texts: What is a "Phantom Clock" RTC, like the Maxim DS1315 and how is it different to "regular" RTCs?

texts:
I am looking for some RTC on the Maxim website and noticed a few rather expensive chips that are labeled as "NV SRAM with Phantom Clock" and there is a dedicated "Phantom Time Chip", the DS1315.
The Interface is just called "Phantom Clock".

After a short look at the datasheet, nothing caught my eye that would indicate a difference to a regular RTC.

Does anyone know what they are and makes these special and expensive?


texts: Why not to use a P-Channel MOSFET in this circuit? It makes more sense, to me since the MOSFET act as a resistor when turned on which is better then the constant volage drop of a PNP.


texts: Designing a triac based regulatable DC supply

texts:
I need about (30V-160V)32A DC for my project. I am trying to build an electronic circuit to regulate AC mains (220V, 50Hz) to produce voltage from 30V to 160V and rectify it to produce DC voltage. With some inspiration from circuit diagrams posted online, I have designed my circuit (Enclosed)
Kindly comment on my method and if possible help me improve my design.

Stay safe!

Edit 1 Note.
1. The required output DC 50-160V 32A, 8 Hour duty, 2. The available input 3 Phase AC 415V, 24A per phase 3. I have got a few BTA 41, some heat sinks, some 470Kohm potentiometers, KBPC3510 diode blocks, and 10 DB3 and 10K ohm resistor each.


texts: PCB outdoor moisture effect and protection

texts:
I have been working on a project that requires me to place a pcb outdoor for days to collect data. It has been done 3 times already, and all have failed with unknown reasons. First I thought my battery is bad, and second time I thought it could be low temperature, third time I thought my circuit is bad. I have done extensive tests and eliminated all the above hypotheses.

What could be problem? My circuit has some very high resistance critical resistor components. Could this be the cause? but I have use hot glue to cover all those components all those times.

What are the precautions and methods to run an outdoor small project for about 1 week?


texts: Why doesn't current leak to ground (DC)?

texts:
In the circuit shown below, I am considering ground to be ideal earth ground (stays at 0V no matter how much current it absorbs). It is my understanding that current flows when there is a potential difference. Thus, I would expect current to flow to both the negative terminal of the battery and to ground. Why wouldn't current leak to ground? I am looking for a physics explanation.

The following two questions have addressed this issue (First, Second), but I am unsatisfied with the answers given. Specifically, one of the answers noted that the voltage source must have an equal out flow and in flow of current to sustainably generate an EMF. I don't see how this would affect whether or not current would leak to ground. Consider a source that doesn't have that constraint (it can infinitely output electrons with some set potential).

Thank you!!


texts: What is a digitally controlled SPDT switch that passes an analog signal?

texts: I thought I found what I was looking for when I found out what an "analog switch" was, but they appear to have a buffer in it, which would convert it to a digital signal. I want to pass an analog signal through. How would I do this?


texts:
I am trying to understand the need for common-mode feedback. In books such as Design of Analog CMOS Integrated Circuits by Razavi, they seem to explain CMFB with a shorted output-input feedback loop - not sure why they do it like that.

Anyways, this brought circuit in mind to me without that feedback loop. Consider

It's a differential amplifier with a PMOS current-source load. M3 and M4 are NMOS devices that are the drive transistors. They have a DC level of Vb2 and a small-signal of Vin+ and Vin-. Since, we are dealing in large signal purpose, I ignore the small-signal pertabations on the gates of M3 and M4.

Let's assume that Vb2 and Vb3  and M1, M2, M3, M4 are designed to handle 80uA. Now, let's say M5 has some error and it wants to pull down 100uA.

The lower 80uA current will win and M5 will be forced into the triode/linear region in order to supply the 80uA . Due to this reduction, the voltage at node A (Vds of M5) must decrease.

The circuit should now be in equilibrium right (ignoring the small-signal voltage). In other words, M1, M2, M3, M4 are all happy that their gate-source voltages are now at the correct level to provide 80uA.

Here come's my question, what happens at the output voltage nodes? Do they go up or down?


texts: Purpose of this pulse shaping circuit for 555 timer input

texts: In the circuit below the inverter is used to switch 12 volts into a pulse shaping circuit (10k resistor, 220-260pf capacitor, diode and 680 ohm resistor), the output of which is used as the trigger to a monostable 555 circuit. As far as I understand you can use a negative square pulse to trigger a 555 timer circuit as long as the negative amplitude is 1/3Vcc. My question is on why the designer of this circuit decided to shape the pulse instead of drive the 555 timer circuit directly from the inverter?


texts:
I'm hoping to identify the IC on this Philips Hue lightstrip controller in order to replace it.

The IC blew after a barrel connector head used had it's polarity reversed, so 24V went in the wrong way and melted pin 5 (top row, middle pin on IC in picture).

Suggestions on how to identify what it is would be greatly appreciated.

Cheers.


texts: How do I learn to design a 50Ω coaxial interconnection/interface?

texts:
I've designed an electronic load for testing power supplies (circuit and photo in this post: Designing a *linear* MOSFET driver stage).

The load can be controlled (programmed) using an arbitrary waveform from a function generator; a typical example would be using a 100mV square wave to test the small-signal step response of the power supply, although large steps, ramps and other wave forms are interesting too.

I used a panel-mount BNC connector to provide the function generator interface, wiring it to the circuit board with a few inches of 24 AWG twisted pair taken from a CAT-5 cable. I connect it to the function generator with a standard Pomona 2249-C-36 RG 58 C/U coax cable.

The external programming seems to work just fine, but I undertook the project for the sake of motivating my learning, so I want to proceed now to study how this aspect would be done by a practicing engineer and learn about the general realm of cable interface design or whatever it's called.

And that brings us to my question: "How do I find the learning resources I need to study this topic?"

A good start would be knowing what the topic is called :)  I found some questions that talked about transmission theory, but searches on that term seem to be focused on high-voltage power transmission. I also consulted my trusty copy of The Art of Electronics, but this topic doesn't seem to be included.

How can I bootstrap myself on this? I vaguely expect I should be adding a 50Ω resistor in there to match impedance, but wonder if maybe running coax with high impedance on both sides is fine too, since my oscilloscope and function generator both seem to do that by default and they use BNC-terminated coax. Also I wonder if twisted pair is appropriate or if maybe I'm introducing some possible quirks in the signal (although I don't think I can see any).


texts: Is there any technical/safety reason to ground off-grid solar?

texts:
Unlike this similar unanswered question I will keep this question here focused and specific.

Imagine an off-grid solar system: panels, charge controller, battery, inverter, AC and DC appliances. Occasionally a diesel generator will jump in.

If we set any legal/regulatory/standard requirements aside, would it be true to say that earthing/grounding such a system has absolutely neither point nor benefit?

If it would be not true, what the technical/safety reason or benefit would be, and how technically would it work?


texts:
I’m considering using a JST ACH connector with my LiPo, but I don’t understand whether the current rating on the data sheet is for aggregate or for each wire individually (which is my guess since they won’t all connect the same direction). The current rating doesn’t seem to line up with the wire gauges though, based on the ampacity charts I’ve been able to find. I’ll lay out my requirements, then my questions.

I’m using a standard 3.7V LiPo, with 1-4” of wiring. I’d like the wires to support up to 1A of current. The wires will be stranded (for flexibility), though I’m not sure how many strands or whether it is copper or aluminum (maybe assume aluminum for a margin of error, since it carries the lesser current of the two). Currently, the wire I use is 30AWG. The wires will be inside a housing with the rest of the project but will not necessarily be bundled or shrink wrapped together.

Questions:

Most ampacity charts show only single-stranded copper ratings, with only tips regarding wire variations. Do these charts apply as much for such short lengths of wire, or are they really intended for use when running long lengths of wire?
How can the connector support such a high current for so small a wire gauge (28-32AWG)? Note that this product page states:

  These connectors have a 2.0 A current rating for both two and three circuits using 28 AWG wire.

Am I just being paranoid? I really don’t want wire burning up near a LiPo. I’m considering selling the project on Tindie, so would like it to be safe.


texts: Meaning of "A voltage source “likes” an open-circuit load"

texts:
I read a book "The Art of Electronics" by Paul Horowitz, Winfield Hill.
In the book, I saw some phases.

  A voltage source “likes” an open-circuit load and “hates” a short-circuit load

  A current source “likes” a short-circuit load and “hates” an open-circuit load

It said "obviously" at the end of the first sentence, but I think I need more understanding of what it's meaning by.


texts:
In an electronic board I've found an LCD Counter and Hour Meter.
Here's the technical information.

https://docs-emea.rs-online.com/webdocs/001a/0900766b8001abd9.pdf

Since it's very expensive, I would like to save some money making it with a custom project (maybe made with a cheap LCD and an Arduino or dedicated micro).

Can I achieve the same results?

Is it so expensive (almost 25$) because it has some advantages or
 particular characteristics?


texts: Flickering on PCA9685 PWM controller with 3W RGB LED and Picobuck

texts:
I'm hoping someone here has some experience with the PCA 9685 PWM controller (16 channel, I2c interface). So far everything is working pretty well after getting the circuit connected properly. I'm using a Picobuck LED driver to drive this high power RGB LED.

The PCA9685 allowed for a PWM frequency of between 40Hz and about 1500Hz. The default is 200Hz. After setting this frequency, I can choose the pulse on and pulse off interval anywhere from 0-4096 (which is the pulse resolution). So if I want the LED on full brightness, I can set On=0 and Off=4095. This works fine and I get a nice solid LED.

However if I start to dim one of the LEDs to say 25% of it's brightness, I'll set the On=0, Off=1000. This dims the LED but sometimes it starts to flicker. I've tried a lot of different combinations of On/Off times and PWM frequencies. Even at 1000Hz it is flickering, and it gets worse when I start to use all 3 RGB components.

I'm driving the Picobuck with a seperate 12V DC source, and it has a heatsink. Do I need a resistor or a capacitor somewhere in the circuit to stop the flickering? All I'm trying to do is get the LED dimmable from 0-100% without any flicker, so I can combine the red, green and blue colors.

Here is a picture of the setup, there are no extra components - just PCA9685 board, Picobuck and the RGB LED. The red/black wires off the Picobuck are going to a seperate 12V DC supply.

What am I doing wrong?


texts: ASIC Verfication Do I need to verify all possible combinations?

texts:
I'm currently doing ASIC Black box Verification.

Suppose I got a module with 200 input ports with 12 bit width each and a one output port with 64 bit width. Lets say, its pure combinational inside.

                                  [11:0]      +------------+
                 inputport 0   ------/------> |            |
                      .        -------------> |            |       [63:0]
                      .        -------------> |     duv    | --------/----> outputport
                      .        -------------> |            |
                 inputport 200 -------------> |            |
                                              +------------+

To test the outputport, do I need to test all possible combinations of all 200 input ports?

If no, then what is a good way in verifying such module?

Is there a good way in monitoring all of the corner cases?

Will the bug(s) will eventually come out during the process?


texts: Finding Vo/Vin for inverting op-amp without input resistor

texts:
I am trying to find the gain (Vo/Vi) of the following inverting amplifier circuit.

In a normal inverting amplifier circuit with input resistor \$R1\$, I can simply use $$ \frac{Vo}{Vi} = \frac{-Rf}{R1} $$ to get the result. However, in this circuit, the input resister R1 is removed.
Assuming it is an ideal amplifier, no current goes in to negative terminal. So, current \$I1\$ and \$I2\$ are the same.
$$ I2 = \frac{(Vo - 0)}{100k} $$
I am not sure how I can include \$ Vi \$ in the equation so that I can calculate the gain.
If I use \$ Vo = A (V^{-}- V^{+}) \$ , since \$ V^{+} = V^{-} = 0 \$, wouldn't it just give me 0?


texts:
One more short question on 555. I am required to say what is the maximum possible duration of the output pulse (or signal). I looked it up online (including the datasheet for 555), but found no such parameter. What does it depend on and what is that maximum value (if it exists)?
Thanks!


texts: Are the specs for the "Ears of the World" challenge reasonable?

texts:
I saw a post today on the Make blog about a challenge to create an extremely cheap FM/SW radio kit for developing nations. The organization sponsoring the challenge distributes donated wind-up powered Grundig radios, but they're relatively expensive, get stolen, can't be repaired, etc.

The specs they are looking for are certainly challenging, but may all be reasonable except for the power. They are asking that the radio be powered by a single AA battery (it may also have a solar cell) and contain a LED bright enough to use as a small lamp.

You can read the specs here: FM Radio Challenge

My question is whether this community thinks that these specs are just written by non-experts. Is a practical device do-able with that power? Assume the price requirement could be met (the solar cell may be the priciest part). If a single AA was chosen due to its ubiquity, would a high quality rechargeable battery still meet the needs?

And yes, I did really want to put this challenge in front of the readers here by putting it in the form of a real question. Note that it is tagged community wiki.


texts: How is a display with colored cylinders instead of flip-discs / flip-dots called?

texts:
The Rossio railway station in Lisbon (Portugal) uses little colored cylinders for parts of their displays (marked in red).

I'd be really interested in getting more information about them, but I couldn't find anything about them online.

The only reference for something similar is http://tpdomain.blogspot.com/2017/08/full-color-mechanical-display.html where someone proposes to build such a display (apparently not knowing, that it already exists).

What are they called?
How exactly do they work?


texts:
I want to build my own dev board (mostly to understand some concepts), and I started from some schematics that I found on the internet, but I have some questions about this schematic:

Why do I need those 3 capacitors (C2, C3, C10) on the VCC pin of the
atmel? And what is with those values?
If I change the values, will it affect the circuit?
If I remove those capacitors from circuit, will it affect it?


texts: Voltage sensing using Arduino with and without common reference

texts:
I wish to make a voltage sensing circuit (range -15V to +15V) using an Arduino's ADC. The problem is that since this circuit will be part of a much larger circuit in which the Arduino is performing many other functions as well, the circuit needs to work both when the Ground of the Arduino and the Ground of the circuit whose voltage is to be sensed are shorted, and when they are not. I do have a waveshaping circuit which works when the grounds are shorted together. Please suggest some circuit or any other way I could approach this problem. The two circuits I have designed can be found at:
!(http://imgur.com/lv0UKya)
!(http://imgur.com/ISq9ou8)


texts: How do I increase the drive current from the arduino digital pins?

texts:
I'm new to the Arduino (using the Leonardo). I am working with a heatplate that gets hot when you apply power to it.

When I use the 5V Vcc pin it works fine. But when I use the digital pins I don't get enough current.

Is there any easy way to increase the amps you can get from the digital pins?

Would somebody have a simple driver circuit?

Thanks for the answer. This is my setup. I don't know exactly how much current the plate needs to get a high temperature fast, but i'm guessing in the range of 0,5 A - 1 A.

So basically, I need to use the transistor as a switch and then use another power supply for the heatplate-thingy ?

EDIT
This is a picture of how I planned to do the setup. Feedback is very much appreciated.


texts:
I'd like to know if I am going in the right direction in my methodology for sizing a thermal solution for some power MOSFETs in a controller.
To give some background, I am switching a couple of different loads, 1 24V@100A continuous max, 4 24V@30A continuous max, and several smaller 5V loads, all using FETs physically near each other. In this controller's application, all of the loads may be max-ed at once, though this is unlikely.
Before any one asks, yes, switching them is necessary. Believe me I tried getting around it, but to no avail :( .
Any way, my methodology is as follows:

Group the FETs thermally under one heat sink to reduce cost and complexity, and since they are already physically near each other.
Calculate the total heat dumped into the shared heat sink at once.
Calculate the thermal resistance of the heat sink from thermal load to ambient to keep the FET with the highest junction to case thermal resistance under or at my max operating temperature.
Slap a margin of 20% on top of the number to build some wiggle room into the design.

Is this a good way to go about solving this problem? My background is Aerospace Engineering, so I tried to take what I learned in Thermodynamics all those years ago and actually apply it, I have no idea if heat calculations are done differently in the electronics world.
Thanks for the help!


texts: Why is balancing used for lithium batteries only?

texts:
I have never heard of a lead acid battery having any electronics to balance it's cells, or even any manual way to balance them.

But I think all lithium batteries have, or at least lithium batteries above a certain size.

Why is there this difference between lithium and lead acid batteries?

Let's say I take four 12V batteries and put in series. Would I ever need, or would it be beneficial, to have any balancing, or can I just pretend it is one 48V battery?


texts:
I implemented the following schematic trying to follow Jon Watte's reply to this question.

There are two things I don't understand:

Why is the probe Q14 showing 4.34 volts?  Why is it not closer to the 12v from the power source?
Probably closely related to the first question: what's the purpose of R15 in this schematic?

PS: I'm a newbie at electronics and well aware of it.  Keep in mind I'm more than willing to read more theory if pointed to the right direction.  Right now I'm a bit at a loss because I don't know exactly what it is that I'm missing.

Edit: added image showing the same schematic with the logic-level pin R6(2) at 0V.


texts: Driving Delta-Sigma ADC with reference clock output from MCU

texts:
I am sending out the  PB clock (32MHz which is PLL multiplied) generated from the internal FRC on a pin to feed into an ADC as a master clock after probing it at 32MHz. This is what I see.
It doesn't look like a pulse in anyway but the duty cycle and frequency almost match up.
Could anyone tell me the possible cause of this issue?
Is it going affect the conversion data rate?
I have also snapped the PCB trace here just in case it could be capacitance from there.
PS: I have traces on both lines and I had an intention of using a stand alone crystal oscillator but totally messed up with the footprint. Luckily I had this alternative.


texts: Can I use a DC power pack (12dcv 3a) with an inline connector rated at 24dcv 2a?

texts:
I have a power pack that is 12v 3a, I want to buy an inline switch so it can be turned off without having to unplug it. The following image is of the inline switch. It is rated for 24v at 2amp. If my understanding is correct, I can just multiply the V by the A and as long as it's lower than rated it's all ok.

Inline Switch: 24v x 2a = 48 watts
DC Power Pack: 12v x 3a = 36 watts
So it's ok to use.

Is this correct? Or am I mistaken and the switch shouldn't be used with this power pack?


texts: NE555 - astable flashing alternative LED circuit

texts:
NE 555 help - astable alternate flashing LED circuit
"In the circuit, the LED1 lights when the output pin has a HIGH state and LED2 lights when the output is in a LOW state." - I couldn't understand this statement in connection with the diagram:

Here I see a normal LED1 connected to output terminal 3 and to ground and I can understand as how Vcc / high output will appear and then the LED will turn on ,
What I can't understand is how LED2 turns on when output is low: we know LED2 is connected to Vcc and the negative terminal to output 3, when current flows through it and turns it on, the output at 3 should be low to have a voltage difference and hence led 2 turns on.
But then when current flows through LED2 - after flowing through 2, where will it travel, as pin 3 is the dead end as the output there is low, can current flow inside the push-pull amplifier (which inverts the output from flip-flop ) and then flow to ground via discharge transistor or am I missing something?


texts: Why a transistor (MOS) changes the output current (Ids) with changes of a load resistor?

texts:
I am a newbie, and I can not understand, why current of the MOS changes if I change the resistor.

Basically, why transistors so depend on load? And how I can calculate changes..

Regards,
Paddy


texts:
i have a problem understanding the transmitting function of SPI in atmega16
the function that i don't understand is

void SPI_SendByte (s8_t data){
SPDR = data;

/* check if operation of transmit or receive is running */
while (bit_is_clear(SPSR,SPIF));

}

i think it should replace the two lines like this one here

void SPI_SendByte (s8_t data){

/* check if operation of transmit or receive is running */
while (bit_is_clear(SPSR,SPIF));

SPDR = data;

}

aren't we suppose to check if busy first , then write the data ??
why we did otherwise , in other communication protocol like UART for example we first check for busy then we write to register , why it's not the same in SPI !!?


texts:
Need to find VR1 and VR2 in the circuit when: A) D1: forward D2: forward B) D1: reverse D2: forward C) D1: forward D2: reverse D) D1: reverse D2: reverse. Show calculations. E=9v R1=10kohms R2= 4.7kohms

I calculated 8.3v for VR1 but I don't know how to calculate VR2. The right side of the chart shows what I got from the meter when I built the circuit.


texts: Why do we use resistors(R1 and R2) in transistor NOT gate?

texts:
Why do we use R1 and R2?
What happens if R1 and R2 are absent?, will the NOT gate still work?


texts:
I am going to be working with many capacitors that can easily kill me (kV range), and I was wondering if there was any kind of industry recommended method/tool for discharging a capacitor to make sure it is safe to handle. Id prefer a general tool that gives a decently high load across the terminals. The only things I could find were seemingly application-specific large value resistors.

The perfect tool in my mind would be a rod of some high resistance, high specific heat material with a thick rubber handle. A resistor with dinky little leads can be dangerous in itself to use, and a longer rod seems just like a better idea.

Suggestions?


texts: Is it absolutely necessary to correct for a temperature drift in the resonant frequency of an ultrasonic transducer?

texts: I'm designing a device which will use ultrasonic transducers in a way similar to sonars. Is it absolutely necessary to correct for the drift in the resonant frequency due to temperature fluctuations? How much will the performance of my system decrease should I choose not to to this? How would I even get around doing it?


texts: Need Programmer's Reference Manual TI Stellaris LM4F120H5QR

texts:
Just searched the Texas Instruments' website for LM4F120H5QR  Programmer's Reference Manual

Found nothing.

Example...

While stepping through some code, I come across this instruction...

  0x4E:  0xdbfg  BLT.N   0x44

...and I want to see what flags affect this instruction, and how the decision is made.

I thought that the name of the document that explains this was The Programmer's Reference Manual.

Evidently not, because I can find no such manual on TI's webpage which has the docs for this chip (THIS PAGE is the only place I knew to look for it).

Question: What is the name of the manual I want ?

Question: Where do I find it ?


texts: Finding Charge of a battery without knowledge of prior charge

texts:
We have a battery connected to some circuitry. Currently, we have all charging of the battery going through a LTC 2944 sensor, and all discharging going through another one of those sensors. We are trying to write software to read values from those sensors and get an idea as to the SOC of the battery. However, every method I am finding online (I.E. by voltage, Coulomb counting, etc) require you to know the previous state of charge of the battery. Does there exist a method of finding what state the battery is currently in, without any prior knowledge of the battery's charge level?

I have found numerous other responses to this, but once again they all require some other knowledge of the battery's current state. Any explanation (or out right refusal) of this process would be much appreciated.

(Edit):

The battery is a Lithium Iron Phosphate battery. From data sheets from the manufacturer, it seems both the discharge rate and voltage stay constant until the battery is fully depleted.


texts: Good way to switch AC/DC (Rectifier) in welder

texts: I am building a homemade welder out of microwave oven transformers.  I would like to have ideally an on off switch and then an AC/DC switch or just having one switch would work too.  AC 120V 60Hz comes in through the wall, gets transformed to high current lower voltage and the leads from that go to a bridge rectifier and that's the output (a little simplified).  I'd like a way to bypass the rectifier using a switch setup so that I could do AC and DC welding. I can't use a polarity like switch with the high current cause the switch will probably burn up or weld together.


texts: Component with multiple VCC and GND pins. Should I connect all of them?

texts:
I want to make a really small arduino using the Atmega 328p and I noticed that it has 3 GND pins and 2 VCC pins.

I measured the pins and it seems that all GNDs are connected and all VCCs are connected to each other.

Can I rely on this feature to make my arduino schematic?
Is it a good idea?
Can I rely on the same idea for other components with multiple VCCs and/or GNDs?

Cheers


texts: How to connect two Ethernet switch ICs together using MII Interface

texts:
I have been searching on how to connect two Ethernet switch ICs together.
I have designed a custom PCB. Beside some other features, it accommodates an Ethernet Switch IC. This works OK. The bandwidth I use is not more than 100 Mbps.
It is time now to expand Ethernet ports by connecting two Ethernet switch ICs together. They will be very close to each other, a few inches perhaps.
*IC's datasheet: RTL8306E*
I have walked through the datasheet but I am stuck at the 6th port.
RTL8306E has 6 ports. I use 5 ports of it as they have Rx+- and TX+- pins.
In order to connect to the other RTL8306E Ethernet switch, I have only port 6 at hand. But this has different interface so called MII.

And some configuration table from the datasheet:

Q1: Is it possible to use MII interface between RTL8306E Ethernet switch?
If so, how?
Q2: If not, can I turn port 6 MII interface into a regular port like the others on the IC? So it would be easier to connect it to any Ethernet switch either by magnetics or without magnetics or just capacitor coupling.
Since I am new to those, I like to hear your opinions and experiences.
Any input greatly appreciated.


texts: Potentiometers: definitions, applications and how to choose?

texts:
I've got some newbie questions about potentiometers that I can't seem to find in my reference materials.

I've been doing a lot of experimentation with potentiometers, and frequently run across linear vs. logarithmic pots. From the data sheets, I can see the graphs and understand how the output is affected by messing with the pot. My experiments have been limited to messing with what's on the parts list and swapping out linear and logarithmic pots to see what happens. I don't see it. Perhaps the difference is too subtle at the voltages or applications (changing the brightness of a blinking led or the volume of a click to a speaker) I'm working with,  but it doesn't help me understand which to use.

What are some sample applications for which one would use linear vs. logarithmic, logarithmic vs. linear, and why?

Also, I sometimes see an "audio" potentiometer. Is this a third type? or is that a synonym for linear? The data sheets seem to match linear pots of the same rating more oftyen than not.


texts: Can I replace a music toy speaker with a 6.3mm jack?

texts: This toy keytar gas an 8 ohm speaker and adjustable output volume. If I simply replaced the speaker with a 6.3mm jack to use it with guitar pedals and speakers that can handle the line level, would I get any other issues? E.g. impedance problems?


texts: joining signal and power grounds together

texts:
I've read some questions and answers here about making 2 separate grounds - one for signal, second one for power. Every question was about the case where the grounds meet each other in one point.

I came across mixer schematic and there are 2 grounds: channel ground (signal ground) and power ground. They aren't joined together, the thing that joins them is a capacitor. First question is: can it work like that? The answer is probably yes, because it's a schematic of a working device that is on the market. Second question is - would it be better to join the grounds by resistor not by a capacitor? I've read and article about HBR (hum breaking resistors) and maybe this would be a proper application of such element?

And final question is - how to run 2 grounds on the PCB? Should power ground or signal ground be distributed as a plane? Or no ground planes?

Extra question is - to which ground should i connect the shield of the shielded cable?


texts:
This is a follow-up question on this answer. I need to communicate with I2C over approximately 10cm and I'd like to use an FFC or IDE cable for that.

Earlier, I used an FFC cable to link a segment LCD screen to a 7106 IC. Some segments flashed a bit, and after some testing I found out that was because of interference between the wires. I used a standard flat IDE connector cable from an old computer for this.

I'd like to know if I2C could have problems with communicating over 10cm of a FFC or IDE cable, when data and clock line are directly next to each other. If so, is there a way to resolve this? Would placing a ground and 5V line in between help?


texts:
I want to do dc simulation of differential amplifier circuit, and this is my .cir file looks like:

When i run simulation, ngspice give me an erorr:

Supplies reduced to   0.1000% Warning: singular matrix:  check nodes vin1 and vin1

Supplies reduced to   0.0000% Warning: singular matrix:  check nodes vin1 and vin1

Warning: source stepping failed
doAnalyses: iteration limit reached

run simulation(s) aborted


texts:
As in Attached pics its wide band flat notch antenna, Why it having two RF cable to connect. Is it for antenna diversity or for somewhat.

Datasheet link is below, couldn't find much info on this.

http://taoglas.com/images/product_images/original_images/FXUB71.A.07.C.001.pdf


texts: Inductor Voltage and Current After Switches Open and Close

texts:
I was given this problem where switch s1 and s2 are opening and closing at different times.
I have already solved for the voltages and currents, but now I need to plot vL and iL at each time. My question is, when I plot the voltage and current, will the values jump instantly? For example, the current at 1 second is 40A and at 3 seconds it is 20A. Should my graph immediately change from 40A to 20A or will there be a linear decrease?
Here is the schematic and the graph showing when each switch opens and closes.


texts:
According to the L293 Datasheet, the Maximum Supply Voltage(VCC1)(supply for internal logic translation) is 36V. It is also mentioned that Max Input Voltage(V1)=7V whereas the Max High Level Input Voltage(VIH) is VCC1.

If my supply to VCC1 is 12V. Will a 12V HIGH logic Level(i.e. Logic HIGH= 12V; Logic LOW=0V) given to the logic pins(1A,2A,3A,4A) damage the IC?
When no motor is connected to the L293D, how much current does the IC draw alone?
I am aware of the fact that the L293D dissipates heat through its GND pins(GND plane).Will a Heatsink placed on top of the DIP package of the L293D dissipate heat efficiently?


texts: Receiving a whole string from USART on ATMEGA16?

texts:
I am trying to receive a string from USART but failed , i want to receive char by char and store them in an array until the user enter '\n' and finally display the string to LCD , here is my code:

char REC;
void USART_Init(unsigned int BAUD )
{
unsigned int ubrr;
ubrr=F_CPU/16/BAUD-1;
/* Set baud rate */
UBRRH = (unsigned char)(ubrr>>8);
UBRRL = (unsigned char)ubrr;
/* Enable receiver and transmitter */
UCSRB |= (1<<RXEN)|(1<<TXEN)|(1<<RXC);
/* Set frame format: 8data, 1stop bit */
UCSRC = (1<<URSEL)|(3<<UCSZ0);
sei();
}

ISR(USART_RXC_vect){
REC = UDR;
}

int main(void)
{
lcd_init(20);
USART_Init(9600);
char data[10];
while(1)
   {
    int i = 0;
    while (REC !='\n')
    {
        data[i++]=REC;
    }
    data[i]='\0';

    lcd_puts(data);

   }
 }


texts: Altium: Design rule for single object in PCB

texts:
I have a polygon pour whose contact to a pad shouldn't have a thermal relief, so the plane can dissipate the component's heat. All other polygons should keep the default rule, with reliefs.

How do I make a rule that targets that single polygon pour?

The polygon is named "5V_Dissipator". I've tried creating a rule that targets this polygon with InNamedPolygon('5V_Dissipator'), but when I repour it the PolygonConnect, which is set to All, always dominates making the contact with the pad have a thermal relief.

I've also tried Name = '5V_Dissipator' and InComponent('5V_Dissipator'), that don't work. I don't understand how this is supposed to work.

If I remove the thermal relief from PolygonConnect (by changing this rule's properties) it works well, the polygon repours correctly.


texts: DC-DC converter current limiting for charging LiFePo4 battery using SLA battery

texts:
I have a DC-DC converter which converts 9-36V to 13.8V with a 20A rating. I would like to use this converter to charge a 100aH LiFePo4 (with BMS, see: https://ca.renogy.com/renogy-smart-lithium-iron-phosphate-battery-12-volt-100ah/) from my car's 12V SLA battery.
From what I understand, the 13.8V output of the DC-DC converter works for charging my LiFePo4, but I don't believe that the converter has any current limiting built in. I assume that this means that when I connect the batteries using the converter, the LiFePo4 will immediately try to draw as much current as possible.
The converter has over-current protection, which I assume means that it will shut off at >20A.
What is the simplest way to add current limiting to my setup? Or... can I use the DC-DC converter as is?


texts:
Solving the circuit below and as part of that I'm figuring out the purpose of these different capacitors.

Coupling capacitors at the input and output to separate bias matters from the AC signal
Emitter capacitor CE to bypass emitter resistance RE in order to boost AC gain

What is the purpose of capacitor CS? I can't seem to figure it out.


texts:
I have this circuit (see first picture.) it's an analog shift register where instead LF386 I use LF398H. This circuit must provide an hyperchaotic behavior for initial conditions x1(0) = l, x2(O) = O.l, and x3(O) = 0. The Sample & hold signal appears once per second and the signal looks like this.(see second picture) where the green signal is S/H1 and the blue one is S/H2. I made a simulation for 10 number generated by the circuit but I saw a problem in the interval [4;5]s the value should be -1.4025 V but in my case my signal stays for a short time in that value after that the voltage starts to increase(see the last picture.) and because of that my next number will have the wrong value. My question is why is this happen and how should I solve it.
BTW I tried with a smaller capacitance than 0.94uF and it didn't worked.


texts:
I have to do a DC DC conversion from 36V to 32V @1.5A. I found some switching regulators, but no linear regulators.
I'm not sure using a switching regulator is the best solution (price, overkill, efficiency) to reduce voltage.

What would you advise?


texts: STM32L031 not running after stopping debugging

texts:
I'm using a STM32L031 with Eclipse for my application. When in debug mode everything works fine. But when I stop debug mode or power off and on again, the STM32L031 stops working.

I had expected that after downloading the code into the chip, it should work whenever I power it on.

And since I'm not using an evaluation board, there is no reset button so I cannot reset it.

How to solve this problem? Or is there a way to reset the chip without requiring the Reset button hardware?


texts: In a simple LDO regulator, is the op amp working in positive feedback?

texts:
Below they're connecting the feedback voltage FB to positive pin of op amp. Isn't this positive feedback ? Because, when the output voltage increases, the feedback voltage increases, which then increases the op amp output.

But my textbook claims that the output voltage is stable because of the heavy negative feedback. I'm not able to see negative feedback here. What am I missing  ?


texts:
During testing on my pcb I am running into a couple of problems the first issue is with either my momentary switch or my MOSFET Q4 – PMV30XPEA. For my switch design, I have implemented Fig. 5 on MOSAIC DOCUMENTATION WEB Latch and Toggle power circuits article, which is quick press on – 3 sec press off. During testing, I have had to hold the switch down for about 5 seconds before it turns off. I am using the switch – KSS221GLFS.

The upper right hand side is where the switch and Q4 & Q5 is located. I'm using a 3.6V LiPo and boosting it to 5V DC/DC converter.

Do any of you have any suggestions as to why this is happening?


texts: Could I use a surface mount thermistor to measure ambient temperature?

texts:
I'm working on a project where a device I'm using has this thermistor, a Murata NCP15WF104F03RC, to measure the temperature of the device itself. This is a surface mount thermistor. The implementation of my project requires ambient temperature sensing, and comparing the two temperatures.

I figured the easiest way to do this would be to use the same thermistor for ambient temperature sensing, as they would have the same thermal resistance curves and other relevant characteristics, which would probably help with precision of comparison.

Are there any glaring flaws with this design decision?


texts: How to make a restart circuit for my circuit

texts:
I have a circuit that is on a shield type pcb and would like to create a "restart" circuit, where the circuit's power is cut and reconnected after a set period of time. I was worried that if the chips in the circuit for some reason gets stuck at least I have a way to hard restart it.

The circuit contains some ADC, PORT EXPANDERS.

The solution that I came up with have me worried on some questions.

I made a circuit like this:

The idea is pretty simple: use an NPN transistor to give power to the whole circuit.

My worry now is: The ADS1115 is an Analog to Digital Converter and connecting its ground pin to not the actual ground worries me that it would affect the reading.

How can I solve this?

I also don't like some weird interference shut the circuit down because of some sudden drop in voltage in the Base(I forgot to put a resistor in the Base).

How would I modify the Base to prevent such event? Should I pull it up and add some capacitors, and only let the GPIO to LOW to reset it?


texts:
I have already looked and found similar things but still couldn't solve my own problem.
I have an input voltage of 9V to 11V and I want to scale it to 0V to 5V. It's better if it is linear but it's not an obligation.
I have tried using an inverter setup with a potential divider bridge at the inverter input but I can never go down to 0, it is always minimum 1.
I am allowed to use LM741 or equivalent.


texts:
We recently acquired a very old saw that accepts either 220V or 120V.
It came with a suicide (male-male) cord, in turn going to a female-socket cable:

which in turn goes to a DPST switch:

in turn going to the motor assembly. The motor details are difficult to photograph:

This thing is somewhat of a death trap. The spades on the switch have already shorted together once and tripped a breaker. The switch is probably dual-pole because it supports 240V, but we are only ever going to run it single-phase 120V. In my imagination, to make this thing safer, I would:

Disconnect the neutrals from the switch, short them to each other and cover the connection with heat shrink
Unscrew the suicide cord plug and swap genders so that the male plug is appliance-side and the female socket is wall-side
Add more heat shrink around the live spades on the switch to insulate them and prevent them from shorting out

Does this seem reasonable?


texts: LED-strips, resistance, and voltage drop -- full on layman question

texts:
When knowledge and ambition diverge-- ask.
I have a number of LED strip lights on my boat.  The ones I use for long periods eventually die, and the ones that only get intermittent use are still going strong.  I have a lot that still work and even more new strips on rolls that i would like not to waste.
The house voltage is about 14.4V, i suspect this is too high, and i'm not willing to change this.  I have used LM 2596 buck converters on a few strips and i believe that has helped.  Nothing about this is expensive but I am remote, and don't have access to shops to buy this stuff, and I also don't want to bring a whole bunch of circuit boards into the world for no reason.
So first question: Is voltage my problem?
2nd question: Can I use resistors to drop the voltage down, and if so how do i calculate the value?
I understand this is a basic question, I just want to fix problems and learn.  I have limited resources and when i experiment blindly i tend to brake stuff before I start getting results.


texts: Is Atheros AR6102 all I need for my Wi-Fi SD card reader?

texts:
I was recently asked to create an iPhone app to allow the user to view, download and remove photos from an SD card. We can't use the card reader originally chosen, and for some reason I thought it would be possible to build an SD card reader.

First off, the Eye-Fi card integrates your typical SD card with a tiny Wi-Fi brodcast that allows editing the card content over the Wi-Fi connection. The link is to the archived card teardown page which I used a lot to understand the mechanics. The page no longer exists. This page is a big help, because I am wanting to take the parts of this card that are not part of the standard SD card and put them in a separate device.

The Atheros AR6001GL isn't around anymore. There are a few chips that took its place. I chose to go with the AR6102. This card has the pins to communicate SDIO and appears to be able to communicate with the SD card without any other chip between. I have read several sources on this card, and I am still having trouble completely understanding how it works.

Will I be sending the commands to directly communicate with the SD card or will I be communicating with the AR6102 and it handle the actual commands to the SD card?

It seems like all I need to do is create a PCB with the AR6102 connected to the SD card contacts, the antenna, and the appropriate clock-speeds, powers and grounds, and I will be able to connect to it over Wi-Fi and start reading and writing. Is all of that really handled for me by the AR6102? Qualcomm Atheros' AR6102 product overview (link) sure makes it seem this easy.

What else do I need to be able to communicate with the SD over Wi-Fi? I feel like the schematics for the application guidelines (PDF) on page 25 is trying to tell me what else I need, but the only part I can understand I already know is needed.


texts:
Reading this topic from "The Art of Electronics" : Integrators

How does RC keep V << Vin?


texts:
I'm testing a board that is having clock issues. The design uses a 40 MHz oscillator, which outputs a clipped sine wave. The clock goes into an inverter buffer to get a 3.3V, 40 MHz sine wave. When scoping the clock, there is some distortion seen on the positive peaks (shown below). I've noticed that the sine wave is fine before going into the first inverter. The issue pops up on the other side of the inverter. My suspicion is that the inverting feedback resistor value might be the cause of the issue I am seeing, however, I can't find anything that could explain the distortion I am seeing with my clock. I've also read that add a small resistor value to the input of the inverter will help reduce ringing as well. Is that the case and can someone explain to me why/point me to a direction where I can learn more?

Any insight is greatly appreciated.

simulate this circuit – Schematic created using CircuitLab


texts: How are the frequencies in 50 GHz channels in DWDM networks used?

texts:
In optical DWDM networks, the spectrum is classically divided into several 50 or 100 GHz channels.

So, let's assume some channel ranges from x to x+50 GHz. On which frequency/frequencies is the signal sent?

It would be a reasonable choice to use x+25 GHz as a frequency to transmit the signal on, however, I was wondering whether one could also use x+12.5, x+25 and x+37.5 for instance, or even more frequencies simultaneously.

How is this usually handled in DWDM networks?


texts: Why do 100 nF ceramic disc capacitors from multiple sources, measured with two instruments, all appear to be below tolerance?

texts:
I have a collection of 100 nF ceramic disk capacitors, which came from three completely different sources. They are all through-hole packages comprising brown disks and two leads, and marked only with the code 104.

My understanding is that, since there is no tolerance code, I should treat them as having a capacitance in the range 80–180 nF (-20% to +80%).

I have two instruments for measuring capacitance. One is a cheap digital multimeter, and the other is a cheap general purpose component tester that I bought as a DIY kit and soldered together. They give capacitance readings within about 10% of one another.

No matter what capacitor or instrument I try, the measured capacitance is about 45–75 nF, which is well below the tolerance range.

Are there any "obvious" (not obvious to me!) explanations for this phenomenon? Bad capacitors? Bad instruments? Some kind of resonance effect?


texts: Brake feature with phase/enable control for DC brush motors

texts:
I'm studying the datasheet of DRV8256E/P, and I need to select which kind of control to use: phase/enable or PWM.
As far as I understand, the PH/EN mode is easier to handle because it requires only one PWM output from MCU (EN) and the other pin is just a digital output that define the direction of rotation.
I'm also aware that the PWM mode allows greater control and table 7-3 shows how to achieve the brake effect with this approach.
My question is: the PH/EN mode is completely unsuitable for applications that need a brake, even very slight?


texts:
I am trying to repair a Revox B77. The issue is that the whole machine is live. I am looking to know if the issue is with the voltage selector or even some guidance as a starting place where to look in order to make it safe. The machine works fine but is obviously dangerous. Any help as a starting point would be gratefully appreciated.
I have made a video and strung together what i can showing the machine Revox video


texts: How do you drill a homemade double sided pcb

texts:
I have a PCB that I am prototyping at home and it is double sided.... When I drill on one face the other face peels up a little.

Does any one know how to avoid this problem?


texts: How Does the Positive Feedback Bring an Oscillator's Poles on the Imaginary Axis?

texts: In an oscillator, there is a positive feedback that injects energy into the system in order to sustain the oscillations. This feedback places the system's poles on the imaginary axis. I'd like to know how the math works, and how exactly the feedback moves the poles from the left half plane on the imaginary axis.


texts: Using PID code different from its mathematics equation

texts:
I asked this question at stack overflow but i did not receive any replies, i think it was the wrong place to ask, so i am re-posting it here.
Short question: How wise is it to change the PID formula/equation based on the needs of your project?
Is it really a technique a proffesional would use?
Longer question: I am making my first PID in embedded MCU (Atmega328p).
I have a hotplate and i want it to reach a certain temperature, and i made it, easy.
As a reference for my PID i followed electronoob's tutorial. what i dont understand from his tutorial, is the line 171 of his code:
  pid_i = pid_i+(ki*error);

His integral is using the error instead of the dt (time lapse). I see in the video (and i understand why he does that)
He actually does this:
/*The integral part should only act if we are close to the
desired position but we want to fine tune the error. That's
why I've made a if operation for an error between -2 and 2 degree.
*/
if(-3 <error <3)
{
  pid_i = pid_i+(ki*error);
}

So the question is how wise is it to change the default PID equations to match your project?
What would you consult me to do to my present/future projects regarding changing the basic PID formula?


texts:
I'm using a NE555 running at 37KHz to generate a carrier frequency for transmitting IR.

Now I need to modulate it using OOK, I know that are various ways to toggle it.
The most obvious way is to toggle the output using a transistor, but I don't quite like the ideia of let it running the whole time, considering it will be most of the time sitting idle.

And I don't know if toggling Vcc would work, I don't know if it oscillate right on, and it will requite a PNP switching transistor rather than a signal transistor.


texts:
The idea of this question came from a DC motor that produces less torque by greater speed.

Can an electrostatic motor produce constant torque at varied speed?
How can I make a mathematic model of this type of motor (for comparison with a DC motor?)

For question #2 as far as I know \$ F = \frac{k Q_1Q_2}{r^2} \$ and the current will flow while charging/discharging the rotor.
Note: Referece motor for my question youtube video.
THis is picture capture from video.


texts:
In order to connect two small electrical circuits, I needed 17 pins. Because of its availability and compact form, I chose the HDMI connector.

The two circuits are connected using an HDMI cable that was provided with a computer screen and everything worked as expected.

I tried with another cheap HDMI cable but it doesn't work and I see some missing connections. However, this cable works for its intended purpose: connecting a screen to a computer.

If I take a multimeter and test the ends of each cable, the results vary.
For the "good" cable, I get the "beep" for all 19 wires whereas, for the "bad" one, more than a few show no connection.

From this SE link, I understood that there are no unused pins in the HDMI standard. Is there any kind of redundancy function or something that could explain why a functional cable seems to have pin conductors between some pins?

Edit
Connections are as follow (bold is connected):
19 17 15 13 11 9 7 5 3 1
18 16 14 12 10 8 6 4 2


texts:
I'm designing this general purpose mosfet controlled output, and I'm used to putting D1 due to possibly inductive loads.

However I was looking into some other implementations and this guy suggests putting a shunt capacitor (C24 in my schematic) to deal with some ringing when driving cables. Looking some more into it, I couldnt find any version of this snubber without a resistor, so I wonder how do I estimate a good value to deal with some possible ringing? Is there a ballpark I can work with? Is it even necessary? I've driven long cables and motors just with the diode without apparent issues. However if there is a remote possibility of needing it I'd like to leave the footprint on the pcb so I can populate if needed. Im looking into driving up to 10A at 12V~30V max.

I'm also looking into putting a totem pole gate driver, is it a good idea to still leave a pull down(10~100k) from Gate to Source? Again I can leave it unpopulated on the PCB, or I can remove it from the design if its absolutely useless/unnecessary.


texts:
I am trying to design a programmable electronic load for testing the PWM outputs of PLC controllers. The outputs operate between 5-36 V and 10-2000 Hz frequency.
The output is supposed to tested for upto 300 mA current. Based on a current sink circuit from the Internet, we designed this particular circuit.

V3 is the µC/RPi Output that we plan to use to control the current output at sense resistor R2.
VOutput1 is the PWM signal that is going to be generated by our PLCs.

Now I have a few questions regarding this circuitry.

When i try to simulate this for lower values of current between 1 mA to 150 mA i always have certain overshoots for a few µSecs before it settles to a square wave signal. Why is it so? Here is the result for 20mA.

After reading few articles on the internet i figured out that it is the gate capacitance that could be causing this problem. In the initial stages of circuit designing i ended up using up mosfets with very small Ciss ( 8pf to 55pf on diff SMD Mosfets). On simulation they gave perfect results.However since i expect a power dissipation of upto 10 W at the Mosfet i have no option than to use a bigger Mosfet but then they have large Ciss which brings the Overshoots with them. Can anyone suggest a solution to this ? Could the OP-Amp controlling the gate voltage be blamed for this phenomenon?
Instead of the LTC6752 i had previously used a normal OP Amp AD8031 as a comparator at U3. Now this particular change i did based on recommendation of a senior. He advised me to keep a normal OpAmp and use the NPN-PNP(BC547B-BC557C) transistor as switch.He said this is because the op amp which i used previously (LM239) was an open collector comparator. And for this particular purpose we need to use an Open Emitter Comparator for which i couldn't find a spice model and hence this solution. Now i am guessing LTC6752 is also an open collector comparator.Because when i replaced AD8031 with this model i didn't find any change in the output.Can anyone explain the reason for using this open emitter configuration here and is it recommended to use any op amp instead of LTC6752?
I was looking at the simulation results and found out that the Feedbck signal goes shortly to 0V and then comes back to µOut value. This short duration when it goes to 0V and comes back to original value causes this Overshoot.The reason we used the Pnp-Npn-Comparator part in the circuit was to prevent AD823A to generate output when PWM signal is at 0V. Now i feel this is what is one of the cause to generate the Overshoots. Is there any way i could limit the feedbck to drop only to the value equivalent to µCout? This way the AD832A won't be generating overshoot before settling as a uniform square wave. I guess using a comparator may solve a problem but i am not sure how.

I am doing this project as a final year project at a company for my undergrad degree.I am not so well versed with electronics and hence the questions may seem naive, but i am hoping to get some pretty good responses that could take my work progress forward. Thank you very much in advance.

I will keep posting updates if i am able to come up with anything at work. :)


texts: Understanding the necessity of Tail Current Source in Differential Amplifier/Simulation (SPICE)

texts:
My objective is to understand the need of the tail current source in a differential amplifier. So, to understand the significance of current source, I tried simulating the behavior with and without the current source.

Without the current source, I was able to simulate and get the amplified waveforms. But with the current source I am not able to simulate and getting the error.

The circuit is below:

It gives the following error:

The Node n003 is exactly the drain of the right NMOS Transistor.

Its mentioned in a Circuit Design book that the addition of tail current source is to reduce the dependence of the bias current on the input common mode level.

Since I did not get exactly the above, I tried to simulate the circuit with the current source. But for some reason it does not work and unable to understand the significance of the current source in a differential pair.

Here is what i tried as an alternate approach:

I tried simulating a single transistor with a resistor at top and a Current source at bottom like below:

So, this acts like a source follower. The voltage at the source changes with respect to the gate. I see that the current is kept constant by the MOSFET action through the variation of the source voltage with respect to Gate.

But for amplification we need Source to be fixed so that Gate potential variation is turned to current variation by MOSFET transconductance. So, to fix the Source potential (to Zero), we can have other MOSFET to the right side operating exactly opposite. So, we have two source followers operating exactly opposite and I replicated this circuit with other transistor like this:

I got the below output:

The top differential waveform is applied at Gate, whereas the bottom differential waveform is got at the Source node, just above the current source. So, source potential is maintained at zero. But the output stays at constant voltage (in my simulation).

EDIT - After grounding the voltages, simulation atleast works but the amplification is somewhat lost at the output. The output voltage looks little wierd:


texts: How do you make a PIR equipped LED light turn on even when you are not there?

texts:
I have two cheap solar LED lights. The PIR equipped one only turns on when it detects you while the other one only turns on when the sun goes down. I want the PIR light to turn in when the sun goes down.
How do I make the PIR sensor trick itself so that the led lights turn on even when I'm not there?


texts: Big loads turns MOSFET's on despite pull-down resistors

texts: I am using a FQP30N06 MOSFET to PWM a motor. When I test it with an LED and a PC fan it worked fine, but when I connected it to a big motor it just turns on by itself. I am using the analogWrite function on digital pins and 1k ohm resistor from gate to source. The Arduino ground is connected to the source, the motor is connected to drain, it’s an Arduino uno r3.


texts: trying to increase current output of a generator

texts:
this is my first time posting here also I'm very new to electrical engineering. i am building a pull cord (like a lawn mower) human powered generator and I'm looking for ways to increase the current output.

since i want the device to be as small and portable as possible i had originally bought a basic gimbal motor that is generally used for drone and thought i would turn it into a generator.

i bought the motor that had the lowest kv rating (31), since thats how many rpms it would makes per volt. i figured if i reverse that and treat it as a generator then i would be able to get a high power output at low rpms. i thought since p=iv then if i have a high voltage reading then the current wouldn't be an issue.

however although i was able to get a modest voltage reading (around 30 volts per pull) i didn't take into account that most of that would be lost to heat as i go and charge a pair of lipos. what i need is a way to increase the current so i can charge the batteries faster. I'm thinking maybe if i can increase the torque that would help. I'm trying to be able to charge the batteries as fast as possible, even if it requires more work.

is there a way to increase the current of a generator? or are there already of the shelf motors that have high current? what if i charge ultra capacitors from the generator instead? i know they can charge faster so will they increase the current?

i am very new to all of this. anything helps!!! :)

thanks,
ita


texts: 74HC86 XOR datasheet say Schmitt trigger "action" - is there anything special about it?

texts:
I current have a Schmitt trigger chip to clean up an output from one of my optical encoders and I am thinking about using an XOR gate to feed in both encoder outputs to double my encoder output frequency. (Its a quadrature encoder)

When I was looking up XOR gate ICs, I saw in the data sheet it literally saying

  All inputs have a Schmitt-trigger action

So does that mean I can fully do away with the standalone Schmitt trigger IC and the XOR gate will take its place as well as being and XOR?

It'd just when it says "action" it doesn't sound as robust as if it were to say all inputs have Schmitt triggers.

The IC is 74AHC86


texts: Want to make a Chia farm of 156 external hard drives

texts:
I have two questions:

How do I not burn down my house
Is there any way I can use less electrical outlets by getting AC/DC splitters?

Question 1:
So basically I got 156 external hard drives. The AC adapter included with a single drive outputs 12V, 3.0A.
I'd like to make sure I don't burn down the house, so here's my math so far:
156 * 3.0A = 468.0A
12V * 468.0A = 5616W
Each breaker can do 15A * 120V or 1800W, right?
So 5616W/1800W = 3.12, so I'd need to use a minimum of 4 separate breakers if I used the AC adapters that came with the drives, right? So I could divide the 156 drives by 4 and do 39 drives per breaker and be perfectly fine, right?
Question 2:
I found some 1 female to 8 male DC splitters. If I wanted to utilize those, I would need a 12V, 24A (8x3.0A) AC/DC power supply, right? Does anyone have any recommendations on how or where to find a 12V, 24A AC/DC adapter? If I found one that does slightly less or slightly more would it work? How would I know?
Thanks!!


texts:
I am laying out PCB for a stopwatch project that I made couple of months ago.
I seem to have taken care of the only sensitive part i.e. crystal, since it is time measuring device.
But I also see that in other projects, where we have 16x2 character LCD, that when I connect CPU there's few mVpp of noise at pins 15-16 of LCD(These are the pin for LED backlight) since I don't think this noise is due to LED backlight where is it coming from.
I measured it using ground spring between pin 15-16. I was told that since that part is drawing high current (20-30 mA) the transient in other part of circuit is reflected "more" here.

Is this true.?

I checked the power line at other points and I didn't see as much noise as I see at pin 15.

This is the layout I am doing, still not complete.

U3 is my CPU.
LCD Will be connected at J6,j7,j8.
J9 is the point where I will connect A boost converter(External PCB).
So Is my Crystal n caps layout correct, and How should I power my LCD, should the trace be very small, if yes then how much(any math), should I share power line between CPU and LCD or should I use star connection for power as well.

Also regarding the Decoupling caps on vdd of IC. Vdd pin is pin 20 and gnd is pin 10, they are as far away as it could be.
Should I connect second pin of cap to pin 10 or to the power supply ground since it's closer to it.

Edit: Added Semi-Completed Layout

Thanks for your suggestions everyone.
Above is top view of my semi-complete layout.
Trace width for pwr and gnd is 40 mil , and logic is 12 mil and for my 20 Hz pulse output it is 25 mil.
Below is it's bottom view:

I wanted to ask one more thing regarding Decoupling caps:
I have read in a datasheet of an OPamp to connect 0.1uF and 1uF to IC's Vcc.
Along the same lines I have connected like 0.1uF and two 1uF to the LCD's Backlight pin, Is it worth doing it or a single 2.1 uF will do the job similar to them.
The whole idea for distributing Caps as 0.1 and 1uF is to have smaller cap handle fast transients and 1uF to provide bulk charge.
Am I going correct.
Also  if you see for IC U4 I have connected Decoupling to gnd through a via, and kept via as close to cap as possible, is it enough or is it going to haunt me after production.?

Thank you very much.


texts: No display at all tests, but shows continuity

texts:
My multimeter buzzer is ok and  sounds when continuity is checked. However, no display on the LCD. Also, no numbers are showing in every tests voltage, resistance, etc.
I have replaced the battery and checked for any damages on the board. No signs of it and have cleaned everything.
How to check if power is supplied to the main IC chips?


texts: A question on current sensing through a very low resistor

texts:
I'm trying to sense the current through a wire, and so far I decided to use a 1mOhm shunt resistor to convert it to voltage. As you see in the below circuit, the current source I1 sources 6A amplitude PWM current pulses(freq. is 1kHz). The idea is to adjust the current by the PWM coming from a uC.

But I also want to regulate this current and for that I need the uC to sense the current. So far I came up with the following circuit which is a LPF with gain:

Above the active LPF here mappes the PWM current to a 0 to 4V DC voltage which will go to one of the ADC of the microcontroller.

The opamp I use is a special amplifier with very low offset drift.
In simulation only this opamp works the rest I tried all causes significant offset in simulation.

The LPF by the way has 20Hz cut off and designed by the filter design tool.

Eventhough this works in simulation, Im not happy with this interface.
First of all, it is SMD and has many cascaded staged to solder.

So my question is:

1-) Is there an alternative easier way to sense this current here. Like a single DIP IC which translates the current to voltage with less soldering effort? Or any other single chip DIP LPF?

2-) How about instead of averaging current by a LPF, what alternative way could be use to send the actual current information as voltage to uC ADC? (I thought measuring the duty cycle but that didn't make sense because I already know the duty cycle which is coded to the uC)

Edit:

I'm unable to solder SMD.

Edit2:Entire circuit(NPNs might not be needed):

PWM Sweep and the output:


texts:
I'm building a circuit to run off of a 7V AC-DC adapter regulated down to 6V for my devices. I also want to be able to alternately run the system off a 6V (non-rechargeable) battery.

What's the best way to isolate the battery from getting charged by the supply and preferably to favor the AC adapter if both are connected?


texts: I've just bought a new Soldering Iron with the intent of making Art, however I seem to have a problem

texts:
I bought this: http://www.amazon.com/Weller-SP40NKUS-Medium-Soldering-Black/dp/B00B3SG7F0/ref=sr_1_2?ie=UTF8&qid=1394083021&sr=8-2&keywords=weller+soldering+iron

The other day so that I can solder together vintage watch pieces into figurines (and yes, I know for sure this is a good way to go about making these), but before my watch pieces came in I wanted to play around with the iron to see what it could do, since I've never soldered before in my life. I've watched some videos of people soldering, but I'm a bit confused as to what I've done to mine. I turned it on, let it heat up, and then touched the tip to the lead-free solder that came with it. Immediately the solder melted onto the tip (Which I'm assuming is called tinning? And I understand that this is a good thing), but when I tried to wipe the solder off the tip, it didn't seem to come off. Once it dried, my tip appeared dark matte grey, and now even a little orange-ish near the base of the tip.
Can someone maybe shed some light on what I've done? I'm not sure if i've just rusted my new tip or not.


texts: FPGA AXI module development - synchronisation

texts:
I am trying to understand AXI interface and have one problem. My module should work as a slave, Vivado has generated required wrappers. Master will be filling 4 registers.
I didn't find any specific signal which tell me that all 4 registers has been updated. I have checked that I can monitor VALID but as far as I understand it, I will don't know (based on this signal) if all registers has been updated.
There is many ways to wrap around this but I am trying to understand how it should be implemented correctly. I don't want to modify generated code as it can be regenerated in the future (except sections for user code additions).
Best regards,
e2p


texts:
does location of the circuit components actually matter in RC high/ low pass filters?

For example, is this also a high pass filter?

And this low pass filter?


texts:
I have designed an antenna for a WPT application. We already have a primary coil with a centered frequency of 13.56 MHz. We want to match the second coil at the same frequency and that's why we need to match the capacitance.

The circuit consists of:

We are working on optoelectronics in this project but one of our members left the team and we need to find a solution for the antenna. We thought that using a matching capacitance would be an "easy" solution for now.

My question is: we calculated the inductance of the antenna (around 0.7µH). We are using the following parameters for the antenna:

wire width = 0.5 µm.
wire spacing = 0.5 µm.
number of loops = 5.

We calculated the theoretical capacitance that is supposed to be 31nF. However, we are designing this antenna for a flexible circuit using the substrate Pyralux 8535R from DuPont. I am worried that this may change the capacitance.

How would you tune the antenna supposing that the theoretical capacitance is right? Any ideas or guidance of how to do this?


texts: Why does the ATmega MCU on the Arduino board have both a flash memory and EEPROM?

texts:
I know that both are non volatile. Flash is used to store my code and EEPROM stores long lasting values (like a hard drive on PC).

My question is why are they of different types? Why can't both be flash or both be EEPROM? Is one cheaper than the other?


texts: ADC over-voltage input protection while keeping accuracy?

texts:
i just want to get the idea for the input voltage protection for a fully differential ADC.

The analogue voltage inputs supposed to be 0-5v, but someone being careless could plug a higher voltage (up to probably around 20v) by accident and blow the ADC.

I have seen zener regulation/clamp circuits, but upon trying them realized that they of course produce a voltage drop. The voltage needs to be unaltered from the one the user puts in, so this does not work for me.

So, what I need is a way to protect my ADC inputs from over voltage as high as ~20VDC or more but still be able to accurately read a 0-5V nominal analogue signal without altering the voltage reading.

and my power supply for the board is 5V, so i only want to limit the input signal to 0-5V. yeah, of course the Voltage must be above 0.

besides, i have only found one overvoltage/undervoltage from TI , It is TPS2400 , but the range of the protection voltage is 3 to 6.9. it's not suitable for me.

so , is there any programmable VOP and UOP chips that i can use?
the ADC that i use is ADS5272enter link description here

Any suggestions? Let me know! Thanks a bunch in advance!

i posted the Zener diode grafic

see that , from -Vz to Vf it is not linear, and i thing it must have an effect on the input singal for ADC


texts: Rectifying reversible polarity battery with minimal power loss

texts:
I'd like to build a battery-powered DC power supply that will accept a single-cell battery in either polarity (i.e. it doesn't matter which way you put the battery in). I'm thinking of using the circuit below to rectify the voltage.

Are there any gotchas? Is there a better design for my constraints (listed below)?

You'll notice that Q1 and Q2 are N-channel MOSFETs. Q3 and Q4 are P-channel. Let's assume they all support positive and negative gate voltages of more than the battery voltage.

The resistor labeled LOAD stands in the place of the rest of the power supply and everything powered by it.

My design constraints for the rectifier include:

Very low power loss (less than 1uA quiescent current; less than 1Ohm resistance)
Support small loads (average of 130uA, peak 20mA, minimum 5uA)
Support single cell Li-ion (3.7 - 4.2V)
Support battery in both polarities

Perhaps importantly, I won't be supporting the case where the battery is inserted one way and then quickly inserted the other way. In other words, I don't need to rectify square waves. For that matter I don't need to rectify AC of any kind.


texts:
I have written and using a STM32F030F4 for toggle a pin. I configured all things and my program is this (I use GPIOA->ODR ^= GPIO_PIN_2 for toggle GPIOA2 in Infinite loop ):

#include "stm32f0xx_hal.h"

/* Private variables ---------------------------------------------------------*/

/* USER CODE BEGIN 0 */

/* USER CODE END 0 */

/* Private function prototypes -----------------------------------------------*/
void SystemClock_Config(void);
static void MX_GPIO_Init(void);

int main(void)
{

  /* USER CODE BEGIN 1 */

  /* USER CODE END 1 */

  /* MCU Configuration----------------------------------------------------------*/

  /* Reset of all peripherals, Initializes the Flash interface and the Systick. */
  HAL_Init();

  /* Configure the system clock */
  SystemClock_Config();

  /* System interrupt init*/
  HAL_NVIC_SetPriority(SysTick_IRQn, 0, 0);

  /* Initialize all configured peripherals */
  MX_GPIO_Init();

  /* USER CODE BEGIN 2 */

  /* USER CODE END 2 */

  /* USER CODE BEGIN 3 */
  /* Infinite loop */
  while (1)
  {
        GPIOA->ODR ^= GPIO_PIN_2; //toggle GPIOA2
  }
  /* USER CODE END 3 */

}

/** System Clock Configuration
*/
void SystemClock_Config(void)
{

  RCC_ClkInitTypeDef RCC_ClkInitStruct;
  RCC_OscInitTypeDef RCC_OscInitStruct;

  RCC_OscInitStruct.OscillatorType = RCC_OSCILLATORTYPE_HSE;
  RCC_OscInitStruct.HSEState = RCC_HSE_ON;
  RCC_OscInitStruct.PLL.PLLState = RCC_PLL_ON;
  RCC_OscInitStruct.PLL.PLLSource = RCC_PLLSOURCE_HSE;
  RCC_OscInitStruct.PLL.PLLMUL = RCC_PLL_MUL6;
  RCC_OscInitStruct.PLL.PREDIV = RCC_PREDIV_DIV1;
  HAL_RCC_OscConfig(&RCC_OscInitStruct);

  RCC_ClkInitStruct.ClockType = RCC_CLOCKTYPE_SYSCLK;
  RCC_ClkInitStruct.SYSCLKSource = RCC_SYSCLKSOURCE_PLLCLK;
  RCC_ClkInitStruct.AHBCLKDivider = RCC_SYSCLK_DIV1;
  RCC_ClkInitStruct.APB1CLKDivider = RCC_HCLK_DIV1;
  HAL_RCC_ClockConfig(&RCC_ClkInitStruct, FLASH_LATENCY_1);

  __SYSCFG_CLK_ENABLE();

}

/** Configure pins as
        * Analog
        * Input
        * Output
        * EVENT_OUT
        * EXTI
*/
void MX_GPIO_Init(void)
{

  GPIO_InitTypeDef GPIO_InitStruct;

  /* GPIO Ports Clock Enable */
  __GPIOF_CLK_ENABLE();
  __GPIOA_CLK_ENABLE();

  /*Configure GPIO pin : PA2 */
  GPIO_InitStruct.Pin = GPIO_PIN_2;
  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
  GPIO_InitStruct.Pull = GPIO_NOPULL;
  GPIO_InitStruct.Speed = GPIO_SPEED_HIGH;
  HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

}

As reference manual has said:

Thus if 2*2=4 that mean each 4 cycle make a toggle in GPIOA2. then frequency ought to be 48/4=12MHz (48 is MCU clock because as you can see in codes I have used PLL and I have multiplied 8MHz to 6). is it correct?

let to impelement the code on MCU. look at my saleae result:

Huh!!!?? is the output frequency correct? is there any point?

Edit:

The assembly for the toggle is this:


texts: Circuit thermal analysis in PSPICE and temperature coefficients

texts: I am tying to perform a thermal analysis in pspice. Resistors needs two temperature coefficients as TC1 and TC2 (if we assume linear change of R vs. T, it's zero) in pspice. But in resistor datasheets (like this) from Vishay, I've seen that TCR is for example ± 200 ppm/K. What does this ± mean? Why TCR is not a single positive or negative number? Thanks.


texts: Matching an amplifier to a video transmitter

texts:
What I'd like to do is to amplify a signal coming from an analog Video Transmitter. I've created a small circuit according to the application circuit description of the "High Gain Driver Amplifier" (Avago MGA-31189). Now I plan to match the input of the amp to the output of the Transmitter and the output of the amp to the antenna in order to get the maximum power. Here are the specs:
Transmitter:
Analog Video Transmitter
Frequency: 850 MHz
Power: approx. 10mW
Impedance: 50 Ohms
Amplifier: Avago MGA-31189
Gamma locations at 850MHz:
Input: mag= 0.071, ang= -113.02
Output: mag= 0.039, ang= -134.54
Antenna: Cloverleaf Antenna
Impedance: 50 Ohms

Q1: How do I transform the input and output reflection coefficients of this amplifier into impedances?
Q2: Once the equivalent impedances have been found, how can an LC network be formed to achieve the required impedance matching to minimize reflections?


texts: Arduino Mega 2560 - Ghost Values on Analog pins

texts:
Yet again in need of your help... I have the Arduino up and running reading 2 external temperature probes.

I'm using a common ground (tried separate ground same result) and Analog Pin 0 (A0) with 1 probe and the second probe connected to Analog Pin 16 (A15).

I am displaying the output correctly on the serial screen but as I have it looping through each of the 16 Analog pins it is displaying a value for those pins that nothing is connected to.

In other languages you should always initialize all variables, inputs & outputs.. is this the same for the Arduino and if so, what is the Correct method to initialize or set the Analog pins prior to reading.

Don't laugh at the code.. ;-)

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

void loop() {
  for(int I=0; I < 16; I++){
  int sensorValue = analogRead(I);
  // Convert the analog reading (which goes from 0 - 1023) to a voltage (0 - 5V):
  float voltage = sensorValue * (5.0 / 1023.0) - 0.04;

  Serial.print("Address = ");
  Serial.print(I);
  Serial.print(" ");
  Serial.print(voltage);
  Serial.println();
  delay(5000);
}
}

The Output on the display is:-

Address = 0 2.01
Address = 1 2.09
Address = 3 1.97
...... Up to the last pin.

Only Pins A0 & A15 should have values.

Thanks Heaps Again...
Mark


texts: Can I combine 3x 1000ma power supplies (wall warts) to get a 3amp supply [answer: no]

texts:
I have a device that requires 3A, 9V.  I also have three 1A power supplies (wall warts).

Can I cut the wires of these power supplies, reconnect them all together in parallel, and use them all as a single 3amp 9v power supply?


texts: resistance measurement problem with digital multimeter

texts:
I accidentally caused a short circuit with DMM common lead while measuring 220 AC voltage.

then when I tried to measure resistance it gives me a reading of 3500 ohm while there is no resistor connected and it gives me 0 ohm when I touched the test probe leads together.
my DMM is DT-9205A

any help please


texts: How can I indicate pin 1 on a SMT package footprint without silkscreen

texts:
Sometimes when I order PCBs from a board house, I omit the bottom silkscreen for budgetary reasons. When I place surface-mount chips on the bottom of the board, I then end up with a footprint that doesn't indicate the chip orientation. This is annoying because it means that I need to verify the component placement and orientation during assembly, and this allows for errors when placing the parts.

How can I clearly indicate pin 1 with the remaining layers in a way that will be clear but not significantly impact the PCB size or cause issues when soldering? I'm assuming that I always have access to a solder mask layer and a copper layer.


texts: Calculate the Thévenin Voltage (Vt) and Thévenin Resistance (Rt) equivalent of the circuit below

texts:
I want to find the Thevenin equivalent circuit but because of the positioning of the nodes a and b I can not visualize it correctly and that causes me to struggle. How wil I calculate the Thevenin Resistor (Rt) and Thevenin Voltage (Vt)?

These are my calculations. But when I simulate (LTspice) my voltages and resistance from the original is not equivalent to the thevenin circuit?


texts: Why I am getting weird a phase change in the following

texts:
This is voltage divider bias for MOSFET simulated on multisim. Some connection are not visible due to probe connection.
When i remove the bypass capacitor at emitter, i get normal phase difference of 180


texts: Determining cut offs frequencies of band-pass filter

texts:
I have an RC network as follows:

simulate this circuit – Schematic created using CircuitLab

As far as I can tell, this has the transfer characteristic:

$$
\begin{align}
\frac{V_{out}}{V_{in}}=\frac{Z_{lower}}{Z_{lower} + Z_{upper}}
&=\frac{
  \frac{1}{j\omega C_1 + \frac{1}{R_1}}
}{
  \left(\frac{1}{j\omega C_1 + \frac{1}{R_1}}\right)
  + \left(\frac{1}{j\omega C_2} + R_2 \right)
} \\
&=\frac{
  1
}{
  1
  + \left(\frac{1}{j\omega C_2} + R_2 \right) \left(j\omega C_1 + \frac{1}{R_1}\right)
} \\
&=\frac{
  j\omega R_1 C_2
}{
  j\omega R_1 C_2
  + \left(1 + j\omega R_2C_2  \right) \left(j\omega R_1 C_1 + 1\right)
}
\end{align}
$$

Am I right in calling this a bandpass filter? How do I find the cutoff frequencies?

Or phrased alternatively, how can I choose my resistor and capacitor values given desired cutoffs?


texts: Transistor Switch Maximum Permissible Resistance

texts:
I have been learning from a series called "The Great Courses". This is a question that modifies a given example with new numbers. No matter what I do, I cannot reach the correct answer, and the book gives no explanation.

The image is a little messy but all given info is there. Is there something I am doing wrong?


texts:
I do hope this post is still within the boundaries or spirit of this forum and perhaps this question is best suited for the chat instead.

I'm sure we all are experiencing (in one form or another) the industry-wide part shortages for discrete MLCC (caps) and resistors, in like the 0402/0603/0805 packages. This part shortage has forced us into sourcing alternate parts (sometimes less than ideal) in a effort to continue design work and shipping product.

Here are my two questions. Even though the only research I put forth is Google/web searches for work-arounds; but do any of you designers have any creative methods or ideas in terms of part sourcing or design considerations for providing (mostly) by-passing/de-coupling using 0.1/0.01uF 25V-100V X7R/X5R 0603s in both current product as well as new designs? Should I continue to design in hard-to-find MLCCs and hope this storm blows over sometime soon?


texts: Finding relay datasheet: HC1-AC240V LR42758 30111H AP311998 3A30VDC 10A 1/3HP 125,250VAC

texts:
I have a dickens of a time finding a datasheet for a spare relay that I want to reuse.  Here are the images of it:

The text from the side there is:

  HC1-AC240V LR42758 30111H AP311998 3A30VDC 10A 1/3HP 125,250VAC

The pins:

The other side showing "Aromat" (but I cannot tell if that is the manufacturer of the coil inside the relay, or the entire relay):

I've web-searched laboriously and came up short.

One datasheet looks close: https://www.alliedelec.com/m/d/2454bde37e51c885d9084c84a437bef1.pdf but I doubt that is the exact one because the breakout for the part number has many more dashes than "HC1-AC240V".

I speculate that the "LR" implies it is a Latching Relay but not sure. I get a lot of search results for "LR42758"

Is there a online search engine somewhere whereby I can put in this information and get back datasheets specifically for it?  Or am I just going to have to chuck it and start with something new (they are not that expensive, just hate throw something useful away).


texts:
Lets say I have a switch with the usual 2 connections + and - I want when the switch if off (power doesnt pass) the circut to close with output wire 1 and when the switch is on(power passes) the circut to open with wire 1 and to close with wire 2 thus changing the output wire.

I tried a few ideas I had with transistors but didnt work out.What is the best way to make one of those?


texts:
I've been working on a remote control made out of a PIC 16F57.
The PIC will wake up on every keypress, send the IR code and go back to sleep.

the remote is working fine, unfortunately I forgot to tie the T0CKI pin to either Vdd or Vss so it's floating. On some remote I can see that the power consumption is quite high even when in sleep mode so I think is due to this floating pin.
Even the datasheet says clearly that to reduce power consumption when in sleep mode the T0CKI pin should be tied to Vss or Vdd.

Is there a way to "disable" that pin or change something in the registers in order to prevent (or minimize) that high power consumption without modifying the schematic?

The problem is experienced only on some remotes, not all of them


texts: How fast should a Triac be switched for a dimming application?

texts:
I want to create a dimmer using a Triac - it will have a duty cycle where it is on for x% of the time, and then off for Y% of the time - my question is how often should this on/off cycle happen?

I was thinking of using a BT137 - this is for a 120V / 60Hz / ~300W max circuit, however if there is an alternate/better option, I would be willing to switch.

I would like to avoid any "humming" noise if possible (which I seem to get from commercial dimmers).


texts:
I have a question regarding very basic op-amp and adc theory that has been bothering me because I haven't found a clear answer to anywhere:

On a 12-bit ADC, if my voltage reference is 1.24 V, my resolution will be ~0.6 mV. If I'm interested in having a resolution of 0.1 mV, will amplifying my sensor's analog voltage range (0 to 200 mV) to cover the entire range of the adc (1.24 V) effectively increase my resolution?

Can I calculate my new resolution by dividing 200 mV by 2048 (= ~0.1 mV) or is the resolution fixed no matter what percentage of the adc range i use? In other words, will using an opamp help me get a higher effective resolution or will it stay at ~0.6 mV no matter the amplification. Is the equation for calculating the new resolution different when adding an amplifier? Do I lose the simple linearity between the output codes and voltages.

As a follow-up question: If amplifying my sensor's output doesn't get me to 0.1 mV. Is there a way I can get down to 0.1 mV using a 12-bit ADC and 1.24 V reference? Are there any external circuit components I can integrate to achieve this? Am I forced to use a separate 16-bit adc and connect it to my microcontroller? Ideally, I want to minimize my circuit's complexity and use the adc in my microcontroller (BlueGiga BLE112) and use an op-amp externally, but I'm open to other ideas.

Thank you for taking the time to read this, and pardon my gaps in knowledge, trying to get past the learning curve as rigorously and best as possible.


texts: Differential signal processing and generation

texts:
I am trying to interface to a Mitsubishi central aircon unit. Based upon the manual, the internal units communicate over a differential bus (I hope is TDM).

I have a screenshot of the signal:

How would I go interfacing to this bus? I realize this requires an opamp in differential mode, but I am unable to find implementation details, besides theory. The idea is to use an opamp to subtract the signal, and have the single-ended output drive a high impedance input of a microcontroller (probably atmega238).

After receiving and decoding, and assuming I understand how the bus is multiplexed (or shared), how would I be able to generate a differential signal?

Even the correct terminology will help.


texts:
I have been reading a design guide by TI which provides full schematics for their reference design seen Here.

There is copyright stamped all over this document as seen below. I don't plan on using their design but it made me think, what if I wanted to use their design? With company's providing reference designs, presumably, they want me to use it and buy their product. I'm confused on the usability/copyright of using manufacturer reference designs, are we allowed to and what are we not allowed to use?


texts: Communicating between 2 Xbee in APi mode using Minicom

texts:
I am working on Xbee in API mode and i am writing a small program in C to receive API frames and process them, but to start with this, i simply wanted to check that how does these frames look like and is API communication is really happening or not.

I have Radio A and Radio B

Radio A - Transmitter
64 bit address - 0013A20040BB1716

Radio B - Receiver
64 bit address - 013A20040BCDE18

I added them both via Xbee USB shield to KDE and started minicom for both. They both are replying to the AT command pretty well. I set APi mode by using

ATAP = 1 or ATAP = 2

and then ATWR and ATCN and checked API mode again by issuing ATAP and get 1 or 2 as reply, that means i am in API mode now.

I used this link to frame API frames to be send from Radio A to Radio B, and this is the frame which i got

`7E 00 10 10 01 00 13 A2 00 40 BC DE 18 00 00 00 00 AE DA BF`

when i send it from Radio A to Radio B, i didn't get anything on Radio B serial on minicom. What am i missing? I had already attached antenna. I also considered this link but instead of using XCTU, i had simply used minicom.


texts: How is the Truth Table of Positive edge triggered D Flip-Flop constructed?

texts:
simulate this circuit – Schematic created using CircuitLab

Consider this diagram which represents a positive edge triggered D Flip-Flop. In the analysis of this circuit, my book (Morris Mano) says that when the value of D = 0 and Clk is set to 1 then the value of the Reset variable and Set variable are 0 and 1 respectively.

How can it make such a prediction? Clearly, output of NAND4 has to be 1 and lower two inputs of NAND3 have to be 1 but the above input can be either 0 or 1. Also, one input each of NAND 1 and 2 has to be 1. But their outputs can be 0, 1 or 1, 0 respectively. Hence the value of S can be 0 and that of R can be 1. Then why is everyone so sure that R has to be 0 making the output Latch always in a Reset state. May someone help?


texts: Why is an op-amp used in this summing circuit? Why can't I add the voltages without an op-amp? Current doesn't go into op-amp, so it goes through the Rf resistor either way.


texts: Why does this analog front end EVM have 4 pins per channel, instead of 2?

texts:
Here is a photo of the ADS1299 EVM from texas instruments. It is an 8-channel low noise analog front end chip.  I understand that for each channel, the potential difference between plus and minus are measured by the AFE, but I am confused -- for 8 channels there are actually 32 pins on this EVM!  I expected 16 (2x8 channels).
See J6 header to the left in the photo.  Note that the two pins are joined by jumpers when not in use.  The top set of 4 pins exposed on J6 are reflective of what the entire header would look like if I removed the jumpers.
I am clearly missing something.


texts: I want to let two STM32 communicate via CAN bus. One as transmitter and the other as receiver. In order to do that, I combined each with a MCP2551 transceiver. As long as the CAN operating Mode was set to LOOPBACK everything seemed to be good: The controller were able to send CAN messages, receive them(their own), and send it via UART to my PC (worked well). As next step I wanted to let them communicate with eachother. I set the operating mode of them to NORMAL. While the transmitter was sending the same messages as in Loopback Mode, and the Receiver was sending nothing (just waiting for any messages to come in), nothing happened. A measurement showed constant 2,5V at the transceivers output (Recessive State), and constant 3,3V at the STM32 TX (PA12). Anyone an idea what I'm doing wrong?


texts: How can I adapt a 3-pin PC fan connector to a 4-pin connector?

texts:
My computer's motherboard uses all four pin fan connectors with no support for speed controlling the older three pin fan connector. The problem is, all the PC fans that I have use a three pin connector. As fan as I know there are no premade solutions available, so I was thinking of building an adapter that sits in an unused drive bay.

I can't seem to find much information on how the four pin fan connecter works. Apparently, it looks something like this:

12 V
0V
Tachometer
PWM

The three pin header is numbered similarly:

Vcc
0V
Tachometer

Could I simply use a logic level MOSFET to do the following?


texts: How does playback rate of an arbitrary waveform generator determine frequency content of that signal?

texts:
I'm trying to clear up some conceptual confusion I have about digital signal processing.

Say I have a 1000 point digital signal (stored in the memory of my arbitrary waveform generator "AWG"), and I set the AWG to read the signal out at 50 MHz. So every sample is getting played uniformly at 50MSa/s.

How does the rate that I set my AWG to play this signal at (50 MSa/s) determine the bandwith of my signal? I am familiar with the Nyquist sampling theorem as it applies to sampling an analog signal, but not how it applies to reconstructing a signal from digital samples.

Does the actual data (raw amplitude values) in the signal affect this signal bandwidth at all? I'm imagining the AWG playing a sequence of values [0 0 0 0 0 0 0 A 0 0 0 0 ...], and if A is really large, wouldn't the DAC need a faster rise time to reach a higher amplitude value compared to if A was small (less energy it would need to dissipate)? This makes it seem to me like the amplitude values contained in the waveform would affect the rate the AWG is playing them out at, but this has nothing to do with the AWGs sample rate??

Thanks in advance for the help


texts:
I am working on a voice recording application. The circuit simply has microcontroller, flash memory and mems digital microphone.

What are the advantages of using a stereo microphone on the quality of sound? If necessary, how should I position these two microphones?

The application does not require localization, beamforming similar complex works, just simple sound recording.


texts:
let's consider the following blocks diagram for a receiver of a pulse RADAR (but I suppose my question regards many kinds of receivers)

My book says that T/R Lim means a power limiter which is inserted after the duplexer (which is after the antenna) in order not to burn the receiver.
Well, my simple questions are:

Is such a power limiter realized with an attenuator (e.g. a voltage divider, or a microwave resistive attenuator etc)? Simply put, is it a resistive attenuator or a voltage/current limiter (e.g. diodes)?

If it is an attenuator, how does it affect the SNR ratio? Does it reduce both noise and signal powers?

If it is an attenuator, why should we attenuate and then amplify with LNA? Why can't we attenuate less (just less than the maximum power the system may work with) and save space and money by avoiding the Low Noise Amplifier?


texts: What happens when the MOSFET isn't conducting, circuit-wise?

texts:
simulate this circuit – Schematic created using CircuitLab

For Vin below threshold voltage, M1 isn't conducting, neither does M2 since Id=0. So what happens circuit wise, how come that Vdd=Vout ( we did this in class)?


texts: Serial diode to universal motor and brush lenghts differs on intermittent run, why?

texts:
A universal motor supposed to be run in two speed stages: full speed / reduced speed and motor will run on intermittent duty like 3 seconds ON / 3 seconds OFF.
So simply I added a serial diode (BY255) to universal motor to run the motor in reduced speed; but one brush wears out faster when other wears out very slow, why?
I suspected from switching transients but surge supressors like NTCs are not a good idea since they need cooling time, and the costs are important if you will talk about PCB circuits which has at least 3-4 components.

Additional details:

Source: 220 V 50 Hz
I measure 120 V on motor (rectifed True RMS value)
BY255: Medium Current Plastic Rectifier (Voltage - 200 to 1300 volt, Current - 3.0 amperes)
Brushes wears out fine & equal when on full speed intermittent duty
When i change the direction of diode, then other brush starts to wear out faster. Diodes' anode sided carbon brush wears out faster (the brush electrons flowing into, conventioal current flowing out)
Motor's contionous work values are 0.45 A, 83 W, 6300 RPM with light but right load.

Edit: I tried another motor with another type brush but continous duty; results are same: one brush (anode side) wears out very fast while the other brush wears out very slow.