texts: Using an Opto-Isolator to detect 120VAC on a Microcontroller

texts:
I am designing a system where I need to know whether or not 120VAC is present on a specific wire.

The system is in line with a fuel pump system, and I need to check to see whether or not the pump is getting power, if not, make an alert that the Emergency Shutoff Switch has been pushed.

The line could be either 0v (Open), 0A @ 120VAC current (Pump powered but not running), 8A @ 120VAC (Pump powered and running).

I really only need to detect whether or not there is 120VAC present.

I have found multiple sources saying that I could use an OptoIsolator, would this suffice?

And how would one wire it? Is it as simple as 120VAC in, 5v out? Or is there additional circuitry that I require?


texts:
I found in a book a scheme representing a terminal connection used in making an ammeter shunt (with the purpose of extending its measuring domain).

I can't understand what the drawing at b) represents. All those resistances want to model the contact resistances.

Then, the book says that in order to make the measurement more precise, we use a "double terminal", drawn here:

What do these drawings represent in real life and why are the resistances arranged as in the first picture, at c) (the delta connection)?


texts:
I need to run 12v across 30 feet of 18 guage wire.  The device on the other end consumes 2 amps.

I have a 12v power supply (rated 3A) and I want to ensure the device on the other end gets the full 12v.

I found this post voltage loss calculation but I'm not clear on something.  If my power supply can put out 3A and the device only needs 2A, does that mean there will be no voltage loss?  (there is no sense wire)  Will the full 12v arrive but there will be current loss?

I'm missing something basic here...

UPDATE:

I found 18 guage copper wire has resistance of 6.385 Ohm/1000 feet.  so 6.385 * 60feet/1000feet * 2 amps = .76v loss.

From the comments it's apparent that voltage loss is unavoidable.  So if I need 12v at the other end of the wire, I will need a power supply with 12.76v output (or adjustable).  I already purchased a 12v switching power supply from ebay today for $8 - perhaps i bought too soon.  Can these power supplies be adjusted (crack open the case)?   Do 12v power supplies really put out exactly 12v?  (Or do they put out 13v assume loss on wire, etc)


texts:
I have been using microcontroller like ARM Cortex M4 32bit based microcontrollers. Now I am thinking to move towards DSPs, but I really don't know how things work in Processors and DSPs, I mean in case of microcontrollers usually you have RAM/Flash integrated in the same chip, you simply use a Programmer/Debugger and develop your systems.

In case of Processors/DSPs, I don't know how to integrate RAM and ROM/Flash and than how to and where to upload my program, I guess it would be the Flash/ROM which will hold my program or the processor will also require some startup code to start fetching data from ROM?

Lets take any example say, I have a TI C2000 Piccolo series 32bit DSP, 10kB RAM and 10kB ROM/Flash.

Now -

How to integrate them?
Which one need to be programmed ROM and DSP or only ROM?
How to program specifically if I am using Piccolo?
Any kick Start material/tutorials to start "Hello world" with DSP/Processor? I am not talking about BeagleBone or RasberryPi etc. as they are operating system based ready made solutions.


texts: Altium: How can I dim the layers I'm not currently using?

texts:
The routes on all layers are fully bright. I want to dim the ones on the layers not currently used.

I don't mean dimming ALL routes (even on the layer I'm currently on) except the one segment I'm selecting.


texts: Electrical Braking: Why does voltage decrease with a decreased rheostatic load?

texts:
So I've been messing around with DC motors and electrical braking. BY placing a variable resistor across the motor terminals of the motor I've been able to vary the braking effect and observe the changes in voltage and current across the resistor, i.e power extracted. During my testing I implemented dynamic braking at 105 rads to ensure transparency and for the majority of my results I found that the voltage across the resistor is consistently 7V upon the instant braking occurs, similar to what I applied to drive the motor.

However, as the resistance is decreased, as is the voltage. It would be expected that the current would be increased, which it is (i=V/R), however I'm unsure why the voltage drops as the resistance across the motor terminals approaches zero. Could anybody explain this?

Thanks for your time in advance,


texts: How can you calculate how much energy a PV panel (known size and wattage) produces in a day given the exact insolation in kWh/m2/day?


texts:
I am trying to gather some info about the M.2 connector.

My end goal is to add Wifi capabilities (e.g. using an Intel Pro Wireless M.2 card) to a Computer On Module system (iMX6, raspberry pi cm3, etc.).

I've been looking on Wikipedia and Google for info about M.2 connectors and all I have found is that M.2 connectors have different capabilities depending of the physical keying. And that Intel Pro Wireless cards use PCIe and USB bus (also some seem to use UART).

Is there somewhere a document giving the pin layout of the M.2 connector, in particular for A-E keyed cards?

Do the M.2 host must provide USB and PCIe or is it USB or PCIe ?


texts: Having difficulties running AC compressors from a generator on a boat

texts:
I have a problem that has me stuck and it’s marine related.

When my ship is on shore power the AC system works perfect with no defects the evaporator and compressors comes on.

When I switch over to generator power, this is the scenario:

When the generator is online the RPM is constant at 1500 RPM and freq is 50 Hz (Where I am uses 50 Hz). I can use all other equipment on the ship but when I turn on the AC the compressors don't start and the rpms and frequency drops and produces a busbar freq low alarm.  Freq drops to ~46 Hz and the rpmss go to roughly 1420.

I have two generators on the ship and the problem exist with either genset. If I switch back over to shore power the AC works fine. Any suggestions?


texts: Implementing analog multiplexers in LTSpice and Cadence Virtuoso

texts:
Is there any model for Analog Multiplexer compatible with LTSpice or Cadence Virtuoso?

A simple 2:1 multiplexer is implemented in LTSpice as a SPDT switch. So how to implement a 4:1, 8:1 or 16:1 multiplexer?


texts:
I am a beginner at electronics so excuse my rather simplistic question.

I would like to know regarding capacitors, if a capacitor is connected in a series circuit (as shown below but with a dc supply), will it discharge?


texts: Under what conditions does jw equal the laplace variable s in an electrical circuit?

texts:
Imagine I've got an electromagnetic actuator and solved the underlying differential equations. I got an solution for sinusodially excitation, as follows (just an example, no physical backround):

$$G(\mathrm{j}\omega) = \frac{I(\mathrm{j}\omega)}{U(\mathrm{j}\omega)} = \frac{1}{1 + \mathrm{j}\omega T}$$

Now I just set

$$\mathrm{j}\omega = s, \quad s \rightarrow \text{Laplace Variable}$$

to get

$$G(s) = \frac{1}{1 + s T}$$

and I claim that this is the transfer function for the electrical circuit feeding the actuator. I'm sure the results I get are correct, but I was told I can't just set $$\mathrm{j}\omega = s$$
without further explication.

So I wonder what are the conditions to do what I've done, how can I proof that both equations are correct and explain that in a correct mathematical way? I feel that everybody (in literature) either just does it or avoids the issue.

Further explanation:

Above system G(jw) shows a low-pass behavior in the frequency domain, means for sinusodially voltage excitation
$$ i(\mathrm{j}\omega) = G(\mathrm{j}\omega) \cdot u(\mathrm{j}\omega) = \frac{1}{1+\mathrm{j}\omega T} \cdot u(\mathrm{j}\omega)$$
I get a higher damping the higher the frequency of the excitation.

But we also know that a transfer function
$$ i(s) = G(s) \cdot u(s) = \frac{1}{1+s T} \cdot u(s)$$
excited by a unitary step
$$u(s) = \frac{u_0}{s}$$
will also lead to a valid solution, namely the typical exponential $$ i(t) = u_0 \cdot (1- e^{-t/T})$$ PT1-behavior.

So what is the condition, that a system which is valid in the frequency domain for harmonic signals in steady-state, is also valid in the Laplace-domain by setting $$ \mathrm{j}\omega = s$$ for the non-steady-state e.g. for excitation with a unitary step?


texts: Surface mounted electrolytic capacitor markings

texts: Is this 22uf / 16v? General rule of thumb for these markings?


texts:
Hello I'm trying to control the velocity of the propeller with the pitch angle. I have a diagram from the factor cp over J and phi (see image: Draw.io diagram), but not a analytical formula.

J = v*60/(nDpi), v: wind velocity, n: rotational speed, D: diameter of the propeller.

I get a motor torque and a rotational speed as setpoint. I should control the propeller speed by changing the pitch angle phi.

My question is, how do I calculate the controller to control the rotational speed?

My first approach was to invert the formula "Propeller Momentenstrecke". So I get the image below, but this is only valid if the Time Tphi is so small, that in this timeinterval the rotational speed changes less. There is a problem, if the rotational speed is very slow, so the output of the 3rd block become very big.

Do anybody knows, how I can control this system, which approach do I have to use? Do anybody know some papers?

edit: I'm talking about a small aircraft with one propeller in front. The maximum speed of the motor is 2500rpm mechanical, its a permanent magnet synchrone machine with 6 pole pairs.


texts:
This is a follow up question to my previous one,(Transistor selection for 5V LED circuit) where I was (kindly) guided to using a MOSFET to switch on this circuit.

My intention to switch this circuit on/off using a capacitive sensor IC such as this: http://www.mouser.com/ds/2/42/iqs904_datasheet-8785.pdf

At moment I'm still testing on the breadboard.  In the diagram below I'v replaced the IC with a simple switch+resistor to represent the output of Pin 3 (presumed to be 3~5 mA @ 5v) The LEDs are 3.6v @ 20mA

The circuit now looks like this:

simulate this circuit – Schematic created using CircuitLab

I'm new to MOSFETS (and actually electronics). From a quick look around it looks like a 2N7002K would work.

Is this the correct choice?


texts:
I'm a bit confused by the datasheet of a LCD (MIKROE-55).
It says supply voltage is 3.5V (TYP), which results in as Supply current of 16mA.

At first I understood this as: "connect K to GND and A to 3.5V and I'm done :)"

But below that table is a graphic showing 2 Resistors (1 on seems to be on boards, 1 external).

So my question: How to connect that backlight? If a Resistor is required, how to calculate its Value.

Full Datasheet can be found here:
Datasheet


texts: When assembling my own USB 2.0 spec cables, I haven't had any experience with frying PCBs they get plugged into (of custom-made keyboards primarily), but I hear stories of it happening. So I'm trying to identify what might cause a DIY'd USB cable to fry a PCB, when it is connecting a peripheral (keyboard) to a host PC? Would transposing the VBUS/GND conductors on one end of the cable do it? Is it even possible in modern PCs that a mis-assembled cable would fry a keyboard PCB? Thanks!


texts: How to combine demux units and other circuit components in order to obtain a bigger demux?

texts:
How can I combine, for example, a number of 3-8 demux units and perhaps other components such as transistors (takes three inputs and has 8 outputs) in order to make a 4-16 demux unit or perhaps even a 5-32 demux unit? How do I use the extra control bits that do not go into the 3-8 subunit in order to obtain a bigger demux?

By a demux unit I mean something like a http://www.nxp.com/documents/data_sheet/74HC_HCT238.pdf -- a demultiplexer


texts: Can I have multiple KNX/DALI gateways on a single DALI line?

texts:
In our KNX test lab we have several KNX/DALI gateways from different vendors (ABB, Ipas, Siemens, etc.). We have 1 DALI line with a few testing devices.

Whenever we do tests we need to physically attach the KNX/DALI gateway of interest to the DALI line. I would like to circumvent this effort by having all KNX/DALI gateways attached to the DALI line at the same time.

My question is: Is it possible to connect more than 1 KNX/DALI gateway on a single DALI line? Would this break a KNX/DALI gateway? What can possibly go wrong?

Thank you for looking into it!


texts: Reading Digital and Analog Signal from Different Sources with Arduino

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I am using an Arduino to read signals from 2 different devices. (This is an automotive project so all 3 are powered by the 12v battery of the car).

The signal from one of the devices is a digital High/Low - where Low is 0v and High is 5V (I've verified this with a meter).

The signal from the other device produces a 0v min, 8.4v max square wave. I am using a 1k and 1.5k resistor to drop the square wave to 0-5v in order to safely read the analog signal with the Arduino. I am using the FreqMeasure library to read the frequency of the square wave so since that library requires the input to be pin 8 of the Arduino, that's where the output of the voltage divider is going.

Here is the schematic for the input of the circuit:

The "RADIO_INPUT" of the schematic is the analog signal via a 3.5mm jack. The "BACKUP_INPUT" is the digital signal also via a 3.5mm jack.

When only 1 of the inputs are connected (for example: just the digital signal, or just the analog signal) everything works exactly how I expect.

But when both of the inputs are connected I get results that I wasn't expecting. I plugged in an oscilloscope to Pin 8 and Ground of the Arduino and when the digital connection was plugged in the analog signal goes to a 2-5v range instead of 0-5v. As soon as I unplug the digital signal it goes back to the 0-5v range as expected.

On the other side, when I connect the oscilloscope to the digital input I read the same analog frequency as I see from the analog signal except in the 0-2v range. Again when I unplug the analog input the digital input works exactly as expected and I just see the 0v Low, 5v High signal.

What appears to be happening is that the signals are somehow contaminating each other but I don't understand why. I assume that there's a problem connecting the grounds but I'm not sure what to do to keep the signals separated.

So my question is: is there anything I need to do to somehow isolate these 2 different signals so that they don't effect each other? Or am I missing something fundamental with reading in these 2 different kinds of signals?

Thanks!


texts: Calculating required power to run 2 modems in kWh

texts:
I am an electronics newbie. I have two modems at home. One is DSL Ethernet modem provided by DSL provider and other is TPLink wireless router. I see they have written Voltage and Ampere written on their backs

DSL Modem:     12 V  0.8 A
TPLink Modem:   9 V  0.6 A

Now I am using W = V . A (Source) to calculate Watts of these devices and I want to ask if I am doing this right?

I am trying to calculate how much power (kWh) these devices need so I may buy battery accordingly.


texts:
I was testing a four-layer PCB and got electric shocks several times when trying to touch the edges of the PCB. The four layers are: top/+15V/ground/bottom layer.

It seems that there are several "white spots" on the edges. And is it possible that the +15 layer get exposed and shocked me? If that is the case, it is quite dangerous.
We manufactured big boards that each one combines several small ones. Then we break each big boards to have small boards which are the final product. So I guess the power layer(+15V) may get exposed at the breaking process. My questions are:

Am I correct?

Is it because we combining small boards into big boards in the wrong way, such that the internal layers get exposed easily?

Is it because our prototype factory did not do a good job?

What are the potential risks under this condition? To the product its self and to users?

Every answer below is great. I chose Olin's because his answer contains most details.
Many thanks!


texts: Reversing the direction of current in an inductor

texts:
Would it be safe to instantly reverse the direction of current in an inductor? The flow of current through it is controlled by MOSFETs.
In case you're wondering, it's for a 1cm long electromagnet with approximately 100 coils with 2-4 amps and a cross sectional area of only 1cm2. Testing this out of curiosity.


texts: HC-06 Bluetooth module, what bluetooth mode I have to use?

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I am trying to connect an HC-06 Bluetooth module to my Android device to send data from my smartphone to my microcontroller conected to the HC-06.

I am writing the Android application and I have a question, according to: Bluetooth | Android Developers: Managing a Connection. I have to Bluetooth modes client and server, which one should I use?

I have seen an example in NeoTeo: Módulo Bluetooth HC-06 (Android), but it uses AppInventor so I can't see the source code.


texts: What is so special in the power MOSFETS IRFD120 and IRFD110?

texts:
I was trying out a hobby project and I was using the IRFD120 and IRFD110 power MOSFETs to control a motor. The transistors worked pretty fine and we simply ran out of them. When I went to buy some more I found out that they are outrageously expensive for a transistor. However, I found the FQP30N06L and FQP27P06 power MOSFETs for normal cheap transistor price. This raised my "sanity" flag. I thought that I knew which parameters matter, yet it seems that there is another parameter so important that it affected the price this much price. I ran a small specs comparison and I got this (comparing N-channel only for simplicity):

FQP30N06L:

Current Rating = 60 A
Voltage Rating = 30 V

IRFD110:

Current Rating = 1 A
Voltage Rating = 100 V

This clearly shows that the FQP30N06L can withstand more power, yet it is ~5 times cheaper than the IRFD110. Is it only the 100 V rating that is making the IRFD110 so special?

I am asking this question because I need to buy large quantities and I haven't used the FQP30N06L yet. Would it be a good idea to replace the stock of IRFD110 and IRFD120 with FQP30N06L and FQP27P06 for hobby project related applications similar to this: youtube.com/watch?v=Y-afnY32RrY?


texts: Hidden wire detector using BJT transistors

texts:
I made a hidden wire detector from this tutorial. It works, but I'm not quite understand why. Here is the circuit:

I used 2SC1815 transistors and the value of R was 1K0. My antenna was made of 300 mm length copper wire with diameter 0.3 mm. I've measured its inductance - it is about 2 uH.

First of all, I've measured the base-emitter junction voltage of the first transistor - its amplitude was about 80 mV. I believed that BJT transistors require about 0.7 V to open, but the circuit was able to detected the wire. How is that possible? The base-emitter junction voltage was 10 times lower, so I thought the transistor should stay closed.

The second question might be silly, but I was not able to find the answer. I realize that electromagnetic field develops the voltage across the antenna. But the antenna is connected to a circuit with only one side. So, which voltage do we use as input? My suggestion is that voltage may only occur when the resistance is high and the field does not need to develop a high current to maintain such voltage. So, maybe the equivalent circuit actually includes the Ra resistance, which is as high as the resistance of open circuit? See the circuit below:

If I'm right, the input resistance of the circuit must be very high too. So maybe this is the key for my first question and the transistor does not open at all? But in such case how on Earth this circuit can work?


texts: How can I center a servo using the FT311D?

texts:
I've got a servo which requires a 50Hz signal (which can be achieved with a 20ms period) and a 1ms-2ms dutycycle.
This is your standard hobby servo. 1ms dutycyle makes it go left (0 degrees)
1.5ms makes it go center (90 degrees) and 2ms makes it go right (180 degrees).

I'm also in the possession of a FTDI FT311D breakout board. With the android phone I got, I can command the FT311D to send the required PWM signal to the servo.

FTDI provides a java interface with which I can communicate with the FT311D.
This interface defines a method SetDutyCycle(byte pwmChannel, byte dutyCycle).

As you can see the dutycycle is of type byte. The documentation says the following about this dutycycle byte:

dutyCycle: the percentage value of the duty cycle,e.g. to set 50% duty cycle, specify this value as 50. Minimum 5%
and Maximum 95%.

My problem is this: I need 5% for the 1ms, I need 10% for the 2ms BUT i think I need 7.5 for the 1.5ms dutycycle, which I cannot assign to a single byte.

I might be missing something here. Or is this totally impossible? Maybe there are other possibilities?

Documentation


texts: Understanding word and instruction on simple microcontroller

texts:
From what I'm reading in this CircuitBread tutorial, the microcontroller PIC10F200 has flash memory of 256 words. PIC10F200 has a constant word unit of 12bits and so the maximum program size I can flash into the memory is 256 words * 12 bits = 3072 bits or 384 bytes. But still, I can't see how the word "word size" or "bytes size" indicate how much I can write into the flash, or how many cycles it takes to run.

Program size: If PIC10F200 has fix 12-bit words size (also the tutorial mentioned each instruction is one word in size). Should I count each assembly operation (or an opcode) as an instruction (i.e. GOTO as one instruction, MOVLW as another instruction)? If I have an assembly program consisted of two MOVLW and one GOTO (assuming labels are not instructions and occupies no flash), then I would have 3 word/instruction * 12 bits = 36bits or 4.5 bytes. But that's not the case and I was wrong. How can I count for myself the quantity of words or instructions I wrote in my assembly other than being just told to by the IDE?

Time to process an instruction: My understanding is that different manufacturers of MCU may have their instructions each takes a varying multiples of word. So if an instruction for a particular MCU's instruction occupies 128bits on flash on a machine of 32bits word size, does that mean it'll take the MCU 4 cycles to complete this specific instruction?

I googled and looked into stackoverflow but am confused with different architectures and abstraction which doesn't help. I want to check my understanding and be able to roughly calculate and time my program and understand why.


texts: DC motor speed control when having relay change directions

texts:
im building a circuit atm that drive a dc motor (24V, 5Amp) in both direction.
(Not using H-bridge because of the high amp motor, I cant find anything at the local store at least).
For now the circuit look likes this:

Which when the Arduino set pin 7 and 8  to HI-LOW, motor got 1 direction. And when LOW-HI is the opposite.(Relay switch the negative and positive connections)

However with this method I cant control the speed of the motor. I would love to make the motor slowly increase it speed.

I'm thinking to use a MOSFET and connect it to the PWM pin on the Arduino this method only works for 1 direction but not when reverse.

I'm lost, can someone point me a direction or giving me some link to go to.
Thanks you first in advance.


texts: Short Circuit in Allen Bradley Micro850 Output Headers

texts:
Unfortunately, I have discovered that the outputs 0 and 1, as indicated by my blue Sharpie marks, have continuity. I have inspected the circuit for hours, and cannot seem to find the source of the short. Could anybody please advise on where the short may be, and how to fix it?
Thank you for your time


texts: How to assess worst case runtime and correctness of an assembly implementation?

texts:
Set off by a question on CodeReview, I revisited "8-bit AVR unsigned division".
Trying much the same as for below 8 bit/8 bit → Q, R implementation, I found assessment of cycle counts of an "unrolled non-restoring bit-wise 16/16 → Q, R" tedious as well as error prone - e.g., overlooking exceeding the limit for conditional branch displacement.
(Using neglected skills and a fitting Atmel Studio 6.2 installation)
; 8-bit AVR non-restoring udiv proof-of-principle, uses about two cycles more than libgcc's
; (<https://github.com/gcc-mirror/gcc/blob/master/libgcc/config/avr/lib1funcs.S>)
;  improved with substituting 8 for 9 and "rol  r_arg1" for "rjmp   __udivmodqi4_ep"
.def    __sor = r21 /* -divisor */
_udivmodq:; 60-68 cycles "+ ret", 20 words. Q = 255, R = dividend when divisor 0
    ldi cnt, 8      ;           init loop counter
    clr __sor       ;   1
    sub __sor, dvsor;   2       __sor = -dvsor
    clr rem         ;   3       there will be four jumps to and fro, tops
    lsl dividend    ;   4
pos_low:
    rol rem         ;           shift dividend into remainder
    add rem, __sor  ;   1       adding to keep carry interpretation consistent
    brcc neg_rol    ;   2       remainder turned negative
pos_rol:            ;           four jumps here, at most; same number to neg
    rol dividend    ;   4       shift dividend (with CARRY)
    dec cnt         ;   5       decrement loop counter
    brne pos_low    ;   6    8
    ret

neg_low:
    rol rem         ;           shift dividend into remainder
    add rem, dvsor  ;   1       adding to keep carry interpretation consistent
    brcs pos_rol    ;   2       remainder restored to positive
neg_rol:            ;           four jumps here, at most; one less to pos
    rol dividend    ;   4
    dec cnt         ;   5       decrement loop counter
    brne neg_low    ;   6    8
                    ;   63 upper bound - tight? 62 because 7 taken brcxs at most?!
    add rem, dvsor  ;           restore remainder
    ret

How should I assess worst case runtime?
How should I assess correctness of advanced implementations, say, along the lines of Fast 16-bit / 16-bit unsigned division for megaAVR?


texts:
I'm looking to see if it is possible to label net names in Altium in some way similar to the concept of component designators (eg R? C?) which would enable me to duplicate a section of a circuit which has several nets, without having to manually re-label them all.

Putting it another way, I have 3 control current sources that all have the same design and so I have only completed the first one on my schematic. If I now go and copy it, there is potential for missing one of the net labels resulting in an incorrect routing.

Whats my best option?


texts:
Many N-Channel MOSFET drivers for high side switches and high speeds have charge pumps that can provide enough current at high voltage to drive the gate high and sink the current back out again. I have never seen this done for high side P-Channel MOSFETS. Are there any circuits or driver ICs that can generate charges 12 volts lower than the supply instead of 12 volts higher?

I have seen Infinion’s application note about high side P-Channels with IR2101, but it requires an external supply. I might as well not use a driver IC at that point.


texts: PSPICE simulation of capacitor voltage and current disagrees with math

texts:
I'm testing a simple enough circuit on PSPICE. The zener has a BV = 220V, so the capacitor has a voltage of 220V until the switch closes.

Using the time equation for voltage of a capacitor: Vc(t) = Vo * e^(-t/tau)

Vc(1ns) = 220V * e^(-1ns/50*500pF) = 211.37V

Vc(25ns) = 220V * e^(-25ns/50*500pF) = 80.93V

Vc(50ns) = 220V * e^(-50ns/50*500pF) = 29.77V

Vc(75ns) = 220V * e^(-50ns/50*500pF) = 10.95V

Vc(100ns) = 220V * e^(-50ns/50*500pF) = 4.02V

Calculate dV/dt:

1ns --> dV/dt = (220V - 211.37V)/1ns = 8.63E9

25ns --> dV/dt = (220V - 80.93V)/25ns = 5.56628E9

50ns --> dV/dt = (220V - 29.77V)/50ns = 3.8046E9

75ns --> dV/dt = (220V - 10.95V)/75ns = 2.787E9

100ns --> dV/dt = (220V - 4.02V)/100ns = 2.1598E9

And using the current equation for capacitors: Ic(t) = C*dV/dt

Ic(1ns) = 500pF*8.63E9 = 4.315A

Ic(25ns) = 500pF*5.56628E9 = 2.78A

Ic(50ns) = 500pF*3.8046E9 = 1.90A

Ic(75ns) = 500pF*2.787E9 = 1.3935A

Ic(100ns) = 500pF*2.1598E9 = 1.079A

Seems great. Unfortunately, PSPICE disagrees.

The peak voltage node R2 reaches after the switch closes is only around 28V. It's clear to see that based on the topology this is just one big voltage divider. There shouldn't be any voltage at all on the top node after the switch closes because the overwhelming majority of voltage is dropped across R1. This doesn't explain why the capacitor releases such a wimpy peak in voltage though.

So I simply decide to test out 500nF, and poof! I get an output that I was expecting for the 500pF capacitor. But, I still don't understand why neither of these simulations discharges the capacitor within the expected time constant of 25ns(4) = 100ns. It should be almost completely discharged at 4tau.

Obviously PSPICE cannot be wrong. What am I missing here?


texts: Simulink battery model with buck converter

texts:
I have created this model in simulink:

Vfc and Rfc are the equivalent of a battery, and the battery is connected to a load R, through a buck converter. The buck converter is implemented with a mosfet, and an LC filter. For the time being I am switching the mosfet from a pulse generator. My problem is that I cannot find a way to stabilize the current on the battery side of the circuit. Obviously due to switching, the current is a pulse.I tried adding a capacitor in parallel with Vfc,Rfc, but it did not work. Here is the current and voltage waveform(scope2):

My question is, firstly, why is current like a sawtooth waveform and not like a pulse waveform? Also, more importantly, how can I make the current as steady as possible?
Here are the values of the components:

Ideal Switches

Vfc=42.2 V

Rfc=0.346 Ω

L=200e-6 H

C=500e-6 F

R=10 Ω

Switching Frequency=10KHz

Duty Cycle=50%
EDIT: By increasing L, sawtooth waveform becomes pulse waveform. Thanks for the suggestion in the comments. Any ideas for the second question? How can I have stable (DC) current on the battery side of the circuit?


texts:
I'm really struck in solving the following question

  The single-phase full-bridge voltage source inverter (VSI), shown in
  figure, has an output frequency of 50 Hz. It uses unipolar pulse width
  modulation with switching frequency of 50 kHz and modulation index of
  0.7. For \$V_{in}=100\$ V DC, \$L = 9.55 \$ mH, \$C = 63.66 \mu \$F and \$R = 5\; \Omega \$, the amplitude of the fundamental component in
  the output \$V_o \$(in Volt) under steady-state is ?

Here is my approach. I'm using the following formula of the fourier series of the output voltage
$$V_{O} = \sum_{n=1,3,5}^{\infty} \frac{8V_{in}}{n\pi} \sin(n\gamma) \sin \left( \frac{nd}{2} \right) \sin(n\omega t)$$
where, \$ 2d = \$ total pulse width per half cycle. \$ \gamma \$ is defined as

I'm getting \$2d=1.5 ms \$ which is giving me answer way much less than the actual. The answer is in the range of \$ 60 - 64\$ V.
What is the procedure for solving such type of problems ?


texts: Connecting multiple cameras to a single CAMIF (Camera Interface)

texts:
I am looking for examples of connecting multiple camera modules to a single CAMIF  for multi sensor still-image acquisition (ie, very low speed per sensor). The broadcom chip used in the raspberry pi supports up to 20 MP sensors. I want to connect 5 14MP sensors.

I assume since one of the signals is the vsync that indicates the end of a frame, an fpga could be used to properly mutiplex across the multiple modules (perhaps having to dump frames occasionally).

Does anyone have an example of someone doing this in the real world?


texts:
I have a sequential (flowing) LED vehicle indicator unit that I need to keep powered for about one second after the input is switched off.

It is intermittently powered from the vehicle's indicator circuit at about half a second on and half a second off, however, although the indicator unit has a power "reservoir" on board it doesn't support the LED's for quite long enough and the sequence is interrupted and restarted which is not the required effect.

I would guess the unit consumes a couple of watts, possibly up to five - my meter doesn't seem to work like it used to so I can't be accurate - and the voltage is a normal 12 V vehicle range.

I don't know too much about electronics, I'm better on electrics and I believe I can do the job with a capacitor, but having web-searched I can't find anything that gives me an answer to what I'll need for the sort of power and voltage I'm using.

Can someone out there suggest a value and type that will get me somewhere near to what I need?

Many thanks.


texts:
today I'm working on a new chipset named : "8-Bit Shift Register/Latch with 3-STATE Outputs" also referenced as "CD4094BC", and I've got the following logic diagram :

On this picture I know that the gate in the red square is a tri-state output, meaning that the output stay undefined if "output enable" input is false, else the output depend of Q1-8.

But there is some symbol that really looks like D-Type Flip-Flop (blue and green square), before I asked here how to know if it's a D-Type Flip-Flop or not and you answered me that it can be recognize by the letter FF in the square and the clock input and the D input. Here I see something that really looks like the D-Type flip-flop except the fact that some inputs seems to be misplaced and outputs are missing or not what I expected them to be. So, if they're not D-Type Flip-flop, what does this symbols mean exactly ?

Here is the truth table I got from the datasheet :

And I don't really get what the outputs value means...
Hi-Z is one of the problem.

Thanks


texts: How many ohms do I need for LEDs controlled by an shift register?

texts: So I've got 6 LEDs, 3 red, 3 green. I'm going to control them using a shift register and either an arduino uno, or an arduino due. Now, I know I'm supposed to use resistors for the LEDs, but I'm really confused as to how many ohms. Everywhere I've looked has told me different things. Could someone explain this to me and show me how to actually calculate this?


texts: Why DC block is used for GPS receiver tested using a simulator via an active antenna?

texts:
Reading up GPS testing using a simulator and came across several articles which suggest requiring a DC block capacitor in the RF path between the GPS Simulator+Attenuators & Active Antenna.

Some explain, the 50 ohm load seen by the receiver is too high making it draw excess DC current from the circuit through the active antenna and pass through ground, which may damage the Simulator Front End or Attenuators, and also some passive components in the Receiver circuit DC current path which may not be rated for that high DC current.

My question is isn't the active antenna 50 ohm itself? Does this apply to just GPS?


texts: How to fix LFO sync by changing component values

texts:
I've built an LFO with a sync output for a modular synth project.

The LFO circuit is based on http://www.electro-music.com/forum/topic-31166.html and the reset part I added into that one using https://www.facebook.com/176989513877/photos/a.10150261457078878.340231.176989513877/10151593786478878/?type=1&theater

So my complete circuit looks like this:

Problem I think I have is that the order of magnitudes for the sync part and the actual LFO, in particular the timing cap - is way off. Thereforethe short timing pulse generated by the sync circuit doesn't seem to be enough to entirely reset the LFO timing cap. This is a scope readout where I'm trying to sync the LFO (triangle) from another LFO (square):

Obviously syncing is going on, but it seems to signal is to short to entirely reset the LFO.

So I'm pondering about the best way to fix this. I'm really new to this but my best guess is to decrease R6 a lot, but I'm a bit  afraid about what will happen then with relation to R7 and the JFET. I would need to decrease it a lot I think if I'm to hope it to be enought to fully reset the cap.

Another idea is to try to extend the pulse, but at this point I'm not even sure if it's C1 or D1 that really sets the limit there. I'm guessing I could increase the value of C1 to make the pulse longer?

What's the best option here?

Update ---
Changed C1 from 1nF to 15nF but it hardly got better, rather it started syncing on downs as well as ups which is not the intention.

--- Update 2:

I was confused - the problem was actually that it synced on downwards pulses too. So that's why I saw partial syncing, the upwards sync was always complete. So I've changed C1 now back to 1nF from 15nF and I have this:

So it's syncing a tiny bit on downwards sync pulses too and if possible I would like to get rid of that. Should I lower the value of C1 even more? Any tips highly welcome!

Update 3:

I've revisited this schematic again now and tried some things, but I realize I don't really understand how the reset is supposed to function.

First off I realized that my timing caps was order of magnitudes bigger than the ones where I pulled the reset schematic from. I have a range switch and timing caps of either 100nF of 1uF as you can see, while the reset schematic was using a timing cap of just 1nF. Since it seemed the pulse wasn't enough to fully reset my timing cap - it merely moved it in a direction, I figured I would lower R7 and R6 for more current to be able to pass through while the FET is open.

So I also found other schematics without any series resistor at all, simply a JFET that would short the timing cap and while trying out values I got all the way down to 0R for R7. However, this made it so that it always resets to 0. My triangle core here is on TimingReset2 while TimingReset1 sits at GND. Shortening the timing cap via the FET simply sets the waveform to ground, but it doesn't reset the direction:

 And it doesn't seem that I can make R7 fix this. And I really don't understand how this is supposed to work to be honest.

What I want is to be able to send a pulse to this LFO and then it will reset in a repeatable fashion. Therefore the idea of pulling it up to wither Vcc or Vdd felt like a good one, so I could have a non-random waveform.

This reset circuit, anyone understand how it is supposed to work and could help me out?


texts: Voltage regulator with heatsink gets overheated

texts:
First of, I'm sorry if I'm using the wrong terms or if I'm pointing out something that is obvious to most, this is not my profession, it's only a hobby.

I have an input voltage of 12V 5A which is needed for a water pump. I'm trying to use the same source too drive a Raspberry PI Zero W together with a bunch of sensors. To lower the voltage to 5V I'm using a voltage regulator, L78S05CV, which I had lying around. It should be able to give me 2A but currently I'm only needing about 0.27A.

The voltage regulator has a heatsink with a thermal resistance of 29 °C/W and the regulator has a thermal resistance from junction to case of 5 °C/W (Rthj-a of 50 °C/W). The regulator dissipate around 1.89W ((12 - 5) * 0.27), which would mean around 64 °C ((29 + 5) * 1.89). Assuming an air temperature of 25 °C it should end up at around 90 °C. The regulator should have a operating junction temperature of up to 150 °C.
Still I do belive that the regulator gets overheated after some time, I can see a drop in voltage to about 2.5V.

I am trying to understand the math here, to see if I need another heatsink with a better thermal resistance or if I should just look at other alternatives.

I have read several other responses to similar threads, but too be honest, the answers is a bit out of my league.


texts: Running a 6V DC LED Bulb from a 8V AC current source?

texts:
I hope that this question has not been asked earlier and is wasting anyones time. I don't particularly remember my ECE101 classes that well - and seek your help!

I own my grandfather's hifi amplifier that has power light indicator that recently burnt out. The bulb is proving too hard to find right now. It was a tiny filament bulb and was powered by a 8V AC current (Schematic says bulb rated 8V 40mA).

I just wanted to check if my math is still alright here.

AC 8V RMS = 8V x Square Root of 2 = 11.3V for the DC LED.

So by using a 6V 30mA led I would take 11.3v - 6V = 5.3V extra current across the circuit.

Then I would then just use V = I x R; so 5.3V/30mA = 176 ohms resistance.

By adding the 6V 30mA LED with a 180 ohm resistor would be a workable solution?

I was also told I may need a rectifier diode and a capacitor to keep a smooth glow? Are either mandatory or just optional?

Finally can I use a full wave rectifier to avoid using the cap? Any idea on how to wire this. Sorry for my basic question but every bit of help would be useful!

Thanks in advance :)


texts: WCDMA , 8PSK signal, 3 G , user end sensitivity, required SNR

texts: Does anyone know how the User End receiver sensitivity for a 3G WCDMA, 8 PSK signal is calculated? and what is the typical SNR required to detect the signal?


texts: How does colpitts and hartley oscillators start oscillation?

texts:
I know LC circuit will start oscillation only when the input current is cut off.
As of colpitts and similar oscillators, how do they oscillate when the input current is still passing in the LC?


texts: I tried to do the steps... Ie = 1.98/100 = 0.0198A Beta for 1st transistor and 2nd one is 2 So total current gain= (beta1 +1)(beta2 +1) Ie/Ib = 3*3= 9 Ib= 0.0198/9 =2.2mA But answers are not matching... someone please help me what's wrong with my calculations


texts: What is the most painless way to get a high current negative voltage power supply from a positive?

texts:
I'm designing an audio DSP and DAC board, and in the analog section, I'm using opamps that take in differential audio signal and turn it into single ended output. Because the signals are AC, they obviously swing below zero, so I will need a plus/minus power supply. Keep in mind, I'm a software guy, and I'm only doing this as a hobby -- not a pro hardware designer.

I've been researching the internet for about a week, looking for solutions. So far, I've found:

Charge pumps: These are awesome if it wasn't for the fact that they only supply maximum of 100mA. Driving 16 audio opamps will need more current than that.

Buck/Boost inverter These suck. They require complex circuitry and can barely supply higher current output than the charge pumps. To me, this is the big and ugly solution.

Cuk topology I don't have enough background in power electronics to fully understand the mechanisms for this one, but it still requires several inductors and some mess of external circuitry. They are also limited in their current output for the most part.

Power modules This would be a plug-and-chug solution, but it takes the fun out of DIY, not to mention they are quite huge and take up lots of board space.

I've seen some configurations where there is a sort of "half-rectifier" diodes arrangement used for generating negative supply, but I don't understand it.

If someone with enough electronics background can explain to me an easy to implement and understand solution to generating a negative voltage supply, it would be fantastic. Here are my constrains:

My input voltage is 12V.
I want my output voltage to be between -12 to -15v (any value there will do)
I want 1 A current output.
I want minimal external components. A few is okay, max one inductor.
Don't care about ripple, noise, isolation, temperature characteristics, or anything else.

simulate this circuit – Schematic created using CircuitLab


texts:
What I am supposed to do is that when J2 is pressed for the first time, it is supposed to start the counter and it should run from 0 - 9 and then back again. When J1 is pressed, the counter should reset to 0 and stay there until J2 is pressed again. However, when J2 is pressed again when the counter is running, the counter should stop at its current number. How can I do that? I am aware that when a logic high is passed to INA, the counter will stop its count and display its current number on the display. But how can I do that? I can only use 2 ICs, 1 NAND gate IC and 1 Or gate IC.

EDIT


texts: Current limit and current gain bjt question

texts:
Contact potential of Vbe in Q2=Vbe-on
I worked out that the maximum current that can go through R2 is Vbe-on/R2. So my question is why does Q2 turn on when the emitter current of Q1 reaches this maximum current?
Thanks!


texts:
I am trying to set the RESET pin, which is set to high via internal pull up, of my MCU (3.3v) to low based on an external pin (3.7v). When the external pin is low, the RESET pin should be Gnd and if the external pin is high, the RESET pin should be disconnected (will get back to high because of the internal pull up). I am new to electronics by i think i found a good solution with a p-type MOSFET.

Source = RESET
Drain = Gnd
Gate = External pin (0-3.7v)

Right now i am struggling with the wide variety of MOSFET's out there (Farnell has 1000). Could anybody please help me to calculate the right values or give me other advice for solving that problem?


texts:
I'm currently just getting involved with electronics, just bought an Arduino starter kit and am fiddling around with it.

Currently i'm on a project which involves the use of a DC(spinning) motor in conjunction with an Arduino, and the book im using states that motors typically require more current that what the Arduino can provide, and that the Arduino can only provide 40mA, which is much less than what most motors require to do work.

However, the book states

  Transistors are components that allow you to control high current and high voltage power sources from the low current output of the Arduino

and

  Motors require special consideration when being controlled by a microcontroller.Typically the microcontroller cannot provide enough current and/or voltage to power a motor.Because of this, you use transistors to interface between the two.

I've done some googling and know the basics of how transistors works (e,g doping, n-type and p-type) but i don't see why attaching a transistor to a circuit/microcontroller that outputs less current that the motor requires magically makes the motor works.

I would really appreciate any clarification and/or explanations.

P.S. I thought that this question might better fit this site rather than Arduino.stackexchange as it is more about transistors in general.


texts: How to extend the input range of a linear voltage regulator?

texts:
I need to generate a fair bit of current (up to 2A peak, much less average) in the 6V-15V range for driving MOSFET gates, and also generate 5V (less than 100 mA) for an MCU, from an input that may be between 6.5V and 60V. I'd like the output of the 6-19V regulator to be ~6V when input is 6.5V, and ~15V when input is >= 16V, and then not go over 15V as voltage goes up.

I've found a number of promising candidates on Digi-Key, but none that has the combination of ultra-low drop-out and high current capacity that I want. For example, the MAX5024 can generate my 100 mA for 5V from a high input voltage, and only has 0.9V drop-out; it can also be used to generate 11V output (which will be less with less input voltage) but only up to 100 mA, and using two of this becomes expensive. 11V is also in the lower end of the gate drive voltage I want to use when the input voltage is high -- 15V would be better.

There are also some cheaper parts (like some Intersil part) that generate 5V and 15V, but require 12V and 20V input respectively, and only generates 30 mA for the 15V output.

Perhaps I can use a reservoir capacitor after the 11V output to supply the transient current of switching the MOSFET gates on/off, and get around the 100 mA limit? As long as the time switching is less than a handful of percent of the total duty cycle?

An alternative would be to use a lower-voltage ULDO (with 16V or 35V max input) and somehow extend its working range by using some offsetting Zeners or resistors in some clever combination -- but I can't quite work out what that would be that would let me extend like that while still having the very wide (> 50V) input range span.

Any advice would be appreciated!


texts: Few queries on how to set real time clock value in DS1307

texts:
I need to integrate DS1307 RTC in my project. I have somehow managed to write I2C code and interfaced it with PIC32. I need to make a logic so that it shows real time values on UART. Now to display it on UART, the values need to be converted into ASCII. So lets say if I set 13 to its seconds register then I am getting this value in I2C2RCV register but on the terminal it is displaying some random ASCII character.

After converting this value to ASCII, I am receiving 51 49 on terminal. I am using below logic for conversion:

//i2cbyte : Received values from I2C

char  i2cbyte;
unsigned char x,y,p1,p2;
char value1[10] ;
char value2[10] ;
 x = i2cbyte & 0x0F;
 p1 = x | 0x30;
 y = i2cbyte & 0xF0;
 y = y >> 4;
 p2 = y | 0x30;
 sprintf(value1,"%d",p1);
 sprintf(value2,"%d",p2);
 putsUART1(value1);
 putsUART1(value2);

So I set 13 and I received 51 49. So what value should I set in my code to get real time value on UART. Is it possible to get values on UART because inside the code I am getting the real time value but to display it outside the code, the values need to be converted which becomes something else. How can I resolve this?

After setting the values in the register of RTC, do I need to use some logic to update it. Datasheet tell that registers are automatically updated. But what happens during programming is  I am setting values to registers and then reading it but the values are not updating. I am always receiving what I am writing.
How to set values

Please help.!

CODE:

int main(void)
{

OpenUART1( UART_EN | UART_NO_PAR_8BIT | UART_1STOPBIT  , UART_RX_ENABLE | UART_TX_ENABLE, (FPB/16/BAUDRATE)-1 );

I2C2BRG = 0xA3;     //I2C Baudrate
I2CEnable(EEPROM_I2C_BUS, TRUE);    //I2C module On

StartTransfer(FALSE);      //I2C Start
TransmitOneByte(0xD0);  //slave address
TransmitOneByte(0x00); //register pointer pointing to first register (seconds)
TransmitOneByte(0x13); //seconds register value
StopTransfer(); //I2C Stop

IdleI2C2(); //I2C wait

while(1)
{
    RTC_read();

    putsUART1(value2);
    putsUART1(value1);
    putsUART1("\n");
    DelayMs(1000);
}

}

//RTC_read function:

void RTC_read()
{
StartTransfer(FALSE); //I2C Start
TransmitOneByte(0xD0); //I2C slave address
TransmitOneByte(0x00); //Register address
StopTransfer(); //I2C Stop

IdleI2C2(); //i2C Stop

StartTransfer(TRUE);    //I2C Restart
TransmitOneByte(0xD1);  //Slave address to read

//Reading from I2C slave
if(I2CReceiverEnable(EEPROM_I2C_BUS, TRUE) == I2C_RECEIVE_OVERFLOW)
{
  putsUART1("Error: I2C Receive Overflow\n");
}
else
{
   while(!I2CReceivedDataIsAvailable(EEPROM_I2C_BUS));
    sec = I2CGetByte(EEPROM_I2C_BUS); //storing seconds into sec variable
}
StopTransfer(); //I2C Stop

    //converting sec to ASCII
    x1 = sec & 0x0F;
    p1 = x1 | 0x30;
    y1 = sec & 0xF0;
    y1 = y1 >> 4;
    p2 = y1 | 0x30;

    sprintf(value1,"%c",p1);
    sprintf(value2,"%c",p2);
}


texts: VREF of FPGA should be grounded if not needed?

texts:
I just started FPGAs. I know that Vref is designed for I/O Banks specially needed for some I/O standards or weak keeping. If I dont need them should I ground these pins or leave them floating( not connected)?

EDITION: specifically I mean XC2S100  in Spartan II group.


texts:
The pin numbers aren't listed anywhere on the board. Where's pin 1? Where's the pin for ground.

This is what it looks like.

This seems to list the pin numbers, but it's not really helpful in this case.


texts:
I would like to ask if anybody knows some technology which is like array of phototransistor with accuracy in mm . Like some display on which I put someting and get by wire data of pixel which are shadowed, just only logic state ( 0 = Nothin/Ligh, 1 = Someting is put down on screen/Dark).

000
010
000

My first idea was solve it by many phototranzistor in matrix, but it haven't that
necessary accuracy which I would need. ( I think even SMD phototranzistor for this are so "big").

Thanks everyone for some help, and I'am sorry for my poor English. I hope you have get it what I've been wrote there.


texts: Why did my textbook use signal energy as a measurement of approximation error, instead of something else?

texts:
TL,WR: Why do we use signal energy as a measurement of an approximation's error, and not something "simpler" like the absolute value of the error?

Background: I'm reading through my textbook for my introduction to signals class, and they have just gotten to a point where they are discussing Fourier series representations of signals.

Specifically, they're talking about the square wave, and how it needs to be decomposed into an infinite number of harmonically related complex exponentials

$$x(t) = \sum_{k = -\infty}^{+\infty} a_k \cdot e^{j k \omega_0 t}$$ and how to get an approximation error, they want to use a finite number to represent it

$$e_N (t) = x(t) - x_{N} (t) = x(t) - \sum_{k = -N}^{+N} a_k \cdot e^{j k \omega_0 t}$$

Then they say,

  In order to determine how good any particular approximation is, we need to specify a quantitative measure of the size of the approximation error. The criterion that we will use is the energy in the error over one period.
  $$E_N = \int_{T} | e_N (t) |^2 dt$$

Why did they choose to use this as the measurement of the error, instead of, say, the absolute value of the error? Integrals are "hard" (by which I mean more time-consuming) math, and I'd like to hear a justification from anyone who works with this stuff closely. I suppose doing it this way might reveal places where the error in the signal spikes, which could be useful information, but that's the only thing that pops to mind immediately.


texts: Does USB supply a "constant" 5V or "up-to" 5V?

texts:
I am trying to reverse engineer a digitizer inside an old laptop. I am fairly certain it is a USB device because I noticed a twisted pair of cables next to a ground wire. Just to make sure it is USB I probed the pin to the other side of (what I suspect to be) D-.  When I did this I saw different voltages flashing very quickly but nothing close to 5V.  I believe the max I saw was 1.2V and min being somewhere around .3V.

I don't want to wire this up to a USB cable out of fear of destroying the digitizer if it can't in fact handle 5V.

This would make sense to be USB VCC if it does offer up to 5V but I couldn't find anything definitive that I could understand at least.


texts:
I've built an array of Infra Red LEDs on a 4x4 grid. I want to get the most power out of these LEDs as I can, but I'm scared I might burn them out.

Right now, I'm using 2AA batteries (1.5V each), which is powering the array.

First of all, the starting volts is 3V right? When I measure the voltage at the other end, I get about 1.5V (There's about 6 feet of cable from the battery to the LEDs).

Even with this powering the array, they get very warm and smell a little. Is this too much voltage?
Help me out here,

Here are the specs for the IR LEDs:
http://www.rapidonline.com/pdf/58-0116.pdf

The array contains 16 IR LEDs, each require maximum of 5 Volts. So surely 80 Volts would be ideal? Then again, that doesn't sound right - and I don't know anything about electronics.

One more thing, I haven't used a resister at all within this array. I normally use one for a normal LED, but the IRs didn't light up at all with it, and works fine without one.

Here is a rough diagram showing you how I have it wired up:

FYI:
I'm hoping to hook this up to an Arduino at some point.


texts: What is the minimum PWM frequency that LT1999-10 can capture with smooth output settling?

texts:
I am referring data sheet of LT1999-10,
My PWM signal is 100Hz duty 5% resolution 8 bit
I have a doubt,
Data sheet - 2MHz bandwidth
Is this IC able to capture 100Hz PWM signal? will output of IC settle as shown in below figure. or goto 0V before seeing next pulse when 100Hz PWM m is applied?
figure shows high frequency PWM with smooth output - a good settling which is i am expecting for 100Hz.


texts: Calculate output impedance of emitter follower

texts:
In AoE's chapter on BJT (specifically section 2.2.3B Input and Output Impedances of Emitter followers), it derives the input and output impedances to be:

$$\mathbf{Z}_{in} = (\beta+1)\mathbf{Z}_{load}\ \ \ \ \ \ \ (2.3)$$
$$\mathbf{Z}_{out} = {{Z}_{source} \over \beta+1}\ \ \ \ \ \ \ \ \ \ \ \ \ (2.4)$$

Input Impedance: take the circuit simulation in the image as an example, where R_b (2Mohm), R_c (10kohm), and R_e (1kohm) each denote a resistor on the base, collector and emitter respectively, and where BJT has a constant of 100 beta or Hfe by default. According to formula 2.3, the input resistance of the emitter follower looking into the base would be ((100+1)*1k)+2M = 2,101,000ohm. With a voltage drop of 555.905mV in V_be inside the BJT, the Thevenin voltage into the base is 10V - 555.905V = 9.444095V.  Hence a I_b is 9.444095V / 2,101,000ohm = 0.000004495A or 4.495uA, and voltage drop of R_b = 4.495uA * 2Mohm = 8.99V.  The calculated values matches those displayed in the simulation. OK.

Output Impedance: if removing Re and Rc, Zout = 2Mohm/(100+1). With Rb and Rc in place, according to AoE formula, Z_source = 2Mohm/(100+1) + 10kohm + 1kohm = 30,801.980198 ohm (the resistance looking into emitter in the perspective of the load, or R_e). Voltage at the emitter would be 10V - 8.990V - 0.555905V = 0.454095V or 454.095mV. I_e should then be 0.454095V / 30,801.980198 ohm = 0.000014742A or 14.742uA. The current does not match that in the simulation, 454mA.

Here the questions:

What I did wrong with my output impedance measurement?
If I just get the voltage drop after the emitter by V_Re = V_cc - V_Rb - V_be = 10V - 8.99V - 0.555905 = 454.095mV, and hence I_e = 0.454095V/1kohm = 454.095uA from my calculation which is 0.095uA more than the simulated value of 454.000uA. Where is this or why did I get this extra 0.0905uA in the calculation? I understand practically there are miscellaneous factors affecting the beta and voltage drop across Vbe, Vbc and Vce, and we are subject to approximation, availability of components, and trials and errors to choose a resistance or output a current to get the job done. But simulations are ideal with fixed values and formulas and I should be getting an exact 454.000uA instead of 454.095uA. So I am either missing or misunderstanding something.

sorry, can't get MathJax to display inline with paragraph using single $ sign


texts:
I'm developing a modular equipment device aimed for industry, very similar to a PLC in terms of electronics. For all field interfaces I am using isolators and ESD protection for robustness and to pass on certification tests.

As my device is modular, I have a backplane so the modules will communicate through it. My doubt is if I can connect the isolated ground of all modules (because if I don't, they will not have the same reference). And I also want to know if this architecture is the best practice for this type of project (modules + backplane).

I've designed this two drawing to help on your understanding.

Thanks


texts:
I want to know the voltage (tension) of every of my components. I have leds, a buzzer, a piezo, a photoresistor, a rain sensor and more.

I have a multimeter and I would like to use it to measure the voltage of the components. I know how to measure current and resistance but not voltage yet.

I want to start measuring the leds. I know they are around 2 volts, but I want to measure them exactly with a multimeter.

This is my multimeter:


texts: Impedance of BNC vs output impedance of function generator

texts:
I'm a bit confused on output impedance of function generator and coaxial cable impedance.

Consider a function generator with output impedance of \$50 \Omega\$. Suppose that I connect to it a BNC \$50 \Omega\$ coaxial cable and then i connect it to my circuit.

I can think of this configuration as  in picture

simulate this circuit – Schematic created using CircuitLab

My question is: how big is \$R_{int}\$? \$50 \Omega \$ or \$100 \Omega\$? And what does contributes to \$R_{int}\$? The function generator output impedance or the coaxial cable impedance or both?


texts: General rule for current flow in op amps?

texts:
I'm a first year student doing elec eng. and I'm wondering about the direction of current in an op amp (Where the current flows from to where it is going). I'm wondering this so I can use KCL to find an expression for Vout, but I usually end up getting the directions wrong.

This is an example of the type of amp I'm asked to detail about in my exams. Is there a rule about the way the current flows depending of the feed back etc?

Thank you for your help!

David


texts: Do I need a common ground wire for differential voltage measurement?

texts:
I'm using this module as a digital scope and function generator. I don't have experience with differential measurements(besides multimeters) and I'm wondering do I need to couple a ground wire between the module ground and the test circuit ground:

I know that a voltmeter doesn't need such a ground wire for differential measurement, but how about in this case do the grounds need to be common? I saw in some cases a common ground wire is needed to prevent common mode voltages to saturate the amplifier; but how come a multi-meter does not suffer from the same issue? Multi-meter can be floating but CM voltages can pass through air via capacitive coupling isn't it?

Basically I'm wondering why in some deferential measurement we need ground but in some we don't. An illustrative answer involving diagrams would help better. I really need two circuit models to compare these to understand the main idea.


texts: Deep explanation on TVS diode voltage suppression?

texts:
I am looking for a deep explanation on why a TVS diode suppresses voltage. All of the research I have done on Google just says 'it suppresses voltage by shunting current', but this doesn't make sense to me. I also couldn't find any information on this device in the Sedra and Smith textbook.

My understanding of a TVS diode is that at the Vbr voltage, it will start to conduct a lot of current. An IV model neglecting other factors (like temperature etc.) looks like this for a bidirectional TVS:

According to this, it makes sense that it passes a lot of current; at a constant voltage beyond Vbr, it could be though of as a resistor with very low resistance. This is where my understanding breaks down.

In a circuit, a TVS is used in parallel with the load:

simulate this circuit – Schematic created using CircuitLab

According to the nodal understanding, the voltage across the TVS is always the same as the voltage across the load. The only explanation for it clamping the voltage which slightly makes sense is that it acts as a voltage divider with Zload. But that would make the clamping of the TVS dependent on the impedance of  the source.

Also, I'm not sure if this model for how the TVS works would make sense for transient events which aren't on the battery, like inductive coupling of a high voltage.

Thanks for reading my question, I appreciate anyone who can correct or confirm my thoughts on this.

TLDR: Does a TVS diode really work by voltage division


texts:
I tried building a toroidal inductor with the following parameters:
OD= 1.400 in / 35.55 mm +/- 0.75 mm
ID = 0.900 in / 23.0 mm +/- 0.55 mm
Ht = 0.500 in / 12.7 mm +/- 0.50 mm
Wire: solid insulated copper 14G
Data sheet for the material: https://www.fair-rite.com/43-material-data-sheet/

For some reason inductor the is not working when a connect it to a battery (doesn't work as a magnet). I was expecting to get more than 100 micro Henry out of it.
Is it possible that is not working because the wire is insulated with thick plastic? What are other possible reasons for it not working?
Thank you!


texts: Are there special rules for voltage division of a high speed clock?

texts:
High speed signals require special care in PCB layout to prevent high speed effects like ringing and overshoot. This obviously applies to clock signals as well.

Provided that one has a high voltage clock (e.g 3.3V) and wants to connect it to a low voltage input of an FPGA e.g 1.2V, one could use a voltage divider.

Are there any disadvantages in general in dividing clock signal like this e.g increased noise or jitter?
How should the voltage be reduced in a high speed signal e.g clock that is 100s of MHz?


texts: 'Information nature' of transfer function?

texts:
Doubt: before I thought I had understood the transfer function, now, I realize that I did not understand what transfer function is it on a structural level , that is how it 'makes a circuit' or is manifested or implemented concretely because I see a translation motion here where function is integrated when a Shift Operator is provided or better, is induced by control system or still better, technically we have a a differential operator of an electric field (a complex field C)

In mathematics, and in particular functional analysis, the shift operator also known as translation operator is an operator that takes a function x ↦ f(x) to its translation x ↦ f(x + a)
Translational motion is movement of an object (in this and this sense) without a change in its orientation relative to a fixed point.

In mathematics, a fixed point (sometimes called an invariant point) of a function is an element of the function's domain that is mapped to itself by the function

I know that the amplifier amplifies in the sense of 'gain', but the gain depends, and I do not understand here, how the transfer function is defined (is just a calculation or it is reflected by a shift operator ? This is not very clear)
What I do not understand is if the transfer function, concretely, can be calculated by an operational amplifier in the physically operative sense of the term because to do this we need to have an linear functional because we need to have a current not a physical movement because we talk about of trasfer function, not about information extraction !

Basically, current doesn’t flow because current is just measurement. It is developed by flow of electrons. Current is rate of flow of charge.

But this flow of charge how is determinated in relation of transfer function ?
A flow formalizes the idea of the motion of current because the direction of current flow is opposite to the direction of electron flow.
The related question is about the 'information nature' of transfer function: is this a signal action like a 'function' (and therefore I ask how it is done) or, if the function, here, is to be calculated in another meaning, that is, something that is extracted or indirectly calculated as a 'behavior' of the circuit, an impulsive response, etc. but.. in this case we should, mathematically speaking, talk about of image function

an image is the subset of a function's codomain which is the output of the function from a subset of its domain

Definition of transfer function is instead

It is often represented as a graph, called a transfer curve or characteristic curve. The transfer function provides information which specifies the behavior of the component in a system

What type of function is this curve ? Exponential, logarithmic.. ? Because if it provide information you need a function to do that, maybe a constant function ?
I find that is method of characteristics for solving partial differential equations, so this is the 'function' of transfer function ? But is not clear if I want to induce a transfer function (Current–voltage characteristic) I need a Semiconductor curve tracer


texts: Sample & Hold circuit not working for negative half cycle

texts:
I have made a Sample & Hold circuit using Multisim but after simulating oscilloscope showing sampled version of input waveform for positive half cycles only. I have used MOSFET as a switch with controlled voltage and its working fine.

My question is why I am not getting sampling of negative half cycle even though MOSFET is open circuited?


texts: Can I put two loads on one battery and both loads draw 3.7v as they expect?

texts:
I have a project in mind where I replace the tinny 40mAh LiPO battery of a "smart band" (Like a Mi Band 1) and replace it with a regular 18650 LiPo battery, so it last a long time without recharging. That would be simple, but what about if I have two of them?

My plan is to wire the battery to a TC4056A 1A battery charging board, and the loads in parallel.

I've been told by a friend that that's fine, but I have absolutely zero formal training in electrical engineering and I'm unsure about what I'm doing... that's where I ask you. :)

Also, would you change something to make the circuit better and/or safer?

Any help is appreciated. Thanks!


texts:
Is there a way to measure AC power/current delivered through 2 or 3 wire cable? I know that from Ampère's Law the total current of both wires is zero, but is there a way to measure power in cable in other methods?

My intention is to measure average power from typical home devices like washing machine, oven etc,but without entering the circuit. I know the RMS voltage of my net (220V) so I need to know the current. I know that there are pen testers which may figure out whether a current is flowing through a certain cable but it's not telling how much current flows.


texts: License free frequency spectrum in Australia

texts: What is the license free frequency spectrum in Australia? Is it 433Mhz or 915Mhz Or 868Mhz? I am trying to do some IOT Project using RF (LORA/ZigBee) modules. I thought it was 433Mhz. But some online sources refers other two.


texts: Is it possible to implement remote controllers with Bluetooth BLE?

texts:
I have been thinking of making bluetooth remote controllers with bluetooth low energy modules that can act as broadcasters and observers (and "peripheral" for set up)

How good would that design be (and if so would it be easy to find such components ?)
Thanks


texts:
I'm using MCP6044 Quad OpAmp (Datasheet) for battery powered PIR sensor, it works fine but draws too much current. When I plug it to 3V source (VDD: 3V, VSS: GND) with no load it draws around 550uA, where I suppose it should be around 3uA (600nA/amp). Let me know if it's something wrong with chip or I do something incorrectly.
Update:
There's schematic I used:


texts: What is the relation between resonance frequency and piezoelectric charge coefficient?

texts: We know that the maximum power is lost at the resonant frequency,where the impedance is minimal. On the other hand, when the impedance is minimized, the charge coefficient is maximized. In resonance frequency amplitude of vibration is maximum.how is possible? Is there a relationship between resonant frequency and charge coefficient?


texts: Where to get stabilitron voltage current characteristics

texts: I am reading Art of electronics of Paul Horowitz. Here is in 1.06 chapter is given is computation of voltage drop on zener diode while applying different voltage sources to them. So I wondered where to get voltage current graph for example of 1N4099 zener diode? There is no presented in its datasheet: http://www.centralsemi.com/get_document.php?cmp=1&mergetype=pd&mergepath=pd&pdf_id=1n4099-4135.PDF


texts: I found this QR code like object on a PCB today. I tried scanning it with a QR code scanner, but I didn't get a result. What is this? If it is similar to a QR code, how do I scan it?


texts: I am very confused on how to interpret this timing diagram?


texts: CMR of "All Inverting" balanced line receiver

texts:
Walt Jung describes following instrumentation amplifier in his "Op Amp Applications Handbook" (pg 454) saying that the value of R5 (gain adjustment) does not have any interaction with CMR.

My LTSpice simulation shows clearly that there's interaction between R5 and CMR.

Did I understand it wrong?


texts: Can BJT transistors be damaged by static electricity?

texts: I'm wondering whether they should be stored in anti-static bags or not?


texts: Can I compute resistive device power consumption at specific voltage knowing its power rated at some other voltage?

texts:
Suppose I have a device containing a heating element and no thermostat such as some simple water heater. It's rated "3500 watts 220 volts" which I assume means that if it's plugged into a properly wired outlet supplying 220 volts it would produce 3500 watts of heat.

A real outlet will have some other voltage - maybe 215 volts, maybe 235 volts depending on the grid conditions and time of day.

I want to know the power of device plugged into a real outlet. I measure the voltage with a voltmeter and it reads 235 volts.

Then I try to apply Ohm's law which says that current is proportional to voltage.

The device manual says that at 220 volts the device power is 3500 watts and therefore draws 15,9 amperes current.

235 volts is 1,07 times greater than 220 volts so current at 235 volts would also be 1,07 times greater and it'll be about 17 amperes.

Then I multiply the real voltage (235 volts) by that computed current (17 amperes) and I get 3995 watts (almost 4 thousand watts).

Is this proper application of Ohm's law?


texts: Low Profile PCB Connector Identification

texts:
There's some connectors on a PCB I would like to make a breakout for, but I'm having trouble identifying the connector type. Could somebody help me identify what type of connector this is, and potentially provide a part number(s) for the end that will mate with the PCB?

Sorry about the poor image quality.


texts:
I have comfortably got to grips with the pic16's now, so I am moving on up to the pic18 series.

However, I cannot get any joy from them.

I have a pic18f4455 and a pic18f14k50 - neither of which I can get to work.  I really want to get the 4455 to go.

I have the usual xtal+2cap oscillator circuit, which is oscillating happily.  I have the usual blinking-led program flashed into it.  But it's just not running the program.  My theory is that the overly-complex CONFIG registers aren't set right.

I am using sdcc on Ubuntu, and I have my config set up like this:

__code char __at __CONFIG1L c1l = _USBPLL_CLOCK_SRC_FROM_96MHZ_PLL_2_1L & _CPUDIV__OSC1_OSC2_SRC___1__96MHZ_PLL_SRC___2__1L & _PLLDIV_NO_DIVIDE__4MHZ_INPUT__1L;
__code char __at __CONFIG1H c1h = _OSC_HS__HS_PLL__USB_HS_1H & _FCMEN_OFF_1H & _IESO_OFF_1H;
__code char __at __CONFIG2L c2l = _VREGEN_OFF_2L & _PUT_OFF_2L & _BODEN_OFF_2L;
__code char __at __CONFIG2H c2h = _WDT_DISABLED_CONTROLLED_2H;
__code char __at __CONFIG3H c3h = _PBADEN_PORTB_4_0__CONFIGURED_AS_DIGITAL_I_O_ON_RESET_3H & _LPT1OSC_OFF_3H & _MCLRE_MCLR_ON_RE3_OFF_3H;
__code char __at __CONFIG4L c4l = _LVP_OFF_4L & _ENHCPU_OFF_4L;                    // Disable LVP
__code char __at __CONFIG5L c5l = _CP_0_OFF_5L & _CP_1_OFF_5L & _CP_2_OFF_5L & _CP_3_OFF_5L;
__code char __at __CONFIG5H c5h = _CPD_OFF_5H & _CPB_OFF_5H;
__code char __at __CONFIG6L c6l = _WRT_0_OFF_6L & _WRT_1_OFF_6L & _WRT_2_OFF_6L & _WRT_3_OFF_6L;
__code char __at __CONFIG6H c6h = _WRTD_OFF_6H & _WRTB_OFF_6H & _WRTC_OFF_6H;
__code char __at __CONFIG7L c7l = _EBTR_0_OFF_7L & _EBTR_1_OFF_7L & _EBTR_2_OFF_7L & _EBTR_3_OFF_7L;
__code char __at __CONFIG7H c7h = _EBTRB_OFF_7H;

I know some of those aren't needed, but I have tried with nothing, just the needed ones, and with everything.  Nothing seems to work.

I don't know what the best way of setting the config registers on this chip is in sdcc - g00gle doesn't seem to have much of a clue unless you're using MPLAB.

So, any clues?  Anything I just haven't been able to see because it's so blindingly obvious?


texts:
simulate this circuit – Schematic created using CircuitLab

I need to build a variable current source that operates off a 36V supply, if possible using a single op-amp and a mosfet. I need to control current between around 10uA - 0.5mA ie very low current. This is for some iontophoresis research I'm doing.

The design I envisage is attached. The zener should give a ref voltage of 2.5V and R3 should give variable current based on I=2.5/R. That's my theory anyway. Anyone able to recommend R values, Mosfet, IC choices? My power source must be 36V.

This circuit would feed into an H-bridge, the output of which would go to an iontophoresis cell which is just two electrodes that connect to (usually) porcine skin (ears), inside a sealed chamber (like a Franz Diffusion cell). Typical resistance of pigs ears is 10k but sometimes we use skin obtained from surgical procedures or cadavers, in which case the resistance is approx 100k. My aim is to test various active molecules in terms of transdermal penetration, so it is quite important to have reasonably stable current for reproducibility. This is more important than accuracy. 36V is a convenient voltage for iontophoresis but in some cases lower voltages are used. For example, to treat hyperhidrosis (excess sweating) of the hands, it is possible to build a simple iontophoresis setup with a 12V battery. However I am dealing with quite large molecules that may require higher voltages.

Thank you!


texts:
To parallel two buffered signals voltage I mean to get (scan) the voltage which has the higher absolute value if they are in the same polarity, and get the summation of two vantage value if they are in opposite polarity. For example

 Vs1           Vs2             Expect output
 3.5v          1.3v              3.5v
-4.1v         -5.2v             -5.2v
 1.7v         -0.6v              1.1v
-2.5v          3.9v              1.4v


texts: 12V to 5V DC-DC converter is outputting 7.5V

texts:
I recently bought these DC-DC converters. But when I apply 12VDC to the input I always observe 7.5V on the scope instead of 5V, I tried with a 680k load still 7.5V. But the datasheet says this is 12 to 5V converter.

What could be the reason?


texts: Max Voltage of Electrical Stimulator for Cardiac Tissue Bioreactor

texts:
I'm designing a bioreactor that will electrically and mechanically stimulate cells in media in an incubator. I'm using monophasic, square waveforms and have a max stimulation level of 12V/cm, else they don't respond. I bought an electrical stimulator powered by a 9V battery and listed in the manual is a peak amplitude of 105 miliAmps at 1000Ohms. When measuring with a voltmeter from one electrode to the other, without touching the electrode, the solution has a resistance of 1900 Ohms.

Will the max voltage drop across the resistor be 9v, assuming the wires are perfect conductors? And with the stimulator, you can alter the current, but not the voltage, so what should I set the current at?

Once again, this will never be tested on humans, so I'm not super worried about messing up, I just don't want to make any huge errors as this is a design project and I've only taken one class for electrical enigneering, being that I'm a bioengineering student.

I thought I could just multiply optimum stimulation level

Thanks for any help and let me know if you need any more info...


texts: Are small signal relays vulnerable to ESD?

texts: I am looking for a small relay to help me with network cables. The system needs to be able to withstand a reasonable electrostatic discharge on the cables. I am using MAX485 network chip, which has 15kV ESD protection so I guess that is a reasonable threshold. The relay I am looking at is Omron G5V-1-5VDC (non-latching). Its datasheet doesn't mention ESD. In fact, I looked at several similar relays from other manufacturers and they don't mention ESD either. I am guessing it is not an issue for such relays? Would it let a 15kV ESD through without burning down?


texts:
This question is related to MOSFET.

NMOSFET's resistance was till now defined in many different ways, for example as:

or  which value varies from 1-50k Ohm.

And there is also drain-source on-state resistance  which is usually lesser than 1 Ohm.

Which one can I actually use in an equation like this one which applies for common source configuration?


texts:
I'm working on an electronic weight scale using MSP430 and I need your help:

I've written the code using Energia and I've used the HX711 module for testing and everything works just fine.  The final project requires everything being on a single PCB, which means I had to give up using the HX711 module (I have to only use the HX711 integrated circuit.) I've remade the schematic that was on the module (see the attachment below.)

I've done some measurements on the circuit and here's what I've discovered:

The Vsup and Dvdd pin are set to 3.3 V as expected.
Base has 2.6 V.
AVDD, VFB and AGND are all equal around 0.7 V.
Also the VBG is 1.8 V.

The schematic is identical to the one attached, but because AVDD and AGND are equal, the voltage that arrives at the load cell is equal to AVDD - AGND which is zero, so I think this might be the issue; I just need a second opinion from you guys (and ways that I can raise that differential voltage.)


texts: Sensor for hand/foot location in relation to a persons body

texts:
I would like to track the movement of a persons hands and feet in relation to their waist.  I imagine them wearing something around their waist that can measure how far away a sensor attached to each hand and foot is.

What kind of sensor would I be looking for to do this?  Everything needs to be attached to the person so can't be a done via a stationary camera.

I thought IR or some kind of sound sensor but would those work when not in line of sight such as when they are walking/running and their feet are behind the front of their waist?


texts: convert 12V PWM circuit to 5V PWM using opamp

texts:
I can convert a 12 V PWM signal into 5V signal, by using voltage divider on 12 volt signal , then directing it to base of NPN common emitter transistor with collector connected to 5V

simulate this circuit – Schematic created using CircuitLab

How can i do same using Op amp ?


texts: Bridge rectifier: What is the purpose of these two elements?

texts:
I found the following circuit in a random video (don't know what it's worth) and have two questions about it. I get that it's a full wave rectifier, and I think I have a decent idea on how it works. However:

What is the 220k resistor for?
Why put the 105JF capacitor in there? This looks to me like a high-pass filter, and I don't see the point at all of doing this.


texts: Weird capacitor looking things shows up in altium when I zoom into the pcb layout

texts: I am using altium for first time for my little circuit project. My layout start showing these weird capacitor looking things in PCB layout. What exactly are they and what are they used for and how do I disable them to show up on layout?


texts: Uninterrupted current triggering transistor base

texts:
I'm still pretty much a electronics-beginner, I'm currently working on modifying a USB game-pad to use switches instead of buttons and I want LEDs to accompany the switches. The basic solution I was hoping to use looked like the following:

simulate this circuit – Schematic created using CircuitLab

Note that when Input 5V to GND is shorted then IC transmits the button as pressed. The current through the LED is 20mA.

The schematic above makes the LED work but the controller no longer recognizes it as being switched on. So, unable to modify the current going through the switch I instead tried to add a transistor with the resistor and LED separate from the switch, similar to the solution here:

simulate this circuit

This makes the switch work again but the LED does not power on. It does work when I remove the connection between the switch and GND so I'm assuming all the current goes through the GND-connection and nothing goes to the transistor base. Am I thinking incorrectly or how should I solve this?


texts:
I am using an IC which is an RS422 driver chip.
There are 4 drivers in silicon and each can be enabled using a mux kind of enabling system.
The screen shot is below -

My doubt is - the input comes in Ain,Bin,Cin and Din.
The differential outputs are given outside at D0,/D0,...etc.
Now, each driver is enabled via the enable and /Enable pins. This means at any given instant, I can enable only 1 driver,right ?

For eg - 00 - driver A,01 - driver B,..and so on and so forth .

Hence-forth, If I want to drive 2 different signals I will need 2 different ICs.


texts: Increasing precision of a practical opamp circuit when the input signal is very small

texts:
I have a sensor which outputs a normally distributed baseband signal with cut-off frequency of 100Hz, whose mean is ~1mV and variance is (0.1mV)2. I want to amplify it about x1000 times by using TL084 opamp (other three opamps the TL084 contains are already occupied for different functions).

simulate this circuit – Schematic created using CircuitLab

I have a practical consideration on this circuit. The input signal is smaller than the input off-set voltage of the opamp which is given to be 3mV. Will this opamp successfully and precisely amplify my signal? If not, how do I increase precision of this circuit?

And how does the input offset voltage appear at the output (suppose that the input offset voltage s 3mV, the input signal is x(t) and the opamp output is y(t))?
a) 1000 times amplified along with the input signal. (i.e.; y(t) = 3V + 1000x(t))
b) Added at the output stage. (i.e.; y(t) = 3mV + 1000x(t))


texts:
I am currently stumped in the design process in creating a method to intercept Bluetooth signals with an antenna and simply outputting the exact signal through another antenna.

Some Background

I develop Automation scripts for testing Bluetooth between my company's product and cell phones, and I wanted to build a tool that will isolate frequencies of a tester's choosing autonomously.

I thought the best way to accomplish this is a Faraday Cage, in which the phone would be placed inside. I have constructed the cage which effectively blocks all RF signals, including Bluetooth.

It was then suggested to me that I attempt to build a Repeater and place an antenna on the inside and another on the outside; then connect the two through the cage. The two antennas would pass the Bluetooth packets back and forth between the phone and system. I could then sever the connection anytime.

The Actual Question itself

I am having difficulty figuring out an effective way to connect the two antenna together and allowing them to pass the Bluetooth signals back and forth. There seems to be many methods, and I am not the most knowledgeable with RF antennas and such. I thought that perhaps an enlightened individual could give me a push in the right direction so I am not going about a random "witch-hunt" for a solution.

Could someone provide a "top-level" idea? I can do any research necessary to figure out the details.

What I've done so far

I bought two 2.4 GHz duck antennas, a coax cable and some RP-TNC connectors off DigiKey. The impedance of all these are 50 ohm. The connectors are rated for up to 4 GHz. Could it really be as simple as wiring the two antennas together?

I've also been reading data sheets on RF transceivers rated for 2.4 GHz. These interface to an MCU through SPI. These data sheets are easy to follow but I can't imagine that SPI bus is quick enough to transfer every packet, especially when it's clocked in the MHz range. This method also feels like overkill.

The obvious trivial solution here is to have a physical mechanism open and close the cage, allowing the Bluetooth signal to escape. However I am reluctant to do this since I plan on cutting on and enabling the Bluetooth signal hundreds of times a night. Mechanics would be bound to fail. Also I can't create a "Band-pass" filter through this method.

TL;DR

Design ideas for a circuit that captures the 2.4 Ghz (namely Bluetooth) RF signals with antenna and passing the exact signal out another antenna.


texts: Using ATtiny 45/85 with HC-05 (Not arduino)

texts: I am working on a project that requires me to use an ATtiny microcontroller with bluetooth module HC-05. I have used the module with Atmega 8 in the past using UART protocol. Can anyone help me in using this module with ATtiny 45/85. PS: I have no idea about programming arduino, and use embedded C language for my projects.


texts: Analog switches able to send bi directional digital information?

texts:
I'm trying to send digital signals from an ST-Link V2 programmer connected to my computer to a blue pill STM32 microcontroller, but I want it to go through a DG412 Quad SPST CMOS Analog Switch.
As far as I can tell I have it all set up and it doesn't seem to correctly program my board.
Is what I'm doing even hypothetically possible? Is there any reason I couldn't send a digital signal from source to drain on an analog switch?
Are these switches bi directional? As in, does the data have to be coming from the source pin to the drain pin, or could data be sent back from drain to source? The SWDIO pin is bi directional, although I don't know whether the blue pill sends any data back during programming.
I'm thinking the other reasons it might not work is due to latency, or missing additional components. I'm pulling the IN lines to GND and the Drain to GND with resistors.
SOLVED: It turns out when the 3.3V went through the IC, the voltage dropped to 2.9. When the voltage was that low the other factors of the IC became an issue. The clock was interrupted by the capacitance of the MOSFET. Also the fact that I used 5V on the V+, V- rails meant the source-drain on-resistance was much higher. By putting 12V into the rails and having 3.3V bypass the IC I was able to make it work.


texts: Are MESFET transistors still used in the industry?

texts:
I was looking for mesfet transistors earlier, because I need some for experiments due to their relatively simple physical structure.
I can't find any of these on rs, farnell and mouser !

So I was wondering if this kind of transistors was still used in industrial applications ?
Why can't I find any ?

ps : https://en.wikipedia.org/wiki/MESFET


texts:
i am trying to implement Lorawan network in Arduino uno and end-devices are in class B.
My question is how i build beacon and brodcast in network ? or there is a command in lorawan mac layer to do this?


texts:
TLDR; how to make a MIDI output withstand shorting it to \$\pm12\$V?

I'm designing a MIDI output in a eurorack modular synth module on a TRS jack (this is a semi-standard non-standard way to save space), where it's quite possible for the user to accidentally plug in anything between \$\pm12V\$ to the output. I obviously need to protect the output, while keeping the circuit maximally compatible with other MIDI devices.

The standard MIDI output circuit adapted to the TRS connector:

simulate this circuit – Schematic created using CircuitLab

where tip, ring and sleeve are of course the pins of the TRS output connector. The buffer is a 74AHCT1G125 with a 5V supply, which also acts as a level translator.

The problems with this circuit are:

if someone connects \$-12V\$ to the tip, the current through R2 is \$77\$mA, and power is \$1.3\$W, so R2 has to be a rather big resistor, and would anyway get quite hot.
same problem for R1 when UART TX is high and ring is connected to \$-12V\$, and further the buffer has an absolute maximum output current of \$\pm 20\$mA, so even if I'd use high power resistors, the buffer wouldn't survive.
The buffers current limit is also exceeded when ring is at \$+12\$V.

So some slightly more clever protection than just bigger resistors is needed. Here's my current best attempt:

simulate this circuit

Here the R1 and R2 are 3/4W resistors (so still pretty big). M3 restricts the current if the tip falls below about 2V, limiting the output current to between \$-12\$mA to \$32\$mA, which the resistor can take. M1 does the same for the ring, and M2 limits the current to about \$16\$mA when the ring exceeds \$+5\$V. The voltage divider R3 - R4 is there to bring the threshold of M1 down a bit, so that cathode of D2 is pulled closer to ground. The specific MOSFETs mentioned here are just examples, I'm yet to decide on the exact part numbers.

Now, according to my LTSpice simulations, this should work. However, there's a number of reasons why I'm not perfectly happy with my solution:

I feel like I'm using a lot of parts for something very simple.
As a specific example of the above, I'm tempted to leave out the buffer and just use the MOSFETs to drive the signal. However, I can't seem to figure out how to simultaneously drive the signal, do the level translation from 3.3V, and protect the components, without introducing even more transistors.
The voltage divider generating the gate voltage for M1 is a bit annoying: to bring the -12V and it's ground return to this digital part of the circuit would break my star grounding (as the star point is on the other side of a connector I can't change at this point). I could leave out the voltage divider (i.e. connect the gate of M1 to ground), but in that case the ring doesn't get pulled quite all the way to 0V, and the loop current (assuming a forward voltage of 1.7V for the optocoupler on the receiving end) is only about \$4\$mA, which is just a tad below spec.

So, I'm looking for thoughts on simplifying the circuit, while still keeping the protection and staying comfortably in the MIDI spec?


texts: Magnetic transformers on the same circuit as electrical

texts:
I'm trying to make a cheap variable power supply for a hot wire cutter. As I will be trying different wire thicknesses and lengths I must be able to control both amperage and voltage. To do this I have a light dimmer wired up to an electrical transformer. This lets me vary the power between 35 and 150 watts. My original plan was to follow this with a variable magnetic transformer/ multiple transformers and switches to control the voltage amperage ratio.
My problem is the documentation for the electronic transformer says it must not be on the same circuit as inductive loads.

How much of an issue is continuing with my current plan? and is there a way to solve the implied problem? ... perhaps with a diode.


texts: How to calculate RPM from a square wave signal Voltage-Time graph

texts: I'm struggling to understand how to show the relationship between the input and output of a hall effect sensor used as a wheel speed sensor through mathematical expression. How can I calculate the RPM if the input gives me a square wave signal? I understand it may be through calculating the frequency, but I feel like I'm missing something.


texts:
I'm researching designs for a simple bipolar output switching power supply and came across the design below in a ST datasheet for the MC34063A.

However, there isn't enough information in the datasheet for me to implement this design and I couldn't find any SMPS topologies in other resources that looked to be equivalent.  I was hoping someone would recognize the topology so that I could find more information on it.

On a related note, are there any other/better designs using the MC34063A (since I have a bunch on hand) for producing +/-7V @ 100mA from a 3V input?  Thanks!


texts: We have qualified one of our magnetic sensors (80 samples, 1000 hours - JEDEC) with zero failures and we are asked to provide a FIT. The product is not repairable so I would think an MTTF would be more appropriate in this case, but in either case, how would you calculate FIT, MTBF or MTTF in this case with 0 failures?


texts: BMG250: Understanding basic gyroscope output?

texts:
I've never used a gyroscope before. I chose Bosch BMG250 from the digikey search results. I was reading the datasheet and other info online on how a gyroscope works and I'm a bit lost. The output of gyroscopes seems to be specified as degrees/sec. The picture below is what I'm using to understand the output of the gyroscope. I don't have the actual part...this is all in paper right now. The picture on the left is from page 66 of the BMG250 datasheet (link below).
So... assume the cell phone is in front of me in the air. my question is what would the output be if I rotate the phone 45 degrees to the right within one second and stop? Will the output of the z axis show a binary output of 45 degrees positive within the "one second" of moving and then show zero after I stop? Forget about noise and calibration offsets for the sake of understanding please. What about the x and y axis outputs... I'm thinking those will not show anything in the output. Is my thinking right? Thanks
Bosch BMG250 datasheet

Thanks


texts:
I was trying to find Norton's equivalent for the following circuit from A to B:

So I decided to start by using the fact that \$R_{th}=V_{OC}/I_{SC}\$, and found out that \$V_{OC}=0\$ so I decided to find \$I_{SC}\$ (\$I_{n}\$ in the diagram) and thus short-circuited the terminals to arrive at the second circuit shown, and it seems like \$I_{SC}\$ can take infinite values.
I know that there are other ways to find \$R_{th}\$, that's what I did in the end nonetheless. However I rather expected to find \$I_{SC}\$ to be zero because \$R_{th}\$ is constant, so I would like to know if anything went wrong here. I'm also a little bit confused because I'm not sure about whether I should include a ground terminal in the second circuit because I don't know how to define \$V_{s}\$ otherwise.


texts: Writing parameters into Code memory at Run time during Initializations - 8051

texts:
I need to make this possibly. I am using keil IDE and the AT89c51RD2 MCU.

At initialization, a function will be called to derive about 1500bytes. I want to write this byte to code memory (byte by byte), because it will never change through the entire program. This I know might take about 2 pages of Flash memory.

How can I possibly do this?

Thanks.

EDIT

I fould this where it appears it can be done.
http://www.keil.com/forum/3483/