texts: RS232 output always follow with an extra 0x0b

texts:
I have downloaded the minsoc from opencores and it comes with a microprocessor along with a rs232 cores. I have configure all the toolchains and download the design on my FPGA.

I run a simple program that adds 1 to whatever the rs232 receives and send it back to computer. So I can see the letters I type being sent back to the computer. But there is always a trailing byte 0x0b whenever I send something.

e.g. If I send A, I will get A0x0b.
If I send AAAA, I will get AAAA0x0b.

Then I write a C program to run on the processor as below.

  while (1){  //endless looping
    //send 16 bytes from computer
    for(i = 0; i < 16; i++) {
        //save the received byte to an array of 16 bytes
        B[i] = uart_getc();

        //pass array value to the AES core
        //this is an IO module using memory map.
        REG8(AES_BASE + AES_DR) = B[i];
    }

    //send the received 16 bytes back to computer
    for(i = 0; i < 16; i++) {
        uart_putc(B[i]);
    }

After programming the FPGA, if I send the first 16 bytes, I will get all the bytes back. But when I send the second 16 bytes, it will insert some extra characters 0x0a 0x0b.
e.g. If I send 3333333333333333, I will receive 0xa0xb3333333333333333

When I send the third 16 bytes (also 3333333333333333), I will receive 30xa0xb333333333333333. And this pattern keeps going as I send the next 16 bytes, 330xa0xb333333333333333...and so on. The 0x0a0x0b keep shifting to the latter bytes.

What are the possible reasons for this?


texts: Av for small signal analysis with BJT for unbypassed emitter and ro in place

texts:
My question is about another question on this site. On that question Z(in) for small signal analysis with BJT for unbypassed emitter and r0 in place Zin is asked for a common emitter configuration with emitter and ro is in place. My question is about voltage gain Av of the same circuit. In Boylestad and Nashelsky Av is given as below without a proof:

However, I find:

$$A_v=\frac{-R_C(\beta r_o-R_E)}{Z_b(R_E+R_C+r_o)}$$

Can you tell me what am I missing or show me how to find the correct answer?

EDIT:

Here is the circuit:

I used the following equivalent circuit for solution:

Then I defined \$V_o\$ as:

$$V_o=-I_c R_c$$

Then from KVL I obtained:

$$\beta I_b r_o-(I_b+I_c)R_E-R_C I_c-r_o I_c=0$$

$$I_c=\frac{(\beta r_o - R_E)}{R_E+R_C+r_o}I_b$$

Replacing \$I_c\$ from \$V_o\$:

$$V_o=-R_C \frac{(\beta r_o - R_E)}{R_E+R_C+r_o}I_b$$

and finally replacing \$I_b=V_i/Z_b\$:

$$A_v=\frac{-R_C(\beta r_o-R_E)}{Z_b(R_E+R_C+r_o)}$$


texts: Charge CR927 battery with small solar cell?

texts:
I am developing a Bluetooth tracking device that uses a single CR2032 battery. Would it be worth using instead a rechargeable CR927 (40mA) battery and a small solar cell, the size they put in watches?

Using this battery might save some space and the main advantage will be that the device will need battery changing less often.

How should I design the circuit? Should I use a charge regulator?

All components are rated at 1.8 to 3.6V. The circuit uses up to 20mA in full active state, and around 40uA in sleep state.


texts: Order of precedence for parallel operator

texts:
In electrical engineering the parallel operator || gives half the harmonic mean of two values. E.g.:

\$R_1 \parallel R_2 \equiv \frac{1}{1/R_1+1/R_2} \$

But how should you compute

\$kR_1 \parallel R_2 + R_3  = \ ? \$

Is there a commonly accepted order of precedence for the parallel operator?

References would be appreciated.


texts: How to release wire from a Eaton Moeller M22-CK10 NO contact block?

texts:
I am attempting to rewire a fan to a M22-CK10 contact block.

The device is shown below:

My first thought was to push in the metal contacts above the red wire on the left.

When that didn't work I tried pushing the contact holding the let red wire.  I experimented with the empty socket on the left but there was no sign of the clamp opening.  There is a green contact button on the rear that doesn't seem to do anything either when I press it.

There doesn't seem to be anything else, I don't want to destroy the contact block and it feels if I force it further I will.

Does anyone know if there is a simple way to release the wire from the contact block?


texts:
Is there any way to test a microcontroller for short-circuit without an oscilloscope maybe using a multimeter? Mine is not overheating, but I cannot register any activity showing it is working.

I tried a continuity test and it came out positive {a short b/w Vs and GND} on both the 'test microcontroller' and another microcontroller that is functional; so, I am at a loss on how to proceed.

Thanks for your help.


texts: PCB connector to bring out pins on an IC

texts: I have a PCB which has a footprint for an IC. This IC is a TQFP package and has about 144 pins. However, not all the pins are brought out on the PCB. I am ready to desolder the IC from the PCB and put it on another PCB which breaks out the required pins. However I am still having some questions as to how to reattach the PCB back to the original one? IS there any other way to get access to pins on the IC without making another PCB? The original PCB has a lot of other connections, so I have to attach it back


texts: What might this term (N sub C) be, calculating ripple current for a buck converter output capacitor?

texts:
I'm reading through the datasheet for TI's TPS54302 step-down converter, and determining values for support components.

There is a calculation to determine ripple current for the output capacitor which is:

$$
I_{COUT(RMS)} = \frac{1}{\sqrt12} \times \left(
\frac{V_{OUT}\times(V_{IN(MAX)}-V_{OUT})}
{V_{IN(MAX)} \times L_{OUT} \times f_{SW} \times N_C} \right)
$$
(Where \$L_{OUT}\$ is the inductor value (H), \$f_{SW}\$ is the switching frequency (Hz).)

I'm not sure what the term \$N_C\$ is meant to be.

Looking around online, other formulas omit this. For example, in this document by Rohm titled Capacitor Calculation for Buck Converter IC, page 4 has the formula:

$$
I_{CO} = \frac{1}{\sqrt12} \times \left(
\frac{V_{OUT}(V_{IN(MAX)}-V_{OUT})}
{L \times f_{SW} \times V_{IN(MAX)}} \right)
$$

Either I am ignorant of what \$N_C\$ is in this context (the datasheet doesn't clarify); the term is optional depending on application; or TI has a mistake in the datasheet.

What is \$N_C\$ in this case?


texts:
I am implementing an ADPLL in an FPGA with VHDL, and I am encountering a problem in correctly implementing the loop filter. The code that I currently have for the loop filter is the following :

library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use work.Support_Functions.all;

Entity filter is
  generic(
    Guard_bits : integer := 7; --Extra Length for guard bits
    Precision : Integer := 12 --Precision of Multiplier Coefficients
    );
  port (
    Sample_CLK : in std_logic;
    Data_in : in std_logic_vector(11 downto 0);
    Filtered : out std_logic_vector((Guard_bits + Precision + 4) downto 0)
    );
End Entity filter;

Architecture RTL of filter is
  Type Slv_Array is Array (0 to  1) of std_logic_vector(Data_in'Length - 1 downto 0);
  Signal Data : Slv_Array;
  Constant Coeff : real := (0.9375);  -- 15/16
  --Multiplication Results Signals
  Signal Mult_result : signed(Precision + Data_in'Length - 1 downto 0);
  --General Adder Signals
  Signal Accumulator : signed((Guard_bits + Precision + Data_in'Length - 1) downto 0) := (others => '0'); --Must be wide enough
Begin
  process(Sample_CLK) is
    Variable summation : signed((Guard_bits + Precision + 4) downto 0) := (others => '0');
    Variable Mult_result : signed(Precision + Data_in'Length - 1 downto 0);
    Variable Data : Slv_Array;
  begin
    if rising_edge(Sample_CLK) then
      Data(1) := Data(0);
      Data(0) := Data_in;

      Mult_result := signed(Data(1)) * Real_to_signed(Coeff,Precision);
      summation := signed(Data(0)) + Mult_Result;
      Filtered <= std_logic_vector(summation);
    end if;
    summation := (others => '0');
  end process;
End Architecture RTL;

With this filter, the PLL is locking in at +-50kHz if the centre frequency which is that of 125kHz at the moment.Is there another way to implement the loop filter, or what am I doing wrong as I am completaly lost ?

Also I am implementing this block diagram in the FPGA so as to make things a bit clearer:

The phase detector (1st block is a simple multiplier)
The loop filter is as described,
The NCO is a COS ROM, 12 bits wide and 14 bits long.


texts:
I'm trying to build a Raspberry Pi cluster (at least 32 Pi's) and I need a convenient way to power them all. So I'd like to design a power distribution board. The distribution board will have USB power ports for each Pi and it will be controlled by an Atmel microcontroller.

I currently have a 350W 5V supply, which can safely supply a hefty 60A. Assuming that each Pi will draw between 800mA and 1A, I should have more than enough power.

With that said, as a new engineer (who specializes in digital electronics), I've only designed one PCB before. I've never done anything with high power before. What design considerations should I take into account when designing the PCB?

I've done a little bit of research and everything seems to point to using a PCB bus bar to carry the high current. I would then branch off the bus to each individual Pi. The other option is to use a high power connector like this one. I'm kind of leaning towards the latter.

With that said I should also probably provide some level protection circuitry for the Pi's in case of a power surge (although my supply, a Cotek AK-350-05, should be able to provide a fair amount of protection itself). I was thinking of placing a 1.5A PTC in series with each USB port.

Are there any other things I should consider? Thanks


texts:
My experiments (using an arduino compatible board)

Without resistor between IN and D5

3V <-> VCC, the relay stays OFF
5V <-> VCC, the relay stays ON

With 10K ohms resistor between IN and D5

5V <-> VCC, everything worked!

My problem

But after working for many hours (about half a day), the relay seemed to stopped receiving enough power to correctly switch the relay. I know the D5 pin received the on/off signal from the D5 pin as the status light on the relay board actually dimmed a bit (and I followed the D5 status from my arduino IDE console)

I've unplugged and re-plugged everything and now it's working again..

Can it be related to the resistor value?

simulate this circuit – Schematic created using CircuitLab

This is the relay module I'm using :
https://www.amazon.ca/gp/product/B06XVV8W9B/ref=oh_aui_detailpage_o02_s00


texts:
I am trying to control an Analog Devices programming resistor AD5254 by a USB to I2C master device from MicroChip MCP2221. The problem I am facing is that each time MCP2221 is waiting for ACK from AD5254, the SCL clock de-assert which i think affect the AD5254 to not be configured properly.
This is what happens :
1. Using MicroChip I2C/SMbus Terminal I am sending the following  :

2. observing SDA/SCL using a scope + I2C protocol analyzer I can see the address+data are ok but after each Ack SCL line drops :

3. I know that the address+data is correct because I am using Analog Devices Evaluation board for reference, and when connecting their SDP-B controller board (UG-277) to the Evaluation (UG-236) the SDA/SCL signals are correct :

Anyone know why SCL drops after each ACK ?


texts:
A bunch of old equipment I use at work (built between 1990 and around 2003) use what my coworkers call "Three Phase Potentiometers". They are rotary potentiometers with 5 connectors. Measuring their resistance didn't give me much sensible information, other than that it is not multiple regular potentiometers in one housing.
They are used to control the position of rotating equipment with a rotating lever, located up to 100m away. The equipment will rotate to the same position as the lever using hydraulics. When both potentiometers are aligned (and the equipment is no longer moving), the voltage between + and - on P2 is 0V.
The potentiometers are wired as followed:

simulate this circuit – Schematic created using CircuitLab

Unfortunately, none of the engineers that designed this equipment work with us anymore. We do still have some techs that know how to solve common issues, but we have no real understanding of the logic behind the design.
I have the following questions:

Can anyone guide me to more information on how this type of potentiometer works?

What are these potentiometers officially called?

What are reasons to use a set up like this? Our newer designs use regular 3 pin potentiometers, and 4-20mA Hall effect transducers today.


texts: Is an omnidirectional antenna a must for a cell phone?

texts:
I have read somewhere (but unfortunately I am not able to remember where) that cell phones do need an omnidirectional antenna.

If it is so, what are the reasons for that? Why a normal directional loop antenna could not be (efficiently) used ?


texts: Help identifying resistor with arrow accross and capacitor with unit "kp" or "k" or value "5/6"

texts:
Can you please help me identity these symbols from a vintage (1960) diagram?
The capacitors units are noted with "KP", sometimes just "K".
What is the rectangle crossed with an arrow? It looks like a potentiometer without the tap connected.

1.what does kp means? pico farad?

2. what is this symbol? 5/6?

3. 47K farad?

4. 22k resistor or diode or bias pot?

The full circuit:


texts:
This is a fairly simple question. Is it possible to use additional circuitry, connected to an Arduino PWM pin, to shift it's phase? As far as I can tell, the Arduino PWM pins can be configured for frequency and duty cycle, but I do not believe that phase can be controlled...at least, not out of the box.

I had an Arduino kit, however I'm taking it back today (too expensive, with a ton of parts that I don't need). If I need to use something other than an Arduino to support phase shifted PWM, then I'm open to that.


texts: Does USB Power Delivery handle USB cables that are not PD-aware?

texts:
I think USB-PD is still fairly new (I don't know anyone who owns a device that has it) but reading wikipedia and info sites does not make it clear what happens when you use a cable that is out of spec in a USB-PD charging setup.

So if I have a host and device that are USB-PD compliant, and my device wants to use say a 12V profile, can I get away with using a normal USB cable? Or will it not charge or charge at a lower profile instead?

What about the edge case where I use the 5V profile at 2A. Technically that is out of spec also since USB BC1.2 is spec'd to 7.5W (1.5A), but many normal cables work fine with 2A in practice.


texts: Displaying character OSL641501-ARA dot matrix LED

texts:
I am learning to control this dot matrix LED (OSL641501-ARA datasheet).
I have seen some tutorials on how to control it with 2 shift registers.
The problem is I am totally confused with the concept of displaying a character on it.

It seems to me that as long as I turn off a dot by

setting both corresponding col pin and row pin to 0V,
or, setting corresponding col pin and row pin to 3V

The unexpected result is, a whole line of dots are effected.

Please tell me what the trick is for it? How can I avoid "accidentally" turning on or off other dots?


texts: Finding complementary PMOS for H-Bridge and connecting Gate-Driver

texts:
I am currently implementing a Half-Bridge using an IRF520PBF (Link to Datasheet) for the lower part of the bridge and I am currently looking for a PMOSFET for the upper part of the bridge (I am aware that I could use the same NMOSFET for the upper part of the bridge as well if I use a high enough Gate-Voltage to switch the upper MOSFET on.)

I basically have the following questions, since this is my first H-Bridge:

(1) Do manufacturers usually provide a "complementary" PMOS for every NMOS they sell and would that PMOS have the same characteristics (e.g. on-state resistance, gate capacitance etc.)?

(2) Is it common in practice to use both NMOS and PMOS or do people prefer to only use one type (maybe for cost reasons or similar)?

(3) Is there anything specific I need to pay attention to in order not to accidentally short-circuit the supply voltage? My concern is that I might switch one MOSFET on faster than I switch the other one off effectively short-circuiting the supply voltage. I thought about using an "asymmetrical" gate  resistor with Diode in order to avoid that (see also the Schematic below). However, this configuration has the problem of potentially interrupting the inductor current leading to large voltage spikes. I am using the following Gate-Driver: ([Link to Gate-Driver](https://octopart.com/lm5112sd-texas+instruments-24848588"Link to Gate-Driver")).

simulate this circuit – Schematic created using CircuitLab


texts: Here I have connected one coil terminal with arduino, which is giving 5V pulses and the movable contact to GND pin of arduino. I saw from literature that it is possible to get 1000-1200 v from a 12v DC relay. I don't understand from where we can measure the voltage and I need to know whether my method of making the relay chattering is correct or not. I need a detailed design for making chattering relay. I need to couple the EMI noise due to the chattering to a data cable. How can I do this?


texts:
I know that bluetooth 4.0 is using layer level AES 128bit for security .

There is something ,which basically is not clear to me.
We are sending data to some BLE 4.0 station , where the station is advertising data, and a mobile phone is picking the signal, than connect to it, and send it data .

What interesting is, that all BLE are advertising public data, that anyone can listen to.
Moreover, even if we use PIN code, the moment i send the PIN code, after connection, anyone can also listen to it, and resend it ,thats because all the communication in the 4.0 is transparent to everyone .

What is the basic method , to secure connection with BLE (using Texas cc5240 chips)  ?

A private/public key ? (seems overkill)
Any other encryption will anyway be transparent to anyone who just listen to my transmutations.


texts: per-charge cost to charge a battery bank at $0.10/kwhr

texts:
Am I forgetting my EE knowledge?

I have a 10400mAh battery bank at 3.8v so it's ~40kwhr?

$4 to charge once? assuming perfect charger efficiency and no power loss to heat


texts:
Apparently, there are some counterfeit USB/Serial FTDI chips on the market.

Searching the web one finds people comparing fake/original ones via opening them mechanically/chemically.

But how to detect fake ones less intrusively?

I mean, the infamous FTDI driver update surely contains a detection routine - otherwise it couldn't flash a zero vendor id on the counterfeit ones.

Perhaps the detection 'algorithm' or similar less intrusive methods are published?


texts: I have an optocoupler and I connect it to 230V, the datasheet tell me the optocoupler has a forward voltage: IF = ± 5 mA VF - 1.5 V, so, for limiting the current I need an resistor of 4.7K - 11wats, but I don't have this type of resistor so I use a Capacitor and a Resistor in series, but my problem is that I don't know how to calculate the value of the capacitor resistance (Xc=?), and if i know the capacitor value, what value resistor should have?


texts: How would I go about replacing a CCFL laptop LCD scrren backlight with LEDs?

texts:
Are there certain kinds of LED(s) that should be used? Is there a certain way the LED(s) should be put? If yes to any of these questions, why? Also, where is a good place from the laptop to get power from for the LEDs? Can I get power maybe from before the CCFL inverter, which is close to the LCD screen anyway?

Update: Here are some links to a page by someone who actually did this: here and a writeup here. And another here and writeup here.

Update: What would be a good way to control the brightness? (to control it using the Fn- keys would be neat if it is easy).


texts: what is the color code of cables in earphones?

texts:
What I see after stripping the cable is this:

copper-red and yellow on right channel

green and stripped red-gren on left

Whose are for ground and whose for signal ?

(edit: I'm asking this for ep-630 but the question I intend is more generic, first to all creative headphones, second, to all headphones, that is if is there a standard for color-coding in such products)


texts: Are there any unexpected effects when printing an inductor on a PCB?

texts:
Suppose I print an eight-layer PCB, with a spiral starting on the top layer and continuing through all the inner layers to the bottom. Assuming I keep the spiral turning in the same direction on all layers, this PCB should act as an inductor. (I could leave a hole in the middle of the spiral for a core, or if not, I could simply leave it air-core. I'm assuming air-core for the moment, for simplicity.) Many calculators are available to determine the inductance of an air-core choke, and to determine the ampacity of copper traces at given weights and widths on both inner and outer layers. The naive design of such an inductor is straightforward.

What I'm wondering about is non-obvious effects. Will the inductance actually turn out like an wire-wound air-core choke with equivalent dimensions and numbers of windings? Will there be additional heating effects due to magnetic coupling between the layers, or between the PCB and any nearby metal? Will the magnetic effects cause physical stresses on the structure of the board? Are there any other reasons this might turn out to be less of a good idea than it seems at first?


texts: Hamiltonian-inspired energy function for power grid stability

texts:
I'm looking at this paper which proposes an energy function for a 3-bus power system example. I'm trying to replicate the results in the paper but am uncertain about the D parameters in Sec III. In particular, the authors verify that with a certain A matrix adjusting the gradient dynamics, the model has a stable equilibrium, but I'm confused about the D parameters in this matrix.

Here is the relevant section:

EDIT1: it looks like the D terms are some sort of rotor damping.

EDIT2 (follow up question): I'm having trouble tying out the dimensions of the A3bus matrix to the Abus matrix. Specifically, the dimensions of Mg seem off. It appears that the g means both slack and generator node, but then I don't see how to fit A3bus into the Abus structure. Any advice?

EDIT3: this paper helps somewhat but is still a bit unclear on the interpretation of the Pi matrices.

Thanks!


texts: How could I go about building a 2-bit comparator that compares two 2-bit numbers and determines whether one is greater than or equal to the other?

texts:
Using an 8:1 multiplexer, I understand there are three inputs, so I'm not sure how I'd go about getting two 2-bit numbers, which would be four variables, not three.  Any pointers on how to get started on this are appreciated.

A   B   C   D   X   Y   Z   X   Y   Z
0   0   0   0   0   0   0   0   0   D
0   0   0   1   0   0   1
0   0   1   0   0   1   0   0   1   D
0   0   1   1   0   1   1
0   1   0   0   0   0   1   0   D   D’
0   1   0   1   0   1   0
0   1   1   0   0   1   1   D   D’  D’
0   1   1   1   1   0   0
1   0   0   0   0   1   0   0   1   D
1   0   0   1   0   1   1
1   0   1   0   1   0   0   1   0   D
1   0   1   1   1   0   1
1   1   0   0   0   1   1   D   D’  D’


texts:
I have a couple of issues with the simulation;

The zener diode has Vz at 4.7V, it is not behaving as expected since it is reducing the supply voltage by 4.7 instead of setting it to that voltage.
The SCR is not triggering and short circuiting the PSU.
Is there a way to add a spice model to a thermal fuse in capture.
Any recommendations on the values of the resistors and capacitor used?

Updated circuit: the current triggering the SCR is negative for some reason, in order to be triggered it should be 2mA.


texts: How to split a Sine wave to two positive and negative parts by real circuit?

texts:
I would like to split a sinusoidal wave to two different positive and negative parts  so that sum of these two parts result the main sinusoidal wave.
i think one way is that using two different branch by diodes to split the positive and negative parts. is there any different real circuit configuration for this purpose?


texts:
Hi, I would like to ask about the behavior of a MOSFET as a capacitor, particularly at the onset of inversion/weak inversion - see Fig 2.6(c)

At this stage in Fig 2.6(c), there is positive charge at the gate
metal/poly contact, then an insulator oxide and then negative ions
(positive holes have been repelled) - this is the Cox capacitor in
the schematic overlaying.
My confusion is regarding the Cdep - depletion region capacitor. What are the two 'plates' or regions of charge accumulation that form the Cdep capacacitor? I assume one is the negative ions (sharing a plate with Cox) and the other is the repelled positive holes. But then, if you see my drawn schematic, that doesn't make sense, since the + charges are on top and negative ions should be on top?

Can someone explain to me how Razavi is extrapolating from the device physics that there is a Cdep capacitance? What are the two regions of charge that form Cdep? Is one 'plate' shared with Cox?


texts: Waveform signal on wirewound resistor VS metal film resistor causes different result? Strange result!

texts:
Hi to all the experts out there, please clearly understand all 5 situations mentioned below.
Take note that wirewound and metal film resistors were used.
At 'situation 4', I thought it was the PCB problem. But when I used metal film together with the PCB in 'situation 5', it worked!
If wirewound resistor is not suitable for analog / switching signal, then why am I not having problem during 'situation 2'?
So, does anyone have any idea or experience on this problem?
Is it PCB can never be used together with wirewound solder lug resistor? If yes, why?
EDIT: Current for situations that are 'OK!' is ~0.9A. Whereas for 'situation 4' which is 'NOT OK!', the current was ~0.4A. Leakage in the PCB? I don't think so. But if yes, why 'situation 5' has no leakage?

Correction: Not 'PCB board', should be 'PCB'. Thanks to JRE.


texts:
I have a design with a very thin and curvy board shape, so any-angle routing is absolutely required.

My favorite EDA software is Altium, so right now I have only two options, both bad, for how to route any-angle:

Every time I want to change routes, export the design to another program that does allow any-angle routing, make the changes, and then import back to Altium
Painstakingly change the x1,y1 x2,y2 values of every individual track segment using the "Properties" popup window

Clearly Altium can represent any-angle tracks just fine (since option 2 does work), there just isn't any way to use the standard mouse controls to do it!

Is there any way to configure Altium or use a plugin so that the mouse controls can freely change the x1,y1 x2,y2 of tracks without snapping to 45 degree angles?


texts: Designing a BJT Amplifier given some constraints

texts:
I am trying to design a BJT amplifier following this model:

Where the beta parameter may vary from 100 to 800, the voltage between the base and the emitter equals 0.6V (active mode), \$V_t = 25 mV\$ and the Early Effect may be ignored.

It can also be supposed that the bypass capacitors simply act as a short circuit for AC and open circuit for DC.

There are three constraints:

Static Power Dissipation < 25mW;
Output Signal Swing of 6Vpp
Maximum error of 5% at the collector current for any variation at
beta

I've been able to show that the voltage between the collector and the emitter will be 3.2V (using the signal swing information), but I don't know what to do next.

Edit:

Calculation that led to \$V_{CE} = 3.2V\$:

The output signal swing yields that the upper limit will be +3V and the lower limit will be -3V. The amplifier will either cutoff or saturate. Also, the circuit is a linear system which means that the Superposition Theorem may be used. At any node, the voltage will be the sum of the polarization (DC) voltage and the signal (AC) voltage. So, using the signal swing and supposing symmetrical output (\$V_C\$ and \$V_E\$ are the polarization voltages at the colletor and emitter):

\$V_{cmax} = V_C + 3V = V_C + v_{omax} = V_C + I_C * R_C//R_L\\
V_{cmin} = V_C - 3V\$

The first equation says that \$ I_C * R_C//R_L = 3V\$ (cutoff condition, no current entering the transistor; \$i_{R_C} = i_{R_L}\$) and operating with the second equation (supposing that the minimum collector voltage is \$V_E + 0.2V\$ which leads to saturation):

\$V_{cmin} = V_C - 3V = V_E + 0.2V \rightarrow V_C - V_E = 3V + 0.2V \rightarrow V_{CE} = 3.2V\$


texts: Problem when debugging ethernet KSZ8081RNB chip on IMX6UL board

texts:
I've been working on debugging KSZ8081RNB Ethernet chip for three weeks now and still, I can't find where the problem is.

First of all, the board I am working on is including an IMX6UL processor and some chips to drive some amplifiers, bluetooth interface...
The current design is inspired from the Evaluation board (EVK) from NXP. I have a configuration around my KSZ8081RNB which is the same on my board and on the EVK. Plus the wiring is equal between the IMX6UL and the KSZ on the two boards.

I have made and upload a U-BOOT working on the evk. It include the configuration to interface with the ethernet chip.
When I use a ping command, everything works great... I can see on my server using wireshark that I have ARP and ICMP exchange. Every packets are coming in and out to the IMX6UL (I have made some traces to be sure)

Now, back to troubles :)

On my version of the board, I have upload the same code and there are the symptoms:
-some of the packets (ARP and ICMP) are entering without problem: when I launch the network loop and ping from the outside world, I can see the packets entering correcly (I cheked it in the IMX6UL) BUT when come the time to give the response, ARP and ICMP packet get blocked by something.. Sometimes the packets gets outside and are read by the server sometimes they wont.

What I have done:
I check power on the KSZ, the type of RJ45 connector, the configuration MDIO of the KSZ, the 50MHz clock and it's jitter. Nothing seems to explain the irregularity of the ping process...

Got some ideas? Comments? Need some more informations?


texts: Voltage across different resistors in a series circuit containing just voltage source, resistor and ground measures the same

texts:
Assuming that the internal resistance of the battery is zero, assuming that the internal resistance of the wire is zero and last but not the least, assuming that the measuring device is ideal and does not draw any current.
In a scenario where there is only one resistor between source and the ground. Depending on the value of the resistor the current’s value is decided.
The voltage across the resistor is same as that of the source voltage.  If the resistor’s value is changed the voltage across it still equal to the source voltage.
But, the resistors control the number of electrons that get blocked and these blocked (accumulated) electrons creates forces what we refer to as a voltage with respect to ground.
If a larger resistor blocks more electrons and a smaller resistor blocks less, then in a simple series circuit with only one resistor between the source and the ground, the voltages across different resistors should be different.
The question is why is it the same ?
My understanding is, the source sends electrons to make the voltage equal to its own level. This is current. These electrons come and settle down on resistor’s top terminal. Before the next batch of electrons arrive, the present electrons would have passed to the ground.  The measuring device is about to show that there are no electrons hence no voltage but before that happens, a new batch of electrons come and the measuring device always shows constant voltage equal to source voltage across the resistor, no matter what the value of resistor is.
So, Can I say that the measuring device is not fast enough to sense that little bit of drop that was present between the two batches of current that the source sent in order to achieve equilibrium.
Is my understanding correct or have I completely misunderstood it ?


texts: Using DTC and for repeated Single Channel Reading on MSP430

texts:
I'm trying to use the DTC to continuously update a variable without CPU intervention. However I am not getting any results and cannot figure out why. Any help would be appreciated.

Here is the method to initialize the DTC:

void initializeDTC(unsigned int channel,unsigned int *pointer){
    // Disable ADC before configuration.
    ADC10CTL0 &= ~ENC;

    // Turn ADC on in single line before configuration.
    ADC10CTL0 = ADC10ON;

    // Set channel, Use SMCLK, 1/8 Divider, Repeat single channel.
    ADC10CTL1 = channel | ADC10SSEL_3 | ADC10DIV_7 | CONSEQ_2;
    // 0 clock ticks, Use Reference, Reference on, ADC On, Multi-Sample Conversion, Interrupts enabled.
    ADC10CTL0 |= ADC10SHT_1 | SREF_1 | REFON | MSC;

    // Put results at specified place in memory.
    ADC10SA = (int)pointer;
    // Only one conversion at a time.
    ADC10DTC1 = 0x01;
    // Repeat conversion.
    ADC10DTC0 = ADC10CT;

    // Start conversion.
    ADC10CTL0 |= ENC | ADC10SC;
    // I've read that trying to start the conversion twice is necessary.
    ADC10CTL0 |= ENC | ADC10SC;
}

I call it like this:

unsigned int temperature;
initializeDTC(INCH_10,&temperature);
// Do stuff with temperature in a loop.

If I've understood the documentation correctly, after each conversion the ADC should start the next conversion because of the MSC bit. At the same time the DTC should transfer the value of ADC10MEM to the value in address in ADC10SA (the value of my pointer). The value of my temperature variable remains at the default value of whatever was in the memory previously (35 thousand and something for me).

I considered the possibility of the DTC having not finished before the next conversion, but the documentation states that the DTC will take at most 4 MCLK cycles. In my application I SMCLK=MCLK and since the conversion takes 8 SMCLK cycles I should be fine in this respect.


texts: Can an incorrect VGA timing kill a modern LCD screen?

texts:
I'm going to play with an Artix-7 dev board with a VGA port (Nexys 4 DDR from Digilent) and I'm a beginner at this.

Assuming the pinout is correct, is it possible to destroy a (very) cheap modern LCD screen if I'm sending garbage/incorrect data to the VGA port?


texts: What is the point of the terminator enable pin of an RS485?

texts:
I am working on programming the logic to test an RS485 controller (reference manual here). On page 8 of the reference manual, pin A2 is described as "Terminator Enable" (TE), which enables a resistors between pins A and pins B.

What is the point of having the option to have a resistor between pins A and pins B?


texts:
I have a question about a probably easy task, but I can't find the right K.

I have the loop with an adjustable gain element given:

$$Q(z) = \frac{H(z)}{1+ K\cdot G(z)H(z)} $$

I have given:

$$H(z) = \frac{z}{z+0.5}$$ and $$G(z) = \frac{1}{z(z-0.5)}$$

$$H(z) \cdot G(z) = \frac{1}{(z+0.5)(z-0.5)}$$ which give the poles 0.5 and -0.5.

I'm not sure how to go from here. Do I have to count the zeros at +/- infinity and how can I get the argument?

The solution is that the system is stable for -0.75 < K < 1.25.


texts:
simulate this circuit – Schematic created using CircuitLab

I calculated the transfer function
 $$\frac{I_L}{In}=\frac{R_1R_2}{s^2L^2+sL(R_1+R_2)}$$

starting from the node analysis at the nodes V1 and V2, so:
$$\frac{V_1}{R_1}+\frac{V_1}{Ls}-\frac{V_2}{Ls}=In $$
$$-\frac{V_1}{Ls}+\frac{V_2}{Ls}+\frac{V_2}{R_2}=0$$

Because I obtain a second order system, this seems quite wrong.

Have I consider the admittances in the node analysis? So:
$$\frac{V_1}{G_1}+V_1Ls-V_2Ls=In$$
$$-V_1Ls+V_2Ls\frac{V_2}{G_2}=0$$
In this case I obtain a more likely:
$$\frac{I_L}{In}=\frac{1}{sL(R_1+R_2)+R_1R_2}$$

But I'am not sure about the node analysis.

What do you think is the correct solution?

Note: In both cases I consider $$I_L=\frac{V_2}{Ls}$$


texts: Radio module resetting when fluorescent tube switched on/off

texts:
I have a PCB powered by an IRM-30-12 power supply (230VAC to 12VDC). On this PCB, I have a MRF24J40MD from Microchip and a Udooneo to drive it + a 5VDC regulator and the 3.3VDC of the Udooneo.

After installing over 300 units in different places, I noticed that some old fluorescent tubes are resetting the MRF24J40MD when someone switches the fluorescent tubes on or off. Replacing the old fluorescent tube with a new one make the trick and I have no more issue with the MRF24J40MD. But this takes lot of time.

My goal would be to design a protection circuit against this that I can plug or solder on the PCB on the 230VAC parts or 12VDC, 5VDC or 3.3VDC parts to protect my MRF24J40MD against resetting. Sadly, I have no idea how to manage this.

I could reproduce the bug at home with a Philips TMX 200 LS fluorescent tube and a Philips S10 starter. After some retries, the MRF24J40MD resets itself and doesn't communicate anymore if the PCB and the fluorescent tube are on the same plug.

EDIT: new measures with the oscilloscope following recommendations in the comments.

The 3.3VDC of the MRF24J40MD comes from the Udooneo. There's a separate power supply for the GSM parts.

With an oscilloscope, I could mesure the perturbations at the 3.3VDC/GND of MRF24J40MD. I made the same measures on the output of main power supply (12VDC) and the perturbations are exactly the same. Here's the result on 3.3VDC/GND with new measurement setup (see below for probe setup):

The probe :

Some schematics (MRF24J40MD and 3.3VDC output of Udooneo):

Hope this isn't a too noob question and someone could suggest some ideas to help me solve this. For the little story, the PCB was designed by a group of junior engineers in a school. I'm a software engineer. That's why I'm struggling with this kind of problem and I can't reach the original designers anymore...


texts: Newbie question: Light weight, temporary power?

texts:
My goal: I'd like to somehow make a nerf dart light up for easy retrieval at night (and to look cool, lets be honest). Putting a cell battery, a switch and an LED in them is a lot of weight and a lot of batteries to buy and switch out. Is it possible to use something like a capacitor to store a very short term charge, and power an LED for something like 1 minute? I'm not looking for long term power... give the dart a charge, and the LED runs for about a minute. Just long enough to go hunt them down.

And yes I know there are lots of other options - glow in the dark darts, UV lights, etc. Looking specifically to make them glow with an LED if possible.


texts: Is there a way to program the ARM microcontroller without solder it to a dev board? I mean, if I want to develop a product based in the ARM architecture I suppose that I have to use one microcontroller for prototyping right? but in the moment I assemble my product, how can I program the rest of ARM microcontrollers? should I give the code to the PCBA manufacturer in order to  program all the ARMs that will be built in every piece?, sorry for my English tho.


texts:
I came across this uncommented Matlab code except for the header:

*************************************
function y=movingvar(X,N)
% y=movingvar(X,N)
% Calculates N-point moving variance of Vector X
% Highly recommend that N be odd (no error checking)
% Note: first and last N/2 points will be unreliable.
% Output will be a column vector.
% Authors: Scott Seidman (scott.seidman@rochester.edu) 1/23/99

X=X(:);
XSQR=X.*X;
convsig=ones(1,N);
y=(conv(convsig,XSQR)-(conv(convsig,X).^2)/N)/(N-1);

y=y(ceil(N/2):length(X)+floor(N/2));
****************************************************

(from http://www.mathworks.com/matlabcentral/newsreader/view_thread/39521)

According to the comments here, it can also be used as a realtime RMS calculator: https://electronics.stackexchange.com/a/135276/53375

I can see that being useful, but I don't understand Matlab.  Could someone please explain what's going on?

I'm academically familiar with convolution, and I do know C.


texts:
I am developing a prototype that connects sensors to a processing unit (an arduino). The sensors reside inside a boot, which is a demanding location: curved, quite tight, and subject to a decent amount of wear and tear. I have incorporated the sensors into a flex pcb that I believe will work in the location, but am having trouble figuring out how to best connect it to the processing unit.

In an idea world, the flex pcb would be a "T" shape, with the T extending outside the boot and connecting to the arduino. But a T-shaped flex pcb will be much more expensive, so at this stage I'd rather use a small PCB and run wires off it.

What is a good way to attach some signaling wires to the flex pcb? I could solder them on directly, but worry about solder taking too much of the mechanical strain. Is there some other simple option that will be secure and not add much thickness to the flex PCB?


texts:
I am using a opto triac rated at 100C operational. It controls an externa SCR in a very common fashion. The opto Is physically located next to a heat source component making the opto temperature rise reach just a little past its operational temperature when tested in a chamber.

In looking around for a higher rated part I noticed that all OPTO TRIACs are rated either for 85C or 100C but nothing above that. The junction temperature is rated at 125C.

Is there a limitation in opto triac design that a higher rated temperature device is not available? Or do I just have to search harder


texts: BGA VCC and VSS shorted after desoldering

texts:
I am really confused with working with BGA chips.

I am new to this but have been following other guides so I thought I should give it a try. I am using a DIY pre heater that has a 800watt IR bottom heater and for the top heater I am using a hot air station with 40x40mm nozzle that's about the size of the BGA chip I am trying to rework.

I am desoldering an Intel JG82855GME chipset chip. I left the board on the preheater and set it to 100°C for 9-10 hours to remove any moisture. Afterwards I removed the BGA  by setting my preheater at 220°C and hot air station at 350-380°C.

It's interesting to note that even though the bottom preheater is set to 220°C, the PCB only reaches about 120-130°C.

Why is that so?

The PCB is about 10x10cm in size while the heater is 12x12cm so the whole PCB is covered completely by the heater.

After I removed the BGA chip I probed its VCC and VSS pins and found a short on those pins. Is the chip dead, or is there still some hope left for it? Is the hot air station a bad choice for this task?


texts: How to Hook-up an LED-Lit Rocker Switch with 115V AC Power W/o Blowing the LED?

texts:
This is the LED-Lit switch I have:

The switch itself is rated for 10A125VAC/6A250VAC but there is also a "12V" label on the switch suggesting that the LED should be given 12V.

Now, if I were to connect my switch with AC source to power my power supply in the following configuration:

, then my led will burn/blow.

How can I hook up my switch to on/off my power supply and have the led lit when powered on?


texts: Continuous relay flipping on power strip only

texts:
I have a Belkin WeMo Insight Switch. For those unfamiliar, it is essentially a Wi-Fi enabled 120V relay with current monitoring circuitry for power consumption monitoring.

So, it works great on all outlets in my house, connected to my APC UPS, etc. But as soon as I try to connect it to this power strip (I have 3 of them and it happens on all of them) connected to my UPS, it starts continuously flipping on and off. I can hear the relay clicking on and off. I called their support and they say my outlet "isn't compatible" which doesn't help me at all. What could be causing this power strip to do this to the WeMo? Everything else connected to that power strip is fine! Note that the WeMo only flips on and off continuously on this power strip. No other outlet causes this.


texts: What does an "E" mean in a resistor value? (ie 150E)

texts:
I'm trying to build a dc motor controller circuit as described here.

But it requires 2 "150E" resistors

From looking online I believe this means 15 ohms but I'm curious as to why, and why I couldn't find anywhere explaining such.


texts:
Using Kicad, how do I go about specifying a trace thickness for power rails larger than the default in such a way that this info can be used by freerouter?

A section or page reference into one of the manuals would be fine, I really just need to know where to start reading.


texts: Suggestions for accelerometer signal conditioning

texts:
I want to use an adxl326 accelerometer to measure vibration in one plane only. The accel is fed 3.3V and returns 1.65V at 0G's +/- 57mV/G

What I want to do is remove the 1.65 bias to get an ac signal then amplify that signal so it is close to -1.65 / +1.65 so that I can add tge bias back and have a dc signal again which is close to the full adc range of 0-3.3V

I considered using an AD8221 Inst amp with no gain resistance on pins 2 & 3 ie unity gain, followed by a PGA112 PGA with SPI control and 1.65V on the ref pin. However, I was wondering if anyone had any suggestions which would not need a -5 & +5 supply?

Please also remember I am an analog newbie!

Thanks, Steve.


texts: How 0.1 capacitor diverts electrical noise on the 5v PWS line to 0V?

texts: I'm not sure how one can prevent electrical noise coming from the power supply from affecting the 0V line. Could one please explain why we have to use a capacitor for that purpose?


texts: 74185 IC (binary to BCD converter) don't work in Proteus

texts:
I try to design circuit that convert 10 bit binary to BCD with 74185 IC in Proteus, but when i run this project output of this IC like this attached picture is unknown(IC don't work! and i didn't receive any error!) and I did active enable. why? and how can give suitable output?

In this attached image i try to convert 5 bit binary to BCD and i test enable input with a LOGICPROBE and change it, but still IC don't work.

EDIT
like this link i use from resistor network and all output were 1.
Weird ULN2003 to 7-segment behaviour in Proteus


texts: How do I calculate the self discharge rate of a lead acid battery?

texts: Okay, like the title suggests, I need a method of calculating self discharge rates of Lead-Acid batteries. Here's the catch: I varied the electrolyte which the batteries were using, replacing sulphuric acid with hydrochloric acid, another one with nitric, and another one with phosphorous acid. Anybody have any idea how I can get around this?


texts: Will adding 1/2 watt resistors reduce the current load of a stepper motor?

texts:
I have a stepper motor rated at 1.8 ohms or resistance per phase, a driver rated at 750mA and a powersupply that gives 12V rated at 1A. This would mean that the motor will draw 6.6A per phase.

If I wanted to limit the stepper so that it cannot draw more power at 12V than the driver can tolerate then can I add 14.2 ohms of 1/2 watt resistors (if there is such a thing) to acheive this?

Is my math correct?
1.8 Ohms + 14.2 Ohms = 16 Ohms
12 Volts / 16 Ohms = 0.75 Amps?

I know that the stepper will not be at full power but it doesn't have to be.

EDIT: Sorry wrong resistance per phase. It supposed to be 3.6 Ohms per phase; would I require 12.4 Ohms of additional resistance per phase?


texts:
It looks to me that the Signal-to-Noise ratio (SNR or S/N) is completely arbitrary and it's set by the user according to his preferences.

Sorry I am amateur on the subject but I don't see any limitation on this value, it can be set according to what the person transmitting wants to do.

The bit / second rate can be adjusted for speed,quality or quantity, I think those are the only variables.

The Shannon–Hartley formula can be tweaked according to a user's needs:

$$ C = B * log_2(1 + S/N) $$

So for example if I have 1 hour to transmit a 64 bit message, I can choose the optimal S/N ratio.

1 hour is 3600 seconds, so I need a bit/sec rate of minimum 0.017778 bit/sec.

And do achieve that I either tweak S/N ratio or the bandwidth.

So on 1 Hz a S/N of 0.0125 would give me 0.017921 b/s which would be enough to broadcast the 64 bit message in 1 hour.
Or I could choose 1 KHz and a S/N rate of 0.0000125 which would give 0.01803 b/s.
Or 1 Mhz with a S/N rate of 0.0000125 which would give 18.03 b/s that would deliver the message in 3.55 seconds.

So are there any other physical limitations here or is this completely arbitrary and it up to the user to choose.

I have heard that if the S/N rate is below 1, you need a special encoding with checksums to make sure the bits you receiver are genuine. So I guess you would need to send more than 64 bits of information in that case. So that could be an additional burden.

Is there anything else to keep in mind?


texts: USB powering batteries without OS support?

texts:
On a bare-metal project I have in mind, I would like to know if I can avoid to implement the multiple USB specs (O/E/xHCI) and still benefit from usb charging my battery. It will run on a almost broken/useless flashed smartphone with one mini usb port.
I literally don't want any usb port for media storage or hid or anything for that project. There will only be one app running.
I was thinking that the already existing hardware usb controller(s) would allow me that, but.. on the other hand, if it is not activated by software, it may be an issue.
Question:
Can I power up my batteries via a usb cable, without software usb implementation? Is there a shortcut avoiding the full usb implementation?
Thanks
Update, to make things clear:
My goal was to use one of my cables, without modification made on it, plug it into my phone, and let it charge. With that information, would you consider that it is still a "yes" to that question?


texts: What is the simplest way to play a sound or wav file?

texts:
I'm pretty new/noob with electronics. I'm trying to reproduce a sound (I'm using Proteus as simulator) in a circuit.

I wasted hours of looking for but I can only found solutions with Arduino or synthetic sounds, I need to reproduce a "wav" sound or any other format, recorded previously.

Which is the simplest method/example to make this?

Thanks in advance


texts: Is this a float charger or trickle charger?

texts:
Below is a simple charging circuit using LM317 and BC547 and it is mostly classified as a float charger in many forums. This seems to reduce the current flow when the battery is fully charged, however does not turn off the charger completely. Hence can this be connected to SLA batteries indefinitely without affecting the battery life? or is this a trickle charger, which should be disconnected after charging.

By definition float charger will only turn on and charge your battery when it has self-discharged below a certain level, whereas a trickle charger continuously emits a small current of electricity regardless of the charge level or even if it's full. It is also mentioned that for SLA batteries, a float charger could be connected indefinitely where as the trickle chargers needs to be disconnected after charging.

simulate this circuit – Schematic created using CircuitLab

Updated components as per recommendation

simulate this circuit


texts:
I'm pretty green with electronics and I've encountered a situation I need some help on. Any help would be greatly appreciated.

I've created a circuit wherein I am inserting a logic-level MOSFET (FQP30N06L (data sheet)) in place of a mechanical switch. Assume I cannot change anything about the other components other than inserting a different type of switch (ie, I can't rewire what is being switched, etc).

In testing the wiring with a 5V circuit with an LED on it across drain and source everything works fine. Connecting the gate to low turns it off, connecting to 3.3V turns it on. Fine.

However, when trying it with my actual load the MOSFET is always on and no combination of pull down resistors and other techniques seem to ever turn it off. What am I doing wrong here? Connecting the GATE to ground does not turn it off. I'm posting a picture of the breadboard that reproduces the problem. Wiring is as follows:

The wire I am interrupting carries 26V @ 30mA.

Gate to +3.3v (to turn on) or GND (to turn off)
Drain to +26V
Source connects to the positive side of the motor.

For clarity (I hope) I've attached a sketch of the circuit I've tried previously and a picture of the breadboard wired up in the most simple way, without all the pull down resistors and jazz.

Some details:
1. The circuit I am replacing is a switch on the positive side of a motor. Assume I cannot change anything about the way the motor is wired.
2. I am currently able to accomplish this no problem with a relay -- I just am doing this to see if I can accomplish the same thing with a (cheaper) MOSFET -- switching 26V DC just doesn't seem like it should require a mechanical relay. Maybe I am wrong and it overwhelms the MOSFET?


texts: High Voltage PWM Motor Controller - Mosfets Explode

texts:
I've searched every post for an answer to this problem.  I've built a motor controller circuit as shown in this diagram.
I made the diagram as accurate as possible.  The diodes on the mosfets were added so that the mosfet symbol would look just like the symbol in the data sheet.
As you can see, it is a very simple PWM circuit using an Arduino UNO board.  A potentiometer foot pedal is attached to one of the analog inputs and that is used to determine the duty cycle of the pwm output on digital output pin 6.

The motor is the smallest 48v motor of this type that motenergy makes, but this is a very big motor compared to other circuits I've seen like this.  It can easily pull about 200 Amps on start up.

The circuit sort of works - when the vehicle is lifted so the wheels don't touch the ground.  In that state, it is very easy for the motor to spin and it doesn't draw as much current.  When the wheels are on the ground, the mosfets explode the moment you start to push on the pedal.  I've built this circuit about 4 times now.  I even used 18 mosfets in parallel in one version, and all 18 exploded instantly. (200/18 = about 7 Amps/mosfet) Each mosfet should handle 32 Amps.

We finally just bought a motor controller from alltrax, and the vehicle works fine, but I am determined to find out why my own motor controller did not work.  I love electronics, and have built many difficult circuits over the years.  I will not be able to sleep well till I find out what I'm doing wrong.

I talked to a technician from Alltrax, and he said their controllers are nothing but a bunch of mosfets and capacitors.  He said the capacitors kept the mosfets from exploding, but he had no idea how they are wired into the circuit.  I think he has a piece of my missing information.

So, can anyone tell me what I'm doing wrong?  How should I add capacitors to fix this?  Could it be the frequency?  We modified the timer on the Arduino so our PWM frequency was around 8000 Hertz, but the Alltrax controller works at a mind-blowing 18,000 Hertz.  I know 18k is small as motor controllers go, but I thought a giant motor would like a smaller frequency.

Also, before you say the mosfets can't be wired in parallel because of slight differences between them, I used exactly 7 inches of 18 gauge wire to connect each one in parallel.  The small wire would act as a tiny resistor and ensure that each one shared the current load.

Thanks a bunch for your replies.


texts:
I'm asked to find IB, IC and VCE.

This is my answer:

I wonder if my answer is true are not. VCE Value is negative, is this true or not?


texts: Difference of amplitude and frequency modulation of lasers

texts:
I found some interesting applications for modulation for lasers. They always talk about some sort of frequency modulation (ex. FMCW)

AFAIK the frequency of a laser is pretty much stable (for all affordable lasers). So the only way to modulatate the laser would be changing the current wich results in a amplitude modulation of the emitted light. Right?

Knowing from RF one would normally use FM to always stay on 100% of power emission. So to clear up the confusion, how can you run a laser diode in AM and FM mode?


texts: Boundary condition for dielectric to dielectric

texts: Now the tangential component of the electric field at the boundary is continuous, but the normal component of the electric field is said to be discontinuous. What is the meaning of discontinuous in this case? Does it mean that at a particular point on the boundary , the normal component of the electric field is not defined?


texts: Specific ADC input not working on Microchip PIC PIC24FJ128GA202, other inputs work fine

texts:
I am trying to get an analog input working on my microcontroller. I am using the PIC 24FJ128GA204. The problem is that a specific input is not working, while other do work.

I want pin 26,  AN9/C3INA/RP15/T3CK/T2CK/CTED6/CN11/RB15, to be the input. Other analog inputs seem to be working fine, but when I configure the input pin to be AN9 the results seem to be floating, even if I ground the input. The samples I get: 3987, 3987, 3988, 3989, 3989, 3987, etc. Below is the code I am using:

void initAD(){
//Pin used for ADC is pin 26 = RB15 = AN9

TRISBbits.TRISB15 = 1; //RB15 is input
ANSBbits.ANSB15 = 1; //analog mode

AD1CON1bits.MODE12 = 1; //set 12 bit mode operation
AD1CON1bits.SSRC = 0b0111; //auto-convert
AD1CON1bits.ASAM = 1; //SAMP bit is auto-set

AD1CON2 = 0; //AD1CON2 all 0
AD1CON2bits.PVCFG = 0b00; //00 = Vss, 01 = External VREF+
AD1CON2bits.NVCFG0 = 0; //AVSS

AD1CON3bits.SAMC = 0b11111; //Auto sample time = 31 TAD
AD1CON3bits.ADCS = 0b00000101; //AD conversion clock 5*Tcy = TAD

AD1CHSbits.CH0NA = 0; //negative is VREF-/AVSS
AD1CHSbits.CH0SA = 0b01001; //channel A AN9

AD1CHSbits.CH0NB = 0; //negative is VREF-/AVSS
AD1CHSbits.CH0SB = 0b01001; //channel B AN9

AD1CSSL = 0;            //No scanned inputs
AD1CON1bits.ADON = 1;   //enable AD module
}

and:

uint16_t ADread(){
while(!AD1CON1bits.DONE);

return(ADC1BUF0);
}

Thanks for reading. If you have any suggestions, that would be great.


texts: H-bridge MOSFET NAND gate driver suffered from logic voltage drop

texts:
I've tried to reproduce the NAND Schmitt triggers circuit to drive my H-bridge MOSFET as per following source:

http://axotron.se/index_en.php?page=34&chapter=0

All my design files are at this GitHub link:

https://github.com/mkeyno/H-bridge2/tree/master/update

It has Enable, PWM and direction pins that are supposed to controlled by Arduino, however my PCB doesn't work yet. I used 74HC132D & CD40106B Schmitt trigger IC and used an LED to indicate each direction, but it never turns on.

Any help is really appreciated.

Updated:
I updated new schematic base on new advises , but still has its issue (logic voltage drop)


texts: Will paralleling forward diodes decrease voltage drop?

texts:
I am using a BAT54A barrier diode, am using this diode because i need this component on another part of the circuit and i dont feel like using another dedicated component.
So the BAT54A is a dual Schottky and i need to use 1 as a barrier diode.

I feel that it would be kind of a waste not to use the other diode, and tried to come up with a good reason to do so. Two i can come up with is an increased max forward current and a lower voltage drop. increased max forward current is not much of a gain because 1 diode is enough for my application, 2 would not be much of a gain.
A lower voltage drop though is a much more compeling. I think paralleling diodes would decrease the forward voltage on the basis of when two diode paralleled in a configuration like above they will share current and a lower current accross the diode would result in lower voltage drop. Am i correct? Are there any demerits in what im about to do ? i guess thermal runaway would be a problem, but i wont even pass a current aobve the max rating of 1 diode


texts:
I have a set of Lumineo 1512 Multi-Colored Clustered lights.  At any given point on the line there may be between 2 and 5 wires.

My Goal
I want a level of my tree to have multiple Junctions, one for each Branch, and just go OUT from the base, and terminate at the end of the branch.  Thus, not having to loop back inward.  Then a final junction going up to the next level to again multi-junction for that level.
My main question is for advice on:

How to split one electrical path into multiple paths to begin with.
How to mitigate splicing/splitting a variable number of wires for each junction with as little waste as possible.

I hope this isn't the case, but I'm not sure if a more experienced person would tell me a splicing method that may require adding resistors or (hopefully not) modifying the control box.  I'll solder if I have to, but it isn't my day job.
My experience: I was an Electronics Tech in the Navy, and have been an IT for a long time, part of which has included some component level repair and soldering.  I'm no pro at anything, let alone these odd 5-wire lights.  Any pointing to documentation or methods is appreciated.


texts:
I was fixing my dishwasher control board, and diagnosed a bad relay. Its coil is still within specifications, but the relay will not close its contacts. It is an easy fix ok, but my question concerns another subject.
What really caught my attention was the physical aspect of the relay package. As you can see in the image just below, it has black mark that erased part of its silkscreen and its center circle is punctured.

While all the other ones on the board are like this:

As you may have noticed, this is the only relay which was produced on a different week (29th instead of 32nd) on the board. My question is the following: does the black mark and the puncture on the bad relay points to an act made during manufacturing or is it its normal failure mode?

Edit: Per Dwayne request, I have opened the relay cover:

Apparently, the bottom contact is not able to reach the higher one, which could indicate erosion as Dwayne suggested. There is a briefly video showing the movement of parts during switch on mode:

https://youtu.be/8EBsf52iyrk


texts: Multimeter reads false overflow on the milliamp scale

texts:
simulate this circuit – Schematic created using CircuitLab

I declare I'm kinda noob in electronics, but I know the most basics and I wanted to take some measurements so I could get used to them in practice.

The setup:
4xAA alkaline batteries in series with little use and measured at about 6V (so definitely not dead).
Battery positive to multimeter to 1Kohm resistance to LED to battery negative.
Multimeter (DT9205A+) black cable connected to COM and the red to mA and the switch pointing to DC current (tested all values).

When the circuit closes, the LED lights up and the multimeter shows 1 on the left (that is overflow indication). That happens with every scale of the DC current measuring setting.
When the red cable goes to the greater current input (up to 20A), it displays 0, but that means it's just too small a value to display anything. I've tested with other setups and the large scale input seems to be working properly.

Since the mA input says it's fused and I'm a noob, I would expect to have somehow burn the fuse. But the circuit closes (the LED lights up) and I've also opened the multimeter and seen the fuse to be ok.

Any suggestion as to what could be wrong (either with my multimeter, or my setup) would be much appreciated!


texts: In ADS, why am I getting such a strange output when sweeping a variable and graphing it?

texts:
I am trying to get the gain of this circuit vs. capacitance. Here is a screenshot of my circuit and results.

Why is the result behaving like this? It should just be one line. Why are there so many lines?


texts: Why is voltage inverse to current in a shunt generator?

texts:
Here is something I read:

  Current in the field windings of a shunt-wound generator is
  independent of the load current (currents in parallel branches are
  independent of each other). Since field current, and therefore field
  strength, is not affected by load current, the output voltage remains
  more nearly constant than does the output voltage of the series-wound
  generator. In actual use, the output voltage in a dc shunt-wound
  generator varies inversely as load current varies. The output voltage
  decreases as load current increases because the voltage drop across
  the armature resistance increases (E = IR).

It seems that the "field current not being affected by load current (hence constant output voltage)" seems to contradict the next line ("In actual use...").

Why is armature resistance increasing with increase in load?


texts: How to open two circuits using one input?

texts: I'm not too familiar with circuits so was wondering if someone could help out with this. I have two separate loops with a source and load each as seen in the diagram. I want to use one set of temp switches (that open when temp is too high) in order to open both circuits and stop the loads. I was looking into possibly using a double pole relay, but wouldn't there need to be power flowing through that switch loop in order to detect when it is broken? Or if there's an easier way of doing this, I'd love to hear! Thanks,


texts: PIC: how to set timer0 to give an interrupt at every 1 sec?

texts:
I am programming a PIC18F67K22 and I've set it to use a 16X4Mhz Internal RC oscillator with PLL enabled.

High level interrupt on TIMER0 overflow
I am using MCC18 compiler.

So how to set TIMER0 to give an interrupt at every second?


texts: Analyse boost converter using the three rules

texts:
I am trying to analyse the boost converter operating in DCM mode below.

By using three rules as here:

Inductor volt-second balance
Capacitor charge balance
Small ripple approximation

This what I got:

First, divide the circuit into three subintervals:

Next, I tried to find inductor voltage and capacitor current in each interval:

Finally, by using two principles above I got:

Inductor volt-second balance:

Capacitor charge balance:

So, as you see output voltage V here is expressed in two functions.

The first one: V = f(Vin,D1,D2,RL,T).

The second one: V = f(Vin,D1,D2,RL,T,R).

For now let's assume that D1 is fixed.

Two function should be the same and so there so be a relation between D2 and load resistance R.

I tried to find that relation but the expression is very complex.

So, I am wondering if my result is OK now.

Could you confirm if my approach is right?

Also, if there is a better way to do that please suggest.

Thank you.


texts:
Kind of a newbie at this, so forgive me if this is a stupid question. I've disassembled a small lifeline alert pendant transmitter that normally runs on a CR1632, can I replace it with two AA's? Are there any disadvantages? Do CR batteries last longer, have more capacity than AA's, etc.?

On a separate note, if I want to replace the batteries with a power supply, can I use a 5v USB supply or would I have to look for a 3v supply?


texts:
I’m doing a PIC MCU based 16 row X 32 column LED matrix design & the display multiplexing is done in the ISR. At 1mS rate I’m getting into the ISR & update each row on every interrupt. For a frame it will take 1mS X 16 = 16mS.

In the main code I do moving patterns (Ex: letters moving). I have a frame time of 16mS. If I want to do an animation like let say I want to move a character from display right to left I need a shift delay (in my words its called animation delay).

I generate this delay by counting frames.For example I use 48mS delay that is 3 times the frame time.

Left Shift();   ; make shift bits on display register (or in inactive buffer)
Delay(48mS);    ; call a delay (shift delay)
Left Shift();
Delay(48mS);
Left Shift();
Delay(48mS);
Left Shift();
Delay(48mS);
Left Shift();
Delay(48mS);

The above will shift a picture 5 steps left.See the attached picture, I'm moving letter "A" to left called an animation.

The problem is while moving I see multiple LEDs moving slightly.How to overcome the above situation?


texts: Calculation of the input impedance of reactance modulator

texts: The figure 1.36 is a circuit of reactance modulator which is equivalent to a tunable inductance. I know the input impedance expression is Zin = (Z1 + Z2)/(1 + gm*Z2), but how to derive this expression?


texts: How to produce time delays in PIC18 ASM programming?

texts:
I'm a newbie with microcontrollers programming. I have a high level programming understanding but I'm getting involved in low lever CPU/Microcontrollers development.

I want to do this simple exercise of getting an array of LED's on and off for 1 second each.

I tried this assembly (thinking about two leds):

    List    P=18F4550
    include <P18F4550.inc>

    CONFIG FOSC = INTOSC_EC ;INTOSC_EC          ; Internal oscillator
    CONFIG PWRT= ON             ; Power-up Timer Enable bit
    CONFIG BOR=OFF              ; Brown-out Reset disabled in hardware and software
    CONFIG WDT=OFF              ; WDT disabled
    CONFIG MCLRE=ON             ; MCLR pin enabled
    CONFIG PBADEN=OFF           ; PORTB<4:0> pins are configured as digital I/O
    CONFIG LVP=OFF              ; Single-Supply ICSP disabled
    CONFIG DEBUG = OFF                  ; Background debugger disabled
    CONFIG XINST = OFF          ; Extended Instruction disabled
;******************************Variables***********************************
    count equ 0x00

;**********************************************************************************

    org     0x0000
    movlw   0x62
    movwf   OSCCON     ;Working at 4 MhZ
    clrf    TRISD      ;D port as output
    ;leds OFF so far

LGHTLOOP
    bcf PORTD,0
    call DELAY

    bsf PORTD,0
    CALL DELAY

    bcf PORTD,1
    call DELAY

    bsf PORTD,1
    CALL DELAY

bra  LIGHTLOOP

DELAY
    movlw   .1000
    movwf   count

    LOOP2
         DECFSZ   count,F

    bra  LOOP2

    nop

    return

    end

I tried simulate it at Proteus software, having this configuration:

I can actually see leds getting ON and OFF but nothing like a second, no matter how I change movlw   .255 at DELAY subroutine. I tried with different higher values and got same wierd behaviour.

What did I get wrong?

Counting the instructions cycles at subroutines with movlw   .255 should be more than 1 second I think. But still simulation shows it faster. Adding two more leds makes it seem even faster.


texts:
I have a DC-DC switching regulator that operates at switching frequency of 260Khz that steps down a 28vdc to 3.3Vdc.
On the same PCB I have a microcontroller and would like to have it's ground plane to be as clean as it can be from any switching regulator noise .

Will a ground moat around the microcontroller helps in this case? I will have a 15mil trace that connects the switching regulator ground to the microcontroller ground.
Your feedback is appreciated.


texts: Full Bridge Inverter with transformer, source current waveform

texts:
I intend to make a 750W DC/AC inverter working with a 24V DC supply. I have simulated the circuit in MatLab using PLCECS toolbox.

Here i use a 50kHz carrier to generate a 50Hz modulated unipolar PWM signal to drive the full bridge. PLECS circuit include a full bridge, a high frequency step up transformer and a LC filter as in the following figure.

Problem is when i monitor the current drawn from the source it is higher than the expected maximum value of 60A and there is a a current in the negative direction as in the bottom plot of the following diagram.
What are the reasons for this and how will it affect if i make this circuit?


texts: Identify transfer funtion given step response

texts:
This is the system with its step response below.

I'm asked to find the transfer function. Note that this is a question from an exam sheet and a computer can't be used.

I can say that it has to do with an underdamped system but will my transfer function have a zero as well? More specifically, will b1 in the following be zero? $$T(s)=\frac{b_1s+b_0}{s^2+2ζω_ns+ω_n^2}=\frac{b_1s+b_0}{(s+a)^2+ω^2}$$

I can also tell that b0 is equal to ωn^2 since the steady state error is zero and that ω=2.

To sum up, I'm having trouble with b1 and a if my speculations are correct.


texts: Saturating BJT on different value than 10

texts:
Is it possible to saturate BJT 2n2222 at beta value different from 10 to 37.5?
this is why 10 to 37.5:

when Ic=1.0mA   ->    beta = 1m/0.1m       = 10
when Ic=10mA    ->    beta = 10m/1m        = 10
when Ic=150mA   ->    beta(min) = 150m/15m = 10
                      beta(max) = 150m/4m  = 37.5
when Ic=500mA   ->    beta = 500m/~50      = ~10


texts: This design does not fit into the number of slices available in this device

texts:
Below is the device utilization summary for the design(Zynq 7010) and the use of Slice LUTs exceeds the availabile number. Previously it was 82% and now it exceeds after adding a block of checksum code 4 times. Is there any tweek to merge LUTs and reduce its consumption or need to make manual optimization in the code?

Below is the synthesis settings:

I have used the following settings for implementation to reduce some kind of resource utilization especially LUTs

*I got some information from this website: Xilinx parameters

After using the above settings, the problem still persists. I am not sure about some settings, whether they are valid for Zynq or not. Any help?


texts: Currently I'm working at equipment containing AC-DC power supply & digital processing board inside same enclosure. I don't have any experience with AC powered devices, so I have a question. According to safety requirement I should connect PE conductor to aluminium enclosure. Is it a common practice also to connect digital ground to the enclosure? In this case PE = DGND (0VD), is any issue here?


texts:
I have just started working on interfacing Nordic semiconductor's nrf52 with SD card using SDK 12.0. I have to write to SD card at a rate of 84 packets per second and each packet consists of 20 bytes. I am using fat file system which uses SPI protocol for writing to SD card.

I am sampling the ADC at 1 ksps (12 bit resolution)and storing these samples in SD card.Here I am writing to SD card based on GPIO interrupt For each write operation I am using following steps: 1)open directory 2)open file 3)write bytes to file 4)close the file.

While writing continuously I am facing following issues :

1) Code gets restarted automatically after writing some kb's into SD card.

2) I am wring only in one file. Still additional files are generated in SD card.

3) while writing to file somewhere in the middle I am getting massage as Unable to open or create file: ank.TXT.

I am using 8 GB SD card for this operation. IAR version 7.4 and SDK 12.0. Does any one has any idea why I am getting these issues?

I have attached my code at this link

have to write to SD card whole data at longer duration without restarting the code.


texts: Differential amplifier with current mirror

texts:
I am having difficulties with sections e and g and would appreciate some assistance/guidance if possible.

As for section e, I figured I could use the following expression for the current to evaluate  \$V_{sd4}\$:

\$I_{sd4}=k_4(V_{gs4}+0.2)^2(1+0.05V_{sd4})\$, where \$I_{sd4}=23.745 \mu A\$ and was found in previous sections. The problem is that this yields \$V_{sd4}=0V\$ and \$V_{01_{dc}}=5V\$, which doesn't seem correct.

As for section g, I believe there's an error here, isn't there? How is \$r_{o6}\$ even relevant to the DC calculation asked for??


texts: SMPS feedback circuit with voltage regulation and current limiting

texts:
i’m self learning electronics for a few months now and i choose my first project to be a bench SMPS.
Since it is my first circuit design ever i really need some clarification.

My SMPS is 2-switch forward topology and i designed it to have:
adjustable output voltage 0-30V,
adjustable current limiting 0-10A

Please review my FB circuit:
Op amps are rail-to-rail, i computed values in the way that op amps are comparing 0-1V on one input(current sense, voltage) and 0-1V on second input(potentiometer adjusting)


texts: Where is the input and output of this circuit?

texts: I was instructed to put in a voltage probe at the input and the output of this circuit. Did I place the probes correctly?


texts: Does polarity of differential DisplayPort signals matter

texts:
I am routing a DisplayPort interface. I know from PCIe that the polarity of the differential pairs does not matter. So if it is helpful during routing I can connect the n to the p pin and vice-versa.

Is the same true for DisplayPort signals? Can I swap the negative and positive signals if convenient?


texts: Floating voltage-controlled resistor with LM13700: How does it work?

texts:
1. The LM13700

The LM13700 is an Operational Transconductance Amplifier (https://en.wikipedia.org/wiki/Operational_transconductance_amplifier) converting a differential voltage into a current output. In the datasheet of this chip (http://www.ti.com/lit/ds/symlink/lm13700.pdf) you'll find many interesting application circuits.

2. A floating voltage-controlled resistor

I'm wrapping my head around the floating voltage-controlled resistor as shown in the datasheet of the LM13700 (Fig. 28, page 16):

I've copied that schematic to the figure below. All the "inner parts" of the LM13700 chip are shown black. All the external PCB-traces and external components are shown green:

Pinning:

FIRST AMPLIFIER
----------------
1:  AMPLIFIER BIAS INPUT
2:  DIODE BIAS
3:  IN+
4:  IN-
5:  OUT
6:  V-
7:  BUFFER IN
8:  BUFFER OUT

SECOND AMPLIFIER
-----------------
9:  BUFFER OUT
10: BUFFER IN
11: V+
12: OUT
13: IN-
14: IN+
15: DIODE BIAS
16: AMPLIFIER BIAS INPUT

3. My question

The datasheet doesn't go into a detailed explanation on how this circuit works. I'm trying to grasp it, to understand the circuit on an intuitive level. Can you help me for that?

EDIT

My question has been answered by @LvW. He pushed me in the right direction, so I could make a detailed analysis (see my own answer below).
Because the resulting VCR (Voltage Controlled Resistor) has very poor current capabilities, I'm building an output power stage. Please have a look here for more details:
Power stage for VCR (Voltage Controlled Resistor)


texts: I have here a schema of a BJT with a speed up capacitance, but I can't seem to grasp why is there a connection to a negative voltage

texts:
I am a student and learning analog and digital circuits. As I was studying I came across this schema.
I have here the circuit. As you can see, there is a connection to Eb=-1V from the base terminal of the BJT. My question is what purpose does it serve? I figured it might be to help drain the capacitor faster when the VIN switches down to 0, but I can't really seem to find any explanation as to why that resistance exists. All schemas related to speed up capacitance BJT that I could find on the internet do not have that resistance. I was hoping I could get some guidance here. Thank you!


texts:
I'm trying to use an I2C isolator IC (ADuM1251) to isolate one of the slaves on my I2C bus.

Without the isolator, the communication works fine. With the isolator, my setup is the following:

I'm using 1μF decoupling capacitors. The master is connected to side 1 and the slave to side 2. The pull-up resistors on each side are chosen so the rise time of the signal on each side falls within the I2C specification.

Using the isolator, a read from the slave will work for a few bytes and then stop working. From the scope it looks to me like the the slave can't drive the bus low.

This results in the master reading the first few bytes correctly and 0xFF for the remainder. The slave should be able to source enough current to drop the lines low (3.3V, 2.2kΩ, max current source per pin is 4mA).

Any advice on how to proceed is awesome!


texts: OpAmp current source does not work as expected

texts:
I'm trying to build a constant current source for 2mA (IEPE accelerometer).
The simulation works as expected:

But the real circuit is sourcing only about 240µA. Vgs is around 2V; I thought this will work with DMP10H4D2S.
Any ideas what's wrong?


texts: Is it possible to use IN1307N without oscillator?

texts:
I am planning to use the Integral IN1307 (RTC) IC as non volatile SRAM as it has power backup facility. I don’t want to use RTC at all, so is it possible to use that IC just as RAM without attaching a crystal oscillator?

Datasheet is here.


texts:
I have found the following schematics:

How to modify this now to work from the Arduino Micros 5V output voltage (I will run it on 5V)?

For diode can I just use 1N4001 or similar diodes?

As this hooks on the serial port I assume that once the Xbee is connected it will be impossible to program the arduino from the IDE just like it would be connected to other device on it's serial port which always causing the programmer to fail with stk500() error. For this I could put in a double sided switch to be able to detach the xbee when I want to program the ardu once the device is assembled.

Thank you.


texts: Circuit that closes at certain voltage (as hotfix)

texts:
(Please note I'm "just" a software developer with some knowledge in EE)
Long story short: We spent an enormous amount of money on 50 boards we have designed for mass programming one of our products. However, we found a problem we did not detect with our tests.
We have a digital isolator (TI ISOW7821DWE, U2) that also features a DC-DC isolator. However, this DC-DC isolator is extremely slow. When applying 5 V to its input, it needs around 5-7 ms to ramp up its output from 0 V to 5 V. With 3.3 V input, it needs almost 9-13 ms from 0 V to 3.3 V output. The LDO supplying the DC-DC isn't the problem, it ramps up its output to 3.3 V or 5 V in <100 µs.
This slow ramp-up causes some MCUs on our boards to not start up properly, hence we can not program it.
We tested this with an "known good" DC-DC that ramps up the circuit from 0 V to 5 V in ~100 µs. Using this DC-DC, everything works fine. However, we have the attached circuit and parts now which we need to stick to and therefore somehow patch it.
Is there an easy way to "patch" the circuit, so it only outputs 5 V or 3.3 V to J3 after a certain threshold is reached (like 2 V, 2.8 V, 3.3 V, 3.5 V or 4 V)? I naively tried to use different Z-Diodes as a replacement for L2, with mixed results. The current drawn by our MCU's circuit (which is attached to J3) is around ~2 mA.


texts: Sharing a HD44870 display between multiple controllers

texts:
I have an existing third party system that has a HD44870 compatible display used for output.

This third party system cannot be changed (for a variety of reasons), and I need to retrofit a device to it, that among other things, 'takes over' the display at times, and returns control to the original circuit at other times.

The display lives on a separate board, connected to the main board with a ribbon cable, and this is my only real option for intercepting the display.

The retrofitted device is an Arduino (Arduino Pro, specifically).

Initially, I was planning to experiment with intercepting the data lines from the original circuit on the Arduino, and passing through the data as appropriate. After some research, I found that this was difficult to achieve reliably while allowing time for other tasks in the code to run.

My current approach has been to have the Arduino permanently connected to the data/control lines of the HD44870 display, and then have the data/control lines from the circuit routed to these via a 74HC367 (tri-state) buffer device, effectively 'cutting off' the original circuit on demand. The Arduino would decide when to return control (by it's connection to the 'output enable' pins of the buffers), and would reconfigure its outputs to be high impedance inputs when releasing control, so as not to pull the data lines up or down while it was not in control. The opposite is also true - while the Arduino is in control, the 74HC637 output enable lines are not active, meaning that they are in a high impedance state.

Unfortunately this has been unsuccessful, with only the Arduino able to control the display. Connections have been confirmed as correct. The Arduino has been using the LiquidCrystal library in 4 bit mode.

A quick-and-dirty fallback would be to use an array of signal relays to switch between the two controllers, but I don't think this is the correct approach for this issue.

For reference, my retrofitted system has no need to know what the original system sent to the display.

So, this leaves me with a few questions:

Should the approach described above be effective in performing switching?
Are there any existing devices designed to achieve this?
Are there any Arduino libraries that may achieve this?
Could the switching cause issues with respect to corruption of commands?


texts:
Currently I have a setup where a 433MHz Transmitter sends a number from one arduino and a 433MHz receiver picks it up for another arduino. The Transmitter and receiver are of the Super Regenerative type if I'm correct (picture below).

My question is can another type of 433MHz Receiver pick up the same signal? A Super Heterodyne Type?


texts: One lipo battery to supply multiple circuit boards

texts:
I want to supply all my circuit boards with one lipo battery. The design is like this.

I need a battery connector cable. So, I made my own battery Y-cable like this.

I use XT-90 connector to connect to lipo battery and xt-60 connector for 3 boards. When I connect my vaccum motor, it couldn't run the motor. Is there any problems in the cables? I use 12AWG for XT-90 Connector and 16AWG for XT-60 connector. Is there any connector for this use?

Is the resistance from all wire and connector caused the problem that cannot turn on motor?

The battery is onbo Lipo 6s 22.2 v 22000mAh 25C

Thanks all.

Converter for Vacuum Motor
Converter for Up Board
Converter for controller board


texts:
I am planning to buy an ATmega328 chip from Atmel, place it in my Arduino board, program it, detach it later, then solder onto a PCB.

Can I just buy the chip and program it on the Arduino board, or does it need to have an Arduino bootloader?


texts:
Nand technology has some issues, which I find it a bit difficult to understand.
It is said in nand devices that manufacture guaranty that a page will have no more than X (4/8/16,etc according to nand device) failed bit.

Is it that the manufacture can really guarantee that there shall never be more than this amount of failed bits is a single page ?
Is it that the failed ecc happens just randomly, after some time ?
Is it that re-program the failed ecc page, shall recover its flip bits to the correct value ?

Thank you,
Ran


texts: Why does a 74HC595N work in LED matrices?

texts:
I have checked a lot of LED matrices, and mostly a 74HC595N shift register is used. In some cases a TPIC595B like below.

Example: Driving LED arrays with Arduino

Circuit from above example:

I understand that for sinking a TPIC is needed, because when all columns are given 25 mA, it would result in a total current of 200 mA. The 74HC595N can only handle 70 mA.

As I understand, the 74HC595 controls the rows one by one. However, if all columns of a row are getting a current of 25 mA, will there be 200 mA through a single source pin of the 74HC595? Or should there be max. 70 / 8 = 8.8 mA per LED? The TPIC can handle 150 mA per pin, so that more than enough.

Can the 74HC595 handle 8 LEDs at 20 mA in the above circuit?


texts: Toubleshooting PCB circuit - strange Zener diode behaviour

texts:
I have two units of a device which I shall call deviceA and deviceB. DeviceB is malfunctioning.

Therefore I compared the resistance values of the same components on the boards of both deviceA and deviceB in order to find the one(s) which have failed. I know this is not the best way to proceed, but being deviceA and deviceB identical, it think it is an acceptable strategy.

I noticed that several components do not share its value with the corresponding component on the other board; I am talking of a 5% to 50% difference.

Then a 8.2v Zener diode, on deviceA it has a 15K ohm resistance, on deviceB its resistance is a some 20 ohm. Therefore I decided to swap the two components in order to check if it was the cause of the defect.

I found now that the swapped components are working the same as before, ie. the 8.2v Zener diode on deviceA it has a 15K ohm resistance, on deviceB its resistance is a some 20 ohm.

Therefore I have to assume there must be some other component on the board which is inducing deviceB strange behaviour.

How would I go on troubleshooting malfunctioning deviceB?

Please let me know thanks.


texts:
If I am putting 6, 9v batteries in series and want to limit the mA at the leads coming off the terminals to 1-4 mA how would I achieve this goal.  The anode and cathode will be a piece of silver wire submerged in distilled water to create an emergency source of colloidal silver.  I know I don’t have to limit it to create my solution, but by doing so, limiting 1-4 mA will produce a much smaller ionic silver particle than at higher mAs.

Thanks


texts: Increasing drain current, decreases common-mode level

texts:
The basic idea behind the CMFB setup is that increased output common-mode level feeds back into the gate-source of the triode devices and causes drain current to increase and hence output CM level to drop again -> I'm confused there - how does increased drain current cause output CM level to decrease.

My understanding was as follows, if drain current increases then if I roughly assume M9, M10 to have some Vds channel drop, then output CM level would roughly be Vdd - R_eq1(Id) and so increasing Id decreases CM level.
But, the other argument is that the output CM level is just the voltage drop of M5, M6/M7,M8 and again approximating as a resistor, that would mean output CM level is R_eq2(Id), so increasing drain current, increases output CM level?

Can someone explain in detail how increasing drain current causes output CM lvl to drop


texts: Using half wave rectifier for low power applications

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Im trying to make a low power application feeding it from a 9vAC, source, i have been reading that i can use a half wave instead of a full wave rectifier, i already did the circuit and been doing tests

Using the osciloscope you can see the wave forms from the Vin, the output of the diode, and finally the output odf the diode using a Avg sampling, im not sure if this waveform is enough to power a microcontroler using 3.3v im thinking about increasing the Cap value, and see how it modifies the rize, however, my main concern here is, how can i justify to do this instead of a full wave rectifier?, and also how can i make sure i will get the steady, 3.3v with as little noise as possible?


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I'm trying to repair damaged power supply. I've already replaced some burned/shorted diode and mosfets. Now I'm struggling with resistor connected between main mosfet's drain and ground. It should be probably 0.5 - 1 ohm one. My meter is reading 0.1 ohm, which is probably too low. I'm not able to read the value from the color stripes properly. They're probably violet, green, white (silver?), red and black. I'm guessing 0.75 ohm ww. Can somebody please help me to confirm this? I've tried to search similar questions, but the white stripe is confusing me.
What does a black band at the end of a resistor mean?

I've temporarily tried to replace it by two 3.9 ohm 2 watts ones in parallel. Power supply seems to be starting ok with them. Haven't tried with higher load yet. With the original resistor, the main fuse gets burned immediately after powering on.


texts: Capacitor - About Dissipation Factor and Ripple current (mA/rms)

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I m actually reading a capacitor datasheet which specifies the ripple current and the dissipation factor. This one:
https://datasheet.octopart.com/CA035M0100REH-0607-Yageo-datasheet-12513699.pdf

As you can see the ripple current and the dissipation factor are given for a frequency. But clearly I will not operate at this frequency... And I would like to know how the ripple current (which is adviced to do not reduce the life time of the capacitors) evolve in function of the frequency? Same question for the dissipation factor.
Thank you very much and have a nice day! :D


texts: How to connect multiple micro-controllers' USB ports on the same PCB?

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I'm designing a PCB with 3 Atmel ATmega16U4-AU micro-controllers on it.

I will be programming them through SPI.

Therefore, I will not be using D+ and D- ports on the USB interface. Then how do I deal with those pins.

Shall I:

Leave them unconnected?
Or Connect them to three different usb ports? (This way looks stupid. I don't want so many usb ports on the PCB)


texts: How can we use the same charge-pumps circuit for varying input voltage?

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As I understood it, a charge-pump increases the input voltage by stages Vout=Vin(N+1). In my example, the two stages of charge-pumps, I have Vout=3Vin. So in case of Vin=5.5V this leads to Vout=5.5*(3)=16.5V which is OK for driving the switch(if the gate voltage requires more than 10V).

However, when the input voltage hits 20V, the Vout=20*(2+1)=60V which is too high for gate voltage of 10V. So, my question is: how can the same charge-pumps circuit is used for all the varying input voltage? See figure below (Allegro A4926 MOSFET Driver)


texts: Using a Wii Nunchuck for data collection

texts: Anyone got a good tutorial on using and Arduino to capture the Wii Nunchuck accelerometer data?


texts: Transformer Voltage unknown number of turns

texts: I am trying to find the Voltage across the open end of the secondary side of this transfromer. I have been given V1=50V, R1=20ohms, R2=20ohms, XL1=XL2=40ohms. I have found the primary current so far using ohms law V1/R1+XL1 but I am stuck with what to do next?


texts: Are solenoid's magnetic field strength more dependent upon N loops or R radius of wire?

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For a project my team and I are experimenting with different sized solenoids. We are trying to maximize the field strength exiting the end of the solenoid as opposed to internal field strength. The solenoid's equation for magnetic field strength typically describes the strength internal to the loops.

As we had tested thinner vs thicker wire, we found the thinner wire with more loops  did better than a thicker wire with less loops. If you were to have insulated wires on a nanoscale, and created a solenoid with a magnitude's worth more of loops, would you be able to create magnets capable of several Tesla?


texts: Bode diagram, why is the phase at origin 90 degrees constant?

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The phase for a pole or root at the origin is given as either + or - atan(w)

So why is this a constant 90 degrees? for w=0 this should be 0 degrees, for w -> inf this should go to 90 degrees, yet we plot it as a constant 90.

I am confused.


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I currently have a setup,AUDIO-> LM386 -> MSGEQ7 ->ATMEGA328p (16mhz)
and it works to light up an 8x8 LED matrix. 16mhz crystal.
each column lights up to represent a frequency: average, 63Hz, 160Hz, 400Hz, 1kHz, 2.5kHz, 6.25kHz and 16kHz.

Now i want to take out the MSGEQ7 because it is $7AUD per chip, i want to make it as cheap as possible. from this link, he takes the amplified input and shifts down the values from 0-1023 to +512 - -512. http://www.waitingforfriday.com/index.php/Real-Time_Audio_Spectrum_Analyser

question:

1) Do i need to do the same? (shift the values down)

2) Instead of having 64 evenly spaced selected frequency, am i able to just choose the value that i want? (63Hz, 160Hz, 400Hz, 1kHz, 2.5kHz, 6.25kHz and 16kHz.) im thinking of using an array of frequencies. my perception of DFT or FFT is that the samples are evenly spaced. if they are evenly spaced a cant do 8 point sample because im using a 16Kmhz crystal and means my max cutoff frequency is 8Kmhz? I will also lose anything below 1Khz?

3) at low samples, is it any more effective to implement a FFT than DFT for 7 frequencies?

4) im reading the DFT and FFT code from Texas instruments:
http://www.ti.com/lit/an/spra291/spra291.pdf
page 38-39. Thank you for the patience im just trying to proceed pretty cautiously


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I have a 195-210V(with ripple) power supply and I need a 180V voltage reference.
This is my best idea so far:

Instead of just connecting a resistor and 180V zener diode in series, I do it two times to get better ripple rejection.
(two zener diodes on the left of course have greater total voltage drop that diode on the right).

This solution is still far from ideal, but it's not very bad.
I think there are better solutions, but I couldn't find or invent them myself.
One obvious solution that has better accuracy would be to connect a few smaller voltage reference integrated circuits in series, and final result probably would still have better accuracy than zener diodes. However this is not a good solution since it would require much more compenents, and zener diode solution ony has 5 components.

Are there better solutions that don't require much more components?


texts: I2C: Do I still need pull-up resistors if I use a logic level converter? I

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Electronics newbie here.
I have the following setup - three Arduino Nanos, a BME280 sensor, an MPU6050 gyroscope, a GPS GT-U7 (Goovvv Tech) module and an 128x64 (1.3in) OLED display. All except the GPS module can use/require I2C connectivity.
According to the datasheet of the BME280 anything above 3.6V is not recommended. On the other hand the OLED display and the gyroscope can work with both 3.3V and 5V. From the Arduino forum it seems that 3.3V is also what is recommended for my Nanos. Since I have different voltage and I decided to buy a breakout board of a logic level converter similar to this one from SparkFun.
For calculating the pull-up resistors I found this article from Texas Instruments..
Since I am really new to all this (I2C, calculating pull-up resistors for a bus, logic level conversion etc.) I am not sure if external pull-up resistors are required in my case. I also realize that the converter doesn't have enough channels to take care of all of my devices so an idea how to solve this (perhaps daisy chain if possible?) is also appreciated.