texts: Why is the load on a darlington pair put before the transistors rather than after?

texts:
Forgive my lack of understanding and if this is answered somewhere I have not found, but...
I have seen lots of answers with regard to how to use a darlington pair to switch, say, a 12V 1A load using a 3.3V 50mA signal (just an example, not all values are determined for my application,) but what I'm not clear on is why in the solutions using a darlington pair, the load is always placed on the high side of the transistor(s). While switching the low side is common and functionally fine, in my application, for safety reasons, I would prefer to switch the high side of the load.
So, is it ok to put the load on the output of a Darlington Pair Transistor?


texts: Final value theorem for transfer functions with more than one pole at origin

texts: One browsing Wikipedia for final value theorem, it is said that final value theorem cannot be used for transfer functions with more than one pole at origin. Why? Can you give an example.


texts: Polarity of the induced voltage on inductor for an applied magnetic flux according to the Lenz's Law

texts:
I'm trying to visualize the Lenz's Law on a practical inductor.

The Lenz's Law says that

$$ \mathcal{E} = -\dfrac{\partial \Phi}{\partial t} . $$

Now, assume that there is a magnetic flux inside the coil is in the given direction in the image below, and magnitude of this flux is increasing in time (i.e.; \$\frac{\partial \Phi}{\partial t}>0\$).

My two questions are:

What will be the polarity of induced voltage on the resistor? Please give an answer like "'A' will be more positive than 'B'.".
What will be the direction of current in the system. Please give an answer like "It will be in the 'R' direction.".


texts: Flyback converter primary and secondary sides power calculation

texts:
The problem is as below.

Input DC voltage is at 12V, transformer inductances are: Lp = 60uH, Ls = 240uH, switching behaviour is controlled by a single NMOS with switching frequency at 60kHz.

For ideal case, is it correct that power at primary winding is equal to the power at secondary winding, and that is the equation for this power.


texts: At what UART baud rate is hardware flow control required?

texts: At low baud rate such as 9600bps, I do not think hardware flow control CTS/RTS is necessary. I believe at higher baud rates, CTS/RTS will be necessary. What is this baud rate? Can one still do without CTS/RTS at 115.2kbps?


texts: Is there a board-to-wire header that accepts a female JST SM 3-pin connectors?

texts:
I've looked everywhere on Digikey and Mouser and can not find a compatible board-to-wire header that can accept a JST type SM 3-pin 2.5mm female that looks like this. ...

Are these connectors available?

These connectors are commonly used for WS2812B RGB LED strings.


texts: What is the difference between scalar array and vector array?

texts:
First question

Whether we declare the array as scalar or vector, we can access each element bit by bit. For example, we can declare two arrays below.

reg scalar_array[0:9];
reg [0:9] vector_array;

always @*
begin
  scalar_array[0] = 1'b1;
  vector_array[0] = 1'b1;
end

I would like to know if the difference exists between two declarations.

Second question

Also, when I declare the two-dimensional array like below, I could access the entire row using the indexing operator[] for the variable declared using a below syntax.

reg[X:X] var_name [Y:Y];

However, I couldn't access the entire row when I declare the array using the below syntax.

reg var_name [X:X][Y:Y];

I would like to know how this concept can be synthesized on the hardware, and if they are both synthesizable, what is the difference between them.

reg [0:9] vector_array_2d [0:15];
reg scalar_array_2d[0:9][0:15];
always @*
begin
  vector_array_2d[0] = 'd1;
  scalar_array_2d[0] = 'd1; //raise the error!!
end


texts: Detecting if 120v AC wire is live with a 2 or 3 VDC line

texts:
For a background, I have 3 DPST bistable (latching flip-flop) relays that I have 120VAC input and 2 outputs. On one side, I have a 120VAC appliance. On the other side I need to find a way to feed it back into a Raspberry Pi's GPIO pins to detect whether it's live. What is the simplest way to accomplish this? I thought about step-down transformers and induction, but the transformer would get expensive, since I can't seem to find any other way to do it besides chaining 120vac to 5vdc and 5vdc to 3vdc and I have no idea how to use induction.

UPDATE:

Thanks for all of your answers. The Bistable relay requires a 0.2s pulse to trigger to switch, so as long as the response time is less than or equal to that, it will work just fine. As such, using a cheap USB charger should work if @Transistor is correct in his assessment about ~100ms response time. However, it seems a bit hackish and I'd rather find something ready to be used in a DIY circuit rather than tearing apart the casing to extract the guts of a product.


texts: Correct EL Driver Rating for 8 Channel Sequencer

texts:
I'm trying to use an 8 channel EL sequencer (found here) to control eight 10-foot segments of EL wire.  I'm having trouble figuring out what the appropriate length rating is that I need on an inverter.  I've read conflicting opinions.  One states I need my inverter to handle the "total" length (in my case 80 feet), while another says it just needs to handle the longest strand (10 feet then).  Which is correct?

I'm looking at this one currently (rated 5 to 15 feet).  Is that enough? Or do I need to find one rated for at least 80 feet? Thanks.

edit

If I need an inverter that can handle 80 feet of EL wire then I'm worried that this will conflict with a sequencer.  If the sequencer turns off say 3 channels (30 feet of the wire), then my load would only be 50 feet I would think.  I've read that this is an issue because the inverter might break if I have less than the minimum load.  Is this the case?


texts: How can I reduce the RMS value for a bridge rectifier?

texts:
I need to reduce the rectified DC voltage.  Is it possible to reduce the RMS value after the bridge rectifier i.e before the capacitor? Practical value (at the capacitor) is 34 DC voltage. I need to reduce this voltage.

Input is 24 VAC, output should be at least 26 V DC.  Input voltage is fixed.


texts: How to find un*Cox from Cadence Virtuoso?

texts:
Suppose we are posed with a problem statement saying to design a CS amplifier with specific gain. How do I design,or how do I get to know the value of gm,un,cox of the mos technology i am using.
P.S: Designing is in Cadence Virtuoso


texts: How to fix a PCB design mistake after manufacturing?

texts:
Newbie 16 years old here.

My project is a mini robot with the pcb as the chassis, lipo battery with charger circuit, and infrared sensors. I used LSM6DS33TR for my I2C accelerometer and gyroscope with 10K "pull-up resistor" according to datasheet, and ATMEGA328P as microcontroller.

It is my first time to design my own industrial PCB board and manufacture it. I manufactured the PCB's with JLCPCB. After sending the files and waiting for delivery, when i spot a mistake from my design. I noticed that I haven't wired the pull-up resistors for my I2C bus correctly because they should be pulled-up to 3V3.

My Questions are:

How can I redirect connections or make modifications to make the SDA and SCL pull-up to supply voltage with PCB being manufactured already?
Should I change the design and manufacture another PCB? (Broke ):)

Here is the entire schematic diagram for the project I made:
(the i2c lines are encircled)

TOP LAYER: (GND Copper Plane)

BOTTOM LAYER: (3V3 Copper Plane)


texts: Self-biased JFET - Midpoint bias: Why set the drain voltage to one-half of it?

texts:
To set a midpoint bias, I understand that ID = IDSS/2 (and by equation, VGS = VGS(off)/3.4).
For calculating resistor values, why set VD = VDD/2?


texts:
I want to make a circuit where the power to mcu switches from mains transformer to dc battery when when mains power is not available.

The basic concept is to use a transistor to stay open circuit to keep the battery from supplying the mcu while the mains transformer is active.

Once mains power goes out it should make the transistor conductive and close the circuit with battery.

In a nutshell when mains power is on transistor is off and vice versa

A complimentary congiguration with pnp would have been ideal but I'm limited to using bc548 atm

Please guide me to the right direction


texts: High Resolution ADC for Noisy Sensors in Variable Conditions

texts:
Intro

In response to this question about adaptive amplifiers, It was recommended that in order to deal with variable conditions, it may be more economical to simply use an ADC with higher resolution so that I don't need to worry about amplification and I can do scaling in software.

Overview

I'm trying to design a data acquisition circuit for body mounted textile-based stretch sensors. The textile varies resistance as it's stretched (about 1 order of magnitude, 10k\$\Omega\$-100k\$\Omega\$ with 30% stretch). The exact ranges will change depending on how the textile is cut, whether it's soaked with sweat, the temperature, how old the material is, how it's mounted, etc. The entire thing needs to be as small as possible because it's mounted on the hand, so minimizing the number of components is a big plus.

Moreover, I'd like the circuit to be reusable for other applications that may have worse performance. For instance, if I use a cheaper version of the textile, my resistance range may be as bad as 100\$\Omega\$ to 300\$\Omega\$.

Signal Path

[textile] -> [Wheatstone bridge] -> [lowpass] -> [instrumentation amp] -> [ADC] -> [AVR]

Requirements

So, I'm looking for an ADC that will meet my requirements. The ADC should be:

16bits+
As easy to use as possible: much better if there is interface code already written for AVR/Arduino...
...yet at the same time as comprehensive as possible: I've seen some ADC's with lowpass filters and PGA's built in – all the better as long as it doesn't make configuration a pain
8+ channels, or if it's easy enough to implement, 2x 4+ channels. EDIT: If I'm using a Wheatstone bridge, perhaps I want 8 differential input channels (so 16 channels)...
I don't think operation voltage matters... (best if not above 5V)
Surface mount
Doesn't need to be cheap (it's a one-off)
SPI vs. I2C doesn't matter I think...
100+ Hz

Research

So far through Googling, I've found the following chips:

Linear devices offer various 16-24bit delta sigma ADCs, some of which I've seen recommended: http://parametric.linear.com/html/no_latency_delta_sigma_adcs?p=5312974
Microchip has a range of options, some of which I've seen recommended: http://www.microchip.com/ParamChartSearch/chart.aspx?branchID=11022&mid=10&lang=en&pageId=79
Analog devices have a number of comprehensive data acquisition chips with amplifiers and filters (no need for external signal processing stuff):

http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7783/products/product.html
http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7715/products/product.html
http://www.analog.com/en/analog-to-digital-converters/ad-converters/ad7709/products/product.html

I haven't looked at the TI chips yet...

and the following tutorials:

http://arduino.cc/blog/2010/11/29/tired-of-a-10-bit-res-hook-up-a-better-analog-to-digital-converter/ (LTC2400)
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1275676171 (TI ADS8341)
http://forums.adafruit.com/viewtopic.php?f=31&t=12269 (MCP3424)
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1248751435 (LTC2410)

Voltage Reference?

Finally, some people have recommended a precision voltage reference, such as the Analog Devices REF19x series. Do you think this is necessary? Resolution is definitely important for me.

Conclusion

Let me know if you have any recommendations! I'm also not sure exactly what I'm looking for, so tips on how to decide are also appreciated.


texts: I am working on a design using an Allwinner A20 SoC, but I am after quite a lot of googling, unable to find the Power On pin, or any pin that is normally used to initiate the power up, would it be safe to assume it will power up when power is applied to all Power pins?


texts: Explanation and solution of an error in Differential Amplifier Current Soruce circuit

texts:
So ive built up the following schematic as a simple current limit circuit. When the current limit is not in place, ie the PNP is conducting "fully", I null any offset errors in the Differential Amp (CA3140EZ Op Amp) which nicely matches the actual voltage drop across the Shunt Resistor and output of the Diff Amp (Pin 6). Everything works perfectly until the current limit kicks in; when this happens the Diff amp always outputs 10-15mA less than the actual Voltage drop across the Shunt. If i now lift the current limit again by increasing ISet the two outputs match perfectly again.
I have spent a lot of time finding the cause of this but to no avail. Can someone please explain to me what is happening and how i can remove this error?


texts: Why would I need a low-dropout regulator?

texts:
I am creating a device utilizing multiple components, all of which have an acceptable operaating voltage of about 5 V. One component has an operating voltage of about 6 V.

I am looking at relevant schematics online, and noticed that this device utilizes a component* I didn't think I needed (TPS763XX, a low-dropout linear regulator).

This is the first time I've ever heard of this component; I've done brief research on it and don't understand it much. Is it used to regulate input voltages for certain components (i.e. were my device to have a 6 V supply, this particular component would create an output of 5 V to be the voltage supply for those devices requiring it?)?

What is this component used for in general, and why does this particular application (a blood pressure monitor) require it?

*Reference component U1 in Table 2 at the top of p.17.

EDIT: fixed link


texts: Nor gate using photodiodes and transistors doesn't work correctly

texts:
I'm creating a circuit for a robot to avoid obstacles. It is created without using any ICs. When the robot meets an obstacle the LED (at the right side of the transistors) should be off because of V_CE is 0.7V and voltage barrier across the led is 1.5V.

My problem is when the robot meets an obstacle it just reduces the light intensity of LED. It means that my logic gate doesn't work correctly. What is wrong with my circuit?

I need to give the output into the opamp.


texts:
I am currently designing a test device for EC-motor drives. During the test I would like to 'switch' from one ECU to another so that the engine phases are switched to the other ECU.
My question: What is the best solution to realize the switches SW1-SW3?
Current ideas:

Relay (SPDT): Expensive, mechanical wear, only a few available for >48V >50A
N-Channel / P-Channel Mosfet Solution: Must be bidirectional? Possible?
Triacs?

Many thanks in advance!

simulate this circuit – Schematic created using CircuitLab


texts: 12V to 5V 3A DC-DC converter recommendations. WS2811 LEDS

texts:
I require to supply 5v to 50 LED pixels WS2811 from a 12V supply.
I have looked at many DC-DC converters and one thing in common is quite a low load capacitance. < 1000 uF and typically around 500 uF.
The spec sheet for the pixels recommends a 1000 uF at the beginning of the string.
I currently have a Murata OKX-T/5-D12P-C on the shortlist.
https://www.mouser.co.uk/datasheet/2/281/okx-t5-d12-33019.pdf
What is the prefered type of DC-DC converter for this type of project?


texts: Using an audio amplifier with differential outputs with headphones

texts:
I'm planning to use TPA2012D2 (http://www.ti.com/lit/ds/symlink/tpa2012d2.pdf) audio amplifier from TI from my headphone audio project.
This amplifier has a differential outputs for left and right audio channels.

My question is, how do I connect this to an headphone jack where I have a common ground for both channels?
Is it possible to use just the OUTL- and OUTR-, and ground the OUTL+ and OUTR+?

(This is the typical application schematic found in the datasheet)


texts: How to choose a collector resistor value for a common emitter circuit according to the output resistance?

texts:
For the voltage divider equation to hold, the output current must be made negligible relative to the current through the resistors.

IR > 10 Iout

I often see that, for the base biasing divider:

IR = 20 IB

I suppose the same conditions must be met also with the RE and RC but cannot find any guides verifying this.

Except when the Vc is almost equal to Vce and hits Vcc and the emitter resistor is momentarily off (almost off with the negligible reverse saturation current through the base-collector diode)from the circuit; RC and (RE+Vce/Ic) form a voltage divider (counting the RE and the transistor in series as one resistor and RC the other).

I know that RC must be as lower as possible than Rout to make the output behave more like a dead end in terms of current. But I don't know the practical rule of thumb for this if any.


texts:
To be able to connect some peripheral to digital input, I'm designing the circuit protection to avoid any possible failure due to over/under-voltage issue. So, I will add a clamp protection circuit.
The requirements I need to accomplish are:

Power Source (Vcc): 3V3
Max Voltage: 3V9 (3V3 + 0V6)
Min Voltage: -0V3 (GND - 0V3)
Max Logic input current: +/- 300nA

The circuit is next:

R1000 is added to limit the current to 10mA.
R1001 is added to limit the input current below 300nA.

My doubts are:

Might the circuit be modified in case it need to support up to 30V input?
Which would be the best option for both diodes (Forward voltage, breakdown voltage, forward current, etc)?
As digital inputs may need to produce a rising interrupt, will be better to add a schottky instead of a zener on D1000?


texts:
I am having a problem with identifying why a high voltage part of my circuit broke the low voltage controller. To start, the basic premise of the circuit is to take a very accurate 0-10V DAC voltage(VCTL) and turn it into 0 to 1000V. This was all done for me as I inherited the box of circuits. The schematic is below. There are two sides, +1000V and -1000 V. The problem is that the -1000 V had a short and when the selector(HV_Polarity_rotary) moved it to connect it to the output(HV-1), it was shorted to ground through C21 and R24. There is a DAC board connected at Vctl, and the negative side of that board is shorted because of this(the current going to the negative voltage of that board is 100x higher than all the other voltages). I checked all the paths to that Vctl and nothing is wrong with any of the ICs or resistors or capacitors.

I don't know what broke the DAC boards but could it be the shared ground? My only problem with thinking this is that only the negative side of the DAC boards is broken and I would think all of them would be broken if it was through ground. Here is the DAC board I am using. The schematic is on page 26.

I guess a TL;DR of it would be can a high voltage/current going to ground effect small ICs on that same ground.


texts: Why increasing bridge ratio improve efficiency?

texts:
From The Bonded Electrical Resistance Strain Gage by Murray & Miller where it says:

For operation with a single gage, and under some conditions with two
gauges, the efficiency can be improved by increasing the bridge ratio.
There is relatively little to be gained, however, but going beyond a
ratio of about 10, which will yield approximately 90% of the ultimate.
Many investigators prefer to use a maximum value of 5 which allows
considerably lower voltage for the power supply with an efficiency
that is above 80%.

What exactly does that mean? If I have a single strain gauge of \$ R_1 = 350 \Omega \$ and a constant voltage supply \$ V_{EX} = 5V \$,
Then for bridge ratio of 5:
\$ I_{\text{ratio of 5}} = {{V} \over {(R_1 + R_2)}} = {5 \over ((350*5) + 350)} = 23.8mA \$
\$ I_{\text{ratio of 1}} = {5 \over (350+350)} = 71.4mA \$ .
Since power dissipation is \$ \propto I^2 \$, the ratio of their efficiency and voltage drop would be
\$ { ({I_{\text{ratio of 5}}})^2 \over ({I_{\text{ratio of 1}}})^2} = {23.8mA^2 \over 71.4mA^2} = 11 \% \$
\$ { ({V_{\text{ratio of 5}}}) \over ({V_{\text{ratio of 1}}})} = {{23.8mA*350 \Omega} \over {71.4mA*350 \Omega}} = 33 \% \$
And for bridge ratio of 10 (\$ R_2 = 10 * R_1 = 3500 \Omega \$), I'll get
\$ { ({I_{\text{ratio of 10}}})^2 \over ({I_{\text{ratio of 1}}})^2} = {1.3mA^2 \over 71.4mA^2} = 0.03 \% \$
\$ { ({V_{\text{ratio of 10}}}) \over ({V_{\text{ratio of 1}}})} = {{1.3mA*350 \Omega} \over {71.4mA*350 \Omega}} = 1.8 \% \$

If I go for a ratio of 10, the strain gauge \$ R_1 \$ dissipates only 0.03% power than that in a bridge ratio of 1 - hence the circuit has reached an efficiency of 99.07%! That certainly not relatively little to be gain ... going beyond a ratio of about 10 stated in the textbook. I think I'm misunderstanding something here.

At bridge ratio of 5, the voltage drop of the strain gauge \$ R_1 \$ is 67% lower than its drop in a 1:1 bridge ratio, but that has no implication that it allows considerably lower voltage for the power supply other than knowing it will take on a lower voltage drop just because a bigger resistance consumes a larger share of the supply voltage. Again, what does that statement means?


texts:
How can I achieve 10k resistance?

I just got my photocell in the mail, totally forgot the 10k resistor. The thing is I have a lot of different resistors in the span 1, 10, 27, 37,56, 68, 82, 100.

Is there a way I can put them in parallel/series and make a 10k? Or do I need a 10k? How does it work?


texts:
I have the need to write a bootloader program on an AVR microcontroller (Atmega32) in order to enable self-programming. I have read various resources on the topic of bootloaders and have come to the following conclusion:

The first address of flash has stored information about where the start of the bootloader program is. Thus, when reading from flash, execution will begin at 0x00 and jump to wherever specified in that location to the bootloader.

The bootloader program must then "listen" for incoming data on a pin. If information is found, perhaps after a specific data frame consisting of a command regarding a reprogram sequence, the bootloader begins saving the incoming data to some other location in flash. Following the end of data transmission, the bootloader must then jump to the flash address associated with the first byte of information during the reprogram phase and begin execution.

It is my understanding that this sequence of events, listening and reprogramming, happens upon every RESET event. If no information is found to be incoming, then normal execution of the code already present in flash (beginning at the same address the bootloader would begin saving to) begins.

Basically something like this:

Given that I know the process of this very basic bootloader program, where might I begin learning exactly how to write this program specifically for the AVR architecture? If size is a concern, I understand these programs may be written in ASM. Considering that I do not know enough ASM, let alone the instruction set for a given controller, I am most likely going to write this program in C.

Any suggestions/resources?

Thank you


texts: Can you help me? Thanks for the answers.


texts: What are the current sense resistors for in the "typical application" on the LTC4370 datasheet

texts:
Datasheet Link Here <==

This is the"typical application" from the datasheet

Short description of my understanding of this ICs operation My understanding of this IC is that it takes two same voltage power supplies and combines their current output. If one supply's V starts to droop, the IC senses that change from Vin1 (or2) to OUT1 (or2), and drops the voltage of the other supply using the MOSFET to continue voltage matching.

I'm attempting to combine 2 outputs from two USB battery packs.

My question is mostly about the current sense resistors, I believe that they are supposed to create a drop in the voltage in order to know how much current is passing, but why is this necessary? When one of the battery's voltage starts to drop, the Vout sense pin should see it and drop the other battery's voltage in kind. No resistance needed? Why does it even need to know how much current is being sourced if all it has t do is match voltage?

Also, compared to the 2mOhm resistance of those resistors, the resistance of the MOSFET and wire connection is much higher. The resistors are also placed after the Vout sense pins on the IC, so how do they do anything?

The goal is to create ~24W and put it through a DC-DC converter to charge my laptop. If there are any obvious problems with this idea, it'd be much appreciated if you point it out! I'm about to buy all the components.


texts: How many wires can I safely fit into this screw terminal?

texts:
I have about 40 positive and 40 negative 18 gauge wires that I am trying to connect to one DC power source.

I have a few terminal blocks to achieve this. Each terminal block has 2 rows of 12 positions and I am trying to minimize the number of terminal blocks I use to wire everything together.

Below is a photo of the type of set up I am going for. My concern, however, is that stuffing too many wires into a single terminal hole is probably an unsafe practice. Is there a best practice for how many wires I can safely stuff into terminal block screw holes? I know the wires must not be tinned but is the number of wires I can fit into a terminal block hole affected by whether the wires are stranded or solid (I have both and wonder which is preferred)?

Also if anyone has a better way to wire these connections together I'm all ears, I feel like there must be a better way of doing this...


texts:
I'm trying to generate depth images from stereo camera at more than 1080b resolution at 60FPS. The problem right now, I would like to do deep learning on that raw data from the video camera. Right now I found a solution from lattice that can take MIPI CSI from stereo camera and output a USB3 signal at max bandwidth 2.5Gbps. That's fine, but I would like to do deep learning on that raw data, so I thought about using Jetson but it's ethernet can handle 1Gbps.
I'm trying to look for a method that can let me stream and do depth imaging on a kit that can do deep learning. I tried to search a lot but couldn't find any solution out there, all of them are limited bandwidth.


texts:
Is it possible to hide particular airwires in eagle, without hiding all of them?

So if there's a net I am not currently interested in, but it has a lot of connections, confusing where other airwires go, I can hide it. I am wanting to do this for GND and +V but, don't want to run ratsnest resulting in a pour.

Any ideas?


texts:
I have a led driver (LPC-20-700) that is 30V and 700mA, which makes it 21W.

I run 10 leds (≈ 2.8V drop) in series with it and it is an constant current device. If I plug my multimeter between, I do get the reading of 700mA.

When I use a little device (AC power consumption meter?) that checks the power consumption of devices I plug into DC, the reading tells me it's only 5.6W.

I can't wrap my head around what I'm missing here. Why are the numbers not equal?


texts: How to find he Kpn,Kpp parameters for the given 130nm CMOS models using LtSpice?

texts:
The model file is present at http://ptm.asu.edu/modelcard/2006/130nm_bulk.pm
I tried finding the value of unCox by finding the value of drain current, gate-source voltage and the threshold voltage for the nmos, but I got varying results for different simulations, varying from 500uA/V^2 to 1500 uA/V^2. Same variation was there in the pmos simulations too. is there a way to find the value of unCox and upCox from the model files?


texts: Cannot extract expected values in VHDL at first clock cycle

texts:
The VHDL design below is supposed to extract the Nth bits from the four values x_0, x_1, x_2 and x_3 and create a new value at every clock but this is not happening.

Find below the design and the generated output for a few forced values for x_0 = 1100, x_1 = 0100, x_2 = 0010 and x_3 = 1011.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.NUMERIC_STD.ALL;
entity gen_input is
    port (x_0,x_1,x_2,x_3 : in std_logic_vector(3 downto 0);
            y : out std_logic_vector(3 downto 0);
            clk : std_logic);
end gen_input;

architecture Behavioral of gen_input is
signal i : integer := 0;
begin
    inst_process : process (clk,x_3,x_2,x_1,x_0)
                        begin
                        if(clk'event and clk='1') then
                            if(i < 4) then
                            y <= x_3(i)&x_2(i)&x_1(i)&x_0(i);
                            i <= i + 1;
                            else
                            i <= 0;
                            end if;
                        end if;
                        end process inst_process;
end Behavioral;

The output generated:


texts: What can be the problems or danger of running a motor slower by simply lowering the dc voltage supplied to it?

texts: Any suggests explaining the consequences of slower a motor by lowering the DC voltage ?


texts: How do I attach my MEMS device to a PCB? I do not have access to a die bonding machine

texts:
I want to connect the MEMS device electrically to a PCB through Au wire bonds. I have designed the PCB for the MEMS device to mount on. I would like to know if there is any way I can align and bond my MEMS device to the PCB if I do not have access to a Die bonding machine.

Any help and ideas would be appreciated.


texts: What's the difference between a "Switching Regulator" and a "UBEC"

texts:
I want to regulate the voltage from a battery down to 5v to power an Arduino and a Wi-Fi webcam. I’m not too keen on a linear regulator as a lot of power is wasted, so that’s led me to look at switching regulators. I’ve also stumbled on UBECs, which seem to do a similar thing.

The two components I am looking at are these:

Dimension Engineering Switching 5V Regulator 1A
Hobbywing 3amp UBEC

What's the main difference between these? Is either one more suitable for my purposes? My load will be under 1A.


texts: I'm recent graduate from top 20 school with bachelors in Electrical Engineering with a decent GPA and fairly good theoretical background. In college I pretty much did what I was told to do, like build and test circuits that were given to me by the professors. I took some higher level courses where I simulated circuits around some given specs. But in the working world I'm having difficulty determining what components I will need to use( for example adding capacitor or a diode) to design a circuit, or just designing anything simple. I guess I have very little ability to think practically. What steps do you think I can take now to become better at thinking practically and become better Electrical engineer? What steps did you take to develop that skill?


texts: Is Inductive Kickback Protection not necessary for AC?

texts:
For DC inductive loads, typically a flyback diode is placed over the motor so that when the current changes instantaneously it doesn't have a chance to build upon the switch contact and then create a spike next switching instance.
However, for AC is typically no protection needed?
For example, if I have an inductive motor that runs on 240Vac (max power of 590W with a current draw of 2.46Arms (at this 590W)) and which is being switched by a relay, does no protection have to be implemented for it? I looked at implementing either a snubber network or a MOV but the engineer I was talking to said it wasn't necessary (and if it was we could add it later)

Hence when in AC do we actually need to implement inductive spiking protection. Also why always is the protection circuits over the relay contacts, unlike DC where for an inductive load it's across that load.
In AC does it not matter when compared to DC since typically AC is switching at a fast rate compared to DC where it is either on or off. As in it doesn't decrease like a sin wave whereas in AC does


texts: Should I add something to prevent kickback on this LED circuit?

texts:
I am new to building circuits.  I am running the following LED circuit:

When I plug it in, there is an occasional "pop" of the LED.  Does the circuit need something like a diode to prevent a current kickback?  Or something else?


texts: Wall power socket outlet: square or sine wave?

texts: Power station alternators, do they produce pure sine wave power? If so, then any rotating generator must produce pure sine wave power. Irrespective of the kind of AVR it has. Is this correct?


texts: Bistable Multivibrator using discrete transistors

texts:
I am trying to understand this circuit but as of yet I still have a number of gaps in my reasoning. So far I have deduced:

(assuming TR1 is ON and TR2 is OFF)

left hand side capacitor charges towards 0.2-Vcc since Vc1 (voltage at collector of TR1) is tied to 0.2V due to transistor being ON (if
trigger input is at Vcc during steady state)
right hand side capacitor charges to a small voltage (difference between Vcc and the voltage at Vc2 (voltage at collector of TR2)
which can be worked out using superposition is very small)
upon negative edge trigger bases at TR1 and TR2 are pulled down since capacitors cannot handle sudden changes in voltage -> hence D1
is turned ON thus turning OFF TR1 --> Vc1 is no longer tied to 0.2V, goes to approx Vcc thus turning on TR2, Vc2 is now 0.2V.

These are my gaps in reasoning:

What is the role of the 220K resistor?
How the capacitors charge/discharge, to what voltages, when do they stop charging/discharging?

thank you for your help!


texts: potentiometer burned up on a 9v VCF circuit (audio)

texts:
I built the top circuit in the schematic below. First I breadboarded it and it worked great. I swapped the 10k resonance pot for a 5k as I didn't have any 10k trimmers handy and used 1000pF cap instead of a 500pF for ground.

The breadboarded circuit worked great. It's a voltage controlled low pass filter, like in a synthesizer. Plugged a guitar in and it sounded great, good sweep from the 100k frequency pot, resonance range with the 5k pot was good. The 1M input trim was plenty to take the higher output of a synthesizer down to a level which wouldn't overload the filter.

Then, I created the circuit on veroboard. The only thing I changed here was switching the little ground capacitor from my 1000pF to a 680pF. As the schem recommended 500pF and I'd used 1000pF with decent results, I figured a value between that wouldn't be too bad.

I built the circuit. Connected a battery, and heard sound. It sounded good. Then when I moved the 100k frequency pot (at this point a small trimpot), it started smouldering and smoke came out. I immediately unhooked the 9v battery. I thought maybe I had a bad pot so I switched it for another - this time a proper 16mm - Same problem. I saw red light inside the pot and lots more smoke this time.

This wasn't long before I had to go to bed, so I unplugged everything and left it. Can anybody tell me what I might have done wrong in order to make this happen? It worked fine on the breadboard. I've built a lot of circuits and I'm used to debugging circuits that don't work at all or sound crackly, but I've never had a fire before!


texts: LCD 16x2: circuit to adjust the LCD backlight by a PWM signal

texts:
I am testing a lcd 16x2 whith msp430g2553. I am controlling the backlight by PWM signal. I am using the P2.4 as output generating a PWM signal. I have connected the anode directly to pin P2.4 of the microcontroller and the cathode directly to GND. In the datasheet, (msp430g2553 on page 24) specifies that the maximum output is 6 mA and, on the other hand, on the LCD datasheet, LCD Datasheet, on page 32, the typical consumption is 32 mA. So ... Why it works if you can only drain 6 mA? Would it be more correct to put a transistor as shown in this circuit?

simulate this circuit – Schematic created using CircuitLab

What should be the value of R1?(The battery voltage varies from 4.2 to 3.3V) I can not find that information in the LCD datasheet, surely because I do not know what parameters I have to analyze.


texts: Why should Vbb not exceed the barrier potential values?

texts:
This has been mentioned in the book

The voltage VBE across the forward-biased junction is very low (for a germanium transistor, VBE = 0.3 V; and for silicon transistor,
VBE = 0.7 V). This requires that the battery voltage Vbb must also be of the same order


texts: What electronic component can interrupt a powered circuit?

texts:
I have an IoT project in which I want to leverage existing bicycle LED lights, which have their own battery power. So, rather than using the current from the microprocessor to power the lights, I just need a way to wire my logic board to the bike light and control the on/off of the light.

I don't have an electronics background, so this might be a very elementary question. Is there an inexpensive electronics component that I can somehow wire or solder onto the bike light that can be controlled by another low-voltage circuit?

The ideal component would be able to switch rapidly on and off, preferably without sound / mechanical parts. I'm envisioning wanting to strobe the lights quite rapidly, again, controlled by the logic board.

If there are more than one kind of component, which might be the best for a small, DIY wearables project? IE: low-cost, easy to hook up, easy to source.


texts: Power consumption while using micro SD card with microcontroller

texts: Micro SD card to log reading from four force sensors connected to the microcontroller. Controller logs reading to the SD card every 15 minutes and goes to sleep.


texts: Can two mosfets (p&n, some characteristics) be used as current sources simultaneously? And what happens if the Vgs voltage change?

texts: Can two mosfets (p and n type with some characteristics) be used as current sources simultaneously? And what happens if the Vgs voltage change in just one of them?


texts:
For my research purpose, I am planning to design one power amplifier (basically, a current amplifier) with the following specification-

Frequency range: 0-100MHz (or at least 0-30MHz)
Output voltage: 30Vpp
Minimum output load: 3Amp
The input current is expected to be very low as it will be feed from a simple function generator (max output current is not specified in the function generator manual, but I think, they should be less than 30mAmp)

Initially, I was planning to use an RF op-amp but later realized, none of the commercial op-amps can drive such high current. What would be the most optimized design for this circuit?


texts:
I am looking to buy an oscilloscope that will last me a few years. Application is everything but RF: digital and analog with as wide a frequency range as possible/affordable. I would like to buy used, but I would prefer Craigslist in the NYC area to Ebay, so I can check it out before I pay money. Yes, I know Ebay has escrow and if the pickings are too slim on Craigslist I'll go that route. I need something that will allow me to do repair and testing on mixed (A/D) systems in the medium-to-near term. My questions are:

What is a good entry level-price range? Barring any definite statement, how much will I spend per, say, 500Hz additional frequency range?
What features should I look for? Again, what is the price point on each feature?
What is a reasonable minimum I should expect to spend?
If buying used, what tests should I perform before paying?


texts: PoE Design for Camera Interface Isolation Question

texts:
We are designing a PoE design to power our camera. The block diagram below is the basic design we are planning to implement.

I want to get some advice to make sure we will not be damaging our camera or harming the user before going any further. From my understanding the PoE Magnetics will isolate the earth ground thus after the PoE Ethernet Magnetics, there is a different ground lets call it ground A. The PoE PD interface IC has a DCDC converter that will output 12V, I read that it is a good idea to add an isolation transformer after the output of the DCDC converter to keep anything downstream of the transformer protected.

If I add the isolation transformer then the ground to my camera is different from ground A, lets call it ground B.

I have two questions:

The MDI Pairs will be going directly to the ethernet PHY on the camera. Does it not send ground A to ground B directly? Ground A and ground B will be the same because of the MDI pairs going to the PHY on the camera. If this is the case, would it not defeat the purpose of the isolation transformer?
Our camera is mounted against a metal chassis that the user will touch when connecting power. What effects will this have on the user and the camera since the user would have a different ground than ground B. We want to make sure the camera does not get damaged.

Please feel free to provide any suggestions or improves to the design to better protect the camera. Thank you in advance for any help or suggestions. I really appreciate it!


texts: How does the D Flip Flop work and WHY does it hold its value?

texts:
I'm trying to grasp and understanding of electronics hopefully to work my way up to building an 8 bit computer.

I'm currently digging deeper into Flip Flops, and rather than taking them that they 'just work', could somebody explain to me WHY Q & not Q hold their values based on the following schematic?

I have drawn this schematic out by hand, following it with inputs each time, starting with 1 & 1 for D and CLK, then removing CLK to 0 as it's edge rises, but I always come out with 0 in my hand workings, however I have physically constructed the circuit and it operates as expected.

So can anybody explain HOW and WHY Q holds its value?


texts:
I am trying to develop a bench power supply. Now, before going on, I do realize that there are really cheap commercial ones available. I have two. I want to develop one my self.

The way I have thought it up: Step down transformer (not center tapped or anything). This will yield a small AC voltage and give me isolation.

I will then rectify that AC into DC and have a smoothing cap to deal with the ripple caused by the loading.

With the transformer, I get isolation. This means that my power supply will be floating. At this point in my design, I am trying to nail the basics down so I am not focusing on capacitive coupling to Earth or Resistive coupling etc.

So with a floating power supply, lets say I am trying to get rectified 15V out. This means that I will have 15VDC from DC Vin to DC Vreturn. But this 15V can be sitting way up in air (since its floating).

Now, when I, for instance, will probe it with a o-scope, I will effectively reference the return of my floating+isolated power supply to Earth (due to o-scope ground connection) and that will essentially bring my 15VDC to earth level from high up "in the air"

The issue: Will o-scope probing any of this design and/or any circuit that will be powered with this power design, cause sparks to fly everywhere? I wont think it would but I dont have a lot of experience with AC rectification (but read up on tons of stuff and simulated my power supply design to my hearts content). DC voltage, I can relatively handle that better

My main point is safety becaz I want to live!.

This maybe a later point to tackle (referring to an earlier statement): I have isolation via step down (non-center-tapped) transformer. Why cant I take a separate earth connection and tie that to the DC return of my power supply (via 100K or 1MEG resistor) and effectively reference my floating power supply to Earth. This way it wont be floating in "mid air"

Thanks for looking guys!


texts: Resistance between VCC and GND drops to 3k Ohms

texts:
I am kind of lost because of this problem.

When my board is connected to my power supply and up and running the resistance between VCC and GND is at about 18M-Ohms.

As soon as I power the board off, and it's no longer running, the resistance between VCC and GND drops slowly to about 3k-Ohms, then stays there.

What could be causing this?


texts: How can I make LEDs brightness more uniform vs. battery consumption?

texts: I have a PCB that has an array of indicator LEDs that blink for about 20 minutes per day. With fresh batteries (2xAA in series, 3 V), the LEDs blink brightly. Once the battery voltage goes down the LEDs become more dim. Is there any way to keep the luminous output of the LEDs more constant as the battery voltage goes down?


texts:
I'm currently working on a hobby project that uses a MS5540C.
It will basically measure the water depth and temperature.

My general thinking was to encapsulate the whole thing (except the sensor) in wax to make it water proof.

Could I use epoxy instead? What general consensus?

added:
The sensor will be dropped to at least 10m - 20m. I'm still playing with the idea of having the sensor...or the whole device (sensor ESP32 and battery) submerged.


texts:
We have just recently bought LED lighting and transformers from a local store. After installing, there's a noticeable flicker, most notably in the "little room" where you have ample time to look (and get annoyed by it).

I have already switched that single LED with another one to verify it's not a defect LED. Now that I'm convinced it's not the LED, I started looking for possible causes.

It seems that this might be caused by not using the right transformer. As I'm just a layman and before going to my local seller to confront him with this, I'd like to be sure I'm on the right track.

Technical details

The transformers are Niko ere 320-00002. and the LED lights are Lightplus Megaman .03285 12V 8W.


texts: Boost the signal of an FM transmitter using an “emitter follower” transistor

texts:
EDIT:
I've seen an alert under my question:
“Please clarify your specific problem or add additional details to highlight exactly what you need. “

Maybe this is due to the fact that I'm not very good to express myself in English, I'm sorry; I'm also a novice about these subjects: so, again, I apologize for my mistakes with the language and for my schematic.
So, considering my exposed limits, I underline the part of my question where I stated “However I have some exact questions about” with a list of four question about the problem which I encountered: I asked If i correctly designed the amplification stage and if there is a better way to amplify the output of the oscillator.

Thank you all for your kind understanding.

I start by saying that I'm doing my “experiments” in a building located in a rural location and that, however, local laws allows to use low power rf transmitters.

Well:  since I need to  transmit an FM signal to a distance of about 30 feet inside such building, and the output signal have to pass through the walls, due to the fact that I don't have the space for a longer antenna, I was thinking to implement an amplifier stage on the output of the transmitter.
The following image shows the full schematic:

Where the amp stage is still not present, and on the base of Q1 there will be a female jack where to  inject the audio signal.

By a search on internet I've found that there are many similar circuits where the amp stage, most of the time is made using a “common emitter” transistor instead of a “emitter follower”, but some of them (few), however, rely on the emitter follower. I choosed the emitter follower configuration because I figured out that the emitter follower has a lower gain (usually almost equal to the input) and so for avoiding to exceed with the output power.  I calculated the values of R4, R5 and R6 looking at the BFR36 datasheet and then I've found an online calculator  where I inserted these values to get the values of these resistors.

However I have some exact questions about:

1) Is the emitter follower shown in my schematic, correctly designed? I have some doubts about the resistor R4 (maybe the value is too much great?)

2) Are R6 and R5 really necessary, or I can just leave R6 and get rid of R5?

3) Will be able, the amp stage showed in my schematic, to boost however the output signal in terms of strength and distance? I mean: is possible to estimate the power boost which I will get?

4) Can someone suggest me some improvements to the amp stage of my circuit or suggest me a different approach, maybe using a common emitter configuration?


texts:
I am studying analog design, and my instructor told me that you could determine whether or an amplifier is stable without knowing the transfer function, or the circuit diagram, just by examining the Bode plot.  Below is an example of an unstable system.  He claimed that it is unstable because there is non zero gain at the 180 degree phase shift point.  My understand is that this only unstable if there is feedback, which we don't necessarily know.

My question is this: How do we know if the system is stable from just the Bode plot?


texts: NPN Transistor in common collector configuration, Vout varies

texts:
I am trying to make a power supply which gives a constant 5V at output with a current limit of 1 Amps. I am using D1047 NPN transistor in common collector configuration, with 5V (low current) voltage from zener diode at the base, and 20 rectified AC from the transformer at the collector.

The problem that i face is that the voltage across the load varies with the change in current, even though the common collector configuration is supposed to give unity voltage gain.

Edit: Circuit Updated.
Voltage across the zener/base of the transistor stays the same. But Voltage at emitter decreases when current through increases.

Input is 40V peak to peak sine.


texts: Do I need to double the voltage with double the motors?

texts:
I am totally new to electronics.

Let's say I am building a DC circuit with a motor using 6V taking 1.28A.
Now, if I build a circuit that uses two of these motors, will I power the circuit with 6V and the circuit will use 2.56A or will I need to power it with 12V and the motors will use 2.56A combined or what?


texts: Stepping down voltage 120 VAC to either 110 VAC or 117 VAC

texts:
I'm a vintage radio collector and I have on my benchtop a Variac that I use for testing out radios.  I wonder if there's a way I can put together something that I can either put inside the radio chassis or in the cabinet area of the radio that would allow me to take the 120 V AC mains and drop it down to either 110 V AC or 117 V AC.

I know there are buck/boost transformers out there but nothing that seems to quite fit what am looking for.

They either allow for other types of voltage reduction that would not be applicable for these radios.

I estimate that the amperage would be probably at least one amp and maybe 1.5 when I turn up the volume on some of the sets. Usually the AA5 would draw probably less than one amp while the other larger vacuum tubes complement radios would probably draw more than 1 amp. I also have discovered that some vintage radio restorers use wire wound resistors that give off wattage and heat and I don't know how to calculate what I would need those resistors to be.

I appreciate any recommendations that may be sent my way.


texts:
It's about an year that I'm using TVS diodes to suppress spikes from the AC motors (240V - max 240W) that drives my roller shutters and protect the solid state relay that actuate the motor.
What is unpleasant is that I got a diode failure every few months (at least 2 times a year).

Is there something I can change to avoid this kind of hardware failures?

At the moment this is my configuration:

TVS diode is a 1.5KE440CA so 1.5kW power dissipation, 376V working voltage, 418V breakdown voltage, 776V clamping voltage.

The relay is a SSR-40DA (40A, 380V)


texts: Is there an intuitive explanation of the classic edge-triggered flip flop circuit?

texts:
I figure there must be a way to understand it in terms of the three underlying latches somehow locking each other out, but I'm not getting it.

Is there a way to understand the edge-triggered flip flop circuit other than trying all the combinations and seeing that it works?

(Diagram from Wikipedia, CC BY-SA 3.0.)


texts: How to size a capacitor charging resistor?

texts:
I'm trying to size a set of resistors for charging a capacitor. The source is a 500V 60Hz AC supply.

The initial instantaneous current is 0.5A sizing the resistors at 125W each. That seems too high because the current decays very rapidly. If the resistors only need charged every 3 minutes or so, how would I size their power requirements?

simulate this circuit – Schematic created using CircuitLab


texts: Impedance of a function generator when off

texts:
I don't have a function generator at my disposal right now. I just want to know what's the typical resistance between + and - terminals of a function generator when it's not putting out a clock?

Thanks


texts: How to decided which bridge rectifier to use?

texts: I am making a torch without batteries ie. It has a neodymium magnet in a 1" PVC pipe with 1000 turns of enameled magnet wire and generates 4.4V AC easily, then I'll put the rectifier and then connect the rectifier to a 5.5V 1F super capacitor which has two 5mm piranha LEDs connected to it via a switch. So now I can't decide what bridge rectifier to use ? I have 1.5 A rectifiers, so would they work ? If not then what should I use ?


texts: Why do we divide by slip in the Rotor equivalent circuit for an Induction motor?

texts:
I was reading this article and everything made sense until the equivilant circuit for the rotor was divided by the slip s. I understand that the current in the circuit would remain the same, but it seems that both the power delivered and how its distributed would fundamentally change. Without dividing by s, the power in being delivered would be $$sEI$$and we wouldn't be able to rewrite $$R/s$$ as $$R+\frac{(1-s)}{s}R$$

Since the resistor would remain as R. Why do we divide by slip and what makes the two situations equivalent?


texts:
I am truly lost. I need some help and a redirection. I am trying to make a chromatic tuner using AT89C2051. My project would only be from C1 until B5.

The signal would be from a cable or stereo jack.

I will be using the ADC0848 for the conversion.

I've been reading up on how frequency works but I can't seem to understand a lot of things. If my ADC and MCU are only 8-bits. How would I determine the frequency of the input in the code or inside the MCU?

I'm sorry if this is a very dumb question. I'm not an engineering student or anything.


texts: Dry or wet etching in fabrication cmos chip?

texts: What types of etching are used in conventional chip fabrication technologies such as TSMC 0.18, dry or wet?


texts: How are small triacs able to “switch” or control high power AC loads

texts:
I am currently looking ways to control or siwtch a max 220v 35A load. Simple magnetic relay rated for such load would work, but i am exploring the other alternatives too.

here i stumbled into triacs, in which solid state relays are made of. I stumbled into this ic

https://www.st.com/resource/en/datasheet/t16t.pdf

and i could not get the grasp on how a small triac such as this one.

is able to switch a high load of 220v 16amps

also am i right that

since 220v and 16 amp is the max rating
i would need 4A(Igt) at the gate and 1.3v(Vgt)??

am i looking at the right numbers?

Thank you!


texts: Programming to read X-10 over USB or Serial

texts:
Does anyone here have experience writing a program that would receive signals from Visonic, or other X10 sensors such as door detectors or motion detectors?

Essentially, I would like to write a program to replace a wireless alarm system, but I want to customize it to work a little differently.

I have seen an X10 USB transceiver available for purchase, but am hesitant to get it, because I don't know if I can program with it, or for sure whether it will work with the devices I already have purchased.

Are X10 devices the same? Is an X10 receiver going to work with any X10 device or is it more diverse than that? (I will probably use Visonic wireless sensors)
Have you ever used a USB receiver and successfully written a program to receive its signals? Do you have a code sample that successfully worked with a certain hardware? Did you run into problems?
Do you have additional helpful information?

Edit: I am up for the idea of using Serial instead of USB


texts:
Will this circuit work for the purpose of making a high voltage LED flash on and off at 10kHz?

I have a NPN transistor to turn the LED on and off. The pad is where the LED will be soldered into as they are attached with wires.


texts: Looking for good articles about reducing crosstalk and other noise in PCB design

texts:
I am designing a rather large PCB with straight parallel traces 20cm long carrying CMOS logic at around 100kHz. On top of that I have 8 MOSFETs supplying 5A switching on/off at around 400Hz which a large copper pour as a heatsink located close to logic traces. I am concerned about issues I may have with noise, and given the size of my PCB (250x250mm) it isn't the cheapest thing and I want to get it right first time if I can.

Rather than addressing my specific issues, I was wondering if anyone knew any good articles/books/resources for reducing noise on PCBs? I would like to read up on it and learn more myself.

I found this, which was pretty good: http://focus.ti.com/lit/an/szza009/szza009.pdf


texts: Can heavy processes running in background cause lag in arduino's serial port communication with a computer?

texts:
I have a Ubuntu 16.04 machine talking to a Uno board. This arduino board is sending 100 chars of line at baud rate of 115200 as fast as possible. Usually I get a line every 7ms to 10 ms (I am going to call this value DT). Let's say, on a good day, when I start my trial at time 0. I receive lines at 0, 0+DT, 0+2DT etc. But on not so rate bad days, I receive lines at 0+DT+t, 0+2DT+t, ... where t is the lag.

This lag can be quite large sometime (upto 200 ms). This lag remains consistent (not surprising). I am suspecting that running firefox/imagej during the trial on the same system might have caused this lag.

But I am not sure. Any pointer on specification/documentation on how kernel handle serial communication would be appreciated. Essentially the question I am looking for: Can other heavy processes cause lag in serial port communication?


texts:
I want to generate a sinusoidal electromagnetic field of a specificed frequency between 30-80 Hz. For that I was going to pass an ac current to the an electromagnet.

What do I generate an ac current of the specified frequency?
How do I make sure the magnetic core of the electromagnet does not saturate between 30-80 Hz to produce a uniform sinusoidal electromagnetic field?

The magnetic field just needs to be measurable from 1-3 meters by a magnetometer. Do I need to worry about the electromagnet heating up because of this?


texts:
I have two transceivers, one for CAN and one for RS485, and both are isolated. Both standards require 3 wires (two differential pairs and one common GND).
I am trying to use one termination connector and depending on which standard I am going to use (CAN or RS485) only one bus is going to be connected to termination connector pins, and question is:
- Is it good to use jumpers for choosing which differential pair is going to connector and if not, what is solution for that?

EDIT:
Could I use ferrit beads (that are anyhow included on lines) and make assembly variant for placing beads on line I would like to use?


texts: Load to Source impedance match for non-constant load impedance

texts:
i have a rf-system that is working in frequency range of 100 MHz and try to match the impedance of the load to the source system (50 Ohm).

So, in general, i know that a network (P- or T-Network) has to be placed between the source and the load to maximize the power transmission between both. This should look like this one:

There also certain calculation rules to calculate the values of the matching circuit to fit between the source and the constnt load at the given frequency.

But know, i dont have a fixed impedance but an impedance curve over a frequency range in which i want to have the best coupling between the systems. The impedance load looks like this one here:

Do you know a good way to make the impedance matching circuit operating in a given frequency range for a given impedance curve. What is a good method to use for this kind of problem.

Thank you in advance!


texts: LTSPICE problem while trying to run third-party model

texts:
I have an error while trying to run a third-party model in LTspice XVII and I am not sure what this means
M1: Only a level 9 B3SOI can have 5 nodes

I am running it on

With the lib code as from the digikey product page
* RU1C002UN NMOSFET model
* Model Generated by ROHM
* All Rights Reserved
* Commercial Use or
* Resale Restricted
* Date: 2011/03/09
******************D G S
.SUBCKT RU1C002UN 1 2 3
M1   11 22 3 3 MOS_N
D1         3 1 DDS
R1        1 11 RTH 562m
D2       22 11 DDG
R2        2 22 270
.MODEL MOS_N NMOS
+ LEVEL=3
+ L=2.0000E-6
+ W=.1
+ KP=46.188E-6
+ RS=10.000E-3
+ RD=0
+ VTO=.77093
+ RDS=20.000E6
+ TOX=2.0000E-6
+ CGSO=147p
+ CGDO=10p
+ CBD=0
+ RG=0
+ N=2
+ RB=1.0000E-3
+ GAMMA=0.3
+ ETA=0.001
+ KAPPA=0
+ NFS=7G
.MODEL DDS D
+ IS=5.1484E-12
+ N=1.2524
+ RS=.12444
+ IKF=4.4627
+ CJO=3.8907E-12
+ M=.52657
+ VJ=.9987
+ BV=20
+ TT=12n
.MODEL DDG D
+ CJO=23.118E-12
+ M=.36358
+ VJ=.57093
+ N=10000
+ FC=-10
.MODEL RTH RES
+ TC1=0.0045
+ TC2=0.000008
.ENDS RU1C002UN

Any idea on how do I fix this?


texts: Powering from a circuit and controlling it at the same time

texts:
I have 24v AC coming from a door bell to its switch. I have removed this switch and using a relay to control it from my Arduino (MKR1000). This works fine.

However I do not want the Arduino to be battery powered. Instead I want to use the same 24v AC, step it down to 5v DC and power the Arduino from it. I can't get my head around this. Is this even possible to be powered from a circuit and control that circuit at the same time? If you can please briefly describe the circuit which can make this possible?


texts: Audiable pops when switching DC biased audio signal

texts:
In my previous question, I have asked how to DC bias audio signal for a crosspoint audio switching matrix (Switch array (crosspoint) and DC biasing of audio signal).

I am using the following circuit to achieve this at the moment. I adapted the original circuit from the answer linked above to avoid picking the noise of the power supply and used external bias point generated using TLE2426 (based on the answer from this question: DC biasing audio signal).

simulate this circuit – Schematic created using CircuitLab

The circuit works and the audio is properly passing it without any audible frequency range loss, but when turning the switch on or off, there is a loud pop audible on the output connected to the speakers.

I have done simulations of this circuit in LTSpice but there are no big spikes visible at the switching moment. I am a beginner in electronics and don't know where to start looking for the source of poping. I don't own a scope too.

Does anyone have any ideas on what in this circuit could be causing these pops?

EDIT 1:

I have added another 10k resistor to the output side. This has helped with the poping a bit. There is still audible pop though, too loud to be ignored.

I have tried lowering 2M2 resistors too, without any improvements.

The updated schematic below:

simulate this circuit

I have chosen 10k resistors with trial and error as it seemed to my ear that when using 10k resistors, there was less poping than with 100k ones.

I am using these switches in the matrix (see my original question linked above) and if instead just connecting audio in to audio out, I connect another effect in the matrix, so the switches are audio in to effect in, and another switch effect out to audio out, where effect in and out are connected to audio effect, and then I switch between effect in the chain, and input directly to output, the pops are much louder.

It might be worth noting that I am using the switch matrix in latched mode, so all the switches are switched at the same time.

Any ideas what could be causing this popping or what should I look for?


texts: Differential input voltage necessary for maximum slew rate in operational amplifiers

texts:
Today I ran into a problem with op-amp slew rate when playing with a design where an op-amp spends a lot of time in saturation, only to occasionally "come down" and regulate the output.
(I'm simulating this using LTspice, and the op-amps are somewhat arbitrarily chosen but it should not affect the question.)
Background
I wanted to increase the slew rate to minimize the time it spent from exiting from the saturation and enter the active mode, but when I replaced the slower LT1013 with a model of the TL074, the slew rate of my signal did not increase substantially. Even when the positive and negative inputs of the TL074 were clearly at least 50 mV apart, it did not reach the full speed. This is much more than the maximum input voltage difference. I also checked that it was not limited by the output current, but nothing there.
Solution?
After a lot of head-scratching I realize that this is because the inputs are not far enough apart. Never having seen this effect before, or at least not thought about it too much, I assumed that as long as the inputs are reasonably different, the operational amplifier will try its best to change the output.
I also remember reading something about this in The Art of Electronics, and when I looked it up, this is pretty much all it has to say about the subject:

5.8.1 Slew rate: general considerations
...
A second consequence is best explained with the help of a graph of slew rate versus differential-input signal (Figure 5.12). The point to be made here is that a circuit that demands a substantial slew rate must operate with a substantial voltage error across the op-amp's input terminals.

Figure 5.12. A substantial differential-input voltage is required to produce the full op-amp slew rate, as shown in these measured data. For BJT-input op-amps it takes ∼60 mV to reach full slew rate; for JFETs and MOSFETs it's more like a volt.

Bingo. TL074 is a JFET-input op-amp. I adjusted my circuits to get a higher differential voltage, and that solved the immediate problem. A separate simulation gave me results similar to this figure, showing that the models in LTspice are at least reasonably true to reality.
However, the increased differential voltage causes other problems, which I would like to avoid.
Question
... or several related questions. I'm not necessarily looking for answers to each of them, but perhaps more of a general explanation.

Does this effect depend on anything else than the JFET/BJT input stage?
Are there input stages where an even lower differential input voltage leads to the maximum slew rate? Perhaps some sort of hybrid?
Even if there are only two types, do different op-amps of the same type (say, BJT) have different levels?
... if so, is this possible to figure out from the datasheet?

I could not find anything about this on the TL074 datasheet, but that's of course only a single sample.
Somewhat related, is there a common solution, or is this where I would start looking at comparators instead? I might go with a comparator of sorts in the final design, but I still find this problem interesting.


texts: Fan speed control - Voltage (0-5V) to PWM (0-100%) with minimum value

texts:
I need to control 12V fans (w/ PWM so 4 pin) with a laptop motherboard which originally had 5V fans (3-pin only so voltage-controlled), so I want to:

use external supply of 12V (or internal from laptop but 12V, don't want to mess with stepping up the 5V)
use LTC6992 (https://cds.linear.com/docs/en/datasheet/69921234fc.pdf) to map 0-5V from laptop motherboard to PWM for my new 12V fans
use a voltage divider (2 resistors - R1=10kohm, R2=2.5kohm) to map 0-5V to 0-1V input of LTC6992
I want to have a minimum value (eg. 50% of fan speed) always and never go below that - was thinking to use another voltage divider to bring 0.5V to the analog input of LTC6992 and only leave the 1st voltage divider to raise that 0.5-1V - anything you see wrong with that approach? Perhaps I need some diodes to not mix those two?

Any other comments/suggestions to the above-mentioned?

Note: I do NOT want to use 5V fans here, I'm making liquid cooling for a laptop (and essentially turning it into half-desktop), already have 12V fans and everything working, this is the last piece :-)

PS: for anybody interested, this is the MSI GS70 Stealth with retro-fitted Corsair liquid coolers (laptop was too noisy when under load and I never take it anywhere anyway :P).

https://www.dropbox.com/s/pnm01z1gvzbdrmb/removing_radiators.jpg?dl=0
https://www.dropbox.com/s/ps5ih695et8ii9x/retrofitting_water_blocks.jpg?dl=0

Thanks!
Lukas


texts:
I've been creating a MIDI Thru box project and was trying to avoid having so many resistors. Points A-G may (or may not) have a load connected to them. Are these equivalent, or do I really need to include a resistor on each branch?

Here's the circuit image

Is the current/resistance/voltage equivalent from the DC supply to each lettered branch in each circuit? More importantly, can anyone explain (or provide a link that explains) how you came to the conclusion? I'm a developer just starting to learn electronics.

I've gotten mixed responses on twitter, and someone mentioned asking here.


texts: Analog input over-voltage protection using Schottky and Zener Diodes. Can it work?

texts:
I'm developing an analog input module based on TI's ADS8668 and want to protect the input channels from over-voltage. According to the datasheet, each analog input channel withstands voltages from -20V up to +20V.

Although my analog signals are expected to be in the range of 0-10V, wrongly connected inputs (e.g. miswiring) could lead to voltages up to +24V on the ADC input channel.

To protect my analog inputs, I tend to use Schottky diodes, as recommended by TI (Engineer It: How to Design Protection Circuits for Analog I/O Modules) and Analog Devices (Protecting ADC Inputs).

I have no supply rail in 10-20V range on my PCB, that I can clamp my diodes to. Therefore I would just place a Zener diode (D3) as shown below, to protect my analog inputs from voltages above Zener voltage.

Simulating this schematic in LT Spice using a 12V Zener results in a system behaviour according to my requirements (see below).

Is it sufficient (and good practice) to clamp my Schottky diode (D2) to the Zener diode without having any positive supply rail (unlike this solution, which uses a shunt regulator)?

Is there anything I need to beware of, especially the power dissipation of my components in an over-voltage case?

Thanks in advance!

simulate this circuit – Schematic created using CircuitLab


texts:
If I fed in ~140 volts at 100kHz to This transformer what is the most power I could get out of it? The data sheet rates it at 36 volts DC 3 amps on one of its three outputs but I am confused by this.

First, the saturation current is rated at 7.4 amps so why is the output current significantly less, especially when the voltage is being stepped down by a 4:1 ratio and the output DC resistance is so low.

Second, if I wire the three identical outputs in parallel will I achieve 36 volts with 9 amps or am I mistaken in how parallel transformer outputs work?

Third, If I wired these outputs in series would I then get 36*3 = 108 volts at 1 amps output?

Lastly, these winding ratios are given with the input voltage across pins 2 and 4 on the primary side, I should be able to put 120 volts across just pins 3 and 4 to get a 72 volt, 1.5 amp output, correct?

Thank you for your time, when working with dangerous line voltage I want to make sure I have everything correct. I ask these questions because while I would think they would carry over from what I see on 60hz transformers, I haven't been able to find a good resource on these switching transformers.


texts: How to stop my motor from resetting my microcontroller?

texts:
I'm assuming (no way to verify) that when the motor pulls too much I get voltage spikes which cuts out my microcontroller. Here's my circuit, any suggestions on how to fix this issue?

The left chip is an hbridge and the center one is a 5v regulator.


texts: Whether Internal source resistance will have effect on the circuit

texts:
Calculate the voltage gain for the network of Fig. 3.12 if the source has an internal
resistance of 100  in series with Vi.Vi=500mV,R= 1K ?

For this problem I had tried a solution but I am not sure whether it is correct or not?
Please Help.
Below is the solution that i have found

Ii = Vi/Ri = 25mA
For this ckt, Ie=Ii=25mA

Since, Ic is approx equal to Ie, Ic=25mA
VL=Ic*R=25V
Hence, Av=Vl/Vi=50.

Is my solution correct?
I am assuming that the internal resistance of source will not have any effect on the circuit.
Correct me if I am wrong.


texts: How to read 24-bit HX711 ADC data using AT89S52 micro-controller, can anybody help me to understand? How I will store 24-bit data in micro-controller?


texts: How to choose between little endian or big endian for the processor settings?

texts:
We have just selected a new processor for our application, and one of the project options available to me is to select the Endian mode: Little endian or Big endian (under Big endian two more choices, BE32 and BE8)

Can you please tell me what factors I should consider to make this choice?

I was under the impression that a processor is either Little endian based or Big Endian. Does this mean that based on the option selected, the compiler would fix the endianess to suit the processor, if required?

Thanks a lot.


texts: Robustness of surface mounting daughterboards

texts:
I am using a "Teensy" development board in a project and would like to attach it to my main PCB including the surface mount pads for the usb data lines.

Are there any reasons I shouldn't just design up a footprint of all surface mount pads and install it during my regular reflow assembly step.

I can see the potential for some kind of thermal stress issue but on the other hand see many castleated radio boards mounted in this fashion.

My only other alternate solution is to persist with through hole design and use pogo pins to mate with the required surface mount parts.

Edit:
To be clear my question is more focused on if it is possible to take an arbitrary non-castellated board and solder it surface mount in a reliable fashion.


texts:
I have the Hilo module running ok on standalone mode through XP hyper terminal.
Can send SMS and calls ok. Hilo baud rate is set at 9600.

I was reading on a forum that the serial library on the Arduino is only good for 9600 baud. I have dropped the rate down to this but does not make any difference. The serial from the arduino is currently running at 9600. I can't get the arduino to download the code to the libelium shield. The code will download with shield removed. But when i plug the shield in and press the reset button nothing happens with the hilo module.

I have the led on pin 13 as a visual cue that the code runs ok and it is. When trying to download from the Ardunio i get the out of sync general error. There are heaps of examples of this error on line but no solution.

If I remove the USB Arduino links on the Hilo shield I can get the download to work without sync errors but will not load into the Hilo of course. There may be a problem with these links, not sure.

If anybody can give me some advice I would be very grateful. I do not have any power supply current issues as per the libelium notes. I have added the capacitor and the supply is fine. Running version 18 arduino IDE. Using Duemilanove with 328 chip.

Thanks, Greg


texts:
I'm working on stocking my home workshop with frequently used parts so I can spend more time tinkering and less time watching my mailbox.

What are the differences between different kinds of diodes?  I've seen schottky, zenner, signal, and rectifier all used to describe diodes, but I don't know what the differences are and when you would use a particular one.

What are the most frequently used diodes that you would keep around to be able to build most common circuits?  And how do you know what makes a suitable substitute when a circuit calls for a particular diode?


texts: Can I use multiple voltage regulators in a circuit safely?

texts:
If I have two different voltage regulators both powered from different sources is it safe if they are both outputting in parallel? If one is on and the other is off?

I made a basic schematic to show what I mean here .

Schematic:


texts: Controller Seems to be going into Undefined Exception on Reset

texts: We have developed a board around STR912FAW47 Micro-Controller. During initial testing we tried to bring up the board by loading a simple program for toggling an output port pin. We are using ULINK2 Debugger and Keil MDK ARM for loading the program. When we try to load the program, it does not get loaded in single attempt. After getting loaded successfully, the program does not seem to be working, as we do not see the desired toggling on the IO port. Then we tried to run the program in debug mode through ULINK 2, the program start working intermittently once after 2-3 attempts of connecting and running through debug mode. Further seeing in detail, it is observed that whenever the program is not working, it is going to Undefined Exception Handler (with infinite loop), instead of going to Reset Handler on executing first instruction after reset. It is very strange, as from the code and flash memory, it is seen that the instruction loaded at the 0x0 address is clearly for jumping to Reset Handler. Can anyone put some light on this behavior?


texts: How to get a 24 V signal generated when the input circuit state changes?

texts:
So I'm an IT guy with no electrical experience trying to figure this out.

How do I set up a circuit that puts out a 24 V signal for a short time or puts out a continuous 24v signal that quickly turns off whenever the inbound circuit state changes? Like when the inbound turns on I need a signal and then when the inbound turns off I need a signal.

I have an incredibly stupid industrial molder that will put out a 24 V signal that changes states at the end of every cycle that did not trigger a tolerance alarm. A good part is made, it turns a 24 V signal on. When the next good part is made, it turns it off. If its on and a bad part is made, it remains on, and if it's off and a bad part is made it remains off.

We have a LED pace counter that increments the part count whenever it receives a 24 V signal. A continuous 24 V signal will increment it once until it is turned off and back on. I need to figure out how to get this hooked up.

I know how to handle this if I had to write a computer program but I have no idea where to even start with relays, circuits, and switches etc.

I've tried playing with the setting on the molder device and even contacted the manufacture and they are no help. When I use the settings they tell me to, I get a continuous 24 V out after one part is made. The only consistent cycle I can get that also uses the built in tolerance is by changing some settings and arriving at the above situation.

Simply doubling the count increment and having it increment every 2 cycles is not an answer either.

I currently have it wired into the circuit that gets triggered every time the safety door gets closes but when line workers get behind, they just open and close the door like 20 times and claim ignorance to what happened.

Also, I'm open to any solution, IDK if there's some other product out there that can add some logic to it. Budget is around $100 but as low as possible is best. The post tags may not be appropriate, I honestly have no idea what to tag it.


texts: Why did he multiplied with the emitter current?

texts: I don't understand why did he multiplied in that equation with the Emitter current (1.618, calculated above), why would it be the same in the collector?


texts: Wireless power transfer through voltage spikes?

texts: I'm sort of digging up something with this question, which relates the the whole wireless power transfer concept.  I've looked at a question about power transfer and Tesla, and I know that there's ways of doing it at a limited distance with resonance and inductive charging.  There's beaming power through microwaves and lasers, and there was Tesla's old concept of sending electricity through the ground, which is unclear but probably also not very efficient (maybe somehow it would be, but of course that info is hard to come by).  So each of those have their own ups and downs, but I wanted to ask about another concept for this.  One of the obscure not real/lost things that comes up with Tesla, alongside the death ray, the tower, the radiant energy, and all the free power stuff is impulse electricity.  So I thought to myself, if that was real, what real life thing could that be?  Then it occurred to me; an impulsive transient.  I know that's a voltage spike that can happen when electricity is discharged through an inductor or through certain other mechanisms.  I think that's usually something they try to get rid of in power systems, since it can damage the systems, but could it be possible to transmit power through some transient phenomenon?  Has any attempt been made to use voltage spikes or transients to transmit power?  Inverse-square law applies?


texts: help reading this schematic regarding high voltage coils

texts:
This is the internal schematic for a high voltage coil used in old black&white televisions:

I want to use it in an arc generator and I want the maximum voltage gain. I know this is obtained by connecting the oscillator output to the least winded coil and the highest voltage will be between the pins of the coil with the highest wind.

But I have trouble understanding which is which. In other words, which pins must be connected to the oscillator output and between which pins will there be the maximum voltage?

here is the picture of the transformer:


texts: Power controller says 0/10vdc command signal what does that mean?

texts:
I have a power controller here and I try shorting these two prongs but it doesn't turn on and give me 12 volts. I'm new to electronic engineering so does the 10 vdc on the manual mean that I have to apply 10 volts dc to the prongs in order for the power supply to turn on?

Here's a pic

For reference, the manual is here (PDF). The connectors are shown by the figure at the top of page 5.


texts:
I am in the process of doing some wiring on my car.
Part of this is adding in a switch panel in. For this I have 4 LED Missile Toggle switch's.
At the moment I use one for some additional lights, this is wired as standard with 12v in, ground and then out to the lights.
However, One of the switches I want to add is for the ECU to change maps. This is done via that particular pin being grounded.
I know I get continuity between the positive and the accessory terminals on the switch so can use that to activate or deactivate the ground. Is there a way though that I can get the LED to light up as well ? I presume I can't just wire 12v into what would normally be the ground as this would send 12v to the ecu ( not a fun game)
Is my thinking on this correct?


texts: Need help identifying SMD, 6 pins, 3x3mm, top marking 82S

texts:
Does anyone know what it might be?
Dimensions 3x3 mm, 6 pins, top marking 82S


texts: Not able to understand the behaviour of PIC18F458 ADC output on PORT B with LED's

texts:
I have recently started meddling with the PIC18f458. The below shows the code in which I have configured the internal 10 bit adc.

#define _XTAL_FREQ 10000000
#include<P18F458.h>
#include <xc.h>
#pragma config OSC=HS
#pragma config WDT=OFF
#pragma config LVP=OFF

void main (void)
{
TRISAbits.TRISA0 = 1;       //Configure RA0 pin on PORTA as Input
TRISB = 0;

//ADC Configuration
ADCON1bits.PCFG3 = 1;       /*Configure AN0 as input channel and select
ADCON1bits.PCFG2 = 1;          +VREF = VDD = 5V and -VREF = VSS = 0V*/
ADCON1bits.PCFG1 = 1;
ADCON1bits.PCFG0 = 0;
ADCON1bits.ADFM = 0;         //Store 8 bit in ADRESH and 2 bits in ADRESL

ADCON0bits.CHS0 = 0;       // Select AN0 as the input channel
ADCON0bits.CHS1 = 1;
ADCON0bits.CHS2 = 1;

ADCON0bits.ADCS1 = 1;
ADCON0bits.ADCS0 = 1;

ADCON0bits.ADON = 1;      //Turn ON ADC
PIR1bits.ADIF = 0;        //AD Interrupt Flag
PIE1bits.ADIE = 1;        //Enable AD interrupt
INTCONbits.GIE = 1;       //Enable Global Interrupts

ADCON0bits.GO = 1;        //Start AD Conversion

while(!PIR1bits.ADIF);
    PIR1bits.ADIF = 0;
while(1)
{

temp = 0;
ADCON0bits.GO = 1;
while(!PIR1bits.ADIF);     //Wait till conversion is completed
PIR1bits.ADIF = 0;        //If completed, clear ADIF bit
PORTB = ADRESH;            //Copy digital data to temp variable
}

I have done the following changes within the code and, as advised, I connected 8 LED's to PORTB in order to check the adc 8 bit output from ADRESH, however, the LEDS are behaving weirdly. The first 4 LEDS connected to PORT - B0,B1,B2 and B3 are constantly ON irrespective to how I vary the input 10K POT while among the last 3 LEDS, one keeps blinking and the second last two LEDS sometimes switch oFF and ON while varying the POT. Can anyone tell me whats happening?. Is there something wrong with the code?

At present I am also working on setting up UART to stream this data for better analysis. In the mean time, any help and guidance regarding this would be appreciated. Thank you all.


texts:
Is it possible for an additional core to have the same functionality and capability as the main core0 ? So two cores (core0 and core2) performing with the exact same responsibilities and capabilities working in tandem. Taking a device SoC such as in a smart phone with three cores (core0 core1 and core2) for example how can this third core (core2) function and behave in the same manner as the main core0 ? Where would this configuration code be found on die within the core0 embedded circuit code on die ?

Chris thanks. What I am asking is it just in theory and is not likely done in practice but can an extra core be embedded in a multi core SoC device typically found in smart phone devices and have the same control (over IO and CPU executions) over the device as the main or primary core0 ? Could this additional core receive all IO data along with the CPU instructions for the entire device ? I hope this explains the question a little better.


texts: Common emitter amplifier gain with load resistor?

texts:
I have a problem I am working on where I have to find the voltage gain of the following circuit with a dc collector current of 0.3mA.

My attempt at a solution involved using the formula A=-(RcIc)/Vt = -(10000*3*10^-4)/0.025 = -120. I am not confident in this solution as I feel like it was too simple and does not account for the "load" resistor. Any advice on where to go from here? I have received a hint to use Thevenin's theorem to transform the circuit but am lost on how that should look.

simulate this circuit – Schematic created using CircuitLab


texts: Proteus Autorouter Not Using Ground Plane

texts:
I've created a ground plane on my Proteus schematic but for some reason the autorouter is totally ignoring it and trying to link all of the ground connections with traces.

How do I fix this and force the autorouter to use the ground plane?


texts: Simplest way to limit current from MCU pin

texts:
I'm trying to build a very simple flyback power supply capable of only about 1mA.  The basis is to supply a PWM wave to a 1-1 sepic inductor (shielded coupled inductor).
The problem is that it would be easy for the inductor to saturate and essentially short to ground.
It feels like there should be a simple and inexpensive way to limit current going to the coil (magical cccs1 below). For example, a FET + a gate resistor that will limit current through the inductor?

simulate this circuit – Schematic created using CircuitLab
Note. the circuit above is obviously incomplete for simplicity sake


texts: Tools/Methodologies for failure mode effect or fault tree analysis (FMEA/FTA)

texts:
We have barely started the process towards medical device certification, and as part of that I am having a hard time wrapping my head around the appropriate way to construct a failure mode effect analysis (FMEA) document for a couple of electronic devices that are past the midpoint in the design process. These devices are to be used in research collaborations, so we are trying to follow a best-effort path that would allow us to design medically-approved devices in future iterations of the design. Our current designs will not be put through a certification process, but we are putting the required methodology in place to make this happen.

Regulatory agencies don't seem to care much about the specifics of the methodology you use, but they will hold you accountable to whatever you choose. This creates a double-jeopardy, you run the risk of specifying too much detail which makes the process unwieldy or specifying too little which makes it useless.

I know that the basic bottom-up approach, which has been mostly discarded, is wasteful and of little use in the middle of the design process. But the top-down approach can lack specificity and might be hard to map to actual components in an schematic.

I have the impression that creating these FMEA documents must follow a systematic process in which every element has gone through some level of review, classification, categorization, and quantization. With the final FMEA worksheets at the end of the process. I now need to put together an FMEA worksheet with none of this in place, so I am trying to figure out how to best proceed.

As an experienced engineer, failure modes have always been in the back of my mind when designing, but all of the documentation I have on FMEA seems artificial or incomplete at best. I know this risks becoming a matter of opinion, but here are the broad questions hoping that some of you have much more experience with this process:

What are the steps required to put together a workable FMEA/FTA process?

If I have an overall system with different levels of subsystems, and I have different categories of harms to a patient, user or the device itself, I believe that these are different trees that interact with each other. How to best divide the problem so that those interactions are captured without falling into the exponential growth due to the many-to-many relational problem?

What methodologies/tools are used for FMEA/FTA?

Intuitively I feel that I need some form of relational database that would allow me to reduce repetitions and easily examine the interactions. There seem to be some existing FMEA tools that simplify this process, but not knowing the specifics it is hard for me to evaluate the usefulness of the tools themselves.

FTA software tools seem more understandable and perhaps useful to me, but I am not sure of how compatible are the methodologies.

How can I better integrate the FMEA methodology into the specification phase of the design?

Right now to me it looks like an afterthought that is put together just to satisfy regulatory requirements after you have schematics and populated boards in hand. But it is clear to me that it should be implemented up-front and made interactive to better inform the design process itself.


texts: Do I need a MOSFET gate resistor? How can I calculate it?

texts:
I got this schematic :

In the image you see I'm driving two infrared LEDs at 40 mA each one with a FDN327N MOSFET.

Attached at D8 there is one of Teensy 3.1 digital output that has HIGH voltage of 3.3 V and a LOW of 0 V.

The R23 Resistor which you see as 0 Ohm resistor is a 10 kOhm pulldown resistor While R3 should be the gate resistor.

I included it as 0 in the case I need it and I got a doubt.

I want to drive the MOSFET as a logic gate MOSFET @ 1200 Hz with the tone library.

Do I need a resistor and if yes how do I calculate it?


texts: Am I exposed to high levels of radiation at my job?

texts:
I made this post because I have a safety concern about my job as medical device tester. I was reading the user manual of the equipment I work with and found the next warning:

“Per FCC regulations, maintain a distance of at least 7.8 inches/20 cm between the Radio Card on the unit and a human body”

I work with 6 units, which each one has a small wireless antenna, but I also have coworkers that work with the same number of units, resulting in 36 units in total.

My question is if there is any risk for being exposed to the radiation of these equipment, by risk I mean getting cancer.

Notes:
The wireless of the units are enabled, but we are not connecting the devices to computers, we are testing other functionalities.

The units operates on the following frequencies with a maximum radiated power of 100 mW:

• 802.11a: 5 GHz band, up to 54 Mbps physical RF specification.

• 802.11b: 2.4 GHz band, up to 11 Mbps physical RF specification.

• 802.11g: 2.4 GHz band, up to 54 Mbps physical RF specification.

• 802.11n: 5 GHz or 2.4 GHz band, up to 72 Mbps physical RF specification.


texts: Is this measurement of a cricuit's output impedance valid?

texts:
The following circuit is a simple voltage regulator. The Vout is maintained at -1V, however the opamp in the circuit has a non-zero output impedance. This is represented by the resistor R1.

simulate this circuit – Schematic created using CircuitLab

I have been told that the following procedure will allow me to measure the output impedance of this circuit.

Remove r4 and measure the open circuit voltage
Measure the voltage with r4 (which has been chosen to be close to the expected output impedance)
Now the circuit is modelled as a voltage divider and the output impedance is found

simulate this circuit

Where Vout is the open circuit voltage measured above, and the second voltage is across R4.

The expectation is that adding the resistor will cause a slight decrease in the output voltage. Now, assuming the circuit was accurately represented by the above circuit, this would all make perfect sense. However, as far as I can tell the feedback loop ensures that the output voltage is at -1V, unless the resistance is so low as to cause the output to be clipped. (The person describing the measurement ensures that clipping doesn't happen by varying V1 and making sure the output changes linearly).

My problem is that if the output voltage shouldn't change at all (it is a voltage regulator after all), so that the result will always be close to 0 Ohms. Again, we are assuming the R4 is not so low that that clipping occurs. The person describing the measurement however expects to find around 70 Ohms, and blames the much lower recorded values (2 Ohms) on the variation of the opamps.

So is there any reason that this measurement would get an answer other than 0 Ohms?


texts: During I2C Slave Transmit, who drives ACK/NACK?

texts:
I'm looking at the ATMega328 datasheet and the Arduino UNO Wire/twi implementation, as well as a logic analyzer trace of a proprietary device I'm trying to send data to.

The device is trying to read anywhere from N=48 to 512 bytes. It keeps driving the clock for N packets (8-bits+ACK), but the UNO stack's interrupt only sends 32 bytes per transaction.

The spec leads me to believe that the master should NACK when it is done, but the wire code in the UNO lib state machine (for slave transmit) drives ACK/NACK when there is still data left.

This isn't clear to me: who drives ACK/NACK on the 9th bit during a slave transmit?

Thanks,
PeterT


texts: Average signal power (signals and systems - discrete signal)

texts:
I am trying to find the average signal power of some discrete functions.

For a finite interval, I can use the formula:

[1 / (n_2 - n_1)] * (SUM n_1 to n_2) of |x[n]|^2

For an infinite interval, I can use the formula:

[1 / (2N+1)] limit(n->infinity) of (SUM -N to N) of |x[n]|^2

I am not sure how to apply these formulas to various discrete functions.  However, I was assigned this problem (homework), and this is my interpretation of it:

x[n] = (-1)^n

Squaring it becomes:

[x[n]]^2 = (-1)^(2n)

Now, because of the 2, I see that the power will always be even.  I see that each term of the summation will be a positive one for n>=0:

n=1:   (-1)^(2*1) = (-1)^2 = 1
n=2:   (-1)^(2*2) = (-1)^4 = 1
n=3:   (-1)^(2*3) = (-1)^6 = 1
...

So, it seems that the summation of this discrete function, if my limits are from n=0 to n=N, is just 1+1+1+1+1... for N+1 number of terms (because the first n is zero).  That is, it seems that the answer, for a sum from zero to N is just N+1.  Is this correct?

I see that for values of n<0, each term will also be a positive 1.

(-1)^(2(negative-n)) = 1/(-1^(2(positive-n)).

n = -1:   (-1)^(-2) = (1/(-1^(2)) = 1/1 = 1
n = -2:   (-1)^(-4) = (1/(-1^(4)) = 1/1 = 1

So, if I have a summation of a finite interval from n1 to 2, it seems that the answer would be:

(n2 - n1) + 1

Is this correct?  For example:

Sum from n = -10 to 10 of (-1)^n = [10 -(-10)]+1 = 21

Now, in this problem, I am not given any values for N.  I am just supposed to find the average signal power of that discrete function.  I see that the formula for infinite interval includes the limit n->infinity.  So, is the answer just infinity?


texts: Adding a potentiometer before or after a passive filter

texts:
I would like to add a A50k potentiometer to control the volume of an audio input for a small amplifier. Additionally, I used some easy passive filtering to remove the lowest frequencies and some highs from the signal.

This is the schematic:

simulate this circuit – Schematic created using CircuitLab

I understand that a potentiometer before the filter will alter the cutoff frequency of the lowpass filter. Adding the potentiometer behind the filter did not have any noticable effect.

Is it safe to assume that a potentiometer after the filter will not alter the frequency response significantly? The used Amplifier is a small PAM8403 board (see here). There is a 10k resistor at the input but I couldnt find any other information about the input impedance of the amplifier.