texts: Simple analogue=>pwm circuit with inverting and noninverting outputs

texts:
I was interested in making an analogue to pwm circuit. I want to feed the output to a differential amplifier that will then drive the gates of transistors. The differential amplifier==>isolation transformer==>gates works just fine. I have studied the 555 timer pulse width modulator circuit, and I would be fine using it if not for the fact that I would strongly prefer two outputs that swing from (Vcc, Ground) to (Ground,Vcc). This way I can be sure the push pull differential amplifier goes negative during the "output low" portion of the duty cycle.

Could anyone suggest such a circuit? I thought there might be a way using a 556 timer in a similar fashion, but I do not know how.

EDIT: Here is a quick sketch of what the circuit looks like:

So I want to have analogue inputs, and pwm outputs fed to a pair of differential amplifiers that boost the signal to higher current (I have a one amp dual op amp). This is then fed to an isolation transformer that switches an igbt.


texts:
I was thrown off by a certain website while learning about a op amp Schmitt trigger design. The layout was the same inverting config as the above schematic but gave a confusing answer to calculating high threshold.

Vout=5v high
Vout=0v low
Vref=5v

For the Vout low hysteresis the calc was:

(R2||R3)/(R1+R2||R3)*Vref

For Vout high hysteresis was

(R3)/(R3+R1||R2)*Vref

Vout low made sense, but if Vout high was 5v I would have thought it would be (R2)/(R2+R3||R1)*Vref.

When I checked online calculator apparently I was correct. Can anyone set the record straight? Thanks.


texts: Why are PCIe Completion Timeouts specified as ranges?

texts:
The PCI Express Base Specification specifies four ranges of completion timeouts:

  A:  50 us -  10 ms
  B:  10 ms - 250 ms
  C: 250 ms -   4 s
  D:   4 s  -  64 s

The Device Control Register 2 allows a specific subrange to be configured by the firmware.

Why are the timeouts specified as ranges? 50 us to 10 ms is several orders of magnitude -- how can firmware know which timeout value from the range is being used by the hardware?


texts:
I recently learned about simple AM transmitters and receivers. Now, I'm trying to apply this and expand my understanding by trying to create an AM radio wave powered LED. I'm a very beginner electronics hobbyist, and I had difficulty learning how to do this online.

Basically, my goal is to have an LED turn on when the receiver is tuned to a AM frequency that is active (actively transmitting), such as 1000 KHz. So, when the receiver is tuned an "empty" frequency, the LED remains off, but as soon as its tuned to a transmitting frequency, the LED turns on.

I know free energy doesn't work so I was thinking of using the minuscule voltage obtained from the AM radio waves and amplifying them using transistors and batteries, to power a LED.

I found a bunch of circuits for AM receivers online, but most of them are too complex for me to understand right now. So, I just want to create an extremely simple AM receiver that has an antenna and that can be tuned using a variable capacitor in an LC circuit (also, I don't need to know what frequency it's tuned to, yet. I'll work on that later). The voltage and current is then amplified using BC547 transistors and batteries, which will power the LED. Nothing fancy-shmancy like ICs or comparators or anything, just using very minimal and simple parts. Thanks!!

EDIT 1:
This circuit I created to amplify the low-voltage AM radio waves doesn't work, and I do not understand why. When the simulation is run, the LED remains off and doesn't turn on, even if I use multiple transistors. (Circuit picture is now removed to make space for EDIT 2).

EDIT 2:
Based on JRE's answer, I created this circuit on a breadboard (both in image and in real life). The green resistor is 1Mohm (I only had 100k resistors, so I put ten in series. The website JRE shared said that it's okay to use 1Mohm instead of 8.8M), and the red resistor is 10Kohm.
I used a 9V battery as the power source, but I also tried it with an old 9V battery that outputs 3.8V. Although not shown in the picture, the battery + is connected to the blue rail on top, and the - is connected to the red rail on bottom.

However, I still ran into a problem: the LED lights up and remains lit as soon as I plug the batteries in, and having an AM transmitter (that is at the same frequency as the LC oscillator on the receiver) close by doesn't impact the LED at all. Did I do something wrong?


texts: Measure inductor coil's resistance using multimeter

texts:
simulate this circuit – Schematic created using CircuitLab

Above is the set-up of my simple experiment to determine the inductance of an inductor. The voltage across resistor R (5 ohms) and inductor L (20mH) are measured using a oscilloscope and labelled VR and VL respectively. Therefore, the inductor coil resistance RL is:

$$R_L=\frac{V_L}{V_R}(R)=2\pi fL$$

The experimental value of VR and VL are 1.9V and 2.4V:

$$\frac{2.4}{1.9}(5)=2\pi (50)(20\cdot 10^{-3})$$
$$6.32\approx 2\pi$$

Hence I can conclude that both the resistor and inductor used are in good condition.

What's troubling me is that when I'm asked to measure the inductor coil's resistance using a analog multimeter and compare the value of RL obtained from the experiment. The multimeter shows a non-zero reading of about 3 ohms.

From my understanding,  ohmmeter provided a small battery to apply a voltage to a resistance to measure the current through the resistance, so shouldn't the value measured using the multimeter be 0 ohms since the battery provide DC current? Even if the multimeter does measure the resistance of the inductor coil, why it's significantly less than (by about 3 ohms) the experimental value?

SOLVED:

VR and VL are actually 1.4V and 1.9V, not 1.9V and 2.4V. My mistake. Now it makes sense. The RL should be:

$$R_L=\frac{V_L}{V_R}(R)=\sqrt{(2\pi fL)^{2}+R_l^{2}}$$
$$
where Rl is pure ohm resistance of inductor coil. Inserting the value:

$$\frac{1.9}{1.4}(5)\: ;\: \sqrt{(2\pi (50)(20\cdot 10^{-3}))^{2}+3^{2}}$$
$$6.78\approx 6.96$$
(Difference by 0.18 due to limitation of the precision of oscilloscope)


texts: Flyback discontinuous mode, double voltage over the switch

texts:
Considering the following simplified flyback schematic.

Which has the following voltage current graphs

Why is there 2*Vin over the switch when the switch is turned off? And why is that change to Vin and 0 so intense?


texts: Lead-Acid battery discharged to 5V - how much damage?

texts:
Something in my bike (USB Charger, Hella Socket itself) has made a short circuit leading to deep discharge of Lead-Acid battery.

Battery was down to 5.2V for time counted in minutes.
I've disconnected load sources and recharged the battery using recovery function.

Now battery keeps at quite rock-solid 12.6-12.4V, but I'm wondering how much damage this undervoltage could made?
Was there enough time to create thick Sulfur coating on electrodes?


texts: calculation problem: single ended to differential ADC interface

texts: I got a circuit from the provider of my chip. It's the ACD driver of single ended to differential conversion. However, i cannot get the same value as they marked above the wires [ eg. 0.5(Vin-Vcm) and +/- 0.25(Vin-Vcm) ]. Can anyone help check how they calculate them？


texts: Why do we use PQ and PV buses when solving a power flow equation?

texts: It seems like it would be much easier to just use the admittance matrix and measured voltages to find all the currents and then just use that to get all the power flows. Why not this instead of the PV, PQ iterative solution using Newton Raphson?


texts:
20 years ago, if you opened up a consumer-level desktop computer its heatsink would be a "metal grill" type device place on top of the CPU.
20 years later, if you open up a consumer-level desktop computer, its heatsink will most likely still be a "metal grill" (albeit smaller) type device on top of the CPU.
How come with millions being spent on microproecssor R+D, trying to reduce heat emissions, heatsink design seems not to have experienced any radical innovation. For a component which plays such a crucial role, I am surprised by this. Can anyone help explain it?


texts:
Underwriters Lab allows DC voltages of up to 30vdc in wet locations, per UL 1838

As best I can tell, this spec does not address the issue of grounding, specifically the relationship of the 30vdc to earth/ground/EGC potential (of the building AC lines powering the driver which generates the DC voltage).  In other words, does this refer simply to the potential between the two conductors (in a two-wire cable), or is some reference to ground (i.e. the EGC in the building supplying the DC voltage) implied.   Presumably the latter, since otherwise the 30vdc could have an arbitrary offset from ground. Given that, must the '-' conductor (or either conductor) be tied to EGC potential, or is it simply required that neither conductor be more than 30v different from ground or the other conductor ?   (For example, in an adjustable system, the '+'conductor 30vdc above ground, and the '-' conductor variable between ground and 30vdc).


texts: Pass parameters to covergroups in SV Testbench

texts:
I am trying to create a parameterized covergroup in my testbench, as follows.

covergroup CG (input int id);

    cp1 : coverpoint tb.gen_block_mem[id].var_x[3:0];

endgroup : CG

CG CG_0  = new(0);
CG CG_1  = new(1);

This fails in elaboration as id variable is not a constant, is there a systemverilog workaround for this. So that I can instantiate covergroups just like parameterized modules?


texts: Why is neutral required in three phase charging of Electric vehicles?

texts:
Talking about both three-phase AC as well as DC fast charging (wherein 3 phase AC is converted to DC) in EVs, I think that the 3-phase rectifier represents a balanced 'load'. Therefore I want to know why is then a neutral required? I ask this because I think that doing away with neutral would mean getting rid of the triple-n harmonics. Is my thinking correct?

Here is a type 2 connector pinout for reference:


texts: ADuM1301 digital isolator - PCB layout question

texts:
We are using the ADuM1301 digital isolator in one of our designs. The PCB layout section from the data sheet states:

  In applications involving high common-mode transients,
  care should be taken to ensure that board coupling across the
  isolation barrier is minimized. Furthermore, the board layout
  should be designed such that any coupling that does occur
  equally affects all pins on a given component side. Failure to
  ensure this could cause voltage differentials between pins
  exceeding the absolute maximum ratings of the device,
  thereby leading to latch-up or permanent damage.

Preventing coupling across the isolation barrier sounds logical. However, what do they mean with "the board layout should be designed such that any coupling that does occur equally affects all pins on a given component side"? If I apply a ESD pulse to one of the signals, how would I prevent "voltage differentials between pins exceeding the absolute maximum ratings" by following these guideline?

EDIT: I forgot to mention that we actually experience reproducible latch up on one existing design (which sadly does not follow any design guideline of the ADUM at all). Now I would like to get it right for redesign.


texts:
I would like to use 555 with a relay to make a reliable control circuit.

I use 555 as mono-stable and the following equation does not work:

  t = 1.1*R*C seconds

R = 51 K ohm

C= 220 uF

The output should be high (1) for about 12 sec but it does not. It is high for 6 or 7 sec only!! then it goes to  low (0).

What causes this error? Is the previous equation ideal and I should use practical one?
I noticed that the 7 sec are constant. They don't change. Will they be constant for ever? If yes, I will increase the resistance to get 12 sec then I will continue building my project.
If 555 is not reliable, Would you suggest me any other IC to control time?

Thank you,


texts: Simple circuit analysis with dependent source

texts:
I am a complete beginner in circuit analysis and while reading the book „Circuit analysis for dummies” I’ve come across the following circuit:

What I don't understand is the "Vx" labelling assigned to voltage across resistor R1 and not R1 + R2 as it would occur from the source transformation applied to the Is current source (later in the text it is explicitely pointed out that Va = Vx). Here is what happens after the source transformation:

Now, according to what wikipedia says (https://en.wikipedia.org/wiki/Dependent_source) the transformed circuit is a voltage controlled current source and the voltage across both the R1 and R2 resistors in series is a factor (Vx) to the current source (gVx), but the book says that only voltage across R1 should be the factor. Could someone tell me where I am wrong?

(Update)
OK, all answers and comments so far tell me that I performed the source transformation too eagerly thus losing the original Vx. As far as I know, the first picture in my question shows the so called hybrid model of the circuit. How would the standard one (i.e. with a BJT transistor instead of the dependent source) look like? How would be the R2 resistor connected in such circuit?


texts: What is Full form of hFE of a digital multimeter?

texts:
In digital multimeter, there is a transistor-check function, and there is a term hFE. I do-not know how-to use-it, however, different Websites say it is a measurement  transistor's gain ("the ratio of the Ic/Ib") such as:  https://www.quora.com/What-does-hFE-mean-on-a-multimeter   ;etc. .

But I want to know, what-is the full-form (full-NAME) of hFE?


texts: Forensics: electrostatic detection circuit for lifting "indentations" from documents

texts:
Wikipedia explains that an EDD:

  ...is a specialized piece of equipment [used to] reveal indentations
  or impressions in paper which may otherwise go unnoticed. The
  electro-physical basis whereby an EDD actually works is [...] a
  surface charge effect created by paper-to-paper friction specifically
  in the area where a writing instrument is pressed down into the
  top-most sheet of paper

It involves plastic film, high voltages, messy toner, and by the sounds of it, quite a bit of practice.

Is it still done this way today? Or is it now done electronically? How easy would it be to make a circuit with the sensitivity to detect variations in the electric field made on paper from writing?

(I want to prove that my wife used my favourite notepad, but don't want to get toner over her new carpet).


texts:
I am from pcbgogo, a PCB manufacturer.

We make the PCBs from Gerber files and sometimes our customers send us Eagle files so we need to export the Gerber files from their Eagle PCB file.
Recently when I tried to export the Gerber I found that the Bottom Silkscreen was missing and I don't know why.
My client said that there is a Bottom Silkscreen layer in his Eagle document, but I am unable to get it to export.

Can anyone show me where I am going wrong, or what I am supposed to be doing?

Any help will be appreciated.


texts: Power control circuit that lets MCU shut itself off

texts:
In his way-cool pocket gameboy video, Sprite_TM shows a circuit design that lets a user power on his circuit with a button, where the ESP32 can later shut itself off. I'm trying to understand what all of the passives are for.

The key schematic is here:

.

I see that when the user presses the button, PWREN rises and turns on his voltage regulator shown below. When the MCU boots, it asserts GPIO on pin 102 to HIGH to keep the power on after the user has released the switch. When the MCU is ready to shut down, pin 102 is placed LOW.

The question is what is going on with pin 1032? I think this is a sense pin that lets the MCU see the button press of the power switch while the MCU is active. But why have the additional 10K resistor in series? And why the 1K resistor between VBAT and the switch? Both of these would seem to be unnecessary with the 10K pull-down but clearly there must be a reason for them.

Thanks for helping me understand so I can recreate such behavior in my own designs.


texts: What is 1.27mm ribbon cable impedance for the "ground-signal-ground-signal-..." configuration?

texts:
In different places, for example here (wiki) or here (datasheet) an impedance for the ribbon cable is given to be in range from 100 to 130 Ohm.

I conclude that:

It is the impedance between two adjacent wires of a cable
for the ground-signal-ground-signal-.. configuration the impedance for every signal would be half of that, that is 50..65 Ohm.

Is this conclusion correct? If not, what is the approximate impedance for the given configuration?


texts: Why do these modules not include IPEX and trace/chip antenna connections simultaneously?

texts:
I'm looking a bluetooth modules for a project i'm working on. I want to have a small form factor version of the board be usable with a trace or chip antenna, and have the option of connecting a external antenna for better performance if need be.

However, when looking at bluetooth modules, i've noticed that the ones that include both options have a selection via a 0R link rather than simply having both connected (see pictures).

This is at odds with things like Nordic's nRF52 dev kit which has both a trace and IPEX/u.FL connector available at all times (see picture).

What is the reason for this? I can only assume that this is due to performance considerations but i'm not sure. Ideally, like the dev kit, I want both connections to avoid soldering to make my selection.


texts: Electronic Plant Watering System Circuit

texts:
I have recently seen one of very interesting concepts and it's circuit diagram is present in the page: Electronic Plant Watering System. I felt that it is very useful in our real life also when we go for any tours.

Coming to my problem, I have a small in-house garden of size 130squre feet with lot of plants. I felt that this circuit is suitable for small place but not for large space like my garden. And also I think it takes lot of time to arrange this for my garden.

So, Can anybody suggest me is it suitable for 130 square feet size garden? And also, I would like to use LM555 timer instead of IC555 timer. What are the modifications to be done to this circuit to set up it to my garden? Are there any other circuits which is simple and suitable for my garden?

Kindly let me know your suggestions. Thanks in advance.


texts: I understand kmaps and I know how to make one from an equation in sum-of-products form. For example, w'x'y'z + w'x'yz. But I don't know what to do when some of the products don't contain all variables in play. For example w'x'y' + wx'y'z'. Do you fill in each grid space that contains that product (for the first product in the earlier example, w'x'y'z and w'x'y'z')? Or do you have to do some boolean algebra, or something else?


texts:
I am trying to model a synchronous buck converter, for which I need to choose mosfet models for simulations. I am seeing that it has various parameters out of which length and width is affecting the simulation results.

What should be the values for length and width in MOSFET parameters for simualtions?

How does it affect \$R_{DSon} \$?


texts: Laplace tranfsorm of capacitor functions and initial conditions

texts:
I may be asking something trivial, but unfortunately, I could not find an answer so far.
Suppose an AC circuit. The voltage of the capacitor is given by $$v_C(t)=Q(t)/C = 1/C [ \int_0^t i_C(τ)dτ + v_C(0)]$$
and the current is
$$i_C(t) = C \frac{dV_C(t)}{dt}$$
Their Laplace transforms are:
$$V_C(s) = \frac{I_C(s)}{Cs}+\frac{V_C(0)}{s}$$
and $$I_C(s)=sCV_C(s)-CV_C(0)$$
According to Ohm's Law: $$Z_C(s) = V_C(s)/I_C(s)$$
By substituting, $$Z_C(s)=\frac{1}{Cs-\frac{V_C(0)}{V_C(s)}}$$
It is known that $$Z_C(s)=\frac{1}{Cs}$$  which obviously occurs from the above equation, if $V_C(0)=0, but that is not always the case. Could someone explain this issue? What happens if my capacitor's initial condition is not zero?


texts:
Our purchasing department requested the AT32UC3B1256 and the supplier has a few thousand in storage. However, those trays have a date code from 2009.

While shelf life is normally not much of an issue with integrated circuits, 10 years is quite a number.

I looked for some general information regarding shelf life. For example TI states:

  [...] TI’s standard shelf life for packaged products is two years from the time it was manufactured to the time it is delivered by TI or a TI authorized distributor.
  TI also offers extended shelf life (ESL) of certain products for up to five years of total shelf life from the time it is manufactured to the time it is delivered by TI or a TI authorized distributor Product warranty is measured from the actual shipment date, not the date of manufacture.

According to supplier, the trays are sealed. What would be the limiting factor for shelf life with respect to microcontrollers? May those parts require long tempering before assembly?

TLDR: Should we be concerned about buying a 10-year-old microcontroller?


texts: How much of a CPU die surface is taken by cache memory in modern microprocessors?

texts:
I am interested in how much of the surface of a modern or older CPU's are taken by cache memory ?

Are there any statistics regarding the size that cache memory takes in CPU dies of today ?

Are the schematics of the cpu's available to the public ? From those schematics can one see how much of the CPU surface is taken by various parts of the CPU ?


texts: Power supply for Audio amplifier : high-voltage based watts or high-current based watts?

texts:
So I have these Philips (FW-V355) speakers, and I want to connect them to my PC via AUX or Bluetooth, ofc I separated them from their original old system/amplifier. In order to realise that, I bought an audio amplifier to power up the two 40+40ohms, 6 ohm speakers. It's (SANWU® 50W+50W TDA7492 CSR8635) from Banggood (http:// bit.ly/2Ab3XM3 ) it's relatively cheap and delivers big power (50w+50w) with positive reviews. Yes it's a little bit over powered but I heard it's better to have overpowered speaker than underpowered, and I also want high volume speakers, with minimal distortion. Now the third component to my setup would be ofc, the power supply to power the amplifier. And here starts my confusion, so I'm willing to buy this one from AliExpress (http:// bit.ly/2BfvdWQ), and they have 12V, 10A power supply, as well as a 24V, 5A version. Both deliver 120W of power. I know I'm getting more than the needed 100W of the amplifier, but again overpowered>underpowered. So my question is which one should I buy, the 24V 5A one, or the 10A 12V One?.

I tried to look online for the answer but didn't find a clear conclusion for my specific case, thus I'm writing this post :).
If you need any further informations abt the speakers ,the amplifier or the power adapter I'm using, you have all the names u need, so feel free to look em all up online (I don't wanna get the 'it depends' answers :D), also I listen mostly to pop/hip hop music, so I'm all abt that bass x). I've heard on a forum that bass woofers would do better on a high-current power supply, and tweeters would sound better on a high-voltage one, but I'm not sure how accurate is that.

Thanks in advance for anyone who's willing to share his knowledge and help me out of this situation.


texts: Measuring Transformer Magnetizing Inductance

texts:
I am trying to fit measured transformer data to the standard mathematical transformer model. I have done the short circuit measurement to get leakage inductances and measured DC primary and secondary resistances.  I have read that to measure the magnetizing inductance Lm and core loss Rc you can either use a watt meter or an LRC meter, neither of which I have. So I am attempting to see if I can get these values by placing a capacitor in series with the primary and use the resonance and amplitude data to get the values I’m looking for.  The transformer model I’m trying to match is:

For the open circuit measurement, to simplify the math (and I’ve read this is valid, but not entirely sure) I’m assuming that due to a low voltage drop across Ra and La that they can be disregarded.  This gives the following model:

Solving for Rc based on measured resonance frequency and amplitude, I plug back in to the above to get Lm. When actually plotting the transfer function however, this does not give matching results, only the resonance point is correct.  Solving at different frequency points gives different values for Rc and Lm.
I’m pretty sure I’m missing something, and that a phase measurement needs to be incorporated into this.

So my questions:
1)  Is this a reasonable way to go about getting the Lm and Rc values that I am looking for, or is there an easier way assuming I don’t have the measuring tools described above?
2)  More generally: Since I’m not getting correct values, is it possible to get correct values for unknowns that can be used in a transfer function by solving for them from a single phase and amplitude measurement?

Thanks.

Update
Based on the response from Tony Stewart I’ve tried a much more simple method. I’ve placed a known resistance R at the output of the circuit, and measured across with the scope to get voltage and phase shift.  Then V / R = I, so I have complex current through the transformer. Then ((V1-V)/I) – Zp = Zm. Does this method sound correct? I’ve used it to re-calculate the short circuit primary and secondary impedances (resistance & leakage inductance), results for the resistances which I originally measured with a DMM aren’t dead on but close, off by about 10%.


texts: Optimum placement, PCB routing for bypass/decoupling capacitors and ground loops

texts:
I've seen various answers regarding routing of decaps, wondering which method is optimum for better power distribution and noise immunity:

Another question is, will this routing cause ground loops? I usually don't share ground vias but in this case, I need a bigger ground plane on the top layer:

Edit: This is an 8 layer board with dedicated GND and PGND ground planes.


texts:
As far as I understand, through holes in PCBs are often plated, hence the term PTH. Letting red denote copper, the first figure shows a through hole which is plated, and the second figure shows one that is not. The thick black line is the pin of a component, while the silver denotes solder applied. I can't figure out why the copper plating (otherwise known as the barrel) is needed - can someone explain why?

With through plating:

Without through plating (why isn't this the norm?):


texts: Split Collector Lateral PNP Transistor SPICE Subcircuit

texts:
This question relates to the book Designing Analog Chips by Hans Camenzind.

I need to simulate a simple (one transistor) lateral PNP current mirror:

I am trying to understand how one can model a "split collector lateral PNP transistor" (Q1) using a SPICE sub-circuit.

The book provides a SPICE sub-circuit for lateral PNP transistors (to model substrate currents at saturation, in addition to normal device operation):

Mainly:

* Lateral PNP Transistor subcircuit
* (modeling substrate currents at saturation and normal operation)
* Inputs: 1 (collector), 2 (base), 3 (emitter), 4 (substrate)
.SUBCKT pnp1 1 2 3 4
* dev   <nets>  model
* -----------------
QP11    1 2 3   qp1
QP21    4 2 1   qp2
QP31    4 2 3   qp3
.ENDS

In addition to the PNP device model parameters. (which I am not providing here).

My main question is how do I go about changing the lateral PNP sub-circuit to a split collector type?

I was inclined to simply add an extra port to the Lateral PNP sub-circuit (i.e. c1, c2, b, e) and keep the collector of Q11 as an internal net, then split this net into two wires connected to the c1 and c2 ports, however:

How does one add "wires" to a SPICE sub-circuit (i.e. to divide currents but keep voltages the same). "Wires are not valid circuit elements, transmission lines are, but this seems really overkill.

I also thought about adding 0 Ohms resistors as "wires" but this seems like a rather hacky solution.

Also is simply splitting the currents a decent model for a split collector lateral PNP?

I know I am probably over-looking something or over-thinking a simple problem.

Any pointer in the right direction will help.


texts: Driving a load on negative rail with a positive signal

texts:
I want to turn the LED on when the 5V pulse is high. I expect a simple circuit consisting of two or three bipolar or MOSFET transistors similar to the erroneous one in the image above. I don't want to add and ICs if possible.

Note 1: I'm not powering the LED from VCC, because I have already loaded the VCC rail heavily; I would be draining too much current if I add the LED too.
Note 2: VCC and VEE are referenced to the GND.
Note 3: The LED is actually a LED inside an optocoupler. I need a circuit which responses in 1\$\mu\$s at most.


texts:
I read around that with an anonymous heatsink, you can measure its temperature when at regimen dissipating P watts. Then, (T-Tamb)/P gives its thermal resistance.
Is that meaningful? Can I do this measurement roughly to stay on the safe side?

I'd like to put the probe in these heatsinks while dissipating a certain amount of watts and see if are close to 5°C/W:


texts: Can you really put 2 transformers in parallel connected to a single voltage 220VAC 60hz?

texts: The 10 volt secondary transformer will be used to ATMEGA328P while the 25 volt primary transformer will be used for logic gates.


texts: Determine gain, Vo/Vin, of an amplifier for values of x

texts:
My Equation of the circuit using the node \$V_1\$ is

$$ \frac {V_1-V_o}{(1-x)R_p} + \frac {V_1-0}{xR_p+R_3} - \frac {V_1-0}{R_2}=0 $$

I would like to know how to eliminate or substitute \$V1\$ from the equation (if it's right in the first place!) so that I can combine with the equation \$V_{\text{in}}=-\frac {R_2}{R_1} \cdot V_o\$ (so that I have \$ \frac {V_o}{V_{\text{in}}}\$ and calculate for values of \$x=1\$ and \$x=0.3\$.

Hope this makes sense.


texts: How layout 5cm x 5cm rectangle in KiCad?

texts:
I want to get a PCB made by dirtyPCBs, which has a great price for boards, as long as it fits in a standard size. For example, 10 copies of a 5cm X 5cm board is only $14.

I'm using KiCad to lay out my board, and want to start with a 5cm x 5cm board boundary (edge cuts) so I know what I'm working with and can tell when I start to use up the available space.

What's the most straightforward way to get a rectangle in KiCad that's precisely 5cm x 5cm?

I don't believe there's a rectangle tool, so I'm happy to make it out of four separate lines; but I'm having trouble working out how to get make something 5cm long, perhaps by entering it in a dialog box or something rather than counting little grid dots :)

Is there a straightforward way to accomplish this?


texts: How do these Zener diodes limit the maximum voltage seen by other circuit components?

texts:
This schematic is given in Texas Instrument's AN-1533 Application Note (Over Voltage Protection Circuit for Automotive Load Dump)

On page 4, the author says that the D3 Zener prevents the cathode of D1 from exceeding its maximum voltage of 35V.
Similarly, this same D3 Zener limits the Gate-to-Source voltage seen by Q2 to 20V.

How exactly is this limiting behaviour happening, and what would be the calculation that shows this at a Vin of 60V?
To me it looks like both D2 and D3 will breakdown and end up taking the full load current.


texts: Need help reading mosfet Safe Operating Area graph

texts:
Im trying to figure out the current limitations of a mosfet(SISA18ADN) I'm planning to use to check how much headroom I have.

The datasheet states Continuous Drain Current that it can handle as 12.1Amps at Ta=70degreeC during 10seconds, and 38.3Amps at Tc=25C with no time specification.

But in the Safe Operating Area graph, apparently for DC it can handle less than 0.2A at 10V..? Am I getting something wrong when reading the graph or when reading the specs?

The Safe Operating Area graph is here:


texts:
I'm really not sure if this is the best place to ask this, but I'm working on a project that requires a sort of 'giant pixel' of sorts, maybe about 4"x4", that can either be dark or light, and can maintain that state with low power (or no power at all, if possible, as in e-ink and things like that).

Does anyone have any suggestions as to what kind of component can fulfill this?


texts: Blocking capacitor? Driving 8 ohm .5 watt speaker with microcontroller

texts:
I'm reading Make: AVR Programming. The next project wants me to try to drive an 8 ohm speaker with a pin from the microcontroller.

I'm no EE, but I do know that 8 ohms is not a lot of resistance, and it seems like  we're going to run into problems running too much current through the microcontroller pin.

The book's solution is to use a "blocking capacitor". For some reason, I'm still a bit skeptical this is safe for my microcontroller. There are no resistors anywhere in sight. Here is the page from the book:

Question: if I don't care about sound quality, is this circuit safe for my microcontroller? The maximum current is supposed to be 40mA per pin.


texts: What makes conical coils that good in microwave circuits?

texts:
Conical coils are often used in microwave technology.

Can someone explain what makes this shape so unique? How does this shape affect parasitic capacitances?

Some conical coil photos:

This is NOT homework question. I'm just curious.


texts: Memory design with 4 256K X 1 Bit IC's to a Z80

texts:
I have a couple of memory IC's lying around (16 of them) which I would like to use in my homebrew Z80 project. These IC's were produced by Samsung in 1988, the KM41256A 256K x 1 bit. I realise I can't hook them all up as the Z80 can't address more then 64K and I'd still like a rom and some IO.

However, I thought I'd use 4 of them to create 16K which seems enough for a test setup. I know I'd need a line decoder for the chip select pins but I'm a bit at a loss how to approach this.

My questions:

First and for most would it even be possible to use these chips? Or
do I need chips with a word equal to the data width of my Z80
(surely this can't be true?).
How much address lines would I need to address 16K of memory?
Which line decoder would I need 2-to-.... ?

I hope I phrased the questions in such a way that they're understandable. I'm completely new to this type of design. I've tried to read up online as much as I could but these matters left me confused.

Thanks.


texts:
Is feedforward used in boost converter operating in DCM mode?
I saw some examples where feedforward is used to control boost converter in CCM but not DCM mode. So I am wondering if it can be used in DCM mode.
Thank you.

Here is an example of boost converter operating in CCM using feedforward:

Link: page 143


texts: How thick (or thin) is the die/wafer inside an IC?

texts: There are packages as thin as 0.3 mm (maybe even less), so I was wondering how thin the actual die/wafer inside them are. I guess the package top and bottom will also need a certain thickness to be useful, so how much is left for the die?


texts: If I look at a signal in its frequency domain, are there some guidelines by which I can tell how that signal looks in the time domain?

texts:
I was studying the Laplace transform and the Fourier transform, and I can't figure out if there is some intuitive way of finding out how a signal looks in the time domain if we know its frequency domain. For example, are there some rules like:

If there is a frequency whose amplitude is approaching infinity then....  (like when there are poles on the imaginary axis in the s plane, like this:

If the frequency graph is decaying towards 0 then....

Because from what I'm reading about the Laplace transform, the position of poles and zeros gives me a better understanding of how the frequency response looks like, but what do I care what it looks like if I don't know what the time domain will look like?


texts: Reduce to line level from 8 ohm, 6 w stereo

texts:
I had a look at another Exchange question, and couldn't quite understand.

I have a set of cheap speakers, 8ohms each with a combined output of 6 watts.

If sqrt(6w/8Ω) = 0.866 v, and the post says line level is approximately 1 volt, what should my amperage be?

How can I calculate for an appropriate resistor?

I have about 10 150Ω resistors at home... will wiring them half and half between speakers attenuate the signal? How many do I need of each?

EDIT (CLARIFICATION):

I want to know how to calculate the resistance needed to reduce a powered signal (6w) to line level.


texts: Pass DC through (passive) highpass filter?

texts:
Background:
I'm a student, working on my final year project.  I am designing a front end for a software defined radio.  We have an IF frequency at 36Mz (and a BW ~8MHz).  We are bandpass sampling this signal at 29MSPs (our signal falls in the 3rd nyquist zone).  The ADC takes a differential input and requires a common mode offset.  This DC offset is provided by a differential op-amp.  We need to filter out the out of band noise from the op-amp and the previous stages before feeding it into the ADC.

In order to achieve this filtering, I have cascaded a bandstop filter (stop bands are at ~1MHz and ~29MHz) with a lowpass filter (cutoff at ~40MHz).  This filters out the out of band noise above 40MHz, as well as below 29MHz while still passing the common mode DC offset.

The problem, is that the bandstop filter requires large inductors (6.2uH).  These inductors all seem to have very low self-resonant frequencies and are thus basically useless.

The question:
Is it possible to design a highpass filter, that also passes DC?  Or is there some other strategy to let the common mode offset pass through my filter, but still cut out the noise in the 0-30MHz range?  Or, to design a bandstop filter with (much) smaller inductors?


texts: Theoretical max rate of input capture for a USB mouse and possible hardware limitations

texts:
I apologize in advance if this is not the correct forum for this question or if the question is too broad to answer.  My background is in computer science and I work mostly in Java middleware so this is a bit out of my area of expertise.

I'm interested in capturing input from a mouse on a Linux operating system as quickly as possible.  Let's assume I am working with a USB 3 mouse on conventional hardware (64bit i7 16gb ram).  Can anyone recommend a way to formulate with some certainty the maximum input capture rate? Or if that is not possible could someone point out the most likely software, hardware, or physical phenomena that would act as the max limiter?

Some of my initial thoughts so far as to the max limitation

The smallest unit of time the system can keep
The transfer rate of USB 3
Speed of the physical signal sent from the mouse


texts: Choosing capacitors for Microwave RF application

texts:
I've recently been given a project to lay out some PCBs which will contain a few Mini-Circuits RF amplifiers, and their associated biasing components. However, since I need to have several stages of amplification, I need inter-stage AC coupling to prevent the bias from each amplifier affecting the other amplifiers in the chain.

That said, I basically therefore need to chose series capacitors for coupling signals in the ~1.420 GHz range, and I do not really have the experience to know what I should specifically be looking for in terms of specifications.

I know I need capacitors with high Q, and probably X7R or NP0, ideally low insertion losses (S21), but I'm really feeling my lack of experience and knowledge in RF when digging through datasheets.

What are the relevant considerations for choosing parts for this kind of application?


texts: Amplify speaker with 9v battery and one transistor

texts:
I started electronics recently and I'm trying to make the most basic mp3 amplifier. I try to amplify the music from my phone to the speaker. My phone already amplifies the sound when I connect it directly to the speaker.

I saw that people mostly use lm386 chips but I don't have one yet. So I retrieved some transistors (F3NK80U, J13009) to amplify the sound from the mp3 player to the speaker. My first questions are :

Are those NPN transistors ?
Are they suitable for audio ?
Are they in TO-220 format and the pins in this order : BCE

I read that the base changes the resistance between the collector and the emitter. So should I connect my mp3 player to the base pin, the 9v battery to the collector and the emittor to the ground ?

Finally, what resistance/capacitance should I use ?


texts: Can somebody identify this keyed connector?

texts:
Pin pitch is 0.079" for both row and column.

This looks like the two-row equivalent of the Molex Pico-blade.

I'm doing some rerouting for the power and data cables on my xbox 360 and I'm unable to figure out which digi-key part I need for this.

Namely, I'm looking for this connector's mating connector, but if I can figure out which series this, finding the mating connector would be significantly easier.


texts: What's the relationship between bandwidth and symbol rate for a modulated signal?

texts: I was hoping somebody could help me with understanding the relationship between the bandwidth of a modulated carrier signal (say using QPSK) and the symbol rate(s) you can transmit across a channel. If anyone knows links to helpful visual representations please link them here. Thanks in advance.


texts:
I'm working with a strip of WS2812B LEDs (https://www.adafruit.com/datasheets/WS2812B.pdf), and am seeing something I didnt expect. When I write out my data to the LEDs I'm seeing the last colour I sent appear at the END of the strip (furthest away from data input). I would have expected the LEDs to shift each byte as they come in so that the last thing the micrcontroller drove out would appear on the LED closest to the micro.

Is this not how these are supposed to work? From what I'm seeing, it would have to shift each consecutive byte by one more LED.


texts: Electro magnetic interferences (EMI) generated by power circuit reset low voltage integrated circuits (ICs)

texts:
The main question here is (explanation will follow):
Is there a way to filter out low voltage oscillations (>10MHz) on pins that have to stay high for the system to function? Oscillations are induced by EMI emitted by power circuit during relay bouncing). RC filters 100Ohm/100nF did not work. Traces are ~50cm long.
[Explanation]:
I'm currently struggling with proper EMI filtering for the low voltage control circuit that is responsible for switching on/off high voltage capacitors using relays.
I realize that the low level part of the circuit has a bunch of design flaws (e.g. the logic signal between uC and shift-reg could've been arranged into a differential pair). But currently I'm trying to figure out a way to modify the circuit with as little PCB modifications as possible.
Here is the essential part of the setup:

Power circuit is operating on fairly high voltage and current, but I don't care about the quality of power of this circuit, moreover I cannot modify it.
The only issue I have to deal with looks like this (the description will follow):

Yellow - Power circuit voltage
Blue - Power circuit current
Green - logic signal (EN or CLR, see schematics)

Green signal represents EN or CLR; it is a CMOS 3.3V open-drain pin. When voltage falls below certain treshold (I guess 1.8V) it is no longer high, therefore the shift-reg resets. It cannot reset.


texts:
This may be obvious to some, but not to me. I am an IC design engineer, as such I rarely do any practical work.  This morning I had to fix some electronics which were custom made by a third party for my company. On removing the front panel I saw this gray box clipped to a bundle of wires (images below), I have no idea what it is or what it does. After 10 minutes of fruitless googling for "gray box clipped to wires" I find myself here asking this question. The inside looks like some type of metal or ceramic. I thought it might be magnetic but it is not.

So can anyone identify it and tell me what it does?

I fixed the problem, which was not related to the wiring.


texts: How would I draw A'B' + B'D + A'CD using only NAND Gates?

texts: I keep getting stuck when trying to draw this out. Mainly because the NAND Gates we are using are 2 inputs one output.


texts:
We have a rather expensive laser diode which is prone for ESD damage. Usually, during transport and usage it either has a metal bar bridging anode and cathode or has to be connected to the power supply to prevent charge buildup. Now, this diode had been moved into a case, with a SUB-D connector connecting it (and other vital parts inside the case) to the controller. The case usually is closed, and thereby preventing the user from attaching and removing the metal bar as long as no power supply is connected.
Therefore, we need another way of protecting the diode from sudden death due to ESD. What kind of options do we have for that? I would imagine an internal relay which either connects anode and cathode directly if no power is applied, or disconnects them and connects the diode to the power source when voltage is applied, but are there simpler options?
The driving voltage usually is around 5-15 V DC, and we have a maximum current of 2 A.


texts: I'm repairing a Nintendo switch dock and I found that a ferrite bead has blown.  The problem is that I don´t really know how to identify the ferrite bead that I need.  Can anyone help me? If it helps the IC receiver is the STDP2550.


texts: How to find a threshold power to activate passive RFID tag?

texts:
Is there any minimum power which a low frequency RFID tag needs to power itself? I have yet not found this information from any datasheet of several RFID tags.

I have a simulation, where I know how strong the magnetic field produced by my antenna is at a given distance, and I would like to estimate the detection distance.

For example if some tag could power itself in a 2 mT field, then I could check at what distance the magnetic field would still be strong enough to power the tag.


texts: ESP32 Wroom doesnt boot up directly after USB power up, however it works fine if you reset it one time there after

texts:
I have been working on a battery powered ESP32 board for the Institute I am working for. It had some other issues relating the voltage regulation circuit that I implemented. Those are solved now after I added some 100uF electrolytic capacitors to the input and output of the LDO. I will change the voltage regulator to a more modern one, that works with ceramic decoupling capacitors in the second prototype.
However one problem remains before I make the order for the second board. The Esp does not boot up, if you dont reset it one time after power up.
I am thinking that this may have to do with voltage regulation again, though I am not sure. Sadly I am not allowed to share the entire schematic but I can say that the parts regarding the ESP32 is the same as those open source ESP32 devkits. And the battery charger and the voltage regulator are as shown below. As I have learned recently the HT7333 is rather slow to adjust itself when a sudden change in voltage on its Input happens. Maybe this crashes the Esp on power up? If that theory is correct then the issue should be solved when I change the LDO. If not what would you say may be the cause of this?

In any case, any help or sharing your experience on the matter would be very appriciated! Thanks in advance.
Edit: The board boots properly if you hold the reset button for 1-2s on power up.


texts:
I'm trying to design a preamp for this electret mic.

I kind of pieced this schematic up from something I have found on the web.

Does that look ok? I'm going to sample the output with an ADC (internal in an MCU), and run an FFT on it.

The opamp is a rail to rail op amp, it doesn't have low voltage offset though, should I care about it?
The IC has 4 op amps on it, should I add another stage or two and lower each stage's gain ? Or should I use the rest as active filters ?

Do I need any filtering or anything like that?

What is the best way to set the gain?

I was thinking of using a potentiometer for R7.

Here is an ac analysis from LTspice:

Here are the LTSpice files for the simulation.


texts:
I want to build several different Arduino projects which use coils, magnets and/or solennoids.  These projects include:

Magnetic door locks
55 lb electromagnets
Magnetic door latches
Relay

I can buy a power supply designed for a magnetic security door lock, but I would rather use my simple 9 or 12 volt wall adapter.

Will I need to add some capacitance for early switch-on power?
Will I need to limit the current after the magnet powers up?
Will I need to add some sort of protection for the Arduino?
Are there other concerns?

How do I build a good power supply for a coil?


texts: Whats the difference between a grid tie dc ac inverter and a normal dc ac inverter for 12 v or 24 v batteries?

texts:
what are technically the differences between a grid tie solar inverter,  which takes as much power from the connected solar cells as possible, on the dc side, to convert it into 230v ac power and a normal battery ppwered inverter, which converts the energy from batteries to 230v ac as required.
What would be the major differences when both inverters would be teared down and the electronic components would be compared on 1 on 1?
How does a grid tie inverter manage to "pull" all the energy possible from the cells? Which component is responsible for that behavior?
Thanks to all those who honestly try to help in advance.


texts: Replacing the thermocouple for a multimeter?

texts:
I bought a no-name but decent multimeter, and it came with a thermocouple. Let's say I broke it in some way. Can I just replace it with any other thermocouple, or is each thermocouple calibrated for one specific model of a multimeter?

I have been looking at thermocouples, eg on eBay, e.g. this one. They write some specs but they don't write which multimeter it fits with?

So does any thermocouple fit with any multimeter (or digital thermometer)?


texts: Part identification in this dimmer switch

texts:
The dimmer in question is a 3 poll LEVITION 600 watt 120VAC 60HZ dimmer.
The three red boxes in the picture below are what I'm questioning. What are those three pieces (and what do they do).

Here are some more pictures of the dimmer switch.

This is how the circuit fits in with the contacts and switch.

Here is the switch front (for anybody that wants to see it)

I have read What are the extra components in this dimmer for?, and it did not help me.


texts: Schmitt trigger inverters or regular inverters for clean high speed data processing

texts:
I made a circuit in which data is passed in from phototransistors (part# PT334-6C) into a microcontroller (part# AT89C4051) serial port via schmitt trigger inverters (part# 74HC14) and a demultiplexer (part# 74HC151).

I do have an option to replace the schmitt trigger inverters with standard inverters (part# 74HC04).

From what I learned, a schmitt trigger is meant to clean up and digitize a signal. Inputs that change in voltage by a tiny amounts when the voltage is slightly above half the supply won't be noticed in a schmitt trigger where as in a normal inverter they may be more noticed because a schmitt trigger requires the input to enter a lower or higher third of the VCC voltage to change output (I think that's the theory).

What I want to know is would a schmitt trigger work beautifully if I had data (of any value) flowing through it at the rate of 115,200 bps? Or are there any properties of schmitt triggers that prevent high speed data flow from working (in which case I'll have to resort to a standard inverter)?

And if there is a better schmitt trigger that is more suited to high speed data in the 74 family of chips, which one is recommended and why?


texts: Charging lithium batteries with solar panels

texts:
Let's say I have a battery pack made from 3 lithium-ion cells connected in a series (making a battery with around 12 volts).
That battery pack has a PCB with balancing function and also protects the battery from over charging, over discharging and short circuit by interrupting the input/output to/from the battery when needed.

If I hook up to the battery a 12 volt rated solar panel (which usually has a very variable voltage, as all solar panels) that doesn't exceed the recommended charging rate of the battery, in my opinion, it should charge just fine because when the battery gets full the PCB interrupts the charging because of the overcharging protection, but i'm no expert so the question is: in theory does this work as fine as I think it does?

If not, would putting some kind of converter to turn the variable output from the solar panels into a proper constant voltage to supply to the batteries, charge them properly (considering the overchargin protection that would be in place)?


texts: Compression and communication power consumption trade-offs

texts:
Let's say I'd like to save battery power consumption when sending data to remote devices connected wirelessly, i.e., sensor networks. One of the ideas may be compressing the data to reduce the number of bytes to send, but the compression process results in power consumption. This compression idea is only valid when the overall battery power saved for wireless communication exceeds the the power used for compression.

I can just guess that the computation power keeps dropping following Moore's law while the communication power still requires good amount of power still.

Do you have research paper, technical report, books, application notes that talk about this communication power and computational power tradeoff? Or any real world usage?
Compared to the power consumed for processing one instruction, how much larger the power consumption for sending one symbol or one byte of data? Hundreds or thousands? Or just tens?
What practical way may be available for measuring power consumption for communication and computation for small devices (micro-controllers)?

Added

I used compression as an example, but I'm working on more sophisticated algorithm to reduce certain kind of information dramatically. I would like to know if the effort is worth trying, in other words, I need to know how expensive to send a data/symbol or whatever the physical layer is sending compared to the price of running the sophisticated algorithm. I don't care about the latency, at least now. I don't care about the physical layer also, I have an abstraction layer with a buffer that I just use to send or receive information.


texts: Newcomer here and a total noob. Ok so coming to the question i am planning to build a battery bank with 18650 cells. I am opting for a 3s4p configuration as its closer to my operational requirements. I want to install a 3s 10 amp bms board without balancing function. Also i shall install balancing leads in such a way that they can connect to 3 individual TP4056 boards with isolated power supplies. First using a constant current source connected to the bms power leads, i will charge the bank to approximately 12.0 volts. Then when the power supply cuts out i want to finish off the charging process throught the TP4056 modules with the goal of obtaining a balanced charge on all 3 cell groups. Will this work? Have i gone horribly wrong and i stand the risk of the whole contraption blowing up in my face? Kindly help!


texts: Use indepenent power sources for Arduino and for breadboard

texts:
I am building a breadboard circuit to be controlled by Arduino. The circuit consists of about 20 bright leds simulating a vehicular lighting system (ten leds for headlight, 4 in taillight, 3 for each directional light, or something like that).

Since these leds would draw up to 500mA @ 6V, I would like to power the breadboard from a wall wart.

But, at the same time, I would like to run my Arduino from USB power, so that I can keep updating my logic until everything works fine.

It is important to note that I plan to drive the LEDs with transistors, their bases connected (via resistors) to Arduino output pins.

So my question is: how should I ground and connect both circuits so that 6V (or more if I change my mind) from the breadboard source does not "reflow" to the Arduino while it is being powered by USB?

It is possible, isn't it? Should I take any special care?


texts: At the microscopic level, what exactly forces us into the "dark silicon" (i.e., the mismatch between transistor scaling and voltage scaling) problem?

texts:
I've read that if you fix the TDP of a chip, you cannot use all of the transistors simultaneously any longer. This leads me to believe that each transistor requires the same power as in previous nodes even though they are smaller; i.e., we cannot use less power to switch a smaller transistor on or off.

Why is this the case? What happens at the transistor scale that causes this phenomenon where we require a fixed power level for switching at the transistor gate (even as the transistor becomes smaller)?


texts: Does RAM always use a big Mux to ‘read’ from its addresses?

texts: I’ve designed a 64 bit (16 words * 4-Bits at each location) RAM in logic simulation software, using simple registers. I had to create a 16-to-1, 4-bit wide Mux (no mean feat) in order to ‘select’ one of these registers, and retrieve the 4-bit output. Does this mean larger RAM modules, e.g a 1KB module of say 128 words, and 8-Bits at each location, would need a 128-to-1, 8-bit wide Mux to select the output? This seems insane for larger amounts of RAM, often present on microcontrollers and the like. Is this simply scaled up as you go? e.g. 1MB of 32,768 addressable locations holding 32 bits each, would need a 32,768 to 1 Mux, with each channel a width of 32 bits?


texts:
In a small railway station, there are three platforms, #1, #2, #3. Up and down trains can enter in platform number #2 and #3, but platform #1 is only devoted to up trains. Design a logic circuit using basic gates for train entry into the station with proper truth table.

I'm not able to completely understand what the exactly the question is asking me to do? What shall be the output operation in such a case? Be it up trains or down trains, there ARE trains entering the platforms all the time. So, if the output shows 0, what would that signify? But I need to show both up and down trains, so I took 1 to indicate the up ones and 0 to indicate the ones which were down. But, what is my operation here? What shall I find out? How do I exclude all down trains from platform 1? Shall I remove the four of the combinations which involve 0( if 0 is taken as down)?


texts:
I am a newbie learning to do ARM development.
I have the following development hardware
Olimex STM32-P207 & Olimex ARM-USB-TINY-H. The STM32-P207 user guide mentions the following:

  Note: additionally, the board can be programmed via JTAG interface but
  there are signals multiplexed with the LCD and the audio, so if using
  JTAG interface for programming you might need to implement a software
  mechanism to stop them or you might not be able to reprogram again

Can anyone explain me what exactly needs to be done so that I don't mess up with my new board?


texts: Does the schottky diode current rating affect the performance of a dc to dc buck converter when loaded? Im using a 1N5822 shottky type instead of a 1N5825 on a National Semiconductor LM2596s-Adj based buck converter design. My output voltage drops when i load the circuit by a 100 ohm resistor or 50 ohm resistor. Drops by nearly 0.25V and 0.40V respectively. My design is not yet on a PCB, im testing it on a breadboard.


texts:
I am trying to calculate input impedence of a MFB low pass filter. What I need is the symbolic expression as simple as possible so that later I fill in the values and get the impedence itself:

I am not sure if I am on the right track...specially about the current directions I choosed. would somone kindly verify the steps?

What I need obviously is a simple equation with no current in it!


texts: Use transitor as a switch to ground audio input

texts:
I have got a probably very dumb question. I was not able to find an answer on the other topics because they always described the use of transistor as a switch for other applications.

I have a circuit with audio signal passing through and going to a speaker. I would like this signal to be grounded unless a 5V TTL signal is on. In this case this will have to go to the speaker. Can I do it with a transistor?

All the example that I found are about something (like a LED) already connected to a a voltage and then with the transistor either grounding its cathode or not and I do not know whether this would work in the other direction (what I would like to do).

Can I use a transitor to ground/mute the audio signal when TTL signal is zero?


texts: How to understand Transmission and Propagation delay formula

texts:
I have three questions below. I would like to understand how their respective answers were reached, this is a question in my current class and everyone in the class has A-Level mathematics experience - I have asked my tutor to explain but they talk very technically and I'm at a loss. I was hoping to get a simple answer from someone in this community, this formula is important to a project I am making - I am making an algorithm that sniffs packets and converts the delay result as png. I need to understand the maths behind it.

For Question 1: Why is the answer 2ms (Why 2m rather than just m) and what does the "Over" signify?

For Question 2: Why is the answer 2LR (Why 2L rather than just L)?

For Question 3: And I just can't figure out what this answer means or how it is reached.

Added Question

(Added Question)


texts:
Ammeter readings:

A1 = 4A

A2 = 2A

A3 = 3A

Voltmeter reading 24V.
Circuit is in AC.
I have to find R1,R2 and L.

While calculating R1 (R1 = 24V/2A= 12 Ohm) seems to be easy, next steps are not particular clear to me. I know that ammeter measure magnitude of complex current, but I cannot utilise this fact.

edit: f=50Hz


texts: Calculating boost converter maximum current output

texts:
I built a simple boost converter from junk parts to step a 9V battery up to around 100V so I can tinker with some neon bulbs. (Schematic below.)

I didn't have any inductors in my parts bin, so  I used a transformer out of a wall-wart power supply. The supply was rated 110VAC in / 13VAC out.  I'm using the primary winding as my inductor.   I do not have an inductance meter, so I can't accurately measure the inductance of this coil.

The oscillator runs at about 1.5kHz, approx 92% duty cycle.

How can I calculate (or at least estimate) the maximum current output of this circuit at approx. 100V?

simulate this circuit – Schematic created using CircuitLab


texts:
I have to solder a chip in a TSSOP-20 package on a board but unfortunately I have no "pcb oven". During the design I had access to a such oven but it's no longer possible. After some search on internet, I found many post about DIY pcb oven. As far as I understood, the heat is monitored to fit the soldering curve on the datasheet.

I don't have time to make this kind of oven or spare money to buy one. So, I wonder if it's possible to solder the TSSOP-20 chip thanks to an "unmonitored" oven?

Note that I'm jus a hobbyist, I do not need a very high quality weld.


texts:
Hello I'm making a project for my intro embedded software class and I need to make use of a timer in a program.  If I'm not mistaken this code should be looping the while for at least 500 milliseconds, but it's not working and I've never done this before on a PIC!  There may be an issue with the data types in the calculation for ms conversion.

Help would be amazing!

#define CLOCKS_PER_SEC 8000000  //Clock set to 8MHz
#include <time.h>
#include <stdlib.h>
int main (void)
{
    //Used to keep track of timer
    unsigned long delta_time, init_time, final_time;

    init_time=clock();  //Take initial clock reading
    delta_t=0;
    while(delta_t < 500)
    {

        //do tasks

        final_time=clock();    // returns total number of clocks
        delta_t= final - initial;  //Calculates total clocks between final and initial

        // converts to ms
        delta_t = (unsigned long)((delta_t/(CLOCKS_PER_SEC*1.0))*1000;
    }
}


texts: What is the dependency of the gate leakage current and the gate voltage?

texts: If I connect the source and the drain of an N-channel power Mosfet to ground and sweep the gate voltage from 0 to U_max. What curve will I see for the gate current in dependency of the gate voltage? Is it linear or exponentially? Is it decreasing or increasing? What can I predict from there?


texts:
I am implementing a 4-20mA current loop to my PIC. I have everything working. I am measuring the distance away from an object. When I hardcoded the distance as 300 the output voltage is 4V and when the distance is 12cm the output voltage is 0.8V. These values are got because the current needs to be 200uA before it enters the current loop. The current loop has a gain of 100, therefore giving 20mA on the output. The resistor I use is 20K.

(300cm) \$ Current = \dfrac{4}{20K} = 200uA \times 100 = 20mA \$

(12cm) \$ Current = \dfrac{0.8}{20K} = 40uA \times 100 = 4mA \$

The problem is I have to work out a formula for the duty cycle to get these values. The formula I am using is D.C = \$ 300 \times 2.2 + 158 = 818 \$ which gives 4V but if i substitute 12 for 300 I get 184 which does not correspond to 0.8V which is what I need. Can anyone help on this, if I am going about the wrong way or what way I need to approach this. Thank you

http://cr4.globalspec.com/PostImages/201012/4-20mA_LT1013_XTR115_3EA2C958-E757-2953-041770EF1E1B4760.jpg


texts: CAN bus with star configuration/long stubs

texts:
I am assisting in the development of a machine, and have been tasked with achieving high speed CAN (as close to 1 Mbit/s as possible) in a star configuration. The restrictions are: each arm is approximately 2.5 meters long; there are 8 arms, probably increasing later to 16, each with a single node at the end; only a single CAN cable can run out/along each arm, meaning daisy-chaining won't work; there will be one central node which will communicate with all 8 others.

If I implement a very short bus (in the order of centimeters) with very long connections to the nodes branching off it, will that work? Alternatively, could I simply connect all 8 together near the central node and terminate at 2 of the other nodes (making what would essentially be a 5m bus)? The central node will be connected to a PCB at the centre, which will act as a junction of sorts.

EDIT: After further research, I found recommendations that stubs be kept to 0.5m or shorter, which is problematic. My current thought is now to have on the PCB one bus and 8-16 transceivers (not including the central one). Each of the 8 transceivers would then be connected to a separate bus, which would be run out along an arm to the node there. I could simplify to 4-8 transceivers, each reaching 2 arms, which would become the 2 ends of that bus, but this could cause problems if one of the arms were to be removed/shut down.


texts: What is the difference between VQFP, HVQFP, TQFP & PQFP?

texts:
VSC7145XRU-31/C  - this IC uses PQFP package

the replacement component for that TLK2201 uses HVQFP package

also TLK2541 uses TQFP

that's why i wanted to know whats the clear difference between them


texts: In case of power failure, how the ROM will store the data?

texts: How the ROM Memory will hold the data even in the case of power failure?


texts: Understanding Negative feedback loop circuit with an Ideal Op-Amp

texts:
The following is given as an example of a negative feedback loop in my textbook, note that the op amp is assumed to be ideal.

However I do not seem to get the logic behind this acting as a negative feedback loop, suppose if \$V_{in}\$ is \$0.01 \$ after passing through the op amp it should be amplified to \$+6\ \mathrm V\$.
Now \$V_{out}\$ is \$+6\ \mathrm V\$ hence the inverting input will also become \$+6\ \mathrm V\$ thus the difference between the two inputs becomes \$-5.99\ \mathrm V\$ thus \$V_{out}= -6\ \mathrm V\$ and this process shall repeat over and over again, would the circuit then just cycle between being \$+6\ \mathrm  V\$ and \$-6\ \mathrm V\$ until the power supply is disconnected?
How is this considered a negative feedback, am I missing something crucial?


texts:
I am trying to interface 1.8v UART and 3.3v UART using NXP app note here. Unfortunately, my circuit does not perform as expected. I am using BSS138 as mentioned in Adafruit and Spakrfun.

When I measure Vgs, it read 0v, but drain and source is somehow connected (same voltage, I checked also using buzzer). Therefore, no level switching happened on my circuit. Is this due to defect in my MOSFET?
After reading about MOSFET, I learn that drain and source will only connect if Vgs >= V threshold which is 0.8 - 1.5 in BSS138.


texts: Transistor getting hot in rail splitter circuit

texts:
I designed and prototyped the circuit below. The circuit works as expected but Q2 is getting really hot during operation. I simulated it in LTSpice and saw that Q2 draws more current but the range is in 700uA.

The input voltage in prototype is around 20V. What may be the reason for the increase in temperature of Q2?


texts: What's the difference between MOSFETs and BJTs (from a circuit analysis perspective)?

texts: When analyzing circuits with transistors in them, when does it make a difference whether they are MOSFETs or BJTs?


texts: Plotting a Bode from a Transfer Function on Matlab

texts:
I need a bode plot for a transfer function from matlab which I never did before. I tried some examples but failed. How to do this on matlab?
Here is the TF:


texts: Should I apply soldermask over SMT thermal pads?

texts:
On page 8 and 9 of the following datasheet, there's a description of thermal pads for this MOSFET: https://www.vishay.com/docs/63302/si2342ds.pdf

What I am wondering is: I will design the footprint on the copper layer to have the shape of the footprint on page 8, with the "copper spreading". This increases the heat transfer, so better cooling.

Should I also leave holes as big as that in the soldermask? Or can I cover up the thermal pads so that the footprint with the soldermask will look like the one on page 9 (standard SOT-23). This way during reflow, the parts will stay nicely in place.


texts:
I'm nowhere near savvy in the electronic engineering department, so despite having read up on op amps/buffers/voltage followers, I'm still just as confused.

I need a pure DC circuit with 2 inputs and 1 output. A 5V input, a variable .2 to 4.2 volt input signal, and the same .2 to 4.2 volt as an output (Having them match up identically is not required, just need to be somewhat close).

Current draw is very small; in the order of .5 mA. This is for a car that has a seperate computer for the 4WD function. Normally the car recieves a voltage signal (throttle position sensor) from a follower inside the main engine computer, but I installed a new computer that no longer has a built in follower. For now, I simply spliced into the TPS voltage signal, which works fine, however the extra current draw for the 4WD computer throws off the 0-100% scale.

Can anyone point me in the right direction as to what I would need to make this circuit? I'm presuming it can be done with a basic BJT or similar?

Thanks for help in advance!


texts: How can I solve for the DC analysis of the CE transistor?

texts:
I'm new at learning transistors and amplifier. I've been studying this circuit and trying to compute the values for the DC analysis but I can't seem to get the same answers when I simulated it in LTSPICE.
This is the given circuit:

These are data from the simulation.
How can I solve for the Vb of Q1 if the resistor isn't connected to the Vcc?
Can I still use this to solve for it?


texts: BLDC Motor - Reason for different number of pole pairs on rotor / stator

texts:
The figure below shows a BLDC motor (TSDZ2 Ebike Motor).
It has 18 stator windings (3 phase -> 3 pole pairs per phase)
and 16 poles on the rotor.
What are possible reasons for this design? Why is a lower pole count on the
rotor beneficial?

Is my assumption correct that the ratio between electrical and mechanical revolutions
is given by the rotor pole count? In this case there would be 8 electrical cycles
per mechanical revolution.


texts: Why doesn't this phase shift oscillator work?

texts:
I have to achieve 100 MHz oscillation frequency. To startup the oscillation,  V2 is modeled as a step voltage source with 10V final value. But I am not getting any oscillation when I try to simulate this on a simulation software.
What is the problem in this design. Please, I really need help with this.


texts:
I connected the circuit below, a transistorized ignition circuit, and it worked for a couple minutes, then it stopped working (engine quit, wouldn't restart).  When it stopped working, I couldn't feel anything that had clearly overheated on the board, and didn't observe any smoke.

I took the board into the lab, hooked it up to a power supply and tested the voltages at various nodes for the points breaker switch being open and closed.  I used a 20 ohm load in place of the coil.

I found that the TIP31 was turning on correctly when the points switch was open such that \$V_c=.02V\$ (collector voltage of the BJT/gate voltage of the IGBT) and Q1's base voltage = .63V, so the TIP31 appears to be working properly.  The IGBT should be "Off" with a gate voltage of 0.02V, but instead I'm measuring a 4.3V drop across the 20 ohm load resistor (which is in place of the Coil shown in the schematic), meaning the IGBT is conducting .21A given a 20ohm load.

I can only speculate why the IGBT failed, and I'm hoping someone that has experience can give me a better idea.  I was to understand that IGBT's were very well suited for inductive load switching.  Did I choose an IGBT that was poorly suited for this application?  Could it have just overheated and burned out without me noticing?  Most importantly, is poor conduction a typical failure mode of IGBT's?

simulate this circuit – Schematic created using CircuitLab


texts:
I was reading a paper where one of the components mention is a bidirectional amplifier that is a voltage-voltage (VCVS) amplifier in the forward direction and current-current (CCCS) direction in the backward direction. To be more specific, if \$V_1\$ is the voltage at the input side and \$I_1\$ is the current at the input side, then:
$$V_2 = A \cdot V_1$$
$$I_2 = A \cdot I_1$$
I do know that there are various feedback topologies that can be used in design of amplifiers but I have very little knowledge regarding the design of bidirectional amplifiers. For instance, designing a voltage-voltage amplifier is quite straigh-forward. It seems that we would need to sense the voltage at the output, convert it to current, and then pass it through a gain of \$\frac{1}{A}\$ to get \$I_1\$. Does this make sense ?


texts:
I want to make an UPS using a LiPo battery for a SIM800l cellular module, I have an SIM800l module attached to a 3.7V wall adapter but I also have connected the SIM800l to a 3.7V LiPo Battery, I want to stop using the battery when there is current from the USB wall charger.

I do not want to use a standard powerbank since these always use the battery.

What about this circuit:

but I would like to know what MOSFET and diode should I choose for a 3.7 Volts input and 3.7 Volts output. Will a BS250P MOSFET work?


texts: Exporting 2D part outline data from Altium?

texts:
Anyone know if there's a way to export Altium PCB part outlines (I don't care about the detailed view of a part, just its physical 2D circle or polygon envelope) to an easy-to-parse output file?

I need to draw some annotations + would like to handle them programmatically rather than manually, using some data processing scripts I am writing. I need to get coordinate data of a few dozen parts automatically, so it's not practical for me to get the coordinate data manually, since it would take me several hours, and I would have to redo it during layout changes.


texts: Is there such a thing as a resistive bus bar to substitute many resistors?

texts: I find myself in the position to design Burn-In racks for a capacitor manufacturing company. I am trying to replace the multitude of resistors on boards that limit the current and isolate each capacitor enduring the burn in conditioning process. This becomes very bulky so I have been trying to compress the rack and keep it cheap at the same time. So if you laid a semi-conductive bus bar on top of a copper bus bar you could then tap off of the semi conductor and connect it to the capacitor to limit the current. That's my theory at least, so is there such a thing and is it possible to achieve a consistent resistance around 5-10kohms?


texts: ESP8266 loses wifi connection on switching a load

texts:
I am trying to switch a roller shutter belt winder (RADEMACHER RolloTron Basic 1100) with an AI-Thinker ESP8266 ESP-12E module. As software ESPhome is used.
Most of the time the ESP8266 loses its wifi connection on triggering the open or close function. Often it does only one action. Sometimes I can open or close 2 - 3 times before the wifi is gone.
I already tried a lot of things and now I am running out of ideas:

Ok, probably a overload/interference on GPIO12 or 14 => Disconnected them and pressed the button on the unit instead - same problem
Then it is a problem with the power supply => A D-Sun 3Ampere step down regulator should be enough.  Just to be sure I also added a 33uF and a 10nF capacitor (the ones visible in the picture.) I even tried 470 uF across the terminals - no effect. Also I could not see any obvious peaks on the little DSO138 oscilloscope (I know, it's not the best for this job.)
Sure it's not the power supply? Ok, power the ESP by battery - same effect
Is the chip entirely down? - I programmed GPIO13 to also trigger the down button. If the wifi is lost the down button is correctly triggered on adding a pull up resistor to the GPIO13. So it is indeed only the wifi that's gone. Furthermore I added 10nF ceramic capacitors to CH_PD and RESET to ensure this pins are kept high, also without success.
Its a bug in ESPHome? No: the same happens with Tasmota
The signal is too bad. Moved directly in front of the router and also disabled non-standard temporary - same problem
Played around with shielding (aluminum foil wrapped in tape) - did not help.

Update 1:
I did tests with another battery powered ESP-12E that has no connection to the shutter winder. The wifi issues are starting at distances around 5 cm (1.95 inches). 10 centimeters away the second esp is working just fine.
Also i noticed resets around every 10th time a shutter button is pressed (the ESPs led was blinking once)
Furthermore i tested the other way round with the original setup:
If the opto-isolator are disconnected and the wires are just connected to
two leds there are no issues - even that close to the shutter winder. The leds can be switched over wifi without resets or wifi issues.
So it seems to have to do with interference (probably caused by the big relays inside the device or by the motor). But how can such a problem be solved without moving the esp outside of the case?
The rollotron and the ESP are already connected to a shared ground.
Update 2:
Today i wrapped the ESP8266 in isolated but grounded aluminum foil and only left the antenna sticking out on the bottom. That did not make things better but i had the feeling that things improve very much if i have my finger on top of the foil.
Here is the module:

Used components:

GPIO12: TLP621 opto isolator with 243Ω resistor on the anode for the up button
GPIO14: TLP621 opto isolator with 243Ω resistor on the anode for the down button
9.1kΩ pull-up resistors on RESET, CH_PD and FLASH
9.1kΩ pull-down resistor on MTD0 (GPIO15)
The ADC pin has a LDR with 10k resistor as voltage devidor (on 3.3 vcc)

Does anyone have further ideas how to solve or troubleshoot this issue?
Diagram:


texts:
With this typical connection, lighting lasts for about 19h.

With this arrangement lasts more?

All batteries are rechargeable Ni-Cd


texts: Protect Pycom Lopy from 12V input signal

texts:
I am in the process of building a water meter counter using a Pycom Lopy. The Lopy operates at 3.3v but my input sensor which is a metal detector (K1208065) uses 12V.

Someone else has already build a similar counter using a raspberry PI with a piface. This is the circuit that is used:

I bought the reed relay (SIL121A7272L) as described in the circuit. However I couldn't get it to work. What I did to troubleshoot is:

Measured resistance between pin 3 and 5 (1k resistance as expected)
hooked up a multimeter in continuity mode on pins 1 and 7, I expected that when detecting metal (pull down the signal) the continuity mode would buzz. However that did not work.
Tried swapping the coil and switch pins (opposite from what is described in the circuit)
Tried using another reed relay, I actually bought two.

After I could not get the circuit to work, I decided to protect my input pin using a simple voltage divider. I used 100k and 33k values, because that is what I had laying around. The result was a voltage of 2.98V which is detected by the Lopy as "HIGH", but the signal is not stable. It jumps around from "HIGH" to "LOW" every now and then.
My thought is that this might be because of the resistor values being to high, is this correct?

Any thoughts on getting the reed relay to work, or getting the voltage divider stable are very welcome. Any other solutions to protect the input are welcome as well.


texts: Converting a external product to accept power from a voltage divider

texts:
I'm currently working on converting this voice recording module to accept power from a 9V power supply. I have successfully soldered the battery connections so the chip can be powered from two wires. When I connect the two wires directly to a 3.3~ishV power supply unit, the chip performs record and playback flawlessly. But when I attempt to wire it to a voltage divider, to wire down the voltage from 9v to the operating 3.3~ishV, the voltage going to the chip only appears to get around 2V (as opposed to the 3.45 that I would suspect). I tried increasing the input voltage from 9V to 12V and the chip still wants to hold at 2V.

Any ideas as to why this is happening? I suspect it has something to do with current, but I left my smarty pants at home today.


texts:
There is a big confusion in my head about debug connectors for ARM microprocessors. If I just take a look at this documentation there are a couple of JTAG connectors mentioned:

Cortex 10-pin JTAG/SWD (usualy 0.05" pitch) which supports JTAG debug, SW debug, SW viewer

Cortex 20-pin JTAG/SWD/ETM (usualy 0.05" pitch) supports JTAG debug, SW debug, SW viewer, trace operations.

Traditional 20-pin JTAG/SWD (usualy 0.10" pitch) supports JTAG debug, SW debug

Now I could only find schematic on how to connect the Traditional 20-pin JTAG/SWD to the microcontroller and it is this one:

To completely understand the schematic I will paste power section as well. This is important, because it looks like entire circuit is powered by JTAG pin 19 which is connected to power regulator and then goes back to the JTAG connector pins 1, 2, 13...

Does anyone have any schematics for the other two?


texts: AXI: Restrictions on slave address spaces?

texts:
Does the AXI specification impose any restrictions on the address space of slaves? I've read the latest version of the AXI specification (chapters A1-C2, ARM IHI 0022H) and could not find anything explicit. The most I could find was the following paragraph on section A3.4.1, "Address Structure":

A burst must not cross a 4KB address boundary.

Note :This prohibition prevents a burst from crossing a boundary between two slaves. It also limits the number of address increments that a slave must support.

This implies the address range for any given slave must itself not cross a 4KB boundary, but it's only an implication. If I'm reading the spec correctly, a slave is free to be assigned a 1-byte range or even a 2-byte range that crosses a 4KB boundary such as 0x0fff:0x1000, inclusive. Is this forbidden anywhere in the spec?


texts: Why can the energy of local computing be written as \$f^2\$,not \$v^2\$

texts:
I saw this formula in this book: Wireless Information and Power Transfer: Theory and Practice

And in the formula 14.8, it said:

\$f_{i,n}\$ is the CPU frequency for the nth CPU cycle required for user i

I want to ask why can the energy be written as the square of frequency, \$f^2\$? the wiki said the energy should be \$CV^2\$, where \$C\$ is capacitance and \$V\$ is voltage. It didn't say that energy is equal to the square of frequency then times effective capacitance coefficient. Does anyone know about it?


texts: How can I seamlessly switch power supplies?

texts:
Quick question, I am not very good with my electrical circuit terminology so I'm not sure what to call what I'm trying to do. When I try to Google "How to switch power supplies" I got inundated with results on switching power supplies, go figure.

I have a RPi that is powered via a car charger. (I found a car charger cable thing, the "female end if you will" at a garage sale, so I have that hooked to my power source!) The female car port... thing... is powered with 12 DC volts via 8 double A batteries in a battery pack. The car charger then powers the RPi. Runs quite a long time for what I do with it! However, I'd like to extend the running life of this.

My idea was to somehow have two alternative power supplies to the RPi charger, a battery pack, and solar panels! I picked up the panels to provide what I need. What I would like to achieve, is the solar panels and battery pack somehow hooked up through some sort of "switcher" if you will. I feel like this could be done with a voltage regulator and a transistor, just not sure how!

Anyways, I would like the solar panel to provide the power to the RPi when it is producing the required 12 volts or so, and then when there isn't good light and it stop producing the need voltage, the "switch" flips the charger over to the battery pack for power, until the panels can produce the 12 volts again, in which case it flips back over to the panel for the supply!


texts:
ATTiny is generating PWM based tones with 32kHz sampling rate. Then I've created R-2R DAC and then trying to amplify it for the speaker.

I need to make low pass RC filter, to cut PWM hiss during playback and some white noise during silence. I have tried to make use of bypass pin but no difference.

So where should I place RC filter and what values in order to filter out PWM hiss and noise during silence?

Update(without scope, I've tried to describe the problem as much as I can):

This is captured on DAC output using sound card, to describe the signal.

Enlarge

actual .wav file of the capture download: https://www.dropbox.com/s/pwakovmu9h695ji/beep1.wav

Since my sound card is not able to capture the white noise I hear from speaker, I've tried to record voice using my phone.

http://www.youtube.com/watch?v=MM2n1Q92hIo&feature=youtu.be

Sec 22 I turn off speaker pin. Sec 31 turn on again.


texts: Best positioning of snubber capacitors for Full-Bridge transistors

texts:
Two options for the location of snubber (film) capacitors.
In the first circuit, both capacitors stand up to before the bridge. In the second variant, each capacitor stands next to the half-bridge.
I suppose that the second option is better, since the emissions of each half-bridge will be extinguished next to it, and not pass through the bridge and are already extinguished before it.

simulate this circuit – Schematic created using CircuitLab
Question: Which snubber capacitor arrangement is better?


texts: I am designing an FM transmitter as a learning experience and for fun, but I am having some difficulty with FM modulation. I am using a VCO with a Colpitts topology and common emitter configuration. For modulation, I am using a varactor biased at 5V with a 1kHz, 5V amplitude message signal, which should allow the varactor capacitance to vary from 9pF to 19pF. I have an RF choke and DC blocking capacitor to couple the input signal to the oscillator. When I simulate my circuit in Multisim, I am able to measure my center frequency to be around 77MHz on the spectrum analyzer, but I am not seeing any frequency deviation on the output signal. Is the deviation too small for the resolution of the analyzer, which is ~9.6kHz or is my message input too weak once it gets to the oscillator? Below are pictures of my circuit and frequency spectrum output. Thanks for any help!


texts:
simulate this circuit – Schematic created using CircuitLab

I am a beginner at circuit design, and I am having trouble using the Vout of differential amplifier as Vref of comparator. The other input of comparator is a potentiometer connected to Vcc and ground.

The problem I'm seeing is that, with a fixed voltage value of 2.32 V at the output of LTC1050, when I change the voltage output of the potentiometer, the output of LM358 also changes incrementally (not switching from 0 to Vcc based on which input voltage is larger, as expected of a comparator circuit).

The op-amp comparator (LM358) works as expected when I set Vref to be the voltage divider output of Vcc and ground. What is different about the Vout of differential amplifier? What should I do differently to make it work?

Any help would be greatly appreciated.

In case you want more info: I am trying to convert PWM to DC, amplify it with differential amplifier, and compare it to potentiometer value to drive an h-bridge. I am stuck at the part connecting the differential amplifier and comparator.

Per suggestion, here is a picture of my circuit. The only added part from the circuit diagram is 7.5V of power supply (2A max current) fed into 5V voltage regulator (L7805CV3) to produce 5V supply for all power lines.


texts: I am using a triac bta41-600b with MOC3083, doesn't work

texts:
I have used the circuit from Datasheet of MOC3083 directly. Problem is triac does not fire. 0.1uF cap is MPF and all the values given in data sheet are used as they are. I am using a 100W incandescent Bulb as load. I have connected 2 AA batteries as input to phototriac.

All the resistors are 1/4 watt standard. This is my first shot at triacs kindly help.


texts: Are voice, text and data shared the same channel in 2G, 3G and 4G networks?

texts:
Are voice, text and data transmitted in a shared channel in 2G (e.g. GSM), 3G (e.g. CDMA) and 4G (e.g. LTE, WiMAX) networks?

In what networks, are they shared? In what networks, are they not?

Btw, if I am correct, time dividing and frequency dividing are both used for implementing sharing a channel.

Thanks.


texts:
1) Why does power gain use a coefficient of 10 unlike the other two?

2) Why can't power gain be negative?


texts: Hardware based MIDI decoding / synthesizing

texts:
I have a lot of old MIDI equipment that was recently given to me by a retired music teacher. I have a lot of interest in it, and would like to make a MIDI synth. It does not need to be high quality or sample based, but I want to know how to implement a MIDI decoder in hardware.
I know that MIDI is just digital signals representing instruments, so I'm thinking something like this.

Yeah, it's not a technical diagram. But basically, I want a really excellent guide to how MIDI works. What the signal contains and so on. I have an arduino ready to act as a PWM generator, and I have tested it. It just needs to generate simple waves (like square waves, NES/Famicom style).
Does anyone know a concise, easy to understand documentation for the MIDI standard? Something like what would be in "The Art of Electronics" (the textbook) if it talked about MIDI at all. Something that a beginner could understand, preferably. I mainly work in analog technology, so this has been a new experience for me.
Thank you. (By the way, I'm not asking you to build it for me; I just want to know where a good document is. I want to do this project on my own. Nothing more complex than simple logic IC's, so don't tell me about those MIDI generating IC's.)


texts:
I'm using the MSP430F5515 variant. I can't figure out any structured reason for it, but the chip clearly resets itself occasionally - i'm logging data and i put a 'known' string that only prints at startup in the code. I'm thinking it has something to do with my manipulation of the Unified Clock System registers, or maybe something to do with the High/Low side Voltage Supervisor functions (which I'm not changing from their system defaults). I'm pretty sure I don't have any kind of stack-overflow (no pun intended) going on, but one can never really rule that out.

Getting to my question here... are there any register settings one needs to assign explicitly in your MSP430 startup code so that the system does not reset? Is there any diagnostics that I can use to determine for what reason (at least "the last") reset occured. I'm thinking using the MSP430FET-UIF programmer/debugger to halt the processor and look at some register values, though my gut says I can't attach to a running processor without resetting it and loading a new program... Any thoughts / advice would be appreciated...

-Vic


texts:
On a 4 layer stackup with signals routed on top/bottom; 2nd layer VCC powerplane; 3rd layer GND powerplane.

How should the VCC powerplane be layed out? Should it be surrounded with a few mm of GND pour like a moat(GND) surrounding an island(VCC)? I would like to stitch gnd vias all around the board so it seems the VCC layer may need some gnd aorund the edges.

Thanks, I am an amateur at layout and trying to do best emi/rf practices.
Note; the board has a GSM module on it but most digital signals do not exceed 2Mhz. There are some analog audio signals and I going to trying to keep that gnd isolated.


texts: How does an op-amp become stable in this circuit?

texts:
i simulated the circuits in an mobile app. below is another circuit with negative feedback

-I understand how the second circuit works(-ve feedback) but the problem is with the first circuit

-Here is how the -ve feedback works(i think):
 We apply 1 volt to inverting input the output keeps falling(since the input is given to inverting input) from 0V and as it approaches -1V the inverting input becomes 0V(approx)and becomes virtual ground.now the system is stable

-But in positive feedback circuit (the first one) the input is positive and so is the output when we feed it back the input only becomes more high and must take the output to +ve saturation but as you can see the simulator is not in agreement with it

-Is it the simulator fault or is my explanation?


texts: Common cathode RGB LED Cube: Can/should it be done?

texts:
I'm planning to build a 8x8x8 RGB LED cube run by an Arduino Uno. This is my first electronic project since highschool ~ 20 years ago so I'm more than a little hazy on the subject and may be making fairly fundamental mistakes/assumptions.

I've seen Kevin Darrah's impressive implementation and wondered if it could be improved or simplified by using common-cathode RGB LEDs. I think that by having cathode columns and each layer consisting of three anode sets (e.g. R pointing left, G pointing right and B pointing to the back) I'd be able to run it with 8 shift registers such as the 74HC595 controlling the 64 columns and three controlling the 24 anode layers. Much fewer than the 25 Kevin is using to control 192 anode columns and eight cathode layers.

So my question is two fold:

a) Is my idea sound or would common-anode be a smarter way to do it?

b) What chips would I need to be the current source and sinks given that I want to get at least 256 shades from each colour in each LED and therefore need to else turn the RGB components on/off extremely fast and the amount of on Vs off time creates a POV effect and dims/brightens the colour, or be able to control the current.

Update with diagrams
Please pardon my terrible drawing skills, made even worse by doing this on a trackpad in Photoshop.

The darker colours are the legs coming from this LED. The fainter colours are the legs of adjacent LEDs. The RGB anodes all go laterally. R & G in opposite directions and blue perpendicular to that. The common cathode (black) forms the column and goes to the base of the structure. Three sides of the cube therefore have anode sets on them and act just like a regular LED cube would by activating (one colour within) that layer while the 64 columns are by the other set of chips. When one column is activated all activated layers on that column light up.


texts: How to design a comparator using op-amp?

texts:
Intention is to design a comparator with following specification:

Input: 0V to 1.65V, Output: Low

Input: 2.1V to 5V, Output: High

This is the TI design doc I have refereed for the design.

Please see the circuit diagram for your reference:
(Highlighted in green rectangle)

For my design requirement, I have recalculated the value of Rx, Ry and Rh as follows,

Rx = 10K
Ry = 5.689K
Rh = 36.67K
( VL = 1.65V, VH= 2.1V and VCC = 5V)

Formulas used are also from the TI doc

But the simulation result is as follows:

Obs: As per the LTSpice simulation VL is 2.02V and VH is 1.65V
It is not matching with the design I have done.

Please do advice why there is a mismatch between the design and simulation. Kindly let me know if further any information required.


texts: We need to measure the impulse response of the EEG amplifier we use in our lab. We don't have so much equipment but, luckily, we have a pulse generator for delivering small electrical pulses with a given current amplitude to subjects for performing tests on pain. I was thinking of using this generator for measuring the IR or the amplifier. My plan is to a 100 Ohm load to simulate skin conductance and then use a voltage divider to bring the voltage within the micro Volt range that can be measured with EEG equipment. Is there anything else that I might need to consider?