texts:
I am trying to learn some low level implementation so I have been trying to interface to a SAM D09 micro-controller via the SWD interface.  I have the chip on a board and I am driving GPIO.  I have found that if I use the Extended CPU Reset in accordance with the uc manual, followed by 50 clocks of SWCLK with SWDIO high and 2 clocks of SWCLK with SWDIO low, followed by read IDCODE(b'10100101), then a turnaround(set SWDIO to high-impedance on my host) the uc responds for the next 28 clock cycles on SWDIO however it is not at all what I expect nor does it seem to conform to the SWD protocol.  It always seems to respond with 0xBF321F0.  This would appear to respond to have both the WAIT and FAULT bit on in the Acknowledge phase.  I cant seem to find any information on whether I need to do anything else to initialize the SWD

EDIT

This is my complete sequence

x denotes the line is high impedance, SWCLK indicates the count of SWCLK going high, SWDIO is the state of SWDIO stable

-------------------------
|SWCLK Cycle|SWDIO Value|
-------------------------
|           |Host Driven|
-------------------------
|          1|      1    |
|          2|      1    |
.......
|         48|      1    |
|         49|      1    |
|         50|      1    |
|         51|      0    |
|         52|      0    |
|         53|      1    |  <- Start of read IDCODE
|         54|      0    |
|         55|      1    |
|         56|      0    |
|         57|      0    |
|         58|      1    |
|         59|      0    |
|         60|      1    |
|         61|      x    |  <- One cycle turnaround(SWDIO is changed to input on host)
-------------------------
|           |Trgt Driven|
-------------------------
|         62|      1    | <- Start of Target response
|         63|      0    |
|         64|      1    |
|         65|      1    |
|         66|      1    |
|         67|      1    |
|         68|      1    |
|         69|      1    |
|         70|      0    |
|         71|      0    |
|         72|      1    |
|         73|      1    |
|         74|      0    |
|         75|      0    |
|         76|      1    |
|         77|      0    |
|         78|      0    |
|         79|      0    |
|         80|      0    |
|         81|      1    |
|         82|      1    |
|         83|      1    |
|         84|      1    |
|         85|      1    |
|         86|      0    |
|         87|      0    |
|         88|      0    |
|         89|      0    |
|         90|      1    |
|         91|      1    |
|         92|      1    |
|         93|      1    |
|         94|      x    | <- Line returns to high impedance
|         95|      x    |
|         96|      x    |
|         97|      x    |
.......```


texts: Why USB type A to micro USB type B aren't all the same?

texts: I have a bunch of USB type A to Micro USB type B cables. Some have two outer (pins 1 and 5) longer than the other three pins, for example. And for some cables, the pins are all the same length - and those can only charge my phone. The ones with two longer pins allow data transfer. What's going on here?


texts: Synchronising self-blinking LEDs (for fun)

texts:
I think most here are familiar with Big Clive's super computer, or one of the many variations.
This effect 'works' because the timing of the LEDs isn't super precise of course. But this got me wondering; would there be a way to have them fall in sync as Mythbusters once showed with metronomes like this?
I know you could just solder 'normal' LEDs to a PCB and use some microcontroller or something to achieve the effect, but where's the fun in that? I'm curious if there's a way to 'nudge' the 'clock' of such a self-blinking LED slightly. Preferably by an analogue feedback loop as with the metronomes; measuring wether a LED is on/off and then using some microcontroller to nudge the timing isn't as much fun.
Ideally the board would run in 'normal' mode (the LEDs flickering randomly) and by throwing a switch the feedback loop is enabled and the LEDs slowly start falling in sync. I am a beginner in electronics at best so I have no clue where to start but I can follow explanations and maybe even turn it into a prototype.
Edit: What a coincidence; Veritasium published a video on the subject an hour ago, about, what, 16 hours after I posted this.


texts: 555 timer to measure variable capacitance

texts:
I've no experience with complicated circuits. Currently thinking about a simple circuit for detecting a variable capacitance, e.g for liquid level or moisture sensing. I came across the 555 timer running in an astable configuration, which is used for such applications. The idea is clear, a change in capacity would change the frequency of the timer, which, in turn, can be monitored. The monitoring could happen with an Arduino. Here is some more background:

A good overview over capacitance sensing is given here: https://www.electronicdesign.com/technologies/analog/article/21796004/use-analog-techniques-to-measure-capacitance-in-capacitive-sensors
Overview over a 555 astable timer: https://dlb.sa.edu.au/rehsmoodle/file.php/466/kpsec.freeuk.com/555timer.htm#astable
A project utilizing this idea for moisture sensing: https://www.instructables.com/Capacitive-Sensor-Reworked-Wemos-With-555-Timer-Ba/

Now, I want to use this scheme for measuring a variable capacitance that is very, very small. Let's say it varies between 20fF to 100fF (this is on the order of \$10^{-14}\$ Farads!). Obviously, this would lead to high frequencies, and thus to a very fast pulse duration of the timers' output signal. The circuit will certainly suffer from parasitic capacitances of the circuit, i.e. noise (see explanation in the first link).
For \$R_1 = 100k\Omega, R_2=1M\Omega\$ and \$C_1=20\text{f}F\$ I calculated a frequency of \$3.4\cdot 10^{7}Hz\$. A change in capacity of \$\Delta C= 1\text{f}F \$ equals a change in frequency by \$\Delta f = 6.8\cdot 10^{8}Hz\$, i.e. the pulse duration changes by only \$\Delta T= 1.48 \cdot 10^{-9}s \$

Is it then somehow possible to resolve a pulse duration of nanoseconds? Is it possible by using a simple circuit (555 timer + Arduino)?
My expectation is that this is not a straight forward thing to do. But would it be possible to simply put a second capacitor (e.g. \$1\text{n}F\$) in parallel to the variable capacitor? This should shift the frequency to much lower values, below kHz. However, a change by 1fF still only changes the pulse duration on the order of nanoseconds.

Assume I'd have a second variable capacitor as reference (see Fig. 2d https://www.analog.com/en/analog-dialogue/articles/liquid-level-sensing-using-cdcs.html). Is it then easier to resolve such a tiny difference?
My naive idea is that the signal of a 555 timer will go through both capacitors simultaneously. Both will modulate the signal differently, i.e. they alter the frequency differently. By relating both signals I can imagine to resolve the small difference because the noise is eliminated (environmental noise occurring in on capacitor will also occur in the second one)?


texts: Can you stack one cpu on top of another, same cpu?

texts: While we have dual cores and quad cores (and now octo cores).  I often wonder if they sit side by side or are they completely stacked on top of eachother.  If either or, what kind of benefits or draw backs will this bring to the motherboard, other hardware and performance overall?


texts:
I built a super wilson current current mirror. The Iin is 4-20mA at 24Vdc. Iin to Iout accuracy was a really bad 5%. I put 100 ohm resisters on the source to ground, and that helped a little. How can i improve the accuracy between input and output? Below is my circuit

here is the simultor link for the circuit: sim link

EDIT: the 500 ohm is the load resistance of the circuit using the mirror. The 470 ohm is the max possible resistance of a PLC that reads the Iin current.

Screen shot:


texts: How can an RC plane receive when the polarization of the antennas is nog alligned?

texts:
We were learning about antennas and their radiation patterns and polarizations.
Our teacher told us that directly on top of a monopole, there is no field. And that if the polarisation is not along the antenna, nothing is received either.

I then posed the situation of an RC plane, and everyone agreed it should not work, according to what we just learned.

In an RC plane there is a monopole in the transmitter and another monopole in the receiver, usually running from nose to tail.

In theory it appears that if I point the antenna directly at the plane there should be no reception at all. Yet this works just fine.

With the same logic, if the plane flies straight away from you, with its antenna pointing at you, there should be no reception. Yet this works just fine.

In theory, if I hold the antenna vertically and the plane flies horizontally, the polarization is perpendicular and there should be no reception. Yet this works just fine as well.

Why?


texts: Approx. V, Amps and Transistor required for ~18cm ,12W Speaker Electromagnet

texts:
I have a large 8ohm speaker with a "12W500" rating,
and another sticker saying 3/38/5 (QC check?)
~18cm Magnet and 30cm Cone.

I want a silent vibrator for chladni plate (vibrating plate)

-Will it run on 12V, 3V 24V? What kind of amps may it draw 200mA 500mA? 1A? 4A? I don't even know ballpark figures!

I know how to make a signal generator from a 555, but i don't know how to adapt this to drive the speaker magnet.

-Do I put the output to a "power transistor" or a MOSFET?
I have only used them for signal amplification before not  power supply..

Any tips, Circuits or transistor recommendations will be VERY appreciated... I am fairly proficient at electronics, but this eludes me completely as it is taken for granted in most instances, or they use a 300€ amplifier....

I already built a signal generator.


texts: high speed differential nets crossing on PCB

texts:
I have 2 ICs working at 9 gbps. Output of 1 IC is differential CML pair and it goes as input to other IC.
  On PCB layout, if both ICs are placed on top (component) layer, one ICs positive pin is in front of negative pin of other IC hence positive and negative pins nets are making cross.
   How can these nets carrying 9 gbps differential CML signal making a cross can be routed? Is making vias a good option to go to another layer?


texts:
I don't really know the whole technology thing so this is why I'm asking.
I bought "20PCS 5mm IR infrared LED 940nm Lamp High Power" for head tracking and I don't know what resistors will be good for it.
can someone can explain to me how it works or what resistors for example? Thx


texts: Use ADC as Analog Comparator (AttinyAVR)?

texts:
I have recently been trying to transition from Atmel's Atmega 328p avr to the newer (and much smaller) attiny416. The trouble is, the 416 only allows you to choose between two positive inputs and two negative inputs for the analog comparator, and I need only one positive but three negatives to multiplex between.

Because the input pins to the chip are fixed in hardware I couldn't think of much except to add an external multiplexer to the device which is not an option.

The ADC the chip has, however, can take input from almost every pin on the 20 pin chip. I have never worked with the ADCs on these chips, but they may hold the answer. Can an adc on an attiny be programmed to act as an analog comparator without the overhead of a digital conversion? I know at the core of ADCs are comparators but haven't found any grinchy tricks to use them in my solution (one positive input and three negatives to multiplex between).


texts: JTAG trace length affecting programming ability

texts:
I've recently had a design made that requires a programming port to be located quite far from the device I'm trying to program. This has meant that my cJTAG traces are around 13cm long. I think as a result of this the programming is a bit temperamental regardless of the programming clock frequency.

I had a similar problem in another design, and resolved it by using 22 ohm series resistors on the TMS and TCK lines near the microcontroller, but that doesn't seem to have worked so reliably with this design. That could be because the distance is greater, or because the lines switch layer a few times on their way from the programming port. There is also a UART Tx/Rx that runs along to the port beside the JTAG traces.

The photo below shows the route of the JTAG and UART traces (top to bottom: Tx, Rx, TCK, TMS)

At the bottom left you can see the series resistors, and an additional 10k pullup resistor on the TCK line which I was the datasheet advised to allow hot-plugging a programming connector.

Right now I'm hoping to find a way to make programming of the devices more reliable, so I'd really appreciate any insight or advice on running jtag over this distance.


texts: Linear regulator (L7805CV) outputting 5.8V

texts:
I am having a pretty strange problem that I am unable to solve. Basically, I am using an L7805CV and it is outputting at 5.8V instead of the specified voltage range in the data sheet. At first I was using it in a digital isolation scheme, but when I was unable to solve the problem I took it out and breadboarded it by itself. I am using the caps specified in the data sheet, .33uF and .1uF

Things I have thought/tried:

Maybe something is iffy with the voltage supply. I've tried 19V and
12V supplies, each providing the same result.
Maybe the regulator is just faulty. I tried three different L7805CVs, all of them having the same result, albeit slightly different output voltages.
Maybe the circuit isn't under enough load. I tried 1k and 100 ohm resistors
and it didn't change the end result. With no load it still gives the
same result.
Maybe the caps are non-ceramic. They are ceramic.
Maybe the caps are bad. I have a voltmeter with support
for capacitor testing so I checked each of them and they were each within
range.

Things you might be thinking:

Maybe it's the breadboard. Yeah, well, it isn't. At the very least I believe it isn't. I had the
original one in a PCB and it was behaving the exact same way.
Maybe you're an idiot. Yeah, well, yeah.

The power supplies I'm using are a 12VDC switching supply, and a 19VDC Acer computer charger I cut the end off of.

For a relevant circuit diagram check the application circuit for the L7805 which I'm sure most people here are familiar with.

After failing with the L7805 I threw in another regulator I had on hand (I can't remember the number but it's 5V) and it worked fine. A pristine 5.17V, well within range of the data sheet.

Using a 1N4148 diode I can drop the voltage within spec on the L7805, but that is, of course, cheating.


texts:
Please take a moment to checkout the simple circuit below:

simulate this circuit – Schematic created using CircuitLab

As you can see, this is a simple circuit consisting of three LEDs in series driven by one 6 volt DC power supply. The LEDs are white LEDs with a forward voltage drop or around 2.6 volts according to my multimeter.

Based on my measurements (using the 6 Volts power supply) there is no current flowing through the circuit at this point and the voltage drop for each of the LEDs is as follows:

LED1=1.642V
LED2=1.702V
LED3=1.607V

simulate this circuit

Ok, now that we have laid out the facts, I was hoping someone could help me out with the following questions.

First question: Why is there a voltage drop between the LEDs? I am asking this because it was my understanding that an LED (diode) that is not conducting current (forward voltage has not been reached) is like having an open connection. Basically, it was my understanding that the circuit shown above is equivalent to the following circuit:

simulate this circuit

And if that is the case, the voltage drop between all the open connection should be zero right? So why is there a voltage drop between the LEDs? What am I missing?

Second question: Why do the voltages between all the LEDs not add up to 6 volts? If I add the LED voltages the result comes up to 4.951 total dropped voltage. This is more than one whole volt missing here. Where did that volt go?

Thank you.


texts: Why is the phase angle in the summation of the phasors the negative arctan?

texts:
I was reading a textbook and came across the following
$$
\\I_1 = Ae^{j0} = A
\\I_2 = Be^{-j\frac{\pi}{2}}
\\\bf{I} = I_1 + I_2
\\If\ A=10\ and\ B=20
\\|I| = \sqrt{A^2 + B^2}
\\\angle I = -tan^{-1}(B/A)
\\I = 27.98e^{j30.4^{\circ}}
$$
From my knowledge, of complex numbers, shouldn't \$\angle\bf{I} \$ be  \$\angle \bf{I} = tan^{-1}(B/A)\$ since both B and A are in the first quadrant?


texts: Mosfet drive for inverting buck boost converter

texts:
I'm working on an inverting buck boost circuit for university and have come up with the following schematic. I'm ordering quite expensive parts so I wanted to get some opinions and advice as to whether it will succeed in driving the mosfet as is!
Another idea I had was to create a rail 15 volts higher than the +15v in and to get a low side driver with sufficient voltage capability, to simplify the design. This circuit is one phase in a three phase converter, so the additional rail would not increase the component count much. I realise I may have to replace the output diode for a low side mosfet to achieve this, but that hopefully should be easier to drive. Would this be a good way to go perhaps?
I want to avoid using a p-ch mosfet also as I'm aiming for 15 amps per phase.
Thanks for any suggestions!


texts: Is it possible to build a binary divider with this design?

texts: So I am working on this ALU, and I have made this 8-bit multiplier based on this design: . Is it possible to adapt this design into a binary divider by using Subtractors instead of Adders, and maybe add some logic gates or do I need to start from scratch on the division unit?


texts: Overcoming vbe in a low voltage application

texts:
I am trying to drive a motor with a sinusoid from a DAC.

DAC can't drive the motor directly. Motor is a 2.3 - 3.6V motor with a peak current of 120mA. DAC max voltage is 3.6 with a weak drive strength. My supply voltage is 3.7V

I would like to maximize my the voltage that goes to the motor, but I can't see a way to overcome the BE or EB junction of BJTs (example shown below) That 0.6V drop is ~ 17% of my voltage range.

What circuit topologies are available that would maximize the voltage range going to the motor (and drive current) ?

simulate this circuit – Schematic created using CircuitLab

edit
Default values from schematic tool removed show general topology vs the actual circuit.


texts: LTspice: Noise simulation AND AC analysis in one plot

texts:
Is it possible to run a noise simulation and an AC simulation independently from one another and
display the results in the same plot?

Or better, is there a way to determine the SNR  in one single plot?


texts: Will Solar Cells charge under a clear plastic sheet?

texts:
I am planning to make a Solar Powered Battery Power Bank. I made one on a small scale and will scale it up. Anyway, there is a risk of rain short circuiting my DIY power bank.

I thought of sealing my NiMH batteries and other circuits in some water proof container, but for the solar cells and the soldered wires behind it itself, I was thinking of just covering it with some clear plastic. Would this be a good enough water proof solution?

I am planning to connect some mini-solar panels in parallel. Would there be any other solutions.


texts: Finding Thevenin Equivalent voltage and resistance

texts:
I'm trying to determine the Thevenin equivalent voltage and resistance across this simple circuit below. I understand the theory but can get difficult when trying to apply it.

Using Kirchoff Loop and junction laws I came up with the following equation:

1) \$I1=I2+I3\$

2) \$Vin-I1R1-I2R2=0\$

3) \$Vin-I1R1-I3R3-Vth=0\$

4) \$I2R2=I3R3\$

Which I found the Thevenin voltage to be \$Vth=VinR3/(R3+R1)\$ and the resistance to be \$Rth = R1+(R2R3/R2+R3)\$

The resistance seems plausible but the voltage doesn't as I would expect R2 to be in the equation somewhere. Any help is appreciated as I am not sure what I have done wrong. Feel free to edit my question for clarity.


texts: What would you call this power supply topology?

texts:
When talking about lab power supplies I am aware of two typologies, linear and switcher. The linear supply rectifies the AC into DC and then uses a series pass element to burn off the excess power to give you a constant voltage or constant current depending on the control mode.

The switcher rectifies the AC into DC and then uses a series pass element to switch the output on and off. The switching is such that when averaged it give either a constant voltage or constant current depending on the control mode.

The last topology uses a triac to chop up the AC before the transformer so that after the output of the transformer and the rectification the final output is either constant voltage or constant current depending on the control mode.

Would this topology be called a switcher or does it have a name i'm not familiar with?

simulate this circuit – Schematic created using CircuitLab

EDIT: Per @FakeMoustache I added and inductor to the switching circuit.


texts:
Background

I already have a (2nd hand) Philips PM 3253 oscilloscope. Although it has many features and is fast (50 MHz) the display is so bad, it's barely usable.

Therefore I bought another (2nd hand) oscilloscope, a Philips PM 3110 (2 channel, 10 MHz) with far less features). The display is much better.

Question

However, when I for example show a square wave on the oscilloscope, it is scrolling very fast, I have about 2 waves per square (cm). I tried moving the X position knob, but that only makes the left or right side being clipped/invisible.

And changing the X Magn. knob changes the scrolling, but in no way I can keep it more or less steady. I tried moving along the entire X Magn range and tried different Time Div. knob values.

What am I doing wrong? I see sometimes pictures of e.g. sinus or square waves which are not moving … or is that because a (very fast) picture is made?


texts: Is there any particular criterion that makes a CPU be called "16 bits" CPU for example

texts: What makes a CPU be called for example: "this CPU is n bits"?


texts: Protecting resistor value for zener diode in parallel with load

texts:
I want to select x as resistance for the protecting resistor (upper).

The zener diode can hold up to 4A

If I was guaranteed to have current through zener lower than 4A, I could consider its voltage to be 5.1V and the voltage through load to be 5.1 V.

But I'm not. So, I can't consider the voltage to be 5.1 V and I can't calculate a voltage drop for protecting resistor in terms of x, because I don't know the current in curcuit because I don't know the resistance of zener.


texts: Connecting Analog Signals Between Boards

texts:
When you have a sensor with an analog output on one board, and an analog-to-digital converter (ADC) on another board, what's the best practice in connecting them together? For example, if you have a single-ended signal, should you twist that signal with a GND wire in the board-to-board cable? If it's a differential signal, should you twist the + and - signals together in the board-to-board cable?  Or should the + and - signals each be twisted with a GND wire in the board-to-board cable? What are the best practices / rules-of-thumb / guidelines in this area for getting best results? If the answer is "it depends" then what does it depend on, and what is the decision making process for determining the right approach in a given context?

Obviously (?) first prize is integrating sensors and ADCs onto a single PCB, having a nice solid GND reference plane, and having routing discipline to separate your analog and digital domains, if that's possible. But I'm focusing on cases where it's not possible to do that.


texts: Good approaches to implement more than one time-critical function using a microcontroller?

texts:
What is the philosophy or approach taken to implementing highly time critical functions in microcontrollers, if there are any?

I am working on a project involving outputting a precise square-wave waveform of varying frequency. I have done this using a timer and an interrupt function. However, even to implement this correctly, I had to calibrate the offset for the number of clock cycles taken during the interrupt service routine. I'd imagine this precision would be disturbed by having another such waveform running alongside (say the frequency needed to be changed at the exact same time). Having a microcontroller each, for every such time critical function seems wasteful.

Take another example, of implementing a clock (as in hh:mm:ss) function. I can't imagine that every high level microncontroller/computer has a dedicated real time clock chip solely to keep track of the time. However, I find it hard to imagine it being accurately measured using the core processor, which is busy servicing a plethora of functions that come at asynchronous intervals in the meantime. I'd imagine the time counting would have offset errors, that change depending on the functions that are running.

Is there a design process or approach to containing or giving a tolerance to the precision achievable? Or does anyone have any pointers or suggestions on where I could find more information regarding this?


texts: Brushed DC motor as generator, characterising the motor

texts:
I've read through the several topics here concerning using a DC motor as a generator but I've failed to answer my question so, apologies, I'm going to ask again.

I need to use a small DC motor as a wind-powered generator in association with an energy recovery chip (TI BQ25505).  This chip will only successfully recover energy if the input voltage to the chip is ~400 mV or greater.  I have tried using several DC motors as generators but the only one I have found which produces a terminal voltage greater than 400 mV when the  breeze is just sufficient to overcome the back-EMF of the generator took 4 weeks to arrive from China and was provided without a specification.

Hence I would like to characterise the generator in order to purchase an equivalent locally.  Here is what I know so far:

Winding resistance 75 Ohms.
Operating speed at "minimum breeze" 12 to 15 Hz.
Voltage produced across 1 kOhm resistor at "minimum breeze" 650 mV DC.

Is there a way that I can convert this knowledge into (or perform more measurements in order to arrive at) the parameters which DC motors seem to be specified in, i.e. terminal voltage, output power, max RPM and max torque?


texts: Why does an additional primary current exist in a loaded transformer?

texts:
I think this has something to do with Faraday's Law but like, I don't get why having a secondary current produces a antiphase secondary current at the same instant. Not all currents produce a direct opposite. Yes I know there is an involvement of inductors, but why doesn't the primary current get some antiphase I1'? Just confused. Thanks.
Taken from Electrical Technology by Theraja, Page 1152 and 1153.


texts: Resistor programming of a boost converter, check my understanding?

texts:
I'm looking at the datasheet for a TPS6103 boost converter, and trying to figure out how to configure it for 5V 1A output. The datasheet is not making this easy to understand.

Datasheet: http://www.mouser.com/ds/2/405/tps61030-450662.pdf

It says this about setting the output voltage.

  The output voltage of the TPS61030 dc/dc converter section can be adjusted with an external resistor divider.
  The typical value of the voltage on the FB pin is 500 mV. The maximum allowed value for the output voltage is
  5.5 V. The current through the resistive divider should be about 100 times greater than the current into the FB
  pin. The typical current into the FB pin is 0.01 µA, and the voltage across R6 is typically 500 mV. Based on those
  two values, the recommended value for R4 should be lower than 500 kΩ, in order to set the divider current at 1
  µA or higher. Because of internal compensation circuitry the value for this resistor should be in the range of 200
  kΩ. From that, the value of resistor R3, depending on the needed output voltage (VO), can be calculated using
  equation 1:

Given all this seems pretty hard for me to parse, I've come the following conclusions that I'm not sure are right. Can someone please tell me I've interpreted this correctly?

It's recommending that R4 be 180KΩ.
R3 would therefore be 1.62MΩ via: 180KΩ * (5V/0.5V - 1) = 180KΩ * 9 = 1620KΩ.
These two resistors would configure the boost converter for 5V output at up to 1A.


texts: Hedge relay current capacity with additional wiring

texts:
I ordered several OMRON “ice cube” 110 VAC relays, contacts rated for 10A (LY2NJ). When I inspected them under a microscope I noticed the contact wires are AWG 24. The rest of my setup uses AWG 18. My gut instinct was to open the relays and solder in some short runs of the AWG 18 patch wire. Was this overkill or prudent? I do require switching 10 A.

The left relay is the original. The right relay with the red wire is the modified relay.


texts: Stacking high voltage and low voltage PCBs

texts:
I am working on a project which involves micro-controller and switches (triacs and EM relays). Due to size constraint, I need to stack one over the other. Here is unfinished relay and triac board which will go on top of micro-controller board of the same size:

PCB description: 220V to 5V offline switcher on the left. It has a switching frequency of 65 kHz. Two transistor driven electro-mechanical relays in between and 6 optically isolated triacs on the right. There are a few connectors for optional sensors.

I have given 4 holes in corners so that I can use spacers and nut bolts to put the two PCBs together. Electrical connection between the two will be made using either a cable or header pins (yet to be decided).

As such what should be the minimum distance between the two PCBs so that high voltage or whatever noise is there in ac lines don't disturb the delicate electronics below?

Is there something which I should use in between to provide added safety to my micro-controller board?

I was thinking of some plastic sheet the same size of PCB or two plastic sheets with a thin metal foil sandwiched between them but I am not sure whether they will have any impact or not.

Any suggestions regarding this will be much appreciated.

Thanks


texts: Protecting microcontroller from drastic changes in load on power source

texts: Is it necessary to protect the VIN pin of a microcontroller (currently arduino micro) when another device on the same power source is switching between 90W and 0W? Specifically, 300 LEDs are strobing, drawing ~18A from li-ion 18650s when on. Might the batteries continue to "push" that much current for a brief period in a way that could damage the microcontroller?


texts: sgmii auto negotiation - how long should this take?

texts:
I am working with LWIP - and an 1G marvell phy, m88e1111 - connected to a Microsemi SmartFusion 2 FPGA design using 10b8b (aka: TBI) interface.

I'm doing something wrong with the auto negotiation and it's probably mostly me, I can't find things that answer my questions.

background:

The internal SGMII phy (in the FPGA) is at MII address 30, the external PHY is at address 7.

The external phy (Marvel m88e1111) is configured via pull up/dn to auto connect on power up and auto-negotiate - This works great with the switch.

It's the INTERNAL phy to the Marvell negotiation that seems to fail (50% of the time) that is a problem and prompts my questions.

When I hunt for docs on the web (google) - I find detail about the process but what I find assumes a lot of pre-knowledge, and I don't find a "for dummies" doc anywhere.

Questions:

1) Is there an order that I should follow when bringing up an interface? Am I required to wait for the External PHY to complete, before I can start the SGMII negotiation?

2) How long should I wait for the auto-negotiation to complete before I declare a timeout?  Once enabled, do I need to restart it again and again?

3) my current system works as follows:

Step 1 After power up - on a timer, every 2 seconds I poll the external phy (I do not have a PHY interrupt)

QUESTION: Is 2 seconds right? Should it be longer?

Step 2 - Wait for external phy to "complete" (link up bit) Typically takes 2 to 5 seconds after reset, and is rock solid.

Step 3 - After ext-phy complete, I test the SIGMII status the link is down, so I start the internal to external negotiation.

I repeat this on the every 2 second timer until I see link up.

Problem: sometimes it takes 20 seconds (10 tries, often more ) to get the SGMII connection up, this seems just wrong, really wrong.

Sometimes (5% case) it takes less then 1 second, I'm expecting 1 second but 95% of the time it is more like 10 to 20 seconds

Question: How long should auto negotiation take? Am I doing something in the wrong order? Or cutting the timeout too short?

Note: I have no means to test (signal integrity) between the FPGA and the external PHY... I don't have a $300K scope at my disposal.

Question: Are there test/debug registers I can use? The Marvell one has something that outputs a test pattern but I don't see any means to tell the other phy, or things like that to "tell me how good the test pattern is"


texts: What is the problem with this circuit? ( MOSFET + OPAMP) Battery protection circuit (draw current from battery)

texts:
I would like the following:

10 X 1.2V battery
left mosfet is the ON-OFF mosfet. I can ON and OFF the whole circuit with the 'SW' switch
The two LM358 opamps sense the 1st battery voltage
IF the voltage drops below 1.11V the right opamp will go high, and the RED LED go light below 1.11V. This is low battery warning led.
IF the voltage drops below 1.0V the left opamp turns off the right mosfet, so no more current consuption from the load (in the simulation this is 10R resistor)
IF battery voltage drops below 1V only the LT1236 and the two opamp still alive, which only draws 1-2mA from the battery.

THE PROBLEM:
 - when the SWITCH is OFF, from V+ (12V) to 1st BAT+ ~30-40mA current consuption.
Why? What is the problem? In the simulation only ~100uA current consuption when the SWITCH is off.

EDIT

The mosfets are close correctly, its not a problem.
The problem when the switch is off ~30-40mA current flows from V+ (the top of the battery, 12v) to 1st BAT+. In this time to current flow from BAT (-) to left mosfet source.


texts:
Assume that I had a circuit as such above.
I was wondering, if I increased the temperature of the surroundings, what would a graph of the temperature/PD graph look like?

I know that Resistance decreases with temperature, as more electrons 'escape' from their atoms, so more charge carriers are available, but would the graph show a general decrease in PD as temperature increases?

Thanks.


texts: Can RS485 be considered a multi-master bus?

texts:
There are some electrical specifications specifically designed for multi-master protocols such as CAN, I2C, 1-Wire, etc. which are classified under CSMA/CD networks.
However, RS485 has a push pull output (with a current limit guard) so when two masters are started sending data at the same time, both frames will  be corrupted and the re-transmission should be handled by the protocol stack. RS485 can be classified under CSMA/CA networks.
Question
Is only protocols implemented on top of CSMA/CD networks considered as "multi master protocols" or can any protocol on CSMA/CA network that somehow implements handshake (ACK) and re-transmission features be considered as a "multi master protocol"?
Specifically, is implementing a multi-master protocol on top of RS-485 possible, or is it considered only a workaround because of the inability of collision detection nature of the bus?


texts:
I already spend a plenty of time for understanding the design which I got from TI WEBBENCH, and gets clear bit understanding of it,but still I have some doubts, of those I want explanation.
Design is :

Why in all the designs which I see the VCC pin of the PWM controller(here in this design is UC1845AJG) is connected to aux winding of transformer as well as with the bridge rectifier output i.e. main line ? The following explanation for vcc pin I got in datasheet but I am confused with it.

What is the use of Qsc near the Vref pin ?

Provides MOSFET rating in design is vds=800v, I want to understand how it is decided ?

Why two schottky diode are used in parellel on output side?

Please point me out to the related article if these question are tool silly too answer.I am ready for more digging.
I will be very thankful to you.
EDIT1: IC i am using is UC1845AJG


texts:
I am using the STM32CubeIDE to setup the UART peripheral. I can check 'USART1 global interrupt' checkbox in the NVIC settings tab. But when I save and generate the source files, I can't find any callback being generated.

Do I need to type it in myself? How would I know the prototype of the ISR callback?


texts:
I am trying to interface a microcontroller (MSP430) with another chip through I2C. Both datasheets (MSP430 and the other chip) advice me to pull the I2C signals up to VCC. Do I need to pull SDA & SCL signals up twice, for the microcontroller and for the chip, or not.
Also each one of the chips specifies the values for pull up resistors, one says 10K and the other one says 5.1K. If the case is to pull up one time, which value I'll use?


texts: Is temperature the only battery charging speed limitation?

texts:
Charging too quickly can cause the battery to blow up due to heat.

But what if I cool the battery down? Can I charge as fast as I want, provided that I cool it down sufficiently?

Can I enforce higher charging speeds by increasing the input voltage, if the battety is colder?


texts:
The bridge is described in this way:

Whit the equilibrium condition, when the current is zero between A and B, I'll have:

$$Z_x*R_2=Z_c*R_1$$

derived by Wheatstone Bridge's relation.

Evaluating the parallel impedances ( \$R_x\; ||\; 1/(j\omega C_x)\$ ), I obtain:

$$ R_x/(1+j\omega R_x*C_x) * R_2 = R_c/(1+j\omega R_c*C_c) * R_1$$

And so:

$$ R_x*R_2*(1+j\omega R_c*C_c)= R_c*R_1*(1+j\omega R_x*C_x)$$

Finally, It's obtained these results:

$$R_x=(R_c*R_1)/R_2$$
$$C_x=(R_2*C_2)/R_1$$

Solutions of the De Sauty Bridge.
But, how are obtained this results starting from the previous equation?

If we had not parallel scheme, as impedance between \$C_x\$ and \$R_x\$, the result should be obvious for \$C_x\$ starting by the equilibrium condition; but, as it is, I cannot figure out which steps are made.


texts:
I'm trying to get my head around transistors and I had some difficulties to understand the various way we can connect a transistor.

For example, here are a few possible arrangment:

simulate this circuit – Schematic created using CircuitLab

In theory, both of those circuits should be equivalent except on the left, the led is on when the base is low and on the right the led is on when the base is high.

The difference I see is that on the left, when the transistor is in cutoff state R1 and D1 aren't affected by a voltage drop through the transistor unlike the schema on the right.

So technically something like this is:

simulate this circuit

Here the arrangement at the top is capable to supply 15v to the gate of the mosfet but the arrangment to the bottom can't barely supply more than 2v according to the simulation.

The question might be a bit vague, but what I'm really interested to know is if there is a list known pattern for transistor arrangement and their pros/cons?

For example, there is the darlington transistor which is pretty much like my last schematic but it seems it doesn't work if you want to amplify the voltage output for a mosfet using a transistor. In my examples, I used a clock but had in mind an output pin coming from a mcu.

For example, I saw on stackexchange someone recommending this kind of pattern:

simulate this circuit

To drive a Mosfet, yet in this particular example, doesn't seem to work in my case. Actually it looks like half of an H-bridge.

Also, in my particular examples, all of the collector have a 12v applied and driven with a 5v logic on/off.


texts:
I was reading an example from a text book. And for this circuit above the author claims when R3 is less than 100 ohm Q3 will not switch. I couldn't figure out the "reason" why. But I verified with LTSpice the author is right. He just doesn't explain the reason.

If lets say R3 is close to zero when Q2 on, why wouldn't Q3 also switch on?


texts: How could using an ungrounded appliance with a grounded extension cord be a fire hazard?

texts:
I came across a tweet recently:

Don’t even THINK about using a 2-prong plug in a 3-hole slot!  Use
only the required number of slots in an outlet or power strip.

Below was a picture of a burned-out grounded extension cord.
I'm hesitant to argue with anyone in the business of keeping our food, shelter, clothing and loved ones from combining with oxygen, but this seemed quite strange; I can't think of any possible way this could be a fire hazard.
The NEMA 5-15 wall receptacles in Canada are grounded by default, for reference.


texts: How to determine max amps over a common ground between AC-to-DC Adapters?

texts:
How can I determine the expected and max current running over a common ground wire between DC of AC/DC converters? Should I fuse the wire?
I have two 5V/40A AC-to-DC adapters (AC is 3-pin each) for x-mas lights (WS2811) and 1 5V/1A adapter (AC is 2-pin) for raspberry pi. My aim is to have the raspberry pi acts as a controller and have the layout look something like this:

with the following differences:

The Raspberry Pi will take the place of the controller and be powered by a USB 5V/1A via the microUSB port on the device
They are 5V supplies

I was planning on going directly from a DC ground on a 5V/40V to a ground pin on the Raspberry Pi, powering the Pi via the normal microUSB interface, and connecting the two 5V/40A grounds like the above diagram.

The main thing I am currently concerned about it how many amps can flow over the common ground and if I am going to burn out the Pi or melt wire that is too small.


texts: Problem with the reset circuit for a MCU

texts:
I need help by understanding the problem with an existing MCU circuit concerning the Reset PIN (STM32 Cortex M0+: STM32L071K8):
It seems something in the circuit is wrong, since it works only when I am connecting an external Debugger which forces the RST signal to about 3,3V.

If I disconnect the debugger, the MCU is not running properly (I have some LEDs on the PCB to prove this). I measured the value on the RST-Pin between resistors R8 and R9 and without the debugger the value is just about 1.55V. Thus, it seems for me, that the pull up resistor circuitry is obviously not working as intended.But I cannot idetify the concrete bug. The design came not from myself and as a SW developer, I just have limited electronics skills.

Can someone please explain me, what's wrong here with this reset circuit and why does this voltage dropped down to about 1.55V?


texts: Using strategic sampling noise to increase sampling resolution

texts:
Dithering is used to add virtual resolution to an oversampling ADC, and for instance this discussion involves some of the math involved, and the criteria.
Take for instance an Arduino with 10 bit sampling. The unit has is the ability to set a digital pin to a random value, or a PWM output to a random value. It also has the ability to define a different Vref for ADC conversions. Would a simple circuit that drove the Vref with a filtered random digital signal between 5V and 1 LSB below 5V be a good solution for low-cost dithering?
The thought is that if the Vref were being altered, then the oversampling benefit would be available on all channels, not just one at a time. I can see there will be an over-read of the raw voltage of 0.5 LSB to be corrected for but this is a simple operation.

(I would add a schematic but the plugin seems to not work at present)


texts: Current return paths: which of the two is the better design?

texts:
Should the ground return path of this microcontroller be forced through the bypass capacitor gnd pin like in the first picture, or will it be better off left floating in the (green) GND plane like in the second picture?

EDIT:

That big ugly far away bypass capacitor:
I am quite bad at hand soldering SMDs and this is what is going to happen for this board... and already ordered my parts... and, it is only going to run at 1
MHz and 3.3V... Still seems like a poor choice ? I just need it to make the board work reasonably well for hobby level.

regarding SMD closer placement vs THT cap placement - it is not clear to me what the THT spacing should be. The IPC2211a standard is talking about

some 0.13 mm clearance in table 6.1 on page 43: first row, column A6
0.75 mm clearance in section "8.1.8 Clearances" on page 58

I went on the safe side with 0.75, but maybe I misunderstood and it is 0.13
Care to comment on that ? Maybe make it an answer for this qeustion


texts: Accesing the PCM Flash Memory on a Nexys 3 Board

texts:
How do I access the PCM flash ram on a Nexys3 FPGA board?

I've got a simple T80 (Z80) CPU core project working with a Core Generator ROM module, but not having any luck with the flash ram. The Nexys 3 Reference Manual suggests using the Reference Designs from the Digilent website, but there isn't actually one for the Nexys 3 board - I've asked Digilent and they say there's only one for the Nexys 2, which I've been through. I've also read most of the data sheet for the flash chip - Micron NP8P128A13T1760E but can't get it working.

So I've put together the most minimal project I can think of: a simple state machine that attempts to read the first word from the flash ram and display the lower byte on the 8 leds on the board. See the VHDL below. I'm loading up the flash ram using the Adept memory utility, but all I ever seem to get its 0xFF displayed.

(Update, I've just found that if I press the button I've got wired to reset it displays 0x06, but that's not what's been put into flash)

My understanding of how it should work is:

Set FlashRP = 1, FlashCS = 1, MemOE = 1, MemWR = 1,
Set address to MemAdr (I've hard coded to 0)
Enable flash - FlashCS = 0
Enable out - FlashOE = 0
Read from MemDB

My test project runs these steps on a 3.375Mhz clock (since that's what the T80 will run at).

One thing I'm not sure about is the Nexys3 Reference Manual refers to some other signals that are common to the RAM and the Flash - namely CLK, ADV and WAIT - but I've not been able to correlate these to the data sheet for the flash chip.

What am I missing?

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;

entity Top is
    Port ( clock : in  STD_LOGIC;
           reset : in  STD_LOGIC;
              led : out STD_LOGIC_VECTOR (7 downto 0);
              MemOE : out STD_LOGIC;
              MemWR : out STD_LOGIC;
              FlashCS : out STD_LOGIC;
              FlashRP : out STD_LOGIC;
              MemAdr : out STD_LOGIC_VECTOR(26 downto 1);
              MemDB : inout STD_LOGIC_VECTOR(15 downto 0)
              );
end Top;

architecture Behavioral of Top is
    signal slow_clock : STD_LOGIC;
    signal led_reg : STD_LOGIC_VECTOR(7 downto 0);
    signal state : unsigned(3 downto 0) := "0000";
    signal state_next : unsigned(3 downto 0);
begin

    led <= led_reg;

    -- Clock Generation
    clock_core : entity work.ClockCore
        PORT MAP
        (
            clock => clock,
            clock_3375 => slow_clock,       -- 3.375 Mhz clock
            RESET  => reset
        );

    process (slow_clock, reset)
    begin
        if (reset='1') then
            state <= "0000";
            led_reg <= "00000000";
        elsif (slow_clock'event and slow_clock='1') then
            state <= state_next;
            if (state = "1110") then
                led_reg <= MemDB(7 downto 0);
            end if;
        end if;
    end process;

    MemAdr <= "00000000000000000000000000";
    MemDB <= "ZZZZZZZZZZZZZZZZ";
    MemWR <= '1';
    FlashRP <= NOT reset;

    process (state)
    begin
        case state is
            when "0000" =>
                -- initialize
                FlashCS <= '1';
                MemOE <= '1';
            when "0001" =>
                -- enable flash
                FlashCS <= '0';
                MemOE <= '1';
            when "0010" =>
                -- enable flash output
                FlashCS <= '0';
                MemOE <= '0';
            when others =>
                -- hold steady
                FlashCS <= '0';
                MemOE <= '0';
        end case;
    end process;

    state_next <= "1111" when (state="1111") else state + 1;

end Behavioral;

Here's the reference material I've been using:

Nexys3 Reference Manual
Data Sheet for the Micron PCM Flash Memory


texts:
I have a 12v 15amp power supply, and I have 5 appliances.
I want to build this circuit in parallel, so voltage here is constant.(12v)So i'm not going to mention voltages.
The first appliance uses 10 amps.The 2nd uses 2 amps. And the 3rd, 4th, and 5th each use 1 amp. How would I distribute the current so that each appliance gets what is required?
I thought of a way, It would probably work theoretically but maybe not practically. In other words I'm not sure it'll work.
I thought of taking 15 wires, and soldering them to the positive terminal, do the same for the negative terminal. So right now each wire is carrying 1 amp.
Then, I would take 10 of these wires (10 positive and 10 negative of course) and connect them to my first appliance which uses 10 amps. Then connect 2 wires to my 2nd appliance, and 1 wire each to my 3rd, 4th, 5th appliances.
Will this work?
Thanks in advance, Mitch


texts:
I am making my own basic bench power supply mainly for testing logic gate circuits, relays, flip flops etc, that I can move around to different locations.

The circuit of the entire schematic will be on a PCB inside a plastic enclosure. It is a 230Vac to 5Vdc regulated power supply. Below is my circuit design:

For the 5Vdc regulator I am using the L78S05CV voltage regulator IC.

Do I need to provide any other additional short circuit/overcurrent protection? According to the datasheet short circuit protection is built in to the IC (see below for sheet)
Any other issues/improvements with this circuit please feel free to say?


texts:
I'm trying to amplify an EMG signal from two electrodes with a INA128. However, I'm not sure how to connect the power supplies. I'm taking the 12V from the wall and using a voltage divider to get +6V and -6V. +6V goes to pin 7, -6V goes to pin 4. What should I connect to pin 5 (Ref)? The "ground" electrode?

Also, would it be wrong to supply 12V to pin 7 and 0V to pin 4?

Thanks!


texts: Voltage gain of common emitter amplifier

texts:
I'm posting this question just to be sure I'm understanding this correctly.

I want to estimate the voltage gain of the following common emitter amplifier either as \$A_v=-4.7\$ or \$A_v=-145\$.

It's pretty obvious that \$A_v=-\frac{R_C}{r_e}<<-4.7\$ due to the shunt capacitor. However, I am asked to estimate the voltage gain at frequencies 1kHz-10kHz. Does anything change at these frequencies? I think I have HPF filters due to the coupling capacitors but I'm not too sure which resistance goes with which capacitor. I'd appreciate any help.


texts: Can I treat two identical capacitors with capacitance \$C\$ in parallel as one capacitor with capacitance \$2C\$?

texts:
Consider a circuit as shown with a battery,
$$ V_b $$

and two identical capacitors

$$ C_1, C_2 $$

(with C_2 being the one that's off to the side). Both have the same capacitance C. The resistor has resistance R.

Before adding the new capacitor C_2, the current in the ammeter is, say, I. The reed switch flips back and forth such that the capacitor charges fully and discharges fully, (only one capacitor at this moment). Thus when the switch is to the right, the capacitor has voltage V and current is V/R = I.

Now when I add the second capacitor,
$$ C_2 $$
can I treat them as a single capacitor with capacitance 2C? If I do, then the current should decrease because:

$$ V = Q/2C $$
$$ I = V/R $$

Even if I consider them to be separate capacitors, Each capacitor will store charge

$$ Q $$

and thus total charge will be,
$$2Q$$

Thus, voltage should be

$$ 2Q/2C = V $$

and current should stay the same. Why is this incorrect?

Note that I understand that current should double because you have twice the charge being stored and at each discharge cycle, the rate of charge flow should double and hence current should double as well.


texts: In your experience, how well do NPN SPICE models replicate real DC current gain

texts: Title, I'm currently running some simulations and noticed that my DC current is in the very rough ballpark of datasheet parameters. Is this normal or does it indicate there may be something wrong with the circuit itself. This is not a question on any particular circuit I am just trying to expand my knowledge on simulations vs. reality.


texts: Which voltage uses the "Kv" parameter in a BLDC (Brushless DC) motor?

texts:
According to the definition of a BLDC by Wikipedia:

  \$K_V\$ is the motor velocity constant, measured in RPM per Volt (not to be confused with "kV," the abbreviation for "kilovolt")[6].
  The \$K_V\$ rating of a brushless motor is the ratio of the motor's
  unloaded RPM to the peak (not RMS) voltage on the wires connected
  to the coils (the "back-EMF").

Since Wikipedia is not a recommended source, I'd like to know if the voltage is reffered to the peak value or the RMS one, and also if it depends on the type of conexion in the motor (Y/Δ).

My confusion starts because I've done a test with a motor I have, bought in Quadroufo. The characteristics of this motor are the following:

\$K_V\$ = 2600
P = 12 (stator)
P = 14 (rotor)

For the experiment, I attached the rotor to a drill. While leaving the velocity of the drill still, I measured the BEMF with an osciloscope. The following is a picture in which I got the results about measuring voltage between lines (sorry about the labels in spanish):

With the frecuency parameter, I got the 'n' (mechanical velocity). Which is n = 2193.428571 RPM (with the ammount of poles in the rotor). From now on it's "conffusing time" about the deffinition of \$K_V\$. Which value of voltage should I use?
Since I don't know which conexion the motor has (Y/Δ) I tried every possibility as you can see in the following chart:

Comparing the chart with the parameter \$K_V\$ that Quadroufo says, the most similar are the ones painted in yellow. Is this confirming that actually \$K_V\$ depends on the conexion type of the motor and also that is not reffered to the peak but to the RMS value?


texts: How do I compensate for Exponential decay in an op-amp circuit

texts:
Using an oscillator, I want to provide a square wave input to the second opamp circuit shown in this TI application note (but using IC741 instead.) The problem lies in the s domain:

I get a voltage input of  \$\dfrac{1}{(s^s+as+c)}\$ at the non-inverting port, which is a decaying signal and I want an attenuated signal.

Also, I cannot seem to understand what C2 is used for, it just seems to contribute to KCL?


texts: Calculate right inset for microstrip antenna to match trasmission line

texts:
So,
I have designed a 2.4Ghz microstrip antenna. I have chosen a dielectric height of 1.5 mm with a dielectric constant of 4.08

I calculated my W and L of the antenna and simulated it in CST. I have tweaked to better fit the S-parameter to 2.4Ghz and I came out with
W=41mm and L=30.2mm

Now, I would like to match my antenna to 50Ω but I haven't found formulas to calculate the inset dimension (width and length).

After various simulations, I came up with a W=1.5mm (same of the dielectric) and a length L=7.16mm but they didn't come with mathematics calculation instead with "random" simulations. (transmission line is 0.035mm thicker and 2.98 wide (why?! I don't know))

You can check a sketch of my antenna with a measure below.


texts: Why are NOR flashes still used when NAND flashes have a bigger size?

texts:
I've seen a few systems that uses a NOR flash to boot from, and a NAND for a bigger filesystem. I've also seen a system with only NAND gets corrupted after files being written to and verified correct.

Are NOR used because it is more liable to boot a system? Or any other reasons?

Have you seen NAND not reliable?


texts: Effect on current draw and voltage when splitting a signal to many places

texts:
I have tried to Google answers to this already, but every search I make comes up with answers to other questions. That said, I'm happy to just be given links if there are already legit answers out there.

So I'm still quite new to electronics. And I have a part of a project in mind that will involve sending an AC audio signals from. An output jack to a great many input jacks. All unbalanced and working between +/- 5V range. If it helps clarify the situation, I'm talking about inputs and outputs on modular synth systems. I wish to preserve the voltage as best I can, and I obviously don't want to blow anything up. So my questions are as follows:

What kind of voltage drop (if any) am I likely to experience per split (or more importantly, how many splits could I get away with before the voltage dropped significantly).

Will each extra input that I send the signal to cause extra current to flow through the output, or will the current just split between each input?

Are there any other things I'll need to consider to avoid any catastrophes?

Cheers in advance for any advice, pete

Sorry for the crap tags, not sure what specifically to tag this with.


texts: AC and DC voltage are constant even though the frequency changes

texts: In the circuit below, why does the AC voltage remain constant even though the frequency increases?


texts:
The following circuit

has D1 which is a diode, and then D2 which I believe is another diode.  I think that the diodes are there to simply act like a flood gate type thing where they are controlling and making sure the circuit does short circuit.  Which would be the purpose of D1, but D2, I don't have an educated guess on it.  What would their function be in this circuit?


texts:
Not sure if anyone can help me with this...
I have a rather large/complex design which so far was syntheziable without problems but with the last (although very simple changes) my iCEcube2 gives me an
unexpected error
Synthesis failed

I cannot find any information what the cause of this error could be. Normally the indicated errors are pointing you in the right direction but this one just seems to be... well, unexpected.
The thing is it seems to be totally arbitrary what causes this failure. I just added a little combinatorial logic to some bits of a vector. If I reduce the amount of involved bits it works. If I keep the amount of involved bits and also use the complete vector for some other assignment it also works.
And what puzzles me the most is that I see the issue with the 2017.08 release but the same design compiles just fine with the 2016.02 release.
So in the end I can just use the older version of iCEcube, but I really like to understand what's causing this...
I'm aware that the chances someone already ran into this are quite small, but I thought it's still worth a shot.


texts: Multiple USB - JTAG devices, how to specify target over Xilinx XMD?

texts:
I couldn't find an answer to this anywhere, so I'll post my hack-tastic solution here with the hopes that anyone else who comes across this same problem can share a better answer.

I need to communicate with multiple JTAG devices connected to the same host using XMD.  I have 2 USB-JTAG devices connected to my Windows 7 host: a Digilent HS2, and a Xilinx Platform Cable USB II, and I need to keep both of these devices plugged in to the same USB hub.

By the Xilinx "Embedded System Tools Reference Manual", it's possible to specify the target device using XMD% xrjtagchain [-cable <cable_options>].  Some of the cable options include using either the Electronic Serial Number (ESN) or USB port.  I prefer using the ESN; I couldn't figure out how my devices were enumerated in the USB list, and so had no luck with XMD% xrjtagchain -cable port USB21, to use an example from the documentation.  I looked at the device information in the Windows device manager and tried several USB port numbers with no luck.

Using the ESN approach, the Xilinx Platform Cable USB II device did not respond with a valid ESN, so I could not address it.

XMD% cableesn
XMD_DEBUG - Executing Command: xrcableesn
XMD_DEBUG - Xilinx hw_server URL=TCP::3121
XMD_DEBUG - Connecting to hw_server at TCP::3121
XMD_DEBUG - Connected to hw_server at TCP::3121
XMD_DEBUG - Target 0: jsn-JTAG-HS2-210249983399=Digilent/210249983399/
XMD_DEBUG - Target 1: jsn-DLC10-000180fe56601=unknown/unknown/
Digilent/210249983399/,unknown/unknown/

The device I need to address is "Target 1", but the ESN is unknown/unknown.

The best I could come up with was to use the following command:

XMD% connect arm hw -cable esn unknown/unknown

This is the only way that worked for me.  Is there a better way?


texts: What is the Zener diode doing in this 123V supply?

texts:
We are fixing up an old Atari game cabinet, and we keep blowing the Zener diode D802. This is a 51V zener diode, but we don't understand what it's doing and so we can't figure out what is causing it to be overloaded.
The concept of operations for the supply is here:

Below is the 110-120VAC to 123VDC power supply schematic (relevant part shaded in white).
The AC goes through a half-wave rectifier at D801, and is smoothed by the bulk 800uF capacitor, C803.
Our local electric grid supplies 120VAC, so the rectified voltage is 170VDC. Somehow, this 170V winds up flowing backwards through the Zener diode with enough energy to fry it.
With an IR camera, we watched a brand new Zener die during a 1 second power blip.
We have pulled the fuse and replaced the load with a 65W light bulb, which seems to be a good fit as a dummy load (about 25% of the fuse's 1.5A rating.)
If we desolder D803, leaving an open circuit, then the system stabilizes at about 74V. Coincidentally, 74V + 51V = 125V, which is that the user's manual says we should see on the base leg for Q801.

What is D802 Zener's purpose in the voltage regulator?
Knowing that we have tested the D803 diode, the R804, R805, R807 and R808, and that Q802 has the appropriate 12.8V on the emitter (this value is defined off screen), what's a guess for where to look for the current sink which is destroying the Zener?

We'd love some insight into how to make this old cathode ray tube Millipede game live again.


texts: Arduino and 3W LED sharing the same power source, is it possible and how?

texts:
I've built a remote control for my 3W power LED with an Arduino UNO and I'm powering the Arduino with a USB cable and the LED with 4x AA NiMh batteries (1.2V). Is it possible to power both my Arduino and my LED with the same power source (meaning batteries)?

I haven't found anything on here for my case. Most questions that revolve around using the same power source are for 5 or 10 high power LEDs with a source of 12V, but I'm only using 1 and I need it to run on batteries.

Specifications of the LED:
Max. Current : 750 mA
Forward voltage : 3.5 - 4.5 V
Max. Working temperature: 60 °C

P.S.: total newb in electronics so sorry if it's a simple question


texts: What happens if the Forward voltage of a diode is not met?

texts:
Ihave been playing around with transistors and diodes lately, and thinking about switching methods and techniques.

I'm not that educated on the matter of "Forward Voltage", but I illustrated a concept I am trying to grasp in the photo below:

In this circuit concept, I have a 1.5V battery hoked up across the terminals of a capacitor, but...there is a cathode of a diode hooked up between the negative terminal of the battery and the negative terminal of the capicitor.

The Diode, attached to a current limiting resistor,can provide a path to the other terminal of the capacitor, but only if the forward voltage is met???

Is that so? Would the diode act as some type of "flood-gate", allowing the battery to store electrical potential in the capacitor, until the pressure is adequate to provide the forward voltage to the diode?

My goal, or what I envision, is that I could hook up a relay or transistor the other end of the capacitor/ battery, and the temporary discharging of the capacitor would momentarily "power" the switch, allowing me to momentarily connect another power source to make a light blink or something.

If the diode funcctions in tth way I assume, then it would probably do this in a constant cycle, and could possibly be timed in accordance to functionality.

I'm just not sure if this is the actual science...


texts: How do I amplify the output current from a photodiode? (In photovoltaic mode)

texts:
I explain my self: we're going to make a photovoltaic cell with severals photodiods in series. Problem: the current isn't really high (I'm in photovoltaic mode, so no external biais source).

I've already looked at the transimpedance amplifier , but the thing is that for me... it just converts the current into voltage (Vout=Rf*I), but it doesn't amplify my input current ....

Are there any other way to amplify the output current ?

I just want to add that these photodiods are used in photovoltaic mode, and that i'm going to load a battery (12V maybe), with the output voltage from the PV cell .
The thing is that I don't know if I really need to amplify the current (I have not so much knowledges in this field), but i thought that it would be great to do it...


texts: Repercussions of choosing a poor audio amplifier

texts:
I have a customer who had an audio system setup in his business a couple months ago, and he's had some issues with it.

The relevant bits are that one of the original amplifiers blew upon initial install almost immediately, he tells me. Upon investigation, I've found that he's using an AudioSource AMP-100 amplifier, which is rated for 60W @ 4Ω or 50W RMS @ 8Ω according to the specs. His speakers appear to be 12Ω speakers (or higher), as best I can tell. (I measured the resistance of the speakers, and from the discussion I had in a chat room with a colleague, it appears that from the measured resistance of 9.6Ω, his speakers are somewhere in the ball-park of 12-16Ω. Obviously this is not a true value, but it's a good estimate. I don't have any actual data on the speakers themselves, he no longer has the boxes and they are ceiling mounted.)

Obviously these speakers have a much higher impedance than the amplifier is rated for, so could this be why the original amp failed immediately? Is there something I'm missing here? (I'm not an audio or A/V engineer, but from my understanding mismatching these values could potentially have significant negative impacts.) He currently has one of these running four other speakers in the building. (They are all wired into the same positive/negative contact set on the back of the unit. As best I can tell, they are wired all in parallel.)

I'd love to use the existing amplifier setup and just wire the additional two speakers into the "B" output if possible, but I'm not sure if I should replace that amplifier with something rated in the 8-16Ω range (and probably a higher wattage).


texts: Stuck Mosfet amplifier analtsis. solving resistor values

texts:
Im working through some questions and am stuck on the first one. It seem so have to many unknowns in the actual question to get any result? I can find gm (conductance parameter) = 1x10^-3(A/v). and i can find a formulae relating Rin to R2 and R2. after this i am completely stuck on how to solves the values? i can only find 4 equations but have 5 unknowns?

id saturation equation
2 KCL equations
and a resistance equation relating Rin = sum of resistances ect ( depending configuration)

Secondly because there is no cap between the signal source and the rest of the circuit when putting it in dc analysis, this makes the circuit very confusing. Suggesting that the gate always has a DC bias voltage of Zero? although because Id is given gm could be solved for and also VGS could be solved.

Also without VDD given how are you ever able to tell if the mosfet is it saturation, triode or cut off?

Is there anything i am missing?

Ive attached image of question and my working


texts: Why is transconductance vs gate voltage graph for a mosfet not constant when drain current is a linear function of gate voltage?(in linear region)

texts:
Id=Kn(Vg-Vth)Vd in the linear region
This should imply that the transconductance is constant for constant Vd(drain voltage) but the graph is something else


texts:
Problem: I want to try to assemble a circuit that would turn a light bulb (230V) on and off, controlled remotely by a PC. Ideally, the control will be over WiFi, next in line is Bluetooth and least preferable are RF and IR. Cost is a consideration and it would really be nice to be able to manage in 50-100$ total (including a newbie's kit).

About me: I'm a programmer and a total noobie to electronics. I want to learn to do such things. I also want my home lights to be controlled from a smartphone.

Questions:

Where to start? What should I know about electronics?
I've read about Arduino, is this what I need?
What components should I buy?
How much should it all cost?


texts: Can I use "ideal diode" in series in solar cells?

texts:
i have a small experimental solar panel system to gain knowledge before moving on large power systems.
My system is 5 solar cells in series, each 5.8V 0,52A (peak power). So total is 29V 0,52A (about 15W). Output is connected to LT8705 MPPT charger.
I have a common problem with shadow of tree moving across the panels during the day so I installed bypass schottky diodes across each panel like this:

I am using PMEG4050 schottky diode, that draws about 0,35V. Not bad but would like to improve it because in larger PV cells this will be a huge power loss.
Can I use the ideal diode controller with MOSFET (like LM5050) as a plug in replacement of diodes here? The loss should be almost 14x lower with 50 mohm MOSFET. But I am concerned about grounding. I think each ideal diode "unit" should be grounded with common ground (can be tha last PV cell negative?). If i understnad the block schematic of ideal diode right, the mosfet should remain off if power supply of any solar cell drop below 5V and should not cause any problem. Or maybe I can use common bias power from solar output to power up all diodes at once with single supply (29 V).
Or I am wrong? On internet there are only mentions about using ideal diodes in paralel, not in series. Any thoughts about this topic is appreciated!


texts: Is the bias of the accelerometer MPU9250/6000 significantly high?

texts:
The bias for Accelerometer of X and Y are very different from 0 when the sensor is flat. The AccZ axis is as expected. I can correct for this bias in code, however I wanted to know if this level of bias is typical of MPU range, if not I may consider getting another one. Sensor: MPU9250. The values should be multiplied by 10, so 0.92 on Z axis is 9.2m/s^2 (acceleration). -0.39 is 3.9m/s^2.
https://invensense.tdk.com/wp-content/uploads/2015/02/PS-MPU-9250A-01-v1.1.pdf
(datasheet)
https://invensense.tdk.com/wp-content/uploads/2015/02/RM-MPU-9250A-00-v1.6.pdf
(register map)


texts: Ohm's Law confusion -- can there be voltage without current?

texts:
I know there has been asked a similar question about this before but I still have some issues to understand the whole voltage and current thing.
( Current without Voltage and Voltage without Current? and
 Is Ohm's Law violating itself?)

Ohm's law states:
$$V = R \times I$$

But what came to my mind is: if either the resistance or the current is zero the voltage will be zero, too (according to ohms law):

$$V = R \times 0 = 0$$ and $$V = 0 \times I = 0$$

I'm not sure if Ohm's law is applicable here. Please correct me if I'm completely wrong or missing something obvious!

So lets say I have a single power supply with a 5V fixed output:

I'm going to measure the voltage with a typical \$10\text{M}\Omega\$ input resistance:

Since there is a "resistor" as a load, current will flow:

$$V = R \times I$$
$$I = \frac{V}{R}$$
$$I = \frac{5\text{V}}{10\Omega} = 500\text{nA}$$

But what if I disconnect the probes? Now we are at a point where it gets really confusing for me:

There will still be a "load" on the supply, since: air is not a perfect isolator so it must have electrical resistance: (I'm assuming \$1\text{G}\Omega\$ here)

Same as before, current would theoretically be:

$$I = \frac{V}{R} = \frac{5\text{V}}{1\text{G}\Omega} = 5\text{nA}$$

So my question is: does this small amount of current really flow? Because if not there will be no voltage across the two terminals according to Ohm's law! This is really confusing and I don't think current will flow because it simply sounds really unlikely.


texts: Serial port controlling a motor bridge--unknown bug

texts:
This is part of a project where I wanted to bypass using a microcontroller and control motors directly with my laptop. I'm using a usb-to-serial cable and use the serial RTS and DTR to control a TA7291P motor bridge which powers two hobby motors. It has worked fine save for a yet untraceable, random bug where linux stops recognizing the USB port after a random time interval (1-20 minutes) for a brief moment, which is long enough to make the program (using pyserial) require a restart. To drive both the motors at the 'same' time, I alternate RTS/DTR in 5ms intervals.

My two questions are:
 Should I be attaching the serial ground to a communal ground(it is currently not connected to anything)?
 Might my abuse of the RTS/DTR functions be causing the bug?

I'm still assuming the bug must be some disagreement between pyserial and linux (and out of the scope of this post), but just in case I'd like to check if it's a hardware cause.

Circuit diagram http://www.e-alexander.net/img/scircuit1.png


texts: Weller EC1301a vs EC1301b (or schematic for EC3001 station)

texts:
I bought a Weller EC3001 station with a EC1301 iron out of my first pay check when I got my first bench engineers job (and that was a very long time ago!!!).  Life took me in a different direction, but (sad I know) I have become really sentimental about my Weller station as retain a keen interest and it has served me flawlessly over the years...

To my horror it stopped working a couple of weeks back (red temp indicator light now just stays on permanently and it doesn't heat).  Spares are hard to come by as these have been obsolete forever, and Weller themselves have tried to help but no longer have the tech sheets etc.  To my surprise I managed to get a EC1301b iron, making a fair assumption that it was likely the heating element and / or the temp sensor that had finally given in.  However, when I connect it the light stays off permanently, and again no heat.

I believed the 1301A and 1301B were the same soldering pen / iron, so I expected it to work, or at least provide the same symptoms if the station itself has a fault.

Does anyone have any info on the EC1301A, EC1301B, EC3001 (station) or even the EC4001 (station)??

Ideally diagrams, pin-outs or anything that can help me confirm whether a EC1301B should work as a replacement for an EC1301A (or work with the EC3001 / 4001 stations).  Or help me diagnose the station if it is that which is faulty.  Ideally I'm hoping they just changed the pin allocation on the 'B' variant as the plug is the same as I could then rewire it or use the parts from the new pen to get my old faithful up and running again.

Sure, I could just buy a new iron - but not sure what a proper send off would cost that feels fitting for my very dear soldering iron ;-)  Therapy is expensive too!!

Many thanks and fingers crossed...


texts: 3mm different color LED resistances for bright light

texts:
I am trying to power a number of different color LEDs with a 5V wall-wart power supply able to deliver 2 Amps.

I tried to make them light with equal intensity and I like them to be bright. (They get quite irritating to the eyes)

I get the following resistances:

blue: 5K, yellow: 350Ω, red: 150Ω, orange: 1K, green: 50Ω

Do the values make sense? The 150Ω and the 50Ω resistances get quite hot.

Am I doing anything wrong?


texts: Relay or SSR for electrical heating from tado smart thermostat?

texts:
I have a Tado smart thermostat system to switch my electrical underfloor heating.

It offers a simple NO or NC switch. This is rated at up to 6A. (Aside: Tado is not a good company. They provide no data sheet and can't answer questions. I regret giving them money.)

I would prefer to avoid the need for a low-voltage circuit; I'm hoping to get around that with an AC-to-AC SSR.

Question: is my circuit going to work and be safe?

Secondary: am I breaking any conventions?

ORIGINAL DIAGRAM:

AMENDMENT 1:


texts: Do switching type AC adaptors limit the current by themselves?

texts:
Do switching AC adaptors limit the current they provide to the rate described?

I have thought that they do not, and that it simply gets dangerous by overheat, but now I am thinking that they might.

I had a power unit with pretty much small capacity (60w) on my mini-ITX computer, and it worked for a while, but after I started to attach usb units and gained current, the computer frequently shut down, so I suspected the power unit's capacity was not enough, and replaced it with a larger one (120w) but kept using the AC adaptor (12V 5A) that was designed for the smaller power unit, and it still shuts down frequently. After calculating the power that I am using, the power unit should be enough, but the adaptor may not. Now I am suspecting that the AC adaptor does not have enough capacity.

A different reason I came to think that AC adaptors limit the current is when you connect a AC-to-usb adaptor to ipad that is not designed for ipad, it does not charge at full speed because ipad requires 2A, which is more than what ordinary usb power supplies.


texts: Understanding of a W65C02 micro computer

texts:
I found a tutorial with a schematic where you can buy a PCB for an old computer with a 6502 microprocessor.

I want to do this on my own with my own PCB (but I test the circuit on my breadboard first) and I have some questions for a better understanding of the design and this old technology (which is quite interesting).

How does the program flow work? As I understand it, I will write the program into the 28C256 EEPROM. The EEPROM is read-only (because of WE high) and so the EEPROM will output the program data which is stored in the address range of 0x7FFF to 0xFFFF. The address bus represents the program counter and so when the program counter increases the address increases too?
Why is the NAND U4C connected with the main clock? If I understand it right, the SRAM of the microprocessor is mapped in the memory region from 0x00 to 0x7FFF, because a15 is connected with the ´CS`. But what is the reason to connect the clock with the NAND?
The memory space 0xC000 to 0xC00F is reserved for the I/O. So the I/O is "mapped in the same region as the SRAM" and when I write to this specific address, I will write into the SRAM and the I/O controller. Is this correct?
How does this microprocessor handle an interrupt? In my understanding, the microprocessor will change the address on the bus to 0xFFFE when an event on IRQ occurs. So I have to place my interrupt code at this specific address in the EEPROM. Is that correct?
It seems that I need an EEPROM programming device to write the EEPROM. Do I have to use some kind of high voltage programming or can I use a microcontroller to write this EEPROM? Otherwise, I have to buy an EEPROM programming device.


texts: Why using resistors with the MAX232 chip?

texts: I earlier built the serial port board from the jal tutorial book, which is basically connecting a PIC and a D-9 directly to the MAX232. Now I'm reading AN1310 on the high-speed PIC16/18 bootloader. In figure 7 on page 6 I see this circuit uses 470Ω resistors on the MAX232 outputs. Will the jal-board work with the bootloader? Can it possibly break down the MAX232 or PIC? And most important: why would I use resistors on the MAX232 outputs?


texts: Finding a faulty chip that draws too much current

texts:
Note that this is a theoretical question - there is no schematic I can show. I will show some schematic, but it will be a very simplified version of an actual circuit, only for illustration purposes.

Assume I have a voltage converter that takes as an input my main voltage (from a power supply) and outputs a certain voltage, for example 1.8V.
It would look something like this:

simulate this circuit – Schematic created using CircuitLab

When connecting my circuit to the P.S, I notice it draws too much current (the P.S shows that).

Since I have multiple voltage converters in my circuit (not shown here), I check resistance between each output of each converter to ground. I see that the resistance between 1.8V to ground is almost 0 Ohms. Now I know the fault is either in the voltage converter or one (or more) of the other components drawing power from that 1.8V.

I desolder the resistor shown in the image to disconnect the converter from the other components and see that the converter is fine, but checking resistance from the point connected to all those components still shows 0 Ohms.

My question is - how would you check which component is the faulty one, without desoldering each suspicious component? As you can see in the image, the 1.8V supply is connected directly to the components, without a resistor/bead.

For the sake of this question, assume I have access to whatever equipment needed (no matter how pricey). I wouldn't want solutions to be limited due to availability of equipment.

Thank you!


texts:
I'm looking for replacement button for Kensingtons "Orbit Trackball with Scroll Ring". I'm hoping to find at least something similar.
Here is how the original button looks like:

Button dimensions

Width: 6.2mm
Depth: 6.2mm
Height: 7.3mm
Height (pressed): 6.8mm
Pin size: 0.7mm
Distance between pins: 4.8mm

There is symbols on top (can see on photo): 'J' and '2'. On the bottom "F3" and "TTC". It is possible to bent pins the way, that they will be sticking at one side, so button could be used as SMD.


texts:
I want to make an electronic device that Measures the wind speed in Beaufort. The definition of the Beaufort scale requires the calculation of an average over a period of 10 minutes. We choose to do this using the following principle (average with forgetfulness): filtre-passe-bas2.gif

For economical and space reasons, we choose to realize the RC filter by numerical simulation in the microcontroller.

Power supply: 3V analog output voltage proportional to the Beaufort scale with 0 corresponding to 0V Beaufort, 3V corresponding to 9 Beaufort (it will not show values above 9 Beaufort)
Interface to the LCD module: SPI (SPIdatas and SPI clk) Wind speed encoded in 8 bits

I think
i can Take readings say once a second (wind speed is relatively slow to change so no need to do it faster).
Add the reading to the previous one and halve the result so you get a running average.
Every 10 seconds send the speed scaled 0 - 9 to the LCD.

It is possible to store and average several readings but with only 16 bytes of RAM and some of that needed for the SPI software!! for me it  hard to code .
The code is highly optimized That's why I come to ask your help :fs: and knowledge. Any ideas is welcome!

I start coding but I have difficulty to store and average several readings  with only 16 bytes of RAM and some of that needed for the SPI software
Can anyone help me please?

movlw           b'00001001'     ;sets GP1 and GP2 as Outputs
    TRIS            GPIO
    movlw           0x41
    movwf           ADCON0

    movlw 0xC7
    option
;****************************************************************************
;***** VARIABLE DEFINITIONS**************************************************
;****************************************************************************
    cblock    0x09

    Delay         ;variable for the delay ,to make delays
    Counter       ;variable to count how many measurements
    LCD_data      ;hold the data to be sent to the LCD
    Counter_data   ; hold the counter for the bits as they are sent to the LCD

    endc
;**********************************************************************
;******************* coding begins*************************************
;**********************************************************************
    ORG     0x000             ; coding begins here
    movwf   OSCCAL         ; update register with factory cal value

start
    clrf LCD_data
    clrf Counter_data
    clrf Counter
    clrf Delay

;***********************************************************************
;                       remaining code goes here
;***********************************************************************
Wait
    movlw .15           ;reload 'Delay' again
    movwf Delay
    movlw 1         ;give TMR0 a start value
    movwf TMR0
Wait1
    movf TMR0,f     ;set Z in STATUS if TMR0 = 0
    btfss STATUS,Z      ;bit test the Z bit, skip if set (= Zero)
    goto Wait1          ;not zero yet so keep checking

    decfsz Delay,f      ;subtract 1 from Delay and see if zero
    goto Wait1          ;not reached zero yet so keep checking
    return
;********************************************************************
; read the voltage on the analog input pin, return result in W
;********************************************************************

ReadADC
    bsf ADCON0,GO_NOT_DONE  ;start measuring the voltage
ADC_Wait
    btfsc ADCON0,GO_NOT_DONE ;skip next instruction if GO/-DONE is zero
    goto ADC_Wait       ;not finished yet!
    movf ADRES,W        ;copy the result to W
    return


texts: Does this TO-220 Package Resistor need a heatsink?

texts:
I purchased this 0.5 Ohm power resistor, which comes in a TO-220 Package, with the aim of pushing 3A through it (i.e. 4.5W)
The datasheet has the following information:

It says it will rise 6.5 K/W, so it should rise 29.25C + 23C ambient = 52.25C. Using my thermometer probe, the temperature on the metal body is well over 150C, so I turned it off.
Have I messed up something in my calculations, or is this datasheet incorrectly specified?


texts: What is the SoC on the ARM9 board TS-7800?

texts:
From Single Board Computers

  The TS-7800 series of single board computers provides 3 times the performance of the TS-7200 series with the same footprint, using a Marvell 500MHz ARM9 SoC.

From ARM9 TS-7800 Xenomai support

  The link you quote provides only very vague information like "using a
  Marvell 500MHz ARM9 SoC" (which can be anything) or "use a recent
  Linux kernel 2.6" (which means they are plain OLD - recent means v3.4
  or later).  This may be sufficient for marketing material, but not for
  answering technical questions.

I found TS-7800 User's Manual. But, I can't find something related to SoC there.

How do I find out the exact SoC this ARM board uses?


texts:
I am designing a non-inverting op-amp circuit that maps an input signal (V3) 0-3.3V to an output signal (Vo) 0.2-2.4V. I opted to offset the output up by 0.2V and then used a second op-amp circuit as a negative impedance converter (NIC) to attenuate the 3.3V input to 2.4V at the output. The schematic can be seen below:

Simulating the circuit using the spice model for the LM258 gives roughly excellent results (as it always does) that I would be happy with:

In reality, when I prototype the circuit, the output hits 2.4V just fine at the high end, but cannot go below ~0.7V at the low end. When I disconnect the NIC and short circuit the inputs of X1 it works just fine at the low end (but of course the output goes beyond 2.4V at the high end). Can someone explain to me why the NIC is preventing the output from going as low as I want it to and how to overcome that?


texts: How to find voltage across resistors with only current sources?

texts:
Hello,

I'm trying to find the voltages across each resistor showed in the schematic, using KCL and KVL. I'm not too sure how to start the problem since there are no voltage sources and I don't know how to find the current from a current source. I was thinking of solving this through node analysis but was a bit unclear of how to do it with current sources.

For V2 (from R2) I tried (2E-3)(2) to get the voltage but the correct answer should be 2.571V.

Thank you for any help!


texts:
I have trouble calculating the current through R4, could somebody help me please.
I thought the current through the resistor R4 can be calculated like this:
Ir4 = I×(R4 ∥ (R3 + (R2 ∥ R1)) / R4), where I is the current from the source. I compared the result to a simulation and it is wrong, I don't know where my fault is. I would be glad about some help

EDIT: R2 and R3 are parallel, redrawn circuit:


texts: 12V PWM controller for 12V fan that gets faster with the COLD

texts:
I need a controller for a 12 V - 1A fan, blowing on the cold side of a Peltier element to keep it at constant temperature. I have the hot side under control.

I have seen multiple cheap PWM ready-to-install controllers online that do the opposite:  make a PC fan faster as the sensor gets hot (like this controller) or (like this controller).

I thought about three speed ranges, (so the fan does not keep readjusting non-stop): fast at 11 °C (52 F), medium at 13 °C (55 F),  slow at 16 °C (61 F). That way the temperature would be measured every 60 sec, and adjusting the fan speed in intervals, allowing the peltier to cool down until the next measurement 60 sec later.

How can I change the outcome of the pre-assembled controllers? Would a PNP transistor work? Or a Mosfet that decreases conductivity as the voltage increases?  I attached an image for reference (but I am a basic electronics user).


texts:
Is it possible to use a transistor with AC?
if you put a diode in there so no current flowed through it when the current reversed, but what could I do about the difference between the base and collector?


texts: How do I get enough rep points to do anything on here?

texts: This site is so frustrating because I just want to make comments or ask further questions on a topic that was not fully answered but I cant!


texts: Best way to generate white noise, DC to 1MHz

texts:
In this question a zener diode is used to generate white noise, and I've also seen reverse-biased transistor base-emitter junctions for this.
Digitally a Linear Congruential Generator (LCG) can be used.

What's the best way to get good quality white noise without spending thousands of euros (or even hundreds)?

For extra credit: how can you judge the quality of an LCG noise generator without a spectrum analyser?


texts: Fastest resistive touch panel response time?

texts:
1/ What is the fastest response time of touch panel?

2/ It seems resistive panel can get under 10ms, but I want a faster panel, is there any one with under 1ms or microsecond response time?

3/ Why electrical switch in IC can get stable in under 1ms while it takes several ms in resistive touch screen to get a stable voltage?


texts: White and Pink Noise Generator Circuit - Cryptic AC Analysis

texts:
The “Electronic Devices and Circuit Theory” book (by Boylestad, Nashelsky) gives a brief description of a random noise generator circuit at the end of “BJT AC Analysis” chapter. (Btw, exactly the same circuit appeared in the IET magazine, April 1976).

DC analysis is straightforward: Q3 stage represents a 'classical' collector feedback bias. At \$V_{cc} = 21 V, \beta=100\$ we get \$A_v = 280, Z_{in} = 1.28 k\Omega\$. No surprises there. However, their description of what happens at high frequencies (where the 3 db/octave filter’s capacitors kick-in) baffles me. The exact quote from the book:

  At a sufficiently high frequency all the capacitors could be replaced by short circuits, and the total resistance combination between collector and base would be reduced to about \$14.5 k\Omega\$. which would result in a very high unloaded gain of about \$731\$, more than twice that just obtained with \$R_F = 1 M\Omega\$. Because the 1/f filter is supposed to reduce the gain at high frequencies, it initially appears as though there is an error in design. However, the input impedance has dropped to about \$19.33 \Omega\$, which is a 66-fold drop from the level obtained with \$R_F = 1 M\Omega\$.

Questions:

Where did they get the unloaded gain of \$731\$? Shouldn't the gain actually be reduced because of the ‘heavier’ feedback?
How they get \$Z_{in} = 19.33 \Omega\$?

EDIT 1 (@analogsystemsrf):

Input impedance equation for collector feedback configuration is:
\$Z_i = \dfrac{r_e}{1/\beta + R_C/(R_C + R_F)} = \dfrac{20 \Omega}{1/100 + 5.6 k\Omega/(5.6 k\Omega + 14.5 k\Omega)} = 69.3 \Omega\$

(from DC analysis: \$r_e = 20 \Omega\$, \$R_F = R4 || R5 || R6 || R7 = 14.5 k\Omega\$)

\$Z_i\$ is therefore \$69\Omega\$ and not \$18\Omega\$ as stated in the book!?

EDIT 2 (@sunnyskyguy-ee75):

DC analysis:

\$I_c * R_8 + I_b * R_4 + 0.7 V = 21 V\$

\$I_c = I_b * \beta \$

\$I_c = \dfrac{21 V - 0.7 V}{R_8 + R_4 / \beta} = \dfrac{20.3 V}{5.6 k\Omega + 1 M\Omega / 100} = 1.3 mA\$

\$r_e \cong 26 mV / I_c = 20 \Omega\$

\$A_v \cong -R_C/r_e = - 5.6 k\Omega/20\Omega = -280\$

AC at some high frequency:

\$R_F = R4 || R5 || R6 || R7 = 14.5 k\Omega\$

\$A_v = -\dfrac{R_F}{R_C + R_F} * \dfrac{R_C}{r_e} = -\dfrac{14.5k\Omega}{5.6 k\Omega + 14.5k\Omega} * \dfrac{5.6 k\Omega}{20\Omega}=-202\$


texts: Cross conduction in class-B power amplifier

texts:
can someone explain me why in this class-B power amplifier circuit, those two signal(driver?) mosfet generate a lot of cross condution ?

the two mosfet i used :  2N7002 and BSS84

Thank you in advance.


texts:
I'm designing a precharge circuit which will carry 200A when closed. I'd like to use MCO150 Silicon Controlled Rectifiers, but they won't handle the current. Two in parallel looks like the most cost-effective way to handle the current I need. However, I'm concerned about thermal runaway.

The effective impedance of any device will vary with temperature. If that impedance rises with temperature, two devices in parallel will share reasonably well. The device carrying more current heats up more, and its fraction of the total current drops. But if the impedance of the device drops as temperature rises, the device carrying more current starts carrying even more. Sharing fails, and one device hogs the current until it dies.

The datasheet for this SCR doesn't seem to address the issue of temperature coefficient. Is it just assumed that SCRs have a temperature coefficient in one direction or the other? If the temperature coefficient is negative, is there a way to force the two SCRs to share anyway? Or should I try another approach, like a single device or a large contactor?


texts: Step up voltage Transformer for more watt?

texts:
Using generator in mountain or underground tunnel location, construction workers from portable generator gets maximum:

  AC Output: 220volt as 200 to 250watt

Now, they need to use a machine for construction activity, where there machine requires:

  AC Input: 220volt as 700watt

Now can they use following pulse transformer to supply 700watt from there generator 200watt?

https://www.amazon.com/dp/B07B9J2RWQ/ref=sspa_dk_detail_1?psc=1

Please advise.

EDIT:

Interleaved method.

Maybe a 700watt/hr Portable Lithium Battery with 500 watt Inverter connected to the generator. (battery)


texts: how to initialize wifi settings in a production IOT device

texts:
I want to build an IOT product that logs/polls values from a server. The problem is that all of the arduino/esp8266 and similar modules that I have found require the user to initialize the device with a wifi username/password. If I want to sell this device to people, what's the best way for them to upload the right username/password to the device?

I'm looking for options/libraries/best practices. The only option I can think of so far is to write a cellphone app that communicates with the IOT device via Bluetooth and is used to upload the wifi settings to the device. This way seems cumbersome, and I'd rather not write a iphone/ios app just for the purpose of connecting the module to the web.


texts: I have a "host" device that does not have a 5V rail for VBUS but has a lithium battery for power.The battery voltage meets alternate mode VCONN specifications (2.7 V to 5.5 V on VCONN). Is it possible to power a "slave" device over VCONN without implementing a PD control scheme and using VBUS?


texts:
So I'm making a board, and this is a recommended configuration for one of the chips I'm using (FT232H). I'm trying to set it in the Synchronous 245 mode. This resistor is to improve clock performance.

I'm just trying to figure out if this kind of diagram means I'm supposed to connect the pin to the resistor back to that pin.


texts: Are there any advantages to an inverted serial prototocol?

texts:
Why would someone implement an inverted serial protocol?  Are there advantages in doing so?  One obvious disadvantage seems to be that an extra device needs to be included in a circuit if the receiving device can't handle an inverted signal.

Context: The Futaba/FrSky S.Bus protocol (commonly used in RC model receivers) uses an inverted UART signal, and almost all discussion about it is how to re-invert it so that common processors can receive the data.  Why did this protocol not simply use a "normal" non-inverted UART protocol?

Why are hardware inverters so prevalent? Seems to touch upon this but doesn't clearly explain (at least to me) the rationale for implementing an inverted serial protocol.


texts: Voltage reference with op-amp buffer and additional filtering

texts:
I commonly see voltage references implemented with op-amp buffers as shown below. That's the simplest way.

However, see below another way of doing it which I found in a meter:

The second one seems it has more robust filtering. Is it really needed? Of course, I don't know why the designer did that. There may be a reason. I'd like to understand under what criteria the designer would choose this topology.


texts: Circuit of a PWM DC motor speed controller for a 12V 10A DC motor

texts:
I saw many circuits for this, most of them were using 555 IC, I wanna use a 12V 15A switching power supply for this motor, so I need a high current PWM speed controller but I don't know how to design it or which component makes it powerfull and capable to be used for high current.
Another question is, the motor has huge initual current, so each time I turn the dial poetentiometer to speed up the motor, how much amps it will draw (more ir less than usuall)? and when I turn it down to stop the motor, will it make EMF/BackEMF until it stops?