texts:
I'm replacing USB Micro and USB B connectors on my PCBs for USB-C connectors, but only using USB 2.0.

So I'm looking for a connector that isn't too complex to layout or hard to solder. I found this one (CX90M-16P, page 6) and I'd like some help on interpreting this land pattern / connections:

Question:
The datasheet lists this connector as a 16 Pin part. However, I count 18 pads - one before A1 and one after A12. I wonder what should I connect the extra 2 pads to? Ground? Leave them floating? Should I ask Hirose or is there some info which I'm not seeing?

Update:

In this other document, these pins are listed as "MID", but still I dont know where to connect them to.

(I was going to ask this but I answered my own question:

Question 2:
It is missing pads A2, A3, A10, A11, B2, B3, B10, B11, which are for the "SuperSpeed" differential pairs. For my USB 2.0 applications, this should be no issue, correct? (Ok I just answered my own question, since USB 2 USB-C cables don't even have these connections as well)
)


texts: Interrupt Service Routines and I2c together

texts:
I would like to ask a question that has been on my head for a while

I have done coding small ISR's for pic and AVR controllers and i have successfully tested them on board.And i have just learned some days ago that you need to keep ISR short.

  So I have this ISR that runs each 2 ms from timer.

Well the doubt I have is  If I have an I2c communication running parallel and then the interrupt occurs, What will happen to the  I2C communication.

Will the data transmission gets damaged?.

If The ISR  takes  2ms to execute, what will happen to the I2C communication meanwhile.

Can it cope with such delays? Or is it my lack of understanding.


texts: What does 'random phase' means in a triac driver?

texts: I'm using  this triac driver  to control a triac. In its datasheet it says 'provide random phase control of high current triacs [...]'. What does that mean? It doesn't have zero-crossing detection?


texts: Is using product circuit within my product legal?

texts: I'm building a smart plug and I want a circuit to convert from 220vac to 5vdc so I'm using a charger circuit  (image source) to deliver the 5vdc I need for the wifi module as it is with no changes made. Can I sell this product under the right terms?


texts:
First, sorrry for my bad english :(

I'm having problems with ESP when I connect CH_PD with 3.3v

My circuit is this:

Simulator: https://123d.circuits.io/circuits/1539895-the-unnamed-circuit/edit#breadboard

The problem in the simulation is: When I connect Vcc only, the ESP turns on the led. When I connect the CH_PD pin, the voltage oscilates between 3.3V and 960mV.

In the real word, the ESP red led turns blinks only one time. With my voltimeter, I only see 960mV

When I use an Arduino UNO to provide 3.3v to Vcc and CH_PD, I have no problem.

Someone know why I'm having this problem? In google I cannot found anything.

Thanks!!! :D


texts: What makes the buzzing sound when touching an audio line?

texts: I recently built an audio amplifier based on the LM386. When I touch one of the input signals with my finger, I can hear a buzzing sound on the output. I checked with the oscilloscope, and there appears to be some kind of voltage signal on my hand with respect to the amplifier's ground. What is this voltage? By what theoretical principle can I understand this?


texts:
I've been trying to follow an example circuit that does some PWM. First I believe that in a configuration something like this with nor & and that the wave should alternate. Violet line is pulsing 5-5V as I needed to happen. Green is a flat line. I need green to alternate with violet and the lamp on the green line I want it to light up along with the lamp on violet.

I have to have made mistake. Does anyone see what's wrong. I've been trying for while on this.

Thank you


texts:
I have long running simulation in Modelsim for VHDL/Verilog designs.
I want to know are there any way to save current simulation progress and resume it somehow in later time?


texts:
Any idea what this audio cable is for?  It doesn't seem to be a mic or a light... totally flustered.

audio cable image 1


texts:
I am hooking up a PIC16F676 to FT232. I already have power hooked and also OSC with 20 MHz and 22pF capacitor.

I am still trying to figure out the proper way to hook up the data/serial or something to program this chip using the FTDI FT232RL.

This is what I have so far:

And my datasheets:

PIC- http://ww1.microchip.com/downloads/en/devicedoc/40039f.pdf

FTDI- https://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf

Overall, I just need to know if it's possible to hook FTDI to PIC16F676 in order to program. If so, then please guide me and once it's done, then I'll try to use c# application to program it (basically a custom tool).


texts:
This is a spinoff of the thread found here: https://electronics.stackexchange.com/questions/115510/proteus-8-error-timestamp-too-small
I have found that a lot of the problems I have been running into were due to the feedback transformer coils not being grounded. I wanted to ask why in the world a simulation software would require that each of the coils on a transformer be grounded, when in real life that is not always the case? It makes no sense to me.
My question is how might I get around this, if it's possible at all? My circuit places the primary inside a circuit, and neither side can be grounded.

The above is the circuit I am using, and the transformer in question is the one labeled "FEEDBACK_XFMR".


texts: Fatal Error for simulation of Full Adder in ModelSim

texts:
I am quite a novice in VHDL, but I decided to practice today my skills on designing a full adder. Simple task I thought, except that I somehow cannot manage to simulate my code correctly, even though when I compile it I dont get an error.

The error states only Fatal Error [file location of test bench] line 21, but whatever I try, I am not able to get rid of that error. If I force values through the command line to simulate my full adder without the test bench, the simulation gives me 'U' signals when I actually mentioned it to be '0'. So I am confused and totally lost; hoping somebody smart out there who can help me.

Here the code of the full adder:

 library IEEE;
 use IEEE.std_logic_1164.all;

 entity full_adder is
 port(a,b,c_in: in std_logic;
 sum, carry: out std_logic);
 end full_adder;

 architecture SumAndCarry of full_adder is

 signal s1, s2, s3: std_logic;
 constant gate_delay: time:= 5 ns;
 begin

 L1: s1 <= a xor b after gate_delay;
 L2: s3 <= a and b after gate_delay;
 L3: sum <= s1 xor c_in after gate_delay;
 L4: s2 <= s1 and c_in after gate_delay;
 L5: carry <= s2 or s3 after gate_delay;

 end SumAndCarry;

And here the test bench I have prepared to test it:

 library IEEE;
 use IEEE.std_logic_1164.all;

 entity FullAdder_tb is
 end FullAdder_tb;

 architecture testbench of FullAdder_tb is
 component full_adder is
 port(a,b,c_in: in std_logic;--You simply replace bit with std_logic
     sum, carry: out std_logic);
 end component;
 signal at, bt, ct, sumt, carryt: std_logic;
 begin
 at <= '0' after 50 ns,
     '1' after 100 ns,
     '0' after 50 ns;
 bt <= '0' after 50 ns,
     '1' after 50 ns,
     '0' after 50 ns,
     '1' after 50 ns;--This is line 21!
 ct <= '0' after 200 ns;
 Lbl1: Full_Adder port map (a => at, b=>bt, c_in=>ct, sum=>sumt, carry=>carryt);
 end testbench;

Hope everything is clear...


texts: Why do I see +1.5V on Din of a WS2811-based LED strip?

texts:
I'm wiring up an LED array I recently purchased (specifically, this one), and trying to identify the correct connections. I'm thrown by an unexpected voltage appearing at [what I think is] Din.

There are three connectors; +5v and ground are obvious. The third is the data line. Although you can't see very clearly in the picture below, trying to figure out which end is Din and the Dout is pretty difficult (the LEDs, ws2811 and supporting circuits are encased in a solid polymer that is virtually impossible to read through).

So it's 50/50. And I've seen comments (like here) indicating there's no harm just trying both ends.

But before plunging in, I thought I'd at least check if there's any voltage on the data line:

At one end (which from visual inspection and my best guess is probably Dout), I see 0V.
At the other end (which I think is probably Din), I'm actually seeing +1.5V). Hmm.

I tried pumping a data signal in the "wrong end" (Dout/0V) and nothing happened. So far, as expected.

But I'm concerned about trying the reverse. It looks like I'm at risk of pumping reverse current into the Arduino PWM output pin I'd be using to provide the signal.

So I'm left with questions, and unfortunately I don't have another working strip to compare.

I'd appreciate any guidance on this:

is +V on Din normal?
perhaps it indicates a problem with the strip?
any hints on safely exploring further?

The picture shows the voltage measurement of Din reference to Ground, with the strip powered by 5V (that's a 1000uF cap across the power lines). A bit fuzzy, sorry - third hand problem.

Edit: solved, thanks for the help!

I did identify DIN correctly, and it seems the voltage was just a floating level. Strip runs perfectly - all LEDs are correctly addressable with full RGB control - with 1k resistor in series at DIN, using an Arduino Uno and the FastLED library with WS2811 chipset selected i.e.

CRGB leds[NUM_LEDS];
FastLED.addLeds<WS2811, DATA_PIN, RGB>(leds, NUM_LEDS);

Update: all sorted!
I asked this some time ago, but I thought worth providing an update. Thanks to the help here, my LED strip project is cranking along nicely. If you're interested, you can see all the details and a demo at fretboard.tardate.com.


texts: IR receivers: how to interpet "Max. Envelope Duty Cycle vs. Burst Length"?

texts:
In the datasheet of an IR receiver IC, intended for remote control applications, there exists this graph.

Why is there such a sharp translation after a certain carrier impulse count?


texts: MOSFET as a switch. Why does the voltage depend on the gate?

texts:
Let's say I have an NMOS, the gate is connected to 5 volts, Vth is 0.7 volts and I want to pass a voltage of 7 using the NMOS as a switch. Can you tell me what will be the voltage at the source?
Will it be 4.3 or 6.3?

In my understanding, once a voltage greater than Vth is applied at the gate, the source and drain are effectively shorted, this means the voltage at the drain should appear at the source.

The reason I ask is because of the picture below. The picture suggests, irrespective of what the drain voltage is, the voltage at the source is always the gate voltage minus Vth


texts: Reading one ADC input on two microcontrollers

texts:
I am trying to read ADC sensor input to two microcontrollers. I am curious since I am sharing the ADC sensor input, will the internal resistance/circuitry of one microcontroller affect the reading of another microcontroller. In one of the microcontroller's datasheet, it's written that if I turn off that uC then its pin goes to pull down mode then this might affect the other uC reading.

Is there any circuitry I should put in between to avoid any interference of other microcontrollers? Like putting RC filter should work I guess. Following is the block diagram of the situation where I want suggestions/ideas for custom circuitry:


texts: Calculation of transfer function in OP-AMP circuits

texts:
In a simple circuit like the following:

simulate this circuit – Schematic created using CircuitLab

I calculate the transfer function using I1 = I2:

Vin = I1*R1 => I1 = Vin / R1
Vo = - I2*Ztotal => I2 = - Vo / ( (Zc * R2) / (Zc + R2) )
H = Vo / Vi = ...

In 2. in my mind I always simplify it like this (and then use KVL):

simulate this circuit

Now I have another circuit and I am a bit confused. This is the circuit and again how I simplify it in my mind like the previous circuit:

simulate this circuit

Now just like the previous circuit I used I1 = I2 and:

Vin = I1*2R => I1 = Vin / 2R
Vo = - I2*(Ztotal + R) => I2 = - Vo / ( R + ( (Zc * R2) / (Zc + R2) ) )
H = Vo / Vi = ...

My questions:

I know the way I try to solve the second circuit is wrong. How should I do it?
In the first circuit (which is an example and I know it is correct) why doesn't I2 split into I3 and I4? What I know so far is that before you get into a new loop the current splits.


texts: What's wrong with my logic in my adder-subtractor?

texts: I'm trying to create an adder-subtracter using only one adder, not gate, and multiplexer. When A = 1000, B = 0001 it results in Q = 0111. If my math is right, that is 8 +(-1) = 7 and 7 = 0111 which is indeed what Q outputs. Now, if I try to switch the values in my circuit as I do in the circuit below I get Q = 1001. Going over my math again A = 1, B = 8 so 1+(-8) = -7 and -7 = 1111 which does not equal the Q output. I'm really confused as to where I went wrong here.


texts: Does L293D consume power when not in use

texts: I am designing a robot using the L293D motor driver, and I have just successfully hooked it up to my micro controller.  I am using two batteries, one two control the motor and one to control the pic micro.  I am wondering if the battery that is used to drive the motor would get consumed when the pic circuit is off.  I need to know this, because in my design i was considering directly connecting the motor supply to the driver without a switch.


texts: Gradually ramping voltage on button press

texts:
I have a circuit with a button and a motor. How would I make the motor gradually ramp up speed over 1-3 seconds when the button is pressed and gradually slow down over 0.5-1 seconds when the button is released, instead of the motor going full speed immediately? The circuit may be either 12V or -12V depending on the desired turning direction.

This is a simplified version of an old electric desk control circuit. The desk moves too suddenly when the button is pressed and I need to slow it down.

As a programmer, my go-to solution for stuff like this is often a microcontroller, but I'd like to try using analog components if possible.

Even though I've had education in electronics back in the day, I don't know if there is a name for what I'm trying to do and how to search for more information about it. I'm stuck googling with too broad keywords. If the analog solution isn't too much more complex than a microcontroller one, please point me to the right direction.


texts: How much energy do Li-Ions/Li-Pos have below 3.2V threshold?

texts: How much energy does a battery still have when a protection chip disconnects it? I know that such discharging kills the battery, but in some cases it would be useful. For example, in drones: when you don’t have enough power to land it safely, you could disable the protection controller and land it using this rest power. You don’t loose the whole drone, only the battery. Also it would be useful in cell phones in emergencies.


texts: What does it mean when a capacitor and it's connectors are marked with a red marker?

texts:
Is there some kind of convention in electrical component maintenance that would explain a red marking on a capacitor?

I found this in my Pioneer SA 5300 audio amplifier and wondered if this carried some special meaning.


texts: Does a supergrid approach confront with distributed generation?

texts:
I have heard many times about supergrids and distributed generations (small scales generation connected close to the loads). In a supergrid scenario, a efficient and clean production of electricity (for instance wind farm plants) can travel long distances and be consumed even in a far different country. However, the distributed generation approach suggests that the generation shall be produced near it is consumed.

Both concept seem to be trendy for future electric systems, but, is not there a contradiction between the two approaches because while one is encouraging to export energy long distances the other one suggests to minimize the "travel" of the electricity from the generation to the consumers? is my understanding mistaken and there is not such contradiction?, and if not, which of them is more sensible for future grids?


texts: Feed a speaker only with positive voltages

texts:
I am using the timer of a microcontroller to create square wave signals from 10KHz to 40KHz, but my microcontroller generates the signal only with positive values (0 - 3.3V). I have generated the same signals from my PC with the sound card, the signals in the oscilloscope have a range from -2V to 2V (at maximum volume) this is 4V peak to peak             amplitude.

So my question is:
If the speaker is able to support 4V of amplitude, will it be ok to use a 0 to 3.3V signal?
Is there any way that  this positive going       signal  can damage my speaker?


texts: LTSpice Instrumentation amplifier simulation output

texts:
I am using an LTSpice model for an instrumentation amplifier (AD8222) to learn how to simulate things in LTSpice.

My output is not what I expected. My model is based on this description: http://www.allaboutcircuits.com/textbook/semiconductors/chpt-8/the-instrumentation-amplifier/

I connected Rg (gain resistor) and set the value at 500 (varied during testing). I set V+ to 4V and V- to -4V. I set the reference voltage to GND.

For the signal input, I connected a voltage source between In- and In+ and set it as both a sine wave (1V 100Hz, or 1V DC). I set it so In- was connected to ground, and In+ was connected to the output of the voltage source.

I simulated the model and checked the input voltage (In+) and the output signal and they do not match. The output signal either outputs a square wave, OR the output is simply constant and does not change with the R_Gain.

What am I doing incorrect? I have done this with the actual physical chip on a PCB I made and it worked. I was able to input a small sine wave, and get a larger amplified signal out. I am curious about what I am doing wrong with the LTSpice model, and how I can fix it.

I tried using the LT1920 and it outputs a DC value for a similar setup as well so I don't think it's an issue with the LTSpice models. I have attached a screenshot of the circuits and simulation results.


texts: how to get more power out of a astable multivibrator?

texts:
Hey I have a circuit like this,

I am powering this circuit with a 6v alkaline battery, the circuit works just fine with 100uf capacitors. But the problem is I want to replace the LED with a dpdt relay, I tried a 6v one I had laying around but it wont budge. Also when I tried the circuit with a 12v battery, the circuit just remains active for all the time. How do I get this to work?


texts:
(Question in response to the comments.)

I have a fixed flat white rectangular whiteboard of dimensions 1 meter by 0.5 meter and pen. I want to track the position of the tip of the pen within the whiteboard, in real time.

I am allowed to have as many different sensors and processors on the sides of the whiteboard as I want, but there are three main restrictions:

The pen should operate freely; no wires or strings between the pen and the sensors are allowed.
The pen should be low power, ideally powerless.
The position of the tip of the pen should be determined with an accuracy on the order of 1mm.

What electronic setup would allow me to compute the position of the tip of the pen within the whiteboard with the above restrictions?


texts:
I am designing an Operational Transconductance Amplifier whose maximum output current should be 15mA. Using Super Class AB amplifier, I was able to get a maximum output current of up to 2mA. The supply voltage is 5V. So to boost the output current, I need to cascade it with a current amplifier with a small gain. What would be the best way to do so?
Can I get a current in mA range using CMOS current mirror technique? Or should I design another opamp and a mosfet/bjt at the output the boost the current?


texts: Ground plane layout for noise suppression/immunity

texts:
I have 7 x A3941 DC motor drivers and they have to coexist on a board with an STM32 MCU and onboard 5V and 3.3V supplies. Since there are a lot of ‘noisy’ components here, will the following ground plane layout be valid for noise immunity/suppression?
The quiet ground is essentially a plane for a few components as per the recommendation in the A3941 datasheet.

EDIT: The current placement layout is as follows,

EDIT-2: Came across this wonderful video a day ago on splitting ground planes and if you should do so. A real eye opener for me.


texts:
I'm creating a library part for a dual MOSFET driver IX442 which has 3 variants, IX4426, IX4427, IX4428.  The difference between the variants is in whether the outputs are inverted from the inputs.

Is there a way to set the pin name for pin 7 (OUTA or #OUTA depending on the variant) such that I can create a single schematic part for all variants and use an attribute to set the pin name accordingly?


texts: Are radio waves naturally polarized like light or is that a function of how they are produced?

texts: I am thinking of let us say AM or FM radio being transmitted by a vertical antenna.  Would the they be polarized vertically or horizontally and wouldn't the angle of the receiving antenna then determine the strength of the signal.


texts: AGC (automatic gain control) circuit for brushless phase measurement?

texts:
Intro: I am projecting a Brushless motor driver which relevant specs here are basically: use with 6v to 60v.
To make it work the circuit's microcontroller needs to analyze the signal that comes from the motor phases through ADC - which can not exceed 3.3v.
The phase maximum voltage is ideally equal to the power voltage and looks like the wave form shown bellow, for the three wires:

So that, if it uses a simple resistive divider to measure each phase:

when the power is 60v, the phase value at the ADC input must be bellow 3.3v.
When the power is 6v (10x lower than 60 volts), at the ADC input it will be 3.3v divided by 10, i.e., 0.33v.

The Problem: Notice that using resistors simply the precision was lost by 10x (more than 3 bits!). This can cause instability at lower voltages and worse control, compared to 60v on power supply.
Solutions? I was thinking about using a AGC to adjust the signal to the ADC input based on the power supply voltage. No meter what voltage on the power supply, the ADC should catch a 0-to-3.3v signal linearly similar to the phase signal. What AGC chip you guys recommend? What else could be a possible simpler solution?


texts: How do I find the current equations for the RLC Series Circuit?

texts:
Let's talk about a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged.

At t=0, the switch is closed and the battery (V1) feeds the circuit.

To find the equation for the voltage across the capacitor, I apply KVL to the circuit and get this:

\$ V_1(t) = Ri + L\frac{di}{dt} + V_C(t) \$

this later turns in to this:

\$ \frac{V_1}{LC} = \frac{d^2V_C(t)}{dt^2} + \frac{R}{L} \frac{dV_C(t)}{dt} + \frac{1}{LC}V_C(t) \$

After a few hours or brain melting, I get the final result for the equation of voltage across the capacitor

CRITICALLY DAMPED

\$ V_C(t) = (At + B) \thinspace e^{-\alpha t} \$

OVERDAMPED

\$ V_C(t) = Ae^{m_1t} + Be^{m_2t}  \$

UNDERDAMPED

\$ V_C(t) = e^{- \alpha t}[K_1 \thinspace Cos(\omega_d t) + K_2 \thinspace
Sin(\omega_d t) ] \$

The question now is: how do I find the current equations for the three cases?

The only thing I can see is that the current on a capacitor is equal to

\$ i_c = C \frac{dv}{dt} \$

If R, L and C are in series, the current is the same for the three.

So, all I have to do is to take the derivative of the voltage equations, that will give me, if there is no error in my math, the current equations...

CRITICALLY DAMPED

\$ i(t) = e^{-\alpha t}(A -\alpha At -\alpha B) \$

OVERDAMPED

\$ i(t) = m_1Ae^{m_1t} + m_2Be^{m_2t}  \$

UNDERDAMPED

\$ i(t) = -\alpha e^{- \alpha t}(K1 Cos(\omega_d t) + K_2 Sin(\omega_d t) ] + \omega_d e^{- \alpha t}(K_2 Cos(\omega_d t) - K_1 Sin(\omega_d t) ] \$

Questions:

is this how you find the current equations for that kind of circuit, if not, please point me in the right direction.
are these equations for the current correct?

thanks

EDIT: I have found this page that gives the same equations for current that I have found for voltage (??)


texts: How do I connect two identical batteries to increase the consumer lifetime?

texts:
If I've got a device that uses a single battery, and with that single battery, the device lasts an hour, and I want the device to last for two hours, I'm assuming I can wire two batteries up and it should work. But how? Do I want to double the voltage (so serial) or double the current? (so parallel.)

Either way, if the device takes two batteries normally, and I want to double the running time, I do a combo of 2 parallel series of 2 serial batteries, right? But if I want to triple the run time, is that 3p2s or 2p3s?

Thanks.


texts:
As you see in the picture above, diode voltage drop is 0V, and the monostable multivibrator is made in CMOS technology with protection diodes. I have problem finding the output of this circuit in some nodes.
So, when the input signal is zero, multivibrator is in stable state, Ve=0, Vd=0, Va=Vdd(logic 1), Vb=Vdd(logic 1).
When the input signal kicks in, I get Va=0, Vb(0+)=0 starting to charge towards logic gate voltage, and Ve=Vdd.
How does logic 1 on Ve influence the capacitor C2 and resistor R2, and any hint on what will happen after NOR gates switch again?


texts: Excessive noise in amplifier circuit when switching from DC power supply to AC-DC adapter

texts:
I'm working on breadboarding this amplifier circuit before transferring to a perf board.

When we power it from an adjustable DC power supply set to 12V, the audio output sounds clear. When we switch to a 12V 5Amp AC-DC adapter, we are getting almost nothing but noise.

We've already switched from one adapter which was providing an uneven output between 10V and 12V, to an adapter which we've measured at a constant 12.6V.

We're using the negative power terminal as our ground.

I would appreciate some suggestions for ways to troubleshoot this issue or any ideas as to why we're only getting clear sound from the adjustable power supply.


texts: Libraries to help port Arduino code to msp430

texts:
Does someone know a nice library which makes coding for TI Launchpad MSP430 as easy as for arduino?

So far I only found Friendly Launchpad and some random code examples.

But I am looking for something that also supports analog readings. Doesn't matter if its doesn't follow the Arduino syntax as long as its simple.


texts: SMPS Constant Current Source only works with low resistance loads

texts:
I'm looking for any advice that can be given to solve this issue.
I followed the design idea from here: buck regulator to CC source and it appears to work pretty well until I started raising the load resistance. 1Ω-2Ω works great, above 2Ω the current starts to fall off.

I first thought I was running out of head room, but with a 45V input the output voltage is only reaching about 30V. I would think that the output voltage should be able to get much closer to the input voltage.

The target Vref is 0.97V for this chip, and it's doing a pretty good job of keeping that until the load resistance goes up.

Any ideas on what to check?
Thanks!


texts: What do the dimensions describing the crimping tools mean?

texts:
The crimping tools usually describe an dimension interval they are capable of working with. For example: 0.5 to 6 mm² or 0,1 - 2,5 mm².

However when dealing with electronics connectors, the dimension that comes my is 2.54mm.

From reading forums I got the impression that 0,1 - 2,5 mm² would work for my 2.45mm connectors but 0.5 to 6 mm² wouldn't. At the moment I can't reason why this is like that.

What does the surface the crimping tool are marketed by represent and how does that relate to the 2.54?


texts: Drawing circuit schematics and export to TikZ

texts: Is there any tool for drawing circuit schematics (by "mouse clicking") which exports to TikZ?


texts: How does the gap between coils and magnets affect BLDCs

texts:
I just came across the doubt about how the space between the stator and the rotor in Brushless DC motors affect their performance.
Of course the further apart coils and magnets are, the least torque it provides, but, smaller gaps do really mean more torque? Is there a point where some other things begin to counteract the motor performance? (not counting the obvious case where the stator literally touch the rotor)


texts: I was asked to design a display that is loop powered and sits between the receiver and the transducer. I was wondering what's the best way to source power from the loop to power my electronics without damaging the receiver and the transducer? There are plenty of those products from manufacturers but is difficult to find a design. Thanks.


texts:
When buying an HD44780 compatible LCD display with a backlight, is there a way to identify the orientation of the text on the LCD based on a standard part number?

I'm asking because I don't want to order new LCD's with backlights and then realize that the LCD has to be switched the other way and my circuit looking funny only to get the LCD to work.


texts: Copy Edit:/ waveform to Sim:/ waveform in Modelsim

texts:
I've loaded my waveforms from a previous simulation by going to File -> Load -> Macro File -> "wave.do". This causes the waveforms to be displayed next to blank simulation waveforms (see below). I would like to use my previously saved waveforms to resimulate.

I've tried right-clicking on an Edit:/ waveform and going to Edit -> Map to design signal -> and then entering the name of the corresponding design signal (e.g. sim:/majority3/x1) but this does not achieve the desired result.

I've also tried simply copying the Edit:/ waveform and pasting it to the Sim:/ waveform, but that didn't work either.

Any comments, suggestions, etc. are appreciated!


texts: How do I make a DC motor rotate clockwise for a random value, then rotate counter-clockwise for the same amount autonomously?

texts:
For my project I need to build a repeatable vehicle without using any programmable devices (eg: Arduino, microcontrollers etc) After activation, the vehicle needs to move straight towards a wall which is a random distance away, make contact with the wall, and come back as close as possible to the starting point. I have decided to use a DPDT to reverse the motor but I still can't figure out how to make the vehicle stop at the starting point after returning from the wall. The distance between the starting point and the wall ranges from anywhere between 1.4m-4.0m.
edit: the whole project has to be built within a budget of 30£


texts: Is it possible to capture a DVB-T mux's signal on VHS?

texts:
What will happen if i tune a VHS VCR's analog tuner to a DVB-T mux's frequency, record the signal on a VHS tape, then use the RF out of the VCR to replay the captured signal into a DVB-T receiver box's RF input? Can i "tune" into the replayed mux and view the transmitted channels? (similarly how a Teletext signal is accessible when playing back a recorded analog broadcast)

A DVB-T mux can have an overall bitrate of 20-25Mbit/s which is like 180MB/minute of data. A 4 hour VHS tape could hold 40GB worthwile of data if it's possible to encode data in the modulation of DVB-T. It's a wild idea but can't find anything about it online.


texts: Designing a VHF Colpitts oscillator using BJT

texts:
I am trying to design an Oscillator circuit which can produce a good sine wave with a frequency of at least 500 Mhz and oscillating voltage of around 10 - 15 volts. The output of this oscillator will be just connected to a two Conducting plates of 1 Square inch(one to Collector output and the other plate to ground, with 1 inch gap between the plates). Therefore the resistive       loading  is  just the tuned circuit losses.

I tried learning to design my own oscillator but ended up getting confused reading the data sheet parameters, especially hfe (Current Gain)  of various BJTs.

I  have been told that in order to get   500MHz I need a transistor  with a transition frequency of 5GHz .I thought that a gain above unity above circuit losses would be adequate for sustaining oscillations .

The things I do not understand are as follows :

How do I set the operating point for the amplifier for a colpitts oscillator to get the desired oscillating voltage?
what is the voltage gain of the amplifier  (Voltage divider bias used for biasing of transistor), thus I am stuck up in calculating the feedback fraction for the amplifier to sustain the oscillations. I understand that the ratio of capacitors of the tank circuit is the feedback percentage, but without knowing how to calculate the voltage gain of amplifier I am unable to proceed further.


texts: Does random access to image sensors require extra hardware?

texts:
Jun Ohta's "Smart CMOS image sensor and applications" says that random access to pixel arrays is possible. Using Row parallel readouts and column decoders, one can select which pixels to readout and which not. Since the sensor outputs only one pixel at a time, it seems to me that the sensor has all the necessary hardware to output a rectangular window, which is a sub-image of the total sensor.

Am I right or does the sensor need extra hardware to achieve a "random capture"?


texts: Why does LM317 burnout when output is shorted in this case?

texts:
LM317 voltage regulator has internal short circuit protection alongside with its thermal overload auto-shutdown, but in the circuit below it will simply burnout when the output is shorted. And its adjust pin gets internally shorted with its output pin.

I know that a pass transistor would strip off the regulator's ability to stand a short circuit and limit current but whats wrong here ?

I built it more then once on different PCBs and they all end up the same way ( killed about 5 regulators till now as i though that something was wrong with my build)

one version of the PCBs i made :


texts: Component identification: 1600A NH & FBH5AA FDMP & W10B 89F

texts: Can't find the component by it number, they look like FETs on a fan PCB but need datasheet.


texts:
I read the Christophe Basso APEC 2011 seminar, about this figure I have some things I can't get it.
1.)Why should need to put the Cdc capacitor in the circuit, what's this function? to block the DC source?
2.)Why need to let Vfb at 2-3V, how to make sure it is in the linear region.


texts: Virtual earth (ground) or "mid-rail generator"

texts:
In a recent question I (rightly or wrongly) said in a comment that calling a mid-rail generator (two resistors and a smoothing capacitor) a "virtual ground" was wrong and that the term "virtual ground" is reserved for when using negative feedback on an op-amp; if the non-inverting input is at 0V (ground) then the inverting input is regarded as a virtual ground due to negative feedback and the op-amp's very high open-loop gain.

I looked on wiki to find that their construction definition is: -

  A voltage divider, using two resistors, can be used to create a
  virtual ground node. If two voltage sources are connected in series
  with two resistors, it can be shown that the midpoint becomes a
  virtual ground if

Wiki then goes on to show this diagram: -

And they have some describing words thus: -

  An active virtual ground circuit is sometimes called a rail splitter.
  Such a circuit uses an op-amp or some other circuit element that has
  gain. Since an operational amplifier has very high open-loop gain, the
  potential difference between its inputs tend to zero when a feedback
  network is implemented. To achieve a reasonable voltage at the output
  (and thus equilibrium in the system), the output supplies the
  inverting input (via the feedback network) with enough voltage to
  reduce the potential difference between the inputs to microvolts. The
  non-inverting (+) input of the operational amplifier is grounded;
  therefore, its inverting (-) input, although not connected to ground,
  will assume a similar potential, becoming a virtual ground if the
  opamp is working in its linear region (i.e., outputs have not
  saturated).

In the first sentence they mention a "rail splitter" then they go on to describe pretty much what I (currently) understand as a virtual ground. I have problems with Wiki's explanation because they started with the words "rail splitter" and, from my viewpoint, a "rail splitter" means "mid-rail generator".

I've provided the wiki explanation (before asking my question) just to show I've done some research on this.

My question is this: -

  Is a mid-rail generator (formed by passive components and sometimes an
  active buffer) a "virtual ground"?


texts:
When an inductor is connected with a voltage source we get equal and opposite voltage on inductor against the source voltage. That equal and opposite voltage gradually decreases with time which allows the current(caused by the source voltage) to rise gradually.

My question is what makes the equal and opposite voltage in an inductor to fall gradually ?


texts: How to control the potential in multiple-electrodes (3 or more) in electrochemical cells?

texts:
Usually, in most cell designs, the concept of two-electrode design is the baseline. The two electrodes are anode and cathode where the electron transfer happens between them. However, I have been reading about 3 electrodes and 4 electrodes designs where the new electrodes are used to control the potential while allowing the working electrodes to deal with the current transfer. However, I wanted to know how to control the potential of my cell and what is the equations for that if I want to build my own multi-electrode cell.
Thank you


texts: Combining two schematics of 1kx3 NOR MOS PROM components into a 2kx6 PROM component

texts:
Today after class we were left with an exercise of creating schematics and combining two components we learned about today. The exercise is to combine two 1kx3 NOR MOS PROM components into a 2kx6 PROM component with floating gate transistor programming. (1k ones also use this).

I wanted to check if my understanding is correct so i'm posting this to get replies on whether something doesn't look right or if something is missing. I am just suppose to draw a memory cell of these ROMs and not the entire logic behind it so sense amps and other write/read buffers are omitted.

I have drawn a decoder which decodes 10 adress lines into 1024 word lines and i have 3 bitlines connected to a pull-up network consisted of p-mos transistors. The interconnections in the memory cell are programmed by floating gate transistors. I have drawn with 3 lines in the base to indicate that.

And finally i connected the two schematics into one 2kx6 PROM component:

Is this how NOR type is supposed to be connected? I'm sort of mixing the NOR and NAND types and am not sure if this is correct. If this is correct how would i make a NAND type since all that's different probably is the configuration of the interconnection transistors.


texts:
In the following post 230V AC to 5V DC converter, lossless , the 1.44 W Universal Input Buck Converter was mentioned.

In the LNK304 datasheet (applications section) , http://www.mouser.com/ds/2/328/lnk302_304-306-179954.pdf, they mentioned that the voltage divider that consist of R1 and R3 will determine the value of the output voltage.

My question is what R1,R3 values will result in 5V output voltage and what will the supplied current be for this output voltage?

Thanks


texts: How to calculate proper R value for RC filters in amplifier power supply

texts:
This is an extension of a question I asked yesterday here regarding power rail sag I was seeing (turns out I was indeed dropping below the regulator dropout voltage).

I'm trying to figure out how I would obtain the appropriate values for the calculations to devise a proper resistor value if I did indeed want to include one or more RC filters in the power supply rails.

If I were trying to implement an amplifier circuit (past the power supply of this schematic, so the everything but the included power supply) and run a variable load of 16 ohm headphones up to 600 ohm headphones to a reasonable volume, how do I calculate this?  The amplifier circuit is just for reference, it wouldn't be this exact one but similar in nature (two stages, gain and buffer)

Amplifier schematic:

PSU schematic I'm testing with from the previous post:

I tried removing the first set of resistors (of the two in series, so now just 10ohms) to make the reservoir larger but still leave one RC filter, but because I'm not quite sure how to calculate the proper resistor value it ended up instantly frying the leftover resistor once powered.

Sorry for my ignorance on the subject.  I have a basic understanding of calculating various parts of a circuit, but this is much more complex than I've tried before.


texts: So I was wondering if there is any site or papers that has fun electrical circuit questions, such as placing the right components on a circuit to make it work, make the light dimmer/brighter by using certain components etc. I don’t want questions that involve calculations, more like placing components questions. If anyone could help that would be awesome


texts: Measure 208v single phase with Current Transformer

texts:
I have a single phase 208v circuit that I want to measure the amps on. What is the proper way to measure the amps?

This is for a connection with 2 hots and a ground wire, no neutral coming from a 120/208 wye transformer.

Do I put the CT on one leg and measure that?

Do I put a CT on both hot legs and average it?

Or do I put the CT over both "hot" wires?

Or something else...


texts: Have a 40 lb wheel that I need to spin at around 3 - 5 rpms. About 20" in diameter. Its for a display. What size/type DC motor would I need? I can figure out the drive system. Thanks


texts: In this datasheet, last page, what does "P. C. MOUNTING" mean in the diagrams?


texts:
I've been working on implementing strain gauge measurements at my company for some stress analysis. There's a chip that I think works the best for our application. It's the PS09 by ACAM. However, there are some problems I've run into concerning the on-board RAM and the consistency of its measurements.

For me, the appealing things about the device are its low-power, temperature
compensation, and SPI communication. These are all things I'm looking for.
So, I was hoping to run some ideas by anyone that has touched on this kind of device before.

There's a lack of talk about the PS09 online. I don't know if that's indicative of lack of usability and/or no one actually knows about it.

Has anyone worked with the PS09 chip?

Here's what I believe is the most recent datasheet: http://www.acam.de/fileadmin/Download/pdf/PICOSTRAIN/English/DB_PS09_Vol1_en.pdf

Please let me know if other details are needed, and I will try to provide them. (Is there, perhaps, another question that might be related to this?)


texts: Can a 24.0VDC/3.0A Power Supply be used with a breadboard?

texts:
I came across a DZ075 power supply.  It says it is +24.0V/3.0A.  Can that be used with a breadboard?  Or do I have to get it to 3.3V or 5V before I plug into the breadboard.  In other words, can it be plugged into the board then make it 5volts or before?

I took the cover off and found there are 8 pins.  The last three are +24V, the middle three say ground, GND, and the first two are not connected, but the pins available and say +5v.

I do not wish to be electrocuted or destroy stuff.

Edit:  Here is a picture:

Edit:  Could I move the connector all the way over to the left?  It would be connecting two 5V, three GND, and one 24V (the connector is only six connections).

Edit:  I'm not sure I should use it.  The amps are high.  From this calculator, http://circuitcalculator.com/wordpress/2007/09/20/wire-parameter-calculator/ it looks like my 23AWG wire is too small.


texts: Simple question dealing with sign conventions in KVL/KCL equations

texts:
I am having a little trouble remembering the sign convention for a voltage source in series with a resistor.  Lets say that the voltage source is on the left hand side of a circuit with its negative terminal on the bottom and positive terminal on the top and the resistor is in series with the positive terminal.

If I am looking for the current through this resistor, will it be positive or negative? Or does it really depend on my the reference polarity that I assign to the resistor.


texts: Determine lead acid battery safe float charge level for a range of state-of-charge

texts:
My question:
I want to know how to determine the highest safe voltage for a given SoC (state-of-charge). Or for a given float charge voltage, determine the lowest safe SoC.
Helpful hints to the solution:
In the answer to this previous question, Olin succinctly states:

Unless the battery is quite low, it can be charged by holding its
voltage at the "float charge" level. That is usually 13.6 to 14.0 V
for a 12 V (6 cell) battery. [...] For a really depleted lead-acid
battery, you have to be careful to limit its charge current.

The links below have been invaluable to me. I don't know if my question is dependent on any particular lead acid battery, or can be roughly determined by generic properties of lead acid batteries.

SLA charging basics
Charging Lead Acid
Lead Acid SoC vs Voltage
Internal resistance vs Capacity
Battery Performance Characteristics
Charging VRLA

(No wonder, then, why my head is gassing)
Background (if necessary):
The problem I'm actually trying to solve is designing a generic charging circuit which connects between a solar cell and a battery connected to a vehicle. The current draw by the vehicle at any time is unknown. Ideally, the capacity of the battery will not be known. Therefore, Olin's suggestion of limiting the charge current is not really an option, as this would be battery-specific. Saying that, The solar cells will be modest - probably at most 5A at a working voltage around the battery's float charge voltage. And the battery's capacity would be in the expected range for vehicles; so perhaps between 30Ah and 100Ah.
Obviously the charging circuit is not to replace the vehicle's charging system. Nor is it even to keep the battery at full charge - but to stop the battery emptying, as far as possible, while the vehicle's engine is not running. So while current is being drawn by the radio, lights, or accessories, or while the battery is relatively empty from said current draw, the solar cells would kick in.
Sorry for the lengthy question!


texts: What is the "thing" that produce radio waves

texts:
From the best of my knowledge, radio signals are generated through some "oscillating" device and are propagated through an antenna.

The signal transmits throughout vacuum and experience some attenuation in dense media.

The receiver which is another antenna has a filter that picks up the frequency.

The peaks of the wave represents a "1" and the valley of the wave represents a "0", this is interpreted as digital signals by a processor and generates the corresponding results.

Can someone elaborate as to what is this oscillating thing that produce radio signal in modern radio device. Is it some sort of crystal or some elaborate circuit?


texts:
I'm looking for an inexpensive and sealed angle sensor. I think of using an automotive throttle position sensor. They can be bought at low price and if they last under the hood of a car they are sealed well enough for me.

I thought that they are just simple potentiometers but according to Wikipedia modern TPS are non contact type hall, inductive or magnetoresistive sensors.

Most of them still seem to have three contacts. My question is how can they be read? I'm going to connect it to Arduino so can I read it the same way as potentiometer?


texts: What voltage rating does the resistor in this circuit need to be?

texts:
In this circuit:

the load is protected from transient voltage spikes by the MOV, which clamps at 1kV.
If the circuit experiences a 6kV spike on the mains supply, will the resistor get hit with 6kV, or since the MOV is clamping at 1KV, will the resistor only see 1kV?


texts: Why is the negative terminal connected to both transformers in this half-wave rectifier?

texts: I found the image below in an old book about vacuum tube rectifiers. Could someone explain why the negative terminal of the load is connected to the 6.3V transformer? I understand why it would be connected to the 350V transformer but not the other one too.


texts: What external influences can a cardiac pacemaker have?

texts:
Since in these days there are lots of different devices and appliances which are sending out all kinds of waves or radiation and different strengths (e.g. RFID scanners, induction cookers, Bluetooth, power lines above earth, security scanners, etc. ), I'd like to understand what of these influences in which strengths can influence a cardiac pacemaker or its sensors?
Does anybody have good and detailed reference for this?
Additionally, I'd like to understand in which ways the pacemakers are secured against external influences and what rules and regulations are in place to avoid that newly built technical devices might harm pacemakers?


texts: I have a latching relay that I don't quite understand.  It's pretty simple as far as operation goes.  If you apply power to contact B, (A is common) the relay latches.  If you switch power to contact #8, it resets.  I just don't understand how.  It looks like the diodes will block power to the coil when applied to #8?  and I don't understand why this works to reset the relay...


texts:
I'm building out a camper van with a solar powered electrical system.

My electrical knowledge is limited to a collage physics and an embedded systems class, so I would really appreciate it if I could get some feedback on a diagram I put together.

System Overview:

1x 100 watt dc solar panel (may expand to 300 watt in future)
EPEver Tracer MPPT 20a charge controller
2x 110 amp AGM/SLA 12v batteries
DC water pump (without pressure switch)
Shurflo Switch Faucet
Various LED lights
USB charger
Black and Decker power inverter (might upgrade to sine-wave)

Key notes:

batteries connected in parallel
breaker switch to kill input from solar
master switch to kill output to peripherals
plan on using a fuse block between all peripherals

Questions

Is there anything blatantly wrong with my configuration?

Does it matter how I connect the positive inputs and outputs to my battery bank?

Should they just go directly to one of the terminals of the battery?

If so, which battery (one is much newer than the other)?

Or can I create a master pole in-between the two batteries?
Can the Input and output be connected to the same point?


texts: Best way to develop a kapton tape cutter machine?

texts:
I'm constructing a machine that cuts kapton tape in a specific length, the way I'm doing is there's a motor that keeps pushing tape forward, when the tape covers an infrared led, the motor stops and another motor cuts the tape like a knife. The only part I'm not so sure it will work is the cutting part, anyone have a better idea?
I'd like to hear some before I spend money buying everything...
Ps: I'll be using an arduino to do all the control


texts: What is the smallest component to send HTTP requests on the Internet?

texts:
I want to build a GPS tracker to put on my bike and I would like to use the smallest components to do it. The idea is to send the GPS coordinates to an HTTP server every minutes.

The problem is all the components I found for GSM or 3/4G are all too big (around 50x50 mm).

Does it exist smallest components? Or does it exist alternatives to send data to a server?


texts: Understanding how to read output voltage of a current transformer sensor

texts:
I am try to understand how to read data from current transformer circuit. As reference  i am reading on this 2 articles: Article1 and Article2. I do not have easy access to oscilloscope which make it a bit harder for me to visualize.

Here is the circuit that Article one and two uses. (PS i am assuming the version where the burden resistor is built in to the sensor already)

What is the purpose of the Equal value resistor voltage divider and the capacitor? How would i compute the resistor and capacitor value?

what would be the reading if probes are directly connected to JACK A and B


texts:
I am looking for a kind of "voltage controlled open-closed switch", "tri state switch" or "solid state relay", implemented with transistors.

Consider a \$200\Omega\$ resistive load, and the \$GND=0\$ to \$VCC=5V\$ range for both a control and an input signal ("inputs to the gate").

A single PNP | NPN transistor, could be the simplest trial, switching from \$OC\$ to \$0V\$ | \$5V\$ if the load is connected to \$GND\$ | \$VCC\$, and only within some ranges of \$V_{E}\$, between \$1-5V | 0-4V\$ respectively.

The PNP with the transistor in the cut zone works well as open circuit: No current, independent of the voltage input and the voltage at the load end (Figure 1 ).

The problem is the PNP as closed circuit (Figure 2). For the given voltage ranges, the transistor is in the active|sat zone, and \$I_C\$ mean valuechanges "smoothly" on the voltage at the load end, instead of being independent of it, hence not achieving the purpose.

Green is the voltage input,
Red is the voltage output,
Blue is the voltage at the load end (GND),
Black is \$I_C\$.

What kind of transistor circuit should I use for implement a more real voltage controlled open-close switch?


texts:
I have been reading much about pulse power handling in THT resistors. I have concluded that for applications with pulses higher than rated power or voltage (like RC snubbers, or on AC line which may be tested to kV surges), the best to use are carbon and metal oxide.
But I could not find any comparison between them.
Does anyone have any afinity for one or the other type ?
This (https://www.digikey.com/eewiki/display/Motley/Resistors) says that metal film are better that carbon type resistors


texts: Proving the state of a diode in a clamping circuit?

texts:
simulate this circuit – Schematic created using CircuitLab
So i have this positive clamper right here. So the diode will be ON at a negative source voltage since the anode side will see 5V which will be at higher potential than the cathode side, right?
So if the diode is ON, we could replace it with a short circuit. If this is an ideal short circuit, we could say that it has zero voltage across it. But is there a way to do the proving here other than the assumption of an ideal short circuit? We have to prove that the diode is ON and that's the only way i think of how to prove it.
Is it also possible that I could instead prove that it is not OFF, because i could simply do KVL? How would KVL with the assumption that it is ON?


texts:
I've been reading about ringing and overshooting and all sorts of things, but all without getting a real "feeling" for how likely these things are to affect my circuit.

I've got a chip generating an SPI signal, traveling about 5cm to a 3.3->5V level shifter, and then traveling ~35cm (yes, it's a very long PCB) to the chip that receives it.  From what I understand, I shouldn't have issues with this: my traveled distance isn't even 1% of the wavelength at 1Mhz, which gives me hope.

What considerations SHOULD I have in mind when laying out the PCB to avoid issues with this signal?


texts: Unable to flash stm32f103c8t6 after erasure, device shows 0 bytes flash size (custom bootloader)

texts:
I have flashed a dfu bootloader from https://github.com/davidgfnet/stm32-dfu-bootloader onto
a fresh stm32f103c8t6 and it was working fine. After I uploaded my binary with dfu-util
the device would no longer show up in usb dmesg so it seems like the bootloader was erased, although the program (a simple blinker) always ran for a few seconds after powerup and then stopped.
The problem is that from now on if I connect the device via stlink it reports a correct size of sram but 0 bytes of flash. I tried flashing with st-flash --flash=64k write ... but it didn't work. Only other thing that comes to mind is to do some kind of a reset so I tried st-flash --flash=64k erase, it looked like it worked but the device still reports 0 bytes flash memory.
What could be the cause of this? Did the bootloader remove some stm firmware required for flashing the chip? How come only flash size is reported as 0 but not sram? Is there a way to reflash the required firmware or is it bricked? I'm lucky to have bought two but still I'd like to rescue the first one if possible.


texts: Ideal transformer primary and secondary inductance

texts: It is said when current is circulating in the secondary of the transformer due to connected load, a flux is produced by the secondary current that is "seen" by the primary  thus a current is drown in the primary to counter the secondary current. What I am confused about is, if the secondary current produces a flux it should have an inductance right? what is this inductance? the same would apply for the primary winding : when the primary current flows it counters the one that it is produced by the secondary. So does it have an inductance? If so where these inductance are shown in the equivalent circuit of an ideal transformer? I dont know but of course I am missing something.


texts:
I usually use 10K Ohm resistors for pulling up or pulling down micro-controller lines.  This is only because I have tons of them.

Recently while looking up pick and place surface mount information I found out that often times the number of types of components you have can play a part in the cost.

For example it might save money to change the 10K Ohm resistors to some other value already present on the board.

Given that, my question is; what factors are in play to determine appropriate ranges of resistance for pull up or pull down resistors?


texts:
When I simulate the circuit on (OrCad) I got an output voltage between (0 to 1) V changing with temperature .
but when I connect the circuit I got the output voltage = -1.85 in minus and different from simulation value , so where is the problem .

and I am sorry about my weak language


texts:
Any help will be greatly appreciated. This may be a very basic question. I have search for the answer and cannot find a solution to my problem. I am currently working on a research project from school. The idea is to make and Arduino flip a 12v relay, just to understand basic EE concepts. I have been able to acquire a circuit diagram from Jeremy Blums Video series on youtube. The problem is I'm not sure how to purchase two parts from the circuit. Specifically the diode and the transistor . Below is the circuit.

Don't get me wrong I have found plenty of tutorials explaining what these part do. I just don't understand how to calculate the specs given the verbiage from the back of the package of these two parts from radio shack. Below is a screen shot from the transistor.

And the Diode is:

I have been unsuccessful trying to find what Vceo, Vcbo, IC, Pd, fr, Hfe, Vce(sat),and Ic(max) stand for and their role into the calculation of the transistor. As well as voltage(vz), current(iz) for the diode.

Again any explanation or simply a link to a site in which I can read about these naming conventions would be great. Thanks you for your help in advance, and I apologize for my ignorance.


texts:
I am trying to use a output signal to reset a counter, but the signal I have is "low when counting" and I need "low during reset".

I want to "invert" an open drain output to a new signal so that when the output is on (connected to ground), the "inverted" signal has voltage or is not connected and when the output is off (not connected) the signal is connected to ground. My source voltage is 12v in an automotive system.

I have been struggling with this for a while and I must be getting confused with the negative logic because each solution I have tried gives me the same signal. I would love to do this with resistors and one or more of these BJT transistors: 2N3904 2N3906 S8050 2N2907 S8550 2N2222 BC337 C1815 BC327 A1015 since that is what I have available already and would work best in the enclosure space I have.

Output: I have a hardware component (LCR-II) with output Aux 1 which is an open drain output common to the negative power input line. Sinking capability up to 1 Amp. Maximum circuit voltage is 12v.

Input: I have another piece of hardware (a digital counter model CUB5B000) with a user input that is internally pulled up to +12 V with 10 K resistance. The input is active when it is pulled low (<1 .0 V)

I usually just work in software, so I'm apparently rusty from my University electronics -- thank you!

Between the work I already did and the answer from @Elliot-Alderson, here is my current attempt at a solution:

simulate this circuit – Schematic created using CircuitLab


texts: Roles of the coupling and bypass capacitors in a CE transistor

texts:
I wonder what the purpose of the coupling capacitors and the bypass capacitors are and the type of effect each capacitor has on the circuit.
As I've understood it, you use coupling capacitors to block DC and avoid interference (what does that really mean?) and the bypass capacitor is to have a short-circuit in the emitter of the transistor (and what does this really mean?).
If I vary the values of C1 and C2, what kind of effect does it have on the bandwidth of the amplified signal?
What happens if we have a large or a small bypass capacitor (C3), what effect does it have?
So in essence, what does the three capacitors do in the circuit, i.e. what low pass and high pass effect does it have?
I have an LTspice schematic that we can get a visualization from.


texts:
A 0.56 kW induction motor is operating from a 240 V 50 Hz supply. Its synchronous speed is 1,050 rpm and its rated speed is 880 rpm. It produces no torque at 1,050 rpm and its rated torque is 6.08 Nm.

Assume a linear τ - ω relationship near synchronous speed, and hence calculate the speed (in rpm) corresponding to 2/3s of the rated torque.

I have used the equation so far that:
0.56 kW/6.08*2/3 = Speed

That answer is wrong, so is anyone able to help me with this one?


texts:
I am currently learning electronic on my own. And I have a question about the circuit below.

Given: 2N6027 is a programmable unijunction transistors. (I'm not sure if that is the right schematic for it)

Question: The objective here is to make the LED oscillates on and off. I have tried all of the three circuits below, but only Circuit 1 works. Why circuit 2 does not work? I believe the resistors R2 and R3 in circuit 1 are connected in series anyway right?

Why does the PUT's gate have to be in between R2 and R3?

simulate this circuit – Schematic created using CircuitLab

Below are the pictures of the Circuit 1

http://examples.oreilly.com/9780596153755-files/mkel_02/mkel_02_098.pdf
http://examples.oreilly.com/9780596153755-files/mkel_02/mkel_02_103.pdf


texts: VHDL Question: Sequential Execution Within a Process

texts:
I've inherited some VHDL code I need to extend. There's a piece in there that looks like a bug to me, but while I'm long-time C developer, I've no experience in VHDL. I understand that processes essentially run in parallel, but within a process, does order matter? In the following code, a CPLD is receiving serial ADC data from a microcontroller. The data stream contains the results from two separate 8-bit conversions and is being loaded into two registers, one bit at a time. However it looks like at the end of receiving the first byte of ADC data, the MSB of this byte is being overwritten with the MSB from the second byte before it's loaded into its register. Is this a bug? I've removed some of the code to make the sample more readable.

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.std_logic_arith.all;
use ieee.std_logic_unsigned.all;

entity CPLD is port(
   ADC_Clk              : in  std_logic;
   ADC_Data             : in  std_logic;
end CPLD;

architecture arch_CPLD of CPLD is
   signal   ADC_Counter : std_logic_vector (7 downto 0);
   signal   ADC_Reg_1   : std_logic_vector (7 downto 0);
   signal   ADC_Temp    : std_logic_vector (7 downto 0);

begin

-- Shift in data from two 8-bit ADC channels
--   ADC_Counter incremented by another process on rising edge of ADC_Clk
ADC_Shift: process(ADC_Clk)
begin
   if (falling_edge(ADC_Clk))  then

      -- Shift in 8 bits from ADC data channel 1
      if    (ADC_Counter = 5 ) then   -- skip over sync bits
            ADC_Temp(7) <= ADC_Data;  -- get MSB of data
      elsif (ADC_Counter = 6 ) then
            ADC_Temp(6) <= ADC_Data;

      -- code omitted for clarity :      getting bits 5 to 1

      elsif (ADC_Counter = 12 ) then
            ADC_Temp(0) <= ADC_Data;  -- get LSB of data

      -- shift in 8 bits from ADC data channel 2
      elsif (ADC_Counter = 13 ) then
             ADC_Temp(7) <= ADC_Data; -- BUG? Overwriting MSB with next byte?
             ADC_Reg_1 <= ADC_Temp;   -- first byte of data to Register 1

      elsif (ADC_Counter = 14 ) then  -- continue getting second byte
            ADC_Temp(6) <= ADC_Data;

      -- code omitted for clarity

      end if;
   end if;
end process ADC_Shift;
end arch_CPLD;


texts: LPC1768 doesn't generate RTC clock while other LPC1768 does

texts:
I have this board with LPC1768 and 32.768KHz crystal but the RTC does not work. By directing RTC clock to the CLKOUT pin I realized that there is no RTC clock so it makes sense that it's not working. But I have another prototype board (a small board) with LPC1768 and this one has no problem with the RTC.
Now I changed crystal and two capacitors (RTC required components) of the prototype board with my board and the prototype board RTC kept working even with my boards components while RTC in my board still does not work with the prototype board components so I'm sure that it's not related to the components and their quality and things like that.
I must add up that besides RTC everything else works in my board without any sort of problems.
I suspect the MCU itself.
Now what do you make out of this ?

EDIT: 1- I almost forgot to mention that the crystal is located pretty much close to the MCU so I really do not suspect the layout.
2- Also the software is the same for this two boards so firmware problems is most unlikely.


texts: DP83848 (Ethernet PHY) 1-bit serial receive data in 10Base-T

texts:
Having trouble getting a Texas Instruments DP83848J working in 10BASE-T mode.

The link partner and local status register agree that the link is in 10Mbps full-duplex mode.  However, instead of receiving 4-bit 2.5Msps data on RXD[3..0] as required by the MII spec, a logic analyzer shows 1-bit 10Msps data.  The only Ethernet standard I can find that describes that type of data is GPSI, which is not part of the DP83848J feature set.

Any idea how to configure the DP83848J to output data compliant with the 10 Mb/s MII Timing spec?


texts: Do I need power supply totalling my current needs to maximum of my current needs?

texts:
My prototype project has these 3 components currently:

US-17HS4401 stepper motor, rated at 12V / 1.7A
MIG-400 6V DC motor, 6V / 10A max (although it was spinning fast enough at 3.75A)
Particle Photon, 5V / 0.5 A
2x L298N driver controller (reduces voltage to motors by 2V)
1x DC-DC LM voltage regulator.

I'm looking to buy a power supply for my project. Looking at this the total current draw is: 5.95A, the maximum draw is: 3.75A

My question is does the power supply need to add up the current required or just provide the maximum required?
Since each device has different current requirement do I need to add a step down module for amps before each device?

What will happen if my device is given more amps than provided? Do I need to place before it any safeguards?

Rough schematic of my setup:


texts: PID implementation for a Humidity controller

texts:
I'm working on a humidity controller which uses PID algorithm to control the process values. I have to implement 2 PID routines as there are 2 process values ( Humidity and Temperature) to be controlled. I read many articles on PID controllers and I believe I understand the significance of each terms.
But the problem is I cannot figure out how each terms are converted to the real output ( varying On/Off cycles of Air heater and a boiler). What I have done so far are
In main routine

reading 2 ADC channels every second

calculating the PID output (value from 0-100) every second
Integral and derivative terms are added to the power calculated every Ti & Td cycles  (programmable in 0-240 seconds). Since my PID output calculation is executed every second ,the very next execution after adding an integral term ( Or derivative) will result in a less power than the previous value (ie when integral or derivative power are added).

In ISR (@ period 2ms) I use 2 values ( On time and off time which are calculated using the PID output and cylic time( also programmable in secs)desired for the output) to change the output.
As you can see the with these timings integral power and derivative power does not going to have any effect on the output duty cycle and  My questions are

Should I increase the period of PID execution time or
Should I retain the value of last calculated integral term ( or derivative) with the proportional term till the next addition of the integral ( or derivative).

I know I will get an idea how to play around each terms when it is tested on the system and after analyzing the response of the system. But I just want to clear my all doubts and to finish maximum part of the code possible before I get a machine to test on.


texts: Help me calculate which transistor I need

texts:
I have virtually zero electronics knowledge, but I am a software engineer, so it's something I should be able to learn.

I'm playing around with a Raspberry Pi, and I want to use it to power a 12v solenoid. I can supply the 12v input from an external supply, and use the Pi to provide the Base input to a transistor, which I hope to use a switch to turn the solenoid on and off.

My issue is that I don't understand how to work out which transistor to use. I've narrowed my search to an NPN type, whereby if I programmatically supply a signal from a GPIO port, this will put 3.3v on the Base of the transistor.
But I'm struggling to calculate which transistor I will need to produce 12v across the Collector/Emitter (ultimately delivering 12v to the solenoid).
I'm not so much looking for the answer, although I'll accept that, but moreover how in laymans terms I can calculate it all.

I'm told I'll need resistors in the circuit also, so perhaps if someone can point in the direction of some grass roots guides of where to start?
Thanks in advance for any help


texts: Loading a shift register without displaying its contents/output?

texts:
I'm making an LED matrix using two DM7495N 4-bit shift registers and one 8-bit shift register. The 4-bit registers are for the anode columns and the 8-bit connects to transitstors controlling the cathode rows. The matrix is 8 by 8. This setup is necessitated by the attiny85 I'm using as the microcontroller, which does not inherently have enough I/O pins to control an 8 by 8.

My idea is to rasterize the matrix, by loading one of the 4-bit registers, while the other is displaying its contents, then switch and keep going through the whole matrix in that fashion. That way, I can keep 4 LEDs on at a time to preserve overall brightness of the matrix. The only problem is that I can not think of an easy way to load one of the 4-bit shift registers without simultaniously displaying its contents, which would display as giberish on the finished matrix.

The attiny85 has 5 I/O pins, unless you count the reset pin, which I would prefer not to use, since it would require high/low voltage programming in order to reprogram the microcontroller. I am using one of the 5 I/O pins to control the data coming into the all three shift registers. Three more pins are being used to control the serial/shift pins of the individual shift registers. That leaves me with one free I/O pin.

Is there any easy way to control which 4-bit register is displaying and which one is loading with that last pin? I have thought of using a not gate and some extra transistors to control which 4-bit register is recieving a higher current on its VCC line, so that it may be recieving enough current to recieve serial from the microcontroller, but not enough to power any of the LEDs that it is connnected to. Would that work? I'm kind of a noob with shift registers and electronics in general, so I'm not sure.

The other way I have thought of is to simply have a transistor for each output of the 4-bit registers, controlling the flow of current to the anode columns. The not gate would control which transistors are saturated depending on which register is displaying and which is loading (The input to the not gate would also be connected to the bases of four transistors corresponding to a 4-bit register and the output of the not gate would be connected to the bases of the other transistors corresponding to the other 4-bit register).

Both of these approaches would require a fair number of transistors, which I would like to avoid, considering that I am somewhat constrained on space. Sorry if this stuff is hard to visualize. If that is the case, then I could try making a schematic. I have never tried making a schematic before, but I could try. Any ideas as to how I could accomplish the effect I want, in the simplest way possible would be greatly appreciated, or just any other insight! Thanks!


texts: If Faraday's law states that Emf is inversely proportional to time, how is it that we can give emf in the unit volts? I'm a second year electrical apprentice, so am I missing some sort of relationship between voltage and time?


texts: Help identify this component (probably some sort of thermal fuse)

texts:
This is a part taken from an old steam cooker. It has two terminals at the top. The first terminal is connected to the phase wire (230 V AC) as it enters the device and from the second terminal it is routed further into the device. For this reason I think it is probably some sort of a fuse.

The two terminals on top are bridged by a two thin metal sheets. There is a vertical ceramic rod that goes through the part, pushing on those metals from downwards. When the rod is pushed up, the metal sheets are disconnected. In the base there is what I guess may be some bimetallic sheet that would push the rod up when the device overheats.

I would like to know if it is indeed a fuse and how is this component called exactly. I tried to find some pictures of fuses but they looked very different from what I have.

As a new member on this site I cannot post that many (that is 4) pictures, so I have to give a link to a HTML page where additional photos are.


texts: How to measure line voltage (220V) with an arduino?

texts:
I'm a Electrical Engineering student and I want to sense and sample the voltage signal  coming from a wall socket (110V - 220V). I came up with the following circuit using a voltage divider with high impedance and a diferential amplifier. I would like to avoid using a transformer because of weight constraints.

Is there a better way to solve this problem?
Should I use a capacitor divider instead?


texts: Relevant dc motor specs for buck converter design

texts:
I need to design a buck converter (controlled by pwm using feedback) for a 24V dc motor under no load. The buck converter output can be controlled to vary between 15v and 24v. I understand that in order to choose a correct inductor value to ensure CCM operation, I need to know the load current, and that the lower the load current, the greater the required inductor value as per this design formula:

The nominal voltage for the motor is 24V
and there is a rated current of 130 mA. The spec also states that for 24V motor models the maximum no load current is 50mA. So for my design what output current should I be using to choose the inductor value? 50mA is the maximum no load current meaning that it could technically be less than 50mA so I think it would operate in DCM if I designed for this value. And I don't understand how the output current would vary when supplying less than 24v to the motor (since the voltage supplied to the motor could be as low as 15v). My intuition is that the current draw would be greater, so I should be considering the worst case scenario, 24V, but maybe this is not true.


texts: galvanized wire as material to construct a sensor matrix

texts:
I did a button matrix using galvanized wires (only one thread, 1 mm thickness) and it works. (But) I don't know, it's a good material o it can melt with temperature? Maybe galvanized metal is a "bad conductor" of electricity, I read about it but nobody explains the reason.

I'm not planning to use it on the outside, it will not move from home :)

It's a little project that will work with batteries, at 5/10 V and 0.5/1A at maximum.

Thanks in advance for your time, and regards!

Edited: The wire I'm talking about is this
It's something like it: https://www.amazon.com/50143-Gauge-Galvanized-Steel-Wire/dp/B001EX57ZK/ref=sr_1_3?ie=UTF8&qid=1524132120&sr=8-3&keywords=galvanized+wire

there are "versions" made from aluminum, iron or steel. Aluminum seems the best in terms of conductivity, copper is better but it gets "oxidation" easily.


texts: Is interfacing the 5V TTL UART with 3.3V microcontroller via voltage divider possible?

texts:
I need to connect my MSP430 microcontroller (3.3V) to interact with a 5V TTL UART camera (http://www.cn-lcf.net/sdp/561974/4/pd-2909996/7575433-2127043/LCF-23M_OV528_Protocol_RS232_Camera_Module.html).

In order to do that I came up with the idea of dropping the camera's TX port from 5V to 3.3V level by a voltage divider.

The MCU TX to camera RX does not need a voltage divider and since it's a TTL camera the 3.3V from the MCU shall be enough to drive the camera's input high (https://dlnmh9ip6v2uc.cloudfront.net/assets/6/d/7/7/4/515385fdce395f0905000000.png).

Will that work?


texts:
I designed a PCB with an STM32 and a micro USB connector. I put a NUF2042XV6T1G between the connector and the STM32 to protect the data lines. The USB shield is connected to system ground via a 120R@100MHz ferrite bead.

The board has a power prioritization scheme going on, so it can be either bus powered, powered via a power supply or from a battery. I tested the prioritization circuit extensively, and the priorities and the make-before-break behaviour work just fine.

However, I noticed that when the board ground is referenced to mains earth via the power supply, the STM sometimes resets when I plug in the micro USB cable. At first I thought that the make-before-break doesn't work reliably, but that is not the case. Then I noticed that it is enough to touch the micro USB plug's shield to the receptacle's shield to crash the CPU. So I had a look at what's going on on the USB shield when not connected to my board:

Above is the shield voltage (referenced to mains earth) when the USB cable is plugged into a cheap chinese USB power supply (no mains earth connection).

Above is the shield voltage (referenced to mains earth) when the USB cable is plugged into a genuine Apple USB power supply (no mains earth connection either). Not as bad as the chinese one, but I'm still shocked (fortunately only figuratively. I don't notice anything when touching the shield with my finger).

I noticed that the CPU does not reset if I touch the USB plug's and receptacle's shield with my finger before connecting the metal parts when plugging in

So the question here is: How should I connect the receptacle's ground to the circuit ground to avoid this issue and stay clear of EMI issues? A high resistance (1M or so) instead of the ferrite bead? Both in series? Both in parallel (makes no sense to me)? Capacitively couple them?


texts: Abnormal Voltage drop reading, 4 wire vs 3 wire, Singled ended input

texts:
I have been given a measurement circuit that is measuring voltage drop across a switch. The idea is that it uses the 4 wire method for measuring resistance. However for our purpose we are not measuring current and are only concerning ourselves with voltage drop.

Using this method we have a repeat-ability issues (Gauge R&R). The reading can be any where from 30mV to 150mV, over 12 repetitions. I believe this is because the 0V/VCC Sense lead is floating away from 0V at the divider. If I tie the 0V sense directly to the 0V at the PLC the repeat-ability issue goes away and I get between 15mV - 21mV.

Would I be correct in thinking that a 3 wire method with no separate sense lead for 0V would make more sense given that the PLC input is single ended?

Note PLC input is a Click C0-04AD-2

simulate this circuit – Schematic created using CircuitLab


texts: What are these inputs for this audio power amplifier?

texts:
I have made a preamplifier with filter but before asking that question I decided to open a specific question about a MOSFET audio power amplifier. It seems an old one and I cannot find its data-sheet so I couldn’t share it. Below is its right inputs and right outputs:

From its banana jack outputs it is powering a 8Ohm 60W speaker. Speaker is used for some experimental setup at low frequencies from 0.1Hz to 100Hz max.

I noticed that they are using sym input which is coming from a function generator set to much higher than line voltages like 1V. One of the reason is that same function generator output also goes to a scope and a DAQ. So basically they don’t use typical audio inputs.

The preamplifier I made will replace the function generator and will be coupled to sym input. But I don’t know the input impedance of this input.

Regarding the photo my question is; what is sym input used for? I couldn’t find what sym and asym stand for? And what can be the ground lift switch?


texts:
I window shopped for a small size battery.  On the battery specifications, there are:

capacity(mAh) : 85mAh
Pulse Current(mA) : 190
Cycle Life(Times) : 300

What does Pulse Current mean? Does it means this battery can supply 190mA at a time?  If there is no resistance between the terminals, can this battery supply power for 190/85 hour?

What is Cycle Life?

Do I have to connect a resistor when I operate the micro motor with 5v 500mA power source? [sic]


texts:
I have a serious hobby coilgun project powered by a 6S (25V) LiPo Battery. Currently i have the LiPo, capable of at least 600A burst current connected to a ~75mOhm circuit for some 300+A of peak current. I have built said system with a Mosfet switch (AUIRFB8409 ~1.4$ each from AliExpress). These have worked, but if the current stays on even a little longer (or maybe vene from just wear) they break. The first switch is exposed to some ~4-8 ms of current, which according to my calculations would only rise to the 300A at the 4ms mark or so (pure speculation).

My question: What are my best alternatives to switch the current?

As i see it:

Parallel 2-4 of those mosfets with strong thermal coupling. Cheapish, would probably work?
IGBT? The high voltage rating is wasted and would not work properly with my 25V? and they seem to either have same current handling as Mosfets or be super expensive and huge
Something else entirely?

Thank you for your time


texts:
Thank you all guys for taking the time to answer my question. I really appreciate it. Now, I think I made a mistake and asked the question wrong. I know that I can use a telephone charger to power up a small sensor instead of batteries (I am using a laser with an LDR and a light-dependent motion sensor - it only works when it is dark). What I may need is a  switch (either with relay or with transistors) to swap between the domestic power supply and the batteries in case of a power shortage.
I apologize, maybe this forum is for advanced users and I am not one. I thank you all twice for that.

→I am trying to build an inexpensive SMALL UPS circuit allowing me to swap between domestic power line and batteries. It would be fine if it could convert from 110 or 220 VAC to 5 or 12 VDC. Is this even possible without making a bulky device or using a transformer?
Thanks a lot for your answer even if it is to tell me it is not possible.←


texts: Rise time and fall time issue in the power MOSFET

texts:
In our automated design due to MOSFET obsolete we have changed new MOSFET which gives us rise and fall time issue at the frequency applied from 10Khz to 500Khz. when we use the power MOSFET as Load and working in MOSFET active/Linear region of operation in our Dynamic load pattern test notifying this issue.
Old Mosfet P/N: sie844df
New Mosfet P/N: sie882df
What are the parameters we have to look in to it to fine tune the circuit?
appreciate all your help in advance.


texts: How to make a pulse source with a changing duty cycle in LT spice?

texts:
I have a power electronic inverter, and I want to make the duty cycle of the PWM dependent on the ratio of "vout/vin", where vout is an AC power source.
Unfortunately, setting .param D= IF(V(vout)/V(vin) < 0.5, 1, 0) doesn't work. In fact, even just setting D to be a sine-wave source doesn't work.
Does this mean that LTSpice params need to be constant, and that a "control circuit" needs to be implemented to get something that can change on the fly?


texts: Power supply or-ing with ideal diodes - priorities?

texts:
My PCB can be supplied by internal LiPo, USB or via an external supply through a data connector that also carries power. Right now, I have the power inputs or-ed with LM66100's.

I'd like to prioritise the supply options as follows: USB > EXT > Battery. The LM66100s always switch to the highest voltage, so that makes USB highest priority. However, the external supply can come from a battery in the other device as well, and so it can be lower than the internal battery's voltage. Since the battery there is larger than the internal one, it should always be prioritised above the internal battery.

I have never designed such a priority switch, so I'd like to ask for pointers as to how to achieve this prioritization.

Some data as requested: The battery voltage (and external supply) is from standard LiPo 1S batteries, so let's say between 3.5V and 4.2V. Current is 500mA max.


texts:
I am trying to simulated in pspice a soft latch on/off circuit but it is not working as expected, even if I double check the implementation. Can someone explain to me why the voltage on the probe is 0.6 V even if the circuit has no "ON" button attached to it in this moment? I supposed to be off since the gate of PMOSFET should be high but it is not. I am almost sure that I did something wrong in the simulation.

Thank you!


texts: LTspice 2 grounds for AC PWM control by mosfets

texts:
I'm working on a AC PWM controller with 2 mosfets. It took me a long time to get this to work in LTspice but i still can't get it to work. I send pulses to the mosfets to generate the PWM modulation on the AC side. Everything works until i want to implement an optical galvanization. For this i would need to define 2 grounds in LTspice and this is the point where things start to get weird. I've already looked on the internet for more information about this topic. In LTspice you can only define 1 ground node, this is the reference voltage from where LTspice starts to calculate. If i want to use a second ground i have to use the COM node. I tried to do this but it still doesn't work. I know my mosfet part works and i know my opto coupler part works. When i try to connect both LTspice starts to behave strange. I've connected the COM node and GND node with a 99M resistor( this was a solution i found online) but this doesn't work at all. How can i get this simulation to run? Attached are 2 print screens. The first is a working mosfet switch, the second is with the opto coupler.
I hope somebody here can help me to get this to work.

Thank you all!


texts: How is voltage split between load resistor and C -> E on transistor?

texts: I am confused by the voltage reading in this simulation as VCE reads as 907V which means almost the entire voltage is dropped over the VCE at the transistor. I assumed that the VCE should be a fixed voltage and the rest should be dropped over the resistor. When I play with different values, then sometimes this is the case and sometimes not. But it seem unpredictable.


texts: Ground potential not at zero in 30y old apartment

texts:
I am living in an about 30 years old apartment in China.

Sometimes when I am touching my Mac Book (aluminium case) I would get little electric shocks. I measured the voltage between my Mac Book case and ground to be roughly 10V, there is a current of around 1mA constantly flowing through me. :/

Another weird effect is, when I am using an LED light in my room, there constantly is a voltage of 30V even when the switch is turned off!! That seems to be some serious ground loops!

When I plug my electric guitar, I am also getting some slight shocks while playing.

So I started to make some measurements with my multimeter.

I found out that when I measure the voltage between the ground pole of an electric plug with a metallic water tap in my room, there is a potential difference of nearly 100V (!). I also measured one phase to ground to be around 120V and another phase to ground to be around 100V, so none of them are being "neutral".

Now the question is: How do I resolve this issue?

I am already using a wire to connect the case of my laptop manually with the metallic water tap (that makes most sense to me to call "ground"). Like that at least I can partially get rid of the little shocks through my body. Now, what would happen if I connected the ground pole of the electric plug (that I have measured to be at 100V) with my water tap? Would that elevate the ground for the whole apartment to "zero"? Or would that be very dangerous?

Don't worry, I will not try it out until I am sure about what I am doing.


texts:
Hi,
I have a 1988 laptop with a blown PSU capacitor (was located in c10).
The capacitor still barely reads 395 (which an online calculator says means 3.9uf) and +35k which means 35v(?).

1) How important is it to replace the capacitor I have with one of the same characteristics?

2) How important is it to have the replacement capacitor a tantalum one?

Thanks.


texts:
I'm building a small PCB project and I need to connect to a third-party accessory that uses the connector pictured below. I've sifted through supplier catalogs looking for it, but without knowing what it's called or what category to search under or anything, I've come up empty.

If anybody has worked on remote car starters before, it's the same connector that Directed Electronics uses for the D2D interface. I can take a few measurements if you guys need.

Edit: The dimensions as close as I can get them are 10.5mm wide x 4 mm tall x 7 mm long. The pitch is 2.5mm, and the distance between the two 'locks' on top is 6mm. The wires are 24AWG.


texts: What's wrong with this SD card CMD0 logic analyzer trace?

texts:
I'm trying to talk to an SD card from an ESP8266, using one of the internal SPI drivers. No matter what I do, the card never responds to the initial CMD0 setup command. I think I'm sending the command correctly, but I never see any activity on MISO. I have:

verified connectivity on the MISO line from the microcontroller to the card;
tried with multiple cards;
tried with multiple card readers;
tried at a variety of clock speeds (currently it's set to about 300kHz)
verified that the internal pullup resistors on MOSI and MISO are enabled

...and now I'm out of ideas. My suspicion is that there's something subtly wrong I'm doing with the initialisation ritual which is causing the card to never wake up. This is the sort of thing which anyone with experience should be able to tell at a glance from the logic analyser trace, right? So here it is. You can see the remains of the init sync sequence on the left (20 bytes clocked with CS high). Then CS goes low, and there's the 04 00 00 00 00 95 CMD0 packet going out; I would normally expect to see activity on MISO in response, but there's nothing. Pulseview's protocol decoder thinks the command is valid. Is there anything obviously wrong here?


texts: Issues with non-inverting op-amp Pspice sim

texts:
I want to build the circuit pictured here in Figure 1:

When I simulate it, this is the result:

For some reason, the output of the op-amp is always 183.8mV and if I work backwards using the expression for the op-amp output, I don't get the correct value for Vshunt.

Here's what I've tried:

Making a dedicated 22V voltage source for the op-amp since, according to the datasheet, the max supply voltage is +/- 22V.
Changing the Rshunt value, RL value, Rf, and Rg values to see if it affects the value of Vo and nothing seems to change it.

What am I messing up here?


texts: Boost Converter unstable with rapid current changes

texts:
This is a follow-up to the question I raised previously on a previous design (Unstable boost converter with short bursts of current draw) where my boost converter was producing large output ripples due to rapid changes in current draw.

Based on the helpful responses I adjusted the design to have a smaller inductor and a boost converter IC with larger peak current capability. Below is the schematic and board design. The schematic is almost identical to the boost converter example on page 13 of the Linear Technologies LT3579 datasheet. The only difference is that I changed the output to 10.5V instead of 12V (should give me better current capability) and I upped the input and output capacitors in an attempt to smooth the output. The board layout is almost identical to the recommended layout on page 16 of the same datasheet.

With both this design and the previous design, the output is very smooth, achieves exactly the V_out it is designed for, and experiences no ringing under normal loads which are either no load or a couple hundred mA. However, the boost converter is connected to a GPRS modem terminal which is meant to be powered by a minimum of 8V. Two conditions exist with this particular modem which will cause it to shutdown or restart:

Voltage dropping below 8V, and
Voltage rippling more than 1V under transmitting load.

The idle and startup of the modem works great, the boost converter's V_out stays steady. However, when transmission occurs, the modem's current draw jumps to 1.2A for about 500ms at a time. This is when the boost converter fails to keep up. There are large dips in V_out during this transmission as shown in the following scope pics:

V_in from a battery at 6.5V.
V_in from a DC power supply at 8.0V

Both experience large ripple in both input and output which cause the modem to shut down. Powering the modem directly from a 9V battery (so long as its voltage is above 8V) allows the device to function no problem but the limitation of >8V severely limits the life of the battery.

Paralleling more ceramic capacitors in the input and output help only marginally. I do believe there is something fundamentally flawed with this design, perhaps in terms of response time. Though I don't know if I have a means to test it, I don't think the boost converter would have any trouble handling 1.2A, it's just the rapid change in current that's tripping it up.

Please let me know if you can help in any way, this is driving me nuts :)


texts:
I have a laptop battery pack with a fried component (visually fried) that has the appearance of a large surface mount resistor (only 2 connectors). It has the PCB abbreviation next to it of "SR1" which I have not been able to identify. It also has "R010" and "FZ67" on it, though I haven't been able to find a component matching those part numbers either. One side of it connects directly to one end of the battery pack.

How do I identify this part?


texts: Can I use a PC/104plus board on a PCI-104 connector

texts:
The problem is: I have a miniPCI card that I need to attach to a motherboard that only has an PCI-104 connector available for expansion. So i found an adapter that is a PC/104plus to MiniPCI adapter. My questions are:

Is PC/104plus compatible with a PCI-104 connector? (I will not be attaching anything else to it). I read wikipedia article which is clear that you can put PC/104 on PC/104plus. It also says that all of PC/104 , PC/104plus and PCI-104 use PCI bus, but it is not clear if I can attach a PC/104plus to a PCI-connector.
And if the above is yes, does it matter that is is not on a standalone stack with its own SBC but just a connector on a motherboard of an embedded PC?

EDIT: As many pointed I misread about PC/104 and it is NOT working with PCI bus, so please ignore it. But it does not change my question because the connector is PCI-104 and the expansion card is PC/104plus which does work with PCI.


texts: How does a pre-amplifier work and why is it needed?

texts:
I am making an amplifier and came across the fact that, if I want to operate a microphone then I will need a pre-amp.

What is the difference between power amplifiers and pre-amplifiers? Do both of them have the same gain, and if so then why do we need pre-amps?

Detailed explanation would be more more helpful to get the concept.


texts: 4 bit and 3 bit comparator with 2 bit comparator

texts:
Hello so I am newly learning Digital logic design and my professor just started design of functional modules. We did comparator circuits: 1 bit, 2 bit & 4 bit. We have also studied how to design 2 bit comparator with 1 bit comparator. Our professor said it is possible to create 3 bit comparator with 2 bit comparator and also 4 bit comparator with 2 bit comparator. So I want to know how to do it. I just need a heads up on how to start it and  understand the logic behind it. If anyone of you can help it will be greatly appreciated.
What I tried:
( I have drawn block diagrams for both of them and trying to proceed from there)
For three bit comparator i am planning to use a 2 bit comparator plus 1 bit comparator. I have succeeded in doing this but what if i have to do it with only two bit comparator? How will i proceed?
For 4 bit comparator I have layered it with 2 bit comparator nd then the 2 bit with 1 bit comparator. I don't know if its the right approach or not. I was able to derive the boolean function for checking whether both are equal but stuck on getting the other functions of the conditions.
I am not asking to solve the whole thing for me I just need a hint, a heads up. After that I think I will be able to figure out the rest of it.