texts: How much interference is allowed to pass FCC verification testing?

texts:
I have a small electronic device that I'm considering bringing to market. It doesn't have any features like wifi or bluetooth, so one of the prerequisite steps before I can sell it is to ensure it doesn't exceed FCC emissions limits for an unintentional emitter.

However, emissions testing can be expensive. I've gotten quotes from 3 different labs, and the cheapest one was $1100, and that if you fail the test, you'll need to fix your device and then pay for an additional test. So obviously, I want to do everything I can to ensure I pass the test on the first try.

I've read online that a good way to get a general sense of your device's emissions before testing is to buy an AM radio and see what effect the device has on it. So I bought a generic $8 AM/FM radio and I found that my device does indeed effect the AM channels. From 10 feet away, I tuned into the clearest channel I could find, and then I monitored the reception as I got closer. From 1 foot away, the reception is still perfectly clear. From 6" away, there's a noticeable whistle and extra static in the reception. From 3" away, the channel is completely static.

I did a similar test with the FM reception, and there was no interference at any distance.

So my question is, how do I determine if this means my device wouldn't pass verification testing? I know my description isn't terribly quantifiable, but is there a general rule-of-thumb for this kind of thing? Is complete disruption of AM reception from 3-6" away considered unacceptable by the FCC? I've been personally using my device, and have had it running continuously for over a month, and I haven't noticed any negative effects.


texts: How to interface an ADC with FPGA through the CLKOUT signal in verilog?

texts:
I have a ADC (TLC2323-12) that (as far as i understand from the datasheet) has two modes of controlling the output of the converted signal. One method is with the input signal SCK that can be controlled from the FPGA whenever you want to shift the value to the FPGA, and the other is way is through CLKOUT which is an internal clock from the ADC that "automatically and bursting" (sorry I'm new at this) spit out the results bit by bit of the 12 bits resolution in total. This last method is described in datasheet as "High-speed" in comparison with the SCK method.

Now, I was able to control the ADC with the SCK method, because I can send the signals from the FPGA top module easily and the pick the value I want, in general I work with only 1 clock. But with the CLKOUT, seemingly this one behave like a second clock, so this is a dual-clock system?

What should I do to properly code the interface when using the CLKOUT method? There are 2 clocks now. The FPGA internal clock and the CLKOUT coming from the ADC that can "announce" to the FPGA the availability of the data.

I was reading around that an easy way maybe is to code an Asyncrhonous FIFO that can write from the CLKOUT and read from the FPGA Clock. is this right?

The interface is Serial, 2 channels.


texts: ATtiny85 pin as output, what is input impedance?

texts:
I am working on a project that involves using an ATtiny85 to deliver a PWM signal to an RC filter. On the other side of the filter is an OP AMP that does not draw any current.

My question is: is it safe to allow a capacitor to discharge back into the ATtiny85 when the output signal is held low? How would I find the input impedance of the output pin when held low?

Is this recommended against? Any help is appreciated!

EDIT

An image of the application (in a nutshell) is attached below:


texts:
If I connect the Rx pin of my PIC18F2550 and GND to another already powered-on circuit, the PIC turns on and starts running code. There is nothing in the datasheet preventing this.
Is this normal?

PS: Rx and SDA are connected toghether, but still the PIC shouldnt turn on at all.


texts:
I am referring a schematic where 16V,10.4V,-7v is generated from TPS61040

R12 and R17 are used to set 16V from TPS61040 IC and zener diode is used to generate 10.4V.

But how -7V is generated, I am not getting. Please someone guide.
Thanks.


texts: How to calculate minimum gate current and voltage of a TRIAC

texts:
I want to use this TRIAC:
http://www.littelfuse.com/data/en/Data_Sheets/Littelfuse_Thyristor_Lxx06xx_Qxx06xx_Qxx06xHx.pdf

but only the maximum Igt and Vgt are given (25mA and 1.3V).  How much current at what voltage do I need to trigger a TRIAC?


texts:
Is there a difference between downsample block (eg. in matlab) versus a register with custom latency or delay block.

As far as I understood, downsample block just ignores the intermediate samples. If I had a register with similar delay, it would ignore the intermediate samples as well, wouldn't it?


texts: What do we mean when we say a transistor amplifies current?

texts:
No site, seems to explain this super well. For example, if current amplifies current then shouldn’t there be a larger voltage drop after, the current, per se, is amplified by 100? But the voltage drop seems to only be very small

  The question I have arises from this, what do we really mean when we say a transistor amplifies current?

So, I am looking for a clear explanation, thanks so much!

When we say that a transistor amplifies current, we mean that it allows much larger current to flow from a much smaller current, it doesn't amplify the current in a circuit. The circuit doesn't make sense and should have another power source that the transistor is acting upon, a transistor is a switch after all.

There are equations that calculate the voltage drop but it is a tiny amount, and almost any circuit will still work with the voltage drop across a transistor, because there it is so tiny, that is.

This is all thanks to The Photon clearing this up, so thank you The Photon!


texts: What is causing this step-up converter circuit to fail when introducing a transistor?

texts:
I built three separate circuits with the intention of making a colored led cycling solar sun jar.

Each circuit works on its own.  With just the RGB ATtiny85 circuit it works with 3x 1.2 volt AA NiMH batteries.  If I reduce the AA batteries to just one, 1.218 volts on its own, and put the output of the LT1073 step-up converter circuit to the RGB ATtiny85 circuit the LED lights up as expected.  At this point I see 3.218 volts at the output of the LT1073.  If I take the battery + and put it to the charging circuit's 2N3906 emitter then the led no longer works.  A reading of the 2N3906 collector voltage shows 1.284 volts when disconnected from the LT1073 circuit.  When I connect it to the LT1073 circuit it reads 0.6 volts and the output of the LT1073 reads 0.592.

These are the circuits of the project:

RGB light cycling microcontroller circuit modeled very similarly to this project, but only using one common cathode RGB led.
LT1703 based step-up converter using a single AA 1.2v NiMh battery.  The circuit schematic comes from the LT datasheet on page 11, only changing R1 and R2 to acquire the output voltage of 3.2 volts.
A simple solar cell charging circuit, see detecting darkness for the schematic.

I assembled the schematic for viewing this circuit by combining images of the three sources and modifying for existing conditions.

Note that the LT1073 circuit is constructed with carbon film resistors where the LT schematic calls for metal film and also I'm using electrolytic capacitors.

I'm puzzled how the introduction of the 2N3906 transistor has resulted in the circuit to fail.


texts: Difference between step up and down converter

texts:
I have bought 2 different PCB DC to DC converters, I would like to use these for converting 5V from a battery pack to 12V.

Only issue is that being the fool I am, I have ordered "step down" converters and not "step up" converters.
Therefor I just wan't to make sure, before ordering anything else. That if the input into the "step down" converter is 5V, there is NO WAY to increase that voltage?
To increase the voltage it has to be a "step up" converter?

When turning the two screws for voltage and current, nothing happens it just stays at 5.08V

I know it is a rather noob question, but while buying I was distracted by the fact that the converters, just stated that they could take 5V-32V to 0.8V-30V


texts:
I'm planning to use 2 PCBs to sandwich some conductive foam - to use it as a  force sensing resistor (FSR).

In order to tie them together and add them to a metalic suport I'll be using M4 metalic screws. My question is:
Will multiple metalic screws (they have low rest. values around 3ohms) that conduct across materials affect (much) of the resistive output?
If so I assume that plastic screws are an alternative.
I avoided using glue since it solidifies and the foam itself is only .5 cm thick.


texts: Measure rise & fall time of MOSFET switching - cheaply

texts:
I'm venturing into building switching PSUs. Voltages on the order of 5-20v, current 1-10A.

To be optimised would be the efficiency of the power MOSFET(s), hence Vgs and Vds rise and fall times.

Ive got a 20MHz 48Ms/s Hantek USB scope - the cheapest I think. An ancient 500kHz Jupiter function generator. And FWIW, plenty to build quick circuits out of.

How can I do this cheaply? The oscilloscope would be great I think, if it weren't for its inability to zoom in on edges! But useless if switching only represents 2% of the time?  Might it be suggested I invest in other equipment? Or is there a clever little an analog / hybrid digital circuit I could bread-board up? (straight forward, effective and cheap - optimistic?)


texts: Why are the two channels of my subwoofer connected by a resistor?

texts:
I bought a new amplifier module for my subwoofer and recognized that the two LFE channel inputs are directly connected on the circuit board via a resistor.
I assembled the subwoofer meanwhile and I missed to take a picture but it seems I can't stop thinking about why that is?


texts: What a green P stands for in MPLAB IDE watch list?

texts:
Hello I'm debugging a C program in MPLAB IDE 8.92 and I have a green P at left o a variable in the watch list.
Does somebody knows what it means?


texts: Unexpected behavior setting non-default I2C address for HT16K33 LED Driver

texts:
The HT16K33 is an I2C controlled LED driver.
The data sheet shows a standard way of setting the I2C slave address:

I have implemented this circuit, but it does not work as expected.
For the default address 0x70, A0, A1, A2 are open. At the default address everything works fine.
When I try to move to 0x71 by closing the A0 jumper in the example above, the device seems to remain at address 0x70.
It responds at 0x70, and addressing I2C at 0x71 fails with no response.
In addition to not responding to the correct address, closing the A0 jumper also introduces a display artifact.   The display segment corresponding to A0 (ROW2) is illuminated in each of the digit positions except the first (driven by COM0).
I thought perhaps the diode was shorted, but after replacing it, I have the same issue.
Full schematic is below. Note that the HT16K33 is designed to sink current on the digit drivers (COM0-7), and source on the segment (ROW0-15). This is appropriate for a common cathode segment LED.  This circuit uses external drivers to drive a common anode LED.


texts:
After some read about ground plane breaks and inductor loops, now I am totally confused about how to design good PCBs.

I made a small example of a two layer PCB. Blue is the big ground place. Red are top ground copper zones that, for whatever reason, cannot be connected between them on the top plane.

I have this question.

It is a good practice to connect those top zones to the ground plane in one single point?

if I use two points, there will be loops in the top or bottom plane?

Or the loop will happen in the ground plane, even if the top zones are not connected?

This is a picture to describe my questions.


texts:
I have two CAN busses which are each terminated on each end by a 120Ω resistor, as shown in the diagram below. The CAN bus consists of a CAN high, CAN low and ground connection. To terminate it, a 120Ω resistor connects CAN high and CAN low.

Sometimes I want to use both CAN busses completely separate but in some situations, I want to connect the devices D3 and D4 together, making a single bigger CAN bus.
To connect the two, I need to remove the two resistors R2 and R3 and then connect the CAN bus together.
My CAN connection currently terminates in a D-SUB connector X1 (at each end D1, D3, D4, D6) to easily connect other CAN devices. At the same time I have a switch (S1) that will enable or disable the CAN bus termination, as can be seen in the schematic below.

What I want to do is to remove the manual operation of the switch S1 by including something in the D-Sub connector X1. When nothing is connected to it, the terminating resistor R1 will connect CAN high and CAN low. But when I connect another device to the connector X1, the resistor R1 will not connect CAN high and CAN low anymore.
I would appreciate any tips that point me towards a possible solution. I should also mention that connecting and disconnecting any device will happen when everything is powered off and does not need to happen during operation.


texts:
I'm trying to implement a PCI express switch; one lane from SoC and, two for mini PCIe ports. Something like the picture below.

But I'm confused with the Tx and Rx connections, the transmitter should be connected with the receiver in every connection, right?

But, the doubt occurs when in the reference schematics that I have for the switch, the connection in a male connector is Tx(of switch)-Rx(of port); like the picture above, and in a female connector is Tx(of switch)-Tx(of port); like the picture below.

Exists a sort of convention (standard or similar) for this kind of connection?


texts:
First off, let me state that I am pretty new to FETs, so I'm still wrapping my head around the different characteristics.
The circuit below is a switch that will trigger a 12v (VIN=12v) signal to be constantly on, based on input from an MCU (MCU_TEL_ON=3.3v logic level).

The DMP1045UQ P-FET I originally used is wrong for the application because its Vgss is +/-8V.
As such, I've had multiple failures of this part.
I'm trying to source a P-FET suitable for the job (~5mA load, acceptable voltage drop of 0.5v and rise time is really not a factor either) and I'm between the DMP3098LQ and the PMV65XP.
My questions are:

Either one of these should work, correct?
The Vgs given my circuit is -12v, right?
What characteristics matter most when selecting a part for this particular job?


texts: Synthesize ATPG Test vectors with 'X' Values

texts:
I am working on synthesizing generated ATPG test vectors and implementing them on an FPGA. However, there's plenty of "don't care" values 'X' in the stimuli and response vectors.

I am not sure how the synthesizer will treat the 'X' values, which will make test vectors comparison to fail. Is there  a technique on how to implement test vectors with plenty of 'X' values?

I am coding in Verilog, my vector length is around 1911 bit with more than 200 vectors to be tested.


texts: making DCA package for DRV8301 with Eagle

texts:
I'm trying to add a DRV8301 componenet (Texas Instruments) in Eagle and it's my first time.
So the componenet package is DCA as indicated in the datasheet.... i followed the dimensions to make this one.
and this are images with the dimensions in mm of the componenet that i maked[!

i've chosed a grid size of 1mm

so i want to know if my componenet is adequat to the datasheet .... thank  you


texts:
I do not understand how a particular parasitic effect is model. I have read that on a coaxial cable there is a problem due to the fact that the external conductor's magnetic field crosses the air around it. This can be represented by a parallel inductance, as shown in the following figure.

But I do not understand the physical phenomenon (and so why we put an inductance in parallel). A part of magnetic field lines go in the air, and so? What does it happen physically?


texts:
I'm trying to learn how Zener diodes work and I think I get the overall concept (regulating voltage to the zener voltage level), but there's one thing I don't understand.  I'm looking at this diode and see that it's zener voltage is 3.3V, but it's max forward voltage is 0.9V.

Why is the forward voltage so much lower than the zener voltage?  Is it because the diode is generally never placed in a forward biased direction (i.e. current should only generally travel in a reverse biased direction)?

Update
I was originally under the assumption that the max forward voltage was the maximum voltage the diode could handle in a forward biased direction.  Thanks to @SomeHardwareGuy for setting me straight.  The max forward voltage is the voltage required to have current flow through the diode in a forward direction.


texts: What is the exact formula relating a DC motor's input voltage and torque produced?

texts:
I'm trying to control a 12V geared DC motor with encoder through an Arduino by an L298D driver for my self balnace bot.

Based on the angles from the attached gyro sensor and encoder, it calculates the correcting torque by an LQR controller.

I need to produce this calculated torque by PWM of Arduino through the motor driver.


texts: Connect RS422 interface with Arduino Uno

texts:
I have a fishfinder,Lowrance Carbon HSD 7, and I want to connect it with the Arduino Uno to let the fishfinder transmit the Sonar data and GPS data via NMEA0183. According to the maker's site, the power/data cable uses RS422 communication having 4 cables which are RX+ RX- TX+ TX-. But the Arduino's serial communication ports are only RX and TX.

I search about the shield that can interface RS422 with Arduino, but there are very few of them. Instead I found RS485 to Arduino.

I've read some articles saying that I can connect the RS422 to RS485, with some conditions(like RS422 is full-duplex but if you connect it to RS485, it will become half-duplex, so the Arduino can only receive data, but cannot send), but I still not understand how should I connect the 4 wires to 2 wires. Should I connect RX+ and RX-(those of RS422) with RX(those of RS485), and TX+ and TX- to TX. If that is valid can I just connect RX+ and RX-(those of RS422) directly to the Arduino Uno's RX and TX+ and TX- to TX?


texts:
I am new here so sorry if i don't ask this question correctly.

I am currently trying to test a bridge rectifier from jameco(part # 103000)

I am applying a 60hZ wave from wave generator with 1V peak to peak.

I am getting a fluctuating DC voltage of 530-650mv and when no AC input is connecting to the rectifier, I am still getting 300mV on the DC output. Can anyone explain this?

Please let me know if you need more clarification/explanation.

Thank You


texts: How to find time constant of battery first order model with unknown capacitance?

texts: The above picture is the first order circuit model of battery. I'm trying to calculate the value of R1 and C1 with specified time varied input and output. In order to calculate that, I have to know the value of time constant first but I have no idea how to calculate that without knowing the value of C1.


texts: Are there ever cases that the heating element is in the base of a soldering iron? I thought that the heating element is almost always in the wand, and the base just provides the power, but a friend thinks otherwise.


texts: Why does grounding my switch cause the fuse to blow?

texts:
I'm working on restoring an old ATV, and I'm having a bit of trouble with the wiring.  When I got the ATV it was missing the ignition switch, so I decided to replace it with this awesome looking switch instead.

Which I'm guessing, internally looks something like this...

After looking at the wiring diagram, I've figured out how to connect the switch.

Click for larger view

When I install the switch like this, the ATV powers up.

However, when I ground the switch so the LED will light...

The fuses blow.

If I don't connect the ground and I connect the pink and black wires to the switches Ground terminal, the LED lights but the ATV is not powered up.

How can I connect the switch so that it turns the ATV on, and the LED on the switch itself also lights?


texts: A capacitor has insulating material between plates and this insulting material does not provide any electrical or conducting path between capacitor plates. But still, capacitor allows DC or/and AC current to flow through it, How?


texts: Estimate the speed of BLDC motor using back-EMF constant

texts:
I want to mesure the speed of BLDC motor using back-EMF constant, \$Ke=Vrms/rpm\$, so the speed is \$rpm=Vrms/ke\$.
What I want to know is how to get the Vrms? Suppose I have DC supply=40 V and the duty cycle = 80% does the \$Vrms = 0.8*40=32V\$? Or the \$Vrms=40*0.8/sqrt(3)=18.47V\$?
Edit:
i already know how to mesure the speed using this equation \$rpm=F*60/p\$
but instead I want to estimate the speed using back-EMF constant.


texts: Measuring voltage 10 times every second with HP 34401A DMM

texts:
I'm trying to measure voltage continuously for a short time using the HP 34401A digital multimeter. To do this I have connected the DMM to my PC via RS-232. The PC is running Windows 10 and I use Termite which is a serial monitor. With this setup I can control the DMM remotely without errors.

Now I want to measure the voltage 10 times per second and receive the readings by the PC. I used the following setting.

VOLTage:DC:RANGe 0.1
VOLTage:DC:RESOlution 0.0001
SAMPle:COUNt 1
TRIGger:COUNt 10
TRIGger:DELAy 0.1

(Trigger source is 'Immediate' by default. I didn't change it)

The DMM sends 10 values to PC, when I send 'READ?' command. But I have no idea the actual sampling rate. With the trigger source of 'immediate' and the trigger delay of 100ms. Can I expect that my sampling rate will be 10samples/seconds ?

If the above setting is valid. Could I achieve a sampling rate of 100 samples/seconds too?


texts: Should I model an ethernet message decoder with byte based instead of bit?

texts:
The steaming interface (for example the Avalon ST)

input logic data[255:0] in_data; // a 256 bits input stream data

The local signals of data like this:

logic[255:0] bit_data;           // local signal for the input data

I have business messages with max length = 1500 bytes (12000 bits)

So I have to model an integer for representing the message length in BIT:

logic[13:0] msg_bit_len; // 14 bits unsigned int with max value = 16383

If I model the data with BYTE based:

typedef logic[7:0] logic8x32_t [31:0]; // a 32 bytes structure

logic[7:0] byte_data [31:0]; // local signal for the input data
byte_data = logic8x32_t'(in_data);

with BYTE based I can model msg_byte_len (max = 1500) with lesser number of bits.

logic[10:0] msg_byte_len; // 11 bits unsigned integer with max value = 2047

In this case 3 bits are saved comparing to BIT based.

It sounds good but I am afraid if there exist any issue with byte base design (for example, the incoming data are not in completed byte).

Please advise.


texts: Inrush current in Apk/us what does it mean

texts:
I'm looking at this LED power driver from a design, and I see it has inrush current speced as 190Apk/400us.    Does that mean there's a 190A spike over 400us.  That seems a little insane, how would ever control something like that to turn it on and off?   Here's the datasheet

Or is that just a rate and I have to use something else to determine peak current?


texts: Can this 1000W ballast be wired for 240V and plugged to 120V to run a 400W MH Lamp?

texts:
I've a 1000W MH ballast. Is it okay to use the wiring for 240V the ballast and use it on 120V? Like does it reduce the ballast to 500W?

I've attached a video for better understanding of how the bulb reacts to the connection.

https://www.youtube.com/watch?v=0UT45zj2hhw

Comparison between a 400W & 1000W ballast

Current draw while running


texts: Where does the flux go when desoldering?

texts:
I have a piece of equipment with a right angle miniUSB port that went bad. After pulling the old port I have a big blob of solder shorting out the traces.

So obviously I must get rid of the blob before I solder in a new port. The main question is this: using a soldering iron, wick flux, where should I apply the flux before desoldering, to the blob to the wick?


texts: Xbee TX pin voltage wrong when booting with UART connected

texts:
I'm interfacing an XBee PRO 900 HP with a Beaglebone Black using UART5 on the BB. I'm using the 5v interface board from Adafruit (XBee Adapter kit - v1.1)

I'm have been having intermittent problems with the Beaglebone not being able to communicate with the XBee - it's not working more often than working - but it works sometimes nonetheless - and when it's working it will continue to work. But if I power the XBee off and on again, it will stop working.

I have checked baud, databits, stop bits and all other settings - I'm confident they are all right.

I found today, that if I power on the XBee without connecting it to the UART on the Beaglebone, then plug the Beaglebone in after the XBee has powered on, it works perfectly. But if I power the XBee on while the UART on the Beaglebone is connected, it usually won't work.

I did a logic and voltage trace of this behavior and found that when the UART is not connected before the XBee boots, the XBee TX pin sits at 3.2v and RX at 0 - which is what you would expect. Once I then connect the UART on the Beaglebone, the TX voltage stays at 3.2v.

But when I power on the XBee with the UART connected to the Beaglebone, the TX voltage only rises to 1v and stays there and no communications takes place. The Xbee still works though, as I can send AT commands via another XBee - I just can't communicate with it via the UART.

I've connected multiple XBees for testing - all exhibit the same behavior. I've also tried the XBee's with my computer using FTDI cable, and I don't get this issue. It just seems to appear only when I connect the Beaglebone UART to the XBee before powering on the XBee. I've also tried the XBee on different UARTs on the Beaglebone - all the same behavior.

I'm stumped as to what could be causing this behavior! Any ideas?

This is a view of the TX/RX logic (LGC) and voltage (ALG) of both the XBee TX/RX pins and the Adafruit 5v adapter TX/RX pins connected to the Beaglebone.

This trace is with the XBee powering on while the UART is connected:

This trace is with the XBee powering on without the UART connected, and then connecting the UART:


texts:
I was recently reading a passage discussing the effects of a replacement (mobile phone) charging plug.

Suppose that the original charging plug is marked 2 A and 10 V and is replaced with a charging plug marked 1 A and 10 V. Although the replacement plug supplies the same charge, the immediate disadvantage is that charging time would increase. However, a lower current would lead to reduced heating effect but the additional point identified is "the phone may draw a current of 2 A which may damage the charger".

Can someone explain what is meant by "draw" in this case and in what way is the charging plug damaged. Just to note: I'm not disagreeing with the statement I just require some clarification.


texts: Why don't power meters measure volt-amps

texts: When large inductive or capacitive loads are applied, the power meter will not indicate and bill you as the electricity gets lost in the lines. Why don't power companies just charge for this?


texts: How did bipolar IC density compare to MOS ICs?

texts:
Historically, how did the density of bipolar (e.g. TTL) chips compare with MOS? How complex could bipolar ICs get before they hit limits? Does anyone have a Moore's law-style graph for bipolar technology?

Edit: A specific number I'd like to know is the most transistors or gates implemented on a bipolar IC.

Background, and what I've found so far:

I'm looking at the TTL 74181 ALU chip (1970, 75 logic gates), which was a fairly advanced bipolar chip for its time. At the time, MOS was somewhat ahead in density with thousands of transistors on a chip. But now MOS ICs can have billions of transistors but bipolar is nowhere near that. That got me wondering at what point did TTL (or other bipolar technologies) stop scaling?

I came across Integrated Injection Logic (I2L), a bipolar technology that was supposed to provide MOS-like density. The TI SPB9900 microprocessor (1976) used I2L and had 6034 gates, which surprisingly is more than MOS microprocessors from 1976. I haven't heard much about I2L, so did it die out?

In 1986 there was the MBM10494 64K bipolar ECL RAM, versus 256K MOS DRAM, so bipolar was still fairly close. I haven't been able to find larger bipolar RAMs, so I suspect that's about the limit. Was the limiting factor power consumption, manufacturing, economics, or something else?


texts:
I'm having trouble designing a power supply circuit for a small microcontroller-based project.

The board I'm building will be powered by a 3.7V LiPo battery most of the time, but it could also be connected to a computer via USB. In that case the computer should be used as power source and the battery should be charged. The circuit to be powered requires around 5V and uses under 200mA.

I've put together various schematics from around the web and I've come to this, but since I don't know much about electronics I'm unable to tell if it would work or maybe burn...

[EDIT: I added a physical switch right after the battery to disconnect it and thus reduce leakage current when the system is turned off]

Here are the datasheets of U1 and U2:

MCP1640
MCP73833

So, here are my questions:

Will this circuit work? What should I change?
If the circuit makes some sense, are Q1 and D1 appropriate? (I have no idea, I found them in one of the many forums I just visited)
Even if this circuit doesn't make any sense, how should the thermistor for the MCP73833 be placed? I guess I should stick it on the battery, but I've never seen a battery with something looking like a thermistor on it, so I'm curious.

Thanks for any answer!


texts: How to install the downloaded model file to pspice?

texts:
I am newbie in pspice.I am using 17.4 version of Orcad.I have downloaded mosfet model from a site.Model includes this files: "device.lib" , "device.olb" and  "device.ind" .I want to simulate this device.What is the meaning of files with these extensions? (.lib,.olb,.ind)How can I install these files to pspice?
edit:I have 3 different file types.And I want to learn the meanings of these file extensions.I haven't .mod and opj file like other topic.my file extensions are different other topic.I've already seen that topic, but it didn't solve my problem.Other topic is very old.(7 years)


texts: Implementing Repeated Start on an STM32 F0 I2C Slave

texts:
I'm currently working on a driver on an STM32F0 that joins the I2C bus as a slave device. Currently there is no mention in the reference manual on how to handle a Repeated Start Condition, does anyone know how to?

I am currently handling the I2C request in the AddressCallback and am able to send/recieve all the data but when I try to detect a Repeated Start using the NACK flag (From RM: The bit is set by software, cleared by hardware when the NACK is sent, or when a STOP
condition or an Address Matched is received, or when PE=0.), the ADDR flag is never set meaning the ISR is never called again.


texts: ESP32 + SIM800L; modem not starting when GPS breakout board is connected

texts:
I have a TTGO that hosts an ESP32 with SIM800L. I want to also connect a GPS breakout board that will be switched on and off using ESP32's pin 15.

simulate this circuit – Schematic created using CircuitLab
As shown in the schematic above, I connected R1 to pin15 and its other side to the base of BC547C (the V2 3.3V + SW1 are there merely to illustrate toggling pin15 that of course is done with the digitalWrite from Arduino IDE). The board has also a "convenient" 5V output, so I thought to use it for powering the GPS breakout board, using R2.
I have successfully used in a standalone test the SIM800L, and another standalone test the GPS breakout (i.e. toggling it with pin15). However, when using both of them as shown in the schematic above it doesn't work. After thorough tests, I realized that the SIM800L modem cannot connect to the network (the circuit somehow affects it). When the ESP32 boots, it writes a logic 0 to pin15, in order to switch off the GPS breakout, and then tries to start the modem, however it fails (i.e. keeps trying to connect but without success).
My limited experience says that this should be an issue of the SIM800L not getting enough current, but I cannot understand why this would happen. I tried a USB power supply both from a PC and phone charger but no luck.
UPDATE: looks like the TX / RX wires from the GPS breakout, create the issue. When I disconnected them, the SIM800 model started working.
So, my question is why this could happen, and if there is a way from software to "disconnect" these pins?


texts: What does short circuiting a RST front IO header do?

texts:
My motherboard has a connector to enable the use of a front panel RESET button:

I would like to simulate the press of the button (equivalent to short circuiting the wires) by a Raspberry Pi, by connecting one (or two) of the GPIO pins to this connector.

What does a short-circuiting do, from a signal perspective? The pins on the motherboard are noted RES+ and RES-, suggesting (wild guessing, which is never good in electronics) that the result is 0? Since GPIO voltage levels are 3.3 V and are not 5 V tolerant I would like to make sure that I am not going into a dangerous land (frying the RPi would be sad, the motherboard - disastrous).

As you certainly guessed, my electronics background is close to nil so thank you in advance for adapting the answer to a beginner entry level.


texts: CV or CC battery charging via SMPS module

texts:
I am using attached SMPS module, it has battery back up UPS function. I read the datasheet and I couldn't find information what type of battery charge scheme I need to use.

Should I use constant voltage charge battery?
Should I use constant current charge battery?

SMPS Datasheet


texts: How to measure the capacity of the battery Instantly?

texts: How to measure the capacity of various types of batteries instantly? What kind of measuring device should I use to do so?


texts: FPGA Timing Constraint for 2 Combinational paths to take the same time

texts: I am trying to do a simple asynchronous FPGA design where I have 2 inputs and 2 outputs, and assign the outputs to the inputs.  I need the delay of both assign's to be near identical.  What timing constraint can I use to set the both to be near the same?


texts: Why can't stepper motors be powered off of 9V batteries?

texts:
According to Adafruit, "you can't run motors off of a 9V battery so don't waste your time/batteries!"

I've been searching around and it seems like most sources do use wall adapters, but without justifying why. What's the explanation for this?


texts: Help Identifying a chip from a Schlage lock

texts:
I'm trying to identify this chip. The info I've been able to gather is the following:

Packaging: it looks like WQFN (perhaps 20 pins???)
Markings: 8524 C3H OEB22 (the 8 could be a B; the O could be a D; the first 2 could be a Z)
The letters X and Y are printed on the PCB next to the chip

Thanks for the help.

I've added a picture. The lock is Schlage BE469


texts: Can a Cockcroft–Walton generator exhibit resonant rise?

texts:
I set up what I believe to be a working royer converter, however I did modify it to use a pair of op amps rather than transistors (see below.)

Anyway, instead of hooking the secondary to an lc tank, I hooked it up to a 3 stage full wave Cockcroft–Walton generator. My reasoning was that it would oscillate at a very high frequency and maximize power transfer as best it could.

I measured the ac voltage going into the CW generator to be ~33 volts. The dc voltage coming out was ~315 volts.

I suspect the CW generator to be exhibiting some kind of resonant rise, but I would be very interested to here a more thorough explanation from someone more knowledgeable. I know diodes can act as varicaps, transformers can act as inductors, capacitors have stray inductance, and op amps have built in capacitors, and there are two small capacitors being used to start the oscillation. So what components would have the greatest contribution to this resonance effect given that no inductors were explicitly used?

Below is a circuit diagram. The diamond shaped object is supposed to be two op amps back to back with their inputs crossed as seen here.


texts:
I'm using three IRLB8721 MOSFETs to power my LED strip. Through an ESP-12F I'm delivering 3.3V to each gate, which should bring me a 12V output, I think. But this doesn't work, I only get 5.8V - 7.6V (roughly). Any tips on what I did wrong? Did I use the wrong parts maybe (that would be strange since I followed a tutorial where it works)?

Here's the datasheet

[Here's the wiring plan][2]

I think I used the wrong mosfet/transistor, used another one. Now it works

[2]: https://chrisklinger.de/wp-content/uploads/2018/04/wifirgb_schematics.png


texts: Picture below is from this web, how to calculate the data rate ? For example, how much kbps is  Bw125Cr48Sf4096 ?


texts: What kind of diode should I use across the load?

texts:
I'm designing a circuit using an ST VN7020AJ high side driver. The application diagram recommends placing a diode from VCC to ground. The document doesn't provide any recommendations on the type of diode. The diagram, below, seems to suggest a Schottky diode, so I selected a BAT60J.

The board will be used in an automotive application and the load will vary with use and will at times be an inductive load. Sometimes it could be LED lighting, other times it might be a motor or mechanical solenoid.

Am I misreading this diagram, and should I be using a different diode? Also, is the diode necessary?

The document also doesn't say anything about Cext


texts: Using Passive RFID tags and UHF Readers for stock take

texts:
Stock take definition: Counting on-hand inventory in a premises in regular intervals to ensure it matches with the inventory count in your inventory mgt software.

Is it viable to mount fixed UHF readers on the ceiling of a huge premises (e.g. warehouse) that holds a lot of inventory instead of having to scan the rfid tags on every product one by one with a handheld reader? We use a fixed UHF reader to do this.


texts: How can I use avrsim to simulate Arduino?

texts:
I found very nice open source avr emulator (this one.)  Since there is uart emulation implemented it can simulate Arduino.

I have some problems with the "board_simduino" example.

I hooked up virtual leds to port B (pins 8-13) - http://gitorious.org/~viroos/simavr/viroos-simduino-simavr/commit/bfaeac1e61f1d6678b3daab7fede9a783d01c098, and they work.

But serial connection looks broken. I can upload sketch (I added ,link=/dev/ttyUSB0 to socat command for that), but after that communication stops working. For example I can upload "physical pixel" sketch but I can't turn on leds. I tried to connect using serial monitor in buily in IDE and from pySerial. It looks like commends are being ignored.

Also in "blink" sketch in the main loop:

void loop()
{
 digitalWrite(ledPin, HIGH);   // set the LED on
 delay(1000);                  // wait for a second
 digitalWrite(ledPin, LOW);    // set the LED off
 delay(1000);                  // wait for a second
}"

I have to remove delay(1000); command because they hang the emulator.

I will appreciate any help. Most important form me for now is uart fixing (run "physical pixel" sketch.)


texts: D/A converter with 0.4 up to 4V voltage output

texts:
I have this circuit:

http://www.malgefragt.net/images/image.php?di=LV13

I want to have as output:

BCD    Voltage
0        0.4V
1        0.8V
.
.
9         4V

My circuit actually doesn't work correctly.


texts: "Electromagnet 5kg DC 3V 5V 6V 12V" - what do these multiple voltages mean?

texts: I wanna buy an electromagnet from aliexpress and many of them are lifter magnets and have 6V, 12V, 24V and 5kg. So if i choose the 6V option does that mean the magnet can lift 5kg at 6V? Why would anyone buy the other options then (same price)?


texts: How do you create a simple and cheap tension alarm?

texts:
Background

I'm creating some party games and someone had the idea to place yarn or string in a hallway, similar to laser grid, that people would have to navigate without touching.

Problem

So I was wondering if it is possible to use something like https://www.sparkfun.com/products/10293 to create a buzzing sound (or a light) when a person bumped into one of the "lasers".

I've seen different tutorials, but most involve things like arduino boards or batteries, both of which are impractical for this scenario. So, is their away to hook up a string to a piezoelectric sensor that buzzes if the string gets bumped?


texts: Identify Mystery SMD component code 470C

texts:
I have a BLDC driver board and am having trouble identifying a component. Its PCB label is X3 so I initially assumed it was a fuse of some type. However it is connected in 3 spots. I searched smd code tables etc but can't find it. Looks like 470C is printed on the component but could be 47OC etc. Also picture of inside  of same component after the guy in the store wanted to prove to me that it was a removable fuse - which it wasn't. Any  help is appreciated.

Thank you for the responses so far. I've drawn a crude circuit diagram which I should have included to start with. Could they be Mosfets? eg BSS138 Found some I2C bi-directional level shifter circuits which had some similarities.
Also Ive tried to get some better closeups of the "pulled apart" component.

I am limited to 2 links so combined images into one.


texts:
I've gotten a little confused with what the definition of the pending interrupt is. That is when will this bit be set to 1 and read by using the RIM instruction.

My confusion is that:

When an interrupt occurs (say RST 7.5):
1. We jump to the vector address for RST 7.5.
2. Interrupts are now disabled.
3. Now while servicing this routine, say RST 5.5/6.5 is held high:

Would this set the respective pending bit to 1? For this, would the pin have to be held high till the service routine is executed and we return to the main program?

OR
Would this set the pending bit and then the user can decide what has to be done.

Second scenario:  Say a RST 6.5 interrupt occurs.
1. We jump to ISR for RST 6.5.
2. Interrupts are disabled.

Scenario 1:
    RST 7.5 occurs. Would the processor jump to the service routine midway of the RST 6.5 execution or would it continue it's execution as the interrupts are disabled, but make the register for RST 7.5 store 1 and then RST 7.5 would be classified as a pending interrupt (bit is set to 1 for RIM instruction). Similarly if RST 5.5 goes high would this be a pending interrupt?

Scenario 2:
In the ISR for RST 6.5 I use the instruction EI explicitly to allow interrupts, now if RST 7.5 occurs would it branch to the service location? and RST 5.5 would be counted as a pending interrupt?

I'm greatly confused by these above scenario's and books have stated them very ambiguously and any help would be great.

Thankyou


texts: Can an LED be used as a receiver and as an emitter?

texts:
I have this idea but I do not know if it makes sense. The idea is to use a red transparent LED connected to an input of a microcontroller. In parallel it is also connected to an output of the same microcontroller.
What I would like to do is detect when a red laser hits the LED. My hope is that the light hitting the LED produces a small voltage that can be detected on the microcontroller. When this is detected, the output turns the LED on for one second. (Obviously while the LED is on, the input is ignored.)
Can this be done?


texts: How to subtract gravity from raw acceleration of an MPU9250 - 9DOF IMU

texts:
I'm working with an MPU9250 and using the Madgwick Filter. For what I know I need to subtract the GRAVITY from my X, Y, Z Acceleration values, basically, some kind of gravity compensation to get linear acceleration values. I was using the following code (q is my quaternion generated by the Madgwick filter):

 g[0] = 2 * (q[1] * q[3] - q[0] * q[2])
 g[1] = 2 * (q[0] * q[1] + q[2] * q[3])
 g[2] = q[0] * q[0] - q[1] * q[1] - q[2] * q[2] + q[3] * q[3]

Then, to compensate the gravity, I subtract gx, gy, gz from my ax, ay, az values respectively. I'm not sure if this is the correct approach to solve this problem and I would like a bit of help. After stripping the gravity values, I need to get velocity. I don't need position so I'm not going to double integrate the acceleration values. By the way, I have to mention that this will be used to measure speed and acceleration/deceleration of football players while running, so I don't need this to be extremely precise.

PS: I read about using a Low-Pass filter to subtract gravity, but I'm not sure if I should be doing that.


texts: How would I wire this battery to the tablet?

texts:
I purchased a replacement batter for an old tablet -- and was prepared to follow the instructions to install it.
Unfortunately, the replacement-battery comes with wires coded differently -- whereas the original is connected with:

Black
Yellow
Green
Blue
Red

the replacement has:

Black
Black
White
Red
Red

Suppose, I plug in the tablet's charger and measure the voltages on the existing contacts -- how will I determine, which wire should go where?
The same battery is marketed for a different tablet, which uses a 5-pin connector. Here are the replacement instructions for that one -- maybe, the picture of the circuit and the batter can help?


texts: ESD safety when working across multiple workbenches/tables

texts:
I am a novice to electronics, and I am currently building a wooden workbench. The workbench will have an ESD bench mount and ESD matting over the entire bench.
I now want to have a small fold-out table (one of those cheap ones that you can buy from hardware stores), which has a plastic surface and metal frame/legs, next to the workbench. I will use this table for computer and pen and paper work. If my wrist strap is attached to the ESD bench mount, then is it safe for me to just "wheel" in my chair from one bench to the other, going from doing electronics and/or chemical work on one bench to computational and pen and paper work on the other?
Furthermore, with this setup, is it safe to have a laptop and/or pen and paper on the electronics workbench itself, and to work with that while I do electronics work?
Since the ESD bench mount is attached to the mains, I want to be sure that I'm not doing anything unsafe (both for myself and my electronics). I would greatly appreciate it if people would please take the time to advise me on this.


texts: Why do some EMI/RF shields have holes on the top and some don't?

texts: I am not talking about cutouts for tall components. I don't think they are for ventilation as they are often covered with manufacturer labels.


texts: connecting more than one Lm35 sensor to ADC pins of Atmega32 micro-controller in Proteus software

texts: I am trying to simulate a heating system using an atmega32 microcontroller, 4 lm35 sensors, and Proteus software for circuit simulation. Unfortunately, whenever I run the simulation I encounter the error:"'Power Supply' (330mV) is outside the specified range (3.5V-30V)" which says that the sensors are not getting enough voltage to start working. This error pops up when I connect more than 1 lm35 sensor to the ADC pins of atmega32(port A). When there is only one sensor it works correctly. Can anyone help me with this problem?


texts: What does it mean that a power supply is 'referenced to mains' and why is that dangerous?

texts:
I was watching a few different videos by BigClive on youtube. He was mentioning the danger of a particular light chain power supply because it was 'referenced to mains'. The voltage across the output terminals was 5v but an electrician's safety wand was still set off by being near the '5v' output.

Based on searching this site, it seems the neutral terminal of mains passed directly through to the power supply to be the neutral for the low voltage supply. Is this accurate?
 And how does this cause the detection wand to buzz?


texts: how do i connect a photodiode detecting laser?

texts:
I want to send data through a tissue using a 850nm Laser diode.

I would like to know how to connect a PIN photodiode on the receiver side?


texts: A good MCU which supports Arduino library but is not as expensive

texts:
I have a prototype working on the Arduino and the application is targeting low cost. So I need to make my own PCB which I am willing to do. But I want to use the Arduino libraries which seem very useful. When I looked at the ATMEGA328p which the Arduino uses it seems to expensive for its price compared to other MCU's out there.

SO I was wondering whats the step I should take. Is there any low cost MCU which AVR themselves make which supports Arduino libraries? The primary requirement is program memory needs to be 32-64kb. So how do I go about targeting low cost and at the same time use existing Arduino libraries so that I don't have to rewrite my code completely?


texts: What is the difference between real ground and virtual ground in opamp?

texts:
I understand what a real ground for a Opamp is.It is a terminal which is physically connected to ground or earth which acts as the reference point for the entire circuit.

But what do we mean by a virtual ground?

And how do we explain it with the help of opamps?

And finally is my understanding of real ground correct or is there something more specific that i can add.


texts:
The circuit diagram of a board I'm working on has parts labelled as "sacrificial components". These components seem to be pairs of probe points connected via a capacitor, and connected to nothing else.

What are these "sacrificial components"? What are their purpose?


texts: What is this type of wire-connector called?

texts:
I am having the hardest time finding something like this on Mouser. I have find things similar, without the screw for example, but never exactly this. Is there a generic name for this type of connector?
If you type something like PCB 2 Way Connector into Google then your search is through, but Mouser apparently has a different naming convention for these little connectors.

This is the closest thing I could find, but I either need a 4-way connector or a 2-way. Ideally I would like to find the same connectors as shown below.

Examples:

Amazon

Another Website


texts: During this experiment, I connected a 10m coaxial cable to pulse generator and at the load end I connected capacitor and inductor one by one, I got these waveforms. Can someone explain me the the reflection?


texts: What supply voltage for the Abracon crystal oscillators?

texts:
I'm considering the Abracon ABM8W-13.5600MHZ-4-B1U-T3 Crystal but I'm having difficulty finding the maximum and minimum supply voltages. Does anybody know how to obtain this information (I've tried emailing the manufacturer)?

Voltage in my project will range from 4.2v to 3.2v.


texts:
I'm little bit confused. Help me please to make everything clear. I want to buy oscilloscope and found two models suitable for me.

Rigol DS1102E
Rigol DS1102CA

But I don't understand the difference between them. I read that DS1102E has 1 GSa/s sampling rate and DS1102CA has 2 GSa/s. OK. But what does it give in practice? Both oscilloscopes have a bandwidth of 100MHz, so I won't find a difference in picture of signals on screen. Am I right? So could you explain me what is the meaning of 'sampling rate' and 'bandwidth' for modern oscilloscopes? And what is the difference between these things?


texts: How does this inverting opamp circuit with adjustible bandwidth work?

texts:
Either my textbook author is a scoundrel or I don't have the prerequisites to understand even a simple op-amp circuit.  I understand how a basic inverting amplifier works and I get how the gain falls off due to the internal RC circuit (miller C).

What I don't understand in below circuit is how the value of the resistor \$R\$ changes the bandwidth. Since gain-bandwidth product is generally constant, this circuit must be very clever to manipulate bandwidth without touching the gain. I'm attaching the full snapshot of my textbook explanation. It says bandwidth varies with \$R\$ and gives equations, but doesn't explain how or why. Please help me understand how this works.


texts: IR reciever somewhow being triggered by cell phone screen?

texts:
First time asking a question here.
I am curious why the TSOP4838 ir sensor is acting eratically when my Google Pixel 2's screen is facing it.
As you can see from the schematic, I have a 555 arranged as a Schmitt trigger, with the output going to the CLK of a 4013 configured as a latch, which ultimately activates the NPN relay driver. The circuit works as expected when facing a 38 kHz IR LED at the sensor, but also falsely triggers when facing my cell phone's screen towards the sensor.
Any ideas?


texts: Is it a good idea to connect aluminum AC mains wires by soldering

texts:
Provided I have an appropriate flux for aluminum and I'm able to solder the wires will this connection be durable?

I'm not sure if it will corrode or not considering aluminum and the solder (60-40 solder) are different metals.


texts: How should I drive a chip where I need to pull pins low in order to enable

texts:
I am wanting to use a FSTD16211 in my circuit. It's datasheet says that pins OE1 and OE2 should be high to disconnect the 2 channels of the bus, and both should be low to connect the 2 channels of the bus.

Therefore, in my circuit, I need to drive these 2 pins as logic high by default, and my ESP8266 at the heart of the circuit needs to be able to pull these 2 pins low to 'enable' the bus.

The question is, how should I do this - what would best practice be? I was hoping to use level shifters wherever possible as that appears to be a good idea in such use cases...but I cannot determine what the correct shifter would be.

I find it hard to understand the levels that would be considered high or low in this circuit as well.

-0.5v - 7v is the input pin control voltage....so what does that mean? would driving that pin at 3.3v be considered 'high'?

Can somebody point me in the right direction here, with a bit more reasoning and detail than simply 'this is the chip I would use', as the explanation is more important to me than the specific answer. In an ideal world, I would be shown how an appropriate level shifter would be wired into a circuit with a brief explanation of the behaviour to expect from that.

Thanks!


texts: Should I use MBED of ARM or native platform of microcontroller suppliers?

texts:
I got a STM32F429I-DISC1 development board from STMicoelectronics and I know MBED support it.

So if I want to learn about ARM and develop a commercial product in the future, should I use MBED platform or native platform of STMicoelectronics?


texts: counter that MSB toggles every 2 seconds

texts:
I want a counter that the Most significant bit toggles every 2 seconds, and gets values 0 and 1.So for example it will have 0 for 2 seconds and after 1 for another 2 seconds etc..
I need it like that because I will connect the most significant bit to a decoder which will show results on FPGA 3starter (50MHZ/20ns)
Does this will work?

 library ieee ;

use ieee.std_logic_1164.all;
use ieee.std_logic_unsigned.all;

----------------------------------------------------

entity counter is

generic(27: natural :=2);
port(   clock:  in std_logic;
    rst:    in std_logic;
    count:  in std_logic;
    Q:  out std_logic_vector(27-1 downto 0)
);
end counter;

----------------------------------------------------

architecture behv of counter is

    signal Pre_Q: std_logic_vector(27-1 downto 0);

begin

    -- behavior describe the counter

    process(clock, count, clear)
    begin
    if clear = '1' then
        Pre_Q <= Pre_Q - Pre_Q;
    elsif (clock='1' and clock'event) then
        if count = '1' then
        Pre_Q <= Pre_Q + 1;
        end if;
    end if;
    end process;

    -- concurrent assignment statement
    Q <= Pre_Q(27-1);

end behv;


texts: Bluetooth advertisement packet format restrictions

texts:
Are there any firm restrictions on the formatting of advertisement data and scan response data for Bluetooth Low Energy?
The sample projects I'm learning from start the advertisement data with some flag bytes and then the name of the device.  Both the flags and the name are also preceded by a length byte.
If I have an observer module that needs to keep track of another beacon module, can I make the beacon advertise any sort of gibberish that I want as long as the observer module knows what to look for, or does the beacon have to have some sort of logical arrangement of data in the advertisement?
Thanks


texts: Connecting different lipo in series to achive high voltage

texts:
I'm not so familiar with lipo and liion but know their dangers.

For my recent project I got an audio amplifier which works well on voltage of 14-18V so I need this range of voltage.
My amplifier is portable so I have little storage for batteries so I chose lipo and liion as they have good weight to power ratio but I dont have same capacity batterys for this.
I have 6 1250 mah liion and 1 3500mah lipo and now the problem starts.

I have small 1s protection circuit.  Can I connect it to 2p3s for 1250 mah liion (1 circuit/2cell i.e 3 circuit in series?)
Can I connect this above setup if possible with my lipo which has its own protection circuit (mobile battery) which gives voltage of approx 16.8v in total (in theory.)
I have a BMS from China which is not actually the BMS I saw video on youtube for it from greatscott and concluded it is just a protection circuit so I designed this my own circuit please help to figure out if it works:


texts:
What should I do to the circuit:

 so that the LED is lit.
Multisim file

I know Q1 does not have ground nor is the VCC connected to the Q2. The above is part of this commercially sold driver board

Note that VCC and Common Ground are controlled by a jumper that is set to Ck. And because of this there is no ground to the first transistor's emitter. The 3V is the 'p' in the second image which is fed from microcontroller. I tried removing the bias voltage (3V), connecting to the ground (changing the jumper).
I would like to point out that in practice, i am using Vcc as a 9V battery that I have on common ground with the 5V from microcontroller.

Note: This is a follow-up on this question that I asked in reddit with no response.

As I was not getting any response, I figured out if i dumb down the circuit to easier level, I might get better response. Please help. I am seriously going nuts!

EDIT 1: I found the manuals of the 7 segment display and driver. Can some one tell me why a common cathode is connected to +ve.

EDIT 2: Based on @jonk comment, I am trying to get it working in Common Anode. The schematic I redrew in Circuit Lab reflecting the jumper changes. I am still not able to figure out how the circuit fully orchestrates and its working. If i connect the Q2 to VCC then when I simulate a DC sweep I am getting a jump from 8V to 12V after Vbe > 0.7. Not understanding why it was not in the cutoff region before.

simulate this circuit – Schematic created using CircuitLab


texts: Why do large power stations' generators rotate at ≥ 1800 RPM?

texts:
Some time ago, over some beers with a fellow EE who's much more experienced than me, we were discussing the unique challenges present in utility-scale power generators, like the ones in nuclear power plants. A single generator can be in excess of 1000MWe, and has all the more exotic stuff like hydrogen cooling, etc.

In passing, my friend told me

  At least they don't have to spin at 3000 RPM, they have many poles on the stator to reduce the need for rotor speed...

Which I thought was a good solution to an engineering problem.

It seems, though, that they don't actually use it often.

When reading about the Chernobyl disaster, I found that the RBMK reactors, and indeed even the modern VVER varieties, use generators spun at 3000 RPM. Excerpt from Wikipedia:

  The turbine and the generator rotors are mounted on the same shaft; the combined weight of the rotors is almost 200 t (220 short tons) and their nominal rotational speed is 3000 rpm.

Also, from the Chernobyl NPP page:

  The Kharkiv turbine plant later developed a new version of the turbine, K-500-65/3000-2, in an attempt to reduce use of valuable metal. The Chernobyl plant was equipped with both types of turbines; block 4 had the newer ones. The newer turbines, however, turned out to be more sensitive to their operating parameters, and their bearings had frequent problems with vibrations.

Indeed, on the night of the Chernobyl disaster there actually were two tests being done about the same time: the famous turbine-rundown test we all know about, and a quite obscure vibration measurement test (it's not widely described, but search for "vibration" here if interested).

Another data point: the only time I went on an inside tour of a working NPP (a VVER design) I noticed that one of their instruments in the control room was sometimes dipping into the redline area, and when I asked, we were told it's the vibrations indicator.

So all in all it seems that vibrations could be quite the hassle, and one has to wonder why they don't utilize the half- or one-third-speed approach, which will allow for 1500 or 1000 RPM on 50Hz grids.

It's evidently done on 60 Hz grids, for example the Bruce NPP's generator runs at 1800 RPM, and GE offers both half-speed and full-speed generators (e.g. see here, pg. 22 and 23).

Question

So the technology to use lower generator speeds is there, but why is it only used for halving the speed, why not divide further? What are the downsides of lower speeds?

The question may be not appropriate for this StackExchange, as the reason may be purely materials/mechanical issue (less RPM needs higher torque, ...). I'm interested if there are EE reasons that make the higher RPM desirable.


texts:
What is the small signal diagram for a PMOS? Would it be the same as that of an NMOS but instead of \$I = g_m V_{sg}\$, for a PMOS we have to use \$I = g_m V_{gs}\$?

Thanks.


texts: Measuring duration and distances between pulses

texts:
I want to know how it is done (or at least how would you do) to measure duration and distances between pulses on a signal in a micro controller(or a better way).

Example: I have a couple of Arduinos and a couple of this RF Transmitter/Receivers(http://bit.ly/oT05Qg) and have a protocol setup that says I'm supposed to receive 4 bits (1111) with duration of 0,5 micro seconds and the space between them as of 1,5 micro seconds. If it is any different, I should ignore the information.

How can I/would you do this?

P.S: The best example in real life I could find was this: http://en.wikipedia.org/wiki/File:Interrogation.jpg


texts: Deducing the value of a variable resistor in configurable voltage divider

texts:
Two variable resistors (RS & RE) and one static resistor (RC) are connected to a high impedance input analog input pin of a micro-controller. The static resistor is connected to ground and the two variable resistors are connected to digital outputs of the micro controller where they can be driven to +V or to ground. By driving RE or RS either high or low in any configuration and sampling the voltage from the resulting voltage divider is it possible to deduce the value of RS, and if so what formula would describe it? The value of the variable resistors is to be considered the same between successive scans.

simulate this circuit – Schematic created using CircuitLab

Not required for the question but RS is assumed to be between 1kΩ and 100kΩ and RE is assumed to between 200Ω and 20kΩ. RC can be any constant.


texts: Arduino Mega and sending data via serial3.print()

texts:
So far I have:

float temp = 22.45;
Serial3.print(temp + "\r");

I knew that code would not work from the getgo.
I am attempting to concatenate the temp variable and a carriage return.  The board that I will be communicating with will only accept a carriage return at the end and not a new line, otherwise I would have used a println().  How do I combine the float value and a carriage return and send it via Serial3?

EDIT

char tempAr[10];
String tempAsString;
String serialData;

dtostrf(temp,1,2,tempAr);
tempAsString = String(tempAr);

serialData = tempAsString + "\r";
Serial3.print(serialData);

The above code seems to work; however, it is still rough around the edges and I will have to change the width and precision values in the dtostrf per decimal place(ones, tens, hundreds);


texts: Using a single resistor for constant current load

texts:
I have a super capacitor (1000F) laying around and I want to measure ESR and it's capacitance. I have access to a 8V/500A power supply and various meters.

If I wanted to charge/discharge the capacitor at constant current (75A) to it's rated voltage (2.7V) and half (1.35V) then I would just need a series resistor that pulled more than 75A at 1.35V?

1.35V/75A = .0173 ohms. So anything less than that with a power rating of over 205 should suffice? Am I missing anything?


texts: BC547 Transistor based Logic level converter reliability in Industrial Applications

texts:
I am using a raspberry pi in one of the systems that I am designing.The High output of raspberry pi IO pins is 3.3V . I want to generate a simple square wave pulse output on one of the IO pins on raspberry pi. However the square wave needs to be of 5V amplitude. Now I wish to make a simple circuit to do the same(Circuit attached)
Note- Voltage Level converter is UNIdirectional and Max frequency of switching is roughly 33kHz Transistor : BC547

This circuit is based on this answer : Logic Converter
Questions:
1.Is BC547 used in moderately critical applications?can I/should I use any other slightly robust transistor? Kindly suggest if any
2.Should I add a diode at the output ?
3.Is BC547 ok in the given switching frequency range?
Thank you in advance !!


texts: Here is my scenario, I have a device that has two heating coils ( AC ) in parallel. The power wire is connected to the beginning of both heating coils and is can't easily be un-crimped. The returns are separate and meet at a wire nut. I want to isolate the larger coil and be able to turn it on and off with a relay, while leaving the smaller coil unaffected. Can I place a relay across the return wire somehow, so it only breaks the return of the larger coil? is the wrong way to do this?


texts: What's the best way to organize components database?

texts:
Thinking of building a local components database which maps company part number to multiple manufacturers.  Assume SQL type thinking.

Option 1.  One table with company part numbers as primary key, fields with component values, names of symbols, and footprints.  Another table with company part numbers as primary key, and fields with manufacturer and manufacturer part numbers.  A join on company part number is performed to get multiple manufacturer part numbers per company part number.  Advantage is simplicity.  Disadvantage is I don't get a list of components and their values for each manufacturer which would be nice, and I need to explicitly maintain the second table which does the mapping, which could have mistakes.

Option 2.  First table same as above.  A different table for each manufacturer with all their components and values.  Join on values.  Advantage is mapping between company part number and manufacturer part number is automatic based on values and I don't have to curate the mapping. Also it would be nice to have a separate list of components from each manufacturer.  Disadvantage is sometimes you want to exclude components based on rohs or something else, so that's a new field in both tables.  Instead of curating an explicit mapping, which could be arbitrary (for better or worse), I now need to curate fields across multiple tables and make sure each manufacturer table has the same schema.

Which is best?


texts:
Question
I would like to import Gerber files into an Altium Designer PCB document for re-using an in-PCB spiral inductor but the importer fails to interpret the Gerber files in a correct way. Has anyone here knowledge on how to import Gerber files into an Altium Designer layout?

Background/What I have tried
The design containing this PCB spiral is a reference design from Linear Technologies and there are design files available for download here (clicking link will download a .zip-file). The design files contains a Mentor Pads PCB file but also Gerber files.

The ECAD system I'm using is Altium Designer 15.1. Since the Mentor PADS PCB file is of binary type I can't import it into an Altium Designer layout document. Altium designer can only import ASCII type Mentor PADS PCB files and I don't have access to conversion tools for converting from PADS binary format to PADS ASCII format. Therefore I tried to import the Gerber files into an Altium layout document. The result is not right at all, there is just a mess of top layer copper.

I have opened the Mentor PADS PCB file into the free Mentor PADS viewer and the design looks like it is supposed to. I have also imported the Gerber files into CAMtastic (the built in Gerber viewer in Altium Designer) and the design looks like it is supposed to. I also tried to export new Gerber files from CAMtastic and then import them into an Altium Designer PCB document but I had no luck with that.

Added to original post (1)
The way I've been trying to do the import of Gerber files into an Altium Designer PCB document is that I open a new PCB document and then I import one Gerber file at a time by choosing File->Import->Gerber File. I stop after the first import since I just get a mess of tracks and pads.

Added to original post (2)
Just opening the Gerber file using the Built in Altium CAMtastic viewer is not the complete answer for me. I would like to transfer some design elements from these Gerber files into a design for reuse.


texts: Burning Intel Microcontroller using AVR programmer

texts:
Is it possible to load hex file created to Intel 8051 micro controller using AVR USBISP programmer

This is the Datasheet..
http://pdf.datasheetcatalog.com/datasheet/Intel/mXqzvzz.pdf


texts:
I want to measure switch bounce, but all I have is access to an old CRO. Based on inputs from this forum post, I tried the HOLDOFF knobs and other buttons too. Nothing worked. In the case of modern DSO's people have suggested using the trigger and I think that may be of use here, but I don't know if it's possible and how.

Btw even though I'd come across this wonderful guide on debouncing, I'd love to run my own tests with the switch I have.


texts: The datasheet for the PCM3168 6ch ADC states that ADC 1-2 is outputted digitally out of DOUT1 and 3-4 DOUT2 etc. How are both of these sent down the single digital pin and how can I handle this digital audio, say send it to a computer via USB microcontroller or other format.


texts:
I'm running a dc motor using PIC16 family microprocessor.
I connect it to my pc, I can send a command to run the motor in certain speed or stop.

It works for small motor (3V, 100 mA). But the moment I use bigger motor (3V, 300 mA), I can only I send 1 command e.g. run fast. After that, the pic refused to process the next command. Even when I turned off the device and turned it on again, the motor still running the last command. It seems like memory hardening or something like that.

I'm not sure what happened
- Could it be a kickback current from motor caused the instability? I'm using TIP120 as motor driver.
- I have put capacitors, diodes around the motor driver. But didn't help.

Can someone help me?

I appreciate your thoughts.


texts:
I am happy to announce that my pocket extra-strong static electricity generator project is now complete and works well.

However there is one problem, I am often getting zapped severely (to the extent I get muscle contractions) by touching the wire that carries out the high voltage negative output even though it is supposedly insulated.

My guess is that the wire is too thin, what is the easiest way to solve this problem? Is it best that I insulate it further with hot glue?


texts:
My teacher says that this signal is DC, but if the polarity varies from 0V to -8V , shouldn't it be AC?
He says that
DC + AC = DC


texts: Transfer characteristic of p-channel JFET

texts:
Considering the output characteristic of the n channel JFET, can we somehow obtain the same characteristic only for the p-channel type of this transistor?

In R.Jaeger's book about microelectronics circuit design, only a vague description was given on how only the polarities are changed, and everything else is left untouched. I suppose that means, that we will either be graphing the same curve in the first quadrant, or in the third also, only using the Vsg voltage.


texts: shorting method of current source and voltage source

texts:
I'm learning electronic circuit and sometimes we need to short just the current sources and sometimes we want to short source voltage. my question is: why if I want to short the current source then we must cut/disconnet the current source, and if I want to short the voltage source I just short it and not disconnect it.

why for example can't short the current source? if I short it then the current will not go to the circuit it will just loop where I've shorted it (so we don't have current on my circuit and just have yeah current on the wire short that shorted the current source, but we can call that we shorted the current source because we don't have current pass to the circuit, so why we are not using this for shorting the current source? instead of disconnecting it?!!


texts: Why do we use the terms AC and DC if they have nothing to do with current?

texts:
It seems archaic, maybe that we use the term AC (alternating current) and DC (direct current) to talk about power systems. After all, it is the voltage waveform we're usually referring to. In my first power electronics class, we learned that the current of a power system often seems to mimic the envelope of the voltage input waveform, but that's hardly the case with active loads.
Why do we use alternating current and direct current as opposed to alternating voltage and direct voltage?


texts:
I am working on a single phase PLL (phase locked loop) and I would like to make a phase shift by using orthogonal signal generator non frequency dependent.
I have found many method like transport delay, inverse park transformation, Hilbert transformation, or Second Order Generalized Integrator (SOGi) but none of them fit my model.
i have to shift alpha which has the same amplitude and phase to the grid voltage to 90 degree by using non-frequency dependent method.
I am working in a PLECS program

I have tried to draw the circuit which is answerd, first after the loop filter I have got a phase shift with 180 then when I connect to flip flop I got zero output. please can you tell me where is my mistake. I have found another answer which is connection between two op-amp first shift by 180 then by 90 degrees but the problem when I apply very high frequencies i don't get a 90 degrees phase shift. please find attach the pictures of two models


texts: Inserting transducer model into a circuit

texts:
I'm not looking for complex explanations on transducer modeling, rather lets assume we have a very simplified transducer model of basically an R and C in series:

simulate this circuit – Schematic created using CircuitLab

On the transmit cycle the circuit will basically look like this with the transducer as a load:

simulate this circuit

However, on the receive cycle, it's not immediately intuitive to me how to model the transducer as a voltage source with the given impedance model.  Is it simply a voltage source with the impedance in series like this:

simulate this circuit


texts: Pin compatibility between STM32L4X1 and STM32F1

texts:
Does STM32L4X1C series have a pin compatibility with STM32F103xx, 107xx or 207xx?

How can I find the other STMs that be pin compatible with the series I want?


texts: How do I convert a PWM signal (with a specific duty cycle) to its respective analog value, for an application in a low voltage, high current circuit?

texts:
I wanted a 16V,50A regulated power supply but could not find it in the market. I also searched for a buck converter for the same current output and could not find anything. So I thought of making it with a high current (60A) motor driver and a 45V, 20A SMPS. However, upon checking the output signal of the motor driver, I found out that it is actually a PWM signal (amplitude: 45V, frequency: 16KHz) and here lies my problem. Since I have a load which can take a maximum of 17V DC at input, connecting my motor driver directly to it is not a good idea. Now I am looking for ways to convert (or filter) this PWM output into an constant DC voltage (depending upon the duty cycle of PWM obviously!) so as to feed it into my load.
Could anyone please help me with the filter/converter design? I read about low-pass RC filters but given the amount of current that I am drawing, I will need an insanely small value of resistance with a high power dissipation capacity (about 800W) and also a very large value of capacitance (which makes it impractical.)
A rough schematic of my arrangement looks something like this:

simulate this circuit – Schematic created using CircuitLab
On a side note, my load is expected to draw 40A current at 16V and I understand that I will need feedback to regulate my output voltage.


texts: I am using a PK243 - 03A unipolar stepper motor, its step angle is 1.8 degrees. I am planning to step the motor periodically on it's starting frequency which is coming out to be 1.3kHz, to see how it makes 200 steps per revolution, what I cannot decide is the step size of the pulse. How long should be the pulse high to get 1.8 degrees?


texts:
For several different projects, I need high current DC power (25-50 Amps). The first project needs roughly 50 Amps at 12 volts, which isn't something one ATX can provide on its own (at least I don't think it is.) So is it possible to wire 3 ATX PSU's 12 volt rails together (each with a diode to prevent back-current) to get this? Or is there an easier way?

The second project requires around 1.5-2.5 volts with as high of a current I can get. I was planning on combining the rails of a few ATX supplies with voltage regulators to get this as well.

I'm still somewhat new to electrical engineering so any advice, knowledge, or other information is greatly appreciated.


texts: Ringing seen when a zener diode is used with series diode as a snubber

texts:
I am trying to simulate the snubber circuit as given in "A zener with series diode"? there is some ringing seen at ouput.

Here is LT spice ckt:

Simulation result shows some ringing at output.

I don't know, why this ringing is there. One different thing than "A zener with series diode"? is inductor. Please suggest the possible cause of this ringing.


texts: Is there a gap in an LED between the plates (post & anvil) or a wire (or are there different kinds of each)?

texts:
I previously believed there was a gap between the plates inside an LED (between the post and the anvil).

However, I recently saw the following drawing on wikipedia (https://en.wikipedia.org/wiki/Light-emitting_diode#/media/File:LED,_5mm,green(en).svg ) :

I noticed that it shows the "Wire bond" which seems to indicate a wire from the post to the anvil.

Question 1

Is there actually a physical wire there?

I always thought the electrons jumped the gap and that there was no wire and that was part of why LEDs lasted so long.

Question 2 - for clarity

If there is a wire there, is it the part that lights up? Or, do the electrons still jump the gap?  (I'm assuming they are conducted on the wire, but just attempting to clarify.)

Question(s) 3

If the wire is there, is this a (more) recent design change to LEDs? Did LEDs of the past have or not have this wire?  Is this a special type of LED with the wire and there are some that don't have it?


texts:
I am designing a prototype 5VDC fan speed control unit. I am using an LM317 as a voltage regulator. This will step the voltage from a LiPo battery or arbitrary wall adapter down to 5V. Pulse width modulation is used for actually controlling the fan speed.

As an alternative means of powering the device, I have been asked to install a female USB port which will interface with a solar powered USB charger being developed by a third party. I was hesitant to install the USB port for several reasons. The first is that the fan can draw about half an amp, much more than most USB ports can safely supply, so if it were plugged into a computer, for example, frying electronics is a possibility. The second is that I have no way of isolating the jack/battery power supply from the USB power supply and if both are connected at the same time, the results could be bad.

I was assured that this is a demonstration and testing prototype only, not a manufacturing prototype, so care will be taken not to misuse the USB port. Now my problem is that I don't want to run the 5V USB supply through the LM317, since the LM317 requires a voltage drop across its input and output pins to function properly.

My questions are:

What would happen if I connected the 5V USB in parallel with the output of the LM317 voltage regulator circuit?
What happens when I supply a voltage to the output and leave the input an open circuit?
Also, does this potentially solve or mitigate the dangers of erroneously connecting both jack/battery and USB power supplies simultaneously?

I have inserted the proposed schematic here.


texts: How to get half frequency square wave from sin wave?

texts:
The task is to get such wave:

I can get square wave from sin wave, but I have no idea how to make it half-frequency. Have some advices?


texts: Connecting a parallel LCD using ST7789 with STM32H743VI

texts:
I have a STM32H743VI that I want to connect to a LCD display that uses ST7789 with parallel interface (8 or 16 bit), the LCD doesn't have the SPI signals so I have to use the parallel interface.

I am wondering on how to use the DMA controller in order to speed up the copies between internal buffers and the screen buffer.

I am planning on implementing a simple driver for LittlevGL.

My questions are:

Which GPIO ports can be used with the DMA controller of the STM32H743VI?
Do I have to use the TIM1/8 timer in order to push the data from the buffer to the GPIO?
Is it worth while to use the Chrom-ART accelerator? how hard is it to use it?


texts:
I have a small circuit which is normally powered by a CR2032 coin cell but also has a SWD header for programming. I made a simple power path switch so that when I am programming, VDD is supplied by the programmer.
The schematic looks like this:

I found that the CR2032 coin cell gets severely degraded after unplugging the 3.3v power. Oscilloscope showed a huge influx of current from the decoupling capacitors (~200uF) in the circuit, caused by the Q1 becoming "reverse conductive" immediately after the 3.3v is removed and the voltage difference causes the current to flow back into the battery.
I'm stuck in trying to resolve this, adding a capacitor in parallel with R1 doesn't solve the issue because the current consumption of the circuit (MCU + Radio) powered by VDD isn't constant (varies between 5uA and 50mA). Thus, you cannot select a single time constant to work for this.
I do not want to add a diode between VBAT and VDD because there cannot be any significant voltage drop during normal operation.
How can I prevent current from flowing back into the coin cell while at the same time not dropping VDD when the switch from 3.3v to VBAT power is made?
Update: I am targeting a quiescent current in the single-digit uA range when the power is supplied by VBAT.
Update: Here is the OP-AMP based circuit based on Andy's suggestion:

Update: Here is improved version of the OP-AMP circuit which adds D2 to eliminate current inrush from VDD to the coin cell when VCC is connected (caused by the limited slew rate of OA1). Note that OPA349 should be used as OA1 and low-leakage schottky diode should be used for D2 (this was the best I could find in CircuitLab).
I'm not happy with the BOM cost of this solution but it might be the best I am able to achieve here.

simulate this circuit – Schematic created using CircuitLab


texts:
I am trying to understand fully the problem with using electrically short antenna to transmit RF signals (i.e length significantly shorter than the intended wavelength).
Currently my understanding is that such an antenna does not radiate : since the length of the antenna is much shorter than the wavelength the voltage distribution on the antenna at any given moment is roughly uniform. In particular there is no voltage fluctuation on the antenna and hence no magnetic field and hence no radiation.
I have been trying to quantify this explanation. The simplest quantification is that the impedance of an electrically short antenna is large, so the power transmitted to the antenna is small. But let's suppose I match the input impedance with the antenna impedance and I crank up the voltage to such an extent that the power transmitted to the antenna is now large. Now even the small variation in the roughly uniform voltage distribution are magnified and a magnetic field appear.
I am wondering if the high impedance is really the only issue that prevents an electrically short antenna from radiating? (Indeed, the antenna now behaves like an RC circuit, but I don't see why this is a problem if for example R = 50, C = 10k and the frequency is in the 10Mhz range and the voltage is very large).


texts:
On many control panels, one finds indicator lights that indicate whether a device is working. I.e. not only whether it is switched on but whether current flows.

E.g. a car dashboard which indicates when a lamp burned out.

My question is: how do these work? Are there ready-made IC solutions? (I have a black box in front of me which has input/output for the power supply of the device monitored and smaller wires to connect to the indicator light.)

Also: another problem is that when lamps that a monitored are replaced by LED, the indicator circuit signals a fault. What is the reason for this? Is it due to the current draw being too low?


texts: Difference between these two buck converters

texts:
I can't find a comparison of various DC-DC CC/CV buck modules, for example googling XL4015 xl4005 lm2596 review does lead to anything that helps me understand their strengths and weaknesses, and which to choose.

Looking to permanently modify an 110V AC lamp containing an LED so I can use it in my 12V car. I realize I could probably just plug the lamp's AC/DC adapter into my 12VDC to 110VAC inverter, but I'm not interested in that.

My plan is to cut the lamp's DC power cord and wire it to some or another buck converter, wired to a cigarette lighter outlet.

The lamp assembly cannot be disassembled without destroying it, so I don't know much about the LED.

Full size image: https://i.stack.imgur.com/0b1La.jpg

The lamp cord plugs into the AC adapter, which plugs directly into the wall outlet. The label on the adapter says Intertek, 7V, 430mA, KMV-070-030-NA-2.

I plugged the cord half way into the wall adapter, then probed the prongs on the end of the cord with a multimeter,  6.75V 200mA.

Here are two modules that I considering, but am just guessing that they would be appropriate. I selected them because they are small (though space is not an issue) and they provide adjustable constant current and voltage output, and have higher max amps than I need.  Besides different buck ICs, they seem to have different coil types. I'm not sure how to interpret either of those differences.

Full size images are here:

https://i.stack.imgur.com/R2cS4.jpg

https://i.stack.imgur.com/Sf3hP.jpg

Info from sellers:
    Price               $3            $4
    IC Mfr              TI            XLSEMI
    IC model            LM2596        XL4005
    Op-Amp                            TI LM358
    Input voltage:      7V-35V        5-32V DC
    Output Voltage:     1.25V-30V     0.8-30V DC
    Output current:     3A max        50W/3.5A Sustained 75W/5A Peak
    Efficiency:         92% max
    Switching freq:     150KHz        300KHz
    Output ripple:      50mV max
    Load regulation:    ± 0.5%
    Voltage regulation: ± 2.5%
    Operating temp:     -40 - +85℃
    Size:               48x23x14 mm   51x26x14mm

Datasheets from mfrs:

http://www.xlsemi.com/datasheet/XL4005%20datasheet.pdf

http://www.ti.com/lit/ds/symlink/lm2596.pdf


texts: What is the actual stall current of a Mabuchi RS550VC-8518 12v DC motor (out of a Dewalt 12v battery-drill)?

texts:
This question is part of a long-winded way of working out the maximum working-under-duress current-load on a 3S Li-Ion battery from a 10.8v/12vMax Dewalt Drill.

The replacement motor for the drill is a Mabuchi RS-550VC-8518. I've hunted high and low for a data sheet but the motor seems too old to have one available. Various listings I've found for these specific motors on E-Bay and the like list the stall current at any where from 3.0 Amps to 10 Amps (with no torque figures given...), while the closest wind I can find on Mabuchi's site (RS-550VC-7525) is rated at a wooping 85A/549nM.m stall  and a similar Kysan motor (RS-550SH-7524) is rated at 32.4A/117.6nM.m stall.

Firstly, can both the figures for the RS-550VC-8518 and RS-550SH-7524/7525 be correct? ie: is there something about DC motors at this scale that could account for such a huge difference in stall current with that amount of difference in wind spec? (I'm more used to 130/180 sized motors...)

If not, which figure is more likely to be correct? 3-10A or 32A or 85A?


texts:
My 6-year-old son has shown some interest in electronics, and I thought I'd get him some basic components (motors, LEDs, buzzers, etc) and let him experiment (using alligator clips and the like -- no soldering at his age!).

The one worry I have is that he'll accidentally short-circuit the battery, which could be dangerous.  Are there battery cases (for standard AA, etc) available for purchase somewhere with built-in overload protection?

Failing that, I thought of soldering fuses to the battery holders.  What would be an appropriate current rating for the fuse?  I was thinking 1-2A, but my electronics expertise is pretty rudimentary.


texts: Always-on socket in-between a 2-way switch?

texts:
I have access to a power cable that powers devices through a 2-way switch, basically:

Is it possible to add an always-on socket in between using L1, L2 and N?
The problem is that either L1 or L2 is live at a given time and, obviously, they cannot be connected together as that would invalidate the 2-way switch.
Does there exist a device that would pass through L1 and L2 without connecting them together?


texts: Replacing radial fuse with ceramic/glass fuse

texts:
Is it possible to replace a radial fuse T5A 250V with a Glass or Ceramic Fuse 5A 250V?
It's for a power supply for a LED TV.


texts:
One of our breakers was tripping every few minutes (which powers an air-pump and a few 12V solenoid valves.)
I went to measure the voltages and everything seemed fine.
As I went over and touched the air-pump's on-off switch, I got a nasty shock from the little metal rim sitting around the switch toggle.
I proceeded to measure the voltage between the earth wire and the physical dirt beneath my feet and measured 240V.
Why is earth sitting at 240V?
A qualified electrician installed the setup, so I'm not too sure what's causing this. Ideas?


texts: Arduino fingerprint sensor turning computer on/off

texts:
Hello everyone,

I have the above circuit connected to my computer. The Pro Micro is running the following program (code HERE):

Check if computer is on or off by verifying if the motherboard LED+ pin is HIGH or LOW, respectively (pin 5)
If the computer is off, check the input from the fingerprint sensor;
If the fingerprint is valid, turn on the computer by setting pin 4 HIGH which in turn switches the transistor and then sets it LOW after a small delay -- mimics a power button press.

As long as the Pro Micro is powered, the setup works with no issues. But when I unplug the Pro Micro, the computer shuts down and I don't understand why. And it's not momentary like a button press. It's like the transistor is on fully, resulting in a long button press.

Can anyone help me understand why this is happening when unplugging the Pro Micro?


texts: I have a two port system which consists of two subsystems. Is the multiplication of S21 parameters of the subsystems equal to that of the whole system?


texts: Weird behavior of pwm controlled servo motor?

texts:
Hello there I have experienced some really weird behavior from servo motor wheni try to control it with pwm. I am using dspic30f4013 and servo motor sg90 tower mini. I configured my pic with 10Mhz input crystal with PLL4.
Here is datasheet for sg90 tower mini servo motor and here is datasheet for my dspic. So to steer servo to position "0" 1.5 ms pulse, "90" ~2ms pulse, is all the way to the right, "-90" ~1ms pulse is all the way to the left. I configured my pwm like this:

void initPWM()
{
  TRISDbits.TRISD1 = 0; // to clear port
  PR3 = 2899; // inserting value for TMR3 period
  OC2CONbits.OMC = 0;
  OC2R = 0;
  OC2RS = 658; //initial duty cycle (This value steers servo to the right)
  OC2CONbits.OCTSEL = 1; // TMR3 is selected
  OC2CONbits.OCFLT = 0; // no flt pin
  OC2CONbits.OCSIDL = 1;
  OC2CONbits.OCM = 0b101; // Continues pwm mode

  T3CONbits.TCKPS = 1; // prescaler 1:8
  IEC0bits.T3IE = 1; // enable interrupt
  T3CONbits.TON = 1; // turn on timer module
 }

When i power on initial value of pwm loaded in OC2RS register steers servo to the right which is ok. Then i load value of 250 in while just to see what will happen and it steers servo motor to the left which is also fine. But when i make simple program to steer it from left to right just for fun to see if it works as it suppose to do, it doesn't. So what happens is that after initial value steers it to right it suppose to go to left and than right and vice versa but it just goes to one side and that's all, and it simply just stay in that position and do nothing, not even a sound of servo tryin to move. I don't understand what is happening, it's like PWM value doesn't get updated or something. Here is my main file:

  #include <xc.h>
  #include <p30fxxxx.h>

 _FOSC(CSW_FSCM_OFF & XT_PLL4);
 _FWDT(WDT_OFF);
 _FBORPOR(MCLR_EN);

 void __attribute__((interrupt, no_auto_psv)) _T3Interrupt(void)
 {
   TMR3 = 0;
   IFS0bits.T3IF = 0;
 }

 int main(void)
 {
   ADPCFG = 0b1111111111111111; // all pins as digital
   initPWM()

   delay_ms(1000); // 1s delay
   while(1)
   {
     for(i = 0; i < 20; i++)
     {
       OC2RS = 250; // to the left
     }
     delay_ms(200);
     for(i = 0; i < 20; i++)
     {
       OC2RS = 658; // to the right
     }
   }
   return 0;
 }

That part above is not working, but when i do it like this it works:

 while(1)
 {
   OC2R = 0
   OC2RS = 250;
   OC2R = 0;
   OC2RS = 658;
 }

But after it does left to right it stops and that's all. I don't know what am I missing. Someone please explain it to me what is happening and why?


texts: How to switch light on by standing on a mat

texts:
I'm working on a project for school. And I have this dance matt. As long as you stand on that matt the light should go on and stay on until you step off the matt again. But I have no idea how to make this.

My teacher says I have to buy a lamp with a remote control and take that apart. But what should I get out of it to make sure it will do what I want?


texts: Get rid of the AC 50Hz noise from circuit

texts:
I made a bread board, this board is intended to measure AC 50Hz signal from sub uV to hunderds of mVs. The entire system is floating, powered from a voltage transformer. The front end is like this, P1 is a BNC connector, and cascaded PGA204 and PGA205 to amplify the signal, and with a 100Hz active low-pass filter following (the filter gain about 2.5, not shown), all my resistors (including the ones used in the active filter) are 0.1% metal-film resistors:

This is the PCB

I noticed yesterday when i shorted the input and probe the amplified signal with 1mV/div with gain x1, the output of the signal is this

When i change the gain to x100, this signal is like this. It seems the noise referred to input about 2uV

When i put my finger near to the Op Amp (used in the active filter) or the input resistor, about 3cm or so, the output is this

And, when i touch the resistor or the Opamp, this situation is worse.

I'v never noticed this situation before. It's apparent there some AC power line noise coupled into the circuit, i want to know

It's this 'normal'?
I wonder if my front end design has some problem, is it ok to use the 'bulk' metal-film resistor?
If the resistor usage is ok, what about my PCB layout, what should i do to minimize the noise.
Are there some 'all-in-one' solution to get rid of the noise?


texts:
So, I have the Stellaris Card from Texas Instruments. I am trying to make a digital output to be an interrupt service. So basically I have a LED on my breadboard that is connected to the card.
Is there a way that I can use this to use digital output as an interrupt source?


texts:
I'm designing a battery holder pcb for 4 18650 Lithium Batteries in series with max output 15A.
The board has 2 layers. The bottom is just a GND pour. On the right there is the "battery pack out" terminal and the balance connector.
I am not sure, if I should use a dedicated polygon for GND pin of the battery pack on the top layer, so that:

the current is guided to the best path and does not follow narrower paths (see green arrows in second image), which would heat up
this GND noisy path (due to high current) stays a bit isolated from the balance connector traces

As first option I've created the design below, where the GND polygon (marked yellow) is separate but not isolated from the surrounding not-high-current GND pour, thanks to vias going to the bottom layer (GND); the vias are placed away from the current shortest path:

The second option (below), is just a ground pour also on the top layer:

Which one is the best? Or maybe there are better alternatives, like no ground pours at all?
Schematic:

Thanks


texts: I ran a 3D gain plot for patch antenna but the result looks truncated. Did I mess up the sweep angles? The theta and phi?

texts: I have been stuck on this for long, using HFSS by the way.