texts: Would a compact welder use MOSFETs or IGBTs

texts:
Want to know why some welders for a given output are much bigger than others. Already found one of the big reasons is needing to run on 120V instead of 220V

How much space does a 220V AC input power supply save compared to a 120V one?

But one thing I could be overlooking is the switching frequency - the faster, the smaller the transformer & capacitors have to be. I know IGBTs have higher switching losses. I did an initial calculation of losses for 400V input (approximate voltage after rectifying 220VAC) @ 15amps (avg) & 100% duty cycle (unrealistic but for sake of maximizing conduction loss). I'm assuming a welding power supply uses the same design as a computer power supply like described here and here.

IGBT (STGP15H60DF):

conduction loss = 15A * 1.6V = 24W

switching loss = 30KHz * (0.14 + 0.21 mJ) = 10.5W

MOSFET (STW70N60DM2):

conduction loss = 42mOhm * 15A^2 = 9.5W

switching loss = Vds * Idrain * freq * (Qgate_drain + Qgate_source) / Igate  (don't know what Igate is, but probably much lower than IGBT)

I can't say for sure, but it seems the MOSFET even switching @ 100KHz will be more efficient than the IGBT, and will allow a smaller transformer & capacitors. So why aren't welders using them?


texts: Variable Timer Circuit w/ Digital Display for Counting Down

texts:
I would like to make a timer.

The timer will have a 7 segment digital display and will work with a microcontroller of some sort.

I would like to be able to put in a time (e.g. anywhere between 0 - 10 minutes) and have it countdown from the input time to zero. I would like to display down to the millisecond resolution as well, but this is not crucial.

I want the timer to be relatively accurate (up to +- 1 second in ~20 minutes).

What kind of circuitry do I need?
Will a 555 timer circuit be able to handle this?
Need some direction to get started! Please let me know what other information is required! Thank you.

So I got:

Arduino
HS420361K-32 x2
MAX7219 backing thingy
16-Key Keypad

I am assuming all of this will work together well. Am I missing anything here?

I will be fiddling with the Arduino software for a while until I figure out how I can/want to do this.

Any tips would be most welcome =)


texts: Choosing an alternate resistor or capacitor in a circuit

texts:
My question may look stupid but it's great trick in case of repairing in a battlefield.

When a resistor or capacitor gets damaged in a circuit and if the required value is not available then what should be the strategy.Choosing a high value or a low value,which would be the best solution.


texts: Is DQM latency during READ always two cycle and independent from CL in SDR SDRAM?

texts:
Reading SDR SDRAM datasheets, i found (and had been surprised) that during READs (with Burst Length >=2) DQM latency is always two cycles.

That statement is given explicitly at least in one datasheet (pp. 29-30):

(Other datasheets are speaking about two cycle DQM latency on read too.)

But i found no explicit or even implicit statement about relationship between DQM latency and CAS latency.

Is READ DQM latency independent from CL?

Why independent, if it is? And why it is exactly of two cycles?


texts:
I am trying to isolate the battery which powers the gate control circuitry from the battery which powers the hight-current load being switched by the MOSFET. Here is the basic circuit configuration:

simulate this circuit – Schematic created using CircuitLab

Do the sources V1 and V2 need to share a ground in order for the MOSFET to switch on and off, or will the circuit function as is.


texts: How do some phone chargers raise their output voltage when loaded?

texts:
I got a Samsung phone charger some time ago. The text on it says 5.3V/2.0A, and when I plug a USB meter on it, the meter reads 5.3V 0.0A. The meter itself consumes a maximum of 0.02W (so 0.004A - safe to ignore).

When I plug in a load that is made up of simply a 5 ohm resistor (labelled 5V/1A), the voltage goes up to 5.45V to 5.50V. When i plug in another 2.5 ohm load (two 5V/1A resistors in parallel), the charger raises its output to 5.55V to 5.60V.

I know it's designed to compensate the resistance of charging cables and it's named "loss compensation", but after dismantling a charger, I found no special parts compared to another Apple one without such a feature.

How is that implemented?


texts: Where can I learn Switched Mode Power Supply Design?

texts:
Recently I've had terrible luck buying those little DC-DC boards from China off of eBay.

We've been trying to build projects where we have some sort of wobbly input DC off of a car or solar, batteries and things.

So I've started trying to learn how to design and build my own DC-DC SMPS circuits.

I'm very new at this, so I'm looking for something that I can use as a calculator (input Vin and Vout, etc) but also I need to understand what's I'm doing and what's going on.

To start with I've decided to take one of our projects which needs an SMPS and build it, something which these little boards off of eBay would probably be unsuitable for.

Project: A portable, battery powered audio amplifier.

I'm going to buy a DIY amp board, deliberately choosing one which requires a high voltage to run (http://goo.gl/Idwos8 or http://goo.gl/11S6TJ perhaps) and are cheap so I won't get upset if I blow it up.

Then, take something cheap and wholly unsuitable to run it off, such as 4xAA batteries.

So, about ~6V in and I need ~30V out.

So there we go, where can I get a design which lets you calculate how to build a 6V to 30V SMPS?

Once I've done that I need to then build something useful.

I though I'd start with a 12V VRLA battery, step that up to 36V.

Problem then is how do I, you know, make it not melt when there is hundreds of watts happening?


texts:
Please forgive me for my ignorance but when it comes to Li-Po I am really not willing to take any risks.

I plan to implement a short circuit protection circuit on my PCB which is basically holding MCU, motor drivers, other ADC's and communication IC's. I am using a 6S lipo to power the full operation. My PCB is working fine. But given that during a short circuit there will be 100+ Amps of current flowing, I need some ideas on which circuits/IC's will help me design an efficient protection circuitry.


texts: Charging series / parallel 18650 battery pack

texts:
I have a 18650 battery cell configured as 4 pairs in parallel
wired in series for 16 volts.  I first CC/CV charged the
paralleled pairs to 4 volts each and stopped the charge
at 50mA.  I would like to know if the same CC amperage should be used in this configuration as for a single cell   Each cell is 3.7 volt 2200mAh CC=1200mAh.


texts:
I have a basic Arduino sketch. It reads from the serial port and prints the chars onto an LCD.

If I use the Arduino's serial monitor and start typing stuff in, it works great and displays each character to the display.

However, I'm trying to use this library to write to the port: https://github.com/voodootikigod/node-serialport

When I try to write to the port, I can see the tx light flashing but nothing appears on the screen at all.

Is there a way to spy on the data being sent down the wire to do what is different between the 2 cases? I apologise for my bad terminology.


texts:
I need to build a system to monitor several (around ~20) voltages over several days. The ~20 voltages need to be measured differentially. Something which could in theory be accomplishes with 3 of these picologgers.

I was wondering, what is the state of the art way to do something like that?. Do the fine people of Picotech use:
a) 8 differential voltages →  8 to 1 Mux → 1 Differential ADC → µController, or
b) 8 differential voltages →  8 Differential ADC in parallel → 8 GPIOs in µController ?

Option a) is cheaper but the 8 to 1 Mux needs to be very fast to cycle thourgh 8 channels and not degrade performance. Do they use CMOS Mux? Also it should be a differential mux.What do you guys think?


texts: Switching power supply between two voltages

texts:
I want to switch the supply power of a low current high frequency load between 3V and 1.8V using a microcontroller. They are powering a CPLD IO-bank that I use as a level translator. Current consumption will be 20mA peak.

I already have the two voltages from regulators to power other things, so I want I really want is to multiplex between the two supplies I guess.

Is there an easy way to switch between the two supplies using one or two GPIO-pins? I need fairly low impedance switching and I can't tolerate any voltage drop.


texts: Soldering to and using proto area on XBee sheild

texts:
This feels like a very stupid question but how am I meant to use this area of protoboard on the Arduino XBee shield - these are straight through vias with no mid layer and so none of the holes are electrically connected. It's too small to sick a piece of breadboard to.

I was expecting it to be connected in rows like bread board / vero board but I've tested with a multimeter and nothing is connected - what am I missing?


texts: How to derive the differential amplifier equation?

texts:
Just playing with circuit theory and tried to derive the equation for the differential amplifier:

$$
V_{out} = \frac{R_f}{R_1}(V_2 - V_1) \\
R_f/R_1 = R_g/R_2
$$
I've seen the solutions based on superposition and based on virtual ground, but I wanted to derive using the ideal op amp equation:
$$
V_{out} = A(V_+ - V_-) \\
V_+ = \frac{R_g}{R_2+R_g}V_2 \\
V_- = \frac{R_1}{R_1+R_f}(V_{out} - V_1) \\
$$
So I went:
$$
\frac{V_{out}}{A} = \frac{R_g}{R_2+R_g}V_2 - \frac{R_1}{R_1+R_f}(V_{out} - V_1) \\
\frac{V_{out}}{A} + \frac{R_1}{R_1+R_f}V_{out}= \frac{R_g}{R_2+R_g}V_2 + \frac{R_1}{R_1+R_f}V_1
$$
Here, A goes to infinity:
$$
\frac{R_1}{R_1+R_f}V_{out}= \frac{R_g}{R_2+R_g}V_2 + \frac{R_1}{R_1+R_f}V_1 \\
V_{out}= \frac{R_1+R_f}{R_1}\frac{R_g}{R_2+R_g}V_2 + V_1
$$
and it's now obvious I've gone wrong somewhere because the equation doesn't look like the expected answer above. There should be a subtraction between V2 and V1, but I have addition instead.
I've tried this style of derivation on a number of op-amp configurations and it seems to work. This derivation of this differential amp should be possible using just the op-amp's equations. Where did I go wrong?


texts:
I keep looking for Audio specific ADCs and the majority of these devices work at low voltages on the analog circuitry (5V for example).

Lets say we want to process an higher voltage audio input signal (let´s say 10Vrms), then a signal conditioning circuit must be placed between the input and the ADC to reduce the input voltage.

Then, after DAC, the signal must be restored to nominal level (in our example 10Vrms).

Won´t this gain reduction at the input and signal restoration at the output increase the overall SNR of the circuit?
Why do manufacturers use this low voltage at the analog input of the ADC?


texts: Terminology for flexible cabling on moving loads

texts:
Words are escaping me - literally.

What do you call a bundle or loop or coil of power/control cabling that connects to an apparatus which moves, pivots, or telescopes during operation where the cable is designed to accommodate the motion of said apparatus by some means of extension/retraction?

You see this in various industrial apparatus such as variable geometry conveyor belts, gantry cranes, draw out equipment in racks or electrical switchgear, airport jet bridges, etc;

There are several different types of designs, but they all have some means of accommodating non-trivial amounts of motion in the connected device.  The most common designs usually have loops of extra cable hanging from pulleys or sections of conduit/duct.

Here is a good picture that shows the kind of thing that I am asking about.  In this instance it is the power and control cable for an overhead gantry crane

http://www.rhclifting.com/s/cc_images/teaserbox_2450395593.jpg?t=1507619289

There is a particular term for this kind of arrangement but I cannot for the life of me recall what it is.

Thanks


texts:
According to my book and teacher :

  It is the Gate voltage at which the depletion region closes the
  channel.

According to some people on the internet and Youtube videos:

  It is the Drain to source voltage, keeping Gate voltage zero, at which
  the drain current becomes constant.

So which one is the pinch-off voltage? Vgs or Vds ?


texts:
I am putting a power mosfet to control my power output. It is a pure DC application. I dont need to switch the mosfet fastly. Turn on & turn off will happen once a day or something like that. Once ON, it will stay ON.

My doubt is, with all the time I have to charge my Gate capacitance, Do I need to supply high current(1A) to charge the Gate. If I have time & i dont need switching, can i go ahead with a 100mA current to charge the Gate. Datasheet of power mosfet is :-

https://toshiba.semicon-storage.com/info/docget.jsp?did=35760&prodName=TPHR6503PL


texts: How do solar powered cars use the energy generated by the solar panels?

texts:
I want to know how companies who use solar panels on their cars utilise the energy generated by the solar panels.
Do they charge the traction batteries with the solar power or do they power the traction motors with it directly?
If they charge batteries with it then how they do it? Do they charge and discharge the batteries at the same time, or do they charge another set of batteries? If they charge another set of batteries to be charged by solar power then how do they extract that power?
If they power the traction motor with it then is it the case that batteries supplying only the extra power required by the traction motor left unfulfilled by the solar power?
If there is any case other than that please let me know.
I have asked these question after learning that some of the companies claim about 10,000 km under the most effective conditions.


texts: Why is the earth a viable return path for power distribution?

texts:
I'm having trouble understanding why the earth is a viable fault path for electricity brought into my home. Isn't there really high resistance? I mean, it's dirt?

Also, let's say I connect the hot wire coming into my house directly to the ground wire. What is the path that the electricity takes to get back and "complete the circuit?"


texts: wcs1800 current sensor (with sensitivity of 66mV/A) output voltage varies unexpectedly with a range of 10 - 20mA

texts:
I am using wcs1800 sensor to read current in the range of 100mA to 30A, even though the sensor has a sensitivity of ~66mV/A (5V input) and ~50mV/A (3.3v input) the output voltage is varied in the range of 10mA - 20mA which makes the sensor unusable to read the current in the range of 100mA. I have tried the recommended capacitor values for output from the datasheet. Can someone help me with a solution to this problem?

Thanks.


texts: How BLE central determine the connection interval

texts: After connection established between central and peripheral, they start communicate at specified intervals called connection interval. As far as i know, the interval determined by central not peripheral. But the  interval specified with 2 parameters min. and max. values that are controllable between 7.5ms and 4s. If 7.5ms min. and 4s max. interval are set, how central specify the exact connection interval? 7.5ms or 4s or between min. and max. ? Secondly, is this parameter constant throughout the communication?


texts: Positive Feedback Of A Summing Amplifier

texts:
I've recently come across a topic that has not been covered in my studies (or at least not as yet). It's positive feedback of an amplifier.

I have been reading this link on positive feedback. From what I've read, positive feedback appears to work as a bistable device. For the output to change from one state to the opposite, the same state needs to be applied at the inverting input, but at a slightly greater magnitude. Which means we would need AC voltage on the inputs to effectively see this. This is the application of how hysteresis works.

I've noticed that the output voltage is saturated by a value that is close to the supply voltage:

Is this as a result of the input being amplified, or is the saturation happening due to the supply voltage?


texts: How to setup a RS-232 Cape for BeagleBone Black

texts:
I'm trying to use a RS-232 cape in a python script. A TU-S9 USB-to-Serial converter works just fine with same code I just change the port. So I don't think it is my code. The only thing I can think of is that I am missing something setup wise. The Cape doesn't come with any documentation (that I have found). I've tried UART 1,2,4 same result. the port will open but it never gets a response from the device. The device is a DirectLogic 05 PLC. I'm using ModBus RTU.

Edit: from what I can tell the UART ports for the beaglebone are listed as /dev/ttyO0, /dev/ttyO1,/dev/ttyO2,/dev/ttyO3,/dev/ttyO4. /dev/ttyO0 is used by the OS though.


texts: 3.7 V to 12 V boost converter - effect on cell

texts:
If I boost a 3.7 V 18650 battery to 12 V with a boost converter, would it affect the durability of the battery?
For example, if I have a 2100 mAh Li-ion boosted to 12 V, would it affect the 2100 mAh capacity of the battery?


texts: Grounding a wire using a chunk of metal?

texts:
So I've made a complex LED grid and it works but has ghosting in some of the rows.

I've given up trying to work out the reason why, but have noticed that when I touch the SCLK wire, or connect the SCLK wire of the TLC5940 LED driver chip to a pair of scissors, or any big chunk of metal, it also fixes the ghosting (pretty much)

So I'm happy with this solution, but would like to understand what's going on. If i connect it to ground instead, it doesn't work. But i presume the chunk of metal has a grounding effect?


texts:
I want to operate the LCC110 solid state relay from a 5V CMOS output pin on the PGA2505. I can see that I will likely need 8mA to drive the relay. However, I don't see on the PGA2505 datasheet if it can drive this current from the CMOS pins.

The input voltage drop of the LED in the solid state relay can be up to 1.4V so it is obvious that[will need to put a 450 ohm (5-1.4)/(.008) resistor in series with the relay. The datasheet for each device are provided below. However, I don't know what I am proposing is okay. The relay is used to switch from ground and 48V.

LCC110 datasheet.
PGA2505 datasheet.


texts:
I am buying a second hand logic analyzer (Agilent 1661A) and I see the terminology such as the following:

100MHz State Speed
Maximum Conventional Timing Rate: 250 MHz full channel, 500 MHz half channel
Maximum Timing with Glitch Rate: 125 MHz half channel

And there are many more. I expect to measure 50MHz signals between FPGA and other custom ICs.

I have the following questions:

For 50MHz measurement, what is the minimum speed I should pick up? (If this were a scope, for 50MHz, I would probably need 500MHz scope to see the signal very clearly)
I need to measure set up and hold times and some other timing parameters, how does the speed of the scope impacts these.


texts: Would we like to have a linear circuit application to cause low distortion at the output port? What about a power amplifier? Is it necessary for a power amplifier to have only low distortion at the output port?


texts: Led head light - preventing Battery contacts from rusting

texts: I have a cheapo Asda headlight who'sbattery contacts keep rusting over. Even if you leave the bloody thing indoors it rusts after awhile. Is there any chemicals I can put on it to stop this from happening?


texts: Connecting two PCBs with different headers

texts: I would like to connect these 2 boards together. Left one has male header, right one female. Ground and 3V3 supply are not pin-to-pin aligned, while all other pins are. What would be the best way to connect these two boards together (besides nasty individual jumper wires or custom PCB between these two)?


texts: Is there any device or way to measure how many watts a computer's processor is using?

texts:
I know there's a device to measure how many watts a computer is using, you get an energy meter you plug the computer into it and it tells you

But I'm interested in finding out how many watts a processor uses.

Is there any device that can plug into a CPU socket as an intermediary and report it, and then that figure could be displayed on an LED or fed out on a wire and read by an arduino or raspberry pi.

Is it feasible and reasonably simple for such a device to be built?

e.g. just as one can measure how many volts a power supply rail is using, e.g. one can check that the red wire is 5V.. So too would it be simple to have a socket that is female one end and male another end and exposes its pins and then would a multimeter or some device connected to it be able to read off the power without interfering with what the processor is doing?

Processors do report TDP but that's a maximum. I'm interested in how many watts it runs at e.g. idling.

added  It has been pointed out to me that watts don't necessarily correlate with heat across processors e.g. an Intel Core i5 3230M is is based on 22nm, the cores are big.. Compared to a newer processor like a 7000u/8000u would be based on 14nm, and AMD's 4000 series is based on 7nm.  It's apparently perhaps a combination of small core and low watts that lead to low heat.


texts: Do I2C wires and 120W (12V) power wires close together cause trouble?

texts:
I'm a beginner with electronics and I'm building my first solar powered robot. I now have a 50cm  long (1.6 feet) small pipe through which I want to put four wires; 2 for the power from the solar panel, and two for I2C to read some sensors. I've got two 100W solar panels, but I doubt I will ever get more than about 120W through it.
I don't know if the size of the wires matter, but currently I'm using 22AWG for the power, and 30AWG for the I2C.
I had some trouble before when the wires from the ESC to the BLDC motor and the PWM wires to a servo where touching eachother. Before I build this part of the robot I now wonder whether I will get into trouble if this I2C and the power are cramped together in the small pipe.
Does anybody know whether this will cause trouble (interference or something)?


texts: Quick Datasheet Interpretation - TI LM1084

texts:
Was wondering if someone could give this datasheet a look over in regards to the max current it can source out.

It's rated at 5A out, but it says under "Current Limit" for LM1084-5.0 at Vin=10V that the TYP current limit is 8A.

I'm putting 12V at 6A into the LDO. Do you think it's safe to draw 5V at 6A from the LM1084-5.0 LDO?


texts:
I have just gotten a URM37 ultrasonic sensor.

I need a way to measure the distance to an object from two sensors (for maneuvering). Can I know if ultrasonic sensors with 2 sensors are suppose to be able to measure dual distances?

Or do I have to get one more sensor?

Also, If i do get one more sensor, does that sensors pulse affect the other ultrasonic sensor?


texts: Understanding of how the trigger connector works on a boom-arm vehicle barrier

texts:
I would like to know how the trigger (TRG) pin works on the boom-arm vehicle barrier. From my understanding looking at the circuit below for an external radio receiver, when the trg pin is grounded is activates the boom barrier.
However what is happing at the trg pin?
Is there a micro-controller pin that is connected to the trg pin. This micro-controller pin then detects is the trg pin is high or low. The micro-controller pin detects a high when the remote is not pressed. When the remote is pressed the trg pin is then grounded. This change in state (HIGH-LOW) then activates the boom barrier.
Is this a correct interpretation?

Second question
From this manual, they say the boom barrier is "Triggered through a normally open dry contact". Does this mean that I must supply the control signal that closes the circuit? Or does it mean I must supply the actually voltage that runs the boom barrier?


texts: Sansui AU 6600 Amplifier restoration Power cement resistor tolerance

texts:
I am restoring my Sansui AU 6600. On the f 2097 driver and power supply board there are four(two for each channel) 3W cement resistors rated at 0.47 ohm

I took all four out of the circuit and tested them and the meter reading is between 0.68 and 0.71 as you can see from a photo.

My question is, as I don't the tolerance looks like they are about 40% over the 0.47 listed in the part list.

Is that OK? Does that mean that after over 40 years the resistors have changed the resistance? Do I need to replace them?

Here is what they look like:

Hi thank you for your reply. I've red your reply, I must be honest but my knowledge is not sufficient to fully understand it. However just for curiosity  attached a photo showing what happened to the resistor R47. Plus a photo of the schematic. This amp was in very bad shape (still is I am recapping it at the moment)as I got it from a friend who had it repaired several times over the years....anyway so the channel (if i remember well the left where the resistor R47 is ) is gone and the two power transistors (2sc898 and 2sa758) are blown out. Actually I didn't find those exact ones but instead there were motorola (genuine or counterfit??)  Mj15025 and MJ15022 . Sorry I am new to this site I tried to give you 5 points but was allowed 2 only. Cheers


texts:
I have a battery operated device which needs to be temperature enabled.  Once the temperature goes above 60C, the device should start operation.  Ideally it'll be like a fuse, and will continue even if the temperature drops below 60C after initial activation.

The device has a microcontroller, so I currently plan to put it into deep sleep and wake it to check the temperature every minute or so, however this will consume almost a microamp of current continuously (to operate the timer needed to wake).

I'd like to reduce that even further.  I'm not aware of any circuit elements that could accomplish this, though, and any circuit designs appear to consume more power. Further complicating matters is that I have less than 32mm^3 volume available for any additional components to implement this.

I'm imagining a piece of wax separating two sprung contacts, but I don't want to develop something myself, I'm hoping such a device already exists at this tiny size.

Are there other options I can consider?


texts: Connecting to Venus GPS, checking received UART message, seems garbled

texts:
I'm trying to integrate to a Venus VENUS634FLPx GPS chip that I bought through SparkFun many years ago (https://www.sparkfun.com/products/retired/9133). I'm connecting to it through UART and I'm getting NMEA messages however they come across seriously garbled. Here is one of the better ones:
b'$GPGGA,121\xbd.000,2400.0\xf87,N,12100.00\xc6V\x8d\x193\xcb\x980,0.0\xfc\xf7\x06\xc6\xd6\x8d\x193\x193\xcc\x96M,\xfd30*67'

Here is the datasheet format for this message:
$GPGGA,hhmmss.sss,ddmm.mmmm,a,dddmm.mmmm,a,x,xx,x.x,x.x,M,,,,xxxx*hh<CR><LF>

The hhmmss.sss is "121\xbd.000" and it looks like some bytes were eaten there. Ultimately what I want to do is check the checksum at the end which is supposedly an XOR of all characters in the message excluding the leading $, trailing *, and 2 character checksum.
I'm using a Raspberry Pi W with /dev/ttyS0 enabled and I have an external power supply powering the GPS chip at 3.3v. The ground from the power supply is linked to the Raspberry Pi as well. The baud rate I'm using is 9600.
My code is Python using the pyserial package v3.4.
Any recommendations on how I can debug this or what I could check would be greatly appreciated. Thanks
Edit 1: python -m serial.tools.miniterm
    (venv) pi@raspberrypi:~/subcommander $ python -m  serial.tools.miniterm

--- Available ports:
---  1: /dev/ttyAMA0         'ttyAMA0'
--- Enter port index or full name: /dev/ttyS0
--- Miniterm on /dev/ttyS0  9600,8,N,1 ---
--- Quit: Ctrl+] | Menu: Ctrl+T | Help: Ctrl+T followed by Ctrl+H ---
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Answer: the grounds from the GPS and raspberry pi were not tied together.


texts:
Does anyone have any opinions about using an EMC Filter to protect vintage electronics? I'm referring to very sensitive jukeboxes, pinball machines and this kind of stuff.

I have some machines that have been hit by surge, though we have them fairly well protected (fuses, surge suppressors) but still, when power tools or PA systems or similar are powered on the same circuit as my vintage machines, something will blow inside (may it be a lamp or Jones plugs or something).

Obviously I don't know much about this stuff. Just trying to think of ways to protect my machines.

Thanks.


texts: Limiting no-load output voltage of a tube amp power supply

texts:
I am designing a power supply for my tube amp. Here's what I have come up with:

Duncan's PSU designer shows that it should work OK (and provide 256V at 320mA). However, should one or both output tubes fail, the voltage would rise to 550V, which the other tubes may not like. Also, since the rectifier is directly heated, it will warm up much faster than the output tubes, probably resulting in too high voltage for a brief time after turn on.

So, I need to somehow limit the output voltage. However, I do not want to use any semiconductors anywhere in the amp. So far, I have come up with one way to do it and want your opinion on it or other suggestions:

simulate this circuit – Schematic created using CircuitLab

R3 is made up of 10x 100Ohm 10W resistors, R2 value calculated so the relay turns on when the voltage is too high and turns off when the voltage gets too low (output tubes warmed up etc).

This would probably oscillate if R2 is not calculated precisely enough or with line voltage variations. Also, it would result in an overload of the power supply when the relay is active and the output tubes start working.

Are there any better ways of doing this?


texts: I'm pretty new to electrical work in general and was wondering how I would open and close a solenoid valve. It says on the specifications that it needs 12 VDC. Do I just take a 12 volt battery and put each wire on the battery (is it that simple)? I've seen people wire up push buttons and Ardiunos which is getting me confused. What would be the simplest way? Do I need all these complicated parts or can I literally just use a battery? Thanks for any explanation to a noob like me, this stuff is pretty intimidating. This is the image of the solenoid valve I have.


texts:
Does anyone know if I can use a single Arduino or Raspberry Pi to control two 32x32 LED matrices as sold on the Adafruit website? Here is a tutorial where you can wire the 32x32 matrix.

Ideally, I'd like to be able to control them separately, but if the wiring only allows simultaneous control of the two, then that is ok.

Than you for your time.


texts:
First of all, let me apologize if this isn't the correct place to ask this. This is the one of the best places for my question that I've seen so far.

I've been designing a box for on my desk that allows me to control separate program volumes using potentiometers. I use the Windows volume mixer and some program volume control a lot, but using this saves me a lot of time (plus I'm doing this for fun and learning).

What it does is take 1 USB signal, and turn it into 4 playback devices. One with music linked to it, one with Discord, etc. Then I have potentiometers to control the signal strength/volume. Then the signals get combined again for the output.

My question is about the playback devices. I don't want to use many USB ports and >3.5mm sound cards/converters, seeing as that will presumably make the sound quality deteriorate. I want to now at step 1 not convert the signal to 3.5mm and keep it as USB, but then I can't use a sound card/playback device. Is it possible for me to find a workaround for this?

So far I have 2 ideas myself but I don't know if they're possible:
1: Add soundcards at step 1 and make the wires to the potentiometers to step 2 tap into the wires running to the soundcards, so that they run in parallel and receive the same signal.
2: Somehow get the USB wires to be seen as playback devices. Unfortunately, I wouldn't even know where to start with this.

Thank you very much for taking the time to read this (long) post. If anything is still unclear about my project, the (rough) schematic and breakdown of the steps are shown below:

Steps:

The one USB cable from the PC gets split into 4 and the 4 USBs get converted to 3.5mm. The converters from USB to 3.5mm will have to be usable as playback devices.
4 potentiometers (1 per 3.5mm cable) are used to control the voume of each specific subject (1 through 4).
The 4 3.5mm cables/channels get fused back into 1. There is 1 potentiometer afterwards for general volume control.
The 3.5mm gets converted to USB.
A switch decides whether the signals of the input gets through. AKA, whether the sound is muted.
A switch decides wether the signal goes to the speakers or the headset.
The USB signal goes into a USB sound card, where it gets altered and converted into 3.5mm. And then the USB signal gets converted into 3 3.5mm signals: Front out (Green), Rear out (Black), and Center/Subwoofer out (Orange) using a USB sound card.


texts: Using ATX power supply in industrial electronic projects

texts:
I have two main questions:
1. Can you use ATX power supplies in industrial projects?
I see lots of DIY projects where they convert an old ATX PSU into a lab bench power supply or powering DIY projects. However, I have not seen any articles on using ATX power supplies in industrial projects that requires high power 12V and 5V rails. Are there any downsides to doing this? (PS: Industrial electronic projects such as embedded systems with various sensors)
2. Why a decent ATX power supply cost significantly lesser than a decent switch mode power supply of the same power rating?
A decent 500W ATX power supply from Cooler Master with 80+ efficiency can cost less than USD$50, whereas a 500W 12V MeanWell SMPS will cost at least double that. Wouldn't it be better to go with an ATX power supply then to power high power appliances such as motors?


texts: How does ADC rate affect this filtration circuit?

texts:
I'm doing some theoretical design for a simple dsPIC-based ADC circuit. Both the device specsheet DS70000657H-page 30 and application note Analog and Interface Guide say that:

AVdd and Vdd can be connected via a choke
AVss and Vss must be connected directly, but you can have two planes that are spatially and electrically separated in the vicinity of their circuit sections, with separate return traces that are connected at the voltage source

Of particular interest:

My ADC conversion rate is very low (on the order of 5 Hz). If I use that frequency, the required values for L and C are very high. To allow reasonably inexpensive parts, using an aluminium 100uF capacitor for AVdd and a 33uH choke, I would have to sample at ~2.8 kHz, which is too fast.

My questions are:

Is the ADC conversion rate referenced in the specsheet an exact rate, or a maximum rate below which sampling is safe?
If the physical sampling rate is non-negotiable, could I use it but then run an internal DSP, such as moving average filter?


texts: Common mode noise mitigation in two pin smps

texts: How does a 2 pin (no earth ground connection) SMPS offer common mode protection? Is it safe to power appliances over it?


texts: Low Input Voltage DC DC Converter to Power LEDs

texts:
The LEDs in my circuit need 3.0V-3.2V  to be illuminated. Energy generated from using a DC motor as a generator and is stored in 1 Farad capacitors with a maximum voltage of 5.5V. I am looking to implement a DC DC converter that will take extremely low voltages (between 0V and around 3V) and increase the voltage above the minimum for the LEDs to extend the time of illumination. The converter needs to be on the small side, as all of this will be packaged in a 3D printed case assembly that can easily be hand-held.

Does anyone have suggestions on specific products or things to keep in mind? I understand that most converters require a minimum voltage to be able to perform their function. Also, would a simple boost converter be preferable over a converter that regulates the voltage at a steady output above the approximate 3V minimum for the LEDs?


texts: What does 25°C mean on a transistor data sheet?

texts:
The background is, I'm trying to understand how well a typical transistor obeys the Ebers-Moll equation at constant (junction) temperature.

See this snapshot taken from the Fairchild datasheet of the 2N3904 transistor.

My question is what is meant by 25°C? Is it

ambient (room) temperature?
The temperature of the epoxy casing?
The actual temperature of the silicon (junction) itself?

Also, how is constant temperature maintained?
Will a manufacturer publish information on how it took its measurements for datasheets?

In general, there is a temperature gradient from ambient to casing to junction. So the junction is hotter than the casing which is hotter than ambient. The temperature in the Ebers-Moll model refers to junction temperature.

My own speculations:

Of course if the answer is 3., we expect all of the lines to be straight since Ebers-Moll gives

$$I_C = I_S \exp(V_{BE}/V_T)$$

where \$I_S\$ and \$V_T\$ are constant at constant temperature and \$V_{CE}\$. Note the logarithmic scale for \$I_C\$. So there is definite deviation at 125°C near \$I_C= 100 \text{mA}\$.

Is this deviation really due to increased junction temperature due to heat dissipated by \$I_C\$, or is there genuine deviation from the model?

I am thinking that it can't be 1. because the junction would get hotter with increasing \$I_C\$ and the line would deviate strongly from straight. For the 2N3904 with \$V_{CE}=5V\$, I calculated that junction temperature increases with \$I_C\$ as 1°C/mA at constant ambient temperature. (\$I_S\$ and so \$I_C\$ increase by about 9% per °C.)

Perhaps they can achieve 3. by taking all the measurements automatically in a fraction of a second, before giving it a chance to heat up.

Any ideas?


texts: How to toggle a reset in a counter made up of JK flip flops

texts:
I have been playing around with a small circuit which at the moment consists only of a counter made up of 3 JK flip flops. Like so:

What I want to add is a reset input pin that will set the 3 LEDs to 0/off but I am not sure how to implement. I know that you need to input a 0 for the J and a 1 for the K to trigger the reset behaviour but this is what I am struggling with.

Any ideas would be very appreciated.


texts:
Firstly, I'll answer my own question by saying that I don't think I have broken it.

However, is it possible I could have? (and also possibly, the power supply I was testing).

I am quite new to electronics and recently purchased a Fluke 115. Having watched a few YouTube videos and looking through its manual, I decided to measure Voltage (V) and Current (A) between a DC power supply and a Mini-ITX motherboard.

So, I Connected the black lead to the common terminal, and the red lead to the V terminal. Stuck the ends of the probes on the outside and inside of the barrel jack. Set it to Volts DC. Measuring voltage fine with normal/reverse polarity. (+/-).

Now I went to try and measure current... sigh...

Using a lead I made with a Mini-fit JR connector on one end, and a soldered DC jack on the other, I snipped the positive wire so I could break the circuit and put the probes in-line. I fitted some crocodile clip accessories from Fluke to the probes, set it to Amps DC and tried measuring. I was getting a zero reading, so I must have done something wrong?

Stupidly, I thought, hmm... I will just double check the meter is still working and tried to measure volts again. Took the croc-clips off, stuck the probes in the jack and pop/flash, a spark appeared. Pulled away quickly.

I had left the red lead in the A terminal :(

Here is why I don't think I've broken it (or the power supply):

Firstly, I did a fuse check by connecting one probe to the V
terminal, and putting its probe into the A terminal. Setting it to
Ohms, it gave me a reading of 0.1/0.2 Ohms. So the fuse doesn't appear to be blown.
After actually connecting the probes in the correct way, I am getting
the correct Voltage still.
Also I figured out why the current wasn't working, and I'm now
getting an acceptable reading of Amps.

Some additional info:

The power supply outputs 19V, and can supply up to 6.32A.
Inspecting my probes, and the black probe where the spark came from has a tiny
little dark patch (very very small).

I normally wouldn't care, but the meter was expensive with it being a Fluke, but I wanted something accurate.
I also don't take chances with anything electrical due to possible shock/fire risks.

Then again, I realise I am an idiot for quickly rushing ahead and measuring things.

But, do you think I've broken anything?


texts:
I'm sure I'm just being dense (or missing some really basic concept) but, in designing an antenna matching network for the MAX1472, I can't seem to find a specification for what the impedance at the output pin ought to be. Is this a fixed number or somehow related to the frequency I'm running at? I'm just not getting how that would be determined.

I suspect this is probably where a VNA would come in handy but they are well beyond my budget and I wouldn't know how to use it if I had one lol.

The datasheet for the device in question: https://datasheets.maximintegrated.com/en/ds/MAX1472.pdf


texts: Combination circuit - how to calculate equivalent capacitance when switch is closed?

texts:
I am stuck in a problem where we are supposed to calculate the potential difference across each capacitor after the switch S has been closed, but I am uncertain how to calculate the equivalent capacitance.
I understand that the two pairs of capacitors are connected in parallel, and the pair themselves are connected in series when S is open. What does the circuit look like when S is closed?
Thanks in advance!


texts: What is a good tolerance for impedance matching or how to calculate losses?

texts:
If you build a microstrip on a silcon wafer, connected by picoprobes via SMA connector and cables to a VNA, what is actually a good match of the impedances of the cables and the waveguide. Is there a formula (if I understand correctly, the Smith Chart can answer this, I'm still trying to understand it completely) to calculate the losses.

Say you are able to structure your waveguides on the silicon by lithography with a tolerance/accuracy of 10%. So the impedance can vary by this 10%. So you might get 55 Ohm instead of the wished 50 Ohm that typical SMA cables are set up to. How much signal loss will this cause?


texts:
I am trying to figure out the size of the coils that I would need to construct to create an electro-magnetic field that would be strong enough to power my device. The device needs at least 1.2V and uses .023A. I am trying to power this device with a spliced USB cords (using the hot wire and the ground wire).

So here is the question, how would you use
 coils to produce a electro-magnetic field to power the device mentioned above?


texts: Do we have a material that reshapes itself depending on applied voltage or electromagnetic field?

texts:
I am thinking to control the physical world by applying signals to a magical material.

The material must have the ability to change its strength from a very solid state to a dough like state back and forth. So for example if I want to grip an object I just need to set the voltage to low and the material becomes like a dough, soft, and can reshape and does the gripping, then I set another voltage and it becomes solid and I can move the object by electrical motors.

Does such a material exists? It is a feasible idea?

I know my question and the idea behind it is vague. But my objective is very precise: "Changing the strength of materials, using some sort of electrical signal", possible?


texts: Simple, Variable High Current Dummy Load

texts:
I'm working on a power supply build and need a dummy load. I've found many mentions here that are good for a few amps, but I need one that's good for 30A or more... at 5V. I thought about just using some high wattage LEDs or something but they all require 30V or more.
Being variable isn't a hard requirement but would be nice. I want to be able to ramp up the current draw until I hit my limiter so I can test it actually works. If it jumps straight to the limit, that doesn't really help.

Any suggestions?


texts: What am I doing wrong with this voltage regulator?

texts:
I have this to try to get a regulated -15V DC:

simulate this circuit – Schematic created using CircuitLab

But my 7915 outputs a (positive) low voltage in the 1-3V region.

I've checked the input voltages and they are good. I've tried two 7915s and they operate the same way. I've tried a higher input voltage and get the same behavior.

Datasheet excerpt:

What am I doing wrong?

Update: pics (the 7915 is the reg on the right)


texts:
I have already been searching the web and COMSOL for a few hours, but I can't find the B-H curve of Structural Steel (more specifically S235JR - EN 10025).
In COMSOL there is a list of Nonlinear Magnetic Materials, further grouped into material types. I assumed that S235JR is either a Low Carbon Steel type or a Stainless steel, but I can't make sense of the COMSOL steel names.
Here is Stainless Steel:

and here is Low Carbon Steel:

Which one has similar B-H curves to S235JR?
Alternatively, if anybody can point me to a database with the B-H curve of S235JR, I would be grateful.


texts: EAGLE - VIAS are smaller on the screen than in the actual gerber

texts:
Hi I have upgraded EAGLE to 9.5 and have one quite serious issue. The VIAS are displayed smaller than in the actual gerber file or manufacturing preview. Do you know the option which will force Eagle to display them the same way? I did not have this problem in the 7.5 version

EDIT
As in the @ThePhoton answer, it is the soldermask stop area. It has confused me.


texts:
I am trying to read a -0.1 - 1 Volt signal using a Raspberry Pi for data analysis and a Gertboard for the ADC and actual voltage reading.

The signal comes from a scientific equipment which has an RCA-Output. A photo of the cable that came with the equipment is below

The RCA male is connected to the equipment and ends in two (+ and -) spaded tongue terminals (Japanese E JST 1.25-S3). I want to connect these two ends to my Gertboard.

What would be the adequate way to do this?

I have thought about creating two cables, each with an spaded tongued end and a "normal" end which can go into the gertboard. I would then join each pair of tongued terminals with a screw. Is this feasible or am I missing something?


texts: Equation for square law circuit modulator

texts:
For DSBFC AM (double side band full carrier amplitude modulation ) the message signal m(t) must be multiplied by carrier maybe $$ Ac*cos(\omega_c(t)) $$
(For modulation)
This modulation is done in reality by using the non-linear characteristics of the diode, where
$$ i(t)=av + bv^2 $$
v=applied voltage to diode
Here we apply
$$ v =Vc(t)+Vm(t)$$
$$  i(t)=a(Vc+Vm)+b(Vc+Vm)^2 $$
$$  i(t)= a*Vc +b*Vm +b*Vc^2+bVm^2 +2*Vc*Vm $$
Here $$Vc=Ac*cos(\omega_c(t))$$
Thus
$$i(t)=a*Ac*cos(\omega_c(t))+b*m(t)+b*(Ac*cos(\omega_c(t)))^2 +b*m(t)^2 +2*m(t)*Ac*cos(\omega_c(t))$$
After simplification
$$i(t)=a*Ac*cos(\omega_c(t))+b*m(t)+\frac{b*Ac}{2} +\frac{b*Ac*cos(2\omega_c(t))}{2} +b*m(t)^2 +2*m(t)*Ac*cos(\omega_c(t))$$
In frequency domain I can clearly understand following components
$$ f(message frequency),f_c,f_c+f,f_c-f,2*fc $$
but my book tells me there are addition components at $$2f_m$
Can someone help me understand where it is?


texts:
I've designed a simple mains detector which I have drawn below.  The theory of operation is pretty simple.  A capacitor is used to reduce the current so that my optocoupler can operate (represented by the LED below). With LTSpice, I get a nice sine wave @60Hz with ~3.5mA.  I have omitted the other side of my opto for simplicity's sake.  Now I'm interested in doing some safety analysis.

The first thing that comes to mind would be to add a high resistor in parallel with the capacitor to reduce the risk of someone getting a discharge from the capacitor, but I've purposely omitted that because it would burn a lot of heat and ultimately I can put this whole thing in a place where no fingers should be reaching it.  The fuse should protect me against the case where the capacitor fails with a short.  An open circuit would simply fail nicely.  Any other thoughts I may have missed in my safety design?

simulate this circuit – Schematic created using CircuitLab


texts: how to connect mic left and mic right to single TRRS mic connection. The first figure shows mic left and mic right connected to microphone output jack. I want to replace this output jack with the TRRS jack as shown in figure 2. the second figure shows Ring2 as the mic connection.


texts:
What circuit or ic can I use to produce sine wave with 30 kHz frequency and 9 Vp-p?

I used XR2206 but the maximum peak-to-peak voltage is 3 V and I need 9 Vp-p.

I will be using this for inductive power transfer. Is it ok if i will use signal generator instead of creating my own oscillator?


texts:
Is it possible to make a fuse holder combined with a contact to use on a pcb?

I'm looking to save space on my board and to integrate the fuse with the contact instead of placing them on a line on the board. Does it even exist?

Just an example to make it alittle bit more clear.
A fuse box like this: https://www.digikey.com/product-detail/en/eaton/BK-HTB-24I-R/283-2711-ND/954291
and maybe a connector head like this: https://www.digikey.com/product-detail/en/jst-sales-america-inc/S2B-PH-SM4-TB-LF-SN/455-1749-1-ND/926846


texts: Returning Currents for two side boards and returning current questions

texts:
I have some questions these are I am not sure:

I have designed a board that has classical 2 side PCB design. Frequency is not a big issue for me but with ESD my CPU resets itself. (CPU clock 20 Mhz, and some data transfer lines at 10 Mhz, 2Mhz, 400 Khz)

How does returning current work for two-sided PCB? Everything is ok for 4-layer PCB with a solid GND or Pwr, but how can I design it for a two-sided PCB to avoid forming EMI from returning currents?
If I use 0603 smd decoupling capacitors instead of 0805 smd decoupling capacitors does it make any difference?
I couldn't understand something with this picture for returning currents. This is Signal/Pwr-Gnd/Pwr-Gnd/Signal Design. The point that I couldn't understand what does it mean to say “Return current on top surface of layer” or “Return current on bottom surface layer”. Isn't that the same place, surface of full of GND?

In fact, I couldn't understand layer2 and layer3. Which surface has full of Gnd or Pwr/Gnd? (sorry for this easy question.) And how does current go from layer2 bottom surface to layer2 top surface? I can see that current goes from Layer3 to Layer2 by via. But how does it travel between the surfacs?

Edit 1

My PCB is complex for one side design. I have to use side 2 too, so that I can't allocate one side for solid ground. I want to learn about these returning currents. I have some Data traces that will handle transfers at 16 Mhz. How can I design returning paths for these? Do I have to worry about them? What is the perfect design for my two sided board for these returning currents? As I said, I can't allocate all of side for ground. And what is the perfect design for my GND and VCC? Huge pieces of GND under high speed data traces or just traces of GND? In fact, I am not sure how to design Vcc and GND for the best.

Edit 2

This is my PCB layout. I think it has design mistakes in it. What are these, in your opinion? Red one is Top Layer, Blue one is Bottom.

I have censored some of parts with yellow. So dont worry about them. Thanks for help.


texts: Possibility of poles with positive real part in RLC filter

texts:
are there the poles with positive real part in any function mode of the RLC filter?

The equation to determine the poles is the following:

$$RLCs^2+Ls+R=0$$

$$s_{1,2}=\frac{-L\pm \sqrt {L^2-4R^2LC}}{2RLC}$$

Thank you for your time.

P.s. I posted this question because my professor said that the poles have always real part negative or zero.


texts: crystal oscillator as backup (or with sync)

texts:
I have a device that generates a 49.152MHz frequency, but depending on its status it can cut it off from time to time. This frequency synchronizes my MCU's audio devices, but it must never be stopped.

Is there a device like this:

Or like this:

Or how can I design a circus to behave like this?

EDIT

Here is a (very simplified) outline of what I should do.

The backup clock generation could be a crystal or (to save money) could be a signal generated by the MCU itself.

If main clock is present the phase between out clock and main clock must be constant, and out clock should have no jitter (or no more than the main clock). When main clock goes off (or UXT is not populated) there should be a transition to backup clock. When main clock returns there should be a transition to it.

However jitter on clock out is not a problem compared to what the phase would be. I'm doing all this to synchronize everything with the clock recovered from the Dante stream. It may happen that the 48kHz recovered by Dante and the 48kHz obtained from my micro (and my crystal) have variable phase shift (e.g. one 48001 Hz and the other 47998). Wanting to avoid an ASRC the only solution is to make UXT master of all the clock domains. But we have to deal with the fact that UXT can shut down biefly the clock or it may not be populated (we have boards without Dante's capability), whereas ADC and DAC must always be clocked. Hence the need for a backup clock.

I have some area and cost constraints, so the solution should be not too big and definitely cheap.


texts: Inconsistent readings between oscilloscopes

texts:
I have a circuit that pulses a high frequency EM field at a rate of 2Hz.  I'm trying to see the accuracy and precision of the circuit, but I see very different readings on two oscilloscopes I'm using:

Here's the one that I think looks "better" or more like what I expect:

And here's the one that I think looks worse:

The second oscilloscope is cheaper than the first, but I didn't think it would be that far off.  Additionally when I zoom in on the timescale, say to about 10ms per grid, the pulses are even in height, it's only when I zoom out that it gets worse.

Is there anything that could be causing this that I'm missing?  I've checked through every setting I could find on the second scope and even tried to run its self calibration program.  I would appreciate any help on this.


texts:
Does anybody know of any online resources that go over the setup of driving ultrasonic transducers, as well as how to receive an ultrasonic echo, and pick it out (for rangefinding)?

I found this article online...but it glosses over it almost too much.


texts:
Modern days, almost any CMOS chip has input clamp diode to clamp their input to the power supply, such as below:

So, in worst input over voltage situation, all energy will finally go to the power supply, right? If the power supply can't sink the current to ground, the power supply voltage will go higher higher, then the entire system will be damaged, what's the proper way to avoid this?


texts: How do floating gate transistors not leak the stored charge?

texts:
I've done my best to read through Wikipedia explanations of floating gate transistors which are used in flash memory. It looks like these transistors have a special region where the charge is "stored" and user circuit has to do certain electrical manipulations to "unlock" the region and alter the charge.

Okay, but how does that charge stay there forever such that the transistor has no need for charge "renewal"? AFAIK memory that uses capacitors for data storage has to be "refreshed" because capacitors slowly discharge over time.

How do floating gate transistors store the charge forever and have no need for "refreshing"?


texts:
I'm trying to make some heated gloves and socks that would work with standard Li-Ion batteries. There are some ready-made solutions out there but they are either very expensive or have small heated areas.
The only options I found so far are some specialty carbon textiles that also seem to be very expensive, or cannibalizing some USB heating pads, which don't seem to work very well according to the reviews...
Assuming that the circuit will work at 3.7V and 0.5-2A (putting out between 2-8W), what would be my options when it comes to choosing a heating element for this purpose?


texts: How and when should I split a schematic component into multiple parts

texts:
Using Altium, one has the option to split schematic components into multiple parts. The examples given within the Altium documentation split chips with multiple discrete components in them, but I have also seen others split large ICs or MCUs into multiple parts. The image below shows how this applies to a small MCU, with both a part for power, and a part for "everything else":

I'm not aware of any standards (like you might have for electrical schematics for example) for PCB schematics, but are there any good guidelines for how/where it is appropriate to split large devices?
For example:
In a board I'm currently  working on, we plan to use this 8 way ethernet switch chip. It's got 208 pins; ~70 of these are power pins and ~30 are factory test pins, neither of which do I need/want near my (slightly more complex) signalling circuitry. There are also chip config pins that again, don't necessarily group with the main switching function of the chip.
The example schematics for the eval board include the chip drawn pin for pin which I don't like personally, but is this the best way to do it?

My current thinking is to have a "switch" part, which includes all the data and LED lines for the 8 ports, a "power" part with all the different VCCs and GNDs, and a third part with switch configuration pins and factory test pins. Can anyone suggest flaws with this method? Does it go against any "best practice" type rules?
TLDR; how should large ICs be split on PCB schematics


texts: Reducing heat dissipation in linear current source used for driving a LED

texts:
I'm currently using a linear current source to drive a single LED as in here. In my case (following the notation in the link), VDD is directly connected to a single cell lithium polymer battery, i.e. Vcc = 3.0 ~ 4.2 V. For the transistor and MOSFET, I am using MMBT3904LT3G(Digikey link) and 2N7002P,235(Digikey link), respectively. Rs is set to 2.2 Ohms. My desired current is approximately 250 mA.

Here is the circuit diagram from the site:

The problem is that there is so much heat dissipated it is hard to touch the PCB board. There are 3 LEDs (and corresponding circuits) in total on a 50 mm x 50 mm PCB (FR-4, 1.6 mm thickness). I am measuring 565 mV (which actually keeps dropping as the PCB heats up) across R2 and a voltage drop of 2.14 V across the LED at Vcc = 4.2 V. I am guessing that most of the heat is generated from Q2, since it has to drop the rest of the voltage which is approximately 1.5 V.

I have considered using a step-down switching regulator to drop the battery voltage to around 3 V, which I certainly think will help the problem. I have also looked on Digikey to find dedicated ICs such as this one. However, both require an inductor that I have heard to be expensive. There also seems to be charge pumps that I am not sure will be effective in my case (LED forward voltage is always lower than the battery voltage).

What would be the best way to go? In the end, I am looking for a cost-effective solution, but now open to any suggestions. And could you clarify whether charge pump LED drivers (such as this) will be effective for my case.


texts: Is there any way to simulate a program run before burning it onto the board?

texts: Programs may, at times, have runtime errors. These are sometimes hard to find and can easily be missed. Is there any way to test the program before actually burning it onto the board ?


texts:
I have an USB-UART cable. The connectors listed are Red VCC, Black GND, Green TXD, White cable RXD.

I want to connect it to a Alfa Hornet-UB board (http://www.youtube.com/watch?v=i58XOF4Rfc4) with pins for GND, TX, RX, VDD. If I connect:

Black (GND) - GND
Green (TXD) - TX
White (RXD) - RX
Red (VCC) - VDD

Will this damage the board?

I want to be cautious because I have previously connected a 3v to the VDD pin, which broke the board.

I assume TX is the same as TXD (Transmit), and RX = RXD?


texts: Solar Panel used in Conjunction with a DC to DC Step Up

texts:
Good morning all,
I am trying to put a little project together where I used a 1 watt, 6v solar panel in conjunction with a 0.9V - 5V to 5V DC to DC boost converter. I hooked up the solar panel to a multimeter and tested it in dim lighting and it was outputting about 3.5V and 130mA. 3.3V is well within the tolerance for the boost converter so I hooked it up to the boost converter.

I took a volt reading at the connection point and now the voltage dropped to about 0.2V. I have tried this with multiple panels and regardless of the no load voltage, it seems to drop to about 0.2V.

The boost converter also has a USB output and when I plug it in to my phone, nothing happens. I have confirmed the boost converter works because when I attach the dc inputs to a 1.5V alkaline, the system powers up. What do you guys think the issue is? Do I need to input a stable voltage/current?

I have linked the products below:
Boost converter: http://www.ebay.com.au/itm/DC-DC-USB-0-9v-5v-to-5vdc-Boost-Step-up-Power-Supply-Module-Mini-PFM-Control-DA-/151285075110?pt=AU_B_I_Electrical_Test_Equipment&hash=item23394b0ca6&_uhb=1

Solar panel: http://www.ebay.com.au/itm/351022647345?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649


texts: Using LTspice to simulate common-mode signal interference in a differential amplifier?

texts:
I'm experimenting with differential amplifiers, and I'm trying to simulate some ways that the common-mode rejection ratio of a DA in the real-world would be decreased. (In other words, ways to increase the common-mode gain of the DA). I've already been able to do this one way by imbalancing the input resistances, which reduced the CMRR, but I'd like to do it with some external interference as well.
I've found out that two types of common-mode signal interference are:

noise signals due to a difference in ground potentials at the transmitting and receiving locations
noise signals due to capacitative, electromagnetic or inductive coupling/interference from external sources

I'd like to be able to simulate one or both of these noise signals on my DA inputs, but I'm not sure how? The first one with differing ground potentials - would that be as simple as connecting the DA and the source signals to different -Vcc terminals? For example one connected to -15V and one connected to 0V? Or am I misunderstanding that?
For the second one, I tried to introduce some magnetic interference with inductors on each input signal (using the images in this previous post reply), but it didn't do anything. Any advice?


texts: How important is gate delay when designing a Circuit?

texts:
First year EE student here, we've been learning about CMOS Inverters in class and about the of logic gates, but it hasn't really been mentioned how much this effects the design of a Circuit in industry and whether it's something that Engineers have to take account of every time they design a circuit with a gate?
If it is, is this something you model using computer software before designing a board?
Was just interested in some feedback on how much gate delay effects design


texts: What is the minimum input voltage to turn on the Transistor?

texts:
Attached is the snapshot of the circuit I am working with.

My aim is to find the minimum input voltage to turn on the transistor (T)

With the following assumption, voltage drop across the resistor R1 is very small,

Vin > 2.7V + 0.6V  ( Zener voltage + drop across V_BE)

That is, minimum input voltage should be minimum of 3.3V to turn on the transistor (T).

Questions

Can someone verify the calculation?
How will calculation changes if drop across R1 also need incorporate?


texts: How can I estimate TL431 output voltage swings based on datasheet alone?

texts:
I am trying to design a series-pass regulator that brings 12V down to 3.3V. If I see a 20 mA step change in current, I would like to stay within a certain output voltage range (±2%).

What parameters in the datasheet can help me figure this out? I see the stability boundary condition charts in the datasheet (p. 17, bottom left, for example) and understand how they work, but it's not clear to me how to characterize changes in the output voltage when a single step change load is applied or shed.

Any suggestions?


texts: Is 1.8V UART compatible with Beaglebone Black?

texts: I want to use a 1.8V UART cable with my Beaglebone Black? Is it possible as typically the Beaglebone supports 3.3V UART level. I am aware that I can use a level shifter for this purpose, but my application needs minimal circuitry and I don't want to use a level shifter. Is there any other possible solution for this?


texts: How can I find a replacement LED to repair RJ45 tester? (re: SMD size, measured with multi-meter)

texts:
I'm trying to fix an RJ45 (CAT5/6 lan cable) tester and I need to replace some LEDs and diodes (SMD and not through-hole).

The tester has 8 LEDs (one for each wire) and only a few are blown so I tested some good ones with my multi-meter.

The LED on the multi-meter showed 1.8v forward voltage and measures 2.0mm x 1.3mm so I'm assuming 0805, but how do I know the correct replacement without knowing the current?

There is also another component which I think is a zener diode.  (black with a white line on one side).  It measured 0.6v forward voltage and 1.7mm x 3.15mm so I'm assuming 1207 size.  Can I replace with any 0.6v forward voltage diode?

Here are pictures of the PCB:

Thanks!


texts: How long will a 32v 15A (500Wh) e-bike battery last outputting at 5V 1A?

texts:
I hope it's okay to ask this here

My e-bike has a Lithium Ion battery (32 Volts, 15 Amps), and it has a USB-A output, marked as 5V and 1A,

I have 3 questions:

How long will this battery last while charging a USB device at the full 1A output? (I'm assuming the reduction in Voltage causes this 15A pack to run longer than my 25A USB power bank?)
If my USB device tries to draw more than 1A (like 2.4A), will it put pressure and damage the e-bike battery? (I know less/more Ampers can't damage my device as long as the Voltage is 5V, but not sure if the e-bike battery will be damaged)
If I use a converter directly connected to battery's 32V output (not the USB output) can I have 220V at maybe 60-100 Watts? or will this damage the battery?


texts: How can I make a latch in AVR without interrupts?

texts:
I want to make a simple circuit that when you press a pushbutton, an LED lights up stays lit until the button is pressed again. I haven't delved into interrupts yet on AVR, and was wondering whether it is possible to do in a while loop.

This is my code:

#include <avr/io.h>

#define INPUT (1 << PINB3)
#define OUTPUT (1 << PINB0)

int main(void)
{
    DDRB = 0x00;        //everything input
    PORTB = 0x00;       //no pud

    DDRB |= 0x1;        //PB0 is an output
    PORTB = 0x00;       //PB0 is low and PUD is off

    uint8_t prev = PINB;

    while(1)
    {
        if ((prev & INPUT) < (PINB & INPUT)) {      //rise edge
            if ((PORTB & OUTPUT) == 0x0) {      //if output was low
                PORTB |= OUTPUT;        //make output high
            } else {
                PORTB &= ~OUTPUT;       //make output low
            }
        }
        prev = PINB;
    }
}

The switch only partially works, I'm guessing because of the nature of the while loop and it storing the previous input really fast.

I believe the problem lies in my method of detecting a rising edge of the push-button. What would be a better method?


texts: Home Automation using Arduino and Android

texts:
I have been doing home automation for my home using Arduino and Android. I have been able to control the device through WiFi successfully.

Here is the scenario.

Since all the appliance that I control has been pre-wired when my house was built, it can be controlled through physical switches from switch board.
Also I can wire up the appliances to control through my Arduino WiFi.

My problem is how to get the status of the appliance? If I switch ON the appliance through my Arduino, I will know the status of each appliance that I control. But how to get the status of the appliance that has been controlled through physical switches? Is there any electronic circuits available to get the physical status of the switch? Thanks in advance.


texts: Connecting primary of two stepdown transformers in series

texts:
My aim is to get 12 volts output from a Stepdown transformer for a circuit I need to construct. Supply voltage at home is 220 volts AC. I can simply use a stepdown transformer available in market. But some times the supply voltage gets doubled (440 V), which can burn out the primary of transformer.

If I take two similar transformer with primary rated for 220V and secondary for 24Volts,  and connect the primary of both in series, then naturally the output voltage will be dropped from 24V to may be nearly 12V. But here I may have benefit to protect my transformer from higher voltage fluctuations. I will take output from only one transformer. The second transformer will just act as a resistance in series of primary. Please comment ...


texts:
I am designing a small network deployment for several buildings without temperature regulation.  In planning the power, I can find very little about acceptable UPS batteries for these conditions.  Lead acid batteries won't handle the year-to-year temperature changes (potentially -10°F to 115°F  [-23°C to 46°C] indoor at site), and I have found very little about alternatives that would be appropriate to provide for "turnkey" UPS solutions like a 2U rack-mount UPS (12V F1/F2 terminal).

It seems like there are a lot of batteries out there that do work in temperature extremes, but they haven't really reached the UPS market.  There are some Lithium Ion and some Lithium Iron Phosphate batteries that claim to work with existing UPSs.

If I drop either of these types in a standard UPS (1, [2]) that is not quite rated for the temperature (most are rated for 22°F to 110°F [-6°C to 43°C] ), would this be safe and last a few years?

I also haven't found much discussion on these kind of scenarios, at least from a networking perspective.  Is there any obvious information I am missing?

Update

I settled on including two thermostat switched 50W heaters in the cabinet, about 5 inches below the UPS.  It is ventilated, but I think these should keep the batteries above freezing.  Leaving this question open, as I don't think this is really an answer to my overall question.


texts: Why use a transistor for getting a Constant Current Source in a circuit with an op amp?

texts:
I have used the above simple circuit for a constant source where \$V_{\text{in}} = -5\$V, \$R_{\text{in}} = 390\Omega\$, \$R_f\$ is the load which ranges from \$110\$ to \$170\Omega\$....would using this circuit for a constant current source for the load be recommended?

As current $$i = -\frac{V_{\text{in}}}{R_{\text{in}}}$$ $$V_{\text{out}} = -V_{\text{in}}\frac{Rf}{R_{\text{in}}}$$ so it should serve as a constant current source, but while browsing the Internet for a constant current source I typically found these sorts of circuits:

Is there a compulsion to include the transistor in my circuit? If yes, why wouldn't my circuit serve the purpose for producing a constant current?


texts: How best to connect two optical limit switches to share one I/O pin

texts:
I'm trying to build a CNC laser engraver using a scrap industrial CNC gantry as a donor. The system already has optical limit switches for the max & min on each axis. I can't use the current controller because it is propitiatory and doesn't accept g-code. Also the wires are already cut!

I would like to use GRBL and the Arduino Uno as the controller for this system but this means only 1 I/O pin for combined max/min limit control per axis.

The limit switches are this type: http://www.farnell.com/datasheets/110958.pdf

They are LOW when the limit flag enters the switch.

How can I connect them so that they will be compatible with GRBL? https://github.com/gnea/grbl/wiki/Wiring-Limit-Switches

Would the attached image work as a circuit by having both limit switches share the same I/O line in parallel? Will the transistor in the limit switch be able to sink the other to ground?


texts:
I would like to determine in software if the PWM output signal is currently high or low.

As far as I know GPIO_ReadOutputDataBit(GPIOD, GPIO_Pin_12) does not work with a GPIO pin set up as an alternate function (AF).


texts: Can I use jumper cables to display my LEDs far away from the breadboard?

texts:
Apologies for a possible very newbie question.
I would like to create a small circuit using a breadboard and a 6V power source.
My goal is to have 10 LEDs running in parallel (each with its own resistor). So far so good : I have watched some tutorials and it seems to work on my end.
However, all the tutorials show the LEDs planted directly on the breadboard. I need them to be up to 50 cm away from the breadboard, and I'm not sure how to connect the LEDs with the breadboard.
My attempt so far has been to put each leg of an LED into the female end of a male-female jumper cable, but since the LED leg is thinner than the hole I tape them together with electrical tape so that they stay bound together, which sounds sub-optimal but works.
I have seen this answer that suggests an insulated hookup wire but it sounds overkill, at least in my newbie eyes : all I seem to need is a jumper cable but with a narrower connector. Is my reasoning correct?
If so (and if not as well), what cable can help me display the LEDs away from the breadboard without using tape?


texts: Can rain damage a device so it drains more power?

texts:
I have a Kindle e-book reader. It got wet while camping in a rain by my stupidity. After the rain, it would not turn on and would not even charge from a powerbank, but it picked up after I left it in a wall adapter overnight twice. However, the capacity of the battery was much less (I would say it went from 3-4 books to one book worth of reading). I bought a new battery. However, the new battery gets depleted as fast as the old one.

Can it be because of the rain? I would assume water would make the device unusable, or would damage the battery, but is it plausibly possible it somehow made the device drain more energy? Another option is that my (non-Amazon) battery is really bad, but I find it suspicious that the capcity seems to be about hte same as the old battery.


texts: I have a 20A ESC, I have connected it to the brushless dc motor as shown in picture. When i apply a 1ms + signal with rate of 50hz it produces beeps but doesn do any thing. i have connected the wire to mc as; the red one to +5 black to gnd, and white to MC for apply pulse. where am i doing it wrong.


texts: How to connect attiny to serial port so that I can use it with Arduino IDE

texts:
I have sucesfully assembled a circuit to use Arduino UNO as a programmer for ATtiny13. However, my plan was to only burn bootloaders to my ATtinys, so that I can program them the very same way I program an Arduino.
Now, I have these parts you can see on the image:
And now, there are two questions that are bothering me:

Is this enough to make a docking station for ATtiny?
Which wires from the serial port should I use?


texts: I recently bought this product. I would like to know what the best way to solder something such as a wire to those metal leads. Any suggestions?


texts:
Can someone explain or give an outline of how the indicators on chargers work?

I have a charger for a device, which displays a red light when connected and not fully charged, but after it is charged it becomes green.
I am guessing it has to be with a voltage checker (maybe a transistor), but can someone explain how they work?


texts: Why does op-amp output impedance / parasitic input capacitance pole cause a noise peak?

texts:
I was simulating the above circuit in LTspice...  I realize the main problem here is the 2MHz peak (which should be fixable with proper compensation), but I'm curious about the smaller 398kHz peak that's seen in the output noise density plot.  This matches up perfectly with the pole that is created by the LT1028 parasitic input capacitance and output impedance (5pF, 80 ohms).  What is the mechanism of this creating an output noise peak though?
I understand that input capacitance increases the noise gain of an amplifier.  However, I'd like to understand why this creates a peak in the noise rather than just an increase in the noise level.


texts: The simplest "adaptive" downward level shift solution?

texts:
I want to build a level shifter circuit for the RX pin of my ESP-12S. The goal is to convert any level between 3.3V and 5V to 3.3V as I might use many USB to UART breakout boards with different output pin level. I tried the divider solution:

simulate this circuit – Schematic created using CircuitLab

But it won't work for 3.3V input as the voltage will drop to a value that's below the minimum acceptable voltage for a logic "1". I want to keep the solution as simple as I can, and I do not want to use level shifter chips. What can I do? Thanks for suggestion.


texts:
I am trying to program an STM32F7 series MCU on a custom PCB (migrating over from a nucleo dev board) but I am having trouble connecting to the MCU. Using STM32CubeProgrammer (the new programming software) I get the error "DEV_NO_DEVICE" and the logfile reads:

12:45:54 : ST-LINK Firmware version : V2J29S7
12:45:54 : Error: ST-LINK error (DEV_NO_DEVICE)

The GUI reports that my target voltage is 3.22V and I have 'connect under reset', 'hardware reset' and 'SWD' selected on the options panel.

Interestingly, I can update the firmware of the board by launching the update window with the STLINK-V2 unplugged, replugging it with the window open and then beginning the update. Beginning the update procedure with the board plugged in results in the error "ST-LINK is not in the DFU mode. Please restart it". The first time I updated, I was able to connect to the chip (I didn't program anything at the time), but not since.

EDIT: Thanks for the answers/suggestions. My spare ST-Link V2 adapter arrived today and trying my luck with that actually solved the problem! Must have been a bad adapter.


texts: How is Crystal Oscillator implemented in digital circuit to generate clock frequency. What part of crystal oscillator makes the clock signal?

texts:
How is Crystal Oscillator implemented in digital circuit to generate clock frequency?
What part of crystal oscillator makes the clock signal?
I know the fact that crystals has its resonating frequency, can someone explain what happens to the voltage at one end and the other end of crystal?


texts: Material whose dielectric constant * [dielectric strength]^2 > 20,000,000,000

texts:
I'm looking for a material or compound, whose dielectric constant multiplied by the square if its dielectric strength (MV/m) is greater than two billion at temperature from -20C to 100C.

It doesn't matter whether the individual values of dielectric strength or dielectric constant are high or low, I'm only interested in the final value.

Also frequency is not a consideration, since this is not for AC use.


texts: pcb board to board connector dealing with ground current

texts:
Recently I am designing 2 separate pcb. one of them will be controller with low current signal paths and the other one will have mosfets to control high currents(about 10A). I am thinking of connecting 2 boards with a board to board connector. I need to carry 3 signal paths, ground and 12V to the controller board. I have a regulator on controller board regulates 12V to 3.3V. both has own ground plane.

the question is I am not sure about connecting grounds with a standard male-female headers, on the controller side I have IC's with multiple ground connections. is there any possibility to occur ground loop, ground current? if yes how can I prevent? is there any special connector types or circuits that does the trick?

the power supply will be plugged into the high current side of course and I am talking about something like this:


texts: Purpose of attenuation before op-amp input

texts:
What is the purpose of putting attenuation circuit before op-amp input? I cant find the actual reason for this topology. Is there any reason behind it? Why we need to attenuate the incoming signal but at the end we amplify it.

Signal input -> attenuation circuit (reduce incoming signal level) -> op amp input (amplify signal level)

sorry for late response.

I attached my circuit diagram.  Basically it just a simple voltage source (from MIC)  + bandpass filter with positive rectifier (range within 5KHz bandwidth)  and this signal will input to ADC for detection.

Based on circuit below, I confirmed the attenuation and gain

Attenuation level : -15.56dB
Gain level : 29dB

If based on above level, can we just set gain of the amplifier to be 13.44dB (gain level - attenuation level)?

I'm thinking to reduce the component used by deleting the attenuation circuit before the amplifier input.

.


texts: Likely places to look to find cheap sources of FPGA? Which devices should I open first?

texts:
I have a large group of new and old devices and I would like to find a FPGA to start poking around on. What products or types will be likely to have FPGAs in them?

I recently asked this question on the reverse engineering stackexchange, but was directed here and thought the question would benefit from the original source that has inspired my search:
http://www.youtube.com/watch?v=VY9SBPo1Oy8


texts:
I'm building a controller for project that has hobby servos. These typically need ~5V to run. The controller will be an ATmega 2560, running at 3.3V / 8MHz. Looking at the reference design for the Arduino board that uses the same ATmega chip, they're using a 1 amp LDO to regulate input voltage down to what they need.

The question has two parts:

If I need both voltages available to me, I assume I should just use two voltage regulators, set for their respective output voltages. Is there a reason to daisy-chain them (feeding the 3.3V one from the 5.0 one?) or should I have them both pull from the battery (12V)?
Given that I'll be running this off a battery source that'll be somewhere between 9 and 12.4 volts (a 3-cell LiPo battery), should I use an LDO, or a buck regulator (I'm a bit out of my depth when it comes to power management). For some reason I'm thinking that an LDO will not be as efficient as a buck regulator at what seems like a substantial voltage difference.


texts: Christmas LED dimming circuit with potentiometer

texts:
I need help.
I would like to dim LEDS of a Christmas tree with a potentiometer.
Here is my electric diagram. (Please note I'm a beginner in electronics.)

I don't know how to choose a good value for the potentiometer. Is my diagram correct?
I noticed that by adding a resistance in series on the postive side of the out powering cable I manage to lower the brightness of the tree, the goal of the project is to be able to adjust the brightness with the potentiometer.
Here is a picture of the power supply.

The Christmas tree 31V P=3.6W


texts: What sensitivity of reed switch should I use?

texts:
For my GCSE Engineering project, I am building a device which attaches to the frame of a bike, and uses a magnet (Attached to the wheel) to detect 1 turn of the wheel (I have also compensated for contact bounce etc.) The only problem I face is that I have never used reed switches before, and I don't know what sensitivity of reed switch to use.

Assuming the bike wheel is 2150mm circumference, the max speed is 13 m/s, the magnet diameter is 50mm and it will be 180mm from the centre of the wheel, I calculated that (hopefully) the smallest amount of time the switch will be directly passing the magnet is 0.0037 seconds.

I thought this seemed like a very small amount of time for a switch to close and open again before 1 rotation is over. A 1AT switch apparently closes at the north pole from the earth itself, so just to be safe i want to avoid disaster from it being too sensitive. Does anyone know what type/sensitivity of reed switch to use?


texts: What does this NPN BJT circuit represent, is it a switch or just a PN diode, and what should this plot look like when we sweep the value of Vbe, and why?


texts: How do I procure SoCs in small quantities?

texts:
I want to design an SBC but I am having difficulty with buying the SoC. I'm thinking of Snapdragon, Mediatek, Allwinner, Amlogic and Rockchip (These are the ones I know, if you know others I would appreciate it if you tell me)

I tried Digikey and Mouser and my search was fruitless. How do I procure such chips in low quantities?


texts: Is feedback transfer function the same as the transfer function for the whole circuit?

texts:
I have a circuit very similar to the inverting band pass filter circuit here:

I was asked a question about the circuit's feedback transfer function. Is this the same as the transfer function for the whole circuit?

Which I calculated to be this (for the circuit above):

$$\frac{V_0}{V_i}=\frac{j \omega R_2 C_1}{1+j \omega R_2 C_2 + j \omega C_1 + \omega^2 C_1 C_2}$$


texts:
Here is what the documentation has to say:

— Command: reset
— Command: reset run
— Command: reset halt
— Command: reset init

    Perform as hard a reset as possible, using SRST if possible. All defined
    targets will be reset, and target events will fire during the reset sequence.

    The optional parameter specifies what should happen after the reset. If there is
    no parameter, a reset run is executed. The other options will not work on all
    systems. See Reset Configuration.

        run Let the target run
        halt Immediately halt the target
        init Immediately halt the target, and execute the reset-init script

From OpenOCD Commands

I open OpenOCD, then in another terminal I run arm-none-eabi-gdb end execute monitor reset halt in order to tell the target to reset and halt the processor, in order to later setup braekpoints and run.

However, the responce from the processor is often different:

(gdb) monitor reset halt
JTAG tap: sam7x512.cpu tap/device found: 0x3f0f0f0f (mfg: 0x787, part: 0xf0f0, ver: 0x3)
srst pulls trst - can not reset into halted mode. Issuing halt after reset.
target state: halted
target halted in ARM state due to debug-request, current mode: FIQ
cpsr: 0x600000d1 pc: 0x00000050
NOTE! DCC downloads have not been enabled, defaulting to slow memory writes. Type 'help dcc'.
NOTE! Severe performance degradation without fast memory access enabled. Type 'help fast'.

Other times, it goes this way:

target state: halted
target halted in ARM state due to debug-request, current mode: Abort
cpsr: 0x600000d7 pc: 0x00000044

Yet another times (within the same run, I just opened gdb and run monitor reset halt a bunch of times):

target state: halted
target halted in ARM state due to debug-request, current mode: Undefined instruction
cpsr: 0x600000db pc: 0x00000038

What are those states?


texts:
I am trying to fit a umo wire into a ac power transformer.
Turns out the jumper wire is just a little too thin.
Any practical ideas on how to fatten them?

I considered dipping them into molten solder.
Or then i thought maybe this wont work, so i thought heating individual small parts of solder, then attaching the jumper wire end to fatten it, then continuing to do so gradually, until the whole jumper wire end is fattened?

Any ideas? Or is there anyone who has dont this already and succesfully?


texts:
I have an hx711 ADC module with 4 50kg load sensors wired in a wheatstone bridge (for a maximum load of 200kg).
When I apply load to the sensors, the resulting values for increasing weights appear to be non-linear, which is the opposite of what I would expect.
I've tried connecting the module to both a Raspberry Pi and a Wemos d1 mini (esp8266) and get the same results each time. I've also tried rewiring the bridge in different configurations, but only one gives any results.
The results I see are as follows:

0kg: 498,000
1kg: 500,000
10kg: 505,000
25kg: 530,000
100kg: 550,000

As you can see the 'correction factor' to grams is approximately:

result / 500 / weight in kg

Is this likely to be a fault with the ADC module, an issue with wiring, or something else I'm doing wrong?
The ADC module spec: https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/hx711_english.pdf
The load sensor spec: https://ae01.alicdn.com/kf/HTB1ZDtuKXXXXXX9XVXXq6xXFXXXI/201492522/HTB1ZDtuKXXXXXX9XVXXq6xXFXXXI.jpg
Wiring schematic (sorry for poor quality - not used the tool before!). The load cells are connected:
1: red -> E-, Black -> 2, White -> 3
2: red -> A-, Black -> 1, White -> 4
3: red -> A+, Black -> 4, White -> 1
4: red -> E+, Black -> 3, White -> 2

simulate this circuit – Schematic created using CircuitLab
The voltage in (VCC) is nominally 5V - measured at 5V on RPi, and 4.8V on Arduino. The Excitation voltage is always 4.17V, regardless of VCC. I don't have accurate enough multimeter to read A+/-.


texts: Layouts - would a joint at 1 point, or 2 be the same?

texts:
I'm currently trying to lay out my first from scratch project on veroboard. While I get connecting things in series and parallel I'm trying to work out if a + shaped connection and a pair of + shapes would be equivalent.

Would they?


texts: Power and energy measurment for embedded system -help needed

texts:
I am trying to measure the power consumption of a low power embedded system. As the embedded system consumes current in random pulses from the battery pack, I am using an oscilloscope to analyze the signal. The blue graph represents current consumed over time.

I want to know how I can go ahead and find out power consumed with respect to the time varying current consumption graph.Various modules in the embedded system consumes current in varying random pulses and I have similar graphs for each operation. How can I accurately measure power consumed and eventually find energy for each specific operation?


texts: Using Li-Po or LiFePo4 for diy motorcycle battery

texts:
Basically just after opinions on using LiPo or LiFePo4 for building a diy motorcycle battery. My current lead acid battery just died and i'm sick of replacing them after 1-2 years.

Background info - Bike is a 2007 BMW F800S with a 400W alternator and 14.4V peak charge voltage. From what I can gather online, the system puts out closer to 13V at idle and has enough current to run everything off the alternator alone at idle.

My problem - LiFePo4 has low current ratings, and LiPo has impractical cell voltages.

Doing some research the lithium motorcycle batteries you can buy online all use LiFePo4 as a 4 cell gives the right voltage range, but they seem to most commonly have a 4 series/2 parallel setup (A123 cells) which gives about 140A peak -  this is below the current lead acid battery which does 200A.

LiPo on the other hand will easily do >200A from a small pack (easy to get packs with C ratings higher than 100) however 3 cell is impractical as the fully charged voltage is 12.6V (lower than alternator output) while a 4 cell pack would mean the resting voltage per cell is around 3.5V, which is close to the discharge voltage on these packs.

Possible solutions;

Use a LiFePo4 pack in 3 parallel config (along with a passive balancer) to give the current. The pack would remain connected at all times as the chemistry is relatively safe. this would mean 12 cells however which is getting expensive compared to lead.
Use a 3 cell LiPo with diode isolator. Essentially use a diode to connect the battery only when the alternator is not running, and along with this use a simple regulated trickle charge balance circuit to keep the pack topped up.
Use 4 cell LiPo and keep the cells at low charge all of the time by using a LiFePo4 passive balancer to keep them balanced at the lower cell voltage.

At this point im leaning towards trying with A123 in 2 parallel and see if it has the cranking current to start the engine easily - this is the tried and tested solution - but would be very keen to give it a go with LiPo.

Thoughts?

EDIT

The bike runs well and the alternator is fine, it just does not get ridden much at all so the lead battery discharges itself. I have a battery charger and can easily sit the battery on charge when it is not being used, but the battery sits behind a large fairing which is a pain to remove, so would rather not have to do this ever time I want to use it
As far as I am aware, the existing alternator should easily provide the current needed to keep a lithium pack at full charge, as long as a balance circuit is used (passive current shunt). I have started the bike many times off a 3 cell LiPo and to start the bike uses very little of the pack (2200mAh) so I doubt the pack would ever see a high depth of discharge


texts: I'm trying to work on a prototype wearable indoor and I am really confused as to how I am going to transfer data fetched from the GPS device to the server. Is GSM module the best option or should I go for WiFi? How can this be achieved and what are my best options?


texts:
I understand how to make state diagram and make combinational logic (gates) to get a boolean equation for the next state bits and the output bit,

but what is the function of ROM here ?


texts: Self Balancing Robot using Computer Vision

texts:
I'm planning to implement a Self Balancing Robot which is usually implemented using a gyroscope sensor which gives feedback to the micro-controller to adjust the position with wheels. I'm looking into an option of controlling using Computer Vision (OpenCV).
Firstly, looking at a similar project PID algorithm implementation using computer vision
i'm convinced that it is not quiet easy to implement without the right tools and good concept.

I have an Arduino Uno board which i will be using for controlling the DC motors. I still have to decide on the Embedded System board which i should be using (Mostly ARM Processor based, like Raspberry Pi, Beagleboard etc), the selection of processor depends upon the speed of the application. A webcam mostly, but i'm looking into other cameras as well.
CMUcam

Control algorithm used will be PID implemented in the Processor. The bound box is what i intend to use to observe the change in motion and then use error correction via a Ethernet port or wireless depending upon the speed needed.

Please do comment about the drawbacks and flaws of the design.

OS of the processor : Linux distro (Ubuntu or Debian), initially i thought about RTOS(Real Time OS), but i guess it is too complex.

Need your valuable feedback.


texts: What is the best way to approximate average current or count battery amp-hours?

texts:
I'm using an INA214 current sense opamp to measure current flowing through a 100A shunt, which is on the low side of a 12V battery bank. The readings are stable under stable load, but vary greatly when the load is either pulse-width modulated, or AC via an inverter.

When I aggregate the opamp output (mV over the shunt = current levels) and calculate the average, the readings are again relatively stable. However, it seems necessary to have a very high sample rate, thus occupying the MCU almost constantly.

Is there a simpler/better way to get a value that represents average current (Ah/h)?


texts: Is it possible to input DC PWM signal to a transformer?

texts:
I need to create a 100-120V 50mA output from a transformer.

I do not need continuous steady output (no need DC 120V a 120V pulsating signal on output is enough.)

N1/N2=1/12.2
secondary impedance 1.2kOhm
primary impedance 8Ohm
The primary current is limited to 0.75A.
-The frequency response of transformer 10Hz to 10kHz.
PWM signal is from STM32F103C8 microcontroller 3.3V DC (PWM frequency 20Hz-1kHz)

I have the following doubts:

Will a 12V DC PWM signal create 120V and 50mA on secondary winding?
Following is my schematic. Is it possible to workout?
Back EMF from the transformer primary winding - do I need a diode across the winding?

The main purpose of this circuit is built a transcutaneous electrical nerve stimulation machine as shown in http://chemelec.com/Projects/Tens/Tens-2-Rev-4.png

Turns Ratio
N3 2-3: 0.11 gage 380 turns

N2 1-2: 0.11 gage 380 turns

and
N1 4-5: 0.21 gage 60 turns

I am using 1-3 (output 120V generation) and 4-5 (input 12V)here.


texts: Are present state and next state equal between two clocks?

texts:
I know things that happen every time clock ticks. Present state and inputs are delivered to the combinational circuits and it produces the outputs and the next state information and sends the next state to the memory elements. Then memory elements(e.g A SR flip flop) read the S and R signals and lock the Q on a new value based on them.

The thing that I don't understand is what happens until the next clock? It seems that there's no apparent obstacle/isolation between the next state and the current(present) state in this time interval... Are they equal until the next clock?
Of course still everything else make sense to me and this is not contradictory to anything I knew about memory elements and flip flops and etc... , because actually, at every clock-tick moment, information from memory elements are read from one epsilon moment before, and the combinational circuits have a delay too, so for a special moment the present state and the next state are different and are really what their names suggests, but in the middle of two clocks, my defective understanding says they should be equal... .