texts:
I am trying to swap dead capacitors in my motherboard. Removing them was relatively easy, but I can not insert the new ones. The solder melted into the vias and the desoldering wire does not suck it out of the hole.
Is there any safe method to remove the blocking solder from the vias?


texts: Transformer to convert 220V split phase to 220V single phase

texts:
I'm a digital guy whose forgotten his "big wire" electrical education. I'm surprisingly unable to find a solid reference for this.

I have a (European) 220V 50Hz split phase source (110V + 110V + GND). I have a UPS which only accepts single phase input (220V + N + GND).

How do I go about finding and how do I wire up an isolation transformer to use my UPS?

Update: This is a ship, not residential/commercial EU power. It is indeed split phase. I've also verified (by plugging it in and measuring output) that the UPS does not work and does need a ground potential neutral.


texts:
I'm trying to implement a total sum that follows this code

SUM = SUM + INPUT

SUM and INPUT are 5 bit signals in binary. I know how to implement the adder and i have 5 D flip flops to store SUM but at the start of the system, SUM is not defined because the input to SUM uses the output from the adder which uses SUM and so on and so forth. I'm not sure how to initialize my SUM to be all 0's. Any advice for building this circuit in general would be appreciated outside of my question.

Thanks in advance!


texts:
I am working on an Arduino board and I have no previous experience with it, unfortunately. I need to sense the voltage signal from a sensor using the ADC of the Arduino. I have an Arduino Due manual which says it has up to 12 useable pins for ADC input. I want to acquire 4 analog signals. However, I have two questions:

I want to fetch the data at a high frequency. So let's say if the sampling time of Due is 60 μs,
A.  will it take all of 4 analog signals at T = 60 μs and then convert them to digital? Or
B. will it take the first signal at 60 μs and fetch the second analog signal from pin 2 at 120 μs and so on from 4th pin at 240 μs?
Which one of these is the correct scenario?

It says that the Arduino Due can take 1M samples per second. Of course, this is an ideal figure. But, will these 4 analog signals count as 1 sample of the Due or 4 samples?


texts: When to choose ZoH method over Tustin in Discrete design?

texts:
Hey guys I am kinda confused as to which method to pick from, in terms for a digital filter. Which method is appropriate for this application and how did you come to pick it?

I want to convert a continuous Filter I already made into a discrete one. I have started it with adding a ADC at the input and wanting a analog output will be using a DAC at the output.

Having a Continuous Filter (H(s)) and having a block diagram of this: The circle is the summer(+|-)

Here is what I think about using either method

Tustin:

ZoH:

Why am I getting so confused on this? I know the ZoH method includes the delay from the DAC and Tustin is just a straight up conversion from S->Z domain. I can't wrap my head around which one to use as I always think when using the ZoH method is just repeats the DAC twice as a DAC will always be there.


texts: Quartus - Export Verilog as Gate Level (FPGA)

texts: I've got a project in Altera's Quartus II software which is written in Verilog. I'm curious if anyone here has figured out how to export the Verilog as a gate level netlist. I'd like to simulate the design in Cadence. I'm interested in the spectral power draw of my design. Any tips, guys?


texts: How much output current I need for IRF830 Mosfet?

texts: I'm working on a project and i need to switch IRF830 N-Channel MOSFET at roughly 100KHz as low-side.so, how much output current I need to drive this MOSFET 4 in parallel?


texts:
I spent some time already and I think I forget about something in my problem.

I have a motor, which single phase is R17 = 2 Ohm. I want to measure a current through it's circuit. I used a shunt with R11 = 5 mOhm. I measure voltages before and after the shunt, so I get the circuit:

R12 and R18 is R = 55 MOhm - those are ADC inputs of my AtMega8.
I used two voltage dividers R13 & R10 and R15 & R14 to output the voltage to ADC-friendly level - in this case ~4 V.
Measuring the ADC would output me almost the same result, because the voltages are different in the level of 0.01 V.

What should I do to output a nice, measureable results (like 4 V and 2 V is a good difference)?

EDIT 1:

I created another circuit with LT6106 as pipe suggested:

I think it worked like a charm. How do you think? Maybe I should add anything else?

EDIT 2:

I had a problem. I can't get fast enough any LT6106 and it's not a cheap one. I wanted to find any on my old boards(PCs, supplies) but I have none.

I have got few desoldered LM358 from ST. I managed to design a simple schematic that amplifies the differential voltage (dropout on R52).

[

What do you think of it now? Is something wrong or something still lacks?


texts: How would I determine the ideal capacitor for a specific application

texts:
I am attempting to replace a Surface Mounted Multilayer Ceramic Capacitor in an Amiga A4000 which is described in a BOM as:

Capacitor, SM, MLC, NPO, 100pF (1206)

However, when I look up this parts on Mouser.com there are 35 possible matches based on the documented criteria.  How would I determine what else to filter down this list by? Visually the Johanson Dielectrics 501R18N101FV4E is the closest match, however, beyond this specific question I'm really looking for "teach a man to fish" kind of guidance to understand what values I need to be tracking down.


texts: See if signal is amplified without an oscilloscope

texts:
I'm an electronics newbie, but I've had some experience with oscilloscopes in college lab. However, I need to design and wire a simple circuit that can read values from an electret mic. Since the electret mic produces really low voltages, I need to amplify it (a preamplifier).

The problem is, I do not have an oscilloscope and thus no way to know if the circuit works. Is there any way of knowing if the signal is amplified (or present) with a multimeter? I refuse to believe that every hobbyist out there who wants to play with audio signals has access to a DSO.


texts: differential trace impedance for USB (90 Ohms) on 2-layer FR4 board

texts:
I am currently working on the USB hub part for a multiport USB-RS232-converter. The current design is for Terminus Tech's FE 2.1 Hub IC. Regarding the impedance of USB signal traces the layout guidelines state:

  DP, DM Differential trace impedance = [DP(45ohm) + DM(45ohm)] = 90 ohm,
      and do not jump the DP DM signals that cause impedance miss match

To meet those requirements I used some online impedance calculators to estimate the required trace properties for a 2-layer FR4 PCB. However, the results I got are not consistent at all:

Hughes Circuits

input values

trace thickness: 1 oz/ft^2
substrate height: 1.6 mm
trace width: 1 mm
trace spacing: 0.15 mm
substrate dielectric 4.5

results

odd impedance: 45.5 ohms
even impedance: 119 ohms
common impedance: 59.3 ohms
differential impedance: 90.9 ohms

Montaro

input values

trace width: 3.35 mm
trace separation: 10 mm
trace thickness: 0.03556 mm
dielectric thickness: 1.6 mm
relative dielectric constant: 4.5

results

differential impedance: 90.035 ohms
single ended impedance: 45.071 ohms

All About Circuits

input values

trace thickness: 1 oz/ft^2
substrate height: 1.6 mm
trace width: 4.15 mm
trace spacing: 14.8 mm
substrate dielectric 4.5

results

odd impedance: 45.0 ohms
even impedance: 36.8 ohms
common impedance: 18.4 ohms
differential impedance: 90.0 ohms

Colorado Electronic Product Design

input values for single microstrip

w: 3.5
h: 1.6
t: 0.03556
epsilon: 4.5

result for single microstrip

impedance: 45.12 Ohms

input values for microstrip pair

s: 15
h: 1.6
Z_0: 45.12 Ohms

result for microstrip pair

Z_d: 90.23 Ohms

EEWeb

input values

trace thickness: 1 oz/ft^2
substrate height: 1.6 mm
trace width: 4 mm
trace spacing: 5.5 mm
substrate dielectric: 4.5

results

odd impedance: 45.0 ohms
even impedance: 38.7 ohms
common impedance: 19.4 ohms
differential impedance: 90.1 ohms

In addition to those calculation I found some other resources with some sample trace properties:

Mikrocontroller.net Forum

trace width: 0.22 mm
trace distance: 0.13 mm
substrate thickness 1.6 mm
resulting differential impedance: 100 Ohms

IBEX

1.6 mm PCB
1.48 mm FR4 thickness to GND plane
35 um copper trace thickness
trace spacing 0.15 mm
trace width 1.12 mm
resulting differential impedance: 90.184 Ohms

Why do those results differ that much? Since I am a beginner in doing impedance controlled PCB design I do not know which resource to trust.
Any hints about dependable trace properties for designing USB on a 2-layer FR4 board are pretty much appreciated.


texts: Shift register 5V VCC and data while 3v3 serial?

texts:
I want to use 5V for VCC and data pins for shift registers (HC595 and HC165) with a common GND while using 3V3 clock, I haven't tested yet. But is it okay to do that ? or it will reduce IC life span ?

The reason of using 5V is that, I do not want to put load on microcontroller and want to directly connect multiple shift registers using an external supply.


texts: Eagle create board from schematic is missing some parts but ERC says they are consistent

texts: I have capacitors C1 through C6 on my schematic, and if I type MOVE C2 into the command line it grabs that capacitor.  But on the board created from my schematic, it is missing C2 and C3 and no other parts (that I have noticed).  If I type MOVE C2 it says C2 does not exist.  When I run ERC it says my board and schematic are consistent.  I have no idea what to make of this, I can't find this anywhere online.  Both capacitors in questions connect a node to GND and on the board layout the capacitor and connection to GND don't exist at all


texts: Is this the correct setting to measure the vref voltage to adjust a trimpot on my A4988 stepper driver?

texts:
I'm trying to adjust the voltage on a trimpot measuring it using a multimeter.

I found a video in which they appear to be doing this (not on RAMPs), and the multimeter is set to the third symbol from the top below (DC voltage I'm not stupid enough to say that the voltage range is going to be the same on my multimeter):

Is this the correct multimeter setting to test this out on a RAMPs 1.4 board?

Also, does she have the leads plugged into the correct ports?


texts:
After purchasing an Arduino board (UNO) I decided not to use Arduino IDE as it lacked some features and all libraries are written in C++. I am coding with C. One thing that I really do miss is a serial interface that allowed my Arduino to talk to PC it is connected to.

So far I am familiar with SPI protocol, and thought to use USB-SPI converter chips, but since I already have USB implemented on the board I decided to seek information about how it is done and what USB consist of.

So far I found that it is UART that talks to a chip on Arduino board, and that chip is responsible for communication with PC.

But can somebody explain to me what actually happens on that board? And point me in the right direction please.


texts: Two lock in amplifiers, almost identical setup, different AC Gain?

texts:
I am measuring a voltage output of around ~110 uV for two thermometers. Other than the placement of the thermometers on the sample and the frequency of the lock ins (7225 DSP
at 11.137 Hz, 13.373 Hz), everything else is kept the same but for some reason the lock ins hits at input overload at different AC gains (40dB and 50dB). Could this be a ground loop issue? I'm not quite sure what else it could be. Thank you for your help


texts: Isp reprogramming of Attiny167 MCU while soldered in a circuit is possible?

texts:
Is it possible to re-program  a soldered attiny167 on a pcb, by using isp, when one of the pins needed (MISO) has a 10K resistor pulled to ground, and the RESET pin is pulled HIGH with a 10K resistor to Vcc?
I’m using a USBasp programmer through arduino IDE.
Two others pins needed on ISP  (MOSI AND SCK) are not used in the circuit and are left floating.


texts: Using optocoupler with MOSFET for dimming a LED

texts:
I have a blue LED which I want to dim using an Arduino, an optocoupler and an N-MOSFET.

For achieving this I assembled the circuit on a breadboard as shown in the pictures, using a YwRobot breadboard power supply to provide power to the optocoupler's transistor, and the MOSFET. I used the Fading example sketch from the Arduino IDE.

When I try to dim the LED in this basic configuration: \$(PWM_{out} → Resistor → LED → Ground)\$
The LED slowly lights up, reaches its maximum, then slowly dims, then the cycle repeats as it should in this case.

But in the circuit it behaves weirdly.
It doesn't dim, it's on full brightness, but when the cycle reaches again zero voltage, it's turned off. No sign of any change in the brightness.
I tried modifying the delay of the cycle and I used a multimeter to measure the LED's voltage. As soon as the cycle moved from turned off state \$(0V)\$ to a slightly higher voltage (I used 1 unit increments in analogWrite and 4 second delay) the LED was on full brightness \$(2,8V)\$.

I don't know what's going on. Maybe I don't need one of the resistors on the optocoupler's BJT side? I tried taking the \$R_3\$ resistor out but then the LED was always on, didn't even bother to turn off so I put it back.

Questions:

What should I change in the circuit to make the LED dim like in the
basic configuration?
Do I need current limiting resistors for the BJT both on the emitter
and the collector side \$(R_2, R_4)\$ in this case? I know that in
the case of FETS, the \$I_D=I_S\$, so one resistor \$(R_6)\$ is
enough.

Here are the schematic and the Fritzing project:

Datasheets:
4N35M optocoupler datasheet
IRLZ34N n-mosfet datasheet


texts: Converting 2.5V and 1.1V from 5V Power Supply with 10ms delay between both!

texts: I'm working on a design where i need to convert 2.5V and 1.1V from 5V power supply respectively. The constraint of design is such that 2.5V rail should come up first and then followed by 1.1V rail. Also, i want output to reach 2.5V with 10ms delay and then another 10ms delay for 1.1V to come up. Is there any off the shelf buck converter which does this? An can you guys suggest what should be the right approach towards this design?


texts: Self cancelling indicator project. Help needed

texts:
I am embarking on a new project to design a circuit for an automatic vehicle signal actuator.

Outline of the project is this:

The problem:
I have a car that has indicators operating on a standard 12v on-off-on toggle switch. As you can imagine this switch gets left on occasionally. Both misleading and potentially dangerous.

The solution:
Replace the toggle switch with a 2 way momentary switch and create a circuit that supplies 12v to the existing indicator circuit for 5 seconds. In addition, the timer is continually reset when a 12v feed from the brake circuit is applied. As soon as the brake feed stops, the 5 seconds starts again.

Effectively, this allows a lane changing signal as well as a solution for waiting at junctions or to cross a stream of traffic with the brake applied.

I'm sure there are many ways to skin this particular cat:

A 555/556/558 and relay solution?
MOSFETS?

Heat dissipation could be a factor as the solution will have to be in a watertight project box.

I am playing around with a 556 on a breadboard but finding a solution that will be robust and won't overheat comes down to experience (which is something I lack).
Any help would be greatly appreciated.

Kind regards


texts:
I am trying to write a vga controller for D1-SOC boards with 640*480 resolution at 60hz. I did a modelsim simulation with it and it seems to be working correctly, but when I program it on fpga it is just showing a blank screen. Can anybody go through it and let me know that what are the mistakes.
Simulation: Start of VS signal:

End of VS signal:

Start of HS signal:

End of HS signal:

Full view of VS signal:

Full view of HS signal:

my code is given below for reference.
//======================================================= // This code is generated by Terasic System Builder //======================================================= `timescale 10 ns / 1 ps module vga_controller(

//////////// CLOCK //////////
input                       CLOCK_50,

//////////// SW //////////
input            [0:0]      SW,

//////////// VGA //////////
output                      VGA_BLANK_N,
output  reg     [7:0]       VGA_B,
output  reg     [7:0]       VGA_G,
output                      VGA_HS,
output                          VGA_CLK,
output  reg     [7:0]       VGA_R,
output                      VGA_SYNC_N,
output                      VGA_VS
);

//======================================================= // REG/WIRE declarations //=======================================================

wire            CLOCK_25;
wire            rst;
reg [9:0]   count_h;
reg [9:0]   count_v;
wire horizantal_check;
reg v_clk;

assign horizantal_check = count_h == 10'd793;
assign VGA_HS = (count_h > 7'd94) && (count_h < 10'd 794);
assign VGA_VS = (count_v > 1'b1) && (count_v < 10'd 526);
assign VGA_SYNC_N = ~VGA_BLANK_N;
assign VGA_BLANK_N = ~ VGA_HS || ~ VGA_VS;
assign rst = SW[0];

assign VGA_CLK = CLOCK_25;
//======================================================= // Structural coding //=======================================================

// Clock divider vga_pll vga_pll_ins0 ( .clk_clk(CLOCK_50), // clk.clk .clock_25_clk(CLOCK_25), // clock_25.clk .reset_reset_n(rst) // reset.reset_n ); //

// counter horizantal

always @ (posedge CLOCK_25, negedge rst )
begin

if(!rst) count_h <=0;
else if ( horizantal_check ) count_h <= 0;
else count_h = count_h + 10'b1;

end
//
// counter verticle always@( posedge v_clk, negedge rst ) begin if (~rst) count_v <= 1'b0; else if (count_v == 10'd 525 ) count_v <= 1'b0; else if (v_clk) count_v <= count_v + 1'b1 ; end //

// wirte on screen always@( posedge CLOCK_25) begin

    VGA_G = 8'b0;
    VGA_B = 8'b0;
    VGA_R = 8'b0;
    if ( VGA_BLANK_N) VGA_R = 8'b1111111;

end
//

always@(posedge CLOCK_25)
begin
    v_clk = (count_h == 10'd793);
end
//
endmodule


texts: Will a 0.400mm thick PCB be too flexible?

texts:
My PCB will roughly have the following stackup:

35um copper foil (tracks)
100um FR4 prepreg
200um FR4 core
100um FR4 prepreg
35um copper foil (tracks)

This gives a total board thickness of around .400mm
Since I've only ever seen 1.6mm boards, I wonder how a .400mm will be. Too flexible? Will the core keep the board relatively rigid, or will I be able to bend it like a ribbon cable? Will there be problems with drilling, assembly? Can I still have a BGA soldered
onto it?

Edit: board dimensions are 80x50mm


texts: LVDS connections for V29 LCD driver board

texts:
I am trying use LP154W02 B1K7 LCD (from Acer 5670 laptop) with V29 LCD driver board. As per datasheet, LP154W02 B1K7 LCD is 2 channel 6 bit, 3.3v, 1680x1050 resultion. Original LVDS connections from the laptop has 1-7 pins used  for power and next 8 pins are used as follows
 9(Odd1_P),12(Odd2_p),15(Odd3_p),18(Odd_Clock_P),21(Even1_P),23(Even2_P),27(Even3_P),30(EvenC_P). Refer attached picture top one.

Bottom LVDS cable (from the above picture) is actually used and surprisingly display worked but text is very grainy. I have used following driver bin file
"MV29P_PNL_M201Z2_1680X1050_DO6L_12V_A_7KEY_NO_LOGO_IR_G32_FAC_LL25_NEC_LL131015_LAMV29"

So here are my questions.

When panel is rated 3.3V but above driver worked. Problem is Text is grainy/pixlated.
Original LVDS cable used only positive connections (9,12,etc) across odd and even pins. Should I use these connections?
If only positive connections (9,12,...) are used, should v29 driver able to drive it?
How come driver software 12V (observe 12V in bin file folder name) worked against 3.3v?
Can we get 3v driver software for v29 board? Is it ok to have 5v/12V, do they not burn the LCD??

Any suggestions are welcome and thanks in advance.


texts:
I have a single sata lane on host side. I want to connect dozens of hard disks to the lane using analog switches or multiplexers, instead of chainning multiplier chips (avoiding possible firmware and driver issue). At any time, only one disk is powered on and is connected to the lane with an analog switch.
My question is, is it possible to route a differential signal (for example, the tx pair from host) through the pins of an array of switches with a pair of 50ohm resistors at the end for impedence matching and avoiding reflection? The analog switches are simple on/off switches. For each switch, one side is connected to the "bus" lane. The other side is connected to the on-board sata connector, which connects to a disk via a cable.


texts: Why fully charge Lithium battery powered devices before first use?

texts:
I recently bought a Bluetooth headset and it turned out to be faulty. On getting the replacement, when I asked the customer care guy to test it after little charging, he refused to do it citing reasons like 'New batteries are in deep discharge and need full charge before first time use'. It is a Nokia BH-221 headset.

Being from electronics background, it seems like a bogus claim to me, since a device supposed to run on batteries will run the same way in its first use or when the battery is running low somewhere down its lifespan. But, I just want to be sure.

I think the device could switch on just normally with whatever remnant battery it has there too, rather than having to charge it for 4 to 5 hours before switching it on for the first time. Calibration of batteries set aside, does fully charging for first time use hold any other significance, or possibly result in the device not working properly at all then on?


texts: Will a 75ohm cable work with (not break) a 50ohm gsm shield?

texts:
I need to have a long (100') stretch of cable from my antenna to a GSM box (remote control for heating via GPRS or SMS), and I need to minimize signal loss. In another (totally different) question someone told me to use a lower-loss cable, such as a RG6, instead of the standard RG58 that is normally used for telecom applications.

Some reading up told me that 75 ohm cables are usually used for longer stretches of cable when you need low signal loss, but that connecting any 75 ohm equipment (cable/connector) will lose you about 5% signal loss (in every such link) due to the "standing wave effect".

5% is of course a loss, but nothing compared to dropping attenuation considerably (like going from 13db to 6db/100'), so I was wondering about doing just that. Cost is not really an issue, so I just want to get the optimal cable.

Are there any other effects, but signal loss, that I need to consider? Can I break my equipment? Should I do something else, like an alternative low-loss 50ohm cable (RG213?)? Can I use some kind of "impedance converter" (tips!) to down-convert from 75 to 50?


texts: I want to be able to switch on a device that requires 5v and 100mA from a Netduino. From looking on the web, I believe I need to use a Darlington array in order to meet the current requirements (since the Netduino pins are only at 8mA max).  Is a ULN2803 the right component to use?  Can it generate what I need with the 3.3v of the Netduino?


texts: What is the mathematical difference between a transfer function and a state transition matrix?

texts:
I do know what the difference in meaning is between a transfer function (output over the input) and a state transition matrix $\Phi$ (describes the unforced response of the system). Yet when looking closer at the mathematics to me it seems like they are both the same. Could someone clarify?

$$\dot{q} = Aq(t)+Bu(t)$$ where A is the state matrix, q the state vector, B the input matrix and u the input vector.

$$sQ(s) = AQ(s) + BU(s)$$
$$ sQ(s)- AQ(s) = BU(s)$$
$$ Q(s)(sI-A) =  BU(s) $$
$$ Q(s) = (sI-A)^{-1}BU(s) $$

where $(sI-A)^{-1} = \Phi$ ie the state transition matrix.

$$ Q(s) = \Phi BU(s)$$
$$ \Phi = \frac{Q(s)}{BU(s)}$$

$\frac{Q(s)}{BU(s)}$ looks to me like the representation of a transfer function and based on the math it looks like the state transition matrix in fact equals a transfer function, yet that doesn't correspond to the interpretation I have of both of those things. Could somebody please elaborate a bit on that?


texts: In the Arduino Uno's basic manual, connections for fading led are given. They have connected led on breadboard. The positive of led is connected through a resistor to the pin no 9 (pwm) and negative to the ground (ground of arduino with a wire). There is also a connection of 5V from arduino to breadboard. The led worked fine without that connection too. Is there any use to it? (It is given in the manual)


texts: 11.1V battery charging with optional solar panels

texts:
We (beginners) are trying to build a paddle streamer with stepper motors and drivers salvages from an old 3D printer. We would like to drive the motors with 12V (or 11.1V) and the control electronics will requires 5V/3.3V (ESP8266 for remote control and/or raspberry pi zero for video streaming from a camera on the boat).
I was thinking of using 3 cell Lipo battery in series but during my research I have found out that each cell needs to be charged separately to prevent over/undercharging. We also would like to have an optional solar panels on the streamer as it will float around freely in a pond most of the day.
We were wondering, what would be the best approach to power such a boat? We are afraid to blow up the battery by making bad choices. For single cells, there are modules, which have all the necessary features (over/under charge protection, overcurrent protection, allowing discharging and charging at the same time? etc.). It has got complicated with 3 cells.
edit: sorry if the question is not specific enough. I can delete it if not fit to be asked here.


texts: I am attempting to recreate a circuit for a PWM, to control a 6v dc motor's speed

texts:
I am using a breadboard and am attempting to recreate the circuit from this post. From the post I am using this image

As the circuit for recreating it. However, I am not getting the results I would expect. On the motor terminals I would expect one of them to be ground (however I am but a simplton) but both are producing voltages. One is producing 9v and the other 7v.
If you feel it would be helpful I can upload some images of the breadboard setup, but Im not sure how visibile everything will be in an image. I have grounded both caps (c1, c2) but as it doesnt show any other groundings maybe I have missed something?


texts: How soft latch power switch in this specific circuit is possible?

texts:
I am trying to understand the soft power switch operation of a LED lamp I dissembled. The circuit of the lamp is depicted below.

The switch S1 can be considered as a momentary on switch (SPST). The power P-mosfet Q1 is used to drive the LED. Q1's base is controlled from NPN (Q3) transistor which when in on state pulls it down. The values of resistors are accurate as indicated in actual circuit. The values of capacitors are not valid as I am not able to measure them, but yet I have difficulty understanding the operation.

As opposed to other soft latch circuits, this one uses just two transistors. And there is no feedback from drain of Q1 to base of Q3. If I have transfer accurately (*with the exception of capacitances) the circuit on diagram it seems a very simple design.

In simulation I can't find the exact capacitor values to make it work as the actual one.

The lamp actually works, as when pushing momentarily switch 1 the lamp turns on and when pushing again lamp turns off.


texts: Reverse Polarity Protection with parallel P-MOS transistors

texts:
There is a well-known reverse polarity protection technique using a P-channel MOSFET like so:

simulate this circuit – Schematic created using CircuitLab

If I use the common BSS84 for this task, it can only handle 130mA continuous current through it. Lets say I want to use the BSS84 to reduce the number of unique parts on my board, but I need to support 200mA continuous current. The battery voltage could be anything from 2.5 to 4.5V. Is there any significant concern with doing the following to retain the circuit protection properties, and increase the current support?

simulate this circuit


texts: OP-AMP outputs constant voltage with no inputs

texts:
I have a standard OP-AMP 741 IC.  When there is nothing connected to the inverting input, nothing connected to the non-inverting input, a 5v rail connected to v+, and v- grounded, the output has a constant voltage slightly less than the supply voltage.  It is my understanding that the output should be zero volts as the difference between the inverting input and the non-inverting input is zero.  Why is this not the case?

I have also tried grounding the inverting input and the non-inverting input, and have obtained equal results.


texts: SNR improvement from placing analog filter ahead of digital filter

texts:
We have designed a PCB containing a data collection circuit for a customer, and their external expert presents this "helpful suggestion":

  Question about signal averaging vs. longer integration times: Averaging \$N=20\$ samples provide us with a digital SNR improvement of \$\sqrt{N} = 4.47\$. However, the signal of interest is slowly varying. So, instead we could integrate the signal longer (say, \$N\$ times longer) and reduce the filter bandwidth by \$N\$, resulting in an SNR improvement of \$\sqrt{N}\sqrt{N} = N\$.

Is reducing the sampling rate and corner frequency of the anti-aliasing filter that much more effective than decimation via a digital filter?


texts: How to compensate for leading power factor?

texts:
Since my job is related to led drivers and ballasts i get confused with some questions. I see that the capacitor that is placed after diode bridges decreases the power factor and when we remove it we can achieve a higher pf. So i think that our power factor is a leading pf.

How do you compensate leading power factor?

Also, why we know most of the loads as inductance loads?
and why do we just have capacitor banks, not inductors bank?


texts:
I have question about reducing number of resistors ... Well, it will be better if I show you the schematics. This is my first scheme:

That's what I have. The thing is, I know what only one LED will be lit at the time, so I thought why don't I use just one resistor like this:

So after I made this scheme , I tried to run simulation in Multisim, and all LEDs were going on and off rapidly and radnom. So my question is: did I do anything wrong here? If I did, what did I do ?
If I didn't do anything wrong, do you have any tips that I should follow (like something I might overlook in this situation) ?

Thanks :)


texts:
This question is related with the one I asked sometime ago about the heat generated when driving a BLDC motor BLDC drive inverter circuit problem. The problem is, the MOSFET chip got heated up obviously even the RMS current is about 200mA. The motor to be driven is 24V 90W BLDC motor with a phase resistance of 0.15 ohms and phase-to-phase inductance of 200uH. The MOSFET and its gate driver I chose was SI4564DY (P+N) and FAN3278.

@Bruce Abbott gave some excellent explanation why the chip got heated up in my last question, but after some digging, I still have some more questions regarding how to select the proper MOSFET.

Correct me if I am wrong, but according to datasheet, SI4564DY is supposed to handle up to 9A at 24V VDS, which I though is more than enough for the bldc motor used, and the "Continuous Source-Drain Diode Current" is 2.3A, which I assumed to be RMS value rather than instant value. So I didn't expect it to become so hot when the RMS drive current is about 200mA, although as @Bruce Abbott pointed out and verified by experiment that current spikes at 15% PWM duty cycle can as high as 2.3A. Even TI has a design using similar MOSFET chip to handle 24V/5A bldc motor without using heat sink. If I drive the motor at full load, I guess the MOSFET chip will burn out. So my question is

Did I select the suitable MOSFET to drive the 24V/90W motor (phase resistance 0.15 ohms and phase-to-phase inductance of 200uH)
Normally, when is heat sink needed for the MOSFET chip? I though SI4564DY is more than enough and heat sink should not be needed, as TI's example shows.
If SI4564DY is actually not enough, what kind of current capacity should I look at when selecting another chip?
To drive a 24V bldc motor, normally at what wattage should I consider using heat sink?

I am still new at handling this kind of bldc motor control and hopefully these questions don't appear to be silly to you gurus.

Edit

Here are some related info. The size of the PCB is 15mm*5mm with mainly the MCU, gate driver, MOSFET and some sensing circuit on it. The PWM freq used is 20Khz, and I did try 10KHz, but no obvious temperature drop. Currently I am using PWM on lower arm N-channel MOSFET.


texts:
How do I know the value of this capacitor?:
The case shows "E0001", "68", and "35k".

When measuring, it shows 84uF (I measured two of the same value). But I can't  see any indication of this value on the case of the capacitor.


texts: What is the process of (digital)IC design?

texts: If you're going to design a digital IC from the bottom up, starting with the actual transistors(and passive IC components) that form the logic gates, do you first simulate the logic gates, flip-flops, mux/demuxes as circuits comprised of discrete components to ensure that they work properly before simulating them as an actual integrated circuit? I've tried doing this with CMOS logic gates by constructing them from discrete components using NI MULTISIM 14 but such simulations do not produce working designs. Or is there a different approach to designing an IC and simulating the circuit to see if it works in theory before it is then fabricated and tested....


texts: A very basic question about VFD output frequency

texts:
I know that a VFD's inverter stage creates alternating voltages at a desired frequency for the terminals of a delta induction motor(stator voltage freq.).

Normally without a VFD the nominal freq. for the motor terminal voltages are 50/60 Hz rated.

In case of VFD use, will the induction motor terminals(stator terminals) voltage frequency be limited to 50/60Hz? On the other hand I see such data where the VFD electrical output freq. is given upto 590Hz as follows:

Induction motors are manufactured for 50/60Hz systems. How come 590Hz limit possible for safe operation? Am I misunderstanding something here?


texts: Can I connect two tv antennas in parallel?

texts: In order to get higher signal level on my pre amplifier to the tv set.


texts: Maximum power which can be asked from a PC?

texts:
I want to attach an external circuit through a six-pin connector to my computer, which is supplied with 220V.

How can I find the maximum power that the PC can supply to the circuit?


texts: What are important uses of the "Net Tie" concept?

texts:
My understanding is that the "Net Tie" is a concept introduced by Altium and useful for Kelvin connections of a sense resistor and can not be applied in any other case.

Although it seems to be a useful feature at the first sight, it can't declare the exact connection point to the footprint, so it's not an exhaustive concept on its own, it still requires developer attention.

Example:

Given the following schematic:

We can either connect actual sense nets as follows (which is correct):

or as follows: (which is also correct):

or as follows (which is not correct):

by considering the same schematic using "Net Tie" concept.

However, if we would always handle a sense resistor a 4 pad component which has "Pin.1, Pin.2, Pin.sense1, Pin.sense2" independent of real pad count and placement; we can exactly declare "how" a Kelvin connection must be made.

As an example, we can define a 1206 resistor package footprint by adding SenseX pads as follows:

Question

Is there any use case for which "Net Tie" is a complete solution?


texts: Which drawing represents an AC generator?

texts:
This was a problem in my text book, and it says: "A magnet bar has been installed in the vertical rotation axis of a coil. Which of the above drawings represents an AC generator?"
Ok, the answer to this question is drawing (a), but I really don't understand it, could anyone clarify it for me? I think that we need to apply Fleming's right hand rule, but in that rule the coil is in motion and in this problem the magnet is in motion, so, I don't know exactly how to apply it here and understand the drawings.
Thanks in advance!


texts: Spice Simulation including Verilog model

texts:
I would like to include a magnetic tunnel junction in a circuit and simulate it. Since LTspice does not have this device, I decided to model it in Verilog.

Now, I am not able to include the MTJ model (Verilog file .v) in the LTspice. Do you have any suggestion? I have surfed the net for hours but I do not manage. I have a MAC.


texts:
I've got a Curiously HPC with two mikroBUS UART modules fitted (1x FTDI232R and 1x RS485 5V), however MCC in MPLAB X isn't letting me map the EUSART2 of the target (PIC18F46K40) to module 2, even though the Curiously HPC schematic shows as having a RX and TX on both mikroBUS module connectors.

It'll let me map ESUART2 to Port B or Pord D, however TX and RX go to Port C on the Curiousy schematic.

Am i missing something or is it just not possible?


texts: How is this circuit a negative resistance oscillator

texts:
I found these oscillator configurations(all are similar) at various sites on the web, but here and here the author says its a negative resistance oscillator. It's a popular oscillator among amateur radio enthusiasts due to its ability to oscillate at a wide range of frequencies, its often called emitter coupled oscillator/differential pair oscillator etc. Such one is even briefly touched on the book Experimental Methods in RF Design

Circuit 1

Circuit 2

Circuit 3

Circuit 4

Circuit 5

Circuit 6
My question is that, is these circuits negative resistance oscillators, if so how is negative resistance achieved in these circuits? If not, how does such circuits oscillate?
EDIT: I found another different circuit that is said to be negative oscillator too. I would like to add it to the question too. The page also contains several other circuits similar to the ones shown above.

Circuit 7


texts:
I'm working on a batteryless mouse, and it will be wirelessly powered by the USB (5V 0.5A), however, I already  stepped up the voltage to 12VDC. From what I understand, I will need a DC to AC inverter circuit to convert the 12VDC to AC for Wireless Power Transfer (WPT). Correct me if I'm wrong, the signal has to be in high frequency (100KHz to 500KHz) to transfer the power efficiently. Can anyone please suggest me a proper inverter circuit for that application? FYI, I'm a mechanical eng. student, if you have better idea for my project, let me know!

Thanks.


texts: I have a 6V motor and another coming on the way. I am trying to create a phone charger on my bike using these motors with propeller blades. I will mount them on my bike and be able to ride and charge. My question is, How fast must I be going to make the motor spin?


texts: Electrolytic Capacitor in Solenoid Circuit

texts:
I was looking at a few solenoid circuits. I came across this one that had an electrolytic capacitor across it (whereas most just seemed to skip it).

Does this capacitor serve any other purpose than to create a smooth voltage particularly in regards to the flyback diode and transistor?
How can the appropriate capacitance be chosen? (More specifically for a 12-volt solenoid being powered from a LiPo or portable generator)


texts: Is this LDR and TRIAC circuit advisable for real time application?

texts:
Would you suggest below circuit?  Will it work for a long time? What are the advantage and disadvantages of this circuit?

https://envirementalb.com/automatic-street-light-circuit/


texts:
I am interested in measuring the output impedance of an high performance DCDC converter together with its board.

Up to now I referred to this document, a very well written one.

I am referring to fig15, here it is for ease of reference (thanks Keysight!)

The DUT is the output of the DCDC converter.

How doest this work? A disturbance is injected on the DC output voltage of the converter by means of the rightmost signal generator. Voltage across the DUT is measured by \$V_T\$, while \$I_{DUT}\$ is measured by \$V_R\$ thanks to the \$1\Omega\$ shunt resistor. Of course \$V_x\$ are vectorial voltmeters, so when the division is performed to compute impedance the number you'll get is, in fact, the impedance and not just the resistance.

Now this all looks very good and nice to me, I understand that a Network Analyzer demodulates the measured voltages at its inputs, getting rid of the DC component inevitably present at \$V_T\$.

But what about ripple? Our DUT can be modeled by a DC generator, a somewhat random ripple generator, and an impedance, all in series. This ripple voltage will be measured by \$V_T\$ but as far as I understand no current would flow in R.

How does this phenomena influence the final measure?

One could argue that ripple has its power concentrated in a narrow bandwidth but some converters out there purposely spread this power over a larger bandwidth, because of EMI issues. How would you deal with that?


texts: Using IR21531 as a simple 1 channel gate driver

texts:
I've bought the only gate driver I've found on the local hardware store (IR21531). I want to use it only to drive a IRF630 with a PWM 3.3V signal.

How should I do the wiring? As you can see on the IR21531 datasheet, this chip seems to be intended only to automatically switch two MOSFET at a fixed frequency.

I don't care if I drive the high or the low side.

Also, if this is not possible (as @Respawned Fluff said), could I use any workaround to drive at 3.3V my MOSFET? I need to drive 200V at 5A.


texts: ADC input filter design for a low sample rate data logger

texts:
I am looking to get advice on anti aliasing filter design for a data logger I am developing, which has a sample rate configurable from 100 ms (10Hz) up to 24 hours (i.e. wake up, take a sample, write to SD card, then back to sleep).
The data logger is using MicroPython with a LTC1857 8-channel 12-bit ADC with SPI interface as shown in the datasheet below. The LTC1857 is capable of 100kSPS but the data logger reading many serial devices and writing to the SD card cannot achieve anything near that sample rate and it is not designed to continuously sample but to wake, sample, write to SD card then sleep.
LTC1857 data sheet:
https://www.analog.com/media/en/technical-documentation/data-sheets/185789fb.pdf
The device is designed to sample signals that are not expected to rapidly change (i.e. liquid level, temperature, battery voltage).
I would like to minimise filtering components so ideally an RC/LC filter or just C and let the end user determine how much R they would like to add to the analog input? The ADC inputs are protected up to 25V which I would like to use and therefore minimise input components.
When the data logger wakes up I can take a number of samples at a time and average them and make this user configurable.
I am looking for anti-aliasing filter design comments (ideally using an RC/LC filter) given the varying and low sample rate. What would be the best approach when using this ADC?


texts:
I have an air purifier I would like to modify the PCB to an always on state at high setting when plugged in.  This would allow me to control the device with and Amazon Echo compatible smart plug.

Important switches on the board

SW2 - Power on the unit which is initially in an off state.

SW1 - Cycle through fan speeds which is initially in the "Auto" state. 4 presses gets you to High, the 5th press back to "Auto".  "Auto" works based on a dust sensor.

SW1 and SW2 are labeled in the PCB screenshots below:

Thanks in advance for any tips or guidance for this project.


texts:
The well pump in my brother's house is wired strangely to me.
A single 12/2 BX enters the disconnect box, white on one fuse and black on the other, and out 2 wires to the pressure switch and out 2 wires to the pump controller.
The voltage across the white/black BX in the disconnect box is 240V.

No 3rd wire going to the pump?
What gives?


texts: Where did a response time of 12us come from?

texts:
Consider this circuit taken from Over Voltage Protection Circuit for Automotive Load Dump

It provides over voltage protection when the input voltage exceeds 19.2V ( as set by R1 and R2).

The turn off delay is related to discharging C1.

Page 4 of the linked pdf says the following ( I have bolded the sentence I am interested in).

  The circuit is designed to actuate quickly but reconnect more slowly. Capacitor C1
  rapidly discharges to
  ground through the LMV431 when over voltage is detected. When conditions return to normal, reconnect
  is delayed by the R3•C1 time constant. Most loads (usually regulators) contain large input capacitors
  which provide time for the disconnect circuit to engage by limiting the transient slew rate. The nature of
  the expected transient along with the available capacitance will determine the required response time. The
  shut off action of this circuit occurs in about 12 µsec. Maximum transient rise times are limited in
  proportion to this time interval by Cload. This circuit was tested with a Cload of 1 µF. Larger Cload is allowed
  and recommended if fast rising, low source impedance transients are expected.

I am wondering if the time was measured or calculated ?
If it was calculated, how did you arrive ~12us ?


texts: Why won't my CAN transceiver receive messages unless there is a long startup delay or a bus analyzer connected?

texts:
I am using a 16-bit MCU, PIC24HJ64GP504, to write a CAN based application. Basically it is communication between my board and one another node which continuously keeps on sending data to my board using CAN at 1 Mbit/s. I am configuring the ECAN module in my PIC24 to work at 1 Mbit/s. I have written the code in such a way that for the first 10 ms the ECAN module will accept all messages coming in from the other side, and after that I have re-configured the ECAN module to accept only those messages with message ID 0x13.

Now here comes the issue.. The other node and my board are powered up at the same instant. The other node starts transmitting messages after 40 ms or so after powerup. But I am not able to get any message from it on my board. Now if I power up my board first, give it some time to reconfigure the ECAN module with new filters and settle down and then power up the other node, then everything works perfectly.

Now the strangest part.. If I have a CAN bus analyzer connected between my board and the other node and even if I power up both the nodes at the same time, everything works fine...no need to power up my board first. I have tried this with three different bus analyzers from different manufacturers and got the same results.

To me it appears that during re-configuration of the ECAN module, it takes some time to settle down. And with the introduction of the bus analyzer in the bus, this time is somehow cut short so that everything works perfectly. But I am not sure what exactly the problem might be.

I have been struggling with this issue for the past seven days.

PS: Today I checked with a scope and found out that if the other node starts transmitting after 170 ms after powerup, then the whole thing works fine. Before that, my device won't receive any messages from it unless the bus analyzer is connected. The worst part is I can't delay the transmission of the other node, the firmware of that node is proprietary.

Also I read in a forum today that CAN needs the 120 Ω resistor at the node to make it working (even though my node does not have one and it works fine, provided given some time to settle after reconfiguration). I suspect the introduction of the bus analyzer somehow changes some network's electrical parameters such that the time taken by my node to settle after reconfiguration is cut short. But I am not sure.. :(


texts: Need help understanding Transformerless Push-Pull transistor circuits

texts:
I am new to electronics and I am currently trying to learn a little more about how NPN and PNP transistors work. While doing some research, I stumbled across a circuit design called the Transformer-Less Push-Pull circuit. The schematic that describe such configuration is shown below:

My problem is that I am trying to understand and reproduce the circuit above but I am just not being successful.

So my question is: Do the schematics shown above represent a real circuit (something that can be physically built and can work successfully) or is it just a sort of circuit analogy?

If the circuit diagram show avobe is not a real buildable working circuit, could someone please point me to some schematics that represents a real buildable Transformer-Less Push-Pull circuit? If at all possible, something simple would be best as I am just a beginner and will most likely get lost if the circuit is not relatively simple.

Thanks.


texts: Is there any issue with connecting the output of an SSR back to its input to implement latching functionality as in the diagram?  I've searched but can't find anything that says definitively whether this is an acceptable or unacceptable configuration.  U1 is a Sensata-Crydom Power Plus DC SSR with 1-60VDC operating voltage and 4-32VDC control voltage (internally current limited but not shown in symbol).  D1 prevents the 28V load supply voltage from shorting into the (non-isolated) 24V control voltage when SW1 is pressed, D2 prevents control voltage from trying to power the load.  The goal is to have the load disconnected when power is removed from the system and not automatically start back up when power is reapplied.  In the past, I've used a PLC channel for this but it seems a bit overkill for such a simple function.


texts: Can Sill Gasket Foam Be Used As Anti-Static Foam?

texts:
Recently been desoldering a lot of parts and was wondering if Sill Gasket is at all similar and sufficient as anti-static foam for storing ICs.
http://insulation.owenscorning.ca/builders/products/foamsealr.aspx
Currently working in construction and this stuff is abundant so it is way easier and cheaper to get hold of.

My other option is to buy WAY more than I need from ULINE http://www.uline.ca/BL_8001/Uline-Anti-Static-Foam-Rolls

Both say they are polyethylene foam. This might answer my question but confirmation would be nice since I have not found anyone else on the internet doing this prior. I hope this can provide reference for others who might be thinking of doing the same.

Thanks in advance :)


texts:
I am Not Good At This, and I am trying to breadboard this circuit here:

http://www.instructables.com/id/DIY-EEG-and-ECG-Circuit/

But I am stuck on the power supply.  The instructions state:

  Regarding power: the easiest way to power the circuit is with 2 9V batteries. To feed your op-amps -9V to 9V of power, connect one battery the correct way, and one backwards. That is, connect the positive lead of one battery to your positive power supply line and its negative lead to GND (ground). With the other battery, connect its positive lead to GND, and its negative lead to the negative power supply line. To "set" GND, you will eventually connect an electrode from your leg directly to the GND line. This will ensure that "0V" is your leg's voltage (unaffected by any head activity), and that all readings will vary from there.

Which is fine, until I can't actually figure out what rails to attach the two 9Vs to.  I think I get the idea that GND happens between the first + and the second - terminal, i.e.

But I can't wrap my brain around how to actualize this.  I put the two possible configurations I can imagine on this image below, with the given schematic that I can't entirely understand:

I've been testing it wired as the 2nd configuration, and it Mysteriously Does Not Work.  Are the batteries hooked up wrong?  If so please help me wrap my brain around how this works and I'll see if my chips are fried or not.  Hopefully not.

If the batteries are hooked up right, don't worry about trying to troubleshoot my other problems.  I can test it indefinitely if i'm at least assured the power is right.

Here's an example of how one person did it:

But I can't be sure how those wires on the right-hand side end, and I'm not experienced enough to guess.

Thanks very much!


texts: What changes when we replace a bipolar junction transistor with another one of same type in the a circuit?


texts: Leaving target processor paused nios ii multiprocessor application

texts:
I m using the multiprocessor tutorial, to have a MPSOC application, but when i finish all steps and running the nios application
I have this message in the terminal,

Using cable "USB-Blaster [USB-0]", device 1, instance 0x00
Processor is already paused
Reading System ID at address 0x0960A190: verified
Initializing CPU cache (if present)
OK
Downloading 07000000 ( 0%)
Downloaded 61KB in 1.0s (61.0KB/s)
Verifying 07000000 ( 0%)
Verified OK
Leaving target processor paused

I have done this work many times but with the some error,
please can any one help me, I m using quartus 9.0 and a de2_70 board thinks wery much.


texts: Noise and what does V/√Hz actually mean?

texts:
Noise figures in (op amp) datasheets are expressed in V/√Hz, but

Where does this unit come from? Why the square root? How should I pronounce it?
How should I interpret it?
I know lower is better, but will a noise figure that doubles also double the trace width on my scope?
Is this value useful in calculating signal to noise ratio? Or what fun calculations can I do with this number?
Is noise always expressed in V/√Hz?


texts:
I noticed that a Christmas Light uses 20 LEDs in series parallel, operated by 2 AA batteries (3V) without a resistor.

I thought you always need a resistor?

Would it be possible to run them on 5V (Arduino) with a resistor? If yes, how can I figure out what to use (I don't have any information on the LEDs).


texts:
I'm using a 5V relay to control wall AC socket to power up whatever AC appliance I could think of. But for the sake of testing I'm using 45W fan. For that purpose an AC/AC transformer (240VAC to 6VAC and later rectified and regulated to 5VDC) and wall socket are fed from the same mains socket.

The problem is that when the relays are engaged or disengaged it causes a voltage spike which can be heard through speakers attached to the same mains socket. What can I do to suppress these spikes, considering that in an extreme situation I might plug-in a 240VAC at 16A appliance going through the relay?


texts: What if we want to clamp/clip current to a certain value or range as we do with diodes for voltage?

texts: I have seen diode clamping/clipping circuits and can see that they can work well with such simple construction. However, what if we want to clamp/clip the current to some value rather than voltage?


texts: Nanosecond interrupt accuracy on a 64MHz microprocessor

texts:
I am currently designing a PCB with a 64MHz nRF52832 bluetooth MCU. I have an interrupt connected to this MCU which needs to be detected with 1-3 nanosecond accuracy.

Unfortunately, the 64MHz MCU has a clock cycle of 15.625ns, meaning the interrupt could be recognized up to 15.625ns late (assuming zero interrupt latency for now). Please note that the interrupt does not need to be acted upon straight away, I only need to know at which time it arrived.

Is there any way for me to use external circuitry to improve my accuracy? I've considered using an external nanosecond timer to measure the offset, and sending that to the MCU every time the interrupt is triggered. Unfortunately, I'm having a hard time finding any timers that can run at this speed.

I am capable of changing the MCU to a faster processor, however nothing greater than ~180MHz - which would still be 5.56ns per clock cycle. For this reason, a creative external solution would be ideal.


texts:
I made a homemade reflow oven and used it for the first time to solder a board. As you can see in the image below, I botched the job and burned the solder connections (not surprisingly, the board does not work). I'm trying to diagnose what went wrong in order to solder this correctly the next time.

My solder temperature profile is (using Sn63/Pb37 ChipQuik solder paste):

Preheat zone (25-100C, 0-75s);
Thermal soak zone (100-150C, 75-165s);
Reflow zone ramp (150-183C, 165-195s);
Reflow zone (183-235C, 195-255s);
Cooling zone (235-25C, 255-376s).

However, my oven exceeded the max temperature and got up to 247C before I opened the door.

The obvious first mistake I made is to let the temperature get above 235C. However, I wonder if I might have made other mistakes as well. For instance, it looks like there might be some mild solder-bridging from solder-ball formation (note that the top left two pins should be bridged). Does that mean that my ramp rate is too high, or I didn't hold the temperature at about 150C for long enough? The other mistake I may have made is I only took the solder paste out of the fridge for about 1 hour before soldering.

Do these diagnoses sound accurate? Anything else that comes to mind? I hope the image is sufficiently clear, but if not let me know what is unclear and I will see if I can take a better picture to satisfy those criteria.

UPDATE 1

Here's the same component after cleaning. I'm having some trouble getting more of the flux off than this using a toothbrush and isopropyl alcohol. The I'm also still getting the error "Device not responding to setup address." in the Linux kernel ring buffer.

UPDATE 2

I resoldered the USB micro receptacle and the board now works. None of the other components (including the one shown) required resoldering.


texts: In this wind sensor, how can I increase the sampling rate (takes up to a minute to update)?

texts:
I am using this LaCross TX23U wind sensor. Although not critical for this question, here is the communication protocol. The manual indicates a wind speed sampling rate of 4.5 seconds.

When the rotary is still, it reads out 0 mph, as it should. Turning the rotary will read a value, for example 5 mph.

Sampling it every five seconds, it takes a long time to reflect a change in rotation speed.

From standstill to a set speed it takes about 4 samples, or 20 seconds, to stabilize. Going from that set speed to zero, it keeps printing the same previous value for about 20 seconds, and then slowly reduces to zero over the next 40 seconds.

I suspect the rotation induces a current which charges a capacitor, accounting for the delay. Still, why would this result in a constant output for 20 seconds when I suddenly stop the rotary, instead of beginning to decrease immediately, even if slowly.

Also, is there anything I can do to improve the response time of the wind sensor? Up to 10 seconds would be acceptable for the project I need this for.


texts: Using Raspberry Pi to turn TV on and off directly (not using infrared)

texts: I am creating a device that requires a TV to be powered on and off when commanded by the code in my Raspberry Pi 3 B+. The Raspberry Pi also needs some sensing ability to know if the TV is on or off, so it can execute the turn on function when necessary, or turn it off when necessary. I am going to eliminate the IR sensor on the TV so it can't be messed with by remotes. I am going to be controlling two TV's in this fashion, independent of one another. My TV has the generic button circuit board that is typical on TV's and monitors. All in all, I am not sure how I will do this from a hardware perspective.


texts:
For a new board I will be building, I will need to generate the following power values:

The current values are max values. In parenthesis, I included the approximate duty cycles.

3.3V Analog - 150mA - (100%)
1.2V Digital - 700mA - (10%)
2.5V Analog - 700mA - (10%)
12V Digital - 100mA - (5%)
3.3V Digital - 500mA - (100%)
2V Digital - 10mA - (100%)

My input is a single cell li-poly battery.

When I should cut off the battery drain? What is the best practice? 3V, 3.2V, 3V? This potentially has some impact on power generation. If I set this 3.4V, I can get rid of the booster for 4.5V I mention below and use LDOs that are directly tied to the battery.
What is the common sense (expert opinion) power generation strategy in this case?

I was thinking

li-ion --> Booster --> 4.5V
li-ion --> Booster --> 12V

4V --> LDO --> 3.3V Analog
4V --> LDO --> 3.3V Digital
3.3V --> LDO --> 1.2V Digital

etc. Basically, generate two main voltages using booster and use LDOs to drop down.

I updated the question added a few details but removed the definition of best. I can probably manage to optimize for cost or power efficiency, rather I am looking for wisdom. An expert opinion that includes pitfalls I haven't thought of.


texts: Using Laplace in this circuit, how to find part C(Vx)?

texts:
I used Laplace transformation to find Vx(s), but I tried to find Vx(t) using the definition, but it didn't work with me. Is there another way to find it?
And about part d, I can use the limit right?
at t<0 : Vc=0 and IL=1A
at t>0 : I transferred all elements to Laplace , the two voltage source became (5/s) and the capacitor resistance is (2/s) , the inductor resistance is (4s) and inductor voltage is (-1) , then I found Vx(s) using nodal  which equal to Vx(s)=(10(s^2)-s+5)/(2(s^3)+4(s^2)+s) , is the answer right or not ?


texts: Multiple switches/FET's on a boost controller

texts:
I'm new to DC-DC converters and I am trying to design a 500W ~12V step up to 50V power supply. I've been looking into boost converters and controllers and I think I need to go with a controller to have FET's that can handle that amount of power. I also believe if I use multiple converters in parallel I will need to synchronize their frequencies. Is it instead possible to use a single boost controller and multiple switch-inductor pairs? If not, is the best idea just to use multiple identical boost controller circuits and synchronize their clocks?

Thanks in advance!


texts: there is already a electromagnetic brake. I'm thinking to use a electromagnetic induction as brake. is it possible?


texts: Specificity? "High-Contrast and spectroscopic-based specificity of optical imaging."

texts:
I came across the following phrase:

  High-Contrast and spectroscopic-based specificity of optical imaging.

I'm wondering what is meant by "specificity" in this context?

Thanks for any clarification.


texts: Target Device ID (0x0) does not match expected Device ID (0x18620000). dsPIC33

texts:
I have a problem with dsPIC33EP256MU810. I'm using PICkit3 and after I want to load the program to the MCU, MPLAB shows the following message:

Target Device ID (0x0) does not match expected Device ID (0x18620000).

I searched some solutions on forums, everything is OK but on VCAP (10uF tantalum) pin I have no voltage. It may be 1.8V, but I have 0 V.

PGC and PGD are working normally. I have this problem on 2 prototype PCBs.


texts:
I have a circuit board with lots of soldered SMD chips. There are a few I2C components connected to the same bus and the bus is also connected to a "bus switch" isolation switch. Unfortunately the bus is behaving weirdly. It seems to have large capacitance, and my microcontroller seems unable to drive the clock signal low.

If this were on a breadboard I could simply remove components until it worked, and if it was a collection of components connected in series I could look at the signals between components to find where they go weird.

But unfortunately I can't modify the circuit (without a lot of effort anyway), and the components are all connected to the same bus.

Does anyone know of any clever ways of debugging this situation? Or would you resort to removing SMD components?

(By the way, this is one of the things I always hated about electronics - the implicit relationships between everything make it really hard to debug!)


texts: Looking for a *fun* way to introduce basic electronics to my kids

texts:
We recently came across this video:

http://blog.makezine.com/archive/2011/04/the-awesome-button.html

and both my six year old and 13 year old thought it was pretty cool.  I am a computer programmer, but never did much with electronics, so I am looking for some suggestions on how to introduce electronics to myself and my kids in a fun lab/project oriented way.

Its a little challenging b/c of the age gap between my kids, but I'm ok if the younger doesn't understand everything.  As long as he can participate in the lab and be involved in what we are doing, he will pick things up along the way.  Likewise, I wouldn't want something so simple that my older son is bored.

A few preferences:

I would prefer to stay away from robotics initially, maybe we can graduate to that, but I am looking for something not quite as involved.
I would prefer that we can bring a programming component into the mix relatively soon, like in the example I linked to above, but that's not a requirement.  That also is something we can graduate into.
I would prefer not to shell out a whole lot of money initially.  Maybe a couple hundred dollars at most, but hopefully less.
I'm ok with learning stuff from a book or videos but my main goal is to give us projects to work on together.  This is mostly about trying to find something to do with Dad time that is fun for us all, learning electronics is kind of a bonus.  The labs or projects are my focus.

So, can you suggest books, kits, websites, or other resources that would facilitate what I have outlined above?

update

@AndrejaKo: I know basically nothing about electronics.  I understand that it involves things like resistors and logic gates, etc. but as to what those things are and how they are used, I know nothing.

I have a multi-meter I bought at Lowes, but that is about it.  If I have to spend the money to get some basic tools & components, thats ok.  I just want to keep the cost down until I found out if this is really something they we are interested in doing together or if its going to die after a few projects.

solution

I began trying to put together an order for the electronic components for the All About Electronics experiments section as well as the first chapter of Make: Electronics.  I had a couple hours into it, wasn't sure I was ordering the right components, and was somewhat discouraged when I happened across a blog that is walking through the Make: Electronics book that mentioned MakerShed's component packs for the Make: Electronics book.  That sealed the deal for me!  I went ahead and ordered the first component pack and the book (which was only $10 if you buy the component pack).

We are going to start out with this book.  If we make it past chapter two, I will go ahead and order the second component pack.  The price has to beat RadioShack and even if its more expensive than ordering the components individually, I'm way sold on the time its saving me.


texts: How these two diodes used in the ciruit protect from the voltage spikes?

texts:
I'm playing around with a simple DIY project, and after about three days of googling and reading stuff I still can't wrap my brain around two Schottkys below:

From the project page:

  The two Schottky barrier diodes act as clamps ensuring that the spikes
  generated by the coil do not exceed the working limits of the PIC
  processor.

I found a few articles on the internet in which diodes are shown connected like this. For example, there's a good one (Protecting Inputs in Digital Electronics) on DigiKey:

In my case the voltage on cathode normally never goes below zero. The spikes produced by the coil are (way) above zero volts too. (Though, I cannot prove nor deny the last statement as I don't have access to an oscilloscope.) So the diode should always be reverse biased.

The only way I can think the diode would be useful here is when the breakdown voltage is reached (which is around 30 volts for 1N5819) effectively shorting the coil to GND. And since the coil discharges quickly, the spikes are non-repetitive and will not cause damage to the diode, provided the current is small (R2 and R4 keep it down to 32 milliamps tops, if my calculations are correct).

In another project which is just a port of the original one, 1N4001 is used, which has a slightly higher breakdown voltage of 50 volts compared to Schottky.

Just before I was about to post my question, I was reading about breakdown voltage and happened upon information about avalanche diodes (the article Diode on Wikipedia):

  At very large reverse bias, beyond the peak inverse voltage or PIV, a
  process called reverse breakdown occurs that causes a large increase
  in current (i.e., a large number of electrons and holes are created
  at, and move away from the p–n junction) that usually damages the
  device permanently. The avalanche diode is deliberately designed for
  use in that manner.

So my questions are:

Can both diodes be used interchangeably in this particular project?
What are they used for in the circuit?
It seems that those are not avalanche diodes. Can these diodes still be used instead of avalanche diodes as long as the spikes duration is short and their current is small?
From the DigiKey article: An important aspect of microcontroller inputs (and the vast majority of any logic ICs) that was left out of the simple model shown in Figure 3 is that they have internal protection diodes that are used to protect the inputs, as shown in Figure 5. These normally forward bias at 0.7 V. According to the datasheets, both PIC12F683 and ATtiny25/ATtiny45/ATtiny85 have protection diodes to both VDD and VSS. Can we make do with just internal diodes then?
PIC datasheet in section 8.2 warns: A simplified circuit for an analog input is shown in Figure 8-3. Since the analog input pins share their connection  with a digital input, they have reverse biased ESD protection diodes to VDD and VSS. The analog input, therefore, must be between VSS and VDD. If the input voltage deviates from this range by more than 0.6V in either direction, one of the diodes is forward biased and a latch-up may occur. Will D1, D2 help to prevent a latch-up from occurring? I suspect that internal diodes would end up forward biased way sooner than D1, D2 breakdown voltage is reached and they kick in.

I would appreciate any input.


texts: IAR EWARM project doesn't run with STM32 startup file

texts:
I'm attempting to test out some basic programs on an STM32L151RD (Cortex-M3) using IAR's Embedded Workbench. I'm using an ST-LINK/V2 programmer. I've downloaded the Standard Peripherals Library and generally have been able to get it working, with one exception. For some reason, if I use the provided startup file "startup_stm32l1xx_hd.s" the MCU just hangs when I load the program, and I end up having to use the ST-LINK Utility software to reset the MCU.

At first I thought the solution was to just not use the startup file, figuring that IAR must've included it (or something equivalent) automatically elsewhere since it compiles, loads, and runs just fine without it. That was fine until I needed to use an interrupt handler for a simple SysTick program, and of course since all of the interrupt handlers are supposed to be defined in the startup file (as I understand it), SysTick doesn't work.

Just to clarify, by "include" the startup file, I just added it to the project source like I would a .c file. If there's some other project setting I need to point to the startup file, I haven't found it.

I've looked over the list of all the files I need to include and compared against the template project, so far as I can tell I'm doing everything right. Does anyone have any input on what the problem might be?


texts: Using a envelope detector to demodulate low voltage signal

texts:
I am currently working on a project in which I have a modulated RF signal at a carrier frequency of 400kHz. The signal itself is fairly low voltage, and I need to extract it from the RF carrier. I was thinking about doing it using a simple diode + RC circuit envelope detector such as this one from here:

The problem with my current approach is that my diode's turn-on voltage is about .63V, but my signal is about 300mV p-p. Is there a simple way for me to DC-bias my signal to about ~600mV? That being said, is it wise to use an envelope-detector like to one I'm currently using for a low-noise application? If so, are there any other good alternatives you know of that would do well at demodulating?


texts: Why does input buffering improve differential amplifier performance?

texts: An instrumentation amplifier's inputs are buffered and many times even amplified and buffered to to its inputs. Why is that so and how do they know how much the signal should be amplified? Couldn't find an "easy" explanation.


texts: How do parallel resistors and capacitors reduces frequency peaking in opamps?

texts:
I'm trying to understand a schematic from the front end of an analog discovery scope. It uses an AD8066 opamp, and has a resistor and capacitor in parallel on the inverting and non-inverting terminals.

These are supposed to reduce the gain spikes at increased frequencies at unity gain.

We can see here at gain=1, the higher frequencies start to spike:

Here is the part of the schematic that says the resistors and caps help reduce this. (5k and 100pf on +, and 10K 150pf on -):

I'm just trying to understand the theory on how it works, and how the values of the resistors and capacitors are chosen.


texts: DFSDM Analog Watchdog does not trigger break for TIM1

texts:
TL;DR
TIM1 break works from BKIN but not from DFSDM analog watchdog

I have timer TIM1 running a PWM output and use a button connected to PE15. PE15 is setup as alternate function 1 i.e. TIM1_BKIN.
When pressing the button I can see that break interrupt flag is set in TIM1->SR register (BIF). The master output enable (MOE) gets disabled and the PWM output on TIM1 turns off. All good.
Now I want to achieve the same with the DFSDM (Digital Filter for Sigma-Delta Modulator) analog watchdog. From Figure 387. Break and Break2 circuitry overview in the st.com stm32h750vbt reference manual RM0433 Rev 7, I can see that both BKIN and DFSDM break goes into the same OR gate. I have highlighted the BKIN with red and DFSDM with green.

Since the BKIN button works I assume my problem is in the green part and backwards. In the TIM1->AF1 register I have enabled BKDF1BK0E which is the dfsdm1_break[0] enable.
To enable the break to trigger from DFSDM analog watchdog I have set Break signal assignment to analog watchdog high threshold event, BKAWH, to 1 for dfsdm_break[0]. However due to the change:

Section 24: Advanced-control timers (TIM1) Updated procedure in
Section : External clock source mode 1, Section 24.3.7: Input capture
mode, Section 24.3.8: PWM input mode and Section 24.3.20: One-pulse
mode. Updated Section 24.3.16: Using the break function, including
Figure 191: Break and Break2 circuitry overview

The previous revision of the document (rev 6) had different break connections, so I have also tried to set BKAWH to 0xf.
I have a current sensor connected to the DFSDM, and I can successfully trigger the DFSDM analog watchdog high threshold flag AWHTF in DFSDM_FLT3AWSR with a lab power supply. I can also clear it with the CLRAWHTF register. But the BIF flag in TIM1->SR is never triggered.
I also managed to disable MOE within an interrupt triggered from IRQ_DFSDM1_FLT3 that checked if the AWHTF flag was set.
Microprocessor is st.com stm32h750vbt
Update 1: If I toggle BKINE in TIM1->AF1 from 1 to 0. The BIF flag in TIM1->SR goes high. However it does not change with AWHTF status.


texts: Measuring Current in Coax Cable Using Clamp on Current Probe

texts:
I once again find myself needing to measure the RF current in a coaxial cable.
The signal in question is a high power (100W-1kW range) signal which is a stepped waveform with a 5MHz fundemental with multiple harmonics (the 7th harmonic is highest of any interest). I have to hand an active oscilloscope current probe of the clamp-on style (specifically Keysight N2893A) which has sufficient bandwidth to do the job. The question is one of building some form of adapter to connect the probe and coax cable.
I did wonder whether the probe could simply be clamped around the coax cable directly, however I'm not sure this will work - AFAIK the magnetic fields of current flowing through the sheild and central conductor should cancel out (?).
In the past I have used an adapter we built which is nothing more than two BNC connectors attached to a metal box (connects the sheilds), and a length of single core wire connecting the signal lines which the clamp can then attach to (pictured below).

Unfortunately I don't currently have access to this adapter, so I am going to need to build a new one.
I can probably cobble together something similar to the previous adapter with bits to hand, but I was wondering if there is any standard or common approach to doing this, or whether the DIY adapter we made previously is the best way to go.


texts: VHDL Compile Error saying "Type of VARIABLE is incompatible with

texts:
I am pretty new to the world of VHDL programming.

In a simple code, I am trying to make a simple BCD adder.

I assigned/declared variable as following

Port ( dipSW : in  unsigned (7 downto 0); ......

signal n1 : unsigned(3 downto 0);
signal n2 : unsigned(3 downto 0);
signal sum : integer range 0 to 31;

Inside the Archetecutre(not in Process), I tried to compile following code

n1 <= 9 when num1 > 9 else num1;
n2 <= 9 when num2 > 9 else num2;
sum <= n1 + n2;

However, I get following error

Type of n1 is incompatible with type of 9.
Type of n2 is incompatible with type of 9
type of sum is incompatible with type of +

Can someone tell me what I am doing wrong?


texts: I have a device (a Raspberry Pi) with the voltage regulator SE8117T33 for 3.3V. From the datasheet it says that the dropout voltage is 1.1V, so the minimum input voltage should be 4.4V, right? I'm a beginner in electronics so I just want to figure out what variables are considered to calculate the ideal input voltage for a voltage regulator. In a tutorial I have the input voltage between 4.75V and 5.25V and I want to understand where these values came from.


texts: Simplest/Cheapest Way to Create 4.5A Test-Load for 12Vdc Step-Down Regulator

texts:
I'm looking for the simplest/cheapest (but safe!) way to build a 4.5A test-load for an LMR14050-based 24Vdc to 12Vdc/5A step-down voltage regulator circuit.

LMR14050 Datasheet

Circuit Schematics

Thanks!

Edit (30.7.18): I commented on the responses below, but it seems my follow-up questions may be rather hidden in all the text, so I figured I'd enter them here to:

As it's a bit hard for me to find the suggested bulbs, I thought of hooking-up 9 of these alternative 5W bulbs from eBay in series to give me more or less the power draw I'm after - Would these bulbs work for the intended purpose?

Also, what would be the recommended capacitor value for each bulb?

Edit (31.7.18):

So apparently the bulbs I found aren't suitable - does anyone know where I can order the correct bulbs (i.e. each drawing 500mA more or less at 12Vdc) online?


texts: Can you use an opto-coupler to isolate the incoming supply from the output

texts: I would like to breakout the 5v and 12v outputs from my PC's psu. This is because of convience and accessibility. Would it be possible to use an optocoupler to isolate the supply coming from the psu? so that in the event of a dead short, it won't cause my pc to reset itself. Am only asking for a minimum 1A output for both rails. Ideally


texts: DC-DC Boost Converter 12V .5A Output, 3.6V, 2A input

texts:
This is an update to a previous post about a circuit for a 6W LED. I've decided to add a boost converter in order to be able to power the LED. I used TI's SwitcherPro Design tool and based it off TPS61087. I can't seem to get it working since the circuit isn't completed but I'm worried that the 2A in won't be enough for the circuit.
Here is the circuit design so far:
Circuit
and the data sheet for the circuit.

Edit:
Now I'm having trouble implementing the boost converter into the circuit...where should the booster be put into the original circuit, right after the battery or right before the LED?


texts:
So I'm going through my textbook and I'm stuck on this problem:

Design a circuit that has two inputs, \$clk\$ and \$X\$, and produces one output \$O\$.

\$X\$ may change every clock cycle, and the change happens at the falling edge.
The circuit samples the input at every rising edge of the clock.
If the input is \$1\$, consider as read a \$1\$, else read a \$0\$. \$O\$ is \$1\$ (for one clock cycle, from positive edge to positive edge) if the last three bits read are \$110\$, with \$0\$ as the most recent bit.

Draw the state diagram. Close to an arc, show \$X=1\$ or \$X=0\$ to indicate whether the change of state happens when \$X=1\$ or when \$X=0\$.

How would one approach this problem?


texts:
I made this exercise but I'm not sure if I made it well.

q=(a+b'c)c'+a'b+ac
q=ac'+b'c*c'+a'b+ac
q=ac'+a'b+ac
q=a(c'+c) +a'b
q=a+a'b
q=1

Is there someone who can explain if I made it well? I have a little problem to apply boolean rules.

----------------------------------------------- I think that I find the correct solution.
(x1) +x'y
=xy+xy'+x'y
=xyxy+xy'+x'y
=x(y+y') +y(x+x')
 so in my case it had to be q=a+b


texts:
Just bought some passive waterproof speakers to be ceiling mounted in the bathroom. They're 80 watt, 8ohm, pretty bog standard. The problem is this - when we have e.g. an iPod plugged into a cheap Bluetooth speaker via a 3.5mm audio cable, it produces an acceptable volume. However, when we connect the wires for the bathroom speakers into a headphone jack and plug this into the iPod, it is considerably quieter, not really loud enough at all.

The speakers certainly have enough power, so is there something else causing the issue here? Could e.g. the Bluetooth speaker have an inbuilt amp, hence why that is loud enough? The speakers were only cheap, so we don't want to go spending loads on an amp - plus there's the issue that if we needed an active amp, that would mean messing about with batteries/power cables in the attic, which is a lot of hassle. Are we just best to return them or is there a simple solution here?

We'd want to be able to play the speakers from a 3.5mm jack so that we could connect it to phones/iPods etc. Any help/advice much appreciated, thanks.


texts:
I am trying to transmit data from one Microcontroller (ATMega8A default clock frequency) to another Microcontroller (ATMega16 16MHz-crystal).

I have setup ATMega16 as master with

DDRB |= (1 << DDB7) | (1 << DDB5); //Set MOSI, SCK as Output
SPCR |= (1 << SPE) | (1 << MSTR) | (1<<SPIE) | (1 << SPR0);//Enable SPI, Set as Master

I have a receive function

 unsigned char ReceiveData(unsigned char Data)
 {
     SPDR = Data;
     while(!(SPSR & (1<<SPIF) ));
     return(SPDR);
}

The SS' pin of ATMega8A (slave) is connected to PB3 and in the main loop I have

for(;;)
{
    PORTB &= ~(1<<PB3); //clear SS' of slave
    Data = ReceiveData(0x05); //sending dummy 0x08 to slave;
    if(Data == 0x08)
        //TOGGLE(SOME_PORT,SOMEPINWITHLED); toggle #defined
    _delay_ms(200);
    PORTB |= (1<<PB3);
}

In the slave device I have

int main() // slave main module
{
     DDRB |= (1<<DDB4); //MISO as OUTPUT
     SPCR |= (1<<SPE); //Enable SPI
     DDRB |= (1<<DDB0);
     char Data = 2, SendValue = 8;
     for(;;)
     {
          TOGGLE(PORTB,PB0); // #define'd TOGGLE(A,B) A ^= (1<<B);

          Data = SendData(SendValue); // exact same as ReceiveData() on master.
     }
     return 0;
}

The led doesn't toggle at the master module but does at the slave module. Could you suggest me what have I done wrong here. May be the master and slave are not synchronized.

Should I check `while(!(SPSR & (1 &lt&ltSPIF) ));` on the slave or `SPDR = Data; return (SPDR);` is sufficient on the slave.
 How does the master know when the slave is sending data? So, when should maser check `while(!(SPSR & (1 &lt&ltSPIF) ));`?

P.S: In the future I plan to use multiple slaves and a single master.

Edit : I corrected from DDRB |= (1 << DDB3) | (1 << DDB5);


texts:
There is "ferrite foil" available on the market, often with self-adhesive layer on one side.
What are typical use cases for this foil? How and where it is applied? I was surprised not to find anything clear in the internet.


texts: Adding third channel to the PIC32 starter kit `DMA chaining and PWM´ example

texts:
I just received my PIC32 starter kit, and played with the demos. I have never used any higher-end uCs than the 8-bit PICs.

One of the new things to me in the PIC32 is DMA. The starter kit came with demo that uses chained DMA transfers to control the pwms and dim two of the leds.

I tried to experiment adding the third led to the chain, but it didn't work out. I believe it is because I don't know how to chain the three DMA channels.

Basically I am trying to get a chain: DMACh0 -> DMACh1 -> DMAch2 -> DMACh0 -> ...

Here is one of the modified versions (Some stock comments and config cut out to get it smaller):

const unsigned short pwm_duty_cycles[] = {...};
#define ARRAY_SIZE                      (sizeof(pwm_duty_cycles))
#define DMA0                            (0)
#define DMA1                            (1)
#define DMA2                            (2) // Added this line

unsigned char srcSize = ARRAY_SIZE;
unsigned char cellSize = 2;
unsigned int dstSize = 2;

unsigned short* volatile pDma_0_Dst = (void*) &OC1RS;
unsigned short* volatile pDma_1_Dst = (void*) &OC2RS;
unsigned short* volatile pDma_2_Dst = (void*) &OC3RS;     // Also added this
const unsigned short* pDmaSrc = pwm_duty_cycles;

#define SYS_FREQ            (80000000)
#define PWM_PERIOD          (25000)

//  pwm_dma application code
int main(void)
{
    SYSTEMConfig(SYS_FREQ, SYS_CFG_WAIT_STATES | SYS_CFG_PCACHE);

    DmaChnOpen(DMA0, 0, DMA_OPEN_CHAIN_LOW);
    DmaChnOpen(DMA1, 0, DMA_OPEN_CHAIN_HI);
    DmaChnOpen(DMA2, 0, DMA_OPEN_CHAIN_HI);   // Added this line, I'm not sure how to set up the
                                              // chaining. What should be LOW and what should be HIGH

    DmaChnSetEventControl(DMA0, DMA_EV_START_IRQ(_TIMER_4_IRQ));
    DmaChnSetEventControl(DMA1, DMA_EV_START_IRQ(_TIMER_4_IRQ));
    DmaChnSetEventControl(DMA1, DMA_EV_START_IRQ(_TIMER_4_IRQ));   // Added

    DmaChnSetTxfer(DMA0, pDmaSrc, pDma_0_Dst, srcSize, dstSize, cellSize);
    DmaChnSetTxfer(DMA1, pDmaSrc, pDma_1_Dst, srcSize, dstSize, cellSize);
    DmaChnSetTxfer(DMA2, pDmaSrc, pDma_2_Dst, srcSize, dstSize, cellSize); // Added

    OpenOC1(OC_ON | OC_TIMER_MODE16 | OC_TIMER3_SRC | OC_PWM_FAULT_PIN_DISABLE, 0,0);
    OpenOC2(OC_ON | OC_TIMER_MODE16 | OC_TIMER3_SRC | OC_PWM_FAULT_PIN_DISABLE, 0,0);
    OpenOC3(OC_ON | OC_TIMER_MODE16 | OC_TIMER3_SRC | OC_PWM_FAULT_PIN_DISABLE, 0,0); // Added
    OpenTimer3(T3_ON | T3_PS_1_64, PWM_PERIOD);
    OpenTimer4(T4_ON | T4_PS_1_256, 100000);

    DmaChnEnable(DMA0);

    while(1);
}

I think the problem is with setting DMA_OPEN_CHAIN_LOWs and DMA_OPEN_CHAIN_HIs. I assume these HI and LOW mean the channel priorities. These only allow me to specify the next channel with either higher or lower priority. How can I make it jump over a channel (ch2 -> ch0)?

I am using Mplab C32 v2.02. This brings up memories, trying to modify the examples to get one more led blink :)


texts: Limiting resistor for zener voltage regulator driven by transistor

texts:
I have this circuit:

simulate this circuit – Schematic created using CircuitLab

And I would like to understand why I need a limiting resistor for the current flowing through D1. I know the theory is quite clear, Ohm law tells me that if I don't have any resistance, the current will be infinite.
But in this case I can limit the current by controlling the base current of Q1. I did some experiments at home, I did the calculations, I built the circuit on my breadboard and actually the current flowing through D1 was the expected (13mA in my case) without installing any resistor.

So, what am I missing? Do I need a limiting resistor? I am asking this because people keep telling me I definitely need one, and I don't understand why.


texts: Input impedances in CB and CE transistor circuits

texts:
Considering the input signal being placed across the Emitter-Base junction directly in both circuits(Common base and Common emitter), and considering this junction similar to a normal forward biased diode, doesn’t that imply, according to Shockley’s equation, that the current in the diode should be the same regardless of any connection? Trying this circuit on Proteus gives me different results though:

So why is this different in the case of a transistor than a normal pn- junction?


texts: Soft i2c with Sensirion SHT21 sensors on Arduino Mega

texts:
I have tried checking with an oscilloscope on the analogue pins when the sensor is plugged in and I don't seem to get anything as I normally would.

The hardware i2c channel works just fine on the mega, its the soft ones I am trying to use that don't seem to work

#include <Wire.h>
#include <Ports.h>
#include <PortsSHT21.h>
#include <SHT2x.h>

//Define soft i2c channels for 3 sensors
  SHT21 hsensor2 (2); // pins A1 and D5 - Sensor 2
  SHT21 hsensor3 (3); // pins A2 and D6 - Sensor 3
  SHT21 hsensor4 (4); // pins A3 and D7 - Sensor 4

//define variables for temp data
  float h, t;

void setup()
{
    Wire.begin();
   Serial.begin(9600);
}

void loop()
{
   // Get data from first sensor hard I2C channel
    float hum1 = (SHT2x.GetHumidity());
    float temp1 = (SHT2x.GetTemperature());
    Serial.println("temp1");
    Serial.println(temp1);

  // Get data from second sensor soft I2C
  hsensor2.measure(SHT21::HUMI);
  hsensor2.measure(SHT21::TEMP);
  hsensor2.calculate(h, t);
    float hum2 = (h);
    float temp2 = (t);
    Serial.println("temp2");
    Serial.println(temp2);

   // Get data from third sensor soft I2C
  hsensor3.measure(SHT21::HUMI);
  hsensor3.measure(SHT21::TEMP);
  hsensor3.calculate(h, t);
    float hum3 = (h);
    float temp3 = (t);
    Serial.println("temp3");
    Serial.println(temp3);

 // Get data from fourth sensor soft I2C
  hsensor4.measure(SHT21::HUMI);
  hsensor4.measure(SHT21::TEMP);
  hsensor4.calculate(h, t);
    float hum4 = (h);
    float temp4 = (t);
    Serial.println("temp4");
    Serial.println(temp4);
    Serial.println("");
    Serial.println("");
    delay(500);
}


texts: Allowing the energy flow INTO the solar panel (photovoltaic), what happens?

texts:
I was watching this video https://www.youtube.com/watch?v=HZf-sm3UXX0&feature=youtu.be&t=3m4s as I was willing to learn how to test my solar array, from 3m4s he's testing the Amps provided by the solar panel simply by using the multimeter and WITHOUT any kind of external load. If I would have a simple battery connected this way it will most likely blow up or experience really high temperatures on the battery case.

Well ... this means that the current is wasted inside the solar panel ? That amperage is converted in heat inside the solar panel ? If the power wasn't used at all then the multimeter won't show a flow of amps.

If YES, this means that I can thaw my solar panels in the winter if I provide them with power ? For example after a snowy day could I just provide power to solar panels in order to clean them up of snow and ice ?

Thanks!


texts:
I want to translate or shift 1.8V to about 2.5V. Now, there are 2 ways I can go about with it. Use an op-amp based circuit as shown below -

Mosfet circuitry -

Which is more efficient and why ?
In one of my posts(Link) one of the contributors stated  - "The only real downside is a semi decent driver is required, a weak one won't cut it." for the MOSFET circuit. Why so ?


texts: Is this way of measuring scope's minimum measurement capability correct?

texts:
In general Vertical sensitivity of the oscilloscopes are in 2mV to 10V/div range.

Neglecting the noise contributions, if the scope has an 8-bit resolution and if I set the vertical sensitivity to 2mV as shown below how can I calculate the minimum voltage the scope can measure or show on screen?

Is this calculation correct:

There are 10 vertical squares so,

2mV × 10 = 20mV

Min dynamic voltage = 20mV/2^8 = 78.125mV ??


texts: Is isolation required for MOSfet gate driver's and microprocessor's power supply?

texts:
I have designed a 62W , 24V-5V buck converter operating at 250KHz.

I am using TI's UCC27200A gate driver and Infineon's Optimos 4.

The problem is that the driver doesn't have any kind of isolation inside it. So any transient jitter on the buck converter's ground could potentially couple its way back to the microcontroller through the driver IC killing both in the process.

I thought of using RECOM's isolated power supplies for powering the driver and the microcontroller.

Would this serve the purpose or should I consider using an opamp voltage follower or consider replacing the gate driver IC altogether?


texts: Can somebody explain how this circuit works?

texts:
I have the following circuit implemented in the control of a thyristor. I know the basic functionality of the circuit, but i need a complete description of every component.

Thank you!


texts: What is the coolest way (using passive cooling only) to step 12V DC down to 5V DC

texts: I'm building a project that needs both 5V and 12V rails which will draw about 1A on the 12V and 0.5A on the 5V. I was thinking of using a 7805 to produce the required 5V but this could generate some significant heat. I am not so much asking if it is acceptable to use a 7805 (I just need a mini heatsink), but rather: are there any ways of doing it cooler? Any tips would be great.


texts:
Possible Duplicate:
  Limiting current from a 5v power supply

I'm trying to build a DIY Xbox Kinect adapter to be able to plug the Kinect into my computer, but I'm getting some shaky information. From what I've seen, the official Kinect adapter (for using the Kinect with an non-slim Xbox 360) outputs 1.08A @ 12V. I've got a power supply that outputs 12V @ 3A and I need to know whether using this will damage the Kinect.

My understanding is that a circuit will only draw as much current as is required for it to operate. For example, I can connect an LED that requires 20mA @ 3.3V, in series with an 85 ohm resistor, to a wall-wort power supply that outputs 850mA @ 5V. Computer PSUs generally have a 12V rail with as high as 50A. I could plug a hard drive into one of those rails (as the only load on that rail) and nothing bad happens, and I guarantee that the HDD isn't drawing 50A.

At any rate, am I correct in assuming that using a power supply rated for a higher current won't damage the circuit, as the circuit will only pull as much as it needs?


texts:
what is loading error in op amp?
I have a voltage regulator with zener diode and op amp.
why do voltage is low in lower loads for example 100 ohm but for higher loads is not it?


texts:
I am trying to create an op-amp amplifier that would work from single 5V supply, and would be able to amplify -100mV to +100mV audio signal to around a 1V peak-peak or so. I've came across this circuit from this article, that could seem to work, but am having trouble calculating the actual values:

simulate this circuit – Schematic created using CircuitLab

From the article I read that R1 and R2 should both be the same and around 42kOhm for 5V power supply. R4 should be R3+(0.5*R1) and thats about it...

So how would I go about actually calculating the capacitor, resistor values needed for a varying frequency signal with maximum frequency at around 20kHz and gain of about 5?

Thank you for helping me!

EDIT:

In the article the author wrote by the ground symbol: "*STAR GROUND". Is it really imporant that I combine all ground trances in the schematic to one point, or can I use a ground plane across the whole circuit?


texts:
i am trying to get a 3x3 matrix with multiplexing up and running. here is my setup:

i have connected each rows cathodes and each columns anodes and connected that one to pins 0,1,2 resp. 8,9,10

the only thing i can get to light is the lowest row, but if i want to light the middle row for example with this:

digitalWrite(8, HIGH);
digitalWrite(9, HIGH);
digitalWrite(10, HIGH);

digitalWrite(0, HIGH);
digitalWrite(1, LOW);
digitalWrite(2, HIGH);

nothing happens.

is my wiring setup wrong maybe?


texts: Active serial configuration flash (EPCS & EPCQ) vs normal SPI flash

texts: Is there a difference between the serial configuration devices from Altera and any other SPI flash memories? I see Terasic uses S25FL256S in their development board instead of EPCQ256, so I wondered how the Quartus II will confirm the device?


texts: Trying to measure start current of a DC motor

texts:
I have an 12V DV electric winch I am attempting to power with a power supply. I am only pulling about 150 lbs and I want to know what the...

Start up current
Running current

The winch starts and pulls the load with a 15A power supply but I was told that the starting current is likely higher than 15A and that I should use a power supply that can supply the start up current otherwise I run the risk of my power supply failing.

I have a DMM but it is only rated at 10A.

I was told to use a DC shunt resistor and test the voltage but I don't know which size to get. Do I get a 10A? 40A? 100A? I was told if it's too low I'll blow it but if it's too high I won't get an accurate reading.

So my questions...

If the winch runs on 15A is that good enough?
If no, then how do I measure the start up current?