texts: Voltage drops to 3V when connecting USB to 5V Source

texts:
I am trying to build a solar phone charger. I have a 18V solar panel and I connected the output to a diode and a voltage regulator. The voltage regulator drops the voltage from 18V to 5V and I can read that on the multimeter during daylight. Once I connect the phone, I can see that the voltage at the inlet of the phone drops from 5V to 3V. The phone shows that it is charging, but actually it is discharging.

I assume that the 5V - 3V drop is due to the internal resistance of the phone and here is one of the questions. Do I need to have a voltage regulator that gives a higher voltage output of 7V, for example? This would mean that with the phone resistance, the inlet voltage will end out being around 5V.

And the second question is why is my phone discharging instead of charging, considering that I have a diode right before the voltage regulator?


texts:
I'm trying to learn VHDL and I came across some example code for a counter that I find somewhat strange.

I understand what it does but I'm not sure why it is written the way it is.

The code is the following:

entity counter is

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

architecture behv of counter is

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

begin

    -- behavior describe the counter

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

    -- concurrent assignment statement
    Q <= Pre_Q;

end behv;

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

Can't we just replace this line

Pre_Q <= Pre_Q - Pre_Q;

with something like this? (I'm not sure if I can do this)

Pre_Q <= 0;

Is there any reason why I should use the first method instead of the second?

I apologize for deleting my previous question but I made a mistake when rewriting the code and I forgot to explain what my doubt really was.


texts: how much bandwidth does a phone call require and how much is the capacity of a single E1?

texts:
How much is the bandwisth requirement for a phone call connection? Considering a non-channelized 1 with 32 time slots how many calls can an E1 support?
Say its 'n'. Does that mean n+1 call will not be connected?


texts: Costs of microcontroller with GSM module

texts:
First of all, I have to confess that I am a noob on this topic ;)

Currently I try to realize a pet project with a microcontroller, which is connected to a GSM module. I've done some research and found several GSM modules, which can be used with AT Commands - e.g. SIM900 or SIM908. But I only found suppliers selling these modules at 15 to 40 euros.

My objective is to develop a hardware, which easily could be scaled in production. But using a GSM module, which costs more than 15 euros, would blow away this idea. Now I have two questions:

Unfortunately I have no experience if these modules are so much cheaper if I buy them in higher quantities. How realistic is a price of 1-3 euros per piece and how many would I have to buy?
Which components do they use in mobile phones? You can get smartphone for as low as 40 euros. And a smartphone not only includes a GSM module, but also more expensive components (display, etc.). So how do the smartphone manufacturer handle this? Do they use a GSM module, too - or do they implement their own solution.

So you see, I am relatively new to this topic. Maybe someone could give me a hint how this industry works? ;)


texts: HTTPS (HTTP+SSL) server - field provisioning

texts:
My goal is secure field provisioning.  Specifically, loading WiFi credentials on a device in the field.  To do this, I wish to set up MCU as a WiFi Access Point with no WEP, WPA, etc - "open".  The securing of the communication shall be the HTTPS layer

Terminal and non-secured WiFi provisioning (WiFi AP + HTTP) is not acceptable

Environment is ESP8266 + ESP-OPEN-RTOS, but question applies to any MPU beefy enough to do SSL

So, in essence, I need an HTTPS server burned into the device.  Making custom HTML page logic is OK, but writing a whole HTTP+TLS stack from scratch I'd like to avoid

mongoose looks promising, but for my environment isn't compiling.

Has anyone else attempted/succeeded in solving this problem?


texts: What happens if the ground of a PCB touches the earth?

texts:
I know that if an object is significantly more/less charged than another object and goes near it, an ESD can appear and then both objects would become balanced. This can happen when a human touches copper pads of a PCB for example.
Now let's consider an integrated circuit working on battery. The ground of the IC is different from the earth, so we cannot presume its potential, it can be anything. Is it possible for the ground to be charged to some kV when the PCB is rubbed against another object ?
Because if it is so, then, if the ground of the PCB touches the earth  (for example, the solder tip of a welding station touches a pad, or my finger with an anti-static wrist touches a component), an ESD can occur, right ? How to avoid this ?
Thanks.


texts: What is the best way to connect an MCU with a crystal and its two capacitors?

texts:
I want to connect an MCU with a crystal and two capacitors. I am unsure what the best way to do that is. I am not talking about how close the crystal should be placed towards the MCU, whether the traces should all be of equal length, or how big the capacitance of the capacitors should be.
Instead I wonder whether the traces from the MCU towards the capacitor should go from the crystal towards the capacitor (see the first picture), from the capacitor to the crystal (second picture), or whether the traces from the MCU should go in the capacitor and the crystal (third picture).


texts: What is this tiny Iphone 4s component C7

texts:
What is this tiny square Iphone 4s component with a tiny label of C7 on it?

I bought few damage iphone 4s trying to fix them, one of the phones' PCB is in a pretty good condition, but it's missing that c7 chip. I want to know what it does and is it possible to swap it from another pcb.

Here is the photo of the pcb for that missing chip.


texts: Lowest power circuit to control low current 240v circuit

texts:
I'm trying to control 6 normally-closed 230v valves using a raspberry pi. These valves draw little current when energised (1W) but do have a maximum inrush current of 550mA. Normally this would be easy -I'd just buy an opto-isolated relay module and be done with it. The problem is that these circuits are going to spend a lot of their time energised during certain parts of the year, and then nearly all their time off at other times. 6 x 70mA is nearly 0.5 amp of resting current on top of the 6W I'm already burning in the valves. Since I live off-grid, I'd like to save as much power as I can, both for those periods when the valves are mainly open and when their mainly closed.. Ideally, I'd also like to be able to power the control circuit directly from the Rapberry Pi, but I don't know if that's realistic - are there devices that can safely switch 230v with a 550mA inrush current that are low power enough to run directly from the RPI?
If I do have to use a relay, the good thing is that these circuits switch infrequently, and response time is not an issue. I guess I could use a bistable relay with some sort of control circuitry to generate pulses on the two inputs as the logic line transitions from 0V to 5V and vice-versa (do these exist pre-made?). But I'm hoping that maybe there's a low-power solid-state solution that will do this "in one"?


texts:
I have started using a TM4C123GXL development board with Keil uVision as the programmer / debugger. I have wrote the attached simple code (see below) to become familiar with using the debugger to see what the MCU is doing in memory.

When I compile and run in simulator, my code won't let me step through the simulation, appearing to be stuck on line 602 as shown below.

I am unsure what the PLL is locked means and what is the cause for this?

EDIT

I have a question based on the link from Tyler's answer below. What should I download from this list?

Thanks


texts: What happens when you increase current to a DC motor?

texts:
Increasing voltage increases the RPM of the motor, but what does increasing current do?

I can't seem to get a straight answer. Some googling has led me to believe that torque increases while rpm stays the same.

I currently have two 24V batteries wired in parallel, and they are connected to a DC motor through a speed controller. I understand that the speed controller works by turning the circuit on and off very quickly to vary the speed of the motor.

I just bought a third 24V battery that I plan to connect in parallel to the other two, and was wondering what I should expect when I hook it up.


texts:
So for the project I am working on I plan on measuring very precise changes in angle, possibly up to 5 degrees of accuracy.

Are polymer ink sensors (the classic Nintendo power glove flex sensor) the way to go?
Can they really be that accurate or are there any other alternatives to measure bend on an attached apparatus pricisely?


texts:
I need to reduce 5v to 1v for use as a reference voltage in an op-amp.

What would be the best way to do this? The simplest solution to me is to use a voltage divider, although I understand others have reservations about this.

Alternatively, a voltage regulator of sorts, although a quick Google, Mouser, Digikey, Farnell search yielded very few results...

Ideally I'm looking for a basic, and easy to understand solution.


texts:
I know several applications where twisted pairs are used and why they are used in those applications, but I would like to know more about the advantages and disadvantages of using twisted pair wires so I can choose appropriately based on what I am designing.

As an example, I understand the use of a twisted pair in differential signaling. This helps reduce noise because both wires receive the same interference which can then be removed by a differential amplifier.

I also remember reading quite a while ago about an induction forge where the power output was significantly lower than anticipated. The guy figured out that the separation of the power leads to the electronics enclosed a large area, creating extra inductance (which acted as a low-pass filter decreasing the power factor). By taping the power wires in a bundle, the stray inductance was removed.

It seems that twisted pairs offer benefits when inductance or induction are concerns, but this is where my understanding terminates.

What are the advantages and disadvantages of twisted pairs, and for what applications does this make them beneficial?

EDIT: The issue of inductance does not appear to be addressed elsewhere, indicating one application for which twisted pairs are helpful, which isn't addressed outside this question. Similarly, a comment raised the issue of added capacitance, which is not addressed in the linked question.


texts: Need to turn on a relay for half a second when constant power is applied with a switch

texts:
I'm looking for what circuit I'd need using basic components to do this task.

Essentially I have a switch that turns on two relays, one of which needs to be on as long as the switch is depressed, but the second I would like to only activate for half a second or so, possibly longer, it's something I would have to test out and fine tune.

What's the best way of going about this.

Edit: I didn't feel like firing up eagle cad so here is a quick and dirty schematic of how I have it currently set up.

Using the example from the link BeB00 provided I added the 555 timer, sans high pass filter into my circuit.

The end goal is to have relay 2 stay on continuously while SW1 is depressed, but relay 1 needs to turn on for ~500ms, and then turn off, until the next time SW1 is depressed.

At the current state, regardless of whether a positive, negative or no connection is made to the trigger of the 555 timer, it does seem to trigger ever half second or so, but does this continuously when power is applied.

I would be able to use a positive or negative signal to the 555 trigger, positive is just the most convenient in it's current state, but the linked page by BeB00 does state it needs a negative signal.

I did have to substitute the suggested 10uf ceramic capacitor for a 20uf electrolytic capacitor, if that makes any difference, however I don't think that it should since it's not interacting with the trigger.

Edit 2: I did find this page which has the 555 timer connected differently, and appears like it may perform the function that I need. https://www.utm.edu/staff/leeb/3b3.htm

I'm not quite sure if the 555 timer example also fires for half a second though or if that is only the 74121


texts:
I am looking to identify the LCD module pictured below and find a datasheet for it, or otherwise determine the pinout and figure out how to properly drive it.

Front

The lines of text on the ribbon cable read: VG-G080851, 1WRNNB, S37104032

Back

It uses a 24 pin ribbon and the 8 labels on the ribbon, the 4 on the right side read D0, D1, FLM, and FM going from top to bottom (scan was a bit blurry in that area)

This unit is a monochrome screen and was pulled out of a Hasbro VideoNow (V1) player. I don't have the tools to sniff the protocol at all, but the unit was working when I first got it. The wiki page for the VideoNow player doesn't provide any useful technical information or resources (as to be expected). A general Google search for the part number doesn't provide any useful information either.

Apparently the module is manufactured by Vision Display System Co., Ltd. (a Taiwanese company), but their website (http://www.vds.com.tw) is down. I've emailed them about a datasheet, but I have yet to hear a response.

How do I properly drive this LCD? or where can I get more information about it or a datasheet?

UPDATE: I ended up wiring up a test rig to figure out how the main board was driving the LCD, but when I was checking the output on the LCD, I realized that the ribbon cable had broken in a couple places and it was no longer working.


texts: Connecting S1 and S2 on SONOFF Mini to 230V

texts:
Can I connect 230V to S1 and S2 on the SONOFF Mini?

User manual:
http://dl.itead.cc/mini/MINI-user-manual%20V1.0.pdf


texts: Current limiting resistor: where is it best to put it

texts:
I'm fairly new to this and I was wondering if it makes a difference if I put the current limiting resistor of a LED on the cathode or on the anode.  Any "best practice" and why?

Thanks!


texts:
Please help me to understand below scenario which is there inside the spef file. I have written only the snapshot, not the full text.
NAME_MAP

*1 foo1
*2 foo2
*3 foo3
*4 foo4
*5 foo5

D_Net *1 <value1>
*RES
…
*CAP
*1:1 *2:1 <value2>
*1:2 *3:1 <value3>
*4:a *5:b <value4>

I understand the first two lines of CAP section and confused about the
last line of CAP section?
Admin, please can you help tagging the right keyword to it? I do not see 'parasitics' in the list. Thanks.


texts: Does a high voltage electrostatic precipitator power supply provide a balanced or unbalanced output?

texts:
Does a high voltage electrostatic precipitator power supply create a balanced or unbalanced electrical output in relation to the primary side/ground? If the device provides an unbalanced output, does the power come off of the negative or positive side?
Here is an example of such a power supply: http://www.ebay.com/itm/High-voltage-electrostatic-precipitator-power-supply-with-400W-60kV-/152550032861. Also, here is a schematic for the power supply:


texts: Component Identification - Latching Relay?

texts:
I have, from my limited knowledge, what may be a latching relay.  It was made by FR Ltd of Wimborne, Dorset.  I presume this is Flight Refuelling Ltd.  It is called a Memstore RSC-68.

Anyone know anything more about this, or where I might find some further info?

It doesn't come up on a Google search.  Presumably a pretty rare item.


texts: Wiring of USB 2.0 hub using a USB-C connector

texts:
I have a USB 2.0 hub with 7 ports and an external power supply. I wanted to replace the USB 2.0 connector with a USB type-C connector.

That connector has the following documentation:

I found the following wiring:
https://en.wikipedia.org/wiki/USB_Type-C#Cable_wiring

I cut off the old connector and soldered the USB connector on. I hooked up A6 with the green wire, A7 with the white wire, GND with the black wire and Vbus with the red wire. Then I connected the hub with my laptop (15" Late 2016 MacBook Pro).

The laptop didn't see the hub. Why not?


texts:
I need to repair some kit that uses several connectors like the one pictured below. The existing connections have become brittle and are breaking off.

The wires appear to be crimped into the connector somehow. Is there a special tool I need to re-attach them?


texts:
I have imported a schematic in PCB and placed components. But one thing is missing, its not showing pads names as they are appearing in schematic. It can only show Designator and Comments of component in PCB but not the pads name.

How can I make them appear ?

Thank you

Added screenshot, how to do like this. Like 1 appearing next to pin 1, 2 appearing next to pin 2. But when I add a header, nothing appears, only the entire component designator appears.


texts: I'm about to order a bunch of capacitors to keep on hand. What are some commonly used values I should stock up on? I know 0.1uF are good to have for decoupling, but what about others?


texts:
I’m trying to repair a 63 year old record player. Opening it up, all of the electronics have aged badly, except for the drive motor, which is basic enough that it operates properly. I know enough about the resistors and capacitors that I can just get modern equivalents that will last much longer than their 50s counterparts, but what I’m concerned about are the vacuum tubes, one 35W4 and a 50C5.

This image is of the tube’s socket pins. The top tube is the 35W4, while the bottom tube is the 50C5. You can see a bright bluish-white line of electricity connecting two pins together. It doesn’t seem to go away until I cut the power. The 50C5 seems to be experiencing spark gaps, if that’s the proper term, between pins 6 and 7, along with making an annoying buzzing noise. I don’t leave it powered on because I don’t know if it will start a fire, explode, etc. Tubes aren’t my specialty, but I know they’re dangerous. Does this mean anything is happening to the tube? Is it faulty?

Here is a picture of the record player schematic.

The white powdery substance is just a 250 ohm Lectrohm resistor, I’m not sure why it uses powder, it is some 60 years old, but it isn’t functional and the resistance has dropped drastically.


texts:
In audio synthesis, we have ADSR envelope;

Now, let us say I wanted to detect A,D,S and R given a signal. We can determine the beginning and end of relevant signal with a simple gate, and find the envelope with an envelope follower. My proposed solution for detecting everything else is look for critical points (first/second derivative test) of the envelope.

Is this a possible/the best solution? What is a ballpark price estimate for 10 units of an IC that will do this? 100 units?

Many thanks in advance

Joe


texts:
I am having trouble with a Digtal Works Simulation of a Ring Counter.
(Version 3.0.5.0, copyright Mecanique)

The on-off button does not clear the flip-flops; the flip-flop to the left
is always on.

(I am  using this in a simulation of a CPU for the computer organization
class I teach.  This will be for the basic control, whether the computer is
fetching an instruction, from memory, doing an immediate operation, etc.)

I searched for "Digital Works" in this Stack Overflow and found nothing.
Of course, I did find and use plenty of information on the web in general
on this issue.


texts: Making a power supply that offers two voltages

texts: I am building a model warship that needs 12 volts and 5 volts to run its motors and a microcontroller.  The ship is powered by two 12 volt lead acid batteries wired in parallel.  I built a power board that, among other things, splits the battery between power out (which will connect directly to the motor controllers) and a LM7805 volt regulator.  I am worried that when the motors (three total) are run at the same time, this will cause a power drop below the regulator's usable threshold.  Is there a way to ensure the regulator receives enough power?


texts: What is an alternative to this rectifier? - GB14C40L

texts:
We've nearly completed an engine swap on a car, which needs to have a piggy back ECU called an EMU to run the new engine.

The trouble is, the new ECU only sends a spark on two of the 6 cylinders. We opened it up, and found 4 out of the 6 rectifiers look burnt and cracked. A new ECU is around £800.

The part number for them is: GB14C40L 327P

I can find the parts on an online wholesale site, but am trying to find them locally.

Is there any alternative to this part we could look at using?


texts:
1) For table 1 of Berkeley paper , why "Input must be valid for at least two clock periods in the new domain." ?

The explanation:

  the width of the input pulse must be greater than the period of the synchronizer clock plus the required hold time of the first synchronizer flip-flop. The safest pulse width is twice the synchronizer clock period.

Could anyone tell why it has to do with hold time of the first synchronizer flip-flop ?

2) For pulse synchronizer or what we known as toggle synchronizer, I do not understand the explanation highlighted in yellow that is given below:

  One restriction of a pulse synchronizer is that input pulses must have a minimum spacing between pulses equal to two synchronizer clock periods.

  This problem is more severe when the clock period of input pulse is greater than twice the synchronizer clock period


texts:
I have a 5w solar panel which shows about 20V open circuit voltage. If I connect it to a load- no current.
The voltage drops to almost zero as soon as I introduce a 2.9 ohm load. I can not detect any current at any load.
Can anyone tell me whether the panel is faulty?


texts:
Another translation, another question.

Original German:
Antriebssysteme dürfen nicht direkt an TT-, IT- und an TN-S Netzen mit geerdetem Außenleiter betrieben werden!

Rough translation:
Drive systems are not permitted to be operated directly on ......

We received feedback from a German-speaking engineer that what we are looking for is "...corner-grounded TT, IT and TN-S systems".

"corner-grounded TT" comes up with 2 hits in Google, leading me to question the suggestion.

The 1:1 English translation would be something like "...TT, IT and TN-S system with a grounded line conductor." Unfortunately, I know about as much about this topic as I know about designing aircraft. Can anyone out there help sort this out?


texts:
so I've just built a circuit and some Arduino code (not shown here) which interfaces between a car steering wheel and its buttons to an aftermarket cruise control system (Command AP500).  The stock keypad for this cruise unit has a weird LED arrangement and if the LEDs are not present, the AP500 cruise control system will refuse to engage.
I have mimicked the LED circuit and it works, but the question is how the microcontroller (unrelated to my Arduino) in the cruise control system is detecting the existence of the LED?  Image of the LED circuit is attached.  Note that the cathodes of the LEDs do not appear to be connected to a ground and both of the cathode circuits have a voltage potential between them and the DC ground. Somehow, the microcontroller in the cruise control unit is able to detect if one or both of the LEDs are present.
I'm assuming it is something to do with the use of a 7.5v Zener diode (and it is only able to detect the Red LED).  Could the microcontroller be measuring the voltage on that wire and detecting a difference in voltage when the LED is lit?  Why does the lead from the microcontroller to the Zener diode have 2.7v on it?   Note that when the red LED is powered, the voltage between pin #2 and DC ground drops to 2.3v.  This is all when the circuits are connected to the microcontroller of course.
Lastly, +12v is permanently on and is not used in controlling each LED.


texts: Solid State Relay/High Voltage Switch unacceptable transient behavior

texts:
I am using a whole array of IXYS CPC7524 high-voltage switches in one of my designs. Although the design of this specific switch is not made explicit, its characteristics and other products in the IXYS product line (such as the CPC1511) leads me to believe that the pass elements are quite probably pass NMOS devices with additional thermal protection circuitry.
The application requires fast switching of voltage/current across the switches (which remain constantly turned on) and we are getting very problematic behavior out of them. This conceptual schematic shows how the switches are being used:

simulate this circuit – Schematic created using CircuitLab
Q1 is used as a saturated switch and M1 as a current source. The slew rate in all nodes was measured and it never exceeds 100V/µs (the CPC7524 is specified in excess of 1500V/µs), however this is what we see on those nodes (everything is turned off after 600µs from the trigger):

Which clearly shows the switches enter a high-impedance state as soon as the NFET turns on, and takes as much as 250µs to reduce their impedance to the point the circuitry becomes properly biased (the chatter in the Drain node (CH1_R) shows instability due to the gain provided by the presence of the switch impedance).
In other scenarios (e.g., higher voltage or a shorter delay before NFET turn-on), the switches simply latch-up a temperature fault (an undocumented behavior) and open the circuitry requiring a power-cycle.

NOTE 1: this is a conceptual schematic. The details of the application are not very relevant. Suffice it to say that I need something that behaves just as a physical and slow mechanical switch or relay, connecting two sides of a circuit that has large fast-varying waveforms. Not a dynamically varying resistor, which is what I am getting with these switches.
NOTE 2: This is implemented in several interconnected PCBs with high-voltage edge-card connectors. We investigated all possibilities (including the possibility of inductive coupling between nearby traces) before narrowing down the problem to the switches. So yes, we are 100% certain the switches are the problem. And we understand the problem well enough to get the switches to predictably misbehave at will. The rest of the circuitry works exactly as designed.

Question
As these switches are clearly not acceptable for our application, before we undergo a redesign using large, cumbersome, and power hungry reed relays (note there are large numbers of these switches), does anyone know if a simpler Solid-State Relay, such as the Vishay VOR2142A8 would present the same kind of problems?
Can anyone suggest a better solution?


texts: What are some good resource for learning how car key and wireless door lock systems work?

texts:
I understand that most car keys include a 434MHz transmitter, as well as 125KHz RFID transponder. The 434MHz transmitter is used for operating the door locks, and the 125KHz RFID transponder is the vehicle immobilizer.

How do I find out how the program running on the microcontroller for the 434MHz transmitter is structured?


texts: In digital logic, when given a requirement of a 64 byte FIFO, is it possible to calculate the width and depth?

texts:
I have an input device that can write in either serial, 8-bit parallel, or 16-bit parallel. I know the input frequency and max write speed of those data formats.

I am given a requirement of a "64 Byte" FIFO, with a word consisting of 4 Bytes. I want to test this generic VHDL code I found online. The constants required to modify are "DATA_WIDTH" and "ADDR_WIDTH". I can see from the code, 1 word is associated with ADDR_WIDTH.

snippet:

...
constant FIFO_DEPTH : integer := 2**ADDR_WIDTH; --given equation???
signal pNextWordToRead : std_logic_vector(ADDR_WIDTH - 1 downto 0);
...

But it also calculates the depth for you. So if I first plug in my word size, I can calculate my depth. Could I also calculate my Data Width as DATA_WIDTH = 64 byte / word size (derived from FIFO size = width x depth)? If I am using the wrong values, how would I calculate my depth properly?

So is the Data width not the same as the FIFO width? If the data width is less than the address width, then it would take more than 1 cycle to write a full address.

This implementation makes sense to me at the moment because my depth is a lot and I properly will not overflow (my read clock is a lot faster too).


texts: How to find the wattage of a power relay?

texts:
I have a relay here -

Is there a way of knowing the wattage of this relay? It could be anything from 0.36W to 0.54W but since I dont have the datasheet I can't tell exactly how much it is.

Thanks in advance


texts: MC34063A switching regulator: LC filter and feedback

texts:
The MC34063A bust/boost/inverting switching regulator recommends using an LC filter at the output, after the filtering cap. This LC filter is optional and there is no mention in the data sheet about including it in the feedback loop. I'm tempted on including the filter in the loop but maybe I'm risking the stability for a small return of some small fraction of volt for the higher currents (and the currents won't be more than 0.5A)

Could it be detrimental in terms of stability? Has anyone tried this with this regulator?


texts:
I'm experiencing some hard voltage drops on my AC power line (measured at 20 points across the house).
The culprits are the washing machine and dryer (as well as our upstairs neighbors washer and dryer). The drops are anywhere between 4V (from 244 to 240) to as much as 15 volts causing our monitors to flicker off for a hot second and our wifi to drop out for a little bit.
Is there anything that I can do to stretch out the voltage drop and prevent it from messing with my devices. I would like to check here before I take extreme measures and start building a power stabilizer for my router, monitors etc....
The voltages meters here need some further calibration. They are 30V too high.
Voltage next to the washer

Voltage next to the dryer

Voltage in the living room

voltage in the bedroom

Voltage of the router (This one is properly calibrated and has a much higher refresh rate)

The sensors I use measure average over 2 seconds. The sensor at the router averages over 0.5 seconds.


texts: Schematics for a simple radio transmitter that can be built only with passive components?

texts:
Fantasized in some of the survivalist, post-catastrophic novels, movies or docudramas is the radio built only with handcrafted or scraped components.

Beyond the popular appeal of this stories, I think there is a core of truth and passive elements are easier to scrap and handcraft, can easily be read and calculalted without a multi-meter or can be easily reused. Resistors/condensers can be put in series or in parallel. Coils can be uncoiled and re-coiled from transformers other coils etc.

Is it possible to build a very minimalist radio transmitter that can be built only with passive components, what would be the schematics for that?


texts:
I am making a custom connector that will carry several signals to a test board including RS-422 RX+/RX- and TX+/TX-. The strange thing is that I didn't find a standard pinout for the DB9 connector used for the RS-422!

So I checked the manufacturer of the RS-422 PCI card in my PC and found their own pinout which means that my test board can only be interfaced to this RS-422 from this manufacturer and won't work on solutions from others?! Is that normal for this "standard" protocol?!


texts: Power factor of a transformer (does it have anything to do with load impedance)

texts:
Let us consider a resistive load R is connected across the secondary of transformer whose impedance is r+jX, so in calculation of the power factor of the supply (here in this case it is the secondary of the transformer ),
Will the supply power factor be : cos theta = R+r/Z  or will it be r/Z only ? Does supply power factor of the system has anything to do with load impedance ?


texts: Splitting a 10amp 2.1mm DC barrel into positive and negative

texts:
I have this AC to DC converter and I want to be able to split out the positive and negative wires from the barrel without cutting off the barrel.

I've been looking at options such as this jack to terminal screw adapter, but I don't think it is rated for 10amps (I want to use close to the full 10 amps).

What are my options? Does anyone know of something that can break out the barrel jack while sustaining the full amp level?


texts: Question on feedback (the topic is in CMOS circuits)

texts:
So right now I'm studying feedback in CMOS circuits (i.e. when there is some sort of connection between the input and the output like in the picture below):

Now during the next step in the example I am looking at, they convert this circuit from a "closed-loop" circuit into an "open-loop" circuit like so:

Now what I know is that the reason we are doing is to find two coefficients A and B where A is the gain in the "open loop" circuit and B is something... I don't know what it is :. Anyway the final answer is of the form A/(1 + A*B). With that being said, I have a series of questions.

Why are the resistors arranged the way they are when the circuit is converted into the open loop form? In other words, how does that conversion work so that I can reproduce that process in a different but similar problem?
What is the meaning of B in the equation I mentioned, i.e. A/(1 + A*B)?
If this is not yet answered by the previous questions, why does doing this whole "closed circuit" to "open circuit" thing work?
PS, here's the entire solution if that helps:


texts: Power supply of board based on tp4056 with protection gives too low voltage

texts:
I have a project on small pocket board with a Li-Ion battery so I made a pcb with power section based on a tp4056 board (with protection), with LP2985IM5X-3.3 stabilizer. TP4056 charges the Li-ion and it works good, on the out I have 3.6V, but when I turn on the stabilizer before it is 0.6V and next to it is ~0.2 - 0.6V. I have no idea how to fix it to work on the 3.3V level. Please, write to me some suggestions. Thanks.
Schematic of power section:

Edit:
I changed MOSFETs connection (look comments) and voltage is fine, everything works good but there is one problem, it doesn't charge li-ion.


texts: SMD LED for microprocessor output without resistor

texts:
I have a very simple problem to solve and I'm surprised there is no common solution for it.

I need to connect several indicator LEDs to microprocessor outputs and I know I need a serial current-limiting resistor. To save space I'd like to have LED that takes 3.3v without resistor. There is a couple out there rated 3.3v but I understand it is not safe to connect it without resistor even though it is 3.3v rated.

Also they are 20mA, I'd prefer 10mA since they are driven directly by MPU with 200mA total output limit.

Since this is such a common problem, I'm sure it must be solved and I might be just looking into wrong direction. Please enlighten me!


texts: Solid state relay (SSR) - alternating polarity

texts:
I'd like to control a slave clock, via a relay(s), which needs an alternating polarity pulse once a second.

The attached circuit incorporates two SPDT relays which do this (one relay activated one second, the other the next, to provide the alternating polarity).

I'd like to use a SSR relay though to avoid mechanical wear.

I've got some SPST DC-DC SSR relays but, as they're SPST, I can't see a way to replicate the circuit I've attached.

Does anyone have any ideas?

Thanks.


texts: Why does a neon lamp indicator on a power strip switch flicker in the dark?

texts:
Neon lamp indicators embedded in power strip switches indicate whether the switch is ON or OFF.
When the neon lamp is ON in a dark environment (lights of the room are off), the lamp begins flickering and it sometimes goes off for a few seconds.
When I switch the lights of the room on, it stops flickering and remains bright. Even when I unlock my phone in the dark near the lamp, it stops flickering!
Is the light-making-mechanism in neon lamps affected by the light intensity of the surrounding environment?

UPDATE: I captured my observations with my iPhone and uploaded it to YouTube. Here is the link of the video:
https://youtu.be/1jlUmEfGHZA
All the lights of my room were turned off. There were no plugs connected to the power strip. The only source of light was the screen of my MacBook Pro, which was not plugged in.  I increased and decreased the brightness of the computer screen during the video.  I then produced two additional light environments using my phone.


texts: Understanding the circuit diagram on a filter

texts:
I have a filter that has these on it:

Funk-Entstörfilter
Drossel
250V~2A HPF F11.180/4
8.84 W Germany 565-3

I also added a picture. In the picture, you can see that there is a circuit diagram, however I can't understand this diagram. In example, how the capacitors are connected? Do these lines that connects inductors mean that they are coupled? I don't know much about it but can they be common mode chokes?

Can you convert this into a schematic that I can understand?


texts: Have I damaged my multimeter by applying voltage in resistance mode?

texts:
I have an VC97 digital multimeter. In resistance mode, I applied the multimeter leads to a battery with a 4.2V charge. I did this twice, and also did so in capacitance mode.

I didn't notice any smoke, and the multimeter seems to function fine on all modes.

I don't understand how applying a voltage in resistance mode may damage the multimeter, and I don't know how to determine if the multimeter is damaged. Can anyone please help?

(Also I promise to read the manual first from now on. Promise.)


texts:
I have an Atmega328p based node with RFM69HW radio, controlling a relay. Power is supplied using a cheap 220V to 5V Chinese power supply (see photo). A 30W led bulb is connected through the relay to mains power.

The problem is, when I run test, which turns on and off the relay once per 5 second, sometimes (once per 5-10) the system just reloads. I checked every part with an oscilloscope and found that the power supply has voltage drop to near zero, which causes the system restart. Checked with different power supply, everything works perfect. Also, without the bulb it works.

Can anything be done to fix the problem?

The schematic:


texts: What is the name/purpose of this component?

texts:
I was wondering what is the role/purpose of the electric component in the red square.
This is the schematic of a 230V single phase induction motor.

What is also not clear to me are the connections on the right side.
The first two wires are neutral (blue) and live (brown). What is the third one? Earth? If yes, why is there an tild sign (AC) above it?


texts: NC (non controllable) fault on primary input

texts:
I am using TestMAX (synopsys) to debug problems of coverage in DC (stuck @) simulations.
I encountered a NC (non controllable) fault in the primary input, why do I get that? is that a bad fault or normal thing to happen?


texts: Sony vaio keyboard dongle - Power issues connecting to another computer

texts:
I have stripped down a very early (2002) vaio all-in-one desktop which has a keyboard with a built in protective cover which I would really like to use on another computer. The dongle was placed under a cover on the outside of the casing and has the rating 5v 100ma on the back. The cable was designed to go straight to a connector on the mainboard and appeared to be USB, I adapted a usb cable to connect but when I plug it in the dongle has too high amperage and windows complains. Is there anything I can do to enable this to connect? The device is seen by windows but cannot power it.

CN2 is for a connect button, CN1 is USB from bottom, Ground data(+) data(-) +5v


texts: Any clever way to provide 3.3V with good current output from a 9V battery?

texts:
I'm sorry for any English mistakes as I'm not used with using it when talking about technical stuff.
I have been using some ESP8266 WiFi modules with Arduino Mega for a project. They work with 3.3V Vcc but require some good amount of current (it can go over 200mA, as seen here http://wiki.iteadstudio.com/ESP8266_Serial_WIFI_Module), which make them impossible of powering from Arduino, and that's why I'm using batteries to power the VCC pin. I keep other two pins (CH_PD and RESET) at HIGH state, but I keep them at 3.3V pin from Arduino, as they seem to steal some precious current from ESP8266 VCC if connected together to the battery and make the ESP8266 unstable.
I used LM1117 because the original idea was to extract 3.3V from 5V Arduino pin for more current output, so an LM7833 would not work. Extracting 3.3V from the 5V didn't work as expected, so I'm using a battery now.

simulate this circuit – Schematic created using CircuitLab

This circuit has been working fine with some ESP8266s, but some of them seem to be requiring more power, since they are failing to get WiFi connections most of the time, taking too many attempts to connect. Also, LM1117 eventually heats quite a bit and drains a lot from the battery.
As you can see, I already power the ESP8266s from over 3.4V (although this level seems to drop a bit once I attach the ESP8266), and I'm kinda afraid to rise this level even more.

Do you have any ideas on a better circuit to provide 3.3V with good output of current for my ESP8266?


texts: How to increase the output current of a dual supply (virtual ground) circuit

texts:
I need to build a dual 5 volts power supply capable of 200mA output current.
I've seen designs using TLE2426 and BUF634, but they cost too much for my project.
Is it possible to use a simple OpAmp circuit like this one (from here):

Which uses a uA741, and then increase the current output by adding transistors to the VGND? Since the VGND needs to both source and sink current, I may need to add two transistors, one positive and one negative, but I don't know how they should be arranged.
If this solution works, what would be the correct design for it?


texts: How did my TV capture neighbour's DVD player's frequency?

texts:
The question might be quite confusing since I'm totally new to electronics world. When I was in school, I had a TV that required a TV Antenna to capture free air channels. So one day when I was just tuning different frequencies in TV Settings, it captured a frequency and started playing video. Later I got to know that frequency was from a DVD player used by my neighbors. So I could literally watch what they were playing in their DVD player on my TV (Without any loss of clarity).

So the question is why DVD player was leaking the frequency?
And how my TV was able to capture those frequencies?


texts: Three phase balanced transformer network with b-phase fault

texts:
100 kVA, 11 kV (delta) : 400 V (wye), Xeq = 0.1 p.u
with a neutral to ground connected through Zn = j0.1 (ohm)

I have a question where the above transformer is fed by a balanced positive sequence three phase source, and parallel delta and wye loads are connected on the load side of the transformer. I am then told that the b-phase drops to zero (not an open circuit).

I see they specified in the answer that there is no zero-sequence current after the fault.

Vo = 1/3(Va + Vb + Vc) Which would not be zero.

My textbook states: "In a balanced Y-connected system, line currents have no zero-sequence component, since the neutral current is zero."
But after the fault we no longer have a balanced system.

1) What is the purpose of stating that it is not an open circuit, what is the difference in this context?
2) Why is the zero-sequence current zero?
3) Does Xeq refer to the leakage reactance only?


texts:
I am designing an On board charger for electric vehicles for my graduation project. And I am confused about testing the OBC. My goal is charging a 400V battery pack, but I don't have a battery pack and probably I won't.

Is it enough to use resistors instead of batteries? If not what can I use for equivalent to battery?


texts: Estimation of Electrolytic Capacitor ESR at SMPS Frequencies

texts:
While working on compensation networks or ripple calculations, it helps to know the ESR for my output capacitors. In high voltage SMPS systems, this seems to be difficult for the following reasons:

ESR if quoted is at 120Hz. - Commonly people will explain to use Tan(\$ \delta\$) to calculate ESR for a given frequency beyond 120Hz... See issue #2.
Tan(\$ \delta\$) seems to not be consistent across frequency (source p. 7) So unless you are close to the often quoted 120Hz, this is not useful.
Does Voltage bias affect ESR? I assume not, but I have not found any info supporting either yes or no.

I have made crude setups to test ESR of capacitors I am planning on using, but I would like to perform it more analytically if possible... Also depending on if ESR is affected by voltage bias, that has a huge affect on the complexity of testing ESR, since this is typically for ~400V output supplies.
Any advice or experts on the 3 points above? I'm guessing the consensus will be to just estimate and test...

Below are a datasheet for reference and an image of the plots from page 7 of the Nichicon capacitor manual I reference above.


texts:
I am building a replacement for dishwasher's controller that burned, using Arduino Leonardo. Arduino is powered through standard 9V AC/DC converter.

Dishwasher uses quite large 220VAC electric pump and a few electromagnetic valves that I control using relay board. Because I was stupid I've bought 12V relay board, not 5V - so I had to power relay board from Vin pin - 9V is enough to do the job.

The layout is pretty tight - I use sealed lunchbox to store the components (wiring is removed at this photo, it looks as a ratnest when fully assembled).

The problem is that serial connection I use to debug my dishwasher code is quite unstable. Sometimes it hangs; if I use TTL wires hooked to pins 1&2 instead of USB I sometimes notice odd characters. Seems that either relays are causing short voltage drops sometimes or the noise from pump and valves are influencing the circuit.

My idea was to add few  electrolytic and ceramic capacitors right on the 9V AC/DC's wire. But what worries me is that I've heard multiple times that decoupling capacitors should be installed as close as possible to the circuit. In my case the length of the wire between caps and Arduino's DC jack will be about 5cm. Is it gonna work or this setup will be useless?


texts: How to wire additional relay for heavier load

texts:
I'm not an electronics student but have a decent grasp on the fundamentals. I am attempting to use an assortment of components to facilitate a driveway gate automation. The parts I have currently are:

2x linear actuators (motors)
remote control receiver/relay
power supply

The problem I have is that I will be wanting to operate the motors at 24V (as opposed to 12V, which would make them slower; yes, 24V is within acceptable operability of motors), and by my calculation, this would push the max current usage to about 14A total. The wireless receiver/relay maxes out at 6A, and I would like to use this remote system for various reasons.

My thoughts are that I could simply wire in an additional 20A relay to operate the motors, but I'm really not quite sure how that should be done. There are so many relay options, I'm really not sure where to start. Could someone perhaps point me in the right direction? Perhaps even a schematic? Thanks!


texts:
I'm searching for some simple 3-wire RTD sensor to be measured using an ADC. I found some options, but I'm kinda confused with how does they works and which one is the best.
First, there is the Weasthone bridge configuration. I found two variations of this circuits, and I cant understant how this compensates the wire resistances Rw.

simulate this circuit – Schematic created using CircuitLab

simulate this circuit
This second one, I think I understand how does it works, but I dont know how to implement this. I can subtract VM1 - 2*VM2 using an AmpOP, but how do I implement a constant current source?

simulate this circuit


texts:
I'm reviewing a schematic so that I can replicate it and I've come across several labeled inductors with no values. From my Googling, It seems that these may actually be ferrite beads. My question is, what kind of ferrite beads should I populate here?

L3, L4, L5 and L6 sit between a 1W audio amp and the output. L8 sits between a single wire data bus line, for reference.

Additionally, on  the first image near R18 (left side of the schematic) the ground is pointing two directions and there's an arrow with a line through it, which I can't find the meaning of via Google. Any idea what's going on there?

Audio Preamp circuit:

Power and I/O:

Thanks!


texts: Using only a rheostat on a LED ceiling panel light

texts:
I have a 40 watt 2'x2' led ceiling panel with a dimmable driver. With the purple and gray 0-10v circuit left open, the light operates at full brightness.

Considering the following (Pathwayconnect.com: Best Practices for Dynamic 0-10VDC LED Lighting Control) "When the purple and grey wires are open (not touching each other or connected to anything else) the dimming signal will be 10VDC and the output of the driver will be 100%. When the purple and grey wires are shorted together (touching each other) the dimming signal will be 0VDC the output of the driver will be set to the minimum dimming level or the driver will drop in to “sleep mode” and turn off the LEDs completely."

In simplest form, applied to a single panel, would it be accepatable to connect a rheostat (approx 2K) across the purple and gray wires to use as a variable series resistor to transverse the range: short to nearly open?


texts: How to simulate a PIC microcontroller using Proteus

texts:
I wrote a simple assembly program and the uploaded it to the PIC16F1939 in the laboratory, and everything worked just as as expected (the LEDs blinked as they were supposed to). However, I tried uploading the same file to the proteus model of the same microcontroller, and nothing happened:

I adjusted the clock frequency. The only problematic part could be the program configuration words. How do I set those? In the pic above you can see the values 0x00 and 0x04 I typed in after the simulation failed with the ones that came as default in proteus.


texts:
I'd like to measure voltage and current for a mains circuit using a microcontroller, and connect this to ethernet. Since I want to have 8 independent outputs, using an isolation transformer to measure the current for each port quickly becomes expensive.
So I thought of just using shunt resistors to measure both voltage and current. This is not a problem for the microcontroller, but it is when interfacing with the external world.

Then I remembered that Ethernet already has isolation. Specifications say ethernet connections are coupled with isolation transformers rated for 1500V .

I was wondering if this isolation is safe enough for a mains circuit? If so, I could build my circuit completely non-isolated and rely on the ethernet transformer for isolation. The device won't have any other means to interface with people (maybe just LEDs, but no buttons or knobs)


texts: How does the physical size of resistors effect replacement of them?

texts:
To expand on my question.I need to replace a 5 band 100k resistor and possibly others but the resistors that I have in my stock of parts for replacements are physically larger than the ones on the current PCB project.
Can I use these as replacements?
How does the physical size of resistors factor in, or does the size even factor into these components?
Further details to describe resistor.The main body colour of both resistors are blue.


texts: Mealy machine to detect sequence of 2 inputs

texts:
I have the following assignment for a project at college and I have a few questions regarding it.

You are to design a Mealy state diagram for a digital lock. Assume that two debounced push-buttons, A and B, are available to enter the combination. An electromechanical interlock guarantees that the buttons cannot be activated simultaneously. The lock should have the following features:

The combination is A-A-B-A-B-A. If this sequence is correctly entered, an output signal is asserted that causes the lock to open.

For any state, three B pulses in a row should guarantee to reset the control to its initial state.

When any out-of-sequence use of the A push-button occurs, an output is asserted that rings a bell to warn that the lock is being tampered with.

Once the lock is open, pressing either A or B will cause the lock to close without signaling an error. Draw a Mealy state diagram for this finite state machine. Indicate what each state represents and what input conditions cause state and output changes. Not everything may have been specified, so write down any assumptions you make.

I have to implement this using only MUX'es and JK flip-flops. My progress so far:

-I have 10 states the machine can be in:

S0 -> nothing happened yet

S1 -> input = A

S2 -> input = AA

S3 -> input = AAB

S4 -> input = AABA

S5 -> input = AABAB

S6 -> input = AABABA (the output should be 1 when we get to this state)

S7 -> input = B

S8 -> input = BB

S9 -> input = A(this would set off the alarm)

-I now have to use 4 JK flip-flops(since the states would be written as Q3,Q2,Q1,Q0) so I have a giant truth table for the current state(Q3,2,1,0), input(A and B), next state and each JK flip flop

-I then proceeded to draw Karnaugh diagrams for each of the J and K functions and minimize them as much as I can(but they are still really REALLY long).

Now the only thing left would be to make the circuit and this is the part where I'm stuck. Having so many variables (Q3,2,1,0, A and B) how should I start making the equivalent circuit? Any help would be greatly appreciated :)

EDIT2: removed a question


texts: Help looking for an AC power transformer

texts:
I am doing a custom project, where I have to heat up a big resistor controlled by a PID and a thermistor.

Normally, I use a 12V 30A power supply, but I would like to design my own power supply, to learn how to do it.

Well, I am now choosing a simple transformer, and I find that they are pretty expensive. Maybe I am choosing the wrong transformer or the wrong provider (I am looking in Digikey).

So, I would like to ask:

For a European primary voltage and 12V secondary voltage, if I need 30A, I would need a 360VA transformer right? I see that many cheap power suppliers are cheaper than the transformer. Ok, those are optimized, but... cheaper than everything?

Which technology is best for this? I see many different types of power transformers, but I don't get the differences.

So, how would you look for a transformer for your own power supply?


texts: How can the Microcontroller run anything else if the interrupt is really fast?

texts:
just a quick question. I am just confused how you are suppose to run anything else if you have a periodic interrupt going off every X amount of seconds.

If I have an ADC being interrupted at 38kHz or about ~26uS how does that leave room  to do anything? Let say I want the ADC to still be triggered every 26uS but I also want to do some math that uses the output of the ADC. Would that mean I need to create another interrupt that execute after the 26uS mark but it needs to finish before the next ADC trigger?

This is assuming the ISR for the ADC as soon as it triggers, its completed.

The way I think of this is a time line of deadlines

If I have an ADC that triggers every 26uS then:

0....26uS....52uS....78uS

Then the task that I want to do math in would need to finish in between the ADC triggers?

0....26uS...[Math Task]...52uS...[Math Task]....78uS

and if I want to write another task along side my math one it would be like this?

0....26uS[New Task][Math Task]....52uS..[New Task][Math Task]....78uS.

So in essence if you want to run anything else, does it need to be faster then your biggest (slowest) interrupt frequency?

Is it viable just to write your task in terms of interrupts and have it in a timeline like above or would you use the while(1) loop etc. Not sure how the while(1) loop would even work when it comes to deadlines.

Too me this seems crazy, What if I want to do audio processing? Sampling an audio signal at 44kHz and implement a digital filter by feeding my ADC values into my difference equation.

Would that mean my digital filter algorithm task:

needs to be faster than 44kHz?
What if its never possible for my digital filter to be that fast due
to the arithmetic and storing past values and what not?
Would it be not implementable then?
How do people like Sonos have MCU doing audio processing and stuff?

EDIT: Taking your suggestions into account I picked up 3 micro controllers for further play testing: Let me know what you guys think.
- PIC18F25K83
- dsPIC33EP64GP502
- STM32L432KC


texts:
In my new project I am using a FPGA and DAC. The DACs CMOS inputs are connected to the pins of the FPGA which are also CMOS compatible.
My question is can I just simply connect the CMOS pins of the DAC with the pins of the FPGA or should I place a resistor in between them?
The distance between the DAC and FPGA is around 1 inch. The frequency of the datapins is max. 20kHz. The voltage level is 3.3V.
In the schematic of the Arty S7 50 FPGA board from XILINX there are 200 Ohm resistor placed infront of the GPIOs. But do I actually need them?
What is the purpose of this 200 Ohm resistors?


texts: DC Motor circuit polarised 2 directions switches

texts:
I'm totally new to electronicS and do not understand a lot and I've read other posts but people seem to be asking different things to me so apologies in advance if this has been covered but I've typed in what I think are correct terms.

I'm doing an art project installation and require a set up so a DC motor is connected to an axel with lightweight things hanging off it. It needs to winds up 1 way and then change direction and winds down another automatically I.e. Without myself being present to flick a switch to change the polarity. I know it can be done using a dpdt switch.

I have a battery compartment with an on/off switch powered by x4 AA batteries (6v) wired to a 6v DC motor that is already geared to run at 30 rpms which is what I want. I have looked into using micro switches and from what I understand? I can't run 1 switch permanently connected even if I e.g. Hang a weight from the axel that when it is lowered into another switch activating it to change the polarity as if this is done it will short circuit.

Is there a cheap way around having it run in e.g. CW and then change to run in CCW after a switch is activated or after a certain amount of time? If possible I'd like to avoid circuit boards as I don't understand or have the parts for this and time is of the essence.

P.s. I'm based in UK so things may not be as easily available.

Thanks for any help in advance.


texts: How long will my x 2 23a 12v battery last running a 300mah camera?

texts:
I’ve brought some WiFi cameras to run in bird boxes but the battery life on them aren’t very good at all.
I’ve tried running them from battery power banks but they switch off after the cameras have reached full charge.
So I’ve now order some a23 12volt batteries, will run x 2 side by side with a step down regulator to 5 volts 300mah.
My question is how long would they last?
A bit more info of the camera, it has a 300mAh battery installed, says in the instructions that it’s DC 5v and has a working time of roughly 100 minutes.
I understand the batteries I’ve ordered are the GP Super 23a 12v which from wiki stats 55mAh each which I’ll run in parallel.
I’m not electrically aware so hope I’m on the right track..
Thank you!


texts: How to run 12V compressor directly off battery?

texts:
I have a 12V air pump (runs out of the car cigarette lighter). It had worked ok the first few times then stopped working, with smoke billowing out of the receptacle while it was plugged into the socket. I opened up the pump's cigarette plug and it was all melted inside. I replaced the entire plug with a new one. The result was that it worked for less than a minute, smoke started coming out, the inside of the pump's plug melted again. Reviews on this air pump from the store I bought it from showed this to be a common occurrence, along with repeated burnt fuses, etc. Except for one particular reviewer who seemed to have found a way around it with a mod as follows:

"...did not want to return the unit to get a replacement with the same cheap cigarette lighter plug, I simply cut off the burnt plug and replaced it with 2 strong alligator clips and an inline fuse receptacle and I now plug the unit directly onto my car battery's post. No more problems !!!!"

I guess I could just get a heavy-duty marine-grade receptacle, but I like the idea of just running off the car battery directly. This seems easy enough to do but since I'm no expert, I have the following questions:

The fuse that was inside the original receptacle was 15A and quite
tiny.  I was told in another forum (that was of limited help) that I
should find a 15A 1.25" fuse.  The fuses at the electronic store
were    labelled 6x32mm.  Since 32mm~1.25", this is the correct size
fuse?
The original fuse was glass.  The store has glass or ceramic and
slow-blow or fast-blow.  Which should I be using?
Is it ok for the in-line fuse holder to be rated at 20A (that's all
the store has) or does it have to be rated at exactly 15A (the same
as the fuse)?
Is my diagram below basically how it all goes together?

BATTERY(+)--[Alligator Clip]---------------------------------------->PUMP(On/Off)

BATTERY(-)--[Alligator Clip]------->[inline holder+fuse]---------->PUMP(Ground)


texts:
Could someone please explain why are there two Schottky diodes in this schematic?
And also why is the VOUT connected through one of them to VIN.


texts:
I spent the day looking for a circuit driver to control a 12V Omron G4A  (rated current 75mA@12v) relay with 3.3v GPIO of STM32, without success. According to my calculations the circuit below should work, is it? if not can you give me the R1 value, and the reference of the diode and the transistor please?

simulate this circuit – Schematic created using CircuitLab


texts: Would AC voltage damage the capacitor if using a low voltage rating capacitor?

texts:
So I have a circuit below:

C1 is 6.3V rating electrolytic cap.
V1 is 6VDC
V2 is 2VRMS

The DC voltage across C1 cap is 6V and I have 0.3V margin. Since the AC voltage at both terminal of the cap is the same, can I safely say this cap will not damage over it's usable lifespan?

simulate this circuit – Schematic created using CircuitLab


texts: Copper dimension around the PCB component's hole (pad?)

texts:
I had my first PCB manufactured (by a Chinese manufacturer). In this first version I only used thru-hole components (not SMD).

I used the latest version of Eagle to design it, without taking care to set the pad (I hope is the correct name) dimension and shape. The program "decided" to use only circular pad around the component's holes for all the components.

Is the size of these pads (the dimension of the copper around the hole) in your opinion correct or it should be a bit larger (from what it is possible to see in the pictures attached)?

I noticed that soldering some components, the solder has not immediately spread on the pad, maybe because they are a bit thin.

I also don't know why sometimes the shape of the copper is oval and not circular in some circuit I have (not designed by me).

I attached pictures of the top and bottom of a zone in my PCB.

EDIT 1:
with your help I would like to understand in which passage something went wrong. Eventually I can write an email to the manufacturer to understand better on their side. I opened the gerber file with gerbv and only switched on the files in the order TXT (drill), GBS and GBL. I attached 2 images with a focus in the second to capture the size of the anular ring (the gerber image corresponds more or less to the first real image but rotated). It is in your opinion the same dimension as in the real picture?


texts: PCB Layout advice for high current buck converter

texts:
I am building a dual high current buck driver for driving two fiber coupled laser diode arrays.  This is my second attempt at a board -- my first attempt had excessive ringing due to the board layout (documented in this earlier question from me).  The design parameters are:

Vin: 8v nominal
Vout: 2v - 4v (constant current supply)
Current set: 50A
Input ripple: 1%
Output ripple: 1%
Switching frequency: 500kHz
Control IC is a MAX20096

The schematic:

I received some great advice in my previous post and I have tried to apply it all to this new layout. I've also found a great set of articles on buck converter PCB Layout I tried to closely follow as well as a careful study of the PCB Layout for the MAX20096 evaluation board.  The layout is now:

4 layers.  Inner layer 1 is a dedicated ground layer.
High current ground is separate from analog ground. They are tied together at a single point very close to the control IC.
Tried to reduce current loop length as much as possible.
Current sense is now done via Kelvin connection routed using differential pairs.

Here are the layouts for each of the layers:

Top Layer

Inner Layer 1 (dedicated ground plane)

Inner Layer 2 (sense, gate drive)

Bottom Layer (Vin, VCC)

Thanks in advance for any advice.


texts: Lenz's law and the magnitude of opposing fields

texts:
The Wikipedia page on Lenz's law says that it is "a qualitative law that specifies the direction of induced current but says nothing about its magnitude."
I am trying to understand how Lenz's law would cause a transformer to behave under the following conditions.

Suppose I have a step down transformer where power is put through the primary coil in one direction only, then stopped, then repeated, at a frequency of 60 Hz. The current is AC, but only moves in the one direction, powered on in a sine wave, and then left off for the same period of time before being powered on again.

When current flows through the primary coil, a magnetic field is produced in the core, which induces a voltage in the secondary. What happens next?
I feel like Lenz's law says that the secondary coil produces a magnetic field in the core the opposite direction of the field produced by the primary, but I'm sure it can't be the same magnitude. What determines the magnitude of the magnetic field produced by the secondary coil?

Edit
Sorry, through a combination of not explaining myself well and also not fully understanding, my question had its flaws. Let me revise the situation and try to explain it better.
The current through the primary is not simply switched on, left on, and switched off, but put through the coil in a half sine wave, shown here in the lower image.

The current flows in one direction but the level of current is constantly changing so as to produce a changing magnetic field in the core. If the frequency and current are controlled so as to avoid core saturation, can this revised set up still induce a voltage in the secondary coil? If so, would the induced voltage in the secondary coil create a magnetic field that would oppose the field created by the primary?


texts: Closed loop circuit vs open loop circuit can current flow?

texts:
So this has been bothering me. Lets say we have a circuit which looks like this below:

If the connection to ground is earth ground, and the positive side of the voltage source is connected so there is a potential difference over the resistor, would current flow to ground with a SINGLE (just one connection important!) to ground. This circuit would be considered an "open loop" in the conventional sense. Thanks!


texts: Is a JTAG programmer capable of any microcontroller which supports JTAG?

texts:
Sorry if my question is very basic, but I couldn't find the answer by searching the internet.
I want to buy a JTAG programmer, but in the datasheet of this programmer there is a list of "supported MCUs". Does this mean that this programmer cannot program other MCUs which support JTAG?
As an example, ST Link V2 says that it is for STM8 and STM32 MCUs. Does this mean it cannot be used to program other MCUs?
What about JTAG programmers which are for ARM MCUs? Does this mean they cannot be used for non-ARM MCUs (even thought they support JTAG)?
If a JTAG programmer could be used to program any MCU which supports JTAG, then what is the difference between these programmers that makes them specific to a specific microcontroller?
I am mainly concerned with programming the MCU, although having debugging capability would be a nice addition.
Any help would be welcome.
Thank you in advance.


texts: Calibrating FEETECH FR5311M Digital Servo

texts:
Hey everyone,
I am owning this model feetch servo motor.

I want to do the following:(with arduino uno)

Read the initial position(angle) of the servo motor
rotate the motor to desired position(angle) and stop it
read the final postion also to which motor is driven (angle)

I tried reading the analog values through the feedback wire in arduino , but found those values to be random. So it is not clear to me , how to do the above steps with a random ADC feedback values. How do I calibrate in such a situation?

https://learn.adafruit.com/analog-feedback-servos/using-feedback

I used the above link to calibrate the Servo motor. In this case my Servo rotates clockwise and anti-clockwise to the same position which was initially set and then starts continuously rotating after finishing the previous task.

Please do help!

Information about the servo: http://www.feetechrc.com/product/continuous-rotation-servo/two-working-mode-digital-programmable-metal-gears-servo-fr5311m/


texts: Fast attack, slow release envelope detector

texts:
EE novice here.

I want an envelope follower for a +/- 1V audio signal which immediately (i.e. within a couple of milliseconds, ideally) increases to the amplitude of the input signal, then falls off exponentially (with decay rate adjustable by a pot) as long as the input is below the current output value.

I know how to make a basic envelope follower with diode, resistor, and capacitor but I believe that will have a slow attack response when the RC time is long.

Any pointers for how to approach this?


texts:
I need to generate a 400Hz 26V rms signal with at least 200mA drive capability. 26V rms means 72.8V p-p is required. It is to drive the rotor winding on a synchro system.

I was planning to use 2 x OPA552 op amps single supply in BTL configuration until I discovered that I need to ground one side of the output. So now I think I need to use a dual supply configuration, but the OPA552 runs out of voltage (max +/-30V) and probably power dissipation too.

I have the 400Hz sine wave signal at 5V p-p at 0 & 180 deg (for BTL inputs).

Two questions:

any suggestions for suitable op amps or other circuit configurations I could use?  Possibly an op-amp driving some transistors or MOSFETs?
what is the best way to get my 0-5V input signal (DC offset of 2.5V) to the correct level to feed a dual supply amp?  I could obviously use a capacitor but I would prefer to avoid any phase shift.

TIA


texts: LC filter applicability for power to output cables

texts:
I am designing a circuit that has a 240MHz MCU and some cables going to sensors so I am wanting to reduce the clock noise getting onto the supply line and going  out the cables by using an LC filter. This seems to be a reasonable approach to me but my searches are not finding much in the way of example circuits that do this.

The only examples that I have found seem to be filtering between a digital Vcc and an analog Vcc which seems analogous. However, I am concerned that cables may present issues due to their impedance and capacitance.

I am wondering if anyone knows of any downsides to such an approach before I go and create more problems by designing a board with an LC filter going to the outputs?


texts: Newbie question about how a simple RC / transistor oscillator works

texts:
I'm just starting out learning about electronics. I have a project in mind which is really just a variation on this circuit:

I've built this on a breadboard, used different values for R1 and C1 and observed change in frequency of the LED flash.
My question is about how the circuit works.
Is it the case that when the power is turned on, C1 starts charging and 'prevents' current from flowing to the base of Q1 until it is fully charged, at which point Q1 is 'turned on', causing Q2 to also be turned on, which then allows C1 to discharge?


texts: motor selection for equatorial telescope mount

texts:
I'm considering building a mount for cameras or telescopes which I would want to move at the rate the Earth spins (i.e., 1/1440 rpm).  I've considered using the mechanism for a clock and just using the hour-hand with a 1:2 gear, but from what I've seen, inexpensive clock movements are not made to support any real torque for moving an object with significant inertia.

More generally, what's the best/most economic motor approach to drive a system with significant inertia at very low rpm?  Speed needs to be consistent and considerably smooth

Are there any good, economical solutions to this?  Ideally I would like to power this with a low-voltage battery pack, so I figure a synchronous motor wouldn't be useful (plus I don't know if they can operate at slow enough speeds).

p.s., this is my first post, so I apologize if there's a better community that I should be posting to.


texts: Is there a preferred encryption scheme for encrypting firmware builds on external flash?

texts:
I have a product that is going to be deployed in large numbers, and I want to maximize the trouble that someone is going to go through to reverse engineer it (a high level of security). It is an internet-connected product based on an STM32 microcontroller that connects to a server to retrieve its firmware update blobs and stores it on an external flash memory.

Here are a few facts about the situation:

~1 Megabyte firmware build size
There is no encryption hardware accelerator on the chip
Since the DFU process is blocking (the system stops working), we need the decryption process to be as quick as possible

Since there is a wide variety of encryption schemes implemented in the STM32 crypto library, is there a preferred encryption scheme out of all of these that I should use to encrypt/decrypt the data being stored on the external flash?


texts: Does anybody know a better way to cool a heatsink that is not a fan?

texts: I am designing a portable distiller powered by the sun. I will be heating the water with a heating coil and then when the water evaporates I will be collecting the stem in a metal tube(not sure what type of tube yet). I need the steam to condense back into the water as fast as I can, so my idea was just to put heatsinks around the tube. I am not sure if that is the best method, should I just put another tube over my steam tube and have a pump push water on the outside of the steam tube? Should I just have two fans one for intake and one for exhaust, or should I just add heat pipes and one smaller 80mm fan? Maybe a 1watt pump, not sure if that will more a lot of water though. Thanks!


texts: Why does this single supply non inverting Op-Amp saturate?

texts:
I have this simple non inverting setup made with a TL082IP Op-Amp and a gain set to 2 (R1 = R2). Since I will only have positive voltage 0V to 5V to amplify, I use for simplicity a single 12V/0V supply voltage (V2).

simulate this circuit – Schematic created using CircuitLab

If I vary the V+ voltage source between 0V and 5V (V1), I would expect Vout varying between 0 and 10V, which is what the simulation give me.

But in practice, everything works fine between 5V and ~0.8V, then between 0.8V and 0V the Op-Amp saturates at +Vsat ~12V.

What have I missed ? I don't really need precision at low voltage, but at least I would like that low voltage at V+ give me low voltage at Vout, how could I achieve this ?

Thank you !


texts: What are some circuit design rules of thumb for mass production?

texts:
When I jump into a new design, if it's intended for mass production, I try to think how cheap I can make it. Are there any rules of thumb I should follow? Here are a couple items that I THINK are worth aiming for:

Minimize component count
Minimize number of unique components (ex. reusing a 10k resistor vs. using a 11k)
Component availability
Connectors vs. No Connectors
Minimize number of components that need programming
Use smallest PCB size
Use the least number of layers
Limit PCB complexity (controlled impedance, buried vias, etc.)
Keep all components on the top only vs. on both sides
Keep trace width and spacing large
Limit complex component package types (lead-less vs. leaded)

Not sure if this list reeks of paranoia or if these are good metrics. I need an adult.


texts: What does it mean when we say an A/D converter has 1 LSB accuracy?

texts: What does it mean when we say an analog-to-digital converter has 1 LSB accuracy?


texts: Is it possible to power a cordless drill from wall socket adapter?

texts:
I have a dewalt 18V cordless drill. I am wondering if it is feasible to build an adapter that can power the drill from a standard US wall socket?

A typical DeWalt drill needs 2.6 amps with no-load. I am assuming this jumps significantly higher under load. Most DeWalt motors have a stall current over 250 amps...

Any insight would be greatly appreciated!!


texts: Which temperature sensor is rugged one and can measure high temperature?

texts:
This is my first question on Electrical Engineering forum. I am preparing an IoT system for rugged and extreme conditions with Raspberry Pi and Arduino. The requirements for this sensor are as follows,

1) should work for high temperature (200+ degree centigrages)

2) should work in oil and water

3) should work in dust

4) should transmit the data with wireless

5) should consume low power

Please do let me know where I can find such sensor?


texts:
My goal is to make a MicroSD to USB adapter myself.
With this question, I saw that I can use a USB2240 controller chip to connect my µSD card to my computer.
In this video, he is using a 1701 ic which seems to be a voltage regulator and everything seems to work fine.
In that case, what are the benefits of a controller chip over just a simple voltage regulator?
Also, in the previous Electrical Engineering Stack Exchange question, the OP put a link about M-Stack, do I need to install it on the USB2240 controller chip to make it work and what is it exactly?
Sorry these questions might be stupid, I am still a beginner. Thanks.


texts: Will winding a single DC cable on a spool cause any issues?

texts:
I wasnt entirely sure how to best word my title, but I am currently facing the challenge that while installing and wiring all my electronic components in their target location I need the cables to be significantly longer than they need to be when my installation is assembled in order to have enough room to perform all the soldering and contacts. To avoid having cables dangling around inside that box I would like to create one or two loops with those cables before the final assembly.
What will be the effects of doing this? The cables are 18 AWG with a thick silicone insulation and will have 5V DC with small currents < 500mA. The total length is roughly 50cm (1.6 feet) and when wound the length will be reduced to half of that. I am manly asking this question because in the army I was always told to completely unspool every cable that I use and was wondering if that is only applicable to those high voltage and high current cables or not.


texts: Why does radar processing always require FIR filters?

texts: Digital signal processing in radar applications is usually done using finite impulse response filters. Why is that the case? Wouldn't the use of an infinite impulse response filtering be much faster and feasible since we are talking about processing in the gigahertz range?


texts: Designing a PWM controlled power supply for a 30W RGB LED

texts:
I am building a DMX controlled light using an Arduino, but I am not sure which power supply I should use to power the LEDs which run at 36v (10 in series, 3 rows) 30W. The main problem is whether or not there is a way to control an LED colour using PWM from an arduino, but it must be able to turn fully off.

Ideally I would like to build the constant current supply myself, but it must be as cheap as possible as I will have to control 48 of them!

Finally, would it be possible to use one power supply for a number of LEDs, even just one colour of multiple separate LED modules, as this would save costs, although they must all still be able to be individually controlled for brightness.


texts: MSP430: How to set a gpio as output HIGH at same instant it is set as output in DIR register?

texts:
In our design, pin 4.7 of msp430 is connected to the KILL pin of the ON/OFF switch IC which is active LOW. So when ever I set the pin 4.7 as output in DIR register, the whole circuit turns OFF even though I set the OUTPUT as HIGH immediately. Is there any way to avoid the output going to low when the DIR (direction) register is set as output?

Here is the piece of code that I used:

P4DIR |= BIT7;  //Set KILL pin as OUTPUT
P4OUT |= BIT7;  //Set Kill pin high


texts: Eagle: PCB layers stack-up and impedance

texts:
I had a PCB board with 8 layers to be fabricated. I have used an opensource deign modified it a bit and want to get them fabricated. The PCB company asked me to provide layer stack and impedance requirements.

  In order to make better PCB, please offer me the layer stack for every layer and the impedance requirements.

I am not sure what exactly to reply with specially regarding the impedance requirements

Here is my layers setting in eagle and regarding impedance control I have an A20 soc and DRAM.


texts: Is it possible to align a mems gyro to approximately true north with no external data input?

texts: Is it possible to align a mems gyro to approximately true north with no external data input - ie nothing input by the user.  I want to put a mems gyro/acc ship on a board and mount the board to a ceiling and have it recognize the approximate direction of north, ignoring mechanical misalignments.


texts: Can I generate a 90° Clock signal with Xilinx's ODELAY for RGMII?

texts:
Some time ago I implemented a GMII interface for my Gigabit Ethernet core. Now I'm trying to do the same with the RGMII protocol. The reference implementation from Xilinx uses IDELAY[|E1|E2] primitives to adjust the input delay. I would like to do the same with ODELAY...

The reference implementation uses two transmit clocks: TX_Clock and TX_Clock90 (90° phase shifted). The normal clock is used for ODDR registers and the phase shifted clock is send to the PHY device.

I know I could generate that clock with a DCM/MMCM or PLL but I don't want redesign my entire Gigabit Ethernet stack to provide a new TX clock for my physical abstraction layer.

I thought, I could use an ODELAY primitive to shift the TX_Clock as desired. But how do I calculate the tap/delay count?

DS182 - Kintex-7 DC Switching Guide - page 28 defines 'ODELAY chain delay resolution' as follows:

\$T_{IDELAYRESOLUTION} = \dfrac{1}{32 \cdot 2 \cdot F_{REF}} = \dfrac{1}{32 \cdot 2 \cdot 200\,MHz} = 0.078125\,ns = 78.125\,ps\$

My IDELAYCTRL primitive is sourced with a 200 MHz reference clock and TX_Clock runs at 125 MHz (8 ns). A phase shift of 90° would means a delay of 2 ns, which equals to 25.6 delay taps of 78.125 ps.

So is it correct to set the ODELAY's value to 26?

Abbreviations:
GMII - Gigabit Media Independent Interface
RGMII - Reduced GMII (using DDR technique)
ODDR - DDR output register


texts: Really out of my wits as to how to completely remove the remaining solder in the 6 pins (LAT,/OE,CUK,DIN,GND,V+). I would appreciate your advice if you have any relevant experience.


texts: Why Cadence not revealing their prices for their software product?

texts:
I contacted the Cadence office as a PhD student and also a faculty member to inquiry their price for an academic license. After 8 emails back and forth I noticed  that they are not willing to answer the simple question of how much we have to pay to get access to Cadence Virtuoso software.

It surprised me a lot and I felt upset and stopped the email communication. I actually fully understand now why people tend to use pirated software instead of paying for it.

I sincerely tried to pay for a license and could not even get a quoted price!

Can someone explain here why do we have such secretive behavior? There is no price list on their website and even when you contact them they don't reveal it. Very strange indeed.

Update:

To make this a better question and not a rant, I should tailor my question:

What other options are available for IC Layout design when Cadence is not an option?


texts: 4 port 12 bit mux is consuming 48 macrocells!

texts:
I'm programming on the coolrunner II cpld. It is running out of resources so I decided to implement my own 4 port, 12 bit mux. After implementation I find that it's using over 40 macrocells. Any way to reduce this number? I've already tried using the optimization techniques with ISE XST, but it has not reduced the number. Here's my code

module mux_2to1_gates(a,b,sel,y);
input a,b,sel;
output y;

wire sel,a_sel,b_sel;

not U_inv (inv_sel,sel);
and U_anda (asel,a,inv_sel),
     U_andb (bsel,b,sel);
or U_or (y,asel,bsel);

endmodule

module mux_four_to_one(a,b,c,d,sel,y);
input a,b,c,d;
input [1:0] sel;
output y;
integer i;

wire mux_1,mux_2;

mux_2to1_gates U_mux1 (a,b,sel[0],mux_1),
                    U_mux2 (c,d,sel[0],mux_2),
                    U_mux3 (mux_1,mux_2,sel[1],y);

endmodule

module muxing( selecting, d1,d2,d3,d4, q );

input[1:0] selecting;
input[11:0] d1;
input[11:0] d2;
input[11:0] d3;
input[11:0] d4;
output[11:0] q;

genvar i;

generate
    for(i=0; i < 12; i= i+1) begin: test
        mux_four_to_one named (d1[i],d2[i],d3[i],d4[i],selecting,q[i]);
    end
endgenerate

endmodule


texts:
I am trying to design a electronic circuit which will only pass voltage between a threshold, like a dual clipper.
The input is a varying DC input and the system (would) allow output only above 3.3V.
Initially I tried to design a negative clipper with bias voltage but then the bias voltage powers up the output when the input voltage goes below the bias voltage, which would be detrimental as I would need to recharge the source.

Please suggest alternate approaches.

Edit 1: The source is a low impedance input ranging in 10 - 30 ohm.
The load is a boost circuit which boosts the voltage to steady 5V.
The voltage tolerance is not an issue because the load can withstand voltage from 2.5 V - 5.5 V.
I would like the bias voltage to not be forwarded to the output, thus when the input falls below threshold, the output falls to zero.


texts: EKF Design And System Augmentation Bearings Only Tracking

texts:
I am hoping someone can help me with some guidance or knowledge on the matter. Basically im setting up a "Bearings Only Tracking" simulation using the EKF/UKF toolbox within Matlab. I have a base system (See below) but require the system to be augmented to build a 4 state velocity model...
My Question/Issue is how is this augmentation done? and what is the significance of adding the additional velocity state.
System Given


texts: Current usage with multiple PWM controlled motors

texts:
I have a circuit that can use 25 A of current max, it is on a 25 A fuse. I am looking to control 4 DC brushless motors using ESC's. The trouble is that the motors are rated at 7A max current. I know that ESC's use a PWM signal to control the speed of the motors, so that means when the voltage is High in the PWM pulse the current will be ~7A for that period of time. I am worried that if I run all 4 motors (even on low speed) all at once, if the PWM signals all go high at the same time then the fuse will blow. Is this idea correct and if so what can I do to avoid this happening?

Further info: I am using these motors and they will be driving a propeller for a ROV. The manual for the esc is here, I believe the PWM frequency is 2Khz (they refer to it as operating frequency so I am not 100% sure).


texts: Protection for power-off case with active input

texts:
My application is roughly depicted in the attached image.

I am sensing a Vin voltage, by dividing down with a resistive divider, then passing the signal through an opamp and an RC filter (not shown) and lastly convert with an ADC.

My concern is: what happens if the board's supply (+5V and +3.3V) is removed but Vin remains? Is that potentially harmful for the opamp / ADC?

If yes, is there a standard way to protect them against such a case?

I thought of intercepting Vin right before the divider with a MOSFET switch, but then I will probably not be able to sense very low voltages, since Vin should be larger than Vth of the MOSFET in order for the switch to be on.


texts: How to calculate RC (in 2st RC lpf) that satisfies fc in real circuit

texts:
I'm designing a two-stage RC LPF (Low-Pass Filter) and I want a cutoff frequency \$f_c=1000\mathrm{Hz}\$.

So, I choose \$R_1=3\mathrm{k\Omega}, R_2=33\mathrm{k\Omega}, C_1=4.7\mathrm{nF}, C_2=47\mathrm{nF}\$, and when I calculate \$f_c\$ with these values, it results \$1000\mathrm{Hz}\$.

But when I feed the input with a white noise signal and measure the output, after plotting the bode plot, I see that \$f_c\$ is actually \$650\mathrm{Hz}\$.

I know that the calculated value \$f_c=1000\mathrm{Hz}\$ is exact only in an ideal situation, and I think the tolerance of circuit elements cause \$f_c\$ fail to reach the sought for value.

But how can I choose the RC element values in order to get \$f_c = 1000\mathrm{Hz}\$ in a real situation???


texts: Controlling a current with another - home-made alternatives to the transistor?

texts:
I have a very basic understanding of how a BJT or a FET works, but I think I got the idea. They are awesome in all regards, except one: you can't make one at home without hot ovens and scary chemicals. The old triodes would be easier to make, except they need good vacuum (better than what I could make at home).

Are there any other components that one can use in the place of a transistor or triode, to control a strong current with a weak one?

I thought of these ways - they are naive ideas of someone fascinated but who barely entered the "Novice" stage of electronics:

make a weaving of insulated copper wire (like a tight grid) and pass other wires through the eyes of the weaving, so a voltage in the weaving (the controller) could scare off the electrons going through the passing wires (the controlled) using its electric field, like how the grid works in a triode, or how the gate works in a FET
put a plate (controller) between the plates of a capacitor (controlled), so when you put a current through the controller-plate, the capacitor's capacity is modified a bit so its reactance changes (I haven't given much thought to this idea, nor to how could it be used, it will definitely sound stupid)
put a cylindrical capacitor (the controller) around a wire (the controlled), so the negative, inner cylinder will be close around the wire; hopefully, charging the capacitor will ... oh wait... the net electric field outside a capacitor is supposed to be 0...

I already assume these ideas are wrong in innumerable ways. Could you please point out some of the mistakes? I hope I'll learn a lot this way.

Transistors and triodes are the best, most convenient, quickest and most efficient for this task. I know it very well, I don't deny it in any way. This question is asked in the spirit of "What I cannot create, I do not understand." and "Know how to solve every problem that has been solved.", as Feynman so brilliantly put it.

I'm primarly interested in control as in amplification with a gain. Switching on/off isn't really enough - I think I'd like to use this thing in an oscillator or RF circuit.


texts:
Heat produced across a resistor can be computed by the following formulae

H=I²Rt
H=(V²/R)t
Going by #1, heat is directly proportional to the resistance whereas going by #2 heat is inversely proportional to resistance.

Which is the right formula to be applied to calculate the heat generated across a resistor & why?


texts:
Is something like this possible ?

parameter width;
wire[width-1] a_net = (width)'b0;

I basically need a variable to control the width of the right hand side. I am planning to use this in an test bench where I just have to change the parameter width at the beginning of the file, and this parameter sets the net width in all other occurrences of 'a_net'.

If this doesn't work - is there any other workaround ?


texts: Ferrite rod antenna matching network for SA606 RF input

texts:
I'm trying to hook a ferrite rod antenna up to an NXP SA606 mixer (https://www.nxp.com/docs/en/data-sheet/SA606.pdf) and I'm not quite sure if I'm interfacing correctly with the matching network. I think the circuit diagram (Figure 16) on page 15 of the SA606 datasheet assumes an antenna with a coaxial connector. I don't know how to substitute an antenna with a coaxial connector with a ferrite rod antenna. The ultimate goal is to make use of the chip's RSSI feature.
As of right now I have it set up like this...

...where L1 is the ferrite rod wound up with magnetic wire. L1 and C1 set the resonant frequency to 457kHz per the equation F=1/(2pi*sqrt(LC)). The part that I'm unsure of is the input impedance matching. I followed the steps shown on page 7 of an application note on the SA605 (https://www.nxp.com/docs/en/application-note/AN1994.pdf) to calculate L2, C2, and C3 to also resonate at 457kHz. But with that Tapped-C network is it necessary to terminate the antenna with the 50ohm resistor, R1? Previously I was trying to do this with the Analog Devices AD8307 Log Amp (https://www.analog.com/media/en/technical-documentation/data-sheets/AD8307.pdf) and I set the antenna side up the same exact way trying to follow Figure 32 on page 17 of the datasheet, hence the 50ohm resistor. Here's how I had it setup with the AD8307...

...where C2 and C3 set the high-pass frequency to around 6.3kHz per the equation F=1/(piRC).
Have I done this correctly? Or am I way off?


texts: I2C/TWI in ATMEGA - where is voltage source?

texts:
While reading about I2C/TWI protocol, i recognized as important part the ability to pull the signal down by any member of the communication. Thus pull-up resistors being very important here.

There are few schematics I found:
http://www.cypress.com/documentation/application-notes/an50987-getting-started-i2c-psoc-1
https://cs.wikipedia.org/wiki/I%C2%B2C
https://www.superhouse.tv/i2c-for-arduino/
All of these schematics contains VCC source for SDA and SCL.

What I do not get is where/what is voltage source in the case of ATMEGA & sensor (or two atmels cpus). In all schematics I have found there are only two cables - SDA ~ SDA and SCL ~ SCL.

I cannot grasp how would that work if there is not external VCC source.
Sorry if the answer lies somewhere here on the stack, I could not find it.

EDIT:

As requested - links with vcc missing

In here https://howtomechatronics.com/tutorials/arduino/how-i2c-communication-works-and-how-to-use-it-with-arduino/ - there is actually both of the schematics (in the beggining one with the external voltage connected through resistor to SDA & SCL) but in the schematics with arduino and two moduls, no vcc.


texts:
Does TI Tiva C uC ADC input is 5V tolerant ?

EDIT:

Found ADC parameters in datasheet http://cl.ly/image/3D1Q3q09470J. Please don't down vote.

Thanks


texts: Unregulated AC-DC adaptor voltage response

texts:
This is my first post. I'm a long-time computer programmer but new to this field of hobby electronics.

I bought a 12V 800mA AC/DC adapter to feed my circuits. Seems it's unregulated since the multimeter reads ~18V at 12V without load.  Reading some information online, I discovered this behavior is due the regulated / unregulated design differences.

For example, I built a simple circuit. I selected 3V on the adapter and connected it to a 1.95V red LED plus a 180Ω  resistor. The multimeter reads the adapter is feeding about 5.5V instead of 3V, so with the LED Vdrop I'm at 30mA, pretty much on the unsafe side for the LED.

I want to know much voltage this adapter yields in relation to the load? Is there some quick calculation or method to acknowledge at which current load the adapter will feed the selected voltage?

Additionally, apart from short-circuiting the adapter terminals, is there some additional caution I must take when working with this kind 1.5V-12V AC-DC adapters?

EDIT:

After thinking a bit, instead of trying a 12V source, I decided to go to the "resistor" route. The circuit is two LED (1 green/1 red) switched by a 12V SPDT relay.

For the LEDs I've resorted to a 1K resistor, assuming 18V source from the unregulated adapter, 2.3 max VDrop and 15mA LED operation.

The relay operated at 12V at stated. I first measured the coil resistance, yielding about 400Ω (confirmed by the datasheet). With 18V this rounds 45mA. I need the Resistor VDrop to be 6V @ 30mA, so I choose a 180Ω resistor (probably 220Ω could be safer).

The circuit worked as I expected measuring VDC=17.80V, Vcoil=11.96V.

Is this a correct analysis? I don't know about voltage regulators yet so  I went with a resistor.

The schematic is:

simulate this circuit – Schematic created using CircuitLab


texts: Ripple counter, reset problem (J-K flip flop counter)

texts:
I am trying to simulate a decade counter using a ripple counter 4 bits and a NAND gate to reset the 4 J-K flip-flops when it reaches 10 (1010).

The thing is it does not reset but goes to 4 (0100) due to the reset on my second flip-flop (it sends a negative edge to the next one plotted on pink) as shown in the plot (the tiny line on the green plot).
is this a failure on the simulation or in the design?
Any suggestion to solve that will be appreciated

the software I am using is a livewire