texts: I would like to design a PCB having PCI 164-Pin on that shown at image. Is there any component I can add to schematic on Altium or should I just put some I/O ports on schematic?


texts: Coaxial cable: how is it possible to define a conductance?

texts:
I have a coaxial cable with internal conductor of radius r1 and external conductor of radii r2 and r3. The material of the conductors has a conductivity \$\sigma_1\$. Between the conductors there is a imperfect dielectric of conductivity \$\sigma_2\$. I am asked to determine the conductance of the dielectric medium.

I have no problems doing the computation when I assume that the current density J has a radial direction. I come up with

$$G=\frac{2\pi \sigma_2}{\ln{\frac{r_2}{r_1}}}$$

My problem is understanding why the current is radial. I think I'm not correctly understanding the phenomena of stationary currents on dielectrics. I know that in this domain the electric field has 2 components: a normal one and a tangential one. The normal one is calculated the same way as it was in electrostatics, by applying Gauss Law. The tangential one, because of the continuity of the electric field is the same as inside the conductor. Now what I don't understand is how there is a current inside the dielectric. Is it because it's not a perfect one? But how is that current radial? Why that direction if the electric field has 2 components? Why don't we have a current in the same direction (longitudinal) as inside the conductors? Can anyone clarify me please? My questions are about the concept of electric currents on dielectric media, and not about the calculation of conductance.


texts: Switching Between Two Circuit Branches Using Basic Components

texts:
I'm working on a project that uses an LDR to switch between two mutually exclusive functions.  So, when it's bright and sunny, do X and when it's nighttime do Y.  The daytime function will involve a PID controller to control a motor (through relays), the nighttime function will cause the motor to "park" and then sleep until daytime.  I've decided to do as much of this as possible using discreet components because the object of the exercise is to learn electronics (and I'm something of a masochist).

I'm looking at each section independently and I decided to look at the LDR switch, thinking it would just be a matter of a transistor ot two.  Using the following basic transistor switch as my guide, I tried a number of configurations to try to get that SPDT action I required.  They all failed - some worse than others.

Most of my efforts involved attempting to cascade transistors by attaching the collector of one to the base of the other with the loads in various positions.  In general, I had two main problems: either the current flowing through one or more of the branches was quite low or one of the branches wouldn't turn off completely (or at least to an acceptable level).

Now I know I'm not using proper load figures as I should to fine tune the operation of the transistors, but I wonder if transistors are the best option for this type of problem.  So, my question is simply this: am I barking up the wrong tree trying to get nicely isolated switch (like a relay - but without using a relay) using transistors only?  I'm guessing this requirement is common as muck, so how is this normally achieved?

-- For the benefit of others:

Here's the best scheme I could come up with to meet the requirement of having two sepatate loads receiving full battery voltage and current (more or less).  Many, many thanks to  gbulmer who put me on the right track here.  The trick it seems is to have a high impendence voltage sensing type component to determine the logic level of the transistor.


texts: How does a single phase shared neutral circuit actually work, physically?

texts:
Okay so this is a two part question. First Question is probably more of an ELI5 question. But I am a fairly experienced electrician (NOT AN ENGINEER mind you.) but I have a generally good working understanding of electrical theory, ohm's law, grounding, neutrals, etc. But I got asked this question today and didn't really have a great answer. I ask for the ELI5 explanation mainly because those are the explanations I have to give to the junior electricians all day.
To elaborate/illustrate a little though, say you have a stereotypical residential shared neutral circuit, properly wired; we use a two-pole, 120/240V 20A breaker in a 120/240 volt panel. Our hots are of course on different phases. for simplicity's sake we'll say the circuit is stupidly simple, and we have each hot go out to a single identical load, we'll say load A and load B, the same distance away from the panel. My wonderment is basically, why do the loads get nearly exactly 120volts? I mean there is still somewhat of a 240 volt circuit there, starting at one pole, going to load A, out of load A along the neutral, to wherever the neutrals branch off each other to the neutral terminal of load B, out of Load B along the hot and to the other pole of the breaker. (really wish I could draw this, lol). And to my understanding, current travels not just on the path of least resistance, but on multiple paths proportionate to the resistance of the paths available. So, hypothetically, though you've provided a neutral path for each load, why is there no voltage applied across the loads via the hots?
...Actually, In writing this question I feel like I may have generated my own answer: is it the resistance of the load of the other circuit that acts as a choke and causes the current to stay within the wiring of the intended circuits? Or something else?
Second Question!
Why/how do the currents cancel eachother out on the neutral. What is happening inside that wire nut, (or other splice point) Are the electrons from one neutral coming down (I speak of this only as a snapshot of the circuit during a single moment in time. I know AC alternates.) from a load smashing into the electrons trying to move up toward the other load? What's happening inside the neutral bar of a 3 phase panel? is it just subatomic chaos in there?
Any elucidation offered is much appreciated?


texts: Connecting Voltage Regulators 7812 in Parallel for High Current

texts: Could I use two L7812 voltage regulator ICs in parallel to get 12 volt and more current that with just one?


texts: Performance changes to metal can transistors installed 40 years ago

texts:
What problems, if any, are to be expected when using 2N4037 metal can PNP transistors that were installed 40 years ago?

I can't divulge much about the design, but transistors are in a voltage regulator that was a spare that sat on the shelf for nearly 40 years, with short yearly tests. The other components (metallized mylar caps,  carbon comp resistors, diodes) all seem to still hold their values within tolerance and work as expected. There are no electrolytic caps in the design.

Are there any common failure modes or pitfalls with these parts at this age and usage level?


texts: How to synchronise DVD-RW spindle motors

texts: Just bought a small DC motor speed controller (two LM324, two IRFZ44N, rated at 250W max output, input in range 5-10 to 30V DC) and started wondering how to synchronise six DVD-RW spindle motors (Nidec L16210A/18C293A160, nothing came from a google search). They have 6-pin flat cable but don't know which one returns the signal for rpm. And that's the problem - which solution (rdy kit or diy) can equal or balance their rpms in ±1-2% range? Seems it offers PWM regulation with choosable direction of rotation by jumpers (RIGHT on/off, LEFT on/off), done by B100K voltage regulator and a 35V 330µF capacitor


texts: Slew rate limiting of bidirectional lines

texts:
Assuming the ICs in use don't offer an adjustable slew rate, if I want to limit the slew rate of a unidirectional digital data line, for example of SPI's MOSI-signal, I can put a series resistor at the source. All clear up to this point.

But what is the best practice to limit the slew rate of bidirectional data, for example in the case of I2C SDA? The source end is not fixed and both parties can send. Put a resistor in the middle as a trade-off? Or use a resistor on both ends? Or some other scheme?

And what if the data line has stubs and is shared in addition, like, again, with I2C with multiple slaves?

Thanks for sharing your expertise.


texts: Is it correct to have a path between the two pads. The width of the path is 8mil


texts: Butterworth passive filters normalized values equation

texts:
Recently I'm reading in-depth about butterworth filters, more specifically about the normalized values the tables give.
Most of the tables give you the normalized values for the case of RL/RS=1 or RL/RS=∞ but I have found a table that gives the values for other ratios too.

Now the equation that these values come from (maybe this not the only way) is the Cauer topology equation that is shown here (equation 10.5.1):

But this equation is valid only for RS=RL=1Ohm so my goal is to find out the general equation that counts in the RS and RL to be able to calculate the normalized values for any resistors ratio.

For some reason I can't find where this equation came from or how it can be changed to include the resistors as parameters.

How can I generalize this equation?


texts: What does this op amp/transistor circuit do?

texts:
Consider this circuit:

simulate this circuit – Schematic created using CircuitLab

It's not clear to me what this circuit does. Here's what I think I understand:

Depending on the position of the pot, the voltage at the non-inverting input is between 9V and 10V
Because of negative feedback, the voltage at the collector of the transistor is also between 9V and 10V (or is it? It's not clear how the second power supply input is affecting the feedback cycle).
The current through the load will be at most 10 A (perhaps this is a current source?).

I'm a beginner and these things are very confusing to me. In addition to a theoretical understanding, I'm also interested in how real (ie. non-perfect) op amps might behave differently and the tradeoffs involved in picking the right op amp for this circuit.


texts: I want to supply under 1.1V to xilinx virtex5 Vccint how to make the volatage?

texts:
I'd like to supply under 1.1v to xilinx Virtex5 Vccint.
The input voltage is 5.
But I can't find any reference how to make like under 1.1v.
Does anyone know how to make it,  please give to me any hint.


texts:
I have a Bosch NDC-274-PT security camera that had the wiring cut off at the base.

It's a POE security camera (though it also supports regular 12 or 24V power), so I was hoping to find typical ethernet wiring inside.  No such luck.

Instead I've got two connectors.  On the first:

Grey - seems to connect to pins 1 and 6 of the coilcraft transformer
Purple
Blue
Green - seems to connect to pins 4 through 5 of the coilcraft transformer

And on the second:

Brown
Black (no continuity with the other ground wire)
Orange
Black - Ground, connects to the cable shielding and ground lug
Yellow
Red

I'm hoping there weren't any necessary electronics in the cable/plug itself.

Anybody know what wires would match up with a typical ethernet jack?  Or is there any way to determine that myself with a multimeter?  Unfortunately I do not have the other end of the cable, or mapping it out would be easy.

Close up of the connectors:

Whole board:


texts:
I'm quite new to the electronics, and I'm currently reading a book to learn it. In the chapter I'm in, the author is talking about relays, so I tried to make a simple circuit using a relay IM46.

Here is the circuit I made:

I understand that the LED is lighting, I don't press the switch, so the current does not flow through the relay (if I might say), so this is logical for me so far. The not-so-logical thing (for me), is that when I press the button, the LED goes off and the other stays off. I don't understand why. From what I understood, as the current flows though the relay, the coil should react and then activate the "other side of the relay".

Well, apparently I'm wrong (or I'm using a wrong relay type). I checked the voltage drop on the resistance, it is about 12V.

The input voltage is 12V DC (as written on the relay).

Does anyone see the mistake I made?

EDIT

As asked, I tried to make the schematic version of this circuit:

When the switch is not pressed, D1 is on and D2 is off. When I press the switch, D1 is off and D2 is on. At least, that's what I want.


texts: So I'm looking to get some LM335 ICs to measure temperature, and I'm confronted by "LM335A" and "LM335Z" models (and possibly others).  Ordinarily I wouldn't think much of it, but there seems to be a reasonable price difference (the Z is about twice the price of the A).  I've tried googling and reading the LM335 datasheet, but I can't seem to figure out the difference between the two.  Or is there no practical difference?  Any ideas?


texts: Can anyone identify this Knowles Donau microspeaker connector?

texts: Can anyone identify this type of connector? I need to purchase a bunch of these connectors.


texts: Is this a good "pure" sine wave inverter design?

texts:
I'm in the initial stages of designing a pure sine wave inverter. My design is as follows:

Wien Bridge Oscillator (5V at 50 Hz) -> Class D Amplifier -> Output transformer

My question is, is this a good design? Are there better designs out there? The inverter will utilize a 12V lead acid battery as its source and output 220V at 50 Hz. The Amplifier will amplifier the signal upto 12V and the output transformer will then step-up the voltage to 220V.

An alterate design that comes to mind is:

Wien Bridge Oscillator (5V at 50 Hz) -> Class D Amplifier (Amplify to 220V)

Since the battery is only 12V, by using a DC-DC Converter the DC source can be stepped upto 220V DC - which the amplifier than utilizes to amplify the sine wave signal to 220V.

How good are these designs? Will they work at all? If not, why so? And if they do, how good are they for a general purpose inverter?


texts:
I have been playing/experimenting with this multivibrator circuit for days. Got some good results and also got many doubts. The npn I am using are S8550 with 100 gain.

here are my doubts/questions:

1, Whenever I use all same values for R1-R4, It will not oscillate at all, for instance 100K for R1-R4, 1u for C1-C2. I also notice that after I replace 100k R4 with 10k, then it will oscillate again. SO what is the relationship between the output and this collector resistor?

2, For another setup, I use 100k for R1 and R4, 1M for R2 and R3 and 680pf for C1 and 20nf for C2. The measured frequency is about 200hz, and my LTspice IV simulation also confirmed that, but when I do the calculation by hand, it is only 70 hz. I am using this formula: f=1/(0.7*R*C) for half of the cycle. what I did wrong here?

20nf=20e-9, 1m=1e6;
rc.7=t;
1/t=f;

20e-3*0.7=0.014;
1/0.014=71; <<<==

680pf=680e-12, 1m=1e6;
680e-6*0.7=476e-6=0.000476;
1/0.000476=2100;

1/0.014476=69; <<<==

3, last question, I am only able to get about 11khz with this circuit. Trying to go faster by using smaller value capacitors, and it simple refuse to oscillate.
The value are 100k for R1-R3, 10k for R4; 680p for C1-C2; What are the reasons for these results? according to the datasheet, the S8550 can go up to 150mhz.

Updated simulations:


texts: Can Altium do via stitch patterns when interactive routing a group?

texts:
I am currently only able to route a group to the next layer with a line of via's like below:

I would like to be able to route them something like this:

It would really save space but it takes a long time to do manually. Googling around doesn't give me much except this

  Via patterns decided by the tool can be toggled between perpendicular to the route or staggered. They can also be toggled interactively.

showing that Altium should be able to do this but I just can't find where you can toggle between various via patterns.


texts: Questions about grounding points for an analog signal transmission

texts:
I'm planning to implement the following circuit I have drawn. But because there is no SPICE for such components I couldn't verify or test any overall workings.

From left to right I will first summarize the signal chain.

The transducer is a uni-polar but balanced transducer and it has three terminals marked as SG_out, SG_ref and AGND. It has normally swing of +/-200mV. I want to amplify this transducer signal and send to a 20 meters far away data acquisition input in a balanced way. Signal interest range can vary between +/-100mV to +/-10V and freq from DC up to 30kHz.

The power supply is a +/-15V dual supply where I marked its terminals as +15V, -15V and PWR_GND.

The fixed gain differential amplifier INA106 is chosen for a stable gain and CMRR for temperature changes.

Balanced line driver is right after the differential amplifier is chosen to ensure the balanced output for the transmission.

STP cable carries line driver's outputs all the way to a differential ended and balanced data acquisition inputs. The STP cable's shiled is grounded to the ground of the data acquisition ground AIGND.

The data acquisition receives the signals Vo+, Vo- from the STP cable.

If the over all wiring is correct, my questions are:

1-) As you see the STP cable carries Vo+, Vo- and shield but not the analog ground of the incoming signal chain. Does that mean I should ground the balanced driver's ground(from its pin3) with a separate wire to the AIGND as drawn in the schematic?

2-) At what point of the signal chain ground(from AGND to AIGND) is better to connect and ground the power ground terminal PWR_GND?


texts: How to make a weighing scale with independant load cells

texts:
Im working on a project for school and I need to make a scale that measures weight and also accurate pressure readings at differnt points.

Is it possible to make a scale using four independant load cells? So that I can find the pressure from each of them and then use them collectively to provide a weight reading.

Or is there any better way to make a design that measures pressure at four different points and also gives the total load weight?

where can i learn more on the subject?


texts: Sharing power source for LED strip and stepper motor

texts:
I'm making an AC powered lamp with retractable console uling 12 V LED strip and stepper motor. Originally no automation was planned so simplest AC-DC converter was bought.
Like this (declared by manufacturer as LED driver):  except that my have lower characteristics:

Wattage = 0..15 W
Iout max = 1.25 A
Output voltage = 12V DC

LED strips (2 pieces) being powered from this supply consumes 310 mA each. Which gives 7.44 W total.

Stepper motor (M42SP-4NP) consumes 300 mA at 12 V resulting in 3.6 W. Winding resistance is 40 Ohm. Also there is some neglectable power consumed by AVR mCU through LM1117 linear regulator.

Is it Ok to power all parts by the specified AC-DC converter or additional supply for motor and mCU should be used?

Also I'm doubting which type of transistor is better for switching LEDs - BJT or MOSFET?


texts:
I'm using the NXP LPC1100 series CPU, which is their most low-power Cortex M0 offering. However, in the datasheet it states that under the most optimal conditions (sleep-mode + all peripherals disabled) it still uses 6 mA, and my measurements confirm this.

How can it be that my smartphone (which has a 1Ghz CPU, and a lot of active peripherals) uses only 3 mA while in standby, when this 48Mhz Cortex uses so much more when not even active?


texts: How do I control a small dc motor with a mosfet?

texts:
I'm trying to figure out how to use a mosfet in order to allow me to use a small voltage to switch a larger voltage / current driving a motor. My son wants to write a program to control his small rc car, and controlling the motors via something like this seems like a good way to go.

I read this page, https://oscarliang.com/how-to-use-mosfet-beginner-tutorial/ -- and I got some irf520n mosfets, connecting them up as pictured.

The large battery pack positive output is connected to the source on the mosfet, and the then I have a wire from the drain to the motor, then from the motor to the negative output of the large battery pack.

I have the small battery pack, intended as a switch, connected positive to the source, and negative to the gate.

At least from reading that page, and trying this, I believe that's what I've set up, but it's not working.  When I turn on the large battery pack, the motor runs, regardless of whether the small one is turned on or not.  Pretty new to all this, so any tips are much appreciated.

I did notice while researching this question that irf520n mosfets are not logic level mosfets, so the 3v I'm applying might not be enough, but the data sheet here: http://www.infineon.com/dgdl/irf520npbf.pdf?fileId=5546d462533600a4015355e340711985 looks to me like it the switch should work with between 2 and 4 volts (it has VGS(th) min of 2 and VGS(th) max of 4 on the data sheet).


texts: R-EXT connection on the STP16CP05MTR LED sink driver

texts:
I'm planning to use a STP16CP05MTR LED sink driver to drive some LEDs in a matrix. The STP16CP05MTR supports constant current by the use of an external resistor marked R-EXT in the datasheet.

The idea is to provide a ~20 mA current to each LED by using one 1 K resistor on R-EXT.

What i cannot figure out from the datasheet is if this resistor should be connected to GND or VDD. Page 17 in the datasheet might suggest GND, but with my limited knowledge I'm unsure.


texts:
A PMDC motor M2 is connected to a constant regulated voltage source. To protect the regulator chip from the flyback voltage, a diode has been added. From the same unregulated voltage source another motor is also driven. The voltage regulator has an inbuilt polarity protection and as such I don't want to add another diode in series with the circuit so as to have an unnecessary drop. Also if a flyback diode is used across M1 motor, it will create a short under reverse polarity.

What will be the effect of flyback voltage generated across M1 motor on the regulator chip? If possible, please show the conventional current flow in the circuit.

[![Block Diagram][2]][2]


texts:
I am setting up an UART protocol that allows the communication between 2 boards; A Master board and a Slave board. The communication between them is going to be like this:
Example 1  :
Master [Tx] -- GET_VALUE--> [Rx] Slave
Master [Rx] <-- 0x05 -------- [Tx] Slave

Example 2:
Master [Tx] -- GET_STATUS -----------> [Rx] Slave
Master [Rx] <-- I_AM_BUSY ------------ [Tx] Slave

Example 3:
Master [Tx] -- START_OPERATION --> [Rx] Slave
Master [Rx] <----------ACK------------[Tx] Slave

Data size is 1 Byte for most of data flow between the two card. That's why I am going to use macros to define these commands:

Example:

  #define GET_VALUE 0x05
  #define START_OPERATION 0x06
  etc ...

In addition to these 1-Byte-data, There is only one element that should be transmitted between the two boards that it's size is not 1 Byte. In fact, I am willing to use serialization to transmit a data structure over UART using a circular FIFO buffer

Example:
Master [Tx] -- GET_STRUCTURE ------------> [Rx] Slave
Master [Rx] <----------STRUCTURE------------[Tx] Slave

typedef struct{
uint8_t var1;
uint8_t var2;
uint8_t var3;
}MyStructTypeDef;

Shall be transmitted over UART in this format "variable_name:valueXXX":

  var1:123XXXvar2:456XXXvar3:789XXX

XXX is a separator

My question is: If 99% of data flow is 1 Byte sized and only 1% of the data flow is not 1 Byte sized, Should I use circular buffer only to get the structure? Is there a better way to standardize the length of data passed over uart?


texts: What is the safest way to remove dust from electonic devices?

texts:
As dust inevitably settles on electronic devices such as televisions, laptops, computers and the like, what is the safest way to remove these both internally and externally?

The definition of safe includes the protection of the device as well as the person cleaning the device. For example, blowing air into a PC may an acceptable solution to rid it of dust however it may not be a suitable option from a health and safety perspective.

I am conscious that using a vacuum may not be the appropriate solution as my understanding is that it results in static electricity.


texts:
I just learned about memory segmentation that is used in microprocessors and I was told that old microprocessors like Intel 8086 had 20 lines of address bus which means that it could access 2^20 memory location.

If 20 lines bus is necessary to access a memory of 1 MB how can a microprocessors access let's say 1TB of memory? Because obviously it seems absurd to make so many lines to access that huge memory.


texts: Design of PID control for a vibration exciter (shaker) without having the plant model

texts: I want to design a PID controller for a shaker. But I don't have the system's differential equation or transfer function. I find the system identification algorithms complicated. Can I design a controller based only on the input and output data and without the plant model?


texts:
How to add solar DC output, Wind DC output and Fuel cell DC output to create a DC bus.
My doubt is, Is it possible to connect the outputs of different type of power sources(considering the DC voltage is same for all).


texts: Is it possible to replace a two way switch with two wall PIR sensors?

texts:
I have a two-way switch for the lights on the staircase and I want to replace them with two-PIR sensors.

I received the sensors yesterday and I discovered that they have only two wires and I am wondering if I will be able to connect the wires to make them work. By having them working I do expect that any of the two sensors to be able to open the lights (close the circuit).

Probably my current configuration is like this:

How do I need to do the rewiring?


texts: how do energy consumption (Ah, kWh) meters work?

texts:
How do devices which measure energy consumed work? For example the ones in solar regulators/chargers which display how many Ah went into the battery and how many went out?

Do they just measure the current for example every second and a microprocessor constantly adds up the measurements, assuming that the current 0.5s before and after each measurement is the same as while they take the current measurement, or do they have a way of really measuring how much energy went through, without referring to such, possibly inaccurate approximation?


texts: Calculating Field strength of a air core solenoid

texts:
I want to build a magnetizer for charging / magnetizing small alnico magnets for that I am thinking to discharge a cap into a air core solenoid.

The magnet to be charged would be kept within this solenoid.

The magnet would be of cylindrical geometry and 5mm dia and 10mm length, after searching on the web I have found that alnico needs a field strength of 3000 Oersted or around 239 kA/m.

I find that Oersted is related to A/mor Ampere/meter as both of these are units of field intensity but I don't know how  to relate oersted to ampere-turns.

To generate this field intensity I would like to know how many turns to wind and how much ampere's to dump into the coil.

Any clues would be of great help.


texts: What is the fastest 7400 series family? Is 74VHC faster than 74AHC?

texts:
What is the fastest 7400 series logic family?

Is 74VHC* faster than 74AHC*?

This list does not seem to be in any particular order:
http://en.wikipedia.org/wiki/7400_series


texts: How can a battery get reverse charged? (other than by being charged backwards)

texts:
I have an old lead-acid car battery that got taken out of my car by AAA 5-10 years ago when it died during a cold winter. I stashed the battery away and forgot about it.
Recently I dusted it off and measured it with a multimeter. It registered -0.189 volts. Kind of weird.
I hooked up a battery charger to it and the battery charger generated an error signal: reversed polarity, even though the leads were hooked up correctly. So, apparently the charger kind of did the same thing as me: test the voltage. When it found out it was backwards it refused to charge it the right direction.
Why does the battery have a reverse charge? Does it just drift negative when it gets sulphonated or something? Or is it an effect of extreme cold?


texts: What's the formal process to determine the IC by manufacturer code?

texts:
I've curious if there's an industry standard method used to determine the IC on a board.  Specifically, I've been wondering as I have an IC that I want to replace. It seems to have failed, but there's not manufacturer mark.  Is there a database somewhere where you can enter the code and get possible hits?  In my case, my bad IC is a "DOT 201 139".

The 201 is the manufacturer identifier, but no manufacturer has a "DOT" to my knowledge.  Also, the SOIC-8 is really tall.  This is enough information if there was central database to probably narrow it down, but I've been unable to find anything through web searches.  I'm sure this problem isn't unique to me, and there must be some way that the IC industry agrees on how to find replacements, no?

update
The circuit drives the gates of IGBTs that then run a solenoid. There's two of these drivers where one turns on and one turns off so that the coil field is bidirectional.  It's weird that it's an H-bridge where the "center" is GND, so it has V+ and V- and then common, which is GND in this case.  The best guess on the schematic is follows (I left off the connection to the 222 resistors):


texts: Easiest way from 2x10 (0.05" pitch) header to 0.1"

texts:
As per title, I have a debug header with a 2x10 0.05" setup on a board I'm working with. This was chosen because of the space constraints. I'm looking for the cleanest way to go from this header to a standard 0.1" pitch header that I can connect my logic analyzer and other debugging equipment to.
For the 2x5 I'm using this Adafruit breakout board[1] that works really well, but couldn't find something similar for 2x10.
[1] https://www.adafruit.com/product/2743


texts: How to adjust red brightness on MAX7219 with RGB LED

texts:
I want to use MAX7219 (datasheet) to control bunch of RGB LEDs. With common anode LEDs I should be able to use up to 16 3-color bulbs in following configuration:

simulate this circuit – Schematic created using CircuitLab

There would be probably needed a resistor to protect the pins DIG 6 and DIG 7.

Now the RGB LED has drop voltage 3.2V on green/blue and 2.0V for the red color at 20mA. This would result in noticeable brightness difference of the LEDs. Is it possible to add 60Ω resistor to each red rail to fix the brightness of red color? The resistor is calculated from the voltage difference (3.2V-2.0V=1.2V) and driving current of 20mA. Given that only one LED is on at each time, this should be enough.

My goal is to control at least 16 RGB LED, in such way that I can control color of each bulb.


texts:
This is a current mirror circuit with 2 op amp stages.
First stage on the left
Voltage from a DAC gets fed into U1 which creates a reference current through Rmir (via the N channel MOSFET) by sensing the voltage across Rset in its feedback loop.
Second stage
U2 (the 2nd stage amplifier) needs to keep the voltage at its two inputs equal as do any op amp. We feed in the voltage across Rsns and the voltage across Rmir to the two inputs respectively.
Non-inverting input
The current across Rmir (reference current) and the resistance of Rmir are constant. Therefore the voltage fed into the non-inverting input is also constant.
Inverting input
The resistance of Rsns is fixed. U2 varies the voltage across Rsns (to match with that across Rmir) by outputting a higher voltage across the MOSFET that then draws more current from PVDD. Hence, across Rsns (and across Rload), we now have a higher current value that is greater than the reference current and that is also constant.
My question is this:
Instead of the constant source that is fed into the non-inverting input of the 2nd stage op-amp, if I feed in the voltage from the DAC directly, why don’t I see a constant current through Rload? I’m aware that the source providing VDAC isn’t a constant current source. But, the current flowing into an op amp is almost negligible right? And it is wholly dependent on the input voltage right?

I know this circuit doesn't work as when I change the Rload to say 2 ohms, the output current changes i.e. doesn't stay constant no matter what Rload's resistance is. Not sure why though.
Also, what would be the feedback loop equation for the 2nd opamp stage with the Mosfet in its way?


texts: Current measurement over a fairly large range

texts:
A part of a circuit I'm building has the following components:

simulate this circuit – Schematic created using CircuitLab

For clarification, the transistor's base is being supplied with current from a different part of the circuit.

V1 is a voltage source, variable between 0 and 35V. It can deliver up to 1amp, however, in sake of the transistor's safety, I'll be limiting the max. current to no more than 250mA.

R1, is a sensing resistor. 0.1% with a low temp. coefficient.

The values of V1 & R1 as shown are arbitrary.

A voltage will be developed on R1 as current passes through it. My intention was to use a current sensing amplifier that feeds a 14 to 16bit ADC to read the voltage.

The problem is that my ADC will have a reading range of up to 5V, probably a bit less. The current sensing amplifier has some internal gain, 20 seems a common one. This makes it impossible to find a single resistor value which will enable me to get readings in the uA range and high mA range.

For example, if 1uA flows through R1 which is 1Ohm there will be a voltage of 1uV across the resistor. Amplified by 20, the current sensing amp. will output 20uV.
With a 16bit ADC and 5V range I have a resolution of 5/2^16 = ~76.3uV so this is will fail to detect anything under 3.8uA and that will be my final resolution. In real life it would be less because of noise, perhaps half of that or a bit worse.

At 250mA the voltage across the resistor is 0.25V times 20 = 5V so that would be the highest value I could measure.

Easy to see that I can not use a larger resistor because that would mean that higher current will go over 5V which means I will not be able to read them. Using a smaller value resistor will cause further loss of resolution on the low range.

What's the way to get "the best of both worlds"?
I can imagine using two resistors, but how do I know when to switch between them and who to "believe"? This current reading will be used to auto shut off in case it overshoots a certain value - it must be reliable.


texts: I am looking into using a 4N32 opto-isolator and am struggling to find information on its pin 6. This looks to be the base of the transistor (darlington). I see example circuits where they appear to leave this pin floating. I am curious to know if I should make a pulldown resistor connection. Anyone have any advise or insight as to what I should do. What pull-down resistance to use.


texts:
I got problem getting around Verilog. I am trying to create a FSM that displays numbers on one of the displays and on the next state to display a string. I did make the string to be displayed separately and the number separately in 2 projects, but I am getting errors when I try to combine it. What I did was to set an always@ loop and place in there a flag in if else statement with two switch cases but I got error saying that is preferable to get rid of the combinatorial logic loop. Is there any way I can combine both functionalities?

Ok, I will post some code, but the main picture is that I have a master state machine and then I got another state machine. I use the other state machine as input to the 7segment display for a single number. But in a different state of the master state machine I have to display a message on the 4 7segment displays. What I got now is:
Here I used CLK in order to make the message

always@(BIN_IN or CLK) begin
if(FAIL==1) begin
     case(state)
           left:
           begin
               HEX_OUT [6:0] <= F;
               SEG_SELECT_OUT <= 4'b0111;
               state <= midleft;
           end
           midleft:
           begin
               HEX_OUT [6:0] <= A;
               SEG_SELECT_OUT <= 4'b1011;
               state <= midright;
           end
//same for the rest
end
else begin
case (BIN_IN)
4'h0 : begin
    HEX_OUT [6:0] <= 7'b1000000;
    SEG_SELECT_OUT <= 4'b0111;
end
//same logic for the other cases

Thanks


texts: High Voltage negative power supply from positive supplies?

texts:
How can I combine two identical 5KV 15 ma power supplies that each are set up to deliver 5kv+ with negative being ground, so that they will deliver TWO -5kv outputs (cathode) and the + (anode) being common?   As in a voltage divider.  -5kv to 0 to -5kv

Schematic Please?

Or, how can I take a 5KV 50 ma transformer with a standard two lead secondary, rectify it and filter it to provide two -5KV outputs with + being common or ground?


texts: Multi-stage fully differential bandpass filters

texts:
I've recently been doing a bunch of research on analog filtering in preparation for a data acquisition system I'm building. For context, while I'm fairly comfortable with FPGAs and digital/computer engineering, I have far less experience with analog circuitry. I've been reading Analog Filter and Circuit Design Handbook as a reference, as well as a lot of material online.

There's one question I have been unable to find an answer to in all these sources. I would like to use differential signals as far as possible in this circuit, ideally all the way to the ADCs. However, I can't figure out how to construct active, multi-stage filters with fully differential signals. I used Analog Device's filter wizard to spec out a 4th order Chebyshev response comprised of two 2nd order band-pass multiple feedback stages.

Here's the result:

I'm now trying to 'translate' it to fully differential form. I had two ideas on how to do this. The first is to use the first stage to convert to single-ended, which isn't ideal and also I don't know if it would work. The second idea uses differential signals the whole way through, which would require swapping out the op-amps recommended by the filter wizard for fully differential ones (no big deal). My question is: will either of these work? It seems highly sketchy to get rid of their grounding scheme like that, but I don't know enough about this to decide if it'll work. Any help or direction to other resources would be appreciated. Here's the sketch of my two ideas.

Thanks!
-Seth


texts: simple explanation of ampers, voltage, watts, current and electricitiy

texts:
Possible Duplicate:
  What is an amp (and other such basic questions) in the simplest possible terms?

How can can this terms be simplified or what are some basic analogy.

let say I have a 9 volts motor. what happens If I put use a 12 volts battery, or what happens if I use a 9 volts battery and it's ampers are really high. Can an air be a conductor of electricity? Can it be like radio waves or wifi that even without a wire/conductor it can travel?


texts:
I have read this page: How to convert amps to kilowatts

I often purchase electricity from a supplier to power computing equipment within a data centre. Some sell me 10 amps, some sell me 2.16 kWh.

When they say 10A, they essentially mean I can draw up to 10A of power (at a usual 240v, single phase AC), continuously, each month (as I am billed monthly). If I purchase 2.16kWh, that means constantly, for a whole month (again it comes from 240v single phase AC feed).

So even though that article linked above states you can not compare amps [*1] and kWh directly, as long as I am using them in the same frame of reference (i.e. the single phase, 240v), can I directly compare them when making my supplier price comparisons for those selling to me as 10A and those selling to me 2.16kWh (assuming they are both providing 240v single AC feeds [*2]) ?

[*1] I understand that amps are an instantaneous snap shot of current, so in this scenario I am really talking about continuous amp hours

[*2] All throughout I have assume a generic power factor of 0.9, just in case you wondered about my dodgy maths :)


texts: cost efficient BOM for total 10x12 16 segment (1920 led) display

texts:
I've already built a few test prototype for a large(ish) 16-segment display board. I want to use a Arduino of ESP8266 to run it, with external power, and ICs for the Characters.

So far, I've been able to make 2 rows, with  8 characters each using a MAX6954 IC chip for each row. I've found 8 characters isn't enough, so I want 12-14. I could just double up and do 16 characters per row, with 2 MAX6954 per row. I want a total of 10 rows. The problem is MAX6954 for me cost almost 30 dollars each. Making the project $600 in IC chips alone, the rest of the parts are <100 dollars.

I've looked into doing a TLC5940 16-channel LED driver per character (about a 1.50 each). However it looks like you can only chain 40 together The following equation calculates the minimum frequency required:
f(GSCLK) = 4096 ´ f(update). I don't know if it would be possible to drive 4 sets of 40 with an arduino, or would I need to chain Arduino?

The AS1130 chip says it can run 132 LEDs (wow) for under 10 dollars. But there is very little documentation for it. I've only been able to find a single library, that is optimized for dotmatrix displays, so I'm not sure if it would work in this use case.

any suggestions appreciated!


texts: Why do some LEDs light VERY slowly when power is applied?

texts: I have a pile of bluish white LEDs salvaged from Christmas lights. They look like ordinary LEDs, with one electrode having a little cup with the light emitter, and the other with a tiny wire going to the top of the emitter. When I apply a milliamp or so from a 9v supply, they light up just fine. If I apply 10 microamps or so, they barely light when power is applied, then get brighter over the next few seconds. It is clearly visible to the eye, and makes them useless for making optisolators with. Obviously the LEDs used in commercial optoisolators don't have this problem. Why do these LEDs do this, and what kinds of LEDs do it?


texts: Is it safe to abruptly remove Arduino power?

texts:
If I have an Arduino, can I abruptly turn the power on and off without corrupting it? If I am designing a product that has an on/off switch, do I need to incorporate a delay before turning off the power so that the microcontroller can do a clean turn off of some sort? Or is it okay to just connect an SPST switch to the Arduino's power line?

(By designing a product, I mean using an ATmega with Arduino code independently on a custom board with other components.)

Edit:
By Arduino I just mean flashing the Arduino bootloader so I can program in Arduino instead of AVR.
The chip I want to use is Atmel atmega328P
I do not need any EEPROM usage.


texts: How do you wire a transformer for multiple output and amperage?

texts:
I'm getting different answers watching the MOT (Microwave Oven Transformer) videos on YouTube.  Some leave the shunt out, some leave it in, etc...
I have a MOT and want to make a 12VDC power source out of it.  I saw one video where a welder uses a transformer and a shunt on a threaded slider to adjust the amperage.
Another has a lead on the winding that is shorter than the main winding and this gives a different voltage.
Q1. Can you have one secondary winding on a transformer and have different voltages from that one winding?  I thought this is how 6/12V battery chargers work.
Q2. Do you need a shunt?  What happens if you wind a transformer without any shunt and if you need to use a shunt, what difference does different shunts make?
Update: looks like a tap can be put in, so the only question left is about the shunt.  Thanks.


texts:
everyone.
I'm new to embedded systems and I want to program a PIC12F675 for a project.

I have most of the code figured, and there is only one thing left. It's the analog input. I tried some tutorials, but they didn't work. They used the function "ADC_Read()" which isn't a standard function in XC8, which I'm using.

So can someone help me with this?
Thank you.

The Config:

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

The Code:

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

void dClock(int delay){
    GPIO2 = 1;
    __delay_ms(delay);
    GPIO2 = 0;
    __delay_ms(delay);
}

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

    char pressed = 0;
    GPIO2 = 0;

    while(1){
        __delay_ms(50);

        if(GPIO3 == 0){
            int delay = ADC_Read(); //Supposed to read analog value here
            dClock(delay);
        }
        else{
            if(GPIO5 == 1 && pressed == 0){
                GPIO2 = 1;
                __delay_ms(500);
                GPIO2 = 0;
                pressed = 1;
            }
            else if(GPIO5 == 0 && pressed == 1){
                pressed = 0;
            }
        }
    }
    return;
}


texts: detect optical transceiver transmit wavelength

texts: Let's say there is a no-name SFP transceiver without a label and without DDM(allows to see manufacturer programmed wavelength data on EEPROM from network device) support. Is it technically possible to detect on what wavelength this SFP transmits? I have used JDSU light-meters previously and they ask user to select wavelength(for example 1310nm, 1550nm), but regardless of the selected wavelength, they will show optical Rx power.


texts: Why are high impedance circuits more sensitive to noise?

texts: Why are high impedance circuits being more sensitive to the noise? They have less current flowing through them, but how is that related to noise, since external noise becomes voltage on the wires, and then current proportional to resistance?


texts: Circular force sensor: some basic questions about its functionality

texts:
Sorry if my question sounds to simple for this forum. I just wanted to confirm the default measure of the output of circular force sensor when it is connected to the breadboard (with resistor)? Does it output force measured in N (newton)? When I slightly touch the sensor with a fingertip, the output value varies around 200-400.

Another question: My final objective is to measure weight categories of objects (light, medium, heavy) using 2 force sensors. Do I understand correctly that the overall procedure is the following:

Calibration:

1) put known weights on top of each sensor and measure the force

2) fit analytical function for each sensor, e.g. some polynomial

Usage:

3) put an object with unknown weight on top two sensors

4) read outputs (force)

5) apply both analytical functions (with known forces) to obtain two weight's measurements

6) calculate an average between two measurements


texts:
Not an electrical engineer, just a hobbyist. But thought this might be the best place to come with my question.
I bought a bike light that uses a single 18650 cell for power, thinking it would work with standard cells. Little did I know, they use a different 18650 configuration than I'm used to. It has concentric positive and negative terminals on the one end, with a non-conductive material on the other side of the wrap. Other than that, it seems like a basic protected Samsung 2600 mAh cell (according to the documentation). Of course, the company way overcharges (no pun intended) for their own replacement batteries.
Just trying to figure out if there's anywhere I can buy 18650s with these same-side terminals, or even just by the terminal connectors and re-wrap some cells myself. I've looked in the usual places (Mouser, battery space, etc.), but it would help if I knew what these are called so I can search for them.


texts: Can someone help me understand how to do this counter ripple? and what to be use as counter (74ls76 or 74ls193). My problem is to make counter like this [0, 2, 3, 4, 6, 7, 9, 15, 14, 13, 12, 11, 10, 8, 5, 1]


texts: Is there a way to prevent the random state of a shift register when power is applied?

texts:
I have a project with two seperate output shift registers and they are working fine. They both have LEDs at the moment but one shift register will eventually be controlling relays and then solenoid valves to control water flow. The issue I have is when I turn the power on, the 8 channels of the shift registers are rarely in the off state. Normally some are on which is no good having the solenoid valves randomly turn on then off when power is turned on. Is there are way I can force the registers to be off when power is applied? The shift registers I am using are both 74HC595N.
EDIT
The green LEDs light up before the MC can initialise the shift register.


texts: Floating LM317 (used at high voltage) protected by two Zener diodes

texts: In Marty Brown's Power Supply Cookbook, I found the following variation of the floating linear regulator. I'm aware this topic has been discussed in at least one other question; the two-Zener wasn't mentioned in that discussion though. My  question for this schematic is why use those particular voltage and power values for the "lower" 5.6V, 500mW Zener. There isn't really an explanation in the text in that regard.


texts: Driving constant current LEDs with constant voltage?

texts: I have about 6 pieces of bar leds in different colors (all of them are 12V, but different power 18W, 12W, 9W ...) I need to connect them in parallel by regulating 24V, but the problem is that the LED with the highest current(18W-Red) is the brightest, but the other LEDs(12W-Blue and 9W White) draw less current, so the brightness is lower.Waiting for your suggestions.


texts: Will a fuse improve the safety of my non-isolated buck converter design?

texts:
I have a power circuit that implements an AC-to-DC rectifier and a non-isolated buck converter to convert a 120 VAC 60Hz signal to 12V and then a linear voltage regulator to step the 12V down to 5V.

The 5V will be used to power a micro controller and there is a possibility that people will touch the pins of the micro controller. I realize that it is not ideal to use a non-isolated power converter, but due to size constraints I do not want to put an isolated power supply with a transformer in the design.

The question is:

Will a 500mA fuse after the 12-to-5V linear voltage regulator make the design safe against electric shock since the buck converter is non-isolated?


texts: Can you make a non-polar electrolytic capacitor out of two regular electrolytic capacitors?

texts:
There was some discussion on this question

What are some reasons to connect capacitors in series?
What are some reasons to connect capacitors in series?

which I don't see as being conclusively resolved:

"turns out that what might LOOK like two ordinary electrolytics are not, in fact, two ordinary electrolytics."
"No, do not do this. It will act as a capacitor also, but once you pass a few volts it will blow out the insulator."
'Kind of like "you can't make a BJT from two diodes"'
"it is a process that a tinkerer cannot do"

So is a non-polar (NP) electrolytic cap electrically identical to two electrolytic caps in reverse series, or not?  Does it not survive the same voltages?  What happens to the reverse-biased cap when a large voltage is placed across the combination?  Are there practical limitations other than physical size?  Does it matter which polarity is on the outside?

I don't see what the difference is, but a lot of people seem to think there is one.

Summary:

As posted in one of the comments, there's a sort of electrochemical diode going on:

  The film is permeable to free electrons but substantially impermeable to ions, provided the temperature of the cell is not high. When the metal underlying the film is at a negative potential, free electrons are available in this electrode and the current flows through the film of the cell. With the polarity reversed, the electrolyte is subjected to the negative potential, but as there are only ions and no free electrons in the electrolyte the current is blocked. — The Electrolytic Capacitor by Alexander M. Georgiev

Normally a capacitor cannot be reverse-biased for long, or large currents will flow and "destroy the center layer of dielectric material via electrochemical reduction":

  An electrolytic can withstand a reverse bias for a short period, but will conduct significant current and not act as a very good capacitor. — Wikipedia: Electrolytic capacitor

However, when you have two back-to-back, the forward-biased capacitor prevents a prolonged DC current from flowing.

Works for tantalums, too:

  For circuit positions when reverse voltage excursions are unavoidable,
  two similar capacitors in series connected “back to back” ... will create a
  non-polar capacitor function ... This works because almost all the circuit voltage
  is dropped across the forward biased capacitor, so that the reverse
  biased device sees only a negligible voltage.

Solid Tantalum Capacitors Frequently Asked Questions (FAQs):

  The oxide dielectric construction that is used in tantalum capacitors
  has a basic rectified property which blocks current flow in one
  direction and at the same time offers a low resistance path in the
  opposite direction.


texts:
On an arduino project I'm working on (ATMega328 at the moment) I have a bunch of vector distance data that I need to use for various pixels in a matrix.

It's a relatively simple calculation:

d = math.sqrt(math.pow(x2 - x1, 4) + math.pow(y2 - y1, 2)) //Not the arduino code

Very slightly modified coordinate distance formula (with exaggerated x values)

I know that a modern computer can do that easily, but is this going to be any slower or faster than having the values for a 22x12 matrix stored as a PROGMEM 2-D array of uchar? (x1 and y1 are fixed at the center point... so one grid only).

These values are basically fixed, I just need to know them. I know that accessing values in flash is much slower than in SRAM but not really sure how many clock cycles that's going to take compared to the above equation. An AVR isn't exactly optimized for such math.

Update: Also, it's not like I only need to look up some of the vector distance values on each pass. On every loop I need ALL of those values.


texts:
I cannot afford a function generator and oscope right now, so I'm trying to learn analog electronics with Spice (MacSpice, to be specific). Below is the Spice model for a simple emitter-follower circuit.  Vcc is 15V, and the input at the base is a 5V 60Hz sine wave with a 0V DC offset.  R1 sits between the transistor base and the sine input, and R2 sits between the transistor emitter and ground.

The output at the emitter has me a bit puzzled and I would appreciate it if anyone has an explanation for the behavior.

* Simple Emitter Follower
Vcc 3 0 DC 15
Vin 1 0 SIN(0 5 60) dc 0
R1  1 2 270
R2  4 0 3.3k
Q1  3 2 4 generic
.model generic npn
.control
tran 1ms 60ms
plot v(1) v(4)
.endc
.end

The output of the transient analysis plot command is below.

I was surprised by this output.  As expected, there is a slight voltage drop in the amplitude due to the base-emitter junction of the NPN.  However, the output is clipped and does not swing below zero.  What would I need to do to catch the negative part of the sine wave?


texts: A 50 kW carrier is to be modulated to a level of 85%. What is the carrier power after modulation?

texts:
I'm getting answer as 36.73KW but in the book its given as 50KW.
My calculation :

P(total) = P(carrier)(1+(m^2)/2)
50 = Pc(1+.85*.85/2)
Pc = 36.73KW.

What am i doing wrong here?


texts: charging a bottom balanced lithium battery

texts:
I'm trying to understand the notion of bottom balancing a series battery of lithium cells and I've reached a sticking point in my understanding. Help would be greatly appreciated.

Once I've individually "bottomed" all of the cells and assembled the battery, I should charge it. I have no balance leads that would permit me to monitor individual cell voltages, and so I don't know if the states of charge for each of the cells are maintaining balance over the charging cycle. If I terminate charging when the voltage of the pack is a simple multiple of the overcharge threshold of a single cell, then am I not at risk of overcharging some individual cell? And if I terminate charging prematurely, then doesn't this defeat the object of balancing the cells to get the maximum capacity out of the battery? In short, how should I determine when to terminate the charging cycle?


texts: What design limitations does a higher-than-average resistance trace impose?

texts:
There's a Kickstarter running right now for a machine that prints circuit boards. Rather than a traditional etching process, they use conductive (silver-based) ink to print traces and pads. It has a resistance of 12 m\$\Omega\$/in^2. What design limitations does this impose? More specifically, what kinds of circuits would I not be able to produce with these parameters?

I assume high frequency things like high speed busses (LVDS?) and printed antennas? Other things?

Note: I am specifically not placing a link to the project here as this question isn't meant as an advertisement for it.


texts:
How do you tell different semiconductors (mainly transistors, sometimes even voltage regulator ICs, etc.) apart? Do they all basically look the same; or are there visual clues to indicate a certain type? I mean, It's easy to tell a FET from a BJT when reading symbols from a schematic diagram. But when it comes to dismantling, troubleshooting, and  repairing consumer electronics; I'm always getting stuck because I can't tell them apart. They always seem to have the same generic TO-92, TO-220, TO-263 appearance.

Failing that; are there any tests I can do, (i.e. with a multimeter) to determine exactly what I'm dealing with?


texts: Why do datasheets document protocols from the ground up?

texts:
I'm reading a datasheets for a component with I2C interfaces.
I can recall the same for datasheets of other components in the past.

In these datasheets they include a full description of the I2C protocol, start bits, address, R/W bit, data bits, ACK and so on.

Why doesn't the datasheet simply states that it is I2C and then document the higher levels specific to the device?
This could reduce the document from 4 pages to 4 paragraphs.

I'm not too familiar with I2C so I can't tell if what is documented follows I2C or deviates from the spec.

Assuming the documentation states that the device is I2C compliant, is it safe to assume that although they go into full detail that what they document is I2C?


texts: PCB drilling - drill bit material selection

texts:
I am planning to buy a bench drill (something like that one) to make small hole, 0.5-1.0 mm.

I recently used a Bosh drill and 1mm steel drill bit to make a hole on a FP4 fiberglass board, but the drill bit broke on the second hole drilling process.

Now, I will buy 0.6 mm drill bit but I am not sure what material it needs to be. Could anyone who knows these equipment tell me what material the drill bit should be made of, so that I can use the same drill bit for long? and what do you think about "Tungsten Carbide"?


texts:
I was looking for a way to make a touch touch switch and i found this circuit on the internet  but the problem is , it goes off automatically after few seconds
is there any way that i can control it manually ?
thank you


texts: Does a Series Voltage Reference referencing more than one electrical block has to be buffered?

texts:
I'm planing to use a Series Voltage Reference,REF3330,  as a voltage reference to three distinct parts of my circuit and i need an opinion regarding the way how to do it. First of all, the reference provides a 3V reference voltage and the input voltage will be 3.3V. This agrees with the minimum supply conditions.

The circuits i want like to reference:
1) Reference of a single ended ADC embedded in PIC uC

2) A voltage divider of 10k-10k to reference an Inamp. (fig 1)

3) A summing configuration to DC bias an sinusoidal negative signal. (fig 2)

My question is do i need to buffer the output of the Voltage Reference ?  I have some doubts if i would win anything with it, first the voltage reference provides more than enough current to supply the three parts within its working limits. Second, has a very low output impedance (2ohms at 1kHz) so it wouldn't unbalance any of the voltage dividers.

Fig 1:

Fig 2:


texts: Can lack of current cause servo motors to burn out?

texts: I am building a quadruped robot from 10 MG996R servo motors. I am powering them with 12 Eneloop AA batteries, but I am starting to see that I might be lacking current. The servo spec says that each motor can draw up to 2.5 A of current when stalling. My servos are stalling when the robot is standing and support its own weight, and it is exactly during this time that one of my servos stopped working. Is it likely that it broke down because it lacked current, or will the servos continue to fail even if I provide ample amount of current to support the stall current?


texts:
I have been messing with AVR's XMEGA line. They are pretty amazing microcontrollers. However, Atmel changed much with this new line. I am trying to detect a pin going low.

I have tried to set the PINnCTRL register to every combination with no luck. I can detect the pin going HIGH but not the other way around. Below is the working code for turning on the LED on pin 5 when pin 6 goes high. However, I wanted to do the same thing, just instead of when pin 6 goes high, I would like to have pin 6 go low and turn on the LED on pin 5.

Anyhow, I have not seen a lot of XMEGA stuff on here, so I thought I would try.

I am using AVR Studio and the ATXmega256A3 microcontroller.

AVR PINnCTRL Configuration Register Table (at least for the pull sections 0b00xxx000)
FULL DATASHEET HERE: http://www.atmel.com/dyn/resources/prod_documents/doc8077.pdf.
On page 131 (section 13.4) this lists the definition of all of table below.  NOTE: the PINxCTRL register contains more than just the pullups for settings.  The bits I am working with are these:
00xxx000 The x's correspond with the listing below.

Table 13-4. Output/Pull Configuration
                                                          Description
  OPC[2:0]  Group Configuration       Output configuration        Pull configuration
     000    TOTEM                     Totempole                   (N/A)
     001    BUSKEEPER                 Totempole                   Bus keeper
     010    PULLDOWN                  Totempole                   Pull-down (on input)
     011    PULLUP                    Totempole                   Pull-up (on input)
     100    WIREDOR                   Wired OR                    (N/A)
     101    WIREDAND                  Wired AND                   (N/A)
     110    WIREDORPULL               Wired OR                    Pull-down
     111    WIREDANDPULL              Wired AND                   Pull-up

#include <stdio.h>
#include <avr\io.h>
#define F_CPU 32000000UL
#include <util\delay.h>

void Config32MHzClock(void);

int main(void)
{
    //Init stuff..
    Config32MHzClock();
    CLK.PSCTRL = 0x00; // No division on peripheral clock.
    PORTCFG.CLKEVOUT = PORTCFG_CLKOUT_PE7_gc;

    PORTA.DIR = (1 << 5);  //Sets pin5 as an output (led)

    //011 PULLUP Totempole Pull-up (on input) is what is set
    PORTA.PIN6CTRL = (0x30);  //Sets pullup on input on pin 6.
    PORTA.OUT = (1<<5);       //Turn on the LED

    while(1){                   //Never ending main loop.
        if (PORTA.IN & (1<<6))  //If pin 6 goes HIGH.
            PORTA.OUT = (0x00); //Turn off LED.

        PORTA.OUT = (1 << 5); //Turn LED back on.
    }
}

//Function to setup clock..
void Config32MHzClock(void)
{
    CCP = CCP_IOREG_gc; //Security signature to modify clock
    // Initialize clock source to be 32 MHz internal oscillator (no PLL).
    OSC.CTRL = OSC_RC32MEN_bm; // Enable internal 32 MHz oscillator.
    while(!(OSC.STATUS & OSC_RC32MRDY_bm)); // Wait for oscillator ready
    CCP = CCP_IOREG_gc; //Security signature to modify clock
    CLK.CTRL = 0x01; //Select sysclock 32 MHz oscillator
};


texts: What is the best USB transfer type (bulk, interrupt, Isochronous Transfers) to be used for implementing a USB oscilloscope?

texts:
I want to build a USB oscilloscope. I was reading about different USB transfer types. Which transfer type is best to transfer the collected ADC samples from a USB oscilloscope to a PC?

Below are a few of my findings. Please correct me and also it would be good if anyone could suggest a good transfer type.

Isochronous transfer - Possible loss of data. Not good for an oscilloscope since each data item is valuable. How much data could be lost?
Interrupt mode - I have no idea if it would flood the USB connection
Bulk mode - Seems the best to me since no loss of data
Control transfer - not suitable since it is not meant for transfering data


texts: How to light an LED controlled by a photo-diode

texts:
I need to get an LED shining brightly when a photo-diode (in the local store it is sold as such, but of course it could be something else, as suggested in the answer of WhatRoughBeast) receives some light. My idea with an operational amplifier proofed to be a little bit complicated (Opamp constant on). I tried to use the phototransistor (there is only one type at the local store, two legged with internal basis), but its resistance (in conducting state) was too high. (The LED lit, but "shining brightly" is different from that.)

I had the idea that a transistor should be able to manage the task. What properties should the transistor "Q1" have (and why those should it be those properties)?

R1: 95 Ohm, LED D3: 3.1V, D2: has R=1852 Ohm when illuminated (and about 400000 Ohm when nearly not illuminated).


texts:
I've been searching for a way to set PCB size in Altium, I can change size using Mouse, but there is no way I found to change it to some values using keyboard.

Like I want to change PCB size to 10" x 1.5" but I can't unless I use Edit Vertices and move the edges.

I read the documentation, but there is nothing in there about specific size.

Am I missing something ?


texts: Is it possible reduce the watt consumption of a 12 VDC radiator fan by using a motor controller?

texts: This fan uses 80 watts and, since it is a car radiator fan, it blows alot of air. I need it to run all night on one car battery. It’s fine if it only blows a quarter of its full power, so I am trying to get its consumption down to 20 watts. I have heard talk of motor controllers and was wondering if one would do such a job?


texts: Can we derive all boolean functions using a 2x1 Multiplexer?

texts:
It is possible to implement all boolean functions using a 4x1, 8x1 or a 16x1 Multiplexer.

But is it possible to implement all boolean functions with a 2x1 Multiplexer? I think it is not, because how would it be possible to implement AND, OR, XOR, etc. I think only NOR can be implemented using a 2x1 Multiplexer.

Am I missing any point here?


texts: Synchronize Outputs of Separate FPGAs Within 1ns

texts:
Edit: I have been able to achieve 560ps uncertainty in simulation by using external PLL feedback through the entire chip. Once I verify in real hardware I will post a complete solution.

I'm trying to synchronize the outputs of two physically separated Spartan-6 FPGAs. Ideally, the skew between the two device's outputs would be less than 1ns.

The outputs are differential pins controlled by an OSERDES2.

One possibility might be to distribute a reference clock to the two FPGAs. The signal would be routed so that it arrives at each FPGA at "exactly the same" time.

The reference clock would be passed through a PLL, with feedback through a BUFIO2_FB device. As shown in the clocking resources example:

Will this feedback mechanism cancel out clock insertion delay, so that the IOCLK is in phase with clock input pin?

The ISERDES2 in the same IOCLK domain would register a reference data signal which simply denotes a particular clock edge to align the output with.

Are there other device variations which will prevent the outputs from being deterministically in phase?

For example I'm concerned the propagation delay from OSERDES2 to output pin could vary greatly between devices. Based on timing datasheet:

Does this specification of 0.94 ns mean that the propagation can be anywhere from 0 to 0.94ns across different devices?

Is there any more sound approach to this problem?


texts: Pressure Sensor KP125, input Pressure to O/P voltage conversion,

texts:
According to the KP125 Pressure sensor datasheet, the KP125 has an input pressure range from 40 kPa to 115 kPa.
Applied pressure is transferred to an analog output voltage between 0.5 and 4.5 V.

If the input pressure to the Sensor is 80kPa, then how would I suppose to know the output analog voltage, since there is no mention of any step-size or a scale factor.


texts: What is the output impedence of this RC Circuit

texts:
I have this simple circuit. And from what I calculated the output impedance seen from the OUT node comes to about \$138.765 \Omega\$.

$$ X_c = \frac{1}{2\pi * 890*10^3 * 10^{-9}} = 178.8257\Omega $$
$$ Z_{out} = R2||X_c = \frac{220 * 178.8257}{\sqrt{220^2 + 178.8257^2}} = 138.765\Omega$$

With an input of 890K Hz sine wave of 2v pk-pk, the voltage at OUT node comes to is about 1.2615v pk-pk.

If I connect a resister of the same value of \$138.765 \Omega\$, the voltage at OUT node should be half ed.

But I see a voltage of 697.843mV instead of 630mV. What is the problem, am I calculating the output impedance wrongly?


texts: Find constants of ideal op amp circuit problem

texts:
Alright, I'm currently learning more about circuit analysis and op-amps using an electrical engineering and measurement book; the problem is that most questions don't have answers, and I don't really understand what they want me to do during this problem.

I've done some OP-amps examples before, but I've always been given the Uin value for that, which I don't have here, so don't really know how to obtain my desired values.

"Uout = A*Uin + B (where Uin is the sensor output voltage), figure out A and B" is the question in the book, and I don't really understand how to obtain the "A" and "B" value. Usually you can just take the two resistor values such as R1/RF, and multiply by the voltage source which in this case is 0; however taking (1.5k/4k)*0 would just result in zero. And even if I did manage to find Uout, I still don't understand how I would get the A and B constants from it.


texts: What is the correct way to implement USB hardware?

texts:
I'm having some problems with my USB hardware that communicates from my STM32F4 microcontroller to a computer. I have problems with certain computer setups, with some types of motherboard the USB disconnects frequently, with other types of motherboard the connection is stable. Reading in some places I realized that this could be caused by the line impedance.

Currently I use 22R resistors in the USB_DM and USB_DP lines. I decided to remove these resistors and leave the line with approximately 0R and also put a pull-up resistor in the USB_DP line. This solved my problem in some disconnected computer setups. But I would like to know the correct hardware so that I do not have disconnection problems between the microcontroller and the computer.

Below in the first image is the first hardware I used. The second image then shows the changes I made to be able to operate USB.

Edit 1: The USB connector remains the same.


texts: Using an IR diode as an emitter and receiver?

texts:
At the recent Maker Faire Berlin, I was told that LEDs can be repurposed as photo diodes. I assume the same is true in the infrared range. This sounds like a nice solution for building a transmitter.

How would a circuit look like for an IR diode used as emitter and receiver?

Background: Communication will happen through a black plastic pipe with a length of 500 mm (20 inches). Data rate will be below 32 kilobaud.


texts: Sockets for leadless ceramic chip (LCC)?

texts:
From different supplier datasheets I unfortunately get conflicting information about the compatibility of different chips and sockets.

Can I use a Ceramic Leadless Chip Carrier (LCC) in a PLCC socket? Most suppliers list the JEDEC MO-47 standard as a compatible chip which has J-shaped leads, some claim that a leadless chip carrier also works. Is this true in general or do I need a special socket (there seem to be very few leadless chip carriers available)?


texts: I have heard it said that a ceiling fan with a built in three speed manual switch should be set on the high speed setting when using an electronic speed control.  I have not found an answer as to why this is.  Is this a true statement or can the manual switch be set on a slower speed and also have the electronic control set to a lower speed as well?


texts: How to select correct SPI flash for specific micro-controller (pic32mx795f)?

texts:
i'm interesting on how to correctly select SPI flash for microcontroller.

specs:

High-Performance 32-bit RISC CPU:

MIPS32® M4K® 32-bit core with 5-stage pipeline
• 80 MHz maximum frequency
• 1.56 DMIPS/MHz (Dhrystone 2.1) performance
at zero Wait state Flash access
• Single-cycle multiply and high-performance divide
unit
• MIPS16e® mode for up to 40% smaller code size
• Two sets of 32 core register files (32-bit) to reduce
interrupt latency
• Prefetch Cache module to speed execution from
Flash

Following are some of the key features of SPI module:

Master and Slave modes support
Four different clock formats
Enhanced Framed SPI protocol support
User-configurable 8-bit, 16-bit and 32-bit data
width
Separate SPI FIFO buffers for receive and
transmit
FIFO buffers act as 4/8/16-level deep FIFOs
based on 32/16/8-bit data width
Programmable interrupt event on every 8-bit,
16-bit and 32-bit data transfer
Operation during CPU Sleep and Idle mode
Fast bit manipulation using CLR, SET and INV
registers

Complete Datasheet

my concerns:

How many bits/pins SPI interface would be the most optimal (32, 16, 8) ?
What is the maximum speed can I get for read/write ?
Should I consider any other interfaces(PMP, Serial, I^2C, etc.) or memory types for best performance?

Purpose: possible code execution , storing audio files ( badgering from network ). I was looking for about 256-512 mb
Thank you.


texts: How many Ah do I need for 12V battery to power 76 LED lights (0.84watt each) using a 500W inverter to power for 6 hours?

texts: Looking to build a power pack with a 12V battery to inverter in order to power 4 string lights totaling 76 LED bulbs each with 0.84 wattage. Total time to keep lights on is 6 hours. How many Ah do I need in a 12V battery to accomplish this? Is there a better solution?


texts: P-channel MOSFET high side switching, Arduino 5V pin and Vcc connection

texts:
In this tutorial,

The author makes this weird(to me apparently) connection of 5V pin of arduino to 12 V power supply, and explains itself by:

  You need to have two power sources - one for the Arduino, and a
  separate 12V power source for the motor. You cannot connect the
  Arduino's barrel jack to the 12V! This will create a common ground
  between your Arduino and the 12V power supply. And it would fry the
  Arduino when you are creating the common VCC needed for this circuit.
  (With an N-Channel MOSFET you don't have this problem since you want
  to have a common ground between the power source and the Arduino)

However, I really did not understand why connecting grounds of two power supplies together and then applying HIGH or LOW to the Gate of the p-channel MOSFET does not do the trick.

So, a little bit help on understanding what is going on would be appreciated.


texts: How do I translate voltages to user-supplied levels?

texts:
I'm working on an AVR/JTAG/whatever programmer. The programmer will interface with chips running at various voltage levels, ranging from 1.8V to 5V. The programmer runs at 3.3V.

The programmer interfaces with the programee through four 3-state pins, which I control from the 3.3V chip, and I need those pins to provide logic levels supplied by the user. I've tried the following (VDD is the user-supplied voltage), but unfortunately, with R1 = 220, the switching was too slow; I'd like to communicate at up to 10MHz.

I've looked at voltage-translator ICs, but the best that I found was SN74LVC8T245, which won't however allow me to tristate each pin separately.

What should I use to perform the voltage translation?


texts: Is it safe to over-volt brushless out-runner dc motor on low load conditions?

texts:
I have a 1100KV brushless DC motor (turnigy d3548/4) rated maximum voltage 19V i want to run it at 25V assuming low load as i mostly need the higher rpm !

whats are the effects of this higher voltage on the motor electrically(coils insulation) and mechanically ?


texts: Why using a IR sensor instead of a IR sensor module (1838B)?

texts:
I bought an Arduino kit and it contains two sensors for IR (if I'm correct).

The first is a looking exactly like a LED but black (but heard it is a IR receiver).

The other item looks like this; which is an 1838B.

Why would I use the first LED-looking like part instead of the 1838B?


texts: Voltage Multiplier - Cockcroft-Walton Capacitance Value

texts:
I want to design a circuit in order to Harvest radio-frequency (RF) signals and get a DC Output to a specific load (i.e micro Watt Battery of a sensor).

Notes to be considered :

input will be between (uV - mV) which is low.
frequency that i am harvesting from is the GSM frequency which is 900-915 MHz
considering this frequency value the capacitance should be really small (pico or nano farads)

During my research i have found that the most used step-up (In terms of Voltage) configurations are mainly three types which are :

1- Transformer Topology (Which is the cheapest and less efficient for such application)

2-Diodes : Rectifiers (Which I am not interested in due to losses)

3-Voltage Doubler/ Multiplier (Which consists of diodes and capacitors such like >> Cockcroft-Walton or any other configuration)

Now the thing is that there are a lot of types of the voltage multiplier, but I could not find any certain reference that can help me through the design of the Voltage multiplier.

For example how to calculate the capacitance values lets say for multi-stage multiplier with N Stages and Vin to Vout specific ratio ?

Such as :
Vin  = 1V
Vout = 5V
N = 5-10 stages (or more depending on the output)

Cockcroft-Walton Topology with 2 stages.

Any advice will be much appreciated


texts: Higher current LED driver for persistence of vision display

texts:
Project needs

We need an inexpensive LED driver IC that:

Can source or sink at least 15mA/LED
Has an SPI-like interface (not I2C)
Has a separate latch pin
Has at least 256 grayscale intensities
Preferably at least 8 channels/chip

Can anyone recommend some devices to consider?  I think multiplexed/charlieplexed devices will not work for this project, but I am open to opposing viewpoints.

Why the project needs this

We are looking to drive 120 RGB leds (320 total channels) in a persistence of vision display. The nature of this device (bicycle-spoke mounted) means that to get the "horizontal" resolution (along the wheel circumference) of 10mm/virtual pixel we need to be able to load a full "column" of pixels (a radius) at 0.746 mS. The latch line is to ensure that the entire column will turn on at once, rather than one-by-one.  1Mhz I2C ends up being slower than SPI: using ATmega chips running at 20Mhz, the SPI subsystem can load 24 16-channel drivers in roughly the needed time (at 12-bits/channel). I2C at 1Mhz and 8/bits/channel (zero overhead) can program 320 channels in 2.56mS or more than 3x the time. Given the architecture of the system, we would really prefer to stay with a single core processor for ease of control and communication.

Previous work

TLC5940 We've used TLC5940 (which can be had on Ebay in quantities for about $1/piece) successfully timing-wise. These drivers can officially sink up to 120mA/chip, meaning 7.5mA/channel (8mA if only 15 channels are used). We are considering overdriving the TLC5940s to reach 15mA/channel (225mA/chip peak), however, this seems unsafe. Is it? Are there ways to overcurrent the LED driver in a more safe manner? The TLC5940 can signal thermal error on one of its pins. The project is expected to be deployed in the environment of high air velocity: heat dissipation isn't expected to be a problem.

75HC595 We have also tried using 74HC595 shift register for this. This has two problems. One is that 74HC595 can only source 8.75mA/channel if all channels are one. The second one is that using a PWM LEDdriver, we need to get 0.746 mS/update because each horizontal "pixel" lasts 0.75 mS. Manual PWMing means that for N linear greyscale levels we would have to update each shift register N times / 0.75 mS, which quickly becomes unwieldy once you realize that brightness is perceive exponentially.


texts:
I am designing a switch for AC circuit. E.g. when I apply a small DC voltage, AC current is allowed to conduct, otherwise there is huge resitance stop the current from flowing.

I found 2 possible solutions on the web. TRIAC or 2 opposite MOSFET in series. But the problem is: the AC voltage is floating, it is not grounded. Its a AC wave produced from H bridge from another DC source. (which use the same ground as the small DC voltage to control the AC current). E.g. I cannot define the gate voltage correctly.

Does anyone know how to achieve the control? Thanks


texts: Below I have a current mirror loaded differential amplifier. Can somebody please Just give me an idea of how to find the drain voltage, vd8. I am stuck because I don't see the relationships that can lead to finding vd8 based on this configuration. Thank you.


texts:
I am using 3.2' TFT LCD with touch pad. LCD has pins RD and WR. What is RD and WR pin?

Is WR for RD also ( for both write as well as read )?

Where to connect RD pin of LCD?

Please see attached pinout of LCD.


texts: How does soft start circuit work in UC3842B?

texts: In the soft-start circuit of the UC3842 marked by the red circle, voltage of the COMP pin increases slowly, so the duty cycle increases slowly, but how does the soft-start circuit control the voltage of the COMP pin?


texts: BlueRay disc reader failed to disengage, how to fix

texts:
I got a BlueRay disk player which is failing to a very stupid mechanical defect. The spin head below this cover is magnetized and when the drive is closed it will raise and slot in the disc in the hole in the middle of the disc, then the small piece of metal will be suck downwards by the magnet to hold firm the disc. However when the drive is not loaded, when I try to eject the tray, I saw the spin head try to lower itself, however it seems the magnet is too strong and the upper plastic piece holding the metal also bends downward to go with the spin head, thus the mechanism is not lowered thus the tray cannot eject.
should this problem be fixed by one of the following?

adding spacer between the plastic piece and the tray to increase distance between magnet and metal piece
somehow stiffen the plastic piece
get a stronger motor for the eject mechanism so that it has enough force to pull down the spin head

I am sorry this does not seem too electrical, but I cannot find another more appropriate stack, kindly tell me if you see one.


texts: Finding thevenin voltage in a common emittor circuit

texts:
simulate this circuit – Schematic created using CircuitLab

β=100, Vbe(on)=0,7, VA= ∞

Lower corner frequency is what actually wanted. In the solutions of the book, it began with finding thevenin resistance and thevenin voltage, then using them, it found IBQ and ICQ.

I get confused because finding thevenin resistance and thevenin voltage means that we have to analyse a pair of circuit nodes. Which two circuit nodes do i have to analyse here?


texts: PFC formula for calculating conduction losses across MOSFET

texts:
I am not able to demonstrate the formula above where Vin is the input voltage of the PFC, Vout is the output voltage, Po is the output power, and Rds(on) is the on resistance of the mosfet. This formula is given into the following datasheet and is used in a 2-interleaved PFC. That's why I think there is a 0.5 factor, if we supposed that the loss are equally distrubued on the 2 Mosfets. https://www.ti.com/lit/an/slua479b/slua479b.pdf?ts=1615697963421

The problem comes from the fact that the rms current of the mosfet depends on the current seen by the inductance during on time and this current follows a sinusoidal on a half period line (100/120 Hz). That's why I think we observe a "Pi". The PFC is working in CCM.

Is there someone who could help me to demonstrate this formula ?
Thank you very much and have a nice day.


texts: how to avoid harmonic on intrrupt for proximity sensor in NodeMcu

texts:
i have 5v IR proximity sensor for measuring pulse output attached in NodeMCu
using intrrupt pin but it gets a random counter on the harmonic environment.

it is working fine in Normal situation what should i do now?


texts: why inductor is getting warm & burn in voltage regulator-lm2576

texts:
I am creating an add-on board for my raspberry pi. I want to power up the raspberry pi from a voltage regulator (LM-2576 o/p is 5v and 3-A).  I also want to drive two dc motors, 3-servo motors, an ultrasonic sensor, and 4 proximity sensors.  I am using two LM-2576 regulators: one is for the raspberry pi, the other is for the drive sensors and actuators.

I believe my regulator is safe, but the inductor is getting hot after a few minutes.  Why is my inductor getting hot? According to the data sheet I am using, it is 100microhenry and can support 3A at 5V.

Is the LM2576 sufficient for the raspberry pi and other sensors?

Is there a regulator available that I can replace both of my LM-2576 regulators with?


texts: Creating a Li-on backup for a 12v router

texts:
I am building a small battery backup for my router with the 12V 0.5A DC input. Main use is to keep the router powered up during load shedding (aka. power cuts / blackouts ) while my backup generator is being switched on.

This is what I'm thinking of using:

Explanation:

Two Li-ion 18650's in parallel
TP4056 charge and discharge protection board connected to input and outputs of the cells. the output from this will be 3.6v  ( the interfacing taken from here )
MT3608 boost converter - configured to step up 3.6 v to 12v  which is fed to router

Will this setup work for the following objectives?

Safely power router in normal use
During blackouts, keep router running with no downtime.
Li-on battery does not explode and lasts 1-2 years  (I am most confused about this since the batteries will always be plugged into the charging circuit)

EDIT (Clarifying)

Duration of a blackout is not an issue since the backup generator provides power. In between the blackout occurring and the generator switching on, there is a small delay - around 5 minutes. It takes 3-5 minute for the router to function normally after reboot. This is an issue when there are alternating blackouts every 30 minutes.


texts: Why is there so much fear surrounding LiPo batteries?

texts:
I've been trying to design a charging system for a small robot powered by a 2S 20C lithium polymer (LiPo) battery. Were I to trust everything I read online, I would believe that the LiPo will kill me in my sleep and steal my life savings. The common advice I read, if you are brave enough to use LiPo batteries, is "never leave unattended", "never charge on top of a flammable or conductive surface", and "never charge at a rate faster than 1 C".

I understand why this is prudent, but what is the actual risk with LiPo batteries?

Nearly every cell phone, both Android and iPhone alike, contains a LiPo battery, which most people, including myself, charge while unattended—often-times while left on a flammable or conductive surface. Yet you never hear about someone bursting into flames because their cell phone exploded. Yes, I know there are freak accidents, but how dangerous are modern LiPo batteries? Why do so many online commenters treat stand-alone LiPo batteries like bombs waiting to go off, but don't even think twice about the LiPo sitting in their pocket?


texts:
I decided I wanted to learn Atmel Studio to be able to work with all their microcontrollers problem being i'm trying to use a brand new ATMega32 with default fuse settings and an external crystal clocked at 16MHz. Of course in software I set F_CPU to 16000000UL for delays, that didn't work. After looking around the internet I was told the MCU uses its internal oscillator rather than external and that i'd have to set it's fuse bits. I was directed to AVR Fuse Calculator, I determined that I should use this configuration:

Is Low Fuse Bit 0xFF and High Fuse Bit 0x99 okay to use? Or is there something that I missed? As I was quite confused while reading the fuse clocking bits.

Specs:
ATMega32,
16Mhz Crystal Oscillator,
22pF Ceramic Capacitors


texts: Analysing a circuit to determine what is in series or in parallel

texts:
This is probably a very basic question but I have the following circuit, I am not sure what is in series and what is in parallel or if they are all in parallel, initially I thought R2 and R3 were in series and then used the sum of their resistances with R1 to calculate the equivalent resistance, that seems to be  off based on some circuit simulation software I am using so I would appreciate if somebody could explain how to calculate the Rt and the logic behind it.

Thanks.

simulate this circuit – Schematic created using CircuitLab


texts:
I've built a fairly simple Temperature logging device on an Arduino Mega 2560 R3. I'm using TMP36's, 12 of them in total to log the data. Each sensors VS and GND pins are connected to common rails and each V_out pin is then connected directly to their own analog sensor pin on the Arduino.

The method for logging the temperatures is to record ten successive measurements on one sensor (pausing for 20ms between each measurement) then averaging those ten values, log that value to a data file, then move onto the next pin, repeating until all sensors have recorded a value. Then, wait until 10 seconds has passed and then repeat the process. (doesn't need to be faster since my experiment is hours to days long).

The first image (labeled Sensor 14) is the plot that i'm getting from one of the sensors attached to my heat source, which is about what I'm expecting (X-axis is seconds, Y axis is temperature in Celsius)

On my last test I only needed to needed to log a few locations and I left the rest of the sensors sitting on the desk essentially measuring the ambient temperature, which I'm 90% sure should be constant. However, I logged the data from the sensors anyways and plotted them for giggles and got the following plot (same axes as first)

This image has a pretty clear periodic temperature change, albeit a very small difference. The results I've gotten from this have no effect on my actual analysis, but the source for the periodic signal is what I'm curious about.

I'm no signals analyst, or electrical engineer, I'm wondering if seeing this type of periodic 'noise' indicative of some type of problem with my test rig or if this is fairly normal to see. (The sensor has a listed +- 2 degrees C accuracy with a 0.5 degree C linearity)

And as a second part to the question, would there be anything 'wrong' with removing this periodic signal from my temperature data? (running an fft on the noise signal, identifying the frequency and then using a bandstop filter to clear it out).

Many thanks for any advice!

(Edit 1)

I made a better plot in python and zoomed in on one section to show how the two signals look over a shorter period of time:


texts: What's the name of this component's package?

texts:
The device is called KY 717 and from what I've been able to find out, it's some sort of rectifier. The solder tab is insulated from the rest of the body.

I was unable to make a better picture. The major division on the paper is 10 mm and the device appears to be 37 mm long. The screw is from what I can see M4 type screw. The soldering hole has diameter of around 3 mm, but is deformed so my measurements could be bad.


texts:
I was reading on a book (Thomas Lee, The Design of CMOS Radio Frequency Integrated Circuits) that in a short channel model, since the phenomenon of drift speed saturation is very relevant, it is a mistake to use the classical formula of the drain current of a long channel MOSFET, i.e. this one (we are supposing a MOSFET in pinch - off region):

It states that in a short channel MOSFET the correct expression becomes this one:

Then it states that, if VGS - VT is not so high, we may anyway use the first formula; if VGS - VT is quite high, we have to use the second one. I do not understand this last statement: in fact the difference between the two MOSFET is their length, and this determines that, with the same VDS applied, there is a high electric field in a short channel Mosfet (and so, speed saturation) and low electric field in a long channel Mosfet (and so, no speed saturation). Why should the choice of the model depend on VGS - VT?


texts: Optical switch operation point derivation

texts:
I have an optical switch part opb840W and I am failing to derive the required information for my application from there. The intended use would be as in the following circuit:

simulate this circuit – Schematic created using CircuitLab
The datasheet is giving two different test conditions for the "on-state". First with Vce(sat) max value of 0.4V and the Ic(on) of 400uA. The second is for Vce=10V and Ic(on)=0.625 minimum.  This information seems to be pretty useless for calculating the R2 value in order to make the circuit work as switch with the specified supply voltage. Am I missing something here? How can I define the R2 value for the application?


texts: LED light intensity drop using 200k range resistors.

texts:
I recently had an experiment in school where I used resistors that were 130k, 140k, 150k, 160k and 170k ohm to dim a red LED. The light intensity was then measured with a Pasco light sensor. The circuit was powered by a 9v battery.

I was wondering, how could I predict how much the light intensity will drop as I change the resistors out?

Thanks in advance!


texts: Help in designing a speaker driven by an LM386

texts:
I'm trying to design a circuit which produces a 17KHz pure sine wave from a speaker using the following components:

PIC16F1783 (microcontroller with DAC)
an LM386 amplifier and an 8-Ohm 1W speaker.

The power supply to the LM386 is 9v.

Since I have many constraints I'm not quiet sure about how to do it. I'm able to create the correct values in the DAC but then I'm not quite sure how to feed the LM386.

It says that the minimum gain is 20, does that mean I have to create a voltage divider before I feed the the amplifier? (1v*20=20 > 9v).
Is the network (0.05uF,10Ohm) at the LM386 output described in the typical application in the datasheet necessary?
Can the amplifier deal with 17Khz?
Should I put a decoupling capacitor in the output?
Should I put another resistor, or is the 8-Ohm speaker enough?

As you can see I'm pretty lost :(
thanks for the help!


texts: Can I run traces through "No Connection" pins?

texts: Several ICs are manufactured in packages with more pins than it supports. For example, the LM317 in an SO8 package has 4 VOUT pins and 2 N/C (no connection) pins. I often want to run traces through N/C pins to ease routing, but wonder if it would make them give up the ghost. If it exists, what is the standard or rule by which manufacturers follow concerning the electrical characteristics of N/C pins? Or do I have to scour the datasheet / do my own testing every time?


texts:
I'm very new to verilog, and I'm not quite sure I'm getting it. I have a 4x16 decoder module that utilizes two 3x8 modules I've included from a separate file that worked under simulation. The problem is even though the test bench is providing the correct inputs, the output is undefined (XXXXXXXXXXX) so I'm pretty sure the 4 to 16 decoder is not returning the output as it should. Any help with this project would be much appreciated.

`timescale 1ns / 1ps

module decoder4_16test;

    // Inputs
    reg [3:0] d;

    // Outputs
    wire [15:0] o;

    // Instantiate the Unit Under Test (UUT)
    decoder4_16 uut (
        .d(d),
        .o(o)
    );

    reg clk;
    reg [3:0] count;

    initial begin
        // Initialize Inputs
        d = 0;
        count = 0;
        clk = 0;
        // Wait 100 ns for global reset to finish
        #100;
        forever #10 clk = ~clk;
    end

    always @(posedge clk) begin
    //  if (count > 3) count = 0;
        d <= count[3:0];
        count <= count + 1;
   end
endmodule

4 to 16 decoder (XXXbrokenXXX)

`timescale 1ns / 1ps
module decoder4_16(
    //inputs
    input [3:0] d,
    output reg [15:0] o
);

    wire en1, en2;
//  assign en1 = d[3];
    assign en1 = 1;
//  assign en2 = ~d[3];
    assign en2 = 0;

    decoder3_8 a(
        .d(d[2:0]),
        .en(en1),
        .o(o[7:0])
    );

    decoder3_8 b(
        .d(d[2:0]),
        .en(en2),
        .o(o[15:8])
    );

endmodule

3 to 8 decoder
`timescale 1ns / 1ps

module decoder3_8(
        //Inputs
        input [2:0] d,
        input en,
        //outputs
        output reg [7:0] o
        );

    //combinational logic
        always @(*) begin
                //conditional cases
                if(en) begin
                        case(d)
                                //converts binary comb to output wire
                                3'd7: o=8'd128;
                                3'd6: o=8'd64;
                                3'd5: o=8'd32;
                                3'd4: o=8'd16;
                                3'd3: o=8'd8;
                                3'd2: o=8'd4;
                                3'd1: o=8'd2;
                                3'd0: o=8'd1;
                                default: o = 8'd0;
                        endcase
                        if (!en) o = 8'd0;
                end
                //default case
                else
                        o=8'd0;
        end
endmodule

Also, any resources you guys found that helped you learn verilog would be awesome as well (instructor only provided the readme text for verilog IEEE that might as well be in Greek).

edit changing the output type from reg to wire fixed the problem. The test bench now looks normal.