texts: Amplify difference between two photodiodes

texts:
I have two adjacent photodiodes in photovoltaic mode, with two transimpedance amplifiers. Unfortunately, my MCU (nRF52840) is one meter away, and I expect a fair amount of noise to enter the system. For my application, the only relevant data is the difference in luminosity between these photodiodes.
It seems the right solution would be to perform true differential signaling for each photodiode, but I can't do it in my case for very specific reasons.
By routing each signal next to each other, I hope that most of the noise would affect both signals roughly equally. My goal is to reject common-mode noise, interference, and maximize the dynamic range at the MCU location.
I am considering the following solutions:

directly route each signal to the nRF52840 ADC in differential mode
use a differential opamp and use the nRF52840 ADC in single-ended mode
use a fully differential amplifier to drive the nRF52840 ADC in differential mode

The first solution would be simple, but I am not sure to get enough dynamic range. I am not familiar with fully differential amplifiers and I am not sure about their usage with non single ended signals.
What solution would be the most appropriate? Can you think of a better alternative?


texts: What's a simpler way to switch between power sources?

texts:
I want to make a device that allows the user to switch between two different power sources (a wall mount and batteries).

I could perform this circuit using two DPDT switches, but I would need to switch the two switches each time I want to change sources. Is there a simpler way to perform this function without using relays?

Here's a schematic of my device as a reference:


texts: Parallel two TPS2115A to get a higher current output

texts:
Can i parallel two TPS2115A devices to get higher current output.
A single TPS2115A power mux can only switch 2A max load. My requirement is to switch 3A load.

As per the datasheet, the device has a REVERSE-CONDUCTIONBLOCKING mode. Will it prevent current OUT form one device getting in to other output.


texts: How can I enable a LDO using the I2C SCL signal

texts:
Can I enable/disable an LDO (more specifically NCV8163AMX280TBG) by using the I2C SCL signal?
This would allow me to turn ON the regulator once a master starts the I2C protocol and turn it off once the master stops communicating via I2C.

If possible, what extra components do I need (caps & diodes probably)?

Any help is appreciated.

PS: The I2C configuration is 1 master to N slaves.

PPS: the regulator turns on at 1.2V and the circuit will be powered from 3.3V

Details:
This will be an array of small sensors and actuators built around STM8L001. There will be one STM8L001 for each sensor and actuator. There is a contraint on cost and the number of wires. Currently I have 2 wires for power + 2 wires for communication.
When the master wakes up it needs a way to wake up the slaves as well.

I currently see the below options to enable this behaviour:

1 extra wire to drive the ENABLE pin on the LDO from the master (master wakes up, starts i2c, enables the GPIO that starts all the LDOs on the slaves)
using MOSFETs to power up/down the entire power rail
using the SCL signal to signal the ENABLE pin on the LDO

The sexiest option is the last one as it is the cheapest.

The below schematic is for the slave. As you can see it is a minimal design using STM8L001 with the ENABLE pin directly on the power rail.


texts:
I'm trying to read an analog value using the ADC of a ATSAM4E microcontroller. The problem i have is that it always reads 2047 or 2046 when the pin is connected to GND and 4096 when connected to VCC. I don't have it configured in differential mode.

Here is the code for it:

void adc_init(void){
    struct afec_config afec_cfg;
    afec_enable(AFEC0);
    afec_get_config_defaults(&afec_cfg);
    afec_init(AFEC0, &afec_cfg);
    afec_set_trigger(AFEC0, AFEC_TRIG_SW);
    afec_channel_enable(AFEC0, AFEC_CHANNEL_0);
}

//every 100ms
printf("CHANNEL 0: %d\r\n\n", afec_channel_get_value(AFEC0, AFEC_CHANNEL_0));
afec_start_software_conversion(AFEC0);

I don't know what the problem is. The ADC clock is 6MHz, so waiting 100ms between conversions should be sufficient to ensure it is finished.

It is a bit suspicious that the value is always so close to half. Least i got was 1790 but these "smaller" values occur after disconnecting the pin from VCC.

Anyone have any idea what it might be?


texts:
I have a Smart Switch (Sonoff Dual WiFi Wireless Smart Switch), and I control it through a Google Home. It works as a contact, like if it was a switch:

I want to control an electric blind, that has this connections:

The neutral is always connected, and, if you power up "Phase Up" the blind goes up, and if you power up "Phase Down", it goes down.

The endstop is located internally of the blind motor.

I have another switch, for manual control, with 2 buttons, up and down, and when you click one, the other disconnects automatically, so you can't press both at the same time.

Any ideas of how to join the 2 circuits, without being able to power up the 2 Phases of the Motor, and being able to control anytime, from the manual switch, or the wireless switch.

Thank you very much.


texts: Best place for a switch when using an always connected power adapter

texts:
I recently bought this: http://smile.amazon.com/gp/product/B00II1MN5I and am planning on using it for under cabinet lighting in the kitchen.

Power adapter:
Model: TNS-1220
Input: 100-240V AC, 50/60Hz
Output: 12V DC, 2000mA

I want to keep it plugged in all the time and control it via some sort of switch/button to turn off/on. If the power adapter is always plugged in, would it consume electricity (it has an LED that lights up when plugged in). If so, would it be negligible?

Basically I want to know if I should:

[outlet] -> [power adapter] -> [control switch] -> [LEDs]

or

[outlet] -> [control switch] -> [power adapter] -> [LEDs]


texts: Measure power usage of battery powered device

texts:
I'm a software engineer by trade so I'm a bit at a loss. Maybe I don't know the correct words to find what I'm looking for.

I have a Bluetooth Low Energy remote control powered by two AAA batteries. I want to monitor the power usage for the device. I understand how I can put a multimeter between the batteries and the device and measure actual power usage, in milliampere, but I'm more interested in how much power it uses over a span of time. Note that the power usage patterns differ between pairing, standby, when sending a key, etc, which is why I'm much more interested in total power used instead of only the draw at ONE moment in time.

Basically I'm envisioning something like an ampere-counter (electron-counter), instead of an ampere-meter. Which would mean that you read out on the end of the day: 20 mAh used. Does something like this exist?


texts:
I am looking for connecters to connect two PCB boards together for prototyping. Can anyone recommend any models in particular.

Features I am looking for are decent price available from some where like Farnell or RS Components in Australia
3 wire mainly doesn't need speacilized tools to make the connects standard pin spacing for  prototyping board
Also up to 10+ connections

I have looked my self but there is hundreds of models and it's hard to work out how they make there connects

Anyone recommend any models that they use?


texts: While performing the controlled impedance routing what about the current flowing through it?

texts: While calculating the conductor impedance the parameters that we consider are the conductor width, conductor thickness, frequency & substrate parameters. For achieving the particular impedance based on the material properties we are fixing the trace width. What about the current which depends on trace width ?


texts: What resistor should I put in series with an LDR for minimum current draw when using an Arduino Nano?

texts:
Is it possible to use 10k ohm resistors without having any noise issues?
I plan on making a solar tracker with 4 LDRs in parallel so a low current draw is imperative - so is a low noise distortion.


texts:
I'm working on a project that needs some decor lighting, the lighting need to be able to render objects, so I was thinking of building a 32x16 LED matrix with WS2812B chips, and control it with a Raspberry pi.

But my concern is the response time of the chips. If I connect 512 chips to the bus, the data will be 12kB. And due to the datasheep for the chip, it can transfer 800kbps, with 50μs reset time. So the matrix will have approximately 8 updates per second.

But how long delay will it be between the first and last chip?


texts: When transformer rating is in kVA, why load is mentioned in WATTS?

texts:
The transformer rating is given in kVA, but the load connected is always considered in watts. Why?

Eventhough, the load active power is represented in watts it has some reactive power, right?

Is the total power consumed by load (active + reactive)  equal to the power supplied by the secondary side (secondary voltage × seconadary current) which is apparent?


texts: Measuring AC current: Is true RMS needed for a clamp ammeter?

texts:
I am looking at getting a clamp ammeter for measuring AC and DC currents, but I will be mostly focusing on AC. I'm on a student budget, so cheap = good.

Many devices do not integrate PFC circuits, and so have non-sinusodial current waveforms, tending to draw most current near the peak of the waveform. Will I need a true RMS meter to measure these accurately? Will the crest factor of the RMS conversion be important?


texts:
Above is the problem and my attempt to solve it. I am not able to get any of the options and I also doubt my approach as unit vector(pho) and unit vector(phi) will be changing continuously throughout the curve.

Please help me with the problem and I will really appreciate if you can suggest multiple ways to solve it.


texts: Changing between multiple bands of PID values

texts: I have to control the temperature of an oven from room temperature to around 600degC. To do so I divide the temperature range into multiple bands eg 0-200, 200-400, 400-600 etc. Each range has a set of PID values, since I have discovered by experiment that one set is not sufficiently accurate. The question is whether I use the target temperature to determine the PID values to use, or whether I use the actual temperature to switch between bands as temperature increases. How is it normally done?


texts:
I have a board with a Lattice ICE40 5LP1K FPGA that does some small jobs like handling communication protocol and some IOs.
My problem is that I cannot compile the project as the IceCube tells me

I2709: Tool unable to complete IOPlacement for the design
E2694: PLL: pll_inst.pll_pll_inst could not be placed
E2693: PLL placement is infeasible for the design

I'm using a PLL of type SB_PLL40_2F_CORE

Now if I free up the global buffer G0 PIOT_46B (exclude it from the pin assignment file) everything works fine.
So I assume the PLL requires a global buffer to be placed, but I'm using pin PIOT_46B as a normal LVCMOS IO, does this also occupy the global buffer?
My Clock is on PIOB_3b.

Freeing up any other global buffer pin doesn't solve my problem, it has to be this specific one as it seems.

I further found some information that it would may help to use SB_PLL40_2F_PAD instead of _CORE but that's only supported for clock inputs on bank0 or 2 but mine is placed on bank3.

Is there any solution/explanation for this issue or do I have to change my board routing to be able to free up PIOT_46B?

Edit It appears that only inputs are not supported, if I define PIOT_46B to be an output the design can be synthesized. But so far I don't understand the phenomenon.


texts:
I've this circuit:

simulate this circuit – Schematic created using CircuitLab

I have a doubt, when I press the SW1 the LAMP1 turns on, when I press the SW2 the light turns on but the P channel MOSFET (IPB120P04L-03) is reverse polarized. What damage can it cause? And can it be resolved? Thanks in advance


texts: Creating a one-digit scoreboard using logic circuits

texts:
I'm creating a one-digit scoreboard on a breadboard. Naturally, I have a BCD to 7-segment decoder and a 7-segment display. But I don't know how to automatically increment the display. (It's for a game, you see, and when someone wins, the score should automatically increment). I'm thinking of using a 74293 4-bit binary counter but I'm stumped as to how I input to it. I understand how the output is encoded but not the input. What kind of input (DC/AC, something else entirely?) does it expect? How is it encoded with the two input pins?

BTW, a pinout can be found at http://www.datasheetdir.com/SN74293+Counters .

Thanks to anyone who'll take the bother. (--,)


texts: How many measurements does a typical phasor meqasurement unit (PMU) capture?

texts:
How many phasor measurements (voltage amplitude and phase angle) does a typical PMU capture from 1) transmission and 2) distribution lines? is it one, three, or more? Does this depend on the topology of transmission/distribution grid, and how do they differ?

I would appreciate it if you could explain in details.


texts: Understanding flyback transformer datasheet

texts: Please see the below image of a flyback transformer I found. I see voltage/current outputs at each secondary winding. My question however is, how are these determined? I thought the output levels are dependent on primary voltage, switch frequency, duty cycle... What is the meaning of these ratings? My best guess is these outputs are based on some "typical" application example which is not in the datasheet.


texts: Two modes of electrostatic force with charged capacitors?

texts:
During a charged state of a capacitor (Regardless of the type of capacitor),

Simple parallel plate:

.png

Parallel plate with dielectric material in the gap:

]3

Supercapacitor:

How is the attractive force between the positive and negative charges much stronger than the repulsive forces between them?

When I look at the diagram's above, it seems like there are two forces acting simultaneously, the attractive forces holding the electric field, and the repulsive force between like charges.

When the supercapacitor(for example, but analogues to the rest) discharges, there is a negative ion that is unpaired with a +Q charge, and the repulsive force from the adjacent negative ion causes that unpaird negative ion to float away from the current collector plate to the electrolytic solution.

Every time I look at diagrams of charged capacitors, I can't help but notice two electrostatic forces acting at the same time.


texts: Are FT2232 interfaces completely independent?

texts:
Reading through the FT2232 dual USB UART/FIFO datasheet, it is unclear to me if the two interfaces are completely independent. In other words, can I configure interface A as MPSSE and interface B as a UART ?

The D2XX programmer's guide mentions the FT_ SetBitMode function in order to configure the operating mode of an interface through its handle, but what happens with dual or quad interfaces ICs like the FT2232 and FT4232: do we get multiple handles for a single device (i.e. one for each interface) ?


texts: High Voltage Indicator based on specific threshold value

texts:
I came across an interesting problem in one of the hobby group discussions - Following problem statement describes the design requirement
1) Input voltage range can be anywhere between 0-500 Volts (It is most likely EV battery pack etc.). They needed a prominent indicator, such as a LED that will illuminate whenever a voltage greater than 60V DC is present across the battery pack.
2) The voltage being present at the connectors must directly control the indicator using hard wired electronics (no software control is permitted).
3) The 0-500V is the only power source available (No external supply / battery can be attached.)

There are 2 design directions I could think - 1) based on TVS diode and a series resistor, which activates an LED after and onward 60 V.
2)  Use resistor divider to bring down 0V -> 500V in range of let's say 0 - 5V. I guess even at 500V, if Rdivider value is high as 500K, even a 0.5 W resistor should work.
then use any over-voltage detection circuit  for LV systems such as this
Am I over complicating/ simplifying things here? Critical feedback / suggestions appreciated.


texts: Designing flyback converter - DZ snubber

texts:
In many examples for DZ snubber zener voltage is calculated from maximum MOSFET rating and some arbitrary choosen voltage leakage (usually a percentage of Vin). They don't even use leakage inductance (available in some transformer datasheets).

It seems rather wrong, I would expect it to depend on Lp and Ip somehow. Or maybe, they use something close to maximum FET rating because it indeed provides best performance?


texts:
Has anyone got an example of coating a Lilypad or some other electronics in resin to make them waterproof.

I'm wanting to make something that is really resilient -> Being lazy i want to be able to chuck it in the washing machine...hand washing is far too much effort.


texts: Simple circuit to power a 4HP 180 V DC motor

texts:
Overview

I'm trying to make a cheap simple circuit to power and control the speed of the motor. It's going to drive a pulley and be used as simple woodsaw.

Problems

Running the motor without a resistor makes it lose control going too fast and smelling like burnt even when the dimmer is set to 120V
Running with the resistor makes the resistor smoke

 Ideas

I may need to change the value of the resistor, or change it for something else to control the current, that's my question: What would fix this circuit ?

Schematic


texts: Initial register value in synthesized design is always 0

texts:
I'm using Altera Cyclone IV EP4CE6 as my FPGA.
Compiling the design in Quartus Prime 18.0.0 Lite Edition.

The State register in the below module appears to be 0 initially even if I specify a different default value (I.e. if I set ST_INITIALWAIT to anything but 0 it doesn't work).

I've tried specifying the default value inline with the definition and in an initial block.

Non-zero initial register values work fine in other modules in the same design, so I'm puzzled why it doesn't in this module.

module CamSetup(clk, ready, error, scl, sda);
input clk;
output ready, error;
output scl;
inout sda;

parameter ST_READY = 4'd1;
parameter ST_WRITING = 4'd2;
parameter ST_ENDING = 4'd3;
parameter ST_INTERIM = 4'd4;
parameter ST_INITIALWAIT = 4'd0;

parameter REG_COUNT = 1;

//truncated to save space (actually updates 170 registers)
bit [1:REG_COUNT][0:2][7:0] RegValues = {
    8'h42, 8'h7a, 8'h20
};

parameter CLKS_INIT = 10;
parameter CLKS_INTERIM = 50000;

reg [23:0] InitiCounter = 0;
reg [23:0] InterimCounter = 0;

reg [3:0] State = ST_INITIALWAIT;
reg [7:0] RegIndex  = 0;
reg [2:0] RegByteIndex  = 0;
reg [7:0] WrData = 0;

wire WrDataRq;
wire I2cIdle;
wire Enable = (State == ST_WRITING);
assign ready = (State == ST_READY);

i2c i2c0(.clk(clk), .enable(Enable), .wr_data(WrData), .wr_data_rq(WrDataRq), .idle(I2cIdle), .error(error), .scl(scl), .sda(sda));

always @(posedge clk)
begin

    case(State)

    ST_INITIALWAIT:
    begin
        InitiCounter <= InitiCounter + 1;

        if(InitiCounter >= CLKS_INIT)
        begin
            State <= ST_ENDING;
        end
    end

    ST_ENDING:
    begin
        if(I2cIdle)
        begin
            if(RegIndex < REG_COUNT)
            begin
                RegIndex <= RegIndex + 1;
                RegByteIndex <= 0;
                WrData <= RegValues[RegIndex+1][0];
                State <= ST_INTERIM;
            end
            else
            begin
                State <= ST_READY;
            end
        end
    end

    ST_INTERIM:
    begin
        InterimCounter <= InterimCounter + 1;

        if(InterimCounter >= CLKS_INTERIM)
        begin
            InterimCounter <= 0;
            State <= ST_WRITING;
        end
    end

    ST_WRITING:
    if(WrDataRq)
    begin
        if(RegByteIndex < 2)
        begin
            RegByteIndex <= RegByteIndex + 1;
            WrData <= RegValues[RegIndex][RegByteIndex+1];
        end
        else
        begin
            State <= ST_ENDING;
        end
    end

    endcase

end

endmodule


texts: Determine version of Xilinx ISE programatically

texts: I'm using the Xilinx toolchain and I'd like to automate (with TCL scripts) some things.  While the ISE Suite can be extensively automated via TCL and their TCL shell (xtclsh.exe), there doesn't seem to be any way for me to programatically determine which version of the Xilinx tools are installed so I can know where the shell resides.  I can't just hardcode the path since each version of the tools is installed in a subdirectory that includes the version number.  I run the risk of invalidating all my scripts as soon as I update to the newest version they release.  This same question has come up on the Xilinx forums, apparently to no avail.  Does anyone know a way (some script/batch file/environmental variable) to get the path to the newest version of the Xilinx executable installed programatically?


texts: Do the optical power and energy of LED vary with distance?

texts:
I have an application with LED and It requires a bigger beam .
I could obtain a bigger beam by incresing the distance between LED and surface. But îs there the possibility to decrease the energy delivered ??? Photo attached.


texts:
So I have been having some trouble with my Teensy and I think I have an idea of what it is but I need some help understanding it .

So I have four 12v RGB led strips. Each color pulls close to an amp so I used 12 TIP31C NPN transistors I had. This works but after a minute or so, or less if all the lights are on full, the Teensy will stop responding and even reboot. I noticed it gets very warm as well. As soon as I turn the lights on another LED I have on a digital pin seems to half in brightness.

The way it's wired is that each transistor's emitter is wired to ground, base straight to a PWM pin on a Teensy, and collector to the individual color of the strand.

I believe what's happening is that I am drawing too much current from my Teensy and causing it to overheat and also using too much power to drive the transistors so that the Teensy cant properly run anymore, which causes it to shutdown.

My problem is that I don't know if I need to use MOSFETs instead of the TIP31Cs or if I can use a base resistor between each transistor and the Teensy. I have no idea what value resistor I'd need or any idea what MOSFET I would need if I use that instead. I spent several hours trying to understand the idea behind both calculating a base resistor and also selecting a proper logic level MOSFET but the concepts escape me for both.

The Teensy outputs at 3.3v and each pin is rated for I think a maximum of 20ma. Something that complicates is slightly is that the length of the LED strips will vary a little.


texts:
I am solving this question given in book (Automatic control system). As asked in (a) part \$G_c(s)\$ of the controller. I solved it and getting answer$$G_c(s) = \frac{F(s)}{E_c(s)}=\frac{100}{s}-\frac{30}{s+6}+\frac{70}{s+10}$$ but the answer in manual is $$G_c(s) = \frac{F(s)}{E_c(s)}=s\left(\frac{100}{s}-\frac{30}{s+6}+\frac{70}{s+10}\right)$$
I know laplace transform and i am not too mature in control theory so please help in solving this question.
I want to know from where this \$s\$ in multiplication is coming.


texts:
I recently tested a little wireless device in a chamber to get its radiated output power.  The DUT sat on a pedestal with a ring of antennas all around it.  The antenna is a little pcb slot antenna, that's supposed to have a uniform gain of 2dBi all around it in the X-Y direction.   It sits off to the side of the product with the pcb behind it.

When I look at my X-Y plane measurements for the TX power I see a lot of the energy shifted to the side away from the PCB.  I assume this is either reflected energy or my PCB is changing the performance of the antenna as a whole system, but I'm not sure.

I put in 5dBm of power and after subtracting the loss for free space from the measurements at the antenna ring I got 11dBm on the right side, and 2dBm on the left side (that's blocked by the PCB).  Can I assume if I increase my TX power to 20dBm that my output power will also increase by 15dBm.  So I'd see 17dBm, and 36dBm accordingly?

I'm assuming I can just do all this as addition and subtraction since it's DB but I'm new to wireless and not entirely sure.


texts: Do the unused HDMI connector pins have dedicated conductors within HDMI cables?

texts:
I noticed that several contacts on a typical HDMI connector are listed as unused. I'm curious, does this mean they are unused in typical HDMI communication protocol, or does this mean they are physically unused?

I'm attempting to re-purpose an HDMI connector and cable to send non standard HDMI signals, thus I'm curious if I can actually use the unused pins.

Question: do HDMI cables have conductors for the 'unused' pins?


texts: Say for example an inexpensive solar calculator or other such similar device with what appears to be lets say a single 2.4V 6uA (microwatt) panel?  Is an MPPT used to get the most panel rather than using the panel directly?  Is there another solution for this class of panel?


texts: ESP32 with CCS811: i2cCheckLineState(): invalid state sda(21)=1, scl(22)=1

texts:
I’m having issues with connecting to CCS811 CO2 sensor using Heltec Automation WiFi Kit Masterhawk ESP32. I am using PlatformIO in Arduino mode to build and flash the code.
Here’s what my wiring looks like:

simulate this circuit – Schematic created using CircuitLab
Here's gist for i2c scanner: https://gist.github.com/sgzmd/9a31350816d173f73df095bdde610ba6
When I run this code on MCU with build_flags = -D CORE_DEBUG_LEVEL=5 I get:
[V][esp32-hal-i2c.c:1486] i2cInit(): num=0 sda=21 scl=22 freq=0
[V][esp32-hal-i2c.c:1682] i2cSetFrequency(): freq=100000Hz
[V][esp32-hal-i2c.c:1698] i2cSetFrequency(): cpu Freq=240Mhz, i2c Freq=100000Hz
[V][esp32-hal-i2c.c:1706] i2cSetFrequency(): Fifo delta=1
[W][esp32-hal-i2c.c:1413] i2cCheckLineState(): invalid state sda(21)=1, scl(22)=1
[D][esp32-hal-i2c.c:1421] i2cCheckLineState(): Recovered after 1 Cycles
Scanning I2C Addresses
.. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..

In the end, nothing is found.
The truly interesting line here is
[W][esp32-hal-i2c.c:1413] i2cCheckLineState(): invalid state sda(21)=1, scl(22)=
If I change resistors to 3.3K or 2.2K, nothing changes. When I get rid of pull-up resistors, it changes to sda(21)=0, scl(22)=0. At this point I tried:

Changing CCS811 sensor, to no benefit
Changing resistors
Using esp-idf rather than Arduino bootloader
Changing ESP32 to a different one: JZK ESP-32S ESP32 Development Board
Following the steps [here]: https://github.com/espressif/arduino-esp32/issues/3079.

I must note that when I connect circuit to my Arduino Uno / Pro Mini everything works pretty much as expected, device can be found and I can communicate with it. I'm at my wit end. Any ideas what could be wrong?


texts:
This problem is really rattling my brain quite a bit.  My current setup uses a wall wart power adapter sending 6VDC to my circuit.  From that I'm trying to lower the voltage to 5V using two resistors.  I have a 220 ohm and 1kohm resistor in series.  '

So far so good right?

My expected output should be 4.92V, this however is not the case i'm getting the full 6V with my meter on one end and -.1V on the other.  I've switched the leads around to see if did something backwards but same result.  Am I missing something?  I'll do up a schematic on request.  This is a bit of an easy issue so don't see the need of one just yet.

Further unnecessary explanation:
This is just a test circuit.  My final circuit will be using sensors instead of the wall wart power adapter but I have to make sure I am correct before proceeding.  That is why I am not using any "load".  Is this the issue?  the fact that their is no load?


texts: How do you find the resulting frequency of sampling a tone at too slow of a rate?

texts: For example, I have a 1500 Hz tone that I am going to be sampling at 1200 samples/second. How would I figure out the tone resulting from this sampling?


texts: PIC12F output pins working differently than programmed

texts:
I'm trying to drive a shift register using a PIC12F683, so I wrote this code for a simple test:

#include <pic.h>
#include <pic12f683.h>

#define _XTAL_FREQ 4000000

// GP0 -> data
// GP1 -> latch
// GP2 -> clock

void clear_shift_register() {
    GPIObits.GP1 = 0;
    GPIObits.GP0 = 0;

    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;
    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;
    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;
    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;
    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;
    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;
    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;
    GPIObits.GP2 = 1;
    GPIObits.GP2 = 0;

    GPIObits.GP1 = 1;
}

void main(void) {
    TRISIO = 0x00;
    clear_shift_register();

    while(1) {
        GPIObits.GP1 = 0;

        GPIObits.GP0 = 1;
        GPIObits.GP2 = 0;
        GPIObits.GP2 = 1;
        GPIObits.GP0 = 0;

        //GPIObits.GP0 = 1;
        GPIObits.GP2 = 0;
        GPIObits.GP2 = 1;
        GPIObits.GP0 = 0;

        GPIObits.GP0 = 1;
        GPIObits.GP2 = 0;
        GPIObits.GP2 = 1;
        GPIObits.GP0 = 0;

        //GPIObits.GP0 = 1;
        GPIObits.GP2 = 0;
        GPIObits.GP2 = 1;
        GPIObits.GP0 = 0;

        GPIObits.GP1 = 1;

        __delay_ms(500);
    }
}

When I programmed the PIC and powered it, nothing happened. So I decided to hook up some LEDs directly to the PIC pins to know what it was doing:

GP0 is OFF all the time
GP1 is ON all the time, but periodically does a one-time flicker very fast
GP2 is OFF all the time

Why am I getting these weird results and how to correct it?


texts:
I have been using PIC18 micro-controller for generating reference signal and a charging signal at 100 Hz rate max. Now I have to generate this charging signal after sensing an external trigger pulse of width 15us with frequency in between 1 to 100 Hz. I am using 4 timers of PIC18 for different purposes and one timer is available.
I am thinking of using external interrupt on rising edge but how to check 15uS pulse width. I mean what if the external pulse only rises to logic high and doesn't go to logic low. How would I know that?
How to verify that the input pulses are in integer format only i.e. 1Hz, 2Hz and not 1.5Hz or any other values?
How to mark limit for sensing up to 100 Hz only?


texts:
I am a new to electronics. I am trying to setup the radio control for the arduino. I hooked up the Reciever's Channel 1 to the Arduino Mega 2560's Digital pin 2, Reciever Vin to Arduino 5V, and Ground to Ard Ground. Here is my Source Code.

void setup() {
        Serial.begin(9600);
        attachInterrupt(0 , blink, CHANGE);
     }

void loop() {
   Serial.println("I AM IN THE LOOP");

}

void blink()
{

     Serial.println("I AM IN THE INTERRUPT");
}

I tried using other interrupt pins,3.3 V instead of 5 and also tried  Arduino Uno and differnt kinds of Interrupt Values like RISING, LOW and FALLING but it constantly prints " I AM IN THE INTERRUPT" without me touching the transmitter. Any suggestions.

[UPDATE]
After a great deal of discussion on
http://forum.arduino.cc/index.php?topic=184283.0
I came to this conclusion. Radio generates PWM signal  .. If you have an interrupt pin connected to a channel. It will interrupt regardless of what you do because it is constantly generating a PWM. So I am leaning towards interrupt is not a good idea for radio control.


texts: Determining resistance of 3 resistors connected in delta configuration

texts:
I have 3 resistors of varying values connected in a delta configuration. I have access to all 3 nodes for measurements. I know that if I measure resistance across 2 points, I'm measuring 1 resistor in parallel with the sum of the other 2 resistors.
Is there a way to determine each of the resistor values as if the circuit were opened (not connected in parallel) without any guarding and without destructively opening the circuit? I'm trying to verify my manufactured resistors in-house prior to sending them out for laser trim.


texts: Which thermistor or temperature sensors are less power draining?

texts:
I am trying to build a low-power system. One of the system parts is a Temperature sensing circuit (0 <T<60 C).
Since I am have limited power (~500 uA 3V). I was lost as to which approach is the best in terms of less power consumption.
[high Accuracy and fast sampling are not necessary]
Types I am looking at:

NTC Thermistor
PTC Thermistor
Digital sensor

Which one have usually better for low power application? and do you recommend a certain model?


texts: What is the unit of measure for a region's power supply?

texts:
So, I'm casually perusing an old issue of Foreign Affairs magazine and encounter a paragraph concerning the ability of Brazil's electrical power generating plants to supply juice.  Said paragraph reads:

"Domestic power supply is expected to rise from 539.9 terawatts per hour (TWh) in 2010 to approximately 830 TWh in 2019, by which time power demand...should have attained 712 TWh..."

The units referred to here, "TWh", seem like the wrong choice to me for two reasons.  First, I believe the unit "TWh" is used to measure energy, not energy rate/consumption.  And, clearly, "TWh" does not mean "terrawatts per hour!"

Should the above statement have referred simply to "TW?"


texts: protection board for 18650, voltage drop? normal?

texts:
I made a power pack using 18650 batteries from an old laptop. All batteries tested individually are good. 4 batteries in 2S format. I used a cheap 2S 3Amp rated protection board I got on Ebay from China. I correctly connected all the terminals and properly soldered, B+/B- to the +/- of the final ends of battery and BM to the middle.

The voltage measured directly at the battery terminals (at B+/B-) is 8.4 volts but at P+/P- of the board it measures 7.5. Which means this board will not produce more than 7.5 volt usable voltage even when the batteries are fully charged to 8.4. Is that expected and normal? or is there a problem with the board.

Thanks for help.


texts: Can Quine-McCluskey Method be used for Product of Sum simplification?

texts:
Can a product of sum function be simplified using the Quine-McCluskey algorithm?
If so, how?
I saw this post on Math SE addressing the same question, however the answer does not explain how the algorithm would work out exactly and the reason for the method working is also not very clear.

Since (A+B)(A+B') = A, QM should work on CNF as well as DNF. I don't see that there is any difference between grouping by 0's or 1's. The only purpose of that (as far as I understand it) is to assure that mergable clauses are in adjacent groups, and nothing in the same group is mergable. I.e., no two clauses with the same number of 1s are mergable, and not two clauses with the same number of zeros is mergable.

Specifically (for the answer on Math SE), I am unsure if the method indicated means grouping based on number of zeroes in the first stage of the QM algorithm and then proceeding as you would for SOP (?!)
Also I don't understand what the post is referring to when it comes to "mergeable clauses" as part of the explanation for why QM should work for POS. Thus, I am not sure on the reasoning for QM working for POS.


texts: is there an XML standard to describe a component's characteristic

texts:
I'm trying to automatize data extraction from datasheet's table. It's still a work in progress but I have good hope for it, some keyword "characteristic, min, max, symbol, test conditions,..." make them easy to spot. I just need more time to work on it.

Appart from the command line debug I'm using, I'm beginning to wonder what kind of usefull output format I should use. I think XML will be a good idea, and I would like to know if a standard that I could use already exist.

note : I'm using pdf2html (xml option) then python to process the file. I'm also using ODSlib to visualize the table recognition.


texts:
hello there guys I have this raspberry pi and I got confuse when shutting down the pi
is use the following code:

sudo shutdown -h now

but the problem is that the pi still has this red LED on I'm confuse if it's ok to unplug the pi? will it damage the SDCARD? or the Pi?

is there any way to completely shutdown the pi inlcuding the power?


texts: Terminating shielded/screened twisted pair correctly

texts:
Theoretically, I can't see a problem if the twisted pair has an end of cable termination that is: -

A single resistor (R) that matches the characteristic impedance of the cable placed across the two ends of the pair or,
Two resistors (\$\dfrac{R}{2}\$) across the two ends of the pair with
the centre-point tied also to the shield/screen.

Practically, when looking through data sheets I tend to see option 2 more than option 1.

Today, I had to use option 2 because option 1 caused a noticeable time lag (about 2 or 3ns) between the two conductors over 50m of cable. This surprised me and I'm wondering why this should be so. The signal I was driving at one end was about 2V logic levels and very balanced in nature (no discernible time difference or noticeable amplitude difference).

Question - why should option 2 be better than option 1 in the set-up I've described and is it possible that there is something theoretically better about option 2?


texts: Why is the efficiency of this LED driver circuit so low?

texts:
I created an LED driver board based on PAM2863ECR http://www.diodes.com/_files/datasheets/PAM2863.pdf

The board includes three identical driver circuits to drive three LEDs.  I'm not able to wire the three LEDs in series in this application.  There is also a regulator and switch to adjust intensity.  The board is typically powered from 6 NiMH cells, so the voltage is normally 6-8V.

The board works fine and intensity changes as expected, however I'm not getting the efficiency I expected.  I never expect to get the max value claimed on the front page of the datasheet (97% for this part), but I expected at least 80% which is what I based the battery life estimates on.  Instead I'm only getting about 64%.

Running a single LED at full output draws 930mA at 1.54V (1.43W), while drawing 340mA @ 6.6V from the input (2.24W), giving just under 64% efficiency.  This is about the same efficiency throughout the input voltage range.  I also changed the inductor to different values of the same series part, from 22uH to 68uH, and the result didn't change.  This is a 2-layer board, and I thought maybe 4 layers with ground and power planes might help, but I can't see it making that much difference.

I'm attaching a PDF of the schematic (in some readers you can click on the parts to see part numbers), and images of the PCB layout.

Any suggestions on what I could try to improve the efficiency?  If not, any suggestions on replacement driver chips that you've seen good efficiency from?

Schematic

EDIT:

Diodes: https://www.digikey.ca/products/en?keywords=MBR140SFT1GOSCT-ND
Inductors: https://www.digikey.ca/products/en?keywords=SRN6045TA-470MCT-ND

Image of the schematic if you prefer it to the PDF:

EDIT 2:
I have done some additional testing.  First I tried adding caps across the LED.  It gave no measurable improvement in efficiency.

I then ran a sweep of the input voltage and saw efficiency drop by about 1% with Vin at 9V compared to 6V.

I rewired the LEDs in series and saw a huge increase in efficiency, up to about 86%.

Finally I changed the 47uF inductor with a 33uF type having 50mOhm DC resistance.  This brought the efficiency up a little more, close to 90%.


texts:
How is the gate capacitance of a MOSFET taken care of by a high current?
How does a high current helps in charging it and discharging it , in a small time?


texts: Need to resolve a trasient on the Output of power supply

texts:
I am designing a fly-back SMPS AC/DC topology power supply, i mount the PCB and when i tested it with a restive load (hot air stove 230V@600Watt-50Hz) y see that on the DC output appears a transient that reset the micro controller.

The block diagram are as follows:

AC INPUT-> Fly-back output 5V -> LDO 3.3V regulator -> Micro controller-Oscilloscope probe.

The transient as the oscilloscope show, inst just one transient pulse, its a number of consecutive transients in a short period of time.

Somebody can help to resolve the problem, i need to maintain the 3.3V to avoid the reset of the micro controller, or at least 2.8V, the photos of the Oscilloscope output are:

Ideas:

I am thinking on use a Zener diode to clamp the high part of the transient to 3.6V (to charge a few energy on the capacitor on the high side transient wave), and then a tantalum capacitor to avoid the 1.23V minimum voltage. This capacitor must be fast to charge because the next transient will happen after 2 uS as we see on the oscilloscope image. But... will it be charged enough in this short period of time?.

Or maybe a filter delete it?, i dont have so much practice with they to think how to use to fix the problem.

Circuit AC/DC:

3.3V LDO circuit:

Oscilloscopes Images:

TOP:

BOT:

TOP-BOT:
It have some errors in text, like the one i put on the relay... isnt the hall sensor. On the new version i am trying to make it will be fixed.

TOP-3D:

BOT-3D:


texts:
I have STM32L052K8T6 (master) and I am trying to communicate with AD7124-4 ADC (slave) via SPI. My problem is that STM stops transmiting clock pulses on SCLK immediately after it transfers all data from tx buffer (checked on external oscilloscope) and ignores request to wait for answer till timeout expire. Slave has no chance to answer when it has no clock to synchronise.

My init:

void initSPI (void)
{
GPIO_InitTypeDef GPIO_InitStructure;

__HAL_RCC_GPIOA_CLK_ENABLE();
__HAL_RCC_SPI1_CLK_ENABLE();

//GPIO - MOSI, MISO, CLK
GPIO_InitStructure.Pin = GPIO_PIN_4|GPIO_PIN_5|GPIO_PIN_6|GPIO_PIN_7;
GPIO_InitStructure.Mode = GPIO_MODE_AF_PP;
GPIO_InitStructure.Pull = GPIO_NOPULL;
GPIO_InitStructure.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
GPIO_InitStructure.Alternate = GPIO_AF0_SPI1;
HAL_GPIO_Init(GPIOA, &GPIO_InitStructure);

HAL_NVIC_SetPriority(SPI1_IRQn, 1, 1);
HAL_NVIC_EnableIRQ(SPI1_IRQn);

hspi1.Instance = SPI1;
hspi1.Init.Mode = SPI_MODE_MASTER;
hspi1.Init.Direction = SPI_DIRECTION_2LINES;
hspi1.Init.DataSize = SPI_DATASIZE_8BIT;
hspi1.Init.CLKPolarity = SPI_POLARITY_HIGH;
hspi1.Init.CLKPhase = SPI_PHASE_2EDGE;
hspi1.Init.NSS = SPI_NSS_HARD_OUTPUT;
hspi1.Init.BaudRatePrescaler = SPI_BAUDRATEPRESCALER_2;
hspi1.Init.FirstBit = SPI_FIRSTBIT_MSB;
hspi1.Init.TIMode = SPI_TIMODE_DISABLE;
hspi1.Init.CRCCalculation = SPI_CRCCALCULATION_DISABLE;
hspi1.Init.CRCPolynomial = 7;

if (HAL_SPI_Init(&hspi1) != HAL_OK)
{
    ErrorHandler();
}

HAL_SPI_MspInit(&hspi1);

__HAL_SPI_ENABLE(&hspi1);
}

I am calling this function:

void SendReceiveData ()
{
    uint8_t tx = 64;
    while (hspi1.State != HAL_SPI_STATE_READY);
    HAL_SPI_TransmitReceive(&hspi1, &tx, &rx, 1, 10000);
}

Even when I have a long timeout it is ignored.

HAL_SPI_TransmitReceive() returns HAL_OK.

Is there a problem in my initialization?


texts: What is the need of Neutral and Phase Metering?

texts:
I'm working on a project where I have to implement a metering IC to measure Voltage,
Current and Power on 230v power lines.

I have to use Atmel's 90E24 single phase metering IC. This IC has two channels one for
 Phase and another for Neutral current metering.

Since, all the current drawn by the load will flow on both phase and neutral (return path)
 then what is the significance of using two line metering?


texts: Determine Polaritry of Aluminum Electrolytic Capacitor

texts:
I have an NIC aluminum electrylytic capacitor and am trying to figure out which wire is positive and which is negative. Forgive me if this is a stupid question since I'm a total noob at this.

This is what's on the datasheet (Source: NIC Components)

The actual cap has the same polarity marking (a rectangle) on its casing. Does it mean that the wire with the marking is negative and that the other one is positive?


texts: Noise being created on Sensor after connecting Power Source to LEDs

texts:
simulate this circuit – Schematic created using CircuitLab

So I posted this issue on the arduino forums and haven't had much luck getting any visuals on it. I have an arduino and shield of which I've configured to work on a 12volt dc car battery. However, I am running into issues with the accelerometer giving me fluctuating readings at rest when I add power to the LEDs.

For example, no power connected to leds, and the arduino is connected to the computer, sensor values fluctuate +- 1 of the normal at rest value. However, as soon as the power is added to the buck sensor (To drop the 12 volts down to 5.5 for the LEDs) my values immediately fluctuate +-5 of this old value. The only places where the arduino and LEDs connect is through my shield at the COM port (a digital output on arduino) and a ground wire that grounds directly to the arduino. The power wire is a separate entity (although in the final configuration they both will be powered by a car battery).

In this instance however arduino is powered by laptop and LEDs through a battery. With the + lead of the battery going straight to the positive terminal of the buck converter. Any idea what gives?


texts: Why erasing SSDs in increments of entire blocks does not damage adjacent cells?

texts: I know that to avoid corruption and damage, SSDs are only erased in increments of entire blocks. But how does that not damage adjacent cells? Why energy-intensive tunneling inhibition isn't necessary when you're whacking a whole bunch of cells at the same time?


texts:
I'm trying to make a 300V H Bridge for an electrostimulator. The circuitry is as posted here, using MOSFET P20NM60GP:

When I tested it with  low voltage supply (just for the sake of safe testing), and a 15 Watts 1kOhm resistor I get the output waveform I desire, that is:

However, when I try to change the supply voltage to 300V (galvanically isolated, safety first!), with the same 15Watts, 1kOhm resistor I get this output:

I didn't take a picture of what that output looks like in 250us but the spikes shown in the image before were not square waves as the ones that showed up in low voltage.
The ground for the Source of the low side MOSFETs is isolated from the one used in the IR2110 and the rest of the electronical devices (microcontroller, ICs, etc)

Any ideas as to why is this H Bridge misbehaving on High voltage? Thanks in advance!


texts: Executing Spice commands written in file

texts:
I successfully executed ngspice commands via the command line.
When I wrote those commands to the .net file, and run that file via ngspice, they didn't work.

The following is my netlist file:

* gnetlist -g spice-sdb ./RC_filter.sch
* Spice file generated by gnetlist                      *
* spice-sdb version 4.28.2007 by SDB --                 *
R1 2 1 1MEG
V1 2 0 DC 5V
C1 1 0 1uF

* Set Initial conditions: Voltage on Capacitor C1 is being set to zero
.IC V(1)=0

.end

When that file is loaded to ngspice, and then I run the following commands:

tran 10m 5s
plot V(1)

They work perfectly.

But when those commands are written in the .net file, right before the .end line, they don't work when ngspice reads the file:

* ... Rest of file

.tran 10m 5s
.plot V(1)

.end

How can I make these commands to work?

Thank you.


texts: Is it possible to clone the settings of an MMA8451 accelerometer?

texts:
I bought a kit on the internet which has an MMA8451 linked to some LEDs and a DF player.
I am trying to duplicate this system. I have built all the hardware required.
When I connect my original MMA8451 to my new hardware it works perfectly.
I do not have the original code for the MMA8451 so I wanted to know if there is an easy way to clone all the settings on the original MMA8451 and put them on the new MMA8451.


texts: Why does adding more coils make my electromagnet weaker?

texts: I've built a couple of simple electromagnets, using a nail (not sure of the material) and copper wire connected to a 1.5V AA battery. I'm really confused because the electromagnets with less coils are noticeably more powerful than the electromagnets with far more coils and I wanted to understand why. Could this be because of the added resistance of the coils? What can I change in my set-up to get higher magnetic field with increased coils?


texts: measuring analog current output with beaglebone

texts:
I'm thinking about using a BeagleBone to measure the flow-rate of a fluid through a pipe. Here is a breakdown of the scenario:

this flow sensor could be used

from the doc, the output is a 4-20 mA analog current
the doc claims there is short-circuit protection (not sure if I know exactly what that means)

the BeagleBone has a 1.8 V max analog input for its ADC, and supposedly sources 2 µA per pin

Does this mean if I wire less than a 90 Ω resistor (1.8 V / .02 A = 90 Ω) between the sensor ground and output, I am good to measure the voltage across that load without fear of damaging the BeagleBone analog input?

Is it that simple, or am I missing some details?


texts: DALI - how do I get control gear that supports ballast status and lamp failure query?

texts:
I'm new to DALI.
I wanted to buy lights that I could query to see if there is a lamp failure.  When purchasing control gear for these lights, how do I know that it supports this feature?  If it lists a specific DTx or IEC 62386 Part then do I know it supports that feature?  Which DTx and Parts support it?
This is a pre-purchase question; I'm not asking how to query a device that I already own to see if it has that feature.


texts: Why should interrupts be short in a well configured system?

texts:
Why should interrupts be short?

I'm currently using STM32 and it has a feature of prioritizing interrupts.

Because of that, I don't see any difference between these two options:

the main loop and interrupts
one big interrupt with a very low priority and the other interrupts

Why should we keep them short? Is it because of caching? Small stack? Or something else? Why can't we just create the whole system on interrupts and make the main loop sleep?

Any ideas?


texts: Will using magnetic base test indicators with breadboards cause electrical interference?

texts:
The situation leading to the question

In the Quick Tips #8 // Precision Helping Hands YouTube Video, a "helping hands" with various names such as "Magnetic Base Adjustable Metal Test Indicator Holder" is used with oscilloscope probes on a breadboard circuit, similar to this:

I am planning on using a separate one of those holders for each oscilloscope probe with my own breadboard (a total of 4 probes for the 4-channel oscilloscope).  But, for convenience of quickly rearranging these holders all around the breadboard, I am considering mounting both the breadboard and the holders with their magnetic bases all on top of some plate steel (needs to ferromagnetic for the magnetic bases to clamp down onto, so cannot be aluminum) from the local big box hardware store. I reason that the steel plate needs to be just large enough to move the mag bases around for clamping down, and just thick enough to avoid the "lever arms" of the base bending up the steel (can't use the 22-gauge el cheapo stuff from the store for this; gotta have something like 1/8" thick steel I believe).

The question

Will this setup shown above cause electromagnetic interference (or actual improvements to isolation against such interference), on the circuit under test, or surrounding equipment such as cables (I doubt the cables will be affected if they have proper shielding), leading to distortion or other artifacts at the oscilloscope?

I'm considering the following possible contributions:

Metal in the arms (probably mostly aluminum but not sure).
Metal in the magnetic bases.
Magnetic fields emanating from the magnetic bases themselves.
Metal in the plate steel.

Extra credit (can we do that in SE??) goes to anyone who can identify how the dimensions (length, width, and thickness) of the plate steel I use as the base for this setup affects the readings.

Oscilloscope is one of the Rigol 4-channel scopes. The scope is not owned by me, so if the specific make/model of scope is relevant, add a comment and I'll update this question with that detail. All scope probes are set to 10x setting.

The circuit under test is a op-amp based circuit similar to the one given by Pulsing Led for Competition - Elektor LABS and thus is not at all a high-frequency circuit.   So, my naive bias here is "No, it ain't gonna matter, so go for it!"


texts: Can I use a 7805 as a current regulator?

texts:
Can I use 7805 as current regulator? My input is 12-14 V DC (battery) and I require output 5V and 500mA or adjustable.

My background is CS so unaware of these ICs. I have searched LM317 and LM338 but I am unable to decide between them. I need to charge 10 mobile (probably 1625mAh batteries) for emergency areas using battery. Can Zener solve the problem because it can limit the voltage? Is there anything that can control both voltage and current? I do not want to use LT ICs because a design requirement for emergency (disaster struck) areas is low cost.


texts:
According to the data sheet these devices should be capable of handling 163A source to drain (though I have my suspicions that those little leads might not be up to that particular job).

I bought ten of these devices from China for just over two pounds sterling, which is already suspicious but cheap enough for tinkering. I want to switch short-circuit current from a 44Ah car battery for 100ms for the purpose of spot-welding tabs onto cells to make up batteries.

I put all ten MOSFETs in parallel and I got a couple of decent welds, but the third attempt shot the MOSFETs to pieces. Would I be correct in concluding that these Chinese IRF1404s are fakes? And if so, how can I be confident about procuring the genuine article?

Thanks for taking the time to read this.


texts:
The arduino website goes into some of these questions, but not in great detail.

So, what is the difference if one were to purchase an Arduino board or make one yourself? What benefits does buying the board have compared to assembling one from various parts?

I've seen that you can purchase the actual microcontroller (ATmega328 or similar) with and without the Arduino bootloader, what does this mean?

How would you go about programming a board that has been assembled separately(presumably without any link with arduino, the bootloader etc)?

Are there benefits of programming an Arduino through an AVR versus USB connection? Is programming in this manner similar to how you program with the Arduino IDE?


texts: How much energy can be stored in a battery?

texts:
Can any one tell how much energy can be stored in the a single battery (12v) ?

If I want to store 10 kWh of energy then how to calculate the number of batteries required.

Editing notes:

power -> energy
 kW -> kWh


texts: How do you properly offset the input on a DC-coupled instrumentation amplifier?

texts:
Given a circuit similar to the above image, where you have a DC-coupled signal that occasionally goes below the in-amp's negative rail (ground in this case because I'm interested in designing for single supply operation), what is the best way to offset the input's voltage so that it's centered around Vs/2 (~= 2.5V here) rather than ground? I'd prefer to stick with DC-coupling but would be interested in AC-coupled examples as well.
As a possibly relevant aside, the attached image is a design reference for an instrumentation amplifier whose input range extends -100mV below ground when used in single supply mode. As-shown the circuit is fine due to the minuscule negative voltage generated by a J-type thermocouple but I'm interested in how to properly design the circuit for a wider voltage swing.


texts: USB Solution to Bit Bang RS485 at a high Baud Rate

texts:
I am searching for a solution to write a ~800 byte data stream at a 10K baud rate from a USB device.
This is going to connect to a piece of hardware that uses a RS485 connection which expects an unconventional data stream (which is why I needed to use a bit bang mode).
I was using a FT232R USB cable to attempt to do this. The only problem is I need to write in a byte at a time to the chip, and I have to deal with the delay of the Windows USB Scheduler.. which seems to be around a ~1ms.
So in order to keep up, I need to write a new bit every 100 microseconds (10K Baud Rate). So at my needed rate, I simply wouldn't be able to keep up. Since the chip can only store a bit output at a time, writing in would take much too long.
Does anyone have any other products they would recommend? I was searching for a solution that would have a buffer, that perhaps I could write a chunk of my data stream (if not all of it) and would allow the datastream to keep up with the 10K baud rate.
The Protocol I need to keep up with is at 10K Baudrate:
Start Bit, 8 Bits of Address, 8 Bits Of Data, 1 Parity Bit, 40 0 Bits, and then repeating to the next 'packet'.


texts:
My senior colleagues and I designed a circuit to sound an alarm when mains goes off and sound another alarm when main resumes. I found two different circuits online: one for power failure detection and the other for power resumption. I merged the two circuits together to get this power failure/resumption circuit:

I have not built it yet. Will this circuit work? What are some tips for best practices with circuits like this one?


texts:
1000w sine wave inverter

I downloaded the above schematic from the web, I constructed it and its functioning OK.

My problem is that this inverter causes distortion in my sound systems even with the tank circuit connected in the secondary winding of the inverter transformer.

I observed keenly and found that this noise is generated in the output side of the inverter.

What can I do to get rid of this noise?

Am using the 1000w inverter on a  2×12v/200AH power banks.


texts: Good evening. I was attempting to do a node analysis on the circuit above when I ran into a problem. Assuming I have my reference node at the bottom below the 2 ohm resistor I come up with my equations for node V1 but run into a problem with nodes V2 and V3. Due to the voltage source I have a no ideal how to deal with that source. I know V2-V3= 25V. Any tips on how to do that? I was thinking of using that relation somehow.


texts: Why do we connect a battery to ground when jumping a car?

texts:
This may seem like a very simple question, but I've searched all over the place and haven't found an answer.

When jumping a car, we connect the + end of the charged battery to the + end of the dead battery, and the - end of the charged battery to the chassis or other metal part of the car.

I always thought that you need a closed circuit for current to flow. But this circuit appears to be open: we are connecting the - end of the charged battery to the ground! Thus, how can any circuit connected to ground have a current?

I believe another way to ask this question is: will jump starting a car still work if I connect the - end of the charged battery to a third (powered-off) car, instead of to the chassis of the car with the dead battery? If so, why? (I've heard people say that jump starting a car only works because the chassis is connected to the electrical components of the vehicle, thus providing a closed circuit since the battery is also connected to the electrical components of the vehicle).


texts: How can I install board files into the Arduino IDE in order to upload my code to the ATSAMD21 Xplained Pro evaluation board. Can I know how can I do it? I Googled it but I didn't get any correct solution.


texts: Identify soldering iron plug and required socket

texts:
What is the connector type for this soldering iron?

I am contemplating fitting it to a private-badge version (DSE T-2200) of the same station that doesn't have the connector fitted, so I will have to either remove the connector on the iron and hardwire it like the existing iron, or else butcher a new connector socket into the station, which I probably prefer.

EDIT Maybe I should redefine the question: What panel-mount male socket should I use with this plug?


texts:
For Y–∆ or ∆–Y transformer:

+ve sequence, quantities on the primary LEAD secondary by 30 degrees.
-ve sequence, quantities on the primary LAG secondary by 30 degrees.

My question does this change the power factor, going through an ideal Y–∆ or ∆–Y transformer (no internal impedance)?
will the power factor before the transformer be equal to the power factor after the transformer?


texts:
I am trying to configure STM32F4 USART peripheral. I thought that USART Receiver pin(RX) must be programmed as Alternate function to USART works correctly and then the data is present on the I/O pin can moves into the USART Receiver Shift register.
I mean that according to the following pictures taken from the STM32F4 Reference manual, when we do configure a pin as Alternate function it gives a way for the data to moves into the Alternate function input(here it is Receiver shift register) but when that pin is configured as Floating input (second picture) the data on that pin is just sampled into the input data register.

So logically i think that USART can't do it's job correctly when Receiver pin is configured as Floating input. but incredibly it does work in a correct way and i dont know why?!
The same Problem has been discussed here : Why is the USART receiver pin configured as “input floating”?

But i couldn't find my answer there.
Edited:
Ambiguous point is that however in Floating input mode the data will also be sent to the connected Alternate functions But it's important to specify which peripheral this data will be sent to.
When the microcontroller starts up from Reset mode, Reset values of almost all Registers is 0 so for instance pin 7 by default is connected to AF0 which that isn't for USART periph. So if we select Floating input mode for that pin and don't determine which alternate function we want to send the data, then the data might be sent to the wrong peripheral instead of USART receiver shift register.
But incredibly without determining the peripheral which we want to select as our Alternate function, USART does the work correctly.  Actually my question is WHY does USART work correctly in this way (without determining The actual Alternate function)?


texts: Direction of terminal blocks in PCB layout

texts:
I am designing a PCB and I cannot find the direction of the terminal blocks. I.E on which side of the terminal block the holes are facing. I believe they are currently looking down but I cannot find any documentation on this

This is eagle by the way.


texts: How is a transistor's input changed from on to off and vice versa?

texts:
I am currently diving deeper into electronics and have been researching silly to find an answer to the one question that is not clear to me.
I am still unsure how a transistor's input is changed from on to off and vice versa without a moving part or a physical action such as a keyboard key click or a mouse click. I think this due to the fact the computer is still running background programs and tasks without in physical action.
The only way that I may of thought of is that current is constantly running throughout the computer and it uses logic gates to change the input signal but in my mind this contradicts the idea of a transistor being that it has an "input" which can be changed.
I have noticed that all examples of this online that I have found whilst researching are always using physical switches of some sorts but this doesn't explain how a computer can still work without a physical action.
Any clarification to clear my confusion or links to where I can find out more on how transistors receive an input without a physical action would be much appreciated!


texts: Veroboard and solder traces current rating?

texts: I am making a "pcb" with perfboard and solder traces.  Unfortunately I need to run up to 8 amps through some parts of it.  In the places where I need to use wires to jump over solder traces I plan on having two strands of 20 gauge copper wire each with their own solder pad. Would normal solder traces be able to carry enough current or would I need to also double up the solder traces in order to prevent a lot of resistance and possible incineration of the perfboard.  Note  I will be using actual brand name veroboard and the solder traces that carry more than 2 amps of current will probably be about 5 inches long.


texts: How does square's device send 3 tracks from the credit card trough a single audio channel at once?

texts:
There are 3 tracks on a credit card. A 3 track reader would need 3 channels to send the audio to the phone for processing. Does iPhone allow the app to turn the other 2 stereo outputs into input channels? If so, is this at the SDK level or do you temporarily override the driver of the audio chip?

Or does the device do some sort of combining of these 3 channels before sending it tru?

What wizardry makes this happen?


texts:
I want a buffer that outputs Vcc (of 5 V) when I give it voltage about a threshold, say 1.5 V. And it outputs Vss (ground) below that threshold.

I have a 4050 CMOS thing but I think it does not have a threshold - it just outputs whatever it sees on the input.

Bonus points if it's pin-compatible with a 4050.

Many thanks
Rich

--- edit ---

I'm not after a specific threshold, it's TTL levels. If it looks like an 'ON', output an 'ON'. Else output 'OFF'.

Sorry, could have been clearer.
Rich


texts: CEM3 or FR4 pcb, which is the lightest material?

texts:
There is nothing about weight in the substrate datasheets I found.

Between CEM-3 or FR4, which is the lightest material ?
What is the average weight by surface for CEM-3 boards ?


texts: Are all Phoenix connectors (of the same size) cross compatible?

texts:
I always seem to be losing phoenix connectors.
I want to buy a bag of them to keep in the office as spares.
Are all phoenix connectors of the same size cross compatible ? Eg. could the same phoenix connector be used on a Lutron keypad, a multi zone audio amp ? (as long as they fit in the slot).
Or do they have other technical parameters i need to be aware of eg. voltage or other ?


texts: Which capacitor type is best suited for pulsed power applications?

texts: I need advice in between MKT (metalized polyester film) and Ceramic capacitors . I am building a pulse discharging system which is required to discharge about 5KV through 10Ohm resistor in a time as fast as possible (say in pico seconds ~ us). Please can anyone advice me which type is best suited for such an application. The frequency of charging and discharging will be about 100Hz or so. I need this for experimentation with spark generation.


texts: External power supplies and DC to DC converters for Computers and notebooks

texts:
Part one :

I have this Question ,

as we know , Most notebooks power adapters are 19.5V output.

While the CPU and GPU works on 12V and the SSD works on 5V . , so the motherboard should have two DC to DC power converters ,

one from 19.5V to 12V for CPU and GPU

and another From 19.5v to 5V for SSD nd harddrives.

mainly the notebook will never need 19.5 V .. so why dont they choose 12V Power supplies for notebooks in General and use 19.5 V power supplies ?

Why bother making two DC to DC inverters instead of just one ?

in case of 12V power supply , they already have 12V ready and just need a DC to DC converter to get the 5V for SSD.

keep in mind that internal desktop power supplies never outputs 19.5 V , it just outputs 12V and 5 V and 3.3 V ... now imagine this power supply external (lol) the place is not a big deal isnt it ?

so back to the main Q , Why all External power supplies used for PC outputs 19.5V and not 12V like in the internal ones ? it makes no sense.

Part Two :

Graphic Cards power ..

As we all know , most mid range to high end Graphics cards needs more power , and they come either with a 6 pins 12 v  plug or 8pins 12V plugs for more power it needs (150 watts to 250 watts)

My question is : If I use an external power supply of 12v outputs and  plugged it into the Graphic cards direclty ,  would it work ? or is it better to use the 19.5V notebook external power supply and add a DC to DC converter from 19.5 to 12V and then plug it into the card?

and in case the 12V works , does it need some kind of Board to make that 12V inline with the card voltage specs ? for more stabe 12V ? or is it Standardized and it will be within specs ?

some cards like the GTX 1070 needs 150 watts 12V input , and some like the 1080 , 180 Watts , and the 1080 Ti 250 watts.

I can find 150 watts external power with 12V output , but sadly anything more than this outputs 19.5 and needs DC to DC board ... example the DELL Notebooks power supply of 330 watts outputs 19.5 volts ...

Part Three :

some ATX power supplies come modular ,  and my question is : lets say I use just one 12V plug and ignore the other plugs , can I use the whole wattage from that single plug ? or is there a limitation of each plug watt?

They say it is single Rail (meaning watt is not divided between Vi) but I am concerned about the plug wattage and the wires if they can stand it or not.

Example : I need to power a graphics card of 300 watts .. and I use an ATX power supply with single rail of 350 watts ... the power supply has the motherboard connectors that I will not use , and has only one PCIe 6 pin plug for card .. but since I am not using it for mother board , can I use one port for the whole 300 watts or  do I need to  take 12 V from the Motherboard plug ?

I can use thicker wires for 300 watts , if the plug on the power supply can stand 300 watts ..

more over , on the PCB of the power supply itself , does it stand 300 watts since it is a single rail or must also be divided between plugs ?

Thanks for your replies .


texts: Hook up bluetooth antenna to an Arduino (Or similar)

texts:
I have a Bluetooth ELM327 adapter that I am using with my car's OBD2 port. I have an Arduino UNO compatible Magpie (Little Bird Electronics) which I would like to use to interface with this adapter.

My current idea is to solder two wires onto the RX/TX lines (If they exist/can be found) or to connect to another component.

The PCB, from what I can find has:

A Beken BK3231 bluetooth chip (Appears to be QFN36?), running off a 16MHz crystal (Best guess from text on top - P16 00M N FAB C)
An unnamed 8 pin chip which connects to OBD2 pins 3 and 11, GND and another two pins off to the processor (Which I suspect might be TX/RX?). From what I can tell the rest of the pins go either to ground or power.
An ELM327 processor under a heatsink blob (At least that's what I think those big black circles are?), which is not accessible for soldering.
A chip labelled 8A825 which I suspect is a voltage regulator.

From this, what what would appear to be the best option for attempting to allow the Arduino to hook into this PCB and/or if anyone has any suggestions as to which pins might be a good place to start for TX/RX or other data protocols (UART/SPI/I2C)? I'm just starting out and wanting an opinion before I go and solder to something I shouldn't or completely stuff the PCB.

EDIT - The board

Bottom right is 8A825, top right is BK3231, middle is the serial converter?


texts: What is the purpose of these elements in this circuit?

texts: I am analyzing this continuous waveform amplifier circuit for a Microwave Motion Sensor. This high gain amplifier is recommended in the datasheet as the signal output of the sensor is extremely small (~1uV). I understand that they are using an op-amp integrator and an op-amp differentiator configurations, but what are the roles/purposes of the circled parts? Could someone please kindly explain it to me as my circuit analysis is a little bit rusty.


texts: Op-amp circuit analysis without input signal

texts:
In the following circuit i need to find the OUTPUT and the current that flows in the zener diode D1, which works at the "zener" breakdown region with
$$Vzener=5,6V$$
The opamp is considered to be ideal.

I cannot understand how this circuit works since there is not an input signal to be applied to the inverting or to the non-inverting terminal of the op-amp and we only have the power supply. I have never seen such a case before and i am a bit confused. Which is the right way to approach it? Any help is appreciated!Thanks in advance!


texts: Difference between current source and voltage source

texts:
I know that the two poles of a battery connected in a closed circuit would act as a voltage source. This is because the +ve terminal is at a higher potential compared to the -ve terminal. This is what drives the current through the circuit.

But for a current source, how does it work. Doesn't the -ve terminal acts like a current source?


texts: VMC Coin mech tube status via an Arduino

texts:
I have a vending system with a VMC connected to a coin mech via MDB.
Also I got an Arduino successfully connected to the same MDB as a cashless device and it is talking to the VMC with no issues.

My question is: How can I get the status of the coin mech coin tubes via this Arduino?

As far as I understand if I need to address the coin mech, my Arduino needs to be the 'master' and as VMC is already present in the system as the 'master' it is not possible unless I remove the VMC from the system and connect my Arduino as the only 'master' to the coin mech.

Could someone please confirm if you have ever tried this scenario?


texts: What are the various interfaces used on memory devices

texts:
There are various external memory devices for temporary and permanent storage of data. This may have interface as simple as RD/WR signal with data-address bus and chip select with output enable. However, more complex memory devices have a more complicated interface and need a state machine on the processor side to keep track of what state the memory is in e.g the DDR RAMs.

Is there some application note or website that gives list of various type of memory devices in terms of complexity of interface and explain how is each controlled via the interface?


texts:
I've been working on a weather station project, and  I used a SIM 900 module to upload the data to a web server. Recently I started using a SIM800-DS for the same purpose and I had to rewrite the code without using the simcom HTTP stack. Here I ran into a problem with http request.

After configuring the module and connecting to the internet, I opened a TCP connection using

AT+CIPSTART="TCP","requestb.in","80"

And then, after sending

AT+CIPSEND

I formed a simple GET request

GET /s64y13s6 HTTP/1.1
HOST: requestb.in

followed by a 0x1a. (I used requestb.in to test the requests).

The module responds with a SEND OK. But doesn't display the server response. ("ok"). After a while, I get this request time-out message.

HTTP/1.1 408 Request Timeout
Connection: close
Server: Cowboy
Date: Tue, 05 Jan 2016 20:05:07 GMT
Content-Length: 0

My question is, is there something more I have to send in order to let the server know I have finished sending the request?


texts:
I've been learning VHDL coding for the past two weeks to be able to understand the VHDL code of what I'll be working on. In other words, I'm still a beginner and I need help understanding some codes that I have came across.

when WAIT_ST =>
CAN_CS              <= '0';
can_init_start      <= '0';
can_read_start      <= '0';
CPU_CAN_WE          <= '0';
mux_sel             <= "00";
CPU_CAN_DATA        <= X"00";
CPU_CAN_ADDR        <= X"01";
ID_START            <= '0';
INST                <= Frame_Type & Sub_Frame_Type;
WAIT_COUNT_N        <= WAIT_COUNT + 1;

if WAIT_COUNT = WAIT_FOR then
   state_n  <= IDLE_ST;
else
   state_n  <= WAIT_ST;
end if;

And there are tons of When statements coming after this one, almost similar.

Help needed to understand what is happening in this loop, thank you!


texts:
How would I go about balance charging either 100 or 75 lipo cells?

This is a very serious question by the way, it's for an electric vehicle and we use either 75 or 100 cells at a go and currently balance them 6 at a time... very time consuming.

Why couldn't we charge them with 100 single cell chargers?
Surely they would then all be at the same voltage and therefore "balanced"?

EDIT:

There are 25 cells in series that make a box and 4 boxes in parallel to make the total.


texts: Best practice to switch +V or GND connection?

texts:
Consider LAMP1 and LAMP2 in the simple example circuit below:

Which is the "better" practice, using the switching component (here RLY1) to break the +V connection to a component that's always connected to GND, like LAMP2; or use it to break the GND connection to a component that's always connected to +V, like LAMP1?

I understand that from a purely theoretical perspective it makes no difference… But my "practical intuition" insists that LAMP2 is a better practice, because it's always grounded; thus you cannot inadvertently energize the circuit with an accidental short to ground. And yet, it seems like many (if not all) example circuits I look at connect things like LAMP1. So probably that means my intuition is wrong.


texts:
I learned that a real-valued time domain signal has a conjugate symmetric frequency domain signal.

However, when I searched a baseband signal [1], I feel that I am missing something. It shows a single-sided baseband signal.

I found another article [2] distinguishing an information signal (figure 1, single-sided) and a message signal (figure 4a, double-sided). And a double-sided signal in figure 4a is what I've seen before.

Which one is right? I mean, both may be right. What am I missing?

Particularly, I want to apply this knowledge to a baseband of Wi-Fi signal (bandwidth: 20 MHz) before multiplied with local oscillator.


texts: I have tried many times testing some Op Amp LED flashing circuits on a breadboard from the internet. So far, none of them works. The photo above is one of my attempt using a LM358. I have double checked my wiring and swap the 100k with 10k and 56k resistors. what is the problem here? why it's so hard to get a led flasher working with an Op Amp? Also I notice some of the circuit diagrams in the internet don't have the left 100k resistor between v+ and non-inverting input. why is that?


texts: What is the RMS reverse voltage for diodes?

texts:
in The datasheet

1N4001 Vr RMS 35V
1N4007 Vr RMS 700V

What is the meaning of RMS reverse voltage?


texts: "Differential Input Voltage" of "Fully Differential I/O Audio Amplifier" (OPA1632)

texts:
I want to use an OPA1632 as a symmetric signal receiver.
The datasheet states:

Supply Voltage, \$±V_{S}\$: ±16.5 V
Input Voltage, \$V_{I}\$: \$±V_{S}\$ V
Differential Input Voltage, \$V_{ID}\$: \$±3\$ V

The last one really concerns me. Can someone shed some light on why the \$V_{ID}\$ input swing has to be that small - or do I misinterpret the term? I thought that differential input voltage = \$V_{IN+} - V_{IN-}\$.


texts: Trouble finding how I can plug in this Molex connector from a Laptop Fan

texts:
I recently bought this fan, I am trying to power it for an external project that doesn't revolve around laptops; however, I don't know how to get power to the fan without cutting off the molex connector and stripping the wires.

I know this is a female molex connector, but I can't find any male heads that even remotely fit this type of product, so I ask you guys if you know of the specific molex connector that I can use to plug into this connector and get power to it.

Thanks


texts: Sporadic Clock Signals from Momentary Switch

texts:
I'm having trouble using a NO momentary switch to send clock edges to a J-Kbar flip flop, specifically the TI CD74AC109E(datasheet).

I have a switch between +5V and the clock pin, and also added a 10k\$\Omega\$ pulldown to the clock pin, so it stays at 0V while the switch is open.

However, when I close the switch, the output responds sporadically; I have the flip flop hooked up so it toggles the Q and Qbar outputs on every high edge on the clock pin, but it doesn't always do that.

I realize that this might be caused by the lack of debouncing for the switch, but as the switch isn't a tactile switch (doesn't go click click when pressed), and the sporadic behavior occurs even when I depress the switch (open it), which makes me think it might be a different problem.

Does anyone have any suggestions as to why this might be happening?

P.S. YouTube video demonstrating the issue I have. I've hooked up an LED to the Q pin to show the output.


texts: Why would this microphone only work while touching the volume control?

texts: My son bought this USB microphone for his computer. It only works if you keep your hand on the volume knob. I assume this is a grounding problem. I took it apart. It looks like the copper wire attached to the housing is there for grounding - it attaches near the rear of the volume knob. But touching that wire or touching any part of the interior of the knob does nothing to get the sound to work; only the front of the knob makes the sound come through. What can I connect to what to get it to work without having to put a finger on this thing? Thanks!


texts: Reviving an overdischarged NiCd 12v battery

texts:
Some time ago I recovered a 12v 1700mAH Ni-CD battery from an ancient Commodore Amiga black and white display laptop. The laptop works perfectly when powered by a 1.5a 12v adapter, but unfortunately the battery is in very bad shape.

Testing it with a multimeter, I got 0.011v from the battery. To verify the multimeter was in the correct mode, I tested a single zinc-chloride AA battery and got 1.652v.

Since the case is sealed and the voltage is so low it's pointless to test the cells. Is it possible to revive the battery?


texts: Is there anything wrong with this particular timer circuit utilizing 555?

texts:
I created following simple timer circuit for one shot operation.

My expectation is it to give 5v as output (for D RELAY and SP RELAY) for certain number of seconds/minutes soon as it got powered-on. Time interval to be selected using the rotary switch (bottom side).

I created this circuit by taking this. Additional things I added are voltage regular part with AMS1117-5.0 and various resister series selectable using rotary switch combined with 1000uF capacitor.

I tested timer part, excluding voltage regular, on breadboard and worked good. Then created PCB with SMD components (except 1000uF and 22uF capacitors and BS170 MOSFET. Those are through hole ones).

I am using a wall adapter having 8.4v for Vcc.

The problem is the timer is not working at all. It even does not give HIGH when I tested it using multimeter put across OUT pin of 555 and GND.

I am not yet good at electronics and took around one day to build the PCB!

Please help me to identify the problem in this circuit.

Many thanks in advance!


texts: Driving a ThorLabs piezo controller with TTL external input

texts: I am trying to drive a ThorLabs piezo controller (https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=2421&pn=KPZ101) with an external +3.3V TTL signal provided by a microcontroller (using an ARM Cortex M4). I configured the controller to be edge triggered: the controller would increment the voltage output by a step size after each trigger. I managed to drive the controller at very low frequencies (up to 5Hz), but for higher frequencies the controller stops incrementing the output voltage. I tried the same thing with a TTL function generator with a proper +5V output and the problem persists. When the controller is driven by the ThorLabs software on a separate PC, it can handle frequencies up to 1kHz. I feel like I am missing something about the proper use of the external TTL trigger inputs of the controller. Any ideas?


texts:
I am rather new to digital logic, so please try to make you answers as understandable/simple as you can. Anyway, In fig 1, everything works as you would expect, where the led(circle symbol in schematic) lights up only when both inputs(bases of transistors) are high. In figure 2, however, when replacing the led with another logic gate, like an OR gate, The AND gate's "output" is always high. I know why this happens (explained on this question): its because in fig.1, there has to be a current flow through the led for it to light, whereas in fig.2, it's basically like connecting the OR gate's input directly to 5v. So my question is, where would I put the output of the AND gate in fig.2 to only turn on the OR gate when both inputs/transistor bases are high?

Fig. 1

Fig. 2


texts: 12 v DC relay coil shows resistance in both ways 86 and 85 or 85 and 86. Why?

texts:
My relay coil 12v measure 100 ohm of resistance between pin 86 and 85 or between 85 and 86. A diode IN4001 is added in parallel to the coil.

However, after adding the diode, the coil has the same reading 100 ohm when measured between 86 and 85, and again vice versa, 85 and 86. Why? Is not the relay supposed to show resistance only in one direction????

Why the relay coil resistance still stays at 100 ohm after adding a diode in parallel with the coil??


texts: While working on a switching setup for a automotive cooling fan, I came up with a question. Can diodes be used instead of a relay when dealing with two switching sources? The main source would be the cars accessory line that is on when the key is turned on. The other source is a dash mounted switch that would let the fan be used when the key os off. Here are the two wiring diagrams.


texts:
Forgive the amateur question - I don't know anything about electronics. I was not able to find any similar questions on this board, but that probably has to do with the fact that I know so little about this field that I don't even know which keywords I should use to find the answer I'm looking for. Sorry if this question- or similar questions have been answered countless times already.

I'm trying to build an "LED Chaser" circuit. For my counter IC I'd like to use the CD4022B (datasheet) where a CARRY OUT signal is triggered once for every 8 clock input cycles.

I was thinking I'd like to power the IC using a standard 9V battery (not super attached to this number, just seems convenient). The datasheet indicates that between 3 - 18 Volts is the nominal range for this IC, so I think I'm OK there.

My question begins here: I'd like to connect LEDs to the eight relevant outputs. I understand that your average LED will melt/explode if put 9 volts across it. May I connect the LEDs directly to the outputs of the IC, with no current limiting resistor? This article has some instructions and notes that I'm following, where the author says the following:

  Thus, when the 4017B is used to drive simple ‘one-LED-per-output’
  displays in the moving dot mode, the LEDs can be connected directly to
  the IC outputs if supply values are limited to 8V maximum, but at
  supply voltages greater than 8V, the LEDs must be connected to the IC
  outputs via current-limiting resistors.

The author is using an 4017B IC instead, which counts to 10 rather than 8, though I can't imagine that there significant differences between the two ICs as far as my question is concerned. However, 8V still seems rather high, no? Again, I have no clue. What if I powered my entire circuit using three 1.5V (AA) batteries in series, so 4.5V? And, if I did add current limiting resistors, would that not also hamper the current flowing into the IC, lowering the Voltage and preventing the IC from operating? I know I'm kind of flailing here.


texts: Can I drive (relatively) high power LEDs from a constant voltage supply?

texts:
I'm trying to tie together a single cell LiPo battery, an MPPT solar charger and a 3W LED

The problem is that the constant current supplies i'm seeing need 6V+ and the LiPo puts out a nominal 3.7

I understand that a big reason why constant current is preferred is because of the asymptotic nature of current draw as a function of voltage, but if i have a battery providing 3.7 (and let's say I run it through a linear voltage regulator), wouldn't this work just as well? If not - why?


texts: Converting MPU-6050's quaternion output to YPR angles

texts:
I am using the I2Cdev library which configures the MPU-6050 to use it's DMP and generate a quaternion output on it's FIFO. The problem is that when that quaternion number is converted to yaw, pitch and roll angles, the pitch and roll angles are limited to +-90 degrees (this constraint comes from the inverse trigonometric functions used in the equations).

What equations should be used to convert the quaternion number in euler's angles that give full information on the sensor's orientation.


texts: How does the conversion between admittance and impedance affect phase angle?

texts:
Wikipedia tells me that admittance \$Y\$ is the reciprocal of impedance \$Z\$:

\$ Y = Z^{-1} = \dfrac{1}{R+jX}\$

which makes plain enough sense to me, except that I've forgotten how complex numbers work from high-school math. If someone gives me an impedance in polar coordinates, say "10 ohms at 40 degrees", is there a trivial way to convert this to an admittance? If it were a simple resistance, calculating the conductance is easy, \$10 \Omega = 0.1S\$. But what happens to the phase angle?


texts: How do I make this LED flasher more sensitive?

texts:
I'm making a circuit which will change brightness level of an LED in tune with music. So far, this is producing some results, but I'm not very satisfied with it:

If it matters, the forward voltage of the LED is around 2.5 V.

The light output of the LED is good enough for me, but the circuit isn't sensitive enough for my taste. The AC source is the speaker port of my radio and the 10 mF capacitor is used to provide AC coupling. I started with a 100 nF ceramic capacitor (the idea came after reading the audio coupling capacitors question), but it gave almost no response. I tried with various other capacitors I have available and when I got into the microfarad range, it got somewhat better. Now I'm at 10 mF and it seems like 20 mF would be just right, but I'm supposed to make several of this devices and the 10 mF capacitors are just too big and expensive (especially since I'd need 2 per device) for this to work.

Right now I'm considering moving to BC546C which should give me higher \$ \beta\$ (420 minimum (up to 800)  compared to 300 which I have in my transistor right now), but I'm afraid that it will make too big impact at the current of the LED and change its brightness level which is now just right.

So how do I make this thing more sensitive other than by throwing bigger capacitors at it?


texts:
it is known that "11" are invalid inputs for a SR Latch. But I do not understand the reason of that. I cannot see the electrical conflict in this structure:

If R = 1, its NOR gate will give 0, for any value of the other input signal.
If S = 1, its NOR gate will give 0, for any value of the other input signal.

So we will get 0 at both output. What is the problem? I may understand that maybe it is not practical useful, but I do not see any conflicts.


texts: How to Efficiently Decode Non-Standard Serial Signal

texts:
I'm an undergraduate member of a research team working on a project that involves an RF-transmitting ASIC, and its wireless receiver which should ultimately send data to a PC.

The receiver outputs a fast, continuous, asynchronous, non-standard serial signal (i.e. not SPI, I2C, UART, etc) so my job is to write microcontroller software to interface the receiver to the computer. Currently my approach is to use edge-triggered interrupts to place the data in a circular buffer and do the whole bit-by-bit decoding process in the main loop. The microcontroller must simultaneously output this data using USB (virtual com port) to the computer.

Here is a problem I'm having, and one I'm anticipating:

I can not process the buffered data fast enough even with my quite powerful 72 MHz ARM Cortex M3 processor. The bitrate is 400 Kbps (2.5 us / bit). For reference that leaves only 180 cycles per bit (including the decoding AND the ISR, which has ~30 cycles of overhead ouch!). The MCU also has to handle a lot of other tasks which it polls for in the main loop.
The USB virtual com port driver is also interrupt based. This makes me almost certain that the driver will eventually have the processor interrupted for so long that it misses the 2.5 microsecond (180 cycle) window in which a bit may be transmitted. I am unsure how interrupt conflicts/races like this are normally resolved.

So the question is simply, what might one do to resolve these issues or is this not the right approach at all? I'm willing to consider less software-centric approaches as well. For example, using a dedicated USB chip with some kind of hardware state machine for the decoding, but this is unfamiliar territory.


texts: Power a device from 12v adapter instead of ac wall adapter

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Specifically, I have an Alarm Clock iPod dock with speakers that gets its power from ac wall adapter, but is only providing 12v. Is there an adapter to go 12V to 12V that will power this?

I want to put this in my camper, but run on 12V so I dont need to be plugged into shore power or have engine/generator/inverter running. I already have inverters and a generator, but this is for when dry camping and not running the engine. I have 200 watts of solar, so I am not too worried about running down my house batteries. I would rather use a standard cigarette adapter than hard wiring it to keep it portable.

Thanks


texts: Help in Thermal PAD and glue calculation (equivalence) in shared heatsink

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Hello if I have 15 chips to dissipate 1W each (thus 15W in total), by math calculation, which of the next three possibilities is better:

1) using a unique shared heatsink @1.7K/W with 0.5mm thermal pad @1.5W/mK

2) using a unique shared heatsink @1.7K/W with 1.5mm thermal pad @8W/mK

3) using 15 heatsinks @25.6K/W each with 0.1mm thick thermal glue @0.9W/mK

By feeling the three performances appear pretty similar: one shared heatsink @1.7K/W seems slight better than the sum of the 15 heatsinks, but the thermal glue is slight better than the 8W/mK thermal pad.

Can we prove the three cases by exact calculation and formulas using MKS metric system please?

I need the thermal resistance model in term of K/W of each of the three mentioned cases (heatsink plus heat transfer material).

I think that calculation are independent from the surface area as it is just the sum of the top of each chip package and it is the same in all the three cases. In any case I give you: area of the top of the chip is 60mm^2 each.

Ambient temperature is fixed. No fans.

This is a real case. Thanks!

(by now don't consider compression ot the pad: I know it is not fully linear with the conducibility: if you have time considering an extra case of a 30% of reduction of the thickness of the pad due to the screws...)


texts: Anolog signal amplification with single supply

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I have to amplify an analog signal 0 - 0.3v from a sensor to 0 - 2.5v which the XBee's analog input accepts and onlt have access to one 3.3v and gnd power supply rail(no negative rail). I've tried the 741 op amp but am getting problems with it and and it doesn't seem to work. If you could help me out with the circuit and the opamp chip that would fit best for this low power application. Thanks!

Update:
So i've found a chip that is mostly designed for single supply use which is the TLV2472 and it does a great job doing this in our final circuit that we have built and tested. The datasheet and an application document we fount helped us build an amplifying circuit that worked for our application.


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I am trying to move an application from the STM32L1 discovery board (which has the STM32L152 chip) onto a PCB containing the STM32L151RC.  On the discovery board, I was able to follow the application notes (AN2606 and CD0026342) to program the uC via USART1.  However, when I use the same boot configuration (BOOT0 is high, BOOT1 is low, USART 2 RX PA3 is low, then I drive the NRST pin low for a RESET) I get no response from the uC when I send it the 0x7F data frame via the FTDI chip (8 bits, even parity, 1 stop).  All VDD's (including VDDA) are given 3.3V with a .1uF cap to ground and all VSS's are connected to the FTDI's ground.

Could someone please offer a suggestion of what I may be doing wrong or what I should check next?  I was operating under the assumption that there was no difference between the STM32L151 and STM32L152 in this respect.  Is that a good assumption?  Do the chips have the bootloader in the system memory by default, or does one have to specify that when ordering them?

This is very specific, but maybe someone has experience with another STM chip.  The application notes show that it is very similar for the STM32F.