texts: Interfacing an ATTiny84 to iPhone from headphone jack

texts:
I'm trying to create an adapter and an application for the iPhone that works very similarly to the Square Up card reader.

The basic communication I'm trying to achieve:

Plug in adapter to phone headphone jack
Start app
Input setting for adapter - the onboard processor will hold two memory location:

fixed memory settings that cannot be changed
memory settings that can be changed from the iPhone app

Upload setting to adapter - Adapter returns a signal to phone to display "Ready" sign
Remove adapter from phone
Data is stored in adapter for external use.

The long term goal is to have the adapter be able to communication with iOS, Android, Mac and PC devices via the headphone jack. For version 0.1 - I'm content with it just working on an iPhone.

I will be using an ATTiny24 for the prototype and then the ATTiny84 for production. I was wondering if anyone else has tried creating such communication protocols and if they have any advice/tutorials/resources I may be able to use to design the hardware around.

Thanks a lot! Any and all help is very appreciated!


texts: Does any practical RC circuitry exist which will perfectly cancel out a pole?

texts:
Firstly, some basic theory….

The transfer function of a simple low pass filter is:-

This transfer function has one pole. The gain goes from 1 to almost zero as frequency increases and the phase goes from 0 to -90 deg. giving -20dB roll off at -90 deg. This transfer function is referred to as “a simple lag”. The gain magnitude Bode plot is:-

My question is - Is there any practical RC circuitry which will cancel out this pole? That is to say circuitry which has a cancelling zero of 1+Ts as its transfer function. This transfer function is referred to as “a simple lead”. The zero would have a gain increase of 20dB/decade at +90 degrees starting at the same w = 1/T frequency as the pole which it is cancelling. The overall result of cascading the low pass pole with the added circuitry would be 0dB gain and 0 deg. phase shift at the output over the full bandwidth.  The transfer function of this pole cancelling circuitry would have a gain Bode plot of:-

Intuitively I would expect a simple RC high pass filter to do the job of cancelling out the pole of the simple RC low pass filter but this is not the case. A simple RC high pass filter has the transfer function:-

As can be seen, this transfer function has a zero, s in its numerator but there is also a pole in the denominator. The high pass filter gain Bode plot looks like this:-

As is apparent from the Bode plot, the high pass filter does not cancel out the low pass filter. In fact if the two filters were to be cascaded, the overall gain peaks at a maximum of ½ that of the individual filters at w = 1/T before falling away and the phase goes from +90 deg. to -90 deg. as frequency increases. (An attenuated bandpass filter).

So in a practical sense, is there any RC circuitry which will perfectly cancel out the phase and magnitude of a pole?


texts: How can you auto-calibrate a conductance sensor?

texts:
Sensors need to be calibrated every so often, so that the voltage/current change due to the change in the conductance is always the same, and the signal conditioning of that voltage/current is always gives the same output for the same input. i.e, it needs to be calibrated to remove gain and offset error that occur over time.

What are the basic principles for auto-calibration? I've looked on-line and on Google scholar but cannot find anything that explains anything clearly.

I am only looking for the basic principles to get me started.


texts: Differential Amplifier with voltage divider for reference voltage

texts:
I'm trying to convert a 0-5 V voltage generated by a DAC to a -10 to 10 V range by using an LM324N OpAmp in differential amplifier configuration.

By choosing R1/R2 = R4/R3 = 4, I expect the output to be SIG1 = (DAC1 - VREF_2) * 4.

Therefore, I have to set VREF_2 to 2.5 V to achieve the desired output range of -10 to 10 V. I'm planning to use a simple 10k/10k voltage divider from +5V generated from an Arduino for this purpose. Does the voltage divider create the desired voltage reference or could there be an undesired output because of the subsequent differential amplifier?


texts:
This plot represents drain current versus gate-source voltage (with different ranges of temperature):

Often the transconductance of MOSFET is defined as .

What is the difference between upper equation and gm = Id/Ugs (without changes)?


texts:
In my application I need a clock that is synchronized across several devices. (A detailed description of my system is given in an earlier question)

It appears achieving precision timing at a software level is not practical, therefore I am looking for a complete hardware solution. In this case I am looking for some sort of hardware that emits a clock that is completely synchronized across several nodes over the air.

Therefore, Are there low cost, short range (up to 20-30 meters) ICs that emit a clock synchronized across several wireless nodes? I cannot use GPS since my system will work mostly indoors.


texts: Separate voltage regulators for different digital ICs

texts: I'm designing a board with an IC that deals with high-speed signals (HDMI and MIPI) and it also has camera (also MIPI) inputs. I was looking at the schematic of a board similar to the one I'm trying to design, and they used isolated voltage regulators for each IC, even for the same level voltage inputs. For example, they used one small 1.8v linear regulator for one IC, and then another small regulator for the camera core voltage, even though there's already a board 1.8v rail. Is this an EMI thing? Is it better to do this instead of using one larger 1.8v regulator for several ICs, which seems for efficient?


texts:
I can't seem to find the answer I'm looking for, or perhaps I'm just really not understanding what I've read. I'm just confused.

So, I'm a college student in a Theatre Production program and an assignment we've been given in our lighting course asks the following:

"You will be staging a production in a small theatre, using only 120-volt conventional fixtures. Power is available from a disconnect dedicated exclusively to stage lighting. It provides 100 Amps, 120/208 Volts 3-Phase. What is the maximum amount of power at 120 Volts available for your lighting gear?"

Is this as simple as calculating the watts with the 100 Amps and listed 120 Volts? If so, is the 208 even really relevant here, or just something to make me overthink (with the whole 0.8PF and the square root of 3 and stuff)?

Many thanks in advance!


texts:
I have an assignment that requires building 4-bit Multiplier in two ways:

1) using only FA1bit and AND logic gates.

2) using only FA8bit(Full adder for 8bit numbers) , Mul2bit(Multiplier for numbers with 2 bits)  and AND logic gates .

i figured out the first way , but i cant figure out how to do the second way .

(of course im talking about binary numbers)

thanks


texts: Touch dimmer with low voltage transformers, needs incandescent to work? Updated!

texts:
I've looked extensively about this topic, and can't find any answers.  Hopefully someone on here can help.

I live in Texas and have 120V power in my house. I'm using a lamp touch dimmer to dim two ceiling boxes in my kitchen.  The sensor wire goes to two metal plates mounted under the lip of my island.  The dimmer works GREAT with incandescent bulbs. But my wife picked out these beautiful low voltage (12V AC) halogen lamps for over the island. There are two, and each lamp has its own magnetic low voltage transformer in the ceiling box. The dimmer will not illuminate the halogens at all by themselves, but it will illuminate and works perfectly if I put any incandescent bulb in parallel with them...

Is there a way to put a resistor on the load side of the dimmer to trick the dimmer into thinking there is an incandescent bulb there that I can hide in the box with the dimmer module?  If so, how much resistance and how do I verify it will handle the voltage?

I have tested many bulbs in parallel and the lowest wattage bulb I can find is 15 Watts and only 82 Ohms and works great. I tried a 1KOhm resistor and it worked on level one dimming, but popped on level two and took out my first 150 watt dimmer.

One idea is to simply put a 15 watt bulb in the attic, but I figured there has to be a better solution.

The dimmer is made by Westek, I currently own the 150 watt and the 300 watt dimmer.  Both do the same thing even though the 300 watt advertises that it works on halogen as well.  All connections are in approved boxes and have cover plates over them.  This has been inspected by the county and signed off on, minus the resistor obviously...  So I'm not concerned about that.

Clarification: The Halogen lamps that come with the transformers clearly state that they are dimmable with a standard incandescent dimmer. The touch dimmers clearly state that they work with incandescent or halogen lights.  I am not trying to make an item that's not designed to work with another item.  I am simply trying to create a larger load so the "old dimmer design" will work with a much more efficient light.

Update:  After researching some more and actually doing my own resistance calculations, I decided to try 5 33KOhm resistors wired in parallel, thus giving me 2.1 calculated watts of dispersed power.  And the dimmer works, but only two stages.  If I put the 2.1 watts of resistors with the 15 watt bulb, it works with all three stages of dimming.  Tomorrow I will go buy more 33KOhm resistors and add another 2 watts of power to the circuit and see if I gain my level 3 brightness, or lack of dimming setting on my dimmer.  Wish me luck.  Either way, we have progress!

*Update #2  Here is the latest...  I put (10) 33KOhm resistors in parallel and added a 1 amp fuse rated for 250V in between the load and the dimmer.  It works great for short amounts of time.  After 10 minutes, the wires on the resistors would heat up to 250*F, the resistors themselves were only 90*F...  I did not trust this in my walls, thus it was removed and replaced with a 3 Watt 120V incandescent bulb that fits in a surface mount socket with a lens cover.  The bulb gets to about 120*F but is outside the wall in the air conditioned room.  My amp clamp doesn't read the load on the resistors cause it's far less than .1 amps.  The total load on the dimmer is .6 amps.  My calculated total power on the resistors was 4.3636 Watts, and the total calculated load was 3.6 milliamps.  I truly could have spent another week finding a better resistor than what was at radio shack and made this work, but I feel better with the indicator light on the wall plate.  Thanks for everyone's help!!!*


texts: Can a transformer output current be controlled by a current limiting switch on the input?

texts:
I have a step down transformer, input of 220/40v, however I need to vary the current on the output.

I understand that by varying the voltage (using a device such as a Variac) on the input I could change the voltage on the output which would change the current drawn, but I'm wondering if there is another way to go about this?

TLDR: is it possible to use a current limiting device, like a light dimmer switch, on the input to control the max current on the output?


texts: Capacitor sizing for small motors to reduce inductive voltage spikes

texts:
I'm working with some small motors for a robot project and I think I had a different component fail due to inductive voltage spikes caused by the motors.  The motors are Mabuchi RC-280 which operate up to 8.4V DC and can draw 2-3 amps each.  I have 4 of these motors interfaced with a 20A motor driver, 12V battery, and an Arduino Mega2650 microcontroller.

I do not have any capacitors connected across the motor terminals and I need to know what capacitance to use.  Other similar motors have small capacitors attached but I don't know their value, and I am unfamiliar with sizing capacitors for this purpose.

Can anyone advise me as to what I might need for this application, or how to determine the size?


texts: Large Battery Cell mounting in Enclosure

texts:
I am trying to figure out the best way to mount a battery like this (http://www.batteryspace.com/polymerli-ionmodule37v10000mah37wh85arate-prewiredwithpcbpl9059156.aspx) onto a 8" x 6" PCB.  There do not seem to be standard holders like there are for 18650 or AA sizes. Are there standard techniques for holding these types of cells in place properly?

Thanks!


texts:
I am trying to generate a 65V square wave very similar to the post found here:
Mosfet PWM signal not square

My load is in a slightly different configuration (i've tried them both ways), but the problem I am having is very similar to the original poster in that the link above.

Basically I'm switching a FET that is in connected to a 65VDC supply through a 10K resistor and placing my load across the FET.  Here is my circuit:

Here are my scope shots.  The blue is voltage across the load and the yellow is the gate signal.

I'm inquiring how I can make that rising edge across the load fast and sharp.  The rounded edge makes me unable to achieve 65V when I increase the switching frequency since the capacitance in the load and my resistor causes the voltage across the load to rise too slowly.  The screenshots show about a 60Hz frequency, but I'd like to get up to about 10 kHz.

My load is a PLDC diffusing film and there is about 1 uF worth of parasitic capacitance built into the material which I cannot remove.  I am also aware that I can reduce the 10K ohm resistor at the drain of the FET, but since my peak voltage is 65V, reducing the resistor begins to put quite a bit of power on that resistor which I'd like to avoid.

The only other way I can think to make this happen is by putting another FET in parallel with the drain resistor and syncing and inverting the gate signal of this other FET such that it will turn on when the other one turns off and vice versa.

But is there a better way than this?

I tried putting the load in place of the 10K ohm resistor with the voltage developing across the load being less.  In regards to the FET not being turned on completely, I am using a frequency generator and have increased the turn on voltage to 10V with no different results so I don't think that is the issue.  See my scope shots below.  Yellow is the gate drive, Blue is the voltage across the FET, Purple is the high (65V), and red is the voltage across the load.


texts: Reading a high rate (400 kHz) analog input with an ESP32 (or Arduino)

texts:
Tried Googling this but I'm not really sure what vocabulary to use.

I have a series of light sensors that will be detecting changes at the speed of 400 kHz (or 2.5 µs). I would like to use an ESP32 to receive this data, but according to my research, it can only detect analog inputs at the rate of 6 kHz (166 µs), much too slow.

Perhaps I have a fundamental misunderstanding of how the sensor works, but my assumption is the sensor looks for changes in light at the rate of 400 kHz and sends this signal (at the same rate?) to the micro-controller. Thus, the signal would need to be slowed down so the micro-controller is able to read it.

Goal:
Determine when an object as small as a marble or large bug passes through a line of light at high rates of speed.

Circuit setup:
A high powered LED that is pointed directly at a light sensor which will need to be activated upon an object passing through extremely quickly by determining when a shadow is cast on the sensor.

I looked in to using delays like this one, but it seems to only allow 1 fixed output and at $1.66 a pop, this project would get really expensive, really fast.

Question:
Is there a part that I'm missing that will allow me to detect a 400 kHz signal with my ESP32's 6 kHz analog input?

I'm fine with using some other device that has such analog capabilities and passing off the data to the ESP32, but all of the devices I have found (Arduinos) have too low of a poll rate for this.

Thanks in advance for any help/input!

Update:
After all of your very helpful comments, I believe what I am needing is a method in which a sensor will respond to changes in light in at least a 5 µs intervals and only send a signal to the micro-controller when the light changes below a certain level (the object passes through the beam of light). I am still not sure how to go about this, however.


texts: How do I remove this Coating from the PCB?

texts:
This is a PCB from a Washing Machine. I am interested in getting some parts out of it. So what is this Coating and what will be the best way to remove it?
It can't be simply pulled like Glue from glue gun, it is quite sticky after 14-15 years and I don't have anything to heat it around except soldering iron.


texts:
I'm familiar with the utilization of Schmitt Triggers when interfacing with low slew rate signals / sinusoidal waveforms. In a recent design, I've been scrubbing our FPGA I/O configurations and noticed that I left the Schmitt Trigger on for a lot of I/O pins that don't necessarily need it (those pins are fed by MCUs / buffers that have slew rates on the order of nanoseconds, so very fast).

I can come up with a reason to use Schmitt Triggers for a slow rising signal, but I cannot answer the question for myself, are their downsides to using a Schmitt Trigger on a fast input? These signals are slow in the sense that they aren't periodic (power enables, etc.) but do have fast edge rates (say 5-10ns rise/fall times).

I've turned them off in my design -- this question is more for my own edification than anything else, and to be able to justify why they should be off.

FPGA in question is the Actel IGLOO (don't think it has any bearing, but just FYI).


texts: Which is the input resistance of the second amplifier?

texts:
If a apply a positive Vs, then D2 is blocked and D1 is working, right? How do I calculate Vo then? I know the formula is: - (input resistance / negative feedback resistor) * Vs, but I don't know which exactly is in this case, or in the case of a negative voltage, the input resistance. R2 = R3 by the way.
Will the first amplifier be short circuited in the negative voltage case?


texts: Remedy for pulling the output to ground in saturation?

texts:
Following ubiquitous common emitter configuration receives 0-5V logic input at its base such that the transistor goes into saturation or cut off mode:

So the output taken at collector is either zero or pulled up to 0.5V.
Well now not really zero but depending on saturation level could be 100mV a bit less. Because Vce never becomes zero.

My question is: is there any sort of remedy to this problem so we get 0.5V and zero outputs instead of 0.5V 0.1V? Does such a remedy be achieved without using more than one transistor? Using one NPN or PNP in total plus resistors and or diodes.


texts: What is the simplest way to make an AND gate using PNP transistors

texts:
I only have 5 PNP transistors and I want to build two AND gates. (for a T Flip-Flop) What would be the simplest way to make an AND gate using PNP transistors? (It can't use more than 2 transistors)

This is the only way I found, but it uses way too many transistors.


texts: My nMOSFET (maybe non existent). N canal with Vgs=0?

texts:
if I realize the following nMOSFET:

is it possible to obtain n canal with \$V_{GS}=0\$?

Thank you for your time.


texts:
One of my clients is experiencing problems with a SMSC LAN8710A PHY that is connected to a Xilinx FPGA. The Ethernet link works perfectly when the board is connected to my MacBook or to my office router, but fails with other partners such as USB-Ethernet adapters. In that case, the auto-negotiation succeeds but the link does not go up and the PHY reports symbol errors through its SYM_ERR_CNT register.

I'm suspecting a signal integrity issue on the board. Is there anything else that could explain this behavior? Any advice about how to debug issues like these?

Update: the symbol errors (there are usually one or two of them) seem to happen shortly after the link goes up. When auto-negotiation is OFF, the symbol error count remains at 1 or 2 and the link works fine. When ON, auto-negotiation re-starts every second or so and the symbol error counter gets incremented every time.


texts: microSDXC Card not responding to SD Interface commands in 3.3V mode

texts:
I want to interface a 64GB microSDXC Card via 50MHz SD Bus mode (not UHS, 400kHz during initialization).
My initialization sequence works fine with the regular 2 GB SD card from my phone up to ACMD41, which is not supported by this card (card responds on CMD_IN while CMD_T is high):

Yet, with the 64GB SDXC, there is no card response at all:

The card is powered and clocked for several seconds before the initialization sequence. It works when I put it into my workstation. CardSelect(DAT3 line) is asserted high during CMD0.

Am I missing something in the specification? What could I be doing wrong? Thanks in advance for the input :).


texts: Selecting a GPS module for a mobile robot

texts:
I need a GPS module to include in my quad-copter for providing GPS based navigation. I found there are many GPS modules available, and there are different kind of information available in their specs.

I'm not sure which module will suit for my need. (Probably it'll need to have a very high accuracy, eh ?)

Please help me with selecting a proper module? I'm currently interested in Skylab GPS Module MT3329 SKM53. It's just $24.48 in eBay. (budget is also an issue :D ).

Will that suit for my need? Or any (better) alternative? (hoping to go with Arduino, if that matters)


texts: 4 Phase 5 Pin high speed motor driving (turbomolecular pump driver)

texts:
I just recently purchased a broken Turbomolecular pump from eBay and repaired it,
now that it works again I need to build a low-cost driver for it.

It has 4 Phases and normally relies on hall feedback which is still working.

The pump is supposed to take frequencies up to 800Hz.

Now the actual question: What driving technique would you recommend for this motor? Simply relying on Hall feedback to regulate power and speed by adjusting driving current/voltage?

Driving the motor like a unipolar stepper motor would the easiest way of running the motor.

What is the typical way of driving such a motor at those required speeds?

Update: This is currently the schematic i am most likely going to use.
I am going to use a microcontroller or some other circuitry to monitor the RPM and thus adjust the maximum current delivered to the windings.
I might add an option to use "pulse density modulation" to provide the speed control at a constant current.
https://www.youtube.com/watch?v=0zlupI0UAGo


texts: How to create LTspice hierarchical blocks/sub-circuits/custom components? "Missing schematic of the hierarchy: "

texts:
I have been using LTspice with groups of components copied and pasted from previous models and this is getting quite ridiculous. I want to be able to create hierarchical schematics but every time I try, I keep getting the error "Missing schematic of the hierarchy: XXXX" from LTspice when running the simulation.

Here are the detailed steps I took (supported by various sources online):

Created a folder in my backed-up drive H: named LTspiceLib
In LTspice, Tools > Control Panel > Sym & Lib search paths, added the absolute path to LTspiceLib in both Symbol and Library. Applied changes.
Created a schematic saved under the name "spdt" in LTspiceLib, as shown:

Created a symbol saved under the name "spdt" in LTspiceLib, as shown:

In the symbol editor, Edit > Attributes, selected "Block" (although I also tried Cell). Left all fields blank (although I also tried typing "spdt" in Value). Saved.
Created a new schematic in which I added the component spdt. Right clicking on it allows be to open both the symbol and schematic without issue, but I can't run a simulation.

What am I doing wrong?


texts:
Can someone please explain the purpose of using the JFET in the configuration attached in the image?
I understand the JFETs are for amplification purpose but I am unable to understand the working of JFETs in below configuration.
Gate of the second JFET is given to the input of OP-AMP. The OP-AMP here is being used as a buffer.
The input to first JFET would be AC signals in the range of 1uV to 200uV  (Brain waves).
The output of OP-AMP is then connected to Instrumentation amplifier followed by high precision ADC.
Also, a resistor is being connected at the non inverting terminal of the OP-AMP and is connected to an external voltage source. Due to the P.D, there will be a current flow as shown in the image and the current will flow to the Drain of first JFET. Is it possible? If yes, please let me know.
Any readable resource will be highly appreciated.


texts: Routing and placement of decoupling capacitor when using power plane

texts:
Is it a bad idea to draw a polygon locally on the top side of two sided PCB as an alternative to proper solid power plane and star routing and place decoupling capacitors like this:

This is how my board looks now. Main 3.3V power net is highlighted. Small polygon on the bottom layer right in the middle is local 1V power plane. Top-right IC is 1V linear regulator. Large thermal pad should be stitched with ground plane. Please don't pay attention to vias close to power pads.

Both ground planes are filled:


texts: 4-bit Finite State Machine with 6 states and synchronous reset using D Flip-Flops

texts:
I have recently began studying Digital Electronics and have hit a wall trying to figure out how to design FSMs. At the moment, I am attempting to desing the FSM in the title which generates the following states: 1101->1011->0111->0101->0011->0010. Am I right in saying that this is a Moore machine and there will be 4 DFFs in this circuit? And what are the inputs for the circuit?

I now need to create the Karnaugh maps and this is where I am really stuck. I understand K maps and can create them, but I don't understand how you determine how many K maps are needed, and what goes in the x-axis and y-axis of the K maps when designing an FSM?

Here is what I have come up with so far:

EDIT

3rd bit Karnaugh Map:


texts: Why is the Schmitt Trigger output fed back to the current source in NE 566 (VCO)?

texts:
I understand the working of the circuit, a Voltage Control Oscillator, except the part where the inverted square wave from the Schmitt Trigger gets fed to the Constant current source/sink. Pins 5 and 6 are maintained at the same voltage so when the modulation i/p voltage is increased, the pin 6 voltage also increases => Constant current decreases => Decreasing charging current for capacitor => A longer charging time => Wider pulses.

I'd appreciate it if anyone could hazard a guess about the Schmitt trigger feedback to the Current source/sink.


texts:
For a project, i would like to power a li-ion battery from a TEG.
For that, i use a step-up converter called LTC3109 developed by linear technology but it was limited in current. I intend to create a system with supercapacitors storing energy and after releasing all to charge the battery.
Is it a good idea?

thank you in advance for your help.
And sorry for my English.


texts:
I made this code and i'm wondering what i have to do to put an enable without a clock.

Do i have to put each line for one if? Thanks in advance.
Like this?

if(enable = '1') then
            if(binInput = "0001") then
            decOut_n <= "1111001"

library IEEE;
use IEEE.STD_LOGIC_1164.all;

entity Bin7SegDecoder is
    port( enable   : in std_logic;
            binInput : in std_logic_vector(3 downto 0);
            decOut_n : out std_logic_vector(6 downto 0));
end Bin7SegDecoder;

architecture Behavioral of Bin7SegDecoder is
begin
        decOut_n <= "1111001" when (binInput = "0001") else --1
                        "0100100" when (binInput = "0010") else --2
                        "0110000" when (binInput = "0011") else --3
                        "0011001" when (binInput = "0100") else --4
                        "0010010" when (binInput = "0101") else --5
                        "0000010" when (binInput = "0110") else --6
                        "1111000" when (binInput = "0111") else --7
                        "0000000" when (binInput = "1000") else --8
                        "0010000" when (binInput = "1001") else --9
                        "0001000" when (binInput = "1010") else --A
                        "0000011" when (binInput = "1011") else --B
                        "1000110" when (binInput = "1100") else --C
                        "0100001" when (binInput = "1101") else --D
                        "0000110" when (binInput = "1110") else --E
                        "0001110" when (binInput = "1111") else --F
                        "1000000"; --0

    end if;
end Behavioral;


texts: Evaluating replacements for a likely blown capacitor

texts:
Background

I have a halogen desk lamp with an internal transformer that recently stopped working (no light when switch goes on; fairly simple failure mode). The bulb still lights upon applying 12VDC directly, and there's no internal fuse I can see. Inspecting the transformer's internals, 120VAC shows fine at the input, and the dimmer pot appears to range reasonably from the range of megohms to zero.

The transformer is a fairly standard half-bridge design (in fact, it's almost textbook out of this application note down to the transistors used, which in this case are BUL39D's (and the cap is either C2/C3 in the schematic on p1).

The Cap In Question

I strongly suspect issues with either the cap, its corresponding transistor, or both, but the discoloration (more prominent when flash doesn't wash it out) makes me suspect the cap first. However, I'd like input on the following things before buying and trying a replacement:

Am I reading the values correctly as 0.22 uF +/- 10%; 250V max?
What type of cap is this in terms of construction?
Other than needing to fit into a narrow space, is substituting a different type of non-polar cap with equivalent values likely to cause any problems in this application?


texts: Charging Two Parallel LiPo4 12v 20ah batteries at the same time

texts:
I am getting conflicting information from the manufacturer. My understanding is that If I charge batteries wired in Serial, they can be charged about 5 times as a unit but then should be charged separately every 5th or 6th time to balance them. If I charge batteries together in Parallel, they DO NOT need to be charged separately charged (albeit, balancing them at the beginning of use is wise and good). I now have someone saying that whether they are charged in serial or parallel they need to be charged separately every 5th time.
What is the best practice and what is acceptable? Thanks.


texts: How would I design a protection clipper circuit for ADC input?

texts: I'd like to be able to protect my ADC from input voltages higher than 5V. What's the simplest protection circuit I could build to have an output like shown below?


texts: How do "Inverter" or "IGBT" welders control CC and CV output?

texts:
I have a question on welding units. A lot of the newer units these days have "Dependable Fairchild or Infineon IGBT (non module)", "MOSFET design for Hobby use" and I can't tell if all of this stuff is just BS that PR is feeding out or if theses units do use MOSFETs, IGBTs,  and Inverters. On Everlast Generator's site, it says stuff like this:

"Because Inverters output power is electronically regulated, you have a wide power adjustment range from nil - 100% enabling you to fine tune them to your specific needs. For instance, with regard to MIG welders sometimes setting 2 may mean inadequate power and setting 3 may be excessive. It is here that inverter welder helps."

Which adds to my confusion. I have tried find schematics on the internet but only have found these:
http://www.irf.com/technical-info/appnotes/an-1045b.pdf

https://www.fairchildsemi.com/application-notes/AN/AN-9742.pdf

http://www.infineon.com/dgdl/Infineon-Welding-Machines-Converters-Using-TRENCHSTOP5+-+ART-v1.0-en.pdf?fileId=5546d46147a9c2e40147ce6f0a197daf

http://danyk.cz/svar_en.html

All of these add to how they work but not how they are controlled. Any information would be great.


texts: Is it okay to charge a VRLA with a AGM charger?

texts: I have a 1000mA charger meant for a 10Ah, AGM SLA battery. I picked up a VRLA, which is 17Ah and I am wondering if the charger is OK for it. When I tried to charge it, the green light never came on, even at the peak voltage it reached at 13.5v. I just removed the power when the voltage got to this, and assumed it was charged. If the charger is not suitable, what would be?


texts:
I am learning to do electronics making a things like a 3d scanner and a CNC. I want to make my own board to control the steppers and I have got the stepper drives, prefboard, arduino, etc. The only part I am struggling on is the wire.
5 stepper - 1.5a pre phase and dc 3.6v
Power supply - 12v 3a.
I have been looking around and its looking like I need 18awg to 22awg but not too sure, getting a little confused and maybe overthinking it. The wire will only be used for very short distance on Prefboard when I dont want to solder.


texts: Measure power consumption of RFM69HCW (radio) using oscilloscope

texts:
I would like to measure the power consumed (or current drawn) by an RFM69HCW 915 MHz module (picture below) connected to an Arduino Pro Mini (on a customized board). I put the radio to sleep for 750 ms, then it wakes up for 250 ms and then goes back to sleep, so on and so on. How do I use an oscilloscope to see the current drawn by the radio module?

Here is what I tried: The RFM69HCW module is supplied with 5 V, which is brought down to 3.3 V using resistors. A voltmeter across the VIN and GND pins show 5 V. In the picture above I circled a pin in red on the RFM69. A voltmeter across that port and the GND pin shows that the voltage toggles between 3.3 V to 0 V, and I guess that is due to the radio going to sleep and waking up.

To reiterate, I know that to measure the current I have to put the probes of the oscilloscopes in series in the circuit. But which pins do I probe?

FYI, I can use the radio to receive data from a transmitter. I can use the data to perform tasks on the Arduino. So the hardware and software work fine.


texts: Connecting Different Devices via RS232 - Worried about Ground Loops

texts:
This is sort of a follow up to my previous question regarding power supply for my telescope. The general advice I got was that I should just ditch regulation and connect the lead-acid battery directly to the telescope and camera. I have read the manuals for both these devices and both state that is is safe to do so as they both have internal regulators anyway.

However, I almost always connect my telescope to the computer via RS232. My computer does not have a RS232 port, so I'm using a Keyspan USB to RS232 adapter. I don't think the adapter is isolated because I checked with my DVM and there is continuity between the grounds of both (that is the USB and RS232).

The problem is my telescope's electronics are known to be problematic when it comes to ground loops. Some people have outright blown the RS232 chip due to this.

My question is, since the computer is going to be connected to the mains and the telescope + camera to the 12V battery, there is no common ground. Am I going to need an RS232 opto-isolater for the telescope->computer connection?


texts:
I did a GSM based alarm system using SIM800L modules.One is transmitter & the other one is receiver.When the transmitter button pressed it will make a call to receivers number & receiver detects this number & make an alarm. The system works fine on workbench.
But when I install this receiver in a police station its not working.Police station there are plenty panels like RF alarm panels, GSM panels, CDMA panels etc…
My panel is a plastic panel (housing is plastic).& it powered from a step down transformer (not a torodial).
How can I solve my problem? Is this interference?


texts:
This week we are having a exploratorium at my high school. We wanted to make an electric circuit, where the contestants have to find the three errors in the circuit. These errors is errors that we have made on purpose, but our problem is that we do not know which errors we should make.

Here is a diagram of our cicuit:

The three boxes that say "Fejl 1", "Fejl 2" og "Fejl 3" is the potential errors. It is in these three boxes we have to make errors the contestants should solve.

These errors have to go in a difficulty in order from easy to hard, being "Fejl 1" the easiest and "Fejl 3" the hardest.

We have thought of putting in a diode that went the wrong way, so they had to figure out that was the error and then turn it the other way around.

I now this may be a vague question, but I really do need your help, and all help will be appreciated.


texts: I have a bin file which contains 8-bit space seperated binary data and I want to load it in memory. In simulation it works fine, the readmemoryb command loads data in reg memory. Is there any way to burn that data in FPGA memory since I want to show that data on nexys 4 board as well


texts: I2C slave not acknowledging consistently

texts:
I'm trying to communicate with a Cypress CapSense module, model CY8CMBR3106S. During initial testing, I used Cypress's CY3240-I2USB USB-I2C bridge, which works perfectly. I then moved to an Arduino for prototyping of my own application. However, I cannot seem to get the Arduino to communicate reliably with the CapSense controller. Using the I2C scanner sketch found here, the Arduino discovers the CapSense controller perhaps once out of every 40 or so attempts.

In an attempt to debug this, I scoped the bus using both the Cypress USB-I2C bridge and the Arduino. I found that the controller always gives an ACK with the Cypress bridge, and almost never generates an ACK with the Arduino. However, other than the different voltages and clock rates (which I have played around with to no avail), I cannot seem to find any major differences between the frames sent from the two different sources which would explain the inconsistent ACKs.

At this point, I am at something of a loss--any advice would be much appreciated. Thanks!

Here are a few scope captures--note that channels 1 and 2 are SCL and SDA, respectively.

Successful communication using Cypress bridge (note ACK after 8th clock pulse)

Failed communication using Arduino (note lack of ACK)

Very rare successful communication using Arduino


texts: Determine copper thicknesses for multi layer PCB

texts: When deciding PCB stack-up generally accept the manufacturer suggestions. Especially they calculate the track impedance more accurate. For my last design I checked the guideliness for the FPGA (Microsemi's IGLOO2) the one I used. I have seen the stack-up Microsemi used in development board. Generally for copper thickness I use 1/2 Oz (H) for outer lates or 1 Oz for internal.  The Microsemi's stack-up  has H (1/2 Oz) and Q(1/4 Oz). What is the point here? Why should I use tinner copper?


texts:
I'm trying to hookup a DS1302 to an ATmega644. The DS1302 pin 6 is a SPI I/O port but the ATmega644 has a MOSI on pin PB5 and a MISO on pin PB6.

How do I go about hooking it up?

This is my current circuit.


texts: Why do they separate some parts of PCBs through making wide holes?

texts:
I have seen several PCB that they have wide holes in some their parts (especially the supply of circuits parts). for example take a look at this picture:

and on the board:

Not sure but I think it is related to the noise, Is it correct?
If so, it's not acceptable to me because other parts of PCBs aren't conductive then how it can transfer the noise?
If so, how much it can be effective?
And my last question is, do they have any special name?


texts: New eagle library: reuse standard package & symbol

texts:
I need to make few components in Eagle, which are all in standard packages, and I can see them in ref-packages.lbr.

The problem is that when I am creating my library I don't see how I can reuse package/symbol from another library, so that I only need to give new names to the pins and that's it? Package list is just empty and I can only draw one from scratch.

Unfortunately, all tutorials I've found in the internets do everything from scratch...


texts: Sequential circuit with more than 10 LEDs

texts:
I need to build a sequential LED circuit that will have more than 10 LEDs in a sequence. The LEDs should blink only one at a time. I know I can do 10 LEDs with a 4017 decade counter easily, but I dont know how to go beyond 10 LEDs in a row. Say I need few tenths of LEDS, maybe 50 or 100 pcs.

I found a circuit with 2 4017s which does 16 LEDs - see here. It says the design can be expanded "indefinitely" by adding more 4017s but it is not clear to me how to do it. Also, it the "reset" circuit part necessary?


texts: Adjusting Output Voltage pot from MeanWell LRS-350-36V power supply to 32V

texts: I'm looking to buy a LRS-350-36 for my project to feed 5x50W LED at 30-34v Vf 1750mA (https://www.aliexpress.com/item/32867490711.html). This PS use a 1U form factor that I must have due space constraints. My question is: can I drop 4V using the adj. pot and have a output of 32V without problem or affect PS performance? Is there any downside of such drop? Another thing that datasheet is lacking is that ajustment range, anyone know the up/down limits?


texts:
I am trying to flash an ESP8266-01.  I connect GPIO0 to GND, and toggle reset to ground and back, to put the ESP01 into flash mode.  The blue led on the ESP flashes once, not twice. It used to flash twice, and I could send AT commands via a serial monitor, and it worked well. I connected to my router and got online.  All good.

I am using a 5v 1A wallwart to power the ESP via LM1117 3.3v.

After trying to upload a program to the ESP via Arduino IDE, things changed.  Now it flashes once, and I get no response to AT commands. No echo at all.

When I put the ESP into flash mode (GPIO0 low), I just get:

ets Jan 8 2013,rst cause:2, boot mode:(1,7)

When I toggle reset (GPIO0 high), I just get:

ets Jan 8 2013,rst cause:2, boot mode:(3,7)
ets_main.c

I tried the following:

Clinic:esptool-master fedfull$ sudo python esptool.py --baud 921600 --port /dev/tty.usbserial-A50285BI write_flash -fm dio 0x00000 /esptool-master/v20ATFirmwareESP.bin
esptool.py v1.3-dev
Connecting...
Auto-detected Flash size: 8m
Running Cesanta flasher stub...
A fatal error occurred: Timed out waiting for packet header

I have Tried changing the baud to 9600, 19200, 57600, 74880, 38400, 115200, and 345600.  The lower rates don't include the 'Auto-detected Flash size: 8m' or 'Running Cesanta flasher stub...'

On further testing:

Clinic:~ fed$ esptool.py --baud 115200 --port /dev/tty.usbserial-A50285BI flash_id
esptool.py v1.3-dev
Connecting...
Manufacturer: e0
Device: 4014

Clinic:~ fed$ esptool.py --baud 115200 --port /dev/tty.usbserial-A50285BI chip_id
esptool.py v1.3-dev
Connecting...
Chip ID: 0x001eb645

Clinic:~ fed$ esptool.py --baud 115200 --port /dev/tty.usbserial-A50285BI read_mac
esptool.py v1.3-dev
Connecting...
MAC: 5c:cf:7f:1e:b6:45

Clinic:~ fed$ esptool.py --baud 115200 --port /dev/tty.usbserial-A50285BI erase_flash
esptool.py v1.3-dev
Connecting...
Running Cesanta flasher stub...
A fatal error occurred: Timed out waiting for packet header

I have rechecked my connection many times.

Does the blue led flashing once only mean anything?  Any idea what I've done wrong.


texts:
I wrote the post with BLDC delta winding commutation sequence, and to this day a believe the findings are true.

But i have an issue that is occurring only in CCW rotation, at about 97% up to 100% duty cycle the motor starts to run rough but at a slight higher RPM (2600 to 3000) in short bursts (like it would have timing advance for short periods).

This is not happening on CW rotation, the RPM is the same in CW vs CCW up to 97% duty cycle, but above that in CCW there is the simptome described.

The strange thing is that this is NOT related to load nor to supply voltage (it is doing the same at 10, 20 even at 100 Amps and at 24, 37, 74 Volts supply), the only relation to the simptome i found is the duty cycle (above 97%).

Note the motor is run in sensor mode with no timing advance (not in SW not in HW), there is no cross conduction, all the drive signals on the gates check out fine the only thing that is a bit strange is that the phase wave forms look different (some pulses in the wrong places) in CW vs CCW, and i can not figure out why. I added a few scope images, they are measured with ground on U phase and channel A and B on V and W phase of the motor.

The question is, what causes the described simptom?

Photo nr 1  CW rotation duty cycle 100% NO simptome.

Photo nr 2  CCW rotation duty cycle 100% WITH simptome.

Photo nr 3  CW rotation duty cycle about 95% NO simptome.

Photo nr 4  CCW rotation duty cycle about 85% NO simptome.

Photo nr 5  CCW rotation duty cycle about 97% WITH simptome.


texts: How to connect Verilog module's output to several wires?

texts:
Say I have a module foo(in1,in2,out); and module mad1(in,out); module mad2(in,out); module mad3(in,out);
While instantiating these modules I want to use the output (out) of foo as an input to each of the mad modules.
Something like this:

input in1,in2;
output out1,out2,out3;
wire w_out;
foo i_foo(.in1(in1),.in2(in2),.out(w_out));
mad1 i_mad1(,in(w_out),.out(out1));
mad2 i_mad2(,in(w_out),.out(out2));
mad3 i_mad3(,in(w_out),.out(out3));

Is that approach correct or should I save the output of the foo module to a register?


texts: Wireless Audio transmission (single TX -> single RX): Clock synchronisation/recovery

texts:
I am searching for a way to stream an audio signal to a single speaker in the living room. (I do NOT need brodcast to multiple receivers / multiroom)

Audio quality is a major concern, since the preamp / amp and speaker are rather good quality and I don´t want to feed them lousy audio data.

To be specific, I plan something like:
NAS(using e.g. Icecast, codec + hardware unclear) -> Bluetooth or WLAN -> Wireless Receiver -> Codec -> Audio Amplifier.

My question is how do I choose the components involved in the wireless transmitting path up to the codec so that I get high quality audio without "Noise" and clicking because of clock deviations between the transmitting side (the NAS server clock) and the receiver codec clock? In other words what hard/software components can I use to synchronise the PC/NAS side codec with the receiving codec? Is there a WLAN/BT protocol which has such a feature built in?

(I assume since I only have on receiver, I could jsut playback the data as I receive it from the sender and the sender takes care of the proper playback rate. But I guess that would result in a huge amount of jitter/audio distortion because of latencies in the wireless channel?)


texts: How to make an Arc welder out of 3500v bug zapper transformer?

texts:
I got a transformer from old bug zapper it has 3500v output  , can I use it to make an Arc welder by removing the secondary windings and put 10 gauge wire windings instead.
I saw some videos on youtube to make it using microwave transformer, can I use the same concept?
Thanks in advance.


texts: How would one create a transfer function for a PWM-controlled BLDC motor? I'm building a controller model in Simulink, and while I've found several references for transfer functions for BLDC motors,  I'm not sure if they would work for PWM control.


texts: What is the definition of "the loading of feedback network on the input/output side"?

texts:
There is the following example:

simulate this circuit – Schematic created using CircuitLab
Its loading of the feedback network on the input side is 40kohm in series. Its loading of feedback network on the output side is 2kohm in parallel.
There is another example:

simulate this circuit
Frankly speaking, they are all from my exercise booklet, But the material related to this concept is really rare.
What is the definition of "the loading of feedback network on the input/output side", and how to analyze it?


texts: GPIO output impedance from Microcontroller Datasheet

texts:
I am building an application around the Texas Instruments TUSB3210 USB Microcontroller (Now obsolete, not on market)

I referred to this datasheet to try and estimate the maximum current that can be safely drawn from each GPIO pin of this controller. The information that I could gather in this regard is

Each I/O port has Schmitt-trigger inputs, with 100-µA active pullup, and open-drain outputs

I am not sure what to make of this information in terms of the maximum current that can be safely drawn simultaneously from all pins of a port, or in terms of the output impedance at each pin (Which would allow me to estimate the former)


texts: Driving an electromagnet with a 556 timer

texts: I'm trying to drive an electromagnet with a 556 timer in a push pull configuration. The magnet has to change polarity rather quickly and sharply about 10 to 20khz. The voltage also has to be variable, between 3 to 15 volts the current draw is in the range of 1amp. What I need is a way to amp the square waves, I was thinking of using a pair of relays driven by the 556 timer in the complimentary configuration that way I can feed through them a varying voltage independently without affecting the 556... Or am I going at this the wrong way?


texts: Ideas to stack multiple PCBs on top of each other?

texts:
My design has a number of boards stacked on top of each other. I would like to connect signals across the boards. The boards all need the same 10 signals running through them (all boards from top to bottom), so that simplifies it a bit.

What could be a possible solution (or type of part) that is simple but also inexpensive for this type of design?

I am OK with any type of connector (vertical, parallel, right-angle, press-to-fit, contact-based, etc.) or architecture really, because if it would allow this type of multi-board passage of the signals, it would bring significant convenience to my design.

Relevant points:

MOST important: I would like the spacing between the boards less than 5 mm. Otherwise, it would make my overall design prohibitively tall.
My standard go-to for just two boards would have been a male-female header-socket combo. But, in the multiple-board case, if I were to have female sockets/receptacles on the top of each board and male header pins on the bottom of each board, then overlap creates an issue with the soldering/placement.
I also considered female sockets/receptacles which have lengthy/extended male ends (so that the same socket could be used as female and male), but these are rather expensive.
The stacked-board count varies for each of several slight variations of my basic design, so I would ideally like a method that works for a variable number of stacked boards.
The number of layers is currently 2 (two) but if necessary, I am open to making the board 4-layer or greater.


texts: vehicle dynamo with MPPT solar controller

texts: I have a 1930's car with a Lucas dynamo. Originally it was a 6 volt system but now 12v. This is done without modifying the dynamo. Unloaded, the dynamo voltage can rise to over 20 volts and of course the working voltage is directly related to RPM. At present the 12 volt battery only begins to charge at 2000rpm engine speed. I've been wondering if a MPPT solar controller could work as a more efficient charge controller. Any thoughts on this heretic scheme ?


texts: Which software should I use to send data to MCU (Atmega8)?

texts: I have made level converter circuit for RS232 to UART using MAX232. But I'm stuck, because I don't know how to send data to MCU. Googling the problem tells me to use hyperterminal but that is not available in Win 8. Please tell me how to do it? I'm using Atmega8 to communicate with PC.


texts:
I am designing an ultralow noise 5V/3A SMPS.

On the DC side, I see the ground (DC) is earthed (chassis ground) using a direct connection 0 ohm or using a Y capacitor. What are the differences between them and whats best for low noise on DC output?

On the positive side (DC) I also see that sometimes it's earthed (chassis ground) using a Y capacitor. Is it recommended to make this connection (if our goal is low noise on DC output)? Is 330 pF enough as a value for the Y cap?


texts: PCB low power self heating component separation

texts:
I am an EE that is fresh out of college and and starting at a smaller company, and I have a question about electronic self heating, and how to keep heat from spreading in a PCB to heat sensitive components, such as thermistors that are being used to measure ambient temperature, currently there is issues in a few designs, where the temperature inside the housing increases by half a degree C with traces run directly to the thermistor without thermal reliefs or and care to trace size. The devices I have seen having trouble are usually attempting to read ambient temperature at .25% accuracy between the ranges of -20 to 85c (currently done on some designs by having two separate boards in the enclosure with small wires run between the two)
The "hot" components are mainly the switching supply, and the MCU, in most cases for some designs I am looking at, they run at 10-20 mW, and the PCB size would generally be around 2in x 4in.
Would it be better to run large ground planes underneath these components to try and dissipate the heat on that side of the board? Or would the heat just transfer to the pcb's dielectric and heat up the thermistor that way?
Also, would it be better to run thinner traces with thermal reliefs to the thermistor to cut back on heat transfer through the traces, or would it be better to run wider traces to try and dissipate heat before getting to the thermistor?
The common value of thermistor I am looking at is a 10k-2 NTC.


texts:
In image my model to simulate PV array & MPPT with buck converter .
The result from this model have two problem:

At t=T=1/f occur current spike in diode current and Vpv up above Voc.
In battery , charger current in t=0 is 3000A ! May be because internal resistor of battery = 0.004 ohm and voltage =12v --> 12/0.004 = 3000A.

How can avoid this problem in my design ?
Any tips can be provided to me to Implementation this design?
(Apologies for my language)


texts: I came across a simulation software called MATLAB. I got to know it takes inputs in the form of matrices, provides output in terms of matrices , all in all it operates using matrices. But it seems pretty weird to me that it uses matrices. Why does it use matrices? How does usage of matrices makes it efficient ?


texts: STM32: the purpose of Even/Odd frame field for isochronous USB transfers

texts:
Implementation of USB isochronous transfers in (at least some) STM32 microcontrollers has a very weird feature.
It's called EONUM (Even/Odd frame) field.
Basically, the value of the field determines on which frames - odd or oven - isochronous transfers will be received by the microcontroller. So, if you're sending your data every frame, unless you flip the value of the field every frame, you'll get exactly 50% packet "loss".
Flipping the field every frame looks really troublesome, and I can't really see how this feature is useful in any way. The manual barely mentions the feature (search for EONUM, SODDFRM or SEVNFRM), but provides no explanation whatsoever.
This looks somewhat similar to data toggle synchronization for e.g. bulk transfer (which is mandated by the standard), but from what I can tell, the USB spec says nothing about such or similar kind of synchronization for iso transfers (my STM32 processor supports full speed only, so PID sequencing has nothing to do with it, either).

The data transmitter and receiver must have their sequence bits synchronized at the start of a transaction. The synchronization mechanism used varies with the transaction type. Data toggle synchronization is not supported for isochronous transfers.
High-speed, high-bandwidth isochronous and interrupt endpoints support a similar but different data synchronization technique called data PID sequencing. That technique is used instead of data toggle synchronization. Section 5.9.1 defines data PID sequencing.

In the end, I simply set EONUM accordingly to current frame number in SOF handler to achieve loss-free transfer.
Can anyone explain the purpose of the feature?
You can find a few mentions of people battling with this feature over the internet, e.g. here: http://www.chibios.com/forum/viewtopic.php?f=16&t=926


texts: How to evaluate the Logic Compatibility with I2C lines

texts:
I have a microcontroller connected to another I2C device.
I'd like to evaluate the I2C Logic Compatibility between the devices.
But since the I2C is an open-drain protocol, the resistors are outside the peripheral and there is no Voh, Vol levels for the I2C pins on both the Microcontroller and the I2C device.
In this case, how to evaluate the logic compatibility between the devices on I2C lines?
My microcontroller is the I2C Master.
It is powered up by 3V3 and external pull ups are also 3V3.
The pull-ups are 10k and the Vih and Vol of the microcontroller are 2.31V and 0.99V respectively.
EDIT:
The I2C information of the device is present in this table. And this is the only table in the datasheet that has the voltage and IO logic related information.
And the Microcontroller I am using is S32K142. This is the I2C Master.


texts: Why do we need to use `avr-objcopy` after `avr-as`?

texts: New to assembly, I'm surprised to see that we need to use avr-objcopy after invoking avr-as, in order to obtain an Intel Hex file, so where does this come from ?


texts: Change internal voltage reference on an STM32L0

texts:
I'm using a Nucleo board with an STM32L073RZ. With an "AnalogIn" object on PA_0, I measure the voltage of a TMP36 (temperature sensor), but the accuracy is not great at low temperature.

I want to change the internal voltage reference to get better accuracy. After a lot of search I haven't found anything. How can I change that on my STM32?

EDIT: On the screen below you can see result of multiple measure of the same voltage obtained with AC laboratory power supply.


texts: Can the output impedance on af op-amp be set to 50 ohm regardless of frequency?

texts:
I want to make a circuit with an output impedance of 50 ohms.

I am dealing with negative photomultiplier tube pulses that in 50 ohm load look like in the picture below:

I want to use the pulses to trigger the one shot sub-circuit described here which uses positive signals:

I understand that I must use a simple sub-circuit with an inverting fast operational amplifier.

Is it possible to  make the op-amp sub circuit have an \$ Z_{out} \$ = 50 ohm so it can drive the one shot sub-circuit?


texts: Level-triggered flip-flops in shift register

texts: I am studying shift registers. My book mentions that level-triggered flip-flops cannot be used to make a serial-in serial-out shift register. What is the reason for this?


texts: Why do electrons move as if on conveyor belt in a circuit?

texts:
For example sometimes people will ask whether it matters what side of a component you place a resistor on. Surprisingly, it doesn't matter because electrons behave as if they're all connected together on a conveyor belt -- if they encounter resistance in one spot they slow down everywhere else. It's not as though it's very fast on one side and then slower on the other.

Why is this the case? How do the electrons "know" to slow down even well before they actually encounter a resistor that may be on the other side of a component?


texts: disagreement between theoretical calculation and measurement of upper cutoff frequency of a circuit based on RG58 coaxial cable

texts:
For a 100 meters RG58 coaxial cable, according to the datasheet, the capacitance of the cable is 10 nF and the inductance is of 25 µH approximately. A sinusoidal voltage is applied at the input of the line with a 50 Ohm source, and the end of the line is connected to an oscilloscope, HZ mode (1 MOhm//10 pF), AC coupling. This give, according to me, the following schematic:

The RG58 coaxial cable is replaced by the lumped element R,L,G,C, G is neglected.
The simulation of this circuit with LTSpice, and theoretical calculation give an upper cutoff frequency of 300 kHz approximately. However, I personally made the measurement with a 100 meters RG58 coaxial cable and the measured -3 dB bandwidth is of 5 MHz approximately. (I don't recall the exact measurement value, sorry)
The coax cable model(picture below) gives a value in perfect agreement with measurement

Once again, I don't have a screenshot of the simulation result, sorry.

I do not understand why the measurement and the simulation of the coaxial cable give a cutoff frequency greater than the one given by taking into account only theoretical effect of the parasitic capacitance. Every physical phenomenon I neglected such as skin effect, or conductance of the dielectric should lower the upper cutoff frequency.


texts:
I have read some about computer memory and the article said DRAM is mainly made from a transistor to direct the electricity and a capacitor to store them. I don't understand how it fills certain capacitors and leaves some open to create ones and zeros.

At first I thought it was just a sequence of electrons and spaces lacking electrons, but I don't see how the next series of electrons after a space would know to skip one transistor and go to the next instead of just filling the first transistor.

Then I learned there is a bit line where one means write and zero equals don't write, but how does it know where to write and not write? Why wouldn't the first transistor just process the write or not write over and over?

Ok, I'm going to add an example to this. Lets say I had four transistors and capacitors. How would I make the first one a one, the second a zero, the third a one, and the fourth a zero?

How does this work?


texts: First time making a circuit schematic/pcb. Need feedback :D

texts:
I'm making a custom mechanical keyboard and was following this tutorial.
This is my first time making a circuit/PCB so I am kind of lost as to if I'm doing things correctly. I have watched and read a decent amount of information but I still feel a bit insecure in terms of I did it right.
My question is if I designed it correctly or did I mess up somewhere (especially the decoupling capacitors connected to the chip)?
I tried to make it use USB-C (USB 2.0) and as well add a rotary encoder into it.


texts: Useful mental models for low-frequency analog circuit design?

texts:
While learning circuit analysis and design (from Introduction to Circuit Analysis and Design by Tildon H. Glisson ), I caught myself with a thought that experienced circuit designers should have a much clearer mental model to come up with circuits they design.

For example, digital logic circuit can be designed with a help of truth tables, Karnaugh maps and other almost algorithmically implementable techniques. (There are some design issues beyond that, like non-ideal signal/clock propagation, but those could be dealt with).

The question is, are there expressive tools, which help create low-frequency analog circuits given input/output conditions and other possible constraints? Is it kind of art, or is one required to memorize useful building blocks and just align those blocks to get the result? I am not speaking of simulation software, but human mental models, compressed most important body of knowledge serving as effective pathfinder in the realm.

I am not even sure if it is explainable at all (for example, if someone asked me how to program software I would have hard time to explain how to program in general), so I narrowed  my question to low-frequency analog circuits, which more or less boil down to resistive circuits and dependent sources (am I right here?). (but I guess, transients is a challenge on its own, and maybe same mental maps help to design in frequency domain too).

I hope this question does not appear as too broad or vague. I believe, if there are answers, they could be as concrete as Karnaugh maps or have 4-6 sentences in their description.


texts:
I have some fridge led light based on basic capacitive dropper. If I connect circuit to AC mains nothing happens. At first I checked all components for mechanical damage and than measured them out of circuit. Mesaured X2 capacitor capacity looks OK, electrolytic capacitor also looks good, rectification diodes have correct forward voltage drop. Zener diode, leds tested. I expected at least one faulty component, but found nothing. I also tried to measure voltage acros zener diode, but I mesured really small value (as expected). I spent a lot of time to resolve this problematic circuit, but without any success. Which component can cause this behavior?

Edit: I tried to replace zener diode, which looks suspicious.
If I connect 9V to rectifier input, leds are emitting light.
I connected circuit to mains and leds are randomly flashing. I measured voltage acros C2, which was 20V and C3 14.7V. New zener was rated to 1.3W, which wasn't probably enought.

Edit 2: I replaced zener diode (rated to 2W), no change, but then measured voltage across all leds and there was about 13V. Leds still randomly flicker. Can be led diode damaged this way? If I connect DC 9V to rectifier input, leds lights, but when I connect circuit to AC leds randomly flicker?

Edit 3: Replaced leds solved issue, thanks for your help! :)


texts: High- and low-side MOSFET gate driver bootstrap circuit

texts:
I am trying to create a simple buck converter on a breadboard using this topology:

I am familiar with the theory of this circuit and believe I have connected everything correctly. The gate driver I am using is the L6385E.

http://www.st.com/content/ccc/resource/technical/document/datasheet/b2/ab/e2/82/c8/bc/42/fe/CD00169717.pdf/files/CD00169717.pdf/jcr:content/translations/en.CD00169717.pdf

Some of the parameters are:

Vcc = 16V

H.V. = 2-24V

L = 33uH

Cout = 3300uF

Cboot = 1uF

R = 10K

The FETS are IRF100B202. I will link the datasheet down below.

I apply a PWM of 62kHz to the Hin, and connect Lin to GND. With Vcc at 16V, Vboot becomes about 13V due to some internal losses. With H.V. around 2V this is fine and the high-side MOSFET is driven fine with a Vgs above 10V. Except, when I increase H.V., I would expect Vboot to rise the same amount, so the high-side FET can still be driven. But the problem is that Vboot does in fact not rise at all when I increase H.V.. This causes the high-side gate driver to stop working, because it can no longer supply Vgs = 10V to the FET.

I have tried a variety of different components and the problem still persists. Am I missing something crucial in the workings of this circuit, or am I maybe using some wrong components? I would appreciate some feedback!


texts: How a zener and a schottky diodes protect laser diode?

texts:
I purchased a strain relief wire SR9C which has a small protection circuit for a laser diode. It says to contain a zener and a schottky diodes which protect the laser diode from ESD. By looking at the PCB board, I drew the following circuit (hopefully correct):

Also, I managed to recognize the schottky barrier BAT54 - L4, however, I do not know what's the zener diode part is, though it says that it is a 3.3V one.

Could someone explain me the function of each of the diodes in the circuit and what kind of protection they provide and to what extent. The detailed answer would be greatly appreciated.


texts:
I understand how using multiple antennas helps improve reliability as it combats multipath propagation through redundancy.
But how does using multiple antennas increase data rate?


texts: Arduino resetting/hanging due to sparks in ac line

texts:
This is the PCB design of the project I have been working on recently (my first pcb design).

The idea is to control ac appliances (fans, bulbs etc) without relays. I am using triacs which are better than relays for such applications. I am using opto-isolators for complete isolation from ac lines. I tried running the arduino using USB cable connected to my laptop (with charger unplugged) as well as wall adapter (12V).

At first, circuit seemed to work fine. I was able to dump the code into the controller and control bulbs (On/Off as well as dim them) using UART. I sent the commands via UART.
However it seems that whenever there is a spark on the ac lines (when I plug in/out a fan), the micro-controller doesn't look happy. Sometimes it resets (which is the better part of the picture) and other times it hangs and I am unable to send commands via UART. I am not sure whether burnt code gets affected as well but sometimes I had to re-upload the code. If I switch on/off a fan in other room, there is no effect.

Possible issues:

1) Absence of ground plane on the PCB.

2) Some sort of EMI due to sparks.

I also tried plugging in a water heater (800 watts resistive load) the same way as fan but nothing happened. So, I think it's the inductive load which is giving problems.

Any constructive solution for this issue will be very much appreciable.

Thanks.


texts: TVS diode specs - clamping voltage lower than breakdown voltage?

texts:
Having read this app note (and a few others) and quite a number of TVS datasheets, I came across one that is bugging me a bit.
All of the TVS datasheets that I have read so far describe the the following concept (below curve is for a unidirectional TVS, but the same principle applies for a bidirectional TVS):

Thus, to generalize, the following seems to always be true:
\$V_{RWM} < V_{BR} < V_{CLAMP} \$
Then I read the datasheet of the Vishay XMC7K24CA and saw this:

From that table, \$V_{CL, max} < V_{BR, min}\$ (and \$V_{BR, max}\$ for that matter). This does not correspond with the general TVS curve above. How is this possible?

EDIT: Yet another datasheet (DIODES DESD18VS1BLP3) that shows the same:

I am definitely misunderstanding something here...


texts: What are the differences between regular and disc Yagi-Uda antennas?

texts:
I've recently started comming across a popular antenna design in the DIY community, which looks similar to the traditional Yagi-Uda antenna (large reflector at the back, driven element in the middle and several directors at the front), but instead of straight elements perpendicular to the direction of the antenna, there are coaxial discs.
For the sake of discussion let's consider this particular design (exact measurements and videos in the link):

I don't know much about antennas beyond the simple dipole and I haven't been able to find any information about this style of Yagi-Uda, so I wonder: Are there any benefits/drawbacks for this disc style as opposed to the conventional rods? I'd assume, that this antenna would be indifferent about polarization (as long as the signal is linearly polarized), but at the cost of gain? Perhaps there would be more noise?


texts: What's the need for voltage detector ICs for batteries/supercapacitors?

texts:
I came across some voltage detector ICs (like the KA75XX) that are designed to detect battery voltage.

I am wondering what's the need for the these when using it with a microcontroller like an Arduino? Since the Arduino has analog inputs, can't you just wire the battery directly to those pins and do an analogRead() with the Arduino? (with an internal pull-up enabled)


texts:
With the parts in the mail, haven't had the time to test, but the simple question: will this work, or what improvements are needed?

What it's supposed to do: a MOSFET switch for 12V, 0.5-3A loads, driven by a 3.3V logic level (which turned out to be too low even for my logic level MOSFETs). The chip starts up with the ports high, MOSFET off. Setting the pin low switches it on.

Then the background.

I'm using a 3.3V logic level NodeMCU board for my project. For this I got myself a handful of IRL540N MOSFETs (after reading forums, and the things are cheap). From the spec sheet I had the idea it would work at 3.3V but no luck there. At 5-6V gate level it opens up fine (I hooked up 21W worth of 12V LEDs to test, worked like a charm, the IRL540N didn't even get warm). But at 3.3V no luck, the LEDs barely lit up.

Using a driver transistor worked, but then it became inverted: port low was the on, so effectively default on, and that's not safe for my project. It has to be default off, so at startup (pins low) it's simply off.

So then I realised I had to use higher voltage, and this is where the optocoupler comes in play. It allows me to pull the gate of the MOSFET to the 12V level using just 3.3V.

The below schematic I devised for the combination with a PCF8574 port expander. Its pins should default to output, high. In high state it can source only 0.3 mA or so, very little, enough to drive a transistor but not an LED. It however can sink at least 20 mA, so that's good enough to drive an LED, or an optocoupler.

The idea behind this schematic: when switched on, the ports are high, no current through the LED, MOSFET gate pulled low, and it's off.

Then when I make the port low, it sinks the current for the LED in the optocoupler, the gate is pulled high, and the MOSFET switches on. The 12V ensures it's saturated.

Load may be lamps or a motor or even a solenoid, D1 is there to prevent the circuit from frying upon turning off.


texts: Symbol rate and optical bandwidth relation

texts:
I am quite new to the field of optical communication, so perhaps this question is so easy.

In reading some papers I have faced to the concept of optical bandwidth. For example, they say the symbol rate is \$25~G~\frac{\mbox{sym}}{\mbox{sec}}\$ and as a result, the optical bandwidth is \$13.33~GHz\$. Note that that have not spoken anything about the waveform being used.

In electrical domain, the bandwidth is related to the waveform being used. The symbol rate determines the duration of each waveform which affects the electrical bandwidth directly. Can anyone explain how it is related to the optical bandwidth?


texts: How to connect a micro controller to a CDC device?

texts:
I have a device that exposes a USB port recognized by a PC as a virtual com port.
I need to connect a micro controller to this device through its USB port.
How should I do? I'm looking for a kind of ftdi that would handle the host side of USB.


texts: How does this LDR controlled light work?

texts:
Consider:

The circuit here works based on the resistance of the LDR. I don't understand how it exactly works. It's said when the resistance in the LDR is high, current flows through R2 and the base of the transistor. Which direction would current flow?

I know the convention is it flows from the positive of the battery. But from the explanation it confuses me that current is flowing from the negative terminal. And if the convention is from the positive, shouldn't the current skip R2 and go through the path of lowest resistance which is R3?


texts: Using TWS-BS-6 and RWS-374-3 for analog audio transmission?

texts:
I'm really new to electronics and thought I'd build a simple walkie-talkie as a hobby and education project.  A friend suggested I consider using the TWS-BS-6 and RWS-374-3 for the radio transmission and reception.  But when I looked at the specification sheets here:

https://cdn.sparkfun.com/datasheets/Wireless/General/TWS-BS-6_315MHz_ASK_RF_Transmitter_Module_Data_Sheet.pdf

https://cdn.sparkfun.com/datasheets/Wireless/General/RWS-374-3_315MHz_ASK_RF_Receiver_Module_Data_Sheet.pdf

There doesn't appear to be analog input or output pins on these boards.  I see digital input/output pins though.  If I were to use them, do I need to consider the use of analog to digital converters and digital to analog converters as well?  I want to make sure I'm not reading these data sheets incorrectly.


texts: Single power supply for multiple 12V devices over long run; LED and swimming pool application

texts:
Hi I am new to this site and have no electrical training, but I am braving the job of installing 4 5M strips of waterproof(IP68) 5050 RBG LED strips on the interior coping of our above ground pool (approximately 65 ft total length). These lights will shine down into the water but will not be submerged. (This video shows what I am attempting but is not remotely helpful in designing: https://www.youtube.com/watch?v=X6A8XivGYEk). Just jump to the middle somewhere to get the idea.

I have researched the requirements for connecting multiple strands of LEDs and understand that I need an RBG Amplifier every 1 or 2 strands to (a) use a single remote and have them all perform the same function and (b) prevent voltage drop.  I have elected to use an amplifier for every additional strand beyond the first one. Each amplifier requires its own power supply.

So my wiring, which I have tested in the house with good results, looks like this (forgive the novice take on wiring diagrams):

The ends of each strip will be run under the pool coping to the exterior of the pool. Once on the exterior of the pool I will attach to the controller or amplifier as shown in diagram. As needed I will solder connections and/or use heat shrink and/or non-conductive silicon.  My intent is to place the non waterproof amplifiers and the Power supplies in a lockable waterproof survival box mounted to the exterior wall of the pool.  (I will have to drill some holes in the box but will make waterproof.)

Being appropriately fearful of 110V and water, I am disinclined to run 4 extension cords around my pool to my waterproof boxes to connect to my 12V power converters.  While I believe I can do this with the utmost care and that I can have all connections positioned so that if failure occurs they will not go in the pool, freak accidents happen all the time.

Now to my questions: Is there a way power my amplifiers from a single power supply/converter (which I can place a comfortable distance from the pool)?  My understanding is that power consumption should not exceed 80% of the supply's capacity.  So if each line of lights uses 75W I need at least a 375W power supply.  From that supply, which also needs to convert to 12V, I would need to make a short (~3') 12V run to my first strip of lights, then 2 longer runs (~18') to the nearest amplifiers, and finally a ~36' run to the furthest amplifier.  Can this be done?  Is there voltage drop to be concerned about if nothing is being powered until it reaches the amplifier?
Any advice, product suggestions, etc are appreciated.

Products I am  using are on Amazon:
SUPERNIGHT-Waterproof-Submersible-Underwater-Controller
and
SUPERNIGHT-Repeater-Signal-Amplifier-Strip
Sorry, as a new poster I was limited on my links.


texts: how to calculate input, output, and feedback resisters of an OP AMP given voltage In/Out

texts:
I'm trying to solve for \$R_{x}\$, \$R_{y}\$, and \$R_{z}\$, given a know \$R_{1}\$, \$R_{2}\$, \$V_{in}\$, \$V_{out}\$,  \$I_{in}\$, \$I_{sc}\$,  \$V_{CC}\$, and \V_{EE}\$,

\$V_{CC}\$ , \$V_{EE}\$, after being measured with a DMM should be \$+10 V\$ and \$-10V\$ respectively

If i measure \$I_{SC}\$,\$V_{OC}\$, \$V_{IN}\$, \$I_{IN}\$. I should have enough information - but I'm not sure of my calculations.

There are some formulas I have found: \$\frac{V_{IN}}{I_{SC}}=r_{1}\$; \$\frac{V_{IN}}{V_{OC}}=\frac{-r_2}{r_1}\$; and \$\frac{V_{IN}}{V_{OC}}=r_3\$

Any help would be greatly appreciated.  Even just helping me setup the simulator too.
[circuitlab]82wj9z[/circuitlab]

simulate this circuit – Schematic created using CircuitLab

EDIT:
I corrected the schematic - I meant for VEE to be on the blue wire. The goal here is to be able to determine what \$r_1\$, \$r_2\$, and \$r_3\$ are just by measuring the voltage and current in/out. Then, I should be able to calculate what \$r_x\$, \$r_y\$, and \$r_z\$ are from \$r_1\$, and \$r_r\$. The second part I really am not sure about, but I haven't been able to test it.

I guess \$r_2\$ is my \$r_{feedback}\$, and \$r_{z}\$ is my \$r_{load}\$?


texts: Why shouldn't electrolytic capacitors be short-circuited?

texts: In the answer to another question, I read that it's bad to short-circuit electrolytic capacitors. Why is that? What happens if I do?


texts: Impedance matching on DC voltage line to remove ringing/reflections

texts:
I'm generating a 6 MHz signal in an Altera FPGA. I am feeding this 1.8 V signal out through a level shifter to 3.3 V to a connector on the board. This is the signal at that connector:

I am then sending this 3.3 V signal back into the FPGA (stepped down to 1.8 V). It comes out of the FPGA (stepped back up to 3.3 V) and is brought out on another connector on the board. This is the signal at that connector:

There is a lot of ringing from reflections on the line which I am trying to dampen. I have put a 33 ohm resistor in series on the track, but it didn't help.

What do I do to match the impedance? I only have hobbyist level electronics.


texts: Solid State Flasher controlling other Relays

texts:
I'm a freshman computer science major, and I still have a lot left to learn in the realm of circuitry, but I have a decent understanding of the fundamentals.

I have made an electric bike, and I wanted to install turn signals. The bike's battery is a 52 volt nominal, Lithium Ion battery (max 58 volts), so all my components must be able to operate on the voltage of this battery (unless I wanted to get a dc-dc converter to reduce to 12 volts, which I don't).

I installed a 60 volt solid state flasher relay to control the LED turn signals, but one problem is that the flasher doesn't allow the signal lights to flash completely on and off. Instead, they flash from 100 percent brightness to about 50 percent brightness. There appears to be some electricity leaking through the flasher. When I insert my body into the circuit, my own dry skin is enough of a conductor to light the LEDs to about 40 percent brightness. (Crazy huh?) So, the LED's apparently don't need very much electricity. Therefore, I expect it might be difficult to use a resistor to reduce the system power enough to prevent the LEDs from lighting at all when the flasher is "open." My knowledge of resistors is still limited, so any suggestions on this approach are appreciated.

Alternatively, my next idea was to use two electromechanical relays to completely break the circuit. I plan to control the energizing of the relays via my dashboard turn signal switch on my handlebars. Observe the following diagram (You'll have to forgive my circuit design skills):

simulate this circuit – Schematic created using CircuitLab

Are there any flaws in this idea? Improvements? Will this work, given I get the right relays? If so, can you point me to the best relay for this (must handle up to 60 volts)?

Thanks!

LEDs:
.08 amps at full brightness
.02 amps at half brightness

Volts across flasher:
2 volts in "open" state
36 volts closed

Flasher Resistance:
512 Ohms with multimeter dial on "2000"


texts: Use TimerOne.h in another microcontroller

texts: Is it possible to use a script using TimerOne from Arduino in an ATmega8 and how would I go about it?


texts: Looking for a button-controlled on/off PMIC akin to those in laptops

texts:
I'm designing a circuit for a custom event console (SMPS', chip reader, screen, controllers, NFC,..) which I would like to power on/off in the same way a laptop or tablet is powered on/off (hold pushbutton for x time). It runs on 12V and thus should be quite comparable to a laptop.
My research has been fruitless so far, so I've come here for suggestions
Also, I'm aware I could use flip-flops, n- and p-mosfets in different arrangements to accomplish this, but I would like just one IC (a few extra Rs, Cs and Qs are no big deal) since the board I'm working on is quite small.
Thanks!


texts:
When the fridge stops / starts I can see the Mouse & Keyboard lights spike or dim, sometimes the mouse stops working. These components are connected to a powered usb hub.

I can't use another power line, I have only 1.

I don't know if the power spike affects my Pc's or Monitor's.

Electronic devices specs:

USB Hub - TP-LINK UH700 - Charger IMPUT 100-240V ~50-60Hz 0.8A   OUTPUT 12V 2A
Mouse Bloody Sniper ZL50 (with lights)
Keyboard Genesis RX85 (iluminated)
PSU Corsair SF750
Display LG 29UM69G 29 inch - Charger IMPUT 100-240V ~50-60Hz 1.4A   OUTPUT 19V 2.53A 48W MAX
Mini PC Asrrock A300 - Charger IMPUT 100-240V ~50-60Hz 1.8A  OUTPUT 19V 6.32A
Laptop Lenovo Y720 - Charger IMPUT 100-240V ~50-60Hz 2.5A  OUTPUT 20V 8.5A

★ Should I get 2 UPS for all devices or just 1 small for Usb Hub?

.

The fuse box for sockets has this fuse: hager ada332g 32B
https://www.hager.co.uk/product-catalogue/energy-distribution/protection-devices/rcbos/reduced-height-rcbos-type-b-30ma-6ka-1-pole/ada332g/91254.htm
32 AMP   230 V   50 Hz

★ I don't know if it's safe to plug 2x UPS 2200va in one wall socket, or if the fuse box supports all of this

I was looking at UPS PowerWalker VI 2200 UPS 1200W https://powerwalker.com/?page=product&item=10120094&lang=en

In final on that line I would have a fridge & 2 UPS


texts: Why led turning on when switch is low in pic starter kit?

texts:
I have a PIC starter kit. I am doing a simple program of turning on led when switch is pressed and then turning them off when switch is released like following:

if(switch==1)
{
  led = 1;
}
else
{
  led = 0;
}

I was actually not able to do above code in MPLAB. Then I found a tutorial online. I used that code and it was working.

Switch is connected to RD7
Led is connected to RD0

CODE

if(PORTAbits.RD7 == 0)
{
  PORTDbits.RD0 = 1;
}
else if(PORTAbits.RD7 == 1)
{
  PORTDbits.RD0 = 0;
}

Now I am confused. Why led is turning on when switch(RD7) is low. Can anyone explain me this logic.?


texts:
In DC circuits, if I have a device that gets switched on and has a large inrush current, I can just put a large charged capacitor near the power switch (parallel to the device) to source the surge. This protects the DC power supply from the inrush current and the DC source can take its sweet time recharging the cap.

In the same circuit, if the power source was AC, then the voltage in the capacitor would be constantly changing. If the device's power switch was switched on at exactly when the voltage in the capacitor was zero, there'd be no energy stored to source the rush.

Is there an AC circuit equivalent to my DC capacitor/in-rush scenario?


texts:
When I started learning about electrical engineering, one of the most important safety guidelines that I learned was that voltages over 36V can be dangerous. As my circuits professor put it, 120VAC will sting, and 240VAC will seriously hurt.

Now that I know more about these voltages and their dangers, I'm confused about mains electricity and how safe it is. I often see people (un)plugging power cables into outlets that are behind a desk or a couch without a clear view of what they're touching - sometimes with two hands to get a better grip, a definite no-no in my electrical labs at school. How dangerous is the risk of, for example, touching a finger across both the hot and neutral lines? Do the circuit breakers in a home really guard against this, or is 120/240VAC not quite as dangerous as I think?


texts:
I've built a simple pc oscilloscope using pic18f4550 and a 20 MHz crystal.

I've made a simple application using vb2010 which is able to show the frequency oscillation on pc. The problem that I have right now is, when I apply a sine wave to my pic project, the sine wave is properly displayed on my pc. But when a sine wave is applied to pic with a frequency of 40 kHz and above the displayed amplitude will decrease, and it will continue to decrease with higher frequencies.

Why is the amplitude decreasing ? How to maintain the amplitude at freq 1 MHz ?

I did not put any buffer opamp before input signal to pic.


texts:
I know, there's an overwhelming amount of information on the Internet about what eddy currents are, but on the fundamental front, I simply fail to grasp how currents could circulate/or even exist in a piece of metal. I always thought that in order for current to flow, conductors must be in different potentials. A solid piece of metal (if connected to a power source, say the positive terminal of an ac) would stay at
the same potential, with every spot on the metal at an equal potential. I can't imagine how current would flow within a block of conductor metal when all of the metal is a block.


texts: Is a copper pour redundant on the top layer of a multilayer (>= 4) board with a ground plane?

texts:
In a multilayer board with a GND plane directly under the top layer, does adding a copper pour to the top layer give extra value in terms of reducing crosstalk and EMI? If all signal traces already have an adjacent GND plane, can a copper pour provide additional benefit?

(Assuming that stitching vias are used appropriately, and there are no unconnected copper islands to act as antennas).


texts: Question regarding operation of a pulse generator circuit with 3 transistors (exercise 2.3 art of electronics)

texts:
The exercise 2.3 in 3rd ed. of Art of Electronics asks: what is the output voltage during the pulse?

I've replicated the circuit diagram from the book below (in circuitlab.com).

I'd be grateful if someone could read my interpretation below and correct any mistakes:

(A great explanation of the operation of the circuit without Q3 and R5 can be found here. In my question I'm just skipping to the part where circuit is generating the output Vout.)

The Q2 is now OFF, and so R4 and R5 form a voltage divider. A voltage divider with R4 and R5 values (1k and 20k) and 5V input would result in 4.76V output.

However, this circuit does not have 5V dropped between this voltage divider: the base of Q3 will be at 0.6V, which means there is only 4.4V dropped over these 2 resistors.

For 4.4V input, the divider will drop 0.21V across R4 and 4.19V across R5, in order to keep current at 0.21mA. This will put the Vout at (5-0.21 = 4.79V).

The second part of the question asks: What is the minimum required beta of Q3 to guarantee saturation?

This part I don't understand.

With 9.4V (C charged to 5V being pulled to ground by opening of Q1 results in base of Q2 dropping to -4.4V) across R3, there is 0.94mA current flowing though C1.

With 5V across R2, will there also be 5mA flowing through that resistor? Depending whether Q1 is still on (the input to Q1 base is a pulse shorter than the desired output pulse of the circuit), there will be 2 paths for this current to flow (CE of Q1 and CE of Q3).

Assuming Q1 is off, does that mean there will be 5+0.94= 5.94mA flowing through Q3? With 0.21mA flowing into the base of Q3, the minimum beta would only be ~28.

Thanks for responses in advance.


texts:
Look past the fact, that this will electrocute me - just for now.
I am building a small bowl with LED-strips inside it, and I need to wire it.
The question is - how?
This is my bowl with 24 * 15cm LED-strips (3.60m):

It needs to light up, so I "just" have to solder the wires to it.
I would like Option 1 was the best option:

But I might need to do Option 2:

Or Option 3:

I'm good with computers, but I never really got how to wire stuff.
Can I get some pointers?


texts: Looking for a 1 to 1.5 mm pitch board to wire connector that locks

texts:
I am searching for a board to wire connector such as this

http://www.alibaba.com/product-gs/216996350/JST_XH_connector.html

except that the one linked has a 2.54 mm pitch and does not have positive locking. Does anyone have any recommendations on a smaller pitch (1 to 1.55 mm) with locking capabilities?

Thanks
Mike


texts:
I havent had much experience with low pass filters but,I do understand what they do.
I was implementing one on an AC signal above.
This is a sampled input, and I dont see how would you call the picture an implementation of a LPF.
From what I thought, frequency is on the horizontal scale , so if the gap between 2 samples/lines was less than a threshold/cutoff, then it would not be taken into account. But I dont see how the height of the sample is reduced by an LPF?

Also, Why do you get varying heights, and not just a straight line, so an AC wave with a DC part on top?


texts: Is it possible/reasonable to generate a 480 x 270 image with an 8 bit MPU, store the image in external memory, upscale the image to 1920 x 1080, and generate an HDMI signal for the upscaled image? Also, is there an IC that can just take an image, upscale the image, and then generate an HDMI signal? Or does the image have to be upscaled beforehand and passed to an IC that can generate an HDMI signal?


texts:
I have an audio application scenario here. The Idea is to power a device (that later produces sound) with USB.

Unfortunately, I have massive static and what sounds like pink (Brownian) noise on GND. I also have a lot of static and other artifacts on the +5V lead, but I figured I can use a low-dropout voltage regulator to get a nice, smooth +3V out of it.

But how do I filter out GND?

Right now, I was experimenting with all sorts of low-pass and high-pass filters, constructed from caps and resistors. The caps, however, introduce artifacts themselves, it it's like two steps ahead, one step back.


texts: How to split a signal between 6 lines while maintaining voltage?

texts:
I'm using an FTDI adapter to power 6 separate strands of p9813 pixels. These pixels are located at least 4 feet away from the FTDI adapter. Each strand requires the single FTDI CTS out to connect to its Clock line.

The problem is that for each strand that I add, the clock connection seems to need to get shorter and shorter, roughly in proportion with the number of strands I hook up. So with 6 strands, I can't use more than 1/6th of the length I was able to use for one strand.

This is problematic because I need to run the clock lines at least four feet to the FTDI. How can I split the clock line to six separate wires while maintaining the integrity of the signal?

I'm using 24 AWG wire.


texts: What type of resistor component is this?

texts:
I have an RCA Victor 35x tube radio and I need to know what type of resistor this is and what it's purpose is?

There is some wire wrapped around the resistor and it's attached to the antenna.

This is the schematic for the tube radio.


texts: Concept of Hysteresis and Threshold point in Schmitt Trigger

texts: I understand the concept of Schmitt Trigger where there is 2 transition threshold points so that input changing between the hysteresis would not create output transitions . The very first observation that I made in this design requirement is the overlap/ hysteresis is between +1 and -1, so shouldn't the threshold be +1 and -1. So can threshold be +2 and -2 as in the options ? Are there more points to consider while deciding threshold ? Can I say as a thumbrule that the overlapping segment of inputs should always be included in the hysterisis that is here between +1 and -1, anything more is always good but that should always be less than the Maximum and minimum that is here +7 and -7?


texts: why the sender's clock might not in the same pace with the receiver's clock

texts:
I'm new to EE, sorry if my question is dumb. I was reading a text book which says:

To correctly interpret the signals received from the sender, the receiver’s bit intervals must correspond exactly to the sender’s bit intervals. If the receiver clock is faster or slower, the bit intervals are not matched and the receiver might misinterpret the signals. Below shows a situation in which the receiver has a shorter bit duration. The sender sends 10110001, while the receiver receives 110111000011.

I have two questions:

Q1. Since time is unique to anyone, how can one's clock is faster than others?

Q2. Why can't we tell each bit by the length it denote? Let's say e.g. one micrometer denotes a signal, so we can have a "ruler" to measure a complete wave length and work out every bit by the standard length?


texts: Measure S21 between 2 antennas at certain frequency using a Spectrum Analyzer

texts:
RX antenna is connected to the Spectrum Analyzer whose reading is regarded as P_RX. TX antenna is connected to a transceiver module that is set to work at the target frequency and emit certain power (P_TX).
Question: Can I deduct S21 from P_TX-P_RX?


texts:
I know this circuit is an oscillator circuit and it senses another signal of same frequency, but I don't understand

the calculation behind it, and
the reason for emitter inductor,
3.9k collector resistor and
others.

Can someone please show me the calculations for this circuit?

I made one myself but I am tired of tuning it. It only receives signal within few centimeters. It receives not only my 27 MHz toy car remote signal but any kind of signal, e.g: walkie talkie signal.

here is the link for that circuit: http://www.talkingelectronics.com/projects/27MHz%20Transmitters/27MHzLinks-1.html

They explained the circuit but didn't show the calculation, and they also didn't mention the inductor value.

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So many ANSWERS in so little TIME.
This is my first post on this site, and all of you made me feel warm, i am really honored. Thank you so much guys, and please forgive me if i said anything that hurts you.
Even if i haven't found any suitable answer but i really found something that is more importent than the answer, you all waste your time for me, that's all i really needed, THANK YOU, THANK YOU AGAIN.
If you know any place where i can start learning RF all over again, then feel free to mention it.


texts:
I am repairing an IP camera that has a blown transistor in the power supply section. The transistor looks like a SOT23 transistor, but it has 6 pins (how is that package called, anyway?), 4 of them connected together. I tried reading the marking, but the best I got was "HC??" or at least I think it's HC, could be HG, BC, BG, 8C, 8G or something like that.

It is a N channel MOSFET (judging by the fact that there is no resistor in series with the gate) with 4 pins connected to the drain (two middle and two end pins), like this (looking from the top):

G   D   D
+--------+
|        |
+--------+
S   D   D

If nobody can identify it, perhaps you could help me choose another suitable transistor. It is used in the primary side of PoE power converter in the device, so the working voltage is 48V, but could be higher. I will try to measure the current trough it (I have connected a TO220 transistor now to find what is causing too much current to be used and burning the small transistor).

EDIT: I managed to read the marking - it's FHC83 or EHC83. Still can't find anything in any marking database.

Also, I identified the driver chip - it's CD40106 - a few of its gates are connected in parallel.

There is also another transistor in there - looks like it's connected in series with the power input, the marking is "61" which makes it "FMMT618", but that is only 20V and would be connected backwards - current going into the emitter and out of collector (for a NPN transistor).