texts: MCU - Minimum list of external components

texts:
I can't find a complete answer for this anywhere, and I want to fill the gap in my knowledge of MCUs.

In MCUs why do I need any other component except, maybe, a voltage regulator and an external clock?
Why do PCBs with embedded MCUs look so complicated?
If I were to design a minimal PCB with embedded MCU (say atmega324p), what is the minimum list of components I should consider, and why?


texts: Make drone fly autonomously from point A to B

texts:
I want to develop a autonomous drone which is able to fly from point A to point B in an indoor location. The drone starts at point A and with a button push it should fly to point B. The points have a distance of around 2m, the drone should land on point B with an accuracy of +- 20cm. There are no obstacles between the points.
I thought about using GPS, but GPS is way too inaccurate for an indoor localization. I also looked into UWB localization methods based on a DWM1000 IC. UWB does work with a good accuracy but it requires 3 anchor points which use the DWM1000 + one DWM1000 for the drone, so I would need 4 of those chips, they are quiet expensive.
I also looked into LIDAR and SLAM and I think this would work to make the drone fly autonomous from point A to B.
Do you know any other maybe simpler solution for the described task?


texts: What is the methology of sending signals via Bi-Direcional MOSFET?

texts:
I am trying to make a simulation by using Multisum 14 for i bi-directional channel for Logic level circuit from SparkFun which use Philips AN97055 IC as a Bi-directional level shifter...

My circuit design

The UN-clear part in this simulation is I'm using the low side or TX_LV to transmit serial data signal from 3.3v MCU to 5v MCU over this LLC, if I send "Logic 1" 3.3v from MCU over serial pin to the mosfet the last will read it as open circuit and don't send 5v in the other site and when I stop sending data "Logic 0" 0v the mosfet will read low pin as open circuit then drive 3.3v from pull up resister to source pin in mosfet and this make the mosfet drain pin connect to ground which the last cause drive 5v from pull up resister to TX_LV pin?

Hope to find some explain about that.

Thanks for everyone shearing his knowledge in this site,


texts: Relay inside oscilloscope (Relay vs other switches)

texts:
When I press the "Auto" button on my scope, I can hear the sound of a relay switching (several relays or single relay switching many times.)

What are the relays doing?


texts: Under what conditions would using a voltmeter be more accurate than an ammeter to measure current?

texts:
Suppose you have a simple circuit with a voltage source V1 connected to a resistor R1, like this:

simulate this circuit – Schematic created using CircuitLab

You could connect an ammeter in series, and then the internal resistance of the ammeter would affect the actual current reading, introducing some error. But you could also connect a voltmeter (with a high internal resistance) in parallel across R1, and calculate current by dividing the measured voltage by R1. There would still be some error due to the voltmeter's internal resistance, but which would be more accurate? Or more specifically, under what conditions (i.e. large/small current, R1, V1, etc.) would it more accurate to use the second approach, with a voltmeter instead of an ammeter?


texts:
As much as I know, the input impedance of a coaxial cable with a characteristic impedance of 50 \$\Omega\$ which is terminated with a 50 \$\Omega\$ load resistor, should be 50 \$\Omega\$ as well. This should be true for any cable length and any wavelength.

However, in a typical datasheet of any coaxial cable the capacitance of the cable per unit length is usually given. I don't understand the effect of this capacitance on the input impedance.

Assuming I have 10m length of a standard 50 \$\Omega\$ RG-58 coaxial cable terminated with a 50 \$\Omega\$ resistor. The capacitance of this cable is 100pF/m. What would be the input impedance?


texts:
I need to design a over voltage protection circuit.
I intend to use a comparator for the said circuit. The reference will be from a standard voltage ref source. While the voltage at the non-inverting terminal would be the output of voltage bus.

Now, based on the comparator truth table - if the 2 are equal the output is zero and if the Vsupply is greater than reference the output is high. Now, wouldnt small spikes in the Vsupply(to the non inv terminal) be a source of voltage corruption ?
How can I ensure a smooth dc level here ?

Also, suppose I want to send the output of the comparator to 2 different MOSFETS,I understand that I cannot just supply it directly as the sourcing current of comparator might not be enough. I might have to have a driver. Would a transistor be sufficient in this case ?


texts:
I'm designing a PCI Express board with an Artix-7 from Xilinx. I'm reading through the PCIe block description and on page 199 it says:

  Section 6.6 of PCI Express Base Specification, rev 1.1 states “A
  system must guarantee that all components intended to be software
  visible at boot time are ready to receive Configuration Requests
  within 100 ms of the end of Fundamental Reset at the Root Complex.”

This is fine. It seems I can easily sequence the power supplies and config the FPGA in 100ms, but I'd like to understand how much time I have anyway.

The document then shows this:

and says:

  Section 2.6.2 of the PCI Express Card Electromechanical Specification,
  v1.1 [Ref 2] defines TPVPREL as a minimum of 100 ms, indicating that
  from the time power is stable the system reset is asserted for at
  least 100 ms

Lastly, on page 201 it says:

  Figure 3-92 shows that power is valid before PWR_OK is asserted High.
  This is represented by T3 and is the PWR_OK delay. The ATX 12V Power
  Supply Design Guide defines PWR_OK as 100 ms < T3 < 500 ms, indicating
  that from the point at which the power level reaches 95% of nominal,
  there is a minimum of at least 100 ms but no more than 500 ms of delay
  before PWR_OK is asserted. Remember, according to the PCI Express Card
  Electromechanical Specification [Ref 2], the PERST# is guaranteed to
  be asserted a minimum of 100 ms from when power is stable indicated in
  an ATX system by the assertion of PWR_OK.

So it seems I should have at lest 300ms from when the power is within 95% of nominal:

100ms until PWR_OK - TPWRVLD
100ms from PWR_OK to end of PERST# - TPVPERL
and then finally I have to be ready to respond 100ms after end of PERST#.

However, Equation 3-1 in the document says:

  FPGA Configuration Time ≤ TPWRVLD + TPVPERL

What am I missing?


texts: What are the different ways of switching 110 VAC power?

texts:
I am working on a project where I need to break the path providing 110V to a motor.

What are different ways of doing it? I am aware of only two ways:

Using a mechanical switch,
A relay.

Are there any other safe, reliable and possibly cheaper ways of doing this? Maybe a solid state solution?


texts: Passing usb data traces underneath of DCDC converter

texts:
RKZ0505D is a DCDC converter which has maximum 85kHz internal switching frequency. It is placed as large surface of it placed directly on PCB.
If USB data lines pass under plastic package of DCDC converter, Does any unexpected disturbance occur on USB data signals because of switching ?
NOTE1: Signals of USB on TOP layer
NOTE2: DCDC converter placed on TOP mechanically

https://www.recom-power.com/pdf/Econoline/RKZ.pdf


texts:
In my project, I use ESP-12F module which has exposed (no soldermask) plated PCB antenna included in design. However I want my PCB to be waterproof and cover whole thing with waterproof lacquer.

My question is: will the lacquer influence the antenna's performance much?


texts:
I am building a small brewery and would like to heat a barrel of aprox. 280 liters of water with an three phase heating element. Its power would be 15 kW. That means that connected to 400V the full curent draw would be 37.5 A and current on each phase would be 12.5 A. Our house has main fuses 3x25A so i assume that wouldnt be a problem. I have asked a former coworker if there are any limitations and he said that current draw on start is around 5x higher than current while normal running. That means that current on startup would fry the main fuses.

So i have two questions

Would i require to install a variable frequency drive for a soft start of the heating element.
Which way is best for turning the heating element on or off apart from manually disconnecting the plug from the wall socket. I am thinking of a three phase relay controlled with a microcontroller such as Arduino.

Thanks.


texts: Simplest Way to step down the 220AC with more than 10% efficiency

texts:
Objective
I want to design a tiny single packaged mains-powered temperature sensor. Possibly as a multi-chip module (MCM) on one small PCB board.
Constraints
The temperature sensor I plan to incorporate:

Operates (Iq) between 1VDC, 10mA and 3VDC, 30mA
It is a 65nm Samgsung fabraction process. So it is very small.

Power source:

around 220V mains powered (single-phase)

Operation without a secondary source (batt, bulk cap, et. al.) desired to minimize size.

The efficiency demanding is just >10% and that is enough for me.

Ideas now
I was intended to design my power converter into a small chip, thanks alot for people's suggestions . I think about charge pump, and different IC modules, the RF powerharvesting, and the possibility for implementing such a device on nm Si process. Above all, microchips that can convert 220V ac to low dc is big-size for me, and also have lots big caps around module; charge pump from Olin's idea, I dont think I can design diode that can support high-voltage on chip, if not on chip, it will be big size(I think); for powerharvesting, I did some research before, and honestly it is good, but RF energy is not very solid, and there are some limitations about the distance. So I go back to the original ideas how to convert voltage. Hope your guys can check if they are right. I will use some regulating stuff(off chip) to regulate the voltage at last, so i just wanna check if the thoughts are right.
1> Linear with the resistors. Input 220Vac to the two resistors,one is 1Mohm, the other is around 10Kohm,figure below:

I know the efficiency is verylow, about 1%, so I drop it. But it is my earliest idea.
2> linear with the capacitor. Since the first way efficiency is so low, I wonder can I use two capacitors to replace the resistors, (figures below) one cap is 1pf, the other is 10fF (the exact values are not certain).

also I wanna design the big capacitor on my pcb board by myself like figure below,so I can mini-size. If the cap value is not big, I can design it on chip.

First I dont know if the fundamental of circuit (the first figure) will work or not, because I never see this before, but as I know, I hope it works. Assume it works, how to design it exactly ( I mean how to design the cap value properly and how to choose the switch frequency properly).
3>  The conventional linear isolating converter:

My question is, in this conventional way, the output current in other designs usually needs big, so the transformer is big, but I just need it very small(1mA~30mA), so according to your view, how big it will be, I know little about transformer design. the voltage ratio is 45:1, and the current is 1:45, how many coils on both sides are good ? How big it will.
if the transformer above is not so big, Furthermore, my design method for the transformer is improved, and I  wanna design transformer on PCB board by myself, like figures below:

in my first figure, I just use one stage transformer, if size is big to design 220V-5V converting, maybe I can design two or more stages to convert like 220V-48V-5V. I hope the transformer (each stage, hope one stage is enough) is less than 1cm×1cm. If that is possible, I WILL do it. And I think the efficiency is good, and also safe.
Above all, I want to improve my design in the No 2 and No 3 method, but I dont know if my thoughts are right or not. Ready to get judgement now.


texts:
I was reading about the LM35 and i found this, he suggested that i must use shielding over long distances, which makes sense, but then he said i must add a capacitor and a resistor,
why did he add them, is the shield considered a capacitive load?
and how will this solve the problem, i tried searching RC damping and all the results were about mechanical engineering.
And about the circled connection, it seems like a connection from the shield to the ground which is necessary, but i already did it on the other side of the shield ( the side of the power supply) should i do it again?
In other words, should the shield be connected to the ground twice or once is enough?


texts:
I am learning electronics so this is a beginners question. Its about the CD4066 IC as mentioned here

https://en.wikibooks.org/wiki/Practical_Electronics/IC/4066

Is the 4066 equivalent to  four independently controllable  relays, where one relay switches on the pair X1,Y1?-Is this the purpose of this IC? So four relays are required to switch (the 4 pairs of audio signals)
X1,Y1

X2,Y2

X3,Y3

X4,Y4

Because in the IC there are four switches that can control the four pairs above. So with this IC 4 speakers are controllable by a digital CPU.


texts: Eagle Hierarchical Modules: Multiple Instances Automatically Sharing Multi-gate Component?

texts:
Say, for example, you design a circuit module that contains one op amp.  Four instances of this module are in your schematic.  From a PCB design perspective (for reasons of reducing BOM cost or board area), it may be desirable to have each of these modules use a single op amp from a shared quad op amp device, as opposed to using four single op amp devices.

Of course, it is possible to do this by having the op amps external to  and at a higher level than the module. But this can cause some confusion in the schematic.

Is it possible to configure a module and/or device such that eagle will automatically allocate gates from shared multi-gate components from within modules as necessary?


texts: Lengthening Thermistor Leads with Different Gauge Wire

texts: I have a NTC thermistor with 30 AWG leads (TDK B57703M series) and wanted to lengthen these. Would it work correctly if I soldered 26 AWG wire to the leads? I know different gauges can mess with resistances and attenuation, so I wanted to confirm if this would be ok or not.


texts:
TL;DR: Can I use a blend potentiometer to blend two audio signals?
I have an Ibanez GSR 200 bass guitar. It has a potentiometer to control the volume of the neck pickup and another potentiometer to control the volume of the bridge pickup:

I find this very annoying. I'd like to have a potentiometer that controls the general output and another that works as a "blend" control which instructs how much signal from each pickup goes to the output.
I found this page where it instructs how to use a "blend potentiometer" to archive this, but I'm fairly new to circuits and I'm not sure if this is what I'm looking for. (Also, what would be the resistance of the potentiometer? Same as the current one, 500K Ohms?)
PS: I'd also like to understand, if this is the correct way to do it, what happens when you roll the potentiometer half way? Are both signals added together?


texts:
I am reading the ARM Cortex M3 reference manual and the concepts "bit-band", "bit-band region" and "bit-band alias" appear.

What is bit-banding?


texts: Deep scratches on the core of transformer

texts: The top and one side of my transformer have a few deep scratches which penetrate the laminate protection and short some of the core sheets. Are there any consquences to that?


texts: "Black box" transformer: Y-Y, Y-Δ, or Δ-Δ connected?

texts:
As a preface, this is purely hypothetical. I know better than to use a transformer without knowing anything about it. I'm just trying to get an idea of whether this is possible, not whether it's a good idea.

Let's say I have a three-phase transformer that I know nothing about. I have three primary leads and three secondary leads, and that's it. No markings or anything, no datasheet, just a box with wires sticking out of it.

Is there any way to determine with external measurements how the windings are wired? I know that I can look at phase shift between primary and secondary to determine whether it's Y-Δ, but if there is no phase shift, is it possible to distinguish Y-Y from Δ-Δ? If there is phase shift, is it possible to determine which winding is Y and which is Δ?

Ideally I'd like answers that only involve measurements and physical properties. I'm aware there are conventions like using Δ on the high side of a Y-Δ transformer, but assume this transformer was wired by someone completely ignorant of any and all conventions and common sense. That means that either side could be Y or Δ without regard to relative voltages, and the neutral wire on a Y connection may not be present. You can assume the transformer is balanced, however, with three identical primary windings and three identical secondary windings.


texts: How to securely solder a wire to a vibrating SMD PCB?

texts:
I have a problem with a "4in1" control unit for a RC helicopter. Due to some problems with helicopter setup, it is currently vibrating heavily which makes things even worse.

The 4in1 unit basically has two PCBs with electronic speed control, accelerometer, radio receiver and servo controller.

The receiver has short (say 2.5 cm) piece of wire which acts as a 2.4 GHz antenna and is soldered to an SMD pad. It is also glued to the PCB with hotglue. The SMD pas is around 2 mm away from the edge of the board towards which the antenna is supposed to point.

My problem is that after a while, the solder joint breaks and so does the glue joint and the antenna falls off. Fortunately, I haven't had any crashes due to that, but I'd rather fly with antenna than without.

So I'm looking for tips how to securely solder a wire to a SMD pad on a vibrating board.
I already tried just resoldering the wire and gluing it with hotglue, but it seems that it doesn't help much.

Here's the photo of the part. The solder ball is where the antenna should be attached. I removed the layer of hotglue that was over it. Here's full size image, for those who dare click it.


texts:
I'm playing with the idea of building an audio noise maker. I found several nice sources. Most seem to be based on PN junction avalanche noise. As a starting point, I put this on a breadboard:

It works, but I'm not sure I understand it completely.

Q1 generates the noise and Q2 amplifies it. In order for the noise to be audible (or exist?) at the output, RT must be delicately tuned. There is a sweet spot, and moving the pot's wiper in either direction away from that spot causes the noise to stop.

Why is this? Why is it not enough to just ensure that the RT voltage divider places Q1's emitter above the BE breakdown voltage?

Note: Don't think it matters, but I'm using 2N3904's


texts: Why does the resistance of an 8x8 LED Matrix have to be on the cathode?

texts:
Looking at these instructions for wiring up a LED matrix ( http://oomlout.com/8X8M/8X8M-Guide.pdf ) I see that they tell me to put the resistors that limit the current through the LEDs on the cathode (output) side of the LEDs.

Is there any reasons for this preference? Could I not put the resistance on the anode side instead?


texts: Assymmetrical vs symmetrical voltage blocking

texts:
I'm studing power electronics.
There is property for BJT, GTO, IGBT which says:
"blocks voltage symmetricaly" or "blocks voltage asymmetricaly"
What does it mean?
What is the difference between each?


texts: Cheap visual indicator for a PA loudspeaker line

texts:
I have a PA system which is outputting at most 200Vrms AC peak, around 100Vrms AC nominal, from the transformer. The current is around 4Arms.
Since the system is comprised of 12 output transformers, and the test system puts them all in the same room, I'd need a visual indicator of which are actually playing and which are in fault.
Which could be the cheapest/easiest solutions to do such a thing? I thought of putting a small light bulb on each AC high-voltage line, but I'm afraid it would not be a good solution.


texts:
A seemingly simple question that bothers me for some time: why the simplest, mass-produced, "offline" (standby) Uninterruptible Power Supplies designed for PC are not having simple DC voltage output (say 300 VDC for Europe)? Because switching power supplies used in PC and monitor sure can work on DC input.

I don't think that an incompatibility with the PFC is the reason because:

Some PC power supply does not even include active PFC
Some do, but operate properly on DC anyway
Some others do, but have problems with "quasi-sine" waveform from these UPS anyway

Or am I missing something obvious?


texts: How to calculate the repulsion force between two electromagnets

texts:
Hi I'm new here and I have ( I hope ) few simple questions.
I'm interested how to calculate (in newtons) the repellent force between two electromagnets facing the same poles at a distance(if is it even possible).
I would like to produce the repellent force of around 300 N and all that connected to a 4.5 V battery.

Thanks in advance


texts: Inexpensive circuit architecture for power supply voltage adjustment?

texts:
This is not a sourcing question; I don't need part numbers or manufacturers.

Most DC/DC converters (LDO, buck, etc) with an adjustable output voltage have you set that voltage using a resistor divider or equivalent.  The divider takes the output voltage and ground and uses them to produce a feedback voltage.

If the output voltage needs to be (digitally) adjustable, then the resistor divider needs to be adjustable too.  The most straightforward way of doing this is to have one half of the divider be a digital potentiometer (digipot) or digital rheostat.  The problem here is that even in large quantities (>3000 units) digipots are very expensive -- even the cheap ones are around $0.40 in large quantities, which can be more than the inductor or even the regulator!

Is there some trick for achieving an adjustable output regulator without needing this expensive component?  Technically a digital resistor is overkill since (if you make the low-leg of the divider the programmable one) you know that one side of the resistor is always at ground.  So I've looked into digitally adjustable current sources but they seem to be pricey too.

Also, in my particular situation absolute accuracy is not terribly important; I can accept the regulator voltage output being wrong by as much as 10-20% (there's enough headroom to avoid damaging other components).  The fine adjustment of the voltage output (down to ~1%) is then done by a software feedback loop that seeks out the maximum operating frequency of the rest of the system at a particular voltage and then finds the optimal voltage=power/performance tradeoff.  So I don't need the output at exact X volts, just X+/-20% and then the ability to nudge it up or down by ~1%.


texts: Unknown motor, specifications interpretation and use

texts:
I got a motor on the picture. Does anyone know what it was used for? My main question is if is it feasible to use it as a barbecue motor or is it too strong? Can I connect it to one or three phases only? I would like someone to explain specifications of motor with easy to imagine answer so that we, that don't know anything about that stuff, can benefit from it.. :)

If specification plates aren't clear enough I can retype them... Please let me know if this is the issue.

[UPDATE]

Current wiring scheme:

Cable from the black thing above (connected with the red and black wire) goes to the back side of the motor as seen there:


texts: How to find voltage across resistors in RC Circuit with 2 voltage sources?

texts:
I've been struggling with this difficult RC circuit that asks for the voltage, Vo, across the R4 resistor.

Edit: Assume that the switch has been opened for a long time, before it is closed at time t = 0 s.

I've already calculated the equivalent resistance for the circuit to be 0.75 ohms, under the condition of the switch closing at t=0 seconds. From there, I found the time constant to be 1.5 seconds. That being said, I am unsure as to how to proceed in solving for Vo.

I was under the assumption that, for t < 0, the left side of the switch would indicate what the initial voltage of the capacitor would be. Since the capacitor lies parallel to the V1 voltage source, I presumed that Vc(0-) = Vc(t=0) = 12 V. Now, I am unsure if this is correct, but since no current flows into the capacitor, it would represent as an open circuit. From that point, it's to my understanding that the final voltage, V_f (where t goes to infinity), needs to be found in order to solve for the voltage across capacitor, vc(t), which represents the following equation:

*vc(t) = V_f + [Vc(t=0) - V_f]e^(-t/RC)

Now I'm not sure how exactly does this relate to finding the voltage across resistor R4, but I do know that as time goes to infinity, the total current flows only through the short circuit of the switch. But is there any part where I'm wrong in my line of thinking? If I simplify the original circuit down to just the R4 resistor, the combined voltage sources, and another equivalent resistor, would that be the final step in solving for Vo?


texts: Reference for Spectre simulation parameters (GPDK045)

texts:
I'm doing some test designs/simulations with the Cadence GPDK045. When I do a DC sim and go to Results->Print and click on a transistor, I see many parameters like the device capacitances, conductances, terminal voltages, etc (see picture below for reference).
Where can I find detailed information on exactly what each parameter corresponds to? For many of them it's pretty clear (e.g. \$g_m, \ i_d\$) but others are less transparent. I was able to find the GPDK045 reference here, but it doesn't describe these parameters.


texts:
I plan to build two RF modules.

One is an analog down converter with a balanced output IF of ~50 MHz
The second in a fast ADC @ 100 MSPS with balanced input.

I want to have them separated for modularity and later reuse.

Everything will use 50 Ohm coax and SMA connectivity.

My question here is how to connect them together:

I can use two coax. One for the positive and one for the inverted signal? But the signal are balanced... What will be the impact of that solution? And then I would have two path for the GND because the coax shielding is connected at both ends... GND loops?
I can first internally convert to an unbalanced signal inside my first module and use a single coax between the modules.

The two modules will by powered independently. If I use a single coax, the GND currents (PSU etc..) will combine with the return current of my signal in the shielding of the coax. This would alter the signal. Right?
But with two coax, the GND current will apply in both cable and alter my two signals the same way. Because they are balanced, this would have no impact. I am still right?

Or do I have to strongly connect together my GND of the two modules elsewhere in order to reduce the GND current in the coax? But because I will have to connect the shield of the coax to GND at both end in order to allow the return currents to flow, what about the GND loops?

What is the common approach, for RF lab equipment for example, when a RF source has to be connected to a spectrum analyser? This is the same kind of issue, the two instruments are connected to the earth, but at the same time, they are connected together by the shielding of the coax. Gnd loops? But this works, as fas as I know.

The issues here is that I don't have any clue of the strength of each described effect.

Edit:

The modules will be powered by a single wall wart that will deliver 12V. But each module will have it's own voltages requirements and will use DC/DC converters or LDO.


texts: Simpler way to enable/disable voltage regulator using DC jack shunt as a switch?

texts:
I am wanting to know if there is a simpler way to enable/disable a switching voltage regulator I'm using. The voltage regulator's datasheet says to pull the EN pin to GND to turn it off, and let it float to turn it on.

The DC jack is being used as the on/off switch in this product. The middle pin is the shunt, and is normally contacting the sleeve/GND when the charger isn't plugged in. When the charger is plugged into the jack, the shunt disconnects from the sleeve, and the NPN transistor base is pulled high through a resistor and turns on, turning off the voltage regulator.

When the charger is unplugged, the shunt pin connects back to GND, pulling the NPN's base to GND and turning the voltage regulator on.

I feel like I've overlooked something and there is a more simple way? Thank you for your help.

The product, charger, and jack are center pin positive.

VCC is a 12V battery.

Schematic:


texts:
I have a few question regarding mbed OS 5's new TCP API:

Some background:

I will have multiple mbeds linked via Ethernet to a PC. The PC, whose IP address is fixed and known by each mbed, initiates the connections (mbeds effectively acting as servers).

The mbed only needs to handle one socket at a time, and the PC should have no problem reconnecting (thereby opening a socket on the mbed) to the mbed, should the connection fail at any point, or the socket is closed by the PC (i.e. the mbed should happily accept and open a socket if there is no open socket).

Question

My proposed approach would be to call accept() on the listener socket, storing the result in a temporary buffer. If the result is NULL (no socket to be accepted), continue. If result is not NULL (we have a pointer to a new socket), close the current socket, and point it to the address returned by accept. All of this, as well as the send() and recv() calls would occur in a while(true) loop.

By accept() returning a new socket, it is assumed that the host (PC) initiated a new connection due to the previous one (which the mbed has no way of telling is now lost) being lost/closed. Therefore, it should be no problem discarding the current socket and replacing it with the new one

Does this seem like a sensible approach?

EDIT:

I've come up with an example of what I was describing above. Hasn't been tested, but should still convey the idea.

#include "mbed.h"
#include "EthernetInterface.h"

// Network interface
EthernetInterface net;

TCPSocket listener;
TCPSocket* client;

// Socket demo
int main()
{

    int remaining;
    int rcount;
    char *p;
    char *buffer = new char[256];
    nsapi_size_or_error_t result;

    net.set_network("192,168,0,101","192,168,0,101","192,168,0,101");
    net.connect();

    listener.open(&net);
    listener.bind(80);

    listener.listen(1);

    client = listener.accept(NULL);
    client->set_timeout(1000);

    while(1) {

        int remaining = 256;
        int rcount = 0;
        p = buffer;

        while (remaining > 0 && 0 < (result = client->recv(buffer, remaining))) {
            p += result;
            rcount += result;
            remaining -= result;
        }

        if (result == 0) { //Peer has shutdown connection
            client->close(); //close socket;

            client = listener.accept(NULL); //block again until new connection comes through
            client->set_timeout(1000);
        }

        if (result == NSAPI_ERROR_TIMEOUT ) { //Assume connection has been lost
            client->close(); //close socket;

            client = listener.accept(NULL); //block again until new connection comes through
            client->set_timeout(1000);

        }

    }

}


texts:
This is the circuit

Can you please explain how did obtain  the AC equivalent circuit


texts: Circuit with 2 reed switches (proximity sensors) output to single GPIO

texts:
I would like to use 2 magnetic proximity sensors (normally open reed switches) to determine the position of a chicken door (vertical sliding door) which in turn controls a motor. If the door comes within reach of the first (lower) switch, the motor should slow down some. When both switches are closed, the motor slows down even more and finally when only the second (upper) switch is closed the motor stops completely.

I would like to use a simple circuit that generates a voltage that can be read with a single GPIO (ADC). I would prefer an output that matches the following truth table:

(S1 = bottom switch, S2 = top switch, x = open circuit)

S1, S2, Output
 x   x  0V
 1   x  1.6V
 1   1  3.3V
 x   1  5V

The output does not need to be in that order, but it needs to be distinguishable (at least 1/4V between states).

If at all possible, I would like to use only discrete components.


texts:
I don't quite understand the concept of the DC current Rating of the ferrite beads.

Let's say we have a ferrite bead with 120Ohm @100MHz and with 3A rated current (and a DC resistance of 30mOhm).

What will happen if the `DC current through the bead increases above 3A? Can I see it as a fuse, that will "break" above the rated current, meaning that after some point no current will pass through it? Or is it totally different?

I have read somewhere on the net that the bead will saturate if the current exceeds the rated value. Does that mean that it will not function normally? Something like not being able to supress the ripple? That its resistance at 100MHz will be lower than 120Ohm?


texts: MOSFET based audio switch generates thumping sound

texts:
I need to switch on and off an audio signal without clicking or thumping. I have tried the below circuit that I designed and simulated in LTspice, but it generates a thumping sound when I wire it up and test it. Also from the simulations in LTspice it can be seen that there seems to be an DC offset when I insert the probe within the swithcing section (between C8 and C9). Also on switching off there is a strange exponentioanl curve seen. I suspect that this is generating the THUMP. The signal from the generator is positive and it never goes to negative values.

I would like to generate a signal like this: S(t) = A * sin(t)
The signal should be smooth turning on and off if A is an exponential function varying between 0-1 and 1-0.

A is implemented in the circuit by the two MOSFETs shunting.

Any suggestions on how to avoid the click / thumping? (I have tried to increase the RC constant R13, C2. It doesnt solve the problem. The reason for the push pull driver is to be able to drive current in and out with the same resistance so the rise and fall times will be similar)


texts:
Is there any analog meter with the needle capable of a full revolution?

I have always seen only instruments where the needle can rotate only a fraction of 360 degrees, for example in the following image the needle can rotate maybe less than 90 degrees.


texts:
I see that LED light is replacing nowadays every old style light. I open one LED bulb and found that had a little SMPS inside it. Those convert AC line voltage to DC to supply the LED.

Wondering we can design to connect LED's on directly on AC line . It will improve efficiency

As per attached circuit. If we can connect LED on Direct AC line

Will it work?
Will it be safe and reliable?
Whether it needed any limiting resistor, since all AC line voltage will be drop on LED . (Vline = 230 V AC, Vp = 230 * 1.414 (+15% tol) = 360 V approx. Total no led is 120 (changed 76 to 120), each led has 3V forward drop).
How much line fluctuation will effect on LED?


texts: Stepper motor driver TMC2209 is powered from microcontroller logic pins

texts:
I am doing my first steps with a TMC2209 V1.2 stepper motor driver and a NodeMCU.
This is my circuit:

I power the motor side via 12 V supply (12 V on the lower rails). In the circuit, this is represented by a 9 V battery)
And I supply the board logic voltage with a MB102 breadboard power supply (5 V on the upper rails).
The jumper on the lower rails of MB102 is disconnected.
I ran into the weird problem. My driver circuit will power up when I connect my NodeMcu to my laptop via USB. But the only things connecting them are the logic pins for "enable", "direction" and "step".
I subsequently disconnected pins and narrowed it down to the step pin, which is switched every 2000 µs.
So I am guessing the current from the "step" pin is enough to supply the driver a little bit. Even the LED on the MB102 is turning on. It's not enough to control the motor correctly though, because its just shaking.
But why can the driver be powered via its digital inputs?
Should I prevent this and how?
Should I disconnect the 12 V motor supply when connecting to USB?


texts: How does the glass screen of smart phones not block the discharge of capacitors in capacitive touch screens?

texts: Glass is one of the best insulators when designing high voltage electronics, and correct me if I'm wrong, but capacitive touch screens work by measuring the charge of capacitors in a grid on the screens surface. The capacitors of a lower charge are closer to the point where someone is touching the screen. So, how does the glass on the surface of the screen not block the discharge of the capacitors into its human conductor? Is there some special type of glass used in these displays which has lower insulating properties than typical glass?


texts: Why does hysteretic current-mode control have variable switching frequency?

texts:
This figure below is from Raymond B. Ridley Dissertation "A New Small-Signal Model for Current-Mode Control".

Here is an except from the document:

  The general implementation of hysteretic current-mode control is shown
  in Fig.
  2.2. The inductor current waveforms are used to control both the turn-on and the turn-off of the power switch of the PWM converter. The
  advantages of this kind of circuit are apparent: no clock or timing
  function is needed, and the current level is controlled between two
  limits. Although this implementation was popular before control
  circuits became available, its variable switching frequency, and the
  need to sense the inductor current during both the on- and off-times
  of the power switch have restricted its use today. This circuit does
  not have any problems with instability of the current-feedback loop,
  and it is not analyzed in this dissertation.

Can anyone explain why this control method has varibale switching frequency? Also why this is bad?


texts: Fan out is the maximum number of inputs that can be connected to a specific output. Why can’t we connect more number of inputs to this output?


texts:
I know this question depends on the component but let's take this one for example : https://www.nexperia.com/products/analog-logic-ics/asynchronous-interface-logic/voltage-translators-level-shifters/74AVCH1T45GW.html
How do you calculate the input signal max frequency ? I know it related to the propagation delay of the voltage translator but I don't get the same data rates as the ones described in the datasheet.
For example, I'd like to translate a 3.3V 100MHz clock to a 1.8V 100MHz clock. Is it a good solution ?


texts: Read and write simultaneously from different indices of an associative array in system verilog

texts: Is it possible to read and write simultaneously (In parallel) from different indices of an associative array in System Verilog ?


texts: How can I control 4 separate Motors from a single H-Bridge?

texts:
I have an interesting problem.
I am trying to control 4 separate actuators at the same time so they lift at the same speed.
Each actuator has feedback and at max draw they pull 12v10A each. The h-bridge can handle that, but I am looking for a way to switch the h-bridge to whichever of the 4 is needing to move to catch up. They all use potentiometer feedback. Relays are too slow at switching so those are out.


texts: Is there any difference between AD620 vs INA128?

texts:
I'm trying to make an EMG sensor.

I've found some tutorials, for example, DIY muscle sensor/EMG circuit for a microcontroller, but my main question is can I make an EMG sensor using AD620 instead of INA128? Because I can't find INA128 in my city.


texts:
I am trying to figure out a way to create a high current ripple through and inductor, similar to that of the ripple the inductor sees in a SMPS. I would like to put a 2A peak to peak 400KHz current through a 10uH inductor. It is alright if it is a sinusoidal waveform rather than the saw tooth the inductor sees in a SMPS.

Ideas I have tried:

-Find a high enough power AC supply that operates at 400kHZ. I have not been able to find a supply with a high enough power rating that can generate 400kHz.

-Use a transformer with a very high turns ratio to step down the voltage/step up the current from a low current signal generator. The issue is that at 400kHz, a 10uH part has a relatively high impedance and I would need a very high input voltage to obtain 2A across that high of a load impedance.

-Use a H-bridge to drive current through the inductor in each direction. The issue here is I need a DC current through the part as well, and I can not vary the inductance or frequency so I am unable to vary the ripple at all.

-Design a buck converter for the DC and ripple current I want. This works, but I need to test many parts at the same time so I would need many buck converter circuits.


texts: Controlling a 240V AC Universal Motor with Microcontroller, Optoisolator & TRIAC

texts:
I got an old washing machine motor(universal) laying around, that I'd like to speed control. I'm new to almost all the components mentioned above, but here is what I currently use:

Microcontroller: Arduino Nano
Optoisolator: MOC3041
TRIAC: 2N6071AB (Replace? Thinking of BTA24-600B)
Universal Motor: UOZ 112 G 55

But after a long search I came across this circuit: http://imgur.com/d9nEwLQ

So first off; I've tried to hook the TRIAC (2N6073AB) to 240 VAC, it scattered into two pieces after about 5 sec. It says it's ment for 400 VAC, so I'm a bit confused. I didn't have a heat sink attached though, but still... Maybe someone got something to add to this behavior?
This is how I connected the TRAIC for testing purposes:

simulate this circuit – Schematic created using CircuitLab

Second; for the circuit above, I bought 1/4 watt resistors, and I cannot understand how they can handle 240 VAC, seems really strange to me. Or maybe they can't? Like the capacitor in series with the 39 ohm resistor, how is that even possible?

Third; What role does the 330 ohm resistor play, why is this one needed? And it also says "for highly inductive loads, change this value to 360 ohms", what value? Is it the 39 ohm resistor? And why change it, is because of the high start current for motors?

Fourth; for the 0.01 microFarrad capacitor, where does this value come from? And from what I've softly read, the snubber circuit is to prevent the phase shift between voltage and current caused by the motor, right? Will these capacitors do: Blue Ceramic Disc Capacitors 1KV 1000V 103PF 0.01uF?

Final question; I've been reading some PDFs about thyristors (inc. TRIAC), and it said:

  "The output of most microcomputer input/output (I/O)
  ports is a TTL signal capable of driving several TTL gates.
  This is insufficient to drive a zero-crossing TRIAC driver."

I guess that's not the case with Arduino Nano since it uses PWM signal? Or do I still need the NAND-gate? And if someone would like to explain why the zero-crossing TRIAC driver doesn't accept certain signals, I would be grateful.

I'm sorry about all the questions, and I thank you in advance. And I'm very surprised of how little I seem to know about the subject. I have a great interest in electronics, and from an educational point of view, should I have far more knowledge than it seems that I currently have. But I'm very eager to learn, so I would appreciate well written answers. My thanks.

Kind regards
MrMongoloid


texts:
I'm trying to use a www.sparkfun.com/products/13879 with one 3 wires load cell I gathered from an old scale, so I reproduced this schematic. However the reading is always the same.
I use the code from a learn.sparkfun.com/tutorials/load-cell-amplifier-hx711-breakout-hookup-guide#arduino-code BUT I do use read() (raw value from the HX711 instead of the user friendly and calibred value).

So I looked at the resistance of each wire (I have the red,black,white wires patterns) and sure it look like the pattern is right (black-red is 1k, black-white is 2k, red to black is 1k).

I looked at my wire, try to redo my wire and the result was the same. So maybe the load cell is broken.

So I tried to use a potentiometer instead (which also have the benefit to be more controlable), so I reproduced this schematic instead and same result, I always have the same value (8388607).
(For each +Active I use a different potentiometer where the middle pin is the output (A- and A+); I tried to connect the potentiometer gnd to GND and try to let them unconnected.

I tried to unconnect the data lines from the HX711 and the value is a negative one meaning the chip should somehow work.

What can I look for or what could I try as a simpler test?

Thanks


texts: Understanding voltage sampling rate of induction motors

texts:
Why it is required to have a sampling rate of at least 4kHz when sampling the voltage waveform of a three phase induction motor?

I find most research papers use 4kHz but they don't state why.

I want to understand why 4kHz as appose to 5kHz or even 10kHz for example. I need this waveform to calculate the RMS.

Thanks in advance.


texts:
My organization (a school) has an FCC license for three frequencies used on our campus for handheld radios (safety) and CB radios (busses). We wanted to record and reflect (retransmit) these signals out over the web so that even those without a radio can listen in the event of an emergency.

I went out and got a scanner at Radio Shack and plugged in our three frequencies. This works like a champ! We hooked it up to a computer and with Icecast and Darksnow, we now have a working "listening post" on the web. The problem started when we tried to move this fully working setup from our office (on the top of a hill) into our data center (a metal box inside a concrete box inside a metal box in a valley). We lost all reception. The scanner has a coax-input however, so I got 50 feet of coaxial cable and ran it to a spot outside the building. Our reception improved significantly, but still isn't great.

The cable isn't plugged into anything right now, because I'm not sure what type of antenna to buy. Our frequency assignment is tight, three frequencies in the 490-500 Mhz range. I think we need something that is fairly omnidirectional. Ideally it would be something compact that won't draw attention or look like an eyesore. I'm having a hard time interpreting all of the information about antenna types.

Will a UHF TV antenna work? Should I be looking for something more specific?


texts: Noise canceling while recording from mobile on PC

texts:
I have a setup in which I have to control mobile Android device from the PC and record the outgoing sounds of it.
The control is done by a USB cable. For audio recording I use a headphones which I cutted off and have soldered a 3.5 mm plug instead.
Each cable functions great by itself - when I connect the audio cable without the USB cable and operate the device and the recording manually, I get clean audio. The problems start when connecting both cables together to the PC - the sound is very noisy and not useable. The strangest thing is that the noise is not consistent - I can get an hour or two of noise free recording, and then it starts.
I've soldered another wire to the audio's plug ground pin and connected it to the PC's schasis, but it doesn't make any difference.
A friend that had a similar problem in the past suggested to use 2 PCs - one for controlling the device and the other for audio recording, but I cannot  do it.
I've thought of applying some signal proccesing method to try to eliminate the noise, like recording short time of noise and then use it as a reference, but it looks like an overkill to me.
Is there any simple solution?


texts: ESP8266 + Logic inverter on Tx = Failure to boot ?

texts:
I'm programming an ESP-12E module using the Arduino support package.
My setup requires a logic level inverter on the Tx pin (only).
I built the following which is working OK :

simulate this circuit – Schematic created using CircuitLab

However the ESP8266 will not boot with that attached to it, I need to unplug it at boot time and plug it back in after. Then everything works fine.

Why is this causing the ESP to not boot ? And how can I make it boot anyway?

(What I tried : a 10K pulldown from Tx to Ground. No effect)


texts: Using 2 Data Flip Flops to create an up counter from 0 to 3 and repeats

texts:
I've done most of the legwork. I've got this design working using 2 set reset(SR) flip flops, but I need to make it using 2 data flips, a.k.a D flip flops.

What I did:

Note the numbers not in brackets are in base 10, the numbers in brackets are in base 2.

State Diagram

Note the truth table for a set(S) reset(R) flip flop.

S R |   Q(output)   |     !Q
----+---------------+--------------
0 0 | no change     | no change
0 1 | 0             | 1
1 0 | 1             | 0
1 1 | indeterminate | indeterminate
    | (sometimes 0, | (sometimes 0,
    |  sometimes 1) |  sometimes 1)

Present State is represented by P.S,
Next State is represented by N.S,
A is my most significant bit of input
B  is my least significant bit of input,
x represnts don't care,
! represent not

P. S | N. S |  A  |   A   |  B  |   B
A  B | A  B | Set | Reset | Set | Reset
-----+------+-----+-------+-----+-------
0  0 | 0  1 |  0  |   x   |  1  |   0
0  1 | 1  0 |  1  |   0   |  0  |   1
1  0 | 1  1 |  x  |   0   |  1  |   0
1  1 | 0  0 |  0  |   1   |  0  |   1

Through K-Map I got:

Set of A = !A and B,
Reset of A = A and B,
Set of B = !B,
Reset of B = B

This is my design using 2 SR flip flops:

If someone could help me create a circuit with the same functionality except using 2 D flip flops, that would be greatly appreciated.


texts: Turning off (collapsing the field) of large inductors

texts:
In a totally unrelated search to something I was looking for, I came across an article from the EPA that describes looking at soil properties through a large inductor for geophysics.

https://archive.epa.gov/esd/archive-geophysics/web/html/time-domain_electromagnetic_methods.html

What struck me is that the premise of the project is that you impart a field into the earth with a large inductive loop, and then you read the results; however, it completely hinges on the fact that you can collapse a field instantaneously (Figure 4 in the link above, now attached below).

How would one actually collapse a large field quickly in practice? I am looking for the nuances of collapsing an inductive load that is large which potentially 1kV+ of kickback.

I found some vague reference to 10 turns in a square of 10m x 10m for 6 gauge wire for 100V at 100A for a system that runs at 120Hz.  If I put resistor across the inductor to collapse it quickly, it would basically put a million volts across the resistor.  There has to be something more elegant to remove the field in an inductor quickly due to this voltage spike; however, it might be as simple as a resistor.

update:
I mentioned "instantaneously" as that is what the figure showed.  I am aware that this is unrealistic.

update 2:
As I've found more system information, I'm not even clear that the coil could get to steady state (what I mean by this is that the flux is already in the earth and thereby the coil has reached 100V@100A).  I'm beginning to think that the system specs are more theoretical than pragmatic.


texts:
Is there any (preferably open source, preferably python; only linux) software for microcontroller board prototyping simulation? I'm an EE and we used spice in classes to simulate circuit level stuff. Is there anything like that?

Is there a specific term for what this would be called? Just simulation software?

Also: I crossposted this on SO because I totally forgot this place existed. Hope that's ok.


texts:
As part of a project, I am writing a program which generates ngspice scripts. For my purposes, it would be very convenient if I could always use the two argument v() instead of using v(node) when I want to compare against ground and v(node1,node2) when I want to use two arbitrary nodes. When I execute "listing", it shows a ".global gnd", but v(node,gnd) returns

Error(parse.c--checkvalid): gnd: no such vector.

Is there a way to get a vector of zeros, or must I hardcode both cases independently?


texts: Is electrical designer same as electrical engineer?

texts:
A job I'm interested in has a title of "electrical designer". The qualifications are either a Bachelor of Engineering or Electronics Engineering Technology.

Is this not an Engineering job? Accordingly, will I be able to gain experience credit towards my  professional engineer title with such a job?


texts: What does the reference designator DB mean when printed on a PCB?

texts:
I have seen this question but I can't seem to find a meaning for DB.  What does DB mean?
Circuit from Plasma Lamp

Circuit from Fluorescent Light bulb
Even my lucky light bulb has it!


texts: How do I get this LCD to work on Proteus?

texts:
I'm trying to display the letter "A" on LM016L (datasheet). I keep switching the E input but I get nothing.

This is my circuit:


texts:
I set up this circuit on a breadboad but it doesn't seen to work correctly.
I used 1 ohm(5%) for the sense resestor and set the voltage using a divider down to 1v but there're 2 issues:

1- the voltage across the resistor is about .8 V and goes down after a little bit I guess because the mosfet on resistance increases with temperature.

2- The mosfet heats up so quickly (it's heat-sinked) although it has a very low on resistance of .025 ohm (irfz44n).

I tried to put a small series resistance with the the gate of the mosfet so it prevent ringing but still the same problem. I even put 10 kOHM resistor to make a schmitt trigger but also didn't work.

I'm using a 12 V, 1 A limited voltage source and LM358 for the OpAmp.


texts: What does an antenna "matching transformer labeled 75 ohm to 300 ohm" really mean?

texts:
Shouldn't it be the other way around? (300 ohms to 75 ohms)
300 ohms coming out from the antenna wires to 75 ohms coaxial cable?

Where does the 300 ohms comes from? is it because most antennas use wires that have 300 ohms impedance by default and you need this matching transformer to bring it down to 75 ohms.

What if the antenna is labeled 50 ohms? can we still use this matching transformer? or it is not necessary in such case.


texts: how can I try to revive this AGM deep-cycle battery which started to perform dramatically below specifications?

texts:
I have a AGM deep-cycle battery, 150 Ah, 12V: Banner "Stand By Bull" SBV12-150.
12V150AhC20.

Up until recently it was working quite OK, I was able many times, for many months, to drain about 170 mA from the battery for a month before recharging it (such a drain should not deplete the battery below 20% full).

But recently the performance suddenly dropped, the last time I tried to charge it, here is what happens: the voltage on the battery without any load before starting to charge was 9.69 V. I don't know why it was so low, because the battery was charged previously only 10 days ago with 16 hours of about 5A charge, at the end of which the voltage on the battery (while still charged) was 14.7 V, and the specifications of CCCV charging of an AGM battery say that an AGM battery is at least 80% full when the voltage reaches 14.1 V, so 14.7 V should be really full. And then the battery was used for 10 days with a load of about 170 mA, so no more then 41 Ah should have been depleted from the battery.

This time (after these 10 days of 170 mA load), I did 20 hours of 2A charge (which should put about 33 Ah back into the battery). The voltage on the battery at the end of charging was 14.0V. Then I disconnected the charger, and the voltage measured on the battery just after disconnecting the charger was 13.0V.

And then I placed a 60 mA load on the battery, which is a very tiny load for such a big battery, and it should go for about 40 days like this on an 80% full AGM deep-cycle battery before the voltage should drop below 12V. But in my case, the voltage dropped below 12V after only 10 hours - this is about 100 times less than what it should be.

Is there anything I can do to try to revive this battery? Is there something like a desulfation or equalization charge that I could try to restore this battery, and how to do it to have the highest chance of success?


texts:
Just a quick one. I'm not sure if the text should be mirrored on the bottom layer of EasyEDA. It seems okay in the 3D preview, but when I upload the gerber to JLC their preview shows it still reversed. What gives?

I threw this layout together, and have since realised it can be done on a single layer :P


texts: Obtaining Anderson's Bridge Balance Equation

texts:
I'm trying to learn Anderson's Bridge Balance equation.I dont know how this value is obtained

Why are they equating the voltage drops across branch one and the sum of the voltage drop across branch 2 and the one with the capacitor?
Please advice


texts: What is the meaning of my fourier transform results?

texts:
I've been experimenting with Fourier transforms, and I'd like to understand some of the results I'm seeing.

I've written a simulator which generates a data stream of length 1/120 seconds, sampled at 33.92 nS intervals. The data represents a half-sine wave generated by an inverter. I concatenated this stream with its own negative inverse, to create a single perfectly symmetrical 60 Hz sine wave 491,352 samples long.

I then ran an FFT of the results using numpy. Most of the results made sense to me: the FFT was the same length as the original signal. Discrete Fourier results are symmetrical about the fundamental, so I have half that many "bins" (about 246,000) to represent harmonics. The lowest frequency content in the original signal is 60 Hz. Per Nyqist, the original signal can not represent frequencies higher than 1/(2*33.92 nS) = 14.74 MHz, which is also the roughly 246,000 harmonic of 60 Hz. So each bin represents one harmonic of the 60 Hz fundamental, with no skipped bins. If I tried transforming five full sine waves instead of just one, four out of every five bins was zero, which makes sense; those bins represent fractional harmonics, which are meaningless.

Going back to my single-wave FFT, every even-index (index from zero) entry of my FFT results is zero. Every odd entry is non-zero, with index 1 being by far the largest. This makes sense if 1 is the fundamental, because the even harmonics won't show up in a symmetrical sine wave. But why is the first entry in the FFT results not the fundamental?

After this, I applied an LC filter, by iterating through the FFT results and multiplying each bin by the filter gain at that frequency. I then did an inverse FFT, giving me the filtered time-domain signal. The result has both real and imaginary components. The real component and the imaginary component, when taken separately, each look like what I expected the time domain signal to look like: a better looking sine wave than I started with, shifted by 90 degrees relative to each other.

But the magnitude is pretty much constant, rather than looking at all line a sine wave. This is not at all what I was expecting. What is the significance of this result?


texts: Can I use an ELV dimmer to dim an electronic switching power supply for LEDs

texts:
I am using a Meanwell 350-12 power supply to power LED light strips which use SMD 5050 diodes. It is an electronic switching power supply. The strips use PWM normally to accomplish dimming.

In this application I would like to use a Lutron DVELV 600 dimmer to dim the LEDs. Will it work or will it destroy the power supply and LEDs?

Thanks


texts: How to charge Polymer Lithium Ion Battery that comes with the Lilypad Development Board

texts:
There is a Lithium Polymer Ion Battery that comes with the Lilypad Development Board from Sparfun. Does anyone know if the battery charges if we plug in the battery to the Lilypad Arduino and connect the Lilypad Arduino using the FTDI at the same time. The battery specifications are in the URL below:
http://www.sparkfun.com/products/731

Here is the link to the Arduino Board which takes power via the 6pin FTDI or via a LiPo battery connected to it: http://www.sparkfun.com/products/10274


texts:
Using measures from a spectral analyzer, I am a bit confused on how to properly compare the power of each spectral line with the fourier coefficients (Parseval).
Take this signal:

Take its spectrum:

My experience with spectrum analyzers being limited, I attempt to compare what I expect with what I read.
The Fourier series coefficients of the ramp signal are:
$$
D_n = \frac{-jA_{pk}(-1)^n}{\pi n}
$$
So I expect a single spectral line on the spectrum analyzer to have power:
$$
P_n = 2 \cdot |D_n|^2
$$
Where the factor 2 is due to the signal being real (taking into account both contributions at -f and f).
And so, for the first spectral line (at n = 1), I'd expect to have:
$$
P_n = 2 \cdot \left( \frac{0.1 \cdot (-1)}{\pi} \right)^2 \approx 2.02642 \cdot 10^{-3} W
$$
Now, converting the spectrum analyzer's dBm to watts:
$$
P_{experimental} = 10^{(P_{dBm} - 30)/10} = 10^{((-13.85) - 30)/10} = \approx 4.12098 \cdot 10^{-5} W
$$
It seems I have a somewhat huge error on this measure. However, it seems the spectrum measures are not entirely uncorrelated with the Fourier series powers, in the sense that the factors between the measures and the actual powers calculated using Fourier series seem constant. It seems to be a simple scaling error.
Maybe I miss something, and I wondered if anybody would maybe see something on the instruments captures I don't see.


texts: How can I add adjustable current to a DC-DC converter?

texts:
I would like to use a DC-DC converter to adjust the voltage and the current too. I would like to use MP2307, XL4015 or something similar what can easily buy.

How to add adjustable current? I dont want to use opamp (like Lm358) because it will be oscillating.


texts: Controlled gain connecting input voltages to opamp

texts:
Suppose we have a charged capacitor and at time t=0 we close the switch and the capacitor starts discharging.

Is there a circuit with an opamp which amplifies it with a controlled gain? I don't want the 100k+ amplification if we just connect the 2 ends of the resistor to the inverting and non inverting pin because I want to translate the voltage difference  to digital values. Help appreciated.


texts: DIY portable bluetooth speaker; charging/battery question

texts:
I'm new to this and i'm doing my first real build for a friend. What I got so far:

Amp: ZK-TB21 Here
BMS 3s 40A balance Here
18 18650 battery on 3S pack
2 x 25W generic speaker and 1x30w tangband mini-sub
One on/off switch
One 12V charge indicator
One 12V 5A DC charger

I've got an issue where i want to be able to charge the battery pack while using the amp.
The amp got 2 power source in, so I figure I would connect one directly to the DC in port, and the other one to the battery pack but I'm not good enought in schematic to figure out where I need to put my on/off switch to cut off power delivery from the battery to the amp without preventing the charge of the battery pack.
I do not have any schematic of what I got so far, but if needed, I'll do my worst on paint to explain it. Don't hesitate to question me and thanks for the help !
Thanks for the answers: here is a pic of the amp :
Left one is DC in, right one is just 2 pins: positiv and negativ
So there is two power input possible.
Thanks again for the answer. That was my guess too (because Aliexpress doesn't send the manuel with the amp ) but here's my problem:

Here's an oversimplified schematic of what i'm trying to do with the dc barrel plug in a 12v 5a power supply.
How can i make sure that the amp is using the power supply and not the battery pack ?
And will the battery pack charge ?
I'm really not sure of what i'm doing.
If this too much hassel, i'll just put two DC female power in: one for charging, one for using directly on the amp.
But i would like to have the option to charge while i'm using it.
EDIT: Well, this is really helpful, thanks everyone for your answers and your help. I'm gonna go to a spare part electronic store near my place to ask for these.
I just have one question left:
Is my 12v 5a power supply enough to charge the battery bank and power the amp at the same time or will it blow ?
And
I thought BMS were charger module too, am i wrong ? Do i need something else to charge my diy battery pack ?
Once again, thanks everyone, i'm learning a lot.


texts: msp430g2553, how can I get a UART baud rate higher than 9600?

texts:
I have an msp430g2553 in its launch pad. I have tried using a baud rate of 19200 with the UART and I get gibberish. From what I have found, something with the launchpad or drivers limits the UART baud rate to 9600. From the datasheets I know that the chip can transmit up to 1MBd, but I can't find anything that tells me how to utilize any transfer rate higher than 9600. What hardware or software do I need to get the msp430 to talk to my computer faster?

P.S. I am using the msp430 to send ADC samples to a C# program on my computer, and that works perfectly at 9600, but I can't make it any faster.

EDIT: "The MSP itself can go as high as 1MBd. It's the USB/ser converter inside the LaunchPad (the so-called Applicaiton UART) that is limited to 9600Bd - its high-speed part is required for the JTAG (debugging) functionality." - source. So how can I set up a USB/Serial connection in place of the launchpad?


texts: What the FPGA dev board to choose: Xilinx or Altera?

texts:
I'm very new to programmable logic world and have never worked with any HDL languages, but I certainly want to get started with FPGA. At the moment the goal is to develop/simulate simple 8bit CPU and maybe (in the future) do some graphic output.

As I understand there are two big players in the FPGA market: Xilinx and Altera. I have very though budget - 40$. Also, I'm a little bit confused of capabilities that varies from board to board (regardless of vendor). For example, some of the boards - even based on the same chip - has VGA port (or COM/RS-232 port), RJ-45 socket and even audio line out/in; some of them just have an array of pins (if so does it mean that FPGA has Digital/Analog I/O?). So I'm curious if it will be possible to "extend" capabilities (eg add D-sub port to output some graphics or phone socket for audio) on the board that doesn't have a required interface.

I need an advice and certainly some explanation what the board better to buy in my "noob" case. I use aliexpress to buy such a things, so here are some examples I've found "appeal":

Cyclone4-FPGA-development-board-with-LCD
Mojo-V3-FPGA-Development-Board-Spartan-6
Altera-Cyclone-IV-FPGA-development-board
ALTERA-FPGA-EP2C5T144C8N-development-board
LCD1602-development-board-xilinx-spartan-6


texts: Trying to Find Minimum Output Capacitance

texts:
I am trying to choose an output capacitor for the TPS6107 boost converter.
My circuit will resemble the example from the datasheet.

Datasheet: http://www.ti.com/product/TPS61070/datasheet/abstract#SLVS5107171
Equations Used: http://www.ti.com/lit/an/slva372c/slva372c.pdf

I need to find the minimum output capacitance so I can select my capacitor.

I am using equation 12, on page 5, from the Equations Used link:
Csub(out,min) = (Isub(out,max) x D)/ (fsub(s) x Delta Vsub(out))

I had to solve for the output voltage ripple, Delta Vsub(out), and the inductor ripple current, delta Isub(L), as well.

I have provided my calculations below, but I think my answer is wrong. I think i may have made a mistake with my units but i'm not sure.


texts:
Radio waves are a class of electromagnetic waves.
Light also is a class of electromagnetic waves.
By shaping a material in which the speed of light changes, we can bend the propagation direction of light, we call this a lens, and we call the speed change rate refractive index \$n\$.
Also for RF we can define a speed change rate as \$\frac{1}{\sqrt{LC}}\$ or \$\frac{1}{\sqrt{\epsilon_r\mu_r}}\$.
We also use the exact same destructive interference in the same way for radomes and Anti reflective coatings.
So here comes the question: why don't we use lenses and  ̶m̶i̶r̶r̶o̶r̶s̶ for RF, for example for focusing RF beams instead of using complicated directive antennas?
EDIT: yes, we actually use mirrors


texts:
I am not too familiar in electronics, but I am currently using them for a Computer Science project.
I am connecting an electromagnetic door lock to a SPDT relay, so that the door can stay on NC and then be opened when I power the coil.
The problem is that I don't know how to to power the common pin as the electromagnet requires \$12\ V, 110\ mA\$. The best that I could find is a \$12\ V, 1\ A\$ plug that I don't think will work due to the power differences.
The link to the electromagnet I plan to use:
https://uk.banggood.com/DC-12V-60kg-Visible-Installation-Door-Cabinet-Magnetic-Lock-Access-Control-System-p-1241735.html?rmmds=search&cur_warehouse=CN
Any help to do this would be much appreciated.


texts:
I am designing a linear step-down regulator using a PNP pass transistor. The output of the regulator is good at no load.

When I connect my regulator to a battery supply, leave it for 2 seconds and then I connect my load (say a 12 V DC motor or a microcontroller), it works good.

But when I attach my load to the circuit and then supply power, my output drops to almost 0 V.

Here is my regulator circuit...

There is a problem in my design. I am trying to analyse it. It would be appreciated if someone could help me.

Above one is a reference image from Texas Instruments.

Input supply (battery)   = 40-50 v

Output volt (for controller) = 12 v (500 ma approx)

Edited:

I connected the input for 7805 in source side by using a transistor to get a constant supply as shown in the image. Now my circuit works better.But pnp transistor heats quite a lot by connecting load. Since it's a low dropout regulator, why it heats much.


texts: Microwave amplifier characteristics - don't undertand

texts:
Please, look at http://www.rfcomp.com/hd24223.aspx (the spec file is downloadable in this page). This is a microwave amplifier, and I have several questions.

1) What is "noise figure" ?

2) What is P1DB ?

3) What is IP3 ?

4) What is VSWR ?

5) Does this power amplifier works like an OpAmp, that is, does it amplify any signal linearly ? is there an input offset like transistors, or is it able to amplify extremely weak signals ?

6) How did they make this amplifier ? the most skilled radio Ham can only design a circuit to amplify up to 3 GH, and it is well known that all diodes and transistors do not switch so fast, every resistance and capacitance have small (but extremely disturbing at these frequencies) parasitic impedances. So, how do they that ? thx.


texts: LED 10mm 8400mcd loses brightness using battery A23 12V

texts:
I have a problem:

I'm supposed to produce bicycle lamps.

The LEDs should be white, and super bright as possible, use batteries A23 12V, with a resistor (I'm using 2 MOhms,) and last for around 48 hours.

The problem is that the LEDs using this configuration, lose brightnrss after 15 seconds (maybe lose 50-60% of the brightness.)

I have tried already with 3 different kind of LEDs,  always with the same result.

By the way, I used the same resistors and same batteries 2 years ago (with leds that worked,) and now I can't find LEDs that actually work.

Basically I ran out of LEDs, but now I can't find the correct leds.

-What is your recommendation?
- What are the correct leds?

Characteristics of the LED I am using and fail:

Tekniske detaljer:

Producent (varemærke): OPTOSUPPLY
Type diode: LED
LED-diameter: 10mm
LED lysfarve: Kold hvid
Lysstyrke: 8400mcd
Lysvinkel: 30°
LED-objektiv: Diffus, hvid
LED strøm: 20mA
Driftsspænding: 2,8 - 3.6V
Montering: Printhul
Front: Konveks
Benafstand: 2,54mm

Any recommendation?
Sorry, Im not an expert, I am a bike mechanic. I used to produce these lamps, and they used to work.

*update: I uploaded a photo of what I am trying to do. I checked that the batteries basically die after few seconds, so I realize that the consumption is extremely high. I need new leds. But I dont know which ones. As I said before, with these batteries and resistors, hundreds of lamps have been produced in 2017 and 2019.
I checked an old lamp, and it has exactly the same "set of colors" resistor, and same battery of course. So the problem is the leds. (or maybe the resistors can be the same color but be different too? I dont think that).

Here is a photo of the "official" lamp that has been produced for nearly 10 years. I dont have specifications of the original leds. They are very bright, and battery last for a loooong time. Maybe the "mcd" is lower?


texts: Why cyclic voltammetry requires three electrodes?

texts:
From Wikipedia:

  The potential is applied between the working electrode and the
  reference electrode while the current is measured between the working
  electrode and the counter electrode.

Why do you need both a reference electrode and a counter electrode? Why measuring the current between the reference electrode and the working electrode is not enough?

Three-electrode setup: (1) working electrode; (2) auxiliary electrode; (3) reference electrode.


texts: USB-C connectors only work on target side, not host side?

texts:
I wanted to turn a short USB-A-to-Micro USB/Lightning cable into one that has a USB-C plug on the host side (because I couldn't find such a thing for purchase). I chopped off the USB-A plug and replaced it with a solderable USB-C connector that I found on eBay. Variants of this connector seem to be common. When I replaced the old plug, I wired up GND, VBUS, an D-/D+.

Unfortunately it's not working and the vendor told me that the connectors only work on the target side:

  The connector is not OTG pinout, it can not connect the host to target.
  The type-c end must be target end.

I'm not sure what OTG has to do with it, if anything.

The picture on that web site says "5.1K resistor", but when I measure it the resistor between CC1 and VBUS is actually 56K.

After a bit of research, it seems to me that the right fix is to remove the 56K resistor to VBUS and replace it with a 5.1K one to GND. In the little PCB attached to the connector and shown in the photo below, that means removing the resistor in the middle position and adding a 5.1K one in the currently empty position on the left. Does that sound right?

Update: Removing the 56k pull up and adding the 5.1k pull down resistor as described did make it work.


texts: How to increase the sensitivity of a 555 timer detecting capacitance variation?

texts:
I want to use the 555-timer as a capacitance sensor for (10pF ~ 250pF) range.
Is there a way to make the frequency change with respect to capacitance change more while keeping the frequency between 1Hz and 30 Hz?

In other words, can I increase \$\Delta\$ f/ \$\Delta\$ C while having a restriction on the frequency range?


texts:
I'm interested in using the SC16IS740 UART-SPI converter to interface with W5500 Ethernet controller which has SPI inputs. Because the datasheet is unclear to me, I'm asking if anybody knows how is SC16IS740 programmed? By UART or SPI interface, or both?

If it uses the SPI interface for programming, can someone recommend a low cost UART-SPI bridge (or converter)?

UPDATE

W5500 is part of a data acquisition system composed of: several sensors boards with MSP432, each having a communication module which will transmit Ethernet over cable or fiber optic, and a "gateway" which aggregates all data from sensors boards and will connect to a local area network. W5500 will be placed at the gateway since

Some modules can transmit over Ethernet cable and other over fiber optic cables.
The communication module is the Ethernet interface of the main board.

In case of transmitting over fiber, it has to convert electrical signals from W5500 to optical. Practically, I cannot place W5500 on the communication modules because it outputs 2 differential signals, thus requiring 4 fiber optic cables. So, a solution would be to transmit using UART (from main board to communication module and to gateway via fibers), thus using 2 fibers, and convert it to SPI (using SC16IS740) at the fiber-to-Ethernet converter, where W5500 would be placed. In this case, the master of SC16IS740 would be W5500, but is not acceptable.

Other solutions: transmit SPI data over fiber (unacceptable because it requires 3 fibers), use another controller to make UART-to-SPI translation.

Ideal case: placing on the communication module an Ethernet controller with outputs for fiber optic cables (I do not know any such controllers) and have and appropriate converter at the gateway.


texts: Implementation of AES algorithm using Systolic architecture

texts:
I need to generate a VLSI Systolic array to implement the AES encryption algorithm with key length of 128 bits.  Following are the possible ways :

Systolic for Key expansion
Systolic in MixColumn
Systolic for the on-the-fly calculation of S-box

For option #3, I am referring to this paper. Figure 2.1 from this paper gives the steps for calculating multiplicative inverse, which is the first step in S-box calculation. I am trying to convert this diagram into a systolic array, but haven't reached a concrete solution until now.

I am also referring to this paper to convert a cyclic algorithm into a Systolic one. However, I am not able to convert the operations involved in the AES encryption into Systolic structure. Could anyone give me any pointers on how to approach this problem?


texts: Send custom GATT characteristics using HM-10 (actually a CC2541)

texts:
Short question - how do I send data as GATT characteristics from a peripheral BLE device (Android UNO + HM-10) to a central device (i.e. an android smartphone?)

I'm working on a BLE peripheral as a learning project right now - I'm using an Arduino Uno and an HM-10. It's going well so far - sensors are working and I can send this data from the Arduino Uno to Android using an HM-10 BLE module (actually a CC2541 clone) on the standard service and characteristic for this device:

Service UUID: 0000ffe0-0000-1000-8000-00805f9b34fb
Characteristic: UUID: 0000ffe1-0000-1000-8000-00805f9b34fb

Working in this way the HM-10 emulates a traditional bluetooth serial connection. All good so far!

What I would now like to do is send the data using accepted GATT services and characteristics. For example lets say I would like to use the Running Speed and Cadence service to send my data in a way that can be viewed by any compatible app. I would need to change the service to 0x1814 and the characteristics to:

Cadence: 0x27A8
Velocity: 0x27A6
Gradient: 0x2763

I believe I could do this by using the AT commands:

AT+UUID0x1814
AT+CHAR0x2763

I think I'm OK with all of this so far, but what I cannot find guidance on is how to define multiple characteristics, and how to send my sensor data to my central device as GATT characteristics.

For example my speed is 10kmh-1 and my cadence is 80 - how do I specify the GATT characteristics for this and notify the central device when they change? Also bonus question - can I include an additional characteristic for gradient?

I've thoroughly searched but cannot find anything on this. Thanks!


texts:
It's been more than 20 years since I've done electronic design and I'm sure I've forgotten nearly everything. Now I have a purpose and want to start with a list of general purpose, readily obtainable transistors for small signal audio. By small signal I mean amplifying microphone output to feed audio cables for example. I presume that such a list might contain only five to 10 including bipolar and FET. I'm not sure I care what the packaging is.

Along those same lines, I don't know if it's possible to make a list for RF transistors, too. I have a feeling that, once I get on a roll, everything will come back to me and I'd like to keep that ball rolling.


texts: Is this how a R-2R DAC for VGA should work?

texts:
I'm trying to wrap my head around if this is how a R-2R DAC should work. I say should for two reasons: (1) because I think I understand the theory behind the resistor ladder of subsequent voltage-dividing, and (2) because I analysed the schematic of a common VGA Pmod from Xilinx, which I would expect to be, well... correct...

So, let's start with the circuit:

With all bits on, this achieves a ~0.7V max, considering the 75 internal impedance of a VGA monitor. Now, I've broken down all the possible combinations and the resulting voltage:

... which, suffice to say, is not what I expected how this should behave. A perfect DAC would be linear. A gamma-corrected VGA DAC would possibly be a curve. But these deltas are all over the place.

So here are the questions: (1) am I interpreting something wrong? (2) Is this how this type of DAC supposed to work? (3) How can we improve over this design?


texts: Specifications of Microcontrollers Is it all same?

texts:
I am complete virgin in Electronics. Though I am very experienced in Programming. I've never played anything with electronics.

What are the Specifications of Microcontrollers ?

  No. of digital Pins:
  No. of Analog Pins:
  SRAM:
  EEPROM:
  Flash:
  Operatng Voltage:

If only these few are the characteristics of microcontroler. Why the come with long pdf Datasheet ?

Now a days they can all be programmed in C. and while coding only the first 5 informations are needed all others can easily be found in headers.  So why don't the manufacturer companies just give out these few infos only and with some links of here and there ?

and If all vendors(Atmel/Motorola/Philips etc..) makes the same thing why professional people don't use AVR much. rather hobbyist people uses AVR.(got this info from another thread Why are Atmel AVRs so popular?)


texts: Why data buses should support 1024 bits, when processor are working with 64bits?

texts:
If the processors are working with 64bits, then why do they need Bus protocols to be as high as 1024bits.

Is it for re usability?


texts: Motherboard with 4 pin and fan with 3 pin

texts:
This is my first question and I'm a little tired to do more and more research. So I decided to ask and please let me go straight to the point:

The fan connector of my motherboard has 4 pin and the original fan has 3 pin. Can I find/buy some other fan (with 4 pin) to control the fan speed with PWM?

P.S.: By curiosity I collected some readings from the 4 pins of the motherboard with Arduino (using analogRead) and parsing the data to 0-5V respectively.

The graph below represents a sample of these data. Now does it makes any sense for you? I mean what can I learn from this?


texts: I need to find a ceramic cap to bypass certain freq on the power plane.  Since voltage can affect the capacitance (voltage derating), and if we consider the impedance vs freq curve (V-shaped curve), does it mean the SRF of the same cap will shift as the voltage varies?


texts: What is the purpose of a Zener diode added to the output of a SMPS?

texts:
I studied circuit diagrams of some computer ATX power supplies. Some of them have got a Zener diode at the very end of 5V stand by line.

The picture shows endpoint of the circuit - the SMPS is on the left (outside of the picture), then there are two capacitors, a resistor and a Zener diode - all parallel to the circuit. The 5 Volt output is on the top right of the picture. I expect the capacitors filter the output, the resistor is necessary to provide some minimum load in order to let the SMPS regulation work correctly. But what is the purpose of that Zener diode? It is rated 6V2, i.e. 24% higher than nominal output voltage. Is it some kind of a protection in case of regulation malfunction? And will it really protect the load from overvoltage? And if so, why is so much higher valued than nominal 5 V?

Sources:

http://danyk.cz/s_atx01aa.png
http://danyk.cz/s_atx01z.png


texts: Best way to deal with voltage loss in batteries

texts:
I'm doing a project with Arduino. I have a small Arduino board that every so often takes measurements from a sensor, but it's idle most of the time -- consuming 6mA. I want to use a small battery to power the board. I have seen batteries like the following one:

https://www.adafruit.com/products/1570

It's a 3.7V 100mAh battery. The board requires an input voltage in the range 3.7-4.2V. So, I suppose once the battery starts to drain, the voltage will decrease and the logic on the board may stop working correctly.

Is this correct? Or will the battery sustain 3.7V during most of its capacity?

Assuming the voltage will go lower 3.7V relatively quickly, I can imagine two possible solutions:

To use a battery with a higher voltage and then use some form of voltage regulator.
To use a battery with more capacity, hoping that the voltage loss will take longer to occur.

Which option is better? Or what are the tradeoffs from an electrical and efficiency point of view?

Is there any other option?

UPDATE

As some of the comments mention, the logic board indeed runs at 3.3V. It accepts a 3.7-4.2V input voltage and it uses a regulator to bring the voltage down to 3.3V. So I suppose a 3.7V battery will be able to power the board at least while it stays in the plateau section of its discharge curve.

With this new information, I guess my original question only makes sense if the board didn't have its own voltage regulator.


texts: What is the influence of an asymetric load capacitance on a crystal duty cycle

texts:
I have a crystal oscillating at 25MHz (datasheet). The recommanded load capacitance is 18pF according to the datasheet.

The crystal is connected to a component where the capacitance on the pin are not the same :
CIO1 = 11pF and CIO2 = 8pF.

I did the calculation to determine what capacitor was needed to connect on the pin :

With 11pF and 8pF on the IO pin the equivalente capacitance is 4.6pF then :

C_x=2*(C_L-C_p)

C_x=2*(18-4.6)

C_x=26.8pF

Then I selected two capacitors of 27pF to connect from each side of the crystal to the ground.

My problem is, since the capacitance on each pin is not the same I believe the duty cycle will not be 50%, because on one side the crystal has a 11+27=38pF and on the other side 8+27=35pF.

Knowing that, how can I theorically calculate the duty cycle?


texts: ngspice - print numbers in engineering notation

texts: Can .print in ngspice be told to print numbers in engineering notation (e.g. vout = 450e-3, not vout = 4.5e-1)? I've searched online and in the manual but could not find anything.


texts:
I worked on my schematic and I did the annotations and made my PcbDoc within the project, once I went to hit the Update PCB Document button from the "design" menu I realised that I don't have one (it's not greyed out, it's completely gone)
It was my first project with Altium designer and I was following the tutorials. I'm using the 21.2.2 version


texts: Can I replace a dual section capacitor in a tube amplifier design with two single capacitors?

texts: I was planning on building this schematic, but found it hard to source their 20/20 dual section cap (C3/C4). Could I replace this with two single 20uF caps, or is it a dual-section for a reason?


texts:
I'm writing code for a PIC18F46K22 using the C18 compiler. I want to write the value of an integer \$n\$ in ASCII over the USART to my PC.

For \$n<10\$, it's easy:

Write1USART(n + 0x30); // 0x30 = '0'

This would work for \$10\le{}n\le100\$:

Write1USART((n/10) + 0x30);
Write1USART((n%10) + 0x30);

But this isn't the fastest possible way, probably.

So is there a built-in function or a function somewhere out there that I could just use instead of rolling my own?


texts:
From Texas Instruments snoaa15, which is an Application Report about overcurrent protection of GaN FETs, in the first page, you can read the following quote:

  Traditional approaches using current
  sense transformer, shunt resistors, or de-saturation detection circuits remain ineffective due to slow
  response time.

So, I stumbled on the matter de-saturation detection (which is widely used in IGBT converters for protection and works very well) is ineffective for GaN technology due to slow response time, and that's why we should use their LMG341X driver, which includes fast and reliable short-circuit and overcurrent protection.

My problem is I am designing a pcb in which I'll make use of GaN in order to shrink as much as possible the pcb size and I don't want to buy the driver since it's really expensive compared to other GaN FET drivers. So to sum it up, is there another effective and cheaper way I can protect my GaN against short-circuit without needing to buy this specific driver?

The circuit I want to design is a simple synchronous buck converter, and for a size cutback I thought of using GaN FETs. The circuit as an overall view looks like this:

Additionally, the footprints are shown in the following figure:

$U_{11}$ is the LMG3410 driver, I would need two of these to make a synchronous buck, which is comprised to the right with $U_{12}$ and both $Q_{5}$, a driver without short-circuit/overcurrent protection (PE29102) and the GaN FETs respectively.

Moreover, the circuit I am designing should not surpass 6A, so this driver becomes kind of useless (not totally since it features short-circuit protection) in this situation since it is capable of 100A of drain current.

Thus, is there another way to protect a GaN without the need of this driver and can be at the same way as effective?

Thank you in advance.


texts: Can you explain how the following garden solar light circuit works?

texts: I found the following circuit in a solar garden light. The cut off white and black wires are from the solar panel. What does the 4 pin transistor do?


texts: Is there a kind of relay that consumes power only when switching?

texts:
The relay must stay in its state. When an electrical impulse is sent to it, it should switch its state and should maintain its status.

So I am really curious about it. Is there such a thing for saving lots of power?


texts:
I'm wondering why pull up resistors in text books are told such that they pull up the voltage to \$V_{CC}\$. Here is a diagram:

When the button is open what will be the input voltage to the micro controller? \$V_{CC}\$? No voltage drop at \$R_1\$?


texts: how can I made a 12vdc to 19vdc booster/regulator?

texts:
This is a fairly specific question, but I think the answer could probably be applied to various voltages.

I would like to make a circuit that will take in a 12-14volt source (from a lead acid) that outputs a regulated 19volts at 5+ Amps.  Would this be easy to do myself?  If so, how?

Thank you.


texts: What is the sample rate of my ATmega88's ADC?

texts:
The sample rate of the ADC of ATmega88 is 15 ksps at 10 bits. If I'm using only 8 bits then what will be the sample rate?
Would it be the same sample rate or it will change from 15 ksps? Will it increase or decrease?


texts: Why is my ESD wriststrap failing with nitrile gloves on?

texts: I have recently ordered some nitrile gloves for the cleanroom of which I am lab manager.  I noticed that when I wear the gloves and test the ESD wrist straps, they are all failing.   Can someone please explain?  I didn't think the gloves would interfere with the wrist straps.


texts: Driving pinball flipper with N-Channel MOSFET

texts:
I am trying to drive a pinball flipper using the circuit below, but after switching the flipper on a few times the MOSFET failed (short to ground) and the voltage level shifter appears to have been damaged (3 to 3.3V on the output pin rather than the expected 5v).

Any help in determining the cause of failure and suggestions for safeguards to prevent flippers being stuck on in the event of a failure would be appreciated.

My values are:

VDD1 = 50 Volts
L1 = flipper solenoid (~2.2 Ohm during initial kick, then 78 Ohm hold resistance)
D1 = 1N4004-T
Q1 is a IRL540NPBF 100V 36A N-Channel MOSFET
U1.1 is a buffer from a 74AHCT125 level shifter, where VCC is 5V.


texts: Ways of making an astable without a 555?

texts:
Similar, but is using a 555 differently, as opposed to not using one at all.
So, for a circuit I am in the process of building, I need an astable, and am attempting to avoid using a 555, partly because of the amount of noise it introduces and partly because I am trying to learn of other ways of doing it.
A quick google returned different uses of a 555 (and the link above is using a 555 to make a sine wave). On the assumption there are other ways of making a 555, what are they, and what are the major pros/cons?


texts: Why does the inner conductor of a coax contribute to magnetic field outside the hollow conductor?

texts:
While studying the coaxial cable, i noticed that the magnetic field of the inner conductor can pass through the hollow conductor (can be calculated in the region 3). However, the boundary condition of the magnetic field at the surface (between dielectric and perfect conductor) of a perfect conductor is known as the tangential component of H (Ht = Js surface current density) and the normal component is Hn = 0. Inside the perfect conductor, we have Ht = 0 and Hn = 0.

So why do we superpose the magnetic field of the inner conductor and the hollow conductor when calculating the magnetic field in the region 3 ?

In this case we suppose that the current flowing in the inner conductor is i1 and in the hollow conductor is i2 (not like the coax,here i2 is not equal to -i1).

Thank you in advance.


texts: Interfacing microcontroller and mains via a relay

texts: I am thinking of starting a project where I will need to interface a microcontroller output and mains for a lighting system. My question is about relays. I have found this one. And I am wondering will it be ok to put 230v through the switch of the relay? Also what am I looking for in the data sheet to tell me what is the maximum voltage that the switch will take?


texts: Find the equivalent resistance of the circuit of 3 terminal voltage source

texts: I am confused by this question. Do we have 3 terminal voltage sources? How should I redraw this circuit into a simpler circuit?


texts: Limiting the current on a PC power supply

texts:
I want to use a PC power supply on three 12V stepper motors. The problem is that I want to limit the current of the 12V DC output to 3A maximum for each of the three motors. The power supply has 34A maximum current that can fry the motor driver circuit.

Any suggestions? Thanks!


texts: the long wires acts as inductor which shutdown and sometimes damage my microcontroller(IC1), for the AC part ill be implementing an optoiso along with triac and snubber circuit (lemme know if you have a better idea) but the SW1 is the part where i'm stuck, usually in simulation they turn the wire into inductor to add the diode (with resistance or zener) parallel to it but in this case i'm kinda lost of to how to snub that switch in addition ill be adding a low path RC filter as suggested in the answers, thanks in advance


texts: Magnetic equivalent circuit with permanent magnets

texts:
I am fighting to understand how permanent magnets are inserted in magnetic equivalent circuits. In the image below is an example, at the left, the physical representation of an Iron core with a permanent magnet and air gap, at the right, the supposedly magnetic equivalent circuit of a permanent magnet.

Now, when I apply the kirchoff voltage law I know I have to get

H_Fe L_Fe + H_g L_g + H_m L_m = 0

but then why doesn't the magnetic reluctance R_m appear in the voltage law? For me, it would be

H_Fe L_Fe + H_g L_g + H_m L_m + R_m FI = 0

why doesn't the last term appear on the voltage law?

Thank you!


texts: What does the CT suffix stand for in voltage regulator?

texts:
Given a regulator such as the LM7812, what does the CT suffix stand for in a voltage regulator in Fairchild LM7812CT)?

I've googled and went through the related datasheets, but could not find the answer to this.


texts:
I'm trying to understand how someone can ground an RF signal (especially relating to microstrip lines).  I think I'm missing something...  Since the impedance of ground is supposed to be \$0\Omega\$, wouldn't all frequencies reflect off it?  I suppose when they reflect off it, that means that the voltage at that spot has to be \$0\$V, which I guess implies an impedance of \$0\Omega\$.  (\$Z=\frac{V}{I}=\frac{0}{I}=0\Omega\$)  Is this how it works?

Thanks.


texts: Why can't I switch an SSR with another SSR?

texts:
I have a DC SSR (Phoenix Contact 2964270) configured with an input of 0 - 5 VDC. It is trying to trigger a system with a sinking input SSR (Phoenix Contact 2966595).  I have a 10K pull down resistor connected to the output of my SSR.

When I disconnect my cable and I connect the device's A2 input to it's 0V it successfully triggers.

When I measure the voltage with my SSR on I see 24VDC. When my SSR is off it only drops down to 14.3 VDC.

Here is a link to my SSR's spec sheet and the device's SSR spec sheet.

simulate this circuit – Schematic created using CircuitLab

What do I need to do to get this A output closer to 0V to trigger?


texts: Is a single channel oscilloscope enough for most purposes?

texts:
So I have spent the past two days going through various budget oscilloscopes and checking their specs VS price.  Most of the information I have gathered has been from here and I am almost sold on an MSO-19.  The only reason I haven't bought it already is that it's a single channel oscilloscope and before I spend £180 on it, I want to make sure it's going to cover 95% of my electronics needs.  I think my major problem is that I don't know what area of electronics I will be going into in the future and so can't predict exactly what I am going to need.

Currently I work as a software engineer and so am already playing around with PICs, AVRs and MSP430s.  I think, in the short term, I will be looking into making small intelligent robots (not bump and turn stuff you see on most hobbyist sites but something with 'character'). I have been in AI for a number of years and whilst I'm no Marvin Minsky, I do know a thing or two about what makes something seem intelligent.

The other thing I have been looking at is this 32-channel logic analyser (Open Workbench Logic Sniffer) which is only £30 and is a more powerful logic analyser than comes with the MSO-19.  Would it be a better idea just to buy that?

I'm open to other suggestions too but I don't want to spend over £250 in total if I can help it.