texts: Routing Current to Many Individual Channels

texts:
Possible Duplicate:
  How to implement an isolated connection matrix

I need to put current on up to 30 lines; one at a time.  What kind of electronics solutions are there to this kind of problem.

I can't drive it directly with a microcontroller because I need 28 VDC.

Response to Comments:

28 VDC
Less than an amp of current
Only needs to switch as fast as a human can press a button. maybe a few times per second max.


texts: Can analogue Hall sensors be used in BLDC for static angle measurement?

texts: Everything I have read on using Hall sensors with BLDC motors appears to use latching hall sensors which provide repeatable latching angles as the magnetic fields change at specific angles. I am wondering if an analogue hall sensor can be used to provide intermediate angles for static angle measurements are ever used? And if not then why?


texts: Is it a bad idea to plug the other end of ESD strap to wall ground?

texts:
I have gone through this answer on Superuser, while it provides good information, I still have a specific question from electrical/electronics engineering point of view.

Is it wrong and unsafe to connect the other end of the ESD wrist strap to the ground point on the wall socket?

What harm can it do and if it’s wrong, why?

I was watching a Youtube video about assembling computers by a user who seems to be a professional and he says he has been in the business for over 2 decades.

The video discourages connecting ESD strap to wall socket ground, it also says that when you connect ESD strap to metallic part of cabinet, remove the power plug from the PSU. However except a reasoning that you could get electrocuted with such a setup, no further technical explanation is given.

I have worked in an IT company that was TL9000 quality certified. This standard demands ESD protection deployment wherever necessary. All relevant test benches there had ESD mats connected to common ground. All terminals had a point to plug the ESD strap’s other end and all those were connected to ground and eventually going to the earth pit. So discouraging  ESD strap connection to wall socket ground (that ultimately goes into the Earth pit) is a totally new concept to me.


texts:
We have a piece of industrial equipment using a phase angle controller (PAC), and are having some issues calculating the RMS power used by the load.

Personally I am of the opinion that you measure RMS voltage and RMS current on the line side of the PAC. This gives you line RMS * PACed current. Assuming a duty cycle of 50%, this gives you 50% of full power. My reasoning is that this follows Kirchoff's law, and that power in is approximately equal to power out on our PAC (efficiency is >90%).

My colleague suggests that we measure the RMS voltage and RMS current on the load side, after the PAC. Assuming a duty cycle of 50%, this gives 50% current and 50% voltage and we end up measuring 25% of full power. His reasoning is that the load isn't conducting for the off section of the cycle, so the applied RMS voltage is lower.

The former gives us a linear ramp from 0 to 100% duty cycle, the latter gives a non-linear response. Assuming our power factor is 1, our mains supply and PAC signals are clean, and the RMS calculation is correct at the crest factors we're working at (it better be, I designed the sensor), which calculation is correct?

Thanks!


texts:
I need to identify an SMD diode on a PCB. Does anybody know what it is?

Its marking code is 96, there are some dot codes above digits.
Its polarity is marked with three lines.
-Its dimensions are 3.5 x 2.5 x 1 mm.
Its role is freewheeling diode parallel to a solenoid.


texts: I am a novice in signal processing so there may be a fundamental gap in my understanding of the concept. I am working on a link which has an error of 1 in 1000 bits which I have to improve to 1 in 1000000 bits? Would a 50% error correction FEC technique be useful? Please suggest a suitable FEC technique.


texts: I found an over-current protection schematic, but I am confused about how the base of the Q3 is wired. Is it connected to a potentiometer? If so, to what terminal?


texts: 478 MHz band, allowed for hobbyist use in USA?

texts:
Somebody advised me to look at this wireless module as a lower-cost alternative to xbee.

I noticed that it operates on the 478 MHz band.  Is this band permitted for hobbyist use in the United States?


texts: Can I create a backside "copper polygon" of the switch node in an SMPS?

texts:
I have an SMPS design that has the following properties:

9-15V input voltage
5V, 3A output
Switching frequency is 350kHz.
Switching controller is a LM25085.
The diode used is a DSSK48-003BS.
The switch is a FDS4953.
It's schematic is as follows (will be bigger if you click, opening in new tab recommended):

Here is the top copper layout. In this layout, bottom copper is a ground fill:

I know that increasing the copper area on the switch node will give me more EMI since it will be a bigger antenna then. Also, I know that breaking a ground plane will make the return loops follow a way rather than "right under the trace" which will yield in an increase in the loop area which will more open the doors to EMI, in addition to that, it can cause a ground bounce if the ground return has high \$\dfrac{dI}{dt}\$, like the return from the diode back to the input capacitor's ground.
With those in mind, if I create a cutout in the ground plane right under the pad of D1's cathode, which is the 2nd pin with a big SW on it on the bottom right of the PCB, and fill that cutout in the bottom layer with copper that is connected to the cathode of D1 with lots of thermal vias to create a heatsink, what are the advantages and disadvantages?
Also, can you critique my SMPS design?
Edit:
My PCBs arrived and it seems like I have connected my MOSFET wrong. I have exchanged drain and source connections, so it didn't work. Dead-bugged the MOSFET and soldered again. It doesn't work after 150mA at Vin=12V and after 130mA at Vin=10V. I have checked the MOSFET is working and changed the controller IC just in case, but no luck. Hope I will solve the problem..
More Edit:
The problem was my dummy programmable dummy load. It couldn't measure the voltage correctly and its min. input voltage was set to 5V. I set the minimum input voltage to 3V and the design is working very good now.


texts:
I'm working on a low power (portable) audio mixing console, fed by audio signals from MP3-Players and mobile phones.

There should be an option to monitor the sound, but as soon as I route one sound from the op amp's imputs to a headphone, it gets attenuated in the mix (of course).

I thought about having a monitor switch that is DPDT and can switch between a dummy-headphone-load and the actual headphones. Is this possible?


texts: What is the simplest analog circuit for integer addition modular 2?

texts: This probably is a rudimentary question. I would like to have a simple analog (switch) circuit for addition modular 2, or \$a_1+a_2+\cdots +a_n \$ (mod 2). Certainly, digital transistors can accomplish this, but I would prefer analog devices if the circuit is simpler. In practical terms, I would like to design a switch circuit to control a light, where fixing all other switches, any one of them can switch the light on and off. For \$n=2\$ or 2 switches, someone earlier has already suggested using two back to back single-pole-double-throw switches.


texts:
I've got a PCB (from a multimeter) that apparently has 2 traces on the PCB burned away.
How they did it, I don't exactly know, but the traces are really gone completely.
The problem is however, that these traces disappeared up to a via they were connecting to...

So little graphical representation("=" = trace, "-" = disappeared trace, "o" = via) : =====-----o

Another complication: if I would solder a small wire through the via, it can't protrude at the other side, because the other side are the sliding contacts of the dial of this multimeter.

So, who's got the best option to repair these traces? Thanks!


texts: Problem with testing 74ls173AN D flip-flop

texts:
I'm building a simple 4-bit computer (a Nibbler) from 74 series ICs on a breadboard. Right now I'm working on 74LS173AN IC registers. I can't make it work. I have connected the input enable (pin 9,10), output control (1,2), and clear (15) to ground and some data inputs to vcc. The output pins (Q1-Q4) are connected to ground via LEDs. I'm simulating the clock signal by swithing a tact-switch on/off (with ground connected by 10k resistor and direct connection to VCC.

I tried different connections and searched web (many hopes with https://www.youtube.com/watch?v=9WE3Obdjtv0&t=14s, but it didn't help). Nothing works. I suspect there might be a problem with clock signal, but I would really appreciate the opinion from an experienced electronic specialist.


texts: Mosfets as a switch for batteries in series

texts:
I am contemplating a way to build a new battery pack for a project that I am working on. However I think that I have run into a problem, but I am not sure.

I have a battery pack with about 27 batteries in series and 15 strings in parallel, as seen in the picture below (just a small sample), My goal, is to isolate (at least down to a small leakage current) a single battery in the pack in case it falls out of safe operating range.

I am thinking about using N-channel mosfets for this job, but I don't know how well they will work in this type of circuit.

Will this work? If not, what would?


texts: DC Resistance of Cat5e Cable and Type 2 PoE

texts: I see that the PoE Type 2 standard assumes a maximum loop resistance of 12.5 Ω/100 m, but cat 5e is specified to have maximum loop resistance of 18.8/100 m Ω. Does this mean that PoE type 2 is not guaranteed to work over the full 100 m Ethernet range supported by Cat 5e?


texts: Supercapacitor or battery with capacitor

texts:
Maybe the question that I ask is completely dumb because I am a complete noob in this, but please help.

So first off, my question is that if I want to charge a 2.7v 500F supercapacitor, can I charge it using a 5v solar panel which practically produces less than 2.7 ( possibly around 1.5 - 2v ), or say a hand crank which too produces a very small amount of voltage but possibly some decent current?
Will I be able to charge the supercapacitor much faster by increasing the voltage or the current?

Second, if I want to use it for charging a phone (the 500F supercapacitor), how long will it take to charge my phone with, say, a 4 AH battery?

Third, the main idea I had about a supercapacitor was that it can acquire all my charges quickly and store it for a considerably longer time than a capacitor, so why not first use a capacitor which would acquire my charges very quickly and then use these capacitors to charge up my battery slowly? Is that even possible?


texts: Measurement of Resistor Parasitics Inductance and Capacitance

texts:
I have seen people doing some measurements of parasitic capacitance and inductance of some resistors, by using a vector analyzer and analyzing the graph of S11 with respect to frequency.

To get this measurement they have soldered the resistor to a type N connector, and that connector has been connected to one port of the Vector Analyzer.

My question is: how can this measurement be correct? It is like putting the resistor under test in parallel to a 50Ohm resistance (since the characteristic impedance of the type N connector was 50Ohm).


texts: LCD cbc016002A29 backlight resistor value

texts:
I'm trying to connect a cbc016002A29 LCD to 5V, and the tutorial I'm following says:

  Next we'll connect up the backlight for the LCD. Connect pin 16 to
  ground and pin 15 to +5V. On the vast majority of LCDs (including ones
  from Adafruit) the LCD includes a series resistor for the LED
  backlight.

  If you happen to have one that does not include a resistor, you'll
  need to add one between 5V and pin 15. To calculate the value of the
  series resistor, look up the maximum backlight current and the typical
  backlight voltage drop from the data sheet. Subtract the voltage drop
  from 5 volts, then divide by the maximum current, then round up to the
  next standard resistor value. For example, if the backlight voltage
  drop is 3.5v typical and the rated current is 16mA, then the resistor
  should be (5 - 3.5)/0.016 = 93.75 ohms, or 100 ohms when rounded up to
  a standard value. If you can't find the data sheet, then it should be
  safe to use a 220 ohm resistor, although a value this high may make
  the backlight rather dim.

Now I'm looking at the datasheet of the LCD and I cannot figure out if the LCD contains a resistor, or not, and where to find the maximum backlight current and typical backlight voltage drop. I suppose I should be looking somehwere in these two lines, but I have no idea what's the difference between array/edge values:

Here's the datasheet I'm looking at:
http://pdf.datasheetcatalog.com/datasheet/vishay/016m002b.pdf


texts: Calculating the unknown charge using the \$2\$ remaining charges in this arrangement

texts:
The overview of the problem and the solution and my thoughts are as below.
"/*" represents about my comment.
We'll handle the \$3\$ point charges in the vacuum.
Firstly the \$2\$ charges are arranged in the same straight line.
The remaining \$1\$ charge is positioned at the above of the mid point of the line segment of the previous \$2\$ charges.
The concrete values of it are as below.
\$q_1:=5.0*10^{3}[C]\$(left side charge of the line segment.)
\$q_2:=-5.0*10^{3}[C]\$(right side charge of the line segment.)
\$q_3:=?[C]\$(magnitude of the top charge)
\$x:=2[m]\$(distance between the \$q_1,q_2\$.)
\$y:=1.5[m]\$(distance between the \$q_3\$ and the any charge of the line segment)
\$f:=8.0*10^{5}[N]\$(force which is created from the \$3\$ charges at the top charge.The direction of it is horizontal from left to right)
Firstly the official answer says that the top charge is a positive charge since \$f\$ is horizontal from left to right.
/* Currently I am unable to get the above statement. */
\$f':=\$the amount of the force between the left charge and the top charge.
\$f'=\frac{1.5[m]}{2.0[m]}*(8.0*10^{5})[N]\$
/* Thought that the approximation of the triangle of the degree of \$45\$ of \$1,1,\sqrt 2\$ was taken. */
\$k:=\frac{1}{4*\pi\epsilon_0}\$
Lastly,\$f'=\frac{k*Q_1*Q_3}{y^2}\$ is true ,so the value of \$Q_3\$ is able to be calculated.
Is it true when the top charge is negative then the direction of \$f\$
will be horizontal from right to left?
If so,please tell me why this could be proven.
Can anyone tell me that why the charge of the top side is positive?


texts:
I am testing out the lock in amplifier with just a single resistor, but there seems to be a downward drift in the in phase voltage. What could possibly cause this to happen? Could it be some grounding issue?

Thank you for your time.


texts: Does each I2C START signal need to be closed by a STOP signal?

texts:
Could two I2C START signals be sent one after another without a STOP signal sent in between? Below is an example of bit banging, where there is not STOP between the first and second START:

int16_t BMP180_readRegister16(uint8_t reg) {
  i2c_start();
  i2c_writeByte(BMP180_ADDRESS);
  if(!i2c_check_ack()){
    i2c_stop();
    return(0);
  }
  i2c_writeByte(reg);
  if(!i2c_check_ack()){
    i2c_stop();
    return(0);
  }
  i2c_start();
  i2c_writeByte(BMP180_ADDRESS+1);
  if(!i2c_check_ack()){
    //os_printf("slave not ack..\n return \n");
    i2c_stop();
    return(0);
  }
  uint8_t msb = i2c_readByte();
  i2c_send_ack(1);
  uint8_t lsb = i2c_readByte();
  i2c_send_ack(0);
  i2c_stop();
  int16_t res = msb << 8;
  res += lsb;
  return res;
}

Doesn't each START sequence have to be closed by a STOP sequence?

Thanks


texts: Ground wire in custom capacitance-dimmable metal lighting fixture

texts:
I'm wanting to design my own lighting fixtures, both for cost effectiveness as well as the design appeal (inspired by a particular designer's lighting fixtures) that uses a wooden base with metal pipes as the structure.

The lighting socket and wiring itself will be 3-conductor, and in the fixture I plan to have a touch-based (capacitance/metal sensor, not reverberation) dimmer controller.

I have verified all of the ratings are within compatible ranges.

The fixture itself will structurally be made up of metal pipes with the light sockets at the end of them (outside the ends of the pipes, not inside - the sockets have casing and everything). The metal pipes will serve as the sensing line's conduit, and consequently the light 'switch'.

My concern is with the grounding. Obviously I'm going to want to ground this thing since the majority of it is going to be metal - especially since the 'switch' consists of touching the metal piping.

However, does this mean by grounding the metal parts, I'll be shorting out the dimming mechanism thus rendering it useless? Or should I have a dedicated 'switch' piece of metal that is not in contact with the rest of the fixture?

Otherwise, should I be focusing more on insulation versus grounding in this scenario?

As per requested, here is a basic schematic:

simulate this circuit – Schematic created using CircuitLab


texts: in Eagle, how to exclude SMD pad from the tCream layer

texts: In Eagle, how do you exclude SMD pads from the tCream layer such that in gtp there is no pad there?


texts:
I'm trying to use daisy-chaining feature on three MAX5318 DAC's.

However, I'm not sure how to do it properly. Do I need to turn CS low, then write 9 byte to SPI DIN, then double-trigger LDAC? Or to double-toggle LDAC after each 3-byte transmission?
Tried all variants, both seems to don't work. Googling internet, I find daisy-chaining with paralleled CS, not DIN, so I can't figure out how to use paralleled DIN version of daisy-chaining.


texts: Switching 240V A/C source between two loads with relays

texts:
I need to swich a single US 240V (hot-hot-ground) power source between two A/C motors, 20 amps max, with an option of disconnecting both. For this project, design aesthetics is very important and I want to use a 3-position selector switch with 90 degree index. Looked all over the net, could not find a fitting selector (rotary) switch that would be rated at 20+ amps 250+V, so I'm looking to use a selector switch that cannot carry the full load, just for switching. The switch I'm looking to use is Grayhill 50K90-01-1-03N that is rated for 75ma at 220Vac.

This necessitates using a DPST power relay, I'm looking at Omron G7L-2A with 240Vac coil. The wiring diagram is roughly as following (sorry, newb here):

...with the following caveats:

a) I couldn't find a 3-position switch widget so the "off" position is missing in the diagram,
b) the load schematic is simplified,
c) double pole relays are intended specifically to break both hot legs from the power source to the load. I couldn't find a way to reflect that in the wiring diagram.

My question is, are the switch and 2 relays the only parts that I need to wire, or do I need something else to limit the current through relay coils?


texts: What does the resistor do when the second switch is closed?

texts: When the first switch is closed, the capacitor charges to 5V. When the second switch closes, capacitor discharges and Vo will rise upto 0.25V, I calculated. However, my question is, when switch 2 is then opened and switch one is closed, resistor is open. What happens to the 0.25V across it? how does it drop off? suddenly or gradually? why? Thanks in advance.


texts: bluetooth: Can i connect multiple hc-05 slaves to one hc-05 master?

texts:
I am completely new to the bluetooth world so please bare with me.

Can one hc-05 be the master and connect to multiple hc-05s slaves? I've done a lot of research and some say it can and some says it can't. It's making me super confused.

I'm working on a project where the master will connect to one slave whenever I call for the master. The other slaves will be on standby. So is it possible to do the connection with hc-05? Or do I have to use other bluetooth modules in the market? And what's the maximum number of slaves that can be connected to one hc-05 master? Thanks in advance.


texts: Why do PNP silicon transistors cost more to produce? NPN is cheaper?

texts:
I got a few suggestions/answers but nothing definite after searching and digging around awhile .. I am not so sure about any of these so correct any of them that you see

Thanks

    Alex Van den Bossche · Ghent University
    Yes, speed is one thing, but a PNP transistor requires 3 times more SI chip surface, so it gets uneconomical when the chip costs are a big part of the component.

    Silane diborane and phosphine gases all react differently .. it is more difficult to control borane p-type doping of silicon also the impurities in polysilicon (it can never be completely pure) act as n-type dopants .. so for quality p-type silicon you have to get much purer polysilicon so n-type silicon is easier
    -- On the Enhancement of Silicon Chemical Vapor Deposition Rates at Low Temperatures - chang1976.pdf

    My last guess was that it is just economics of scale .. NPN are simply far more mass produced so supply and demand .. but it had to start out that way for a reason


texts: Should I use Magnet Wire as a conductor in this experiment?

texts:
I need to run a few wires from a HMC5883L compass sensor to a micro-controller to process the data. Can I use magnet wire to carry the signals from the sensor to the micro-controller or would the signals between the wires interfere with each other?

There are about 5 or 6 individual wires running from the sensor to the micro-controller. Is this a bad idea or should I get some thicker wire?

The team is just worried that the signals might cross over. This is the last part of the experiment that we need to do and we just want to know if the wire will hold up.


texts: Pad with 4 pins in allegro cadence (orcad)

texts:
Sorry for silly question, but how to draw pad with four pins? It's not just a custom shape of pad, it has 4 pins.

Thanks


texts: How to do insulation resistance measurement on a SMPS

texts:
Can anyone explain how to measure the insulation resistance of an isolated SMPS PCB?

Is it correct to tie ACL and ACN and apply one terminal there, and the second terminal goes to the ground of the secondary part of the circuit? or Do I need to test between ACL-ACN, ACL-Secondary Ground, ACN-Secondary Ground? Do I need to test ACN-to the plastic enclosure of the PCB as well, or is it only needed for AC Dielectric Withstand Test?

I am using Farnell's brand Megohmmeter(looks like rebranding from uni-t)


texts: Simulating a TI microcontroller in Spice

texts:
I have bought a microcontroller from Texas instruments: MSP430F6779. I would like to simulate in a circuit along with other components: resistors, op amps, sensors..

What program allows me to do that? I have searched the spice library for microcontrollers on ti.com but it is not there... Does anyone have an idea?


texts: Can I "sum" internal ADC channels to achieve extra bits resolution?

texts:
First of all I am a newbie in electronics.

I am building some weight scale applications using (as seen everywhere) load cells wired to a HX711 ADC and a ESP8266. I am now giving a try to the Texas Instruments CC1312R MCU (datasheet), still work in progress :)

The CC1312R features include a 8 channels 12-Bit ADC. My needs require at least a 16-Bit ADC.

Since this internal ADC provides 8 channels, I was wondering if I could somehow serialize them to achieve some extra bits resolution, thus not having to use any external ADC, is that possible?

Thanks for your help!


texts: Keep an Arduino Nano and 24 WS2812Bs alive if the power drops for a second

texts:
Im working on a project for a pinball machine, working on a arduino controller and beacon boards to replace old filament flashers,
The supply voltage to the new arduino controller and beacon board will be drop out from time to time for a max of 1 second, this is because the old LEDS would flash.
The project is to replace the old filament lights with the master board and light beacon (both PCB) that is always on regardless if the power drops for a second.
Is there a way that i keep the master and the beacons powered even when the power drops for a second.
the light beacons are 6 WS2812b-minis with their own 100uf capacitors
the master board is 1 arduino nano with 2 dip switches
the light beacons are powered by the master board though IDC cables


texts:
I plan to run about 4-5 arduino pro micro in my backyard to handle controlling of solenoid valves for garden watering based on measurements of soil (so we keep it well watered).

My question regards the supply voltage, I wish to use cat 6 over maybe a 20m run in total to supply both power and RS485 networking over the twisted pairs.

Based on previous answers regarding cat6 I know the amperage should be fine assuming all arduino even run full without sleep around 45mA that's some 250mA.

The solenoid valve says 8w at 12v which is 0.6A, assuming the current is required to keep it open (not closed - is this correct?) which I'd hope so otherwise loss of power would cause it to open.

I guess I'd need to run 12v anyway, should I run 12v and 5v down the pairs? If I run just 12v I need a linear voltage regulator, which get quite hot does that mean they are inefficient? If I run 5v as well, how well does 5v perform over that distance due to voltage drop on cat6 pairs?


texts: I want to generate two references pulses (Rising and Falling) generated from rising and falling edges of the reference pulse clock signal.  How can I do this with CMOS logic ?


texts: Resistor getting hot - up to 50°C. Is it an issue of the resistor wattage or nature of the resistor?

texts:
I am using an FOD817DSD optoisolator.

According to the datasheet:

CTR: 300% - 600% @ 5 mA
VF = 1.2 V (typical) @ If = 20 mA.

We have 10 optoisolators on the PCB which is connected to some other board IO pins. There is no proper information on required IC for the third party board. I assumed max 15 mA is sufficient for any digital IOs.

I have used 12 V supply through 1k SMD resistor (tried with 125 mW, 250 mW, 400 mW) to the optocoupler input. Voltage on input pin is 1.15 V (I can get 1.2 V If the resistor is 540 ohm, but heating > 50°C) and collector voltage is 5 V, everything works fine. But all 1k input resistors are getting heated up to 50°C. Even though I tried with 400 mW resistor.

I found this formula in the datasheet, CTR =(IC / IF) * 100%.

IF=(12 V - 1.2 V) / 1k = 10.8 mA But am getting 1.15 V instead of 1.2 V. So power dissipation in the resistor is P = 10.8 * 2 mA X 1k = 117 mW. I have used more than 125 mW rated resistors. Why is it getting hot?
As per the formula “IF” should not exceed 17 mA because given IC max is 50 mA. What then is the meaning of "VF is 1.2 V @ IF is 20mA" as mentioned in the datasheet?
The heating is the same for both 125 mW and 400 mW rated resistors. What is the role of resistor wattage here?
If we use higher wattage resistors will they also heat up to the same temperature or will the heating be reduced?
Is there something wrong with the circuit? Will heating break the resistor or reduce its performance? How I can reduce the heat?


texts: Best way to install arm-elf-gcc onto a Linux machine

texts:
Hey folks,
I'm working on a device using arm-elf-gcc to compile code for a MakingThings prototype board.  My development machine is a Linux box running Ubuntu 9.10. On a different linux box using Ubuntu I got arm-elf-gcc running ok by manually building and installing gcc, after 3 or 4 tries.

I'm trying to pick the best way to install the toolchain, but there doesn't seem to be a best way AFAIK. Setting up on 9.08 and 9.10, both seem to fail except for when I manually build and install the environment.

I have tried  Emdebian packages and CodeSourery, and neither of those worked well.

Does anyone have any other good suggestions for doing an arm-elf-gcc setup on a Linux box?


texts: What would be the combined dielectric constant of two dielectrics in series?

texts: Let's say we have two parallel conductor plates. In the middle, there is not one but two layers of dielectrics made of different materials. If we know the relative permittivity of each dielectric, how could we couple it to get a single dielectric constant?


texts: Constructing a sine wave generator circuit using LTSpice

texts: I am trying to make this particular Wien Bridge Oscillator (WBO) circuit using LTspice. Ideally I should get an output sine signal. Although I can't seem to make it work. Anything wrong with what I did here? It only shows this straight line with no change in Amplitude.


texts: What does this circuit with an analog video signal to the emitter and a TX signal to the base of a an NPN do?

texts:
The CAM1_AHD is the signal coming from a camera and it goes to the TVI receiver as well as to the emitter of the transistor. The video signaling scheme is analog. The TVI receiver is TP2825 and in the datasheet the pin 42 which is what the PTZ_TXD is connected to, says "Upstream data signal output. Unconnected when not used".

The TVI receiver is modeled as shown in the screenshot below


texts: MSP430G2553: measure the voltage of a non-rechargeable 3.6V battery

texts:
I am designing a circuit to measure the voltage of a non-rechargeable 3.6V battery. This battery powers the microcontroller (http://www.ti.com/lit/ds/symlink/msp430g2253.pdf) with which I want to measure its voltage.I simulated both circuits and they seem to work, which do you think is better? Thanks in advance.

simulate this circuit – Schematic created using CircuitLab

Mosfet 1: http://www.onsemi.com/pub/Collateral/2N7002L-D.PDF

Mosfet 2: http://www.onsemi.com/pub/Collateral/BSS138-D.pdf

Mosfet 3: https://www.infineon.com/dgdl/Infineon-BSS84P-DS-v02_07-en.pdf?fileId=db3a304330f68606013118ac7a9b4549

Best regards,

Fran Martin


texts:
I've designed a gate drive transformer, but I'm not sure if I did it right, so I need approve from experienced ones so I can send design to dealer for production.
Transformer is a double ended(3 winding) gate drive transformer, I'm going to use two of this transformers to drive a full bridge. Ratio is 1:1:1, frequency is 30kHz
Here is the core information:

When I drive a single mosfet with 12V totempole, it drain 0,1A from power supply and each transformer will drive a half bridge so two mosfets, that means 0,2A.
so I calculated required AP first= ((0,2A)x12V) / ((0,017)x(0,2T)x30kHz) = 0,0235cm^4 AP required.(0,017 is a constant I found from some sources for full bridge applications, since each transformer will be driven with two totempoles(push-pull) that means a full bridge will drive transformer, my assumption.)
than I calculated the AP from core= AexAw = (0,124cm^2)x(0,23cm^2) = 0,0285cm^4 AP.
Since the AP from the core is greater than the required AP, I assume core is suitable.
than I calculated the turn = 12V/(4x30kHzx0,2Tx0,0000124) = 42 Turns. (0,0000124 is Ae in m^2)
finnaly I calculated inductance with = 12V/(2x3,14x30kHzxL) = 0,2A, L=0,3mH
so it become, 42 Turns each winding with 0,3mH inductance with the core I attached.
am I doing right?


texts: How to wire a phocos any-grid inverter 220 v 60 HZ with two wires to a water pump 220 with 3 wires (split 220 v)

texts:
How to wire a phocos any-grid inverter 220 v 60 HZ with two wires (European style) with one hot wire 220 v and another ground, to a water pump 220 v with 3 wires (split 220 v,  two 110 v hot wires and ground) US style.
Phocos ANY-GRID HYBRID INVERTER Charger PSW-H (5 KW) 48 v batteries, 220 volts output


texts: perfect square wave cannot be played back

texts:
If I produce a square-wave by creating a sine wave first and then doing,
if x >= 0 return 1, else return -1
this produces a "perfect" square wave(python code).
Like this the audio signal cannot even be played back.

But if I slightly randomize the signal
if x >= 0 return rand(0.9999,1), else return rand(-0.9999,-1)
it works.

Even though I'm confronted with this in the context of programming
I assume that people from this forum will know the answer.


texts: How to find the resistance of a diode operating in reverse breakdown region?

texts:
I am tasked to find the small signal resistance of a diode operating in reverse breakdown region (not forward bias).

  Method 1: Is using the small signal resistance formula correct even in
  the reverse breakdown region?

  $$r_d = \frac{nV_T}{I_D}$$

  Method 2: The I-V curve in reverse breakdown region seems to be
  steeper than the curve in forward bias region. If I use the derivative
  of current w.r.t voltage, then the resistance is close to zero due to
  the steep gradient.

Which is correct, or are they both wrong? If so, how do I go about solving this?


texts: How to create a smart 3-way positional switch?

texts:
Looking at this switch as an example: https://www.directindustry.com/prod/tacthill-kynoppe/product-192123-1963276.html
I have a similar 3-position switch in my garage that controls a water pump. Central position = off, down = permanently on, up = timer.
My goal is to replace this switch with a smart switch that I can incorporate into my home automation. Ideally I'd love a z-wave compatible one, but I'll just be happy with any if it stops me having to visit this switch regularly.
Does anyone know if there are such a smart switch, if not, maybe I could build one even with an arduino if need be, but it'd be nice to not have to buy all those parts, particularly the z-wave transmitter.
Any guidance at all on how I could achieve this goal would be great.
Thanks


texts:
I have a choice of voltage (6VDC, 12VDC or 24VDC) to power a solenoid component rated at around 2.5W.

Depending on different voltages, it will result in different current consumption (ie. I@6VDC = 2.5/6 = 0.417A)

I will have a grid of 100 solenoid devices powered via a single external power supply (reverse current protected). This means that other components will not be impacted by my voltage & power solution.

If in the end of the day, the energy is consumed in Watt-hours, what are the reasons why one would go for 6V, 12V or 24V?


texts: Problems programming LPC1343 microcontroller in Ubuntu

texts:
When I copy a binary that works on a lpc1343 to the mounted usb-device representing the lpc1343 flash, the binary file is changed and does not work. Doing the same with the flash mounted via usb on Windows or Mac OS does not have the same problem. What could be the problem, and how can it be fixed?

Edit: The problem seems to be the vfat implementation in Linux which seems to prefix 0s before the file to be transferred.


texts:
I had posted about my project earlier in this forum:

PID algorithm implementation using computer vision

Now I am currently stuck in a stage whether I am concerned whether I chose the wrong actuator.

The stepper motor controller needs input in terms of number of steps and time duration of rotation. I find it very difficult to estimate a base scale to do the calculations as my angle of tilt varies according to both the parameters. I had been discussing this with someone and he suggested that I use a servo motor because I was planning to use the OpenCV Kalman filter algorithm. According to him, if I plug in my motor commands into my input vector matrix, I can actually get a value between 0 and 255 that could be used to operate my servos. I am looking forward to hear your thoughts whether I should switch to a servo or try using a stepper.

My main concern is that my maze's ball keeps spinning back and forth even for a small tilt in the maze and I am not following a standard approach in determining the tilt required for my maze to go to a point


texts: Is it possible that my UV LED is emitting white light? If so, how would I filter out the white light?

texts:
I recently purchased a 365 nm UV LED, and set up the proper circuit.  When I turn the power on, the LED lights up very dimly.  Is this white light (that's the color I saw) being emitted from the LED? If so, are there any methods (preferably inexpensive) for blocking out only visible light?

The specs for the UV LED can be found here:
http://www.mouser.com/ds/2/228/LZ1-00UV00-257812.pdf


texts:
I have a board I'm working on with a coworker; we are debating whether to go 4-layer or 6-layer board, and would like to use 6-layer but haven't found a reasonably priced fab house.

Is there any reputable PCB fab house out there that has good pricing on small-quantity (3-10 pcs) 6-layer PCBs? (approx 5"x6", nothing fancy) The best we've been able to do is about US$700, whereas there are specials on 2- or 4-layer PCBs that are in the $200-$300 range.

clarify background info: the board has 3 widely-used nets = AGND, DGND, +5V, which basically spells 5 layers, and there doesn't seem to be much advantage to 5 vs. 6. We've looked at sharing the AGND and +5V layers, that's an option; we've looked at routing the +5V by hand, that's an option; we've looked at combining AGND and DGND nets and living with the noise. The right thing to do from an engineering standpoint is a 6-layer board, but if it's going to be 2x the price it may be cost prohibitive given our particular situation (further details are beyond the scope of this forum).

clarification: (the board was made last year for $$$, but the question is still valid)

I asked about 6 layers and I meant 6 layers. The background info is only for educational purposes. As far as cost tradeoff judgement goes, here's where I was coming from:

For a shop that is interested in high-volume ultra-low-cost, you can either spend more time to design a 4-layer board well because of layout constraints, or rush through a 4-layer board design and hope it works.

Same thing for a hobbyist without much money wanting low quantities.

For a shop that is interested in time-to-market, you can either spend the money and use a 6-layer board, or rush through a 4-layer board design and hope it works.

We were in the middle, and had a coworker who was leaving, so I had to go with something that worked; we didn't have time to respin. Cost turned out to be not as much a barrier as I thought, but in some situations I get flak from management when cost is high, and it's really helpful to have a modest price option so I don't have to deal with that.


texts:
I have connected a SST26VF064B 8Mb flash memory IC to an ATMeag1284 as shown in the following diagram. My plan is to talk to it using SPI.

Note that all capacitors in the schema are 100nF.

When reading the JEDEC ID I do not get the expected values. First I set the SS line to low, then send the command 0x9F, then read 3 bytes (by sending 0xff dummy data) and finally pulling the SS line to high again. The datasheet tells me the ID should be 0xBF 0x26 0x43 for the specific device I have (see page 24). I suspect something is wrong with my SPI connection. However, the Oscilloscope reading of the SCK, MOSI and SS line look as expected. Also my code correctly decodes the pattern on the MISO line as 0x7c 0x20 0x6f. You can find the Oscilloscope readings below.

Furthermore I tried to read the status and configuration with the 0x05 respectively 0x35 commands. However, both of them return just 0x00. According to the datasheet at least the configuration register should contain a 1 in factory settings at the 3rd bit.

The following code is run on the ATMega1284:

#define F_CPU 8000000UL

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

void setSSLow() {
    // Drive SS to low
    PORTB &= ~(1<<PINB4);
}

void setSSHigh() {
    // Set SS to high
    PORTB |= (1<<PINB4);
}

void SPI_MasterInit(void)
{
    // Set SS, MOSI and SCK output, all others input
    DDRB = (1<<PINB4)|(1<<PINB5)|(1<<PINB7);
    setSSHigh();

    // Enable SPI, Master, set clock rate fck/128
    // Sample on rising edge, output on falling
    SPCR = (1<<SPE)|(1<<MSTR)|(1<<SPR0)|(1<<SPR1)|(0<<CPHA)|(0<<CPOL);
}

char SPI_MasterTransmit(char cData)
{
    // Start transmission
    SPDR = cData;
    // Wait for transmission complete
    while(!(SPSR & (1<<SPIF))) ;

    char receivedData = SPDR;
    return receivedData;
}

char buffer[3];

int main(void)
{
    SPI_MasterInit();

    // Send 'Read JEDEC ID' command
    setSSLow();
    char status = SPI_MasterTransmit(0x9f);

    // Get data
    for (int i=0; i<3; i++) {
        char data = SPI_MasterTransmit(0xff);
        buffer[i] = data;
    }
    setSSHigh();

    _delay_ms(1000);

    while (1) {
        // Do nothing
    }
}

SCK and SS

SCK and MOSI

SCK and MISO

I'm now at a point where I can't think of anything else to do to try and debug this issue. I would be very helpful to any help you can provide! This is the first time I'm using SPI and it is very hard for me to debug hardware as I have a software background.

UPDATE 1

I double checked everything today and everything looks correct to me. However, I still get the same output when reading the JEDEC ID. As mentioned in the comments below, it is a repeating byte sequence:

7c 20 6f 84 0d f0 81 be 10 37 c2 06 f8 40 df 08 1b e1 03

As I had the same chip in the 16 pin housing I quickly soldered a breakout board together and replaced the chip. Surprisingly I get exactly the same behavior. I definitely think there's something wrong the way I do it, but I don't yet see how...

UPDATE 2

As I already mentioned in the comments, I managed to get the Memory chip working in with an Arduino. So I investigated further. I loaded the code I used on the ATMega1284 directly on the Arduino. And guess what: It worked out of the box. So there must be something wrong with the ATMega I'm using. Additionally I quickly wrote a software SPI implementation using other pins then the ones used by the hardware SPI. And this works as well. I'll try to get my hands on another ATMega1284 and try with that one. My guess is that I broke something in the ATMega1284...

UPDATE 3

By accident I just managed to communicate to the SSTV26 using hardware SPI on the ATMega1284. I still had cables connected to SS, MOSI and SCK that were not connecting to anything else. When I touch these cables, the communication works. When I don't touch them it does not work. I suspect there's something floating. I don't have the tools at hand at the moment.


texts: Can I run 2amp/1.76v stepper motor on drv8825 driver?

texts:
I do electronics for fun and need help understanding the principles when coupling stepper motors and drivers!
I have this type of stepper motor: kh56km2u027 and a drv8825 stepper driver, and was wondering if they would run safely together.
In the motor label, it's written 1.76V 2A and the driver can operate on 8.2V-45V 2.5A(peak)
There are few things that get me confused, like:

Labeled amps -> does it mean that it draws 2A in total whatever the case? (so I assume the driver can run it)
amps-per-phase -> what's the difference when it's labeled: 2A and 2A per-phase?

Or is there anything else I'm missing here?
Thank you!
Edit: Forgot to mention that I power the driver using 12V/10A supply and the logic through Arduino board.


texts: Having trouble properly driving a MOSFET

texts:
I'm trying to build a pure sine wave inverter in LTspice (Image 1) but I'm running into some trouble. So far, it consists of three main parts:
The SPWM generator generates an SPWM signal from a 200kHz sawtooth wave and a 50Hz reference sine wave. This works fine, although it would be replaced by a µC in 'real-life'.
The second part is an isolated dual gate driver using the UCC21520, this is mostly based on the typical application schematic from the datasheet (page 27). There are two main differences: In my circuit, ground is in between the two 325v supplies while it's on the bottom in the datasheet. And in the datasheet, both outputs seem to be connected to the same supply, even though they're switching MOSFETs that are at different voltage levels, which seemed odd to me.
I think this part is working fine as well, even though the output (Image 2 and 3) does look a little wonky and contains big spikes at seemingly random intervals.
The third part is where I'm trying to actually drive the MOSFETs (C3M0075120K). On the output of the half-bridge, I would expect to see an amplified version of the output of the driver, but the voltage is dropping way too slowly after the driver goes low and doesn't even hit 0v before the next pulse (image 4).
The simulation also runs very slowly and often fails to converge at some point.
Download link to all required LTspice files:
Simulation.zip
Unusually hot MOSFET:
70w mosfet at 1kw out.zip
Image 1:

Image 2:

Image 3:

Image 4:


texts: How can I change a +/- 5V Sine Wave to a (0 to 5V) signal for an ADC

texts:
I've been digging into this for the past couple of days and I could really use some help. Here's the details:

Input: Sine wave going from +5V to -5V

Output(needs to be): 0V to +5V [0v when input is -5v and 5v when input is +5v]

I understand that I need to reduce the amplitude by 0.5 and there needs to be a +2.5V offset, I just don't know how to get there.

I've tried a few op amp setups with my 358 and 741 but have not had any success.
Any help would be much appreciated. Thanks!


texts: How to get the gain for this MOSFET amplifier?

texts:
This is a common drain MOSFET amplifier:

simulate this circuit – Schematic created using CircuitLab

This is its small signal model at low frequency:

simulate this circuit

I am at a loss as to how to find Vout/Vin. Vin, in this case, is just Vg not Vgs since the source node is not connected to ground.

My analysis:

Since all of the current source's current is going thru r0 from Vout to GND,

$$\frac{V_{out}}{r_0}=V_{gs}*g_m$$ or
$$\frac{V_{out}}{r_0}=(V_{in}-V_{out})*g_m$$.
After some algebraic manipulation, you get
$$\frac{V_{out}}{V_{in}}=\frac{r_0*g_m}{1+r_0*g_m}$$.

I know $$r_o*g_m=(\frac{\delta I_d}{\delta V_{ds}})^{-1}*\frac{\delta I_d}{\delta V_{gs}}=\frac{\delta V_{ds}}{\delta V_{gs}}$$.

I don't know what to do after this. My professor's solution says Vout/Vin=1. How?


texts: Replace laptop's usb surge protection chip

texts:
I am fixing an old laptop from 2008 (eMachine e525) on which everything works fine expect the 2 usb ports that are not powered.

I found this video¹ from Ingmar M. on youtube (very helpful video, thanks!) and I tried, like him, to desolder the 6 pin chip that is said by this user to be a surge protection component. Now the 2 ports are working fine.

I would like to know if I can replace this component so that I can safely plug usb devices. The problem is that I am not able to find a corresponding datasheet. The text on the tiny component reads (I think) "0635" on first line then "0926" on the second line. Orientation of the chip: the text is written alongside the longest dimension, if placed in reading position then the usb connectors are located north of it and there is an orientation dot in the south-west corner.

¹ Even if the video is about a e527 computer the motherboard looks identical to the one in my e525.

I used my multimeter in continuity mode to identify the pinout:

The 6 pin chip is visible in the center of the image:

Here it is removed:


texts: Turn 3 input nor gate into 4 input nor gate in d flip flop

texts: I am making a negative edge triggered d-flip flop using the schematic attached, I have already put in the reset (attached) but the reset needs me to have a 4 input nor gate, which isn't provided in the program I'm using. What I am asking is how I would turn this 3 input nor gate into a 4 input nor gate. I was thinking something like what I drew on the side of the diagram, but I don't know if it would work.


texts: L298 IC motor driver - how to wire and use correctly?

texts:
EDITED. I found that my supply of 3V was insufficient as there are voltage drops across the transistors. I replaced the 3V supply with 4.5V and the motor ran fine - although now my 3V motor has 2.5V across its terminals (3.3V to 0.8V). I did not think that DC motors exhibited any voltage drop since the current through their coils is constant. What can be done about this? And how would you calculate the voltage fed to the motor ANYWAY? I found it to be 3.3V simply because I measured it.

I have read over the data sheet for the L298 and it seems quite simple to use. Using one side of the chip (i.e. one H-Bridge) set IN1 to 5V and IN2 to ground to conduct from OUT1 to OUT2. Also, to enable the H-Bridge ENA must be 5V. That is all the wiring needed aside from some stabilizing/filter capacitors and flyback diodes.

So, to not mess with all of that I have simply purchased the Sainsmart L298 Driver module. Below is a photograph of the module and I have drawn on it to illustrate the pins that I have wired.

*Note that I have not included the 5V to ENA because (shown towards the bottom left) the board has some jumpers connected so the pin is always 5V.

Also, there is a state switch at the bottom right. From my experiments, and from what I have read, if the button is depressed (closed) then then VCC is tapped and regulated at 5V for the logic circuitry and the 5V (far right of the bottom screw assembly) can be used to power external circuits. If the button is OPEN then VCC is not regulated and you must supply an external 5V supply to this pin for the logic.

Now, my motor is only rated MAX at 3V DC, so obviously I have to leave the switch open and supply the two sources independently.

What I have noticed:

If I have everything wired up exactly as I have shown in the depiction below (but without the motor!) it works fine!

I have put a multimeter across OUT1 or OUT2 to ground as my microcontroller code executes (simply code to run one way then reverse direction), the polarity of the pin changes as expected.

If I place my motor across a 3V supply momentarily - it runs!

If I place the motor leads into OUT1 and OUT2 (after I have verified that the voltage polarity switches) nothing happens. Actually, the indicator LEDs that show direction (that were working prior) no longer light up with the the polarity of IN1 and IN2 changes.

What the heck is happening? Could it be that the board is not supplying the current required to turn the motors? These motors are quite small and the Absolute Max current draw of the L298 is 2A for a single bridge. I checked the datasheet for these motors and they draw 2.2A at stall and 300mA no load.

Here is the schematic for the actual L298 pin soldered to the above board. As you can see, the wiring scheme that I provided above should work just find. OUT1 should conduct to OUT2. The board just includes protection diodes and filter capacitors.


texts: Why is my LCD stop to work correctly when my pump is running?

texts:
I have a 8x8x8 lcd/led/button module (tm1638 chip) connected to my Arduino r3. When I attach a pump (GPH350, 1.5A, 12V to the same power supply (12V, 5A) - my display stops working correctly (only part of the text is displayed) (and sensor report invalid data).

The same setup works without the pump or when the pump is running on a separate power supply.

Is this because my power supply isn't strong enough? Isn't 5A enough? Is there anything I can except running 2 PSUs or using a more powerful one?

Can I prevent this by using a capacitor? How do I find out what size it should be?

Photo v1

Photo v2

Edit: I've changed my curcuit, added a 1N4148 and a larger capacitor. And there is a new photo.

Edit 2: Since there seems no way around buying an oscilloscope and the good people who've helped me on this are running out of ideas I decided to abort the mission. Thanks for all the help.

simulate this circuit – Schematic created using CircuitLab


texts: I have a battery charger that uses a 24VDC 300mA wall transformer. The transformer died, and the closest replacement I could find was 24VDC @500 mA. The new transformer did seem to charge the battery pack just fine, but the next morning it too was dead. Is it possible that the higher amp rating caused it to burn out? Or should I rather suspect that the battery charging circuitry has become defective?


texts: What kind of MOSFET use as a switch touch on, touch- off

texts:
What kind of MOSFET (or other component you suggest) will be the adequate to use as a switch (touch on, touch-off) with the following information:

Power In = 2.7 to 6.2 V when on.
Power out = close to zero when off.
Switch on = with momentary contact button with less than 6V and stay on until the contact of the same  momentary button to turn off (and stay off until the next momentary contact turn it on)
Power = two coin cell batteries component (CR2032 times 2) total 6V
Vibrator pancake motor Intensity = 100mA + LED = 30mA

If you could please advise me, it would be very nice. Thanks
Juan Marin


texts: Questions about the front end design of amplifier circuit

texts:
Question 1:

Recently, i'm working on a design which needs to design an INA front end. The most used circuit like this (please omit the component values):

You see, the two 10M resistors which provide the path for biasing current are at the most front of the circuit. But occasionally, i saw designs like this:

The 'biasing resistors' come to the back, just before the INA. Which one is right, or which one is better?

Question 2:

In ADI's application note: Designing Amplifier Circuits: How to Avoid Common Problems, they give a similar circuit:

And they suggest:

  In these circuits, there will be a small offset-voltage error due to
  mismatches between the resistors and/or the input bias currents.
  To minimize such errors, a third resistor, about 1/10
  th their value
  (but still large compared to the differential source resistance),
  can be connected between the two in-amp inputs (thus bridging
  both resistors).

They suggest to parallel a smaller resistor to bridge the unbalanced input. But why not reduce the value of the 'biasing' resistors directly. Are there any differences?


texts: SRAM works with short read cycles, fails with longer ones

texts:
I observe a rather weird behavior of an IS62WV51216BLL-55TLI SRAM chip connected to an FPGA. When I run it with the shortest read cycles possible, it works as expected:

(here, I read the expected value 0xCF9C3063. One tick is 6.25 ns)

However, when I try to use longer read cycles, it mysteriously fails:

(here, I read the value 0x136000D0 instead of 0x1360EC9F. One tick is 6.25 ns)

As you can see, the right data appears on the data bus at some point, but is quickly replaced by a bogus value. This happens sporadically at a different address every time, and re-reading the same address a second time works fine:

(here, I read the value 0x18E06439 the first time, and the expected value 0x18E0E71F the second time)

Does anybody have a reasonable explanation for this? Is there something wrong with my read cycle? Here's the read cycle from the datasheet above, for reference:

All my diagrams were made with SignalTap (logic analyzer built into FPGA) running at 160MHz. All output pins of the SRAM controller are registered:

// ** Output Pin tcm_address_out

reg                       tcm_address_outen_reg;

always@(posedge clk) begin
 if( reset ) begin
   tcm_address_outen_reg <= 'b0;
 end
 else begin
   tcm_address_outen_reg <= 'b1;
 end
 end

reg [ 19 : 0 ] tcm_address_out_reg;

 always@(posedge clk) begin
 tcm_address_out_reg   <= tcs_tcm_address_out[ 19 : 0 ];
  end

assign  tcm_address_out[ 19 : 0 ] = tcm_address_outen_reg ? tcm_address_out_reg : 'z ;

The tcm_address_out signal is then connected to the sram_addr pins seen on the diagrams above, which are in turn connected to the A0-A18 pins of the SRAM IC. Other pins are connected in a similar manner. The length of wires/traces between an FPGA pin and a SRAM pin is about 10 cm. The SRAM IC has 1uF + 100nF ceramic caps between GND and VDD pins of both sides.

PS. I have tried to keep \$\overline{CS}\$ asserted the whole time, which didn't improve things. I have also tried a modification where \$\overline{OE}\$ is asserted 12.5ns after \$\overline{CS}\$ and is deasserted for 12.5ns between consecutive reads (while keeping \$\overline{CS}\$). That didn't help:


texts:
Strangly when i insert an audio to audio cabel into the the smarthphone audio jack the multimeter shows me max. 0.1 V.

But if the cabel is just half inserted in the audio jack the multimeter shows me a Voltage of 2.4V

Can someone explain how this is possible and how much Voltage i can exepct from and smarthphone audio jack?

I am mearsuring between ground and mic on a headset connector.


texts: RFID race timing system using raspberry Pi?

texts:
I would like to build a race timing system using UHF RFID passive tags. I have seen self build systems described as per the following link which is being used in races with apparent success:

http://www.letsrun.com/forum/flat_read.php?thread=5518905

The major cost of such a system seems to be the rfid reader, so I wondered whether it would be possible to achieve similar results by substituting the commercial uhf readers listed with multiple raspberry pi 2b devices andlong range uhf reader module?

Is this realistic? What are likely to be the problems, constraints or deficiencies when compared to the commercial rfid readers?


texts:
I'm working on a project and read that decoupling caps should be connected across the VDD and VSS pins of PIC microcontrollers(or rather all microcontrollers?). I'm using a 9V battery with a 7805 voltage regulator as the source and have two decoupling capacitors connected with the regulator like so:

So do I really require the decoupling capacitors across the VDD and VSS pins or is it okay to not use them?


texts: How to adjust the brightness of a small LCD(21V) with a potentiometer?

texts: I want to adjust the brightness of a small LCD with a potentiometer. How can I use a 555 timer to make a PWM which can give out an output of 21V from a 5V input?


texts: Make my own microcontroller ARM M0 board: do I need bootloader?

texts:
I did buy one of these cheap all in one microcontroller, but instead of using a standard Atmel, like the ones on the Arduino boards, it uses a more powerful ARM M0 chip.

Now, I would like to buy my own M0 (picking a SAMD21G18)  and make my own board, exposing only the pin that I need, but I can't find info about a critical piece of info: How do you program the chip?

The board that I did purchase, has a USB to serial chip, I believe; and it has a rom with a bootloader, so when it is in a state, you can put code on it, while when in regular state, it execute the program.

I would like to do something similar, adding a USB to serial so I can upload firmware updates if needed; but I am not sure...could I program the chips in a different way, and save on the hassle to even put a serial to USB converter?

Also is there a standard bootloader that many arduino clones use? They all seems to work in the same way, with ARduino IDE; at least to my eyes.

Hope the question is clear enough; this is my first attempt at making a breakout board from scratch. Thanks.

Found this post which has some relevant info

https://web.archive.org/web/20150906201126/https://hackaday.io/project/7355-minimum-zero-compatible-sam-d21g18-d21e18-board

This person made a minimalist board with a SAM D21G18 chip; it show the finished product, some videos and schematics, so it is a good starting point.

From my findings, the chip has already the USB functionality, to upload on the ROM the code, but you need to use the Atmel own IDE. Still looking for details, but it is a good start.

Since nobody replied; I assume that nobody was aware of this link, so it may be useful to others.


texts: What should I do with unused USB differential pairs?

texts:
EDIT:

I want to interface with a legacy board through a high density connector. There are some USB lines on the connector that I do not wish to use.

These lines are connected to an FT232RQ on the legacy board. On each line there is 1k of series resistance and the data+ line has a 1.5k pull up to 3.3V.

On my new board should I tie these two lines directly to ground, together, or leave them totally unconnected?


texts: Complete synchronous USART implementation

texts:
I've been studying about USARTs and I haven't seen a consensus on synchronous USART implementation among MCU producers.

First of all, there are transmit and receiver clock lines on some serial connectors (e.g. 25-pin RS-232 connector). However, I couldn't find any USART device (within a MCU) which provides both of these lines.

Secondly, as far as I learn, synchronous mode doesn't define start and stop bits but some synchronous USART devices use these bits.

Thirdly, some synchronous USART devices, such as in PIC16F882 (page 171), use a bidirectional data line to transmit and receive data. Hence, only half-duplex synchronous transmission is possible with these devices.

I want hands on experience on a complete synchronous USART device using a common serial connector like 25-pin RS-232. Here are some ideas come to my mind.

Bit banging may be an appropriate way to study about protocol (but not device itself).

Custom hardware design would be a good experience but it's pretty harder than dealing with ready devices.

Combining two PIC16F882s, one for receive only and one for transmit only may be a solution.

My problem is I cannot find a complete(!) device to study USART, write some code, inspect registers etc. I need suggestions and I'm open to new suggestions and references.


texts: Passing control voltages to multiple isolated power supply channels

texts:
I'm designing a programmable bench power supply (PS) that has multiple isolated channels (each powered by a separate transformer winding).  I like the idea of isolated channels so that multiple channels can be connected in series to generate dual-polarity output (like -15/0/+15 V).  The idea was to use a microcontroller (MCU) to set the output voltage and current limits of each channel using analog voltages from the MCU's DAC (or an external DAC IC controlled by the MCU).  Given that channels are able to float with respect to one another, what would be the best way to ensure that the control voltages sent from the MCU to each PS output channel are properly referenced to the channel's voltage level?

The options that I've come across so far are to either:

(analog approach) use an isolation amplifier between the DAC and each PS channel
(digital approach) use a separate DAC IC for each PS channel and digital isolators to interface each DAC with the MCU.

I'm curious to know if there is a standard approach to this type of problem as I imagine that this comes up in many bench supply designs.  Thanks!


texts:
Am I correct in thinking that this chip has 0.5mm pin pitch? I don't know where to look for it on the details of the chip!

When I google for '144-LQFP' I found a link which suggests it is 0.5mm pitch but I would like confirmation!


texts: What are the risks of running a floating ground through insulated wire underground?

texts:
I've created a circuit that is powered with a floating ground off of a transformer.  I'd like to count pulses from a meter by having the meter complete the floating ground side of the circuit but I'm concerned about running insulated floating ground through the earth and what the implications might be.

simulate this circuit – Schematic created using CircuitLab


texts:
I'm working with PIC16F18855 and have some problem with select memory bank via BANKSEL. In listing I see strange message and it's not working properly.
0000   0020           00030         BANKSEL PORTA
0001   018C           00031         CLRF    PORTA
0002   0020           00032         BANKSEL LATA
0003   0196           00033         CLRF    LATA
                      00034
0004   003E           00035         BANKSEL ANSELA
Message[302]: Register in operand not in bank 0.  Ensure that bank bits are correct.
0005   01B8           00036         CLRF ANSELA
                      00037
0006   0020           00038         BANKSEL TRISA
0007   30FF           00039         MOVLW   B'11111111'
0008   0091           00040         MOVWF   TRISA
                      00041
0009   30FF           00042         MOVLW B'11111111'

ANSELA is a part of BANK 30/
This code I took from Datasheet for PIC16F18855. I've used MPASM 5.87.
Sombody knows whats the problem?


texts:
I am attempting to build a simple circuit to to control sound on my Android phone.  All the controls are accomplished by tying a control pin to ground, so all I do in between is just about resistance and pulses.

1 button press=play/pause
2 presses=skip forward
3 presses=skip back

obviously play pause is easy, I just need a switch, but for the others I want a separate switch I can just press once, meaning in pressing it, it should close the circuit, open it, close it, and open it again in order to skip forward.  the durration is not critical, it just has to happen withing a couple seconds and the pulses must be probably 100 milliseconds apart or so.

SO, how might I go about this?  the circuit needs to be small, so avoiding IC's would be good, but I feel like I am at least going to need a timer.


texts:
I'm designing a system with an ARMv7 processor. My host processor support SDIO protocol and I wish to use this unit to connect the host to a Memory card and a WiFi module that both are compliant with SDIO Card Specification Version 2.0

My question is, What is the difference between simplified and full version of SD Memory Card Specification and does simplified version adequate for the above case or I need to buy full SD Specification somewhere down the road.

Note: We are not going to sell this product so I don't have any concern about the legal issues.


texts:
Background:
       1.5% of products which use STM32F107 didn't work after using 3 months; Lithium battery is the power supply source. The products were used in car. This phenomenon suddenly occured without any pridication. According the record in product, the temperature is normal(25 Centigrade).

Problem Analysis:
       The voltage at VDD is 3.3V. The NRST reset do not work. After disconnecting the power and connecting again, the chip could recover and work again. And this problem could not be reproduced in our lab condition.

Additional information:  the chip use STANDBY mode to shut down and use WAKE UP pin back to work.

The schematic is attached below.(Only the core components displayed)

Is the schematic wrong or did I missed something?


texts: Why is this capacitor hooked up to a 9volt electric motor?

texts:
I took apart a sharper image personal fan run by a 9volt battery.

I understand a resistor is sometimes necessary, such as when preventing light emitting diodes from burning out. How about a 9volt motor run on a 9volt battery? Is a resistor necessary? Can a capacitor substitute for a resistor in some cases? (that was my guess as to why it has a capacitor) Is the function of this capacitor to slow the fan down, and if so does that mean running it straight to the battery might burn it out?


texts:
The LM7805 datasheet recommends a 0.33uF cap on the input and a 0.1uF cap on the output. The LD1117-3.3 datasheet recommends a 0.1uF cap on the input and a 10uF cap on the output.

I am building a circuit that will run off the 12V battery in a bus. I need two supplies - 5V and 3.3V, the overall current consumption being <200mA. I have an LM7805 to generate the 5V supply and it then drives an LD1117-.3.3, to generate the 3.3V supply. The circuit I have designed is shown in the figure below.. My questions are as follows:

Is it OK to also add a 470uF electrolytic cap on the input of LM7805? I am hoping for additional protection against fluctuations in the 12V supply from the bus battery.
Is it OK to skip the 0.1uF on the input of the LD1117-3.3 since the output of the LM7805 already has a cap of this value?
The LM7805 recommends a smaller cap on the output compared to that on the input, whereas the LD1117-3.3 recommends a larger cap on the output compared to that on the input - any insights in to why this is the case? I am just trying to understand whether there are any gotchas in connecting the output of the LM7805 to the input of the LD1117-3.3!
Can the 0.33uf and 0.1uF be ceramic (SMT) caps?
I have some off the shelf power regulator boards that use the LM7805 but have a very large electrolytic cap (1000uF) on the input and another electrolytic cap (10uF) on the output. Why would they deviate from the recommended values of the decoupling caps?

Thank you very much for your help.


texts: Programming ATtiny84 using Arduino (Leonardo)

texts:
I am trying to program the ATtiny84 using an Arduino (Leonardo). I have seen this Shrinkify video. -and I have been following this Programming tutorial.

I have connected everything and am using Arduino 1.0.1 software. I uploaded ArduinoISP to the Arduino, selected "board" ATtiny84 (Internal 1 MHz clock), and selected "programmer" Arduino as ISP.

When I try to upload the blink example, I get this error:

  Binary sketch size: 880 bytes (of a 8,192 byte maximum)

  avrdude: please define PAGEL and BS2 signals in the configuration file for part ATtiny84

  avrdude: Yikes!  Invalid device signature.
           Double check connections and try again, or use -F to override
           this check.

What am I doing wrong?
Should I upload by pressing "Upload" or "Upload using programmer"? (I have tried both - with same result)
What does "use -F to override" mean?

Update:

I have now found that my problem is that Leonardo can not be used like this. I will investigate further.


texts:
I am new at digital design and I have a problem.
I need to get the number of zeros. There must be 4 inputs and I must use only half-adders.
I tried everything I know but I could not solve this. Do you have an idea?


texts: Pad dimensions and land patterns for QFPs

texts:
I'm putting together a footprint for a 100-pin, 14x14mm TQFP, and I'm finding conflicting designs.  The pitch and width of the pads are all basically the same, but the length and centering of the pads horizontally varies a good deal.

The following images are from the Microchip packaging specifications document (see page 282-283), so that we can have names to use for the dimensions.
Physical Package:

Recommended Footprint:

There's a table with numbers for each dimension, but the exact details aren't really important here.

Where should the pin go on the pad lengthwise?

 Should the pin be centered on the pad?
(C1 = D - L) If so, what should Y1 be?  L, L+tolerance, 2L?
 Should the inner edge of the pad line up with the inner edge of the pin?
(C1 - Y1 = D - 2L)  If so, how far should the pad stick out in front of the pin?
 Should the pad and pin have some other dimension?

Note that the question is basically moot if Y1=L.  I'm assuming that I'll want a little extra pad to hit with the soldering iron.

It might be relevant that L1 is allowed to vary by ±25%, which feels like a bigger variation  if you read 'between 0.45 and 0.75mm'. It might not be relevant.

I'm interested in solderability, avoiding invisible solder bridges under the chip, routing traces underneath (and outside of) the chip.  Of course, I don't want to use absurdly long pads for heat dissipation and board space reasons.


texts:
I own a Peavey Valve King 100 Amplifier and would like to hook this up to my audio card's line-in without blowing stuff up, so I thought I should get a loadbox with a built-in speaker simulator. I will only be using one of the speaker outs of the amplifier as the loadbox only has one input.

The amplifier itself has the following specs:

100 Watt RMS
Adjustable Resistance (4/8/16)
Two speaker out ports (parallel)

The load box/speaker simulator has the following specs:

Type: Passive
Dummy load impedance: 16 ohms
Input type: Unbalanced
Output type: Balanced, unbalanced
Max. load: 100 watts RMS

Would this imply that I should set the adjustable resistance on the amplifier to match the load box? Or should I only get an 8 ohm loadbox since the speaker outputs on the amplifier are parellelled?

Sorry for the extreme layman's terms.


texts: Need help modelling the circuit with parasitic capacitance of a power supply in this scenario in SPICE

texts:
A single-ended source is connected to an inAmp of a data-acquisition board as follows:

As you see above, the shield is shielding the twisted shielded pair cable. The shield is tied only to the earth ground. AIGND is not connected to earth ground.

I want to make a very simplistic simulation in LTspice, to mimic this scenario when there is a 50Hz common mode noise comes through the power supply to both lines as common mode interference.

Below is my attempt:

There is something missing or wrong in above model.

I want to model the circuit where the common-mode interference comes through the SMPS power supply. Power supply need not to be modeled juts the noise like in my circuit. But there is also shield and the AIGND is not earth grounded.

How can I fix this to make it more realistic?

My second attempt:

edit:


texts:
I am having ferrite core T60006-L2063-W517 Ferrite Toroids /Ferrite Rings Core 63x50x25 58.6uH@10kHz.
I wanted to measure inductance of the core from datasheet it shows,
Ferrite Rings Core 63x50x25 58.6uH@10kHz what does this mean by the way..?
Inductance test without DC-magnetisation :
Setting values: Ieff x N = 40 mA
f = 10 kHz
Specified value: 44 µH ≤ AL ≤ 85 µH
but doesn't ring a bell can anyone suggest me on this please...?
Datasheet of  T60006-L2063-W517


texts:
I have some rather simple Altium project, which basically consists of two pcb's:

Audio Signal Input PCB (PCB 1). On this PCB are placed (for now) RCA Jack and Straight JACK pair (one for left, second for right channel):

Audio Signal Input Selector PCB (PCB 2). On this PCB there is relay for Input Signal Switching:

Now, both PCBs will be connected not with PCB vias, but with physical coax cable. How do I designate Audio Signals Ports on both PCBs, so I can connect them in Top Schematic with some kind/version of port, which is ignored by PCB router? To simplify, I want to show the coax cabling connection in schematic, but to ignore it in PCB design phase, because the connections will not be physically on PCB?


texts:
I have a KXPS5-3157 Accelerometer, that outputs 0.330 to 2.97 VDC

http://www.futurebots.com/3157.pdf

The zero-G offset is 1.65VDC (VCC/2)

1G of gravity = 1.65VDC + 0.440 = 2.09 volts = ZERO to cancel out gravity

I want to "zero" the output of the accelerometer strictly in hardware. I was thinking of using a Differential Amplifier, and inputting -2.09 and the output of the accelerometer to zero it. Not sure if this will work, my application is as follows:

The sensitivity of the accelerometer is 440mV/G

I want to zero out of the accelerometer on the Z axis to cancel out gravity, so subtract 2.09 volts.

Then I want the output of the accelerometer to swing positive G's Positive voltage, and negative G's negative voltage.

I want the accelerometer to output negative and positive voltage corresponding to the -G and +G's, canceling out the affect of gravity also

The supply voltage is 12volts, for the opamp, the accelerometer uses 3.3V I'm assuming a would need a rail to rail opamp?

Think I solved this playing in multi-sim:

I just cant find the correct voltage divider pair to get exactly 0V


texts: What board should I use to control my 3D printer

texts:
I'm trying to build a simple experimental FDM 3D printer as a hobby.
As I said it's a simple printer with only basic functionalities such as receiving the slicer file to print from a slicer software from PC and sending back the print status to the PC.

Following are other functionality of the printer:.

Sends the X and Y coordinates of the printhead and Z cordinate of print platform to the PC.
Sends the temperature of the cartridge heater to the PC with the help of a temperature probe.
Send the number of layers printed  currently.

Now in order to achieve the above mentioned functionality and control the printer via the PC, what microcontroller motherboard is ideal to use? Is using Arduino Uno ideal enough? Or should I use Arduino Mega or any Rasbery Pi board.


texts: Effect of using buck converters in parallel

texts: What is the effect, downside or purpose, if any, of using buck converters in parallel? For example, to connect the Vout and Gnd together on two converters. Could this be used to increase the current capability? Assume that the converters are identical in design.


texts:
I'm transmitting a buffer array from inbuilt USB of PIC 18F controllers and sending this to a GUI.  I am able to detect the device properly (enumeration). But the GUI crashes some times, without any reason.

I assume it is a transmission/interrupt problem as whenever I'm sending a constant number it does not crash.  But whenever I'm doing an ADC operation and sending the corresponding value via USB, it crashes.

This made up my assumption that USB transmission or interrupt handling needs to be handled properly.

I'm new to the USB protocol and tried with this working code.

I have no problem regarding enumeration, but when transmits the crashing occurs.

The format of the code is:

 main()
{   usbinit(); // usb initialization

       while(1)

{
      x=do_adc();
      UsbTasks(); // does usb works
      yourtasks();//sends the buffer

}

}

I would like to understand what might be the cause behind this anomalous behavior.

As noted below in the comments the USB stack is set for polled configuration.  How should I manage the ADC read?

If I do:

while(1)

    {

          UsbTasks(); // does usb works
           x=do_adc();
          yourtasks();//sends the buffer

    }

Will it make any change?  Or is this not the best way to send ADC values?


texts: Which is harder on the power grid: a winter cold spell, or summer heat wave?

texts:
Just a wonder of mine, as I sit here listening to my heat pump struggle to maintain.

For the Q, assume the North East USA.

I think Summer heat waves are more difficult for the grid due to A/C load combined with the complications heat brings to power distribution systems.

I'm guessing that even an extreme winter cold spell is probably easier on the grid than summer heat--I assume this due to: furnaces are more likely installed in climate zones where electric powered heat pumps are poorly suited (heat pumps being a poor choice in areas with frequent low temps).

In other words:

Sumer Heat Wave

everyone running A/C
plus distribution issues

Winter Cold Spell

most running furnaces (electric operated, but other heat source)
some with heat pumps within their limits
fewer with heat pumps inefficiently operating beyond spec

I think a heat wave is more difficult for the grid.


texts: Bootstrap drive for 2-transistor forward converter

texts:
I need a driver for the high side switch in a 2 transistor forward converter as follows:

First, I thought a bootstrap circuit would be fine because during the freewheeling phase, the highside FET's source is slightly below 0 volts, so a bootstrap capacitor could easily be charged. And during startup, I turn on the lowside FET only, so the bootstrap cap can be charged.

However, this turned out to be not reliable enough. I think the reason is that the primary inductance of the transformer is too high, so there is not enough time to charge the bootstrap cap.

Is there a solution for the problem?
Almost for sure it will not be possible to use an IC because the DC voltage is way beyond 600V, which is the usual range of those integrated low and highside drivers.

I found out it works reliably as soon as it has been able to switch a few times, this is indeed due to the highside source being pulled towards ground during freewheeling. But the startup is the problem.


texts: Virtuous: Differential Input Single Ended Output Design Enhancement

texts:
I am trying to design a low power, fully Differential Input Single Ended Output amplifier with gain of atleast 50dB. I am using a VDD of 1.5 Volts using MOSFETS. I want to have maximum swing and my circuit along with different node voltages and MOSFET Parameters are shown in the attached picture. I want to have Vdsat for each and every MOSFET to be around 0.1~0.12 Volts. In the picture, the very first Voltage source that is connected to 2nd matched PMOS pair is vbias3 variable. The second Voltage source which is currently set to 1 V is vbias2 variable and the tail source biasing voltage source is vbias 3 variable. Later I will replace all of these voltage sources with a biasing generator that I will design later. The two matched pair NMOS (T-6,0,5,8) have channel width of 4uM and PMOS (T-1,4,2,3) transistors have Channel width of 8uM. The Tail current source NMOS T7 has channel width of 8uM. All of the transistors have channel length of 220 uM.

I am trying to have my output (the middle node between T1 and T0) to be at centre of the rail voltage (1.5V) so that I can maximize my swing. However I am stuck at this point and no matter what I do I can't bring that point down to ~750mV and have the gain of 50dB.

Need design help with following:
- Bring down the Vdsat for top 4 PMOS to around 0.1~0.12 V
- Bring the output node(currently at 1.037 V) down to 750 mV by keeping the gain as high as possible to maximize the swing.
- Have all the MOSFETS operate in saturation

NOTE: Please don't worry the Tail current source NMOS as Vdsat seems to be greater than VDS in the current screenshot, however I can easily put my MOSFET in saturation by just bringing the biasing voltage down by 5mV.

Any help to achieve the above requirement would be greatly appreciated.

IF ANY OF THE DESIGN PARAMETERS ARE NOT CLEAR PLEASE ASK HERE FOR CLARIFICATION.


texts: When is using non-standard laptop chargers safe? and why?

texts:
Looking at using the charger for laptop A to charge laptop B results in a lot of different recommendations, so I am not sure what to believe in.
Especially I find that many websites give recommendations without explaining the science behind it, making it hard for me to discern the validity.

So, my question: When and why is it safe to use a specific laptop charger for another laptop?


texts:
i started to build an infrared transmitter (commander). I use 4 pushbuttons for left, right, up, down. These buttons are pulling down when pressed. I used internal pullup resistors. My prboblem is that the arduino is seeing one pin as high (not changeable by pressing button) and the other pins as low (not changeable by pressing buttons). It is not recognizing the changes.
I tried the following to solve:

First i used Pulldowns and the result was the same. Then i searched for an alternative and found pullupp. The same Problem.
I tried other pins. Same Problem.
Checked the soldering connections. Everything is OK.
Then i measured the voltages for the first pin. When nothing is pressed
the voltage between pin A0 and Ground is 0V and when pressed the voltage between pin A0 and Ground is 0V.
I took external resistor (1k) instead of internal pullup. Know the probelm with the single one is solved. The voltages when pressed and not pressed are OK. But the controller pins are not recognizing the changes.

The last point is very strange i expected 5V when not pressed and 0V when pressed.
Here is my code:
    #include <IRremote.h>
    #include <IRremoteInt.h>

    IRsend irsend;

    // The configuration of the output pin will be made by the library
    // The output pin is a different one for different arduinos
    // Arduino UNO:  Output = D3
    // Arduino MEGA: Output = D9
    // You will find a full list of output pins on the website:
    // http://z3t0.github.io/Arduino-IRremote/

    #define TASTE_HOCH 19       //A0
    #define TASTE_RECHTS 22     //A3
    #define TASTE_UNTEN 21      //A2
    #define TASTE_LINKS 20      //A1

    int aktiveTaste = 0;        //Taste die momentan gedrückt ist

    void setup()
    {
    pinMode(TASTE_HOCH, INPUT_PULLUP);
    pinMode(TASTE_RECHTS, INPUT_PULLUP);
    pinMode(TASTE_UNTEN, INPUT_PULLUP);
    pinMode(TASTE_LINKS, INPUT_PULLUP);

    Serial.begin(9600);
    }

    // main program loop
    void loop() {

    Serial.print("TASTE_HOCH: ");
    Serial.println(digitalRead(TASTE_HOCH), DEC);

    Serial.print("TASTE_RECHTS: ");
    Serial.println(digitalRead(TASTE_RECHTS), DEC);

    Serial.print("TASTE_UNTEN: ");
    Serial.println(digitalRead(TASTE_UNTEN), DEC);

    Serial.print("TASTE_LINKS: ");
    Serial.println(digitalRead(TASTE_LINKS), DEC);

    delay(3000);

    if(digitalRead(TASTE_HOCH) == LOW){
       aktiveTaste = 1;
    }
    else if(digitalRead(TASTE_RECHTS) == LOW){
       aktiveTaste = 2;
    }
    else if(digitalRead(TASTE_UNTEN) == LOW){
       aktiveTaste = 3;
    }
    else if(digitalRead(TASTE_LINKS) == LOW){
       aktiveTaste = 4;
    }

    if(aktiveTaste > 0){

    // The transmitter sends in this example the signal A90 (hex. dezimal   form) in the encoding "RC5"
    // It will be transmitted 3 times after that it will make a 5 second break
    for (int i = 0; i < 3; i++) {
      irsend.sendRC5(aktiveTaste, 12); // [0xA90] signal | [12] Bit-length signal (hex A90=1010 1001 0000)
      delay(40);
    }

    aktiveTaste = 0;                    //Keine Taste gedrückt
    }
    }

And This is the output of serial print:

What is the cause for not recognizing changes?


texts: What the output isn't correct when I use a switching power supply?

texts:
I have a circuit that it is a STM32F103RET6(Reference Manual) board and one LCD. everything work very well just one thing! PWM! when I use my J-Link debugger to supply the circuit(or USB connector), the PWM is correct. look:

But when I use my switching supply, the output is:

My switching supply is this and I'm using this module to make 5v from my switching supply. the schematic of my board is this:

Please note that when I use my switching supply, everything work very well except PWM.(I mean even the MCU and LCD work very well). in fact, the problem that I have is just PWM. What's the problem? how to figure it out?


texts: after programming PIC, can no longer run debug or reprogram

texts:
OK, I have written a few basic programs in MPLABX C18 for both 18f4550 and 18f46k20.  Eventually got them to compile and test/debug correctly and run on the PIC.  After I choose, "make and program device" It works but I can no longer run debug or re-program the chip.  Always says the device doesn't match, etc.  Here is what the output window says:

Connecting to MPLAB ICD 3...
Firmware Suite Version.....01.28.07
Firmware type..............PIC18F

Target detected
Device ID Revision = 7

The following memory area(s) will be programmed:
program memory: start address = 0x0, end address = 0x1ff
configuration memory

Programming...
program memory
Address: c Expected Value: 6a Received Value: 36
Failed to program device

Any ideas?

Thanks


texts: Under severe power constraints I'm considering disabling the watchdog.The MCU is to work as a stepper motor controller in a watch and drive a simple bar display too. What can the consequences be? (Project is not of DIY/hobbyist type).


texts: Confusion about why voltage of a cell decreases as it's used up and how it relates to current

texts:
Electromotive force is equal to internal resistance times current plus resistance of other components in the circuit times current.

$$\varepsilon = rI + RI$$
Therefore:
$$V= \varepsilon-rI$$

What I'm really confused about is this graph:

This graph relates to battery being used up. This means decrease of voltage (why?).
According to the graph as voltage decreases, current increases.
The only way I can explain it using the equation V=e-rI is that for some reason internal resistance r increases and as eloctromotive force stays the same, this means decrease in voltage V so both sides equal each other again. But wait! According to the graph current was supposed to increase and the above reasoning doesn't account for that. Please explain in your own words step by step how you can explain this graph using the equation V=e-rI.


texts:
I'm really confused in the following question,

  The flux linkage (\$\lambda\$) and current (\$i\$) relation for an electromagnetic system is \$ \lambda = (\sqrt i / g\$ ) . When
  \$i = 2 A\$ and \$g\$ (air-gap length) = 10 cm, the magnitude of mechanical force on the moving part, in \$N\$, is?

My approach,
$$f  = i \frac{d \lambda}{d x}$$
$$ |f| = \frac{i \sqrt i}{g^2} = 282.84 $$
But the answer is in the range 186-190 N


texts: Is there a demux IC that allows a default signal (not just digital 0) to go to the non enabled outputs?

texts:
I am trying to control multiple servos using a Demux and I want the selected output to have one pwm signal and then all of the non selected outputs to receive the same default pwm signal instead of a digital 0. This way all of the non activated servos will hold in one position and only the single activated servo gets a signal to rotate it.

I know I can just do this with logic gates, but if there is a specific IC that does this or there is a name for what I am describing I would like to be pointed in the right direction.


texts:
I'm planning to build an automatic switch box for line inputs to my speakers. The switching itself seems fairly straightforward (a pair of de/multiplexers), but I don't know how to detect the audio signal, it should also not interfere with the signal itself.

The switch box will be controlled by an Arduino or something similar, as it needs to have some kind of timer so that it wont switch back and forth randomly if there are multiple inputs active.

So, how do I detect an active audio signal using an Arduino? (or similar) Will it interfere with the signal itself? How? How do I avoid that?


texts: Where is the C API reference for the MSP430? CCS version

texts:
I see a lot of sample code and tutorials, but where is it documented that symbols (defines) such as P1OUT and P1DIR are available and what are their semantics?

I see a list with one-phrase comments in the header files, but that's the same as browsing through source code. I am looking for a technical document: an API reference or at least a Programmer's Guide.


texts: Can you damage logic gates by connecting two outputs together and powering one?

texts:
As the title says, would this cause problems in a circuit, and if so, how do you get around it (other than connecting them both through an OR gate)?

Furthermore, could you stop this with a buffer? Can a buffer act as a diode (at least not die)?


texts: NPN transistor slow to turn off even when operated outside of saturation region

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I am currently studying how transistors react and behave to simple signals. I have the following circuit:

A square wave of approximately 83kHz is applied. The transistor used is a 2N5551. The resistor values were carefully chosen to try to avoid transistor saturation. However, with this setup, slow turn-off time is still experienced. Measurements were taken with a PC oscilloscope and are shown below. The full data can be found here.

The y-axis is voltage, the x-axis is time. All voltage levels are relative to ground. The 3-images are not aligned at the same point in time, but the clock signal should help with comparing the graphs. One full cycle is around 12 microseconds, and the on-time and off-time of the clock signal is 6 microseconds long. The clock signal was generated with a 555 timer, the duty cycle is very close to 50%.

As it can be observed in the Collector and Clock graph, when the clock turns to 0V, the transistor stays on for almost 3 microseconds before it fully turns off and the collector settles to 5V. This can also be observed in the Base and Clock graph, where the base of the transistor is at around 0.75V for almost 3 microseconds before it starts transitioning to 0V. The Collector and Base graph helps show that the transistor is not operating in the saturation region since Vb <= Vc. Vc seems to fall below Vb for a very short time, but I do not believe this is causing saturation. In fact, a Schottky diode would not help at all since the voltages are very close to each other. Hence, this should not be a storage-time issue. I have also ruled out the transistor input capacitance (of max 20pf) to be the problem as I believe I would see similar delays in turn-on time in that case. Additionally, the RC time constant would be 0.3 microseconds (5RC = 1.5us) at the input.

What could be the problem?

Edit/Updated

Following the accepted answer, adding a reverse diode accross the base resistor solved the issue. The updated graphs can be found in the same document, under the Solved Trace sheet. For convenience, the updated image of the Collector and Clock graph is shown below:


texts: Difference between >> and >>> in verilog?

texts: What is the difference between >> and >>> in verilog/system verilog? I know that == tests for only 1 and 0, while === tests for 1, 0, X, Z. So how is that similar to the shift operator?


texts: To Clear or not to clear ARM Cortex-M NVIC interrupt pending

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Do I need to clear the pending status of an interrupt in the interrupt service routine of an ARM Cortex-M0 MCU?

Could not find information on this on the web.


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I designed a PCB with STM32F411RE and a couple of sensors.
Before and after mounting components on the PCB, I checked the Vcc and GND pins for short circuit and I did not see any problem.
I am using SWD programming and I connected my ST-Link V2 to my board and successfully loaded the program.
Everything was normal for a few minutes. Approximately 3-5 minutes after, the MCU disconnected from the PC and then I checked the Vcc and GND pins and observed a short circuit.
Interestingly, as time goes the resistance between Vcc and GND pin increases by itself.
After that, I just mounted STM32F411RE, reset pin configuration and Vcap. I connected my board to PC and loaded the program successfully.
After a while the power pins shorted again. I just uploaded a simple LED blinking test program.
My board schematic and PCB images are below. Please help me to find my mistake.


texts: Running a Microcontroller with Selectable Voltage (3.3V/5V)

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I'm working on a non-volatile SPI memory chip programmer.  My design sends individual data bytes over USB to an MCP2200 (USB to serial converter chip), then the serial data is sent to an ATMega48, which is responsible for writing the data bytes to the memory chip.

I did find this question (Selecting 3.3v or 5v to supply EEPROM by µC output) and I'll probably use a circuit similar to what is featured in the first answer.  However, in terms of effects, it only discusses the memory chip being programmed, and not the effect of switching operating voltages on the MCU in the programmer.

So, my questions are:

1.)  If I use a solution similar to the one in the above question and I programmed the ATMega48 with a 5V programmer, what happens when I run the MCU at 3.3V?  Will it work or will I damage something?  (I'm mostly concerned about the integrity of the memory cells, but any other danger areas would be of interest too.)

2.)  Once I flip to 3.3V, will there be an issue going back to 5V, such as the 3.3V logic level not being sufficiently high to be counted as a '1'?

EDIT:  The power rail on the programmer provides power to the MCP2200, the ATMega48, and the memory being programmed.  As a result, voltages will never go above VCC.


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I am using LTspice to simulate a circuit that has a PWM driving a pulled-up sensor using a NPN BJT.

When the PWM truns off I see a droop of about .6Volt.

What's the best way to get rid of it? Should I use a capacitor in parallel to the BJT?

My circuit is:

                    +------/\/\/\/\------+
                    |                    |
  PWM source ------NPN                   +--- PWM consumer
                    |                    |
                    |                   12v
                    |                    |
                   GND                  GND


texts: How to calculate: watts for AVR, VA (volt-ampere) for UPS

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I intend to buy an AVR or UPS, and I want to add a few external HDD's & a few Mini PC's.

I need to calculate how much power is used by every device so I don't overload the AVR or UPS

EXAMPLE: External HDD Charger data:

INPUT: 100-240V  ~50-60Hz  0.5A

OUTPUT: 12V  1.5A

1. How do I calculate watts for AVR (Automatic Voltage Regulator)?

Total devices W sum must be a bit under 600W for the AVR to work OK.

  Model LE600I - Maximum output power capacity: 600 W or 600 VA

    DATA FOUND HERE

      https://www.apc.com/shop/uk/en/products/Line-R-600VA-Automatic-Voltage-Regulator/P-LE600I

        Documentation PDF: Automatic Voltage Regulator Line-R LE600I/LE1200I

V * A = W

Do I use 100V or 240V ?

100V * 0.5A = 50W -----> AVR 600W - 50W = 550W Remaining unused

240V * 0.5A = 120W ----> AVR 600W - 120W = 480W Remaining unused

?????

2. How do I calculate VA (Volt-ampere) for UPS 2200VA (Uninterruptible Power Supply)?

Total devices VA sum * 2 must be <= 2200VA for the UPS to work OK

V from OUTPUT * A from OUTPUT = VA ???

12V * 1.5A = 18W ??? ----> 2200VA / 2 - 18W = 1082VA Remaining unused

This is all the stuff I know now. Please correct me if I'm wrong.


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i need an amplifier to amplify my electrolyte microphone sound and put output to sim800l . currently i just experiment with amplifiers to find good gain for sim800l mic input.
some one advise me to use common emitter as pre amplifier . so i found this circuit on the internet and check the simulation in Proteus 8 software.
in theory this circuit work great .i add electrolyte microphone to input of circuit in reality. i just can hear very weak audio in output but without amplifier and just connecting electrolyte microphone to sim800l sound is much better.

edited: i want to know why i cant amplify my voice in real circuit . i check all wire connection and its not wire problem


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In EMC there is an equation for charactristic impedance (If I am not wrong) that is defined as:
$$Z_w = \frac{E}{H}$$

As you know \$E\$ is expressed in Volts and \$H\$ as Ampers.

I had the exam today and for sake of confusion of students, the teacher brough this values in dB. But I actually needed this value in pure ohm (no dB) to solve the next part of question. The values were:

\$E = 100\frac{mVdB}{m}\$ and \$H=80 \frac{mA dB}{m}\$

I am not sure if I did correct, but I went ahead and did this:
$$Z_w = 20\log\frac{100}{80} = 1.93 \Omega$$

Is this the correct? If not, how to handle this?

This is really confusing, in our study book the same question is presented by just E and H in normal way! for example E is 50mV/meter and H is 40 mA/meter...either I am so stupid or teacher is a troll!

UPDATE

First, Thank to all for the feedback. I asked my teacher the correct soloution and it appeard to be solved in this way:

$$Z_w=\frac{E}{H}=\frac{10^{\frac{100}{20}}}{10^{\frac{80}{20}}}=10\Omega$$