texts: Floating power supply: voltage difference fixed but separate voltages not?

texts:
I have a +/- and GND power supply. The GND should be fixed to earth ground, and asking the supply for 5V gives \$\Delta v = v_+ - v_- = 5V\$.

If I use a voltmeter against the positive and ground terminals, I get \$v_+ - v_{GND} = 0V\$. No problem, the supply is floating. If I also check the difference between the ground and negative terminals, I get \$v_- - v_{GND} = 0V\$.

That's confusing, because \$\Delta v = v_+ - v_- =(v_+ - v_{GND}) - (v_- - v_{GND}) = 0V \ne 5V\$. So the + and - terminals of the supply are constantly floating and not fixed, but their difference is fixed? Otherwise if either of the terminals was fixed, I should see a difference between that and GND.

Also, is there any benefit (e.g. protection from leakage current) to short the GND and - terminal and get my voltage off the + and GND connections rather than +/-? I'm concerned about damaging my device.


texts:
This is from the mechanical drawing for the XSON6 package in this datasheet (page 13).

What do the gray rectangles represent? Note that they don't have any measurements.


texts: Turning on and off pin change interrupts ATtiny85

texts:
I know that pin change interrupts can be turned on for the ATtiny85 by enabling PCIs using the GIMSK register, then setting which pins to turn it on for by using the PCMSK register, then lastly calling sei() to enable them. The following code achieves this:

GIMSK = 0b00100000;
PCMSK = 0b00011111;
sei();

I am somewhat unsure as to how I'm supposed to turn them off. Is cli() all that is necessary, or do I need to reset the registers as I did in the following snippet:

GIMSK = 0b00000000;
PCMSK = 0b00000000;
cli();

Any insight would be appreciated. I am using the Arduino platform.


texts:
I'm making a laser spirograph for a school project. It requires speed control of three motors. I used a simple 555 astable circuit with a pot for control, then the output goes into the base of a power transistor to make a PWM ground. I had indicator lights for all of them, and when the motors are off, I get a got a good pulse, but when I turn the motors on, they just stay at the same speed no matter what I do, and the indicators go dim (parallel to motors with a resistor). I think it might be because its just sucking the power from the transistor or something, but I can't be sure. Any help or Ideas?
Schematic:   Note: There are three of these modules in the circuit.

Transistor Package:


texts:
I am building simple LC receiver. I have to use a 30 mH coil and "catch" 30-40 kHz frequencies.
By my calculations I need to use +- 800 pF capacitor. Unfortunately I have only 100 pF capacitors. Will the resonance frequency change (a lot) using 8 parallel 100 pF capacitors?


texts:
My trusty electric fly-zapper broke, so I opened it up to have a look in case it was something simple. I have to say I was a little surprised by what I found inside: the capacitor reads 473K, meaning the capacitance is 47nF (I was able to confirm this with my multimeter).

As the charged voltage of the fly-zapper is about 2.5kV, that gives a total charge of around 120uC. I'm surprised this is so high - as electrical regulations usually say anything above 45uC can be dangerous (see, for instance, IEC 61010-1).

My question is: how is it possible this got through the regulations? Surely as it's almost 3-times the safe charge for a capacitive discharge it should be considered dangerous?

PS: this particular fly-zapper (The Executioner) doesn't have a protective 3-layer grill like some: it's pretty easy to touch the live terminals and it just feels like a static shock.


texts: Not that far from where I live there are 6 towers that appear to be for cellular purposes in a perfect grid. You can see them in the picture I took from google maps. In the center of the road are lights, but on either side you can see 3 poles. Is there something special going on here, or are these just 6 towers that have been placed in a grid for convenience? They are far to far apart for any phased-array type stuff, unless they are operating at a few tens of MHz.


texts: Any native Mac OS X environments for getting started with VHDL / FPGAs?

texts: The title pretty much sums up my question: Are there any native Mac OS X environments for getting started with VHDL / FPGAs?


texts: Best visualization of electric current and voltage

texts:
So, I want to know what the best way to visualize what is actually happening in a circuit. I typically visualized it with the Drude model, where the electrons are like free-flowing balls and the atoms of the circuit are fixed in space. It makes sense to think of voltage as being an application of an electric field across the wire that accelerates the electrons and resistance as the atoms in the way that the electrons hit. It also makes sense that when the electrons hit the atoms, some of their energy is given to the atoms and make them move faster, thus increasing their kinetic energy, and producing heat.

So, I like the Drude model, but it leaves a lot to be desired. For example, it makes no sense to me to think of electrons as "hitting" the atoms as the nucleus of the atoms are so far away from the electron cloud, it seems counter-intuitive as to why the two would "collide."

So, I just want a better model to visualize everything in my head. Which models do you use, and what are their advantages and setbacks?

Thanks.


texts: Function called in ISR and Overlay Directive -Keil / 8051 core

texts:
My C code has an ISR, where a decision has to be made to execute a particular function "A". Now I know that its not good to run a function in an ISR. But in this case of my application, I do not see another way out. After calling the function "A", I noticed a sudden jump in the Data Consumed size and the sudden WARNING L15 explained in  KEIL EXPLANATION OF WARNING.

I am certain that function "A" is not executed in a reentrant fashion, but it sure uses up physical memory; both function "A" as well as functions it calls. (This I believe refers to the variables declared in the functions).

Firstly, is there any way I can work around avoiding that shoot in data memory space?

Secondly, I want to apply the method 2 as shown in the keil explanation. But I do not know how & where exactly to insert the OVERLAY directive in my code. At initialization? At function Declaration? Before Function definition? Where exactly?

WARNING EXAMPLE in my Code

*** WARNING L15: MULTIPLE CALL TO FUNCTION
NAME:    _IECLOC_FUN/DATA_ACCESS
CALLER1: ?C_C51STARTUP
CALLER2: TIMER_ISR/TIMER

WARNING MEANING

Corrections, suggestions, Code examples and links will be appreciated. I hope this question is clear.

Thanks all.


texts: How to decide whether or not to use isolation in a circuit that has a microcontroller and a 48V DC supply?

texts:
A potential divider connects a 48V(worst-case) battery supply and a micro-controller for voltage sensing. Is it enough if I take care of the resistor values of the potential divider so as to limit the current,within the microcontroller's limit or should I opt for an isolation circuit? I can understand the reason behind the use of isolation in power supply circuits, for they are provided as a safety measure to counteract the unexpected behavior of the AC mains. Can DC act as unexpected as the AC mains? What factors decide the necessity if an isolation in a circuit?

The circuit looks like this:


texts:
Is the process of burning a bootloader (JChristensen's mighty-1284 to be precise), on an Atmega1284  microcontroller  same for both DIP (Atmega1284p) and tqfp (Atmega1284-au)?

While searching online I found very little information about the tqfp version of the chip.

Also, I would like to use internal or external 8 Mhz oscillator (crystal) as my board should run at 3.7V from lithium ion battery charged with MCP73831 lipo charging chip. Should I just change the fuse settings in the Arduino IDE boards.txt file (and should I use the fuse bits from Atmega1284 datasheet) or there is something else that also should be done?

Here are my schematics:


texts: Help with simple voltage divider question

texts:
I have had a complete mind blank on how to solve what should be a relatively simple voltage divider question. Here is an example of the circuit in question.

simulate this circuit – Schematic created using CircuitLab

I need to find the voltage across R3 using the voltage divider formula. So I am trying to somehow combine R1, R2 and R4 into one resistor in series with R3 so I can use the formula, but I am getting confused on how to go about it.  Any tips would be appreciated. I am not after the answer, I want to know how to do it so I can also apply it to other problems in the future. Thanks


texts: Potentiometer volume control for a piezo buzzer in bridge (2-pin) configuration

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I have a 10K potentiometer that I'd like to use to control the volume of a piezo transducer/buzzer, which is driven by one or more MCU PWM-capable pins (ranging from 0 to 3.3V). Originally, my configuration looked like this, using a single pin:

simulate this circuit – Schematic created using CircuitLab

I need to adapt this to use a bridge configuration across the piezo buzzer, using two separate PWM-capable pins, similar to what's shown below, except with volume control somehow:

simulate this circuit

The bridge configuration has a number of advantages, like increasing the overall max volume and allowing emulation of two channels (similar to the Arduboy2 or toneAC library).

Is there any simple way that I can effectively scale two separate signals with the same potentiometer? Preferably, I'd need to stick with simple through-hole components.

Some things I've thought about:

Using diodes somehow, maybe in an ORing configuration, but I don't think this will give the desired effect.
Since I do have a DAC available on my MCU (SAMD21E), I can mix the two audio signals (square waves) in firmware and output on the DAC pin, using the configuration in diagram 1 to control the overall volume.

Thanks for any help or advice.


texts: USB connection with overvoltage protection

texts:
I'm trying to design a circuit from scratch with a 5V supply, USB connectivity and an AVR chip, for the sake of learning more about building power supplies, and implementing over-voltage protection on for example USB ports.

The last thing one would want to do is burn a USB port on quite an expensive MacBook Pro.

So where can I get a fairly decent explanation on how overvoltage protection works, and how I could design my circuit?


texts: Why should the subthreshold swing value be small?

texts:
I am given to understand from the link below that a small value of subthreshold swing in MOSFETs implies that there is a better on-off current ratio. But, a small subthreshold swing would imply a large subthreshold slope and hence, at sub threshold values of Vgs, there'll be a larger value of current than for a smaller subthreshold slope. It should follow that the static power dissipation will be higher. Isn't this an undesired characteristic? Also, why is a better on-off current ratio desirable and how does one justify that a higher subthreshold swing value leads to an improved on-off current ratio?

The source of my information: http://www.iue.tuwien.ac.at/phd/stockinger/node13.html#e:sts


texts: Powering high-power laptop from DC without inverter

texts:
Context: We live full-time in an RV (a travel trailer) while traveling around the US. We have 300Ah of 12V Lithium batteries, a 3,000W inverter and 600W of solar. Although we have an inverter, it has a parasitic draw of ~35W (~3A). We camp off-grid ~90% of the time with no hookups - just sunshine and fresh air!

We currently have two laptops which draw power from USB-C - we're using 12V adapters to power these. We need to upgrade to a more powerful laptop (for video editing), and that will obviously have higher power demands. One contender is a Dell laptop that uses a 240W 110VAC power adapter to produce 19.5VDC @ 12.3A. Given our intended usage, I can foresee extended periods of the laptop running at maximum capacity - high CPU/GPU usage, etc.

I'd like to power this directly from DC power if possible. We're already doing this for an Intel NUC using a DC boost converter. However, 240W is a lot more power than the NUC is drawing!

Questions:

Do the Dell power adapters have any fancy electronics (e.g. negotiation like USB-C PD) or do they just output a steady 19.5VDC? Is this something I should be weary of on other brands as well?
Any other reason why I can't just use a DC-DC boost converter and the right sized barrel connector to charge the laptop? The wires could all be short and high gauge - no worries there.
Any recommendations on a high-quality, high-efficiency DC boost converter that could accept a fluctuating input (typically 13.0-14.4VDC) and output a constant 19.5VDC?

The alternative would be a small, dedicated inverter just for the laptop, but I'd rather not do DC-AC-DC conversion at all (given the implicit inefficiency) if not required.

PS - yes, we may need more solar anyway...!


texts: Clean/reduce static in electret microphone caused by "dirty" Raspberry Pi pin output voltage

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I'm currently trying to wire up an electret microphone to a Raspberry Pi. I just figured out how to wire it up to a button cell battery after a couple of days of struggling. Still learning electronics so bear with me.

simulate this circuit – Schematic created using CircuitLab
I want to remove the button cell, and replace it with the +3.3V to GRND pins on the Raspberry Pi 3B+, but the problem I'm encountering is when connecting ground to the ground pin on the Pi, I get a lot of audible static in my voice recordings.
I'm assuming that this is because the ground pin isn't limited to -3.3V like with my button cell.
Is there a way to limit the negative voltage potential of the ground pin?
My instincts tell me that using a capacitor can accomplish this somehow, but I'm not sure of the approach.


texts: Determining the logical function of the circuit with diodes

texts:
simulate this circuit – Schematic created using CircuitLab

Entry voltages, \$Vin_1\$ and \$Vin_2\$ can be either 5V, for logical 1, or 0V, logical 0. \$V_{cc}=5v.\$

Find \$R1\$,\$R2\$ so that \$Vout\$ is, at least, 4V in the state of 1 and 1V, at most, in the state of 0.

So explanation that I got, but didn't understood, is that if one of the entry voltages is 5V, then node a will be at 4,3V and that other diode will not conduct. (How so?) And after that we can see that there must be a current through D3. It's supposed to be an OR function.


texts: First PCB (raspberry pi hat)... can't find short circuit

texts:
INTRO:
Hi there, everyone. I'm working on a RaspberryPi hat PCB that drives 10 solenoids and takes in 5 inputs. I designed the PCB on EasyEDA and had the boards printed at JLCPCB and used their SMT service to pick and place the components.
ISSUE:
When I plug the power supply in, the voltage drops from 24V to negligible millivolts. When the power supply is unplugged I can read 24V fine. Two components get warm after about 2 or 3 minutes at which point I unplug the power supply to hopefully not damage anything (Q1 and U2 as seen below).
I would be grateful if someone could take a look at the schematic and the pcb layout and possibly give me direction on where to go from here.

Things I have Tried:

Continuity test across U1 input terminals beeps for a short bit and then stops... I have figured this is from a capacitor filling up.
I have tried putting an LED across the 5V and GND pins where the raspberry pi usually sits to see if I needed to draw some load but this had no effect.

I have not tried plugging a raspberry pi in as I don't want to damage the pins.
Possibly Helpful Notes:
Power Supply - 24VDC 2.1A |
Solenoids - 24V .2A |
Sensors - 24V |
Raspberry Pi 4 - 5V 2A
I am a complete novice at circuit board design and electricity in general, if I left any information out of this post that is needed let me know and I will hopefully clarify as quickly as I can.
Thank you for any help you can provide,
Daniel Cloran
UPDATE: I have fixed the short based on brhans help... the D1 diode was flipped! I am working on adding an output capacitor based on the datasheet.
I am now using a different board with a replaced Q1, and I am getting about 1.7 V out where 5V is supposed to be. I have been reading the Fine Manual and know you can calculate output voltage with Vout = 1.239 * (R1+R2) / R2... (R3 and R4 in my case) which should give 5V's out - 4.956V = 1.239 * (30+10) / 10. I've measured the ohms of the resisters, reading about 18k and 8k on this board, 24k and 10k on a different board... these should still give values above 1.7V. Would the output capacitor increase this voltage in some way or just smooth the voltage? Any ideas?
Adding the output capacitor fixed the problem! Thank you all for the help... the board works as intended for now, but I will work on fixing the tracing issues in V2.


texts: Simple light bulb operated by button and optoisolator triac

texts:
I'm new to the world of electronics and I have a quite simple question.

Can I control my light bulb with something like this schema?

Power source is regular AC 230V (~320Vrms) source.

Here is The MOC3052 data sheet.

I want to control this using Arduino but is the underlying principle OK or not?

EDIT:

Modification with respect to Spehro's comments:

But now I do not know how to connect the TRIAC :)

EDIT:

Would this circuit be OK?

Now the optocoupler is switching the triac.


texts:
I am a bit confused with the given information to me (written in Bold letters below). If i could get some more ideas and clarifications it would be really helpful.

Given:

BC 547 transistor (in use)
Beta =600
Emitter current = 1mA
VRe = 1V
Current through R1 and R2 is 10 times larger than IB.
Make VCE about the same as the voltage drop across Rc for the largest output swing !!


texts: After installing capacitor, circuit is not working anymore

texts:
In order to eliminate potential voltage spikes from my wall charger, I added a 6,3V 220µF capacitor to my circuit. A very simplified drawing is below:

However after installing the capacitor, I am unable to measure any voltage, even after having it powered on for a while. A USB charger is used for this circuit.

What could be the reason for this? Could the capacitor be broken or am I using it wrong?


texts: How to detect if a nearby parked car has started engine?

texts:
We have a project with a machine servicing a car parked next to it. It's comparable to a car washning machine.

Before the machine is started, we need to be 100% sure that the engine is off. Also, if we detect that the engine is turned on during the process (which takes severa minutes), the machine should withdraw its operation immediall, to avoid damages.

The machine is supposed to refuel the car without any manual action by the driver.

Electrical cars are not a part of our current plan. But it certainly is relevant that some cars stop the engine when the brake is down.

Our problem is to detect whether the car parked at the machine is running or not. We have already been thinking of these solutions:

Microphone listening for engine sound. Problem: In a noisy environment, we might have too many false alerts, when a big truck is parking close nearby.
IR camera looking for hot exhaust gas. Problem: We have tried that and can't see any significant changes whether the engine is on or not
Camera detecting whether the engine lights are on. Problem: Not all cars have lights on when engine is running. Not all cars require the driver to push the brake to start the engine.

What other options do you see for us?


texts:
I'm trying to convert my board outline .dxf file to .max for Orcad 10.5. I applied exactly the same steps as described in OrCad Help; however, I obtain nothing but an empty page at the end process. If anyone using Orcad 10.5 still exists, it'll be very helpful.

Thanks.

Answer: If it happens to anyone, try saving .dxf in IntelliCad with older version of AutoCad.


texts: Mounting components on both sides of a PCB

texts:
I'm designing a PCB with a microcontroller ,CAN transceiver, sensor (I2C) and linear regulator. I want to make the PCB as small as possible, so my thoughts were to use both sides of a two layer stack up. I've never done this before, only ever using one side of the board for components.

My primary concern is what should I avoid putting back to back? for example I'd make an educated guess that it would be poor choice to put the linear regulator directly behind the microcontroller.
Should I avoid comm lines (I2C UART CAN) crossing over?


texts:
This resistor array is provided with a +/-200ppm/°C temperature drift.

I understand that is the maximal allowed drift.

However, does it means, within in single package array, is it likely that all resistor will have a somewhat similar temperature dependency, or can it vary significantly from one resistor to another (again within the same array) ?


texts:
I'm currently working on setting up a logic circuit using ICs (SN74LS08N, HD74LS04P and CD4075BCN) and LEDs. I looked at their datasheets and I found that the maximum voltage supply to the ICs is 5.25V.
Which type of battery should I use as the source?
I currently found 2 solutions on the internet, one is getting a 9V battery with LM7805 voltage regulator IC and the other one is connecting 3 AAA batteries in series.
Which one is better for my circuit?


texts: Some questions about a simple high voltage circuit

texts:
The schematic below occurs as an example circuit in a set of lecture notes that I'm using. It is a circuit for building up a high voltage across the capacitor \$C\$ using a constant voltage \$V_0\$.

I understand how the circuit works, but would like to know the following.

What is it called?
Is it used in practice?
If so, how does one operate the switch and what kind of switch is it?

For questions 3, could one for example use a diode with a high frequency sinusoidal bias voltage to achieve the rapid switching that is needed for high voltages?

simulate this circuit – Schematic created using CircuitLab


texts: What is meant by 8-bit resolution on the AD8802's PWM input?

texts:
I am using a PCA9685 (outputs 12bit PWM) to control an LED driver, AP8802. The LED driver datasheet states (on page 11, paragraph 2):

  A Pulse Width Modulated (PWM) signal with a max resolution of 8-bit, can be applied to the CTRL pin to change the output current to a value above or below the nominal average value set by resistor RSET.

What I would like to know is if it is possible to use the ICs together or will that not be possible, in which case why?


texts: Why is this two-inductor circuit first order?

texts:
I have the following circuit with two inductors. Apparently this is a first order circuit (judging from my solutions for \$ i_1, i_2\$; and circuit simulations) but it's not intuitively clear to me why.

Unfortunately the circuit parameters/initial conditions are a bit vague. I'm not given the exact form of \$I_0\$ (I assume it's most likely a step at t = 0 of height \$I_0\$). I'm given that \$ i_1(t=0)=I_0/2 \$. \$ i_2(t=0) \$ is not given.
My instinct is that since these inductors can't be combined in series or in parallel it should be a second order circuit. I see that there's a current source in parallel with each of the branches, but since the current isn't necessarily split the same way between each branch it seems that the branches will be coupled (that is, I don't believe it's the same thing that's happening in this similar question).
Some initial analysis:
$$
I_0 = i_1 + i_2 \\
\frac{dI_0}{dt} = \frac{di_1}{dt} + \frac{di_2}{dt}
$$
Assuming that \$I_0\$ is constant in time after t = 0,
$$
\frac{di_1}{dt} = - \frac{di_2}{dt}
$$
And,
$$
-V_R-V_1+V_2=0 \\
\frac{di_2}{dt} = \frac{di_1}{dt}+ \frac{R}{L}i_1 \\
\frac{di_1}{dt} = -\frac{R}{2L}i_1 \\
i_1(t) = c_1 e^{-t \frac{R}{2L}}
$$
I can do the same thing (making use of \$ i_1 = I_0-i_2 \$) and solve for \$i_2\$:
$$
i_2(t) = c_2 e^{-t \frac{R}{2L}}+\frac{R}{2L} I_0
$$
I haven't solved for the coefficients but I think that's not important since the initial conditions shouldn't affect the order of the system, as far as I'm aware.
I think the biggest assumption I made here was that \$I_0\$ is constant in time, resulting in \$\frac{di_1}{dt} = - \frac{di_2}{dt}\$. The other thing is that since \$I_0 = i_1 + i_2\$, maybe this makes the branches "linearly dependent" (if that's the terminology here)?
I had thought that inductors/capacitors not being series/parallel reducible is the condition for them forming a higher-order system, but is that actually just a sufficient and not necessary condition?
Edit: It's occurred to me that if the source were set to 0 then the inductors would be in series. Not sure if setting inputs to 0 is how you're supposed to determine that stuff or if it's irrelevant/coincidental.


texts: How to ensure serial transmission and reception of required data without any garbage values in the 8051?

texts:
I'm trying to continuously transmit the character 'L' from the microcontroller 8051 to the PC at a baud rate of 9600. The frequency of the 8051 is 16 MHz, and I accordingly loaded the BRL register with "0XFC" for baud rate generation. However, I can see a stream of garbage values on the hyper terminal; I even tried changing the auto reload values from 0xFB to 0xFF to no avail. Is there any way for me to generate the exact Baud Rate in the microcontroller or a way for me to fix this problem?

Edit: Also, even if I transmit just a single alphabet from the PC to the controller, and the code is written in a way for the controller to echo everything sent from the PC sometimes the character the controller sends in response is different from what I'd sent.

My code is as follows:

#include "reg_c51.h"

char uart_data='L';

void main (void)
{
    SCON = 0x40;
    BDRCON &=0xE0;
    BDRCON |=0x08;
    BRL=0xFC;
    IEN0 = 0xF0;
    BDRCON |=0x10;

    while(1)
    {
        SBUF = uart_data;
        while(TI==0);
        TI=0;
    }
}


texts: Could LM317 in basic regulator configuration (see description) fail to regulate?

texts:
So I have a regulator using a 317 in a basic configuration. One minor change is the introduction of a 10uF electrolytic capacitor between \$R_{ref}\$, and ground.

$$R_{ref} = 240 \Omega$$
$$R_{adj} = 1k \;\text{linear} \times 2 \;\text{(series)}$$

$$V_i = 15.1V$$

$$V_o = 1.25 \Big(1+\frac{R_{adj}}{R_{ref}}\Big)$$

Any value of \$R_{adj}\$ below \$R_{ref}\$ should give me 1.25V.

Values of \$R_{adj}\$ above \$R_{ref}\$ hopefully will yield correspondingly increasing values at \$V_o\$.

What I see instead is as follows -

There is no load connected as yet. This supply being constructed to bias a varactor; the output reported below were against ground.

\$V_o=15.1V\$ for \$R_{adj} = 0  \Omega\$
\$V_o=13.9V\$ for \$R_{adj} = 2K \Omega\$

Do I have a bad 317?

EDIT: Turns out a loose connection was the problem. I flipped the perforated board over to take a gander at the soldering; when I flipped it back I could vary the voltage using the pots. Thank you, all!


texts: Does Arduino ADK shield for android, serves like a regular USB host shield?

texts:
I'm from Argentina and the guy whom I bought the Arduino accesories from doesn't have any USB hosts. But he has this.

I'm not interested in connecting an Android phone to it but I certainly would in the future. Right now I'm only interested in connecting a DSRL camera and a Joystick with USB.

In this article here, it says "Support USB HOST mode，support HUB protocol".

Just to be sure, does it have the very same functionality as a regular USB host shield?


texts: Designing a PI controller for a first order system

texts:
I have a first order plant:

$$ b/(s + a) $$

That I'm trying to control using a PI controller:

$$ \frac{(K_ps + K_I)}{s} $$

I closed the loop with unity feedback to get this transfer function:

$$\frac{b(K_ps + K_I)}{s^2 + (a + bK_p)s + bK_I}$$

With this, I can place the poles and zeros where I want.

I have \$a\$ and \$b\$.

I'm stuck now with how to choose \$K_p\$ and \$K_i\$ such that I have no overshoot and zero steady state error.

I want to minimize rise time.


texts: What effect does Permanent Magnet have on an air-core coil?

texts:
Given an air-core coil of known inductance and a given frequency of applied voltage, you can predict the coil reactance, the current, and the voltage/current phase relationship.

What effect, if any, will a permanent magnet placed at one end of the coil have on the predicted properties of the coil?

Additionally, if the reactance for the given frequency is altered by the magnet, can the applied frequency be changed such that a new reactance (in the presence of the magnet) can be matched to the original reactance without the magnet.

The former paragraph is at the core of what I'm trying to get at, because I want to know if the magnet will have any kind of transformer effect (parasitic or otherwise) on the oscillating coil.  Will the presence of a magnet simply change the inductance of the coil, or will it cause other behaviors (similar to those seen when two coils share mutual inductance)? Or is there something else altogether I am missing?

The arrangement of coil and magnet is end-to-end as the field polarities would be aligned along their axes like this:

 coil <--> magnet
_//////_  [N | S]

The arrangement would also allow for the magnet to slide into the coil, thereby creating a sort of magnet-core coil.


texts:
I am wiring up the solar system in my van and I need help with claryfing some things up.

I have a Phocos CA08-2.2 controller and in the manual one can read:

  Be aware that the positive terminals of the controller are connected internally and therefore have the same electrical potential. If any grounding is required, always do this on the positive wire.

Right, but there is a remark later on that actually corresponds to my situation:

  If the device is used in a vehicle which has the battery negative on the chassis, loads connected to the regulator must not have an electric connection t the car body. Otherwise the Low Voltage Disconnect function and the electronic fuse function of the controller are short circuited.

So clearly I am missing something because it sounds contradictory to me. In the very first paragraph it says that "any grounding should be done on the positive wire" but later on it says "if you have your battery grounded on the negative side, then...". How should I understand this?

I figured the following circuit and after reading the manual about grounding the positive, I got my concern.

(I skipped the controller loads that are not grounded, and solar connectors in the solar controller for the clarity.)

So all in all - I have my 12V battery connected to my van chassis. Is it safe to connect the solar controller such that the controller negative connector will be grounded because the battery is grounded on the negative?


texts: dsPIC 30F6012A will not read RD9, appears to be software problem

texts:
I'm using a dsPIC 30F6012A. I have two PCBs with this chip, both displaying the same symptoms, implying it's not one-off damage. RD9 is definitely being driven to five volts, confirmed with a multimeter. Older versions of my firmware read digital input RD9 without problem. Newer versions do not; RD9 is always read as low, regardless of the actual voltage on the pin. There are no differences between the code versions that are obviously related to RD9. RD8 and RD10 read correctly. I've updated MPLAB X and the XC16 compiler to the latest versions, without effect.

What software issues could cause a digital input to always read low?

The relevant assembly for my current compliation is:

177:                       TRISD = 0xFF07;
002214  2FF074     MOV #0xFF07, W4
002216  881694     MOV W4, TRISD

debounce_input_state.RTR = PORTDbits.RD9;
0027C6  8016A4     MOV PORTD, W4
0027C8  DE2249     LSR W4, #9, W4
0027CA  624261     AND.B W4, #0x1, W4
0027CC  FB8204     ZE W4, W4
0027CE  620261     AND W4, #0x1, W4
0027D0  DD2249     SL W4, #9, W4
0027D2  804346     MOV debounce_input_state, W6
0027D4  2FDFF5     MOV #0xFDFF, W5
0027D6  630285     AND W6, W5, W5
0027D8  728204     IOR W5, W4, W4
0027D2  8845C4     MOV W4, debounce_input_state

I've tried different reads of PORTD in different places, without apparent benefit or change. LATD is never referenced in my code, and the reference to TRISD above is the only reference. Forcing TRISDbits.TRISD9 to 1 immediately before read doesn't have any benefit. There are only two peripheral attached to the same hardware pin, and they're explicitly disabled, and should not interfere with digital input in any case.

Debugger agrees with my observations: PORTD<9> never reads high, while <8> and <10> do. TRISD<9> is set high. PORTD<9> is shown as going high in the debugger on my old firmware. Relevant code from old firmware is as follows:

172:                       TRISD = 0xFF07;
002210  2FF070     MOV #0xFF07, W0
002212  881690     MOV W0, TRISD

530:                       debounce_input_state.RTR = PORTDbits.RD9;
0027E0  8016A0     MOV PORTD, W0
0027E2  DE0049     LSR W0, #9, W0
0027E4  604061     AND.B W0, #0x1, W0
0027E6  FB8000     ZE W0, W0
0027E8  600061     AND W0, #0x1, W0
0027EA  DD0049     SL W0, #9, W0
0027EC  8045C2     MOV debounce_input_state, W2
0027EE  2FDFF1     MOV #0xFDFF, W1
0027F0  610081     AND W2, W1, W1
0027F2  708000     IOR W1, W0, W0
0027F4  8845C0     MOV W0, debounce_input_state

It appears to be semantically identical, just different register names.


texts: Calculation of unknown components in "unbalanced" bridge circuit

texts:
A Bridge is a mechanism that is use for measuring unknown values of passive elements in circuit. Generally a DC excited bridge use for resistance measurement (ie. Wheatstone bridge) and AC excited bridge (ie Schering Bridge) for reactive components like capacitor or inductor.

simulate this circuit – Schematic created using CircuitLab

In general use of bridge, whether DC or AC excited, to measure unknown component, one can vary one or two components values. When the bridge is balanced which means Va and Vb in schematic is equal; with proportion of components one can define the unknown value.

Almost any tutorial tells about balanced condition calculations. Of course they are voltage indepedent and with proportion of components one can easily calculate values.

Question is, in the case which we want to find unknown component value without balanced condition(unbalanced condition) of course with measured voltages of Va and Vb, how can we do that?


texts:
For selecting a transformer, I stumbled across the following equations for
obtaining VA and IAC (citation here).

I am dealing with a full wave bridge rectifier with a capacitive load. The wiki
explains to use these two equations:

$$IAC = 1.8 \times IDC$$

$$VA = 1.4 \times (watts + (2 \times IDC))$$

I am curious how the equations are derived for both IAC and VA. Also, would watts be the power from the rectifier? For my power supply design, I need my max IDC to be 3 and VDC to be 15.


texts: I am designing this charge pump for a pll. But the control voltage always stays between 1.7 and 1.8V. Because of this the VCO after this always oscillates at its higher end of frequency. What parameter should I change to reduce this voltage to around 1V so that the control voltage is properly generated for corresponding vco oscillation frequency? Iref is 20uA.


texts: How to calculate values for my variable DC power supply

texts:
I am making a variable DC power supply via Multisim and the values are given to me is V1=7, V2=15, Imax(load)=209mA (both V1 and V2 is DC value which is on U1.)
I am using resistors, an LM317 voltage regulator, and a variable resistor to change my voltage to my V1 to V2 and 2 capacitors.
The issue I am facing that I am not able to get calculate correct values for me to work for resistors, capacitors and Imax(load). but This what I have done fo far:

VPeak=Vrms*sqrt(2)
CS=5Io(maybe I max)/Vp100
R1=250 as a constant
R2=R1*(Vout-1.25)/1.25
CF=1uF Tant capacitor as a constant
I tried to apply ohms law to get desired Imax(load)=209mA on RL, but my DC value decreases and it does not even reach to the required mA, (I applied ohms law when my variable resistor is at 100%).

This is the circuit I have drawn so far in Multisim, feel free to improve it and tell me what I have done wrong.
File: https://drive.google.com/file/d/1i-NSvtno15pmKutNENA5YVsf4ckoWuCC/view?usp=sharing


texts: Because of an oversight a part that has a footprint SOT89-ECB (PNP-BJT), ended up on my board, but when I tried to find a transistor that actually has compatible pin configuration I came out with nothing. So what is the point of even having a footprint like that in a standard library (I used Eagle, but when searching I found this footprint in other libraries as well)? Are there actually compatible parts that I did not find?


texts: What is equation for the 555 timer control voltage in monostable

texts:
How do i get the 555 timer in monostable output frequency when there is voltage apply at control voltage. I only able to find the formula for astable which is
Orignal post:-
What is the equation for the 555 timer control voltage?


texts:
After searching, I was unable to find a clear answer so.....

Looking at datasheets for different microcontrollers and other chipsets, a pull-up or pull-down current is often mentioned instead of a resistance.
From what I understand, resistors are hard to implement in silicon and/or take up a lot of space, so instead something like a current mirror circuit is used, and the datasheet quotes a pull current.

When modelling this in a circuit simulator, should I insert a current source in place of where the pull up/down resistor would be (between pin and supply or pin and ground), sourcing/sinking current from/to the pin respectively?

In Thevenin/Norton analysis ideal voltage source is considered an ideal short circuit, and ideal current source is considered an ideal open circuit, so if the circuit model has an ideal open circuit where the current source is then how does the voltage at the pin get pulled up to the supply for example, for a source between pin and supply?

Thanks


texts: What are the units of the measurements that come out of an accelerometer?

texts:
I'm pulling samples out of this accelerometer that I've configured for high resolution mode:

and I'm trying to understand the units of what's coming out.  Some places online seem to indicate just au (arbitrary units), some say mV / g, and this seems to indicate mg.  When I gather samples, I see values go beyond 2000 which makes me think I'm exceeding the range I configured for.

I also realize there are different types of accelerometers but can't seem to find out which type this one is.  Is there a way to map the units to something more meaningful than au's?


texts: Frequency locking for averaging resampling

texts:
Background

I've done a long one-shot measurement of a periodic signal by an oscilloscope. Thus, I've captured around 250 periods of a signal. The signal itself is a pseudo-random binary sequence at the output of a low-pass filter. Here is how a tiny portion of the signal looks at the oscilloscope:

Now I want to imitate the way this signal would be sampled by a coherent receiver (one that would precisely know the clock frequency \$ f_c\$ of the signal generator) with averaging (that is, the receiver would select identical segments from each period and average over them). To do so, I define a periodic (averaging) sampling function \$g_p(t)\$:

$$
    x[n] = \int x(t) g_p(t - n/f_c) dt \\
    g_p(t) = 1/L\sum_{l=0}^{L-1} g(t - lN/f_c),
$$

where \$N\$ is the number of samples in the period, \$L\$ is the number of observed periods and \$g(t)\$ is an elementary window that selects one sample (e.g. Hamming window). Also, note that the sampling frequency of the oscillograph is by an order of magnitude higher than the clock frequency \$f_c\$ of the binary sequence.

Now comes my first, minor question: Is my flow of thought generally OK?

Main problem

I do not know the exact value of the \$f_c\$ and want to estimate it from the input data, having an initial guess and refining the result by solving an optimization problem. My thinking is that I want the periodic sampling function \$g_p(t)\$ to select as similar data fragments as possible. Intuition suggests that we could look at the variance of \$x[n]\$:

$$
   \text{Var}\left\{x[n]\right\} = \mathbb{E}_{g_p}\left\{x^2\right\} - \mathbb{E}_{g_p}\left\{x\right\}^2\\
   \mathbb{E}_{g_p}\left\{a\right\} \stackrel{\text{def}}{=} \frac{1}{||g_p||}\int a(t) g_p(t) dt.
$$

So far, this equation will give us a variance (a.k.a. measurement uncertainty) for a single sample of a receiver. I expect that this value should achieve its minimum if we've picked the correct \$f_c\$.

For stability reasons, I form the cost function as a combined variance from several samples. One sample will probably give a noisy result, and taking all samples requires too much computational effort.

Unfortunately, as I do a sweep over the search space, the cost function does not show any sort of convexity. Note that the initial guess is located in the middle of the X axis.

Could anybody give me a hint about what I could possibly be doing wrong?

Also, I've got a strong feeling that I am reinventing the wheel. Does anybody know how this problem is called properly so that I can google for it?


texts: Is this symbol another version of a ferrite bead symbol?

texts:
I saw this symbol in the schematic of the ADPD2140z eval board. From what Ive seen online, ferrite bead symbols are usually slanted rectangles with right angled corners. This is slightly different, but is this also a symbol for a ferrite bead?

Here is an image of the component E1 in question:


texts: Viable alternative for expensive MLCC capacitor?

texts:
I'm thinking of building and selling a product which uses a DC-DC isolator. I've been prototyping with Recom RI3 3W Isolated DC-DC Converter Through Hole, Vin 5 V dc, Vout 9V dc, I/O isolation 1kV.  The latest datasheet suggests an EMC filter using a 10uF 100V MLCC capacitor to meet EN55032.  These capacitors are expensive, and so might affect the viability of my product.

For my own purposes, the prototype works fine both without a filter, and with an aluminium capacitor in place of the MLCC one.  Are there other types of capacitor I could use which might enable me to achieve FCC and CE compliance while keeping down the cost of components?


texts: Adding Hysteresis to Supply Voltage Supervisor

texts:
I am going through this TI-APP note - Voltage Supervisor,with hysteresis.

I am not able to understand WHY they have derived the below equation 1 & equation 2 in the App note (page 2 & page 3)

I understand that the equation is obtained by using the KCL at the nodes.

My questions :

Why should I apply KCL there?
How is performing KCL there linked to finding the voltage at which RESET pin will change its state?

Please explain


texts: what is the maximum range of citizens band radio computation

texts: i have been computing the maximum distance for a citizen's band radio. i don't know if my computation is correct because the answer is so large, appx. 280000km. what do you think is wrong with my computation please help. or please teach me how to solve for the maximum range for citizens band radio. thanks for your help :D


texts: Solar charge controller low wattage panels

texts:
Do I need a solar charge controller for low watt/low battery voltage situations?  This site says that they are generally not needed:

http://www.solar-electric.com/solar-charge-controller-basics.html

For instance, I want to use a 2w 5.5v panel to charge 3X 1.2v AA batteries.

Do I need to use a steady state voltage to charge the batteries, or can I get away with just a zener diode to limit battery flow to the solar panel at night?


texts:
I have a high voltage(let's say +-100Vpp) sine signal of 500khz and i want this signal to be phase shifted(+ve) by 0, 90, 180 and 270 degrees.
That is a circuit which has 500khz input signal and 4 outputs with 0, 90, 180 and 270 degrees phase shifted.
I do not want any attenuation in the circuit. I have looked into op-amp/transistor circuits with RC Components. But have not come very far with that yet.
Sugestions?


texts:
I'm trying to design an inverter and I'm using 2 IR2110 as gate drivers but my MCU board PWM outputs are open collector, I've added a pull-up and transistor to feed IR2110 with 5V pulses but it's not working.

Here is the full bridge and gate drive I'm using:

and here is the pull-up and transistor schematic I'm using between IR2110 pwm input and mcu open collector output(ULN2003A):

simulate this circuit – Schematic created using CircuitLab

Thank you for your help.


texts: A switching mechanism which when fails should fail open to cut off the power to the load

texts:
I am working on a circuit design where a heater (10 Watts) load is switched ON and OFF using a relay.
The relay is in turn switched ON  and OFF from N-MOSFET.
MOSFET is switched ON and OFF using a Micro-controller and an Opto-Isolator.
Our concern is that in case of MOSFET failing short/closed the relay will always be ON and the heater will stay ON.
Is there any way in the switching circuit design to cut off the power in case of MOSFET failing short? Or is there a way that MOSFET always fails OPEN?

Thanks in advance for your time and help.

simulate this circuit – Schematic created using CircuitLab


texts: Half-bridge gate driver fried, how can I make my design work?

texts:
I made a half-bridge following the recommended schematics from the IRS2184 datasheet.
However when I powered it, it triggered over-current and got quite hot.
Here is are schematic and routing.

I checked my pcb for shorts and didn't find any.
At first, altium didn't place the pins at the correct place on the IC so I had to modify them according to this schematic
What could make it work ? Thank you!


texts: decoupling capacitor's inrush current effect on usb filtering

texts:
I am confused about 2 different articles about decoupling capacitors and usb filtering.

First one: https://www.autodesk.com/products/eagle/blog/what-are-decoupling-capacitors/

this says i should use 2 different decoupling capacitors for each ic. One for high frequency(0.1 uf) and one for low frequency(10uF) noise. This makes great sense.

The second one is about usb voltage filtering. http://andybrown.me.uk/2015/07/24/usb-filtering/

This article says "It’s a little known fact that the USB 2.0 standard mandates a maximum of 10µF in parallel with VUSB to limit the inrush current"

So the problem is, i have 3 ics. with each has 10 uF in parallel i get way more impedance between 5V and gnd since they're all parallel between 5v-gnd.

Is using only 1 piece of 10uF at the end of filter instead of placing 3 pieces 10uF for each ic enough?

Edit:
One ic is pca9555 nxp.com/docs/en/data-sheet/PCA9555.pdf? (could not seea cap value on this) other is mcp2221A ww1.microchip.com/downloads/en/DeviceDoc/20005565B.pdf


texts: why cannot use permanent magnets for large electricity production

texts: Why cannot use permanent magnets for large electricity generation as they donot require power to produce strong magnneticfield


texts: I know this subject has been covered but I have a specific question regarding zener characteristics for microcontroller GPIO protection in vehicles where nominal voltage could be 12 or 24VDC.  CircuitLab asks for Rs and Iz.  I wanted to use as small a package as possible for space consideration but 100mW packages advertise a dynamic impedance of 100ohms or more.  Running the DC sweep simulator made the voltage at Vout easily rise well above 5V.  With the 220mW package, the impedance is advertised at 19ohms.  Running the simulator shows me good up to 60+ volts which is my goal.  I feel like the simulator can't really function properly without a more detailed model and that the smaller 100mW package would probably be just fine?  Would appreciate any thoughts on this. This circuit is more or less based on this Digikey white paper. I didn't feel the input clipping diode to be worth the space it took so I omitted it.


texts: How could I build a headphone stereo to mono converter?

texts:
I have a friend who is permanently deaf in one ear but has normal hearing ability in his other ear.

When he listens to music with headphones or earbuds, he can't hear one of the channels which degrades his listening experience.

I'd like to build him a compact stereo to mono converter. Ideally, it would have an input 3.5mm stereo jack and an output jack that delivers the converted mono sound.

I've tried the simple circuit below using two jacks where I connected the channels using resistors, however, his devices detect the short circuit and won't play the sound. Using sufficiently large resistors I can get past this, but the volume is too low to be usable.

I think I should use an op-amp, but I am not sure which configuration is the best. Should I use a summing amplifier? Do I need a 9V battery to supply power, or could I run this on AA or AAA batteries using rail-to-rail op-amps? Which op-amps should I look for / avoid when it comes to audio quality?

I don't have many restrictions on what I can do. I'm an Engineering Physics student and I have access to nearly any circuit component, a 3D printer, a machine shop, and a PCB mill through my university.


texts: How to compute the output impedance of this current source that makes part of a OPAMP

texts:
Here's the schematic:

i would like to find the output impedance of current source IF1 (seen on that rectangle covering a led, T6 and 2 resistors).

Now, i already have the values of IF1,RF2,RF1, Q-points of all transistors and also gains and output/input impedance's of all 3 stages . I believe to be able to solve this problem if i put use the pi-hybrid model but then what?

Would like to add, i also know the base/colector/emitter current of T6


texts:
I am currently trying to use the LMR61428 boost converter IC with the configuration in the attached schematic and having an heating problem with the inductor. The inductor gets very hot very fast even though it is able to carry more current than the intended peak current. The IC is able to function but it shutdowns itself as thermal management starts to work. Is there anything wrong the with schematic or the component selection. The Mosfet is controlled by a microcontroller ATTINY84. The input voltage for the system is 8 volts.
Inductor used in PCB


texts: Need a device that can take single input and covert to a keyboard key press on USB

texts:
Let me explain what I'm doing currently.

We have made a finger heart rate monitor, each time your heart pulses a transistor is switched on via its base. The collector and emitter of the transistor are then wired to a dismantled USB keyboard. The wires are wired to the P key on the keyboard.

Each time your heart pulses the letter P on the keyboard is pressed.

While this works its large, fragile and ugly.

Anyone know of a pre-made USB device that can simulate a key press from our heart rate monitor?


texts: Uni-Directional Electret Microphones and an Arduino

texts:
I am currently trying to connect an electret microphone to an Arduino. I have found many circuits to do this but some don't work.

I have tried one such circuit with a LM386 with no success.

Yesterday, I came over this question which is extensive but still does not answer some of my questions. The first being how to connect the electret microphone in this schematic:

My Arduino and electronics understanding is limited and the projects I have done previously havn't used electret microphones.

My current understanding is that I should connect the second pin of the microphone to GND but I don't really know.

I have found many other schematics that work in a similar way but from what people said on the post I mentioned above, I think this is the best one for what I want to do.

My project, sorry for not talking about before in the post, is connecting uni-directional micrphones around a circle to an arduino to tell the direction the sound comes from.

If anyone has a better schematic or any ideas, please let me know.

EDIT:

Another question is that (c1) 22uF TH Ceramic capacitors are hard to source, are there any other options?


texts: A circuit to prevent parasitic powering of FT232RL by MCU, will it work?

texts:
In a previous question I asked how to prevent the MCU TX pin (3.3V when idle) from powering an FT232RL Usb to Serial chip via the TX line:

Preventing parasitic powering of FT232RL by ATMega328P

I ended up going for a solution where I brought TX and RX low if no more valid communications were detected within a certain time.

This however is still not satisfying. I don't wan't the FTDI chip to be powered at all if no USB voltage is present. Now I have created following circuit:

FTDI3V3 is the 3.3V output from the FTDI LDO that is powered by USB. Switch SW1 simulates the USB power coming on (halfway through the simulation). MCU_TX is a square wave simulating TX activity, and FTDI_RX is the input into the FTDI chip. This should be 0V when SW1 is open.

Simulating the circuit gives the desired behaviour:

Is there something I have missed?
Does the circuit adequately simulate the connection?
Is there an easier alternative? Would a dual supply buffer work?


texts: A trio of questions about radio/smartphones

texts:
I know that smartphones can receive FM radio using earbud/built-in antennas, but can they receive amateur radio frequencies (144 MHZ?) and if so, how?

Is there a way to sending out radio waves and have them received as a call by smartphones?
Is there any other way of transmitting audio to smartphones in an area independent of cell towers/satellites etc?


texts: Connecting capacitor to the ground and potentials question

texts:
I am a newbie trying to enter the world of electronics and currently struggling with getting a good grasp of basic concepts of electricity. I understand that electrons which usually produce the current are moving from points with lower potential to the points with higher potential.

Consider the following situation which confuses me:

Somehow we arranged two plates of capacitor to be charged. Consider also that positively charged plate has actual positive charge on it and negative plate has actual negative charge on it. So the upper plate is now having the higher potential than the lower plate and also has higher potential than the ground. The electrons are attracted to the higher plate by means of electric field. Now imagine connecting the lower (negatively charged) plate to the ground (assume ground's potential and charge is zero). Will electrons be moving from the plate to the ground or will they stay concentrated on the plate? And if they will move wouldn't it be opposite to the assumption outlined before?

Will the situation be different if positive charge was not present on higher plate. So the upper plate and ground have both the same zero potential?


texts: Advice on RF component for wireless doorbell

texts:
I'm trying to build a custom wireless doorbell, similar to those you can buy everywhere (example). I just need to emit a single signal and receive it elsewhere, to make a buzzer sound.

I've already got all the components except the RF device needed for communication. My requirements are: ~30 mts. distance, maybe passing through one indoor wall and not to be too expensive (you can buy one of those complete doorbells for less than $20). Ideally, I would trigger this module using a microcontroller operating at 3.3 or 5 volts, and as I'd hand assemble this, SMT components should be avoided.

Any advice?

Thanks


texts: How to reset a 4026 counter IC when it reaches 6 for electronic dice

texts:
I'm trying to build a circuit to simulate a dice roll using a 555 in astable as it's heart. The output pulses are counted by a 4026 and then fed into a 4511 BCD to 7 segment decoder.

It works perfectly and counts from 0-9, but I cannot get it to reset at 6 and start from 1.

I have tried to take jam input 1 high and then take the preset enable pin high when the counter hits 7, but nothing happens. I did this by using a quad input AND gate. Inputs 1, 2 and 3 were the binary code for 7 (1110) and input 4 was the clock signal inverted, so it would only work when the clock was off. This did not work and it just got stuck on the number 7 without resetting.

Have any of you had experience with this type of circuit? What can I do?


texts: Using on and off switches and logic gates

texts:
So I have 2 switches Representing:

Bit A
Bit B

And then I have :

AND gate
OR gate
Not gate
Some other gates like adder and comparator

I used the method described here because the Adder & comparator gates always get the input as 1 however the switch is on or off here. Which is connecting the switch between input to gates and the ground , connect the led between the vcc and the output from gates and it works fine for those 2 gates.

But 3 probems occur now :

For the AND gate nearly work as an OR gate:

 - When the 2 switches off: the led is nearly off though I can still see very
 very low illumination

 - When either switch is on: led illuminate with full power

For the NOT gate the output is weak and it kinda go and come (like the LED is vibrating but with light effect)
For the OR gate inputs are always seen as 1

 -when switches are closed: lead illuminate nearly with third of its potential

 - when both are opened: led illuminate with full power.

So is there a way to use those switches correctly ?! I know it is wrong with the switches connection as when i try the input with either with Vcc for 1 or Ground for 0, they work just fine.


texts:
I'm currently learning about signal modulation and fail to figure out the modulation of this signal - maybe someone can help me with it?

The software is GNURadio and the device capturing the signal is a bladeRF SDR. The device producing it is a remote control for home automation. A button was pressed to produce the signal. I'll try adding a new screenshot showing the signal in more detail. the documentation for GNURadio is here: gnuradio.org/docs

I would assume it's ASK, maybe with Manchester encoding. But what makes no sense to me are the long zeros with the small ones.


texts:
I have a PCB with a USB2244 USB to SDIO bridge IC connected to a Raspberry Pi Compute Module 3+. I (think I) designed based on the schematic circuit for the USB224x evaluation kit EVB-USB2240-IND. When I connect the evaluation kit to the USB port on the previous revision of my PCB, the Pi CM sees it just fine. My new PCB has the USB2244 onboard with no external USB ports. Unfortunately, it doesn't seem to be enumerating properly. It starts up, appears to talk briefly, and then shuts down.

In order to isolate the Pi CM as a configuration issue, I unplugged the compute module and soldered a USB-A cable to the circuit to plug into my Windows laptop and had similar issues. I then plugged the same USB cable into a Pi 4 and logged USB packets with Wireshark, but I don't really know how to interpret those logs properly.

Here is my schematic for the USB2244. The reset and USB data lines go to the Compute Module socket. Note that the USB2244 datasheet claims that it has all required termination/pull resistors for the USB data lines built in.

Here's what I know from testing so far. I'm not sure what to look at next. Feeling stumped.

The USB data traces on my PCB were properly specified for controlled impedance.
The RST_PN pin remains high throughout the failed enumeration.
The USBDP line on my PCB does float high before connecting the USB cable, so it is attempting to advertise itself.
The USBDP line stays high after the failed enumeration.
The oscillator does run for a short period of time during enumeration and does look to be approximately 24MHz, but it then stops. I don't know exactly when this happens relative to the rest of the process.
The USB2244 does not show up in a lsusb output on the Linux system after the enumeration failure.
The SD card I'm testing with is known-good.
The USB data edge transitions look reasonably clean, even with the test cable tacked on.
When plugging my test cable into another Linux system, I get the following outputs in dmesg (mostly errors). There was an SD card plugged in for this test. The "attempt power cycle" line probably doesn't accomplish anything because the USB2244 is self-powered from my PCB.

[157703.323082] usb 1-1.1.3: new full-speed USB device number 28 using xhci_hcd
[157703.423293] usb 1-1.1.3: device descriptor read/64, error -32
[157703.643243] usb 1-1.1.3: device descriptor read/64, error -32
[157703.863053] usb 1-1.1.3: new full-speed USB device number 29 using xhci_hcd
[157703.963263] usb 1-1.1.3: device descriptor read/64, error -32
[157704.183265] usb 1-1.1.3: device descriptor read/64, error -32
[157704.303438] usb 1-1.1-port3: attempt power cycle
[157704.963098] usb 1-1.1.3: new full-speed USB device number 30 using xhci_hcd
[157704.963283] usb 1-1.1.3: Device not responding to setup address.
[157705.183259] usb 1-1.1.3: Device not responding to setup address.
[157705.403150] usb 1-1.1.3: device not accepting address 30, error -71
[157705.503069] usb 1-1.1.3: new full-speed USB device number 31 using xhci_hcd
[157705.503218] usb 1-1.1.3: Device not responding to setup address.
[157705.723203] usb 1-1.1.3: Device not responding to setup address.
[157705.943116] usb 1-1.1.3: device not accepting address 31, error -71
[157705.943460] usb 1-1.1-port3: unable to enumerate USB device

This is the Wireshark USB packet capture log. I believe the 1.8.1 device is my USB2244 -- I plugged it into what I believe to be Port 3 of an external hub connected to my Pi 4.

This is a logic analyzer dump that should line up with the Wireshark packet capture. I see a bunch of "Unexpected packet SETUP" going on.


texts:
I don't have a lot of experience into detailed / calculated selection of DC motors based on their specs. Now, I'm starting to do it for robotics competitions as I'm progressing to more serious ones. My questions are:

I know that when you increase the voltage, the speed(RPM) of the dc motor increases, but is it proportional(Linear) ?
Does the stall torque also increase when you increase the voltage across the motor? (not above its rated limit, but above the voltage at which the specs are given)
When you use a motor driver, will it draw the stall current from the battery when the motor is stalled? As the Li-ion I'm planning to use can't deliver so much current...
How do you select a motor driver? (other than based on the stall current it can handle)
Generally spur gear DC motors don't have encoder on them and the ones that do are very costly. So how do you attach a rotary encoder to the motor/wheels? (any ideas)

Thank you for your time and patience.


texts: How many ePWM instances are there in a TMS320C28x Piccolo DSP chip?

texts:
In this reference manual, it is written that:

  [Page 11] 1 Introduction
  ......
   Cross coupling or sharing of resources has been avoided; instead, the ePWM is built up from smaller single channel modules with separate resources that can operate together as required to form a system. This modular approach results in an orthogonal architecture and provides a more transparent view of the peripheral structure, helping users to understand its operation quickly.

  In this document the letter x within a signal or module name is used to indicate a generic ePWM instance on a device. For example output signals EPWMxA and EPWMxB refer to the output signals from the ePWMx instance. Thus, EPWM1A and EPWM1B belong to ePWM1 and likewise EPWM4A and EPWM4B belong to ePWM4.

My questions are,

How many ePWM modules are there in one single TMS320C28x Piccolo DSP chip?
What does it mean by an ePWM instance? Are those software instances or hardware instances?
How many ePWM instances are there in one single TMS320C28x Piccolo DSP chip?


texts: use battery to generate weak electric field?

texts: i am a biology student interested in how marine animals react to weak electric fields.  My professor and I want to do a trial experiment and were hoping to rig something up ourselves for cheap.  Is there a simple way to generate a very weak electric field in sea water (on the order of microvolts)?  I thought of using a battery with two leads placed about 1 cm apart to generate an electric field that is essentially localized to the ends of the lead.  A 1.5 volt battery is way too strong though.  Would it work to add resistors?  How best to calculate the amount of resistance needed - or is this just ridiculous to even consider?  Is there an off-the-shelf solution? Or do I need to tell my professor this is impossible without specially engineered equipment?


texts:
I'm having difficulties finding complex impedance of the following circuit:

What I did first is find the impedance of \$C\$ and \$R\$ in parallel, which is:
$$\underline{Z}_{CR}=\frac{R}{1+j\omega CR}$$
Then, I added two inductor impedances:
$$\underline{Z}_{CRL}=2j\omega L+ \frac{R}{1+j\omega CR}$$
and finally calculated the parallel of that with capacitor impedance \$\frac{1}{j\omega C}\$ which yields:
$$\underline{Z}_{in}=\frac{\omega CR+2 \omega L(1+(\omega CR)^2)-j(1+2\omega CR^2)}{\omega CR + j(2\omega ^2 LC(1+(\omega CR)^2) -2(\omega CR)^2 -1)}$$
However, I'm not getting the correct result:
$$\underline{Z}_{in_{correct}}=\frac{R(1-2LC \omega ^2) + j2L\omega}{1-2LC\omega ^2 +j2RC\omega (1-LC\omega ^2)}$$


texts: what is the difference between a master slave flipflop and edge triggered flip flop in terms of circuitry and performance?like the aim they serve i.e. one transition per clockpulse of the final output, is same then how are they different?


texts:
I have an ADC module. The board contains sensitive (10-100MHz) analogue parts and a high speed serial link (Aurora). The link uses scrambling algorithm, and I can choose the bit-rate. (I have much less data than the theoretical maximum of the link.)

My goal is to reduce the digital link disturbance on the sensitive analogue part.

We know the spectrum of a (scrambled) digital link.

(In a real application the fpattern is ~0Hz.)

The total power of a DC balanced square function is constant and independent on the bit-rate. So I hope that the power on the lower frequencies will reduce if I increase the bit-rate, because the full spectrum will be "more broadband" Am I right?

I cannot find mistake in my theory, however it is hard to imagine that higher frequencies makes less noise.

If I am right, should I choose the bit-rate of the link as fast as possible? (To reduce the disturbance of the analogue part)


texts:
I made a UPS with (2) 12v batteries connected in parallel with a handful of small devices (router, modem, HDD) connected at all times.
Once a day I would like to charge this unit using a 7 stage automatic charger:
http://www.vmaxtanks.com/assets/images/technical%20info%20folder/manual-BC1215.jpg

Since there are devices that constantly draw small amounts of power, the charger never finishes charging.  It stays on stage 3 and never gets to the end.

What would be the best way to handle charging where disconnecting devices from battery is not an option?


texts: When using an open-drain output to drive an NPN transistor, can the base resistor be replaced by a pull-up?

texts:
Assuming the value of R1 is the correct value for the base resistor for the given motor L1, is it okay to omit the additional base resistor, used in push-pull applications, for an open-collector output?
To my understanding, when the open-collector output goes low, the low impedance path will not affect the transistor negatively, as there is no/minimal potential difference between the open-collector output directly connected to the base and ground, therefore turning-off the transistor.

This is my proposed solution using an N-channel MOSFET, based on the helpful answer of @Spehro Pefhany:

I'd much appreciate feedback on this proposal. Will it work with a good margin both at 5V and 12V motor (L1) voltage and over a temperature range of 10°C to about 85°C?
These are the links to the datasheets:

N-channel MOSFET:
https://assets.nexperia.com/documents/data-sheet/2N7002BK.pdf
Temperature sensor IC with open drain thermostat:
https://www.ti.com/lit/ds/symlink/tmp101.pdf


texts: Will a Lock-in amplifier induce a dc voltage when an ac modulation is applied to a junction?

texts:
As it is well known, by applying the ac modulation, the current across can be expressed by a taylor expansion as:

assuming a nonlinearity in the derivative conductance. An additional dc current appears. Is this correct?


texts: Can I use a touch screen from an old Blackberry on a Raspberry PI?

texts:
I have a pile of old Blackberry phones with capacitive touch screens and I'm hoping they can be reused as, at the very least, output devices for Raspberry PIs or even microprocessors.

Is this even a thing?

What specs / properties should I be aware of in order to determine the viability of any of these screens as output devices for Raspberry PI etc?


texts: Need help on building a passive Dim-to-Warm LED array

texts:
I have started a project for my home lighting, I'm trying to build a DC LED module which would change the color temperature from 3000K to 1800K as dimmed with reducing current. I'd like to do it mostly passively without any current sense or threshold circuitry. I also want it to run on my current TRIAC dimmable constant current driver.

The most sensible way I could find to do it is to use two different temperatures of LEDs, route all the current to warm array in the beginning of dimming range, later ramp up the current of the cool array for the rest of the dimming range. Maybe, prefferably, completely turn off the warm array at the end of the dimming range.

Firstly, I'd like to share my current "progress" with you, if you can call adding a resistor as such:

I was able to come up with a very simple circuit to do it, I kept the number of warm LEDs in series low, thus the total forward voltage, put a series resistor to them, then parallelly connected the cool array with higher number of LEDs in series. The LTSpice schematic and DC current source sweep analysis results given below:

The red curve is for the cool array, green for the warm array.

However as you might have quickly realized, the series resistor dissipiates up to 800mW of power at the maximum brightness, and also the warm LEDs stay on at the end of the cycle(not really a big issue though). For a total of 4.8 Watts power consumed in the circuit, 0.8 W is directly wasted on the resistor.

I've seen some other Warm-to-Dim passive DC LED modules online, some add a transistor, some just use the resistor approach. Here is an example of such arrangement with transistors, but i wasn't able to figure out the circuitry from the pictures:

I can just speculate that the transistor assisted circuitry is much more efficient since the transistor or MOSFET just switch current instead of dissipiating the unwanted amount.

I failed on designing some transistor or MOSFET circuits, I tried to sense the current on the warm LED branch, then feed it to the transistor so the cool branch could turn on after some set current.

Maybe me being an amateur hobby electronics guy, originally a mechanical engineer, couldn't see the obvious thing they've done there, or couldn't come up with a very simple transistor arrangement to achieve it.

Can you recommend me a circuit that:

Use minimum number of components even at the expense of performance
Doesn't waste as much current as the resistor circuit i was able to build
Have it's crossover current adjustable with the value of a resistor
And possibly have the warm LED branch completely turned of at the maximum current level?

Thanks in advance for any help provided!


texts:
I'm trying to create a 1hz sine wave oscillator. This is my current design:

Frequency is given by:
f = 1/(2pi*RC)

where
R = Rs = Rp
C = C1 = C2

For a frequency of 1hz, RC has to be:
1/2pi

The current values of R and C are pretty close to 1/2pi:
R2/R1 is loop gain, and I've set it quite high as a larger loop gain makes the oscillator start quickly (if it was slightly above 2, it takes ages to generate the oscillation).
The sine wave in the design is heavily distorted, and it's difficult to measure the actual frequency - The frequency counter doesn't show anything (I'm assuming it's because the frequency is too low, or the waveform is too distorted), and the oscilloscope doesn't plot the wave for long enough for me to calculate frequency manually (by measuring the period), it always disappears (I think the calculations are too long).
This is what the oscilloscope outputs:

(That's about as much as it will plot before the wave disappears and is plotted again)
I would just like to know, is there a better way to try create a 1hz sine wave oscillator, or is there a way to tweak my current design to reduce the distortion, and hopefully get an accurate reading of the frequency using multisim somehow.
Thank you!


texts: Designing a growing box using a resistance wire as a heating element

texts:
I'm trying to design a growing box that will maintain a stable temperature for the seeds germination.
I'm planning to use an Arduino with a temperature sensor to control a heating element. I'm thinking of using a resistance wire as the heating element, as it is a simple and cheap solution.
Let's say the size of the box will be 1 m3. I'm not sure what the insulation of the box will be, but I'm considering either a plastic box, or an old refrigerator.
The target temperature is 30°C (86°F).
I need to choose the right heating element and determine what power supply to use for that heating element.
I've already done some calculations to reaching this goal.
Power needed to heat up the box
First of all, I need to determine how much power is required to heat up the box to the target temperature.
Let's assume that the temperature is 20°C and I want to heat it up to 30°C in 30 minutes.
I used an equation from https://www.engineeringtoolbox.com/heat-up-energy-d_1055.html to determine the energy required to heat up a substance.
m = 1.2 kg (the mass of 1 m3 of air)
cp = 1.006 kJ/(kg°C) (specific heat of the substance)
dT = 10°C (required change of temperature [30° - 20° = 10°])
t = 1800 s (heat up time)
\begin{align}
 &\mathrm{q = \frac{m \cdot c_p \cdot dT}{t}} \\\\
 & \mathrm{q= \frac{1.2~kg \cdot 1.006~kJ/(kg°C) \cdot 10°C}{1800~s}=} \\\\
 & \mathrm{= \frac{1.2 \cdot 1.006~kJ \cdot 10}{1800~s}=6.7~W}
\end{align}
So the required power to heat up the box to the target temperature in 30 minutes is 6.7 watts.
This is the first time that I have calculated something like this. Please tell me if I made a mistake. Does this mean that I need a heating element that consumes 6.7 watts?
If so, let's continue:
Calculating required voltage to power the heating element
I have three resistance wires. Each one of them is a meter long. It is specified that they have the following resistances: 5.4 ohm/m, 20 ohm/m, and 55.4 ohm/m.
Assuming that I need 6.7 watts to heat up the box, and that I choose the 5.4 ohm/m wire, I can calculate the required voltage from the formula:
$$\mathrm{P = \frac{V^2}{R}}$$
$$\mathrm{V = \sqrt{6.7~W \cdot 5.4~\Omega} = 6~V}$$
Therefore, the required voltage using this wire would be 6 V, which I can achieve with 4 AA alkaline batteries in series.
Conlusion
I am a beginner in electronics, so I need a bit of help. Am I on the right track, or is it what I wrote above complete nonsense?
What would you recommend as a power supply for this task?
From what I know, the lower the resistance, the greater the power. But is it okay to use a resistance that low in a circuit?
If you have any other recommendation, feel free to share them.


texts: Power an LED for little time without battery

texts:
I am in need of powering an LED (need to chose which) without an appropriate power source.
I have a 1.8V/3.3V voltage source with very low current capability and I want to use it to power an LED with 10/100 mA sink.

Any ideas? I thought of a cap but the design is SMT and Farad-rated caps do not suit very well.

EDIT:

Sorry for being vague, my fault.

Here are some numbers: my DC source can provide 7 mW maximum continuously, the design is SMT and the PCB has to be very small (a circle of about 3-4 cm radius) .

For the LED: it is a white LED that would act in a "flashy" way, but the longer it's on, the better. Moreover, it should have, at least for a short amount of time (in the order of 10 msec), a CONSTANT current flowing. Let's assume the LED needs 10mA for that amount of time.


texts:
On a early version of the system I'm working on, an Arduino Mega was being used to read some analogue values using its ADC. Something critical to the application was for the ports to be always in high impedance state, except at the moment of measurement, when they would be changed to low impedance. Once the measurement was done they would be set back to high impedance. This was done by changing the mode of the Arduino port (output for high impedance, input for low impedance). This method was being used to sample the small voltage that apears on the terminals of an LED when light shines on it. The small charge that gathers (thanks to high impedance) sinks into the ADC when the port is set to low impedance, and this allows for a measurement.

The system has now moved on and I need to do the same readings as before but now using a Beaglebone Black (BBB). The BBB has a built in 12-bit ADC.
Is there a way to toggle the BBB ADC ports to high/low impedance?


texts: Night LED Lamp with PIR Sensor - Guide to calculation parameters

texts:
I would like to make some LED lamps for night use, therefore at low intensity, just enough to see where you are walking, but almost without waking up. ;-)
It should only turn on when it detects movement and turn off after a certain time.
It must work at low DC voltage (because it is common to have small unused power supplies or easy to build a battery pack).
The basic circuit:
Source: https://www.instructables.com/LED-Light-With-PIR-Motion-Sensor-Soft-Onoff-and-3y/

Among the many circuits available on the net I chose this one, for a few reasons.
Employs a common PIR sensor, requires few components and appears set to not consume more than necessary.
Not least and unlike many other similar circuits, it includes an RC (Time Constant) filter for soft-on, soft-off functionality, which I'd like to keep.
Unfortunately, the author does not explain in detail all the calculations made.
Simply I'm not experienced enough to do without it.
So I would like a small guide that highlights the right procedure, formulas and calculations to define the value of the components, for a specific LED array.
How to adapt the circuit to a given load avoiding waste of current, and perhaps how to verify that it works in the best conditions.
The first revision of the basic circuit, should have:
Basic parameters:

HC-SR501 PIR sensor for motion detection.
Use of standard 5 mm. LEDs (see the table), single or LED array (always of exactly the same type of LED)
Regulated DC power supply between 5 and 12V (15V max.), chosen according to the number of LEDs used.
Soft-on, soft-off function (RC Time Constant filter).

Notes and Questions:

The Author used the BJTs he had (2N2222A). The NPN transistors I have are: BC547B/C, BC548B/C (all, max 100 mA), PN2222A (500 mA), MPS2222AG (600 mA) and SS8050 (1.5 A).
Among them, which ones would be the more suited for this circuit?
Since in a Darlington pair it's the second transistor (TR2) that does the hardest work, is it better to use different transistors or to keep an identical pair anyway, perhaps to simplify the calculations?
My multimeter can measure the hfe of NPN and PNP transistors. I guess this can help.

Circuit Rev. 2
Thinking about a second revision, I would like to know how to add an LDR photoresistor to detect ambient light and activate the circuit only below a certain threshold.
I've seen many examples, but I don't know how to integrate it into this specific circuit.
Thank you in advance.


texts: Why are bipolar transistors often used with the base at vcc?

texts:
I often find transistors used as shown below. Note that the BJT to the left is being used in a strange configuration, where the base is being pulled permanently high.

What on earth is the transistor supposed to achieve in this odd position?

On a related note, I've occasionally seen people use a transistor in place of two diodes. However, my own experiments show that this simply does not work. For example, in the diagram below, replacing the input diodes with a single NPN transistor would significantly change the behaviour of the circuit.


texts:
I am trying to establish a suitable power supply for a device that I have that runs of 24VDC.

In the operating manual that I have for the device it says to ensure that a "grounded power supply" is used to prevent damage to both the device and the user. Also included in the manual was a schematic something similar to the following:

simulate this circuit – Schematic created using CircuitLab

The manufacturer of the device also sells a suitable but somewhat pricey power supply for the the device that looks like a normal power supply to me with a live, neutral and earth on the input.

All of this basically got me wondering about the internal anatomy of a bog standard power supply...

Does the power supply that the manufacturer sells for this device do something like this:

simulate this circuit

Or is this how all power supplies with L,N & E pins work?

As you may be able to tell, I am a little confused but hopefully you get the general jist of my problem.

If someone could shed some light, it would be very much appreciated. Thanks.

To clarify, this is the sort of thing that I am expecting to have to buy:
http://uk.rs-online.com/web/p/desktop-power-supply/0188781/


texts: Any reasons why my 18650s go very hot when I charge them?

texts:
I have some PanasonXX 18650 batteries the grey and the green one

I charge them in 2.5A 4.3v but I found that the green battery is very hot after I charge it about an hour later, I don't know the exact temperature but I can barely use my hand to touch it because its very hot.

But at the same time all my grey batteries are just a little bit warm, any reasons for this situation? As I'm afraid it will catch fire.

Thank you


texts: Resistors in parallel but with a capacitor in between them?

texts:
If I have a source between two resistors in series, can I just add the resistors and place the source below,under them?
If I have some element in parallel like a capacitor, between two resistors in parallel, are the resistors still in parallel?

If so why?

simulate this circuit – Schematic created using CircuitLab

Is it the same as:

simulate this circuit


texts: Making my own PCB connectors, but having trouble with high frequency signals

texts:
I'm making my own PCB connectors using the "multicomp" range of crimp connectors available from farnell (ex. http://uk.farnell.com/multicomp/2226a-04/crimp-housing-1-row-4-way/dp/1593508 with terminals at http://uk.farnell.com/jsp/search/productdetail.jsp?SKU=1593529&MER=baynote-1593529-pr), but while I'm able to get a good DC connection and solid mechanical connection (the terminals don't pull off easily), the AC performance of the resulting cables leaves a lot to be desired; I don't have a lot of test equipment here but with a simple home-made test (wiring them up to an FPGA development board and looping back to the same board and seeing how fast a signal I can send through them and receive it reliably), it appears I can only get up to about 500KHz before I lose the signal.  I'd have expected to be able to do better than that, as I've seen this type of connector used for signals I assume must be higher frequency than that (e.g. USB2).

Any ideas what I can do to improve the performance beyond this?  What kind of frequency should I be able to usefully achieve with this type of connector?

EDIT: I'm putting them onto CAT6 cable.  Is this a suitable cable or do I need something heavier?


texts: Find the Norton equivalent of circuit using superposition

texts:
Exercise 3.23a of Kaufman, 2005:
Find the Norton equivalent of the circuit in Figure 3.125:

I've run into some trouble when answering this question.  The Norton equivalent resistance is clearly \$R_N=R_6+R_7\$.  The Norton equivalent current can be found using superposition.
In the first sub-circuit, \$I\$ is changed to an open circuit, and \$I_N=v/(R_6+R_7)\$.  According to the answer I was provided, this is the only term.  This implies that the current from the other sub-circuit, in which \$v\$ is changed to a short circuit, is \$0\$.
I don't see how this can be the case.  My thinking is that from \$I\$, I need to use the current divider relation to determine what portion of the current passes through \$R_4\$, then again at the junction of the short circuit when \$v\$ used to be, and once again to see what portion passes through \$R_6\$.
If \$R_1\$ or \$R_2\$ were not present, the given answer would make sense to me, because all no current would flow through the resistors to the right of where \$v\$ was, but since they do exist, there is some resistance in all paths back to \$I\$, so the current divider formula should apply.
Can someone correct/affirm my thinking on this?


texts:
I'm trying to PWM some high power LEDs from a isolated control line using a FOD8342. It worked on the bench when prototyping, but now it's part of the final design it seems to work for a minute then blows up the FOD8342. It may have been when prototyping I didn't test it enough....just proved it worked then moved on.

I'm not sure if the FOD8342 is designed to do low sided switching like this. The datasheet figure 23 seems to imply it is? I'm not really sure though.

In use it'll have a 400Hz PWM signal controlling it, but for testing I've been manually switching the control lines. Currently replaced the FOD8342 twice.

Any help is greatly appreciated. I've checked the build and manufacturing seems to be inline with the design which makes me think the concept is wrong.


texts:
I'm at the point where I'm stuck on communication issue and thinking on finally getting an oscilloscope. To my beginner surprise, wasn't expecting them to be so extremely expensive, so I was looking around and found old school oscilloscope for super cheap.

The guy who is selling the scope is claiming it can be used for 'Arduino' projects, but I'm a bit skeptical about monitoring binary data with this.

Only thing I'm confused about is CPU MHZ vs BUS MHZ. The oscilator datasheet says

The amount of CRT rays: Single beam
Range of measured voltages: 20 mV - 200
The range of measured time intervals: 8 ms - 0.5 sec
Bandwidth: 0 - 5.5 MHz
Input channel resistance: 1 Mom
Input channel capacity: 50 pF
The minimum duration of the sweep: 0.2 ms / div
Maximum scan duration: 10 ms / div
Calibration voltage signal:  50 mV

I'm worried about '5.5 MHz'. For my current problem, I need to use it to detect TWI communication problem, since the BUS runs at 100khz or 400khz, then as far as I understood I can perfectly do this.

Now I don't understand what will happen if I try to measure output of the AVR pins directly (without TWI, just random blinking pins with few ms interval). Am I gonna face the following issues:

If my AVR is running at 8Mhz and doesn't have any sleep between the
pin outputs, this oscilloscope won't be able to pick it up?

Basically I can't use this oscilloscope to monitor ports if my AVR is running at higher than 4Mhz?

Thank you!

EDIT: Another alternative I thought I could do is to take another ATMEGA328, enable ADC, and send the result over WIFI/Bluetooth, technically I could make a very simple oscilloscope myself, correct? The only issue 'displaying' the data, measuring it shouldn't give me any trouble, if I'm looking to measure AVR's? Thanks!


texts: RSL10-SENSE-GEVK Read analog signals on accessible pins

texts:
I am new to the RSL10 chip and I can't figure out how to read analog signals with available pins on the RSL10-SENSE-GEVK demo board.

Is it possible to configure the AOUT pin (TP3) to read external voltages?
If that isn't possible, can the GIO_SPARE read an analog input and use AOUT as a digital output?


texts:
Normally what kind of signal flows through the wire connecting the headphone jacket and the headphone?

I wonder whether there is a standard regulating them. And what wavelength, volts, watts, amps, noise acceptable.


texts: How to calculate the zero input response of the current through an inductor?

texts:
The question is find the current through the inductor when the iL(0-)=.5A.
The top picture is the posted solution. My solution is on the bottom. They are not the same and I realize that I should not have a u(t) term in my solution as we are only dealing with the initial condition of the capacitor.

My question is why do they have the admittance of the capacitor over the total admittance instead of admittance of the inductor of total admittance?

Also, are our schematics fundamentally different?

I know there are other ways to solve this but this is the only way we have learned so far so I will be expected to do it this way on my midterm this Wednesday.


texts: How do I compute the average and RMS of a series of triangular pulses?

texts: I'm trying to calculate the Average and RMS values of the current through a diode with the waveform image attached. I'm struggling to work out which equations to use. Any feedback would be appreciated.


texts:
I've heard the terms schematics and PCB designs used interchangeably as well as used distinctively. Are these one in the same, or do they represent to different sets of blueprints? If the latter, what is the difference between them and what different types of information do they convey?

For instance take this Arduino example: it shows separate diagrams for Schematic and Board.


texts: Why can a square wave (or digital signal) be transmitted directly through wired cable but not wireless?

texts: Like ethernet cable, optical fiber. We have a square wave signal, do we just send that squre-wave signal directly down along the cable? If we do send it directly, why we can not send the square-wave signal directly into the air wireless channel? What is the reason behind? Is it because the cable or wire are more stable but wireless is very unstable?


texts: How to calculate a Voltage divider's resistance values from a required current

texts:
I have this exercise (not homework!) where I need to find at what point, using a pot, I will let enough current pass through a BJT base to let 70mA cross a relay's coil. I have trouble determining how to do this.

I know I first need to calculate the required BJT base current, which is 100 uA given that the transistor used in the exercise has a gain of 700.
Then, I am not sure how to use the variable voltage divider to determine the voltage at the BJT's base node, which will let me calculate the potentiometer's resistance at that point.
Can someone help me understand? Should I use KCL?
Thanks!


texts: Voltage drop across a single resistor and across two resistors

texts:
I have been having difficulty understanding voltage drops across resistors. Now, I know the theory and how to apply Ohm's law.

The question is why does the voltage drop across resistors of the same resistance vary from the first circuit to the second circuit? Does it have anything to do with current? Why does it happen? I am trying to find an intuitive explanation as to why it happens.
Thanks!


texts:
I was reading about String DACs here https://www.allaboutcircuits.com/technical-articles/voltage-mode-r2r-dacs-operation-and-characteristics/

and I saw

Is the highlighed wrong? I mean, if just SW4 was on, shouldn't the output analog voltage be 1/2 Vref, since there are 4 resistors above SW4 and 4 below


texts: How to make a step down DC-DC converter fail safe?

texts:
I'm planning to power some high power colored LEDs with a buck converter, using a microcontroller to control the switching to maintain a constant current. I'm also considering a simpler, switched capacitor converter.

It seems unlike a step up DC-DC converter, a step down converter has a fail deadly mode of being stuck in the on state. So, what can I do to protect my LEDs in case that happens?

The obvious answer would be a fuse, but is that the best way? What do laptop power supplies do?

Update:
My input voltage will be 3.7 - 5V, and will have multiple output voltages:  2.3V for red LEDs, 3.8V for green LEDs, and 3.5V for blue LEDs, and all with a current of 1 amp per LED.


texts: Variable Frequency Oscilator (MHz Range)

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For a small hobby project, I need something that is able to variably and smoothly oscillate between the range of 300MHz-500MHz depending on a potentiometer (or some other sort of variable input). The output would be SIN. Any suggestions or admonishments would be very much appreciated!

Thank you in advance!


texts:
I'm working on a project in which I have to build a rover and remotely control it. Remotely controlling in the sense with basic forward and backward movement, as well as the right and left movement. This is perfectly done. But I want to turn the rover to a specific angle automatically when I give a command to it.

Like if I send a command \$30^0 \$ right, the rover should stop and turn to \$30^0\$ to its right with respect to its original position and start moving forward. I just want to know if there any sensor available to find the Angular Displacement. I know IMU sensors like Magnetometer, accelerometer, and gyroscope is used. But still, I'm so curious to know is there any other sensors available to find the angular displacement precisely and with greater accuracy.


texts: Powering 16 super bright blue LEDs with Arduino

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What is the best way to power 16 super bright LEDs using an Arduino Uno to achieve max brightness?

Each LED has the following characteristsics:

IF Typical (mA) = 20
VF Typical (V) = 3.2
IV Typical (mcd) = 3700
IF Max Continuous (mA) = 30
Preferred Series Resistor (ohms)
5VDC = 91
9VDC = 300
12VDC = 430

(http://www.jaycar.com.au/productView.asp?ID=ZD0132)

Output from Arduino pins = 5V.
Power suppply is 12V, while the final will be an Automotive ~12V rail.

I've used two LED calculators:

http://led.linear1.org/led.wiz
this site says I should use 16 LEDs in parallel with 100Ohm resistor on each one.
http://www.hebeiltd.com.cn/?p=zz.led.resistor.calculator
this site says I should use 16 LEDs in parallel with just one 5.625Ohm resistor.

The Arduino Uno has 14 digital pins outputting 5V.
I would like to use the least amount of 5V digital outputs, and the least amount of resistors necessary, while maintaining maximum brightness.

Hope you can help :)


texts:
Somebody who can help me calculate the potential to ground in point a,b,c and d? I would appreciate a good explanation, because my head gets all messy when the circuit has more than one power source.

Have worked out: A=6V, b=14V, d=0V, but I'cant figure out C. I tried to calculate the voltage, which I set to 14v-8v+6V = 12V. Then I found the current in the circuit to be 0,6 A, and the voltage drop across each resistor to be 6 V.


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I plan to use one of these to throw two switches at the same time:

http://www.digikey.ca/product-detail/en/74HCT4066N,112/568-7854-5-ND/1230913

The switches should be closed when the voltage from this debounced circuit is high:

Which diode to use on my RC switch debounce circuit?

This is the pin layout from the switch documentation:

Which wires connect to which pins? These are all the wires I will use:

5V DC [pin 14, Vcc]
Ground [pin 7, GND]
Schmitt Trigger output [???]
Circuit 1 wire 1 [???]
Circuit 1 wire 2 [???]
Circuit 2 wire 1 [???]
Circuit 2 wire 2 [???]

Upon trigger, I would like Circuit 1 wire 1 and wire 2 to be connected at the same time that Circuit 2 wire 1 and wire 2 are connected.

Please let me know if anything else seems wrong with what I'm trying to do here. Thanks for your help!


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I had some legacy equipment that was no longer needed, so before getting rid of it I opened it up to remove any hardware I might later have use for.

Inside I found a nice Wenzel 10 MHz OCXO:

The oscillator has no info online, but I called Wenzel and they were able to dig up a 1-page datasheet:

I tested it and it works wonderfully. I manually steered the frequency to our master clock reference, by tweaking a small voltage applied to pin 6 (Electrical Tuning). I didn't use pin 5 (V Reference) for anything.

My questions are:

1. What is the purpose of pin 5 (V Reference). Should it be connected to ground of the +/- 5 VDC tuning voltage?

In my testing I needed to supply a negative voltage, approx -1 VDC, to achieve a near zero rate between the OCXO and our master clock. But I didn't bother with pin 5 and it still worked.

<edit: #2 below was answered sufficiently by Peter in the comments>

2. There is a hole on one side of the oscillator. And far inside the hole is a tiny screw. The hole is threaded. So, I think the hole is dual purpose: to provide access to the screw (which must be for manual frequency tuning); and provide a mounting option. I just need confirmation that this is correct.

Thanks


texts: How to design a control bit to turn unsigned binary into two's complement?

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I am designing a 4-bit comparator using only basic logic gates (and, or, nand, xor, etc.) In its current form, the comparator takes two 4-bit unsigned binary numbers (A and B) and compares each bit value from most to least significant and determines an output: A > B, A < B, or A = B. Pretty simple.

However, I am trying to add a control bit to signify whether the input is unsigned binary or two's complement. The default state, 0, should signify that the input is in unsigned binary, while 1 signifies that the input numbers are in two's complement.

I'm having difficult understanding how or where in the circuit to implement the control bit. I understand that one method is to implement an adder, but I'm not sure if it would have to exist outside of the circuitry I have already designed, and the control bit would switch between two circuits that exist almost independently of each other. I'm sure there has to be a more elegant, integrated solution. If you could just point me in the right direction, I would greatly appreciate it!