texts: Draw Amplitude and Phase Spectrum for given signal

texts:
The above problem was asked in my class test. I understand that this waveform has a hidden symmetry.

x(t) = Square wave with p-p A + (A/10)

So, I can write fourier series expansion for it. As square wave contains odd half wave symmetry, so only odd harmonics of sin are present.

x(t) = sum[(2A/npi)sinnwt] + (A/10)

I am stuck here. How can I draw amplitude and phase spectrum from here?

A plot will be really helpful to understand.


texts:
UPDATE: Code snippet already done below. Not sure if correct.

I implemented the routine which is found in Microchip's datasheet in order to reset the EEPROM memory (24LC512)in case it hangs up.  But not sure it is correct.

Many people in the internet commented on doing this, but no code "in the wild" yet. Maybe it's about time...

http://ww1.microchip.com/downloads/en/AppNotes/01028a.pdf

I made a draft. I am asking for comments as I can't test this.

Wire1.end();
    const int SDA=70;
    const int SCL=71;

        pinMode(SDA, OUTPUT); //70 -> SDA1
       pinMode(71, OUTPUT); //71 -> SCL2.

         /* Send START condition */
        //A HIGH to LOW transition on the SDA line while SCL is HIGH defines a START condition.
          digitalWrite(71, HIGH);
          delayMicroseconds(5);
          digitalWrite(SDA, HIGH);
          delayMicroseconds(5);
          digitalWrite(SDA, LOW);
          delayMicroseconds(5);
          digitalWrite(71, LOW);

             digitalWrite(SDA, HIGH); //WRONG?? " while allowing the SDA line to float,"  https://www.microchip.com/forums/m898899.aspx
       //send 9 clock pulses to reset slaves
       for(int i = 0; i < 9; i++){
           digitalWrite(71, HIGH);
           delayMicroseconds(5);
           digitalWrite(71, LOW);
       }

         /* Send START condition */
         //A HIGH to LOW transition on the SDA line while SCL is HIGH defines a START condition.
         digitalWrite(71, HIGH);
         delayMicroseconds(5);
         digitalWrite(SDA, HIGH);
         delayMicroseconds(5);
         digitalWrite(SDA, LOW);
         delayMicroseconds(5);
         digitalWrite(71, LOW);

           /* Send STOP condition */
           //A LOW to HIGH transition on the SDA line while SCL is HIGH defines a STOP condition.
           digitalWrite(71, HIGH);
           delayMicroseconds(5);
           digitalWrite(SDA, LOW);
           delayMicroseconds(5);
           digitalWrite(SDA, HIGH);
           delayMicroseconds(5);
           digitalWrite(71, LOW);

Wire1.begin();
```


texts: What is happening to the flow of electricity in a magneto when you shut off power in a lawn mower or plane?

texts:
I just learnt, mostly by reading about something else, that magnetos are the primary sources of ignition in planes and other types of engines. The article I read said that it was important that a P-lead was working properly because if it wasn't, then moving the blade or propeller could instantly start it up, and there would be no way to shut it off until it ran out of fuel or oxygen (the latter of which would be hard to do). Or maybe cutting the wires would do it.

I also found a question on Aviation SE and posted a comment but thought I'd ask here just in case.

I kind of understand how grounding works, but I don't have a full understanding of it. I know that one type of grounding is to send excessive electrical build-up into the ground's surface via a grounding rod or pipe. The other end of the grounding wire would be connected to the metal casing of the appliance. I imagine it like a damb having an emergency valve that would open if the flood was too severe, and it was about to burst. Another type of grounding is used as a reference point to measure voltage.

Is there another type of grounding that magnetos use to stop the flow of electricity to prevent them from starting the engine?


texts: Ethernet to SPI converter Differential line importance?

texts:
I hope someone can shed some light in this, I am laying out a Ethernet to PI zero HAT and will be using the enc28j60 controller from microchip. People have reported getting 2.8mbps up and down speed on average with cheap modules form china with same chip.

My question is will impedance matching and differential parts make a big difference on traces 14.20 mm in length?

Copper 0.035mm T
Trace width 15 mil
trace <> trace space 4 mil
FR 4 material
1.55mm thick
2 Layer

When I do the impedance matching and calculations this will give me 107 Ohm Differential.

Or will I be better off just running normal routes and adding O ohm resistors in-line just in case there is a problem?
Example of matched traces

Example of unmatched traces


texts: Power supply transformer question, double primary

texts:
I'm trying to make a circuit to look like this one:

This is from ATM90E26 Application note, this IC needs to be connected to mains in order to measure voltage (220VAC) and current. I tried to look for information about the transformer "TD35-18A-220V"(turns ratio, inductance, etc) but with no luck, all I found was a link to buy bulks of 1000 pieces and no specifications.
So I started to look for a similar one and found this one from wurth elektronik: 750342104

According to datasheet for 78L33 maximum input voltage is 18V, so the position of terminal 2 of the transformer (I mean the ratio of (1-2):(2-4)) should be specific to get that output level from terminals 2 and 4, as in the circuit on the first image (terminals 3-1).
From isolated side (terminals 6-10) should be power for digital control electronics, microcontroller and the rest of the circuit (250mA top current). And an isolator (SI8651BB-B-IS1R )to connect the microcontroller to the non-isolated from mains ATM90E26 IC.
My question is if I'm looking at this the correct way?
Is the turns ratio for (1-2):(2-4) a percentage style ratio?, meaning if 220V is the voltage between 1-4, then, if I looking to obtain 15v between 2-4, terminal 2 will be at the 6.81% of the turns between 1-4?
Does this means that the transformer needs to be specific and not "off the shelf"?
Thank you!


texts: Triac BT 136 not working with load connected to MT1 terminal but working with load in MT2 Terminal

texts:
Triac BT  136 not working with load connected to MT1 terminal..
but working with load in MT2 Terminal.
Please see the below connection diagram in working and non working cases.
If its bidirectional device(like a mecanical switch or relay), when load connected in MT1 or MT2 terminal it should work..


texts:
Many Lithium Ion batteries have an internal chip (a protection circuit I guess).
Are External protection circuit (like the TP4056) really necessary due to internal chip?
I can't find the answer on internet, everybody tells to use a protection but I never understood if the internal chip can act as protection without another circuit?


texts:
I have a peltier dehumidifier  that works with 9V 3000mA power.With this electrical power input the cold side keeps a 10-12 °C temp difference from the outside temp.ie external temp=22 °C the cold side peltier module has approximately 10-11 °C.
If I set an another dc input ie 12V 3000mA does the cold side reduce the temperature a little more?ie reaching at  8-9 °C?
Thanks a lot for your time


texts: Testing and safety requirements for selling homemade electricals

texts:
I am currently researching and designing electrical audio equipment, example devices:

Tube and solid state guitar amplifiers
Guitar effects pedals
Mixing / filtering units
Synthesizers

Some of these devices will be mains powered and some low voltage.

For context I am in the UK and hold a Masters' degree in Electrical and Electronic Engineering.

I have had friends, relatives etc approach me to ask if they can buy some of my products.

At present I do not plan to make a business out of this but it could be a possible future consideration.

The price I would be selling the equipment at would not warrant £1000's of test certification, as I do not have the money for this I would prefer not to sell if test houses are the only option.

My primary concerns are safety and liability.

What safety standards do I need to comply with and can I self certify?

Can I remove / reduce liability by selling as a kit product / prototype?

I notice people online selling amplifier kits, presumably they are not liable for incorrect wiring / use.


texts: Is there a way to periodically change the circuit a power supply is connected to?

texts:
I am attempting to build a device that contains an Arduino, a motor driver, and some motors. I'm using an AC to DC converter to power the device with 5v. What I'm trying to do is I want the power supply to be connected to a battery charging circuit at night and then in the morning I want the power supply to be connected to the motor driver. The battery then supplies power to the Arduino. Does anyone know of a way to do this? Would a relay be able to do this?

Thank you!


texts: Calculating ripple voltage across sense resistor (SEPIC DC-DC Converter)

texts:
I am designing a SEPIC DC-DC converter based on the LT3758 (Analog Devices). In the data sheet the maximum switch ripple current percentage is calculated using the ripple voltage across the sense resistor using the following equation

My understanding is that since the typical SENSE current limit threshold is 100mV, the ripple voltage across the sense resistor is 110-80=30mV, but I am no where near convinced of this.
This is the datasheet for the part. The equation is on page 15, Sense current limit threshold is on page 3 and a block diagram is on page 9.
Any help would be appreciated
Here's the block diagram:


texts: Resonant Frequency of LC Circuit in Switching Converter

texts:
Why do we set resonant frequency of LC circuit in a buck converter to be less than 10% of Fsw?
For example, if Fsw is 300 kHz, why should resonant frequency be around 30KHZ.
I am guessing it is due to voltage spikes at resonance, but can't it be just twice, if that's the case?


texts:
I am connecting a load to a Li-ion battery (4.2V), but I don't know how much maximum current can pass through a Li-ion battery. When I know it, I will connect the load accordingly.

What is the maximum current which can pass in a Li_ion battery?


texts: Should this cold-junction compensated thermocouple-to-digital converter (MAX31855) output an accurate temperature?

texts:
I'm currently using the MAX31855 cold-junction compensated thermocouple-to-digital converter in a project (datasheet). Using SPI, I'm able to read the temperature feedback. From an electronics standpoint, everything appears to be work fine and I can even breath on the thermocouple and the temperature will go up. However, the problem I've noticed is that the temperature readings aren't very accurate.

My setup:

U1 is the MAX31855.

X2 is a two pin female header link

Using this type K thermocouple (link)

This chip then communicates with an arduino via SPI.

My relevant code:

float SensorMAX31855::read(void)
{
  uint16_t temp;

  digitalWrite(PIN_SPI_CHAN0_MAIN, LOW);
  temp = SPI.transfer16(0x00);
  Serial.println("First two bytes:");
  Serial.println(temp);
  digitalWrite(PIN_SPI_CHAN0_MAIN, HIGH);

  temp &= MASK_MAX31855; // MASK_MAX31855 = 0hFFFC

  return (float)(temp * 0.0625);
}

Note: I should probably be using a signed integer for the temperature (per the data sheet), however, I'm just trying to do validation in which I know my temperature should be positive.

Problems:
First off, over the course of 20 seconds, I'm getting temperature readings that range from 12C - 18C without even touching the device (I assume vibrations may affect the reading). Should the temperature reading be this jittery? My guess is no.

Second, the temperature should actually be 21C room temperature. However, my readings all appear to be below this number. Should I be expecting an absolute temperature? Or do I need to adjust for an offset?

Third, when reading the internal reference temperature, it came out to be a value of 26C. Does this seem warm given that the device is at room temperature?

Possible Answers
It's possible that I've introduced some bad junction during the physical assembly. Would landing a K type thermocouple into a female header introduce an offset error or noisy reading?

Is it possible that this behavior should be expected? I realize the thermocouple can read a large range of temperatures, however, it still seems pretty noisy.

Any thoughts/ideas would be appreciated!


texts: DC circuit schematic has both positive and negative supply as well as ground?

texts:
I am trying to breadboard a DC circuit schematic (a sawtooth voltage controlled oscillator, to be precise). In the schematic there is a positive supply, a negative supply and ground (+4.5V, -4.5V and a ground, respectively).

I understand some things about the potential difference and the reference voltage. I tried to connect every pin which in the schematic is connected to the ground, with the negative supply. But I am sure that is not correct. I did a bit of research and now I know that the potential voltage difference between the positive and negative supply must be 9V and the ground is in the middle of this difference.

The problem is, I have a power supply device that has only Positive and Negative supply. So, what do you propose I do? I do not feel that it is correct to connect to the ground, every pin connected in the negative supply in the schematic. I am sorry if this exact question is asked again, but I am searching everywhere, even in stack exchange for over an hour now. Thank you in advance.


texts: Is it possible to power a 12v power board with a lithium battery, while keeping it charged via a solar panel. Or would I need to have two batteries and somehow automatically change them over when the battery was running low?


texts: What parts would one typically use for automated PCB testing?

texts:
I have a circuit board in production, primarily through-hole, to the tune of ~400 units per year. Each one is manually inspected and tested. The board has ten distinct voltage rails, four voltage feedback amps, three current feedback amps, a microprocessor with particular response characteristics, and a few other parts. That's a lot to check.

I'm considering building an automated test rig for all that. I think a PCB that feeds the appropriate input stimuli, observes the responses, and gives a go/no-go would save me a lot of time. I'm reasonably confident that this is done, commonly. However, the techniques used to do it are unknown to me.

I imagine a test rig with a circuit board of the same footprint as the unit under test (UUT). It would have a microprocessor, appropriate protection and scaling circuitry, and a large number of vertical pins sticking up from the board. Mount points would also stick up from the test rig for the UUT. When the UUT is mounted on top of the test rig, the bottom of the board makes contact with the vertical pins, allowing the test rig to feed stimuli to the UUT and observe responses.

This seems reasonable, and I have the idea I've seen something very much like this before. But the details elude me. What sorts of pins would be used on the bottom board? (Part numbers would be great!) Would I need to put specific kinds of test points on the UUT, or can I get away with just contacting the clipped pins protruding through the board? What other concerns might there be?


texts: Creepage and clearance of through hole resistor

texts:
Recently I found a resistor broken on a PCB. It is a MOF type 1/2W through hole resistor. I found that the resistor is directly placing (touching) on a PCB Live trace and I know that the potential difference between the resistor and the trace is about 220Vac. There is a small hole on the resistor and a burning mark on the PCB trace. Therefore I presume an electric arc was formed between the resistor and the PCB.

Then I read the safety standard EN60335-1. For the part describing creepage and clearance, it has a remark: "Lacquered conductors of windings are considered to be bare conductors" As I know common MOF resistor body is just a lacquered coating,

I would like to ask is this resistor considered as "Lacquered conductors of windings"? If so this is violate the safety standard.

If this is not, is a MOF through-hole resistor body touching a Live PCB trace violate the standard?

Appreciate if you can provide strong supporting document or information.

Thank you very much


texts: How to use single constant current source to power parallel LEDs safely and efficiently?

texts: Can we connect the identical LEDs in parallel powered by the single constant current source efficiently and safely at the same time? How can we do this in most efficient and safe fashion?


texts:
I have designed a photo-sensing array that consists of phototransistors (RPM075PTT86) and n-channel fets (see circuit below) duplicated 25 times. This is a very simple circuit that works OK, but I have come to realize that it is very hard to locate a defective fet among those connected to the common 'wired or' bus. The original circuit did not have the 10 ohm resistors, making it tough to identify a shorted or defective fet. Note that the 25 sensors are split into two groups to avoid leakage problems. I put the 10 ohm resistor in as a 'current sense' in the hopes that a shorted fet will be close to ground at the drain, while normal ones will be a little higher in voltage (Id x 10). In this circuit Vcc is 5V. I have not implemented this but I plan to in the next spin. The question is, given the bus array, what's the best way to locate a bad transistor? Some possible approaches:
1. Shine a light on the array (all transistors off). If the bus is low short it to 5VDC and the shorted transistor(s) will smoke and burn, maybe
2. Use a sensitive ohm-meter to find the current path- none of my meters are sensitive enough, you would need a nano-ohmmeter
3. Use the method of the drain resistor to detect current, probably the most effective

Is there a better way? Can the circuit be improved?


texts:
I have some nice gear motors that run on 12 to 24 volts, and want to use them in a medium-sized mobile robot -- maybe 30 cm * 30 cm for the base.  I only expect it to run indoors, or possibly outside in nice weather.  If it had a half-hour run time, that'd be fine.  [If this is successful, though, I'd like to make a bigger robot that can withstand the out-of-doors, but probably only in nice weather].

I'm wondering what sort of batteries to use to power the motors.  These are the choices I can see in order from what I think is best to worst.

Use one or two 12 V (lead-acid) batteries.  This is sort of what I'm leaning towards, but I'm worried about how bulky and heavy it would be.  A car battery would be far too large and heavy.

I already have a charger that claims to be "ideal for car, SUV, light truck, farm equipment, boat, deep-cycle, RV, motorcycle, ATV, snowmobile and lawn tractor batteries."  I imagine it would charge any 12-V lead-acid battery.
Use some 9-V rechargeable batteries.  They appear to typically be a little less than 9V, but it appears that there are 9V and 9.6V varieties.  I would have to get a charger.  These would be light, compact, but they won't last long.  (230 mAH seems paltry compared to a 5 AH 50 AH car battery.)

I would need to have two in series, and, I suspect, have two or even three series in parallel.  That adds up to quite a few batteries and starts to negate the benefit of the small, compact batteries.
I could use 2 to 4 6-V batteries.  (I didn't realize you could get rechargeable 6V batteries).
AA batteries, and lots of them.  10 to 20 1.2V NiMH batteries, though, will take a fair bit of space and mass and be take a long time to charge.
Specialty batteries (like those used in RC vehicles).
Some combination of the above -- say, two 9V batteries and a 6V battery.
Any sort of battery and a DC-to-DC adapter.

The first two options seem like my best choices.  What would you recommend?


texts: Is a base resistor always needed in a single transistor inverter circuit?

texts:
For the circuit shown, I'm trying to figure out if I need a base resistor or not.

What I'm looking to accomplish is a simple logic inverter to hold a power amp's active low shutdown at logic low until the tube warms up to a stable temperature.
I'm planning to leverage an existing inrush current limiter to drive the shutdown imput. (The idea for the inrush limiter is to extend the life of the tube filament by letting it come to temperature slowly, based on what I read in this article: https://audioxpress.com/article/constant-current-for-heater-tubes-extend-the-life-of-your-amplifier-s-vacuum-tubes)
The tube filament and inrush limiter form a voltage divider. When the circuit is at room temperature, the ratio should be about 20:200, making the voltage at point A logic high. When the circuit comes up to operating temperature, the datasheet for the inrush limiter says its effect will be negiligible (I'm assuming near zero reistance) so the vast majority of the voltage wil be dropped across the tube heater. This makes point A logic low.
This arrangement is exactly opposite of the active low requirement of the power amp's active low shutdown input.
Researching transistor inverters, I came across several that look like what I have in the schematic, with Rb, Q1, and Rc.
My question is this... Do I need the base resistor?
I'm thinking no, because I'm technically using voltage divider bias, with the tube filament and the inrush limiter forming the resistor network. But, the current flowing through these elements is about 150 mA. Normally, the voltage divider resistors in this type of biasing are calculated to pass a lot less current. Is there any possible harm to the transistor with these small resistance values and this large current?
If I think in terms of current amplification, and the transistor's beta of about 200, the ratio of Ib to Ic should be 1:200. Ic is limited to about 1mA by Rc. Does this arrangement dictate the base current can never be more than 1/200th of 1mA? It would seem so to satisfy the 1:200 current amplification. Or, is it a one way function where Ib controls Ic, but limiting Ic does nothing to limit Rb? In other words, Rb is still needed to limit the base current to a reasonable value? This does not seem to fit with the idea of voltage divider biasing, but I have never tried it with such a low resistance voltage divider.
I would prefer to not blow up a transistor to find the answer. Can anyone tell me if the Ib:Ic ratio holds true both ways, or do I need Rb to limit base current?


texts: Frequency mixing at low frequencies (with AD835)

texts:
I am using the AD835 to downconvert signals from around 1 kHz to around 10 Hz. While testing I found that the mixer behaves differently when using for example an LO at 1 MHz and RF at 999,99 kHz opposed to an LO at 1 kHz and RF at 1.01 kHz - both yield the same IF at 10 Hz, but have different amplitudes. Calculating the amplitudes using the given transfer function
$$
W=\frac{(X_1-X_2)\cdot(Y_1-Y_2)}{U}+Z,
$$
where \$X_1,X_2\$ and \$Y_1,Y_2\$ are either of the differential RF or LO inputs, \$U=1\$ and \$Z\$ an additive term set to zero in my case, I can not match the results (which of course should be equal regardless of the frequency range of the RF and LO as long as IF is the same)?! Just for convenience the equation I get out of this assuming two sinusoidal signals:
$$
\frac{A_1\cdot A_2}{2\cdot U}\cdot \{[cos(\omega_1-\omega_2)t-\varphi]-[cos(\omega_1+\omega_2)t+\varphi]\}
$$
with RF amplitude \$A_1\$ and frequency \$\omega_1\$, LO Amplitude \$A_2\$ and frequency \$\omega_2\$ and phase shift \$\varphi\$, if there is one (at first I generated both LO and RF with function generators with unknown phase shift, later I used a NI 6361 to generate signals with known phase shift).

While reading the datasheet again very thoroughly I noticed all plots being for frequencies starting in the MHz range. In general the mixers I find are designed for high frequency applications. In my opinion at least in theory there should not be a problem with low frequencies though.

So my question is: Is there any reason why this multiplier (and also others that specify the 3 dB maximum frequency and are wideband) should not work for low frequencies? If there are, are there recommendations for mixing devices or other approaches that fit my frequency range (from some kHz down to around 0-100 Hz)?

AD835 Datasheet


texts: Cap's on H-Bridge... Seem a bit redundant?

texts: The Below is a H-Bridge Schematic from this site: http://www.societyofrobots.com/schematics_h-bridgedes.shtml. Wouldn't the 10-100nF cap be rendered useless by the 10000 uf cap? Wouldn't the caps just have a equivalent capacitance of 10000 uf + 10-100nf


texts:
I've been studying some ESC (electronic speed control) circuits for BLDC motor control and something always catch my attention. In many of these schematics there's often a resistor connecting the controller IC to the power MOSFET. As the MOSFET gate is an isolated connection what's the reason for such component? I mean, if I remove the resistor shouldn't the circuit behave the same?

simulate this circuit – Schematic created using CircuitLab


texts:
We have 3-phase electric network. How to determine phase sequence (L123 or L132) from 2 line-to-line voltages U12 and U32? I prefer computationally simple solutions. Is it possible to determine phase sequence without computing phase voltages (which seems to me to complicated if searching generally valid solution for assymetric systems).

The solution looked for needs to be a mathematical algorithm. I am not searching circuit design. I need to write computer program for this. Lets say we know amplitudes and phases of vectors U12 and U32:

\$U_{12} = |U_{12}| \exp \left[j \left(\omega t + \phi_{12}\right)\right]\$

\$U_{32} = |U_{32}| \exp \left[j \left(\omega t + \phi_{32}\right)\right]\$


texts: Can a Dependent source be dependent on itself?

texts:
I am looking for the Thevenin Resistance here. However, I have no clue what to do with \$i_b\$ and the source dependent on it.
This is the entire circuit.
\$i_b\$ is the current through the 5\$k\Omega\$ resistor. In this case, There is an open circuit across terminals a and b and so there is no current flowing through the 10\$k\Omega\$ resistor.
Meaning that all of the current flowing in the circuit is \$i_b\$.
That presents this problem, because there's a dependent source that is dependent on the current \$i_b\$ and they are in series. Hence, the confusion and the question.

Equations:
KVL along outer loop CCW:

Sidenote:
\$I_{sc}\$, short circuit current across terminals a & b, is easily obtainable by a KVL on the outer loop, the relationship of the current through the 10\$k\Omega\$ resistor and \$i_b\$, (Which is \$4i_b = i_b + 3i_b\$ :: KCL in the middle top node), and it is -1.8mA.


texts: How does the secondary coil of a transformer affect the primary coil? How is it in case of Step-up and step-down transformer? Does it obey Lenz's law?

texts:
What changes will (of voltage, current, energy, power, etc) happen to the Primary coil, if an AC supply given to the primary coil, but;

Secondary coil circuit is turned OFF (Open),
Secondary coil circuit is turne ON (closed), with a High, but finite- resistance load,
and
Secondary coil is turned ON (closed) with a LOW resistance load;

in case of A. Step Up transformer, B. Step Down transformer.

Please also explain, how Lenz's law is applicable in case of these 2 types of transformers, Lenz's law states the induced current will try to hinder the cause.

But so-far I know (may be correct or incorrect), in a transformer, when there's supply to primary-coil , but the secondary coil-circuit is open (off), (that means , no current on secondary coil)  there's little flow in the primary coil, but when the secondary coil-circuit is turned-ON (that means, current flowing through secondary coil), the current on primary coil increases.

& That means current on primary coil, not at-all hindering the source, rather enhancing the source current.

And this seems very much contradictory with Lenz's law.

How a transformer then obey Lenz's law? if not, then why?


texts: The Electronics Involved in Instruction Fetching

texts:
I would like to know how the instruction cycle works at an electronics level. I am new to electronics.

In order to limit the scope of this question, I am just focusing on the first step of the cycle, "instruction fetch". I understand the high-level descriptions like from Wikipedia (below), so here I am wondering the details of electronics involved.

Specifically, I am wondering like how many flip-flops, gates, buses, whatever else involved, and what is connected to what (at a high-level). I am new to electronics so I'm not too familiar with all the components involved, so don't really know how to explain the detail I am hoping for. I guess basically down to the voltage. If there are any transistors. If there are any magnets, optics, etc.

For example, "There are x number of flip-flops, each connected to a central data bus made out of s, which is connected to x. The electrons flow from y to the central data bus on a wire (typically made out of copper) to the flip flops, which is the initiation of the instruction fetch process. This then triggers w process in the t electrical component which induces a voltage change to cause a sequence of voltage changes to then send the resulting "information" (electrons sent in packets passing through the bus on the copper wires to the flip-flop [entry point] to be stored in a voltage difference) is sent back to the ..." As you can see I have no idea what I'm talking about, but that is sort of the idea of the level of detail I am looking for. The whole process doesn't need to be described, just looking for an introduction to the pieces involved. Trying to make the connection from the Wikipedia-level description down to the level of voltages, materials (silicon/magnets/etc.), and components (transistors, flip-flops).

Thank you so much for your help.

  (1) The fetch step is the same for each instruction:

  The CPU sends the contents of the PC to the MAR and sends a read command on the address bus
  In response to the read command (with address equal to PC), the memory returns the data stored at the memory location indicated by PC on the data bus
  The CPU copies the data from the data bus into its MDR (also known as MBR, see section Components above)
  A fraction of a second later, the CPU copies the data from the MDR to the instruction register for instruction decoding
  The PC is incremented so that it points to the next instruction. This step prepares the CPU for the next cycle.
  The control unit fetches the instruction's address from the memory unit.


texts: Stopping the clock without gating the clock

texts: How would one go about making a shift register which only shifts when an enable line is high? The obvious answer is to pass the clock and enable through an AND gate, but that breaks the "don't gate clocks" rule. Another possibility might be using a mux to select the input of each flip-flop to either be the previous flip-flop's output, or to feed its own output back to the input. That would work for the shift register, but is there a better way? How are similar effects achieved in complex designs, where portions of the functionality can be temporarily stopped to save power?


texts:
This is the error message when trying to run a simulation for one of my models

--------------- INFO(ORPROBE-3209): Simulation Profile: SCHEMATIC1-bias ---------------
INFO(ORPROBE-3183): Simulation running...
** Profile: "SCHEMATIC1-bias" [ c:\users\softwareengineer\desktop\musical tesla coil\orcad\gate driver\gate driver-pspicefiles\sche
Reading and checking circuit
ERROR(ORPSIM-16363): Command invalid in subcircuit
Circuit has errors ... run aborted
See output file for details
INFO(ORPROBE-3188): Simulation aborted

Note the "See output file for details". I DO NOT KNOW WHERE IT IS. AND I CANT FIND OUT WHERE IT IS DESPITE GOOGLING IT FOR THE LAST HOUR.
Can someone please tell me where this output file is so i can maybe have a meaningful error message which tells me what is wrong.
I myself am a software developer and if i designed it, it would give a file name, line number, index in line and snippet too with the error. You wouldn't even need to open some hidden error file because it would print the error to the damn console. Maybe not everyone has common sense like I do I don't know but this is driving me nuts.

All i want is a meaningful error message so i can begin to work out what is wrong with my model.


texts: usb keyboard with many simultaneous key presses

texts:
I am looking to make a keyboard that allows for 2 or so keys pressed at the same time by the same finger. ie s and w would both register and a total of 8-10 keys registered at 1 time.  the keyboard matrixes dont really allow for such. As such I suspect I will need to use quite a few inputs per chip. since I can get away with only needing 1 hand about 26 keys at the same time I might be able to do a twin matrix and split parts between the 2 hands sections so qhx7 could all be on 1 line instead of 1qaz which would cause blocking. the down side would be trace routing.

im not opposed to having say the left had being all direct inputs and then all the rest of the keys as a matrix.


texts: How to improve symmetry of +/-1 gain circuit?

texts:
In an attempt to have a square wave with a voltage-controlled amplitude, I've made this little circuit:

Unfortunately, when negating, it has a slight offset from -Vin.

I assume this is because the BJT doesn't pull all the way to ground.

What are easy ways to improve the symmetry of this circuit? Ideally I'd be shooting for <1mV error between the positive and negative sides.


texts:
I'm looking into designing a display to show and adjust brake bias.  I'm planning to use a rotary encoder in order to select through menus.
Unfortunately, I'm having a hard time deciding which model of rotary encoder to use in order to withstand all mechanical forces present (g- foces, vibrations, etc) and also give a good mechanical feedback to the driver (helping the drive be sure that he actually rotated the encoder).
Taking a quick look, I've founds this model (Mouser link) PEC11H-4120F-S0020, I've choose it because it has a push button inside and appears to be robust, but I have no clue if it will work properly.
What should I look in order to determine if it will work as intendend?


texts: Using super capacitor alternative to battery as a backup power for laptops

texts:
I'm interested building my own battery pack using a series of super capacitor, something like this : http://youtu.be/z3x_kYq3mHM

I plan to use it as a power backup solution for my laptop. Based on what i've been reading on the internet, using super capacitor to store energy are much more faster compare to using lithium battery and it weights more lighter than the lithium. After discovering that idea, that made me really interested in building one to be used as power backup for my laptop.

Now I can just charge the battery pack separately (by regular outlet or solar) and when I'm low with battery for my laptop I can charge my laptop again using that battery pack.

I really don't know how efficient is this idea and if this is viable to be used for a laptop battery pack. I'm also not sure how long will the battery pack last once it's hooked to a laptop (eg Macbook Pro) and if I series a bunch of super capacitor will it still weight light enough to be carried along with a laptop.

I'm interested to hear your thoughts.


texts: Which type of aluminum capacitor should I choose?

texts:
Well generally I am confused, same values and almost same size. One of them is an SMD electrolytic and the other is a through hole electrolytic with long thin legs.
Where should I use which capacitor?
Actually I need more detail information. I would appreciate it if you could share some documents or videos.


texts:
I'm quite new in programming PICS, but have already done some projects. All of them were working fine. But now I'm stuck with a very simple one and I don't find out what's wrong. I'm pretty sure that's due to some really silly mistake, but due to the lack of debugging support of the PIC12F508 I do not know how to find my mistake, so I decided to ask you guys.
The problem is, that the LED (connected to GP5 which is configured as output) is on at first, then is switched off after approx. 1 second and then never goes on.
I expected it to blink once a second...

Here's the code where the bug is hidden. I'm staring at it hours now, but I don't find it. (Ah, btw.: running the code in the simulator is working fine. The error does not occur.)

START

    MOVLW       .199                    ; no WakeUp on pin change, no weak pull-ups, timer source internal, don't care, prescaler for timer0, 1:256
    OPTION                              ; set options

    MOVLW       .0                      ; all GPIOs are outputs
    TRIS        GPIO                    ; set tristate register

; the pre-scaler is set to 1:256, which means that every 256 µs the timer
; is increased by 1. This is done 256 times until it overflows. During this
; time 65 ms have passed. 15 times 65 ms are approx 1 s. So we need to do the
; loop 15 times

RestartLoop:
    MOVLW       .15                     ; 15 loops
    MOVWF       LoopCount               ; write into file register (correctly defined)
NextRound:
    MOVLW       .1                      ; set the TMR0 register to 1
    MOVWF       TMR0                    ; it should not be 0 as the logic below would not work
                                        ; I know, that's not good practice, but at least it should work
CheckTimer:
    MOVF        TMR0, W                 ; read current timer value into W
    BTFSS       STATUS, Z               ; has an overflow occurred and it is 0?
    GOTO        CheckTimer              ; no, read timer value again
    DECF        LoopCount, F            ; yes, decrease the loop counter by 1
    BTFSS       STATUS, Z               ; is the loop counter 0?
    GOTO        NextRound               ; no, then restart Timer0 and wait again until it's 0
    MOVF        LED, W                  ; yes, read the file register LED into W
    BTFSS       STATUS, Z               ; is it 0?
    GOTO        MakeLEDOff              ; no, LED is on, switch it off

    BSF         LED, 0                  ; yes, LED is off, switch it on
                                        ; set bit 0 in the file register LED
    BSF         GPIO, GP5               ; switch on the LED
    GOTO        RestartLoop             ; restart the 1 second loop

MakeLEDOff:
    BCF         LED, 0                  ; clear bit 0 in file register LED (should be 0 then)
    BCF         GPIO, GP5               ; switch off LED
    GOTO        RestartLoop             ; restart the 1 second loop

    MOVLW 0x55                      ; your instructions
    GOTO $                          ; loop forever

    END

Any clue why this is not working as expected?

One more thing that might be of interest is the setting of the configuration bits:

     __CONFIG _OSC_IntRC & _WDT_OFF & _CP_OFF & _MCLRE_OFF

Best regards,
Boxy


texts:
In a page on Ramp Generators I found this peculiar circuit which is said to be superb in its linearity. But I can't make sense of it. It doesn't discuss any of the actual R and C values.

I can see that Q1 and Q2 are mutually exclusive in on and off state. If V_i or what that means is above ground it turns Q1 on which turns Q2 off. The graph of V_i appears to say it should be negative, below 0V, but I already don't get why that should have to be the case? 0 is 0, off is off. Why negative on the base of an NPN?
Now I can see how C discharges through Q2. But Such discharge would be rapid. So how can that make a gradual and linear falling ramp as in the diagram? I suppose to do that the R_B2 must be only slightly on so current through the base of Q2 must be much limited.
I have experimented with that a little in LTspice, but it was hit and miss. And the charging time was considerable. I couldn't make Rc small enough before the linearity would disappear. How do you tune this thing?
And then I found another article which was a bit more complicated and used 4 different voltages. And there too I could not find any suggestions on how to choose the resistor values and the formula showed values that weren't even in the schematics (i.e., 2 capacitors when there was only one).

How do you dimension these things? I understand they may be only about principles, but I was intrigued by the simplicity of the first circuit and I could almost get it to work, but not fast enough for the 60 Hz that I need it.


texts: Can an OpAmp work shortcircuited to ground?

texts:
I am curious to know if an OpAmp can be work fine shortcircuited to ground.
Datasheets normally have information about the shortcircuit current that the component can deliver, but I understand that this is meaningful when you want to supply other components.
But what about the OpAmp itself? Would it suffer if it is permanently driving its shortcircuit current?

This could be usefull when you have large capacitive loads. (Not interested in stability problems here)

An application note or any official information will be greatly appreciated!


texts: How do I read the output from a guitar patch cable?

texts:
I am curious about how guitar patch cables and amps work.

I am trying to read the output from an electric guitar using an analog to digital converter, but I'm assuming I need to power the guitar in some way since I did not get any output.

How does an amp take the input from an electric guitar?

Thank you!


texts: Choose the right components for an MMIC amp

texts:
currently I'm studying MMIC amps
like this one:

From what I can understand, these MMIC claims to be wideband, and I guess that the operating frequency is given by the components around the MMIC.

Let's take a look to the recommended application circuit for the MAR-8 (datasheet):

First of all, the first important component is the bias resistor: is determined by the given supply voltage for the circuit (eg if Vcc is equal to 7 volt, the bias resistor must have a value of 88.7 ohm; if the Vcc is equal to 12 volt, otherwise, the bias resistor must a have a value of 226 ohm).
Another thing that is not clear to me are the values of the two capacitors "Cblock" and the value/presence of the inductor, since, on the above datasheet, the inductor is also stated as optional; I guess that the values of Cblock capacitors and of the inductor will determine the working frequency, am I right?

Well, let's take as example this wideband amp kit:
RF wideband amplifier which claims to be able to operate from 0.1 Mhz to 2000 Mhz, and the supply voltage can go from 6 to 12 volt. Is not very clear to me: this kit seems provided with fixed values components: so: how is possible that we can apply a supply voltage from 6 to 12 volt, if there is a bias resistor with a fixed (and unknown) value? And is the same for the inductor and Cblock capacitors: if the inductor and these capacitors will determine a specific frequency, how, this kit (which is provided with fixed value components), would be able to achieve a very wide range of frequencies? Or is just a waste of money, since, maybe, wouldn't be able to work as claimed?

Ok: can someone explain me how to choose Cblock capacitors and the inductor (and why the inductor is stated as optional) to have a MMIC able to effectively work in a wide range of frequencies? And maybe can someone explain/show me a practical example with a schematic, eg, to achieve a MMIC circuit which is able to work from 800 to 1000 Mhz?

Please consider that I am a "newbie" about these subject, so I would appreciate a clear and exhaustive answer.

Many thanks.


texts:
I recently read an article (http://www.eejournal.com/archives/articles/20130506-batteries/) that seemed to indicate that "supercapacitors" are starting to approach the energy densities of batteries for some applications. That was in 2013 so I imagine things may have moved along a bit more since then.

I am now curious as to the relative weight and energy density of the two, and specifically I am thinking of how these might be used in drones where weight is an issue.

Does anyone have any information on this or maybe links to any articles comparing the two please?


texts: Transfer function of Op-Amp-Twin-T Filter

texts:
I have the following circuit and wanted to find out the transfer function of the whole circuit (which includes the non-ideal op-amp as well - modelled as a VCVS - H(S) is DC gain with some poles).

I tried the following:

1-To model it as a simple Op-Amp with feedback network with the transfer function as shown below:

But with this, I could only model an opamp with a constant dc gain and with poles. But the Input capacitance and output resistance of opamp (non-idealities) are not included.

2-To include the non-idealities of the op-amp (input capacitance and output resistance), I tried to analyze with a different approach with the feedback network modelled as a Two-port network - something like below:

Somehow I got the h12,h11,h22 by solving the twin-T bridge (using Delta start transformation -> combining the parallel resistances -> then finding voltage gain, input and output resistances) using mathematica, but the relations got more complicated and it was of third order which I feel it was not correct.

I modelled the two-port network using h-parameters since it was a voltage-current feedback. But should i consider it as a different feedback structure (like a voltage-voltage feedback) and then try? or Is there any other method to get the whole transfer function?

Any help or guide in getting a simplified expression for the whole transfer function (with feedback and non-idealities) of the above circuit will be helpful.


texts:
I asked a question here about calculating the resistance an unknown resistor using superposition.
As part of the answer I was given $$I_1=I_3\frac{R_2+R_i}{R_1+R_2+R_i}$$ and $$I_2=I_3\frac{R_1}{R_1+R_2+R_i}$$  as the third case of the superposition method involving a current source.
 My confusion is that firstly, I understood that the current divider rule was $$\frac{I_0}{I_n}=\frac{R_{sum}}{R_n}$$ and the above answer is opposite.
Secondly I see \$R_1\$ in parallel with \$R_2+R_i\$ so I don't understand why $$I_1=I_3\frac{R_2+R_i}{R_1+R_2+R_i}$$

I have the feeling there's something that i have fundamentally misunderstood.

My understanding is $$I_n=\frac{V_n}{R_n}$$ and the voltage in a parallel circuit is $$V_n=V_{total}=R_{total}\cdot I_{total}$$ so that $$I_n=\frac{R_{total}\cdot I_{total}}{R_n}$$ which is just what is says here. What people are telling me on here seems to be that the resistance in the other branch divided by the total resistance is equal to the resistance I'm looking for.

I've looked for proofs, but I seem to just find the formula which I knew to begin with, which I'm being told here is wrong. What am I missing?


texts:
I am currently using an STM32F401RE that I have to interface with a SIM800L GSM module via UART. In a first "toy example" I used Arduino and found no problems, but passing to the STM MCU I am unable to receive any kind of answer from the module.
I am starting to suspect that the output voltage levels of the board are incorrect for the GSM module. SIM800L requires an input signal between 2.5 and 2.8 Volts, that Arduino (5V) can easily provide, and that I was able to provide also with a converter from my PC USB. Trying to dig into the MCU datasheet I got stuck into this table.

Honestly speaking I am not properly an electronics guy so I am not able to fully understand my MCU UART TX pins to which line of  the table belong, but however it is quite obvious that potentially in none of the reported cases I can really get the voltage required by GSM board. So my questions are:

May my suspect about wrong logic levels really be the fault in my connection?
If so, how can I adjust my MCU pin voltage to adapt to the GSM module?

EDIT:
I connected the MCU to the GSM module as suggested by the datasheet of the productor for 3.3 interfaces (obviously rx-tx, tx-rx the image is faulty). The only pins involved in my case are transmission and reception and ground and supply, so ignore the rest for the UART protocol.

For what concerns the code there is not so much to speak about, simple transmit and wait for a response in polling or interrupt mode. UART is set in 8N1, as Arduino SoftwareSerial that I successfully used does by default. Peripherals initialization code was automatically generated by CubeMX. Messages are correctly send by the MCU, just by checking with a terminal. Doubting about hardware is my last idea, but in this case I can't see other options for my short experience.


texts: What is the proper way to reset attiny85?

texts:
I have 3 attiny85 on my pcb. And I want to have software controlled reset for them. A separate STM32F0 microcontroller is responsible for the reset. I have two states from the STM32F0 to pull up and pull down an IO pin. And I have directly connected the output of this IO pin to IO2 on this schematic. And the RESET pin on this schematic goes directly to the 3 reset pins of the 3 attiny85 chips in parallel. So, basically if the stm32f0 is powered off, I want the attiny85 chips to be in an ever lasting reset state or non-functional state. As soon as the stm32 comes online, and it pulls the IO2 ping high through software code, I want the attiny chips to be functional again and running their specific firmware codes. Now, if the stm32f0 for any reason want to just reset the attinys, a software pull down of the IO2 pin should reset the all 3 attiny together. That's the plan. Not sure if the circuit diagram show below is the proper way to do this. Need some suggestions on how to achieve this goal.

BTW both the stm32f0 and attiny85 is running on 3.3V supply thus making them both compatible in terms of 3.3V logic.


texts: Is it possible to move individual pads of a component separately ? Since diodes and resisters has long legs, they can go over.


texts: Why KCL does not apply in case of this bjt circuit?

texts:
Here in this problem current Io is taken as Ic (collector current), but I think that it must be divided into two parts one part flows from 180k resistor and another enters into collector of bjt, the second part which enters into collector should be treated as Ic.
But it is not the case so where am I making mistake in analysis?


texts: How to drive a sensitive, constant-current, 1MHz resistive device?

texts:
I am currently working with sensors which are mostly resistive (100 to 600 ohms on average) and need to be fed with a controllable bidirectional constant current (from -1mA to +1mA with a resolution of approximately 1µA).

I need to measure the switching behavior of the sensor which manifests itself through a binary change in the resistance of the device : the high resistance state is usually between 10% and 150% higher than the low resistance state.

The switching frequency is up to 1MHz, it may occur at random intervals and is quite fast (~ 1 nanosecond settling time).

Another problem is that the sensor is extremely sensitive to ESD and other voltage surges : a voltage of more than 400mV or a current of more than 1mA will kill it in less than a nanosecond.

I designed a tunable constant current source circuit based on the explanations found in the book Current Sources and Voltage References: A Design Reference for Electronics by Linden T. Harrison.

There are several limitations to the design :

first, I don't really like using 15V potentials in the circuit as the sensor is super sensitive but the fast/precise op amps seem to need higher voltages. It would be ideal to be able to power the whole thing from a simple 9V battery. There are some op amps working with lower power but they all seem to be surface mount while (at least for now) I need DIP packages for practical reasons.
then, I tried this circuit using a simple resistor to simulate the sensor. When I shorted the sensor with another resistor to simulate a fast resistance change, the current did not settle fast enough (few microseconds) and there was a short but big voltage spike (around 1volt) at the sensor level before it triggered the protection diodes. Ideally, I'd like the protection diodes to never have to trigger
also, there is a huge noise problem : anything I measure in the circuit has around 10mV noise, even with decoupling capacitors everywhere. But this may also be due to my experimental setup.

So my questions are the following :

Is this circuit even suitable for such an application ? Maybe should I choose different components ?
How can I make it work without using a 30V power supply but just a smallish battery ? (I can't find suitable DIP opamps for low voltage operation)
Are there some effective ways to prevent dangerous voltage spikes while the system is turning on/off and when the sensor switches or gets connected/disconnected on the fly ?

Thank you very much.
I hope this topic will be helpful for other people trying to drive constant current resistive sensors that are sensitive to voltage spikes.

EDIT : Sorry for the misunderstanding : I am not trying to actually see the nanosecond switching process, just to detect switching in real time


texts: How to turn Flashing LED into constantly glowing one

texts:
So I have one detection circuit with LED that flashes continuously when something is detected (1-2 sec interval). That's a bit nerving while it happens when you drive, especially at night.

I don't have any option to view or modify the code, so it would be nice if I can "hack" this LED to glow continuously....can I do it somehow with some active components?

Tnx in advance

I don't have any schematics of this thing.
It is a Sensor device that detects when a car is in your "blind spot". So it blinks slowly when something comes in the zone, and rapidly if you put your turn light on....so that's basically a problem for a Cap while it will soften than all the impulses? right?

The LED is packed in a case where just two wires came out, so i need to look later onto the PCB to make it clear if it is with GND or Vcc regulated

And it is definitely a LED controlled with a micro controller


texts: Differences and conversion between encoding techniques (NRZI, Manchester, MLT3)

texts:
I'm currently reading a lot about different encoding techniques for data transmission, in particular ethernet, fiber (and usb). 10Base Tx ethernet uses Manchester encoding for data transmission. But it is not used for 100Base Tx or 100Base Fx. Instead MLT3 or NRZI encoding is used. I read that this has something to do with the speed (frequency?) limitations of the techniques. But where does this limitation come from? Is it dependent on the media (fiber, copper), the distance between the transmit and the receive side or is it somehow inherent to the applied technique?
Could I maybe use Manchester encoding for a high speed (100 mbps) optical data link over air or for a cable link if the distance between both sides is only some centimeters?
Related to this question: Is there a way to convert encoded data from e.g. MLT3 to Manchester or NRZI encoding? Most ethernet chips for 100 mbps use MLT3 encoding but for my application I probably need Manchester encoded data as input.


texts:
In a previous iteration of a PCB layout, I added a ground plane fill as recommended by many tutorials online (eg Sparkfun). By default Eagle creates thermals to ease soldering to the ground plane, but in practice I still struggled to get good (timely) heating on all my ground-plane pads.

Thus I'm wondering, in the next iteration, either to avoid adding the ground plane (my design doesn't really need one, mostly very low speed signalling), or if I can increase the thermal spacing (or other settings?) in Eagle so I don't create another soldering headache.

(I'm hand soldering the PCBs, no fancy reflow or similar. A preheat of the boards did help ease the soldering issues but still a chore for every ground-plane pad. And my iron is decent enough, although not a premium one)


texts: How do I put a high-speed pulse through a digital logic chip?

texts:
I have a system which uses a 3ns pulse to trigger some downstream circuitry. When I hook up the trigger generating circuit directly to the downstream circuit, everything works fine. When I route the signal through an Altera Cyclone V FPGA there is a problem. When I route the signal through a Xilinx Coolrunner II there is the same problem, but it is not as bad.

I can't measure the 3ns pulse well because my fastest scope is 1 GHz (I think the rule of thumb is 5-10x bandwidth for digital signals).

Xilinx Coolrunner II datasheet: http://www.xilinx.com/support/documentation/data_sheets/ds094.pdf

Altera Cyclone V datasheet:
https://www.altera.com/en_US/pdfs/literature/hb/cyclone-v/cv_51002.pdf

The signal is just going in the logic chips and coming out, it is not being manipulated at all.

I had a guess that the input capacitance of the logic chips is the problem, but the Xilinx chip has 10 pF vs the Altera 6 pF, so it doesn't make sense that the problem is worse on the Altera chip.

What settings or circuit parameters affect putting fast pulses through logic chips? I'm expecting to hear things about drive strength and timing constraints but I am not sure and have never messed around with those things.

Thanks in advance, and any feedback on my question asking is appreciated as I am new to stackexchange.


texts: Trying to plot input and output resistance for a single BJT in LTspice

texts:
I'm trying to plot a single NPN transistors's own input and output resistances in common emitter configuration looking into the base from input and emitter. I showed below with arrows that the plot I'm trying to achieve is how the input impedance and output impedance varies with Vbe:

So the collector voltage V3 is fixed at 5V. The input voltage V1 = Vb is fixed at 1V. And what actually varied in DC sweep is the emitter voltage Ve. So this causes the Vbe to vary between 300mV to 900mV as follows:

To see the dynamic input resistance the green plot is D(V(Vb))/D(I(V1)); and for the output resistance(seen as shown in the right arrow) it is D(V(Ve))/D(I(V2)).

Is this way of plotting correct?
The green plot is almost zero regardless of Vbe. Is that expected?

And here below is if I don't use derivatives:

I'm confused which plots really represents the input output resistances.


texts:
So I'm trying to use a zener diode to limit the voltage across a capacitor - specifically, to 2.2V.

As you can see, I'm using a 9v supply. The zener is in series with a resistor - either 100 or 100k, can't quite remember which, didn't make a difference though. In parallel with this is a 16V 2200uF capacitor in series with another resistor, also 100-100k iirc.

There's a schottky to the left (in series with the zener) to prevent capacitor discharge, as well as a resistor in series with all of them (this was

simulate this circuit – Schematic created using CircuitLab

added later - had no effect).

As you can also see, the capacitor voltage is well above 2.2V, at least 7V and counting. The zener seems to be having absolutely no effect on the circuit. I've tried it with multiple ones - you can see the packet, it specifically says zener voltage 2.2V. It's definitely not a problem with frying the zener, since I have a very high resistance in series with it. What on earth could the issue be?


texts: How do I build and use my own VHDL library?

texts:
I am trying to create a components library in VHDL. I have many .vhd source files with different components. Ideally I would like to be able to instantiate them in a design using the same method as a standard library.(or similar)

example:

library my_lib;
use my_lib.something.all;

And build a design using these components structurally.
Ideally I'd like to keep these as separate files because there are attached custom symbol (bds) files associated.

The symbols only matter when using Active-HDL (10.1) Being able to pull these files in and use them in the block diagram file would be great!

I would be using Aldec Active-HDL(10.1), Xilinx Vivado(2014.2), and Altera Quartus (9.1 web).

Any help would be greatly appreciated.


texts: Negative Voltage Generator for Low Voltage ( +1V ) Input

texts:
I am working on an analog circuit. I can only use a +1V power supply. My design requires a negative rail, so that my level shifter will work.

Attempts:

  I have already seen Build Your Own Negative Voltage Generator
  and I cannot use this because a diode would eat up 0.7 V. A Schottky would still eat up ~0.1 to 0.3V.

I need some way to get a near perfect way of converting input +1V to a ( -0.9 to -1 V ) output.


texts: Having trouble uploading code to TM4C123GXL from Code Composer Studio on Mac

texts:
I am using a Mac to develop a program for my TI EK-TM4C123GXL board. However, I am having trouble actually uploading the code to the board. I keep running into the errors below. I copied the header file for the board to my project but still no luck. I have considered running parallels for windows but I would like to avoid that. I think it is possible to upload through Mac since I am able to successfully upload a sample project through Energia onto the board

CORTEX_M4_0: GEL Output:
Memory Map Initialization Complete
CORTEX_M4_0: Error initializing flash programming: Cannot read 0x400FE000: data is not present
CORTEX_M4_0: Loader: One or more sections of your program falls into a memory region that is not writable.  These regions will not actually be written to the target.  Check your linker configuration and/or memory map.
CORTEX_M4_0: Trouble Reading Memory Block at 0x0 on Page 0 of Length 0x4: An error occurred accessing memory
CORTEX_M4_0: File Loader: Verification failed: Target failed to read 0x00000000
CORTEX_M4_0: GEL: File: .../.../Debug/example.out: Load failed.


texts: When does it matter whether I use a carbon composition or metal film resistor?

texts: I'm struggling to understand the practical difference between carbon composition resistors and metal film resistors. From what I've read, metal film resistors tend to be available in more precise tolerances than carbon composition ones. Other than that, are there any differences between the two?


texts: Using a DVD diode to create a mag-lite laser

texts:
So, I decided I wanted to make my very first foray into some basic electronics. I decided I was going to attempt to make a laser mag-lite, as per this hack here. The steps seem pretty straight forward, so I figured it would make a good first project.

I wound up getting (not thinking about possible differences) the laser diode mount for the DVD reader in the XBox 360. I'm now in post-mortem mode. I extracted the diode with no issue, and through some trial and error I figured out the correct 2 pins (out of four on this diode). Once I got those extended and plugged into the mag-lite, it glowed red for a few seconds, then I started to smell some ozoney-smelling "burning" and then it went out, and now it is apparently dead, and will not light again.

So I'm looking for confirmation/input why it failed, as I have my theory. My working theory is that since this was a "reader" diode as opposed to a writer, it has a much lower energy usage... and so the 3V of the mag-lite batteries were way too much for the poor little diode, burning it out. Is this a likely theory?

If so, would the speed of the burner (16x, etc.) being used make a difference? I don't know if the laser is any different based on the speed or if that just indicates differences in the speed of the spindle and the lens actuators in the laser assembly.

As one related question, in project directions for this kind of project, most of them talk about "finishing" the end project with a laser control circuit. What exactly does the LCC do?

P.S. If someone with the rep could maybe create and tag this Q with the following tags: dvd, mag-lite, post-mortem I'd appreciate it.


texts: How to connect a microcontroller to PS/2 port as the PS/2-keyboard?

texts:
The voltage of output signals of my CPLD MAX II board is 3 volts. Can I connect this board to open collector of PS/2 motherboard-MCU?

So, if I want to send a "zero" signal, I'm sending "one" to the transistor base, right?


texts: What special problems are there if I use two radio modules on the same board?

texts:
I have to develop a project that basically receives and sends data on a Bluetooth LE module, and then changes the stream a bit and re-sends or receives that information on another radio module in the same case. The frequencies will be different. The Bluetooth needs to only transcieve a few feet, but the other frequency will have a somewhat longer range, probably 2 to 4 miles.
I plan to have the modules physically on the same PC board, but on opposite ends. This will be in the US and possibly Canadian and EU / UK markets later.

I plan to use a 4 layer PC board of about 4 x 3 inches. It will be powered by rechargeable Lithium battery so I need to to run it on about 3.5 to 4 volts.

I had planned to use a PCB antenna for the BTLE but maybe an attachable antenna to the module for the other radio.

Are there many special issues I'll need to look out for when using two radios at once?

What other gotchas will I have to look out for? If I use modules that are both already certified with the FCC will I still need to receive intentional radiator certification? or just passive radiator?

I don't believe this is the same as this question this question because I'm going to use a lower frequency for the other radio, possibly the ISM bands.

There will not be two Bluetooth modules on the same board.


texts: Scattering Parameters and different load

texts:
I am somewhat confused as to the correct usage of s-parameters. Looking at the problem statement below, would the S-parameters given need to be "transformed" due to the load impedance being different than the reference impedance for calculation purposes?

In other words, can calculation be performed using the given values to find voltages or power at port 2 directly or do the values containing a_2 or b_2 need to be "transformed" to the correct reference impedance?

I hope this makes sense. I have skimmed various literature on the subject but most seem to only deal with matched loads, perhaps someone could clarify or guide me towards literature which deals with such cases.


texts: Transformer has continuity but no power on secondary coil

texts:
Background: Electronics novice, attempting stereo amplifier repair for educational purposes. Amp (Pioneer VSX-519V) blew when the input was removed while at high volume.  Careful visual inspection does not sight any damaged components.

Am in the process of learning how to check a transformer.
The first two wires (black/blue) on primary have continuity, 1.7ohms, and 110v AC is present to the terminals that supply power to the transformer.  There is no voltage present on any of the output terminals.

There is a second set of thick wires from primary coil:  three wires (yellow-red-yellow) that have also proper continuity, but no voltage.

The secondary coils have two groups of three wires, and one group of six wires. Each group has continuity, and expected resistance's, but there is no voltage (AC) present anywhere.

There is no continuity between primary and secondary windings.

--

Question: based on the above, does this transformer have a problem?  I do not presently understand why all the other readings look good, but I have no AC voltage on any secondary windings.

UPDATE:

When the transformer is taken out and tested on the bench, it is fine. (that was a good lesson).
When the transformer is installed, something else is "tripping" and cutting power to the transformers primary coil during startup.


texts: Switching circuit transistor NPN, load has voltage and current though transistor is off

texts:
I am confused about the switching of this circuit. I can control the V1 input line. Output line is R4 load line. My Vbase (V1) is 0V, and Vbe is 0V. Transistor is off and collector should see 0V. That is the graph which I added. But, the 5V still supplies voltage and current to the R4 load.

How can i make this switching circuit? In this even if its off I see 5V on R4 and current.

Some other scenarios I tried: remove R3 100ohm. In that case there is 5V and 5mA on R4 which makes sense.
Another case: remove R4 and have R3. In that case I see 5V across Q1 and no current. But there is still a potential difference that my device input will be able to read correct (despite no current)?


texts:
I have a bit trouble here. I need to have a bluetooth device (preferably cheap) to be placed on my room. Then I want my buddy phone to pick up and pair with that bluetooth device. I have developed a program for Android that is basically to check if the phone is paired to the unique MAC address the bluetooth device have. The rest of the stuff will be handled by the program on the phone.

The trouble is: I can't find any bluetooth device that could run itself on a certain voltage (I dont mind any since its on a PSU) What I've tried so far is the USB Dongle. It won't work without being connected to the PC whatsoever. By it won't work, I mean I can't search for it in my buddy phone when it is not connected to a PC. Another thing is an A2DP Bluetooth Dongle. It works, but my buddy phone also goes to silent since all the audio output goes to the A2DP.

Anyone can help me find a bluetooth device that can run itself? I don't need re programmable stuff since it will be used only for verification.

Thanks in advance.

EDIT: "Questions seeking recommendations for specific products or places to purchase them" I never asked for places to purchase them, please re-read.
I don't know what's wrong with the question. My goal in this question is just to find what works by sharing what didn't works to me. If I already known that "tiny board" thing is a HC-05 or in other name a Bluetooth Module or if that thing will work, I wouldn't ask. Just now I also discovered that they did include one of those HC-05 inside of my toolbox.


texts: What component should I start when soldering multiple components?

texts:
I'm creating a PCB and this will have an STM32 MCU on it.

Just like this picture, my custom PCB has

STM32 MCU LQFP
USB connector
BGA QSPI memory
SMD crystal 32kHz
Buck converter QFN
Sensors VFQFN, SOIC
Pin Headers
0402, 0603 metric chip resistors and capacitors
ELECTROLYTIC CAPACITORS, height 5mm

Since each component are packed to each other (it's a small PCB so each of them is quite close like 0.8mm),

I'm concerned about which component to start solder. If I start soldering pin headers, I think these will make a hassle to solder chip resistors nearby.

I'm curious; which part do you start solder in a smart way so that you don't mess up or damage nearby components? Thanks for your answers.


texts: USB charge controller avaliable for hobbyists?

texts:
I'm interested in creating my own USB charger. For a basic circuit, I obviously can short (through a resistor, for safety reasons) between D+ and D-, creating a DCP, hence letting the device draw 5V/500mA from a circuit built around LM7805 (with safety precautions).

The question is, is it now, as of 2018, more advanced charge controllers are available to the general public?

For example, there are modules available from various Chinese manufacturers, built around uP9616, which supports QC. Using a complete module, obviously takes out all the fun in building, not to mention lack of features I'd like to have (V/I display at output). I've been searching for days, but I cannot find any IC available to the general public. Am I missing something or should we accept 5V/500mA?


texts: Why do emitter-degeneration resistors linearize an emitter coupled pair?

texts: Is there a mathematical derivation of the following curve for an emitter coupled pair with degeneration resistors? I can't seem to find anything online


texts: I'm trying to build a circuit that gives the user the option of using the functions of a particular IC or not. In this case, the LM1881N which is a sync stripper. It is fed a composite video signal, removes the video information and outputs a composite sync signal (csync) which will then go to a monitor. I want to have the option of switching between composite video and csync but I'm unsure of the simplest method of switching. I've considered a DPDT switch that will bypass the IC and send the composite video signal directly to the monitor but I'm not certain if this will work or what possible ramifications this option may have.


texts: What is the physical difference between a 12V and 24 DC motor?

texts: I've read the answers given for this similar question and they compare the performance of a 12V and 24V motor based on the power relationship (for the same mechanical load, twice as much current is drawn for the 12V as the 24V motor). However, I'm trying to understand what physically must change in a motor's design to enable it to operate efficiently at 24V versus 12V or vice versa?


texts:
I read the Christophe Basoo article The TL431 in Switch-Mode Power Supplies loops: part II
About how to choose the resistor I have some questions I would like to ask.
On page 13 and page 14 (Watch the LED series resistor value)
There are my questions
1.) Why the VTL431 voltage is 2.5V, how to know this value

2.) I can't understand the equation(25), what is this sentence meaning.
Maybe is my English skill is not good so I can't get it, can someone explain it to me?


texts:
For my phone I want to wirelessly charge my devices as fast as possible using the cigaret socket (Automobile auxiliary power outlet).
I bought a wireless charging pad which on the back states.

input: 5v = 2A  output:5w
input: 9v = 2A / 12V =1.5A  output:10W

Now I found a plug for the cigaret socket that says (12W/2.4A) How do I know if this makes it possible to charge at the highest speed possible?
The socket is 12 volt so I guess the interesting part is (12V =1.5A  output:10W) is 2.4A good in this case or is it to much?
note: im absolutely clueless when talking about electricity so an eli5 explenation would be great.
I thought watts = volts * amps So why does it say 12V = 1.5A  output:10W


texts: How does this circuit with three transistors work?

texts: I don't understand how this circuit works. Its a clap switch circuit with transistors. I would appreciate if someone could explain how the current flows through the circuit and which transistor turns on or amplifies the current to turn on the LED at the end when the piezo detects sound. What i mean by this is the path of the current when the piezo detects sound.


texts: What Is the timer period of a timer of a Pic

texts:
This is causing a bit of confusion to me. I'm assuming that timer period of a timer is the time that it takes for an increment of timer. Am I correct?

It works the same way for 8-bit and 16-bit timer, right?
In this case I suppose that if both increment at the same time that the only difference is that one will count till 256 while the other to more than 65500.

Do the timer always count to its maximum value, in the case of 8-bit 256, till it overflows or it depends of the time period that we set?


texts: What does a bad voltage regulator look like?

texts: I have a 7805 5V regulator here and it has a white like substance on it, kind of like when a AA battery leaks acid. Is it bad?


texts: How to choose an inductor for a LCL filter?

texts:
I am trying to make a voltage generator. I used an inverter and it is controlled by a PWM signal. I used a LCL filter to filter the output signal since it is rich in harmonics but in the choice inductance I found a problem, it is necessary that this inductance is of value 3.9 mH, supports a current of 3A and only 2 pins, the problem is that all the inductances that I find them with 4 pins my question is there a problem for me if I use this type of inductor and in the common mode branch are there any undesirable effects on the current or the characteristics of the inductor?

inductance datasheet:https://eu.mouser.com/datasheet/2/400/b82725s2-1527604.pdf

here is the electrical schema:
here is the simulation:


texts:
Imagine the following situation:

'considering that we have the environment of room temperature ..'
EEPROM size: 512 byte.
EEPROM endurance: 100,000 write cycles
logging data: 4 bytes every 3 minutes.

there is endurance wear leveling algorithm which adds 2 bytes for each data
so total is writing 6 bytes every 3 minutes.

which means we have (480 writes per day) or (2880 bytes per day)

so if we cycle these 6 bytes over 510 bytes does this mean that we have:

= equivalent of 51,000,000 bytes (510 * 100,000)

and it 'may' last for around 48 years?


texts: Properly source varying negative voltage using Arduino

texts:
How can I properly source a varying negative voltage using an Arduino? I would like to use the 5V supply pin on the Arduino, scale it down (dynamically) to an appropriate voltage, and convert it to a negative voltage to be used as a negative supply source.

I've seen posts that use the ICL7660 negative voltage converter to supply a negative voltage. I also would like to get as close to 0 volts (a very high negative voltage, ex: -0.1V) as possible.

From my knowledge, there are two ways of doing this:

First Method:

Scale 5V input voltage using digital potentiometer
Use some IC to convert output voltage of digital potentiometer to a negative voltage

Second Method:

Convert 5V input voltage to a -5V using some IC
Scale -5V using a digital potentiometer

Are there any downsides of sourcing the FSR with either of these two methods? What specific components would you recommend? I have a MCP4231 digital pot (but won't work for second method since it doesn't take negative voltage).

The end goal is to be able to source a varying negative voltage (controlled by a digital pot that I can alter using software) without any extra batteries. I would also like to get a good amount of variation between -0.1V and -5V.

I am trying to use the negative voltage to source the Flexiforce force sensitive resistor here (the Vt in the picture below):

Also any advice for a different electronic frontend circuit that provides similar control of the dynamic force range would be helpful!

EDIT

Per @DrFriedParts advice, I have used his circuit to eliminate using a negative voltage source altogether. However, when simulating the circuit and implementing it, I don't seem to get an output different than 5V.

Here is a snapshot of the circuit:

The output is always 5V, no matter what values I change for Rs (the sensor) and Rf (feedback resistor). Am I doing something wrong? Shouldn't I apply a bias voltage much lower than 5V (like 0.5V) so the output will be from 0.5V to 5V?


texts: Can I use the STLink on a Nucleo to program a 5V board

texts: I want to use the STLinkV2 on the nucleo board I have to program an external STM32f4, and I have the SWD pins connected according to section 6.2.4 in the documentation.An earlier unsuccessful attempt to use an ftdi breakout didn't work, but the 5v Vdd could power the board. However, the STLink cannot since it's 3v3, so I need to power both boards.  I'm worried that when I power up the second board I may damage the programmer, since the STLink is 3v3, and Vdd on the target board is 5v. I know some of the pins are 5v tolerant, but I'm not sure which ones, and I don't know how to proceed. My current plan is to connect only ground and the data pins and leave Vdd separate, will this work?


texts: QUCS simulation radio transistor amplifier

texts:
I'm trying to design a small amplifier for AM signals to use before the usual diode-C-R detection (the reception in my area is very poor). I devised a QUCS simulation as below:

The diode and detection circuit is shorted or deactivated because I wanted to analyze first just the transistor output.The DC simulation shows approx the values I calculated for the biasing (1 mA quiscent current, 0,7V bias on the base and 4,5V on the collector) but when I run the AC simulation I get very strange results:
[![Simulation results][2]][2]

Up left is Ve and Vc, up right input (measured at the "antenna") and output (measured at the 2kOhm resistor), low left Vb (base voltage) and low right the input.

I appreciate inputs on how to solve the problem as well as how to design a regenerative feedback for the circuit.

UPDATE: further experimentation made me realize that the antenna can't be floating, it has to be connected to ground. Point is: if I connect it through a capacitor (let's call it stray capacitance) the output gets smaller depending on the size of the capacitor (the bigger the smaller the reduction). If it's tied directly (or the "stray" capacitor is big enough) the input gets correctly amplified but the "positive" part gets squished (negative feedback?):

Can anybody help?


texts: Second Order Bandpass Filter vs Second Order High Pass and Low Pass in Series

texts:
Is using a second order bandpass filter less effective than using a second order high pass filter and a second order low pass filter one after the other?

I tried a bandpass filter to filter out frequencies between 0.5Hz and 15Hz, and found that there was still quite a bit of noise.

Then I used a second order high pass filter and a second order low pass filter one after the other and found that that eliminated more noise than a bandpass filter.

Why would a bandpass be worse than a high pass and low pass one after the other?


texts:
I’m a Jack of all trades sort of guy but have basically zero electrical knowledge..
That being said.. I want to use a live.. real plant...to turn on and off a light. I tried a touch switch replacement but it didn’t meet expectations... touching the soil or the stems would trigger the switch but the actual leaves didn’t work..
Would anyone know of a way to strengthen the signal so it reaches down the leaves? Or of another way to make it happen? Perhaps messing with a proximity sensor?
I have such a lamp...one that I fixed recently, it’s 40 years old and works great.. I replaced the ground lead and the copper foil that it ran to... underneath the soil ..
I looked at the electronics and they were pretty old-school… I was hoping not to have to re-create that but rather use something new  and groovy..
my 1 year old granddaughter plays with it all the time so I want to make her one for Christmas..
Ideas?
Thanks Eric


texts: Does an induction machine actually consume reactive power?


texts:
I have a problem in powering my wireless Panasonic landline telephone. It works on 9v power with a transformer that work on 220v and gives as output 9v and it works fine with this way. I try to power it on 12v battery using a circuit that transfer 12v tp 9v with 1Amp
But the sound of the telephone speaker has an annoying noise i don't know way. So i need a help to fix this problem. I tried to use a capastior for smoothing the DC current but i didn't get any better.


texts: Why diode voltage is equal to source voltage when source voltage is less than 0.7?

texts:
In the constant voltage model
when the source voltage is less than 0.7, Why diode voltage is equal to source voltage not source voltage minus depletion region voltage?


texts:
I'm working on a project and I need a sensor that can measure the temperature (in a room).

Is there any temperature sensor that is easy to use and can provide value through Java API ? Cause my project is written in Java.  (I tried product from http://www.advanticsys.com and found that it is very difficult to use).


texts:
I'm looking for the datasheet for a Sony ILX186K linear CCD sensor I've salvaged from a document scanner. This part was discontinued several years ago and the datasheet seems to be unavailable online through the usual means (extensive google searching). I've also contacted Sony Semicon however they claim to be unable to provide the datasheet due to the product's discontinued status.

Since the scanner I salvaged this sensor from (Epson Perfection 3490 Photo) is not functional, I'm not able to reverse-engineer the interface, however I'm expecting some of the pins to be a pixel clock and read-out gate, based on the information I've found for other sensors. I've traced out the schematic of the original circuit and identifed some of the pins (the analog outputs) but cannot discern with certainty which of the remaining pins are for the (suspected) clock and gate functions.

Whilst I can probably figure it out by injecting some signals in the right places, it would be nice to have the datasheet before I move on. Does anyone have a copy of the datasheet for this sensor?


texts: Why do I get constant DC 2.5V when level shifting +/- 5V to 0-3.3V (LM741 op amp)?

texts:
I'm using RPi 3b+ with ADC (MCP3208) to monitor AC signal (+/- 5V). Since the ADC can't read negative signals, I tried to level shift it using an op amp (LM741).

I tried to make this connection (the supply voltage has been changed to +-15V):

I made a simple voltage divider circuit by using 2 1k resistors from 3.3V of my pi and connected it as the V Ref for my op amp.

I am using this setting from myDAQ:

And what I got from is a constant DC 0f 2.527V:

Any idea what went wrong?

EDIT:

I've changed the supply from 3.3V to +-15V as some of you have mentioned, and my the VREF pin of my ADC now has also been set to 1.65V same as the VREF for my op amp. The result is:

Is it correct to assume that LM741 is bad for level shifting because I am still not getting 0-3.3V?


texts: Value of Green as Multiplier for an Inductor Color code

texts:
I was going through the Internet searching for the Color code table for an Inductor.
The more or less same table which I got is :

I have got an inductor  :

So I cannot find out the Value of this inductor because Green as a multiplier in the table is left blank. Is the Color coding on the inductor wrong? What is it's value?


texts: Which ARM debugger hardware should I used to debug?

texts:
I read here about ARM programming, pag 252, about ARM debug hardware, but I don't understand which hardware physically tools is used in practice.

  ARMv8 processors provide hardware features that enable debug tools to provide significant levels of control over core activity and to non-invasively collect large amounts of data about program execution. There are two broad classes of hardware features, invasive and non-invasive.
  Invasive debug provides facilities that enable you to stop programs and step through them line by line, either at the C source level, or stepping through assembly language instructions. This can be by means of an external device that connects to the core using the chip JTAG pins, or by means of debug monitor code.

Can you show me this external device ? I suppose it is a debugger but how model is used ? After this debugger is connected to a PC, how software is used with this debugger ?

I need to debug an embedded ARM baseband processor.


texts: S-parameter measurement of a 3-port splitter

texts:
I am looking for possible ways to measure s-parameters of a 3-port power splitter (1 input and 2 outputs). It is similar in concept to a wilkinson, but also provides matching and none of the ports are 50 ohms. A parallel matching network would probably be the correct thing to call it. Measurements will be taken on wafer, from 1-60GHz.

There are three options I know of. One is to terminate one of the ports with 50ohms and take 2-port measurements. The second option is to take a 3-port measurement. Since the outputs are symmetric and no odd mode exists, the third option would be to short the outputs to create a 2-port.

The problem is, the two output traces are about 10-20 times the width of a 50ohm line, with spacing near the minimum allowed. If I connect to the output ports with a wide line or taper, I'll have moding and coupling errors. If I connect to them with a 50ohm line, I'll get errors due to the large step in width.

simulate this circuit – Schematic created using CircuitLab

I'm considering placing two identical splitters back to back and taking a 2-port measurement. The outputs of each splitter would simply be shorted together, solving the wide line issue. I have done this in the past with langes, phase shifters, and other structures, but never tried to extract the parameters of one structure.

simulate this circuit

I feel like there's a way to extract 3-port s-parameters from the 2-port measurement, since the structures are mirrored and symmetrical. I have found plenty of papers that reference info from back to back measurements, but I can't find any that try to deembed to a single structure.

Can 3-port s-parameters be extracted from my 2-port measurement? It may not be possible to create a full 3-port matrix, but which s-parameters could be extracted?


texts: 25 W soldering iron not working properly?

texts:
I have a FULGORE soldering iron (quite an unknown brand, isn't it?) and I think it is not working properly but I would like to hear the opinion of experts.

The iron, as mentioned in the title, operates on a nominal power of 25 W, but I have found it quite difficult to use - I think it is not transferring enough heat to the parts to solder.

After letting the iron heat up for about a minute or so, I try to melt solder to the tip of my iron, and it is possible, it just takes a couple of seconds; it is a lot easier melting solder on the sides than on the thinnest part of the tip though.

But then, if for example I wanted to solder two wires together, I would put the tip in contact with either of the wires, and stick the solder wire to the joint, waiting for the wires to get hot enough to melt the solder. This takes forever though, with this iron.

What could be wrong with my iron? Is it perhaps the iron itself?


texts: I'm trying to determine proper circuitry for starting a sump pump, but am unsure of what components I need. Originally was going to just use a relay, but have read suggestions for contactor+overload starter as well as start/run capacitors. Also not sure if this is dependent on what is already provided by the manufacturer, as some of the pumps I am using have thermal protection or pressure switches. The operation needs to be fast on/off.


texts: How to charge a 18650 battery pack with BMS

texts:
I am planning to built a batterypack using unprotected 18650 cells (2600mA) to power a DIY boombox with the TA2024 AMP. The pack will initially be 3s2p (expandable to 3s4p using battery holders that can hold 4 18650 cells). I want to use the following protection module/BMS

http://www.ebay.com/itm/271808179403?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Now my question is if I can just use a 12 volt 2A switching power supply and connect this to the BMS to charge the pack or do I need a more inteligent Li-Po/Li-ion charger.

The battery is:
https://www.fasttech.com/products/1420/10002357/1170800-authentic-samsung-icr18650-26f-18650-3-7v-2600mah

Thanks for your reply.


texts: Tradeoffs for creating higher order butterworth filters

texts: I am working on a bandpass filter to filter the output from a hydrophone. This is my first time designing a filter and using a cookbook from TI, I built a 4th order Butterworth filter with two partial 2nd order MFB filters. The filter is working as expected when tested in ltspice but the rolloff is not as steep as I want it to be. To get a steeper rolloff, I am thinking about cascading 2 or more of these 4th order filters and create higher order ones. Is that ok or are there any tradeoffs for doing so, other than the increased complexity of the circuit? Will the PCB layout difficulty increase? Are there any better approaches to get both a flat response at mid frequency (the bandwidth is only 10% of the mid frequency) and a good rolloff? Is using a Chebyschev optimization instead of Butterworth a better idea for my use case?


texts: Microchip IS1678S Questions - wanting to implement SPP as simply as possible

texts:
I'm looking for a solution to implement Blutooth Classic SPP on a chipset. What I'd like is everything to be on an external chip, so I don't have to run any sort of Bluetooth stack on my STM32 which is my system processor.

The IS1678S looks like it might do the trick, but I have recently been poorly advised by TI on this topic with one of their chips, so I am being a lot more careful before I present a potential solution. The datasheets/apps notes for this device are clearly not written by a native English speaker and some of the things are unclear (or at least are to me).

Has anyone used this device? Is it possible just to hook it up to your micro, tell it [the IS1678S] to go to SPP in Classic mode, pair it with am external bluetooth node and have it send raw data to and from your own micro to an external unit such as a laptop? The kind of thing you can do with things like the old Bluegiga BT modules such as the BT121 and older. I think the term cable replacement is sometimes used; I'm looking for a wireless UART basically.

The really important thing is that I don't need any sort of Bluetooth stack on my STM32.

Please note I cannot use a module on this application, this is why I'm looking at an SoC like this.


texts: How do I wire LED light based zone for DALI dimming?

texts:
I understand the concept of DALI but I’m having problems understanding how to wire a zone.

Let’s say one of the sections of my living room will have 5 x 5W /350mA LED downlights that I would like to dim.

Do I need a DALI driver per fixture and group them? The cheapest I could find on Amazon costs 30€, which means dimming of 5 fixtures would cost me 150€?

Or I can get a DALI driver with 60W (like this one) and wire 10 x 5W LEDs for just around 130€?


texts: What happens if I use a DC adapter with a15v output with a PC monitor with a 14v rating?

texts: I have a PC monitor with a 14v rating but it's original DC adapter  is broken. Can I safely use a similar DC adapter from a similar monitor, but with 15v output instead? How likely is the 14v monitor to suffer a burnout?


texts: I live off grid. My question is this. I run off a 3000 watt generator and my next step is this. Run a generator to a battery bank charger overcharge protected. Then to 10 deep cycle AGM 12 volt batteries, then to a 5000 watt 12 volt inverter and from there to my cabin. Will this work to save on fuel or should I look for a better plan? any suggestions would be appreciated.


texts: Identification of unknown device with a coaxial connector

texts:
I would be interested to know what this device is, if anyone can identify it?

The screw fitting at the base is just a coaxial fitting and there appears to be nothing much on the inside and no visible way of fitting anything. It's copper plated so no heat has been applied. Possibly army or air force, and I am guessing from 1950s - 1970s. It's about 150 mm long


texts: In current mobile phones, what are some specific techniques that prevent handling noise (rubbing, jostling) from being picked up by the microphone?

texts: I've noticed that when using my smartphone the vibrations from my actions aren't picked up, or are picked up very faintly by the microphone. I've worked quite a bit with microphones and I know it must be a non-trivial problem. Does anyone have experience in this arena?


texts: UL certification and laser tag equipment

texts:
We are a 32+-year-old laser tag equipment company. We purchase parts overseas and assemble them in the US and have hundreds of installations all over the world.

We have been told by 1 location that they are required to have all equipment UL certified.  All of our charging bricks (any cord that plugs into the wall) are UL certified but the laser tag suits and targets do not have a UL sticker on them; if the brick is UL certified is that acceptable?  All of the equipment is low voltage. The suits run off a battery that is plugged in at night to charge.


texts: Vbus pin Hardware connection on STM32f407 Discovery board

texts:
I have a wired mouse connected to STM32F407 discovery board. Could you please let me know what is the hardware connection required to achieve this setup? Should pin PA9 needs to be connected to something on the board and is there any way to call the eventcallback function. My main issue is that the wired mouse is not sensed by Vbus. Its voltage is 0V. Could you please help me on this?
I debugged the code. the  USBH_UserProcess  is not getting invoked when the code is run.Could someone please let me know as to how to invoke this function?


texts: Unexpected Output from Widlar Current Source Simulation

texts: I am trying to design a Widlar current source to drive an RC circuit/IC 555 timer. I am having some trouble simulating the current source correctly. I am using LTSpice IV and I am using their 2N2907 transistor model. I have checked my calculations twice, but the Simulated Vbe is too high and the currents are all in pico amps where they should be in milliamps. Any help would be appreciated.


texts: Run 12 VDC micro-processor from 480 VAC power supply

texts:
I am trying to power a 12VDC (~3 amps) microprocessor module from a 480 VAC grid power. Can I use a 480 VAC to 24VDC (https://www.automationdirect.com/adc/Shopping/Catalog/Power_Products_(Electrical)/DC_Power_Supplies/24VDC,_3-Phase_Input/PSB24-060S-3)

and 24 VDC to 12 VDC
(http://www.ebay.com/itm/SUPERNIGHT-24Vdc-to-12Vdc-5A-Converter-Step-Down-Regulator-Module-60W-/400611133627)

for proper functioning?


texts: 2.4 GHz versus 434 MHz transceiver for home automation

texts:
I am working on a project that uses an Arduino Uno R3 and will have one receiver and one transmitter. I'm going to use this for home automation within my home in India. I want to know which transceiver would be better, a 2.4 GHz or 434 MHz module? My requirement is a 100 meter range.

Also, I would like to know if I can use an ATTiny along with the transmitter?


texts:
I just stated using Vivado in a new project and would like to put the project files under SVN.

Vivado seems to create all the project files under the project name (say proj1):

/<path to the project>/proj1/
                            proj1.xpr
                            proj1.srcs/
                                       constrs_1/
                                                new/
                                                    const1.xdc
                            proj1.runs/
                            proj1.data/
                            proj1.cache/

My question is what are the files I need to put under SVN other than the XDC and the XPR file?


texts:
How do I increase the area of the yellow square (the pad) on the transistors?
The way it is now is just too small for the tracks.
(I need the area to be something like the resistors).