texts: Can I use a 2N3904 transistor in place of a 2N4401 if I flip it around?

texts:
I want to do a composite video mod for a Colecovision.  The mod (http://www.benheck.com/Games/Coleco/Video_Mod.htm) calls for an NPN 2N4401-ND.

The only NPN transistor I currently have is the 2N3904.  However, the pins are reversed.

Could I simply flip the transistor around and use it? So that the pin that goes to the collector goes to my collector, etc.?

Thanks


texts: Translating Stepper motor driver outputs (A-,A+,B-,B+) back into clk,en,step

texts:
I have a rather weird problem that makes it necessary to sense the four wires off of a bipolar stepper motor(A-,A+,B-,B+) and translate them back into the pins that controlled the stepper motor driver (clk,dir,step).

First i'll outline what I've tried:

mcp3008 ADC - This guy burned out right away. (I'm assuming because the stepper motor drivers for a nema17 output roughly 1.2amps per coil).
Looked for higher spec ADCs but I'm somewhat lost.

Questions:

Is there a better way to do this than using an ADC into a microcontroller?
What sampling rate would I need to "sense" the stepper motor drivers micro stepping and translate them back/ how to calculate this?
what ADC resolution would be acceptable/ how to calculate this? ex. 12bit, 16bit...
What voltage would be "safe" (I know a nema17 is approx 4V, but I'm worried that another stepper will be higher).
What ADCs are available that meet these spec? (above and below).

SPI or I2C
atleast 4 channels or (I can get four 1 channel ADCs).
through hole component package.

Thank you anyone who responds to all or either of my questions! This is my first post so I hope I was clear enough.


texts:
Jack Ganssle - The Firmware Handbook States

Orient the CPU chip so it’s possible to connect an emulator, if you’re using one. Sometimes
the target board is so buried inside of a cabinet that access is limited at best. Most emulator
pods have form factors that favor a particular direction of insertion.
Watch out for vertical clearance, too! A pod stacked atop a large SMT adaptor might need 4
to 6 inches of space above the board. Be sure there’s nothing over the top of the board that
will interfere with the pod.

What does he mean by emulator POD? What exactly is being emulated? If I am actually plugging a CPU into something, my intuition is that nothing is being emulated.

Can someone give me an example of a use case of an emulator pod in the embedded system design process?


texts:
I generated USB VCP code for "STM32F103C8T6" with STM32CubeMX. I'm trying to send  received data by STM from PC, to an Arduino board using UART. The code works good for data with little size, but when I want to send bigger data the received data in Arduino is corrupted. I'm using "Teraterm" and "Realterm" for sending data from PC to STM32.
I modified the CDC_Receive_FS for sending data via UART in DMA mode, here is the code:

static int8_t CDC_Receive_FS (uint8_t* Buf, uint32_t *Len)
{

    HAL_UART_Transmit_DMA(&huart3, Buf,(uint16_t)* Len);/* same problem with HAL_UART_Transmit_IT*/
    USBD_CDC_ReceivePacket(hUsbDevice_0);//Getting ready for receiving next data
    return (USBD_OK);

}

I sent this

{1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40}

and received

{1 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 20 21 22 23 24 2}

The USART baud rate is 19200, and in STM32, size of Received buffer, APP_RX_DATA_SIZE is defined 640.
What should I do?


texts:
What is the Difference Between the Normal Opamp LM741 and the Audio Power amplifier LM386..
I mean in both the circuit we use the concept of voltage compensation, then how come LM386 is called power amplification also,
What is the difference between Operational Amplifier and Power Amplifier though in both the circuit we are using external supply to drive the circuit?
Can a operational amplifier be power amplifier?
I am currently using LM386 with a microphone to amplify audio signals,
Can I replace the Microphone with Ultrasonic transducer and the amplifier still work?

Thanks,Regards


texts: Is there a component that will provide an elevated SMD pad?

texts:
Is there a surface-mount component I can put on a pad, that simply has another pad on top that I can solder something on to?
Here is a side view showing pins above the pads that would need bent down to contact the pads:

Here is a top view to show how the pins align with the pads:

We found that edge-mounting a TO-Can package to a PCB will really save a lot on manufacturing. However, it comes with fairly long through-hole pins that are taking up too much space. We could trim the pins, but then we cant bend them enough to reach the pads on our 0.062" PCB. We can't make the PCB thicker because we're also end-mounting a connector that constrains the PCB thickness.
Someone here had the idea of using high-resistance SMD resistors. That could work but it seems like you wouldn't get much soldering area on top.
Mechanical strength should not be an issue since the whole assembly will be overmolded and encased in plastic.
I looked through what seemed like hundreds of right-angle receptacles, etc. to do the job, but couldn't find anything.
It needs to raise it 1.5-2mm above the PCB surface.
Any suggestions or solutions would be appreciated!


texts: The capacitance parameter in varistor data sheet

texts:
What is the meaning of the capacitance parameter in the datasheet of a varistor?

For example: I have noticed that 7mm 430 varistor voltage(07D431K) and 14mm 430 varistor voltage (14D431K) have the same max continuous voltage and the same maximum clamping voltage, but the larger varistor (14D431K) has higher maximum surge current, higher rated power, and higher reference capacitance. The others parameters I understood, but the reference capacitance parameter I didn't understand.

How does its capacitance value influence the circuit?

For example: if I protect a circuit with a varistor between its 220Vac input power source lines, what will be the difference, according to the capacitance aspect, if I use the one with the lower capacitance or the one with the higher capacitance?


texts: Power electronics problem: battery charger

texts:
Given the next circuit, I have to charge the battery of 12V with the one of 48V with a power transfer of 480W.

simulate this circuit – Schematic created using CircuitLab

Since inductors don't consume power on steady-state and switches are considered ideal, the average current \$i\$ taken by \$V_2\$ has to be \$40 A\$. Also, the average voltage drop across the inductor must be \$0\$ in steady-state so, let \$D\$ be the duty cycle and \$T\$ be the period of commutation:

$$
(V_1-V_2)DT = V_2(1-D)T \quad \Rightarrow \quad D=0.25 \quad (25\%)
$$

Now, how can I get the average \$40 A\$ to get the \$480W\$ on \$V_2\$?


texts: Why is the variance of the beta value among BJTs much lower in the saturation region than in the forward active region?

texts: In my electronics lab, we measured the beta (Ic/Ib) values of BJTs in both the active and saturation regions. While the betas measured in the forward-active region varied massively between different BJTs (even of the same model), there was virtually no variation among beta values in the saturation region. Why is this the case?


texts:
I am trying to get my arduino working over wireless (via bluetooth).  I would like to send serial signal though it via bluetooth, but I am having some difficulty getting the bluetooth module I purchased actually showing up on any of my computer's bluetooth scan.

This is the skimpy datasheet for the module.  It was made by someone in China (an individul, not a company - and that is why I do not really understand it)

Any help as to how I can get this connected to my PC would be great.  ---Thank you---

Here is the bluetooth module that I have...

Here is the complete setup...


texts: Using a MOSFET to turn on a car alarm siren

texts:
I'm trying to control a 130dB siren with a pic microcontroller.  I figured the best way to do this was with this MOSFET since the siren pulls about 1A.  I had some problems when connecting this to the Pic, so I created a simple test circuit to troubleshoot it:

I couldn't find a voltage regulator in the schematics program, so please assume that the +5 source is a voltage regulator connected to the same 12V source.  Anyway, the problem is that when I apply power to the circuit (without applying power to the gate), the siren sounds, but not as loud as it should be.  When I connect +5V to the gate, the siren turns off and then even after opening the switch it stays off (i.e. it won't make any noise).  My initial thought was that I had a bad MOSFET, so I tried a different one with the same effect.

FYI, when I connect the siren directly to 12V it works fine.

Any idea why I'm seeing this behavior?


texts: Control large voltage supply using smaller voltage

texts:
I have a 6 volt supply that I need enable/disable using another 3 volt supply.

If I use a PNP Darlington set-up like this:

Then I get just under 6 volts at the Output node.

My problem is that I don't have any PNP transistors but I do have several NPN transistors and I was hoping that setting up a NPN Darlington would give me similar results, but building something like this yields about 2 volts at the Output node:

My question is; is there a circuit I can make using NPN transistors (2N2222 to be exact) what will give me a voltage close to V2 voltage when V1 is enabled?


texts:
I'm working with a pivot irrigation system, and I need to detect when one of the wires goes high with 120VAC. I'm currently using a 100K resistor and an opto-isolator (TLP290-4). The circuit always indicates when the voltage is 120VAC. The wire I need to monitor travels 1/4 of a mile in conduit with several other wires with 120VAC and three wires carrying 480VAC three phase power. Occasionally, I get 65VAC on the line I am monitoring which causes my opto-isolator to saturate enough to signal a high voltage. I believe this happens when higher current is required by the other wires going down the length of the pivot. The 65VAC has no negative effect on the pivot and is present on all pivots. I tried increasing the resistance to 200K, but the problem persists.

Is there a simple circuit I can add to only allow saturation of the opto-isolator if the voltage is greater than 100 VAC?


texts:
I have a function F(w,x,y,z) = wx'+w'z'+y'z'

Using P.O.S., the function becomes: F=(w'+z)(x+z)(w+x+y)

If I was asked to implement the function with a two-level NOR gate circuit, I assume this means I may only have NOR gates. However, one of the terms have a NOT, and makes it three-level?
Here's my implementation with "only" NOR gates:

Is my implementation two-level or three-level. How can I make it two-level if it isn't?


texts: How is called this peculiar rounded segment display system?

texts:
There are a number of industrial displays which use 23-segment columns to show semi-rounded alphanumeric characters and simple icons. An example photo:

I cannot find anything about this system, like its name or a concrete product.


texts: How does electrical power relate to Ohm's law?

texts:
I have some difficulty grasping these concepts. Let's say, for example, a power source of 10W operating at 5V is connected to a load of 0.5 ohms. According to Ohm's law, it is expected that a current of 10A should flow through the circuit. However as given above, the power is 10W so a current of 2A is expected, using the voltage-power relationship.

My question is: What is the expected current in this particular case and why?


texts:
Can I combine the TLC5955 outputs in this way to connect one 350mA RGB LED? I calculated that 6 mil at 1 oz Cu would be enough for 32 mA.
What thickness of PCB should I choose for heat removal from TLC5955 (32 mA * 48)? Probably need a radiator? I've never ordered a PCB, I made just a few simple single-layer PCBs myself. This is the first two-layer PCB with interlayer junctions - Vias. I installed EAGLE on the recommendation of PCBWay and drew this layout. PCBWay will print Via with a 0.3 mm hole and a ring around 0.5 mm for $5? I drew pairs of Via to avoid problems with metallization of the holes, I think this is a smart solution for delivering 32 mA from one layer to another.
Basically the led will glow red, so I chose direct connection for red, without Via. The blue one will have the least intensity, so I chose a long track with Via for it. I don't know how to draw polygons for the heat sink yet, so I've marked it this way for now. There is no connector for connection yet. I am open to opposition points of view.


texts: Why is resistance across my arm-span so much less than across my face?

texts:
This sounds like a strange question (it is) but, from a purely biological standpoint, why is the measured resistance across my hands (I measured 120k\$\Omega\$) so much less than across my face? I thought to ask this because the distance across my face is much less than my arm span.

More specifically, what makes the tissue in my face so much more resistant to charge (ion) flow than my entire arm-span?

P.S. I used a standard multimeter with resistance set at 2M\$\Omega\$ to get my readings - across my face doesn't even give a reading (too much resistance)


texts: Motor/driver for smoothest and most constant speed

texts:
Which type of motor/controller can maintain the smoothest and most constant speed in the range 300 - 1000 rpm with minimal vibration? ie: low cogging torque, etc.

I have an application in mind which requires spinning a 100mm diameter 0.5kg static load.

I have been advised to consider the following options, most of which I know nothing about and need help deciphering them:

sensorless low kV BLDC motor with FOC control
PMSM with space vector modulation
high current control bandwidth
HAL sensored brushed DC motor with many (odd numbered) commutators
encoder with high current control bandwidth
rhombic winding

One example development guide can be found in microchip website and video demonstrations of similar setups here and here


texts: Why can the IS31FL3731 only handle 32 RGB Leds when it can handle 144 Regular ones?

texts: I am looking at using the IS31FL3731 IC in a project soon, but I am confused as to why the data sheet says that the circuit can only use 32 RGB LEDs when it can use 144 regular LEDs. The data sheet says that the remaining LEDs in the Charlieplexed array not being used by the RGB LEDs can be used, but only for LEDs that are not red. Is this because the forward voltage for red LEDs is lower than the forward voltage for green and blue ones? If this is the case then could this be compensated for by matching the forward voltage of the red LED to that of the green and blue LEDs using a resistor?


texts: Bulk capacitor needed for USB device that is always attached?

texts:
The USB spec calls for a bulk capacitor of no less than 120uF on each downstream port. I have a total of 7 ports on my USB Hub, 6 of them are connectors where you can attach USB devices, however there is one internal device: FTDI's FT232R VCOM IC. This device is always attached and I'm wondering if I still need the bulk capacitance.

Based on what I've read of USB design guidelines the bulk capacitance is there for when you attach a device you don't cause too much droop on other ports.

Any advice?

Schematic:

Distribution Switch:

VBUS:

FT232RL and RS232 Transceiver:


texts:
I have 2 capacitors  charging in parallel and then switching them in series to discharge into a wound coil of known inductance. My capacitors are 4nF 2000V and the charging voltage is 1000V. So at the moment they are switched in series they act as a 2000V 2nF capacitor. They discharge into a coil connected in parallel. The resistance of the coil is 2 Ohms the capacitors' ESR is 1 Ohm and an extra 100 Ohm resistor is added in series with the coil.
- I expect a voltage drop of (4 Ohms)*(10A)= 40V . As a result I expect I=V/R=950/104=9.1 Amps as a pulse on the coil. However all i end up with is a massive 700 Volt load drop.
I think it has to do with the oscilloscope draining the capacitors while I detach the charging source and switch them in series. Switching them in series is done with triacs after I detach the charging source.
Is my thinking right or have I not done something else correctly?


texts:
Not necessarily electrical, more engineering;

I'm trying to build a UV LED exposure box to aid in the PCB etching process. There are plenty of guides around, but they all seem to involve haphazardly throwing LED's onto some perf-board with little thought of hotspots/LED coverage. Sure, enough LED's on one board are certain to guarantee adequate UV exposure, but I'd like to put a little thought into precision/accuracy.

However, I've long since forgotten the necessary math skills to do this... I imagine the best arrangement would be a series of equilateral triangles of LED's. The LED's should be spaced so that given some fixed distance (z) away from the LED's and given some variable coordinate (x,y), the brightness remains consistent. It's probably impossible to have exactly the same brightness at all points, but I find this problem interesting and worth the effort.

Some specs to work from: the LED's I have in mind are 5mm flat tip, clear UV LED's with a viewable angle of 140 and intensity of 1200 mcd.

The way I understand it, half of the viewable angle is the angle at which the LED's intensity is half of the intensity at the center. I can't seem to find any good technical documentation on how intensity varies from the edge of the viewing angle to the center, and I'd greatly appreciate any pointers on that. I'm hoping it's somewhat linear, but am very doubtful.

Anyways, any thoughts on this or links would be greatly appreciated. Thanks!


texts: How do different methods of transmission line termination compare?

texts:
It seems to me that there are three ways to terminate a transmission line:

at both ends
at the load only
at the source only

simulate this circuit – Schematic created using CircuitLab

the coax shield is grounded, and the buffers have power supply connections as usual, and these are \$50\Omega\$ transmission lines.

What are the advantages and disadvantages of each, considering:

we might want to transfer power (as to an antenna) and not information (as in a digital circuit)
the signal may be analog
the transmission line might not be ideal (discontinuities in the middle, etc.)

What is common practice in typical situations:

high-speed digital circuits
low-power RF (between stages, receivers)
high-power RF (transmitters)


texts:
I will do basic IOT project with esp-wroom-32.
but I am machanical student. I need to help please check my design.

my component:
- esp-wroom-32
- button
- pad-resistor
- locig level converter
- ft232rt ( but i don't found library)
- pins
I am sory for my english.

enter image description here


texts: Passing port/pin to a user defined function in 89c52 code

texts:
I want to pass a pin value in user define function in 89c52 code like given below

#include <AT89c52.h>
sbit myBit = P1^5;
void f(sbit recievedBit){
     recievedBit = ~recievedBit;
}
void main(){
   myBit = 0;
 while(1){
        f(myBit);
        //some delay here
   }
}

But it give me build error.

I also tried 'bit' type insted of 'sbit' as function argument , this time no error but nothing hapen at pin.


texts: Electronic load MOSFET drain to source current suddenly increases

texts:
My questions:

Why would the drain to source current of MOSFETS suddenly increases.
What can be done to resolve it?

I am aware that there is supposed to be an increase in current as soon as the gate voltage of the MOSFET reaches the threshold voltage, but I would like to determine whether the behavior of my electronic load is typical because the increase seems too sudden given my minimal increase in voltage.

Introduction to setup and circuit

I am building an electronic load that uses three parallel IRF640 to control the current. It is for testing our solar panel strings so the voltage applied to it is approximately 100V at open circuit and it will receive a current of at most 2.5A. This is within the maximum values of the MOSFET. I have addressed the maximum power problem/heating of the MOSFETS by adding 20 ohms 400 Watts in series to the drain of the MOSFET, so it does not heat up by a noticeable amount at any point. The MOSFETS are also attached to a heat sink to minimize heating further.

Here is my circuit (I'm unable to add images directly)

The circuit behaves as expected at around 40Vds. As I slowly increase the voltage applied to the gates of the MOSFETs, the drains to source current steadily increases.

Problem

The problem occurs whenever I increase the voltage across the drain to source. Initially the current would increase as expected in earlier tests, but as I reach 4.1V or somewhere around that number, the drain to source current suddenly jumps from a mere 0.7A to 3A (maximum current of supply).

Here's an example of my tests at 80v Vds

Vgs -- Ids

0 ---- 0

1V ---- 0A

.

.

.

3V ---- 0A

3.2V -- 0.1A

3.4V -- 0.2A

3.6V -- 0.3A

3.8V -- 0.5A

4.0V -- 0.7A

4.1V -- 3A <--- As you can see here. It suddenly jumps up at the tiny increase in gate voltage


texts: I'm curious how a laser knows which layer to read in a single side dual layer DVD. It seems like it could easily read data from the second layer while it's shining through scanning the first.


texts: So using an Arduino I fed 5v to a white LED, nothing happened to it. I fed 5v to a yellow LED, and within a few seconds it started to smoke and burn itself out. My first question is how toxic are these fumes? Second, why do different colored LEDS have different voltage/current maximums?


texts: Can I measure the voltage noise with True RMS function

texts:
I have a measurement setup with which I want to measure high voltages. Now I want to evaluate the noise this setup produces (preferably in V/sqrt(Hz)). I short circuited the input and I am now measuring the output of the setup produces. The output signal is not terminated (HighZ).
I am using a picoscope so I can digitally filter the signal and calculate the True RMS values of them.
The "signal" is already filtered out by using ac mode. Am I correct in the assumption that I now can use these true rms values as my voltage noise?


texts: Controllability/Observability in Controller/Observer form

texts: I understand that a necessary and sufficient condition for controllability is that no single pole of the system is cancelled by a zero in all of the elements of the transfer-function matrix. And the same goes for observability. However, if I express my system in a controller form, despite a pole-zero cancellation, the system is controllable, though not observable and a corresponding conclusion for an observer form. This violates the 'iff' condition. What explains this?


texts: I2C temp sensor and an Arduino wifi shield not working together

texts:
I am using an arduino wifi shield and a TMP102 with an arduino uno rev2.

With boards older than rev3 you have to add a jumper from the 3.3V to the IOREF pin for the wifi shield, see here: http://arduino.cc/en/Guide/ArduinoWiFiShield

But when I do that the temperature sensor would only read -0.06 celsius as if its address would be different. (It is using i2c, its ADD0 is grounded, just like here: http://bildr.org/2011/01/tmp102-arduino/ )

Without the jumper the sensor is working fine, but the wifi needs the jumper for starting up.

What should I do to make them work together?


texts:
This is related to Is it okay to keep a USB charger plugged into the cigar lighter? - I have a 12v charger that is connected to a phone dock with an integrated micro USB connector.

The difference between this and the linked post is that there is an LED on the 12v plug that lights when power is supplied. Am I ok leaving this charger plugged in to the 12v socket when the car is parked? How much drain on the battery would the LED and empty dock cause? How long would it take to drain the battery enough to cause starting problems?

Edit: The 12v is powered on ignition off.


texts: Initial condition of Schmitt Trigger Circuit

texts:
I am trying to understand working of the following circuit;

It has Input from 0 to 7V and based on the Input value Output A to D will be High or Low but ...

Is it Inverting Schmitt Trigger comparator circuit?
Which Output will be High or Low at first? Out A or D?
How other Outputs will switch accordingly?


texts: Why is DC motor speed and torque direction the same, whereas in a generator it is the opposite?

texts:
What’s the relation between speed and torque in a DC machine. I know it’s inversely proportional but how?

Torque is nothing but twisting moment right? If torque increases then speed must be increased, but it’s wrong. Why?


texts:
I'm just trying to clarify the transmission line concepts in my head. Now wikipedia (that great source of always reliable information) defines the conductance in the transmission line as

The conductance G of the dielectric material separating the two conductors is represented by a shunt resistor between the signal wire and the return wire (siemens per unit length).

Now just to confirm this would be in effect the 1/R where R is the internal resistance of the capacitor? If so what is the benefit of modelling it in this way as opposed to just a second resistor in series with the capacitor? Is it purely mathematical for the telegraphers equations - or is there something deeper?


texts: Send alert tone to pc from microcontroller via serial communication

texts:
I am learning microcontroller for couple of weeks. Yesterday, I have learned how to establish serial communication between PC and microcontroller. I can send texts to pc's hyperterminal from mcu and send text from pc to mcu.

Now, one question arises in my mind. It is how can I send control words to pc from mcu, say send an alert tone to pc from mcu? Is it possible?
Thanks. BTW, I am using PIC microcontroller.


texts: How to control multiple tiny PWM controllers with one "master" MCU; DIY LED array

texts:
My question is, how can I control multiple tiny PWM capable controllers, like this https://www.sparkfun.com/products/retired/8897, with one "master" MCU for the purpose of controlling LED arrays?

This is where I came upon the idea: Microcontroller with lots of PWM outputs

I'm an aspiring biologist attempting to construct an LED device which I can use for photosynthesis research. The device will be a series of containers with LEDs embedded in the lids. It's based off of this paper.

They don't provide much in the way of a how to, so I'm attempting to sort of reverse engineer the device.

Individual LEDs are typically somewhat variable in wavelength and intensity output at a given current. I will be testing the wavelength and intensity outputs for each diode and each array and adjusting the PWM and possibly the current in order to have several containers all with lids producing the same, or close to, spectral power distribution and total light intensity.
My thought is to have one of the tiny controllers in each container lid and a master arduino or other such MCU to which I can upload any changes in spectrum or intensity I'd like to make. This seems like a great setup due to the flexibility of being able to add additional lids/tiny controllers and being able to change the spectrum and intensity for future experiments.


texts: ATMEGA 2560 => MCP4725 => FC-33 => Electronic Pressure Regulator

texts:
I am purchasing a regulator that accepts a 4-20mA control. I am hoping to interface this to an ATMEGA2560 microcontroller.

I am looking at using a MCP4725 DAC driven by the I2C bus of the microcontroller to provide a 0-5v output signal with a resolution of .0012 V. (https://www.adafruit.com/product/935)

Output of the DAC would go to V+ and COM input of the following FC-33.

To go from that output to the 4-20mA output I desire, and to gain isolation between devices I am hoping to use an FC-33 signal conditioner to read the 0-5v output and convert to the 4-20mA output. This should be a supported configuration through the DIP switches. (https://cdn.automationdirect.com/static/manuals/scdatasheet/fc_33.pdf)

The current output of the FC-33 will feed the input signal for this regulator. https://www.alliedelec.com/product/smc-corporation/itv2030-01n2l4/70070679/

Is there anything else I would need to make this work? Is this overkill?

Thanks for any and all help.


texts: Input flexibility for powered vs. unpowered sensors

texts:
I would like to design a flexible input interface for my embedded device, which will see a mixture of sensors connected. The sensors themselves (e.g. thermistors) will be two-wire, with the data/signal wire being pulled up to 5V prior to interfacing with an ADC. The issue I'm trying to address is that some sensors will interface with my device, which will then provide 5V pullup and GND, whereas some sensors will have an external 5V pullup and GND, with the single data/signal line interfacing with the device.

Example of case 1 (unpowered):

Example of case 2 (powered):

Is there a way I can design the device circuitry to account for both scenarios? I would ensure the device GND is shared with the powered sensor GND, so my focus is on the 5V pullup. Can I use an IC of some sort to enable/disable the pullup resistor, such that the line up to 5V is open-circuited for powered sensors?


texts: composite (RCA or A/V jack) output Passive splitter

texts:
Im trying to connect one CCTV camera feed to a TV and an USB composite encoder at the same time.

my question is, would something like this do it?

I have doubts about impedance issues, in which case what would be cheap DIY solution?


texts:
First what is my final goal: to drive 24 RGB LEDS using a microcontroller connected serially to a Micrel MM5450 LED driver. It would be nice to be able to drive all of them individually (72 LEDs), but I'll settle (as I did) for multiplexing and only driving one color at time. In the case of the MM5450, I'm using 3 outputs to drive 3 transistors, one for each color.

Now here's the problem I'm having.

I'm using the PLCC44 package, which seems to show some differences from the standard text in the datasheet. For example, the datasheet refers to 35 bits of data, but the PLCC only has 34 output pins instead of 35 in the DIP.

Just to get my feet wet, I've wired 4 LEDs to output pins 1 to 4 and left the rest disconnected. I've wired VDD and VSS (no decoupling capacitors), put a 100K pot on pin 21 (brightness control) and a 1nF on that same pin as the datasheet suggests.

I tried wiring DATAENABLE to GND, to VCC and to a pulldown resistor, but it didn't work as well.

The symptoms are that after I send data using the timing as indicated in the datasheet, I get weird results. For example, if I send all bits zero, at power on, only leds 1 3 and 4 will light up. Reset the uc and then led 2 3 and 4 light up.
If I send just bit one high, then led 1 and 4 light up, and then when I reset the uc leds 3 and 4 light up.
Just to clarify, when I say reset, it means that I assert the reset line of the microcontroller, which starts my program again (and sent a bitstream to the led driver).

I can't see a clear pattern of what's happening here. Anybody with more experience on this chip (or a suggestion of a completely different chip that will achieve my goals) to help me?

Cheers

Edit:

Ok, did some more tests and hooked a storage scope to data and clock. Here are my findings:

Clock and data are doing exactly what I'm telling them to do. As suggested, I placed clock and data on my PORTB and the data enable on my PORTC, if that matters.

My data sequence looks like this:
data: starts low
data enable: starts high
data sequence: 0 - [data enable low] - 1 - 34 bits of data - 0 - 0 - [data enable high]

Right now I'm working in the 10ms pulses. Since I'm using a breadboard connected to my devboard via long clip wires, I've analyzed the shape of the clock and data signals for any ringing and signal was pretty good.

From the symptoms, it seems that my bitstream is out of sync with the chip... I'm out of ideas


texts: Will an electric arc occur if there is a large enough resistor between voltage source terminals?

texts:
I want to create a multi select voltage divider from high voltage (1-2kV), but the switch (50V rated) is not rated for high voltage.
Should I worry about an arc being created if I have a 10MOhm resistor between the switch and the voltage terminals?
(R1 and R2 from schematic are rated for high voltage - 2kV)

simulate this circuit – Schematic created using CircuitLab


texts:
So this might be a stupid question and I really should know the answer to it but I am having difficulties with a circuit I have made to drain a battery.

The basic idea of this circuit is that I have a battery and some current sink as a load to drain this battery, this load will be triggered by a pulsing signal every 25ms and be on for 25ms, and the current being drawn is ~100mA, just in case you were interested that is.

So I left this circuit running overnight, so for about 16 hours and when I returned, the battery readings hadn't decreased at all throughout the test. Not only this but on previous occasions when I have tried to do the same thing, the battery has appeared to have gained power as the voltage readings increased over the test period. The voltage is being measured fairly often by an ADC which stores the results onto a computer so I can easily look at what's happened throughout the test.

So that's the issue I am having leading me to ask this very silly question.

How does the current flow through a battery?

So this is my very basic diagram of what I am doing.

I measured the current coming out of the battery and that was fine, but then I measured the current going 'from' ground to the negative terminal of the battery and got the same as what was coming out. I thought to myself, can current be coming from this ground pin? And I really couldn't think of the answer, probably because it's early on in the day and my mind isn't working properly yet but still it is concerning me that I do not know the answer.

In all honesty the multimeter I am using to measure this current would appear to imply that it is flowing the other way to what I have drawn in my little diagram but I think that's because it's not very good or wants to measure things in terms of the flow of electrons rather than conventional current. But I digress, that's another battle for another day, again probably me doing something wrong.

Anyway any help with any of the issues I have mentioned would be great but mainly the battery current flow would be nice, a diagram would really help me grasp what you are talking about a little bit better as well!

Thanks!


texts:
I'm trying to make a little carry lantern which uses a super bright 3.7V LED at 1Watt (those hex shaped ones) powered by a Li-ion 3.7V battery. Now I've seen the idea of pulsing an LED to reduce the overall power consumption on the battery but I'm wondering if there is any way of doing this without the use of any IC.

I've read up on something such as an avalanche transistor which seems to be pretty close on what I'm aiming for. I've noticed people talk about the fact that during pulses you can go over the LEDs rating depending on the duty cycle (IE 50% cycle can go to 200% of the LEDs current rating) as long as you have a way of mitigating the heat properly.

I'm not too bothered if I over supply the LED and reduce it's lifetime. I would really like to know how to easily pulse an LED without an IC (or easy to build). Could I also control the current to the LED?


texts: Stepper motors: feedback to detect successful step?

texts: Is it possible to have a stepper motor driver circuit detect if the motor has successfully stepped, ie not stalled, or stepped too quickly? (Not microstepping).


texts: Protected Li-ion batteries charging / discharging in parallel?

texts:
since there is no longer good source of high quality pouch flat type Li ion cells, I am considering to use high new smartphone batteries from service packs.

I need bigger capacity - about 10 - 20 Ah, so using 4Ah cells I am on 3 -5 cells in parallel. I am using single cell scenario  - 3S1P or 5S1P.

Are there any drawback in charging all these cells in parallel with original PCM? I know that PCM will disconnect each battery randomly during charge and discharge. It seems that during charge I need charger with 4 A charge current max to fully protect case that only one cell`s PCB is allowing to charge.

Am I missing something?

P.S.: I dont want to remove PCMs from these pouch type batteries, soldering can be quite tricky and dangerous on these soft plastic packages...


texts:
I have recently run across integrated passive filter network chips such as the IP4251.

How do I know when I need something like this? In my day to day life I would probably say okay, this IO needs such and such filter cap or decoupling cap. I would never have said, however, that I need a specialized filter package, nor have I ever seen a datasheet that recommends one.


texts: Signal(s) form a combinatorial loop VHDL

texts:
I was trying to implement Dual-priority encoder but I get following warnings during synthesize:

  WARNING:Xst:2170 - Unit prEnc : the following signal(s) form a
  combinatorial loop: done, first<3>, req[0]_done_AND_6_o, f.

  WARNING:Xst:2170 - Unit prEnc : the following signal(s) form a
  combinatorial loop: f.

I got no idea how and where my signals form a combinatorial loop.

Here is the code.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;

entity prEnc is
port( req : in std_logic_vector(7 downto 0);
        first : out std_logic_vector(3 downto 0);
        second : out std_logic_vector(3 downto 0)
);
end prEnc;

architecture Behavioral of prEnc is
signal f, done : std_logic ;
begin
process (req,f,done)
begin
    first <= "0000";
    second <= "0000";
    f <= '0';
    done <= '0';

    if req(7) = '1' then
        first <= "1000";
        f <= '1';
    end if ;
    if req(6) = '1' then
        if f = '0' then
            first <= "0111";
            f <= '1';
        else
            second <= "0111";
            done <= '1';
        end if;
    end if;
    if req(5) = '1' and done = '0' then
        if f = '0' then
            first <= "0110";
            f <= '1';
        else
            second <= "0110";
            done <= '1';
        end if;
    end if;
    if req(4) = '1' and done = '0' then
        if f = '0' then
            first <= "0101";
            f <= '1';
        else
            second <= "0101";
            done <= '1';
        end if;
    end if;
    if req(3) = '1' and done = '0' then
        if f = '0' then
            first <= "0100";
            f <= '1';
        else
            second <= "0100";
            done <= '1';
        end if;
    end if;
    if req(2) = '1' and done = '0' then
        if f = '0' then
            first <= "0011";
            f <= '1';
        else
            second <= "0011";
            done <= '1';
        end if;
    end if;
    if req(1) = '1' and done = '0' then
        if f = '0' then
            first <= "0010";
            f <= '1';
        else
            second <= "0010";
            done <= '1';
        end if;
    end if;
    if req(0) = '1' and done = '0' then
        if f = '0' then
            first <= "0001";
            f <= '1';
        else
            second <= "0001";
            done <= '1';
        end if;
    end if;
end process;

end Behavioral;


texts: Download a file from web browser to Micro SD card

texts:
I am trying to do a web server to store a file (mostly MP3) on a Micro SD card.

I have stm32f407-discovery and w5500 and a Micro SD card reader (unbranded manual pcb drawed).

How can I open a web server with w5500?
How can I write files on the Micro SD card with the sm32f4?
How can I download files from the web browser onto the Micro SD card?


texts: Calculating the gain and phase shift of a phase shifting circuit

texts:
I want to calculate the gain and the phase shift of the phase shifting circuit below. My approach is to derive equations to different meshes using Kirchoff's law, and then calculate the ratio between Vin and Vout in the frequency domain.

But obviously, it is too hard to simplify the equations (at least for me). Are there any other (easy) methods to calculate it ?

--Thanks

simulate this circuit – Schematic created using CircuitLab

EDIT:
I want to derive a formula for the gain and the phase shift. Not to calculate 'a' value.


texts: Can someone explain what each pin does on an LM3914 dot/bar graph chip?

texts:
I got an LM3914 chip to control a ten segment bar graph, but I am confused on how to wire it. The date sheet is not helping me with what pins do what and how to wire it.

I need to know how it works and please don't be hyper technical I am still new to electronics.


texts: Is there a rectifier scheme for tri-phase which is more efficient than the bridge rectifier?

texts:
Because of the topology of tri-phase bridge rectifier, every phase is active (i.e.; feeding the load) only for 33% of the time. It feels like we are not fully utilizing all the three phases, and because of that the output impedance of the rectifier is higher than it could actually be.

Is there an alternative rectifier form which utilizes all three phases (or all N-phases in general). For example, by pumping charge in a storage element in a sub-interval of one period, and using it in another sub-interval.

Assmue that the load is always resistive.


texts: Undefined parameter name error in Hspice

texts:
I am trying to run this Hspice code in Spectre.

I am getting this error

Can anyone help me what is the mistake?


texts:
I am trying to construct a circuit to control an LED in a bike light kind of circuit. This circuit must be designed so that a button press can change the current setting of the light.

So for instance first click turns on the light on slow blinking, one more click goes to fast blinking, a third click to continuous light and a fourth to turn it back off.

I have been trying to Google my way to an answer, but can't seem to find any reasonable circuitry or inspiration to design such circuit.

Hope someone can be of help pushing me in the right direction.

Thanks in advance


texts: How can I eliminate the loop in this diagram?

texts:
I'm really sorry to open some series of questions but since the issue is complicated I decided to open a separate question for a particular thing for not creating confusion:

There is the red loop in below diagram which might be causing the EMI pickup I was told here. And then there is a second loop across the power supplies and the earth GND, usually is capacitively coupled.

It seems my main issue is the red loop. The long wires and the loop I guess pick up EMI.

But how can I physically star ground and minimize that area of the red loop or eliminate the loop? Or without any stargrounding is there a possible way to elimiate such spike only at node X.
Here is another illustration where blue lines are showing grounds:

How can I filter the spike like noise due to EMI at the DAQ input node X? Are there ways worth to try?  The spike occurs at all supply outputs but it is only an issue if it appears at node X in my case because of a software thing not hardware upset. Would a filter and an optocoupler be worth to try?


texts: Extremely noisy signal after voltage follower/buffer

texts:
I am trying to create a voltage follower for my CCD linear array. When I measure the signal with oscilloscope directly from the CCD outptut - the signal is reasonably clean. However, when I measure if after the voltage follower, the signal is extremely noisy. Distorted?

The analog output from the CCD fluctuates between 5V and 8V. The readout rate is around 1MHz. Therefore, I am using AD8004 OpAmp 250MHz bandwidth, 3000V/us. I power it with -Vs=0V and +Vs=12V.

Putting a 10uF cap on the power line next to the IC does not help. Please, help to find the reason of such noisy output.


texts: What are some simple ways to reduce Arduino power usage?

texts:
For a quick and dirty project, what are some of the simplest ways to reduce the power use of an Arduino?

Imagine the following setup:

A typical Arduino Nano, hooked up to a pair of DS18B20s and one of the mini OLED screens. Power comes from a cellphone battery hooked to a TP4056 board, which then runs to a small 0.9V >> 5V boost board, both common eBay items.

The idea is to make a basic platform, to which additional functionality will be slowly added, such as a wireless link and data-logging. For now, though, the situation is as described above.

The obvious start would no doubt be killing off unnecessary LEDS , or at least, tacking on extra resistance to make them fainter. Maybe finding how to reduce the brightness of the OLED screen would also be an obvious step, and that green LED next to the ON switch isn't necessary...

But beyond this, what simple steps could be done in coding or hardware load-out could help get more battery time?

(This question relates to a specific level of embedded system enthusiast, namely, the intermediate level, someone who isn't yet confident enough to dive into the depths of the AVR assembly language, but rather someone who already grasps the basics of how electronics and embedded devices are put together in a system (In other words, myself..). There are differences compared to the How can I get my atmega328 to run for a year on batteries? question, and more specific to the actions I practically can take.)


texts: I am trying to build a waveform amplifier and having no luck

texts:
Simulation works

As expected I am seeing a gain of 10. I built the circuit and I am seeing much less gain(in some cases negative gain) and extreme clipping.
Is there something I'm doing wrong here? It's super confusing to me that it would work so well in simulation then not at all in measurement. Any help or advice is appreciated. Trying to build a waveform amplifier with a gain of 10 to amplify the voltage coming from the signal generator because its max output is 10vpp. Thanks.


texts:
According to LM358 datasheet from TI it should be capable to reach GND when operated from a single power supply in linear mode. Thus I have decided to use it as input buffer to an ADC as shown:

with 1.65 V implemented as:

However it is not doing what I expect. In the following image CH1 is showing the + pin of C3 and CH2 is showing "ADC_INPUT":

Any idea?


texts: A question about "Coin Cells And Peak Current Draw" App Note

texts:
I'm trying to understand this small TI's app note called Coin Cells And Peak Current Draw, but I don't get it.
This white paper is interested in increasing the battery life of coin-cell-powered systems.
More specifically, embedded systems using an RF module to communicate.
The paper's conclusion is that adding a decoupling capacitor will increase lifetime.
To prove their point, they create 2 tests :

Without a capacitor
With a capacitor

Honestly, I don't understand the results:

Without a capacitor

With a capacitor

I just don't see why those images are proving that using a decoupling capacitor is a good idea.
Also, the paper completely ignores the capacitor leakage current.
Is there something I'm missing?


texts: How are headers soldered in PCB assembly?

texts:
During large-quantity PCB assembly/soldering, are SMD (surface-mount) headers traditionally easier or harder to assemble than DIP (through-hole) ones?

By easier/harder, I'm concerned about differences between the two in terms of assembly time/cost. I'm designing a board where I would like to make a better-informed choice between the two.

I suppose the only way there would be a difference in difficulty between the two is if one of them were manually soldered, so another way to ask the question might be:

Are both kinds of headers soldered by hand to this day, or is one of them machine pick-and-placed with some customized reflow profile so as not to melt the plastic?


texts:
We were learning about full adder and half adder circuits and how overflow might occur in them. My professor told that for a full adder of n bits the range is  [-2^(n-1) , 2^(n-1)-1]. What I don't get is why is -2^(n) also in the list.
For example if I am using 4 bits and then I add -4 + -4 = -8 which in 2's complement form is 11101, and then on performing the usual operation of discarding carry and checking the signed bit the answer comes out to be 0.


texts: How do I build a 10uA current source/limiter?

texts:
I need a constant current of 10uA through a variable resistor in the 100k values. I need to inject the current into that resistor and I need the resistor to be connected to Ground such that I can measure the voltage across it with a microcontroller(writing this I figured I could just read the voltages in both points and substract them, but oh well). So how do I do this with discrete components? I heard that current mirrors don't work with discrete components. I don't know if using an operational amplifier and a sense resistor, I would be able to source/sink such a small current. Is a current limiting circuit better? I don't really need to inject the current, I just need constant 10uA.

What's a reliable, stable and fairly exact 10uA current source/sink that I can build with discrete components and without any IC's as I don't want to wait for themto ship to me?

Edit: I'm working with supply voltages in the range 5v-12v

Edit 2: 1% accuracy is just fine. Heck, even 5% accuracy is fine, anything below 10% is fine. My load is a 220k resistor at it's maximum (it's actually a 100k thermistor, but that's as high as it will get). And my supply would be 5V, so in order to get 10uA through it, I would need to supply about 2.2V, so no problem there.


texts: Can anyone help me to identify the SMD capacitor in this photo? (at least I think it's a capacitor!)


texts: What's the interest for these breakout boards?

texts:
I'm wondering what's the interest for a breakout board or at least these ones :

Shift Register Breakout - 74HC595 - 2.95$

Shift-In Breakout - SN74HC165 - 3.95$

I'm wondering this because, take a look at the price, now take a look at the part price... Even in DIP package instead of SMD.

For me they look like beginners marketing traps to make a lot of money from the "maker trends". But I think I'm missing something.

EDIT : Re-ask my question to avoid opinion based answer. Or buying guide related.

Why would you buy and use these breakout boards ? What's the benefit ?


texts: Oscilloscope Output with its positive terminal touching human's body and negative terminal left open

texts:
it once happened that when I touched the positive terminal of the Oscilloscope input probes letting its negative terminal open, I observed sinusoidal voltage signals with 0.5V peak to peak and of frequency nearly 50Hz. I don't understand the exact cause for these signals. When I touched the other, negative terminal output signal reached zero with a very little noise...(with the positive terminal connected to the body..) Is it because the power lines near the place I observed these are 50Hz and those induced a potential difference across me with respect to the supply ground which is also the ground of Oscilloscope... or something else.. When I touched a wire or a resistor with positive terminal of Oscilloscope.. there was no change in the Output.. Its because the equivalent model of our body includes capacitance and inductance with resistance.. If so then actually how we are being induced with such voltage signal..?
Actually the discontinuity in signal is because of the difference between the frequency of actual signal and sampling frequency of my camera.


texts: Help to understand output levels of clock buffer

texts:
I'm dealing with clock buffer and trying to determine how output levels depends on the input. I'm using information from the datasheet. Here is the table with information:

I don't understand the information in this table completely.
We see that output high voltage is measured at the certain conditions.
The supply voltage is VDD=Min=1.65. The input voltage is VIH or VIL. I don't understand that. I expect the output voltage to be measured at the certain input voltage.


texts: How to measure acidity of a breath condensate?

texts:
Is there any way to measure an acidity of a breath condensate? That is to measure a pH of an exhaled breath condensate. I would like to use such a sensor to daily measure my acid level in a breath condensate and correlate it with heartburn attacks as well as a measure of the impacts of my diet.

This can be very useful for patients with GERD (acid reflux) or those who suffer from a bad breath caused by the gastric acid in their stomach.

Note: ideally I would like to use it with the Raspberry Pi. For now the guys from Raspberry Pi SO sent me here saying it's a cool concept but sadly there is nothing off the shelf.

Edit: While doing the research on this question I found this interesting article on different ways of measuring the gastric acid secretion:
http://www.researchgate.net/publication/49780488_Review_article_Methods_of_measuring_gastric_acid_secretion
http://www.ncbi.nlm.nih.gov/pubmed/19279471


texts: Instrumentation Amplifier REF pin maximum voltage

texts:
I'm a spanish engineer student doing my end-of-degree project. I need to remove the offset of a strain gauges bridge and i'm trying to make the calibration automatic, using a DAC (digital to analog converter) that will introduce a positive or negative voltage in the REF pin of a instrumentation amplifier (i'm using INA118, but INA126 is also avaiable).

I don't want a manual calibration via potentiomenter. I've seen in the INA118's datasheet a similar circuit: Figure 27. Optional Trimming of Output Offset Voltage ( http://www.ti.com/lit/ds/symlink/ina118.pdf ).

I've seen other questions like "What is the reference pin on an instrumentation amplifier used for?" where they say "Yes, you can do a voltage shift through InAmp's REF pin", but it didn't helped.

The problem is that when i gave 6 negative volts to the REF pin in a +-2,5 supplied INA118 it burned... So i need to know what are the limit voltage in the REF pin???? With -2 volts in REF there was no problem (the limit is the supply rails maybe?)

Thanks all!


texts: What is the difference in this specific breadboard wiring?

texts:
As an absolute layperson in electronics I just found out that an LED only lights up when connected like in figure 1 but not when connected like in figure 2. And I just don't get why?

I know an LED is a diode and current can only move through it in one direction, but that's the case in both constructions. I don't see a difference in both constructions.

So why does it obviously make a difference?

figure 1 (battery not depicted):

figure 2 (battery not depicted):


texts:
I want to operate a 12V automotive fan with a 3.3V uC signal.  The (37-year-old) centrifugal fan draws 3.2A for about 100ms at startup and then a steady 1.2A while running for a maximum of 30 minutes.  Originally, I used a Panasonic 12V, 25A automotive relay (www.farnell.com/datasheets/1809465.pdf) and 2N2222 NPN BJT.  I also added a 100Ω resistor and 100nF cap across the contacts.  The circuit works fine on the PCB I prototyped.

I assembled a second circuit and replaced the relay with a 27A P-channel power MOSFET (www.farnell.com/datasheets/1712479.pdf).  Assuming I understand the data sheet correctly, there is already a diode present so that component was deleted as was the RC snubber.  I can also operate the fan now at various speeds using PWM.  This circuit also works fine on the breadboard.

There are similar threads but I haven’t noticed a consensus on whether a power MOSFET is considered a suitable replacement for a relay.  I don’t need the PWM option and am unsure if it is even advisable to operate the fan at anything other than its designed parameters.  The MOSFET is $1.50 but the relay is only $3.50, not a consideration for a one-off.  Should I prefer one design over the other?  Should I use a FET rather than the 2222 BJT if I want to use PWM?  Is the RC snubber necessary for the relay?  Is there anything else I haven’t considered like excessive heat when using the MOSFET?


texts:
As well all know, using an LED without some sort of current control is a bad idea. One of the most basic types is a simple Ballast Resistor, paired with Ohm's Law. Based on Vin, Vf, and the desired Current, we can determine the resistor needed.

But in broad strokes, what is the best scenario for choosing a resistor? Given an LED with 20mA at 3.3V Forward Voltage, with a very close (Variable) source voltage, how much headroom does the resistor need for optimal control?

If we provide too much headroom (Vin of 12V) for a single 3.3V LED, we are just wasting energy and require a higher wattage resistor. If we provide little head room (Vin of 3.4V), we give the LED only 0.1V, is that enough? Changes in Vf and If due to temperature look like it would cause a looping cause and effect situation.

So the question is, for optimal control, how much headroom in terms of voltage, should the resistor need?


texts:
Faraday-Lenz's law was easy when I was in 12th standard. But it became more complex when I jumped to Engineering. Recently when I was studying about inductors and how they oppose changes in currents, I found out that Faraday-Lenz's Law becomes little weird because based on my observation I found out that this law "doesn't work" (frankly speaking)! Here's the story behind my observation:

Suppose you have an AC voltage source of 240 volts peak and 60 Hz frequency connected to an inductor of 10 mH inductance (wire's resistance is negligible so that the impedance is only due to the reactance of the inductor). Now if I switch on the Ac supply, it is found out that the voltage across the inductor is 240 volt peak and the reactance and current through it is 3.7699 ohms and 63.6622 amps peak. The voltage polarity is as shown.

simulate this circuit – Schematic created using CircuitLab

Now if we apply Kirchoff's Voltage Law to this circuit, it works as expected. But then I don't seem to understand that 'how' this inductor opposes current. Because in my opinion if the inductor opposes current then the polarity markings on the inductor should be reversed then only we can say it generates a back emf. But then the Kirchoff's Voltage Law would not work if the polarity markings are reversed.

Now I think I didn't understood the topic of how inductors oppose currents in an AC circuit.

And also if it generates a back emf to generate a back current then where is the back emf and the back current and why it does not affect the voltage across the inductor and the current through it?


texts:
I have made a homemade CNC for double sided pcb protoyping. I use flatcam to convert excellon files in gcode and then use UGS to send this gcode to arduino. I tried to drill a pcb size 180x140 mm having four registration holes in the corner, but when i match the drilled PCB with the printout of excellon files they don't match.

I tried to calibrate the CNC axis but the result is same.

I also tried to check whether the print is proper or not, so tried to print in landscape orientation as a result most of the drills match but some do not.

What possibly be the solution of this error?

[EDIT]
new board drilled and the inconsistency remains.

design on flatcam


texts:
Im trying to store some data in the 24AA01 EEPROM using the PIC18F13K22. Since I am awaiting the components, I thought I will go ahead and simulate it in Proteus.

This is my code (XC8 compiler based).

#include <xc.h>
#include "config.h"
#include "uart.h"

void i2c_writebyte(char x);
char i2c_readbyte();

void main(void) {
    OSCCON = 0x43;  //2Mhz
    TRISBbits.RB4 = 1;
    TRISBbits.RB6 = 1;
    TRISCbits.RC5 = 0;
    LATCbits.LATC5 = 0;   //Low to Enable Writing

    SSPADD = 4; //100kHz
    SSPSTAT = 0x80;
    SSPCON1 = 0x28;

    char a = 'y', c;

    uart_init();

    i2c_writebyte(a);

    c = i2c_readbyte();

    print(c, 1);

    LATCbits.LATC5 = 1;   //High to disable Writing
    while(1);
    return;
}
void i2c_writebyte(char x){
    try:

    SSPCON2bits.SEN = 1;    //Start bit
    while(SSPCON2bits.SEN != 0);

    SSPBUF = 0xA0;
    while(SSPSTATbits.BF != 0);
    while((SSPCON2 & 0x1F) || (SSPSTAT & 0x04));
    if (SSPCON2bits.ACKSTAT !=0){
    print("1", 1);
    return;
}

SSPBUF = 0x0;   //Address
while(SSPSTATbits.BF != 0);
if (SSPCON2bits.ACKSTAT !=0){
    print("2", 1);
    return;
}

SSPBUF = x;   //Byte
while(SSPSTATbits.BF != 0);
if (SSPCON2bits.ACKSTAT !=0){
    print("3", 1);
    return;
}

SSPCON2bits.PEN = 1;    //Stop bit
while(SSPCON2bits.PEN != 0);
}

char i2c_readbyte(){
    char x;
    try:
    SSPCON2bits.SEN = 1;    //Start bit
    while(SSPCON2bits.SEN != 0);

    SSPBUF = 0xA0;
    while(SSPSTATbits.BF != 0);
    if (SSPCON2bits.ACKSTAT !=0){
    print("4", 1);
    return;
    }

    SSPBUF = 0x0;   //Address
    while(SSPSTATbits.BF != 0);
    if (SSPCON2bits.ACKSTAT !=0){
    print("5", 1);
    return;
    }

    SSPCON2bits.SEN = 1;    //Start bit
    while(SSPCON2bits.SEN != 0);

    SSPBUF = 0xA1;
    while(SSPSTATbits.BF != 0);
    if (SSPCON2bits.ACKSTAT !=0){
    print("6", 1);
    return;
    }
    SSPCON2bits.ACKDT = 1;
    SSPCON2bits.RCEN = 1;
    while(SSPSTATbits.BF == 0);
    x = SSPBUF;
    SSPCON2bits.ACKEN = 1;

    SSPCON2bits.PEN = 1;    //Stop bit
    while(SSPCON2bits.PEN != 0);

    return x;
}

I use the UART to tell me at what point the ACK was not received. The oscilloscope also confirms that when I check the waveform.

Why isn't the EEPROM providing an ACK? Is it a simulation bug or am I doing something wrong?

Changing the pull-ups to 10k and 4.7k had no effect as well. I used an I2C debugger to see if the correct data was going but I saw something like this. Can anyone help me intepret this?


texts:
What will be the phase of the current trough the coil:

I think that I can find it using:

$$\arg\left(\underline{\text{I}}_\text{L}\right)=\arg\left\{\frac{230\sqrt{2}e^{\frac{\pi\text{j}}{2}}}{\left(5+\frac{8\cdot9\text{j}}{8+9\text{j}}\right)}\cdot\frac{8}{8+9\text{j}}\right\}=\arctan\left(\frac{40}{117}\right)
\approx18,875^\circ$$

Where \$230\$ is the effective input voltage.


texts: May RJ45 connector with magnetics connected in series?

texts:
I have a dev board with a RJ45 connector which has magnetics integrated. I need put it into a case and mount another RJ45 on the panel, sadly I have only another connector which also integrate the magnetics. If I can use a cable simply connect the RX-, RX+, TX-, TX+, of my board connector to the RD-, RD+, TD-, TD+ pins of the connector on the front panel, but left the CT pins open?

Update:

I've tried that, and it works, at least. But more explanations are welcome here.
And is it a good or bad design?


texts: Why ring oscillator showing irregular graph ?

texts:
I'm trying to design ring oscillator in CADENCE using 180 CMOS .Instead of showing inverted clocking output , output changes in less then millivolt ranges. When I connect only 9 inverter like this schematic:

output graph for last 3 nodes are like this:

zoomed view of this graph is:

this changes happening in less then nanovolt rage which should be considered as nothing but noise ( I presume )

If I increase the number of CMOS significantly (45 CMOS) then this graph become this where variation still do not cross milivolt range:

I did not do any calculation for this, as for a simulation purpose, I thought it would not be necessary I'm not looking for any specific frequency right now.Provided mosfet should be sufficient for sample design.

Where could I make mistakes ? What kind of calculation should I do to fast to design this ring oscillator properly ?


texts: Why is the source voltage 1/4 of the supply voltage applied to the drain in a voltage-divider JFET circuit?

texts:
According to a Junction Field Effect Transistor (JFET) article in ElectronicsTutorial, the voltage across the source resistance is equal to 1/4 the supply voltage applied to the drain/gate for a class "A" amplifier. Quoting from the article:

  This common source (CS) amplifier circuit is biased in class “A” mode by the voltage divider network formed by resistors R1 and R2. The voltage across the Source resistor RS is generally set to be about one quarter of VDD, ( VDD /4 ) but can be any reasonable value.

I set out to verify this equation by using it in a question that I was attempting to solve, a simple DC biasing equivalent voltage-divider JFET circuit with 2N3819 as the JFET component for my circuit.

Assuming that:

R2 = 150k Ohms
ID (Drain Current) = 3mA
IDSS (Saturated Drain Current) = 10mA
VDD (Supply voltage for DC bias) = 20V
VDS (Drain-source voltage) = 7V
VGS (Gate-source voltage) = -3V

I set out to find the unsolved resistance values and the required voltage values. Based on using VS = VDD/4 and other equations like Shockley's Equation and the KVL equations concerning the gate/gate-source/drain-source voltage:

Vgs = Vg - Vs
Vds = Vdd - IdRd - IdRs
Shockley's Equation
Voltage divider rule for finding the gate voltage, Vg

I was able to find the calculated voltage values (which will be used to compare with the simulated results):

Vg  = 3.643V
Vgs = -1.357V
Vs  = 5V
Vd (drain voltage) = 8V

The calculated resistance values were:

R1 = 673459.2173 Ohms
RS = 1666.67 Ohms
RD = 2666.67 Ohms

Plugging the calculated resistance values into the simulation gives me:

It seems that VS = VDD/4 is correct, albeit with slight differences in the value between the calculated and simulated results:

Vg (simulated) = 3.643V [matches calculated value]
Vs (simulated) = 5.117V [differs from calculated value with difference of 0.117V]
Vgs = -1.474V [differs from calculated value with difference of 0.117V]
Vd = 8.19V [differs from calculated value with difference of 0.19V]
Id = 3.07 mA [differs from original value with difference of 0.7mA]

Now that I have verified that the equation is actually correct, I want to ask:

How is the equation VS = VDD/4 derived?
What causes the difference between the simulated and calculated values? Is it because of additional factors (like wire resistance) that the simulation software considers when showing the simulated results?
Is there another way to find the calculated resistance/voltage values without having to use the aforementioned VS equation or the graphical method?

Thanks.


texts: STM32H757I - EVAL BOARD to learn Embedded Systems

texts:
I wanna dive into the matter and learn Embedded Systems. I am waiting for this board. I've read some blogs, earlier posts on this topic, watched some videos and I have a couple of questions:

Does one have to be an expert in C to start learning this | learn all the C Programming stuff before Embedded Systems or can we pick it up along the way?

As far as I saw, I would start learning it at register level. I read about what that would kinda mean, and that's the way I would like to learn it. I mean, learning how to work with registers would make me a better professional, I suppose.

I found no course on this stuff, except for a new release on Udemy, by 'Mutex Embedded' . I have no idea if that's a good course. Has any of you taken it?

I found some books on General Embedded Systems, or Embedded Systems with xxxxx, but using other languages, boards, approaches, and so on. But nothing like 'STM32 register level programming', using (embedded) C. Isn't that common?

PS: 'Beginning STM32', or 'Making Embedded Systems' seemed to either not be the approach or level I'd like or be too general. Is it really like this?
I am gonna take Control Systems now, and would like to learn some Embedded Systems. That's why.


texts: Connecting potentiometer with on/off switch to audio board

texts:
I have a B10K potentiometer with an on/off switch, trying to connect this to an audio bluetooth board (Dayton Audio KAB-215 2x15W).

My question:
The potentiometer has 8 pins an I have a hard time figuring out where to connect the different cables, can't find any suitable diagrams.

To the best of my knowledge I know that I have to run the power and speaker cables through the potentiometer, but in which order?

Any hints or tips is much appreciated!

SOLVED! Uploaded image above for future reference


texts:
I live a couple miles past where "normal" high-speed internet is available, and for years I have used a radio WAN link on a 70' radio tower to connect to my ISP in town, 4.65 miles away.  I have a clear line of site, and the signal is plenty strong.  However, I've been having major issues with interfering transmissions spiking the noise floor and disrupting my signal.  The ISP's techs have done what they can (polarization, switching channels, etc.) with the radio's internal antenna, but it hasn't solved the problem.   The issue isn't lack of signal, but too many noise spikes.

My last option is to build an external antenna for the 5.8Ghz radio capable of mitigating the interfering transmissions.  I have a decent electronics background and shouldn't have any issues building an antenna after I decide what to build.  However, I am new to antenna design.

Possible routes:

High gain parabolic antenna.  This assumes the parabolic antenna's directionality will limit the reception of interfering signals.
Build a RF-reflective tube or cone around the radio so that only direct waves will hit the antenna.  (Would only be workable if it could be done with a porous material to limit the wind loading.)
Make a two-wave length beverage antenna.  These seem to work well for ARL folks, but I haven't found confirmation that they would work as well at 5.8ghz.  Also unsure what the impact of the ground points being on the earth-grounded metal tower.  (IOW, will the tower cause noise if it carries the antenna's ground to the ground rods at the base of the tower.
Use a multi-antenna system, either to subtract out back ground noise, or to increase signal to noise.
Something else

What approach would most likely do the most to increase my connection's signal-to-noise ratio?

Other relevant data:  The radio mount on the tower can sway about +/- 1.5 degrees in high winds.


texts:
I'm using a MOSFET to buffer my signals from a CPLD. The signals travel external to the PCB using long (from 1m to 10m) wires and then come back to the same PCB - the wires are actually the component under test. The pull up resistor, R2, is situated on the input side of the PCB. I was probing my signals when I noticed that my fall time is very fast (4.4ns fall time) yet my rise time was 264ns. Here's my schematic of the buffer:

Here are some captures from my oscilloscope:

The circuit actually works just fine. I've had a unit under long term testing and I've had zero issues so far. I am just curious what could cause asymmetrical rise/fall times. My theory is that it's because I'm using the MOSFET in open-drain configuration. The 1K pull-up resistor slows down the rising edge of the waveform and if I used a smaller resistor, the edge would rise quicker.

NOTE: Please ignore the ringing on the falling edge. I've asked a separate question regarding that.


texts: Buck converter as a LED driver with NO LOAD

texts:
I am proceeding with a design of a LED driver using an LM3405.

I don't read anything related to what happens when the load is not present, on the datasheet. As you may have already read, this is the configuration adopted.

But with open load, the output does not simply goes to Vin? When the MOS will turn off, the charge pump put Vin on the BOOST. If this is true, I will destroy the BOOST pin, which must no exceed the relative voltage between SW and BOOST pin of 5.5V!

Is there any sort of protection in the IC, something that I can implement additionally or something that I've even forgot? Are there any other issues related, except for the classical ones in literature about switching converters?


texts:
This is my second day of learning PLC online. I am doing a simple ladder diagram, and I came up with the following diagram:

The process I have in mind is as follows:

As the switch is closed, the belt is activated. Afterwards, the IR Sensor is activated, turning off the belt, and initiating the timer. For the duration of 5s, "ValveD" and "ValveU" are both turned on. During the first second, "Press" is also turned on. After the 5s and the reset of the timer, I wish to have the belt start moving again (Note that at this stage the IR Sensor is still off), and the cycle is repeated. I am not sure of the correctness of the diagram, however. Moreover, I am not sure how can I add a memory to indicate that the timer has already ended, and the belt should start moving again (OR DONE with the IR Sensor?) Also, when I simulate, the timer keeps resetting and restarting itself, although video tutorials online showed that all timers stopped after they reached their preset time.

So is there a reason why the timer is always working, or does it depend on the used software? Moreover, is there a need for the Switch and IR Sensor inputs to be in the 2nd ladder, since the belt is enough to control the timer. Thank you.

EDIT: This is my final circuit. The first time I tried simulation, I remember it working exactly as desired. However, minor issues happened and Rung 0 was deleted, so I had to add it again, exactly as before. However, now the timer keeps repeating itself. Also, this is the timing diagram of the PLC.

                ________________________________
Switch      ___|
                       ____________
IR sensor   __________|            |______
                ______           _________
Belt        ___|      |_________|
                       _________
Valve D     __________| . . . . |______
                       _________
Valve U     __________| . . . . |______
                       _
Press       __________| |______________


texts:
i read the datasheet of irm=20-5 which is a AC DC power module it takes a input of voltage of 85-305VAC
and converts into 5V DC at output ,in the datasheet it is written that the withstand voltage is 3KVAC like i can apply a input voltage of 3KVAC ,will it damage the component.
Datasheet: https://www.meanwellusa.com/productPdf.aspx?i=682


texts: using high and low switch together on a load

texts:
in the below picture is a test method im trying to make it work

if succeeded, I will implement it in my LED clock project
I'm making a four 7 segment LED using 12V led strips as 3x3 bits for every segment
The method to control the the segments is by using the 74595 shift register to call each LED
and using the "high side" "low side" transistors as switch to call the LEDs
by making a common among the LEDs (common cathode or anode)

Anyway, I have very little information to rely on and need an expert opinion.
Is the circuit in the diagram correct?

(original)

If yes, how can I calculate the resistance value for R1, R2 , R3?

what are the power rating should I be using?

I used for the low side switch R3 = 300 Ω
and for the high side switch R1 = R2 = 1 kΩ

But when I tried it, the Q2 transistor was getting really hot.

As for the Arduino code, a simple blink for the digital pin high and low states.


texts: Fringe field effect in cylinder conductivity cell

texts: In a coaxial cylinder conductivity cell with the inner electrode electrified and a dielectric liquid between them, how is the fringe field effect dealt with? Is the effect as severe as in a parallel plate cell and if a guard electrode is used where is it placed?


texts: Why do I need transistor in the following mains power failure circuit?

texts: In this main's power failure alarm circuit, when main power is connected the diode is reverse biased and so the buzzer is off. But when main power is not connected, the diode is forward biased and so the buzzer gives the alarm. So the switching in this circuit is being done by the diode, so what is the transistor doing in the circuit? If the transistor is being used as a switch, then why it is needed as the diode is already doing the switching?


texts: Calculating run time for a device with variable current draw

texts:
I recently built a small microcontroller-based project for a friend that consumed different amounts of current at different times. I wanted to calculate the run time for a given battery type (but discovered the area of my brain that used to know algebra seems to have gone missing).

The device draws 2mA of current for 2s, then draws 20mA as it sequentially lights LEDs for 500ms.

I originally tried to calculate the average draw: In 3 seconds it consumes (2 + 2 + (20 * 0.5)) 14mA or an average of 4.67mA per second. Therefore, a battery with 2400mAh should be able to power the device for (2400/4.67) ~514 hours or 21.4 days.

This math seems incorrect to me, though I am not sure why. I didn't expect the run time to be over a few days.

Whether my calculations are correct or not, can you explain a simpler or better method to calculate run time for circuits with variable current draw?


texts: Is it possible to control 12v pump only with arduino (no 12V battery)

texts: I want to control a 12V pump with an arduino (it is actually a WeMos D1) and I would like to avoid the use of an external battery (to avoid that they run out of battery without me noticing it). I have seen a lot of options using a 12V battery but I would like to know if it possible to do it without one or it has no sense.


texts: Is the total resistance of a resistor static once the tolerance is applied?

texts:
If a resistor is described as having +-5% tolerance, is that a fixed value, or could it vary while the resistor is in use?

To explain further, if I have a 10K+-5% ohm resistor, and I measure the resistance with my multi meter and get a value of 9750, will my resistor be at 9750 ohms of resistance in my circuit consistently, or could it vary anywhere within the tolerance (assuming it's functioning properly, of course)?


texts: Difference between charge-sharing and charge-redistrbution

texts:
I've come across these two phenonmenon in several places but I want to know - what's the difference between them in a general two capacitor circuit case (not related to SAR ADCs)

Like if I have two unequally charged capacitors in parallel with a switch in the middle. When I close the switch - does charge sharing occur or charge redistribution?


texts: I am trying to figure out how the I & Q signals for a frequency modulation have to look like. How do I generate a FM modulated signal with an IQ mixer?


texts:
I am studying Microelectronics by Behzad Razavi, 2nd Ed., where in the frequency response chapter it uses the "Dominant Pole Approximation" to find one of the poles easily from a quadratic denominator in the transfer function (he did this as the coefficients involved were HUGE.. it was a calculation involving the high frequency response of a MOS common source amplifier).

Is the this approximation used only to simplify calculations? What intuition can we gain from such an approximation?

He did not include any bode plot with this particular analysis.


texts: Is there a standardised noise source symbol for circuit diagrams?

texts: Does anyone know of any standard symbol for a noise source, for example of one wants to represent the Johnson-Nyquist noise, what is best to use?


texts:
I'm building a circuit of PIC18F4550 and trying to connect to PC as an HID device. It has already worked for once (the circuit was correctly recognized and installed on PC) but afterwards something wrong happened with the circuit and I had to rebuild it. However, it no longer can be recognized on PC although I checked the connections and replaced almost all the components including the PIC, and the code supposedly works fine. I just noticed that when I measure VUSB, the AVO gives about 0 V although it is supposed to be 3.3V as the USB internal regulator is enabled. Any hints, please? Thanks a lot
Edit: Here is the schematic I'm following.

Edit: Here is the project settings in MikroC Pro for PIC


texts: Understanding when to use basic Components

texts:
So I understand AVR assembly for the most part, and generally understand the overview of microcontrollers. but when it comes to specific components (besides the obvious stuff like resistors/batterys) I dont understand what they do....and more specifically WHEN to use them?

Stuff like Capacitors,Regulators,Inductors,Crystals,Etc

Where can I find a generally overview of When and what these components do? to further my knowledge. I can of course wikipedia the definitions....but I more want to know when I should use these specific things because I figure it's probably a good idea to know more than "what" they are and also What to use...


texts: How many addresses are required for this system?

texts: If a system has RAM containing 16K bytes with each of them needing their own distinct address and on top of that it has 16 peripherals and they each require 2^4 distinct addresses, then how many total addresses are required for this system? Based on what I know about memory, I think it's 2^16k + 16*2^4 however I'm not sure how to translate bytes to bits. I know that if a system has 15 bits then it requires 2^18 distinct addresses but what about bytes?


texts:
Sorry for the dumb question, but my electronic skills are even lower than basic level.

I need to switch on a relay when PC turns on. I made a simple scheme on the run, but I'm afraid it isn't good enough not to damage the USB controller.

I tested it on EveryCircuit, and it draws about 50mA current. My only doubt is about directly connecting the relay coil to USB power. Is it good or I need to change it?

simulate this circuit – Schematic created using CircuitLab


texts:
I would like to create a circuit board that can toggle between 3 states, only with the press of a button.

So when pressing the button, the board should go to the next state, and at the last state, should loop back to the first.

The 3 states are like this, using 2 LEDs:

LED 1 is on, LED 2 is off
LED 1 is off, LED 2 is on
Both LEDs are off

Can I create a simple circuit board that can do this? If so, how would it be designed?

(Disclaimer: I only know high-school electronic stuff, but I can solder pretty well)


texts: Biasing of CE amplifier with emitter resistor for specific gain

texts:
I am trying to design a Common-Emitter amplifier to the following specifications:

Midband voltage gain of 50
Frequency range 100Hz to 20kHz
Load \$5k\Omega\$ with a coupling capacitor (not shown below)
12V supply lines
Input source resistance \$100 \Omega\$

Using a 2N2222 BJT transistor and the following CE configuration:

I've drawn the small-signal model as follows, assuming that in the midband coupling capacitors are treated as shorts and bypass and load capacitors are treated as open circuits:

I began my design by picking a maximum current. I want to keep that low so I choose \$2mA\$ and plot the IC vs VCE curves for this specific transistor in a spice simulator:

Choosing a point half way on the load line for symmetrical swing, I obtain:

\$V_{CE} = 6V\$
\$I_C = 1mA\$
\$I_B = 5.5\mu A\$

I calculate \$ \beta = \frac{I_C}{I_B} = \frac{1mA}{5.5\mu A} = 182\$
\$R_c = \frac{V_{cc}}{I_c}=\frac{12}{2mA}=6000 \Omega\$
I pick \$R_E = 0.1R_c = 600 \Omega\$ based on a rule of thumb for beta stability.
Now I would like to design my bias network \$R_1, R_2\$ to enforce the bias conditions above and also give a gain of 50. The voltage gain expression is given as:
\$A_v = - \frac{\beta R_c || R_l}{r_\pi + (1+\beta)R_E}(\frac{R_i}{R_i+R_s})\$
I first calculate
\$r_\pi = \frac{V_T}{I_B} = \frac{0.026V}{5.5\mu A} = 4727 \Omega\$
\$R_{ib} = r_\pi + (1+\beta)R_E = 4727 + (183)(600) = 114527 \Omega\$
Solving for the input resistance:
\$A_v = 50 = \frac{182(6000) || (5000)}{4727 + (183)(600)}(\frac{R_i}{R_i+100})\$
Giving \$R_i=92.02 \Omega\$
\$R_i = R_{thev} || R_{ib}\$
Some algebraic manipulation results in
\$R_{thev} = \frac{-R_i R_{ib}}{R_i - R_{ib}} = 92 \Omega\$
I write a loop around the Emitter-Base loop as:
\$ -Vcc(\frac{R_2}{R_2 + R_1}) + R_{thev} + 0.7 + I_E R_E = 0 \$
Selecting \$R_2 = 6000 \Omega\$, \$R_1\$ is solved for \$50 000 \Omega\$
Simulating the circuit and running a dynamic DC analysis shows that the bias conditions are enforced:

However I am confused because when I work out \$R_i\$ as:
\$ R_{i} = R_{thev} || R_{ib} = \frac{1}{\frac{1}{6000} + \frac{1}{50 000} + \frac{1}{114527.27}} = 5117 \Omega \$
And furthermore the thevenin resistance of \$R_1, R_2\$
\$R_{Thev} = \frac{R_1 R_2}{R_1 + R_2} = 5357 \Omega\$
I would expect these values to be the same as what I worked them out to be previously from the voltage gain equation (\$92 \Omega \$)? In simulation this method seems to work however I can't understand how the input and thevenin resistances have seemingly changed value. Could anyone explain what is happening here?
I'd also be interested to know how more experienced designers would approach this simple design problem. I find that my courses at university are very theoretical and so I tend to over complicate the designs. In practice I suspect that designers tend to take more of a heuristic approach to circuit design rather than solve equations like this.


texts: I've been creating a library with symbol for OrCad according to the naming convention IPC-7351 and I cannot understand one thing. What does the letter "N" stand for in the example given below?


texts:
I am trying to understand the circuit diagram of a typical opamp

I have 2 questions:

1)Can't we use a Darlinghton pair instead of the configuration of Q5 and Q6?

2)I dont understand how Q4 converts the differential voltage of Q1,Q2 to single ended voltage which is
fed to the gain part.


texts: Why does voltage sign matter for electrical devices and components

texts: If you look at the specifications for certain electrical devices, computer hard drives for instance, the voltage requirements would be something like +6.6v or +12v. Why does the sign matter? Why couldn't -6.6v or -12v work? I thought when it came to voltage, only the magnitude of the difference of voltages matter?


texts: How do I calculate the gain of an op-amp summing amplifier?

texts:
So if I have a summing amplifier circuit like the one below:

I know the Vin1, Vin2, and Vout value and the circuit is designed such that Vout = -(Vin1+2Vin2) but how do I calculate the gain? I know on a normal op-amp circuit with one input source the gain is just Vout/Vin. But if I have two input sources then will my gain be Vout/(Vin1+Vin2)?

On PSPICE I set the DC and ACMAG values for the input voltages to 2V, and Vout is -6. So it works out right, but still what is the gain?


texts: STM32 ARM header files for use with Eclipse and GCC

texts:
I'm a mechatronics (mechanical and electrical) engineering student and want to learn how to program ARM microprocessors. I've  used Atmel ATMegas previously. I'm using a mac and being a student I don't want to use expensive software so I've installed eclipse, Yagarto and openocd as per this blog post. What I want to know though, is where do I get header files for individual chips, as I want to program in C not assembly?.

I'm planning on using STM32 chips as these and NXP's LPC chips seem to be the most popular and STM32 chips seem to be more advanced. I've found that there are some header files when they are part of development boards such as for the STM32F103RBT6 when part of STM32-H103 from Olimex but I can't seem to find header files for other chips in the same family.

A secondary question is, are there any tutorials for C programming of STM32 chips or Cortex-M based chips? I can't seem to find any tutorials that go through the basics such as blinking an LED.


texts:
I built a constant current load to test out some battery banks that I'm building. The constant current load is based off Dave Jones' "Dummy load". When I built it, the op-amp I had on hand was the LM358 and the circuit works as expected. Now I wanted to replace the op-amp as it was a chinesium branded LM358 one for a locally sourced NE5532 of which I have about 20. According to the datasheet the layout is pretty much like the LM358 so I thought I could just replace the fake IC with a proper op-amp. With the NE5532 in place, I cannot control the current. It just draws the maximum the DUT can put out, even with pin 3 (set-current) grounded.
I know it's not the perfect op-amp for the job but using it for such easy non-critical & non-precision jobs has to be possible.

I'm clueless why it won'w work in my circuit. Please check if I'm missing anything.


texts: How can I identify ferrite bead material?

texts:
I am working my way through the book "The Electronics of Radio" by David B Rutledge", which details experiments on the various parts of the circuit as one builds a "Norcal 40A" transceiver, as a practical way to learn about electronics and amateur radio. It is a very good book.

The driver for the Norcal 40A power amplifier is a 2N2222A transistor, and the kit lists a ferrite bead to go over its base lead. This bead is not mentioned in the book, but it is in the kit's component list and circuit diagram. The specified ferrite bead is 0.146" diameter and 0.138" long, of #64 material, but, unfortunately I have lost it, probably long gone up the vacuum cleaner hose.

In my "come in handy" stock I have a bag of anonymous beads, and also some labelled FX1242 (all the correct size). So, my question is, can I use the FX1242 instead, or, if not, can I easily identify a suitable bead from the mixed bag, if there is one.


texts: How do I find the Thevenin resistance and its corresponding voltage?

texts:
simulate this circuit – Schematic created using CircuitLab
In this circuit, how do I find the Thevenin resistance and its corresponding voltage?
I know the technique of shorting voltage sources and making current sources open like so:

simulate this circuit
I don't where to go from there.
Is the 16 ohm not part of the resistance calculations anymore? If so, do I just add R3, R5, R2, and R4 in series?
Secondly, when finding its Thevenin voltage, I'm confused since I know that a voltage source and a resistance in series can be transformed into a current source that has a resistor in parallel, but in this case, the voltage source only has a resistor in parallel, not in series, so I don't know where to go from there.


texts: Interrupt being called before complete execution of ISR

texts: What happens when an interrupt is called again before the execution of the ISR is completed?


texts: What is the name for this rotary switch scheme?

texts: I am trying to figure out just exactly how this rotary switch works and what it's called (so that I can research it). There are usually 6-8 pads which are shorted to a common pad through fingers. That's easy enough... however, I don't believe these are acting as individual switches if that makes sense. I think they are multiplexed to one pin.


texts:
I’m developing a huge project, very cool but very complex, is a “water printer” based on the work of a Japanese artist. I’m an electrical engineer so I’m very good at electronics and software dev, so most of the project is already done, I made a computer controlled interface that can control several solenoid valves at the correct rates to “print” an image using water and gravity, here you can see an example of an early stage of my project simulating the valves with just LEDs.

I never worked before with solenoid valves, I bought some on ebay from Hong Kong, but I made I mistake, this kind of valve need a fixed amount of pressure to displace the actuator so they are very slow to close (not good for this project given the fact that I need a droplet), also I just find valves form 1/2’ (which are very big) and  for about 10 bucks, taking in consideration that even if they work I will need about 100 of them, I can’t afford 1000 dollar for this.

I decided that the only way to solve this is building the valve, but I’m not very good imagining mechanical actuators, so I need the help of creative minds like yours guys.
I’m just going to simplify what I want, imagine that you need to control the flow of water of an fish tank pipe using an electric signal, that’s it, what do you think? Let your imagination fly! :)


texts: Switching a relay through a wireless connection

texts:
I want to create a circuit which will wirelessly drive a relay. I only have a little experience with Arduino. I know what peripherals I need, but I don't know what micro-controller to use. I made a list and I need to know if the components will work all together with the microchip PIC18F26K80 microcontroller, or if you have any other (cheap) suggestion.

a relay like that
the uln2003 to drive the relay from the microcontroller
a Wireless RF Transceiver(10 pin) 915mhz
a programmer like that
ethernet magjack (to be able to send and receive tcp/udp packets)


texts: How to set high on rise edge, low on fall edge?

texts:
I have two switches which turn on a bulb, and basically I want "the last one wins" scenario.

Initial SW1: 0, SW2: 0

SW1: 0->1 Out: 1

SW2: 0->1 Out: 1

SW2: 1->0 Out: 0

SW2: 0->1 Out: 1

SW1: 1->0 Out 0

The logic I need basically is on rising edge of any input, set output high, and on falling edge of any input, set output low.

However, all flip flops (that I know) can only do rise edge or fall edge, so how do I implement this?


texts: Simple MOSFET switch circuit PCB design in altium.

texts:
I've always been a bit confused by altium designer. I am trying to create a small FET switch PCB for the following 3 speed DC fan system:

So for each output of the PWM ports used in this image I am producing 2 identical MOSFET switching circuits with off board connections to the UNO and one of 2 DC fans. Here is the schematic for the switch circuit:

And here is the PCB I have created by importing from the schematic:

So the problem I am having is that no ratnest appears between pin 1 of the FET and the other pin on R2. I have tried updating the changes from the schematic to the PCB already and I can't see why it wouldn't be there looking at the schematic. Any suggestions?

Thanks in advance,

Simon.


texts: Transistor with emitter resistor calculation

texts:
I can't seem to get over this but this seems to be the basics in electronics.
I have an NPN darlington transistor TIP122 and have built to simple test circuit around it with Rb = 150 ohm, Rc = 80 ohm and Re = 6.8 ohm.
My base supply Vbb = 3.3V and collector supply Vcc = 20V.

I have used the equation from this site as mentioned for emitter biasing.

  Ie = (Vbb - Vbe)/(Rb/beta + Re)

However I am getting different values theoretically and practically.

With Re = 6.8 I get theoretical Ie = 273mA and practical Ie = 222mA then
With Re = 6.8||6.8 I get theoretical Ie = 535mA and practical Ie = 228ma.

I don't understand why could this be happening, how does the emitter resistor work in the transistor circuit... can you help me out?


texts: Veriog:How to pass a register to a module?

texts:
Assume we have a module with 32 bits output like this:

module ModuleLow(foo,...);
output [31:0] foo;

Now we want to use it in another module ( a very simple example!):

module ModuleHigh( ..,reset,..);
input reset;

wire [31:0] fooWire;
reg  [31:0] fooReg;
ModuleLow module1(.foo(fooWire), ...)

always @(posedge GCLK)
 if(reset)
    begin
      fooReg<= fooWire;   // TRIAL-1: fooReg<=  12345.....;  => 2.3ns
    end
 else
     fooReg<=fooReg+1;    //TRIAL-2 :  fooReg<=fooWire+1; => 18ns

This is a very common method of passing a value between modules ( wire -> reg ). But in my case , it leads to a 2028 bit wire that noticeably reduces the speed of a Spartan-III down to 12ns.

I tried these:

1- When I replace the statement   fooReg<= fooWire   with a number ( like:  fooReg<=12345....;   TRIAL-1 in the code) , the performance jumps high (GCLK timing constraint value <2.5 ns)  .

2- When I use the wire itself ( using   fooReg<=fooWire+1;    TRIAL-2 in the code example) the performance drops even more (18ns)

From these experiments I concluded that it is much more design friendly to use registers inside a block instead of wires ( routing and DRC problems? ).

I was thinking if there is a way to omit that intermediate wire between modules . This can remove the wiring in "TRIAL-1" part ( initial assignment ) that leads to a higher performance. Something like this:

ModuleLow module1(.foo(fooReg), ...); // using registry without a wire.

I think this is illegal in Verilog (ISE WebPack v14.7 gives error as lvalue assignment problem) but I am looking for some trick or something if exists.


texts: Negative and positive cycle of AC current, Half wave rectification and Full wave rectification

texts: Can someone please explain to me precisely what the negative and positive cycles of AC current are, what full wave rectification is and what half wave rectification is?


texts: Ceramic chip antenna design with shorted pads

texts:
I'm very new to RF and I'm considering using a Pulse W3013 antenna on my next project but I just can't understand the layout recommendations on the datasheet.

The antenna has only 2 pads but the layout recommendations shows 3 pads, 2 of the pads are connected to the ground and the other is the feed from the transceiver, soldering the antenna on the pads will short the feed trace with the ground on one pad, is this normal or is there something i'm missing?

Antenna

Layout recommendations

I've seen other designs where one of the pads of the antenna is connected to a trace that from what I understand is used for fine tuning the antenna but this design is completely different so I'm kind of lost.

I already have seen this question but this looks like it is the opposite situation because here is the antenna that shorts the feed with the ground.


texts: Help with dropping voltage on 1000w dc power

texts:
I've been struggling for a few weeks trying to find a way to lower the voltage coming out of my new solar panel array (35V DC, 36amps, 960watts).  I have an inverter that will not accept voltage over 30volts.

I've been looking at resistors, voltage regulators..etc  but very few options for that wattage.  I also tried puttting a load in parrallel and series on the circuit..no luck

I did manage to find a 1000w 25ohm resistor on Ebay, but I can't seem to calculate the outcomes with any accuracy.

NEW**  Would a 30V 40amp Rectifier Diode work???


texts: Problem with Proteus Simulation of Buck Boost Converter - please help

texts:
I built the attach circuit, I was simulating a solar panel buck boost voltage regulator to regulate the output voltage.
The problem is that while it works and shows the appropriate output. It doesnt't show the current, I attached probes in the circuit, but it shows I have little to none current passing thru the circuit.

It just seems like only voltage is passing thru the circuit and there is no current.
Is there a way to also simulate a solar panel with a power rating?

P.S: I based the buck-boost circuit from here
http://www.onsemi.com/pub_link/Collateral/AN920-D.PDF
STEP UP/DOWN SWITCHINGREGULATOR OPERATION p. 18
enter image description here