texts: Using Super Capacitors with solar cells and batteries to help save my dogs

texts:
I am looking to make a dog feeding mechanism that will operate regardless of power outages.  The main point of this query initially is to figure out how to work with the materials I have (or can get) to store enough power to run a small Arduino or two for a non-predetermined amount of time.
I have a small collapsible solar pack that is 5v 8 watts, made for slow charging phones and stuff camping.  I have started experimenting with Super Capacitors and currently have 6, 2.7v 500F Samwah (MH47765) caps. I also have a rather large supply of 18650 Li-Ion batteries.
I am having a problem understanding how to balance charge my supercaps.  I am also unsure how to approach power distribution between each segment. I have a small converter that takes 0.9v-5v and outputs 5v at approx 96% efficiency(claimed). I have the necessary parts for a lm2596 5v switching voltage regulator circuit.  I may have pre-assembled ones out of china as well as enough to make 7 or 8 more.
Would it be prudent to regulate the voltage or the solar cells to the caps with the small 5v buck converter or better to do that after the caps?  if I use the lm2596 it seems like it would be just as good to use the arduino's onboard voltage regulator?  The Diodes have have from the lm2596 are 5amp Schottky diodes; are they appropriate for balancing purposes?
The idea of charging two 2.7v caps in series to 5v and then when full, perhaps use a relay to switch to another pair maybe another pair after that. This would maximize power harvesting from the sun. Then once two pairs had charged I could use a relay to put two pairs into a series at 10v making the use of the onboard or lm2596 voltage regulators work, possibly utilizing extra energy to charge some of the li-ion batteries as well?
The system would need to be able to run a real time clock, or could be simplified to work with the sunrise and set. It would need to trigger the feeding mechanism twice a day. So I should have lots of "extra" stored power to pour back into Li-Ion batteries.
The problems:
I live on an island (Guam) and we get very bad storms and typhoons. The power system on the island is antiquated (WWII Diesel)and we suffer from rolling blackouts frequently and prolonged outages during stormy periods.  I goal is to ensure food is provided to two 95lbs (44 Kilograms?) German Shepherds.  I have to travel off island for medical and if a bad storm hits the pet sitters may not be able to get to them.
This doesn't talk about the feeding mechanism side of this but I figured one step at a time.  I am happy to add this for those who are curious or if anyone thinks it may affect the approach so far, but I am trying (and failing) to keep this shortish.

Any ideas, creative alternatives, or any help understanding my options would be very much appreciated!


texts: Arduino turning a knob left and right with Digital PWM

texts:
I am trying to find a way in order to turn an car amp's bass level knob left and right using an Arduino's digital PWM pin. I am thinking that a stepper motor would be the correct motor to use in order to do this or no?

Also, would there be a better fitting motor to do what I am looking to do without much needed modifications to the bass level knob in order to attach it to the motor to turn it?

The bass knob looks like this:

Any insight would be great!


texts:
In the circuit below, I have noticed that when the DC motor (12V) is disconnected, everything works nice. The LCD correctly displays what arduino sends to it. But when I connect the motor as indicated and the arduino sets EN12 to HIGH and 1A to high (2A being LOW) and the motor starts, the display suddenly overwrites some of the fields with weird symbols (see the second picture). This continues even after the motor is stopped and the number of rewritten fields increases everytime the motor starts (arduino no longer manages to overwrite those fields).

I thought that L293D should isolated the circuit with the motor. I even measured the current coming from arduino into the breadboard and there was no obvious change or increased draw due to motor starting (i don't even know why there should be but I was trying to figure that out).

Is there a mistake in the circuit?


texts:
I am not sure of the results I have found for the quality factor of this bode plot.

I am using the \$Q=\frac{\omega}{\Delta}\$  formula but found incoherent results (\$Q=3865\$).


texts: Target type std.standard.bit in variable assignment is different from std_logic_1164.std_ulogic?

texts:
Sorry if the format is not good but I'm new with that..
I'm trying to select a bit from an unsigned signal to be assigned to a bit variable but it doesn't work!!
I've tried to assign it in a process but it doesn't work too
The following errors appear

** Error: D:/Electronic Engineering Faculty/FeeSparc/The_very_last source_code/cache_mem/cache_mem.vhd(70): Target type std.standard.bit in variable assignment is different from expression type ieee.std_logic_1164.std_ulogic.
** Error: D:/Electronic Engineering Faculty/FeeSparc/The_very_last source_code/cache_mem/cache_mem.vhd(71): Target type std.standard.bit in variable assignment is different from expression type ieee.std_logic_1164.std_ulogic.
** Error: D:/Electronic Engineering Faculty/FeeSparc/The_very_last source_code/cache_mem/cache_mem.vhd(114): VHDL Compiler exiting

Any help with that please?

--Cache design
--2 sets, 2 ways, block size=4 words
library ieee;
use ieee.std_logic_arith.all;
use ieee.std_logic_1164.all;

entity cache_mem is port (
c_add : in unsigned(31 downto 0);
c_d_in : in unsigned(31 downto 0);
c_clk : in bit;
c_wen : in bit;
c_d_out : out unsigned(31 downto 0);
c_hit : out bit;
c_dirty : out bit;
finish : out bit);
end cache_mem;

architecture arc_cache_mem of cache_mem is
type cache_type is array(79 downto 0) of unsigned(31 downto 0);
signal cache : cache_type;
signal set,sel : integer range 0 to 1000;
signal hit_0,hit_1:bit;

begin
--set 0
  --block 0
cache(0)<=x"00000000";
cache(1)<=x"00000001";
cache(2)<=x"00000002";
cache(3)<=x"00000003";
cache(4)<=x"01000000";
  --block 1
cache(5)<=x"00000005";
cache(6)<=x"00000006";
cache(7)<=x"00000007";
cache(8)<=x"00000008";
cache(9)<=x"01000001";

  --set 1
    --block 0
cache(10)<=x"00000010";
cache(11)<=x"00000011";
cache(12)<=x"00000012";
cache(13)<=x"00000013";
cache(14)<=x"01000002";
  --block 1
cache(15)<=x"00000015";
cache(16)<=x"00000016";
cache(17)<=x"00000017";
cache(18)<=x"00000018";
cache(19)<=x"01000003";

set<=conv_integer(c_add(7 downto 4))*10;
sel<=conv_integer(c_add(3 downto 2));

process(c_clk)
variable dirty_0,dirty_1:bit;
variable temp_0,temp_1: unsigned (31 downto 0);
--variable out_0,out_1:unsigned (31 downto 0);
begin
temp_0:=cache(set+4);
temp_1:=cache(set+9);

----HERE IS THE ERROR----

dirty_0:=temp_0(25);
dirty_1:=temp_1(25);

 if(c_add(31 downto 8)=temp_0(23 downto 0) and temp_0(24)='1') then
   hit_0<='1';
--   case sel is
--    when 0 => out_0<=cache(set);
--    when 1 => out_0<=cache(set+1);
--    when 2 => out_0<=cache(set+2);
--    when others => out_0<=cache(set+3);
--  end case;

elsif(c_add(31 downto 8)/=temp_0(23 downto 0) or temp_0(24)='0') then
  hit_0<='0';
end if;

if(c_add(31 downto 8)=temp_1(23 downto 0) and temp_1(24)='1') then
  hit_1<='1';
--    case sel is
--    when 0 => out_1<=cache(set+5);
--    when 1 => out_1<=cache(set+6);
--    when 2 => out_1<=cache(set+7);
--    when others => out_1<=cache(set+8);
--    end case;

elsif(c_add(31 downto 8)/=temp_1(23 downto 0) or temp_1(24)='0') then
  hit_1<='0';
end if;

if(hit_0='1') then
--  cache_out<=out_0;
  c_hit<='1';
  c_dirty<=dirty_0;
elsif(hit_1='1') then
--  cache_out<=out_1;
  c_hit<='1';
  c_dirty<=dirty_1;
else
  c_hit<='0';
  c_dirty<=dirty_0 or dirty_1;
end if;

end process;
end arc_cache_mem;


texts: What is the name of this item contact pin?

texts: I am making a box with lights inside of it. These lights are UVC lights, which will sanitize any items put inside. I have attached a photo; I would like to know the name of this item. I know it is some contact pin, but I am not sure which. Must I have this be custom made? As you can see, there is something gold on the right side of each photo; that is what I am looking for. What is the name of that item? if you would like more the product name is Tidie, they are on Indigogo


texts: Output voltage calculation for full wave bridge rectifier

texts:
What would be the calculation for the output voltage of this full wave bridge rectifier?

Thank you.


texts: Pcf8574ap to to manage the 4 address pins of 4067 multiplexer?

texts:
I have a question.

I have a 4067 multiplexer connected to my Raspberry Pi, 4 GPIOs turned on or off, control the channel of the multiplexer.

My problem is that if no channel is changed, my code is working great (LEDs connected for test on those GPIOs turned on and off accordingly).

So I am thinking of connecting a pcf8574 so I can drive the 4 address pins of multiplexer with five volts! Am I on the right path? Is it possible? Should I start thinking differently?


texts: Can an I2S speaker and microphone share the same I2S clock? What about word select?

texts:
If one is very tight on GPIOs, could an I2S TX and RX share any pins?
Edit: The device I was thinking of was the ESP32, connected to an I2S microphone and speaker, for example SPH0645 and MAX98357A.


texts: How is CC3000 placed in Simple Configuration mode?

texts:
I've ordered a CC3000MODR and soldered it to a simple breakout board. In the First Time Configuration it mentions a Simple Configuration mode:

The CC3000 is placed in Simple Configuration mode and begins looking
for beacons or probes
...
In order to perform the first time config procedure, the CC3000 must
enter that mode. In this section it is assumed that the first-time
configuration process can be triggered externally on the CC3000
device. For example, a user may press a button to initiate the
process.

Since the document assumes that the first-time configuration process can be triggered, I can't seem to find how to put the CC3000 into the Simple Configuration mode. Can anyone explain to me how this is accomplished, given that I have a simple breakout board?


texts:
I want to realize a wireless keypad using ESP-32 and a matrix 4x3 keypad, connected via Bluetooth Low Energy to a master unit. I want to use deep sleep mode of ESP-32 when the keypad is not used but I need to wake up the ESP when a key is pressed, while not loosing the input. As far I understood, the matrix keypad needs the CPU running in order to understand which key has been pressed. Is there maybe some other way or component that I can use for this?
Thanks for your suggestions.


texts: passive probes and accurate measurements

texts:
I have read somewhere that if we have a 100 MHz oscilliscope then we can measure only the waveform of 10 MHz accuratley with an error of 1%.

My question is that if passive probes are used then will the measurements will be totally accurate upto 100 MHz of 100 MHz oscilloscope with an error of 1% only.

OR for the accurate meausrement till 100 MHz waveform I should must have a 500 MHz oscilliloscope with passive probes also?


texts:
I have always been taught to driver an LED using an MCP using the following method (Driving the pin high) as shown in the diagram below:

However I have recently seen LED's being driven using the following method as shown in the diagram below. I assume in this method the LED is driven when the digital pin is set to low. Which method is best practice and why?


texts: How to add a 5V USB output to the base of a mass-produced custom table lamp to add phone and tablet charging capabilities

texts:
I am a lighting designer that just released my first table/desk lamp design. I would like to add a USB charging port to the base, so people can light their desk and charge their phone or tablet.

What I would like to do is get a bulk amount of USB ports like I am finding on eBay ("DC-DC Converter Step Up Boost Module 1-5V to 5V 500mA USB Charger") and mount them right into my custom-designed lamp base and connect it to spt-1 or spt-2 standard lamp wire that plugs into the wall.

How can I connect the USB port to the lamp wire so when the lamp is turned on it will charge the consumer's device?


texts: Electronically programmable buck converter module

texts:
I need a electronically programmable buck converter module.

Because I do not trust my skills to approach high-frequency circuits, I thought I would modify one of these very cheap pre-built modules as a basis:

From the datasheet of the MP2307DN controller, I suspect their circuit is as follows:

Can I remove R1 & R2 from these modules and:

replace R1 with 100k fixed resistor
replace R2 with a DS2890 1-Wire digital potentiometer?

Is there any downside to having the potentiometer in the lower leg of the voltage divider? Is there anything I am overlooking?

Edit 1: Attempt at implementing Andy aka's answer:


texts: Best battery to power a Microcontroller outdoors

texts:
I live in a place where the temperatures can range from -20°C to +40°C in different seasons. I need to power a small micro-controller that uses very low energy with a solar panel and a battery. Which kind of battery is more suitable for this work? It must have the following characteristics:

It should resist to temperatures from -20°C to +40°C.
It's not important to store a lot of energy, 500mAh will be fine.
It should output at least 5V. If less I will have to put two or more batteries in series.
It should not require maintenance.
It should live for a decade or more.
It will be pretty always charged since the solar panel will be directly connected to it (or maybe, via software, I can make some cycles of charge/discharge).

which battery do you recommend?

Explanation of the project

I'm following an IoT course at my university, and I'm free to propose a custom project that will be part of the final exam. I thought about a series of small boxes that will allow us to check if a parking slot is free or not. The box will be build with my 3D-printer and it will include: a small solar panel with a maximum power of 9V * 50mA in the best case (size 60x80mm); a battery of at least 500mA that will be charged by the solar panel; a proximity/distance waterproof sensor that will check if a car is parked on the slot; a MCU with WiFi to send data to an other sensor or to a master with a raspberry pi. I will take inspiration from internet for the routing of packets through this "network" of boxes. Not all boxes will be directly connected to the master box.... We are already experimenting plastics to build a box strong enough to resist to the wheels of a car. The solar panel will be protected with a non-scratchable piece of plexiglass. Sensors will be cleaned from leaves and earth by rain, by road-cleaners and by the wind. Our roads are very clean. The major problem we are facing is to choose the best battery to be used in this "extreme" application. In winter, at night, the temperatures can drop up to -20°C while in summer, during sunny days, it's possible to reach +40°C.
Finally, we will develop an App that will give you the nearest free parking slot.


texts: STM32F103 - Simple blinky, but voltage on TMS & TDI

texts:
I'm having some trouble getting my STM32F103 to work as I intend.
On my working board (previously flashed with Espruino firmware) I have LEDs attached to TMS TCK and TDI lines.

After flashing it with .bin generated by System Workbench STM32 I get a dim light off of these LEDs.

Here is the code I used (my actual code is much longer but suffers from the same symptom):

#include "stm32f1xx.h"

void delay(void);

void main(void)
{
  // I/O port C clock enable
  RCC->APB2ENR = RCC_APB2ENR_IOPCEN;
  // Set PC_12 to output
  GPIOC->CRH &= ~(GPIO_CRH_MODE12 | GPIO_CRH_CNF12);
  GPIOC->CRH |= GPIO_CRH_MODE12;

  while(1)
  {
    GPIOC->BSRR = (1<<12);
    delay();
    GPIOC->BRR = (1<<12);
    delay();
  }
}

void delay(void)
{
  volatile unsigned int i;
  for (i = 0; i < 20000; i++);
}

Pin C12 does what I intend for this simple test.
What must I do to have it stop the TMS/TDI activity?

Side question; the .bin generated by System Workbench STM32, does it include everything that is needed? Aka the HAL?


texts: Selecting a value for resistor to make initial capacitor voltage a certain amount

texts:
In the above question, I found the amount of R1 to be 31.6k (R1 = 31.6KΩ) and I worked out R2 in this way:
5 * (R1 / (R1 + R2)) * R2  (first calculate the current in R2 branch and then use V = IR formula)
Which makes the R2 = 0.40001.

The book says that v(0-) = 5R2 (somehow short-circuiting R1).

Am I missing something here?


texts: What are the basics of making a rechargeable battery pack?

texts:
We have a device that runs off of a AC adapter, or a pack of 8 AA batteries. Since in normal use we use both, it would seem to make sense to have the battery pack recharge while using the AC adapter - instead of throwing the rechargeable batteries into a separate charge each time they're depleted.

What are the basics of designing/modifying the existing battery pack and AC adapter to implement that kind of charging?

A quick observation shows that the battery pack looks to be just the cells in series, with a capacitor (perhaps for protection from voltage spikes, it's powering a motor).

My thoughts are that I'll need to make sure the AC adapter can provide enough current to power the device and charge the batteries. The pack will have to somehow be modified to charge the cells in parallel (right?) while powering the device in series.

Other than those vague ideas, I don't know where to start/how possible this is. So what are the basics I need to know when it comes to building this kind of charger?

Slight Update: I know I need a circuit to control the recharge, I'm not just looking for a circuit to build, but the basic purposes of that kind of circuit. How does it monitor the charge (and determine when charging is needed)? What are the basic components involved and their purposes?


texts: What is the current development status of Transparent OLEDs?

texts:
As far as I can see there are some working prototypes, but has this technology reached the market in a stable way?

Does anybody know what's the current status of the TOLED technology?

Also do you think would be possible to add a capacitive touch layer on top of a TOLED?


texts: Phase Shift Oscillator | Theoretical Frequency Mismatch

texts:
I am working with a few colleagues to build a transceiver system 100% from scratch. A necessary component here is the local oscillator system - we have opted to use a phase shift oscillator to generate our target frequencies. Below is the oscillator circuit we built, modeled through LTSpice:

As I understand, the frequency output should be determined according to the relation:
$$f = \frac{1}{2\pi RC\sqrt{2N}}$$
Where N is the number of phase-shift networks and R,C are the values of resistance and capacitance in these networks, respectively.

Based on these assumptions, the above circuit should have N=3, R=10,000, & C=270E-12 - the sinusoidal output is expected to be very near 24KHz. However, both the simulation and actualized circuits are producing a frequency double this, in the vicinity of 47-50KHz. Have I made a poor assumption? Have I overlooked something simple? Why is the actual frequency output double my expected value?


texts:
I need two 5.1V Zener diodes for a small project.

My knowledge in electrical engineering are severely limited, but have some boxes with components that I have taken from various electronic equipment. Among these are a few, what I believe to be, Zener diodes. Looks like this:

Old picture: http://i.stack.imgur.com/91zpw.jpg (from web)

Edit: Here is a picture of the stash. The ones at the bottom are the “otherwise colored as described below.” (My hand is a bit more steady then what the lines would suggest :P)

Inscription on the ones I have are:

  3 |   2  |  1 |  1  |  1 |   1  | 1 | <- How many I have
----+------+----+-----+----+------+---+
 48 | I N4 | 56 | 13Z | 13 | 5.6Y | 9 |
 H  | I 48 | B3 |     | B2 |      | 1 | {- Inscription
    |   ST |    |     |    |      | C |

I also have some that looks similar to the one in the picture, but they have blue instead of black "paint" as well as a silver line on the end with the paint (inside the glass). Of those I have 12 without markings and three with the marking: T5. Not sure if these are Zener diodes.

Question is if I am in luck and any of the ones I have can be used.

Anyhow it would also be nice to know if those inscriptions bear any meaning one can decipher.

Schematic:


texts: Custom board causing strange oscillations on SPI lines

texts:
Question
What could be causing the following corruption on my SPI lines?

Background
I have designed a daughter board which is connected to a Bajie Development board (first listing on this page). The Bajie board utilizes a Xilinx XC70Z010 SoC. On the daughterboard, I am attempting to control a Texas Instruments LMX2572 frequency synthesizer over SPI. But the analog board has injected a pattern that is corrupting SPI transmission (See above image.) Upon closer inspection, the comb pattern reveals itself as a series of small packets (see image below.)

My first inclination is that this is the result of clock interference. I have a 100 MHz clock connected close to the LMX2572 on the analog board. However, these packets are not at 100 MHz but are at a much lower frequency (6.66 MHz).
My question for the forum is this. What common board design mistakes may have caused this pattern to emerge?
There is a similar pattern on SPI lines of the SoC side of the transmission.

Could the corruptions on the analog side be related to the SoC side? This was my thought but both corrupted patterns emerge even when the two boards are disconnected. And the SoC side corruptions appear despite the code being stopped at a breakpoint.


texts:
I am currently building a cable and would like to possible reduce any EMI. Three signals ( GROUND, ANALOG SIGNAL AND VCC) are connected to the encoder. I plan on twisting the Ground and VCC to cancel EMI and shield the twisted wire with aluminum foil. What should I do with the Analog Signal to reduce EMI? I assume the cable to be around 15 ft long.
Note: There are motors, processors and radios around.


texts: differential grounded coplanar waveguide, GND-sig-sig-AVDD instead of GND-sig-sig-GND

texts:
I know we can route microstrips on top of both ground and power planes, but can we use Grounded coplanar in this arrangement?

bottom is GND
In top layer we have one GND and a PWR.
All gaps are 0.15mm
Working frequency: 12GHz

1.Will it damage integrity of signal? Why?

2.(The question has been added refering to marcus mullers comments) I've used this design because Analog Devices has used it on his own reference design. But will it advantageous since the field will confine in between two microstrip. (I think it helps at least to prevent field to propagate through PCB material.) And will Differential GCPW cost of design worth it to switch to it from simple microstrip?

Analog devices reference design:

1.UG-864:

2.UG-866:


texts: L6203 H-bridge output current rings in response to step input

texts:
I have an L6203 H-bridge connected to a brushed DC motor, and today I was testing the worst-case voltage drops across my 1Ω current sensing resistor with the motor stalled. My setup is as basic as it can get, with 5V 490Hz PWM driving IN1.

When I looked at the sense resistor voltage on a scope, I noticed huge artifacts right on both the rising and falling edge of the PWM waveform. I looked closer and the artifacts were current oscillations at about 20MHz, with amplitudes on par with the eventual maximum current draw (~3A). They grew with duty cycle and were also consistent between cycles. Below is an oscillation at the rising edge:

Compare to the signal over a whole pulse:

My probe are grabbers, hooked across one of the two sense resistors in parallel.

I have a hunch that this is a byproduct of the bootstrap capacitors interacting with the motor windings, because the ringing reminds me of an RLC oscillator. However, I'm confused that the amplitude would change with the duty cycle, almost in an anticipatory way. I suspect that it has something to do with the charge differences on the capacitor leftover from the last cycle, but that's beyond my understanding of the L6203 ends.

I'll be hooking this into a microcontroller ADC, and that -6V spike looks very unfriendly. Is this a byproduct of the charge pump as I suspect, and can/should I do anything about it?


texts:
I would like to detect a set of objects (width and height) as they pass through some sort of line sensor in a conveyor line. Something like this (transversal view):

Not sure where to start...

What type of sensor is the right one this for this scenario?
Any thoughts on how to integrate a sensor like this into an Arduino board?
If nothing comes to mind, what other approach would you recommend?


texts: I have a panelized board that I would like to put some nice, rounded corners on, is there a way to specify this so that the g-code can be automatically generated?


texts: How to measure time difference between 2 signal changes in verilog?

texts:
There are two signals sig, enable - and I wanted to find the time difference after which enable toggles after sig falls. ( >Sig Low to Enable toggle< time)

I understand that always@() block can't be nested inside another, so I tried the following approach:

  realtime toggletime ;
  realtime sig_low;

  always@(negedge sig) begin
   sig_low = $time ;
           @(enable)begin
               toggletime= $time - sig_low ;
               end
  end

My idea was to trace sig, and whenever it goes low, note the time (in sig_low) and from that point, trace enable and whenever it changes note the difference between that point and the earlier sig_low value.
But this isn't giving me the required result. Is there some other way of doing this?

*The sig signal is a periodic pulse that goes low say, every 500us. enable is a signal that toggles at sporadic intervals. I am trying to measure the time elapsed after the latest sig low after which enable toggles.

*Both are synchronous to the same clock. They don't trigger at the same time. If there are multiple neg edges, only the last edge is of interest.


texts: Need help identifying Li-ion battery pin order on pager

texts:
I have several PERCOMM E80 pagers that are missing batteries. Usually I use my test battery with clamps on + and - to power up various electronics and it works like a charm. But not on this one. There is very little information on it online other than the FCC documentation. There are 4 pins that connect to a battery so maybe the device needs to be connected to the BT and BSI pins to power on, but I can't figure out the order. I've tried the - and + clamps in every combination possible but no luck. All I know that if I connect them to the middle ones, the battery shorts. I know the original battery was 3.6V and mine is also so no problems there.
Please click on the photo below to see the PCB. I can provide a better close-up later, if it help.
Photo:


texts:
I want to convert analog output of an accelerometer to digital codes.

I understand that the sampling rate of the ADC should be with reference to Nyquist criteria.

Please let me know how to decide on the resolution needed.


texts: Art Of Electronics - Bypass capacitor across D1 in Figure 1.82

texts:
In the below picture, I am struggling with the text, in parenthesis, that says "You could similarly add a bypass capacitor across d1 in figure 1.82"

Can someone explain this to me?  What is the capacitor doing if added and why?  I realize that at higher frequencies, its impedance, resistance drops, but across d1, how many ohms is a diode that is already forward biased?

The earlier text described using a capacitor to reduce the thevenin equivalent resistance of a voltage divider used to provide a cutoff value for a clamp.

Figure 1.82 uses D1 to put .6 volts at D2 so that it is just on the brink of being forward biased and D1 and D2 respond similarly with changing temperature.

Main question I am stuck on is
"You could similarly add a bypass capacitor across d1 in figure 1.82"

What does this do and why?
Thanks for any help.


texts: Interfacing an LPC2148 with a CAN module

texts:
I need to implement the CAN protocol to communicate between two LPC2148s. Now I am planning to use SPI for communication between a microcontroller and a CAN controller and then the CAN protocol for communication between two nodes.

Why do we need CAN transceivers? What does a CAN controller and a CAN transceiver do individually? Or in short, how does data from one node to another node flow?

I know this may be long answer, but I am not finding any resource on the Internet which can tell me all about communication from one node to another through SPI-CAN.


texts:
I was trying to find the output of the LM317 PWM circuit obtained from this EDN article: (Circuit).
I want Vout in terms of PWM. Below is my analysis. May I know it is correct or not.
will all the OPAMPS be able to sink the minimum load current required by the LM317. May I know the things to be taken care of while selecting the OPAMAP?
If wrong please let me know where I went wrong


texts: Parallel Usage of Buck Converters | LM2596 Module

texts:
For my application, I need three voltages +5V, +15V, -15V
Initially, I was using wall socket plugs to connect two 15 volt adaptors, in which I connected the + and - together and considered it as ground, and used that common ground connected to another wall adapter (5V)'s negative to get a common ground, and all my voltages +5V, +15V and -15V.
Since this is cumbersome, I wanted to streamline my power supply, I got a USB-C PD adaptor (capable of giving 20V), and three off the shelf module of LM2596 from amazon, along with a USB-C PD power negotiation chip (zy12pdn). However, wiring it up as mentioned above leads to a short.
Below is the circuit diagram that I am using, previously it was wall adaptors, now its buck converters, now this leads to a complete short and stops USB-C PD from working.

Can adding diodes help the situation?
Is there something wrong with this approach?
How can I fix it?


texts:
I am working on Altium Designer and I would like to create a subcircuit from existing components. To be more clear, I want to be able to create a new part from a schematic I already draw. For a very simple example, if I draw a capacitor and a resistor in parallel, is there a way for me to create a new component called "RC part" with 1 input and 1 output ?

The goal of this would be to simulate each part of my circuit separately.

I've seen that I can create a new "sub-circuit" but it looks like I can only write it in SPICE and I am not familiar with this.


texts: AC-DC converter, transformer modification how-to

texts:
I would like to wire an AC-DC converter based on a datasheet schematic. I try to describe my problem. I would like to increase the max current output. The AC->DC converter has a bjt driving a transformer at about 10 khz. I can manage how to change that driver to supports higher current, but how change the transformer ? I've got the information for the transformer wiring at 1 A output. There is also a feedback coil on that transformer, that I suppose it is not necessary to change, am I wrong ?
Here is the schematic I'm talking about.

EDIT
Maybe we can generalize this question, how to design transformer for AC-DC converters ?


texts:
I have a university research that i am conducting right now. My objective, as a first step, would be to phase shift an NRZ signal at high frequencies >40GHz, assuming this signal is already locked using a PLL.

We were advice to start by finding a way or the circuitry that can coarse phase shift the signal first by 45degrees, and then fine shift the signal to the smallest degree possible. I have searched but haven't found any help online or in IEEE papers, they are usually ambiguous or not very specific.

I would like to know if this accurate small phase shift is possible at high frequencies and what is the circuitry involved.


texts: Guitar to iPhone JFET pre-amp circuit issue

texts:
I am following this tutorial to build a simple JFET pre-amp to connect a guitar to an iphone.

This is the schematic:

I have soldered the components as per the schematic directly onto the 1/4" mono jack for the guitar.

The issue is it only works when I have one finger touching the 3.5mm jack's mic wire/pad and another finger touching the 1/4" tip connection (blue dots on image). Is this an issue with grounding, with the diodes or ...? I am at a loss here.


texts: run bldc motor with arduino and l298 driver

texts:
I am trying to learn controlling BLDC motors without using an ESC, but using Arduino and a driver, instead. At home I found an old DVD driver and took out the motor, which was Nidec Slim 24C, http://www.nidec.com/en-NA/product/motor/category/A010/B010/P0000010/ , with 5-wires: u, v, w, COM, fg. I know, normally BLDC motors have three wires (u, v, w). I understand in this one COM is the center point, and fg is the feedback info line.

I had some L298N modules at home and decided to try them. Normally, with 3-wired BLDC one would wire the motor such that u-v, v-w, w-u, are energized. But with L298 it did not look so easy, I wired each pole against the COM, in sequence; and I was able to run the motor. Phases are connected to L298 output lines 1,2,3 and COM is connected to +5V on L298. Although not as fast as rated (6000rpm), but about 1000+ rpm, or so, smooth and quiet, I was able to get a stable (and high) speed by playing with the delay parameter between phases. Here is the simple Arduino code:

int u = 2;
int v = 3;
int w = 4;
int EN1 = 5;
int EN2 = 6;
int f = A0;

int val2 = 6000;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(115200);
  pinMode(u, OUTPUT);
  pinMode(v, OUTPUT);
  pinMode(w, OUTPUT);
  pinMode(EN1, OUTPUT);
  pinMode(EN2, OUTPUT);
  pinMode(f, INPUT);
  digitalWrite(u, LOW);
  digitalWrite(v, LOW);
  digitalWrite(w, LOW);
  digitalWrite(EN1, HIGH);
  digitalWrite(EN2, HIGH);
  digitalWrite(w, HIGH);
  delayMicroseconds(val2);
  digitalWrite(u, HIGH);
}

void loop() {
  // put your main code here, to run repeatedly:
  delayMicroseconds(val2);
  digitalWrite(v, HIGH);
  digitalWrite(w, LOW);
  delayMicroseconds(val2);
  digitalWrite(w, HIGH);
  digitalWrite(u, LOW);
  delayMicroseconds(val2);
  digitalWrite(u, HIGH);
  digitalWrite(v, LOW);
  if (val2 > 2000) {
    val2 -= 10;
    Serial.println(val2);
  }
}

My question is, whether this implementation is a correct one - to be used in the future for any BLDC motor?

By connecting each phase against the COM, do I loose any speed and/or torque?
With 3-wire only motor how would I use the same logic. Somwehere I read about "Virtual Center Point", by connecting all three phase leads together, with equal weight resistors in serial. Will that give me the same result as real center point?

EDIT1: Yes, "Virtual Center Point" works. I tested with 6 Ohm resistors connected serial to (secondary/parallel) leads, connected together, instead of COM pin, and it worked OK.

EDIT2: I modiefied the code, such that it slowly accelerates by decreasing the delay time. I could go down to 2000 microseconds, i.e., 2 milliseconds between phases. So, roughly I think one revolution takes about 10 milliseconds, which makes 100 revolutions per second, and 6000 rpm. My resistors had low wattage, so they got very hot (no current limitting or control), so I stop when I see 2000 microseconds.


texts: How good is this crystal oscillator design?

texts:
I'm designing an Atmega328P-AU based WiFi development board for my school project, and as you know, crystal oscillators may take some effort to layout, especially when we have a WiFi module.
I've been reading AVR PCB LAYOUT for OSCILLATORS practice file, but I still don't know if my design is correct.
Any advice or suggestion is appreciated!

EDIT 1:
 Just renamed the top plate as GND:

EDIT 2:
   Changed capacitor's position:

EDIT 3:
    Reduced length of wire that connects XTAL1 and XTAL2 to MCU


texts: what dependence does the intensity of a normal LED(the one used for DIY projects) follow with respect to distance?

texts:
What is the dependence of my led's output with respect to distance.

I am guessing that since the LED inside the glass pane it is somewhat like a wire. Thus, it might follow inverse proportion with distance.

If I'm not to think of it as a wire then the best choice would be to think of it as a point source which would then make the proportionality inverse of distance square.

Is any of the two right? If not, then please give some details of the right proportionality.


texts: Why are they connecting the input signal parallel to the dc source?

texts:
My textbook says the voltage across \$BE\$ would be \$0.7+v_i\$. But this looks incorrect to me based on the shown circuit. It seems the \$v_i\$, \$V_{BB}\$, and the base diode are in parallel. We are connecting an ac source in parallel with a dc source. Isn't this kind of a contradiction ? Some how I don't really see how the input ac signal superimposes over 0.7. We should not connect voltage sources of different values in parallel right ? Appreciate any help. Thank you !

simulate this circuit – Schematic created using CircuitLab


texts: How is it possible a dead old Lithium battery becomes charged after opened?

texts:
I opened a lithuim battery salvaged from my old laptop battery pack. I checked million times that it is 0V and it was by the time i was opening it. For some reason i would love to know, it is now MAGICALLY charged up to 3.99V and that scared me so i left it aside keeping it cool. It has no protection circuit. So is oxygen reacting with Lithium metal and creating such voltage? Or is it really charged?

Update:

I'm charging the battery that was spot welded in parallel to the battery #1. Just for tests and observing its temp. The battery #2 also holds 0V (which also assures that bettery #1 was definitely 0V) so if it stays like that I'll open it and see if it suddenly charges as well up to 4V and what is the reason.
Also I sealed up bat#1
 Here's bat#2:

I did a 100R load on the battery #1 and here's the data:

-T=0                        3.96V

-T=10 min              3.91V

-T=20 min              3.91V

-T=30 min              3.90V

-T=1 hr                    3.87V

-T=1 hr 30 min       3.86V

-T=2 hr                    3.84V

-T=4 hr                    3.78V

-T=6 hr 30 min       3.72V

-T=9 hr                    3.67V

-T=11 hr 30 min    3.61V

It took a long time so i stopped at 3.6V

Graphed by T. Stewart using data above
Using Ic=CdV/dt \$C=V/R*dt/dV~\$ with units \$~= [F]=[V/Ω*[s/V]]\$ for R=at 10k load 11h

Next test 100 Ohm load to 3.0V (faster test) taking two measurements; with load and without. This will measure C2 and ESR. Voltage readings were unstable at first ( double layer effect) but averaging 20 F rising to 40 Farads.

Note that a fresh 18650 cell ranges from 5000 Farads to 10kF so this dead battery will have much higher ESR and C1 <1% of it's initial capacity (unknown).

However it still useful for Volatile Memory backup.
 Momentary short circuit current will also measure ESR.


texts: I understand that photodiodes should be reverse-biased, my question is, should I follow the same convention with phototransistors?


texts:
This is  a question based on electromagnetism.

Screenshot of the question  and all the necessary stuffs are given below,

This is the figure ,

And the choices that are given,

First choice

Second choice

Third choice

Fourth choice

Last choice

Now let me give you the things that I have tried

I have found the variation E.M.F with time, and it is shown below,(I am not sure about its accuracy, so please let me know the accuracy of it)

To have a variation of velocity, there should be acceleration.And to have an acceleration there should be a force.

And here, there should be an induced  current  formed in the loop, so because of that there may be a force acting on the loop which
leads to have a change in velocity.

But what is the correct variation?

I have to admit that I don't  know the accuracy of the above things that I have mentioned (So please let me know the accuracy of those)

So what is the correct answer?


texts: What is the difference between CMOS and Pass-Transistor Logic?

texts:
My friend and I are taking our first digital systems designs course this semester. Our professor has introduced to us two different type of circuit designs; CMOS and Pass-Transistor Logic. The professor isn't very accessible, and we've searched the internet trying to understand the difference between CMOS and Pass-transistor logic, but a lot of the explanations were beyond us. We would really appreciate if someone would explain to us in layman's terms what the difference between the two is, the advantages of each, etc.

Thank you!


texts: How to connect a power supply on the battery socket of a laptop?

texts:
I am doing some long-term measurements of power consumption on a laptop. Down below I show a photo of the battery connection pins.

I am trying to trick the laptop into thinking that runs on the battery; you have the schematic diagram of the circuit (without the power measuring circuit).

But with the following setup doesn't work. What am I doing wrong? I don't know what kind of data takes the laptop from C1,C2,C3.

Can someone help?


texts: How to create high voltage dividers without blowing up resistors

texts:
I figured out that it took around 75 volts to light up a neon bulb I had. I want to make a high-voltage meter with a few bulbs specifying certain amount of volts. So as a first test, I just hooked up two 22 mega ohm resistors in series to create a random voltage divider.  The divider burned up and the resistors got damaged. How can I create a divider to display different voltages for different neon bulbs and how can I prevent high-ohm resistor damage?

The high-voltage power source that I supplied was a ZVS flyback driver with a 12 volt battery and I estimate the voltage of about 2K.


texts: How small should I make my shunt resistor?

texts:
I have a small multi-junction solar cell that I will be taking measurements of short-circuit current and open-circuit voltage periodically in order to approximate an IV curve for the cell.

I have decided that the best method to measure the current is a shunt with an op-amp providing amplification to a microprocessor. I have previously used a hall effect current sensor, but interference from a nearby source of magnetic fields contaminated my readings. A shunt is more tolerant to this sort of issue.

The solar cell will be providing a voltage of between 1v and 2.5v, and a current of 5~20mA. What resistance should I use for the shunt resistor, and how should I consider a resistor for this application?


texts: How to find stepper motor's rated current to set current limit?

texts:
I am trying to set the current limit on a NEMA 17 stepper motor. I found a tutorial but it's asking about the current rating. From my stepper motor datasheet, the only information related to current is the following: Rated Current (Amps/Phase) = 1.68 A.
In the online tutorial that i'm following, this is the example given for their stepper motor: NEMA 17 200steps/rev, 12V 350mA.
So, i'm quite sure that the current rating that is being asked is not 1.68 A.
Maybe i need to calculate the current rating??

Edit: Here are the more complete specs for my hybrid stepper motor, model: MT-1703HS168A

Rated Current (Amps/Phase): 1.68

Holding Torque (kg.cm): 4.4

Resistance (Ohms/Phase): 1.65

Inductance (mH/Phase): 3.6

Inertia (g.cm2): 54

Detent Torque (g.cm): 150

Weight (kg): 0.28

Recommended voltage: 12 - 24 V


texts: Will my 16 gauge wire eventually set my home on fire?

texts:
The fan relay draws 6.0A. That is a safe current for 16 gauge wire. The safety fuse is tripped at 15A which is too  much 16 gauge wire.
References: The below pdf link shows the Installation Instructions for my thermostat.
http://www.kele.com/Catalog/22%20Thermostats_Controllers/PDFs/SuitePro%20Installation%20Instructions.pdf. On page 2 in the specification section shows Safety Fuse Amps at 15A. Fan Relay Amps is shown as 6.0A  for 120 Vac which is what I have.
Background: My super installed three of these thermostats to control our Fan Coils in various rooms. So far we have had no issues. Recently, a Fan Coil tech came in to replace the motor and told me that the wires that is being used are too small in diameter and therefore dangerous. The length of these wires are about 2-3 feet. The work was done 4-5 years ago.
My Question: I understand if there is no power surge, there won't be any issues. If there is a power surge, would the 16 gauge wire burn before the fuse is tripped? Even if fuses are supposed to trip at 70% of their capacity, the surge may still first burn the 16 gauge wire before the fuse is tripped, wouldn't it? So far so good. But, I keep wondering if one day it would set my home on fire.
Thank you for your time and feedback.


texts: Procedure for finding the right MOSFET, diode and resistor to make a solenoid valve open/close?

texts:
I need a right MOSFET to make a 8 valves open/close about 15 times per second! It needs to switch very fast. Anything that can slows the speed of the valves is not desirable.

From what I see the valve is operating at approximately 12VDC, 0.55A.

I want to be able to control these valves with Arduino Uno or Mega and even possibly with Duo in the future. (with 5v output signal)

The valves are Airtec 2P025-08

I did my best to choose the right MOSFET. I don't care about the price and I'd rather to choose extra bucks to be on the safe side and make the circuit last longer.

So far I have chosen this MOSFET:  Fairchild Semiconductor FQP50N06L It is a power MOSFET but to me it is nothing wrong with it to make me go for logic MOSFET.

My questions:

Why should one choose a logic MOSFET for such an application? The gate voltage seems fine with me. And some of the websites list this model as logic/power MOSFET!
What is the exact procedure for choosing the right MOSFET?
Is my Arduino capable of providing enough current to control 8 of these MOSFET to make the valves open/close? I mean is it able to provide enough ampere at digital outs? vales has an external 12v battery themselves.
I don't know how to choose the right flyback diode? Does it have to be able to handle several times of the normal voltage and current passing through the circuit? Is IN5401 (100v, 3 A) enough? or Should I choose one with higher Ampere rating?
What resistor should I choose for the digital to ground pin of Arduino? I have seen 10K for such applications but I don't know how they choose this number for it!
Is Schottky diode more proper for this application!? If yes how can I choose the right one?
And the most important question. Is making the diode series with a resistor going to affect the speed of the circuit? I read somewhere that it can affect it in negative way when opening and closing at very fast speed is important. Or am I wrong?. But wasn't able to find any explanations. Speed is crucial for me. If a resistor can help me, What should be the value of the resistor for my application?
And do you think that the chosen MOSFET is going to do the job for me?

Thank you very much :-)


texts: Unable to find any info about the SMPS IC

texts:
Below is the image of SMPS IC. I am reverse engineering a SMPS AC DC converter and find out this IC. But unfortunately, I am unable find any link or datasheet for this.

Can anybody help me in getting any useful information about this IC.


texts: Copper cable diameter for large current device

texts: I am looking to install a 12V DC bow thruster in a boat. The device draws up to 500A but is only used on and off for a few seconds at a time.  I have an 800AH 12V battery stack but it's 8 metres away.  Can this be used? If so, what size copper cable should I use?


texts: Since in potentiometer we control it by rotate its knob anticlock wise or clock wise...so in that place i want to control it by using MOSFET and Arduino means the working of the knob i want to control it automatically by giving signal from the Arduino after sensing...so is there any possibilities of doing this...in short I want to use Arduino MOSFET in place of potentiometer so rotating of knob is not required... the R1 is the potentiometer i want to use this point automatically with the help of arduino


texts:
Good day all,

I was wondering if there are ways to stabalize the AC voltage between 220 - 230VAC (standard mains voltage in Europe) if the mains output voltage drops say for example 200VAC?

I am asking because I have a 12V Voltage Regulator and when the VAC voltage is below 220V the voltage regulator does not output 12V.


texts: I am Making an 8x8 Led Dot Matrix Display following this guide https://www.insidegadgets.com/2010/11/07/fun-with-8x8-led-matrix/ as you can see it requires a "ULN2803A Darlington Array (of Transistors)" I need to make this Project now and i dont have time to order the IC. Is it possible to make the required IC using Transistors. If so do i need special ones or can i use anyone Such as the 2N3904


texts: Among these two transistors, which has larger gm?

texts: Two transistors have same Vp and Vgs but transistor 2 has double Idss than transistor 1, which will show larger gm?


texts:
I have a circuit involving a DC motor and voltage regulator as following:

simulate this circuit – Schematic created using CircuitLab

What would I realistically wire the ground to? Would it be the negative side of the DC motor or some random hunk of metal? (Side note: am I using the voltage regulator correctly here?)


texts:
I want to use a MOSFET as a switch driven by my micro controller unit.

The idea of the schematic is to enable on/off power ability to a load ("R_LOAD") of 150Ohm. The MCU_PIN is set HIGH which flows current to GND through an NPN transistor. This pulls the gate of the P_Channel MOSFET LOW, which connects the source to drain providing power to the load.

I have assembled this circuit as shown with an STM32L151 to control the MCU_Pin, NPN Transistor, and a P_Channel MOSFET. The circuit is powered by a 3.3v power supply capable of 150mA continuous.

However the circuit crashes the MCU on the moment MCU_PIN is set High. I believe the problem arises from this circuit because bi-passing the two transistors and making a connection from +3.3V directly to the R_Load does not crash the MCU, and there is no short from MCU_PIN to any other line.

Did I choose parts that are not well suited for this use case?
What about the circuit is causing the MCU to crash?


texts: LPC1768 - Green LED when LDR sees light, Red LED when LDR is covered

texts:
I have been trying to achieve a task I am working on and I believe I am almost there. It successfully changes colors whenever I cover it but when it does, the red LED keeps blinking instead of it remaining open in a constant manner.

void Task5(TestAdmin &tester, PwmOut &r_led, PwmOut &g_led, AnalogIn &ldr)
{
    while(tester.testRunning()) {
        g_led.write(1); //turn off
        r_led.write(1); // turn off

        float value = ldr.read(); //takes the reading from the LDR(Light Dependent Resistor)

        if(value >= 0.4) {
            r_led.write(0); //turn on
        } else {
            g_led.write(0); // turn on
            wait_ms(2);
        }
    }
}


texts:
I was wondering what the best way to measure the standard tPHL, tPLH parameters was in HSPICE. Specifically I was wondering the best way to address the negative values I am getting.

I have a circuit with 2 connected inverters terminating a capacitor to ground.

I am attempting to measure the high-low time by looking at when the signal starts and stops.

I am confused as to the why when I measure tplh2, the time for the second inverter to fall and rise I get a negative time.

What is going on here?

* 2 inverters, and negative delay
.LIB 'models15.txt' MOS
M1 OUTa IN VDD VDD pch L=1.5u W=6u
M2 OUTa IN 0   0   nch L=1.5u W=3u
M3 OUTb OUTa VDD VDD pch L=1.5u W=6u
M4 OUTb OUTa 0   0   nch L=1.5u W=3u
CL 0 OUTb 1p

VVDD VDD 0 5
VIN IN 0 0 PULSE 0 5 3n 1n 1n 7n 20n
.DC VIN 0 5 0.05
.PRINT DC V(IN) V(OUTb)
.PRINT DC V(IN) V(OUTa)
.TRAN 100p 100n
.PRINT TRAN V(IN) V(OUTb)
.PRINT TRAN V(IN) V(OUTa)
.measure tran tphl1 trig v(IN) val='0.5*5' rise=1 targ v(OUTa) val='0.5*5' fall=1
.measure tran tplh1 trig v(IN) val='0.5*5' fall=1 targ v(OUTa) val='0.5*5' rise=1
.measure tran tphl2 trig v(IN) val='0.5*5' rise=1 targ v(OUTb) val='0.5*5' fall=1
.measure tran tplh2 trig v(IN) val='0.5*5' fall=1 targ v(OUTb) val='0.5*5' rise=1
.OPTIONS LIST NODE POST
.END

Output

.TITLE '* inverter circuit'
 tphl1            tplh1            tphl2            tplh2
 1.054e-10        5.715e-11        9.190e-09       -6.982e-09


texts:
Is there a magnetic switch (like a reed switch) but with no moving parts?

I need a switch that can be turned on by a magnetic field but won't move around due to tremendous shock absorption.


texts: What does the word "characterize" mean in an EE context?

texts:
UPDATE:

The key distinction I think I was missing was that characterization happens on the bench (as opposed to on an engineering pad or with a computer simulation). It is empirical.

There are other important notions in the background, like we want to understand a device's actual behavior well enough to reliably deploy it in an actual system in an actual environment, and this is what motivates us to characterize.

I encourage you to review all the answers.

Apologies to respondents and readers for any mismatch between question and answers resulting from my edits attempting to make it less a matter of opinion.

I got my BSEE in 1986, and promptly started a career in software development. Now that I'm "reclaiming" my electrical engineering education, I've had occasion to read quite a bit and watch a lot of videos on EE topics.

I've been struck by how often the word "characterize" has arisen in the discussion. It has never been accompanied by a definition for its use in this context, but that's not terrifically surprising. I'm familiar with the dictionary definition of course, but there seem to be connotations that are not immediately clear to me, like:

"Why would a EE invest time in characterizing a device or instrument?"
"What would be his or her primary objectives in doing so? What outcomes, once achieved, would cause them to stop characterizing, considering their objectives achieved?"
"In what ways am I already naturally occupied by characterizing devices, circuits, or whatever, just that I'm not using that word to describe what I'm doing?"

Can someone help me understand what more specific meaning it connotes when used in an EE context?

It seems to be pretty fundamental to the electrical engineer's role, and perhaps to any engineer's.


texts:
Hi,

I am working on a hydraulic unit that has two LVDTs (position transducers). I don't know what is the purpose of those dash lines. I wasn't able to find my answer on Google. My experience tells me those dash lines could mean they are mechanical linkages or optional connections, but neither case makes sense to me.


texts: Three phase systems - when is potential of a star node equal to zero?

texts:
I had to find total impedance of the following three phase circuit with symmetric line voltages:

I've been told that nodes 1 and 2 can be connected because their potentials are equal (zero).After connecting these two nodes, resistor R and inductor L are connected in parallel.Why can we connect these two nodes (/ why are their potentials equal to zero)?I know that in symmetric systems with one generator per phase (three generators in total) and one star receiver, node analysis shows that node potential of the receiving star's node is zero, but what happens in this case?


texts: Test to identify active source in electrical network

texts: I have a black box of a N-port electrical network and I wanted to know whether inside this box is there any active source of energy (i.e battery) present or not, so is it possible to determine active sources without opening the box? And how to do it (what test are required at ports ) ?


texts: Generate an 40MHz Clock on an FPGA with 100Mhz clock

texts:
I'm trying to generate a 40MHz clock on a 100Mhz FPGA and I find it a kind of struggle using Verilog code.

I redirected the clock to a pin to check the 100Mhz functionality:

assign pin1= clock; //gives me a 100MHz clock
assign pin2= ~clock;  //gives me a 100MHz inverse clock

The always block:

reg clock1;
reg [4:0] prescaler1;

always @(posedge clk) begin
    if(reset==1'b1)begin
        clock1=1'b0;
        prescaler1=2'b0;
    end else begin
        if(prescaler1==2'b01) begin
            clock1=~clock1;
            prescaler1=1'b0;
        end else begin
            prescaler1=prescaler1+1'b1;
            clock1=clock1;
        end
    end
end

That gives me 50, 25, 16.66 and 12.5MHz depending on whether the prescaler set to 0, 1, 2, 3.

Is there a trick to doing it?

It is a Zedboard Zynq-7000 Z-7020. XPS lets you assign 4 PL fabric clocks but I believe they have to be in multiples of 33MHz.

What's the difference between ARM_PLL, IO_PLL and DRR_PLL?


texts:
I was trying to simulate a circuit on Capture CIS lite, but I kept getting an output signal which was nothing like I expected. When I tried putting the probe on the sine source, it seems like the source is actually the one outputting the incorrect signal. The simulation is a parametric sweep with the amplitude voltage as the parameter, the range is from 0.5 to 0.65 volts and the the increment 0.01 volts. As you might see, I have deleted the AC parameter but the same result occurs when assigning it a value such as 1.

The circuit, if needed is this:

and the output I am getting is this:

As you can see it is completely linear, which shouldn't happen in a sine source.

Thanks in advance.


texts: Interfacing two devices using transistors

texts:
I have a microcontroller and a small video/still "spy" camera (like these) that came in a case disguising it as a car remote. The microcontroller is a TI MSP430 value line model, though I could use an ATMEGA/ATTINY via arduino if the MSP430 doesn't work out.

I have the two devices sharing a ground, but each is powered by separate batteries because the camera wants about 4.7v and the MSP430 runs on 3.3v.

I'm trying to use a pair of transistors to act as the Power and Function buttons on the camera, in order to use it as a time lapse controlled camera. I removed the push buttons on the camera's board and wired the contacts up to the emitters and collectors of the two transistors.

My basic circuit diagram looks like this:

When I test it on a breadboard with LEDs hooked up to the transistors instead of the camera, my program works fine. It "presses" the power button for 2.5 seconds to turn the camera, then sends brief pulses on the Function button to tell the camera to take a picture.

But when I connect the camera, the camera turns on, waits a few seconds, and turns it off. When I check the function button's transistor, it looks like it never even triggers.

My question is, should I be using transistors this way? Or did I screw something up?


texts: Long range (~15 km) low baud-rate wireless communication in a mountain environment (no LOS)

texts:
I'm trying to implement a point-to-point communication system in a mountainous environment where the base station and the client are at least 15 km apart, without any line of sight (LOS). The base station could have more transmission and receiving power than the client, which should be portable (ideally, it should be light and battery powered). The data rate is very low with a 30 character string being transmitted every 10 minutes.

I saw that XBee-PRO® 868 modules claim a range of 80 km in LOS, but in a severe environment like a wild mountain place, how well would it perform? What are the alternatives?


texts:
I am trying to put together a circuit that can charge a 3000F Maxwell supercapacitor in about 10 mins.
I am looking to use a 150W laptop adapter and a Buck converter.
Problems that I am encountering:

No High power Buck converters with 2V-3V output to charge supercapacitor safely
I do not have enough knowledge on the concept of having several Buck Converters in parallel to increase power output.
Cost


texts: What does this statement about fiducials mean?

texts:
Found this slide and I didn't understand the last statement.

  All fiducials should have same image one layer down

Are fiducials not top/bottom layer registration targets during assembly ?
Are/Can fiducials used during manufacturing to align layers prior to lamenting them ?


texts: Is the 3dB turnover and 45° correspondence only valid for low pass filter transfer function?

texts: I have been reading at some systems that at 3dB point the phase shift becomes 45°. But is this fact only valid for low pass filters?


texts: How to solve voltage dependant voltage sources in parallel to a resistor?

texts: I just started learning about source transformation and came across this question. I get that I can replace the current sources with voltage sources in series along with the resistors in series as well. But what do I do about the the voltage dependant voltage source and resistor in parallel at the middle of the circuit? Turning the vdvs to current source wont help me since the resistor would still be in parallel. What am I missing?


texts:
I am a software developer (using high level languages like .NET,C,C++ etc) trying to understand how computers work at a lower level. I never studied any Electrical Engineering at university. I did GCSE Electronics.

I understand conceptually what a clock tick is i.e. tick-phase (low), followed by a
tock-phase (high).

Say I have a simple circuit like this:

Is tick when the current leaves negative and tock when it reaches positive?


texts:
I've noticed mains voltage tends to be 120V +/- 10% for 108-132VAC.

How would you go about building a regulated AC-to-AC power supply which works off of mains and outputs 120VAC with a much lower (less than 1%) variation?

The output must be a sine wave at 120Vrms.

Edit: For those asking, the output would be fairly low, 1.5A - 2A, 2.25A max.

Circuit to be powered:

Expected input: 0V-5.5KVrms sine wave at 60Hz

Simulated output: +/- 0-100KV DC.

The objective here would be to connect components in the order:

mains --> power conditioner --> variac --> 1:46 center-tapped transformer insulated for high voltage --> Cockcroft Walton Multiplier outlined above.

To achieve a variable 0-100KV DC (effectively 0-200KV DC with both channels factored in) power supply.

I am not certain the power conditioning stage is the way to go but assumed it would be since it is much easier to stabilize low voltage (120Vrms) than it is to stabilize high voltage (5.52KVrms.)  Relatively minor ripple of 5% will grow into +/- 10% by the end of the CW stage at full power, yielding around 20KV off of the expected value - not an insignificant amount.


texts: What is the type of memory of a USB Flash drive and on a hard disc?

texts:
I know there are different types of memory such as ROMs,DRAMs,SRAMs,etc.
I don't understand what is the type of memory on USB Flash drives that we use so often and on the hard disc of a PC. Can you please explain me?


texts: 3 phase controlled soft starter and motor vibration

texts:
I want to make a soft starter for 3 phase induction motors. TRs are SCR pairs and ZCs are the zero-cross timing respect to line voltages (400V), not phase voltages (230V). I control the firing angle of the SCRs with their ZC timing:

TR1 with ZC-12
TR2 with ZC-23
TR3 with ZC-31

When I turn fully ON all of the SCRs, there is no problem. However when I control the firing angle there are some range in the firing when the motor starts to vibrate and makes bad noise.
I don't want to share my program but I'm almost sure that it works as it should, because I tested it with a resistive load and I measured the current whit a scope.
My question is: is it right how I firing the SCRs respect to zero-cross (TR1 with ZC-12 and so on)?. How the big companies trigger the SCRs? I mean are they firing the SCRs separately like I did, or firing in pairs at once, for example: turning on TR1 and TR2 at the same time, respect to ZC-12. TR2 and TR3 respect to ZC-23...?


texts:
Hello! Can you tell me the benefit of having the differential amplifier connected the way shown in the image. Also what's the purpose of devices in green circle and what's the benefit of placing it there?
Thank you!


texts: Is there an excuse for a 20ft Cat6 Ethernet cable to have 36μH on all wires?

texts: I was just measuring the inductance of the 20ft (6m) Cat 6 Ethernet cable I just bought. I'm aware that 525 nH/m is what's expected for each wire, so that ought to have been 3.15μH. I've measured consistently a 36μH inductance for all the wires, which is 10 times what's expected. Is there an excuse for this??


texts:
Here's a relatively simple question: What is wrong with my code below?

I am trying to blink an LED from GP2 pin, but am getting confused when it comes to setting GPIO pins and registers, and its a bit different too because the 509 doesn't have an ADC. Would really appreciate some help.

Thanks (code below).

#include <xc.h>
#include <pic12f509.h>

#pragma config OSC = IntRC      // Oscillator Selection bits (internal RC oscillator)
#pragma config WDT = OFF        // Watchdog Timer Enable bit (WDT disabled)
#pragma config CP = OFF         // Code Protection bit (Code protection off)
#pragma config MCLRE = ON       // GP3/MCLR Pin Function Select bit (GP3/MCLR pin function is MCLR)

#define _XTAL_FREQ 4000000
#define LED GPIObits.GP2

int main()
{
    TRISGPIO = 0x00;

    while(1)
    {
        LED = 1;
        __delay_ms(1000);
        LED = 0;
        __delay_ms(1000);
    }
}


texts: gain of inverting op amp with resistor on input

texts:
I´m trying to figure out the transfer function of the attached op amp circuit. I came to the conclusion that v_out = - v_in as as the two resistors in the upper path are equally sized, and the non inverting input is on ground potential.
However this is a task from one of our exams which I try to solve and it seems that my solution isn`t right according to the following tasks, however I got no solutions to this exam.
Do I miss something?

Kind Regards

Marc


texts:
I have stereo differential (meaning each left and right speaker have 2 wires) headphones. The specs say that impedance of headphones is 8 ohms. I need to drive this headphones with a dac with built-in headphone driver.
  All the dac chips i have searched (from analog devices(adau1772) and asahi kasei(ak4373) )  which can drive differential left and right channels have mentioned in datasheets that this chip can drive 16,24 and 32 ohm headphones. I cant find a dac or audio codec which says it can drive 8 ohm headphones.
My questions are :
1) can i be wrong in understanding the specs of differential stereo headphones? Can two 8 ohm speakers add up impedance to 16 ohms?
2) if we assume that headphones impedance is 8 ohms, what will happen if I drive this headphones with chip whose datasheet says it supports minimum headphones impedance of 16 ohms?
3) can you suggest any dac or audio codec chip which can drive 8 ohm differential headphones?


texts:
I'm planning to use 9 or 10 of 12V 7AH (or possibly up to 35 AH) SLA batteries in series to power some LED bulbs.

Can I charge these in series, and if so, is it safe to assume that I just multiply the charging voltage times the number of batteries? Are there any other considerations I'd have to take other than as if I was charging a single battery?

Thanks in advance!


texts: STM32 ADC current measurement with Center-Aligned PWM trigger

texts:
enter link description here
I'm trying to make an application like the link.
Yellow mark PWM, Purple mark Resistor current waveform. It should not be forgotten that the heating resistor also exhibits inductive properties.
I am trying to read current from the inverter with an insulated current sensor. For testing, I use a 10ohm heater with a single inverter channel. This heater resistor is somewhat inductive. Vbus voltage 24V. So the max. It can draw 2.4A current.
I am doing this application on STM32G4. When the sampling point starts the conversion in the middle of or near the high side switch, I read the voltage value corresponding to the maximum current of 2.4 A.
When the conversion starts with the low side switch open, I read the value that is 0A.
So this means that INJ ADC takes a single sample. How is the average current obtained according to this technique. ST's motor control application does it like this, but how is it able to read average current?


texts: One-clock increment operation in a three-bus CPU architecture

texts:
In his chapter on CPU design, Edward Bosworth introduces the following three-bus architecture:

One of the main design aims of this circuit is to be able to increment the program counter PC in a single clock cycle. According the the accompanying text, this is achieved by driving B1 from PC, B2 from the +1 constant register, asserting the add signal on the ALU and driving PC from B3:

PC <- PC+1: PC -> B1, 1 -> B2, add, B3 -> PC

The obvious question is then, how can the PC register drive B1 with one value while simultaneously loading another value from B3?

I can come up with two possible workarounds, but both have obvious issues.

The transfers do not happen simultaneously. For example, B1 is driven on the rising edge, whereas the signal is loaded from B3 on the falling edge. But then, when we stop driving B1 the signal would vanish on B3 in the absence of another register in the path. If you do use an intermediate register somewhere (in the ALU?), you really are just doing two-cycle increment using half-cycle cycles.
The PC register is actually two registers, one for output and one for input, that are not connected when the register is loading. But then you would need some sort of "equalization logic" that could turn out to be non-trivial.

So what is going on here?


texts: Fastest time a PIC can set and clear a pin

texts:
What is the fastest time a microcontroller (PIC16 in this case) can be set and cleared? It is defined by the frequency, but I don't know the formula to calculate the fastest time that a single pin can be set and cleared.

Assuming the frequency (XTAL) is 20MHz, and there are no delays in between, what is the time needed for the pin to be set and cleared?

For example:

RB2=0;
RB2=1;
RB2=0;

What is the time that RB2 is high?


texts: Atmega328P FTDI 5V USB Serial Communication

texts:
I am working a Atmega328P and FTDI 5V USB Cable to get a Serial Communication between the Micro-controller and the PC. I am using Tera Term for receiving out from Micro-controller.

I am using an FTDI 5V USB Cable with 6 pinout.

I have following connections as

FTDI------->ATmega328P
VCC-------->Power
GND------->Ground
RX--------->Pin3

I am using the following code:

int main(void)
{

    UBRR0H = (BRC >> 8);
    UBRR0L = BRC;

    UCSR0B = (1 << TXEN0);
    UCSR0C = (1 << UCSZ01) | (1 << UCSZ00);

    while(1)
    {
        UDR0 = '8';
        _delay_ms(1000);

    }
}

But I am not getting any values back in my Tera Term screen. I have done the appropriate settings with my Tera Term for serial.
I am kind of stuck with this for sometime now. Please can someone let me know, if I am doing something wrong?


texts: What is the technical standard name for the USB connector used for Samsung Behold phone

texts:
I am in search of the technical name for the connector used for charging and data transfer in samsung behold sgh t919. One end is USB standard, what is the other end named? Is it an International or proprietary standard?

For photograph, please see http://www.walmart.com/ip/Insten-INSTEN-USB-Data-Charging-Cable-For-Samsung-Behold-Eternity-Omnia-Impression-Instinct/28883424

or

http://www.cellphoneshop.net/usbdacaforsa59.html


texts: Can any microphone approach the sensitivity of the Human ear in the same mass/volume?

texts:
I recently dropped a very tiny object onto the floor in a normal room (mass probably low milligrams). I heard it hit the ground. I would like to build a circuit that could "hear" such a small sound and register it. The caveat here is that I also want the same kind of dynamic range, so its not just a matter of amplifying an ordinary microphone zillions of times.

I am also aware that the surface response of the floor was a factor, but how does one go about duplicating the sensitivity of the ear?


texts:
I have an idea that I am trying to explore. I use 48V headway cell packs to power my various electric bicycle projects. Trying to balance charge a 16s pack can be a problem. I had the idea of using less expensive single cell charging boards, that way every cell would be charged to the right level, no stopping the charging process by the BMS when a cell gets too high.

I purchased some of these to test with,
PCB single cell charge board
, but before I try to install them I thought, shouldn't these be isolated?

Is it as simple as adding the appropriate diode on one side of the charge board (like on the right in my awesome drawing)? Or do you need a diode on each side of the charge board? And if this is the case.. what diode should I use?

With this setup also, a smaller 5V PSU with enough amps could be integrated into the pack also so it can be charged anywhere.. you dont need a big charger at a location.

The Arduino in the picture is just an idea. It would monitor pack and cell voltages like a BMS. I think the overall cost on this would be more than a BMS and a charger, but I think the benefit from it would be much greater!


texts:
I want to interface two MCU's, one is at 3.3V and the other at 5V. The problem is that the 3.3V device is sensitive, and can't handle 5V signals, so I need to step the RX line on the 3.3V device down from 5V to 3.3V. Is it possible to use a voltage divider on a serial line, or another simple way of accomplishing this without using a level converter IC?

UPDATE
I haven't tried using a divider yet. I have implemented a TTL converter from Adafruit, and it works, at 9600 baud, but not at higher speeds. I have a certain amount of noise in my system, which I have a hard time getting rid of, and suspect this is the reason. I suspect a divider will be worse in this case.


texts: calibration working in DDR2/3 memory devices

texts:
Does anyone know exact working and what will be blocks present inside the calibration module of DDR2/3 memory devices?

Any information related to calibration process of DDR2/3 SDRAM's is appreciated..

Thanks


texts: Extend wireless Qi charging with a coil in the middle

texts:
I have a question regarding wireless charging. Traditionally, you have two coils, the charger and the receiver for wireless charging with Qi (from what I understand).

Would you be able to have an additional coil in between the two and extend the range from charger to receiver by a few millimeters? I'm very unsure of the science here, so I thought I'd ask here.

Here's a really garbage diagram of what I'm thinking: https://imgur.com/a/ncjwxyh


texts: Battery Charger in Parallel with System Load Current Sharing - Power Path Control

texts:
Currently, I'm building a project which can either run connected over USB or via a battery. The project itself switches between either high current draw at around 450mA or low current draw at 50mA.
Right now, my circuit is designed such that my battery charging circuit is using a TP4056 in parallel with my main system load. The battery is connected to the TP4056 as well as a boost converter to 5V [more accurately, 4.6V]. An example of the schematic is below, assume all supporting components and diodes are there.

The System load is, at worst case, drawing 450mA continuously, driving about 80 LED's at 5mA and some support circuitry. The TP4056 battery charger IC is limited to a current draw of 400mA through a resistor on it's programming pin. However, the USB is limited to 500mA, according to standard USB specs.
This brings a problem since the total power needed is greater than the power budget. My goal is to prioritize the system load, giving it the full 450mA when needed, leaving the remaining 50mA for the TP4056. When the system load drops to a low power state at 50mA though, the TP4056 should get the remaining 400mA it asks for.
How can I accomplish something like this? My understanding of parallel devices is that they split current based on resistance calculated using Ohms law. However, I don't have a way of measuring resistance on my system load as it's a dynamic system.
Edit for more power info:
One of my primary concerns is, when USB is connected, driving the project exclusively off USB. Hence, I'm boosting the battery to 4.6V, well below USB min-voltage standard, so the circuit will always "pick" the USB voltage over the battery. I don't need the battery to supply additional current if the USB can't keep up.
I am aware there exist chips like the MCP73871 which have "power path control." Would I be better off switching to that chip instead of my current circuit?


texts:
I having an interesting issue with some cooling fans that came with a used pop up camper.  I'm proficient in electronics and this one just doesn't make any sense to me.  These fans are designed to be put in the camper like a portable box fan you would use in a house, but are much smaller.  They run on 12VDC and plug into outlets in the camper which are connected to a car battery.  When you turn a fan on it will run for about 30 seconds then the speed steadily declines and the fan stops.  If you switch the fan off, wait a few seconds and turn it back on it does the same thing.

I have taken these apart and they are really simple - power comes in from the plug, goes to a switch, then the motor and then (the weird part) to a capacitor in SERIES with the motor and then out to the plug.  I've never seen this.  I've seen lots of capacitors across little motors like these to clean up RF, but not in series like this.  To me this explains why the fan slowly shuts down - the capacitor charges and then becomes an open spot in the circuit.

To make this stranger, two of these fans exhibit this behavior and a third one does not.  They are all wired the same (though the capacitor on the one that works appears to be of a larger rating).  Maybe that capacitor has shorted?

Any thoughts?  Did someone in China make a whole bunch of mis-wired fans?  Am I ok to move the capacitor so that it is across the motor?  Or just get rid of it?  Or is there some motor thing that I'm unaware of?

Thanks, -D

Bruce and Dave - Thanks for the comments.  I'm not familiar with a PTC.  Here's a pic of the component -

The markings on it appear to be FUMC CHINA on one side and on the other side
a symbol that looks like nested X's and 72 then x030 on the second line

The unit that works properly says
LP60 then 040 on the second line

I did do a search on 'LP60 040' and sure enough the first hit was a PTC.  So it looks like this is a PTC.  I did see where the stores selling these fans state that the motor is 'thermally protected', so then this must be how it is protected - this little guy senses too much current flow and then shuts down?

If that's the case all I have to is replace these and the fans will work again.

Thanks !!!


texts:
I am new to electronics, so please excuse the noob question.

I have an 8 ohm 1/4W speaker.  I would like to get the loudest sound out of it that I can.  Based on my understanding, which may be entirely wrong, the maximum current that can go through it without damaging it is

I = Square root ( P / R )
= sqr ( 0.25W / 8ohms )
= 0.176A.

To get this current at 5V, I need an over all resistance of

R = V / I
= 5V / 0.176A
= 28.3ohms.

Since the speaker has 8ohms, I need a resistor in series of 28.3 - 8 = 20ohms.  I have a 22ohm resistor that I am using.

Is this correct?


texts: What is the simplest way to generate PWM without a Microcontroller?

texts:
What is the fast and elegant way to generate PWM without a Microcontroller to control a servo motor? With potentiometer or other ways to control the duty cycle with fix period.

sorry about the mess, I want to control a hobby servo.


texts: Correct type of wire for simple DIY projects involving soldering

texts:
I am making my own bluetooth speaker which will require me soldering wire to PCBs etc. However, I am unsure of which type of wire to buy for the project. I understand that positive and negative wiring is typically red and black, with speaker wires typically being black and white.

Am I requiring standard strand wiring that I will need to twist to strengthen before soldering, or should I be looking for solid core?

I have found this Ebay wiring that looks ok, but I am just wanting a bit of guidance.

For your information: The voltage expected through the circuit will be approx 5 - 6.5V with a current of between 1-2A


texts: FPGA - Is it possible to change the pin direction/type during runtime?

texts:
On an FPGA, is it possible to mimic the behaviour of something like an Arduino, whereby the code running on the chip is able to designate a pin as an input or output?

Let's say the FPGA is configured as a processor. Further, lets say that we have three registers designated for controlling IO pins much like the Arduino equivalents:

  Each port is controlled by three registers... The DDR register, determines whether the pin is an INPUT or OUTPUT. The PORT register controls whether the pin is HIGH or LOW, and the PIN register reads the state of INPUT pins set to input with pinMode().

How can you get the FPGA to use a register (like DDR) to change the direction of the pin, based on what the running program updates the register to? (By running program, I mean the program running on the processor the FPGA has been configured as).

I'm not sure if this is possible given how during pin assignment for synthesis you have to specify the pin direction. But hopefully I'm wrong? Could this be done somehow by using 'bidirectional' pin mode?


texts:
I am a software developer trying to understand how computers work at a lower level.

I have managed to create a few simple circuits, one which lights up an LED.  I have noticed that all the instructions advise you to connect the components in a certain way.  Please have a look at the circuit here.  The LED is connected to column E and column F.  Why can't you just connect the LED to G7 and H7 and the black cable to F7? Why does the LED plug in across the gap?

I seem to remember something about this from school.  I have checked my GCSE textbook and also two textbooks which I am working through.  I have also Googled it but I cannot find an answer and hence the reason for this very basic question.


texts:
I stumbled upon the most uncommon thing. An 8-PIN DIP IC with part number (OP277PA.)

However, the datasheet is nowhere to be found and I've done my research.

Is it possible that it is an OPA277P, or is it its own thing?

Does anybody have a clever way to test if it is a low noise precision opamp?


texts:
As far as I understand, "filter order" is the number of poles or roughly the number of capacitors in an active filter. The higher the order the sharper the roll off.

I'm trying to make a second order Bessel filter with a gain of 500 but what is meant by "stage gain"?

More importantly I wonder what is the relation between an active filter being unity gain and "filter order"?

What I mean is that: If I want to both filter and have gain should I forget about 2nd order and higher filter? As far as I saw in examples an active filter can only provide gain only if it is 1st order. 2nd order and higher order active filters are very good for filtering but they don't provide gain they are unity gain filters(?). Is this correct?

edit:

edit 2:


texts:
I have no background of electrical engineering so if my question sounds stupid then accept my apology in advance. I want to calculate the power loss during the transmission. I am using the simple formula which is

$$P_{loss} = Resistance \cdot I^2$$

Where P is power loss
Resistance is in Ohms
and I is the current

Replacing the I by P / V
Where V is the voltage
now the formula looks like

$$P_{loss} = Resistance \cdot \Big( \frac{P}{V} \Big)^2$$

If the value of resistance is 5.24 Ohms and voltage is 50 kV and the value of P is 940 kW then I get the value of P(loss) = 1852 W which does not seem intuitive.

Looking for your guidance (if i am calculating wrong). Accept my apology in advance if my question bothers you.


texts: ESD control to protect personnel inside container van

texts:
we are doing a simulator project inside a 30-foot container van. All equipment will be grounded to a central earthing point. Each grounding connection should be less than 2ohms.
Van will be used on land and on ships.
Operators inside van will be trained according to simulation requirement (eg bus driving, tank operation, aircraft combat etc).
What ESD control can we put in place to protect personnel from ESD shocks/zaps? we don't want them wearing wrist straps due to nature of simulation training.


texts:
This is related to decoupling capacitors on Vcc pins of MCUs. Most of my designs I usually put a sprinkling of a 10pf,10nF and 1uf or so to filter out any differential noise, and other noises on the very high,median and low frequency ranges. It has worked always. No doubts and is quite recommended by many vendors and also on their eval boards they have the same values(more or less).

But, is there a method to this madness. I was going through a rad hard MCU datasheet (for academic purpose) and stumbled on a line. The link is given below -

So, there is a relation between the peripheral switching frequency and the value of the capacitor. Is it so ?
If so, is the only factor the peripheral frequency or would other factors play in this ?


texts:
I'm trying to build a speedometer for my car, using the output from the cars speed sensor. The speed sensor outputs a sine wave. here it is on an oscilloscope:

as I understand it, in order for the arduino to be happy, this signal needs to be between 0 and 5v.

It seems that the peak to peak of this wave is about 8v-ish, which means if I somehow "chop" the negative voltage off of this signal, I should be left with something like 0-4v which is what I need.

How do I go about reading this signal by the arduino? I'd like to keep the circuitry simple due to the harsh(ish) environment that it'll be sitting in.

I've seen some people suggest simply a diode and a resistor, and others suggest op amps, schmitt triggers, and other concepts I'm not strong on.

Any help is very welcome!


texts: Photodiode circuit Op Amp and amplification failure

texts:
I am trying to build a photodetector circuit to detect and amplify the output signal of a fiber laser. I started with testing my fiber pigtailed photodiode on a breadboard as shown.

simulate this circuit – Schematic created using CircuitLab

It worked as I expected. Voltage increased as the light output increased etc. My first question is,

When I increased the light output, the voltage value increased with a nice sensitivity but as the output increased voltage value started to change only with broad output intervals and then at one point, increasing light output did not change anything.Here are my measurements:

Up to 2.3 mW light output power voltage quickly reaches 9.4 V then until 14 mW power it only rises to 9.6V and it stays around 9.62 V for further increments.

Am I missing something very fundamental here? I was expecting the voltage value to keep rising as I increased the light.

Next I wanted to build an amplifier circuit to amplify the signal. The circuit I tried is the same as the one in the figure. I didn't use the optional resistor. Specs of the circuit are:

OpAmp: ADA 4897-1
Photodiode
Rf= 10k to 1M Ohms
Cf= 1pF
Photodiode Bias: -9V
OpAmp +-Vss: +-5V

simulate this circuit

However when I connected everything, power supply showed that -Vss was using more than 7 Volts and OpAmp started to get very (smoking)hot. And before it got hot I didn't get any useful value from the output. It showed something around -5 volts which was surprising because the signal must have been inverted and therefore it had to be positive. Nothing changed as I changed the light output.

I tried the same circuit by using 7V batteries as Vss sources with a new OpAmp. Again I did not get anyting. The voltage at the output was lower than the value with only 10k test circuit and as I increased the Pf up to 1M, voltage dropped. This is again very interesting to me because I know that Rf determines the gain and as it increases output signal should incrase. One other thing is that the output voltage is always around the Vss. Could this be a clue for something?

What is wrong with my circuit? What causes these weird results? Is there something wrong with my OpAmp? This seemed something quite easy to build but this is my second wasted week on this. Please explain things as clear as possible. I feel like a caveman in a spaceship. I can't proceed further. Please help this poor man.

Edit: To be more clear, all the voltage values which describes -Vss is negative. I did not neither gave nor read any positive voltage value concerning  -Vss of OpAmp.


texts: How to create an interrupt based on potentiometer value(s)?

texts:
I am using an Arduino to power a motorized potentiometer and I wanted to know if there is a way to create an interrupt (stop the motor) when the potentiometer reaches within a certain range of values (like in one case stop motor if the potentiometer is between 1023 and 1000, another case between 500-600, and another between 0 and 100)?

I'm using the motor driver l293d, if that is helpful.


texts: How to conduct mesh analysis on a current source in series with a resistance?

texts:
How can I do a mesh analysis of the following kind of circuit? I'd normally put up Kirchoff's voltage laws for each of the two loops. If the current source wasn't in series with a resistance, I'd write down the voltage law for the complete sling (R 3-4-6-9-8) and the relation between the partial circuits, but in this case, I don't know how to handle the current source.

How can I conduct a mesh analysis?


texts: Power of audio amplifier not matching specifications

texts:
I have a Cerwin-Vega CV-2800 audio amplifier which is rated for 600 watts at 8 ohms, 900 watts at 4 ohms, and 1400 watts at 2 ohms. I also have two PWR247T-100-1R00F 1 ohm resistors rated for 100 W; each of these has a measured resistance of 1.2 ohms.

In my first experiment, I wired the amplifier in series with one of the resistors and an inductor which I had wound myself. The inductor has an equivalent series resistance of 1.1 ohms and an inductance of about 3 mH at a frequency of 50 Hz. (The inductance was calculated using the method shown here under the section "Measuring with a sinewave"; I found the phase angle between \$V_x\$ and \$V_g\$ to be \$-20.56\$ degrees.) The circuit is diagrammed below:

simulate this circuit – Schematic created using CircuitLab

I fed in a 50 Hz sinusoidal signal, and turned amplifier up until right before the -20 dB light came on. At this frequency, the reactance of the inductor should be \$\omega L = 2\pi(50)(0.003) = 0.94\$ ohms, so the total impedance of the circuit should be \$\sqrt{(1.2 + 1.1)^2 + (0.94^2)} = 2.49\$ ohms. I measured the voltage across the resistor, the inductor, and the entire circuit and found them to be 4.07 V, 6.2 V, and 9.275 V in amplitude, respectively. I calculated the power consumed by the circuit and found it to be

$$
\begin{align}
P &= IV\\
&= (V_{R_1}/R_1)V_{\mbox{total}}\\
&= (4.07/1.2)(9.275)\\
&= 31.46 \mbox{ watts}
\end{align}
$$

This was much lower than the wattage that the amplifier was rated for, so to determine whether it was something to do with the inductor, I made the load purely resistive. In a second experiment, I wired two of the PWR247T-100-1R00F 1 ohm resistors in series and connected them in series with the amplifier (no inductor at all). The circuit is diagrammed below:

simulate this circuit

I measured the voltage across the entire circuit and found it to be 9.2 V in amplitude. I calculated the peak power using this voltage and found it to be

$$
\begin{align}
P &= V^2/(R_1 + R_2) \\
&= 9.2^2/(1.2 + 1.2) \\
&= 35.27 \mbox{ watts}
\end{align}
$$

Both of these are much less than the 1400 W that the amplifier is rated for. What is the reason for the difference?

Edit: Some comments suggested that because I was not measuring the voltage right before clipping, I was not calculating maximum power correctly. This is true, but I did drive the amplifier once until it started to clip and remember the voltage not exceeding 15 V, about 50% more than the 9.7 V it reaches at the -20 dB point (can verify these numbers in a few hours). This is still only about 100 W of power.

Edit: The voltage clipped because I was looking at it on a NI-DAQ whose range is -10 V to +10 V. See my answer below.


texts: VNH5019 Motor Driver reverse polarity protection

texts:
So I managed to fry one of these drivers. It was rather simple - It was end of the day, and I plugged the power supply in reverse polarity (24V), and it blew up.

Now, I wondered - How come there is no reverse polarity protection? Turns out there is, but only up until 16V. However, the maximum recommended input voltage of the chip is specified to be 24V, saying it can survive up to 41V. Anything above 24V produces over voltage protection to shut it down.

They even call the design "robust". https://www.pololu.com/product/1451

Is this design indeed "robust" or considered good, if it provides reverse polarity protection only up to 16V, although people may operate it at higher voltages? Would it not make sense to protect against reverse polarity at least within the specs?


texts: Simulation / Emulation of an I2C EEPROM MEMORY (M24LC16B)

texts: I'm using iBurner3.2 I2C Bus EEPROM Programmer to write and read from an I2C EEPROM MEMORY (24LC16B) using COM Port, I want to simulate the behavior of this specific I2C EEPROM, is there any software tool that can simulate/emulate its behavior. Thanks in advance.


texts: Stellaris Launchpad: Register to store value that can be read after soft-reset

texts:
I am working with an LM4F120 Stellaris Launchpad. In my firmware I want to trigger a soft-reset but only once. When the firmware gets out of reset it should read from a register to see wheterh the sot-reset already happened and if so branch to another piece of code.

Do you know of any register where I can store a value and from which I can read back the same value even after the soft-reset?


texts: In the picture below, the input of the rectifier is 690VAC max, so the DC output can reach up to 1kVDC. The DC output goes to a low power DC/DC Converter. In the picture on the left, I'm using a single varistor for transient protection. In the picture on the right, I have three TVS diodes in series. Would the two cases accomplish the same task? As far as I know, TVS are faster than MOVs and can absorb less energy.


texts:
What is output voltage of series voltage reference IC (for example MAX6100) when input voltage is below minimum input voltage? Is it zero volts, or something else?

Didn't find answer to this from data sheets I was reading.

Thanks.


texts: Timer (output compare mode) not working on stm32f411re

texts:
I am using an stm32f411re nucleo board. I am trying to configure the Tim2_ch1 module in output compare mode.
I have written the code by referring to the reference manual:
https://www.st.com/resource/en/reference_manual/dm00119316-stm32f411xc-e-advanced-arm-based-32-bit-mcus-stmicroelectronics.pdf
code:
//PA5:TIM2_CH1

// clock frequency:16Mhz

#include "stm32f4xx.h"         // Device header

// toggle led at 1hz using TIM2 output COMPARE MODE

int main(void)

{

 RCC->AHB1ENR |=1;

GPIOA->MODER |=0X800; //PA_5 is configured in alternate function mode

GPIOA->AFR[0] |=0X00100000; // Tim2_ch1 is assigned to PA_5

//TIM2 OUTPUT COMPARE CONFIG

RCC->APB1ENR |=1;

TIM2->PSC |=1600-1;

TIM2->ARR |=10000-1;   //clock frequency is divided by prescalar and auto reload

TIM2->CCMR1 |=0X30;

TIM2->CCR1 |=0;

TIM2->CCER |=1;

TIM2->CNT |=0;

TIM2->CR1 |=1;

while(1)

{}

}

This code is not working. Is there any issue with the code?


texts:
I have a custom board STM32WB55CGU6 with a reset pin connected to a pull-up resistor and a capacitor as shown in the schematic and PCB layout below (connected to the reset pin 7):

Using an oscilloscope, I obtained the following signal below between the resistor and capacitor of the reset as well as VCC:

Normally, from what I understand I am supposed to obtain a value of 3.3V at this point. I think that there is a problem with the capacitor but using a multimeter, I am able to obtain a value close to the actual value of the capacitor. Any other ideas on why I would have this?
UPDATE: After removing the pull up resistor as recommended, the signal remains the same.
Also, here is the full schematics. Please note that for the moment I have modified it slightly, changing the pins of PA13, PA14 to SWDIO and SWCLK respectively to test the PCB using a ST-Link V2.
In addition to this, I have weird signals in my SWCLK and SWDIO pins.


texts:
I am trying to understand how I can setup the UART peripheral to receive 9 bit data blocks.

I am using the ST IDE (STM32 cube IDE) and the Nucleo-F103RB board. I can setup the peripheral in 9bit mode using the STM32 Cube. But the HAL function to transmit/receive data still uses an 8bit pointer to a data buffer.

HAL_StatusTypeDef HAL_UART_Receive(UART_HandleTypeDef *huart, uint8_t *pData, uint16_t Size, uint32_t Timeout);

How can I receive the 9th bit?


texts: Solving simple parallel/series without Req

texts:
Given the following circuit with three resistors, R1=100Ω, R2=200Ω, R3=300Ω:

To solve this using the \$R_{eq}\$ trick:

R_eq = 1/(1/200 + 1/300) =  120
5V = (100 + 120) * I
I = 5/220 = 0.0227A

How would I do this verbosely, creating all the systems of equations using Ohms/Kirchoffs laws to solve for this? I don't necessarily care about the actual solving of it, but more about setting up all the equations from each of the various series/parallel nodes.


texts:
I am trying to design a backup power system around the LTC4015 battery charger. I am looking for a battery balancing circuit to balance the charges in the batteries.
4 Batteries used are with 3.2v 400mAh nominal characteristics, connected in series to form a battery pack.
Should i use an active or passive BMS? The active system will have a higher cost but better efficiency. Given that the system will be always plugged to electricity and the batteries are only for backup wouldn't it be better to use the passive approach?
Any good IC or system recommendations for this application?