texts: Low voltage AC to DC for energy harvesting

texts:
For an energy harvesting application, I need to charge a capacitor using induced voltage due to the movements of a magnet inside a coil. The generated voltage is typically low frequency AC (4-5 Hz) with maximum 0.1 Vpp. This makes it extremely inefficient to use a traditional bridge rectifier, as the voltage is well below the active treshold of the diodes. What circuit could I use for the purpose?

I tried stepping up the voltage from the coils via a transformer (25:1) with no success. There also seems to be readily available ICs for the purpose, but they are unavailable at this time in my location.  Also, it is worth noting that the capacitor should charge solely using the output of the coil, no external voltage supply is available.


texts:
While studying forwarding in RiscV cpu I saw the following claim:

But I can't understand why we can't do forward in this case, why in different conditions we were able to do this and now we can't?
It was mentioned that the reason is that clock time isn't enough which I don't understand.
Why the reason isn't the fact that we can't forward something that isn't calculated yet?


texts: Help understanding schematic (voltage regulator)

texts:
I got this voltage regulator that I wanted to use with a DC source (30V switching power supply from a printer).
(full schematic here )

However, I see that input of the voltage regulator MUST be powered from an AC source (transformer). I think it uses a trick to obtain dual voltage for the op amps.
1. Is this correct?
2. How do I modify the schematic so that it will work with DC input?


texts: PCB Copper pour without making Schematic

texts:
I have a problem with ground Copper pour for the PCB.
I'm using EasyEDA.com to designing my PCBs.

But because i usually make my PCB directly without Drawing its schematic so i can't make the ground Copper pour because there are no GND detected by the system.

So i'm wondering if there are way to Copper pour without drawing the schematic?

Following image just an example:


texts: How to completely turn off device when float switch is open

texts:
Background

Below is the circuit I designed to open a solenoid valve after a delay from C2 (represented by L1).

S1 is a float switch which closes when a resevoir goes below a given level. The reason S1 is not directly in line with the source is the school of hard knocks lesson that the reed switch (inside the float switch) fuses from the current through the solenoid.

My problem is that the reference voltage being provided by R3 will constantly drain current, even when the valve isn't activated by the bias at Q1. I thought about putting both the inverting and non-inverting inputs on S1, so that neither the inverting nor the non-inverting inputs will have a voltage, but what would the effect be here?

Questions

I vaguely recall that if the two inputs are at equal voltage the output will be zero? Is that correct?

If not, are there other suggestions for stopping wasteful current in the circuit?

PS

This the first circuit with a specific function in mind I've done from scratch, so ... other design flaws/suggestions you see, feel free to mention :)

The LM386 is just the op amp I have handy. I didn't feel the need to get a comparator because it's a delay of 7+ seconds, so the slow switching isn't really a concern.

Also R3 is actually 240K.

Edit: Per comments, modified image
Would this be the correct way to implement the PMOSFET?


texts: AC motor 3 wiring how to connect to EU plug

texts:
Hello electronics stackexchange,

a friend gifted me an electric motor he didnt need any more. It looks exactly like this ans also has (nearly) the same numbers on it :  https://www.aliexpress.com/store/product/390210-001-390209-001-12V-server-fans/1913237_32589390473.html

I have use for this one, but am not sure how to connect it to my power supply (Germany, EU Plug). Is this an more or less easy task or am I better off just not touching it?

Greetings


texts: Is it true that copying is the most CPU intensive operation?

texts:
A mech engineer said that copying puts more load on the microprocessor than "other" operations (e.g. moving data or creating the same amount of new data). Is this true? Can you elaborate? I understand that the assembly instructions are different but not how copying is "more intensive" ?

With copying what is meant is probably something like memcpy in C and with moving what is meant is probably the MIPS instruction mov between registers or between primary memory.


texts: How to Allow Shorts Between the same Net in Altium

texts:
I have some pads and tracks that are different primitives but are the same net in an Altium layout.

Altium keeps flagging these as ShortCircuit DRC violations, but they're the same net, so I don't want to keep seeing these come up.

How can I shape a DRC rule to ignore shorts between nets that are the same?

Thanks


texts:
It is known that a decoder take n input and can have 2^n output. Each input only constitute to 1 unique output.

However, I read that seven segment display decoder can take multiple input bit and produce multiple output bit as shown in picture below.

*image cited from www.electronics-tutorials.ws/combination/comb_6.html

I am confused about this concept that why seven segment display decoder can  output multiple bit while the theory said that a decoder can only produce 1 output bit. For example in the image below, multiple input bit only output a single bit.

*image cited from en.wikipedia.org/wiki/Binary_decoder

Definition of decoders: [cited from en.wikipedia.org/wiki/Binary_decoder]

  A 1-of-n binary decoder has n output bits, and the integer inputs bits serve as the "address" or bit number of the output bit that is to be activated. This type of decoder asserts exactly one of its n output bits, or none of them, for every unique combination of input bit states. Each output bit becomes active only when a specific, corresponding integer value is applied to the inputs. For example, output bit number 0 is selected when integer value 0 is applied to the integer inputs.

Any expert please help to explain this concept. Thank you.


texts: Why does a C4467 transistor turn off slowly when collector-emitter current is low

texts:
I built the following circuit

simulate this circuit – Schematic created using CircuitLab

The clock has an amplitude of approx. 5 VDC. It's provided by a 555. I used two different values of R2 for my tests. The first test was R2 = 6 ohms. The second test was R2 = 10000 ohms.

I used my oscilloscope to record the clock signal and the base voltage. The blue graph is the base voltage, the yellow graph is the clock voltage. This is the result of the first test.

This is the result of the second test

As you can see the base voltage returns to 0 in the first test almost immediately.

In the second test, the base voltage takes approximately 30 microseconds to return to zero. During this time, the transistor continues to conduct. Why does this only happen when the collector-emitter current is low?

Test of solution provided below

I located a SR306 diode. Datasheet here:

http://pdf.datasheetcatalog.com/datasheet/diodes/ds23025.pdf

This diode is a poor choice for this application, but still applicable.

I set R2 = 10000 ohms for this test. R1 is still 100 ohms. Here is the waveform again with the existing circuit.

The switching of the transistor still lags behind the clock.

Here is the waveform with the diode connected from the base to the collector

The transistor follows the waveform faithfully now. Here is a closer view of the switching transition

It still takes around 2000 nanoseconds for the transistor to turn off, but this agrees with datasheet.

Interestingly there is some oscillation on the base, but it is not significant. It has an amplitude of only 100 millivolts.


texts: Choosing multiplexer to convert current to different voltage

texts:
I want to convert 0-20mA current to 0-1V , 0-5V , 0-10V with different resistors using a multiplexer, but the problem is that my output voltage is not correct and off more than 1V.

I know that different multiplexer have different Ro and current leakage(which is the most important), but how can I calculate this error and what else do I have to for look in datasheet to choose a correct multiplexer, or if you know a part number that can work for this purpose.

The goal is to convert 20mA X 500ohm = 10V, or 20mA x 250ohm = 5V


texts: Will this power supply fit my LiPO charger?

texts:
I just got my brand new LiPO battery charger. It is require 12 volt pover supply.
I saw people are using car battery, pc power supply to this charger 12 V. but i'm not sure  about current it is require.

Here is spec:

Operating voltage range: 10.0~18.0Volt
Circuit power: max.50W for charging, max.5W for discharging
Charge current range: 0.1~5.0A
Discharge current range: 0.1~1.0A
Current drain for balancing Li-po: 300mAh/cell
NiCd/ NiMH battery cell count: 1~15cells
Lithium battery cell count: 1~6Series
Pb battery voltage: 2 to 20V
Dimension: 135×100×40mm

Will it be ok if i use for power supply  plug in transformer which outputs 12 VDC, 800mA?

Dont wanna damage any of them.


texts: Is it possible to control a DC motor with Microstepping driver?

texts:
Today I found that electronics dealer have shipped me a Microstepping controller (A4988

-module: http://www.robotshop.com/media/files/PDF/datasheet-1182.pdf

-on-board chip: https://www.pololu.com/file/0J450/a4988_DMOS_microstepping_driver_with_translator.pdf -)
along with two DC motors. And he claimed that it is possible to control two DC motors with that module. But how?

I checked two of these datasheets that are provided above, however, I still feel confused about if this module is a stepper motor controller, it will constantly change the polarity, which is something that I don't want, so how can I control two dc motors simultaneously with it? Also I need to be able to control the speed, via PWM or what is available. Any guidance would be really helpful!


texts:
I would like to better understand how to find the zero of the transfer function of a circuit by inspection using fast analytical techniques.

simulate this circuit – Schematic created using CircuitLab

For example if I have this simple circuit I know that in order to find the zero I have to fix 0V at the output and look for which\$\ s\$ the condition is verified.
In this case to have \$\ V_{out}=0\$ I need that the impedance \$\ 1/sC + R_2 = 0\$ and this condition is verified only for \$\ s=-\frac{1}{CR_2}\$.

Now my problem is: if I have 0V at the output it means that the current through \$\ R_1\$ is
\$\ \frac{V_{in}}{R_1}\$.
Now this current must flow through the capacitor C and R2, and the voltage of node Vx will rise to \$\ V_x=V_{in}\frac{R_2}{R_1}\$.
But in this case it means that I have a positive voltage drop across C from Vout to Vx and so the current through C must flow in the opposite direction with respect to our assumption. What is wrong with this reasoning?


texts: Selecting the correct wire for very short power transmission

texts:
Looking for the thinnest wire for very short distance power transmission.
Supply is 5V, 10A. Ambient temperature is 35C.
There are 5 consuming elements, each consuming 10W.
The elements are linked together with wires, 10mm apart.
Looking at wire tables, it seems that 20AWG is the correct wire to use but this is for "Chassis Power Transmission" and I can only assume it is more of a thumb rule.
Using a PCB trace calculator, for transmitting 10A over 10mm the recommended trace is 0.25mm^2 of copper, same is 23AWG wire. As distance is very short, voltage drop isn't a factor.
Is there a more accurate way to determine the minimum wire gauge other than "try and see if it works".


texts: How do I detect a switch opening with an Arduino?

texts: I have brought some Honeywell Actuv PIR (Passive InfraRed) detectors. I know that zone wire contacts become open circuit when it's triggered. How can I detect this using my Arduino?


texts: I tried to get a panelized PCB from Altium using the embedded array option from the PCB Doc file. But, I get a continuous board edge around each of the PCB replicas: it would actually need mouse bites or tab routes or V scores. So, I imported the Gerber and drill files into Camtastic and deleted the board edges. I tried exporting the edited board edge file but gives me jagged lines all over. What should I do?


texts: Where do the return currents go for a MCU with multiple Vdd and grounds?

texts:
I am reading this article on mixed signal design: https://www.maximintegrated.com/en/app-notes/index.mvp/id/5450

When signals have really high speed, the return current will tend to follow right under the signal traces. Let's say a MCU has a SPI module. And power inside MCU is supplying the SPI module. The SPI module is then sourcing currents to an IC through signal trace A.

The return currents from the IC will try to follow right under trace A and go into the SPI module and then go into the power that supplying the SPI module.

The process is shown in the following diagram:

My question is: if a MCU has multiple Vdds, which power pin does the return current head to? In the following diagram, both pin 19 and pin 48 are Vdd for MCU. Which power pin supplies current for the SPI module?

I ask this question because I think it is highly related with PCB Layouts: where the return currents really go.


texts: Error when passing wire of different size to module input

texts:
I have a module to display a base 10 number on my 7-Segment display.

module displayN(input [13:0] n, input clk, input [3:0] an, input [6:0] seg);

    wire [3:0] d1 = n % 10;
    wire [3:0] d2 = (n / 10) % 10;
    wire [3:0] d3 = (n / 100) % 10;
    wire [3:0] d4 = (n / 1000) % 10;

    display4(d4, d3, d2, d1, clk, an, seg);

endmodule

It takes in a 14 bit number and computes the digits and hands it off to another module which actually displays it.

Right now I am working on a program which uses a USB-UART connection and displays the value of the last byte sent on my 7-Seg.  Here is my top level module.

module uart_top(input clk,
                input rx,
                output tx,
                output [3:0] an,
                output [6:0] seg);

    wire [63:0] count;
    wire [7:0] out;

    uart_receive r(clk, rx, count, out);

    reg [7:0] oreg;
    always @(out) oreg = out;
    displayN d4(oreg, clk, an, seg);

    ila_0 i(clk, rx, out);
endmodule

This code is currently working.  When the output of my uart receiver changes I copy the output to a register, and then send it to my display module.  This seems to work correctly when I try it on my card.  I am assuming that even though the module is expecting 14 bit it just fills 0 for the upper 14.  However, when I try to pass "out" directly to the module like displayN d4(oreg, clk, an, seg); I get some error about a black box.  Why can I do this for a register but not a wire?

Here is the exact error message I get during synthesis.

 [Project 1-486] Could not resolve non-primitive black box cell 'displayN' instantiated as 'd4' [/home/chase/vivado-workspace/UART/UART.srcs/sources_1/new/uart_top.v:37]

Here is the schematic.

Also here is the uart_receive.

module uart_receive#(parameter BAUD_RATE = 9600,
                     parameter CLOCK_SPEED_MHZ = 100)
                    (input clk,
                     input rx,
                     output reg [63:0] read_count = 0,
                     output reg [7:0] data);

    localparam SAMPLE_BAUD_RATE = BAUD_RATE * 8;

    reg reading = 0;
    reg [8:0] bit_stream = 0;
    reg [3:0] bit_index = 0;

    wire sample_tick;
    baud_gen#(SAMPLE_BAUD_RATE, CLOCK_SPEED_MHZ) s(clk,, sample_tick);

    wire baud_tick;
    baud_gen#(BAUD_RATE, CLOCK_SPEED_MHZ) b(clk, !reading, baud_tick);

    always @(posedge clk) begin
        if(sample_tick && !reading && !rx) begin
            reading <= 1;
            bit_index <= 0;
        end
        else if(baud_tick) begin
            bit_index <= bit_index + 1;
            bit_stream[bit_index] <= rx;

            if(bit_index == 8) begin
                reading <= 0;
                read_count <= read_count + 1;
                data <= bit_stream[7:0];
            end
        end
    end
endmodule

It seems to work if I remove the ila_0 i(clk, rx, out); which is the Integrated Logic Analyser I was using for debugging.  I always had out hooked directly up to it even when I was using the resister in displayN. I wonder why out could not be connected to both of them at a time.


texts: How to switch between two digital signals?

texts:
How can I switch between two PWM signals? I would like to control a servo motor by two different PWN source. these two PWN signals are coming from two PID controllers.

I want to switch between these two signals by an Arduino. here is a schema of what I want to do, but the problem is that I can't find the right switch.
what do you suggest?


texts: Is this a safe way to operate an H-bridge with SPDT relays?

texts: I am trying to create a circuit to drive a hand drill motor as seen in this drawing with just relays. The current formation to make it go forward, switching 2 and 3 at the same time to make it go backwards, and switching 1 to make it stop. I expect it to be ~18V at ~20A when running. Do I need flyback diodes for this to work correctly and if so how would I go making that calculation and selecting that part? When switching 2 and 3 at the same time is there anything I should be concerned about?


texts: PIC, SPI problem with SD card and other devices

texts:
I'm using a PIC24H as a master connected with a microSD card, ENC28J60 and a MCP28S08 port expander. I'm using the FatFs library for a microSD card and the Microchip TCP/IP stack for ENC28J60.
All works fine, but I have some little problems that I can't explain...

The main problem is that the microSD card fails the initialization. To fix this problem I have to put a pull-up resistor (10k) on SDI (MISO) line.
With it, the SD card works fine, and after initialization I can remove it and the card keeps to work, so I think the problem is really only during card initialization.

I can reset (MCLR) my PIC without a problem, but if I "power-on reset" (POR), it then I have to use the pull-up resistor.

Anyway, this creates another problem... If I use a pull-up resistor on the SDI line, then the MCP28S08 can't read the correct value of the GPIO port. To resolve this, I have to remove the resistor and then (without resetting the MCU too) starts to work good.

I noticed that when I remove the resistor and MCP starts to work, then I can add back the resistor without a problem because MCP keeps working... why? This make no sense...

My circuit is on a breadboard, maybe there are some interferences on my circuit?

Could it be a timing issue?

I think an oscilloscope can help me to find out this problem. Now I use a Saleae logic analyzer, but I can't find the problem with this, because it can tell me only when a signal is 1 or 0... Can a PicoScope 2104 USB oscilloscope help me with this?


texts: Can anyone explain this high-frequency "alien voodoo black magic"?

texts:
I was casually watching Mike tear down a spectrum analyser (13:30 is the relevant part, 16:50 is the awesome part), and he came across what he aptly described as "weird messed up alien voodoo black magic stuff":

As a layman, I can only nod in agreement with his description. Do we have any sufficiently experienced alien-voodooologists around to explain what this madness is all about?


texts: Regarding OFDM (Orthogonal Frequency Division multiplexing)

texts:
Could you please briefly explain the IEEE 802.11a OFDM packet structure? In particular,

What is meant by "symbol" here?
What is the purpose of the packet preamble?
What is a "short training symbol" and what is its purpose?
What is a "long training symbol" and what is its purpose?
What is a "signal field" and what is its purpose?

Why are we using 52 sub carriers in a weird way? I have searched a lot but nowhere could I find some basics. Could you please explain it properly?


texts: Ultra Miniature Coaxial connector what does 50ohm stand for

texts:
In my current project I designed a PCB board for the ESP8266EX chip. Instead of making an onboard antenna, like in the datasheet described, I have placed this
connecter. The goal is to be able to choose a bigger antenna with higher dBi.

Since the board will be placed inside an enclosure, I need to somehow connect the antenna with the connector via cable. The datasheet describes the antenna pin for 50 ohm impedance (when using the pi matching circuit). The connector on the lcsc page somehow says 50 ohm also. Does this mean, if I add a 50 ohm antenna, I'll have 100 ohm impedance on the pin that is meant to have 50 ohm on? Or does the 50 ohm impedance on the connector stand for the ability to connect a 50 ohm impedance antenna to it?

Thus further I'm not quiet sure how to search for the coaxial cable... nor the antenna. Big websites like amazon don't seem to have anything when searching for "Ultra Miniature Coaxial (cable)". Is there a special website for these type of applications?


texts:
I have the following exercise:

Design a circuit that takes a 2 bit binary and makes it x^3 (x cubed), using a decoder
of your choice.

I thought to do it with a 3 to 8 decoder, because I have 2 bits of input, and 4 bits of output, since the largest output is 11011 (which is 27 in decimal).

I have managed to get to a truth table. Input = \$x_0x_1x_2\$. Output= \$a,b,c,d,e\$.

\begin{array}{|c|c|c|c|c|c|c|c|}
\hline
 x_0 & x_1 & x_2 & a & b & c & d & e \\ \hline
    0 & 0 &0 &0 &0 &0 &0 &0\\ \hline
    0 &0 &1 &0 &0 &0 &0 &1\\ \hline
    0& 1 &0 &0    & 1 &0 &0 &0\\ \hline
    0 &1 &1 &1 &1 &0 &1 &1\\ \hline
\end{array}

However, I am not quite sure what should I do now. I have to get to a function to represent it in gates? How can I make a karnaugh map from that table?

I am aware that I would have to add three more outputs to the 3 to 8 decoder, but they will be just "don't cares".

Your help is appriciated.


texts: Charged capacitor doesn't allow impulses to pass

texts:
I tried this circuit and was confused about the theory of capacitors.

Here's what I'm supposed to do: on pressing S1, the capacitor is charged and the led blinks for a second. On pressing S2, the capacitor discharges.

When I try to press S1 without discharging the capacitor again, the led doesn't blink. Now capacitors are supposed to allow change in voltages across them i.e. the led should blink when the capacitor is charged, right? Why doesn't it?


texts: Virtual SPDT with half-bridge and op-amp comparator

texts:
I have the following circuit composed of an op-amp comparator and a mosfet half-bridge:

I would like to "confirm" the following:

if VBUS is floating, nothing will happen. Especially, there will be no current flowing from 4V2 (source) to SINK.
if VBUS is a source at 5V, then there will be current flowing from VBUS to SINK which voltage will be a little bit less but close to 5.0V. There will be no current flowing between VBUS and 4V2.
if VBUS is a sink, then there will be current flowing from 4V2 to VBUS which voltage will be a little bit less but close to 4.2V. There will be no current flowing between 4V2 and SINK.

If this is not correct, what is is wrong?

PS: Datasheets:
https://www.vishay.com/docs/70880/70880.pdf
https://www.st.com/resource/en/datasheet/lmv331.pdf


texts: I have a power transformer with 120 and 220 volt primaries for ~650 volt from the secondary.  If I wanted lower voltage from the secondary, is there any reason I couldn't run my 120 volt line voltage into the 220 volt primary of the trafo and achieve the desired result?


texts: Turning a Subcircuit block into a Transfer Function for faster simulation in SPICE

texts:
Is there a way to take a sub circuit definition (.subckt) and have SPICE (or in my case LTSpice) take the Transfer Function for it. Then have SPICE refer to this Transfer Function whenever a component with this .subckt definition is inserted in any schematic, the transfer function is used.

As far as I know, a .subckt can only be defined as a netlist, not a Transfer Function.

The real issue is that I'm having some trouble getting my circuits converging fast enough (simulation can take tens of minutes to finish). It's probably because I'm starting to use more and more constant current sources.

Any tips?


texts: How does the high inrush relay handle the inrush current?

texts:
I was searching through the high power relays(16A, 240AC) and found that some manufacturers have high inrush capability relays and that too upto 100A inrush current. Below are some examples (one is latching and other one is standard)

Pansonic https://www3.panasonic.biz/ac/ae/control/relay/power/dw/index.jsp

Omron
http://omronfs.omron.com/en_US/ecb/products/pdf/en-g5rl.pdf

Can someone help me to understand how these relays would handle the inrush current ? Some internal schematic if available ?

Also since these relays have 100A inrush, can they not easily work with 1HP (240VAC) pumps?


texts: Role of zener diodes accompanying High power UV Diodes

texts:
I am looking at the wiring diagram of two 1 W UV diodes and one datasheet suggests to put one zener diode in parallel, the other suggests to use two opposite zener diodes in parallel.

I am very curious and would like to learn something instead of blindly following instructions. Why are those diode recommended ? Why the difference between the two wiring diagram? Parts are similar and from the same manufacturer.

Also, it is not clear wether or not these zener diode are to be added in the electronic design or if they are included in the packaging. Does anyone know?

DATASHEET 1

DATASHEET 2


texts:
http://cactus.io/hookups/sensors/light/ldr/hookup-arduino-to-ldr-sensor

I have the following circuit which was running for a long time but at one point something broke and it started producing high values such as 4133 or 30412.

I used the recommended 10K pulldown resistor, although some other guides recommend 100k this setup was working for me for a long time.

What I use LDR is an unknown brand, something cheap chinese what you can pickup for arduino kits so I checked a generic data sheet:

Cell resistance
1000 LUX     400 Ω
  10 LUX       9 kΩ
Dark           1 MΩ

My measurements show something similar. If I put my finger on the LDR the dark resistance is around 0.3 Mohm and when I point a strong flashlight to the LDR the resistance goes down to about 800 ohm which seems to be normal for me.

While the circuit was working properly it always produced values from 0-1023 and dark usually meant under 200.

What can cause this?


texts:
I' trying to record guitar using line-in. But there's a noticeable noise in the recordings, and it is present even when guitar is unplugged (only cable is connected).

As you can see its clearly mains hum. But what I think is strange is that the amplitude of the hum kind of depends on how close I am to the cable.

At 2 seconds mark i moved away from the cable, then came back at around 20 sec, at 26.5 I laid my hand on the cable (on isolation, not on the plug), which resulted in that huge amplitude change (amplitude had been adjusted by me to show it more clearly).

Is there any way to fix this so I can record my guitar wihtout noise?


texts:
I'm designing an ATmega328 PCB with an optoisolated TRIAC controlling a 100W (~ 0.5A, 230V, PF = 0.98) load. I'd like to monitor the current with the processor and report an error if the current drops. The load is an electronic ballast driving 3 fluorescent lights and they are wired so that if one goes out, all of them go out. Therefore I only need to know if there is current present and not really measure it.
So far I've encountered 3 different solutions:

A current sensor IC like ACS712 that uses the Hall effect (I later found out that ACS712 is not suitable for mains voltage)
A shunt resistor with an opamp (galvanic contact problem due to Vcc on opamp)
A current transformer for galvanic isolation and shunt resistor like in the previous point

I have no idea which one is the easiest to implement (and cheapest) and which one is the safest. I'm not really sure about the exact circuits I should use for either of the solutions.
I'd really appreciate some help on this matter as well as an appropriate circuit. If there is more information needed let me know.


texts:
I'm trying to troubleshoot an inoperative dishwasher. The dang thing won't fill with water. It's a 2000 vintage machine. No solid state elements anywhere.   I've traced all the circuits. Chased down the obvious potential root causes.

Note those X elements are matching points that open or close depending on the location of the control cam.

One thing I'm very baffled by. The controller has a small 1/4 hp motor which spins the control knob 360 degrees at a very slow, geared down rate. My problem is that there are a few elements that are powered in parallel to this motor. With the motor in the circuit I read ~10 vac across the motor, where I'm expecting to see 120 vac.  I'm guessing because of that my solenoid water valve won't work.

I've never worked with AC motors before. Is this normal?  What is odd is that the motor appears to be working just fine. I'm not seeing any excess heat, etc.

Any ideas here?  Is there some sort of crazy internal components that would pull down the voltage under load?


texts: Best practices for electronic circuit designs for controllers with backplanes (PCB layers, decoupling, filtering, etc.)

texts:
I have been browsing for best practices for PCB electronic design for awhile. I'm an electronics engineer, a bit rusty (been more involved with PLC programming and project management for the past 10+ yrs), and I have made lots of microcontroller based circuits, most of them tested on breadboards but not many translated into final PCB forms, so I understand it is one thing to get something working perfectly on a breadboard and another very different reality to get it in PCB prepared for production. I'd like to hear best practices recommendations from the forum, as there is a vast number of highly experienced design engineers here and would also like to take your POVs into account, not just from literature (well links to literature also work). Recommendations for microcontroller based designs in regards to protection and robustness of designs, such as decoupling capacitors, where to locate them, most common values, mixed
signal PCB recommendations, number of layers and power/signal tracing locations, advantages of using discrete designs over off-the-shelf, what has worked great for you or has made a huge difference (whatever tiny the change), etc. that sort of input is welcome. Also, in particular, design recommendations for low speed comms (10 mbps or less) backplane designs and also application of fuse types and when to consider these, or harmonic filters or TVS protection in power lines is particularly appreciated.


texts: Why mah drops while charging 9v battery?

texts:
I made a simple 9v battery nimh and nicd charger according to this
Circuit

I modified it after it and i use something like the image

I need 16mAh per hour to charge a 160mAh 9v Battery and i manage to have an led as the image shows in it, but as i used my multimeter to measure the amps as the A sign indicates it starts charging at 16mAh and it drops down by 0.1 every some seconds in the beggining and as the time goes by it slowly again drops by minutes, after couple of minutes the 16mAh went down to 15mAh.
I can only imagine how the mAh will drop after an hour cause in order for my 9v battery to be fully charged it needs about 10 hours.

Is this normal or am i doing anything wrong here in the image circuit ?


texts:
As part of a college project I have to design a working Class-D audio amplifier.

One of the first challenges is to generate a triangular wave at a frequency arround 100kHz.

In order to do this I have in mind generating first a square wave (using a 555 timer in an astable configuration) and then integrate it. Then I encounter some problems:

The device has to be single powered (5V taken from a USB plug)
Becouse of that limitation I cannot use a simple Inverter Integration using an operational amplifier.

Any ideas on how to solve my problem?

Thanks in advance, and sorry for my bad english :/


texts: System Generator:How to know how many clock cicles are nedeed for my FFT block?

texts:
I would like to know how many clocks cycles the FFTv4_1 require?
Does anyone know how to determine the required clock cycles?  I am using the System Generator 9.2i version.

Thank you so much!


texts: Conductivity monitoring to detect integrity loss of glass coating of steel

texts:
I have an application where the integrity of the glass lining of a  glass coated steel vessel needs to be monitored.

In theory, once the integrity is lost anywhere there ought to be contact between the fluid inside the vessel and the underlying steel. The fluid inside is conductive, say water with salts in it.

In practice, would one be able to monitor the conductivity change and trigger an alarm?

To make the problem specific, say the vessel is 10,000 L capacity (cylindrical) and the glass lining is 2 mm thick (if that matters). Is it realistic to be able to detect a lining breach by monitoring conductivity?

Any other ideas for a detection system?

Alternatively, could the capacitance of the liquid-glass-steel or the air-glass-steel system be monitored? Would one expect the capacitance to change significantly if the glass gets a small breach?

To add more context:

If the breach in glass lining is detected early enough then there are ways to patch it up. Hence the goal is to try and catch the breach as small as you can. There's no breach that's too small since these linings are used in corrosive environments the smallest breach will allow the corrosive fluid to progressively eat away the underlying steel and then widen the breach.

i.e. It's only a matter of time for a small breach to turn into a large breach.


texts: Potential difference between these points

texts: I do not know how to approach this problem or which theory to apply. Could you please help me to find out the potential difference between the points A and B in the circuit given below.


texts: Can I exceed the 120mA per channel on the TLC5940 if I use external resistors in series with LEDs?

texts:
Datasheet

The TLC5940 drives 16 channels of LEDs at constant current using PWM. I assume the 120mA limitation per channel as described in the datasheet has to do with how much power the HTSSOP package can dissipate.

I'm trying to power LED strips of varying lengths on each channel of the chip, and these LED strips have current-limiting resistors integrated in them. Since the current is being limited by the resistors in the LED strips, can I go above the 120mA-per-channel limitation in the datasheet, since the dissipation is happening in the strips, instead of in the chip?


texts:
I am trying to analyze the I2C commands sent by a PC software to R3910 DSP chip

The software uses a programming box (provided by the same company that manufactures the R3910 chip) to communicate with the chip via I2C. The software can send commands to do things like mute/unmute the chip, change parameters, enable disable features, etc. The chip has dedicated SCL, SDA pins and logic high on these lines is around 1.29 V, logic low is 0.

I am using the Analog input pin of an LHT00SU1 logic analyser and PulseView software to view changes on the SDA and SCL lines. The SCL line seems to show a normal pattern, consistent with what would expect an I2C command to look like. A section of the total data collected on the SCL pin when sending the mute command from the PC software is given below:

The SDA line, however, looks normal at some places and distorted at others.

The first few cycles on hte left side of this figure look ok, and what I would expect on an I2C line, but in the middle the picture looks sort of strange, for example logic low not going all the way to 0, while at the right I am not sure what is going on at all. I get this same patern on the SDA line if the repeat the experiment with a higher sampling rate for the logic analyzer. I have seen a
similar pattern when viewing the SDA line using a high quality oscilloscope so I am thinking this is not related to the sampling frequency of my logic analyzer.

Am I getting the correct reading on the SDA/SCL lines?

The current hardware connection looks something like this.

simulate this circuit – Schematic created using CircuitLab

The pins from the programmer are connected directly to the I2C pads on the chip, while I hook the SCL, SDA and GND pads directly to my programmer. The actual circuit looks like this:

I have read in some blogs that I2C lines require pull up resistors, but the R3910 chip's sample schematics do not mention any pull up resistors. Plus I can control the chip using the PC flawlessly (so the I2C signal itself is not damaged) and the data in the SCL line looks normal as well, so I am assuming the chip has internal pull ups for the I2C lines. I connect the programmer with the R3910 chip on a desktop PC, while I use the logic analyzer on a separate laptop running on battery, so the logic analyzer and programmer are completely separated from each other (I read about grounding causing issues when connecting cheap logic analyzers and programmer for device under test to the same PC).

What is causing the distortion on my SDA signal and how can I make it look better on my logic analyzer?


texts: EMC considerations for driving a solenoid via PWM over a long cable

texts:
We're designing a circuit which essentially has the topology shown below. We're driving an inductive load (24V, 3.8Ohm solenoid - max avg current = 2A, but peak current can be 6.3A) using PWM. Unfortunately, the distance between the controller and the solenoid is quite large (8m).

simulate this circuit – Schematic created using CircuitLab

I'm quite concerned about the EMC implications of driving a high current PWM signal over such a long cable. I was thinking of mitigating it by doing the following:

Using a twisted pair cable to cancel out magnetic fields and eliminate electric fields
Adding large tank capacitors in parallel with the 24V supply and ground to reduce sudden current spikes going through the power cable. (Thanks to this post).
I can control the PCB layout at the microcontroller to make sure that the current loop for the PWM signal on the PCB is minimised.
I'll be adding unpopulated footprints for a series resistor and parallel capacitor on the MOSFET gate drive signal to experiment with reducing the edge rate of the PWM signal to reduce any high frequency components.

What other steps can I take to help avoid any EMC problems with this?


texts: I am new to electronics... Can a logical gate treat negative voltage as a logical 0 and the ground voltage as logical 1 ? Or should the voltages allways be between 0 and +12V ?


texts:
I am designing a 4-layer PCB with 16 channels of LVDS (differential signalling, 480MHz). My layer stackup is Signal-GND-Power-Signal. A microstrip design for the LVDS channels is usually traces over a ground plane. However, I was wondering if it was possible to also have a controlled impedance differential pair on the OTHER signal layer, in which the adjacent copper plane is NOT ground, but in fact a power plane (in this case 3.3V).

If this is possible, would it be a good idea for some LVDS channels to run above this power plane, but then on the subsequent connector (That connects these LVDS channels to another board), that connector is referenced to ground (ground lines distributed throughout cable to minimize ground loops, instead of the power rail)?


texts:
Lets take under consideration a 3 state buffer, such as this one:

Since the datasheet doesnt provide the information about the internal build of the buffer, I was wondering either it is safe to assume that in case the chip is not powered up (0V between VCC and GND), the output is in High Z state? Should one worry about any load at the outputs in unpowered state?

I imagine there is a mosfet P + N half bridge at the output.


texts:
I'm designing a circuit that has a built in single cell LiPo battery with its charger for a gsm circuit. The board feeds from a 12V power supply and uses the battery as a backup, and when the power supply goes out the battery must power the load and when the supply goes back battery should begin charging and the load should be fed from the power supply. I used two Schottky diodes to select between the two. But I'm not sure what is happening when the battery is being charged and powering the board at the same time. Another problem is that both regulator circuits supply 5 volts but how can I make it use the step-down regulator (power supply) when both regulators are working? My load uses 5V and 1~2A and maximum drop out should not get over than 600 millivolts.
Thanks

simulate this circuit – Schematic created using CircuitLab


texts: Commercial Availability of Bare Metal Automation Controllers

texts:
When I think of commercial automation controllers, I typically see 2 levels of system complexity.

First, at a lower level, PLC's programmable with ladder logic, structured text or another 61131-3 language.

Then, at a higher level, RTOS controller systems.

However, looking at the major commercial vendors (Omron, Mitsubishi, etc.), there appears to be a dearth of intermediate bare metal MCU automation controllers that allow full embedded programming in C or a comparable language but do not have a full OS. Such a device would achieve real-time control through a real-time clock and interrupts.

I can certainly conceive of industrial systems that require more complexity than what structured text allows, but not the full complexity of an operating system.

While this wouldn't be much more than an industrial i/o-ready Arduino or AtmelXMega pre-assembled with accessories, why don't major commercial vendors develop this line of products?


texts: If I change the hardware/chipset of a USB product, should I change idProduct or bcdDevice?

texts:
The product looks outwardly the same, with the same model number, but the USB brains have been completely replaced, and the circuitry's been modified to fit them.

The operating system needs to see different IDs in order to keep the drivers separate, right?  But should I change the PID/idProduct, or should I change the bdcDevice?  I'm assuming the real life consequences may be different from what the USB standard intended.

idProduct

Product ID (assigned by the manufacturer)

bcdDevice

Device release number in binary-coded decimal; silicon revision increments this value
0xJJMN for version JJ.M.N (JJ – major version number, M – minor version number, N – sub-minor version number)

Hardware Semantic Versioning suggests the major version number should be changed, at least.


texts: Meaning of transfer function in s evaluated at a complex number

texts:
From the pole-zero plot, you can compute the system frequency response by assuming a locus of test points along the \$j\omega\$ axis.

Figure from: http://web.mit.edu/2.14/www/Handouts/PoleZero.pdf

\begin{align}
|H(j\omega)| &= K \frac{r_1\ldots r_m}{q_1\ldots q_n}\\
\angle H(j\omega) &= (\phi_1 + \ldots + \phi_m) - (\theta_1 + \ldots + \theta_n)
\end{align}

This means that if I stimulate \$H(s)\$ with a steady-state sinusoidal input,

$$A\sin\omega_1t$$

at the output I'll get

$$A|H(j\omega_1)|\sin(\omega_1t + \angle H(j\omega_1))$$

Question

Evaluating \$H(j\omega)\$ means I'll get its magnitude and phase response when it is stimulated with a steady-state sinusoidal input

$$A\sin \omega t$$

If I evaluate \$H(\sigma + j\omega)\$, what kind of input does that imply?  Does that mean I would stimulate the system with a decaying sinusoid?

$$Ae^{-\sigma t} \sin (\omega t + \phi)$$


texts: Can we consider that ethernet or RS-232 (RS-485) networks have no ground connection between the two ends of each cable?

texts:
This is for a huge home theater.

I have a power transformer that converts 380VAC between two legs of a 3-phase power system down to 230VAC, with a center-tap of the secondary being our "neutral" for this secondary. (FYI, there are three such transformers, connected between phases A and B; B and C; and C and A. All this is needed.)

A hundred feet away we have a Lutron lighting panel that operates at 230 VAC from one leg of the same 3-phase power, on the same breaker panel, to neutral.

The lighting system is controlled via a Crestron system powered at the above-mentioned transformer, with control from the Crestron to the Lutron via RS-485.

If the RS-485 cabling makes a connection from the chassis ground of the Crestron system to the chassis ground of the Lutron, it looks like we have a HUGE ground loop. Hence the question, which I'd like to generalize:

Do ethernet, RS-232, and/or RS-485 essentially isolate grounds at the two ends of their cables?  Do they carry a ground through?  Does it depend on the equipment?


texts: Impacts of low-pass filter on micro-controller board

texts:
I have a micro-controller board, driving small DC servo motors and I control the angle via a PWM signal (50 Hz) and everything is alright.

However, there is an oil gas motor, running next to the board, causes the DC  servo motor to oscillate and a noise enters to my board.

I decided to to add a low-pass filter (L-C-L) after the DC regulated voltage (5v). I do not know the frequencies of the noise which are coming from that motor. So I am thinking to put a low-pass filter with 10 Hz as a cut-off frequency.

Would my new filter attenuate that PWM 50 Hz signals that drive my DC servo motor. Furthermore, the controller is running on a 20 MHz, would the filter degrade my controller performance ?

If the filter would not work, I guess I have to know the absolute range of frequencies I should band and then use EMI beads which block only a specific range of frequencies.
But the problem is that the range of noise frequencies can not be determined.


texts: Do i need a resistor in this led circuit?

texts:
I have made a circuit with two (3v) LEDs in series. Connected to a 5v supply from an adapter with usb. (1.5Amp)
I belive in series circuit each led gets around 2.5v which was enough to light them. However they both burned out after a short while. With Ohms low it would mean i dont need a resistor in this circuit! But now i think I should need one. Confused as to which resistance to choose and how to place this in this series circuit!?!!!?
Please help
I know its might be a very basic question!


texts: Page 18. of http://www.ti.com/lit/ds/symlink/tlv5606.pdf shows a polarised capacitor. In a case like this, does it really matter whether the capacitor is polarised or not, as long as the capacitance value is as specified?


texts: Low/Mid/High 230V Fan Control with RaspberryPI

texts:
I have fan 230 VAC 300 W, Relay SRD-05VDC-SL-C, and RaspberryPi,

what other equipment i would need to be able to control Fan 230VAC with RaspberryPi?

I want to go 0/1 with relay, and in mode:1, be able to control Low/Mid/High Fan Speed.

Thanks


texts: I need to be able to power my office pc up from home so I can remote in, but my router has proprietary voip firmware that's getting in the way.  I've been looking and looking, but I'm just not turning up a solution.  I wish I could figure out a way to get a low-power gadget connected to the internet so I could remote (telnet? ssh?) into that and get it to power a relay on the pc's power-on button.  Any suggestions?


texts: Dead or alive: Operational transconductance amplifier

texts:
My first experience ever with an operational amplifier was with an LM3900 from a Philips experiments kit and these kits date from a long way back in time, when I was a young boy in primary school.

I rarely see designs with operational transconductance amplifiers. Are these type of devices (not necessarily the exact type mentioned above) still being produced, newly designed? Is it worth the effort to design a new circuit with them or are they soon to be remembered in melancholy?


texts:
I hope this is a pretty easy question for you guys.

I know for frequency modulation (FM) for fundamental frequency you have the expansion

$$output = J_0(\beta)V\cos(\omega t)\pm J_1(\beta)\cos((\omega \pm \omega_m)t)+...
$$

I am wondering what is the equivalent for the third Harmonic?  is it

$$output = J_0(\beta)V\cos(3\omega t)\pm J_1(\beta)(3(\omega \pm \omega_m)t)+...
$$

or

$$output = J_0(\beta)V\cos(3\omega t)\pm J_1(\beta)((3\omega \pm \omega_m)t)+...
$$

thanks for your input.


texts:
I have a relay that I picked up from Radio Shack a while ago, and now I have a use for it, but I don't have the datasheet, and can't seem to find it online.

The top says GEO 3F-12V3
Below that it says 12VDC, which I'm hoping it's the coil voltage.
Near the bottom it says 15A 125VAC.
It is a SPDT relay, if that helps.
I just don't want to over volt the coil.


texts: CAN BUS Termination Resistors For CAN Logger Device

texts: I am making a CAN logger device that will be connected to the vehicle OBD port. Since the CAN bus inside the vehicle is already terminated, do I need to terminate the BUS lines on my device end, right before the line feeds to the CAN Transceiver? Please check the attached picture. The J1939+ and 1939- are the BUS lines available on the Vehicle OBD port. I have read that if the stub lines are not too long(<0.5m) , termination is not needed. The stub lines in my case is much less than 0.5m.


texts:
Can someone explain what "common-mode" noise is, and how it can be problematic?

I understand "noise" on a signal in general.  If I have a "noisy" +5V rail on a circuit board, I'm not going to be getting a constant value of +5, it will be bouncing around above and below that nominal value... ... but still relative to circuit COM.

My very vague understanding of "common-mode" noise is that it is where both sides are varying equally together.  (This is where my understanding breaks down)  That is, the pair is bouncing around with respect to ... ... to what?  Earth ground?


texts: Crystal oscilator not oscilating on a PIC

texts:
I am experimenting with a PIC16F84A at the moment.

I can get this working fine using an RC network for the clock.

When I switch to using a crystal (the usual xtal across pins 15&16 with 2 caps going to ground from the same pins) I am not getting any clock at all.

The PIC is the 20MHz version, and I have tried all the crystals I have - 4MHz, 14.3MHz and 25MHz, and numerous different capacitors rangeing from 22pf right up into the uF range, but all I get is what appears to be a logic high on pin 15 and a logic low on pin 16.

Yes, I have changed the program config to be _XT_OSC (I have tried them all), but to no avail.

I am using gpasm to assemble the program and pk2cmd to flash the PIC in circuit under Ubuntu.

Any clues?

Edit: diagram:

            22pf
16 o----+---||----+
        |         |
        -         |
       |=|Xtal    +---+
        -         |   |
        |         |   _
15 o----+---||----+   - GND
            22pf

(a little crude, I know ;) )


texts: When would I use a voltage regulator vs voltage divider?

texts: When would you use a voltage regulator vs a resistor voltage divider?  Are there any uses for which a resistor divider is particularly bad?


texts: How much power can a thin wire handle before heating too much?

texts:
If I have a copper wire 25um in diameter and 3mm long, and I'm running AC current through it at 3GHz, how can I calculate how much it heats up given a power and duration? The wire is immersed in oil at room temperature, and I don't want to burn the oil, even at the wire's surface. The oil has dimensions about 3mm\$\times\$3mm\$\times\$0.15mm and is in contact with a large chunk of aluminium on one of the flat sides (the wire is suspended about 0.1mm away).

Eg. 16W @28Vrms for 10us (it's a 50ohm system) with 50% maximum duty cycle

Is  this something I can look up, or do I need to plug it into a simulator?


texts: What is this adhesive tape that comes in some parts?

texts:
I think this is a Mylar tape, but why they come with it? I guess its so to make the Pick and Place machine job easier?
And why is so common to find them holding cables inside some laptops? Just because they are fire resistant?


texts: While solving this question using Quine–McCluskey algorithm , I am getting total EPIs as 3 but by definition , it is giving 2 EPIs. I am attaching both solutions. Please correct me where I am wrong.


texts:
I was thinking of building a DIY IR Spectroscope but for this, I need to find an IR diode that can do variable wavelengths. So far I have looked at Farnell and Mouser but all the diodes I have looked at seem to be fixed on a wavelength.

Is this possible? or would I need some sort of filters and optical equipment, if so which parts would I need?

Thanks.


texts: Routing USB, DVI and Ethernet signals on a large PCB vs using long cables

texts:
Properly routing USB, DVI and Ethernet signals over long distances (30 to 40 cm) on a PCB seems to be relatively challenging (skew, characteristic impedance, cross-talk, etc.). Yet using the standard off-the-shelf cables appears to allow proper signal transmission over meters without putting too much thinking into the design. (see for example USB tech doc suggesting 18inch as max trace length on a PCB http://www.usb.org/developers/docs/hs_usb_pdg_r1_0.pdf but most USB cables easily going beyond this value).

Do our colleagues here with experience in high-speed signal routing agree? Are USB/DVI/Ethernet cables a trivially easier solution for tens of cm? Intuitively shielding of a cable against EMI and cross-talk seems easier than achieving the same performance with a 4-layer PCB. But then skew control seems easier with PCBs than with twisted pairs. Are we overdoing it by trying to route USB, DVI and Ethernet over 40cm instead of just using cables, even if somewhat untidy inside a production quality enclosure?

How would a top tier design team approach the PCB routing versus cable decision for 40cm signal paths inside an enclosure?

thanks in advance for your comments

Addtional info:
To answer the question why I need to take USB/DVI/Ethernet signals as far as 40cm on a PCB, consider a medium size (40cm wide x30cm deep) lab instrument enclosure with a front-panel TFT and multiple back-panel USB/DVI/Ethernet connectors. The MCU/CPU on the main PCB needs to be within 5cm or so of the front-panel TFT (limited by the available flat cable) but the interface connectors need to be at the back of the instrument, >30cm away from the MCU/CPU providing the interface signals. Internal cables are clearly a possible solution. But given the dimensions of the enclosure and internal PCB, routing end-to-end is also possible. The question is, what would be best practise: cables or routing on a large PCB?


texts:
I designed a 50 Watt voltage doubler rectifier with rated input 12 VAC and output 48 VDC. The circuit configuration and simulation result are presented in figure below.

2 unit IRFP460 power MOSFET implemented in this rectifier as switching component. These switches are driven by TLP250 with Vcc = 18 Volts.

I checked MOSFET's gate-to-source voltage (Vgs) and found that there is an unexpected transient voltage at rising and falling edge.

What is the effect of this transient voltage to rectifier circuit? Can it affect the value of input current and output voltage?

This is full configuration of circuit.


texts: How to do thermal analysis of a P channel high side drive circuit.

texts:
I have to design a PCB where one of the features is such that every time a stepper motor is moving a fan switches on. A high side P channel FET driver has been suggested as shown below:

I just need to know what kind of heat this switch will be producing. I know it will only be very small given that FETs are low power devices but I am struggling with this basic theory a bit. It doesn't say what the drain to source resistance (Rds) is for when Vgs is -12 V it only gives to for when Vgs is -10V and -4.5V.

None of the graphs give this information either. I figured that if I knew Rds on for Vgs=-12V I could calculate the power dissipated across the FET (If i can also find the drain current at this value as well) and thus find the temperature at the junction using the thermal resistance of the part (159 degrees celcius per watt).

I am just very inexperienced at reading data sheets and would appreciate it if someone with more experience could push me in the right direction.

https://www.diodes.com/assets/Datasheets/DMG2307L.pdf2

Thanks,

Simon.


texts:
This is more of a general question of the embedded electronics industry. At the moment I'm planning on building a device with a similar requirement to the Nest products. Essentially, I want to have a WiFi hotspot from this device that I can connect to with a nice browser UI and can see live sensor data.

My initial approach was to use an Arduino and an ESP8266 to achieve a prototype and then to create a PCB using just the Arduino's ATMega328P MCU with the ESP8266. However, I soon realized that displaying nice interfaces and incorporating a standalone ESP8266 IC itself on a single all-in-one PCB isn't really possible.

I'm now looking into use an ARM Cortex based chip like the STM32 which is what Nest actually uses in one of their products along with another ARM Cortex based NXP chip. After looking through STMicroelectronics site, I could only find full WiFi modules compataible with the STM32. There was no WiFi IC or anything.

I see so many companies that have these really nice UIs and intuitive ways of connecting their IoT to your home network with a nice browser setup process. However, when you look at the hobbyist area, it usually only has a single browser page with one text line displaying the sensor data.

My question is: is it feasible for a single individual to be able to produce a standalone product with a single PCB that incorporates an MCU/WiFi functionality for IoT operation? And if so what's the best route for me to go?


texts:
I'm working on a project that involves multiple (many) BGA packages, namely interface converters such as Ethernet PHYs connected to a central FPGA.

I've already worked out a (tentative) layer stackup in terms of what signals will run over which layers, but I need a good strategy for assigning pins. Obviously, a PHY will fan-out in a pretty distinct order, but I'd like to have a decent idea of how to assign the pins in an informed manner so that way I'm not having to get shifty with vias to rearrange the trace order during the layout.

To illustrate, the interface I'm working with is standard GMII, so a 16-bit bus with control signals. What are some good methodologies for assigning pins from an FPGA that correlate into the most logical fan-out order for traces leaving the FPGA?


texts: Incorporating ALD1106 SPICE model in LTspice

texts:
I'm trying to incorporate a SPICE model of an NMOS IC, the ALD1106. I've used it before in class, but it's been so long that I've forgotten how to incorporate the files into LTspice in order to properly use it. Luckily, I found some SPICE models from ALD's website located below:

Link to SPICE models here

I've extracted the files, and I've included the following files in my schematic with the '.include' command: ALD_TECH.TEK, IC_TRAN.lib, and Ic_mod.lib. I've also opened up IC_TRAN and created a component model of the 1106 with the correct pins and everything, but I consistently get a warning that it can't find the definition of model "DPS". Can anyone please give me some advice on what to do next?


texts: How does this op-amp photodiode circuit behave?

texts:
I am trying to understand the inner workings of a photoelectric object sensor I have in my hands. (modulated with 24 kHz) Here is the very beginning of the receiver part:

simulate this circuit – Schematic created using CircuitLab

This doesn't look like other photodiode detection circuits I have seen around. This actually doesn't look like anything I saw before. It seems like there is a band pass filter in the non inverting input. Then, the filtered signal is amplified by -10, and sent to the output.

Am I correct?
What are the pros/cons of this configuration against other classical photodiode configurations?
How can I calculate the corner frequencies for such a band pass filter? (If it is one)


texts: Transmit power vs. Transmission power, is there a difference?

texts:
I was reading a scientific paper, and the authors sometimes use the term "transmit power" and sometimes "transmission power".

Is there a difference in terms of correct English usage?

Examples:

  we propose to adjust the transmission power used for...

.

  we propose to use transmit power control in order to...

.

  a higher transmit power of a sender should not be...


texts: Can I use lithium coin cell battery CR2320 for discharging about 80 mA at 3 V?

texts: I need to use a coin cell battery as a source for supplying 3.0 V at about 70-80 mA for about 2 hr per day. The coin cell battery I want to use, its spec sheet doesn't tell me much about what I want to get out of it. Here is the data sheet link: http://data.energizer.com/PDFs/cr2320.pdf. 80 mA seems a lot for me for this little coin cell batteries as they are only used for very low power electronics but I am not quite sure if it could be applicable to my case as the data sheet is not very clear to me.


texts: How to choose ADC Anti-aliasing filter cut-off frequency in thermocouple readings?

texts:
I am reading a thermocouple in an industrial environment. Thermocouple output is read twice a second. ADC performs 50/60 Hz filtering internally.

I had the intention of using a filter with a cutoff frequency between 10-100 hz (not Kilohertz) to completely filter out most frequencies, but Many circuits that I have seen have simple RC anti-aliasing filters with cutoff frequencies higher than 1khz. Am I missing something here or is this simply due to those circuits having a much higher sampling rate? In other words, what problems could arise if I use a filter with very low cutoff frequency?

Sample filter circuitry shown in red below:


texts: SPI and UART of atmega32 were not working when atmega32 was interfaced with ad7705

texts: I was trying to read 16bit ADC ad7705 by atmega32 and send the value read through SPI communication of atmega32 to real-term software by using UART of atmega32. I found that there was no transmission of data. However, when I wrote a separate program for atmega32 with its UART only(no use of SPI in the atmega32 program), it was sending data in real-term. Can anyone look into this problem and advise me the necessary steps for making SPI and UART of atmega32 work together?


texts:
In a circuit the voltage drop is equal on all main "branches".

In this diagram the Zener diode has 3.6 break voltage:

simulate this circuit – Schematic created using CircuitLab

In the example above I can calculate that the voltage drop on R1 will be 5-3.6=1.4 and current 1.4/100 A. On the second branch the voltage drop on R2 will be 5V. This would imply that if I lower R1's value, the voltage drop on R2 should still be 5V. But if I reach a short-circuit state(resistance very small) then of course I am wrong about R2.

Where am I wrong? I think some infinity case will arise about the current in the second case which would allow an exceptional case about the voltage...

Note: I am most certain that a simple Kirchhoff rule would solve the problem but I am more interested in solving this with Ohm's law and common intuition(like voltage splitting in an intersection and currents adding to zero in nodes)


texts:
For a lossless line, you have \$Z_0=\sqrt{\frac{L}{C}}\$ and \$VF=\frac{1}{c\sqrt{LC}}\$.

For a line with R, L, G and C parameters, we have \$Z_0=\sqrt{\frac{R+j\omega L}{G+j\omega C}}\$.
But how the formula changes for the VF parameter?

Considering the coaxial cable example, one could say the VF not only depends on \$Z\$, but also in the geometry of the cable, hence a more real expression for VF do not exist?.


texts: What code issues could persist past a reset? (STM32F103)

texts:
I have a project running off a Bluepill board (STM32F103C8T6) that ceases to function only after it runs for ~6 hours. Up to that point it behaves totally normally, and UART logs don't indicate anything out of the ordinary until it just stops. This has made it very painful to debug since it's so difficult to gather information and attempt iterative solutions.

The only lead I have is that when I find the device in the hang state, it cannot be reset properly. In the first few (correct) hours of operation, rebooting the device plays a speaker and blinks an LED. After the hang, resetting results in a solid LED - no sound, and no operation past that point.

Only when I power cycle the device does it return to normal operation, and then everything works exactly as I want it to for another ~6h before it hangs again.

Conventional wisdom would suggest this is a memory leak or a timer overflow, but I don't see how either of those could persist past a system reset! The Bluepill is attached to I2C and SPI devices, but even when those are removed from/returned to the circuit it does not reset properly, and there's nothing else in the circuit that can hold state. I've also heard that an unconnected VBAT could cause this but it's connected to VDD, and reading the datasheet shows no unexpected NRST behaviors.

I'm reluctant to post all 250 lines of code for this project because I haven't been able to narrow down the cause of this at all, so I'm trying to stay general with this question. What kinds of code bugs are capable of surviving an MCU pin-based reset, but not a power cycle?

EDIT: Here's the schematic. VBAT was manually connected to the 3.3V pins later.

EDIT: This is terrible form for stack overflow but here is a pastebin of the code. I hope to condense this to only the problematic code ASAP but due to the massive repro time I've had issues narrowing it down.
https://pastebin.com/nKDyzRKa


texts: What would be the waveform of output coming from rotary spark gap with ac input?

texts:
If I have an input of ac current 50/60 hertz into a capacitor of 40nanofarads and after that a rotary spark gap(2000-5000 discharge per second) , what would be the waveform of output? And how will the waveform change in case of static spark gap?
I am trying to understand tesla coil.


texts: What is the difference between ID-1 sim & Plug-in Sim cards?

texts:
Firstly, please forgive me if this is not the right place to this question. I was confused and couldn't understand where to ask this question.

I want to know in simple terms, what are difference between ID-1 sim cards and Plug in sim cards.

I found the gsm standard documentation from here. Please tell me the difference between ID-1 sim & Plugin sims


texts: Interfacing Vernier equipment and microcontrollers

texts:
I am the president of my high school's robotics club. We own several VeX robot kits which we have been using for a few years now.  The physics department also owns several Vernier LabPro sonic rangefinders. To save money, I want to be able to utilize the rangefinders in a navigation challenge. However, I do not know if it possible to do so mostly in software, i.e. without constructing interface boards.

The Vernier website provides that the five applicable pins are Echo, Init, AutoID, V+, and GND, in that order.  My question, for anyone who is familiar with this equipment, is: is it possible to connect to these pins through the inputs and outputs on a VeX so that the incoming data (Echo, I believe) can be used for ranging, or am I asking too much of this hardware.

Thanks in advance.


texts:
Goodmorning all,

Here my very first question so I may be asking something that is may be already answerd but I couldn't find,

My question is : How is current limiting achieved in modern IGBT based welding equipment? I do have a DC TIG welder myself and I am just curious how to achieve a max current setting from let's say a very wide range between 5-180 Amps?

I have googled quite a lot but I can't find anything that is helping me understanding this aspect of power electronics

The only thing that gets close to it is the  CS8312 that controls the gate of the IGBT for a specific max current through the IGBT.

Any help suggestion is appriciated!

Cheers


texts: How should I isolate AC and DC on a small PCB?

texts: I am designing a small PCB (1"x1") and it will have some DC logic traces (5V and GND) and some high frequency AC power traces (100V 1000Hz 50mA). Are there any special considerations I need to take for isolating these from each other, more so than I do for a typical all-DC board?


texts: Shielded twisted pair balanced transmission line implementation

texts:
I want to send a signal from board 1 to 2 through 20 cm line. I have four channel in differential, First I add them, can I send them through shielded twisted pair like this:

Do I need a buffer? why?
Is R14 and R13 needed, since obviously the resistors are in balance? Why?
How we can create controlled impedance twisted pair? but I think it's needed if we have such small wavelength compared to transmission line.

Some note:

R12,R3,2 is for level shifting and balancing load.
+ = 4.5 V, - = 0 V
receivers resistors can change to be the same in top and bottom entrance.(I don't know what impedance is good, isn't it the highest?)
transmitters resistors can be changed to determine transmitter impedance.(I don't know what impedance is good, isn't it the smallest?)
My summing amplifier reference:

Here I want to trick and move OpAmp in receiver side, but I'm not sure is it possible to move that in other end of balanced line?
also there is other question about summing.


texts: New multimeter probes don't fit my multimeter

texts:
This seems like a silly question, but my research is failing to yield results...

I ordered some new probes for my multimeter because I needed things like alligator clip leads and the little wire clips instead of just the pointy spikes.

Problem is they don't fit. Well, ok, they do "fit" (I can insert the plug in the hole) but the contacts don't touch, rendering them useless.  Looking at other sets of probes, they all seem to have this sheathed attachment, and none have the simple banana plug that the default probes came with.

Is this multimeter just too low end to fit standard probes?
Are there multiple multimeter probe plug standards?
What is this plug called so I know what to search for? (ones a "banana" plug, right? What's the other?)
Are there adapters I can buy?

Success!


texts:
Okay so I was replacing some sockets the other day and accidentally got a small shock (for some reason one upstairs socket was not connected to the upstairs sockets breaker...)
Anyway I only felt a small tingle in my finger and I'm trying to discern what happened. I was sat directly on top of carpet, and the breaker did not break upon being shocked. Which of the following is correct:

If I only touched one wire it must have been the live wire. The only way I could have felt a shock from the neutral is if there was a significant current draw elsewhere, but the property is empty with next to no appliances plugged in. So it must have been the live. In that case why did I only feel it in my finger? The current would flow down my arm to my legs and to ground. I get carpet is a great insulator but even so surely I should have felt it somewhere other then my finger? Also shouldn't the breaker have switched upon current flowing down live but not detected back on neutral (even if this current was tiny)?
I somehow bridged live and neutral with my finger. The current only flows between a small section of finger and thanks to the high resistance of my skin only a small current flows. The breaker doesn't switch because this is perfectly normal behavior. What I don't understand is from what I have read I would expect my finger to at least burn slightly, rather than a small tingle and no discernable mark on my finger. Also since I would have to have touched one wire first (law of probability) I suppose it would have had to be neutral then live (else we're back to 1)?


texts: Standards Compliant High DC Load Safety Interlock System

texts:
I have a single AC-DC supply (42V @ 600W) which supplies three motive loads. Each motive load is physically separate and has its own cover which prevents the operator from gaining access to the moving parts.
Opening one of the three covers should result in the motive power being removed from the exposed moving parts, but the remaining covered loads can continue to operate.
Functionally, this is not a problem. Three safety approved interlock switches used with each cover which in turn control one of three 30A automtive style PCB mounted relays. All done. The single 'bulk' DC rail goes to all three relays and then each of the three loads is powered according to whether its cover is open or not.
But...doing this in an approved manner is tricky. I'm talking IEC 62368-1:2018 (3rd edition) here, the replacement for IEC 60950. This demands that any relay used for interlocks is subject to its own approvals (IEC 601810-1). I have yet to find a relay that can break this level of DC current (~18A) which carries this approval.
So, I looked at the problem from a different perspective: choose a modular AC-DC supply for the 42V@600W (notionally three off 200W 42V outputs) which can then have their ENABLE signals controlled by the state of the cover interlock switches. Nice work, you say....and I would agree until I start to speak to PSU manufacturers who then point out that their enable inputs are not rated (approved) for use as interlock inputs. Doh! (it's a single point of failure issue; an opto-isolated enable input can have its optotransistor outputs shorted together, thus rendering the enable input disabled!)
So I really don't want to have three separate AC-DC PSUs with a safety interlock on the mains input side, but this is the solution I appear to be converging towards....really? What have I missed?
I cannot be the first person to come across this issue - so why the blank faces everywhere?


texts: Help identifying potentiometers or switches on an old oscilloscope

texts:
Im completely rewriting my question to better clarify my question.

I came into possession of a oscilloscope and tone generator (see below) from the early 1960s.  They didnt work and upon looking at the 1960s electronics inside, I had no desire to repair them.  However, they would be great for an Arduino or Raspberry Pi.  I am going to restore the outside of the units.  I decided to gut the insides of both units, completely stripping the electronics out.  After researching the units, I found out both of these were kits that someone put together and soldered by hand.  I applaud whoever did this, they had far more patience than I would have had.  The original owner is probably turning in his grave after what I did to his equipment.  Actually, there is chance he might still be alive.  But I digress...

As I said before, I am not trying to repair these units.  They have been stripped bare.  I removed the knobs from their posts.  I was able to clean and restore the knobs.  Since the knobs have a distinct look, I wanted to use them if possible.  I want to put some modern switches/potentiometers in their place and attach the old knobs to them.  The posts look like the picture below.

So I was asking what is the name of the parts I should be looking for?

Dampmaskin answerd the question in the comments saying D-Shafts.  Many of the original dials are doubled up, with one dial pointing above and the other pointing below.  If I can find a D-shaft that can accommodate both, that would be awesome.  However, I would settle on removing the bottom dials if I need to.


texts: How to load immediate negative value in a register?

texts:
For example on 8-bit AVR given a register r16 I do something like ldi r16, 44 and this way I can give it positive values from 0 to 255.
But if I want negative clearly in two's complement I can get a range of -128...+127 but I can't do that like.

ldi r16, -13

And furthermore how does the microprocessor know whether I want all 8-bits for positive 0...255 or negative -128 to 127? Thank you very much for your help.


texts: What are the effects of the different design parameters when building a linear motor?

texts:
I am trying to build a so-called "ironless" linear motor. Conceptually, they are quite simple. Linear motors, generally speaking, are just like rotary motors but "unrolled." As I understand it, the ironless variety is composed of bare coils of wire embedded in a resin matrix. Unfortunately, there is where the simple part ends. Roughly speaking, it follows intuitively that the more powerful the magnets, and the closer the coils are to them (because of the inverse square law), the greater the force of the motor will be. Obviously, the magnets and coils should also be as uniform as possible to ensure that the behavior of the motor is in turn uniform.

In essence my question is this: for magnets of an arbitrary strength and dimensions, what is then optimal coil design? What gauge of wire, how many turns, what diameter/width/length, etc.?


texts: Linear power supply and mains filtering and protection

texts:
I'm designing my first linear power supply for my project which needs dual rail 12V (the regulation from 15V to 12V is on another board, 7812 and 7912).
The +12V (+15V) rail will draw about 250mA, the -12V (-15V) rail will draw less than 10mA.

My main goal is robustness and reliability. So I put effort to mains filtering and protection.
There is no specific noise I want to protect from. Just noise and spikes that are reasonable in standard household.

I went through many schematics from the internet.
This is what I have created so far:

(I do not have 3D model for the transformer, so it is not rendered in the middle)

Did I make some obvious mistakes here?
Or are there some reasonable improvements to make (to improve reliability, and safety)?
The X1 and Y1 capacitors have to have specific value? Have to be calculated? Or it just almost doesn't matter?


texts: mysterious gadget That makes whinnying sound. help identifying circuit board plz

texts:
I found this little gadget in one of my spare rooms in a bunch of old electronics and cords. I didn't make it and I don't know who could have. I've tried identifying it and nothing.

I put a little power to it and it makes a whinnying sound. I will take pics of it from outside then the board. Someone went to great lengths to close it up used a thick black composite maybe jb weld? I had to shave down and cut into the end in  order to open it.


texts: How much current can a computer power supply deliver when used as differential power supply?

texts: I have a computer PSU which has +12 and -12 volt rails. Although on the side of the supply it says that the -12V line can only deliver 0.5 A, I have tried connecting the +12 and -12 lines across a 5 ohm resistance in order to get 24 volts across it, and when I measured the current it said 4.6 A. Why does this work? How safe would it be to use this method to get 1.5 A at 24 volts for longer time intervals?


texts: Delay function in Arduino microcontroller

texts:
Arduino IDE has a "Blink without Delay" example code. In here it comments:

  "Turns on and off a light emitting diode(LED) connected to a digital pin, without using the delay() function.  This means that other code can run at the same time without being interrupted by the LED code."

Could you give me some insight what is meant here?


texts:
I am using this(also below in question) circuit to drive a motor, and I heard I should put a decoupling cap in there to smooth out voltage spikes. I have been told to put it close to the ic, and I have also been told not to put it in front of the ic, but between the battery terminals. Where should it go? Here's an image of how I have it worked out on the breadboard:

circuit:


texts: More energy efficient: writing in a SD card or transmitting by BLE for long period?

texts:
I need to store about 1 adc sample per second on a wireless project for about 10 hours. The problem is the energy. What is more efficient a constant transmission on BLE or writting each second on a SD Card. Also I was thinking in two boards that can do the job because it has all in in them (The SD module and the BLE module)

RedBearLAB for BLE Alternative

or Adafruit Feather M0 or Adafruit Feather 32u4 for writing on SD


texts: AVR Atmega164P UART / ISP programmer problem

texts:
I am having a problem with the USART on an Atmega164P.  When the ISP programmer is connected everything works fine.  If I disconnect the programmer then all I get is garbled serial and the chip won't respond to characters that I send.  Here's the code

void USART_Transmit( unsigned char data )
{
/* Wait for empty transmit buffer */
while ( !( UCSR0A & (1<<UDRE0)) )
;
/* Put data into buffer, sends the data */
UDR0 = data;
}

void sendString ( unsigned char str[16] )
{
    int i=0;
    for ( i = 0 ; i < len ( str ) ; i ++ )
    {
        USART_Transmit ( str [ i ] );
    }
}

Assorted functions call sendString and they all work fine until the programmer is disconnected.  Then nothing works.

The connection to the PC is a USB->TTL Serial adapter.

On the electrical side I've checked for common ground / ground loops, different voltages on the programming pins, and other inputs that might be affecting the programming pins.  Nothing is connected to the programming pins except the programmer itself.

We also tried plugging the programmer into a USB wall charger.  This made the chip function as expected, as did connecting it to a laptop running only on battery.

We also connected the RESET line to VCC both with and without a pullup resistor, neither of those tests yielded successful results (still received garbled serial).


texts:
I am working on a Robot-project where a sub task is have to check how many and which RFID-tags are placed in a bucket.

Multiple tags will be placed into the bucket - so I run into the problem with RFID-tags colliding with each other. The reader will be connected and programmed via Raspberry Pi. From my research so far I have come up with the following 3 options:

1 RFID reader at the buttom of the bucket. This has to be a reader able to read the multiple tags at the same time, since the tags will be laying on top of each other. Example of reader: https://www.sparkfun.com/products/14066

2 RFID reader on the side of the bucket. Should read the tags passing by as they are thrown into the bucket. Would not required that the RFID reader is able to read multiple tags at once, but the reading should be fast enough to catch them passing by. Example of reader: ADAFRUIT PN532 NFC/RFID

3 Same concept as 2 but minimizing the space and using slides to hopefully give a bit longer time for reading the tags. Example of reader: Same as in 2

I am aiming for the most simple and most secure solution.

How would you guys do this, and what kind of RFID hardware would you recommend to go with the Raspberry Pi connection.


texts:
I did an experiment on full-wave rectifier with capacitor, and trying to calculate the energy that the capacitor supplies to the output.
The picture above is the graph that I got through an experiment (full-wave rectifier) using logger pro.
The red line shows the normal output without capacitor, and the blue line shows the smoothed output with capacitor.
The question I want to ask is that, is there a formula/equation for solving the energy supplied by the capacitor? I want to find the area bounded by 2 lines (Integral of blue line curve - red line curve).

The AC supply was 60hz and 6V.
The capacitance for capacitor is 100uF


texts: (Very Basic) Confused on Reading a Datasheet and Calculating Inductor Ripple Current for a switching Regulator

texts:
I am using this component for a project, however, when reading the datasheet I have just become confused about a couple of things.

Datasheet : http://www.ti.com/lit/ds/slvs569f/slvs569f.pdf

I am just trying to calculate the output voltage ripple for my Cout capacitor. Just say the ESR was 0.05 ohms, for example, is the inductor ripple current :
(IL1(pk)-ILoad(max))*2. Hence say ILoadmax was 1A, then just say I get the IL1(pk) as 1.2A. Hence is the inductor ripple current referring to the peak to peak inductor ripple current? So it would just be 0.4 A? Hence the output ripple voltage would be 0.4*0.05?

*Note the numbers used here are just for example purposes


texts: Single supply inverting OP amp. Problem: half signal at output

texts:
I have built a simple inverting amplifier circuit with LM4565 operational amplifier. But only half of the signal appears at the output of the circuit and the gain looks wrong as well. Could anyone give me a tipp what is the problem? Thanks.

Circuit:

Expected behavior, with 500mVp-p signal:

Expected behavior, with 100mVp-p signal:

Measured circuit with 500mVp-p signal:


texts: nMOS passing 1's poorly and pMOS passing 0's poorly

texts:
I came across the statement in a digital design book that "nMOS transistors pass 0's well but pass 1's poorly" and "pMOS pass 1's well but 0's poorly".

What exactly do these statements mean and why is it so? Also, what is the reason that AND and OR gate can't be simply formed but they have to be formed as AND=NAND->NOT and OR=NOR->NOT?


texts: How do I calculate the power rating of the two 100 milliohm resistors in this circuit?


texts:
I'm working on an extremely compact circuit, and I'm trying to figure out the best way to current limit three LEDs. The issue is that they are RGB LEDs, so there are actually 9 of them. They dont need to be driven individually, so only three control inputs are needed, but I'm having trouble figuring out a compact way to tie them together.

I can't just put them in parallel (because of possible minute Vf differences), and I don't have enough voltage to put them in series. The voltage drive varies between 3-6 volts, and I want a current of around 10mA in each of the LEDs, +/- 10%. I'm controlling them with a 1.8V mcu, so I was just going to use a mosfet for switching, but I need something to limit the current more precisely than just having a resistor. Any thoughts?

It's very important that it be compact, because every mm2 counts here. I know I could use a purpose made chip, but I haven't found any that are small enough and have enough inputs. I certainly wouldn't want to be using 9 PSSI2021SAYs (although three would be ok, but how do you tie the LEDs together?).


texts: 50 mOhm F SMD resistor identification HELP!

texts: I have been trying to identify this resistor so I can order replacements as several are bad in my device. It’s fairly large. 11mm x 5mm? This is an estimate in reference to the nano2 smd 7a fuse in the socket near by and several other components on board. I have provided a picture with the component circled in red. Any help is greatly appreciated. 50mOhmF SMD resistor. .05ohm or 50M ohm? Any part numbers provided for replacement much appreciated. Most of the ones I find are much too small 6mm L x 3mm W. Thanks!!!


texts:
All I can find is a female configuration like this, but need a male configuration.:
BougeRV 50 Amp RV Power Outlet Box,Enclosed Lockable Weatherproof Outdoor Electrical Nema 14-50R Receptacle,125/250 Volt For Temporary Hookup RV Camper Travel Trailer Motorhome Electric Car Generator
Is there such an exterior box like this with male configuration?


texts: Connecting an Arduino oled display without a breadboard

texts:
I am new to Arduino and over all electrical and computer engineering. I need some help with connecting an OLED display to my Arduino. The problem is, I do not currently have a breadboard. If I need a breadboard that is fine, but I would prefer to go without it. I would also prefer to go without soldering it to the board, as this is a temporary project.

I need to connect the display to the VCC, GND, SCL, and SDA pins and ports.

I have an Arduino Uno R3.

Here's a link to the the display on Amazon (hopefully this is needed info.)
https://www.amazon.com/gp/product/B00O2LLT30/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

Here's a picture of the display itself.


texts: Is this how logical operations and a computer work?

texts:
I was watching this video and trying to figure out how a computer really works. At the start the following diagram appears:

Basically what I understand is that in order to form a logical output like AND, there is a need to have a combination of transistors in order to create a frequency (signal?) that has the value of an AND. Is this right?

Please don't go too rough or too theoretical on me, as it is the first electronics video that I've seen and I don't have the minimal understanding of electronic terms or knowledge of electronics to understand hardcore processes.


texts: Representing AC sine wave with common anode/cathode RGB LED

texts:
I have a AC sine/triangle wave I want to represent with single red/green LED. When positive side goes up then green light increases and opposite for negative/red light.
This is pretty simple with two separate LED's, but I'm not sure at all how to go about this with RGB LED that has common anode/cathode.
There are two big issues to solve:

There is dead zone area where voltage is too low to trigger the LED.
Perceived brightness curve is not linear, it takes more power to make it brighter each step. So it probably needs some kind of linear to exponential response.

I managed to make this with separate LED's:


texts: nrf24l01+, enhanced shockburst with two "masters"

texts:
I want to connect a Raspberry Pi to a handheld ARM MCU-based device which contains a display and some buttons to show information from the Pi and transmit commands. I want to use nrf24l01+ 2.4GHz transceivers for that.

I'm pondering with how to setup the communications link and especially whether or not to use Enhanced Shock Burst (ESB). ESB is very practical since it supports auto-ack and hence could relieve me of manual ack-management which is a hassle especially on the MCU-based device. However, from how much I have understood from the datasheets, ESB requires one device to be a primary receiver and one device to be a primary transmitter and only the latter initiates a new transmission, even though the former can transmit data in it's reponse. In my case, this is problematic because both devices receive external events that trigger the need for a data transmission.

I've been reading around and there is basically three possible solutions to this problem:

Configure one device as PTX and one as PRX and have the PTX send empty messages to give the PRX a chance to send it's data in a response packet. This seems to be done by some projects. I see the downside of continuously having traffic on the air which is bad for battery powered devices. Furthermore, the PRX still needs some buffer to store the messages until a transmission comes in and the message can be sent in the acknowledgement.
Configure both devices as PRX. If one device needs to transmit a message it switches to PTX role and transmits the message. The advantage is that there is no continuous traffic on the air and both devices can transmit the messages as needed. However, I didn't find that this is being done anywhere. So I wonder if this is possible or if there are other caveats with this solution?
Ditch Enhanced Shock Burst and make an own protocol. The least favored solution as it involves more work and puts more load on the controller. The automatic retransmit feature sounds very good and it would be a shame to put this potential to waste.

So I wonder if anyone had this problem already and how you solved it. I would especially like to know if there are problems with possibility two.


texts:
It's a mixed part question:

1) Is there any way to add 2 wavelengths outside of the visible spectrum to create a wavelength in the visible spectrum?
2) If this is possible, would those wavelengths be safe?


texts: Can this circuit board control DC motor bidrectionally?

texts:
I bought these "motor speed controllers" from Ebay recently with the intention of controlling the speed and direction of a DC motor:

http://www.ebay.com/itm/Universal-DC10-60V-PWM-HHO-RC-Motor-Speed-Regulator-Controller-Switch-20A-New-/291341338166?hash=item43d54c0636

However when I hooked it up to my microcontroller and tried running the PWM code, it did not work. When I played around with the included switch, it seems like the board can make the motor drive from speed 0 to max speed, but not change direction, like controlling a fan!

Is it possible to use the linked circuit board to control directionality of the motor? I got confused with the terms "motor controller", "speed controller", etc, and fear that I may have just bought a dozen of these that I can't use because I need bidirectional control.

Thanks!


texts: ESP32 Breakout Design Question: Wall power + USB?

texts:
How do you handle a device that is plugged into wall power but needs to be programed by USB. This device would also need to be able to run off USB power (via battery) if wall power isn't available.
Details: I'm working on an esp32 breakout board. To power it, I've got a voltage regulator that outputs 3.3VDC from 100-240VAC. I also have a step-down converter that can take the 5VDC from the USB and output 3.3VDC.
It seems to me, in the event where the device is connected to wall power AND you need to program it via USB, there could be an issue if the two voltage outputs are slightly different. How is this usually handled? Is there a circuit between the two 3.3V outputs to block power from the USB when plugged into the wall?


texts: DSP for single-precision control signal generation

texts:
At present I am frustrated by the limitations of fixed-point arithmetic on a microcontroller for a quadrotor aircraft. The aircraft I am experimenting with is using an ATMEGA. I got to thinking, would it be possible to replace the ATMEGA with a single-point floating unit equipped DSP?

My requirements are:

12 bit ADC
single percision FPU
100 Hz control signal rates
would like gcc as a compiler toolchain

The existing control board has specifications listed online. It uses an ATMEGA1284P, and that is the part I am looking to replace. That would mean the CPU clock should be at least 20 MHz and there needs to be around 32 output pins, some of which support I2C.

If you have experience with DSP controllers and have some recommendations for this project. CPU part numbers that are available from digikey or online would be even better.

EDIT: latency changed to rate


texts: How to calculate circuit noise in dB from measurement

texts:
I've never quite understood how to calculate the noise in dB from an analog circuit at the output of the ADC.

This is my measurement:

It is a 16bit ADC, as we can see there is roughly a +/-1 bit, or +/-2 bits, depending on what sigma is considered for the distribution.

Here is the data distribution:

One bit is equal to 1, the signal is at around 40'000.


texts: beaglebone black doesn't autoboot when powered over jack or vdd pins

texts:
I have a BBB and it works quite well however when I power it over the Barrel connector or over the vdd pins rather then use the usb connection it doesn't automatically boot. When I put the barrel connector and usb in at the same time and then remove the usb it continues running. This is running on ubuntu arm. I have tested that the power supply is between 4.95 and 5.04 V and is capable of sustaining this to just over 1 Ampere

Edit
it appear the BBB does boot when supplied with 4.7 V lab power supply at ~0.4A power consumption. So that suggest something is wrong with the power supply. But how do I test it seeing I was able to verify that it can supply 1A at 5V.

This power supply works by feeding a 12V battery into a step down to convert it down to 5V if that matters.


texts:
I'm contemplating a new project that is to build a Tesla coil.
After poking Mr. Google for some design, I found 2 popular schematics, one by Richie Burnett and the other by Chester Lowrey. The 2 designs are similar but one thing catch my eye. In both approach, they use a diode to build a half rectified DC input to the bridge but the sizing of the diode and their number differ. In the Burnett's design, he use two 1N5408 in series (rated at 3A/1000V)...

and in the Lowrey's design, he use a single 30A/400V.

In the first design, using 2 diodes in series doesn't add much to the circuit since the intrinsic characteristic of the diode is not change (except for the double voltage drop!). And in the second design, 30A seems to me a bit overrated.

So my question is : What would be the right spec for this diode and what are the calculation I could do to derive it?

Thanks!


texts:
I built a STemwin Project with Cubemx and run this project on STM32F429ii based PCB. Every time when it reached the GUI_INIT() which was related to the memory allocation, it ran into HardFault_Handler(). I debugged this issue and found it was caused by the Timer while the only timer in this project is TIM1 for Timebase source. I can't understand how can Timer cause the HardFault? Can someone give me a clue about this issue? Thank you.

Here is some debugging information:

->SP value when HardFault occur

->LR value in Stack

->Assembly code position

->C code position

Edit:
Problem is solved. When the SDRAM clock frequency drops from 72Mhz to 36Mhz, the emwin runs well. The SDRAM controller needs to be check and reconfigured later but the emwin is ok.


texts: How to create a bluetooth module that is both a master and slave?

texts:
I'm working on a project that involves having a bluetooth module be a master and slave. I am a dummy when it comes to these things.

Basically i need one device like an iPhone to be able to communicate to two bluetooth speakers. But the bluetooth speakers need to be able to speak to each other.


texts: Where do I find a cheap developement board?

texts:
I know how to program in C and I'm really interested in microprocessors and I would like to be able to buy a really cheap microprocessor that I can plug into my computer and program in C. I've seen some kits but they are very confusing looking or they are $60+.

I'm looking for something simple, I study electronics at school and my teacher thinks it's a great idea and he will help. All I need is a cheap