texts: Using two different clocks in my assertion

texts:
I am using SystemVerilog to write assertions in order to test the behavior of my design. In my design I have two clock :
the usual CLK_int and another clock called I2C_IF_SCL_out.
In the specification of my design:

SDA_Tick_shift= 01 for one CLK_int period, 10 CLK_int periods after falling edge of I2C_IF_SCL_out.

What I am asking is can I use two clocks in my clocking block @(posedge CLK_int) and @(I2C_IF_SCL_out)?


texts:
I'm designing a CAN-based platform using the Microchip MCP2551 transmitter. The circuit looks like that:

Notice the unconnected pin VREF. I tested the circuit on a prototype and CAN is working. What is the purpose of that pin VREF, which is described in the datasheet as voltage output reference? Could you suggest some applications using VREF? If I don't use it is it ok to left it open?


texts: (logic level) Gating the output of a 900hz (5v p2p) oscillator

texts:
Seems a simple enough problem this, and perhaps all that is needed is confirmation of approach (although a better solution always appreciated). So the problem:

I have a 555 based square wave based oscillator (clocked at roughly 900hz 5v p2p)  which i need to gate the output to enable/inhibit to the Power Amp section of the design (audio use only). I can't use a specifically clocked PWM output pin on mcu (all in use for other needs).
I don't really have room to push in an AND gate to the output (on the target PCB), so was thinking of a classic emitter follower (npn) with the 'collector' fed by the output of the 555, the 'base' driven by an mcu (arduino 5v) output logic pin, and the output to the power amp taken across the emitter and the emitter resistor. In my mind, on low (from the 555) fed to the collector, the transistor will be off, and the emitter, pulled to low either via the emitter resistor or low oscillator output  (depending on Vb logic level from the mcu).

Not spectaculary excited about Vbe drop , but can live with it (if its circa the 0.6v expected).

Anyway the question(s)
a) is the right way to proceed or is there a better solution (bearing in mind the small pcb space available and my reluctance to make the space for either a 8pin or 14pon standard logic gate ?

b) is there a different approach for generating a logic enabled 900hz audio tone ? (I found using a nand oscillator with enable fed to the first nand wasn't reliable for fastish logic switching from the mcu - I suspect because of interupting the charge/discharge of the RC network on Gate 2 - but happy to guided).

Hope all this made some sort of sense, have a nasty feeling I am missing an obvious solution to this.


texts: How do I get the value of 0b011 from the primary oscillator with PLL in a DSPIC33FJ128GP710A

texts:
http://ww1.microchip.com/downloads/en/DeviceDoc/70593d.pdf, here is the link for the data sheet it explains in section 9 as to configure COSC<2:0> of OSCCON register to one of the following. I am using primary oscillator with PLL it is represented as 011 as shown below. But when in code it is written as OSCCONbits.COSC!=0b011. I want know in value 0b011, I think that 011 represents the primary oscillator with PLL, but what is 0b which is attached as prefix to the value.

bit 14-12 COSC<2:0>: Current Oscillator Selection bits (read-only)

                111 = Fast RC oscillator (FRC) with Divide-by-N
                110 = Fast RC oscillator (FRC) with Divide-by-16
                101 = Low-Power RC oscillator (LPRC)
                100 = Secondary oscillator (Sosc)
                011 = Primary oscillator (XT, HS, EC) with PLL
                010 = Primary oscillator (XT, HS, EC)
               001 = Fast RC Oscillator (FRC) with Divide-by-N and PLL (FRCDIVN +PLL)
                000 = Fast RC oscillator (FRC)


texts: is it good to attach an extra battery parallel to a small-inverter system

texts:
I have a small inverter system.

Desire:

increasing Power-Bank's battery backup

Possible Solution:

Want to connect another similar battery in parallel to the older battery. Or probably two new batteries discarding older one.

Request:

I have no idea if this is feasible. Is this a good idea?

If not , could you please suggest me some better idea?

Thanks,


texts: Help for understanding a jargon on PCB designing

texts:
I am trying my hand in PCB designing recently and I came across an article where it offers tip for PCB designing and everything made some sense to me except the below one? The tip goes this way

  When laying out PCB’s, make sure all signal references have an
  individual trace back to the common node. Do NOT daisy chain common
  reference points. This will result in hum and noise in analog
  amplifier circuits.

Well am trying to figure out what exactly this statement come to explain, I have tried forum of that site but no response from them. Can you guys kindly help by explaining the above statement in simplified version so that beginner like me could understand them please?


texts: What happens if a branch prediction overwrites a value?

texts:
We are just learning about branch prediction so I might not totally understand how they work, but as I understand it, the branches are set to predict either taken or not taken. The pipeline will start processing the next instruction or two before the branch is decided. Once the branch is decided, if the prediction was correct nothing happens but if the  prediction was wrong, the pipeline simply switches to processing the correct instruction at the next clock.

This leads me to my question.

Say I had some assembly like this:

loop: addi r1 r1 1
sub r2 $0 r3
...
...(other random things)
...
bne r1 $0 loop
sw r2 0(r1)

If the branch were predicted as taken, the values of r1 and r2 would be overwritten before the branch was resolved and then sw would have the wrong values.
How does one deal with this? Is this just an inherent problem in branch prediction or is there a protocol for storing those values until the branch has been decided?

Thank you!!


texts: Can i use IR2110 for two independent MOSFETs?

texts:
Can i use IR2110, and feed it with two independent PWM signals, to drive two independent MOSFETs, each controlling a separate motor? (or high side and low side inputs/outputs of this chip gonna affect each other?)

i.e. two of this circuit, each controlling a separate motor's speed ... (and each motor's speed needs to be controlled independently)

http://www.bristolwatch.com/picaxe/images/m1.jpg


texts: Pc power supply Ac in rush current overloading inverter

texts:
I have a PC consuming 400 watts hooked up to a 220 VAC automatic backup 1500VA 12V dc inverter since AC grid line is not 24/7 in my country.

The main problem is that sometimes when the AC power goes down the inverter successfully turns on and backup up power is provided to the PC with no problems. Other times the inverter makes a strange sound and the PC restarts.

Using a cheap DSO oscilloscope and an ACS712 module the problem seems to be high inrush current reaching 15 A during the switching time of the inverter which is around 12 milliseconds.

I have tried the following with no success:

1) A thermistor of 3.5 ohms for a certain time then shorting it with a relay. This did not limit the inrush current.

2) A 20-ohm high power resistor for a certain time then shorted it with a relay. This method limited the current but the PC restarted. Probably due to a voltage drop at this current level.

3) A solid state relay with zero crossing trigger to facilitate the slow rise of current. This minimized the inrush current but the problem remained.

4) An attempt for a soft switch using a triac and angle phase control

Is there any other way to make this work?


texts: How to efficiently read a battery voltage level with ADC

texts:
There is a circuit powered by a battery (3V button cell) and another circuit with a microcontroller (Attiny85 in my case) reading perfectly the battery level (through ADC3 pin) each 5 minutes interval.

                              --------------------
                              | *                |
                          -----                  -----
  Circuit+                | 1 |                  | 8 |------------- +5V
     |                    -----                  -----
     |              ADC3  -----                  -----
     +--------------------| 2 |                  | 7 |
     |                    -----     ATTINY85     -----
     | BAT+               -----                  -----
     |                    | 3 |                  | 6 |
 /-------\                -----                  -----
/         \          GND  -----                  -----
|   3V    |     +---------| 4 |                  | 5 |
|  Cell   |     |         -----                  -----
\         /     |             |                  |
 \-------/      |             --------------------
     |          |
     | BAT-     |
     |          |
     +----------+-------------------------------------------------- GND
     |
     |
  Circuit-

As commented bellow by @michael-karas, according to datasheet, the Attiny85 has an input leakage current of 0-1 µA.

So, the question: Is there any circuit configuration or software tip to minimize the battery consumption by the Attiny85?

A friend of mine suggested this solution where R should be higher enough to minimize RTC circuit overvoltage and allow ADC readings to vary proportionally to the cell battery voltage:

simulate this circuit – Schematic created using CircuitLab


texts: How does the BRGE instruction work in assembly? Why is this code not functioning properly?

texts:
.cseg
ldi r16, 0x01
ldi r17, 0x01

add r16,r17
cpi r16,0xFF
brge greater
jmp less

greater:inc r1
        jmp done

less:   jmp done

done: jmp done

I'm writing some assembly code in AVR studio 4, and I'm not sure how the branch works. When I compare r16 (which should have the value 2) with the value 255 in hex, the branch brge (greater than or equal to) jumps to the "greater" label, which then increments r1 to indicate that the value was greater than 255. This doesn't make sense as 2 is not greater than 255. What am I doing wrong?


texts: Which circuit is better? (Op Amp Question)

texts: These circuits are for sub pA current detection. Each circuit has the same gain, however; shouldn't the multistage amplifier be theoretically be faster than the single stage gain? TINA TI simulations say they are identical, but I want to know what you guys think. What are the pros/cons of each? Thanks in advance for the help!


texts: Learning how my circuit works (PWM a 5V USB fan)

texts:
I'm new at electronics (my new hobby) and got a lot of good responds from you guys so hope you can help me out with this one as well.

I got this an USB fan that I wanted to modulate by controlling it with some PWM.

First I did the following

simulate this circuit – Schematic created using CircuitLab

D5 is the Arduino digital pins outputting the PWM. It gave a lot of noise - so thought that it might have something to do with the capacitor (C1). Just for fun I moved it around and it worked! The LED was not flickering anymore so I added another LED to see the output (like a control).

simulate this circuit

It works and I should be happy (I am :D ) - but I have some questions I hope you can help me with.

Why didn't my first attempt work _____ ? (would it work with a
MOSFET?)
Is the capacitor adjusting my PWM to a linear voltage that
partially opens the transistor _______?
Is the diode (D2 1N4007) placed correctly to protect induction _? (noticed that the swapping the wires of the fan does not change the rotation direction - it just don't rotate..)

Suggestions are very welcome since next step is to put it on a pref-board


texts: Types of finites state machine in FPGA design

texts:
There are 2 types of FSM:

1- block of combinational logic + clocked block that hold only the current state

2- clocked block

For example, if we take a look to how an SDRAM controller is made, most of the controllers are composed by combinational block + clocked block, and only just a few of them are written using just one clocked block.

-What are the main considerations to choose one type or another?

-Regarding to the SDRAM controller, why most of the people choose the first type?

Thanks in advance!


texts: LVTTL signal splitter - delay - combine circuit

texts:
Pulsed laser driver provides NIM logic level output for synchronization at the laser repetition rate (20 MHz)  https://www.nktphotonics.com/lasers-fibers/product/superk-evo-industrial-white-light-laser/

The NIM signal is converted via NIM to LVTTL converter. NIM2TTL converter has < 5 ps timing jitter.  After NIM2TTL the signal looks like this:

I am planning a circuit with following functionality:

SPLIT the LVTTL signal into 2 signals.
   DELAY one by 25 ns.
   COMBINE them together.

Combined signal (40 Mhz) will be used as a triggering signal for another laser so that the second laser emits pulse with some overlap to the pulse in the 40 MHz signal. Practically we shift the second laser trigger signal by picosecond delayer, +- 50 ps makes some noticeable difference in results, probably +- 100 ps would be okay. The circuit will be in room with stable temperature.

This is the circuit I have so far:

Considering the desired functionality I would have following questions.

Would be

PI6C49CB04BQ, Low Skew, 1-TO-4 LVCMOS/LVTTL Fanout Buffer  suitable as a IC to split the LVTTL signal into two signals?
https://www.diodes.com/assets/Datasheets/PI6C49CB04BQ.pdf
DS1100LZ-25+ Delay Line : suitable as a fixed delay line? Not considering < 1ns jitter requirement, would be this IC suitable in principle?
https://www.mouser.co.uk/datasheet/2/256/DS1100L-1291925.pdf

Mouser website mentions logic family 74LS. Datasheet doesn't specify the maximum frequency.

https://www.mouser.co.uk/ProductDetail/Maxim-Integrated/DS1100LZ-25%2b?qs=sGAEpiMZZMtcQMvy0tpsilNMExKZh%2FbYWt4YZpoWTXM%3D

Would 74LS logic family be capable of processing signal at 20 Mhz ?

74ALVC32 Quad 2-input OR gate - be suitable as LVTTL combiner?
https://www.mouser.at/datasheet/2/916/74ALVC32-1597313.pdf

I apologize for very broad question.

Question was edited to provide broader context. Initially the question was about how to split LVTTL signal. I kindly appreciate all your hints and advices.

Added information about NIM2TTL converter's timing jitter.


texts:
I am using a dc controller like this:
https://www.amazon.com/SZMWKJ-Wireless-Controller-Positive-Inversion/dp/B07CG4Y3N9
to control a linear actuator. The controller has a 10A fuse, and the linear actuator like this:
https://www.amazon.com/ECO-WORTHY-330lbs-Tracker-Actuator-Multi-function/dp/B00NM8H5SC/ref=sr_1_3?crid=263J4MFPX2PNS&dchild=1&keywords=linear+actuator&qid=1606961951&s=industrial&sprefix=Linear+actu%2Cindustrial%2C562&sr=1-3
The 10a fuse on the controller keeps blown when I actuate. Is there a reason why?


texts: How to add a controlled amount of jitter to a signal

texts:
Background

I am developing a digital clock and data recovery circuit and am now getting into the evaluation phase, focusing on testing the limits of the design and finding potential strengths and weaknesses. An important metric of this particular design is the tolerance to jitter in the asynchronous input signal. To evaluate this metric, I have a test setup in mind as below.

simulate this circuit – Schematic created using CircuitLab

Problem

To ensure the results of the testing are meaningful, it is desirable that the jitter have these characteristics:

Random or pseudo random
Gaussian distribution
Standard deviation of noise is parameterized and can be swept (JITTER CONTROL above)

This doesn't seem like an easy thing to accomplish. Is there relatively simple way to inject a controlled amount of jitter into a test setup?

What I have so far

I've given it some thought and research and I have two potential ways to implement this in hardware.

If the test circuit transmission clock is significantly higher than the DUT, then the output can be oversampled. Then, extra samples can be added or removed from the output to inject a discrete amount of jitter. This jitter won't be perfectly gaussian due to the quantization noise. But if the test circuit's oversampling rate of the transmission data is high enough, this concern can be mitigated.
The test setup by Kubicek et al. (below) uses an optical transmission with a variable attenuator to achieve the desired effect. Its not at all obvious to me why this would achieve the above, but a spectrum analyzer should be able to determine if it works as intended.

I understand my question omits many details about the design and test setup. This is intentional as I want to keep this as conceptual and general as possible. I want to avoid this becoming a design-specific post in favor of creating a post of permanent reference value.


texts: Why does an Instrumentation Amplifier need a reference?

texts: I am working with the INA826EVM board and I am wondering why it needs an additional op-amp for a reference in the Instrumentation Amplifier?


texts:
I want to bitbang a Prolific PL-2303HX. There is the library libftdi which enables bitbanging on the FT232 chip. Can I make it work with PL-2303? When I try using libftdi it gives in the error "Can't open device".

Anyone knows how to make this work?

When I try to open the device with the example code in libftdi (changing the vendor and device id to

f = ftdi_usb_open(&ftdic, 0x067b, 0x2303);

I get the following output

rick2047@ubuntu:~/work/libftdi$ sudo ./a.out
[sudo] password for rick2047:
unable to open ftdi device: -6 (ftdi_usb_reset failed)


texts: What "rule of thumb" to use for mapping -3dB frequency to ideal response for 2nd order Sallen-Key?

texts:
For a first order passive filter (RC circuit), we often reach for a the familiar 10X rule. If the -3dB corner frequency is f, then "ideal" frequency response starts at 10f.

What similar factor can be used for a second order Sallen-Key filter which is critically damped (C2 = 2C1)?

If, say, the -3dB roll-off of such a low-pass filter is at 25Khz, until where do we consider the frequency response to be as flat as we would by the 10X rule for RC filter for the same corner frequency?


texts:
I've built a smoke stopper circuit that I want to use once my 1st quadcopter will be built. It's basically a simple circuit that sits between the LiPo battery and the drone, that lights a lamp if a short happens on the quad's end.

I've slightly modified the circuit from what is visible at the link above.
A second switch (Hi) includes the higher power lamp.

simulate this circuit – Schematic created using CircuitLab

I have two questions in regards:

Is the indicator LED correctly placed? I tried the circuit without
it and it works as intended. I wanted a confirmation on this part.
The LED should light up if I connect the battery and the "Power"
switch is ON, so I can have a visual feedback.
What if I want to use a DPDT switch (momentary type, ON-OFF-ON), as
a test for the lamps? Without attaching the drone, I would use it to
test the two lamps, based on the side I engage. Is it possible at all?


texts: Verilog — The proper way to reset an output signal back to zero on the next clock edge?

texts:
Occasionally writing some FPGA-targeted Verilog code at my job, I often need to drive output signals high during one clock cycle exactly. Sometimes I use the following “trick“ to achieve this (let me show a simple example):
module SignalEvery10thClock(
        input clock,
        output reg signal);

    reg [3:0] count = 0;
    always @(posedge clock) begin

        // The trick.
        if (signal)
            signal <= 0;

        if (count != 10)
            count <= count + 1'b1;
        else begin
            count <= 0;
            signal <= 1;
        end
    end
endmodule

The code like the above seems to synthesize and work just fine (at least, in Synplify and Verilator). However, I don't have a clear understanding why it even compiles successfully: the assignment to signal seems ambiguous in the case when signal == 1 and count == 10.
What this ambiguity synthesizes into?
Can the synthesizer deduce that the case when both signal == 1 and count == 10 are true isn't actually possible?
Is writing code like this considered good or bad practice?
What is the proper way to reset the output signal once next clock arrives?


texts: How is microphone's frequency response determined

texts:
It seems this is the chicken and egg problem. To be able to determine the frequency response of a microphone one needs a speaker that has a known response. To be able to know the response of a speaker one needs a mic with a flat response.

Is there some trick used or some device(essentially a microphone) that is "provably" to have a known frequency response?

I know there are reference microphones that supposedly have a flat frequency response BUT the question is, how did they get to that point in the first place.


texts: Why do I have 120v coming out of a 240v cable

texts:
Me and my dad have a small project at the moment for one of his amplifiers he uses with his band, on a hot day the amplifier overheats and conks out so we decided to fix an old pc fan we had lying around and blow air at the heat sink. but to make it one compact unit we want to get power from the same source as the amp. So I found an old 12v ac to dc power supply and thought simple job solder it onto the pins on the inside of the casing and job done.

Now how it looks is that there is standard 3 pin power cord going into it, the socket of the 3 pin power cord is connected to a small pcb with some pins coming out and a few pins have cables attached, I can't remove the pcb so I can't see how it was soldered to find out the positive and negative terminals. So I get out my multimeter to find out. I found the positive terminals, there are 3 and 2 have cables attached, great that leaves one spare. The same goes for the negatives.

I'd like to connect my fan to the switch as well the problem is that the voltage difference between the negative and the positive is 120v as far as my multimeter shows, even though it should be 240v. The only reason I can think of that maybe the system is designed for America. But whats even more confusing is if I try other pins it goes back to 240v which is what I need for my power supply.

Does anyone have an explanation for this, I'm only a little bit of tinkerer and I'm definitely not an expert, I don't tend to handle large voltages like this only when I fit some sockets on the wall but there must be some reason why the voltage drops from 240 to 120.

I hope I explained it well enough, I can get pictures if anybody needs me too.

The pins in the red circles are positive

The pins in the blue circle is negative

The pins in the green circle is earth connecting to the casing

The one in purple is also negative put it says its 120v

If I try to connect the purple to any red I get 120v
If I try to connect the right most blue with any red I get 120v which is also the negative wire going to the switch.
If I try to connect the middle empty pin with the upper empty red pin I get 240v
but If I try to connect the right blue pin with the empty red pin I get 120v

I would like to connect my negative by the switch so the fan switches on or off based on the switch but it only gives me 120v out of some reason and I can't figure out why. The 3 pin power cord supplies 240v and this pcb connect directly to the 3 pin power cord just behind it so its not like there is a step-down transformer behind it.


texts: How can I determine the cause of parasitic oscillation in a Teac A-R630 preamp stage?

texts:
The amp exhibits intermittent crackling noise, which I think is parasitic oscillation as it stops immediately I touch the base of Q409 with a scope probe or an insulated screwdriver. The amp will function perfectly for most of the time, but occasionally exhibits noise on the LH channel independent off the volume control but mute-able with the balance control which is on the front panel pcb after the preamp o/p. I've changed Q411, 414, 415 to avail. I've tapped components and used freezer spray. I don't believe the noise source to be intermittent component breakdown because of the way it stops as soon as some electrical contact without mechanical force is made at a Q415 base or Q409 base. What could be the cause of the noise?
 The schematic appears to confuse LH and RH. I have the speakers connected to the correct terminals, the balance control works in the correct way, the input phonos are correct, but when I inject a mains hum signal by touching Q409 base (when amp is working ok) it comes from the LH o/p, and Q402 gives me RH o/p.

EDIT: Changing out Q412 seems to have eradicated the noise: it would seem that my grounding Q415 base through a 10uF capacitor was causing a current spike which temporarily banished the noise in Q412. Previously I couldn't imagine an electric connection stopping (for a while) a noise caused by intermittent component breakdown: now I know it can. BTW neither freezer spray nor shaking/tapping were any use in this case.


texts: Current Injection Via Jumper Design Help

texts:
I am currently designing a circuit that uses a 5V 2A power brick. The circuit requires a current source and I have seen good efficiency with Ohm's Law. The current is variable through a 2k potentiometer. However, now I need to design a circuit that gives the user the option of using the pot or using a current generator. This is what I had in mind for a very simple circuit:

simulate this circuit – Schematic created using CircuitLab

Is this a kosher way of doing this? The 5V is always on meaning current is always flowing through the resistors but is leaving the switch open (open circuit) good practice?


texts:
Good afternoon,
I may have a silly question but I'm new to all this and I build a circuit with a Mosfet in it. I have a Arduino hooked up to the gate. And I'm powering a led for this instance. The mosfet works perfectly so when I send a signal to the gate of 100 the led dims.
But my question is: Is there a way that I could keep the gate that amount open. So lets say that if I break the gate connection with the arduino the gate should still be on 100 open instead of 0/255.
Thanks in advance,
Stijn


texts: How does the 4th satellite in GPS know the time offset?

texts:
Going through the working of GPS technology, I came to know that at least 4 satellites must be visible to solve for the location with considerable accuracy. Going through most of the resources, I can visualize how three coordinates of the location are determined.
But there is an error in this calculated location due to the timing offset. So this calculation is invalid. In order to make the calculation valid, the timing offset must be considered. And this is the propose of the 4th satellite.
How exactly does the 4th satellite know the timing offset?

If we talk about the differential GPS, the actual base station's location is compared against the GPS determined location and the timing offset is calculated and transmitted to the receiver within certain coverage area. But if we talk about direct communication between the satellite and my mobile phone, the actual position is to be determined unlike the base station where it is already known.
Hoping for a clear and more visual answer (rather than mathematical) from this community as always. Thank you!!


texts:
It is my understanding that the mains distribution system (poles along the road, where I live) has occasional earth ground connections of the Neutral wire. Maybe every pole, or just every few poles, to shunt lightning hits to ground. Is this true?

If so, I was wondering if there is a loss due to current also flowing in the earth, parallel to the neutral wire. On one hand, adding a lossy conductor in parallel with a good one should not result in increased loss. On the other, I was taught that "electricity flows on all paths that are available", and that Alternating Current flowing down a ground rod, through an earth path and into another grounded conductor or rod, is very lossy.

Is there any additional loss in the transmission system due to the grounding of the Neutral wire in multiple places along its length?


texts: Problem with performances of a control scheme

texts:
I am trying to prove with Matlab that if I have an improper system and I place poles at higher and higher frequencies the performances of the system improves. In particular I am considering the following two degree of freedom scheme:

and my code is the following:

s = tf('s');
P = 1/[(1+s)*(1+0.05*s)^2];
C = (s+1)/s;

tau_1 = 0.1;
CF_1 = [(1+s)*(1+0.05*s)^2]/((1+tau_1*s)^3);

tau_2 = 0.01;
CF_2 = [(1+s)*(1+0.05*s)^2]/((1+tau_2*s)^3);

tau_3 = 0.001;
CF_3 = [(1+s)*(1+0.05*s)^2]/((1+tau_3*s)^3);

T1 = (C+CF_1)*P/(1+P*C);
T2 = (C+CF_2)*P/(1+P*C);
T3 = (C+CF_3)*P/(1+P*C);

figure;
bodemag(T1,'r',T2,'b',T3,'g'),grid
legend('tau = 0.1','tau = 0.01','tau = 0.001')

so what I expected is that the performances with respect to the reference tracking increse as tau gets smaller, but if I do the Bode plot, what I get is:

from which I don't really see much of an improvement. Moreover if I change some values:

which is somenthing that to me does not makes sense because I should have that with $\tau =1$ I should have better performances than with $\tau =10$, this because with $\tau =1$ the pole is at higher frequencies that with $\tau =10$.

Can somebody please help me solving this problem?

Thanks in advance.

[EDIT] If I plot the step responses I see the same problem:


texts: BTLE synchronize advertising beacons with phone scanning

texts:
In a BTLE master/slave connection, the master and slave devices synchronize their frequency hopping. Along with the connection parameters (like interval, slave latency, supervision timeout) this allows the master and slave to sleep between connection/transfer events.

With Beacons that advertise (and a phone that scans) it appears that no timing coordination can be accomplished. Basically the beacon advertises at some configurable rate and duration, while the phone listens for an independently configurable duty cycle and duration.

Certainly without establishing a connection the advertiser and scanner can not closely synchronize, but it would seem possible. For an advertiser to broadcast its payload as well as its advertisement settings, and then for the scanner to roughly synchronize its sleep/listen timing to those settings.

Obviously if the phone wants to discover other BTLE devices it would have to scan in the standard manner. But for catching subsequent advertisements of these type of previously heard beacons, the receive window seems like it could be much smaller (even with the wide PPM clock tolerances).

Can this already be achieved some way that I am not aware of? What am I missing?


texts:
Despite having a degree in electrical engineering, sometimes I still don't get the fundamentals of electricity. Can someone please explain the electric potential diagrams in the following link: http://www.physicsclassroom.com/class/circuits/Lesson-1/Electric-Potential-Difference

If one were think about electric potential as analogous to gravitational potential, there should be a gradual decline from the high potential (+) to low potential (-). Why isn't that seem to be the case?

If in circuit A, the potential has already reached zero at point C, how can the charged particles continue their journey to the lowest potential (point D)?

I have few more questions but these are the most pressing ones and it would be lovely if someone could find time to address these. Cheers.


texts:
Imagine there are two rooms. Room 1 has a light bulb and a switch to turn in on/off, and room 2 as well has a light bulb and a switch to turn it on/off.

What I want to do is - connect a radio player to both switches, so that it would work as OR switch:

both switches are turned off - radio is off.
one of the switches is on - radio is on.
both switches are on - radio is on.

I think I successfully modelled how it would work using DC (I think):

But would it work the same way if using AC power?

P.S.

Based on received answer, I decided to simply use two separate radio devices. Each of them connected to corresponding bulb. Both radio devices are set to the same radio station, same volume and it gives desired result.


texts:
I am trying to develop a robotic system that has a distributed DAQ system with one main computer that has the high level control loop.
I have a question about the data that has to be transmitted every second to the processing computer. I did a 'quick' calculation about the how much data we want to sent to the main computer and then an estimation about how fast we can send it through the can bus.
The baudrate of the CAN bus is: 1Mb/s (bit)
The amount of bits we have to transfer is:
IMU: 4 (mag,accel, gyro,euler) * 4 (x,y,z, time) * 16 bit (resolution) = 256 bits
Analog: 5 * 12 bit (resolution) = 60 bits
Encoders: 3 * 17  bit (resolution) =   51 bits
With a total of  367 bits.
This means with the CAN bus, we have a 1.000.000/ 367 = +- 3k Hz sample frequency on the main computer

Could you guys check if this is a correct way to acquire a ballpark figure for the updaterate.


texts:
I have built a tube amplifier and modded it with a line out for headphones based on this article.

I measured the output voltage on the artificial "line out" is peaking around 4-5V.
As a reference I also tested what my mp3 player delivers and that is around 500 mV

is it safe to introduce 5 V to my mixer (Behringer Xenyx 502) line in?

the manual specifies that the line ins are "designed to handle typical line level signals".
based on this post typical is around 300mV, however it may peak to 3 V

I might have answered my own qustion, but a confirmation would be nice

thanks


texts: Why does the power supply into the op amp change from DC to AC?

texts:
This is an AC power supply made from transformers, and is rectified into a positive DC supply and negative DC supply.
Without the op-amp the supply generates ~15V and ~-15V.
However, when the op amp is added, the power supply starts generating AC rather than DC.

What is the problem and how could I fix this?


texts: I'm working on some acceleration data, looking at vibrations and at what frequencies they're occuring. The recorded periods are fairly long (~1 minute) and I was wondering, what's the difference was between doing a FFT on the whole 1 minute data set and taking the magnitudes, vs doing fourier transforms for each second, taking the magnitudes, and then averaging them at the end?


texts: How do the NEC Article 460 requirements apply to small capacitors mounted outside of equipment?

texts: NEC Article 460 discusses the use of capacitors in electrical circuits outside of equipment.  However, these requirements are designed for large power capacitors, oftentimes using liquid dielectrics or cooling systems, and enclosed in metal cases that must be grounded, with their own protection and disconnecting means.  How would the Article 460 requirements apply to a small capacitor (say a 100nF X capacitor), with no liquids and a nonconductive case, deployed directly into an electrical circuit (say, for interference suppression)?


texts: Small Footprint Single Pulse 500ms per minute LED 3.3v

texts:
I'm quite new to electronics, so hopefully I don't offend anyone by asking a question badly.

I'd like to make a circuit that uses a CR2032 (3v) button cell to pulse an LED (3mm blue clear super bright - forward voltage +-3.3v) for half a second, once per minute.
The half-second part is quite important to me (1 second would be far too long), but the minute portion of the time scale is of less relevance (It could pulse once every 55 seconds for example, and that would be fine).

I'd like the final build to be as small as possible (in terms of form factor) and ideally to use analog components (best case) to keep the build cost-effective.
At a stretch, I would also be happy to use something like a 555 timer, but as I understand it, its no simple task to have the LED spend more time off than it does on when using 555's, because of how they work.

Given the size, cost and voltage constraints, what direction should I be looking in to get started ?


texts: Verilog - Weird blocking/nonblocking problem

texts:
In the rst block in the following code I get a strange error whenever I use non-blocking assignment/ The State_SENDSYNC last for two cycles even though it's supposed to only last one cycle. Changing to blocking assignment fixes the problem, but I am baffled as to why. Shouldn't a mux get inferred either way?

always @(posedge clk, posedge rst) begin
if( rst ) begin
    currentState <= State_IDLE;
    nextState <= State_IDLE;
end else begin
    currentState <= nextState;
end
end

always @(posedge clk) begin
nextState = currentState;
case( currentState )
    State_IDLE: begin
        if( laneOpen ) begin
            nextState = State_SENDSYNC;
        end
    end
    State_SENDSYNC: begin
        nextState = State_SENDDATA;
    end
    State_SENDDATA: begin
        if( !laneOpen ) begin
            nextState = State_IDLE;
        end
    end
    default: begin
        nextState = State_IDLE;
    end
endcase
end


texts: PROTEUS 8.9 version Error: No model specified for CLOCK#000C. (Fast help pls.)

texts:
I did everything on my project, but I am getting these errors. How can I fix it?

No model specified for CLOCK#000C.
Simulation FAILED due to partition analysis error(s).


texts: RC low-pass filters for op-amp power-in pins?

texts:
It has been a long-lived tradition of mine to put an RC low-pass between the power supply and each power-in pin of each op-amp, where R is typically 1 to 10 ohms, and C is either 0.1uF ceramic, or that in parallel with a, say, 10uF tantalum:

simulate this circuit – Schematic created using CircuitLab

My thinking is:  the decoupling capacitor is supposed to be a low-impedance path to GND for switching/high-speed signals that originate inside the op-amp, so that they do not propagate to the rest of the system;  by placing a resistor in series I not only make the path to GND low-impedance, but the path to the rest of the system now has substantially higher impedance compared to just connecting directly.

Does this make sense in general?  Or am I wasting my time, money, and PCB space in placing next-to-useless resistors?


texts: Data errors from network device at high ambient temperature(60C)

texts:
I have a Raspberry Pi Compute Module 3 based network device that I am trying to get working at high ambient temperatures (up to 60C).  When I run TCP packets through the device, I get checksum errors indicating that bits are being corrupted somewhere in the data path.  Besides using the Compute Modules, an FPGA and microcontroller are used as the data processing elements as part of the PCB.

I have reasonably ruled out the Compute Modules as the problem as they have a heat pipe design that keeps them cool enough. And the test outlined below seem to validate this as well.

The data processing components also exist on a separate PCB. I used that separate PCB to test the Compute modules and those components (FPGA and MCU with relevant power converters) at high heat, with one being in the chamber while the other was not.  The only time this failed was when the device was used in the normal configuration.  The external data processing PCB was even able to go up to 90C ambient.  The only difference between these components are the buck converters to deliver power.

Is it reasonable to guess that the buck converters are what are failing and causing fluctuations in voltage to the other components which causes them to process data incorrectly?  Would anyone else have any other possibilities as I am stumped?

Edit for clarity:

The network device's data processing section uses the same design as an already existing PCB/device.  So the FPGA, MCU and all other components, except the buck converters, were taken from that design and integrated into the network device's PCB.

The "normal configuration" is when the network device uses the components that are found on its own PCB.  I have also tested:

the network device inside the test chamber with wires coming out connecting to the data processing section on the separate PCB.  This gives no errors which leads me away from suspecting the RPi as this essentially isolates the 2 sections
the separate data processing PCB in the test chamber with the network device outside at room temperature.  This device was able to reach 90C ambient, so this tells me that the FPGA and MCU are also not failing.


texts: Connect 16 outputs to as few pins as possible on a microcontroller

texts:
I would like to control 48 outputs from a microcontroller, with individual access to each of them.
But let's focus on 16 outputs.
My initial solution involved a 1:16 demultiplexer and 16 (actually 8 dual) D-type Flip-Flops (DFFs). 4 pins would be used to set the address on the demux, 1 pin would be connected to the input of the demux and outputs would connected to the "clock" signal of the DFFs. Finally, one pin would be connected to the Data input of each DFF. That means in total 9 chips and 6 pins.
Thanks to a comment here a few days ago, I have now a new solution that involves 2x 8-bit addressable latches and a 1:2 demux i.e. 3 chips. I've looked for a 16-bit addressable latch but couldn't find one.
To control 48 outputs, I essentially triple the circuit, but also in the first case, I have 3 clock pins. So I can set the target address, set my "value" pin, then send a clock edge only to the right target.
Would anyone have a better option? Ideally, keeping direct access to any output. I'm having a look at things like shift registers though.
Anything I²C, SPI or any other bus is out of question.
Speed-wise, 100 Hz is the target (per output).


texts: Best practices for running ICs with 12V vs 5V rails

texts:
I'm working on a circuit that needs 12V to trigger high-power LEDs (via a Power FET).  However, to accomplish this, I also need a variety of ICs; right now I have a TC4427 for driving the FET's gate, a 556 for one-shot pulse generation, and a ATtiny84 to trigger the 556.

The FET Driver and 556 can both run off a VCC as high as 12V; only the microcontroller requires a voltage as low as 5V.

Right now my plan is to power the driver and pulse generator with a 12 volt VCC (with 0.1uF film + 4.7uF electrolytic bypass caps), and use a small 200-300 mA switching regulator like an ADP1111 to provide a small 5V rail for the microcontroller.

Is this good practice?

I only expect the FET / LED to be powered on ~1% of the time, 5% maximum; I presume this means that the 556 and TC4427 should have very low power draw most of the time.

My other options:

Use a linear regulator like a 7805.  I'm concerned the FET Driver will need enough current at 5V that the regulator will get quite hot.
Use a beefier buck converter than the ADP1111 to provide a 5V / 1-2A rail.  I'm trying to avoid SMD parts at the moment, but this is an acceptable solution.

I'm a bit new to figuring out good power management, and would appreciate any advice as to how to best practices for dealing with ICs that can accept a variety of supply voltages.


texts: Why is Comparator Output Offset by -5V with a Unipolar Supply?

texts:
This circuit works as desired. It switches at 10mV.

But the output is offset by -5V. That is, LOW = -5V and HIGH = 0V, which isn't desired.

How to make the outputs LOW = 0V and HIGH = 5V?

Link to simulation on Falstad/Lush in comment, below:


texts:
I'm currently routing a schematic with Altium (10), it is very small and I use a lot of 'any-angle' traces. Altium can more or less route them 'fine', but the problems really begin when moving traces.

On this schematic I am often dragging and pushing traces, however, whenever I try to drag a traces that connects to an 'any-angle' trace or an 'any-angle' trace itself it will immediately change the 'any-angle' trace to 45 degrees as shown below.

"Restrict to 90/45" is not enabled, and as I said routing a new trace at any-angle works 'fine'.


texts: Timing of delay for autocorrelation processing of a signal

texts: When processing a periodic signal to remove noise, by using autocorrelation, a time delay is required. Is there an algorithm that a circuit can "use" to figure out how large this delay needs to be? Does such a circuit - one that can figure out the required delay of a signal for accurate autocorrelation processing - exist? Is there a canonical example? Or does this delay need to be hardwired into the circuit and changed by trial and error?


texts:
I have a PCBA that seems to have failed due to poor wiring (no water damage). The screw terminals are for 230V AC input and electrical load relay.
What isn't clear to me is what exactly is the "white fluff" on the leg of the resistor. I believe it formed during the failure.

So the question would be - What is the white stuff on the leg of the resistor and how does an electrical failure cause it? Does it indicate some other issue with the component/board/process?
Thanks


texts:
I am a software guy who hasn't been under assembler level. I have a project in my mind but I don't have sufficient knowledge on electronics. I have been searching in the internet for help, but I couldn't find anything satisfies me (maybe I don't use right keywords). I am not familiar to electronics world, I bought a soldering set last weekend, first time in my life.

About my project, I want to control my electric toy cars from my laptop via wi-fi. I searched internet for guidance. I have seen similar questions, but answers were same: "Use bluetooth". I don't want to use bluetooth, that's the point.

Last weekend I bought a soldering set, a Pertinax, some set of peripherals and an ATmega328P microcontroller. I will control my electric toy cars with ATmega328P, I will deal with microcontroller-car interface. But, the point I am suffering is microcontroller-laptop interface. I am familiar with assembly language. I dealt with MIPS ISA and 8051 microcontrollers when I was undergrad. So, coding won't be problem (I hope), but hardware is.

By the way, I don't want to use pre-done equipment like Arduino. I want to understand every detail of my circuit. What I'm asking here is a spark, recommendation. A book, a video tutorial, a webpage, a document, anything helpful is appreciated.

At the end, cars must be able to connect to LAN, or send/receive data from all the devices connected to same LAN network.


texts: Connecting shielding for high and low voltages

texts:
I have design a power distribution PCB with high AC(230V) and low DC(<10V) voltage power rails. Both are going to be connected to my board by separate cables. Each of those cables have shielding wire, i.e. a high voltage cable have four wires, three for phases wires (connected in delta configuration so there is no neutral wire) and shield (I am sure I'm not confusing shielding with PE if someone could ask). Similar situation with low voltages, few hot and ground and single shield wire.

Should I keep shielding for high and low voltage on separate layers or can it be connected to the same PCB layer?


texts: Does this article's appendix contain an error (is the heating system described integral control)?

texts:
I am confused by the primer on control theory found at the end of the following paper, which concerns an instance of integral control in a biological system. Since it concerns integral control, I thought electrical engineers might be better able to answer. I apologize if the article is behind a paywall but it is a very popular paper evidently, so you may be able to google for a pdf.

Yi et al. (2000). Robust perfect adaptation in bacterial chemotaxis through integral feedback control. http://www.pnas.org/content/97/9/4649.abstract

Within the primer, the authors use as an example of integral control a heating system where the power setting on a furnace is proportional to the difference between a thermostat's set point and the ambient temperature. The claim is that this is not proportional control because the temperature in the room is the integral of the heat released, and the system is responding to error in temperature. I thought an integral control system would need to keep track of past temperature deviations from the set point. Is their argument accurate, and if so, could someone explain?

To be slightly more specific, one reason I have trouble grasping their argument is that, I imagine, if a window were left open (so that heat was constantly being lost from the room) then the heating system would never adapt but would operate with droop just as a proportional heating system would...right?

Thanks for your help!


texts: How to read the value of this capacitor?

texts:
I came across this capacitor in a voltage converter which was converting 9V to 5V. This capacitor was connected at the output of M7805CT (i.e. between the 5V and common terminal) in parallel to another 470μF electrolytic capacitor. I cannot find a definite value of this capacitor. Different websites are providing different values of this coded capacitor. Here is the screenshot of what google search returned.

Please help in decoding the value of this capacitor.


texts: Why is digital serial transmission used everywhere? i.e. SATA, PCIe, USB

texts:
While looking at SATA, PCIe, USB, SD UHS-II it struck me that they are all the same: digital serial bitstream, transmitted using differential pairs (usually 8b/10b coded), with some differences in link/protocol layers.
Why so? Why did this become the standard?
Why are there no widespread system communication protocols that heavily employ some advanced modulation methods for a better symbol rate? Am I missing something?
This is not a question of "serial vs parallel" but a question of "digital signaling vs modulated analog"


texts: Tapping the battery from an UPS to feed low voltage devices

texts:
My UPS powers one 120V AC device and a whole bunch of small 'bricks' that end up rectifying things down to 5-12V DC. Instead of using the 'bricks', my idea is to tap the battery directly, and use DC-DC converters to get down to desired voltage.
  Would this result in better efficiency? Would it even work? Any potential pitfalls?


texts: Effect of core losses on inductance in high-frequency LC circuit?

texts:
How will the core loss (hysteresis and eddy current loss) in an LC circuit at high frequencies (about 800kHz) affect the inductance of the inductor. When I measure the frequency I can see that it will increase. Moreover the voltage will decrease (Why does this happen?).
I thought that the only cause for making this happen is that the inductance decreases since the frequency is defined as
$$f = \frac{1}{2 \pi \sqrt{LC}}$$
and the capacity stays constant which means that the only way for the frequency to increase is a decrease in inductance. What exactly will make the inductance decrease and how can the reduction of inductance be calculated?


texts: High Resistance PCB materials - reasons behind it?

texts:
I like to know if there is a relation between using a high resistance (the more expensive stuff) and environment noise effect on circuit.

The reason is I heard for high frequency or sensitive applications, PCB's has to be made with high quality - high resistance materials. Is this count as a way to fight with noise or loss of signal? What can be the very particular reason of such design?

Also, using high-resistance top layer on PCB's would account for preventing interference between individual traces on PCB it self?

Here is the link to the article which made me start thinking about this!:
http://www.pcbdesign007.com/pages/columns.cgi?clmid=9&artid=21182


texts: How to avoid/reduce heat for three 1W LED's?

texts:
I'm asking on behalf of a colleague who wanted to make solar powered lighting for poor people.
Electricity generated by solar cells are stored in a car-battery sized 12V battery, and that current is passed to three 1W LED's which operate at 3.3V. She's tried connecting it in series and parallel, but she says the circuit heats up and the LED's don't work for a while, but when it cools down, the LED's glow again.

She wanted to know:
1. How to prevent the heat formation, so that the LED's would glow continuously?
2. How to efficiently convert 12V to the three 3.3V of the LED's (series/parallel)

Using thermal paste was far too expensive (they're making it for poor people).


texts: Why do most N Channel MOSFET Circuits have the Source Pin tied to ground? + Circuit Question

texts:
I've noticed, when looking around the internet, that almost every circuit showing the usage of a N-channel MOSFET has the load before the drain, and the source pin is tied to ground.

From what I understand, the following is true:

  Vgs is the voltage difference between the Gate and Source that is required to fully turn on the MOSFET, causing it to act like a very low impedance connection between the Drain and Source pins.

I'm assuming the following:

  Because of this, it is much simpler to make the source pin ground, and to input at least Vgs to the gate to turn it on.

Is this correct, or is there another reason to have the Source tied to ground?

With that out of the way, I'm trying to build a circuit that will turn on an LED, and provide input to a Raspberry Pi (Max 3.3V input, shown as 'SIG_25%') when 'SENS_25%' is on. 'SENS_25%' being on means anywhere from 50kΩ to 600kΩ between 5V and the MOSFET input. When off, it is open, and the 1MΩ resistor prevents it from floating. The circuit shown currently is able to (not fully) turn on the LED, but the output at 'SIG_25%' is too low to be detected by the Raspberry Pi (Tested at 0.44V).

I believe the reason that this doesn't work as intended is that the MOSFET in the circuit (IRF530N, the only one I had laying around) has a too high Vgs value (2V min, 4V max), and the input is too low for it (When 'SENS_25%' was 470kΩ, the gate was measured at 3.39V), turning the MOSFET into a somewhat large-value resistor across the drain & source.

I want to know, if I find and use a MOSFET that has a maximum Vgs of less than 3V, would my circuit work?

The LED in the circuit is just a plain old color LED, Vf of ~1.8V, 20mA optimum current.

I cannot place the 'SIG_25%' above the MOSFET, as when the MOSFET is turned fully off, I measure 4V there, which both makes the signal useless (It would always be on), and it is too high for the Raspberry Pi to handle safely. This is also why I placed R2 at the Source pin, as I couldn't think of a better way to do this.

Here is the circuit I've currently got:


texts: A question about randomization in verilog

texts: I am now working on a verilog testbench file and I want to get a random value in my code, but I have found that Questa Sim uses the same seed again and again. I have read through $random in Verilog doesn't seem to be working and tried typing -sv_seed random in the transcript window, but the program doesn't understand my command. Can anyone give me some hints?


texts: Hello i want to know how to calculate the equivalent T network resistors in the inverting amplifier below (the answer is 10M but i dont know how) ,i dont need formula but indepth circuit analysis ,thanks


texts: Getting rid of static charge in fuel tanks

texts:
Back in the olden days, fuel trucks had a chain suspended from the axle to the ground to dissipate the explosive static charging fuel will buildup from sloshing around inside a tanker.

I remember them being banned, but what replaced the chains?


texts: Could somebody tell me what this item is please. It is black, circular about 6mm diameter and 2mm thick in this case. It has two leads which are soldered to the two opposing flat sides. It is part of a solid state ignition system


texts:
I want to make a lamp without a switch, just a pressure sensor under resin and an Arduino.

Can the pressure sensor work under the resin?


texts: removing parts of an air core transformer field

texts:
I sometimes need air core transformers for contactless energy transfer of small powers (usually less then 1 watt).  However, on rotating machines, sometimes a bearing is needed in proximity of the energy transformer. The bearing than gets some coupling to the transformers field and as it's steel just forms a shorted winding, consumes some energy.

Now I have the case of a larger bearing, spanning about half of the transformer coils plane. Obviously, it will short out much of the energy transmitted.

I wonder if it would be possible to remove the inner part of the field, by adding some reversed windings of the bearing diameter to the primary coil. The primary field would then be constricted to the outer part of the primaries core area I guess, leaving the bearing uncoupled. But how many windings would that take? The same amount as there are forward windings in the outer coil?

The situation is most likely this:

red: coils, grey: interfering metal, non-metal parts omitted.


texts: Thévenin equivalent with a dependent source

texts:
I'm working in a circuit with some switches and it has the same configuration but different elements between ab. I am not sure if is possible to get a Thévenin equivalent of the next strange subicircuit to simplify calculations:

simulate this circuit – Schematic created using CircuitLab


texts:
I'm trying to power a little pump (http://www.amazon.com/gp/product/B00JWJIC0K) with a solar panel I have.

I've stepped the voltage out of the panel down to 12V with a buck converter. The panel is currently outputting 4A which should be plenty but the pump won't come on. I did buy a 2nd pump in case the first one was bad but no dice. From my limited understanding, as long as the voltage matches the pump the output from the panel shouldn't matter as long as it's high enough.

Would too much wattage prevent the pump from starting?

Thanks!


texts: Reverse biased diode formula in Ebers-Moll model

texts:
As far as I understand in an PNP transistor the base voltage Vb is higher potential than the collector voltage. So since Vb>Vc the base collector junction is then reverse biased:

But in Ebers-Moll model one of the diode current is Icd as shown below:

And this Icd is formulated as follows:

Icd = Ics * (exp(Vcb/Vt) - 1)

But isn't such a formula for a diode valid only for forward biased diode?


texts:
I am trying to run some simulations on capture(PSPICE) for a school assignment and then compare the results of them with the results that i got when trying these circuits in the lab. However the results are completely different and i can't find any mistake in the circuit. The circuit is this:

What's supposed to happen is to get a sine waveform of 4V pp on the collector of the transistor with a phase difference of 180 degrees from the original for a certain value of the {r} resitor.The resistor gets its values through a parametric sweep starting at 10k, ending at 300k and with an increment of 10k(the value of the resistor for which i got the output that i wanted was 111kΩ ).All i'm getting though is this waveform:

which is clearly a distorted signal and with a pp voltage bigger than expected.
Thanks in advance to anyone who tries to help.


texts:
I have a Raspberry with a rain sensor connected. In order to avoid electrolysis on the rain sensor I would put a transistor (2N3904) in the circuit to power on the rain board only few times per day, read the sensor, then power off. I would ask if the circuit I drew is right.

In the scheme I put a “Vibration Motor” just for simulating the circuit (see attachments). In my case it will be substituted with the board of the rain sensor: the GPIO pin of Pi with 5v (my sensor works with 3.3v but I used 5v for showing two different sources) will be connected to Vcc pin on rain board, the Collector of the transistor will be connected to GND on the rain board and the Emitter will be connected to GND of Pi. The Base of the transistor will be connected to a GPIO pin set as output (3.3v). A python script will put this pin = True at specific intervals.
Could the above circuit work?
Forgive me if I made any trivial mistake.
Thanks


texts:
From my previous posts Insight into cavity resonators, Visual understanding of EM fields within a rectangular metal container I have slowly gained a better insight into cavity resonators and thereof. I have the following scenario setup inside a rectangular metal container. The container size is 12.03m by 2.39m by 1.84m (lxbxh). Additionally, inside the container I have placed 4 antennas equally spaced, this is shown using the green squares (ignore the red dots/balls). The frequency of these antennas is 915MHz.

In terms of the multimode aspect, I am not too sure if this is necessary to take into account since my aim is to not make a resonator but just to see the interference within the container created when the antenna radiates its energy in the container.

In the event I do need to take into account the multimode aspect, I also know that an example of a multimode cavity is a microwave oven. How can I then test the EM field inside the container for the EM fields but not for the application of heating the contents?

I want to then use this information to see if when I place RFID tags on pallets of goods inside the container, which regions will result in the RFID tags receiving no power due to destructive interference and which regions will result in there been power. I know when the goods are loaded on to the contiainer the EM field will change but that is a topic for another day, For now I am assuming the contianer been empty and place this tags in it. So first I need "to see the interference created within the container when the antenna radiates its energy in the container"


texts:
I just started learning Thévenin's Theorem. My textbook gives the following example:

I'm referring to online sources such as this to complete this problem. However, all of the circuit diagram examples that I find online are highly similar and unlike the textbook example.

Using my naive understanding, I removed the 4 kilo-ohm resistor and shorted out the 20V and 0.7V (diode) voltage sources. We then have  6 kilo-ohm resistor and 4.9 kilo-ohm resistor in series. Calculating the equivalent resistance, we get $$\frac{(6 k \Omega) (4.9 k \Omega)}{6 k \Omega + 4.9 k \Omega} \approx 2.7 k \Omega$$

But I suspect that I'm doing this incorrectly.

I would appreciate it if people could please take the time to explain this example.

EDIT: I misread the source material, which uses a parallel circuit as an example. Since we have a series circuit, the equivalent resistance would be $$6 k \Omega + 4.9 k \Omega = 10.9 k \Omega$$


texts:
Sorry for a trivial question. I have a transformer with a tapped secondary coil: 12(blue wire)-0(black wire)-12V(2nd blue wire). I need to use it as a 12V supply source, so can use 0-12VAC (either side of a tap, one blue and the black-ground).I understand that in this configuration I only get a half of the rated current. However, what happens if I short both sides of the tap (both blue wires together). Can I get a full current? or because of the phase difference between the blue wires I get nothing (or maybe even both windings blown?).
Is going for a bigger transformer -  the only option? (I am restricted in space inside the electronic enclosure).


texts:
I found an LCD monitor on a rainy day and I had to completely disassemble it in order to remove all the water. When I dried everything and reassembled it, its colors were inverted!

I wasn't really too careful, so maybe I did something wrong while reassembling it. But I'm curious, what kind of error could I have done for it to simply invert colours? Which part would even be able to do that and how?


texts: Ceramic resonators and ultrasonic vibrations

texts:
I'm encountering a problem with a ceramic resonator as soon as our device is subjected to ultrasonic vibrations (ultrasonic cleaning bath).

Our device uses a semi-custom IC which integrates the oscillator circuit, it's a simple Pierce oscillator with the matching resistors built into the ASIC. It is optimized for the Murata CSTCC_G_A 2 MHz ceramic resonator.

If our device is put into an ultrasonic cleaning bath (electronic is sealed) the resonator starts to act up. What I can measure with the oscilloscope is a spurious frequency of around 66 kHz which is close to double the frequency of the ultrasonic bath (35 kHz). I measured this at the oscillator input of our ASIC.

It looks like this (in run mode):

There are some variations which can happen like a combination of both frequencies:

Now I understand that a ceramic resonator contains some sort of piezoelectric ceramic element which has the resonance frequency you like. It being piezoelectric of course also means that external vibration will be transformed into a voltage. But the amplitude just seems so massive, that it seems like I hit another low frequency resonance of the resonator.

Is there a way to reduce this effect so no 67 kHz oscillations will occur?

My first try was to half the feedback resistance Rf of the Pierce oscillator (externally) but that didn't change anything.

My second try was to use a resonator vom AVX/Kyocera, the housing is made differently, so I hoped it would behave differently. But my hope was smashed - it's the same there as well.

I was thinking about a high pass filter structure in the oscillator circuit, but I'm not quite sure on how I'd do that and if that would even help.

I find it a bit hard to find the right keywords to do an effective internet search on this topic. Most stuff I found is concerned with higher order vibrations of the crystal itself (like 2 MHz -> 8 MHz vibrations) and how to suppress them.

Additional info you may skip:

We need a stable frequency for our measurement. The device is required to withstand -40 to 125 °C which limits options significantly. The device is low power running with just around 1 mA @ 3 V, the oscillator takes around 60 µA and shouldn't take much more than that. I haven't contacted Murata or AVX/Kyocera so far - communication with Japanese manufacturers were a bit difficult last time, so I'm asking here first.

Part number of the currently used resonator: Murata CSTCC2M00G53A-R0

Part number of the resonator used in the previous device: Murata CSTCC4M00G53A-R0

Part number of the AVX resonator tested: PBRV2.00HR50Y000


texts: How to choose the transistor and the resistors connected to it

texts:
I am using the regulator TL497 in the case of I(pk)>500mA so I need an external transistor for that but in the datasheet they don't mention how to choose the transistor and its resistors does anyone has an idea about that ?
Datasheet:http://www.mouser.com/ds/2/405/tl497a-405896.pdf


texts: Should I worry about ground loop in power supply circuit for 3G modem or WiFi?

texts:
Can someone explain clearly what is ground loop and when we should worry about it?

Shall I worry about it when I connect two USB wires in parallel to deliver power to my 3G modem?

I have something like this:

I was asking about this earlier, here is my question:

Raspberry Pi and USB modem - can I connect it like this?

I did it, it works, but in comments under another discussion (here) one guy (ppumkin) pointed, that this will be ground loop. I know what ground loop is, I know how that can ruin audio quality in hi-fi system, but... can ground loop like this affect 3G modem or WiFi sensitivity or cause other issues?

I have ground loop with 2 USB wires 1m (~3ft) length, wires are very close...


texts: Why long pipelines are preferred over high CPU clock?

texts:
Why modern CPU vendors prefers increasing the maximum length of the pipeline over increasing the clock?

Accordingly my understanding, increasing either increases the number of gate switches and so increases the energy dissipation.

So if both provide the same effect, how one is better than another?

Increasing the pipeline even has a disadvantage: it may be hard to use the full pipeline length in all components of a CPU, so it is wasted.


texts: Why the sector erase time change in the new Nor flash cause the driver cannot work?

texts:
I'm working on an application involving NOR flash chips.  I had to switch chips halfway through the design process.  The stated differences between the new and old chips are only 'Device ID' and 'sector erase time'.  I thought I could get by without rewriting my flash driver given the small differences, but the driver for the old chip doesn't work with the new one.

Why does the sector erase time matter so much for the driver?  How do I change it?


texts: Creating selectable "block" from selected group

texts:
I have several connectors on some PCB in Eagle PCB Editor and I've placed connector pins description table to every of it and for instance, let's take a look at connector J5, which is highlighted at the moment:

Now, the table has been created using WIRE and TEXT commands, applied to layer 21 - tPlace. Now, the problem is, if I, for instance, want to MOVE the table somewhere else, I have to use command GROUP and select it segment by segment:

and I can move, rotate od do whatever I want with it. Now, is it possible to create some kind of object from selected table so I can avoid segmented selection in future?


texts: Powering 9216 leds @5V, @24V with converters

texts:
I am struggling with a power supply question. I would like to power up and control 9216 LEDs -- strips of 144 LEDs/meter (WWA SK6812 - just like the RGB kind).
These are powered at 5V and draw 43.2 watts per meter at most (when the three leds are lit up)

Right now I have two solutions to solve this but I am not sure if are OK.
My concerns are the following :

I don't want to risk my life. There will be a lot of current in the cables and I want to know what to expect if I get electrocuted, and therefore equip myself with the right gear to avoid any accident. Or maybe I am just too careful and I misunderstood my old physics courses :).
I am concerned about cable heating. Which kind of cable should I use for the two different scenarios if one or both are correct?
Should I need shielded cables to avoid any data corruption because of powering cable passing nearby the data one?
If the lengths of the cables are to big, could I be seeing voltage drops?

You will find attached the schematics of the two solutions I came up with.
I am really not an expert in this subject and don't want to make any mistakes. I hope it's ok to ask for a question that is probably not that complicated.
If you have a simpler solution for this please feel free to share! :)

Cheers!

EDIT
Improvements after Phil G's answer

Thank you very much Phil G, I really appreciate your help, and this has helped me A LOT.

I rethought the design of this power supply yesterday. Based on what you were saying about the problems that might occur when daisy chaining the strips, I ran a calculation for the 5v power supplies feeding the strips in parallel.

The project has changed a little and I chose to use 30m of 60 led/m instead. These led strips draw 18w per meter.
I need 4 meters between the power supplies and the farthest away strip.

I am not comfortable with AWG since I am in France so I found this formula which works for low voltage :

S = 0.017 x L x I / PT

S = cable section (in mm2)
L = length of the cable (back and forth, in meters)
I = intensity (in amperes)
PT = acceptable voltage drop (in volts)

So for 5 volts, each of the lines carry 18w / 5v = 3.6A
I want to loose maximum 2.5% of the voltage. This gives 5 x 0.025 = 0.125V
For each power lines : S = 0.017 x (4m x 2) x 3.6A / 0.125V =~ 3,9mm2

This is not possible as the cables would be way to expensive and hardly manageable. Besides, I want to keep things lightweight to be able to reuse the gear. The 5 volts power supplies are to big.

So I went back to the converters solution using two 24v 500w power supplies. This involves longer cables but lower current. I would need 9m cables maximum from the power supplies to the led strips. This way I also need a terminal block that connects all of the lines together. The converters are about 4cm x 3cm x 2cm, so really not that big. They can be put right next to the led strips and power two of them at the time.

For 24 volts, each of the lines carry 18w * 2 / 24v = 1.5A
I want to loose maximum 2.5% of the voltage. This gives 24 x 0.025 = 0.6V
For each power lines : S = 0.017 x (9m x 2) x 1.5A / 0.6V =~ 0.765mm2

From the power supplies to the terminal blocks :
At most, I plug 16 led strips on one power supply -> 16 * 18w / 24v = 12A
For each cable -> 0.017 x (0.3m x 2) * 12 / 0.6 = 0.204 mm2

From the converters to the led strips, I use one cable per strip.
S = 0.017 x (0.5m x 2) x 3.6A / 0.125V =~ 0.48mm2

I could use 0.75mm2 section cables, but because I want to keep the voltage drops as low as possible I will probably use 1mm2 cables.

Here are the schematics as a sum up.

Do you think that it would work?

Thank's again!


texts: Voltage value after generators in the power grid

texts:
What is the value of the voltage before the step-up transformers and right after the generators in the power grid?
I mean the generators connected to the high voltage grid through step-up transformers. What type of power plants are they? I know that voltages change country by country, but I want to know the average value


texts: how will a connector affect a transmission line?

texts:
I am laying out an RS485 driver and read a few design guides which recommend a 120 Ohm termination resistor. This makes sense since the characteristic impedance of twisted pair cables is in the 100 Ohm to 150 Ohm range.

However what confuses me, is how would the signal be affected by the impedance of the PCB? There is also no mention of the connector impedance?

Should I be routing the RS485 traces as short as possible to mitigate transmission line affects on the PCB?

I understand the basics of transmission line theory, however I don't think I fully understand the implications of transmitting between two mediums. Transmission lines make more sense to me when the source and load share a consistent medium.


texts:
I would like to know if it's possible to split a HDMI signal (generate by raspberry pi or equivalent) to a deserializer (TFP401APZP) and to a micro HDMI.

I have a source going direct to the TFP and I want to add a extra micro HDMI to have ability to export this signal to outside. Because it is embedded product I don't want to deal with an active HDMI signal splitter.

Every TMDS signal pair have impedance matching, length matching from source connector to the TFP and from those track to the extra connector. Length matching is for each diff pair and for group.

Thanks in advance for any help.


texts: How to interpret the raw temperature value coming from this sensor?

texts:
I am using a LIS3DHH. It is an accelerometer but has a temperature sensor inside as well. It is read out using SPI interface. I believe that I have followed the boot sequence properly and am storing the data correctly. However, some things do not make sense. One of these is the temperature sensor reading.
The temperature sensor characteristics are contained in section 2.3. The temperature value is read out from address 25 and 26. The section 7.7 discusses these registers. It can be seen that the lowest four LSBs are all zero permanently so that the temperature reading itself comes to 12 bits rather than 16 bits.
The 16-bit reading I am getting is 0xFEC0. The table 23 says that "The value is expressed as two's complement sign. 0 LSB represents T=25degC ambient".
The 0xFEC0 I am able to read out is -320 in two's complement. If I divide this by 16 I get -20. Both of these are far from the room temperature. What is going on here?


texts:
I have a battery-constrained device with STM32L011. Right now I am using Nucleo-32 development board. In the end I want to use suspend mode with RTC to wake up every couple of minutes. First I want the RTC to generate an interrupt using the wakeup function.

I can see in my UART log, that the RTC is running (RTC_TR is incremented), I can also see that RTC_ISR is initially 0x23 and in the next second it is 0x423, which means that WUTF flag has been set. However no interrupt occurs.

My ISR just turns a LED on and clears EXTI flag. When I do EXTI_SWIER |= BIT17; the interrupt fires correctly (so I guess that EXTI and NVIC are set correctly). My problem is that even though the interrupt is enabled, RTC is running, WUTF flag is set - the interrupt does not occur. I have no hard faults, nor resets.

This is my RTC code:

RCC_APB1ENR |= BIT28; //turn on power control circuit clock
PWR_CR |= BIT8; //unlock the RTC domain, set DBP in PWR_CR
RCC_CSR |= BIT0; //rurn on LSI
while ( (RCC_CSR & BIT1) == 0); //wait for LSI to be ready

RCC_CSR |=  BIT19;  //put RTC into reset
RCC_CSR &=  ~BIT19; //take it back out of reset

//RTC on, use LSI
RCC_CSR |= BIT17;
RCC_CSR &= ~BIT16;

RCC_CSR |= BIT18; //RTC enable
RTC_WPR = 0xca; //RTC unlock
RTC_WPR = 0x53;

// RTC Initialization procedure (see reference manual)
RTC_ISR |= BIT7; //set INIT bit, request RTC stop
while ((RTC_ISR & BIT6)==0); //wait for RTC to stop

ISER |= BIT2; // enable RTC IRQ in NVIC (via EXTI line)

//wakeup configuration
RTC_CR &= ~BIT10; //clear WUTE bit
while( !(RTC_ISR & BIT2 /*WUTWF*/) ){} //wait for the bit to be set
uart_puts("RTC_ISR=");
uart_puthex(RTC_ISR);
RTC_ISR |= BIT10/*WUTWF*/; //has to be set before writing to WUTR (manual 22.7.6)
RTC_WUTR = 0x9C0; //very short wakeup period
RTC_CR = BIT14 /*WUTIE*/ | BIT10 /*WUTE*/ | BIT0|BIT1 /*WUCKSEL - RTC/2 wakeup clock*/ ; //enable wakeup function and interrupt, RTC/2 clock

RTC_ISR &= ~BIT7; //start the RTC (clear INIT bit)

EXTI_IMR |= BIT17; //enable RTC alarm going through EXTI 17 line to NVIC
EXTI_EMR |= BIT17;
EXTI_RTSR |= BIT17;

This is my UART log (repeats approximately every second):

------
Hello
RTC_ISR=c7
wutr=2496
RTC_ISR=23
RTC_TR=0
RTC_CR=4403
EXTI_PR=0
wutr=2496
RTC_ISR=423
RTC_TR=1
RTC_CR=4403
EXTI_PR=0
wutr=2496
RTC_ISR=423
RTC_TR=1
RTC_CR=4403
EXTI_PR=0
wutr=2496
RTC_ISR=423
RTC_TR=2
RTC_CR=4403
EXTI_PR=0
wutr=2496
RTC_ISR=423
RTC_TR=3
RTC_CR=4403
EXTI_PR=0
wutr=2496
RTC_ISR=423
RTC_TR=4


texts: stm32f2xx HSI configuration does not work correctly

texts:
I'm using below settings (in SystemInit function) to configure a STM32F215RG MCU to work at maximum speed (120MHZ) with USB support:

    RCC_DeInit();
    RCC_HSICmd(ENABLE);
    while(RCC_GetFlagStatus(RCC_FLAG_HSIRDY) == RESET);

    /* Flash 3 wait state, prefetch buffer and cache ON */
    FLASH_SetLatency(FLASH_Latency_3);
    FLASH_PrefetchBufferCmd(ENABLE);
    FLASH_InstructionCacheCmd(ENABLE);
    FLASH_DataCacheCmd(ENABLE);

    /* HCLK = SYSCLK */
    RCC_HCLKConfig(RCC_SYSCLK_Div1);
    /* PCLK2 = HCLK/2 */
    RCC_PCLK2Config(RCC_HCLK_Div2);
    /* PCLK1 = HCLK/4 */
    RCC_PCLK1Config(RCC_HCLK_Div4);
    /* Configure the main PLL clock to 120 MHz */
    RCC_PLLConfig(RCC_PLLSource_HSI, PLL_M, PLL_N, PLL_P, PLL_Q);
    /* Enable the main PLL */
    RCC_PLLCmd(ENABLE);
    /* Wait till the main PLL is ready */
    while(RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET);

    /* Select the main PLL as system clock source */
    RCC_SYSCLKConfig(RCC_SYSCLKSource_PLLCLK);

    /* Wait till the main PLL is used as system clock source */
    while (RCC_GetFlagStatus(RCC_FLAG_PLLRDY) == RESET);

& here are PLL config params:

#define PLL_M      16
#define PLL_N      240

#define PLL_P      2
#define PLL_Q      5

But seems there is a problem with HSI because MCU does NOT start to work after restarting.
But when I configure it to use HSE instead (with 8MHZ crystal, PLL_M=8) the MCU works as expected.
Is there any mistake in my configuration?


texts: How to test/connect the CAP-150 capacitive sensor

texts:
I am evaluating a few sensors for an application at work, and I'm having some troubles figuring out the correct way to connect/test this sensor: Gems Sensors' CAP-150. Datasheet here. I want to connect it later on to an ATMEGA324PA.

I know I'm using the Dry Sink variant, but I can't make any sense of the BLK/BLU switch diagram, nor the 300mA max load.

What I think I should do is supply the sensor with 5VDC at the BRN wire, GND to the BLU wire and then check the BLK wire for status change at one of the ATMEGA's pins. Although, the 300mA warning is confusing me, because it's specified as "continuous switching current" - on the other hand, the current consumption is rated at under 10mA.

I know that the ATMEGA can source the 10mA without any trouble, but does the 300mA warning mean I can't supply beyond that current to the sensor? In the configuration I described, is there any scenario where this could happen?

Can anyone help me clear this out?


texts: H Field in a Rectangular Loop Carrying Constant Current

texts:
Question: A rectangular loop carrying 10A current placed on \$z=0\$ plane as shown in figure. Find \$\vec H\$ at i)\$(2,2,0)\$, ii)\$(4,2,0)\$, iii)\$(4,8,0)\$, iv)\$(0,0,2)\$.

I just tried to draw the figure for the first point.

From Biot-savart law,
\$\begin{align}\\
\vec H&=\frac{I}{4\pi\rho}\left[\frac{b}{\sqrt{{\rho}^2+b^2}}-\frac{a}{\sqrt{{\rho}^2+a^2}}\right]\hat z\\
&=\vec H_{AB}+\vec H_{BC}+\vec H_{CD}+\vec H_{DA}\\
\end{align}\\\$
Now, \$\begin{align}\\
\vec H_{AB}&=\frac{10}{4\pi\times 2}\left(\frac{6}{\sqrt{6^2+2^2}}+\frac{2}{\sqrt{2^2+2^2}}\right)\hat z\\
&=0.659\hat z\\
\end{align}\\\$
\$\begin{align}\\
\vec H_{BC}&=\frac{10}{4\pi\times6}\left(\frac{2}{\sqrt{2^2+2^2}}+\frac{2}{\sqrt{2^2+2^2}}\right)\hat z\\
&=0.188\hat z\\
\end{align}\\\$
\$\vec H_{AB}=\vec H_{CD}=0.659\hat z\$
\$\begin{align}\\
\vec H_{DA}&=\frac{10}{4\pi\times 2}\left(\frac{2}{\sqrt{2^2+2^2}}+\frac{2}{\sqrt{2^2+2^2}}\right)\\
&=0.563\hat z\\
\end{align}\\\$
\$\begin{align}\\
\therefore \vec H=&(0.659+0.188+0.659+0.563)\hat z\\
&=2.069\hat z\\
\end{align}\\\$
But, the answer is given \$1.964\hat z\$
Please anyone confirm it if there is any fault.


texts: 15A 125V smart plug being used to slow charge electric car

texts: So my car is using a charger that from what I'm told is both level 1 and level 2 capable. What I'm getting from the car is that its slowly drawing 8A continuously untill charged. The plug I have in the wall is a standard NEMA 5-15 120V 15A plug that has an adapter that adapts it to the NEMA 6-20 240V 20A plug to fit the charger. I bought a smart plug that is rated 125V 15A to be able to beat the variable peak hours my company sends out. My question is will this thing melt? So the charger from what I read adapts to what the socket is in terms of power draw same as the car and the car is only set to 8A 120V draw. Is this going to work?


texts:
I need to select a LDO with output voltage of 12V for my design.My load requirement is 1.2A,only for 2ms.So I have chosen MIC29151-12WU regulator which is capable of delivering 1.5A of load current.
Since my load consumes 1.2 A only for short duration,I am thinking to use an low load current LDO with output bulk capacitance to meet the design requirement.This brings down my cost of LDO.But I am not sure about the pitfalls.Could someone advice me on this?


texts:
I'm looking to rewind a brushless motor to run at maximum efficiency for a given voltage and RPM.

let's say given the supply voltage is 12v, I want it optimised to run at a constant RPM of 4000 and drawing no more than 0.5 amps.

how do I calculate the wire size and number of turns?


texts:
I am using Altium (Ver 14). I designed the board and all seemed fine. But, when I edited the same PCB today, it behaves funny.
I have quite a few polygons on my PCB. Previously the polygon would connect to the relevant nets and nothing else. But now, when I edit the polygons, they merge with almost everything and not just the net that it should pour over.
I am attaching a screen shot.
I am also attaching the polygon properties. The type of polygon is the "Pour over same net objects". So, it should not pour of all and sundry.

Can anyone help me on this please ?


texts: What is this cable-joining black shell component called?

texts:
What is the name of the oblong black shell thing that is (presumably) connecting the two halves of the cable? There is a small one and a large one shown in the image below.

I've searched around for electrical cable connectors/joiners, but haven't been able to find this exact part. They seem pretty common, I have seen a few on USB cables I have.

I'd like to buy some of these for a project, so if you know what to search for on eBay to find these, I'd appreciate it.

EDIT: Thank you for the answers. I was actually looking for some sort of in-line compartment to hold a little circuit, and was surprised to learn about ferrite cores.

image source


texts:
I want to build a small box with two audio inputs and two audio outputs, with two switches to control the current input/output. Something like this: http://www.youtube.com/watch?v=mQzLnt0_-zU

I've wired up the following diagram in CircuitLab for how I think this should work:

https://www.circuitlab.com/circuit/4nq8kz/audio-toggle-box/

Do I have it right? Am I missing something? How can I add some LEDs to show which audio source/output is current? I was thinking I could probably power some small LEDs directly off the audio sources with a diode and/or capacitor to smooth out the AC audio, does that make sense?


texts: Does the load at where Pmp of a solar panel is oberved change with temperature?

texts:
After reading up on solar panels, I know that the max power that a Solar panel can supply (\$P_{mp}\$) will drop as the temperature increases. The \$V_{oc}\$ will decrease a lot more than \$I_{sc}\$ increases, so the Fill Factor will go down.

But this is the one thing I haven't been able to find an answer to.
Say, \$P_{mp}\$ of a solar panel that has a temperature of 25 °C is observed at a load of 20 KΩ. Will the load where the solar panel has its \$P_{mp}\$ change at a different temperature, and if so, will it increase or decrease?


texts: Is there any surprises in using high bandwidth instrumentation amplifier

texts:
Due to the unavailability of EEVBlog's uCurrent (A tool designed to assist with measuring low standby currents) I would like to build my own similar tool, in particular I would like to achieve a higher bandwidth to allow better operation when used with an oscilloscope for analyzing micro-controller sleep current.

While planning my design I came across the Analog Devices AD8421 at the $15 mark it is a reasonably pricey op-amp but thought it would make a good selection for a task like this for the following reasons.

High Input Impedance (30Gohms)
High gain range (1-10000)
Good bandwidth at high gains
Low input noise
Large supply voltage range

I am not used to designing gear with such high-speed amplifiers, is there any gotchas to be aware of. Could it really be as simple as the below circuit. The idea being to break into the current path somewhere (at a voltage within 9V of earth) and connect through J1, and then to hook an oscilloscope to J2.

I am more interested in getting an accurate waveform shape with low noise than an accurate magnitude.


texts: Differential ADC for Load Cell Measurement or In. Amp?

texts:
I've been tasked to design a circuit which measures the peak impact force of a crimping press on a terminal. I am using a load cell under the press as a sensor. The load cell outputs 20mV (differential) at full scale (4000 kg force). The impact is quite fast - an entire crimp is over in about 20-30 ms!

The approach I've come up with is as follows: feed the load cell's differential output to an instrumentation amplifier (gain ~ 200) which in turns a peak detector and that in turn is fed to a 10 bit ADC on my AVR. I've tried this approach and while it works quite well it's not repeatable enough. The noise in the system makes repeatable measurements difficult. Please note: I've only tried this on a veroboard and haven't yet tried it out on a PCB. I intend to do that soon.

The 2nd method which occurred to me was that I could use a differential ADC with built-in gain of, say, 200x+ and directly obtain the result that way. The only downside is that I'm not reading the peak value - but I can always do some processing and find the peak value. Is the second approach inherently better?

I am also open to other ideas. The goal is just to measure the peak force and then compare that with a programmed range in the MCU to see if the force was too high or low.


texts: Throughput increase/decrease by how much percent

texts:
I am learning computer architecture and organization. I am stuck in the following question. Can someone please help me?

The stage delays in a 5-stage pipeline are 300, 200, 100, 400 and 350
picoseconds. The second and third stages are merged into a single stage with delay 350 picoseconds. The throughput increase/decrease by ………… (percent).

This is what I tried:

Throughput of 1st case T1: 1/max delay =1/200
Throughput of 2nd case T2: 1/max delay= 1/350
%age increase/decrease in throughput: (T2-T1)/T1 * 100
= (1/350 - 1/200)/(1/200)*100
= -42.8
So the throughput decreases by 42.8%.

But the correct answer is given to be 0. I don't understand why?


texts: When do we need an Operating System in Embedded System Design?

texts: I have written plenty of bare metal code for PIC and x86 processors.  Can someone tell me how and when should I need an operating system?  Conversely, what application or situation can be dealt with or without an operating system as well?


texts: I am learning about avr programming and i know we have to use avr/interrupt.h library to use interrupt but my main reason to learn avr programming is to program without any library so i want to know, how i can handle interrupt without using any library including avr/interrupt.h, please if possible make small program that run ISR


texts: How do I interpret BST/SW voltage rating vs BST/GND rating in data sheet?

texts:
I'm reading the datasheet for the NCP81151B-D MOSFET gate driver / half bridge.
It has a standard bootstrap configuration where the switched note (drain + source of the totem pole N-FETs) is tied through a diode and acts as a charge pump to provide drive voltage for the high-side FET.

What I don't understand is this specification:

  BST Bootstrap Supply Voltage
  35 V wrt/ GND
  40 V  50 ns wrt/ GND
  6.5 V wrt/ SW
  7.7 V < 50 ns wrt/ SW
  −0.3 V wrt/SW

(taken from http://www.onsemi.com/pub/Collateral/NCP81151B-D.PDF )

Consider switching a 20V load.

When the gate driver is in the low-on configuration, the SW node would presumably be close to GND, but that means that the SW/BST voltage difference will be 20V minus whatever charge voltage is built up in the capacitor. This will clearly be higher than 7.7V by a rather large margin when the capacitor is empty.

The only way these specifications would make sense for the application, in my mind, is if the maximum voltage was the HIGHER of (SW + 6.5V) or (35V.)
However, it doesn't specify that in the data sheet, and thus my engineering reading of this is "the device will fail if you exceed either of these voltages."

How should I know what the correct reading is? ONSemi doesn't list a mail address in their contact section.
Has anyone used this part and know for sure that the "higher of" reading is correct?


texts: How much silver is needed in a silver-zinc battery, per kWh?

texts:
I'm trying to figure out how much silver is theoretically needed per kWh for a silver-zinc battery.

From this data page, I gathered the following:

But I don't know which of those equations are used in primary and secondary silver batteries. And I don't know how to plug in the electropotential number into some equation to figure out how much silver can hold how many joules or kWh of energy storage.

BTW I did see this question and someone's recommendation to put it on Chemistry.SE, but I clicked that link and found it removed/migrated from there. So that is why I post it here.


texts: Series or parallel lithium cells for 5v portable power supply?

texts: Would it be more typical to connect 2 lithium cells in parallel or series, where a 5v output is required, and the cells should be charged from a 5v supply? Is this due to efficiency, safety, cost or some other factor?


texts: What causes those oscillations in a comparator circuit

texts:
I designed a simple class D amplifier based on theory (output stage not pictured):

Layout(ish, the board was modified in a few places, the whole top part is a separate PCB soldered into where some really bad design was dremeled out):

The IC not on the schematic is LTC3261.

After assembling it I measured the inputs and outputs of the comparator with an oscilloscope and noticed some unexpected oscillations:

1 is -, 2 is +, 3 and 4 are the outputs.
What causes those? How should I eliminate them?

EDIT: I added a 470K feedback resistor which partially solved the problem (accidentally swapped channels 1 and 2):

Is there anything else I should try?

EDIT2: I accidentally found out the ringing is gone when measuring only the outputs (with no resistor added) indicating the oscilloscope is at fault somehow? Shouldn't the 13pF capacitance be too small to cause such a strong effect?


texts:
I'm building a JTAG programmer for the old Motorola 56k devices and I want to add some circuit protection before having some boards built. I'm more of a firmware/digital guy, but here's what I came up with based on this TI whitepaper. However, I was told it would not work because (I believe, this was a few weeks ago so my memory is foggy) because I wouldn't get current to turn on/off the transistors.

The idea is not necessarily to protect against the technician from reversing the programmer orientation, but rather to provide some protection in the case that the device being programmed is powered backwards. So, in other words, in the case that the 56K is powered backwards (something I'm guilty of doing because the wire colors were reversed on the unit I was given), it would more or less damage the programmer too.

So the idea is that pins 4,5, and 6 should normally be connected to ground and pin 11 should normally be connected to 3.3V. But if the polarity is reversed on the candidate device, the opposite would have happened. In this case, my hope is that both the PMOS and NMOS transistors would be turned off, thus preventing current flow. Based on the above diagram, is this true? Is there something else I need to do to make it work? Perhaps switching out the transistors for relays to avoid the aforementioned current flow issue?

---Edit---

Here's a higher-level diagram of what I'm trying to do.

simulate this circuit – Schematic created using CircuitLab

Of course, assume various DC-DC converters are present in the DUT to step down from 24V to 3.3V


texts: I have an AC to 18v DC, 25MA, power supply (wall wart) that is used for a guitar flanger pedal. The supply generates some ripple noise into the pedal's audio (it is not there when using batteries). The supply has a transformer, two diodes, and a 1000uf 25v capacitor. I changed the cap, but the hum is still there. The diodes seem OK. Would changing the cap to 2200uf help or should I try something else? Thank you.


texts:
I want to use two IRFP260N for DIY Inverter 12-220V.
I have CD4047 and I want to use it as driver. What resistor value can I put between CD4047 and IRFP260N Gate?


texts:
I have some lipo batteries I'd like to test.  Ideally it would do the following:

how much time does it take to discharge to minimum allowed voltage?
how flat is the discharge curve?
how many mAh were discharged?
what's the maximum discharge rate?

For my own educational purposes, I'd like to try an arduino-based project to gather the raw data, sending the data to a connected computer for analysis.  Doing this for a single cell would be fine... I'm assuming I would just repeat the circuit for the maximum number of cells in the battery to be tested.

Any pointers to such a circuit?  What components would be used to:

put a steady load on the cell?  Nice if it were easy to change the amp draw.
measure the cell voltage
measure the current flow

Ideally, each of these components would be readable, and the project would be mainly reading values from the components and sending the data over the serial line.


texts:
I am attempting to build a “Useless Machine” from scratch.  Here is a video of the device: http://www.youtube.com/watch?v=Z86V_ICUCD4 .

Also [if you want to], Google "The Most Useless Machine EVER! instructables" and click the first link for instructions on how to build it (I would link it directly but I am only allowed to post two links)

Now onto the question: I need a geared motor (or continuous rotation servo) with enough torque to rotate a 5cm arm that will lift an approx. 60 gram wooden lid and flick a switch. I was wondering if this geared motor will suffice: http://www.robotgear.com.au/Product.aspx/Details/700-Dagu-LBD-Little-Black-Duck-Gearmotor-and-wheel-kit-Pair.

Also, as I am powering it with 4 AA batteries, would you know how I would be able to lower the RPM of the motor from 100RPM to 50-30RPM while not sacrificing the torque of the motor.

The way I have written this post might make me sound like a real novice at electrical engineering, and that’s mostly because I am a real novice at electrical engineering. So please, if you are able to help me, write your answer like you are speaking to a 10 year old.


texts:
I'm trying to get ATTINY85 to trigger ONLY on HIGH interrupt, but no matter what combination of bits I set for GIMSK and MCUCR, I can't get it to work;

Here's my code:

#define F_CPU 1000000UL

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

int main(void)
{
    DDRB  = 0b00011000;

    setup();

    PORTB = 0b00010000;

    while(1) {}

    return 0;
}

void setup()
{
    GIMSK = 0b01100000;
    PCMSK = 0b00000010;
    MCUCR = 0b00000011;
    sei();
}

ISR(PCINT0_vect)
{
    PORTB = 0b00011000;
    delayms( 100 );
    PORTB = 0b00010000;
}

Based on the datasheet, if I set the bits in MCUCR the following way, I should be able to accomplish my result with the last option:

ISC01 ISC00

0     0         The low level of INT0 generates an interrupt request.
0     1         Any logical change on INT0 generates an interrupt request.
1     0         The falling edge of INT0 generates an interrupt request.
1     1         The rising edge of INT0 generates an interrupt request

I tried all combinations, but absolutely nothing changed. Then I changed:

GIMSK = 0b01100000;

To

GIMSK = 0b00100000;

That made the interrupt trigger on HIGH, but that's where it left off, if I connect pin to high again, the interrupt is not triggered, same if I connect it to LOW. Only the first time when the controller is turned on and pin is connected to HIGH.

How can I make the interrupt trigger only when the pin gets HIGH, not both - HIGH and LOW. I want every time I press a button, interrupt to trigger, but NOT when I release the button. Any suggestions? Thanks!