texts: Is it possible to create a T flip-flop without using a clock? I really need one, but I can't use one with a clock because it requires a signal shortener.


texts:
I'm confused on the two equations(refer to the figure: enclosed in red square)
This is a 4-stage pmos charge pump, I understand why its delta Qg is multiplied by 4(underlined red) same goes with the delta Qgb and Qgt (refer to the circuit) however,
In the second circuit above wherein it's a 2-stage PMOS charge pump, it confuses me on where did it get the multiplier 4 for the highlighted delta's Qg, Qgb and Qgt.

Can somebody help me figure out this one.

4-stage clock pattern:

2-stage clock pattern:


texts:
I have 10x 6p 18650 batteries. 13AH.
I found a protection circuit.
My issue is that I don't know how to charge the batteries. I could use a power source but I got it from my school and it isn't mine.
They sell for 500+$ so it's out of my budget.
I couldn't find much information for 2s+ battery pack.


texts: Puzzle: diode polarity in a vintage tachometer circuit

texts:
Once again, I'm trying to reverse engineer an old tachometer circuit--1970s vintage this time.

There are three diodes on the circuit board, and two have absolutely no markings whatsoever. Can anyone deduce the polarity of the two labeled with question marks in this diagram?  [I don't know how to write a schematic.  Below is an attempt to show the components in their configuration on the original circuit board.)

Below is a composite image of the components and the connections on the circuit board. The jumpers are not shown


texts:
Background -- I have in my possession a schematic for an ASIC NMOS chip developed between around 1985 until 1992. It's copyrighted and I'd rather not get into the details of of what its for, but my goal is to capture the schematic and convert it into Verilog as accurately as possible to preserve a "perfect" copy of the chip.

Most of the logic is very straght forward, however, there are times when a gate is drawn in parallel with the output of the first gate tied to the 'bubble' of the second. Here's a pic:

This same schematic uses this same parallel structure for other gate types, such as this:

It's also not a tristate enable, as that shows up on the schematic, as shown here for driving an output pad:

As always, thanks for the help.


texts: 12 V DC Li battery voltage regulation question

texts:
I recently bought a 12 V 50 Ah Li battery with the intent to use it for a 12 V DC trolling motor for a boat. The trolling motor runs at up to 30 A. I have read that lithium batteries tend to output higher voltage than the range acceptable for the motor. (Ranges listed at up to a max of slightly over 14 V, for use on a motor that I believe is rated to 13.x) I was wondering if there was a regulator of sorts I could use that would only allow 12 V to 13 V to pass through to the motor. I would need this to be relatively safely done, with no worries about excessive heat or anything, as I would prefer this be inside of a battery box essentially on top of the battery itself.

I don't have the battery yet to do testing to see if I really am getting those voltage levels, but it was a concern other people had when talking about lithium batteries for trolling motors. I am familiar with many low voltage applications, but I struggled to find a product that would do this. Any help would be appreciated. Thanks.


texts:
I'm trying to find the Thevenin equivalent network for the circuit below.

But whenever I solve the equations, I always end up with V(t)=2V_a - 3i_s and
can't get any expression showing V(t)~i(t) relationship. There's no way Thevenin resistance does not exist, but I can't get the grip of where i(t) appears..

I've tried short-circuit(V=0)/open-circuit(i=0) method along with putting test voltage between the terminals. The problem is that I can't get any expression that relates i(t) to V(t). Can somebody help me and find the v-i relationship for this circuit?

Thank you for reading my question.


texts: Detecting AC current using saturated current transformer -- variation in saturation ampere-turns of magnetic cores

texts:
In another question someone asked about using a transformer (in current transformer mode) to detect current through a power line. The purpose of circuit was not to measure the current, but was only intended to detect current. The threshold current in the power was not defined, but let's assume the power line current is either 0 or some known value. If the current is present, the circuit should light an LED. Again, the LED is not specified, but lets assume 20-40mA.
Now, if a current transformer were to measure, say a 20A power line, and give an output of say 20mA, then the turns ratio would need to be somewhere around 1:1000. That is a rather tiresome ratio to wind by hand. It could be split into 2 transformers one 1:31 and the other 1:32, and that would be approximately 1:1000. However, it occurred to me that in an application where we only need to detect current, and not necessarily measure it at all accurately, one might exploit the saturation of a core to limit secondary current.
Out of curiosity, I began poking around to see how cores are spec'ed and to see if I could find an appropriate core to detect, say 20A, and generate 20-40mA at a max of 2-4V, with a much smaller turns ratio.
Of course, one of the things that needs to be known is the maximum ampere-turns for the core to saturate. Ok, choose a material, and the dimensions of the core, and go from there. However, I ran across this article which claims that saturation properties have considerable variation from manufacturer to manufacturer, and furthermore, may vary from one batch to another because manufacturers farm out their production to other manufacturers.
Now, the article in question suggests checking saturation current with an LRC meter together with a DC bias current. OK, good advice. But my question is, whether saturation ampere-turns really varies a great deal for identically dimensioned, and supposedly similar material cores, or whether the article was just giving friendly advice, and possibly also promoting the sales of LRC meters. :-). (A specific brand is mentioned). If anyone has experience using magnetic cores in saturation mode, I would appreciate knowing your experience in this area. Is it reasonable to expect that saturation ampere-turns to be within, say +/-40% of calculated values, based upon nominal saturation characteristics of magnetic material?


texts: Does anyone have any sample code or suggestions to help me to interface my 100 pin uc3a1512to a device via RS-485?

texts:
I am attempting to connect and control a device which only accepts RS-485 input. I wish to communicate to this device via my existing UC3A1512. Does anyone have any existing source code or examples that may help me to create this interface?

I need a method of outputting date via RS-485 format.

I do not need to establish round trip communication, I simply need the ability to send commands to the device.

I have looked at Atmel's website and also on AVRFreaks and I see nothing of value to my project.

Any help is welcomed and appreciated!

I originally posted this question on StackOverflow before I knew of electronics.stackexchange.com


texts:
Firstly, apologies that I'm not an electrical engineering enthusiast, I just have a piece of hardware that's stopped working, and I want to get it solved.

I have a midi keyboard, and some of the keys have stopped working. So I opened it up and cleaned the contacts with contact cleaner.

The same keys don't work. I tried pressing the pads directly, and they don't work.

Does this just mean that the contacts are burned out and there's nothing I can do about it?
Or is it possible that the cause of this is some where else? (On the multi-pin plugs?).


texts: Pulse Generator - I (Art of Electronics)

texts:
In the Art of Electronics book, I don't understand the following phrase

  .. because current is flowing down through R3, trying to pull it up.

Why does this current try to pull the cap up?

Collector of Q1 is saturated and 0V, and base of Q2 is -4.4V, so does this mean its flowing through C1?

In this case, why does it even have to change since no current would flow from -4.4V to 0V. ?

Also can electrolytic capacitors charge on either side?


texts:
Can someone explain how the nodes behave when an error is detected by one or more nodes?
I have tried understanding it from the CAN Spec but it seems complicated.
When do the Transmit and Receive error counters increment and by what values?

Thanks


texts: Is there a limit to the number of kilo-watt hours an AAA (or AA) battery can hold?

texts: Or in other words, is there a limit to total battery capacity? Is the limit a physical one or is it an economical one?


texts:
Hello friendly friends.

In my wood shop I have two separate 220V circuits, A and B. B is new and I want to use it to drive the dust collection (1800W). Now I want it so that when I power on one of the machines (1500W+) driven by circuit A the dust collector will power on too.

Simple, I thought, just buy a relay and hook it up. So I bought an Eltako R12-100-230V relay (See amazon, I cant put a link in here).
I then connected the phase wire of A trough connectors A1 and A2 and the phase wire of the dust collection to 1 and 2.

Alas it doesnt work. Instead when I power on a machine, the relay will click and cut the power of A!???

I am now unsure wether I use the wrong relay or hooked it up wrongly.

This is what I have:

And If I understand NMF++ from the comments below right then this is what I should do:

Here's what I have atm:


texts: wirewound adjustable resistor. Something I missed?

texts:
I am by no means an expert on electronics, but I thought that I had a fairly good grasp of the basics. That is, until 10 minutes ago.

1 picture ~ 1000 words, so here is what I have:

The yellow wire is +12VDC and the black is ground.
From one end to the other, the resistor is 1KOhm, I have measured and confirmed that.
But for some reason, if I place the multimeters positive probe on one end of the resistor (not the one where the yellow wire attaches) and the negative to the black wire going back into the PSU, I get 12.04V which is exactly the same as when just placing the probe directly on the yellow wire.

How come there is no voltage drop even though the current is going through a 1KOhm resistor?

The resistor is rated for 100W (dunno if that is important).
All I want to do is drive 2 10W LED's that are rated for 9v-11v.

What am I doing wrong? What have I not understood correctly here? Did a bit of googling but with little luck.

Many thanks for any help :)


texts: Cheap narrow field lens to detect red laser light?

texts:
I want to monitor a red laser dot at a distance, say max 50m. I'm looking for a cheap lens array of sorts that I can place in front of a light detector (haven't an idea yet what I'm going to use yet - fast photodiode?)

My guess is that I'll have a lens with a red filter between the lens and the detector and then I'll read the light intensity. The red laser is the standard ones that can be bought at any gadget and toy store. Do they have a lens array in them that can be used in reverse?

Any ideas? Out of the box thinking?


texts:
I'm student and I'm working on a school project. The project is a radio transmitter.

My question here is only about the frequency modulator part.

Here is my circuit :

Here is my output signal (blue) and input signal (brown) :

As you can see there is no modulation what so ever.

According to my teacher, my output should look something like this if my oscillating frequency is 93 MHz and my input signal is at 9.3 MHz:

My oscillating frequency is supposed to be 93 MHz. Here is how I did my calculations:

The *1.3 is just to make sure I respect the Barkhausen criterion

Do you guys have any suggestions to get an output at 93MHz when I input a signal at 9.3MHz?

Edit : I know the oscillating frequency can be calculated with the formula above but how can one theoretically calculate the amplitude of the oscillation and what affects it? I'm guessing RC and RL. Any suggestions?


texts: Switching an LM317BTG on/off using a microcontroller

texts:
We're using an LM317BTG to power a 4V modem (the LM is connected to a 12V battery). The modem can produce peak currents of up to 2A during transmission bursts. Under normal operations, the modem consumes anywhere between 100mA and 300mA.

We would like to be able to switch the LM317BTG on/off using a microcontroller (digital IOs rated at 5V/couple of mA).

I'm thinking a transistor of some sorts could be used here? I've already used NPN bipolar junction transistor (BJT)  (like the 2N2222) to switch low-power devices on/off but I guess I need something more powerful than that?

Do I need to use a MOSFET, or is a Darlington also possible? And how should I hook it up in the circuit? I would like to use a digital IO of the microcontroller (0V or 5V) to switch the LM317BGT on/off.


texts: Writing batch files for simulation in Modelsim/QuestaSim

texts:
I am trying to compile a design that consists of multiple files. There are library files with the primitives, than netlist files for the design, test vectors files used with the testbench and the test bench file itself. There are multiple cases that need to be tested and for this I may have to write a lot of testbenches and a lot of vector files in which only a couple of lines or so change. I think that it should be possible to use "pre-processor" directives in the verilog to simplify this task. Thus I write a batch file that has a list of vlog commands to compile everything. Within it I define some constant (like we do with #define in C language). Later in the verilog vector and testbench file I can use `if to find out if some part of the file should be compiled or excluded.

Now I have done this type of thing in C but not verilog. Can someone provide me with what steps and commands I need to use. Please note that I shall write a batch file with list of vlog commands and  call it from within QuestaSim using the do command. This will compile all files that I need for simulation and also is expected to contain the "constant". Within the testbench I want that depending on value of someconstant "passed to it", different sections of the code in the file will be compiled. These different sections are enclosed in ifdefendif This can be done in C using #ifdef, #endif, #ifndef, and #define pre-processor directives. Note that I am using QuestaSim which is similar to ModelSim, more like its big brother. I have never used this "pre-processor" feature of verilog before.

The problem is that, the batch file contains commands for questasim while the files being compiled contain verilog instructions for hardware description.

So the question is, how do I do this or is it even possible to do this?


texts: Electricity through water can injure a person?

texts:
I have maybe a simple question.I would like to know if current can travel through water and can injure a person.

For example as shown below(A little funny picture!!!) a man watering his grass and his garden from rubber tube and his hand is in contact with water(which doesn't appears in the followning picture but we can make this assumption).Also in garden there is nearby a worn cable and has a high current leak.So when this man throw water by mistake on this cable, can be electrocuted?Can current travel through water and injure this man?


texts: How to correctly simulate a simple LM2907 circuit in LTSpice?

texts:
I'm trying to convert the frequency of a 0-5V square wave, which ranges from 0-20kHz, to a voltage using a simple LM2907 (8 pin) circuit.

Using R1 as 100k, I've calculated C1 to be 416pF for a maximum output of 12V @ 20kHz.

However, when I do a transient simulation, all I get is an exponentially shrinking output voltage starting at ~2mV.

What simulation settings should I use in LTSpice to verify the linearity of my frequency-to-voltage converter? Transient, DC operating point? Some kind of sweep?

Here is my circuit:
alt text http://img840.imageshack.us/img840/6758/lm2907ftovtest.png


texts: How to create encrypted spice subcircuit/schematic and use it as symbol in other schematics?

texts:
In LTspice XVIIx64 I want to create a subcircuit and use it in other schematics but the content of the subcircuit should not be visible to other users. The users are students who are advised to find out the content/components of a filter or resonant circuit by doing AC analysis.

I know how to create subcircuits in LTSpice and how to define symbols and use them in other schematics. However there is the disadvantage the I have to supply symbol and corresponding asy-Schematic in order that the symbol can be used in the top schematic. By suppling the asy-schematic the components values can be seen by opening the file. There is also the -encrypt function in LTspice as a xviix64.exe execution command and I am able to encrypt the underlining asy schematic. Creating a symbol for it and placing it in the top level schematic results in simulation that LTspice says: "Trouble generating netlist for SPICE run".

Are there any other possibilities to get this working?


texts: ASDA-A2 Delta Servo Drives including two types: 220V and 400V series that it seems the difference is input voltage of the Servo Derive. but i doubt 220VAC or 400VAC is line to line voltage or line to neutral voltage of The local electricity grid? and if it's refers to line to line voltage, is it possible to feed 220VAC Servo Drive with 400 VAC (line to line voltage) with some considerations or not?


texts: Using digital and analog signals in the same cable

texts:
I am working on a project with 3 PCB : PCB1 is the master, it communicates with two slaves, PCB2 and PCB3.
PCB1 is powered by a battery and it redirects the supply to PCB2 and PCB3. Each PCB includes a microcontroller and an RS-485 transceiver.
There is a cable from PCB1 to PCB2 and another from PCB1 to PCB3. Both cables are the same. There length is approximately 50 cm. They include 6 wires : 4 wires for the RS-485 (the communication is full duplex), and 2 wires for the supply.
It looks as follows :

I need to add an ECG sensor on PCB1. It simply measures the potential difference between two analog inputs. The first input needs to be connected to one pad on PCB2, and the other to another pad on PCB3. I was thiking of adding 1 wire in each cable to make the connection. It would look as follows :

But there would be analog and digital signals in the same cable. Is this a problem ? If so, what are the solution to transmit digital and analog signals at the same time ?


texts: Why use a three opamp instrumentation amplifier?

texts:
This TI application note shows this typical instrumentation amplifier (InAmp) with three opamps (p.4):

Further down the page the following two opamp InAmp is shown:

The former is more common (I think) and easier to understand, but is there a good reason to prefer this one over the other? After all it's more expensive since a third opamp is needed.
Also, the two opamp version doesn't have R3 or R4 in its \$V_{OUT}\$ equation. Is the amplification really independent of their value?


texts:
On a skiing trip I saw a string of solar powered multicolored lights that someone had thrown in a tree such as this:

All the lights were initially lit.
As the night progressed I noticed that the red LEDs darkened, then the green and only blue remained. This runs counter to my intuition which would suggest that the battery of the circuit would run lower (and probably no dc-dc converter since its a cheap chinese string of lights).

My question is: How would a progressive drop in voltage from a battery produce the red, then green then blue lights darkening? (When it should be the other way 'round if they are in parallel)

What kind of circuit from a battery with a dropping voltage could produce this result?


texts: Is dependent source really a device like a battery or is just a model as we model transistor with dependent current source?


texts: Suppose a RF module has passed CE EMC tests. Must the CE marking be printed on the module itself in order for the approval to be valid if it is to be used in an end product?


texts: Wide range and high precision current measurement

texts:
I need to measure current over a large range from a few µA up to 2A. The application is sensitive to noise at later calculations with the measured current. My idea is to use different shunt resistors which are bypassed as needed.

Has anyone some experience with this situation and has already selected a bypass switch for that purpose? My first idea is to use a simple bistable relay but I don't know how much that would affect noise behaviour on low current measurement.


texts: Calculating the DC voltage and current needed to obtain certain heat with a resistor

texts:
What formulas can be used to calculate how much volts and current is needed to get a resistor to heat up to a certain temperature?

I need to get a resistor (or a few next to each other - for more heated surface area) to heat up to about 200 degrees Celsius. It needs to be powered via DC power supply, preferably a few AA-alkaline batteries.

Can you please assist in what I need to look for in constructing this?


texts: What is magnetization resistance and how to calculate(or measure, or estimate) it?

texts:
What is magnetization resistance? How to calculate or measure or estimate it?
Edit: I'm trying to build a smps simulation on simulink, in transformer block I have a parameter named magnetization resistance and I don't know what to write here


texts: Problem with stacked power mosfet simulation

texts:
I'm trying to build a Circuit Lab simulation of a stacked power mosfet pulser as described in this paper. The simulation runs for 10 ms. After 5ms, the switch flips and the voltage at 'StageOne' drops accordingly, however, the 'Output' does not drop. I think it's supposed to drop because the capacitor C1 keeps the gate slightly positive relative to the source of M2 which should result in M2 opening, however, I'm not an electronics engineer and I'm just guessing my intuitions around the operation of the circuit aren't certain. Can anyone please advise as to what I'm doing wrong?

simulate this circuit – Schematic created using CircuitLab


texts: I have solar panels does the bi-directional service head control power factor?

texts:
I have solar panels, had them for three years now. The first two years my summer bill was 3-20 dollars a month. Last year I received to bills in a row that were around 90 dollars. I called to someone come out to see why. The service tech came out and pulled out a laptop. He connected to my outside service head magnetically. It showed a lot of information even Power Factor. The PF reading was .65 I didn't like that so he changed the service out. The new service head read .85 better but I would like and think it should be .9 or better. I asked the rectifier company if they within there panel controlled PF? They said they have nothing to do with that.

So one question is does the outside my bi-directional service head control PF?

The other question is are "utilities companies" required to maintain a PF band?


texts: How long would a fully charged 230AH 12V battery last when using it with a 12V->230V DC>AC inverter, drawing an average of 1500 watts power?

texts:
This sort of battery.
This sort of transformer.

Powering a 1500Watt PA for how long, and how do you work out the AH when using a transformer?
As best as I can figure out it would be something like:
230AH * 0.85 (roughly 15% lost through the transformer) = 195.5AH
Using 1500 watts with 230 volts means the current required would be (I=P/V) = 1500/195.5 = 7.7Amps
This would mean the battery would would last for 195.5AH / 7.7 amperes = 25.4.hours, which seems very unlikely.
I changed the formula to use the voltage of the battery instead of the transformer:
Using 1500 watts with 12Volts means the current required would be (I=P/V) = 1500/12 = 125 amperes
This would mean the battery would would last for 195.5AH / 125.amperes = 1.6 hours, which seems more likely.but is it correct?


texts: Help Identifying/Decoding Ceramic Capacitor

texts: I am having a difficult time identifying a high voltage, ceramic capacitor that I need to replace. I've tried at length to research this myself to no avail. I am hoping that someone out there can help me with this. Apart from the first line on the capacitor which I am reading as 220pF ±10%, I don't know how to interpret the rest. I cannot find a meaning for the symbol at the bottom that is a half circle with a bowtie in the middle of it and what does the tilde mean in this context? Cannot determine the voltage etc Thanks!


texts: Could a lower bandwidth or rise time oscilloscope be used for measuring a stable phase shift between two channels?

texts:
I’m trying to design an experimental setup to measure the speed of EM waves transmitted from a small solenoid antenna (It won’t transmit effectively but I have to make the antennas more “point like”) driven by a common emitter based Colpitts oscillator at varying frequencies between 1MHz and 10 MHz; and recieved by an equivalent solenoid antenna connected to an adjustable capacitor tank circuit (or maybe a CE amplifier if need be) or maybe simply grounded. Antennas will be positioned at varying distances from 0.4 m to 2 m; very short electrical distances.

I will be measuring voltage and current waveforms (sine) at both sides simultaneously. Because of the ratio of the distance between the solenoids to the wavelengths, I expect that the measured waveforms (when superposed together on screen) will look like almost completely overlaping. Therefore, an oscilloscope which would discriminate the phase differences with fine enough resolution/accuracy in time  is required.

First thought was that, if the delay time expected is “td” then an oscilloscope with a bandwidth like maybe “(1/2td) Hertz” would do well here (the waveforms could be seen without considerable distortion in terms of time). For 1 m distance, that would make 150 MHz (at -3dB) but for shorter distances that wouldn’t be affordable for me.

The next specification of interest is the rise time. It’s often recommended to choose a scope with a rise time less than 1/3 of the rise time to be measured and that’s even less affordable.

These tips seem to be based on the assumption that the measured waveforms would be non-repeating (would need “triggers” to indicate them). But I will be measuring periodic waveforms. Could that be an advantage?

Assuming that the sampling rate is good enough, is there a “trick” to using cheaper scopes for measurements on stable sine waveforms?

One could suggest “why not simply increase the scale of the setup, like in the phase shift method to measure distances, and get away with it?”. I will hopefully continue these measurements with other antenna types sometimes in the “very” near field so sooner or later I will be facing this problem.


texts: Obtain transfer function of op amp circuit

texts:
I'm trying to find the transference function H(s) of the next op-amp circuit:

I get the next following equations:

When I put the equations together, this is an absurd. How do I solve this?


texts:
I've recently switched over to Atmel Studio 7 (AS7) for one of my AVR projects and after a bit of fiddling around have worked out how to get the "Custom Programming Tool" to correctly upload compiled firmware to a target device using the command:

"$(SolutionDir)\avrdude\avrdude.exe" -C"$(SolutionDir)avrdude\avrdude.conf" -patmega2560 -cwiring -b115200 -D -v -Uflash:w:"$(OutputDirectory)\$(OutputFileName).hex":i -P\\.\COM5

While this works successfully, AS7 seems to think it fails every time because it outputs verbose information. If I look at the output window for the custom programming tool, I get the verbose output from avrdude as expected, but it AS7 treats it all as error messages:

ERROR:avrdude.exe: writing flash (12578 bytes):
ERROR:Writing | ################################################## | 100% 2.05s
ERROR:avrdude.exe: 12578 bytes of flash written
ERROR:avrdude.exe: verifying flash memory against ATMega2560\AstroEQ6Mega2560.hex:
ERROR:avrdude.exe: load data flash data from input file ATMega2560\AstroEQ6Mega2560.hex:
ERROR:avrdude.exe: input file ATMega2560\AstroEQ6Mega2560.hex contains 12578 bytes
ERROR:avrdude.exe: reading on-chip flash data:
ERROR:Reading | ################################################## | 100% 1.47s
ERROR:avrdude.exe: verifying ...
ERROR:avrdude.exe: 12578 bytes of flash verified
ERROR:avrdude.exe: safemode: lfuse reads as FF
ERROR:avrdude.exe: safemode: hfuse reads as D8
ERROR:avrdude.exe: safemode: efuse reads as FF
ERROR:avrdude.exe: safemode: Fuses OK (H:FF, E:D8, L:FF)
ERROR:avrdude.exe done.  Thank you.
Process exited with code 0

Clearly avrdude completes successfully, and the program is downloaded and running. However all those "ERROR:" prefixes are really annoying, especially as at the end of the process I get an error window insisting that the custom programming tool failed.

Has anyone got any experience with setting up the custom programming tool and could tell me how I need to adjust the programming tool command so that its output does not show up as errors?


texts: Code Running from Debugger but Not Without it

texts:
I am using WindRiver JTAG Debugger to debug my code.
Whenever I run the code with Debugger connected, Code works correctly but If I disconnect it, It fails to even Start!

Has anyone faced such kind of Problems?


texts:
Hello I'm trying to understand the value in microfarads of capacitor labelled,
C791 103(2)
And how to calculate if the SI unit is not given thanks..
diagram below

One more question if you don't mind please... what about resistor? It's value is labelled 3.3


texts:
I am currently trying to design a 16 nibble RAM on logisim, whereby it takes 4 data input lines.
However, what I am having the most trouble with is converting the 4 address lines into a single input, such that the RAM circuit should read a 4-bit piece of data as input and set this as the value of the nibble that is defined by the address bits.
For example, if Data = 1000 and Address = 0011, then in the next Clock cycle the value of 4th nibble of the RAM should become 1000, and also this value should be displayed on the output.
I know it involves a multiplexer, but what would act as the 4 selector bits?


texts:
The question is straightforward! I have searched the internet on basically everything written on this board and I can not find it. Anyone who could help me with that, or help me with using it would be a great help!
PS:I can provide more info, if something isn't clear in any of the pictures or you have a question about what it looks like in an area just comment and ask, and I will clarify.
PSS: There is nothing(in terms of words) on the back of the board.

Edit: The board interfaces with a small camera (what the 2x16 input array is for). And is mounted on a rotating x and y platform with two servos (not connected to it).
Also it is made to go with a [cRio]: http://www.ni.com/compactrio/

(Links for photos)


texts: Unable to program ATSAML21 PCB via SWD - Problem with connection?

texts:
Well, I'm officially stumped (and so are several other engineers)...

I have a custom PCB running an Atmel ATSAML21E18B microcontroller, which I'm trying to program through an Atmel ICE debugger / programmer. After some initial problems with the board (an ungrounded pin which has now been grounded), I managed to get a nice stable voltage of 3.3v running through the board from 3 AA batteries going through an LDO on the board.

The next step was to upload a simple test program which blinked a couple of LEDs on the board to make sure things were all nice and working. I plug the board into the Atmel ICE via a 10 pin SWD header on the board, open the device programmer in Atmel Studio and do a voltage read - 3.3v as expected. Try to get the device ID, and I get the following error:

I've tried knocking down the SWD clock to lower frequencies as suggested by a few people, but no luck. I also tried using the Atmel ICE on the L21 Xplained Pro board, and everything works fine there, so I know that the programmer isn't the issue.

I've had a few other engineers look at the boards and the schematics, and they can see no obvious errors. We all checked the datasheet to make sure that the connection between the mcu and the 10 pin header was as described in the datasheet.

Honestly, I have no idea what's going on here. Below is a copy of the schematic:

If anybody here has even the slightest inkling of what the issue might be, please tell me. My head hurts from banging it against the desk!


texts: Supercapacitor backup circuit - why seperate charge and discharge path?

texts: I am learning about super capacitors in a backup power application. I see a lot of examples using diode networks or FETs to separate the charge and discharge paths. Why is there so much effort put into separating the charge and discharge paths? Why would the example circuit I drew work? Someone mentioned the voltage drop over the limiting resistor may cause an issue? The 3V3 regulator would be powering an MCU.


texts: Why VDDIO is more than VDDcore supply in VLSI/ integrated chips?

texts: I have a question on different power supplies in a integrated circuit. I have seen VDDIO supply is more than VDDCore. If the input signal is more than the power signal, won't it affect the device?? Explain the purpose of this variations..??


texts:
Let's say I have following three sinusoidal waves.

 1. x1(t) = A*sin(2*pi*1000*t) i.e, f = 1 kHz
 2. x2(t) = B*sin(2*pi*1500*t) i.e, f = 1.5 kHz
 3. x3(t) = C*sin(2*pi*2000*t) i.e, f = 2 kHz

So when I get the signal y(t) = x1(t) + x2(t) + x3(t),

Is there any way to determine the common frequency such that the y(t) will start repeating itself? Can it be directly evaluated as smallest common multiple of these frequencies? For example, 6 kHz for this case.


texts:
Refer to this question I had asked a few days back:
PWM DAC Filter explanation

Hi, It is getting extremely difficult for me to create the PT0 and PT1 signals as given above. I am using a dsPIC30F device. Two PWMs are created with independent duty cycle control, however, the duty cycle change happens by controlling falling edge, where as the above demands that PT0 must have fixed falling edge and variable rising edge...how to achieve that?

On the other hand, I am thinking of using a simple 4th order sallen-key LPF to filter out most of the PWM fundamental...and set its cut-off to say less than half of the PWM fundamental. My sampling frequency for the DAC output (yes, I am sampling my own DAC output) is LOW about once in every 25ms.

Can I remove the left over ripple, by using a small LC filter in line with the DAC output...this works in voltage regulators...will it work here. The output is going to drive a high input impedance OpAmp...so current drive capacity is not in question.

Any pointers?


texts: SMT32 HAL UART crash on possible overrun

texts:
I increased my baud rate from 56000 to 115200 and my serial communication stops working when pinging continuously after 10-20 seconds. I am running at 16 MHz.

As far as I know HAL driver will handle overrun, among other errors by clearing the flag and calling the error callback function. If that is the case then if I get an overrun due to the increase in speed it should be cleared and my communication should continue working after that.

I have found also that increasing processor speed to 32 MHz "fixes" the issue but I don't want to rely on that. Perhaps it just takes much more time for the error to come.

Is my understanding correct? Are the UART flags cleared automatically by HAL drivers? Do I need to clear them myself or handle them in some manner? Is there something I am missing?

I basically use HAL_UART_Transmit_IT() and call HAL_UART_Receive_IT() after it finishes and do nothing else.


texts: How to perform estimation of maximum output low voltage V(ol) and delay(tplh) in a 4 input Pseudo NMOS NOR gate using LTSpice?

texts: How should the inputs be provided to realize the same in the schematic diagram created?


texts: Current at specific moment in bridge circuit

texts:
At the below circuit i need to calculate the current Iab at 300 μs,can i apply voltage division to get the voltage across the appropriate  resistors(30KΩ and 120KΩ)and by applying ohms law finding the currents and by using KCL at A find the Iab(t)?I am concerned as to if the use of voltage division is allowed across the 30KΩ and 120KΩ.
Capacitors initial voltage is 300V


texts: How much larger should a plated-through hole be than lead diameter to get good solder wetting?

texts:
I'm designing a new PCB where I have a whack of connectors that have to line up with the metalwork.  These are a two-piece Neutrik XLR connector where the insert is soldered to the PCB and then mates to the shell already mounted on the chassis.  There is NO wiggle-room once the insert has been soldered to the PCB - the insert is a sliding fit onto the shell with almost no perceptible side play.

One series of connectors is easy - the solder tab is a thin rectangle.  The Plated-Through Hole is perhaps 5 mils larger than the width of the tab and I get great solder adhesion to the flat sides of the tab.

The other series of connectors is more problematic.  All 4 pins are round.  Thus, I want to have the holes as small as possible while allowing for good solder adhesion over the full length of the pin.

If the exact insert position on the PCB wasn't so important, I'd simply have my usual 10 - 15 mils of clearance.  In this case, though, I have 12 to 24 connectors on a single PCB and need to ensure that all of them are as close to the proper location as possible.

I've spent some time with Google and have already looked at some of the guidelines here.  Specifically, In pin-through-hole, how much bigger should the hole be than the pin?  and In pin-through-hole, how much bigger should the hole be than the pin? and What pad hole (drill) size is appropriate for a given through-hole lead diameter?.

Unfortunately, none of those address the issue of solder wetting and adhesion of component leads in Plated Through Holes in a PCB.

I should mention that we are using 63/37 Tin/Lead solder and that these connectors will be wave-soldered using AZ2331 Water-Soluble Flux.

Our PCB fab house is pretty good when it comes to delivering boards with PTH holes having the correct finished diameter as specified in the drill file.

I'm looking for guidance on how much clearance around the component lead I should have in order to get good solder wetting and adhesion.


texts:
I want to build a 1 watt led driver,  the led requires 350mA@3.2V approximately.

I bought a LM317( 0.5A and 1.5A versions) for this purpose but I can't figure out the schematics of the LM317 and since I burn a lot of stuff so I decided to ask here first.
How much would the efficiency be?

My power supply: 2A@5.2volt-DC


texts: why we use LNBF instead of simple dipole antenna, at the focal point of reflector of satellite dish antenna?

texts: LNBF is made of horn antenna, waveguide, half/quarter wave dipole and some circuitry on PCB. I know Horn antenna is used to match impedance between waveguide and free space but my doubt is, why we dont use half/quarter dipole antenna  directly instead of using horn antenna, waveguide and all?


texts: delay on cmos inverter while increasing W of nMOS and pMOS

texts: We have one CMOS inverter and a fixed capacitance as load , for example 0.1pF . As an experiment we increase W of nMOS and pMOS and each time we increase W, we find the delay of the inverter (using spice). We notice that while increasing W, the rate of decreasing delay is dropped. Why is this happening ?


texts:
I am modeling a low voltage single phase electrical distribution system with a step-down transformer using LTSpice (source is 480Vrms step down to 120Vrms). In LTSpice instead of setting the turns ratio, the inductance of the primary and secondary winding is set. However, I cannot find inductance values in low voltage transformer datasheets, and the results of my simulation seem to depend on the actual value of each winding, not only on the ratio.

For example, if I set \$L1=16\mu H\$ and \$L2=1\mu H\$ I get the following result for the current through R5 and R4

but if I set \$L1=16 H\$ and \$L2=1 H\$ I get the following result for the current through R5 and R4

It makes sense that the magnitude of the current will be different since different L values produce different impedances, so what is the best strategy to model this step-down transformer?
Thanks.


texts: How to radiate a positive oscillating voltage?

texts:
I am trying to build a simple AM transmitter, transmitting only a carrier wave and thus silencing the noise on my radio standing next to my circuit.

I built this circuit on a breadboard.

It's a simple positive square wave oscillator designed to produce a frequency between 618kHz and 1934kHz, roughly the range of my radio. When simulating, this indeed produces the square wave intended.

At the output of my oscillator I simply put a wire on my breadboard acting as an antenna.

This however doesn't influence the audio coming from the receiver in any way.

What did I do wrong?

Update: It is not per se my intention to just jam a nearby radio. I try to get this circuit or something similar to work, as an early step in establishing a solid understanding about RF-communication. I try to radiate something controlled at a variable frequency. Just a carrier wave and thus silence seems the simplest to do.


texts: Which transistor should be used as a switch for a load of 5 V, 100 mA

texts:
I'm new to electronics. I want to use a transistor as a switch for a load of 5 V and around 100 mA.
And what should be the base current or voltage to activate the transistor. Please help me.


texts: Build output voltage graph as a result of the integration on an ideal integrator

texts:
Picture related is an original task(in Ukrainian):

Translation of the task 1(till «Задача 2»):

Build the graphic result of the integration on an ideal integrator if R=40 kOmh, C=20 uF and the input signal is show in the graph( where U1=1 V, U2=2 V, t_i=i*delta t, delta t= 2 seconds). Maximum output voltage of the operational amplifier equals +-14 V

U_вх   -   U_input

U_вих -   U_output

Me, trying to solve it:

I have a graph how does input voltage change. I need to find how does output voltage change.

Voltage is the potential difference, so to find voltage in out, I simply need to find the potential of the out node.

The first step is to find the potential of the node after R. Then I have to find how does potential changes after capacitor, and what is the potential of the amplifiers out. The result will be potential after capacitor at some time + potential in the amplifier out.

I don’t know what to do with capacitor when I have non-harmonique signal. I know that capacitor charge time is 3RC and the current through it falls exponentially.

I remember that in last lectures professor explained that we should make an equations for each intervals on the graph, like y=ax+b for output signal. This equations comes from definite integral of what I do not remember...

Well, I found this:

I think I should put instead y U_out, and instead x U_in (exactly voltage in amplifier, not just input voltage ). Hmmm, maybe it is the whole solution? I just integrate from t0 t1, got the line equation for this interval, integrate from t1 to t2 and the same

Can you figure me?


texts: Can Radial Electrolytic capacitors blow up from AC?

texts:
I'm into model railroading, and I was modifying one of the cars to have extra LEDs.

There are 2 wires going through this car that connects to the tracks to receive power. I cut the red and black wires, connected everything correctly to the right polarity for the LED and the capacitor. So I apply full power to the car, 18 volts. The capacitor can take up to 50V (220uf).

All seemed fine, I cut the power to the train and the LED stayed lit for a few seconds as it's supposed to. So I decided to give it full power again and leave it so it can charge the capacitor. All of sudden I started hearing noises then BOOM!!!! The capacitor exploded around my face and burst into flames nearly killing me and destroying my house.

Here's how it looks like.

The film is completely out. I asked one of my friends and he said it's because the power going through the wires is AC and it can feed negative polarity to the positive wire.

Regardless, next time I must use a diode to keep the flow only "+" to the "+" leg. So my question is Why has this happened?

I'm now traumatized of ever using capacitors again.


texts: Decomposition of a square wave with a duty cycle of 40%

texts: I'm studying the decomposition of a square wave with an amplitude of 500mV and a frequency of 80kHz. With a duty cycle of 50%, I have obtained a negative exponential graph but with a duty cycle of 40%, I've got a very weird result and was wondering if whether what I have done and calculated is correct?


texts: shortcut to change layer/add via while routing in Altium doesn' t work

texts:
I'm trying to change my tracks during routing to pass from bottom to the top, or from top to bottom using +/- buttons, but neither numerical buttons neither +/- buttons from keyboard buttons are doing anything.

I see there is people who face this problem but I don't see how they finally solved the situation. When I  go to DXP menu, customize shorcuts, I found next layer and previous layer aptions linked to "minus" and "plus" buttons.

If I'm not drawing tracks, this commands is changing the shown layer for the next or the previous one. But it' s not adding any via or changing the track I'm drawing.

When I press the change layer button while a track is being drawed, the selected track doesn' t change the color and any via is painted. Its color stills being the current layer color, it doesn't change because it can't change from current layer to the next or to the previous. I don't know what's the problem, or how to pass the track from top layer to bottom layer with a via automatically as it's seen at examples and tutorials.

What are exactly the combination of buttons and commands to get the desired behavior?
I think I'm doing something wrong, I'm doing this way:

1.- draw a track until the pcb point of change,

2.- once there I click with left button (mouse) the track one time.

3.-Here, I press the change layer button.

4.- Here I was hopping to change the track layer. Instead of this, the current layer doesn' t change,  neither via is appearing, when I follow drawing the track it can only still drawing within the origin track layer.

Any suggestions?

Thanks in advance.


texts: How to detect when an item has passed by a sensor up to a distance of 10cm?

texts:
I'm looking for a way to detect a join in a conveyor belt up to a distance of 10 cm away from the the belt. My original idea was to stick magnetised rubber strip on the underside of the conveyor belt and use a Hall effect placed under the conveyor to detect when the strip passes by. When the strip passes by  I can determine that this is where the belt has been joined.
The issue with this is that the Hall effect will only detect a field of this magnitude (magnetic field strength similar to a fridge magnet) up to approximately 1 cm. As it is on a conveyor belt, I don't want to use something strong like a rare earth magnet to get a detect. I also can't use a sensor that uses light or relies on reflection as the environments tend to be very dirty.
Is there an alternative way to get a non-touch detect from a sensor up to a distance of 10 cm away? I only need a yes/no binary detect, nothing more.
Edit: As asked for in the comments:

Belt material is either rubber or rubber with steel cord for strength
Speed is anything up to 5 m/s.
Belt thickness can vary up to 30 mm.
Sensor needs to be placed to the side of the conveyor or to the underside. It can't be placed above the conveyor.
Belt join is made from large steel clips. If a metal detector is placed further down on the belt, I want to be able to warn the metal detector that these clips are approaching in order for it to ignore them. I want to do this with something simpler than an additional metal detector.
Dust material would specifically be from somewhere in a quarry or a coal mine. Dust from rocks and rock-like materials


texts: Tips for desoldering difficult to desolder mini transformers

texts:
I have to replace a couple of small transformers without destroying the PCB or the transformers.

Unfortunately my phone camera is unusable so I need to describe them and what makes the situation so hard for me.

The transformers are almost cubical with a little more than 1cm in size. They consist of two E shaped parts of ferrite, that are sitting on a plastic base. On opposite corners there are three pins on each side, close together (total of 6, lets call them winding pins). On the other two (opposing) corners, there are on each side one pin that is part of a kind of metal clamp (lets call them clamp pins), holding together the E shape. If you remove those clamps, then the E shape falls off, and you have direct access to the wiring. The whole thing is mounted on the PCB with almost no space under it.

Now for my problems with soldering:

applying too much force will easily break the plastic that the 6 winding pins are molten into
applying too much heat will loosen the winding pins (plastic melts), and ultimately dissect them from the plastic bottom, which will rip the winding attached to them of. Or when pushed from below, push the pins into the windings.
removing the clamp pins first is possible, but then part of the ferrite comes of, and the windings are on some plastic tube kind, which will be dangling and ultimately rip of the winding wires from the pins.
The pins do fit really tightly into the holes, and even when removing all of the solder I can, they are stuck. I have tried to empty one of the holes as good as I can, and clean one of the pins as good as I can, and I need to apply quite some force to get the pin into the hole again.

What worked ok-ish so far is to apply only a tiny bit of pressure from the backside to the pins with a short amount of heat, and then try to support it from the other side with little force until the solder is solid again.

But this takes like 100 rounds until one gets of, and even then the plastic is a bit molten (btw. varying temperature between 250°C and 350°C didn't seem to make any difference here).

What else could I try that allows me to get off (at least most, I have lowered my expectations) of the transformers in one piece?


texts: ADXL345 acceleration data readout looks strange - STM8

texts:
after finally finding out how to create a software SPI connection i now can successfully read the data from an ADXL345 acceleration sensor. But they look rather strange to me, this are some sample values:

X: -252 Y: -532 Z: 9616

These values are measured in +-16g mode with full precision (so basically we have 4mg/LSB). These values are in mG (e.g a value of 1000 would represent 1G). I don't quite understand why the Z-value is so high?

I initialize the ADXL345 with this code:

write_command = ((0x00 | 0x31) << 8) | 0b01001011;//set SPI 3wire & 16g range & full-res
write_command = ((0x00 | 0x2D) << 8) | 0x08; //Enable measurements

I send the values over uart to an UART / USB converter. The values are changing if i start to move the sensor board so i think my reading part is correct:

//read X-Axis
x0 = readRegister(0x80 | 0x32);
x1 = readRegister(0x80 | 0x33);

//read Y-Axis
y0 = readRegister(0x80 | 0x34);
y1 = readRegister(0x80 | 0x35);

//read Z-Axis
z0 = readRegister(0x80 | 0x36);
z1 = readRegister(0x80 | 0x37);

//convert in milli-G [4.0mg/LSB] in +/- 16g mode @ full-res
x = ((x1 << 8) | x0);
y = ((y1 << 8) | y0);
z = ((z1 << 8) | z0);

*x_val = x * 4;
*y_val = y * 4;
*z_val = z * 4;

Do you have any ideas what i do wrong at the data processing part?


texts: Arduino MEGA ADK: read data from usb(not serial)

texts:
I'm new on this field and I've spent my last 3 days searching for a way to read some data from a usb device(http://www.willow.co.uk/TelosB_Datasheet.pdf). It sends packets of 12 octest and all I want to do is to read 2 of them. I want to be able to set the transfer speed and the data buffer . . . I guess.

This board has a integrated usb device PORT. I've read about USB shield 2 Library but I've seen it helps connectiong with a Android phone. I'm sure it's a simple solution but I'm not able to find it.

Do you have some advices where should I find something?


texts: PCB ground connection for shared power/data bus system

texts:
I have a wireless device that is connected to a shared power and data bus, similar to below. The bus can be shared by up to 5 devices and I don't know what it will be connected in advance.

I connect the bus connections directly to my PCB, shown on the below schematics and layout part. It doesn't sound correct, but I don't know the shared bus connection should be connected to my PCB properly. Can anyone help me with it?

Shall I connect the GND of the bus to my GND via balun or what?

I have two concerns:

My system shouldn't be effected by noises from other system or vice-versa (EMI related issues)
My layout has a PCB antenna that is tuned for a specific ground area. When I connect my device to the bus or when a new device is connected to the bus, it'd increase the ground area, so that it'd effect the tuning of my antenna, is it right? If it'd be the case gow can I avoid it to happen?


texts: Circuit feedback with mutual inductance on a toroid

texts:
I have been reviewing a circuit for the past few days and I am hoping to get some feedback to verify my thoughts as to how the circuit is working. This is a driving circuit for an ultrasonic cleaner and I am trying to figure out how to improve manufacturing consistency.

Here is the circuit:

There is a digital control circuit that simply turns the driving circuit on and off. I included a note for where it connects but I did not include the digital circuitry. I've also circled what I consider the most important component in the system (and also the one which I suspect is causing the most problems). This system is powered by a 120VAC 60Hz US outlet.

Here is what I have figured out so far:

1. When the user powers on the ultrasonic cleaning, the relay applies power to the driving circuit. The RLC oscillator must start up fairly quickly.

2. The RLC circuit made up of L5-A, C15 and R16 begins oscillating. This oscillating circuit then drives the transformer L7. From what I can tell, Q5 and Q6 are BU406 transistors with heatsinks.

3. L5-C is a feedback loop on the inductor and is used to auto-tune the oscillator circuit to the ideal driving point of the piezo transducer (42kHz ideal operating point). This is a hand wrapped inductor and I've included a picture below. As you can see, the white and yellow wrappings (L5-A and L5-B) are pretty good but the L5-C wrapping in red insulated wire is pretty loose.

I am trying to figure out why some of the units we get back from the manufacturer work well and why others have very weak cleaning power. I think the problem lies in the tuning feedback.

In order to drive the piezo element the circuit needs to drive the transducer at the frequency with the highest current draw. From what I understand L5-C is supposed to change the impedance of the L5-B and L5-A inductors to force the RLC circuits to oscillate at the right frequency. My concern is that manufacturing variations in the inductor wrapping put the tuning circuit out of the frequency range for which the auto tuning will work.

Does anyone here have any thoughts or advice on my analysis? Is there anything I am missing? Also, if anyone has any ideas for improving or tuning the circuit I'd be interested in hearing them. Let me know if I am missing any information and I'll update my question to include the missing information.

Thanks!


texts: No clean solder VS no clean, water soluble

texts: Is there a difference between "no clean" and "no clean, water soluble" solder? I am being told there is no difference but I find the "no clean, water soluble" harder to use.


texts: How will a motor respond as a generator?

texts:
Consider a permanent magnet motor which consumes maximum 12V @ 1.2A and turns at 1000 RPM.
If I run this motor from a different motor at 1000 RPM then will it produce 12V @ 1.2A?
What will happen if I run it at 2000RPM?
Also wanted to understand how the same motor acts when used as a generator.


texts:
I am trying to feed this voltage measured by the oscilloscope to a voltage comparator.
By design the voltage should swing between +0.7 and -0.7. BUT since the voltage is not referenced to ground I am really having a hard time wrapping my head around what should be connected the comparator, and HOW should I connect them.

Since the voltage am trying to feed to the comparator is not referenced to ground, I can't just get away with connecting the op-amp negative rail to ground right?

Just bear with me one more moment, what I am trying to say is if for instance I feed a signal that has a magnitude of 0.7 does that mean it's 0.7 higher in voltage than the op amp ground, or is it independent of the op-amp ground?
I mean if for instance I connected the comparator negative rail to 0.7V and then feed a 0.7 to any of the inputs would I be effectively feeding the op-amp 0 volts since they are both at the same level.
So I guess what am trying to ask is, what are the relation between the + and - rails of the op-amp to it's inputs. what should I connect the - and + rails of the comparator.
I am really confused about what a ground represent in this case.


texts: How to build a human chain detection circuit?

texts:
I've seen devices that detect a human chain.  For example, they detect when 1 or more people (possibly several) hold hands to close a circuit between two distant metal objects.  I've tried to find instructions on how to build a circuit like this, but without success.  The one's I've found so far are $300, which is too expensive for my application because I may need a few of them.

Can anyone point me to a circuit diagram on how to build one of these?  It could either be a "stand alone" circuit with a simple 0v/5v output or it could be implemented using the GPIO's or ADC's of something like an ESP32.

UPDATE: I found this example using a Darlington resistor.  I'm a bit suspicious of it, but given that I'll have a micro controller that can vary the input threshold that could allow me to "tune" it.  Any option on the pros/cons of using a Darlington like this instead of an Op Amp like MattMan suggested


texts:
we have a few LED string lights that use 3 AA batteries and eat through batteries about once a week. I would like to replace the AA batteries with a USB battery pack I have which has about 8,000 MAH. Since AA batteries are 1.5v and standard USB is 5v, is this as simple as cutting an old USB cord and finding the correct positive / negative cables to wire to the empty AA battery enclosure? I am not sure if the +/- .5v would make a difference? Is there an easy way to find out which wire from the old USB cord is + and -? Am I nuts or will this work?

Thank you!


texts: Output Impedance of a DIP8 Crystal Oscillator

texts:
I would like to make a module for OOK transmission using a generic DIP8 Crystal Oscillator, and this is what I currently have.

How is the output impedance of a Crystal Oscillator determined?


texts: Constant voltage, variable current source

texts:
I am a chemical engineering student doing my master's in control theory on a magnetorheological dampers.

The dampers I plan to purchase need 12VDC input and can handle current between 0A and 1A.

I am completely lost at what is possible to do and how to do it.  Is it possible to purchase such a device or is it simpler to build it?  I also need the current to be changed by some output from my Raspberry pi or arduino.

Are there any resources that I could read to have at least some sort of knowledge before I ask the electrical engineering staff at the faculty?


texts: How use ferrite bead to reducing noise from charge pump?

texts:
Old senior design project and in schematic I see he uses ferrite bead and capacitor after charge pump voltage output befor connecting to opamp input

Circuit very simple:

charge pump uses MAX232 to get +- 12V output from 0-5V input
+- 12V output rails from MAX232 having ferrite bead and capacitor in line
output of above connected to Vdd/Vss of dual rail opamp

Any way of knowing how much ripple reduced from output of charge pump because of using ferrite bead and capacitor in line?

Any measurement to select value of ferrite bead and capacitor?

I also interested as I see ferrite bead and capacitor in line on Arduino board also but they give no value in schematic!


texts:
This might be a simple, silly question, but I am wondering why I can't just connect a DC motor to an arduino board to have it running. One pin to the ground and the other to one of the PWM outputs.

I just did the sweep tutorial for a servo motor http://arduino.cc/en/Tutorial/Sweep and it works fine. I know that a servo has more electronics in there with pot providing feedback.

From what I understand to drive even a small DC motor I would need more circuitry (an H bridge?) or another shield dedicated to driving motors. I can understand this if I was driving some relatively big DC motors.

But I am trying to understand why a small DC motor with a ground and PWM input would not work. Especially for a brushed a motor like this one http://music.columbia.edu/~douglas/classes/motor_mania/DC_simple2.jpg

Surely its just a matter of DC current passing through the wire. Is it the inductive charge building up in the coils that can cause reverse current back to the board thats the problem.

Basically, from a conceptual point, given I have a ground and a voltage (albiet a pulsed one), what do I need to do it to make it drive a DC motor.


texts: Connecting common of relay with main cable of 240VAC

texts:
I trying to control my turntable switch with Arduino. This is a toggle switch with 3 wires one wire is for CW rotation the other one is for CCW and the other cable is main with 240VAC. I am using this relay shield; from this shield I am using two relays with this this connection idea:

simulate this circuit – Schematic created using CircuitLab

So basically one relay is controlling on/off and the other relay will control rotation in CW and CCW. For now I have tried this connection with two 12V LEDs and it's working fine. But now that I need to use my turntable, I think I should connect common of first relay with the main of 240V AC and I am not sure if I can do this or not (how safe it is).

What am I trying to achieve is better described here: Triple pole triple throw relay


texts:
I have come across a question that is very near and dear to my heart and I am in the hopes that somebody can answer this new years eve question of mine per se.

So I am wondering, if I were to run two 2.7V 360F super capacitors in parallel and attach them to a 5V step-up regulator, could I supply 500mA @5V (or very close to 5V) for about 2 hours?

I did some math from equations that I found online and I was wondering if the above question is plausible based off of the values stated above.


texts:
The project I'm starting with requires multiple development-boards connected with CAN buses.

Is it possible to put two CAN ports on an STM32F407G board?


texts: Crystal reference and capacitors for w5500

texts:
I'm selecting the caps for the crystal oscillator of the wiznet W5500. The standard Load Capacitance for 25Mhz crystals is 18pF. I found out that the hardware guideline claims for a Load Capacitance crystal (CL) of 18pF, and taking into accout the formula to select CL0 and CL1, and assuming Stray Capacitance (CS) of 4pF...

CL1 = CL0 = 2 (CL - CS) = 2 (18 - 4) = 28 pF

If you take a low CS of 3pf, it gives 30 pF, and if takes a high value of CS like 5pf, it takes 26pF.

Why, then, in all reference schematics I found (including wiznet schematic reference), CL0 and CL1 are 18pF ???


texts: A question about using a dual secondary transformer as a center tapped transformer

texts:
Above is transformer in question. And in case here is the datasheet: http://www.farnell.com/datasheets/2026060.pdf?_ga=1.56694762.1111228725.1474151580

As you see this is a single primary 6V dual secondary transformer. There is no center tap. And I measured with an ohmmeter that it seems like the two secondary outputs are not connected to each-other.

I'm trying to use this transformer as a center tapped one at the secondary side. The aim is to create a +6V 0 -6V split supply. If I connect B and C together would that be the center point(0) of a +6V 0 -6V transformer where A and D are the new terminals? A -6V D +6V relative to the new middle zero point(BC). I wanted to be sure before I try it and cause a possible hazard.


texts: what is an average CPH speed for hand SMD assembly?

texts:
What would be the average speed (an experienced) person would assemble surface mount components on to a PCB?  Assuming they have desk that is correctly set up (pick and place station) and the PCB has solder paste already applied.

Reason for the question:

Pick and place machines talk about components per hour (CPM) speed, interested to know how to compare this against a person. Looking into doing small runs (100 units) of a product, need to determine if I hire staff or purchase a small scale pick and place machine instead.

I know Sparkfun say they do this sort of work by hand, but I have a part count of 90!


texts: PSpice PWM duty clycle generation from PID controller

texts:
I am trying to implement an ideal PWM controller in for an analog circuit I have in ORcad PSpice. Ideally I would use the SLPS tool for simulink, but unfortunatelly we do not have the licence for it so I have to look for a workarround.

The circuit is a Half-Bridge amplifier which gets four PWM signals to control the two transistors (two signas turn on the mosfets, and the two other turn them off and keep them that way). So what I would like is for the PID to give a control signal from 0 to 1 V or something like that and for that voltage level to control the duty cycles of the four square wave generators I have or to somehow make the PWMs I need. Something like if the PID signal is 0.4V the duty cycle is 40% (0.4). I tried something like in the image, but I get the following error:

.PARAM  vin=2.5 t_tot=1.5us freq=32k t={1/freq} d={v(v_duty)}
--------------------------------------------------$
ERROR(ORPSIM-16131): Expression - use previously defined parameters only

Can anyone help me with this?
It is for my master thesis.

Cheers,
Camilo

edit: it was suggested to use a comparator. Unfortunatelly that does not solve the issue in my case as that way I would have only one PWM, I need to generate something like this:

the comparator idea (as I understand it) would only work for both "off" signals. The full period of all signals is 32 kHz, the duty clycle of both off signals is the same and could be generated by the comparator. The on signals have one 1.5 us pulse (the top is always 0V with a 5V pulse, the bottom is the contrary) and the pulse kicks in after the deadtime (1.5 us) has passed (deadtime starts on a flank of the off signal)


texts: How would I use a transistor to switch my DSL modem?

texts: I am newbie to electronics and just know a few basics. I want to switch on my DSL modem so it can start with my computer on. I think a transistor connected to USB +5V voltage would be simple and best. I will get base voltage from USB and collector voltage from modem DC adapter (about12 V and at 500mA). I am wondering which transistor is the best and how set base voltage. Thanks!


texts: How does NAND FLASH cells retain data without requirement for external power?

texts: RAM cells need constant refreshing, however NAND FLASH cells can retain data for years together. What makes this possible ?


texts: How to design drone power tether system? (high power with ultra light cable)

texts:
There are drones that are powered with power tether from the ground station, and such drones can be airborne 24/7, not only 20 minutes when using batteries.

I'm very interested to reverse-engineer how such power tethers could be constructed. Such system needs to usually be able to transfer around 500 W and 30 meters (100 feet) in length.

Main restriction for designing such system is weight of tether cable which should be as light as possible, ideally less then 1 kg (2.2 pounds).

Which approach is better - high-voltage DC voltage or high-voltage AC?

Also by using high voltage we have two drawbacks - operator safety and cable insulation weight increase.

When using AC we can also choose to go with very high frequencies, is there any benefit in using high frequency and get better power transfer?

So what would be ideal combination of voltage to transfer high power on light and thin cable?

is there any special type of cable that would allow for high power transfer but keep weight low?

Example of such system: https://www.youtube.com/watch?v=VHwEb86s2SI


texts: How to avoid short circuit when connecting a microcontroller and device using I2C bus?

texts:
I am attempting to connect an 8051-compatible microcontroller to an accelerometer using the I2C bus.  Both devices operate at the same voltage, 3.3v.
However, I am failing to understand something: won't a direct short be created when the microcontroller asserts a logic HIGH on either SCL or SDA and the slave device attempts to hold the line at logic LOW?  I don't understand how to avoid this...

How can I make the MCU float the lines instead of placing a logic HIGH on them?  I realize I can change the state of the lines to "input" instead of output, but is that safe to avoid a short circuit?

As I see it, the following scenario could happen:

If the MCU switched from 'input' mode to 'output' mode, couldn't the pin be in the HIGH state, even if you set the pin to LOW, then set input mode to 'output'?  Won't the input voltage change the state back to HIGH due to the pin being in 'input' mode, before it has a chance to switch to output mode?  Then for a few uS you would be outputting a logic high, before the MCU executed the next instruction to turn the pin to LOW.


texts: What's the difference between the LM2917 and the LM2917-N?

texts:
The schematic I'm looking at says to use an LM2917. The  specs from the TI site use  both LM2917 and LM2917-N and the shop on ebay uses both names too.

http://www.ebay.com/itm/like/270864373784?lpid=82&chn=ps&ul_noapp=true

http://www.ti.com/lit/ds/symlink/lm2907-n.pdf

Is this some kind of naming convention I should know about for the future?


texts: Dallas 1-wire Digital Thermo - issue with strong pullup

texts:
I have 2 Dallas/Maxim DS18b20 digital thermometers connected in parasitic-power mode. If I include a strong-pullup as shown on p.6 of the datasheet, the nearer device gives good data; the further one reads back 85C (== the reset value). If I disconnect the strong pullup, I get valid temperature readings on both devices.

I omitted the MOSFET switch on the pullup and connected the strong-pullup i/o pin directly to the one-wire bus, floating it by making the pin an input with no pullup.

Why does the strong pullup not work as expected?
Why do the devices work OK without one?

simulate this circuit – Schematic created using CircuitLab

Sensor read function:

 int8_t DSSensorsSample(TempSens_t t[SENSORS_REQD], uint8_t nsens){
   for( TempSens_t *p = t;  nsens-- > 0;  ++p ){

      p->type = p->addr[0];

      ds.reset();
      ds.select(p->addr);
      ds.write(0x44, 1);        // start conversion, with parasite power on at the end
      pinMode(DSSTRONGPULLUPPIN, OUTPUT);
      digitalWrite(DSSTRONGPULLUPPIN, HIGH);

      delay(1000);     // maybe 750ms is enough, maybe not
      // we might do a ds.depower() here, but the reset will take care of it.

      pinMode(DSSTRONGPULLUPPIN, INPUT);
      digitalWrite(DSSTRONGPULLUPPIN, LOW);

      p->is_present = ds.reset();
      ds.select(p->addr);
      ds.write(0xBE);         // Read Scratchpad

      for ( uint8_t j = 0; j < 9; j++) {           // we need 9 bytes
         p->data[j] = ds.read();
      }
   }
   return( 0 );
}


texts: Can I fabricate a PCB using this schematic?

texts:
I am a newbie to schematic and electric circuit design. This is one of my first schematics and I am thinking of making a PCB out of this one.
I want to ensure my PCB will work after fabrication. It uses an ATmega328P as microcontroller and also has an MLX sensor, an LCD and an ultrasonic sensor.
I have attached the schematic with this post.
Please give me suggestions if you have any. I want to know whether my PCB will work or not if I fabricate it using this schematic.


texts:
What is this exactly? It measures 0.14" (3.55mm) wide x 0.22" (5.56mm) tall x 0.09" (2.26mm) thick, likely a DO-214AA or SMB package. Circa 2016. Removed and photographed.

Out-of-circuit it measured as an 18v bidirectional TVS using a 100k resistor. See where the Vishay SM6T18A is marked "LM7" and SMBJ15A is marked "LM" but these are both uni-directional. Application is bidirectional (IGBT gate clamp.) Thanks for looking.


texts:
I would like to calculate the power usage of an idle motor. The motor drives state a power usage of approx 8-10% of full load.

Would it simply be the case of taking 8-10% of the motor's power rating (in kW) and multiplying by the number of hours to obtain the kWh usage?

Also, I've been told that the 8-10% power usage at idle allows the motor to start up much faster? I've tried researching but haven't found anything stating this..


texts:
I have the following doubts about a p-n junction diode:

1) If we short the diode ( connect it's terminals together without any power source) then how is the Kirchoff's law across the loop satisfied?

2) If the diode is forward bias, people say that the built in voltage Vin decreases by V. That is the new built in voltage is Vin-V. But what I don't get is shouldnt the voltage across the diode be V? How does a Kirchoff's voltage equation across the circuit look like?

3) Similarly, in reverse bias why does the applied voltage V add to the built in voltage?  Shouldn't the voltage across the diode be V in the opposite direction?
How does a Kirchoff's equation for this circuit look like?

Any help would be appreciated. Thanks :)


texts: STM32CubeMX not showing the resolution in ADC

texts:
I am trying to use ADC in stm32f103 micro-controller. I use STM32CubeMX to configure the ADC. Based on the videos I gave seen on YouTube, I must be able to configure the resolution of the ADC (8, 12 or 16 bits) in STM32CubeMX but I can't Here is what STM32CubeMX let me to configure:

I use STM32CubeMX 5.10, However when I tried with 4.27 still didn't help.


texts:
I'm trying to understand how USART of ATmega works. I read some pages and I've picked information about it. To test functionality I've written this code:

#define F_CPU 16000000
#define BAUD_RATE_115200_BPS  8

#include <stdint.h>
#include <avr/io.h>
#include <util/delay.h>
#include <stdio.h>

void Transmit(void);

unsigned char data[] = "Data transmitted...";

int main()
{
    unsigned int ubrr = BAUD_RATE_115200_BPS;

    UBRR0H = (uint8_t)(ubrr >> 8);
    UBRR0L = (uint8_t)(ubrr);
    UCSR0B = (1 << RXEN0) | (1 << TXEN0);
    UCSR0C = (1 << USBS0) | (3 << UCSZ00);

    DDRB = 0b11111111;

    Transmit();

    while(1)
    {
        while (!(UCSR0A & (1 << RXC0)));

        //data[0] = UDR0;
        //data[1] = 0;

        sprintf(data, "%d", UDR0);

        Transmit();

        switch(UDR0)
        {
            case 'A':
                Transmit();
                PORTB = 0b11111111;
                _delay_ms(2000);
                PORTB = 0b00000000;
                break;

            case 'B':
                PORTB = 0b11111111;
                _delay_ms(500);
                PORTB = 0b00000000;
                break;

            default  :
                break;

        }
    }
}

void Transmit(void)
{
    int i = 0;

    while(data[i] != 0)
    {
        while (!(UCSR0A & (1 << UDRE0)));
        UDR0 = data[i];
        i++;
    }

    _delay_ms(100);
}

I can send data without problem, but I can't receive correct data. If I send "A", I receive ASCII code 161 or 225 and with "B", 162 or 226. I don't understand where the problem is.

For tests I'm using Arduino Uno (ATmega328P 16MHz).


texts: Controlling the brightness of LED panel via GPIO pins

texts:
I'm trying to control an LED panel like the one in this link.
I notice it comes with an LED driver. But what I'm wanting to do is to be able to control the brightness of this light through the GPIO pins on a Raspberry Pi.

I've seen that I could do this through a PWM light dimmer. But I'm not too sure how this sort of dimmer would connect to a LED driver seen with the LED panel.

Could someone point me in the right direction? Maybe I need a different PWM light dimmer?

Thanks very much!


texts:
I am thinking about buying a benchtop (small, low cost, only to be used during initial design of the products) reliability test chamber. What are the key features I should check for ?

I am thinking of temperature and humidity control.

Where I would buy a good low cost one? (Perhaps a list of reputable vendors?)


texts: Does a switching supply always need load

texts: I'm looking to use a switching supply from an old computer for a project. The project runs a motor that turns on and off based on a timer, powered by the switching supply. Do I run any risk running the switching supply while not under load (ie: when the motor isn't running?)


texts: Why does the inverting amplifier not work with my separate circuit as an input?

texts:
Hi, I've set up these two circuits and they both work separately. But no matter what I do I cant seem to connect them (from where the blue probe is to where the wave input would be). I feel like im missing something simple.
Does anyone know how to help. I've also tried using a simple potential divider for an input, but with no luck...    btw. Im kinda new to electronics so im probably being just dumb :/


texts: Low ESR decoupling capacitors - how to design against ''ringing''

texts:
I would like to use solid polymer electrolytics for decoupling in my designs instead of standard electrolytics for their longer lifespan and substantially lower ESR for marginally increased cost

When choosing decoupling capacitors its frequently mentioned that the lower ESR has a greater tendency to cause ringing so its advised to use medium/high ESR capacitors.

How would a circuit/PCB be designed to avoid power supply ringing with Low ESR capacitors without artificially adding ESR with series resistor as this defeats the purpose of using low ESR parts?

Very low ESR ceramic decoupling caps close to the load is standard practice, how is ringing not an issue there?


texts:
Intro

My apartment has a simple door intercom system which uses a hybrid two-wires line to carry both the receiving and transmitting audio signals for each floor unit. The wires are connected to each other in parallel. Wires other than Audio are the Power (Vcc), Ground, and a Video line which isn't relevant to the question.

simulate this circuit – Schematic created using CircuitLab

Problem

My goal is to build a circuit which could feed a normal audio line (not a microphone) to the system, and extract another normal audio line out from it. The problem is that the idle voltage of the intercom audio wire seems to be an odd 14.6V which I can't interface. (I tested and it isn't the intercom power.)

I don't know how to get a normal audio signal out (which could be connected to a recorder or a sound card) and how to feed the line with audio from an mp3 player, or any regular AUX jack.

I need a simple, modern circuit to incorporate into my modern project, with these requirements in mind. Also, feedback/echo elimimation is preferable, but not a must.

From my understanding, a normal audio output has a typical maximum peak-to-peak voltage of 3 volts.

I googled quite a lot of keywords, but none seemed appropriate. Please provide an understandable explanation on how would I go with designing such circuit.


texts: What is the "screen of the cable" for medium/high voltage cables?

texts: I heard that for medium and high voltage cable, there is something called "screen of cable". What does this "screen" do in the cable? Why is it part of the cable construction?


texts: how to provide a steady voltage, in case of source voltage drop due to heavy consumers in the circuit

texts: I am designing an arduino circuit in which the power source is a battery connected to some heavy current consumers, these consumers are intended to work for short time and infrequently, my question is how to provide my arduino with a steady voltage, I am thinking of using capacitors to serve the arduino while these heavy consumers are working but I am not sure how


texts: How can I create two ac signals with a voltage controlled phase offset?

texts:
Is there a fairly straightforward analog circuit (resistors, capacitors, transistors, etc) to generate two sine waves of the same frequency and introduce a relative phase offset between them?  So I'm looking to generate:

Sin[wt] and Sin[wt+c]

where w is frequency, t is time, and c is a constant that can be changed by some other dc voltage.


texts:
Single WS2812b LED are connected over 35 meters (115 feets) UTP Cat. 5e cable and it's not working as expected. Getting wrong colors. Another WS2812b placed in parallel (not chained) on board close to MCU which drives them works as expected. 1st one was working fine also this way (i.e. in parallel) when it was connected via short wire.
Adding 74LVC1G125 buffers on both sides didn't helped.
Other pairs in cable are used to provide +12 Vcc for other devices & +5 Vcc to drive LED.
Wire resistance are only 1.9 Ohm, i.e. 3.8 Ohms two way. So I guess it might be the capacitance part which mess things up? Or could this be some sort of noise coming from +12V power nearby (it drives low power motor, but WS2812b doesn't works normally even when it's not working).
Any suggestions to try? I'm thinking about differential bus transceivers, like SN75176B for example. But probably there is simpler way keeping 1 wire only?
Update 16 July: Here is how oscillogram looks like on separate long 1 wired DATA. This is an output from MCU, at the MCU end:

This is how it looks like at the wire end on the LED side without resistor to ground (but with in-series 75 Ohm resistor):

And here how it ends up when resistor to a ground added close to LED (as suggested in comments):


texts: Below is the schematic of the sequencer I designed. Does splitting the clock signal into several inputs cause problems with system stability? I have marked with colour the place where the signal was split. Is this the right way? Or should I do it differently? Thank you.


texts: For a Quartus project what files must be added to a git repository?

texts:
A Quartus project generates huge number of files as we proceed with design compilation and debug automatically.

Provided that I wish to add my Quartus project to a Git repository and not just the hdl files, what are the files that I must add? The objective is that when we clone the repository, we can just open the project and click compile to compile the design. Nothing else needs to be "fixed" in this time.

Git is used for version control by the way.


texts:
The tripping threshold is between 0.5 and 0.7 times the rated voltage

I will like to confirm the above statement. If my rated voltage is 215V, assuming we picked 0.5 setting, does this means that the tripping threshold for a particular device (e.g circuit breaker) is 215V * 0.5 = 107.5V? In other words, the circuit breaker will trip when the voltage reached 107.5V?

  Circuit breaker closing is possible only if the voltage exceeds 0.75 times the rated voltage

Likewise for this, does this means that I can only close the circuit breaker if the voltage exceeds 161.25V (215V * 0.75)?


texts: Old ATX PSU: Could +5VSB have a minimum amps requirement?

texts:
I'm trying to use a small ATX power supply (version 1.0 connector) as a bench power supply. I've found that it only turns on intermittently. I've tried with ~1A load on +5V, and 0.2A on +3.3V .

I accidentally shorted +5VSB to ground, and it turned on. Now I find I can reliably turn the power supply on by momentarily attaching a load to +5VSB, maybe about 0.2A.

Is it possible that this PSU needs a load on +5VSB to start up (but not to keep it running)? An "ATX Design Guide" online lists only 0.0 amps as min current on +5VSB. Is it more likely that the PSU is damaged?


texts: Interrupt when a variable passes a threshold

texts:
I am programming the code for a LM4F120 Stellaris Launchpad, and I need a method to activate a software interrupt when the value of a particular variable exceeds a predefined threshold value. When the value gets lower than the threshold value, the interrupt should be disabled.

For example, the variable name is flag and the threshold value is 200. Whenever flag gets above 200, the interrupt should be activated. Whenever flag gets below 200 again, the interrupt should be disabled.

How can I implement such a thing?


texts: I am trying to connect W3113 antenna to my RFID UHF reader. The datasheet of the reader requires me to use 50 ohm microstrip line. However, I do not find where I can draw microstrip. Is it still the regular routing? If not, how do I draw the microstrip line in EAGLE? Thanks!


texts: Pin value of a GPIO pin set as high impedance

texts:
I am using an STM32F4 discovery board and my intention is to set one of its GPIO pins at high impedance, which I have done as below:

GPIO_InitStruct.Pin = GPIO_PIN_12;
GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
GPIO_InitStruct.Pull = GPIO_NOPULL;

From my understanding, in order to configure a pin at high impedance, it's mode is to be input. Am I right?

If I read the status of this pin, I get a value of 1. I am not sure if the pins at high impedance should return a 1 or 0. Could someone please help me understanding this.


texts: Why is printf() bad for debugging embedded systems?

texts:
I guess it's a bad thing to try to debug a microcontroller-based project using printf().

I can understand that you have no predefined place to output to, and that it could consume valuable pins.  At the same time I've seen people consume a UART TX pin for outputting to the IDE terminal with a custom DEBUG_PRINT() macro.


texts: Finding the equivalent Thevenin generator

texts:
I have 2 circuits of which I'm supposed to find the Thevenin's generator equivalent.

I solved the first one (hopefully correctly), but am unsure how to solve the second one.

The result of the first one is: TE = 3.75 V (TE being the Thevenin equivalent of the original E).

If we add R4 (parallel with R3), I get lost.

For the first circuit, I used the formula TE = (E * R3) / (R1 + R3)

How would I go about solving the second circuit?


texts: How do I gradually vary the pulse width in the "VPULSE" model? I tried using parametric sweep but it does not produce the correct waveform or I don't know how to do a parametric sweep in transient mode. Here is a screenshot of the schematic. I want the "PW" to vary from 1u to 15u gradually so that I can see the capacitor voltage waveform with respect to time.


texts:
New to electrical engineering and designed the following circuit board to improve my skill, particularly with an Arduino Micro:

The idea is relatively simple: the Arduino Micro drives eight buttons attached through a 5 Pin Molex Picoblade connector at D2 to D9, with 10K (pull up?) resistors to the connections, grounded and energized at 5V. However, I can't seem to get the high signal when simply bridging in the molex the GND line to the pins (thus "pressing" the button, as far as the microcontroller is concerned).

What mistakes did I make? What can I do better next time?


texts:
I need a high side switch. I thought about using a p-channel MOSFET. The source will be connected to around 50V-60V. How can I drive this MOSFET? I can't find a driver which can switch between 60V and 45V in order to put the MOSFET on and off. They all switch between ground and Vcc, which is generally below 25V. How is switching a high-side p-MOSFET at 60V done? My control signal is at 3.3V.

EDIT:
I want to avoid a second power supply. The microcontroller used for the signal generates a signal for a low side n-MOSFET as well.

EDIT 2: The goal is to drive a chopper for a motor, so the switching frequency I was thinking about is around a few kHz.


texts: Is it possible to create a (depletion mode) MOSFET using only single type of semiconductor?

texts: If I understood JFET diagram correctly, the p-n junction is only used to isolate gate. Using same principle, would it be possible to construct a MOSFET with no junction at all, i. e. a single semiconductor type transistor?


texts:
When do I start having to worry about regulatory issues if I sell a product that boosts DC to DC voltages in the 80-100 volt DC range (.5 to 3 amp range)

How safe is 48V DC? is the closest i came on a search.   Any help with good search terms?   It seems 50 volts is the magic number..

What Regulatory Requirements are Really Necessary for Sale in the USA?


texts:
I'm designing a low-noise, high-bandwidth (100 MHz) pre-amp using JFETs. The choice for JFETs was because it needs to operate with large source impedances (>10 kΩ).

I spent a while looking for a suitable JFET (high g, low input C, good noise-figure). I came across ones from CEL (for example, the CE3520K3 (datasheet, home page) with g = 50 mS , NF = 0.5). They don't specify input capacitance, but it must be sub-pF given the operational frequencies. What's the catch? The datasheet does specify large gate currents, so current shot noise will be high. Does anyone have experience working with such devices?


texts:
I'm taking apart some old electronics, and I see an inductor with the following on the label:

TV
1415
-B

Here's a photo:

I searched online but what I found was that there should be three digits: two for the μH and one for a multiplier.  Eg: 432 would mean 43 μH, with a 10^2 multiplier, so 4300 μH.  But I found nothing about 4 digits, or those other characters.  What do they mean?


texts: Why altering open loop gain is necessary in amplifier's frequency compensation..?

texts:
The text says that "the amplifier requires compensation because its basic open loop gain is still higher at frequency where internal phase shift are reaching  180 degrees..This turn negative feedback to positive at higher frequencies which causes oscillation."

My question is that why they tell to roll off the open loop gain…rather than it should be closed loop gain because oscillation develops when negative feedback is turning to positive at higher frequencies, so feedback anyhow is necessary to cause oscillation..and when we talk about feedback we mean about close loop gain…then from where open loop gains comes into picture…??


texts: Why is sine wave preferred over other waveforms?

texts:
Why did scientists chose to go with sine wave to represent alternating current and not other waveforms like triangle and square?

What advantage does sine offers above other waveforms in representing current and voltage?


texts:
I bought and soldered a dirt-cheap flashlight kit from China. I'd like to understand how it works, though - specifically, why it uses a combination of a PNP and an NPN transistor (schematic from the product page is below).

If the circuit does end up in a steady (read: frozen) state, then the inductor acts as just a wire - so the LED ends up just being directly connected to the 5V (which wouldn't bode well for its longevity). EDIT Was wrong here - this was battery-driven, so 1.5V, not 5V!.

Therefore this circuit clearly is not meant to arrive at such a steady state - it is designed (presumably) to oscillate. Unsure why one would want that - but even if that is the case, couldn't that be achieved by just a single transistor - whose base would be driven by the cap, placed between base and ground? i.e. voltage rising on a charging cap reaches 0.6V, transistor opens, flashes the LED, cap charges again...

I am clearly missing something here - why the two transistors?

P.S. Amateur at electronics, go easy on me :-)
P.P.S. I could add a link to the product, but I don't want this post to be misclassified as spam.

UPDATE: Simulated it in LTSpice:

... and see now that it boosts the voltage! Which makes perfect sense, now that I realize the LED needs more than 1.5V (the AAA battery I added in).

How does it do that, though? More Googling under way, now that I know the purpose...

2nd UPDATE

My theory so far: the 20K pulls down the base of the PNP to ground, so initially the PNP is on (V_BE negative, more negative than 0.6V) - which means that NPN is also on (V_BE also much higher than 0.6V). Both transistors are therefore strongly ON - and current therefore flows through the inductor via Q2 to ground. But no current goes on the LED - since that has a higher voltage threshold - it needs more than the battery's 1.5V.

This is where I start to lose the thread.... I believe that current also flows through the inductor to charge the cap via R1... I am guessing that at some point the Q1 goes off (and therefore, so does the Q2). But I am unsure how the cap does this "cutoff" - as it is charging, the V_BE voltage keeps increasing, so I am unsure how the Q1 ever gets to cut off...

Looking at other stuff in LTSpice I am more dumbfounded - e.g. it shows that the current of the inductor is always negative:

Scratching head... Any help/advice from electronic gurus most welcome.


texts:
I'm going to use one of those LED-buttons to switch a certain (5V) appliance. It's possible to use a couple of connection types:

Le left side scheme is OK, but I don't like it.
I would go with the right side one, but the problem is in that situation the voltage drops... 5V drops to ~3V and 12V to ~10V...
I think should be due to an "embedded" resistor protecting the LED.

In your opinion, is there something I can do to circumvent this problem?
(I need all the 5V).

Thanks.


texts:
So I have this design here where I talk via JTAG from a microprocessor to a CPLD.

The JTAG protocol is done via bit-banging of four GPIO pins.

This connection is just very infrequently. It's just for the initial programming of the CPLD and may be used if a bitstream update is needed.

Now the question: What should I do with the JTAG interface during these idle times? Right now I have the interface pins at high-z state, but I could also drive them low or high.

What's the best practice?


texts:
I want to make an "IR beam break sensor" as per attached schematic.
I would also like to add some sort of “time delay” to the schematic. When the beam breaks and the relay gets activated, I would like the relay to stay activated for a couple of seconds after the object has passed through the beam.
Anyone got any ideas has to how I can achieve that?
Cheers
Spike


texts:
I'll be fixing a motorcycle soon, trying to know if it's possible to have two or more positive wires (connected directly to the battery terminal) but only one negative.

There is a usb converter AND an auxiliary light, hence the need for two positive wires.

Let's say the wires are rated for the current draw that will be used, so there is no further margin for a direct and more simple one positive one negative for both. Will the negative wire have overcurrent problems?


texts: Current limiters using transistors and diodes

texts:
I have been experimenting with simulating current limiting circuits. I am trying to limit current to ~500mA given a fixed 4.8V source. I started a question based on a conventional 2-transistor current limiting circuit over here based on the following schematic . . .

Rather than make that question more convoluted, I thought I would ask a separate question to determine what the difference is between the above circuit, and another variety that I found commonly using google image search that involve use of diodes. The 1-transistor variant of these looks like the following . . .

1 Transistor

Then there is a circuit with another transistor added

2 Transistor

... and finally there is a circuit that looks like a similar configuration using 3 transistors . .

3 Transistor

What are the differences between these diode based circuits and what are their advantages/disadvantages compared to the current limiter shown at the top of the page?


texts:
I found this circuit in an older post. I was thinking about using this in place of a contactor to break under load. The load would be at 500V 300A DC. There would be overcurrent protection in line with this. I do realize that this would be less efficient than a contactor and maybe more expensive. What am I missing? There seems to be little information out there about using an IGBT as a relay or contactor and I assume it's for a reason. What forums I have found people have said it would be too dificult but the explination stops there.

I'm currently using this IGBT (FZ600R12KE3) in a small setup switching 350V 30A about 20-30 time a day and have not seen any issues yet.


texts: Why is there alternating current in my wall socket?

texts: Why is the standard of delivering electricity to our homes is via alternating current, and not direct? As far as I know almost every electronic device has an AC»DC converter because their internals use direct current.


texts:
I would like to plot a sliding average of some voltages and currents. Ideally I would just add a new trace with some expression, but all expressions that I found so far only operate on single values.

Are there any expressions (like absdelay for B sources) that would do the trick?


texts:
I am developing a wireless device which stores data by sampling an Analogue sensor at a specific time. The only 'wires' to this device are the two power wires. I am using a 12V AC power supply and I am wondering if I can send a 'clock' signal using the power line. The clock rate I am looking to achieve is from 10Hz to 400Hz. Can anyone point me in the right direction of how to do this.
Many Thanks
Stuart.


texts: Is it safe to make arduino read negative voltages from the analog inputs?

texts:
Hope all is well.

I need the arduino UNO to read negative voltages, and I am worried that it might destroy the arduino.

What I am trying to do with the Arduino is to be able to read voltages from two of its analog inputs, then graph them in Labview.

The arduino will read voltages that makes the above graph.

If UNO can't do negative voltages, are there any other arduino model that is capable of reading negative voltages?

If it can't read negative voltage, do you guys have any suggestion how to make this happen? Because OPAMP inverter won't solve this issue.

Thanks a lot.