texts: Solder sticks to PCB (not just the pads!)

texts:
I'm having a severe problem with solder adhering to the FR4 PCB material. I made my boards (myself, my first time) using positive developer and etchant on a pre-sensitized board. I washed the etchant off with nail polish remover.

It's so bad, I can take the iron and "paint" solder on the board. Flux (kester flux) doesn't seem to help at all. I don't know why this is happening or how to rectify it; searches on google only turn up page after page of people who just don't know how to solder (i.e., "solder won't stick to board."

Any advice or insight is extremely welcome.

I scoured it per the advice given below, and to my surprise, the "PCB" came off and revealed that even though I could see all my traces, the whole thing appeared to be copper. Considering I tried to follow instructions to a T, what could have gone wrong here and how do I fix it (or fix it on the next board)?


texts:
Latency comparison between the addition of dependent modules vs independent modules?

For example, a 32-bit adder made up of thirty-two 1-bit adders. Each 1-bit adder calculation depends on the previous adder for the Cin value. Thus, the adder modules in this component are dependent of each other. Obviously, adding additional dependent 1-bit adders into this component would increase the overall latency (delay from input to output) of the component.

What about a component with independent modules?

For example a 32-bit 2-to-1 MUX made up of thirty-two 1-bit 2-to-1 MUXes. Each 1-bit 2-to-1 MUX only needs 1-bit from the 32-bit inputs. Thus, the modules are independent from each other.

Would adding additional independent 1-bit 2-to-1 MUXes into this component increase the overall latency? If so, would the latency be less than equally-complex dependent modules?


texts: Step potential (or voltage) near electric power lines

texts: I am not familiar with these topics, and my question is related to this one: Can a high voltage line kill a person without touching it?. In school I heard about step potential, which as far as I understand is essentially the potential difference between the feet of a human in an inhomogeneous electrical field (the example used lightning rod in the instant of a lightning stroke it causing a high current rushing through it). I am not sure if I explained it correctly, but if I did, then my question is: does this phenomena pose a danger around electric power lines? (By the way our teacher told us that the best we can do in such an electric field is to close our legs so our heels are touching each other.)


texts: Why is a toroid most often used as the top load on a Tesla coil?

texts:
For the Tesla coil that I've built, I'm using a hollow metal sphere as the top (capacitive) load for the secondary circuit. But more often you'll see a hollow metal toroid used.

I'm getting streamers about 2 ft. in length from my coil now using the sphere. Could I expect to see better performance (even larger streamers) by using a toroid? And if so, why?


texts: Is it possible to import altium libraries all at once

texts: I am trying to setup my own library folder without using the altium 365 or the vault feature. Is there a way I can install all the intlib/pcblibs+schlib all at once or make it part of a project template? Without needing to go through every folder and installing it manually every time


texts: High quality, low-noise, pre-amp circuit for condenser microphone (with phantom power)?

texts:
EDIT

Suggestions so far, and reference to another question indicate that a discrete FET based input stage, perhaps followed by a particular low-noise IC for a second stage, might be a good approach.
I have zero experience with FETs in analog situations, so any pointers (actual circuits make great pointers :) on that would be hugely appreciated.
Also, I'm still have no clue how to generate 48 Volts from what will probably be a 9 v battery, nor the best way to integrate that as phantom power on the input. On the latter part, I'm guessing a simple capacitor coupling would protect the input stage from the power voltage, but I suspect there are "thump" and noise considerations in all that too. Again, any guidance will be most welcome.

Mostly for the fun of it (i.e. I don't really care that I can probably buy this pre-made cheaper, but I do want to build something of high quality) I'd like to build a pre-amp for a condenser microphone.
My main criterion for this would be low noise, though the response should be reasonably flat out to 20 kHz (which is the upper band of the condenser mics I would use this with) and minimal distortion (yes, I realize those aren't really quantitative descriptions, but my pre-amp tinkering in the past (perhaps 30 years ago) suggest the latter two weren't the hard part, but the noise was always the bit that bugged me.
Of course, this needs 48 V phantom power, and I need to generate that too (which I've never done before, so that's very definitely a key part of this question).
Can anyone offer suggests for circuits? Or perhaps recommend a resource? Perhaps a book, website, whatever?


texts: Advice for 25-50 Mbit SPI lines - PCB design

texts:
I would like to ask some advice for my layout design.

I am working on a layout design. The designed PCB will be a Beaglebone Black (BBB) extension card. It is a four layer PCB with the following stack-up:

signal/GND
GND
Power
signal/GND.

On the circuit there will be four devices (SI8652) which are connected to the BBB with SPI interface. With this extension board, I want to reach approximately 25-50 MBit speed over the SPI. The SPI lines (SCLK, MISO, MOSI) are placed on one layer. No through hole or any vias on these traces. The four SPI devices are connected in a row. The SPI line's lengths are not matched.

And my question is: Will I have any problem with the speed? Do I need to do something with signal integrity? Do I need termination resistors, filter capacitors... and so on for the SPI lines?

UPDATE:

Any advice is welcomed!

Thanks.

UPDATE:
It is working well at around 35-40MHz SPI clock speed.


texts: Silk to Solder. Design rules error in altium

texts:
I was just wondering if an overlap of the silk and the solder was bad for the manufacturing, will it cause circuit cut out on the traces? example:

All my error are always clearance problems related to silk and solder. Is it that important?


texts: Is there a guide how to identify connectors?

texts:
I have a couple of connectors which I like to identify. Most of them are on my motorcycle.

This forum contains lots of questions about individual connectors and I don't want to add another one. There must be a professional way how to identify connectors. But how?

In the moment I start with this page
https://www.digikey.com/en/resources/connectors/index
and then I go down to the details.

Sometimes that works fine, but often there are still a couple of choices which look almost the same.

And sometimes that company just does not have the connector I am looking for. And then?

Is there are clear practical way step by step how to identify any connector?

Edit: Maybe I should ask as part of this question if it is possible at all to do this. Do (motorcycle) manufacturer use existing connectors? Or do they (often) have their unique connectors which can't be bought anywhere else?


texts: How to identify the circuit has negative feedback or positive feedback?

texts:
I am having difficulty in identifying whether feedback is negative or positive (i'm not talking about feedback topology)

My teacher told that there is a method in which, after deactivating independent sources, we break the loop and move from that breaking point around the loop, then and return to it after traversing some path.  This allows us to determine the loop gain

He says that we can break it at any point that we wish but he always breaks it on Opamp's output.  He said that is for convenience without giving reason; in his demonstrations he always moves from output to input to output.

If the calculated loop gain is negative then the circuit has negative feedback.  If the calculated loop gain is zero zero then the circuit has zero feedback.  If the calculated loop gain is positive then the circuit has positive feedback.

After that  he gave some examples (in all examples there was at least one op amp present).  But I want to know: does this method only work for op amps, and if it not works for all circuits then why not?

Please give me insight into intuition behind such method.  Sorry for the long question

thank you for  answering


texts: Running a 3ph motor rated for 380v star on 220v delta

texts:
I've got an old Soviet 4kW motor, made in 1983. The dilemma is that the nameplate info states a Y-connection/380v/8.7amps and I want to run it on delta using my VFD which produces 3ph 220v. All my other motors are rated for both 220v delta & 380v star and I've never had a situation like this, so I was wondering what are the dangers of running a motor on delta if that's not specified?

Thank you in advance.


texts: Can LED Driver chips drive the LED with continuous ON DIMMING?

texts:
I am assigned with the design of a LED driver with 1 A current and 5 V system power. The customer wants to control all the LEDs with simple switches, nothing digital is involved. So I am thinking of using this LED driver:

http://www.monolithicpower.com/DesktopModules/DocumentManage/API/Document/getDocument?id=66

I thought that if I apply 5V system supply to EN/DIM pin via a switch I can get a constant continuous current(1A). And when the switch is OFF, LED will turn off.

These are diagrams in the datasheet also:

And here is the description for EN/DIM pin:

On/Off Control Input and Dimming Command Input. A voltage greater than 0.7V will turn on
the chip. When the EN/DIM pin voltage (with respect to INGND) rises from 0.7V to 1.4V, the
LED current will change from 0% to 100% of the maximum LED current. To use PWM
dimming, apply a 100Hz to 1kHz square wave signal with amplitude greater than 1.4V to this
pin.

So I am a little confused. I thought Analog dimming was the thing I was up to. However, in pin description, it says apply 100Hz to 1KHz square signal. So question is simple as this. Do I get constant Current for over half hour if I apply constant 5V to EN/DIM pin, or it does not work that way?


texts: This is a general question. I have a specific task that I am working on. For this task, my solution requires around 300 multiplexers with all of them 16 inputs and 16 bits per input, and a single output. Naturally, at the end of the line I also need 300 demultiplexers obviously. Is this just too much? I am basically trying to find an easy, clean and non-demanding way to route some wide signals in VHDL.


texts: Multiplication of average voltage and current?

texts: Multiplication of \$V_{rms}\$ and \$I_{rms}\$ gives average power. What things we get if we multiply \$V_{avg}\$ and \$I_{avg}\$??


texts: Where does JTAGSEL connect to on a JTAG header?

texts:
I'm busy working on a PCB design for an Atmel SAM3S ARM chip. The following image is a screenshot of the JTAG 20 pin header schematic:

On the CPU, there's a pin for JTAGSEL, and looking through the 1000 page datasheet, I'm not entirely sure where this connects to on the JTAG header?

Am I completely mistaken, is this a signal that gets pulled high/low to select between JTAG/SWD?

Can anyone shed some light?


texts:
I have the following question that I can't seem to figure out. The question ask to solve for the impedance of a 3ph transmission line. I've found the De (distance relative distance) and XL using the formula (u/2pi)*ln(De/GMR) and converted the unit. However, when it comes to the last step, this is where I went wrong (not sure if it is me or the answer key).

To find Z, I did
            Z = 10 mi *(Rac + jXL). From the table, Rac at 20C is .0693 (ohms/1000ft). When I converted it over to (ohms/mi), my Z = 3.65+6.21j

The solution used the Rdc but I thought this is a 3ph 60hz which is AC. Why are they using Rdc value from the table to solve for Z?? Please explain.


texts: How to deal with D+ and D- on the end of a device that will be charged only?

texts:
This is the opposite of the question posted here:

What is the ideal way to handle data pins D+ and D- on a USB power adapter to be compatible with fast charging on devices?

While that question is focused on how to design a charging port so that devices will be charged from it, I'm curious about designing an end device that I want to be charged with maximum current from all potential ports, if I don't need to use the data ports of the USB for anything else.

My device has a Li-Ion IC that self limits and can charge my Li-Ion battery up to 2A.  How do I tell chargers to give as much current as they can?  If I short D+ and D- on my board, I will appear as a dedicated charging port.  Does that mean that wall outlets will give 1.5A or more if they can, and that laptop hubs or other sources may limit out at 500 mA?  Is there any chance of a proprietary charger requiring something else other than D+ and D- being shorted in order to maximize charge current?

Edit:

I'm looking to make my own variant of this PCB from Adafruit.  While the part is made to only supply up to 500 mA (despite the schematic labeling), I want to make a version that can charge a 4,000 mAh battery at 0.5C.  I also want to remove the USB connection to the AtMega so it can't be reprogrammed.

So take the BQ2425 series for example.  I know this is also a "power management" chip which also takes care of regulation in addition to battery charging.  But there aren't any equivalent MCP73831 chips I could find that do simple battery charging, just with a higher current.

The point still stands though.  If my USB is meant to sometimes pull 2A if the chip is charging, or much less if it's fully charged and maybe just powering the MCU, what do I so with the USB D+ and D- lines on my PCB?  Already the two answers I've gotten don't agree, one says short them and one says leave them open.


texts: I have an Arduino UNO r3 and powering it up with 9v battery. But arduino run strangely (led 13 won't turn up correctly), how could this be?


texts: Best method for trasmitting multiple video feeds at once via Bluetooth or WiFi?

texts:
If I want to transmit several video feeds via Bluetooth or WiFi what would be the best method to do so in order to save on bandwidth, increase speed, and maintain quality?

I wanted to know what is the best method for doing so when using a microcontroller on a builtin PCB, not a PC.


texts: Measuring the rotation angle of stepper motor

texts: I have a hc-sr04 ultrasonic sensor. I am considering to put this sensor on a board which rotates by stepper motor. Sensor starts to rotate and detect an object during this rotation. Is there a way that I can measure the rotation angle of the stepper motor? Or can I get the number of steps that stepper turns after detection? Microcontroller is ARDUINO UNO. I read some answers about this topic but it is not clear yet.


texts: What are essential prime implicants in this example?

texts:
F(A,B,C,D) = Sum (0,2,3,5,7,8,9,10,11,13,15).

The prime implicants are represented in different colours as below and the equation of the function is found to be F = B'D' + BD + CD + AB'.

I tried to identify all the essential prime implicants (epi) and all the terms which made them epi.

Can you tell me if I found all the terms and epi?

1st epi: B'D'

Terms that made B'D' epi: 0,2

2nd epi: BD

Terms that made BD epi: 5

3rd epi: CD

Terms that made CD epi: 3


texts: How to make Microcontroller enter into ISP mode

texts:
I am using P89LPC954 micro-controller from NXP.

In the user manual it was mentioned that microcontroller comes with inbuilt    firmware from the factory which is required for entering into ISP mode.
But when i tried to load hex file using chip prog programmer it's not able to load the file into microcontroller(in ISP mode).
My friend suggested that these microcontrollers must be programmed for the first time using parallel programmer and then on wards we will be able to program using ISP mode(chip prog). It worked well.
As manufacturer claims it has inbuilt firmware to use ISP directly why do i need to use the parallel programmer for the first time

Could someone find anything which i'm missing to get the MCU into ISP mode.

Note: HEX file programmed through parallel programmer contains both application code as well as firmware code included as a assembly file.


texts:
I have a very, very simple requirement for a bluetooth module/Arduino solution.  I want to periodically scan for and report the device ID for any bluetooth devices present.  Actual logic regarding further identification of devices would occur downstream.  I believe that even SDP is overkill for this application.

In very simple terms, I want to use this information to inform my home automation solution whether or not certain individuals are home.

I'm quite comfortable with Arduino development and interfacing with hardware; have done extensive work with XBee and other RF devices, but have little practical experience with bluetooth development.

My question is this: is this as trivial an implementation as I'm assuming it will be?  Should most bluetooth modules available be capable of supporting this requirement?  Does anyone have suggestions regarding a specific module which would be a good fit?  I'm looking for the lowest-cost solution possible, as most available bluetooth modules seem to be massive overkill for this problem.


texts:
I'm trying to implement this formula :

$$
output = \sum_{i=0}^{N-1} (input[i] ~~ \text{xor} ~~ input[N - i - 1]) ~~ \times ~~ 2^i
$$

The input has \$ N \$ bits and the output has \$ S = N/2 \$ bits.

This is what I have:

library IEEE;
use ieee.numeric_std.all;
use IEEE.STD_LOGIC_1164.all;
use ieee.std_logic_unsigned.all;

entity eq is
    generic (
        N : positive := 4;
        S : positive := 2
    );
    port (
        I : in std_logic_vector(N-1 downto 0);
        O : out std_logic_vector(S-1 downto 0)
    );
end eq;

architecture arch of eq is
begin
    process (I)
        variable total : integer;
        variable temp : std_logic_vector(S-1 downto 0);
        variable zeros : std_logic_vector(0 to S-2) := (others => '0');
    begin
        for k in 0 to N-1 loop
            -- do the xor operation first and store the bit at the end of an std_logic_vector of total length S
            temp := zeros & (I(k) xor I(N-k-1));
            -- multiply the above std_logic vector by 2^i, convert to integer and add to the total
            total := total + to_integer(unsigned(shift_left(unsigned(temp),k)));
            end loop;
    O <= std_logic_vector(to_unsigned(total,S));
    end process;
end arch;

I keep getting type conversion messages. It throws this on the line with total := total + ...:

  Error: Near std_logic_vector ; type conversion expression type cannot be determined uniquely

When I try to fix a particular type conversion, another one pops up.


texts: Pull-down resistor value for FSR's voltage divider circuit connected to Arduino

texts: I am working on a project which includes two FSRs (force sensitive resistors) connected to an Arduino Uno. I have each FSR setup as in http://www.instructables.com/id/FSR-Tutorial/?ALLSTEPS, but each FSR is connected to a different analog In pin. My question regards the value of the pull-down resistor in the voltage divider circuit. In any tutorial I have found online a 10k resistor is recommended but I'm not sure why. I have a feeling its to do with the FSR's sensitivity but havnt found an explanation anywhere.


texts:
I'm trying to configure an XBee with the X-CTU tool using Wine. I followed the steps given in this tutorial.

I plug the USB in and check the kernel logs to see on which serial
devices it has been attached:

userk@dopamine:~/Programs/Matlab/bin$ dmesg | grep 'FTDI USB Serial
Device converter now attached'
[474.287844] usb 3-4: FTDI USB Serial Device converter now attached to
ttyUSB0

So the XBee is connected to /dev/ttyUSB0.

Then I create the corresponding softlink with: (this might be the problem)

ln -s /dev/ttyUSB0 ~/.wine/dosdevices/com5

I open X-CTU Add the COM5 port and click the Test Query button but the following window appears:

I don't have any reset button on the explorer board I'm using to connect the Xbee to the PC.
It's probably a mapping problem between the linux dev files and the wine com ports. This process works on Windows, but I prefer to use Ubuntu...
Do you guys have any advice?


texts:
I'm looking for a small, 32KB or so SRAM device that two MCUs can read or write (at two different times; I don't need simultaneous reading/writing.) It would be good if it used a serial interface as well.

The problem I'm trying to solve is sending data between two devices without the other device having to pause to receive this. I would transfer an audio sample into the buffer, then the other chip, as required, would read the audio out, and do something with it.

I've found serial SRAM's like Microchip's 23A256/23K256, however, they seem to have a single serial interface. Is there any way to have two chips accessing this?

Additionally, the receiving device only has 2KB data memory free (maximum) so it looks like using DMA or some similar transfer mechanism through I2C or other interface will not work.


texts: Limiting NFC distance between reader and tag

texts:
I plan to do a PCB with an MCU and it will include one NCF reader IC + PCB antenna in the same board. I have pre-selected one of the following ICs:

Texas TRF7970A: https://media.digikey.com/pdf/Data%20Sheets/Texas%20Instruments%20PDFs/TRF7970A.pdf

or

ST CR95HF: https://www.st.com/content/ccc/resource/technical/document/datasheet/d2/cc/cb/f6/7c/63/48/75/DM00025644.pdf/files/DM00025644.pdf/jcr:content/translations/en.DM00025644.pdf

Both ICs support ISO-14443 and ISO-15693. According to Wikipedia, ISO-15693 specify a maximum read distance of 1 to 1.5 meters.

My application is an electronic lock for doors and, for security reasons, I would like my NFC reader IC could read the tags only within a little distance range, at around 15 centimeters (~6 inches) of maximum distance. Is this possible?

My board is to be an active NFC reader that will read and external passive tag.

Or will I need another solution for NFC reader IC to reach such maximum distance?

EDIT: I want the reader IC to be able to read/write external tags, and also with the smartphone via NFC.


texts: Power factor correction for LED lighting on a generator

texts:
I'm the electrician for a club that builds an illuminated carnival parade float, and historically we've lit our float using around 10,000 x 40w incandesant lamps powered by a 800kVA 3 phase generator.

Times are changing, and you can no longer buy 40w incandesant lamps easily anymore, and the cost of diesel and generator hire is expensive, so I want to look at using LED lamps instead.

Due to cost, it's really only viable for me to buy very cheap LED B22 lamps from China, with a basic built-in power supply with a poor power factor.

Wiring up a purely resistive system was easy, but I'm struggling to understand and research how to do this correctly without causing a high current in the neutral.

To balance the system, I've heard that I need to either add a resistive dummy load to each phase, or use a power factor correction capacitor, but I don't know how to calculate the size/rating of these.

Can anyone point me in the right direction or explain how to do this?


texts: What's wrong with my1943/5200 Mosfet Amplifier? Blown on first run

texts:
I have just brought an 1943/5200 mosfet based amplifier board. Shopkeeper said it's rated for 24-0-24 AC.

So I connected it with 24-0-24 transformer like this in image below.

As soon as I turned the power supply, I heard a loud hum from transformer, Like it was on full load. and few seconds later cap. on left side blown.
(I have also got a loud noise from my speakers also like I have passed 24VAC through em.)

I have no Idea why this happened. Did I made some mistake?
Is circuit is actuality meant for 24-0-24 DC?
What now? can I still revive my circuit? What are the components which might have died in the process? are my mosfet's are still okay?


texts:
Can anyone please explain me the working of the circuit attached?
I believe the op-amp U1 is connected to provide a stable DC voltage at the non inverting terminal of U3. Is my approach correct?
The circuit is able to source a stable DC current of 50uA.
However the first challenge is to reduce the output current to levels of about 6nA and 6uA.I was able to get around 6uA while tuning some components randomly.
However I am not aware about the effects.
What tuning should I target in order to get the same?
Second challenge is to obtain a AC current out of the circuit. The frequency can be around 30 Hz.
Can I use an op-amp based oscillator instead of VG1 to get the variable frequency current source?
If yes, can someone please guide me for the same?
The input voltage VG1 is 2V DC in this case to obtain 50uA.
I know the current required is very less considering the noise that will be induced in the system. However is it even possible using op-amps or do I need to start looking for some other solution?


texts:
Many cables have multiple grounds.  Why?

For example, according to Wikipedia:

  The SATA standard defines a data cable with seven conductors (3 grounds and 4 active data lines in two pairs) and 8 mm wide wafer connectors on each end.

In general (not specific to SATA), why do cables need multiple grounds?  Are there different reasons for multiple grounds when cables are used to transmit data vs. power?

From what I've read, it sounds like one of the main reasons to have multiple grounds is to lower impedance... but why is low impedance so critical for a ground line?


texts: What's this yellowish stuff on this PCB?

texts:
I took this op-amp IC out of an electronics kit. It's on a PCB and soldered to some longer leads. There's some yellow/brown goo on the back of the board, and I'm not sure what it is.

You can see it in a stripe through the middle, and partially covering some solder joints:

I can scratch it with my fingernail, and it feels kind of like rubbery plastic, much like hardened glue.

What is it? Will it interfere with soldering/desoldering?


texts:
Lets say we have an MCU with 10/100Base-T MAC support and we would like to communicate with the 1000Base-X SERDES backplane. How can we do that? Does PHY ICs make an upconversion?

Best.


texts: Measure current of 51 kHz signal and ideas for increasing range of AM signal

texts:
I have built the following circuit:

I got it from http://www.discovercircuits.com/PDF-FILES/PIPEFINDER1.pdf
It works Ok and generates around 520 kHz in the wire, but I have some questions.
I measured the current through the 'wire' to be around 20 mA which is obliviously a long way from 9/100 = 90mA why the difference? The few ohms of the MOSFET on resistance can't account for that difference. Can 520 kHz current be measured with a multimeter to give an approximate current?
I would like to boost the signal power as I can only detect well from a couple of feet.
I thought I could increase the current to around 180mA as the MOSFET can cope with 200mA.
Any other suggestions for increasing range?
I am using thin speaker cable for the wire (I un-twisted the internal cables) but perhaps coax would be better or would it be worst because of shielding effects?


texts: Optimal Breaker Configuration for Split Phase Mains Power

texts:
First, let me preface this by saying this is entirely theoretical. I don't plan to install anything myself, and I'll contract a licensed electrician to do any of this work, so please don't feel the need to post warnings, disclaimers, or otherwise explain the dangers of mains electricity.

Given that, I have learned that my utility company provides 240V to the meter at my house. There is a breaker box immediately downstream of the meter, and it services 100A at 120V (so it becomes split-phase at some point). After a bit of conduit, I have my current breaker panel, with its circuits going off into the house.

Assuming that I am correct in that there is a center-tapped transformer stepping the meter voltage down to 120V from 240V and, therefore, provides two phases (we'll call them "Phase 1" and "Phase 2"), this means I have 240V, Phase 1 120V, and Phase 2 120V available to me, even though I am only using Phase 1 120V.

I want to have three total breaker panels, one for each Phase 1 and 2, and 240V, but there is also that 100A breaker immediately following the meter to deal with.

My question is, what is the best way (schematically) to install 300A (I can get up to 320 from the meter without an upgrade) of breaker to protect all three circuits?

My current thought is that I would need a 300A breaker on the Phase 1 hot wire and a 300A on the Phase 2 hot wire. Is this correct, or is there a simpler/better way to arrange this?


texts:
This if a fairly simple question. I have some APT43M60L MOSFETs with a fairly high on resistance. They get quite hot and waste a lot of power in my induction heater. They work great but get really hot really quick.  I tried IRFP250M MOSFETs, they also worked great, but I just needed a little more power.

We all know that putting 2 identical (or near identical) resistors in parallel halve the resistance. For example, two 1k resistors in parallel would make 500 Ohms.

So does this concept apply to parallel MOSFETs? Could I simply put 2 of these APT43 MOSFETs in parallel to lower the on resistance without any drawbacks?


texts: Programming 16F84A With K8048 software & a custom Hardware (With CH340 USB2Ser)

texts:
After reading Manoj's Work about how to program some PICs with USB to Serial Adapter, I decided to try myself to program the 16F84A with my CH340 USB-SERIAL adapter
Materials :
Software : Cygwin + K8048 Pic Programming software designed by Darron Broad & used with Velleman PIC programmers.
I wrote a Configuration file  .k8048 with this parameters relating to my hardware:

DEVICE = /dev/ttyS0
SLEEP = 6000
BITRULES = PGD_IN_FLIP | PGC_OUT_FLIP | PGD_IN_PULLUP
BUSY=0

My Custom hardware:

 CH340 USB to Serial Adapter : Support BREAK + CMOS levels (0v - 3.5V) -->for this reason I used a bidirectional level shifter on DATA (DTR) line.

Problem: When I use this with 16F84A the software returns Device not detected.
I checked all the pins one by one separately, all work fine.


texts:
I have an Arduino controlling a NEMA 23 motor using a digital stepping driver (DM542T).

I am trying to have it go a a given speed in RPM (60), but when I try it results in a very jerky movement of the motor that does not go at the expected RMP

Here is my Arduino code:

int driverPUL = 7;    // Pulse pin
int driverDIR = 7;    // Direection pin

int stepsPerTurn = 200;
int RPM = 60;
float stepsPerSecond = (stepsPerTurn*RPM)/60;
float waitInMilliseconds = (1/stepsneededPerSecond)*1000;

void setup() {
  pinMode (driverPUL, OUTPUT);
  pinMode (driverDIR, OUTPUT);
}

void loop() {
    digitalWrite(driverPUL,HIGH);
    delay(wait);
    digitalWrite(driverPUL,LOW);
}

In the  motor documentation I have the following table but I'm not sure what impulse/turn means.

EDIT

Here is the DM542T settings, it is configured to the 4.20 A and 400 Pulse/rec settings.

Any help would be welcome,


texts: Common voltage of 2 op amps instrumentation amplifier

texts:
I am trying to build an amplifier for a strain gauge sensor using the 2 op amps instrumentation amplifier design provided in the Texas Instruments note: https://www.ti.com/lit/an/sboa247/sboa247.pdf?ts=1605266073942&ref_url=https%253A%252F%252Fwww.google.com%252F.

I was able to derivate the expression for voltage gain of the amplifier, but I have troubles understanding the expression for the common voltage gain and also why the total resistance of the bridge is 4 X 120.

Can someone provide an explanation for my dilemmas regarding the common mode voltage of this amplifier design? I appreciate your help!


texts: 3.3V to 5V logic converter using p-channel mosfet

texts: I am trying to convert a 3.3V logic signal to 5V logic signal. I am using a p-channel MOSFET and I can not get it to send the full 5V signal through. Below is the circuit I am using.


texts: Running a 12V PWM Water pump on a 5V fan output with tacho input

texts:
So on my 3D printer from Prusa they use 5V fans and monitor the fans by the tacho signal.

I want to replace the hotend with a water cooled version and still want to have the safety feature to turn off the hotend heater when the fan is not running. Well, in my case the water pump.

The water pump is a 3pin water pump as used for PC water cooling running on 12V.

So 2 problems I have to solve, one is the difference in power for the fan voltage and the 2nd is the difference in voltage for the tacho signal.

The idea I have is to use a DC-DC step down module to convert the printer main power 24V to 12V. Then use a MosFET to use the 5V power output from the printer to switch the 12V with the MosFET.

For the tacho signal I was thinking of a simple resistor with Zener diode to convert the 12V signal to a 5V (5.1V to be exact) signal for the printer input.

Has anybody a better idea?

Maybe with diagram and recommendations for the parts?


texts: Is there anyone who understand this symbol of Jetson nano based board schematics?

texts:
I am reading schematics of Jetson nano based board, that contains some symbols I have never seen before. Is there anyone understand this symbols?

you can find full schematics here: https://github.com/antmicro/jetson-nano-baseboard


texts:
I am designing an amplifier circuit using TDA2030A, but now I am stuck in providing power to the circuit. As mentioned in the datasheet, I copied single power supply circuit for my amp. But the simulation in proteus is showing an error if I just test the same single power supply circuit from the Datasheet, but if, I provide it a negative supply (split power mode), the simulation works.

Circuit similar to that in the datasheet for a single power supply. (Not working)

These are the two circuits from the datasheet. (I want single power supply)

I want to drive a 5W speaker, please tell me what I am doing wrong in the circuit.
secondly, is it good idea to transfer the second circuit (Proteus simulation) to the breadboard and check it.
If possible please tell me how can I provide a split power supply to it using only one 12V 2Amp adapter.
Thankyou


texts: When grounding conductors in electrostatic problems, is the reference point of electric potential defined at infinity or the ground?

texts:
I am confused about the meaning of 'grounding' in electrostatics. My textbook claims that any grounded conductor has zero electric potential, but it seems to me this claim can have two different meanings:

It is zero as the new reference point, which means 'grounding' is actually just a way to define a new reference point for the potential in the problem.
Infinity is still the reference point but any grounded conductor has zero potential in reference to infinity.

If it is the latter, how can this be proven? Why is it not possible to arrange distribution of charges around the grounded conductor in such a way that the work done by taking a unit charge from infinity to the conductor is not zero?


texts: How do I calculate how long my robot's battery will last?

texts:
I am building a robot with multiple types of sensors, 2 motors for locomotion, and 2 motors to control a robotic arm. I am using a variety of color, IR, tilt sensors and such.

How would I factor in all these components to determine a length of how long my battery will last?

Let's say I was using a 7.2 V/1600 mAh battery. How could I determine its length of life using the voltage and current of each component?  What calculations do I need to make?


texts:
I have a sensor that output signal values 5-15V. I wish to translate the given signal using op amp to 30-50V. Can u help me with the values of resistors and circuit diagram which shows sensor as well.
Is it necessary to use buffer circuit?


texts: Conflicting information on Qualcomm quick-charge 3.0 standard

texts:
Out of many fast charging protocols, Qualcomm quick-charge 1.0/2.0/3.0/4.0/4+ is a prominent one. I tried to find the specification of quick-charge 3.0 protocol.

However, the material spread across the Internet is conflicting and confusing.

Disagreement in max voltage, current, power:

Wikipedia: Max current: 2.6A or 4.6A, Max power: 18W (9V*2A), Voltage: 3.6V-20V, dynamic with 200 mV increments
Belkin: Max current: 2A or 3A, Max power: 36W, Voltage: 3.6V-12V
Qualcomm: Max current: 2.6A or 4.6A, Max voltage: 22V

Voltage levels:

Android Authority says,

  The major new feature with 3.0 is INOV (Intelligent Negotiation for
  Optimum Voltage), which allows for a fined tuned power output and a
  more optimized charging cycle. Firstly, different batteries require
  different charging voltages. Version 2.0 supported four modes at
  varying power levels, 5 volts/2amps, 9V/2A, 12V/1.67A, and a 20 volt
  option. Quick Charge 3.0’s INOV communicates with the device to
  request any voltage between 3.2V and 20V at 200mV increments, allowing
  for a wider selection of voltages.

The above sounds like there are numerous voltage levels supported in steps of 200mV between 3.2V and 20V. However, the specification of Mi India Standard Charger (MDY-08-EW), which is a Qualcomm quick-charge 3.0 certified charger, speaks something else:

  Output current: DC 5V=3A / 9V=2A / 12V=1.5A

It seems like the voltage levels are fixed, just like quick-charge 2.0 standard.

My questions/confusions regarding quick-charge 3.0 are:

Where do I get official Qualcomm quick-charge 3.0 standard specification?
Are the voltage levels fixed or stepped in 200mV?
What are corresponding current and power ratings?


texts:
I'm looking for more information on how to connect a panel mount switch to a PCB.

Switch Diagram:

I've read that it's generally bad to connect this kind of mechanical device directly to the PCB (since it's a more likely part to fail).

Since there won't be a panel for the device I'm trying to make, how can I attach it to the PCB in a sane way? This is just a hobby project that I want to have some switches for easier testing. It's not a critical component.

I've tried searching but I can't find something that fits this. Perhaps I'm using the wrong terminology.

Specific questions:

Should I use a "terminal block" for this purpose?
If so, what specifications should I look for? I think it's 3 pin, 7.1mm pitch, but I don't know what to do with the tab width of 4.8mm.
Am I just missing some alternative method that would be better for my purpose?


texts: Portable 12V power supply with UK AC output

texts:
I'm new to this community and starting with EE. I am trying to create a portable set of speakers using some old speakers with UK Plug.

Speakers Rating: 230V 50Hz 0.3A

My current understanding from some research is that I would need:

Battery box
1 sealed rechargeable battery
Auxiliary Socket
Power Inverter (UK W/ UK plug)
Switch

So the idea for wiring this would be:

Please ignore the messy wiring example.

Could anyone help confirm is this the way to do it ?

One more question... What connector do I use for this:

Thanks in advance!


texts:
I am a newbie in FPGA world, working out on Verilog these days. I have thought of a couple of Projects for my FinalYearProject at my college. One of them is Handheld Ebook Reader. Well, I will workout the other things required, what i am most concerned about is, How am i going to read a pdf file through FPGA.

Well, in the project, i will be interfacing a MicroSD card module with FPGA, the FPGA would read the file from pdf and would display it on LCD, interfacing with LCD wouldnt be a big problem as i have got a couple of good resources for that, interfacing the memory card module too. But the thought that has been troubling me in choosing this project is, how am I going to read PDF. I may work on the pdf which has texts only, i wont work on images, on the other hand if i plan to work on images as well, i will have to do a lot of work for several tasks, say for zooming in and others.
  Kindly help me on this.
  Plus, i am pretty keen about this task. Kindly tell me if this can be done more easily with microcontroller. I have a little bit of experience working with them.


texts: State space modeling with disturbances using Matlab

texts:
I am doing a project which involves modeling a quadcopter in state space form using matlab. I first had to linearize the quadcopter equations of motion, and now have to implement them in a matlab state space system.

In order to do this I need to put the linearized differential equations in this form:

$$
\dot{x} = Ax + Bu
$$
$$
y = Cx
$$

The issue I am having is that one of my state equations has a constant term because of acceleration due to gravity. The equation in question is shown below, with Vz, v1^2, v2^2, v3^2, and v4^2 all being state variables, and everything else constants:

$$
\dot{V_{z}} = -\frac{K_{d}}{m}V_{z} + \frac{KC_{m}}{m}(v_{1}^{2} + v_{2}^{2} + v_{3}^{2} + v_{4}^{2}) - g
$$

How am I supposed to accompany this term (-g) into matlab's state space model?

My only thought is to use the state space model with identifiable parameters, and include the constant in the disturbance matrix K, but I am unsure of how to go about that, never having used a disturbance matrix before.


texts: Measure small voltages in a high voltage circuit

texts:
I'm troubleshooting an oscilloscope where the cathode voltage is ca. -2000V respect to ground and chassis. There are parts of the circuit (eg. the heater filament, or the blanking / un-blanking circuit) which generate low voltages but they are connected to HV supply lines. Eg. the heater secondary is generating 6.3V in AC but one of the wires is connected to the -2000V to keep the voltage difference of the cathode and the filament within spec for the CRT.

How can I safely measure these low voltages (eg the 6.3V across the filament) within the high voltage circuit?

I have a CAT II 1000V multimeter and CAT III 1000V probes. I assume that the isolation they provide is not sufficient to safely measure in such an environment. If I understand correctly the rated voltage is not just for the voltage I want to measure but it's also a rating of isolation towards the "outer world". Meaning that even though the multimeter and the probes are floating at -2000V the isolation they provide is still rated at 1000V making them not suitable for such a measurement.  What options do I have?


texts: Closed Loop system with a second order dominated response on the verge of instability

texts:
I have the forward path transfer function of C(s)G(s) = K/s(s+3)(s+7) and want to find K so that it is second order dominated on the verge of instability.

But i'm not sure how to find it when it is on the verge of instability, the only thing i could see when researching was that maybe its when C is very high?

I also found K when (both being second order dominated) when critically damped (I set the damping ratio to 1) and got K = 14.577 and when underdamped with a natural frequency of 2 rad/s and got K = 17.

Any help will be greatly appreciated and sorry for the bad formatting.


texts: K-Type Thermocouple, Instrumentation Op-Amp and Arduino

texts:
I am Trying to read in a K-Type Thermocouple to a 0-5V Arduino Uno.

I Can read my Thermocouple directly using a Fluke meter on temperature setting giving me the correct value of 21°C, but when I switch to mV setting I read 0 mV on my Fluke.  Similarly on my Arduino I am reading 0mV or some garbage hits (0.3xx mV, 1.9xx mV) every 10 readings or so that I assume is noise.  My room is 70°F or 21°C so I expect to see 0.838mV according to the K-Type Thermocouple table

I have made a test load that produces 0-54mV

The INA121P Instrumentation Op-Amp works as expected giving a 50x gain on my test load when I use Rg = 1 kΩ resistor between pins 1 & 8.

So as stated before when I replace my test load with my K-Type Thermocouple, I read 0mV on Vo (expected should be 0.838 mV x 50 = 41.9 mV)

I have not included my Cold-Junction Tref in the Circuit yet, but I have my thermistor reading properly using the Steinhart-Hart equation in other tests.

In my code I will be dividing off the gain to get back to Vtc in mV.  I am using the K-Type Coefficients to curve fit my thermocouple.

My overall questions are:

Until I add my cold junction should I expect to be reading 0mV on my TC?
Answer:  Yes since TC and Tref are at the same Temp no differential occurs. Thanks @TimWescott
How can I get rid of the "noise" is 0.01 μF in the ballpark or should I change that value?
Would you recommend any changes to my approach?


texts:
in a device I have bought there is this potentiometer with switch:

It has 5 pins instead of 3 as a normal potentiometer: two of them are connected to VCC and GND, the other ones i do not know (there is not a schematic of that device).
Do you know the equivalent circuit of this potentiometer with switch? I need for it because I want to measure the voltage across one portion of the potentiometer while tuning it.


texts:
im having problems understanding the behavour of the hybrid parameter hre in the bjt AC model.
im using the pi equivalent circuit to simulate the relation between hre and Ic (Dc value). i am not considering Rb Rex Rc or Ccs so the model is simplify to al the remaining elements

my problem is that when comparing the graphic i obtain by simulating this equivalent circuit with the datasheet graph i dont understand why there is a change in the slope of the curve. im using the 2n3904 transistor parameters, down below i post the graph i obtain by aplying the gray meyer equations for the components values and the graph of the 2n3904 datasheet

im using the values of the spice models parameters that the datsheet of the 2n3904 provides as the data for my theorical model

Anyone has any idea whats effect is causing the change in slope? i could not find any information in electronics books or searching on the web

Sorry for my bad english
Cheers!


texts: Altium: keep out joins to through hole pads

texts:
I have a keep out on the bottom layer that covers a heat dissipation plane. I don't want traces here, as I want the plane to be effective at dissipating the heat.

Keep out main properties:

Restricted for Layer: Bottom Layer
Keepout Restrictions: Track

The issue is that I have a through hole component on this area, that is routed on the top layer. The keep out is preventing a clearance area around the THT pads, effectively shorting them to the plane.

Illustration of the issue:

As it is, it seems that the keepout creates a copper pad that is overlayed on the region, besides preventing the auto-router from entering it.

EDIT:

Curiously, in the 3D view the copper seems correctly managed, even with the keepout:

What happens is that the clearance area is there, but because the keepout is blue (placed on the bottom layer) you can't see it.

So, my question becomes: Doesn't the keepout participate in the bottom copper layer, despite the fact that it shows as blue?


texts: How to measure the output impedance of a Zener diode in avalanche?

texts:
I'm trying to measure (on the bench) the output impedance of this:-

simulate this circuit – Schematic created using CircuitLab

It's a Zener diode, and the applied voltage is sufficient to cause the avalanche effect.  The signal at the output looks like:-

which is a log normal distribution spanning about 3Vp-p.

My approach is to calculate the RMS voltage of the output, add a load resistor and then measure the difference in RMS values.  From that I can determine how much voltage is 'dropped' across the circuit's internal impedance by the current flowing through the load resistor. And thus obtain \$Z_{out}\$.

I don't have the RMS code yet so I can't try it, but is this the correct approach?

NB. Looking at the signal plot, 90% of the peaks are independent of each other.  There's only a slight correlation as the signal is almost pure white noise.  Is an RMS calculation even possible?


texts:
(source: next.gr)

I have the following question regarding this circuit:
How is the opto being used to trigger the base of the triac?The collector of the photo-transistor is connected to the base of the triac. As per my understanding of npn transistors, the current flows from collector to emitter. But in this case the collector has no power source attached to it. So how would this photo transistor provide a signal pulse to the base of the triac?


texts: What is the identity of this shiny insulator?

texts:
fig: Shiny layer

I've seen many times, on  metallic objects, a kind of insulator layer is given (I've tested its resistance with multimeter and it shows infinite ohms).

The layer is greenish-gold in overall color, but have colored patches that may vary from red to green.

It is seen on small transformers(above image), switches, fan-regulators, etc.

The layer change its color, and colored-bands shift their place when the parts get heated.

Now , what is the identity of this golden insulator? What is its resistivity and other characteristics?

And also, what is the identity of another, reddish-colored insulator used in electromagnetic coils? also, what is its resistivity and other characterisics


texts: 1 voltage regulator for all components or 1 voltage regulator for each component?

texts:
Is it a good idea to only put 1 5volts regulator to power all components or 1 5volts regulator for each component? If I only put 1 5volts regulator to power all the components would that affect, reduce or divide the 5 volts to power all the components?
The components that needs 5 volts power are ATMEGA328P, PCF8574P, 2x16 LCD Display, HX711, Load Cell, and 5 push buttons.


texts: How can I simulate in PSpice the model LM13700?

texts:
Hello to everyone and apologies if this question has been asked before, but I am searching more than an hour every time before I post.

I want to simulate the LM13700 Operational Transconductance Amplifier in PSpice. I downloaded the specific spice model from Texas Instruments. This is not the first time I implement a spice model to PSpice, so it is 100% done right.

The problem is the pin setup. The Spice model is one such Operational Amplifier and not two, as the model taken from the official datasheet.

More specifically, the spice model has 9 pins named (watch carefully the numbers close to the end) "1,2,3,4,5,6,7,8,11" without 9 or 10. There is no specification as to which pin is which in the datasheet.

The model in the datasheet, on the other hand, has 16 pins and it is specific as to which is which.

Is there any way to know what the pins do exactly just by looking in the spice model code? Thank you in advance.

Here is the complete spice model code:

.SUBCKT LM13700/NS  1 2 3 4 5 6 7 8 11
*
* Features:
* gm adjustable over 6 decades.
* Excellent gm linearity.
* Linearizing diodes.
* Wide supply range of +/-2V to +/-22V.
*
* Note:  This model is single-pole in nature and over-estimates
*       AC bandwidth and phase margin (stability) by over 2X.
*       Although refinement may be possible in the future, please
*       use benchtesting to finalize AC circuit design.
*
* Note: Model is for single device only and simulated
*       supply current is 1/2 of total device current.
*
******************************************************
*
C1  6  4  4.8P
C2  3  6  4.8P
* Output capacitor
C3  5  6  6.26P
D1  2  4  DX
D2  2  3  DX
D3  11 21 DX
D4  21 22 DX
D5  1  26 DX
D6  26 27 DX
D7  5  29 DX
D8  28 5  DX
D10 31 25 DX
* Clamp for -CMR
D11 28 25 DX
* Ios source
*
F1  4  3  POLY(1)   V6 1E-10 5.129E-2 -1.189E4 1.123E9
F2  11 5  V2        1.022
F3  25 6  V3        1.0
F4  5  6  V1        1.022
* Output impedance
F5  5  0  POLY(2)   V3 V7 0 0 0 0 1
G1  0  33 5         0 .55E-3
I1  11 6  300U
Q1  24 32 31        QX1
Q2  23 3  31        QX2
Q3  11 7  30        QZ
Q4  11 30 8         QY
V1  22 24 0V
V2  22 23 0V
V3  27 6  0V
V4  11 29 1.4
V5  28 6  1.2
V6  4  32 0V
V7  33 0  0V
.MODEL QX1 NPN (IS=5E-16     BF=200 NE=1.15 ISE=.63E-16 IKF=1E-2)
.MODEL QX2 NPN (IS=5.125E-16 BF=200 NE=1.15 ISE=.63E-16 IKF=1E-2)
.MODEL QY  NPN (IS=6E-15     BF=50)
.MODEL QZ  NPN (IS=5E-16     BF=266)
.MODEL DX  D   (IS=5E-16)
.ENDS


texts: Is it possible to remove the envelope from an LED "filament" bulb and still have it work? Are they in an atmosphere?


texts:
I have used the circuit below to switch between two power sources. The purpose was to have a backup power source once the other is switched off by a controller in the system.
While testing the operation of the circuit I have noticed that when one of the sources is ON (15V at VS1 for example) and the other is OFF (VS2) there is a voltage of(14V) at the anode of the OFF source schottky(VS2 in this case).
Could the reason for this be the diode parasitic capacitor charging through the reverse leakage current?


texts:
I am designing a photodiode sensor that will sit on a computer monitor and will output a +5V TTL signal if the screen is displaying and image and a 0V signal if the screen is not.  The prototype circuit that I built works almost as expected (schematic below).

Prototype Photodiode TTL Circuit

The one problem is that the signal when the screen is turned on transitions (drops to 0V and then back up to 5V) every ~4 milliseconds (I am only recording the TTL signal at 2kHz).  I tracked down the cause of this and the culprit seems to be the PWM for the LCD monitor back light.  If I turn the brightness of my screen all the way up the unwanted transitions go away and the signal is a pristine 5V for the duration of time that the image is on the screen.  Unfortunately looking at a monitor that is set at 100% brightness is unpleasant to say the least.  Since I only need accurate TTL onset I was thinking that modifying the circuit above to include an RC-debounce circuit should fix my problem.  I am wondering if the revised schematic (below) would work as drawn.  The reason for the different opamp is that I am laying out a board using SMT components and ordering from Mouser instead of using parts that I could find at Fry's (that have been on the shelf since 1970).  I am also aware that I have no bypass caps on my IC's and that my pinouts are a little wonky (figured I'd use actual circuit symbols instead of the rectangles that my eagle library has for the chips that I'm using).

Revised Photodiode TTL Circuit

The thought with this circuit is to replace the inverter with an OR gate and use an RC circuit to the other input of the OR gate.  The idea being when the photodiode is on that the OR gate's output will be high and the inverter's output will be low turning on the MOSFET and allowing the RC circuit to charge.  Then when the photdiode sees a monitor PWM event the inverters output goes high shutting off the MOSFET and allowing the RC to begin discharging.  This event also causes the OR gate input connected to the opamp to go low but the other OR gate input is high because it is tied to the discharging RC circuit keeping the output of the or gate high during the the monitors PWM events.  The output would only go low when the photodiode sees a sees the screen off for more then the RC time constant of my "debounce" circuit.

Am I missing anything? Will the circuit work as drawn?

EDIT:
The leading edge of the logic needs to be accurate (not delayed) but the falling edge can be delayed without affecting the use of the circuit.  The output of this circuit needs to go from low to high (when screen goes from black to white) in less than 0.5ms and needs to transition from high to low (white to black) in 10ms or less. This diagram hopefully shows what I'm trying to achieve

Actual is what I see, the transition in the middle of this line is what I am trying to get rid of.  I think the line marked acceptable is how the revised schematic would work.


texts: How to know if the generator is dissipating or generating power?

texts:
How do I determine whether current/voltage generator is generating or dissipating power. For voltage supply I'm quite sure it depends on current direction, if they are the same, then it's generating. Is it same for current generator, higher voltage on +, it's generating, else dissipating?

Edit: DC circuit.


texts:
I am routing a JTAG signals through an Altera FPGA to a TI MCU. The signals are TMS, TCK, TDO, TDI, nSRST.

I can also connect the JTAG directly to to the MCU as there is a 10 pin jtag header exposed on it.

If I route the signals TCK, TDI, TDO, nSRST through the FPGA and connect TMS directly to the TMS to the 10 pin jtag header on the MCU then it will flash the device.

However, if I route TMS through the FPGA the flashing fails.

I have analysed the TMS signals both through the FPGA and directly to the 10 pin header on the MCU and both look equally nosiy.

Would anyone know any properties of the FPGA that would contribute to this error.

Also could anybody suggestion a solution. Would latching the signal work and if so could anybody explain this in further detail.


texts: PIC 18F: Can A/D (+) Reference voltage exceed Vdd?

texts:
I am considering using Pololu's P-Star 25K50 dev board for some simple LiPo cell testers.

This board is a complete system with on-board voltage regulator, USB micro-B jack and the Microchip PIC 18F25K50 microcontroller.  Most of the pins on the controller are brought out to pads along the edge of the board.

Because this board offers USB connectivity, I am considering using USB to power the board.  That means that the controller Vdd might be in the range of 4.8V to about 5V.  Total system current is expected to be only 1mA or so above the current consumed by the micro.

Because I want to measure single LiPo cells, I need the analog inputs to be able to handle input voltages of somewhat more than 4.2V.  The micro has several available analog-capable channels multiplexed into a single 10-bit A/D converter.

I'd like to use an external 5.12V reference that feeds the A/D converter's (+) Reference input.  This will give me nice, human-readable voltages with 5.0mV resolution.

With previous projects (not involving USB), I simply powered the entire microcontroller from a buffered copy of the 5.12V reference, then fed the reference itself into the A/D (+) Reference input.  That's not as easy with this board.

I'm wondering if it is possible to power the micro from about 5V but have the A/D (+) Reference sitting about 120mV above that rail - and have the A/D converter function correctly.

The datasheet (DS30000684B) is completely lacking this information - there is no guidance as to the limits on the reference voltage other than to say that the voltage on any pin should not be higher than 0.6V above Vdd.


texts: Current measurement on low resistance sources

texts:
Most of the devices to measure current at micro amps level or lower recommend a input resistance of more than 1kOhms.
(As for an example , shorting the ammeter leads, which is essentially what happens on connecting the low resistance source, produces noise in 0.5 mA range)

How do we measure current from sources which have very low resistances?


texts:
I'm using a BM2S, i.e. Battery Manager board for 2 18650 li-ion batteries in series. This tiny board uses 2 FS8205A FETs for current/voltage upper/lower limits as a protection (board: http://www.ebay.com/itm/2S-3A-Li-ion-Lithium-Battery-18650-Charger-Protection-Board-7-4V-8-4V-HM-/401019234956 datasheet: http://www.ic-fortune.com/upload/Download/FS8205A-DS-12_EN.pdf).

So I connected this board to my 2 18650 batteries, the output is connected to a voltage reg. LT1529CT set to have an output of 6.2V.

The output of the LT1529CT is connected to a LED driver with 3 modes which draw 30mA, 110mA and 250mA.

The thing is that when I remove one of the 18650 from the battery holder and put it back the LEDs remain off until I (accidentally) create a temporary continuity between pins D12 and S1 of one of the FETs, then LEDs come on as expected.

Can someone explain that to me and give me an advice on how to make the LEDs come on event after replacing the batteries?


texts:
I had to charge my car battery two days ago. I used another car's battery to do so.

I accidentally reversed polarities (+ with -) and vice verse. There were very strong sparks.

I was trying to understand the reason behind it mathematically, but I couldn't find any

reason behind this behavior online.


texts: Why Air Conditioner's voltage stabilizer shows bizarre approach to the desired voltage?

texts:
I've been observing my Air Conditioner's voltage stabilizer for many days  and I saw a bizarre pattern .Our country has standard lines of 220 VAC AT 50 Hz
Now since few days we've been experienceing voltage drops down occasionally to 170 and mostly stays at 190 to 195

Now the way voltage stabilizer approaches the 220 VAC seems bizarre to me:

V_in  | V_stabilized

190   | 235

195   | 240

200   | 210

215-219 | 220

Now you can see 190 approaches 235 but as we come close t desired Volatge(220) it is automatically stabilized to 219-220

Can you explain the working/reasoning behind this?

Are all the volatge-stabilizer/regulator made like so ?

^Any value or interval is omitted because I don't have data for them


texts: Finding an affordable integrated USB MCU

texts:
I'm in the early stages of designing a development board around Cypress Semiconductor's PSoC 3 and 5 range of chips. Much like the Arduino, I'd like the programming experience to be very easy, and that means being able to program it and interface with it without having to buy a separate programming cable.

I've tentatively settled on a solution similar to the Arduino's: embed a less powerful MCU with built in USB support on the board, and have that MCU act as a USB interface to the main processor. Unlike the Arduino, though, I'd like the communication MCU to act as a programmer via the SWD (Serial Wire Debug) interface.

With that in mind, I need an MCU that meets the following requirements:

Two U(S)ARTs, one capable of being used for SWD, one as a regular UART for user defined communication with the main MCU.
Native full-speed USB interface.
Cheap in small-medium quantities (~100).
Ideally, no external crystal required for USB operation.
Ideally, available in a hand-solderable package. Definitely not BGA, preferably not QFN.

Big bonuses would be if it's an architecture with a well supported OSS toolchain or shallow learning curve. Even better (but less likely) would be if there was already example code for implementing an SWD or JTAG programmer on that platform.

My current candidates are the ATMega8U2, which meets most of the requirements, but isn't as cheap as I'd like and requires an external crystal, and the C8051T623, which is cheap and meets the requirements, but seems to have limited toolchain support and isn't an architecture I'm familiar with. (Edit: It also seems to be non-stock now, which more or less rules it out.)

Can anyone recommend an MCU that meets these requirements?


texts:
Is there a special grade for electronic components made to be used in medical devices such as life support systems?
I have read in most data sheets that "this product is not to be used in life support systems".
So is there a medical grade version for every devices like "medical grade" Atmega 328?


texts: Can I turn on an LED, only if the switch has been closed for a desired amount of time?

texts: I'm trying to use a ball switch and an Arduino to turn on an LED. I only want the LED to turn on if the ball switch is closed for 20 seconds. Does anyone know how to do this? Thanks.


texts: Imagine this scenario? Would the person feel anything or be injured?

texts:
Imagine an individual touched a high voltage line (like a bird) without touching any ground. For sake of illustration, imagine that this high voltage line was at a 100 Exavolt potential.

Would the bird or person notice anything when they touched the line, since they were not also touching ground?

Now, imagine that the bird flies away from the line and lands on a ground line, after having touched the hot line (i.e. the bird is no longer touching the hot line and is far from it). Would the bird notice anything in this case?

Obviously, if the bird touched both at the same time it would be electrocuted.


texts:
I want to drive multiple strings of XTE LEDs (total of ~36 LEDs). The relevent (-ish) specs are as follows:

I_f,max = 1.5 A
Desired I_f = 0.5 A
V_f = 2.94 V (0.5A @ 85C)

According to some calculations, I found that the larger the voltage dropped across the resistor the more stable the LED current is with shifts in supply voltage. Voltage drop ratio between resistor and all LEDS in a single string determines some part of current stability. Is this generally true when looking at voltage source deviations? I have looked around and haven't found something that explicitly confirms this.

But I don't want to use a large resistor as too much is dissipated in the resistor. For simplicity, I want to choose a small [resistance] resistor and use a power supply with tight voltage tolerance (1%, according to some Meanwell HLG specs). Will the right PSU be enough to maintain a fairly consistent voltage and thus consistent current?

Here is my follow-up concern, will thermal runaway be a large concern because of the small resistors? Say I use 2 strings x 18 LEDs = total of 36 LED. This is using a constant Voltage source, not a CC source.

How big of a voltage difference should I expect between each string of LEDs due to dissimilarities at the per LED basis?

Would splitting up into smaller series strings like a 4 x 8 LEDs while still using the same ratio of (Voltage drop over Resistor)/(Voltage drop over all LEDs in a string). Is thermal runaway better/worse/no different in this scenario?


texts: I am studying on my own how the PC works and I can't understand one thing. A 32 or 64 bit processor differs for its ability to allocate 2 ^ 32 or 2 ^ 64 addresses for the cells of the RAM. What I do not understand is how big a single cell is. Does a single cell contain only a 0 or 1 or it is bigger (like 1 byte). And also, is the "dimension" of the word related with the CPU architecture?


texts: detect the pressing of 220v push button by MCU

texts:
i need to detect the pressing of 220v push button using any 5v micro-controller.what i do to get 5v signal to use relay of 220v coil..

here is a sketch show you what i mean

should i modify the circuit ?

what is the suitable value of R1?

thank you


texts: Coaxial cable test with VNA to estimate Wave Velocity and Attenuation

texts: I'm doing a lab course concerning microwave measurements, during which I'm supposed to test an open, short and 50 Ohms terminated coaxial cable. The cable is connected to a VNA at the S_11 port and for each cable type, the phase as well as the magnitude (in linear and log scale) were being measured in the frequency domain. The task is to estimate the wave velocity in the cable (and from that the cable length) as well as the attenuation. I assume this is a really basic problem but I'm completely new to the field of electrical engineering, so I'm stuck at how to start. All I found is that the velocity can be estimated using the phase/ the "period length" of the phase since obviously it has a periodic behavior.


texts: Full-wave rectification for clock signal from wall power

texts:
I have built this power supply and clock signal extractor exactly as shown:

http://electronics.howstuffworks.com/gadgets/clocks-watches/digital-clock4.htm

I have double-checked this and the rest of the clock multiple times.

However, my clock runs twice as fast as it should (each second, it counts to 2 instead of to 1.)

After spending about 5 hours trying to figure out what I did wrong, I read an unrelated article about half-wave vs. full-wave rectification. I then realized that perhaps the problem is with the instructions.

Given that the bridge rectifier in the supplied diagram is full-wave, wouldn't the clock signal from this diagram actually be 120 hz and not (as labelled) 60 hz?

The specific rectifier used is Jameco part # 103018.

edit: said "unrelated post" mentioned above:
http://www.dutchforce.com/~eforum/index.php?s=ce079f0f532f189320af403ffacb6866&showtopic=18061


texts:
I am trying to drive a "piezo atomizer" which is pretty much a transducer from what I can see.

The specs on the transducer are as follows:

-30-50VPP

-Resonant frequency fr: 190 KHz±5KHz

-Resonant impedance Zm: ≤250 Ω

-static capacitance Cs: 2.2nF ±30%

-Test Condition: 25±3 °C 40~70% R.H.

-Cs => LCR meter at 1KHz 1Vrms

I thought I would be able to drive the transducer using the following circuit. I can get the the transducer to creak small bubbles when its in water but I can not get it to act like it should (a small humidifier).

This is what I am getting from the net that connects collector of the npn and the negative lead of the piezo.

Any suggestions as to where I am going wrong?

simulate this circuit – Schematic created using CircuitLab


texts: How can I connect a USB Joystick to the arduino to control a Canon DSLR?

texts:
I'm starting in the Arduino world. I've been reading a lot on the subject and I have a few questions regarding a project in which I'm trying to get involve.

I want to control my Canon EOS 7D with a joystick using Arduino. I ran with this two projects.

http://www.instructables.com/id/Arduino-Lens-Controller-Synchronized-ZoomFocus-/

http://www.instructables.com/id/Building-the-YaNis-EOS-Controller/

Both have parts of what I'm trying to achieve. The main doubts that I have are related with the USB port. If I want to connect a USB Joystick to Arduino and then the Arduino to the camera using USB, Do I need to have two USB host shields?

How is it that in the first example the Wii gamepad is connected straight to the Arduino? Can I do that with an USB generic gamepad?

If I start the project with a regular USB gamepad, Do you think I'm going to be able to replace it with a wireless gamepad on the future?

Is it possible to take advantage of the USB port that, the Arduino UNO already have?

As you can see, a little of orientation would be good!, THANKS!!


texts:
I'm working on a project in school were I have the PMP4862 circuit as a reference. Unfortunately the flyback is no longer available.

How can I modify the circuit to use available parts?

I wonder if you know any equivalent flyback or if you can recommend another power supply that can be used for the same LED driver as in PMP4862 and can handle an input voltage between 85-260 V AC. Since I can't just change the transformer without change values on resistors and capacitance on the whole circuit, right?

Feels like I've been searching everywhere without getting wiser :/


texts: Simple frequency deviation to voltage converter

texts:
I have a capacitive sensor connected to a 555 timer wired as an astable multivibrator and the free running frequency is 60kHz. When the capacitance of the sensor changes, the frequency of the 555 also changes. The maximum frequency deviation from the center frequency is 20kHz, i.e lowest frequency (60kHz-20kHz) is 40kHz and I want to convert this frequency deviation to voltage. I need a simple circuit using a 555, OPAMP, transistor etc.

I would prefer not to use the LM331 frequency to voltage converter.


texts: Forward converter magnetizing current and active clamp

texts:
Can somebody explain why the magnetizing current starts at a negative value?

Also, the highlighted part below kind of gives me a hard time to comprehend. Does this mean that the voltage across the capacitor is changing from one value to another instantly when S2 closes? I was taught that capacitor voltages can't instantaneously change. Also what does having large value of this cap have to do with the voltage being constant? Thanks!


texts: Why is the ground of the component, SP1050-04BTG, connected to the Power Supply of POE?


texts: Split-phase 230VAC transformerless capacitive power supply for 5V@30mA regulated output -- series cap?

texts:
I'm a hobbyist developing a hybrid power switch (electromagnetic + solid state) for a resistive electric stove (8kW max) top. I have a profoundly autistic, disabled adult in the house and I need a fairly specialized system to automatically shut off the stove if the kitchen is vacated for any reason. It also requires a code to enable it. And there are a few other "features." We've kept the breakers off for years, but things are changing so that is no longer acceptable and we need to reactivate the stove now. But with safety features customized to our special needs here.

The entire system is in two physically separate parts. One is the control panel -- battery powered only and placed less than 2 meters away from the hybrid switch system. A signaling method with very low false positives will be used from there to the hybrid switch micro. The hybrid switch micro uses a MOC3023 to control an EMR and a MOC3063 to control a pair of SCRs (I prefer a pair of these over a TRIAC for several reasons.) Unless I find a better way, there are two sets of these, one for each split. The SCRs are used ONLY for a few cycles, with the EMRs once engaged no longer requiring the SCRs until shutoff.

The problem is in supplying power to the sealed (plastic) module that contains the hybrid switch optos and micro. That part of the switching system is buried into a counter/wall area and needs to be self-powered from the 220VAC split phase system it switches. No batteries, etc. I like transformers, but the weight and bulk put extra risks in the work ahead and will also complicate other applications at a later date. So I would like to resolve this issue now with a transformerless system.

There are quite a few schematic pages but I'm posting just the preliminary transformerless power supply section above. I'm most concerned about C1. I gather it should be an X class capacitor. If it fails "short," the only protection I've got will be the 100mA fuse. I'm also ill-informed about MOVs and their correct specification for an application like this. And there probably are areas where I'm ill-informed that I don't even know about. Regardless, I've been "tasked" by family to "solve this stove problem" and solve it I will do. So there is no stopping that. The only question is about getting it done with risks reasonably mitigated.

I already know the advantages of galvanic isolation. A CHEAP COTS solution that has small physical volume and is designed for delivery of 5V in the area of 30-50mA would be interesting. Price and physical volume and weight are important and so is total dissipation. I want the supply and the load together to be under 1 watt total. That can be safely ensconced in a cavity. I also hope to put the micro and the rest (not shown) on this same board in SMT to keep it all as small as I can. But I could sacrifice that hope.

Technical comments about safety are very much appreciated. Bear in mind I'm solving an unusual set of requirements. I have approached local stove-top sellers, and a few of the national manufacturers, about their units. Some have disabling modes -- but the way they work doesn't help. I have researched other options and I believe I may be stuck doing some part (or all) of this. I have already built and tested the hybrid relay system, with optos, using a COTS power supply and it appears to work as well as I'm able to judge it.


texts: Generate ultrashort rise times with photoconductive switch or photodiode

texts:
I am trying to produce voltage pulses with very short rise time (<15 ps), medium width (20 ns) and amplitudes up to 15 V. As a promising candidate I selected photoconductive switches and ultrafast photodiodes. However, I have limited knowledge about electronics at all and thus, even less knowledge about these devices. Do you think it is possible to produce pulses like that by applying a constant bias DC voltage (for example 15 V) to the switch/diode and send a laser pulse with approx. 20 ns width to the photosensitive area?

I already found photoconductive switches at Hamamatsu and Laser Quantum that might work. In particular, I am talking about the G4176-01 and the Tera-SED3, respectively. However, I cannot imagine how to connect these switches. For the Tera-SED3, one would have to use the ground as the output but how to deal with the grounds than without violating the impedance?

I appreciate any help, advise, new insights and ideas. Also, if you know another supplier of photoconductive switches or photodiodes that might work for my purposes, I would be very grateful if you share these with me.


texts: AC single phase induction motor - phase difference problem

texts:
I want to build and AC single phase induction motor. There's the following schematic for its construction.

This motor can only work if there's a 90º phase difference between \$I_1\$ and \$I_2\$ as you can see written here, on the Construction section. I did some circuit analysis and I found the following relation:

$$\bar{I}_2=\frac{w L_1}{wL_2-\frac{1}{wC}}\bar{I}_1$$

So, according to this relation, there only can be a 0 or 180º phase difference between the two currents. Did I do something wrong?


texts:
I'm using the program Logisim to create very simple circuits as I am just beginning to learn about the different logic gates and such.

In the Logisism program it has in-built features already such as a Counter, Register, D Flip-Flop etc. I'm trying to create a D Flip-Flop without using the inbuilt features and instead using the logic gates that make it up. I know a D Flip-Flop looks like this:

So I created it like the above picture in Logisism, I'm wondering how I can add Clear functionality where if CLEAR is equal to 1 then it resets it.

Another queston I have is using the Logisism program, the in-built D Flip-Flop looks like this:

It has input CLOCK and D with Q and NOT_Q output with a CLEAR. When I try to go to create a sub circuit from the D Flip-flop I made above, it doesn't provide a CLOCK input:

It just has D input and Q, NOT_Q outputs. How do I make CLOCK an input?


texts: Signal is missing in the sensitivity list and expression truncation

texts:
For the following module I get several warnings ,can you advice me how to solve them?

Line 22: Result of 17-bit expression is truncated to fit in 16-bit target.
Line 25: Signal  missing in the sensitivity list is added for synthesis purposes. HDL and post-synthesis simulations may differ as a result.
Line 26: Signal  missing in the sensitivity list is added for synthesis purposes.

module module_cell1( in_85,in_86,in_87,out_13,clk,rst );
parameter DATA_WIDTH = 16;

// Interfaces
input clk;
input rst;

input [DATA_WIDTH - 1:0] in_85,in_86,in_87;
output [DATA_WIDTH - 1:0] out_13;
reg [DATA_WIDTH - 1:0] out_13;

//clk state
reg [DATA_WIDTH - 1:0] clkState;

// Procedural Assignments

always @ ( posedge clk or negedge rst )
begin
if (~rst)
    clkState <= 0;
else
    clkState <= clkState + 1;

//Clk based State
case (clkState)
1: out_13 <= (in_87)?in_86 : in_85;

endcase
end

endmodule


texts: Which are the the valid VHDL compiler pragmas?

texts:
I know you can stop VHDL code from being compiled by the synthesizer:

-- pragma translate_off
assert thisDoesNotGetSynthesized();
-- pragma translate_on

BUT, there are also other ways to write this, including -- synopsys translate_off.

Which are all the valid ways to turn off synthesis? Is there a definitive list on which are valid pragmas?

Additionally: what are the syntax rules for these pragmas? Is the whitespace in the pragma important? Can the pragma occur anywhere in any comment, or does it need to be the only thing in that comment?


texts: Cooling circuits in a hot loft with dusty air and bugs

texts:
I have a home-made home-automation system that includes a CCTV unit, circuit boards for controlling PIRs and outside lights, a UPS and power supplies.  In the summer the loft gets hot (>40C) and the CCTV gets even hotter and is operating outside of limits.

The air is full of dust, fragments of loft insulation and bugs, so I want to re-circulate the air inside the cabinet - pull air from the top of the cabinet, cool it, and blow it back through the bottom of the cabinet?

How can I cool the recirculating air?

If I use Peltier chips, the power supply for them will be inside the cabinet.  It will be like leaving the fridge door open to cool a room.


texts: Difference between DC operating point and Transient operating point

texts: I've been simulating a circuit using synopsys and I'm just wondering what's the difference between DC operating point and Transient operating point?


texts: How can Chua's circuit work without having a power supply?

texts:
I am now analyzing the following Chua's circuit.

The triangle at the bottom denotes zero electric potential (I struggle to find the right symbol). \$N_R\$ is the Chua's diode. So the circuit is non-linear.

This version of the circuit can be modeled by the following system of ODEs, which can be found on Wikipedia.

$$ \frac {dx}{dt}=\alpha [y-x-f(x)],$$
$$ RC_{2}\frac {dy}{dt}=x-y+Rz, $$
$$ \frac {dz}{dt}=-\beta y. $$

x(t), y(t), and z(t) represent the voltages across the capacitors C1 and C2 and the electric current in the inductor L1 respectively.

My question is, how can this circuit work if it does not have a power supply? The only component supplied by the battery is the opamps inside the Chau's diode. Such power supplies are not part of the main circuit, so how can the main circuit gain power? The initial conditions of the differential equations are $$x=y=z=0, t=0$$ (since all electric potentials are zero before we finish connecting the circuit). Those initial conditions will generate the solution \$x=y=z=0\$ for all time.
If that is the case, then how can we observe the double scroll pattern? Everything should be constantly zero.


texts: I was wondering if anyone could help me identify this capacitor. It doesn't appear to have a capacitance value, unless it's the text at the bottom, which is partially scratched-out and illegible. 6.0 J, 250V DC/160V AC. I just need to find its capacitance in Farads, so any assistance would be greatly appreciated.


texts:
I am asked to determine what the unknown component (Zs) is. I know that the maximum power theorem states (after derivation) that the

$$P_{\text{load}}=\frac{V_{\text{th}^2}}{4R_{\text{th}}}$$

I would be able to find the thevenin voltage and resistance if there were all resistors in the circuit but don't know what to do in this case. Is there a way to determine what the unknown impedance is? I know that a capacitor has always a negative impedance and a conductor = positive impedance but I don't know about the resistor.

How do I find the determine the component of Zs?


texts: What type of op-amp configuration is this?

texts: If you need more info I will provide it. The op-amp board is piggybacked on an inverter driver board.


texts: how does a transistor behave when it's broken?

texts:
I'm trying to get a circuit to work (linistepper driver) and I suspect I may have fried the drive transistors (tip122's in this case).

Are there common behaviors of broken transistors?

does c->e short? b->e? open?

Can I measure with my multimeter to get any meaningful information?

is it possible for devices to half break with degraded performance?

I'm looking for generalities. I also have an old stereo which has a broken channel.

I'm not particularly good at desoldering, so it'd be good to have some confidence that I'm looking at the right component.


texts: Why do library book detectors make my headphones buzz?

texts:
Whenever I enter or exit a library while wearing headphones (cheaper intra-aural type), I hear loud buzzing as I pass through the book detector gate. I can vaguely speculate at a high level that there's some sort of field that detects something on the books, and that field also interferes with headphones, but that answer is unsatisfying.

How do library book detectors work? All the sources I find are uncredible and slightly conflicting, but it appears that the tag on the book has some sort of circuit that is wirelessly charged or discharged when a book is checked in/out. Somehow a field detects when a capacitor is charged.
What is it about headphones that makes the buzzing? Does whatever field interfere with whatever mechanism by which the headphones make noise?

Somewhat simpler explanations are preferred (I've taken intros to circuits, electronics, and signals, but not much beyond that).


texts: Does the voltage difference have an effect on the electrons' speed?

texts: If voltage means the pressure that makes the electrons move from the negative side to the positive one doesn't that mean that the more the voltage there is the faster the electrons move? But the electrons have the speed of light right? does that mean that it will exceed the speed of light if the voltage was big enough.


texts:
I'm currently working on making a battery I salvaged from a mowing robot usable. It doesn't have a datasheet or anything, since it was made specifically for the robot and wasn't intended for consumers. That's why I can only use measurements and the sticker on the front to get any data like voltage or capacity. I get most things on this sticker, 2 of them however, I don't understand the meaning of.

First, in the same line that gives me Voltage and Capacity, there is a seemingly random number. Does anyone know what it means? Probably nothing actually concerning the technical stats of the battery, but I just want to make sure.

18.5V / 2.1 Ah / 38.85 WH    1546

Then there is the thing I can only assume is the name of the battery: 5INR 19/66 Rechargable Lithium-Ion Battery. I know it might just be a name, but INR for example, specifies the type of said battery as a lithium manganese nickel battery. I don't know if the numbers mean anything, but again, I just want to make sure.

Here's the entire thing.

https://www.trgo-agencija.hr/baterija-automower-husqvarna-105-305-586-57-62-01.html


texts: Servo Regenerative Braking and Li-Ion Battery

texts:
I would like to power two of HSB-9370TH with one or two of these 7.4V Li-Ion Battery in parallel.

I notice that the HSB-9370TH has regenerative braking, and my current application will have constant back and forth movement. It seems to me that I definitely want to take advantage of the regeneration to extend battery life. I'm not sure how this works with a Li-Ion Battery though. Will the battery simply accept the regenerative charging safely when directly hooked up to the motors? Will I need any additional circuitry to properly take advantage of this?

The battery has an IC so I feel like this should work fine, but want to make sure.


texts:
I am trying to design a circuit to switch 12V 90mA on/off using an Arduino Nano as the trigger.
Is there an optocoupler/transistor/MOSFET that can tolerate 12V at 100mA on the load side while still being switched by 5V from the Arduino Nano without overtaxing the nano?
I've tried a FQP30N06L MOSFET but the connection between the [S]ource and [D]rain pins allows enough voltage/current to flow when the MOSFET is in LOW state to keep that 12V circuit closed enough to run the load device. I added a resistor between Source and Drain to lower that voltage to zero in Low state but that also has the affect of dropping the 12V output to 11V when the MOSFET is switched HIGH.
Any advice would be great. I've been beating searching Google and SE for a few days trying to solve this.
Added - Data Sheet for the FQP30N06L MOSFET
The Load is an OBD2 reader for car diagnostics. Model: LAUNCH Creader 3001

I ended up using a HE3621A0510 reed relay to switch the ground of the OBD2 reader on and off. It worked great. Unfortunately now the reed relay stays closed when the Arduino trigger power is removed, until I tap the relay. Then the circuit opens again and shuts the OBD2 reader off.
Though the measured load current of the OBD2 reader (90mA - mind you this was measured with a digital multimeter) was far less than the the reed relay capacity (500mA), I feel there must be a spike in the current at startup high enough to weld the relay contacts a little. I have tried multiple reed relays of the same model number and they all do this, so it shouldn't be just a single defective unit.
Any chance a resistor in line with the load could help keep that inrush down or should I use a fly-back diode to stop it entirely?


texts:
I am working on a design which involves an FPGA having an external clock, the clock source is supposed to be programmable clock synthesiser, however this needs to be programmed at power on by the FPGA to output the correct clock frequency. I don't have great experience in this domain, but I am kind of sure that the FPGA will not operate correctly without an appropriate clock.

My solution to this is to use a 125MHz crystal, which is connected to a programmable clock multiplexer. At power on the FPGA will receive the clock from the oscillator, after this it will program the clock synthesiser and switch the clock source on the clock multiplexer. The purpose of this is to have a precise phase synchronised system. My BIG issue with this is that I don't know if it is safe to disrupt the clock being delivered to the FPGA and if it will remain operational during this switchover phase. Hopefully someone may have a better idea of how FPGA's behave with regards to the clock.

The FPGA in question is a Xilinx ZC7Z010 Cortex A9. I am welcome to other ideas, but the FPGA most certainly needs to be clocked by an external oscillator.

Many thanks for reading this.


texts:
I've built an LM3405 LED Driver, which works (seem) well. The LED have a 3.2V of Vf and works at 700mA. The regulator uses an external boost voltage of 3V (from an LDO). Reading the datasheet of the LM3405 I can't find any information on the buck converter dropout voltage, but I see a full load regulation only at Vin > 5V. (11/03/2016 EDIT: 4V)

There is a general rule or something to know that?

Moreover, the regulator have an internal Rsense on the drain of the MOS (which is used to correct the feedback and it is NOT the external shunt resistor), which can cause the drop, but I can't find its value.


texts: 12V 1A over CAT5 ethernet cable about 12 metres long

texts:
I'm setting up a CCTV system and already happen to have an ethernet cable in place. I intend to send the video signal through the ethernet cable to another room where my DVR is positioned and I have an UPS. It would be nice if I didn't have to buy another UPS for the camera and could use the ethernet cable to transfer power from where I have my DVR and UPS as well as send the video signal through it.
Has anyone ever risked 12v 1A through a CAT5 ethernet cable? Would a real engineer say this is definately a no go? (I'm not a real engineer, just a DIY layman.)
I'm assuming that the ethernet cable is only good for 5V 1A max. Not 12v 1A.
What are the professionals opinions?
Thankyou very much - Si


texts: 4 Layer PCB Local Pours on Signal Layers

texts:
I'm in the middle of placing components on my first 4-Layer PCB. Layers are Sig-GND-Vcc-Sig. I2C/SPI/UART, up to 20MHz MCU, nothing exceptionally fancy.
I have decided to check with the community whether I'm doing things right. I use small polygon pours with a pair of vias for the ground connection for small groups of decoupling or bulk caps, so I was wondering if I'm doing it right. Because if not, I better restart while I still haven't wasted too much time on doomed layout.
Here is an example of my boost converter, output of which is supposed to go down to the power plane (which doesn't take the entire layer, but bigger rectangular part of it).
The boost converter itself is this: Datasheet (if anyone wants to have a look; I need 1A at most).

Please, roast my layout and tell me why this is bad and how can I improve it (I don't expect it to be good considering I'm losing 4-layer virginity here). Thank you.


texts: Can an opamp be neither in linear region nor saturated?

texts:
I'm trying to build a voltage controlled DC current source. For this, I built this circuit:

A little bit of context. The voltage supply is 5V. Current range must be from 0mA to 30mA or so. Load will be an LED but for now I'm just connecting the collector to Vcc and measuring current with an amp meter. The transistor I'm using is BC337 and the opamp is OP07 connected to 5V and 0V. Vset is a PWM filtered with an RC circuit. Rset is 100 ohms.

Now for the part that doesn't work. For voltages above 1V, 20% of Vcc, in the input Vset, the circuit behaves as expected. That is, I get a 10mA current at 1V and I get Vset/Rset current for every Vset until the transistor enters saturation around 30mA.

For voltages under that, the opamp does something I'd never seen before, it operates neither in linear nor saturation region. As I start lowering the voltage on Vset, both inputs separate, the inverting input lowers less and less until it gets stuck at around 500mV. So the final result is that I have 0V in the non inverting input, 500mV in the inverting input and thus 5mA through Rset. This is obviously not linear region because there is no virtual short circuit. However, the voltage on the base isn't Vcc, if it were Vbe would be huge and I'd get a bigger current. Instead, it gets stuck at around 1V.

How can the opamp do this? What sort of operation is this and how do I stop it?


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I am trying to use the following MOSFET (N-Channel) to turn an IC on and off.
http://www.diodes.com/datasheets/ZXMS6004FF.pdf

In my test circuit I connected 5VDC to the drain of the MOSFET and then connected the source to the V+ supply pin on the IC. The Gnd pin of the IC remains tied to ground. For some reason when I apply positive voltage to the gate of the MOSFET it turns on but I only measure about 2.5VDC at the supply pin of the IC and this is not enough for the IC. Any ideas what I am doing wrong here?


texts: What should be input and output for CA3020A power amp circuit and how to implement it?

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I am trying to rig up Figure 1b and Figure 8 circuit from datasheet  to test the power amplifier CA3020A.
Not able to understand the datasheet my doubts are

figure 1b what are values of vcc1, vcc2 ,ein and how to check output w.r.t input. What is meaning of class b power amplifier
figure 8 what should I determine in this and how do I verify the input and output.

My main objective is to check CA3020A component and if any other method is there kindly suggest I am a beginner so kindly explain

CA3020A


texts: What Can Be The Cause Of Low Voltage After Resoldering?

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I had to resolder mosquito zapper's black and red wires back after zapper fell on the floor and black wire detached and later red wire detached when i was trying to solder black wire back. After resoldering wires, the zapper no longer produced sparks as it did previously and its electricity did not kick away mosquitoes at all anymore. Can it be that i used wrong material for resoldering? It was solder of 67/33 i think from China with 2% flux:

UPDATE: Here are 3 new close-up pictures where you can see in better details:


texts: How do I edit thermals on pads in Eagle?

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I have a ground plane and would like to increase the number of gaps in the thermals of a ground pad. I have more than 9 amps running through this ground pad and need to increase contact.

It looks like the default number of gaps is 4. I want to increase that to 8. You can apparently change this number easily in other pcb design software but I haven't been able to do it on Eagle. Also, I don't want the component to be modified in the library for every instance of the part, since the pad might not always be connected to a ground plane.

I don't want to remove the thermals all together since that might make soldering more difficult.

Looking at the ground plane, the polygon just makes a cross on the ground pads. Do I have to manually draw a new polygon pattern over each pad or is there a shortcut?


texts: What would happen if a diamagnetic material is placed within a capacitor, instead if a dielectric material?

texts: In capacitors dielectric materials are sometimes inserted between the parallel plates.  What would happen if a diamagnetic, or a paramagnetic material is inserted between the parallel plates of a capacitor?  How would it change a capacitors ability to allow an AC signal to pass?


texts: Why current is constant during storage phase in reverse recovery experiment?

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This is a simple schematic of reverse recovery experiment.

As you can see, there is a constant current phase in the curve known as storage phase. My question is, why
current is constant during storage phase? I have read in references that during this phase, injected minority carriers (in forward bias) will recombine.
it's OK, but I could not find any convincing answer for my question in related references. I would appreciate if you could kindly help me.


texts: suggestions for solar charging battery-operated device

texts: My battery-powered wireless device draws about 50mA @ 5V. I’m thinking of powering this off a 12V 7Ah SLA battery that is topped up with a small solar panel (12V, maybe 500mA or so). 12V to 5V will happen with a DC-to-DC converter. Can I just connect a solar panel (with diode) straight onto my battery or is this where I need a charge controller? If the latter, what is the reasoning behind it?