texts:
I am working with PIC24FJ192GB106 (64 pin package), and the I2C module is driving me crazy.

here is the code:

int counter = 1;
address = 0b01110000; // ADD7 = 0111000 ; W = 0;
cmd1 = 0xFF;
cmd2 = 0xFF;

I2C1CONbits.I2CEN = 0; // turn off the I2C1 module
wait(100);
I2C1CON = 0x1000; // default settings of I2C1 module
wait(100);
I2C1BRG = 39; // set the baud-rate generator -> 100 kHz SCL, Fosc = 8 MHz
wait(100);
I2C1CONbits.I2CEN = 1; // start the I2C1 module
wait(100);

IFS1bits.MI2C1IF = 0; // clear interrupt flag (just to make sure)

(*)

I2C1CONbits.SEN = 1; // initiates Start condition
while (I2C1CONbits.SEN == 1 ){counter++;}; // wait until Start condition is executed

I2C1TRN = address; // send data
while (I2C1STATbits.TRSTAT == 1 ){counter++;}; // wait while data is being send + ignore ACK from slave

I2C1TRN = cmd1; // send data
while (I2C1STATbits.TRSTAT == 1 ){counter++;}; // wait while data is being send + ignore ACK from slave

I2C1TRN = cmd2; // send data
while (I2C1STATbits.TRSTAT == 1 ){counter++;}; // wait while data is being send + ignore ACK from slave

I2C1CONbits.PEN = 1; // initiates Stop condition
while (I2C1CONbits.PEN == 1 ){counter++;}; // wait until Stop condition is executed

TRISE = counter; // show counter on LEDs

From (*) and on NON-OF THE CODE IS EXECUTED. There is no response on pins (measured by oscilloscope). The I2C1 is located on not-remappable pins SCL1 - pin 44, SDA1 - pin 43. Pull-up of 4.7 kOhm (3.3 V) are hooked up. I have also tried to set corresponding bits in ODCD to 1 (digital pin), and 0 (open drain). TRISD is set to input (0xFF) (but I have also tried output option).

I suspect that none of the bits SEN, PEN and register I2C1TRN is set, because the "counter" remains the same value. Considerring that the PIC has 8MHZ clock and I2C only 100 kHz, there has to be time for at least one counter++, while waiting.

Is there anything, that I can do? (Except changing the PIC). Have I missed something? What other options of debugging do I have?

P.S. The PIC is otherwise fine. Other modules (PWM, ADC, UART) work perfectly. Internal oscillator is (remarkably) precise (measured on oscilloscope on reference clock pin). All other pins work (portE register).

P.S. 2

here are my settings for the PIC24

OSCCONbits.COSC = 0b111; // current oscillator selection bits // '111' FastRC Oscillator with Postscaler(FRCDIV)
OSCCONbits.NOSC = 0b111; // new oscillator selection bits
OSCCONbits.CLKLOCK = 1;// if FCKSM (config word) is disabled (then FCSM is disabled) the NO EFFECT   //OSCCONbits.IOLOCK -> lock function
OSCCONbits.LOCK = 1; // PPL Lock Status bit // when OSCCON.COSC = any non PPL clock mode then NO EFFECT   //OSCCONbits.CF -> to be READ in case FCSM has detected a failure (FCSM is disabled anyway)
OSCCONbits.LPOSCEN = 0; // Primary Oscillator Sleep Enable bit // [0] - Primary Osc continues during sleep mode
OSCCONbits.SOSCEN = 0; // Secondary Oscillator Enable bit // [0] - 32kHz Secondary Osc is disabled
OSCCONbits.OSWEN = 0; // Oscillator Switch Enable bit // [1]-changes from OSCCON.COSC to OSCCON.NOSC/[0]-nothing

CLKDIVbits.ROI = 0; // Recover on Interrupt bit // [0] - Interrupts have no effect on the DOZEN bit
CLKDIVbits.DOZE = 0b000; // CPU Peripheral Clock Ratio Select bits // [000] - 1:1
CLKDIVbits.DOZEN = 0; // DOZE Enable bit // [0] - CPU peripheral clock ratio is set to 1:1
CLKDIVbits.RCDIV = 0b000; // FRC Postscaler Select bits // [000] - 1:1


texts: Do rotary encoders really have no bounce?

texts:
I've always needed to add debouncing code, when handling switch inputs on microcontrollers.  While I've only used three different types of switch, they all needed debouncing.
My (two) rotary encoders appear to have no "bouncing" on their P and Q outputs.
I've looked at the logic-analyser captures of phase and quadrature and they're absolutely clean.  Not a single spike, over dozens of turns.
Is there something about the design of rotary encoders which make this true?
Or is this just a coincidence?


texts: Looking for an "SMA signal polarity inverter"

texts:
I found one of these lying around in my microwave/RF lab and I was wondering if it has a technical name and if I can build one myself:

It has SMA connectors at the two ends. It flips the polarity of the input signal and also attenuates it a bit (~10dB).

It's currently hooked up in a signal pathway which carries a "sync signal" spike train at 10MHz and 0-2V DC. We are using one of these guys to flip it into an NIM (nuclear instrumentation) compatible spike train of that goes 0 to -1VDC.

Searching online for "SMA signal inverter" or " SMA polarity inverter" doesn't give any useful results. I see many search results on reverse-polarity SMA adapters but that's something completely different.

It turns out this thing has two pieces - an "inverter" (the shrink wrapped piece on the left) and a standard 10dB attenuator which is easily available off the shelf.

I don't understand how the inverter works. After unwrapping the shrink wrap on one of them I see something that looks like this:

The resistance for the 4 terminal combinations are all close to ~2 ohms on a multimeter i.e. basically short circuit at DC.


texts: Mains Power indicator maximum current draw

texts:
I am building a circuit like this:

From here.
This got me wondering how much current can I draw from a circuit like this?
The question would seem to be what is the wattage of an capacitor?
Edit:
What I am trying to ask is can I draw 100mA or 1A? And how would that affect the components?


texts:
Something that confuses me is why AC and DC relays are not swappable in an application.

For example, I am looking for a 12V (DC coil voltage) relay that its contacts can withstand cold-switching of a 40V/2A DC signal. I found some RT 314 SPDT 12V relays in the lab bin, and I want to use them for this DC application. But nowhere in its datasheet, it has mentioned anything about contact specification in a DC application. Does this mean this relay can not be used in any DC application?

I mean if they can switch 16A,250VAC....why can't they switch 40V/2A DC?

Isn't the relay contact just a conductor?

Thanks to @SteveG This is the DC-LOAD graph in the datasheet that I did not spot myself:

If not, Do you know a pin compatible relay that can be used in a DC application 40V/2A contact rated?


texts: Finite CMRR even with ideal tail current source (body effect)

texts:
In Razavi's Design of Analog CMOS Integrated Circuits 2nd edition page 123, the diff-pair below is included with a comment about how even if the tail current source is infinite, if the transistor pair do not have the same \$g_{mb}\$ then a change in the input CM level will produce a differential output voltage.
I'm not sure how this is possible. Thinking from a large signal perspective: assume that with some initial input common mode there are some bias currents \$I_{D1} \neq I_{D2}\$, \$I_{D1}+I_{D2}=I_{SS}\$. If there is an increase in the input common mode, then the source node increases (otherwise the \$V_{GS}\$ of both transistors increases and so both want to conduct more current, but that's not possible since then \$I_{D1}+I_{D2} \geq I_{SS}\$), thus the drain currents don't change as a result of \$V_{GS}\$.
Razavi says that if \$g_{mb1} \neq g_{mb2}\$ then there will be a change in the drain currents. When \$V_P\$ goes up, then yes the \$V_{BS}\$ of each transistor changes by the same amount and since the body transconductances are different the current change in each branch should be different. But for both NMOS devices the decrease in \$V_{BS}\$ makes both devices want to decrease their currents, which shouldn't be possible if their sum is fixed, just like in the case above. Am I missing something that makes this case different?


texts: Are PTC resettable fuses fast enough to protect from shorts?

texts:
Time to trip of most of PTCs is about 0.1 seconds. In case of short between VCC and GND the current will be very high (maximum a power supply can provide) for at least 0.1s. Isn't it enough to burn out one of the components usually present in series with PTC: voltage regulators, power FETs, ferrite beads, etc?

To be specific: I have a device which is powered from USB bus via 500mA hold current PTC, 5V->3.3V LDO and ferrite bead. In case of short the current will be about 20-25A (this is what PC power supply can provide) for a period of 0.1s, afterwards a PTC of PC side or PTC on USB device will trip off power. Does LDO and ferrite bead survive 0.1 s of high current (and also does PC survive)?


texts: Difference between @* and @(*) in Verilog

texts: What is the difference between always @* and always @(*) in Verilog-2001?


texts: avrdude error - stk500_getsync(): not in sync: resp=0xff

texts:
I am using my Arduino Uno as a programmer to program my ATtiny85. I uploaded the ArduinoISP sketch to my Uno. I double checked my wiring, did some googling, but I still can't figure out why I get this error:

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

when I run this command:

sudo avrdude -p t85 -c avrisp -P /dev/ttyACM0 -b 9600 -U flash:w:src.hex

Any suggestions? Thanks!


texts: How does the voltage go negative on the BJT base in this simple flasher?

texts:
I'm trying to get more specific in my understanding of electronics, and, like any adult learner, am realizing I have to correct some basic misunderstandings or gaps in my knowledge of fundamentals.

Consider the following flasher circuit. I've paused the current cycle at a point where the voltage on the base of one of the BJTs is negative. I wonder how does this happen? I don't understand how +9v can be dropped over the 100k resistor and the BE junction past 9v. Does the capacitor pull voltage out of the ground in order to balance the charge?


texts: Charging capacitor with higher voltage power supply

texts:
I have a maxwell 1200F 2.7V ultracapacitor which I charge using a 16V supply and a voltage divider in parallel with the capacitor. It's a really slow charge.
I also have a 4V supply which has higher current ability. I want to charge the cap directly from it.
I was wondering if it is safe to charge it up directly with that supply. It will be under constant supervision and I will disconnect it as soon as it hits 2.5V. Is this safe?
If you think it can be done, can you post some references and sources for further reading? I don't want a supercap blowing up in my face...


texts: Is there a name for this kind of comparator?

texts: I have two analog signals, and I need to generate digital signal (to use as an interrupt for an MCU) when the voltages differ more than a certain amount. It's going to be some sort of comparator arrangement, but does this have a name? Window comparators are in the right kind of area, but aren't differential.


texts: Help Understanding BJT "On Characteristics" in Datasheet

texts:
I am currently in the process of designing my first transistor circuit and I am using another as a basis to work off of. In this process I am trying to learn how to read a datasheet, as in university so far, we have rarely used them. I am using a 2N5089 NPN transistor for my design and below I have posted the part of the datasheet in question. First, what exactly is Base-Emitter On voltage? I think this means the voltage required to forward bias the BE junction, but I figure this would be a minimum value, not a maximum. Secondly, why does the hFE for the first scenario have a maximum value, but the other two do not (just hyphens)? Finally, is V_CE of 5.0 V a good bias point? The design I am basing off of, when simulated with a generic NPN, gives a V_CE of roughly 5V, so this makes me think so.

The final picture is the DC analysis of the amplifier I am working on in case it helps. I used 800 A/A as it is the average of 400 and 1200.


texts: Flat flex cable soldered to PCB is developing a short circuit over time

texts:
I'm facing the issue that an OLED display develops a short over time and stops working. The short always occurs at the solder point where the flat flex cable gets soldered to the PCB.
Touching the shorted pins with the soldering iron fixes the short and I can use the OLED again but after at least a few hours the pins are shorted again.
How can this happen? The OLED was hand soldered. Is there anything specific that has to be done to properly solder these connectors?

The short also always appears at the Chip Select and Reset line. This problem occurred on 3 different PCBs. So it's a bit weird that its never different pins.

Datasheet of the OLED module: http://www.buydisplay.com/download/manual/ER-OLED0.91-1_Series_Datasheet.pdf

Here a picture of the surrounding circuitry:


texts:
I have this textbook problem I am not sure how to go about doing it:

A 3 phase, 460V, 60HZ, 20KW induction Machine draws 25A at a power factor of 0.9 lagging when connected to an equivalent power supply. The core loss is 900W, stator copper loss is 1100W, Rotor Copper loss is 550W, Friction and Winding Loss is 300W. Calculate:

A) The air gap power
B) The mechanical power developed
C) The output horse power
D) The efficiency

I calculated the Pelec to be 17927W and the pshaft is given as 20KW. Why is my power drawn lower than my output shaft power? I thought you had to subtract all the losses from pin to get the pout. I dont understand whether it is a motor or a generator, or how you would go about subtracting in the case of a generator.


texts:
Can somebody tell me why R_o2 is RD
Why dont we take Rs into consideration ?

Their answer is Ro2=vt/it = Rd

My question is why didnt they take in consideration Rs and the current source?


texts: 230V AC to 24V AC Transformer Wiring (Black, Red, Brown, Brown)

texts:
I'm setting an irrigation controller and I need a 24V AC source to switch the irrigation solenoids.
Since I have 220V AC, I asked the electrical store for a 220VAC to 24VAC transformer and they gave me this one, but I'm unsure how to wire it. Which wires should connect to live and neutral on the 220VAC supply and which are live and neutral on the 24V output? My best guess is that the black wire is used on both the input and output as a common neutral, but don't want to chance it.
The below sticker came with the transformer:

The transformer has 4 cables, one black, one red and two brown:

Any advice appreciated!


texts: Large current spike in turn on boost converter

texts:
I have a circuit that boost voltage from 12V to 120V, the problem is the current in inductor is too big, around 5A, the circuit and the simulation in LTSpice is like this

the red line is the current, and the blue line is the voltage across zener diode, i just want to the big voltage without much current. how can i limit the current for around 1A? it is okey for the voltage to have a longer settling time
thank you


texts: Developing photoresist PCB with UV bank note checker

texts:
I'm just looking into developing a photoresist PCB. I bought a kit that contains a photoresist single sided PCB, developer solution (in powder form to mix with water), etchant, and a tank.

I have printed my circuit diagram on an inkjet transparency.

The only thing I was missing was a UV light to develop the photoresist. I tried it with a standard lamp and had no results after ~20 minutes, so I figured I needed a genuine UV light. It's too dark in the evenings this time of year for me to be able to do it outside.

I am looking into buying one of those bank note checkers that shops use to check for counterfeit money. It's a downward facing 4W bulb - here:

http://www.maplin.co.uk/p/mains-powered-uv-fluorescent-light-source-mw36p

Will this be sufficient to develop my photoresist? I don't need it done in a hurry and don't mind waiting a long time.

Update: Well I'm happy to confirm I got decent results from using the note checker, OHP inkjet transparencies, and some positive photoresist from Maplin. I just did a test, around 8 minutes under the lamp, then I got called for dinner! So about half an hour later, dunked it in a reasonably weak developer solution - maybe 100ml of water and two or three sprinkles of Sodium Hydroxide.

As you can see, the one closest to the camera turned out well (the scrappy bit on the side is because I cut the board with tin snips - not a great idea - and had a bit of the protective film left which I peeled away. It made for a good comparison). It's a bit weak in places, but those square pads on the right are perfect. The one behind it, not so much. I think I overexposed that one. It was the cheap board that came with the kit.


texts: Program only runs when debugging in GDB - using Open OCD and Olimex arm-usb-ocd-h jtag to program at91sam3su

texts:
I'm trying to make my Atmel at91sam3u cortex-m3 arm chip make an LED blink.  I have a Olimex ARM-USB-OCD-H jtag programmer, and I'm using Open OCD running on OS X to program my chip.  I'm using the provided Open OCD startup scripts for the jtag programmer and my chip.  I have no trouble compiling and linking the program, and I seem to be able to successfully load the program on the chip.  However, the LED only blinks when I run the program via gdb.  It works whether I step through it or run it continuously.

To make it work in gdb, I first run 'openocd' and then in another terminal (gdb feedback ommitted):

$ arm-none-eabi-gdb blinky/blinky.elf
(gdb) target remote :3333
(gdb) load
(gdb) cont

This works without any issues and the LED blinks.  Ofcourse, when I exit gdb, the program is stopped, and the LED is left in whatever state it was at that time.  If I click the chip's reset button the LED goes to a neutral (slightly on) state.

To try to simply program the chip, I run 'openocd' and then in another terminal:

$ telnet localhost 4444
> halt
target state: halted
target halted due to debug-request, current mod
xPSR: 0x81000000 pc: 0x00080107 msp: 0x20000598
> flash write_image blinky/blinky.elf
wrote 3044 bytes from file blinky/blinky.elf in 0.314594s (9.449 KiB/s)
> reset run
TAG tap: sam3.cpu tap/device found: 0x4ba00477 (mfg: 0x23b, part: 0xba00, ver: 0x4)

There are no errors, but the LED does not blink, it stays in a neutral state.

The linker script sets the program (.text) to be put in flash0 memory.  Thus I've tried setting gpnvm bit 1 as that is the sram vs flash boot select bit according to the at91sam3 datasheet.  This did not help, and it seemed to have prevented gdb form running properly.

Do I need to maybe flash the board with some sort of bootloader that can load programs from the flash0 bank?  I assumed that the chip came with this.

I have not yet been able to load the .text into sram instead of flash0 as I've had trouble changing the linker script I have to do this.

Note:
The at91sam3u chip is on a custom pcb designed as part of a student design project.  Thus, it is possible that a mistake was made during the pcb design... however, I would think that in that case it would not run properly in gdb either.

Thank you.


texts: Calculating the cut off frequency of a filter circuit if you know all the component values

texts:
I realise this might seem like a rookie question, and there must be plenty of info out there about it, but I am so new to electronics  I don't understand the information I'm finding well enough.

Basically, I'm trying to build a 3rd order butterworth filter from a schematic. I don't have exactly the same capacitor values, so I'd like to know how to calculate the cut off frequency resulting from the components I do have. I'm certain this formula is also on the same Web page, but again I'm so inexperienced, I'm struggling to figure out which of the many formulas it might be.

This is the circuit diagram:

And this is the website it comes from:

http://www.electronics-tutorials.ws/filter/filter_8.html

Any help here would be much appreciated, and explanations as to how to recognise the right formula and why would also be awesome! I like to work towards self sufficiency whenever possible.

Pete


texts: Organization of large memory using memory blocks

texts:
I found the following question in a test. I am not looking for an answer to the question per se, but I am having difficulty understanding the part in bold, as explained below.

  A main memory unit with a capacity of 4 megabytes is built using 1M×1-bit
  DRAM chips. Each DRAM chip has 1K rows of cells with 1K cells in each row. The
  time taken for a single refresh operation is 100 nanoseconds. The time required
  to perform one refresh operation on all the cells in the memory unit is?

As far as I know, an m x n memory chip has m rows of n cells each. Hence, the given chip should have 1M rows of 1 cell each. How come the bigger memory unit built out of it has 1k cells in each row?

What is the mistake I am making here? Is my understanding of the memory chip specification incorrect, or is there a way of reconfiguring memory chips to have more columns per row that I do not understand? Can someone please explain this to me?


texts: Simulation of a chopper type E (four quadrants) in pspice

texts:
Im trying to make a chopper working in the four quadrants based on these idea

translated to this circuit

But it cant be simulated, psice gives the next log

ERROR -- Convergence problem in transient analysis at Time =  63.61E-06
         Time step =  31.28E-21, minimum allowable step size =  1.000E-18

the time of simulation is 10 ms
I dont know if the circuit is well implemented.
It got stuck at 95% and send me the dialog

but thats all and dont grasp the idea of the error


texts: Generate a higher-than-power-supply voltage with capacitors

texts:
I want to design a circuit which is able to generate 8-10V from a power supply of 5V by chargin parallel caps and switch them to series connection (by using transistors) so they reach the desired voltage. I'm not sure how to do this.
This is what I have thought:

Explanation (please correct me when I'm wrong):

The caps. are put in parallel/series by a series of BJTs controlled by a clock signal (2Hz).
During the rising edge, Q10, Q12 and Q13 are enabled, and all the other BJTs are off. This puts C7 and C8 in parallel with the 5V power supply, so they charge.
Then, during the falling edge, Q11 and Q2 are enabled and the other BJTs disconnected. That leaves C7 and C8 charged at 5V in series (so they should mimic a 10V power supply if I'm not wrong), and in parallel with C9. As far as I understand, at this moment C9 should be charged until it reaches 10V (ignoring losses).
When the caps. are in parallel, they are in series with a 220 ohm resistor (R34). That gives a time constant of 0.439ms (220 ohms * 2e-6 farads). Having that the clock is working at 2Hz, they should have more than enough time to charge I think.
When the C7 and C8 are in series, and in parallel with C9, there is no resistor so they should charge C9 very fast, right? The discharge will be very quick as well, but for now I only want to see some ~8V moments at C9.
RL is a resistor used to simulate a load.

The result I get at C9 after the simulation finishes is that it stays at 4V. If I remove C9 and probe the voltage at C7, it switches between ~4 and ~8V depending on if they are in series or parallel due to the action of the clock.


texts: Wheatstone Bridge Single-Element Varying

texts:
So, this book is saying that when V_B is 10V, R is 100ohms, and delta R is 0.1 ohms, The linearity error is 2.5mV - 2.49875mV = 0.00125mV.
I don't quite understand where 2.5mV came from.

If I use the equation on top, I get 10*(100/(100+100) - 100.1/(100.1+100)) = -2.49875mV, and if I use the equation on the bottom, I get (10/4)*(0.1/(100+0.1/2)) = +2.498751mV.

Why am I getting the opposite sign? what do those four equations represent? and why is the error 0.00125mV and where did 2.5mV come from?

I know this is a dumb question, but this has been driving me nuts..

Thanks in advance.

https://www.analog.com/media/en/training-seminars/design-handbooks/Op-Amp-Applications/Section4.pdf


texts: Why do you need a thicker wire when wire length increases?

texts:
Question:
So far I've found that the thickness of the wire influences the resistance. A thicker wire has less resistance. Also, the length of a wire has a linear correlation with the resistance. 2x length = 2x resistance. So your wire resistance will be length / thickness, but that doesn't explain why the thickness should increase with length. What am I missing?
Elaboration:
I can think of two consequences of what I've explained above: first, with a high wire resistance, your voltage will drop and you might not get the voltage you need. Second, having a thin wire with lots of amps will potentially melt the isolation and be a hazard.
So let's say we would accept any voltage loss and just don't want a hazardous situation. We take a wire of 1m. Then we run a certain amount of current though it which will produce heat in the wire. Now we double the wire length to 2m, so double the resistance. We run the same current through it which will produce double the amount of heat, but over double the amount of length. Unless you're coiling your wire I don't see how it should make for a more hazardous situation.
And the other way around, according to this calculator http://www.solar-wind.co.uk/cable-sizing-DC-cables.html if you have a 1cm wire and running 100 amps @ 12 volt you can do with 0.5 mm2. How is that possible?


texts: One-wire concept for WS2812B - adding signal onto DC

texts:
I would like to reduce the amount of lines for a string of WS2812B RGB LEDs for a project. In my understanding two lines should be sufficient, since we can modulate the signal onto the DC line.

Similiar questions have been asked and answered on this platform: "How to couple a signal on to a DC line", "Injecting a communication signal over DC power supply lines" and proably more.

So I went ahead and simulated an according circuit in LTSpice. Below you find my circuit and the simulation result.

(All plot curves are voltages; Red curve is the input signal, blue is the dc+signal mix, green is the demodulated signal and turquoise is the demodulated DC. C4 symbolizes the 15pF input impedance as per datasheet and D1 approximated the power consumption by the RGB LED. ws2812.txt contains a random 5x24 bit signal modulated as per datasheet for the WS2812B).

As you can see, the modulation and demodulation seem to be working just fine, except for the huge overall oscilation/swing.

My guess is, that that comes from the effective LC-Circuit formed by C1, L1, C2 and L2. I played around with this circuit for hours to get rid of it, but was never really successful. My best attempt can be seen below: I added one 5V-zener-diode for the demodulated signal branch. (Please note the different colors for the voltage plots.)
(All plot curves are voltages; Green curve is the input signal, blue is the dc+signal mix, red is the demodulated signal and turquoise is the demodulated DC).

According to the WS2812 datasheet the resulting signal should be ok, except for the continued swing on the signal line after the actual signal ended. I was wondering if I was doing anything wrong and/or if there was a better solution.

One thing to keep in mind, is that there should never be any voltage dropping element in series with the dc part of the line, since we want to add several of these circuits in series and each needs a dc component of 5V.


texts: Why does AT91SAM7X microcontroller have different instruction modes?

texts:
The AT91SAM7X microcontroller has several instruction modes:

TDMI32bit
TUMB16bit
Jazelle8bit

Each of these modes has its own instruction code.

Why did Atmel make a 32 bit micocontroller (TDMI32bit) but make 16 bit (TUMB16bit) instructions the default?


texts: I bought the new Dayton 3 phase 208/230vac blower model #3HMJ8.  There is 3 wires red/white/black and next to the diagram for each wire on the blower is a letter.  I don’t know what these letters mean..  my goal is to have it hooked up to a clothes dryer cord/plug that’s 240v so I can just plug it in and use as a fan as needed..  can anyone tell me how to hook his up....  graingers instructions are horrible I emailed them no reply yet


texts: Find Thevenin equivalent voltage - Circuit Analysis

texts:
I am trying to understand how to calculate Vth (between the blue Volt meter and the grey volt meter).

I have calculated the current correctly using KVL. However, I can't find a way to calculate Vth. According to the simulator the result is: -7.746v but I do not know how to get to this result.


texts:
which of these spring terminals suits better AWG30 wires?

I've found 3 types:

PCB Mount type (rated for 26 to 20AWG)
Wago/lever type (rated for AWG28-12)
CH-3 type (i've found no rating for these)
other solderless terminals you suggest?

Most of them are signal wires only. A few of them will drive some current  within the USB specs (<500mA).
The installation spot won't vibrate much (it's a box over my desktop).
I am mostly interested to avoid damaging the wires due to excessive pressure.


texts: Falling edge detector sometimes doesn't work

texts:
I have a falling edge detector built based on a D flip-flop as shown in the following figure:

Components: 74hc74, 74ls04n, 74hc08
A sample output is shown below (I invert the output since I need it as an active low):

My question is why it sometimes doesn't detect the falling edge?

Thank you all so much!
The problem was the logic analyzer sampling rate and frequency as @Elliot Alderson mentioned.
I re-configured the PulseView and finally could capture the output correctly (indeed there was nothing wrong with the circuit itself)


texts: I got a model from net and want to open it, but I encounter with this error. Can somebody there help?


texts: To determine wheteher the 18650 li ion is protected battery

texts: How to do correct test and determine whether a 18650 li ion is protected or non-protected battery?


texts: Is it better to use mains power or an external power supply for a rack mount unit?

texts:
I've seen many rack mount audio units that have an IEC connector for direct mains power, and others that have a DC jack for an external power supply (12V DC for example).

What are the advantages and disadvantages of the mains vs. external power supply route? In terms of design difficulty, manufacturing cost, safety, etc.?

From what I can tell, an external power supply would be easier for design of the unit and less expensive. And there are of course additional safety requirements for the mains voltage route. But I'm curious to know more specifics.


texts: In the figure given below, assume that the diode and op-amp are ideal. \$V_{i}\$ varies from +1V to -1V. How will the output voltage \$V_{0}\$ vary?


texts: Switching between two power sources when getting to threshold

texts:
Im not exactly from the EE field and I would happy for guidance. long question a head:
Im trying to build a circuit for keep running Raspberry Pi using solar panel + rechargeable battery.
I came across this nice article. on the bottom of it, there is section of Power Sharing which seems like good and working design. but the thing is that this design talking about two scenarios:
1. what happens when power source connected (both load and battery getting current)
2. what happens when power source disconnected (load getting current only from battery)

Now, I thought to use that design and add the solar panel so it will feed both the load and the battery.
On sunny day, we have no problem, both the load and the battery getting current:

The issue is what happens on bit cloudy day. the solar panel could output much smaller voltage than 6v so it will be necessary to detach the solar panel from the P-Channel-Mosfet, so the load will get its current only from the battery.
If I keep the wiring like this:

The voltage could be not low enough for influence the Gate and feed the load only from battery + the DC-DC will not react good to 3v\2v\1v because it minimum voltage is ~6v.
So I understand that there is a need to disconnect the solar panel , so the gate will 'turn on' the mosfet and current will flow from Drain to Source and feed the load + disconnect the charge controller. so we have two options:
option 1:

option 2:

So, I guess my questions are:

The main question- How can I disconnect the solar panel (option 1 \ option 2) when the voltage gets under threshold voltage (for example 4v)? there is a need with another power source of that threshold for comparison (less preferred option)? if there is a way implementing it without chips \ minimum waist of current from solar panel (I guess with mosfets) it will be very helpful.

The values on this example are not set yet (solar panel + DC-DC conv + pull down resistor), Im looking for DC-DC that can get as input range of ~3v to >15v and output 5v but couldnt find one, minimum input is about 6v.. is there unit that can implement that? (the rest of the values will be set according to DC-DC input volatage)

Sorry for the long question :)
Thank you all!


texts: Resolved: Howto re-wire Sony Simulview 3D glasses for Dual Play Support

texts:
Circuit board here:

These active shutter 3D glasses work by alternating a shutter lens on and off in sync with the TV and the resulting effect is that 120 Hz refresh are used for left eye, and the other 120 Hz of refresh are used for the right eye, which produces the 3D effect.

Black Ops. 2 offers a mode when playing split screen with a friend to use "dual play". Dual play is a passive 3D technology uses the opposite polarized lines on the screen to work. These new sets come with "dual play" glasses which is essentially a dual left eye pair and a dual right eye pair so that player one and player two each get a 2D full screen.

My TV allows me to place the 3D mode in to "top and bottom" mode and when I do this mode after activating "dual play" in the game, it works on my active 3D TV perfectly, however the problem is the glasses are alternating instead of giving both of my eyes left and both my buddies eyes' the right POV.

We could play this way, if I kept my left eye closed and he kept his right I closed the whole time but that is actually harder than it sounds.

So after doing a ton of research the most cost effective way to achieve what I want to do is to rewire two pairs of these glasses to give me both left or both right instead of alternating.

I've already taken a set of shades apart. The main circuit board sits right there in the bridge of the nose, the right lens is on the right and the left is on the left. As you can see the very top right corner has to connections and the top left corner has two connections. These are the connections that connect to the lens' that tell it when to flash its shutter.

I understand what I need to do, is to make this pair a LEFT LEFT pair, I would have to disconnect the right lens and then run a wire to the left side but IN PARALLEL - apparently series will not work for this.

I will get a voltage meter tomorrow so I can figure out which one is positive and which one is negative, but lets just say for example the outermost pins are the negative, and the inner most pins are the positives. How would I run the wire so as to keep the circuit parallel?

Does this sound like it will work?


texts: Spike in inverter output waveform due to Cgd coupling

texts:
So while analysing the waveforms, I have noticed spikes in the ouput during input transitions for gates like inverter, nand etc. and so I was asked to look up Miller effect to explain the phenomenon. After reading through the topic (how Cgd appears across the input and the output) I found that this is caused due to the capacitive coupling of the input to the output by the gate drain capacitance. I can neither grasp the theory behind this completely nor can I figure out how the spike decays back to the supply voltage after a few moments. Can someone give me a detailed explaination for this effect.
PS. this is what the waveform looks almost like except that the spikes appear when output switches to one and when it switches to 0 (opposite to the waveform) like:


texts: Cadence Virtuoso 6.1.6 is EXTREMELY slow while simulating

texts:
I'm running Cadence Virtuoso 6.1.6 through a remote desktop to computers at my school. These computers run Fedora 22. I'm simulating a ring oscillator VCO on Cadence, but it is taking literally FOREVER to complete the simulation. Here is the schematic of my VCO -

I have a vpulse generator which is attached to the feedback loop (as can be clearly seen in the above figure). I have a feeling that this pulse generator is the main source of the problem because the really slow simulations started after I added this component into my schematic.
Here are the parameters I have set for the pulse generator, just so you can get an idea -

I started simulation and it takes about 20 minutes to get to 12%. When I click the "Plot Outputs" button in ADE L, it shows that the simulation hasn't even started oscillating yet...and the estimated time of completion ranges from 1Hr16Min to 3Hrs+!
Has anyone else encountered this problem? If so, how can this be solved?
EDIT: I used the Ultrasim simulator on Cadence which simulates thousands of times faster than spectre, which was the simulator I was using before.


texts:
For some ADCs and DACs I'm using I need a 24.576MHz clock (96kHz * 256). Obviously I can use a low jitter audio clock generator. However, I have a AM335x processor available that claims to have a low jitter clock (ADPLLJ). Could I use this clock? It appears that it can be divided and multiplied to reach that frequency and it would save some trouble of getting a clock generator and a crystal oscillator if I could use this low jitter clock. The clock is explained in the AM437x reference manual. The clock also exists on the AM335x but the reference manual only mentions it briefly.

AM437x
AM335x


texts: Would this circuit work as a binary calculator?

texts:
Forgive me if this is a stupid question with a poorly drawn circuit diagram. I've never really made anything electrical before, so this is all very new to me.

I've recently been wondering how transistors can be used to add numbers together, and learned that it is done using logic gates. I thought I'd try to understand how this could be done, by drawing a circuit diagram for the half adder of an ALU. The below image is what I came up with...

For those unaware of how binary addition (for a single digit) works, the intention of this circuit is for neither LED to turn on if neither switch is closed, for only the top LED to turn on if only 1 switch is closed, and for only the bottom LED to turn on if both switches are closed.

This can be represented by the following truth table:

Would this circuit work correctly, in the way I have described? If not, how can I change it so that it would work?


texts: Why use a pull-down resistor with a LDR and microcontroller?

texts:
I am looking at this:
http://learn.adafruit.com/photocells/using-a-photocell

It's connecting VCC <-> LDR <-> resistor <-> GND. And the analog input is between the LDR and the resistor.

I understand than a resistor may be necessary to control the current (in case the LDR resistance is very low). But Why can't I just do the following:

VCC <-> LDR <-> resistor <-> Analog Input

And forget about the pull-down?


texts: How do I get a KCL equation involving Vin in this circuit?

texts:
simulate this circuit – Schematic created using CircuitLab
I've been scratching my head with this one. The circuit below is a small signal equivalent circuit of a PNP CB amplifier. I'm trying to get the transfer function Vout/Vin. I was already able to find Vout/Vbe using KCL across the node Vout. Now i'm stuck with the equation for Vin. Could anybody help me get started?
Here is what I got for Vout/Vbe where Rout = R3//R4:
$$\frac{v_{out}}{v_{be}}= \frac{g_{m}R_{out}*1-\frac{sC_{2}}{g_{m}}
}{1+sR_{out}C_{2}} $$
Edit: I made quite the mistake in the schematic.
Edit(2): Here is the old schematic:


texts: Buck converter quiescent current is too high

texts:
My circuit uses a LMR50410Y3FQDBVRQ1 buck converter to convert an input voltage from a LiPo battery to a 3.3 V supply voltage.

The first batch of the PCB uses the 3.3 V fixed output variant (LMR50410Y3FQDBVRQ1), so I don´t assemble R203 and R204. R203 is replaced by a zero ohms resistor and R203 is unassembled.
I have connected the PCB with my laboratory power supply and a multimeter for current measurement and my multimeter (and the power supply) displays a ~7 mA supply current.
Why does the design draw that much power without a load? Texas Instruments writes something like a few µA in her datasheet.


texts: What are these spots on the PCB that are by the mounting holes?

texts:
When you look at the board, there is a weird part of the PCB right of the top left mounting hole. There is also another one above the top right mounting hole.

****                            ↓ Here's one                                            **

This image is directly copied from https://arduino.cc/en/Main/ArduinoBoardUno.

What are these? Is this just created when this is manufactured (to grip to to move the board or to grip during solder mask creation), or does it serve a purpose (something to hook a multimeter to)?


texts:
Is the following test bench correct?
I tried to use a text file with the content

00
01
10
11

to test an architecture of an and port.

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use ieee.std_logic_misc.all;
use std.textio.all;

entity my_and_tb is
end entity my_and_tb;

architecture tb_arch of my_and_tb is
    component my_and is
    port  ( x, y : in std_ulogic;
           z : out std_ulogic);
end component;
signal x_tb, y_tb, z_tb : std_ulogic;
begin
my_and_inst : my_and port map( x => x_tb, y => y_tb, z => z_tb);

tb_process : process
    file my_input : TEXT open READ_MODE is "my_input.txt";
    file my_output : TEXT open WRITE_MODE is "my_output.txt";
    variable my_line : LINE;
    variable my_input_line : LINE;
    variable my_output_line : LINE;
    variable x_bit : bit;
    variable y_bit : bit;
    variable z_bit : bit;
begin
    while not endfile(my_input) loop
        readline(my_input,my_line);
        read(my_line,x_bit);
        read(my_line,y_bit);
        x_tb <= to_stdulogic(x_bit) after 5 ns;
        y_tb <= to_stdulogic(y_bit) after 5 ns;
        z_bit := to_bit(z_tb);
        write(my_output_line,z_bit);
        writeline(my_output,my_output_line);
        wait for 10 ns;
    end loop;
end process;
end architecture tb_arch;

Basically the simulation with ncsim is blocked...
Update...

Same problem for this example (is a flip flop d, and basically the clock make me confuse, i thought it was ok but it isn't... could you help me?)

library ieee;
use ieee.std_logic_1164.all;
use ieee.std_logic_misc.all;
use ieee.numeric_std.all;
use ieee.std_logic_textio.all;
use std.textio.all;

entity ff_d_tb is
end entity ff_d_tb;

architecture ff_d_tb_arch of ff_d_tb is
component ff_d is
port(clk, d : in std_logic;
     q : out std_logic);
end component;

signal clk_tb, d_tb, q_tb : std_logic;
begin

ff_d_comp : ff_d
port map(clk => clk_tb, d => d_tb, q => q_tb);

clk_process : process
begin
    clk_tb <= '0','1' after 5 ns;
    wait for 10 ns;
end process;

ff_process : process
    file in_file : text open READ_MODE is "input.txt";
    file out_file : text open WRITE_MODE is "output.txt";
    variable l_in : line;
    variable l_out : line;
    variable q_loc, d_loc : std_logic;
begin
    while not endfile(in_file) loop
        readline(in_file,l_in);
        read(l_in,d_loc);
        d_tb <= d_loc after 5 ns;
        wait until falling_edge(clk_tb);
        q_loc := q_tb;
        write(l_out,q_loc);
        writeline(out_file,l_out);
    end loop;
    wait;
end process;
end architecture ff_d_tb_arch;


texts: Why is my Verilog code for Mealy-type sequential circuit not working?

texts:
I am supposed to write code for a circuit which outputs (z) 1 whenever the 2-bit input (x) is either 00 or 11 for two consecutive clock cycles. I feel like I'm close, but I can't figure out where I'm going wrong. Help! It's 1 module and 1 test bench. I also attached the waveform and state diagrams. For some reason the output (shown in red) is 1 whenever the input is 00 or 11 (shown in yellow), regardless of the previous state.

module EqulNchecker
(
output reg z_out,
input [1:0] x_in,
input clock, reset
);
reg [1:0] state, next_state;
parameter S0 = 2'b01 && 2'b10, S1 = 2'b00, S2 = 2'b11;
always @ (posedge clock, negedge reset)
begin
    if (reset == 0) state = S0;
    else state = next_state;
end

always @ (state, x_in)
begin
        if(x_in == 2'b11) next_state = S2;
        else if(x_in == 2'b00) next_state = S1;
        else next_state = S0;
end

always @ (state, x_in)
begin
    case (state)
        S0: z_out = 0;
        S1: if(x_in == 2'b00) z_out <= 1; else  z_out <= 0;
        S2: if(x_in == 2'b11) z_out <= 1; else  z_out <= 0;
    endcase
end
endmodule

module test_EqualNchecker();
wire z_out_test;
reg [1:0] x_in_test;
reg clock_test, reset_test;

EqulNchecker M0(z_out_test, x_in_test, clock_test, reset_test);
initial #260 $finish ;
initial begin clock_test = 0;
    forever #10 clock_test = ~clock_test;
end

initial fork
    reset_test = 0;
    #10 reset_test = 1;
    #20 reset_test = 0;
    #30 reset_test = 1;

    x_in_test = 2'b00;
    #40 x_in_test = 2'b10;
    #60 x_in_test = 2'b11;
    #80 x_in_test = 2'b00;
    #100 x_in_test = 2'b11;
    #120 x_in_test = 2'b11;
    #140 x_in_test = 2'b10;
    #160 x_in_test = 2'b11;
    #180 x_in_test = 2'b00;
    #200 x_in_test = 2'b00;
    #220 x_in_test = 2'b10;
join
endmodule


texts: How much is impedance of a typical hands-free speaker and how much power is needed to properly drive it?


texts: What transistor setup to use for level shifting to create a logic ENABLE signal (for DC-DC converter module)

texts:
I want to create an ENABLE signal driving a Murata OKI-T/3-W32P-C DC-DC converter, where the P stands for Positive Polarity of the On/Off Control line: the line has an internal pull-up, which means that the converter is on when the Control line is open or high, and off when pulled to GND.

So what I have right now is a DISABLE signal, based on an N-channel enhancement-type MOSFET (2N7000).

From what I read online, the easiest way to turn this setup into an ENABLE signal would be to use a depletion-type MOSFET, but I understand that these are rarely used? Or are there depletion-type MOSFETs that are generally recommended just like 2N7000 and other general-purpose transistors?

If not, what would be the right way to go here? connecting the DISABLE signal to Vin using a pull-up resistor, and add another transistor at the low side to pull down the DISABLE signal when the ENABLE signal is activated?

Follow-up:

So here's the adjusted schema following @peufeu solution (thanks for providing a complete solution + explanation):

Which leaves me with the question whether this is the general way to go, or whether the MOSFET-based solution can/should be used when Vin is not as high as 32V:

In the datasheet for this OKI-T/3-W32P-C module I see that there is simply a switch symbol. But in the datasheet for the ABB ABXS002A3X41-SRZ module (fig. 27 on page 11), for example, there is a N-channel/enhanced MOSFET in the circuit. Is that because the max Vin in this case is only 16V? which means that a 2N7000 could be used directly here, as its max Vgs is 20V continuous?

Similar thing in the datasheet for the Murata OKL-T/6-W12 module: Fig. 7 on page 15 shows the P-channel/depletion setup (for a module with negative logic) that I initially thought I could use. This module has a max Vin of 14V, so in this case a MOSFET would be able to handle it without level shifting? And if so, what transistor would be a good candidate?


texts: Red laser that has a higher power output at 400nm than 623nm?

texts:
I am doing experiments using a red (623nm) LED. However, when I measured the power output I noticed that it is higher at smaller wavelenghts. I did the measurements using two different power-meters and both gave me that result.
First, I am confused since I though LEDs should only emit light in a small wavelenght range.
Second, I don't understand how I can see the LED as red when it emits light in all the visible light spectrum and emits even more in the blue/violet range that in the red range..
The LED is #9008097 in the following datasheet:
https://asset.conrad.com/media10/add/160267/c1/-/gl/000180735DS01/datenblatt-180735-ledxon-9008097-highpower-led-modul-rot-3-w-865-lm-10-2-v.pdf
Thanks in advance!


texts: Single supply op amp to convert 0-5VDC to +/-2VDC (microcontroller to line level)

texts:
I am generating a 0-5 volt sine wave using an arduino with a DAC.
I would like to level shift this signal (DC bias?) by -2.5 volts and have a gain of .8, so that I end up with a line level sine wave.

Thus I am trying to design a single supply op amp with the following equation:

$$V_{\text{o}} = (V_{\text{i}}-2.5) \times 0.8$$

I found this white paper that is supposed to describe a way to do this but I'm having trouble following as I am new to op-amps.

https://www.eecs.umich.edu/courses/eecs452/Labs/circuit4.pdf

Does anyone know of a way to do this with a single op amp or IC?

The frequency range of 20Hz to 20KHz must be preserved.


texts: Can nRF52 simultaneously use Bluetooth and act as USB HID Keyboard?

texts:
I want to ask something related to the use of the nRF52 as a HID keyboard (USB host).

I have already played around with the SDK example ble_app_hids_keyboard and tried to understand it as much as I could.

Now I want to use to use the nRF52 as a bluetooth dongle. On one hand it has to be able to connect to another device (another nRF52 - serving as the keyboard) via bluetooth and on the other hand transfer this data to a PC as a USB.

So the question is whether the nRF52 can be configured like that, act as a USB host and communicate via bluetooth to another device at the same time?

I have some knowledge on how the USB and HID protocols works, however it is not enough to manage to succeed on this issue.

Thanks for the replies.

I did not mean to connect a keyboard to the nRF52832. I meant to have the nRF52832 act as a keyboard, which I have already done and then use its Bluetooth capability to connect it to a USB dongle, which then would transfer the data to the PC.

My problem is the dongle. I thought that I could maybe use another nRF52832 to implement the dongle, but I am having trouble with it. However, after some research, ai figured out that one of the most popular USB dongle chips is the CSR8510.

However I do not know how to program it. All I could find is that people have bought some 500€ development kits which they use to program the chips.

ai would like to ask you guys if you know any method to program the CSR8510 wothout having the development kit?

Thanks in advance.


texts: Could a "non-dimmable" LED lamp be dimmed with PWM?

texts:
I have some experience with house wiring, and more recently gained some experience with 5mm RGB LEDs and an Ardiuno.

In that, I learned about PWM for dimming an LED.

I suspect that the standard wall dimmer an electrician installs is just a variable resistor. I could understand that doing weird stuff if there is some transformer or something in the non-dimmable led lamp.

I found that you can get solid state relays for an Ardiuno that can handle 250V AC and 2 amps. Since they are solid state, I suspect I could turn them on and off fast.

What happens if I PWM a standard "non-dimmable" LED lamp? Is there some complicated circuitry (that I don't yet understand or know of) that will interact poorly with a PWM power source?

(That does bring me to realize that for the PWM to work well, it should operate at a speed that doesn't have any weird "Lowest Common Multiple" effects with the AC supply that would be visible).


texts:
Regarding a MAX10 board. The whole design inside the MAX10 is clocked from a single clock using verilog's always@(posedge clockin).

If connect directly a 80mhz clock to a Max10 input pin and define this clock inside quartus's .sdc file. The compilation gives no error / timing requirements are met with solid margin.

For BOM simplification, the external clock is changed to 8mhz. So I use a altPLL megafunction to multiply clock by 10.

Then, I get multiple warnings:

Warning (15055): PLL xxx is not fully compensated and may have reduced jitter performance because it is fed by a non-dedicated input
Timing requirements not met (inst5|altpll_component|auto_generated|pll1|clk[0] setup slack: -2.197, endpoint tns:  -8.124) on the PLL output.

To my understanding, the first warning indicates the PLL input may not use a dedicated clock input pin. However were tested, one by one, every clock input pin available on the chip with no change at all. Currently using "clk0p".

Regarding the timing not met, no matter the PLL output frequency set (80mhz, 40mhz, 20mhz, etc, the slack remain negative).

Worth mentioning: If setup either PLL input or output pin as "global clock" in the assignment editor, they are marked as "ignored QSF Assignment" in the fitter's report. Also, the PLL output is reported to be 50% duty cycle, so it shouldn't behave worse than the use of a external 80mhz clock.

How could a altPLL generated clock generate so much trouble and ruin the design? Thank you for your inputs.

Ic: 10M02
Tool: Quartus 16.1


texts: Where do electrons go after reaching GND in this Arduino Mega design?

texts:
When examining the EAGLE file for the Arduino Mega that I downloaded from their official website, I noticed that the ground (GND) is not connected to anything other than the C4 component, which means electrons flows from +5V through the C4 component into the GND.

When I look at the actual board, I see that the GND is indeed only connected to the C4 component and has no path connected to anything else at all.

Does that mean when I plug in the Arduino board to a power source, the electrons from +5V just start piling up at where GND is, since there is not an outlet for it? Won't there come a point where there are so many electrons piling up at GND that electrons at GND start repelling the electrons flowing from +5V, and the circuit just stops working?


texts: N MOSFET Issue in Battery Charging Circuit

texts:
My project uses a USB connection to charge a LiPo battery. The LiPo has built-in circuit protection. Everything works fine when hooking the +5V line straight from the USB hub to the battery's positive terminal, and connecting the grounds.

I want to use an LED to indicate that the USB cord is plugged in. The LED should be turned off when the USB cord is unplugged.

I thought using a N MOSFET would be a simple solution - the +5V line from the USB going into the drain, the battery connected directly to the source, and the gate pulled up from the +5V USB line through a resistor. Then I can simply add an LED and resistor on the +5V USB line, which would light up when the USB line was being powered and wouldn't see the battery voltage when the USB isn't plugged in (because the gate would be at zero potential).

Here's my circuit:

I am using the nMOS contained within this IC: FDC6333C.

Unfortunately, the datasheet doesn't explicitly name the pins as 'drain', 'source', and 'gate'. I know there are many different MOSFET symbols used, and I am currently assuming:

pin 1: gate
pin 5: source
pin 6: drain
current should flow from drain to source

The IC's pMOS pins are not being used and aren't connected to anything.

The USB port supplies 5.16 V.

I noticed the following behavior, which I am trying to make sense of:

The LED remains lit when the USB cord is unplugged. I assume this is due to the internal diode within the MOSFET allowing current to flow from the battery to the LED.
I see a 1 V drop across the transistor even when I do not have the battery attached. This puts the 'battery' line at a mere 4 V, which would be unable to charge the battery up to it's max value of 4.2 V.
Switching the source and drain pins seems to provide expected behavior. The LED does not light up when the USB cord is unplugged. With the battery unplugged, I only see a 0.3 V drop across my transistor, which is an adequate voltage to otherwise apply to the battery to charge it.

Here is the data that I took over all possible permutations of USB and battery being connected and different source and drain arrangements:

My initial conclusion is that my interpretation of the datasheet was incorrect - namely, that pin 5 is the drain and pin 6 is the source.

Is the fix really this simple? Or am I missing something more fundamental here? Is there a simpler way to achieve my goal? I am a relative n00b, so all help, advice, and criticism is appreciated.


texts: Transistor latch circuit - what's the capacitor for?

texts:
I've been studying this transistor "latch" circuit over the past couple of days and I think I've grasped most of it, but I'm not sure about the purpose of capacitor C1.

https://circuitdigest.com/electronic-circuits/simple-latch-circuit-diagram

If I understand correctly, the operation of the circuit is as follows: When the input is high Q1 turns on which in turn causes current to flow through the base of Q2 to the collector of Q1, turning Q2 on. Feedback to Q1's base from Q2's collector keeps Q1 turned on, which in turn maintains Q2 on.

As for the capacitor, I notice that if I don't include it sometimes the circuit won't latch, but I'm not 100% on the reason why. I thought perhaps the purpose of the capacitor was to allow Q2's base current to flow briefly in the event that Q1 is momentarily turned off?


texts: LTspice XVII: Subcircuit pin names in Operating Point analysis

texts:
Is there a way to have subcircuit names show up in the Operating Point analysis?

For instance, I have this test circuit:

Here, the pins are named A and K for the opto's LED and C and E for its transistor pins.  In Transient analysis, measuring the currents is intuitive:  the traces are named Ix(U1:A) for anode current, Ix(U1:C) for collector current, etc.  But when I run an Operating Point analysis, the pins are simply numbered:

EDIT: Below is the subcircuit model.

.subckt TLP383 1 2 3 4
R1 N003 2 2
D1 1 N003 LD
G1 3 N002 N003 2 {gain}
C1 1 2 30p
Q1 3 N002 4 [4] NP
.model LD D(Is=1.2e-12 N=1.6 Cjo=30p)
.model NP NPN(Bf=610 Vaf=140 Ikf=15m Rc=1 Cjc=19p Cje=7p Cjs=7p C2=1e-15)
.ends TLP383

The {gain} value for -GR and -GB is 3.25m and 6.78m, respectively.


texts: Lets say I have an audio source and I want to enable a digital output when a sub-audible CTCSS tone is present at 100Hz. How can I electronically achieve this?


texts: incandescent bulbs on Christmas light string allowed?

texts:
Is connecting 6.0 V and 2.5 V incandescent bulbs on same light string allowed? In a 50 light bulb string I like to put two 6.0V bulbs and cut off 5 light sockets.
The total voltage in the string will be 19.5V.


texts: Ferrite core selection for boost converter using push-pull topology

texts:
I'm trying to build a boost converter with the following specifications.

Switching Frequency: 100 kHz
Maximum Input Voltage: 14 V Nominal
Input Voltage: 12 V
Cutoff Input voltage: 10.5 V
Power rating: 1000 VA
Transformer type: Push-pull transformer for boost converter
Number of primary windings: 1 - Center tapped (10 V - 14 V)
Number of secondary windings : 1 (350 V)
Number of auxiliary windings : 1 (15 V, 2 A)

The thing I'm confused about is how to select the right core for this design. I know that this design would need a EE core but rest selection parameters are what I'm really confused about. Such as selection of operating flux (Bmax) (is it based on power, current or it's independent), core material, interpreting Al value given in the datasheet, selection of core with respect to power rating of the application. I read articles from "tahmidblog" here about transformer design. There he explained rest of the parameters calculations excellently but choosing a core particularly is what I'm not understanding clearly.
Please help me understanding it, for example how to select a core material depending upon power?


texts:
I want to ask if it's a good practice to add or leave room for an AC termination with a driven clock signal like SPI CLK. With a driven clock signals I mean something like a clock that it isn't always active.

Since a driven clock can be assumed as a signal data line, if answer is affermative, should AC termination added to data lines to improve reliability?


texts: Need to level shift, buffer, and distribute a long distance, a 1.28 MHz signal

texts:
Not sure how to tackle this issue. I have a 1.28 MHz digital clock signal with 0 = 0V, 1 = 1.5V. I need to buffer it and split it for distribution, some of the outputs will travel approximately 100 feet. I'm flexible with the output voltage but I was thinking 5 TTL. The high voltage requirements of 5V may slow it down.
Option 1) Find a clock buffer distributor chip that works, then use line driver chips
Option 2) Use a voltage comparator circuit to change levels (or a different technique), then buffer distribute and line drive
Option 3) ?????


texts:
I opened up the case of an old toy to take a look at what is inside.

The device had what seemed to me a bizarre LCD display with a controller(or microcontroller?) I have never seen before(middle image).My question is:what kind of display is this,what kind of controller&how does it all work together?Note that the LCD is attached on with the help of two rubber bands(first image) and can easily be removed or be placed back without soldering or desoldering it.Also,what's the role of the black cover placed in the middle?


texts:
I am designing a device and I'm confused on calculating my total amperage required.

I have designed this device to have 3 main circuits in parallel that all take 5 V from the same power source:

First is some LEDs,
second is a microcontroller circuit to control those LEDs, and
third    is a few USB charging ports for phones etc.

I've estimated I will   need at most 600 mA for the LEDs, the microcontroller circuit will take next to nothing but I am using 200 mA as the max current it will pull, and the    charging devices I think will at most need 12A. (I have 4 in parallel
   that take 0-3A input, is 12A correct?)

So am I correct in thinking this will need 13A max?


texts: Electrical circuit / transformer in series?

texts:
I would like to pull out 5v 3A max in series from an already existing connection from the mains 240v 40A connection.

Current circuit:

What I would like to implement:

What are the possible problems with this setup? What device should I use to pull out the electricity? If possible I want to retain a 240v across the load.


texts: 2 pin crystal oscillator : Crystal Oscillator Circuit explanations

texts:
I want to understand how can I make a crystal oscillator circuit with a 2 pin oscillator.

I did some research and I have this from this website (section Crystal Oscillator Circuit) :

Or same on this one (section Crystal Oscillator Circuit Diagram) :

I don't understand at all which values of resistors;capacitor do I need to use neither how to calculate them...

Second of all if someone can also explain to me why this second blue schematic on the right in the picture above...

Finally I did this screen from this YouTube video where the crystal seems need to be on the left:

So I'm a little bit lost...Can you please explain to me those three things (first schematic; second blue schematic and why this totally different schematic - which seems working as we can see later in the video - from the YouTube video)?

Thank you very much !

EDIT

@Bimpelrekkie I just want a sine output and that's it nothing more.
As I can see on your link they're talking about square wave even if he said  that "The first inverter really produces a analog signal.It will be more of a sine wave than a square wave" it won't be a clean sine on the output am  I right ? They gave values for given frequencies, how did they calcute those values ? For example 12.288MHz, what are the values for C and R2 ?

@Fredled Thanks to your link it seems that I will need a Pierce Crystal Oscillator :

My question is still here, how can I know the values for those capacitors ; R1 and radio frequency choke...


texts:
I have an RF signal (5ns pulses every 200ns) coming out from a SMA connector on FPGA board (Spartan 3E Starter Kit). I want to send this signal back to the FPGA using one of the on-board pins.

So, I cut of one end of the SMA to SMA connector cable, hoping to use it for inputing the signal back to FPGA. I tested the waveform on the oscilloscope to find that the output signal was in mV range instead of around 3.3V range (input signal).

So, have I made a mistake? Is there any alternative way which I could follow?


texts: Very weak LED dimming with combined PWM signals using 555 timers

texts:
First of all, here's the circuit:

What I'm doing here is using 2 PWM signals generated by 555 timers to control the warmth of the LEDs and the brightness. The top 555 is the brightness control and bottom one is the warmth. For the warmth, I run the same signal through an inverter so that when I change the duty cycle of the bottom 555 timer, one LED gets brighter and the other darker. For the brightness, I combine the top 555 with the bottom PWM signals using AND gates.

This circuit works, but the only problem is that when I finally combine the signals, the lowest brightness setting is not dim enough. Both of the 555s duty cycles range from 95% to 5%. On the other hand, the warmth control works perfectly fine. Could this be of the big difference between the timer frequencies? Or perhaps there are some design flaws in the circuit?

Also no, using an MCU is not an option. Thank you for your help.

EDIT: Forgot to add to the circuit, but I have added decoupling caps at both 555s to reduce noise.


texts:
I've made a custom board with an AT90CAN128, and I can't get my USBTinyISP to connect to it.  I've verified the programmer is good, as it connects to a 328p and a AT90CAN128 on a dev board fine.

I made a second board now with a spare IC, and only soldered the IC, an ICSP connector, and a 10k pullup resistor for RESET.  I can not get that one to connect either.  My board does have a 16MHz crystal, while the second board does not.

I can find no solder bridges or mistakes so far on my board.  I bought this exact IC from Digi-Key.  I thought all Atmel AVRs were shipped with ICSP fuses enabled.  Am I missing something, or am I going to need a high voltage programmer?

Current consumption is 40mA, that includes the power LED, a 3v3 regulator, and a MCP2561.


texts: gizDuino(arduino clone) doesn't power up with 7.4v battery

texts:
So i am using an arduino clone gizDuino. Im connecting it to a lcd module. I successfully connected all the pins in the diagram, but when I connect it to the microcontroller the backlight doesnt power up. so I tried a 7.4v battery connected to the VIN of gizduino and one to the ground. It worked proplerly. I got the lcd module working(but without battery its not working). Then all set up and im ready to go to present my project but suddenly the gizduino doesnt power on when I placed the battery. I dont know what happened, I thought my board had a short circuit but when I connect it to the computer it seems working fine. Is anyone experienced this before to their microcontroller. PLS help.

NOTE: I haven't noticed any burn or smokes when I hooked up the battery


texts: In practical FSM next state is function of current state and current inputs, what if next state is function of current and previous state?

texts:
A long time ago I came across an interesting FSM in which the next state was a function of current state and previous state, along with the current input values. Here previous state is not the state from previous clock cycle but the state that FSM had before entering the current state.

Is there a special name for an FSM where next state is function of current state, current inputs AND also the previous state?


texts:
Can anyone identify the connector on the right of the picture?

A picture of the same, taken from a different angle:


texts:
I'm trying to design a \$3*8\$ decoder using pass transistors.

I found an implementation with TG on the web (transmission gate) as the following picture, but I can not design one with pass transistors. I need help to get some ideas about the design. what about \$2*4\$ or \$1*2\$?


texts:
I'm doing some proactive maintenance on a vintage games console from the late 70s. There are a couple of linear regulators which I thought would be prudent to replace whilst I'm at it. Unfortunately the markings on one are nearly illegible and on the other are completely gone. (They were covered by some tape which took the markings off when I removed it)

I know the marked one is a LM78M12x - the 'x' is illegible. The other is a 5v regulator confirmed with a DMM. I have searched for schematics in vain.

The question is what suitable modern replacements should I use here? Are there any other clues I can look for which might help?

Can I cause any problems by choosing the wrong ones e.g. LM7805 instead of LM78M05?
Should I go with a modern switch-mode version?


texts: Designing a resonator circuit: drive level considerations?

texts:
When you design an oscillator circuit for a Quartz crystal, you have to take the maximum drive level of the crystal into consideration and add a damping resistor to keep the actual drive level below that value.

For ceramic resonators I seem to be unable to find a conclusive answer if I have to do the same.

I found the FAQ by Murata stating:

  Q: Is it necessary to consider drive level for CERALOCK®?

  A: Variations of drive level have small influence on CERALOCK®, so it is
  not necessary to consider drive level for CERALOCK®.

Which would indicate that it just doesn't care. I've also not found any mention of drive level in the datasheets of the resonators.

Still keeps me wondering how much drive level I should be aiming at, surely I can't just pour 1 W into the resonator and hope it'll work for 20 years.

So questions:

What is the maximum drive level for a ceramic resonator?
Is there a recommendation on the minimum drive level to provide a stable and resilient (against external disturbances) oscillation?


texts: Arduino bot that can find a specific sound signal

texts:
I am working on my senior design project. It is an Arduino controlled robot.  I am trying to figure out the best way to implement sound localization.  It seems straight forward, at least two mic's, Fourier Transform the signal, calculate the phase difference.

My problem is that I would like to be able to focus in on one particular frequency, so it isn't just trying to find the source with the biggest amplitude.  Does anyone have any recommendations on how to do something like this.  I have not used microphones ever, can someone recommend a good one?

I would like it to have a pretty decent range, like a small living room or bedroom.  I am thinking of using a very low frequency so I don't have to worry about such a high sampling rate.

I am using an Arduino Uno for anyone familiar with it.  I am doing Computer Engineering so I am pretty familiar with EE terms, but I am still learning about signal processing this semester, I know that I should use a bandpass filtering of some kind, but what would be the best way of doing it?

If you know of any examples other people have done, or schematics it would be very helpful.


texts:
i am trying to understand the behaviour of an RC integrator for \$f>>1/RC\$, i.e. in the integration domain.
I know that at the capacitor i have \$V = \int V_{in}/RC dt\$; experimentally i find that when i use as input square waves with tunable duty cycle (but fixed frequency such that \$f>>1/RC\$) i have an approximate constant voltage at about the mean of the input signal (that obviously increases as the duty cycle increases).

I can't really understand why. I can approximate the integral with the mean, but then i have \$ V= \bar{V_{in}} T/RC \$ with T the period; this however tends to zero as T < RC!!

Thank you very much, i am using this to have a "tunable" voltage generator from Arduino, i know it works but i want to understand why it is working!


texts: How to write to DDR3 and SATA3 using Virtex 7 FPGA and Uart?

texts:
I have a virtex 7 FPGA and for my larger project I need to setup the communication between an FPGA's PCIex8, SATA3, DDR3, and Uart.

I was wondering how to go about doing this?  I can't use the softcore processor. I want to just use the FPGA to be able to directly send data from UART to DDR3 or SATA3.  I am fine with setting up one at a time and can figure out the arbitration later.

I searched opencores.org but I only could find some stuff related to SATA2.

I have a vc709 fpga board.


texts: How to determine what ballast for fluorescent lights?

texts:
I am creating a UV Cleaner, but this is my first time working with fluorescent bulbs and I wanted to make sure I'm doing it correctly.

I got the following fluorescent bulbs:
GT15T8 Philips UVC Bulb

The following ballast: GE432-MVPS-N

The following connectors for them: T8/T12 Lamp Holder Tombstone

I was reading the ballast operating specs and I don't seem to see anything on it that says that it's compatible with the bulbs, but it supplies the correct amperage and voltage, so I assumed it would work. I haven't yet tried it, but I'm not sure how to tell what kind of ballast I need for a given bulb?

Ideally, the ballast would allow the bulb to be switched on and off pretty regularly with about 10 minutes of runtime in between.


texts: Translating 9 - 13mV to \$\mathrm{O_2}\$ level

texts:
Output of O2 sensor varies between 9 - 13 mV. For example for this sensor link.
First I thought it 9 mV for %0 and 13 mV for %100 level. After reading this link2, I understood that I was thinking wrong.
How can I read O2 level from analog voltage? Do I need multiplying by 5 for %100 level? (e.g., 9 x 5 - 13 x 5 => 45 - 65 mV.) That is correct?


texts: Why am I getting "Grammatical Error" in LTspice?

texts:
Why am I getting "Grammatical Error" in LTspice the instant that my transfer function denominator goes from a 2nd order to a 3rd order system? See below.

Please note that the transfer function depicted is not the actual TF that I'm checking for. It's the 1st one that I have arrived at as part of a "check and test" process to see why the actual TF receives the same message.
If the \$s^3\$ term is removed from the TF, the circuit would simulate without no problem. But, the moment that I include an \$s^3\$ term into it, I get the "Grammatical Error" message.
Any insight that anybody can provide will be very much appreciated!!


texts: I am looking at this PCB board I've got and these pads are terrible looking.  It still works, but this sure doesn't look right.  What can I use to clean those up?


texts: Connect Wind turbine to existing solar inverter with MPPT

texts:
Currently I am doing research on connecting a 3.5 kW wind turbine to an existing grid tie solar inverter with MPPT. It would be very nice to use the widely available PV inverters and connect a wind turbine or both solar and a wind turbine to different input channels. I know wind and solar systems are different in a number of ways but I am not yet an expert on this subject. But I was wondering if someone could tell me the flaws and what should be improved.
The generator of the wind turbine will create a three phase AC sine wave that is going to be rectified to DC and filtered. For over Voltages I am planning to use Voltage detection with a breaking circuit in case of over Voltage and to stop the turbine from rotating when the inverter disconnects from the grid.
I am unsure if the MPPT used for solar applications could work for a system like this. I could also add a boost converter to supply a steady Voltage to the inverter if that would help.
I have spoken to an inverter manufacturer and they also have to possibility to turn off the MPPT function for their inverters. So designing a custom MPPT system could also be the way to go perhaps.
Another thought: Do I require a transformer attached to the generator for galvanic isolation?
So my question is, could the proposed system with a wind generator attached to the MPPT of a solar grid tied inverter work? What to improve?


texts: Query on Edge triggered D-flipflop using SR-latches

texts: When clk is 0 and during this time let us assume d is 0 this drives r and rbar to be 1. Isn't this a forbidden case of SR latch?? After this state if clk and d becomes 1 at the same time wont it cause a indeterminate state at r??


texts: Problems connecting ST-Link V2 and STM32F4 discovery board

texts:
I'm unable to connect to my STM32F4Discovery board using an ST-Link/v2.

I've removed jumpers from CN3, connected the cables correctly but the utility tool won't detect anything...

Using the ST-Link/v2 manual:

PIN1  (VAPP)      -> VDD
PIN7  (TMS_SWDIO) -> PA13
PIN9  (TCK_SWCLK) -> PA14
PIN20 (GND)       -> GND

Here is the physical connection:

And software settings:

This is the error message that I get when trying to connect:

Here is the log message that I get in trace:

ST-Link/V2 device detected
Target voltage detected: 0.601975
Driving NRST low
Error getting target IDCODE: if SWD, check SWD connection
Error (4) while initializing ST-Link in SWD mode

Please help, it's driving me mad...


texts: How to control IR led using ESP8266 (out pint at 3.3v) and MOSFET to obtain high IR range?

texts:
I have an ESP8266 circuit which must send IR messages via 5mm IR LED.

During initial tests I used an Arduino with schematic below.
The OUT_PIN high value was 5V. It works like a charm, and the IR range was very good.

simulate this circuit – Schematic created using CircuitLab

Switching to ESP8266 I left the previous schematic unchanged. Supply voltage is still 5V with a simple regulator to 3.3V for the ESP, but IR LED is still connected to 5V.

The OUT PIN high value is 3.3V (due the micro works at lower
    tension compared to Arduino)

My issue is the IR led barely turn on when IR message is sent (checked with smarphone camera), so the range is very poor.

How can improve the IR range?

I'm not very good to analog electronics, so I think may be an issue with mosfet type/position in the circuit.


texts: If a clock edge matches with data output edge what should SPI read?

texts:
I have an analog to digital converter that reads in and sends data out on falling edges. I also have two MCU's the FEZ Hydra and the FEZ Cobra. I've noticed using the oscilloscope that the data into the ADC and the data out of the ADC is exactly the same, however when reading the data on the computer that the MCU's have stored I get different values.

Since the ADC only sends outputs on falling clock edges, whenever the data output bits change from a 0 to 1 the Hydra reads in a 1 while the cobra still reads in a 0; and whenever the data output bits change from a 1 to 0 the Hydra reads in a 0 and the cobra still reads in a 1. It seems like the Cobra doesn't give enough time between the negative clock edge and reading of the input to allow for the update to happen.

I am using microsoft's spi library. My question is: Is there anyway for me to delay the SPI read function? What is the reasonable output in this situation supposed to me?

Note: There is a 60ns delay on data access time on the ADC.


texts: Is this the ideal parallel circuit or is this a combination of series and parallel?

texts:
This is more complicated than I originally thought.

So this looks like two series in parallel, but now this doesn't look so straightforward.

Here is the same circuit as a picture, I just drew it as a diagram above.

This is the way that my christmas tree lights are wired.

I am not sure what kind of circuit this is.

I tried to draw a standard basic parallel circuit in the below pink picture (top) and tried to chop off one end of it and emulate what they tried to do for the christmas lights (bottom). But I don't think it worked.

It's just that the christmas lights circuit doesn't seem like I would expect a parallel circuit to look. Which is why I got confused in the first place. In the picture below, (bottom), this is what I originally thought they had done with the christmas lights.

I don't understand why they did it differently. Is the way they did it correct or is the way I did it correct? Or is there a better way and we are both wrong?

EDIT: I just realized what I did above in pink I just turned a parallel circuit into a series circuit.

What is the best way to chop off one end so you have a parallel circuit of two series circuits? Is what they did with the christmas lights the correct way to do it?

Update: To make it easier to visualize, I just showed the actual wiring as one length instead of wrapped around:

To be honest this looks like a series circuit. I wonder if I had it all wrong and this isn't a parallel circuit at all?

UPDATE 2:

Ok so I finally gave in and unwound a whole new light from start to finish and I discovered that it is wired completely differently. Here is the real schematic.

Here is the same real diagram drawn wrapped around.


texts: Robot picking a person from other objects

texts:
I need some ideas of sensors to use so my tank can drive towards humans and seek them out.

Distinguishing them from the background.

Assume the human is standing still / quitely

Any ideas?

looking to use an Arduino as the controller - though if there are better options please let me know.


texts: I have to detect a magnet with an Arduino for a personal project. I was wondering if using a magnetoresistor and detecting the current drop was possible. I understand that using a Hall effect sensor is the easiest method, but I wanted to know if it was possible. How would I integrate it in this case.


texts:
I want a master node consisting of a TI Stellaris Cortex M3 core connected to what can be up to 32 slave nodes of TI MSP430 (or possibly more Stellaris slave nodes). These will be maximally 0.5 meters between master to most distant slave. Bit rates of around 0.5-1mbps will be needed. What kind options are available for internal communications?

From docs they both seem to support SPI, UART and I2C.

SPI will from what I find, need 1 selector wire pr node. Way too many wires.
I2C seems easy, but for from docs I get the max speed is 400KHz. Too slow without degrading quality or maximum number of nodes.
UART seems to acheive the speed, but can it be used outside of A to B communication?
Did I miss anything?

Update: As noted in comments, updated I2C speed for msp430 to 400KHz. Still too slow though. Also the network is purely one master and n slaves.


texts:
I recently saw this video that did inspire a little bit of interest on my part.
https://www.youtube.com/watch?v=IrB-FPcv1Dc
It appears that when the drain of a N channel mosfet is connect to the gate it can act as a diode. Also according to this video it can do that very efficiently. So I messed around a little bit on a very primitive inverter that I built a while back. I tried to rectify the output current of the inverter which was stepped down to 12 volts ac.
So I tried to use the transistors as diodes and my results where the following.
I tried an NPN and I got 8 volts of DC on my multi meter.
I tried the MOSFET and got less than a volt even without the gate being connected. Simply put the Mosfet acted a lot like a wire and had no effect whatsoever.
So I am curious how would you achieve rectification using transistors and is it even possible.


texts: How to build a 3-input NAND gate from 2-input NAND gates or a 3-input NOR gate from 2-input NOR gate?

texts: For NAND, I am doing a truth table for it and then truth tables for all the possible combinations, but as you can see the process is very long and I am still yet to get an answer. Same goes for NOR gate. How do you go about it?


texts: How do I lay out a 28 pin DIP socket pattern using GSchem?

texts:
How do I lay out a 28 pin DIP socket pin pattern in gSchem?

I imagine that I can lay it out manually but is there some sort of library component I can use?

VERSION: 1.6.1.20100214


texts: So there was an ant that somehow got inside my screen. How do I remove it?

texts:
Wondering if it's possible to remove the LCD screen without damaging it.

I noticed there are six black metal thingys at the back of the module that is twisted up holding the LCD in-place, is it safe to untwist and remove it? What do I have to know before doing so? I assume that is how the ant got in there the first place.


texts: Finding the Base-Emitter Voltage in an NPN Transistor

texts:
The problem asks to find the the real value of base-emitter voltage, \$V_{BE}\$ and the corresponding \$I_C\$, and \$V_{OUT}\$ in the figure below:

\$V_{CE(sat)}\$ is given but the transistor is not necessarily in saturation mode; in fact, it's likely operating in the forward active mode so I need to solve for the actual value of the junction voltages first to determine its mode of operation. Only \$V_{CC}\$ is given and I have too many unknowns. I've tried using circuit analysis, KVL, and KCL techniques in addition to the transistor equation but there are more unknowns than there are equations that I can think of. Any idea? I just need enough equations. Thanks!


texts: Understanding Atmel 9x60EK Shutdown Circuitry

texts:
I'm trying to understand the shutdown circuitry behind the Atmel 9x60 Evaluation Kit:

So for normal operation, J3 is OPEN.

The processor drives SHDN high (which I assume means "run"), the following happens:

Q3 conducts, causing the STARTB line to go to LOW.
Q4 loses the gate voltage, causing POWER_EN to go HIGH.
Q5 also loses gate voltage, causing MIC2800_nRST to go HIGH.

But when J3 is CLOSED, POWER_EN will remain HIGH as well as MIC2800_nRST, regardless of how SHDN is driven. (Obviously this would mean that the MIC2800 remains in power-enabled and keeps the power rails active).

The confusing part for me is that MIC2800_nRST is shown as an output from the MIC2800-G8YSML:

Does this mean that the shutdown circuit and the MIC2800 both drive the MIC2800_nRST line? In this case, why is Q5 there? POR in the MIC2800 is an open-drain output. Assuming that J3 would always be OPEN, it doesn't seem to serve any purpose since driving POWER_EN low will remove power from the rails and turn the processor off anyway. It looks like it just makes sure it is either a weak pull-up or a strong pull-down.

Datasheet for the MIC2800


texts:
I am a beginner at logic gates/circuits and would appreciate some help constructing a running LED light system. The concept is to have a row of 20 LED lights that start flashing, one after another, after receiving a certain input. The only two options are for the rightmost LED to light up and then go left, or for the leftmost LED to light up and go right. Only one light will be on at a time, and each light will stay on for 5ms.

The system takes a 2-bit input, where "l" means "left" and "r" means "right:
l r
0 0    -- "Off" (see below)
0 1    -- start at leftmost and run right
1 0    -- start at rightmost and run left
1 1    -- "Off" (see below)

There is also a 5-bit number can turn on one LED at a time, or be set to "Off":
00000   -- "Off"
00001   -- L0 (leftmost LED)
00010   -- L1
00011   -- L2
...
...
...
10010   -- L17
10011   -- L18
10100   -- L19 (rightmost LED)

This is essentially as far as I've gotten, apart from making a finite state machine that describes what I said in the beginning. I'm only interested in using logic gates at this point. I would just appreciate a push forward so I know where to start with this. I know I'll need to be using a D flip-flop. Thank you for any help you can provide.


texts: How can I emulate two analog joysticks (potentiometers) with an Arduino?

texts:
I have a quadcopter (Syma X5C) that I really want to control with an Arduino. Since I have the ability to write programs to my Arduino to make the quadcopter fly autonomously, I want to modify my "hack" my  quadcopter remote to allow the Arduino to be interfaced with it.

After opening up my quadcopter remote, I figured that the fastest way for me to programatically fly my quadcopter is to desolder and remove the existing two joysticks and replace them with digital potentiometers which will be controlled by the Arduino.

I almost thought I could do this, however, most digital potentiometers only use the SPI protocol to talk to the Arduino. If I need to control the 4 axes of the two joysticks, I would need more than one SPI digital potentiometers. Also, I am not sure my Arduino would work with more than one SPI module. I was trying to look for an I2C potentiometer, but I was not able to find any cheap ones available.

Is there a way I can control my quadcopter remote without the need to use a digital potentiometer? Please give me detailed suggestions, preferably with a diagram.


texts: How to understand dynamic range of op amp from TI's book

texts:
I am reading TI's op amps for everyone.
I am very confused about its description about dynamic range as follows

I have some questions about it,

Since it is the maximum output voltage the op amp can achieve and the minimum output voltage the op amp can achieve, why should it be as follows: $$V_{OH(MIN)}$$ $$V_{OL(MAX)}$$

What does 'the most positive power supply voltage' mean in this text?

Actually, I have no idea what dynamic range is according to this material which should be authoritative. Can anybody give me more intuitive view of relationships between dynamic range and power supply?

Thank you!


texts: Is it OK to have data lines and AC in the same multicore cable?

texts:
I need to provide the following over sections of 1m multicore cable, totaling around 15m.

240v AC
5v DC
GND
RX
TX

Will the AC cause problems for the Serial data?


texts:
What is the exact meaning of the term dc drop in transistors?
In solving the problem in the image given below , I was asked to find the dc drop across the collector resistance as shown in  circuit so I thought it may be voltage drop but it is not as can be seen the solution(pdf link in comments)

  ${Any\ Help\ Is\ Greatly\ Appreciated}$

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texts: Understanding EGSM-900 (LTE 8 band) electromagnetic spectrum

texts:
I am trying to fully understand the physical layer of the GSM standard. For doing that I am looking at the E-GSM-900 band (mostly used in Europe). In my country these frequencies has been assigned to the network operators as follow:

Table headers: Block, Uplink, Downlink, Operator, Concession, Expiration

So I set my spectrum analyzer to see the Downlink frequencies for that band (925.1 - 959.9 MHz):

Central frequency: 940 MHz
Frequency span: 30 MHz

And I am able to see this:

According to ETSI TS 136 211 V10.0.0 the modulations used are:

Downlink: OFDM
Uplink: SC-FDMA

And looking into the next spectrum intervals:

930 - 935 MHz
940 - 945 MHz
950 - 955 MHz

It seems to me that it looks like OFDM modulated signals. But what is the first chunk preceding this OFDM blocks? Precisely the intervals:

925 - 930 MHz
940 - 945 MHz

What are they? Which signals are modulated there and in which modulation schema? I do not know if I am looking to the wrong standard (there is this huge mess between GSM-LTE bands), or if it is just my network analyzer configuration, or something else. I hope you shed some light on this.

EDIT: Added waterfall and time snapshot


texts: Using mixer grinder circuit breaker in a electronic circuit

texts: I'm thinking of using a 5A mixer grinder circuit breaker in an electronic circuit which uses a 2200mAh Li-Po battery and a 5A step-down voltage regulator. Is it safe to use such a circuit breaker in this application or should I go with a normal panel mounted fuse? Is there anything I should consider?


texts: How to apply reciprocity theorem to h parameters?

texts:
I know the result is h12 = -h21, but it's strange since h12 = V1/V2 and h21 = I2/I1.

Reciprocity theorem says that ratio of excitation to result must remain same if they are interchanged, how do you arrive at that result from the statement?


texts: Minimum cover for this K-MAP to find minimum SOP; which is better, and why?

texts:
I used this K-MAP to find the minimum sum-of-products expression for this collection of minterms.

I see that minterm-one could also have been "covered" by grouping it with minterm-five.

I opted to "cover" minterm 1 with the largest possible group: (0,1,2,3), which is the green circle on my K-MAP.

Since both combinations of groups result in a minimum SOP of 5 terms, which would be considered "better" in terms of hardware/gate implementation?

Am I correct to assume that the my larger group is better, as it eliminates one more literal?

Or am I wrong, and would group (1,5) be better than group (0,1,2,3) for finding a minimum SOP?


texts:
I can see traces that connect the corners of where the button is mounted, but it seems to me then that the contacts should be always connected via the metal dome button. There's nothing in the middle on the PCB where the button makes contact whenever it's actuated. Could someone explain to me how these particular switches work?

Thanks!


texts: Selecting best Heat Sink for TEG (Thermoelectric generator)

texts:
I am trying to solve a puzzle about selecting the right heat sink for my TEG, but I am really confused and lost with lots of equations. Here is the Specification of my TEG (TG12-2.5-01L)

Module Width = 29.972 mm
Module Length = 34.036 mm
Module Height = 3.937 mm
Max Temperature (Tmax) = 250 °C
Th = 230 °C
Tc = 50 °C
Efficiency = 5.02 %
Power = 2.71 W
Open circuit voltage (Voc) = 9.56 V
Thermal resistance = 3.33 °C/W

What I want to do is maintain a temperature difference of max 50 °C. So in order to do this I need to have a good heat Sink which will radiate the heat in the air faster. So how can I calculate which heat sink I actually need? What do I need in order to calculate this? Which heat sink is the best and how do I know if it is good or bad?

Any information related to this will be really helpful.


texts: How do I use an Arduino to switch another IC's pin (reset) to ground?

texts:
I'm a releative newbie.  I'm using an Arduino to control a Cowlacious audio board that uses the ISD1700 chipcorder series of chips.  Periodically, I need to pull the reset pin on the chipcorder to ground to reset it to it's original state.  It seems to me that with the low currents involved I should be able to do this directly, but I'm not having luck.  Using an Arduino pin set to digital out and leaving it HIGH except when switching doesn't work (I assume the chipcorder doesn't like the voltage when it's high).  How can I get this to work?

P.S. I know I could use a transistor as a switch, or some sort of relay, but do I need to do that?


texts: Best way to make LEDs flash in time with a music source

texts: Could someone suggest the best circuit to make LEDs flash in time with a music source directly connected to the circuit? BTW the circuit needs to run off batteries, I've seen circuits using TIP31 transistors, but are they any good?


texts: Protecting circuit from railway's high voltage

texts:
I am designing a control system which is going to be installed near a functioning railway. The system has many interfaces that are externally connected to different devices, it has Wiegand, RS485, Ethernet and a few digital IO pins.

I am currently thinking of using varistors on every pin except the Ethernet of course, current limiting resistors to avoid short circuits and fuses on power pins. Are TVS diodes/Zener diodes or opto coupling necessary or is the varistor enough in this case?
(The MCU is likely going to be an Atmega1284 or another AVR8)

My question is what are good practices and solutions to avoid EMI and ESD and any other interference caused either by humans or the railway? I know Ethernet and RS485 are protected, we will be using shielded cables for those.


texts: Explaining large current spike in RC circuit for multisim simulation

texts:
I am simulating the circuit shown in the figure below. In the simulation, switch S1 is repeatedly opened and closed at irregular intervals in short succession. The relay, K1 has a flyback diode attached for emf suppression from the relay coils. When R1 = 0, probe 1 measures massive currents up to 30A, despite there being a DC resistance of approximately 300 Ohm (in the relay coil). When R1 = 1 Ohm, the maximum current at the probe is approximately 15mA.

My question is, how is a 30A current possible through the probe if there is a large series DC resistance present? Is it due to some phenomena with the flyback diode, or is it maybe a bug with multisim? Why does the 1 Ohm resistor make such a large difference?


texts:
I am building a circuit for a custom application. I have an old Toyota truck, and I keep leaving the headlights on, because there is no warning buzzer!

I have designed a circuit that takes 3 inputs:
* Headlights on
* Driver's door open
* Engine off

I want to build this using integrated circuits, and have it supply 12V to a piezo buzzer when the above 3 conditions are met. Here's what I'm thinking:

Will this work? I studied electronics in college, but haven't done anything with it since!


texts: Need help with modeling an overloaded battery

texts:
I wish to model a battery for a small computer game, a battery which will be subjected to heavy loads and deep discharge. The model doesn't have to be high-fidelity, just a rough approximation will do. I want to display both the current and voltage, and watch how they change as the battery runs out of juice.

I have a loose grasp of the basics, V=IR and so on, and can calculate these for a steady state circuit with an ideal power source but am lost when dealing with a more realistic battery model.

If I understand right, I can add add load to my battery, and figure out the current being drawn, and deduct that from the battery capacity in Ah, giving me a decreasing value for the "juice" left in the battery. But I get a bit lost thinking about what happens when the load is such that the current being supplied is very high. I assume the voltage should sag, but how can i model this? And is this current limit and voltage sag also connected to the available capacity of the battery?

I have read about representing a battery as a voltage source and a series resistor, but am a bit lost in how to use this. Should I be increasing the series resistance in relation to the decreasing capacity? What is the nature of that relationship, if so?

My apologies if this is not very clear, I have tried my best with the terminology.


texts: Why can't dual port RAM be read out using the Quartus In-System Memory Content Editor?

texts:
Here are the screen shots from Quartus;

When I want to instantiate the single port RAM, I get option to assign an instance ID and thus read it using the ISMCE (In-System Memory Content Editor). However, this is not so when it comes to the dual port RAM. Why?