texts: Which oscilloscopes can reliably measure losses in an inverter for an AC motor?

texts:
For my next project at my workplace I am looking for an oscilloscope which gives me good support in measuring the losses in one of the half-bridge switches over one commutation period. The last time I did this the measurement results were far off from reality as the scope just added switching and conduction losses where the letter ones were totally wrong due to offset errors of the voltage probe. Furthermore it was not possible to select a certain interval over which the losses should be averaged. In short, I am looking for something that can:

Distinguish between switching and conduction losses
Calculate conduction losses based on an Rdson I enter (or even reliably calculate it)
Average losses in a specially defined interval
Make calculations based on all acquired samples within the interval, not just of those printed on the screen

I addition I hope to be able to calculate the junction temperature of the switches my measuring the forward voltage drop of the body diode at certain current values.

The commutation frequency of my signal is between 50 - 150 Hz, PWM frequency is 10kHz, voltage rise and fall times < 100ns. Off voltage on the switch is 30V, on voltage <100mV.

At the moment I am considering either a LeCroy HDO4000 or a Keysight 4000 S-Series oscilloscope with the additional power measurement software. If the software works the way I hope, this will save me a lot of time during development. The manuals of these packages however only show measurements performed on DC-DC converters, nothing on DC-AC converters.

Does anyone of you have experiences with these tools or other recommendations?


texts: Automatic high torque swinger from a motor or a spare CD drive

texts:
An idea that comes to my mind to swing a baby swing automatically is using a CD drive eject - close function , I have several such drives I dont use and I dont want to use a computer to  do the periodic control eject \ close. Can I attach an auxiliary circuit which just helps in periodic open-close motion of the CD drive. Also, are there any other ways to make the swing automatic , what I need is just a backforth motion to couple it with the swing?
The major requirement is high torque high amplitude swinging which the modern fisherprice swings lack and babies love.
weight : should withstand 1 to 12 Kg babies
Could be used with any normal swing to convert it to auto swinging with all safety aspects fulfilled.
Here is the typical swing:

Note: Some babies wont just sleep unless they are swinged continuously hence the question.
Note : CD room requirement is no longer valid.


texts: op amp single supply with nonlinear gain below 1 and start offset

texts:
Is it possible to create a circuit with an op amp (single supply) that have a nonlinear gain (below 1) slope and a start offset?

See image
Green = input
Red = output


texts: Designing power supply with 5v and 3.3v from a 12v supply with switching regulators

texts:
I have 12V DC coming in from a power brick and I need to supply 5V @ 1A for USB and 3.3V @ 5A max for mSata and PCIe.  I basically need to make a small atx power supply that I can integrate on my custom board and I don't need every supply that comes with a full ATX, just 3.3V, 5V, and 12V.  I would like to avoid using a linear regulator because of heat.  I also need the chips to be large enough that I can prototype a circuit on a breadboard.  I like the TO-220 package size that most of the linear regulators use.  What regulator family should I be looking into?  I have looked at a few different types but I was overwhelmed by all of the choices.

I designed a power supply using the TI power architect tool which used some very small chips and I had a board made based on that.  When it came time to assemble (chip I do by hand), the chips are very tiny and it is impossible to debug.  Needless to say, the board does not  work.  I have tried reworking it a few times, but no luck.  The chips I used were:
http://www.ti.com/product/tps40305
http://www.ti.com/product/tps40304

I'd like to start all over and make a proper working prototype on the bench before making another board.


texts: How same frequency signal with different power are produced?

texts:
My router have settings to configure transmission power and as i know energy of a signal is given by
$$
E = h\nu
$$
where

\$E\$ is the energy of the signal,
\$h\$ is Planck's constant,
\$\nu\$ is the frequency of the signal.

My question is how transmission power can be changed since energy of signal is constant?


texts:
I am sure there is an obvious answer to this question, so I apologise in advance.
I ordered some matrix board, but what arrived has no solder pads. Every matrix board I have used has the solder pads, and so I am not sure what to do. The board has the holes, just no pads... Is this board for a different purpose?, or is there a way to solder circuit components to this board?


texts:
Shown below is the PCB of a panel controlling an electric scooter. I accidentally managed to pull out all the wires so they looked as in picture 1.
I wrote to the company who advised me to solder it as shown in picture 2 . But after a few tries, one of which led to some smoke and burning I am now left with picture 3

As you can see, I managed to pull out a solder pad altogether (which led to the blue wire). On reading some other posts around this, I asked the company if the connection was used at all or was just a dummy. But any advice on what I could do to salvage this? The other side of the circuit is the LED panel itself and I haven't so I don't have a way to get to the other side of the pad. It seems wasteful to me to throwaway the entire scooter just because a few wires were loose but on the other hand I'm not very good at this and with the experience where there was smoke, I'm a bit scared as well since the scooter is used by my son. It all connects down to a 4000mAh, 25V lithium ion battery.
Edit 15th March, 2021 - The company responded saying that the blue wire has no role and is a dummy. Would it be enough then to just solder the other 5 wires back into place?
I'm wondering also what could have caused the smoke and burning and what might I have done wrong which I avoid in the next try?


texts:
I am planning to make a dew heater for a camera lens to get rid of condensation, using resistors wired in parallel, then distributing them around the circumference of the lens. Diameter of lens: 65mm
Total power output: 6W
Power Supply(powerbank): 5V, 2A, 20Ah
Resistance for each resistor: 120 Ohm
Resistor power rating: 0.25W
Power output for each resistor: 0.21W
Number of resistor required: 29
I Will probably insulate the wire with tape, and wrap the resistors in cloth around the lens.
Is 6W too much or sufficient for this use? Any suggestions? Thanks.


texts:
I am thinking of making a capacitor, just for fun/for studying purposes. And I thought of the following exercise.

In my local store, there exists rolls of polyethylene food film and aluminium foil. Theoretically, I can take a couple of both, and put them in a "sandwitch" manner, while shift layers to the left/right (to make poles for current collection). Then just roll. Okay, english is not my native, so I draw an illustration:

What I want to know - is how to estimate resulting capacitor parameters?

Given:

roll length L
layer width w
aluminum thickness a
plastic thickness p
bobbin diameter b

I want to know:

breakdown voltage V = ?
capacitance C = ?
short circuit current I = ? (at full charge, edges are instantly shorted with zero-resistance ideal superconductor)

Also, consider everything ideal:

no air gaps between layers
ideal winding, no tensions/etc
normal conditions density, materials are non-compressable.

PS. This is theoretocal question, for sake of study and understanding relationship between parameters. If you have spare weekend evening. Many years ago I havent learned it at school (neither at institution). So today it would be good if I could learn something from it. Thanks.


texts: Must exposed pad (EP) for thermal dissipation be connected to ground for testing on breadboard

texts:
I am testing a MCP8063, 8-lead 4 mm x 4 mm DFN package with exposed pad.

I have it deadbug to fit onto a breadboard. I have yet to get it to run a motor. Must the EP be grounded in order to test the IC chip and if so, how much surface area of the pad must be grounded to be sufficient? Also, as inferred, this particular chip is not mounted on its own pcb for testing, hence EP not grounded, how should I go about grounding the EP as it is now just hovering over the breadboard?


texts: What are some good older devices that I can scrounge i2c or spi modules from?

texts:
I am a newcomer to electronics design and I'd really like to start fiddling with making my own circuits.  I have a raspberry pi which has both I2C and SPI interfaces, and I'm wondering if there's any classes of older equipment that might have these sorts of chips?

I don't have the equipment to desolder or handle surface-mount components properly, so anything I'm trying to take chips from would need to be through-hole.

I have many older computer systems laying around, I'm assuming that due to the prevalence of SMBus that there's likely some of those chips on a motherboard that could be salvaged.

Are there any better places to look for I2C or SPI chips?


texts: Transistor level design of flip flops - Is the complementary clock necessary?

texts:
Below is one of many different ways to design a Master Slave D Flip Flop.

simulate this circuit – Schematic created using CircuitLab

Of course a lot of details are glossed over, transistor sizings are not mentioned etc.

One thing that is striking in this design is the need for complementary clocks.  These are often generated locally with yet another invertor.

My question is this: are there FF designs that only use one clock? And what would they look like, and what would their short-comings/advantages be?


texts:
Can anyone give me any suggestions for some good gated voltage integrators that aren't continuous, and more like a boxcar integrator?   I want to integrate the the total voltage across a pulse coming out of a PMT in around a 10ns interval, and sample that interval once at the end.

I think, perhaps, something like this: http://www.thinksrs.com/products/sr250.html but can't seem to easily find IC chips for that purpose-- could I get some pointers please? Many thanks!

EDIT: thanks for the comments, I'll have a periodic source to know when to reset after 10ns.


texts: This used to work before I installed Quartus v10 to ensure backward-compatibility. Now I get no hardware found in Quartus both v13 and v10. The USB-Blaster used to show up, then I installed Quartus v10 to support old .ptr files and now the JTAG connection with the DE2 board is broken. Why? Is it because I installed Quartus v10? Then that is not logical. What is the explanation and what should be done?


texts:
I've got a big 560 uF, 400 V capacitor and I've tested it with a meter and the capacitance is within spec, same the ESR and it has a vloss of 0.8%. So all seems fine but then I came across this video geizer test'in. In his case there were obvious signs of capacitor damage so it was easy to see what was wrong even though the meter said it was fine.

He did the same and appeared to have a good capacitor capacitance and the ESR was good but when he connected up to a power supply as he cranked up to voltage the more it leaked.

So what tests should be performed?

And given that I do not have a power supply that will go up to 50 V how can I test the leakage at higher voltages or do some test in substitution?


texts:
I am trying to control a MCP4131 digital pot from my Raspberry Pi using this
library.

Using the GPIO pins, I am "emulating" an SPI interface. I bring the ChipSelect pin to low, write my byte, then bring it high again.

When I plug my meter into the wiper, I get a constant voltage. It's not changing. Is there something wrong with my code in POT.cs?

class Program {
    static void Main(string[] args) {

        GPIOMem cs = new GPIOMem(GPIOPins.GPIO_17);
        GPIOMem clock = new GPIOMem(GPIOPins.GPIO_23);
        GPIOMem sdisdo = new GPIOMem(GPIOPins.GPIO_22);

        var pot = new POT(clock, sdisdo, cs);

        while (true) {
            for (uint level = 0; level <= 127; level++) {
                pot.SetValue(level);
                Thread.Sleep(100);
            }

            for (uint level = 127; level >= 0; level--) {
                pot.SetValue(level);
                Thread.Sleep(100);
            }
        }
    }
}

Pot.cs

public class POT {
    private GPIO clockpin;
    private GPIO mosipin;
    private GPIO cspin;

  public POT(GPIO SPICLK, GPIO SPIMOSI, GPIO SPICS) {
        clockpin = SPICLK;
        mosipin = SPIMOSI;
        cspin = SPICS;
    }

    public void SetValue(uint value) {
        Console.WriteLine("here");
        cspin.Write(true);

        clockpin.Write(false); // #start clock low
        cspin.Write(false); // #bring CS low

        BitArray b = new BitArray(BitConverter.GetBytes(value));
        Console.WriteLine(value);
        for (int i = 8; i > 0; i--) {
            mosipin.Write(b[i]);
            clockpin.Write(true); //cycle the clock
            clockpin.Write(false); //yucle the clock
        }
        cspin.Write(true);
    }
}

Please note: all the 3 GPIO pins are working as they should.


texts:
I own a Revo Blik radio that has developed a flaw: the display doesn't completely light up anymore when activating the device. When you're close by you can make out what it says, but not from a regular distance. It sometimes flickers to full brightness a few times before failing.

I opened it up and there is a white led mounted on the side of the display, I suppose serving as its backlight. Since opening it up, it flickers constantly when the device is in operation.

I'm not really sure how to proceed from here to diagnose the problem. As a physicist and programmer, I think I have the necessary background to understand and fix the problem (if possible), but I have little experience with working with the hardware itself and specifically don't have any substantiated hypotheses as to what could cause this behavior, other than a hunch may is simply be a faulty contact along the power path to the LED, like in a buzzing lightswitch. Is that possible or doesn't that happens with these low voltages?

Does anyone have an idea what the problem may be and how I may proceed from here to fix this problem?

Edit:
As requested, I added some photos. They can be seen here (if you hover over the photos, there are some descriptions of what you see, but they are not all complete; if you click on a photo, they become somewhat larger and display the full comment). The led itself is hidden under some adhesive tape that I'm not sure I should remove: I think it fixes something underneath in place, although the entire display seems to be stuck to the board pretty solidly.

@AndrejaKo: immediately after booting, the led emits at full strength for ~ one second. After that, the flickering starts. I don't have the means to identify a specific (average) frequency, but it's easily visible by the eye. I would say it's between 5 and 20 Hz: the intervals are irregular. Certainly not so slow I could count the flickers and certainly not so fast that I have a hard time seeing it is flickering.

@Oli Glaser: I've tried tapping the board and touching/pressing various components, but that didn't change anything. I'll try to get my hands on on a hairdryer and something to cool the device. I failed to identify a specific IC as the one that drives the led. I need to disassemble the device further to follow the lines.

@Majenko and JustJeff: if it's a dry joint, applying some pressure to the right component should result in the flickering stopping, right? That would be just like the buzzing lightswitch?


texts:
In a digital circuit like a cell phone. If a switching ic has it’s reference point as PGND, separate from the main GND (4v Main vcc coming from battery), but they’re tied together, then

What exactly makes them separate from one another?
Why have two references?
What would happen if the switching ic’s PGND were to be jumpered to the main vcc GND?


texts:
So based on the responses from this thread:
Ethernet Interface PCB layout requirement (if any)  I made an Ethernet interface layout the best I possibly could using 2 layers.

The circuit is of the following:

*the ethernet jack I am using has a different pin out than the one shown in this schematic so pay no attention to that.

I have separated the ground layers of the signal traces from the rest of the circuit. Also I have added an additional ferrite bead connecting the signal grounds to AGND. My thinking was that this would further isolate the signal traces and since they are differential there should not be any DC current to AGND anyway.

How is this layout scheme? Is it satisfactory? Is the ferrite bead to AGND a good or bad idea?


texts: What is the maximum negative output voltage of an emitter follower with a split +10v/-10v supply?

texts:
I'm perplexed by a passage in Horowitz and Hill's "Art of Electronics" (1st ed., p. 54).  They present the reader with a simple emitter follower circuit.  The input voltage is a 10v amplitude sine-wave.  The transistor itself is fed +10v directly to the collector.  There is a 1k resistor on the emitter, which is supplied with -10v.  According to the authors, the sine wave input will be preserved at the output.  The positive peak will look just like the input at almost full amplitude but the negative peak will clip at -4.4v.  I can't for the life of me figure out where they got -4.4v.  If the power supply is split +10/-10v, wouldn't the output clip at -10v, not -4.4v like the text says?

I tested the circuit on EveryCircuit and the output clipped as expected at -10v.  Here is the circuit I built to try to figure this out for any EveryCircuit users.
http://everycircuit.com/circuit/6493906064375808
I'm a novice here, and having an impossible time figuring out if I've simply misunderstood something or it's a misprint.


texts: I am using a P Mosfet in the schematic, pin 1, 2, 5, 6 are all connected together. How is this done in altium?


texts: How is power demand variation of supercomputers handled at power plants

texts: When a supercomputer is given work and all processors begin work there would be a large spike in demand.  Do large supercomputers communicate with power stations to notify them of demand changes from changing workloads?


texts: Beaglebone Black PWM Driver for 12VDC 1.05A Motor | Drive from Positive Side

texts:
I have several 12VDC 1.05A pumps I am using in my hombrew system which I would like to drive via PWM on my BBB. Each one will have a hall effect flowmeter attached so that I can get flowrates, totals, and drive the pump to maintian a flowrate. I have seen how to control the motor using a mosfet (on the bldr website), but it drives from the negative side of the motor. Is there a way to control the motor from the positive side? The reason I ask is that I would like to use a common ground for the pump and flowmeter, and if I am driving the pump from ground, it will throw off the flowmeter readings.

Any thoughts?


texts: Calculating resistance of series/parallel circuit

texts:
If I have a configuration of 5 resistors as follows:

simulate this circuit – Schematic created using CircuitLab

How can I calculate the expected total resistance between A and B, given only values for R1-R5?

edit: okay, here's what I've tried so far.

I intended to find the expected voltage drops across each resistor, and from there I knew I could easily find the total resistance of the circuit.

First, I observed three loops in the diagram: R1,R3,R4; R3,R5,R2; and R1,R2,R5,R4.  I remember from  my old electronics class that the voltage drop around each loop in a circuit should always equal zero, as follows:
$$
v1+v2-v4-v5=0\\
v1+v3-v4=0\\
v3+v5-v2=0
$$
(Assuming that current is flowing from A to B, I further assume that it is flowing down through r3.  If this is wrong, then the value for v3 would just have the opposite sign, and all would be well).

The sum of currents flowing into a point should equal the current flowing out, so I have these equations as well:
$$
\frac{v1}{r1}=\frac{v2}{r2}+\frac{v3}{r3}\\
\frac{v5}{r5}=\frac{v3}{r3}+\frac{v4}{r4}\\
\frac{v1}{r1}+\frac{v4}{r4}=\frac{v2}{r2}+\frac{v5}{r5}
$$

So now I have  6 equations in 5 unknowns... and if these equations are correct,  then there should be one redundant equation.  However, plugging them into a cas such as maple cannot find any unique values for v1-v5 in this system (an infinite number, in fact), suggesting that there are at least 2 redundant equations above.

Does this mean that there is no unique resistance for this circuit fragment, or what have I done wrong?


texts: Wireless Electricity Transmission model not working. Why?

texts:
I made wireless electricity transmission model using the principle of magnetic inductive coupling to transfer electricity between two separate coils. The model is very simple, known to everyone and lot of resourses available in internet.
My circuits are as bellow...

I am using BC547 transistor. The transmitter coil have 12 + 12 turns and receiver have 24 turns. Initially I started with DC 3.3v supply, 1.2k ohms resistor for base. Only one thing that i have no idea what is the awg of the magnet wire! I collected the wire from a small on board transformer from smps. I am using solder less breadboard.

But nothing happens. No electricity transmits ! I checked all the circuit diagrams. Tested continuity with multi meter. Everything was fine. I also tested the transistor and also changed with another piece. But nothing works.
So then i switched the base resistor to 220 ohms through 100k many values but no result.
Then I increased the supply to DC 5V and tried with many resistors. But still no result. Now the transistor started to get some hot.

Then I switched to 12 V DC. Now I can see a very little flash in led (brightness not more than 5 percent) for only about one tenth of a second. But this time the transistor becoming very much hot withing 3 seconds. So I disconnects switch immediately.

So where is the fault? I have found in internet this is working fine for others. Can anyone tell where is the problem? Please don't ask me to use other transistor, BC 547 working fine for others. So try to find the fault.
Thnx in advance.


texts: Fujitsu offers ferroelectric RAM modules, including in "RFID LSI" format. I have no idea what those are, and the engrish documentation doesn't help at all.


texts: Distribution-side voltage regulation and Low voltage ride through (LVTR) curve

texts:
Nowadays, I see that photovoltaic systems have Low-voltage-ride-through capabilities. So in case of a fault, when the voltage is decreased, they remain connected to the grid and provide reactive power in order to support the voltage. In order to do so, they decrease the active power that they inject.

Low voltage distribution grids are mostly resistive. So, voltage regulation is more effective by injecting active power rather than reactive (R/X >1) So, why we inject reactive power?


texts: Why are registers being turned on to 1 before reset/on button is hit on FPGA?

texts:
I am writing a really simple program on Verilog for my FPGA to have an LED blink once a button is pushed. Here is the code I have written:

module hello_world(
   input ron,           //reset button (ron = reset/on)
   input clk,           //clk, on board clk is 25 MHz
   output reg led1,     //led to blink
   output reg start);   //problematic signal

reg [22:0] led;
always @(posedge clk) begin
    if(!ron) begin
        led <= 0;
        start <= 1;
    end

    if(start) begin
        led <= led + 23'b00000000000000000000001;
        led1 <= led[22];
    end
end

endmodule

I know there are probably cleaner ways of doing this, but I'm just doing this way, and there is a really weird problem that is occurring. The 'start' register is being set to 1 before I even hit the 'ron' button (reset/on button) and I have no clue why. This problem is happening with any register that I assign 1 to in the if statement.

I tried simulating it in ModelSim, and it seems to run fine, but on the FPGA board (Polmaddie7) it assigns start to 1 before the button is hit.

I would appreciate any help on this please. If I have left any information out that would be helpful to understanding/answering this, please let me know.


texts: Adding Transistor to Maintain Voltage Across Proprietary Switch

texts:
So, I purchased a camera trigger that moves the camera and then triggers the shutter. I wanted to change when the camera shutter was triggered so I purchased a cheap eBay delay timer relay. I knew the camera trigger was basically a switch, so I intended to use it to trigger the delay timer, and then have the relay switch the camera shutter signal on the other end. The camera side is working as intended, but I am having issue with the trigger side.

It appears that the camera switch is not just an on/off switch, but resists a portion of the electricity normally open, but is fully switched normally closed. The trigger signal output is 4.5v, with the switch NO (measuring from trigger to ground) I show about 0.5v, and NC I should 0 volts.

EDIT: I have since measured the resistance as 460ohm NO, 100ohm NC; I have updated the schematics to represent this

Unfortunately, this change is not enough to actually trigger the timer. Using a different camera trigger I was showing 1.5v NO, but that still was not enough to trigger the timer. When grounding the trigger directly the timer would trigger. So, what I gather from this is that the timer needs a greater change than the 0.5v or 1.2v to ground that my camera triggers are putting out.

My idea was to add a transistor to switch the trigger signal to ground, using the camera switch as the base and pulling power for this operation directly from my 5.3v source.

I have never used a transistor before, so I do not know if this would actually achieve my intended desire, nor what sort of transistor I would need to purchase. I would also like to limit the current from my battery going through the switch as it's just a trigger signal, but I am unsure of how to do that.

I have attached 2 schematics to show where I am currently and what I was intending. My experience in this field is rather limited, so please let me know if there are any glaring issues with the schematics (besides my disconnected relay).


texts:
I had tried to make a simple homemade DC motor using 8V DC, Cu coil and a permanent magnet. But it doesn't rotate. Here are the things I did:

I made a coil with 6-7 turns using Copper wire.
Support is given to coil,through which I had given the supply.
And, a permanent magnet is placed under the coil.

The result is that, it is not rotating.
What should I do?

Here is the picture:


texts:
Relays have output different ratings on their case.

Just For eg..output DC 100v 25 amp, 60 volt  45 amps.

Now, I would like to output 25 to 30 amps under 12v voltage DC supply.  Since the rating  (voltage and power)) is within the specified above intervals, any harm in supplying the relay with 12v DC to output 30 amps.

Thanks.


texts: Do I have match impedance while routing PAL video tracks?

texts: I am designing a PCB with PAL video output. PCB contains 50ohm and 100 ohm traces. The connection between RF coax connector is very close. So 75 ohm traces are 80 micron for my stack-up. I am confused whether to route them so thin track or not. Signal bandwith is 15MHz. Any suggestions?


texts:
I've just finished reading Charles Petzold's book, Code: The Hidden Language of Computer Hardware and Software. In it Charles explains building relays into gates, gates into logic components, and logic components into computing machines.

He talks about the book TTL Data Book for Design Engineers which first came out in 1973. (I'm assuming people had lists of TTL gate chips prior to this). This talks a lot about the Texas Instruments 7400 series of logic gate chips.

Now to me it seems you could combine TTL chips (or relays or transistors) into a CPU using the instructions in this book. But everything online says "use FPGAs instead! It's easier for that scale! [Unless you're getting the concepts and want to see the end to end view]". Fair enough - some pragmatism is good - it depends on what the outcome is.

When you look at the structure of an FGPA - it appears to only have slightly more complexity than a 4-bit adder.

Now I don't know when the first four-bit adder was invented. (My guess is it came out of Claude Shannon's work on boolean logic in 1948).

Now we know that the first FPGAs in chips went on sale in 1984. But people but have been building them out of TTL, transistors and vacuum tubes before that.

So somewhere between 1948 and 1984 someone must have thought of the idea of FPGAs.

My question is: When was the concept of the FPGA invented?


texts:
I'm trying to build a Christmas light show, using a netduino (arduino clone). There are plenty of tutorials on the web, however they always lends themselves to US power supplies. Could someone please recommend to me the best way to switch a 10A 240V power suppy (x8 for different lights) via the 5v arduino supply? I can't cut into the lights themselves, so I would be switching an extension cable, hence the high amperage. I have found suitable relays online however they are rated at a 12v switching supply.

Thanks!!


texts: How can I direct an RFID reader to only read in a specific direction?

texts:
I'm trying to control the reading direction of an RFID reader, to only read in a specific direction.

I made a drawing to exemplify my question.

In the image you can see the setup I want to have. The difference between the two, is that image to limit the reading area of the RFID. The question is how this would be possible to do?

Any input to my question is welcome, since I'm not experienced with RFID technology.

The solution I want to achieve, is the one in image 2, where I limit the reader to not include nearby tags.


texts: Dual Coil Latching Relay with LEDs - Opposite LED Triggers on Trailing Edge

texts:
This is my first time using dual-coil latching relays (Kemet EC2-5TNU), and I'm running into some strangeness when breadboarding out the below circuit:

The coils switch without issue when sending a pulse to either transistor, and the LEDs simultaneously pulse without issue as well. The thing I'm seeing is when I release the voltage driving the base of either transistor...this causes the opposing LED to do a brief and dim pulse. As an example, I'll pulse the SET coil...on the trailing edge of that pulse, instantly the RESET LED will pulse dimly. And vice-versa.

I know this is probably very 101, but I just can't seem to find an explanation in my searches. I have flyback diodes in place as you can see. Is it possible (using the example above) that when the SET coil's magnetic field collapses on the trailing edge of my trigger, it's inducing something in the opposite coil somehow, such that the opposite LED is getting forward-biased for a moment? Yeah, I'm spit-balling here obviously.

I did find an extensive Omron app note that recommended putting an extra diode in series with the Set or Reset coil when doing certain configurations (Page 23 here). Those configurations didn't seem to apply, but I figured I'd at least try...and lo and behold, it did indeed fix the issue. But I'm curious as to the why? Here's the updated schematic for that:

I'm scratching my head, since besides the shared VCC and ground, they're independent circuits...right? Wondering if somebody might be willing to give me a hint as to what is happening here. Is it really necessary that I have those extra diodes to use a latching relay like this, or are they just a band-aid for something I'm overlooking here? Thanks for any input!

Edit 1:
After Jasen’s comments I decided to open up one of my latching relays to get a visual on it. For the record I had a whiskey and made a burnt offering to the relay gods first. Picture should be attached if anybody is curious.

Edit 2:
OK, so I scoped it with my original circuit above (without those extra 2 diodes D3 and D4)...I put the probe at the Collector of Q1, which is part of the Reset circuit...then I pulsed Q2 to trigger the Set coil. On the trailing edge of that pulse, the scope shows a dip of about -4V from the Reset coil before coming back:

So I'm thinking the presence of this momentary negative voltage is forward-biasing the LED. And the reason the Reset LED no longer pulses with D3 in the circuit is because during that negative voltage, D3 is reverse-biased...thus the LED never sees the negative voltage and stays in its inactive state. Does that make sense?


texts: Designing an LC output filter for a DC-DC Boost high power system (2 MW)

texts:
I am currently designing a dc-dc boost high power system. The input voltage is boosted from 1 kV to  1.2 kV. The rated power is 2 MW and the switching frequency is 2 kHz. Due to the boost concept of operation, the output current shows strong ripples due to the switching mechanism. I have been advised to design a simple output filter to reduce the current ripples and also minimize the voltage ripples.
If I used only C output filter it will have no effect on the current ripple, that is why I am looking for any literature that might help me design an LC output filter, taking into consideration that my system is in the megawatt range.


texts: PWM that can handle rapid on and off cycles?

texts:
I am working on a prototype project with a large electromagnetic solenoid. I want to be able to vary the strength of the solenoid via a PWM (preferred), or constant current.

The issue I’m having is that I want to turn the solenoid on and off rapidly (1-150 Hz). I am currently using a bench power supply at about 1500 W and a large solid-state relay that is triggered by a proximity switch. The bench power supply is operating the solenoid, but it’s hard on the power supply to be turned on and off rapidly. I have tried a PWM controller, but it had a soft start feature which retarded the power to the solenoid.

I need an amplifier or motor controller that can handle rapid and continuous "instant on" and "instant off". The solenoid can handle a maximum of 96 V and 500 A for short periods of time and ultimately I want to run the system from batteries.


texts: Fine-pitch SMD pads on flex PCB using coverlay rather than soldermask

texts:
SMD: "Solder-Mask-Defined"
NSMD: "Non-Solder-Mask-Defined
I am making a thin flex-PCB (0.2-0.3 mm) on which I am going to mount a component which has SMD pads.
I would like to also make the pads on the PCB as SMD rather than NSMD, but I am worried about the production tolerances as well as mounting tolerances of the coverlay usually used on flex-pcbs instead of a liquid solder-mask.
So I am here hoping that someone with more experience working with flex-PCBs and coverlay can tell me whether I can make these pads as SMD using coverlay, or how else I should go about making SMD pads on flex-PCB, or perhaps tell me that it is not possible or inadvisable.
Below are screenshots of the spacing between the pads, the purple pads are the openings in the solder-mask/coverlay and the red pads are the underlying copper pads.
I have done this before on rigid PCBs and I would be comfortable with these dimensions/tolerances if it was not a flex-PCB with coverlay.


texts:
I am having some problems trying to figure out the voltage between node a and b(Vab). The part that is confusing me is where the 4A and 3 Ohms are parallel. How do I know what the current will be going through the 3 Ohm resistor?

Can you just assume it to be the same as its input current(2A)


texts: Why doesn't the LM7805 circuit short circuit?

texts:
I'm new to electronics and have made some simple projects using a LM7805. I'm using the following schematics:

I don't understand why this circuit works. Why doesn't it short circuit? I thought electricity always takes the "easiest" path which in my opinion would be the following:

Why does the electricity even bother going through the 7805 to begin with while it can just fill up the 0.33uf capacitor and then go right through it back to the battery?


texts: Internal constant current driver for LED short circuits and blows when connected to AC main (120 V) without DC load

texts:
I have AC 85-265V to 0.3A 8-12W DC 22-40V Internal constant current power supply for LED spot lights. This is the exact model https://www.lightinthebox.com/en/p/0-3a-8-12w-dc-22-40v-to-ac-85-265v-internal-constant-current-power-supply-driver-for-led-spot-lights_p1875439.html?prm=1.18.104.0
When connected to the AC main (120 V) the driver short circuits by the AC connection  points, resulting in a large spark and destroyed driver.
However, this does not occur if the DC output is wired to a 32 V LED chip, and the driver works fine.
Are internal constant current drivers required to be connected to a load (e.g. LED COB) before the AC current is switched on?
If this is the case, how would I prevent the driver from short-circuiting in the event that the LED chip dies?


texts:
Some batteries last twice as long if they are kept to 80 percent of their maximum charge. It's good to add a small adjustment to undervolt a charger output by 0.5 - 1V. Myself i have a CC/CV charger that is .5 volts too high for a given BMS.

How can I take the voltage down by .5 - 1V at the output?


texts: Detecting device/bulb/socket state without using ACS217

texts:
I am planning to do home automation using Arduino.

It includes a manual switch and can be also controlled by Arduino.

My problem is I want know the status of the bulb/device or socket.  Recently I learned about the ACS217, the problem with ACS is it can measure very large current more than 1 amp.

So I came up with the design below.  Should I go ahead with this or are there better solutions?


texts:
I'm trying to use a Load cell with the INA 125P amplifier with my FRDM KL-43Z board. Currently, I have it connected like so  with the Arduino being replaced with the KL43Z analog input (Port B bit 0), 5V and ground pins.
What I have decided to do is use the ADC module of the KL43Z code (MCU Expresso):

 SIM->SCGC5|= SIM_SCGC5_PORTB_MASK;
    PORTB->PCR[0]=0x000;

    SIM->SCGC6|= SIM_SCGC6_ADC0_MASK;
    ADC0->CFG1=0x40|0x10|0x04|0x00;
    ADC0->SC2 &= ~0x40;
    ADC0->SC1[0]=0b001000;

  volatile static int i = 0 ;
  while(1) {
        i++ ;
        while(!(ADC0->SC1[0]&0x80)){

            }
        result= ADC0->R[0];
       printf("res: %d\n", result);
      ADC0->SC1[0]=0b001000;
    }

The result of the ADC register value fluctuates greatly. Sometimes it will sit at around an average of 64 but will then change values significantly and decrease. Applying a force to the load cell seems to have no effect.

If anyone could provide some tips or shed some light on my situation it would be greatly appreciated as I am new to working with this kind of equipment.

Additionally, what would be the ideal gain resistance. I have tried using a 75 Ohm resistance, (20 kg load cell 1mV/V) but have also seen a video that uses one around 33 Ohms, so I'm not certain what value is ideal. Load cell data sheet is available here.


texts: MOSFET vs Diode Based Peak Detector Circuits

texts:
Are diode based peak detectors inherently superior to MOSFET based peak detectors? The Internet seems to think so, based on the amount of information that is available.

When you search for peak detector circuits, you find a huge amount of information on diode based circuits like this,

but you find very little information on MOSFET based circuits such as this.

I only found one decent MOSFET circuit reference: Analog CMOS peak detect and hold circuits. Part 1. Analysis of the classical configuration.  It calls it the "Classical Configuration", so it seems like it's been around for a while.

In my limited breadboard testing, I've found that with the right op amp and MOSFET, the performance of the MOSFET circuit is far superior.  Perhaps that is the reason, i.e. the potentially non-trivial task of finding the right combination of op amp and MOSFET?  It would seem that finding the right op amp and diodes would be a similar issue for the diode case.

EDIT:

This is an example of a MOSFET based circuit which works well for a repetitive 10 KHz signal.  From the discussion below, it seems that low frequency may be a special case where MOSFETs are potentially better than diodes.  It also seems likely that the repetitive nature of the signal benefits the performance of the circuit.

EDIT:

Just to show the capabilities of a MOSFET based circuit on repetitive waveforms at high frequency ...

A previous question was looking to measure the peak amplitude of a 2 MHz 240mv sine wave.  They were having trouble getting better than 5%-10% accuracy using diodes and op amps.  The circuit below measures a 2 MHz sine wave with ~1% accuracy using a comparator/MOSFET based circuit.  The schematic and LTSpice simulation are shown below.  The average output across the window is 2.7476 vs the actual peak of 2.750.  After removing the a 2.5V common mode, that is 247.6mv measured vs 250mv actual.

EDIT:

I has been pointed out that this not really a Peak Detector in the most common usage of the word, since it only works well on repetitive waveforms.  In that sense it is more of a peak amplitude circuit.

EDIT:

As requested, below is the response of the circuit to white noise.  Specifically, a behavioral source with V=4*white(2meg*time) .  It still seems to work pretty well.  The only real issue is the time that it takes for the output to decay to the lower level when the input amplitude changes, but in many cases that is not a concern.


texts: Using High side current sensor as a low side current sensor

texts:
I have a very small question to ask. Is it ok if a high side current sensor such as the MAX9929 be used as a low-side current sensor as well? Or should I look for some parameter in the datasheet. The reason why I ask this is because this MAX9929 is bi-directional, therefore current can pass in both directions, so that is not an issue. What I am finding confusing is if it is ok to use it as a low side sensor, since how will the IC know if one of its input is pulled to ground ? Won't it only note the voltage across the sense resistor.
(I ask this question since in my circuit, there is some switching which will make the current sensor go from the high side to low side, also I have tested the IC with one of the input pulled to ground, and it worked, but I want to know if it is the right thing to do from a theoretical perspective)
Thanks for the help


texts: Convert an analog audio signal to digital with a PIC and send the data through serial to a PC

texts:
I want to convert an analog audio signal to digital signal and send it to serial input in my computer. How can I do this?

Microcontroller used: PIC18f452


texts: Bias-tee for adding multiple frequencies to a DC line

texts:
Objective - To add multiple frequencies on sine waves onto a \$24V\$ DC Line.

Each frequency block (\$F_1, F_2, ...\$) generates a sine wave of unique frequency within the given range. When the \$n^{th} \$ frequency block \$F_n\$ is switched on, it's frequency must be added to the 24V line regardless of any frequency present along that line.

I have used bias-tee circuit to combine the frequencies. Each yellow block  has a \$100nF\$ coupling capacitor.

Sine wave generation method : Square wave to sine wave converter

Frequency Range : \$8KHz - 24KHz\$

Number of Frequency Blocks \$N\$ : \$10\$

Current\$/\$Frequency Block : \$10mA\$ at \$24V DC\$

L1 Inductor Rating :

Inductance : \$470\mu H \pm 10\%\$
DC Current Rating : \$420mA\$
Self-Resonant Frequency : \$100KHz\$

Coupling Capacitor : \$ 100nF, 50V\$

Issues -

There is a lot of high frequency distortion when detecting the signal over the power-line. (The power-line wire is \$2\$ core, \$1.5mm^2\$, \$25m\$ between each device) How do I resolve this?
The sine waveform (from one block) gets distorted when more than one frequency block is connected. How do I isolate each block but still allowing the signal to flow through?
I have used a buck-converter to convert \$24V - 5V DC\$ within each frequency block. It has huge capacitors in its input. Is that the problem? Will a diode at the input do the trick?
I don't get any sine-waves (added) at the power-line, for more than 2 blocks. Do I need to change the \$L1, C\$ values?
Do I need an end resistor after the \$N\$ blocks, connecting the positive and negative?

If this design could be improved, kindly suggest so.

Thank You.


texts: High pass filter - Cut-off frequency calculation doesn't match simulation

texts:
I have made the following simulation with the circuit you can see below:

I'm asked to find the cut-off frequency for this filter. From the simulation, it looks like it \$f_c = 500 \text{Hz}\$ or somewhere around there.

However, if I use the formula for cut-off frequency I get something totally different.

\$f_c=\frac{R}{2\pi L}=\frac{500 \Omega}{2\pi \cdot 10 \text{mH}}=7960 \text{Hz}\$

Am I using the correct formula, or is my interpretation of the simulation wrong?

I hope someone can help me.


texts: Is it required to use separate pull ups in level shifting using I2C isolatator ADuM1250?

texts:
I have a I2C Master as a MCU operating on 3.3VDC.

And a slave MCU operating at 5VDC.

I want to communicate between these two devices using I2C.

For level shifting 3.3V to/from 5V purpose I am using a I2C isolator ic ADuM1250.

At master side, 4.7kohm pull ups are used for communicating with other slaves at 3.3V.

Is it required to connect the pull up resistors at isolator second side i.e. 5V side?

If yes then what should be its value?


texts: Running an LDO (AMS1117) at maximum voltage

texts:
I'm wondering about running an LDO regulator, the AMS1117 specifically, at its maximum rated voltage.  The datasheet says 15V.  I've got a project where I truly need 15V.  I want this project to be plugged into the wall with a regular plug, not with a wall-wart or USB, so I'm going to add a Meanwell AC-DC converter with 15V output to the inside of the project.  The project has a little uController board with an AMS1117, 15V max.  Ideally I'd like to just use the 15V to get 3V3 in my project using that board, very low current requirements for the 3V3.  But in everyone's experience, is that maximum on ICs an actual real-world number, or is it only in an ideal lab setup with perfect airflow and controlled at 25C with perfect humidity, etc, etc.

Thanks.


texts: How to calculate opamp input noise for DC input?

texts:
I'm trying to design a circuit with an operational amplifier (OPA625). The input signal is amplified and sent to an ADC. In order to estimate the input noise, I'm using the following equation from an Analog Devices tutorial:

$$
v_{n,\text{rms}} (F_L, F_C) =
v_{\text{nw}} \cdot
\sqrt{F_C} \cdot
\sqrt{\displaystyle\int_{F_L}^{F_C} \frac{1}{f} \mathrm{d} f}
$$

$$
v_{n,\text{rms}} (F_L, F_C) =
v_{\text{nw}} \cdot
\sqrt{F_C \ln{\dfrac{F_C}{F_L}}}
$$

\$v_{\text{n,rms}}\$ — input noise RMS

\$F_L, F_H\$ — frequency bandwidth

\$v_{\text{nw}}\$ — voltage noise density in the white noise area

It's quite easy to calculate the noise for the specified bandwidth. But what happens when \$F_L\$ is close to 0? In the Analog Devices' tutorial I mentioned earlier, \$0.1\text{ Hz}\$ is used as a lower frequency limit, but how close it should be to 0? How do I estimate the noise for DC input?


texts: Calculating necessary transistor for LED switching

texts:
I have only just started to play with electronics (literally less than a week ago) and have purchased myself some cheap Arduino Nano clones, as well as some LEDs, resistors (only 10 ohms at the moment, but more varieties are coming), a breadboard and some jumper cables.

The reason I've got into this is that I also make scale models and want to light them up with LEDs and fibre optics. I may play with Bluetooth connectivity etc as a later date, but first, my issue with multiple LEDs and their power requirements.

Please excuse and correct me if any of this is wrong, its all based on my current (and probably incorrect) understanding at this point...

The Arduino Nano has 15 digital I/O pins and 6 of them use PWM. These pins output 5 V at a maximum of 40 mA (20 mA is recommended).

I want to run 4 LEDs from one of these pins. The LEDs I have are 3.3 V and 20 mA.

This means that I'll either not be able to light them (9.9 V / 20 mA if I run the LED's in series) or I'll damage the Arduino if I run them in parallel (3.3 V at 60 mA).

I came across a video (Here's the link) that discussed this issue, and suggested the use of a transistor to get around it, and the video makes sense, but it never mentioned how to make sure I get the correct transistor for my project.

Is there a simple way to calculate which transistor I want/need? For instance in my case, I have 4 LEDs, each one needs 3.3 V and 20 mA. What should I look for in a transistor to handle this, and how do I calculate it for myself?


texts: Advice about microsd current consumption

texts:
I'm designing circuit with STM32L0 MCU that storage some data in microSD via SPI interface.

I have power budget of 5V @ 500mA via VBUS so, I would like to estimate microsd's current consumption.

I have seen two posts(1, 2) about microSD current consumption.
to sum it up, the answers in both posts says that current consumption is variant and vendor specific. it differents from microsd to another.

could you please suggest me what to do about it?
How should I design the circuit with a variant gap of current consumption?

For example, limit the microsd's current consumption to 150mA and put current limiting IC at microsd's VDD pin?

EDIT:
my circuit also contains 8ohm 0.2W speaker that power from 3.3V power rail. speaker's current consumption is about 160mA. only the speaker and the microSD alone current consumption is about ~300mA.
the application should record data on demand from UART and write it to micro sd card in real-time. every 2sec the system should write data, 16Kbytes, to micro sd card. meanwhile, the application should play a couple of sounds in different frequencies. my concern is to exceed VBUS current consumption (500mA) while the speaker and the microSD are on


texts: How does the substrate voltage change the state of the MOSFET?

texts:
I understand some formulas for determining whether a NMOS transistor is activeis VGS > Vth and if its in saturation you take the drain-to-source voltage VDS => VGS - Vth

But how does the substrate voltage play a part in determining this behavior? For example the image below

If I were to change the substrate voltage from 0 to 5V. Could I turn ON/OFF the transistor and affect the region of operation?


texts:
See photo of PCB and SMB with marking EGE.
I cannot find any info on what the component is.  Any ideas or thoughts?
It appears to be on the 240V output from the relay which runs to a 15W halogen globe.   Both those EGE appear to be parallel from multimeter testing.


texts:
Electronic projects that aren't in a box are fragile.  I have a project completing soon that has a reasonably complex control layout.  It's going to need some manner of control panel that includes plenty of writing and has different sections.

I can think of a few options:

Get a panel engraved
Print the panel on a color printer and laminate it.

Option #1 is the most professional but can be expensive.  Therefor I am exploring option #2. Once the project works, perhaps dropped the cash on option #1 will be a consideration.

I'm wondering what software other board members use for this sort of thing.  I've used a nice drafting package called Draft IT from CADlogic to draw the panel.  Now I realize I need to color it.  I don't think the free version (or any version, for that matter) of the software supports color.  This means if I produce a PNG file using DraftIT, color it with some other software, and then need to make a change to the original drawing, I'll have to redo all my work.

Here's the latest cut of the control panel.  It isn't quite ready - I haven't marked where holes need to be drilled.  I'm working to ensure the control layout is ergonomic and that the controls actually fit.  Like icebergs, many controls are bigger underneath...

So we see a lot of text in the upper left.  It's a table that defines the behavior of the rotary switches represented by the large circles at the bottom.  The seven smaller circles represent 10mm LEDs.  The three small rectangles represent toggle switches. The remaining medium sized circle is a speed control knob. Overall dimensions are 10" x 5.25".

So as you see, I have a lot going on here.  I need the text to be readable; I would like the main power switch denoted by a read box. I'd like the column of LEDs and the toggle beneath also within a colored box as they are related.

How can I make this into reality, people?


texts:
I have found optocoupler 220V to microcontroller circuit design like on photo:
optocoupler 220V to MCU

I wanted to use it to check 220V presence/absence with MCU.
I need help with understanding how it works.
I assume that R1 is for current limiting, and that D1 provides full-wave rectification, but I don't understand purpose of D2 and C1. C1 is high so its impedance is low to use it for current limiting. I assume that purpose of C1 is to filter full-wave rectified voltage but I don't understand how. Also I don't understand polarity of C1.
Any advice? Thanks!


texts: Why doesn't the shaft of a running induction motor cause an electric shock?

texts:
Source: learnenginering.com

Source: learnenginering.com

Source: Wikipedia.org

Source: Own photo.
Here are some parts of an asynchronous induction motor aka squirrel cage type rotor. As clearly shown by the pictures, the squirrel cage is firmly mounted to the shaft, or vice versa depend on how we see it. As we know that in an induction motor, the powered coils in the stator will induce current in the squirrel cage of the rotor, then the induced current will generate a magnetic field and the Lorentz's force makes the rotor turn. As current is now flowing in the squirrel cage,  the shaft should be electrified (there is current too.)
If so, then why does it not cause an electric shock when we touch it?
The most frequently I touched is water pump and fan, which at least through the bearing, the shaft is connected to the cover/body.


texts: Can't seem to get PWM timer to work on STM32F4 Discovery

texts:
I've been messing around with going back and forth from datasheet, programming manual, and reference manual trying to better understand how to use the STM32F4 Cortex-M4 micro controller. I don't like the way that the pre-defined libraries lay everything out for you, so I'm doing it the more manual way - it's a personal preference which greatly helps me understand the inner mechanisms of the micro controllers.

My problem is that the PD12 output isn't doing anything at all, though the timer is counting and resetting.

Here is my code:

#include "stm32f4xx.h"

volatile unsigned int i;
int main(void)
{
    SystemInit();

    RCC -> AHB1ENR |= RCC_AHB1ENR_GPIODEN;                  // Enable usage of GPIOD
    RCC -> APB1ENR |= RCC_APB1ENR_TIM4EN;                   // Enable usage of TIM4

    GPIOD -> MODER = (0x10 << 24);                          // Alternate function for PWM on PD12
    GPIOD -> OSPEEDR = (0xFF << 24);                        // High Speed on PD12
    GPIOD -> AFR[1] |= (0x2 << 16);                         // AFRH selected AF2 (TIM4; CH1) for PB6

    TIM4 -> CCMR1 |= (0x7 << 4) | (0x1 << 3);               // PWM Mode 2, channel 1 output compare preload enabled
    TIM4 -> CCR1 = 0x0199;                                  // 10% duty cycle (arbitrary)
    TIM4 -> PSC = 0x0000;                                   // No pre-scaler
    TIM4 -> ARR = 0x1000;                                   // Reload at 0x1000

    (*TIM4).CCER |= TIM_CCER_CC1E;                          // Enable CH1 output
    (*TIM4).CR1 |= (0x2 << 8) | TIM_CR1_ARPE | TIM_CR1_CEN; // Divide clock by 4, auto-reload, and start timer

    while(1) {
        // Do nothing, used for debug
        i++;
    }
}

Here is the debug output during the "Do nothing" state in the while loop - note that the TIM4_CNT is constantly counting.

For reference, I used the following tutorials:

Text Tutorial
Video Tutorial


texts: Question about differential signals and feedback

texts:
Let's consider, for example, this circuit:

During lessons, our professor always assumed perfect differential input (two signals with the same dc value and with equal and opposite amplitudes). As a consequence node 1 will be an ac ground due to symmetry and the small signal differential gain can be easily found:

Now the question: when I close this circuit (or in general every circuit with a differential pair stage, which is the input block of an op-amp) with negative feedback, I will not have a perfect differential input, thus I am not allowed to use the previous differential gain (which was actually found under the assumption of differential input). Let's consider for example this basic circuit:

You can see that the non-inverting terminal is fixed to the analog ground, thus it can not change in a differential way with respect to the inverting terminal.
In a similar question I wrote, I've been answered that actually you can always write a couple of signals as the sum of a common mode signal and a differential signal, and since a well-designed op-amp has a common mode gain wihich is much smaller than the differential gain, we can neglect the common mode gain (and thus use only the previous expression for the differential gain). Now I would like to have some hints on how to proceed with the analysis in this case. For example, considering the previous inverting configuration, I tried to decompose the input of the op-amp:

where vx is the voltage at the inverting terminal. Is it correct? How to proceed with the analysis?

Thank you

Edit for the comment:

For the telescopic configuration, the differential gain was found under the hypothesis of differential input signals:

When we close the feedback around it we get:


texts: How to infer the max current output of this function generator from its datasheet/specs?

texts:
I need to figure out the max current a function generator can output from its signal waveform output. Here is its datasheet. But there is no such parameter here.

The output voltage can swing from -10V to +10V.
But I cannot find any detail about the maximum load or current. Can we say it can source current for a load down to 50 Ohm? Does that mean it can source max 10V/50Ohm = 200mA?


texts: How long can the leads protrude for a typical selective solder machine?

texts:
I have an LCD who's leads extend about 10mm past the board surface.

Can a typical selective solder machine fountain reach this high?

If not, any suggestions on the best way to handle long protruding LCD leads like this?

Thanks!


texts: Frequency of motor vibration with different voltage

texts:
I'm using a motor shown in the link below.

http://www.adafruit.com/product/1201

The product page is not showing the detail of how the frequency of vibration changes with different voltages. I sent email to Adafruit, but they said they don't have any information about that nor data sheet for the motor.

Do you have any information about this or do you know where I can get the data sheet of the motor?


texts: Keil Error: L6406E: No space in execution regions - Using STM32F103RE

texts:
I have written a sample EMWIN Project in KEIL using its package manager, shown below.

When I use the Build Project icon I get the following error:

.\Objects\test.axf: Error: L6406E: No space in execution regions with .ANY selector matching rtx_conf_cm.o(.bss).

As shown here:

My keil code can be found here:

The csource Code

  NEW Update:

  So my IROM1 && IRAM1 setting shown below:

  So have I could change those constance for solving this error?

What is causing this error?


texts: Current through inductor as a function of lambda

texts: While reading some introductory text I encountered this symbol, which i know is called lambda but i do not know what it means. I have not taken many advanced math courses yet. I understand the concept of the integrals shown previously but it was always showed as a function of time (t) but in this specific case it is shown as a function of that symbol.


texts:
I recently bought a Nexus 4. I had a couple of spare chargers laying around. I used a charger that apparently had an issue exactly like: https://www.youtube.com/watch?v=mrpBTG0a6K8. If I used my own charger the phone was completely fine. The touch screen didn't glitch out. I tested the "bad" charger with a multimeter and the voltage was a constant 5 volts. Since my multimeter doesnt have the ability to measure amps, I am assuming the glitchiness was coming from an unstable current source. (?). The "bad" charger is 5v at 1 amp. The nexus 4 can go up to 1.2 amps.

Since most forums dealing with this problem are in android forums and the people aren't as technical as I like (the most technical it ever got was "the charger is faulty"), I am wondering if anybody knows the true cause of the problem. I confirmed it is not hardware because when I plugged in my old phone and the issue is the same. It also seems like this problem is quite massive (look at the amount of results on google)

I would also like to know if there is any damage done to my phone. (The "bad"charger was 5v 1 amp and the nexus 4 can handle 5v 1.2 amp.)


texts: BJT PNP AND ZENER DIODE Circuit Analysis Problem

texts:
I am facing problem in solving such mixed circuits with PNP bjt,and Zener diode.
I solving a problem but my results are different to the solution.
Could you tell me if my procedure is correct?
I don’t know the difference especially in the r1.


texts: Large round (20 or 24 inch) LED or OLED display?

texts: Is their any such thing as a 20 or 24 inch round LED or OLED display? I've searched and searched to no avail and I am wondering is that even possible?


texts: Simple amplifier circuit for a synth chip

texts:
I have bought a SID chip with the intention to build a simple synth. I'm pretty confident with the digital aspects of using it but I'm not very familiar with the analog ones and specifically I would want to convert its output signal to something that can drive head phones or be fed into a stereo.

This is the data sheet for it:
http://www.waitingforfriday.com/index.php/Commodore_SID_6581_Datasheet

The output Signal specification looks like this:

This open-source buffer is the final audio output of SID, comprised of the three SID
voices, the Filter and any external input. The output level is set by the output
Volume control and reaches a maximum of approximately 3 volts p-p at a 6 volt DC
level. A source resistor from AUDIO OUT to ground is required for proper operation.
The recommended resistance is 1 KOhm for a standard output impedance. As the output
of SID rides at a 6 volt DC level, it should be AC-coupled to any audio amplifier
with an electrolytic capacitor in the 1-10uF range.

What type of circuit would I need to build in order to plug in a pair of weak head phones or feed it into a stereo? Off the shelf components and pointers to dyi projects providing this feature works for me.


texts:
So I bought this digital meter from radioshack because it tests capacitance. I have several caps on a TV power board, most of which are 47uf and 470uf with various voltages.

when I check with the meter, it gives me readings like 4.851 with no symbol, so I cant set or tell which scale it's on. SOME caps are coming up low, like 2.556 on a 470uf cap. Those caps are not bulged at all, but are they bad? Am I reading them wrong?


texts: What do the numbers on transistors mean?

texts:
I am trying to get into electronics. I'm planning on getting several general-use transistors for arduino projects, I know that a 2N5551 will do what I need. I just want to know what the assosiated numbers mean. For a 2N5551, the Collector − Emitter Voltage is 160 V, the Collector − Base Voltage is 180 V and the Emitter − Base Voltage is 6 V. Are these the max voltages that may pass through? The Collector Current − Continuous is 600 mA, it has a gain of 80. Wouldn't that mean that I'd need a current of 7.5 mA (600/80) going through the Base to turn the transistor all the way (I'd get 600 mA going from the collector to the emitter)?
The datasheet of 2N5551


texts: How to power a circuit that needs +9VDC, GND, -9VDC?

texts:
While I have an assortment of 5V, 9V, 12V wall-warts, but I don't remember ever seeing one that is 18VDC and trying to avoid a trip to specialized parts shop, since I have all other components of a circuit (of a microphone mixer) that I am building.

Here is the circuit in question:

(Source: http://www.aaroncake.net/circuits/mixer2.asp)

As one can see, it requires +9VDC, -9VDC and GND. I've never built such circuits that have negative potential (I know it is relative). Wondering if someone can help illustrate / explain, if it is possible to power this somehow using a 9VDC wall-wart ?


texts: Is a voltage regulator considered an IC?

texts: I'm currently sorting my electronics, but I'm not sure if a voltage regulator is an IC. I can't seem to find any information and I am struggling to understand whether certain components are ICs or not.


texts: How i make simplification/abstraction circuit in proteus?

texts:
I have make 4bit ADDER only using basic logic gates, if i want make another component it will make full of space, so i want make ADDER be simple in proteus like an Integrated Circuit.
Here my own work, which we can see the Input on BOTTOM and the output on TOP, while Bottom Left is my design.
I want make Simple like bottom-left square at that image, but how to connect the pins from digital logic to that square pins?


texts: How to find the equivalent resistance for this network of of resisitor using the basic parallel/series combination?

texts:
You can only use the simple techniques you use to combine parallel and series resistors. Nothing else.

The difficult thing about this network of resistor is that: every node besides a and b has 3 or more branches connected to it, so none of them are in parallel.

Each resistor has 1 Ohm resistance.


texts: voltage divider -- for detecting higher voltage in ADC

texts:
I am working on a BLDC sensorless motor. I need to detect BEMF Zero-cross event.
My Motor is working on 24 Volt power.

Now I need to detect the back E.M.F. As refered in this application note.

My MCU is working on 5V. And ADC range is 0 to 5V.
I need to convert the BEMF feedback signal to ADC channed in this.

As we know voltage divider rule says:
Vo = (R2/R1+R2)Vin

In Figure I :--
Now signal (U) which I need to feed is applied at the middle of the two resistors R1 & R7.
So what is the value of voltage VU ?

In Figure II :--
Sum of U,V,W  is applied at the middle of the two resistors R11 & R15.
So what is the value of voltage VN ?

Also, what are the roles of capacitors C1 & C4?

Please can someone explain the MATH behind this ?


texts:
Does anyone know if there is a way to cause a interrupt via software?  Right now I am setting up a timer at a very low timeout 1ns and then using that to cause the interrupt.

Sorry if this is a dumb question... I think there has to be a better way to do this...

Thanks,

Riley


texts: Need help setting up sweep function for signal generator

texts:
I recently bought a signal generator from Amazon.  The model I got was the UDB1205s but I believe my question applies to any of the manufacturer's signal generator in the UDB120x series.  A similar unit appears to be sold as the DDS SG100x series.

Frankly, I have no idea who the manufacturer is.  It was shipped directly from China, and has no markers except for the model number on the bottom.  It is sold by several distributors.

It generates sine, triangle and square waves from 0.1 Hz up to 5 MHz.  It also has a sweep function.  I like it a lot, and it performs just as advertised.

The problem is, there was no manual sent with the product, either printed or electronic, and I cannot find one online.  I have used an earlier version of this product (UDB 1000x series) that did not have the sweep function, and I was able to figure out all the functions by just playing around.  However I have not been able to figure out the sweep functionality on this unit.

Obviously one needs to be able to setup the starting and ending frequencies.  But regardless of what frequency I set the unit to, if I enable the sweep function the frequencies go from 1 KHz to 10 KHz and then repeat.

Does anyone here have experience with this unit, or know where an electronic copy of the manual can be found?


texts: LED intermittently fails but works when voltmeter applied

texts:
I have an LED in a home project.  It's in a simple loop with a resistor and the GND and V+ ends connected to appropriate pins on a microcontroller.  The LED works properly for extended periods of time - including cycles of both on and off at appropriate times according to the software on the microcontroller - but then eventually stops working, meaning that it stays off even in cycles when it should be on.

The LED is physically connected to two lead wires, soldered with "pigtails" between wire and lead of the LED.  I originally thought that physical connection was broken, but I've opened it and there was no signs of that being loose.  I re-soldered it anyway, with no change in behavior.  I also had the full thing apart at a time when it was working, and I could tug and twist any segment of the wiring without causing it to fail, so it seems that nothing is loose.

Now the really strange thing, in my opinion, is that the LED will always start working again when I try to measure voltage across the leads.  Apparently even the slightest touch of the multimeter probe will "fix" the problem and the LED goes on (provided, of course, that I run the test during an "on" cycle).  I only need to touch one side to observe this, which I believe is always the V+ side.  There is voltage when I take the measurement, although that's redundant by that point since the LED is on, which also indicates a voltage.

So, it seems that there is voltage across the LED when there should be, that the LED is not burned out because it can be made to work again, that the physical connection is apparently solid.  I'm beginning to suspect some sort of failure of the LED itself, but I have not idea what that would be.  I could cut it out and replace it, but that's a bit of work that I'm not sure will solve the problem.

Is there some sort of internal failure mode of an LED that would explain this type of behavior?


texts:
I'd like to make a custom module to control the LED in my windshield but I don't know which parts I need.
Here's an example I've made in Javascript to show you exactly what I want
http://www.patriceguillemette.com/led-example.php


texts:
I bought at Amazon Germany an oscilloscope SainSmart DSO203 NANO. Unfortunatedly it came without any manual.

Do you have manuals for oscilloscope? Any help would be appreciated.


texts:
I've got some TLC5940 PDIP package ICs coming in the mail in a couple weeks or so, and in the meantime I'm designing a couple boards for them.

I'm trying to figure out if the TLC is short enough that I can stack another PCB on top using some headers, or if it's higher then a standard .1" header, but the datasheets aren't shedding any light on it.

The datasheet contains the dimensions of the 2 surface mount packages, but their missing the dimensions for the DIP package o.O

Link to the datasheet: http://www.ti.com/lit/ds/symlink/tlc5940.pdf

If anyone could shed some light on how high the TLC5940 is, that would be awesome!


texts:
I have an arduino project that is almost finished.

Now it controls a series of ShiftBrites(ShiftBrties being 10bit RGB LED's) now they use a simple 4 wire configuration(Data, Logic, Clock, Enable) and +5v and GND. its all done over a wireless setup. ShiftBrites are connected to a Arduino and an xBee module. (My basic setup http://ashleyhughesarduino.wordpress.com/2010/08/01/shiftbrites-and-the-arduino/)

The Problem is that the arduino can only output so much juice(Current) before everything starts smoking, my question is how would I connect it up so that the +5v comes straight off the power pack from the wall?

Connect to the Vin point on the arduino? or Connect the +5v before the arduino?
???

Thanks Hughesy


texts:
I am working with a Dataq DI-1100 whose specs tout:

  "The analog inputs offer a fixed measurement range of ±10VFS..."

VFS looks like a unit, but I find the language confusing.  Researching turns up statements like,

  "where VFS is the full-scale input voltage that is determined by a reference voltage"

My training is in mathematics.  A range may be given with a unit, such as voltage, and the fact that an interval is given clarifies that the values obtained will lie between the interval's min and max.  I would expect the statement to simply say "a fixed measurement range of ±10V".

Is VFS indeed "voltage full-scale" and, if so, is there more to "full-scale" than simply the interval of possible values?


texts:
I am studying this time delay circuit and am curious to know the purpose of the 4.7kΩ resistor.
As I see it, it has no purpose. I've built and tested this circuit with and without it and see no difference. Anyone have any insight on this?


texts: Is it possible to get both a +15V and a -15V from a 24V power supply? This is for powering a controller MKS 2179A.


texts:
I'm trying to get a voltage in a range from a potentiometer.

The potentiometer theorically varies between 22k and 40k (R1 in the shematic) but I'm unsure as I currently don't have it in my hands.

I want to "convert" the potentiometer value to a voltage in [0v-5v].

simulate this circuit – Schematic created using CircuitLab

Here, I first convert the impedance to a voltage trough a voltage divider (R2/R1+R2), and then I input this in a differential LIAO.

It should substract Vc from Va and multiply it with R4/43 and I should have :
Vout = (R4/R3)(Va-Vc)
which would give me a value in the right range.

But the problem is that It actually won't work because the second voltage divider won't just behave as if Va was a regulated voltage source, and with Thevenin theorem, you can find this equivalent circuit (here just for Va - Vb part) :

simulate this circuit

And then I have Vc = 1.91011 Volts while what I'd want there is Vc = 5*(22k/44k)(68k/78k) = 2.17949

How can i do ?


texts:
I'm playing with UDN2981 source driver IC. But its inputs are so sensitive that the noise collected by connector wire switches them on. A simple touch is enough to set it on, but actually I don't want to make a touch sensor :)

I tried using pulldown resistors, but only under 1K worked successfully in all conditions, which is too small for pulldown, I think.

Are there other tricks to avoid false switching?

EDIT: added schematic

It should display 3


texts: Benefits of top and bottom ground pour in multilayer boards with proper ground plane layers and stackup

texts:
I'm trying to get some analytical feeling for the use of ground pours on bottom and top layer in multilayer boards with proper stackups such as (for example).

Top

Gnd

Sig1

Power

Power

Sig2

Gnd

Bottom

Every signal net has an adjacent ground plane and the internal signal layers are shielded if the power planes are carefully laid out.

I'd like to take an example. Every now and then you see DDR routing areas poured with bottom and top ground pours on multilayer boards but the benefit seems to be marginal from an EMC perspective and maybe even degenerative with regard impedance matching for the top and bottom signals.

The pours in this situation won't add any shielding to traces bellow since there is already a ground plane just bellow. These pours also add to the asymmetry of the copper distribution which increases the odds of the board bending during heat treatments. They also make rework harder due to higher thermal conductivity.

A upside for these pours though in some cases is increased thermal conductivity around dissipative electronics.

So overall is there any analytical evidence for pouring on top/bottom layers in multilayered boards with proper ground planes for other reasons then distributing heat from power hungry packages ?


texts: What would be the expected accuracy in speed and position of a sensorless vector drive motor?

texts:
I am looking to do some speed-varying torque tests on a system and drive it with a sensorless vector drive motor. However I'm now unsure of what to expect for accuracy on speed or position at low speed?
The waveform may be sine, triangular or square, and the pole count may be between 3 and 9

Is the requested motor speed respected, at least on average with the drive, or does it slip?
How much angular misalignment might be expected between the achieved position/phase and speed versus the requested position and speed?
What would I expect for the output of a continually varying speed request against a varying load? Is the error on the order of a few degrees or a few revolutions?
What motor layouts, permanent magnet etc. are compatible with vector control?
What influence does waveform shape and pole count have on the positional accuracy?


texts: Relationship between I2C drawn energy / power consumption and data rate

texts:
Referring to just what the I2C lines draw, am I wrong thinking that the higher the clock frequency the shorter the time there will be (the same amount of) current flowing through the pullups and thus lower power consumed?

side qeustion

I don't think I am going to reach 100 kHz, that's way over the limit of my hardware. I am alternating between about 32 and 4 kHz. Will the same resistor value (3.3k @ 3V) be good for both?


texts: implement MOSCAP in an FPGA (or another digital IC)

texts: Can I implement MOSCAP in an FPGA? I mean can I connect drain and source of a transistor to gnd and gate to another node? It can be another device other than FPGA. Thank you.


texts:
I'm designing a very long transmission line between a master node a some slaves far away connected by a bus where only 3 wires are used:
 - A DC power supply (24vdc)
 - B Digital comm
 - C Ground

As there is only a communication wire, half-duplex is mandatory, so all slaves only answer when master asks them.
The distance between nodes may by up to 100 m (110 yd), and up to 20 nodes may be installed. May be 2 Km long!!

By other designing reason, a relay may isolate the communication line from the rest of the slaves, they get inaccessible, this is ok. And the voltage on this line may be 5v or 10v depending on other conditions.

As I'm afraid of typical transmission problems (reflections, impedance-mismatch, etc) I have chosen a speed of 1200 baud.

My question is how may I estimate the impedance questions, how to overcome impedance variation. Is that speed low enough? Can be higher?
Is this a realistic circuit?

This is the basic circuitry:

And in the master and slave nodes, this is the communication diagram:

The X2 component is a microcontroller with the asynchronous terminals connected. It writes '0' when Q1 is on, otherwise a '1' is transmitted.
The U1 comparator adapts the slightly high voltages to TTL levels. May be the plus-minus connection is reversed, doesn't matter at this design stage.

Resistors R3 and R4 (10k) have the function of polarize the diodes D1 and D2.

Please give me some light of how to save time of frustrating real tests. May be R3 and R4 have to be lower...
But please take into account that Vb must be almost '0' when Q1 is activated.
Current carried on line B is very low (as the 250 ohm resistors limit it), a low voltage drop is expected.

Thanks!


texts: I’m trying to manipulate the harmonics of a square wave, and my circuit is not working

texts:
I am trying to build a circuit that can boost or cut multiple harmonics of a square wave. I am trying to use a graphic equalizer gyrator circuit. I have had very little luck with this. Any suggestions would be much appreciated.

Here is my circuit. It is a square wave generator feeding a schmitt trigger feeding a single band of a gyrator graphic equalizer. It will work in a limited capacity for this single band, but this equalizer circuit does not seem suited to what I’m trying to do. The fundamental frequency is 289.363Hz, and I am trying to create a circuit that can selectively boost the first six harmonics.


texts:
I read that :

A generator products electrons that it sends into wire
The electron motion is due to the repulsive behavior between electrons

So to increase the voltage (speed of electrons?), generator have to produces more electrons or send more into wire. That will increase the speed of electrons because electrons have now more kinetic energy (V=J/C).

But in this case there are more electron so the current is automatically increase too. Indeed I=C/S, the number of electron by second.

So for a power of 100W for example, how it is possible to produce 1000V with 0.1A and conversely ?

I'm really not sure to have well understood, can you please correct my mistakes and answer my question ? Thanks!

EDIT :

I understand that electron speed is calculated with the area of the conductor (its diameter) and the current. More the area is small and more the current is high, more the velocity increase.

I understand the comparison of the voltage with pressure but i still don't know how you can increase this electron pressure. If it's not by adding more electron into wire, what is the method ?


texts: Rough calculations for heatsink and mains current

texts:
I'm designing a rectifier to output two voltages. Because of the output voltages, I'm using two transformers to get the needed input voltages as shown in the schematic below:

simulate this circuit – Schematic created using CircuitLab

Previously, I had an issue with the in-rush current, but after tinkering around with it, I managed it by using two transformers with different current ratings which also helped by isolating each regulator so that one won't affect the other in terms of input voltages. My concerns this time around are the power dissipated by the regulators and from mains power.

Each regulator outputs a maximum of 0.5 amps. Running this circuit in LTspice, the ICs are giving off roughly 4 watts each. Based on this, adding a heat sink to dissipate that wattage should be enough to keep the IC from burning out. Is there more to it than just putting an appropriate heat sink onto an IC? Assuming 4 watts each, after reading from other posts, the heatsink would need to be rated for 8.75 degrees per watt in ambient temperature.

Regarding the mains voltage, since it's powering two transformers, I'm worried about the current draw from it. My simulation doesn't seem to model the mains current draw, but assuming an ideal transformer, with the relation of the turns ratio and current being \$I_{sec} / I_{pri} = 1/a\$, I could just use that and estimate the appropriate current draw to select a fuse?


texts:
I'm using an LM7805 in voltage regulator mode.

Vin is 15V
Vout is 5V (regulated)
The attached load draws 200mA

How to calculate how much power the LM7805 would dissipate in this setup (and whether or not I need a heat sink)? Couldn't understand it from looking at the datasheet.

P.S. I'm asking because it gets quite hot, which I didn't expect. Checked the attached load, it is around 0.2A, so well within the limit of 1.5A.


texts: Does 8b/10b decoding take running disparity into account?

texts:
What's unclear to me in reading literature about 8b/10b encoding is how it is decoded.

How an 8b word is translated to a 10b symbol clearly relies on the running disparity.  But when it comes to decoding a 10b symbol, it seems like one could decode it to 8b without taking the running disparity into account.  Yet, it would seem advantageous to error detection if one took running disparity into account when decoding.

Is it standard to consider running disparity when decoding 8b/10b?


texts:
I have a question about calculating the admittance between buses in the single line diagram shown below:

The solution I have been given shows that the admittance between bus 2-2 is found by adding the admittance between bus 2-5 and bus 2-4. Is this correct?
Why do we need to be calculate the admittance between bus 2-2? I thought we would only require calculating the admittance between different buses?
Thanks


texts: Standard way to tension a string using a motor?

texts:
I am dealing with a design that requires me to tension a small string, about 5 inches long with a diameter of about 1-2 mm, and then keep it under tension (lock it in place) without the use of additional power. Is there any standard way to tension a string such as this using a motor or electronic components, or does anyone know if components exist that are available for preview from manufacturers that will do this?

Let me quickly clarify the tensioning requirements here with a visual aid. I'm looking for something like this:

I need to program a microcontroller to activate/deactivate the black body in the image. When activated, it should tension the string up to a maximum amount of tension and then lock it in place after some period of time while supplying power to it. When it is activated again (while it is in the locked state), it should unlock the string. Is this possible, and how? Thanks in advance for any help! It is greatly appreciated!


texts:
I have a Beckhoff EL2008 8-channel digital output terminal that I took apart because I'm using an ASIC that is inside the module, Beckhoff's ET1200.

There is essentially a ring of ground pads,some with vias, surrounding the ET1200 inside the module (they all beeped out to the ET1200's ground pins).

I can understand if they're just there for bonding the ground planes, but why expose them?

Through past experience, the ET1200 is a tremendously sensitive device, and this leads me to think that they're exposed for ESD protection, increasing the likelihood that they would conduct the discharge instead of the ET1200.

Can anyone conclusively describe their purpose?

Thanks for looking.


texts: Solar panel resistance and external voltages?

texts:
How does the resistance theoretically behave for most commercially available photovoltaic modules, when an external DC voltage is applied to them, with and without illumination?
It's common to wire solar panels of the same voltage in parallel, in order to provide greater current or greater resilience to partial shade. Presumably, it can be inferred from this that solar panels consistently have considerable resistance (relative to their rated voltage) when not illuminated— otherwise, having different light intensities on the parallel modules would cause significant current and waste heat to go through the panels at a lower voltage.
Is this correct? Do solar panels always/generally have enough resistance to prevent an external voltage around their nominal voltage from inducing a current in them when they're not illuminated?
If so, what is the behavior of commercially available photovoltaics as that resistance is challenged and overcome?
Does their output power decrease when external voltage is applied to them, and as that voltage is increased?
What happens to their resistance (and at what rate) as light starts shining on them and they start producing their own voltage?
How does one determine the maximum external voltage to which a solar panel can safely be subjected? Presumably, at some point, you'll overcome its resistance and either send a lightning scorch mark across it or melt it (if there aren't any quantum or metallurgical shenanigans before then). Is that point a product of its material, open-circuit voltage, or manufacturer decisions? And what exactly happens when you reach it— What is the failure case from shorting (an external voltage) across a solar panel, and how do you get there?
And lastly, how non-linear or asymmetric are these behaviors? Without illumination, do solar panels have higher resistance in one direction than the other? Are they more vulnerable to being burned by external voltage in one direction than the other?

The specific motivation behind this question is to be able to use solar arrays in parallel with other DC power sources without modifying the load (and ideally while gaining the benefits of both and damaging neither), but information about the mechanistic basis of such a setup would be much more valuable.


texts: Why are there no easy-to-solder SMD diodes in 0603 packages?

texts:
What seem to be the most popular SMD diodes currently come in SC-79 packages, but they super tiny and really hard to hand solder...

...and they also can be a hassle even for reflow.

So I thought I'd replace them with easy to solder 0603 equivalent parts, but all the parts I can find on DigiKey have footprints with bottom exposed pins that are even harder to hand solder...

There are also some SOT-23 diodes that would be easy to solder, but are not as easy a swap out because they are a different shape....

Why don't diodes come in normal, easy to hand solder 0603 packages?

Is there some other 2-pin package that they do come in that is easy to solder and is easy to swap out for the SC-79 footprints?

NB: Of course Light Emitting Diodes do come in all manner of nice 0603 packages...

...and for prototypes I have been using them in place of the normal diodes (sometimes the feedback is actually nice!), but it is not always practical to use LEDs in place of a normal diode (if you need a low-drop shottky, for example).


texts:
I recently bought an el-cheapo night light for $1 just to see how they manage to get the costs so low. I expected to meet an el-cheapo voltage regulator at best or even a bridge rectifier but alas! None exist here. I just can't figure out how or why the circuit here works with mains (240V) voltage. It does get warm during operation but I wasn't going to use it anyways so it is just a learning prop for me. I have no idea what the SOT part labelled "J6" is and if it's a transistor, what kind. Please help me figure out how it works and what that "J6" could be.

edit: R2 is the LDR, the other resistors are SMD resistors and the capacitor is an electrolytic cap.

The board looks like this:

and I've drawn the schematic as is:

simulate this circuit – Schematic created using CircuitLab


texts:
I've read that speed of rs-232 depends on length of cable. There are many different tables that describe this dependency. But speed although should depend on voltage of Rx and Tx signals. How maximum theoretical speed of rs-232 depends on voltage? How can i calculate this speed at +-5V and +-12V?

Theoretical baud rate means that we know capacity of the cabling C and inductivity L. Transmitter and reciever are ideal. They can give any waveform. Does the voltage affects baud rate in this terms?


texts:
I'm having troubles with a 3D printer. I need to change a motor for a more powerful one. For doing so, I 'll have to add an external small circuit to amplify the current but not the voltage given by the main board. After trying to understand the uses of MOSFET or OP amps, I feel a bit lost.

There's my configuration:

I can use an external 12v from the power supply
I need to get 1.7A from 0.9A (4V)

How do I amplify current for a stepper motor?


texts: Instrumentation amplifier: function of resistors at the input

texts:
I was wondering:

what is the function of the 2 resistors(R4 and R5) in series with the input pins of the given Instrumentation amplifier?

Thank you!


texts:
The above circuit is from Operational Amplifier Adder.

Now remove feedback resistor and op-amp, and get the output. From the answer of the question, I know how the end result for Vout would be, assuming load resistance exists.

But now suppose that there are N inputs, and there is some load resistance RL. Can anyone show me a simple way or equation of quantifying how load resistance makes the sum result diverge from the ideal value? (The question comes from the fact that adding parallel resistances involve ||, which when expressed into final output takes a lot of time to expand and I still do not know whether there exists a general formula for any N inputs.)


texts: Can someone explain how to do KVL in this circuit?


texts: how to implement sequence detector (multiple sequence)

texts:
i'm working on a problem of implementing a sequence detector that outputs 1 whenever I detect 0010 or 100. What disturbs me is 0010 'or' 100 part. I know how to implement single sequence detector (so if I only have to detect 0010, I only need 4 states and after 4th state i go back to 2nd state with (0/1) and so on.)

State A (0/0)-> State B (0/0)-> State C (1/0)-> State D (0/1)-> back to State B and so on..

However, I also have to detect 100 too. I see that for 0010 if I add 0 in the end, i get 00100 which is both 0010 and 100 at the same time. So in the case where I get 0 after state D, should I go back to state B with 0/0? But then I already went back to state B (from state D) with 0/1 so the two 0's overlapp..


texts: What connector is this on an LED strip light?

texts:
I managed to find some scrap LED strips. I noticed that these have some peculiar connectors on them.

Does anyone recognise what connectors these are?


texts: Nearby jail's signal jammer affecting cellphone and devices using 2.4GHz band

texts:
I just rented an apartment that seemed perfect at the first sight.
However, once I moved in, I noticed a lot of instability on my cellphone signal. I found that odd, so I did some research and discovered that there's a jail in the neighborhood using a cellphone signal jammer system.
I didn't care too much at first, because I don't make or receive phone calls frequently. Actually, I could live a happy life using telegram/whatsapp calls over the 5GHz band from my internet router, since this frequency range doesn't seem to be affected.
The problem is that the jammer is affecting older devices that need to connect to the router over 2.4GHz, as well as bluetooth devices.
As a layman on the subject, is there something I can do to at least weaken the jammer's effect on my devices? Maybe doing something to the windows/balcony door, so they work similar to a faraday cage, I really don't know.


texts:
I think this question may have already been answered, in a way... But I am not satisfied.
I'm reading this book about creating a NOT gate and it mentions that electricity flow from the collector to LED2 connected directly to ground stops when the transistor begins conducting.

Question is, why would LED2 stop if it is connected in parallel?


texts: Is it possible to calculate junction temperature from case temperature without knowing the power dissipation?

texts: Is there another constant or something I should be looking for?  I understand how to use say Theta JA or Theta JC and power dissipation to get to the temperature, but what if I don't have the power dissipation is there another method?


texts:
I am trying to understand the PDF From the following URL: Spansion Application Note

Under the heading Flash Address Pin Labels, it describes that "In word mode there is no means to individually select a byte within a word".

Can someone explain why this behavior?

In Table-1 & Table-2 of the same document in one case A(-1) is shown as 0 and 1 respectively. Is there any correspondence between them or it fixed?

Thanks for your time.
Best Regards,
GSR


texts: Yagarto: Do not include the standard header files

texts:
I am using a recompiled version of the GCC toolchain for the ARM platform, called Yagarto. The compiler comes with a "standard library" called Newlib, and "standard headers", such as stdio.h.

For my project, the licencing of Newlib is not suitable, so I have used a printf function from somewhere else. The problem is that it seems the build-in header files are implicitly included in every .c file, and I'm getting the following error:

  c:/yagarto4.6.0/lib/gcc/../../arm-none-eabi/sys-include/stdio.h:182:5: error: conflicting types for 'printf'

Is there a way to have Yagarto not load the standard libraries by default?


texts: Which of the following microcontrollers can talk to a CC3000 WiFi chip?

texts:
I need to build a hardware device that consists of a microcontroller and a CC3000 WiFi chip. I would like to use any one of the following microcontrollers built by Texas Instruments:

MSP430F2491
MSP430F249-EP
MSP430F29
MSP430F2370
MSP430F2350
MSP430F235

Which of the above MC's are suitable for communicating with the CC3000 WiFi chip?


texts:
I am currently building a SEPIC converter. The signal arriving from the MOSFET driver to the MOSFET seems all good, however the Vds doesn't seem to follow the drivers signal and it makes the MOSFET conduct most of the time, therefore shorting the circuit. Anybody knows how to make this work properly?

Note: there is no load connected, Vin = 4 - 8V, Vout should be 12.5V, PWN circuit (PIC) is powered by a 12V supply

Thank you!


texts:
I am design a transistor switch circuit.

Ic = 1mA-30mA
Ib = 1mA
Vce = 7V-18V

This is the transistor which I am going to use as an NPN Switch

Can someone tell me how to read the Fig 7 graph. In the graph, the gain value is fixed at 20.
But according to my application, Max Ic/Ib = 30. How to take values from that graph. I just want to understand and ensure that my transistor will act only in the cut-off and saturation region.

Or in other words,
In the below attached image, I would like to understand the gain values within the highlighted boxes. In other words, What would the gain range in the Cut-off region, Saturation region and active region. Can someone help me understand the gain with respect to the transistor regions.

Thank you.


texts: Electro-mechanical relay durability curve

texts:
For general-purpose electro-mechanical relays, it is often mentioned in datasheets the number of cycles under various categories of load (AC1, AC15, DC1, DC13 etc.). For example, the following image:

My main interest is DC-1 and DC-13 curves, as I want to use contacts of my relay to drive another electromecanical relay. I know that DC-13 loads are typical relay coils without any protection (freewheeling diode or snubber RC) and DC1 is a non or light inductive load.

My question is: if I add protection means (freewheeling diode or RC snubber) to DC-13 load, can I use the DC-1 curve instead? My intuition makes me say yes because the reactions of an inductive load (inductive kickback, high voltage and current surge) are suppressed by the protection. However, I need more concrete proof than just intuition.

Can anyone who has came across the same challenge spare me some time, please
Thanks in advance.