texts: Can an ADC be damaged by applying a higher voltage than VREF but that is still within specs?

texts:
Take the following example:
A SAR ADC that is rated for 5v and 3v3 operation is operated at 3v3 (for both VDD and VREF). Someone is a bit careless and applies 5v to one of the inputs. Can this permanently damage the ADC in any way?

A slightly detailed explanation for why or why not would be appreciated.


texts:
I have an immediate need (for a stage play) to take the audio from the microphone of a telephone handset and feed it to a Shure M67 audio mixer, familiar to anyone who's been in radio for a while (mixer PDF). Note that the schematic of the unit is on the last page.

I took a gamble and just soldered two wires to the two pins on the microphone and fed it directly to one of the inputs on the mixer to see if it might be "good enough". It moves the needle, and I can hear myself in headphones, but the audio controls are turned all the way up and there's a lot of noise, of course. Note that there's also a "line input".

I'm hoping the only problem is an impedance mismatch and someone can figure out a resistive matching circuit for me since it's been too long since I've done that and I need it by Thursday (and I'm panicing). Can someone help me out, please?

EDIT: Note that the schematic of the unit is on the last page.

Here's a picture of the phone with a line connected to the microphone and running to the XLR connector: http://i.imgur.com/DULOG.jpg

And here's the back of the mixer that it connects to: http://i.imgur.com/1GuPj.jpg

EDIT2: I just realized I hooked up to the earpiece and not the microphone but I wouldn't think that would matter but maybe I'm wrong.


texts: What type of switches are used by impulse relays?

texts:
I am looking for a switch for impulse relay. These switches are bi-stable switches and return to the original state after being pressed.  Hobby push button switches do not cut it for me because I need a more elegant solution, and I could not find google for a product or the more appropriate term. Doorbell switches are an option but is not really favorable because of the doorbell sign and sometimes its design really looks like a doorbell. I am looking for something that resembles an ordinary light switch but is mono stable.

I know it exist because in this video you can see the switch is used, also Schneider use these switches in their impulse relay guide, but does not even mention a product code.

I was hoping someone would know the proper search term for these switches.


texts: Questions regarding voltage divider for micro controller sensing

texts:
I am beginner trying to develop two voltage sensors for attiny85 microcontroller. I have two separate voltage levels that I want to sense using the attiny. One of the voltage supply is 0V-5.5V and is fluctuating very often within that range, and I want to detect the voltage every second or so through attiny85 analogread function and record it inside a log. I want to use the VS1 sense line from the schematic and connect it directly to any analog pin of the attiny85. And the SIN is directly connected to the supply voltage. On the other supply, I have linear 0V-2.7V which is connected directly to the CVP pin. And the VS2 is connected directly to another analog pin of the attiny85.

The attiny85 is being powered by a separate 3.3V supply. And the reference voltage I want to use is 1.35V inside the software. So, 0V-1.35V inside the attiny analogread to detect this 0V-5.5V fluctuating range and 0V-2.7V linear range.

Now, the questions:
1. Is my voltage divider circuits feasible and a good approach for these two types of voltage measurements?
2. Is it possible to improve the voltage sense circuitry, to get better accurate readings?
3. What high quality good brand SMD components I could use for these voltage sense circuits and their eagle library parts suggestions?

Any suggestions and tips would be highly appreciated. Thank You.


texts: Extrinsic semiconductors: why can't electrons/holes in the band gap conduct?

texts:
Normally, no electron energy states exist in the band gap, the gap between the valence band and conduction band in a semiconductor.

However, if we dope the semiconductor, i.e. add donor (n type) or acceptor (p type) atoms to it, we introduce new electron energy states in the band gap!

Take for example silicon, in which we introduce phosphorus, which is a group V element and thus a donor atom. This will introduce extra filled electron states just below the conduction band.

Now, this all happens at 0K, so no current can flow (this is logical as electrons don't move at this temperature, even with an electric field applied). But if we raise the temperature e.g. until room temperature at 300K, the electrons gain energy and can jump into the free energy states in the conduction band. These electrons in the conduction band can now conduct electricity.

Now, my question is: why can't the electrons in the band gap conduct current? Why do they have to be in the conduction band in order to conduct electricity?


texts:
I have a question regarding the usage of op amp to measure battery voltage. I know there are battery gauge IC's dedicated for that, but I'm trying to do this to both understand the op amps better and the other one is that this solution should be cheaper since I don't need a super precise measurement.

So, I had this circuit and math in mind:

VIN - Battery (Li-Po 2S 6-8.4V range)

I'm using a voltage divider with R1 and R2 to get 1/10th of the input voltage and feeding that into op amp that is configured for gain of 3. So my calculation is:

VMEAS_BATT = (VIN / 10) * 3

which would give me an VMEAS_BATT range of 1,8V to 2,52V (when battery is full).

I would feed that voltage then into MCUs ADC input and read and do the math to get the battery voltage reading.

Can you please help me by checking if this is a "sane" circuit, is math correct and at the end what would be other practical considerations that I would need to consider to make this circuit work?

Thanks!


texts: I stuck a 450 V 10 µF capacitor in a 110 AC wall outlet and it exploded... why?

texts:
When I put it in the outlet it "popped" with some oily gray smoke. Honestly I thought that the voltage rating on the capacitor meant you could feed at least that much voltage through it, but clearly I'm missing something fundamental.

I am glad I tried this with a rubber gripped wrench.


texts: My apartment's mains voltage rises from 220 V at noon to 245 V at night

texts:
I'm Egyptian, and the standard mains voltage in Egypt is between 220 V to 240 V.

The mains voltage in my apartment keeps rising daily from 220 V at noon to 245 V at night.

Should I worry, and what should I do?


texts: Drive a 12v indicator lamp/LED from AC mains

texts:
I want to switch a mains input on and off using a latching switch (which is appropriately rated). The switch supports illumination via a packaged LED, driven by 12V, either AC or DC. The current draw of the packaged LED is tiny: 6mA.
What is a good (power efficient, low part-count) way to generate the 12v (either AC or DC) supply from the AC mains input? There are many solutions in the 1amp+ range, but I wonder if there is some easier solution for this application? I can find all-in-one Buck converter modules but again they're in the 1 or 2A range which seems overkill to drive 6mA. But they are cheap and simple to install.
The switch
The indicator lamp


texts: Under which circumstances would CAN communication still work if there is no bus termination?

texts: The bus termination is needed to prevent reflections. Does this mean that it may be possible to get a working communication with a low data rate, since then reflections might not interfere with the new message?


texts:
I have denatured alcohol which, according to wikipedia, is composed of roughly:

85% ethanol
10% water
3% methanol
1% aceton
1% pyridine

My solution has a blue color.
Can I use this as a replacement for isoprop. or pure ethanol to clean my PCBs?


texts: How hard would it be to hack a "personal soundtrack shirt"

texts:
I imagine this is an unusual question for this SE site but here it goes.
I just bought a "personal soundtrack shirt" from  think geek.
This shirt is really cool.  It comes with a built in speaker an amplifier (batteries not included) and a wired remote.  To take an up close look at the whole setup here is a slideshow of some snaps...
https://picasaweb.google.com/sethspearman/ThinkGeekPersonalSoundtracksShirt?authuser=0&feat=directlink
Or to open the gallery without the slideshow...
https://picasaweb.google.com/118009251505460036032/ThinkGeekPersonalSoundtracksShirt#
I want to use this to make a christmas sweater with a tree and ornaments.  I want to activate songs by clicking ornaments on the tree.  In other words I want to essentially replace the wired remote with my own wired remote (or hack the existing one by disassembling it and making the buttons so they can be placed randomly on the sweater.)
How would I go about doing this?  I have very limited knowledge of electronics but I am pretty handy and technical.
Bottom line...how do I "hack" the wired remote on this thing or make my own wired remote?  IS there a way to power the current wired remote (assuming I could use the white wire) and then push each button on the wired remote to see what signal is sent for each button push?


texts: How do oscilloscopes and multimeters recognize waveforms?

texts:
Let's suppose that I am measuring a real-time periodic signal with an oscilloscope. Then I know that the oscilloscope is able to calculate the average value of the periodic waveform, and maybe even the rms values for higher harmoincs.
Now: in order to perform such calculations, the oscilloscope must be somehow aware that the signal is indeed periodic, and moreover it must be aware of how big the period is.
My question is: how can the oscilloscope get these informations from a real-time evolving signal? Does it recognize the waveforms pattern as the time goes by, or something like that?
The same question may be raised for multimeters, which can often perform such calculations on real-time periodic signals


texts:
I have (2) 12v 60amp hour batteries connected in parallel used as backup power for my electronics.

I have (2) chargers, 12V 6amp.
Is it safe to use both chargers at the same time while the batteries are interconnected?

If i decide to expand my parallel connections to 4 or 5 batteries can I use 4 or 5 chargers on each battery while the batteries are all connected?


texts: The simplest circuit to translate from RJ11 to my PC

texts:
Assuming that you don't want to get a functionality, it doesn't need to be a DSL modem, you want to study some signals and you only need an input starting from an RJ11 and going to a PC; what is the simplest circuit X that you can build for the Y interface/bus that you can usually find on a standard PC ?

for example Y can be:

USB
RS232
RJ45
SATA ( ? )
...


texts: Do I need an external oscillator for STM32 if I'm going to do PWM, ADC, UART and DAC?

texts:
Do I need an external oscillator for STM32 if I'm going to do PWM output, ADC measurement, UART communication and DAC output?
I don't know the desired precision and accuracy. I just want it to work.
My goal is to send a UART command to my STM32 and it will answer me back with a responce that includes measurements. That's it.
So I don't know when I need to use an external oscillator. Do you?


texts: Smoothing potential 30kHz noise in battery "switcher"?

texts:
I've created a circuit that switches individual  items of avionics (for my glider) between two 12V batteries. The idea is that I can switch items between battery A or B depending on how the batteries (and my power requirements) hold up over the course of a flight.

There are five individual instruments. They nominally draw from 100 - 500 mA, but some (the radio in particular) could spike up to 5A. wiring is specified for at least 5A, and each output has a 3A fuse (aside from the radio, which has 5A).

I originally started with the following circuit (the diagram shows 2 functional blocks of the five) -- 5 groups of P-channel FETs. Instruments are switched on, and between batteries, with individual on-off-on toggle switches at the gate of each FET. Capacitors at the gate provide enough debounce to prevent power cutting out when switches are moved from position A, through off, to position B.

This circuit works fine, but I neglected to notice the bypass diodes on each FET. This means that, if one battery depletes  significantly more than the other (or if,  for example, one battery is not connected), current from one battery circuit makes it into the other. I'd like to avoid this.

The obvious solution is two diodes at each output, but as battery capacity is at a premium in a glider, I'd like to avoid the voltage drop.  I'm considering adding two of these (SM74611) to each output, as they have the lowest voltage drop I can find. However, the datasheet suggests that the voltage drop spikes periodically, with a frequency of about 30kHz / duty cycle 99%.

I'd like to avoid sending this spike off down wires to the instruments -- not that they can't handle it (they're designed to accept unregulated 12V from batteries), but to avoid the potential associated noise, which could impact sensitive radio / FLARM antennae.

Will it be enough to stick electrolytic caps across each output, or should I be looking at a full-on LC filter? Or am I barking up the wrong tree altogether?

Any and all advice much appreciated.


texts: I2C EEPROM only first attemt to read correct

texts:
I have very strange problem in my circuit. Namely, I have 24LC01 EEPROM connected to my PIC32. I made "library" for reading from and writing to the memory. What is happening is that only first reading of data gives me correct data, while every later attempt gives me wrong data.
The experiment is following. I wrote one page with 0x30 (0 Ascii character), so from address 0 - 7. Next I read 8 bytes starting from address 0. First reading is correct and I print 00000000. Next attempt to read fives me 0 and 7 unknown characters. This happens in the same manner until MC is restarted.

Here are some waveforms.

On the first wave, you can see that control word is sent, it was ACKed by the slave, then comes the memory address at which to start, in this case 0. Then comes ACK and repeated start event. Next, control word is sent again, but this time with reading flag set. After follows first charcter 0x30, and so on, till the 8th.

At the end if the first reading attempt, you can see that NACK after the last byteis sent, followed by the STOP condition on the bus.

Next, you can see start of communication of the second attempt. First control word is sent correct and was ACKed. Next came address where the data should be read from (again 0), it was also ACKed. Next master sends repeated reading command, and the second control word with reading flag set (btw address of the device is 1010xxx). The second control word was also ACKed, and the came first byte from the memory location 0, which is 0x30 and as you can see it is also ok, but at the end of that byte SDL goes high and stays there till the end of the reception.

On the next photo is shown the end of the wave. As you can see SDL was always high, and only STOp condition is sent at the end.

What might be the problem here?


texts: How to upload code to AtMega2560 using JTAG ICE 2.0

texts:
Background : I'm used to code in Arduino(Uno, Mega, Esp32, Esp8266). But this time i have to code directly on AVR Atmega 2560 Chip.

I have AVR JTAG ICE 2.0 (like this one) and download several program such as CodeVision AVR, Atmel Studio 6.0 and 7.0. I can make hex file from CodeVision but i didnt know how to upload the code. How to do that?

(I work both on windows and linux)


texts: Trying to figure out available resources on MSP430 LaunchPad

texts:
I'm just starting to mess with the MSP430 and have some simple apps working fine.  However, now I want to use it with an LCD and am trying to determine if I'm short on I/O.  For sure, I'll need to use the 4-bit interface, and I also need 3 outputs for E, RW, and RS.  On top of that, I need to talk to my computer over RS232, but not via the built-in COM port-over-USB.

I've been looking over the documentation and can't figure out which lines the onboard FET is using.  The situation I'm in is, I'd like to debug my application, but then need the FET.  If the FET uses the TX/RX lines, then I can't test my serial code.

So the questions I have are:

What's the best documentation to look at to figure out the answer to my question?  I've been Googling and reading the MSP430x2xx Family User's Guide.
Do people typically break up applications on the MSP430 into more logical groups to get around I/O shortages, and then combine at the end and hope for the best?  This is the approach I would typically use.  For example, I could use a different set of lines for TX/RX to test the software serial feature in one application, then test the LCD w/o serial support in another application.  Then at the end, I could reassign the TX/RX lines and combine the features.


texts:
I have an ordinary Weller soldering iron with a conical tip, which I fear does not transfer much heat to the area. Since I am planning to do a dead bug project I thought it would be better to get a flat on the tip of the iron, possibly by grinding it so it looks like this:

However, I am told that this will not work because the tip is not actually solid, but is plated, and if I grind it, then the plating will get ground off. Is this true?

Can I just buy an alternative tip and then install it somehow on the iron, or do I need a special kind of iron that supports interchangeable tips. The type of station I have is an older analog station which is one piece with the holder and sponge on top and a strip of LED lights that indicate the temperature.

UPDATE

My Weller is an S4240. On examining it closer, it has a knurl and screw on sleeve. When this is unscrewed the tip slides out and apparently can be replaced.


texts:
I have this MOSFET Driver IC 16 Pin Package
Specification - Maximum Drain Voltage 16V. Maximum Drain Current 7.5A
EDIT:
Schematic :

All the Enable, Sen and Sel signals will be provided by a separate MCU. MCU Datasheet
But the below tests are done by isolating the Microcontroller section and giving the signals separately from a power supply and monitoring the output behaviour at the load and the output at the multisense pin.
I am giving an external 5V Input to the MOSFET Gate (at pin 1) from this 30V 3A/6A Power Supply - Power Supply Datasheet
So, I am giving 5V to the gate from the power supply and 16V to the drain of the MOSFET (TAB = Vcc) from another similar power supply. I Connected a load of 7.5A between the output pins of the IC (pins 9 -16) to ground. (Electronic Load Used - Constant Current)
I turn ON and turn OFF the gate voltage to the MOSFET. But When I turn off the 5V input to the MOSFET, I am getting voltages like this (Observing strange switching behaviour during falling):
If Drain Voltage Vcc = 16V

However, If I reduce the drain voltage to Vcc = 9V
The I get this,

I am not able to understand why this behaviour is occuring when I give High Vcc to the IC.
Then, to check the fall time of the power supply (the channel which was connected to the enable gate of the IC)
Fall time was very high. Like in the order of 50ms.

Then, I gave the Input to the gate of the IC using AFG1062 a function generator.
I checked the fall time of the FG. It was around 1ms.

So, now I gave the gate input using the FG itself and set the drain voltage Vcc to 16V using another power supply.
Now, I am not getting the strange switching behaviour during the gate disable time.

My questions :

Why did I get that strange switching behaviour during the fall duration when I used the Power Supply instead of FG? I figured that I could solve the problem if I provide low fall times to the gate input of the IC. But what is happening if I give a fall time so high in the order of 50ms? I tried to look up the fall time or the voltage droop parameter in the power supply manual, but I could not find it. Can someone explain me why this is happening and how to understand this behaviour? What should I look for over here?

Why that strange behaviour was occuring only at Vcc = 16V and not when Vcc = 9V?

Why do the power supplies have high rise time and fall times when compared to an FG? What actually determines the value of rise and fall time in general electronics as well?

Please help me to clarify my doubts.


texts: Is there a disadvantage to not having a power switch on a logic circuit?

texts: I'm building a digital clock using 40xx series IC's. Currently you just plug it in and it's on. Are there any major drawbacks or disadvantages to not having an on/off switch?


texts: I fried these two components by plugging in the battery the wrong way. What are they? I read SMDs have an ID which helps identify them but since they are burned i cannot read the ID. If i replace them would it be possible to use a similar component?


texts: Flow of current, isn't make potential difference?

texts:
I've learn some electronic knowledge at school and so confused by some questions.

Q1. IS it possible a flow of electricity without an electric field?

Q2. I've learn that moving of particle with electric charge in electric field makes potential difference. Then, let's suppose no resistance in wire. IF Q1 is true, wire with a flow of electricity makes an electric field, and in the electric field, an electron moves. Then potential difference must exist. But when measured, there is no potential difference. ( I learn there is ESR in battery, but I wonder whether moving of electron dosen't make any potential difference or not.)

Sorry for my bad English, but I hope someone could help me to find answer.


texts:
I have a Microsoft Surface Pro tablet which, when charging from the included power adapter, gives a slight tingling feeling when touching anywhere on the Magnesium shell.

This is a commonly reported problem with the Surface Pro and Microsoft are willing to replace affected units free of charge.

Out of curiosity, I would like to measure the voltage on the case with respect to ground. The AC adapter is a 2-prong device which uses a IEC standard figure-8/shotgun connector (no ground pin) and outputs both 12V and 5V DC.

If I take a multimeter and connect one lead to ground, and the other to the case of the tablet, will I damage either the multimeter or the tablet? My understanding is that the voltmeter input is a very high impedance and as such a negligible current should flow.


texts: 4 pin headset pinout / pushbuttons interface

texts:
You all know smartphone headsets. Most of them have a microphone integrated and additional pushbuttons for increasing/decreasing the volume or to pause the current track. I am wondering how this is working. The plug has 4 pins. I assume one pin is GND, two are for left and right audio and the fourth is for the microphone. So how are the pushbuttons connected then? There are three pins missing.

Maybe the microphone pin is used as bidrectional pin? If it is so there must be a protocol which declares which button was pressed (like UART). Also I don't know where the power suppy should come from. All the headset gets is an analog audio signal from the master device.

Connector:

Pushbuttons:


texts: Reduce switching noise on autotransformer

texts:
I am trying to achieve the same thing they are talking about in this post, which is controling an autotransformer via software. I accidently even got the exact same autotransformer, but instead of a relay/SSR board from ebay/aliexpress I wanted to be fancy and built my own board, driving the relays by shift register via mosfet drivers.
This all works well until I connect a load. Switching even an incandescent light will generate enough noise to load the shift register with garbage and wreak havoc on the outputs.
I've read this post and I think snubbers might be the way to go, but I'm not quite sure where to put them and how to calculate the values for R and C.


texts: How to control LCD monitor with micro controller?

texts:
I would like to control my PC monitor.
After disassembly I found the control buttons are implemented like this (just more data line and buttons)

I would like to control it (with ESP2866)
With the first button which is alone in a DATA line 1 there is no problem I just simply pull down with one of the GPIO like this and it is working flawlessly (I don't use any resistor because expecting in the other side there is)

With Data line 2 I’m having trouble with the same approach the button with the smallest resistor is triggered from other button. I try to use resistor, transistor but it just got worse.

Please note ESP is working a bit higher voltage than 3.24v it is 3.26v
Also connected the ground wires

I wonder how should I try to interface with this?

Thank you


texts: From the above I/V characteristic we can conclude (and this is what books say) that during saturation collector current is very limited and tends to zero. How is that possible if during such condition there is siginificant current flowing from base to collector. So it can not be zero in any way.


texts: Reactive power of a discharged capacitor

texts: I was wondering if a DISCHARGED capacitor connected to a grid gives to this one a positive reactive power. Is it yes? If not, it's true to say that only charged capacitors gives positive power to the grid? And my last question is: the capacitor banks connected to the grid are charged or dischaged?


texts:
If I use n-channel MOSFET (IRF3205) for high side switch, I need a gate driver for that MOSFET to turn on.
For high switch the mosfets gate require higher voltage than it vcc.
I have to switch 50 positive supplies, so I have to give more than 50 V for the gate to turn it on.
http://www.irf.com/product-info/datasheets/data/irf3205.pdf

But in datasheet Vgs= ± 20, what that vgs exactly means.


texts:
This is probably stupid, but I have become very confused and would like someone's help.

I have brought some equipment from the usa, and these run on 110v. Where I live, I only have 220v. I brought an ac adapter, but became confused with something.

The adapter says "input 110v 50 Hz, output 220v 50w". My question is, is this a step up transformer or a step down transformer? Which is the input and which is the output on the adapter? Since my equipment runs on 110v, will plugging this adapter into a 220v outlet work, or is it the other way around?


texts: HP C8941 Photosensor operating voltage and circuit

texts:
I have at my disposal a photosensor (Optical encoder) with "C8941-80018", it has three cables: Black, Green, and Blue.
I want to know the Operating voltage for this optical encoder and a circuit to use it with Raspberry pi (Preferably) or Arduino.
Please find this related question about the same Photosensor.


texts: Why is there a big difference between the temperature parameters of these regulators with the same name?

texts:
I have two datasheets for the same TL780–05C regulator one from Texas Instruments and another from MOTOROLA. I'm looking at the data for the TO-220 packages.

I need to estimate the total junction temperature without a heat-sink, and for that I will use the following formula:

Since I calculated the power loss P and know the max ambient temperature TA; what I need now is the parameter called θJA which is the thermal resistance between the junction temperature TJ and the ambient temperature TA.

Almost all basic parameters like the max output current, max junction temperature ect. are exactly the same. The inner circuit representative schematic diagrams look a bit different.

Now for the one from MOTOROLA the temperature parameters are given as:

And here is the temperature section from Texas Instruments:

My question is: These two regulators have exactly the same names where normally I would think all their critical parameters are very close. But the θJA differs a lot; one is given as 62.5°C/W and the other is as 19°C/W. This is a ratio of more than three. Is this something expected and usual or am I interpenetrating something wrong here?

(It is only by accident I came across this otherwise I would take granted that the θJA would be the same value no matter who the manufacturer is)


texts: Powering a latching relay through a 5V step-up booster is no reliable

texts:
First some context:
I'm building a MySensors node to replace a thermostat.

The board is powered using a 3xAA battery pack, logic use an Arduino Mini 3.3V powered through a 3.3V Step-Up converter.
The relay part use a dual coil latching relay powered using a 5V Step-Up booster. Additionaly the booster is enabled on-demand using an high side switch.

Implementation details:

5V Step-Up booster
Dual latching relay G6BK-1114P-US

The issue

At first everything worked fine, then after 2 weeks the relay stopped switching the heater. I replaced the battery using NiMH ones but still no luck. With regulated 5V or brand new alkaline everything works as expected.

After some tests here is what I gathered:

regulated 5V in input: OK
brand new alkaline batteries (~4.7V): OK
NiMH batteries (~3.6V): NOK
relay starts to fail when VCC < ~4.2V
whatever the input voltage, the 5V booster act as it should (outputs 4.98V)
when leaving the high side switch activated (instead of on-demand) tests results are the same.

I'm running out of ideas to debug this problem, everything seems to be within specs, any ideas to investigate this further ?


texts:
I can not identify the exact model of this transistor.

It reacts as a bipolar NPN Si transistor with EBC pin configuration (first image left to right,) not ECB! This seems to be made by Siemens. Package is TO92.

Any idea?

It's from old store, just found plenty ot them ~500pcs. I did successful test:  middle to left p-n junction ~0.6V; middle to right p-n junction ~0.6V; also LED test -ok.
Аlso the diode glimmers at base current through the fingers.

I think these transistors were prepared for mounting and then abandoned due to the unusual configuration of the pins. You can see the cut pins of the exact length. It's kind of like a rare coin.


texts: Is there a way to prevent switching layers when laying tracks in KiCAD?

texts:
When I lay tracks in KiCAD on the back Cu layer (v5.1.0, Windows) I have the front Cu layer toggled invisible in the layer manager. I also have the selector arrow set to the back Cu layer.

I have the track tool selected and click on an empty bit of the board, if there is a track under the cursor on the front side it immediate makes the front side visible again and switches to the front layer which is incredibly annoying. Is there a way to switch this behaviour off?


texts: Nonlinear equation solvers in SPICE simulators

texts:
We have an assignment at the Parallel processing class, the target is to implement a Non-linear Equations solver on cuda based on Newton Raphson method and to interface this solver with an application that deals with nonlinear set of equations. We wanted to interface our solver with circuit simulators. We have picked up an open source simulator and every time the simulator is performing a DC operating point simulation it will invoke our cuda code. At this point we wanted to compare the performance of our solver against solvers implemented in other circuit simulators such as

LTspice
Ngspice
Qucs

And also other software solvers e.g. Matlab optimization toolbox

We have tested these solvers against a circuit [which should map to a huge set of nonlinear eqns.]

The circuit netlist is generated by a script where the number of the nodes is given. We have formulated the set of nonlinear equations governing the above circuit as the following

The unknowns x[i] in this set of equations are the voltage nodes and the current at each resistor

We have managed to write this as a matlab function to test this circuit against matlab nonlinear solver algorithms featured in the optimization toolbox.

function F = non_linear_diode(X)
% Len(x) is always even 2*d
d = length(X)/2;
F = zeros(1, d*2);
i = 1e-3;     % Current source magnitude
r = 50;       % Resistors value
c1 = 1e-15;   % Diodes I_s
c2 = 0.0258;  % Diodes N*V_th

F(1) = X(1) - X(2) - i*r;
F(d) = X(d) - X(d+1) - X(2*d)*r;
F(d+1) = i - c1*(exp(X(2)/c2) -1) - X(d+2);

for ii = 2:(d -1)
    F(ii) = X(ii) - X(ii+1) - X(ii+d)*r;
    F(ii+d) = X(ii+d) - c1*(exp(X(ii+1)/c2) -1) - X(ii + d + 1);
end
F(d*2) = X(2*d) - c1*(exp(X(d+1)/c2) -1);
end

We have also written a script to generate Spice netlist for this problem

def gen_ckt(num):
    ret = ""
    for i in range(1, num):
        ret += 'R'+str(i)+" "+str(i)+" "+str(i+1)+" 50\n"
        ret += 'D'+str(i)+" "+str(i+1)+" 0 DI1N4004\n"

Where DI1N4004 is our diode model defined in the netlist. When testing the above solvers against the problem with 70,000 nodes i.e.  140,000 equations and unknowns

Matlab runs out of memory
Qucs takes forever
All the spice based solvers somehow solved this problem in less than 2 seconds

We actually have no idea how spice solvers managed to avoid this memory problem, and even when testing this problem against fewer number of unknowns e.g. 3,000 the spice solvers always outperform matlab and qucs. Though as mentioned in [1] [2] [3] spice uses the damped Newton-Raphson approach to solve circuits with nonlinear components which is the same as all the solvers mentioned above

Matlab Fsolve : dogleg method [Newton + Trust-region + steepest decent] [4]
Qucs : damped Newton-Raphson [5]

My questions are

How spice managed to solve such a huge system of nonlinear equations quickly and without running out of memory ? is it exploiting the circuit structure making use of the repeated elements ?
Is this example fair enough ? i mean do we need to consider more practical circuits ? and if so can any one give an example for a circuit(s) where DC operating point simulation might be the bottleneck of the simulation time ?
In [6] the authors mentioned  ISCAS85 benchmark circuits should we consider these circuits in our tests ?
Is the DC operating point the simulation type we should be targeting ? i mean should we focus to interface our solver to other types of simulations e.g. the transient analysis ?

References

1 : http://www.ni.com/white-paper/5808/en/

2 : http://www.ecircuitcenter.com/SpiceTopics/Overview/Overview.htm

3 : http://www.electronicdesign.com/boards/taking-peek-under-hood-your-spice-circuit-simulation-engine

4 : https://www.mathworks.com/help/optim/ug/fsolve.html

5 : http://qucs.sourceforge.net/tech/node16.html

6 : http://www.mos-ak.org/bucharest/presetnations/Lannutti_MOS-AK_Bucharest.pdf


texts:
I want to make a 100W high power LED headlight for bike, but the problem is that LED releases a lot of heat, and I'm using a 150W boost converter to convert 12V to 30V ( minimum operating voltage of 100W LED), to reduce the heat I have to reduce the current to 1A(from battery it is 6A), and for that I'm thinking to use l7812
which is a 12V linear voltage regulator but, it will not be able to handle that much amount of current I think so. Can I ue linear voltage regulator or sothing else?
I'm experienced with printing PCBs using toner transfer and also with soldering.
I'm confused what to do please suggest me a solution
LED specs- 100W 32-35V  3000mA  Genesis's 30Mil


texts:
(Source: Designing Switching Voltage Regulators With the TL494, Page 25)

What does the output of this opamp give? Use approximated values if necessary.

The reference voltage is \$V_R = 5V\$. Denote the opamp output as \$V_e\$.

Considering that the opamp will work in the linear region, we equate the inverting and non-inverting input voltages.

$$
\dfrac{R_9}{R_8+R_9}V_o \tilde= \left[V_e -
\dfrac{R_4}{R_3+R_4}V_R \right] \dfrac{R_5}{R_5+R_7} + \dfrac{R_4}{R_3+R_4}V_R \\
\dfrac{R_9}{R_8+R_9}V_o = \dfrac{R_5}{R_5+R_7} V_e + \dfrac{R_4}{R_3+R_4} \cdot \dfrac{R_7}{R_5+R_7}V_R \\
V_e = \dfrac{R_5+R_7}{R_5} \cdot \dfrac{R_9}{R_8+R_9}V_o - \dfrac{R_4}{R_3+R_4} \cdot \dfrac{R_5+R_7}{R_5} \cdot \dfrac{R_7}{R_5+R_7}V_R \\
V_e = \dfrac{101}{2} V_o - 50 V_R \\
V_e = \dfrac{V_o}{2} + 50(V_o - V_R) \\
$$

The result I found doesn't make sense, because the opamp is always saturated to the positive rail voltage.

EDIT: There was a sign error in my original post. MathEE corrected it. Now the result is meaningful. The output is the 50 times the voltage error (excess voltage) at the otput + 2.5 bias level.


texts: How to clean up ringing / noise on rising edge of CMOS output?

texts:
I am feeding an interrupt input with the output from a CMOS Schmitt inverter.  The falling edge of the inverter is nice and clean, But the rising edge is really dirty, and can get downright ugly at times. (See pictures)

Why is the ringing so much worse on the rise than on the fall???
What might be causing this noise on rise and how can I clean it up?
(Note that the "ringing" on rise does not happen in a consistent manner, with some cycles it is far worse than others.)

The inverter is a 74AHC1G04, with 5V supply.  Processor is LPC1517 at 3.3v.  The connection between the two is < 5mm.  Both parts share a ground plane on layer 2, but have separate power planes on layer 3.

(Input to inverter is an H11AA4 AC optocoupler, with the point to obtain a zero cross signal.)

[![Relativly clean falling edge][1]][1]
Clean!

[![Dirty rising edge[![][2]][2]][2]
Dirty! (8 seconds of persistence)

Zoom in on a dirty example (1 second of persistence)

Inverter input and output, triggering on inverter rise.

Argh, I had 4 snapshots to post, but I can only post 2 with my current "reputation" on this board.


texts:
I got my peltier device three days ago and plugged it in as soon as I could with a heatsink. On the first few runs it got cold enough that there was condensation forming on it's cold side.

But now when I run it, it barely even gets cold, so much so that the side towards the +12v gets cold but the side towards the ground terminal out right gets hot to the touch.

I'm pretty sure this isn't a heatsink problem because it was working fine the first day. What could the reason be? Is my peltier malfunctioning or is something else at fault?

P.S. the humidity of the environment has been more or less the same the past few days so that isn't a reason.


texts: leds in parallel, switched with NPN transistors

texts:
I have the following circuit designed to drive 3 PWM pins off a 3v3 Arduino Pro Mini -- one pin for each of R, G, B in this set of 5 RGB LEDs.

simulate this circuit – Schematic created using CircuitLab

5 RGB LEDs of this type.

My questions are:

is this a reasonable design?
how do I determine the resistor settings for both the base transistor resistors, and the LED resistors?
is there a way to simplify/minimise on power wastage, resistor usage, etc?


texts: Why is there negative sign as well as positive sign with currents flowing into node for KCL

texts: I was studying single node-pair analysis and where i encountered this issue. I dont get why in the last line we have written -v1/100 and -v1/25 when current is flowing into the node but at the same time+o.2v1 when it is also entering the node.


texts:
How can I keep multiple libraries of a similar type grouped, say multiple terminal blocks with a different number of pins. I want to have a drop down menu that says "Terminal_Blocks" with several different sizes under that.

Something like this:

Terminal_Blocks

     T_BLK_3

       Symbol      Package

     T_BLK_6

       Symbol      Package

     T_BLK_10

       Symbol      Package

I can't use variant since they don't share the same symbol but I still want them grouped since they are all terminal blocks.


texts:
Is it possible to use star-to-delta transformation on this specific circuit below? If it is possible, can someone give me a hint on how to do it?
I tried to do delta-to-star transformation and got the answer, but unsure with doing star-to-delta transformation on this circuit shown below. Please enlighten me on this. Thanks!


texts:
I am really confused with the difference between steady state error and actuating error. My teacher gave the following notes on this topic and explained using 1 example. He said that there will be 2 types of problems

Case of non measuring and E(s) not specified in the problem
Case of measuring or when E(s) is labelled in the diagram

Other teacher explained saying that

Case of steady state error -> E(s) is specified in block diagram
Case of actuating error -> E(s) is not specified

He showed this below problem and said it is a case of Actuating error.

I am also attaching his youtube link here
https://www.youtube.com/watch?v=IsCtCgNE6S0&t=235s
Please explain this topic clearly and guide me on how to attempt problems like this.


texts: Diode emission coefficient and saturation current

texts:
I have created a Zener diode model in LTSpice, and now I am trying to simulate it with different values of the saturation current (IS), emission coefficient (N) and breakdown voltage (BV) using Spice.
These terms are not entirely clear to me, so analyzing the results of my simulations would be problematic. This is my understanding of the above in layman's terms:

Saturation current - This is the maximum reverse current caused by the combination of the minority particles in the p and n junctions, beyond which the zener diode enters breakdown voltage and this current exceeds rapidly, likely to damage the diode.

Emission coefficient - This concept is not clear to me. From what I read online, it is a value between 1 and 2. Closer to 1 means greater forward bias. But how do I apply this to my Zener diode simulations?

Breakdown voltage - The voltage which is greater than the barrier potential, beyond which the reverse current is not longer negligible and increases greatly.

I would appreciate if the accuracy of my understanding of the terms could be confirmed. Also, how do I put all this together to analyze and conclude my results of varying IS, BV and N?


texts: Finding voltage across capacitor in series and parallel

texts:
Here's my circuit:

simulate this circuit – Schematic created using CircuitLab

I want to find the voltage over the 20uF capacitor; however, what I come up with is 50V which does not seem correct based on the voltage source.

Here's how I got 50V: combine the six caps (the three parallel on each side) to get a circuit as shown:

simulate this circuit

So, $$C_{eq}={1\over{ {1\over60} + {1\over20} + {1\over30} }} + 40=10+40=50uF$$
Here is where I think I'm doing something wrong:
$$Q=CV=C_{eq}V=(0.00005)(20)=0.001C\;\;\;\;\;\;\;\;\;V_{20}={Q\over C_{20}}={0.001\over{0.00002}}=50V$$
That is how I got my 50V over the 20uF cap. Was that the correct way of doing this? Is that the right answer? If not what did I do wrong?

Thank you for any help! Hopefully, that is enough work shown.

EDIT: If the 40uF cap can be ignored (makes sense), then,

$$C_{eq}=10uF=0.00001F\;(found\;above)\;\;\;\;\;Q=C_{eq}*V=(0.00001)(20)=0.0002C$$
Then,
$$V_{20}={Q\over C_{20}}=0.0002/0.00002=10V$$

My final answer is V=10V, is that correct? Seems a lot more reasonable. This should be right since after finding the other capacitors voltages and then doing KVL, the sum of the voltages across the caps comes out to be zero.


texts:
What is the function of the two resistors arranged in parallel with the transistor? Do they also limit the current to the transistor?

The full circuit is this:


texts: Differences Between " P1SEL |= BIT5 + BIT6 " vs " P1SEL= BIT5 | BIT6 " in embedded C

texts: Is there any difference between " P1SEL |= BIT5 + BIT6  "  vs " P1SEL= BIT5 | BIT6 ". If there is , what is it?


texts: Non inverting OpAmp with NPN amplification factor > 1

texts:
I need to amplify the output range of a DAC chip from (0-3.3 V) to (0-10 V). Unfortunately, I cannot simply use an inverting OpAmp circuit, because the output needs to stay positive with respect to digital GND.

Is it possible to use an NPN transistor in the feedback circuit, in order to achieve the amplification factor of 3? I ran simulations with LTSpice, and below circuit gave me the expected results - R3 is supposed to lazily simulate the input impedance of the device to be controlled by 0 to 10 V. Frequency of the operation is below 1 kHz.

I am not an electronics engineer and am seeking for advice, for perhaps better alternatives.


texts:
I am using the MCP6N11-010 in a current sensing circuit (Battery charger). i would like the output of the INA to show the difference in inputs starting from 0v going up to VDD but cant seem to get the configuration correct. I initially just tied VREF to ground but got no incremental changes. I then decided to put VREF at VDD/2. SO the output to from the amp is at VDD/2 when the input are the same and then  at (VDD/2)+ input difference * gain. This seems to work but is not what i want. Does anyone have an idea on how to achieve getting the reference to 0v ? Should i perhaps be trying the MCP6N11-100 version of the amp ?

Here are the schematics:

The above image is of the 0v ref voltage circuit, the one below is the ref voltage tied at vdd/2.


texts: How to make 1 bit permanent memory circuit?

texts:
I would like to make a simple circuit to store or save 1 bit of data. The circuit should be able to remember the state of an LED ( on or off ) even if the supply is disconnected from the circuit. I need it to work like a hard drive, flash memory or SD memory card of cell phones.

I made a circuit as shown in the picture, The output is an LED in series with 470 ohm resistor. I use two bush buttons to charge or discharge the capacitor so the output LED is on or off.

After disconnecting the supply or turning off electricity, The circuit was able to remember the state of the LED for few minutes.

After 2 or 3 minutes, the capacitor discharged completely and the circuit lost its data.

How can I stop the capacitor from discharging ? or how can I slow the rate of discharging so that the circuit lose its data after a week or more ?

In this circuit I uses 555 as an inverter ( not gate ) but I may use any other IC's , My aim is just making a simple permanent memory.


texts: How will my power/current draw change if I switch from 120 VAC to 12VDC?

texts:
I'm designing a heater to run off of a 12V battery at a field weather station. As I have no formal electrical training, I'm having a challenge coming up with an effective power budget. Note: This is similar to other questions posed on this Stack Exchange, but I haven't found anything that's quite answered my question. I also know that I could measure these once my circuit's assembled, but I'm hoping to avoid the cost of buying the components if I can get help deducing the answer beforehand.

Heat will be supplied from a resistive element designed to keep household pipes thawed. This element is designed to run off mains power, i.e. 120 VAC, and consumes 7 W/ft under this configuration. By my calculations, this means (7 W / 120 V =) 58.3 mA/ft of current. There should be no problem switching to DC input according to the best answer on this thread, but when I switch to battery power, I don't know how power/current draw will change. I envision 2 cases:

  Case 1: Element draws same power at lower voltage, requiring 10X higher current.

  7 W / 12 V = 583 mA draw

  Case 2: Element draws same current at lower voltage, giving 1/10 power output.

  12 V * 58.3 mA = 0.7 W

I need to know how this will behave so that I can budget battery power effectively. If the heater draws the same power at a higher current cost, my batteries will need more powerful/frequent recharging. If the heater draws lower power, my batteries will survive longer, but I'm assuming that this will come at the expense of poorer heating ability.

UPDATE SEPT 27: In searching for a 12V DC heat tape, I found the following link: http://www.oemheaters.com/t-dc-powered.aspx, which definitely steps through this discussion well, and provides a formula for the new power consumption of a 120V device running on 12V. The formula is as follows:

actual P = rated P * (applied V^2) / (rated V^2)

When you plug in my numbers:

actual P = 7W * (12V^2) / (120V^2) = 0.07W or 1/100 the power, as answered below...


texts: How do I wire this motor's terminal plate, and is this motor continuous duty?

texts:
I don't know much about motors, but I have one in mind for my purpose.  You can see an image of it, and I'd like to know how to wire the terminal plate. I plan to use a belt from the motor shaft to turn a shaft on a spherical container for several days.  Can anyone tell me if this is a continuous duty motor?  I'd be grateful for anyone's help.

Specs:
Synchronous Motor 60KTYZ 110V AC 60Hz 80 RPM CW/CCW 14W Gear Motor
Rated voltage: 110V AC
Rated frequency: 50 ~ 60HZ
Product model: 60KTYZ
Product size: 60mm*60mm
Input power: 14W
Output power: 3.4W
Input current: 63mA
Outlet shaft diameter: 7mm
Shaft length: 18mm
Out shaft position: middle and out shaft
Rotation direction: positive and negative bidirectional (CW/CCW)
Application environment: Temp (-15 -40 OC) Humidity = 90%
Noise: less than or equal to 35dB
Insulation class: E class
Security authentication: CCC, CE, RoHS.
Speed: 80 RPM


texts:
I need to affix a ground strap to my PCB. A strap similar to .

Ideally I want to simply screw this to the board. Are there captive nuts available for this purpose? I can't find anything via a standard source Digi-key or Mouser. I see that PEM makes some but after inquiring I have to order a full reel. That's much more than I need or want.

Also, is there anything else I need to be concerned with in this situation?


texts: Connecting top and bottom SMD component pads using via

texts:
I am working on a 2 layer board and the PCB will be a double sided job. Some components on the top layer will have exact mirrors on the bottom right under them. My question is, for SMD components, can I just connect those pads with a via right in the center of the pads?

Does this affect electrical performance or production/assembly in any shape or form?

The reason: The bottom layer is a copper pour for ground and I have pads that belong to GND net so why not?

Please see the picture below (for demonstration porpuses I have moved the top component a little bit higher).

P.S. The components are TVS diodes (SM8J36CA). But my qustion is more general and is about wherever the pad size allows hosting a via in its center!


texts:
Is it possible to cascade several different ICs on the same data line, in order to use less CS pins, by tying the digital output of each to the digital input of the next? I am familiar with this approach on similar/equal devices, but I'm not sure if there are some additional issues I should be watching out for.

EDIT: By digital output I pin the output pin many SPI devices provide, e.g. MAX395 or 74HC595 Shift registers.


texts: Can I get 7A of current from two 3.5A rated batteries (without an increase in V)?

texts:
I have two variable batteries with the following specs:
Li-polymer
Capacity : 20000mAh / 74Wh
Input (for charging) : DC 15 - 19V (1.3A max)
Output : DC 12V / 4A
         DC 16V / 3.5A
         DC 19V / 3A

Now I have a Gigabyte mini CPU that comes with a 19V / 7A power cable.
My intention is to make this CPU portable by providing it with 19V/7A using the batteries.
Is there any way I could wire two of these batteries up to get my required 19V/7A?
If I connect two batteries in parallel, I know the capacity doubles. Would that be able to provide what I need?

I'd really appreciate some help on this, thanks!


texts:
What is the input and output impedance of a transistor? And why do we care about it?

I am reading chapter 2 of Art of Electronics, and the author writes a lot about input impedance


texts: Crosstalk between Wires in a single Twisted Pair

texts:
I was reading about the Twisted Pair Cables, and how they implement Balanced Line methodology to cancel out all the noise. All fine and good.

However, I just couldn't grasp this one simple doubt:

  When we are twisting two wires (in a pair) close up, which are carrying equal but opposite signals, aren't they going to interfere with each other? Isn't this interference going to add noise?

I couldn't find the answer to this simple doubt anywhere. Perhaps, I am missing something very fundamental.

_____________________________

Note: The original question appeared to refer to wires in multiple pairs. The OP has advised that he is asking about interference between the two wires within a single pair. The original subject line and text has been edited to reflect this.


texts:
Does  a transistor have an internal resistance, because when I run a circuit simulation in proteus I discovered that bc547 has a collector to emitter resistance of 99ohms... Does that apply to real world applications??

As you can see, there was supposed to be a 9 volt drop on collector but there was a remaining 0.04 volt meaning transistor resistance.


texts: Asymmetrical load distribution on Li-Ion cells within a battery pack

texts:
I am designing a battery pack with 18650 Li-Ion cells. Each cell is installed on a seperate PCB and the PCBs are connected over wires to form a 2s4p configuration. I am aware that this is not an ideal Li-Ion pack configuration as cells typically need to be connected to each other with the lowest resistance connection as possible. However, this is not possible for this application.

When the load is connected, the current is spread asymmetrical between the cells. The physically closest cell to the load will carry 50% of the load current and the farthest only 10%. The "good" news is, the load current is low and below 1/2 C for each cell.

I am aware that this will lead to increased balancing effort. How will such an asymmetrical load distribution affect lifetime and performance of the pack?

EDIT:
Refere to schematic below. The 5mOhm resistor represent the wires.


texts: Low Current Consuption on a Voltage Inverter

texts:
I'm working with a uC and a Bluetooth Module. I need the lowest current consumption in this project because it is intended to be a mobile device. Thus, I'm using sleep modes on the uC. Now, I've encountered a problem:

The Bluetooth module has to receive a High level (3.3V) on an input pin when the uC is in sleep mode (to let it know that communication can't be done right now). Problem is when uC is going full sleep mode (as I want) all pins go low (0V). Therefore, I think I should use a voltage inverter.

I have researched and found two possible options:

to use a common transistor as a switch inverter. (base connected to a resistor and uC pin, collector to a resistor and Bluetooth Module input pin, and emisor to ground)
to use a logic gate inverter as 74HC1G04.

I got a few questions:

Is it really that simple to use a logic gate inverter? What is the down side? why do people use transistors?
Which option would get the lowest current consumption?
I have seen some transistor switching guides. They talk about the load current needed to turn on a motor, bulb or whatever they want to have at the end of the transistor switch. But in my case, I have a input pin of a low energy bluetooth module which I believe does not need a big current load... So, any comment on how to know what current is needed for this to work?

Btw, I am a noob in Electronics Engineering and I am ready to learn!

I'm using  a Atmega328 as uC and a RN4020 as BLE (bluetooth low energy).
Thanks for your help!


texts: Design a NMOS with low drain-source resistance

texts:
I am designing a reference circuit, and currently in the step of outputting a large current(80mA) through a 180nm technology diode-connected NMOS. The problem is, as I have tested, the current curve result is best for my work if I have small drain source resistance in the NMOS. However, my NMOS is limited by its technology, thus the value of W is maximum 200u, and L is minimum 350n. I have tried this maximum value of W/L, and the result is still nowhere near optimum.

My question: is there any possible way to even lower the resistance, W and L modifications asides? I would hope to have as low as 50 or 10 ohm. Extra component is also welcomed.


texts: how to calculate power budget calculation for new project? Need basic steps to start

texts: Could you please let me know how to calculate power budgeting of new project. What are the things i need to consider while power budgeting. what are the main points keep in mind while doing safe and effective power budgeting?


texts: Detecting a break in continuity where no voltage drop occurs

texts:
I have a solar charger on a vehicle which I need to protect:

Schematic is down there... The charger connects to the main battery, and the solar panel, but the manual specifically states that you MUST connect the battery 1st, THEN the panel, or the controller can be damaged.

The issue is that there is an external safety battery cutoff that allows the battery to be disconnected for maintenance - so someone could knock the cutoff and remove the battery without having disconnected the solar panel.

Now, it's easy enough to imagine putting relay in the solar panel line, but the question is how to control it - once the panel is connected & the sun's shining, the controller is feeding charge out to the battery so both sides of the cutoff will be getting volts, and for safety the battery side of the cutoff should really be isolated & dead when the switch is open as it likely means the cables are removed & dangling.

To clarify the situations we can experience are:

On the controller side of the cutoff we may be getting battery voltage coming out of the controller, or we may not if it's dark.

On the battery side of the cutoff, we may get full battery voltage (battery connected but cutoff open), or we may have a complete open circuit (battery removed).

We need to detect the cutoff being OPEN, NOT the absence of a battery

I'm looking for suggestions that are simple, low-power, and robust (automotive systems can have serious currents & transients, cutoff is rated to handle 100A). If it helps, there is a 2nd supply available (vehicle has two batteries) so the circuit can use some 12v power from elsewhere.

Thanks in advance!

simulate this circuit – Schematic created using CircuitLab


texts: Undestanding LIS3DSH datasheet and AN339 Application Note - Intepreting accelerometer data

texts:
I am reading LIS3DSH accelerometer datasheet and I have some questions regarding following text:

  2.2  Understanding acceleration data

  The measured acceleration data are sent to OUT_X_H, OUT_X_L, OUT_Y_H,
  OUT_Y_L,  OUT_Z_H, and OUT_Z_L registers. These registers contain,
  respectively, the most  significant part and the least significant
  part of the acceleration signals acting on the X, Y,  and Z axes. IEA
  = 0 IEA = 1 Startup sequence AN3393 14/100 Doc ID 018750 Rev 2 The complete acceleration data for the X (Y, Z) channel is given by the
  concatenation  OUT_X_H & OUT_X_L (OUT_Y_H & OUT_Y_L, OUT_Z_H &
  OUT_Z_L) and it is  expressed in 2’s complement number.

Now, since accelerometer readings are 16bits in size, I know I have to merge the values with AND function, like it states in quote from datasheet?


texts: Is the "antenna aperture" the same as the "hole in the shield"?

texts:
Is the concept of the "Antenna Aperture" the same as a hole in a electromagnetic shield? The wikipedia article is quite vague, and I am a newbie in this field.

For example if we have an electric device and we put it in a steel box, that has sufficient depth. But the steel box has 1 piece of 1 cm hole in it. That should block any signal up to 29.979 GHz, since the maximum wavelength that can leak out from that hole is 1 cm.

Is this the same concept as the "Antenna Aperture", if not then what is the relationship?


texts:
As presented in the picture, there are 2 Arduinos in 2 separate rooms, hooked up to the power sockets (controlling a SSR circuit for each socket).

I need a simple approach to make A1 notify A2 (in some requested circumstances that are not relevant for the problem). A simple sign of any kind sent by A1 and recognized by A2 would be enough. I cannot run additional wires, I cannot use wireless transmission, therefore the only option left is through the mains. Any ideas on how to do it? Thanks.


texts: Implementation ideas for software defined radios

texts:
I find Software defined radios interesting, and was searching for ways to learn about it.

One way is getting your feet wet with devices like USRP products.

However, USRPs are rather expensive.

What are alternatives/less expensive suggestions for getting a software-defined-radio implementation?

I would like to use it to eventually build things like a GSM base transceiver station, etc. in a budget-friendly way.


texts: Do they place tiny switches with passive resistors or are they using fets in the ohmic region ?


texts: What is the simplest, cheapest way to amplify a 5V signal in the 2 MHz range to around 40V? I need this in order to power a piezoelectric element.


texts:
For a project I've been working on, I've re-designed a working PCB schematic so that it uses all SMD components and now features an ICSP header. The board is essentially an LED driver controlled by an ATMEGA168. It is Arduino compatible and the PTH version works fine.

I've assembled the new board, but I cannot seem to program it using my AVRISPMkII. Since this is the first time I've done anything like this, I'm struggling to figure out where to start when it comes to debugging the board. When I'm trying to communicate with the board, I get one of two error messages. These are:

avrdude: stk500_getsync(): not in sync: resp=0x00

and

avrdude: stk500_getsync(): not in sync: resp=0x66

As far as I'm aware, this fault is due to not being able to communicate with the board. I was wondering if this could be because I've damaged the ATMEGA while soldering, messed up the circuit design or something else? How can I debug this sort of thing?

[Edit - removed the link to my schematic for privacy, now the problem is solved]


texts:
As an example, lets say I'm looking to convert 24V to 12V for a circuit that draws 800mA.

I understand that a standard linear regulator is going to dissipate 9.6W so is out of the question here. So if I look on RS Components I find a DC-DC converter THD 12-2412WI and a switching regulator TSR 1-24120.

Am I right in assuming that the 12-2412WI is a DC-DC Buck converter? If so, considering the size, cost and efficiency, why would anybody ever use it as opposed to the switching regulator? Is there some advantage to using one over the other? I've tried looking online but I'm only seeing people compare linear regulators to switching regulators which I don't feel is quite what I'm looking for. Or have I made a mistake in my assumption of how these parts work?

Edit: If I've made the correct assumption and the THD 12-2412WI is a buck converter then will it's circuit not be the same as the TSR 1-24120? If so, why such a difference in parameters/size/cost?


texts: Can you have "directional" wireless power transmission (to power an LED)

texts:
I've tried to research this, but the only circuit examples I can find use an "oscillating field".
I have a project where I would like to put two differently colored LEDs in an object, and depending on where on the "base" (or controlled by an MCU) one or the other color will light up.
My idea was to use "wireless power transmission" (because I don't want to put a battery in the object) and then control the direction of the field to dictate which LED lights up (similar to a "biderectional LED").
But I can only find circuits that use AC (to be more efficient‽), either with a capacitor & transistor or just a transistor and "self oscillation".
The Rx-coil probably can't have a bigger diameter than 2 (3cm MAX), the Tx-coil could be at least Ø5cm (potentially a bit bigger).
ETA: The distance between the coils could be minimum/best case ~5mm (with PLA plastic between them)
ETA2: This for an "interactive display piece": One location in the object lights up yellow, everywhere else it lights up blue.
It will be on for 8+ hours every day (which makes me hesitant to use batteries in the object).
Any suggestions?
Or will it just not be possible to do it on such low power?


texts: What could be the reasons for a stepper motor stuttering with an A4988 driver?

texts:
I am using an A4988 Stepper Motor Driver, which is controlled with an STM32F767ZI on a Nucleo 144 board. The stepper motor takes 12 V with a maximum of 350 mA.
When powered, the motor simply flickers and stutters, but moves at a negligible speed.
Here is a circuit diagram of the setup, with voltage readings taking from a multimeter:

The potentiometer has been set correctly.
The same results occur even with two other A4988 drivers.
For reference, here is the code (though I don't believe this is a software issue):
main.c
#include "./headers/stm32f767xx.h"
#include <stdint.h>

int main(void)
{
    initMotor(0); // initialise the motor
    initLed(7); // initialise the led
    unsigned long a = 0;
    while (1)
    {
        if (a == 50000)
        {
            toggleLed(7); // this LED flashes a little quicker than twice per second
            stepMotor(0); // output a pulse to the driver to step the motor, attached to PA2
            a = 0;
        }
        a++;
    }
}

./drivers/led.c
#include "../headers/stm32f767xx.h"

void initLed(int pin)
{
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOBEN; // enable the GPIOB clock
    GPIOB->MODER |= (0x1 << (pin * 2)); // set to output
    GPIOB->OTYPER = 0x00; // push-pull mode
    GPIOB->ODR = 0x00; // set output register to 0 across all pins
}

void toggleLed(int pin)
{
    GPIOB->ODR ^= (0x1 << pin); // toggle the pin
}

./drivers/motor.c
#include "../headers/stm32f767xx.h"

void initMotor(int step_pin)
{
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOAEN; // enable the GPIOA clock
    GPIOA->MODER |= (0x1 << (step_pin * 2)); // set to output
    GPIOA->OTYPER = 0x00; // push-pull mode
    GPIOA->PUPDR |= (0x2 << (step_pin * 2)); // pull down the pin specified
    GPIOA->ODR = 0x00; // set output register to 0 across all pins
}

void stepMotor(int step_pin)
{
    GPIOA->ODR |= (1 << step_pin); // output to the pin specified
    GPIOA->ODR &= ~(1 << step_pin); // reset the output back to 0
}

With this code, I was expecting the motor to take steady and even steps, rather than the backwards-and-forwards stuttering it does.
I would appreciate any suggestions for the direction I should take from here, or any suggestions as to what the issue could be.

After some discussion, I updated my code a little to slow it down, here it is:
(only included the updated files)
main.c
#include "./headers/stm32f767xx.h"
#include <stdint.h>

int main(void)
{
    initMotor(0);
    initLed(0);
    uint32_t a = 0;
    while (1)
    {
        if (a >= 150000)
        {
            toggleLed(0);
            stepMotor(0);
            a = 0;
        }
        a++;
    }
}

./drivers/motor.c
#include "../headers/stm32f767xx.h"

void initMotor(int step_pin)
{
    RCC->AHB1ENR |= RCC_AHB1ENR_GPIOGEN;
    GPIOG->MODER &= ~(0b11 << (step_pin * 2));
    GPIOG->MODER |= (0b01 << (step_pin * 2));
    GPIOG->OTYPER &= ~(0b1 << step_pin);
    GPIOG->PUPDR |= (0b10 << (step_pin * 2));
    GPIOG->ODR &= ~(0b1 << step_pin);
}

void stepMotor(int step_pin)
{
    GPIOG->ODR ^= (0b1 << step_pin);
}


texts: predicting the charcteristics of Filters

texts:
I would like to know one thing that say if you know Processor word length(TMS320VC5510 DSP)
it accumulator and guard bits can you make a guess about filter characteristics to be used for this architecture. just to be more precise lets put following values as an example.

The processor word
length is 16 bits and it has a 40 bit accumulator with 8 guard bits
So what kind of filters (Filter Characteristics ) you can use for the above mentioned architecture and how you predicted i mean by analyzing what?. what i can do so far is that may be a loww pass filter with range around [-3,3) can be used.

Regards


texts:
I'm trying to replace two Data Safe NPX-35, 12V, 8.5Ah SLA batteries. When I called support to figure out what to order (before pulling the actual batteries out) they said that any 12V 9Ah SLA would work...

So, should I go with the 12V 9Ah or just get the exact 12V 8.5Ah SLA?

Thanks for your help!


texts:
I have the board and I have done some interfaces with it so far. Now I'm trying timers and interrupts, and I don't have an oscilloscope to examine square waves.
Is there any simulation software for it?
or shall I use any cheap chip I have to develop some input capture software to work as an oscilloscope and interface it with TM4C123 ?


texts: Connecting servo to Arduino over long distance - Servo not working anymore

texts:
Recently I bought a couple of Makeblock's large servo's. I am     not really familiar with Makeblock's products, I am a big fan of Arduino's and Raspberry's. But I have      not used these  servo's before.
For a project I'm currently working on I connected the servo's as described in the scheme below.

But here's the weird thing: everything worked for about an hour, both testing on 20cm as on the desired 12meter distance, just switching between 70 and 100 degrees. Unfortunately, one of the servo's started 'hitching': it was just moving up and down a couple of degrees, very fast. Even helping manually did not resolved the issue. After switching off the power and the arduino and restarting everything, the servo completely stopped working. It just doesn't do anything.
 Later the exact same thing happened to the second servo....

I'm guessing I'm making a very n00b mistake here but I am   completely lost (is it even possible to control the servo using a normal Arduino, instead of the maker board)?
So before blowing up yet another servo I figured to ask the experts for some advice, being you :smile:

Any thoughts and suggestions would be more  welcome!

Edit: just had the chance to measure the output. Both the Arduino output as the other side of the 10m cable show the following:


texts: detecting if an object is present using a sensor of some sort

texts:
Yesterday I when I came home I found my soldering iron was still switched on from few hours before. I have one of those big aluminium holders you get with expensive soldering stations. I was wondering if it's possible to mount a sensor where the red blob is in the picture.

Pseudo code

if object is there then
    //start timer
else
   //stop and reset timer
end if

if 1 minute has pass
 //switch off
endif

Is that easy to do? I would need help selecting a solid state relay too and never wired one up.  Preferably isolates line and neutral conductors like a British socket does.


texts: ADC speed for precision medical instrument

texts:
I am studying a bio-medical instrument where glucose in blood is measured using light reflection principle as shown:

Below equation is used to determine glucose level:

LED is blinked at fast rate and both LED's ADC reading is taken using single photo diode which is used as sensor. Since single sensor is used, I have to switch LED and corresponding ADC is stored in single channel ADC.

SPI based ADC is preferred in this case since it will be fast compared to I2C. But due to unavailability of SPI port pins, if I implement it with I2C, does it makes a difference considering switching of LED's takes place at high rate?

Thank you.


texts: I have calculated the inverse transfer function of a low pass filter, and was wanting to design a circuit so that the original filters effect will be cancelled by its inverse. What would be the most effecient way to achieve this?


texts: Line and load regulation testing of flyback converter

texts:
I have designed a flyback converter with dual outputs. I have the following queries for performing line & load regulation tests for the same.

1)To perform line regulation on 25 V rail, should I keep the 5.7V open (no load) or load the 5.7V rail(percentage of load??)

2)Similarly to perform line regulation on 5.7 V rail, should I keep the 25 V open (no load) or load the 25V rail(percentage of load??).

3) For load regulation test on 25V rail with a min and max load. should I load the 5.7V(percentage of load??) or keep it open(no load)

4)For load regulation test on 5.7V rail with a min and max load. should I load the 25V(percentage of load??) or keep it open(no load)

Anyone Kindly advise on how to perform line & load regulation test for dual output flyback converter


texts:
I've been doing some research about how to fully charge a lead-acid and AGM battery. However I have some questions and need some guidelines for proper implementation.

Basically I am trying to find out if:

There is an optimal voltage or current to use during pulse charging. I know the voltage can be higher but does the .1C charging current rule apply for example?
If I were to setup a solar PV system, would you recommend modifying the circuit in such a way that pulse charging technique is applied to the battery array for charging?

Would really appreciate some sort of open source reference for this especially from someone who's tried it as it seems a good amount of documentation around this is proprietary or patented.


texts: How are current and voltage out of phase in capacitive circuit?

texts: We say that in capacitive circuit the voltage and current are out of phase. Current is 90 (degrees) ahead of voltage. What is the physical explanation for this effect? How can current flow through a capacitive circuit, when voltage is zero i.e when voltage has a phase angle of 0 and current has a phase angle of 90?


texts: Why does my GPIO only show 2V when connected to the Gate Termina lof NTE2390?

texts:
I've got a circuit set up with a motor that matches this diagram.

When a 3 V power supply is connected to the Gate terminal, the motor spins.
However, when I replace the 3V supply at the Gate terminal with a GPIO pin that I've measured to be 3.3 V when I turn it on, the motor doesn't spin when I turn on the GPIO pin.

Further measurements showed that when the GPIO is hooked up the Gate terminal of the MOSFET, it only achieves 2 V when turned on.

Why is this happening and how can I fix it?


texts: How to picture sinusioidal wave in transmission line(electrical circuit in general) ?

texts: I have a friend who keeps asking how does a sine wave flow in transmission line. I've tried explaning him that it is the folw of charges in either directions but he isn't convinced yet . Can somebody give me a better explaination so that I can point him here to get the answer.


texts: I read a datasheet and I found variable defined as unsigned char near Sample_X. What is this, and how does this differ from unsigned char Sample_X?


texts: How can a shift register be used to debounce a switch?

texts:
This is the problem:

This is the proposed solution:

What I don't understand:

The button bounces in the setup/hold time of the input of the circuit, making the FF go into a metastable state whereby it may settle to High or it may settle to Low. How then can the next FF in the shift register sequence get the initial input correctly?

In other words, if the button bounced at a critical time which resulted in the first FF going low, how then can the next FF interpret the original signal (button press) correctly?


texts: Heat problems when using 5 buck/switching converters in a double isolated enclosure?

texts:
I want to use 5 step down converters (220 VAC -> 5V DC) inside an enclosure inside an enclosure (double isolation).

The step down converters are similar to these. There will be 5 of them, where one is connected to an RS485 transceiver (MAX1485CPA), and the other 4 have each an optocoupler (6N137) and RS485 transceiver (MAX1485CPA).

The inner enclosure is completely closed, plastic, and just big enough to contain them with about 1 cm / 0.4" space between each converter.

In the outer enclosure (also plastic) will only be XLR (DMX) connectors and max. 10 small LED lights.

Also I will use a fuse (1A?) for safety.

Questions:

Will heat be an issue? If so, should I make 'holes' in both enclosures for air flow?
As you can see I cannot screw the devices in an enclosure (no holes), so I want to glue them  (upside down with the yellow flat area glued for a maximum and a flat glue area). Besides that, I'm intending to use wooden popsicle sticks to 'physically' make sure they never can touch each other (by glueing them somehow between the converters. Is there a problem or better solution (without having to buy new converters)?

Update

After a discussion it is best to use a switching supply with enclosure already around it (being an amateur):

5V 3W mini power supply module Hi-Link HLK-PM01


texts: How to detect very hard impacts with piezo?

texts:
Normally I'm a software guy, but I've recently decided to try my hand at some electronics projects. What I want to do is make my own impact sensor for target shooting. What I'm picturing is a piece of AR-500 steel for the target, and a sensor that can detect when the round hits the target. I've started by using an Arduino Uno, a piezo and 1MOhm resistor, like in the arduino tutorial.

My main problem is lessening the sensitivity of the piezo, so that I don't get false positives. For example, if the round hits in front of the plate and splashes dirt on it, I don't want it to pick that up. Or if the round passes by, I don't want the sonic boom to trigger it either. Currently I have it set that so that a light tap on the piezo sensor housing won't set it off, but a harder tap will (with a threshold of 100 from my arduino adc).

My question is, will the piezo output max voltage with a hard tap from my finger, or will it send out a really high voltage if I were to hit the steel hard with a hammer (to simulate a rifle round). If the voltage will keep increasing as the impacts increase (is there a limit?), then I guess it's as simple as reducing the voltage coming out of the piezo. If the voltage hits it's maximum output prematurely, is my only option to isolate the vibration with rubber mounts, or padding or something so that it takes a good wallop to set it off?


texts:
Can you guys provide some feedback on my layout for this TP562200 buck regulator? I'm using it to take a ~12V and drive a servo. The supplied resistor values should provide about 5.1V, which is within the range of what the servos want. This will be used on a board that's got some sensitive components (GPS, sensors, etc.), and controlled by an ATMega2560. I'm only turning the regulator on when I need to drive the servos (which is typically a few times per minute).

I've tried to follow their reference design and reference layout (pages 13 and 21 respectively). I'm including them here for convenience:

One thing that confused me is that their reference design includes two input caps and two output caps, while their reference layout has 1 of each. I opted for the former.

My schematic:

My layout. The plane on the top left is V_OUT, top right is V_BATT, and top center is ground. The bottom layer is ground as well. The trace coming in from the left is the EN signal.

One thing that worries me a little is that they're recommending a 4-layer design, and that's not an option for me (hobbyist level resources, both for layout and manufacture). How does that impact the layout consideration for the trace connecting the boost cap and the SW node?


texts: How is this circuit for level converting (5V3.3V) working?

texts:
Does anybody know, how is this circuit exactly working? It is level converter between 5V and 3.3V logic and it is bi-directional.

I have some theory, but I am not sure with it (I never worked with MOSFET before). And what is that diode for?

I take this image from SparkFun's datasheet (level converter).


texts: What is the relationship between EM radiation and Current Usage?

texts:
I would like to find out what is the relationship between the EM radiation an electronic device emits, and the amount of current it uses.

So basically the relationship between: Hertz & Decibel vs. Ampere & Volt

We know from the law of conservation of energy, that the amount of energy that goes into the system is the same that it goes out of the system. Now discounting the amount of energy that is transformed into heat via some resistance, I would like to know how much Watts of current does an A hertz wave with a B Decibel strength does it need?


texts:
What will happen if rotor diameter is increased in an induction motor?

How the torque changes ?

How the performance will change?

How the pf will change ?

What will be the disadvantages?

This was asked in an interview for a scientist position in BARC India. Please help me with this.

I only know that output rating of machine is proportional to (D^2)LN

where
D-Diameter
L-Axial Length
N-Speed

So, I can say that output rating will increase. But I am not able to comment on other factors.


texts: Capacitance of 2 angled conducting plates

texts:
I have to determine the capacitance of 2 conducting plate (fringe fields are ignored) with a certain area (5m^2 here) with a gap separating them (4mm here). The second plate is inclined at an angle of 45 degrees. The dielectric between the plates has Epsilon_r = 1.5
Now I have found a solution online by applying the boundary problem, and the result is 444pF. However, in my major we don't cover differential equations so we have to solve this problem using the "Gauss' method" by assuming one plate has a charge Q while the other has a charge -Q then getting the electric field and the voltage. From there we can get the capacitance by C = Q/V
Now, if we ignore the fringe field the electric field would only by in the direction of the angle Phi (assuming cylindrical coordinates are used).

However that doesn't achieve the final results after getting the voltage. What's wrong here? What's the correct procedure to solve this problem?
Here is how the book list the way to solve these problems:


texts: Confusion: Power Bank and Mobile Charging

texts:
MI Power Bank 10400 mAh rated power bank. It has 93% conversion rate. It uses the USB standard to charge phones, so I am assuming a 5V output voltage. So the total energy 'content' = \$10.4A \times 5V = 52\$ Wh. Energy that can be converted = \$52 \times 0.93 = 48.\$
Now an Iphone 5S battery is rated to be \$5.92\$ Wh.

So, the total number of full Iphone 5S 'full charges' should be \$48 \div 5.92 = 8.1\$. We should thus be able to charge an Iphone 5S \$8.1\$ times.

But, as you can see on the MI Power Bank page, it says, it can completely charge the Iphone only \$4.5\$ times.

What am I missing?

[Mi 10400 mAh Power Bank]
[IPhone 5S specs]


texts: Read value from analog input of an AVR microcontroller?

texts:
I have added a photoresistor to ATMEGA328P-PU. I'm trying to read the value from the analog input, but I don't understand how to assign the value from analog input to integer value (photoResistorValue in while loop), so I can work with it later.

#define F_CPU     800000UL
#define BAUD      14400
#define BRC       ((F_CPU/8/BAUD) - 1)

#include <stdlib.h>

#include <avr/io.h>
#include <avr/interrupt.h>

#include <util/delay.h>
#include <util/setbaud.h>
#include <avr/io.h>
#include <avr/interrupt.h>

double dutyCycle = 0;

int main(void)
{
    DDRD = (1 << PORTD6);

    TCCR0A = (1 << COM0A1) | (1 << WGM00) | (1 << WGM01);
    TIMSK0 = (1 << TOIE0);

    setupADC();

    sei();

    TCCR0B = (1 << CS00) | (1 << CS02);

    while(1)
    {
        // int photoResistorValue = ..;
    }
}

void setupADC()
{
    ADMUX = (1 << REFS0) | (1 << MUX0) | (1 << MUX2);
    ADCSRA = (1 << ADEN) | (1 << ADIE) | (1 << ADPS0) | (1 << ADPS1) | (1 << ADPS2);
    DIDR0 = (1 << ADC5D);

    startConversion();
}

void startConversion()
{
    ADCSRA |= (1 << ADSC);
}

ISR(TIMER0_OVF_vect)
{
    OCR0A = dutyCycle;
}

ISR(ADC_vect)
{
    dutyCycle = ADC;
    startConversion();
}


texts:
I built a small fermentation chamber (cooling box) based on the peltier modules. I know this is not very optimal way as peltiers are not very efficient, but I had my reasons for choosing this way.
Basicaly I was satisfied - it worked decently. I used 2 pieces of TEC-12706 of which each has:

Qmax ~57W,
Imax 6.4A
and Vmax 16.4V.

I used an old ATX PSU  which can deliver 18A max and supplied peltiers with 12V. I regulated the temperature of the box with simple arduino based regulation (just ON/OFF via 2 relays). All worked, but I would need a bit of more cooling power. So I ordered 2 pieces of TEC-12715 of which each has:

Qmax 136W,
Imax 15A,
Vmax 15.4V.

What I am trying to achieve now is having better regulation and not just on/off one as I read this is not very good for the peltier modules.
I read quite a nice "answer".
It explains nicely how to create PWM based regulation for the peltier module, but it counts with the max current of ~6 amps. Is it possible to achieve similar pwm regulation circuit but for my setup which would either regulate 2 peltiers separately (2 circuits, each with max ~15A) or both peltiers (1 circuit with max ~30A)? I am wondering if I could modify the parts parameters of the circuit described in the link above to match my max current or if any other modification (adding MOSFETs, coils, diodes) will do the job. Or should I consider completely different solution?
Any suggestions are welcome.


texts: ESP8266 3.3V and ADAFRUIT TRINKET 5V I2C communication

texts:
I try to learn I2C with this diagram as an exercise.
I want to read my ESP8266 IO events from my 5V adafruit trinket.

I2C MASTER ESP8266ex

Operating Voltage 2.5 V ~ 3.6 V
Operating Current Average value: 80 mA

I2C SLAVE TRINKET 5V

On-board 3.3V or 5.0V power regulator with 150mA output capability and ultra-low dropout.
Up to 16V input, reverse-polarity protection, thermal and current-limit protection.

I read on i2c-bus.org voltage-level

  Since I2C is an open drain concept the VCC level as such is not
  critical for the operation as long as  all components on the bus can
  accept the voltage on the IO pins and are able to detect the logic
  levels.

It's seems to be not the case here, the ESP8266 only accept 3.6V max and trinket use 5V, then I search a solution :
bi-directional-logic-level-converter-hookup-guide
With my Raspberry as 3.3V power source for LV and the Trinket 5V OUT pin as 5V powersource for HV.

This tutorial use the N-channel BSS138 but i have not this MOSTFET only the N-channel 5ln01sp

This my schematic for the moment :

Can I use the 5ln01sp MOSFET instance of the BSS138 ? (I suppose that yes after having consulted the data sheet of each one but I am not sure because of my low level of knowledge.)

As a beginner, could my scheme work without drawbacks, did I forget something ?

Thank you for your help and your time.


texts: Can a trace connect to a pad on the top layer?

texts:
I'm making my first two layer PCB and have am unsure of whether it's ok to connect a trace to a pad on the top layer (if the pad is on the bottom layer, that is). Here's a picture to show what I'm talking about:

Is the method shown on the right allowed?


texts: How can I program GALs on a shoestring budget?

texts:
GALs may be obsolete technology, but they're still readily available, and are dirt cheap.  For a hobbyist like myself, they're ideal for small projects that need something a little faster than a low cost microcontroller.  But the catch is, programmers are expensive.  The cheapest I can find is an unbranded device supplied by a chinese vendor and which costs over £30.
Unfortunately, the datasheets don't help.  Lattice's datasheet for the GAL16V8 I plan to use just says there are commercial approved programmers available, and doesn't give any indication how those programmers actually work.
There are hobbyist designs available.  There are a lot of recommendations out there for GALblast ... but GALblast has a few issues, not least of which is that it's designed to run from a PC with a parallel port (none of my current PCs have one any more), there doesn't seem to be a schematic available (just a PCB layout and assembly instructions), and the software designed to control it is a 16-bit Windows program (which won't run on my 64-bit system).
What other alternatives do I have?  I'm happy to put together a system with a microcontroller and appropriate voltage converters (I presume that like 80s era EPROMs a GAL is programmed using a 12V supply?  Even that isn't clear from the datasheets...), but I can't find any useful information how to actually perform the programming.
Edit
Doing a bit more searching, I found this project, which still depends on a parallel port and 16-bit software, but is at least better documented than GALblast, and more recent too, so it seems more likely that the designer will respond to questions about it.  The name of that designer seems familiar too...


texts: How is precise control over motor as in Segway achieved?

texts:
When I read about Segway I always wonder how such precise control over the wheel motors can be achieved.

I mean if the rider wants to go one foot forward, then one foot back, he leans forward, the motors start rotating the wheels, then he leans back and the motors change direction instantly and then when he's back he stands straight and the motors stop.

Again, to achieve balancing motors will rotate in perfectly controlled manner at whatever speed is needed to balance the Segway.

From my experience with electric motors found on various stuff like power tools and sewing machines those are pretty hard to control precisely. For example, when a variable speed drill is started it just accelerates at whatever rate and actual rotation rate will largely depend on the load - whether I drill wood with a 2 millimeters bit  or hard steel with a 10 millimeters bit.

How do systems like Segway achieve such precise control over electric motors?


texts: How to light on/off LEDs controlled by a LED driver?

texts:
I want to use a step-down LED driver and configure it to deliver a constant current to some LEDs. This one looks nice:

https://www.diodes.com/assets/Datasheets/AL8843Q.pdf

I can control the brightness with a PWM signal into the CTRL pin. But how do I control the on/off of the LEDs?

Should I send a PWM signal with a 0 % duty cycle (is it possible?), or switch off the LED driver with an external transistor?

In the datasheet they seem to make the distinction between PWM frequency and switching frequency. Moreover they are talking about a soft-start which is 0.1 ms. Does it apply only when the LED driver is supplied with current, or each time the PWM signal reaches 0?


texts: Commercial analog to digital converters using sub nyquist sampling rate

texts: Are there any commercial analog-to-digital converters (ADC) that use a sub-nyquist sampling rate, i.e., exploit the theory of compressed sensing in order to sample using a data rate that is smaller than the nyquist rate.


texts: Can you calculate internal resistance of battery by shorting it?

texts: Can I measure the current of a battery by shorting the circuit and by ohms-law divide the voltage of the battery by the current measured to get internal resistance?


texts: Contact deterioration, arc forming on high power DC switcher

texts:
I have a problem on a switch contactor on high power load control.  It is expected because the load is up to 200 amperes at 48V DC, resistive load.
How do I protect the contacts from a full load turn off and prevent the arcing on the contacts?
The resistive load is low ohmic resistors that draw 20 amperes each from a high capacitty battery. Yeah, they are big.
The contactor is rated 200 amperes continuous load, the coil is 24V.  Kink.
It is a Brazilian part, used for motor start, but can be used continuously.
If it is not possible to upgrade the design what other components are ideal for DC high load switching?
There is "nothing" on the circuit except the resistor, the contactor switch and the battery, switch on low side.


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I'm working on PWM power supply to supply a load which needs a constant current of 1 mA and 2.5V of operating voltage. The Pulse width Ton is 1 to 10 µs Maximum and Toff is 10 ms which results in a duty cycle of 0.1% Duty Cycle. The main purpose is to reduce the average current consumption of the whole device since it's needed only to operate during that short pulse. Now this comes to several issues. One is delivering a constant current using something other than a current limiting resistor whilst having a fixed supply voltage of 2.5 V. All that has to be provided during that Pulse. The rest of The time the power supply shouldn't consume more than 1 µA. A buck step-down converter is a good way to start for providing the right voltage and efficiency at a certain load, a device like TPS61098. One question about PWM switching buck converters. During the Toff time the current is supplied from inductor which means it needs to drain more current from the battery to maintain that constant and average load current. Am I correct here ? So in other words, the average output and the input current will be the same ideally. There are plenty of DC-DC converters, do you have any suggestion of one which can provide the behaviour I described? The circuit might be similar to LED driver where you can dim the LEDs using PWM input.

To conclude, there are two possible options here. One can control the buck converter using external PWM input and is able to operate with the timing i mentioned (1µs min enable time). The second option would be to supply my PWM timing generator from the buck converter and drive the load from the PWM generator. In both cases, the buck converter should be able to limit the current and voltage and consuming below 1µA averagely.

Your support is much appreciated.

Edit:
The PWM pulses are generated from A MCU. I need a fixed voltage with a current limit. The device is considered linear. The voltage is 3V and is from a battery.


texts: How to print data from register(8051) to terminal(serial monitor)

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I have written a program that uses printf statement to write to the TERMINAL program using serial communication. Now, for my actual code, I want to transfer the content of my register and display it on the terminal window. How do I do that?

The test code is:

#include <REG51F.H>
#include <stdio.h>

void main(void){

 SCON = 0x50;   /* SCON: mode 1, 8-bit UART, enable rcvr */
 TMOD |= 0x20; /* TMOD: timer 1, mode 2, 8-bit reload */
 TH1 = 253; /* TH1: reload value for 1200 baud @ 16MHz */
 TR1 = 1; /* TR1: timer 1 run */
 TI = 1; /* TI: set TI to send first char of UART */

  while(1){

      printf("Test\n");
    }
   }


texts: MCP73831: VBat Voltage drop with new uncharged batteries

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I made a circuit for charging a 40mah lipo battery (381018),  my problem appears when a new uncharged battery is connected. The battery measures 0V at the begining, when it's conected the VBAT pin only goes to 1.58V, so the battery is not getting charged at all.

The problem doesn't appear if the battery have some voltage on it, in that case the battery charges normally.

I have a 25k (0402) resistor connected to Rprog, if I change that resistor to 10K the problem dissapears but I'm charging a 40mah battery with 100mA, it's not safe.

1) Could the problem be the size of the resistor (0402)?

2) Should I put an special array for the 0V uncharged batteries?


texts:
I have multiple mcu's that are configured to communicate with bus topology. I have 10 pins (4 of them is occupied by now)

I need to debug (update firmware online, etc) all of these mcu's. I read this article but I didn't understand how to achieve the goal.

Question: How can I daisy chain these mcu's?

MCU: STM32F407VG

Debug protocol: SWD


texts: RTD 100 hooked up to Lee Dickens BD-300 Isolating Signal Converter, Issues Reading the Output

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I have a three wire RTD 100 probe and a BD-300 Isolating Signal Converter. I wired up the BD-300 like the datasheet said to, and the unit powers powers on and indicates that it has power (red LED is on). However I do not get a stable voltage from the output pins. I have my multimeter hooked up black to output pin 7 and red to output pin 8. The voltage that I get cycles from 0mv to about 400mv and
then repeats.

If I read the center lead of the RTD (while hooked up and powered on) and an outside lead, I get about 110ohms which looking against this table tells me I'm in the ball park for the right temperature. So it seems like my probe is good to go.

The converter did come with a funny looking yellow resistor looking item with markings that I can't make out, bridging to the 4 and 6 input pins.

Any help with this or pointing me in the direction to do more reading would be greatly appreciated, my google searches have turned up nothing other than advertisements (I probably don't know the correct search terminology).

If it matters my end goal is to be able to read the temp value, accurate to 0.1 degree, and use it with a PID loop to control mash temperatures for homebrewing. So if there is an easier way to interface this probe, I'm all ears!


texts: How to verify whether an electrical appliance is properly grounded?

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I read that an electrical appliance/equipment that is not properly grounded can kill people, especially if it uses mains socket where the current drawn can be high. In fact, even a simple microphone can kill. https://en.wikipedia.org/wiki/Leslie_Harvey
How to verify whether an electrical appliance is properly grounded to protect my family?


texts: Power Electronics - Voltage Sensor Layout

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I have the following voltage sensor to place in a layout of a low voltage converter (800 V dc link).
The input voltage dividers need to be located in the power-stage section of the PCB. The question is as follows: should the differential + LPF opamps be located close to the control stage or should they be close to the voltage dividers?
Pros of being close to the voltage divider: the second output has a low-impedance path to the controller.
Pros of being close to the controller: possible noise pickup on the Vin_MCU trace is quite low.
This will be a hard-switched converter.


texts: Input and Output impedances of Current and Voltage Amplifiers

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I read that Voltage Amplifier have high input impedance and low output impedance, and Current Amplifier have low input impedance and high output impedance. If this is true what is reason for this as I could not find one. FETs have high input impedance and can act as voltage amplifiers, I think this confirms that voltage amplifiers have high input impedance.

On the other [hand] when we come to Common Collector and Common Base Amplifiers, the former one high input impedance but have voltage gain of less than 1. Is that not violate the basic property voltage amplifiers?

Since it have high input impedance, should it not have high voltage gain?

Similarly the later one have low input impedance but have significant voltage gain and no current gain, again opposite to the property of current amplifier?