texts:
I want to try and create a "motion sensing plane" where users can have contact points (their hands) detected when it passes through an invisible plane.  Think of it like a giant tablet touch screen, except you can pass through it and there's no actual screen.  The important thing is that I am able to locate not just that motion is detected, but WHERE on the invisible plane.

I've been trying to figure this one out, and was thinking about using a pair of IR sensors for the task, but I'm not totally sure that it will work.  I've attached a rough sketch of what I'm considering, but I'm open to suggestions.  I have a roughly $200-$300 budget for this.

Sketch:

Here are my requirements:

The plane is roughly 8ft tall by 10ft wide, and stationary while in use
The plane does not need accurate motion sensing at the edges of the plane (roughly 1 ft from edges of plane is not important)
The information needs to be able to be passed to a PC for processing, ideally via USB but other methods are acceptable.
Ideally I want to be able to recognize "push"/"pull" motions.  I was considering a second layer of IR sensors, so you'd have a "front" and "back" set that would deliver rudimentary depth sensing.  I don't need something more accurate than that really, just a "shallow" and "deep" touch sense.
I also want to allow anybody to simply come up and use the plane without preparation.  For instance, another alternative I was considering was a Wii Remote setup with reflective gloves or something much like the Johnny Lee samples from years ago, but if possible I'd like to avoid needing equipment on the user side.

Thanks everyone!  I appreciate any and all ideas on this topic.


texts:
I bought this USB to TTL cable: https://www.amazon.co.uk/dp/B01DC0S13M

Since it apparently uses the PL-2303HX chip, I downloaded the driver for Windows here: http://prolificusa.com/portfolio/pl2303hx-rev-d-usb-to-serial-bridge-controller/

After that, I connected the USB to the PC and the TTL pins to a single board computer. Unfortunately, my PC hasn't detected the cable, because Device Manager doesn't list a COM port for it.

Is there a way to check if the cable is faulty? I don't have any other USB to TTL cable, so it could be something besides the cable.


texts: Finding the period of a continuous time signal

texts:
I have the following continuous time signal:
$$x(t) = \sum_{n=-\infty}^{\infty}e^{-(2t-n)}u(2t-n)$$ where \$u(t)\$ is the unit function. I had previously determined that this signal was not periodic. However, it seems that it is. However, I'm not sure how I'd determine the fundamental period of such a function. Here is my work so far.

$$u(2t-n) = 1 \text{ for all } n \leq 2\lfloor t \rfloor \text{ and } 0 \text{ for all } n \geq 2\lfloor t\rfloor + 1$$
$$e^{-2t}*\frac{e^{\lfloor 2t \rfloor}}{1-e^{-1}}$$
But how do I proceed from here?


texts: I'm a totally newbie to altium and there's one thing that totally annoys me: I don't see any scrolling bars on the sides of PCB editor. Normally, screen scrolling is done by clicking middle button on mouse and dragging the pointer, however when I do that in Altium I zoom the screen in/out. Can anybody help me please?:(


texts: What is the significance of Input Resistance and Output Resistance in CE,CC,CB amplifiers?

texts:
Common Emitter, Common Collector and Common Base amplifiers have their specific purpose with differing voltage/current gains. For example, I know for a common collector has a voltage gain of approximately one, lagging behind 0.7 volts and has a high current gain.

But each amplifier configurations also have differing Rin and Rout characteristics, namely

CE Amplifier - Rin ~ moderate, Rout ~ moderate
CC Amplifier - Rin ~ large, Rout ~ small
CB Amplifier - Rin ~ small, Rout ~ moderate

Why is this information regarding input and output resistance important in these amplifiers? What purpose do they serve?


texts: Analog multiplexer or analog to digital converter to add analog inputs to NodeMCU?

texts:
I asked a question yesterday about the best analog multiplexer to use to add a few additional analog inputs to a NodeMCU. Someone recommended using an ADS1115 analog to digital converter. I am using this for an automatic garden watering project, where I need to read the values from multiple capacitive soil moisture sensors. Here is a link to the sensors- https://www.aliexpress.com/item/33042209039.html?spm=a2g0o.cart.0.0.52713c006kRBs8&mp=1
My question is, would an analog multiplexer or analog to digital converter be better for this project?
Thanks!


texts: Using a capacitor to properly power a servo

texts:
I recently attached a servo to my Arduino for the first time. I ended up needing a 470uF capacitor wired like this tutorial shows because my servo was freaking out and causing my laptop to throw "power surge" warnings (I have my Arduino connected to my laptop via USB).

Although I'm glad I got this working, this leaves me with several concerns.

Why was a capacitor necessary to "stabilize" my Arduino? In other words, why was it the solution to my Arduino being able to properly power my servo?
In that tutorial I linked above, there is a Fritzing diagram of the circuit with the capacitor. Can I assume this is a capacitor wired in parallel with the servo? Why parallel and not series?
What's so special about a 470uF capacitor (vs., say, 100uF)? I just used a 470uF because thats what the tutorial said to use, but what math could this number have been based on? In other words, how might I have arrived at this number myself?
I've heard capacitors can be extremely dangerous to work with, after all they store power. I'm now afraid to even touch the capacitor on my breadboard! How can I tell if its safe to remove the capacitor (even after I've disconnected the Arduino from its power source)? I have a multimeter but I'm not sure what setting/range I could set it to.


texts: What kind of part on the board below? Or it's a part of another part?


texts:
In our project, we have a 12V to 5.4V buck controller implemented with discretes.
Buck controller has input PWM signal from ASIC.
As part of protection, we have implemented a comparator(here i am not showing) to pull PWM pin to GND whenever Output voltage is exceeding 5.6V.
that circuit sketch is as follows.

I don't know how to implement LVCMOS Output in LTspice i have implemented using PUP_SW,PDN_SW and 10 Ohms impedances.
From PWM_OUT we have Other MOSFET driving circuitry etc which i have not mentioned here.
Over voltage protection circuit is implemented by components R3,M2 & S3(OVP_SW).
Expectation is
In normal operation (when output voltage <5.6V,) M2 gate will be at LOW level, So, it will not disturb the PWM_PROT(PWM Protected) net.
But when Output voltage >=5.6V, M2 gate will have HIGH Logic which drives M2 which pulls PWM_PROT net to GND.
My question now,
My PWM output(LVCMOS 1.8V) from ASIC can source Max 24mA.
Is this circuit works as expected?
i am seeing at over voltage event current over 100mA flowing on the path R4,S1,R6,R3,M2 to GND.
To keep this to safety level i want increase R6 to ~100 Ohms.
But i am checking whether it will slow down the rising & falling edges of PWM_PROT.
Whether LVCMOS Outputs can handle this over current internally?


texts: What is this dumbbell looking symbol on this schematic? (looks like jumper pad, but with a short)

texts:
Regarding to SJ1 and SJ2 in this schematic:

On the board it looks like two ordinary copper pads but with a thin connection between them. Is it meant to be a way to open the circuit by scraping off the copper between the two pads?


texts: Measuring high-side vs low-side current, different readings?

texts:
simulate this circuit – Schematic created using CircuitLab
I'm measuring current consumption of several different handheld devices (calculators, flashlights, etc), at the [lithium] battery. Using a simple Uni-T digital multimeter set to mA, I'm measuring current separately between '+', and separately between '-'. I see some devices which show slightly different readings between '+' and between '-'.
One no-name calculator, for example. When in use, I'm seeing a small difference of -53.2mA at '+' vs -52.8 mA at '-'. After about 5 minutes of inactivity, it automatically turns the display off, and for almost exactly 120 seconds measures -1.57mA drain when measured between '+', and -0.08mA drain when measured between '-' of the battery, then both readings drop to about 0.0 mA. I am assuming it goes to some sort of a deeper sleep mode. But what is the most likely explanation for the discrepancy in measurements?


texts: Regulator and charging in a portable device

texts:
There are quite a few similar posts on this subject but I'm a little confused about the best way to proceed in my specific project. All my previous regulators have been linear types (eg: 7805, LM317 at best) - nice and simple. For me anyway.

The project I'm working on needs 3 voltage outputs from a Lithium (lipo or li-ion) battery - 3.3V, 5V, 12V.

3.3V @ 500mA (estimated) main rail for the ARM based system on module. ARM can be at full power, standby, or off. This requirement doesn't look too onerous. Stackexchange has some good posts in this area.
12V @ 250mA for sensor system A. Switchable from the ARM (or a PIC or some such).
5V @ 2.5A for sensor system B. Switchable from the ARM.

Plus the battery needs to be recharged. I can use one or two cells although it might not be up to me. Two cells might be easier given that I can boost to 12V and derive 3.3V and 5V from the 8.4V line.

I'm not sure about the best way to proceed as there's a blizzard of chips out there. I was hoping someone has used a nicely behaved one that combined charging and regulated outputs. For example, Microchips MCP7383 can charge LiIon fine and a chip like the TPS63020 is a buck/boost regulator to give you 3.3V but other chips combine the charger and the regulator which seems a better idea.

If I use a single cell LiIon I get 3.4/3.5V to 4.2V. Is that too tight for 3.3V, especially given the power draw when I turn on the 5V boot circuit. Should I first boost to 5V and use that to get 3.3V? And then use another boost to 12V?


texts: RS422 charachteristic impedance and its variants

texts:
This is regarding the RS422 bus hardware.
I have a receiver that has Vih of 1.8V and a max of Vcc(3.3V).

Supposing I link a driver and receiver up. The driver,as per the EIA RS422 standards state that it can supply +/-6V differential. But since its dc levels I am reckoning it will be in the range of 6V and 0V.

Now, the receiver has a Vih of min 1.8 to 3.3V.
I have posted this before but somehow I am not able to understand how I can directly interface them without a voltage divider. But using a voltage divider has its issues of impedance loading. I understand RS422 has a charachteristic impedance of 100Ohms. Now, I am just analysing the effect of passives on the charachteristic impedance on the addition of extra passives. So, supposing, I add some resistors as shown, what will the impact be ?

Also, I have a requirement that states that Differential input voltage
 Vdi - 600mV < Vdi < 6V(each voltage inside this range is interpreted as a signal). But, I selected a receiver as stated -

.

Will this work out ?

I just looked at this RS422 receiver  - RS422 receiver.
The Vid = -12V to +12V. What is the reason for such different Vids in
the same standard ?


texts:
I have seen patented hardware designs at the level of generic digital block such as shift registers, flip-flops and adders. If a chip maker were to include such a design deep within an ASIC, how can patent holders uncover copyright infringement? Do patent holders really go around planting industry spies to get blueprints, or engage in etching open mass produced chips to deduce internal logic?

On another note, is it ethical to glean ideas from patents and include it within commercial products?


texts: Some help with buzzer schematic and reducing power troughput

texts:
I have a water tank with a built in simple 'float switch'. It acts like any other switch. Last year I tried connecting it to a buzzer so that I would know when the tank would be empty.
This burnt out the switch almost instantly, so I came up with something much too complicated for my likings:

Some things to note:

My battery system is 24v
The timer relay is 12v (hence the transformer), when powered it connects the output pins for 5 seconds (the length of the alarm).
I only added the entire 'switching part' to reduce the current, because when I would put the switch between the supply and transformer directly it would 'burn out' after 1 use.

From the start on I have found that the buzzer is not loud enough. So I am planning to 'upgrade' to a 12v buzzer with 85db. And I thought this would then be a good time to simplify things. See below:

Now the main question is:

How do I avoid burning out the switch? I thought of adding a resistor, but at 12v and lets say 100ma (the pull in for the relay is 50ma and the nominal use of the buzzer 25ma), the resistor would get too hot, wouldn't it? The switch is rated 500ma max. fyi.
Should I stick to the in my opinion over complicated old idea? I would like to make it a lot simpler and not have to use the extra 1.5v battery.

Thanks!


texts: How the wiring of IR emitter detector pairs work

texts: Attached is an image from the book I am going through. I don't quite understand the schematic and was hoping someone could explain it to me, including the use of the resistors. Like, does it matter where on the ground line the A0-A4 pins are connected? I have this all wired up and it's seems to be operating quite strangely.


texts: How can PMOS eliminate body effect but NMOS doesn't?

texts:
I have a question on the body effect of MOS transistor. In particular, how does the body effect in PMOS be eliminated (by connecting bulk to source together) while this similar technique doesn't do the same to NMOS?

The answer to this question is given by:http://www.onmyphd.com/?p=body.effect
It is saying that PMOS is fabricated as N-well such that such PMOS are physically seperate from each other (seperate from other well) so that you can connect bulk to source to each one of them individually. On the other hand, NMOS shares a common substrate, so if you were to connect the source and bulk, you will have to do so for all NMOS.

However, I still don't see the reason doing this in NMOS will cause any problems at all.


texts: What is the difference between DC base current and signal current in CE transistor amplifier?

texts: I came across a sentence that " if the DC base current has to be 10 times the signal current....".I could not understand, what is DC base current as I have just read about Input current and Output current? And also what quantity (like current gain{beta}, ratio of current through collector and current through emitter, etc.) is the mentioned statement asking for?


texts: Bootstrap circuit for high-side MOSFET driver

texts:
I am very familiar with the operation of bootstrap drivers on MOSFET driver ICs for switching an N-channel high-side MOSFET. The basic operation is covered exhaustively on this site and others.

What I don't understand is the high-side driver circuitry itself. Since a good driver pushes and pulls large amounts of current, it makes sense that another pair of transistors exist within the IC to drive the VH pin high or low. Several datasheets I've looked at seem to indicate they use a P-channel/N-channel pair (or PNP/NPN). Taking away the construct of the IC chip, I imagine the circuit looks something like this:

simulate this circuit – Schematic created using CircuitLab

It seems that we've just introduced a recursion problem.  Assuming the node marked as "floating" can be any arbitrarily high voltage, how are M3 and M4 driven that doesn't need yet another driver to drive the driver (and so on and on)? This is also assuming the high-side driver is ultimately controlled by a logic-level signal of some kind.

In other words, given an arbitrarily high floating voltage, how is the push-pull drive of M3 and M4 activated by a logic-level signal that originates from off the chip?

Point of clarification: The specific question I'm asking has only to do with activating the high-side push-pull bootstrap drive with a logic-level signal. When the high-side voltage is relatively low, I recognize this is trivial. But as soon as the voltages exceed typical Vds and Vgs ratings on transistors, this becomes harder to do. I would expect some kind of isolation circuitry to be involved. Exactly what that circuitry looks like is my question.

I recognize that if M4 is a P-channel FET (or PNP), another bootstrap circuit is not necessary. But I'm having trouble conceiving of a circuit that will generate the proper Vgs's for both M4 and M3 as the external transistors are switched back and forth.

Here are screen captures from two different datasheets that show a similar circuit to what I drew above. Neither go into any detail about the "black-box" driver circuitry.

From the MIC4102YM:

And the FAN7380:


texts: How to remove folded battery from phone without starting a fire?

texts:
I was trying to replace the battery in my phone, but since it was very well glued to the phone, I accidentally folded it in half. This immediately caused some dark brown smoke to come out from it, so I took it outside.

A few hours later, it seems to have stopped making smoke, and the bottom folded part looks very swollen.

I'd like to take it out, but I'm scared it will do something like in this video. Is there anything I can do to avoid it from catching fire? Also, are the fumes it releases dangerous?


texts: Linear Frequency Dependent IQ Distortion

texts: I want to design FD (frequency dependent ) IQ (In-phase,Quadrature) distortion that changes the phase mismatch linearly like a+b*K ( where K is  1 to 64) and amplitude remains constant to test my estimation algorithm against it. I need this filter to be in time domain before FFT but changes the IQ imbalance parameters across different subcarriers(hence the name FD) .I wonder how to achieve this ? I was thinking something like  H = alpha *exp(2*pi*1i*(a+b*K)) as the frequency response and just take the IFFT of this and convolve with the signal. Do you think this is correct , any help will be appreciated ?


texts: I bought a soldering iron from market. I used it for about 15 minutes and it worked great, but after that, when I touched the soldering wire to the tip of the soldering iron, I got a threatening shock. Can anybody tell me what happened?


texts: What probe/tip to use to clip into a PCB test point?

texts: I need to have a digital logic analyser connected to a test point of a PCB board I'm developing for. To be clear, I mean the little ~0.5mm hole kind of test points. What kind of probe would allow me to plug into them without me having to solder it permanently, constantly manually hold it in place, or create a test point fixture?


texts:
I'm working with an STM32F4 Discovery board and I've come across a bit of unusual behavior that I'm hoping someone can explain the cause of to me. My goal is to configure a timer to trigger an interrupt at 100 Hz (i.e. 10 ms period). It's important for my project to have this value be as close to 10 ms as possible. My system clock is configured at 168 MHz, and the timer I'm using is clocked on the APB2 bus, which is clocked at 84 MHz, but since timers operate at double their bus's clock speed, my timer's clock is effectively also at 168 MHz.

To get my period of 10 ms, I would have to configure my prescaler and period values in the TIM_TimeBaseInitTypeDef struct to 16-bit integer values. The initial values I chose were 60000 for the prescaler, and 28 for the period. 168 MHz / 60K = 2800 Hz. Then setting my period to 28 should give me an update event at 100 Hz.

I'm fairly positive that my math checks out, however, when I measured out the time when my interrupt was firing, my period was something closer to 10.33 ms, rather than the expected 10 ms. After playing around with other settings, I decided to try and change the prescaler and period values to see if the timing settings changed. To my surprise, they did. For the period values that I did try, I plotted them out in this plot below:

Two main observations that I see:

1) Swapping the period for the prescaler and vice versa results in the same measured period

2) The closer the period and prescaler values are to each other, the closer the measured time is to the desired period.

Does anyone know why this is? It seems to me there's no difference between the pair (60000,28) and (1344,1250) in terms of calculating the period (i.e. they both multiply to 1680000)

Edit: I've added a link to my code here.

Edit2: I feel like the comments are deviating from my intended question. My issue isn't that I can't get a 10 ms period. My question is WHY setting the prescaler and period to values further apart from each other results in a less accurate period?


texts: Modern replacements for old DRAM memory chips

texts:
I have an old video card for a computer from the 1980s era, but unfortunately the memory chips on it have gone bad.  As it's quite a rare device today, I would like to repair it.

Unfortunately I can't find anywhere that sells pin-compatible replacements for the old 4164/4464 and 41256/44256 ICs.  These were apparently quite widely used ICs - the 41xx is 1-bit memory, and the 44xx is 4-bit memory, with the xx64 having 64k addresses and the xx256 having 256k addresses.  All are 5V TTL logic.

Is there an easy way to replace these failing chips?  If there are no compatible replacement chips being manufactured anymore, is it possible to find a chip that's similar enough that it could be substituted with minor modification?  What would I be looking for?  These are DRAM chips, so I'm not sure if they could be substituted with SRAM chips or newer types of memory ICs, since the DRAM refresh may be too slow for newer chips to maintain the data.

The chips on this card appear to be arranged in two independent banks of four 4464 chips each, but I have other failed cards with different arrangements so it would be nice to aim for the more general case of 1-on-1 chip replacement rather than trying to replace a group of them with a modern larger capacity chip - only since that solution may not work elsewhere.


texts: Frequency response measurement problem with mobile phone: same (wrong?) readings for different speakers

texts:
I have built some bespoke speakers and tried to measure their frequency response.
My rig is:
Source:
Android phone Samsung A3 as a source, playing frequency sweep using Android's Frequency Generator App 20Hz-20KHZ.
Amp: NAD 3020,
Speakers: bespoke transmission line with driver's Fs =84Hz, tuned at 60Hz. My calculations show that's where the bass roll-off should start.
Measurement:
Samsung A3 with DaytonAudio IMM-6 measurement microphone (Working range 20Hz-20KHz +-1dB).
I carry out measurement in an ordinary room, without much draping, at about 30 cm away from the driver, so I do not expect to see any nice smooth distribution.
What I see is shown in the image below. Which I believe is wrong, since the roll-off should be at about 60Hz. I've measured the other speakers I own and I can see very similar frequency response, although their woofer driver has Fs = 60 Hz and should play much deeper than the first speakers I measure. The result below is captured with the Spectroid App, but I tried a few other with the same effect.
On the picture, my reading is red (max hold in Specroid), yellow is the current sweep.
Could anyone shed the light as to what I'm doing wrong:

Is it possible that the mobile phone only produces useful bass from 100Hz Or the amp is wonky? That sounds hardly plausible as the music plays rather nicely, with full-bodied punchy bass.
Is it microphone's fault? I also tried to plug the microphone to a tablet and the laptop and use devices' own microphone - with very similar result.
Is it the software fault?
Is it the room or my method that is to blame?

And finally, has anyone successfully measured their speakers's frequency response in a similar ad-hoc set up and how did you go about it?
PS: Sadly all the equipment I have at my disposal is what I listed above, plus the multimeter and the solder. I'm a proper noob when it comes to electrical engineering and signal measurements - the simper suggestions are the better!


texts: DC motor speed control: 12VDC 700mA fan motor powered by 7.2Ah sealed lead-acid battery

texts:
I am using a 7.2 Ampere-hour Sealed Lead Acid Battery to power a 12V DC motor which is driving a fan, and I need to understand how to control the fan speed.

When I power a 12V DC LED strip directly from the battery there are no issues, so the battery works fine. But when I instead connect a DC motor or a DC Fan directly to the battery, the speed is way too fast and I am concerned about possibly damaging the motor.

The motor takes about 500-700mA current. I have seen in many answers that 500mA capacity would mean the device would draw only 500mA, even if higher amperage is available. Is this also true of DC motors?

Can someone guide me on how I can regulate the current supplied by the battery, to control the speed of the motor? Since I am just starting out, I want to understand how to implement both a fixed-speed control solution and a variable-speed control.

Would simply adding a resistor in series with the load reduce the supply current and thus control the fan speed? If so, how would I select the component and would there be any other issues? Or is there a better solution?


texts: Use battery voltage rating or fully charged voltage?

texts:
I am using a 3.7V (18650) battery, but its fully charged voltage is 3.85V.

When calculating a resister for an LED circuit, do I use the battery's voltage rating (3.7V) or the fully charged voltage (3.85V)?


texts:
I am planning a low key game console for my own leisure, based on the VGA signal.
I have implemented parts of it on breadboards with lots of wires, but it is very
error prone, thus my move to the FPGA world.

Goal:

Resolution around 240 columns x 240 lines and 8 bits / pixel.
Double Buffering for smooth animations.
Micro nova mercury FPGA board (XC3S200A) and 512 KB external SRAM.

Questions:

What is the best way for implementing the double buffer ?
The SRAM device would be a problem when continously accessed from the signal
generator part since it would lock out the writer part for setting pixels.
The blanking periods are too short for doing this.

If I would go down with the resolution (132 x 132 @ 8 bpp) I could use
the block RAM (288 K bits or 36.000 Bytes). Are there any
disadvantages or problems which I don't see yet, when using up the block
RAM for such an application ?

Thanks!


texts: Inductor behavior when connected to inverter

texts: I was working one of my project wherein i was supposed to connect inductor to an inverter and inverter's output would be fed back to inductor. However my observation is that whenever inductor is connected to inverter, inverter output frequency reduces. I am unable to understand what is causing that. Can somebody help me understand this.


texts: Firmware protection on AVR and PIC controllers

texts:
Can someone extract the HEX file that I burn in a microcontroller I provide them?

If that is possible, how can someone ensure that their code is secured in embedded systems? In the case of PIC and AVR microcontrollers, how can one protect their firmware from being reproduced?


texts:
Say I've got a 5V circuit that draws 30W. 1Ws is a joule, so to run this circuit for 1s I need 30 joules of energy.

The amount of charge stored in a capacitor is \$\frac{1}{2} CV^2\$; solving for \$C\$, I'd need a 2.4 farad capacitor to run my circuit for 1s. That's pretty big.

But say my circuit only drew 30 W at an absolute maximum, and only for very brief periods, like, say 0.25 s at a time. Mostly it was drawing 20 W or so. Which means mostly a 25 W power supply would be plenty enough to drive it. Could I use a \$0.1F (= 2.4 F \times 0.25 s \times 5/30W)\$ capacitor to "take up the slack" of that extra 5 W the power supply isn't rated for?

Have I got the theory right, and would this work in practice?


texts: What is a stub on PCB and what is it used for? Stubs exist with PCB traces and also vias, why?


texts: I have a front end module that generates an ECG signal that varies from +/- 1.5 V. I need to shift this signal so it goes from 0-3V. I have looked at some other threads to try and understand the circuit better, and I found a thread from a few years ago featuring a very similar project to this one (The only difference was the input and output values, being +/- 2.5 and 0-5V), but all I was able to glean from that was that R2 and R1 should be a 2:1 ratio, but other than that I'm not really sure where to go. I still need to find the V+ voltage when Vin is +1.5, Resistor values for R3 and R4, and the gain, but I am pretty stumped.


texts: Is the pullup resistor on the reset pin of the TCA9548A multiplexer necessary if I do not intend to ever use the reset pin?   The datasheet says to "Connect [RESET] to VCC... through a pull-up resistor, if not used."   If the pin is not used do I really still need a resistor?   Will the IC ever try to assert that pin low for any reason causing a short?   I can't think of any other reason why they would recommend a resistor.


texts: Can I use the following power supply as a constant fixed current source?

texts:
Might sound silly for many of all but is this device's knob for the current for obtaining constant current or limiting the max current? Can I use this Dc power supply to obtain a constant current regardless of the resisyances? If not what would u prefer as an adjustable current source? Here is the device:
http://electronics123.net/amazon/datasheet/ps613u.pdf

When feeding a DC motor with this the motor spins faster when increasing the current knob. Im a bit confused if it is only for limiting purpose or not.


texts: Making a super efficient line following robot that runs on super capacitors for as long as possible

texts:
I'm trying to make a line following robot that runs for at least 20 seconds on a 2F super capacitor (5x 2.7V 10F super capacitors in series with protection circuits.) So I'm working with 13.5V and 182 Joules of energy.
My first thought was to use an Atmega8A in standalone configuration that draws almost 18mA. But the Arduino Nano draws around 20mA peak, so I decided to use an Arduino Nano and replace its 5V regulator and get a 3.3V one. I'll be using a QTR-8A IR sensor array that draws about 60-70mA. Both the Nano and the IR sensor array will run at 3.3V.
I'm confused about the motor drivers and motors.
I know I should've made my plans around the motors as these are going to draw the most amount of current.
My entire robot's weight is about 400gm. I was thinking about using the 12V 220RPM pololu micro metal gear motors but I'm not so sure. As for the motor drivers, I was thinking of using a TB6612FNG. I don't actually know if other good alternatives exist. So, I need some suggestions for regarding the motors and the motor drivers.
What do you guys think of my setup? I'll also appreciate some suggestions on how I can conserve more power for better runtime of my robot.


texts:
I purchased two MLX90614 boards from aliexpress here.
They are both higher accuracy ( GY-906 DAA => 0.2°C, 3V) versions for medical instruments. I tried to hook one to Arduino nano (3.3V) but once hooked up, Arduino did not want to start. Upon investigation, I see that I am measuring zero resistance between Vin and GND. I presume it is faulty board, probably voltage regulator problem. However when I inspected the second board (that I did not yet hook to anything I measure similar thing - short circuit between Vin and GND).
Could there be anything that I might be missing other than that both boards are faulty?
Update, attaching photo per request, there is not much to see.


texts:
I have a Raspberry Pi, a 74LS245, and an ATTiny85.
I connected the Pi to the Tiny through 1k resistors, and am able to use SPI to program it, no problem.
I have added a 74LS245 inbetween, to electrically isolate the attiny.  On a new AtTiny, I'm able to program it without issues, so I have apparently connected the pins correctly.
The issue is that when the device is programmed to have an output pin PB2 as high (I was testing), the SCLK is then unable to be driven low, and then programming can't happen.
Sadly, I'm not an EE by training or even by practice, and I'm kind of at a loss for how to "correctly" make the 74LS245 overpower the output pin of the ATTiny.
I'm hoping I've been explicit enough, and if there's a diagram I should be following, I'd love to see it.
Edit:
Some follow up experiments:

DDRB = (1 << PB2); PORTB |= (1 << PB2); causes the issue repeatedly.
Set PORTB to zero, and it doesn't happen.
When the SCLK can't be driven by the 74LS245, it can be driven by the Pi.

However, only if it's directly connected, and not through the 1k Resistors I have between the Tiny and the 245.

There is no modification needed for MOSI or MISO.  Those work directly being driven by the 74LS245, and the device doesn't care what condition the pins are in before.
The reset functionality is operational, and the pins are driven to a hold.  On PB2, however, this is a "1" is the port had previously been set to out.


texts: How to achieve clearance for the mechanical pin and vias from ground plane in PCB Editor?

texts:
I am a beginner, trying to learn the PCB Editor myself. I have to assign layer-2 as ground plane. I managed to assign layer-2 as GND as planned. But, now my mechanical pin and other high speed signals are connected to the this ground plane. How can I achieve the clearance with vias and mechanical pins from the ground plane. I have checked the constraints and the spacing has kept as in the reference design.
I have attached the reference board layout and my experiment layout snaps for your reference.
Reference board layout

My Layout


texts: Why are these Fourier transform values not as expected?

texts:
We are being taught Fourier Transform in our EE course this semester and I have several questions about it. The answers do not need to be rigorous and mathematical, all I need is an intuitive 'feel' of the Fourier Transform. I may be completely wrong at certain points so feel free to point it out.

Is the FT of a continuous function \$ x(t) \$ approximately equal to the DFT of the discreet-time version of the same function?
In other words, if

\$ X(\omega) \$ if the FT of \$ x(t) \$
\$T\$ is an array containing closely spaced values of time (for example [-10:0.001:10])
\$y\$ is an array containing \$x(t)\$ \$ \forall\$ \$ t\in T\$
\$ Y \$ is an array containing the DFT of y
\$ Y'\$ contains values of \$ X(\omega) \$ for corresponding \$ \omega\$
Then is \$Y \approx Y'\$

Can someone please explain the result of the following code

t = [-10:0.001:10]
x = sin(t)
y = fft(x)
z = abs(real(y))

I expected z to be an array of real numbers containing a sharp peak as the FT of a function gives the spectrum of frequencies contained in the fourier series representation of the function. But it turned out that the maximum was 4.32 and the mean of all values of the array was 0.55, which does not seem to be what I expected.
Is there something wrong in the way I am interpreting the fourier transform? How do I need to proceed if I need to calculate the frequency spectrum of this function?


texts:
Interested in Embedded Systems, I'm coming from Computer Science background.
There is a thing that I can't get my head around for awhile about pins of GPIO.
Let's say that we have a port which is associated with two register (direction register and data register) and that we set a certain digital pin as output. When we set the bit to 1 in the data register, corresponding to that output pin, does it mean that the microcontroller starts providing constant voltage to that pin? If so, is the voltage provided through the data bus to the data register (which I don't think it to be the case) or is there a wire from the pin to power source to get the voltage?


texts:
For the Ethernet application in my design using RMII interface, I need to drive two CMOS loads (two reference clock pins, one of a Freescale Kinetis K60 Microcontroller and one of a TI's PHY chip) through a 50MHz oscillator. The oscillator specifications mentions the "output load" parameter as 15pF. As per the datasheet of microcontroller and PHY chip, the input capacitance of pins is given in general as 7pF.

Will it be ok if I drive these two pins through only one oscillator output?

The reason for using single oscillator is that it will clock both the micoronctroller and the PHY reference clocks together almost skew-less, and it will also save some cost by avoiding the use of an external clock buffer.

Any help would be highly appreciable.


texts: average voltage and the RMS of pulse width modulation

texts: I have a DC motor works on 12 volt and  i wanted to control it using transistor-NPN- i connect the base of transistor with timer 555 which generate PWM so the 12 volt also will be generated as PWM the question is the real voltage that will reach to DC motor will be the average value of 12 volt PWM signal or it RMS(root mean square)


texts: Creating PCB or breakout board for sensor/ICs

texts:
I want to buy a BMA180 accelerometer to learn programming SPI and I2C devices (the sensor supports both). This is the link to the sensor on eBay and below is a picture of the sensor:

How do I work with that?

I haven't found a ready made breakout boards to solder it.

Should I buy an SOP to DIP converter?


texts: WLCSP MCU's - what hardware is needed for programming these tiny chips?

texts:
I just received my DigiKey order of some Atmel ATTiny4 MCU's from DigiKey.  I wanted to tinker with one of the smallest MCU's I could find, and this was one of them.

It is, in fact, so small because it is wafer level chip scale packaging (WLCSP), described here.  This image from that document indicates scale.

This question may be very naive, but how do I "hobby" with a chip this size?

I cannot directly plug it in to a breadboard. (Unless there is some socket I can buy that I am unaware of?) Programming the chip is the next step, but I do not know what hardware I need to interface with my PC.  There are plenty of tutorials out there on the web that show to program a DIP (with an Arduino, for example).  I cannot, however, find any information on how to program these tiny chips.

Is this even possible for someone (me) tinkering out his apartment?  Or are these chip sizes primarily sold to manufactures of electronic devices with automated systems for integrating these chips?

Note:  I am not sure how to tag this question.  Feel free to edit.


texts: How do I connect light bulbs to an alternator on a bike?

texts:
Some friends and I are working on a school project and need a bit of help. The basic premise is that we’re using a bicycle (which is kept stationary) to spin an alternator and power some lightbulbs. Here are the specs of the alternator:

We’re wondering what kind of bulbs we can use (and wattage and voltage) and how to connect them (series or parallel). We’re also worried that the output of the alternator might be too high for the bulbs, will we need resistors or anything like that?

Please let me know if there’s any other information I can provide to help.
We don't know much about electrical engineering ourselves.

Any advice would be appreciated, thanks!


texts: High frequency small signal model of PMOS vs NMOS

texts:
Here's the high frequency SS for NMOS
https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-012-microelectronic-devices-and-circuits-fall-2005/lecture-notes/lec11.pdf
http://imgur.com/a/HNGaY
Stack exchange picture insert wouldn't accept an imgur link

What changes for PMOS? The only problem is the arrow directions for the current sources and I'm not sure if there is a way to figure it out with reasoning instead of redoing the derivatives to get the current sources

My gut instinct is that even though now the source is higher voltage than the drain in PMOS, the final high frequency SS PMOS model ends up similar to the NMOS but I don't have the intuition for why the current source in the high frequency NMOS picture above had current going down from gate to source so I'm not sure if that direction should be reversed for PMOS


texts: I see servos a lot on robots that seem to be connected from both ends. Are there servos where the shaft are on both ends of the servo?


texts: Is there an IC to make a split power supply from a single power supply?

texts: I'm trying to find the easy but a somewhat stable way to create a split power rails Vcc Vee for the opAmp applications. Any specific known IC for this purpose?


texts:
I'm constructing a power supply based on solar cells backed by batteries. The solar cells deliver between 0 and 4 A, depending on the time of day, while the charger I plan on using, the LT3652, has a maximum charging current of 2 A. I've started to consider running two of the chargers in parallel in order to utilize the full 4 A, but I'm very uncertain about how they will behave drawing on the same current source.

Does anyone have any hunches, ideas or opinions regarding this setup? A rough sketch of what I'm talking about can be seen below (note: this is not meant as a circuit diagram, just a sketch of what I mean -- don't let the fact that it's drawn using circuit symbols confuse you, it's more like a flowchart).

Sorry about the vagueness/scope of the question, but I don't have much experience with charging circuits and want to avoid doing something stupid.


texts: MCP23017 with NODEMCU v3 (lolin) i2c doesn't work

texts:
I want to use NodeMCU v3 with MCP23017 that has MAX6675 at the end. Everything is on circuit please see the image. MAX6675 (U3) doesn't want to work with MCP23017.

First MAX6675 (U4) works perfectly fine using MAX6675 library

 MAX6675 max(D5, D7, D6);
 max.readCelsius(); //gives proper temperature

For MCP23017 Im using Adafruit_MCP23017 library
I have tested MCP23017 with simply code. Led is blinking so Im assuming that is not broken.

Adafruit_MCP23017 mcp;
mcp.begin(0);
mcp.pinMode(0, OUTPUT);
mcp.digitalWrite(0, HIGH); //LED lights up
delay(1000);
mcp.digitalWrite(0, LOW); //LED turns off
delay(1000);

I slightly modified MAX6675 lib to use adafruit_MCP23017 to digital Read/Write. Here is my github repo.
Finally im trying to read MAX6675 (U3) connected through MCP23017 (U2) using that code:

  Adafruit_MCP23017 mcp;
  mcp.begin(0);
  MAX6675_MCP max_mcp(mcp, 1, 2, 3);
  Serial.print(max_mcp.readCelsius());  //displays 0 or NAN

Assuming:

1) U4 / U3 works connected straight to NodeMcu

2) MCP23017 works because of flashing led

And my question is: Why MAX6675 (U3) doesn't want to work connected through MCP23017 (U2)?

Where I made mistake?

If my question is not well written, please correct it. Thanks!


texts: Shield EMF from power cable with aluminium foil

texts:
There is a big electric cable behind a wall.  On the other side, I read around \$2 \mu W / cm^2\$ of EMF at distance about 3 feet from wall.

Is there any way to shield this using aluminium foil?  I tried placing a 1 foot x 1 foot rectangular foil between source and meter, but I got no reduction.


texts: How is circuit topology chosen in analog designs?

texts:
Suppose I'm an experienced analog designer, e.g., RF, power electronics, ADC.

How does choosing a circuit topology fit into the overall workflow for a typical work assignment? I imagine my manager will be responsible for a larger system, like a whole RF to digital pipeline, and will ask me to do a specific component like a power converter or an oscillator. I imagine the workflow for my oscillator is something like,

1) Using some amount of intuition and experience, choose a circuit topology given the requirements.

2) Perform calculations to estimate critical component values, using scripts to optimize.

3) Repeat 1 and 2 if a given circuit topology wasn't a good choice.

4) Tape-out or some other form of pre-fabrication, etc. etc.

In practice, how does #1 play out? Do designers generally have a bunch memorized and ready off the top of their heads, with one or two go-to's to try first? How often do they need to learn new topologies, or develop new ones entirely? When multiple topologies might work, what metrics might be used to consider which to choose first? What resources or references do they use to look for new topologies when familiar ones don't meet their requirements? How might this work-flow vary between RF, power, low-frequency, embedded vs IC, etc.? Examples or case-studies would be really appreciated.

I ask in part where, coming from a mostly coursework background, usually topology is fixed and "design" just involves analyzing circuits to choose their parameters. The open-endedness of "build an oscillator with given specs", when there's dozens of feasible oscillators out in the wild, sounds overwhelming, so I want to understand the heuristics and thinking that are used to deal with this.


texts:
I am currently working on project involving piezoelectricity and I'm in need of some advice. I'm pretty much a beginner, but I've been doing lots of research. I just need input to help fill some gaps. The question I’m trying to answer is, “How much energy is produced when piezoelectric elements are placed on top of the keys of a laptop and what percent of the energy required to charge a battery does this represent?”

I’m going to go about answering this by collecting the following measurements:

What is the average amount of energy generated per keystroke on the piezoelectric-equipped key?

How much energy is stored per average keystroke on a piezoelectric-equipped key wired to a capacitor?

How much energy is generated and stored when the same procedure is used but with multiple keys wired in a circuit?

How does this amount of energy compare to the amount of energy required to charge a battery?

My first step will be determining the average energy generated per keystroke by a piezoelectric-equipped key. Next, I will wire an element on 1 key and connect this to a capacitor in order to measure the energy stored under these conditions. I will then link multiple keys with elements to a capacitor in order to see how they function as a unit. From there, I will build an entire prototype with piezoelectric elements embedded with the keyboard of a laptop. At the end of this, I will compare how much energy is generated to the amount of energy needed to recharge a battery to see how much potential there is for recharging it.

Some of my questions are:

What units should I be using to measure “energy”?

How can I ensure that each time an element is struck, it is with the exact same amount of force?

How can I directly compare the number of keystrokes it takes to charge a capacitor to how many it would take to recharge a battery?

What is a good type of battery to compare to given the scale of what I'm working with?

Any general feedback/corrections/advice?

Thank you so much for getting this far, I really appreciate any help :D


texts: Inverter resistance and calculation confusion

texts:
I'm using a 1200W pure sine wave inverter and a series of extension cords to power devices in a mobile home.  When charging my laptop, I noticed it was charging slowly.  According to my battery monitor when the laptop is plugged in it consumes roughly 0.8A or 10W.  I then plugged directly into the inverter instead of the extension cord and it consumed roughly 2.78A or 34W for charging the laptop. Great.  Must be a faulty extension cord, or just low quality.  I then tried a tiny 250W space heater and did the same: it drew the same 250-270W it is rated for both when plugged into the extension cord and when directly into the inverter.  So why does the laptop power draw drop significantly and not the heater?
By standard, the laptop charger converts 100-240V AC at 1.2A to 19V DC at 2.37A, for 45W charging.  The battery monitor is wired into the 12V DC current before the inverter and reads the total load of the inverter.  If the laptop charger pulls 1.2A at 110-120V, wouldn't that mean the current drawn from the 12V system is somewhere around 12A then?


texts:
I am currently working on Super OSD - an on screen display project. http://code.google.com/p/super-osd has all the details.

At the moment I'm using a dsPIC MCU to do the job. This is a very powerful DSP (40 MIPS @ 80 MHz, three-register single-cycle operations and a MAC unit) and, importantly, it comes in a DIP package (because I'm using a breadboard to prototype it.) I'm really getting every last bit of performance out of it running the OSD - the chip has about 200ns or 10 cycles per pixel on the output stage so the code has to be very optimised in this part (for this reason it will always be written in assembly.)

Now I was considering using an FPGA for this because due to the parallel architecture of such a chip it is possible to have a simple logic program running the OSD. Things like drawing lines and algorithmic code would be handled by an MCU, but the actual output would be done with an FPGA. And some simple things like setting pixels or drawing horizontal and vertical lines I would like to integrate onto the FPGA, to improve speed.

I have some questions:

Will it cost significantly more? The cheapest FPGA's I found were ~£5 each and the dsPIC is £3 each. So it will cost more, but by how much?
The dsPIC fits in a SO28 package. I would not like to go bigger than SO28 or TQFP44. Most FPGA's I've seen come in BGA or TQFP>100 packages, which aren't an option at the moment, due to the shear size, and the difficulty of soldering them myself.
How much current is used by an FPGA? The dsPIC solution currently consumes about 55mA +/- 10mA, which is okay at the moment. Would an FPGA consume more or less? Is it variable, or is it pretty much static, like the dsPIC?
I need at least 12KB of graphics memory to store the OSD graphics. Do FPGA's have this kind of memory available on the chip or is this only available with external chips?


texts: Auto Power on circuit when Electricity returns

texts:
I have setup a homeserver.. But there is lot of power outage in my location so when the power comes back i need to pess the power switch manually.
Is there a circuit which will just short the the push button once every time power is given to the Circuit.


texts: What will gain be when both the zener diodes are conducting?

texts: I have seen in solution that they have considered both 10k and 20k to be parallel when both the diodes are conducting. How will 10k and 20k be in parallel when zener diodes are conducting? Why are we not considering the drop across zener diode when both diodes are conducting?


texts: Measuring Efficiency at Various Loads in LTSpice

texts:
If one wishes to know the efficiency of a circuit in LTSpice, it is reasonably simple to set up the simulation to give you an efficiency report:

Select Simulate -> Edit Simulation cmd and select 'Stop simulating if steady state is detected'.
Rerun the simulation.
Select View -> Efficiency Report -> Show on Schematic. The efficiency report appears on the schematic.
(Instructions stolen from this website, other sources are available)

This efficiency report is useful for more than just in/out power, but also where the losses are: diodes, transistors, transformers etc. as shown here:

However, this only works if, there is one fixed input (a voltage source) and if there is one fixed output (a current source or resistor called RLOAD)

Which is fine if you have a known fixed load, or only a couple of fixed states.

Is there a method to get the full efficiency report out for a bunch of points? For example, I have a DCDC converter and I need to know how it performs when 0.1, 0.2, 0.3 .... 1.9, 2.0, 2.1W is drawn, and where the power goes (U1, U2 etc).

I'm sure there is a way of doing a batch of runs for a set of options, but I cannot find how to do so for the efficiency reports.


texts: Where to get stepper motor with integrated encoder

texts:
I'm looking for a stepper motor with an integrated high-resolution encoder for some force-feedback experimentation. Maybe something like this: http://www.opticalencoder.com/pdf/CM-300.pdf

It need not be a large motor, and I was hoping to get the thing for $50 or less.

Can anyone point me to somewhere I can buy small quantities of such a thing?


texts: I found our old casette player and bunch of empty casettes in attic, also they are in excellent situation. I wanted to record a mix tape for nostalgia but there was no aux input, only an old microphone. So, I bought a fm transmitter and tried to record while broadcasting songs. Sound was very good on radio but when I tried to record it, it came with huge background noise. I tried removing microphone and sending sound from mic connections, but it is still noisy. Does anyone have any idea what the source of this sound could be? Can I get rid of it? (Player works fine, my old tapes sound good)


texts:
I have this circuit working on my breadboard.  This circuit does exactly what I need in term of effect but so far I have not been able to find a way to get more current to the LED output.  I need to be able to run either this circuit or one that does the same thing but with a 1/2 watt or 1 watt LED.  I also need to be able to manage or set the strobe rate.

Is it possible or possible to use some variation on this?

=============================

EDIT/UPDATE

I tried using a couple of different Darlington transistors (the one on the breadboard now is a Fairchild Transistors Darlington PNP Epitaxial Sil US HTS:8541408000 ECCN:EAR99

No luck so far. When the BC557 PNP is replaced by the Darlington the circuit powers the LED up slowly (too slow) then it fails to shut off.. Q1 does not turn off.. Apparently for some reason the discharge of the electrolytic does not drop the voltage low enough to turn off Q1 let alone keep it off for any length of time.. I tried a few changes of resistors but no luck.. Apparently I have not fully grasped the dynamics at work in how/why Q1 shuts off and why the Darlington has changed this.

I am still new to this stuff though I have been studying up...

I need to get this circuit or a very similar one to FULLY power optionally a 1/2 watt LED or 2 half watt LEDs, so from 120ma to 240ma, depending on resistors. Edit(and power input is really 5vdc)

Thanks,

Jim


texts:
I encountered stange behavior of stm32f405rg while working with CAN. My setup: beaglbone black connected to stm over CAN bus. Data transmitted successfully, beaglbone is able to receive data correctly however ACK is not generated because of extra STM32 impulse.

CAN bus configuration:

Bitrate: 25kBit/s.
Time quanta: 2500nS.
Propagation + first phase length: 13 time quantas.
Second phase length: 2 time quantas.
SWJ length: 1 time quanta.

These settings are equal for BB and STM.

Here what I got. Data presented on image is correct:

However there is problem with ACK in circled region. Here it is:

As you can see STM32 tries to transmit something while BB generates ACK for the message. What are the possible reasons for that?

Thank you!


texts:
I'm very much an amateur tinkerer when it comes to electronics.  My formal training amounts to the digital electronics requirements from my CS degree in the early 90s.  I'm also a bit of a blinkenlights fan, having grown up in the 60s and 70s.

All of that said, I have some older (< 10MHz) computers that I'd like to create some "front panel" displays for.  To this end, I'd like to "tap" the address lines and bring them out to LEDs.  I'm concerned about (intuitively... not with any informed knowledge):

Feedback into the bus lines from the additional line driving a transistor that drives an LED each.
Drawing too much power through the address line in an effort to drive the LED.

My thoughts are to create a simple high impedence buffer that drives a transistor that ultimately powers each LED.

Am I way overthinking this, are my concerns valid, and am I missing anything important that I should be worried about but haven't thought of?


texts: how should i design variable current source of 4-20mA with 24Vdc input?

texts:
I am trying to design current source of 4-20mA variable with 24vdc input. The circuit can read one output at a time and variable from 4 to 20mA.

When input varies between 0 Volts and 24 Volts, the current source should vary from 4 mA to 20 mA correspondingly. The input voltage will be constant somewhere between 0 and 24 Volts, at any given point of time, and the corresponding sourced current should be constant at that time.


texts: Should I default to pull-up or pull-down resistor with tact switches?

texts:
I understand the basic use of a pull-up or pull-down resistor, including the specific case of using it with a tact switch.

When both are an option I was wondering whether I should favor one over the other and if so, why?


texts: SPICE - How model body for EMI in a EEG system

texts:
I was wondering how can I model the patient body in a EEG system to perform some simulation analisys. I started from this article which explains the coupling between the body and the EMI and the successive common mode voltage calculation.
Now I'd like to perform a simulation keeping in consideration the coupling of the body whit the EMI source (in particular the coupling between the two ground, the earth and the system one).

I tried whit this circuit (keep in mind the figure 5 in the article linked above)

but i don't know ho to model the coupling between the two grounds. Can anyone explain if it's possible? How Can I model correctly the patient's body?


texts: Selecting coaxial cable and connector for PCB referring to required frequency

texts:
I want to transmit my 24GHz signal from PCB through coaxial to antenna. I wonder how to chose best match for it, also the power is -5dBm, 50 ohm. It's based on ADF5901 2ch PA. I have found two good site but still I think I didn't found my way:

https://www.rosenberger.com/us_en/test-measurement/precision_connectors/

http://precisionconnector.com/

https://www.te.com

Most of them are for cable and not for connecting to PCB, specially I want it to be surface mount. The cable will be too small, the antenna is placed on other board and have few Centimeter distance from transmitter, I want it's cable be flexible and thin.

It is my first project on RF board I have zero experience, please help to chose the best cable and connector.


texts:
I have a question on Boolean algebra

I have to simplify the following expressions-

(1)   x = ABC+A'C (where A'=notA)

    = BC(A+A')

    = BC(1)

    = BC

(2)   q = R'S'T'(R'+S'+T')

     = R'R'S'T'+S'R'S'T'+T'R'S'T'

     = R'S'T+R'S'T'+R'S'T'

     = R'S'T'

(3)    z = (B+C')(B'+C)+A"+B'+C"

(4)    y = (C'+D')+A'CD'+A'B'C'+A'B"CD+ACD'

Im new to the Boolean algebra and want to know if the first two questions(1&3) are correct.

and if possible,i need some help simplifying the last two question(3&4) I have no idea were to start

Thanks


texts: Opinions for motorhome mains AC switching circuit design

texts:
We are located in Europe, and building a motorhome. Currently I plan the electrical wiring for the mains 230V AC.
We will use a 24V / 230V 2kW inverter from battery, but when we have the possibility we would also use external AC. For the safe switching between the internal and external power, I designed a circuit, with the following points in mind:

for external power, we plan to use the EU standard mains plug (https://en.wikipedia.org/wiki/Schuko), because this is what we can find on most places in Europe (* we not really use campsites, rather wild camping and / or staying at friends places)

the inverter and the external source is not allowed to be connected at the same time

when the external power is used, we would like to automatically charge the motorhomes battery bank

if the external power source has any faulty or abnormal wiring (eg. the order of the L, N, E is incorrect, or any of them is missing) the isolation relays should not engage

the motorhome must have his own RCB and MCB, which we will use also for the inverter and external power

So I've came up with the following schematic, which I also built and tested for all the possible cases: it should work only if all 3 wires are present and all are in the correct order. Please take a look and tell your opinion, if it is safe or if it can be optimised in any way?
*to make things a bit more easy to follow:
0)
all the relays have small current coils (less than 6mA), so they will not trip any existing RCB (the lowest rated RCB on the market is 15mA, this coil uses 3 times less current)
1)
R7 is there for the case when the L and N are present and are in the correct order, but E is missing. In this case the current goes through both relays, K2 and K1. But because the current is weak, causes an abnormal functionality, sometimes engages the relays, sometimes not. For a safe function, if there is no earth, it must not engage K2, and must engage K1. R7 helps for both relays, in this aspect.
2)
K0 is used to completely isolate the external power, not only L and N, so if from any reason it is high voltage on the E line (faulty earth), it should not output on the whole vehicle. It is connected only if the external power has a safe ground
3)
SA on the schematic is a 255V surge arrester
Thanks!


texts: "RF energy harvesting" Can rf transmitter be a rf signal generator?

texts:
I'm trying to build an rf energy harvester. But having some problem.

The harvester should collect the 915MHz signal.

Can I use 915MHz RF transceiver + 915MHz amplifier as the rf signal source?
How do I determine the value of the capacitor in the picture? I had read some paper but they didn't tell how to choose the capacitors.

The purpose is to receive ambient 915MHz RF signal. In order to do experiments, I need a stable signal source so that I can change the distance and see how is the efficiency


texts:
complete electronics novice here unfortunately. Please bear with me.
I'm after some kind of switch (latch/flip-flop?) that will interrupt a momentary switch held in its 'on' position when another momentary 'reset' switch is pressed but also requires the 'on' switch to be released and then pressed again before triggering. This is to control a motor that is currently driven by a mosfet circuit so I'm just after a logic level signal to feed into it.
e.g 'on' switch held -> motor starts -> 'reset' button pressed whilst 'on' switch still held -> motor stops -> 'on' switch still held -> motor still stopped -> 'on' switch released and then held again -> motor starts
I apologise in advance for the total lack of terminology. If I can just get pointed in the general direction of something it would be greatly appreciated.


texts: Simulating a circuit consisting of MOSFETs

texts:
When simulating a circuit consisting of mosfets, when can you say that the MOS should be in cut-off, saturation. or linear (triode) region?
Specifically a charge pump circuit utilizing PMOS.(refer to the figure below for the circuit)


texts: Is rated current supposed to vary based on voltage?

texts:
Recently I have been reading a lot of datasheets and noticed that many manufacturers specify a current rating for their products (especially connectors) without specifying at what voltage the current rating applies (except for a max voltage).  This seems super counter intuitive for me as when the voltage increases you will have more power (watts) moving through the component that, in my mind, should affect the rated current.  So at a lower voltage you should be able to pass more than the rated current.

Some examples of this:

https://www.molex.com/webdocs/datasheets/pdf/en-us/0475070010_PCB_HEADERS.pdf
https://www.vishay.com/docs/31017/rcwp99.pdf (this one specifies a rated power but that is just for the voltage drop across the jumper.  What is the rated voltage at that current?)
https://www.hirose.com/product/en/download_file/key_name/FH34SRJ-10S-0.5SH%2850%29/category/Specification%20Sheet/doc_file_id/43118/?file_category_id=9&item_id=05801251550&is_series=

These datasheets make it seem as if there is a physical property that attenuates current flow no matter the voltage when I think it is based on voltage and current.


texts: How to calculate bias resistor values to drive IR diode

texts:
I'm creating a circuit to do communications via a digital serial infrared link.  My requirements are for the link to support relatively high speeds (maximum serial bit rate is 4,000,000 bps or 4Mbps) and for it not to draw a unreasonable amount of power; both requirements derive from the fact that I'm intending to drive this with a Raspberry Pi.  The driver for this is a UART TX line directly from the Pi.  I've chosen the Kingbright APTD3216F3C-P22 IR transmitter and a BC817-40 as the driver transistor (mostly because I have a lot of them leftover from an earlier project!).  If it matters, this will be on FR4 PCB with 0402 resistors.
Calculations
Here are my calculations for the various resistors.  When the transistor is on, I want to drive 15mA of current through D1.  Since the forward voltage drop across D1 is about 1.2V, and \$V_{CEsat} \le 0.7V\$, and the supply is 3.3V, I calculate the value of R3:
$$ R3 = \frac{(3.3 - 1.2 - 0.7)\text{V}}{15\text{mA}} = 93\Omega \approx 100\Omega$$
For R1, I am driving it with 3.3V and \$250 \le h_{FE} \le 600\$ for this transistor, so I calculate the resistor from the required base current times a factor of ten to make sure it's driven into saturation:
$$R1 = \frac{V_{in}}{10I_B} = \frac{3.3\text{V}}{150\text{mA}/250} = 5.5\text{k}\Omega \approx 5.6\Omega$$
To accommodate the higher speeds with clean transitions, I have R2 and used the rule of thumb that it should be about 10x R1.  (Is there a better way to calculate that?)
When I do a SPICE DC sweep of Vin, however, the transition isn't very sharp, so I'm inclined to decrease R1 and increase R2, but I'm not sure what values to choose without just guessing.
Questions

Are my calculations correct and reasonable?
How should I increase the switching speed of the transistor?
Is there a better design method?  How should I choose the resistor values?

Schematic

simulate this circuit – Schematic created using CircuitLab


texts: Working out theveni. Voltage with no voltage source

texts: How do i get the thevenin voltage having worked out the load impedance and obtained it as 3.415 -j0.7317 ohms


texts: What protection measures to consider when switching many loads at the same time with shift registrers?

texts:
I'm developping a programmable load board  with many of these load steps to test LDO or DC/DC converter Output.

As you can see, what changes is the resistor R6  to provide other  current load values. The inputs of the transistors are the outputs of two shift registers (I'm using the 74HC595 Shift register from NXP. ). The LED is an extra to see the status directly on the board.

I'm concerned about the latching of the output from the shift registers to the transistors and how the load value transition looks. It will change many loads at the same time with different current values changing from on to off and vice versa. The total load will be measured at the output of the LDO as the total of the currents flowing in the resistors. I dont't have inductive elements in my circuit , but are there some tips with which I can optimize the  current value transitions? Is this enough as it stands ?

Thank you !


texts: How to filter noise in a 12v system introduced by an inverter?

texts:
I have an RV with a 150 Ah battery bank and SureSine 300W 115V inverter. Due to space constraints, the inverter and the rest of the DC loads share about 6 ft length of wire to the batteries, but otherwise it’s a fairly typical setup.

The media center and speakers are running on the 12V and they pick up high pitched noise when the inverter is running, it gets worse the more AC loads I have.

The inverter probably already has bypass capacitors, but would it help if I added more? How do I choose the correct size? Would it help if I added a big ferrite bead on the positive rail going to the inverter? The peak current there is about 60A.

Also, does it make sense to filter the noise just at the media center as it uses a fraction of the power the inverter does?

Edit: I have a multimeter, but not much besides that to diagnose this.


texts: Looking for electronics and sample code to drive commodity inkjet cartridge

texts: I'd like to drive an inkjet cartridge, such as an HP 94 using a micro such as an Arduino or MSP 430.


texts:
I'm simulating an oscillator that I have designed for a 40kHz oscillation frequency. I simulated it in Orcad and I got a flat signal. After some research, I found that it's due to the program not calculating any noise or something to start the circuit.

I added an Ipulse to simulate noise - didn't work.
Skipped initial bias point calculation - didn't work.

Do you have any idea how I can kick start my circuit ?


texts:
I ordered a set of DC rocker switches that were advertised as "4A 12V DC SPST"

I was planning on using one to power an Arduino based project using 5V DC which will draw no more than 1 to 2 amps.

What I received were switches labeled as

10A 125V AC / 6A 250V AC

I wrote to the vendor and this is their reply:

"They will work with DC current just as well but not the other way around if they were specifically DC."

I have already returned them, as I have no intention of using a switch rated for AC on a DC circuit, but the exchange with the vendor left me with two questions

1) What is the logic (if any) behind arguing that it is safe to these switches on a DC circuit? Is it that 12V is so much lower than the 125/250V AC rating?

2) what does he mean by "not the other way around"? Do DC switches not work with AC current?


texts: How does the Zoom ADC exactly zoom in (Practically)?

texts:
I am trying to understand the actual working of this specific Zoom ADC (diagram below), which is a 2-Step ADC with coarse (SAR) ADC and a fine (Sigma-Delta) ADC. I understand it theoritically but could not think practically on how it exactly zooms. I could write down step by step in brief on what i understood and where i got stuck (highlighted in bold).

I am referring to the below architecture:

As per my understanding, it operates as follows:

The ADC in the forward path called a coarse ADC samples the input to a few MSB.
Then the output of the coarse ADC (Y coarse) is used to adjust the references of the DAC.
Then the sigma delta loop turns on and then a fine conversion (the remaining bits) are found using the usual Delta Sigma modulation and a decimation.

In a high level, the coarse ADC sets some reference and the fine ADC kind of wiggles small around the reference until it reaches the correct average value.

Conceptually, it looks like this:

I understand the working of a normal single bit sigma delta loop where the feedback DAC outputs a 0 or 1 (VCM or Vref) depending on the output of comparator. But I could not think on how changing this Vref to a different value would zoom.

If anybody could guide on how to think this zooming process practically, it would be helpful.


texts: Help identifying D1047 transistor (pic included)

texts:
Who can help me identify this transistor?

It came out of a Chinese micromotor power supply.

Text on top is "D1047 905".

Can I substitute it with other transistor?


texts: Easily accessible material for DIY transformer core?

texts:
I want to make a transformer that steps down mains AC voltage. My researched showed that the best kind of material for core would be laminated iron sheets. Unfortunatelly, these are very hard to buy. Looks like you can only get ferrite cores online.

So is there some different material, that is easily accessible by regular hobbyists, that can be used for making transformer cores? It should be able to buy it in local stores.

I'm aware that I could salvage core from old electrical appliance like TV or microwave, but that is cost inefficient if you don't already have that appliance. So I'm looking for some better alternative.

Edit - I'm located in Eastern Europe, if that helps.


texts:
Can I charge series of 4 Maxwell BCAP3000 supercapacitors with constant current method using an adjustable Power Supply, and exceed the voltage rated for single cell?

What I mean is to charge the series of 4 ultracaps, that should be able to charge up to 10.8V, and have voltage higher than 2.7V on the power supply. I'm sorry if this question is somewhat silly, but this is my first take on supercaps connected in series. I've done single cell tests but never exceeded rated voltage on it. Therefore I have this small concern to solve.

They are rated for 2.7V. I have the manufaturers' balancing transistor boards attached to the cells, so single cell should be protected, but I am unsure if they are working since no LED is shining so far.

EDIT: Answers and comments provided solved my problem so this topic can be closed. Thanks for all of the concern and replies.


texts: What is the purpose of this capacitor connected to the pad?

texts: What could be the purpose of capacitor C17 in this 8Mhz series resonant circuit?


texts: Better approach for maximizing Cooling Fan Life Expectancy

texts:
We are working on a product which is extremely cost sensitive. It generates a lot of heat so we are planning to use a heat sink. For those 'very rare edge causes' where heat sink alone cannot cool down the system, we have also equipped the system with a cooling fan.
Due to cost constraints, we are planning to go with cheap 12V DC cooling Fans (basically used parts, the ones which don't come with a guaranty). So now we are focusing to judiciously use the fan ONLY when absolutely required (The tests show heat sink alone can keep the system cool for ~75% of scenarios).
Our system can tolerate a max. temperature of 85 °C.
To maximize the fan's life, we'll have to reduce it's wear and tear. And to do that, we have to decrease it's usage. For this, we have come up with two different solutions (there might be even more possible, we are open for suggestions!):
1. We control the fan's rotation.
We switch it on at a (relatively lower) 60 °C but at very low speed. Basically, the fan's rotation is directly proportional with temperature (like laptops). But because cooling fans rapidly lowers down the temperature, so even if running at 35% speed, the system will cool down rapidly and the fan can be switched off (say at 50 °C).
2. We raise the trigger point to ~70 °C.
The fan is switched on at full speed at 70 °C and switched off at, say ~60 °C. Fan speed is not controlled.

Which approach will work better? You may assume that our design is perfect in terms of heat transfer. The device is vertically mounted and hot air can easily escape from upper face (while cool air enters from bottom face). Assume no hot air is trapped inside the device.
Approach #1 tries to minimize power consumption (thus wear and tear), but it does not minimizes fan usage time.
Approach #2 tries to minimize fan usage time (at the expense of power consumption).
So more Power Consumption for less time or less power consumption for more time, which will work better?

We have tried to weigh both of these approaches on following factors, but due to limited experience, we have been unable to choose which one is better:
1. Amount of dust deposited
More dust means more resistance and thus more power consumption leading to more wear and tear.
2. Air Temperature
Hotter air moving across the fan means more heating of fan coil, thus causing more damage and reducing fan life.
Approach #1 looses at Factor #1 but wins at Factor #2.
Approach #2 looses at Factor #2 but wins at Factor #1.

Please we are looking forward for an expert advise on this matter. We have already looked into this, this, and this but are still stuck. Please forgive us if it is plain obvious, we have very little experience in dealing with such issues. We do not intend to ask a subjective question but to discover and learn about the best industry approach for such cases (if there is any?).

EDIT 1 Providing some more technical details.
Expected lifetime: min 5 years. Environment temperatures vary between 0 °C to 50 °C. Device can tolerate maximum of 85 °C.
What is the average / max power consumption?: Fan consumes ~1.32 Watts at full speed. System consumes constant ~10 KVa.
How big is the fan? Fan diameter is 73 mm.
How much dust is expected in the environment? If there is any, how do you prevent it from interfering with the passive cooling?: It is going to be a consumer product and thus we have to expect a dusty environment. Being vertically mounted, theoretically, only some dust should stick inside the heat sink's grooves (reducing it's surface area and heat conduction).
Currently we have nothing to prevent this. Any suggestions for the same? i'll have to contact the the pollution department to get the exact data. i will get the data and revert back.
How many start / stop cycles of the fan are to be expected?: This depends upon the kind of approach we choose. But the way i see it, it depends how often we cross the 'critical' temperature without any fan (in the current prototype the fan is always running). For that we'll have to conduct some tests. We will publish the results in a day or so.


texts: Scattering matrix Transmission Matrix lasers

texts:
I would like to ask if anyone can suggest me a good tutorial about Scattering and transmission matrices for lasers.
I am really struggling with some issues and the majority of the literature analyses them from the microwave perspective.
To be honest I find it very difficult to understand even the very basics, like how do we derive the transmission and reflection coefficients and where do all these things find application.


texts:
I have an atmega16 which I need to clock to at least 16MHZ. How do I know what fuses to set? The fuse calculator gives you a choice of low, medium and high frequency. What does that mean?

Is there a limit to how fast the chip can go despite you put a crystal in?


texts: Forward bias voltage across a pn junction diode

texts: Why must the forward bias voltage across a pn junction diode always be less than the built-in potential barrier? What happens when you apply a forward bias voltage across a pn junction diode that is larger than the built-in potential barrier? Where does the rest of the voltage go?


texts: How would one approach to solving for the resistance between any two nodes of a fully connected graph with an arbitrary number of nodes n and arbitrary resistance between them ? (resistors omitted from image for clarity)


texts: Does USB power delivery support arbitrary voltages?

texts:
I'm looking for a USB power delivery power adapter to charge my Canon EOS RP camera via its USB-C port. Canon sells its own adapter for insane prices, and the Canon adapter is apparently nothing but a USB power delivery adapter, so according to my logic, a cheaper adapter should work.

One adapter (90 W) I'm looking at says in the specs:

5-18 V / 5 A, 19-20 V / 4,5 A

Another adapter (65 W) I'm looking at says in the specs:

5 V / 3 A, 9 V / 3 A, 12 V / 3 A, 20 V / 3,25 A

The adapter with only 5V, 9V, 12V and 20V is significantly cheaper.

According to Wikipedia, USB power delivery supports 5V, 9V, 12V, 15V and 20V in its different versions. Wikipedia doesn't say anything about adjustable voltage. The cheaper adapter entirely lacks 15V.

Because of the adjustable voltage, the 5-18V, 19-20V adapter seems like a better purchase. But, does USB power delivery actually support freely adjustable voltage? Or is the freely adjustable voltage of the more expensive adapter just a marketing trick?

The higher power of the first adapter doesn't matter to me as charging a feeble 7.4V 1040mAh battery doesn't require that much power.

Edit:

A report on the 'net says:

Just incase anybody was wondering... I got the official Canon PD-E1 USB-C adapter (it's included with the battery grip) and the output listed on it is 5V/3A and 9V/3A.

...so I guess the 65W adapter should work.


texts:
I'm working on a kitchen vent with built-in lighting. It uses two G4 light bulbs wired in parallel - these are supposed to work at 12 V DC. I've already replaced them once in the past, albeit for regular ones (the old one burned out). Recently I've decided to upgrade from these light bulbs to 12 V 3.5 W LEDs, also with a G4 socket. The newly installed LEDs were dim, so I checked them using my car battery. They were fine, and once I got my eyesight back I also checked the voltage in the light bulb socket of the kitchen vent in question.
It appears that the kitchen vent uses 4 V AC to power its light bulbs, and that voltage is only measurable if an old light bulb is plugged into at least one of the sockets (and shines as bright as expected) and, I repeat, they are wired in parallel. Without the light bulbs it's only 0.3 V AC across the pins.
Could you explain why a kitchen vent supplies 4 V AC to its lighting and how can a 12 V DC light bulb shine at full brightness at this voltage?
Poland (230 V, 50 Hz)


texts: Why do AC-to-DC adapters have long cables on both ends?

texts:
Why do AC adapters have long cable on both ends? I believe that almost everyone using one would want it either directly next to the gadget it is powering (even possibly joined together with it if possible) or next to the power plug (possible made into a single unit with the power plug). It is inconvenient to have it hanging in the middle of a power line. Is this simply a design flaw, or does it have particular reason?
If I were to replace either the AC side or the DC side cable with a very short one, does it have any difference between the two options electronically?


texts: Is the average of instanteous power equal to real power?

texts:
simulate this circuit – Schematic created using CircuitLab
I'm trying to understand if the average of instantaneous power is equal to real power. My reasoning is that the reactive components average out to zero and from there the average of that signal will give you just the power dissipated by the resistor. Is this true or do we always have to use P=IVpf.

Thanks


texts: Ok ive built a 240v ac to 24v dc power supply to run my zvs driven flyback transformer. The guts of this psu is still out of the box because I'd like to install a 12v pc cooling fan. My question is, and I'm still quite new to all this, can I run a 24 to 12v dc/dc 7812 circuit in parallel with the 24v zvs supply? Post rectification of course. It might sound a silly question but id rather not fry anything by just smashing things together and seeing what happens. Thanks in advance for your help guys


texts:
I am using an ATtiny841 microcontroller as an I2C slave, but I have difficulty finding information on it. So for, all I have are application notes and reference code for TWI and USI module.

It seems like ATtiny841 has a unique TWI slave interface, which is slightly different. Although I could write out the code manually it would really help if there is a standard sample code that I can refer to.

Any suggestions?

Thanks in advance.


texts: How is it possible to program an ATTiny over USB without a USB to TTL chip?

texts: I have been testing out my Digispark and the board has no USB to TTl converter chip and yet you can program it over USB. Is it possible to do this with an ATmega328p for example?


texts: LM311 output stays at Vee regardless of input voltage

texts:
I have wired up the LM311 circuit shown in the figure below. It should work as follows (at least to my understanding), when V+ (pin 2) > V- (pin 3) the output (pin 7) should rise to 12V and when V+ < V- the output should fall to Gnd. I have applied a 1kHz square with an amplitude of 1V swinging around Gnd to pin 2 (V+), see scope image on the second picture. I expect a square wave from 0V to 12V on the output but instead it stays at approximately -12V (CH2 on the scope image), so i.e. at Vee. Even when I apply 12V on pin 2, the output stays at -12V.

My question: Why is this happening? Shouldn't it also produce a square wave on the output? Is there an error in my circuit?


texts:
I'm trying to take a simple measurement of ~2.4 GHz (WiFi land) with an RF spectrum analyzer (Tektronix RSA607A) but have so far been unsuccessful.  On the RF In port I have an N-BNC adapter connected to a meter-long BNC cable, which is connected to a BNC-SMA adapter and WiFi antenna.  All items in the chain are spec'd at \$50 \Omega\$.

All I am able to measure, however, is noise.  I tried using several different cables, reattaching all connections, and even plugging the whole shebang into a Tektronix MSO3054's RF port.  I 'know' the spectrum analyzer is working -- I plugged a waveform generator into RF In by way of a BNC cable and said N-BNC adapter, and the analyzer successfully measured a 1 MHz sine wave.

I'm sure it's something trivial, but we don't have any RF-experience persons around to consult.  Does this setup appear obviously incorrect somewhere?


texts: Powering SMD 5050 strip via LM2596 DC/DC converter

texts:
I decided not to order / use the power supply typically sold with SMD 5050 kits.
I heard a lot of explosion stories regarding those dodgy stuff.

I want to make my own (power supply to drive SMD 5050.
Using: a DC adapter found at home hooked up to LM2596 converter.

Facts:

From what I gather, LM2596 regulates the voltage AND can supply 1 to 2 amps of power safely (more requires heatsink?).
A single SMD 5050 chip uses 0.24 w of power.
SMD 5050's run on 12v.

My question:

Is it safe to assume that I can connect any number of LED strip blocks (with each block having 3 LEDs each using 0.24w, therefore ~0.75w), as long as total amps do not exceed what LM2596 AND power adapter attached to it can supply (being max 2 amps)?

My calculation:

watt = amps x volts means each LED uses 0.02 amp.

So if I have 30 blocks == 90 LEDs.

90 * 0.02 = 0.6 amps.

Would it work fine?
And if I just connect a single block needing 0.02 amp, would it still work fine?
What would happen if I connect more LEDs and exceed the amps LM2596 can provide?

I don't want my leds burning in day 2 and learn about this subject.

I'd very much appreciate it if all questions were answered.

Thank you!


texts: Shift-register seems to read wrong input data

texts:
Here the schematic of a small board with a 74HC595 shift-register:

Here the detail of each output. They are connected to QB..QE.

Nothing is connected to the collectors of BJTs and the board contains no other components.
The signals (SER and SRCLK) come from an external MCU that drives the lines with an optocoupler.
The MCU takes care of the correct output bits and the common "trick" to derive the RCLK signal from the last clock bit.
On my bench all works like a charm. I have several boards (and several MCUs) and all is fine.
But the very same setup tested on a customer's system leads to a weird behavior: when there is at least one bit enabled, sometimes also other outputs go high.
I checked with the oscilloscope to find some spikes or other noise (the system is surrounded by a lot of DCDC converters):

The signals seems quite clean to me. To set a bit high a spike should be reach more than 3V during the clock edge. Please note that if I send all zeros it never happens that an output goes high. If the noise would be there, it should act regardless the actual data.
What if this is an xy problem? I mean, what else can lead to an high level on the outputs other than put the SER signal high during the clock edges?


texts: Transistor is not switching-Raindrop sensor with LED (Later Buzzer will be used)

texts:
I am creating a small application in which on detecting the water the Buzzer will ring. But right now I am testing with LED instead of Buzzer.

Raindrop Sensor datasheet link: https://components101.com/sensors/rain-drop-sensor-module

I am using a Raindrop sensor:

And RGB LED:

I don't need any MCU in this project. I connected the sensor to the 5V and GND and connected the A0 (Analog Pin) to the Positive of LED.

Note: 5V and GND were supplied from Arduino UNO

Like this:

simulate this circuit – Schematic created using CircuitLab

But LED turns on as soon as I connect power to the circuit. And when I drop water on the sensor LED turns OFF. Opposite of what I want. So I thought of using a transistor as a switch to turn LED ON on detecting water.

Below is my circuit:

simulate this circuit

But this isn't working at all. Any guide on how can I get it to work with or without transistor.

New Try

simulate this circuit


texts: What really causes series inductance of capacitors?

texts:
Doing some research in selecting capacitors for high frequency applications, concept of equivalent series inductance comes up a lot. Apparently all capacitors have this parasitic inductance which appears in series with the capacitance of the component. If the ESL is high, in high frequencies this inductive reactance can even cancel out the capacitive reactance, and the cap essentially acts as a resistor which blocks DC.

But why is the ESL so significant? Sure, caps have wires, but I would imagine the rest of the circuit has much more wire and therefore much higher parasitic inductance which would be much bigger problem than the short component leads. Otherwise caps are just plates with a dielectric in between, so what is it about them that causes us to worry about ESL so much?

When it comes to electrolytic capacitors, I found one explanation: It was explained that as the cap is basically a long piece of foil rolled, there is definitely a lot of inductance since the roll of foil acts kind of like a coil. But I don't think this makes sense at all: It's not like the current travels along the foil! The current builds up an electric field in one foil, which again produces a current in the other foil. But this field appears across the foils, not along it, so this explanation makes no sense to me.

So could somebody explain this phenomenon to me, preferably in the context of both ceramic and electrolytic capacitors?


texts: Why Im getting shifted phase in the output voltage?

texts:
Why im getting shifted phase in the output voltage in this differential amplifier?
and how can I eliminate this shifted phase?

Second question is, I need to make a gain of 50 in the amplifier below, I got and Re of 1ohm is it ok? or there is other way to make this gain with higher resistor? Cause I dont sure that 1ohm resistor is legit...


texts:
Would connecting a resistor to the positive input of an amplifier make any difference in its output and if not why in some schematics there is always a resistor attached to the opamp positive input?

simulate this circuit – Schematic created using CircuitLab


texts:
Can this board be used to upload sketches to the Arduino. I tried by hooking the TX port on the FTDI Basic Breakout  to RX port(Pin 2 on the Arduino) and RX port to pin 3 on the Arduino. But so far I am not abl to upload anything.

The driver for the board loads fine.

Thanks for any feed back.


texts: Hows does this 12v relay works with transistor voltage drop?

texts:
I'm working my way through "Make: Electronics" by Charles Platt and came across the following schematic:

As someone who just recently got started with electronics, what I can't wrap my head around is how R1 relay works after Q1's voltage drop. I have built the same circuit only with different power source and relay, both 5V instead of 12V as suggested by the book and what seems to be happening is that the emitter voltage is bellow the relay trigger voltage (12V in the schematics and 5V in my case since I'm using 5V relay and source). From what I have been reading around the internet and communities like this, the emitter voltage in this configuration is supposed to be limited to the base voltage minus ~0.4V or so. Due to the 10K resistor, once the transistor is triggered, the base voltage will be under 12V, thus the emitter voltage will also be under 12V and the relay will not close. That's basically how my thoughts are at the moment and I need help spotting my mistakes.

Edit: I believe this question is being misunderstood. I'm not asking how a self-locking relay works. I'm asking how a 12V relay is being triggered when the voltage on its coil (from Q1 emitter) is bellow 12V (I'm checking it with a multimeter and theres a voltage drop across the transistor).


texts:
I'm trying out a Make Project: Sound-O-Light Speakers

It has this diagram:

The LED's are backwards in this diagram, right? The "arrow" (anode) part of the LED should be hooked up to the positive (+) voltage of the battery?

EDIT

The description says:

  Solder the battery snap’s red wire (+) to the LED chain’s anode, and
  the snap’s black wire (–) to the TIP31 transistor’s emitter, the right
  leg as you face the front side with the legs pointing down. Then
  connect the LED cathode to the transistor’s collector, in the center.

So it looks like the battery and LED schematics are each upside down, but the + and - in black circles are correct?


texts: Are there downsides to larger watt inverters other than cost?

texts:
I have an RV and I plan to buy a pure sine wave inverter to convert 12V DC to 120V AC. The larger watt inverters cost more but they give me more flexibility to run more powerful things (although perhaps not very long). However, most of the time, I'll be using low watt things.

Are there any downsides to larger watt inverters other than cost (assuming the two inverters pull the same current at no load for the lights, etc.)?


texts: fast 5v High Side switch controlled bz 3.3v

texts:
For my led cube, I need to switch 5V (common anode layers) with 3.3v (pic32). This should happen at a high frequency. In recent builds I used pfets, but because I'm using 3.3v now, a pfet wouldn't really completely shut down. I want to switch high side since I'm using stp16s for controlling the low side.
What IC/method would you suggest for switching the led planes? I target a frequency in the MHz's.


texts: Why does this current skip the resisitor?

texts:
I refer to Figure 3.82 in this text book and shown below:

Why does iN = 2A? The book says 'Since all of the 2A current flows through the short, iN = 2A'. However, why doesn't some of the current flow through the 2Ohm resistor?


texts: Is it 'ok' to solder an IC's thermal pad directly to a ground plane?

texts:
I plan on using this boost converter on an electronics project. I've got a question regarding the thermal pad on the bottom of the IC: is it okay to solder this directly to a ground plane?

A couple concerns:

The datasheet (pg 21) shows a specific ground plane connection. The thermal pad appears to land on a small section of copper that is then routed to the ground plane. Why is this?
How difficult will it be to solder if I extend the ground plane under the chip? I assume the heat will transfer much faster, thus will my design be difficult to solder (assuming I use reflow)? Refer to my current implementation below.

I understand that the thermal pad is meant to radiate heat away from the IC, so it seems like my implementation would satisfy that. For that reason however, it might be a pain to solder...


texts: How long can 0-10V wires for valve control be?

texts:
I'm thinking about controlling a valve for fan coil coolant from a distance of approximately 10 meters.

The control signal is 0-10V, and the impedance of the regulator is stated to be 100k ohm.

Let's say I provide 5V in at one end of this wire. In a typical residential environment, what will be the observed voltage at the other end when loaded with 100k ohm?

Will I see ripple of 10s of mV, 100s? Even volts?

Let's say the cable goes parallell with 230V wires for many meters, and someone is opeating a household mixer nearby the cable, for example.


texts: Contradicting ideas about differential signal route, confining fields vs Increasing impedance

texts:
By initial sense I think we must:

keep pair intra-distance as close as possible for field cancellation.
Fill surround of pair with GND plane and have via near to it to confine the fields, prevent incoming interference and making it.

The source have 200 ohm differential impedance and the load is 1k differential. I've decided to terminate the line with end termination. Now I must raise the trace impedance to 200/100 ohm to terminate it by 200/100 ohm by:

Increase intra-space as more as I can.
Remove surrounding  GND plane.
Reduce trace width.

And these are contradicting each other can you explain why?

My working frequency is 12.2GHZ. (With respect to @ThePhoton)

2 helpful link: Differential impedance and Differential Trace Design Rules - Truth vs Fiction .


texts: CPU and Memory Burn-in during production

texts:
I am looking to implement some burn-in to exercise the cpu, memory, and flash of our assembly during production.

What is used in the mass production world to burn in these components before any high level software is used?

My current strategy is to write/read on cycle from memory for some time, then perform a hard computation on the cpu (crunch SHA or similar). In a simple ARM utility (run on bare metal)

The architecture is a simple computer, ARM G20 cpu with nand flash, seperate application flash, and sdram. Unfortunately JTAG is unavailable at this time.


texts: Displaying ASCII codes to an 7x5 LED Matrix

texts:
I want to know the best way to display ASCII binary code to a 7x5 LED matrix (cathode). The way I'm thinking to approach right now involves an decoder for each column (containing 7 bits, regarding the lines), and a multiplexer that receives the 35 decoded entries and outputs 7 bits. There is also a shift register in the same clock as the MUX to set HIGH in the columns the multiplexer set LOW the lines that are supposed to light. I wonder if that is the best way to do this, considering that the column decoder would be huge. Thanks for your time!
PS. Also, I forgot to mention, I am using a FPGA for this project


texts:
How to determine the voltage gain and input/output impedance of the following circuit given that R1=273.56 and R2=2325?
I have been trying to calculate the voltage gain through solving small signal ac analysis (Hybrid-pi model) but eventually wasn't able to find the solution.
Do we have to follow any systematic approach in order to solve such problems?