texts:
Hi I built this mic preamp circuit for use with an electret mic.

The mic I have is this PUI AOM4544 electret mic

I have plugged this mic preamp circuit to my soundcard line in. But I think the gain is so low that I cannot hear anything. I built this to use as a measurement mic. I tried measuring the output from the mic alone without the mic preamp ( supplied 3v power to mic) using a voltmeter; I measured 0.001V ac when I blow at the mic. Is this mic preamp circuit a wrong one to use ?


texts:
I have a very old printed circuit board here that is used to control 2 pneumatic cylinders. There are 8 solenoid valves that control if the air goes in or out to a side of the cylinder.

Now the printed circuit is old and needs to be replaced, so I am trying to rebuild it with an Arduino.

The only strange thing I noticed was that there are only 4 NPN transistors (TIP122's), which I assume work as a toggle switch, the air can go in or out of each side of the cylinder.

But how is this done? I can't really create a schematic because the printed circuit is completed glued up.


texts: Connecting the MFRC522 RFID Reader/Writer to PC

texts:
Referring to the MFRC522 RFID Reader/Writer  rfid reader writer module.
How do I configure its UART so it can talk to an rs232 port of a PC?

The answer is probably similar to this question

https://arduino.stackexchange.com/questions/30719/how-to-program-an-nrfl01-rf-module-that-is-connected-to-a-pc-via-a-usb-to-uart-t

which point out that it not easy to write PC software (not suprisingly) for a arduino module with same interface. So the question is then -is there an existing PC software for this?


texts: I have a lipo battery of 11.1V,3s,5200mAH. What is the meaning of the 25C discharge current? How much current does it indicate? How do you interpret it?


texts:
I have tested a simple RLC series circuit for plotting current vs time using two versions of LTspice and I am getting different results!The input is 1 volt dc.R = 2 ohms. C = 1 F and L = 1 H. Initial conditions for C and L are zero.Thus this is a critically damped circuit and the analytic solution is i = t e ^ (-t).Thus the peak value of the current occurs at t =1 second and is near 360 mA. The following graph  will show you that I get correct response in the LTspice version 4.23e and get half the value of correct current in the version 4.23I. Is there a bug in the later versions?
Ashok Ranade

Circuit:


texts: How do I create the layout for this rotary encoder on a pcb?

texts:
I am very new to designing boards and I am trying to do a board layout that contains a MODEL EN11-HNM encoder but I am not sure how to handle the tabs that provide the mechanical strength while it is on the board.

I have laid out the three pins as it shows in the diagram titled "pcb layout" (in the linked datasheet) but there are also two, unlabeled squares in that diagram that appear to be where the tabs are.

My inclination is that there should be holes there, but the diagram doesn't suggest it (at least to me). Any help is much appreciated. Thanks!


texts: Maximum sampling frequency of Arduino (internal vs external ADC)

texts:
I am studying the Arduino ADC.
I learned that the maximum sampling frequency of the Arduino ADC ( e.g. Due) is 1M sample per second.
As the Arduino ADC has only a 12-bit resolution I must use an external ADC with a 16-bit for higher resolution.
What is the maximum rate at which this Arduino can receive the sample signal from the external ADC? How can I find that?
In the case of Arduino's own ADC, it was 1M sample/Sec. But I don't know what can be the sample rate receiving limit for Arduino if it uses an external ADC. My knowledge is basic level so I am not able to understand the datasheet.


texts:
what kind of circuit structure can I use to obtain high output impedance?
In my design I need an amplifier whose output impedance is extremely high,which structure can do this? I read in Sansen's Analog Design Essentials that a cascode circuit will do, but I don't know how to bias it. So would you kindly show me the complete circuit?

in fact I am designing a circuit like this:there is a block whose impedance have been matched,but I need a block in series with it, so I need the new block to have high impedance.


texts:
I am creating a circuit with a 9v battery as its power source. For the sake of extended hours of usage, would it work to put another 9v battery in parallel, since placing it in series would make the supply 18v, which is too far away from 5v for the 7805 to deal with.

Bottom line, would it double capacity/lifespan, or would it go up in smoke?


texts: Altium: STEP File of Board with Multiple Layer Stacks Exports Incorrectly

texts:
I have been having this issue for some time and have not yet figured out whether it is a user error or an Altium bug.

I have a PCB design with two layer stackups:

In the Altium 3D view it looks good. You can easily see where the different layer stacks are applied:

However, when I export to a STEP file and open in SolidWorks, the entire board is a uniform width:

The STEP export seems to ignore the layer stacks and just exports the entire board (or flex) as one solid piece. Altium claims to support rigid-flex and flex designs, but this export failure seems to be a significant problem. Is this a known bug, or am I using the tools incorrectly?

UPDATE: It appears the 3D-PDF export does it correctly, but I really need a STEP file:


texts: Arduino Ethernet not visible in Router Status

texts:
I am trying to send over my code to my Arduino Ethernet board via the Adafruit FTDI friend. I am using the 1.0.4 version of the IDE and have the following settings:

Tools -> Board -> Arduino Ethernet
Tools -> Serial Port -> COM 3

The sketch is sent over to the board without problems or errors... however I am unable to see the IP of the board when i check my "attached devices" in my routers settings menu.

Here is a snip of the code I used:

  byte ip[] = { 192, 168, 9, 199 };   //Manual setup only
  byte gateway[] = { 192, 168, 9, 1 }; //Manual setup only
  byte subnet[] = { 255, 255, 255, 0 }; //Manual setup only

  // if need to change the MAC address (Very Rare)
  byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };

  EthernetServer server = EthernetServer(199); //port 199

void setup(){
  Serial.begin(9600);

  //Pins 10,11,12 & 13 are used by the ethernet shield

  pinMode(2, OUTPUT);
  pinMode(3, OUTPUT);
  pinMode(4, OUTPUT);
  pinMode(5, OUTPUT);
  pinMode(6, OUTPUT);
  pinMode(7, OUTPUT);
  pinMode(8, OUTPUT);
  pinMode(9, OUTPUT);

  //Ethernet.begin(mac);
  Ethernet.begin(mac, ip, gateway, subnet); //for manual setup

  server.begin();
  Serial.println(Ethernet.localIP());

}

Here is a screen shot of the router settings:

And this is my Arduino ethernet hookup:

What could I be missing?


texts: NPN Circuit simulation doesn't agree with book

texts:
I'm trying to understand an exercise reported in Microelectronic Circuit Design by R. C. Jaeger & T. N. Blalock (4th ed, p.237).
 $$\beta_F = 50, \beta_R = 1$$.

I don't agree with the discussion they make.

  Figure 5.19 displays the results of simulation of the collector
  current of the transistor in Fig. 5.18 versus the supply voltage V CC
  . For V CC > 0, the collector-base junction will be reverse-biased,
  and the transistor will be in the forward-active region. In this
  region, the circuit behaves essentially as a 1-mA ideal current source
  in which the output current is independent of V CC . Note that the
  circuit actually behaves as a current source for V CC down to
  approximately −0.5 V. By the definitions in Table 5.2, the transistor
  enters saturation for V CC < 0, but the transistor does not actually
  enter heavy saturation until the base-collector junction begins to
  conduct for V BC ≥ +0.5 V

Why does the fact Vcc > 0 automatically implies reverse bias on collector base junction? What if Ic is sufficiently large to produce a voltage drop (on the resistor) bigger than Vcc? In this case the collector base junction will be forward biased, so that the saturation region starts at Vcc clearly different from 0...

In fact, it is essentially what happens if I try to reproduce in SPICE simulation the circuit.. the dark blue line represents Ic which strangely doesn't agree with Fig 5.19!

Spice schematic:

I'm a beginner in electronics and SPICE, so I'd like to know where I am wrong.


texts: Latching relays connected in parallel not working as expected

texts:
I have a project I'm working on where I need 4 relays to open when power is applied to the board and close when power is lost. I need to use latching relays to conserve power as the device could be left powered for a long time. I have looked around for a solution and found the circuit here (starting on page 43) and discussed here.

I built and tested the circuit using one (1) EC2-3SNU single coil latching signal relay successfully. Even though my calculation per the document required around 187uF, it works perfectly with just 22uF. I also simulated this in Falstad simulator and it works, but with a bit different capacitor values.

The question I have is how can I modify this to work for 4 relays (or more for that matter) while keeping BOM count low? Thinking paralleling them is the best choice, I decided to do a test. Testing with 1 relay worked with 22uF. To get 2 relays working in parallel, I needed about 400uF. I then added the 3rd relay and added capacitors in parallel until I got about 1mF and it still didn’t work. At this point it’s too large a capacitor anyway to make sense moving forward. If I created the circuit (1 transistor, 2 diodes and cap) for every relay, it would significantly increase the BOM count.  Am I making a fatal mistake by assuming I can parallel the relays in this fashion? In my test circuit, I’m adding 100uF Tantalum capacitors in parallel to get higher level capacitances (for the test only). Is this an issue? Do I need a single capacitor for the test? I simulated 4 relays in Falstad simulator with a larger capacitor and it seems to work just like the circuit with 1 relay.

simulate this circuit – Schematic created using CircuitLab

Furthermore, using \$Cmin>\frac{4*L}{Rcoil^2}\$ formula from TE’s application note, the capacitor calculation for 1 relay is 148uF (Where R=90 ohms from datasheet for the relay and assuming .3H inductance). For 2 relays in parallel, I assumed the inductance and resistances can be calculated as if they are in parallel as well. Therefore, Rtotal = 45 ohms and Ltotal = .15H. With these numbers, the Cmin is 74uF. However, with my test and Falstad simulation result, I found I needed more capacitance not less. I feel like I’m really missing something when I’m paralleling the relays?

I also figured out later on that the standard BC547 is rated for 100ma. With each relay requiring 33ma to pick-up, I probably can’t test with more than 3 relays. Could the third relay be maxing out the transistor? I don’t have a scope to test current spike. (Will order a higher rated transistor in the meantime).

No freewheeling diode was added here as it would prevent this circuit from working as the required reverse current would simply bypass the coils through the diode. Does this mean the transistor will have a short life?

I have searched all over trying to solve this. I feel like I’m not accounting for something when paralleling the relays. I may be way off track or really close to the solution. The goal here is to reduce BOM count by paralleling the relays, using 1 or two large capacitors and one transistor switch for all 4 relays. Any help in shedding light on this as well as better alternatives would be greatly appreciated.

UPDATE: So I skipped the transistor switch part of the circuit and manually switched the circuit from +5 to GND per the TE app note. And each time, it worked perfectly for all 4 relays in parallel with just 100uF capacitor. This tells me, the fact that I have them in parallel may not be the issue. It may be the transistor not fully turning-on on power loss. Would a depletion mode P-Channel FET work better in this case?


texts: Arduino controlling separate traffic light

texts:
I have an arduino that can turn on 3 LED's separately. I also have this traffic light (12v with 3 plain-old lightbulbs) that, when plugged into an outlet, turns on all of the lights.

What could I use to "gate" the power to the traffic light using the arduino? I'd like for the two devices to remain on their separate power supplies.

Looking for some kind of connectors to solder between each of the three lightbulbs that I can gate using simple currents from the arduino. Any ideas? (I'm obviously a novice, so any help is appreciated!)


texts: Register file write- back for pipelining vs multicycle implementaion for MIPS processors

texts:
We know that in multi-cycle implementation of a MIPS processor, the R type instruction takes 4 cycles.

However, in the pipeline implementation of MIPS, for R type instructions, 4th stage (MEM) is present but nothing significant happens (during that stage). The  actual register file write-back occurs in the 5th cycle (WB).

Why doesn't the write back happen in 4th cycle itself (for pipeline) ?


texts: I was trying to remove stains on a fiber optic party tie using bleach, however it seems a small quantity has leaked inside the controller overnight, causing some corrosion and preventing it from powering up. What household products can I use to clean the damage?


texts: Need help tracking down the source of a delay between timer interrupts on SAM MCU

texts:
I have a project that outputs a series of values to DACs with a precise timing interval. The problem is that sometimes there is a delay longer than expected between the system timer interrupt in which the DAC values are updated. This leads to jitter in the output. I need help figuring out what is causing this delay. The only other user code running than the timer is handling of incoming USB packets containing the data to be output.

Things I have tried:

Decreasing the priority of every single interrupt other than the timer
Disabling any kind of sleep mode that might require time to wake up from
Decreasing the USB packet size to make them faster to process (though because of their interrupts having lower priority it shouldn't interfere with the timer anyway)

But nothing has worked so far.

The full code is here: https://github.com/Grix/helios_dac/blob/master/firmware/AtmelStudio_helios/lasdac_mainfirmware/src/main.c

The MCU is an Atmel ATSAM4S2B (32-bit arm cortex-m4)

Any ideas?

EDIT: I found the problem, it was the interrupt priorities. I set the priorities at bootup, however the CMSIS library SysTick_Config() function actually resets the priority for the systick every time it is called, so I had to manually correct the priority every time I called this.


texts: Help finding a design house to build our MP3 player

texts:
We used an Asian design house to design, program and build our custom MP3 player. The chip we used (Sigmatel) is no longer avaialble and the DH does not do this type of work anymore.

We are looking for a reputable company with relevant experience to help us create a new PCB for our existing plastic case.

We are considering moving to an Atmel chip (UC3) - any suggestions/comments?

We are a small company working in a niche market and are looking for a smallish (user friendly) company to work with.

Any suggestions?

We are based in Australia.

TIA


texts:
I'd like to clarify some concepts about microwaves that I still can't understand it at all. I'm reading Pozar's Microwave Engineering, more specifically stub adaptation in the Smith Chart. The circuit to be matched is the following one:

As I don't have the impedances in the transistor, but the reflection coefficients, Pozar suggests to see the circuit as follows:

So that the matching circuit should be obtained with the following criteria in the Smith Chart:

Anyway, what I can't understand is this criteria. I mean, starting from the source reflection coefficient, and moving to the generator, the first element would be the transmission line, that is in series, so why change the impedance to admittance? Wouldn't be more logic to move from the plotted impedance to the 50ohm impedance circle, and after that, change from impedance to admittance, and then cancel the imaginary part with the shunt stub?

Appart from that, I can't understand clearly that, having a generator (source) and a load (Z0), when moving from the transistor towards the generator, the movement sense in the smith chart is towards load.

I'd appreciate a lot if anyone can help me with these issues!


texts: Is there a simple way of converting a dc voltage to a sound that can be transmitted by the audio of a av sender and then converted back to a voltage.? Out-of-sight farm gate has a video camera attached to a 5.8G wireless "AV" sender for the video. I need to know when the gate is opening. Gate controller shows +12v when opening, zero when not. I just need to be pointed in the right direction. Thanks.


texts:
I am trying to create a tiny little watch that is supposed to run off a coin cell (because it is so tiny) and basically just a microcontroller with a 30ppm 1Mhz oscillator that counts upwards. The whole thing is then supposed to be controlled by a single button that lets me change the time by flipping bits.
The idea was to connect 11 LEDs to the MCU (5 for hours 0-24 and 6 for minutes 0-60) and mount the battery to the back and the mcu+osc and the led on the front, so it looks a bit techy.
The problem is, that low power LEDs that would run for a sufficient time >6 months without battery replacement, are barely visible in daylight and those that would be needed too much energy.
So here's my question: Is there anything that is sort of similar to an LED in that they are simple to control by a tiny microcontroller and that have a clearly visible state change, eat little energy and readily available and fit the purpose? (I am planning to add a second button that just connects an LED to the battery as a  way to use the watch at night).

I was thinking of just using one of those calculator B/W LCDs with a fixed display, but for a binary watch, I would need to have a special one printed which is not very easy.

I was also thinking about just disconnecting the LEDs by default and having to press a button to show the time, but I have something in my right hand already during most of the day.

Does anyone have any idea about this?


texts: An help with my practice: a common relay as latching relay

texts:
I'm looking for some help, since, currently, I'm “studying” the latching relays. I am aware of the fact that exists pre-made latching relays of two categories: the first one with two coils: the first coil is used to energize the relay and block its contacts in the active state (eg the common on the normally open contact) and remember this position also after a disconnection of the power source, and the second coil is used to de-energize the contacts to block and remember, again, the contacts in the default position. Then I heard of latching relays which are provided with only one coil: the two states are achieved according by the direction of the current flow on the coil.
Then I've found this page http://www.reuk.co.uk/Latching-Relay-Circuit.htm which explains the fact that is possible to implement a “latching system” just using a common relay.
Well, so I've done an attempt to experiment, in a practical way, how a common relay would be able to do the “trick”: in the following image there are two schematics of the wiring: the first one, on the top, is the wiring which I've found on the mentioned web page, the second one, on the bottom, there is the wiring which I've attempted to make, but unfortunately the relay doesn't work at all.

Consider that the power supply, from an AC adapter, is properly working (12 volt DC – 1000 mA): in facts, if I tipically energize the relay in the classic way on the coil, the contacts 2 and 7 closes to 1 and 2.
Is the same for the two buttons: they are properly working.
What I expect to see with my wiring, is to “attract and block” the contacts 1 and 2 and at the same time achieve the same situation with 8 and 7. I'm doing something wrong? Can someone tell me why this experiment doesn't work?

Kind regards.


texts: How optical sources having narrower spectral width gives higher data rates?

texts:
How optical sources having narrower spectral width '\$ \Delta \lambda \downarrow \$' gives higher data rates '\$ R_B \uparrow \$'?
For example: Laser having lower spectral width gives higher data rates ,similarly LED having higher spectral width gives lower data rates

My Thoughts:
For Laser: Typical spectral width \$\approx  1\$ nm
Let us consider the wavelength of light \$ \lambda= 1000 \$ nm,then
$$\because \frac{\Delta \lambda }{\lambda}=-\frac{\Delta f }{f}$$
\$\implies \Delta f= 300 GHz \quad \because f= \frac{c}{\lambda} \to f=300THz \$
$$\implies R_{B_{max}}= 300Gbps$$
Similarly,
For LED: Typical spectral width \$\approx  20\$ nm
so,for the same wavelength of light \$ \lambda= 1000 \$ nm
\$\implies \Delta f= 6 THz \$
$$\implies R_{B_{max}}= 6Tbps$$
But,this contradicts the fact that optical sources with narrower spectral width  gives higher data rates,
So, where i have done the mistake? Any help please...


texts: Is it true that when extending a high watt appliance with a extension cord I should use a thicker (higher AMP) cable than the cable of the appliance?

texts:
I am an European, so I am not sure if that matters.

All I know is that I need a cable with the right amp or wattage throughput capability. Our cables are named as 3x1.5, 3x2.5, 3x3.5 etc, I guess that is 3 cords that are 1.5 cm thick, 2.5 cm thick, etc..

So I have heard the following and wanted to debunk it if its a myth. If let say an appliance of mine uses a 3x1.5 cable which has max 4 KW throughput, do I need a thicker extension cable than the original cable that this appliance use? Or I am good with the same one as long as the capacity of the cable is higher than the appliance itself.

It seems very pointless to me, but it makes me anxious when using random extension cords on higher wattage units like oil radiators and washing machines, as I never find them thicker then the appliance cable itself.


texts: Can you use an directional Antenna to sniff packets at a very long distance?

texts:
A normal wifi dongle can be configured in monitor mode to sniff out packets . What determine the range of distance the wifi dongle can sniff out? is it determined by what protocol the wifi dongle is configured to listen too? e.g. 802.11n which can transmit up to 250 m / 820 ft , does it also apply to listening for packets?

My second question is I want to extend the range of where I want to sniff packets , Would an directional antenna be useful for this purpose ? Can a directional listen to packets at a very long range?


texts: Why does the voltage of a zener diode match the voltage at Vout?

texts:
In this circuit, if:

Vin = 9V
Vz = 5V

I understand that Vout will be 5V. Does that have to do with Kirchhoff's Voltage Law? How does the zener diode, if it drops 5V to ground, cause Vout to also be 5V?


texts:
I had an 9V alkaline battery connected to a resistive bridge, that stepped out the voltage to several analog channels. I was testing the analog channels over temperature and when it got below 10C I noticed that the battery voltage noise went from >1uV to 10's mV. As I have always thought that batteries were a stable source I started checking my analog electronics, only to find it was the battery.

Has anybody characterized this noise or the temperature it starts at?
Where does it come from (what physical processes)?
Does this apply to all battery chemistries (Do all battery types get noisy with lower temps)?

Edit - More stuff:
This is not mechanical, a test engineer and I ruled that out. The electronics are not at the same temperature, and are not powered by the battery. The battery is a reference. There are sensors that we use that we normally take down to temperature that the analog electronics are connected to and there is no problem with noise with the regular sensor. The noise is coming from the battery

Edit - Final word:
So you don't have to read through loads of comments, I'll post the result here. When I woke up this morning I thought I would heed the council of a few users and double check the mechanical setup. I suggested that the tech look things over and redo the solder joints with leaded solder instead of the lead free. After that things worked great, I had less than 1uV noise going down in temp. So I apologize for not listening to comments about mechanical.


texts:
schema http://www.electronics-tutorials.ws/logic/log47.gif?x98918

When A is powered, why does the current go to the ground and not to Q?


texts: Analog low pass filter noise versus anti-aliasing effect

texts:
I am designing a nano-volt-sensitive, 32-bit ADC system for research.
The signal of interest is 10~100 uV and DC to 100Hz the goal is 10nV sensitive system.
The signal will be amplified by a pre-amplifier with a gain of 2000 and will pass through an analog filter for anti-aliasing purposes.
Since the 32-bit ADC (LTC2508-32) will operating at 4k SPS, I would like to add a low pass filter to attenuate the signal over Nyquist frequency, 2kHz.
Here are my questions:

How should I balance the noise added by the multi-stage analog filter and distortion from aliasing? How can I evaluate the effect of aliasing after ADC as an equivalent input-referred noise or any other method so that I can fix the specification of the analog filter?
For the specified analog filter, what methods can I apply to suppress noise as much as possible? (ex. noise from resister.) Would the *LTC2057 be a suitable opamp for the job? Any keywords for further research would be appreciated.

*add Jan 27: ltc2057 datasheet https://www.analog.com/media/en/technical-documentation/data-sheets/2057f.pdf


texts:
I am trying to amplify a MG811 CO2 sensor to a range readable by an ATMEGA2560 (0-5v). I have other analog sensors, so do not want to change ref voltage on Atmega. I have found a module that scales the signal and want to replicate the circuit from the documentation, but want to make sure that the schematic I have is correct. It seems from the module documentation that the sensor operates in a range of 100-600mV (though this is different from the datasheet which shows a range between about 260-350mv). The module uses a LMC662 dual op amp.

(source: digikey.com)


texts: KiCAD - Errors when designing shield schematic

texts:
I finally finished my first schematic and everything looked great. I went ahead to perform Electrical Rules Check.
There were many errors.
Most of them were:
Pin connected to other pins, but not driven by any pin.

Pin not connected (use a “No-connection” flag to suppress this error).

I used bi-directional pins exclusively.
Also note that I used the Arduino shield template. Maybe I had to declare all pins not used as NC?
If you want, I can upload the schematic file somewhere.
Here is a picture of the schematic:

My questions are these:

I get that i should put the NC to all the pins not connected, on the arduino header pins to the right. But what about those that have a name on them like IOREF, +3.3V, +5V, Vin etc?
What do i put on these?

Is it ok if i leave the pins bidirectional?

Should i put only two power tags? One for Vin at the power jack, and one at GND at power jack? Is this correct?

EDIT:


texts: Can a capacitor provide enough current to be used as a fail safe for a servo?

texts:
Here's my situation. I'm planning to use a servo (like the ones used in RC models) to rotate a chunk of lead between two positions: 0º and 180º. Since I'll probably be powering the servo from a wall outlet (and a voltage regulator), it's important for this application that I have a way of automatically returning it to 0º position should the power fail.

Apparently the most common way to do this is with a spring, but there's the issue that the servo will be using power to fight the spring even when not moving. I found out that capacitors can be used for this: the capacitor charges when everything is working, and if the power fails the capacitor can power the servo long enough for it to return to 0º.

This is very strange. The servo pulls around \$1A\$ of current and takes around one second to do the half-turn, which implies that the capacitor would have to store around \$1C\$ of charge. This would mean either extremely high capacity or extremely high voltage.

And yet it seems that this is a thing that exists and is used for even bigger motors than mine. Can capacitors really provide that much current for that much time? Or am I not understanding something?


texts:
After looking over this question and the answers received, it prompted me to wonder:

Given pulse signals generated by a uC, what kind of slew rate on an op-amp will you need to reproduce the waveform cleanly?

Example:  Assume you have a project where you generate pulses 10uS in length on a uC pin that go into an op-amp in a buffer configuration.  What is the minimum slew rate required to reproduce the waveform at the output of the buffer without introducing an integrating effect?  What is a good rule of thumb to use?


texts: How to check DC polarity using a multimeter

texts:
How can we check DC polarity using multimeter?

If the DC cable (the positive and negative end) is connected in the cable rack (terminal block) how can one identify which cable is positive and which cable is negative?


texts: What do you call the connector type which is soldered on PCB and it holds cables by pressing on them by screws?

texts:
Here is a picture of two of them:

I searched for these connectors in Digikey and Farnell for an hour, but couldn't find anything similar. Can you please name these connectors for me and/or give a link to their subcategory in one of these part seller websites?


texts: Use Preformed inductor instead of coil for FM Transmitter

texts:
I want to build this transmitter:

The inductor in the schematic says 0.1uh so I figured I could get some of these and use them instead of making my own like it describes in the picture. I would be using these.  Do you think they would work? Any information appreciated.


texts: In this circuit what is the function of this resistance in parallel with a capacitor

texts:
I understand that the capacitor produces a resistance proportional to the 50 Hz of the mains input current, in this case 220 volts
But why is that resistance installed in parallel, what function does the resistance have?
Thanks


texts: Netduino Plus 2 use built-in usb for communication

texts:
I want to use a Netduino Plus 2 for a commercial product. The thing is that this product is required to be able to communicate with a PC over USB and I want to know if there is a way for me the use the buil-in micro usb connector for communication. I know I can simply use an external usb serial adapter but that would be costly and impractical and I do not plan on having any pins available for it. I could though open then for programming if needed but not for use in my product.

I have found this article http://forums.netduino.com/index.php?/topic/1514-driverless-pc-netduino-communication-using-usb/ but it seems that it is not compatible with the newer firmware. I have also read that the new Plus 2 comes with hardware that makes theis more possible but I could not find any references as of how to use it.

Do any of you know if and how I can do this?


texts: What are these things in my LED light string?

texts:
So I have a string of LED lights that has gone out. I know it's in a series, as none of the lights will go on, however another string plugged into the end will light up.
I first changed out every bulb I could find in the string, and checked each wire connector was secure and had contact.
I went and got a non-contact voltage detector. My electrical experience is very rudimentary if it isn't showing already.
I checked the voltage on the first bulb in the string, and it has current according to the detector. Then I hit these things. There are four of them in the string, between the 2nd and 3rd light, and the 4th and 5th light. They're only between the first series of 20 lights (2.5, 3.5, 12.5, 13.5 if we talk positions) and nowhere else in the string.
The voltage detector get zero voltage after the first one. So, exploring what I could, I spliced past the first mystery block and then the next bulb has voltage as well.
After bypassing the mystery block there's still no light down the entire string, despite the voltage creeping one bulb farther in the line. I didn't want to bypass every one of the blocks for fear of causing a nightmare string on the LED strip, or ruining any part of the programming of how the lights work.
Can anybody help me out identifying what the black nodes are so I can try to replace the first one in the string and hopefully restore these lights?


texts:
So I designed a module which can read multiple voltage and current(4-20mA) inputs. This module has been designed with the use of Max11609. After receiving the PCBs and testing them, I observed a strange thing. When I supply a voltage to any channel, the other channels also display some values in Arduino serial monitor. The schematic and layout of the chip is given below;

So when I provide voltage input to channel VIN1, the below digital readings are observed:

VIN1 -> 767

VIN2 -> 460

VIN3 -> 135

VIN4 -> 0

Now VIN1 is absolutely correct and shows the digital value corresponding to voltage supplied. But why are other channels showing such erratic behaviour ? Is it because of cross talk or could it be because of the sampling interval between subsequent channels ?

PS: I am using this code.

Thanks in advance !!!


texts: Silicon purity and electronic feature density

texts:
During development of an integrated circuit it is my understanding that you require a silicon purity of 99.99999999%.

Has this always been the case? In 1971, had the first commercially available microprocessor (Intel 4004, 10 micron process) reached this level of purity?

How has the purity of silicon for electronic purposes increased as the feature size (gate electrode width) decreased?

I've searched online for multiple days with little success. I'm aware of Silicon purification processes and really only seeking a definitive data set on the increase of purity during feature reduction; if any at all?


texts: Convert a non-isolated converter to an isolated converter

texts: Is there a way to convert a non-isolated converter(such as R-78C5.0-1.0) to an isolated converter.


texts: Can I safely take power from one USB socket and data from another?

texts:
My car has 2 USB sockets that provide power and also serve as a data link for audio, etc. from phones to the entertainment system. The entertainment system also accepts a Bluetooth connection for hands free and audio, etc.

The audio connection via USB provides more features than the connection via Bluetooth, for example album art is displayed on the entertainment system and I can seek to a specific point in a track.

The downside of using the USB connection for data is that i must also use it for charging and it doesn’t provide much current.

I also have a 12v to USB adaptor in the car that provides 2.1A and charges the phone much more effectively.

My question is; is it safe make my own wiring to take power from the 12v to USB adaptor and data from the car’s sockets so that I can get the advantages of 2.1A charging and the data connection to the entertainment system?


texts:
I am designing a Pulse Oximeter.
The SpO2 probe has an IR LED and a photodiode.

I need assistance with the algorithm for calculation of SpO2.

I'm aware of eg Wikpedia and similar sites and I have referred to many papers for the SpO2 calculation, understood till calculation of modulation ratio. But different equations were used in different papers, which they say that they obtained by calibration results. That's the problem. How to calibrate the Sp02 level?


texts: LED lights if two or more switches are on at same time

texts: I have a need to know if two or more of eight switches are on at the same time. The supply voltage is 12 volts dc. The switches are SPST. I have looked at digital circuits but have yet to figure it out. Any help, please.


texts: Setting current source as active load in LTSpice

texts:
I don't understand what Parasitic Properties: This is an active load means in LTSpice provided as an option in the current source configuration window. I plotted out the schematics, one with the active load checked and the other without, and compared their traces.  Without being checked as an "active load", the current source behaves just like how a current source should be - supplying a constant 2A current (upper schematic). If I then checked the "active load", current stays at 2A only when \$ V_1 > 0.5V \$, and if \$ V_1 = -2V \$, the current source miraculously supplies -16A!

It makes no sense to me that the current source can sink 16A while I've already fixed it a DC value of \$ I_1 = \$ 2A - where is this extra 12A comes from?
I don't understand how a load can be modeled as a current source. Isn't a load a component or a sub-circuit that sinks current and dissipates energy? Current source supplies energy to the circuit - how could it supply and dissipate energy at the same time (i.e. suppling 2A current to the circuit but dissipates \$ 16A*2V=32W \$ ?!

Perhaps a related question here: LTSpice active load current generator soft saturation


texts: I have a device which has a dc barrel jack with inside + and outside -. If I plug in a barrel connector which has 2 wires to connect to a DC voltage source (battery) how do I know which wire to connect to the positive terminal and which wire to the negative terminal?


texts:
I am using a 555 IC to get 10KHz-50% square wave.Everything goes as expected Except for large ringing(About 2V above the normal 9V high voltage) during the rising Edges of output.

I put 0.1uF and 10uF bypass capacitors at Vcc pin.

Is it normal to have this amount of ringing ? or I can improve the circuit to reduce this Ringing further.

Note:C3 is 0.1uF not 0.1F as in the schematic


texts:
I have been teaching my son the basics of electronics by taking apart his old toys. We got to the level where we can fix things and put them back together. Last weekend we spent several hours putting the circuitboard of RC car #1 into RC car #2, because we lost the controller to #2, but still had the controller for #1 (which we completely disassembled).

I had to remove the connectors to the motors, because we had wires from yet another RC car #3. So we replaced the connectors for the motors on the circuitboard. Everything was working great, we were almost done, but I noticed that one of the motors was working only about 50% of the time. I thought it might be because the solder job was incomplete, so I touched it up at the junction I’ve circled in RED in the picture.

After that everything broke. Neither motor would work at all. When I plugged in the charger, the red LED which lights up when it is charging would flicker really fast. I’m not sure what I did, or how to fix it, or even if I can fix it...


texts: Energy level of the created holes when electrons from the Silicon atoms occupy the holes due to acceptor atoms

texts:
I read in an article that the addition of acceptor impurities contributes hole levels low in the semiconductor bandgaps so that electrons can be easily excited from the valence band into these levels leaving mobile holes in the valence band.
My question is- what will be the energy level corresponding to the holes created after electrons from the Silicon atoms occupy the holes due to acceptor atoms.
Is the energy level the same as the valence band? If so, then those holes can be easily occupied by other electrons of the valence band. Am I correct in this concept?


texts: How do I Implement Soft Clipping in an Audio Circuit? Or should I just Attenuate the Signal?

texts:
I am designing an audio circuit that takes in line-level audio, amplifies the audio using an amplifier (most likely this 3.1w amp - http://www.ti.com/product/tpa6211a1#parametric) and outputs the amplified signal to a 1w nominal, 2w maximum speaker.

To ensure that I do not overload the speaker I have been recommended to implement soft clipping. So am looking for details on how to implement soft clipping. I prefer the solution to be analog rather than digital, as my signal path, including the amplifier are all analog.

Someone also suggested the best way to deal with protecting the speaker is to attenuate the signal. If this is a better solution, where do you do you attenuate. Before the line-level signal enters the amplifier or just after the amplified signal leaves the amplifier? And how much should I attenuate the signal (or at least what ranges)?

Questions:

Soft Clipping or Attenuation?
If Soft Clipping, then what does an analogue circuit look like?
If Attenuation, where do I attenuate, before or after the amplifier? And by how much?


texts: Strange output from latch connected to comparator

texts:
I'm trying to make a latch (in ltspice), so if the comparator output (A) goes low, the latch will trigger and C will go high. C should stay high, irrespective of whether A goes high or low after that. I'm getting strange values on ltspice. Must be missing something basic... I've tried with different op amps too (lm324, lm358, tl072), same results. Also, with and without the resistor between A and B. Also with single ended supply. Also, changed around the resistor values. No difference. Should try it on breadboard maybe?

Voltages at A, B and C
A    B    C
5    4.4  0.6    A and B disconnected
0.5  20m  5      1K between A and B
20m  20m  5      A and B shorted
5    15m  5      1000 meg resistor between A and B
5    4.4  0.6    10000 meg resistor between A and B (~60 pA flowing A to B)

What's going on?

edit: circuitlab seems to be giving correct results. maybe an ltspice thing?

simulate this circuit – Schematic created using CircuitLab

Update: I tried this on the breadboard, and the circuit did not work properly, just like LTSpice predicted. So although it should work in theory, just like circuitlab simulates it, it did not work in practice, just like LTSpice predicted.

I had to play with the resistor values, and it sort of seemed to work only if I added a 1K to the base of the NPN. Also, I had to set all resistor values to 1K. Also, this was with the BC547/BC557 as that was all I had with legs. However, the circuit was finicky, and the output went high without reason, if I barely touched the PNP base sometimes. Probing with the multimeter would turn it on many a times. It was just not stable.

Of course it only sort of worked with the LM393. The LM358 can not turn it off, guess why? (The LM358 output is not high enough to turn off the PNP, so the circuitlab simulation is horribly wrong.)

My guess is that LTSpice simulates some sort of noise in the picoamperes to approximate the real thing. Breadboard would just make it worse. I tried this with a single ended supply.


texts: Could I assign different events to SysTick event handler?

texts:
Trying to blink LEDs on STM32 dev board (F303 discovery) using SysTick interrupt. This is the snap of the simple code I wrote :
void SysTick_Handler(void) { GPIOE->ODR ^= 1<<14 | 1<<10;}

Nothing special. However, there are different color LEDs on the board, so I thought it would be great if I could take some input from user about color and blink that color LED, using interrupt.
But while defining the event handler I am not supposed to change the structure of definition (right?).So the handler can't take parameters.It would only handle a particular event. Is there a way I could do different events on same handler? Or do I have to use different timers?


texts:
I'm trying to implement RS485 link between mcu and pc. I'm using MAX485 for testing my setup.

Question: I can not receive bytes if I use termination resistor. Why? How to solve this?

History:

If I place a termination resistor (120 ohm), it is obvious that A-B pins are no longer high impedance. According to the datasheet, if A-B pins are not in high impedance, MAX485 ic's RO (Readout) is low while listening. If data line is low right before transmission starts, this sequence is not accepted as a valid sequence. That's why I can not receive any bytes if I use termination resistor.

I solved this problem by removing termination resistor. This put the MAX485 IC's A-B pins into a high impedance state, which turns RO pin (Pin #1, the TX pin of this IC) into high state while listening. Since the TX pin of this IC is high right before transmission starts, I can communicate as intended. But I know I will need to use termination resistor.

What is wrong with this setup?

Circuit Behaviour:

On the PC terminal screen, a key is pressed
The USB/RS232 converter generates a sequence from its TX pin.
STM32F407 receives this character, and simply echoes it via its TX pin.
MAX485 ic receives this character, converts it a differential signal.
Other MAX485 ic gets this differential signal and converts to the character.
USB/RS232 converter gets this character via its RX pin.
Received character is shown in the PC terminal screen.

Test case: Setup is correct if you can see pressed character in the terminal screen on the pc.

(I know I mixed the TTL levels and CMOS levels since I don't have appropriate IC's right now. Conversions made by resistors.)

This is my test circuit:

This is the truth table of MAX485:


texts: Is resistance the derivative dV/dI or the ratio V/I?

texts:
I'm trying to understand the justification for turning off independent sources when calculating the equivalent resistance in Thévenin's theorem.
This answer explains has a good explanation but it assumes that resistance is the derivative of the voltage with respect to the current, dV/dI. I'm trying to relate this to Ohm's law.
For a resistor, the relationship is linear so dV/dI = V/I = R.
But for an ideal voltage source, dV/dI = 0 (short circuit) while the ratio V/I has some constant value depending on the current passing through it.
Similarly for an ideal current source, dV/dI = Infinity (open circuit) while the ratio V/I has some constant value depending on the voltage applied accross it.
So my question is does this mean that Ohm's law has a general form which is R = dV/dI and for the resistor (linear case) this is also equal to R = V/I? Or am I missing something?
Thanks in advance.


texts: Delay circuit having different high-to-low and low-to-high delays

texts:
I'm trying to design an integrated circuit that can implement a delay of approximately 100 ns, working with a 180nm process. With this process, an inverter has a delay of picoseconds, so it would require too many of them in a chain to achieve such a delay. I decided to use the following circuit

It is acheiving the delay I was looking for. However, the delay is just for the low-to-high transition, in the high-to-low the delay is much lower, and I can't understand way. Here are figures of the circuit used for simulation and the results

Any explanation for the behaviour? I was expecting it to have the same delays. The inverters are ratioed Wp/Wn = 2 to achieve symmetrical propagation delays.


texts: Gate Driver topology for Buck boost Converter

texts: I am implementing inverting Buck-Boost Converter in hardware as shown in the picture attached. The output of this converter is negative. so I will have an issue with its gate driver. The gate driver of high side MOSFET will face negative voltages at the source. so the gate driver that I have used IR2110 will not handle the negative voltage. Can you please suggest me the gate driver topology spacillay for inverting buck-boost converter.


texts:
I need to get an LED blinking at in the 1-5Khz range.  I will use a photo detector to sense the blink rate to identify a drone.

The drone will be passing though a hoop about 1 foot from the sensor.

Think of it as being similar to a short distance, Li-Fi, visible light communications, PHY layer design.

Ideally the LED needs to remain as bright as possible and remain at a constant blink speed even as the battery discharges.

Weight is an important criteria for this design, so every gram possible needs to be shaven from the circuit.

On-board voltage is 3.7volts.


texts: Having difficulty simulating Parallel capacitor inverter at falstad.com

texts:
Here is the circuit: from Falstad.com
The circuit crudely converts 125vdc to 250vac. The main idea of the circuit is that: the thyristors will be pulsed 180 degrees apart, 60hz. the capacitor will charge to twice of 125vdc every cycle (125vdc from the dc source + 125vdc induced on the other half of the primary coil) and help one thyristor to cut off its currents, while another thyristor is being turned on. Then the capacitor can again charge to twice of 125vdc, this time, the other way.
I am having difficulty in the following 3 areas:

how to set up a thyristor, I have failed spectacularly. current in the thyristor just travels everywhere, not sure if the website's simulation is doing it right.
the voltage across A and K of my thyristors are way more than 1v across. I have no idea what I am doing wrong here. I was suspecting the internal resistance of thyristor was too high.
The circuit is just not working. both thyristors are conducting. One conducting is supposed to shut the other one off.


texts:
From what I understand, a strip of WS2812 LEDs use PWM to adjust the brightness (and thus current draw) for a given LED.  If I attach several strips in parallel, each with its own data pin from my uC, would it be possible to multiplex the strips so that each strip is only every on at a given moment? I'm hoping that by doing this, the current draw of the entire setup will be reduced.

From the following thread it seems like the answer is no:

  You must understand that multiplexing and PWM both have the same effect, from the point of view of a single led. They both reduce the % of time that the current flows. Therefore the average current falls and the led is less bright. There is no magic that can keep an led as bright while the average current is less.

and

  Do you mean having separate strips and show the pattern on only one strip at a time, but change what strip is showing quickly so as though it appears that all the strips are on?
  There are two things wrong with this:

  1) The PWM rate in the strips are slow so you can not turn them on an off that quickly. So you will see flicker on the strips.

  2) The strips still end up being dimmer and use exactly the same amount of current on average as if you just reduced the brightness.

Could someone please explain this in more detail?

As a thought experiment, if I had multiple strips of just a single LED, if a LED is only actually ever on a fraction of the time (PWM), and if you time things right so that each strip's "on time" is offset just a bit so that no two strips turn on at the same time, then current should be reduced.  What am I missing?

Edit

Perhaps one of my assumptions is incorrect.  When a LED is being PWM-ed, I'm guessing that the current draw over time looks identical to the PWM wave. Therefore, I'm wondering why you couldn't have the current draw for the other strips be timed to go on when the others are low.


texts: Routing Digital Signals to an Analog Circuit

texts:
I'm working in a mixed (analog and digital) PCB layout where I need to route some tracks from digital to analog ground area. They are general I/Os signals to control MOSFETs and clocks/data signals (around dozens MHz). The board is dual layer and I used this Texas article as reference: http://www.ti.com/lit/ml/sloa089/sloa089.pdf

The grounds are arranged as following image, red is digital ground plane and blue is the analog one. The grounds are connected each other at a single point (although not represented in the image) close to the plug of the power adapter, in top of the board. The issue is about the better way to trace those signals to analog circuit. I've read that digital signals should not come into analog ground, seen that is not possible in this case, my idea is to bring the tracks from digital into analog planes by two gaps (purple rectangles in the image), the central one would have the clocks/data signals and the right one would have the I/Os. The gaps positions are somehow related to components placement where signals will be connected to.

As you can suppose the analog circuit is sensitive and the aim is to find out a good solution to prevent noise and interferences coming from digital signal or its return. Is the proposed solution a good way?

[EDIT: 2015/12/02]

The analog part contains a CODEC which is connected to CPU.

I already have a prototype board which was designed following the arrangement showed in the image (except by the purple areas). This prototype is suffering interference from digital circuit, is possible to see some spikes in the FFT analysis. The spikes only happen when CODEC is working.


texts: Device that fetches a web API call via wifi showing the result through a display

texts:
I would like to build an electronic device that periodically checks some web internet API giving the result through a display.
This device should have:

Wireless shield to connect to the internet through some available connection (wep, wpa)
LCD display to show the API call results to the user
Some way to configure it remotely via http
A speaker to alert the user with some rudimental bell sound (Optional)
A second LED display to visually alert the user of some new fetched result (Optional)
Battery operated (Optional)

I have found this project that looks good but does not give any insight about the used components.

I'm just looking for some general input since I'm really a newbie in this field; is this project too complex or is it possible to realize it?
Do you have any suggestion on which components do I need to realize something like this?


texts:
I'm trying and want to learn how to use the PWM Switch Model by DR.Vorpérian , both for the voltage mode(VM) and current mode (CM) model.
I've read some about the models in "Switched-mode power supplies" by Christophe Basso.
However a book can't answer questions, so I hope this thread will be useful on the the way of learning.

Question 1)
If I've understood the PWM Switch Model correctly for both the VM and CM case, the model can be directly  inserted in any simulation so long it's "rotated" correctly for the current topology, without any modification or calculation necessary because the model is just a linear model of the switch?

Question 2)
Which means I can add an infinity amount components outside the so called PWM switch model without the need of modifying the function of the model?

If the answear to the above questions is "Yes" wouldn't it be possible to use the models presented at Bassos webpage which are derived for LTspice?

The model I'm talking about can briefly be found here:
https://www.onsemi.com/site/pdf/pcim_basso.pdf

Yes I do wonder if the LTspice models available on bassos webpage is complete. In that way that they can toggle between CCM and DCM operation and do not need any modifications.

@laptop2d answer

The idea off the model is to simulate the SMPS behavior in a much quicker way than actually components to analyze the circuit in a big scope. To be able to look at the transition between CCM & DCM and to analyze the transfer function and make the circuit stable before moving on to a more real component simulation.

My question do need knowledge about the “PWM switch model” to be answered correctly. If I’ve understood the PWM switch model correctly it only need to be derived once to be implemented in any topology, which in that case means that I don’t have to derive every model to be able to simulate a circuit quickly and tweak them. Which you have to do with the state space averaging (SSA) method which requires that you rederive the average model every time you add or take away any component.

So my questions are; if the PWM-switch model is correctly described for LTspice att Basso’s webpage, can they be used directly? Without any derivation? For any topology? for both the CCM & DCM case for the VM & CM-model?


texts: Why using capacitor in transformer less ac to dc converter

texts:
I saw many transformer-less power supplies using capacitive resistance of a capacitor.

But I don't know exactly what the reasons are for using capacitors instead of normal resistors .

I guess two reasons:

Capacitors are more isolated than resistors.
Capacitive resistance waste less power (is it right ?)


texts: EMI Noises - when controller is powered up

texts:
I have one sensor which I need to interface with my controller using SPI communication. The manufacturer of the sensor tells that both controller and sensor should be on same PCB. When we asked manufacturer that if we can mount sensor and controller on different PCB and connect via cable. They told that it will work when connected via cable in a noise and EMI free environment.And they recommended to place both controller and sensor on same PCB.

My question is what activities can lead to noises generation when the controller is powered on?

Waiting for the reply.

Regards


texts: Calculating gain of an overall system. Analogue electronics

texts:
Our professor has given us a review for a upcoming exam. But he has never done anything like this question and it has stumped a quite few of us. We are hoping someone can walk us through this so we can understand, as he will not assist.

  A modular two amplifier system consists of a first stage amplifier with an open loop gain of 100, an input impedance of 25kΩ and an output impedance of 2kΩ, and a second stage with an input impedance of 2kΩ and an open loop gain of 50 and an output impedance of 500Ω.

  Calculate the gain of the overall system.

  Using a single op-amp, specify a third modular amplifier, using the original two in the order or otherwise, such that the input impedance of the overall system is 20kΩ, the output impedance is 2kΩ, and the magnitude of the overall voltage gain is 2000.

I thought you could just multiply the gains (gain = - Z2/Z1) of each op amp together, but some classmates disagree with me.

Should I approach it with op amps or signal circuit equivalents? Does a voltage divider have anything to do with it?

I can attach screenshots of circuit diagrams we have tried.


texts:
Can I use the output of an NPN proximity switch as the input to an LM7805 (positive input) voltage regulator? I'm a little confused on PNP vs NPN, but I'm reading as fast as I can. Also I see that they make an LM79xx series of VR's that, I think, accept a negative voltage as the input, would this negative voltage come from an NPN style device?
Thanks, Jim G.


texts: What should be the size/package of Bob Smith Termination resistor?

texts:
We have run into a layout issue where the size/package of the 75R resistor used for Bob Smith termination on unused Ethernet pins is in question. The current package of this resistor is 1206 and we want to reduce it to 0603 size. Can this be done?

As far as I know or can think of, it can be done without any problems. But just want a confirmation. Some brief justification would also be helpful.

Thanks.


texts:
I have two cheap soldering irons, one of which was given to me. I was also given some solder (of unknown quality), which I recently used up. I bought some cheap solder from Harbor Freight. I've used both a wet sponge and steel wool to clean my soldering iron.

With both soldering irons and both solders my soldering iron tip would slowly be eaten away during use.

Is this normal for soldering iron use in general? Which factors would cause or worsen this?

I'm trying to determine if buying a quality tip and some decent solder would be enough, or if I will need a quality soldering iron to keep this from happening.


texts: Is it possible to pick up noise in an audio circuit through the ground / earth wire?

texts:
In an audio circuit, such as a guitar's electronics (the only thing I ever dabble with!), I have always thought (probably simplistically) of every point along a continuous earth path being essentially all at the same voltage (a 'zero volt' reference voltage).

However, I was wondering - if you extend an earth wire from some point along that path, is it possible for that in itself to introduce noise to the circuit by changing the '0V' of the earth reference? (Possibly I am wondering "What is the difference between a long earth wire and an antenna" - but I don't know enough about antennas to know if that's what I'm asking :)


texts: Circuit to dim 40A/12V LED chain with PWM (Arduino output)

texts:
We have about 170 feet of LEDs (12VDC, 2.88W/foot) wired up in one chain. Currently they are driven by two switching power supplies (12V/27A).

We'd like to control the whole chunk of them together, dim them via an Arduino's PWM output.

Most dimming / extensions boards out there are very limiting in their load. See Sparkfun Mosfet board 10256 - it has a Mosfet ready for up to 30A, but PCB tracing and components limit it to a usage of 4A. Or this 4-channel Mosfet board - each channel can sustain 10A, but the power input terminal can only sustain 16A.

Is there even a way to wire the whole current for all LEDs through one channel (=one Mosfet?), or is this impossible due to component limitations? Could i use for example several of these smaller boards and then simply add their outputs together and feed the whole LED chain with one input? Or are there any hardware devices out there that are build to sustain higher currents (like wall dimmer switches, those seems quite sturdy...)?


texts: transimpedance amplifier based on a capacitive feedback current amplifier

texts:
I am trying to understand the circuit in this publication.
The picture below is the simplification of the circuit.
I do not understand the role of the cascode configuration part of the circuit.
Appreciate any inputs or reference to other publications that similar with this.
From the paper, the whole circuit is a transimpedance amplifier which is based on a capacitive feedback current amplifier. The output current is dumped into the load resistor to get the output voltage which is later buffered.

There is other circuit which I think is similiar, but using single ended opamp here. Here is the picture.


texts: NE555 monostable timer circuit restart timer when trigger grounded in between

texts:
I had made an NE555 timer IC based delay circuit (monostable mode) which keeps output HIGH for 10 seconds when trigger pin is connected to ground momentarily. But what I want is if I ground trigger pin again (momentarily) within the ten seconds, it restart the ten-second timer i.e. start timer again from that moment and keep output pin HIGH for another ten seconds. Any way to do that?

Below is my circuit Diagram.

Update: actually i am trying to replace the Arduino in my motion sensing relay circuit. Arduino is programmed in such a way that if motion is detected it turns relay ON immediately and if motion is not there then turns relay OFF after 1 minute. Also if there is any motion detected within that minute then the timer restarts. I think using Arduino just for that is a waste. Please suggest.


texts: Connecting a Red/Green LED Cluster to an Arduino

texts:
Complete novice at electronics, how can I connect this LED cluster to an Arduino?

I have a 12V battery pack to power it.

If you are able to provide wiring diagram / fritzing that would be much appreciated.


texts: Is this high frequency filter schematic correct?

texts: I'm trying to filter the high frequency AC.


texts: What is this component? It looks a bit like a capacitor, but not exactly, and it is labelled L1 on a small circuit board where there are capacitors labelled C2 and C3…


texts: Why optical disk CD/DVD use spiral tracks, as opposed to cocentric tracks used in hard disks and floppy disks?

texts:
I'm not sure this is the community in which should I ask this question, if it isn't, I'm willing to transfer it.

According to this article:

  Track positioning also follows two different methods across disk
  storage devices. Storage devices focused on holding computer data,
  e.g., HDDs, FDDs, Iomega zip drives, use concentric tracks to store
  data. During a sequential read or write operation, after the drive
  accesses all the sectors in a track it repositions the head(s) to the
  next track. This will cause a momentary delay in the flow of data
  between the device and the computer. In contrast, optical audio and
  video discs use a single spiral track that starts at the inner most
  point on the disc and flows continuously to the outer edge. When
  reading or writing data there is no need to stop the flow of data to
  switch tracks. This is similar to vinyl records except vinyl records
  started at the outer edge and spiraled in toward the center.

There should be reasons why choosing one strategy over another in each case, Pros and cons. Wich are they?


texts: Negative Edge Trigger and Asynchronous Clear not working in ModelSim

texts:
I have created a 4 bit counter with the following inputs and outputs

clockN: active low clock

clearN: active low clear

cP: When high, the counter counts.  When low, the counter stays the same.

eP: Active high.  This activates the tri-state buffer at the outputs

When I simulate this, and assert the clearN (N meaning active low) at t=0, it does not actually clear until the next positive clock edge.  I do not understand why.  Also, each time qOut counts up by one, it does it on the positive clock edge even though my code is telling it to do it on the negative clock edge. My code, testbench, and modelsim output are shown below.

Here is the counter code

    --Program Counter for SAP-1

LIBRARY IEEE;
USE IEEE.STD_LOGIC_1164.ALL;
USE IEEE.STD_LOGIC_UNSIGNED.ALL;    --This is required when doing additions to STD_LOGIC_VECTORs

ENTITY PROG_COUNT_SAP_1 IS

    GENERIC(size: INTEGER:= 3); --This is the size of the register

    PORT(
        clockN, clearN, cP, eP: IN STD_LOGIC;
        qOut: OUT STD_LOGIC_VECTOR(size DOWNTO 0));

END PROG_COUNT_SAP_1;

ARCHITECTURE Behavioral OF PROG_COUNT_SAP_1 IS
    SIGNAL valueBeforeTriBuffer: STD_LOGIC_VECTOR(size DOWNTO 0);

BEGIN

    PROCESS(clockN, clearN, cP, eP)
    BEGIN
        IF(clearN = '0') THEN
            valueBeforeTriBuffer<=(OTHERS=>'0');

        ELSIF (falling_edge(clockN)) THEN

            IF (cP = '1') THEN
                valueBeforeTriBuffer<= valueBeforeTriBuffer + 1;
            END IF;

        END IF;

        IF (eP = '1') THEN
            qOut<= valueBeforeTriBuffer;
        ELSE
            qOut<=(OTHERS=>'Z');
        END IF;

    END PROCESS;

END Behavioral;

Here is the testbench

    library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;

entity TB_PROG_COUNT_SAP_1 is
end TB_PROG_COUNT_SAP_1;

architecture test of TB_PROG_COUNT_SAP_1 is

--create time constant
constant CLOCK_PERIOD: time:=2 us;

--create constants for all generics.
constant size: INTEGER:=3;

--create signals for every port
signal clockN: std_logic;
signal clearN: std_logic;
signal cP: std_logic;
signal eP: std_logic;
signal qOut: std_logic_vector(size DOWNTO 0);

begin

dut: entity work.PROG_COUNT_SAP_1
generic map(size=>size)
port map(clockN=>clockN,
    clearN=>clearN,
    cP=>cP,
    eP=>eP,
    qOut=>qOut);

--simulate the clock
clockNSimulation: process
BEGIN

    FOR count IN 1 TO 16 LOOP
        clockN<= '0';
        wait for CLOCK_PERIOD/2;
        clockN<='1';
        wait for CLOCK_PERIOD/2;
    END LOOP;

END PROCESS clockNSimulation;

--simulate the clearN
clearNSimulation: process
BEGIN

    clearN<='0';
    wait for  3 us;
    clearN<='1';
    wait for 7 us;
    clearN<='0';
    wait for 2 us;
    clearN<='1';
    wait;

END PROCESS clearNSimulation;

--simulate the cP
cPSimulation: process
BEGIN
    cP<='1';
    wait;

END PROCESS cPSimulation;

ePSimulation: process
BEGIN
    eP<='1';
    wait;

END PROCESS ePSimulation;

end architecture test;

Here is the output waveform from modelsim:


texts:
I am looking at a MCP3008 datasheet and it says that it has a maximum current drain of 150uA, and a typical current drain of 100uA.

I am building a voltage divider to knock down 96V to 3V. As this is for a solar car, I would like to reduce the amount of current and power used. I would like to be able to read a maximum voltage of 115V, and a minimum of below 75V, and be able to waste the least amount of power nessassary. How does the current drain factor into my calculations?

My calculations are as follows:

Using ohms law with E=115V I=0.00015, I get 76666 ohms
Using a voltage divider I get R1 = 76666 and R2 = 2053.55

Are my calculations correct? Can I knock more power out of this circuit?


texts: Why would an 8-order LPF switched capacitor have a less steep roll-off curve (MAX7405)?

texts:
As as I understand it, a higher order LPF will have a steeper roll-off curve. Something like below would happen if we increase the number of order for the LPF:
Normal LPF frequency response curve:

However, when I tried to check the frequency response curve for the 8-order LPF switched capacitor, MAX7405 datasheet page 5, it shows a less steep curve behavior which is similar to a normal second-order LPF.
8-order LPF MAX7405 frequency response curve:

For a 1k cut-off, I expect a -40dB drop at 2kHz - but the 8-order does not seem to behave like that. Does anyone know why?


texts:
I'm working on a school project and my team needs the smallest GPS possible. With some help from stackoverflow, we found https://www.sparkfun.com/products/11571 from sparkfun.

This is good enough to prototype, but we were wondering if smaller GPS's exist out there just for knowledge's sake.


texts: NTC Thermistor circuit, ADC conversion, compute temperature

texts:
Here's the schematics of my NTC - ADC  circuit,

ADC 10bits, ADCVCC 2.56V

Vin = 5V

Someone can explain me how i get RT, the value of resistance of NTC from ADC value?
thanks.

I'm using the voltage divider formula:

Vout = ADCVCC * ADC_value / 1024
BETA = 3950
R25 = 4700
RT = 10K / (Vin - Vout - 1)
T = (1 / (1/298.16 + 1/BETA * ln(RT/R25 )) - 273.15

But I got wrong results:

the range of my temperatures are:

adc = 1    -> T = 344 °C;
adc = 1023 -> T = 8

How I have to set up the ADC in AVR? with internal voltage reference or not?

do i have wrong formula?

I need to read "exact" temperature in range of -10°C to +30°C more or less.

I've tried already with SH equation with coefficent A,B,C
but i've got worst results!!!

I think I've don't understand the schematics of NTC - ADC circuits...

And set up my ATMega with wrong parameters.

Someone can try to explain me how to convert my ADC value to Resistence of thermistor with this schematics?

Thanks in advice for help.

[EDIT]

My setup for AVR ADC:

ADMUX |= (1<<REFS0) | (1<<REFS1);
ADCSRA |= (1<<ADEN) |(1<<ADSC) |(1<<ADIE);
ADCSRA |= (1 << ADPS2) | (1 << ADPS1) | (1 << ADPS0);

and the formula used to get Resistance from ADC value:
    Vin  = 5V
    Vref = 2,56V (AREF)

Vout = adc_val * (Vref / 1024.0))
RT   = 10k / (Vin / Vout - 1.0)

This code match the schematics? Is it correct my ADC set up with those schematics?
thanks in advice.


texts: How to work out (Hfe) AC Forward current transfer ratio for ZTX650 BJT Transistor?

texts: Please can someone suggest to me how to work out the AC Forward current transfer ratio for this BJT Transistor (ZTX650 BJT Transistor) used in common emitter. I looked on the data sheet (herewith is the link http://www.mouser.com/ds/2/115/ztx650-186634.pdf) but it does not mention this. Can someone please give me just a hint/suggestion to work this out? Is it simply hf = ic/ib (i always thought this was for DC beta(hFE))?


texts:
I've been looking at the SM74611 Smart Bypass Diode from Texas Instruments and am very impressed with the reported reverse leakage current (0.3uA at 25C).  Considering the device has a N-Channel FET, 0.3uA of Drain-Source leakage current @ 25C is nothing to scoff at considering that most FETs usually have a Drain-Source leakage current of 1uA.

At first I thought this discrepancy could easily be explained by finding the right FET online, but I quickly realized that I would spend days trying to find said part as this parameter is usually not specified in the parametric searches.

Does a sub-1uA Drain-Source leakage current FET exist, or is there some trick to get a smaller leakage current from a typical FET?


texts: LC circuit with series diode (finding the linear average)

texts:
I've the following series LC circuit:

  Find the (linear) average of the current trough the diode. The ideal is a ideal component. The initial conditions in the circuit are equal to zero.

MY WORK

I first shorted the diode (so pretend the ideal diode is not in the circuit). Using Faraday's law I can write:

$$\text{V}_{\space\text{in}}\left(t\right)+\text{V}_{\space\text{C}}\left(t\right)=-\text{L}\cdot\text{I}_{\space\text{in}}'\left(t\right)\tag1$$

Now, I also know that \$\text{V}_{\space\text{in}}\left(t\right)=\sin\left(2\pi\cdot t\right)\$, \$\text{I}_{\space\text{C}}\left(t\right)=\text{V}_{\space\text{C}}'\left(t\right)\cdot\text{C}\$ and \$\text{I}_{\space\text{C}}\left(t\right)=\text{I}_{\space\text{in}}\left(t\right)\$. Where \$\text{L}\$ is the inductor value (in Henry) and \$\text{C}\$ is the capacitor value (in Farad).

So, I can also write:

$$
\begin{cases}
\frac{\text{d}}{\text{d}t}\left(\sin\left(2\pi\cdot t\right)\right)+\text{I}_{\space\text{in}}\left(t\right)\cdot\frac{1}{\text{C}}=-\text{L}\cdot\text{I}_{\space\text{in}}''\left(t\right)\\
\\
\text{I}_{\space\text{in}}\left(0\right)=0\\
\\
\text{I}_{\space\text{in}}'\left(t\right)=0
\end{cases}\tag2
$$

Which gives:

$$\text{I}_{\space\text{in}}\left(t\right)=\frac{2\pi\cdot\text{C}\cdot\left(\cos\left(2\pi\cdot t\right)-\cos\left(\frac{t}{\sqrt{\text{C}\cdot\text{L}}}\right)\right)}{4\pi^2\cdot\text{C}\cdot\text{L}-1}\tag3$$

Using the given values:

$$\text{I}_{\space\text{in}}\left(t\right)=\frac{6\pi\cdot\left(\cos\left(2\pi\cdot t\right)-\cos\left(\frac{t}{\sqrt{3}}\right)\right)}{12\pi^2-1}\tag4$$

Plotting function \$\left(4\right)\$, gives:

(I used Mathematica to make the plot)

  Now I put the diode back into the circuit and it will cut every negative part of the current. So every negative part of the current will become zero and only the positive parts of the current are flowing in the circuit.

To find the (linear) average I need to find:

$$\overline{\text{I}}_{\space\text{D}}=\overline{\text{I}}_{\space\text{in}}=\lim_{\text{n}\to\infty}\frac{1}{\text{n}}\int_0^\text{n}\text{I}_{\space\text{D}}\left(t\right)\space\text{d}t\tag5$$

Where \$\text{I}_{\space\text{D}}\left(t\right)\$ is the input current (\$\text{I}_{\space\text{in}}\left(t\right)\$) with all the negative parts blocked.

Now, I tried to find the values for \$t\$ when \$\text{I}_{\space\text{in}}\left(t\right)\$ equals zero:

$$\text{I}_{\space\text{in}}\left(t\right)=\frac{6\pi\cdot\left(\cos\left(2\pi\cdot t\right)-\cos\left(\frac{t}{\sqrt{3}}\right)\right)}{12\pi^2-1}=0\space\Longleftrightarrow\space t=\frac{6\pi\cdot\text{k}}{\sqrt{3}\pm6\pi}\tag6$$

Where \$\text{k}\in\mathbb{Z}\$

  From now on I do not know how to continue.


texts:
Trying to find the Thevenin equivalent voltage for the circuit on the picture below.
This voltage is supposed to be found at the round dots to the very right in the circuit.

According to the answer sheet the answer is supposed to be 16V for the Thevenin voltage.

However I keep getting the wrong answer and I don't understand why, I'm pretty new to this so there might be something very basic I'm overlooking. I've tried several variants, but still keep getting the wrong answer, should I overlook a resistor or something?
Any help highly appreciated.

I found the \$R_{th} = 7.18 k\Omega\$

\$R_{parallel} = 2.18 k\Omega\$

\$Uth = 22V \times \dfrac{5+8}{5+2.18} = 39.8 V \$ but should be \$16 V\$


texts: Designing yet another BJT amplifier given some constraints

texts:
Sorry for asking a question about the same subject as my last question, but I am once again stuck on a BJT Amplifier design problem.

Where the beta parameter may vary from 100 to 800, the voltage between the emitter and the base equals 0.6V (active mode), Vt=25mV and the Early Effect may be ignored.

It can also be supposed that the bypass capacitors simply act as a short circuit for AC and open circuit for DC.

There are two constraints:

Input impedance > \$2k\Omega\$
Maximum possible output signal swing

What have I already done (\$i_C\$ is the polarization current which runs through the collector):

I found the signal swing equations:

\$ V_{o_{max}} = 19.8 - i_C(R_C + R_E)\\
V_{o_{min}} = -i_C * R_C//R_L\$

I also found out that the imput impedance will be \$r_\pi = \frac{\beta V_T}{i_C}\$ from the small signal model. One can infer that if the input impedance > \$2k\Omega\$ for \$\beta = 100\$, then it will continue > \$2k\Omega\$ for \$\beta = 800\$. So we can work with \$\beta = 100\$, which yields:

\$R_i = r_\pi = \frac{\beta V_T}{i_C} = \frac{100 * 0.025}{i_C} \rightarrow \frac{2.5}{i_C} > 2000 \rightarrow i_c < 1.25mA\$

From now, I don't know what to do. I have already tried some values for \$i_c\$, being able to calculate the resistances (only supposing symmetrical output) and I noticed that bigger \$i_c\$ gives biggers signal swing. How can prove that? Also, how can I solve the problem without supposing symmetrical output (having one less equation [\$ |V_{o_{max}}| = |V_{o_{min}}|\$])?


texts: I need some help with finding out how to power LED's (And how "power" works in circuits in general)

texts:
Ok, I am new to electronics, but I am getting a general idea. I need some questions answered to secure my knowledge:

If I have a device that consumes 5V and 600mA, will a source with more than 600mA work? If it does, explain to me how this works. Is it because the whole entire circuit just consumes the amount of current what it needs inherently?
How would the Voltage, Amperage, and Resistance work out if I had 2 LED strips in parallel, each taking 5V and 600mA? Please explain the math.
When making a circuit in general, what values need to balance out to make it stable? (Is it open and all you need to limit is voltage for components? What roles do amperage and resistance do to make a circuit work?)

I know I am asking the wrong things or have an incorrect knowledge, so please be patient with me and point me in the right direction. Any help is appreciated, thanks!


texts:
I have built a Binary to Unary (kind of) circuit on my breadboard.
It looks like this:

simulate this circuit – Schematic created using CircuitLab

There are three switches that represent "binary number", and according to that switches' combination, number of lit LEDs change to represent that binary number.

So for example:

A B C     LEDs
0 1 0     _____OO
0 1 1     ____OOO
1 0 0     ___OOOO
etc..

But with different ABC combination my LED's are lit with different luminous intensity...

I am wondering how do provide equal current and voltage for LEDs and make them light up with equal luminous intensity independent of switches' combination.
Probably I'm not understanding some major law in electronics.


texts: Minimal circuity for a simplex video transmiter?

texts:
I have a use case where I want to place a small video camera element at a "remote" location and be able to record the video from it. The issue is that I can't run any wires to it, it can't transmit in any RF band and there is a very good chance whatever I use at that end will have to be disposable.

The solution I'm considering is to build a support circuit that gets the camera to dump the video to a serial line and use that to drive one or two LEDs (TxD and maybe clock). With the right optics and a pickup, I an use that as a simplex link. The question then is: how simple can I make the support circuit?

An Ideal solution would consist of a battery, an oscillator and the LED(s). I suspect I might need some amps, maybe a second clock and likely a little logic. What it would take likely depends a lot on how the interface to the selected camera works. (BTW, Googleing for SPI cameras and not getting Spy cameras is non-trivial.)  I expect the camera and the battery will more or less consume the whole budget so the rest is going to have to be dirt simple and cheap.

Is this a viable project?

Edit: The kind of complexity, price and size (and video quality) I'm thinking of is something on the scale of this device. Note that I'm not including the dev board to plug it into as that would be one the receiving end of the link (and thus not potentially disposable). OTOH, from the images on that link, it seems the camera element has a ribbon cable attachment and I'm guessing is not a serial device.


texts: Inverting buffer - simple circuit, weird problem

texts:
i want to make a unity gain inverting buffer. It's usually done by placing 2 equal resistors - in this case R1 = R2 = 47k. I wanted to simulate it in LTSpice and something is definitely wrong. Is this simple circuit designed bad?

thanks


texts: Cat8 Inline Coupler Female to Female (No tools)?

texts:
There are Cat7 keystone inline couplers that are female to female like the following image where you can plug in cat 7 into both ends no tools required.

I've been unable to find one for Cat8. The only keystone inline couplers I can fine are female on one end, but the other end is meant for bare wire, where you presumably cut off the ethernet plug of the wire, using a tool to strip it, and match up wires, etc.

While yes, for many that maybe an easy enough process, my question is, why are there seemingly no cat8 inline couplers female to female like the cat7 one shown? Is it that cat8 is simply still relatively new and that most of the people using it are fine cutting the wires. Or is it, with Cat8 specifically, the other method wouldn't work because there would be performance loss not hard wiring it or such?
Also when searching online the ones with require splicing the wires are marked as "no tools", which I presume means less tools needed than previous methods. So makes it hard to search for no tools since it doesn't bring up an option like the cat7 which really is no tools, and just plug and play.
Pardon my ignorance as there maybe a very well known reason on why it doesn't yet exist for Cat8.


texts:
I noticed that RISC-V, like some other RISC architectures, by convention treats register 1 specially, using it as the link register, holding the return address for function calls.

If most code follows this convention, since instructions are aligned to 4 bytes, then r1 will follow that alignment, so the lower two bits will be predictably zero, and could be hardwired to zero, saving a few transistors. (Admittedly a tiny saving on the scale of today's chips, but it makes a good concrete example.)

But of course this is only a convention. r1 can be used otherwise; as far as the hardware is concerned, it is a general-purpose register. That doesn't mean code is particularly likely to need to treat it as a general register with all 32 bits available (since there are thirty other registers that can be used that way), but it does mean in an out of order implementation, it participates in register renaming.

When the register renaming circuitry is mapping architectural registers to a larger number of physical registers, would the existence of special registers complicate things? For example, had the architecture been defined so that the low two bits of r1 were hardwired to zero, would an out of order implementation then have an extra complication of having to track the fact that such and such a particular physical register is actually a renaming of that special register, so as to be ready to throw away any 1's that an operation might try to write into those low two bits?

Or, more generally: once CPUs start going out of order, if some registers are treated specially, does the hardware then start needing extra logic gates to keep track of which registers are renamed from the special ones?


texts:
I would like to create a project to implement an asynchronous counter (I am just learning about sequential circuits), in which 2 8-segment displays will receive input from some sensor and will indicate how many times this sensor has been activated (say, a distance sensor).
I am just starting out, so I don't really know what sort of components I should use and how exactly I can begin this project. I would appreciate it if someone could provide me with a helpful link or a component list that I should buy (I think I might need an amp-op?) and to give a description on how I should proceed with this project.
Any help deeply appreciated.

EDIT: Here's specifically what I need help with, perhaps I was too vague:
a) How to use the 8-segment displays by feeding information from an asynchronous counter.
b) How to make a signal return a logical '1' once it crosses a certain voltage threshold from a sensor
c) How do I interface the FSM counter I designed with the IC's that I should use from the 8-segment display?


texts:
How do I obtain the falling delay driving by signal A:

Data:

NMOS W/L=1/.35

PMOS W/L=2/.35

Resistor-NMOS= 1/2 and PMOS5 Kohms.micro

Cgate=Cdif=4/3fF/microm

Cmetal-ground=100fF

Cmetal-metal=39fF

Rmetal 800 ohms

1.-When B is not switching

2,-When B is switching simultaneously in the same direction than A

3.-When B is switching simultaneously opposite to A


texts:
I am using the LMD18200 H-bridge to drive a DC motor using a 20kHz PWM signal. This chip has a current sensing output which produces a current of about 377uA per Ampere flowing through the motor (recirculating currents are ignored). I would like to read this output at around 100Hz using a 3.3v ADC.

How can I simply and efficiently smooth out the current sense output ?

I know how to use a low pass RC (or RL) filter to smooth out a voltage source but I am not totally sure of how such a filter would behave in presence of a current source. Any help would be much appreciated.


texts:
I try to implement brushless motor driver using IR2301s driver. I start with testing the driver without MOSFET's. Here is scheme:

In datasheet for IR2301s given this picture:

If I understood correctly I expect to see oscillating on LO if there is oscillating signal on LIN and unconnected HIN, VS. I got it. But when I send oscillating signal on HIN while LIN and VS are unconnected I don't see oscillating on HO. THere is stable 6 V on HO. Input signal amplitude is 3.3 V. I've tried to change VCC up to 12 V, change capacity of C1 and C4 from 1uF to 100uF without luck. Where I am mistaken?


texts: What does 50%TTL - 10/90% RF mean for a switching speed measurement?

texts:
I understand what switching speed is and why it's important, but I'm confused on the description of switching speed that I commonly see in part specs, like the one below:

Diode Spec with Switching Speed Notes

Many refer to a 50% TTL - 10/90% RF, but what does this actually mean? And what does this tell us about the switching speed?


texts: What is the need for a pull-down resistor in this schematic?

texts:
here at the second page: http://www.skyeinstruments.info/index_htm_files/W200P%20Windvane.pdf

there is an external 470k resistor in parallel with the measuring device. it seems like the manufacturer wants users to connect this before measuring. but doesnt data acquisition boards  and other measuring devices have already huge input impedance? what is this resistor for?


texts: How to connect Arduino Lilypad USB to MicroSD breakout board?

texts: I'm trying to connect the Arduino Lilypad USB to a MicroSD breakout board. I'm unsure which pins to use for the CS, DI, DO and CLK connections on the MicroSD board.


texts:
I wrote a code that takes an analog input from a potentiometer and controls the frequency of a clock pulse. So, the idea is to increase the frequency when I increase the pot and decrease the frequency when I decrease the pot. It should change at a constant rate.

The problem:
When I change the pot, the frequency changes, but not in a constant rate. For example, when I increase the pot, the frequency may decrease and if I increase the pot more, it may increase again. And so on.

Here are some examples of when I keep ONLY INCREASING the pot:

The Config:

#pragma config FOSC = INTRCCLK
#pragma config WDTE = OFF
#pragma config PWRTE = OFF
#pragma config MCLRE = OFF
#pragma config BOREN = ON
#pragma config CP = OFF
#pragma config CPD = OFF

The Code:

#include <xc.h>
#include "config.h"
#define _XTAL_FREQ 4000000

void delay(unsigned char freq){
    for(int i = 0; i < (int)freq; i++){
        __delay_ms(1);
    }
}

void dClock(unsigned char freq){
    GPIO1 = 1;
    delay(freq);
    GPIO1 = 0;
    delay(freq);
}

void InitADC(){
    ANSEL = 0x11;
    ADCON0 = 0b00000001;
    CMCON = 0x7;
    VRCON = 0;
}

unsigned char GetADCValue(){
    ADCON0 = 0b00000011;
    while(GO_nDONE);
    return ADRESL;
}

void main(void) {
    TRISIO0 = 1; //analog input
    TRISIO1 = 0; //output
    TRISIO2 = 0;
    TRISIO3 = 1; //mode
    TRISIO5 = 1; //pulse_button

    char pressed = 0;
    GPIO1 = 0;

    InitADC();

    while(1){
        if(GPIO3 == 0){
            GPIO2 = 1;
            unsigned char freq = GetADCValue();
            dClock(freq);
        }
        else{
            GPIO2 = 0;
            if(GPIO5 == 1 && pressed == 0){
                GPIO1 = 1;
                __delay_ms(500);
                GPIO1 = 0;
                pressed = 1;
            }
            else if(GPIO5 == 0 && pressed == 1){
                pressed = 0;
            }
        }
    }
    return;
}

Other than that, everything works fine. Could someone help me with that?
Thank you.


texts: Converting/scaling a voltage range ([0v - 5v] to [-5v - +5v])

texts: Can anyone explain how one would convert one voltage range to another? I'm going to need to convert a range of 0 to +5 volts into a range of -5 to +5 volts. How would this be accomplished? Thanks!


texts: Can somebody help me solve this. I need to find the equivalent resistance of these resistors. I really don't know where the trick here is. If somebody could help me I would really appreciate it


texts:
I'm trying to understand if the SRAM in the STM32 is solely for speeding up the execution, or it is also considered additional storage.
Take STM32G031 as an example with 32KB flash and 8KB SRAM, and assume the compiled binary has following:

16KB .text
4KB .bss
4KB .data
4KB .rodata

Is it correct that (.text + .bss + .data + .rodata) needs to be smaller than 32KB to fit into the flash, and during boot sequence the .bss and .data are copied into the SRAM?


texts: Some electronic equipment designs are designed to clearly specified noise standards, so filter design is carried out to attain those specs. However, say you were designing a piece of DC-powered pro-audio equipment (could be anything though), where there aren't any clearly defined standards, and you wanted to filter the DC power supply coming into a linear regulator, which powers all of the analog electronics. How would you go about determining what noise amplitude to aim for at the output, over what frequency range?


texts: How to find number of winding turns for a three phase induction motor

texts:
How to find number of winding turns, number of winding wire and wire gauge (Size) of a three phase induction motor.

I know these motor parameters:

KW/HP
frequency
voltage
RPM
number stator slots
core length
diameter of stator

Is it possible to calculate the number of windings from this information?


texts: Why does a 74LS189 RAM chip light-up an LED connected to its re-inverted output when data word is HIGH while a 7489 RAM chip cannot?

texts:
I have thought on it a lot and summarizing my confusion here. I have two SN7489N chips whose Ioh is 20uA (not sufficient to light-up an LED). Correct me if I'm wrong that Ioh is the maximum current it will draw when output is high (i.e. when memory word is a low bit in case of 7489)? On the other hand, Iol is 12mA (i.e. when memory word is a HIGH bit)?

So, when I attach a hex inverter to the outputs of the 7489, which has its own Ioh and Iol readings in its datasheet, what will be my final Ioh and Iol?

Also, how can a 74LS189 chip light-up an LED connected to its re-inverted output (using hex inverter) when data word is a HIGH bit while a 7489 cannot even when datasheets of both show similar readings for Iol (i.e. 16mA)? [Source: https://youtu.be/uYXwCBo40iA?t=610 for 74LS189]


texts: A way to 'digitalize' a wheatstone bridge

texts:
I am currently using a Wheatstone bridge to determine the resistance of a NTC thermistor and feed the difference to the setpoint (analog potentiometer) as the error signal to a PID controller, giving me a way to stabilize the temperature of a sample in conjunction with a TEC to a very good degree.

Now, I'd like to have a way to instead control the setpoint digitally using a microcontroller. The first way I thought of was to simply replace the analog potentiometer by a digital one:

simulate this circuit – Schematic created using CircuitLab

However, the selection of suitable digital potentiometers (able to have 5V at one terminal and possibly a small, negative one at the other) is quite limited and the best one I could find (AD5292) has a temperature coefficient of ~30ppm/K, which is very high for the required accuracy. Additionally, the Digipot gives me a setpoint resolution of ~0.02°C, which I'd like to push down to 0.01°C.

What do you guys think of instead replacing the potentiometer by a fixed resistor, and comparing the voltage after the INA with the output of a DAC and using this difference as the error signal for the PID loop? Would this give me the best performance? (Noise/Stability of this circuit is required to be on the order of milli-Kelvins or even less)


texts: Confusion over clocks in FPGAs / Verilog

texts:
I just purchased an FPGA and I am learning Verilog but I have run into a few confusions, most of them regarding the clock.

My first question is, how does sequential logic work? Are the assignments made, one per clock cycle, or does the sequencing somehow propagate at maximum speed, determined by gate delays?

My second question is, how do frequency multipliers work? I saw an article which used one to get a 250MHz signal on a chip clocked at only 50MHz. How is that possible? If the chip is capable of operating at such higher frequencies (limited only by gate delays I would presume), then why isn't the chip just clocked at a higher frequency to begin with?

How does combinational logic in an always block work? I thought always blocks were executed on events, like positive or negative signal edges, and ran sequentially, so I am fairly confused on this point, as I have seen blocking assignments inside always blocks.


texts: Switching power supply reverse driving protection circuit

texts:
I have already "designed" (more like followed the reference design from TI) a buck regulator based on the LM3671 (https://github.com/volium/PowerSupply_lm3671) and I've been very happy with the results, ripple is good for my needs and 600 mA is more than enough for my application (simple MCU/LCD related project).

The design is based on 5v (USB VBUS) to 3.3 volts, see following schematic:

However, I have already killed at least one of the LM3671 I had because I connected the programmer/debugger, which also provides 3.3 volts to the same net, and after looking around I found that indeed, "Absolute Maximum" rating for the SW and FB pins is VIN + 0.2v. (I found that specific piece of information on the Adafruit forum for their LM3671 regulator)

So, with all this in mind, I know I should either:

a. Remove the 3.3V input pin from the programmer

b. Add some circuitry to prevent the main +3.3V net (actually, the SW pin of the LM3671) from seeing the +3.3V provided by the programmer/debugger, based on some FETs?

I know a) is the easiest, but not the best option in my opinion, since I'd like to be able to program the parts eventually without having to connect the main power supply (via USB). And b), well, I really don't know how to implement b).

I really really appreciate the help.


texts: What can be alternatives to BF494 transistor?

texts: I am currently working on a project which involves a RF Amplifier. I found BC494 to be quite suitable for the same. Though, I am looking for its alternatives since I couldn't get one of these.


texts: Can leaving rechargeable batteries in the unplugged charger for a few weeks cause batteries to lose their charge?

texts: Is it okay to leave rechargeable batteries in charger even if it's not plugged in?


texts:
I'm using an FQP30N06L to dim a 1W LED being driven by a constant current supply. This MOSFET has a \$V_{GS}\$ threshold of 2.5V, which is why I picked it since I'm driving it from a 3.3V PWM pin on an Arduino. It works fine when the drain-source voltage is under 6V or so. When it gets to 9V, it stops turning on. I always understood N-channel MOSFETS to be the way to go in this scenario precisely because they can be driven from a low voltage relative to drain (as opposed to having to drive down from a high one for a P-channel). What am I missing? What parameter should I be looking at to understand?

\$V_{GS}\$ chart for reference:

Schematic of how I'm using it for reference:

simulate this circuit – Schematic created using CircuitLab

In the schematic above, M1 is getting stuck off, but I can turn it on by bringing Gate to Drain


texts: Transducers versus Sensors - applied to mobile robotics

texts:
I am doing some basic research for an upcoming personal project, learning everything I can relate to mobile robotics. This project will be used for my personal portfolio.

So, my questions are very specific, relate to mobile robotics.

Definition of transducers, because sometimes I am confused with sensors, is hard for me, to provide a clear cut example to my colleagues. What I know is the fact the transducers convert one form of energy to another form (wiki definition and Handbook of Robotics (2008, Springer), a close example are: a photovoltaic cell, where to acquire solar radiation converting into electric energy. What applications do we have applying to mobile robotics? Is there a way to know, when I handle a device, knowing what sensors and transducers because I know there are some sensors, were worked for both ways.
Daily life applications of transducers that can be a model of reference and mental reference.