texts: How to correctly interpret relay schematics

texts:
I am copying a schematic in EAGLE to make a battery protection board (https://www.homemade-circuits.com/battery-over-discharge-protection/)
I am very unexperienced in writing relays in schematics, and am unable to know exactly how to wire up the relay in the schematic editor, because the relay symbol is very different than what I am accustomed to. Not to mention, the names of the pins is the only thing I have to work with, since that's the only help they give. (The relay they show in there schematics has no schematic resemblance whatsoever):

Below is a schematic of a typical relay, Displaying the pin names:

(Courtesy of circuit-diagramz.com)
Below is another Schematic of the same type of relay from Autodesk EAGLE. I wrote the same names for the pinouts in green, but I'm not 100% sure if I'm correct. For starters the switch is flipped upside down, and for another, instead of N/O and N/C. it just says 'S' and 'O':


texts: Durable, UV-resistant labeling for electronics enclosure

texts:
I'm not sure if this is the right forum for this question. I'm asking here in hopes that someone has dealt with this.  If this is the wrong forum, please do not vote me down. If necessary, I'll simply withdraw the question.

I need to apply labels that indicate switch functions to the exterior of an electronics enclosure that will be used outdoors.  The enclosure is made of polycarbonate and fiberglass. The labels must be permanent, waterproof, UV-, chemical and abrasion-resistant.

I've tried applying water decals and coating with epoxy and UV-resistant clear top coat, but the results are inconsistent.

Any recommendations?  I'm not looking for a specific product (as I think this would be against forum policy), rather for general guidelines.  Do you use commercially available label material or some other solution?


texts:
I need to find a device I can use in place of the MC14495-P1 binary to hexadecimal LED driver.  This part is sadly very scarce and very expensive these days.

The device is a 16 pin DIP with +5V on pin 16 and Gnd on pin 8 (standard logic chip arrangement)

The closest I have come so far is a 14 pin PIC16F and a bit of reworking of the PCB, but that's going to be a pain in the sphincter as I have to do about 80 of them.

So I am wondering if there is a programmable device from one of the other manufacturers, like Atmel, Maxim, TI, or whoever, that is 16 pins with the power laid out like I need and all the other pins available for IO?  I haven't found one as yet, but if anyone has any suggestions I'd be very grateful.

Oh, and they have to cost < £1 each.


texts:
Why is the positive terminal of the DC source connected to the primary of the  transformer?

Link to random inverter circuit I found online


texts:
I'm working with an Arduino Due and four 5V TTL pressure sensors. I'm using this logic level converter to convert from the 3.3V Due to the 5V sensors. I've been having problems using all four at a time, so I broke out the oscilloscope and noticed a voltage level problem. When I have one device plugged in, logical low is ground. When I have two devices, it creeps up a bit. Three devices, it creeps up to around 2 volts. When I have all four devices plugged in, logical low is around 2.5 V, which is above the logical low threshold for the Due, and thus, nothing works. Does anybody have any ideas on how to fix this?

EDIT: forgot to mention, when I say "logical low," I mean on the TX line. The RX line is fine.
EDIT 2: Added link to data sheet in the post instead of in the comment, and added more detailed schematic, if it helps. All sensors are hooked up the same way as the in the detailed schematic.

Here is a cartoon-y schematic:

Slightly more detailed schematic:


texts: Circuit to increase current of arbitrary waveform generator

texts:
I am trying to create a setup for some Physics experiments - so my background is Physics, not Electrical Engineer that can do circuit design. But I can put a circuit together. I need to amplify the current of a signal from an arbitrary waveform generator. I also need to make sure that any amplification circuit I attach to the waveform generator cannot damage the waveform generator.

The current hardware I have is a Tektronix AWG610 Arbitrary waveform generator and a Tekpower TP3005T Variable Linear DC Power Supply, A constant current or constant voltage power supply it can go up to 5amps. The waveform generator is capable of 400 fs Edge Timing, which I need to preserve as much as possible on the amplified side.

So I am looking for a circuit diagram that would be able to use the signal from the AWG610 and use it to basically modulate the current from the power supply or alternatively basically amplify the current of the AWG610 generated wave form using the separate constant current power source. But If possible I would like the amplifying circuit to be a little more flexible and be able to handle higher amps for when the power supply is upgraded, so maybe 100amp in future. I also need the amplifier to be able to support from low frequency up to at least 1Ghz.

The waveform maybe arbitrary, might be just pulses or a really noisy erratic waveform.

My budget is around $300.

Thanks, any help is much appreciated.


texts: Does there exist an IC that allows on-the-fly routing of signals?

texts:
Do there exist ICs with N input pins and N output pins which, either via EEPROM setting or via on-the-fly control by a microcontroller, allow one to route each of the N inputs to ANY of the N outputs?

In other words, for example, one might use it to connect the incoming line on Input1 to the outgoing line on Output6, and connect Input2 to Output3, and Input3 to Output1, and so on (regardless of whether the signals are SPI, or I2C, or standard digital lines, etc)... And later change up the order.

If it exists, what are such ICs called?


texts: Can we short JFET source and gate junctions as shown in the circuit?

texts:
Is the below circuit accurate?

The way the circuit is drawn in the question it looks like the source current is entering the gate, which is not possible since ig = 0 (excluding very low leakage).
Also, how the source current would return to the drain to be a close or complete circuit in the way it's drawn in the question there is no ground nor a return path from the source back to the drain right?
In my humble opinion I suspect it's as I draw it below:


texts: I have a 555 timer which outputs an enable high 500ms after power-up. So it is basically a step response at t = 500ms. I am tasked with processing this enable signal with a 20 Hz square wave signal such that the ouput of the circuit that I'll make will only output the enable signal when the 20 Hz square wave is currently low. My usual way of doing this is make a microcontroller circuit, monitor ports to check state of the 555 enable signal and 20 Hz signal, and make a LATbit = 1 only if ((PORT_20Hz == 0) && (PORT_555_enable == 1)). However, without micro and only hardware, I am lost on how to start the design.


texts: Confused between push-pull and open-drain

texts:
I am planning to use i2c based port expander (earlier I was using atmega328P's GPIO) for inputs and outputs. On a digikey search, I found MCP23008, MCP23009 and MCP23017 as possible replacements. Out of these three, only MCP23017 is push-pull. Other two are open-drain. I have an understanding that push pull can actively source and sink and open-drain cannot actively source. I am not very sure how does this affect my use case and hence I need some expert advise.

Here is the use case:

SS1 and TRIAC1 are supposed to go on GPIO of port expander. SS1 is supposed to be digitally read and TRIAC1 is supposed to be driven HIGH or LOW.

As such does it matter whether I use open drain or push pull type? If yes, which is the better option? Also, I want to keep the component to a minimal. Ex - I want to drive the triac driver directly by the port expander rather than using another transistor. So, please take this in consideration as well.

Note: Both circuits will be replicated 4-10 times on the PCB and hence the requirement of port expander.


texts: Protective earth bonding for multiple AC-DC PSUs

texts:
I'm building an LED curtain, and trying to make it as safe as I can in limited time.

We're using WS2812B strips driven off 3 Fadecandy boards.

I've got 3x Mean Well RSP-150-5 AC-DC PSUs (Datasheet: http://www.farnell.com/datasheets/2547987.pdf ) going in the box, on the plate as shown. The box will be fed with a fused, filtered, switched, panel mount IEC inlet. The box is plastic, any metal in it will be bonded to the plate in the picture.

I'm planning on connecting earth from that inlet directly to the mounting plate.

The power supplies are screwed directly to the plate.

Is this right?

Should I connect the earth screw terminal of each power supply to the same bond point used to connect the earth from the IEC inlet?

Should I connect all -V rails on the PSUs together? They'll be connected in the USB hub/host anyways, should I give them a beefier connection in common elsewhere?

Should I connect all -V rails to the protective earth?

Thanks!


texts: Spice model for analog devices instrumentation amplifier giving unexpected outputs

texts:
I'm trying to do noise analysis with the AD8421 (although the specific in-amp doesn't matter). Right now I have two time dependent voltage sources on the inputs of the amplifier and the output seems to only follow one of the inputs.  Also this signal is centered at the top voltage rail and seems to move to the bottom when the inverting input is around (~0.9 V).  Here is what I am using for my test.

* pins for clarification
*.SUBCKT AD8421  IN-  RG-  RG+  IN+  -Vs   REF  VOUT  +Vs
xinamp 1 0 5 2 7 0 6 8 AD8421
rg 5 0 1000k
rl 6 0 1000k
vsr1 7 0 -20
vsr2 8 0 20

vss1 2 0 sin(0 7 1k)
vss2 1 0 sin(0 0.9 1k)

.probe
.op
.tran .1m 4m
.end

Shouldn't I be getting the difference of the signals?  I'm not sure what I'm doing wrong here.  I've tried different Spice models from analog devices and they seem to do the same thing.

Here is another attempt by grounding the inverting input and applying a 4mV source on the amp input.  This time different gain resistors were used.  At a very high resistance the output is at the top rail while lower resistances will move it down.  Instead of increasing the gain the gain resistors increase it to a limit then decrease it.  The image below display resistance 5 50 and 1k.  After 1k the gain drops again and the output shifts to a higher voltage.


texts: Can a short circuit damage nearby devices?

texts:
This happened yesterday and left me scratching my head.

We had a badly built power extension cord in our office. Inside it has 3 wires - live, zero and ground (hope I got the terminology right). When plugging in a phone charger, the live wire touched the ground wire and blew a fuse. However it appears that a notebook power supply that was already plugged in the same extension cord was also damaged. Now, when plugging in that notebook charger (anywhere), it too blows a fuse.

What I'm wondering is - how could this happen? As per my understanding of electricity, the live wire touching the ground wire should simply cut the power to the notebook power supply, since all the current would now flow from the live wire to the ground wire and away. There should be no high voltages produced in the nearby devices. Is there any other mechanism as to how this could have happened?


texts: Using Ethernet cables cable for sensor wiring

texts:
I'm exploring the pitfalls of using an Ethernet cable for extending sensor cabling.

The term Ethernet cable is used ambiguously on purpose to denote an "easily available 8-wire cable whose category is defined by the constraints".

I'm looking to extend the following (or similar) sensors:

The signalling going through the wires can be analog or I2C, or some other type of digital signal. Ideally, I'm looking for a common solution that could extend the sensor 30m away from the gateway.

What I'm currently doing is patching the cable with tape and pairing two sensors on a single Ethernet cable:

Everything seems to be working for the distances tested so far (less than 5m) but this seems to be a very hacky, non-deterministic approach and I don't know at what point potential errors can be contributed to actual cabling issues.

Is there an industry standard or a 'more correct' way to do this?


texts: Why does the signal generator voltage change in this circuit?

texts:
In this circuit, when I measure with an oscilloscope the square wave I get this:
(The switch S is open in both measurements)

But when I change the R2 resistor to 15 Ohm, I get this:

Why does that happen?


texts: MIMO with STBC example - How to derive SNR?

texts:
Conosider 2 x 2 MIMO system with the channel matrix H :
$$
H = \begin{bmatrix}
1&1/2\\
0&\sqrt{3}/2
\end{bmatrix},
$$
and transmit signal matrix S :
$$
S = \begin{bmatrix}
s_1&-s_2^*\\
s_2&s_1^*
\end{bmatrix}.
$$
Let the total transmit power be P, and the noise power be \$\sigma^2\$.
How can I derive SNR after STBC demodulation?

I think that this problem is related to the formula
$$
\text{output SNR} = \max_{w_t , w_r} \frac{E[|w_r^H H w_t s|^2]}{E[|w_r^H n|^2]} = \frac{|u^H H v|^2 P}{\sigma^2 |u|^2} = \frac{\lambda P}{\sigma^2}.
$$

But I cannot understand what the formula
$$
\max_{u,v} |u^H H v|^2
$$
means. Because there is no explanation of the matrix u and v..


texts:
How do I make a different usb wire type out of two different usb wires? For example, say I have two standard usb-to-micro-usb wires and I want to make one usb-to-usb and then one micro-usb-to-micro-usb. Could I just cut and strip both of the wires and then solder the two remaining usb heads together to make a usb-to-usb? (Same thing goes with the other micro USB heads)

With that, I can charge my device through my makeshift usb-to-usb connected to a female usb hub!


texts: Obtaining maximum light from IR led for distance sensing

texts:
I'm working on a project and I'm using IR LEDs and photodiodes to measure the reflected signal. At the moment the IR LEDs are always on and drawing 100mA.

It works really well except for times when there's ambient light from either the sun or inside lighting. Is not a great deal but it makes moves or drowns out particular Tigger points. If the distance is small then there's not really a problem.

So I thought , as I don't really need the IR LEDs to be constantly on due to only reading them every 1ms, that I could pulse the IRs on when needed take the reading then turn them off.

Because of the pulse it means I can go up to the peak current value of 1A. Instead of the maximum of 100mA continuous..

The data sheet says for peak current of 1A

Conditions--Pulse Width≦100μs and Duty≦1%

So I understand this as it can be on for 1A for a maximum of 100us but must have 10ms gap between pulses if the pulse is on for 100us....

So I would like to know if my understanding is correct and that by using this pulsing techique it will give a stronger signal to remove ambiguities from the reading caused by ambient light


texts: Connect arduino to COM pin of a NO NC button

texts:
I probably have a basic question but i'd like a confirmation on my solution.

I have finished my arduino breadboard prototype which is using some basic momentary push buttons along with pull down resistors. See diag, left side.

Now it's time to build that into some real box with arcade push buttons. They have a COMMON, NC and NO pins. I have to place a dozen of them in a row and was wondering if i could simplify the design to avoid the resistors and the wiring effort.

I came with the solution on the right of the diagram. Arduino input signal pin is on the button's COMMON pin ; then 5V on NO and GND on NC.

With this solution i can simply connect all the NO together, all the NC together and just have dedicated wires between COMMONs and Arduino input pins.

But i'm wondering whether removing the pulldown resistor might generate some real problems. I can't see them since :

NO and NC can't be connected together so no risk of short circuit
in a stable situation, a signal pin will never be floating. If, when switching from NO to NC, there is a very small lapse of time where COMMON is not connected to either 5V or GND : whether the read signal will be the previous one or the next one makes no difference (previous = as if there was no floating, next = what will be in the next millisec)
in case of rebounds, well, that's the same pb with pulldown resistor.

What do you think ?


texts: Can I connect 2 AAA battery chargers in parallel (to use them as a power supply with higher mA·h)

texts:
What I'm trying to do is to make an emergency power supply for a fishbowl (In my country, the power goes out very often). When the power goes out, a relay will connect the 8 batteries in parallel to the compressor. When the power comes back again, the chargers will re-charge the batteries.
I need more than 4 batteries in parallel to make the compressor work for a longer time (4 batteries only last about 4 hours).

Edit (see comments):
I'd like to connect the batteries of the chargers in parallel (one cable from battery (+) on charger 1 to battery (+) on charger 2 ,and the other from (-) to (-). I think the question is also valid for many chargers, but I only have two. The chargers have to remain plugged, so when the power comes back, the batteries are charged again. I would add a wireframe if I only know how.


texts: SMPS: Current Mode Instability (aka “sub-harmonic oscillation”) - Can we ignore it?

texts:
Currently I am designing a Constant Current charger for a capacitor which charges it from 0 to 350 VDC using a peak current mode controller.

As we expected from simulation, I see there are sub-harmonic oscillations in reality at a duty cycle of 50% and higher.

But as I am charging the capacitor from 0V to the input voltage of 350V (D=100%) means the sub-harmonics occurs only for a short time and when it's charged I set the duty cycle to 100%.

Can I ignore/accept the sub-harmonic oscillations for a short period of time, or should I make a slope compensation to fix it?

Thank you for your time.

The oscillation looks like this:

And is similar as reality.


texts: Most efficient way to drive a low power LED at half brightness

texts: I'm working on a small project where efficiency is very important (every mA counts). I need to drive two red 3528 LED's in series and only have a 9V DC source. I want the LED's to be only around half the brightness than what they would be if I drive them with the voltage/current that's in the spec sheet. If I take an adjustable switched DC converter and turn this up to the point where I like the brightness, would I still need a resistor? And would this be the most efficient way to do it? I was surprised to see that if I hook up the DC converter it already uses up 4mA even without load. That's already the same current as what the 2 LED's alone will be using. Just wondering if a 5V voltage regulator + resistor would use more current.


texts:
I am thinking about using peltier for both heating and cooling to maintain desired temperature profile in small area (2ft square at max)
Can continuously changing polarity damage peltier module and more importantly, will it be as efficient in reverse polarity?
Note that it will only be turning on once a minute for a few seconds to maintain 38°C
What side should I put/face inside the enclosure, forward or reverse?
Ambient weather swings alot from 30 to 43 so heating and cooling cycles can both be considered 50% of the time because enclosure will have the ability to hold the temperature as it will be sealed.


texts: Routing Packets in a Wi-Fi network (802.11)

texts:
Say we have a router (capable of 802.11 protocols) and some number of devices that are configured to communicate with this router. I have learnt about how devices/nodes use CSMA/CA to transmit data, and other mechanisms such as RTS/CTS & NAV, to help prevent collisions in the wireless medium.

However, I haven't been able to find an answer to a subtle issue. If one device intends to communicate with another device, then would it be possible for the devices to communicate directly with one another (assuming they are within each other's range)? Or would they still have to send packets via the router?

I just feel that a significant latency is introduced if the devices have data to send to each other, but have to still route packets through the router. The same CSMA/CA scheme could be used to coordinate transmissions between the devices directly.


texts:
This is the current going out from the Vsin-source and below is the circuit I simulated.

Could someone explain to me why the current looks like this?


texts: How do professional companies test a low power wireless network performance?

texts:
I have designed a 5 point low power wireless network using 868 MHz modules and want to test the wireless connection performance indoor. The points are going to be fixed to the wall and placed above each other with each one located in a separate floor (so there are 5 floors). My questions are:

The parameters that I care about are speed, signal strength and error rate. How do professional companies evaluate the performance of such a wireless network? How do they find the maximum limitations of a wireless network? Are there any other important parameters?
Each PCB has a horizontal antenna and for the time being I have the PCBs without boxes so I can't mount the PCBs to the wall. I am thinking about just laying the PCBs on the ground. I don't like the fact that the antennas are going to be close and parallel to the ground to get the test done. Is this an acceptable close enough approach? What would professional companies do to test the wireless PCBs before manufacturing the boxes? Would they settle for doing the tests on a bench?

Thank you in advance.


texts: Convert PWM to Analog using a DAC chip in order to emulate a Potentiometer for audio

texts:
I'm trying to control audio level/gain (from line or amplified signal) using an Arduino. I do not want to use SPI, for this project I can only use the PWM outputs, thus I do not want to use a digital pot. I found some related questions here, but they do not fully explain how this approach applies to audio applications.

From the PWM I know I can use a low pass filter, but I want to save time and space using a DAC chip. One option is the TDA1543 (http://www.docethifi.com/TDA1543_.PDF).

So my questions are:

How do I connect the PWM and audio in/out using the DAC TDA1543?
Will this approach work as an audio pot controlled by PWM or is there a more straightforward option?

The TDA1543 has 8 pins:

1: bit clock input

2: word select input

3: data input

4: ground

5: voltage

6: left channel voltage output

7: reference voltage output

8: right channel output

Where do I connect the PWM, and audio in and out? I believe I also need to indicate the resistance somehow or add resistors such as in a 10K pot (amplified) or 100K pot (line).

Any help will be very much appreciated!!


texts:
I want to switch a Thermoelectric Peltier Cooler (TEC1-12705) (12V - 77 Watts) using an Uno.  I am an engineer but not an EE so I could use some guidance on circuit setup.  There was a very good discussion on the page below but I need a bit more assistance on R values etc..

How to drive a MOSFET with an optocoupler?

I have the following:

optocoupler - 4N35
MOSFET - N-Channel MOSFET 60V 30A

Here is my circuit:


texts: Does every PIC chip need a Boot-loader like the Arduino chips do?


texts: Unsure Whether PCB Components Are Leaking

texts:
I am having problems with my air conditioner as it does not seem to be able to cool the room well. The fan seems to be a bit slow, so I opened the AC and check the PCB as some tutorials on the internet suggested.
It is then I found something unusual on the PCB. Some components seem  to be wrapped around white matter.

I wonder whether those are normally there (like a glue)? Or does it indicates that those components are leaking and need to be changed?
Thanks a lot!


texts: Can NRF24L01 use IEEE 802.15.4 and 6LoWPAN protocol?

texts:
I'm new to embedded systems and wireless sensor networks. I want to make a wireless sensor network which is based on 6LoWPAN protocol for monitoring application. As stated on Wikipedia, 6LoWPAN runs over IEEE 802.15.4 protocol. What I want to know are:

Is it possible to use NRF24L01 transceiver for IEEE 802.15.4 protocol? If it is possible, how can I achieve it?
If NRF24L01 can be used for 802.15.4, can I use for 6LoWPAN protocol?

By the way, I plan to use STM32 for the nodes and Raspberry Pi 2 for the gateway.


texts:
I have built an Arduino obstacle-avoiding car.
After uploading the code, the car does not move.
It beeps for three seconds, waits three seconds and repeats continuously.
I am using a 9V battery connected to the Arduino DC power jack and one 9V battery in PWR EXT.
Parts I have used:

Arduino Uno
L293D motor driver
4 DC motors
servo motor


texts: Is a decoupling capacitor theoretically required across the supply pins of a Hall sensor?

texts:
I am using the Hall-effect sensor OPTEK 3075S to ensure every step commanded to a stepper motor is executed. In the datasheet, they recommend connecting a 100nF capacitor across he input pins for "stable operation". I have been successfully using this sensor without cap with short supply wires for months, and now that I am planning on using this sensor after a few tens of meters I wonder if this is required.

I know it is easy enough to add the cap anyway (although I would need to build another PCB), but I do not like to add components without understanding their added value:

how would the current source of the Hall element (which apparently is a voltage regulator across a constant resistance) be less stable without cap, given that there is nearly no load, and that the power supply rejection is not so important (since this is a digital sensor)?
Certainly the opamp is the one which may become unstable? Is it possible that stability would only result in unstable transients but the output would not be affected after the step has been made?
Is there a way to quantify/estimate the gain in stability margins by adding the cap in (with respect to what? Supply variations? Hall element output?)?

Note: the sensor state transitions are located dead-on between two steps (45° per step) for stable output for every motor positions, and the motor step rate is 5 steps per second.


texts: Are IEC 60601-1-2 medical emc and FCC compatible?

texts:
I must comply with the medical EMC standard IEC 60601-1-2 but wireless modules do not come certified to this standard.
For example, telit fn980 is certified to FCC, RED, etc.
Are FCC certified devices automatically compatible with 60601-1-2?


texts: Resistors within a Darlington transistor

texts: I've been considering replacing a 2N3904 and TIP31C with a TIP102 in one of my circuits (PWM LED dimmer), and have noticed in the TIP102 schematic resistors leading from each of the bases to the emitters. My current circuit doesn't have these, and I was wondering what purpose they serve and if my circuit should have them regardless.


texts: 555 timer to work once per day for 30 minutes

texts: I was wondering if I could use a 555 timer to turn on a PI once per day for about 30 minutes. I want to use the 555 because it will take power from a photovoltaic source.


texts:
I'm a total beginner when it comes to electrical engineering and I'm getting slightly confused with circuits and LEDs in particular (or probably my whole 'understanding' of electronics but I hope it's just LEDs).

Side note: I'm not intending to play with mains voltage for now, I'm just trying to get the theory down.

So, my question is: Do LEDs care about getting (way) too much volt?

For example, take this circuit I just sketched out:

From my understanding, this circuit should feed 20 mA to each LED (240V / 12000 Ohm = 0,02A)

However I'm not using any kind of voltage dropper or anything, the LEDs are still getting a pretty high current ( 240 V / 6 components = 40V per LED, minus the x Volt they drop(?)).

So my question is: Do LEDs actually care if they have that high amounts of current passing through them, as long as the Ampere value is fairly low?


texts: How to select the correct DC servo motor

texts:
I have to buy DC servo motors for a project. The problem is, I don't know how to pick the correct one. I'm going through the datasheets from different companies, and the models they sell are based on peak stall current, continuous torque at stall, rated speed rpm, rotor inertia and so on.

The information I have is the weight of my load, the power supply, the resolution I want, and the diameter and pitch of the leadscrew. Using this information, how do I select the appropriate motor?


texts: Is there a limit of series connected LEDs when driving them with AC?

texts:
I want to drive as many as possible LEDs with AC grid voltage.

Assuming that there are \$n\$ LEDs connected in series, the voltage drop on the will be \$2.2nV\$. Then the voltage on the capacitor will be \$220V-2.2nV\$.

The capacitive reactance must be

$$ X_c = \dfrac{1}{2\pi(50Hz)C} = \dfrac{220V - 2.2nV}{100mA}. $$

The value of the capacitance follows as

$$ C = \dfrac{100mA}{(220V - 2.2nV)(2\pi (50Hz))}. $$

If everything is correct up to this point, I want to ask my question.

What limits the value of \$n\$? Of course, \$n\$ cannot be higher than the value which would make the forward voltage drop on the LED group higher than the peak value of the AC sinusoidal signal. But, is there any other physical limit below it? Is there anything that would make the circuit performance drop down, or break down something if I choose \$n\$ incorrectly?


texts: Use 74LCX245 level transceiver for SPI / I²C

texts:
I need to convert the levels of the SPI and I²C busses of a 5 V microntroller to a 3.3 V card reader and EEPROM memory so I chose to use the 74LCX245 since it's a bidirectional transceiver.

But it's only unidirectional at the end because you've to set a pin to tell it in which direction to translate the levels.

Can I still use it? Since SPI and I²C have data lines that need to enter to the microcontroller they will be 3.3 V. Because it will translate "Microcontroller -> 74LCX245 -> card reader", but there is no way to shift the data coming out of the memmory card with the same transceiver.

Microcontroller: PIC 18F2550

Is there any way to do it? Using the same device or should I end using the N-channel transistors?


texts:
I've installed new car audio into my car. It works fine for a few months now.
There is a USB port on the car audio for charging. Before actually using it, I wanted to test if it is safe enough and outputs about 5V.
So without giving a second thought, I grab my multimeter and set settings for direct voltage measurement. As I touched USB port ground and +5V pins, there was a pop in speakers and car audio shutted down, which pretty much indicated a short circuit.
After the incident I checked youtube video on how to measure USB port with multimeter. In the video, man used small metal pin between usb port pin and multimeter positive probe. (https://www.youtube.com/watch?v=xvSg1RiYDKQ)
So, as I understand, small metalic pin plays a role to reduce current?
But how come measuring car battery or wall socket is fine by using multimeter probes, but not with USB port? Why short happened?
I have little knowledge about electronics and probably shouldn't stick multimeter probes in things, but curiosity took the best of me. Would appreciate any help or links to understand the issue.


texts: what is the easiest way to make a gate that detects if something passes through a gap?

texts:
I have a home project with a device with an opening that is about 20cm (8 inches) wide. I want to attach two sensors on the sides of the opening, such that if an object passes between them, a switch is shorted (either momentarily and then disconnected, or as long as the object stays in between).
What is the easiest way to do this?
I am a software engineer but I work "close to the metal" - I am reasonably good with EE: I can solder, use meters, put together my own computers from parts. If you tell me what the method is and what the required parts are, I can probably figure out the connections required.

The objects I want to detect passing, are big, at least a quarter of the size of the opening - 5 cm, and they do not move quickly - they may spend at least half a second moving through the opening.
False positives - I can have them occasionally, say once an hour. False negatives are less OK - I would like to have, say, less than 10% chance of non-detection.
The thing is on a balcony shielded from rain, sometimes it is very dark, sometimes it is sunlight.

The objects are cats :) The device is a litter robot, which, while otherwise a perfect device, suffers from one stupid design choice, where a cat depresses a spring upon entering, which is highly unreliable - sometimes the spring gets "stuck" and won't depress, sometimes it stays depressed all the time, and this varies even if the spring is not adjusted and is kept clean. Detection of cat passing through the opening by means of tripping an electronics sensor would be far preferable.

I guess a single "Proximity sensor" that detects a moving object within 20cm or 8 inches, that was not there before, would be good.


texts: Can I program an MCU directly from USB if it supports USB?

texts: If a microcontroller has USB functionality, can I program it directly from a USB port? Can I design the PCB without a USB to serial converter? What are the precautions I should take? The example that came to my mind was STM32F070 series.


texts: Which is the best rechargeable 9v battery with high capacity?

texts:
I was looking for rechargeable 9v batteries with high capacity?
I found "Energizer Ultimate Lithium - Battery 9V Li 1200mAh" on that site bellow.

http://www.com-solutions.co.uk/products/Supplies/Batteries/Energizer/635236-Energizer-Ultimate-Lithium-Battery-9V-Li-1200-mA?prodid=1285097&info=8

But there is not nothing written about rechargeable property!
I need to know: is "Energizer Ultimate Lithium - Battery 9V Li 1200mAh" as a rechargeable battery?

Or is this "Energizer Advanced Lithium 9V Battery" as a rechargeable battery?

http://www.amazon.com/Energizer-Advanced-Lithium-Batteries-Count/dp/B008OE4I8O/ref=sr_1_1?s=hpc&ie=UTF8&qid=1415025812&sr=1-1

If it is then help me to find another one which has more capacity.
If it is not rechargeable battery, then help me to find any rechargeable 9v batteries with high capacity. Please!


texts: Giving device variable input/setting capabilities

texts:
I am working on a device which allows the user to set a certain variable value. So instead of turning something on or off, the user can set a value at some point on a continuum. For example, suppose I have a microcontroller that blinks an LED every x number of seconds. The user can select any value between 1 and 10 seconds, simply by turning a knob of some sort. The microcontroller would interpret the 'position' of the knob, and accordingly set a value for the delay.

So I looked around at electronics I own which posses a similar capability (things like radios, speakers, fans, etc.). I noticed that some of them use what I now know as a potentiometer. Sorry if this is really beginner level stuff. I know I can use the potentiometer to retrieve an analog value, and I can confirm that this satisfies my objective perfectly.

So what I want to know now is if there are other ways to achieve the same result, or are potentiometers the best and most economical way of doing this? My preference would be to have a knob like mechanism, or sliding mechanism.


texts:
I have two JST sockets that I want to connect together.

First is on this: https://www.sparkfun.com/products/8786 second is on this: https://www.sparkfun.com/products/10161

Is it possible to connect these together via cable made of two of these put together?  https://www.sparkfun.com/products/8670

Would black to black or red to black be the right way to do this. Is this safe? Is this common?


texts: What is the required VA rating of the transformer in this LTSpice power supply?

texts:
I have this circuit that I'm going to build, including the transformer. It is a simple power supply, with RC filters and one choke, I know all the voltages and currents.

Because I will design, wind and build the transformer myself (I already know all of that as well) I need to know the VAs that it must withstand.

I know that the total current load pulled from the transformer will be more than just the sum of all the DC sources because the capacitors pull reactive power that is not "used" by the circuit itself but just shuffled back and forth to keep the voltages at the nodes clean and constant.

I also know from past experience, that to find the VAs, it is not as simple as just multiplying the rms AC voltage (green, 358VAC) and the rms current flowing through the transformer (red, 1.21A) because the shape of the waveform as well as phase has a lot to do with it. The AC voltage is a sinewave, but the AC current flowing through the winding of the transformer (L2) has spikes. For example, if I just multiply both values I get ~433VA which is a lot more than I would expect.

So, the solution is to ask LTSpice to do the work for me and ask it to plot a graph of the power consumed (pink). The problem is that it shows the average value, not the rms, and there is the dilemma. Are those 144W average the VAs that the transformer will be working with and thus, the figure I have to design the transformer around? If not, how can I calculate or approximate the RMS value from that AVG value?

EDIT:
This circuit is the power supply for a 50W vacuum tube amplifier I'm designing. The power consumption of a commercial amplifier that puts out 120W is claimed to be 300W, so the reading LTSpice is giving me does make sense, it is a little higher still considering that the transformer will have more windings that will draw an extra of about 35W in total, but that's because efficiency overall decreases with power, so the 144W is in the ballpark, I just want to confirm it.


texts:
I have a power supply that buzzes when nothing is connected and is silent when there is a power drain. What could it be?

It's a PC power supply that I used to power an LCD through its 12 V line.


texts: How to simulate VHDL program without FPGA

texts: I want to learn VHDL, and I wonder if I can find any tool that allow me simulate a VHDL program without having an FPGA. I do some search in internet, and I found this list of HDL simulators, but I still don't know how to implement a VHDL program in a simulation.


texts: ARM compatibility between vendors, with and without RTOS (FreeRTOS)

texts:
I would like to know how much compatibility can I expect between ARM MCUs from different vendors.

For example, let's say I write a firmware using C language for a Cortex M0 using its CAN peripheral. Will I be able to port it to a Cortex M0 from a different vendor with no changes? (or at least minimal changes) Or peripherals are completely different between them?

And what about if I use an RTOS like FreeRTOS? Does FreeRTOS abstract from the hardware so I'm able to port my software easily?

Finally, are all ARM Cortex M0, M4, etc from all vendors supported by FreeRTOS? Or only specific models of specific vendors?


texts: Identify the problems in this Verilog snippet

texts:
I think that the code below is wrong because it uses blocking (=) instead of non-blocking (<=) assignments but since there is only one statement in the always block is this an issue?

Also, it is sensitive to op but it also updates op within the always block, will this create some sort of loop condition?

Are there other problems with it?

always @ (a or op)
begin
  op = a + b;
end


texts:
Can you run a BLDC motor backwards without damage?

Is it OK to drive a model airplane BLDC engine backwards while landing, so it gets a little "reverse thrust" and come to a stop a little quicker on the runway?

Is it OK to drive a model helicopter BLDC motors backwards so it can hover upside-down?

Or do I need to design the hardware so that it never drives the motor backwards, under any circumstances, no matter what the pilot on the ground does at the transmitter?


texts: Using UART clock 3.6864 Mhz for a microcontroller

texts:
I want to use a 3.6864 MHz external oscillator to clock my ATMEGA328p to ensure 'error free' serial communication. When I looked at this page, I see that 3.68464MHz is also represented as 2*1.8432 MHZ.I'm at a loss as to what this means. Does this mean that I'd have to use two 1.8432 MHZ clocks to somehow generate 3.6864 MHz?  Or does it just show me how this value (3.6864 MHz) came to be? If the former is true, how CAN I generate 3.6864MHz with two oscillators at a lower frequency? Are oscillators available at these 'multiple' rates of 1.8432MHz?

Will this communication will truly be error free as the page linked claims?

How would I connect the oscillator to the microcontroller? The datasheet confused me a bit because section 8.4 makes it seem that I place the oscillator between XTAL1 and XTAL2, while 8.8 suggests that I connect it to XTAL2 with XTAL1 not connected. So there's some confusion there, though 'm inclined to think that the latter is what I'm looking for. But, how can I connect the two pins of an oscillator to just the XTAL1 pin?


texts: How would i set up an Arduino to do time lapse photography?


texts: FDRE with RST tied to 0 to synthesize a value at reset at 1: hardware value not correct, why?

texts:
Here is the code of a developer (let's ignore the name of the signals):
always_ff @(posedge clk) begin
  if (rst) begin
    buff_eop    <=  1;
  end else if (tx_usr_axis_tvalid & tx_usr_axis_tlast & tx_usr_axis_tready) begin
    buff_eop    <=  1;
  end else if (tx_usr_axis_tvalid & tx_usr_axis_tready) begin
    buff_eop    <=  0;
  end
end

Synthesis result:

Truth table of the LUT:

I'm unable to explain the developer why the code doesn't produce the correct behavior in hardware (but does it in simulation)

UUG974:

Using a proper "else" doesn't solve anything:
always_ff @(posedge clk) begin
  if (rst) begin
    buff_eop    <=  1;
  end else begin
    if (tx_usr_axis_tvalid & tx_usr_axis_tlast & tx_usr_axis_tready) begin
      buff_eop    <=  1;
    end else if (tx_usr_axis_tvalid & tx_usr_axis_tready) begin
      buff_eop    <=  0;
    end
  end
end

Assumptions

The FDRE's reset value is 0, the compiler tries to synthesis that using LUT and a feedback.

Conclusion: Any registers have to be reset to 0 and nothing else, this should be a developer rule.

The only explanation I can have is looking at the logic table, it stays forever in the Q=D state that might be undefined (or 0 here) forever.

even though the reset signal (that isn't the FDRE's reset) is high, something prevent the FDRE to become high for whatever reason. Looking at the LUT's truth table, the output should be 1 when I4 (our rst signal) is high.

It works in simulation.

Test from nanofarad's comment:
module top(
    input logic clk,
    input logic rst,
    input logic tx_usr_axis_tvalid,
    input logic tx_usr_axis_tlast,
    input logic tx_usr_axis_tready
);

(*mark_debug="true"*)logic buff_eop;

always_ff @(posedge clk) begin
  if (rst) begin
    buff_eop    <=  1;
  end else if (tx_usr_axis_tvalid & tx_usr_axis_tlast & tx_usr_axis_tready) begin
    buff_eop    <=  1;
  end else if (tx_usr_axis_tvalid & tx_usr_axis_tready) begin
    buff_eop    <=  0;
  end
end

endmodule


texts: Hourly electrical load profile data for domestic home: where to find?

texts:
I need at least hourly data for individual households' electrical load profile for a renewable energy system model.

I've had a look online and struggled to find such data. For example I've found this

but not only is it 20years old, it looks like it isn't from an individual house.

The UK Household Electricity Survey, which monitored a total of 250 owner-occupier households across England from 2010 to 2011 would be ideal, however the actual data they collected I can't find.

Their report, here shows the report etc, but not the actual data.

Where might I find the actual electrical usage of a household? Could energy companies provide this?


texts: Can a transistor's emitter and collector be used interchangeably?

texts:
I'm trying to understand the standard TTL NAND Gate in TTL level.
But confused with the transistor Q1 operation in the diagram below:

Apparently when A and B are together HIGH, the Q1 base-emitter junction is reverse biased.
Collector-base junction is on the other hand forward biased. So the current flows through R1 and turns on the transistor Q2. So far so good up to here.

Here is my question: How can a BJT(probably npn) transistor such as Q1 can operate in such way? I mean when I learn about transistors the base emitter collector connections are very important. But from this Q1 I conclude that one can use base and collector interchangeably. Is that right?


texts:
The data sheet states:

"Integrated 3.3V level converter" on the UART and CBUS pins. (https://cdn.sparkfun.com/datasheets/BreakoutBoards/DS_FT232R.pdf).

I just want to confirm that means it's rx pin can accept 5v and will handle any level shifting internally automagically.


texts:
I am at a loss of whether I need to use an FPGA or a microcontroller.

I need to build a robot that can chase my cats around and shoot them with a water gun.  So there seems to be a number of parallel processes going on, including:

ultrasonic detection
color detection
motors
infrared remote commands
navigation
other stuff

Should I do this robot on FPGA?  I mean programming it in C on a microcontoller would be super easy if I could use pthreads or something.  Not interested in maintaining a bunch of finite state machines, I think doing it in just logic gates would be hard too?

Or maybe I need something like parallella or raspberri pi with a breakout board?


texts: How do I repair the solder of this component?

texts:
The chip is a chip that is surface mounted to the main PCB.
This solder gave out and separated from the PCB as shown below.

I'm not very well skilled in soldering, but it seems a bit too fine for a normal soldering iron. Should I use solder paste and a heat gun? Or is there a better way?


texts: Implications of routing same signal on top and bottom of PCB?

texts:
What are the implications of routing the same signal on the top and bottom of a PCB?

I have a situation where it would save me a via to do this just for about 3mm.  I'm routing an I2C signal to a connector on the bottom side whilst my pull-up resistor is on the top side.  Components are constrained to the top side, and there are other top-side signals that make it impractical to route the I2C signals on top.

When SDA is low, current will flow from the pull-up resistor to the connector pin and most of it (minus the slave's leakage current) will flow to ground through the master device (green trace on the PCB).  Therefore the current on the top and current on the bottom will be flowing in opposite directions.  Using the right-hand rule I believe the fields in the traces will cancel between the traces and everything will be peachy (i.e. EMI emissions won't compound).  But my signal integrity chops aren't too sharp -- am I overlooking something?


texts:
I would like to use a microcontroller to control when a pump turns on and off. I will use a 12 volt battery to supply both the dc motor for the pump and microcontroller. How can I interface the microcontroller with the dc motor?

Thank you stackexchange community


texts:
Is it possible to charge an 3s (3-cell wired in series) lipo battery with a balanced charger (and using the balanced charger port of the battery ofc) and connect a load to the discharge port of the battery at the same time?

For example using:

Charger: http://www.hobbyking.com/hobbyking/store/__7637__Turnigy_12v_2_3S_Basic_Balance_Charger.html

Battery: http://www.hobbyking.com/hobbyking/store/__92447__Turnigy_700mAh_3S_30C_Lipo_Pack_XT30_.html

My concern is that the charging is done by wiring the cells in a semi parallel way (all ground are tied together and each positive are going to the charger) and drawing is by connecting the cells in series - wouldn't it short circuit the battery?


texts: If temperature is not an issue, what can be said about the different ceramic dielectrics

texts:
Let’s assume we have a circuit whose operating ambient temperature range is well-regulated to 25+-5C. Besides cost, what would be the use cases for the different ceramic dielectric types? In other words, what would be the applications is which a specific ceramic dielectric would perform better or worse than others? Can we make any generalizations?

I know that ceramic capacitor letter codes are supposed to indicate temperature dependency of the dielectrics, but is there something more that can be said about it as all of these questions suggest?

ltc3525-datasheet-states-that-capacitors-must-be-x5r-or-x7r-not-y5v-why
Why-do-manufacturers-strongly-discourage-using-x7r-capacitors-in-ac-signal-and...
What are Y5V or Z5U capacitors good for?
Ceramic capacitors microphonic bandwidth
Do multi-layer ceramic capacitor specifications vary within a dielectric class?

I also know that package size affects the parasitics and thus the resonant frequency and loss of the caps. That some dielectrics are not available in smaller packages and higher voltages, and that many ceramics exhibit piezoelectric/microphonic effects (which ones?). Can all of these factors be condensed in a few rules of thumb?

I have also noticed that manufacturers datasheets seem to assume a specific application for the capacitors, for example by not specifying leakage, resonances, or losses in some of them.

But, if ambient temperature is not a factor, what capacitor would be best for a specific job. Is self-heating an issue for the application/specific type?

All of my commercial circuits so far have not been cost-sensitive, so I just specify X7R, X5R, or NP0 for all ceramic caps, as I see those suggested in IC datasheets. But is there something more than temperature dependency behind those suggestions?

Should I pay more attention to the cap purpose? E.g., use X5R/X7R just for power bypass and regulation, but NPx for anything that is in the signal path? Can any generalization be made, or it is an issue that requires detailed reading of the (very incomplete) manufacturers datasheets?

In short. Are there any general principles that can be applied to simplify searching for parts during a design?


texts: How to estimate the peak current of DDR3L DRAM and design a power supply

texts:
I am designing a board which will have 5x DRAM DDR3L Micron MT41K512M8DA-107XIT:P (\$V_{DDQ}=1.35V\$). The question is, how to estimate the peak current consumption of the DRAM and then design a power supply?

In their datasheet Micron specifies Burst refresh current \$I_{DD5B}=160mA\$.

However, this is just an avarage current measured over time as the DRAM Refresh command is executed repeatedly. I need the peak current to design my PSU.
I checked Micron document TN-41-01 "Calculating Memory System Power for DDR3". It discusses just average power consumption, not peaks. It shows some example graphs with averages and peaks; for an example see below - the blue line is average given in datasheet, the green is the real current profile, but no actual values are given. It seems peak currents are manufacturer's secrets...

Who has an experience with power supplies for DDR3L? What other pitfalls are there?
I already know about VTT and VREF requirements; for that we could use TPS51206 if needed. But for the \$V_{DDQ}\$ supply I hesitate between TPS51916 (a complete DDR supply), and a general TPS54620 that we plan to use for other supplies.


texts: Class-D Amplifier working outside audio range frequencies?

texts:
I've been wondering what could possibly limit the use of class-D amplifier to audio range frequencies. When I look at some class-d amplifier specs, it seems that a lot of them can't reach great linearity at the end of this range.

Why can't we use them above that limit ?

Is the modulation method part of the answer ?


texts: Audio: Digital Potentiometer is Noisy Compared to Analog Potentiometer

texts:
I am building an A/V switch that I would like to have a headphone output with adjustable volume, controlled by a microcontroller. As a test, I connected an audio source to a potentiometer (input to a, wiper to headphones, ground to b) and had clean sound at whatever volume I adjusted it to. Now I'd like to do the same thing with a digital potentiometer and I'm running into weird audio distortion.

If I set up using the STYLE 1 diagram, the audio comes out just fine at max volume but 'crackly' at anything below that. On a whim, I tried adding some series capacitors as seen in STYLE 2, and this makes the problem go away at certain low volumes but certain middling volumes have the same crackly sound.

While I tested this, ARI and ALI were connected to the audio output of a nintendo 64, and ARO and ARI were connected to either my tiny audio-technica earbuds or a taotronix soundbar.

Is there a name for the problem I'm running into, and how do I avoid it?


texts: Confused with diodes and conventional vs real current flow

texts:
What would happen in the following hypothetical situation?

pd : images below

A diode must actually receive the electron current and voltage on its negative side, i.e. the N-side.

And that is why we connect the positive side of the battery to the anode and the negative side of the battery to the cathode of the diode, because in reality, a diode receives voltage and electrons from the negative side of the battery, because in truth, the current and voltage flows from negative to positive.

And I know that we, like everywhere else, we use conventional current but...

What if, for example...

We have two diodes in one circuit.(light light-emitting diodes)

One diode A is located above the circuit, and it needs a bias forward of 0.7 V to turn on, if it does not receive that amount, it will not let any electrons pass through it.

The other diode, called B, is on the right side of the circuit, and needs a 0.4V bias forward to light up.(let current flow)

And so, with the battery on the left side of the circuit, the battery is 0.6V. So this battery would let us turn on the B diode but not the A diode.

The battery has the symbol + up and - down, like all the others.

So...

in this case, wouldn't the diode led B light up without the need of  the diode A to pass current?

Because according to the conventional current model: the voltage and the current would come out from the + side of the battery, it would go through Led A, and Led A would not receive enough forward bias, so the electrons would be stuck, and the voltage would reach Led B, but the current would not, so Led B would not light up.

Although according to the model of real current direction: the voltage and current of the battery would come out from the - side of the battery, it would go through the cathode of led B, with enough forward bias (+0.4 needed for led B) and the current and voltage would come out from the anode of led B, this current and voltage would reach the cathode of led A, and because it does not have the necessary forward bias, it would not turn on ...

So, based on the actual current direction, wouldn't diode B light up, even though no current passes through diode A?

Thanks :-)

images here


texts: I have disassembled a phone charger today and I have found some interesting feature that I do not understand, I have marked it on the picture. Left side of this structure is connected to P1, that is pin which is inserted into the socket in the wall. Paths on the right side are connected to output wires. I can't figure out what is the purpose of this structure and why these pads look like  forks.


texts: analog to digital conversion using operational amplifier

texts:
I have found this circuit. It's a RFID tag reader. It uses 2 op-amp to make the analogic to digital conversion.

I don't understand how does it works.

Can anyone explain how does it make the A/D conversion please?

Link to the circuit: http://www.serasidis.gr/circuits/RFID_reader/images/125kHz_RFID_reader_schem.GIF


texts: importance of PCB/Trace antenna position relative to components

texts:
This might be a very novice question but I could not find the answer anywhere. When I encounter wireless modules such as the ESP's the trace antenna is always above the shield.

Would performance be negatively impacted if the trace antenna would be positioned to the right or left instead? (please also see the image)


texts:
I have been learning about digital electronics and playing with some simple integrated circuits like the 7400 series. The 7400 chip, for example, has four NAND gates and I understand some of the uses of this chip. I can see from, for example, Texas Instrument's website that these simple type of chips are still sold.

It seems that most electronics today is very small like laptops and smart phones. So my first question is:

What is the use of simple integrated circuits like the 7400 chip today besides as chips used for learning? Where are they needed?

Where can these chips be found in products that are produced today?

The second question is related (and I don't think it makes sense to start an entirely new question on this, but correct me if I am wrong):

Are basic logic chips, like the 7400, still being produced large scale today?


texts: Can i use 47 kilohm potentiometer instead of 50 kilohm potentiometer?

texts: I am trying to build a circuit from a schematic I found on Internet. The circuit uses 50 kΩ potentiometer. But I have only 47 kΩ potentiometer and 100 kΩ potentiometer with me. Can I use them instead of 50 kΩ potentiometer?. will the circuit work with them or will it fry the circuit?


texts:
As part of a current-to-voltage preamplifier that I'm working on improving, I'm trying to model the current source of an scanning tunneling microscope (STM). The way it works is described below (based on my understanding), with the block diagram shown below. Given a material sample, it is biased at some voltage level. The STM has a special tip, and a current passes through the tip from the biased sample, with the STM using that current measurement as a way to view the surface of the sample. The tip starts at X=0, and it moves up/down until the computer measures a specific current. Once it sees that current, it moves on to X=1 (or whatever the next point is) until it reaches the end. Think of it as scanning in a grid-like motion.

simulate this circuit – Schematic created using CircuitLab
This block diagram may be more complicated than I'm making it, but this shows the rough idea of how it works based on my understanding. That tip current is converted into a voltage for measurement later on. In LTspice, I was simulating the current as an ideal current source, but how do I model the parasitic capacitance between the tip and the sample? Is there a standard value that is used to model the parasitic capacitance, or does it vary?


texts: DC MMF and flux density variation in space

texts: If flux density produced by DC current is sinusoidally distributed in space why do we say that DC MMF is space invariant?


texts: Hall Effect Sensor Wiring for Crankshaft Position Sensor

texts:
Please forgive my ignorance in my description. I have looked around and been unable to find what the following symbols mean: on wire number 51 there is a black filled circle with a dashed circle encompassing wires 1868 and 1869 going to the hall effect sensor. What does this mean? Also, what does the "sideways Z" symbol across those wires mean?

Electrical Schematic


texts: Why are there unconnected exposed pads on PCBs

texts: I've seen this in several designs. What purpose do these serve?


texts: Using both PWM and Timer2 interrupt in PIC18F25k50

texts:
Background

I'm working on lead-acid battery charger and experimenting with battery desulfation.

I want to draw current vs time graph on graphic LCD and see:

how high current spikes I have
measure RMS of my current if possible

I expect something like this on ADC input:

Question

Can I use Timer2 interrupt when PWM is already using Timer2 in PIC18F25k50?

I want to use that interrupt to "synchronise" my ADC measurements with PWM and catch  current spike.


texts:
I want to make a combined MIDI In/Out/Thru + MDX Output shield, so I can order/design just one shield for all my needs.

It is intended to use the shield for Arduino Mega which has 4 UARTs, and I want to stack multiple of these on top of each other, and use jumpers to select which UART pins will be used for MIDI In/Out (1 UART = 1 MIDI In + MIDI Out).

For the DMX part, I could do the same, not thought about that yet, I probably need one DMX output, so I just use the DMX output of one shield and not use the others (maybe not even solder the components for it).

Also, maybe in the future I want to move to Arduino Due, which is 3.3V, and I might need an alternative routing for some components.

What is the best way to create this flexibility (especially for the UART pin selection)?

I was thinking about the following two solutions:

Solder pin headers and use jumpers to make the correct connections; because the device will be transported a lot, I might glue the jumpers.
Solder pin headers and I solder small wires as jumpers (like permanent wires).
Use resistors to make the connections, 0 ohm like a jumper, and do not solder the other connections.
Dip switches.

But maybe there are better solutions I didn't think about.


texts: How to measure RF power with an oscilloscope?

texts:
I'd like to measure the RF power coming from an RF amplifier using an oscilloscope.

The signals are sinusoids with a frequency of 50-120 MHz. The maximal power coming from the amplifier is 20 W, which is attenuated by a -3 dB RF attenuator. This power is delivered directly to the load (50 ohms), which is an ultrasonic transducer. The cables used are SMA coaxial cables.

I'm planning to put a T-splitter between the load and the attenuator, and use that to send the signal to a high frequeny digital oscilloscope set to 1 megaohms.

However, the oscilloscope can only handle 9 V RMS on its inputs at such a high frequency. So I thought that I could use a compensated 1:10 passive probe to attenuate the signal. But now I see that these probes aren't designed for frequencies like 100 MHz, and to cut the coaxial cable arrangement (for the probe) may not be the best idea, either. What is your opinion?

Alternatively, we've got some 50 ohms -3 dB RF attenuators, so I could wire them in series and put them between the T-splitter and the scope set to 50 ohms. Is this going to work? Won't they present a different load to the amplifier? Do I need to set the scope to 50 ohms in this case, or can I leave it on 1M (so it can handle a greater voltage)?


texts: Does any of those internet tips to recondition Li-ion batteries actually work?

texts:
If you google "fix liion battery" of similar, you'll get the following tips on various sites:

Fully discharge and charge battery - this sounds like completely bad advice since discharging Li-ion batteries under 1V permanently damages them
Freeze the battery for 24 or more hours - I think freezing the battery increases risk of rupture due to thermal contraction/expansion
Shock the battery with 5V - this advice is based on some Li-ion battery sleep mode, I don't really understand what it's about
Connect the battery anti-parallel to another working battery - I don't see how this is different from using charger, but if it doesn't work it will multiply the amount of broken batteries.

So is any of those common tips viable, or are they just dangerous experiments that yield nothing?


texts: Calcultions to choose between a transistor (switch)

texts:
thanks in advance :).

I am a little bit confused, i need to turn on a led lamp (5watts), using a light sensor from my Arduino. I was reading a lot of theory the past two days. Here is the deal:

What i understand is the next:

To choose the transistor i need the current, voltages and pose consumption of the load. And also i need to limit the current to the load from the source and put a resistance from the arduino too.

1st: I need a lamp of 5 watts(led lamp).
2nd: I have a 12 volt battery at 7A/H.
3rd: My arduino gives me 5V and 40mA.

Since i need 5watss i can find the current to turn on my lamp using P=IV. 5W/12V=.416amperes.
Then i need to limit the current from the source, if i have 7A, i need to waste (eat 6.5 Amperes). I Find a resistance capable if this using I=V/R, R=V/I, R=12V/6.5A, R= 1.84 ohms (or 2 ohms).

Then i got the resistance from my load at my input. Now i need to find a transistor supporting that values and the resistance from the base to my arduino. How i do that?.

I Know the currents must be additive then IB+IC=IE, since i know how many current i have from IC and IB i can use kirchoff laws to find the resistance from my arduino.

IB+IC=IE, then IB=IE-IC, then VB/RB=IE-IC but then IB and the associated values VB and RB depend on the transistor?, finding a model of transistor i find how many current i need to swicht some current from C and the i need to couple that current from the data sheet with a resistance to switch the arduino?.

I am missing something? or i am wrong at everything? :S


texts: Can somebody please analyse this circuit

texts: Can somebody explain to me how this circuit works? i understand that it is an audio amplifier circuit and it inverts the signal, and inverts it again, but i am not sure why this is the case. also ignore the question marks next to some values.


texts: I am trying to design a system that will transfer data between two storage devices on a PCB, preferably using USB 3.1 as speed is a major concern in this design. However, my understanding is that I would need something to serve as a host controller to actually transfer the data between the storage medium. In my research I've been unable to find any microcontroller that has USB 3.1 capabilities. Is there any other way I can transfer the data at high speeds, or a method of using a microcontroller with a separate USB host controller without any significant loss of speed?


texts: One Channel Relay Board with NRF24 / WiFi connectivity with built in power supply

texts: I have been looking out for a board which has a one channel relay along with some wireless connectivity such as a NRF24 module or a Wemos D1 Mini attached to it aong with a built in power supply. Is any such module available and if not is there any custom module whose gerber file I can use ? I need this to create any bulb socket or plug socket into a smart plug or smart light.


texts: Can a spice library contain different component types?

texts:
A pretty simple question that I'm having a hard time finding the solution to on the internet. I have a spice model of a diode in parallel with a resistor that represents leakage. It is a subcircuit model as seen from spice but is used as a diode. Could I include this model, defined by .SUBCKT in a .lib file full of traditional diode models that have only have a regular diode model, defined by .MODEL?

Thank you in advanced.


texts: Why mosfet is preffered over voltage divider for voltage level shifting

texts:
Before writing this question I read several similar threads, but didn't found the answer I am looking for. When we need a voltage level shifter the first thing that come to the mind is a voltage divider. But in certain cases in the industry, a MOSFET inverter is freferred when it comes to digital voltages involving input to a FPGA or Microcontroller.

For example, if I have 5V output from a device to represent Logical 1 where the PMODs of FPGA can read a maximum 3.3V for logical 1, I need a level shifter for sure. Whenver I tried to use a voltage divider circuit as in B of the below image, I was recomended to use A in the image. Even though A ouputs inverted logics and needs manupulation in the software to invert values read, it is always preferred. I never got an answer for that but it could be related to pull up resistor behaviour of the LVCMOS.

So my question is why A is preferred over B when it comes to digital inputs to FPGA and Microcontrollers?


texts: What mechanism happens inside a resistor for potential drop and constant current?

texts:
What process happens inside the resistor just after being connected to a battery?
I am trying to get a picture of it.

On applying a potential difference, the electric field it generates pushes the electrons to the lower potential end and in the way to the other end these electrons collide with ions and loose energy.

Is it that the electron has zero energy by loss of potential in the form of extra kinetic energy (besides random motion) on leaving the resistor? Is all the energy lost in the resistor? What mechanism causes all the energy to be lost in the resistor and zero energy in form of extra kinetic energy?


texts: Do practical implementations of LC filters have a limited bandwidth over which they operate? ie. Would they start to attenuate less as the frequency of the input signal get very high (MHz->GHz)?


texts:
I have a decade voltage divider used for range switching in my project. I need a way to switch the multiple different voltages that the divider creates into one output, sort of like a multiplexer shown in the diagram. The device also needs to be able to tolerate 500v on the input, but does not need to be able to switch it to the output.

I have tried mosfets in a simulation, but could never get them to work. If I can't find anything else, I could just use relays, but i'd rather not as they are expensive.

Any help would be great, thanks.


texts:
I have a speaker with the following specs:

Max. power -  600W
Impedance - 4~8 Ohm
Freq. response - 45Hz-20KHz
Sensitivity - 98dB/W/M

The tweeter of the right speaker is not working so i want to replace it with new one but i cant decide how many watts should i buy. I read somewhere that the 600Watts of the speaker is the total wattage of the woofer and the tweeter and should be 1:10 ratio.

I am deciding to buy a new tweeter with the following specs:

Power: 300 Watts
Impedance: 8 Ohms
Sensitivity: 104 dB / W / M
Freq. Response: 2kHz ~ 20kHz

is it okay for the given specifications of the speaker or it'll not be compatible?


texts:
Below is a picture of PCB that has a bunch of copper(?) points for connections.

What are these connections called and how would someone solder wires to these points.

When trying to solder 30 AWG wires it would seem to work if it was a one-off but when there were multiple next to each other it seemed too tight.

Also what does TB stand for (each point seems to be named TBxx)


texts:
I am working with ili9341 TFT Display with STM32F0 MCU. And TFT display was connected with 3 configuration.
I am confused between sending the "command" and "data" using spi communication.

So can anyone guide me, for sending "command" and "data" to TFT display using stm32's spi configuration.
(Like I have make some pin high or low for "command" & "data" transferring)

Thanks


texts: I designed a touch PCB keypad what can I do for silking and covering

texts:
I want to design a custom keypad for my board. I put my board in a Plastic box 15cm x 19cm and the box has a simple box door.

I want to put a keypad and a 2x16 character LCD in this door to control the board.the box must be water resist. I want to change or modify this door so that it looks beautiful. currently I want to design a Capacitive touch keypad but what is next or how can I put it in the box. My question is what kind of keypad do you suggests and how much is the cost? I can even change the box if a better suggestion.


texts: Keyboard matrix and its microcontroller type

texts:
I'm planning to make a custom 108 keys keyboard from scratch. Unfortunately, I'm currently stuck in a circuitry situation. Is there a lean matrix that I can go with for this and what kind of microcontroller should I use?

I know this sounds very stupid (mainly because I am entirely new to this field), but is there a maximum amount of key switches for each pin on a microcontroller? If so, how do you tell? Is there a calculation for this?


texts:
I'm trying to build a half H-bridge using an IR2104 driver. I want to use it for driving "high power" things such as a brushless motor (100V, 40A), or high power LED (200W).
But it doesn't work as expected: When I increase the "power" voltage (50V on the schematic) to more than 10V, the voltage at the output of the half H-bridge (Uout) doesn't increase to more than 10V. I measured the voltage between the gate and the source of the IGBT Q1, there is nearly no voltage difference (0.3V). Q1 and Q2 are FGH40N60. The Arduino is powered by an external 12V power supply, so the Vin pin of the Arduino also outputs 12V.
On the input side of the IR2104, I have an Arduino Uno which sets IN (pin 5 on the Arduino) to 0V (LOW) and pulses -SD (pin 3 on the Arduino) 5 microseconds HIGH and 1 microsecond LOW in the main loop.
Can somebody help me to increase the output voltage to be nearer to the power supply voltage?
The code on the Arduino is:
void setup() {
  pinMode(3,OUTPUT);
  pinMode(5,OUTPUT);
  digitalWrite(3,HIGH);
  digitalWrite(5,HIGH);
  delay(500);
}

void loop() {
  digitalWrite(5,HIGH);
  delayMicroseconds(5);
  digitalWrite(5,LOW);
  delayMicroseconds(1);
}

And the schematic:


texts:
I have a System Sensor B401 model smoke sensor.
I want to connect it in 2 wire mode. I want to connect multiple of this smoke sensor in daisy chain fashion with EOL resistor. I read on the internet that it has 2 wires which is a supply as well as detector line.
When there is no smoke, this sensor operates as an open circuit but when there is smoke, then this sensor acts as a short circuit. I wanted to know what is the voltage level on supply line (2 wire) when the smoke is detected (when it gets shorted due to smoke.)
Datasheet link for the sensor is https://www.systemsensor.com/en-us/Documents/B401_Manual_I56-0338.pdf
Also when it becomes short, won't it cause problem to the supply line(2 wire?) What kind of circuit can I use to detect alarm?


texts: What kind of ranges exist for potentiometers?

texts: I am building a small dc motor that is driven by a 2v AA battery. I want the potentiometer to adjust the speed of the motor by increasing and reducing the current through the motor. For this i am using a potentiometer, but the current i have is for very high resistance. What are the common ranges potentiometers operate at? Does it exist a potentiometer that ranges from say 50 ohm - 0 ohm? Or maybe somewhere similar to that? Like the standard range for those meters with the lowest resistance.


texts: Laser tag IR LED beam reflection problem

texts:
I built a laser tag gun using an Arduino,but there is a problem. When I use it indoors with lens or without I have beam reflections. If I shoot on the wall the reciever also claims a "hit." Is there a method to prevent the beam reflection?
I'm using IRremote.h library. For recieving the message I use a TSOP32236 reciever and I use 8 degree angle IR LED.
    #include <IRremote.h>

const int RECV_PIN = 7;
IRrecv irrecv(RECV_PIN);
decode_results results;
const int led = 10;

void setup(){
  Serial.begin(9600);
  irrecv.enableIRIn();
  irrecv.blink13(true);
  pinMode(led, OUTPUT);
}

void loop(){
  if (irrecv.decode(&results)){
        Serial.println(results.value);
        if(results.value == 2704){
          digitalWrite(led, HIGH);
          delay(100);
          digitalWrite(led, LOW);
          }
          else {
            digitalWrite(led, LOW);
            }
        irrecv.resume();
  }
}


texts:
I work with Xilinx Vivado 2020.1 and a set of selfwritten AXI Stream components. My VHDL code allows to set the length of TDATA, TUSER, TID... freely over generic. This works perfectly until try to include a Xilinx IP. For example, lets assume we want to include a FIFO IP from Xilinx into our code. To generate the IP I need to know all parameters, then I can run a TCL command to generate this IP for me.
But at the time I could do this, I don't know the parameter setting yet.
Of course I could now generate every possible combination and use "if generate". Brrrrr..... Sounds awfull.
As I want to package the code into an IP of my own, I will be able to set the parameters for my set of generics over the GUI.
I was looking for a possibility to generate the Xilinx IPs according to the configuration made on the xgui. This should be possible using some TCL functions.
Have you experienced this issue and how did you solve it?


texts: Gated clocks and clock enables in FPGA and ASICS

texts:
Please correct me if I am wrong. I have generally read that for FPGA's gating the master clock is a bad design practice and that one should use master clock & clock enable whenever circuit needs a divided clock and use a PLL for multiplying the master clock.

Does the same principles apply to ASIC designs as well ?

What are the safe design practices when circuit needs a divided or multiplied clock ?


texts: How to get 5v 2a from low voltage, high amperage solar panels

texts:
I am attempting to make a usb solar charger from 8 solar panels.
Each solar cell rated as such:

Max Voltage: 0.574 V
Max Current: 2.915 A

From what I understand if I connect 8 of these panels in series, their voltages add up to a total of 4.592 V @ 2.915 A

Firstly, how can I set up a circuit so I get a steady flow of 5V and a maximum of 2A from the solar panels, while still allowing for headroom, meaning that if ideal weather conditions aren't met, causing the panels' voltage and amperage to drop, I would still get 5V but amperage could be allowed to drop?

I've browsed the web for up-step voltage regulators but they mainly deal with maximums of 500mA. What other solutions are there, or can I hook up multiple voltage regulators to get a max of 2A? Additionally 8 solar panels is the maximum amount of panels I can fit on my project.


texts:
Under what circumstances should I prefer a continuous rotation 'servo' to a DC motor, or vice versa?

It seems to me that to use a DC motor, I'm going to need three pins from an MCU -- two for forward/backward/brake/coast and one for PWM.  On top of that, I'll need an H-Bridge.

For a continuous rotation servo, I'll only need one signal pin and some code to send proper timing signals.  I can't control the speed of the servo, can I?  Also, it must have something akin to an h-bridge inside the motor, which surely ups the cost, but the motor will always be geared, which is a plus.

So, what are the pros and cons of each, and when should I choose one over the other?


texts: Are vias underneath a SMD component without a thermal pad useful for cooling?

texts:
I want to cool this bridge rectifier from Diotec in my circuit to minimize radiated heat by placing a small copper area directly underneath it and connect it to a larger copper area on the opposite side of my 2-layer PCB through vias.
Is this technique useful for cooling the component even though it does not have a dedicated thermal pad?


texts: least GSM power in dBm required to send an SMS

texts:
I deploy an application in the forest using an M2M module (SIM968). I have read through its datasheet but I am not able to find out what is the least GSM power that should be incident inside the forest to perform a simple SMS transmission or a GPRS transmission. (I guess both use 2.5G technology, please correct me if I am wrong)

Attached is the 2.5G coverage map of the network provider and I am interested in knowing if I would be able to transmit am SMS or perform a very small (of 10-15 bytes) TCP/IP transmission when the coverage is at -105dBm.

p.s.

I had a conversation with a network engineer of a respective provider, he advised their cut off point is at -102dBm.


texts: How can I use transistors to work as an SPDT relay using the common pin as input and NC/NO as outputs?

texts:
PS: If you're impatient, you may skip to THE_POINT below:

Basically, this is for various lights in a car - indicators, park/rear light, brake light. I want to convert the simple output from non-American cars to lights similar to the American standard - in other words:

pure red rear lights where the brake light bulb also works as indicator
side markers that are lit when park light is on, but turns off when the indicator light goes on, making them blink alternately from the indicators
side markers still blink when the park light is off, but in this case they blink simultaneously with the indicators (but, I wouldn't mind if they would blink alternately)

In other words:

BRAKE XOR INDICATOR
PARK XOR INDICATOR

I've implemented this many times using Single Pole Double Throw relays.
For normal light bulbs, you only need 4 SPDT relays converting the 12V or floating signal to proper 0V or 12V, one for each of right indicator, left indicator, park light, brake light. You connect ground to the Normally Closed pin of the relay 12V to the Normally Open and use the common pin as the new output.

For the indicators in front, which uses double bulbs, you connect park to 5W and indicators for the 21W connector and ground to ground. This works even without the relays.
For the side markers you connect park light to one side and the indicator to the other side of the bulb.
For the rear blink/brake light, you connect the brake light to one side and the indicator to the order side, You can't a use double (5W/21W) bulb with rear light on the 5W connector because then there will be no light when both the indicator and brake light is on, not even rear light - which is wrong.

Now, this is all fine, but it further complicates things if you want to use LED light, and they obviously won't work with 12V on the wrong side, so I now need:

2 relays using brake light as one input and left/right indicator as the other input - the output goes to the red brake/indicator light
2 relays using park light as one input and left/right indicator as the other input - the output goes to both front (orange) and rear (red) side markers

It feels a but wrong though, to use relays that sometimes draw more power than the LED lights they drive, so I wish to do is using electronics instead.

THE_POINT:

What I'm looking for then is:

(A) a circuit that have two inputs which are 12V when on and are floating when off, and outputs 12V if either of the two inputs are high, and 0V if both are low or both are high. This is exactly the same as a logical XOR gate - and yes, I'm considering to use one of those with a mosfet driver if it gets too complicated.
(B) a circuit that takes a floating-when-off and 12V-when-on signal and turns it into proper 0V when off and 12V when on, and which can drive a couple of amps.
(C) if it saves a few components on A, we could use B on all inputs and then deal with 0V instead of floating.

EDIT:
Using the diode bridge trick, here's the circuit so far (exactly the same for the brake/indicator light - just replace the park light input with brake light.
Obviously, there are two indicators, left and right, so the total number of relays is now 4 - Brake, Park, Left Indicator, Right Indicator
What I'm looking at now is a way to replace the relays making the signals 0V/12V, for cost, size and reliability reasons.


texts: I'm stuck with this simple PIC16F program. Help please!

texts:
I'm just getting started with PIC programming and I'm giving up already. I just want to make an LED blink! I'm working with a PIC16F1773, MPLABX IDE v4.05 and Pickit3.

These are the configuration bits that I've defined in a header file:

// CONFIG1
#pragma config FOSC = INTOSC    // Oscillator Selection Bits (INTOSC oscillator: I/O function on CLKIN pin)
#pragma config WDTE = OFF       // Watchdog Timer Enable (WDT disabled)
#pragma config PWRTE = OFF      // Power-up Timer Enable (PWRT disabled)
#pragma config MCLRE = OFF      // MCLR Pin Function Select (MCLR/VPP pin function is digital input)
#pragma config CP = OFF         // Flash Program Memory Code Protection (Program memory code protection is disabled)
#pragma config BOREN = OFF      // Brown-out Reset Enable (Brown-out Reset disabled)
#pragma config CLKOUTEN = OFF   // Clock Out Enable (CLKOUT function is disabled. I/O or oscillator function on the CLKOUT pin)
#pragma config IESO = OFF       // Internal/External Switchover Mode (Internal/External Switchover Mode is disabled)
#pragma config FCMEN = OFF      // Fail-Safe Clock Monitor Enable (Fail-Safe Clock Monitor is disabled)

// CONFIG2
#pragma config WRT = OFF        // Flash Memory Self-Write Protection (Write protection off)
#pragma config PPS1WAY = ON     // Peripheral Pin Select one-way control (The PPSLOCK bit cannot be cleared once it is set by software)
#pragma config ZCD = OFF        // Zero-cross detect disable (Zero-cross detect circuit is disabled at POR)
#pragma config PLLEN = ON       // Phase Lock Loop enable (4x PLL is always enabled)
#pragma config STVREN = ON      // Stack Overflow/Underflow Reset Enable (Stack Overflow or Underflow will cause a Reset)
#pragma config BORV = LO        // Brown-out Reset Voltage Selection (Brown-out Reset Voltage (Vbor), low trip point selected.)
#pragma config LPBOR = OFF      // Low-Power Brown Out Reset (Low-Power BOR is disabled)
#pragma config LVP = ON

#define _XTAL_FREQ 8000000       // INTOSC 8MHz

And this is the actual code:

#include <xc.h>

void main(void) {

OSCCON = 0x72;

TRISB = 0x00;
PORTBbits.RB0 = 0;

while (1) {

    if (PORTBbits.RB0 == 0) {
        PORTBbits.RB0 = 1;
    }else {
        PORTBbits.RB0 = 0;
    }
    // Delay for 1 sec
    for (int count = 0; count < 20; count++) {
        __delay_ms(50);
    }

}

return;
}

I've defined the OSCCON register as 0x72 following the datasheet but nothing lights up. I'm measuring a constant voltage of 0.42V in RB0.

EDIT:
The datasheet:

I'm powering the PIC through the Pickit3. RB0 is connected to a resistor in series to the LED and to ground.

What am I doing wrong?


texts: Does color rendering index increase with brightness?

texts:
I've been reading about LED strips and thinking about switching to those from my serial incandescent lamp setup, and I can't figure out if CRI (color rendering index) is tied to a certain standard brightness value (it has to be measured at some standard values, right?) or if no matter how dim or bright the light is, it will always be the same.

So, for example, if you take one strip section worth 2000 lumens and its CRI is 80%, will the CRI of the objects in a room increase if you use multiple of these strips?

I haven't had an opportunity to experiment with that and compare the stripes in a natural environment, so excuse me if the answer to that is very obvious.


texts: Definition of single-ended vs. double-ended SMPS

texts:
I have seen references to switched-mode power supplies as being either single-ended or double-ended.

How are these terms defined and contrasted with respect to SMPS design?


texts: Correct place to attach shields for twisted pairs

texts:
I have two PCBs connected by a cable containing 5 sub-cables:

6v power through a custom made coaxial cable (similar to that found on laptop power supplies).
2x 100mbps LVDS through 100ohm impedance screened twisted pair.
2x 1mbps CAN through the same 120ohm twisted pair cable.

Each LVDS cable is terminated at the RX end with a 100 ohm resistor. They have foils screen with drain wires.

Each CAN cable is terminated at both ends with a 120 ohm resistor. They have foils screen with drain wires.

Isolated 24v power is delivered to the left board, where it's switched down to 6v (non-isolated). Both boards contain their own 3.3v DCDC regulator (non-isolated) for the local electronics.

My questions:

At which ends should the shields be connected? I assume the LVDS shields should be connected at the source end, as shown in the diagram.

Since both ends of the CAN buses are sources, should both ends of the CAN shields be connected to GND?

Added:
Both PCBs are housed in plastic cases, and there is no attachment to earth.


texts:
I am planning to buy a Tesla coil from Alieexpress. When it arrives I wonder what are measurements I could take to make sure iit is safe. For example: how/where can I measure if the primary coil and the condesators do properly discharge after it has been switched off and how fast?

Interestingly the primary coil of the coil I want to buy is made from isolated wire (means there is some sort of PVC shielding around it just like a normal household cable would have). Is then charge/discharge of the primary an issue at all?


texts: How many amps between batteries that are wired in parallel?

texts:
How many amps will flow through the cables between my batteries if I have 2 batteries wired in parallel?
Let's look at a simple example:

We've got 2 batteries in parallel, and one 12v lamp that requires 3 amps. The wire from the battery to the lamp will require a wire that can handle 3amps, but how many amps will go through the cables between the batteries in this example?


texts: Adding momentary switch (push-button) to NodeMCU

texts:
I want to add 2-pole momentary push-button (switch) for my covers.
Integration goes through a NodeMCU and ESPHome.
I'm having a hard time understanding the schematics for this switch:

I'm not sure how to connect the inputs/outputs to a NodeMCU in order to have a response in my logs.
(Only one pin for example D1 to be reactive when I hold my push button.)


texts: FET H-bridge has slow convergence for the last 10% of output voltage: why? (DRV8874)

texts:
I have a board with 9x DRV8874, as described in another unrelated thread there.
The driver switches fast to 90% of VM when ON (0V when OFF) then converges slowly to the final value (time constant~=100us). When the PWM frequency is increased (but still <40kHz specified), the convergence flattens to an average value which deceively resembles bipolar transistors VCEsat varying with duty cycles. The average voltage applied to the load therefore depends on the duty cycle, which cannot be calibrated easily.
Some snaps of the OUT1 voltage (no load connected, measured straight at the IC pins):
Low PWM freq

Zoom on top

Nominal PWM freq

High-ish freq (sorry, other duty cycle)

And here is how the average voltage varies not linearly with the duty cycle (nominal freq, CH1 is the motor supply, both cursors are set where OUT ends up being at the beginning and the end of the cycle). Notice how the OFF and ON voltages go up with increasing duty cycles.

I think I managed to model this behaviour using the following model. Vs0 is a constant voltage change when switching, so Vs is shifted up by as much as the voltage at the end of the exponential decay. I'm calculating deltaV and deltaVs for each infinitesimal change in duty cycle and I animated a plot changing the duty cycles, and I have a matching behaviour. Does that help locating the cause?

(Erratum: k is supposed to be k+1 on the second PWM cycle)
When a load of 12Ohm is connected these figures barely change (drop due to RdsON).
Where does this come from and how can I remedy to it?
Datasheet: https://www.ti.com/lit/pdf/slvsf66


texts: LED glowing a bit even when Transistor is in off condition

texts:
The LED is connected in between an NPN bjt and 2.4K Resistor at 30V
A few of these tend to emit a small amount of light even when the transistor is off condition.

Vce (of glowing at off condition) is 28.15
wheras Vce (When LED is off when Transistor is off) is 28.55/28.60V

Nominal current for the LED is around 10mA.

If this is due to the transistor, what is the reason?


texts:
I am getting 7 volts from a power supply source which I need to step down to 3.3 V for powering up my 2.4 GHz zigbee MCU (TI CC2530 + CC2592 amplifier).

I am using a linear regulator to step it down. My schematic is as shown below:

Randomly I am seeing MCU resets and brief communication failures. I checked the power line waveforms and they look like these (with ac coupling):

Input (7 V line):

FFT looks like this:

Output (3.3 V line)

FFT looks like this:

I can do nothing about the input. What should I do to ensure a better power line for the MCU in order to get rid of resets and communication failures.

Note - same circuit works fine if I power it up from my bench power supply.

EDIT (solution posted below):

I followed @analog's solution but with different values (because I didn't have the values that he mentioned):

Setup:

Waveforms with 180 ohm load on the 7 V line (ac coupling):

Waveforms with 33 ohm load on the 7 V line (First one is DC coupling and rest are ac coupling):

EDIT: Adding more waveforms.

Both probes connected at Vout. Tested at no load and 33 ohm load conditions. Yellow line is DC coupling. Blue line is ac coupling. No load voltage is roughly 7.5 volts. At 33 ohm load, the voltage drops down to roughly 5.7 volts.:


texts:
This is the circuit I'm given:

And after disabling all of the sources, I'm now trying to calculate the equivalent impedance (which would be the Thevenin impedance):

But I'm stumped on how to combine the capacitor and the 2 kohm resistor. Seems like a dumb thing to ask but are they in series or parallel? I've debated myself on both counts. There's a trivial loop there so they are in parallel. But there's a trivial node connecting these two so they are in series? Am i just being dumb here and there's an obvious answer?


texts:
I read about Static Hazard. We know Static 1-hazard is: Input change causes output to go from 1 to 0 to 1.
My note covers a Circuit as follows:

My notes says: When B=C=D=1, for any changes in A values, it's probable to have Static Hazard 1.
But I think:

for 1 to 0 transition of A static hazard 1 can be observed.  for 0 to
1 transition of A no hazard can be observed.

anyone could describe my sentence is correct or my note say the correct sentence. which of them is correct ? why? Thanks.


texts: can you put 2 tv antenna on the same mast for better reception?

texts: I live about 40 miles from Toledo and 60 miles from Ft Wayne. I have a directional antenna now that only pulls in either market.  I think I can get Toledo with an omni directional antenna but I need the directional antenna for Ft Wayne and I would like to have both available.  Can you put 2 tv antenna on the same mast for better reception? And does just being on the same mast combine the signals or do you have to wire the antenna together into the cable wire?


texts: I know this is "noob-ish",but where do you actually put in the Thevenin calculation. Particularly I have this circuit and I know the Thevenin will be like this, my question is why is R4 on the top(I know why it is R3 + R4 down)?


texts:
Today when I was going to measure charging current in BQ2057WSN charging circuit (Input Supply: 12VDC, Battery: 7.4V,6600mAH) by putting a multi meter in series with Q1 (shown in figure) and measured the current at the battery end is 300mA and at the same time the current drawn from the power source is also 300mA(though the charging current is set at 600mA). I have also observed today that before inserting the multi meter, the battery terminal voltage was 7.39V and the circuit was drawing 600mA from the power source. And after inserting the multi meter in series with Q1, the battery terminal voltage become 7.44V and the circuit was drawing 300mA from the power source. Why so?

Also,When I was doing the same experiment ( putting the multi meter in series with Q1) with a battery (7.4V,6600mAH Li-ion battery)having voltage 6V, I have found that both the current drawn from the power source as well as current in the battery terminal was 600mA. But, when this was doing with a battery having voltage 7.39V, the current reduces to 300mA with insertions of multi meter. Why the current is different in these two case as in both the cases the batteries are not fully charged?


texts: Electrically Grounding a Large Heatsink to PCB Layer Ground

texts: I have a 100x100mm board that is directly attached to a same sized heatsink on one side (touching heat producing IC packages). The board is 4 layer, with a large ground middle layer. Is there any reason I should NOT be connecting the heatsink screw hole mount pads to this middle ground layer?


texts: Simple connection from through hole pad to through hole pad

texts:
I am making a convertor board in Altium where some lines need to be switched with transistors while others just go from pad to pad and nothing else.
I tried to draw a wire in the schematic and added net names which are not showing in the PCB. I can draw a connection from pad to pad without net names but can't draw polygon pour.
Any help is appreciated.


texts: How does ripples in dc affect working of a dc motor?

texts: In the circuit provided here ,the supply voltage to the motor(+24 V ) is not a steady dc . It is the output of a full wave rectifier. how does it affect the working of a dc motor.?


texts:
I can draw a resistance or conductance in LTSpice, but how can I draw an impedance component? I've seen them drawn as unfilled rectangles before. I've tried searching the component list for "impedance", but nothing relevant shows up.

Do I have to split it into reactance and resistance?


texts: How to avoid damaging vacuum tubes and gas-filled tubes during soldering?

texts: Is it possible to damage a vacuum tube or gas-filled tube while soldering to it (thermal shock?), and if so, are there any special precautions that should be taken while soldering tubes to avoid damage?


texts: Why are inductive loads an issue for the power grid?

texts:
I understand from

Power = V_rms * I_rms * cos(phi)

Being phi the phase difference between current and voltage.

The power consumed by the a circuit is reduced in the case of having inductive or capacitive loads, i.e. motors.

In a factory, for example, why does one get a penalty fee in the power bill in the case of having many inductive loads?


texts: What causes ions inside of a lithium ion battery to move between the cathode and the anode?

texts:
I understand that inside of a lithium ion battery, the ions move from the anode to the cathode internally during discharge in order to attract the electrons to move from the anode, through the wires, to the cathode. On the other hand, the ions move from the cathode to the anode internally during charge in order to attract the electrons to move from the cathode back to the anode through the wires.

However, I don't understand what causes the ions to move to the cathode during discharge, and what causes them to move to the anode during charge.

What's the driving force here that I am missing?