texts: tri-state / high-z / high impedance output with gpio input

texts:
The Li-ion charger I'm using (MCP73831/2) has a tri-state status output.
The datasheet says that the STAT pin outputs High-Z when inactive or complete, and Low while charging is active.

Whats the best way to hook this up to a nRF51822 GPIO?

Can I directly wire the stat output to a GPIO input, and then use an internal pull-up on the GPIO pin?

The nRF51822 is not 5V tolerant, but I don't think it will be damaged with a high-impedance output. Is this correct?

Relevant datasheets:

nRF51822

STAT output description (page 15, Table 5-1), reproduced here:


texts: In an answer by The Photon he mentions 'Manhattan routing' in regards to PCB design. I haven't found a lot of relevant information about this term on the internet; therefore the question: What is Manhattan routing?


texts: Introducing third winding in Transformer

texts: What would happen if I wind another winding (call tertiary winding with the same number of turns) on the transformer core and apply an AC voltage to it which is in phase with the primary voltage but is a different value in magnitude? Let's say that the primary voltage is V1 and the impressed tertiary voltage is V3. The flux with only the primary would be V1/(4.44fN). What value would the new flux settle for? In effect, what would be the flux value if there are two primaries?


texts: Bootstrapped resistor: a current source or open circuit?

texts:
The upper resistor is bootstrapped: \$i_\text{small signal} = \dfrac{v_{in} - v_{out}}{R} = 0\$.  According to The Art of Electronics (p. 97) said resistor is a current source (with \$i=0\$A ?). Why is it replaced with a current source instead of an open circuit?

Another thing is the return-to-ground of the ac coupled input. If the resistor is replaced with an open circuit then there will be no path for the ac signal to the ground. If the resistor is replaced with a current source (assuming \$i=0\$A) you still have the same problem, right? So how is the return-to-ground realized in this circuit?


texts: How do I implement a tri-state buffer for a vector in VHDL?

texts:
I want to implement a tri-state buffer for a input vector, triggered by an enable vector, where every bit of the enable vector enables the corresponding bit of the input vector.

Something like this but with multiple enable bits:

A single tri-state buffer looks like this:

Y <= A when (EN = '0') else 'Z';

(example from: https://startingelectronics.org/software/VHDL-CPLD-course/tut16-tri-state-buffer/ )

It could look like this (but that one doesn't work...):

[...]
signal Y : std_logic_vector(N downto 0);
signal A : std_logic_vector(N downto 0);
signal EN : std_logic_vector(N downto 0);

Y <= A when EN = (others => '1') else (others => 'Z');

Is there a way to declare this in VHDL or do I have to write a buffer for every bit?

Edit:
To clarify I'm searching a short declaration for this:

Y(0) <= A(0) when EN(0) = '1' else 'Z';
Y(1) <= A(1) when EN(1) = '1' else 'Z';
[...]
Y(N) <= A(N) when EN(N) = '1' else 'Z';


texts: How powerful would this motor have to be?

texts:
I’m attempting to make and electric barrow (like a wheel barrow) which needs to push up to 100 kg up fairly large hills. I’m assuming it needs to be 24 V but I don’t know what power (watts) or what ever it needs to be.

Could anyone help?

Additional information:

Speed = 5 mph
20 % incline


texts: 2N7002P MOSFET N channel complementary P channel

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I want to start creating CMOS logic gates, maybe a binary adder or something, but first I need to know which parts I will be using.

I searched for the cheapest N channel MOSFET, found it (2N7002P), but now I don't know which P channel would fit it the best.

What should I look for?
What parameters should match?
Do you guys know any alternatives?
What parameters should be matched?
Here is the link to the 2N7002P: Clicky


texts: Why is this LPF design passing frequencies above resonant in such magnitudes?

texts:
It's been a while since I have worked with filtering so I decided to simulate a circuit to see what I had forgotten. I used MultiSim for my circuit simulations but will present the design using the schematic tool on Stack Exchange. I designed a RC LPF like this:

simulate this circuit – Schematic created using CircuitLab

I inserted the AC power supply as a source of electrical noise; this source is an RMS supply - so the oscillations of 1V RMS are actually about 1.4V. Here is the plot of only the noise voltage.

The resonant frequency of this RC network is 5kHz. As such, my thought was that most of the 10kHz signal should be attenuated. To make sure I ran an frequency sweep in Multisim to verify my predictions.

Looked good to me. We should expect approximately -7.24 dB at 10kHz (which is about 0.188*noiseVoltage = 0.188*1.4 = 263mV). That is to say, I was expecting the output voltage to vary from 12V +- 263mV.

This is what I saw when I ran transient analysis on the circuit. I set -12V DC offset on the sinusoidal voltage source so the plot would display only the noise component.

We are actually seeing 607mV fluctuations at the output; this is about 43% of the total amplitude available before the LPF. The attenuation is high as expected, but not quite as high as I was thinking it would be.

I must be missing something here. Any ideas?


texts:
I have been working my way through The Art of Electronics by Horowitz and Hill and I've just started the chapter on Transistors. I am having some difficulty in understanding this transistor circuit:

The text explains that "When the switch is closed, the base
rises to 0.6 volt (base-emitter diode is in
forward conduction). The drop across
the base resistor is 9.4 volts, so the base
current is 9.4mA." What I don't understand is why the voltage drop across the base resistor is 9.4 volts? Surely the voltage across the resistor should be 10 volts (0.01 amps times 1000 ohms) and this would mean that the entirety of the source voltage is dropped?

The text also mentions that this is an example of transistor saturation.

Many Thanks in advance


texts: What is a mutli-bit port (4-bit, 8-bit, ..etc.)

texts:
I've been researching XMOS multicore microcontrollers lately so that I can use them soon.  I've worked with many development boards, even made a few of my own, although there is one thing that I don't understand about their controllers.

When they discuss the pin descriptions of any controller, they describe some as being 1-bit, and others being 4-bit or 8-bit or something.  How can they be multi-bit? I thought that if the pin was digital, it is 1-bit because of its nature.

Apologies,  I didn't give the actual datasheet. Here:
https://www.xmos.com/en/download/public/XS1-L16A-128-QF124-Datasheet%28X8006F%29.pdf

on page 6


texts:
I'm planning to drive two white leds like these (datasheet) with PAM2803 driver (datasheet) and a single cell lipo battery.

Before ordering a pcb, I'm testing on a breakout board. With a 0.13 Ohm shunt resistor, I'm expecting a 730mA current.
As test load, I'm using a 2 Ohm resistor (5x10 Ohm in parallel). The result should be 1.46V on the resistor.

From the sheet, the device should be powered between 0.9v and "forward voltage of the led - 0.2v"

I'm powering the test system with 1V which is between 0.9 and 1.46-0.2 = 1.26v.

I'm using a 2.4 µH inductance (FDSD0420-H-4R7M=P3 : datasheet) and MBRA210LT3G schottky (datasheet).

The result is not the one expected: resistor voltage is 690mV thus 345mA.
If I increase the input voltage, the current increases too.
What's wrong?

Here's a picture of the board. It's not easy to see on it.
Shunt resistor is soldiered just between the pins. Capacitors are on top of their tracks.


texts: Driver circuit for heating element (nichrome wire)

texts:
For my project, I need to heat up a nichrome wire (which acts as a heating element) and provide a power of 100mW to it. I have already done computation and I need current of approximately 22mA to generate that power, also the voltage that will be generated across the heating element will be 4.51V. I am planning on using a NPN BJT as a current driver to limit the current at a constant rate and because my current requirement is lower than 1A, I think NPN BJT will be a better option than using MOSFET. I am using MCU connected to this nichrome wire through current driving circuit.

Since, I'll have to provide a source voltage for the driving circuit, I plan on using a 3.6 V battery. The problem that I am confused about is, will my circuit work properly with 3.6V at source? Does 4.51V generated across heating element have any significance in regards to this?
I researched about load switches which use P-channel MOSFET, because of it's lots of advantages, I  am confused if it will be a better choice or not, if someone can suggest.
Also, I read on a website that while using MCU, it's better to use a high side switch, since MCU always needs to be ground. So, on using an NPN BJT, wouldn't it work properly?


texts: NPN inverter alternative that takes up less space on the board

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Here I have an NPN inverter circuit which consist of 2 separate NPN transistors and 3 resistors. It does the job, but it takes too much space on the board. Is there any alternative to this circuit that take less space? Can I use something like this https://eu.mouser.com/datasheet/2/348/vt6x12-1535580.pdf ? Is this the best alternative I can find or there's a better option?

Use case:
This circuit is controlled by MCU through the base pin. The logic level voltage of the MCU is 3.3V. The use case here is it to trigger pairing mode on the BT chip using it's supply (1.8V) as the logic level on the BT module should not exceed 1.8V


texts: Problem in creating one-shot impulse circuit

texts:
I am a student in university and I have a problem to be solved.
I have to design a circuit that gives just one pulse (not periodic signal) when the 220V source is active. I will give 220V to the circuit and out will be one-second high. And I want to take feedback just one time even if source is connected. I tried 555 timer with one-shot impulse but it didn't work for me. Also if it is possible output must be 8-12 volt.
Thank you very much. Here is my circuit


texts:
Does external noise (not electrical noise) affect system voltage? If so how does a source of sound energy distort a voltage waveform?

https://youtu.be/4TCnYYpZxEc

What exactly is happening in this lecture at 46:50 when the professor increases the noise of the chain saw?


texts:
I have just started with electronics. I made the very simple circuit on Falstad, but there is an issue with the resistance.
I have a 5 volt power supply connected to an LED with a resistance of 0.088ohms connected to a 220-ohm resistor.
According to my calculations, the current flowing through the wire should be 22.718 milliamperes.
I am getting the correct value when I connect the 220-ohm resistor to a 0.088-ohm resistor but I am not getting it when I connect the 220-ohm resistor to the LED.
Here are the screenshots:
LED with resistor

Current =  14.54mA
Voltage=5V
Total resistance = 220.088ohms

Resistor circuit:

Current =  56.718A
Voltage =  5V
Resistance =  0.088ohms

Thank You!


texts: How is it ensured that (computer) hardware (such as motherboards or processors themselves) does not suffer from from wrong signals due magnetic induction between wires?


texts: AC->DC supply, how to deal with chassis ground being connected to digital ground?

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I have an external triple-output AC-DC supply with the following output pinout:

On the power supply, "ground" (pin 2) is internally connected to the ground wire of the mains plug. I'll refer to it as "earth ground" (it's "AC GND" in my diagrams below).

Current Configuration

With the PCBs that I already had built, "common" (pin 1) is connected directly to the board-sized ground plane; let's call it "digital ground". There are various connectors on the board, such as a USB jack and an analog input connector. The connector shields/shrouds are connected to the digital ground plane where they are soldered to the PCB, and the shields/shrouds are also connected to the chassis/enclosure. The image below shows the configuration:

The device is used for measuring very small currents. The DC power supply's +12V and -12V outputs drive sensitive amplifier, DAC, and ADC circuits.

My concern is that since earth ground is left floating, the enclosure could theoretically become energized due to a fault. The voltages in my circuit max out at +12V / -12V, but does that even matter from a safety standpoint?

Possible fix for existing boards

I've read this answer to the question Should chassis ground be attached to digital ground?, and the way I understand it, I'll be OK if I just connect earth ground to the chassis at the power input connector, since my chassis is connected to the shrouds of all the input connectors already. Without making new boards, that's really the only thing I think can do right now anyway. Could this turn my device into an unintentional radiator since digital ground is connected to the shrouds too? Could it also put more noise in my power? Any other serious concerns?

What to do with the next version

Ideally, I think the grounds should be hooked up like this, so that AC ground is isolated from the rest of the board, and there is no way for the chassis to pass current except through external faults or a serious internal fault, but the current would go to earth. I could change the layout so that the next batch of boards are hooked up like the diagram below. Do I have the right idea?

Plastic Enclosure

I have one more issue that complicates things further... This device is intended to be produced in two different configurations: in the primary configuration, the enclosure is aluminum. However, in the other configuration, there is a plastic enclosure. This means the only exposed conductive parts are the connector shrouds. Of course I'd like to use the same board if possible.

What's the safest way to deal with the exposed conductive connector shrouds? Should I leave them floating, or just connect them to digital ground? The plastic enclosure does have an internal conductive coating, but I don't think I can make a reliable connection to it (let's assume I can't).

I have already read this other question that is very similar, but I have a different issue since I'm working with an existing board that already connects chassis ground and digital ground.


texts:
I want to create a board that has both high speed digital components (specifically the SAM3X8E - from arduino DUE) and an analog audio circuit.

The analog parts were originally a shield to the arduino. The reason I want to create a mixed mode board to combine the two circuits into one, is because I used to have a lot of noise. After searching, people suggested that this is noise from the digital circuit and I will have to remake the board.

This is a link with the original question. There you will also find a picture of the schematic of the shield.
Proper Decoupling

My question is how do i ground the whole thing. I have seen many different approaches in threads like these:
How should I connect AGND and DGND (LINK 1)
Star point in schematics           (LINK 2)
For Multiple ADC circuits PCB layout grounding, why is "single point ground" important?

single-point-ground-imp     (LINK 3)
So do i need to have different GND planes for digital and analog? I was considering using tha 'Star ground approach' but the first link said it is the least efficient.
Trevor_G also said (in the second link): "For this kind of circuit, integral single ground and power planes with appropriate layout to keep the signal loops as short as possible is much better."
So I have only one common ground plane?

Then reading these two guidelines:
https://www.maximintegrated.com/en/app-notes/index.mvp/id/5450
http://www.hottconsultants.com/techtips/split-gnd-plane.html

I found out that one GND plane is all that is needed. But many things were unclear and lost in theory. For example, do i have to separate the two planes? If yes, do they have to join in one place?
Do i need to 'cut' the two planes? If yes, where exactly do i cut? What happens when the analog signals, enter the digital side of the board? Like when the analog information enters the ADC of the microcontroller?
If there indeed is a cut, how am i supposed to route the traces?
In general, how do i design the GND layer?

What i will do:
*Keep the digital parts away from the analog parts - upper copper layer (thanks peufeu!)
*Use two regiulators, one for the digital side and one for the analog side
*Avoid digital power and digital signal to pass in the same area as the analog side (on all layers)

An extra question:
*I saw in the stackexchange link 3 to keep the power sources on the digital side of the board. That includes the analog regulator as well? But the analog power trace will have to pass through the digital side... But when the analog signal enters the ADC of the microcontroller then the analog signal enters digital side as well. So is it impossible to separate them?


texts:
I'm interested in Verilog, but I have a question. I tried to implement modulo without using '%` operator. So I made it this way:

while (c>=d) loop
    c <= c-d;
end loop;

Is it right?  Any suggestions on where I made the mistake?
This is a modulo.vhd
[[
[
This is a tb_modulo.vhd
[


texts:
Does changing the source voltage (i.e. voltage of the battery) affect how long it takes for a capacitor to charge in a circuit?

Am I right in saying that since the capacitor charges until it reaches the source voltage that a larger source voltage will mean that it takes longer? But if the capacitance is the same then how does this work?


texts: Problem with high current draw in circuit design

texts:
I am working on a project where I've taken an LDC1612evm (inductance to digital converter) and removed the connected micro controller portion to communicate with a TM4C123G LaunchPad via I2C. I have been able to get the circuit working correctly when connecting the launchpad to my computer through micro usb, the circuit looking like the picture below (the pull-up resistors are for the I2C communication)

I connected an ammeter to the LDC input to determine the current draw of the chip, which being 5mA was within the operating limits found in the datasheet. For the end product, this circuit is going to have a 12V source passed through a MC7805CT 5V regulator to control this particular section. I have attempted to simulate this as is shown in the below diagram

Here is where the problem occurs. When I read the ammeter I see a current of 500mA flowing into the LDC which, not surprisingly, instantly damages it.

So my question is what is causing the huge current draw?

I have checked the LDC input voltages and in both cases I get the expected 3.3V. It has been suggested that the micro controller section of the ldc1612evm has a regulator on it thus by removing that portion the regulator is bypassed allowing for the higher current draw, but from what I can tell from the launchpad's datasheet power schematic the 3.3V output contains a similar regulator, so I don't understand why that would be the problem.

Thank you in advance for any insights into the cause.

EDIT: changed out the wiring diagrams for schematics


texts:
This is the LTSpice model of the Fairchild 2N7002 NMOS transistor.

.model 2N7002 VDMOS(Rg=3 Vto=1.6 Rd=0 Rs=.75 Rb=.14 Kp=.17
 mtriode=1.25 Cgdmax=80pCgdmin=12p Cgs=50p Cjo=50p Is=.04p
 ksubthres=.1 mfg=Fairchild Vds=60 Ron=2 Qg=1.5n)

The equation of a saturated N-MOSFET is

Reading the SPICE .model, I had thought that for this Fairchild 2N7002, the parameters were Vth = 1.6 V and k' = 170 mA/V².

Then, using LTSpice, I've obtained the ID vs. VDS characteristic of the Fairchild 2N7002:

Acording to the equation, for VGS = 3V, I should get a current of ID = 170 / 2 x (3 - 1.6)² = 166 mA, but in the plot I get 140 mA.

Acording to the equation, for VGS = 4V, I should get a current of ID = 170 / 2 x (4 - 1.6)² = 489 mA, but in the plot I get 378 mA

Etc.

Moreover, if you treat Vth and k' as unknowns, you can compute them from the plot. For example, using the curves VGS = 4 V and VGS = 3 V, solving the system of equations 140 mA = k' / 2 × (3-Vth)² and 378 mA = k' / 2 × (4-Vth)². Then you get, k' = 0.1158 A/V² and Vth = 1.4452 V.

But if you use other curves, you get differente results. For example, using the curves VGS = 6 V and VGS = 5 V, solving the system of equations 700.36 mA = k' / 2 × (5-Vth)² and 1.088 A = k' / 2 × (6-Vth)². Then you get, k' = 0.08511 A/V² and Vth = 0.9431 V.

So, according to the plot, Vth and k' are not constants but variables.

So, why I get this difference? Which parameters are the true ones: those from the .model or those from the plot? Should I get this parameters from the datasheet instead?


texts: How to connect auto cut off circuit with battery level indicator?

texts:
Guys I want to make a circuit which cut off the power automatically when the battery is full.Also,it will show the battery level. I found a circuit diagram on google and I want to build something like that,but the problem is that the battery indicator and power supply units are different.What I want to ask:please help me connect everything the right way.I posted images below.
Should I connect the power supply directly to the battery and connect the indicator with the battery?
Can you please give me a diagram showing how to connect it all?
Youtube video Link

Working Principle:

Normally, for mobile phones,the battery level is shown in dot or bar form. This lets you easily recognise the battery level. Here we present a circuit that lets you know the battery level of a device by increasing or decreasing the number of LEDs that are glowing. It uses a total number of ten LEDs. So if three LEDs glow, it indicates that the remaining battery capacity is 30 percent. Unlike mobile phones where the battery-level indicator function is integrated with other functions, here only one comparator IC (LM3914) does it all. The LM3914 uses ten comparators, which are internally assembled in the voltage divider network based on the current division rule. So it divides the battery level into ten parts. The circuit  power supply for its operation from the battery of the device itself.
It uses ten LEDs wired in a 10-dot mode. The use of different coloured LEDs makes it easier to recognise the voltage level on the basis of the calibration made. Red LEDs (LED1 through LED3) indicate battery capacity of less than 40%. Orange LEDs (LED4 through LED6) indicate battery capacity of 40 to less than 70% and green LEDs (LED7 through LED10) indicate battery capacity of 70 to under 100 per cent. The brightness of the LEDs can be adjusted by varying the value of preset VR2 between pins 6 and 7. Diode D1 prevents the circuit from reverse polarity battery connection. The tenth LED glows only when the battery capacity is full, i.e., the battery is fully charged. When the battery is fully charged,the relay-driver transistor T1 conducts in order to energise relay RL1. This stops the charging through the normally open (N/O) contacts of relay RL1.
For calibration, connect 15V variable, regulated power supply and initially set it at 3V. Slowly adjust VR1 until LED1 glows. Now, increase the input voltage to 15V in steps of 1.2V until the corresponding LED (LED2 through LED10) lights up. Now the circuit is ready to show any voltage value with respect to the maximum voltage. Because the number of LEDs is ten, we can easily consider one LED to represent 10% of the maximum voltage. Connect any battery in order to test its voltage at the input probes of the circuit. By examining the number of LEDs glowing you can easily know the status of the battery. Suppose five LEDs are glowing. In this case, the battery capacity is 50 to 59% of its maximum value. Assemble the circuit on a general-purpose PCB. Calibrate it and then enclose in a box.


texts: AC Power measurement ( digital sampling)

texts:
i want to measure AC power and i want to know what is the best and safest way to digital sample AC voltage and AC current?
For AC voltage: We can use

voltage divider and feed it to ADC with reference eg -5V to 5V ( non isolated)
transformer to transformer from 230VAC to 5VAC and feed it  to ADC (isolated)
use voltage divider and isolation opamp or ADC ( isolated)
are there any other options?

For AC current: We can use

shunt resistor with opamp to adc ( non isolated and high dissipation on shunt)
shunt resistor with isolation opamp or ADC ( same as above with isolation)
current transformer ( can you suggest some ?) ( isolated)
hall effect sensor ( can you suggest some?) ( isolated)
are there any other options?

Because i need to sample the voltage and current at the same time i need two ADC, but i'm not sure what delay will be introduced for voltage ( if use any option from above) also for current  ( if use any option from above) ? And if delay is introduced how can i synchronize the two ADC?
List of priorities:

size
price
low power ( as possible)
complexity

The voltage is 230Vac and max current 16A and if possible current resolution 100mA
Br.


texts: Use one GPIO output to set two inputs to opposite states (low and high)

texts:
This is all still very new to me so apologies if this is a silly question.

I have two LDO voltage regulators, each of the ENable pins are different, to enable them one ENable pin must be LOW and the other ENable pin must be HIGH.

Is there a simple way to do this using a single GPIO output?

I'm thinking I can set the GPIO output to either high or low and send that directly to one of the LDO's and then invert it and send it to the other LDO, however, I'm not sure what I would use to do this inversion.


texts: Calculating propagation delay for a logic circuit

texts:
Given the above combinational logic diagram, How to calculate  the propagation delay?

AND->OR->AND-NOT
NOT->AND->NOT
I see the above two longest paths. So what I understand is just take the maximum of these
two.
But is it fixed what's the propagation delay for an AND GATE and other gates?
I am not sure about the numbers.


texts: Extrapolating parameters for SPICE model for a Silicon Photomultiplier

texts:
I've been working on a circuit involving a silicon photomultiplier, but I'm having trouble modeling the SiPM in LTspice. I found an article below that shows a proposed model for an SiPM in SPICE:

Article: http://www.sciencedirect.com/science/article/pii/S0168900213007389

My problem is that I don't know how to extrapolate parameters for the model, such as the quenching resistance and capacitance as well as the inner junction capacitance and the internal resistance. I'm trying to model it based off of the MicroFJ-60035 SiPM provided by SensL found here:

http://sensl.com/products/j-series/

However, the parameters that they give don't really tell me much about the necessary parameters for the SPICE model directly. How can I get the parameters needed from the datasheet? As a reference, my circuit that I am trying to build is the recommended readout circuit found in the user manual.


texts: Why would this logic gate use negative voltages?

texts:
I'm reading a data sheet for a hex buffer with enable- a pretty simple logic DIP.  Here's the logic diagram and pin assignment:

This all makes sense to me until I look at the electrical parameters.  VCC=0V?  VEE=-5.2V?  It seems to me that this part could be used with VEE=0V and VCC=5.2V with no issues- after all, it's just an issue of potentials, right?  But if that's the case, why would anyone ever specify parameters like this?  I feel like I must be missing something.

Edit:  OK, I was missing something big an obvious.  I get that it's ECL.  But- could I still use it like normal, with VEE=0V and VCC=5.2V?


texts:
I am using MC34063 in step down configuration but the converter switches off every cycle. Following are the calculations and specifications:
Vin - 9 to 12V
Vout - 5V
Imax - 0.3A
Rsc - 0.36 ohms
L - 47uH 1.6A
Ct - 270pf
I have tried reducing the current limit resistor value (Rsc), but it didn't help. The usable current is below the designed rated current. I have attached an oscilloscope image showing the output voltage ripple on channel-1 and switching transistor emitter (pin-2 of MC34063A) voltage on channel-2.
Note that the transistor switches off completely causing a low frequency ripple in the output voltage which is unnecessary. Kindly help.


texts:
simulate this circuit – Schematic created using CircuitLab
In this condition, RL=infinity so the voltage gain of the output at the node R5 and Q1 can be obtain as below
$$A_v=\frac{4800}{450}=10.67$$
Verified with simulator which is in good agreement

simulate this circuit
However, now the output is connected to a bypass capacitor of 5.3micro farad and my simulator showing a gain of only 3, understood as there is current flow into the 5.3micro farad capacitor that pull down the voltage gain and from youtube https://www.youtube.com/watch?v=-MyVscG-Pew&t=363s I understood the gain is gain is
$$A_v=\frac{4800||R_{effective}}{r_e'+450}$$
Is the $$R_{effective}=R_7||R_8$$ so that theoretical value of $$A_v=3.73$$ or the calculation is actually more complicated than this?


texts:
I am currently learning the basics of electronics using the website allaboutcircuits.com. I find this site a huge help and I can recommend it to anyone trying to get into electronics. There is only one problem however: the tutorial uses spice 2g6, part because of its simplicity and its help in getting the learner get 'to think like a coder'.

I would love to be able to follow up on the suggestions, but I can't find any working download of sprice 2g6. Does anyone have one, or does anyone know a good replacement that is exactly as educative and simple?

Thank you for your efforts.


texts: Extend the time delay of an asserted WDT active low

texts:
I am new to electronics and would appreciate any help. I am trying to design a watchdog timer circuit using the TI WDT (mfg part # TPS3813K33DBVT). I am using it to reset an Arduino (I wish to use an external WDT).

So far so good, it works a treat and I have it asserting an active low to the reset pin of an Arduino. If the WDT is not tickled within the window the Arduino resets as expected. When the reset line is asserted it is held low for 25ms per the datasheet.

I would like to make a change and this is where I am stuck. Instead of asserting the Arduino reset pin I would like to temporarily cut off power to the Arduino. i.e. power cycle for around 60 seconds. The reason is that I will have other modules attached to the Arduino that may not necessarily observe the reset and would need a full power cycle to reboot properly.

I was thinking of using an IC load switch for this purpose like FDC6330L which is essentially always on. Asserting the reset pin would turn off the FDC6330L for 25ms. My attempted circuit is attached .. how can I extend the delay of 25ms to 60s? The max time delay ("td") of the TPS3813K33DBVT is 30ms.


texts: What is the full form of RT resistor in RT?

texts:
Here is the datasheet of the TI switcher using in my design
http://www.ti.com/lit/ds/symlink/tps54620.pdf

Could you please help to find the full-form of RT in RT resistor?
Attached is the relevant screenshot for reference.

Thanks
VT


texts: Switch between the current source with the highest amperage

texts:
I have two current source. Both are about 5 volts. I want to charge my phone with the highest current source out of the two, so if the highest current source (2.1 amps) is gone, it will switch to the lesser (1 amp) source.

The current setting:
I have my tablet in my car. The tablet is set to wake up, set the displayTimeout to 30 minutes, and start playing music when 2.1 amps is connected. When I turn my car on to ACC or ON, 2.1 A is sent. When the car is turned off, the tablet detects no current, stops playing music, turns screen off, and sets displayTimeout to 7 seconds.

What I noticed is my tablet barely drains battery when above 50%, but under that it drains to 0% so fast sometimes I go to my classes at College and when I drive home I see and big ugly 0% screen.

Future:
What I plan to do is either buy a rechargeable power bank that charges the tablet when the car is off, or just charge the tablet even when the car is off by connecting it straight to the battery. The only problem is the tablet cannot detect a change between car on and car off. It can only see if the current has been changed from 2.1 amp to 1 amp, so I want the tablet to stop music, turn off display etc when it detects 1 amps.

What I think might work:
I'm thinking if I splice the two current sources together, it will just add to 3.1 amps which isn't a problem for my tablet (right?) since it only draws what it needs.

I say current source, but it's just two basic usb cords that get's it electricity from car chargers, so it may not be a current source but a voltage source? I'm taking circuit analysis this semester so forgive me!

My question:
I don't want to use a physical switch to switch between them, but I may have to. What should I do that can have my tablet use the 2.1 amp by default, and switch to the 1 amp when the 2.1 amp cannot be detected. I think I read that diodes are required but they cause a voltage drop. Would my splicing idea work?


texts:
I'm using STM32L031 in TSOP20 package on custom board. User can control it with encoder, which contains also push button. Endoder push button is connected to pin 3 on package(PC15), which is right next to NRST on pin 4. There is  a 100n capacitor placed on NRST pin, 100n and 4u7 on VDD and 10n and 1u on VDDA. Board worked well for few days, but now, pressing encoder button causes restarts. PINRSTF flag in RCC_CSR register is set, so reset came from pin. All other functions I use (I2C display, PWM generation, ADC, encoder clocking timer) work well.
Power supply is stable, I haven't noticed any change when I pressed the button.
I checked, that pins aren't shorted. When I push the button, NRST is pulled to about 0.3V. I tried to measure resistance between NRST and button traces, but haven't got any meaningful values.
Is it possible, that pins are somehow shorted internally? I thought also about flux contamination or humidity, but I cleaned whole board with alcohol multiple times and it's placed on pretty dry place.
What else can I do to troubleshoot this problem?


texts: Household appliances commercial project EU certification

texts:
I got a job to do a household appliances with wireless remote control. I’m working as embedded developer in current company, but we haven't had to certificate our solutions and I'm looking for advice.
The first level of this job is to make a prototype of the machine. However I want this prototype not to demand too many modifications during the certifications process before entering the EU market.
As for my internet research, I know that the necessery things to do are: certification EMC, RED, LVD and additionally norms IEC-60335 and IEC-60730 for Class-B machine (household appliances).
Has anyone of you designed or made a household device controled by MCU?
Is following norms IEC-60335 and IEC-60730 demanded? Are making the tests obligatory for the norms? Or only the producer statement is enough to let the product enter the market?
What documents are needed to conduct the test of this kind of appliances in external laboratory (PCB circuict schematic, list of norms, elements list, software architecture, code source, code/libraries certifications etc.)?
For Class-B device necessery is to use mechanisms self-test peripherals of MCU (such as CPU, RAM, Flash, Watchodgs etc.)?
But the producer of the chip (Nordic Semiconductor - nRF5) I chose doesnt provide the self-test library or the support for this kind of tests. Can I go through the certification process implementing this kind of self-test by my own or using for example only watchdogs?
For example, ST Electronics provides certified library of this type of self-test for free. However its wireless modules are more difficult to get and much more expensive than nRF modules.
I would like to use nRF modules because its precertified with FCC/IC etc.
And here I have another question: whether the certification of my own remote controller with precertified module on my own PCB circuit with battery (CR2032 3V3) supply and 4 buttons is as expensive as using a not precertified radio module?
UPDATE:
To precise: my goal is to designing and making a prototype a remotely controlled cooker hood. I have wanted to use RF modules in remote controller and mainboard cooker hood. The LED lights and turbine (low voltage 10V) would be controlled by the MCU. The voltage to mainboard would be provided by the 12V power supply.
As I found out the norm IEC-60730 divides the household devices in to 3 classes:

Class A - Control functions, which are not intended to be relied upon for the safety of the equipment. Examples are: room thermostats, humidity controls, lighting controls, timers, and switches.
Class B - Control functions, which are intended to prevent unsafe operation of the controlled equipment. Examples are: thermal cut-offs and door locks for laundry equipment.
Class C - Control functions, which are intended to prevent special hazards (e.g., explosion of the controlled equipment). Examples are: automatic burner controls and thermal cut-outs for closed, un-vented water heater systems.
[https://www.nxp.com/docs/en/application-note/AN3257.pdf]

Theoretically it would be possible to define that control as Class A - lightning control, timers and switches. It would make the process of designing easier, because the software systems of safety aren't demanded in this class. Unfortunately the control of a turbine makes this project as device of class B.
Thank you for your answers, I hope they would be useful to others in the future, because the subjects of meeting the standards, safety regulations, certification of products and the right way of conducting the project are not well described on the internet and this is the next step after the own DIY projects.


texts:
OK, so my problem is the following:
I have a commercial box with mechanical DPDT-switches for controlling valves by changing the polarity of 2 wires per valve. The box has 7 relevant switches, which I need to control further down the line with an Arduino. This Arduino gets signals from a separate computer over serial which switch should be in the on or off Position. When the Arduino is powered off the mechanical switches in the commercial box should function as without anything in between. Ideally the mechanical switches should overrule the Arduino in the off position. So the perfect states are as follows (-1 indicates no power):

I came up with the following schematic using SPDT-Relays, if you know of DPDT-Relays that work nicely with arduinos and I could order off amazon.de, that would make things a lot easier.

Problem No. 1 with this approach is that the mechanical 0 signal does not overrule the arduino. I guess I would have to read the signal into the arduino and make an if case for switching the relay? Problem No. 2 is that I think the arduino can't handle the 14 Relays (I have only an 8-channel at the moment) Based on the specification I found in an amazon description it needs 20mA for every relay, with 14 coming to a total draw of 280mA which is above the 200mA rating for the output pins of an arduino I found online. I'm guessing a possible solution could be using transistors to switch the relays?

One other idea I had would be using NOT-Gates with NPN-Transistors, since the maximum power draw of the valves seems to be 500mA at 12V (fuse in the commercial box is 500mA, the real current is probably lower). This would require 14 NPN-transistors if I'm not mistaken, which I have already. There is also probably an easy way to use some logic gates to get the "overruling" of the mechanical switches.

As a quick background on why I want to do this:
The equipment I want to control is an agricultural sprayer. Ours has 7 zones which can be turned on and off with mechanical switches. Earlier this year we built a diy-solution for autosteering the tractor (Cerea) and now want to control the sprayer at the same time. The arduino receives signals over the serial connection from the computer running the autosteering program. The signals determine which zones should be turned on, based on where the sprayer has already been. The manual override of individual zones is helpful at the sides of the field which the autosteering software doesn't know about.

If you have any ideas how to implement this let me know!


texts: Why can't a combination of two diodes connected back to back act like transistor?

texts: I saw an explanation of the transistor working here by Bill Beaty. I absolutely loved it. But I'm not entirely sure why the action cannot be achieved by two diodes connected back to back by a metal piece in between. Here's what I'm thinking, Metal wire obviously has large number of charge carriers in it so any electron in base that accidentally enters the metal will cause a small current at the other end of the wire by pushing an electron into the collector region just like it happens in case of transistor. Where did I go wrong? And where does the mechanism fail exactly?


texts:
I'm developing an application with goal to achieve maximum throughput from device. By throughput i mean maximum amount of "cores" running at max frequency.

So, we have: Virtex-6 XC6VLX240T, ISE 14.4

Main module: UART, data prepare and data collection from submodules

Each submodule connects to main module via interface:

(
        clock              : in std_logic;
        reset              : in std_logic;

        data_input         : in std_logic_vector(31 downto 0);
        data_flag          : in std_logic;

        done               : out std_logic;
        data_ready         : out std_logic
)

Regarding device resources we can fit around 230 cores + main module to fully utilize device capacity.

Main module + 64 cores run perfectly fine at 200 MHz. 128 cores - synthesizer says max achievable frequency around 140 MHz, which is not good. I looked at floorplan in PlanAhead: all of my critical paths are the lines connecting main module and submodules.

I tried to register these lines:

signal reset_corebuf              : std_logic_vector(NCORES - 1 downto 0);
signal data_input_corebuf         : std_logic_vector((NCORES * 32) - 1 downto 0);
signal data_flag_corebuf          : std_logic_vector(NCORES - 1 downto 0);
signal done_corebuf               : std_logic_vector(NCORES - 1 downto 0);
signal data_ready_corebuf         : std_logic_vector(NCORES - 1 downto 0);

process (clk)
begin
    if (rising_edge(clk)) then
        for i in 0 to NCORES - 1 loop
            reset_corebuf(i) <= reset;
            data_input_corebuf((i + 1) * 32 - 1 downto i * 32) <= core_data;
            data_flag_corebuf(i) <= data_core_flag(i);

            core_done(i) <= done_corebuf(i);
            data_core_ready(i) <= data_ready_corebuf(i);
        end loop;
    end if;
end process;

and nothing changed, but i feel that should be better, right ?

What am i doing wrong and what the general idea to optimize such architecture ?


texts: LTSpice "Error:undefined symbol in:" problem

texts:
Below is my schematic for a relay SPDT symbol I’m creating. I've posted this question in the Digikey forums, but I am not sure they actually answer LTSpice questions

You may notice I’m not yet very proficient with LTSpice. Getting past that, You’ll notice the spice directive on the top right corner. What I’m trying to do is this:

Regardless of what voltage POS is, V4 = 5 unless POS=<0

:: Here I thought the expression u(POS) * 5 would work because u() returns 0 or 1 depending if the parameter is 0 or > 0

Since it is SPDT both electronic switches (ADG1201) have the same input COM1 but each has a different Output. The switch turns on when Mom = 5. So U1[In] =0 and U2[In]=5 when Mom = 5. Also, U1[In]=5 and U2[In]=0 when Mom=0

:: Here I tried to modify the expressions with the .func statement along with If statements.
In my test Circuit, the Spice Error log reads:
Questionable use of curly braces in “v4 n004 0 {z}”
Error: undefined symbol in: “[z]”
Questionable use of curly braces in “v5 n006 0 {y}”
Error: undefined symbol in: “[y]”
Questionable use of curly braces in “v6 n005 0 {x}”
Error: undefined symbol in: “”
Questionable use of curly braces in “v4 0 {fnvoltmod(v(pos))}”
Error: undefined symbol in: “(if((v)>0,z=u((v(pos)))*5))”
Questionable use of curly braces in “v5 0 {fndecy(mom)}”
Error: undefined symbol in: “(if(([mom])>0,y=0,y=5))”
Questionable use of curly braces in “v6 0 {fndecx(mom)}”
Error: undefined symbol in: “(if(([mom])>0,x=5,x=0))”
Fatal Error: Multiple instances of “V:x1:4”

How do I accomplish what I am doing using Spice directives?
I wouldn’t ask this question if I hadn’t already searched the web for an answer. I think I don’t understand how to use Spice Directives on a schematic properly. I’ve read the LTSpice help and expanded help on the wiki site - but I can’t seem to find schematic rules with spice directives.
In short, please help me understand.


texts: How do I assemble this using the following circuit?

texts:
I'm a third year Computer Science student and have decided to create a pulse sensor for my third year project. I'm mainly interested creating software to visualise results but I thought it would be cool to attempt to actually build the device also.

I'm attempting to follow this guide but having difficulty reading this schematic:

So far, this is what I've come up with...

1) Connect 1 leg of the LDR to 6v power and the other leg to the base to base (B) of Q1.

2) Connect C of Q1 to a 1k resistor and then connect that to my 6v (Unsure how I'd connect this to my 6v if the 6v is already connected to leg of LDR)

3) Connect Q1 (B) to R3 and then to ground.

From here I'm a little lost, would appreciate some advice.

I'm also a little confused to how I connect multiple things to ground/power. Will each connection have its own wire running to ground or do I need to create some sort of T like junction from the existing power/ground wire?

I've tried to give this a go in advance so I'm not just poaching for the answer but would appreciate some help.

Thanks in advance.


texts: What is difference between Qmax and Design Capacity of battery parameters?

texts:
I'm working with the BQ27742-g1 (Texas Instruments) Fuel Gauge.

I have some confusion about battery parameters.

What is Qmax and Design capacity? Are they the same or different?

What is the configuration value for Qmax and Design capacity if my battery is single cell 4600 mAh?


texts: Chassis potential of an old transformerless valve / tube TV

texts:
Long, long ago, some friends and I in school used to try to repair old valve (tube) TVs.  Most commonly the repair was just by cannibalizing another old set; we did not have any budget for spares but we brought some sets back to life.

Many of these sets had no power transformer and just directly rectified the mains.  This was the UK and, at the time, the nominal supply voltage was 240V RMS so a peak of about 340V which the circuits were designed to run on.  Hence it was not safe to touch the chassis.

I am wondering at what potential the chassis was with respect to ground.  Let's make a few simplifying assumptions.

Supply is 240V RMS.

Neutral is 0V with respect to ground.

No transformer.

Full wave rectification with perfect diodes.

Smoothing is just a capacitor.  I forget how sophisticated the smoothing might be.

I think that the smoothing is irrelevant.  For half the AC cycle, the chassis with be connected to the neutral line and hence at 0V.  For the other half cycle, it will be connected to the live.  So, I want the RMS voltage of the resulting waveform.  A little bit of maths gives me an RMS of 120V.

Does that seem correct?


texts:
I tried simulating a basic comparator configuration in Proteus with only a single supply. The reference/trip-point is 2V. However when I simulated the DC transfer curve, all negative input voltages are saturated to +VCC and not to the lower rail voltage (+1V).
Why can't a single-supply comparator handle negative inputs? Why won't the output be at the lower rail when the noninverting input is negative?
The comparator that  I used is LM311 with pull up resistor at the output.


texts:
Correct me if I'm wrong, this is my understanding of MIMO:

Is this how MIMO is able to increase data rate?


texts: Two's Complement Multiplication Overflow

texts:
I was reading through a textbook of mine and found a question that I really can't figure out. It asks to find a pair of two's complement numbers which will result in an overflow if they're multiplied together using a 4x4 array multiplier, and I'm not really sure how to go about finding them. The exact question is "Give an example of the multiplication of two numbers (in 2’s complements), using a 4 bits x 4 bits array multiplier, to show that an overflow occurs" in case I misinterpreted it

From my understanding of binary multiplication, a 4x4 array multiplier just takes two 4-bit numbers and represents the product as an 8-bit number. As far as I know, any two unsigned n-bit numbers multiplied by each other can always be represented by 2n bits, so an overflow can't occur when an array multiplier is used for that, but I don't really understand how that translates over to two's complement and why it would be any different.

My initial thought was to work backwards since binary multiplication is just a series of additions and figure it out that way. I know that if you add a pair of two's complement numbers, you can check if their addition causes an overflow by looking at the most significant bits. If both the operands' MSBs are the same but are different from the sum's MSB, that indicates an overflow. While this is great and it makes sense to me for addition, I can't figure out any way to connect that requirement to the question asked.

I really don't have any ideas on where to go from here, and the Wikipedia article (my textbook doesn't really cover this all that well) on two's complement numbers seems to suggest that you can properly represent the product of two n-bit numbers with a 2n-bit number even if they're in two's complement, so I'm not even confident that a solution exists and I think I might just be totally misunderstanding the question. Any help in understanding this would be much appreciated.


texts: Connector data sheet: meaning of "Current Rating ... 6 adjacent contacts"

texts:
What does a connector datasheet (such as page 2 of this datasheet ) mean by

"Current Rating: 2.1 A (Gold plating, 6 adjacent contacts)"

Does it mean

Each pin can handle 2.1 A each, when up to 6 adjacent contacts are carrying current? (so a total of 12.6 A per connector spread across 6 pins)
Up to 6 adjacent contacts can carry a total of 2.1 A? (so 350 mA per contact)
Up to 6 adjacent contacts can carry a total of 2.1 A out and 2.1 A back? (so 700 mA per contact)
Something else?

(Related, but I suspect a slightly different question:
Current Rating of JST connector PER PIN)


texts:
How do we calculate the DC power consumption of a multipole resistive network, if we know the currents of all the poles (pins) and all the voltages between the poles?
Let's say for example, that we have a 4 pole. The first pole has a voltage of 10 V (to an arbitrary reference gnd) and an amperage of -1 A (1 A flows into the network through this pole). The second pole is 5 V and -4 A, the third is 3 V and +3 A, and the fourth is 1 V and +2 A. What is the dissipated power?
Is it even possible to calculate the power from the pole currents and voltages or we need the actual inner structure of the network?


texts: Why is my IC giving abnormally small voltage outputs?

texts:
I just got some new battery holders, with 4.5V and 6V respectively. I hooked up the 4.5V holder to a SR latch IC, and while it did hold a state, the LED was abnormally dim, despite having no resistors in between the output pin and LED. The schematic for my design is below:

simulate this circuit – Schematic created using CircuitLab

Half the time I couldn't see it at all, even when I set the latch. I tried another LED, and the same thing happened. I tried the 6V power source, and the LED didn't get any brighter. Can anyone explain what's wrong?


texts:
We need to make a logic circuit, the given function is:

f= (AB) + (not(C)) + (not(A)D)

I already tried a bit, and I can manage to make a circuit with 7 NAND gates but not with less...
Could anyone help me with that, please?
I also added a 3 NAND input gate, which is not allowed...

simulate this circuit – Schematic created using CircuitLab


texts: LM324N transimpedance amp for photodiode: Too low output, smaller feedback resistor gives greater output, not lower

texts:
I'm trying to build an optical power meter using a photodiode in photoconductive mode and a LM324N OpAmp:

simulate this circuit – Schematic created using CircuitLab
However, the output voltage signal is very low. Exchanging R_f for a smaller resistor or even shorting it gives a higher output. According to https://en.wikipedia.org/wiki/Transimpedance_amplifier, V_out / I_in = -R_f, so I would expect a smaller R_f to decrease the gain, not increase it.
Please help me understand what I'm doing wrong.
Thanks!


texts:
I've been looking at this part for an hour, and I can't for the life of me figure from the datasheet two relationships.  I have relationship A? and relationship B?, which I am struggling with.  I don't have the part in hand (it's an obscure Asian IC... of course...).

I'm not a master at building footprints, but I have laid plenty of QFNs and usually a datasheet provides a few more of the center to center relationships.

I feel like Asian ICs are the worst offenders with these kinds of under-detailed documents.

This one is crazy because it is not symmetrical.  Is it possible to figure out A? and B?

I feel like there must be some assumptions about how the pads are centered to each other or something else here...  I don't know want to use an assumption to layout a board though.

1)A?

What am I missing in this relationship of distance of the two pads in A? -- ?

You are provided with K, which I take as the edge of the relief pad to the edge of the pad.  We know the pad size (.4mm by .120mm).

So how could you determine the distance from the row of 14 pads on the top, to top of the first pad in the 10 pad row (I'm calling that distance A?).

2)B?

For B?, is the assumption that the pads are symmetrical to the 5mm package length?  So, you could take the 14 pads + pitch, an and infer there is an equal offset of space on each end?


texts: How would I drive about 440 LED's without breaking the bank?

texts:
Alright, I'm trying to create I guess an LED matrix display(?) so that I can make essentially a text display using 8x5 LEDs per letter, to make 11 letters in total. I'm definitely willing to learn a lot and NEED to learn a lot as I have little experience with something like this. My goal is to be able to display individual letters to make the display show like "Hey there" using 5x8 LEDs for each letter.

I'm looking to use possibly an arduino device, but as they have limited inputs, and I need about 440 inputs.. how would I make this work? I've researched a bit and it seems I could do something related to this https://www.circuitspecialists.com/blog/build-8x8-led-matrix  . Would this be my best bet maybe? How would I extend this from 64 to 440 in terms of delivering it to the arduino device?

Also I would like to ask what arduino device might be best for this, and what accessories I might need that aren't mentioned in that page, if the provided link is a good idea.

Edit: Sorry for being somewhat vague. I'd be using 5mm Red LEDs and I only need to be able to turn on and off each individual LED. https://www.circuitspecialists.com/bag-red5mm.html


texts: Deactivating RF modulator circuit, should I cut off the supply voltage as well?

texts:
I asked a qeustion about this mod I'm doing to my Amiga 1200, but unfortunately I asked two questions at once, and only one question got answered. This is about removing an RF modulator from the computer's PCB and getting rid of electrolytic caps that are associated with the RF circuity and making sure that the leftovers aren't causing any trouble.
Here's the part of the schematic that shows the situation as is:

R = replaced electrolytic capacitor
X = removed part that is not going to be replaced
? = should I remove these?
Removing R237 and E232R would cut off the IC (it's a Sony CXA 1145M) mono audio out and video power supply line repectively from going to ground. Mono audio input has already been disconnected from the IC (AUDIO_IN pin 8 not in picture) because there was an electrolytic cap before the input, but maybe the video encoder will now amplify noise and still give an output voltage at AUDIO_OUT (9)?
I'm a beginner when it comes to electronics and looking at this from my point of insufficient knowledge what I'm worried about is that without the RF modulator consuming power, the remaining resistors are overheating or something.
I doubt I will ever revive the RF output part of this computer ever again, so to be on the safe side I can live with removing a few SMD parts. What I mostly care about is that the remaining components do not interfere with the rest of the computer, consume unnecessary power or might even overheat.


texts: What components of a DRAM (specifically LPDDR) memory do the power rails VDD1, VDD2 and VDDQ supply the power to?

texts:
I'm working on a project that tries to understand the power consumption of LPDDR memory under different operating modes such as active, idle, self-refresh, deep-power-down mode. With my experimental setup (which i'm not at the liberty to discuss details about, sorry) I am able to measure the current drawn by the mentioned three power rails of the LPDDR memory (at mA granularity) under different operation modes. However, to understand the trends in my measurements I need to know what components of the DRAM memory are mapped to which power rail.
From reading the JEDEC standard, I do understand that VDD1 and VDD2 are "Core Power" supplies, and VDDQ is the I/O buffer supply, but I'm not entirely sure what exact components are supplied by each of the rails.
I would greatly appreciate any help.
P.S. My background is not in electrical engineering so please try to dumb-it-down.
Thanks!


texts: Porting MikroC code to MPLAB for PIC16F1508 adding extra noise to ADC

texts:
I decided to start using MPLAB with XC8 after I started reaching the 2k code size limit in MikroC. The problem is that since all the Mikroc libraries are proprietary and there are no libraries available for the PIC16F series in MPLAB, I had to write my own ADC functions.

These are the two functions I wrote to set up my ADC using the datasheet:

void ADC_Init(){
    PIR1bits.ADIF = 0; // Clear interrupt flag
    PIE1bits.ADIE = 0; // Disable ADC interrupt
    INTCONbits.PEIE = 0; // Disable perriferal interrupts

    ADCON2 = 0; // No ADC Trigger

    ADCON1bits.ADCS = 0b111; // Select internal RC clock source
    ADCON1bits.ADPREF = 0b00; // Select VDD as Vref
    ADCON1bits.ADFM = 0; // Left justify, upper 8 MSB in ADRESH

    ADCON0bits.ADON = 1; // Turn on ADC Module
}

int ADC_Read(char channel){
    ADCON0bits.CHS = channel; // Set channel, must be between 0 and 11
    __delay_us(5); // Wait some arbitrary acquisiton time

    PIR1bits.ADIF = 0; // Clear interrupt flag
    ADCON0bits.GO_nDONE = 1; // Start acquisioin

    while(ADCON0bits.GO_nDONE) {} // Wait for the conversion to finish

    return (ADRESH << 2) | ADRESL;

}

The input signal that I'm reading in is pretty noisy to begin with.
In my MikroC program with the library ADC functions, the noise floor on the samples ranged between 60 and 100 (10-bit ADC). By noise floor, I mean the range of values the ADC was reading with no input. Noise from the rest of the system I suppose.

In MPLAB with the above functions, the noise floor has shot up 200 to 300. On a 10-bit ADC, this much noise is unacceptable. I run the ADC_Init() function once outside my main program loop, then use the ADC_Read(..) function in my program loop.

Any ideas on why the noise is so much more? Or any ideas on how MikroC get this performance? I suspect it has something to do with the way I configured the ADC.

EDIT

In response to Olin's answer, I believe the 5us "acquisition time" might be a misnomer, that delay is there to allow the holding capacitor to charge after changing ADC channels. The datasheet shows an example for a 10kohm signal impedance needing 7.4us charge time. My signal impedance is only 700ohms, so I figured 5us should be more than enough. As for the circuit, it has not changed, only the software has. And the signal I'm measuring is a slightly noisy digital signal coming out of a MSGEQ7 filter IC.


texts: Why does working processors harder use more electrical power?

texts:
Back in the mists of time when I started coding, at least as far as I'm aware, processors all used a fixed amount of power. There was no such thing as a processor being "idle".

These days there are all sorts of technologies for reducing power usage when the processor is not very busy, mostly by dynamically reducing the clock rate.

My question is why does running at a lower clock rate use less power?

My mental picture of a processor is of a reference voltage (say 5V) representing a binary 1, and 0V representing  0. Therefore I tend to think of of a constant 5V being applied across the entire chip, with the various logic gates disconnecting this voltage when "off", meaning a constant amount of power is being used. The rate at which these gates are turned on and off seems to have no relation to the power used.

I have no doubt this is a hopelessly naive picture, but I am no electrical engineer. Can someone explain what's really going on with frequency scaling, and how it saves power. Are there any other ways that a processor uses more or less power depending on state? eg Does it use more power if more gates are open?

How are mobile / low power processors different from their desktop cousins? Are they just simpler (less transistors?), or is there some other fundamental design difference?


texts: Chip resistors: how much power can they *really* dissipate?

texts:
For a variety of reasons, I'm currently considering a design for a linear regulator that uses some input resistance to help it regulate a higher current than it could handle on its' own. The issue is thermal: the regulator is nominally rated for more than the 100mA or so that I'd like from it, but the input voltage is high enough that the dissipated power would trip the thermal shutdown.

While most resistors have a power rating (for instance, the 0805s I'm considering are typically rated for 1/8W) I'd like some more detailed information. There is quite a bit of interesting literature describing the various common IC packages, covering things ranging from thermal resistance to the many effects of layout, convection, etc.

Sadly, this is not the case for resistors! The best reference I've been able to find on this topic is a short app note from Vishay, which you can get here:

http://www.vishay.com/docs/28844/tmismra.pdf

Specific questions:

Does anyone know of a better treatment of the thermal characteristics of chip resistors?
What does the power rating of the chip really mean? At what temperature? Is it soldered onto a board? Which kind? What thickness of copper is involved?


texts: When is it allowed to use non-isolated PoE?

texts:
Currently I am designing a circuit that is required to be PoE powered. We are debating whether to use an isolated or a non-isolated supply.

The device is wall mounted and in a plastic enclosure. No metal parts are exposed to the end user.

This answer said that this is the only requirement to be able to use a non-isolated DC-DC converter, but I would like to know if someone can reference an actual document were this is stated. It will be sold in Germany, so there may be additional regulations that do not apply to the whole world.

EDIT: To be clear: we are designing a powered device not a PSE.


texts: Exposed Pad on a mixed signal IC, ground plane connection and power supply decoupling

texts:
I'm using a DAC with an exposed pad (NC) bottom. The datasheet specifies that the EP should be connected to ground ([EDIT]Presumably [/EDIT] for heat dissipation, but heat concern is not noted in the data sheet ) but is not connecting internally in the IC, and since the DAC is my only mixed signal component it is my star ground point as well, I'm connecting it to the analog ground plane in the board.

My question is about the best practice when it comes to exposed pad connections. Specifically when it comes to attaching the IC ground and the power supply decoupling is it ok to connect the ground pin and decoupling cap through the Exposed pad to ground or is it better to have individual vias for the decoupling and ground connection?

To Illustrate:

vs


texts:
My PIC datasheet (PIC24HJ128GP202) specifies three parameters to configure the PLL which are N1, N2 and M. Each of them have to satisfy some clock frequencie ranges in input/output of each block inside the PLL. I looked all around the datasheet and did not found the answer for this question:

what happens if I do not respect these ranges?

I mean, in the final output for example. The frequency should be between 12.5 MHz and 80MHz. What happens if I select PLLPOST (N2) which leads me to 80.5 MHz? Or yet select a PLLDIV (M) which leads me to 201MHz (when PLLPOST intput should be between 100-200 MHz)?


texts: DS1100L Why Would You Want a Delayed Signal?

texts:
In a circuit I am looking at, a frequency output is fed to a micro-controller for pulse counting and also goes to a DS1100L-25 (Timing Delay Element IC). The output (all five taps) of this IC goes to the micro-controller as well. I am struggling to understand why/how this component would be used and how a delayed signal as well as the original signal help?

The input has a maximum input frequency of 10KHz (not 1MHz). The output from the micro controller is SPI.

simulate this circuit – Schematic created using CircuitLab

My initial thinking was that it would help with accuracy somehow but I cannot work the mechanism/logic behind this.

TLDR;
Why would you need a delayed signal as well as the original for a pulse counter?


texts: Is there any smaller in size version of AT89C5131A-UM microcontroller? Or a small size microcontroller that has the same function as AT89C5131A-UM? I'm finding a mircocontroller that can be placed inside a key fob (Transmitter) .


texts: Why is the first band on a resistor never black?

texts:
I'm taking an electronic circuit analysis class, and I was asked to give the color of the 3rd band of a 1MΩ resistor. My answer was blue, thinking it could be black-brown-blue (01 * 1MΩ), but the automated quiz said the correct answer was green (brown-black-green).

So I did some research, thinking there were just multiple correct answers, and I read in a few places that the first band on a resistor is never black (0). Why is this? Does a black first band have some other meaning? It would really help me remember it if I knew the history or reasoning behind it.

This question has been answered. For further reading on zero-ohm resistors mentioned in the answers and comments here, I found these questions and answers helpful:

What is the usage of Zero Ohm & MiliOhm Resistor?
Zero ohm resistor tolerance?


texts: How do I tap into a power supply's standby wire?

texts:
So I'm working on an Arduino project, I'm going to make a circuit board that's going to be inside my computer. The circuit needs to always have power, after a bit of googling, I found out that the standby (purple) wire seems to be perfect for what I want. I took an old computer and did this.

The LEDs barely glow, so it seems I don't draw enough power from the power supply. So I'm wondering, if it's because of the way I tapped into it? or if it simply doesn't provide enough current?


texts: Why is this amplifier inverting that voltage?

texts: Can somebody please explain to me why the output here is the negative of the "input"? I really can't wrap my head around it...


texts: about Synplify VHDL (code imported from Xilinx ISE)

texts:
Good day,

Need some help. Start to work with Synopsys Synplify. Import my Xilinx ISE project (fully work).

Try to run and receive - "No matching overload for to_integer" for this line

rgb(7 downto 0) <= color_lut(result_reg(to_integer(unsigned(x(2 downto 0))-1 )));

What can I do to adopt this piece for Synplify?


texts: Impedance Matching Resistors on MII Ethernet Lines

texts:
Microchip is taking forever to activate my account so I will ask this here...

I am using the KSZ8081 PHY for MII Ethernet.

https://www.mouser.com/ProductDetail/Microchip-Technology-Micrel/KSZ8081MNXCA?qs=sGAEpiMZZMvdy8WAlGWLcC4eczfQr1zYEy39QIyqxLk%3d

The evaluation board schematic has 33 Ohm impedance matching resistors on the RX MII signal lines but NOT the TX MII signal lines.

In past experience with other PHY chips (TI DP83848 specifically), there are series resistors on both the TX[0:3] and RX[0:3] lines.

Why does KSZ8081 not have them on the TX[0:3] MII lines? Would it be a good idea to include them or should I follow the evaluation board exactly?

Here is a screenshot of the KSZ8081 eval board schematic...


texts:
One of the most useful ability of MCUs is generating PWM signal. For example ESP32 duty resolution can be lowered down to 1 bit in which case the maximum frequency is 40 MHz.

With such fast clock speed a 200-500KHz and 10-12 bit resolution is more than enough to build a switching buck or boost converter:

simulate this circuit – Schematic created using CircuitLab

Is there a down-side in using of MCUs PWM to build a switching regulator? (am I going to face any problem?)
What advantages switching regulator ICs (like LM2596 or XL6009 etc) have over this method other than simplicity and ease of use?


texts: What it is the maximum "real" current by the collector that can be drawn from ULN2067B

texts:
I am building a 5-volt-to-24-volt DC converter using ULN2067B. According to the datasheet this device can support 1.5 A per darlington per collector.

Does that mean that all the darlingtons can draw 1.5 A at the same time? If no, how could  a beginner in electronics have checked that while reading the datasheet?


texts: Is the use of this IEC filter proper for the this application?

texts:
Here is the IEC module which has filters. The question is about using the IEC filter on the very left side in the below Figure.

Below from left to right there will be a power flow.
Right after the first IEC there will be line and neutral buses shown as circle nodes. From there I will be six AC mains access. I drew only three. Most of these will also have the same IEC modulesat their AC input. I hope the illustration explains the scanrio it well:

My worry is can a an IEC filter be used for multiple AC mains entries or even cascaded as shown? Or are they only to be used with a single unit such as a power supply?


texts:
tl;dr: Assuming I'd had a BeagleBone perfectly manufactured from the open-source schematics+layouts, what would be necessary to get it to the same level of functionality as a newly-unboxed BeagleBone?

Alternatively, how would one unbrick a BeagleBone that refuses to boot from either flash or eMMC, assuming the hardware was all working perfectly.

Follow-up question is here.

I've been experimenting with basic embedded boards - hand-soldered low-end ARM/AVR processors which are flashed directly.

If I wanted to make a working clone of a BeagleBone, what would be necessary to get it to the level of functionality that they have out-of-the-box?

So after spending ridiculous amounts of time and money on manufacturing a clone of a <$100 off-the-shelf board, what would I then need to do in order to be able to just plug an SD card in, hold down the boot-select button, and boot the board off the SD card?

I'm assuming that before U-boot on the SD-card / eMMC is invoked, there is an earlier bootloader which is flashed onto the Sitara.

So the order would be:

Image on Sitara is run from flash, and configures a serial UART interface, external hardware, etc.
Depending on state of boot selection button, that image either loads U-boot from eMMC, or from SD card, and jumps to it.
U-boot then loads kernel and initrd, passes device-tree data and command-line to it, then jumps into it.
Linux boots
"Profit!"

On these more complex boards, how would that first-stage bootloader be flashed on?
How could I use a BeagleBone to develop and test my own first-stage bootloader?

Ok, I've found that there is some ROM code on the Sitara, which checks a few bytes on the eMMC and boots if it appears valid.  It checks the SD card if the eMMC doesn't appear valid.

My question now, which I will re-ask as a separate question:
Does this ROM code come on the Sitara itself, or otherwise how would one obtain and flash it?  Is it open source?  Is it a binary blob in the Sitara SDK?  Is it immutable and built into the Sitara before leaving TI's factory?


texts: Calculating resistor's value to use it with a LED

texts:
There's something about the LED formula that I don't understand.

It says that if I have one LED with a forward voltage of 3V and a forward current of 20mA then if I want to drive my circuit with a 6V battery, the formula to determine the resistor's value for the LED is:

$$\frac{(6-3)V}{0.02A} = 150\Omega$$

In a circuit with the elements connected in series the amperage is the same anywhere.

So by using the formula differently:

$$\frac{6V}{150\Omega} = 0.04A$$

So does the LED is actually driven by 0.04A?

The formula is of course correct, but I don't understand where my logic is mistaken. Can someone help me?


texts: Break away/Break in angle in Root Locus method

texts:
We are learning Root Locus in our introductory controls course, and one thing has really been confusing me.
When the poles are on real axis, is the breakaway angle always 90 degrees? Is there a simple example of a transfer function with real poles that has a non 90 degrees break away/ break in angle? What about a system with not necessarily just real poles? Can it have a non 90 degrees break away/ break in angle?
Thanks in advance


texts: Voltage Cutoff Circuit for battery based application

texts:
Here is schematic of battery charging circuit. The battery voltage at 100% charge is 4.2V and it gradually decrease and is 3.2V, discharging below 3.2V will affect the battery life.

How to make sure, the battery supply is disconnected automatically from the load when it reaches 3.2V or less and when voltage is above 3.2V, it gets connected to Load,

What can be added in the circuit? The circuit should be simple and low on BOM.


texts: How to compare power requirements for different control design approaches?

texts:
I am trying to fairly compare different control design approaches. As an example, below I present two similar but different techniques which are:

Control system with state feedback
Control system with state feedback and observer

The plant input is voltage.

What I have done

I designed both systems on Simulink, with the idea that I would be able to check the input to the plant and get an RMS and current reading to get instantaneous power.

Both plants are the same, and so is the input.

I am trying to get a voltage and current reading after the summing junction, before entering the plant so I am using the Multi-meter block by Simulink. However I get no available measurements:

Am I using the wrong tool to get read the VRMS and current?

Any suggestions on how I can compare power requirements for these two different control design approaches would be appreciated.

This could be an alternative technique: What is the output of a PID controller (or any controller in general)?


texts: Bias T for modulation of VCSEL laserdiode

texts:
For my project, I would like to design a Bias Tee for a VCSEL laserdiode, because a modulation is required. The bandwidth is 20 KHz - 10 MHz. My steps are shown below:

As a reference, I have used the formulas of Bias t from wikipedia and this site.
The RF input of the bias tee is a RF input voltage which is converted to an AC-current by using a resistor (R1) in series with a capacitor. The DC input is just an input for the DC-current as it is directly connected to a laser driver with a limiting resistor (R2). However, I have some doubts with regard to choosing inductors due to the SFR (Self resonance frequency), the maximum frequency where an inductor still behaves as an inductor, is relatively difficult to search for with 2-3 times higher than the maximum frequency.
Thus, I would like to know whether these steps(in image) are correct and second, do you have tips for me to choose inductors?


texts: Varistors set to ground or case by isolated ground/case

texts:
I have a isolated ground from the case in my device. The Supply Voltage is +24VDC with Ground and separated CASE, so no safety issues.
On any signals coming from the case (Plugs) I put varistors, but should I put them to the Ground (Electronic) or to the case for EMC?


texts: Can we replace an embedded system design with a general purpose computer or a smartphone?

texts:
I am a newbie to embedded systems design so this question might seem very fundamental in nature.

I have been working as part of an Avionics team to develop an on board computing device for a unmanned aerial vehicle which would need to interact with various subsystems like camera, ir sensors, actuators, etc. We will be using a customized board design for this purpose, the cost of which comes to approx. 200k INR. Someone at work proposed why not use the chip inside a general purpose computer for the purpose or even a smartphone. The computer would cost between 50-60k while a smartphone would cost 20k which is cheaper than a customized board design. The idea seems ridiculous because of obvious reasons.

Firstly, the power consumption for a laptop board would be far more than any electronic board. But the same can't be said for a smartphone.

Secondly, an onboard computing device will require much more interfaces than a general computer/smartphone  would provide.

The electronic board can be interacted  with using several development kits like Vivado which I don't believe is possible in PCs/phones without an OS. I am not sure about this point.

Lastly, any smartphone/pc will be prone to bugs by design. We generally see laptops crashing and phones not reacting to touch commands which we can't afford in a real time based system like an unmanned aerial vehicle.

I gave the above arguments but none seem to be compelling enough to make someone of a non technical background understand this point. Is there an obvious/compelling reason which would prove the validity of my points to someone who doesn't have technical knowledge and is only concerned about bringing down the costs?

Edit: The unmanned vehicle needs to be mil-grade precise in our application, so it will need to handle a good amount of data efficiently that too in real-time while interacting with various sensors like camera, ir sensors, etc.


texts: Converting a 2.54mm pitch header to screw terminal blocks

texts:
I'm trying to avoid soldering or modding of any kind as I'm 7,000 miles away from where the project is based! I'm trying to come up with a simple solution I can get a layman to do on my behalf. I have the following IO board: http://www.phatio.com/ which exposes 2x14 IO ports (2.54mm pitch pin header connection) but need to convert the connections into screw terminal block type.

I was thinking of using some angled double pin header connectors and then connecting them to pluggable screw terminal blocks (http://www.metz-connect.com/en/products/311661) but the smallest size I can find is 3.5mm.

Anyone have any suggestions or a better/alternative idea? (screw terminal blocks are a must)

Thanks


texts: Enable input to an integrated circuit and button

texts:
Suppose i have a scheme that includes integrated circuit with enable input and i want to use mechanical switch in order to activate enable input. For example:

So i've heard that, whenever we are using mechanical button to enable some circuit, we need to avoid direct connection to integrated circuit, instead it is recommended that we use something like this (D flip flop, AND gate and NOT gate) in this configuration because, by directly connecting mechanical button to a IC we can cause a circuit to behave unexpectedly due to mechanics of a button. It could cause a low state to be detected like a high state due to noise or something. Now, has anyone here encountered that kind of problem, is it really necessary to add all of these elements to prevent errors, how this configuration decreases the probability of wrong detection?
Any help appreciated!

EDIT:
This question is not about if i should debounce this circuit or not, since i know i should, question is, is this scheme representing good debouncing circuit and how?


texts: Why does an accelerometer have an offset error when at its +1G position when calculating tilt angle on single axis?

texts:
For my axis calibration, I find the slope with Vin values at 1 and -1 G positioning of the accelerometer relative to the axis I am interested in, using this formula (x is g and y is Vin values)

I then use this formula to find the tilt angle from my subsequent Vin readings

I find that I get a measurement of -90° at -1G, but an angle of 85° at +1G. Where does this error come from?

Edit:
it is interesting to note how negative G direction has a much lower error percentage:

The calculations are as follow:
calPG and calNG are the voltage read from the x axis at -90° and +90°
Vin are the following V readings from the x axis, once slope was found
G is gravity
offset is optional, you can give it the value of angle measured at theoretical 0° (when the cube is placed so no acceleration is on x)


texts: For a 4 layers PCB (with ground plane), covering with ground polygon on Layer 1&4 necessary?

texts:
For a single or double layered PCB board, usually I will cover all the empty spaces in the layout with Ground.

This is the 1st time I am designing a 4 layer PCB layout.
Layer 1: top signal (high speed)
Layer 2: Ground plane
Layer 3: Power plane (5v, 3.3v, 1.8v)
Layer 4: bottom signal (normal speed)

Since now I already got a dedicated Ground plane (Layer 2), my question is:
After finished all the routing, for Layer 1 & 4, should I still cover all the emptied space with Ground as well?


texts: I have some problems with the PCB (connections doesnt show, etc) and pins missing on the PCB is one of them. Any idea on how to fix this?


texts: How does one go about programming a PIC microcontroller?

texts:
I am working on my first project using a PIC microncontroller, a PIC12F675.

How do I load a program onto the microcontroller?

I bought this programmer to start, but don't really know how to use it.

I'm working with Windows 7.
I installed WinPic800 but it doesnt seem to be detecting the programmer when I plug it in via USB.
When I click "Read All" (or any other function for that matter), I get the error "Failed to open Ind.#0".

Can anyone tell me what I could be doing wrong?

Thanks


texts:
I am designing RF layout on PCB, my PCB is in Circular form,

In Pic 1, is my current layout in PCB, since this chip antenna is dipole in nature , so to form the dipole antenna there should be mirror area  opposite to antenna with Ground plane with same length ( like pic 2 ), but due to PCB size and shape , I can't keep this.
Q) So as per pic 3 , other ground area can be consider as half portion of dipole antenna or not. I have the matching component install on board, will they help if any problem happen due to this layout.


texts: Ideal Voltage/Current Source Circuit Analysis

texts:
I am trying to understand what it going on in this circuit diagram and how to go about solving this problem. I am told to find Vx given that the current in the central wire is zero. Does this mean that I can interpret the circuit as if the center wire (in which the current is zero) isn't there?

I think that I am still confused about how ideal current sources behave in circuits -- how to calculate voltage across them, whether they have resistance and how to calculate it if they do.

Currently, the only way I think I can think of solving this problem is by interpreting the diagram as if the center wire is not there, and then finding Vx such that 4mA passes through the 1k, 5k, and current source in series.

Any help would be greatly appreciated!

-Matt


texts: If a wind farm is connected to grid so as to transfer any excess power, how to make sure if power flows from turbine to grid and not from grid to turbine? One possibility is turbine could act as a fan by absorbing power from grid.


texts: Comparing different through hole matched BJT options for exponential voltage to current conversion

texts:
I have an interest in analog audio synthesizers and I'm in the process of analyzing and prototyping vintage synth VCOs in order to get a grasp of their inside workings. All schematics I've looked into so far like MFOS's VCO, the Bergfotron advanced VCO, Jim Patchel's No tempco VCO(see page 5) and the ASM-1 VCO use a matched BJT as their exponential converter (a 1V/Octave convention is widely used in analog synthesizers). Its task is to convert a control voltage (CV) exponentially to a current driving the oscillator core.

Now, some of these chips like the intersil CA3046 that I'm currently using are obsolete, the MAT03 is scheduled for obsolescence and who knows what happens in the near future...

That's why I want to compare my options and learn how to substitute one with the other, altering the original circuits if and as needed.

A search on mouser revealed 2 possible series. 3xxP14-U by THAT and MATxx by analog devices, the second being more or less 4 times more expensive than the 1st considering they are dual ICs against quad. The other obvious differences is VCBO which is 9V higher for the MATxx series, CE saturation voltage which is 50mV for the 3xxP14-P and 120mV for the MATxx, DC collector current and gain bandwidth product.

This got rather confusing for me when I started looking into their datasheets because (I need your verification on this) I think they are expressing the same quantities in different ways. Nevertheless, I'm feeling a bit lost and that I don't know exactly what I'm looking for.

So to make this as clear as possible, I would like some help understanding:

What are the most important factors when comparing substitute matched BJTs (what to look for in the datasheets)
How to deal with differences between parts (scaling input and output Vs and Is) and if this is at all possible
Are there any 'out of the box' devices that perform exponential voltage to current conversion at the 0-10V , maybe 0-12V range or maybe +/-5V (I would love to give you a current range but i haven't managed to calculate the expected output current values)?


texts: ESP32 ADC not good enough for audio/music?

texts: I've heard that the ESP32's ADC isn't "good" enough for audio purposes. It's a 12 bit SAR ADC with a sampling rate of 200 ksps which is much higher than most consumer products use (44.1 kHz). Does 200 ksps not correlate to a 200 kHz sampling rate. I couldn't find much in the datasheet when it came to calculation times. What am I missing?


texts:
I recently started a project and decided I required a PIC24E. I've been looking for resources to use an Arduino or Serial port to program the MCU, but none of the articles I found support the PIC24E.

Another thing I noticed is that these resources are abundant with providing support of PIC "F" models, such as PIC16F and PIC18F.

Here are the resources I am reffering to:

http://www.winpic800.com//index.php?option=com_content&task=blogcategory&id=18&Itemid=64
http://www.ic-prog.com/
http://arduino.cc/forum/index.php/topic,92929.0.html
https://sites.google.com/site/thehighspark/arduino-pic18f

I was wondering, why is the "F" model so popular?
Is it a coincidence that this model is popular among people who program their PICs with Serial ports or Arduinos?


texts: What is the name of the sensor that most inkjet printers use to keep track of the print head's position?

texts:
I've been trying to build a cheap X-Y-Z table using mainly bits of old CD drives and printers I've got lying around. Since the printers already have a good single axis I would like to be able to, rather than having to buy a stepper motor and rebuild it, just repurpose the optical tabe the printer uses to keep track of the print head's position and keep the same DC motor. I've been able to extract the sensor the printer uses without damaging it or any part of the track, but I've been unable to find what the proper name of this sensor is, let alone documentation describing how to use it.

The sensor in question is in a black, plastic housing with a slit that the tape fits into. There are six pins on its underside that solder to the board, two of which come from something on top of the slit and four from something underneath. The black housing is labeled '6536' on top and '15' and 'DSO' underneath. My first guess is that the top is an LED while the bottom is a light sensor of some kind, but beyond basic checks (applying a weak current through the possible LED in either direction did not cause it to noticeably light up) I'm not sure how to get any more information out of it safely.


texts: Transient time of a circuit and pulse width

texts:
I'm taking a course on Analog and Digital Circuits, and in the course material, in a passage regarding pulse signals, I found the following statement:

  Relation between the transitory regime of a circuit and the pulse signal

  Any state switch of a circuit implies generation of a transitory regime, taking a bounded time
  For a pulse signal, the swing times between levels must be lower or comparable with the period of the transitory regime
  For a pulse the repetition period T must be much greater than the duration of the transitory regime

(emphasis mine)

But I didn't understand why the second one would that matter for a simple diode, which was used as an example.


texts: why torque motor doesn't overheat if stalled for very long?

texts:
why torque motor does not overheat if stalled for very long,
could some explain how. If used in servo mechanisms where cooling(nature or forced) in nearly impractical.


texts: Would my Audio LED display circuit work?

texts:
Would this circuit work? It's supposed to display the frequencies of the audio signal connected using LEDs by driving them with an LM358 Op-Amp.
Edit: fixed the reverse polarity of U7
Edit 2: I made a sweep of the frequency response of the filter, seems to work


texts: I am trying to build a voltage buffer for a piezoelectric record player cartridge. The amp built into the record player doesn't provide the necessary impedance. I have tried multiple circuits including one I found here, an emitter follower, and an op amp voltage follower using an LM741. All of these end up with noise coming through louder than the audio itself. I have tried connecting the input and output directly on the breadboard in case the wires or breadboard were the issue, but it sounds fine when I do this. The issue only seems to occur when I put some kind of voltage buffer in place. I have tried powering the buffer from both the turntable's power supply and a 9V battery. The noise seems to come from the turntable motor, as it increases/decreases frequency as the motor speeds up/down. What can I do to eliminate this noise or troubleshoot the issue?


texts: Gain of common-emitter BJT amplifier with bypass capacitor

texts:
I have this common-emitter BJT amplifier:

simulate this circuit – Schematic created using CircuitLab

The text book says that with a bypass capacitor, the gain is -Rc/re, where Rc is resistor R6 and re is the internal resistance of the BJT. The internal resistance of the BJT is found by computing VE = VB - VBE (VB is found by voltage division, VBE is 0.7V), then IE = VE/RE = VE/R7, then re (internal resistance) = 25mV/Ie

Now I want to simulate this circuit and use simulated values to directly compute the gain by dividing the output by the input voltage, so I can compare with the theory, but I do not know exactly what is the input and what is the output. Are they taken right before and after the BJT, or right before and right after the caps, or...?

I have tried to take different combinations of output/input but the result does not even come close to the theoretical -Rc/re.

Any guidance will be appreciated. Thank you.


texts: feasibility of transmitting uncompressed 16-bit PCM audio through bluetooth

texts:
I wonder about the feasibility of this idea, and whether this is something worth doing more research on.

I am trying to send 16-bit 16 kHz single channel microphone audio via bluetooth, from one android device to another in real time.

For this I use the AudioRecord class to capture mic data in the transmitter phone. I capture 64 samples at a time (64 samples of 16 kHz audio = 4 msec) and store it in a short array. I have already connected the transmitter and receiver via bluetooth and I am running Google's sample bluetooth chat application.

What I want to do is send the 64 shorts as chat message to the receiver, and play it back in the receiver as AudioTrack.

For this I am assuming that getting the 4 msec worth of audio samples from AudioRecord and the time required to play them back in AudioTrack happen quickly.

Also I am assuming that all data I send through the Bluetooth chat app are using RFCOMM, although I haven't really found anything explicitly stating this. I have read after some google searches that Bluetooth's maximum data transfer capability is somewhere between 2 to 3 Mbps, and even considering a lot of this is used up by Bluetooth profile overheads, RFCOMM should have a data transmission rate of around 400 kbps (I only read this in someone's blog so might not be accurate and it's possible this is where I went wrong).

Audio at 16 kHz would be 16000 samples/sec, which is 16000 sample/sec*16 bits/sample = 256 kbps which seems to be lower than the maximum data transmission rate for bluetooth that I have been able to find online.

In my first attempt the received audio sounds very choppy and is completely unrecognizable. I have tried reducing the sampling frequency to 8000 Hz which gives similar results. Is what I am trying to do even possible using bluetooth?

I did find some sample code which transmitted audio over bluetooth using the Serial Port Profile, but there is a very long delay in the transfer and the app is prone is crashing, and sometimes the audio transmission just doesn't work. My question is not about just transmitting the microphone audio samples from transmitter to receiver, which I am fairly sure is possible, but about doing this in real time.


texts: Merging / Concatenating Buses in Altium Designer

texts:
In Altium Designer 14.3 I am trying to merge two 16bit buses into a 32bit bus with one of the input buses becoming the lower 16 bits and the other the upper 16bits of the output bus. Below is an image if my attempted method.

When I try and compile the document I receive the following error: Duplicate Net Names Bus Slice \Y[31..0]. I get how Altium thinks that I am trying to redefine the \Y net however I don't see a better way to merge the two buses together other than breaking out all the pins of the separate two buses and merging them together. This is how I would do the design if it were a FPGA HDL schematic.

How should I do this?


texts: what happens when transistors are interchanged in CMOS?

texts: A basic cmos inverter will have a P-transistor upside and N-transistor down side. what happens if we reverse the p and n transistors?


texts: Is this a parallel circuit? How can I tell whether it's parallel or not?

texts:
Is this a parallel circuit?  Can I collapse it and make one equivalent resistor of \$2/3\Omega\$?

Also, will someone confirm whether or not I got the right answers for the unknown voltages and currents?  \$I_o = 1.333\dots\text{A}\$, \$I_x=2.6666\dots\text{A}\$, \$V_o = 4\text{V}\$.

I found \$I_o\$ with current division: \$(1/3)\times(4) = 4/3 = 1.333\text{A}\$
and \$I_x = (2/3)\times 4 = 8/3 = 2.6666\text{A}\$

(Update: I see my mistake. I was multiplying by 4V instead of 6A when current dividing.)


texts: Problem with Tracing wire in Proteus PCB designer

texts:
I have a problem with tracing a wire with width of T200. Im using Proteus 8.5. I'll do it with no problem and no DRC and CRC error, but when i see 3D model i see some parts of the PCB copper that is incomplete.

and this is correct one.

can you guide me please?


texts: DFROBOT Gravity SEMG sensor component identification

texts:
Well, a wire got pulled, and a pin came off.
I have a DFROBOT EMG sensor that has a broken smd component. I need to identify what it is. The picture is shared.
I couldn't find a schematic so from what I can tell by looking at the PCB in hand,  it is a rectangle with four pins, each at a corner. Two pins at a side are connected to 3.3V and GND respectively. And the two pins that go out the other side, go on their own. I ripped out the 3.3V pin.
When I check the continuity from GND to the other two pins, none are shorted and the DMM gives a value of 713 and 570 respectively.
Furthermore. The two pins have a resistance of 1.2 megohm between them and the resistance between GND and the two pins are infinite if measured in one direction and 1.2 megohm if interchanging the probes.
From what I can tell, I think it's some sort of a diode. But I really need the help figuring this out. The component is about 2x2 mm.
Thanks.


texts: How do you use a fuse with a rating of Amp-Hours?

texts:
Sorry, this may be me being slow, but...

An amp-hour is 1 amp over 1 hour - simple enough. Now I have 2 fuses - one is rated in amps, the other in amp-hours. Can I I use one in place of the other? What is the ratings leeway?

In general, what should my approach be when dealing with amp-hours in design/troubleshoot terms? When should I use components rated in amp-hours in my designs? Which components are most often rated in amp-hours? When can I replace amp-hour rated components with amps?


texts:
What is this component, a capacitor, resistor or conductor?

I have a portable pH meter but cannot measure alkali/basa. I think the sensor working perfectly: out 0-5V equals 0-14pH.

I try to measure with omh scale, the result over 1M sometimes over 4M, when I measure with the  capacitor scale the result is 2nF.
I try to change with resistor of 100K, with a capacitor of 10uF but pH meter cannot measure.

Thanks