texts: Solenoid actuates unreliable when driven through raspberry pi

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I'm driving a solenoid from a raspberry pi zero W. The solenoid doesn't work reliable, sometimes it doesn't move at all. When I position the solonoid so that it points downwards (so that gravity helps), it always works. When I drive the solenoid straight from the power supply it actuates reliably.

I'm using this schematic with some slightly different parts:

My parts:

single 5V 2.1A power supply instead of two separate ones
1k resistor (also tried 2.2k)
5V solenoid (measured coil resistance: 5.6 Ohm)
TIP122 transistor
1n3001 diode

It seems like the voltage across the solenoid is too low, but I measured it, and it's around 5V as it should be. Edit: I measured this without the solenoid, this is wrong. With the solenoid I'm measuring around 2V. This seems to be the problem.

Where am I going wrong?

Solution

So, thanks very much to all the answers, I realized that the voltage across the solenoid was simply too low (2.5V), due to the characteristics of the TIP122 resistor I was using. So I switched the TIP122 for a IRLB8721PbF mosfet, and It's working slightly better: around 3.15V across solenoid.

I would prefer to have the full 5V across the solenoid, but this seems hard to achieve given the 3.3V GPIO output on the raspberry, which will not turn a lot of transitors/mosfets fully on. I tried driving the mosfet using the transistor, but this gave an even lower voltage. If I read the datasheet correctly the IRLZ44N would give a better result, but that wasn't available here. See for more information: Using MOSFETS with 3.3 Volt.

Anyway, 3.15V seems enough to drive my small solenoid reliably, so that's good enough for me. Again, thanks very much for the answers!


texts:
I need to understand this circuit (at least to a basic point). I know it's supposed to be a radio but I need to break into stages in my head to get what's happening. I am going to try to describe it but I definitely need help.
First, there is the antenna , that's supposed to "grasp" a signal. The signal runs into the two inductors, which are placed as such in order to, in L1 a magnetic field is created. This magnetic field will cut across L2 and it will induce a voltage at its ends ("transofrmer") . Untill this part of the circuit, I think we call this a "tuner".
Then from the diode to R2, we call this part "demodulator" , maybe it is used to extract noise from the signal (?) .
Then we have our first, amplifier created with a "TL071", then another and another one and finally the speaker. I am not really sure why we need that many amplfiers or what exactly resistances such as "R7" in the exit of "TL072A" are supposed to do.
I would like to draw in my mind at least, a sketch of what each part of this circuit does , any extra information is welcomed.


texts: Packaging polarity indication of a supercapacitor (polarity indicated by arrows)

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I obtained some supercaps from an auction site.
As is often the case for low cost components from such sources, these do not have supplied data and such branding as there is does not appear traceable.

I would like to know if there is a standard for polarity for such devices and how likely it is that generic devices such as this one follow the "standard".
My samples have an arrow on the label which may indicate polarity, but this is uncertain.

To make my query specific, but also liable to be generally useful, here is a set of closely related questions:

What is the polarity of this supercapacitor (4F, 5.5V)?
How was the polarity determined in this case?
Is there a standard for polarity for such capacitors?
What does the arrow indicates?

Some details of specific product here

Including this diagram:


texts: LED PCB bulb - how much cooling do they need, what is their maximum temperature

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I am building a SAD (Seasonal Affective Disorder) light box - its a super bright light.

The specs of the LEDs I am using:

50W Warm White LED IC High Power Outdoor Flood Light Lamp Bulb Beads Chip DIY
 Lighting color: warm white
 Color temperature: 3000K
 Beam angle: 120 degree
 Working voltage: DC 32-34V
 Working current: 1500mA
 Power: 50W
 Luminous flux: 3800LM
 Size: 52 x 46mm

Although these specs don't specify the maximum temperature they can handle prior to failure, what temperatures can LEDs typically withstand?

As a ball park figure I can tell you an Intel CPU is recommended to stay below 70°C but can handle upto 100°C at most - but I don't know what the thresholds for LEDs are!

I'm using a coolermaster i30 on a 150x150mm copper plate to cool 9 of these LEDs, the i30 is supposed to be able to "cool to 320Watts", which I would assume means it can keep a 320 Watt CPU below 70°C


texts: Need help in designing of circuitry. (Power Electronics)

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The circuit is supposed to detect ambient light and react accordingly.  When there is high illuminance the LED should be dim and when there is low illuminance the LED should be bright.

The transistor is supposed to drive up the current and the NE555 is suppose to control the duty cycle.

The NE555 is supposed to give out high duty cycle when there is low light and give out low duty cycle when there is plenty of light. But the problem is the frequency changes along with it.

Is there a way to change the duty cycle without changing the frequency?

Circuit design.


texts:
I found a TV-Set in a dumpster, and checked if it's still working.

Indeed it is somewhat functional, but the picture is distorted:

(screenshot of the TV)

Depending how bright the picture is, it get's more or less vertically "compressed", where the upper half is more compressed than the lower part.
The brighter the picture, the more compressed it becomes.

There is also a combing effect, and the picture seems horizontally slightly shrunk.

When the picture is very bright, as in almost white, the screen flashes, and sound disappears.

Also, the brighter the picture, the more 50Hz noise I can hear from the speakers.

I suspect either the V-control IC to be broken (TDA3653B), or one of the capacitors connected to it.

Or, some of the AC/DC capacitors might be dried out or otherwise broken.

Any suggestions?!


texts: Is this a reasonable design for a high-speed level shifter?

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I wanted to try designing a device that will use an RS-232 interface. RS-232 works at +12/-12V - I know I can use a MAX232 as a level converter, but I wanted to try designing my own (this is a hobbyist project).

I designed this circuit in Falstad CircuitJS, and it seems to work quite well in the simulation. (Click the link for a demo)

simulate this circuit – Schematic created using CircuitLab

CircuitJS shows it working acceptably at up to 50MHz - though at that frequency I'd expect I need to simulate more parasitics, and I don't need that level of performance anyway.

Is this design more complicated than is needed for its purpose? It seems like quite a lot of components. Have I made any beginner mistakes?

Circuit explanation:

The circuit formed by R1, Q1, R5, R9 and M2 should be easy to understand - when the input signal is high, Q1 turns on, which pulls down M2's gate through R5, which turns M2 on, which pulls the output high. When the input is low, Q1 is off, and the gate recharges through R9, which stops pulling the output high. (The mirror-image circuit on the bottom half will turn M1 on and pull the output low).

At high frequencies the gates do not recharge quickly enough through R9 and R10, causing excessive power dissipation when both M1 and M2 are turned on. To alleviate this I added Q6 and Q2. When Q1 turns off, the gate starts charging through R9, and when it reaches Q2's threshold voltage, Q2 turns on, which turns Q6 on, which very quickly recharges the gate. .A separate inverter could have been used to control Q2, for another small improvement, but it would add even more complexity. R9 is smaller than R10 because the top half has less voltage to work with (12V instead of 15.3V) and I found this made a surprisingly large difference in the turn-off time in the simulation.

Note the part numbers (IRF9530 etc) were added by CircuitLab, and aren't specific components that I plan to use.


texts: How do I tell if my amplifier is voltage-to-voltage, voltage-to-current, etc

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I have an amplifier, which is essentially an amplifier and a motor driver in one (link to data sheet), and I'm having an embarrasingly hard time trying to figure out what/how much it is amplifying.

I have my amplifier hooked up to an external power source, which has an amplitude of 28V, and to my motor. I have an MCU generating a PWM signal that e.g.  has an amplitude of 3.3V and a dutycycle of 50%, which is fed into my amplifier.

This PWM signal, as far as I understands, is therefore responsible for switching the FETs of the amplifier from OPEN to CLOSE and vice versa, which in turn is responsible for the average amplitude (currents/volts?) going to my motor.

Now when I have this all hooked up and running, and my dutycycle and power supply is as mentioned above, it would result in 14V (=50/100 * 28V) across my motor and this then draws about 200mA from my power supply.

What is then exactly getting amplified here, and what am I supposed to calculate as gain? Is it simply supposed to be the voltage relation between the signal being generated by my MCU and my power supply (3.3V vs. 28V) or is it the current relation between the signnal from the MCU and my power supply (64mA vs. 200mA)?

Any help is much appreciated as I am completely baffled by this problem.


texts: IC to count number of inputs that are on?

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I have 8 wires, and I want to count how many of these are in a high state and convert this to a 3-bit binary signal. If the count of inputs that are high is greater than 4, I don't care what exact amount of inputs are on beyond that point, I just need to know whether more than 4 are high. So I only need 3 bits of output, if that makes sense.

i.e. if 1 wire is on, output 001, if 2 wires on on, output 010, etc. and if 7 or 8 wires are on output 111.

Is there an IC that can help me do this easily?


texts: Charging rate for deep cycle 12v battery

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I have a 75 AH deep cycle battery(AGM) and I have a battery charger with 2 modes, 5.5A for car, 2A for motorcycle, as far as I remember, lower charging rate is usually better for longer battery life and better charging, my questions are if what I remember is even true, and if so, does long charging affects the battery? For example, maybe lower charging rate might be better, but if it takes very long to charge it makes it worse?
Long story short, which mode should I use, the 5.5A or the 2A? Thanks :)


texts: Using a MOSFET array to create a basic H bridge

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I still have this big old rc car and i wanted to make it live again since I lost the radio. I wanted to take the UPA1556AH that is inside the rc to make a H bridge and control the servo motor direction so it can turn (it is not the best idea but i don't want to wait for components). I've never created a H bridge so I'm a little confused with the schematic and the datasheet. Probably I'm very wrong. Here is the datasheet: UPA1556AH and here is the H bridge was looking for:
Is it possible to make it with that internal connection?
Thanks!


texts: How does this circuit go into latch-up mode?

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The circuit is shown below. What it is supposed to do is to oscillate, and allow for the light bulb to flash periodically.

simulate this circuit – Schematic created using CircuitLab
That is all well and good, but I want to know exactly, how it works. However, while I was messing around with the values of C1 and C2, I had stumbled upon something incredibly interesting, yet annoying.
For when the ratio of C1 to C2 is less than some value(this value depends on the capacitance of C2), the circuit will go into latch-up mode after oscillating for random period of time. Try as I might, I couldn't seem to figure out why. So I ask, how does this circuit go into latch up mode, and why does the ratio of C1 to C2 matter?
My C1 is 0.1uF and C2 is 0.01uF and it oscillates for a random time before it latches up.
For a C2 of 0.01uF, the minimum capacitance I managed to get it to oscillate it at is when C1 is 0.47uF.
I have been doing up a document for this, and I will share it. In case someone wants to know how I think the circuit works. Feel free to edit it...
https://docs.google.com/document/d/1Vp0m1JMxUysZ_kG1tjhBMVTL83eYdVbjilB-7E_DXl8/edit


texts: Measuring high voltage, floating, negative voltage potential

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I need to measure a floating high voltage in my DC/DC converter. See image below of the schematic which outlines in very basic terms the output of my converter.

I am able to measure the -6kV with a simple voltage resistance chain, as you would expect.
I originally had attempted the exact same with the -3kV voltage and kept realising the results were not as I expected. This is because my control circuitry, of course, is referenced to ground - as will be my DSP which has a maximum 3VDC input before tripping a fault condition and turning off all switches.
My question is fairly basic and I am almost embarassed to ask it. But what is the best way to measure such a voltage, if it is not referenced to a ground point? As can be seen, the high voltage is already "referenced" to ground through a high voltage 250K load. There should be -3kV across both of these loads under steady-state. This confugration may look strange but gives the direction of current flow required to emulate the behaviour of my DC loads.
I have tried using a differential amplifier to measure the voltage drop across an additional series resistor in the feedback chain across the -3kV voltage, to no avail. I have scoured the internet but have either missed a solution or tried it to no avail again.
Please do let me know if anyone has a solution to this. I have already figured out how I shall isolate the 3kV and 6kV signals, but not how to get an accurate reading to my DSP ADC of the floating voltage. Another solution could be the use of an isolated error amplifier such as https://www.mouser.co.uk/ProductDetail/Analog-Devices-Inc/ADUM4190ARIZ?qs=sMtB33eOQTIXR4llky2wIA%3D%3D&gclid=Cj0KCQiA34OBBhCcARIsAG32uvOXJ_v8Re_2o49-YBgnN7ZVRP4OQS_o2UBEGdcpuoNERIbt00whGQ8aAnBWEALw_wcB - since we can connect it to ground through the isolator. I am confused as to how best set up the primary side of the device, however. Possibly this is where a diffferential amplfiier may be handy.
Any advice appreciated.


texts: Analogy electric circuit and magnetic circuit - Power

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Here are a table which do the analogy between electric circuit and magnetic circuit. Nevertheless, there is no analogy with power dissipation …

Nevertheless, It is said that in a transformer with an air gap, the Energy is concentrated into the air gap… This is where the reluctance is maximal as the permeability is lower. If we consider the flux constant as the air gap is small. Then we can Apply the relation P = R*Flux ? What do you think ?

Thank You very much !


texts: How to convert analog output from sensors to digital without microcontroller?

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Okay, I want to make this clear - I am from computer science background, and would require more explanation than an average electrical guy.

The scenario, I have piezoelectric and LDR sensors, which give analog output of course. I plan to transmit the output from this using a serial 434Mhz RF Module, which will be received by a Raspberry Pi on the receiver side and processed further. Now, I am using HT12E encoder to encode 4 lines of parallel data, which according to my knowledge is 4 digital inputs, each of which I plan to use for 4 different sensors. I have setup the transmission part, and got the RF working.

The question, can I convert the output from the sensors to digital output, without using a micro controller, and send it to HT12E to encode, if so, how can I achieve this? If I have to use a micro controller, what would you recommend, Arduino or RPi, portability is important for me, and as far as I know, RPi doesn't have inbuilt ADC and is much bigger? Ideally, I would like to use the first method without micro controller mainly for portability and power consumption reasons. Please ask me about anything if I haven't been clear.


texts: why neutral does not shock. how can a neutral be neutral in ac current?

texts: When I probe my city mains with one probe in the live and one in earth (which should be 0 volt) it shows a voltage of around 250v. But when I probe the neutral and the earth it shows no voltage. I know that current runs in one direction for 50 times in a second. So the neutral should act like live for 50 times in a second. Then neutral should show some voltage with the earth, which it doesn't. If you touch the neutral wire you won't get shocked but if you touch the live the wire you get shocked why and how?


texts:
I'm a DC guy but I think my calculations could work in AC too.
I just need confirmation before start putting things together

Ok, I have a 3D printer it draws 5amps, 220 volts
its internal power supply can't hold up for 10ms ( average relay operation time )

So I'm thinking about using AC power.

based on my calculation:

Energy = Power x time ( in sec)

Power = Voltage x current

so my total Jouls in second is

5x220x1 = 226 j/s
ok I need to feed 226 jouls for 1 second to keep my printer active for relay to switch

now, to be on the safe side I want double my uptime.

I believe a 50uf  is more than enough
Am I right?

I wan't to put the capcitor in paraller with the printer and the power source


texts: What happens if you connect both sides of LED to positive?

texts: If I connect the positive and negative side of an LED to positive will anything break? I ask this since I want to use an Arduino pin as a transistor. Low would be ground and high would have the same voltage so nothing would happen.


texts:
I'm trying to wrap my head around the watchdog timer on the ATTinyX5 series. So things I've read made it seem like you could use it for making the program do something specific ever N seconds but never really showed how. Others made it seem like it would only reset the chip unless something in code reset it's count in the meantime (which seems to be the "normal" usage).

Is there any way of using the WDT like you would TIMER1_COMPA_vect or similar. I noticed that it has a 1 second timeout mode and I would really love to be able to use that to make something happen every 1 second in my code (and preferrably sleep in between).

Thoughts?

*Update: * Since it was asked, what I'm referring to is section 8.4 of the ATTinyX5 Datasheet. Not that I fully understand it, which is my problem...


texts:
Is a power amplifier able to generate power?
Does a power amplifier draw power from a supply?
Does a power amplifier dissipate power itself?
If a power amplifier draws power from a supply, does it dissipate all of the indicated power drawn?


texts: Identifying a SSOP (standard sum of products) expression

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Say you're asked to identify a standard sum of products (SSOP) expression from 4 or 5 options...

3 of them are definitely not SSOP (variables are missing between the terms)... however two of the options are...

None of the above.
AB'.

Solution: It is possible for AB' to be of SSOP form. Not knowing the domain allows this to be constructed.

Z = AB' is valid & of SSOP form...

 | A | B | Z |

 | 0 | 0 | 0 |

 | 0 | 1 | 0 |

 | 1 | 0 | 1 |

 | 1 | 1 | 0 |


texts: About the leakage reactance of transformer

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As known the transformer's equivalent circuit can be developed as below:

Assume the \$V_{1}\$ is the voltage applied to primary side, and \$V_{2}\$ is the voltage developed at the secondary load.

Now, let the primary side open circuit, and apply a voltage to the secondary. My colleague argued that, because the primary side current is zero, the leakage reactance at the secondary will not exist, that is, the \$X_{i2}\$ will be zero!
But I think it will be still there, because there is always some flux that does not flow through the transformer core.

Which one of the above points is right?


texts:
If there is a terminal block that has both a current and voltage rating, I am curious what are the risks of going above the voltage rating (but still staying under the current rating)? Would the likely scenario be that the isolation between adjacent terminal screws break down and cause arching?

I'm not planning on going outside the specs, but am just curious.


texts: Arduino + gyro/accelerometer == flight controller ...?

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Can I use the combination of an Arduino Mega + MPU-6050 gyro/accelerator module instead of a flight controller? Is there something else needed?

It is said that the gyro/acceleration can be used to maintain the balance of the flying vehicle. How is this achieved?

Is it a must that a gyro/acceleration module is read at a higher rate, almost like continuously?


texts:
I made two simulations of real opamp and ideal opamp, why are results so different if other params are the same?

Model I took from maxim site http://www.maximintegrated.com/en/design/tools/modeling-simulation/spice/operational-amplifiers/orcad/MAX4239.LIB


texts:
For a new project I am looking to use 8 layers and I am currently figuring out the layer stack I want to use. As for usage, I will most likely go with:

Top
GND Plane 1
Signal 1
Power plane 1
Power Plane 2
Signal 2
GND Plane 2
Bottom

And for an overall thickness of ~1.6mm (because the PCB will be plugged into a connector directly) I was thinking about using four 200um cores and three ~180um prepregs.

However, I just checked the layer stackup proposal on multi-circuit-boards. Unlike me, they did not use 4 cores and 3 prepregs, but 3 cores and 4 prepregs, with electroplated copper on the outer layers.

What are the advantages/disadvantages when using 3 or 4 cores?


texts: What happens when the AC frequency of the primary side of a linear power supply is too high?

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When the frequency is too low, the inductance of the primary transformer coil becomes less effective = less efficiency, more wasted current and even lower Hz will lead to a short circuit.

Let's say, instead of 50 Hz (Europe, Asia, Japan) or 60 Hz (Americas), the primary AC frequency is frequency is 70 Hz, 80 Hz, 100 Hz, 200 Hz, 500 Hz, 1 kHz or even more.

What would happen? Which is the first part that would fail, and why?


texts: Error deriving temperature from thermocouple amplifier

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I'm using a K-type thermocouple to read the temperature of a 3D printer hot-end.  To amplify the thermocouple voltage I am using the Analog Devices AD8495 chip. This chip is mounted on a custom-made board, I've included the schematic and layout of the parts below.

I have discovered experimentally that the temperature measurements produced by my firmware from reading the ADC the AD8495 is attached to are off by a factor of between 20-30% of the "actual" temperature as measured by a commercial IR thermometer that I have.

I have tried swapping out different thermocouples, different thermocouple extension wires (and I checked the polarity of the extension wire is correct and that there are no shorts in the extension wire), and multiple different versions of my board to check that it wasn't an error in the particular AD8495 on the first board.

Across all of these equipment changes I'm still seeing a consistent discrepancy in temperature measured by the thermocouple and temperature reported by the IR thermometer. Not only that, but the error seems to be proportional to the actual temperature of the device, so at temperatures near 25°C there is a small error of only a few degrees, but at temperatures around 150°C the error is as much as nearly 60°s!

My experimental data (and some derived error calculations) are available here: https://pastebin.com/Qq9Fj7cb

I have validated that the firmware is correctly calculating the temperature from the ADC reading by taking measurements of the output voltage of the AD8495 and calculating the temperature by hand using the supplied reference voltage of 1.24V and the transfer function described in the AD8495 datasheet.

From my reading of the data sheet, the measurement error I am seeing most closely resembles a gain error, however the actual measurement error is nearly 100 times greater than what I would expect given the maximum gain error specified in the data sheet.

I'm stumped at this point, and any further troubleshooting steps or measurements to take to help clarify what the issue is would be much appreciated.


texts: Analog Devices `SOIC_N` and `MSOP_N` Recommended Footprints

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I do not know if this is on topic, but which are the recommended footprints dimensions (or a reference document) for the SOIC_N and MSOP_N Packages?

In analog.com I can find only the outlines, and in the Ultra Librarian app, suggested by Analog Devices, the program do not show me which is the package, so I am not sure what I am having. I was unable to run the .PrjSrc scripts in Altium 16 either.

Normally I ended looking at some Google Images for a standard manufacturer, but never the same manufacturer, always an approximate guess for every package, not a specific procedure with the proper dimensions.


texts: I hope I'm not asking something preposterous but I'd like to understand how 120V USB power adapters work so that I can think about how to put one onto a board that I'd like to have made. The main problem is I don't know what to call them other than "USB power adapter". Can you tell me what components are involved and what resources I can look at to learn more? Thanks.


texts:
How can I convert DC 1. 5V (R20 cell) to DC 2.6V with as much as possible amps?

I would like to charge 500F supercapacitor with it. (I can use only 1 R20 1.5V cell).


texts: How to calculate the LNB output frequency from a satellite transponder?

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There's a lot of sattelite tracking sites and other information sources that give tunning information as 'Ku band, elevation NN⁰, home transponder = 11015H'.

The question is, what 11015H means?
Considering Ku-low band to be 10.70-11.70 GHz, and the universal LNB I have with local oscillator in 9.75 GHz I'm thinking of:

11015H > 11.015GHz Horizontal polarity
11.015GHz - 9.75GHz = 1265KHz //the IF of that transponder in the LNB output

Well, tunning that frequency in fact gave me the proper transponder, but and for Ku-high band? Local oscillator is 10.6 GHz, and using the same math gives me 415KHz -that's out of the expected 950-2150 MHz L band range. What I'm doing wrong?


texts: Is there a reason why lower voltage batteries are preferred for high AH?

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I was looking at these batteries and considering whether to use a 12V battery or multiple 2V batteries for backup power. In any case, I came across this battery by Exide Tech - GNB Flooded Classic H1T - with a nominal capacity of 2504–4000 Ah, 20 year design life @ 25 °C. However, this is only sold in 2V cells. So is the case for the GNB FC NXT of capacity 621–2620 Ah. However, for the GNB FC MCT, they have a 192 Ah variant which comes in 4V.

This isn't an isolated case. The GNB FC TCXG with nominal capacity 50–280 Ah also only comes in 12V or 6V. Similarly, for the Absolyte GP (however, here they do mentioned that the 2V cells are paralleled).

Now this isn't for just 2V. As for the Absolyte GX 2000–6000 Ah Batteries, they are only given in 4V.

Now I understand that batteries that are rated in Ah are supposedly expected to provide low currents for a high amount of time. Wouldn't a higher voltage be preferred for that? I get that when you string 6 2V batteries together, you're essentially getting a 12V battery.


texts: AVR atmega328p - Can I use port C as digital output pins?

texts: I'm currently trying to connect a 7x5 dot matrix to an AVR ATMega328p. I'm already using port B/D and I would like to use port C so that I have extra output pins. My question is, can I use port C as digital output pins without ruining the microcontroller? I know that this port is normally used for analog-digital conversion. If so, do I need to add additional configurations inside my C program?


texts: AMS117-3.3 is giving 4.3v and also magnetic field in PCB

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I am trying to build a small circuit using an ESP8288-12E, 4  5V relays and a 74HC595 shift register as the main components. To power the whole circuit I am using a Hi Link HLK 5M05 5V/5W switch power supply module.
Here is how I planned the whole circuit:

If it is difficult to see in this image then I can provide PDF as well.
I took this AMS1117-3.3 to get 3.3V from my 5V power supply. Instead of 3.3C, I am getting 4.2V on my PCB. I am not sure why this is happening.
I am attaching my EasyEDA file for the PCB design also.

One more issue I am facing is that when i take my multi-meter probes near to the circuit the relays are triggering automatically. I didn't connect the ESP8266-12E on the PCB yet, as I am not getting proper voltage on ESP8266-12E VCC pin.
Any suggestions, why this issue might be happening? Any suggestions will be helpful!
If someone wants to have an EasyEDA access I can provide for this project so can visualize the same issue more easily.
https://oshwlab.com/nehul.splendit/shift-resistor-sn74hc595-with-4-channel-relay
Here is the link of the same project.


texts: Custom CAN-FD PCB - what to watch out for?

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I'm designing a PCB which will communicate with a vehicle through CAN-FD at up to 2 Mbit/s.

The connection to the vehicle is made though ordinary twisted-paid CAN wire (around 2m) to a Mini Universal MATE-N-LOK connector on the board.
From there, it's approximately 15mm of 8 mil trace to the MCP2558FD CAN-FD tranciever, and approx. 6mm of trace to the termination resistors and decoupling capacitors.

The Teensy 4.0 I use for controlling this has an integrated CAN controller, but it's only available through SMD pads on the bottom side of the PCB. (https://www.pjrc.com/teensy/pinout.html)
Therefore, I soldered a short wire to those pads (~20-30mm) and plan on then soldering the wires to a hole in the PCB near the CAN transceiver (around 12mm of trace for the TX line, 5mm of trace for the RX line).

Do I need to consider anything special here? It's my first "high-speed" signal application.

Does the length / impedance of the CAN-FD traces on the board (between transceiver / connector) matter?
Would the MATE-N-LOK connector be an issue?
Is 2m of "external" CAN wire too much for signal quality? For now, the Teensy will only listen to messages on the bus, without receiving anything (using the MCP2558FD's "silent" mode), but I'd like to be able to send data in the future.
Is it a reasonable idea to transmit the 2 MBit/s UART (between Teensy / transceiver) through external wires? Other options (pogo pins (low availability), castellated holes (SMD components on the bottom side of the Teensy), SMD headers (different height compared to THT headers)) seemed suboptimal as well.
Could I route other signals (in this case, current signals up to around 30 mA) on the other side of the PCB, or must I retain an uninterrupted ground plane there?


texts:
I want to create a schematic for the following behaviour:

I want an ESP-12e (ESP8266) microcontroller similar to an arduino, to be able to control 10 RGB leds , changing their colours from blue to green to red and all shades available in between those colours.

I have designed the following schematic to achieve this behaviour having researched options:

The question I have as per the schematic note is - which 9V regulator would I use , given I need around 600mA from it I am finding it hard to find one within the schematic libraries and additionally, finding an actual regulator to buy appears difficult.

I have a question about the design and that is as follows: As I understand it, I can control the amount of brightness of Red, Green and Blue from my LED by controlling the amount of voltage sent to those pins, however, the 2N2222 is on, or off - with no space in between, so does that mean in this case as my GPIO pins fluctuate to control shades of colours, the LEDS in this case will be Red ON or OFF, Green ON or OFF and Blue ON or OFF - or have I misunderstood how this bit works.

Many thanks!


texts:
I have old flash that generates about 170V on it's trigger when it's charged and ready to fire. When flash fires, voltage drops to zero, and rises to 170V as flash charges...
I need that flash connected to 4N35 optocoupler. As i can tell from datasheets, it can withstand only 70V, so i need a way to drop voltage.
So, whats the best way to do it? Use resistors? Power adapter? Or simply use other optocoupler?
Schematic should like similar to this one:

I am interested in what's going on with 4N35 which has F ( flash ) marking pin 5.
Except, this one is obviously made for newer flashes, and they do not generate high voltages on their terminals.


texts: Find the voltage at FE/OX interface of FEFET transistor

texts:
I've been reading an article about this type of transistor and I can equation the circuit when we just consider the voltage at the interface between the ferroelectric capacitor and the MOS capacitor. However, the authors present the MOS capacitor as the series combination of the capacitance between the drain and the gate interface and the capacitance between the interface and the source.
They present the following equation:
$$
dV_{IS} = \frac{dV_{GS}}{1-\frac{C_{GI}}{|C_{FE}|}} - \frac{dV_{DS}}{\frac{{|C_{FE}|-C_{GI}}}{C_{GDI}}}
$$
I've tried to model it as in the diagram below, but I still can't find the above solution as I don't believe I can use Thevénin  as the circuit isn't linear. Could anyone help, please?
Here's a link to the article: https://ieeexplore.ieee.org/document/7970179

simulate this circuit – Schematic created using CircuitLab


texts:
In order to maximize power transfer, and minimize signal reflection, one would impedance match between a output load and an antenna and between an input load and an antenna.
However, is there any impedance matching between the two antennas that is required to maximize power transfer? For example, if one has a 50ohm matched TX and a choice between a 75ohm or 50ohm matched RX, which would provide higher power transfer and why?


texts: How does one change only the frequency of an alternating current?

texts:
Suppose standard voltage, current, and frequency AC power is readily available for a project that requires the available standard voltage and current, but also requires an arbitrary number of cycles per second not equal to the number of cycles per second available.

What components affect the frequency of alternating current?

Eg:
Provided: 60Hz 120v 1a
(Converter Goes Here)
Required: 10Hz 120v 1a

What would such a converter consist of?


texts:
I'm trying to understand Verilog Race Condition X's propagation and Metastability with http://www.sunburst-design.com/papers/CummingsSNUG2000SJ_NBA.pdf document.

Because that concept is very confused to understand clearly.
So Now I'm trying to make a simple example verilog code to understand their concept. But it's quite a bit difficult.

What is the difference Verilog race condition, X's propagation and Metastability?

So far, from my understanding,

Verilog race condition is when we use blocking assignments in sequential block then blocking assignment execute simultaneously. this is race condition so to prevent this problem, we use non-blocking assignment in sequential block.

always@(posedge clk)
a=b;
always@(posedge clk)
b=a;

Especially, I don't understand about X propagation concept and Metastability concept

From my understanding, X need to be handled by simulator exactly. X need to be propagated to out exactly instead 0 or 1.
But so many articles are handled by optimist, a pessimist.
So I'm confused this concept what exactly do I need to know this X propagation topic?

So I want to know how to have a test the x propagation at real fields?


texts: Critique for my short circuit indicator and guidance to improve it

texts:
This circuit was designed to save electronic components in the assembled board from damage. It gives warning beep if there is a short circuit in the assembled board.

Thus it helps to switch off the power supply immediately to save valuable components. If the circuit board is OK, Green LED lights indicating that power supply is normal. If there is a short in the PCB tracks or pins of components, Green LED turns off and Buzzer sounds indicating the short circuit.

The circuit uses two NPN transistors BC 547 to sense the short circuit. If the assembled board is normal, current flows from the power supply through polarity protecting diode D2. The Assembled board gets power and Green LED lights.

At the same time Q2 forward bias and its collector goes to ground potential. This makes Q1 off due the absence of base bias. Buzzer and Red LED connected to the collector of Q1 remains off. If there is a short circuit in the board under test, D4 reverse biases and Q2 turns off. Now the base of Q1 becomes high and it conducts. This turns on Buzzer and Red LED to indicate short circuit.

Now, I'm using general purpose components here, what I want its to make this circuit "universal", or at least usable for currents up to 10 Amps, I have some questions,

Would this circuit be able to replace slow blow fuses up to 10 Amperes?
How can I adapt this circuit for negative voltages?
Adding 1mH choke inductors right after D2 could help me out to stop transients from destroying my circuit in a worst case scenario?

Any feedback about how can I improve this is welcome


texts:
I am attempting to learn about the inner workings of FPGAs and how the high level VHDL/Verilog becomes the working FPGA. I understand the gist but I still feel like I am missing some details. I am familiar only with Xilinx but would like to get a general understanding, if there is much difference between tools.

What I understand thus far is that Xilinx compiles my vhdl into a netlist in an NGC file which is then converted into a bitstream. The bitstream is then placed into the flash PROM of my FPGA. Every time I fire up the board the netlist is loaded from the PROM into the gate-array.

Is it possible to reverse engineer what's on the FPGA or even just read the design off of the PROM?


texts: Why does inside of my sphere appear to be getting darker?

texts:
This a fully enclosed sphere containing a web cam, white led and photo resistor in exactly the geometric arrangement shown.  The led glows dimly (via fixed dropper resistor).  It runs at about 9 mA.  It's light reflects off the inside of the sphere and the web cam takes pictures of the inside of the sphere.  The photo resistor is there to measure relative light levels.  The system is theoretically in a steady state (including temperature which hovers around 29 deg.C). and there is no extraneous light.  This is what the camera sees:-

and this is that image's histogram:-

The thing is, it's not steady state.  These are the photo resistances and histogram means in two experiments each taking three weeks  The initial number is at the start, and the second number is at the end of three weeks.  They gradually change from one to the other as I measure them.

69.4k -> 136.5k, 33 RGB -> 1 RGB
28.7k -> 55.7k, 49 RGB -> 21 RGB

Both times the photo resistance and histogram mean drops very significantly, in experiment 1 almost to zero.  The inference is that the inside of the sphere is getting darker as time goes by (measured in weeks).  This question regarding photo resistor stability was inconclusive but cannot explain the shifting histogram.

It's difficult to judge by eye, but I think that the LED is getting slowly dimmer.  Occam would suggest so, but I have used two brand new LEDs so they would have both behaved like this.  The generic LEDs were both from a cheapo bulk eBay purchase.

Q1.  Can this be explained from an electronics perspective?

Q2.  Can anyone suggest any further investigation(s) I can undertake?

EDIT.

I came across something called current crowding which seems to fit my problem. I can't follow the link though due to a flight failure...


texts:
With reference to Vasiliy's answer on this question
Why can't two series-connected diodes act as a BJT?

"excess electrons from the P side of the forward biased diode can not be swept to the P side of the reverse biased diode through the metal wire in "BJT like diode configuration". Instead, they are swept to the power supply providing a voltage bias to the common terminal of the diodes."

Can someone please explain Why this would happen ?


texts: Strange Voltage Levels in a Multi-slave Full-duplex rs485 bus

texts:
I am working on a project using rs485 bus for communication. Here are design parameters:

Bus can include 1 master and 30 slaves
Configuration is full duplex using 4 wires.
All slaves attached to SLAVE(Y-Z) -> MASTER(A-B) for transmitting
All slaves attached to SLAVE(A-B) -> MASTER(Y-Z) for receiving
Master is always listening. (Receive Enabled)
Master is always driving. (Drive Enabled)
Slaves are always listening. (Receive Enabled)
Slaves are always NOT driving. Except when they want to send data then drive enable. According to the datasheet, When not drive enable, the outputs are high-impedance.
Master and all slaves are using max491.
There is a single 12V power source. Every slave and master is connected to this power source as parallel to each other and has their own step down converters to produce needed voltages. Thus all system share a common ground.
I tried failsafe biasing on master side and it worked. With failsafe biasing 4 slaves and 1 master communication is working fine. (but question is about 20 slaves biasing calculation)

OBSERVATION

These plots are excel plots simplified from actual scope measurements

When the system is made up with 1 slave and 1 master, voltages on Slave Y-Z bus (slave transmit bus) are like this:

Thus communication happens successfully.

When the system is made up with 2 slaves and 1 master, voltages on Slave Y-Z bus (slave transmit bus) are like this:

This way, communication happens successfully. As we see there is a change in voltage levels. Comm happens because voltages are still on the correct sides of middle senseless zone (which is +-0.2v from the center)

When the system is made up with 3 slaves and 1 master, voltages on Slave Y-Z bus (slave transmit bus) are like this:

This way, as you can see, no communication happens because voltages are on the wrong side of the senseless zone. And levels are strange (to me).

Going further analysis, I made 4 slaves and 1 master config. Here is the result:

Voltages go up a little bit more.

The voltage difference between Y and Z line in each config shows the max491 has some serious impedance on the line when in high-impedance mode.

I bought these max491 chips from a local dealer then checked the price from digikey. What I saw is my prices are 3 times lower than digikey prices for the chip. Maybe the chips are clones. I don't know. But I have to use them.

QUESTION

The question is how can I calculate this "parasitic" impedance and build a biasing circuit for this and what may be the reason? I am a little bit confused. I am going to build 20 slave and 1 master configuration and I cannot imagine what the voltages are going to be.

NOTES

There is no problem on slave receiving bus
This observations are nearly the same when master side termination resistor used.
There is no possibility of 2 or more slaves transmitting at the same time. There is a hardware sync built in. This is tested.

Edit

The schematic is like that. Nothing more. Average cable length between slaves is 1.5 meters. Cable is CAT6 - UTP8. For transmit and receive, twisted pairs are used.


texts:
I am trying to get -13.5V from mc34063.

On the first design, I used 8DIP package MDR34063AP and no problem getting -13.5V.

On the second design changed the package to 8-soic and used S1B-13F (100V 1A diode), which are replacements with same characteristics.

However, after 2 seconds IC starts to consume more and more current gets hot and burns.

When I increased the R22=1R resistor to 2.5R, it doesn't overheat but I can't get -13.5V anymore. It stays around -9V.

Any comment or help would be really useful,

Thank you for your time.

Design 1

Design 2


texts: In VFDs, could motor current parameter be set higher than the actual motor's current?

texts:
What could happen if 0.5 hp motor is connected to 7 hp VFD with the motor current parameter set to the maximum value of the VFD? let us say 14 Amp.

How could that affect the motor?

The current rating of the motor is about 1A.

Would that affect the acceleration and the deceleration of the motor?

Would that in some circumstances overload the VFD?

EDIT:

What are the side effects of connecting a low power ac motor to a high power VFD without taking so much attention to the motor current parameter of the VFD?


texts:
I have to filter a power control circuit and as usual I am using lots of capacitors in parallel. Some of these capacitors are Tantalum or Aluminium Polymer types, with ripple current ratings of 3 amps or so... in normal operation the ripple current will be just fine,  but when the battery is first attached to the circuit I expect that the capacitors will behave like a short circuit, consuming a huge inrush current that exceeds its ripple current.

Do I have to worry about these and make some sort of slow start circuit to charge the capacitors, or it's just fine?

Example circuit:

simulate this circuit – Schematic created using CircuitLab


texts: How did this simple nmos level shifter break my STM32?

texts:
I'm trying to read some 12V square wave signals from an old car with an STM32. I built some level shifters like shown below to down-shift (and invert) the signal so I can hook it up to an GPIO.

simulate this circuit – Schematic created using CircuitLab

After hooking it up, my STM32 discovery board went black and never returned, so I'm assuming some pin got an overvoltage somewhere and I'm trying to pin it down. Is it possible that my level shifer circuit somehow "leaked" voltage and broke my STM32?

Thanks for any suggestions.


texts: I have a string of 10 LEDs in series. Occasionally some LEDs area breaking and the entire string stops working. Can a TDR (Time Domain Reflectometry ) or other measurement be used to determine which LED specifically is broken? I have never used TDR for anything other than impedance measurements. The LEDs are encased in plastic so cannot be measured or accessed directly.


texts: How is the resistor value for boost conversion calculated?

texts:
I'm looking at MCP1640 and in Section 5.2, an equation for calculating RTOP is presented. However, the two examples underneath have RBOT = 309kOhm. How did that come about? Is 309kOhm some standard value? Without fixing a value for RBOT, one could only derive a ratio between RBOT and RTOP.

The second circuit on page 2 uses RBOT = 562kOhm though. Is RBOT meant to be arbitrary?

Thanks


texts: Fixing electrical controller (with joystick) on Pride Quantum 600 power wheelchair

texts:
The momentary switch is bad on a Pride Quantum 600 power wheelchair.  The picture is below.  It turns on, but you have to hold the rubber button/switch in the correct spot with the right temperature before it will turn on.  What could be the problem or cheapest way to fix this?  The part to replace the entire controller (what you see in the picture is $1750).  The part number says J6, but the Jazzy and Quantum use the same controller.

Pride J6 Joystick Controller with Flying Leads (Part #: ELEASMB5009)


texts:
I couldn't find any topics relating specifically to this sort of thing, and even tried asking folks over on Reddit at /r/buildapc, but I didn't get many responses or many people know if it would be possible to safely apply a conformal coating to PC components that would or may be exposed to water when doing a watercooled PC build. This is mainly to try prevent any accidental leaks from damaging components while doing a watercooled pc build.

I've read many other topics of conformal coatings being applied to smaller electronics and works fine even after being exposed to water or moisture as if nothing ever happened. My searches brought be to this topic: Waterproofing electronics by dipping into polyurethane or lacquer.

Now obviously I'm not planning on dipping components straight into anything, I'll be instead doing a spray-on application for a thin evenly coating. I just need to know if I can apply the same kind of conformal coating and everything working out alright, for example this product here which is a high temperature silicone based conformal coating which seems like the best option for PCB components. I have read other bits that some conformal coatings may contain different solvents that may not be suitable for electronics and such that may be exposed to water or moisture. Nobody's probably ever attempted to do this sort of thing for PC components by applying a silicone based conformal coating to protect against water and moisture, since this is a larger scale for electronics, but it's something I'm willing to experiment with.

with Water Cooling PC builds there is no direct exposure to water, and it's assumed that all fittings are properly seated and watertight sealed with O-rings, but there's never a 100% guarantee that they won't fail unexpectedly and accidentally leak. Now I'm not interested in hearing people say things like "Oh well if you're worried about water leakage then maybe you shouldn't do watercooling." Say what you will, I've heard it all before, and this is an experiment to try something nobody's probably ever attempted before just to see if this works in an application like this.


texts: Implementing periodic sensor data storage and GPRS transmission

texts:
Hardware setup

I am using custom hardware driven by a TIVA TM4C (specifically, TM4C123GXL) to control a microgrid with battery energy storage, solar panels, four loads controlled by relay, and a SIM900 GSM GPRS module. Users can push buttons to toggle relays, or send an SMS to toggle relays.

Three ADCs record battery voltage, total load current, and total load power.

I am writing C code using Keil u4.

What I'm trying to do

Log the relay states and ADC voltages on a regular interval (once per minute?) as well as each time a user manually toggles a load
Periodically (once an hour?) send the accumulated data via GPRS to an http server

This data can be used to make sure the microgrid algorithm is functioning optimally and properly handling solar resource availability, battery state, user inputs, etc.

My question

Do these time intervals make sense? Should I log more or less often? Transmit more or less often?
Should I use EEPROM to store the values before transmitting, or just hold them in memory, since it's a short time interval?
What's the best way to implement timers? I have several 32-bit timers with 16-bit subtimers, and several 64-bit timers with 32-bit subtimers. I'm unclear on how/why to use different timer arrangements for different tasks.


texts: What is this solar power RC circuit doing?

texts:
I am a CSE student working on a project.

We are using a solar powered microcontroller. The solar panel's power goes through a fuse and an RC circuit with a varistor to the charging system.

What does this circuit do and is it possible for the capacitor to be replaced with a smaller value one without compromising its function?

6V solar Panel
Varistor with 5.8V working voltage and 18V shunt voltage


texts:
Refer below schematics used for sensing and power supply. LT1026 is used for +/-9V for op-amp, OP-amp is followed by ADC AD7674.

It is observed that noise is picked by ADC and fluctuation observed for same Analog input for ADC.

Is there any issue in design? please someone guide. Thanks in advance.


texts: Step-down transformer AC to DC voltage conversion problem?

texts:
I got a step down transformer from an old black and white CRT TV that is about 18v 0 18v, 10A AC current output. I wanted to convert AC to DC, so used four 1N4007 diodes as a bridge rectifier. When I checked with a multimeter, it indicated +24v 0 -24v DC, so I wonder how that happened.

What happened to increase 18v 0 18v AC to +24v 0 -24v?

Did I do something wrong?

If so, what is the right way to do it?


texts: Why output of square wave signal after bypass capacitor is a triangular wave?

texts:
I understand square wave contains many sine waves of different frequencies as so does triangular wave.
My impression with bypass capacitor is that the higher the frequencies the better it attenuates those signals. Therefore, I hope to see a fundamental sine wave output for both square wave and triangular wave input. However, in reality, at high frequencies, output from triangular wave is a perfect sine wave ; but output from square wave is a perfect triangular wave.

At medium frequency, output from square wave looks like exponential charging & discharging curve, that one I can understand. But what I don't understand is its output at high frequency.
Why is it so ?

My circuit setup is simple, small amplitude signal fed directly into capacitor to ground. Output is taken from capacitor too.

Here is the circuit setup, very simple:

The above observation can be seen on all capacitor ranges, however, it is easier to see on not so small capacitor like 0.1uF. In short, at high frequency, output from square wave turns into a triangular wave.


texts:
Hi. I installed LTSpice in my macbook pro late 2011 with this specs:

OS: Mac OS high Sierra 10.13.6
Graphic: Intel HD Graphic 3000 512MB
RAM: 16 GB

somehow I got a bug when i moved a component or wire which showing a shadow of footprints along the moving trajectory. (shown in image)

has anyone encountered the same problem? I've tried to searched the answer but didn't find the same case anywhere. Anyone got an idea?

Thanks for helping. I know this is not 100% EE, let me know if I should post this in stack.


texts: Using external oscillator for MSP430 Timer

texts: I'm want to use an external low frequency crystal (32kHz) for the timer in my MSP430G2553 and the internal oscillator at 8MHz, but in the datasheet I can't see how I should use the external crystal for the timer. As there only appears to be one pin(TACLK). So how would the design for the oscillator look?


texts: Is there a measurable increase in the output of solar panels during the solar maximum?

texts:
During the solar maximum do solar panels benefit from a measurable increase in power output?
Clouds and weather conditions certainly contribute to ups and downs in power output, but on average do we generally see a measurable increase during the years when the sun is at the maximum of its (on average) 11 year cycle?
"During solar maximum, ... the solar irradiance output grows by about 0.07%" 1
"Grand solar maxima have shown some correlation with global and regional climate changes." 1


texts: How to give analog input from 3.5 mm jack to FPGA (Spartan 3e)

texts:
I am working on a voice transmission project by using Spartan 3e. My code works just fine. My problem is that I give analogue input to adc side by using a potentiometer and see the changes (as digital) on leds ( digital output is assigned to leds). Here is the problem,I  cut a headphone into two and connected 3.5mm jack side to my phone to play music. There are 3 cables which are golden, blue and red. Golden one is connected to "GND" pin , Red one goes to "Va" pin (at adc input). I didnt touch the blue one.

When I play music,I  see no change on leds despite the fact that I did see by using potentiometer. What am I missing ? Do I have to setup an external circuit before giving the analog signal to Va input ?

Thanks in advance.


texts: Why the extra transistors in this current mirror?

texts:
I'm trying to understand the unusual current mirror circuit below. The current controlled by R2 is mirrored to R1. The strange feature of this circuit is that Q1's collector and base aren't connected directly as in a normal current mirror, but through two diode-connected transistors (Q3 and Q4).

What is the purpose of Q3 and Q4? I haven't seen this on current mirrors before. I looked at other current mirror circuits (Wilson current mirror, cascode current mirror) and this doesn't match. In LTspice, this mirror circuit functions, but I don't see any advantages to it. It seems to work just as well if I replace Q3 and Q4 with a wire.

This circuit is inside a chip I'm reverse engineering. The two-diode current mirror appears multiple times, so there must be some reason for it, but I can't figure it out. Any ideas? Does this circuit have a name?

simulate this circuit – Schematic created using CircuitLab

(Ignore the part numbers in the schematic.)


texts: How to UPS-protect this "dual source" setup?

texts:
I'm analyzing how to best protect a setup comprised of a NAS/Router/Wimax from power surges.
A very simple diagram is this:

When I write "dual source" (term which I just invented) I mean that the surges could come from either the 220V or the Antenna.

SoHo scenario: my main objectives is to protect the NAS & Router from surges, blackouts and brownouts. A bonus would be to keep my internet up & running during outages.
Of course the underlying objective is not to degrade my data line.

So far I have found 5 options of my setup:

I connect to an UPS the Router & NAS AND break the data connection between the PoE and the Router with the UPS. This should solve my main objective completely: Router and NAS will be safe and at the most, the PoE injector/antenna will be fried.
I connect to an UPS the Router & NAS AND break the data connection between the PoE and the Router with the UPS AND I use a ethernet surges protector between the antenna and the PoE. This should solve my main objective completely and add extra security.
I connect to an UPS the Router & NAS & PoE. My fear is a surge coming from the antenna and killing everything. However this is based on the assumption that the surge can jump from two of the UPS output outlets.
I connect to an UPS the Router & NAS & PoE AND I use a ethernet surges protector between the antenna and the PoE. This should solve in theory everything.
I connect to an UPS the Router & NAS & PoE AND I use a ethernet surges protector between the antenna and the PoE AND break the data connection between the PoE and the Router with the UPS. This should solve in theory everything and add extra security.

All three appliances have an external adapter. The UPS is likely to be an approximated sine wave (like the APC Backups Pro). Surge protector something like the PNET1GB. The antenna doesn't appear to be connected to ground with a dedicated cable. It's like one of these:

So the questions:

What is the best setup in terms of protection? Among the ones presented or any new one.
Can surges actually come from the antenna?
is it useless to break the data line twice? (surge protector between antenna and PoE and UPS between PoE and Router)


texts: I am building a guitar pedal, and I would like it to run of a 5 V rechargeable battery instead of a 9 V battery. Does anyone know how I can accomplish this? Thanks for reading!


texts: How do I do calculation in CircuitLab? How do I provide +Vcc and -Vcc to the OpAmp?

texts:
Here is my simple circuit. I would like to test whether the output is correct as per manual calculation. According to manual calculation, Gain=3.1, Vo=10.54V.

My question are:

How do I do that calculation?
Is my way to do +Vcc and -Vc connection correct? Which both should be connected to +12V and -12V respectively.

simulate this circuit – Schematic created using CircuitLab


texts:
I have read that tank circuit is used for radio tuning. When we tune a radio we change the variable capacitor, hence the value of LC changes. This would result in a change in the resonance frequency. My question is how relevant is this technology to today's application of tank circuit.

Are they still used in modern radios, for example in my 2016 model car, or there is a new technology for radio tuning.


texts:
I would like to use a CR2032 battery to power the internal RTC of the SIM900 gsm module. The datasheet (given in the link) says that the battery should be rated at 3V. They also give the following reference circuit for non-rechargable batteries (like CR2032).

I am confused about the diode in this circuit. As far as I know the forward voltage drop of a diode is 0.7V at average, which leaves only 2.3V for the RTC. Will that cause any problems, knowing that the datasheet says the battery should be rated at 3V?


texts: LTspice - Simulation of a variable inductance

texts:
I would like to better understand how LTspice works with the variable inductor defined by using the flux through it. I have some troubles to understand why according to the above post the formula of the flux as to be integrated... It is said that it is internally integrated? What does it mean? Does it mean that LTspice is observing dI and not i(t)?
How to model an inductor using a behavioural voltage source in LTspice (to get time-dependent inductors)?
Here is the formula according to the Faraday's Law and the relation between the voltage and the variation of current across an inductance:
$$d(Flux) = \frac{L}{N}dI$$
If we time integrate the above equation, we obtain:
$$Flux(t) = \frac{L}{N}i(t)$$
And that is the relation that we have to enter into LTspice. So in this case we have to integrate if we have a relation in function of dI.
According to me, I think that by observing the current $$i_{L}(t)$$ LTspice tries to adjust the coefficient $$\frac{L}{N}$$ in order to maintain the above relation equal.
So suppose I want to modelize an inductance. I know how the permeability change according to the excitation field H:
$$µ(H) = µ(H=0)*f(H)$$ where f is a function which I know
Then, $$B = uH$$
If I consider that the magnetic field is homogenous over the all surface of the inductance S, I can say that
$$Flux = B/S$$
Then If I do the same approximation about H around a wire but on a curve l:
$$H = NI/l$$
I can say that:
$$Flux = \frac{NI}{lS}*[µ(H=0)*f(\frac{NI}{l})]$$
In this case we do not have to integrate the relation for having the flux. Isn't it? What do you think?
Thank you and have a nice day!


texts: What are good practices for traces on the "mains" side of a relay?

texts:
I'm trying to switch a reasonably sized load (800W at 120VAC), so let's call it 7A using a PCB interfaced to a microcontroller.

Obviously I need to make sure that the relay I'm using can support this load, and I can use the circuit calculator to figure out the trace width for a given thickness.

For example, this PCB has a relay with thick external traces (86 mil) and a two-layer signal plane (the dashed line area). However, I'm not crazy about the separation at the terminals themselves. My goal is reliability and longevity.

I guess it's a broad question, but I'm very new at this, and would love for some guidance on "best practices" for high(er) voltage traces like this.

Thanks,
Chris


texts: Rectifying failed MCU crystal oscillator design

texts:
I am working on an SMD hobby project (2 layer board) where I use a STM32F405 MCU running at 3.3V, clocked from a 25MHz external crystal. Being impatient, I hastily designed a board and ordered it. However I have apparently missed a whole lot of points regarding PCB design in regards to the external crystal.

The result did not work so well, as you might expect. When I switch to the external oscillator, the CPU seems to run. But the MCU clock is very slow, and switching a GPIO ON and OFF in the main loop yields an approximate 1 kHz square wave (I've not had time to check the frequency using a clock out pin yet).

The crystal is oscillating at 25 Mhz, but I only measure a sine wave with slightly below 500mV p-p amplitude (using a x10 Oscilloscope probe). I would expect this to be closer to the 3.3V supply voltage (I cannot find much documentation which states what is to be expected.) I also do not understand how the MCU is running at all, as it definitely does not halt in the loop waiting for the oscillator to start. But it does not run at the correct speed at least. So any hints at what's going on would be appreciated.

After studying the topic of MCU crystal PCB design in more detail, I've got a fairly good idea about what I got right and where I failed spectacularly. But I am still quite confused to what is the definitive correct way to do this.

The stuff I got correct:

Traces to the crystal is short, at around 6 mm from the MCU.
Traces are symmetric.

The stuff I got very wrong is:

I used a ground plane under the crystal and the tracks to the MCU, likely causing a very high stray capacitance.
I completely misunderstood the "guard ring" concept. I added a top layer fill zone (surrounding the the crystal), stitching it to the ground plane instead.
Using a 25 MHz crystal instead of an 8 Mhz one. The PLL setup suggested by STMCubeMx seems to divide the input down to 1 Mhz, before multiplying it up to 168 Mhz. So an 8 MHz crystal should work fine I guess.
The reset line runs right under the crystal. However, that in turn is connected to the JTAG and a button, and is otherwise passive.

I thus suspect the stray capacitance of the design explains the low Vp-p in the 25MHz oscillator. So as a first remedy, I'm planning to switch to a 8MHz crystal in order to just get it working. Does my assumption here make sense, and would an 8 MHz crystal have a better chance of working on my bad board? (I would like to get the current board working, even if the design is sub-optimal/really bad).

Of course, the final plan is to make a second revision board where the design is fixed. But there are a couple of things which I still find confusing in documents I've read so far:

Some documents recommend NOT using a ground plane under the crystal, but place a guard ring around the circuit and connect it to the nearest MCU ground pin. This makes sense to me, however:
Some other documents recommend placing a separate ground plane under the crystal (in addition to the top layer ring), and connect this to the nearest MCU ground in one place. However, I do not quite see how this would be better than my current design capacitance wise, as the "separate" plane would then also be connected to the main ground plane. I do understand that RF noise wise it would be way better. But it contradicts my assumption that stray capacitance is the reason my current design produces such weak oscillation output.

So any explanation regarding this apparent contradiction would be appreciated. Also, any other pointers to me regarding the "best way" to lay out my Rev2 board would be greatly appreciated.

EDIT: Pictures of the PCB are found below. C3 and C4 are the capacitors and R6 (which is in between the Caps) is Rext. (Sorry for the bad contrast).


texts: Deriving the formula from 'scratch' for charging a capacitor

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So the formula for charging a capacitor is:

$$v_c(t) = V_s(1 - exp^{(-t/\tau)})$$

Where \$V_s\$ is the charge voltage and \$v_c(t)\$ the voltage over the capacitor.

If I want to derive this formula from 'scratch', as in when I use Q = CV to find the current, how would I go about doing that?

Same with the formula for discharge:

$$V_c(t) = V_s \cdot e^{(-t/\tau)}$$


texts:
I’ve been spending a lot of time looking at different low noise voltage regulators, and it dawned on me-why am I not just putting a filter on the output of the regulator I already have?  What are the cons to using a filter. Why are there so many ultra low noise ldo’s when you can just filter the output as much as you want. I feel like I’m missing something.

I’m using a voltage divider at the output to cut the voltage in half. Two 10 k resistors. I also already have a 20 uF cap in parallel with the second resistor to ground. I’m trying to get rid of noise below 70 Hz. Should I just bump up this capacitor to a much bigger one?


texts: Is it possible to connect LiPo level indicators in parallel?

texts:
I've never studied the terminology of electrics so I had a hard time searching for whatever I'm asking. If this is a duplicate please mark it as such :)

I've got four battery packs in series to produce a higher voltage output, it all works great. I also have four individual battery level indicators, however these are connected separately over each battery like so:

However, from what little I know it should be possible to connected them more according to this picture:

I'm thinking it might give the wrong readings if one cell is higher than lowest one?

The indicators are one of these classic alarm ones:

Again, I'm sorry if the descriptions are off or the terminology isn't there.. This isn't my main field and I'm a home brew enthusiast :)


texts: Arduino-controlled slot cars - alternative to MOSFETs for speed control?

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I'm attempting to control the speed of two slot cars in a set using Arduino.

Each car is controlled by a controller with a variable resistor that looks like this:

They're wired in parallel to the same 17V DC power supply:

Simplified:

For Arduino control, I experimented with manipulating a single car's speed using a MOSFET. It worked really well. Using a PWM output on the Arduino, I was able to pulse the MOSFET on and off to throttle the current and change the car's speed. The behavior of the MOSFET seemed to be exactly the same as the variable resistor controller; the resistance, voltage, and current fluctuated the same way on various parts of the circuit.

Enter car B. I added a MOSFET to the setup and mimicked the MOSFET wiring for car A, grounding them both to the Arduino ground. The result looks like this:

Here's a sketch:

Close up, MOSFET A:

MOSFET B:

At first, all seemed well. I sent signals to MOSFET A and successfully changed Car A's speed. I stopped Car A and pulsed MOSFET B, and I was able to control Car B's speed just fine.

Then, I turned Car B to a constant speed, and sent a signal to MOSFET A while Car B was still running. Car A started, but Car B's speed immediately dropped as a result of running Car A.

I hooked a multimeter up across the rails of Car B and watched its voltage while it ran on its own. Then, sure enough, when Car A started running alongside it, Car B's voltage dropped dramatically.

I figured this was because of my wiring configuration, so I left the multimeter on Car B, and made one change. I replaced MOSFET A with the original slot car controller:

I started running Car B again using its MOSFET. The multimeter showed a steady voltage, so I began to squeeze Car A's controller (the variable resistor), and Car A's speed increased. This time, however, unlike using a MOSFET to control Car A, the variable resistor did not affect Car B's voltage at all. Car B remained at a steady speed the whole time.

Any idea why this happens? The MOSFET seemed to function the same as the variable resistor (empirically) with a single car, but had totally different behavior with two cars in parallel. Is it because the MOSFET is not really changing resistance to current, but just switching it on and off, so it opens up another path for current to flow fully every time it closes? Is there an Arduino-controllable alternative to a MOSFET that would fluctuate actual resistance like the variable resistor? Digital potentiometer? Servo hooked up to a potentiometer? ;) I'm really curious what the difference is and what causes the major differences in behavior.


texts:
The GRBL library for Arduino looks very comprehensive but I like to understand how things work before I try to build them. Something I don't understand is how these systems get positional feedback.
I know it is common to set a Z point for a given tool, but this is just an offset. As far as I can tell from my reading it all depends on a combination of timing and stepper motors successfully executing exactly as instructed. I find it hard to believe that nothing ever gets out of synch.
Is there some kind of ongoing reality check other than stop switches to prevent out of bound travel? How does it work?
How do they measure slop and backlash to compensate for them?
I can think of ways I might try to do it but I've never seen my imagined feedback systems on any "real" CNC machine, so I have to ask.

Thanks to Spiro for a fabulous answer, but it led to me finding this response to a request for closed loop support in the GRBL github issues. It's the position of the maintainers.

I think the general idea is to never run into the problem of losing position. The motors and drive system need to be robust enough to handle the cutting forces. For open loop control, like Grbl, this is mandatory. For closed loop, this is still pretty much mandatory. In my view, closed loop control only gives you the ability to catch the error. In a properly size CNC system, the errors willl be nonexistent or very rare.

Well... crumbs. How am I supposed to build a fancy machine that finds the crookedly mounted billet and figures out its own offset and rotation ?
My desire for feedback arises more from fears of belt stretch but as Spiro points out ball screws are a better answer. A really expensive better answer, but that's not Spiro's fault.


texts: I'm building a mining rig and is planning on using a ESP120 HP 3kW 52V power supply. I've seen someone get it down to 48V with this mod, but I wonder some one got it down to 12V? Or is it not possible?


texts: Implementing High Pass Filter in Simulink

texts:
I am trying to implement the following block diagram using Simulink in Matlab.

I am having trouble getting the high pass filters to work properly.

To do the filtering, I am using the First and Second order filters from the SimScape toolbox.

Using a step source I am getting a sort of result, but I cannot work out how to adjust the cut off frequency for the first order and damping ratio for the second order filter.

Are these the best blocks to use, or is there a better one. If so, how do I tune the filters to work as I require?


texts: Charging batteries in series when they are connected in parallel in the circuit

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I'm new to electronics and I'm trying to build a charging circuit for NiMH batteries. There are four batteries in total. Two are in series, and the other two are in series. Then these are connected in parallel. I need to be able to switch them all to series when I plug in the USB for charging. I have an idea and please tell me if it will work. If not could you give me a way, thanks.

simulate this circuit – Schematic created using CircuitLab

The batteries i'm using are the Eneloop xx which are 1.2v so the USB would work because they add up to 4.8v. I was doing research about charging nimh batteries and found out that it is best to charge them in series and not parallel. So if this wont work than could you help me figure out what will switch it to series?


texts: FPGA filter - sinusoidal wave at clock frequency observed in filtered signal

texts:
I am using an FPGA to implement FIR filters, specifically for this question I have implemented a 12 point moving average filter. At the moment I am just using a signal generator as an input to the FPGA and putting in a pure sine wave at various frequencies. Now, my filter works as expected and has the expected frequency and phase response, however, in my output signal I see another sinusoid at around the clock frequency of the FPGA I am using. I have set the clock on the FPGA to be 40MHz and 10MHz and the sinusoid in the filtered signal occurred at around 40MHz and 10MHz respectively in these 2 cases so it is definitely proportional to the clock frequency.

I was wondering if someone could explain why this might be and what I could do to remove it? (I could use an analogue low pass filter after my filter to filter it out for example [although I'd prefer to remove it entirely since for my application low noise is ideal and adding more components will add noise])

I have uploaded a couple of youtube videos of what I see on the oscilloscope when I put in a sinusoidal signal generated by a signal generator (shown in yellow in the video) and what I see out of my FPGA filter (shown in blue).

Video 1 accompanying question for stackoverflow

Another interesting thing I observed, which may help in diagnosing what's going on, was that at certain frequencies this second signal disappears completely, in the following video the FPGA clock is set to 40MHz and I set the signal generator to generate 11MHz, 10Mhz and 9MHz sinusoidal waves. (The approximate frequency of the wave can be seen in the lower right of the screen) At 10MHz you can see that this high frequency signal seems to disappear. (this also coincides with a point of very high attenuation - the filtered signal is very flat)

Video 2 accompanying question for stackoverflow

If anyone has any suggestions of what might be causing this or how to get rid of it, it would be much appreciated.

Additional Info as requested:
I'm using a NI 5781 as my ADC and DAC it has a 14 bit Input and 16 bit Output. Data sheet is linked here: ni.com/datasheet/pdf/en/ds-212.

I'm putting in a sinusoid that has 1V peak to peak and a 0.5V DC offset - i.e. a sine wave between 0V and 1V.


texts: 5v / USB standalone surge protection? Buck/boost boards?

texts:
Not an engineer, but relatively handy. This is just out of my depth on what is possible (and hopefully, commercially available)
I had a 1/4 second brownout/blackout that fried all my wyzecam v2 (I tested with fresh wall wart PSUs to make sure they weren't the problem, no luck). I took a look at the circuit board and it looks like everything is surface mount, too small for me to just replace/test w spare capacitors (my default first step to try to fix anything electronic), so I'll have to buy a bunch of new cams (thank goodness they are cheap).
More than half my cams are in enclosures that have very little room for more than the camera - definitely not enough for a large surge protector or power strip. I looked on my favorite overseas parts website, but search terms like "standalone USB surge protector" just result in pages and pages of plug-in strips and other stuff that isn't relevant to my needs. I'd welcome suggestions on better search terms, but given that I didn't find a commercially made in-line 5v-5v USB surge protector, I was wondering if a buck or boost converter (maintaining the same voltage in and out) would offer any surge protection. And- if it matters what type of converter, then what components or keywords should I be looking for before buying?
2 of the cams have battery backup using an single-cell 18650/UPS board, but that wasn't marketed as having and surge protection properties, so I'd put surge protection in front of them as well.
I appreciate any suggestions and insights from the community on my options for small 5v-5v surge protection. I know nothing will be perfect or protect against everything, but something has to be better than nothing... I don't expect to be safe from lightning, but hopefully I can mitigate surges associated with momentary brownouts/blackouts?
Many thanks for your expertise!


texts: How to place decoupling capacitor in four-layer PCB?

texts:
I searched a technology document about placement of decoupling capacitors and the main idea is shown in the following picture:

I think it is reasonable but do I have to put the decoupling capacitor and MCU in the same layer? it is not convenient for me to place other devices. So i choose to place the decoupling capacitor in the bottom layer

My PCB is a four-layer(signal-power-gnd-signal) one and when I split power and  gnd layers the two vias closing to the pins of MCU in the above picture will not be included in net of power and gnd layer. Does it have the same nice performance as the case f in picture one? Do i have to take of inductance of vias in this case?


texts: Circuit's power budget and power dissaption

texts:
I'm a designing a circuit that I'll prototype soon.

I'm curious about how should I determine my power budget for the circuit?
Could you guys please suggest me how to do it?
Should I calculate each power rail Watt and sum it?
Do you have any suggestions for 'excel' table for this?

I would like to hear suggestions please or to know how the pros do it.

I assume that power budget estimation is important because according to this estimation I choose, for example, a voltage regulator. according to the power estimation (W) of rail - the power shouldn't deviate the power dissipation of the voltage regulator - Am I right?

Thank you very much, also forgive me about the newbish question :)


texts: What kind of led would be used for this keyboard

texts:
I have a project that involves this keyboard, it has 12 sections on the pcb marked UX (X being 1-12) for what I guess are for leds. If I'm correct what kind of led would I buy for it? Something like this?

Edit:
Here's a picture


texts: BJT Switch with a Diode from Base to Emitter

texts:
In this circuit, the diode is supposed to force a higher input voltage to turn the LED on, however when I created it on a breadboard I measured about the same input voltage (without the diode) to turn the LED on. My lab assignment then provides the second circuit with the diode grounded to the emitter terminal with a 330 Ohm resistor, which solves the issue and makes the input voltage to be higher than it was previously by about the turn on voltage of the diode. I don't understand how putting the resistor in place could solve the issue at hand.

Rb = 20K Ohm, Rc = 270 Ohm, Diode(1N4148), 2N3904 Si BJT Assuming BJT β =200 for calculations, 351-3230-RC LED (Vγ = 1.7V).


texts:
I am using Quartus SignalTap to debug my FPGA design:
I always been persuaded SignalTap is not accurate !!
This is what i found:
I monitor the reset signal with SignalTap :Reset toggles around, meanwhile same signal is steady at 1 in the oscilloscope.

SignalTap settings:

Clock source: 48MHz
Reset : PCB signal (same monitored signal)
Sample depth: 1K
Storage qualifier type: Transitional

The Questions :
Any ideas why doesn't Signaltap agree with my oscilloscope??
what are this software limitations?


texts: How would you connect a LVDS display to a laptop motherboard supporting natively a different display?

texts:
I'm planning a project of building a 4:3 laptop based on existing (modern) components.
As 4:3 displays are not manufactured anymore the idea is to take one from a old laptop, like a thinkpad T60. Then use modern laptop motherboard and components and put all that in a custom shell.

My main worry is that I don't know exactly how the LVDS interface is working. As the modern motherboard is going to be specific to the 16:9 display with which it's going to come along.

I think the LVDS interface is quite standard, though I think there are different 'version', so I guess the customization is probably on the software side?

Do you know how exactly a laptop motherboard is setup to a specific display? Is it coded in the bios? Or is there a LVDS controller chip that has a specific firmware flashed into? Any hints how you would do that?


texts:
I've designed S-R and J-K Flip Flops, their truth tables as I searched on the web, examined all of results on it and wrote as in the picture. Because of designing alternatives, I am confused and not sure about it at the moment. For example, when I search S-R or J-K Flip Flops, Google shows me lots of truth tables and designing which are different with mine. Can you please check whether this is correct or not? If it is not correct, what kind of changing must be done?

"Tanımsız which has been written for Q=0, Q'=1 means undefined/invalid."


texts:
Do small cylindrical potentiometers exist? I'm creating an LED "pen" which will change color corresponding to the position of the twist of the pen.
Imagine one of those pens that retract when you twist them. Instead of a pen tip, I would like to use that same motion to control a potentiometer. I haven't been able to find anything that could fit in a pen, or in that cylindrical package.

I guess, my actual question is, does something like this exist? Or an alternative that would have the same effect?


texts: Plugging in an oscilloscope in a land of non-grounded outlets

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Background: I have only one outlet in my house that remotely approximates a proper equipment grounding conductor (it's bonded to the mains ground point via the armor of 50s vintage AC, which is better than the rest of the house, which was wired with 50s vintage NM which lacks an equipment grounding conductor), and it is the outlet for the garbage disposal in the kitchen.  I can use it on a short-term basis by setting my gear up on the kitchen table and using a grounded extension cord to reach that outlet; however, that's not an acceptable situation long-term, and running a new home-run to feed my test instruments is not happening any time soon.

Is plugging my oscilloscope into a non-grounded outlet ever going to be safe, or is a GFCI insufficient protection against shock when you have an oscilloscope plugged into a circuit that lacks an equipment grounding conductor?  (We plan to install GFCI protection throughout the house in the near future to bring it up to the NEC 2014 provisions for a house which lacks EGCs in the wiring.)


texts:
Consider the following system:

where:

The motherboard contains a LCD controller (SSD1963 from Solomon Systech) and other components (application processor, solenoid drivers, power supplies, etc.)
The display board contains a white LED backlight driver and re-route LCD signals.
The TFT LCD (AA050MC01 from Mitsubishi) has a digital RGB interface (24-bit of data).
The pixel clock frequency is set to 30MHz.
The electrical ground cannot be connected to the chassis ground.

I would like to reduce radiated noise and improve noise immunity at a maximum in order to pass EMC compliance tests and therefore I need your advices. For your information, I did EMC tests on the first prototypes which showed a few peaks near 70MHz and between 100MHz and 200MHz that overlap the pattern by ~5dB. Refer to my other post for an analysis of one of these peaks.

Question 1

How can I calculate (or estimate) the required source terminator resistance of the RGB interace signals if I don't know the LCD controller output impedance nor the FFC cables characteristic impedances?

Is a source termination sufficient in this case or should I use other termination techniques?

Question 2

What kind of noise suppression filters should I add and where (on the motherboard only, on both cards, etc.)? Shall I prefer ferrite beads or capacitor type filters?


texts:
I am a little confused as to what happens to the input thermal noise value as it passes through an attenuator.
As I understand if you have a signal of 10dB and passes it through a 6dB attenuator it will reduce to 4dB. But for a noise of 10dB there is an added noise coming the attenuator itself, but is the overall output noise just equal to \$N_{0} = k_{B}TB\$.
Also if the input thermal noise is coming from a 300K temperature and moving to an attenuator at a lower temperature e.g 50K, how is equation affected?


texts: How can I wire a Mini-USB to Micro-USB cable?

texts: I'm trying to figure out how to connect the pins from a Micro-USB connector to a Mini-USB connector. I'm assuming it's more complex than just connecting the +5V to the +5v, GND to GND, D- to D- and D+ to D+. What else am I missing? Thanks so much in advance!


texts:
i wanted to ask what logic designs are used in industry for different logic functionalities?

So for example XOR gate:
The 1st image would probably save more space on a circuit, but for the second design NAND gates are more convenient but require more space?

Are these assumptions correct, and are they any other propositions to be aware of?


texts:
I've been looking around online for information on when I should use different finishes. I've found plenty of pro's and con's about each finish, but very little information on when I should choose one finish over another. The rule of thumb we have been using is if you need a high solder reliability use ENIG gold, otherwise a RoHS friendly finish (either lead-free or silver or whatever the manufacturer recommends).

However, a lot of what I have been reading seems to suggest the ENIG is great if we need to store blank boards for a long time, or if using BGAs which need to have a very flat surface to help promote soldering correctly. I have found very little information supporting ENIG as making a high reliability solder join.

My question then is when should I specify ENIG, or HASL, or some other type of finish?


texts: How to calculate the current output of a mosfet?

texts:
Suppose one know \$V_{gate}, V_{Drain}\$ with \$V_{souce} \$ connect to a resistor \$R\$ and then connect to the ground.
The aspects of the mosfet was also known.

How to calculate the linear portion of the output current? i.e. the relatively linear current output where it's not in saturation region, and the voltage on the resistor?


texts:
Sorry, will provide more information now.
I am working through this question from an all about circuits webpage (See attached webpage link) and have having trouble seeing how they calculate an impedance value.
Here is the example circuit:

Their method uses the reciprocal method for finding the parallel impedance of a capacitor C2 and inductor L combined in series, and then in parallel with a resistor R. I have worked out the capacitor and inductor in series ok. The LC series impedance is -j1.525k ohm.
I cannot get the same answer they have in the table that I have circled below in my calculator using the circled parallel forumula:

What I am asking is could someone show me what numbers go in that formula to get their answer I have circled in the screenshot?
This is the webpage of the question I am following if you want to see it:
https://www.allaboutcircuits.com/textbook/alternating-current/chpt-5/series-parallel-r-l-and-c/
Thanks David


texts:
I am trying to play a sound when two devices are more than a certain distance apart, say 30ft.

Some notes:

The device this is for is very small, about the size of a large keychain
I would like a wireless solution
There may or may not be a line of sight between the two devices, e.g. they could be in a different room in a house
As far as error tolerance, this distance does not have to be exact, say 30ft +/- 10ft even

I am a programmer and am very green with hardware, so I am hoping to be pointed in the right direction. Thanks very much in advance!


texts: Capacitor calculation for current pulse to solenoid

texts: Let's say I have a power supply 48V/100mA (4.8W). However, I have a push pull solenoid which will draw ~8W (48V/170mA) for about a 50 mS pulse. Can my power supply provide this extra power for that time with a proper capacitor, or do I need to increase the nominal power of the power supply?


texts:
What are your personal policies for selecting which nodes should have testpoints?
Can a testpoint be used as a node for powering a circuit?
Does a testpoint on a line create a stub, subject to interference or crosstalk, making it better to not have a testpoint in some situations?
Do you put testpoint on I2C and UART RX/TX lines for debugging?


texts:
We are trying to charge a 3.7V LiPo 150mAh battery with a 30W 12V Solar Panel.

The circuit we're using is a simple derivative the of the MPPT Solar Charger for Sparkfun's Sunny Buddy:

Our circuit is almost the same, except for on our prototype board, we use different resistances for \$R_3\$, \$R_6\$, and \$R_2\$. This is done to set the float voltage to 4.1 V as described in the datasheet for the LT-3652 2A Solar-Powered Battery Charger.

When powering the circuit with a DC supply, everything works OK. When supplied with at least 6.5 V, the circuit "turns on" and supplies a small but significant charge current to the battery at around 60-100 mA (to measure this, we cut the trace at JP5). With the solar panel disconnected, we measured ~15 V with a voltmeter.

However, when the solar panel is connected to the circuit, the voltage is a consistent 4.485V and current is drawn from the battery since the charger is "off" (circuit will only "turn on" with >=6.5 V power supply). Even when we connect another 6V @ 9W solar panel, we still measure 4.485V. We have tried using the two separately and in series, all of which maintain the 4.485V.

We considered exposing the solar panel to more light. However, since we measured the same voltage from different panels, we think the circuit itself is the problem.

How do we "turn on" this circuit with the solar panel(s) connected (how do I approach this / what do I try next)?

Note: I've read the datasheet & know a good amount about the LT-3652's capabilities.


texts: Does the RoHS standard apply to variable frequency drives?

texts: I'm having a bit of a disagreement with a customer about whether RoHS applies to variable frequency drives and comparable equipment. This is complicated by my understanding that RoHS is being rolled into CE, so CE marking will also imply RoHS compliance. Are VFDs required to be RoHS compliant?


texts: Why is the pole of RC circuit \$\frac{1}{RC}\$ instead of \$-\frac{1}{RC}\$?

texts:
In a RC circuit, we choose the voltage of capacitance as the output voltage.
Then the transfer function (TF) is $$\frac{1}{1 + RC \cdot s}.$$ According to the definition of a pole of a TF, let \$1+RC \cdot s=0\$, then \$s = -\frac{1}{RC}\$
Why I have seen so many times on text books that the pole is \$\frac{1}{RC}\$?
Thanks!


texts: Wiring and programming a shunt with Arduino for 2 way current sensing

texts:
I am trying to develop a battery monitoring for a solar system. I have a shunt which is rated at 500 A, 50 mV. and I want to measure current in both directions here. I plan to use the amplifier by AdaFruit ADS1015 to amplify my signal to the Arduino.

The problem is that the shunt sees current in both directions while charging the battery, the current flows to the battery and while discharging, the current flows from the battery to the system.

If I ground one side of the analog output of the shunt, then I would only get single direction of current flow.

How do I wire up a two way current sensing circuit to an Arduino or AVR?


texts: Why are my traces in eagle highlighted after I moved a component?

texts: Good day, I am currently working on a PCB in Autodesk Eagle and was almost done routing when I had to move a component and now I have all these traces that are highlighted with lines and I don't know what it means or how to fix it. It seems like it is telling you there has been a change of some sort. Is there a way to accept the change so that all of these highlighted traces are fixed at the same time? Thanks!


texts:
There are absolute and gauge pressure sensor types as follows:
https://ie.rs-online.com/web/p/gauge-pressure-sensor-ics/8212393/
https://ie.rs-online.com/web/p/absolute-pressure-sensor-ics/7176527/
I need to measure the atmospheric (barometric pressure) analog way. They are both similar and I am confused which one measures the atmospheric pressure.


texts: Computer won't post / Beep unless Unplugged for a few hours

texts:
I'm experiencing this issue for almost a year now. It is slowly getting worse. My motherboard is Gigabyte GA-Z77X-D3H and my PSU is Corsair CX600. The source of the problem most likely has to do with either one of these two components. I have built this PC 6 years ago. Thus this problem started to appear after 5 years. Motherboard is compatible with LGA 1155 chipset only.

As i mentioned, the PC won't beep/boot properly unless unplugged for some time. This time can be 30min, 1 hour, or a few hours (last time -today- it needed 2 hours). I have to unplug all cables from the chassis to bound the causes of the problem. My case (Mid Tower) is a bit cluttered now with all the cables, but i have them all separated and making sure that no cross contacts, or shorts are occuring, so i'm probably ok there.

I have replaced the CMOS battery, the fault isn't there. RAM Sticks, GPU, Storage drives are all working properly. I have also recently installed a custom fan speed controller. Finally all caps on the mobo look fine.

Could someone suggest me some methods i could try to identify which one of the 2 components is failing, or whatever else may be wrong? Thanks in advance.

EDIT

I forgot to mention that once the computer is powered on properly then there's no problem at all. I can leave it on for days without an issue.


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I am planning to add a 50A current sensing shunt resistor to my project. I want to use the ADS1110 ADC+amplifier IC to measure the tiny voltage drop.
The problem is that the current can range from 40A to -15A , and I also want to measure the negative current. How should I proceed?

simulate this circuit – Schematic created using CircuitLab

On the schematic the "load that can be a generator" is a motor with a regenerative braking system. sometimes it is a load, sometimes it charges the battery.


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I have a 5V 1000mA solar cell which I have connected to two 18650 3.7V 3400mA batteries in parallel.  The solar positive comes in through a 1N4007 diode (cathode toward battery)and then a latching relay before going to the positive of the batteries.  The latching relay disconnects the solar cell when the battery is charged to 4.2V and reconnected when the battery discharges to 3.4V.  The batteries are connected to a 5V boost regulator, powering an Arduino Pro Mini which for most of the time is in sleep mode.  Every two hrs the Arduino wakes up and performs some tasks for about 3 minutes.  During this time the batteries also power an ESP8266-01 through a 3V voltage regulator for about 2 minutes.  When not connected to the solar or at night the power drain is about 1/420V in 2hrs.  However when exposed to sunlight (in Tucson, AZ in April) sunlight is about 30º off directly overhead it only gains 1to2/420V in a 2hr. period.  It used to get  more, about 4/2hr period.  I am at my whits end as to why it is not charging more.  It should be.  I am attaching a schematic of my wiring. (sorry I'm not an electrical engineer so schematic might not be that great.)
Can anyone see where I have done something wrong keeping the solar from charging more or some way I can get it to charge more?


texts: What could be causing a very small voltage between mains grounding and a water pipe

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If I measure the voltage across the ground prong of a receptacle and a water pipe, I get around 42 mV of voltage. The ground prong is connected to a grounding conductor, which is connected to a ground bus bar at the main panel, which is connected to a #8 AWG conductor, and finally connected to an 8ft. ground rod.

The power system is: 240 V, 60 Hz split-phase (residential)

These are my questions:

What could be causing this voltage? Is this an induced voltage?
Or is this just a measurement error of my multimeter?
Is this voltage a safety issue? Should I be concerned?


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I want to be able to sense the presence of a vehicle in a parking space.  What type of sensor could I use to do so that wouldn't require invasive (digging asphalt) installation?

This must be a low-power solution.  I've thought about using a photoelectric sensor, but I don't think that's a good idea as it would detect ANY object and not just a vehicle.