texts: Load frequency calculation of quartz with its load capacitance

texts:
After web researches and a first discussion about general comprehension, I am a bit lost with the load frequency calculation:
I see a design which uses two 33pF external capacitors (C1 and C2),with a uC which has two 4pf input capacitors (Cin and Cout) and with an guesstimated stray capacitance of 2pf, the above formula gives a c_load = (4+33)*(4+33)/(4+33+33+4)+2 = 20.5pF

This design uses this configuration with the following quartz ECS-.327-CDX-1128 which has the following characteristics:

FL = 32 768Hz (load frequency)
C0 capacitance = 2 pF (shunt capacitance)
C1 capacitance = 3,7 pF (mean of 3,0 and 4,4pF) (motional capacitance)
CL = 6 pF (load capacitance expected to get the load frequency above)

I use the following formula to get the series frequency Fs (thanks to all the quartz characteristics above), which I use then in the same formula but changing the load capacitance value with previous calculated one.

I got:

Fs = 26 632 Hz
Fl (with Cload = 20.5pF) = 28 813 Hz

Even if load capacitance specified is not respected here, I am surprised that the load frequency is such far from the frequency expected. Indeed, this not the same order of magnitude as it can be pointed out at TI application report , as shown below, where the frequency drift is more about some Hz or ten of Hz (note: this is an example, quartz characteristics are not the same)

So I guess I am misunderstanding something which makes me make wrong interpretation leading to a wrong calculation. Can you help please ?
I have found another formula here, as shown below, but the result (Fs = 26 070Hz and FL=28 292Hz) are still really far.


texts: Battery Ampere-hour rating vs Battery Amps (not an experienced user)

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I have almost no experience whatsoever with the technicals of electronics so this is probably a very easy question for someone who does.

Do you know if a battery with a 200Ah rating can put out 200A for one hour or are there limitations? According to this website's third paragraph (Battery Ratings - Chapter 11 - Batteries And Power Systems), you can.

  For example, an average automotive battery might have a capacity of about 70 amp-hours, specified at a current of 3.5 amps. This means that the amount of time this battery could continuously supply a current of 3.5 amps to a load would be 20 hours (70 amp-hours / 3.5 amps). But let’s suppose that a lower-resistance load were connected to that battery, drawing 70 amps continuously. Our amp-hour equation tells us that the battery should hold out for exactly 1 hour (70 amp-hours / 70 amps), but this might not be true in real life. With higher currents, the battery will dissipate more heat across its internal resistance, which has the effect of altering the chemical reactions taking place within. Chances are, the battery would fully discharge some time before the calculated time of 1 hour under this greater load.

But wouldn't that mean you could hook up a 200Ah battery and ask it to put out 12000A for one minute or 720000A for a second?  That seems very unrealistic, lol.  I'm trying to find the proper kind of off grid battery that can power a microwave through a 3000 watt power inverter.  The microwave needs 1800 watts and the battery needs to be 12 volts so that would mean I need about 150 amps, I'm wondering if a battery with a 200Ah rating could do it?


texts:
I have a question of combining 2:1 to form single 8:1 multiplexor

This is acheivable by using 7   2:1, with 4 of it at the first level, 3 of it at the second level, and 1 of it at the third level.  Then you just hook up the control bit of the first level together, and the second level together and so on. But my question is for the 3 bits "control bits", do you need another decoder or something?


texts: How to limit current using voltage regulator

texts:
I have a cheap little generic voltage regulator board which should allow me to select both the output voltage and the maximum output current, but I can't get it to limit the current properly.
The board is based on a LM2596 and looks very similar to this one:

and as you can see it only has two potentiometers, can't get much simpler.  So what I have is a power supply feeding the left-hand side with 7.5v and what I'd like is 6v out of the right-hand side up to a maximum output current.

It's immediately clear that the left-hand potentiometer controls the output voltage, and I can select 6v output without problem.  Note that there is a red/green LED on the right, and with just a voltmeter across the output, the LED is green (apparently indicating 'no load').

Now I'd like to limit the current, but whichever way I turn the right-hand potentiometer, the output current is unaffected.  I can turn the potentiometer apparently endlessly in both directions, and never reach a stop - which is a little surprising.  At first I thought the potentiometer might be broken or not connected at all, but there is a point where turning the potentiometer changes the LED from red (load) to green (no load).  But the output current flowing through my load doesn't change at all, which I can't understand.  Also the input current is not affected.

I'm sorry this sounds like such a trivial problem to solve but to put it in concrete terms, I have 7.5v coming in, 6v coming out, and a 50 ohm load.  So it's trying to draw 120 mA and I'd like the regulator to limit it to say 90mA.  I'm assuming that if I turn the potentiometer in the correct direction far enough, the output current will be limited to 90mA and the output voltage will drop accordingly.
Instead I see the output current constant all the time, no matter which way I turn the right-hand potentiometer - and as I said it seems to turn endlessly.
Am I not understanding the way this current limiting should work, or have I got the wrong kind of board for what I'm trying to do?
Also, what's the significance of the LED changing from green to red even though the output current doesn't change?


texts:
I want a hard power switch for some battery-powered BLDC motors, but the currents (5A, up to 20A transients) and voltages (up to 60V) limit the kinds of switches I can use.

Because I want some small pretty switches that have the same effect of a hard switch, I've come up with this design with a voltage regulator and solid state relay:

The DPDT switch controls flow to the coil of the SSR as well as the ground of the voltage regulator, resulting in 0 standby current, ideal for my batteries. Because the electrical requirements are less demanding on the coil side of the SSR, I cam less constrained to the switch I use.

Are there any reasons why this design wouldn't work or should be avoided?


texts: The ratio of the current to base vs the current to the collector

texts:
I'm doing an experiment while reading the self-study book by Kybett "electronics self teaching guide" In the experiment I measure the current to the base and collector of a NPN transistor then observe that the ratio is basically constant and consistent with the manufacturer's specs.

But my ratio isn't constant. In addition I'm having trouble locating "beta" , the ratio on the datasheet. I see one mention of "beta=10" this is nothing like any of the values from my test.

Here are my data. What am I missing?

Rb=base resistance
Vc=base collector voltage
Ib= current base
Ic=current collector

Rb                  Vc            Ib                Ic            Ic/Ib
1Mohms         6.89 V          8microA            1.51mA         189
690kohms       6.25 V         12microA            2.17mA         197
470kohms       5.24 V         17microA            3.20mA         188
220kohms       1.89 V         36microA            6.57mA         182
194kohms       1.07 V         41microA            7.40mA         180
147kohms        .247V         54microA            8.24mA         152??
 94kohms        .173V         85microA            8.31mA         97.76???
 47kohms        .137V        171microA            8.35mA         48.83?????

What is going on?


texts: Powering multiple circuit boards from one wall wart

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I've got two home-build Halloween props that currently run from multiple battery packs.  I want to switch this to a single wall wart.  Here's what I need to power: 1 arduino, 2 Cowlacious audio boards, and 1 Cowlacious Scary Terry servo board in the one prop, and one servo board in the other.  9 volts is a fine input voltage for the power input on each, and ideally I've love to use the barrel connectors on each, since it gives a nice firm connection even when I jostle the setup.

What do I need to look for in a wall wart?

Can I just rig up wires with barrel connectors on one end in parallel off the wall wart?


texts: How do I eliminate a "Missing expression in .." error message in LTspice XVII simulation

texts:
I am completely new to using any type of SPICE program for evaluating electrical circuits. However, having joined the ECAD movement, I have at my disposal a teaching guide on using LTspice IV and the software version LTspice XVII.
Therefore, I was bound to come up with compatibility issues; although I am not sure that this is one of them.
Basically, I have created a diode library to use with my circuits. However, when I attempt to run a simulation with the schematic that requires this library, I get the following error message "Missing expression in ..." (see attached picture).
Please note that the simulation works fine when the ideal diode within LTspice is used instead.
Any insights that you can provide will be very much appreciated.


texts: Open loop gain of non-inverting amplifier

texts:
How can I find open loop gain of this non inverting amplifier. I searched for answer but couldn't find the answer. Using formula Gain=1+R2/R1
I am not able to figure out values ofR2 and R1


texts: Why I get 'u' even after initial the signal to '0'?

texts:
library IEEE;
use IEEE.std_logic_1164.all;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity TOP is port
(
    CLOCK: in std_logic;
    Rdata_ADC: in std_logic;

    CLK2_ADC : out std_logic;
    CS_ADC  : out Std_logic;
    CS_DAC  : out Std_logic;
    SCK_DAC  : out std_logic;
    Mosi_ADC : out std_logic;
    Mosi_DAC : out std_logic
);

end TOP;

architecture behavioral of Top is
    signal Send_S, CLK2: std_logic;
    signal MOSI_DAC_S: std_logic :='0';
    Signal CS_DAC_S: std_logic :='0';
    signal DOUT_VALUE: std_logic_vector (11 downto 0) :="000000000000";
begin

    A0: ENTITY work.ADC(behavioral) port map
        (CLK=> CLOCK, R_DATA=> Rdata_ADC, CS=> CS_ADC, MOSI=> Mosi_ADC,
       CLk2=> CLk2, SEND=> Send_S, Dout=> DOUT_VALUE);

    A1: entity work.DAC(behavioral) port map
        (SCK=> SCK_DAC, CS=> CS_DAC_S, MOSI=> MOSI_DAC_S,
        CLK2=> CLK2, SEND=> SEND_S, Value=> DOUT_Value);

   CLK2_ADC <= CLK2;
   MOSI_DAC <= MOSI_DAC_S;
    CS_DAC <= CS_DAC_S;

End behavioral;

Why I get 'u' even after initial the signal MOSI_DAC_S and CS_DAC_S to '0'?


texts:
I have a relatively simple setup where I have an Arduino Mega reading a pressure transducer (transducer specs) and then I'm just watching the voltage readings over serial. It seems that I'm getting bad readings because I'm getting voltages from 2.1 to 3.5 without any pressure beyond ambient and this transducer reads from 0-8000psi so something is quite wrong if it is reading ~4000psi. Below is my Arduino code. And I have the circuit schematic below as well. In my circuit I have the leads from the pressure ducer directly into the Arduino and they are around 30cm long. Let me know if any more information would be useful, does anyone have ideas as to why I would be getting wonky readings and what I can do to chase down this bug? I have done this setup on two separate but identical pressure transducers with the same result.

#include <Arduino.h>

int press1 = A0;

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600); // set the baud rate
  Serial.println("Starting code");
}

void loop() {
  // put your main code here, to run repeatedly:
  Serial.println("Running code. Voltage is:");
  int sensorValue = analogRead(press1);
  float voltage = sensorValue * (5.0 / 1023.0);
  Serial.println(voltage);
  delay(2000);
}


texts:
On the following figure, LIN is used to build subnetworks from a CAN bus:

Is there any standardized way to interface these two buses (e.g. for addressing a LIN node from a CAN node)? I read an article on Hackaday that states that this is the case:

  There is even an optional transport layer spec that is compatible with CAN bus and makes it easier to integrate the local LIN cluster with the bigger network.

However, I cannot any specification related to this. Is this really standardized or is everyone doing it differently?


texts:
I am using PCB123 to do a PCB layout and I have a part with some oddly shaped pads specified in the part's recommended footprint. It seems that in the footprint editor, there are only 3 options for pin shapes. Therefore, I chose the closest one (square pad) and then extended them to match the recommended footprint using filled polygons in the metal layer.

The footprint in question belongs to the Luminus Devices XNOVA 3020 led, datasheet here

My problem is that I get DRC errors indicating that the polygons are too close to the pins. I cannot find a way to tell the footprint editor that the polygons share the same net as the pins. Normally on the general layout, I can specify to which net the polygon belongs, however in footprint editor, this menu is grayed-out.

Does anyone know how to solve this problem?


texts:
I'm working on a proximity detection project to drive up to 25 IR led on 38Khz with 3.6v mcu.I'm planing to make them parallel with 100 ohm resistor (limit their current to 20ma for each led).MCU pwm pin can not handle 500 ma (may be less because of PWM but for safety reason I assume max), so as you guess I need to use BJT or FET to drive them. Because of some project restriction, I want to use only one mcu pin to drive IR Leds on 38Khz, and other pins for each photo diode sensor.

My questions are,

I can connect different number of led (up to 25) depends on application or if any led in this parallel line burn or not work properly some reason, will it be a problem ? The reason I'm asking that; load of FET's or BJT's will change regarding to count of led in the parallel line.If so, how can I solve this problem ? Shortly , what kind of circuit should I use to drive safely 1 to 25 parallel led without damage any mcu pin, drive electronic or any other leds in the parallel string.
Which BJT or FET should I use ? I have BD135 and IRFZ44N now.I want to use them because to make running prototype.If one of them fit my project, I can change more suitable (current,price etc) BJT or FET later.

Thanks


texts: Finding a gain bandwidth product using a test frequency

texts:
For GBP datasheet parameters of Op-amps, I have seen datasheets with test conditions like gain and Rl, but there are also datasheets with ftest as their conditions. How do we calculate the GBP of the product by using the ftest? Is 'ftest' the cutoff frequency where the gain drops -3db?

Like this op amp, conditions for GBW contains ftest:
http://www.farnell.com/datasheets/1830512.pdf
'GBW Gain-Bandwidth Product fTEST = 20kHz, RL = 10k'


texts: are electrolytic capacitors bilateral or unilateral element?

texts:
Capacitor is a bilateral element (provides same impedance if direction of current is reversed)- what I studied in Classification of elements.

I was wondering about electrolytic capacitor. If it is a bilateral element then it should provide the same impedance when current is reversed. But polarity is important for electrolytic caps(how they are connected in circuit, -ve terminal usually goes to ground).

So, is it  bilateral or unilateral? and if someone can give more details about the same.


texts:
I've come across many equations in microchip datasheets that are based on this value and am looking for a central place to lookup definitions.

F_OSC = oscillator frequency

T_CY = 1 / F_CY = time to execute one assembly instruction?


texts:
I'm trying to adapt the actual circuitry below in order to get the current consumption that comes from the VCC_12

My question is:

1) What value and tolerance should I use for Rsense?


texts: Requirement of pul down resistor of 10k for Input Shift Register (74HC165) after the input buttons

texts:
Im trying to learn input shift register to increase number of inputs for my Arduino. And in googling I found this schematic

I think its not for 74HC165, but I believe its almost same way for 165 also. But my concern or confusion is the resistors there. What is the purpose of those resistors there, which are connected to ground??


texts: How to implement a delay in my reset state or idle state in VHDL to wait for 100ns upon power up?

texts: So how would you actually implement the "waiting for 100 clock cycles" in hardware/VHDL  ? Just use a counter in the idle state that waits 100 clock cycles ?  What would this look like ?


texts: Experiments to convert analog 10ns pulse to digital 10ns pulse

texts:
My objective :

converting laser pulses from photo diode ranging from 10nA - 100mA (60dB dynamic range of incident power) to digital format, for measuring pulse width exactly

pulse width 10ns and repeating at a rate of 20us

EDIT: Modifications: photo diode current ranging 100nA -10mA

My problem statement

what i tried is a conventional approach using a TIA and limiting excess current at TIA input and using 3 additional opamp stages as i have to see the 10nA as 50mV , so i can fix a threshold of 25mV , i can limit the excess current to avoid saturation of opamps,the problem is the more number of opamp stages, they came because of GBWP as i require atleast 120dB of gain at 100MHz(1/10ns), this is done(simulated model) and i was able to achieve calculation of pulse width, but i did not like this !

My Idea !

  what i am thinking is to boost the 10nA current to atleast 1uA and any
  way current limiting is taken care now i can detect pulse at low gains
  itself ! and i can overcome the stability problems at high gain

am i thinking wrong ? is boosting such a low current is possible ? any way i should be ready keeping the fact that "this will boost my dark and noise current also " in mind

EDIT:

sorry that i have made some serious claims, may be due to underestimating the design problem

here below i have the schematic and results obtained,and the results were not at all up to the mark as expected in the comments

schematic:

10nA input perfectly output is preserved

1uA input

1mA input

my simulator shows me some noise analysis results which looked impressive, but i have to find out how they are calculated

noise analysis results

At the end the pulse width is not all maintained, my current implementaion failed due to saturation of opamp i believe, any how doors open for the comments and criticism


texts: IRF540 power Mosfet 12 volt motor gate resistance

texts:
I have a IRF540 power Mosfet driving a 12 volt motor. Currently I am using a 100 ohm gate input resistor, It is working fine. What I want is the maximum gate resistor value that I can use and still drive it properly with 8 Volts DC, This does not need to be an exact value just some approximation will do.
In most case this is a steady state voltage so timing is not a real consideration.
The only reason for this is if the IRF540 shorts out, I do not want it to take out the driver IC as well. I know about heat sinking and current protection circuits but sometimes this still happens.


texts:
I found two vias that were supposed to connect to two leads of a capacitor were shorted together on a 4-layer PCB. One of the vias is connected to ground. They are not shorted in the KiCAD model (checked multiple times using DRC).

EDIT: After obtaining a of the board and I confirmed that the two vias weren't originally connected. Therefore I am assuming I must have created the short to GND either by overheating that via or some other error. I have resolved to not use that via and instead solder the components together over wire.

FYI - photo not available due to confidential nature of work.


texts:
I'm trying to simulate the above circuit in Pspice, but I am getting the error:
ERROR -- Voltage source and/or inductor loop involving X_F3.VF_F3
You may break the loop by adding a series resistance

is it possible for power and current values to be zero?


texts:
does anyone know if it is possible to buy or build a really small tracker that uses wifi only.

I'm hoping to begin a masters studying bats, possibly in China, I expect in China the areas that the bats fly around will be at least partly covered by the wifi network. GPS is still mostly too large for 50g bats, radio tracking would work but then I need to chase them and find out where they are and would have a lot less data points. It would be nice to just be able to recatch them and download approximate data of where they went from a microSD.  I expect someone might sell this type of thing  somewhere (probably in China :) ) but if not I have built things before so I would be interested in basic suggestions for how to go about that too, just not sure if I could make it small enough if I was doing it myself.


texts: Altium Shortcut to cycle through all PCB layers one by one

texts: I wonder if there is any shortcut in Altium to cycle through all layers of a multilayered PCB one-by-one? That is to say that when the shortcut is first entered 'Single layer mode' is selected and only one layer is displayed first and then when the shortcut is entered again then the next layed is displayed in 'Single layer mode'.. and so on.


texts: Single voltage power supply to +/- rails

texts:
I have a wall wart coming into my circuit in the DC barrel jack shown in the picture. I want to have a positive and negative rail for my op amps as I am unsure of the effect of biasing my signal lines.

Is this how it would be done?

Or should I just bias my signal lines to sit at 10v and have my op amps opperate at 20 and 0 v.

Is there any real difference in a coupled output?

Thanks


texts: Schematic shows some resistor values as DNE

texts: What does it mean on a schematic when some resistor values are listed as DNE?


texts:
I've got a BOOST-DRV8711 dev board (http://www.ti.com/tool/boost-drv8711) to have some fun with the DRV8711 IC.

I'm interested in stall detection, to detect when the motor looses steps.
Using a general purpose MCU I wired the SPI and the STEP/DIR pins. I'm able to read/write the internal registers and to move the motor.

To try this feature I set these parameters:

torque = 128, smplth = 200 us
microstepping = 1/16
sdthr = 0xFF, sdcnt = 1 step, vdiv = / 32

All other settings are left on their default value.
This is the motor I'm using (with no load):

http://www.applied-motion.com/sites/default/files/HT17-268_RevC.pdf

I set the motor to run @ 1000 step/s and I clamped the axis, but nothing happened (I was expecting the stall led turns on).
Because the stall condition is met when the BEMF drops below the sdthr value I reduced both torque and speed settings - with no luck.

I'm using the most sensitive settings to detect a stall condition (maximum value for sdthr and lowest value for vdiv). Running the motor at a very low speed (down to 10 step/s) I bet I should detect a "stall".

Perhaps I miserunderstood the datasheet?


texts: How to model/get a capacitor to discharge slowly at first?

texts:
Typically, a capacitor discharges fast at first, and then discharging slows down until it approaches 0. Is there a way to slow the initial phase of discharging, so the capacitor does not immediately discharge so quickly? It should start discharging slowly, speed up, and slow down again.

My goal is NOT to generally slow down discharging - I would like to change just the "shape" of the curve describing its discharging. Ideally, the resulting shape would resemble an S-shaped or logistic curve (in reverse, since it goes from high to low).


texts: Where is the pole introduced by the RC circuit?

texts:
I've implemented a circuit under a suggestion which solves stability issues when driving a MOSFET with an high capacitance, using an OpAmp. Now, the circuit suggested is this one, in which is modeled the MOS and AC1 is used to model the error in the loop (which can be another question, since I'm not so familiar with these models):

The introduction of C1 instead of open circuit and R1 instead of short circuit, will reduces the bandwidth down to the R1*C1 pole, annihilating high frequency oscillations and increasing the margin phase. Mathematically/electrically speaking, I can't see this pole in the output current flowing in Rs, so I don't understand how it can reduces the bandwidth. In the practice, this circuit works very well: it actually annihilates any oscillation.

I can't understand how.


texts:
I am looking for a way to convert a + 24V square wave coming from a cnc controller, to -5V. The frequency of a square wave will vary from 15kHz to 35kHz.

What methods would you suggest?

Thanks for your attention.


texts:
Have a Vex 393 2-wire motor and I'm using a 6-40V PWM driver @ 5A max.

My question is this...

The Vex was spec'd at 4.8A stall current and 0.37A no-load current at 7.2V.

From what I've read here and elsewhere it would appear that it would be okay if I run this motor using PWM sourced with a 12V battery as the PWM will limit the current flow and not burn out the motor.  I'd need to start worrying if I was to use a 100V source but at 12V the risk is minimal or non-existent.

However the conflicting info I have seen seems to say that it should only be run with 7.2V but this is coming from websites that are talking about specs for some robot competition and of course the Vex site which has its own controllers that only run on 7.2V.  I'm thinking that the 7.2V might be a max allowed to keep the playing field even and the Vex controller is using a driver chip spec'd for something like 4-8V Vcc?

I just need confirmation my initial thinking is correct and that I CAN use the 12V PWM to run the Vex motor even though it has been spec'd at 7.2V.


texts: Why are null measuring methods considered to be very precise?

texts:
I heard a professor saying "it's a null method, so it is very precise".
He was talking about the force balance pressure measuring method.
I think in this cathegory of methods one can include the Wheatstone bridge (with balanced arms) or other methods where a galvanometer is used.
But why is this more accurate than other methods? My intuition tells me that the accuracy of a non-zero reading can be "more affected" by many factors..., but i'm not sure...


texts: How to reduce the AVR MCU footprints on PCB?

texts: I want to make my circuit board very small. I have seen many smaller boards with complex circuit. But I am not sure how do they do it? Is it all Custom circuit implemented on VHDL or some micro controller core printed on circuit board like the Black portion on the image below. I am new to PCB designing. Any suggestion would be appreciated.


texts:
I am not Electrical engineer but I am taking digital logic classes. I have a homework but I didn't understand how to do it. This is the question :

The temperature control logic accepts an 8-bit code representing
measured temperature in binary. The measured temperature is compared with a specific field
temperature. Design and draw a logic circuit which produced “1” if these two binary values are
equal.

How can I compare if these values are equal? 8-bit means there are 8 inputs? I am really stuck here because nobody showed us similar problems in class. Can anybody help?


texts: Anybody recognise this connector on an LED module?

texts:
I purchased a handful of these Luxeon K16 LED arrays a while back, they are surplus units from a Toshiba DLP projector if I'm not mistaken. They have solder pads onboard, but also feature a Molex-type of connector as well:

Link to product on eBay

At first I thought this may be a 3 pin Molex EZ picomate, but the side latching is different, and it is not the same connector style. I have been having great difficulty figuring out what connector will fit these boards, as I would rather use a plug-in solution in powering these boards.

Several of the sellers of these do not have any useful information (thoroughly unsurprising!) on these, other than that they are surplus.

Any help would be appreciated!


texts: Maximal operational pressure of tantalum and electrolytic capacitors

texts:
I need to design a device that have to operate in an high pressure environment (Nitrogen gas). The operational pressure may vary from 1bar (atmospheric) up to 20..30bar gauge pressure. The regular working pressure will be around 10bar.

So, the device contains a switching voltage regulator with LM2674-5 that needs input and output capacitors with relatively high value - something like 100uF.

It is pretty obvious that the usual electrolytic capacitors with liquid electrolyte will probably be crushed by such pressures.

But what capacitors to use? Are the tantalum capacitors more pressure resistant?


texts: Input impedance depending on length of coaxial cable

texts: Why does a coaxial cable terminated in a load ZL that differs from the characteristic impedance Z0, have an input impedance which generally depends on the length of the cable?


texts: Identify sot-23 smd component and possible replacement

texts:
I need help identifying this rusty smd component (sot-23 3 pins).
It comes from an early 90's sony discman.

Thank you!


texts:
I was reading about flip flops where author is convincing that it's better to use flip flop than latches. He gave following reason for it.

  As seen from the block diagram of Fig. 5.2. a sequential circuit has a feedback path from the  of the flip-flop to the input of the combinational circuit.Consequently, the inputs of the flip-flops are derived in part from the output of the same and other flip-flops.When latches are
  used for the storage elements, a serious difficulty arise. The state transition of the latches start as soon as the clock pulse changes to the logic-I level.The new state of a latch appears at the
  output while the pulse is still active.This output is connected to the inputs of the latches through the combinational circuit. If the inputs applied to the latches change while the clock pulse is still at the logic-I level. the latches will respond to new values
  and a new output state may occur. The result is an unpredictable situation.since the state of the latches may keep changing for as long
  as the clock pulses stays at the active level. Because of this unreliable operation. The output of a
  latches cannot be applied directly or through combinational logic to the input of the same or an- other latch when all the latches are triggered by a common clock signal'.

Can anyone explain me in simpler language what author actually want to convey to the reader. Or can explain in his own words for better understanding.
Thanks in advance.


texts:
Often I see in circuit diagrams that the circuit is connected to the ground:

I understand that this creates a reference for zero potential, but why does all of the current not simply flow right into the ground?  I must have a fundamental misunderstanding somewhere.


texts: Things that to be considered while choosing electronic components to get high Durability

texts:
Creating the Electronic circuits is Ok not so much complicated for experts. But needs to think about the persistence of the electronic circuits. Its very difficult to make the circuits to work for life time. But its important to have the long run electronic circuits.

Of course it depends on individual components that we assemble on the PCB. And are there any factors that need to be keep in mind while choosing and assembling the components to have high durability.


texts:
I have RGB LED(s) similar to the the 5mm in the pic. I have had success in uploading the example Blink program and testing it with a single LED connected to pin 13 of my Arduino Nano/ATMEGA328.

The LED timing is correct as per the program - One second OFF and One second ON - however, the colors are emitted at random.

Is there someway I can programmatically instruct the LED to display particular color at particular point of time. For example, first emit only Blue, then Red and so on.

Here is the code (its standard example with Arduino IDE):

int led = 13;
void setup() {
  // initialize the digital pin as an output.
  pinMode(led, OUTPUT);
}

// the loop routine runs over and over again forever:
void loop() {
  digitalWrite(led, HIGH);   // turn the LED on (HIGH is the voltage level)
  delay(1000);               // wait for a second
  digitalWrite(led, LOW);    // turn the LED off by making the voltage LOW
  delay(1000);               // wait for a second
}


texts: Can I modify this LED Light Circuit board to not strobe and just stay lit?

texts:
I'm looking for anyone who might know if I can modify this small LED light circuit board to not strobe?

I want to use it for my van as indicator lights, I've only managed to find these that will fit over existing holes etc. It strobes at the moment and I just need it to be a solid light. So when the indicator provides power in increments it will just light up. It currently has three wires coming from it, Red, Black and Yellow.

I assume there must be something controlling it to make it strobe? Any ideas?


texts:
I am looking for a simple solution to power my sailboat motor, it’s 48V 12kW, so it’s quite beefy. I have eight 24V lifepo4 cells (4.5kW) each, a 24V DC generator and a 2kW of solar, I would like to draw both 24V and 48V from the bank and also have the ability to charge at the same time.

I was thinking of having two banks, charging one, while using the other. I need a sensible, safe way of handling the switching. Does anyone have any ideas?


texts: Not getting acknowledgement from MPU 9250 I2C slave using STM32F401RE

texts:
I am using an STM32F401RE development board to communicate over I2C to an MPU9250 based breakout board sensor. So far I have set the start condition, and sent the slave address/write bit to the device, but I am not getting any acknowledgement. I have tried slowing down the SCL frequency to 50KHz, and speeding up the rise time, but still nothing. The slave address I am sending to the device is 0x68. I am relatively new to bare metal programming, so any advice would be much appreciated.

Code from I2C header:

void I2c_Init(uint8_t slaveAddr) {

  I2C1->CR1 &= ~I2C_CR1_PE;
  RCC->AHB1ENR |= (1ul << 1); //enable gpio clock
  RCC->APB1ENR |= (1ul << 21);// enable i2c clock

  GPIOB->MODER &= ~(3ul << 16);
  GPIOB->MODER |= (2ul << 16); //set pb8 to af mode
  GPIOB->MODER &= ~(3ul << 18);
  GPIOB->MODER |= (2ul << 18); //set pb9 to af mode

  GPIOB->AFR[1] &= ~(0xF << 0); //pin 8 i2c af
  GPIOB->AFR[1] |= (4ul << 0);

  GPIOB->AFR[1] &= ~(0xF << 4); //pin 9 i2c af
  GPIOB->AFR[1] |= (4ul << 4);

  GPIOB->OTYPER |= (1ul << 8); //set pb8 to open drain
  GPIOB->OTYPER |= (1ul << 9); //set pb9 to open drain

  GPIOB->OSPEEDR &= ~(3ul << 16);
  GPIOB->OSPEEDR |= (2ul << 16); //set pb8 to fast mode
  GPIOB->OSPEEDR &= ~(3ul << 18);
  GPIOB->OSPEEDR |= (2ul << 18); //set pb9 to fast mode

  GPIOB->PUPDR &= ~(3ul << 16);
  GPIOB->PUPDR &= ~(3ul << 18);

  I2C1->CR2 &= ~(0x3F << 0); //reset freqyency bits
  I2C1->CR2 = I2C_CR2_FREQ_3; //set register bits to 0x00000008 8MHz
  I2C1->CCR &= ~(1ul << 15); //set bit 15 to 0 sm mode
  I2C1->CCR &= ~(0xFFF << 0); //clear bits 0-11 for scl
  I2C1->CCR |= (0x28 << 0); // setup scl clock as 100Khz by 5000ns / PCLK 125 = 40 (0x28) /////////////50hz 20000ns/125 = 160 = 0xA0
  I2C1->TRISE &= ~(0x3F << 0); //clear bits 0 -5;
  I2C1->TRISE |=  (0x03 << 0); // set rise time to 1000/PCLK = 0x08 + 1 ////////for 300ns//////  300/125 = 0x02 + 1
  I2C1->OAR1 = (1ul << 14);
  //I2C1->OAR2 &= (1ul << 0);
  I2C1->CR1 |= I2C_CR1_PE | I2C_CR1_ACK;// | I2C_CR1_POS;

}

int write_i2c(uint8_t slaveAddr, uint8_t dat) {

  I2C1->CR1 |= I2C_CR1_START; //start bit init
  while (!(I2C1->SR1 & I2C_SR1_SB)); //wait for start confirm
  I2C1->DR = slaveAddr & ~(1ul << 7);// ~I2C_OAR1_ADD0; // send slave address and write bit
  while (!(I2C1->SR1 & I2C_SR1_ADDR))  // wait for address confirm
      if(I2C1->SR1 & I2C_SR1_AF)
          return -1; //if ack fail return
      if(!(I2C1->SR1 & I2C_SR1_AF))  return 2;

  I2C1->SR1; //sr read
  I2C1->SR2; //sr2 read
  I2C1->DR &= ~(0xFF << 0); //clear data reg
  I2C1->DR |= (dat << 0); // send data
  while (!(I2C1->SR1 & (I2C_SR1_BTF | I2C_SR1_AF ))); //wait for data confirm

  I2C1->CR1 |= I2C_CR1_STOP; //stop bit
  return 0;
}

Scope output:

Setup:


texts:
This is kind of a strange request, but im looking for something that could remotely power a Hard Button switch.
The kind of switch im referring to is like the ones on a computer power supply.

I was looking at all sorts of motors and such....but couldn't quite figure out what would do the Job. Maybe an Arduino with some sort of Network Enabled function that could drive some sort of Mechanical lever.

It's an odd request I know, but does anyone have any ideas?


texts: I am trying to simulate a current driver using TIP31 transistor for a speaker with known resistor and wattage. Can anyone please help me find a PSpice library for speakers? If there is not a library, how can I simulate the speaker only with information about its wattage and its resistor?


texts:
I need help with something I'm building because I've hit a dead end.
 I need this PIR sensor.

To activate this pump off a 9v battery.

The problem is the power output from the sensor isn't enough to power the pump. I tried a transistor but still nothing and all my research has led me no where. I wired it up from a similar question asked on this site but it's still not working.

If anyone has any simple advice it would be greatly appreciated as I have zero knowledge of these things and only going on what I've researched off the internet.
Thanks.


texts: So I am in the midst of learning circuitry, and cannot for the life of me understand what dictates the direction of current in a DC Motor/Generator. I understand that a charge applied to the negative and positive of a DC motor will be converted to mechanical energy. Conversely, it is also easy to understand that applying mechanical energy to the shaft will result in an electrical charge available via the positive and negative leads. What i don't understand however is if you were to hook a dead battery to the leads and applied mechanical force to the shaft, would it charge the battery? And furthermore, what would prevent any accumulated charge from backflowing and turning the generator into a motor?


texts: Transmission line: Why do longer traces cause signal reflections?

texts:
As the question says, I want to know why do longer traces/longer lengths of non-terminated signals of the PCB cause reflections and not the short length ones? I am ignoring the negligible amount of reflection a short trace may cause. I am not new to transmissions lines and impedance matching, but somehow I am not able to recall why exactly is reflection is more prominent on long non-terminated transmission lengths?

Is it because for longer trace there is higher chances of encountering discontinuities on the signal path, thereby causing reflection from that particular discontinuity, and even with the termination in place at the source, the signal gets reflected before it reaches back to the termination where it should ideally die off?

I would really appreciate your answer. Even if you link me to some document that answers this question well, it would be great.


texts: Are bipolar logic familes like ECL/CML used currently for radiation hardened computing devices?

texts:
According to this

article, even though it's 30 years old, ECL is more radiation resistant than normal CMOS chips by a factor of 1000. It is also less susceptible to DPA side-channel attacks. So in particular, are ECL chips used on military hardware/spacecraft current?


texts: Non-Standard computer PCB, finding enclosure to mount

texts:
Edit******
Thank you for replies. My bad for not including the board! Here it is:

Its the NVidia Jetson TK1.

There is a thread, for example, here, with a list of compatible enclosures. http://elinux.org/Jetson/Enclosures. I might get one of the 3D printed ones. OTOH, there is something I prefer more which is the Silverstone PT13, but it looks like the board is plopped into the case without the screws being installed. I'm unsure if this is proper practice and if the board would short-out as a result. Plan on using this board quite a bit so having it on several hours at a time won't be unusual.

Edit******

I'm a computer hobbyist looking to learn embedded programming on a specific platform and searching for a case to accommodate the non-standard size PCB (compared to PC case standards).

Board is 127 x 127 mm.

Power supplied via external power supply brick.

My main concern is the PCB standoffs. I don't know much about this issue. My only experience in this issue is assembling PCs where I line up motherboard to ATX mounts in the case and screw the board in.

I've found 3d printed options covering the top and bottom only of the board. Its an option but I prefer an enclosure/case to keep the board more protected from dust and pets.

What options do I have to mount the board? I don't want to leave the board in the open sitting on cardboard or a desk. I'd prefer if the board were held in place and in a proper traditional case/enclosure. The board doesn't include a backplane and I don't care much for one so long as the board is covered from all sides with hole for cables for keyboard and such. Board does generate heat so there will need to be vents in the case / enclosure.

Thanks in advance for feedback.


texts: Find p-MOS frow battery switch application

texts:
I'm designing a switching circuit between USB (5V) and Battery (li-ion 3.7V) for a portable device, below is shown the schematic:

As you can see if correctly chosen the P-MOS switches between USB and Battery, indeed I actually have a problem choosing the right MOS.
Let me explain:
Suppose Usb is not attached then we only have the the Battery. Then at the DCDC input I must have at least 3.5V (200mV dropout). I've 2 question:

Since I cannot afford any voltage drop can I eliminate the Schottky diode? (or it's extremely needed for inverse current...).

I initially select the PMV27UPE since from the datasheet it has a ultra low active resistance  but emulating its behaviour with spice it has a voltage drop of .7V... Where did I make a mistake? (is it a problem it's working in linear region even if for switching purposes?)

Additional info: I need a maximum of 500mA delivered to the Load.


texts: What is the reason for multiple ground connection and multiple testpoints on this PCB?

texts:
Please, have a look at the image:

The biggest pad at the top is the negative terminal of a battery holder. Through 0 Ohm resitor above it goes to a capacitor across a DC motor (not shown). Below the diode and off the image it goes to a ground of a charger connector.

Just below the pad there is a thin trace, leading to a small capacitor and a 5 pin SOT-packaged something. And a bit lower there is yet another ground connection, that is leading down to transistors and below.

I do agree on keeping DC motor noises as far as possible and it it well demonstrated here via 0 Ohm resistor up. But it is a mystery to me, why would they split ground connection more and more? They could've taken the first split and led it immediately to transistors. Or they could take the second split lower -- near a diode bottom left. Or they could lead a thick trace instead of split.

Is there any real need to split it so many times?

I also wonder, what is the purpose of so many test-points? This ground has 3 testpoints, traces near also have 2 test points. If they are at the same trace, at the same potential, what's their purpose?


texts: Altium: Stitching vias applying for multiple nets in multiple channels

texts:
I'm tryint to add stitching vias to my multichannel project.

I have 5 nets for via stitching to be applied on each channel and 3 channels in the project. So 15 nets in total.

Looks not too much to make apply stitching manually, however I feel that this is too weird not to have an ability to do it by net class or something.

Manually applying stitching will prone to mistakes (I can miss a net or apply stitching to a wrong net by mistake) and time consuming (especially if my project would have more nets and more channels).

Is there any better and more automatic solutions?


texts: How do I make the turn off and turn on time equal in a NPN transistor?

texts:
I have a simple NPN switch, see the diagram.

I feed a 100KHz square wave (TTL) to the base of this transistor and it turns on very very fast (a few nSec) but it doesn't turn off as fast, it almost takes 2uSec for it to turn off. (I am looking at the collector of this circuit). The diode is a laser, transistor is run off the mill NPN (datasheet). I also tried with another NPN from ONSemi which is faster (at least what I think) same story.

Why the transistor doesn't turn off as fast?

How can I make it turn off in a few nSec?

Is it better to use a MOSFET than NPN in this case?

** UPDATE **

I have added a 1K instead of that NA capacitor pad and use a faster BJT, things improved a bit. (Actually, I found that the BJT is similar speed but lower collector output capacitance, 2pF vs. 6pF). Anyway, now I see turn off about 120nSec. I will add a speed up cap and report results from here.


texts: Sense capacitive change then apply high voltage

texts:
When an insect touches two of my wires the capacitance between them changes. This can be detected. Now after a change is detected i want to put high voltage on those two lines. I am afraid however that such a high voltage will kill the microcontroller sensing the insect. Is there a way to properly do this? I have considered using relais to cut the sensing wires after a detection, but those might die out too fast. Say I want to put 3kV on the line, can maybe a high isolation mosfet can do the trick? Are there cheap(er) options?
With kind regards.


texts:
This is an FM transmitter circuit found in Internet   Link.
Before doing ,I'm simulating in multisim. Since there is no mic input,I have given sine wave  generator

1).What is frequency of wave must be given in the place of MIC(Audio signal range).

As per the information , here BB109 is used as fm modulator.

2).Can anyone Explain me about BB109 operation as fm modulator.?.

3).Can we give the solar energy as source ?.

4).How to set fequency of transmitting signal as 102 Mhz or anything else ?


texts: Which electronics components should I always have on hand?

texts:
I am thinking about ordering up some parts for every day use. I am thinking about making one big purchase so as to minimize on shipping and other charges.

What are some of the components that any electronics hobbyist should have around ALL the time?

To put a little more scope: typically working with Arduino's, PICs and sensors. 5V - low current projects.

Looking for: component, value or range (if any), manufacturer (optional)

For example -  Resistors, 1K through 100K 5W


texts: Is circuit design based on min/max values good practice?

texts:
Time and again I am arguing with a colleague of mine about the question above. When I design a circuit for mass production (> 10k/a) I want to make it robust against every possible variation of component parameters that I know about. This means for example:

BJT parameters like VBE, current gain etc. vs. bias and temperature
Tolerances, temperature dependences, aging and soldering drift of passives
Lifetime of components

Furthermore I consider any violation of absolute maximum ratings under normal operation conditions as unacceptable.

As I understand my colleague he just deems it a useless business to care about parasitics and the like. Just put it all together and try if it works, that's it. Put some pieces into the heat chamber, age them and if they still work afterwards you're done. He has more experience in designing commercial electronics than I do, but I really don't like such an approach. I am convinced that as an engineer I should have thought about any part of a circuit before I build it up for the first time.

Is my approach just sick perfectionism or has it something reasonable? I have already discovered that a lot of electronic designers don't care about robust design...


texts:
I'd like to use a transformer to improve the performance of our SR5184 preamp.

The signal recovery SR5184 is an ultra low noise preamplifier. It has 0.8 nV/ √Hz input noise and a bandwidth of 0.5 Hz - 1 MHz. It's noise figure is shown below.

We use it to amplify nV signals of a cryogenic low impedance load (< 1 Ohm with leads).
The frequency range of interest is a few Hz to at least 400 kHz. Even a turn ratio of 1:10 would boost the SNR significantly.

The Question is:

Are there commercially available transformers that match the requirements?
Which companies could manufacture them?
Is that even possible with room temperature transformers?

Update:

I found some transformers covering an even larger frequency range, e.g.:

J2100A injection transformer (1 Hz - 5 Mhz; ratio 1:1)
J2101A injection transformer (10 Hz - 45 MHz; ratio 1:1)
LL1575 CCTV isolation transformer (20 Hz - 11 MHz; ratio 1:1)

Sadly they just have a 1:1 ratio. But I guess with a bandwidth reduction an increase in turn ratio should be possible.


texts:
Can I safely replace 2N3904 and 2N3906 with BC337 and BC327 in an audio amplifier circuit since both pairs are NPN, PNP?

simulate this circuit – Schematic created using CircuitLab


texts: Identifying a part from game console controller

texts: I need help identifying the following part. It came out of an old console game controller. It's labeled "SUP A9 103J". Googling it did not help. It's got ten pins and it was soldered into a space labeled "x9". I think it's some sort of crystal, but I'm not sure.


texts: Can I reduce rpm further of a gear motor by using PWM?

texts:
I am working on a project where I need to move the object from one point to another in a dead slow speed , The object doesnt weight more than 5 pounds .
I found a DC gear motor with has a RPM of 0.5 but I thinks its still very fast for my requirement .
This is the motor :
http://www.servocity.com/html/0_5_rpm_gear_motor.html

This is the PWM :
http://www.electronickits.com/kit/complete/motor/CKMX033.htm

Please suggest a way where I can reduce the speed drastically (Either simply using a potentionmeter or any variable device) . motor needs to be small the rest doesnt matter .Or you can propose me a entirely new solution .


texts:
I've been asked to help repair a keyboard. On examining the keyboard I found the issues (circled) in the below image:

A tear in the middle of the ribbon cable
A tear across the end of the short side of the cable where it entered the PCB connector

My original idea to repair this was to desolder the left side, buy a replacement ribbon cable, and then resolder and connect it. Unfortunately I've been unable to locate a replacement part.

My only other idea is to remove the insulation over the smaller tear and solder on small wires to bridge the tear. Then to remove the insulation on one side at the end and attempt to reinsert it into the PCB connector. Given the size of this cable I doubt my ability to solder the cables to rejoin them.

Does anyone else have any suggestions for an alternate method of repair?


texts: Fuse position in relation to load and switch

texts:
Where should fuse be in relation to the power, switch and load? Any suggestions on a better approach or tips on the matter would also be helpful.

  POWER > [FUSE] > SWITCH > LOAD

  POWER > SWITCH > [FUSE] > LOAD


texts: Reading a low voltage signal from a battery connected to a transformer

texts:
So currently I am trying to read the current draw from a battery that is being run through a transformer to generate an arc to light a gas burner. I have a roughly 1 ohm piece of wire that I am measure the voltage drop across by having it at the end of the circuit between the ignition system and the battery where I have an Arduino uno analog input reading the voltage drop form one end while the other is connected to ground.

The issue I am having is that the transformer pops up the voltage to a several thousand and then the arc occurs like a normal igniter and the burner has a ground wire screwed into it that connects back to the ignition system/ battery but the voltage across the small wire I have is still showing up as a extremely high voltage and consistently screws with my micro-controller causing me to have to restart it.

I was looking at using optocouplers to measure voltage but it still doesn’t seem like it would help me finding the actual draw on the battery (when I took a current measurement-connected from the battery positive to the ignition system I read upwards to 20 A when the igniter is sparking but that doesn’t seem right for 4 AA batteries.

On the hand of optocouplers I was also looking at if they would actual give me an accurate voltage reading of the system or if the voltage would be too low when it wasn’t sparking to be read from(below 1 V I suspect).

If I can just get the voltage to a reasonable to expect value (considering right before it enters the battery’s negative node It should be roughly Zero volts if I connect the negative end also to the ground Pin if my microcontrollers. Then I have a 16 bit ADC that shouldn’t be able to read accuracy of up to 7.8125 uV or defiant at roughly 61 uV.  This also makes me concerned though if the amount of amperage that “apparently” is in this circuit would fry the ADC. The multimeter was saying my analog input pins were hitting almost 1 A but again that seems way out of order considering my board isn’t a smoldering heap yet.

So really my questions are:
Any idea what’s causing this high voltage/current that my multimeter is reading coming in and out of the battery?

Is this the actual voltage/current or is something off?

Would an optocouplers help reduce effect on the circuit from the transformer and if reading extremely low voltage values will that actually care across as a proportionate value to the other side of the optocouplers?

Thanks for the help!

Edit: I am measuring the current by taking the measured voltage across the 1 ohm wire with Ohms law on the microcontrollers. However the 20 A I measured was from a multimeter. Along with the 1 A I was getting through the analog pins.


texts: how to transform 120V AC to 5V DC 5A load using flyback transformer circuit? Setting frequency - low cost, low footprint - change load capacity

texts:
i am using a flyback transformer circuit to keep the footprint small and cost efficient. Its been suggested to me to keep the frequency high so the transformer can remain small.

how is the frequency set in a flyback converter circuit?

Which components are different when transforming a load of 400mA or transforming a load of 5A? (i am using 5A, though most of what i see on Google is people looking to transform to 400mA for 30-60V DC)

is this something i can find load measurements on my components for, if so, which components measurements should be reviewed when changing the load capacity to a greater amperage?

this is my application .. 120V AC -> flyback transformer circuit -> 5V DC 5A power draw

the others i have seen are 30V DC -> flyback transformer circuit -> 5V DC 400mA power draw

the power draw is much greater in my circuit, i am looking to find what changes there are.

the flyback converter circuit i am designing is going to change AC to DC also. I think (don't know, looking for confirmation on) a typical flyback transformer changes DC to AC and then back again in it's typical application. So it does not matter whether it is AC or DC on its first input?

i am going to use a tool called WEBENCH - its available from Texas Instruments https://webench.ti.com/ . suggested to me by @user4578 on the post that lead to this
Which buck converter can be used for 120 V AC to 5 V AC rated at 5 amps? - on that post it was decided to use an isolated transformer circuit to step down from 120V AC instead of the buck converter i had originally intended.


texts: Any open tool for graph plotting for determining PID tuning parameters?

texts:
I have gone through several PID implementations and its tuning tutorials, documents and all. The Best tuning tutorial was PID-without-a-PhD.pdf . But has not been of much help. I can say it works some.

I am working on a Magnetic Levitation project. Please go through the link (Barry's Maglev) for an example. I am able to levitate the magnet keeping an aluminium plate below. Current progress: Video.

I want to perform it without the aluminium plate.

My question is how to start with graph plotting and all. I've seen and been attracted towards the graph only. Say take the PID-without-a-PhD.pdf file and just look at the plotted graphs. How to get that? which open tool to start with?

I have tried building and working on some self made graph plotting tool. The plotting against time is not satisfying, and hence the gain determination.

[If there are any self explanatory auto-tune algorithm available! : this is not my question now.]

I want to restart fresh with hard systematic approach. Any help will be god like helpful. I don't want to go with trail-n-error method. As that didn't help.

I am using AtMega2560, a coil, a stack of 2 neodymium magnet, a nicely working H-Bridge.

....Update1....

Also a hall sensor for feedback.

........

....Update2....

Now I have its transfer function with me. I am studying LTI Transient-Response Analysis using Python. The issue is I have a matrix of transfer functions. I might be wrong because what is called what, I don't know exactly. Will learn it soon.

........


texts: ICSP / ISP issue when programming ATmega328P

texts:
I've designed a custom PCB that I'm trying to program through ICSP using AVRISP mkII and I've run into some issues. I'm using Arduino IDE for programming, but I don't think this is relevant. The IDE says that the programming was successful, but the program does not run. I've tried with a few different programs using different pins, all with no luck. I had a different PCB before for the same application and it worked fine. In the second version of the PCB I used more pins on the CPU and thus needed to use the programming pins as GPIOs as well. I have some pull-down resistors on those lines, because they are driving MOSFETs. I suspect these resistors are the problem, but I haven't tried removing them since they are 0402 size and will be hard to solder back on in case I'm wrong. Am I right to think the pull-down resistors are the issue? Is there anything else I've missed?
Here are the schematics where you can see the exact connections.

I'll be grateful for any help I receive.


texts:
I have a store-bought battery powered LED light assembly that is controlled by a microswitch.  The light is installed in a hard to reach place so I wanted to hook it up to a cheap ASK wireless receiver with a remote.  I bought the RF M4 (http://www.adafruit.com/products/1096) from adafruit.  It's built around a PT2272.

I didn't do enough checking on the light's circuit ahead of time and it turns out the microswitch in my light assembly is on the ground side.  What is the cheapest way to make the RF M4 switch the ground for me?  I was planning on powering the receiver circuit with a standard 9V battery which is within the specs for the chip.  I was thinking a transistor circuit, but I'm not great at designing those.

Just as a quick overview, the M4 receiver here puts out Vcc on the D2 pin when it receives the signal from the transmitter.  I couldn't tell from the PT2272 data sheet (http://www.adafruit.com/datasheets/PT2272.pdf) if there was a way to get D2 to go to ground instead.

Also, in my light assembly the only current going through the switch is the pulse for the switching circuit to turn the lights on.  The LED current does not appear to go through the switch since the light stays on after releasing the momentary switch.

I'm still a beginner so I really just don't know which way to go from here.


texts: How can I power a device that requires 5-7V and 2.5-6 mA with what I have?

texts:
I have voltage pins on one device that outputs 6.23V DC and 70 mA DC. What type of circuit do I have to build that can power up another device that requires 5-7V DC and 2.5-6 mA DC using my 6.23 V source?

EDIT
The source outputs about 60-80 mA current, not 0.1 mA


texts: Momentary switch 12 V motor reverses game

texts:
I am trying to figure out how to control a dc motor with a momentary switch as a trigger and limit switches for stops. The trigger needs to be momentary because I need three of them in parallel at different locations, so that it will operate if any of them are pressed.
The simple sequence is as follows:

Press button
Motor runs forward until limit switch is pressed then hold
Press button
Motor runs reverse until limit switch is pressed then hold


texts:
I am doing my own project making a basic audio recording device using microcontroller's ADC to get the audio signal from electret microphone and saving data to microSD card. I'm using STM32L476RG Nucleo board and external discrete components. Below is the simplified schematic of the application.

There is an anti-aliasing filter (440 ohm resistor and 100nF capacitor).  Removing it does not change results.

The ADC works based on 8 kHz timer output in DMA mode, so my code based on ADC control is pretty simple: I start the timer and ADC in DMA mode and wait for half complete and full complete interrupts where I simply write ADC data to microSD, then the cycle continues and the audio data is continuous in the time axis.

The problem arises when writing data once the half complete or full complete DMA interrupt occurs. During that time the current increases (that's my hypothesis) and the voltage on the VDDA (ADC source/reference pin) changes. The consequent result - periodical spikes in the audio data exactly at the time of DMA half/full conversion complete interrupt. As of approval I tested changing SPI speed (for microSD communication) which showed that reducing speed had longer spikes and increasing speed had shorter spikes.

So there is the 8 bit audio signal in Audacity. The upper signal is while talking and the lower is being in silence. The audio recording excluding the regular ticking (spikes) is completely fine.

I have tried bypass capacitors and filters which did not improve the audio. Also tried using CR2032 cell battery for microSD, but apparently the voltage was too low for microSD to function.

Are there any hardware or software decisions/solutions I can implement that would get rid of this problem? I prefer fixing it in hardware first, but keep using the MCU's ADC.

There is the schematic of Nucleo Board for MCU and VDDA/reference pin powering.


texts: Circuit to safely power-down Raspberry Pi

texts:
I want to use a Raspberry Pi as an XBMC server in the car.  The XBMC docs say that you should always use the shutdown command before disconnecting the power.  I don't want to have to (tell my wife to) log into the Pi and shut it down before turning the car off - I want to be able to

I've been thinking that it should be possible to create a simple circuit with a capacitor and probably a diode to detect when the power supply was disconnected (and raise an interrupt on one of the GPIO pins) but the capacitor would provide current long enough for the system to shut down properly.

Does this look correct and sufficient?

The circuit will be powered by a car battery - 12.6 to 11.7V.  The Raspberry Pi takes 5V (5.25 to 4.75V) and draws 700-1200mA.  I haven't timed it yet, but I'm guessing the shut-down process probably takes around 5 seconds.

So I suppose what I need to know is:

What kind of capacitor would I need to store enough charge to keep the Pi going long enough for XBMC to shut down properly?
Given that the Rasperry Pi's GPIO port takes 3.3V, what's the best comparator/op-amp to use (I suppose I could use a couple of resistors to bring the output down from 5 to 3.3)
Would there be any benefit in having the GPIO line normally high or normally low?


texts:
I recently bought 2 12V lead acid batteries (AGM type) for my mobile music needs where I need 24V, so I discharge them in series.

At the moment I charge both batteries separately, which is a bit annoying. So I would like to charge them in series, but I am not yet sure if this is a good idea.

When charging them separately I use a bench power supply with current and voltage control set to 14.1V. So, when charging them in series I would set my power supply to 28.2V, but then one of the batteries starts gassing and when measuring the individual batteries I see a voltage difference of about 0.3V.

So, am I doing something wrong here, is it just a bad measurement and nothing to worry about or is it generally a bad idea to charge batteries in series?


texts: Converting Open-Drain to Active-High (low voltage, low power)

texts:
In my design, I need an RTC (PCF85263A) to enable a boost converter (TPS61021A) after the RTC alarm triggers an interrupt. The interrupt pin on the RTC (INTA) is open-drain, but the enable pin on the boost converter (EN) is active-high. This is a problem.

When the alarm triggers the interrupt on the RTC, the INTA line is held at 0V, and when the interrupt isn't active, INTA is high-impedance. However, I need it the other way around: the EN pin needs to be held up to battery voltage when the alarm interrupt is active.

My first guess is to use an N-channel MOSFET logic inverter to achieve this. The input, of course, would have a pull-up resistor to VCC.

simulate this circuit – Schematic created using CircuitLab

However, the battery voltage VCC can go as low as 0.9V in this design. Another important requirement is that the power consumption be as low as possible while the RTC is "sleeping" - before the alarm triggers an interrupt. The RTC uses 300nA and the boost converter has a shutdown current of 500nA, so my power budget can take about 1-2μA more during sleep.

As such, I am not sure if this MOSFET inverter will be the most power-friendly option. Additionally, a MOSFET might not be the right choice for such low voltage - I assume that I must browse for VGS/VCE/VSAT choices at or below 0.9V.

What would be a power-friendly transistor choice to convert an open-drain, active-low output signal into an active-high signal for an input pin?

My design originally used the TPL5111 power gating timer instead of an RTC. It has a proper push-pull, active-high enable pin to wake the boost converter. Unfortunately, it can only "go to sleep" for up to 2 hours at a time. I thus want to migrate to an RTC so that my device can sleep for days or months instead; having the device wake up is a power-costly operation.

Edit: This PNP solution forgoes a pull-up at INTA. Credit to Tim Wescott.

simulate this circuit


texts: Confusion regarding component JUMPER-PAD-3-2OF3_NC_BY_TRACE

texts:
I am working on deploying a open source hardware project.In the list of components, they have mentioned one of the components as PAD-JUMPER-3-2OF3_NC_BY_TRACE_YES_SILK_FULL_BOX with value     JUMPER-PAD-3-2OF3_NC_BY_TRACE.I tried to search on net but not able to figure out what is this.Since, I am maths major not electrical engineering, so I have hard time in figuring this.
Please help me to figure out what is this and if possible how can  I make arrangement for this.Thank you.


texts:
Considering the design limitation of hardware (clock speed, memory, etc…), is there any better way to write IF statements more efficiently in C language (e.g. run on Arduino), more specifically the following piece of code of an embedded software?

if (A >= 476 && A <= 524) A = 500;
else if (A >  524 && A <= 860) A = (A * 1.4) - 760;
else if (A >  136 && A <  476) A = (A * 1.4) - 685;
else if (A > 860) A = 1000;
else if (A <= 136) A = 100;

A is passed as value by a sub-routine and this value is then transformed into a different value according to its position in a set range (of values). It has to run as fast as possible!

UPDATE!

A is a variable of integer type i.e. int

SUMMARY:
I summarized here the options I learned from you:

a) improve structure

consider first comparison for most probable inputs;
eliminate && operators.

b) eliminate floating point calculation
c) create look up tables
d) assign more adequate variable type
e) write code in abbreviated form (*= , += , -= )

a) Indeed, I already put the comparison 'if (A >= 476 && A <= 524)' first, because I expect most of the values passed by the subroutine to be within the first range. So most of the time the program doesn't execute the next if statements.

b) I reviewed the floating point calculation and consider it a bad choice for this piece of code. It definitely can be avoided by using a divider of integers.

c) The lookup table seems a good idea but not for this application, because the program has at least 3 more of such clustered comparisons. Memory might become a problem.

d) The variable was assigned as int although it would never really become negative. Unsigned int is what I assume is better. But I would say it doesn't make the code faster.

e) Writing the code in abbreviated form seems also another improvement idea. I just don't know for sure how different compilers might interpret that or if it really saves so much time.

Thank you.


texts: Finding times in first cycle with given voltage

texts:
I have the question "The instantaneous value of voltage in an a.c. Circuit at any time t seconds is given by:
$$V = 100\sin(50\pi{}t - 0.523)\ \rm{V}$$

Find:

The times in the first cycle when the voltage is -40V."

Here is my attempt:

My final answer is t = 5.949 ms however the solutions say that the answer should be 25.95 ms.

Where have I gone wrong ?


texts: Bipolar stepper motor driving by Micro-controller Xmega

texts:
I am using Bipolar stepper motor Haydon Kerk 25343-05. My driver IC is DRV8833.
The micro controller I am using is ATXMEGA16A4U.

The bipolar stepper motor has 4 wires. 4 PWM output pins of Microcontroller go to the driver chip which in-turn drives the stepper motor.

The step angle of the motor is 7.5 degree. If I name the wires as A,B,C,D; what kind of input pattern should be given to drive the motor forward. Should I give delay after each step, If so, how much delay should I give?


texts: Purpose of the capacitor which is placed in parallel to collector and emitter of the transistor?

texts:
Can someone explain the purpose of the C469 capacitor, which placed in parallel to collector and emitter of the transistor?

Edit: Sorry for the mistake, C469 is parallel to CE


texts:
I have a variable resistance, 1K to 1M. As it varies due to external factors, I want to be able to pick a X value in between 1K and 1M so that once it reaches X even if the resistance increases the resistance is capped to X.

For example. I want to limit the upper bound to 1.7K. As the variable resistance crosses 1.7K I want the resistance the circuit sees to stay at 1.7 instead of keep increasing.

What kind of circuit can I resort to in order to achieve that behavior?

Requirements:

When variable resistance value is below upper bound X the value seen should match the value of the variable resistance.
The resistance is probed keeping voltage constant


texts: How to determine which topology a BJT is configured to from a given circuit diagram?

texts:
As far as I understand, a BJT in any given circuit must fall in exactly one of the following configurations:

-Common emitter.

-Common collector.

-Common base.

So my question is:

Are there any other configurations a BJT can be in? Are these 3 configurations the only possibilities for a BJT to be in?
How can I determine which configuration a BJT is configured to from a given circuit diagram?


texts: Buck converter charge battery control output voltage

texts:
I have a buck converter charging 8 series of Li-Ion batteries ( 8 x 4.2 voltage of charging) with a source of 36 V. I am using this schematic (from here):

I know that for a resistive load, the output is controlled as
$$V_o=D V_{in}$$

But, here the load is not resistive. How to control the output voltage? can we control it as above without feedback?

Does duty-cycle D = 8 x 4.2 / 36 works here?


texts: Can I wire multiple brushless motors in series or parallel?

texts:
EDIT: As Bruce Abbott pointed out in his answer, it's not possible to connect 3-wire brushless motors in series, since you don't have access to both ends of each winding. Oops. So, the more relevant question is whether there are any potential problems with wiring multiple motors in parallel, other than the increased current draw.
ORIGINAL QUESTION: I'm working on a design that requires a large amount of torque in a very confined space. Due to this and other requirements, my best options seems to be to use two motors to drive a single load. The shafts would be connected together, so the two motors would always maintain the same relative orientation.
I would like to avoid using two motor controllers, so I'm thinking of wiring each phase of the two motors in series (i.e. phase 1 of motor A is in series with phase 1 of motor B, etc.). I would have a single encoder on one of the motors, which I would be using for position feedback and for sinusoidal commutation. I'm expecting that this would effectively allow the two motors to act as a single larger motor, with double the voltage required for a given speed. Is there any reason this wouldn't work, or any potential issues I need to watch out for?
One thing I'm worried about is that I would need to make sure that the connection between the two motor shafts is "clocked" correctly such that the rotors of both motors have the same position relative to the stator windings. There will inevitably be some error in this; I assume that this would just slightly reduce the torque for a given amount of current, but perhaps it would cause other issues?
Some additional information, in case it affects the answer:

This is for a positioning application which uses a haptic operator interface. This uses the motor current to calculate the motor torque, which is then used to provide force feedback to the operator. Therefore, one of the main requirements is very low torque ripple.

The motor speed will be very low (from 0-100 RPM).

The motors I would be using are the EC-4pole motors from Maxon.

I will likely be using the EPOS4 motor controllers from Maxon.


texts: Cheapest way to power an LED from an Android phone using Bluetooth

texts:
I recently wanted to make an Android controlled LED using Bluetooth.
The obvious solution I could think of is using a HC-05/06 module with an Arduino.
However I believe for just lighting an LED,  this method is overkill,  and not really cheap.
Also I wouldn't want to use an entire Arduino board for this as a lot of its functionality would go useless.
And I only need to transmit a 0 or 1 through bluetooth-nothing else.
So is there any cheaper way of Bluetooth controlling the LED?
I would prefer something with minimal features that serves the purpose.
(Being just a high school student I don't have much experience and resources to do the same so please guide me accordingly).
Thanks!


texts: how can i turn off or on LM2576 through pin 5. i want it turn on for example when input voltage is above 10 volt and turn off when input voltage is below 10 volt .


texts:
Is there a simple way of calculating the power (kW) of a 3 phase heating element?

I have 3 elements mounted in a pack and inserted into a tube and there are 12 tubes, so 36 elements in total. They are connected in delta. I have 22ohms between L1+L2, L2+L3 and L3+L1.


texts: How did four-course LF radio navigation ranges have their beams other than at 90° / 180° angles?

texts:
The four-course Low Frequency Radio Range system used for aircraft navigation (in the US and elsewhere) in the 1930s and 1940s used a pair of directional antenna (with figure-of-8 shaped radiation patterns) at 90 degrees to each other.  One antenna would transmit the Morse code pattern for "A" (⋅-) and the other for "N" (-⋅), as follows:

When the aircraft was on course, the signals from the "A" transmitter and the "N" transmitter would be at equal value and overlap to form a continuous tone:

If the antenna patterns are at 90° and the transmitted power is the same for the two signals then the system provides four different courses that a plane could fly (or eight, counting reciprocal courses away from the station).

Examining charts for actual installations, however, one often sees that the four courses are not at 90° angles:

How was this in practice achieved?  I can see that by increasing the relative strength of one transmitter compared to the other the courses could be adjusted so they crossed at other than a right angle (like this, for the top diagram, supposing A is stronger than N):

\ N /
 \ /
A X A
 / \
/ N \

But how would it be arranged to have asymmetrical patterns such as the one in the Stout Field diagram above, where the opposing courses are not at 180° angles to each other?


texts: Should I look at nominal or max battery voltage for choosing resetable fuse?

texts:
I am building a LED/Camera control circuit that is going to be using a 14.8V Li-Ion battery as a supply. I want to put a resettable fuse to prevent short circuits from blowing up too much since this is going in water.
At first I chose a 16 V fuse thinking it would be enough, but looking at the battery voltage at max charge, it reaches up around 16-16.4 V.

When I spec my fuse, should I look at the nominal battery voltage or the Max charge battery voltage?


texts: Dealing with coupling of PWM noise into Hall-Sensors as spikes in BLDC driver circuit

texts:
I have designed the first revision of a BLDC driver board (based on STM32 and DRV8323 chips). Right out of the bath (after writing the firmware of course) I noticed that the coupling of PWM into the hall signals is very terrible!

The motors that I have designed this circuit for are rated at ~20Watts. Their hall sensor only works at 5V or higher. I use the XOR mode of the STM32 timer to capture and generate commutation event...the STM32 is 3.3V...but I assume it can tolerate 5V input but I do not know what is the hysteresis for detecting a low or high signal when the GPIO pins are configured in XOR mode:

At below 100% PWM, I get a lot of noise. The yellow trace is one of the hall sensors (the blue is commutation event). I only have 2 probes so I could not capture all 3 sensors and the commutation event (pulling an gpio high and low before and after updating timer output). As you can see, the noise over the hall sensor is quite bad:

I blame 2 things:

1.The layout: As I did not have prior experience, and because there are 2 motor connectors, I routed the hall sensors very close to the phase signals (greens are phases and yellow are halls).

2. Motor Cable:
The motor cables are just 8 wires next to eachother (no twisting) for almost 50cm...so even if I did the best layout in the PCB the cable itself would cause the coupling issue.

I have tested the driver with 100% PWM (meaning no switching) and everything looks much better (the noise is very small and limited to when the half bridges switch at hall sensor update). So I really need to take care of this noise. I know that I can mitigate this effect in the software (e.g. by inserting timeout and other filtering methods...) but nothing can beat having a nice clean signal anyways.

So to make it short here is my questions:

1) What can I improve in the layout? separation of hall sensors and phase signals into different connectors?**

2) I will tear apart the motor cable and separate halls from phases and make them twisted pair...before I commit this, do you think it makes sense?

3) Should/Can I use a level-shifter and perhaps a Schmidt trigger to remove the noise and convert 5V to 3.3V before feeding it into the STM32 controller? If so, what chips do you suggest?

UPDATE:

Here is the RC filter for hall sensors, placed near MCU input.


texts: PCB designing: facing problem in connecting pushbutton

texts:
I decided to learned PCB designing using EAGLE 7.1.0. So I first of all I go through this video then through this video.

Now I started designing a board for ATmega16 microcontroller. For this I simply connect a resistor on RESET pin, And check it on board layout, till now every thing fine. Now I decide to design a library for push button, for this I follow this video then this video.

Now I connect this push button with RESET pin to complete me reset circuit. Now, when I check out Board layout, there no connection between ATmega16 and push button. Here is schematic and board layout

Schematic;

Board layout:

You can see Push-button is not connecting to the chip. Why?


texts: Is it possible for a digital multimeter to be modified to read 10 times the ac voltage?

texts: I would like to modify a kit multimeter so the ac voltage can be read ten times larger for teaching purposes. The test bay has been set up on 24 V AC but I want the students to be able to read 240 Volt AC with the modified meter.


texts: Driving a low current solenoid with a low voltage H-Bridge

texts:
I'm trying to drive a solenoid to create a magnetic field. I've got a constant current controller circuit that supplies the current I need, but I'd like to control this using an H-Bridge so the the polarity can be changed and/or the coil can be turned off quickly. (<1ms)

I'd been planning to do this with an IC H-bridge, but am running into problems. Typical currents for my application are ~10-300mA which can require voltages of 5mV or less. The current controller is capable of supplying this and regulating itself, however the H-briges I've seen can't operate at such low voltages.

For instance, the SN754410's datasheet says:

  The SN754410 is a quadruple high-current half-H
  driver designed to provide bidirectional drive
  currents up to 1 A at voltages from 4.5 V to 36 V.
  The device is designed to drive inductive loads
  such as relays, solenoids, dc and bipolar stepping
  motors, as well as other high-current/high-voltage
  loads in positive-supply applications.

The SN754410 has seperate supply pins for the logic circuits and for the outputs but the lowest recommended voltage I can find for the supply of an H-bridge is around 4.5V.

How can I quickly turn on/off a solenoid that only requires mVs and mAs?


texts: Will hooking up a HF coil to a HF opamp nullify the induction in the coil?

texts:
I want to measure an oscillating magnetic field using a coil. Using a small self-spun coil, I can already measure very decent 100 KHz signals by hooking each end of the coil up to an oscilloscope.

I want to eventually pump the frequency up to 10 MHz. Using my extremely basic coil+oscilloscope setup I can already measure this for fairly strong oscillating magnetic fields but the fields that I'll be measuring will be much smaller. I can therefore not just hook my coil up directly to the oscilloscope anymore, but will need to amplify the signal.

My problem is as follows: if I want to push my signal through some filters, then those filters will invariably have some capacitance and resistance. Hooking up my coil to non-neglectable capacitances turns the whole thing into an electric oscillator, whose resonance frequency lies (for decent coils) far below 10 Mhz!

The solution I came up with was first passing the signal through an opamp, to "restart" the circuit:

simulate this circuit – Schematic created using CircuitLab

I do have some opamps that can handle 10 MHz signals. The datasheet for the OPA6999 shows that it works just fine for these frequencies (page 7).

But won't I run into the same problem using this circuit? Won't the opamp introduce capacitance and inductance on the left side of the circuit that could significantly decrease my resonance frequency, unless I use a tiny coil?


texts: How much current can Solderless Breadboards handle?

texts:
I'm working on a project with a few stepper motors. I want to breadboard them so I know the circuit works well before creating a physical PCB.

Each of the three motors is rated 2A, but I'll be prototyping with 1A (controled with driver chip) at 12V. How dangerous is this much current on a solderless breadboard? It's a cheap one I picked up on eBay, so I doubt that it's made with super high quality materials. I won't be leaving it plugged in for extended periods of time and it'll always be supervised with me there if it receives power. Is this a bad idea?

Note: each of the motors will be on its own rail with its own wire coming from the power source.


texts:
How can I create an "IF AMPLIFIER TRANSFORMERS" in PSpice?
Which one should I choose? "Forward" or "Two Winding"?

And if there is no problem, just according to this site (https://www.electronics-tutorials.com/filters/if-amplifier-transformers.htm#:~:text=IF%20amplifier%20transformers%20are%20simply,coupled%20by%20an%20active%20device.), tell me how much should I put the values of the inductor, resistance, and transformer ratio?
Circuit:

I need a "RED IF" in this circuit!
Input:
Carrier: 1.6 Vp-p | 200-400 kHz
Message: 0.3 Vp-p | 1 kHz


texts: I need a basic primer on interpreting vacuum tube datasheets

texts:
I am building a prop for a film that needs to have a bunch of glowing vacuum tubes on it. Unfortunately, beyond basic "valve theory", I'm not finding a lot of information about how to interpret the datasheets.

Very simply, what I need to figure out is how to safely make a bunch of tubes glow. I don't have the tubes I've not designed the circuit because I'm mystified by the datasheets. Whether I make a circuit and fit tubes to IT, or whether I buy tubes and design a circuit around THEM is irrelevant at this time. Until I can interpret the datasheets, either option is impossible.

Consider: this ECC81 tube datasheet. Heating voltage is 6.3V, current is 300mA and under the "Typical Operating Characteristics", the anode voltage is 100V at 3mA. Looking at the pin configuration and notes (on this particular datasheet at least), I can't make heads or tails of how to read it. It looks to me, for instance, like pins 4 & 5 get the heater current (f), but then what the heck is pin 9 (fc) ? Further, it looks like pin 6 is the anode input (a), but what's pin 1, designated by a'?

With my limited knowledge, I'd send 6.3V to pins 4 & 5 and watch the healthy glow. MMy gut-level reaction though, is that's only half a circuit. So what's the other half? I would think I'd need to somehow draw off of the cathode and dissipate that power somehow...but when all I want is the glow, where does the back half of the circuit lead to? Am I making any sense here? Part of this is that I'm not quite sure I'm asking the right questions. Help!


texts: Icom IC-7100 amateur radio circuit - is this a designed short?

texts:
My Icom radio has suffered what appears to be an over voltage fault. It's brand new and it appears as if the DCDC charger/regulator in my car has generously donated extra electrons to the radio and auxiliary circuit. Shame.
Looking at the HV (Vin) path, there's a strange circuit design around the MCU reset circuit. There's an LDO circuit which I cant quite make sense of. It appears to be powered a current limited 5V supply, which holds the CE (enable pin) high when it's on?
But what is happening with the HV input into the CE pin on IC6402, Isn't there a designed direct short between the HV input and ground?


texts: Testing an h-bridge using the power supply and/or signal generator to control a DC motor

texts:
I'm using the DRV8836 (datasheet here) from Texas Instruments and can't seem to get it to work. Does it require a PWM (pulse from the signal generator) or am I able to drive it with only the DC power supply? I'm a bit confused with how this chip works in terms of what type of input the PHASE pin expects. I know that the ENABLE pin can just be pulled high by a DC power supply. I am using the PHASE/ENABLE mode, but what is the difference between this mode and the IN/IN mode?

What I want to do is to control a DC motor with this H-bridge and a microcontroller, but for now I just want to test if I have the chip soldered onto its adapter board properly, which I have on a breadboard.

Here is my set-up:


texts: How to short two points(2 wires) without using relay

texts:
I have made a circuit with ESP8266 which triggers a relay. Actually, I want to bypass a button which is on a 3rd electronic device, which is a closed box with a very complex circuit.

I have soldered out the connections of the switch from that device. By using relay I can short that, but a relay is bit bulky,

Is there any other way to achieve this? (The other device is a DC operated device)


texts: Best way to amplify the photoresistor signal

texts:
I have the following schematic.

simulate this circuit – Schematic created using CircuitLab

And it graphs to an almost stratight line. It is supposed to be a heartbeat sensor. From what I have read, I come to know that amplification is a must. But my knowledge of electronics is very limted and I need guidance.

I am emitting a red. My photoresistor responds to IR signal very poorly and I had to use the red one.

Am working with Arduino Uno board.


texts: I have acquired a korg 49 key midi keyboard which has 7 keys that do not work.as set of 5 together then 2 more 2 keys away. what could cause this issue? I have cleaned and tested the contacts and they are fine. could it be one or more diodes in the matrix stopping the keys sending a signal or more likely to be a processing error or chip failure?


texts: Name of slightly-less-than-2mm pin connector?

texts:
I have a couple of these: https://www.alibaba.com/product-detail/Automatic-meter-reading-Lora-low-power_60213414513.html

The pins are such that a 2mm female connector will nearly fit - i.e. the pins are slightly closer than 2mm.

What is this connector called and what is it's dimensions?  Is it non-metric?


texts:
In layman terms, why doppler spectral power density has U shape?

Does this mean that frequency components with maximum doppler shift have maximum power?

I am confused with the interpretation of the doppler spectral power density U-shaped graph, for example the one at https://blog.taitradio.com/2015/09/23/9-channel-concepts-every-system-designer-needs-to-understand/.

Additionally, I found this source: https://www.sharetechnote.com/html/Handbook_LTE_Fading.html. Does this mean that the U-shaped graph actually depicts probability density of frequency shifts and has nothing to do with the power/amplitude?


texts: Programming microcontrollers in ASM or C & how it's done

texts:
Just to clarify on these topics:

If I were to program a microcontroller in ASM I would use an assembler, of course. The assembler would compile the code into opcodes (machine code?)(generally 1:1 ratio) which would then be converted into HEX file. It is this file that is actually read into memory and used to program the controller? I read that the HEX file contains the actual location the data (part of that data frame) is to be stored in memory as well as the data to be written there.

If I were program a microcontroller in C (or some other language) what are the restrictions? It would be necessary that you use a C compiler, of course. But, is it that we must use a C compiler that is specifically designed to work with microcontrollers or a specific architecture?

I know that different architectures have varying instruction sets that are incompatible with others, but how is this dealt with and how does all this relate to a CPU that exists in a computer?

I have surely confused topics here and possibly embarrased muself, but I have been reading on these topics for a while today and wanted to clarify everything at one to mitigate further confusion.

Thank you,


texts: Really loud, yet compact, long(-ish) duration, battery operated -- hooter / siren

texts:
Is it possible to design  a small / compact, hand-held siren (i.e. with a loud hooter), that is battery powered and fits into something like a 3"x3"x2" box ?

The requirements in more detail:

Hooter that is small, yet loud enough (not sure in decibel level terms, but something similar to what one finds in Residential Intruder Alarm systems).
Can operate off battery power (e.g. 2-3x 1.5VDC AAA cells) s.t.
a. Hooter can sound a pattern for about 10minutes
b. While circuit, which includes a NO/NC latching push-button switch, requiring "push" detection, can operate for few weeks (if not months).

The conflicting design constraints in my mind are:

Small / cramped space that this whole thing needs to fit into
Hooter loudness and duration required (knowing that these things draw a lot of current, and typically operate on 12VDC)
Everything running off small (size and number of) battery pack.

The requirement of few AAA's instead of say LiPO is to keep the cost as low as possible, and keep things simple (i.e. to the extent I can deal with electronics).

Happy to elaborate and clarify, and very happy to have alternative suggestions. Note that the use case is, someone presses a big-round button (not sure what it is called, but the type you find in lifts, and in industrial controls that start/stop conveyor belts etc.), on a small hand-held box (no wires, self-powered), when they are in distress, and it makes a hell-raising racket to draw attention.


texts: Finding the Time Constant (Tau) of a 2+ Capacitor RC circuit

texts:
How would you go about finding V across the leftmost capacitor after reaching a steady state and having the voltage source is set to 0V? Is it possible find the time constant for the leftmost capacitor [and then apply Vc0 * e^(-t/RC)]?

And how will the discharge times scale with two loops (as shown here) or a third loop compared to having just one?

There's no need for a complete solution, but I'm genuinely curious and would love your thoughts on a good way to approach the problem.

What we know so far (Thanks JensenR30):

The Voltages across both capacitors is 4 V
After deactivating the source, Vc of the right loop alone would be 4e^(-t/0.0001) V

Would it is possible from there to find the Thevenin equivalent for the leftmost capacitor?


texts: Two 6v batteries in series charged by two separate solar panels

texts: I have two solar panels -  first 30 watt 2 amps second 40 watts 2.3 amps, and two 6v deep cycle batteries in series on my RV. My question is: can I simply use two separate charge controllers (max 7 amps each) and run the neg and pos connections from each to the same pos and neg terminals on the batteries?  Or do I have splice the wires and use only one charge controller?


texts: Interpretation of block diagram for proportional feedback system with respect to time

texts:
Suppose we have a proportional feedback and that the system is modelled by a block diagram i.e

where C is a constant. Do we think about this as a signal "moving" in time around this loop or is the time the same everywhere inside these blocks and for all signals?

How does one keep track of which t, say for y(t_j), corresponds to u(t_i)?


texts: Significant DC current on precision DMM despite not being connected to anything

texts:
Disclaimer: I'm not a EE professional (I have a background in physics though), so please bear with me if the question seems banal, obvious or just plain stupid.

We have a Keysight 34465A DMM, which, according to the data-sheet, has DC-I measurement accuracy of 50 pA (typ) at it's lowest range of 1 uA when the input is close to zero.
When the device is set to this setting (auto-zero enabled, 10 PLC) and nothing connected, the display fluctuates within a few pA around zero. As soon as a probe cable is connected to the common port (labelled "Input LO"), the display shows a measurement value of between +2.5 and +3.0 nA DC. If it is connected to the current sense port (labelled "Input 3A"), it shows values of around -50 to -150 nA DC! The probe is a simple passive test lead (Keysight 34138A). If two such leads are connected to these two ports, the displayed value remains in a similar range, unless they are shorted, where the measured current is again within a few pA around zero.

To me, i's absolutely puzzling to see any DC current beyond the specified accuracy of the device when "it is not connected to anything". The best I could come up with is an AC current due to EMI that somehow reduces the device's accuracy via the induced noise. However, the values seem very high to me.

So here are my questions: What is the origin of these currents? Is this to be expected or is it a hint to a problem with the device or the workplace? In view of those issues, how do I measure currents with nA accuracy coming from a high-impedance source?


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I am building a framework for a data acquisition system where the controller sends a (integer/float) data in to the GUI. I have done some ground work on data types and compilers and found out that each integer/float takes 2/4 bytes each.

My doubt is that how to club this integer/float byte in to one and show them as the real  integer/float value in GUI.

This is a part of GUI programming I trust, but all data communication were sending data in byte and later clubbing those and displaying as float/int.

eg case:

step1: controller sends float data to the GUI.
step2: Controller and compiler splits the data in to 4 bytes.
step3: Gui recieves 4 Bytes.
step4: Gui converts Receieved 4 bytes in to float and displays it on the GUI.

I need more clarity on step 4.

So if we need a float/integer in the GUI, how should we club the data coming from the communication ports (USB/uart)?

This would be helpful to build my understanding and clear my doubts, if you suggest your opinions.


texts:
From Razavi's Design of Analog CMOS Integrated Circuits, question 2.6a asks to plot \$I_x\$ vs. \$V_x\$ as \$V_x\$ varies from 0 to 3 V in the circuit below. The solution manual states that:

$$V_{sg} = (V_{dd} - V_x)\frac{R_1}{R_1 + R_2}$$

However, this doesn't seem right. I think instead:

$$V_{sg} = V_{dd} - (V_{dd} - V_x)\frac{R_2}{R_1 + R_2}$$

What should \$V_{sg}\$ be in this case?