I even replaced the 20% ceramics with 5% npo caps and still nothing.

I think now the lucky units were working because the crystal load capacitance and ESR happened to be spot-on.

What I want to try to do since people here consider ebay as a flea market is buy crystals from digikey. But there are two types I could possibly choose from.

One with 18pF load capacitance and one with 20pF load capacitance. The ideal frequency I'm looking for is 22.1184Mhz.

When I look at my tracks between the crystal leads they're probably too close together and I should probably increase the parasitic capacitor value when calculating my crystal load capacitance value.

One source on the internet claims this math for crystal load:

 CL = C/2 + StrayC

Because the caps I will use are 5% 33pF, its actual value would be between 31.35pF and 34.65pF

Now diving those capacitor numbers by two, we get 15.675pF and 17.325pF respectively.

People say the normal stray capacitance value is between 2 and 5pF but isn't mine more due to tight track spacing? I don't understand. So if it was 2pF then values would be:

  17.675pF and 19.325pF

Which means an 18pF load capacitance crystal is my best bet, but my stray capacitance is probably higher since I'm using a socket for my micro controller.

If its 5pf stray, then values would be:

20.675pF and 22.325pF

Which means a 20pF load capacitance crystal is my best bet.

Somehow I think the 20pF load crystal is better for my situation but I could be wrong.

Am I best to choose a crystal with 20pF load capacitance or 18pF load capacitance? and yes I will still use a standard IC socket for the micro (AT89S52) that uses this crystal.


texts: I am just learning Pulse with modulation technique. Is There any way to create a pseudo analog voltage using PWM from the digital output of ATmega16? How can it be done?


texts: Transistor Q's: Switching a Positive V when Base goes negative (and the other way 'round)

texts:
I thought I knew enough to get this working, but apparently I don't...

I have a waveform going between +5 and -5V at audio rates.

When the waveform is above 0V, I want to charge a capacitor from -15V rail at 20mA.
When the waveform is below 0V, I want to charge a capacitor from +15V rail at 20mA.

The cutoff point doesn't have to be right at 0V, it can be a diode drop above (or below) that. I have a Bipolar power supply of +/- 15V.

I can get it working the opposite (charge positive cap when Voltage goes high) and I know I can just use an op-amp to invert the incoming signal, but I'm sure it can be done without adding additional parts..


texts:
Should the attached diagram have a fan-in of 4 or 8?
Do resistors and resistance also count as a fan-in,
since it acts like an input as well?


texts: Why we need two resistors to control the gate voltage of a PUT transistor?

texts: Looking the follow schematics you can see two resistors 15k and 27k that are controlling the gate voltage of the PUT (programmable unijunction transistor) transistor. My question is why we need two resistors to control the PUT's Gate, while we can do our job with only one carefully selected resistor?


texts:
I know that an interrupt should be as short as possible, however, what is short?

My routine is quite long, but has quite some if-statements, so the execution time is short. But maybe it still is considered (way too) long.

Will my code cause problems (in the future)? Currently I have only one interrupt, but I want to add later more (for DMX control for example). This one is to handle MIDI input.

It is meant for an STM32F103C8T6 (72 MHz) and later STM32F446ZET6 (168 MHz).
The debug statement are temporarily.

void HAL_UART_RxCpltCallback(UART_HandleTypeDef *huart)
{
  if (huart->Instance == huart1.Instance)
  {
      // Don't overwrite existing data.
      if (((_RxHead + 1) % BUFFER_SIZE) != _RxTail)
      {
          // Check for sysex.
          if (_SysexReceived == 0)
          {
              if (_RxByte == 0xF0)
              {
                  _RxBuffer[_RxHead] = _RxByte;
                  _RxHead = (_RxHead + 1) % BUFFER_SIZE;
                  _SysexReceived = 1;
              }

              // No sysex, skip active sensing/timing.
              else if ((_RxByte != 0xF8) && (_RxByte != 0xFE))
              {
                  // Add byte.
                  _RxBuffer[_RxHead] = _RxByte;
                  _RxHead = (_RxHead + 1) % BUFFER_SIZE;
              }
          }
          else if (_SysexReceived < MAX_SYSEX_LENGTH)
          {
              // Sysex: add byte.
              _RxBuffer[_RxHead] = _RxByte;
              _RxHead = (_RxHead + 1) % BUFFER_SIZE;
              _SysexReceived = (_RxByte == 0xF7) ? 0 : _SysexReceived + 1;
          }
          else // SysexReceived >= (or ==) MAX_SYSEX_LENGTH
          {
              // Too long message, only write last 0x7F.
              if (_RxByte == 0xF7)
              {
                  _RxBuffer[_RxHead] = _RxByte;
                  _RxHead = (_RxHead + 1) % BUFFER_SIZE;
                  _SysexReceived = 0;
              }
          }

#ifdef __BUFFER_DEBUG
          __ReceivedBufferData[__ReceivedIndex] = _RxByte;
          __ReceivedBufferHead[__ReceivedIndex] = _RxHead;
          __ReceivedBufferTail[__ReceivedIndex] = _RxTail;
          __ReceivedBufferSysex[__ReceivedIndex] = _SysexReceived;
          __ReceivedIndex++;
          if (__ReceivedIndex == __RECEIVED_BUFFER_SIZE)
          {
              __ReceivedIndex = 0;
              __ReceivedRounds++;
          }
#endif
      }
      else
      {
          _Error_Handler(__FILE__, __LINE__);
      }
   }
}

Update:

After fixing some problems somewhere else in the code and slightly different ranges in some if statements, it works quite well. Only many and big sysex-messages makes it a bit sluggish but that's not related to the ISR.


texts: For the resistor circuit shown in the picture, what must be the missing resistance to give a total resistance of 252 ohms?

texts:
After my calculations, I keep getting 1100 ohms, but the back of the book is saying 85 ohms. 85 seems to fit in better with the other numbers, but I can only get 1100 to add up.

Here's my calculations:

1/(1/(x + 16) + 1/180) + 22 + 75 = 252

x = 1100


texts:
I found a comment on a blog post stating that NB-IoT doesn't support roaming:

nbiot do not support roaming (you must have sim from the operator that have the infrastructure). nbiot also lacks support for handover (you can not maintain connection while moving out of range of cell A and into range of cell B.
in short, NBIoT (LTE NB1) is a mobile standard for stationary objects.
if you want roaming and handover you have to go with LTE Cat m1 (not to be confused with LTE Cat 1) or wait for LTE NB2.

I wasn't able to correlate this informations with other sources. Is this statement true? Is this a technical limitation due to the specification/implementation?


texts:
I'm practising on compensators and the root locus. A very common problem in my textbook is to find the value of a variable for the minimum settling time of the system.

I have no trouble drawing the root locus for the variable but I can't decide on the right value. I only found a formula for second order systems but that doesn't cover most of the cases.

I also tried inverse transforming to find a result in the time domain but I usually have an exponentially decaying component multiplied by a sinusoid and it gets more complicated.

So , what's a general technique to calculate settling time ?


texts: Soft latch switch seems incompatible with boost voltage regulator

texts:
I am using a lithium ion battery to power a circuit board at 5V. I am using the LM2623 boost voltage regulator, which works fine when the battery is hooked up to the circuit board. I would like to add a soft latch switching circuit between the battery and the voltage regulator.

I have successfully replicated this soft latch circuit on a breadboard. I am able to use the soft latch switch with the battery as the input voltage to light up an LED. There are no issues whatsoever with latching. I am also able to use the soft latch switch with the 5V output from the voltage regulator as the latch's input voltage.

The P-MOSFET I am using is the IRF9510, which is rated up to 100V and 4A. The voltage regulator doesn't ever pull more than 2A to handle its switching circuit.

The N-MOSFET I'm using is the ZVNL110A.

Works:

battery --> latch switch --> LED

battery --> voltage regulator --> latch switch --> LED

Doesn't work:

battery --> latch switch --> voltage regulator

This non-working set-up has strange behavior at the output of the voltage regulator. Upon clicking the button in the switch circuit, the voltage out of the regulator will spike to about 1.3V and then slowly decay down to 0V. This decay takes at least a minute or two, which has me thinking that this issue has something to do with the fact that the load is capacitive and that is why the switch won't latch. I am wondering whether this is a result of the switching circuit within the voltage regulator circuit, or due to the input/output capacitors to the regulator circuit. For all I know, it could be malevolent fairies who don't want my circuit to latch.

I don't think the problem has to do with the P-MOSFET being unable to handle the current that the voltage regulator wants to pull from the battery, and I know it isn't the battery's discharge rate that is somehow limiting the current into the circuit. I also don't believe it is the N-MOSFET's current limitation in the switching circuit causing the problem, because I don't believe that component ever receives an excessive amount of current or voltage.

I am a relative n00b when it comes to electronics, so any help would be much appreciated. I can provide more info if needed.

---Edit---

I tried monitoring the voltage at the gate of the P-MOSFET to get to the bottom of this. When I have 3.7V coming into the latch circuit, the gate reads 3.65V. If the voltage regulator is not attached, clicking the button will bring the gate voltage down to 0 V. If the voltage regulator is attached, however, clicking and holding the button only brings the gate voltage to 3.32V.


texts:
We are using an (XD-V5-01) to measure an AC current but what we are not sure of is how responsive devices like this are.

Do they accurately reflect the current being measured instantly (100-200 ms)? The spec sheet states 'Less than 1 second', but is this similar for all current transducers?


texts: Will the Boolean equation change when we reduce the CMOS transistors in a static CMOS logic?

texts:
We are doing a project about a multiplier. Two of my teammates are assigned to make the transistor level designs of the adders, subtractors and few barrel shifters. My prof has told me to make a structural level Verilog modelling of the same multiplier. He then instructed " When your teammates reduce the number of transistors for the adders and subtractors, the boolean equation changes. Put those boolean equations in the Verilog Code and we'll have the optimized multiplier". Our team is slightly confused, since the Boolean equation has nothing to do with the transistors but just the logic to be implemented.
So TLDR ; If the number of transistors in a Static CMOS logic design are reduced, will the Boolean equation change significantly?


texts: What Does 8 x 20-µs and 10 x 1000-µs Mean in Surge Testing Terminology

texts:
I'm trying to understand the meaning of

  8 x 20-µs and 10 x 1000-µs

standardized transient impulses (or sometimes it's called a waveform). But what does it actually mean. Why is there a multiplier in front of the time unit?

The quoted line above is constantly mentioned in surge testing document. But no where in the document does it mention what is the meaning of it.

Most Google search results point to Datasheet values. Maybe I'm searching for the wrong search term.


texts: I am troubleshooting a relay driving board that uses an MIC5891 to drive a 12VDC relay (86Ω coil). The load supply voltage into the 5891 is 12V. When checking an output with no load I get 12V. When I put even a small load on the output (115ma measured), (it can handle 500ma) the voltage drops to 10VDC, but the input supply voltage still stays at 12V. All the other outputs are off, so I'm not overloading the driver. Why does the output voltage drop with a minimal load?


texts: How electric poles are distributed and placed

texts:
Complete newbie to anything electricity-related so would appreciate an answer I could easily understand!

I'm wondering how electric poles are placed around an area by an electric utility company?

Are they distributed across an area in a way that benefits any party in any way like saving energy, saving on poles construction or what not?

Also I'm guessing as an area progresses and new buildings are built I'm sure the way the poles were initially placed is not as optimal as it could be for the new buildings around. Is this a common practice of rearranging the poles to better fit the new changes? Do electric companies do this often? Is it cost-effective for them to find the best new "layout" to replace the poles? How do they do that, if ever?


texts: What is the potentiometer for on ultrasonic module JSN-SR04T-V3.0?

texts:
I bought an ultrasonic module. It works fine. But I'd like to know how the pot on the module works.
Thank you.


texts:
The first step in a TWI transmission is to transmit a START condition. This is done by
writing a specific value into TWCR, instructing the TWI hardware to transmit a START
condition. Which value to write is described later on. However, it is important that the
TWINT bit is set in the value written. Writing a one to TWINT clears the flag. The TWI will
not start any operation as long as the TWINT bit in TWCR is set. Immediately after the
application has cleared TWINT, the TWI will initiate transmission of the START condition.

This is a statement from the datasheet of ATmega328P (pg 223). What I don't understand is why is it necessary to set the TWINT bit, when I have an operation to perform (i.e. to transmit the START condition)? After all, it has mentioned:

The TWI will not start any operation as long as the TWINT bit in TWCR is set.

And what does the application has cleared TWINT mean? If I am not wrong, application is the program to be uploaded into the micro-controller. If this is true, then the program should first set the TWINT bit and then reset it again. I am not getting the point it is trying to explain.


texts:
I am new at Altium, I am trying to connect 8 wires but using a bus. I have read about this in Altium's web page but I doesn't explain too much about how to connect buses on the way I need. I want to connect in this way:

I know pin count doesn't match on both sides but that is my idea. I would like to connect the buses whit a Port or Netlabel if it were possible. I have tried on this way:

But it is not being connected when I import on my PCB design. How is the right way of doing this ?


texts: Current is flowing out of both base and collector of my BJT

texts:
I have a 2N2222A BJT transistor and I hooked it up like follows.

I measured voltages at a couple of points (with respect to ground) and I drew them on the diagram. You can see (using Ohms law) that there is current flowing out of both the collector and emitter. Furthermore the voltage between the C and E pins was 0.

I cannot square this with the model from my textbook.

Vce = 0, so that there should actually be no current entering the collector, let alone a large negative current like in my diagram.

Something to point out is that I have connected both C and E pins to ground. But I think that should be the same as a common emitter configuration with a 0 voltage on the C pin. The other thing is a 1MOhm resistor between emitter and ground, which does not appear in the common emitter topology.

Is this behavior explained by the characteristic curves in my textbook or are there other exotic effects going on?


texts:
I am quite new to electronics and I would like to combine these 2 circuits together so that during complete darkness on the LDR, the LED would turn on instantly and when light falls on the LDR there would be around a 1 or 2 second delay before completely shutting off. I would like this to keep running and not just a one-time thing where once the LED completely shuts off, the LED would not light up again even in complete darkness.

The circuit would be running of a 5V DC power supply and powering an LED array.

I have the 2 circuits below working separately, but have no idea how to combine them together.

I tried connecting the delay circuit to the output of the dark
sensor (LED) but it did not work.

I would like to achieve the desired effect:

https://www.youtube.com/watch?v=DXRto0dwZbM&feature=youtu.be


texts:
I am designing a circuit which uses a CMOS decade counter to activate and deactivate pairs of transistors in turns.The problem is:will the IC be damaged if the current of one of the outputs(activated) reaches another output(deactivated)?

Here is the datasheet


texts: Power dissipation in triac driver optocoupler

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This is a typical circuit for opto couplers:

What should be the appropriate wattage for 180 ohms resistor?

I think power dissipation should be minimal because in off state, there won't be any current and in on state, the voltage drop across resistor will be very small. As such is it advisable to use 0603 package resistor?

Power rating for 0603 was given as 1/16 watts - 1/10 watts in various articles.

Right now I am using 1206 package and it's working perfectly.


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I put this circuit together to demonstrate latching properties of SCRs but I'm finding that the SCR doesn't behave as I expected it to from the datasheet values.
Specifically, I found that in the circuit as shown it will light when the switch is opened but not latch (i.e. it turns off as soon as the switch is closed again.) If I swap the LED for a small lamp it works fine. After some experimenting I found that it takes about 25 mA to latch.
So the disconnect for me is that according to the datasheet typical latching current is .2 mA and maximum is 5 mA. I know that the test conditions for those numbers are Vak = 12 V, Ig = 20 mA. I think for me Vak is ~ 7V (including LED Vf) so I guess that could explain it, but unfortunately there are no relevant graphs to refer to for more information. (Also I have tried with much higher gate currents with no difference.) Am I reading the datasheet wrong? Any other insights?
Update:
I added a 1k resistor between the switch and ground and now the circuit works as expected. So new question: why is the pulldown resistor required to make this function? Does it have something to do with jitter on the switch?

simulate this circuit – Schematic created using CircuitLab


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I feel like this has been beaten around the bush in a couple other topics, but I am hoping to find something a bit more definitive. I am looking to control a Peltier thermoelectric cooler.

I've got a 24VDC PLC with a couple tools at my disposal:

Analog thermocouple inputs
Analog outputs 0-10VDC, 4-20mA, 12 bit
Digital outputs 500 mA, 24VDC
PID ladder block in PLC software

I would like to use the PID in conjunction with one of the output types to drive the Peltier at full power (12VDC, 5A). I need some way to convert either of these outputs to a 0-12V controllable constant signal (As pointed out in other threads, the Peltier will wear out if cycled/supplied PWM input).

Some thoughts...

PWM controlled buck converter (haven't found one, but maybe I'm searching for the wrong things??, everything I have found is trimmer controlled) w/ 12V power supply
Use RC circuit to change PWM to analog (or analog output) and combine with MOSFET to control a 12V power supply
DC motor controller to step to required voltage, then RC circuit to smooth

Ideally, I'd love a box that takes 12V 5A in, and a 24V PWM duty cycle dictates the voltage % to an output. It seems like this should exist, but I don't know what to look for.

Also, lest it be too obvious, but unsaid, I am not super experienced with electronics design, nor am I seeking to be an expert. My intention is only to move what I have to move, heat what I have to heat, or in this case, cool what I have to cool. Therefore, I'm not looking to tinker too much, the most direct, robust solution is definitely the best here even if it's not the cheapest.

Thank you all!