texts: Pullup or direct drive when handling active low inputs/resets?

texts:
Active-low reset inputs seem to be a holdover from TTL logic where the falling edge was faster than the rising edge, so the falling edge was decided as more important to increase the maximum possible frequency.

I'm not so sure how relevant that is with modern CMOS but it's still very easy to find chips that are active low reset (my circuit board design, which uses some old-school 74XX chips, all have active low reset. Even the Microcontroller is active low reset). I'm guessing there's reasons beyond the technology used as to why this still pervades (such as active low would reset on a brown out condition, chips would reset on power-on, tradition, etc.).

Something that I haven't really thought about until now, is what would be the better design when driving active low logic (specifically resets on other chips) from a microcontroller. Is it better to:

A. Drive the resets directly from the microcontroller, with a 1 for an indefinite period of time, or

B. Add a pullup resistor to Vdd and use the microcontroller to briefly pull down to 0

Option B adds more footprint and cost (BOM), but I would guess it would be more stable, since it's passively being tied up to the non-reset position, and uses less static power  consumption (even if negligible) on the uC since the output would be high for only a brief blip. Also trivial, but the programming would also be a little easier (Reset = 1 resets the line). Option A is simpler but, but an unintended reset on that line would cause the system to fail. A full power cycle would be needed to recover the system.

I also think about what position I would like to be in better with my design if the reset line also were to fail permanently -- if it were pulled up by a resistor, the system could still remain mostly functional, but if it was just the microcontroller driving the output, everything would be stuck in reset (completely nonfunctional). I've never heard of a single pin failing on a microcontroller though.

For an active low data line, I would never consider option B. There's no justification to add that many pullups.

I'm guessing there's no practical difference between the two (i.e., microcontrollers are reliable enough to drive a solid 1 for long periods of time without glitches), so I should go with A to save on cost and footprint. Is either option clearly better?


texts: Low-power design using TPL5111 and RC constant activation for it

texts:
I am designing a low-power device using TPL5111 connected to a coin cell (2.5V-3V) and am wondering if I can switch it on and then automatically off after a certain amount of time delta.
The delta is not fixed, but would like it at 10s.
My question is: can I use a resistor+capacitor and use the RC constant to charge the capacitor and turn off the TPL5111 (pin DONE) after 1 tau? - 1Mohm and 10uF.
Schematic of circuit:


texts: Identifying component from i2c trace & obscure SMD marking

texts:
I wanted to poke around one of those sub-10$ smart bands, so I got a couple of them. I opened it and I was able to identify some major components from the SMD markings, including a Dialog DA14580 MCU, XC6206 3V 200mA LDO VReg, XT4054 Battery Charger IC, ...

This smart band acts as a pedometer, so my best guess is it's using a tiny accelerometer. There's this chip marked 3FL MS, that is either a 4x4 BGA array, or an LGA-12 / LGA-14 / LGA-16 package (I can see 4 shiny solder points under each side of the chip), and I think that's it. Sorry for the pic quality, that's the best I can do with this homemade webcam microscope.

Searching the marking led nowhere, but fortunately, there are test points for i2c, and I was able to confirm that my cheap logic analyzer works (I was able to decode the i2c traffic for the SSD1306 OLED Display). I can see two other addresses : 0x1E & 0x18.

0x1E is only used when the watch boots up, and the MCU only writes to this chip.

0x18 however is constantly polled, approximately every 0.8 seconds, and there's a lot of read from the MCU. This should be my accelerometer.

0x18 seems to be the address used by ST micro for their line of accelerometers, so far so good, but I can't find any datasheet with registers corresponding to the traffic I'm seeing.

The i2c capture can be found here :
https://gist.github.com/melka/ac3150315e38d3e691aa3cb7923fdbbd

The most interesting one would be standy.csv, since it only show the "cycle" of polling that 0x18 chip.

I've been searching all of ST's datasheets for this magical 0x3F register that would send back 30 bits of data, but I can't find anything.

What would be the next step in identifying this chip ?

edited : added photo


texts: Is it possible to filter out noise to a pulse counter when there is no twisting or shielding on a long conductor?

texts:
simulate this circuit – Schematic created using CircuitLab

I have an application where 400'-450' of 14 AWG solid core cable was buried to connect a flow meter to a shed.  I built this circuit to count the pulses, but I occasionally get long episodes of false pulses reporting.  When I was able to catch this in the act, the scope showed noise with a max voltage of 9 VDC and a min of -1.2.  The resonance lasted for a about 100 micro seconds.  I wish my scope wasn't so old, I'd love to export the image and share it.  I placed a 0.043 uF capacitor in parallel with the 100 pF, but it seems that it only increased the rise time and did not seem to address the noise issue.

I used the switch symbol to represent the pulse meter. The net that starts between R2 and C1 and ends at the switch represents the 400' 14 AWG solid core cable.  The return ground conductor has the same characteristics.
Is there a way to filter out this noise without washing out legitimate pulse signals, or should I give up and start digging?


texts: Can I determine 2-port s-parameters from 1-port measurements?

texts: I have a 1-port impedance bridge. Can I get the four s-parameters of a 2-port device by measuring each "sending" port with the "receiving" port terminated in Z0 and reversing the measurement to get the remaining parameters in the other direction?


texts:
I need to build a simple voltage regulator that can drop voltage from 24V(from a DC power supply) to 3.7V and supply at least 2A or more(up to 5A if possibile).

Can I just use a 2 resistor voltage devider? Or should I use a voltage regulator?


texts:
I have a ceiling fan that only operates on low speed.  I am fairly positive that it is a bad capacitor.

It is a five wire capacitor that has 2.5uF/250V, 4uF/250V, and 4uf/300V.  I can't seem to find a replacement capacitor with the same capacitance and voltage ratings.  What (if any) degree of tolerance could I expect from this type of capacitor.  Can I replace it with another one that has different specs?


texts: About transformers: very little primary current if the secondary is unloaded

texts:
This extract is from a popular electronics book:

  ... a transformer of turns ratio \$n\$ increases the impedance by \$n^2\$. There is very little primary current if the secondary is unloaded.

I'm thinking about the emboldened part. Please see if the following argument is correct: If the secondary is unloaded, its current is zero, so the secondary can be neglected (as if it doesn't exist at all), and the transformer can be modeled as a single inductor with inductance of \$L\$. And according to the relations

$$X_L=2\pi\nu L$$

and

$$V=X_L I,$$

\$L\$ must be large if primary current is 'very little'.


texts: Difference between differential line transceiver & differential line driver and receiver pairs

texts:
What is the difference between differential line transceiver & differential line driver and receiver pairs ?
Line transceiver is used as translator in either unidirectional or bidirectional; whereas line driver receiver pairs is used to produce differential output and convert back to single-ended at the output. Am I correct ?


texts: The mean value of phase noise as a stochastic process

texts:
What is the mean value of phase noise as a stochastic process?
Where can I get a theoretical analysis of this topic?


texts:
How can I calculate the polarization parameters for each MOSFET transistor?
There is an internal resistance in the input signal of 100k. RS1 = RS2 = 423 \$\Omega\$ and Vdd = 17 V.

I got two values for \$V_S\$ for the first transistor and I wanted to know which one would have to choose for the transistor to be in the saturation region. The \$V_S\$ values I obtained were -0.283 V and -3.193 V. (please check if it is correct). I used:

\$V_{GS}>V_T\$

\$V_{DS}>V_{GS}-V_T\$

\$V_T=-0,95\$

\$\frac{\mu_0 C_{OX}W}{L}=1,5\,mA/V^2\$

My calculations:

First transistor:
\$I_{RD1}=I_{RD2}\$

\$\frac{V_{DD}-V_D}{R_{D1}}=\frac{V_S}{R_{S1}}\$

\$I_D\approx I_{D\,SAT}=\frac{\mu_0 C_{OX} W}{2L}(V_{GS}-V_T)^2\$

\$I_{D\,SAT}=1,5\times 10^{-3}\times (-V_S+0,95)^2\$

\$\frac{V_S}{R_{S1}}=1,5\times 10^{-3}\times (-V_S+0,95)^2\$

\$0,6345V_S^2-2,20555V_S+0,5726=0\$

\$V_S=0,283\,V\$ or \$V_S=3,193\,V\$

So:

For \$V_S=0,283\,V\$:

\$V_D=15,93\,V\$

\$V_{DS}=1,73\,V\$

For \$V_S=3,193\,V\$:

\$V_D=4,92\,V\$

\$V_{DS}=1,73\,V\$

Check that the transistor is in the saturation zone to know what value for \$V_S\$ to choose:

For \$V_S=0,283\,V\$:

\$V_{GS}>V_T\$

\$-0,283>-0,95\$ check!

\$V_{DS}>V_{GS}-V_T\$

\$15,65>0,665\$ check!

For \$V_S=3,193\,V\$:

\$V_{GS}>V_T\$

\$-3,193>-0,95\$ false!

\$V_{DS}>V_{GS}-V_T\$

\$1,727>-2,243\$ check!

I do not know where the error will be. It should be false under both conditions.


texts: What's the Difference between shunt battery charger and battery protection IC?

texts:
I don't understand well the difference between shunt battery charger and battery protection IC. Here, component datasheets that I would want to use :

shunt battery charger : http://cds.linear.com/docs/en/datasheet/4070fc.pdf
Battery protectio IC : https://cdn.sparkfun.com/assets/learn_tutorials/2/5/1/DW01-P_DataSheet_V10.pdf

May I use them at the same time?
Do you think they're compatible?


texts:
currently I'm wiring my converted RV. I've a 12V system and want to connect 12V LED lights. I don't want to use RV or rocker switches. I bought standard house light switches. After a lot of research I figured out that I can use them in my 12V system. All of my LED Lights will consume not more than 2,4 amp, one of the switches is designed for 15 amp.

Ok here my question. Is it possible to share the positive wire from the breaker box with both light switches and go back to the breaker box with a shared negative wire?

I want to use T wire connectors or something similar. The reason is because the DC breaker box (Blue Sea Fuse Block) has only one free slot for connecting. The alternative is to connect two wires on one screw of the breaker box. But I think this will be same result.

What do you think? Will this work or is there a better alternative?


texts: Normalize values from different MEMS 3-axis accelerometers

texts: I have to find a solution to uniform values on 3-axis accelerometers on different android devices. I mean, a device with a specific accelerometer, subjected to the same acceleration, return values, for each of 3 axis, that are different from the values returned from another android device with different accelerometer.


texts: Is this a good inverse parallel SCR drive circuit?

texts:
I have a design for a dimmer circuit, but I am unsure of its correctness or if there are issues with it.
It's meant to be controlled by a 50% duty cycle PWM signal - the dimming responds to the phase angle between the PWM wave and mains AC:

simulate this circuit – Schematic created using CircuitLab

EDIT: An earlier version of the schematic had had frankly ridiculous resistor values on the voltage divider, but they should be correct now.

I'm also not sure if there even are half-bridge optocoupler ICs like that. I could just use individual optocouplers but if anyone knows of a specific part that would be helpful.

The main motivation for this design is to reduce the number of output transitions the MC will need to make to control the device.

The device would be controlled with a waveform like this to adjust the dimming level:

Note that I've included what I'd have to output to control a regular triac at 50% for comparison.

Would this design work? Is it a good design? How can I improve this design?


texts: How to instantiate module with variables

texts:
I declared alu_result as a reg because I need it to be a variable data type for my case statement. But when i do this, I cannot pass it my write_data in my datapath_tb module. Is there some work around where I can get this to work?
module alu(input [31:0] input1, input2, input [2:0] control);
parameter SIZE=32;
reg [31:0] alu_result;
reg overflow;

always @(*)
begin
    case(control)
        0: alu_result = input1 & input2;
        1: alu_result = input1 | input2;
        2: alu_result = input1 + input2;
        3: alu_result = (input1 < input2)?1'b1:1'b0; //unsigned, no additional bits to worry about
        4: alu_result = input1 ^ input2;
        5: alu_result = ~(input1 | input2);
        6: alu_result = input1 - input2;
        7: alu_result = (~(input1 + 1) < input2)?1'b1:1'b0; //2's comp is ~ & +1
        default: alu_result = input1 & input2;
    endcase

    if(alu_result > 32'hFFFFFFFF)
    begin
        overflow <= alu_result;
    end
end
endmodule // alu

module datapath_tb();
parameter SIZE = 32;
reg clk;
reg write;
reg [4:0] write_addr;
reg [31:0] write_data;
reg [4:0] read_addr1;
reg [4:0] read_addr2;
wire [31:0] read_data1;
wire [31:0] read_data2;
// Instantiate the register file
Register rf_1 (.clk(clk), .write_en(write), .write_addr(write_addr), .write_data(write_data), .read_addr1(read_addr1), .read_addr2(read_addr2), .read_data1(read_data1), .read_data2(read_data2));
// Instantiate the ALU
alu #(SIZE) alu_1 (.input1(read_data1), .input2(read_data2), .alu_result(write_data)); //Line in question
// Create a clocking signal
 always begin
   # 10;
   clk = 1;
   # 10;
   clk = 0;
 end

  initial begin
  // Write DIGIT0 into register 0

  // Write DIGIT1 into register 1

  end

endmodule


texts: What makes one microphone better than another, and how do I make my own?

texts:
I am curious about microphones and have a few questions.

What is the key component in them which makes one better than another?
What does it take to build a high quality microphone on my
own? I'm looking to purchase a good microphone, and was looking at
the Blue Yeti as an example, so that just got me wondering. I
know it is better than my dollar store microphone, but want to know
why.
Just for kicks, I purchased an el-cheapo Condensor Microphone (2.2K Ohm, 1.5V) to toy around with, but I have little idea regarding its limits. What would a microphone like this one be useful for?


texts: Can I use VHDL/Verilog to program a micro-controller?

texts: I wanted to know if I can program any micro controller (not CPLDs /FPGAs) using VHDL/ Verilog? If so, what are the steps and the required tools for the same?


texts:
I was reading this document from cypress website on Various storage capacitor options for nvSRAM. In page 2 , under the heading 'key characteristics' (see link below), I came across various values for capacitors for different densities of nvSRAM.(e.g. 4 Mbit parallel nvSRAM-  68 μF with 10% tolerance)

My question is this: What basis did they use to arrive on particular value of a capacitor?

Capacitor options- nvSRAM


texts: Reliability of DS18x20 temperature sensors

texts:
I'm using Maxim's DS18x20 (I've actually got more than one variant) 1-Wire temperature sensors to log the temperatures in various rooms in my house once a minute.  About one reading in a thousand, I get something completely bogus back.  In the middle of a sequence that's gradually rising from 65F to 70F I get something like -32.1F or 15.64F.

Has anyone else had that kind of problem, or is this something wrong with my setup?  If this is just a known issue with these things, I'll have to do something like taking three readings and throwing out the outlier.

Just a few statements about my setup:

I'm running at 3.3V
I'm checking the checksum of the reading as it comes back to the arduino, and it matches (or I think it does - there could always be a bug in that code).
These are running off of normal power, not parasite power.
I have the 4.7K pullup resistor in place.
I'm only using a single sensor on each sensing platform.
The sensor is on a PCB attached to the arduino that's reading it.
I see the same problem reading from a variety of different arduinos (diecimilla, pro-mini, homemade custom)


texts: So in my electronics textbooks I see brief mentioning of PNP transistors but very little description of current flow and there are no actual equations or formulae for calculating collector current, collector voltage, and V[CE](collector-emitter potential difference). So how does one compute these properties and how do they differ in transistor action from NPN transistors(which are far more common)?


texts:
Ok, while I was going from a negative voltage to a positive voltage, I switched the leads connecting to the PSU. Normally this inverts the voltage, but I forgot I had it connected via BNC so all it did was connect the source to ground and the ground was hooked up to my oscilloscope channel input (1MOhm). I wanted to ask if this would have done any damage to the oscilloscope (current was 1.5A)? To me, the answer is no. But, I am trained in a different field and wanted to ask people who can comfort me because I have surprisingly never done that with a scope before :)

Also, I am used to scopes that can switch input impedance. I saw this answer in another topic, but I can get a 50 Ohm input impedance by using a splitter with a 50 Ohm termination, right?

Thanks!


texts: Push button for different actions in every press?

texts:
I'm trying to learn some electronics and I have something in mind that I don't know if it is possible to achieve.

I've worked before with micro-controllers (Arduino, etc) and I know I would be able to do this with code, but I would like to know if this is possible without any code/micro-controller.

I would like to have a push button and 3 LEDs.

First time you press the button, first LED will light.
Second time you press the button, second LED will light (and the first one will be off).
Third time you press the button, third LED will light and the second one will be off.

If you push it again, every LED will be off. And then the process will start again with every press of the button.

I hope I was able to explain it correctly

Is this possible??

Thanks a lot.


texts: NPN BJT common emitter amplifier input impedance

texts:
I am trying to find the input impedance of this circuit.
In this circuit 10K resistor is load.
I looked at my book but could not find any circuit looking like this because none of them has C1 capacitor. The input impedance must be 27K and beta of the BJT is 300.
Can you help me?


texts:
I’m trying to repair a powered recliner touch sensor, and I’ve isolated the part that I think is the problem. The issue is, I don’t know what it is! In the first image, you can see that it has three pins, and the text “1AME”. In the second image, I tried to follow the PCB traces and draw up a schematic of the part.

I think that this is the part causing problems because the 10k resistor was measuring about 2.3k. On another, identical recliner (they are in a couch), I was reading the full 10k, and that recliner worked!

I know through a continuity meter that the “goes somewhere” part of the schematic is tied to +24V, but I don’t know if it is a direct path.


texts: I have found it very difficult to find what actually happens with primary and secondary generated flux in transformers, I understand the normal transformer theory but it doesn't add up in reality! I am hoping someone can shed some light. Simply put, if magnetic lines of flux cannot cross or actually cancel does this mean that the secondary coil is an air core?


texts: Low cost position detection using a diy "encoder"

texts:
I'm building a machine that is adjustable, so there is this mechanical arm that can be in 5 different positions. I was thinking on building a custom encoder, I can easily make holes in each position so that they are detected by 3 optical reflective sensors, each different combination of holes will be read by a PLC (24V power supply). But all I can find are very expensive optical reflective sensors above $30 and that's out of budget. Pretty sure there are inexpensive solutions out there, can anyone give me some pointers in the good direction please?
EDIT:
a quick diagram to explain better, the moving part will be positioned in the small cut so no precision issues, I just want to detect in each of the 5 positions it is, but using the smallest number of IOs possible.


texts: 12V to 24V 3A boost converter using LM2587

texts:
I'm trying to build a 12v to 24v boost converter. I have an output current requirement of 3A. I'm thinking of using two LM2587 5A Flyback Regulators in parallel like this: http://www.ti.com/lit/an/snva552/snva552.pdf

Will this circuit work for me? (keeping in mind that LM2587 has an Input Current rating of 5A)
How do I calculate the required inductance values?


texts: Triac partial conduction without gate current?

texts:
I'm using the circuit below in a custom PCB to switch on and off an electrovalve.

I assembled partially the PCB, just to verify some voltage across the triac. I didn't connect the MOC3021 and R40 at the moment.

I plugged the 230V main AC and measured the voltage across the two terminals X10-1 X10-2, and strangely (for me) I measured 148 VAC! Note that GND230 is only a label to distinguish phase and neutral in the schematic. I was expecting that, since the gate is disconnected the A2-A1 was at high impedance and any voltage would have been measured between A2 and A1.

As extra test I connected a bulb lamp between X10-1 and X10-2 expecting that it would switch on with 148 VAC. Instead, when I plug the 230 main AC, the lamp is lighting for a very short time (<0.5 sec) and then it switch off. In this condition the voltage between X10-1 and X10-2 the value is zero as expected.

What happen that I don't understand?

As a secondary question, what could be a right value for R40?


texts:
Here's the data sheet if it helps.
https://www.cui.com/product/resource/pdqe15-d.pdf
The DC\DC converter is an isolator unit so the left part of the circuit doesn't us a traditional GND, which leads me to be unsure of you -Vo would affect a polarized capacitor. I'm also worried CY2 would discharge into C3 and cause problems.
Also does the rating on C3 matter? the DC/DC converter outputs 24V but the data sheet doesn't mention a specific rating for C3. It does mention ratings for several other capacitors which leads to believe C3 doesn't have to be rated to a specific value.


texts: AD620 //Output saturation//Data acquisition

texts:
I am working on a data acquisition project ,I have to get data from a pressure sensor of 5 pins(similar to a load cell) Using AD620 inst.amplifier.

I have used a gain set resistor = 390 ohm so gain is roughly 130
Output of sensor is 2mV/V in this case 0 to 10mV(fullscale)

sensor details :

Pin1 = Vcc
Pin2&3 = Sensor output
Pin4 = Shield
Pin5 = Ground

I want to power circuit using +5 volts.

I have made a circuit on general purpose PCB which is shown below

------Questions-------

Output seems to jump to saturation and again to zero.
Is the circuit Correct or I have messed up something?
Should reference voltage be grounded as I have done here?


texts:
I'm developing a fixture tool to test a custom PCB with ST Bluenrg1 (STM32 M0 core + bluetooth).

This fixture tool has its own MCU working at 5V.

I would like to flash automatically first previous to test the pins of the board, but I'm looking for a best solution to do this without spending 600 EURO in a "Flasher ARM" (which allows stand-alone flashing via hand-shake protocol).

The idea is to use the MCU of the testing tool to ask the Flasher to start the upload of the firmware, and answer to the Testing Tool if it has been done correctly or not.

I'm checking options with raspberry + OpenODC, raspberry + usb STlinkv2, looking for flashers with stand-alone mode... but I'm getting a little bit confused with the best option (best option with relativelly low cost).

Which solutions do you use when want to program your MCUs without computer?

UPDATED:
I’m using SWG protocol to program it with a computer and a STLINKv2 programmer. I do it by hand, previous to test the connections in the testing fixture tool. I would like to include this programming step in the Testing fixture tool, and make it as simple as possible, as this will be done in the warehouse by other people (the idea is the testing tool to upload first the code and if everything is Ok, test the connections)


texts: Measuring the resonance point of a piezo ultrasonic transducer

texts: I assume it will be something along the lines of feeding it a sine wave via a resistor and measuring the signal across the resistor as the frequency changes. Does this sound viable? Also, on resonance does the current maximize or minimize? A complication is that it presents as a capacitor. [Also, I have no way of measuring the sound output]


texts: What are these two 3-pin components in a high voltage board?

texts:
I'm trying to fix a circuit from a waterboiler in my RV from 1982 (truma BO 128). It is responsible for opening the gas valve, creating sparks and monitoring the flame. The problem is that the voltage of the sparks is too low to jump the spark gap on the board.

I checked all condensators and diodes. They all seem to be fine. There are two components which I can't identify:

Both have three legs:

Component on the left: the diagonal legs are shorted. The other ones have 160 Ω resistance.
Component on the right: only the two left legs are connected on the board. They are shorted. On the top is the high voltage connection to the spark gap inside the burner. The legs on the bottom have 134 Ω resistance to the spark connection.

I'm also unsure what creates the high voltage. I would expect a transformer, but can't see anything like this.


texts: how to wire a 12 lead motor for lowest possible current draw

texts:
Im on a job where a blower motor that was a 20amp load, was replaced with a 46Amp motor. The bucket can not be replaced for a larger starter, there is no more room in the MCC. The owners do not want to replace the motor, the blower has been rebuilt around the larger motor blah blah blah. Im wondering if there is any configuration of a 12 lead motor that would allow the motor to run at a lower current.
I was thinking about using a WYE configuration, that would reduce my current by 1/(sqrt(3)) but that still wouldn't be enough. I need to cut the current in half, or even a little more.

Is there a wiring configuration for a 12 lead motor that can deliver current reduction roughly half of the low voltage delta configuration?


texts: Drive multiple LEDs ON together using PIC Microcontroller

texts:
I am using a PIC18F2420 microcontroller (I can change if required). The task is to drive up to 20 Power level indicator LEDs along with a few other LED indicator & switches using PIC. I can imagine connecting the anode of all 20 LEDs to the rail (~ 30V) and connecting cathode of each LED to a PIC I/O pin. But this would mean 20 I/O pins reserved just for this - waste of many I/Os. External I/O expander would add cost and only gives 8 more I/Os with ICs like MCP23008. Cost and PCB real estate is important consideration..
With Charliplexing LEDs, I can only turn ON 1 LED ON at a time. I don't want to drive them at duty cycle with reduced brightness..

How can I drive up to all 20 LEDs ON together with best usage of the PIC I/O pins? Do I really need a controller with so many pins that I have to assign 1 pin for each LED only? LEDs connection scheme drawing would be helpful to understand..

I don't want to turn all 20 LEDs on/off at the same time as a group..These LEDs are level indicators and as per the user input, I need to turn each next level indicator LED ON by keeping all lower level indicators ON as well, as level is increased by user and turn off each highest level LED off one at a time, as level is decreased by the user..


texts: High Side Switch Flicker during Power Up

texts:
I have some problem with a P-channel mosfet used as high-side load switch.
Everything works fine beneath the power up moment.

You can find the schematic in the picture below.

During Powering the circuit with 28V the following happens (blue channel: Gate; green channel: Drain):

I suppose that this flicker occurs because of the Gate Capacitance of the MOSFET, but I am not sure. Does somebody of you have an idea on how to solve this problem? During this period the output signal should stay at GND level.

Furthermore, I want to tell that on the input there will be a 5 kHz PWM coming from a Microcontroller. As I said before, after the power-up, there are no problems.
Edit: The PWM is started after some ms.

Regards
Armin


texts:
As of now, I have been programming my Xilinx Spartan 6 using JTAG. I now want to load the FPGA image using SelectMap with my STM32 processor. (See this document (pages 33ff) for more information about SelectMap on the Spartan 6.)

At the moment I have a .bit file, and I'm loading one bit every clock cycle. I've been told that the .bit file may have to be converted to a .bin file somehow, and that the loading sequence should end with some "extra" clock cycles.

Neither of these points seems to be mentioned in the linked document. Should I convert my .bit file to a .bin file? Should I have "extra" clock cycles after loading the FPGA image?


texts: potentiometer as voltage divider and taper

texts:
assuming that I'm going to change the potentiometer value (now is 50K linear) to 100K linear, should I also change the value for R1 and R2 in order to keep the same taper and the same power consumption as the 50K potentiometer?
I guess R1 is there to provide a more reverse log response


texts:
Playing with electronics I discovered a strange behaviour of a Graetz bridge. This is my scheme:

The corresponding output looks like this:

I don't understand why I have a additional peak once a period.

When I add a charge, in my case a resistor as shown in the following scheme, the output looks like learned at school:

Does anybody know, why this behaviour occurs?


texts:
Simple gates of the types we describe here are available in 14-pin
  packages (two pins of which are needed for the power supply). As it
  costs virtually nothing to add extra gates to the silicon chip, only
  the number of pins (i.e. external connections to the chip) limits the
  total number of gates in a physical package. Thus, an inverter
  requires two pins, so that six inverters are provided on the chip.
  Similarly, a two-input AND/NAND/OR/NOR gate needs three pins, so four
  of these gates are put on the chip.

With relation to Number of gates in series, the question:

1: Are pins described here same as What exactly are 'pins'??

2: Why does an inverter require two pins and power supply two pins?

3: Suppose that there are three gates and two inverters. So if we have 14-pin package, is it possible to do this in the package?

4: If I am mistaken, can anyone provide what the quote is saying?


texts: How to query wires that are connected to selected component in Altium Designer?

texts:
I want to apply special rule only to components with myFootprint and all connected wires to it.

AD can select all components with that footprint with this query HasFootprint('myFootprint').

I also know that it can select and query out all wires with IsWire but the question is about filtering-out just connected wires to queried component?


texts: Is operating relay with 3.3V instead of nominal 5V harmful?

texts:
I am testing the Songle SRD-05VDC-SL-C 5pin 5V 10A Relay without any module board.
It works with 5V as it is supposed to.
It also works with 3.3V pin and digital out pin of an Arduino Nano.
If I operate this relay with 3.3V, will it cause any problem in the future?


texts: What do I need to learn for solving these

texts:
simulate this circuit – Schematic created using CircuitLab

The network 'N' contains only 2 elements. If the response for unit step excitation is i(t)= e^(-3t) A for t>=0. Determine  elements and their connections?

What do I need to learn for cracking these types of problems.


texts: "The D-PHY specification defines the maximum lane flight time to 2 ns." Why?

texts:
I'm hoping someone can explain to me why the maximum lane flight time matters.
Impedance matching, skew, attenuation, etc. all make sense to me as a natural limitation to how long an interconnect can be, but I do not see why the absolute time the signal travels would be a limitation.


texts:
Im trying to design a maximum strength electromagnet. I have a soft iron core that is 1.3" (33mm) round by 1.9" (50mm) long and I'm using 12 volts of input and my wire gauge is 18awg. Unfortunately I don't have the proper program to achieve this task. I was wondering if there was anyone with the know how that could help.
Thanks Warren.


texts: how to find the frequency of this nonperiodic composite signal?

texts:
I'm new to electrical engineering, sorry if my question sound dumb. Below is a nonperiodic composite signal plot:

As you can see this is a nonperiodic composite signal in 1s and I know that if the composite signal is nonperiodic, the decomposition gives a combination of sine waves with continuous frequencies.I don't know how to use fourier analysis to decomposite this composite signal into simple sine waves.

Can I just make a quick conclusion to say because the signal completes 4 cycles in one second, so the frequency is 4Hz?

PS: This questions originates from my textbook's description of signal received by an old-fashioned analog black-and-white TV. It says

An example of a nonperiodic composite signal is the signal received by an old-fashioned analog black-and-white TV.A TV screen is made up of pixels with each pixel being either white or black. The screen is scanned 30 times per second.If we assume a resolution of 525 × 700 (525 vertical lines and 700 horizontal lines), we have 367,500 pixels per screen. If we scan the screen 30 times per second, this is 367,500 × 30 = 11,025,000 pixels per second. The worst-case scenario is alternating black and white pixels. In this case, we need to represent one color by the minimum amplitude and the other color by the maximum amplitude. We can send 2 pixels per cycle. Therefore, we need 11,025,000 / 2 = 5,512,500 cycles per second, or Hz. The bandwidth needed is 5.5124 MHz.

So I'm going to simplify this and connect my textbook's description to my original question. Let's say I have a tiny TV that only has 8 pixels. So I am sending the signal in the picture, representing 8 pixels, the high amplitude represents "white" and low amplitude means "black", so the signal in the pictures represents the pixels(from pixel 1 to pixel 8) in the TV should be "wbwwbwww", then according to the textbook, We can send 2 pixels per cycle, Therefore, we need 8 / 2 = 4 cycles per second(4 Hz).


texts: Issue with driving multiple LEDs via transistors

texts:
I am attempting to individual control multiple LED-based light sources via PWM.  Now I am somewhat familiar with transistors and their usage, and had no issue setting up one instance of this control scheme.  However when I added more transistors to the circuit, I ran into a problem.  It seemed that only one PWM signal, would control all of the lights.  I am new to schematics and schematic design so I could use some help figuring this out.  The schematic, as I think I built it, is below.

simulate this circuit – Schematic created using CircuitLab

The wiring was done with this article as reference, specifically the "light" example.

The power source is 12V 6A, which is more than enough to drive the lights I am using, which are 12V LED boards.  I won't be using an Arduino in the final implementation, but I am using it currently for testing, so assume that is where the PWM is coming from.  Oh, and the transistors are TIP31 NPN units.

As I said previously, the issue is that when using the circuit, the lights will only respond to one PWM signal and they will both use that value seemingly.  Otherwise it works just fine.  My only thought is that it could be an issue with them sharing a common ground?  But if so, what is the best way to isolate them?


texts:
Assuming you have these two batteries:

Battery A: 12V, 15 Ah = 180 Wh
Battery B: 5V, 20 Ah = 100 Wh

Can you use battery A to fully charge battery B?

Battery A has less capacity (with respect to charge) compared to battery B, but battery A has more stored energy at 180 Wh.

It seems like there are two ways to think about the transfer (in an ideal case):

Ah: After charging, battery A is left with 0 Ah and battery B is 3/4 charged with 15 Ah.

Wh: After charging, battery A is left with 80 Wh and battery B is fully charged with 100 Wh.

This seems like a situation where, using a water analogy, you have a smaller amount of water (in battery A) trying to fill a larger vessel (battery B). The smaller amount of water is at a higher pressure (and therefore greater energy), but that doesn't make up for the fact that there isn't enough water.

Is this correct? Or is stored energy (i.e. Wh) what really matters and electrons are somehow pulled from the environment to make up for the deficit in stored charge (Ah)?


texts: How to use a reference design in datasheet?

texts:
I'm trying to gain a better understanding on what this is and how to use it. I know this is a datasheet for SAMB11 SoC, more specifically the reference design on page 50 is what I'm inquiring about.

In a general sense, is a reference design the simplest/fastest way to get the target component up and running, or is this one of many examples of how to implement this SoC?
Is it safe to use this as a starting point depending on how I'm using it? I guess I'm wondering when this circuit is built what will it give me?

Thanks for your patience and time.


texts: Schottky diodes question. Which will power the board? Battery or USB?

texts: Given this diagram, where Vcc is a 3.3V supply powering an Arduino, if I were to connect both a USB and a battery at the same time, which will be used to power the board and why?


texts: Timing two parallel lines on FPGA [Beginner]

texts:
So let's suppose I want to do certain action based on certain signal.
I have signal "nx"; if it's 1, I want to "NOT" an X input(16bit) and if it isn't, I want the X unchanged.

My idea was to do both and fanout it into MUX and decide which output to use based on the "nx" bit. But I'm not so sure if it would work in real hardware (or even FPGA for that matter), because the lane that doesn't change anything is gonna be carried out faster than the one with "NOT" gates in it.

Is my understanding correct ? And if so, is it problem even on FPGA (do those operations really "eat" clock cycles) ? And if so, how would you go about it to solve this simple problem ?


texts: How to create a circular polygon pour cutout in Altium Designer?

texts:
It is possible to choose "polygon pour cutout" from place menu and create one by clicking multiple points. but how can I create a circular one?

I am using Platform Build 26245.


texts: Can't Tesla Powerwall 2 draw DC from solar panels directly?

texts:
As one may know, Tesla Powerwall 2 comes in two versions: AC (with internal inverter) and DC. This question is about the DC version which comes with this coupling diagram:

We know that solar panels generate DC. So, on the diagram above, what does the hybrid inverter do with DC coming from the solar panel? Can the latter not be plugged into Powerwall directly?

Also, related question: if there was no grid involved (i.e. completely autonomous system), could the inverter be DC->AC only (not hybrid)?


texts:
I am designing a motherboard which requires 2 PCIeX4 connector, the standard PCIex4 connector and M.2 KeyM connector. but my CPU has only x4 PCIe_TX and 4x PCIe_RX lanes, but we will be using only one of the connector at the a particular time.
I was thinking of using a dual PCIe mux chip like TI TMUXHS44128 for TX and RX lines and for reference clock I was planning to use a clock mux.
Can anyone recommend a design by which we can do this?
https://www.ti.com/document-viewer/TMUXHS4412/datasheet
I have attched the below block diagram for reference.


texts: What does a 'scaling factor' mean for an ADC?

texts:
I'm using the analog input on the Controllino Maxi Automation to determine the temperature of a 10K NTC thermistor. I'm having some difficulty understanding how the ADC works.
On a regular arduino nano, this code from Adafruit works okay, only off by a degree. But on the Controllino it's off by anywhere between 6-10 degrees. Fine tuning the parameters (temp @25C, series resistor and B coff) doesn't help at all.
Looking at the documentation they mention a scaling factor (last couple lines in the image below) but I'm not sure how to apply it or what it means.

I assume this means I can't just convert straight from an ADC value into a voltage reading?
#include <Arduino.h>
#include <Controllino.h>

// which analog pin to connect
#define THERMISTORPIN A0
// resistance at 25 degrees C
#define THERMISTORNOMINAL 10000
// temp. for nominal resistance (almost always 25 C)
#define TEMPERATURENOMINAL 25
// how many samples to take and average, more takes longer
// but is more 'smooth'
#define NUMSAMPLES 5
// The beta coefficient of the thermistor (usually 3000-4000)
#define BCOEFFICIENT 3895 // datasheet - https://www.mouser.com/datasheet/2/240/Littelfuse_Thermistor_Probes_Assemblies_Threaded_U-1372560.pdf
// the value of the 'other' resistor
#define SERIESRESISTOR 9760

void setup(void) {
  Serial.begin(921600);
}

void loop(void) {
  float reading;

  reading = analogRead(THERMISTORPIN);

  Serial.print("Analog reading ");
  Serial.println(reading);

  // convert the value to resistance
  reading = (1023/ reading)  - 1;     // (1023/ADC - 1)
  reading = SERIESRESISTOR / reading;  // 10K / (1023/ADC - 1)
  Serial.print("Thermistor resistance ");
  Serial.println(reading);

  float steinhart;
  steinhart = reading / THERMISTORNOMINAL;     // (R/Ro)
  steinhart = log(steinhart);                  // ln(R/Ro)
  steinhart /= BCOEFFICIENT;                   // 1/B * ln(R/Ro)
  steinhart += 1.0 / (TEMPERATURENOMINAL + 273.15); // + (1/To)
  steinhart = 1.0 / steinhart;                 // Invert
  steinhart -= 273.15;                         // convert absolute temp to C

  Serial.print("Temperature ");
  Serial.print(steinhart);
  Serial.println(" *C");

  delay(1000);
}

The schematic editor didn't have the thermistor symbol just btw


texts: Noisy amplification and low light: photodiode and op-amps question

texts:
My formal education was in mechanical engineering and I’m well trained in some CS as well. Yet here I am on an electrical project (that will eventually turn CS). I have been lost and confused for many months now and could really use some specific help.

Project scope/goals:
Measurements from the sample to photodiode should be in the 0.3 to 3 picoAmp range. An array of photodiodes will detect this small amount of light. Right now I’m just trying to get a circuit working for a single photodiode at that extremely low light range. Time response can be long or short because we can hit the sample with the laser for a long time without any problem. The laser rep rate is ~76MHz versus the approx. detector bandwidth ~23KHz so there shouldn’t be a problem with signal decay.

Materials:

S10355 photodiode (we are looking to replace, suggestions would be awesome)
Powered breadboard with +5V, +15V, and -15V supplies
NI USB-6211 for measurements
Op Amps we have around(happy to buy more as needed)

TLC271 (0 to +15)
TL031 (-15 to 15)
MCP603 (0 to +5)
MCP6002

Large resistors: 10Meg, 22Meg
Resistor kit (100 ohm to 900k ohm, lots of values)

‘Ideal’ Circuit simulation (that doesn’t really work but is good for visualization):

Adapted from book:

I chose my resistance total based on amplifying 0.3picoAmps to 1 Volt. The book also describes a way to do this with a single op amp but I haven’t gotten that one to work even a wee bit. The only other way seems to be a tee-network but this causes proportional noise gain as well which wouldn’t be appropriate for my application from what I can tell.

Major problem:
There appears to be so much noise even at ~no light~ conditions (there’s never no light but I can get close), that the voltage readings are maxed. Since we are looking at subtle changes this makes it pretty unclear. I read about making a pseudo-ground for the cathode of the photodiode and set one up at 1V from the +5V of the breadboard. This doesn’t seem to do as the forum post indicated or maybe my gain is so high I need a mV or pV pseudo-ground? Not sure. I have also read that choice of Op Amp is critical, and I’m not sure I have the right ones for the job right now, could this be hindering linear response and ground levels?

Power turned off/no light Vout:

Power turned on/no light Vout:

Future problems: I know to eventually implement any of this on a PCB board (for the full array of photodiodes) I will have to be exceptionally wary of noise for detecting such low current levels. Do you have some tips for this? There’s a nice noise analysis in the book but I don’t fully understand the ee concepts I am working around to be honest.


texts: When we calculate the dynamic resistance \$r=(\frac{dv}{dI})\$, for any n-p junction, how is it different from the normal resistance \$R=\frac VI\$? Does the equation for the voltage drop (The fermi potential drop, and not the absolute Galvani potential) work if we use the dynamic resistance with the instantaneous current (\$V=Ir\$)? Does the power dissipation relation, \$P=I^2r\$ hold in case of dynamic resistances? If it does, is power dissipated as heat even in case of the n-p junction? I think it is unlikely, as the hole-electron recombinations are the dominant phenomenon here, and I am unsure whether those can produce heat.


texts:
The schematic of Klipsch SW-12 is on Page 15-17 of the following service manual:

http://www.audiolabga.com/pdf/SW12-15%20I.pdf

R87, R88, R89, and R90 get pretty hot.

[The schematic's Sheet 3 with the above resistors highlighted added 2/12/17.]

The schematic indicates they should be all 750 ohm 5W and the originals are 750 Ω 5 W 5 %; however, the service manual's part list indicates that they are 1.5 kΩ 5 W.

One of them reads only 426 Ω (off the circuit), so I'll have to replace it for sure.

Questions:

What would happen if I replaced all of R87, R88, R89, and R90 with 1.5 kΩ 5 W resistors?
If the amplifier operates with 1.5 kΩ resistors, will it run cooler?

[Added 2/9/17]

The four resistors are on Sheet 3 of the schematic, POWER AMP section, left side. The four resistors are vertically aligned.

[Added 2/10/17]

The following resistors do fit and seem to be stocked by distributors in the USA now.

= = = = = = = = = = = = = = =

TWM series by Ohmite:

[H x W x L: same as the original; same pin spacing]

5W 750 ohm 5%

5W 1K ohm 5%

5W 1.5K ohm 5%

Datasheet:

http://www.mouser.com/ds/2/303/tww_twm_series-25614.pdf

= = = = = = = = = = = = = = =

SQM series By TE Connectivity:

[H is 13 mm greater than the original's, but W and L are the same - will fit; same pin spacing]

7W 1K ohm 5%

Datasheet:

http://www.te.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=1773285&DocType=DS&DocLang=English

== = = = = = = = = = = = = = =

MCPR series By Multicomp:

[H is 13 mm greater than the original's, but W and L are the same - will fit; same pin spacing]

7w 750 ohm 5%

Datasheet:

http://www.farnell.com/datasheets/1679919.pdf?_ga=1.72813905.374067655.1485773361


texts:
I want to make a power connection between my PCB and an accumulator. I need it to handle up to 100A, and to be mechanically very strong, because it will be on board of a buggy car model.

In the prototype I made with a Perfboard (dot pcb) I split the big wire into 16 smaller sections, and I pass each of them through a different hole. Then I solder all together in the bottom.

Wires and connectors are standard from model hobby:

Connector to the accumulator is a EC5
Connector to the BLDC engine is a Triple 3.5mm bullet connector

That works really well, as it is both strong and accommodates the large wire in quite a small footprint. I've used a similar technique to retrieve output current from the half-bridges underneath the dissipator.

Now I would like to make a printed circuit, and I would like to replicate the same kind of connection, but I'm unsure how to proceed:

Creating a component that contains multiple through-holes, too close to each other fires up plenty of design rules error.
My PCB editor (Proteus - Ares) believes that each through hole is a different connector, so it is awkward to create a component.
I prefer to remain as standard as possible because I order my PCB to a commercial manufacturer.
Some comments suggest to use a PCB bus bar. I understand that this would make a great connection, but I don't see how I could possibly fit them in a circuit that goes onboard of a model car. Circuit is a BLDC controller, and has 2 power inputs and 3 power outputs.

I would welcome any idea, including creating the connector in a different way, or using a different PCB editor.

Edit

Chris Stratton suggested to look at an actual commercial ESC module. I should have started by that. Here is the disassembly of one:

Now I have more questions:

It looks like the power cables are soldered to a metallic area reinforced with small dots. Someone knows what it is?
On the other face there are a kind of slab. Is this a power bus?


texts: Are most RAM/Memory cells done with Inverters?

texts:
As far as memory cells go (SRAM/ROM/Registers) in simple chips everything i've looked at seems to use the Two-Inverter CMOS schematic (Just from readings/googling and such).

In I guess "real life" chips are Registers/ROM/etc.. created using Inverters or something different (like an SR latch.....etc...)

That being said what kind of Latch/Flip Flop are most commonly used in Computer Architecture (Like a Counter or Adder or Shift Register)?

Since there are like 8-9 different types of Latches/Flip Flops all together (I've heard JK is most 'versatile' but that doesn't necessarily mean it's used the most)


texts:
I am new to Altium designer and had a question. For all of their generic component libraries from the Altium vault they only have 0603(1608 Metric), 0805(2012 Metric) etc.

From looking at mouser/digikey it seems like the normal 0603 and 0805 footprints are far more common. Why would Altium include the metric versions?

And if my previous statements are correct, does anyone have a good Altium library with non metric footprints?

Thanks in advance,

Mitch


texts: Is the measurement accuracy of a test instrument consistently the same?

texts:
Let's say, for example, an oscilloscope (could be a multimeter, power supply, or other type of equipment) has a voltage tolerance of +/- 3%.  I input a signal with a known voltage and determine this oscilloscope is measuring and displaying the signal's voltage at 2% above its true value.  This is within spec so I can't complain (but I'm a little annoyed).

Now, assuming environmental conditions are the same (e.g., temperature), will this oscilloscope consistently report ALL voltage measurements at 102% of their true value?  And if this is the case, can I add a 2% offset factor to the values displayed to achieve better accuracy?


texts: Possible to parallel PC power supplies & increase voltage to 14 VDC?

texts: I'm in need of 14 VDC @ 100 amps. Switching power supplies are available but too costly. I have enough supplies left over from various desktops to assemble such a beast it's just how? This is to power a 500 Watt HF amplifier so solid voltage regulation and excellent filtering is a must. I've found projects to convert a PC power supply as a multi-voltage bench supply but nothing found to increase the 12 volt rail to 14 volts and then parallel for greater current.


texts:
I need a way to reuse my PCBs that I designed before in my new board as a module. the problem with multichannel design is that I should change some component names in schematic, so I can not use the previous designed PCB with copy and paste (for example I have C2 in 2 modules)
Any idea?


texts: LM317 Voltage Regulator + ammeter = firecracker?

texts:
simulate this circuit – Schematic created using CircuitLab

I don't know what I'm doing wrong. Perhaps someone can explain this. Is there any reason an ammeter would cause a voltage regulator to explode?

I'm trying to understand how to use the LM317 voltage regulator with a potentiometer to reduce 12 volts to a variable voltage between 1.25 and 10.5 volts. The 12V is generated from an ATX PC power supply, and the circuit I am using can be found here: http://www.electronics-lab.com/articles/LM317/

The only difference to the above schematic is that for R1 I am using a 680 ohm resistor, and R2 would be a 5k ohm potentiometer but I haven't even gotten that far yet. After building the circuit, I connected a multimeter to the output of the circuit and shorted what would have been the potentiometer (therefore simulating 0 ohms or full open) and read 12.5 volts. It read steady for several seconds, so I switched from volts to amps on the multimeter, and POW! The LM317 was no more.

Perhaps there is something fundamental I am missing, but what would cause this? Are my calculations (using the above website as a reference) completely wrong? If so, what would I need to do to accomplish my goal of taking a 12V supply and using a potentiometer to vary the output in as wide of a range as possible? Would there be a benefit to having a fuse (perhaps 1 amp) on the input voltage?


texts: Why does cable length matter so much when source is high impedance?

texts:
My beginner’s electronics book has now started to teach me about microphones, specifically Electret microphones.

While searching the web for more info, I stumbled upon an article where the author mentioned that when a microphone has high impedance it is critical to keep the cables connected to the microphone as short as possible or else the signal would degrade significantly.

I have been trying to make sense of such statement but so far I have failed miserably. No matter how I think about this I can’t imagine why a cable with such small impedance compared to a microphone’s huge impedance would matter at all.

Could someone please help me undestand this phenomenon?

In case it helps, here is a link to the YouTube video where this is mentioned.

Thanks.


texts: Attaching a Type K thermocouple to a breadboard / prototype board

texts:
I'm looking to prototype a low-cost thermocouple interface board.  It needs to output a voltage, as opposed to using SPI like several of the ICs I have looked at, since it would be fed into a 10-bit ADC present on a servo drive.  I found a potential IC in the AD8497, but now I have to figure out how to connect the thermocouple to the IC on my board.  Long term, it would need to survive linear accelerations of up to 6m/s^2.  Vibration is not much of an issue, but I haven't quantified that yet.

I have read that it is possible to solder a Type T thermocouple, but this requires a fairly expensive thermocouple (I found them for about $70), and I haven't yet found an amplifier IC... so I think I'm stuck with the Type K thermocouple.

I've read a helpful post that outlines a few connection methods, such as high temp solder, adhesives, and constant mechanical force, but none of those appeal to me.  I'd prefer to go with a PCB-mounted mini receptacle like the one used in the Arduino Thermocouple Shield, but Omega seems to only sell them in lots of 100.  I found another nice one, but could only find sources in India and the UK!

Can anyone suggest other options?  I would have just bought Ryan McLaughlin's Single Thermocouple Interface since it's exactly what I need (but maybe not the right form factor), but he doesn't have them in stock anymore due to part shortages.  Ideally, I would like the board to be flatter, so a different receptacle is preferable (like the RS Electronics one I linked to in the UK)


texts: Ground connection in differential signals

texts:
Do I need a ground connection when connecting differential signals between two systems?

I was thinking this should not be needed, but how will common mode voltage at the receiving end behaves? Without connected the ground between the two systems, I probe the inputs at the receiving end and observe that the inputs rides on a 10V peak to peak 60Hz(probably interference from the power line). As there is a +/-5V common mode limit on the receiving input, this probably causes the erratic behavior that I'm now experiencing.

Will an earth connection at both systems help? Or a ground connection is still needed for connecting the differential signals?


texts: SMD ferrite beads to supress noise when driving mosfets

texts:
I design a simple circuit activates fan when processor heats up.
I started reading more, and I found a very interesting element a ferrite bead in smd form. It has 0.3ohm resistance, Imax 150mA and Impedance 120ohm (at 100 MHz).
I read that, this can be used as a gate drive resistor series with a lower value resistor to drive mosfets and this method reduces parasitic noise.

Is it a good idea to use ferrite bead in this circuit?
I don't have oscilloscope.
FAN: Sunon MF50100V1-1000U-A99, DC 5V, Imax 180mA, Vapo-Bearing™ technology


texts: How to select between a first order and second order filter according to the application?

texts:
I'd like to build two filters:

One that rejects all frequencies except the fundamental.
One that responds to AC currents between 25 and 400Hz. This would be a band pass filter.

Even though I'm planning to learn how to do this by software, when it comes to op amps, how do I know when to use a first order or second order filter? Or multiple orders.


texts: 12 V to 5 & 3.3 V regulator issue with Arduino and ESP8266

texts:
I built an electronic circuit that uses the Arduino IC (ATmega328P-PU) IC, and the ESP8266. I moved out the IC Circuit from the Arduino Board, and moved it into my own board, so that I could free myself from using the Arduino system, just using the IC.

The system that I am building has 4 water sensors and will trigger a web request when the sensor is triggered.

Everything works OK when I use the 5V and the 3.3V regulator built into the Arduino Board, but when I build my own, the 5V starts to get too hot very quickly. I know that the ESP8266 uses a lot of electricity, but I don't know how to support it with my current regulator setup. Also, usually about 3 seconds into it being powered on using a 12V power supply, it will stop working all together.

Note: I basically did moved my IC Board much like this: https://www.arduino.cc/en/Tutorial/ArduinoToBreadboard

The Parts that I am using are as follows:

Addicore 5V 1.5A Positive Voltage Regulator L7805CV in Antistatic Foam (5pcs)
5pcs Addicore 3.3V 950mA LD33V LD1117V33 Voltage Regulator in Antistatic Foam
3-pack NEW Atmega328p-pu Chip w/ Arduino UNO Bootloader
Makerfire 4pcs ESP8266 Serial Wireless Wifi Transceiver Module Esp-01
100 Pcs 6 x 11mm 100uF 25V Radial Aluminum Electrolytic Capacitors

Here is my circuits.io, it has the setup and the code:
https://circuits.io/circuits/2554003-button-press-wifi-with-esp8266/

R1: 10k
R2: 1k
R3: 2k
R3: 220
C1: 100u 20v
C2: 100u 20v

My basic and wiring schema for the ESP8266 setup is like this: http://www.martyncurrey.com/arduino-to-esp8266-serial-commincation/

Again, it works GREAT when the breadboard's power is using the Arduino's built in power regulator.

Also, please note, that I just tried this too, and everything wanted to start burning up just as it would have before: http://electronics-diy.com/3.3v-and-5v-power-supply.php

My question is: what am I doing wrong?


texts: A question about parallel diode configuration

texts:
In a textbook when mentioning a setup to measure a simple 10uA ammeter's internal resistance, they recommend to connect two diodes with opposite orientation in parallel with the (ammeter). The setup is to measure the internal resistance of the ammeter.

They claim these diodes will conduct around 0.6V, and will protect the meter movement during overdrive.

This is what I understand from what they mean, so I draw it in LTspice (please left-click to enlarge the image):

As you see current keeps increasing with the input voltage. But this doesn't make sense to me. (L1 and R1 represent the analog ammeter)

Am I understanding and drawing something wrong here? How would diodes protect the ammeter.

Edit:

Here is the circuit response with a realistic power supply:

It dramatically limits the current but still above 10uA. I guess 200uA is not a problem since the power dissipation is around 0.2mW?


texts: Thevenin Equivalent with dependent sources

texts:
For this problem, I am trying to find the Thevenin equivalent of the circuit. Is there any way to do repeated Thevenin to Norton transformations to solve this? Or is the only way to solve the open circuit voltage and closed circuit current.

If so, when trying to find the closed circuit current, does the wire from the short from A to B short out both the dependent current source and the resistor?


texts: 12v input vs 7815 voltage regulator outuput

texts:
I've made a quick test where I put 12V from a dc power supply to a 15V regulator - so the "input" was lower than the voltage regulator output.

When I measured it, I had a 5V output, and it was what I'm looking for intially, and the regulator wasn't hot.

So I would like to refer to your expertise and ask you if it is a good way to get 5V without any issue like a current drop for example, which is crucial for the working of my components?


texts: Altium Designer PCB project Ground fill polygon cant connect to one of same net component pad

texts:
I'm finishing one of my pcb layout, in this case is a multilayer one.
the trouble is that design rule checker find me 5 unconnected GND pads but the trouble is that this pads are close to a copper ground polygon (connected to ground) but it does not connect to pour.
If i try to add a net manually when it repour the ground polygon it delete this new connection. this is an error!

here my screenshot:

as you can see, in the bottom of the page ther are the design rule checker outputs. and on the center of the screen there's a GND pad unconnected to the close gnd copper fill.

How can i solve this trouble?

thanks


texts:
How can we evaluate the approximate output impedance of the VCCS (Voltage controlled current source) based circuit at port \$ V_0 \$ ?

My Approach:
To calculate \$ Z_{out} \$,equivalent circuit will be :

Applying KCL at \$ V_0 \$ ,we get:
$$\huge I_t + g_m v_{R_{in}}= \frac{V_0}{100k} + \frac{V_0}{R_{in}}$$
$$\implies I_t + g_m (-V_0) = \frac{V_0}{100k} + \frac{V_0}{10M}$$
$$\implies I_t = 0.01 V_0 + \frac{V_0}{100k} + \frac{V_0}{10M} \quad , \text{as} \space g_m= 0.01S$$
$$\implies \frac{10^7}{10^5 + 10^2 + 1}=\frac{V_0}{I_t}$$
$$\implies Z_0 = 99.89 \Omega \space \approx 100 \Omega$$
But answer is given as \$ 100k \Omega \$ !!
so where is my mistake? please help...


texts:
I am making a solar tracker and was checking different methods for Sun Light Sensing.
This one is what I was going to use, which is pretty simple arrangement of LDR sensors, which go in shadow if panel is not perpendicular to sunrays.

However I came across some commercial trackers which use different sensor and arrangement, for eg,

Can anyone explain how this method works and which sensors are they, because it seems to have some advantage over the first arrangement.


texts:
can someone please help me to solve this problem?
This is the scheme:

I can't recognize where the voltage can turn because all the diodes are blocked.


texts:
I have been giving a problem were I have to design 1-bit subtractor, which performs single bit binary subtraction. It has three inputs: the digits ai, bi (bi is subtracted from ai) and the borrow from the previous 1-bit subtractor Bi-1. The outputs are Di (the difference) and the borrow Bi from the next 1-bit subtractor. Present all four stages (truth tables of the both functions, sum of products, minimization and logical circuits). During minimization follow the same approach that we used in class for 1-bit adder design.

I have search around, but I still cannot figure out how to approach this problem. If anyone could shed some light it would be greatly appreciated.


texts: Designing an anti-static enclosure for sensitive electronics

texts:
I was a little disappointed to discover that I managed to fry a brand new Raspberry Pi camera module. After testing on multiple hardware and triple checking all the connectors, I was forced to conclude that I fried the module on board through static discharge.

Since then, I've ordered another one but I'm concerned I will also eventually kill the new one (these modules are particularly sensitive to static discharge) so I am thinking of buying or making some sort of enclosure for the module to help protect the sensitive electronics on board.

I understand there are precautions that should be taken when handling sensitive electronics such as wearing a earthed anti-static wrist-strap or touching a earthed water tap prior to handling.

However, what about when the device is installed? For example, will a plastic case build up enough static charge that will eventually discharge through the module? Should an enclosure be made of metal (and tied to the ground pin)? Will it be sufficient protection if I cut up pieces of an anti-static bag and wrap it around the module?

What are some measures I can take to prevent static discharge from being a problem?


texts: Definition and Explanation of Insertion Loss and Return Loss

texts:
I'm trying to understand the physical meaning on Insertion Loss and Return Loss on a transformer, specifically RF transformers.

The values are often quoted as figures of merit in datasheets, but I'm having trouble understanding how these values affect the operation on a transformer.

I've seen other questions about these concepts elsewhere on the forums, but they seem to discuss dealing with how to handle them in circuits and components rather than their meanings and effects.

The Wikipedia articles on this are somewhat confusing to me.  Could someone please explain, perhaps with a mathematical example, how this all works?

I'll give an example of what I'm looking at:

For a given RF transformer, the Insertion Loss @ 10 MHz is 0.5 dB, and the Return Loss @ 10 MHz is 25 dB, with impedances of 50 Ohm.  Let's say I put in a 1 V, 10 MHz sine wave, what happens?

How does this effect the signal on the secondary winding?  If the windings are 1:1, are these losses the same if I run the signal from the secondary to the primary?  Does this change how impedance is transformed across windings?  What if the winding impedances aren't the same?  Thanks!


texts: Manage Software Installs of your Semi Mass Manufactured Product

texts:
After you get an assembly house to put together your product:

what are the typical approaches to install your software on every one those product? Is this something the assembly house typically do?
Also, is normal to test every manufactured product?


texts: Determine angular position from two potentiometers

texts: I am trying to generate a continuous angle based on the output of the two potentiometers that are inside my device. The pots are shifted by 180 degrees and are capable of spinning continuously. How can I use the signals from both pots to determine direction while also getting a continuous angle function? I understand how to do this with rotary encoders but am having difficulties doing the same with this device.


texts:
Altera CPLD EPM570 series have four global clocks(GCLK0-GCLK3)，I want to assign two clock sources to CPLD: one from oscillator and one from a MCU. From "GLOBAL SIGNAL" part of "MAX II Architecture"MAX II Architecture, i get confused.the structure is shown below:

why does CPLD have four clock output? I think it should only have one output connecting one of four global clocks. Does it mean that four clock output will serve different logicals? and is it safe to assign different clock sources to different GCLKx?


texts: Counter with 4 flip flops jk synchronous from 1 to 12?

texts: I wanted to create a circuit that would count from 1 to 12 to make hours counter for the digital clock. I work on logisim. I already made counter mod 13 but don't know how to adjust from 1 to 12 (not show 0). Can you please help me?


texts:
I'm trying to learn more about high order filter design, with my goal being to design an 8th order Butterworth lowpass filter in spice, then in the real world.   I've been reading a filter book I have and I was trying to follow this  tutorial here.

I was doing ok up until this point:

  From the normalised low pass Butterworth Polynomials table above, the
  coefficient for a third-order filter is given as \$(1+s)(1+s+s^2)\$ and
  this gives us a gain of \$3-A = 1\$, or \$A = 2\$. As \$A = 1 + (R_f/R_1)\$,
  choosing a value for both the feedback resistor \$R_f\$ and resistor \$R1\$
  gives us values of \$1\$kΩ and \$1\$kΩ respectively, ( \$1\$kΩ\$/1\$kΩ\$ + 1 = 2\$ ).

I don't understand how they went from \$(1+s)(1+s+s^2)\$, and all of a sudden they know the gain from that which you use to calculate your resistors.   There's no more explanation, this basically reads to me as if you start with this polynomial table, then a wizard appears, and now you know your gain.

So how did they go from the polynomial to the gain?   The 8th order equation is even larger:

  \$(1+0.390s+s^2)(1+1.111s+s^2)(1+1.663s+s^2)(1+1.962s+s^2)\$

Does that imply that I will have different gain settings for each stage?


texts: Drawing One-sided Magnitude Spectrum of Transmitted Signal in dBW

texts:
Question

The voltage waveform measured at the 50ohm antenna terminal of a 11750-kHz AM (DSB-LC) short-wave broadcasting transmitter is shown in Fig. Q3.

How to draw the one-sided magnitude spectrum of the transmitted signal in dBW?

My Work

Now we know that \$f_c = 11759*10^3\$Hz and \$f_m = \frac{1}{T} = \frac{1}{0.0025} = 400\$Hz.

For Signal,

\$V_{m(rms)}=400/\sqrt{2}=200\sqrt{2}\$V

\$P_m=V^2/R=(200\sqrt{2})^2/50=1600\$W

\$P_{m(dBW)}=10\log(1600)=32.04\$dBW

For Carrier,

\$V_{c(rms)}=1000/\sqrt{2}=500\sqrt{2}\$V

\$P_m=V^2/R=(1000\sqrt{2})^2/50=10000\$W

\$P_{c(dBW)}=10\log(10000)=40\$dBW

a. I wonder that :
The modulation index should be only 0.4. The ratio \$V_{c(rms)}\$ over \$P_{c(dBW)}\$ is too high. My calculation should be wrong?

b. The term "One-sided Magnitude Spectrum" means that I only have to draw either USB or LSB?

Thank you for your help.


texts:
I was wondering what are the professional SPICE programs for simulating analog circuits in the industry now. For example, where the big companies like Atmel simulate their microcontrollers, or a company like Texas Instruments simulates their op amp design. Also, which programs you would suggest to an electrical and electronics engineering student to learn for analog circuit design bearing transistors that make him ready for professional life.
I would be glad if people with experience answer this question. Thank you.


texts: Building SMPS using L4960: How does the choice of inductor affect circuit operation?

texts:
I've decided to conquer my fear of switched-mode power supplies and build one. Right now, I have a L4960 regulator.

Its datasheet recommends use of a 150 μH inductor rated at 5 A. My problem is that I can't find such an inductor. I can either get inductors with lower current rating (for example 150  μH at 1 A) or inductors with smaller or higher inductance (for example 100 μH at 10 A).

So my question is: How is it calculated that 150 μH 5 A inductor is needed?


texts:
I have an Xbox One controller where the X button did not work anymore. I disassembled it today, to find the reason for this. It turns out, there is a hole in the motherboard near the X button:

There was this sticker right above the hole (it seems that "XJY" is an abbreviation of "Shenzhen Xinjiaye Electronics Technology Co., Ltd.", which is a chinese company that builds such motherboards):

Now to my question: is it possible that the adhesive of the sticker in combination with the flowing electricity on the motherboard has caused a corrosive reaction, resulting in the hole? I think there is no mechanical cause, since the wires in the hole are still largely intact and the "missing" part of the motherboard was not inside the controller.


texts: How to Measure Very Large Capacitance e.g. Super/Ultra Capacitors

texts:
I have recently acquired a couple of mysterious ultra/super capacitors from my brother. Apparently he doesn't remember any of the specifications or even brand... To further complicate matters, they have no meaningful identification information stamped or printed on them. (There is a bar code label with alphanumeric code but a quick Google search using it found nothing.)

Looks like it's time to fire up the Scooby-Doo Mystery Buss, 'cause were going on an adventure folks.

First, I figured I'd try to measure the capacitance. Since my LCR meter isn't specified for enormous capacitors like these, I had to get creative with my test equipment.

Taking basic physics into account, we have that capacitance is proportional to the stored charge per volt across the capacitor:

$$ C=\frac{q}{V} $$

where the accumulated charge in the capacitor is the integral of the current through the capacitor:

$$ \int i(t)dt=q$$

Using a current source to charge the capacitor we can simplify the calculations, using only delta measurements of the charge and voltage across the capacitor.

$$ C=\frac{\Delta q}{\Delta V}=\frac{i\Delta t}{\Delta V} $$

With my Advantest R6144 current source I can then charge the capacitor at a set current and simply measure the voltage across the capacitor using my Tektronix DMM4050 in the trendplot mode.

Picures of Test Setup

However, this is where I start to see some rather large numbers. It's possible the capacitor really is ~2200 farads, but that seems a bit high. Admittedly, the capacitor is quite large at ~5.5" long by ~1" radius.

And now some questions for the fine folks of Electrical Engineering Stack Exchange: Is this method a viable means to measure super capacitors? Or is there a more suitable method that I can apply to measure them? Also, does the capacitance of super/ultra capacitors significantly change vs. voltage of the capacitor? E.g., are these measured results predictive/indicative for higher charge voltages. I would reckon the capacitance should fluctuate some, but I doubt its that much. Probably at worst it's a few hundred farads, but I'm no expert on the matter.

Also, and somewhat more importantly, how would I find the maximum charge voltage without destroying the capacitor? Would a constant current charge of say 100uA over a few weeks till the voltage reaches some sort of equilibrium with self discharge work. Then back off a couple hundred milivolts and call that the max charge voltage. Or will it just reach a tripping point and self-destruct while spraying electrolyte all over my lab?

Finally, how do you determine the polarity orientation of the capacitors? These are not marked in any way, and both terminals are identical. I cast my bet with the residual voltage stored in the capacitor. I assume the dielectric absorption/memory effect from previous charging knows the correct direction...

At any rate, it's sort of fun to try and determine the characteristics of these capacitors. But it's still a touch aggravating that there are no useful markings on them, like polarity orientation, manufacturer, ect.


texts: These 105ESM components appear to be capacitors. What are they, and which datasheet may I refer to?

texts:
I received a mixed-bag of various components from a friend and while I can identify the majority of them, there were a few of these inside. They appear to be small ceramic capacitors with a resin package measuring 6mmx5mm. The package is marked 105 ESM on one side, and 50(V|U) ACW on the other.
I found this page which seems to indicate that they may be a 1.0 micro-farad capacitor.
Here are macro images of each side of the package. The images may be clicked to view the full size:

Thank you in advance for any help!


texts: PWM dimmer for off-the-shelf 12v LED bulbs

texts:
I am building a PWM dimmer for loads of up to 10 off-the-shelf 12v LED bulbs.  Here is my current circuit.  I'll describe a fundamental problem and I ask if I'm missing something here.

The driver (everything outside the dotted box) contains a basic astable 555 configuration for generating a square-wave of adjustable duty cycle.** .  The right-most component is a potentiometer for adjusting the duty cycle; this one is voltage-controlled for simulation convenience, but in real life it will be a digital pot chip.   The square-wave (the 555's OUT pin) gates a power nMOSFET (a Darlington NPN pair would work too). The bulb (dotted box) contains a full-wave rectifier with low-pass filtering (for use with 12vac), and a simple LM317 current source (yet these bulbs are $2 each). The driver needs to be able to work with up to 10 bulbs, connected in parallel, though I've only simulated one here (multiple bulbs will not affect the simulation significantly, I believe, as long as the FET can handle the current).

The problem is that if the pot is too large (say 100K) then the frequency of the PWM waveform is low enough (about 100Hz) that flickering becomes evident under some conditons, but if it's too small (say 10K) then the frequency is high enough (about 1KHz) that the bulb completely filters it out and almost no dimming occurs (see waveforms).  The too-fast case is actually a little more complicated: when OUT is high the bulb turns on quickly, but when OUT goes low, the bulb's capacitor has to discharge via the 57ma current through the LEDs, and recH/recL drops low enough for the current source to collapse little, if any.

The only solution is to simply make the best compromise between flickering and dimmability (a 200Hz frequency might be the ticket, but apparently disturbing visual effect can still occur with saccades).   Or to use LED bulbs designed for DC operation, which probably don't have such a honking cap.

PLEASE NOTE: I am well aware that better way to dim LEDs is with an adjustable constant-current driver.  But I need for this driver to work with THIS bulb (in as much as it's typical of off-the-shelf 12v LED bulbs).

** One finds a variety of 555-based PWM generators on the web.   They config the duty-cycle setting resistors/pots in different ways among pins 2/6, 3, and 7 (and some don't even use pin 3); and some even feed the charge/discharge ramp into an opamp comparator and adjust the comparison voltage. Possible advantages of these other circuits are unclear to me, and this one seems simplest.   In any event, none of the alternatives is likely to help with the current problem.


texts: What is the maximum voltage gain that this amplifier can provide?

texts:
Consider the following amplifier circuit operated with a supply voltage
\$ V_{CC}=+3V \$. Assume \$ V_{do} = 0.7V, _A=∞, =100, V_{sat} = 0.3V, V_T = 25mV, V_{do} = 0.7V\$.

I am stuck on this problem. I have tried drawing a small signal model for the circuit, but I do not have values for any of the resistors. I cannot find the small signal parameters \$ g_m, r_{pi}, r_o \$ because I do not know the value of the DC current flowing through the branch.

Note: This problem did not come with a schematic.


texts:
I'm thinking of increasing my 3G USB modem's signal reception using an antenna. I know a UMTS(2.1 GHz) antenna is recommended.

I need to know whether a WiFi (2.4 GHz) antenna will do the job (as I can find one easily); will it?

(I found that two frequency ranges won't intersect, if the antenna is built properly !)


texts:
I've read this statement online when it comes to driving the stepper motor
"Do not connect or disconnect the stepper motor from the driver when energized"
What does this exactly mean. And what will happen if I disconnect the stepper motor from the driver? How will this damage the motor drive?


texts: Which type of LEDs is a good source of light and can replace the sun

texts:
There is often no sun were I live so I need some advice for building a LED matrix that can replace the sun light and possibly avoid bad wavelength. UV produces vitamin D but
upon reading are-uv-leds-really-dangerous? I'm unsure about UV.

Which wavelengths is preferable?
How much LED power?


texts:
First the background.
I’ve got a customer who wants to drive the inputs of an instrument from a separate signal generator.
One of the inputs I designed correctly (series resistor and diodes to the supply rails.) but the other is just straight into an opamp input.  (I didn’t expect someone would want to use an external source… but also the design is ~10 years old and I didn’t know as much back then.)

So when the instrument is powered up there is no problem.  But if someone was to apply an external signal and the instrument was not turned on it would overdrive the opamp input.  The opamp in question is an opa227, but I hope this question can be of broader scope.  The typical opamp spec sheet says you can over drive by 0.7 volts over the supply rails.   I set up a little test circuit (yeah a piece of white protoboard.) and sent in square waves from my sig. gen.  (1- 20 Vp-p).   Now exactly what happens depends on the power supply and the rest of the circuit.  (The built in opamp protection circuit can power the supply rails.)  But I think the worst case will be a dead short on the supply.  So that’s what I did.  It then looks like the built in protection circuit is a diode to the rail with a 10-15 ohm resistor in series.  And at 20 Vp-p (10 V peak) I was seeing 5.2 Vp-p (2.6 V peak) at the opamp input.  I let it run for several hours this way, and though I didn’t do any exhaustive testing, the opamp still seemed to work fine afterwards.   (2.6V at 140 mA ~360mW of power dissipated)

So here’s the question: Can you over drive opamp inputs above the absolute maximum rating on the spec sheet? (I’m pretty sure we have all been prototyping something and turned off the power supply with the sig. gen. still connected.)


texts: Is there such thing as an active-low, logic level mosfet?

texts: I need to make a logic level switch that will turn on when the input signal is 0V (active low). I figured using a MOSFET is the best way to go, but I'm not so sure if there are active low MOSFETS.


texts: How to make a very large lookup table in Verilog?

texts:
I have a requirement to make a verilog module that takes a Gray code integer i and returns the Gray coded integer i-1 using combinatorial logic only.  When I look up examples of Gray decoding, for instance, a lot of them use sequential logic.  I also need it to work on integers of size >20 bits.
The solution I came up with is to write a Python script that generates a verilog file for the appropriate bit width.  I first tried using a big case statement in an always @(*) block as in this 3-bit example:
module gray_decrement(input [2:0] x, output [2:0] xm1);

always @(*) begin
    case( x )
        3'b001: xm1 = 3'b000;
        3'b011: xm1 = 3'b001;
        3'b010: xm1 = 3'b011;
        3'b110: xm1 = 3'b010;
        3'b111: xm1 = 3'b110;
        3'b101: xm1 = 3'b111;
        3'b100: xm1 = 3'b101;
        default: xm1 = 0;
    endcase
end
endmodule

That doesn't compile with an Error (10137): Verilog HDL Procedural Assignment error at graycode.v(1051): object "xm1" on left-hand side of assignment must have a variable data type.  If I make xm1 an output reg it doesn't synthesize how I need it to.  So I went back and redid it as a really big assign statement using the ? operator as in this 3-bit example:
module gray_decrement(input [2:0] x, output [2:0] xm1);

assign xm1 = x == 3'b001 ? 3'b000 :
    x == 3'b011 ? 3'b001 :
    x == 3'b010 ? 3'b011 :
    x == 3'b110 ? 3'b010 :
    x == 3'b111 ? 3'b110 :
    x == 3'b101 ? 3'b111 :
    x == 3'b100 ? 3'b101 :
    3'd0;

endmodule

This works great and synthesizes properly, but after 10 bits (i.e. 1024 elements in my nested ? operation), Quartus errors out with parser stack overflow error.
So the question is what is the best way to extend my assign statement so that it could have ~2^20 lines in it?  Is there some generate magic that I could use since the arithmetic is dirt simple?  Or will I have to do some of the logic simplification in my Python preprocessor?


texts: ATTiny85. How do I use the reset pin as an analog input or digital output?

texts:
According to this datasheet, the ATTiny85 has 6 I/O pins if we include the reset pin. I used five of them to charlieplex 18 LEDs and I need another one to use as analog input.

Would it be possible to use the reset pin either as an analog input or as a digital output? If so, how? I tried controlling LED's with the reset pin, however it kept resetting my board really fast, so that's not how you do it.

Which is simpler, reset pin as analog input or as digital output and how would I manage that?


texts: Overdriven LED's vs electronic flash : Feasibility

texts:
I have been trying to make a DIY fast strobe light. I am fairly new to LED's though.

My requirements is to have a very fast optical sample of falling raindrops. basically to photograph rain so that the drops are visible individually and not show up as a streak in my photograph.

In average conditions, I find a normal flash to work quite well. But the problem is the lifetime. I know that a normal flash lasts for somewhere well into 50k or 100k flashes. The typical flash time is in around 30 - 100 microseconds. But if I wanted to leave it unattended to continuously take photos, say every minute, the flash lifetime will probably run out quick.

I have come across the LED strobes which use LED's instead of flashes for the purpose.

I wanted to know if its practically possible to achieve a comparable light output using LED's.? ( I have a feeling its not possible )
Since the intended purpose will need short bursts of light. If I use high power LED's and overdrive it but reduce the time interval when it is on to somewhere like 10 microseconds, will it work without blowing out the LED ?

I appreciate everyone's view. Thank you.


texts: How to amplify electret microphone to range from 0-5V with bias of 2.5V?

texts:
I'm new to op amps and have tried many circuits but don't get the results I expect. I know I must do some math but I get so confused. I thought my question is really simple but it turns out it's not.

I just want to amplify an electret mic to 5V. Thus 2.5V bias with no input, then 0 and 5V as min and max for signal. Must I build this circuit and just change the values?


texts:
What is the proper method or device to convert 48V to 3.3V?  Total current consumption at 3.3V would be from 60mA to 150mA.

I found several voltage regulators, but they do not have the required capacity (7W, 45V * .15A).

Likewise I tried doing it with voltage dividers but the capacity is likewise too small.


texts: Question on the close loop gain and bandwidth of this OpAmp configuration

texts:
The OpAmp configuration below has two switch:

The close-loop gain and bandwidth on switch 1 is:
:  A_v(CL) =1 and bandwidth of 1MHz

I don't understand why at switch1 the gain is 1, I thought it will be zero since its common-mode signal.

And if ever the gain is really 1,why would the upper bandwidth be 1MHz? I learned before that:
$$f_{2(CL)}=\frac{f_{unity}}{A_v(CL)+1} $$
So the bandwidth must be:

$$f_{2(CL)}=\frac{1MHz}{1+1}=500KHz$$
Why at switch 1 the closed-loop gain is 1 and not 0 and why the bandwidth is 1MHz and not 500KHz(if ever the gain is really 1)?


texts: PCB Through Hole Pattern for Non-Standard Wide DIP-6

texts:
Should I use a 2.75mm pin pitch for this Fairchild MOC3023TVM, or should I stick with 2.54mm(100mil) spacing? Notice the alignment on the dimensions from the datasheet in the figure below (2.75mm = Center to Edge + 1/2 Pin Width):

I've put together some nice PCBs in the past, but mostly with SMDs. And always with the luxury of recommended/standard patterns. What hole/pad size would you use if you were making a custom pattern for this part? I was thinking 0.9mm/1.8mm, which I derived from here. It's the PCB fab I was thinking of using for this project [Sorry OSHPark, I'll be back! :)]

Here's the fab's design rules: PCBway

Here's another helpful "rule-o-thumb" reference: Wikibooks

EDIT-OK, so here is the pattern I'm going with for the first/proto spin. I'll make another edit once I build it up. Thanks everyone for your help!


texts: What kind of a sensor is this to detect metal rotating?

texts:
I looking for this fat component (brown ) on a PCB:

This component using in a textile mill. There is a small metal (buckle) rotating around a disk and this sensor detects whether this small piece of metal is rotating or stopped.


texts: Multiplexer for multiple parallel flash?

texts:
I have one 8 bit flash interface on a MCU. I multiple flash ICs. Each flash IC has one 8 bit parallel interface.

One option is to use a multiplexer. The other option to tie all of the parallel interfaces together and turn only one flash IC on at a time. Turn off as in leave VDD floating.

What should I use?


texts:
I'm planning to do some audio DSP soon but I would like to know if I can connect an ADC directly to a DAC without a processor in the chain. My main reason is to test preamp circuitry.  I would like the ADC and DAC to be 24-bit at 48 kHz, and I have many options ADC and DAC-wise.  I would also like to use I2S for communication so when I add a DSP, it will work seamlessly.

Is it as simple as connecting the clock and data lines?


texts:
The code in the figure below creates an unnecessary latch.
a) What statement(s) should be written and where to remove it?

signal next_p, p: std_logic_vector(1 downto 0);
signal a, b, c, d, q, next_q: std_logic;

process(select,a,b,c,d)
begin
  if (select=”00”) then
    next_q<=a;
    next_p<=”00”;
  elsif (select=“01”) then
    next_q<=b;
    next_p<=”10”;
  elsif (select=“10”) then
    next_q<=c;
                      <------- next_P isnt assigned here (latch?)
  else
    next_q<=d;
                      <------- next_P isnt assigned here (latch?)
  end if;
end process;

process(clk)
begin
  if (clk’event and (clk=’1’)) then
    q<=next_q;
    p<=next_p;
  end if;
end process;

I cant really find the latch at this code.. But i have some thought that next_p in the if-else statement isn't defined which leads to a latch ? But I'm not 100 percent sure if that is the answer, can someone help me to understand where the latch occurs?

regards

a student.


texts: Choosing resistors for an LED lighting panel

texts:
I want to build an LED lighting panel (something like this: https://manioscinetools.gr/en/product/fv-z180-ultracolor-5600k-led-light-panel/). To do so, I am thinking of an implementation with LED diodes placed in parallel.

I wonder if the two schematics above are equal. The first one is a classic schedule solution, while the second is an alternative one in order to avoid non necessary parts (The total resistor has a value multiplied by the number of the single resistors.)
I should note that the LEDs will be turned on/off all together, and that they have the same characteristics concerning the forward voltage.
Any suggestion would be appreciated.


texts: i don't understand the KVL solution to this question?

texts:
this is part of the solution of a previous exam and there are some things i don't understand about it

1- why did he assume the value of current at the 12
Ohm resistor to be 0.5A without any calculations?

2- how did he assume the polarity of Vx in the bottom?

3-if we didn't assume the current of the 12 Ohm resistor can we figure it out by doing a KVL loop between the 12 Ohm and the 6 Ohm resistors?


texts:
We have used TPS75633KC on our custom board. The supply to the regulator is provided from a common point, to which different boards have been connected. We are observing heavy noise introduced in the output and when we isolated the custom board by providing supply from an external source, the noise in the output was absent completely.

We also used an oscilloscope and high impedance probe to measure the ripple noise and it measures around 600mv.

We followed the same application circuit mentioned on the datasheet of the regulator.

We have used 1uf and 10uf at the input and 47uf and 0.1uf at the output. These Ceramic capacitors.

Can somebody help me with this?


texts:
I'm considering using some IRLZ44NS mosfets that I have with an ESP32 that runs at 3.3v. Looking at the datasheet it says:

VGS(th) - Gate Threshold Voltage - min: 1.0v, max: 2.0v

It seems like this will work, but I saw some other posts that refer to people using these mosfets unsuccessfully with 3.3v at the gate.

Here is the datasheet for the specific part that I purchased:
https://static6.arrow.com/aropdfconversion/e4de403d6464383ac0f3e8f5420ce415f093cb18/irlz44nspbf.pdf

I want to use the mosfet as a switch to turn something on that also uses 3.3v (probably 1A max current). Figure 3 on the datasheet looks like I could pull up to ~10A with 3v.

Am I misinterpreting the datasheet? It looks like this part should be fine with 3.3v at the gate.


texts: Choosing sampling rate according to the bandwith reponse in accelerometer datasheet

texts:
In an accelerometer's datasheet, the bandwidth response in the x and y axis is 350 Hz.

There is another information related to the internal sampling rate (shown below). I
don't know how these two are related to each other. What is the maximum frequency at which I can acquire data from this accelerometer?

I would like to get the acceleration data as accurate and fast as
possible. What sampling rate do you recommend?

Edit

I'm using an Arduino Mega. The sensors is a tri axis accelerometer mma7260Q, here is the complete datasheet.

Maybe the Bandwidth response values are related to the internal low pass filter.


texts: What is the condition for a signal to be invertible?

texts:
I have seen, y(t) = x(t+5) is invertible, with inverse being y(t-5).
But y(t) = sin(5t) is not invertible, why?

What is the test condition to see whether a signal has an inverse or not?


texts: How to decide to cuttoff frequecies of filter in case of using ADC( Flow: Analog-signal to ADC to bits to fir_filter to filtered_output)

texts:
FIR filter has to be used for removing the noise. I don't know the frequencies of the noise that might be adding up into the analog feedback signal I am taking.
The ADC has takes just a voltage value from a as a feedback and gives 16 bits digitize value as the output. Whatever voltage value I measure on the board using the voltmeter I can calculate it using the 16 bits on my screen (teraterm).
My apparatus consists analog feedback signal then i am using ADC to digitize the value now I have to apply FIR filter to remove the noise, Now I am not sure which noise the noise which added up in the analog signal from the environment or some sort of noise comes there due to ADC ?
Well the voltage which is coming from the Wheatstone bridge is that is affected by some type of noise, if yes how can decide the frequency cutoffs to remove the noise?


texts: Question about using variable reluctance sensor

texts: I am integrating a variable reluctance sensor into my project. These take the the signals produced by inductive pickups and convert them into nice square signals that a processor can use. Quite often, the voltages produced by inductive pick ups can be very large (> 100 volts). Becase of this, most of these sensor inputs are rated over 100V (see the LM1815 or the NCV1124). However, one sensor IC, the MAX9926, appears to have inputs that are limited to Vcc. This doesn't make sense to me. Am I reading the datasheet wrong or do they expect you to take care of clipping the voltage before the IC input?


texts: A question about ferrite bead used for differential mode filter

texts:
At high frequencies sometimes ferrite beads are used instead of inductors as normal/differential mode filters. I draw Figure 1 and Figure 2 below showing LC and Ferrite bead C differential filters:

Let’s assume we want to quantify the voltage attenuation at 1MegHz. For. Figure 1 case I can write:

Vout / Vin = Xc / |Xc+Xl|

where Xc is the capacitive reactance and Xl is the inductive reactance. But as you see the denominator is actually the vectorial/phasor sum. It means at particular freq. there will be resonance when Xc=Xl and current will reach maximum ect.

What if we use a ferrite bead instead of an inductor as in Figure 2; will the denominator be vectorial/phasor sum or scalar sum? Imagine the ferrite bead impedance is given as 100 Ohm at a particular freq. and by chance the Xc is also 100 Ohm at that freq.; in that case will the denominator be zero or 200 Ohm? Or will it be sqrt(100^2+100^2)?


texts: Reading 2 Quadrature encoders using a single Arduino Due

texts:
I am working on an autonomous robot in my summer vacations. I am currently working on running the motors of my robot in a closed loop. In order to do so, I have to interface two Quadrature encoders of the motors with the Arduino Due that I have. My motor encoder have 3200 Edges per Revolution. I have read the Atmel SAM3x8E datasheet and have successfully tested one encoder. It appears that TIOA0 and TIOBO are used to read PHA and PHB of of one Encoder which correspond to Pin 2 and 13 of Arduino Due. I am not using Index pin (TIOB1).

It seems that I can only interface 1 quadrature .Is their any way I can use Quadrature decoder to read 2 encoders instead of one. As I have stated earlier I am not using the index pin. So, maybe there might be a way to decode to encoders using the three available pins as shown in the above diagram. I don't want to use Interrupts to do this job.

Here's is the link of SAM3x Manual:
http://www.atmel.com/Images/Atmel-11057-32-bit-Cortex-M3-Microcontroller-SAM3X-SAM3A_Datasheet.pdf

Link of Motor that i am using:
www.pololu.com/product/2824


texts:
I have to replace a USB-C connector. After desoldering I found a rather uncommon footprint. Has anyone seen this footprint before and knows where to find a new connector of this type?
Thank you!