texts: What is the modern way to do small scale programmable logic?

texts:
I am designing a circuit for an electronic coil winder. It has a few binary counters, equality detectors, 7 segment decoders and flip flops.

How it is possible to get all of this logic onto 1 programmable chip without resorting to totally retro technology?

Is there something like a GAL that can is well supported for programming on a modern computer?

I can easily make it from standard CMOS or TTL chips, but it would be a good learning opportunity to try programming my own logic.


texts:
I have a hobby project powered by a micro-controller (particle photon if you must know). One of the features is 3.3V, 100mA max output. Each digital data input is able to drain or source a max of 25 mA. It communicates over:

I2C
SPI
analog GPIO
digital GPIO

I am currently rapid prototyping on a breadboard. Would it be sensible to add resistors to any digital pin and 3.3V out to protect the board? Almost all auxiliary equipment is CMOS and I only need a switching frequency of 1 kHz (save for I2C and SPI). According to the datasheets all auxiliary equipment should use less than 20 mA of the 3V3 rail (save for burts of course).
My question: is something like the drawn circuit below sensible? Could it be an issue that Vdata is higher than Vin?

simulate this circuit – Schematic created using CircuitLab


texts: Why do vibration sensors use a negative voltage?

texts:
I've started looking at some industrial vibration monitoring sensors for a project and it seems like there's a number of brands that use negative outputs voltages. Many are eddy current sensors with specified supply voltages of -24 VDC and output voltages of -2 to -18 VDC. It just struck me as odd seeing as how many instrumentation devices revolve around the 4-20 mA, 0-10 VDC standard.

Why the negative voltages?

Applicable datasheets:

Emerson AMS EZ 1000

Bentley Nevada 330100-50-01 Prox Transducer System

The two above are what's being replaced and a suggested replacement from a supplier. After reading a couple of comments I went on the hunt to find more datasheets and lo and behold, I can't. It seems I've misspoken and jumped the gun here. Regardless, I think my question just changes to: why are these two vibration sensors using negative voltages?


texts:
Here is the datasheet of the MQ9 sensor
I would like to be sure about the current drawn by this sensor. The datasheet doesn't say anything about that, but tt says the power Ps heating comsumption is about 340mW and the heating time is 60 to 90s
Is the current drawn just for 60 to 90s (o I=Ps/Vcc=340mW/5v=68mA) or should that be calculated when RL is inserted?


texts:
I just built an HTPC. It's got a bright white power-on indicator LED that is in fact needlessly bright and, which is worse, blinks when the pc is in suspend mode. I want it to be less eye-catching.

I suppose I can wire a resistor in front of the LED to dim it, but I've no idea how to select the proper value.

(and/or)

Can I wire a capacitor in front of the LED to make it's "very binary" blinking into a somewhat smoother wave pattern, sort of pulsating? I really don't care about the specific wave form, I just want it to draw less attention (making it glow constantly, but dimmer, in suspend than in power-on would be just fine, if that's a simpler thing to do).

I've no idea about the ratings of the components involved. I'm sure the LED is being driven at 5V (I can check), and I suppose it draws somewhere between 20 and 200 mA.

Can you help a feller out with some component choices based on such poor specs?

Update: I have soldered together a 2200uF capacitor and two 100k potentionmeters -- see photos here. I have tried to recreate Spehro Pefhany's diagram (dead bug style, it's gloriously hideous) and I can report a 50% success: the dimming works nicely, but the blinking seems to be completely disabled -- it's always on (at whatever brightness I choose) and I can't detect even a hint of variance regardless of how I adjust the 2nd pot.

Have I (despite triple-checking) put it together wrongly? What should I change to restore at least some blinking?


texts: Impedance magnitude and phase error - Mathematical formula

texts:
Today I read a paper on which there are the terms magnitude error and phase error relative to a comparison between measurements performed with a biosensor and with a benchtop electrochemical impedance spectroscopy (EIS) tool.

Maybe it means that:

$$magnitude \,\,\, error = \mid \mid Z_{tool} \mid - \mid Z_{biosensor} \mid \mid$$

$$phase \,\,\, error = \mid \angle Z_{tool} - \angle Z_{biosensor} \mid$$

?

Thank you so much for your time.


texts: Norton Equivalent of Capacitively Coupled LRC Circuit

texts:
The diagram below is a schematic representation of a microwave lumped element notch filter. The goal is to analyse the parallel LRC circuit and derive an expression for \$S_{21}(\omega)\$, where port 1 is at the source and port 2 is measured across the load impedance \$Z_0\$, which could the input to an amplifier.

simulate this circuit – Schematic created using CircuitLab

My attempt at simplifying the circuit is shown below, where the resonator impedance has been condensed into \$Z_{res}\$ for clarity, where

$$Z_{res}= \left(\frac{1}{R_r}+j\omega C_r + \frac{1}{j\omega L_r}\right)^{-1} = \frac{R_r}{1+j\omega R_rC_rx},\,\\\text{where } x=\frac{\omega^2-\omega^2_0}{\omega\omega_0} \,\text{and } \omega_0^2 = \frac{1}{L_r C_r}$$

simulate this circuit

My question is, is the transformation from a to b legal? And if so, how are Cc and Zres related to Cc' and Zres'? Also if anyone has any advice on alternative methods to simplify this circuit, I would appreciate any feedback.

Thank you for your time.


texts: Solution for a set of non-linear equations

texts:
I am trying to solve the following equations for \$\delta\$ and \$K\$.

I have tried Matlab function fsolve, but unsuccessfully. I also tried Wolfram Alpha and, again, no success. Matlab returns a value of \$0\$ for both, but I know their values. Can anyone help me with this? The correct values are \$\delta = 1.8\$ and \$K = 1.098\$.

UPDATE

To solve these equations I used the least squares method, which enables me to solve sets of equations that have more equations than incognitas that are not linearly dependent.

I used Matlab to solve doing a function with a set of equations

function F = equations(x)

F(1) = (x(1)-x(2)+0.004);
F(2) = (-1000*x(1)- 3000*x(2)+ 2000*x(3)+ 8);
F(3) = (1000*x(1) + 1000*x(2)- 2000*x(3)- 12);

Then I created a code that allows me to use the equations together with the "lsqnonlin" function that provides the solution of the equations.

%% Code to solve the equations

clc
clear all
format long
fun = @equations;

options = optimoptions('lsqnonlin','Display','iter', 'Algorithm',...
'levenberg-marquardt','MaxIterations',1500,'MaxFunctionEvaluations',15000,...
'FunctionTolerance',1e-20,'StepTolerance',1e-20,'UseParallel',false);

% Initial Guess
x0 = [0;0;0];

x = lsqnonlin(fun,x0,[],[],options)


texts: Is A Diode Affected By Amps Drawn From Power Source

texts:
I'm an almost complete newbie to the electrical tinkering circuit so go easy with me please.

My scenario is this: Radio control set up, 2 x 11.1v 5000mah batteries connected in series, runs directly to the Electronic Speed Controller (ESC).

I need to put a switch in-line to cut the power (from source) as and when desired.

I'm going to use a (3-pin) MOSFET with a 1-3v Gate and a max. A throughput rating of 180A, maximum V throughput rating of 40v, however, from the same power source I want to add a 3A switch to activate the gate, so I need a voltage regulator to step down from 22.2v to 3v (all fine I can do that).

However, during usage the Amp draw from the battery may reach 80A! How does that affect my voltage regulator that's spurred off of the same power source? Will it fry it if the AMP draw goes up from the ESC?

What if I added a diode in front of the VR to control the flow of current? Would I need a special diode to be able to stop the Amps flowing to the voltage regulator?

Any help is appreciated, thanks.

UPDATE: I think this is what I want, but I want to know, would I need one way diodes before the Voltage Regulator to stop the AMP draw messin' with it?


texts: Protection for arduino on two direction dc motor?

texts:
Basically I don't want to use an h bridge, I just want to protect my arduino when changing the direction of the motor.
The code i use:
void setup() {
  pinMode(2, OUTPUT);    // sets the digital pin 2 as output
  pinMode(12, OUTPUT);    // sets the digital pin 12 as output
}

void loop() {
  //ROTATE TO RIGHT
  digitalWrite(12, HIGH); // sets the digital pin 12 on
  digitalWrite(2, LOW); // sets the digital pin 2 off
  delay(1000);            // waits for a second
  //ROTATE TO LEFT
  digitalWrite(2, HIGH);  // sets the digital pin 2 on
  digitalWrite(12, LOW);  // sets the digital pin 12 off
  delay(1000);            // waits for a second
}

Scheme used:

I am using "dc motor 130" (3V-6V), I want to protect it from anything that could damage my arduino, giving it such use, and protection if the motor gets stuck, using a 1N4007 diode or resistors...


texts: Replacing potentiometer with a hall sensor in PWM DC motor control module

texts:
I have a DC Motor Speed Controller (PWM) that uses 100KΩ potentiometer to adjust motor speed. And I also have an electronic throttle pedal that used 49E Hall-Effect sensor (+5V, 0.8-4.2V signal, 1KΩ). I want to use this pedal with this speed controller.
I measured voltage drop on the potentiometer and it is 5V. Confirmed that pedal's signal changes from 0.8V (released) to 4.2V (fully pressed) when given 5V. What would be a right way to replace potentiometer in speed control unit with Hall-Effect sensor? Note, that I would prefer to preserve full speed control range (from  0% to 100%).
If you curious about my application - replacing binary on/off throttle in kids ride on car.
UPDATE 1
PWM controller built-in potentiometer works like that:

Max speed: GND to wiper = 0V, wiper to V+ = 5v
Min speed: GND to wiper = 5V, wiper to V+ = 0v

And Hall-Effect pedal is opposite:

Max speed (fully pressed): GND to signal = 4.2V
Min speed: GND to signal = 0.8V

So as drop-in replacement pedal will behave more as a break :)
UPDATE 2
On further examination, it appears that potentiometer's GND (I mean, one of its legs that I referred above as GND) is connected directly to input GND of PWM controller (where negative terminal from battery goes). So, from practical standpoint, it's probably safe to assume that I also have GND - Xv at my disposal (Xv however is variable, since it's coming from unregulated battery). But I think this extra voltage source makes this question less general and less useful for other people...


texts: If I make the tungsten filament on a light bulb thinner with more twists will it make more heat?

texts: If I make a incandescent light bulb with a sturdy and thicker filament will it also increase the temperature or just make it more durable?


texts: I am trying to select and ADC with single ended inputs which can input positive and negative voltages (around +500mV to -500mV).  Due to the nature of the system I am selecting it for, the voltages cannot be DC biased and also cannot be amplified (in other words the exact DC level is the information).  I was wondering if it would be possible to set the reference voltages to REF+ = 500mV and REF- = -500mV, while the power supply is 2.5V to -2.5 V (the ADC allows for true bipolar operation).  For instance the ADC I am looking at is an Analog Devices AD7176-2.  I noticed in the data sheet that the limits for the reference is that their total voltage difference can be 1V, but the tests they have are only for +5 V to Ground supply, not bipolar operation.  Hopefully someone has experience with operating an ADC in this mode.  Thanks


texts: Sensor to ADC Filter Design Tutorial Suggestions

texts:
I am looking for a few good resources on the web to advance my knowledge of filter design for interfacing to an ADC of an uC.

I am looking to brush up on a few things:
Determining proper cut off frequency,
Type of filter selection,
when to use buffers, how to select the proper gain if using buffers

I have been searching the web but I am having trouble finding a general tutorial of, Here is your sensor, here is how you would go about interfacing to an ADC.


texts:
I am working on an idea these days which is related to the designing and development of a ear phone which enables us to select a single voice and boost it out of many without any noise.Which will be very much useful when we are in a crowed. The frequency of everyones voice are distinct and therefore we could use several miniature audio receivers to process the multiple voice.Therefore we could eliminate unwanted sound and noise while we are in a crowed and concentrate on single one.

Guys I need suggestiona on this topic and please do help and correct me if I was wrong.I am new to this platform.


texts: why my “pid” parameters(Kp,Ki and Kd) values are not showing up in pidtuner tool?

texts:
I am trying to implement PID controller in matlab,but pid parameters(Kp=350,Ki=300 and Kd=50) values are not showing up in my pidtuner app for base line response as shown highlighted in attached photo
My code is below
clc
clear all
close all
kp=350
ki=300
kd=50
m=1
b=10
k=20
num=[kd kp ki]
den=[1 0]
num1=[1]
den1=[m b k]
sys1=tf(num,den)
sys2=tf(num1,den1)
A=series(sys1,sys2)
sys3=1
B=feedback(A,sys3)
step(B)
xlabel('time')
ylabel('amplitude')
pidtool(B,pid)


texts: Can an mbed device be damaged by something drawing too much current?

texts: The mbed has a pin which supplies 3.3V regulated current. I think it can supply up to 100mA. If this pin is used to power a device, and the device tries to draw 150mA, then what can happen? Is the mbed in danger of being damaged?


texts: we are designing a fairly compact PCB for a communications device. We are looking at using BLE as a link for voice to a separate microphone, and BT Classic to be paired with a smartphone. We are using pre-certified modules, and they will located on the PCB about 20mm away from each other (can extend this to 40mm if need be). Is there a risk of interference between the 2? We are transmitting audio in both cases so interference would be particularly noticeably. They both operate at 2.4GHz, but I understand they have different frequency hopping techniques, and hoping this will allow for coexistence.


texts: How do I set the clock speed fuses on an ATtiny85 when using an Arduino as a programmer?

texts:
I'm following this tutorial, programming the ATtiny85 with an Arduino, using it to play some tones (through a piezo speaker). I'm struggling with getting the tones at the right pitch (I'm creating the wave forms manually, as the tone() function is unsupported on the ATtiny85).

I believe the problem may be down to differing clock speeds on the Arduino and ATtiny. I understand the clock speed can be altered on the ATtiny, how do I accomplish this using the arduino environment?


texts:
Here's a module with castellated pads attached to an eval board:

(source: alicdn.com)
Looking closely at the wires interfacing with the castellated pads, they're clearly soldered to the eval board. However, they don't look like they're soldered to the module, but rather they're being pressed against the pads with the tension in the wire. It also looks like the free end of the loops are protruding down into a channel cut in the PCB.
Do these kind of connectors/metal loops have a name?


texts: Can tcs3200 be interfaced with msp430? If yes then how?

texts: I am using tcs3200 in my protean I am confused about which controller can I use other then arduino. Kindly help me in this.


texts: Creating and Receiving Electromagnetic Field with RaspberryPi

texts:
I am trying to make a basic HLEM (Horizontal Loop Electromagnetic) device for my undergraduate thesis but I haven't started yet, just researching that can I build it myself without sufficient help. I am geophysical engineering student and also a programmer but I have limited knowledge on electronics.

I have 2 loops. First one transmitter and second one receiver. Transmitter should create 2kHz and 6kHz electromagnetic fields at the same time. And receiver can capture primary and secondary fields and record it.

Can I build it with Raspberrypi with/or Arduino with basic circuit boards and modules that can I buy from the internet? or why I can't?

Thanks

More information: http://www.epa.gov/esd/cmb/GeophysicsWebsite/pages/reference/methods/Surface_Geophysical_Methods/Electromagnetic_Methods/Frequency_Domain_Electromagnetic_Methods.htm

Sample Loop :


texts: Transistor(BJT) Zenner diode voltage regulator circuit

texts:
calculate the regulated output voltage of a series voltage regulator circuit as shown in figure

Given \$ R_1 \$= 3.3 kOhm, \$ R_2 \$= 2.2 kOhm,\$ R_3 \$=5 kOhm,\$ R_4 \$=10  kOhm, \$ V_z\$=10 V.

simulate this circuit – Schematic created using CircuitLab

Method followed in my book:

$$V_{R2}=V_{BE2}+V_Z=0.7+10=10.7 V$$
$$V_{R2}=V_o(\frac{R_2}{R_2+R_1})$$

But the second equation is valid only  if current through zenner diode is 0. Please clear my doubt. If there is a way of evaluating this circuit without approximation then it will be highly helpful if you would post the solution.


texts: How to modify/size a single transistor in LTspice?

texts:
I am trying to size the Q1-Q0 current mirror pair so that the emitter area of Q0 is N time as large as that of Q1.
If I try to change the model of the 2N2222 NPN transistor (for example by changing the ratio Is, the saturation current, of Q1-Q0), then this change would apply to all 2N2222 NPN transistors in the circuit. I was wondering if there is any way to design/size a "single" transistor or MOSFET component?

Note:
I have also looked into this post but it doesn't solve my problem. Am I missing something?


texts: inductor resistor variance for a buck regulator circuit

texts:
Thanks to some very helpful folks in another thread, I've selected a buck regulator for a microprocessor project that draws on automotive current, i.e., reducing 12v to 5v with about 2amps of power. I have selected the TPS62133AQRGTRQ1 IC (automotive rated) and have found a viable regulator circuit schematic for my application. The schematic calls for an inductor coil rated at 2.2 uH and 35 mOhm. It specifies a specific inductor manufacturer/partnumber (Abracon Corporation ASPI-0530HI-2R2M-T2), but I'd like to search out suitable replacements. I can find LOTS of 2.2 uH inductors... but none so far are rated at 35 mOhm. Many inductor specs seem not even to include Ohms (although surely their respective datasheets would if you dig in to each one.) So my question is, how much variance in rated Ohms is typically acceptable... if there even is a "typical" range. I'm probably and intermediate amateur when it comes to electrical theory, but I can imagine that ohms would be related to current, i.e., higher resistance, less amps. If that's right, then I would reckon that I'd need to find a coil that's pretty similar, i.e., not from off from .035 ohms. Am I in the ball park?

Here is the schematic:


texts:
Background: I am a non-EE (an 0x11? :^) thrust into the world of embedded systems design. I started this project with a only college physics-level understanding of circuits, but I'm gradually learning.

The design I'm working on consists of several sensors, an SD card, and a TI CC1111 SoC. The CC1111 includes an 8051 core, a USB controller, and an RF transceiver. My design is based on a reference USB dongle design provided by TI.

The device will typically operate on battery power, using 2 AA batteries in series (or potentially 4 AA batteries in parallel pairs), unless connected to a USB port. I'd like the device to switch over seamlessly between USB and battery, without a microcontroller reset.

I'm looking for a circuit to switch between the two power sources (batteries or USB bus). From what I can tell the simplest thing would be to use OR-ing diodes. The problem here is that I'd be wasting power (current x forward voltage drop of diode), and that's something I want to avoid.

One option I'm considering is the LTC4412 power controller, recommended in answer to someone else's question.

Question 1: Does this look suitable?

One concern I have is the delay in switching over from USB bus power to battery power when the device is disconnected from USB.  According to the LTC4412 datasheet, the turn-on time for the MOSFET gate can be up to 175 us. I don't want the CC1111 (or the digital sensors) to reset. Looking at Figure 1 in the datasheet (see too the discussion of bypass capacitors on page 5), the trick is to properly choose a value for the output capacitor, C_out. I calculated a value, but I'm not sure if my approach is valid.  If you'll bear with me:

The CC1111 is normally operating at 3V from 2 AA batteries. Suppose it could operate at only 90% of that (2.7 V). I use the current drawn by the load (my device) and the nominal voltage (3V) to come up with an equivalent resistance (V/I).  Based on my measurements and summing currents taken from datasheets, the device can draw a current somewhere between 35 mA and 70 mA. This gives me an equivalent resistance in the range of 43 Ohms to 86 Ohms.

If I want the voltage to drop to no less than 90% after 175 us (the LTC4412 gate turn-on time), then after doing the math I get a time constant (RC) of 1.66 ms. Using 40 Ohms to be safe, I come up with C > (1.66ms/40 Ohms) = 42 uF. Maybe add another 10% or 20% for safety, so say 50 uF.

Question 2: Is that approach and calculation valid?

I pulled that 90% number out of thin air. The CC1111 datasheet says that 3.0 V is the minimum voltage, so I'm not sure what I'm doing is kosher. Should I use some kind of step-up converter to get, say, 3.3V out of the batteries?

Thanks in advance for your help (and for reading so much text).


texts: Not getting the expected output from my switching regulator

texts:
I am working on a project using a TPS54202H switching regulator.
The power supply is currently in 12V DC @ 60mA and am expecting a 5V output.
I followed the datasheet schematic but when I power it up I am receiving a square wave at the output that peaks at about 200-300mV. The square wave is telling me that there is some capacitor interference (I believe,)  but I am not sure how to fix this.
I am currently stuck and not sure where to go from here.

Reference Design

Schematic

PCB Layout

Output

Components used:
L1
C4
C5 & C6
C7 & C8
C9


texts: Automatic Alcohol Dispenser: What is the Resistor's value for transistor?

texts:
I wanted to assemble the circuit below

Link: https://www.instructables.com/id/DIY-Automatic-Alcohol-Dispenser-No-Arduino-Needed/
I read about the transistor's datasheet and I found out that the current base is -3A max rating. These are my following questions:

Why does it need a 1k ohm resistor? Since voltage is only 5v
What would happen if I remove the 1k ohm resistor?
How to compute the value of the resistor for the transistor's base? I saw formulas in google but still confuses me.

Your answer and explanation is gladly appreciated. Thanks


texts: i have an arduino board when i use analogeread to read the value of A0 without connecting any wire to it ,gives me a value not zero in serial monitor. is my arduino dead or what is the problem? i would to know what happend to my arduino and how to fix


texts: How to turn continuous signal into a short pulse using logic gates?

texts: Basically, I want to turn a continuous "1" into a short "1" pulse then "0". I'm new to logic gates, apologies if it's too obvious.


texts: For discmans and walkmans who operate on 1.5V, 3V, or 6V, what current output (in amp.) of DC/AC convertor, as alternative to using batteries, should be used? The discmans and walkmans do not specify the current input on their labels nor manuals.  Thanks.


texts: Calculate the minimal MOSFET source current needed for 12 TTL MOSFETS

texts:
This is definitely a beginner question as this is the second PCB I ever designed but you can't learn unless you do something. (It's an optimization of an older board I have to do as project.)
I would like to know how I could calculate the minimal (or best) current needed for my 12 TTL MOSFETs as I am looking for a good power source right now.
I am using IRLL014 MOSFETs, the gates are connected to an MCP23017. The signal comes from an ESP32. As these are N-MOSFETs my VDD is 12V.  They have an SSR as load.
If I look into the datasheet I can find \$V_{DS}\$ to \$I_{D}\$, depending on \$V_{GS}\$ - The GS is 5V as it comes from the MCP. So if I look right it should be around 9-10 amperes which sounds insane, as in a worst case scenario I may need to switch ON all the MOSFETs at the same time and drawing 100 amperes sounds just wrong. Obviously I don't need that much but would they work with lower current? If so, how much?
As for why I need a voltage regulator - The input voltage is 24V maximum and needs to be regulated down to 12V for VDD but the highest current with a fair price I found for these is around 3A while everything above is way more expensive.
Could you help me and teach me how to calculate the needed current for my PCB?

simulate this circuit – Schematic created using CircuitLab
I made a simple schematic as an example to make a visual representation (won't work for simulation.)
EDIT:

SSR 1
SSR 2

Pictures of the original schematic:

Buzzer comes from the ESP32 directly here.


texts: How can I observe rectifier switching noise?

texts:
I understand there is such a thing as rectifier switching noise. I would like to observe it on the bench, but I don't understand its causes well enough to design a test setup.

Once in hand, I'd like to use such a setup to characterize various rectifier diodes and perhaps other circuit variables as far as their "noisy-ness", and perhaps experiment with snubbing networks to counteract the noise.

This question originally arose for me in the context of the design of a linear bench power supply, summarized in this question:
What is the thought process for specifying an EMI bypass cap on line transformer secondary?

The circuit I was learning from had a capacitor across the AC inputs to the bridge rectifier. I initially interpreted it as an EMI bypass capacitor, but concluded after the discussion it's role is a simple snubber for the rectifier switching energy.

When I took the capacitor out, I couldn't observe any switching noise at all, and the mystery began.

Since then I've started studying switching converters, where I expect the diode switching demands are more severe; so I have a renewed interest in understanding the underlying noise phenomena and developing the ability to characterize and predict them.

Is there a useful simulation configuration and/or bench setup that would allow me to observe the switching behavior of rectifiers that gives rise to their switching noise?


texts: Routing traces of different width onto an IC on a 4-layer PCB in Eagle

texts:
I am finishing my design of my buck/boost converter using LTC3780 IC on a 4-layer PCB.

Those 1mm blue width traces will carry 2-3 amps.

I need a way to connect those traces of the same layer (blue) onto the IC pins.
What I temporarily do to "fix the problem" was connecting it through vias but those vias add unnecessary impedance for a trace that's the same layer as the pin itself.


texts: Is it necessary to make the exact number of turns in each arm of the armature of a motor

texts: When making a motor is it necessary to make the exact same number of turns on each arm of the armature,let's say it should be 400 turns on each arm, would a difference of 2 to 5 turns extra on one arm change anything?


texts: how do i make led strip flash with the beat (subwoofer) without risking burning them out and im using a car amplifier that kicks out 1250w peak for the subwoofer i tried using a multimeter i got around 45v and a current around 5A from the amp i tried using a npn transistor but it went so hot that i burned my finger and the current coming out from the amp breaked through the base into the emitter into the leds and bruning them out whats your recommendations ?


texts: Advice regarding AC current measurement using a microcontroller

texts:
The goal is to design a simple and compact (as simple and compact as possible) module to perform AC current measurement (for one or two 220V loads) using a microcontroller. One of the issues is that I have limited 'analog' knowledge.
Here are a few design constraints that I need to observe :

the measured load may vary from a LED light bulb (~5W) to a laundry washer / heavy duty tool (like a circular saw); the target loads are generally household appliances/tools, not industrial 'heavy' loads; probably most loads will be in the 5W-200W range. Having a single board with optional/interchangeable parts is acceptable (hence my approach with Hall sensors; see below)

the microcontroller must be either an ESP8266 or an ESP32, because it needs to connect to an existing proprietary network using a specific protocol (not the object of this post).

existing modules that will be replaced (that are currently designed without current measuring capability) may control one or two loads; this means that there is a fair density of components (the microcontroller module board, power supply, two compact relays - APAN3103 - and related discrete components)

the power supply must be 3.3V to avoid logic level shifting (both ESPs run at 3.3V)

the module must ideally fit into a round (50mm) junction box

So far I have put up a circuit using an ACS712 for +/-5A and an ADC1015 for the conversion using the differential mode and the CPU is an ESP32; I'm comparing the output of the Hall sensor to the voltage I get from a 1:2 divider, since I'm measuring AC.
Calculations are done using the 'Filters' library for getting the RMS value out of the measured samples; the library has been slightly refactored for plain C (it is originally written in C++).
However, I'm faced with a couple of problems :

since it's AC, frequent measurements must be taken to perform calculations. I managed to get up to 1000 samples per second; any higher that that and the microcontroller cannot assign enough time to the wi-fi stack. The Hall sensor is capable of 3x that rate.

the RMS value seems too low for a single LED light bulb (a value of about 15 for a 11W load), and precision seems poor; highest load I've tested so far is 75W and the RMS value is at about 68.

when no load is present, the output of the Hall sensor is not stable; it fluctuates by about +/-0.02mV around the calibrated 'zero' value; I'm calibrating this since the voltage divider is not entirely precise due to resistor tolerance (I think).

retrieving the measured value from the ADC through the I2C interface take the most time

The reading cycle uses an 'inverted' operation (read available value then trigger next ADC cycle), in order to allow the CPU to do something else while the ADC performs the conversion; something like this :
function timer_callback() {
   var value = ADC1015.getMeasuredValue()
   // ... calculate
   ADC1015.triggerMeasurement()
}

However, my timings show that this function takes some 500 microseconds to complete, so the 1000 samples per second must be close to what it can be done using this approach. Most of the 500us, around 400us is spent on the I2C communication, which is set to run at 1MHz.
I'm looking for advice on how to improve :

the analog part

is the Hall module appropriate ?
should I have used a CT ?
is there any other practical circuit for my scenario

the digital part

mainly how to get the digital information faster to the CPU (even if it is probably not 100% the proper site to ask this)

Thanks in advance.


texts:
I have a 2V regulator circuit which is used to drive a microcontroller (EFM32G222F128). On the output of this regulator I have a delay switch type circuit (see image below) which is used in order to allow the reservoir capacitor to charge enough in order to deal with the initial start up current of the \$\mu\$C.

The circuit as it is works fine, however, should, for any reason, the \$\mu\$C draw too much current (the regulator is only rated to allow a low current out) the output of the regulator will drop below 2V, thus causing the \$\mu\$C to lose power.

When this happens the voltage appears to latch at ~1.7V and power needs to be removed for a few seconds before the circuit will power up again properly.

I have put this down to the NX2301P not switching off properly once the voltage has dropped below 2V. This is sort of part of a bigger issue with this delay switch...

Say I remove power to the circuit, the regulator output voltage drops away slowly (a couple of seconds) and once it actually passes the 2V mark it drops more quickly down to about 0.5V where it only trickles away and I never really see it drop to zero without getting really bored waiting. If I try to turn power on during the 'quick discharge' region, the output won't go back up to 2V, it will latch at the 1.7V mentioned previously. I have to wait for the output to level out to around 0.5V before it will be able to go back up to the 2V steady output.

Is there a way I could, preferably using discreet components, improve the delay switch so that if the voltage output of the regulator drops below 2V, the PMOS will turn off and allow the circuit to sort of reset and get up to 2V before turning back on?


texts:
simulate this circuit – Schematic created using CircuitLab

Hi, usual apologies here, total enthusiastic amateur noob, etc.

The situation is: a Common Collector NPN transistor.

Question: Is it okay to omit the resistor R2?  (that is, R2 = 0 Ohms)?

The way I understand it, when the switch is closed, the voltage at the Emitter (as indicated) would be 5V – 0.7V = 4.3V. The reason for that is that both the Collector and the Base are connected directly to 5V, and that VBE must be 0.7 V for silicon-based transistors. Therefore the voltage drop from the Collector to the Emitter will 0.7 V rather than the normal 0.05 to 0.10 V.

But if that is the case, if I want to calculate the value of R2, the total voltage drop is the same, irrespective of whether I calculate it through the loop containing the switch, or going through the transistor form the Collector to the Emitter. Therefore IR = 0 for the Base resistor so that R2 must be 0 Ohms.

Elsewhere I came across the injunction: “Do NOT omit the Base Resistor!” so now I’m uncertain.

(I’m really trying to design a circuit to drive an PWM input to an H-bridge from an Intel Edison, so the above is not my complete circuit – it just crystallises one of the many current conceptual difficulties I have. This particular part has to do with an AND gate, so there will at least be another transistor and a pull-down resistor, and so on.)


texts: Low Pass Step and Low Pass Pulse sith Vextor Network Analyzer

texts:
I have an extremely basic question about time domain measurements with Vector Analyzer. It is something that is not explained in simple words in all datasheets/guides (maybe they think it is obvious and trivial).

Basically, with time domain settings, a VNA measures S parameters and finds its Fourier Transform, in order to get a time domain representation of them (S11(t), S12(t) etc).

Now, the Fourier Transform of a function is one and one only function (there is a unique correspondence between time and frequency domain). But with VNA we may set Low Pass Pulse or Low Pass Step modes, and the resulting function of time will be different. Why? And which mode should I use to find the correspondence impedance (for instance with the formula: Z(t) = ( 1+ S11(t)  )/ ( 1- S11(t) ) )?

Reference: here


texts: Design carbon surfaces on printed circuit boards with Eagle

texts:
I am in the process of creating a circuit board that will later be assembled with conductive rubber for the buttons. For the contact areas I found that carbon is used (please correct me if I am wrong).

How can I design such contact surfaces with a tool like Eagle so that they can later be printed by a manufacturer?


texts: Repurposing FT232 UART pins as parallel out

texts:
Background

I am trying to build a USB Bridge circuit as part of a larger project.
What I mean by that is, I wish to control a parallel out circuit based on information transmitted by the host computer.

Application Details

The idea behind the project is to have a USB powered Nixie Clock. A Nixie Display unit has a high operating voltage of about 150V. The power supply part of the project will take care of stepping up 5V DC (up to 500mA due to USB limit) to 150 V (Vdc), 5mA (0.75W).

We want our initial design to have no onboard clock circuitry, instead, we want the time and date information to come over a server lookup from the USB host computer.

Parallel Pin requirement:

Due to a power limitation, our design will rapidly switch between the 6 Nixie Tubes (HH MM SS) such that only one is lit up at a time. This is where the parallel out requirement stems from.

We need 6 pins to select the tube whose anode is pulled up to Vdc and 10 pins to choose the digit that currently glows. These final outputs can come from a decoder, but the system will still have 16 states.

So atleast 4 parallel pins are a requirement. However it would be better to have 3pins for tube control + 4 pins for digit control Since these will be interfaced to decoder ICs I believe, there is no significant current requirement for them.

Possible Solutions

A good solution could be to use a general purpose USB microcontroller such as the TUSB - 3210

However to keep things simpler, I have considered using a USB - UART interface chip such as the FTDI series of devices - FT232R (Single UART) and FT2232 (Dual UART, for more functional pins)

So what I want to be able to do is to program the pins available as per my will, without regard for their UART protocol functionality. I wish to avoid using the FT232R on-board EEPROM due to a lack of experience with using such programmers. This prevents me from using the control bus (CBUS) pins.

My questions about doing this are

Is doing this a good idea, is it a common application of FT232R?
I am on a tight power budget since I want to make a Nixie clock front end work using just USB power. Would the 3210 prove better for this application, considering the fact that USB controller will be a single package solution whereas a UART based solution would need some extra (Although low power) Decoder ICs?

Some useful information about the FT232R datasheet

Page 7 - 10 pin functionality.

I am very new to big controller based projects, please provide feedback on how I could make the question better, provide more details...


texts: A basic question about direct access to the GPIO registers by the μC units

texts:
Following diagram shows the AVR architecture for Atmega328P from this source:

And below is a simplified diagram for MSP430 micro-controller:

I'm trying to understand whether these two architectures are very different in one thing.

And that thing is this: If I look at Atmel's diagram I see that the Instruction Registers(CPU registers) have direct access to GPIO registers. But in MSP430 case only the Memory Address have direct access to the GPIO registers.

I thought in all micro-controllers GPIO registers can only be directly accessed through the memory. Am I interpreted something wrong here?


texts:
In my project i'll use modbus protocol for serial communication over RS485. There are more than 320 slaves which seperated equally in 2 groups. Every 16 slaves are powered from the same supply and isolated from others galvanically(Master'll be isolated from all the slaves). i attached a pic to make it clear. My first question is if there is any wrong in this design?

Secondly I want to synchronise all the slaves over 10ms period pulses that are derived from master microcontroller. How can i achieve a precision synchronisation, say that the tolerance is not more than 1 or 2 microseconds(what type of bus, single or differential signal, where to isolate, ...)?

I add another bus type:
In second picture suppose each bus lenght is 150 meters. Which bus is more robust? Does anyone have advices for any improvement?


texts: What is the fastest I/O planning for FPGA?

texts:
There are many timing strategies that can improve FPGA speed ( as Timing constraints , planning the clock regions ,....).
One of these strategies is selecting optimal places for I/O pins and floorplanning the logics. In fact we first select best I/O places and then we can place the logics,....  This process starts from I/O placement and that's what I don't know which strategy leads to best performance.
These are strategies I thought about as a Starting Point of pin placement:

1- In the picture below ( Xilinx Spartan 3), one may select all in/outs in one bank (arrow-1) and a Global Clock for example on bank-4. This leads to minimum distance for all pins and also minimum noise from GCLK pin external leads  but it is far from the GCLK line.

2-  path-2: crosses GCLK path but inputs and outputs are far from each other ( I saw somewhere that horizontal pathway between inputs and outputs is the fastest way but can't recall where I read it !! )

3- path-3: being close to clock pin may impose some noise from its EXTERNAL leads and components.

There may be many other strategies that I don't know. Can anyone give me a hint or method of thinking as a start point?

1)


texts:
I'm working on a wireless sensor network and would like to know what it would take to shut down the regulator during deep sleep.

MCU: STM32L151C6T6
Regulator: TPS63001
Radio: RFM69HW
LCD: some chinese ILI9341 TFT
Batteries: 2xPanasonic NCR18650 Lithium in parallel

I'm planning on going 3.3v, because I will allow the user to push a button to display readings locally on an LCD and that is saying it needs 3.3v. Otherwise I would go lower. Everything else supports 1.8v.

So my question is, if I have a node deep sleep, can I set the EN pin on the regulator low and depend on either the power supply caps or the inductor to to retain enough power to keep the MCU alive so it can wake up in 5 minutes? How do I know how long I'll have? Should I throw in a supercap too? Is it even worth it to try to turn the regulator off, or when there is no draw will it not burn energy?

Peak current will be under 200mA. When sleeping, nothing should be running except the MCU in stop+RTC or low power run mode, which is, according to the datasheet, 1.2 uA and 9uA, respectively. I'm sure some inefficiencies in my design will require wiggle room.

Thanks a lot and any feedback on any of the above is greatly appreciated.


texts: Building circuit to amplify small sensor signals using an Instrumentation Amplifier and 24-Bit ADC

texts:
I'm a beginner when it comes to circuit design and I have spent the last few weeks doing research on this topic. I have now chosen some ICs (Instrumentation Amplifier and ADC) and would like to build the circuit. However I have some questions left, which I hope some experienced folks can help me with.

Sensors:
I have multiple of these CMP10 pyranometers: Datasheet of CMP10 Pyranometers
This passive sensors have two outputs: HI (+) and LO (-)
Here are some specs from the datasheet above:

This sensors measure the sun radiation and depending on the radiation they output a signal in the range of 0 mV up to 20 mV.

I would like to read it with a microcontroller, thus I need some good amount of amplification. In order to get a readout that is as accurate as the sensors, I would need to get to a resolution of 5uV per step. I know this is probably not trivial at all and requires a pretty good PCB design to get even close.

I calculated that in order to get down to 5uV steps, I need at least an ADC with 19-Bit operating at 2.048 V reference voltage (that would make about 3.906uV steps/resolution).

After my research, I learned that 19-Bit is pretty much what you can expect from a custom PCS design (if at all), that's why I have chosen an ADC with a ref of 2.048V (because going up to 5V ref, I would need at least 20-Bit to reach 4.768uV steps/resolution).

ADC:
So I have chosen this ADS1219 ADC (24-Bit): ADS1219 ADC Datasheet
I need an I2C-Interface which this IC offers. Also this ADC has an internal 2.048V ref and an internal low drift oscillator.

Instrumentation Amplifier:
To properly amplify the signals that I will feed into the ADC above, I chose this  AD8227 instrumentation amplifier: Datasheet of ADS8227 Instrumentation Amplifier
To get a signal from the sensors (initially from 0mV - 20mV) amplified for the reference voltage of 2.048V of the ADC, I would use x 102 Gain (825 Ohm gain resistor) to amplify a 20mV signal up to 2.04V.

I want to connect multiple of these INAmps to the ADC (as the ADC is a 4-channel).

I can now connect the pyranometers to the INA like shown in the picture below (for differential measurement):

The complete circuit would look like this:

Some questions I have:

I'm using a rail-to-rail INA and supplying it with 2.048V only (using an LDO) to amplify the voltage to a proper value so the ADC (with a ref of 2.048V) can map the analog values accordingly. Although this is a rail-to-rail INA, do you think there could be problems missing values because it will not swing completely to rail on the output?
On page 21 of the datasheet of the INA it says a current return path must be provided. On the schematic I marked the return path I created between the sensors and the INA in blue color. Can I do something like this, when considering to measure the sensor signals differentially? If not, how would I provide a return path in this case?
Is it a good idea to work with 2.048V reference voltage in my case or would you go with 5V? As the ADC has an internal 2.048V ref and can be powered with up to 5.5V, it should not be a problem? Do you see any other problems regarding accuracy here?
The chosen ICs seem to be pretty accurate. Do you see huge issues in this case going for like 18-19-Bit accuracy/resolution here, with the provided system/idea?
On page 1 of the ADC datasheet, there is a schematic of the device. One can see that there are internal signal buffers right in front of the ADC, so I guess there should not be a problem going with the INA output directly to the Analog Input of the ADC?

Thank you!
It is a lot of text, but I still hope that some of you experienced people can give me some hints on my questions or if the direction this project is going is completely wrong. I highly appreciate any input from you!

I posted another question regarding amplification using only the ADC IC and its internal PGA here:
Question: How to use the internal PGA of an ADC IC


texts: Peak-to-Peak vs Mean Voltage Measurement

texts:
I am using an oscilloscope with 2 probes to measure the average voltage across a resistor over time.
In regard to the measurement modes for the 2 channels on my oscilloscope, I am not sure whether to choose mean(average of data values) or Peak to Peak(difference between maximum and minimum data values). Maybe it doesn't really matter, but I hope to gain some clarity in this.
Thank you:)


texts: I have trouble with finding out resistance of a resistor. It has 5 bands but somehow I cant get the code right.


texts:
Can every divider and coupler that provides 3dB amplitude divison and 180 degrees phase difference be used as balun?

Rat race coupler and lange coupler provide the two conditions mentioned above.

If I place a λ/2 transmission line after a Wilkinson divider, overall structure satisfies the conditions mentioned above.

My question is, why do we use a different name for these kind of devices if I can already implement them with couplers and dividers?


texts: Problems with a non-inverting op amp configuration when input voltage is too low

texts:
I currently have a very simple op amp circuit for a non-inverting amplifier, using a UA741 with the gain set as 2.  I have a sensor that outputs 0-2.3V and I'm attempting to amplify it up to 0-4.6V.  The set up for the op amp is below.

The problem is that when I test this circuit under about 2.5V the amplified output voltage just sits at a steady 4V.  Is this a problem with the chip, or is there something I need to do in the circuitry?  I was going to try an LMV324 as well, but I would have to power it with a lower voltage which made testing the circuit more difficult.

Any insight is appreciated.


texts: Calculating Joint (Load in lbs or Kn) requirement for a compression lug on top of a bus bar

texts:
I have found myself in an interesting scenario that is actually more mechanical in nature but maybe you guys can point me in the right direction.

I am having a hard time finding any ISO, IEC, or ANSI specs that dictate a proper way to calculate the force required needed to make a bolted-jointed connection using a terminal on top of a bus bar.

Problem Statement: I need to find the torque value required for my bolted connection that can easily see 2,000Volts.

I am using a Burndy compression lug with M12 hardware.  Burndy gives no recommended torque value and said it is dependent on the hardware.

For the 10.9 Grade hardware I am using, with a 75% proof load, this value is 70FT*lb.  Very easy to get this information, no problem here.

The problem is, I am using a belleville washer, the supplier for the belleville washer is saying I should not exceed 40 ft-lb, and they are recommending 26-34ftlb.  34ftlb will fully flatten the belleville washer.  Let's go with the average here and roll with 30Ft*lb.

Assuming the bus bar and terminal I am using will not yield to 30ft-lb (I am still waiting for exact copper grade from these suppliers so I can get the exact yield strength), but now I am worried that maybe 30FT-lb isn't enough for this connection regarding the clamp force needed between my terminal and bus bar.

Any advice? Any standards that someone may know of?  Any electrical drive guys out there? :)


texts:
I have built a custom stm32f429 board. It uses SPI, I2C, UART and CAN for communication with various sensors. This is my first stm32f429 board, i've designed boards around stm32f3 and f1 series before. I'm using SWD interface via the stlink-v2 debugger/programmer. The STLink utility recognizes the board without any issues and i can even program the chip with STLink.

However with openocd the board is detected without any issues, but i run into the following error when doing a "reset halt" from the telnet session.

"target stm32f4x.cpu not halted"

Following are the openocd commands i use:

openocd -f ~/openocd-0.9.0/tcl/interface/stlink-v2.cfg -f ~/openocd-0.9.0/tcl/target/stm32f4x.cfg

In a separate window

telnet localhost 4444

My initial diagnosis was that this is definitely related to the NRST circuitry. So i checked if PDR_ON is connected to Vdd since according to AN4488, if PRD_ON is pulled to GND the internal power on reset and power down reset circuitry is disabled. PDR_ON voltage is 3.275V, which is the same for all VDD pins. VCAP1 and VCAP2 are at 1.132V and i'm using 2.2uF caps on VCAP pins.
External reset circuit is pretty simple. I have attached the relevant snapshots of the schematic here for reference. Please do let me know how to proceed with further diagnosis or if i've missed something in the design of the board.

P.S PDR_ON is connected to Vdd. In the schematic it is left unconnected.


texts: LTspice: Simulating a Van Der Pol Oscillator

texts:
I am trying to simulate the oscillator with an RLC circuit with the initial condition V(V1) = 0 and D(V(V1)) = 0. Since LTspice does not allow initial condition with time derivatives, I set the initial current of the inductor to be -6A. (Initial resistance is 1/3 ohm, and initial current through the capacitor is zero.) The node V(V1) does show a limit cycle behavior, but the amplitude(around 1.2V) is different from the numerical result in Mathematica(2V). I have set all serial and parallel resistance/inductance/capacitance to be zero for the components. Any suggestions on what could be wrong? Thanks in advance for any advice!

Edit: I have also tried using a physical circuitry to initiate my circuit. Yet the voltage of limit cycle is still 1.2V.

Also, if I change the resistance in my Mathematica file to be 1/(3*V(V1)*V(V1)-1) instead of 1/(1*V(V1)*V(V1)-1), the voltage response is exactly the same as the result in LTspice. (The first plot in the picture below is when I change the expression of the resistance, and the second plot shows the overlap with LTspice result.)

On the other hand, all voltage responses scale proportionally as expected. For instance, when the resistance in Mathematica is 1/(V(V1)*V(V1)-4), the amplitude doubles and becomes 4V. The amplitude in LTspice also doubles to be around 2.4V when resistance is 1/(V(V1)*V(V1)-4).


texts: How to choose a capacitor for filtering an audio signal?

texts:
I've recently become interested in analog synthesizers and have successfully built this VCO from MFOS.

The VCO outputs a signal that varies from 0 to about 10 or 12V DC at 28mA. I want to bring this down to (roughly) line level so I can record it without blowing up all my stuff.

Using Ohm's law I figure that a 20Ω resistor should bring the voltage down to about 0.5V. Does that sound right?
I'll need to use a capacitor to filter out the DC bias of the signal (right?) How do I calculate what capacitance value I need?

Edit:

Here's a link to the schematic for the main part of the oscillator. The output I want to tap (at least at first) is the sine wave output next to R49 (near the bottom right.)


texts: Using relays to switch between video outputs

texts:
I have a simple question: would I be able to send a video signal (composite) to each relay per camera? The reason is that I only have one video input but need to be able to use two cameras (not at the same time, though).

I have my drawing that I sketched out of what I think the hookup may need to look like.

I wasn't sure if a relay would work since I was thinking the relay itself would mess with the video signal when the magnet engages the pin inside.

I will be using this type of relay with an Arduino:


texts: Should a frequency-controlled motor use a circuit breaker with a B or C trip characteristic?

texts:
In our company, a discussion is raging on whether a motor with a frequency controller should be protected with an automatic circuit breaker with B or C characteristic.

The B-camp's argument is that, because of frequency controllers or soft-starters, the inrush current on a motor is much lower so a B trip characteristic should be sufficient. The C-camp believes that using B characteristic is just not allowed.

Are there any reasons to still use a C-characteristic circuit breaker?


texts:
This board has two counter inputs.

But is there a way to figure out whether the counter counts each rising or falling edges? Rising or falling edges?


texts:
I'm switching a solenoid with a relay. The relay has failed after just a few hundred operations, I suspect because of the flyback from the solenoid.
I have a P6KE20A TVS diode that I want to use to protect the relay contacts.
Now I wonder, does it matter whether I place it parallel to the solenoid or parallel to the relay contacts? Does the fact that it's a TVS diode have any influence on placement? (Unfortunately it is unidirectional I believe.)

simulate this circuit – Schematic created using CircuitLab

simulate this circuit


texts:
I want to build a device that would recieve a NFC TAG and send it via Bluetooth to the Mobile Phone, that has Bluetooth enabled.

I am searching for some basic articles or some starting points on how to accomplish this.

I am thinking that I'll need some sort of uController that will transfer the bytes between NFC chip and Bluetooth Module.
But I don't know how to proceed on this step.

Any advice would help me a lot.


texts: How to convert a digital signal from 24V to 5V

texts:
I have an industrial automaton that gives me a digital signal (24V or 0V) on its outputs and I want this signal to control an integrated circuit, but the integrated circuit only takes a TTL signal in its input (0 to 5V).

I think it can be controlled if I convert the 24V/0V signal to 5V/0V. How can I convert this signal?


texts: Can I identify live or neutral wire with Klein CL1000

texts:
I don't have one of those simple voltage detectors but I do have a Klein CL1000 meter and I need to identify the live and neutral wires from a plug in a socket.

It's a two prong socket in Central America, 120 Vac 60 Hz.

How can I identify the live or neutral wire of a CL1000 with only a clamp meter?


texts: What does this schematic symbol indicate? (Bent line)

texts:
I'm looking at a schematics of a power system, and encountered some schematics I find quite strange.
As you can see, the schematic contains a lot of bent lines. I have two hypothesis:

It indicates jumpers, see this question.
It indicates fuses

As you can see, the horizontal line in the bottom is labeled "30m Cross Over Jumper Spectron 10". This of course, strengthens hypothesis 1. I think it also makes sense, seeing there are connectors you can connect/disconnect. However, I don't see why you would need three of them for just one single branch. Also, the system is subsea, I don't know if you can use jumpers the same way you do in "normal" systems.
I think it looks similar to common symbols for fuses, but again, I don't see why there should be so many. (And fuses on the bottom of the ocean doesn't seem like a particularly good idea).
Additional information:

The distances are small (from the red arrow and down, the schematic has been updated. Above the red arrow, the cables may be long). The transformer is very close to the load (compressors).
The horizontal cable at the bottom goes to an identical parallel setup (100kVA transformer, 36.5 kW load etc.).
The entire system is subsea.
The power umbilical is several km

Update:
Here's a more complete schematic.

Does anyone know what the symbol means?


texts: How can I find the frequency of oscillation of this sawtooth oscillator circuit?

texts:
Simple question: how to find the frequency of oscillation of this circuit?

simulate this circuit – Schematic created using CircuitLab

My attempt at answering the question is the following:

Suppose we are observing the circuit at when the voltage on the capacitor is zero. Q1 is ON and Veb is equal to 0.8 roughly. Applying KVL and neglecting base current through R2 (assume voltage at R2 equal to 10/11*9=8.18V) we get that voltage drop on R5 should be 0.02 V which implies an emitter current of Q1 of about 1.81 micro ampere. Assuming the collector current is roughly equal to the emitter current we can see that the capacitor needs 0.295 seconds to get to a voltage 4.5+0.8V which is going to turn on Q2 and Q3 for discharge. But that time gives me a frequency of about 3.43 Hz which is 1 order of magnitude off of what I read on the oscilloscope (45 Hz). Why is this so?

EDIT: Vcc is 9V


texts: I didn't understand why we are subtracting load voltage from output open circuit voltage in part (c). What is the logic behind it?


texts: Using a switch detect IC with negative voltage

texts:
I am designing a circuit where a negative voltage signal can have multiple levels, eg -12, -8, -6 depending on the circuit state.
I am looking at several switch detect ICs such as TI's TIC12400 that seems to work with -40V up to +60V on its inputs.
How do I set up a switch detect IC such as TI's TIC12400 or NXP's CD1020 or CD1030 to generate an interrupt whenever my signal changes its voltage, eg from -12 to -8 or from -8 to -6? Is this even possible without additional op-amps/comparators?
TIC12400 datasheet: https://www.ti.com/lit/ds/symlink/tic12400-q1.pdf?ts=1611867637102&ref_url=https%253A%252F%252Fwww.google.com.tr%252F
CD1020 datasheet: https://www.nxp.com/docs/en/data-sheet/CD1020.pdf


texts: BLDC motor design, physical appearance question

texts: Excuse me if this is a dumb question, but I always wondered why are BLDC motors usually quite short in comparison to their diameter? Is it due to some electrical properties that make this design the most effiecient? How would you compare two motors that both take up the same volume but the first one is short and has a large diameter and the other one is long and has a small diameter (if it's even possible).


texts:
I wanted to use solenoids in previous projects and have been let down by the fact that I can't find them here in Egypt. Plus they are a bit expensive. My question is: is there an alternative that it easy to control and cheap? If not, can you direct me to a way to easily make my own solenoids with limited materials (since I need 31 in a specific project)?

EDIT: I need to push or pull no more than 1". Please no links to buy solenoids.


texts:
Why when I put even a light load on the bridge rectifier output shows 100Hz ripple?

simulate this circuit – Schematic created using CircuitLab

SR240 datasheet


texts:
I want to hook up a resistive touchscreen to an ADC.

I'm new to electronics and experienced in developing software.
My intention is to learn, I would much appreciate it if you could nudge me into the right direction, pointing out the problems, rather than handing a solution.
Also I'm not native to the language, I might not get the words quite right, my apologies.

I got a 4-wire resistive touchscreen glued to the TFT panel "CFAF320240F-035T (320x240)"
and a "LPC2138" microprocessor board.

I have a 12V 300mA DC power source.
The source is powering the microprocessor, which is regulated to 3.3V;
and the backlight, using an uC output pin, transistor and resistors,
So i got 12V and 3.3V right away.

The ADC is specified with
 - 10Bit
 - voltage source interface resistance 40kOhm
 - analog input voltage 0..VDDA; VDDA being 3.3V here

The documentation has little specification on the touchscreen,
by using a meter i got a resistance span of
 - 300..600 Ohm.

I do not want to use an Op-Amp or a TS-driver-IC just yet.

In the following I just worked with the horizontal direction on the TS.
These are all assumptions, I have absolutely no idea if or where I am wrong!

(Figure 1)

R8-300 + R-TP1-300 is the touchscreen, I don't know how to present that more adequately yet.
By using a voltage divider, ignoring the ADC's resistance, i get a usable voltage span of maximum 0,5661V;
at R_TS = 300 Ohm ADC_IN becomes 1.4139V,
at R_TS = 600 Ohm ADC_IN becomes 1.98V;
With the ADC that gets me 17%, or a span of 7 bit, about 175 points on the screen.
It also draws 3,8mA +- 0,6mA;

Now I would like to have at least 320 points horizontal.

(Figure 2)

This is where I got so far.
There are no numbers yet, since that is still a bit of a struggle for me,
I'd prefer to get the heading right first
- On the left I use the touchscreen plus resistor R6 to get the control current down.
- Next, T1, R1, R2 and R4 build up a current source which will be pulled down by
- R3 and T2.
Using R10, R6 and R5 I can manipulate the offset, using R3 I can scale the output.
C2 I put in since I believe I have to filter the ADC's input.

Is that an applicable approach?
Where am I wrong or where do I miss things?

Thank you for your time.


texts: Does disconnecting the Tx+ and Tx- wires in the ethernet cable make it Unidirectional for Packet (TCP) sniffing

texts:
The DCSW-1005(10/100Base-T) Ethernet switch/TAP can be used as a network TAP (as well as Ethernet switch), in which a copy of outgoing and incoming packets associated with Port 1 (Target port) are forwarded to Port 5 (Monitor port).

The Packet_analyser sniffs the packets between the TCP_server and the TCP_client using port_mirroring enabled DCSW-1005(10/100Base-T) Ethernet switch/TAP as shown in the figure.

That means the Packet_analyser doesn't have to send any TCP hand-shake siglals (which will be taken care by actual TCP_client) but still receiving all TCP packets involved between the TCP_server and the TCP_client, hence I cut the TX+ and TX- wires of the cable C3 (cat-6 Ethernet cable, which will carry data from Packet_analyser towards Port 5 of the switch) thinking it will make the cable unidirectional, but it is not working.

So how can I receive the packets with TX+ and TX- wires from Packet_analyser are open (cut).


texts: MOSFET have big voltage drop across Drain-source?

texts:
I tried with IRL544 and IRF540N (N channle mosfets)by connecting load(12v-0.45A)as this image.

Above image is only to show my schamatic.

When ieasure voltage across drain and source it is around 3.7V(both).
As i expected it should be lower then that. Is there something wrong with schematic?


texts: What points do you need to measure in PCB according to IEC 601? Is it the closest distance between any conductive parts? For example minimum air clearance for means of operator protection in secondary circuits, so I measure the closest distance between any conductive part in secondary circuit? I know air clearance and creepage distance principle, but don't know how to use in practice.


texts: Wheatstone bridge with capacitors needs to be balanced

texts:
Given the Wheatstone bridge shown with AC input, how does one obtain the relationship C2*R2=C1*R1? The impedance between any nodes does not appear to be able to simplified in a way that would make the relationship easily visible through transfer function analysis.

simulate this circuit – Schematic created using CircuitLab

This question originally came from here: https://electronics.stackexchange.com/questions/105983/wheatstone-bridge-with-capacitors


texts:
I've built simple current source with current limiter. Regulated part of the circuit is supplied by 10V from Lab Power Supply in which I set also current limit to some value.
Idea is that U1 pushes current through M1, so that Power Supply reaches its current limit and is forced to lower the voltage - thus reaching voltage set on R2 potentiometer. In addition to that, U2 is preventing whole circuit to draw too much current - it has priority over U1.

it works fine. In reality, however, it works for small currents, but as soon as I increase maximum current using potentiometer R7, difference between voltage in point A and point B start to increase. So for current limited to 20mA I get 20mV difference. For current limited to 70mA I get 40mV difference.

Anyone got idea why difference is increasing with current? How can I fix this?

simulate this circuit – Schematic created using CircuitLab


texts: Strong H fields: electronic items susceptible to thier damaging effects and how to shield them

texts:
This is another question related to magnetic fields.  I'm trying to determine the thickness of copper foil that would be required to shield common electronic items from H fields of about 133 A/m over a range of frequencies from 1-1,000 MHz. I'm shooting for 50 dB of attenuation, and I'm trying to include cost and other practicalities among the considerations.

Based on the fact that 35 microns of copper foil attenuates an H field by 8.6 dB at 4 MHz, I calculated that a 407 micron thickness would be required to provide 50 dB of attenuation at 1 MHz. This is twice as much shielding as what's required at 4 MHz, four times as much as what's needed at 16 MHz, and much more than what's required at 1 GHz. In short, it's overkill for most frequencies.

So, my question is: what kinds of electronic items are most likely to couple damaging currents in a very strong H field at 1-36* MHz? Any item that contains a coil antenna that's sensitive on any of these frequencies would make the list. One item that comes to mind immediately is an AM radio (which might lower the lowest frequency of interest to around 500 kHz or lower, although this would require a thickness of copper that I think would be impractical).  I can't think of any other kinds of items that would contain loops or coils long enough to couple an H field at these relatively low frequencies.  Any suggestions? (Again, please consider a range of 1-36* MHz.)

* I chose 36 MHz as an upper limit, because 68 microns of copper would be required at that frequency, and I think this might be a reasonable thickness. It might not be the best thickness based on how many types of items would be susceptible to damage at lower frequencies, though, so I'm open to suggestions.


texts:
In this circuit there are several things required like the inductor and diode current, and the average power of the inductor, but what does really puzzle me is how can calculate the zener average power?

simulate this circuit – Schematic created using CircuitLab

I understand that the average power of any inductor is zero, but I don't know for the zener.
The inductor current is

$$i_{L}=\frac{1}{L}\int V_{CC}dt$$
and this would be the same current on the zener because when the transistor turns off the diode try to maintain the inductor current and breaks down.

The instantaneous power of the diode is \$I_{z}V_{z}\$ , but which is the average power?


texts:
I've used some SN74141 BCD-TO-DEC/DRIVER I had laying around to drive some nixie tubes recently, and I have also seen someone on the internet use HV5622 High Voltage Shift Register. I looked at both devices datasheet, but I can't find  any information about why the work with high voltage, how much voltage can they take or why they act as a GND connection (as in the example below from http://www.instructables.com/id/How-to-Control-a-Nixie-Tube-with-an-Arduino/).

PS. By acting as GND I mean that the tube is discharging through it, has this something to do with High Voltage capabilities?


texts: I came to know that in transmission line if I send only the phase to the houses and make the neutrals to ground then the circuit works. How does the circuit fill up without having any closed contact with the neutrals of both side.


texts: Getting started with AVR programming concepts

texts:
I am trying to get started with programming the AVR. I have chosen to use Atmega328P (which is in my Arduino Uno). When I did web search regarding the initial steps for learning the AVR programming, I came to know that the microcontroller requires a special program called "bootloader" to initailize the sketch we have created using the Arduino IDE. The bootloader checks if data (program) is present in RX pins. If the data is present, the bootloader grabs the program and places it in the flash memory. This process of loading the program into microcontroller takes place through UART protocol. In other words, the bootloader lets the program to be loaded into the microcontroller. I think I have understood the concept upto now. Any corrections are heartly welcome.

My actual confusion starts when I don't have any bootloaders in my microcontroller. I have my program ready to be loaded into the flash memory.But there is nothing to let the program to be loaded into the microcontroller. There is no bootloader, so there is nothing to let the program into the memory. This is where the programmer comes in action. The programmer takes .hex file from the PC via USB protocol. Then it sends this file to the microcontroller via SPI protocol(Since MISO-MOSI-SS pins are used). My question is:

Q1- Why don't I need bootloader to upload the program via SPI protocol. Why can't I upload the program to the microcontroller via UART protocol when there is no any bootloader present? What lets the microcontroller load program into its memory without bootloader when SPI protocol is used?

I went through various resources available to grab a concept of these things but I often get confused one way or other. I was studying "The Art of Electronics" and I am getting even confused regarding my first question. The book says:

"Contemporary microcontrollers use internal nonvolatile
(flash-memory) storage for program code, which you load (while the μC is in-circuit) by one of several methods. You
usually do the loading55 with a commercial “pod” (officially
called a “device programmer”), which you buy from
the chip manufacturer or third party. If you buy a development
kit (Figure 15.24), it will often include a programming
pod, along with software (for compiling, simulating,
assembling, and loading), and with a circuit board on
which there’s a microcontroller and other hardware (digital
and analog ports, LEDs, a serial port, a programming
header, and perhaps some display device). Here are the several
loading protocols: UART serial-port bootloader, SPI serial-port bootloader, JTAG serial-port bootloader, Proprietary serial-port bootloader, USB serial-port bootloader, Parallel loading."

Is the writer trying to tell me that the program I am uploading via SPI protocol is the bootloader? I can't rule out this possibility because the bootloader is uploaded into the microcontroller by the use of SPI protocol as well. Here's a tutorial from Arduino website.

Next part I have been studying is regarding the process of uploading the program into microcontroller. I have made a simple LED blinking program in Atmel Studio 7 and I have it's hex file ready to be transported to the microcontroller. I am taking this analogy to understand how hex file is uploaded into the microcontroller.

I have considered my hex file to be a product to be delivered to customer (microcontroller) by the seller (PC). The vehicle to be used is a delivery van (AVRDUDE). But the problem is the river between the seller and customer. So I need a bridge to connect them. This bridge is the "programmer". Is my analogy correct? If not, please help me understand what is the propose of AVRDUDE and the 'programmer'.


texts: Can anybody explain why my tongue gets a reading on a multimeter. Do I have a current? Why do i have resistance? Why do some things have resistance? I am very confused.


texts:
I want to calculate power loss across a resistive load during a 1 ms interval. The experimental setup is such that the voltage and current through the load varies the whole period of 1 ms. I have 10,000 voltage and current values within this 1 ms period. I am exploring the best way to find the power loss in this case. I have tried multiplying each instant's voltage and current (P= vi), and using trapz function in Matlab, I tried to find out the energy loss value (E=trapz(t,P)). However, I want to learn about the better ways to calculate power loss across the load over the 1 ms period.

Thanks.


texts:
I've been trying to build a simple audio pot to be controlled with PWM with an arduino, but I'm not sure why it doesn't work. I could do it with a LED (not directly which is simple, but with a FET), but audio seems much more complicated.

Here is the schematic so far...

simulate this circuit – Schematic created using CircuitLab

I probably need to connect something to the ground of the Arduino, I tried a few things but it didn't work.

The datasheet for the JFET is here:
http://eu.mouser.com/ProductDetail/Fairchild-Semiconductor/J202/?qs=ljbEvF4DwONNF0IklNND3Q%3d%3d

I just want to be able to control the level like a digital pot.

Any suggestions?

Thanks!


texts: I am breaking into the world of FPGA development at my internship for an aerospace company. I keep coming across the term "Dual-Purpose Pin" in the documentation for the Max 10 family of FPGA devices. I cannot figure out what this means, since these pins seem to each have one purpose (like DEV_OE, for example) yet they are referred to as Dual-Purpose. Can someone explain this to me?


texts:
I am trying to design a 4th/6th/8th passive low pass filter. The filter is used after a DAC to generate a fixed frequency sine wave. The DAC will export a square wave at 1kHz. So the pass band of the LP filter will be 1.5kHz with stopband at 3kHz.

There are various information on the internet to implement an active lowpass filter. The reason for us to use passive filter is to avoid noises brought by OpAmps and reduce the number of OpAmps at the same time to reduce cost. Of course a voltage follower will be applied at the output of the passive filter.

So here comes my question.. How to design a 4th/6th/8th passive low pass filter?


texts:
I've this RC filter circuit (r is connect to earth on the bottom):

My Vin is a square wave:

With Laplace transform I derived that:

$$Vout(s)=\frac{r}{r+\frac{1}{cs}}\cdot Vin(s)$$

and this square wave has a laplace transform of $$Vin(s)=\frac{\text{A}\tanh\left(\frac{\text{T}s}{4}\right)}{s}$$

So, when we substitute that in,in the equation for Vout(s) and calculate the inverse laplace transform, and plot that function I got this:

  Q: Why do I get (from the theory) this strange output voltage?


texts: ATTiny45 Quadrature Decoder Pull-Up resistors

texts:
I am trying to use the ATTiny Quadrature Decoder from here.
The schematic that I have attached here has two external 10K Pull-up resistors.
I have looked into the ATTiny45 datasheet and it seems that the I/O pins already have pull-up resistors that you can enable. My question is why would you need external pull-up resistors if you could just enable internal ones?


texts: 1.5V-rated MOSFET doesn't react to a gate input of 1.8V

texts:
I am not really an electronics specialist, but a software engineer (so excuses if I 'm asking stupid questions).

I am trying to use a microcontroller GPIO output rated at 1.8V. When this pin becomes high, I want to enable a 12V relay. I am using a N-channel MOSFET from freetronics

The specs for the MOSFET can be found here.

For some reason the 1.8V seem insufficient to drive the MOSFET although it is specified for 1.5V min. I've tried a standalone setup using a 1.5V AA battery and that doesn't work either. But if I apply 3.3V with the same setup, it works (just so you know my wiring is OK).

Unfortunately my microcontroller (Intel Edison) only has 1.8V GPIOs.

Am I missing something?  How can I make this work?  Should I use a different MOSFET? And if so, which one?

Your help is much appreciated.


texts: DALI - Read Energy Consumption of a Luminaire

texts:
I have been trying to find a command to read information about the energy consumption of a luminaire using Dali, yet couldn't find anything on the documents.
Is this possible to read information regarding energy usage?


texts: Inverting Charge Pump with Push/Pull Stage

texts:
I am trying to build an inverting charge pump capable of supplying ~80-100mA at the second stage.
Since the PWM signal must source the current, I decided on using a push-pull stage based on this article, which advertises the following schematic:

I build this circuit (only two charge stages; that's enough in my case), but am using Vin = 12v, PWM = 5V, as well as BC327/337 transistors due to the higher current load.
However, loading the circuit causes the transistors to get very hot with the advertised R1/R2 and the CE driver stage.
I tinkered with those values but was not able to get a satisfying result. The Vbe of the upper transistor does not allow it into cut-off (I think that's the problem).
I have since looked at different push-pull designs, class AB and D amplifier stages and their biasing using both resistors and diodes, as well as other schematics, but have been unable to come up with a satisfying result.
1. How can I get a clean 0-12V square wave at the collector junctions of Q1/Q3
2. Is there a better way to drive this charge pump with a square wave
I will likely use paralleled LMC7660 drivers in the final circuit, but now I would really like to understand why this isn't working and getting it working
EDIT:
As suggested, I have tried separate CE drive stages for each transistor, but the base voltage of the top PNP (Q2, red trace) appears to be misbehaving. The NPN base voltage trace of Q1, green appears ok:


texts:
Could you please help me to identify this connector ? Could you please advise me a reference for a corresponding mating connector ?
Additionnal information:

24 pins.
0.5 mm pitch.

Edit: Successfully solved thanks to your help. It is a AXK5S24047YG connector, to be used with a AXK6S24447YG mating pair.


texts:
Welcome all. I need some advice with Sallen-Key topology. I used Analog Devices tool for my design and I admit it nice quick and easy. However, I am struggling with one detail. When studied control systems I remember fact that difference between Bessel Butterworth Chebyshev and Elliptic filter is polynomial. In Sallen-key we control what type of filter it is by changing duping factor. As far I remember we can use following formula: Q=1/(3-A) and that dumping factor = 2/Q. Assuming that these are correct.

Is my assumption that after appropriate components are selected for particular frequency (R1,R2,C1,C2) I can change type of filter by simply changing the ratio of R4/R3 as A=1+(R4/R3).
If first statement is correct how does Analog Devices filter tool achieve different LPFs using only unity gain op-amp arrangement?


texts:
I have designed a circuit which powers a small microcontroller (50 mA max) by USB. The circuit (I hope) will allow a laptop or PC to occasionally attach to the microcontroller to download collected data. I have some questions on my design shown below:

Do I need both diodes D1 and D2? Or Just D2?
The microcontroller board will be continuously powered thru J1. Can I hot-plug a PC or laptop on J3 to occasionally monitor and download data?


texts: Is there any relation between the output voltage stability and the choice of resistors for this adjustable regulator?

texts:
The following LM317 adjustable voltage regulator example uses R1 & R2 to adjust the output voltage:

And the datasheet for the output formula is given as:

Now instead of using R1=4.2k and R2= 10k one can also use:

R1 = 420 and R2 = 1k or

R1 = 42k and R2 = 40k  ect.

So we can obtain the same output voltage when R1 and R2 are as small as hundreds of ohms or very big as tens of kOhms or even more. I can see that Iadj changes with resistance values.

Regarding the options of R1 and R2 values, is there a reason to chose one option to the other? From power perspective one might chose tens of kOhms. But that makes the Iadj very small. Is there any relation between the output voltage stability and the choice of resistors here? What could be the correct way of reasoning?


texts: Car blinker setup, turning off parking lights when blinker signal is high

texts: I have a basic idea of how to do this, but I could use some help. Not sure what transistors to buy. LED is less than 5 watts. Voltage may fluctuate 12v-14v. I came up with this circuit. Input from blinker relay should cause the second mosfet to be pulled to ground. Is N-channel a proper choice?


texts: How to deal with optimal power flow problem in MATLAB?

texts:
I am writing an optimal power flow (OPF) program. OPF is an optimization problem in which some decision variables like Generation, Load dispatch are adjusted in power flow program so as to minimize the objective function (usually cost of generation).
I am using fmincon Matlab function to solve this problem. Like any optimization problem, OPF have some linear and nonlinear constraints. These constraints are added to the problem to guarantee the feasibility of the solution.
I wrote these constraint in Matlab, but I am getting infeasible results which is due to constraints. The constraints of this problem are as follows:

In Here I have posted part of my code that I need to supply the constraints to fmincon. Please check if I wrote the constraints are correct .

Note:I used IEEE New England test system to run OPF on it. This test system contains, 39 Buses, 19 Loads,10 Generators, 46 Lines.


texts:
This will be my first attempt to control a 110v device (high voltage, by my standards!).  Initial tests will be on a table lamp; eventual target may be a small 500W heater.

How should I wire the 110V device to the screw terminals?
Other than putting the unit in a plastic project box, what safety precautions should I take?
If the project box has a metal lid, should I attach the 110V ground wire to the lid?
what are the abbreviations NC, COM, NO?

This is the device I will be using:


texts: Photodiode : Transimpedance amplifier or integrator?

texts:
I'm doing an amplifier for a photodiode. In my search I see the transimpedance amplifier is the most used. I will use a ADC just after. The value of my feedback resistor will be 100 MOhm.

I've done some more research and I found some information about the integrator. I know how it works but what are the mainly advantages/disadvantages between the integrator and the transimpedance configuration (bandwidth, precision, level of current to measure,...)


texts:
I have an old camera which Im tinkering with and when I opened it up I found that the battery (liPo) is puffy. As I dont have a spare I can't replace it and Im beginning to doubt myself that its safe to just put a wire there instead. I will be plugging it in to a 5v usb.

TL;DR: Can I put a wire in place of a battery?

Edit: It has a built in 5v usb port, which is what I intend on using to power the device. I would like to know a safe way of removing the battery, so that it will only be powered when plugged in.


texts: I am studying about the 8255A PPI. In Mode 0 of it, it says that the outputs are latched and inputs are not latched. What exactly does it mean?


texts: Brushless DC motor runs fine in one direction but not another

texts:
We have changed BLDC motor suppliers and are seeing a new problem.  In the old system the software commanded the motor to move 5 steps of X hall counts then stop.  With exactly the same electronics and software but with the new motor (which may have different hall sensors), the motor moves it's 5 steps but at a much reduced speed.  We just got the motors today and don't have the full specs on it yet.  Any ideas as to what could be causing the problem?  I've attached 3 pics.  The first one shows a scope trace on the U phase hall sensor output of the original good motor.  The 2nd pic shows the same hall sensor output on the new problematic motor.  The third pic shows the circuit diagram.  The hall sensors are connected to J9 at the right of the diagram.  J10 is the motor connector.

Thanks a great deal for any help,
Fred


texts:
I am currently designing a 6 layer board that has a couple of DC-DC converters on it. The largest one is a buck that transforms 12V to 5V with an ouput current of max 7A.

Layer 2 would be GND, layer 3 power. The others are signal/GND.

Is it good pratice to put the power plane on an inner layer (layer 3)?
If so, is it possible to place the input capacitors like this (only top layer shown):

EDIT:

Here is a bigger picture of the Buck. Only a draft, not all components are connected yet, but you get the idea. Also only top layer shown. I place the input capacitors this way to save some space on the PCB.
Note, before the buck, there is a battery charger, which also has output capactors.


texts:
I'm wanting eventually to interface some memory to my fpga.
This will require pins on the fpga that can both read data and write output to the ram.

I'm far away from doing any of that yet, but as a learning exercise wanted make a simple module in verilog that when a direction signal is '1' output a signal to a pin, and when it is '0' reads a value from that pin.

But I can't get anything to compile. I'm not completely inexperienced with verilog but feel I'm missing something fundamental here rather than just having a simple typo in my example.

This code doesn't compile, I'm looking for either how to make it work, or even just a pointer to what I'm fundamentally missing to make bidirectional signals work. If it matters I'm using xilinx tools and plan to synthesize this to an xc3s50 or similar.

// This doesn't compile...
module test(
    input  clock,           // The standard clock
     input  direction,  // Direction of io, 1 = set output, 0 = read input
     input  data_in,        // Data to send out when direction is 1
     output data_out,       // Result of input pin when direction is 0
     inout  io_port     // The i/o port to send data through
     );

always @(posedge clock)
begin

    // If direction is 1 then set
    if (direction == 1)
    begin
        io_port <= data_out;
    end

    if (direction == 0)
    begin
         data_in <= io_port;
    end
end

endmodule

edit The errors I get are -

ERROR:HDLCompilers:247 - "test.v" line 16 Reference to scalar wire 'io_port' is not a legal reg or variable lvalue
ERROR:HDLCompilers:106 - "test.v" line 16 Illegal left hand side of nonblocking assignment
ERROR:HDLCompilers:247 - "test.v" line 21 Reference to scalar wire 'data_in' is not a legal reg or variable lvalue
ERROR:HDLCompilers:106 - "test.v" line 21 Illegal left hand side of nonblocking assignment


texts: Replacement for three terminal capacitor

texts:
One of capacitors on my IBM 5150 motherboard burned out, so, I'm looking the way to replace it. I tried to google to identify this capacitor:

It looks like it's a 10 μF 16V three terminal capacitor, but I was unable to find anything like this on ebay, so, probably, I'd better to make a replacement using two capacitors, but, I have no idea how to make it. I would very appreciate any help because I really want to resurrect this motherboard.

here is another image (i decided to cut it from pcb, because I don't want to do something irreparable with my soldering iron, as I understand this board has several internal layers):

Thank you very much!

P.S.> I've made one more picture which is representing polarity. So, it's getting -12V on outer pin.


texts: Possible to reliably run USB over a non-standard USB cable?

texts:
I'm planning on building a device for my car that sits somewhere in the rain tray or behind the dashboard.  It will use automotive connectors so that things are sealed, easily connected and disconnected, etc.  I plan on having it be controllable/configurable over USB, but I still want the unit to be sealed.

How feasible would it be to run the USB connection through the normal pins of the sealed connectors?  It would be regular stranded conductors in the 18-20ga range, and I'd probably have to bundle, twist, shield and heat shrink them myself.

Is this a reasonable approach or is there something better I should be looking at... some specialized USB connector or something?


texts:
I am using a 74LVC8T245 buffer from Texas Instruments to interface 3.3V to 5V signals with my 3.3V microcontroller, here is my circuit:

The IC is powered by a 3.3v LDO Regulator MCP1702T. Now, when I put a 5V signal on Port B the 3.3V supply goes to 4.2-4.5V! Why is this happening? AFAIK I can go up to 5V with this IC even powering it with 3.3V.


texts: From prototype to printed board - who does the translation from wired proto to circuit board

texts:
The question is broad, and I am sure that there is more than one way, but the generic sequence should follow a common pattern, and that's what I am looking for.

I basically would like to move from prototype to a board, designed to fit the components that I need (chips and IC on single boards on my prototype).

So I need some knowledge about who actually does the translation from proto board (bunch of wires, Chinese breakout boards, on a proto board) to a printed circuit

Could anyone give me some advices about where to start? Is there a specific category of worker that does this job? I assume "Electronic Engineers", but it is a field that I do not know, since I am a SW Engineer.


texts: Calculate voltage of a 16-bit differential ADC that gives a two's complement value

texts:
I am working with a 16-bit differential ADC and I would like to know the difference between this latter and a single ended ADC especially: How to calculate voltage from the ADC value ?

Is it like this:

Voltage = IN- + Vref x Code/2^n-1

EDITED: According to the datasheet, the ADC gives a two's complement value. How to calculate voltage from this value ?


texts:
I'm working with a mid-infrared (~4um) photodiode model Lms43PD-03-CG (Datasheet) and a matching LED (Datasheet). (I can't switch from this photodiode/LED pair) I'm trying to make a functioning photodiode amplifier but have not been able to get the photodiode to respond.

I've tried a basic photodiode amplifier but no feedback resistor value would work. I tried adding a capacitor to stabilize the trans-impedance amplifier but no values appeared to work. I tried biasing the positive input of the op amp to not ride the rails, and still nothing.

I've recently started experimenting with using photoconductive mode (to increase the power source of the photodiode), but don't know/can't find much information about designing a photoconductive photodiode amplifier. I even tried using Analog's design tool but photodiode's specifications our outside of their photodiode parameters.

This is the design that I'm looking to design around with the photodiode being reverse biased. I am connecting the photodiode amplifier to a lock-in amplifier once I get the photodiode responding to light and creating a voltage response. I am checking the output signals with an oscilloscope.

Some other important information:

The op-amp I am using is the MCP6002. The desired frequency is at most 10kHz.

Here are my questions:

In the photodiode datasheet, there is a reverse voltage of 0.1V. Is this the same as the breakdown voltage, the max voltage that photodiodes may safely receive?
Would this circuit require a capacitor? If so, what equations should I use to determine this capacitor value? I've tried several such as TI's photodiode design guide to no avail.
What should I be cautious about designing this photodiode amplifier? I'll make sure to bias the positive input to avoid the rails.
What else could be causing this circuit to not respond? No matter how much I shine a MIR LED to the photodiode from a short distance, it doesn't respond.


texts: Faster quadrature decoder loops with Python code

texts:
I'm working with a BeagleBone Black and using Adafruit's IO Python library. Wrote a simple quadrature decoding function and it works perfectly fine when the motor runs at about 1800 RPM.
But when the motor runs at higher speeds, the code starts missing some of the interrupts and the encoder counts start to accumulate errors.
Do you guys have any suggestions as to how I can make the code more efficient or if there are functions which can cycle the interrupts at a higher frequency.

Thanks,
Kel

Here's the code:

# Define encoder count function
def encodercount(term):
global counts
global Encoder_A
global Encoder_A_old
global Encoder_B
global Encoder_B_old
global error

Encoder_A = GPIO.input('P8_7')  # stores the value of the encoders at time of interrupt
Encoder_B = GPIO.input('P8_8')

if Encoder_A == Encoder_A_old and Encoder_B == Encoder_B_old:
# this will be an error
    error += 1
    print 'Error count is %s' %error

elif (Encoder_A == 1 and Encoder_B_old == 0) or (Encoder_A == 0 and Encoder_B_old == 1):
# this will be clockwise rotation
    counts += 1
    print 'Encoder count is %s' %counts
    print 'AB is %s %s' % (Encoder_A, Encoder_B)

elif (Encoder_A == 1 and Encoder_B_old == 1) or (Encoder_A == 0 and Encoder_B_old == 0):
# this will be counter-clockwise rotation
    counts -= 1
    print 'Encoder count is %s' %counts
    print 'AB is %s %s' % (Encoder_A, Encoder_B)

else:
#this will be an error as well
    error += 1
    print 'Error count is %s' %error

Encoder_A_old = Encoder_A     # store the current encoder values as old values to be used as comparison in the next loop
Encoder_B_old = Encoder_B

# Initialize the interrupts - these trigger on the both the rising and falling
GPIO.add_event_detect('P8_7', GPIO.BOTH, callback = encodercount)   # Encoder A
GPIO.add_event_detect('P8_8', GPIO.BOTH, callback = encodercount)   # Encoder B

# This is the part of the code which runs normally in the background
while True:
    time.sleep(1)


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