texts: Correct formula for LED current-limiting resistor?

texts:
I'm trying to work out what value resistor to use in a LED circuit. The equation I'd use to do this is:

$$ R = \frac{V_{cc} - V_f}{I_f} $$

Seems logical, and makes complete sense. The answers to the question How do I calculate the resistor value for a simple LED circuit? confirm this too.

I have the following LEDs:

\$ V_f = 3.3V \$
\$ I_{f_{typ}} = 20mA \$

Using a 5V power supply:

\$ V_{cc} = 5V \$

Plugging these into the above equation gives:

$$
\begin{eqnarray}
R & = & \frac{V_{cc} - V_f}{I_f} \\
  & = & \frac{5V - 3.3V}{20mA} \\
  & = & 85\Omega
\end{eqnarray}
$$

All good so far.

However, if I use the calculator at http://led.linear1.org/1led.wiz, that gives me 100Ω. If I use the ElectroDroid app on my phone, that gives me 85Ω.

So, I assume that the linear1 calculator is using a different method of calculating this resistor value; is there some better way of doing this?


texts: BSS138 levelshifter draws 35-40mA current when one side is grounded?

texts:
I completely rewrote my question as I found the source of the issue is related to the level shifter only.

This is the circuit for a 3.3V to 5V bidirectional levelshifter, used frequently.

My problem: I have the same circuit, and I built it 3 times now to go sure.
When I connect one side (3.3 or 5V) to ground the other side also goes to ground (works so far).
However, it draws 40mA current!

This caused my atmega128 to saturate the port pin current, effectively raising the voltage above 0V.

I simulated it on pspice, it says the current draw has to be at 500uA (10k pullups).

I tested it on 3 different BSS138 mosfets, they show the marking K38 on top (smt devices) which seems to be right (so it is the right mosfet).
I am clueless, why does it draw so high current in low state ?


texts:
I have a circuit design coming together that uses either of 2 sockets to plug in a controller.  The idea is to allow a user to enable either of the controllers to control a radio using SPI.  In the design, the user is only allowed to plug in one controller or the other.
The SPI clock frequency is 25 MHz. I have 22 Ohm (changed to 33 ohm) resistors located at the source the SPI Signals.
The issue here is; in doing this, the SPI lines will always have an open circuit tail or stub trace (maybe 2-3cm) attached between from the radio to the unused controller socket. In the picture below, if the Controller-A is plugged-in and the SPI socket is not used, a short unconnected trace (stub) will exist on the board.
So the question is: will this short stub be of significant concern to SPI signalling or is it best to add selection jumpers.  Is it common practice to not worry about these extra tails when they are electrically short like this? Selection jumpers add trace length and cost.

Here is a revised sketch of the situation with a little more detail.  Based on the comments received, this appears to be acceptable so long as the stubs are electrically short.  It seems to me the resistors at the ends of the stubs are of no concern.


texts:
For driving a valve based on the datasheet we should limit the max current that flow into the solenoid. If we have an AC valve we should take the inrush current at the start-up into account and apparently for the dc valves we don’t have the inrush current however the DC coil have a higher wattage rating when it’s cold. So again we need more current in the start-up. Having high and low voltage on the solenoid cause the damage and it might burn the valve. If we want to limit the current by inserting a series resistor we should have a high wattage resistor (i.e. having max 2.4 amp for 24vdc we should have 10 ohm resistor – 57W!). How about H-bridges ?

I wonder to know what the best practice for driving a valve (Ac or dc) is. I would be appreciate if you give me some references or book to read.

Thanks

P.S:
for this type of valve (Standard 12vdc), Coil resistance is 3 ohm and max current is 2.6 so we should reduce the amount of current somehow.


texts:
I recently got TS68000 microprocessor. My final goal is to build a simple computer based on that CPU.

For now I am trying to find a way to single step it.

I found schematic below by John Tsiombikas and I tried to introduce it but I failed...

Below is run using 10MHz clock.
I de-bounced my switch (used with pull-up resistor to revert the logic) and connected it to SN74LS93N (4 input NAND - Schmitt Trigger) - 3 pins are set HIGH and 1 is driven by button so when I press the button the output goes HIGH

Output of this gate is connected to MM74C74N (Dual D Flip Flop) - D-Flipflop - output(Q) is connected to second D-Flipflop
Second Flip Flop Q' output are both connected to  - dual Input NAND gate - output from this gate is what I am after(DTACK).

However when I press the button is stays HIGH for longer than 1 clock cycle as explained in John's video

Not sure what am I doing wrong...

P.S - I hope you can read my writing... I am not the best drawing schematics...


texts:
Per the Seeeduino specifications here, it says:

  DC Jack & Vin Input Voltage

  7V to 12V (lower is preferred). Maximum is 20V. If input lower than 7V
  and switch set to 5V, then VCC at AVR is about 2V below the input.

So two contradictory statements back to back.  Input voltage is 7-12V, and maximum is 20V.  What should I make of that?  I have a 16 volt power source that I'd like to power it from.  Will that work?  Would a higher input voltage limit my current draw since the voltage regulator has to burn off the extra power?  Any other limitations?


texts: Could madgwick be a math error in the c # example?

texts:
We gave the same input data to C# and Matlab examples. The values on the quaternion outputs were different, although their inputs were the same. These examples can be downloaded from Madgwick website.
https://x-io.co.uk/open-source-imu-and-ahrs-algorithms/

Comparing Matlab and C#, we realized that, there're two missing *2 factor in C# code.
// Reference direction of Earth's magnetic field
_2bx = (float)Math.Sqrt(hx * hx + hy * hy);   // 2* missing
_2bz = -_2q1mx * q3 + _2q1my * q2 + mz * q1q1 + _2q2mx * q4 - mz * q2q2 + _2q3 * my * q4 - mz * q3q3 + mz * q4q4;   // 2* missing

After multiplying by 2 these lines, outputs overlap with each other.

I don't think much of Madgwick might not have noticed this, or did we think one point wrong? (They have videos using with C# example..)


texts: Op amp LM324 as pre-amp to LM3915 LED VU Meter

texts:
simulate this circuit – Schematic created using CircuitLab

I have made a LED VU Meter using LM3915 and added a low pass filter too. Then I've tried a basic op amp circuit using LM324 (inverting and non inverting) to amplify the LM3915's input, but it doesn't work. It only lights up the first led, it doesn't work like a VU meter should. Can anybody show me how to use an op amp like the LM324  with the LM3915?

My LM3915:

The two LM324 circuits I tried:


texts: "The following branches form a loop of rigid branches (shorts) when added to the circuit" error in Hspice

texts:
simulate this circuit – Schematic created using CircuitLab
I am trying to do the transient analysis of this circuit.
Given, Initial Conditions I(L0.1-)=10A, I(L0.4-)=20A
simulator lang=spice
R200 1 0 200
R40 1 2 40
R60 2 0 60
L0.1 2 0 0.1 IC=10
L0.4 2 0 0.4 IC=20
.OP
.TRAN 1m 50m
.END

I am getting this error
Fatal error found by spectre during topology check.
        FATAL: The following branches form a loop of rigid branches (shorts) when added to the circuit:
            L0.1:1 (from 2 to 0)

Can anyone help me what is the reason?


texts:
I have the next circuit

simulate this circuit – Schematic created using CircuitLab

\$V_{BB}\$ and \$V_i\$ represent the output voltage of a previous stage of a circuit. Assuming that \$\beta = 200,r_x = 0, V_A = \infty\$, what would be the input resistance of the circuit (i.e. the resistance seen from the base of Q1), the output resistance of the circuit (i.e. the resistance seen from the node \$V_o\$) and voltage amplification \$A_v = \frac{v_i}{v_o}\$=?

I'm having trouble dealing with R2. I thought of expressing these parameters as follows:

\$R_i = r_{\pi 1}+\beta \cdot (1000\Omega //r_{\pi 2})+\beta \cdot 50\Omega\$

\$R_o = 50\Omega //(\frac{r_{\pi 1}}{\beta}+1000\Omega//\frac{r_{\pi 2}}{\beta})\$

Is this ok? And regarding the amplification, I have no idea of how to calculate it. I hope you can give me a hand.


texts:
I'm planning on a little experiment with a friend. We're gonna be using 2 Xbee series 1  modules at 3.3V and 50mA. One of the Xbee modules will be sealed in a music instrument and I was wondering: is it possible to power it using energy harvesting?

The instrument will be in constant vibration while in use, frequency will be from 80Hz to 350Hz, concerning the amplitude I don't have a clue yet as I'm building it, but it isn't constant for sure as it changes according to the music. The instrument is about the size of a guitare with a slightly different shape,it is made of wood.

The power supply needs to allow a range of action from 5 to 10 meters to allow freedom with the instrument.

The radio can't go to sleep while in use , and needs to reach 250kbps in order to tansmit sound data with a quality near mp3.

What kind of device or electrical circuit could I use to do so? Is it even possible to have 3.3V with energy harvesting ?


texts: Average lifespan of COM-12986 Addressable LEDs?

texts:
I am working on a project where I need to ensure that LEDs will work for at least 5 years (powered 24 hours/day). I need LEDs to be addressable like COM-12986. Would this be a good choice (the LEDs don't need to be RGB they can be red (620nm in wave length))? What is the average lifespan of COM-12986 LEDs?

I've read on Electronics Weekly that in average an LED can last for up to 50,000 hours, is this correct?

Could I increase the lifespan of an LED by using PWM at 50% duty cycle?


texts: Suppose between two nodes there are multiple passive elements in series - does the order of these elements ever matter?

texts: Intuitively I feel the answer is no, because terms in Kirchhoff's equations are commutative but I am really not sure.


texts:
I saw the following somewhere and I'm trying to make the following with NPN transistors but I'm having some trouble.

simulate this circuit – Schematic created using CircuitLab

I want to make a circuit where, when I apply a voltage to input1, output turns on, feeding back into input2, so that input1 and 2 are both on. And when I remove voltage from input1, input2 stays on thus output stays on.

And I did it like this:

simulate this circuit

So SW1 is input 1. D3 is output. If I remove the wire connecting node x to node y, my circuit functions as an OR gate. To make the circuit above I keep SW2 open at all times. When I close SW1, I hoped D1, D2 and D3 would turn on, but only D1 and D3 turned on. So naturally, when I opened SW1, D3 turned off, which is not what I want. I tried this in falstad and it didn't work either.

So my question is: how can I correct my circuit so that it does what I want it to do (as I described above)?

I made an edit to the diagram. I removed SW2. D1 and D2 don't have a role other than to light up when the transistors are up.

Second edit: I fixed the direction of D3 and rearranged the way the circuit was feeding back into Q2.

Kindly,


texts: Increase in gain of CP micro-strip patch antenna

texts: I have successfully designed my circularly polarized patch antenna shown below. I used the slot method. Which as a bandwidth of 23MHz and a resonance frequency of 915MHz. Though the bandwidth is small it is more than sufficient for my application. The axial ratio achieved was 1.7dB at 90 degrees. However, the gain is rather disappointing at -1.5 dBi. Does anyone know of methods I can use to improve my gain?


texts: Design a Cascode amplifier using suitable topology to meet the specifications( by Varying W/L ratio) . VDD is 3.3V

texts:
CONDITIONS

Output swing has to be at-least 80% of VDD (> 2.64 in this case) .
Power supply rails available are VDD and ground only.
Only one current source can be used in the design IREF = 50μA.
Every bias voltage needed has to be generated by designing proper circuits.
Use of Resistors is not allowed in the design.
Use a load capacitance of 1pF on both the output terminals.
ICMR should be 0.2VDD to 0.8VDD
Phase margin has to be at-least 45o.

SPECIFICATIONS TO BE MET:
3dB frequency in rad/sec = 10 K± 5%
Power dissipation (mW) = 3.0± 5%
Current Gain = 35± 5% dB
Voltage gain(Av in dB) > 45 dB
MY ATTEMPT:( I cascaded a CSA with Cascode Amplifier ( in order to have higher swing at out2 node) )

I am getting current gain too large and output swing lower than the required values for both of them.Also 3dB range isn't even available on the Voltage gain(Vout2/Vin) plot.
What all should I vary to obtain the required values?


texts: DDR2-SDRAM Termination methods: passive vs. active

texts:
for a project I'm designing I am currently using a simple parallel Resistor Termination on the DDR2-Traces. But I'm wondering, what is the advantage of using a voltage regulator with serial-termination?

Lower BOM/placement-cost?
Lower power requirements?
Something I'm totally missing?

Additional information:

My current design with 4 chips employs 54 terminations in total. This is done with 100 Ohm resistors. So we've got 1.8V/200Ohms = 9mA. 9mA*54 = 486mA plus reference voltage generation etc. it's more than 500mA unless my calculation is totally off. That results in nearly 1W of power dissipation just for the termination.

Are there any good guesstimates what the effect of an active regulation would be in a real world scenario?


texts: Noob question: blinking leds with pn2222A and 9v battery

texts:
I'm kind of new here. I've been roaming around the forum for a while trying to figure out how to finish up this circuit I'm building and really need some help.

I'm trying to build a blinking LED circuit using 39 5mm yellow 2Vf 20mA LEDs, pn2222A transistors, and a 9V battery. I have the LEDs wired in 2 parallel strings(one string containing 12 LEDs and one containing 27 LEDs). From what I've learned so far, It would've been best for me to wire them in strings of 3-4 with each string having its own resistor, but I have them wired, soldered, and held in place already so I prefer not to dismantle everything and start over.

This is what I have so far:

simulate this circuit – Schematic created using CircuitLab

Sorry, part of the post is missing for some reason. Allow me to start over.

I'm working on an art piece that contains a spinning object which represents planet Earth. I'd like to add lights to the spinning earth and making the lights battery powered is best. I can't use a slip-ring to run power to everything because a slip-ring won't fit. The spinning Earth as a 8" diameter. I should be able to install all the components (battery, lights, transistors, capacitors, resistors, etc.) to the spinning object, as long as the overall circuitry is light-weight and simple.

I have resistors ranging from 10-10k ohms, pn2222A transistors, 10 and 100uF capacitors, and AAA & 9V batteries. So is there a better way to make 39 lights blink in a light-weight, remote, and efficient fashion?

Did I mention I'm way out of my comfort zone but really really really need this to work?


texts: Headphone/Line out voltage for driving a LED?

texts:
I'm currently messing around with infrared LEDs and controlling my TV and various other devices from it. I have the spec and want to write a short Python script to generate these codes, and thus turn my computer/phone into a universal IR remote. I also have a receiver LED which I can use to record signals using my sound card.

I initially decided to use the GPIO pins of my Raspberry Pi and modulate them for the required amount of time, but it turns out that there's too much context switching latency to do this. I installed a LIRC kernel module which works fine, but now I want to go further.

I want to use my line out/headphone jack to drive an infrared LED. However, I'm really not very good at EE, and I don't have the tools to check the voltages. I read on another post here that the line out generates 1.something volts, and that I need to add a resistor so it has some impedance to avoid frying the sound card, but I can't figure out the values.

My LED requires 1.5 V max, but I understand I can push more if it's only for a pulse. I'll be generating the waveforms, so is there a dB level I could generate to give me adequate power to drive the LED, but not burn it? What's the voltage of my sound card at peak level?

Thanks!


texts: Why can't RGB or bicolour LEDs produce a decent yellow?

texts:
I have several different RGB LEDs and bicolour red/green LEDs, from different suppliers.

I find that, with the appropriate resistors, they can produce a perfect orange and cyan; and a barely acceptable magenta. One thing they cannot produce, however, is a tolerable yellow. It looks awful.

Given that our eyes see yellow simply as a combination of red and green; and given that TVs and computer monitors successfully render a lovely yellow on a daily basis using nothing more than red and green pixels; why is it that my LEDs are utterly incapable of the feat? I have tried googling for answers, and come up empty.

Of course, each colour will have its own forward voltage, but I have allowed for this by providing different resistances; or, in some cases, adjustable PWM signals. But no matter how I vary the amount of red vs. the amount of green, at no point is a decent yellow produced.

Sadly, due to the limitations of cameras, I am unable to provide a realistic illustration of the pathetic yellow they produce. But suffice it to say that it's a sickly, unpleasant colour.

Now, maybe I just have low quality LEDs. But still, any shade of yellow should be possible from the correct ratio of red and green. Even if the green is a bit red-shifted already, surely I would simply need less of it?


texts: Simple Metronome Circuit w/ Linear Pot Control

texts:
I'm trying to design a square wave oscillator to control an LED with a LINEAR frequency control range of ~0.017 Hz to ~17 Hz (1 BPM to 1000 BPM).

EDIT

Oli's excellent answer and circuit indeed make the duration between discharges linear wrt the control voltage. However it's not clear to me how to scale the input as suggested. Even with a large capacitor the control voltage range is narrow and the circuit throws a huge amount of current around.

To get the usual BPM range for music of between 40 and 240 BPM, that corresponds to periods of 1500 ms and 200 ms respectively. A BPM of 120 is exactly 500 ms.

I have another circuit that I believe also correctly linearizes the period based on the size of a resistor (e.g. a potentiometer):

Could a current mirror like the one above with a different ratio be used to scale the control voltage / resistance? How?

As it is, the circuit would require an R4 of 14.5 Mohm to yield a period of 500 ms (120 BPM). I need the value to be exactly 5K (10K pot in the center position).

Note that I think adding an emitter resistor (R2) to the load will scale down the current (wildar current source?) but it also seems to ruin the linearity.

EDIT 2

Here's another version. That string of parallel transistors provides a 4:1 ratio step-down current mirror so that resistors can be smaller. It also makes the control current relative to ground which is nice depending on how you power your op amp.

Despite the extra parts, the're mostly transistors so the build is probably not as complicated as the schematic looks.


texts:
I'm in a Linear Circuits semester II class, and we're going over 2 port networks. State space equations show up on the practice exams but not the lecture slides or book.

I was wondering if they were another name for the z, y, h, g, T or t parameters, and if not, how to find them. I'm not sure if they're going to be on this exam but I'd rather be safe than sorry.


texts: 4-bit decrementer using four Half Adders

texts:
Like the title mentions, is it possible to design a 4-bit decrementer using just four Half Adders? I know it's possible using 3 Full Adders + 1 Half Adder, but I don't seem to find a way to do that using Half Adders.
Half Adder and Full Adder Design:

simulate this circuit – Schematic created using CircuitLab
By adding 1111 (2's complement form of -1) to the 4-bit input and ignoring the final carry, I'm able to get the decremented value of the input in S3 S2 S1 S0 using a half adder and three full adders connected in series. Is it possible to do this by using only half adders?
NOTE: I'm quite new to this subject and this site, so if there's anything else needed, please do tell me.


texts: What is the best oscillator to be used in a capacitive soil moisture sensor?

texts:
I am working on this project where I am going to make a soil moisture sensor. The principal that I'm going to use is the change of capacitance of the soil with moisture. What I'm going to do is make a capacitor that would be buried under the soil, and connect it to an oscillator. Then I'm going to get the output frequency from the oscillator and use it to calibrate and measure the moisture level of soil. I know there had been several discussions about this project on this site and elsewhere on the internet but non of them answers my questions.

When thinking about which oscillator would best suit my project, the thing which popped into my head was to use a 555 timer based oscillator. Then after some research on the internet I read that an oscillator based on 74HC00 (NAND IC) would give better results. I'm including schematics of both the oscillators here. First one is the 74HC00 oscillator and the second is a classic 555 timer based one.

My first question is, Why 74HC00 based oscillator is suitable than a 555 timer based one? or are there any other suggestions (which I love to hear)?

The next question is rather subjective.

After getting the output frequency I am planning to connect the circuit into a speaker and make the frequency audible. That is, a pitch varying sound would be generated when the frequency changes. To do this, first I thought of feeding a sinusoidal wave as the input voltage, then send it through a quadrature oscillator and get a sinusoidal wave as the output. A capacitor in the quadrature oscillator is replaced with my sensor capacitor. This method is in contrast to the other two methods (using 74HC00 and 555) as discussed above as both of them are generating square waves as the output. This very much relates to the audio which I will get as the output.

So my second question is, would it be practical and worthy to use a sinusoidal oscillator instead of a square wave one if I want to get a frequency in the audible range? Are there any perks of using a sinusoidal wave to get a sound instead of using a square wave?


texts:
I was re-watching this video about how CPUs are made and at the time of the video the link points to, I thought "Isn't there some EMI problems with all those transistor signals flying all over the place?" Possibly some small amount of radiated interference or something.

And that is my question, is EMI a consideration when developing an IC and if so, how is it solved?


texts: Current and voltage direction in source-free RL and RC circuits

texts:
Question on obtaining the ODE

RC circuits :

Why is it that the current flows through the capacitor and the resistor when the voltage source is disconnected. Shouldn't it flow from the capacitor to the resistor since the voltage source is disconnected ?

RL circuits :

Why is it that the current flows from the inductor to the resistor here, but in the RC circuit it flows through the resistor and inductor. Also why is that the polarity of the inductor becomes opposite of that of the resistor when the voltage source is switched off.


texts: For common emitter configuration of a PNP transistor why is current 0 when emitter-collector voltage is 0?

texts: For common emitter configuration of a PNP transistor why is collector current 0 when emitter-collector voltage is 0? Does'nt the emitter-base voltage affect it?


texts: Soil moisture sensor circuit how to link the whole scheme

texts: This is a soil moisture sensor circuit, composed of the following blocks: oscillator (green), the electrodes (yellow), amplifier (blue) and rectifier with Trigger Schmitt (red). The schematic turned out bigger than I expected, since first I made each block separately. Now I don't know how to link the blue part with the red part, where exactly to put the wire


texts: Crash when reaching the end of executable

texts:
I have an executable that crashes after main has finished all its instructions, and the last assembler instruction is executed. Just before the program crashes, I do disas on GDB:

   0x2001c054 <+84>:    movt    r3, #16384      ; 0x4000
   0x2001c058 <+88>:    ldrh    r3, [r3, #16]
   0x2001c05a <+90>:    uxth    r3, r3
   0x2001c05c <+92>:    str     r3, [sp, #0]
   0x2001c05e <+94>:    bl      0x2001c0f8 <scream>
   0x2001c062 <+98>:    mov.w   r3, #0
   0x2001c066 <+102>:   mov     r0, r3
   0x2001c068 <+104>:   add     sp, #28
=> 0x2001c06a <+106>:   pop     {pc}
End of assembler dump.

Now if I go to the next instruction (ni in GDB) I get the following in GDB:

  0xfffffffe in ?? ()

Also, OpenOCD (which I use to communicate with my STM32F2 board) gives the following error:

  Error: address + size wrapped(0xfffffffe, 0x00000004)

How can I tell my executable to exit gracefully?


texts:
Could anyone please help me to draw the wiring diagram for this connections?

I have made this circuit but the problem is that I must attach the diagram of how all of these are connecting with each other

I have searched on the internet and I found that the second diagram looks like my diagram with some exceptions like R2 must not be used (this is my prediction)

Now could some please help me to say if these points are correct or not?
A) The schematic diagram must show that one transistor is connected to next one by connecting emitter of one of them with collector or the emitter of both transistors are connected together?

B) the base of one transistor (left one) is connected with emitter or collector of another one(right one)?


texts:
USB 2.0 Full Speed (12Mbit/s) and USB 2.0 High Speed (480Mbit/s) are both specified as having a maximum cable length of 5m.

Why does Full Speed not allow a longer cable length, given its much lower bit rate?  (I'm assuming that it's a voltage drop problem, rather than waveform issues, but I do not know.)

How can you extend USB 2.0 Full Speed to 20m (cat5 cable) using active adapters at each end?

i.e. What do devices such as https://cpc.farnell.com/pro-signal/usb-boosta/usb-booster/dp/CS16464 contain?


texts: Designing an Inverting Charge Pump (Dickson)

texts:
I was given this circuit. Can somebody explain how this works to create the negative voltage and to lock in the voltages for the source switching?

I need to make +-15 somehow. How would I scale capacitors and change this?


texts: Magnetic field expression in a rectangular waveguide

texts:
I was reading the chapter of Fundations of Microwave Engineering (Robert E. Collin) about transmission lines and waveguides, and I have a question about the electromagnetic field in a rectangular waveguide.

Precisely, it consider a generic TE[m,n] mode and it gets the following equation for the magnetic field along z axis (propagation axis):

If we multiply that quantity by the function Zh(z) = P+ * exp(-kz) - P- * exp(kz), which represents the direct and reverse travelling waves, we get the total magnetic field component along z axis, with P+ and P- determined by the excitation power.

Then it says that The constant Anm is an arbitrary amplitude constant associated with the nm-th mode.

What does it mean? Has it a precise general value for each mode? For instance, which is its value for TE[1,0]?

Here the complete proof of that equation:


texts: Can I connect all ground connectors via the ground fill?

texts:
I am working on a very, very simple two-sided PCB design that connects one 8-pin header with 6 audio jacks, each of which has its right channel and ground connected.

All grounds are connected via lanes, but it seems like I could also use the copper ground fill for that.

Can I do this or could it cause possible harm?

For reference, the board I'm working on:

The orange lanes are ground and on the bottom of the board.
The yellow ones are on top.
Copper fills are left out.


texts:
Okay, so I am completely confused now. First off, I just purchased two xbee units and the pin spacing does not match up with a breadboard .. so I need more hardware.

Anyway, this is what I have:

XBee 2mW PCB Antenna - Series 2

XBee Explorer USB

What else is needed? What is the best way to interface the second xBee (not on the explorer/computer side) ? What kind of board?

With this board: https://www.sparkfun.com/products/11373
Do you just solder some header pins on the underside of it?

As an aside: Is there anything within a reasonable price range that you would suggest gettingh from SparkFun? I might as well purchase something else that I will probably end up using since I will get charged the same freight either way


texts: Simple capacitance sensor on PCB - how to draw?

texts:
I have implemented simple soil moisture sensor and now I would like to create PCB for it (I have prepared couple of prototypes using waterproof marker).

My general question is, what is the right way to draw something like this

using for ex CircuitMaker as a part of bigger PCB which will also have active elements.

Should I create custom element with this shape for pads (which is not very good because custom element have fixed size, every time I will change size of PCB for my project I will be forced to redraw it) ? Is there a way to do "free drawing" of pcb on the board when performing routing ?

Could you be so kind to direct me to the right approach here ?


texts: If a DAC does USB in and S/PDIF out, what does it do?

texts:
I have a USB DAC (Creative SB1240) and their recommended connection is to take an S/PDIF or USB in (to the DAC) and an S/PDIF out (to a receiver). This is how I have connected it and it does sound better than my laptop directly going to the receiver.

The question is:
The DAC is taking digital in and giving a digital out. Where is its conversion capability being used here? If it is not the conversion capability, then what magic is it doing here?

Software Used:
FooBar player & WASAPI.


texts: How accurate is a ripple counter (using D flip-flop) in measuring the frequency of a signal?

texts: I have two oscillating signals S1 and S2 whose periods are always different by a very tiny amount (~10-50ps). Can I use a D-flip-flop ripple-counter to measure S1 and S2 individually, and then subtract the 2 measurements to find out what is the delay difference between S1 and S2? If yes, how accurate would the computed delay difference be compared to the actual delay difference?


texts:
Normally I've always used the L293D chip to drive my motors, but for a new project I am working on I will be using motors that I'll operate between 2.5 - 3.5V and I intend to power them using a single 3.7V LiPo battery.

I would obviously be way out of spec for the L293D for both VCC1 and VCC2, so I am wondering what another good option would be to drive these motors at a very low cost.

I will be using an Arduino Pro Mini (3.3V version) to provide the necessary logic signals.

EDIT: I would like two of these (or similar, perhaps of slightly higher quality) motors on my robot and I would like to be able to drive each independently forward or backward. Pulse width modulation to enable speed control of the motors would be really great, but not necessary. The reason I am going for these motors is because I would like my robot to be powered by a cheap and light power source, and 1 cell LiPos are the lowest cost solution I can find. I would consider 3x AAA batteries, but doesn't seem like they'll comfortably meet the voltage spec for the L293D.


texts: Help with my LED multiple bulb circuit (beginner)

texts:
I will start by saying I've been researching how to create circuits for a few days coming from knowing nothing, so if anything I say sounds dead wrong I apologize.
What I'm essentially trying to do is create a small modular lamp containing 1 LED bulb per "block", and each block can be plugged into the previous adding more "nodes" to the lamp. I've created the basic circuit diagram and found the parts I would like to try to use and I was hoping you could tell me if it could work or if I'm way off base.
For the power supply I would use a 12 volt 2.0 amp wall wart. This would plug into the bottom of the first block via this 2.1mm barrel jack. From there onward each block will have the same barrel jack on the top of the block that can be plugged into via this 2.1mm male adapter at the bottom of each subsequent block. Inside each block I will be powering a single 12v 2watt LED.
I only want to power 5 of these blocks. Having my math checked at another forum showed that the 5 block at 2W each = 10W divided by 12volt = 0.83amps so even with some built in margin of error I'm under the 2amp from my power supply.
However, I read the tech specs of the barrel jack I linked and it says it has a rated current of .5amp. Is that per block (2W/12v=.16a) or is that for the whole setup meaning it can't handle my .83a?
Also I was wondering if there was any way to go about limiting it to just the 5 blocks? Assuming someone else got a hold of these plus some spares and plugged in say 8 blocks it would overheat and be dangerous correct? Is there a way to build in a shutoff past 5 mechanism?
I don't know how to use those fancy mockups I keep seeing so here is a MS paint rendering of what I'm talking about:

(the arrows are to indicate the direction the blocks are being plugged into each other)
Would this work?


texts: How to step up unregulated ~0.2-1V to regulated 5V

texts:
For a school project, I am building a small hydroelectric generator. It uses a 10v, 600RPM/v brushless Tower pro 3520-7t-8 motor, which, when geared up (I'll spare you the calculations here), should be spinning at around from 150 to 800 RPMs. So, in other words, it will be putting out, depending on its speed, approximately 0.2 to 1V.

I will run the output from the motor through a three-phase rectifier (it uses six diodes) and a capacitor for some smoothing, and then on to the 5V regulator, which I am asking about here. The final idea is to have a USB output to, for example, charge a phone.

To summarize, what is the easiest and most efficient way to get from unregulated 0.2-1V to regulated 5V?


texts: So, I've hooked up 2 leds to a 3.3v rail on my breadboard and they both exploded, Does anyone know the effects of the smoke that comes out of them? I think I inhaled some of it.


texts: In thevenin's and norton's theorem why do we dont remove the dependent sources in calculating the thevenin's resistance. And secondly,why do we only use 1 ampere/1 volt source to find the thevenin's resistance when there is a dependent source?


texts: How to generate electricity from clockwise or counterclockwise rotation?

texts: Can something that rotates freely in space generate electricty when it spins from both the clockwise and counterclockwise direction, or could you only draw electricity from a clockwise rotation?  What's rotating is something like a water wheel, but it can tilt and rotate in either direction, and actually does.


texts: How many measurement samples does a typical phasor measurement unit (PMU) transmit in each communication session?

texts:
Given a smart grid network, how many measurement samples (voltage and phase angles) does a typical PMU capture from a transmission line?
I know that in each communication session, a PMU transmits roughly 200 to 300 bytes, but what are these bytes? Could a PMU (in practice) transmit less data? For instance, is it possible to transmit only 1 phase value and would this be useful for state estimation?


texts: Measuring loop Gain and phase of of a flyback converter

texts:
I have a flyback converter based of the LT3798. The converter takes a rectified AC (120Vac,60Hz) and steps it down to 24Vdc. It uses a third winding on the transformer to power the IC and to generate a feedback voltage.

I basically followed the spec sheet's design examples and I now have a working prototype. It seems to work well as it regulates the output voltage at 24V with a load of 750 ohms to 10 ohms. The output does get a bit a noise/ripple on it with the 10 ohm load. That may be able to be fixed with a larger capacitor or LC filter on the output. Something I plan to test later.

What I am curious about is how to measure the gain and phase margin. I do not have a vector network analyzer, but I have seem where you can use an o-scope to to measure the amplitude and phase difference between an injected signal. This is what I am trying to accomplish now. The only problem is that most of the examples I have seen show an injection point that starts at the output of the converter and is in series with some kind of feedback resistors. Mos examples are similar to this:

I understand this. The ac signal "rides" on the dc voltage and causes a disturbance in the feedback loop. Lots of examples on the web that show/explain this.

The problem I am having with my circuit is that the feedback path for the voltage is through a third winding and is not a steady dc voltage.

Can the same technique used in Figure 1 be used on my circuit?

I am using a 120Vac to 16Vac, 60Hz transformer (TRIAD FD5-16) for the injection transformer. I have somewhat of a frequency characteristic chart that I made by using a function generator and measuring the amplitude on the input and output of the transformer at different frequency. I  figured I could use that to compensate for the lack of flatness over the a wide frequency range.

Here is my shcematic:

I would really like to be able to measure the phase and gain margin. Not just to check for stability, but at this point it is somewhat of a learning experience!

I have read that you can capture the output of the converter after a load step to see if there is any overshoot and that will tell you if the system is stable. Is that the method that I should be using? Can anyone point me in the right direction?

Thanks in advance


texts: What is the name of the connector that is similar to an RJ45 but instead of eight lines, it has ten?


texts:
sorry in advance as english is not my mother tongue.

I have been using electron flow point of view for ages for analyzing and designing circuits (disclaimer: I have a background in computing - not electronics), learning with Floyd "electron flow" version and it's been working great... until I met flyback converters...

In all documents I have been reading, they all basically say, in a nutshell, that in the primary, when the switch is on, energy is stored in the transformer core - which acts like a simple coil - and that no current is flowing in the secondary, and as soon as the switch is off, polarity reverses on the secondary, and current flows.

It's all based on conventional current paradigm. Now if we take the electron flow point of view, there are some problems.

Electron can not flow on the primary and not on the secondary at the same time. Otherwise, any transformer with no load on the secondary would have a strong current on the primary and burn.
Regarding the secondary diode which is said to "block" the current while the primary is on, it clearly shows that the electrons can flow - because conventional current is the opposite of electron flow. Electrons are indeed charging the capacitor. When the primary is switched off, then the electrons are blocked by the diode and have only one way to flow: to the load.

It seems very strange to me that virtually all flyback papers say that energy is stored in the transformer core, whereas electrons are all gently stored in the capacitor on the secondary side....

Am I completely wrong or what? I am a bit puzzled actually by the fact that conventional current view can be very misleading when compared to reality ...

All comments welcome. Thanks a lot.


texts:
Is there a formula describing the relationship between bit error rate, frame size, and normalised effective throughput?

to clarify, normalised effective throughput is the same as channel utilisation.

so far I have "throughput = 1/(1+2a)" where "a = tprop*R/L" (tprop=propagation time or delay,R = bit rate), however I am unsure how bit error rate fits into this - does bit error rate have much to do with bit rate.

Any help/pointers/where to get help would be appreciated. are there any other forums that I should post this on?

EDIT:
Just to give some more background info:
basically this is for a project(topic: analysis of optimal frame size and bit error rate relationship on lossy links), where we have to write a MATLAB GUI (graphical user interface) and the inputs are bit error range (ie max and min bit error rates) and frame size range (max and min frame/packet sizes). We have to calculate the normalised effective throughput of the link from those inputs, and make a 3d graph.(x:BER, y:FSR, Z:throughput)

@clabacchio i was talking about general parameters - L stands for number of bits in a frame.

@kellenjb we haven't been given any info on how errors are handled, so i suppose we just make an assumption. (and i deleted the other posts, sry about that)


texts: I am trying to use two different SPI buses on one Teensy 4.0. However, from the programming side, I am not sure how to implement this. I can assign CS pins and initialize SPI settings for different devices, but I am not sure how to take advantage of the second SPI bus. It seems to me that the code I have seen always assumes there is only one. Could anyone point me in the right direction to implement this?


texts: Ideal wireless channel (coherence time/bandwidth)

texts:
Wireless channels can be characterized as either slow or fast fading based on their coherence time and signal length. Similarly, they are either flat fading or frequency selective depending on their coherence bandwidth in relation to the signal bandwidth.

Are some of these characteristics (or combinations) generally more desirable than others? In UMTS, spreading techniques (CDMA) are used to artificially increase the bandwidth and make the channel frequency selective. Thus, wanting to achieve frequency redundancy.

On the other hand, LTE and Wifi use OFDM(A) to create many narrowband channels/subcarriers wich are flat fading. However, in these cases it seems important that the channel is also time selective or fast fading to allow for forward error correction.

Does this mean that generally frequency and time selective channels are more desirable and the channel should be at least frequency or time selective? Or does it depend on something else (what?), such that different characteristics are more beneficial in different scenarios?


texts:
I'm currently using ATmega32 device with external clock speed of 16 MHz . the problem when i use a delay of for example 16,000 ms in the software, it actually delays only a 1000 ms in actual world. I mean the uC CPU divides the delay time by the clock frequency in MHz to make the delay (16,000 ms / 16 MHz). Also when i use a 8 MHz clock with the same amount of delay it would make a delay of 2,000 ms.
What would be the reason for that?

Edit "Here is my code"

include avr/io.h>

include util/delay.h>

include stdio.h>

include stdlib.h>

define F_CPU 16000000

define BAUD 9600

define BRC  ((F_CPU/BAUD/16)-1)

void USART_Init(unsigned int brc)

{

// set baud rate

    UBRRH = (unsigned char) (brc >> 8)  ;
    UBRRL = (unsigned char) brc ;

    UCSRB = (1 << TXEN ) | (1 << RXEN) ; // enable receiver and transmitter
    UCSRC = (0 << UMSEL); // setting Asynchronous mode
    UCSRC = (1 << UCSZ1) | (1 << UCSZ0); // set communication number of bits (8 in this case)
}

int main(void)
{

    USART_Init(BRC) ;
    while(1)
    {
        char c;

        _delay_ms(32000);
        for (int i=0 ; i<=3 ; i++)
        {
            if (UCSRA & (1 << UDRE))
            {

                UDR = i;
                _delay_ms(8000);
            }
        }

    }
}


texts: Problems reading the Delkin Micro SD 16 GB using SPI

texts:
I have been working with SD Cards and micro SD Cards for a while.

I am using Part1_Physical_Layer_Simplified_Specification_Ver6.00 for reference.

I am able to do successful card initialization, read and write for other micro SDs like ATP 8GB SLC, Panasonic 8GB SLC etc. However when I am using Delkin 16 GB SLC (and also Swissbit 8GB SLC), although I am successful in card initialization and write, when I am trying to read then I am not getting start block token 0xFE and there are around 512 Bytes of junk data before it becomes normal again.

The pattern is as follows (using the Beagle SPI analyzer):

After writing the following (only the first 24 bytes are shown, but the pattern is the same):

If I am writing 0xA0. Please refer to the following image:

If I change the bytes written, then bytes read are also changed and there is one to one correspondence as well between the bytes written and bytes read. But the bytes are not the same.

I am verifying the data is written successfully using the SD Card reader with HxD hex viewer.

For the first case:

For the second case:

It doesn't seem like the voltage to SD card is varying, as I checked it on the oscilloscope and it remains 3.3 volts during the read.

I am using F28377s Launchpad from TI as the microcontroller.

I would like to get the inputs from you. What exactly can I try to fix this problem?

Edit1: Exactly same behavior is observed for Swissbit 8GB SLC. The same images above can be applied to Swissbit. The data read for Swissbit is same as Delkin.
SPI clock before initialization is 200 kHz and after initialization is changed to 1 MHz.

Edit2: Please look at the oscilloscope images below (i have changed the clock frequency to 225 KHz):

Edit3: The second oscilloscope image, immediately follows the first oscilloscope image. The first image is the read command and response whereas the Second image is sending 0xFF and waiting for start data block token, which is 0xA8 in the second image as 0xFE is bit shifted by 2 bits. You can look at the decoded hex data of the oscilloscope in the bottom of the oscilloscope images. They are same as my Beagle SPI Analyzer Debug Data for example 2 (where I am writing 0xA0 and reading back 0x28).

Edit4: As per Anonymous' suggestion, I have updated my code such that before every command and after CS LOW, I send 8 clocks before any actual intended SPI transmission. After the command response completion, I send 8 clock cycles just before CS HIGH and 8 clock cycles just after CS HIGH. Command response completion in SD Read case means when we have received the last CRC byte. Command response completion in SD Write means when the card stops sending the busy signal after writing. Similarly, I have applied to other commands as well.
Also, I don't do CS HIGH until the command and its response are completed. For e.g. in SD Read Case, I do CS LOW and I send the command, get the command response, get the start block token (0xFE), get the CRC and then I do the CS HIGH.

Thanks.


texts: 2-layer PCB design, through hole technology and ground plane

texts:
I am designing the layout of a PCB for audio applications (no digital electronics, only analog).

All components are through hole, the PCB is pretty large (about 16cm x 10cm) and has 2 layers. Plated through hole are supported by the technology I am using. The circuit has a dual supply.

Which (and why) of the following is the best solution for routing signals, power supply tracks and ground?

TOP layer: ground plane; BOTTOM layer: signals and supply lines;
TOP layer: signals and power supply lines: BOTTOM layer: ground plane;
TOP layer: ground plane and supply lines; BOTTOM layer: signals;
TOP layer: signals; BOTTOM layer: ground plane and supply lines;


texts:
I know this question may be very stupid, but it comes from a true beginner, and a Google search came up inconclusive.

When porting high or low the input pins on an integrated circuit (particularly CMOS), are the input current sinked or sourced ? To me it makes sense that they would be sinked, but I am not finding the information on it, as googling with the terms 'sinking' or 'sourcing' just brings up pages about those terms.


texts:
We have this oscillator and for it to run the initial condition is Vout to be V+.

How is this done? Shouldn't it be equal to 0V from the schematic?


texts: Why does a Sallen-Key low-pass filter improve ripple in my PWM to DC voltage converter circuit?

texts:
The original low pass filter converts PWM to DC voltage.
You can see the nasty ripple on the ouptut in the oscillscope:

Sallen-Key improvement:

What exactly is happening with the Sallen-Key that makes it have less ripple?
Try to explain it by identifing the effect that causes the  basic low pass filter to have a downward ripple on the falling edge of the PWM signal. Is it due to a capacitor C1 discharging?? If it is due to C1 where is the current going when the PWM is on a falling edge/ 0 volts?


texts: How are MBIM transaction ID's supposed to be used?

texts:
Situation
I am developing a product that will use this Sierra Wireless HL7618RD Cat 1 LTE modem. I am interfacing to the modem over USB using a small SoM running a Debian flavor of Linux. The modem is configured so that it appears to udev as having:

a serial interface (/dev/ttyACM[n]) for sending AT commands, and
a Mobile Broadband Interface Model (MBIM) interface (/dev/cdc-wdm[n])

I am interacting with the modem primarily over the MBIM interface using the tools from package 'libmbim-utils':
# apt policy libmbim-utils
libmbim-utils:
  Installed: 1.18.0-1
  Candidate: 1.18.0-1
  Version table:
 *** 1.18.0-1 500
        500 http://raspbian.raspberrypi.org/raspbian buster/main armhf Packages
        100 /var/lib/dpkg/status

especially the 'mbimcli' and 'mbim-network' tools.
Design Requirements
In short, the scripting that manages the cell module using mbimcli and mbim-network has to be fairly robust, good enough to handle things like dropped packet sessions and dropped registration, bad weather, blackouts, etc.
I cannot use ModemManager because I've had issues with it.
My Question
How am I supposed to use MBIM transaction ID's (TRID) with mbimcli? When should I specify one, and when should I not?
A lot of examples, and even in the source of the mbim-network utility, make use of the --no-open=[$TRID] and --no-close sometimes. Am I always supposed to specify a transaction ID every time I communicate with the modem in any way? What does it mean to specify one or not specify one? I can run, e.g.
mbimcli --device-open-proxy --device=/dev/cdc-wdm0 --query-registration-status
and get a perfectly good response. I did not acquire or specify a transaction ID.
Research so far
The only other place I've seen this question directly asked is on the libmbim mailing list here, and the guy that answers refers to the USB specification for MBIM here. I understand what he is saying in his answer, and the purpose of a transaction ID given in the MBIM standard from USB.org.
I also see the [mbim-network]() source getting and recording a transaction ID as a temp file at /tmp/blahblah.


texts:
I have simulated the following circuit and am curious to the position of the load resistor. The circuit switches an ac signal using a pulse. It seems to be common to have the load in the position or R2 and the signal is as it should be. The blue plot represents thecurrent through R2. However the current through R1 is a pulse (same as firing pulse) and does not represent the ac signal at all. Why is this?When the triac is open the current should be the same through both.

Edit 1:
Added plot of voltage at V2:

Edit 2:

Gate resistor has been added. Device switches as expected however there is a large voltage drop. Vout is now 200V instead of 400V. There is a lot of current flowing back out through the gate through R3.

If I change any of the component values the simulation freezes so I cannot even try anything else. Why is this happening?

Thanks.


texts: confused about behavior of relaxation oscillator

texts:
I'm just starting to learn about electronics by working through Charles Platt's Make: Electronics book and I'm on experiment 14, which is a relaxation oscillator for an LED.  I should note that in the schematic below, I wasn't able to figure out how to add a PUT (2n6027), so 'D4' is in fact a PUT.

When I increase R3, my intuition tells me that since I'm increasing the capacitor time constant, the capacitor should take longer to charge and thus I should see a longer time in between flashes.  In practice, exactly the opposite happens.  As I increase R3, the LED flashes more and more frequently.  If I put in a 10K resistor for R3, the LED flashes so quickly that it appears to be staying on continuously (or the voltage across the anode of the PUT stays continuously above the gate voltage for some reason).  Why does the frequency of the LED flashes increase, rather than decrease, when I increase R3?

simulate this circuit – Schematic created using CircuitLab


texts: How do I calculate needed pixel clock frequency?

texts:
If I want to have a resolution of X * Y pixels, updating in frequency f. How do I calculate the pixel clock speed?

Example:
1280 x 1024 @ 85Hz usually have a pixel clock of 157.5 MHz, but how do I calculate the needed pixel clock?

Need to know to select DAC and DSP.

Edit:
Usually the Front porch is: 16 pixels 1 line, Synch width: 144 pixels 3 lines. So this is a total of 1688 x 1066 @ 85Hz. But, still the pixel clock formula should be the same regardless of the extra lines and pixels.


texts: Best way to simultaneously control two servos positioned horizontally and vertically?

texts:
I'm trying to set up a C program where a servo (servo1) sweeps to a position, waits a few seconds, moves to another position and repeats 4 more times. Another servo, positioned vertically, (servo2) is supposed to move up and hold its position, especially during the period where servo1 is waiting. I have servo2 running in an infinite loop as a separate thread, but I am unsure if if this is the best course of action.

The problem is that servo2 either falls and loses its position if it is not consistently receiving a signal,
or if it keeps getting a signal, it constantly hums and sometimes jumps around. I'm not sure if it jumps because if there are interrupts in the background (I'm using a cubieboard running linux).

I'd like servo 2 to not jerk around at all. Any help or suggestions on implementation would be appreciated.


texts: Solar panel as day/night switch for a load

texts:
I'm using off-the-shelf components to power a buck/boost LED driver and charge a battery from a 6V solar panel.

To power the LED driver from the battery at dusk only, would I have to use a MOSFET like shown below, or is another component needed; or do I need something very different altogether?

Thanks in advance!

Edit: I think I have understood that I need a PMOS in my case (instead of a transistor like in this PV solar panel darkness detection circuit). And a resistor between PV solar panel and PMOS gate. Am I understanding this correctly or not? If yes, how would I calculate Rg?


texts:
Can we declare Generate if-for statement?

module prac#(parameter m=3)
(input x, input[2:0]a,b,output[2:0]c);
wire [2:0]f[0:3];
genvar i;
generate
if(!x) begin : d2
    for(i=0;i<=m;i=i+1) begin:dd
    assign f[i]=(a & b);  end
end
endgenerate
endmodule

It is saying that 'x' is not a constant.
I want to instantiate a module multiple times based on control signal. Here x is my control signal. Is it possible?

Thanks in advance.


texts: Reason behind choosing the compensating resistor for input bias current in op amps

texts:
I found the following explanation online on determining the values used for the compensating resistor:

In either case, the compensating resistor value is determined by calculating the parallel resistance value of R1 and R2. Why is the value equal to the parallel equivalent of R1 and R2? When using the Superposition Theorem to figure how much voltage drop will be produced by the inverting (-) input's bias current, we treat the bias current as though it were coming from a current source inside the op-amp and short-circuit all voltage sources (Vin and Vout). This gives two parallel paths for bias current (through R1 and through R2, both to ground). We want to duplicate the bias current's effect on the noninverting (+) input, so the resistor value we choose to insert in series with that input needs to be equal to R1 in parallel with R2.

Although it is a 'crisp' and simple explanation, I don't understand how it is true, since the current flowing through R2 won't directly go to the ground, but will probably enter the op-amp at the output (op-amp as a current sink). Also, it might go through a few more resistances before going to the ground, since Vout isn't directly connected to the ground.


texts: Finding out unknown voltage using mesh analysis

texts:
How to find out the voltage v3 in the following circuit using mesh analysis?

I tried to solve it by considering the dependent current source as a super mesh and eliminated it.

The equations I got are:

8 - 6*i1 + 2*i2 +3*i3 = 0 ------------ this equation belongs to the loop that contains 80 V source.
30 - 70*i3 + 50*i1 -20*i2 = 0 --------- this belongs to the loop that contains 30 V source.
15* i1 - i2 + i3 = 0 --------- super mesh equation

The current values I got after solving the equations are:

i1 ~ 0.95A
i2 ~ 11.35A
i3 ~ -2.9A

which translates to V3 = 40 * i3 = 116 V

But the solution in the book says V3 = 104.2 V

Can somebody please tell me where did I go wrong?


texts: How to check if a SMPS transformer is working properly

texts: I recently came about one such transformer while fixing a boiler PCB and I suspect it's damaged. How do I test it?


texts: I'm aware that inductive loads like relays need a flyback diode.  Since a motor is also an inductive load, I'm inclined to put a reverse-biased 1N400x diode across the terminals of this fan.  However, I've never heard any mention of using flyback diodes with fans.  Am I correct in thinking I need a diode, or is there some reason why I wouldn't?  Thanks!


texts: Connecting telephone hybrid d-sub pins to a switch?

texts:
I acquired an old analogue Studer Telephone Hybrid with a built in Dual Relay Card. When I recieve a call, I want to send the output not through my telephone but through the XLR outputs of the unit. So I need to switch the output (and input) in the hybrid itself. For that there is a 15-pin d-sub connector and, from the manual, the following info on how to connect the pins: https://photos.google.com/share/AF1QipMnKU5zqQfsvyuhKgIdgySpBArVNtKNA87xsd3ITXn4nZTT7-T8jYQNCZPm7-tVtA?key=V3RNWThFTDdtcWpvZWZYNFB0WjR3WFZxbTg1bEVn

In case the link becomes unavailable, here's an ASCII transcript. If this is the d-sub connector:

-----------------------------------
 - o8  o7  o6  o5  o4  o3  o2  o1-
  - o15 o14 o13 o12 o11 o10 o 9 -
   -----------------------------

then these are the connections:

                             ___________
 ___                        |    ______
|---|-----------------------|---|---
| - *___*   o   o   o   o   *   * -
|  - o  |o   o   o   o   *___*   -
|   ----|----------------|-------
|       |                |

So apparently pin 7 and 8 as well as pin 9 and 10 are bridged. Does that mean that the pins are just soldered together? Unfortunately I'm new to electronics, and I can't quite figure out which pin goes where. I have a push-button switch (an EAO 31-261.025 with a lamp in it) which has 6 terminals that look like this:

 ---------
|o 1   3 o|
|  -   +  |
|o X1 X2 o|
|         |
|o 4   2 o|
 ---------

and I have soldered on the pins 1 on the d-sub to pin 1 of the switch and then pin 9 and 10 both onto pin 2 of the switch. Turning on the hybrid destroyed the 200mA fuse, so I probably made a mistake. How do I correctly connect the switch to the 15-pin d-sub connector?

EDIT 1

Judging from the third picture of the shared album on Google Photos, the switch connected to the d-sub needs to short the pins 7 and 14 (and/or 8 and 15 depending on channel). After opening the hybrid up, I saw that the pins 1 and 2 as well as 14 and 15 had a blob of solder between them, so apparently I don't need to connect these myself!

The wiring diagram in the third picture should look something like this:

     _______diode____[   ]______
    |     __diode____[   ]__    |
 ---|---|-------------------|---|---
  - *,,,*   o   o   o  _o___*   *_-_____*
   - o   o   o   o   o|  *,,,*___-_____*/    <--- switch 1
    ------------------|--|-------
                      |  |
                      *-.*                   <--- switch 2

where the commas refer to internally bridged pins.
Since I can't figure out this EAO switch I found a generic DPDT slide switch with 6 terminals. Now I have (replaced the fuse and) soldered the terminals like this:

 ----------
| 7 o  o 8 | <-- pins 7 and 8
|          |
|14 o  o 15| <-- pins 14 and 15 as ground
|          |
|   o  o   | <-- nothing soldered on here
 ----------

Having tested that, it still wouldn't switch (but at least my hybrid keeps turning on). Did I solder the d-sub pins to the wrong terminals or did I miss out on something? Or may I have destroyed more than the fuse at my last attempt? :(


texts:
Using 12V DC (max 3 amp) linear actuator in a standard car,
I need to use some micro-switches in the power circuit to prevent the actuator powering, if it's not in the correct position i.e. won't start until it is in a position where the micro-switch is closed.

Looking at ME-8111 whose specs say:
AC-15   Ue: 250V, le: 6A
DC-13   Ue: 220V, le: 0.3A
My question is: Will this switch work fine? (The 0.3A bit gets me.)

Thanks for any insight. I've googled and read so much, but still don't know the correct answer.


texts: How are Operating Temperature Bands Determined?

texts:
Manufacturers like Maxim, Altera, and many more seem to adhere to a commonly defined range of temperatures for applications. For instance,

Full military (-55°C to +125°C)
Automotive (-40°C to +125°C)
AEC-Q100 Level 2 (-40°C to +105°C)
Extended industrial (-40°C to +85°C)
Industrial (-20°C to +85°C)

What is the rationale behind these ranges? Are they just an aggregate of temperatures that these applications usually operate in? Or are they calculated using a formula of some kind? Who came up with these?


texts: When does separating digital and analog ground make sense, is it essential, and when is it not? Should I separate the grounds in this project?

texts: I created a simple sequencer design based on several digital chips. The circuit is powered by a simple 7805 voltage regulator. When designing the board, I separated the analog ground of the power circuit from the rest. Is it right and make sense?


texts: Why I cannot edit waveform in ModelSim Intel?

texts:
I would like to create my own testbench for the code vhdl. I tried to use the edit function from ModelSim but it does show blank as you see on the picture.

what could I have missed?


texts: Voltage value changed after a while at the output of voltage regulator (TPS5430ddar)

texts:
I want to convert 7.4 V to 3.8 V.
Voltage regulator works correctly for a few minutes(appromaxitely 3 minutues). The problem is output voltage level of regulator steps up to 4.9V after a few minutes.
The regulator is connected to a gsm module which has  a peak current of 2 A. The schematic of circuit is attached.
How can I fix this problem?
Thanks...


texts: Calculate voltage and current in an op amp

texts:
Hi I have a op amp circuit that i need help in calculating some values (see image, Å=A in further description)

The values i have are:

                  RF =  0.4 kΩ

                  RA =  70 kΩ

                  Ri =  0.14 kΩ

                  RL =  0.7 kΩ

So for E= 100 mV what are a) Uut and b) IA ?

I have tried doing Uut=EF=E(-RA/(RF+Rk/2))=-6.363 V which was wrong. I thought it was a differential op amp, so i found the F formula in the book, but i don't know if that is correct to use here.


texts: Chinese Adjustable 60W soldering iron problem

texts:
I bought a 60W Adjustable soldering iron from China last year. I think it's designed to run at 220v because it is not hot enough when connected to 120v. It measures about 200 degree C. So I decided to see if I can fix it. there is a 500k pot and a 100k resistor. I guess by changing this voltage resistor, it probably will increase the temperature. so I changed the 100k to 75k, and measured the temperature again, and it didn't go up. then I changed the 100k to 500k, and it went up to 230 degree at max, still not hot enough.

There are my question:
1, there are 4 terminals for this soldering iron. I think 2 of them are the heating lines and 2 are the temperature sensor lines. Can I ignore the controlling circuit, and connect 120v ac directly to the 2 heating lines? because the adjustable temperature circuit is useless.

2, It has a lm358 op-amp and a TO-92 package 600V 97A6 M922 Bidirectional Thyristor. This thyristor is tiny. Can it really output 60W??

3, the circuit pcb trace is very thin on the ac lines, is this bad design?


texts:
This lecture shows how to create ac model for buck-boost converter.

What I am confused is the equivalent circuit model for inductor loop equation
on page 38.

As you can see from the model, there are two dependent voltage source   (square boxes), \$D\hat{v}_g \$ and \$D'v \$,  and one independent voltage source (circle symbol), \$(V_g -V)\hat{d} \$.

What is the basis to distinguish/know which one is dependent or independent source here?

For example, why is \$D\hat{v}_g \$  considered as dependent source? I thought it is an independent source because \$\hat{v}_g\$ is the input voltage and it is independent source. However, I am wrong here.


texts: Why DDR3 RAS timing have to be greater than RCD + CAS timing?

texts:
By definition, tRAS is the minimum delay from when a particular row in a bank is activated, to when it can be closed with a PRE command.

I have seen claims numerous times that tRAS should be > tRCD + tCAS . Also I've seen DDR parts recommend tRAS to be way over even this number. For example, in a DDR3 with 8-8-8-24. tRAS should be 24 while tRCD and tCAS are 8.

I agree tRAS comprises of the time it takes to select the Row (tRCD). But I've noticed in some examples that, the controller doesn't have to wait for the full-tCAS Latency before issuing a PRE. This is especially true in back-to-back transfers, here's a picture I borrowed (it shows only 1 READ transfer but is actually a part of a back-to-back READ):

So clearly from this diagram, the row need-not be active for the full tCAS. Then why does tRAS have to be greater than tRCD + tCAS?

My understanding is, it takes only tRTP (minimum read to pre delay) for a block of 8n bits to be latched into the FIFO buffer. After this, there is no need to keep the row active. Then why is tRAS supposed to be so high?


texts: PWM signal to "real" analog signal with low load dependency

texts:
I am designing a circuit that allows me to regulate an Arduino PWM output to a stable voltage reference (PWM to 0-5V ideally) dependent on the duty cycle. So far my approach has been to attach a low pass filter which works ok. However the output voltage, of course, varies depending on load. I've been considering buck converters but I havent found a buck-IC where I can control the output voltage with a PWM signal. Should I design my own buck converter? Or do you know a good component for this purpose?

Summary:

Input signal: PWM (0-5V) with different duty cycles
Desired output: Analog voltage between 0-5V that I can regulate with duty cycle. As independent on load as possible.
PWM frequency ≈500Hz
The required output current is 0-10mA.


texts: Do the high / low levels of an I²C slave's response have to be of identical voltage as the levels of the I²C master's message?

texts:
I've got an IC (a TDA7318) with an operating voltage of +9 V. It's gonna be controlled by a Raspberry Pi 3B (output signal voltage: V_high = 3.3 V). Now I'd like to make sure that the responses sent by the TDA to the Pi do not exceed 3.3 V, as otherwise it might get fried.
So here is the "general" version of my question: When the master sends signals at V_high = 3.3 V into the I²C bus, does the I²C spec require all slaves to send their responses to the master at the same V_high level?
In this special case, my question reads as follows: Will my IC use a V_high = 3.3 V for the responses it sends into the I²C bus even if its V_cc is 9 V? Or should I rather use a level shifter for safety?


texts: No amplification with LMV358 compared to LM358 in crude current sensing

texts:
I am trying to build a current sensing circuit (two channels), with no requirement of precision (i.e., is current passing over some threshold whatnot). The (somewhat generic) circuit I am implementing is this:

The circuit works as expected with LM358 of TI. But I insisted to use a Rail-to-Rail opamp and got this LMV358 from Diodes Incorporated.

I used 470k %1 as R2's and 3k3 %1 as R1's in the circuit. The output is around x0.9 of the input. The gain is not around 140 as expected. My shunt resistor is 20mOhms, and current is around 50 mA. So my input voltage difference happens to be around 1 mV. My supply is around 5.1 volts.

However, it does not work.

I take the LMV358 out of the PCB, resoldered the LM358, and everything works fine again. Actually, when I attached the LMV358 first, only one channel (one of the dual opamps) was working. Once I detach it and attach to an independent breakout-board, it works fine.

Isn't this kinda weird?


texts: I made a 15v solar panel from garden lights which supplies 50mA of current in direct sunlight. For some reason it doesn't power a simple dc motor which can run on a 1.5v battery. Why isn't it powering the motor, but can power an LED? Is it a lack of amps? If so, how can I increase amperage?


texts: via in pad, thermal via, or something else?

texts:
So recently while watching a video I came across this:

to me this looks like a pad with a bunch of vias in it. I haven't encountered multiple vias in the same pad before. I tried to search images of one, but couldn't find any. So is this something else? It seems a strange design choice to me because:

wouldn't all the vias be bridged together? if so, why expose the interconnection, here, in this way?
How did the manufacturer manage to cap all of these without solder flowing all over the over pad. I don't see evidence of any masks.

(for context: the first images is a bottom side of a micro usb connector on an Asus Transformer T102HA, this is the top side)

I thought these might be thermal vias (which would make sense considering the charging port will heat up during use)

Thanks for taking the time to read this. If you're familiar with this design pattern and could alleviate my curiosity, it would be greatly appreciated.

The video the first two images came from can be found here.


texts: Power output neccesary to power multiple USB devices at once?

texts:
If I have a device that requires 5V and 2A to function, what kind of power supply would I need to power 4 of these devices at the same time to their full capacity?

Here is an example setup:

Power bank-Portable Charger 30000mAh 2USB Ports (Output 5.0V 2.0A)

USB Hub-4-Port USB 3.0 Hub

Device-Electric Cloth Heater Pad Heating Elemen

=====================================================================
Based on this battery, im pretty sure the portable battery must be able to at-least give off a total of 8 amps..

ZeroLemon ToughJuice 30000mAh 7A Output Portable Charger
t

But im willing to bet it needs more than that to maintain that sort of power for over two hours. I wonder if a USB hub can handle 4 amps in a single cable...


texts: How to use MCP73831 with multiple voltage sources correctly?

texts:
I'm trying to use an MCP73831 with multiple voltage sources (one is from a 24VDC to 5 VDC regulator, the other one is from a standard USB) but I'm having a bit of a problem.

For the moment, I'm only trying without connecting both voltage sources at the same time, but I tested with the both sources independently.

The problem appears at my status pin when I want to recharge my battery. When the battery is fully charged, the status PIN seems locked and it never reaches its assumed voltage (5V).

This is my circuit (the filtering capacitors are not shown in this schematic, but I added it according to the value specified in the datasheet to do my test):

Here is the value of the stat PIN of the MCP73831 with a fully charged battery (yellow signal = stat pin, purple signal = VBAT).

Everything else is working fine (charge, regulator) except the value of this stat pin. It seems it will never go to it's high state (VDD = 5V). It stays at this voltage forever.

When I remove the D21 or the D22 diode, the problem completely disappears and I obtain the good response (yellow signal = stat pin, purple signal = VBAT):

I thought it could be caused by the voltage drop of the diode but I still have 4.75V at the VIN Pin. It's normally enough to make the MCP73831 working (from the datasheet, the minimal VIN is 3.75V) and the 3.3V regulator (from the datasheet minimum of 3.3V, 3.80V at the VIN PIN).

What could do such response?

How could I use the MCP73831 with multiple voltage sources if I can't use the diode to "separate" these voltage sources?

I'm pretty sure I can't use the two voltage sources at the same time if I'm removing the diodes (D21 & D22) but maybe I'm wrong?

Edit 1 : @Cisco25 :

I removed the NMOS22 section from the STAT pin, there is my result with the diode (yellow signal = stat pin, purple signal = VBAT): I didn't see it at first, but the signal is not stable in terms of frequency on this test.

Again if I remove the diode, I obtain the same result than previously (a constant VDD=5V signal as the battery is charged).

Edit 2 :
Thank's to Cisco25, I identify the problem was still there without all the transistors and the 3.3V regulator.

There is my exact circuit, I really don't know why with the diode the status pin stay "in charge" with the led turned on.

When I remove the diode and replace it by a single wire, I got the right VDD value on the stat pin.

When I short-cut the diode, I got the same problem, like if my diode had still an influence on the circuit.

Is it possible that my problem comes from the fact my diodes are Zener ?

There is the schematic :

Status pin in yellow, battery voltage in purple with the zener diode :

Status pin in yellow, battery voltage in purple without the zener diode :

Edit 3 :

I modified the schematic as you said :

It worked correctly this time :

What is the problem doctor ? :-/


texts: What are some good ideas to practice on the MSP430

texts: I've got 4 launchpads (I'm a hog, I know, I got 'em while I could) and I'm getting used to the programming, e.g. the timers, ADC, PWM, LPM, etc. I don't have a lot of money and would like to do some projects to solidify my knowledge. What are some little projects I could do on a budget to have fun? The blinky apps only go so far.


texts: 19.5V to 15V - what's the best way to lower the voltage?

texts: The problem is: I've got a power supply capable of outputting 19.5V 4A. I need to lower the voltage to power up a laptop that requires 15V and 2A. Which way is the best to do it? Construct a voltage divider from some resistors? Use a LM317?(datasheet says it can output "in excess of 1.5A" - what does it mean? That it will tolerate 2A?)


texts: Analysing Signal quality through pogo pins using Hyperlynx

texts:
I have successfully modeled Linesim and boardsim schematics for quite a few designs in the past and we have been able to do the required SI simulations. I had one question though: On one of our multi-board designs, we connect one board to the other using DE-50 pogo pin by IDI and they do not give any R,L and C values for the pins. They just specify the Length = 1.703", Diameter = 30mils and Resistance of 50 mohms. What is best way to model a pogo pin or any other connector for that matter in Hyperlynx LineSim / BoardSim? Any suggestions? I would think that the best way to do this is to have a lumped circuit equivalent for pogo pin but the manufacturer wouldn't provide any parasitic values.

Thanks for the help.

-Sandeep.


texts:
Good day, I have purchased the following charge management controller:

MCP73831T-2ACI/OTCT-ND

I'm using the following diagram:

But, the LED (D1) never lights up, with or without battery. When measured, the STAT pin is always 3.7V, and the VBAT pin, is always at the same voltage of the Battery.

I'm using ceramic SMD capacitors for C1 and C2, and SMD resistors for R1 and R2. Both, capacitors and resistors, are 0805.

Measurements, with battery:

VBUS = 5.1V
VBAT = 4.0V (Current battery voltage)
STAT = 3.7V
PROG = 3.54V
VSS =  0.0V

Measurements, without battery:

VBUS = 5.1V
VBAT = 0.0V (See note 1)
STAT = 3.7V
PROG = 3.54V
VSS =  0.0V

I have also removed the PCM circuit from the battery, but it did not work.
The battery is labeled as 3.7V 700mAh, DS 902540.

When the battery is disconnected, the VBAT voltage starts decreasing from 4.0V to 0.0V, slowly. Is this normal?

Thanks in advance.


texts: Designing a switching system for solenoids on Raspberry Pi

texts:
As part of a project I'm working on, I'm having a Raspberry Pi GPIO pin activate three solenoids, but the pin itself does not supply nearly enough current (each solenoid requires at least 1A, close to 1.5A optimally). I'm trying to set up some sort of switching system with a secondary power source. My first idea used a CMOS switcher, but I ended up using spare parts I had lying around and it didn't work perfectly.

Is a CMOS setup good for what I'm trying to do? If so, what specific MOSFETs should I look into; if not, what would be a more efficient way to tackle this problem?


texts: What is the practical reason for associating cut-off frequency to %50 power attenuation?

texts:
Historically when speaking about lets say an analog low-pass filter, the cut-off frequency of that filter is defined as -3dB.

So this is the frequency where the output sinusoid signal's amplitude attenuates to 0.7 of the input(Voltage-ratio). When squared this ratio we obtain %50 which is the Power-ratio.

It is very obvious that once upon a time it was decided the cut off-frequency should be the frequency which causes a %50 power loss of a particular frequency sinusoidal signal input.

My question is: what could be practical reason defining it %50? Isn't %50 still big amount and how could it be associated with being filter. I could make sense if it were chosen %95 for example.


texts:
I am trying to numerically generate the output voltage of an RC Filter to that of Plot 1 using the following formula.

Using the following code:
dt = 1e-6;
stop_time = 20e-3;
t = (0:dt:stop_time);
fin = 50;
w = 2 * pi * fin;
Vin = 10 * sin((w*t));

R = 100e+3;
C = 33e-9;
RC = R * C;

Vout = (1/RC) * Vin * dt ;

However this generates what is shown in Plot 2 which is a scaled down version of the input signal and is in phase.
What is the correct way to obtain the numerical results?
Thanks.
Plot 1:

Plot 2:

Edit 1:
Using Vout(n+1) = Vout(n)+((Vin(n))/RC) *dt
integrates (Plot 3) but does not generate the output voltage (Plot 1)
Plot 3:


texts: How is interpolation performed when a sampled sequence is upsampled?

texts: When a sampled sequence is upsampled, zeroes are inserted between the original sample values. But how are the zero values used to effect an increase in the number of sampled values?


texts: Filtering Voltage Spikes on Split Power Cable

texts:
I have a test set up that can more or less be broken down like below:

simulate this circuit – Schematic created using CircuitLab
The splitter shown is custom made for testing, here is a drawing:

PCB1A + PCB2A pass the 12V line through to the Mini-ITX CPU board, which can be powered by 12V directly via the 4 Pin ATX connector; it does not need the full 24 pin ATX connector. PCB1A and PCB2A each have a PMOS to allow cutting power to the Mini-ITX, however they do not condition the power at all, i.e no regulation, boosting, etc.

I notice that if I power cycle Mini-ITX-B using PCB1-B, Mini-ITX-A also power cycles as Mini-ITX-B comes back online. Probably due to a voltage spike or dip.

I do not notice this with any other combination of assemblies, i.e. A-C, B-C, A-D, B-D, etc.

Notice that A+B are both tapped off of 1 output of the splitter, and are the shortest cables. I'm guessing this has something to do with it.

Does anything obvious jump out as to why this is happening? And, hopefully, is there an easy fix (i.e. a big cap, or ferrite bead somewhere)?


texts: What are the variables describing in this equation?

texts:
For my course, we have to use this formula when calculating the speed of a DC motor.
I know V, I, R and Φ, but i'm not totally sure what c, Z, p and K are.
I think p is number of poles in the motor.
I think Z is number of turns.
But I have no idea what C and K are.
Annoyingly there is no mention of this in the lecture notes so was probably described to us vocally.All other formulas on the internet use different values so i haven't been able to figure it out.
Any help is much appreciated!
Thanks a lot -- A very stressed Electronics student
Full formula sheet:


texts:
I'm designing a buck converter to feed the following loads:

A control circuit 3.3V/100mA
A 80V solenoid which has a DC resistance of 300 ohms. This means a current of ~270 mA.

My plan is to generate 80V from the buck, followed by another switching regulator to get down to 3.3V.

The solenoid will be ON just for about 30 ms, i.e., no continuous power. The max power for the control circuit is 3.3x100mA = 330mW, that's OK. But the power for the solenoid is 80x270mA = 21.6W. As the solenoid will be ON just for 30 ms, do I really need to design my buck converter to be 22W?

Higher power means higher cost and more vulnerable to thermal issues. I think I can lower the power and use a capacitor to supply the peak current for the solenoid. Any suggestions?


texts:
I'd like to have redundant power supplies to power an array of four hard drives. Each drive uses 5V at .6A (3W) and 12V at .45A (5.4W), for a total of less than 10W each. The four drives will have data lines to a separate PC which doesn't have the available real estate internally for the four drives, hence the external enclosure.

I gutted a PC chassis, installed a cage to hold the drives, made a custom SATA power pigtail, then connected that pigtail to the output from an eight connection (four pair for this purpose) terminal/barrier block riveted to a PCI slot cover (juuuust the right size). I'm using two standard four pin molex connectors to supply power to the input side of the barrier block. The like wires are joined from each molex adapter to one of each pair of input terminals, and each pair on the input side are jumpered, thus supplying three connections at the same potential. I need the additional connections for fans and such.

As it is now, I've only used one power supply. I need to know how to connect two PSs such that they're both on and supplying power, but at any point if one dies the remaining one supplies power to the drive array. I don't want a standby scenario involving relays because the moment of time it takes to switch the relay may cause data loss. I'm okay with both supplying 50% power all the time. The circuit this machine is on has battery backup, so the likelihood of both dying simultaneously is infinitesimal.

See below for an image of the actual setup

Now to the point of my question. I imagine just tying the like wires together would cause power to feed back (wrong vocabulary?) into a power supply if voltages weren't identical, or when one dies the good one tries to supply current to the bad one. Would soldering diodes on each molex pigtail before the barrier block inputs be suitable to avoid one power supply from feeding current to the other in the event one fails or the voltage fluctuates? If so, how do I select what type of diode to purchase? I can spec a capacitor or resistor, but I've never needed to install a diode in any custom PCB circuitry. See below for proposed schematic.


texts: Numeric literal constant in VHDL treatment

texts:
I was wondering if there's a special way to treat numeric literal constant in way similar to C language... i.e. in C we can do something like:

1LL //signed long long
1ULL //unsigned long long

etc

is there something similar in VHDL that I'm not aware of?


texts:
I have designed a lot of 2 layer PCBs so far and am trying to slowly move to 4 layer versions.

One of the major challenges I'm currently facing in that aspect is the acceptable stack up of the layers of the PCB.

I'm currently using the following stack up as I am dealing with a high voltage application.

Could anyone tell me if the stack up I'm going with is accurate? I have attached a screenshot of my current settings in Eagle.

My concern is with the blind vias connecting layers 1-15 and 2-16. Would a pcb manufacturer be able to achieve these interconnects?


texts:
I have an air pump that currently runs on AC, but I want to run on a solar/battery system that's 12V DC. The internals of the pump include a transformer to reduce voltage from 120 (I haven't been able to test the output voltage yet). From there, there is a magnet which powers a lever that squeezes a bellow. The magnet appears to go back and forth based on the oscillation of the AC current.

So my question is, if I were to remove the circuitry and power the magnets directly, could I get away with a square wave oscillator? Or could that somehow be damaging to the components that should use a sine wave oscillation instead?


texts: PCB Panel Size for Maximum Manufacturability

texts:
What is a reasonable panel size to choose when ordering panelized PCBs from my manufacturer if I want to be able to get them assembled by as many PCB assemblers as possible (i.e. I haven't decided on which assembler to use yet, and/or I may change to a different assembler in the future).

Also, are tooling holes needed on the tooling strips, or are just plain tooling strips sufficient?


texts: How does cold weather affect the electronics

texts:
At

Why exactly do chips start malfunctioning once they overheat?

Sharptooth asked a very nice question about how does overheat affect electronics. That raised me the question of what does cold weather do to them. Allmost all datasheets define maximum ratings for operational and storage temperatures.
It is understandable that temperature affects semiconductors functioning a lot but can IC's be destroyed by using them in cold conditions?


texts: What happens when running a LCD at lower clock speed

texts:
I need to display a still image (just the same grey color all over, so no need for difficult calculations what to display where) using only an Arduino Duemilanove (ATMega 328) and a Sharp LCD panel (datasheet)*.

However the datasheet assumes a clock speed between 50 MHz and 80MHz, way to much for a simple Arduino. What will happen if I try to use the monitor at a much lower clock rate? Remember, I try just to display a uniform, non changing color. Will the display begin to flicker? Also, what might happen, if I fade the color?

* It is part of a project to demonstrate what's possible using an Arduino and old electronics. So I restricted myself not to use any other complex bought electronic (your definition here). A small IC may be in order, a completely new board not.


texts: Why are there no high intensity tri-color LEDs that have red, yellow, and green?

texts: All the bi color, and multi color LEDs, especially through hole type, only come red and green. Or red green, and blue. And there's none with yellow. I know as a builder and designer of outdoor model railroad signals, and live steam scale signals, this would be a godsend if they were available. Also the red is so dull, they're hard to see, even with stepped lenses. To get them to mix with green, you have to put so many resistors to get red and green to blend for yellow, that you lose light. What's an alternative?


texts: Confusion regarding piece wise linear diode model

texts:
I understand that when you have a diode that is in forward bias, it can be modeled by a resistor and a voltage source, as seen in the top right of this diagram.

However, I'm confused about the negative bias region (modeled by the bottom left corner resistor/source combination).
If the anode of a diode has positive voltage with respect to the cathode, why isn't the resistor/source combination modeled like this?

I feel like I'm missing something really fundamental here.

Thank you for your help

EDIT to include further questions requiring clarification:

(1) Using the forward bias diode model. If I use a positive voltage (1.6V) source greater than the "turn-on-voltage(0.6V)", I get a positive (clock-wise) current which is the same as the value given in the piece-wise linear diode model graph.

However, when I use a Voltage less than the 0.6V "turn-on-voltage", I get a negative current. What is this negative current telling me?

(2)

Also, assigning a voltage of -7.2V and using a clockwise current loop. Why do I get a value of -110mA when I should be getting -100mA according to the graph?


texts: Does anyone have a manual or spec regarding an NEC JAPAN 45006705-210 0356MP010

texts:
As the headline states.

It seems to be hard to get! The µC is in use in an Ferroli Arena A30 boiler.
A datasheet could help to know how the pin configuration. A manual should even be more awesome.
Thanks for any help.


texts: is an electronic device/component really burn?

texts:
I often read/hear that "my device is burnt" or "... component is burnt due to over voltage" or ".. ESD (board) is burnt when I hold it" etc.

I wonder why "burn" is used to describe it? Is something really burns or is it just a term to describe that the component/device cannot be used anymore as something burns?


texts:
I am doing simple ADC test with potentiometer on STM32F103C8, it seems to work fine for 5 seconds or so, but then the whole uC just stops - even while loop stops doing what it is supposed to do(so I guess it doesn't even leave interrupt routine when it fails).
It probably has to do something with ADC initialization, but I can't see what exactly is wrong.
Below is my ADC.c with ADC initialization and my main.c(note that I outputting "1" and "2" just to monitor if it is still doing while loop stuff - and it doesn't, everything freezes)
If it is not initialization, then maybe it is hardware problem, but with such circuit I can't think of anything that can go wrong, board has capacitor for ADC and I even tried to put another one between signal and ground, nothing...

UPD
OK, Now I look like a total idiot... It turned out that it was not microcontroller that got stuck, but the LCD. I tried to change it to different LCD (it was 4x20, changed to 2x16) and it not halting now. I noticed that it is if I would fiddle the wires a little bit it would halt with bigger probability, so probably if the connection is not solid 100% of time LCD encounters some kind of internal error and got stuck, it does not happen with other LCD for some reason. Apparently vibration from me touching breadboard did something to connection and LCD freaked out. So whoever encounters same problem - try using different LCD, check the wiring(try to fiddle it to see if it affects anything), check if driver code is good, etc.

ADC.c

void ADC_init(void)
{
    GPIO_InitTypeDef adcpin;
    ADC_InitTypeDef MyADCinit;

    ///
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOB, ENABLE);

    adcpin.GPIO_Pin = GPIO_Pin_0;
    adcpin.GPIO_Mode = GPIO_Mode_AIN;

    GPIO_Init(GPIOB, &adcpin);
    ////

    ////
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_ADC1, ENABLE); // Turn on ADC clock
    ////

  /* Initialization of ADC */
  MyADCinit.ADC_Mode = ADC_Mode_Independent;
  MyADCinit.ADC_ScanConvMode = DISABLE;
  MyADCinit.ADC_ContinuousConvMode = DISABLE;
  MyADCinit.ADC_ExternalTrigConv = ADC_ExternalTrigConv_None;
  MyADCinit.ADC_DataAlign = ADC_DataAlign_Right;
  MyADCinit.ADC_NbrOfChannel = 1;

    ADC_Init(ADC1, &MyADCinit);

    // specify channel we want to use
    ADC_RegularChannelConfig(ADC1, ADC_Channel_8, 1, ADC_SampleTime_55Cycles5); // Rank - the order number by which scanning is done

    // enable interrupts on ADC
    NVIC_EnableIRQ(ADC1_2_IRQn);

    // enable interrupts on the end of conversion
    ADC_ITConfig(ADC1, ADC_IT_EOC, ENABLE);

    // Turn on ADC
    ADC_Cmd(ADC1, ENABLE);

}

main.c

#include "stm32f10x_gpio.h"
#include "stm32f10x_rcc.h"
#include "HD44780.h"
#include "ADC.h"
#include

uint16_t data_adc;
char adcResult[4];

void ADC1_2_IRQHandler(void)
{
    if (ADC_GetITStatus(ADC1, ADC_IT_EOC) == SET)
    {
        ADC_ClearITPendingBit(ADC1, ADC_IT_EOC);
        data_adc = ADC_GetConversionValue(ADC1);

        LCD_GoTo(0,0);
        sprintf(adcResult, "ADC = %d", data_adc);
        LCD_SendText(adcResult);
        LCD_SendText("   ");
    }
}

int main (void)
{
    RCC_Configuration(); // Configure the system clocks.
    LCD_Init();          // Initialize the LCD.
    LCD_Clear();         //Clear the LCD.
    delay_ms(1000);
    ADC_init();

    while(1)
    {
        delay_ms(10);
        ADC_SoftwareStartConvCmd(ADC1, ENABLE); // check functional state... wtf is that
        LCD_GoTo(0,0);
        LCD_SendText ("1");
        delay_ms(100);
        LCD_GoTo(0,0);
        LCD_SendText ("2");
        delay_ms(50);
    }

}


texts: Can a 5V regulator connect directly to a voltage divider to obtain a 2V output?

texts:
In my circuit, a lm78l05 is used to provide +5V voltage to other parts. And now I need another +2V source to shift my input signal from +-2V to 0~4V as the ADC ad7682 limits the input signal range from 0~4V.

Can I just connect the lm78l05 with a simple voltage divider(maybe made by ada4841)?(as the picture showed)

If yes, any parameters I should consider carefully such as the opamp offset current/voltage or input resistance of opamp?

If no, any good suggestion to achieve the goal?

Thank you very much!

simulate this circuit – Schematic created using CircuitLab


texts: Transistor as a switch for normally closed operation from a Raspberry Pi GPIO

texts:
I was hoping to get some assistance with using a transistor as a switch in a circuit that I am working on. The project is to integrate a Raspberry Pi into an old Playstation 2 housing while utilizing the power supply board from the playstation and integrating the power button already existing on the PS2 case to turn the Pi on and off.
The button is a momentary push button on a circuit board and I would like to utilize the button as well as the LEDs on the small PCB. There is a switch on the back of the PlayStation that controls the mains power to the DC power supply in the PS2. When this switch is turned on, the red LED should receive power from the 12V PSU indicating that the unit is in "standby", and when the power button is pressed and the Raspberry Pi is turned on, the red LED should turn off and the green LED will be turned on.
I will use the GPIOs in the Pi to make these changes. The button PCB has a flat ribbon cable that I will use to connect the 7 pins of the button PCB. For the LEDs to function, +12V will be supplied when the PS2 power supply is turned on (from the master switch on the back of the PS2 which turns on the 12V PSU). The PCB has the LEDs and resistors already integrated.
My thought was to use a PNP transistor for the red LED on the cathode side, as it would allow current to flow through the emitter-collector when the base is 0V, which will be the normal state when the PSU is powered on. When the Raspberry Pi turns on, i can have a GPIO set to high to send voltage to the base. I am unsure if the GPIO alone can give enough voltage to turn off the transistor.
My next thought was to use an NPN transistor to actuate the PNP transistor, but I dont know if I am doing this correctly and how I should size the base resistor for the PNP (R108 in the drawing below) and even if it is needed at all.
Does this look correct and/or is there a better way to accomplish this, or could I get away with just the PNP (R108) connected directly to the Pi's GPIO? Thanks in advance!


texts:
I have a tilt sensor where I want to measure a 10 degree angle. The 10 degree angle is on a machined ramp. The ramp has a built in "level" 0 degree section in it. Basically what I want to do is be able to find if the sensor's voltage is in its tolerance +/-3.5% measuring the angles. However, to zero the sensor I want it zeroed for what the ramp is sitting on, say if the ramp isn't at true zero. So I'm trying to calculate a delta I could use for a reference so the ramp doesn't have to be compared to true zero, but compared relative to what the ramp is sitting on (a table for instance).

The sensor works as a potentiometer. The sensor is excited with 4VAC

And the sensor has two sides, one side should be 2VAC, and the other is 2VAC when the sensor is level at 0 degrees. When the sensor is tilted one side increases and the other side decreases proportionately adding up to 4VAC.

I think I would just measure the sensor at level 0 degrees

measure the sensor at 10 degrees

Say one side reads 1.998V and the other reads 2.002V

The first side error is (2.00 - 1.998 = 0.002V)

The second side error is (2.00 - 2.002) = - 0.002V

Would I just keep track of which side I'm measuring, then just subtract the first side error from what I'm measuring.

And since the second side error is negative, I add this error to the second side measurement of what I'm measuring?

But not sure how to make it so it is relative to the 0 degrees on the ramp and ignore if the whole fixture is truly level.

This sensor changes roughly 43mV per degree, so if the fixture was set on a sloped table the reading will be off, I want to ignore that the fixture is sloped, by subtracting that difference to make it zero in the sensor measurements.


texts:
In 'Franklin F kuo's book it is written that
"The zeroes of transmission of the ladder occur at the poles of The series branch impendences or at the zeroes of shunt branch impendences"
here is image of ladder
But I don't understand why overall transfer function's zeroes are due to zeroes of shunt branches and Poles of series branch impendences?
What is mathematical or intuitive explanation of it?