texts: Step response of voltage inverter and RC filter homework question

texts:
This is my solution so far:

Vth would simply be the output of the inverting op amp which is Vth = -(Rf/Ri)Vi
Rth would simply be R2 || R3.

simulate this circuit – Schematic created using CircuitLab
And now we have a simple RC circuit with a DC source. So at t = inf, its right to assume that the capacitor would just charge to the V of its source. Am I right?
And then the step response would be:

Using the total response formula of an RC circuit (wouldn't go to all the derivation)

V(t) = (V(0) - V(steady-state))e^(1/RC) + V(steady-state)

Tau would just be C x (R2 || R3)

So the step response would look like
V(t) = (0 - Vth)e^(1/(R2||R3)C) + Vth
Did I get this right? I'm having doubts because it's an op-amp and i'm not sure if i'm oversimplifying things.


texts:
I asked a question some time ago about crossing clock domains
Design practice crossing clock domains and async signals.

One of the "rules" is to never synchronize multi-bit signal bit-by-bit, because of timing glitches between individual bits.

I have now a design, where I need to cross a multibit signal from a 27MHz domain to a 54MHz clock domain.

I have no more FIFO's left in my fpga, so is there any way to do this without using an async fifo?

Is it possible to synchronize the multibit signal, and set some timing constraint, so I at least get an error if timing is not kept?


texts: Can I use a 40V schottky on a system which may suffer a 40V reverse fault?

texts: I've heard that the Vrrm of a diode is a maximum, and the diode should not be continuously exposed to it. I'm using a PMEG4010CEJ diode, a 40V/1A SOD323 diode. Basically, the power input is a 33.6V 8S LiPo battery, which could be reversed. The diode is in series with the power input and protects a buck converter against a reversed supply, which would damage it. To add a bit of a margin, let's say the system has to sustain a maximum -40V input fault. Can this diode (or any 40V diode) handle it, or do I need to use a 50-60V diode (more expensive)?


texts: What is the difference between the servo track and the line track of a motorized potentiometer?

texts:
I have this motorized potentiometer, which I would like to control with an STM32 microcontroller.

As far as I understood there are several parts in this device:

a potentiometer
a DC motor
a conductive knob for touch sense

I need all of these. There are 2 connectors. The 2 pins connector is for the DC motor. Nothing special there. But the 7 pins connector is described this way:

pins 1 2 3: line track (R1)
pin T: touch sense
pins 1' 2' 3': servo track (R2)

The touch sense is straightforward. I guess 1 2 3 is the potentiometer. But what is 1' 2' 3' then? I measured with a ohmmeter, and it seems to be the inverse potentiometer, which doesn't make sense to me.

The question is: what am I missing? I found this related question, but with no answer.


texts: Inductive energy when 12V relay coil is released

texts:
Maybe this question is non-sense.
If I have a commom 12V relay (12V, 400 ohms coil) WITHOUT having a flyback diode connected to it, and driven by a low-side protected transistor/IC like ZXMS6004FF (the internal over-voltage protection would do the diode job). The datasheet of the transistor shows it withstands to a 90mJ "Unclamped Single Pulse Inductive Energy".

This is for a very specific project question. Would the transistor get damaged?

Datasheet of ZXMS6004FF:
https://www.diodes.com/assets/Datasheets/ZXMS6004FF.pdf


texts:
I have built a little thermostat based on BMP280 temperature sensor over I2C, ESP8266 Lolin v3 and STX882 433Mhz transmitter.

I have not added additional pull-up resistors or decoupling capacitors.

Everything works fine when the components are out of the enclosure (see picture), but when I put them inside the enclosure the BMP280 readings start to 'oscillate' as shown in this picture

I am not an electrical engineer and the only thing I can think of is that there is some kind of interference between the transmitter and the BMP280 or I2C bus.

To give you and idea I am also attaching two pictures of the thermostat.

Any suggestion?


texts: trying to 'grab' information ( data ) from a computer usb and using it in a programe ( python )

texts:
I was wondering if i could use my own computer to interact with the real world.So, if i have a sensor of some sort  plug it in via USB or a certain information from a USB , then can i get the data from the USB and upload it to a programming language (like python)?

Does it mean I can also send data to the ports from a programming language?

if i could obtain the information then can you give me a web link or some name of a book which discusses about USB ports and the libraries and drivers for this purpose
,thanks?


texts: Tryng to programm 27C256 chip in proteus

texts:
I've made a simple circuit in Proteus with 27C256 chip.
I have 4 variables or input (A, B, C, D). I have 8 functions to implement.
I wrote mi functions in a text file and saved it with the extension (.bin)
https://i.stack.imgur.com/WPDD0.jpg
After I edit properties on the chip and load the saved bin file and run the simulation all works well except that it doesn't do what it suppose to do.
I do not know how to write mi functions in the text file so the Proteus simulation works.
I never done this before and i have to make this as a project for college.
Can someone help me with how am i suppose to write mi functions in the text file so when I run the simulation it does what it is intended to do?
Thank you in advance.


texts: Which value will be used in an always block?

texts:
Here is a verilog code: (This code is not for synthesis)

`timescale 1 ns / 1 ns

module test;
    reg r1, r2, r3, r4;
    reg clk_at_time, clk_from_clk;

    // Initialize signals
    initial begin
      r1 <= 1;
      r2 <= 0;
      clk_at_time <= 1;
      #200
      $finish();
    end

    // Generating simple a clock (period time is 10ns)  (as expected)
    always #5
        clk_at_time <= ~clk_at_time;

    // Generating a clock based on the clk_at_time.
    // This clk_from_clk is always equals the clk_at_time (as expected)
    always @ clk_at_time
        clk_from_clk <= clk_at_time;

    // r1 and r2 inverted at all posedge event. (as expected)
    // r3 is constant 0 (as expected)
    always @(posedge clk_at_time) begin
        r1 <= r2;
        r2 <= r1;
        r3 <= clk_from_clk;
    end

    // r4 is constant 1  ???!!!??? HOW ???!!!???
    always @(posedge clk_from_clk) begin
        r4 <= clk_at_time;
    end

endmodule

And the waveform of the simulation:

In the code there are two clock: first is the traditional clock generated by time always #5 the second is generated by this clock always @ clk_at_time The two clocks are always equal (as expected)

The strange thing that if I use the clk_from_clk in clk_at_time's block the previous value will be used of clk_from_clk. (OK), BUT if I use the clk_at_time in clk_from_clk's block the NEW value will be used of clk_at_time.

Clarify:
See the waveform: clk_from_clk and clk_at_time are equals always.

See code: r3 and r4 are analog:

r3 is in clk_at_time's block and driven by clk_from_clk
r4 is in clk_from_clk's block and driven by clk_at_time

So if clk_from_clk and clk_at_time are really the same r3 and r4 should have be equal always. BUT See the waveform: r3 is always 0 and r4 is always 1

HOW? What is the rule?


texts: How to understand capacitor reading: 0.1uF + 2x2500pF?

texts: I have an old electrical motor from the 1970s. It does not work as it should, and I suspect the capacitor attached to it. It has two legs and reads: 0.1uF+2x2500pF ~250v. I am not familiar with that "+2x2500pF" way of writing it. What should my multimeter read when measuring and what is the idea of the way to write its capacitance? Currently imy multimeter reads something like 0.177uF when connected to the two legs.


texts: I need to vary / delay a voltage to an HT coil, thus delaying the spark

texts:
I need a way to slow/vary the signal to a coil so as to retard the ignition on my Moto Guzzi motorcycle. I'm wondering if this can be achieved by delaying the signal created by the points/electronic ignition to the coil, can this be done? The reason for this is I only want to adjust firing of 1 cylinder as manual adjustment not possible (RH cyl)

Can this be done easily?


texts: Characteristics of TN LCD shutters/light valves

texts:
I want to drive an LCD shutter, which are often found in 3D glasses, with a very low duty cycle (short time transparent, mostly opaque) but also a high frequency.
The TN shutters seem to be limited to ~120hz. Pi cell shutters have a higher frequency at 1000hz. However I cannot find an online store for these, which is why I want to stick to TN shutters.
What limits the TN shutters to this low frequency? Could I drive them higher at low duty cycles? It's hard to find datasheets on these and the ones I found didn't specify rise/fall times, which I figure is the limiting factor.
If I would drive them at a frequency that is too high, with a low duty cycle, can I expect dimming when transparent?

For any others interested in this topic viewing this, I found this source regarding driving LCD shutters, which was really helpful:

https://hackaday.io/project/9676-shutter-glass-tests

Clarification on usecase: I'm interested in using an LCD shutter for limiting exposure of standard CMOS cameras. There are better ways to do it, but this is the one I'm interested in.


texts: Do I need to worry about VSWR when antenna efficiency already includes return loss?

texts: When I pick a WIFI chip antenna, the datasheet usually shows many parameters like VSWR and efficiency.  Given the efficiency already takes all the losses into account, why do I need to care about VSWR?


texts: Problem with making 1 bit RAM memory using transistors

texts:
I'm trying to make 1 bit RAM using four transistors (2 NOR gates).
I built two copies of the following circuit:

I connected a LED to the output "F". Also, I connected another LED to the output of the second circuit (because I built two identical copies) to test them before I continue.
The problem is that when I connect any input of both circuits to HIGH, the two LEDs turns off rather than one LED.
That means the outputs of the two circuits are somehow connected together. In other words, when the base of any transistor is HIGH, the transistor works as a short circuit (wire) for the 2 LEDs so that they both turn off.
I thought I was mistaken and completed the circuit as shown:

But the result is that the LEDs are always off.
What can I do to separate between the two outputs Q and Q'?
Does a floating input mean it is LOW?
Note: I used only R1 and R2, and I didn't use R, R3, and R4. I connect the bases of the transistors directly to the positive terminal ti make them HIGH.


texts: LiFePo4 2 Cell Series Charging with MCP73223

texts:
I want to make a charger for two LiFePo4 cells in series. As I'm aware, charging cells in series may be problematic, due to slight differences on each cells, that may charge one and not the other, being this situation getting worse with time.

I was looking specifically for a IC that would assist the charging, despite having too many external electronics and/or microcontrollers doing the job.

I came across Microchip's MCP73223, which contradicts the need for balancing, claiming to be a model to control 2 cell in series charge.

So, since this IC seems to fit perfectly on my application, the questions are:

Is the need of balancing that critical that even charging only two cells in series will have great repercussions on the charging along time? Why?
If the question for the first question is yes, why would one of the big IC manufacturers develop and sell a chip that induce us on doing something technically wrong?


texts: PCB Design - How much length can I2C lines differ by?

texts:
I am designing a PCB that uses I2C communication and was wondering how much length the SCL and SDA lines can differ by.

EDIT: Clock frequency can be anything from 95kHz to 400kHz. Is there a standard?

EDIT 2: Pull ups are 10kΩ. Is it an issue if the pull up is high? and what if there are multiple pull -ups on the SCL and SDA lines?


texts: For a 'customized' arduino consuming less energy making use of Attiny85 vs PCB Fabrication?

texts:
Currently I am working on a prototype project where I try to move a servo (6V) according to the level of light that is recognized by a photodiode making use of the ISR function. A torch light is used as the source of light.

First, I have built this project successfully making use of an arduino uno.
After that in order to reduce the energy consumption I have made an Arduino on a
breadboard making use of an atmega328 microcontroller adding sleep function using the jeeLib library.
It worked well.
Now I want to go to the next step with this project to design the prototype into a functional tool/device.

I was planning to customize an arduino and solder the servo (6V), photodiode etc.

I have researched to on this topic and read carefully the following link
(How to go from newbie to manufactured?)
and learned that creating a customized arduino might emerge to be an exhausting task; especially for a newbie to electronics like me.

At the same I am wondering whether there is a way to skip going through a PCB Fabrication.
Now I came to learn that I might use an attiny 85 using a perfboard that can be used to program a servo and ISR function as well. Attiny 85 also consumes less energy.

Given the fact that I 'only' need to control a servo (6V) depending on the voltage
going through a photodiode I do think that an attiny85 microcontroller might be
a decent way to realize my project with less effort. I am aware of the little EEPROM and Flash size.
However as already once in a discussion ( My Atmega328 seems to be overkill, what should I use instead?)
apparently not all program that work with arduino uno will work with attiny 85.

Can you tell me whether there is a way for me to skip working with a pcb manufacturer to finalize my project? Is using an attiny 85 microcontroller a good alternative for my project?


texts:
I have a clock divider implemented as follows:

module sync_out(
  input clk,            // This is the FPGA system clock
  output reg sync       // This is the generated sync signal to be tested
);
  localparam
    SYNC_OUT_CLOCK_RATIO = 20;

  reg [10:0] counter;   // Clock counter reset when reaching CLOCK_RATIO

  initial begin
    counter <= 0;
    sync <= 0;
  end

  always @(posedge clk) begin
    counter <= counter + 1;

    if(counter == SYNC_OUT_CLOCK_RATIO) begin
      counter <= 0;
      sync <= ~sync;
    end
  end
endmodule

Here clk is the main clock, and sync is the divided clock outputted directed out of the board. Now ISE gives me the following error:

Place:1136 - This design contains a global buffer instance,
   <clock_deskew_0/BUFG_inst>, driving the net, <clk>, that is driving the
   following (first 30) non-clock load pins.
   < PIN: sync_apbinterface_0/pclk_test_select[15]_AND_253_o4.A4; >
   This is not a recommended design practice in Spartan-6 due to limitations in
   the global routing that may cause excessive delay, skew or unroutable
   situations.  It is recommended to only use a BUFG resource to drive clock
   loads. If you wish to override this recommendation, you may use the
   CLOCK_DEDICATED_ROUTE constraint (given below) in the .ucf file to demote
   this message to a WARNING and allow your design to continue.
   < PIN "clock_deskew_0/BUFG_inst.O" CLOCK_DEDICATED_ROUTE = FALSE; >

What exactly is the problem here, and how can I fix it?


texts: Step-up Voltage for Bluetooth Dongle to Increase Range?

texts:
Here's a bit of background to my enquiry:
Recently I've had a project that involved me upgrading my laptop as much as possible, to get it to a standard where I'd have to buy a new machine if I wanted better performance - since its a pretty low end model designed with planned obsolescence it wasn't very hard (or expensive).

Part of this involved in taking the external USB Bluetooth dongle I was using and implementing it inside the shell - which I was able to do via a conveniently placed header with USB protocols, where all I needed to do was make a cable as shown in photo below (at the bottom).

Now this worked really well. I was extremely happy to take that frustrating dongle and put it inside and free up another USB port. However, this port that I was using was only 3.3V compared to the original 5V port of the USB - thankfully the dongle still worked.

This question has two parts:

Since the dongle is now running from 3.3V I've noticied a huge decrease in range, which I really notice when streaming audio via Bluetooth to my home stereo to the extent where I basically have to place the laptop right next to the speaker. I came up with an idea for a solution: To use this step up to convert the voltage back to 5V since for wireless, voltage is more important than current. Does this sound right? Is that a good solution? Any better ideas?
Now flowing from that, does a 5V VDD line from USB need 5V D+ and D- rails? Since the step can only step up one rail, and the original D+ and D- rails would be left at 3.3V. Would the dongle be able to function properly with a 5V VDD and 3.3V D+ and D- rails?

Really appreciate it. Any better ideas for how to restore range (other than putting the dongle back in its external USB port) would be killer too!

Cheers fam.


texts:
I need to communicate with this DUAL DAC by using SPI : MAX 5223 Dual DAC

There are 2 DAC outputs in this chip and I am confused that how can I select and write to the specific one. There is CS pin with this explanation in datasheet:

  CS: Chip Select. Active-Low. Enables data to be shifted into the 16-bit shift register. Programming commands
  are executed at the rising edge of CS

I believe this is for selecting this chip not related to choosing output. So I have these 2 questions:

How can I write to OutA or OutB? If I transmit data with SPI, how will I choose which output source that will be active?
Since this one is DAC, I will need to send fractions like 1.5, 2.3 etc. There is no command in datasheet for it, so how can I send values like I mentioned above?


texts:
My realy says "Switching up to 16A (max. 3680 W / max. 2500 W continuous)". Does this really mean I should not have it connected to loads over 11A, in a 230V system?

What would be an example of switching load and continuous load in this case?


texts: What are the tradeoffs between control vs software algorithms (in charge pump PLL)?

texts:
I have a grid signal (45-65 Hz) that I've sampled with an ADC and put it through an IIR LPF so that noise does not effect the zero crossing detection.

All I want is the frequency of the signal. Now what are the advantages/disadvantages of using a software implemented charge-pump PLL vs just averaging the time between the last few zero crossings?

I know much better PLLs can be used to find the frequency, but given I only have the zero crossings what method will offer the best result.


texts: how to find minimum acceptable current through voltage divider driving transistor

texts:
I'm using a BC557 transistor to control a LED and a uC to control the transistor. The transistor itself is controlled using a voltage divider.

It was suggested to me to use resistors around 100K + 10K for the divider but I'm curious as to how do I figure out what the best resistor values would be? The system is supposed to run on battery so I guess that the lower the current draw, and if that is the case then why not use essentially infinite Ohm resistors for the divider?

I have looked through the datasheet but it does not seem to mention a minimum base current.


texts: I am trying to create a synchronous boost dc-dc converter. I have attached the circuit diagram but I am getting stuck with simulation as a simulation error occurs. The signal generator has a square wave of 5V.  I am using Multisim and there is a popup that says "A simulation error has occurred. Would you like to run the Convergence Assistant to attempt to resolve this problem automatically?" In multisim the voltage across the resistor increases to 2.11V and then the error pops up. Any help would be greatly appreciated.


texts:
I'd like to use an SD card using an SPI interface. My microcontroller uses GPIO logic levels of 2.8V. Do I need a level shifter, or can I connect the card directly? I've had a look at the Physical Layer
Simplified Specification, which mentions:

High Voltage SD Memory Card – Operating voltage range: 2.7-3.6 V

But I'm not entirely sure where to go from there.


texts:
I am developing an embedded system and attaching a uSD-card to it in SD mode (not SPI). The requirement is such that I have to switch the uSD card connectivity between two ports so I am using 74HC4053 as a switch. I have verified all the connections and they are fine. Now when I plug my uSD card and attach one of the ports to a uSD-card reader, the card never responds. Even though I can see that CMD and CLK signals are reaching the uSD card all fine, the card never responds to the commands on the data lines. Any idea what can be going wrong here?
In the same configuration, I used TI's CD4053 (which is lower speed than the CMOS based 74HC4053) and it works fine. I wonder what can be the problem in my circuit. The only intriguing thing I can see in the datasheets of CD4053 and 74HC4053 is that the former has a much lower rON ~5 ohm while the later has ~50 ohm.
Below is a simplified connection diagram


texts: Undervoltage/capacitor problems with Raspberry Pi

texts:
My question is about the correct way to add a capacitor to a circuit with a Raspberry Pi driving a servo.

I have seen undervoltage events in the logs of my app when the servo runs so I added a 470uF/25V capacitor as instructed e.g. here, but the undervoltage events still occurred.

So then I tried replacing the 470uf capacitor with a 1000uF/16V one and noticed it was very hot and the end seemed to be bulging out slightly so I immediately (and carefully) removed it. I did not notice that issue with the 470uF capacitor.

I didn't take any pictures either time, but I was careful to attach the negative pin to ground (black) and the positive side to 5V (red). Both capacitors had the negative side marked on the body and that lined up with the shorter lead.

So on the one hand, I think I did it right, but on the other hand the 470uF capacitor didn't resolve the issue and the 1000uF one clearly wanted to burn up, so maybe not?

Lastly, and this hopefully doesn't explain all my problems, I know servos draw too much power to be fed from the Raspberry Pi's 5V pin, so I am powering it by splicing into the USB wire that powers the Pi. It's plugged into a USB adapter (TROND G2U) that claims 2.4A per USB port. No other high-drain devices are plugged into the Pi so when I did the math it seems like I should have plenty of power to do this hack, other than the voltage drop at the moment the servo turns on.

So to confirm:

I do want the negative pin for the capacitor wired to ground and the black wire on the servo?
I do want the positive pin for the capacitor wired to 5V and the red wire on the servo?
Is my USB splicing hack that I thought was so smart actually a terrible idea and somehow causing all my current problems?

I don't want to try again until I'm sure I'm doing it right so I don't destroy another capacitor, the Pi, the servo, the whole project, my house, etc. Any guidance would be greatly appreciated, even if it's to (politely) tell me how wrong I was on any or all of the above.

Thanks!


texts:
I am trying to read data from a circuit I created recently. But I do not understand if there's something I have missed in the same, since everytime I read data on my microprocessor, it always tells me that all inputs are LOW. I am using few opto-couplers PC817 for reading signals that are in terms of 24VDC.
I tested the optocouplers after activating them and it is working as expected, however I read nothing on the 165's. To test, I supplied 24v to one of my opto-couplers, and on the output I could read a resistance (using a multimeter) of 122 ohm when active.
I can share the code (Arduino - C) if needed, but I think this is more related to circuit/connections not the code.
Below is my circuit diagram.

Note: I have shown 4xPC817 optocouplers and 2x74HC165 in daisy chain configuration (to keep schematic simple). But I have 3 such 74HC165 and all data input pins have one optocoupler connected, so it means there are 24 such opto-coupler.
Update
I checked the voltages and below are the numbers on testing:

Between optocoupler Pin 1 and 2 - 1.14 VDC (Resistance 122 ohm)
(Active) Between 74HC165 Pin GNT and Data Input Pin - 0.02 VDC
(Inactive) Between 74HC165 Pin GND and Data Input Pins - 4.02 VDC


texts: Divergence of Et in TEM propagation in transmission lines

texts: I was going through MIT opencourseware https://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-013-electromagnetics-and-applications-spring-2009/readings/MIT6_013S09_chap07.pdf and I didnt understand exactly why in equation 7.1.37 and 7.1.38 in page 192 the divergence of transverse electric field is taken as zero ? The only reason this would be true is if the region is source free but we clearly see that this field does setup a surface charge density on the surface of the transmission line so intuitively and mathematically why would the divergence of Et be zero?


texts: Is there any pattern or standard to through-hole resistor sizes?

texts:
I've long been under the impression that a quarter-watt resistor has a standard package, and a half-watt resistor has a standard package, etc. But I've recently gotten through-hole resistors which are not in the expected package size. I've done an analysis of a few thousand of the top stocked through-hole resistors at Digikey, and I see no pattern.

3.5 +- .3 mm length seems to be one grouping, which I would normally have thought of as a 1/8W resistor. But Digikey has resistors listed in this size range of anywhere from 1/8W to 1/2W.

6.3 +- .3 mm length is another grouping, which I'd normally call a quarter-watt resistor package. But the wattage is anywhere from 1/8W to 1W.

Similar groupings can be observed around 9mm, 12mm, 15mm, 18mm, 22.2mm, 26mm, and 45.2mm. This makes creating our internal part numbering scheme problematic; we can't just assume a quarter-watt resistor is in a "quarter-watt package", if such a thing there be.

So is there a set of size standards for through-hole resistors? And is there any relationship between those size standards and the wattage of the resistor?


texts: How to use a N-Channel MOSFET for high side switching?

texts:
According to my research, mostly N-Channel is used for low side switching and P-Channel is used for high side switching. But if I want to use N-Channel for high side switching, what are the ways and what are the drawbacks of using N-channel for high side switching.
What I understand is the use of some kind of charge pump or bootstrap(haven't understood this yet), so that the Vgs can be made greater than Vin. But it would be great if someone properly explains this in a easy way.
Please help.
Thank You.


texts: Transistor operating point problem doesn't make sense?

texts:
Find the operating point of the transistors T1 and T2.

I've been given this problem and when I try to apply Thevenin's theorem on resistors R2, R3 and then try to calculate \$I_{C1}\$, I get \$I_{C1} = 0\$ and have no idea why.

simulate this circuit – Schematic created using CircuitLab

Sorry for the not so good explanation I'm new in this community and new in the electronics domain, it isn't really my strength. Any help will be appreciated.

Applying thevenin's on R2, R3, we get:

simulate this circuit

If we take the loop with V1, R1, T1, V2, using K2:

$$Vcc - 0 = U_{EB}+I_{B1}*R1+ V1$$

$$I_{c1}/\beta_0 = (Vcc - V1)/R01.$$

With \$\beta_0 = 100\$ and \$U_{EB} = 0.6V\$ and approximating V1 to 9.6 we get I_c1 = 0. And it's really weird.


texts:
Currently designing a circuit consisting of 50 Ohm rated ICs. Between two ICs (switches), I will place a BP-filter made out of discrete components (high-Q inductors and capacitors). The filter will probably be 7th order.

My question:
Is it necessary to match the impedance of the filter to the ICs, or to the characteristic impedance of the circuit? If so, how can it be done?

Oh, and the frequencies will be in the 100-300 MHz area.

Thanks.


texts: What is the best way (low cost) to obtain a 5v isolated output from 24v batt? The 5v isolated is only for power transceivers so not to much current output is required


texts: Extending DS2408 IOs with MAX7219 or 74HC595

texts:
I have an idea of building a model traffic lights node with Arduino. One node should serve the whole intersection with all the lights from all directions.

I want to use a 1-wire DS2408 to identify the node by its factory set unique id and have its 8 IOs for different lights.

One node should have more lights (for difficult intersections more than 30-40). I want to use some LED driver like MAX7219 or shift register like 74HC595 to extend these 8 IOs to 64.

Can something like this be done? Can I use DS2408 (1-Wire 8-Channel Addressable Switch) and extend its IOs? Or what would you suggest?

I want to use this 1-wire protocol for better scalability and easy node addressing, let's say I want to build a model city with 100 intersections.. Thank you.


texts: Discrepancy between MATLAB and Simulink closed loop response?

texts:
I have a closed loop system which I am testing in MALTAB and Simulink, expecting the same output.

MATLAB

num_plant = [0.0001 10];
den_plant = [0.005 5 0.6616 61.01 2.11 20];
G1 = tf(num_plant, den_plant)

num_controller = [46615 6526 5.722e05 2.389e04 2.001e05]
den_controller = [1 404 41605 162000 200000]

C2 = tf(num_controller, den_controller)
G2=G1*C2; %G1 is same 5th order TF as Simulink
new2 = feedback(G2, 1);
step(new2)

Note:

G1 =

                       0.0001 s + 10
  --------------------------------------------------------
  0.005 s^5 + 5 s^4 + 0.6616 s^3 + 61.01 s^2 + 2.11 s + 20

C2 =

  46615 s^4 + 6526 s^3 + 572200 s^2 + 23890 s + 200100
  ----------------------------------------------------
     s^4 + 404 s^3 + 41605 s^2 + 162000 s + 200000

SIMULINK

According to the official documentation, feedback should be doing what I am presenting with blocks in Simulink. Surely I am missing something. I checked the code and everything should be the same in both cases. What is the reason for this discrepancy?

AS per JonRB's answer:

>> which step -all
C:\Program Files\MATLAB\R2018a\toolbox\control\ctrlobsolete\step.m
C:\Program Files\MATLAB\R2018a\toolbox\shared\controllib\engine\@DynamicSystem\step.m  % DynamicSystem method
C:\Program Files\MATLAB\R2018a\toolbox\ident\ident\@iddata\step.m                      % iddata method
C:\Program Files\MATLAB\R2018a\toolbox\matlab\system\@system\step.m                    % system method

Anything suspicious?


texts: How can some USB chargers produce larger total amperage than others?

texts:
From a quick survey of wall-mounted USB chargers with more than one USB port, it seems that the total amperage provided, for a given number of ports can vary significantly.
For instance, I saw 2-port chargers producing either 2.4A or 1.2A in total.

What is the difference, in terms of build quality and components, between chargers with the same number of ports but with different power?


texts: Does a device such as an inverse triac exist?

texts: i am building a circuit for a quiz show lockout buzzer application ( the type were the first light to turn on is the only light that turns on). I have imagined a circuit that could do the job except i require a part that would effectively do the opposite job that a triac would do. That is, it would conduct until a current is applied to its gate at which point it would stop conducting. It must be a device that operates on low current (order of milliamperes) and DC. So far, i have learned of the device called the gate turnoff thyristor which is close to what I am looking for except it's for high current applications. Does anyone know of a device that would do such a job?


texts: How to send raw data to IEEE-1284 Parallel Printer Cable?

texts:
At my university we have to do some project using parallel port (I know ridiculously old port). We bought a USB to Parallel Printer cable used to connect old parallel printers and the device is an IEEE-1284 Parallel Printer this means I can't see any LPT1, LPT2, LPT* in hardware devices.
Following this guide and using this program to send data we tried to send data to parallel port connecting:

BUSY (pin 11) to any Ground (pins 19-29)
SELECT (pin 13) to +5V
STROBE (pin 1) to ACK (pin 10)

We added a Generic printer as the webpage says:

I then installed a printer by clicking Add A Local Printer from
Control Panel → Printers Then select the Port to be USB001 (Virtual
Printer Port for USB).
Select from the list of printer Generic / Text
Only This loads the proper driver. Then from the Printer Properties
Advanced settings I turned off Spooling the Spool Print Documents
selection and selected Print Directly To The Printer.

This works perfect I see my printer in Ready state when plugin in the cable so the port is the correct one. When I try to send data using the Microsoft program no matters what I send .txt files, raw file containing 0xFF or 0x00 to toggle the entire data port nothing happens on the Data Port. Some status pins go to high or low state permanently no matter what I send so at least I know something is reaching to the port.
What else can we try? Is there any way to get it working? We already spent the money on this cables so we want to try to get them working.
Thank you very much for your help!


texts:
I'm reading The Art of Electronics(3rd), and I'm just stuck with exercise 1.19. Here is the question:

  Explain why L∝n² for an inductor consisting of a coil of n turns of
  wire, maintaining fixed diameter and length as n is varied.

I'm not expecting a long complete mathematical explaination, because the book only gives me a little information, claiming that that should be enough.

My idea: I∝1/n(because practically a wire does have some resistance), and V∝n. As a result, L=V/I∝n². But I also notice that an ideal wire shouldn't have any resistance. So I'm confused now…


texts: Can I dunk a peltier (TEC) module in ethanol?

texts:
I would like to remove the silicone rubber that surrounds the edge of the unit. My intention is to use the TEC as part of an optical power meter: it is painted black on one side and the terminals are connected to a voltmeter after amplification with an op-amp.

I read that ethanol helps to break up the rubber sealant but I am worried that it may damage the stuff on the inside of the TEC unit.

Are there other solvents I can try to use? I have some acetone readily available.


texts: If all parts in a product are FCC or CE certified then do i still need to apply for certification for the complete product?

texts:
I am building a CNC product and all the electronics parts we are using are either FCC or CE certified. Do I then have to obtain a separate certification for the product as a whole ?
Also any idea what are the labelling requirements for such a product ?


texts: Will my relay operate with a 12V battery and simple switch?

texts:
If I have the following components:

12v Car Battery
12v 2amp relay
push button switch (normally open)

Can I simply just link all three components in series and expect the following:

The relay to fire
The relay to live

Or do I have to add additional components (resistors etc)?

The relay in question is this one: http://www.maplin.co.uk/2a-miniature-dpdt-latchingrelay-37529


texts: Can you identify this DIODE or its logo?

texts: Can you identify this diode or its logo? I'm hoping to at least learn who manufactured it to narrow my search.


texts: Is there a systematic way to simplify multiple output boolean functions?

texts:
While studying boolean function simplification I often find things about Karnaugh maps and the Quine–McCluskey algorithm, but I find little about the case of multiple output boolean functions.

In terms of digital circuits, I know that you can reuse the output of gates to get simpler circuits. But, is there a systematic way (algorithm) to get the optimal circuit according to some cost criterion (number of gates, size of gates, etc.)?


texts: Trying to understand what is needed for simple circuit simulation

texts:
I'm working on my Capstone project and a major component of it involves designing a circuit that works with the IOIO-OTG, some motors and a battery. I'm trying to find a free circuit software that will allow me to import component design files from Sparkfun and design working circuits. The idea is to design the circuit fully before building it to ensure we don't fry any expensive equipment.

However, when I started looking for software for my platform (OSX), I was confused as to what I really needed. There are some applications which draw circuits, but don't simulate them. There are others that will take VHDL code and burp out a circuit. Then there's all the "Spice" variants. Finally I tried the Eagle application (which is the file format of the design files from Sparkfun), but found out it isn't actually free and might not do what I need.

Can anyone help me shed some light on what kind of tools I need to develop properly designed circuits using readily available design files?


texts:
i want to display the voltage level through a Potentiometer over the serial comm line(RS-232) in pure ASCII. I am trying to do this using MC9S08AW60 on the Board-DEMO9S08AW60E.
So, if the potentiometer is at 50% position, on Hterm it should show as following:

050%

Now for this(6 bytes) i need to be able to convert decimal to ASCII and transmit the same over RS232. I cant seem to find the logic behind conversion of decimal to ASCII.

questions:

logic for conversion of decimal to ASCII?
any better ideas?
if this question is outside the scope of this forum i am more than willing to change it to the appropriate forum.

Consider the following code:

if(TPM1SC_TOF == 1)
   {

     bob = ADC1RL;
     dummy = (bob*100)/255;
     if((SCI1S1 & (1<<7)))
      {
       SCI1D = dummy;  // at this point i would like to send the percentage of the
                       //potentiometer value!
      }
     TPM1SC_TOF = 0;
   }

Please take note of the attached block diagram!!


texts: STM32F4 LIS3MDL Magnetometer Hard-Iron Effect Elimination

texts:
I am using LIS3MDL 3 axis magnetometer sensor for car detection project. while I am using raw data, I understand that if sensor is exposed to hard-iron effect then this sensor can not read old values.

so how can I eliminate this effect and calibate sensor for stabile working.

thank you for all.


texts:
I have 3Amp (max) 12v DC brushed motor and power supply. I'm thinking of turning this motor on/off and (maybe) control its speed with a transistor. I'm not an expert in electronics at all (I'm a programmer).
Another variant is using relay, but I see transistor as a better solution. To control transistor I want to use Arduino signal.
So I tried to search for a transistor that can maintain 12v and 3amp and use signal of 0-5v, but it seems there are no such transistors. So my question to you - is my way of solving this problem is right? Or should I use relay for it (but obviously I can not control the speed of the motor with the relay).


texts: How Macbook Pro detects an external microphone through TRRS jack?

texts:
An audio port on a MBP is a combination output. If you plug in 4-conductor 3.5mm connector (TRRS) like the one on Apple earbud with microphone, it appears that that port can be use as an input.

I just bought a bare male TRRS audio jack. (without cable, it is for soldering your own) When I plug just that into the MBP, the MBP did not change the output to "External Microphone" as when I plugged an earbud with microphone to it. So I am wondering how did the hardware detects the mic? Does it communicate with the other end by some means?


texts: Filtering a Square Wave into a Sine Wave

texts:
I am trying to Filter a +-4V odd inverted square wave into a sine wave. How should I go about doing so?

So far I have computed the Fourier series of my particular input signal to be:

Which I know to be correct. I am trying to isolate the first harmonic frequency to get my sinusoidal output, which is 1Hz.

I am trying to use an active feedback filter using a TL072 op-amp. So far I have only simulated on LT-Spice and I am getting this output and I cannot figure out why.

I used the frequency band .3 Hz to 1.7 Hz with a corner frequency (.3^2 + 1.7^2)^(1/2), and an Av Gain of 40. I computed R1 and R2 and then computed a common C that would center the frequency range at the corner frequency. They are shown in the circuit diagram.

This is where I got the filter design and model equations from:

(Scroll to Infinite Gain Multiple Feedback Active Filter at

https://www.electronics-tutorials.ws/filter/filter_7.html)

I have tried bumping up the input square wave voltage offset so that the op amp minimum output doesn't limit the output, but I seem to still be getting that effect. I have to use an Active filter design in order to do this.

Here are my square wave output and sine wave output together:

The top starts to look like a sine wave but then the bottom half appears to not pass through the filter. I am thinking that I have the op amp configured incorrectly. When I remove the ground from the - terminal, it crashes the simulation.


texts: Well I am trying to make RPM and reading steps values 0-24 Volts. but in square wave there are a bouncing point which is illustration with red arrows marked. it makes electrical noise generation and it causes misleading to RPM. I'm using hall effect sensor to read values. what do you think this could be caused by?


texts:
I'm not sure if my intuition is a correct thing.

This is type 3 compensator included in feedback of buck converter.
The problem is, that I cannot fully understand how Vref works.
At first, I understood like that in steady state, which means there's no variations, capacitors are being open circuits, so there's so negative feedback at this compensator.
So $$ V_{-} = V_{o} \beta $$
where $$ \beta = R_{4}/[R_{1} + R_{4}] $$
If the reference voltage is ground, that compensator is saturated, and it's a problem.
So, We intentionally give the reference voltage that equals to V-, and DC output will be ground.
After that, if output variates, the compensator will amplify the variation.
But it has a problem too, that Ve is input voltage of amplifier that makes PULSE signal, so
if we make Ve zero upon my intuitions, it cannot operate as PWM mode.
So I think I'm making mistakes, or missing something. Please help..


texts: Driving 5V mosfet with 5V tolerant pins on 3.3V dsPIC33F

texts:
I need to drive a MOSFET (IRFZ44N) with a microcontroller (dsPIC33FJ64MC202). The problem is, the PIC runs at 3.3V and the FET's Vgs(th) lies between 2V and 4V, so there will be times my PIC won't turn it on. But, the PIC has some 5V tolerant pins. How can I use them?
The datasheet says:

Up to 5.5V output with open drain configuration on
5V tolerant pins with external pull-up.

and

11.2 Open-Drain Configuration
In addition to the PORT, LAT and TRIS registers for
data control, some port pins can also be individually
configured for either digital or open-drain output. This
is controlled by the Open-Drain Control register,
ODCx, associated with each port. Setting any of the
bits configures the corresponding pin to act as an
open-drain output.
The open-drain feature allows the generation of
outputs higher than VDD (e.g., 5V) on any desired 5V
tolerant pins by using external pull-up resistors. The
maximum open-drain voltage allowed is the same as
the maximum VIH specification.

It seems so obvious but I still don't get it... How do I wire this circuit? What code do I need to make this work?
Note: I can't change either of those components. That's what I've got to work with.


texts: Transistor used as switch not working when connecting a water solenoid valve

texts:
As a summer project I am trying to create an automatic irrigation system. To do so, I created a circuit with a single transistor which will move from saturation to off and thus behave as a switch.

simulate this circuit – Schematic created using CircuitLab

http://www.electronics-tutorials.ws/wp-content/uploads/2013/09/tran46.gif?81223b

After a few days struggling and learning, I successfully managed to make it work:

V1=0 ===> Vout=9v
V1=3.3v ===> Vout=0v

The next step is to connect a 9v water solenoid valve to Vout and to earth, so that when V1=0 the valve opens and when V1=3.3v the valve closes. I tried the valve connecting it directly to the 9v battery and to earth and it works. However, when I connect it to Vout it does not work. I measured the voltage in Vout when it is 9v and as soon as I connect the valve, Vout drops to around 1v. What is happening? Is it perhaps that the valve is like a resistor and so I need to recalculate the value of the resistors?


texts: High Voltage on PCBs: design and layout questions

texts:
I am designing a PCB that has high voltage (DC) on it. It will be located on a CubeSat (so, space).

The PCB (HV-PCB) will receive the HV (3 kV max) from a DC-DC converter through a Coax cable; the purpose of this PCB is to filter the HV through an RC circuit and then distribute it using connectors and cable to 16 detectors (they are on another board, see below) to provide them with bias.

The HV-PCB will also host another filtering circuit for another HV (<300 V) and will also distribute it to the detector board using connectors and cables.

a) are there particular materials that I should consider for the PCB?
b) can the two circuits live together on the same HV-PCB? My guess is that the best thing to do is to have the components well separated (spatially) on the PCB.
c)in terms of components, is there a particular family of components that I should look into, that are suited for my application? (HV, space).

In general, do you have references (pdfs, youtube videos, tutorials, standards) that might be useful for the design of a HV PCB?

Thanks for the help!

EDIT: tried to be more specific with my questions; on the other hand, I still need to stay generic, since I am asking for some guidelines/suggestions. Hope it is good enough.


texts: Is it possible to convert SPI to UART without a microcontroller?

texts:
I was wondering about converting SPI to UART only in that direction, not the other way around, without using any microcontroller or bridge.

If synchronous can be seen as a particular case of asynchronous communication, wouldn't be somehow possible to make the Rx just read the input? (At least in the case it was an uninterrupted flow of bits.)

Of course, the baudrate should be matched... but are there any other limitations I'm missing?

Cheers!


texts:
After trying a lot on QTouch Matrix for ATmega8,It didn't work for me. So sharing the trouble here.

I have taken reference from this beautiful article. Here he had provided a schematic and PCB design also. I have followed the same schematic and PCB layout, used same code for ATmega8 @16MHz crystal and with fuse bits: 0xc9ff, still it is not working at all.
I got calibrating message on terminal, then after that, when I touch the Pad, it displays random numbers on terminal and that was only for three keys! others are not working.
also those three keys are not working covering with a plastic sheet.

If somebody can direct me towards right path and give some tips, it would be better for me to move ahead.
schematic diagram:

I have set up ATmega8 on General Purpose PCB. touch Pad is connected through jumper wires.Below are Images of the test setup.
MATRIX PAD:

MATRIX PAD Wiring:

TEST SET UP:

ATmega8 Board:


texts: Choosing the right capacitors replacement to fix an LCD Monitor Power Board

texts:
I want to change the capacitors on my LCD monitor power board.

The power board of the LCD is the following:

The 3 of them who have the upper part popped are 820uF 25V.

If i remember something of electronics that part is some kind of filter.

Is correct to assume that I can take bigger capacitors keeping the same voltage, this should make the filtering better right? I ask this because by buying them on online shops is not always possible match all the same specs, for example can I replace them with 3 x 1000uF 25V ?

Also, should I check something else before buying them? I remember people talked also about Low ESR or something like that? Someone can explain me what it means and help me pick the right replacement for a case like this?


texts:
This is probably obvious, but since I still don't have an engineering education, I ran into this problem:

What does dV/dt mean? What does it affect on a TRIAC?


texts: What is the simplest sound generating circuit?

texts:
I'm relatively new to electronics, and have no formal training other that what I picked up through my electrical engineer father. I solder well, can read schematics, have assembled kit projects with a rough understanding of how all the parts work, and know basic electrical terminology and principles. Ohm's law is about as far as my electical math skills go.

So while this may seem like a very basic question to a more experienced and better trained person, please bear with me.

I spent a couple weeks messing around with some LEDs. I started by just hooking one up to my power source. Then, what happens when I add a resistor? What about a capacitor? what about resistors in parallel vs. series? From just playing with my breadboard, I now have an LED that blikcs randomly. Impressive? Nah...but I figured it out myself, and feel that I truly understand it.

Now, I want to design a synthesizer from scratch to give myself an understanding of how specific components affect sound. Starting from the most barebones circuit that can make a noise, I want to add a pot, then some capacitors, then some 555s...you get the idea. I just want to start with the basics and play around to see what happens.

Finding that circuit is proving to be quite difficult. I'm looking for a circuit more complex than hooking a speaker directly to a battery but less complex than http://www.musicfromouterspace.com 's Wacky Sound Generator (which, while simple compared to a real synth is still a lot more complex for me to truly understand what component A vs. compoent B does).

In essence, I want to find the sonic equivalent of Battery-to-Speaker and start playing with what can happen in between.

Electronics golf: what can produce sound with the minimal number of components?


texts: mini PCI-express 52-pin connector, signals W_DISABLE# and PERST#, I/O drive type

texts:
The picture below is from PCI-Express mini card v1.2 specification.

My doubt is about the 2 signals below, they are inputs.
********** W_DISABLE# (pin 20) **********

active low input
when implemented, this signal requires a pull-up resistor on the card
used to disable the radio without resetting the radio module

********** PERST# (pin 22) **********

active low reset input, 3.3V compliant

Can these inputs be driven by 3.3V push-pull outputs? If W_DISABLE# requires a pull-up on the card, do it need to be driven by an open drain output?
Regards.


texts: If I use diodes in a switched DC-DC converter like the output diode on a Buck converter, and the converter switching rate is 50KHZ, how do i choose the right diode? what do I have to look for in the diode DataSheet?


texts: Bi-directional High-side NFET switches -- drains or sources connected together?

texts:
TL;DR:

When using two N-FETs to implement a high-side switch should the FETs be arranged so the drains are connected together, or the sources?

Some additional facts about the current design:

1) A boost supply is being used to drive the gates above high side.

2) The gates of the two FETs are tied together.

3) The supply voltage is ~40V -- bigger than the Vgs rating (+/-20V) of the FETs.

More details:

I'm working on a battery management application and need a bi-directional high-side switch to block current to/from the battery. One way to do this is by putting two FETs back-to-back, in opposite directions, as below.

edit: Note that the arrow in the diagram suggests these are PFETs. As far as I can tell, this is a typo, and should be the other way around (MAX1614 is a high side N-FET driver.)

However, opinions on the matter seem to differ as to whether the protection FETs should be arranged with sources tied together, or drains. If you look carefully at the pictures, you'll see that the FETs are arranged with drains connected together in the first, and sources tied together in the second.

As far as I can see, the first design is fine as long as the supply voltage does not exceed the Vgs specification of the FET. However, if the supply is above that, then the maximum Vgs sustained by the FET closer to the load (the left one, in both diagrams) will be the supply voltage. This will happen when the gate is driven low (i.e. to ground) whenever the gates are turned off.

Am I missing something? Is there another, more clever way to do this that I just don't know about?


texts: Anyone know the premise of this PCB assembly note?

texts:
The assembly note states:

  Bake bare PCBs in a clean and well ventilated oven prior to assembly at 125*C for 24 hours.

Why is this necessary?


texts: How does a hall effect wheel speed sensor work?

texts:
I have been researching how a wheel or crank speed sensor works in vehicles and am having a hard time finding a hard truth.

I think I understand how it works simply. That the sensor detects a change in magnetic field and thus produces a hall voltage. The image below makes sense.
But internally what is going on?

I have seen other images that show a magnet inside the sensor and thus producing a magnetic field. So when the metal rotor or crank comes close to the sensor is that magnetic field reduced or changed enough to then set off the sensor? Therefore, would producing a magnetic field at the end of the sensor produce a signal?

From "How To Mechatronics" Youtube Channel.

Ultimately, what is the magnetic field around the sensor doing that triggers the sensor?


texts:
I've found this solenoid online.
In my current project I try to generate fake recoil for a lasertag marker.

Now my question is:

Can I determine the time the solenoid needs for completing one cycle?

One cycle means powering the solenoid until full length (18mm) is reached and then snapping back in its original state. Basically I need to know if i can complete the cycle in under 70ms.


texts:
I want to automate my motor so that it gets automatically switched OFF when my tank reaches the full load level.So I chose a sensor to be kept at the tank's maximum position... then a MCB connected to it and this is connected to motor's supply.. So only one path is available for current to flow to the motor that is this MCB path... When the sensor electrical signal  is produced.. it is coupled to an amplifier that amplifies the signal high so that MCB turns to OFF position and motor is switched OFF automatically...
Iam pusueing BE 2nd year and I dont have any pre requisitive knowledge on Motor/Sensor so can you help me out with the basics of both electrical devices
Is my project feasible by only me?
What else do I need to do to fulfill my project?


texts: How fast can we measure using IR sensors

texts:
Supposing I have an repeatedly object passing through IR sensors and I am looking at the output waveform. What is the maximum frequency the output waveform can have?
I think this maybe related to the frequency of IR rays used for detection but I am unable to come up with a concrete logic as to why it may depend on that.
PS: ignore other limitations such as the speed of the object to give rise to such high frequency and measuring instrument limitations.


texts:
I have an LCD with 16 segment pins and 8 backplanes. I have already figured out that a full cycle is 32ms, and know that the operating voltage is between 1v and 10v. I was wondering if there was a driver ic that I could use to drive the LCD with my Arduino.
(edit)
It is a raw LCD and has 24 pins going into it, 8 of which are com pins and 16 which are data pins. It is NOT a 16 segment 8 digit display. I have made a chart of what segment turns on according to the com-data combination. I have made my own labeling system for the segments to make the chart more organized. A-F represents the com pins and 1-16 represents the data pins.


texts:
I needed to drop the voltage(5V -> 4,2V) for a small IC(consumes ~2A peak), and used what I could find laying around.
Is this a valid way for dropping the voltage? The resistor turns very hot, but perhaps that is expected?
If I were to re-do it with out limitations in components, what would be the best approach?


texts: Could modern electronic chips (e.g. ARM and Intel processors) operate for millennia at sufficiently low temperatures and clock speeds?

texts:
More broadly, what the practical maximum a modern silicon chip could be expected to last (assuming it operates at some temperature above 77K, and it has stable power)?

For example, I expect diffusion of dopant materials to over time make it lose it's properties. I believe diffusion rates are roughly exponential with temperature, so one might expect an \$e^{77\alpha}\$ as opposed to \$e^{273\alpha}\$, which is roughly \$e^{200\alpha}\$ times slower.

To clarify the applications I have in mind, take the Clock of the Long Now, which is being designed to last over 10,000 years, but made out of massive mechanical components. Another application would be sending interstellar objects at velocities practically achievable today: it would take about 80,000 years for the voyager probe to reach Alpha Centauri. Radiation shielding isn't that much of a theoretical problem since it's a matter of scaling up the shielding mass surrounding the probe (if you can launch and accelerate 1 probe, you can launch and accelerate 1000 shielding probe-masses at 1000x the cost).


texts:
I'd like to use MX-FS-03V 433MHz transmitter together with a Raspberry Pi (RPi).
The Raspberry Pi's outputs have 3.3V, but the MX-FS-03V operates on 3.5-12V (the higher the voltage the higher the transmission distance).

In my understanding, when connecting the MX-FS-03V's VCC to 12V, the DATA input pin must use the same voltage. Is this correct?

The RPi provides 3.3V and 5V, but no 12V. What would be the most simple way to let the MX-FS-03V operate on 12V?


texts: 230V AC triac dimmer for single phase motor and LED lightbulbs

texts:
I successfully developed produced my first AC Triac dimmer board, which works fine on resistive load like regular light bulbs. It also works fine for an AC motor the last 2 years. However, in order to use it for inductive loads  (LED light bulbs and apparently motors too) I should add a snubber circuit.

In comparison to the old circuit, I've added R10, R4 and C3. This the old circuit which is currently in use:

I don't fully understand how a snubber circuit works, but is this the correct implementation? Would I be able to dim dimmable LED light bulbs with this solution?


texts:
I am building test rigs and need to trigger motion detectors remotely. I would also like to avoid using a light source. The devices I've encountered all use an Excelitas 968 pyroelectric sensor (http://www.excelitas.com/downloads/LHi%20968%20PYD%201398%20-%20High-End%20Pyro.pdf); I'd like to remove it and use simulate its signal instead. But I've struggled to find out what I'd need to do, right down to what signal the sensor itself produces.

How can I simulate this pyroelectric sensor?


texts:
I got into FPGA design last year for a project, and had some success with a Xilinx Spartan 6 dev board using ISE. I could do everything with this low cost board and ISE 14, which is free. I needed an embedded processor and used the excellent PicoBlaze - again thanks to great documentation this all worked very well and the project is currently in daily use.

Like many successful projects I can see things growing in future. I still have a fair amount of capacity on the FPGA, but the issue with PicoBlaze really is lack of a C compiler. I would like to find another processor that is very low cost or free, but for which I can build with gcc or whatever.

I had a look around opencores and some interesting things there - but a bit hard to tell what is actively maintained and has a user base. Can anyone recommend free/low cost embedded processor(s) that work well and are reasonably well documented?


texts: Highly integrated RF front-end chipset RFX8055 issues

texts:
In this datasheet of RFX8055 (CMOS 5GHz WLAN 802.11a/n/ac RFeIC WITH PA, LNA, AND SPDT switch), they mention "5GHz Power Amplifier with Low-Pass Harmonic Filter".

If this filter is meant for filtering intermodulation products then it should better be bandpass filter right? (as intermodulation has sometimes \$f_1-f_2\$ low pass component too)
They also mention "High Power Capability for Received Signals in Bypass Mode", the mode in which LNA is bypassed. Does this just mean that the chipset is able to handle high power in LNA bypass mode or is there any other important implication?
Whats the purpose of "LO rejection" in this chipset? Generally, LO rejection parameter is considered in dealing with RF mixers right?


texts: How to transmit a packet through WiFi interface with specific data rate?

texts:
I am doing a project called 'Device free wireless sensing through WiFi'. In the literatures, researchers using PC and WiFi routers to send and receive packet, the channel state information (CSI) can be obtained by using the 802.11n CSI tools. In my project, I am planning to employ one Raspberry pi (or PC) to send 802.11 wifi packets to the air, another Raspberry pi would act as receiver and operate on monitor mode to capture the packets that the transmitter send and then extract CSI for the further analysis. I have already obtain the CSI from the raspberry pi receiver successfully by using nexmon csi tool. Therefore, what I need to do next is build the transmitter to send some packets to my receiver, so that I can capture the CSI value between specific transceiver pair. But I have no idea what tools I should use to send packets and what kind of packets I should send. My question is:

What tools I should use to send packets, so that my receiver can capture the CSI?
What packets I should send to the channel?


texts: Switching for UPS battery (without time delay)

texts:
I have bought a battery charge up board as here. It provides two modes on the EN pin:

1) ground EN pin, the board will charge up the battery from 5V charge source only.

2) float EN pin, the board will charge up the battery from 5V charge source and the battery will drain (provide power) at the same time.

Now, I would like to use this board as a UPS. I have connect a relay at the EN pin, when there is electricity at the 5V charge source, the relay switches to GND. When there is no electricity at the 5V charge source, the relay switches to float.

However, the relay uses a split second to switch from one side to another, making the devices restart at the split second.

Anyway I can switch the EN pin without interrupting the devices? Thanks!

EDIT: I'm powering boards like Ardruino, 5V input, max. 2A


texts: Why do only thick wires have less resistance?

texts: I have learned that the thicker a wire is, the less resistance it has. However, this is not the case for other things such as a wall. If a (non-metal) wall is thicker it does not have a lower resistance. Why is this? Thanks in advance.


texts: Ohm's Law vs. Conservation of Energy Misunderstanding

texts:
I am currently misunderstanding the relation between Ohm's Law and the law for conservation of energy. I am referring to the example (in the book "Foundations of Analog and Digital Electronic Circuits" - Anant Agarwal and Jeffrey H. Lang, page 97):

The example uses \$V^2/R = P\$.
When I check the result (which is 0.5V) against \$V = R\cdot I\$; then I get a voltage that is 2V instead; since \$2\mathrm{mA} \cdot 1k\Omega = 2\mathrm V\$.

What am I doing wrong?


texts:
I'm trying to make a BLDC controler, and I'd like to use an atmega168 as microcontroler and N-FETs (x3) to control the motor.
The microcontroler will output a PWM that will control the motor's position.

I've seen several Brushless controlers and the one I have here seems to have several transistors before driving the actual FET. (see image)

Why is that ?
Thanks for your help


texts: How to wire 2 Female USB plugs into a "Y" USB connector?

texts:
I want to make a USB Y connector from a PC USB backplate it is faster than buying one, fun and educational, (a usb hub is 20 dollars here).

I have many PC USB backplates available to wire into a hub so i had a go:

I  wired all the wires of the same color together in Y formation, but i can only use one of the usb plugs at a time, and not both.

Is there a way to switch round some of the colors so that they are useable concurrently?

I thought USB was simply in series / in parallel.


texts: Question about earth grounds for remote control of VFD via a DAQ system

texts:
A single-ended earth grounded PCI data acquisition board's analog inputs and outputs are controlled by a PC.
The daq board has also analog outputs. One of the analog output is controlling the motor speed. It does that by controlling the 0-10V VFD drive input via an isolation amplifier which isolates the grounds of VFD and the daq system. I tried to draw the system above. The mootor and VFD are close to eachother and  the DAQ system is 20m far away.

The fan motor is a 3-phase (3-50Hz) 22kW AC motor prim delta: 380V.
This is the VHD drive in use.

I'm trying to prevent noise or common mode noise.

Recently I've been told to check the potential difference between the daq earth and the VFD earth grounds.

How should the system be properly grounded to earth?

Should the potential difference between the earths be zero?

Does anyone have experience with such system?


texts:
The markings are 5L = 104 and I can’t find much about it online.

Please let me know if you can help.


texts: Designing a high frequency amplifier and needing an oscilloscope

texts:
I need an oscilloscope to bench test an amplifier I've building. I haven't got any.

I thought If I limit it to 20kHz, it can be used as a sound amplifier. Would simply judging by the sound be enough to diagnose just a sound amplifier? If in case it is, would there be any way to tell if it works to much higher frequencies?

I just don't want deal out that much cash right now and I've always spent very little for every single equipment/supply that I acquire.


texts:
I have been doing this for years (on automotive projects) but the need finally arose to clarify:
When using a SPDT 12V relay (with internal flyback diode), should I isolate the ground trigger when using a micro-controller?
I suppose I could drag everything out and measure current when switching (I am thinking there is none), but I am charging a battery that will likely not complete tonight.
Should I use an optocoupler, or can I simply feed the ground in one pin and trigger output on another?
Oh yeah, Arduino UNO is the target controller.
Thank you

Edit://
Maybe I should also clarify the relay wiring:

(will be replacing switch with Arduino)

Note that the previous description was incorrect.  Please see diagram drawn from circuit.


texts: Will a stereo amplifier with a power supply range of 12V to 25V DC run off a 12V car battery?

texts:
If an amplifier has a power supply input range of 12V to 25V will it actually run off a 12V DC battery system such as a 12V solar system? Here is a link to an example amplifier:
https://fosiaudio.com/collections/old-version-sale/products/bt10a-bluetooth-4-0-stereo-audio-amplifier-receiver-2-channel-class-d-mini-hi-fi-integrated-amp-for-home-speakers-50w-x-2-tpa3116


texts: Quartus Prime: Automatically program .sof file after compilation

texts:
I found a resource on Automatic Script Execution so I know how to create a .tcl script that executes when compilation is complete. I'd like to know what needs to be in that .tcl script to automatically program the generated .sof file. I found this snippet but it doesn't seem to do what I want. Can anybody offer advice?

qexec quartus_pgm.exe -m jtag -c 1 -o "p;output_files\filename.sof"


texts: Galvanic Isolation with Voltage Equalization?

texts:
I need to equalize the ground voltage between the input and output of an isolated DC-DC power supply while still maintaining galvanic isolation. Is there a way to do this?

The reason I need this is so that I don't exceed the maximum isolation voltage rating on the DC-DC power supply.


texts:
Electrician from Australia here. Just having an issue with a heater fan in a bathroom for a client. According to the diagram I have posted, I can wire a second fan up to this and it should all work.

The issue I am having is that because of the permanent supply to the unit, once that thermal switch goes above 55C it supplies power to both the fans via the 20W 330ohm resistor. By adding a second fan as drawn by the diagram, this also will be powered in an over current situation via the resistor.

The issue is, I don't believe the manufacturer has realised the implications of having a second fan fed from the ceramic resistor, and it heats up and blows the thermal fuse at 93C.

So what wattage resistor is required to power the 25W main fan in the unit, and a second 60W fan external to the unit?

I tried working it out as below;

Current draw of main fan = P/V = 25/230V = 0.1A

Voltage drop over resistor= I*R= 0.1*330= 33V

Power dissapated by resistor with main fan= V*I= 33*0.1 = 3.3W

All OK

With the second fan of 60W in the circuit, we now have 85W load.

Current draw of main fan = P/V = 85/230V = 0.37A

Voltage drop over resistor= I*R= 0.37*330= 122.1V

Power dissapated by resistor with main fan= V*I= 122.1*0.37 = 45.17W

45.17W on a 20W resistor- Houston we have a problem.

Is my maths and methodology correct??


texts:
The objective of the circuit below is to get the difference of the hall effect output and a 1 volt reference, then amplify it.
When I first built the sensor and tested it, it worked very well. This is how it behaved:
when no magnetism was present it would be outputting around 0.3 volts, and when south pole magnetism was present it would output 4.5v.

After leaving the sensor connected for a few days it "decided" to switch directions (sorry for the poor terminology), meaning:
When no magnetism is present it outputs 4.8v and it would no longer react to south pole magnetism, but when a north pole magnet is present it will go to 0.5ish volts.

Why would it all of a sudden flip? @Spehro Pefhany pointed out below a mistake I made by adding 0.1uf capacitors. I removed these, and it did not change anything but did I potentially damage the chip?

Edit

I think I may have solved why it "flipped", but still need a solution. When I physically rotate the hall effect sensor from 0 to 180 degrees, the signal inverses from 4.9v to 0.3v. So I am assuming this is from external noise? The sensor itself is nowhere near a magnet or current carrying wires when I perform this test. Any ideas?


texts: Blocking capacitor causing signal to go low in otherwise working amp/rectifier circuit

texts:
I'm making a simple amp > voltage doubler rectifier circuit to drive an lm3916 meter circuit and when simming to choose between JFET, BJT or OpAmp (just for my learning, I'm looking to a Jfet in the end I think) I have this weird behaviour I don't understand.
The basic circuit works fine

I go to add a blocking cap for real world use

And the input goes low to -7v or so, rendering the output unuseable. N001 is OpAmp Non-Inv input
But add a resistor to the input stage

And it all works again.. What is causing this? I don't know why the coupling cap causes the circuit to 'not work' without an input impedance of some sort, separate to the OpAmps near infinite impedance. I simmed many different values of R3 and as long as there's 'some resistance' it works, but given what I know about OpAmps, and the fact that it works without a coupling cap I have no idea what causes the fail when I add the cap..
Any advice well appreciated!


texts: Is there a reason to use smps regulators over modules

texts:
I'm just discovering that TI have switch mode power modules as well as regulators. For example they have the LMZ12001 which would be significantly easier to use than the TPS62150 regulator.

Elektor had a recent project based around the TPS62150 regulator and one of the comments on their website was a reader suggesting to just using a Murata OKI part. Less expensive for one thing.

Is there a good reason to use the regulator part over the module in any applications? Maybe in high volume as the cost might be lower but for the average engineer (ie: me) I can't think of any reason not to go the "easy-as-a-7805" route.


texts: Any downside to using a charge pump for an op-amp negative supply

texts:
Background: I'm often building audio op-amp circuits for various purposes, and for small projects usually prefer single "wall adapter" supply. So for a ground reference I'll either use a simple resistor pair with a capacitor, or better, a spare OP amp configured as a virtual ground, to make my 1/2V point point. But then there's the external ground referencing issue. Since there is only one supply, all ins and outs need blocking capacitors. If I use the "stronger" op-amp developed virtual ground, I can let that ground be the reference for all I/O, thus eliminating lots of capacitors. The downside there is that since ground is really 1/2V, doing this means I can forget about sharing the power supply with any other connected devices. But recently I've been toying with the idea of using a charge pump to create a V- supply, using a separate op amp package. Typically like this...

This would then allow me to use one side of the single supply (negative in this case) as my reference ground again. And so in larger circuit where there are a LOT of ins and outs (perhaps an audio mixer), it would seem using a stand alone charge pump for my negative supply should eliminate the need for a great many capacitors on all the I/O points, and I'd still be able to share the power supply with other small circuits (provided they use a negative ground scheme).

So my question is, is there any major downside I'm missing here? It would seem that as long s the circuits don't need to drive significant loads (that would pull at the V- supply), there might be a lot of advantages to this method. I know there is some issue because with the diode based charge pump, -V won't exactly equal +V. But there are ICs like the CMOS based TI LMC7660 which will do the charge pump function for me with a more accurate -V output and a lot fewer parts. Opinions?


texts: Arduino - Trigger an iPhone's touch screen with no human interaction

texts:
I'm trying to replicate part of this experiment. Specifically, I want to touch the screen with a cable and some aluminum foil whenever I send a signal from an Arduino pin. From the blog post linked above:

  For communication from the Arduino to the Android tablet I'm using a relay to vary the capacitance of a aluminum foil taped to the screen. [...] A relay allows me to float the foil or pull it to ground, effectively changing the capacitance. This is much more reliable, but requires a bulky relay. I think with some more experimentation I'll be able to find a solid sate solution.

This is how my circuit looks like right now:

Basically I have a relay switch switching from ground to float every second.

This works intermittently. Sometimes the screen stops accepting real touch from fingers until the cable is disconnected from the screen.

How can I make this circuit more reliable? How can I make this cable 'touch' the screen whenever I send a signal from the Arduino board?

EDIT 1: I was able to isolate the problem a little bit. If I put my hand behind the phone, even a few milimiters away from it, the trigger works. Otherwise, it won't. See: https://vine.co/v/bIeWP0pdvuP.

EDIT 2: If I connect the charing cable to the iPhone and touch the other end (the USB shield that gets connected to  the computer) it works. I tried to connect that end to ground and works intermittently. It looks like a ground problem. The arduino is connected via USB to my laptop so I guess that's where my ground comes from.


texts:
I bought the 74189 TTL RAM chip and hooked it up but I can't seem to get it function.

simulate this circuit – Schematic created using CircuitLab

I hooked it all up and set the D1 to HIGH. Then I hold CE down, press WE then let go of CE. If I did this according to the datasheet then pressing CE should cause the LEDs to to show what I stored. They don't. (Yes I know the LEDs are inverted but the chips sense outputs are inverted too)

Here's the datasheet and the store page: http://www.jameco.com/Jameco/Products/ProdDS/49883.pdf -- Datasheet
http://bit.ly/1oZL7hy -- Store Page


texts:
I am trying to control a PC fan using a micro-controller(STM32F0)

According Intel's PWM fan spec, the fan will pull up the PWM signal to up to 5.25V.

This signal must be pulled up to a maximum of 5.25V within the fan.

The pin I am using is only speced to 3.3V.

How do I protect it?

Edit:

Clarification, I am talking about the PWM signal send from MCU to the fan. The one on pin 4. Not the feedback signal.


texts: How Much Current is Usually Used with IR Transmitting LEDs, in Remote Controls?

texts:
If you take various Remote Controls from your home,
such as for a TV, Audio System, TV Box, etc,
and measure the current that is supplied to the IR LED in the remote,
what would be common current values for it?

I am talking about the current in the peak of the square wave of course,
and not some average value that takes both "0" and "1" parts of the square wave into account.


texts:
so I have a transformer (3kva 120vac -> 240vac) that runs great but blows the breaker occasionally on startup. So I'd like to add a soft start. This is an industrial control environment so I could build a circuit myself, eventually, but an off the shelf component would be better.

The only soft starts I see online are specifically for motors. Would a motor soft start work here, or am I going to have to build one myself?


texts: What is the impact of unhandled exception on microcontroller peripherals?

texts:
I always assumed that when an unhandled ARM exception occurs (i.e segfault), the microcontroller just stops executing code. This assumption comes from debugging observation: most MCU I worked with stopped in an assembly routine when segfaulting.
As I'm building more safety-critical applications, I want to better understand what is the effect and impact of those errors.

Can I assume the peripheral will stay configured as is?
Can I assume the GPIOs will stay in their current state?
Is the unhandled exception behaviour defined?

Tips and resources to learn more about the fundamentals are appreciated.
Thanks for your time.


texts: How do radio stations broadcast information?

texts:
I have noticed that modern FM radio stations broadcast simple text information about them. While this does not affect the analog sound, it can be decoded by most modern FM receivers, including my mobile phone.
I wonder how is this information encoded. I believe that if I knew a name of the process I would be able to find a very specific documentation.


texts: Overcoming the logic level translator limitations

texts:
Good morning everyone,

I have a STM32F407 microcontroller running on 3.3V logic level, and I have a plethora of peripherals that I want to connect to it. The problem is that these peripherals run at anything but 3.3V level. Some of them are 1.8, some are 2.5, and a couple of 5V devices.

Immediate solution that comes to mind: programmable logic level translator. There are a lot of dual supply bi-directional level translator ICs available; I can turn these into "programmable" ones with the help of digital potentiometers.

My only problem is the common requirement of logic level translator ICs: Vcc > Vl, i.e. voltage on one side of the translator must be strictly less that voltage on the other side. But what I want is:

controller side logic level: fixed at 3.3V,

GPIO side level: anything from 1.8 to 5 V.

Are there any solutions to this problem (either through ICs or discrete elements), or am I asking too much?
Thank you in advance.


texts: Reverse Voltage Protection with a P-channel MOSFET

texts:
I'm looking to use the P-channel MOSFET approach to reverse polarity protection as described here and here (fig 5). Basically this picture:

I've seen that circuit topology used, for example, here, but I'm not convinced that schematic is accurate (maybe you can comment). The way I see it, I can either connect the Drain-pin to the Input Voltage, or the Source-pin to the Input Voltage. Does it matter which way I connect the P-channel MOSFET, or is the protection symmetric about the drain-source channel and all that matters is that the D-S channel is in series with the input voltage?


texts:
I want to be able to output lipo battery voltage to a display the remaining juice in the battery much like a fuel gauge. It has to work for 1s to 6s batteries and it would be ideal to work using an AVR microcontroller. A lot projects out there are focused on 1s batteries and they normally use a voltage divider connected to ADC. I know for a fact that a voltage divider will drain the battery quickly so you have to use a mosfet or something similar to pulse the voltage. I'm fine if the solution is close to accurate and not really intending on using TSSOP packages or other SMT ICs. I want to be quickly breadboard this and prototype as well.

Any schematics or thoughts about how I can achieve this variable voltage sensing ?


texts: Purpose of pins on side edge of QFN package

texts:
I have a QFN part that contains exposed pins on the side (in addition to the bottom). It looks like the quantity and spacing of the side pins are perfectly matched with the bottom pins, except there are a couple little smaller pins in the corner. Here is an image of the side view:

What is the purpose of these? I'm kind of hoping I can solder to the side pins instead of the bottom pins since it's sometimes hard for me to tell if the bottom pins are shorted/open


texts:
I'm need to calculate the how long it will take to charge a battery using a solar cell. I am not taking any charge curves into account, I just want to get a close answer before I run the experiment. I have attached the battery specs as well as the solar specs. I tend to get lost as I go down the rabbit hole with the calcs. Could someone please help.

My Battery calcs:

3.2mA*4.2V=13.44W

1600mAh / 13.44W *4.2v = 5hrs (im not sure if this is even close)

My solar calcs:
wh=(mAh)(v)/1000
1600mAh*4.2/1000=6.72wh
6.72wh/0.000198W = ?

I am not an EE and I feel like im all over the place. Thoughts?


texts: Working on a legacy system that requires a full DMA controller (external DRQ/DACK mechanism) CPLD or FPGA vs Microcontroller

texts: I'm working on a system that involves a legacy ASIC that requires a DMA controller. My current implementation is based on the STM32, but as you might know, the STM32 doesn't provide external DRQ/DACK mechanism for the DMA peripheral. I was wondering if a CPLD or FPGA can fill the gap and solve the problem for me. I have never used one in my designs, but referring to DMA controller IP cores available from Intel/ALTERA, I didn't see DRQ/DACK signals used in their implementation. Any ideas?


texts: Regenerate IRK for NXP QN9020 Bluetooth Low Energy Peripheral

texts:
According to Bridging the GAP: Bluetooth LE Security Part 3,

IRK Re-generation
Each time you clear your peripheral’s bonds, and open it up to a new pairing, you should re-generate your IRK. Why? iOS will not pair to your peripheral if there is already a record for your peripheral under “My Devices” in iOS Bluetooth settings. Generating a new IRK is sort of like labeling your peripheral as a brand new device with a new BD_ADDR. This will allow users to pair to your device a 2nd time without needing to go into Bluetooth settings and manually “forget” your peripheral.
This does have the side effect of having your peripheral listed multiple times under My Devices, once for each pairing and bond.

How would I go about regenerating the IRK using the NXP SDK for the QN9020?
Can someone provide me with a example of this?
Resources

Bluetooth Low energy random address generation - Stack Overflow

Bluetooth Low Energy SMP Pairing | NXP Community


texts: Can anyone please tell me the exact purpose of 3 resistors connected with MCS2 contact?

texts: Can anyone please let me know the exact purpose of the three resistors connected in series with MCS2 contact? Any help would be appreciated.


texts: Ringing/Noise on smps output while BJT turns on

texts:
I am trying to build a 4watt SMPS with 5v output.The design uses BJT switching in quasi-resonant mode. Though I could get the 5V output, I am observing ringing in the output which is increasing the Vpp. I am pretty new to SMPS design and couldn't figure out what is causing this ringing. All that I could sense is, this ringing is caused by the leakage inductance of the secondary winding & the capacitance of the rectifier diode. Please correct me If i am wrong.

The blue waveform is between the transformer's secondary winding pins and the yellow is between the output bulk capacitor pins.

I tried with 20MHz bandwidth as well, nothing much changed.

The ringing is observed every time the BJT is turned on(that's my understanding from the waveform, apologies if I am wrong). This ringing is increasing the Vpp and I want to reduce it. I tried adjusting the AC side RC snubber across the primary winding, but it did not help.

Then, I tried to add a RC snubber across the rectifier diode thinking that this might be because of the secondary leakage and rectifier capacitance, but I did not observe any change. I want to understand what causes this kind of ringing on the output.

Please help me understand the resons behind this ringing.

Some more info:

Operation; DCM
BJT: NXP PHD13003C
Output rectifier diode: 1N5819
Bulk cap: Low esr, rubycon 470uF/10V

Thanks everyone for your responses, Here is the layout

Links to components I used,
Output bulk: Rubycon 470/10V
Diode: 1N5819

Schematic:

Added one ceramic cap & increased the output capacitance. Now, I dont see any high frequency ringing the the peaks have also reduced to 50mV. Thanks for teaching me about ceramic capacitors


texts: If a datasheet doesn't state I2C address pins have pull-up/down resistors, does that mean I must connect them?

texts:
I've got a handful of DS75S+ temperature sensors.  They're SO-8 and I'm going to solder them onto prototyping boards for use with a Raspberry Pi.

I want to set the addresses sequentially so I have the option of using as many as I like on one Pi (up to 8, but I only have 5).  The datasheet says nothing about internal pull-up/down resistors on the address inputs, so does this mean they're floating? Tying them high is trivial, tying them low might be a little messy.  But I don't want to set it floating only to find later that I've caused a problem (especially as, once tested, I'll probably pot them in epoxy).

The "Detailed pin description" says "7 A0 Address input pin." etc., there's no typical circuit and the block diagram has nothing of any help.

I've seen how do you typically tie the address pins and WP pin of I2C device? Do these lines need a pull-up/down resistor or just tied directly (closed) which has a helpful answer that unfortunately starts "Completely dependent on the specific IC you are using, and would be listed in the data sheet. " which isn't true here


texts: Arduino mega - best replacement for atmega 1280

texts:
I wonder if it is reasonable to replace atmega1280-16PU of a bricked arduino mega board?

If yes, does soldering in there a bigger uC make sense? i.e. atmega2560 ?

What microcontroller would fit there best?

I will not have problems with soldering. But a new mega1280 is half the cost of a new arduino.

I need this board for RepRap Mendel Prusa, so I think the 2560 version would be better...

Any suggestions?
Thanks, Martin.

EDIT:

We now know that the pinouts are the same. But the old version of arduino MEGA which i have has an FTDI chip for communication and the newer ones have an atmega8 or atmega16. The schematics also differ.

So there is a possibility that the new bootloader will not work in the old board. So I would have to use the old 1280 bootloader which is pointless.

It is not worth the time to investigate it further. I will simply stick to the ATmega1280 chip.

Thank you all for participation.


texts: why does the model s use multiple batteries?

texts:
The Tesla Model S and NASA's Robonaut both use a battery pack that consists of an array of hundreds of battery cells.

Why don't the engineers just create one giant cell?


texts:
I have an FPGA design Quartus that compiles and works correctly for a cyclone IV EP4CE15F17C8 (42% used).

I'm trying to migrate same design to a smaller FPGA EP4CE10F17C8, but when changing FPGA device I get compilation errors related to a PLL Megafunction I have:

  Error (176554): Can't place PLL "top_level_d9620:top_level_d9620_comp|pll25MHZ_b:G5|altpll:altpll_component|pll25MHZ_b_altpll:auto_generated|pll1" -- I/O pin clock (port type INCLK of the PLL) is assigned to a location which is not connected to port type INCLK of any PLL on the device

I don't know how to avoid this error. Is there a workaround for this? Even if I remove the PLL, I get many errors like this:

  Error (176337): Cell top_laser:top_laser_comp|gene_freq_dpi1:U35|retard_t40[0] fed by 5 non-global control signals -- only 4 control signals may be non-global

Any ideas?


texts: Replacing fried relay for solenoid valve

texts:
I have a sink faucet that operates with a capacitive sensor, if I touch anywhere on the sink it turns the water on, or off. After around a minute it automatically turns off if left on.
The sensor connects to some kind of relay with a single wire (no positive/negative pair), which is also connected to the 6v dc in, and the solenoid valve out. I have observed that reversing the polarity of the current to the valve allows me to open/close it. The valve will stay open closed until I apply the opposite polarity current. Is the capacitive sensor reversing the polarity, and the current then discharging to close the valve again?
I have read about h-bridges and dpdt relays. My question is, could I replace the fried component controlling the solenoid valve with one of these components? Would I need a resistor to have the valve shut off after a set time?


texts:
I read in many tutorials that the inner clock in a micro controller are less accurate (%10) than the external crystal clock. When I generate variable frequency pulses by using a micro controller does that mean I am suing the inner clock and the pulses are not accurate enough? Some tutorials play with the registers and obtain any pulse frequency.

My question is, for example if I use AVR such like in Arduino Uno board and play with the registers does that mean I will use the inner clock? Is there a  way to obtain more accurate pulses?


texts: Cassette Input From TRS-80 - Design Review

texts:
I'm working on getting an input from a cassette for a TRS-80 microcomputer (of 70's vintage). This is what I've worked up. It is a second order high pass active filter with rolloff frequency of 2kHz in a Sallen-Key topology with a unity passband gain, and I've used this as an input to a 555 timer with with appropriate threshold voltages.

I'm wondering if anyone has any suggestions, tips, pitfalls, tricks, things I've missed, notes, etc., that could help the design.

The output is just being dumped to a 1Meg resistor for simulation purposes - I'm assuming the thing reading this voltage will have a sufficiently high input impedance not to load the 555 timer's output.

I tried to pick reasonable values. I can upload the LTSpice schematic and waveforms if anyone's interested in following along!

Thanks all!

[Edit] R67 is a carryover from the original TRS80 schematic I was working from - it is to provide a path in case of DC offset. ;)

[Edit 2]
Updated alternative schematic - using a second op amp open loop, changed design of filter stage to provide some gain. It should work if the second op-amp has a low enough internal capacitative load (something comparators don't have to contend with). I'm using an op-amp and not a comparator though because I am trying to get it done with one chip.

Any comments appreciated!
Thanks!

[Edit 3]
I have received some excellent tips from John Dunn, Consultant at Ambertec, P.E., P.C.
If U1 and U2 are on the same chip, and U2 is being used as a comparator, there could be several problems.

Quoting John, "Depending on specific devices properties, an op-amp’s high and low output voltage saturation levels may not be close to the rail voltages. Also, transitions from one to the other may include bursts of oscillation. A true comparator won’t have these issues.

Another sticking point is that for some dual and quad op-amps,  the op-amp specifications for linear service may not be met if one device in the set is railed. There can be undefined cross connections between the op-amp sections which can corrupt op-amp number one let’s say, if op-amp number three is being used as a comparator and is at either its high or low rail output limit."

John is an excellent guy who runs the Analog Developments group on Linkedin and was kind enough to provide some great insights. :)


texts: PID control: What does it mean that an ideal derivative term is not causal?

texts:
On Wikipedia, it says: https://en.wikipedia.org/wiki/PID_controller

  An ideal derivative is not causal, so that implementations of PID
  controllers include an additional low pass filtering for the
  derivative term, to limit the high frequency gain and noise

Can someone explain in simple terms what does it mean for the derivative to not be "causal"? What is the implication of causality?


texts: How does one compute the ripple currents seen by an active PFC output capacitor?

texts:
Suppose one is designing a single-phase power-factor-corrected power supply, with a known average current load:

The ripple current seen by the output capacitor is critical. If that current is too high, the capacitor will heat up, and its lifespan will be reduced. But how does one compute the ripple seen by this capacitor?


texts: Selecting a damping resistor for crystal oscillator circuit

texts:
I'm building a data acquisition board with an ADAR7251 ADC. I'm trying to figure out the crystal oscillator circuit, and am stuck on the damping resistor. The relevant datasheet is https://www.analog.com/media/en/technical-documentation/data-sheets/ADAR7251.pdf, page 21.

I'm planning on running the crystal at 19.2Mhz.

I understand how to determine the loading capacitors based on the load capacitance of the crystal, and know I should be selecting the resistor to achieve the desired drive level of the crystal. However, I have no clue how to go about determining the correct resistor value to achieve the desired power level. I've seen other examples (such as https://www.crystek.com/documents/appnotes/pierce-gateintroduction.pdf) of finding the resistance values when the feedback resistor is known, but I can't find it specified anywhere in the ADAR7251 datasheet.

How should I find the damping resistor value?

Here's the schematic from the ADC datasheet, it's pretty straightforward:

Thanks for the help!

-Seth


texts: Daisy Chaining Shift Register Concerns and Fan-out Limits

texts:
I've been tasked with massivly expanding some GPIO of a microcontroller, and my inital thought was to chain a bunch of SN74HC595 and SN74HC597 shift registers, however to get the ammount that's required I'm looking at 32x PISO and 32x SIPO shift registers. This seems like a lot and I'm concerned about a few things....

Would the 25mA Sink/Source of my Micocontroller be enough to drive all 32x clocks/latches/resets..etc? If not, could I use a number of buffers to drive blocks of 8x shift registers in parallel? Such as below?

I'm assuming as long as the shifting/clocking of data through the chain isn't too fast I can limit the effects of propergation delays?

Anything I've missed that I should be worried about? It seems wacky but in principle ok? Any particular design or layout considerations?


texts: Draw power from a portable mobile charger to power circuits

texts:
I usually power my beginner prototype circuits using mb102 power supply board, but it needs an external elimeter to draw power and then regulate it.

I was looking for a portable solution for my 5 volt and 3.3 volt circuit needs and came up with using a portable battery charger for mobile phones.

I tried powering up a simple transistor and LED circuit with it but it wouldn't power-up.

I feel that there is some load sensing circuit in the portable charger which doesn't detect these low power circuits.

I also tried connecting different resistors to the charger, the charger outputs 5 Volts for a few seconds and then again shuts down and doesn't stay ON continuously.

It would be really comfortable to use a portable charger since it could be charged using a phone charger and would be very handy.

What can I do to make the charger output power on low loads?


texts: 5v clock feeding 3.3v microcontroller - resistor+zener acceptable?

texts:
So I've used a resistor and diode to level-shift from 5v to 3.3v, but that's been for general logic - the fastest thing I've done with that is 9600 bps serial.

I now have a need to feed a 3.3v powered microcontroller (an ATXMega32E5) from a 10 MHz clock signal, which I only presently have available as a 5v square wave (an output from an NB3N551 powered at 5v).

I propose to use a 10 kΩ series resistor followed by a 3.3v zener diode. Circuitlab simulation seems to show this would work, but I am not sure I trust it to be a complete enough simulation.

simulate this circuit – Schematic created using CircuitLab

Is that simple zener clipper likely to work acceptably, or is something more sophisticated called for?