texts:
I am working on a project that has a micro-controller that needs to keep track of time over long periods, the project will be powered of mains power for the vast majority of the operation time, but I wanted to incorporate a backup battery for blackouts, or I'm clumsy and knock the plug out or something.

I have a few tiny li-po batteries that I have unused from a past project and wanted to try and reuse one. I also wanted to try and keep the circuitry simple without needing exotic ICs. As far as the charge cycle for li-po batteries is to charge at a constant voltage, with the current being limited to a certain value, this usually being done through a special purpose IC.

I wanted to know if it would hurt an Li-po or pose any safety hazards if I was to charge the battery just using a voltage regulator and a largish resistor to limit the current to a few milliamps.

I am pretty new to circuit design and this is what I thought would be a good starting point, I just wanted to be able to check here first because of the danger in li-po batteries being charged incorrectly.

(The resistors on the voltage regulator should set it to approx 4.2v)

Any comments and tips would be appreciated.

EDIT
I should have mentioned that, when connected to the wall outlet it will draw a couple hundred milliamps, but I plan to have it sense when disconnected and go into a sleep mode only keeping track of the rtc, I don't have any numbers yet but I anticipate a current draw to be less than 10uA I did play around with the idea of using a large capacitor but unless I am doing my calculations wrong using a 10mF capacitor I would get a few hours at absolute best.


texts:
I'm working with I2C and I have been using python library to communicate with a magnetic sensor.
Now I am working with a different chip and it makes me wonder if I get the right concept or not.
The only difference in new chip is that the register values are 2bytes.

Suppose

Chip address is 0x30,
register address is 0x11
and data that I want to write is 0x22

This is how i2c works To write to register address:
- write(chip address, register address)
- write(chip address, data)

This is how i2c works To read from Register:
- write(chip address, register address)
- Read(chip address, No of bytes)

Please correct me if I'm wrong.

I've been using a python library quick2wire for this. In this library we can use a function called writing_bytes(chip address, register address, data)

How does it decide which is register address and which is data?

If the chip's register address is 2bytes, it will set pointer to address+data in writing_bytes function?


texts: Common mode RC filter of High-BW differential line

texts:
I'm using a fully differential analogue chain, using 20Hz HP, 3MHz LP and x2 Gain. My signal of interest is fully differential with a 200KHz fast modulation and a 100Hz sawtooth ramp. The high frequency chirp but may change within the range of 50KHz to 1MHz. I've therefore ensured a flat pass band (0dB) from 100Hz to 1MHz.

The differential structure will naturally attenuate CM signals, however the industrial environment the system will be working in will contain a number of high amplitude common mode signals.
I've therefore decided to use common mode filtering capacitors (\$C_{cm}\$) on the input differential line, right next to the input termination resistor.

What I need to do, is provide further CM only filtering of 50Hz, 100Hz 1KHz etc but not interfere with my differential signal path.

Unfortunately, adding suitable common mode capacitors $$F_{cm} = \frac{1}{2\pi R_1C_{cm}}$$ acts to change my 3MHz low pass differential response. If the differential filter is $$F_{diff} = \frac{1}{2\pi(R_1+R_1)(C_{diff}+C_{cm}/2)}$$ I cannot get common mode filtering as far below the differential as I'd like, as \$C_{cm}\$ acts to swamp \$C_{diff}\$ in the \$F_{diff}\$ equation.

How should I go about common mode rejection of lets say 50Hz mains hum, while keeping my differential mode 100Hz to 1MHz pass band?


texts:
I see that there are "pinless" moisture meters on the market, e.g., http://www.omega.com/pptst/HHMM257.html that look like this

My understanding is that they measure the amount of reflected RF. Perhaps, it's because liquid absorbs RF. However, different materials absorb RF differently - how could this type of measurement be reliable?

Also, why do they use a round RF transceiver rather than a dish for receiving?

Thanks


texts:
I am trying to read and write to a class 10 - 2GB SD card from STM32 with the help of FATFS R0.11, but f_mount() function is returning FR_NO_FILESYSTEM error code. I have tested the same code on a class 4 - 2GB and class 10 - 16GB SD card, and it worked perfectly. What am I doing wrong here for this specific SD card?

Code:

FIL filTest;
FATFS fs;

FRESULT initSD()
{

    disk_initialize(0);
    FRESULT res;

    res = f_mount(&fs, "", 1);

    if(res != FR_OK)
    {

        return res;

    }

    res = f_open(&filTest, "test.txt", FA_OPEN_ALWAYS | FA_WRITE | FA_READ);
    return res;

}


texts: Three-phase rotary converter wiring questions

texts:
I am installing a 30 HP three-phase rotary converter on a 200 amp service in my home shop. I intend to run a CNC milling machine with a 15 HP motor. I am using 2 AWG wiring in 1" shielded conduit from the panel to the converter, and from the converter to the machine. I'm using a 150 amp breaker at the panel. I am really just asking if there is anything I should know or look out for with this type of project, and if the materials I've selected are appropriate. I would love to hear from anyone with experience installing 3 phase rotary converters.
Thanks for your time!


texts: How to balance antiphase Rx coil in metal detector?

texts:
In this question How can I drive an LC tank circuit to get a nice and clean sine wave? I learned to get clean oscillation waves of a tank circuit (Tx) and consequently its reception through antiphase receiving coil (Rx). The Tx and Rx arrangement is shown here.

The question is if both antiphase Rx coils cancel each other why i am getting following signal at Rx.

The yellow is Tx and blue one is Rx signal.
How to balance Rx coils to completely cancel each other?
Feed back after suggestions:
@Andy advised to use balun and suggested the turn ratios too. I constructed and used in two ways.

Primary center tapped left open
Primary center tapped attached to ground of secondary.

I got major cancellation effect when I adjusted position of both Rx coils. Thus the Rx signal reduced from 10+ mV to around 1.5mV.

I am planning to re-construct the coil system with precise distancing and grooves on pipe surface to ensure straight circular loops.
Any further suggestions are welcomed.


texts:
I have to study VHDL from 0 and i'd like to have an option that runs under a linux kernel instead of NT/Windows: any tips?
I can also really appreciate some good links to good VHDL resources for a beginner, thanks.


texts: USART communication problem on PIC18F6722

texts:
I am trying to use enable USART communication on a PIC18F6722 microcontroller.  More specifically enable the receiver and attach a receive interrupt to it.

The datasheet describes the relevant bits as such

RC2IE: USART2 Receive Interrupt Enable bit
1 = Enables the USART2 receive interrupt
0 = Disables the USART2 receive interrupt

CREN: Continuous Receive Enable bit Asynchronous mode:
1 = Enables receiver
0 = Disables receiver

For some reason this piece of code doesn't do it though:

PIE3bits.RC2IE = 1;
RCSTA2bits.CREN = 0;

I want to set both of these to 1 although it isn't working.  Any ideas?

I previously asked a similar question although I didn't get any useful information


texts: Magnetic induction with varying rpm: Dealing with excess energy

texts:
I would like to get some advice regarding the following scenario:
I want to build a cheap, small generator for an energy harvesting application. There are magnets on a rotating shaft and off-the-shelf inductor(s) are positioned (fixed) near this shaft. After the inductors the voltage is rectified and then a power management IC takes over (boost/buck, storage).

At 1000 rpm the system should provide enough power (~10 mW) for the circuit behind it. But the rpm can vary between 1000 and 20000. Once the rpm are higher than 1000 there is excess energy. Therefore I have a find a way to deal with this excess energy. Either get rid of the excess energy or maybe prevent the generation in the frist place.

Using multiple inductors and switch them on/off depending on the rpm was an idea.  But this would take quite some effort with rpm detection and circuitry, depending on how many inductors I would use. So I am looking for easier solutions.

A mechanical solution to increase the gap between the inductors and magnets is not possible, bc both are fixed in place and there is not much room at all.

Zener diodes could be a thing, but dissipating the energy as heat may not be the most suitable way, bc the thermal conductivity of surrounding materials is not good.

Do you guys have any ideas how to deal with this issue?


texts:
I want to implement a few chips for battery management and due to the ADCs of each cell working at bigger voltages each, and each chip(I have to cascade thre ICs LTC6803-4) with a maximum voltage lower than the battery maximum, I have thought if this implementation would work:

I have seen something similar in the application example of the datashet of the IC:


texts: I am wondering if this little guy will work or if it will fry my router. Router is a UniFi AC Pro requiring 802.3af Gigabit PoE. I don't have one laying around so I came up with this. Its a voltage doubler providing (tested) 70v dc unloaded to the output lines on the ethernet cable from the 24 volt ac input. I do not have the 24 watt resistor to verify the 0.5amp requirements of the design and without over/under volt protection I don't want to just plug it in all willy nilly without verifying that it should theoretically function. I am not a EE student, this is just a hobby so be nice with the reply's please.


texts: Unexpected dominant pole in active-RC circuit

texts:
Consider this active-RC circuit:

simulate this circuit – Schematic created using CircuitLab

it should exactly realize the RLC high-pass filter with one zero:

simulate this circuit

It realizes the same equations and so the same transfer function. This model has been used to obtain an analog, elliptic, high-pass filter with a low (about 0.01 Hz) cutoff frequency.

After a simulation (with negative resistor values, supposing that they are realizable), the active-RC transfer function seems to be the same as the RLC-prototype, but with a difference: a new and unexpected pole at a very high frequency, about 10 GHz.

After \$ f = 10 \ \mathrm{GHz} \$, the transfer function decreases regularly at 20 dB/decade and it is no more flat as it should be.

The opamps were realized through ideal VCVS generators (Voltage-Controlled Voltage Source), with a high gain (\$ 10^9 \$ at least).

If the order of the filter is increased, the pole decreases is frequency. For an eight-order circuit, it is at about 100 Hz!! And it is intolerable.

The RLC-prototype used for the 8th order circuit is

simulate this circuit

And it does not have any 100 Hz pole, despite of its active-RC realization (I don't draw it for shortness).

The simulator used is Spectre (from Cadence) and the values for the RLC prototype are taken from "A. B. Williams and F. J. Taylor, Electronic filter design, 3rd edition, McGraw-Hill, 1995" (both for the 3rd and 8th order filters).

So, are there in the topology of the active-RC some elements that could be generate such a pole? Or are there some undesired parasitics automatically inserted by that simulator?

Google didn't show anything useful.


texts: Relation between power consumed and MCPS (million cycles per second) consumed on a processor

texts:
I have been working on a ARM cortex A8 board on MP3 decoder.

While doing this I have a requirement saying the MP3 decoder solution I am doing should consume 50 mW. This generated few questions in my mind when I thought about it:

I recall that there is some relation between the Core Voltage applied (V), the clock frequency (f) of a processor and power consumed (P) as something like, P is directly proportional to the voltage and frequency squared.
But is the exact relation. Given  operating clock Frequency, voltage of a processor, how can we calculate power consumed by it?
Now if I get the power consumed from step (1) at some clock frequency, and I am told that the decoder solution I am giving, can consume only 50 mW, how can I get the maximum limit on MCPS, which will be the upper bound on the MCPS of my decoder solution running on that hardware board?

Can I deduce that if power obtained as in step (1), say P, is consumed at frequency f, so for 50mW, what is the clock frequency and calculate accordingly the frequency. And then call this frequency as my code MHz (MCPS) upper bound?

Basically how does one map (are there any equations?) power consumed by a software to MCPS consumed?


texts:
I know that the total harmonic distortion (THD) in a power system with n harmonics is calculated by the below equation:

THD=\$\frac{\sqrt{(V_2^2+...+V_n^2)}}{V_1}\$

but what about any single harmonic? Is it true that calculate harmonic distortion specifically caused by third harmonic (for example) this way?:

\$3^{rd}HD=\frac{V_3}{V_1}\$

if it's incorrect then, how to calculate it?


texts:
My dad is an Electrician and I myself am an Electronics Design Engineer, and to this day he still hasn't been able to give me a good reason for this.

Consider the two following pictures/situations - both the same case, but with neutral not tied to earth in the second. Apologies for the poor diagrams, but imagine they are sticking a fork in a plug/knife in a toaster/etc. in order to touch active.

In the first picture, the person gets an electric shock. Classic case. This is because there is 240VAC difference between the person's hand, and the earth at their feet. The key thing to note here is that it was the 240VAC difference that caused the shock.

In the second picture, the person is touching the active wire again - however, since earth is not tied to neutral, there is no guaranteed 240VAC difference. None. Like hooking up only 1 end of a battery to a light, this situation has no closed circuit. Thus, the only way to receive a shock is if a person held active and neutral at the same time - which you would have to be trying to kill yourself if you did that somehow (i.e. my point is, most electrical shocks are caused by active -> earth potential, not active -> neutral - and, tieing neutral to earth does nothing to prevent active -> neutral potential shocks).

Yes, earth might be floating and could be "any" potential with reference to active, and it's nice to tie it to neutral at power stations, transformer outlets, and outside our house with an earth stake so "we know" what potential it sits at. But you could make that argument that it could rise to some dangerous potential about any isolated power supply. So I don't think that's a solid argument and the only reason. On top of this, isolated transformers/power supplies are sometimes used for the sole purpose of protecting from shock - so why don't we just isolated the whole earth from our power grid? Haha.

Obviously, earthing chassis would no longer be necessary either if neutral was not tied to earth - because touching the metal casing would not be dangerous if for some reason the device became live (i.e. same as situation 2).

TL;DR: is the only reason we tie earth to neutral so that we know the ground beneath us is 0V with respect to active? Or is there some other reason?


texts: How to connect LED to output device to show the output state without any voltage drop so that it can be sensed by MCU?

texts:
I am using an NE555 timer to get output from one of my output device. The basic function of NE555 timer here is to toggle the output of my output device which was successful but I need to attach a LED to the output of NE555 to show the output state.
When I directly connected the LED in parallel to the OUTPUT pin of NE555 and Measured voltage across OUTPUT pin and GND the voltage drops to 3.2 V but I need it to be 5 Volt so that I can sense the output of NE555 using MCU.
Can anybody let me know how to connect an LED to the output of the NE555 (Source) without any voltage drop?
Regards,
Mr.B


texts: If I try and fix my laptop power adapter can I damage my computer or endanger people?

texts:
I have a CR-48 Chrome laptop adapter. It is bent at the end which plugs into the computer. I have to jiggle it and tip it against a wall to make it charge.

My novice understanding is there are two or three wires inside the jack. I'm thinking I should be able to use a knife to peel back the protective cover and correct the problem.

If I use a knife to peel it back is there anything I should be worried about like damaging my computer or making it dangerous for people?

This is a link to a replacement part so you know the specs: http://www.amazon.com/gp/product/B003NJUPQE?ie=UTF8&tag=chromebooking-20&linkCode=as2&camp=1789&creative=9325&creativeASIN=B003NJUPQE


texts: When I run 24VAC into a full wave bridge rectifier followed by a 220uF electrolytic capacitor to turn it into ~32VDC, the  source has two wires. Does it matter in what order I connect the AC wires to the input to the bridge rectifier? If so how do I determine which wire goes where? I suspect that it's totally symmetric on the input side, but I'm am full of doubt when it comes to AC. Sorry if this is just a really dumb question.


texts:
I'm currently using the following opto-isolated relay board: URL

Everything is working correctly, I can switch on and off a small light without any problems. Now as soon as I plug in a larger load like a water pump (120V 1.2A) it flicks on and quickly off. Now I would expect this if the relays were under powered but they are 120V / 10A relays. Am I missing something, is there something else in these board designs that are limiting me?

Any help is much appreciated.

Updated:

Solution:
I have stumbled on to the problem trying your guy’s battery suggestion. I have a shift register that is consolidating the input pins to the relay board. When I was hooking up the battery I decided to bypass the shift register too. Low and behold it works both battery and direct power. It seems the shift register is causing all kinds of problems with the inputs, the worst being it is terrible inconsistent (Fails to shutoff sometimes). I will create another question targeted around the shift registers once I know more. Thanks for you help guys.


texts: Harmonic simulation of microwave power amplifiers

texts:
I am working on microwave power amplifier design for 2.45 GHz, 300 W using LDMOS (part no.:MHT1004N). I am using Agilent's ADS for the simulations. I want to know what exactly is harmonic balance simulations?

Observation:
When I vary the order of the simulation from lower to higher value, my simulations more accurately match to that of the datasheet value of the given transistor. At lower values of the order the circuit fails to simulate.

Doubts:
What is the significance of this order?
How does it affects the simulation?
And what can I expect when I realize the RF-PA?
What type of source I'll need to use to make sure the physical realization and the simulations match to an extent?


texts: Trouble Understanding Bitstream Frame Addressing

texts:
I am trying to understand how Frame Addressing works in FPGA bitstreams.

From what I understand a frame is 1-bit wide, goes from top to bottom and is identified by a unique 32-bit address. This address for the frame is composed of Block Address, Major Address, Minor Address and Word Address.

Looking at a bitstream with a HexViewer I can see the 32-bit words that are going into the device.

In the above picture we have the address in the bitstream and two words per row (HxD wouldn't do 1 word per row, oh well). At 0x48 we have 30 00 40 00 50 00 46 A1. I've managed to puzzle out that these are CMD words for a Type-1 and Type-2 packet header. After this are a series of words used to configure the device.

What I do not understand is how the address we see in blue in the above image relates to the frame address. The Xilinx Documentation (XAPP452) provides tons of information about the structure of the frame address but where is it actually used?

Looking further down my config file I'll see a non-CMD word, such as 0xFFFFFCFC. I have the address for where it is in my bitstream but I would like to know the frame address for where it is going....


texts:
I need to calculate the PF of supply V2, a 3-phase generator that is operating in parallel with another generator (11kV star-connected). Both the generators are equally sharing the mechanical load of 3000kW at 0.8 PF (lagging).

simulate this circuit – Schematic created using CircuitLab

I put together the above diagram with the supplied information. If I calculate the total Apparent power (s) as 3750kVA (3000kW/cos(36.87)) and the total current as 246.03A at an angle of -36.87 degrees (3750kVA/sqrt(3)*11kV*0.8).

This gives me an apparent load of 44.71 Ohms at an angle of 36.87 degrees.

How would I go about finding the PF of each of the generators? Is it even possible given the supplied information?


texts: Controling a regular residential 110V/15A circuit switch (or relay) from a PC

texts:
I am a software engineer by trade and also a rather skilled and well rounded (residential) builder with a special interest in wiring.  I have rewired my entire two-unit house, panels included and seen it all.

In the course of home remodelling, I was wishing to be able to control every single electric control on every circuit in my house remotely using an Android app.  To make that possible, I would need every single switch/thermostat to be upgraded into a relay and have cat5 cable run alongside every Romex cable to each control on one side and into a PC (or some other cheaper form of a CPU hosting device with a modem) which has a static IP online, on the other side.

Of course, that is a huge project, whose biggest parts would be making relays that can be controlled from a PC and writing software to control it all, web services, mobile app etc.  So the first step in R&D would be to actually make something like that -- unless, of course, it exists already.

Is it possible to buy a relay that, on one side controls a regular 110V residential circuit, and on the other can be flipped using a PC?

A residential feature like this could be used to, e.g. report and control temperature at home remotely, turn the heat on 30 min before arriving home etc.  You could even mount a web cam and watch your pets remotely.


texts: How to draw digital timing diagrams for documentation?

texts:
I have read through many electronics documentation over the years and I have really wanted to draw the timing diagrams for digital signals using some software.

I have seen https://wavedrom.com/tutorial.html and their diagrams seem very detailed and well suited for higher-level technical documentation.

However, say you are writing documentation for beginners, you would prefer diagrams like this diagram explaining Serial Communication or this diagram explaining SPI communication drawn by user Nick Gammon in his answers here and here, which seem to be far more simple with text annotations and other helpful stuff like marking our regions of interest, etc.

The diagrams drawn by Nick would be great for documentation when you are just starting out on some digital electronics subject. Seems to me he is using some kind of software with a template of some sort to make his diagrams so uniform every time.

I even tried to contact Nick Gammon over stackexchange through comment or private messages but my reputation is too for that it seems.

So, can someone tell me how to draw these simple timing diagrams?


texts:
Please excuse me if this question is a very obvious one, I have searched on here but my electronics knowledge is very very basic.

Here's what I'm trying to do, I have taken an old Android phone apart, which has 2 surface mount buttons (Volume Up/Volume Down). I am trying to integrate this phone into a different case so it can act as a head unit for a car, and what I'd like to do is wire an incremental rotary encoder to these 2 buttons, so when I turn it clockwise, the volume up button gets 'pressed' and viceversa.

I'm a bit lost when it comes to rotary encoders, I have read up on gray code and all that but I'll admit I'm still very lost.


texts: How to drive a SPI bus over 5 feet of 26AWG wire?

texts:
Below is the circuit I am trying to achieve. The endpoint is a 5V device but my microcontroller (SPI Master) is a 3.3V device so I have to do the voltage translation.

My question is what kind of a circuit should I use to drive the SPI signal over a long wire like that? The circuit I have now (shown below) really distorts the signal badly.

The signal looks quite bad with just the 5 feet wire connected.


texts: How to improve the full bridge / half bridge start up time?

texts:
I am trying to find out a way to improve the rise /start up time of a series LC circuit placed in a full bridge (or half bridge) circuit.

Here is a simplified schematic. The circuit works very well, the voltage across the inductor reaches 500V, the resonant frequency is at 100kHz+.

Image A shows what happens to the voltage across the inductor when the bridge starts to oscillate (PWM inputs activated).

For the existing LC values this translates into approximately 0.5 ms of build up time.

I discovered the following:
If the bridge is stopped and Q1/Q4 are set to on while Q2/Q3 are off then the capacitor stays charged.

If POINT A is briefly grounded (using a piece of wire) then when the grounding is removed the capacitor discharges into the coil thus creating an instantaneous rise of the voltage across the coil - see Picture B.

This showed me that in theory is possible to reduce the oscillator rise time to zero if there is a way to discharge previously stored energy into the LC tank at start up.

Does anyone know to to address this issue?


texts: Share same input with 2 different 32AVR Microcontroller

texts:
I'm developing a circuit with two warm-redundant micro-controllers.

Each uC has to read I2C, analog and digital signals from the rest of the circuit. Should I route the signals directly to the two micro-controllers or should I use some kind of multiplexer?

What about the outputs?

The uC is a Atmel UC3C

Thank you very much for your answers!


texts:
Is it possible to analytically calculate Idss for JFET?
I tried by setting voltage gate-source to zero, and then finding the drain current, but it doesn't seem to match with the given value?


texts:
This is my first question.

I have a package that contains the following type:

type t_rgb_64x48 is array(0 to 47) of std_logic_vector(63 downto 0);

and is being used in my file.vhd file.

file.vhd contains an entity that contains the type of the package mentioned earlier:

RData_in : in t_rgb_64x48;
ColumnAddress_Start : in integer;
ColumnAddress_End : in integer;
RowAddress_Start : in integer;
RowAddress_End : in integer;

It also contains a signal with its corresponding type:

type t_vgaram is array(0 to 479) of std_logic_vector(639 downto 0);
signal s_rstorage : t_vgaram;

I need to access s_rstorage through the following statement:

s_rstorage(ColumnAddress_End downto ColumnAddress_Start)
      (RowAddress_End downto RowAddress_Start)
        <= RData_in(ColumnAddress_End downto
                      ColumnAddress_Start)
                  (RowAddress_End downto RowAddress_Start);

to store the value of RData_in to s_rstorage and making sure that they are of the same width in 2D.

The problem is this error:

Type of s_rstorage is incompatible with type of RData_in.

I know that they have different types as the cause of the error. But how do I fix this problem?


texts:
Firstly let me tell you, I don't have much knowledge about the transistors in circuits.
I am having a transistor S8050 D 331, and it's connected like on the schematic below.
The problem I am having is when I apply input square wave signal above 300 KHz. The transistor is not following that fast. Is that normal? In data sheet it says 150 MHz transition frequency.

simulate this circuit – Schematic created using CircuitLab

Output at 100 kHz of input signal:

Output at 300 kHz of input signal:

Output at 500 kHz of input signal:


texts: WFI instruction slowing down SYStick interrupt

texts:
I've configured my Infineon relax kit for max frequency(120 MHz). I've set my SYSTick for a periodic interrupt of 10 ms. For power saving, I use a WFI assembler instruction whenever my processor is idle. WFI (wait for interrupt) should put the processor in low power mode until an interrupt occurs. So my processor should wake up after every 10 ms. But somehow, this WFI instruction slowed down my interrupt frequency to almost 3 times and it wakes up on every third interrupt.
What can be possible reason for WFI not waking up on every interrupt?


texts: How does this circuit compensate for current hogging?

texts:
In The Art of Electronics by Horowitz & Hill, there’s a section about current mirrors with multiple outputs. We're then given the following circuits:

It's then described how the circuit shown in Figure 2.49 doesn't compensate for current hogging, since if load 1 was removed, the corresponding transistor will saturate and pull more current than the other transistors connected to the common reference base.

The solution to this is then given via Figure 2.50, where compensation for current hogging is provided via an extra transistor connected at the collector of the "programming transistor" on the left. This extra transistor effectively pulls the voltage of the programming transistor's collector down to 2 diode drops below \$V_{CC}\$, moving it further into the forward active region of operation.

What confuses me is this: if you remove load 1 from Figure 2.50, the corresponding transistor will still be saturated there, just as in Figure 2.49. With that said, how does the extra transistor resolve this?


texts: How to Control SM1 Inverter Drive Frequency with Arduino?

texts:
I am back at trying to control the frequency of an SM1 AC inverter drive due to the fact that I never got it going the first time. However, this time I would like to use an Arduino. The manual for the TB Woods SM1 AC inverter is here.

As I understand it, the best methods for controlling the frequency are PWM or Rs-485. My questions for each are as follows...Note: As stated before, I'm no expert, but I love to learn.

PWM

I think this lacks the detail I am looking for. (0-60Hz in 1/10ths of an Hertz.) However, how would I hook it up to the SM1? A schematic would help. Do I use terminals M0-M5 (page 11 in the manual)?

RS-485

Again, do I use terminals M0-M5? I can't seem to find any setup instructions for sending commands like run, stop, go to 55 Hz, etc... Does anyone know what a sample Arduino code would look like in this configuration?

My application is fairly simple. A warper (spool winder) is running several threads onto a spool. As the spool becomes more full, the motor speed needs to be decreased constantly so the tension on the spool remains constant. The inverter drive runs the motor and an Arduino, hopefully, controls the speed of the motor through the inverter drive.


texts: Trying to understand how a darlington transistor works

texts:
From my understanding the point of a darlington transistor is to take one voltage and boost it further than what a single transistor is capable of.

I can't understand how it is actually doing that, though. Looking at the diagram below, E (Emitter) would be ground and a voltage is applied to B (base). At a sufficient voltage, The transistor is "switched" and now the voltage that is C is now the base voltage of the second transistor. Then the second transistor can switch and C can flow to ground. Why is this second transistor in place? It seems like it could be eliminated.


texts: How to connect LED Matrix into Arduino using MAX 7219?

texts:
I have:

2 8x8 LED Matrix, and
a MAX7219 Chip.

Q: I just wonder how can I connect that to the Arduino Duemilanove?

I have been googling but I couldn't find out how.


texts: Connecting a 5V 10A 2.1mm x 5.5mm Power Supply to a PCB

texts:
I have designed a system to control LED light strips (Adafruit NeoPixel strips) using an Arduino from a C# program in Windows. I have been through the prototyping phase with a breadboard and a single strip of lights. The system works well. Now I want to design a PCB to act as a hub for for multiple strips of lights so that when I connect them in parallel, I won't incinerate the breadboard.

My system run off of 5V and has a theoretical maximum current of 8.16 Amps (with 3 strips of lights). I already have a 5V 10A power supply with a 2.1mm x 5.5mm barrel jack. The high amperage of the system is where my questions about safety begin...

First, how should I go about connecting the 2.1x5.5mm barrel jack to a PCB? I could use a DC Barrel Jack connector like this (https://www.pololu.com/product/1139), but those are not designed for more than 5 amps. I could use multiple connectors on the PCB, but the splitters that are available all seem to be very low quality (and my final product won't be very clean looking). If you know of a different connector (say, MOLEX) that might have a higher Amperage rating, I would be open to finding a 2.1x5.5mm adapter.

Second, how should I go about distributing the power for the 3 light strips? I am using https://circuits.io/ to design the PCB and the maximum trace width is 80mil. Could I run 3 80mil traces originating from 1 connector? One for each light strip?

Thank you!


texts: Arduino LED Cube 8x8x8 with a Led Driver (TLC5940NT )

texts:
Me and a group of friends need to make a college project and decided to do a LED cube that can graph mathematical functions. We do not know how to code very well, and are very new to Electrical Engineering. We decided that we are gonna build the cube using an Arduino Uno. After searching quite a few cubes decided to build this:

http://www.instructables.com/id/How-to-build-an-8x8x8-LED-cube-and-control-it-with/?ALLSTEPS

We choose this one because its very easy to build, and doesnt have a bunch of componente we dont know(and specially, arent avaible in our city). Problem is the A6276 LED drivers are discountinued. We wanna try building the cube using the TLC5940, which we already have. Problems is, we dont undestand the new features of the TLC5940, and after reading many times the Datasheets we still dont know if we can use the TLC LED drivers instead of the A6276. So i am asking how can we use the TLC5940 to make a multiplexing 8x8x8 LED Cube using Arduino Uno.

I know there are many guides to do Led Cubes, and many include Arduino in them, but there are only few for big Led Cubes , and even less guides with the simplicity like the one we choose. And, i couldnt found a 8x8x8 guide that used the TLC5940. Please, help me, our heads are melting trying to find a solution!

Datasheets:
(Cant post 3 links, but google TLC5940 datasheet, first result)
http://www.allegromicro.com/~/media/Files/Datasheets/A6276-Datasheet.ashx

The cube will be built using single color 5mm LEDs.

Please, answer this prayer!

And thanks for at least taking your time reading this! ;)


texts: Getting starting designing CMOS ASIC - What is the must have software?

texts: What software should I use to design a pipeline of gates? The design will be implemented on TSMC's 350nm process. A list of must-have software to design a basic gate circuit, and ASIC solutions would be nice.


texts:
I have in the back of my brain a project involving wearable "transponders". These would be worn around the neck like a lanyard or a piece of jewlery. For simplicity, they should be able to charge by induction, so when I take it of, I only need to place it on a powermat-type surface, and it would be ready for the next day.

Is this something that is feasable for home-projects today?


texts: Are those two AC bridges equal. If not, how do they behave differently?

texts:
I do not understand if the following circuits are equal or if there's any difference in how they behave.

I assumed that it depends on the current, but then I have seen both used with AC and DC, so now I am confused whether or not it's a mistake or the circuits are just equal.


texts: Error in the gain, Amplifier, DAQ system

texts:
I have a strain gauge with maximum output of 5mV. I want to amplify this signal 1000 times in order to use my DAQ system to read it (the analog input range is 0-5V for DAQ connector).

I have purchased a MAX9613EVKIT+ (schematic below). The default gain factor is 10, but I want to change the R5 and RC3 from 10k ohm to 1 Mohm to get a GF of 1000. The thing that I noticed is the input impedance for the analog input channels is between 500k and 1M.  If I use a 1M feedback resistor, and assume 1M for connector, will I have 50% error on my gain? Or is only the R6 important for DAQ system?

In other words, is it OK to use R5=RC3=1 M ohm? What is going to be the error in the gain?


texts: Stepper Motor Big Easy Driver Undervoltage?

texts:
I am trying to get a Phytron Vss42.200.1.2 bipolar 4 winding stepper motor to work, controlled by a BigEasyDriver breakout from an Arduino Mega2560

The Design voltage on the Phytron stepper is 42Vdc. The maximum voltage on allowed on the BigEasyDriver is 30Vdc so this is what I am powering the breakout board with.

I have uploaded a basic sketch, one of the examples(Example 2) from the BigEasyDriver website http://www.schmalzhaus.com/EasyDriver/Examples/EasyDriverExamples.html

The motor is not driving any mechanical load and is still on my desktop. See picture.

When this sketch is running the motor vibrates and turns ever so slightly (maybe 5 to 8 degrees) clockwise and then anitclockwise. I have tested the same code and wiring with a 12V basic stepper (changing the 30Vdc supply to 12V) and it works nicely, rotating 3 to 4 revolutions anti clockwise and then returning the same number of steps clockwise.

Will I be able to use this BigEasyDriver breakout to control the stepper motor or is the voltage too low and not sufficient to move the rotor? Or is there other settings such as step duration that would help this?

Thanks!


texts: Can buck converter increase current if voltage step down?

texts:
I am using 50 W solar panel(20V @Open Circuit/ 3.5A @short circuit) to charge my 4V/100Ah battery(found from industrial scrap). I tried charge battery using buck converter but as it get pulse input current from source, i can charge battery at maximum of ~3.3A@4.8V. As this battery rated at 100Ah it can charge upto 10A.
How can i increase the current to increase charging speed? Buck converter is not perfect selection for this application. Does any other DC-DC converter do this? Or i should modify buck converter or else?


texts: How to read and display data from a CO2 logger connected via RS-232?

texts:
I got a Licor CO2-Logger (Li-820) for a scientific experiment. The Li-820 outputs an analog signal (voltage) and also offers a serial communication via a RS-232 port. I would like to sniff the serial communication with an Arduino Uno and display the CO2 values on a LCD display such that I can control the analog signal that is logged in a computer system. I want to display both the analog and the digital signal.

I use a RS-232 level shifter to connect the Licor CO2 analyzer to the Arduino Uno, and I can sniff the COM port successfully both with the Arduino serial monitor and a sniffer program.
Over the RS-232 port the Li-820 device outputs an XML-like line that is as follows (Line breaks and indentation added for readability):

<li820>
  <data>
    <celltemp>5.1252350e1</celltemp>
    <cellpres>9.7159633e1</cellpres>
    <co2>5.2527637e2</co2>
    <co2abs>7.7893261e-2</co2abs>
    <ivolt>1.1386718e1</ivolt>
    <raw>3950702,3808028</raw>
  </data>
</li820>

I would like to parse that information for the relevant part with the Arduino Uno which is the <co2>5.2527637e2</co2> ("CO2" value) and first output it to the serial monitor. Next, I will display that value on a LCD display. This last step should be a minor problem.

So, how can I parse the information for the relevant bits and then display it to the serial monitor?

I looked into many examples on the Internet. A modified version of the working code from here was the closest I got.


texts: BJT transistors: can one see them as voltage dividers or should they be analyzed differently?

texts:
I am currently reading The Art of Electronics 3rd edition and I am struggling to understand basic transistors.

On page 77 there is an example circuit with a PNP transistor driven by an NPN transistor. The second paragraph asks a question and in parenthesis it says "make sure you understand why", which I don't!

I am struggling to understand the voltages and currents present in this circuit. Can I treat the resisters as a simple voltage divider and perform ohms law and KVL/KCL as a normal circuit or do I have to analyze the circuit differently because of the transistor?


texts: yet another burned MOSFET issue in H-bridges

texts:
I'm trying to get into how H-bridges could be utilised in a heating/cooling peltier module for a personal fun project;
I designed the circuitry (shown below), which BTW your feedback and suggestions regarding the whole design is much appreciated, the problem is as soon as I'm switching ON the DC source(12V@3A) I'm burning the high-side P-MOSFETs. the DMP3056L could theoretically be able to handle 3A with Id_max of (-4.3/-3.4A for Vgs of -10/-4.5V) according to the datasheet; on the other hand, with Rds of (50/70mOhm for Vgs of -10/-4.5V) and considering the 3A drain current the dissipated power should be: 3^2 * (0.05 or 0.07) = 0.45-0.63 Watts and again according to the datasheet the temp rise should be 91C/W which I doubt that could cause a significant rise in the temperature to be the reason for the burning of MOSFETs.
Am I missing something here?
Datasheets:
https://www.diodes.com/assets/Datasheets/DMP3056L.pdf
https://www.diodes.com/assets/Datasheets/ZXMN3F30FH.pdf


texts:
Update Please evaluate this third attempt:

This is my first electrical project, so please be gentle with me. I know very little about electronics.

I'm building a machine that has a crank that users pull. The ideal behavior is that when a user releases the crank from its lowered position, the circuit will drive the load (represented by the lamp) for a few seconds, then turn off. Translated: When S1 is first opened, C1 drives X1 for a few seconds, then X1 shuts off. When S1 is closed momentarily, the cycle repeats. To be clear, X1 isn't driver while S1 is closed. I expect that there are better solutions with a different type of switch than S1 (instantaneous button), but in the greater mechanical context, it seems like the only practical choice for the project.

Here's a diagram of my first attempt at the circuit. Please ignore the actual quantitative values, I just want to get the circuit working conceptually. Please let me know if I got the diode directions right. Also, the load is actually a relay, I just wasn't able to find the symbol for that.

My conception is that when S1 is closed, C1 charges via D1. When S1 opens, C1 discharges via X1. I think the main weakness is that C1 is connected in parallel with the short circuit to V1. What do you think?

2nd attempt:


texts:
I see some ultrasonic sensors have legs with different length, such as below. Does it means they have polarity?

Are there any differences taking different leg as the signal pin?


texts: PCB Layout - Best way to hand solder under pads

texts:
Currently i'm drawing a pcb board in Eagle. Can't get a viable solution to allow people easy handsolder this component (WS2812B).
I will have 60 of this in the PCB, and i like to use them instead of RAW LED because it already contains the capacitor and resistor, so it will spare 60x4 solder joints. Also i find the price lower than source led + capacitor + resistor.

PCB is to be hand soldered like a KIT. No autoplacement machines.

My main ideia is place them at top layer and do vias to solder from bottom layer. Is it viable or there are better solutions?

Regards


texts: Crystal load capacitance for low power applications

texts:
According to Silicon Labs' app note on microcontroller oscillator design, larger load capacitance on crystals increase power consumption and increase startup time.
What are the actual numbers like in terms of power dissipation? Would there be any practical benefits to use a 9 pF crystal over a 20 pF crystal? Are there any drawbacks?


texts: For a binary up/down counter with synchronous clear and preset , my question is what is the exact function of the preset here ? I have done many searches but every source assumes that the reader knows what is the preset function is and just mentions that the counter does have a preset input.


texts: How may noise voltage and noise figure be compared?

texts:
For instance, comparing the
MIC920
and the
BGA2818,
it's expected that since the latter is intended for application as an RF LNA and the former is general-purpose, the BGA2818 would out-perform the MIC920 in RF applications. But how could this be proven?

The MIC920 specifies only an input noise voltage; let's assume they intended to write nV instead of V:

And the BGA2818 specifies only an input noise figure:

The "naive" comparison would be (following the Maxim App Note 2895):

BW for my application = 5 kHz

Gain of MIC920 ~ 85dB

Output power noise density:
$$V_{IN} = \left( 11 \frac {\text {nV}} {\sqrt{\text {Hz}}} \right)
\sqrt{5 \text{kHz}} = 778 \text {nV}
$$
$$
P_{IN} = 10 \log \left( \frac {778 \text {nV}} {50 \Omega \cdot 10^{-3}} \right) =
-48.1 \text{dBm}
$$

$$P_{OUT} = -48.1 \text{dBm} + 85 \text{dB} = 36.9\text{dBm}$$

$$P_{NOUTD} = \frac {36.9\text{dBm}} {5\text{kHz}} =
7.38 \times 10^{-3} \frac {\text{dBm}} {\text{Hz}}$$

$$NF = 7.38 \times 10^{-3} \frac {\text{dBm}} {\text{Hz}} +
       174    \frac {\text{dBm}} {\text{Hz}} - 85 \text{dB} = 89 \text{dB}$$

Is this calculation valid?


texts: how to increase the current from the LTC3108 chip

texts: I am currently trying to do body temperature thermal harvesting using thermoelectric module. The voltage obtained from the module is around 50-60mV. There are not many chip out there is able to boost such low voltage to 5V. My requirement is actually harvest body heat to charge an electronic device, say a smartwatch/ smartphone(need at least 5v,1amp). I am not sure it's possible until i found the ltc3108 from linear technology. The chip is powerful as it can boost mV up to 2.3, 3.3, 4.1 or 5v. However, the current output from ltc3108 is super small, where i think i can get only about a few milliamp. Anyone has idea to improve this ? I saw some said using a supercapacitor could work (from youtube), i don't really understand how a supercapacitor could work, as it is charge up to its rated voltage via current input right ? meaning if using a few milliamp could take a very long time to charge. And when it is discharging, could it harm the load device ? because the current from supercapacitor is very big right ? I saw a quite similar project posted in youtube. The schematic is shown below. Anyone mind to explain how it's circuit work ? I think he is not using ltc3108 here. I would really appreciate your help. Thanks in advance


texts: PCI-e. Using raisers to turn 1x and 16x to two 8x

texts:
I am doing a supper-budget-ghetto computer project.
Just wanted to ask a theoretical question: could spliced up risers be used to turn one 1x and one 16x slot to two 8x slots? I think they share a common bus soo...?

I know that I could do necessary tinkering and soldering, just wanted to ask you guys before I spend some money on actual risers and cut them to pieces :)

I've found similar question (Can i run several links through single pcie x8 connector?), last comment to accepted answer looks promising but I wanted to make it more specific


texts: Intuitive way to think of transistor saturation current?

texts:
I am having a hard time understanding what saturation current (denoted Is in my textbook) actually means for a transistor.

For a diode, it makes perfect sense, it's the approximate maximum reverse current that will go through the diode when it's under reverse bias. (Or at least that's my understanding; correct if I'm wrong)

But what does this mean for a transistor? I see that it appears in equations all over the place but I don't understand what it means intuitively. Maybe it would help to ask if I wanted to measure saturation current of a transistor, what would I do?


texts: Can I connect two charge controllers, one controller to lithium ion battery and the other controller to AGM battery. One 400 watt PV

texts:
Can I connect two 12 volt charge controllers to my 400 watt solar array?
I presently have a 12 volt 40 amp MPPT controller connected to a 12 volt 200 Ah lithium ion battery.  I would like to connect a second 12 volt, 30 amp MWP charge controller that I have purchased and connect it to the same solar array in parallel and power two AGM batteries.
I hope this makes sense. I want to charge the second battery bank AGM separate from the lithium ion battery for obvious reasons (as you know, lithium ion doesn’t require a float etc.).


texts: USB Hub on Embedded Target disconnects and reinitializes causing a crash on Linux Host

texts:
I have an imx6 embedded board which is connected through FTDI/USB to a linux host. The embedded board runs a Yocto linux. I send commands to the embedded board through a serial interface (ie. write to the USB device /dev/ttyUSB0). The Linux on the embedded board runs in its RAM, with NFS file system.

I have been observing the following behaviour. After a few commands over the serial communication, I get the following error on the target:

<..>USB modem converter now disconnected from USB0
qcserial: 2-1.1:1.0 device disconnected
usb 2-1.1: config 1 has an invalid interface number: 8 but max is 3
usb 2-1.1:config 1 has no interface number 1

Also, the error on the host is:

[ 5015.112569] usb usb1-port2: disabled by hub (EMI?), re-enabling...
[ 5015.112578] usb 1-2: USB disconnect, device number 2
[ 5015.112955] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0
[ 5015.112975] ftdi_sio 1-2:1.0: device disconnected
[ 5015.383005] usb 1-2: new high-speed USB device number 6 using xhci_hcd
[ 5015.531596] usb 1-2: New USB device found, idVendor=0403, idProduct=6011
[ 5015.531599] usb 1-2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 5015.531601] usb 1-2: Product: Quad RS232-HS
[ 5015.531603] usb 1-2: Manufacturer: FTDI
[ 5015.532206] ftdi_sio 1-2:1.0: FTDI USB Serial Device converter detected
[ 5015.532247] usb 1-2: Detected FT4232H
[ 5015.532381] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB4

Now the undesired effect is also that ttyUSB0 is now ttyUSB4, which causes my program to crash.

Could someone give me some suggestions to fix this issue please?


texts: designing a mains powered car jump starter

texts:
Would it be possible to jumpstart a car using mains power?
I'm talking about a device that plugs into a 240V AC mains power outlet, and clamps onto a 12V DC lead acid battery.
Here are the main specs on a typical (and my) lead acid battery:
Cold Cranking Amps: 550
Reserve Capacity Minutes: 95
Amp Hours: 55
So, to the average consumer, it would basically be like plugging an extension cable into the wall socket and the other end just clamps onto the battery terminals.
Is it possible to do something like this with a stepdown transformer or some kind of bridge circuit or voltage reducer circuit or similar?
even if it's not an ideal solution, i'd still be interested to experiment and explore this avenue.
Thank you for your time.


texts: Is a bit error rate close to 1 just as desirable as one that is close to 0?

texts:
Let me explain the premise. If you have a communication system, and you know with a very good confidence margin what the bit error rate is, would you be able to exploit the properties of high bit error rate by simply flipping the bits? For example, imagine:
0 1 0 1 0 1 1 1
Is sent as a package to a satellite, which reads:
1 0 1 0 1 0 0 1
Where the bit error rate is .875. If we know that this is the error, we could randomly select a bit that is incorrect and in the worst case, this would result in a bit error rate of now 1 (we assumed that the last bit was the culprit):
1 0 1 0 1 0 0 0 <- Bit flipped (estimated to be the one that is incorrect)
Then, we flip the bits completely to reveal the real bits we first transmitted.
This situation sounds too good to be true, so in the real world, what is preventing us from doing this procedure and is this actually applicable in some scenarios?
EDIT: Appreciate immensely the responses, I will try to respond to each one.


texts: Is it possible to wire an accelerometer straight to lights?

texts: I am currently working on a personal project and was wondering if there was any way to wire an accelerometer to an LED light to illuminate the light when a set g-force is achieved. I am not too advanced in programming a board to analyze the data and transmit it. Any help would be very much appreciated


texts: Can I use ST-LINK (or clone) for programming non-ST ARM{7,9} and Cortex A chips?

texts:
Can I program non-ST ARM926 or ARM7TDMI and Cortex-A chips using ST-LINK and ST-LINK clone? I've searched ST's website and I haven't found anything about this. If no, what is the cheapest way to do this? Do you know a way that is cheaper than buying a J-LINK?

I've read this answer, but it does not cover ARM926 and Cortex-A chips. Specifically, I want to flash Allwinner-A13 CPU, Atmel AT91 series and i.MX6/i.MX233 series.


texts:
What is a Class-J Amplifier configuration?

Does it work in a push-pull configuration similar to an A/B?
How is it physically different to an A/B?
Where can I see a basic schematic?

I have read through the literature on IEEE Xplore on the efficiency of Class-J amplifiers over wide bandwidth; but I still cant understand how the configuration actually works.


texts:
Is it possible to separate the positive and negative portions of an AC voltage wave into two separate lines, where one line has the positive voltage portion (and is neutral when the source is negative), and another has the negative voltage portion (and is neutral when the source is positive)?

Here's a diagram to try to clear up any misunderstandings:

simulate this circuit – Schematic created using CircuitLab

So if VMI's output looked like this:

VM+ and VM- would look like the following:

If it matters, this is purely hypothetical; I don't plan on trying to build said circuit anytime soon.


texts: I've a 12V 80A motor, for drive this i'll use a H-bridge with mosfet, in order to divide the current per H bridge we can drive a motor with 2 H-bridge? I'll use mosfet, we cant put mosfet in parallel


texts: how to put physics formulae/laws together and make transformer?

texts:
i want to make a transformer, i studied all the formulae of physics, for magnetic flux, Emf, mutual inductance, inductance, transformer equations, turn ratios, solenoid etc. but still i can not put all these formulae together and make he transformer.
All i know for the desired transformer is,
input voltage= 12v , input current= 6.25, output voltage= 220v, output current= 0.57.
the transformer is 125watts step-up.

there is a simple technique to design transformer, using tables and constant 42. but I want to know,

how to put laws of physics together and find the number of turns for this transformer?


texts:
I was browsing for push switches on Element14 and due to the vast amount of choices, I wanted to narrow down my search. However I stumbled across the filter category "Switch Operation" and was confused as to the following terminology:

X-X
X-None-X
X-On-X
Where X can be either "On", "Off", "(On)", "(Off)".

Currently, I know the brackets mean momentary which I assume is the state when the button has to be held or pushed by the user. I also know that a SPST with switch operation of On-(Off) is a NO pushbutton and Off-(On) is NC pushbutton, but the existence of other possibilities just confuse me. What do they mean?
There seem to also be filters that seem to be weasel words. So there's "latching" and "Push-On Push-Off" along with "Push-Pull" and "Pull-To-Cheat". Are my assumptions correct?
I even tried to look in the datasheets but they don't really define much, like what is On-(On) vs On-On.


texts:
Being just a beginner I'm really getting confused of pull-down resistors.
Please have a look at the diagram below. Here there is a 10k pull down resistor is connected to ground and the pin 2 of arduino. Whats really the purpose?

Is it really to avoid shorting between the 5v and ground??
So if there is a LED (load) in the circuit when the button is pressed do we really need the pull-down resistor?

Also if the button is connected to an external source (5v battery) do we need a pull-down resistor in that case as well??

One more question, if I have 5 buttons to pin 1-5, So do we just need a common pull down resistor say 100k for the 5 buttons?


texts: Why was Mini USB deprecated in favor of Micro USB?

texts:
Mini USB connectors were standardized as part of USB 2.0 in 2000. In 2007, the USB Implemeters Forum standardized Micro USB connectors, deprecating Mini USB connectors four months later.

Why? What are the advantages of Micro USB over Mini USB that made USB-IF rip out an existing standard and replace it with another one that's basically the same thing?


texts: Why is the Nyquist data rate lower than the Shannon data rate?

texts:
In the book Computer Networks, the author talks about the maximum data rate of a channel. He presents the Nyquist formula :

C = 2H log\$_2\$ V (bits/sec)

And gives an example for a telephone line :

  a noiseless 3-kHz channel cannot transmit binary (i.e., two-level)
  signals at a rate exceeding 6000 bps.

He then explain the Shannon equation :

C = H log\$_2\$ (1 + S/N) (bits/sec)

And gives (again) an example for a telephone line :

  a channel of 3000-Hz bandwidth with a signal to thermal noise ratio of 30 dB
  (typical parameters of the analog part of the telephone system) can
  never transmit much more than 30,000 bps

I don't understand why the Nyquist rate is much lower than the Shannon rate, since the Shannon rate takes noise into account. I'm guessing they don't represent the same data rate but the book doesn't explain it.


texts: How to build a USB controller having knobs, sliders, and switches

texts:
How does one go about building an interface for a USB device that allows interfacing pots, linear/log tapers, and momentary/toggle switches to a computer?

If someone could give me a high-level description, I would appreciate it.  I can read spec sheets, so understanding details is not a problem as long as I know where to find the sheets.


texts: Heat dissipation in a DIP Solid State Relay

texts:
I am working on an application that switches a high power (15 W typical, 100 W maximum) resistive load at 230 VAC (RMS) from a 5 VDC control line. For this I plan to use a Solid State Relay. I am currently planning to use the AQH3213A from Panasonic, but I am concerned about the heat dissipation of the part. The load will be switched on regularly anywhere from a few seconds to a few minutes. I performed the following calculation for power dissipation under maximum load conditions:

$$
P = I_{Load}\bullet V_{TM}
$$
$$
= 0.435 A \bullet 2.5 V
$$
$$
=1.09 W
$$

However the datasheet (or any other information I've been able to find from Panasonic) does not list any thermal resistance values for the DIP package the SSR uses.

How can I figure out how hot the SSR will get under maximum conditions, and whether I need a heatsink? Furthermore how could I effectively heatsink a DIP 8?


texts:
I'm trying to send The PORTB to the serial port and receiving the data on pickit2 UART mode..

void main()
{
  TRISB = 0xFF;
  PORTB = 0;
  UART1_Init(9600); // Initialize UART module at 9600bps
  Delay_ms(100); // Wait for UART module to stabilize
  while (1)
  { // Endless loop
    UART1_Write(PORTB); // and send data via UART
    Delay_ms(500);
  }
}

I'm using MikroC pro. and the problem is I'm not getting proper data.

I've connected pullup resistors to each pin of PORTB and all i get is

RX: E0

which means only RB5, RB6, and RB7 are pulled up rest pins are low.

also noticed if i try to pull down any pin of portb then only these pins cause the value to change. any ideas what might be wrong?


texts: In my work with electrical iron, I have done a lot of research to try to understand how to determine the quality of it.  Is there a simple way to test for the saturation point?  Some of the methods I read about involved very expensive BH curve tracers, and with some of them you were supposed to use a specific size and shape of a metal sample.  I was hoping to take a stator or rotor and test the iron quality without destroying it.


texts:
What I'm looking for is to be able to solder a mechanical pressure plate/arm to a PCB, where a plastic tab can be inserted.

This contact (when connected) will complete the 3.3V/5V supply and turn on the device. Similar to how some manufacturers put the little plastic tabs in the battery housing so that all you have to do to start using the device is to pull the tab out.

In the picture above, the red rectangle would be the PCB viewed side-on. The blue component would be the little conductive arm/plate which naturally wants to close and make contact with the other little blue area. The orange line would be the plastic tab preventing it from making contact until removed.

Any ideas if such a thing exists and what it would be called?


texts:
I wish to build a little decent power supply for my IoT devices, would like also to implement more protection from the live 230V AC side and I decided to put a fast blow glass fuse in a nice holder, thermal fuse SF70E and a varistor for HLK-PM01 AC-DC 5v/600mA Converter module.

Now the questions are:

I found example regarding the varistor value 10D561K, and I don't understand why it's not like 10D241K or 10D271K (this is what I have at home)?

I would make it like this:

Also for the max. 600mA load on the DC side, what fast blow fuse value should I use on the live 230 AC side 200mA, 500mA, 750mA or 1000mA?


texts: Why does the collector current direction remain the same in saturation and active region?

texts:
The collector current direction remains same in both active and saturation state where the former puts the base collector junction  reverse biased and the latter puts the base collector junction forward biased. How is it possible?

Question inspired from https://www.quora.com/Why-do-collector-current-flows-from-collector-to-the-base-even-in-transistor-in-saturation-state-when-the-base-collector-junction-is-forward-biased


texts:
Is it safe to assume that

I just needed a simple yes or no before I precede any further into the problem.

Thank you in advance


texts:
I'm rather confused by the behaviour of an LED here, I wonder if someone can get my head around it?

I have a microcontroller-based circuit @3.3V (using an LM2937 LDO regulator) driving a standard LED (2V ish voltage drop, 20mA If) via a digital output. So far so simple.

When I use my circuit simulator software...if I connect the LED directly to a 3.3V source, with no series resistor, it tells me it would draw 14mA ish. This is ok for the LED and my PIC I decide, and connect it up. Sure enough, when I do so, my ammeter tells me that 10-11mA flows through the LED. Great...no problem, I think to myself.

However, when I connect it to my bench DC power supply @3.3V, it displays ~100mA as the output current. A separate ammeter inline shows the same...a second ammeter agrees. However, the LED doesn't pop.

What's going on here?


texts: Understanding oscillation frequency for SAF-C509 processor

texts:
Good day.
For the time being, I'm reversing automotive ECU which has Intel51 architecture processor - SAF-C509 by Infineon/Simens. Its command exection part has 6 states with 2 phases for each state. Hence a single machine cycle is executed within 12 semi-phases.
One can add an external oscillator to set frequency of the processor. Lets assume that this frequency is 16MHz.
The user's manual on the processor says:
XTAL1 and XTAL2 are the output and input of a single-stage on-chip
inverter which can be configured with off-chip components as a Pierce oscillator.
The oscillator, in any case, drives the internal clock generator.
The clock generator provides the internal clock signals to the chip at half
the oscillator frequency.
These signals define the internal phases, states and machine cycles.

Now, I can't see in any obvious way what exactly is oscillated at that frequency. Is this 16MHz/2 frequency for semi-phases or something smaller?
Rephrasing the question: what's the frequency of machine cycles with 16MHz oscillator connected to the processor?


texts: Calculating inductor voltage in a second order linear circuit

texts:
I was trying to solve the following second order linear circuit:

I managed to calculate all parameters but one: the Voltage of the Inductor at t=0, that is necessary to define the B parameter of the solution.

I tried to calculate it considering the closed network of the inductor, R2 and the capacitor.

The voltage of the capacitor should be 28.57 V.
Considering the circuit a t=0, R2 has the same voltage (the capacitor at t=0 can be considered as an open-circuit, so they have the same voltage). So the Inductor Voltage should be (-, probably) 28.57 V (-) +28.57 V=(-)57.14 V. But, considering the inductance (0.1 H) the solution is:

Instead of 571.4 V.

So? Should i consider the circuit at 0+ instead of 0-? Or i forgot something?


texts: What is the max voltage 74HC4067 IC can withstand on output side when non of the channels are selected?

texts:
I have 74HC4067 (ESD 200 V)
Vcc 3.3V
Switching voltage 3.3V
Input voltage 3.3V
In my application when non of channels are selected, 16 output pins will have connection to 100V 9mA source one pin at a time ,
What is the leakage current to ground if 100V is applied on output side?
will ic damage due to this 100V?


texts: Is there a relatively inexpensive form of double sided tape that would be safe to use (i.e., low static) for mounting a sensor?

texts:
Apologies in advance if this question would be best directed elsewhere:

I am working on a wearable project, and would like to attach two small IMUs ( see product page here) to some fabric.  Each sensor has only one mounting hole, and so thread alone has been insufficient to provide a secure attachment.  I was considering switching to something adhesive, and asked the representatives from the store that sells the sensor what they might recommend.  They suggested double sided tape, but cautioned that anything cellophane-based might pose an ESD risk.

My question: What kind of double sided tape might be safe to use for my project?

I've done a search for anti-static tape, and am not sure how to evaluate the very wide range of options that appear to be available.  Ideally, I could find something at a relatively low cost, and I am not looking for a super strong hold (this is just a simple prototype, and I'd like the option of repositioning the sensors if I need to).

Thanks in advance for your time!


texts: Is there a standard replacement for three stacked LR1154 cells?

texts: Some years ago I have seen a battery which alone could be used to replace three stacked LR1154 ("LR44") cells but I can't remember the name now. C... something I believe. I found this picture, if it helps, it's literally three LR44 shrinkwrapped:


texts: Can you adapt 5 pin intercom headsets to work over a 3 pin clear-com system?

texts: I'm new to an old theatre that had a clear-com system installed in it 30 years ago. The headsets all died before my time there and I'm looking at getting some new. All the plugs in the walls are 3 pin XLR, but it seems like 3 pin headsets are hard to come by (and expensive) these days, so I'm wondering if I can simply adapt a 5 pin headset to plug into the 3 pin plug, but it's my understanding there are at least 4 conductors needed for mic and sound. Would a common 3 to 5 pin adapter work in my case, or what could I expect if I invested in the new headsets and tried it?


texts: Confusion with Bode plot in LTspice when using a voltage regulator

texts:
To experiment(out of curiosity) the effect of a low pass filter for an SMPS switching noise I wanted to try a filter where an LC cascaded by a linear regulator as shown in below diagram, I obtained the AC analysis in LTspice.

I don't know anything about the output impedance of the SMPS so I chose is as 1 Ohm. Then I swept the input between 0.1Hz to 1 Meg Hz.

But why in the Bode plot Vout starts from -180dB but not 0dB?

EDIT:

Following some comments I superimposed the noise on a 24V DC as shown below:

The AC coupling caps C4 and C3 are there to view the noise component at the input and output.

Here is when 1V 100 kHz square wave noise(with 1p rising and falling edges) is superimposed on the 24V DC:

Here is when 1V 100 kHz sine wave noise is superimposed on the 24V DC:

Below is when 1V 0.1 Hz sine wave noise is superimposed on the 24V DC:

And finally here is the AC response when superimposed on the 24V DC:

It seems in the AC response at 0.1 Hz the y axis shows around -70dB. This corresponds to a voltage ratio of 3162 and for 1V the output would be expected as 320uV which almost matches to the 0.1 Hz transient response noise amplitude.

Are these results expected in practice? If so it seems to me the linear regulator works as a very very strong low pass filter.


texts: What difference will it make on the output between these two circuits?

texts:
In the above image there are two figures, Fig(a) consists of force sensor connected to a resistor in a simple voltage divider configuration, and its output is fed to an ADC. Now coming to Fig(b), its the same circuit as Fig(a), however in this case the voltage divider circuit is followed by an op-amp in voltage follower configuration.

The circuit in Fig(a) does not have any output offset voltage, whereas the circuit in Fig(b) has an output offset voltage of 650 mV. I know that the circuit in Fig(b) is mostly preferred over the one in Fig(a) due to the op-amp having high input impedance, but I don't understand what difference it makes in the output fed to the ADC. Now my questions are as follows:

What is the difference between the two circuits with respect to the output being fed to the ADC i.e. in Fig(a) and Fig(b). And why is the circuit in Fig(b) more preferred than in the Fig(a)?

2.The OP177 op-amp has pins 1 and 8 for trimming the offset i.e. 650 mV using a POT, however this isn't working. So why isn't the offset nullification working?. The POT has 3 terminals among which, 1st and 3rd terminals are connected to pin 1 and pin 8. And the middle terminal is connected to +Vss(pin7) for offset trimming.


texts:
I want to practice more bipolar transistor, more specific Common Emitters.
Can someone give me any source where there are exercises with solutions of Common Emitter Circuits .

i just want to go  exercise and go through them and then check if I have done them correctly


texts: Effect of metal resistivity on the characteristic impedance of microstrip line

texts:
We know that the characteristic impedance of a microstrip line is given as follows:

In general the metal resistivity is so small that Z0 can be taken as sqrt(L/C). But if the metal resisitivity is not that small? Then according to the equation, this resistivity should affect the Z0. Is it true?

I did simple Agilent Genesys simulations of microstrip lines to see the effect of the metal resistivity on Z0 but surprisingly it didn't affect Z0. When I increase the metal resistivity, it only increases the attenuation. Any idea and help is appreciated.


texts: Fully differential opamp with weird behavior

texts:
I have a fully diffrential opamp that is configured like seen in the below picture:

I have a series of Frequency sweeps (differently scaled input) that I performed and measured with a VNA. The weird part is that it looks so skewed:

Blue is the expected amplification according to calculations (should def. be true) while the colored dots are the sweeps at different input amplitudes each color.

The OpAmp s configured to amplify approximately 29dB. So according to the Datasheet this should be zero issue up until 100MHz (it's on page 6 of the ISL55210 DS). Since I sweep only up until 50MHz I am very confused how it results in this broken curve .. It's also not a circuit that's very complicated ...

EDIT: I measure the DUT like seen below, except that there is a 1uF Capacitor in between the adaptor and the VNA to block any DC:

The input is generated by an AD8331 which works 100% properly as verified in separate measurements. The AD8331 is connected with two 270 Ohm Resistors.

I would be grateful for any hint what I could check ...

P.S. The peak at the beginning is not less strange ...


texts:
Imagine you were trying to write a C routine for an 8bit microcontroller that converted a desired timespan (be it seconds, milliseconds, hertz, etc). to the corresponding hardware timer preload value (taking into account the clock source and frequency of the timer).  The goal is to make the function as easy as possible to use, with as few arguments as possible.  What would this function look like?

Would you pass in a uint32_t representing the desired hertz of the timer (0 = 0Hz, 1000 = 1kHz, etc.):

void set_timer(uint32_t hz);

Would you prefer using a uint16_t representing kHz instead (0 = 0Hz, 1 = 1KHz, 10 = 10Khz)?

void set_timer(uint16_t khz);

Or would a 32bit fixed point argument be more desirable (to be able to represent fraction of hertz)?

void set_timer(q15_16_t hz);

Or would this fixed point value represent seconds instead of Hz?

void set_timer(q15_16_t sec);

Or would you use a 16bit fixed point instead of a 32bit fixed point.

Or would you even dare want to use a floating point?  Or what about a half-precision float?

What do you think?


texts: How to apply Thevenin's theorem to the equivalent two-port circuit of receiving antenna?

texts:
This circuit is adopted from page 633 of the book of "Field and Wave Electromagnetics, 2ed" written by David K. Cheng.  According to his description:

The equivalent internal resistance obtained by Thevenin's theorem should be $$Z_{22}-\frac{Z^2_{12}}{Z_{11}}$$. And I have confirmed this equation is right by finding another paper 1 giving the same equation. However, it seems to me, with shorting $$Z_{L}$$, it should be $$\frac{Z_{12}V_1/Z_{11}}{\frac{V_1}{Z_{11}-Z_{12}+\frac{1}{1/Z_{12}+1/({Z_{22}-Z_{12})}}}}=\frac{Z^2_{12}}{Z_{11}Z_{22}}(Z_{22}-Z_{12})+\frac{Z_{12}}{Z_{11}}(Z_{11}-Z_{12})$$, which clearly not leads to equation (11-101). Which part of my derivation is wrong?
1 Collin, R. E. "Limitations of the Thevenin and Norton equivalent circuits for a receiving antenna." IEEE Antennas and Propagation Magazine 45, no. 2 (2003): 119-124.


texts: High-gain feedback amplifier design using ADA4004

texts:
I am trying to design a feedback amplifier with ADA4004. My desired gain is about 42dB@2kHz. Is it possible to design a stable amplifier with such gain using ADA4004?

The ADA4004`s GBP is 12MHz. The slew rate is 2.7V/us. The output voltage range is -2V~2V.
Here is the schematic:

simulate this circuit – Schematic created using CircuitLab

I have simulated it in Multisim and found that the phase margin is larger than 90 degree. Is it OK?


texts: Time constant vs Length of Pulse in RC circuit

texts:
Reading through "The Art of Electronics", I came to a statement where the writer states that the time constant (t) of RC circuit must be many times bigger than the Length of pulse you want to couple through the capacitor.
These are the words from the book:

you might use a
blocking capacitor to couple pulses, or square waves. In
such situations you encounter waveform distortion, in the
form of “droop” and overshoot (rather than the simple amplitude
attenuation and phase shift you get with sinusoidal
waves). Thinking in the time domain, the criterion you use
to avoid waveform distortion in a pulse of duration T is
that the time constant τ=RC>>T.

Imagine a situation where I need to couple 1us rectangular pulse. Following the book, let's take time constant t=100us.
According to my understanding, time constant is the time required for the circuit to respond to the change. So, whenever the rising edge of the pulse comes in, the circuit is going to take 100us to respond. But the pulse would have already died by the time this circuit settles.
I thought this condition is valid since it wont let any fluctuations happen whenever the pulse is in either high or low state. But in the case of switching from one state to another, I think this condition is invalid.
What is the actual thing going behind the scenes?


texts: How to get output voltage of microphone?

texts:
I am really confused at this moment. I have the following microphone: http://www.farnell.com/datasheets/1660938.pdf

What I want to do is make a actual dB meter with this sensor. So I would net to know how much the voltage changes for example when the sound changes with one 1dB? How do I calculate that with the above datasheet? It has something to do with the sensitivity but what and how?


texts: Throughput and speed of data transmission cables

texts: What are throughput and speed limiting factors in an ethernet or any other type of cable which is used for data transmission?


texts: Reading UART from device that has floating ground

texts:
I am powering an ESP32 over a less-than-ideal power line, that has 4 Ohms of resistance. In order for 5V to arrive at the device, I apply 7V to the power line, such that when 250mA of current are flowing, 1V is dropped on both the power line and the return path, resulting in 5V difference at the ESP's linear dropout regulator.

I would like to connect my FT232 serial-to-USB converter to the ESP's UART to diagnose the device in this environment, but am afraid I can't because

the device's ground is 1V above my laptop's ground
the device's HIGH signal would be at 4.3V instead of 3.3V
the device's LOW signal might not be low enough to be interpreted by the FT232 (1V)

What options do I have to still be able to read data from this UART port safely?


texts: LiPo Charging Voltage and Operating Voltage problem

texts: I have 3 Lithium Polymer batteries. I would like to hook them up in series. The voltage would equate to 11.1V. If I have a LiPo charger does it require 11.1V input to charge them?


texts: Is it safe to unplug power, from a working LCD monitor?

texts:
I've built a system using a pressure sensor on my chair, which in-turn controls a switching-relay such that when I get up from this chair, power to all my LCD screens is switched-off by the relays, automatically. That is, I do not have to manually press the power switch on each of the LCD monitors.

So, the question is - is it safe to remove power from working LCD screens in this way ? Can it cause problems for the LCD monitors in some way ? Is pressing the power switch on the LCD, result in a different method of switching the LCD monitors that is better ?


texts:
I want to create a waveform for the agilent 33220a waveform generator. It is a 40us arbitrary wave that I have designed in the keysight waveform builder pro via the Benchvue software, however I want it to then wait 1 second at 0 V DC (or just off) before the same wave is pulsed. There are not enough sampling points available to do this in the same .wvf file, due to the high sampling rate needed for the 40us waveform.

Is there a way to do this with the 33220a, for example telling it to not send any signal for 1 second without requiring any samples, or by using a high sample rate for the first 40us and then a much lower rate for the 1 second period?


texts: Some general question on verification from scratch

texts:
I'm not a huge expert on hardware verification, I mean I know what the purpose of verification is (basically check if the system what it is expected to do) and I've used some tools for verification, usually I design an equivalent in Software using C/C++ language and than I compare somehow the VHDL/Verilog equivalent against this.

However it seems like most of this tools are not free, I was wondering if it is possible to use some very simple verification technique from scratch. Most of this tools as far as I know they use first order logic to after analyzing both Software and HDL code. Is there some very simple approach (other than exhaustive simulation) that could easily implement by him self to check the equivalency?

Maybe there's some very simple algorithm that can be easily used, and I'm not aware of.

Thx


texts: Are there 5V battery packs available without a boost converter?

texts: Looking for a 5V portable power source without switching or conversion noise.


texts:
I just created my first FPGA project. I created a small FPGA PCB with some slide switches to input values to the FPGA. Sadly, I did not debounce them properly with hardware, as you can see in these oscilloscope images:

How can I debounce the switches in "soft"ware on the FPGA? I found some examples online, but they didn't work for me. My internal clock is 16MHz.
Edit:
I am using a TinyFPGA Bx module. According to the datasheet, the inputs are built with Schmitt-Triggers. Looking at the images of the osci, those „steps“ are weird behaviors between slide switch and input. For hardware debouncing, I used a 10k resistor and 10n capacitor. The wierd voltage rise / fall creates some wierd Fpga behavior. Why could that be and how could one filter the signal to be „just one jump“?
Edit:
Solution: My clock was not unbounced. I solved it using Verilog.


texts: Bad Residential Wiring - Dead circuits and circuits go on and off randomly

texts:
We moved into a home that is about 30 years old ten years ago.
Our hallway lights are on a a circuit that is usually dead, but occasionally comes on for a few minutes or so, sometimes a few hours.  When I turn the panel off to do work, that sometimes seems to make these lights come on.
We have at least one circuit that is almost always dead.  I have one outlet in our master bedroom that works, but it has 3 black wires that are not hot tied together.  There are three other outlets in the room and I'll add more details about those soon.
The other day, I tried connecting the 3 black wires to the hot wire to see if it out make one or more of our dead circuits alive.  Instead it melted the plastic wing nut.  I smelled the plastic smell in at least one other room that had 3 dead circuits.  So, I am guessing that maybe I need to connect these black wires in a different way.
Can someone please explain how I go about connecting these black wires, maybe one by one?  And, how I test to see that things are safe and working.
I bought a Kaiweets HT112B multimeter because it looked somewhat easier to use and maybe has some neat features that older multimeters don't have.  I also have 3 circuit testers that tell me if the outlet is wired correctly and also shows the voltage.  For our house, it looks like it is usually 118 or 119.  I can add more details to this question as time goes by.
I really appreciate the suggestions so far and I will update this question with more information after I hire the right electrcian(s) to help.  Diagnosing this problem is time consuming and I'm hoping it will make sense to try and repair our wiring rather than opening up the drywall and ripping everything out.


texts: addition of external footprint to ki cad

texts: I have downloaded a .stp file of MAX14878 foot print. I tried to add it to the library through manage footprints options. It shows a table where it is added. But I am not able to find it during edit symbol fields for the project. Can anyone help me in adding an external footprint to kicad. I use version 5.1.4


texts:
This is a normal sequence for an SPI Read:

I want to code for an SPI slave. How is this normally done? How can the slave respond so quick  (in the next bit!) with the appropriate data out after it has received the address of the register the master wants to read?


texts: How to drive this MOSFET with a microcontroller?

texts:
I'm trying to drive a motor with a 7V battery pack using the 5V pinout from a microcontroller. The pinout is connected to the gate pin of an IRF510 MOSFET.

This is my current circuit:

The simulation clearly works fine, but when I make the circuit the motor keeps turning when pinout is 0V, only more slowly. I recorded these voltages:

Voltage across motor when pinout is ON: 6.55V  (this is fine)
Voltage across motor when pinout is OFF: 5.77V (should be 0V, I want it to stop)

The current through the motor is 0.2A regardless of voltage, but the drop in voltage when the pinout goes off obviously causes the motor to slow down a bit.

I've tried tying the gate to ground (ground pin of the microcontroller) with a 20k resistor, but this had no effect. If I understand it correctly, I only need to worry about a transient voltage when the microcontroller itself is physically switched off? I'm also not sure if I should use the ground of the microcontroller or the ground of the 7V battery pack (all the diagrams I've seen use a common ground).


texts: With an N type MOSFET you let the current flow from the drain through the source when a high enough voltage is applied to the gate. With a P type MOSFET which direction is the current meant to flow? From the source through the drain or the other way around? thanks


texts: Can I do anything with this LCD? I doubt it

texts:
Right, so I have ripped the 1.7" (ish) TFT module out of an HP PhotoSmart C4780.  Despite HP's best efforts I can plainly see that it is made by AUO.  No model number on it though.

Now, I have never had anything to do with TFT screens before now, but I want to have a play.

The screen has a single mylar strip connector, and I can see which of the connections break off to the back-light, so that's not a problem.

From what I can see the rest of it doesn't need anything 'special' - the board it normally plugs into is powered by a PIC16F727, so it must be possible for me to interface it to some other PIC instead (I have a selection to hand).

But how do I get started?  I don't even know what connections to expect there to be on the mylar strip, and how to work out what should be where.

I have found some AUO data sheets, but none for a 1.7", only 1.5" and 2" and upwards, though I have identified one possible 1.7" model - A017CN01, but I can't find a data sheet for it anywhere.

Any pointers would be most appreciated.

****Update:****

I think I may have just found a data sheet for this device - I'm still none the wiser though...

I see it has a serial data (SPI-like) interface to it - ideal for PIC usage.  Nothing in the data sheet about how to use it.  Would this interface be likely to be common to all AUO devices?


texts:
I've got a power supply that is suposed to provide 5V of DC voltage, I use it for powering an LED Strip (WS2812B) and I've measured the voltage right after turning it on and it's about 7V (for no more than half a second) and then it normalizes to a stable 5,1V.

I wanted to know if this could be a problem, or is this scenario just normal and nothing will happen to my LED Strip


texts: Looking for a device to detect the amount of smoke

texts: I'm building a cold smoker monitoring system. With cold smoking you need to maintain consistent levels of smoke and not necessarily a consistent temperature like with hot smoking. I'm trying to find a sensor to use in the PID loop. Does anyone know a smoke sensor that gives a level of particulate smoke and not just present/absent? Even a course level should be sufficient to detect when levels are low and either more wood is needed or more heat. Preferably something with I2C or a linear/semi-linear analog reading.


texts: After creating the linux boot image from the tutorial for the zedboard, I tried creating a socket application to talk to the computer. The Zedboard would be the server and the program in visual studio would be the client. When I try to run the program from the linux command prompt, it pops up with "error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory". When I ran a hello world program from the sd card on the Zedboard, it did not give me this error and worked just fine. Could this be a cause of the includes I am using? Both the client and server were written in C++.


texts:
I'm going to start a project in my University in a few week. Since it is a collaboration between my University and a very important company I cannot say too much about the project itself. So I try to give here just the needed amount of information, that describes the problem. Hopefully I can describe it well enough to make it understandle for you.

Problem: A microcontroller sends data trough a bus (it can be RS485 or CAN. This is not yet specified) to up 12 devices:

There was a little bit of disappointment about this design, because somebody involved in the project dislikes the presented solution (some people want to cable directly the microcontroller with each device) because of redundancy. The reason behind this design is that we can write and implement a protocoll to transmit data to every device. Thats nice and extremely efficient, since I can send data through package of informations.

Some of my colleges dislike this solution because of the lack of redundancy. If for any reason the bus it going to be interrupted (one wire breaks up, mechanical movement on the cable, etc...) some device could not get their information (which is vital for the life of the system) and really a lot of damage can happen. The worst case is when the connection breaks between the master and the first device. Then all devices are lost. This case should be avoided at any cost.

I want to avoid this. So I was thinking about a solution where there are at least two bus for communication to let communicate the devices in case one bus doesn't work anymore. So I have in my mind the following design:

But I have a problem:
I want to send over each line the same information. The device should be able to read only one. So both line should merge into one channel before being read by the device.

Questions:

Is this form of redundancy acceptable? Or should I rethink my design?
Does make sense to merge both lines into one before going into the device? Or should have the device at least two separate RS485 or CAN ports and then merge the information by software?


texts:
I am trying to design a PCB layout for a component which requires elliptical pads. I am trying to do it with two arcs but I didn't get an ellipse.
Can anyone suggest how to draw ellipse on eagle? Is there a best way?


texts: Amplify piezoelectric transducer voltage

texts:
I have an audio-band piezoelectric transducer with a 17 kHz resonant frequency (among others). I'd like to use this transducer to acquire from an MCU an FSK modulated audio signal.

When I plug the transducer into the oscilloscope (with a 1 MOhms input impedance) and I observe the FFT of the voltage produced by the transducer, I observe a peak, with an amplitude of ~100 microvolts.

This amplitude is obviously too low for the ADC of the MCU, so I'd like to amplify the signal, but I don't have any idea how to do it.

How would you recommend to do that? For any purpose, transducer capacitance is supposed to be 13 nF at 120 Hz, according to the datasheet.

Thanks!


texts: Digital current affects analog signals, but why not the other way around?

texts:
My course text only says that if we have a conductive coupling then the digital current will affect the analog signal because it causes certain voltage drop in the common wire. But it doesn't say anything about analog signals affecting the digital.

Can someone give me a simple explanation?


texts: How to: The basics of transformer VA calculation for voltage regulation using full wave rectification

texts:
Likely this procedure has been repeatedly discussed here. But I want to put the pieces together in this certain domain.
So let's say we need to get +/-12V at the outputs rated at 1A using classic voltage regulation circuit like this:

and we need to calculate transformer VA for it.

So we need to:

Rectification

Our max current is 1A and output voltages are +/-12V so the 1A/50V should be fine, let's say 1N4001. To calculate diodes drop I have to multiply 2 conducting diodes (thanks to gbulmer) by forward voltage drop of 1N4001 (1.2V) getting 2.4V.

Regulation

7812 and 7912 as mentioned in data sheet will drop 2V each.

So finally we should loose around 2.4+4V = 6.4V of total voltage drop.

Transformer

Now, when we have our losses we may calculate the required VA of transformer. To get 12 volts out of regulators, we have to count our 6.4V drop, right? So then:

x = V(sOut)*1.4141-6.4v = 13V

6.4+13 = 19.4

19.4/1.4141

x = 13,71897319850081 (14V)

where V(sOut) - is transformer secondary voltage and 1.4141 is peak voltage factor.

So now when the V(sOut) is known, then transformer secondary VA is 1A*14V = 14VA and primary VA (mains - 220V) =

IpVp = IsVs

Ip*220v = 1*14

Ip = 14/220 = 0,0636363636363636A

The question: whether this calculation claims to be correct?


texts:
I'm sure this belongs to the "every once in a while asked again" questions, but I've read several posts on this site and also on other sites and haven't found an answer to two of my questions, yet.

LINE-Trigger

The LINE-Trigger is supposed to trigger whenever the signal has 50 Hz as frequency.
It makes sense to me that 100 Hz, 200 Hz, and so on are triggered, since instead of one period it does 2.
However, when I put in an 75 Hz signal into the oscilloscope it still triggered and I dont' understand why. The points where the 50 Hz signal is 0 are also points where the 75 Hz signal is 0, but while the 50 Hz one is increasing (if it's a sine-signal) the 75 Hz isn't.
So does it really only matter that the signal is 0 at time 0 and then after 1/50 seconds it's zero again?

EXTERNAL-Trigger

The second question I have is about external triggering.
According to the sources I read "the external signal is used to trigger". For me, this sounds as if the oscilloscope triggers, when the input signal is exactly the same as the external trigger signal.
However, I used a function generator and used the external trigger output and also let the oscilloscope display the signal, it was a square voltage.
I then gave a sine input (which I wanted to use the external trigger to trigger for).

(For me) surprisingly, it still triggerd even tho the sine signal had a different form than the external trigger (square voltage).
The sine signal was increasing when the square voltage was positive and the sine signal was decresing when the square voltage was negative.
So not only the shape was different but also when the sine signal reached it's peak, the external trigger jumped from negative to positive, so the 0 points didn't match.
The only way I could explain this to myself is that the oscilloscope only triggers when the frequency of external trigger and input signal are the same.

Sorry for that much text, I just wanted to show you that I have already thought about this and I'm not just to lazy to read other posts.


texts: How do I connect this 3.3V system and 6V ish system together?

texts:
I have an old 'Cybot' robot I built from a kit. I'm trying to mount a Raspberry Pi on it to act as brains. I'm a computer programmer, but my electronics knowledge is very limited. Have access to basic tools like multimeter etc.

So far I've disconnected the bit I'm pretty sure is the motor driver board from the rest of the Cybot internals and I'm wondering if I can just wire it directly into the GPIO pins on the pi?

Schematics for the motor driver board I'm trying to connect are here:
http://lpilsley.co.uk/cybot/driver.htm

I'm thinking the driver board has transistors so the GPIO pin isn't connected directly. Is 3.3V enough to trigger the transistor? Do I need to connect the grounds of the systems together?


texts: When is a 6.3V capacitor not a 6.3V capacitor?

texts:
I'm building another (!) rather large WS2812B-based LED installation project and I'm now at a point where I'm suffering from what looks to be a power problem. The standard advice is to put a large capacitor (1000 µF, 6.3V or higher) across the power rails, as close as you can to the supply.

I bought a bunch of said capacitors (EEU-FC0J102) but omitted installing them when putting the whole thing together the first time because I didn't quite understand the datasheet of the Murata OKR T/10-W12 DC-DC converters I've installed to feed the strips. It has what I took to be dire warnings that "Excessive capacitance can make step load recovery sluggish or possibly introduce instability" and "Do not exceed the maximum rated output capacitance listed in the specifications" (which I take to mean those under "Maximum Capacitive Loading" earlier in the datasheet.)

SO... given all that I was going to try installing the capacitors I've got. Two questions:

Are those capacitors an appropriate voltage spec? I've had a warning that 6.3V caps for a 5V system is not enough of a derating and I might pop them. Is this a serious risk?
Are those capacitors an appropriate capacitance and "ESR" rating according to the Murata's datasheet—and if they're not, does it matter much? (This is a one-off project, I'm not going for UL listing or anything.)

With a bonus round: because of the physical constraints of my project (everything's stuffed into a narrow tube), I may need to mount these caps on short (~5cm) wire "tails". I get the impression this is a bad idea, but I may not have any choice. What are the ramifications of this?