texts: Finding the power difference of the current source E1?

texts:
When the switch is closed, the current I2 = 100mA, the task is to find Pe1 before the switch is closed and after it's closed and compare them.

Now I know that $$\Delta P_{E_1}=P_{E_1}^{\left(2\right)}-P_{E_1}^{\left(1\right)}=E1\left(I_1^{\left(2\right)}-I_g\right)$$

I am not sure how to start the task, finding and Thevenin equivalent for the rest of the circuit in respect of the branch with the switch isn't possible as not enough information is given.. any hints, if it's hard to provide a complete solution I would like some tips/hints in the right direction, like what theorems should be applied to solve this.


texts: Circuit that randomizes shut off time to LED's from 1 - 3 seconds when switch is thrown

texts: I have been asked to create a circuit that drives a set of LED's that when switched off uses a random timer from ~1 - 3 seconds before the lights go off. This will be used in a light signal box for a motorcycle roadracing start signal. The starter will turn the box on (3 rows of LED trailer tail lights for example) then when the bikes are all grided up and ready, the starter will flip the switch to "off" and then a random time between ~1 - 3 seconds the lights go off and the bikes launch. Can you all point me in the right direction? Thanks!


texts: I am developing the signal conditioning of the conductive polymer which gives the resistance change when the force/strain is applied to the sensor. To develop a signal conditioning, first the transfer function of the sensor should be defined. so how can i calculate my transfer function in terms of strain.


texts: What is this dark copper-less PCB feature?

texts:
Excuse the title, I'm not even sure what to call it, as far as I can tell it isn't a component but a copper-less layer of PCB showing?

It's on a 'Zoom H1' microphone/recorder's PCB, as seen in EEVBlog #271 - Zoom H1 Recorder teardown. (As far as I noticed it didn't get a mention in the video.)


texts:
Hi I've build this simple circuit :

I believed that closing the S3 switch (after the C1 was fully charged) the PNP transistor instantaneously would discharged the C1 capacitor.
Instead the discharging time is affected by R1 value (as you see on the scope screen).
I don't understand why.
Any idea?
Thanks in advance.
Update
Hi thanks to all for replies.
Yes I've understand the issue.
The only thing that is not yet clear to me is why, if I remove completely the R1 resistor, the discharging time goes to zero (and this is comprehensible) but I see a very high Ipp (not I)


texts: When I run the schemetic in LTSPICE,waves don't change direction.Why aren't waves changing direction here?

texts: What pulse should I set to produce a waveform like in the graph?


texts: Are there any microcontrollers with integrated H bridge for DIY servo?

texts:
I want to build my own servo system. It will get a PWM as input then move an object according to this input. I have a motor, potentiometer feedback, microcontroller with separated H-bridge.

Since I need a lot of these I want to use an IC with both H bridge and microcontroler on same chip. Like the one we find in servos.

Are this chips available for sale, or are they made by servo manufacturer for their own use ?
Are the PID parameters (Pi, Di, Ki) inside changeable ?

Question edited after  Wouter van Ooijen comment.


texts: How can you conduct a simple test for a MOSFET?

texts: Is there a simple way of conducting a test on a MOSFET? For example, testing if a transistor is in good condition or not by using a multimeter. Can the same test work for a MOSFET?


texts: total transfer function of a LTI System with feedback

texts:
I have calculated the transfer function of such systems many times, but now i feel like I`m going around in circles.
I have drawn a few help-signals to help me solve it, but they are dependent of one another and no matter how many times I replace the values, I just finish where I started.
I must calculate the total transfer function of the system from the attached image. The coloured lines are the help-signals that I added and their description is below.
Any help is appreciated]1


texts: Can I cut off a USB C plug, and replace it with a USB C socket

texts:
I need a USB C (female) to USB 3.0 Micro B (male) cable. Unfortunately, I can only find a male - male cable.

Is it possible to cut the USB C plug off, and solder the wires to something like this:

Or is it more complicated than that? If it makes any difference, the USB 3.0 Micro B is the upstream port of a USB hub, and they USB C cable goes to the computer.

I'm a bit paranoid about killing a MBP USB port!

I know that female - female adapters do exist, but I need to cram this into a very small space, and they're all too big.

To clarify:

Currently:

USB A(male)--|
             |
             |
             |
-------------|------------------|
|             ------ usb 3.0 .  |
|                    micro B on |
|                    PCB(female)|
|                               |
|                               |
---------------------------------

What I want:

USB C(male)--|
             |
             |
             |
             |
             |(USB C female receptacle mounted to keyboard chassis
-------------U------------------|
|             ------ usb 3.0 .  |
|                    micro B on |
|                    PCB(female)|
|                               |
|                               |
---------------------------------

Update:

The keyboard is a Das Keyboard 4, and the PCB looks like this:

So that port you see on the left of the PCB is a USB 3.0 Micro B connector, and that black wire threads its way along the top of the chassis, out of a hole, and then 6 feet later, terminates in a USB A connector.


texts:
I have a device I designed which utilizes 32 SK6812 LEDs (RGBW neopixels).

I am experiencing noise in the 1.2khz range (SK6812 LEDs use a 1.2khz PWM signal to control color and brightness) and its associated harmonic frequencies. This noise is most apparent in the 5v line on my device (the SK6812 LEDs are powered on this line).

The device is powered by a modular rack which has +12v, Ground , -12v. The 5v power for the SK6812 is supplied by a switched power supply that drops +12v to 5v5, which goes through an LDO and then to the 5v line where the SK6812s are connected.

The noise is apparent on other modules connected to the same power rails. These are mostly analog audio modules, and when they are completely silent, when the gain is boosted 65db, the noise becomes apparent.

Here is a photo of the spectrum of the noise recorded:

Here is a photo of the spectrum of the rack with my device disconnected completely:

I am pretty certain that this noise is coming from the LEDs because (1)the noise is only apparent when the LEDs are on, and changes slightly when different LEDs change color, and (2) because most of the noise heard is at the same frequency as the PWM rate for the LEDs.

One obvious solution is to increase bypass capacitors, and possibly use higher capacitance aluminum electrolytic in addition to my 0.1uF ceramic capacitors

My questions are these:

1) What value (and type) of capacitor do you recommend to lower low frequency noise in the 1khz - 5khz range? With 30 LEDs, how many would you reccomend?
2) are there any clever (and cheap) ways to isolate my device completely where it connects to the rails? Ferrite Beads? Inductors? What type do you reccomend?
3) I plan on moving to a solid ground plane (I am currently using a hatched - which I recently found out doesn't help) as well as adding a ground plane to the top layer (2 layer board). Do you think adding additional copper on ground might help the bypass capacitors work better?
4) Anything else I am forgetting to ask?

Thank you!

Edit:
When measuring with a scope I get 530mVpp on the 12v rail with LEDs on, and 480mVpp with LEDs off

on the 5v line, I get 540mVpp with LEDs on and 500mVpp with LEDs off


texts: Converting an arbitrary pulse to logic level

texts:
Background:

I'm trying to measure the time interval between (4) different pulses with a baseline of ~2V and rougly 1.6V p-p . Currently I'm using the ADC on an STM32 to sample the four channels.

However, since I'm using the ADC its slow and the resolution of the time differences suffers.

Problem:

I want to convert each pulse to a logic level, like in picture 1, so I can poll them using IO pins instead of the slow ADC.

I've messed around with an op amp differentiator in Multisim but I can't quite realize what I want. Is an differentiator the way to go or are there some other solution. Remember, I'm really only interested in the start of the different pulses.

TL;DR Converting an arbitrary sine-ish pulse to a logic level, how do I?

Edit:
My differentiator design I've been messing with, it doesn't quite work for some reason.


texts: Actual reason why I have distortion in lower part of this square wave amplifier (level translator application)

texts:
I am designing a simple level translator using 2 transistors connected in series in LTSPICE simulator. I tried with one transistor but the output from the collector pin is 180 degree out of phase, as is usual with common emitter circuit. With 2 transistors, I get this distortion in the lower part of the step in LTSPICE waveform when I attach a probe at point "A" (this would get into stage 2 also.) This goes away when I increase emitter resistor value.

Can anyone tell me the exact reason why the lower part of the step has a hook in it and goes still lower when I try to go lower than 2.25 volts (which I need?) My aim is to go lower on the lower part of the step of the wave to get the "0" to satisfy TTL needs at output of this circuit (under 1 volt.) I don't have any problem in the higher part of the square wave.

The circuit (first picture), input waveform, output waveform with two different emitter resistors, 300 ohm and 50 ohm. Both are distorted on the "downs." I would like to know the reason!


texts: Reducing electromagnetic interference in underwater acoustics cables

texts:
Our college underwater robotics team has a passive acoustics system with four hydrophones that provide an analog signal typically between +/- 200 mV corresponding to the sound wave at that point in time. Our setup is as follows (per channel):

simulate this circuit – Schematic created using CircuitLab

We have a hydrophone with a single-ended output connected to a bandpass filter with cutoff frequencies at around 15KHz and 50 KHz (our signals of interest are in the 25KHz-40KHz band). This signal is then passed through a waterproof connector to a digital oscilloscope inside our waterproof hull. Inside the hull that have multiple thruster cables that add significant noise to our acoustics signals, and we are attempting to mitigate that. Our current proposed solutions are, in increasing order of complexity.

Wrap aluminum foil around the thruster and hydrophone wires
Twist the ground wire for each channel around the signal wire
Convert the signal to a twisted differential pair outside of the hull and convert to single-ended just before the oscilloscope
Use a coaxial cable for the entire run (This would be very expensive for us as we would have to purchase coaxial waterproof connectors)

Besides the (ungrounded) aluminum foil, which did not seem to help much, these all will require significant teardowns in our configuration and are difficult to test.

Is there significant difference in electromagnetic interference rejection between using a twisted single-ended pair vs differential pair? What are other ways that we can increase our signal integrity in a cost-effective way?

Edit: Some more information on the system
The wires are roughly 3-4ft long in total run length. The hydrophones are HTI 96-Min hydrophones. Unfortunately I do not have the input/output impedance of it, as I don't know the exact specifications (They were donated 14 years ago). The filter is composed of a 2nd-order passive high-pass filter which we made out of two 22ohm resistors and two .1 uF capacitors, an LTC1654 8th-order low-pass filter configured to a cutoff frequency of 50KHz and with unity gain, and an LTC6910 amplifier with a gain of 16. The oscilloscope is a Picotech 2000a with an imput impedance of 200 kOhm/8 pF.


texts:
I just started trying to use KiCad (complete newbie), and I have a very basic question about using power inputs with hierarchical sheets.

Let's say I want a single LED on a hierarchical sheet, while my main sheet simply contains a battery.

Should I use hierarchical labels to connect power from the main sheet to my hierarchical sheet, or is there another way?

For instance, the main sheet:

And the hierarchical sheet:

Is this the correct solution? I initially tried to used the +9v and GND elements in my hierarchical sheets (many of them in a single sheet), but KiCad complains that some of them are not driven.

I found lots of topics discussing this, but nothing I can really understand, nor related to hierarchical sheets.

If I need to use hierarchical labels for connecting power, then when should I use +9v and GND?


texts: How much voltage and current to charge a 24V battery?

texts: If I have two 12V 18A batteries and I want to charge them in series making a 24V 18A battery, how much voltage and current do I need  to charge this 24V without damaging the batteries?


texts: Should I connect the computer VBUS line to the 5V line of the board?

texts:
I am doing a project that needs USB communication with my microcontroller.
On the board there is already a 5V power supply. I would like to know if it is correct to connect the VBUS line from the computer with the 5V line that already exists on my board (put L4). Or should I leave VBUS floating? (remove L4).

I have no experience with USB development, I know the need for U10, but how I should feed U10 pin 5 to me is still dubious.


texts: How do I find out at compile time how much of an STM32's Flash memory and dynamic memory (SRAM) is used up?

texts:
I have the answer for Flash memory, but the RAM question still eludes me.

Arduino has this super nice feature which displays flash and RAM usage right at compile time. Ex. in the image below you can see that this Arduino program uses 2084 bytes of flash (6%) and that global and static variables use 188 bytes (9%) of dynamic memory, or SRAM.

When I compile a simple blink program on an STM32F103RB Nucleo dev board in the System Workbench IDE I'd like to know the same thing: how much Flash and RAM is used, and how much is remaining?

When building completes, System Workbench shows:

Generating binary and Printing size information:
arm-none-eabi-objcopy -O binary "STM32F103RB_Nucleo.elf" "STM32F103RB_Nucleo.bin"
arm-none-eabi-size "STM32F103RB_Nucleo.elf"
   text    data     bss     dec     hex filename
   2896      12    1588    4496    1190 STM32F103RB_Nucleo.elf

When I look at the binary output file, "SW4STM32/Debug/STM32F103RB_Nucleo.bin", I see it is 2908 bytes, which is the sum of text + data. Therefore, that must be my Flash usage! Since I have 128KB of Flash, that means I am using 2908/(128*1024) = 2% of the total Flash space.

But how do I figure out how much SRAM my global and static variables are using, and how much is available for local variables (like Arduino shows)?

I don't have a clue what any of this stuff means yet, but if this is helpful to help you help me, here is the output from objdump -h STM32F103RB_Nucleo.elf:

$ objdump -h STM32F103RB_Nucleo.elf

STM32F103RB_Nucleo.elf:     file format elf32-little

Sections:
Idx Name          Size      VMA       LMA       File off  Algn
  0 .isr_vector   0000010c  08000000  08000000  00010000  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  1 .text         00000a1c  0800010c  0800010c  0001010c  2**2
                  CONTENTS, ALLOC, LOAD, READONLY, CODE
  2 .rodata       00000028  08000b28  08000b28  00010b28  2**0
                  CONTENTS, ALLOC, LOAD, READONLY, DATA
  3 .init_array   00000004  08000b50  08000b50  00010b50  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  4 .fini_array   00000004  08000b54  08000b54  00010b54  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  5 .data         00000004  20000000  08000b58  00020000  2**2
                  CONTENTS, ALLOC, LOAD, DATA
  6 .bss          00000030  20000004  08000b5c  00020004  2**2
                  ALLOC
  7 ._user_heap_stack 00000604  20000034  08000b5c  00020034  2**0
                  ALLOC
  8 .ARM.attributes 00000029  00000000  00000000  00020004  2**0
                  CONTENTS, READONLY
  9 .debug_info   00006795  00000000  00000000  0002002d  2**0
                  CONTENTS, READONLY, DEBUGGING
 10 .debug_abbrev 000013b2  00000000  00000000  000267c2  2**0
                  CONTENTS, READONLY, DEBUGGING
 11 .debug_loc    00000d0f  00000000  00000000  00027b74  2**0
                  CONTENTS, READONLY, DEBUGGING
 12 .debug_aranges 000002e0  00000000  00000000  00028888  2**3
                  CONTENTS, READONLY, DEBUGGING
 13 .debug_ranges 00000378  00000000  00000000  00028b68  2**3
                  CONTENTS, READONLY, DEBUGGING
 14 .debug_macro  00001488  00000000  00000000  00028ee0  2**0
                  CONTENTS, READONLY, DEBUGGING
 15 .debug_line   00003dcc  00000000  00000000  0002a368  2**0
                  CONTENTS, READONLY, DEBUGGING
 16 .debug_str    00066766  00000000  00000000  0002e134  2**0
                  CONTENTS, READONLY, DEBUGGING
 17 .comment      0000007f  00000000  00000000  0009489a  2**0
                  CONTENTS, READONLY
 18 .debug_frame  00000610  00000000  00000000  0009491c  2**2
                  CONTENTS, READONLY, DEBUGGING


texts: STM32 clamping diodes - what is the maximum input voltage?

texts:
As you can see on the attached picture from a reference manual of STM32F7, GPIO pins have internal clamping diodes to protect from overvoltage.

But what maximum voltage can I put into the pin? I know that 5V is max, and 4V is max for VDD. But what would happen if I put, let's say, 10V into the pin? Shouldn't the diodes clamp this overvoltage?
What parameter of a diode decides how many Volts can be clamped safely?
If I want to use external clamping diodes, let's say 1N4148, then what will be maximum voltage that I can put into the pin?


texts: Inconsistent Gain with Instrumentation Amplifier

texts:
I'm trying to prototype an instrumentation amplifier with OPA2111 as the first stage and INA105 as the second stage on a breadboard. The circuit diagram is similar to this:

Power rails are connected to a +-15 V power supply, inputs of the first stage are connected to a function generator, with two channels, which inputs 2 180° out of phase sinusoidal signals and output is connected to an oscilloscope.

With this setup, the output waveform comes out as a clear sinusoidal signal with an acceptable gain. However, when I change the frequency of both channels to another frequency and change it back to the original frequency, I get a different gain every time. This gain level ranges from 1.5 to 20, whereas, normally, my amplifier should have a gain of 6.

I thought that there may be some issues with the lab equipment or the op-amps, and I used different equipment and op-amps.However, I got inconsistent gain levels every time. I also separated and recorded the outputs of each stage and the problem seems to be caused by the first stage as its outputs have different gain every time. What could be causing this problem?


texts: What does voltage output from an SMPS look like when inductor is saturated?

texts:
I've built a buck smps around the LM2734X. This is meant to power servos, running off a 12V battery source. Scoping the +5V line using smaller servos, I see a stable voltage, with a peak to peak of 50-100mV. When I plug in a bigger servo (it's a B1226, and I've been unable to find a legitimate datasheet for it), I see the following on startup:

I'm using an inductor that's got a 1.2A saturation current. I've been seeing input currents of about 200mA on startup (@12.6V), but once saw it spike up to 400mA momentarily. That got me thinking that the DMM may not be fast enough to show this power on spike, and that I may actually be approaching the limit of the SMPS and the inductor.

Does this look like the inductor saturating? I'm particularly confused by how even the spikes are - they seem to be right at 20ms increments.


texts: How do we have a fixed current in this case?

texts:
If we are doing a current-to-voltage converter we can use negative feedback on a common-emitter configuration. Using npn transistors would look like so:

We are using a fixed current input and it forces the base-emitter voltage to be the corresponding value according to the Ebers Moll model. So my question is, how can we make the current input exactly what we want so it is mirrored on the other side?

I don't really know how it is possible to feed the exact current we want to the dual-transistors without having to calculate the voltage V1 in equilibrium for \$I_c\$.

If we increase \$I_c\$ then \$V_{BE}\$ would increase, which would make the voltage drop across \$R_1\$ to decrease (in a smaller amount). In order for the control of the current to be exact, when would need to calculate the precise increase we need in \$V_1\$ to reach the desired \$I_c\$ current so the base-emitter voltage is exactly what is needed to drive the second transistor. How can we keep the current exactly how we need it?

I appreciate your help.


texts:
I purchased a SZBK07 CCCV Step Down Buck Converter and I was hoping to remove the TRIMPOT and replace with a potentiometer how ever there was a Orange SMD thing bridged between the 2 and 1 pin's on the PCB, This has fallen of and I can not find it. I replaced the Trimpot with a  potentiometer  of 100k (Same as trimpot W104) it how ever smokes and the output voltage does not adjust, I tried a 330ohm resistor in place of the unknown SMD but this just makes the LED light on the buck not turn on and output is 1.5v non adjustable. The Potentiometer is for the VCC as in the diagram below.

IMAGE OF SMD (White in this case directly below the orange wire on the two pins)

DIAGRAM OF SZKB07

Here is another picture:


texts: Understanding the Difference Between Two Capacitance Sensors

texts:
I'm slowly beginning to understand more about how these work thanks to answers I have received on this site. I believe one area of confusion for me has been I've looked at two differently designed Capacitance Sensors, and I believed they were basically the same, but now I've come to think that they are not.

Chirp!

http://wemakethings.net/chirp/

Other one

http://zerocharactersleft.blogspot.ca/2011/11/pcb-as-capacitive-soil-moisture-sensor.html

From my new understanding, Chirp! is only providing one "plate" and the other version is providing two. But hopefully someone can explain this more clearly.

Thanks very much in advance.


texts:
I'm trying to build RGB led color picker from ladyada.net tutorials.
http://www.ladyada.net/make/eshield/examples.html

I build ethernet shield, installed on my Arduino Duemilanove with ATMEGA328 and then load the sketch from ladyada web site.
http://www.ladyada.net/make/eshield/LEDcolorpicker.pde

This code dosent's work for me, until I break line into two separate and re-merge at runtime.
I need to remove some piece of code to make it works.

After burning 3 times this sketch on my Arduino, it seems not to responde anymore.
On extensive log I see:

     avrdude: Version 5.4-arduino, compiled on Oct  9 2007 at 11:20:31
     Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/

     System wide configuration file is "/Applications/Arduino.app/Contents/Resources/Java/hardware/tools/avr/etc/avrdude.conf"
     User configuration file is "/Users/emaaaa/.avrduderc"
     User configuration file does not exist or is not a regular file, skipping

     Using Port            : /dev/tty.usbserial-A9007MIy
     Using Programmer      : stk500v1
     Overriding Baud Rate  : 115200
     avrdude: Send: 0 [30]   [20]
     avrdude: Send: 0 [30]   [20]
     avrdude: Send: 0 [30]   [20]
     avrdude: ser_recv(): programmer is not responding
     avrdude: stk500_recv(): programmer is not responding
     avrdude: Send: Q [51]   [20]
     avrdude: ser_recv(): programmer is not responding
     avrdude: stk500_recv(): programmer is not responding

Anyone have some ideas ?
I tryed on 2 different arduino 2009, same results

Thanks.


texts: Fiber optic transceiver for lower speeds

texts:
I am trying to figure out if a QSFP-DD transceiver can break out 8x 10G lanes if I make/use a 1:8 fiber optic breakout cable. It seems like most Transceivers are rated for one speed only, so if I get a QSFP-DD transceiver (such as a 400G-SR8), and break it out to 8 × 10G SFP+ transceivers, will that work? All the QSFP-DD transceivers seem to be rated for breakouts of 50G or 25G.
I tried reaching out to local vendors but they were unsure as well. I know QSFP and SFP are supposed to be backwards compatible, but that seems to be only for cables and not transceivers, so if I can use a QSFP+ to 4x SFP+ cable but then I'm losing 4 lanes of data? I may be also misunderstanding that as well.
Any guidance would be greatly appreciated.
Thanks!


texts: Pulse-excited integrator reaching infinite potential?

texts:
I was given the following Op-Amp circuit to analyse and to find the potential V_out as a function of time, with V_in defined as the Heaviside step function:

$$V_{\text{in}}=\begin{cases}0\mathrm{V} & t<0 \\ 1\mathrm{V} & t \geq0\end{cases}$$

simulate this circuit – Schematic created using CircuitLab

I first begin by finding Vo as a function of V_in, by equating currents and using that the current going into the inverting input of OA1 must be 0A:

$$\frac{V_{\text{in}}}{R}=C\frac{\mathrm{d}V_{0}}{\mathrm{d}t}\implies V_{0}=\frac{1}{RC}\int_{-\infty}^{t'}V_{\text{in}}\:\mathrm{d}t$$

Then again at OA2:

$$\frac{V_{\text{out}}}{R}=\frac{V_0}{R}+\frac{V_{\text{ref}}}{R} \implies V_{\text{out}}=V_0+V_{\text{ref}}$$

Combining the two equations gives:

$$V_\text{out}=\frac{1}{RC}\int_{-\infty}^{t'}V_{\text{in}}\:\mathrm{d}t+V_{\text{ref}}$$

When we use V_in as defined above and with R = 100kΩ, C = 10µF and V_ref = 10V, we get:

$$V_{\text{out}}=\begin{cases}(t+10)\mathrm{V} & t\geq0 \\ 10\mathrm{V} & t<0\end{cases}$$

However, this means that we end up with:

$$\lim_{t\to\infty}V_{\text{out}}=\infty\mathrm{V}$$

Which suggests that I've done something very wrong here? Or is this just a consequence of using the ideal Op-Amp assumption?


texts: Can the direct current output of a photodiode pass through a capacitor? If so what effect are they having in this circuit?

texts:
I am studying RC filtering in order to try and understand this circuit which was previously discussed in(What kind of filtering does this op-amp perform?).
The answers gave advice on testing the response to a sine wave sweep which should show it's filtering of undesired noise/interference such as mains electricity at 50/60Hz. I want to follow the path/modifications to the signal itself which to my knowledge is a direct current produced by the photodiode. Can this current pass through the capacitors and if so how?
I am trying to identify sub-components of the circuit and learn what effects they are having, please correct any misunderstanding:
1.The two 100K resistors are there to introduce an offset voltage so as to center the Op-Amp output at 2.5V? They do not have any additional effects?
2.The feedback path from Vout through two series resistors R6 (feedback resistor)& R5 forms another voltage divider. The fact that R6 is far far larger means only a very small voltage difference will be seen at VIn-.
3.Lastly, the feedback branch R5 and C4 appears to me to be a differentiator but I am unsure how to test this in simulation as I am interested in how the circuit processes the signal of interest - a varying direct current, rather than the AC noise of a sweep signal.
Any advice or input appreciated.


texts: I am studying the datasheet of an ultrasonic transducer (Murata MA58MF14). I understand the maximum input voltage unit (voltage peak-to-peak), but I do not understand what exactly the sensitivity unit "Vop" is?


texts: Linear Actuator using Relays, MOSFET, and PWM

texts:
I have a 29V Linear Actuator that I want to control - both direction and speed.
For the direction I used this 4-channel relay module, but I only used 2 relays on it.

I was able to successfully control the direction of the actuator. However, upon activation of the relays, the actuator creates a strange sound or force. Hence, I thought of implementing a ramp up/down using PWM.

I found out that the relay module I am using has hardware limitations when it comes to PWM. After some research, I found a schematic below:

I have some questions regarding the circuit:

First and foremost, is the circuit safe?
What is the function of that 29VDC with a snubber diode that pulls the Normally Open signal of the relays up?
What is the function of the BJT?

I appreciate any response that comes out. Thanks!


texts: Can a 12V LiFePO4 battery be charged using a car battery?

texts:
I plan to charge a 12v LiFePO4 battery using a charger specifically designed for that purpose, but I would like to know alternative methods of charging this battery without a dedicated charger.
I understand that to charge this battery, the power source for charging must be near the correct voltage and within a safe range of amperage. I also realize charging will not be very efficient or cannot 'top off' the battery without a dedicated charger, because of how a dedicated charger varies voltage to charge at highest possible amperage first and then holds voltage constant and reduces amperage to top the battery off. Still, being able to bring a battery from say 11.5V back up to 13V would be useful.
How can a 12V LiFePO4 100Ah battery get a charge from common automotive or household electronics? For example, can it be hooked up to a car battery with jumper cables, then the car occasionally started and left to run for a bit to keep the car battery charged, using a multimeter to check charger and charging batteries' voltage? If not, for the sake of learning, could someone explain why this is not safe or doable?


texts:
This is an external protection circuit for an analog to digital converter. I have modelled the resistive sensor as a voltage divider.
I have used pull down resistor R14 to avoid floating input then I have used a voltage follower. After that I have used voltage divider (R15-R16) to scale the input voltage range from (0-10V) to (0-5V,) after the second stage buffer I am using a RC low pass filter and I am using a schottky diode as a positive voltage clipper for over voltage protection.
I am using R18 to model the high input impedance of analog to digital converter.
The issue that I am facing is that when the sensor gives a voltage of 4 volts, the divider makes it 2V but at final_adc_in I am getting a voltage of 2.1 V.  I am getting a voltage drift for every sensor input voltage.
Any suggestion for reducing this voltage drift to minimum?


texts: How to use the simulation in atmel-studio properly?

texts: I wanted to start a bit µC development with the Atmel Studio 6.2, and therefore my first step was to compile a small program for simply switching a pin from HIGH to LOW and back all the time. I took the source code from here: http://jaxcoder.com/Projects.aspx?id=788781549. Everything compiles well, but when I run it and want to watch the IO-ports in the simulator (IO-view), the PORTD does not change (but it should). So, am I using the wrong view to take a look at the IO-ports, or am I doing something else wrong?


texts: Why does the complex representation of a voltage \$V\cdot\cos(\omega t + \phi)\$ use the cosine function?

texts:
A voltage across a circuit component at time \$t\$ can be calculated by \$V\cdot\sin(\omega t + \phi)\$.

However, in the section of my book that introduces complex numbers to represent voltages, it is stated that a voltage \$V\cdot\cos(\omega t)\$ can be represented by \$V\cdot e^{j\theta}\$ where \$e^{j\theta} = \cos(\theta) + j\sin(\theta)\$.

My confusion arises from the fact that the actual voltage is its amplitude times the cosine function and not the sine function since it is a sinusoid. Is this an error or I am just confused?


texts: Would joining pads of a pi-filter eliminate impedance changes from line to pad? Would it cause problems with alignment during reflow?

texts:
This is a 2 part question:

Would joining the pads, such as on the lower pi-filter pictured, cause any problems with alignment of the components during reflow soldering?

Would joining the pads result in less loss of the signal? I am wondering if joining the pads would prevent losses or reflections from changes in impedance which would occur in the two gaps between the thin transmission line and the thicker pads, shown by the neon green arrows. On my board the transmission line will be 50Ω and the pads will be 26Ω. Would the impedance changes in the gaps cause losses or reflections? If there are losses, how significant would they be?


texts: Suppression of current in the ground plane

texts: I’m designing an antenna with two polarisation. The stripline from the two polarisation are close in one layer therefore the isolation between the two pol is degraded because of some current flowing in the ground plane. What would you suggest to suppress those current?


texts: what is the logic behind these ladder lines

texts:
I have a ladder diagram for timing porpose.(keyence KV-24DR)
some instructions are repeated many times but I dont understand what are these for.
can anybody help me?

the confusing thing is that the program increments a number(I think it should be positive) and then compares it with '0' !!!

2002: Always ON relay

LDA(DM0021): load A from data memory #0021

ADD(#00001): Adds value specified by operand to contents of internal register, and inputs result back to same internal register.

CMP(#00000): Compares content of internal register and value specified by operand.

DW(#00000)(DM#00021): writes #00000 to data memory #000021

here is keyence programming manual:

https://gofile.io/d/jITBhK


texts: How can I use an oscilloscope to measure voltages that are referenced to nodes several hundred volts apart?

texts:
In my organization, we often use four-channel oscilloscopes to check out products. Each probe reference might be several hundred volts away from the others, which makes using standard scopes problematic. As best I can tell, there are only a few 'scopes on the market with the required level of channel-to-channel isolation, all from Tektronix, all costing at least $4,000. I would like to reduce this cost.

Another option would be to use differential voltage probes with a cheaper scope, but those are also very expensive, and we run the risk of someone forgetting and connecting a non-differential probe to the cheaper scope and blowing it up.

A third possibility would be to build my own isolators or differential mode probes for use with a cheaper scope. But I suspect that gets complex very fast, especially when one does not typically build such precise things.

A fourth possibility would be to use several PC-based USB oscilloscopes, each connected to a USB isolator. But I've never seen a system that allows multiple USB scopes in the same software, and I suspect there would be serious synchronization issues.

edit:

I have very low bandwidth, sample rate, and accuracy requirements; this is part of a test stand for a 360 Hz inverter, so if I can see an 20 mS window with 10 uS granularity, a 600 VAC RMS sine wave with 10V granularity, and a 5V feedback pulse with 100 mV granularity, I'm done.

What is the cheapest way to achieve my goals reliably?


texts: Why, in a passive circuit with a sinusoidal input, do all voltages and currents have the same sinusoidal behavior as the input?

texts: I am familiar that in any circuit composed of linear passive elements and a sinusoidal input, all voltages and currents through and across any element will exhibit the same sinusoidal behavior and frequency as the input; that's how passive filters work in fact. But I can't figure out or find a concrete/straightforward proof for why this happens, if not plain observation.


texts: how many resistance do i need to safe the LED of PC814?

texts:
if i have a input of 5v (arduino HIGH) on the LED of a PC814, how is the value of the resistance that i must use before that, so i don't burn the led?

http://www.datasheetcatalog.org/datasheet/Sharp/mXtzyru.pdf

i couldn't find the voltage that it supports on the datasheet, maybe i just don't know how to read it, help!


texts: My fans are not marked with a withstand voltage between the circuit and the plastic case; what is best practice?

texts:
I'm designing a new series of products in metal chassis containing plastic fans. The fans' power supply is referenced to the negative DC rail of a variable-frequency drive, and the fans are mounted to the grounded chassis. That means the fan is required to withstand a ~3kV hipot between its mounting holes and its internal circuitry. The fan is not marked with such a rating. However, we have a long history of products using this configuration. Those products are UL-listed, and every unit is hipot-tested before it goes out the door. We've never seen a failure.

Is there an industry-standard best practice in this situation? Would it typically be considered acceptable to rely on an unstated voltage withstand, as long as it was tested on each unit? Or would best practice call for the fan to be isolated from the DC- rail (or alternately, insulation to be added around the fan)?

EDIT: To clarify, our user I/O is floating, not referenced to anything. (We do prefer to keep our customers alive and not blow up their equipment.) It's only the fan that's in question.

The fan is blowing air into the box, so the "guts" of the fan are opposite the fan from the fan grill. And the voltage on the fan is stepped down to 24V from the incoming DC bus. The only high-voltage differential involved is between the fan's internal power supply and the unit chassis.

On one hand, I want to say that a history of thousands of units and UL's testing to get the units listed should be sufficient; I think it's pretty clear we don't have a safety issue as long as the user grounds the box and fuses the units as instructed. On the other hand, I hate to rely on an unpublished spec for the fan. Both arguments seem valid. The question is, which one is the more "correct" way of thinking?

FURTHER EDIT:
The fan I'm planning on using is here:
http://datasheet.octopart.com/4715KL-05W-B50-E00-NMB-datasheet-14433727.pdf
However, I don't see its relevance. I'm not trying to identify a solution to a design problem. I have two solutions I'm trying to decide between. Which solution is better from a standpoint of best practice?


texts: Trying to Decipher Pin Function of A EM Relay (Data Sheet Included)

texts:
Thank you for reading this.

Goal: to understand the functions of pins of EC2-3NU, a single coil non-latching electromechanical relay.

Data sheet: https://content.kemet.com/datasheets/KEM_R7002_EC2_EE2.pdf

Relevant portion:

Note: I could not find anything else regarding pin functions for the intended model in the data sheet.

My understanding: From the picture, it seems that pin 4 and 9 are the "common" pins, pins 5 and 8 are the "normally open" pins, and pins 3 and 10 are the "normally closed" pins. If so, then why do we have two of each pin? Is this relay capable of controlling 2 separate outputs?

Thank you again.


texts: Is there a thin metal film that I can solder wires to?

texts:
For instance, I bought some Dremel bits and inside the packaging were these small extremely thin pieces of metal film. Not sure what they were used for or what metal they were made out of.

It accepts solder and I was able to connect wires to it. Is there a specific name for this type of material and does anyone know where I can get more?

I ended up using it as a makeshift "connector pad" to add surface area to the end of a tiny wire I was using to connect to a battery.


texts: Matching LED brightness from different supply voltages

texts:
In an earlier project, I used an LED to indicate power (this 12V model). The PSU delivered +15V. I adjusted brightness with a 5k series resistor. According to the datasheet, this particular white LED has a forward voltage of 3.8V. According to the same datasheet, I slightly exceeded the max operating voltage, but it seems to have caused no problems so far.

I now want to use the same model LED (I have several left) on a different project which has a +20V PSU, and I want to match the brightness of the LEDs on the two projects. While exceeding the 12V LED's rating by using a 15V PSU might have worked, 20V seems like it's too much. I thought I'd try a voltage divider here, as follows (iCircuit screenshot, old circuit on the right, new circuit on the left):

According to the simulation, the LED receives the same current and voltage in both cases, and the resistors dissipate pretty small amounts of power, so should not overheat. Is this a reasonable approach?


texts: Connecting a multi-PSU server on different lines with different earthing

texts:
I am currently preparing to set up a new server which has two PSUs (for supply redundancy). Of course it would be logical to connect them to different sources, but the situation I'm dealing with sounds somewhat concerning to me, even though it might not be.

The situation is as follows (both lines 240V):

Line A: Neutral and ground joined in the breaker box, marked as TN-C (to be connected via UPS)
Line B: Ground not connected to the breaker box, but just between a few outlets (older installation with a few newer outlets), though it might be connected properly in the near future

Despite the PSUs being completely separate, the earths would be connected through the enclosure one way or another.

Is connecting earths on entirely different lines (on a server especially) a terrible idea?

If earthing is a concern on the currently disconnected earth on line B, should I connect the earth on that to Line A?

And if this setup is a bad idea, how about connecting both PSUs on line A, but only 1 through the UPS?


texts: Voltage Regulator Max 3.8v, Lipo cell ok?

texts:
I have a device (IC) with a built in DC-DC regulator that is rated for 1.8v - 3.8v with an absolute max of 4.1v. I would like to use this device with a lipo cell but, my understanding is that these are at 4.2v when fully charged. Is this asking for trouble? If so, is there a simple way to "trim" that top 0.2v or so off the top without having to add another regulator? Thanks.

Here is a link to the device datasheet

I'll add a little more detail on my system requirements. It's an MCU/RF transceiver that has a built-in DCDC converter. It will consume 3-4mA 90% of the time and <30mA while transmitting. The converter as stated above is rated for 1.8-3.8v. I also need 5v for a small LCD display at <1mA. I would like to power all of this from a small lipo cell which provides 3-4.2v. I recently designed a similar system without the built-in converter. I used s step-up converter to 5v and a step-down to 1.8v. The system worked great, except that these converters are almost $5 each. I'm looking to reduce my BOM cost if possible. I would like to utilize the built-in converter and find the cheapest and most efficient way to get this done. I'm wondering if a Zener would be a good way to trim the voltage down to 3.8v. And then I guess I would just bite the bullet and pay for the single step-up to 5v.Thanks for any ideas.


texts: Altium: Position components following Step/DXF File

texts:
I'm new to PCB design and new to Altium. I manage to figure out the following:

Create my own footprints for odd parts and using the wizards.
Import the board shape from a DXF file.
Import the board shape from a Step file. Which is neat because it automatically creates pads for holes and everything.

Now I've been going through the wiki and can't really find on how to correctly position parts according to the DXF information or the Step file created pads. I now a little bit of autocad and I know you can use commands like "Select", "Middle", "Move", "Center", etc.. to aid you in the movement and placement of figures. But in altium I cannot figure it out. I don't just want to eye-ball it. As the mechanical restrictions are there for a reason.

In the case of the pads automatically created by the Step file importation, can I place pads over pads? I ask this because of course this pads belong to my parts, and I already have a footprint with the correct pads but I don't know how to link them together. My best guess is I should delete them ones created by the step file and position my footprint instead, but if that is the case, how do I accurately position the footprint?

Check this example PCB here I created from a Step file:

Bigger Resolution


texts: How do I terminate a directional coupler?

texts:
I'm using a directional coupler for a radar application using frequencies of 5.3-5.9GHz. The directional coupler linked above is matched to a 50ohm characteristic impedance.

How do I terminate the isolation port to prevent reflections? Various sources online just say that I should terminate with the characteristic impedance, but is it sufficient to place a short microstrip at the isolated port and then via to a common ground plane? Is it bad to use the common ground plane? Do I need to worry about RF vias here, or is a regular via sufficient? I've seen a design that uses a 0402 49.9ohm resistor between the isolated port and a via to ground (connected by short microstrips). Does that provide any additional protection?


texts: Do I have to use a sense resistor? MC34063 Step-Up

texts:
Do I need to use a sense resistor for the MC34063 Step-Up Circuit?

I would like to step-up my voltage from 5V to 40V. After doing the math, I've found that I will probably need a 0.16 Ohm Sense Resistor.  First of all, I can't seem to find any through-hole sense resistors, and second, I can't find any at a low enough value for this.

So my question, again - Do I need to use a sense resistor for this circuit?  What does it actually do for this circuit?


texts: 3-Phase Theory vs Practical example confusion

texts:
In theoretical examples, 3-phase circuits are shown as either Wye or Delta type. Wye obviously containing a neutral line.

Recently I watched a Youtube video where the uploader re-purposed an old motor and turned it into a generator. The motor (from what I can tell) is wired in a 3-phase Wye type setup (circled in red). See figure 1 below:

Note: The figure resembles the actual model. There were no other connectors shown aside from the X,Y,Z as shown above.

EDIT: We are assuming the motor has now been converted and is being used as a generator.

Scenario 1: Now lets pretend lines X,Y,Z are led off and connected to a Delta-type transformer.

Q1: How does this complete the circuit if there is no neutral or ground? Will the current return path occur during the negative cycling of the other two phases?


texts: FM Receiver's Oscillator resonating to a frequency, but its modulated?

texts:
In an FM, the frequency is modulated. So whatever reaches the receiver is not a constant frequency. This being the case, at Receiving an AM/FM Signal: "In an FM radio, the detector is different, but everything else is the same. In FM, the detector turns the changes in frequency into sound, but the antenna, tuner and amplifier are largely the same as for AM" is confusing me.

How can a tuner tune to single frequency (as in AM) in FM while fundamentals itself say frequency is modulated?


texts: Converting boost controller to sync boost controller using H-bridge or 2 gate drivers

texts:
I am trying to reduce power losses in a boost led driver. For example TPS92690, uses a MOSFET and a diode for boost mode. Is it a bad idea to use H-bridge instead, or two gate drivers (one in straight and one in reversed modes) with 2 MOSFETS, so one signal from controller will drive 2 MOSFETS like in synchronous converters?

I need to drive 5A led. The diode will dissipate 0.5V*5A=2.5W power, is it right? I assume a MOSFET will dissipate less.


texts: Basically I need some demultiplexers to switch between 24 outputs. The data inputs would be connected to counters for the addresses. I'm currently using 74ls138 3-8 line demultiplexers. Is this possible?


texts: IRS2336 inverter shutting off at low frequencies

texts:
I am currently working on a project where the core is controlling a hybrid stepper motor. Unfortunately I am having issues with controlling the current properly to in turn control the stepper motor.

I can start with showing the problem, as someone might find clues or at least tips of what can be wrong from seeing that! and then walk through the setup later.

So what happens is that the current supplied is abrubtly shutting off from the inverters I have controlling the two phases of the motor. And it only happens at lower frequencies. This is how it looks like when running the motor slowly (5 rpm):

(This is just an open loop speed control running fixed sinusoidals through both phases with 90 degrees phase shift)

On the contrary when running the motor at higher speeds 15-200 rpm the current gets supplied just fine no problems:

So, as to the setup, both phases are driven by an individual IRS2336 inverter chip

which are driving some Si7148DP mosfets in a H-bridge setup.

The current is measured by an ADC and sent with SPI to the host, which is a FPGA realtime setup.

As far as the schematic of the full inverter solution, it is not something I've designed, but rather inherited with the project and I have looked at the schematic and it seems to comply with the data sheet of the IRS2336. And seeing the solution works flawlessly at higher frequencies (and both higher and lower amplitudes of current) I don't feel that's where the issue lies.

For me it feels non intuitive that there is more problems with changing the current slowly than it is to change it more rapidly! (for the actual hardware that is at least).

What I have done so far to try understanding the problem:

Measured the true current draw with an oscilloscope in the phases, and the current measurement is working correctly, the readings are true.
Checked the FAULT signal that is integrated in the IRS2336 chip, and it is staying high, so it doesnt seem to be that the inverter chip that actually shuts off.

So maybe there is something wrong with the controlling of the actual IRS2336 chip? At this moment I don't have access to the code controlling that but I might have to try find it the coming days.

My first intention was to put this up here and see if someone has encountered something similar before when dealing with inverters/H-bridge drivers and have  ideas on what might be the issue!

Thankful for any advice,

Best regards, Mattias


texts:
I have a question, in a circuit is there an electric field across a resistor?, and if yes then how is that electric field generated?.
The reason im asking this is that ive been thinking lately that an electric field should be necessary in order for a voltage drop to occur across a resistor. However reading online i see things like " resistor produces friction which does work on a charge dropping its voltage", this seems wrong to me.

pls correct me if im wrong, any help would be appreciated, thank you.


texts: The explanation of MPPT and its main function

texts:
I think the main function of MPPT is to find the max output power for us to let the power efficiency become the MAX.

However,i am still not quite understand MPPT.Is MPPT a schematic or an algorithm?We usually see a point of MPPT ,which is the top point of the output power curve.then what should we modify to let the output power become and keep the value which is the same as MPPT?

Maybe i don't ask the question clearly,but i have done my best to ask my question,i hope someone can understand what i ask,and tell me the answer.


texts: Heavy duty voltage resistor to decrease voltage from 120V to 100V

texts:
I have number of devices (total output 10000 Watts) that do run a bit hot when connected to 120V and are running in hot environment.

Our research (using variac) have shown that dropping the voltage to 100V does the trick. The wattage drops too (this is not a concern) and the devices does not run hot anymore.

Does anyone know what can be used to drop the voltage from 120V to 100V considering heavy loads upto 10kW (100Amps)?


texts: This IC produces 29.6 kHz square wave and there is no external components. What it can be? I looked at all codes and I can’t find it.


texts: How to measure the current in different brands of alkaline batteries?

texts: I need to measure the current in different brands of alkaline batteries - 1.5v AA and AAA, as well as 9v (6F22) - using a multimeter, and a resistor as load. How much resistance must the resistor have in order not to "blow up" both the batteries and the multimeter?


texts: Just how accurate is the frequency of US Wall Outlets?

texts:
I have a submersible pump for which I'm trying to determine the variability in flow rate, to high precision. Since this is just an impeller driven by an AC motor, what is the % error in frequency of a US wall outlet? Is there a commonly accepted 'ballpark' value, such as 60 hz +/-0.5 hz?

My suspicion is that for most electrical grids, this largely depends on the citywide usage throughout the day.

I apologize because I have an inkling that my question is poorly presented -- that being said, if anyone knows of where I can find real-time data regarding the West Los Angeles electrical grid, I'm all ears. Thanks!


texts: 3.7V Rechargable battery as arduino power supply

texts:
I have an arduino and a telit GM862 module which requires 3.4V-4.2V power supply. So far I have constructed a 12V limiter to plug it into a car power supply and a step-down converter which converts 12V to 3.8V so the custom board which consists of arduino and telit is plugged into a car power supply and arduino is powered with 12V and telit with 3.8V.

Now I would like to modify the project such that the board could be powered by 3.7V Li-ion or Li-Po battery or 12V. To do that I would still need a step down converter which converts 12V to 3.7 (or little higher) when plugged into 12V charger and 3.7V to the voltage required to power arduino as the battery so the battery would power both, telit module and arduino.

Has anyone constructed a similar project that could serve as a reference for the project I would like to build? I would be very thankful if anyone could suggest any helpful resource or name any ICs which are useful to construct such step-up and/or step-down voltage converters.

Thank you!


texts:
I am using a EFM32GG990 microprocessor and I am trying to get it to read a voltage using it's on-board ADC. I have made a circuit that I wish it to measure, both the loaded and open circuit voltage for the battery and the readings I should be getting are around 2.5-3V or somewhere around there, but when I actually set the chip up with the circuit it reads the voltage to be around 1.6V open-circuit and 0.9V loaded which is well of the mark.

I am not entirely sure whether it is a software problem or a hardware problem but I have assumed hardware for now as when measured with a volt meter aswell while it is set up, it also reads a much lower voltage than expected.

simulate this circuit – Schematic created using CircuitLab

This is the circuit diagram of what I am doing and as you can see there a three different loads, one is always on and the other two are triggered intermittently depending on whatever I choose it to be. I personally can't see any issues with this but if anyone does and could help me out, that would be great!

EDIT:
Something interesting is that it all works with use of a power supply instead of a CR123A battery...


texts:
Website for the wiring

In the schematics circled orange and purple I see a transistor to what I think is connected to a black wire and black and red wires connected to each other. Are these junction points where I have to somehow connect the wires?

I'm a bit confused because with only two endpoints on the wires they all seem to connect together to fit into one pin on the arduino board and I don't see how I might be able to do that


texts: DC motor that drives a flywheel and a DC generator simultaneously

texts: I have a project that I am analyzing a DC motor that drives simultaneously a flywheel (rotational inertia) and a DC generator. My doubt is, when I am creating the mathematical model of it, I would have the regular open loop DC motor transfer function and this is going to the DC generator? Also, the DC generator used is just another DC motor that it is acting as a generator. I am finding this quite confusing. Could anybody give me a hint?


texts:
I have one MCU powered with 3.3v acting as an I2C master in the BUS and 4 slaves, one of them is 3.3v logic and the others three are 5v logic.
It's ok if they share the BUS, connecting the 5v devices to the BUS using a MOSFET level shifter and the 3.3v device directly to the BUS?.


texts: Using LEDs in an output of a power supply with a voltage divider

texts:
First time posting here; it is also my first time making a power supply as a group project (been in charge for the schematic). I've already learned about transformers, rectifiers, filters, and regulators (basic stuff). However, I'm having problem with loads connected after the regulator. Like a typical power supply, I'd like my output voltage to be specific (0V, 3V, 4.5V, 6V, 9V, and 12V in my case). I was able to emulate this by using a rotary switch and a bunch of resistors as voltage dividers. However, I'd like to add components where each voltage output will have a specific LED as an indication which output voltage is being drawn from the output terminals.

Here is my circuit for the whole power supply:

So basically, I'd like to add an LED for each switch. How do I go about this? I can't just put it adjacent to the switch since it'll result to a different voltage reading from the voltmeter, right? Should I just use a bunch of Zener diodes in different voltages instead of using a voltage divider. Also, how can I maintain a constant brightness of the LED considering each output voltage is different.


texts: Switched-cap/charge pump only way to generate negative rail voltage for op-amp?

texts:
I need to design a daughterboard that gets mounted directly to a piezo mic to condition the signal before transmission. Part of the conditioning is a full wave rectification.

Thus, as you'd expect with a transducer we'll read a differential voltage dipping as far down as -2.5V on the differential amp. Despite my searches I suppose no one yet makes a "single supply" instrumentation op amp that generates its own negative reference? (>-0.3V).

Size is imperative here and being able to exclude even an SMD switched-cap/charge pump to generate my negative reference would be highly useful. Any suggestions?


texts:
I have an old PCB that I need repair, but the PCB is so old that I would prefer to make a new one.
After I studied its circuit and made a new PCB, I found the new PCB doesn't work. The output from opamp is different on the new PCB.
What kind of circuit is this?
Old PCB V1=2.93, V2=3, and Vo=6.22
New PCB V1=2.90, V2=2.93, and Vo=2.72

EDIT:
Here's the full schematic:


texts:
Here are two routings:

Which is better? On one hand, the first is bad because ground ring is one-turn coil, hence induction current will be appear. On other hand, the second is bad because potential in the opposite points of ground plane will differ when current is big. I'm confused.


texts:
I use I2C communication with two stm8s boards.

My master code:

I2C_GenerateSTART(ENABLE);
I2C_Send7bitAddress(0x30, I2C_DIRECTION_TX);
I2C_SendData(0x61);
I2C_GenerateSTOP(ENABLE);
delay(1500);

My slave address is 0x30. I send 0x61.
I analyzed stm8s master board with ossiloscope. I see from lister:

Address:30R

Data: anything

Missing ACK: X(with red background)

My signal from master board with stm8s:
[![enter image description here][1]][1]

what could be the problem for missing ack? And, is it true address and data values? Thank you!

And,

My master arduino code:

Wire.beginTransmission(0x30); // transmit to device 0x30
Wire.write(0x61);              // sends one byte
Wire.endTransmission();    // stop transmitting
delay(500);

And this picture from master arduino code with ossiloscope:

Here, adress is 30W, but adress of my stm8s master code is 30R.
I changed this line of the stm8s master code:

I2C_Send7bitAddress(0x30, I2C_DIRECTION_RX);
//I2C_Send7bitAddress(0x30, I2C_DIRECTION_TX);

But adress is still 30R.

code of this line:

/**
  * @brief  Transmits the 7-bit address (to select the) slave device.
  * @param   Address : Specifies the slave address which will be transmitted.
  * @param   Direction : Specifies whether the I2C device will be a Transmitter or a Receiver.
  * This parameter can be any of the @ref I2C_Direction_TypeDef enumeration.
  * @retval None
  */
void I2C_Send7bitAddress(uint8_t Address, I2C_Direction_TypeDef Direction)
{
  /* Check function parameters */
  assert_param(IS_I2C_ADDRESS_OK(Address));
  assert_param(IS_I2C_DIRECTION_OK(Direction));

  /* Clear bit0 (direction) just in case */
  Address &= (uint8_t)0xFE;

  /* Send the Address + Direction */
  I2C->DR = (uint8_t)(Address | (uint8_t)Direction);
}

and

/**
  * @brief  I2C transfer direction
  * Warning: the values correspond to the ADD0 bit position in the OARL register
  */
typedef enum
{
  I2C_DIRECTION_TX = (uint8_t)0x00,  /*!< Transmission direction */
  I2C_DIRECTION_RX = (uint8_t)0x01   /*!< Reception direction */
} I2C_Direction_TypeDef;

/**************************NOW*******************************************/
I changed my stm8s I2C master code:

I2C_GenerateSTART(ENABLE);
I2C_Send7bitAddress(0x30, I2C_DIRECTION_TX);
I2C_SendData(0x60); //I have no idea, i tried it and works for write/read selection
I2C_SendData(0x61); //my send data
I2C_GenerateSTOP(ENABLE);
delay_delay(1500);

Adress is 30W, now. It is true because i want to write to slave. Then, I saw this signal from ossiloscope:

This signal is same with Arduino master transmitter.

But, I can't see signal of the data. What could be the reason for this? Missing ACK or another thing? I don't know, but data signal is no of the arduino signal. Missing ACK?

Thank you!


texts: Replace one Voltage Regulator by two coexisting regulators (NOT in "parallel")

texts:
First of all, I know that I cannot simply parallel two voltage regulators to double my output power. At least not without actions to keep the two regulators "balanced" as was discussed here:

2 Voltage regulator wired together to produce higher amperage possible?

Also, I want to use a synchronous step-down converter with integrated FETs, so I know no way of adding such a "balancing circuit" because there is no easy way of sensing the currents ofthe two ICs.

Now to my question: Suppose (just an example) that I need 5 amps at 3.3V, is there any flaw with just using 2 regulators with 2 x 2.5A that are NOT in parallel, but only with the same GND connection supplying different 3V3 regions on the target PCB? So the idea is, power the core components like processor and near peripherals with the rails of one of the regulators and the rest of the 3V3 peripherals with the rail of the second regulator.

Of course, then there is the case that e.g. peripheral A and the processor are powered from two "different" power rails, which could have a few percent of difference in there nominal output voltage. But even though, I don´t think that there is a problem with "crossing currents".

My thoughts so far:
Example 1: Processor is supplied with 3.3V and its pin drives an input of peripheral 2 which is supplied with only 3.2V. There is no problem with this as long as peripheral 2 can accept input voltages that are 0.1V higher than the supply (which most devices accept! Of course the tolaerance level has to be greater because both rails have some ripple...)

Can you tell me if there is any flaw in this thought and am I missing something else to be considered?


texts:
I am planning to use M.2 daughter card in a design. I know that M.2 form factor support various type of cards like LTE, Wifi, BT, SSD etc. My doubt is that what is the host side interface for these cards.

If I plan to use a SATA M.2 SSD, what interface will it use to connect to my processor? Will it be SATA? Can anyone share standard pin out of M.2 connector?


texts: burying the neutral to used less cable for welding a long way from the power source

texts: Of course we are not talking about code or best practice, but hypothetically if someone wanted to do some welding a few hundred meter from the closed power point could he/she run one hot conductor to the site and just bury the neutral in the ground and get to welding?


texts: Adding Second LED strip and power supply to controller

texts:
Excuse the quality of the picture below.
I have a single power supply connected to an LED controller and a single LED strip. I would like to add a second LED strip but will need to add another power supply. Could someone please tell me how this needs to be wired?


texts: What is the NEMA and IEC schematic symbols for a Variable Current Circuit Breaker or Adjustable Trip Circuit Breaker?

texts:
I really need a depiction of a variable current circuit breaker (VCB) for a single line drawing of a new MCC cabinet. We are putting in a 40 to 100 amp 3 phase 480 Volt circuit breaker and this is something I haven't had to draw in AutoCAD before.
I ended up just drawing a regular circuit breaker with a dash line going left to a variable dial indicator with tic marks, labeled 40A to 100A with an arrow at a 45 degree angle. I added an annotative field to the right of the circuit breaker with a default of 70A.
But I was also interested for how to show this both for a NEMA and IEC symbol.


texts: Mathematical model of the temperature of resistors/heatsinks?

texts:
I want to model the transfer function of a resistor mathematically, and am after some resources / tips on if it's possible to do so.

For example, if I put 1V into a 1 Ohm resistor, I want to know how long and how (shape) it will take to reach a steady state temperature, given 25 deg C ambient.

I.e.

$$
\frac{T(s)}{V(s)} = ???
$$

Where T(s) is the laplace transform of temperature T(t), measured in say Kelvin.

I understand there are a lot of factors which will affect this model (material, size, shape, ambient (?)), but I'm not sure where to even start. A datasheet shows the heat rise at a certain load, but not really how it gets there. I can't find a time-domain function for the temperature rise either.


texts: Drive an older VFD tube via an Arduino et. al

texts:
I have a beautiful old itron DP95A4 tube that I would like to use as a small display to visualize some data.
I suppose I'd need a driver and some sort of multiplexer, preferably used with an Arduino or similar.
Could anyone push me in a generel direction or did someone actually do something similar here?
Edit: Added picture as mentioned in the comments.


texts: what is the dc component in the output of diode half wave rectifier circuit will it be the average value or the rms value of the output waveform?

texts: In the book the average value is given but as it is the dc component i think it should be the rms value? Input is sine wave of amplitude 10V.


texts: State Space model of a positional servo system. What are these parameters?

texts:
I am trying to solve a problem related to state space modelling of a positional servo system. I am stuck in the last part of the question. The full questoin is shown below:

  The following question refers to the following plant state-space model with the sampling time being 0.1s.

To my understanding:

% returns K matrix
K = place(A,B, poles);

initial_state = [0.4 0 0]';
desired_state = [1 0 0]';

I do not understand the meaning of \$h\$ in \$M_o(t) = 0.07h(t-3)Nm\$ and the subsequent control signal. (Thank you @Chu for pointing this out)

The control signal is given by \$u(k) = K[x_d - x(k)] = r - Kx(k)\$ but I have no mention of the value for \$x(k)\$ and \$r\$. Knowing \$x(k)\$ I would be able to get the control signal.

If these terms are not given as part of the question should they be obtained frmo knowledge of positional control servo systems? How can I proceed with the question if I do not know \$x(k)\$ which I need to get the input signal?

EDIT

I have still been unable to solve this issue.

\$x(k)\$ referes to the state vector which in a positional servo system would represent the angular velocity, displacement and current. I am thinking that this shuold be equal to the initial condition \$x_o\$

Going through Ogata Control Engineernig I come across a similar system:


texts: Virtual ground in positive feedback op amp

texts: In negative feedback Op amp Virtual ground condition is satisfied but in positive feedback it doesn’t why?


texts: answer verification for Superposition question

texts: I am trying to solve the superposition question, but unsure of the answer. If possible, please help.


texts: When should one use an external crystal for this MCU given that the internal oscillator is much faster?

texts:
I am looking at this MCU and was wondering if it makes sense to use an external crystal.

Extracted from the datasheet pg1,

*Clock management
– 4 to 32 MHz crystal oscillator
– 32 kHz oscillator for RTC with calibration
– Internal 8 MHz RC with x6 PLL option
– Internal 40 kHz RC oscillator

– Internal 48 MHz oscillator with automatic trimming based on ext. synchronization*

The internal oscillator can be up to 48Mhz. The external crystal is between 4 - 32 Mhz. Why would one use an external crystal when the internal one is faster than 48Mhz given that external crystal costs money and occupies space? When should one use an external crystal?


texts:
I know there are at least two questions related to this on stackoverflow but neither really answer my question, and in any case, both questions got downvoted. What I am after is an operational understanding of how an op-amp integrator works. I know how a simple RC circuit can integrate, what I don't understand is how the feedback loop in an op-amp configuration helps. I understand how feedback works in a noninverting amplifier. I took the figure below from www.electronics-tutorials.ws. This web site has an explanation but I don't follow it. My understanding so far is this:

Apply a positive voltage to input vin. Current flows through Rin resulting initially in a non-zero voltage at X (Correct?).
Due to the high impedance of the op-amp at X, we can assume that all the current then flows to the capacitor (initial discharged).
The capacitor starts to charge resulting in a voltage across the capacitor.
The difference in voltage at the two op-amp inputs (the positive input is at zero, hence the difference is negative) resulting in the output, vout, going negative (we assume that vout was zero initially).

My question is what happens next? How does the feedback act to bring the difference between the two inputs back to zero? Or have I got this wrong?

I am very familiar with the proofs for showing that the configuration will integrate but they don't give any real intuition and many videos, wikpedia, and books but almost all regurgitate the proof without giving much insight. I'm after an intuitive understanding, not a mathematical proof.

Out of interest I also redrew the op-amp circuit next to the RC integrator shown below which gives the suggestion that the op-amp is amplifying the small vollage across C (assuming high R1) while having high impedance from the resistor/capacitor node. Not sure if that is a legitimate way to look at it.


texts:
I have a load (more specifically a Raspberry Pi 3 B) which requires a voltage of 5.2V and needs around 2-3A current. It should be powered by a LiPo battery with a capacity of 6000 mAh. In addition to that, the battery should be chargeable with a power supply (in less than 6 hours) and at the same time power the load.

As far as I've understood I first need a DC-DC booster to reach 5.2V but also a charger module that is safe.
I cannot build such a module from scratch because LiPo powering can be quite dangerous and I'm not a battery expert.
But it seems like there is not such a module to buy online, especially when it comes to the 5.2V/2-3A requirements of the load.

Now my question is: Is there actually a way to achieve all this? And if yes, which components do I need to build a charger with an integrated booster?


texts: connecting -Vin and -Vout on a DC / DC converter

texts:
I'm making a small board for a DC / DC converter.  Can I tie -Vin and -Vout together and think of them as GND?  Is there some noise advantage to keeping them separate?

Edit: the converter one of the Murata UWE series linked here, the UWE-12/6.


texts: How does this circular polarized antenna work?

texts: I recently obtained an RHCP antenna, but when I opened it to investigate what's inside of it I found it to be different from the conventional RHCP polarized antenna. I have included pictures in this post, so hopefully, someone can give me an idea of how it operates, such as why is there any antenna above the bottom one?


texts: How does vibration motor create motion in particular direction?

texts:
I am building an autonomous robot for robot swarm reasonably small in size (say 30mm x 30mm). I was analyzing such robot's locomotion and found that coin vibration motors are used widely as opposed to generic DC motors with wheels. I get that the the coin vibration motors are very cheap and can keep the overall size of the robot fairly small, whereas with DC motors, wheels will be involved which will make the overall body size of the robot bigger compared to using vibration motors.

My question is how do coin vibration motors create forward motion. Say a robot uses two of these motors. How can it be determined which direction the robot will travel and WHY? Is this something to do with centripetal forces?


texts:
I am having an issue with 32.768khz crystal connected to an Atmega328P (which I am using as an external source to timer2 in asynchronous mode to wake up the Atmega from sleep every second).

On a breadboard everything works fine and as expected.

However upon assembling the circuit on a PCB, the AVR never comes out of sleep. For some reason the crystal is not oscillating

Can someone explain what is the right way to design the PCB as far the crystal is concerned to ensure correct operation (including selecting the capacitors). I have read about it here n there but never given much thought to it.

To remidy the issue, I tried the following but none of them worked:

Tried multiple crystals
Soldered the crystal directly to Atmega328P TOSC1/2 pins
Added 22pf/10pf caps connecting the crystal pins to GND

Here's a close up picture of the crystal attached to the PCB. I had to add some jumper wires because I broke off the traces trying out multiple crystals.


texts: This is probably a dumb question, but I am sort of confused. What direction does a cap discharge when a system is turned off? For example, decoupling caps that go to ground. When I shut a system down, does the current flow to ground or does it flow in the reverse direction toward the supply (since it is now 0). Would putting a resistor in series to ground have any effect?


texts: INA219 bus voltage depends on supply voltage

texts:
I tried to measure voltage with INA219A connected to Arduino. As datasheet says INA219 works from 3V to 5.5V supply voltage but I get different values for bus voltage when I change supply voltage. Here are some values I get, when I measure Arduino's 5V output (which is actually 4.6V):

At 3V supply I get 4.54V,
At 3.5V --> 3.34V,
At 4V --> 2.93V,
At 4.6V --> 2.48V.

I've measured bus voltage myself as voltage between GND and Vin- as mentioned in datasheet and get 4.6V regardless supply voltage.

All was connected like in the picture below:

Edited:

I tried to supply INA219 from batteries and measure Arduino's 5V. When I supply 3V I get nearly 4.6V what the multimeter shows but when I supply 4.5 V I get 2.5V. The same question remains regardless INA219 is powered from batteries or potentiometer.


texts:
I am trying to write a simple, stand-alone TCP bootloader for an AVR micro-controller.

Right now, I have got a collection of APN that weigh almost 14KB memory. The application code will establish a TCP connection with the server,using the network's APN that was stored in the program space and checks with the server for any updated application code. If server responds positively, the code will restart controller itself to enter into the bootloader program. The bootloader will fetch the application code and store it in the program space.

My question is, How can i make the stand-alone TCP bootloader without depending on the application code for establishing TCP connection. As bootloader is only limited to 8KB of flash memory, How can i store the 14KB of APN+4KB of bootloader code into this 8KB boot section?

Application code:

  initiate TCP connection using APN in pgmspace;
  check server for any updates;
  if(yes)
  restart;
  else
  normal function;

Bootloader code:

  request server to send the updated application code;
  receive code and flash the application code;
  goto application code address;

EDIT:
  My main concern here is, if suppose, something went wrong while flashing the new application code, then bootloader cannot connect to the server and i fear there is no other go but program it with a programmer


texts:
I have this proto kit shield - to make the history short, I bought long time ago, didn't touch it and I "found it" back today.

What I didn't find was a tutorial, assembly instructions or even a schematics. Any direction?


texts: Fuse Bit settings in ATmega128 Micro controller

texts:
I am working with ATmega128 board. The datasheet states

  ATmega128 is by default shipped in ATmega103 compatibility mode

In ATmega103 mode, the MCU both serial communications cannot be used and even some IO port operations are restricted. I want to disable ATmega103 mode, as I need both serial communications, external oscillator, and so on. To do this I need to program the fuse bits, and I need help in this issue. I am using AVR GCC compiler on Linux and AVRDUDE programmer to program the ATmega128.


texts: Identifying a resistor with implausible or impossible color bands

texts:
How can I find out the value of this burnt-out resistor from a power supply?

I've tried a few online resistor calculators and every single of them gives different values ranging from 0.1 ohms to one gigaohm. I've tried substituting gray for silver, reading the bands from both directions and leaving out the last band. My multimeter gives readings over 2 MOhms.

Edit: The resistor was on the hot primary side of the power supply, residing between the transformer and some SMDs on an otherwise through-hole design. A 0.1 ohm shunt resistor for current sensing is a likely candidate. Looks like many if not most online resistor calculators freak out when they see a gold or silver band where they would expect a normal color.


texts:
I am facing the following problem. I need to power my device (RC airplane) with 2 separate battery packs 12 V each in order to extend the capacity. Connecting them in series will not work, as the power stage is not prepared for that. When I connect 2 battery packs in parallel, and there is a difference in their voltage, they will charge each other, thus a large current will flow making them explode even. I thought of a simple fix for that, it is visible in the below schematics:

simulate this circuit – Schematic created using CircuitLab

With those 2 diodes I loose some power as voltage drop, but there is no current flowing between the batteries.
What If I wanted to add a "voltage" balancing circuit in between them? Lets say if one battery is voltage is only 9 V, because its discharged a little bit, then the 12 V should charge it with set by me current, ie 2 A max. One could design a circuit for that but it would take some time and its not worth for this application I believe. Instead, I wonder either there are such IC's readily available? Bidirectional chargers of some sort? Could not find anything my self, but maybe I dont know how to name them?
I would appreciate all help regarding this problem.


texts: Interface Mobile SDRAM (1.8V) with 3.3V SDRAM controller

texts:
I am looking for a 256Mbit SDRAM module in BGA format, to buy in units of 1000. However the cost for these modules are extremely high for packages using a 32bit bus in standard 3.3V voltages, however Mobile SDRAM running at 1.8V is available for the 32bit bus at half the price, or lower!

I am wondering if it is possible to 'overpower' these modules to 3.3V (probably not very likely) or get away with connecting the SDRAM without using many buffers?

I would appreciate any input.

Regards,
James


texts: How to calculate power supply for 100x loads @ 3V 700mA

texts:
I'm currently designing a setup using 100x loads that requires a 3V 700mA supply ea.
The loads are connected in parallel with the main power supply. I'm a bit doubting about my power supply dimension and I don't think I'm calculating this right... But, it should be something like 3V 70A? Is that right? The thing is that 70A is a bit scary and I don't really want to play with such big current. I would like to have an opinion.


texts: Single-phase thyristor full bridge rectifier vs three-phase thyristor full bridge rectifier

texts: For Single-phase thyristor full bridge rectifier compared to a three-phase thyristor full bridge rectifier, with regards the input current harmonics, does the three- phase rectifier have an advantage over the single phase rectifier?


texts: Hack for connecting two terminal blocks?

texts:
If I bought some of these connectors.

Is there an easy way to connect two of the green terminal blocks together? i.e. I would end up with a male to male DC adaptor.

Could I do this without having to use a cable that connects both of the green ends together?

Can I insert a double headed pin connector directly into a terminal block (you know the ones you get as part of universal charging kits).

Or does such a connector already exist?


texts:
This is a sensor arm of a hard disk containing a GMR or TMR magnetic sensor and a coil for creating the write field (1-3 GHz at around 2 Tesla as far as I know).

I'm counting 6 conduction lines, GMR sensor needs a four point measurement, the coil 2 lines. But what I'm unsure about, is this the "top" of the arm pointing towards the magnetic plate (or is this the backside view) and sit the GMR sensor and coil both in the silver rectangle at the front or only the coil, and what kind of electronics is embedded in that little black box, all conduction lines lead firstly to this, than some seem to go from there to the silver top.

It seems by measuring with a multimeter, that even small DC currents degrade the coil, so this thing is normally driven with AC current and skin effect decreases the heating. What kind of magnetic field is created by this coil (narrow band or broad band, does someone know some values?). Sorry for many small questions, just wondering if someone can shed some light on the details of such a electronic device besides the data I mentioned.


texts: Device for toggling power to another device via raspberry pi GPIO?

texts:
So I have a PTZ camera and a siren. What I'm trying to do is trigger the siren when the camera detects motion.

The camera hooks up via PoE, but the siren just has a 12 volt connection, so it has to be triggered by another device.

The camera has the ability to send out an SNMP trap when it detects motion. I have a raspberry pi set up that listens for that SNMP signal. When the camera tells the pi that motion has been detected, I want to trigger the siren via some intermediary device that the pi can talk to over its GPIO. My problem is that I know nothing about hardware and have no idea what sort of "power switch" device I'm even looking for on amazon.

To recap, I have a camera. When that camera detects motion, a signal is sent to a raspberry pi. When the pi gets that signal, I want it to activate a dumb siren that runs off 12v. What is the device that I need sitting between the pi and the siren to allow power to flow the siren only when a condition is met in a python program running on the pi?

My background is in programming and I know next to nothing about hardware so any info would be helpful!


texts: Building a VFD for a split phase (capacitor run) motor?

texts:
I'd like to get variable speed on a very tiny lathe (Taig, 4" swing). I've got a dishwasher motor I'm planning on using for it, which is rated for 3600rpm at 60Hz (it's about 1/5HP). But it's a capacitor-run motor (no centrifugal switch) and I think that means I have direct access to both windings. Any recommendations for building a VFD to drive this? I am fairly well versed in basic circuit analysis, just never designed much to deal with 110V.
I understand the general operating principle of a VFD, I'm just not sure how to make the low-voltage sinusoids I can easily generate control the 110V I'd get by putting a rectifier on mains voltage.
Alternatively, if there's a not-very-expensive commercial product I can use for this, I'd love to know. I don't want to spend more than about $70 on this project, because at some point it'll be cheaper to buy a brushless industrial sewing machine motor off Ebay.


texts: How do I add an external Bluetooth antenna to this circuit?

texts:
I want to disconnect the PCB Bluetooth antenna and add a U.FL SMD for an external antenna.
Can someone please advise me what to cut/add/solder?


texts: How can I identify an SMD diode marked SX DG?

texts:
My question is based on the attached picture of a diode which says SX DG but I can not find this diode.
The diode is taken from PoE 63v part of IP camera attached with MB6s ke47

SXDG SX DG


texts:
I've been looking all over for days but there doesn't seem to be a header pin.
I'm looking for a 21 position header pin with a 1.27mm (0.050") pitch.
Can someone point me into the right direction.


texts: How many / which electrodes should I use as input for an RLD (right leg drive)?

texts:
When reading through the datasheet of the ADS1298 (an analog Front-End for Biopotential Measurements) I noticed the schematic on page 42 (see below):
It is possible to select or deselect the positive and negative input of each channel with corresponding configuration bits (RLDxP and RLDxN).

I have two questions regarding this flexibilty:

RLD is used to reduce the CM noise with negative feedback of the CM signal to the patient. This typically requires me to sum both the negative and the positive input, otherwise I would not only feed back the CM part, but also parts of my signal.
So why would it be useful to select only the negative or only the positive input of a signal? TI offering an additional register to make this possible suggests to me that there probably is a use case for this.
I guess it does not make sense to switch different inputs to the RLD amp between my measurements (reading all 8 channels at 2kSPS), because this feedback loop has some settling time and I want to keep this loop running stable. So I assume the typical application will be to set the RLD config once and than keep it running like that for the most time (unless something happens, like the detection of a loose electrode). This means I won't use Ch1 inputs for the RLD when measuring Ch1 and Ch2 inputs when measuring Ch2 and so on.
Do I typically simply use all my input channels by closing all switches or would I choose one input channel and only use that for all the measurements?
In case this is depending on the application: I want to build a wristband with 8 EMG electrodes, but I would assume this to be similar for ECG or EEG.


texts: Reduce signal noise detected by accelerometer due to interference from a motor (caused by reverse neutral current)

texts:
EDIT AND IMPROVED QUESTION:
After working at it, I figured that the problem was that my DAQ is reading the current that flows back into the DAQ through the neutral wire. My DAQ is powered with DC power. If I were to throw in a Schottky diode or a reverse polarity diode, would I be able to eliminate the problem where the DAQ overwrites my accelerometer's data with the voltage data it gets from the reverse flow? I know that these diodes draw voltages around 300mV to 600mV, but the readings from my accelerometer will be in the 400mV range, and I don't know if the voltage draw from the diodes would affect the data read from the accelerometer in a significant manner.
EDIT 2:
Also, it turns out that there is a disturbance caused by the motor's EMF. The air has currents of about .1A when measured by a multimeter, and the current between the accelerometer fluctuates between .7A to 1.7A.

ORIGINAL POST:

I have an accelerometer (AC208-1D by CTC). This accelerometer could give proper readings when I would shake it in my hand (the right frequency and the right gs). However, once I turned on a motor (3-phase motor that is connected to a 1-phase to 3-phase converter plugged in to the wall), the accelerometer could no longer read inputs from me shaking it, even though the excitation that was read when I shook the accelerometer was greater than the excitation from the noise.

This is the bare signal (no filters) from the accelerometer while it's placed where it needs to be for an experiment, and the motor is off:

This is the bare signal with the accelerometer in the same place and with the motor plugged in to the same outlet as the accelerometer's daq, and the motor has power supplied to it (motor not running):

And this is the bare signal with the motor plugged in to a wall outlet about 40-50ft away from the daq's outlet with the motor still receiving power (motor not running):

The noise caused by current being supplied to the motor seemed to be the same, just with the thinner spikes going in different directions. I thought that the noise could be generated just from the motor's EM field since it is a .5HP motor, but based on my measurements of the EMF, I think that this isn't really what's causing the problem.

This is the EMF measured in microTorrs of my phone sitting on top of the motor while it is off:

This shows a large peak when I turn the motor on and it stays constant until I turn the motor off where it receives another peak:

However, the following two measurements measure where the accelerometer sits. This first picture is my phone's reading while the motor is off:

Then, this picture shows when I turn the motor on at about 9-10s and off at about 15-16s. The large dip shown past 20s was from me picking up my phone.

So, from the information above, I don't think that the problem has to do with the motor producing an EMF when it is receiving current. The wire connected to the accelerometer has foil and braided shielding, and the shielding is attached to the daq's ground, and this wire is far away enough from the motor that the motor's EMF should be negligible. I was wondering what I could do to remove this noise caused by the motor just existing with current flowing to it.


texts:
I would like to find a microcontroller but I don't know how to make a choice!

Currently I know I will need my device to be able to:

Check the battery level
Include a timer
Have at least two interrupts
Supply 3 devices sometimes with different level power (2 different motors)
Small
Low Power
Have I2C

How can I go about figuring out what microcontroller to use?


texts:
I have this schematic

The e- is connected to a resistance R1 and a voltage source V1.
The e+ is connected to a resistance R2 and a voltage source V2.

I want to calculate the differential input voltage.


texts: How do you identify Pin 1 based off these pictures?

texts:
This is a test question in a study book about electronics. I cannot find the answer and have no idea which picture identifies a pin.

Am I missing something? Any help on the right answer along with why that answer is correct would be helpful.


texts: Don't understand working out for phasor of output voltage

texts: We had a question in class which the teacher was working out about phasors but i can't understand the last two parts of the working out. why did he suddenly change the angle into a negative value and divide the amplitude by root 2? Vs is 10.


texts: Low power local area radio controller chipset

texts:
I have a project where I need to remotely control up to 128 individual relay boards within a maximum 30 meter radius. I need each of these wireless relay controllers to be uniquely addressable to ensure the correct relays are opened and closed.

Ideally, quiescent power consumption for the relay remote controller circuit when not in use will be a few microamps and just a few milliamps when receiving or transmitting.  I only require the ability to remotely open/close each relay based on its unique ID and to read back the overall status of each unit periodically. There is no need for a full blown MCU at each relay node (which usually means higher cost and power). I’d like to find a low-power wireless modem with the ability to interchange just a few bits of status and control information no more often than once every few seconds to conserve power. I need an integrated circuit that implements the radio, modem and digital I/Os, ideally for a few dollars per unit in volume.

I’d like to use an Arduino compatible board to supervise the array of relay controllers as a central management point.

Can anyone suggest a chipset or module that I can use for this purpose?


texts: Would bypass capacitors of a voltage regulator which powers an I2C device and the bus cause issues?

texts:
I'm planning on powering a 3.3V I2C sensor and its pull up resistors with a linear LDO regulator.
http://www.farnell.com/datasheets/2108564.pdf

The output of the LDO aswell as the sensor's power pins require bypass capacitors.
Wouldn't said capactiors together with the pull up resistors act as low pass filters and thus mess up the signals?
Calculating the cutoff frequency and lowering the bus frequency accordingly would be one way to solve this I guess.
But wouldn't this problem occur with every I2C sensor since every supply voltage trace has buffer or bypass caps on them?


texts: Full wave rectifier with capacitor filter

texts: In the figure-1 what is the point of connecting wires to earth? Can we connect all these earthed wires together as in figure-2? (that will make more sense)


texts: How much average power delivered to each antenna?

texts: I am confused if the characteristic impedance of line 1 is simply 50 ohms. Also, I know that \$P_{av} = P_{av}^i + P_{av}^r\$, but I do not have the voltage amplitude \$|V_o^+| \$ so I am unsure how to proceed.


texts: Is it possible to make a circuit that can convert binary to decimal?

texts: I know that computers use binary to calculate instructions and perform tasks. But essentially no one I know can convert binary to decimal. I am working on a calculator project currently, and the problem I have is converting binary to decimal for display and utilitarianism. But all of the converting circuits I have seen have converted it into hexadecimal instead, and no one knows how to read hex either. How can I convert binary to decimal and vice versa?


texts: How design a circuit to control a switch?

texts: I would like to know how I can design a circuit that can control the switch in the diagram below? Output of the circuit should provide TTL operant to open close the switch that control a 12 V DC.


texts: How to read different IV charts in the "component tester"?

texts:
I am doing a "comparison test" of 2 cards with the component tester. My component tester has 4 different test modes. LOGIC, LOW, MED and HIGH. LOGIC (10V 10mA), LOW (10V 100mA), MED (20V 5mA) and HIGH (50 0.5mA). When I compare 2 cards (when I touch the probes to the same points), LOGIC displays the same IV graph on the screen on the oscilloscope screen in both MED and HIGH mode. But in LOW mode, the graphics are slightly different. Especially in the positive (zone 1) stretch part, the right side looks a little swollen.

The visuals are as follows.

The other card on LOW mode:

How to read this difference. I wonder which part of the circuit had an error. To be able to fix faster, first I need to check which parts. what could be the reason for this different graphic? can you help me.


texts: Two Types of Screwdriver Rotary Switch Dials Available

texts:
I was looking at some rotary trimmer switches:
http://www.grayhill.com/assets/1/7/DIP_Series_94H.pdf
And noticed that the flush screwdriver dial is available in two different designs for the same part.

The fact that the same part offers both (rather than some parts offering just one design and other parts offering only the other design) seems to imply that the dial design functionally matters somehow in some applications. But I can't think of a situation where it would actually matter. Has anyone come by a situation where it does?


texts: Experience with lead-free synthetic solder paste?

texts:
I'm looking to start working with solder paste as I'll be making a batch of SMT boards.  It seems that most people use lead-based solder paste that requires refrigeration.  Vendors charge a hazardous materials fee that seems to be around $25 plus they will only ship overnight with a cold pack.  So if I want just one or two syringes, the shipping can be double the product cost.  Plus I have to keep it in a separate refrigerator or at least triple-bag it in my food refrigerator.

But I also see available lead-free synthetic solder paste (like Amtech's SynTECH-LF) that incurs none of the extra charges or special handling, although I'd refrigerate it anyway.  I'll likely be using hot air soldering initially and then switch to stenciling and a toaster over.  Does anyone have any experience with this synthetic solder paste?  How difficult is it to work with?


texts: The influence of change in voltage source on my circuit of 2 diodes and 1 resistor

texts:
I saw this circuit in an electronics' book .
In the first image , the voltage sources are the same for the 2 diodes, that's mean every diode will have 0.7 V and the resistor will have 4,3 V.

The problem was with the 2nd image, if I increase the first source voltage by 1 mV and decrease the second by 1 mV , the answer that the resistor will maintain its voltage to 4.3 V but what will change is the diode voltage :

Vd1 = 5.001 - 4.3 = 0.701;

Vd2 = 4.999 - 4.3 = 0.699;

Can anyone tell me what will happen in the 2nd circuit, more explanations by a circuit analysis or any method to understand.