texts: How were four wires replaced with two wires in early telephones?

texts:
In this video, when A wanted to talk to B, a microphone was connected to a distant speaker using two wires (A → B).
When B talked to A, a copy of above was used in the other direction (B → A) using two more wires.
This required four wires:

But then it says the two-way communication could be made by using just two wires:

How was this possible? Wouldn't the current from the microphone affect the speaker on the same side?


texts:
I want to connect my DVD player which has a SCART output to a computer LCD monitor with VGA input. The DVD player supports the Progressive scan mode. It supports both PAL and NTSC.

I've built this adapter and it "works":

In PAL mode, the monitor is showing 800 x 600 @ 50 Hz and in NTSC 640 x 480 @ 60 Hz.

Only one problem: the image is greenish. First I thought I miss-connected or didn't connect R and B signals, but if I look at the picture it has red and blue colors too. White picture appears green. Red and blue appear darker than normal. There is a green tint over the picture.

One thing I noticed: the whole signal is transmitted via the green wire. I can disconnect all, if I leave green and ground connected I get picture. The two transistor circuit appears to have no use at all because it works the same without it (as long as I provide R, G, B). This makes me believe that the green signal is also carrying sync data (sync-on-green).

I've tried adding potentiometers, capacitors over green signal but with no luck. The picture disappeared. I've tried all possible settings on my DVD player. It only works with progressive scan enabled.

UPDATE: I guess I found the cause on http://www.curtpalme.com/CRTPrimer_17.shtm:

  If you connect a component signal to an RGB input, you’ll only get a green image. The R and B output will be very low.

It is exactly what @DoxyLover said.

What can I do to make the green color less intense? Will a simple transistor voltage amplifier for the Red and Blue channels solve things?


texts:
Sorry if this is not a question in the classical sense of stack exchange.

What is the cap that locks the wires called in the attached picture? I've not been able to identifying them with a fair bit of googling. Posting here as last resort.

Many thanks.


texts:
Let suppose a 256 bit memory controller is installed on a PCB with GDDR5 memory modules.

In normal mode you can split the lines into 8 group of 32 bit and drive 8 modules x 1Gbit (128 MB) = 1 GB of total frame buffer memory.

In clamshell mode you can split the lines into 16 group of 16 bit and drive 16 modules x 1Gbit (128 MB) = 2 GB of total frame buffer memory.

The question is: how is it possible to address 128 MB using only 16 bit?

Does it use multiplexed addresses?

What about the throughput, is it really the same on both configuration?


texts:
I have a board with a mix of voltages. It wound up being one voltage to one side of the board, and one to the other. I'd like to make this board 4 layers instead of the original 2. Is there any reason I shouldn't split the internal +ve voltage plane into two? A 3.3 VDC on the left and a 12 VDC on the right on a single internal layer? I'd keep a single ground layer for all.

I don't immediately see an issue with this and it would save cost from needing 5+ layers.


texts: Trying to get (more) accurate readings from thermistor (electronics, math, and code inside)

texts:
So I'm trying to get accurate temperature readings off this TDK B57164K472J thermistor...

It's connected in series with a 1 K resistor, and connected to an ESP8266's onboard ADC.

The thermistor has a Beta of 3950, and the datasheet includes a table for resistances between -55 and 150 C.

In my attempt to increase accuracy, I calculate the Beta myself for the interval the thermistor's resistance is in using the following equation:

B = 1 / ( 1 / T1 - 1 / T2 ) log ( R1 / RR2 )

Then I try to determine the temperature using this equation:

T = T1 * B / log ( R1 / R2 ) / ( B / log ( R1 / R2 ) - T1 )

The full code can be viewed here: https://pastebin.com/ECQHruKN

Factors that are possibly affecting accuracy: The ESP's interval voltage reference reads 3.56 V, it's supposed to be 3.3 V, and my multimeter reads 3.26.

I'm not sure about signage, that is whether my terms should be positive or negative, or when they should be the other.

I'm not sure about my circuit... it's simple for me to learn, but I've seen more complex thermistor circuits, I wasn't just sure how to implement them, and even less confident that I was going to be able to troubleshoot them.

Help would be greatly appreciated.  Thank you.

Schematic

simulate this circuit – Schematic created using CircuitLab


texts:
I'm having problems with my design. I put the schematic here, maybe someone can find an error that I didn't find yet.
EDITED[I forgot the schematic, sorry...]

The microcontroller, dsPIC, has the fololwing current characteristics:
Typical ......................................................... 41 mA
Maximum ..................................................... 60 mA
Maximum current into VDD pin ...................... 300 mA
The FT232R' operating Supply Current is:
Icc1 Normal Operation ................................... 15 mA
Considering the Led current as:
I_led ...........................................................  10 mA
The total current would be at worse case, something aroud 325 mA, maybe a bit higher.
Below, the are 2 photos of my self-made PCB. The smd chip is the LM1117 SOT223. I put saliva on the Tab output pin and it instantaneously evaporated, I could hear and feel it, it was very hot. So, I think it was at much more than a 100°C.
What could explain it, why it became so hot , and what can I do to fix it in another version ?

With my best regards.
(click for larger images)


texts: Why have a bulk terminal at all? (MOSFET)

texts:
I must be overlooking something but I really don't see the need to have a bulk terminal. I am studying the body effect whereby it somehow interferes with the threshold voltage. I don't fully understand it because I'm finding creating the terminal in itself counter intuitive.

I am told that it must be connected to the lowest or highest voltage in a circuit, depending on n or p channel. First of all, if this interferes with the threshold voltage, wouldn't my supply rails directly interfere with the mosfet since they could be 1V or 15V. Not to mention if there was noise in the power supply, it would directly transmit through, no?

What would happen if there was no body terminal?

Why does a BJT not need one?

Do enlighten me.


texts:
I need to turn on an electric ballast without connecting the fluorescent tube, since I'll use the ballast's output to power another device.

My single-lamp ballast has 4 output wires. This is how they are supposed to be connected to the light tube:

If I plug in the ballast without nothing connected to it, I get no voltage between pins 21 and 24 (the ballast doesn't turn on). I discovered that this is because the ballast needs to "sense" the filaments of the lamp in order to turn on. So I tried adding two plastic film capacitors between pins 21-22 and between 23-24, and now the ballast turns on when I plug it in, but it shuts off after about 3 seconds.

I thought about replacing the capacitors with high-wattage resistors in order to simulate the filaments and keep the ballast turned on. Would this work? Do you have any better idea? Thanks.


texts: How does same capacitor with different dielectric affects the circuit?

texts:
I am working on a project and finalizing 0.1uF capacitor with 50VDC(decoupling). I am finding with different dielectrics. My question is how does two diffrenet capacitor having same capacitance and footprint and voltage rating but only diffrent dielectric will affect my overall effect on circuit. Capacitors I was looking are mentioned below
1 C1206C104M5RAC
2 C1206C104Z5VACTU

Thanks


texts:
I am working on a project consisting of a sensor and receiver connected via Bluetooth 5.2. When the sensor receives a start signal from the receiver, it will begin sampling readings at ~10kHz and storing them to a buffer. After a few seconds, once it has filled the buffer, readings will stop and it will then slowly transfer the data to the receiver for processing.
I need to figure out how to measure the latency between when the receiver sends the start signal and when the sensor receives it. The obvious choice would be to send a notification via BT, but the latency here would be variable and far too large. I would need something faster than ~50µs
The sensor and receiver are in close proximity (<30cm) but in an extremely hot and vibrating environment. There is no possibility to occasionally synchronize their clocks physically. PCB space and battery capacity is limited on the sensor, but not on the receiver.
Is there some type of IC with this dedicated purpose? Something with an antenna connection and trigger in / trigger out logic signal?
I have some experience with microcontroller design but little with RF design.


texts: How to superimpose a synchronization pulse on a 12V DC power line

texts:
I have a 12V DC to DC isolated converter powering a remote display.
The DCDC is connected to a 12V supply.
I would like to add a 1ms or so pulse on that every second that can be detected by the display unit that then has an exact tick.
Crazy idea maybe, but is it feasible?
Edit: I am concerned about the power supply side. How to get 12V plus say a 1V pulse on top of it? And then isolated. Or .5V or -1V. Total current is max 100mA.  The remote side I will be able to do figure out later. I do not expect that to be too hard.


texts: Can bluetooth LE detect a touch using proximity?

texts: How accurate is the proximity feature in BLE, can I detect if two BLE are touched tougether?


texts: Induced eddy currents and the power grid frequency

texts:
Eddy currents induced in let's say a metal increase with the increase of rate of change of magnetic field. They increase with a square of both peak magnetic field and frequency.

Now imagine a system with one coil and a metal being put next to it so that the eddy currents are induced inside of it that are heating the metal. If I have the coil connected to a power grid with a 50 Hz frequency, the eddy currents will be smaller than if I had it on 100 Hz. But what puzzles me with this is that if I just increase the frequency of the power grid, the eddy current losses will skyrocket, while power expended calculated by P=U*I will stay practically the same.

If I increase the frequency by a lot I would by this logic break the 100 % efficiency. So what actually happens here? Where does the additional power come from when I greatelly increase the frequency?


texts:
I have a 5V hobby circuit that will be externally powered from a wall wart, with way less than 1 amp. For full flexibility, I'm thinking of using a simple LM7805 regulator - but that has a 7V minimum. Since 5V supplies are becoming ubiquitous, I'd like to allow that too - but then I'd need to bypass the regulator.

What would be the impact / effect / damage if I simply provided a jumper that shorted the regulator's input to the output for semi-permanent use with a 5V supply? Use a 9-12V supply: remove the jumper. Use a 5V supply: add the jumper. I'd leave the input and output capacitors to do their thing: it won't harm the 5V case.

Would the regulator be at minimum consumption because the output was already at 5V? Or would it struggle at full load with the less-than 7V input - or worse, short output to ground?


texts:
I am trying to build a comparator using the LM 393.
Just a basic design where I my Vref 3V is produced by 100/150 Ohm voltage divider.
The input signal is a pulse from a geiger sensor as below:

However, the output signal is not a square wave of duration of ~100us as expected (when Vin > Vref). The duration is rather for the full duration of input pulse, as shown in the second picture:
I am wondering what I might be doing wrong. The Vref does not seem to affect at all. I have tried changing the Vref to 2V, 2.5V etc. The other thing to note is, when I apply a continuous power supply to the input,ie, a DC sweep from 0-5V or 5V-0V, I can observe the cutoff at 3V/Vref. The output goes high or low in accordance to the input. It only does not seem to work when i am trying to process the signal pulse from my sensor.
What could I be doing wrong?
Thanks.
ADDITIONAL Details.
My High Voltage circuit has stopped working, so I am unable to use the Geiger output at this moment.
This is the LM393 connections. I had already used a 10K resistor from output to VCC for the graphs in the previous post.
Unfortunately I am unable to do dual trace as none of the other 3 channels are working in the oscilloscope unit. (I swapped probes and channels. The problem is with the channels for sure). So, I have taken some new pictures.

In order to really test the LM393, I have generated a Sinusoidal signal using R-2R ladder and arduino. This time around, the LM393 did seem to behave characteristically. I have elevated the Vref to 3.5V by adjusting the voltage divider.
Please note the 3 pictures below.

You can note the Vref at 3.5V
This is the sinusoidal signal fed as Vin
The output trace. You can clearly see, if you follow the time divisions, the width of the square wave corresponds to that part of the Sin signal above 3.5V. I have tried this by varying the Vref, and the width of the square wave does change accordingly.
So I am led to believe that previously it must have been the nature of the GM output pulse responsible for the unnatural behaviour of the LM393.

Any suggestions are highly appreciated. May not be the right place, but any hint on how to process pulse signals from a geiger counter into TTL levels?
Thanks.


texts:
I am working on a TI's TM4C1294XL LaunchPad with KEIL and I had a problem at the begining. I installed all the drivers for both USB and KEIL then I succesfully upload TI's blinky example to board it worked without a problem. After that I add some very basic code, in the default program it only blinks the PN0 user LED and I add some code to blink PN1 additionally but nothing has changed. PN0 LED still blinking but PN1 is not. I tried to blink other onboard LEDS PF0, PF4 but the result is same.  Here is the code:

#include <stdint.h>
#include <stdbool.h>
#include "inc/hw_memmap.h"
#include "driverlib/debug.h"
#include "driverlib/gpio.h"
#include "driverlib/sysctl.h"

/**
  * @brief  Program main function
  * @param  void
  * @retval none
  */
int main(void)
{
    volatile uint32_t ui32Loop;

        /* Enable PORTN peripheral access */
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPION);

    /* Check if the peripheral access is enabled. */
    while(!SysCtlPeripheralReady(SYSCTL_PERIPH_GPION))
    {
    }

    /* Enable the GPIO pin for the LEDS (PN0, PN1).  Set the direction as output, and
       enable the GPIO pin for digital function. */
    GPIOPinTypeGPIOOutput(GPIO_PORTN_BASE, GPIO_PIN_0);
    GPIOPinTypeGPIOOutput(GPIO_PORTN_BASE, GPIO_PIN_1);

    while(1)
    {
        /* Turn on the LEDS. */
        GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_0, 0x01);
        GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_1, 0x01);

        /* Delay for a bit. */
        for(ui32Loop = 0; ui32Loop < 1200000; ui32Loop++)
        {
        }

        /* Turn off the LEDS. */
        GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_0, 0x00);
        GPIOPinWrite(GPIO_PORTN_BASE, GPIO_PIN_1, 0x00);

        /* Delay for a bit. */
        for(ui32Loop = 0; ui32Loop < 1200000; ui32Loop++)
        {
        }
    }
}

I have been working on ST's microcontrollers for over 2 years but I never have that kind of problem. Is it possible to problem caused by some write protection feature?


texts: USB Link state is dissconnected while exiting from deepsleep

texts:
I'm developing USB Hibernation feature on on of the platform which use Synopsis DWC3 USB controller. When USB alone resumes from suspend state there is no issue.

But I'm facing an issue while my device is resuming from deep sleep. While resuming the Link state comes as 4 (Disconnected) which leads to USB re-enumeration.

From hardware team there is a query regarding this issue which i'm not able to understand. Please see below,

  In deep sleep we observed:

  a micro-frame peak signal amplitude much grater than expected (almost the double);
  an undesired zero-level offset before the micro-frame.

  These misbehaviors matches the hypothesis of a missing Single-Ended 0 (SE0) termination on one of the stream facing ends. Since the host is the Suspend/Resume master that works correctly with any other USB 2.0 device, we should suppose that device end misses its High Speed (HS) 45 ohm (namely) termination connection at end of Resume phase.

  By specification device must connect HS termination within 1.33 us since Resume end (USB D- falling edge), so this is normally done by the USB 2.0 PHY hardware ready to react in advance since Resume state started. We observed that the device detects Resume state start correctly, by increasing power consumption in few milliseconds, indicating a prompt reaction to exit deep sleep state. Resume will last not less than 20 ms that is largely enough to prepare USB 2.0 PHY to be ready to answer to Resume end detection and relevant SE0 termination required by HS communication link.

  If device SE0 misses, then the host-monitored increased signal amplitude occurring at first micro-frame causes the host to enter an High-Speed Disconnect state, followed by USB reset, FS to HS negotiation, re-enumeration, etc.

Could anybody explain what is the above query?


texts: I am new to CMOS technology and I am trying to learn about CMOS logic gates. I have a problem with transistors sizing. As far as I could understand the main idea is to obtain equal rise and fall times. But, for example, how can one achive such thing on a NOR gate? If both nMOS transistors are ON the capacitor will be discharged faster than if only one of the nMOS transistors were ON. Have I understood something wrong?


texts: bridge rectifier connected to a raspberry pi gpio

texts:
I'd like to connect a bridge (full wave) rectifier to my Raspberry Pi (RPi), GPIO pin 22 (configured as an input). I have configured the rectifier such that it has a 120VAC input and 3VDC output (I used a voltage divider on the DC output). The circuit works fine. I'm able to power an LED from the 3VDC output. Now my question is, how do I connect this 3VDC output to the RPi? Do I just tie the grounds together (rectifier DC ground to RPi ground) and then connect the bridge rectified 3VDC to the RPi GPIO pin 22? I measured a 68V difference between the RPi ground and the bridge rectifier DC ground. I decided to hold off on connecting anything until I figured out why there is such a large voltage difference between the two grounds. Any help would be appreciated. BTW, the RPi is being powered by the same 120VAC source that is connected to the AC input of the bridge rectifier.

Here's the circuit I ended up implementing: 120VAC Detector Circuit


texts: Integrated Circuit Layout Design - Dynamic Flip Flop?

texts:
I need to create a dynamic flip flop like this:

In integrated circuit technology, at mask layout level. I then want to create an 8bit register, using 8 of these flip flops, with a common CLK signal. So that register will memorize an 8-bit vector on an positive edge of CLK, something like this:

So I created the flipflop in IC like this:

But it seems somewhat ugly, and I don't know exactly how I'd fit it in my 8bit register. Do you have any ideas how I'd go about doing that? Maybe change the layout, or make it smaller?
I used minimal sizes for the NMOS transistors, and optimal PMOS sizes for having symmetrical edges 1->0 and 0->1 (Width of PMOS/NMOS = 2.4)

Any ideas? thanks!


texts: Engine cranking corrupts SPI driven 7segment display

texts:
I am driving six 7-segment displays with SPI using MAX7219 and ATmega128. This is for displaying various engine parameters like rpm, oil pressure etc. for large marine diesel engines (>100 kW). The system runs on 24V DC from lead acid batteries (automotive type) stepped down to 5V with the help of Mornsun DC-DC converter (URB2405 - Isolated DC-DC converter).

The system runs fine when the engine is firing smoothly (approx. >900 rpm) and was recently tested on a test bed for 2.5 hours without issues. However, the display malfunctions completely and is very unreliable when the engine is cranking.

After debugging this for many days and fixing lot of stupid mistakes (forgot to add flyback diodes for a few on-board relays :( !!) I still have very poor display reliability while cranking. When the display malfunctions, either garbage is displayed on the 7 segments, or all segments light up or it goes blank.

I have added a 1000uF/63V capacitor and a MOV before the DC-DC converter to reduce supply fluctuations while cranking. However it is still very unreliable. I feel that the controller is working ok during cranking and it is only the display which malfunctions.

I am looking for some suggestions for power supply stability during cranking or large transients. I have tested a few things and am about to test if the following improves the situation :

Use shielded cables connecting the display PCB to the controller board to prevent noise corrupting SPI
Isolate high current carrying cables (starter motor relay coil, stop solenoid relay coil etc.) from signal wires with shielding and route them differently inside the enclosure
Add a 0.1uF (104) cap between the 2 grounds of the DC-DC converter to reduce noise on the 5V side
Power the whole thing from an off the shelf automotive power supply which provides all the standard protections. Any suggestions ? (Input 24V, Output 5V, 600 mA max 3W)
Reduce cable length to improve SPI reliability (Although currently the total length: track + wire is less than 1 ft so not so hopeful this would make any difference)
Increase decoupling cap for each MAX7219 from 10uF to 470uF
Use very large capacitor for maintaining voltage while cranking

I still feel I am missing the crucial reason why the display malfunctions. Voltage dip should not really be a problem as the DC-DC converter is rated to provide smooth 5V for a wide input range of 9-36V. Even if the battery is discharged, I doubt if the voltage will drop from 24V to less than 9V, so it is a mystery why the display goes blank or displays garbage.


texts:
I have been trying to create a simple switched capacitor for my circuit, yet I must be doing something wrong and can't understand why it won't work.

When the MOSFET is ON, VGS=3.2V, whereas when it is OFF, VGS=0V. I want this 1pF capacitor to be addes to my circuit, which operates in the range of 4-6GHz. Normally, when the MOSFET is OFF, the capacitor should "see" an open circuit and not contribute its capacity to the circuit. However, no matter if the MOSFET is ON or OFF, I get the same result:

Can somebody please tell me what's going on here?
Thank you in advance!!!


texts:
In the following circuit, consider the op-amp to be ideal (gain = ∞ , input resistance = ∞) and transistor beta is 20 A/A

Initially I was using virtual ground concept here but in the given answer transistor is in cutoff so voltage at -ve terminal is 5V. Is this circuit providing -ve feedback to the op amp or not. How can it be cutoff? We have to find current throug 1kΩ resistor and voltage at collector.
My answer : 300 uA
Given answer : 0A


texts: Thin wires - tips for stripping and soldering?

texts:
Any tips for stripping and soldering thin, tiny wires like these below, (maybe even thinner!)?

Initially, I would think of using a knife for stripping because wire strippers will definitely not work. Then with soldering, too large solder flows are highly unwanted. Someone recommended to heat a small bit of solder onto the soldering iron tip and then letting it flow to the joint. Any recommendations?  Thank you!


texts: Circuit protection with TVS and polyfuse

texts:
I have a 36V system that has to be protected against 1000V surges as described by IEC61000-4-5. Some SMC TVS diodes are rated for this exact purpose and are able to conduct the surge pulses without damage.
Problem solved?
However: In many posts here and elsewhere a polyfuse is placed in front of the TVS diode. The reasoning being that you then get DC overvoltage protection, and even reverse polarity protection if the TVS is uni-directional. But as far as I can tell no polyfuse on the marked is rated for the currents or the voltages involved with transient protection.
Why is this such a popular circuit? A TVS diode's purpose is to conduct high energy pulses, but that purpose is invalidated by the introduction of a polyfuse.
Secondly: It therefore seems impossible to get both DC overvoltage and transient overvoltage protection at the same time. DC overvoltage will destroy a TVS, transient high voltage will destroy a polyfuse.  Are there other components that can be used?


texts:
I sometimes see differential filters like this:

And sometimes this :

Basically sometimes there are 3 caps (2 going to ground on each input), sometimes I only see 1 cap ( 1 differential cap, none going to ground).

Which way is the correct way to do the input filter? What happens when you only use 1 cap instead of 3? Does it matter? When does it matter? What's the advantage of using 3 caps? Meow?

Thanks a lot


texts:
So, I've been reading up on clock skew. I came across the fact that clock skew can be incredibly useful, in the sense that positive skew can be used to speed up the circuit by increasing the clock's frequency.
Then why are there so many measures taken to completely eliminate clock skew? It seems to me that having a controlled amount is extremely beneficial? Are there any harmful effects of clock skew?


texts: Can I charge Ni-MH battery with modem power supply?

texts: I bought a 8.4V 3800mAh Ni-MH battery from eBay. Unfortunately, its charger is not working. I searched about charging Ni-MH batteries on the web. Can I charge this battery with TP-Link power supply which has an output of 9V and 0.6A? I think 0.6A might be too much for this battery but I am not sure. What would be the ideal voltage and current to charger this battery?


texts:
I'm designing a color organ. My circuit so far:

Quick description: Input signal is .2V pk-pk. Voltage after amp is 4V pk-pk. 2N7000 needs 2V to turn on, so it should turn on when the frequency I want is passed through the filter, but any other frequencies are decreased in amplitude.

My problem lies after C2 at node Va. What I expect there would be an amplified wave of my input centered on the x axis (if the y axis was measuring voltage.) Instead what I find is my amplified input shifted up by 1 or 2 volts. So even though my AC signal decreases at node Vb as frequency increases, it is still biased by that +1 or +2 volts, so the MOSFET stays on at all frequencies.

I've tried a number of things so far. First, I tried discharging the caps, but that seemed to have no affect. I tried adding a large resistor in parallel with C3, but that didn't help much either. I really don't know what's going on here or how to fix it, so any help would be greatly appreciated. Thanks in advance!

EDIT: I also chose large values for my filter because previously it was too small and the lack of impedance was causing a voltage loss at higher frequencies. I am also aware of the nasty clipping my amplifier gives me at the moment. I plan on fixing it later.


texts: RC filter with an square wave input (checking my math and find my error, if it is somewhere)

texts:
I've this RC filter circuit (r is connect to earth on the bottom):

My Vin is a square wave:

With Laplace transform I derived that:

$$Vout(s)=\frac{r}{r+\frac{1}{cs}}\cdot Vin(s)$$

and this square wave has a laplace transform of $$Vin(s)=\frac{\text{A}\tanh\left(\frac{\text{T}s}{4}\right)}{s}$$

My math (H(x) is the heaviside-stepfunction):

So, when we substitute that in,in the equation for Vout(s) and calculate the inverse laplace transform, and plot that function I got this:

  Q: Why do I get (from the theory) this strange output voltage? I choose T=1/50 (so the frequency is 50 Hz) and A=6 and R=1980ohm and C=4.7microfarad

EDIT:

When I make A=-6 and remove the 'floor'part I got this:


texts:
I want to drive a 2.2" QVGA LCD that has I80(Intel 8080) interface.

I found that other people did it with microcontrollers that have XMEM(Atmega64) or FSMC(ST) .

Now I want to know if it is possible to do it just with GPIO ?


texts: Why does this current source absorb but not deliver power?

texts:
Question (Extracted from a book):
Determine the voltage across each current source, the current through each voltage source, and the power delivered or absorbed by each source.

Official Answer: Ix = 16 A, current through 20 V source is 6 A, voltage across VCCS is 12 V, and voltage across the CCVS is 8 V; 20 V source delivers 120 W; 10 A source delivers 200 W; VCCS absorbs 192 W; and CCVS absorbs 128 W.

Confusion:

10 A source delivers 200 W, 10V source delivers 200W, and CCVS absorbs 128 W. I have no problem with those, the current flows in the same direction as 10A, 20V and in the opposite direction of CCVS.

VCCS absorbs 192 W. This doesn't make sense. The current flows in the same direction as VCCS (0.8 Vab). It should deliver and not absorb power.

This seems like double-standard to me. The rules are: if the current flows from - to +, the source delivers power, and on the other side, if the current flows from + to -, the source is absorbing.

Why did the solution say the source is absorbing power and not delivering power?


texts: How to insulate more of my fluke test leads

texts: these are the test leads I own, I am wondering if there is a something I can purchase to shield the exposed metal more to avoid incidents. I heave the little plastic shield that comes with them but they are to wide to fit in the type of terminals I use, is there any accessories I can purchase to help me with this. I preferably don't want to buy new test leads


texts: Are there any latching transistors without relays?

texts: I am currently working on a diy 4 bit computer but I have ran In to a problem. In order to create bytes that can be changed by my processor I need to have some kind of transistor that latches to true as soon as it is given a signal (imagine a piston or actuator hitting a latching button any time a signal is sent). I don't own any relays and I would prefer to have this component in a IC form (if it exists) and I wouldn't mind buying them, but I'm just wondering if there is a way to make my own without relays.


texts:
(sorry for the wall of text, I tried to give as much Info as possible)

I am pretty new to electronics and am working on a project regarding controlling the flow of a pump (BLDC based). End goal: Apply a sinusoidal supply around a variable DC offset with variable amplitude (at least +-4V) and frequency (0-10 Hz, low Freq). One big hurdle is definetly the pump... The manufacturer only provides a very short explaination of the electrical aspects of the pump. Unfortunately, I HAVE to use this model.. Datasheet (I am using M400-S180): https://docs.rs-online.com/9836/0900766b8162656f.pdf. Currently I am using the XR2206 kit for the modulated sine wave. It has a DC Bias of 6V with an Amplitude of +-4V (8Vpp). But it only gives out 20 mA which is not enough to power the pump (I measured the internal Resistance of the pump: 2V - 0,09 A - 22 Ohms, so I guess it needs at least 0,1 A to start). So I wanted to use an bjt common collector amplifier (PNP) to boost the current. I watched some videos and tried to calculate the right resistor values. Basically I assumed Beta=10 and wanted Ie=200mA so Ib=20mA.I am not sure how to calculate Resistances with AC so I assumed to use Vrms? Vmax=10V -> Vrms=7V, R1=7V/20mA = 350 Ohms (used 330). R2=7V/200mA= 35 Ohms. At the time I did not have 35 Ohms at hand so I used the next smallest, 17.5 Ohms so double the current.

It worked okayish. The pump started and amp/freq modulation was possible via the XR2206. But the max Vpp changed from 8 Vpp (+-4V) to 3 Vpp (+-1.5V) and also the 17,5 Ohm resistor got pretty hot because of the large current. Also, the Vrms of the Output was only 5V. I am not quite sure why the amp dropped but maybe its because of the difference in output impedance of circuit and input impedance of the pump? (I am honestly a quite a bit confused by impedances so this could be complete rubbish). Also the circuit was not so good designed as I found out through more videos.

I now tried on using a two stage amplifier: Common Emitter (NPN 2N3904) + Common Collector (PNP BC640). I used a better more stable circuit and calculated the Common Emitter circuit values. C1=10uF (AC coupling, I tested with an Osci so no calculation here). According to the tutorials I_R1 = I_R2 >>I_B and I_C = I_E. I wanted V_E = 0.6V. V_B = V_BE+V_E = 1.2V. I_E = 50mA and Beta = 100 according to the Datasheet of the NPN, so I_B = I_E/100. I_R1 should be some 50 times higher than I_B (so we have a stable amplification), I_R1 = 0,012A. Lastly R1 = 1000Ohms, R2 = 100Ohms. V_E=1/2 Supply = 600mV, and with I_E = 50mA; R_E = 10Ohms.

Vpp_out=10V from Vpp_in=8V. I could not test it with the pump because the current was not amplified yet. So I now tried combining both amplifier with a new Common Collector circuit. Spoilers: It did not work. So I left the Common Emitter as was and said I wanted I_E2 to be at least 120mA. R7 = 12V/120mA = 100Ohms. I_B2 = I_E2/100 = 1,2mA. I_R3 = I_B2*50 = 60mA. R_3+R_4 = 12v/60mA = 200Ohms. Oh.. pretty low, so I settled for I_R3 = 48mA, R3+R4 = 250Ohms so R3 = 220 Ohms R4 = 47 Ohms.

Well as I already teasered it did not work. Amp Modulation was reduced to +-1V (2Vpp). The pump did turn on but the whole circuit drew more than the 120mA calculated, It was around 300mA. Since then I have tried numerous simulations on LTSpice so I dont have to build up/down circuits every 10 mins but until now no success. Can anyone suggest me a direction where I can head to or point out the flaws in my circuit/calc? Does anyone have a clue why the amplitude of the sine wave dropped? Also: Sorry for the Variable-formatting, pretty messy!


texts: Watt-squared-seconds: unit of safe operating area?

texts:
In the datasheet of Linear's LTC4364, page 15, the safe operating area (SOA) of a MOSFET is described as:

  For short duration transients of less than 100ms, MOSFET survival is increasingly a matter of SOA, an intrinsic property of the MOSFET. SOA quantifies the time required at any given condition of VDS and ID to raise the junction temperature of the MOSFET to its rated maximum. MOSFET SOA is expressed in units of watt-squared-seconds (P2t), which is an integral of P(t)2dt over the duration of the transient. This figure is essentially constant for intervals of less than 100ms for any given device type, and rises to infinity under DC operating conditions. Destruction mechanisms other than bulk die temperature distort the lines of an accurately drawn SOA graph so that P2t is not the same for all combinations of ID and VDS. In particular P2t tends to degrade as VDS approaches the maximum rating, rendering some devices useless for absorbing energy above a certain voltage.

I've never encountered W^2s (watt-squared-seconds) before, and no datasheet that I've seen expresses SOA in W^2s -- rather in graphs of I_D vs. V_DS.  Does anyone have any insight into how it's calculated based on datasheet graphs?  Or how it's derived?


texts: How to connect an extra serial port of Arduino Mega to computer?

texts: As you know Arduino Mega has 4 serial ports. I need one extra serial port besides the one which is connected to computer via usb cable. So I want to use one of the other 3 serial ports. But they are just pins. Is it possible to use any other serial port with usb to connect to PC and if so how can we do that? How can I connect those two RX TX pin to a usb for connecting to computer?


texts:
I am working on a control circuit for a heater. The circuit has a temperature controller (not included in the drawing), an overtemp controller, I/O going back to the PLC providing "heater ON" and "heater overtemp" status to the operators in the control room, and a strobe light on top of the heater panel.

Green on the strobe light indicates that the heater is ON. Amber indicates that the level of water in the tank that the heater is heating is low; this is controlled by a float switch in the tank. Red indicates that the heater is in overtemp condition.

One of the permissives required for the heater to run is that the drive controlling the pump should be in run mode: NO contact CR in the drawing. This is so that the heater doesn't run dry.

The circuit is working the way it's supposed to but I feel like it could be improved...and that's why I am posting here. I'd appreciate if you guys pitch in to simplify my design while satisfying all the requirements.

For the curious ones, the main temp controller (Yokogawa UT35A) has a 4-20mA signal going to a step controller which then controls 4 heater banks based on PID. I didn't include that because that was designed and installed by the manufacturer. I only did the overtemp and status indication part of the project.

Stack exchange wouldn't let me upload a DWG or a pdf file, so I am attaching a snapshot of the dwg. Hope it's legible.


texts: Regulate ~350V spikes (duration nanoseconds) to logical level 5Volts

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Use standard 5.1Volt zenerdiode?

Can I trust that with zener diode it wont leak over 5 volts, concerning fast raising high voltage spikes. How about resistor sizing, the input goes to Arduino digital input pin.

The application is bit weird car ignition distributor sensor signal approx 350Volts. Its not the kVolt line which goes to sparkplug.


texts: Measuring quiescent current of a voltage regulator

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I purchased 10PCS Socket Adapter plate Board For NRF24L01+ Wireless Transceive module and would like to know how much current/power it will draw as I want to run a project on batteries.

A close-up of the unit is below.

Using a multimeter, I measured the following current from 7 of these units (powered from 5.2V source):

4.67, 3.85, 4.70, 4.58, 3.93, 3.78, 3.80mA.

I scratched the power LED off another unit (LED is between GND pin and IRQ pin), and measured 3.28mA.

My question is, is the current I can see (minus the LED current) the quiescent current of the 3.3V voltage regulator?  Also, there is no nRF module plugged in to the socket; does the regulator need a load before I can measure its power usage?

I think this is the regulator -
Advanced Monolithic Systems AMS1117 1A LOW DROPOUT VOLTAGE REGULATOR, and there's a row in the datasheet with these values:

Thanks.


texts: Floatable power supply one one side of isolation amplifier

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I am making a circuit where I need to float one part of the circuit with (-200V) I am using isolating amplifiers ISO124 to isolate that part of the circuit.

An image below should explain what I am trying to say.

The part in the orange box is isolated and floated to -200V (floating ground, FGND). The problem I am having is finding  power supply  for the op amps on the floatable side of the circuit. The parts outside the orange box can be floated easily with any +- 15V power supply. What do I do with the part inside the orange box?

I have researched a bit and found several DC-DC isolated power supplies, but I am not sure how to float them so that I can have 200+15 V and 200-15 V power supply for the opamps in the floatable region.

I guess what I am asking is if there is a isolating  power supply device something like this?

Where there are three terminals on the output side ( right) and I can float it to whatever I want. If not? what other choices do I have. I have seen many people using optocouplers and isolating amps, there has to be something people do to power opamps in the floating side.

I can use the DC-DC isolated power supplies, but I not only have to float the FGND, but also the rail voltages of the op-amps relative to FGND like so:

I want the rail voltages to be FGND+15V and FGND-15V and not, FGND+30V and FGND .


texts: How do actively driven mosfets or transistors react to floating source?

texts:
Attempting to add some lights to a car's "intelligent" lighting system. Want to make sure I understand how my n-channel mosfets will react to losing their ground, while their gates are still connected.

simulate this circuit – Schematic created using CircuitLab

My circuit is a load on a n-fet, with either their gate pulled to ground, or logic level GPIO (I will be using logic level mosfets, probably not 2n7000s). The lighting system either has a mechanical relay, or most likely a n-fet itself. The n-fet would likely be controlled by PWM.

In this scenario, how will M1 and M2 react to their sources floating? Will they be damaged, will my micro controller be affected somehow? Would they react differently if the gate is pulled high or pulled low? Secondly, would NPN transistors work any better?


texts: AD9553 PLL (Failure to Synchronize lock)

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I have been using the Analog Devices AD9553 Eval Board, I am operating it as a clock translator, inserting a 10MHz LVDS differential signal and setting the device to produce a 100MHz LVPECL differential signal. I aim to operate the device in the LBW region (B=0.17KHz) as my signal is not expected to deviate in frequency by drastic amounts.

At first I had issues with phase locking all together, but this was remedied (so may it seem). I can observe the lock signal remain high for the majority of the time, dropping low rarely.

However my main concern is that my system is supposedly locked - my 100MHz LVPECL signal does not stay stationary on the oscilloscope when triggered from the sinusoidal 10MHz reference signal. I am observing the sinusoidal reference signal as I cannot probe the LVDS signals when connected to the PLL (my scope only has 1M and 50R termination modes and this interferes - Scope:TDS5104B). I know there is not a problem with the LVDS conversion stage as all those signals are stationary on the scope.

I have had a play around with the values in the registers but to no avail (N Div etc). I have attempted to use the debug mode to view the PFD signals etc from the LOCK pin but they show nothing on the scope, the only one I can observe is the XTAL clock. I take it that because there are no signals on the PFD div 2, PFD ref div 2 and the PLL feedback div 2 - that there is a problem with my reference signal, values or the device.

Regarding my setup, I am prototyping the system on breadboard, I do not know if this could be a cause of problems (I have kept the wire lengths as small as possible and have a COAX going from the breadboard to the EVAL board) , but I am confused as it says the PLL is locked - but is infact not locked to its reference source. Attached is one of the combinations I tried from the EVAL board wizard software.
AD9553 Datasheet: http://www.analog.com/media/en/technical-documentation/data-sheets/AD9553.pdf

Guidance & Advice would be very much appreciated.

Thank you for reading this.


texts: Charging two batteries with one solar panel

texts: I have two batteries connected in series. However, I'm using it to separately get +12V supply and -12V supply. I have a 24V rated solar panel, and was wondering if it's possible to charge the two batteries while in operation. Would it be possible to to connect the two terminals of the solar panel to +12V and -12V terminals? Does it not matter if I'm using a common ground from the terminals?


texts: Measuring RF power of a communication signal

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I am running a software radio application. I need to measure the power of transmitted ofdm signal. The issue is that FCC has regulations of -50dBm/Hz. So I understand that if i need to send a signal at a bandwidth of 1Mhz, the the maximum allowed power -50dBm*10^6 which is 0.01W or 1mw.So i am trying to measure the power at output of my USRP transmitter. I just brought an oscilloscope and measured the sinusoidal signal peak to peak voltage in the oscilloscope. It was 7.2 v peak to peak. I was unsure how to use v^2/R because i don't know the resistance. when i assumed resistance to be 1, I got the power output to be 39dBm. I then checked online and found that you need to measure power spectrum. So that  means I need to know power at frequency of transmission. I need a RF power analyser for the same.

How is the power at frequency spectrum related to analog power measured by oscilloscope at the output of antenna?

What should i measure and reduce if i need to keep it within desired FCC regulations? Is the power of the frequency spectrum constant?


texts: Car security solution - designing the right motion detector

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My car gets broken into quite frequently. The car is right outside of our bedroom window. The break ins happen at night, and we never hear them! They must be very sneaky.

I would like to design (or find a plug and play solution) for a motion detector that I will place inside the car that is either battery powered or something that can plug into the car adapter. When it senses motion, I want it to send a signal to our bedroom window so that we can call the police.

Here's an amazing diagram of what I want to happen.

Can you please suggest a design or a plug and play solution that I can use to do this? I know there are many motion detectors, but I would specifically need something that will work at only a 1 meter range because it should be inside of the car sensing any movement INSIDE of the car, and ignoring everything outside.

I don't know if this is relevant, but the windows are tinted.


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The BJT and MOSFET can be modeled using the Hybrid-pi model. I only know that the transistor can be modeled with linear elements like that, but I don't know why.
There are a lot of things that confuse me: (Please use BJT as example)
Model circuit from the Wikipedia page:

The current of a transistor is usually exponential to its voltage. But why is that relationship approximate to linear in this model?
Is there any restriction on the limitation of voltage, frequency or anything else to ensure the difference between the model and actual value is under negligible error?
Are there any books or any other resources to prove the hybrid-pi model from scratch?
Currently, all the resources I can find just say what the model is. There is no source in details about how this model is developed.


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I'm working on updating our products, but there are a number of constraints. TL;DR I can't change the parts that would make this really easy.

We have devices that interface to our control panel using a three wire system. +24 VDC, 0 VDC and a signal line (bi-directional) that roughly varies 0 to 5 VDC. People do all kinds of fun things in the field and we get more then the allotted voltage on the signal line (~ > 5 VDC). I can't protect against everything but I know what the common failures are and I can work to stop that from being an issue. I'm thinking I can use an op-amp diode clamping circuit to get what I want (a peak clipper/clamper). I want the voltage to vary 0 VDC to 7 VDC, and anything over 7 VDC to + 24 VDC just gives me 7 VDC out of the op amp. I can scale that back down to the 0 VDC to 3.3 VDC range for the micro ADC. This allows me a number of things:

I have sufficient resolution to distinguish the voltage levels I need.
+24 VDC on the signal line is no longer an issue.
By extending the range of the diode clamping and down scaling, I have a new state where we can determine that the installer did it wrong (and certain other failure modes can be seen).

So I built this circuit on a bread board today, the voltages are not the exact ones, it just a proof-of-concept and I'm limited in power supplies on hand (I'm not going to get into the failure to equip the shop correctly).

simulate this circuit – Schematic created using CircuitLab

From what I found on-line this should work just dandy, but it doesn't. The op-amp is rail-to-rail in and out. All literature shows that this should vary from 0 VDC to 12 VDC smoothly then clamp at 12 VDC and not change beyond that up until the rails. I get about 7 VDC out of the op-amp with no input.

I'm doing something wrong or this isn't even right and I'm not smart enough to understand why. My knowledge is meh as my education was alright and it's been almost a decade between graduating and having to do any work that requires understanding.

Ideas?


texts: Which power source/elements are better for a spot welder?

texts:
I'm going to build a spot welder for the batteries of my RC models, but started thinking which power source is the better choise:

12V car battery with higher start current (500A+)
Transformer which is usually a lot more expensive, and need expensive additional elements to be used for spot welding

I'm assuming that during welding the car battery variant is good to be disconnected from the power grid (not connected to the charger) during welding and also there's a need for momentary switch for high current (50A+ or more) plus a starter relay 12V alos rated for at least 500A


texts: Does an Arduino serial port expect 8-n-1 or 7-e-1?

texts:
I am exploring serial communication using the arduino, and so far I haven't had too many problems. Till now at least. I'm using an external module for reading a capacitance(the module is an DN060-02v04 from JYETech) and it's supposed to transmit automatically a lot of information about its readings. According to the documentation that came with it, it transmits in 8-n-1 format at 38400bps fixed. Simple enough, I am using SoftwareSerial and have the baud rate set correctly. I am supposed to get a string of bytes representing ascii characters, however the numbers I get back don't really seem to correspond to anything usable. I'm thinking maybe the arduino is trying to read in 7-e-1 format, but I'm not sure because I can't find any information about it. I could also be doing somethign else wrong, but I really can't think of anything. So the actual question: Does the arduino communicate using 8-n-1 or 7-e-1?

More details: I am using an arduino UNO, running on linux, and using arduino version 1.0 to program it.

EDIT: Source code:

#include <SoftwareSerial.h>

//                       rx  tx
SoftwareSerial capSerial(2, 13);
int tmp;
int next;

void setup()
{
  capSerial.begin(38400);
  Serial.begin(38400);
}

void loop()
{
  if (capSerial.available() > 0)
  {
    tmp = next;
    next = capSerial.read();
    Serial.print(next);
    Serial.print('\n');
  }
}


texts: Power amplifier - Drain voltage should be pulsed?

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I am trying to bias the power amplifier QPA1022. I am planning to bias this amplifier by fixed gate voltage and pulsed drain voltage.For this I am using MABC-001000-DP000L for the same.
I am unable to interpret from the datasheet whether this amplifier can be supplied with pulsed drain voltage.
There is mention of some "pulse width = 100uS" in test conditions. Is this the ON and OFF time for the Drain voltage ?


texts: What do you mean by a Wattage of an incandescent bulb?

texts: How do I interpret the wattage of a bulb. For example when it is said that the bulb is rated for 60 W , what does that mean?


texts: Writing the KVL equations for ideal and non-ideal transformer

texts:
According to my textbook the following linear circuit

simulate this circuit – Schematic created using CircuitLab

Follows these KVL equations in phasor forms

\$Vs=(R_2+L_3jw+L_1jw)I_1-jwMI_2\$                 for the first loop

\$0= (jwL_2+R_3I+jwL_4)I_2-jwMI_1\$               for the second loop

How would this formula changes when the transformer is ideal?

According to ideal transformer definition \$L_1\$ and \$L_2\$ are infinite.  How can this be interpreted in the above equations?


texts: At which frequency is given a capacitor value

texts:
I am wondering what is the frequency ty value of a capacitor is given for.

For example if you look at the datasheet of the GRM32ER60J107ME20L if you look at the caracteristic on page 2 figure 1 you have Z = 0.2Ohm for f = 120kHz.

Then you have: Z = 1/(2 * PI * F * C)

=> C = 1 / ((2 * PI * F * Z) = 63µF.

The problem is this capacitor is a 100µF capacitor.
I understand the value changes with the frequency but what is the frequency for which the value 100µF is right?
Is it always the same frequency?


texts: Beginning programming for Atmel uProcessors

texts:
I'm taking the next step, going from my Netduino into the smaller microcontrollers from ATMEL (since there is no really tiny (tinier than the netduino) stuff running .NET).

Also have some experience with ATML and some (silly) assembly coding back from when I went to college. Assembly isn't my thing, my minimum requirement is C.

I'm looking at the ATTiny84 and ATTiny85 microcontrollers.

Since I don't have a Arduino Uno or whatever, I would need a programmer. The Atmel AVRISP STK500 USB ISP Programmer should do, but is there anything else I need to program the microcontrollers?

The plan is to put it in a breadboard, connect the programmer to the microscontroller and AVR Studio should do the rest?

Now there is some stuff I don't understand. Is it optional to put a bootloader on it? As I understand it you can put Arduino bootloader on both of them, making them able to run Arduino stuff which in turn could simplify the programming?

What is the process here, do I use the AVR Studio to flash both of the microcontrollers with Arduino tiny and then do the rest of the programming in Arduino?


texts:
I am using an STM32F302C8T6 and ST-LINK v2. The MCU should normally be pulling NRST high through its weak pull-up resistor, however it's being held low somehow. This prevents me from being able to flash.

BOOT0 is tied low. If I hold NRST high with a PSU at 3.3V with current limiting to 5mA, the debugger can pull NRST low temporarily to reset the MCU and flash reliably.

This is the MCU schematic:

The only thing that was connected between NRST and the debugger was a TVS diode that I removed (D41).

I am seeing this behavior across multiple boards with similar schematics.

I suspected that D42 was backdriving the MCU as I was reading 3V on the open drain STATUS_R/G/B inputs, so I removed D42.

After re-reading the datasheet, I realize that I should have a 0.1uF decoupling cap from NRST to GND. I don't think that is the problem though.


texts: I try to explain what I see when I unplug capacitor from below circuit, and put it back inversely. So after the capacitor has been flipped voltmeter shows +6V and slowly dischares to 1,5V and stops there. It may seems to be normal at first but when I strat to think what happened I cannot understand it. Let's go back to the beginning, it is what the circuit below depicts. Capacitor is charged to 3V thru 10Mohms of voltmetter, so it has equal amaount of charge on each plate but with diffrenet signs. So one plate has X columbs of positive charge and other X columbs of negative charge. Now after we unplug capacitor and put it back inversly we have a situaltion in which negatively charged plate is now connected to positive terminal of battery and positive one to negative terminal of battery. So what happens? As I said, multimeter shows 6V and slowly discharges to 1.5V. First why 6V? If the negative cap plate is connected to positive battery terminal it should dissolve all negative cherges it has previously and gain these positive ones making this closer to the other plate charge therefore lowering the voltage. Why it isn't the case? Why then it stops discharging at 1.5V?


texts:
I have some difficulty to understand the schematics for the following anemometer: http://www.fondriest.com/pdf/rm_young_05103_manual.pdf

I have confusion at 5 points.

Here is the schematics:

In the manual it states: “Avoid a short circuit between the wind direction signal line and either the excitation or reference lines. Although there is a 1K ohm current limiting resistor in series with the wiper for protection, damage to the potentiometer may occur if a short circuit condition exists” But when I look at the circuit diagram it seems to me like there is no problem if wind direction signal line and the reference line shorts. It seems like there is danger if wind direction signal line via the 10K potentiometer comes to dead spot and shorts with the excitation line. Do you think there is a problem if wind direction signal line the 10K potentiometer comes to dead spot and shorts with the reference line?
What is the use for the capacitor C1 at the circuit diagram which is connected in parallel with ac signal output for the wind speed?
What is the use for D6 and D7? Could you give an example when are they beneficial?
In the manual it states: It is important to note that, while the sensor mechanically rotates through 360°, the full scale wind direction signal from the signal conditioning occurs at 355°. The signal conditioning electronics must be adjusted accordingly. For example, in a circuit where 0 to 1.000 VDC represents 0° to 360°, the output must be adjusted for 0.986 VDC when the instrument is at 355°. (355°/360° X 1.000 volts = 0.986 volts). Is total dead spot 5° form only one side or it is at  both sides as 2,5°+2,5°?
In the manual it states: “To prevent false readings, signal conditioning electronics should clamp the signal to excitation or reference level when this occurs.” Is that about the dead spot part in case of short circuit? Does a zener clamp work for that purpose at the signal output?


texts: Placement of the microcontroller on the back of the board with LEDs

texts:
I am designing a board with 9 SK6812 LEDs.
On the back of the board I want to place the Atmega328P microcontroller.

I have doubts whether the heating of the LED can affect the operation of the microcontroller?

Board Thickness: 1.6mm
Two layers


texts:
I've a relay with Maximum contact voltage of 24VDC @ .5A.
Switching capacity of 12W. So can I use the relay contacts for 110VDC and 5mA.
As it is much lower than the Switching capacity.

If it can be used how is the de-rating determined? (When manufacturer does not provide any info)


texts:
I am reading the microchip's LoRaWan Gateway manual. On Page 48, I got stuck at receiving side on the LoRaWan RF circuit. It looks like they have some sort of LC Low Pass Filter. I have used this online tool to calculate it's cutoff frequency. It gave me following reading:

Results:

F = 3.3553e+9 [Hz]

Z = 31.623 [Ohms]

I am not sure about the Resistor in between them. Please help me in verifying my interpretation of the circuit. The part of schematics that I am referring has been posted below:

Can someone help me in understanding the part of the circuit that have been encircled. 1257_RFINA and 1257_RFINB goes to RF inputs (Single-ended) of two different RF transceiver chips (SX1257). TA1567A is SAW Filter and SPF5043Z is LNA.


texts: What does it mean when a battery still has high voltage but doesn't deliver current?

texts: All the dead batteries I tested had very small voltage and no current under load except one strange battery that had about 2 volts but no current. What causes this different type of dead battery?


texts: what is the best method for device location services

texts: I am working on a side project at home and need a way to detect when an object is in certain rooms of a house. GPS is not practical because the difference between my living room and bedroom would be too small. I was wondering if bluetooth has measurement capabilities? Or if there is some product that already does this?


texts: How to determine a current is AC or DC by use of analog multimeter?

texts: How can one determine a current is AC or DC by use of an analog multimeter? Or its workaround with rudimentary tools or equipment ?


texts: How do Vivado and Vitis determine where stack and heap are located?

texts:
Been taking advantage of lockdown to learn how to work with softcores and C on Vivado/Vitis, using a Digilent CMOD A7 board I have.

I managed to get the out of box demo built and running, but I hit a problem which was that the board always died on the memory test routine. I also had some erratic behaviour of the USB programming/debug link. The memory being tested is the external 512KB SRAM on the board.

Eventually I realised that the system was set up so that that external RAM is used as heap, stack and so on, so the memory test was stomping on the system working memory and causing the crash.

Looking in my build files, I did indeed find two copies of the linker script in my tree. One of them defines the FPGA internal memory as the working area, the other (the one in my Vitis build) defines the external RAM. (I'm not quite sure how I managed this, but I did have to do quite some fighting with Vivado/Vitis to get running.)

But when I try to replace the file in Vitis with the good one, it complains then that the board config is not valid. So I guess that the linker script cannot be manually edited like this. It seems that working memory is defined somewhere in Vibado, and then ends up as part of the board config.

I searched the Xilinx docs for something on this, but could not find any place in Vivado or Vitis where the working memory used by the system is defined.

Can anyone explain to me how to reconfigure my system to use internal FPGA memory for the processor stack, heap, etc?


texts: Board mount AC/DC converter design concerns

texts:
I'm going to use board mount power supply (IRM-30-12) for first time. It has class 2 protections as per datasheet.
Does it really protect my digital circuit in case of Hazardous situations like lightening and others?

Should I place any switching regulator/ battery charging components on its either side of PCB?


texts: When looped, memory address not being displayed sequentially while skipping intermediate memory

texts:
I am trying to run through a sequence of memory and display it on the command window. Here is the code:

int addr[10];              //Address addr is 32 bit
for{int i=0 ; i<10 ; i++}
{
  int *p = &addr[i];        //Pointing to the 32 bit addresses from 0 to 9
  cout<<p<<endl;            //Display the pointed addresses
}
return 0;
 }

Output:

 002AF948             //address of addr[0]
 002AF94C            //address of addr[1]
 002AF950            //address of addr[2]
 ....upto i = 9

Question: In the output, Isn't the address of addr[1] supposed to be 002AF949 instead of 002AF94C?. Why is it skipping the memory addresses 002AF49, 002AF4A, 002AF4B and then displaying addr[1] address as 002AF94C?. The same thing happens with addr[2] also.

Why is the pointer skipping these intermediate 32 bit addresses when incremented?


texts: remove all components from a board with oven/heater?

texts:
I've seen a couple of comments on the 'net that it's possible to mass-remove components from a circuit board by heating the whole board (in an oven, or over a heater) enough that the solder will melt, and the components will fall out if the board gets a sharp tap. This sounds like both a very bad idea, and a very bad idea, at the same time.

Questions:

How hot would the air around the board need to be?
At what temperature would components start getting damaged?
What components would get damaged first?
Is there a reasonably reliable and safe way to do this? (I.e. one that doesn't require melting lead in an oven that must later be used for cooking)


texts: supplying power for in-system programming

texts:
For this PCB there will be a voltage regulator that provides 3.3V from 12 VDC. There will also be a 6-pin connector for doing In system programming via SPI. The SPI programmer is going to be an Arduino Uno, which will provide its target uC (and the whole board) with Vcc.
My question is how should I route the Vcc on the board ? Should there be any kind of decoupling (jumper ?) between the  voltage regulator to be used when in ISP mode ?

Went to How should power be supplied for in-system programming? but - not quite what I am looking to know.


texts:
I've noticed that sometimes electronic engineers switch terms or have more than one term for the same thing. I wanted to ask, specifically in this question, what are these terms referring to:

Resistance looking into the base
Resistance from the base
Resistance looking into (the) "X"
Resistance from (the) "X"
Input impedance (or Thévenin equivalent?)
Output impedance (also Thévenin equivalent?)
If you think there is another term that might be worth clarifying that you know, I'd appreciate it!

Thanks a lot.


texts:
I recently bought a few of FOTEK SSR-40DA relays believing that they are 40 A.
Anyway I've burned one of then connected to my boiler, and I've opened it, and it turns out that they actually having BTA25 triac inside, which is 25 A.

I wonder if I can directly replace it with BTA41 (which is 40A)?


texts: Is there any SMPS controllers with CPU core inside?

texts:
I heard that there is an SMPS controllers combined with CPU core. Or (which is the same in another words) a CPU controller with a wide peripheral to control an SMPS.

Tried to search in Google like "programmable SMPS controller", "SMPS controller with CPU core" and some others but didn't find anything combined in one chip: all I found was a special purpose PWM controllers without any programmable core or a general purpose controllers.

I think that Microchip has something like that.

Can you give me a clue which direction to look?


texts: i am trying to map this schematic onto a virtual breadboard but i dont understand what the 10k potentiometer symbol represents. am i supposed to connect the 5v terminal to the positive end of a battery and 0v to negative end. The virtual potentiometer also has three pins with the middle one labeled wiper while the other two named as terminals so where do i connect the pins?


texts:
Firstly, sorry for my english. I'm not very confident with this language but i'll try to give my best for you guys :).

So, now i will talk about my main problem.
For my school project, i have to create an ambilight system/board (with composite signal or S-video) without computer like the Scimo but i can't buy the Scimo for that.

I made a lot of research about that and i saw this component  http://www.ti.com/lit/ds/symlink/tvp5150am1.pdf which can make the AD conversion for us and give 27Mhz digital signal if i well understood, right ?

But now i need a µController which can get this signal, get all pixels, make the calculs and then control a strip led.
As a composite video is like a 525*625 resolution, i need for my µController 1Mbyte RAM because we have (525*625= 328 125 pixels and 3 colors per pixels so 328 125 * 3 =  984 375 Bytes needed)

But i also need a µController which can follow the tvp5150am1 at 27Mhz (with digital input).

I watched lot of µControllers but as i am a beginner in µControllers, i don't really know what i need to choose. Currently, i saw this one https://developer.mbed.org/platforms/FRDM-K64F/ which i think can handle my project or the Leopard Board 368.

But i'm not sure for the first one and i think the second one is too expensive for my project...

So can you say me if i can choose these µControllers and the tvp5150am1 component ?
Don't you have a µController which can be like the Scimo and have the video decoder integrated ?

update:

Thx for your answers !

Firstly, i forgot to tell it, but i can't use Raspberry Pi too. My teachers said that it's prohibited because it would be easier (not sure for me ^^).

Secondly, I'm totaly agreed with you that i don't need all pixels for my project. So the real main problem isn't the RAM. I haven't though about that I could skip 75% of pixels which i don't need.

But the main problem is always the digital read speed which is needed (27Mhz). Because i'm not sure if, per exemple, an ARM-M3 with 80Mhz clock is sufficient to get digital values at 27Mhz. Isn't it like analog reads ? Which can take several cycles frame to get a value ? Or the digital read frequency on a ARM-M3 80Mhz is 80Mhz ?

Per exemple, do you think this one is okay https://www.olimex.com/Products/ARM/Atmel/SAM7-H256/ for the project ?

I also though about decrease the fps like Tom L. said, but how can we make that ?


texts: Circuit to generate few microvolt pulse signal from volts pulse signal

texts:
I need to create a circuit which converts a pulse to very low voltage pulse (micro volts). This circuit output goes to an amplifier circuit.  Right now, I created a circuit using a voltage divider and op-amp (AD8512) HERE IS THE LINK. So I can change the input amplitude and output amplitude varies. This circuit is working fine in actual hardware as well.
This Circuit behaviour is fine:

input --> output
5V --> 151mV
2V --> 61mV
500mV --> 15mV
100mV --> 3.46mV

My pulse generator can not go below 100mV pulse but I need for example a few micro-volts for testing. I need to test circuit with a pulse having amplitude from 1uV to 1mV. Is there any better circuit for such kind of voltage change.

Update:
Circuit input and output pictures added. R1 = 100KR and R2 = 100R

Voltage Divider Input: -3V pulse

Voltage Divider Output:


texts: Finding voltage gain and current gain using the load line in a common emmitor transistor amplifier

texts:
So this question is really annoying me for a while so I needed some help.

I am given the output characteristics curve for a CE transistor amplifier. I also managed to draw the load line. They have given me the transistors dynamic input resistance and asked me to find the voltage gain and current gain of the amplifier given the peek of the signal given at the base.
Any help on how to proceed would be appreciated. Thank you ^^

Edit: the question and the curve https://imgur.com/gallery/GqH1DcF


texts: Accelerometer Bosch BMI055 returns 8 bit overflowed values?

texts:
I try to use a BMI055 Acclerometer and the output is driving me crazy.

I have set it to 2G sensitivity at 1000Hz, that means I have an output between 0 and 4096 (12bit).
The output is said to be two complemented, so I expect 2048 to be 0G

The sensor is set up to be as flat as possible using gauges.

Now I am asking it in a loop for it's FIFO data (1 frame bypass fifo) which returns me 6 bytes .
According to datasheet: LSB X MSB X LSB Y MSB Y LSB Z MSB Z

LSB X needs to be right shifted 4 times and ORd with MSB X which is left shifted 4 times.
So I receive a 12 bit numer.

Just analyzing the X values shows that MSB X is jumping between 0 and 255 !

Code:

temp[0]=(result[1]<<4) | ((result[0])>>4);

This shows LSB MSB 12BIT-unsigned

Data X:  1       0       0
Data X:  85      255     4085
Data X:  201     255     4092
Data X:  201     255     4092
Data X:  221     255     4093
Data X:  157     0       9
Data X:  49      0       3
Data X:  181     255     4091
Data X:  229     255     4094
Data X:  17      0       1
Data X:  161     255     4090
Data X:  117     255     4087
Data X:  221     255     4093
Data X:  5       0       0
Data X:  209     255     4093

It should return me 2048 as X is at 0G.
4096 would be 2G force.
0 would be -2G force.

When putting X on -1G and +1G the values seem to be correct (1000 and 3000).
Just the center 0G is at 0/4000 depending on minor vibrations instead of the expected 2046-2049

It is 4 in the morning, I guess I oversee something very critical.
Enlightment please


texts:
I have this delay circuit. I am trying to delay the power to R1(which will be an android phone) by 1 second. SW10 is my SPST relay. Can i replace the relay with something cheaper and physically smaller without losing significant voltage across it as the phone requires 5V and 500mA.

I tried using npn transistor and does not work due to low HFE ratio and high voltage drop, like in the picture below:

Darlington pair but could not make it work due to their high voltage drop as well.

Enhancement N-fet might be a solution? but I am just not able to figure it out. If someone can draw me a circuit, I would be high grateful.


texts:
Here is the datasheet and drawing of the antenna on this link

I need to stick out the antenna from a thick metal enclosure, how much of the antenna should stick out? Is it 19 mm (the black rubber part), 24mm (till connector) or another length?

In case it is 19 mm, how poor would it be if 15 mm sticks out?

I use it for a 2.45 GHz application.


texts: Question about time constant of RC circuit?

texts: I simulate the RC circuit in proteus. And I realize that when I increase the value of RV1, I see the time constant nearly not change. Could you explain me why ?


texts: Should a rectifier or TVS diode be used as a flyback diode?

texts:
I'm trying to design a circuit for a relay similar to the following (except using SMT components):

When I went to Mouser to try to find a suitable SMT diode to use in place of the 1N4001, I noticed there are four main categories:

TVS Diodes (21,395)
Rectifiers (9,872)
Schottky Diodes & Rectifiers (8,259)
Zener Diodes (15,726)

I'm pretty sure Zener & Schottky diodes are not supposed to be used as flyback diodes, which leaves TVS Diodes and Rectifiers.

Looking on Wikipedia, a TVS diode is shown as:

I did a little searching online and it seems some designs use a Rectifier like the 1N4001, while others use TVS diodes. I couldn't find a clear answer as to which is better.

Is there any advantage to using a TVS diode over a Rectifier diode for flyback applications such as a relay circuit?


texts: MPLAB programing: Questions on USART initialization code

texts:
I have just started using MPLAB for microchip Atmega128. I had a few questions regarding the following code segment for USART initialization which I found in the product documentation.

Do I need to declare variables like, URRH, URRL, UCSRB at the start of the program. The documentation didn't specify this but the compiler is giving me

" 'UBRRH' undeclared (first use in this function) "
error.

UCSRB = (1<<RXEN)|(1<<TXEN);

As I understand this, RXEN and TXEN are supposed to be 1 bit each, but then how is the above expression valid?

#define FOSC 1843200// Clock Speed
#define BAUD 9600
#define MYUBRR FOSC/16/BAUD-1

void main( void )
{
     ...
     USART_Init ( MYUBRR );
     ...
}
void USART_Init( unsigned int ubrr )
{
     /* Set baud rate */
      UBRRH = (unsigned char)(ubrr>>8);
      UBRRL = (unsigned char)ubrr;
     /* Enable receiver and transmitter */
      UCSRB = (1<<RXEN)|(1<<TXEN);
     /* Set frame format: 8data, 2stop bit */
      UCSRC = (1<<USBS)|(3<<UCSZ0);
}


texts: What happens to unreceived signals? (Like WiFi, Bluetooth etc.)

texts:
I'm curious how signal dispersion works. When I access a site on my computer I am sending a request to my router to then get some information from some server.

Does this signal request just completely fill up the air around me
until something picks it up or is it a straight shot to the router
because it knows where it's going?
And what if it doesn't find the router? Does the signal just disappear or disperse into the ether?


texts: Does driving an microcontroller's GPIO when it is powered off weaken the chip?

texts:
We are using the LTC5800-IPM microcontroller in a project. The way our design is now, the IC's GPIO pins will sometimes be driven high (to 3.3V) or low when it is powered-off. Will this weaken the chip? The absolute maximum ratings state the voltage on any digital I/O pin is -0.3V to VSupply+0.3V. If the answer is no, could the IC be weakened during power up?

The LTC5800-IPM does not have the most detailed datasheet. If it is not clear for that device in particular, I'd be interested to know for CMOS microcontroller GPIOs in general.


texts: What is the difference between Bare metal, RTOS and SoC?

texts:
Having just recently gotten into embedded programming using PIC microcontrollers, I am trying to understand the difference between Bare metal, RTOS and SoC.
Online searches reveal contradictory definitions and meanings.
For example, Semiengineering state that "An RTOS is code written on bare metal" and arduino.cc state that "If you programming controller without using any [RT]OS it's a bare metal approach".
The implication is that some code written on bare metal can be considered to be RTOS, whilst others may not be.
Therefore, my question is when can embedded programming of microntroollers be considered programming of bare metal and/or RTOS? And where does SoC fit into all of this, if at all?
Any insight that anyone can provide will be very much appreciated!


texts: Design synchronous reversible counter with d flip flops

texts: I have to design a sync reversible counter with seq 0 1 3 5 6 10 0.I tried writing the numbers on 4 bits with current and next state but I get stuck at Kmaps. What I tried is in the pic below. Is it wrong to try solving it like this?


texts: calculate op amp outputs problem separately

texts: I was quite confused of this problem since I cannot find the Vo2 using KCL for Vo1 - Vo2 but in the problem, it just said dont use KCL for output voltage. Is it the way op amp operating or I am confused don't know anything about it.


texts:
EDIT: The question was completely edited because the major problem - overloading - was solved. One of the units in the OpAmp was damaged, so it was malfunctioning when connected to the load.

Currently, I use a function generator and a simple voltage divider to create a required signal to drive a galvo-mirror (no datasheet available, the coil resistance was measured 16-17 Ohms). The circuit below works, but it is oversimplified, and I believe, there should be additional circuitry to stabilize, protect, etc. the circuit.

The other problem is that my signal is derived from DAC and comes out as a saw tooth wave ranging 0-5V (see the schematic below). Scaling the output of the DAC to feed into the OpAmp is not a big deal - I use a trimmer R1 to make the wave range from 0 to 1.6V. The next step is to offset the wave to the same voltage as the other input (in this case +2.5VDC):

What are the additional components that should be introduced to the circuit, excluding bypass capacitors, that would ensure proper/better performance of the circuit.
What would be a good way to offset the voltage between R1 and the OpAmp input without introducing any additional active components (transistors, OpAmps...)
The principal schematic would be appreciated.

It seems trivial to simply provide 0-1.6V wave to input1 and provide 0.8VDC to the second input of the amplifier, and no deed in offsetting the wave. However, it makes the signal to slightly rail out, so I prefer to run the voltages in the midrange at 2.5V.


texts: How to measure a fast-varying RF power in a circuit?

texts:
I have a circuit which generates an RF signal to drive a device, and I want to test it. For my application, I require the RF power to vary with a high frequency (of around 100 Hz), and the RF signal itself is in the range of 50-200 MHz.

I have a spectrum analyzer, but due to the fast varying of the magnitude of the RF power, I don't know whether I can observe the 'power envelope', ie., measure how the power varies, with a frequency of 100 Hz.

Is there any way in which I can reliably measure the variation of RF power envelope with time (100 Hz in this case)? What device is most suited for this purpose?


texts:
I am developing a commercial design on STM32 and am considering porting it to MAX32660 (another ARM MCU) due to the smaller footprint and lower cost for devices having 64KB+ RAM. However, the MAX32660 datasheet does not describe a code readout protection feature. Is there a way to prevent code readout on the MAX32660?
My minimum requirements are:

Prevent reading the flash memory from SWDIO or JTAG.
Even when the flash is protected, it must still be possible for custom bootloader code on the MAX32660 to overwrite regions of flash, without disturbing the custom bootloader code or the protection of all flash.

Does this feature exist somewhere? Is it documented?


texts:
I am starting my EE degree.  I must purchase a myDAQ and a kit.  The kit lists many logic ICs and I have most of them, but some of what I have are 74S instead of 74LS series.

Will the extra power draw on the 74S ICs cause issues with the myDAQ?
 or do I need to bite the bullet and buy the parts?

(on digikey, I am NOT paying their markup on their stupid kit).

The parts kit consists of things like or, and, xor etc.... gates and can be found here: https://www.studica.com/us/en/NI-Hardware-Only/und-student-ni-mydaq-bundle-ee202-electric-lab/796087.html

Edit  In case anyone else runs into this in the future, it turns out not to matter for the UND EE201L course.  We had minimal fan-out and most of the labs were just to use specified inputs to create specified outputs and make a led blink/turn on/ turn off.  There were no high speed requirements and I wasn't driving high current loads, it was just an intro to logic gates and how to build circuits with them so I doubt it would have been an issue to use the 74S parts instead of the 74LS parts. It was a good learning experience though and the myDAQ is a decent tool to have in my tool box since I don't own a quality function generator (yet).  Just in case, I ran power from my bench top power supply instead of the myDAQ


texts: How charge redistribution takes place in this switched capacitor DAC?

texts:
So, I've trying to understand how this DAC works and until the moment it states that the Vref is connected to S1. At this moment, it says a voltage \$ \dfrac{V_{ref}}{2} \$ is added to \$ -A_{in} \$, although it doesn't matter the voltage at the capacitor in any exact moment, \$ V_{ref} \$ would force the voltage at point A to be only \$ \dfrac{V_{ref}}{2} \$ without this previous addition since it's a voltage source applied into 2 capacitors of value C in series.
So the question is:  Why is there a -Ain summed onto the value \$ \dfrac{V_{ref}}{2} \$?


texts: Fuses in Series for High Voltage Where Maximum Current is Low

texts:
I'll start off by saying that I know this not a recommend practice.

I'm looking to build a regulated power supply that can supply 1200VDC at 300mA. The supply consists of a transformer, xenon tube rectifier bridge, a choke input filter (5H), and the pass tubes of the regulator.

I have found 315mA 1000VDC fuses, but have been unable to find any fuses of a higher voltage rating below 2.5A. Being that the maximum fault current isn't very high (limited by the transformer windings, rectifier impedance, choke winding, and pass tubes), would fuses in series be effective?

From what I can see even if one were to blow and maintain an arc, the second fuse would blow shortly. The two should then be enough of an arc gap to extinguish it, right? The 1000V fuses are the ceramic shell sand filled type, and since I'd only be exceeding the voltage rating slightly I'd be surprised if the first fuse didn't quench the arc itself, but I'd rather be safe.

In the event both fuses fail to break the circuit, it would inevitably blow the mains fuse. Also if anyone knows where to get fuses rated for a higher voltage at that current and they're not obscenely expensive I'm all ears.

Thank You


texts: Can anyone identify this battery connector?

texts:
It's a fairly common sort of connector, I think it's the same one that's used for GoPro batteries and a lot of cameras too, but I can't find out the name of it or where to buy just the connector.

The male part of it is 3 blade prongs.

I want to build a couple of spare batteries to replace this one rather than pay a rather extortionate OEM rate, but I don't want to cut into the device so I'd like the connector to match.

Thanks in advance!


texts:
I'm using TLC5945 LED driver. Microcontroller (I'm using LPC1343) must provide a clock for it's  internal PWM timer/counter. Maximum allowed clock speed is specified as 30MHz.

I will have several boards with TLC5945 daisychained. Boards will be connected via board-to-board connectors or short ribbon cables, the width of one board is 10cm. I will have max 4 of them connected in series.

Probably I won't be using full 30MHz, but nevertheless I want to do it right - how do I route/condition the clock signal keeping it intact?

If I add a buffer like 74HC245 on the output of every board, I will get a 10ns delay after every buffer, I don't want that. Should I use specialized "zero delay" clock buffers? What kind of termination scheme should I employ?


texts:
I need help as I'm new to electronics.

I need to identify a diode in a PCB that I'm currently working on. Do you have any idea or advice on how to identify the diode?

The diode which I need to identify is D1 in the picture below.

IC1 is a Vishay TCST1030 Transmissive Optical Sensor with Phototransistor Output - datasheet here

Q1 is an NPN transistor (SOT-23) datasheet here

Below is the circuit diagram that I drew, based on the PCB.

simulate this circuit – Schematic created using CircuitLab


texts:
I have a signal that consists of N frequencies all with unknown phase and frequency(N) = frequency(N-1) + 2Hz. I would like to selectively scale the amplitudes of some of those signals in such a way that I can change which frequencies to scale and how much to scale them on the fly.

Is this possible?
How complex of a circuit would this be?

Analog? Digital? or Both?

Where should I start?

Thanks


texts: Whats the difference between a Launchpad and a Development Kit? Many launchpads like the TI's Stellaris/Hercules launchpads even support In circuit debugging capabilities via USB. This eliminates the need of purchasing a JTAG debugger.


texts: Hello I wanted to build this serial to usb converter with ft323R, but I don't understand the small marked part on the left bottom. I found the same thing in other schematics too. I know where to connect gnd, but why is the line longer than it should be? And I don't know the Vcc part too. Thanks.


texts:
I'm to the task to design a BJT Common-Emitter Amplifier with resistance at the emitter as in the figure, and for that I need to:

get the values for \$R_{1}\$, \$R_{2}\$, \$R_{C}\$ and \$R_{E}\$
given \$I_{CQ} = 3\text{mA}\$ , \$V_{CEQ} = 6.5\text{V}\$ ,\$V_{CC}=13\text{V}\$ and \$\beta = 380\$ for a BC547C transistor.

Currently I'm able to analyze correctly the circuit given the resistances, but the reverse process, that is, getting the resistances values given only the operating point is what is giving me problems as there is various "rules of thumb" and considerations to make, I'm trying to use the "1/3 rule of thumb" (\$V_{E} = V_{C} = V_{CE}= V_{CC}/3\$) but I'm not getting the expected results \$V_{CE}\$ since \$V_{CE}\$ is already given.

How can I go to design this circuit?


texts: Limiting Cold Side Temperature on Peltier

texts: I'm trying to cool my computer's CPU by sticking a peltier between the CPU and the heatsink, however I don't want to deal with preparing my motherboard and for condensation. Therefore I want to keep the cold side temperature to 50/70*F. How do I regulate the cold side temperature? Is it by limiting voltage or current?


texts: fastest way of doing on/off-modulation of a LED?

texts:
I need to modulate a LED quickly (multi-megahertz range) on/off. It's a high-power LED. I have had some trouble locating any well-known methods to do this. Simply switching the voltage with a FET turns on the LED quickly but the fall-time will suffer, and to solve that, I guess there are some different solutions, for example maybe switching in a reverse bias for a short while? Any ideas?

I think the underlying problem with the turn-off is that the charge-carriers make the p-n junction act a bit like an inductor in that the current will keep on going for a short while after turning off the voltage gradient, but I haven't found any reference on this.

I know that a laser-diode can be modulated much faster.

EDIT: since this question has a lot of views, let me add some context - the application for this was a 3D camera using a time-of-flight CMOS sensor. Essentially, you send out light, it bounces on the scene to be imaged, and the image sensor can discern the phase difference between the sent light and received light. Faster and deeper modulation means better resolution and less noise in the 3D image. In this particular application, 20 MHz was the target modulation rate.


texts: Why the mean squared value of a random noise signal at a single precise frequency is zero?

texts:
I am reading about noise from this lecture (page 9/31). However, I don't understand this point. Could anyone explain why mean squared value is zero?

  The mean squared value of a random noise signal at a single precise frequency is zero.


texts: I am working on a Double Leaf Bascule bridge spanning across a river that needs rehabilitated. The bridge is driven from a ControlLogix PLC consisting of 4 racks on the nearside span. Power/control is sent to the farside span via a single submarine cable installed in 1987. We are attempting to install a 5th I/O rack on the farside span to control various relays/encoders. The problem is there's no ethernet cable inside the submarine cables for the farside I/O rack. The options are to use either a Coaxial cable (RG-11) or a shielded twisted pair. Could we install a media converter on both spans (ethernet->coax->ethernet) to communicate with the farside I/O rack?


texts:
I'm using Atmega128L controller. One of the primary tasks is to control a linear actuator. The actuator supply and controller supply are different(initially it was designed to share a common ground). The relays that are used to control the actuator uses the same supply as the controller. All other inputs and outputs are through isolation. The 3.3V line to the controller is not that noisy, even during relay turn on turn off.
The issue I'm facing is related to microcontroller reset. This reset occurs when the actuator hits the inbuilt electrical limit switch(which cuts off motor power). Apparently this is the time when the motor uses maximum power.
The code flow is in such a way that a normal reset wouldn't affect its functionality. It would recover seamlessly. However when the reset occurs, the controller seems to malfunction, skips done part of code, not following proper initialisation procedure, executes functions which are in memory but are not called anywhere in the current code.
Because of this the controller shows some illogical error state (as per code), or corrupts the Ic's that it is interfaced with. Most of the time a proper power on reset or external reset makes the controller work properly.
How can I make sure that the controller gets reset properly?
Edit:
Pardon me for the poor handwriting.

Edit:
I don't deny that there is a noise in nanosecond range in 3.3V supply. I'm very much concerned about the controller's response to the noise. I expect a proper brownout reset or watchdog reset when the noise occurs, instead of PC jumping to random location or stack getting corrupted.
My controller works with 8Mhz external clock, Max speed is 8Mhz


texts: Why less protection on a GPIO RS485 board compared to an UART RS485 board?

texts:
When I search for RS485 board (to be used for my Arduino to control DMX512), I find mostly two types:

GPIO / TTL based (which I want to use), like TTL RS485, which mainly has a MAX485 and some resistors/capacitors. This one works with DMX512.

UART based, like  UART RS485, which has also thermal/polyfuses and TVS protection. This one I don't want to use because I want to use UART for other purposes.

Would it be useful to recreate the GPIO based version, with additional polyfused/TVS circuitry?

I cannot find a GPIO/TTL based version with more protection, why is this?

(note I will only use RS485 (DMX) output, not input).


texts: Multiple voltage dividers : finding resistances in a circuit

texts:
I have to set the battery voltage to 14.5V from the first divider, then from that I have to attenuate it to 1V to feed to the input of an op amp. Now this  answer is inspiring but doesn't solve my purpose. Maximum I can assume the R2 & R4. R3 & R5 still unknown.
Please help.


texts: H(s) in closed loop transfer function incorrect?

texts:
I need some help verifying the transfer function of this amplifier circuit stage. The below circuit has a gain of 20 from the result of Rf and Rg.

Below is the nodal analysis equation where G is used to show conductance.

The problem I am having is that I have 2 transfer functions in a feedback loop. G(s) and H(s), the op amp open loop transfer function and the closed loop transfer function. When they combine in feedback loop I get a final transfer function of G(s)/(1+G(s)*H(s))
My output transfer function however seems to have gain bode plot of less than unity!

Green curve = output transfer function
Blue curve = G(s) op amp open loop transfer function
Orange curve = close loop H(s)

Shouldn't the amplifier stage, well, amplify?  I can clearly see that the math works out to make it less than unity gain, but how is the output voltage going to be amplified?
For example: at DC the math works out to be -26dB, gain of ~1/20. Similarly, the closed loop gain is around +26dB.
When applying H(s) to G(s), in feedback it became net negative.  But to apply a real voltage at the input and expect an output, let's say for 1 volt input @DC, Vi=1,  Vo=ViTF -> Vo=10.05011=0.05011.
The problem here is I am missing 1/x somewhere to get the proper gain of 20. I thought the transfer function is Vo=TF*Vi not Vo=1/TF *Vi?


texts: Best circuit to get an array of signals with the same frequency and edge-synchronizable to a reference but individually controllable duty-cycles?

texts:
I am looking to build a circuit to control five different FET drivers individually. The input signal would be a single shot from a function generator, which should produce five output signals, with the same frequency and phase but the duty cycles need to be individually controllable. Basically, I am trying to replace five function generators (synchronized to the same clock) with one single function generator and a circuit board due to limited resources. The outputs need to have only two levels i.e pulse wave

EDIT: Olin's suggestion (using a MCU) or a FPGA seem to be the best options but any analog alternatives are much appreciated. Thanks :)


texts: Converting from int to string for AVR ATmega32

texts:
I am trying to read data from the ADC and display it on a HD44870 compatible LCD with an ATmega32. As the data from the ADC is a 10-bit unsigned integer, the LCD expects a string, some conversion is necessary. Below is the function i wrote to accomplish this conversion.

char *int_to_str(uint16_t num, uint8_t len){
    uint8_t i;
    char *str;
    str[len]='\0';
    for(i=(len-1); i>=0; i--){
        str[i] = '0' + num % 10;
        num/=10;
    }
    return str;
}

However, the above function does not work. I just get a blank display where the numbers should be displayed. I am currently using itoa() and it works. However, i would prefer to write my own since size of the resulting executable is critical. Thank you.


texts: Gain of single input differential amplifier

texts:
When performing the small signal analysis of the circuit shown below, with \$ V_{1} = V_{in} \$ and \$ V_{2} = 0 \$, and output taken from \$ V_{02}\$, I consider the small signal model for half of the circuit, adjusting \$ R_E \$ into two parallel resistors of \$ 2R_E \$ . However, when asked to find the overall gain, by combining results for the differential and common mode gain, the textbook suggests in the small signal analysis \$ V_{in} \$ should be taken to be \$ \frac{1}{2}V_{in} \$. This gives the corresponding gain as \$ \frac{-h_{fe}R_{C1}}{2}\left( \frac{1}{h_{ie}}+\frac{1}{h_{ie} + (h_{fe}+1)2R_{E}}\right)      \$.

Is this to do with the idea that the common emitter point is shunted to an intermediate value between \$ V_{in} \$ and 0 ? Are the common mode and differential inputs being assumed to represent half of \$ V_{in} \$ ? I am a bit confused. Thanks.


texts: Small microcontroller with USB host peripheral

texts:
I'm trying to find microcontroller with low pin coutn that has USB host capabilities.

I know this can be done with big PIC24 or PIC33 microcontrollers, but I wonder if there are others chips that can do , easily.


texts: Can I "integrate" the data from an accelerometer to record a motion trajectory?

texts:
I would like use an accelerometer equipped device to record a motion trajectory, as high-resolution and low-noise as possible. For instance, let's say I run a jogging route of 6 kilometres, returning exactly back to the location I started from. So I have the idea that I could possibly do without a GPS module and just record at constant rate the data from an accelerometer, say an ADXL345.

My questions thus:

can I use a 3-axis accelerometer to integrate twice, from
acceleration to velocity to distances?
if the constraint is that I return to the exact location from where
I started, can I apply an error-correction to the trajectory that
compensates for drift, so that the last (x,y,z) coordinate of the
recorded and integrated data becomes identical to the first one?
say I run from location A to B and back to A again. If I apply the
mentioned drift-correction, do I still have a meaningful/correct
position of spot B?

If not, how would I achieve this? Do I have to combine the accelerometer with a GPS?


texts:
I'm trying to set the lock bits on my ATMega328p-pu, using an Arduino UNO as an ISP.

this is what happens:

>avrdude -c arduino -p m328p -P COM4 -b 19200 -U lock:w:0xFC:m

avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.03s

avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: reading input file "0xFC"
avrdude: writing lock (1 bytes):

Writing |                                                    | 0% 0.00s ***failed;
Writing | ################################################## | 100% 0.16s

avrdude: 1 bytes of lock written
avrdude: verifying lock memory against 0xFC:
avrdude: load data lock data from input file 0xFC:
avrdude: input file 0xFC contains 1 bytes
avrdude: reading on-chip lock data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: verification error, first mismatch at byte 0x0000
         0x0c != 0xfc
avrdude: verification error; content mismatch

avrdude: safemode: Fuses OK (E:FD, H:DA, L:FF)

avrdude done.  Thank you.

I'm very new to using avrdude and have no clue how to proceed with debugging this issue.

EDIT: I've tried using another chip, but exactly the same response.